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11,763,418 | https://en.wikipedia.org/wiki/Luminescence%20%28journal%29 | Luminescence: The Journal of Biological and Chemical Luminescence is a monthly peer-reviewed scientific journal publishing original scientific papers, short communications, technical notes, and reviews on fundamental and applied aspects of all forms of luminescence, including bioluminescence, chemiluminescence, electrochemiluminescence, sonoluminescence, triboluminescence, fluorescence, time-resolved fluorescence, and phosphorescence. The current editor-in-chief is Yi Lv (Sichuan University). It was established in 1986 by John Wiley & Sons as the Journal of Bioluminescence and Chemiluminescence and obtained its current title in 1999.
Abstracting and indexing
Luminescence is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2020 impact factor of 2.464, ranking it 55th out of 87 journals in the category of "Chemistry, Analytical".
Highest cited papers
According to the Web of Science, the most-cited papers published in Luminescence are:
"The red-edge effects: 30 years of exploration", Volume 17, Issue 1, Jan-Feb 2002, Pages: 19–42, Demchenko AP.
"Imaging of light emission from the expression of luciferases in living cells and organisms: a review", Volume 17, Issue 1, Jan-Feb 2002, Pages: 43–74, Greer LF, Szalay AA.
"Analytical applications of flow injection with chemiluminescence detection - a review", Volume 16, Issue 1, Jan-Feb 2001, Pages: 1-23, Fletcher P, Andrew KN, Calokerinos AC, et al.
"Reporter cell lines are useful tools for monitoring biological activity of nuclear receptor ligands", Volume 16, Issue 2, Mar-Apr 2001, Pages: 153–158, Balaguer P, Boussioux AM, Demirpence E, et al.
References
External links
Biochemistry journals
Academic journals established in 1986
Wiley (publisher) academic journals
English-language journals
Monthly journals | Luminescence (journal) | [
"Chemistry"
] | 430 | [
"Biochemistry journals",
"Biochemistry literature"
] |
11,763,512 | https://en.wikipedia.org/wiki/Biomedical%20Chromatography | Biomedical Chromatography is a monthly peer-reviewed scientific journal, published since 1986 by John Wiley & Sons. It covers research on the applications of chromatography and allied techniques in the biological and medical sciences. The editor-in-chief is Michael Bartlett (University of Georgia).
Abstracting and indexing
The journal is abstracted and indexed in:
Chemical Abstracts Service
Scopus
Science Citation Index
According to the Journal Citation Reports, the journal has a 2020 impact factor of 1.902.
Notable papers
The highest cited papers published in this journal are:
'High-throughput quantitative bioanalysis by LC/MS/MS', Volume 14, Issue 6, Oct 2000, Pages: 422 - 429, Jemal M. Cited 178 times
'Analytical Chemistry and Biochemistry of D-Amino Acids', Volume 10, Issue 6, Nov-Dec 1996, Pages: 303–312, Imai K, Fukushima T, Santa T, et al. Cited 79 times
'Fluorogenic and fluorescent labeling reagents with a benzofurazan skeleton', Volume 15, Issue 5, Aug 2001, Pages: 295–318, Uchiyama S, Santa T, Okiyama N, et al. Cited 74 times
References
External links
Biochemistry journals
Academic journals established in 1986
Wiley (publisher) academic journals
English-language journals
Monthly journals | Biomedical Chromatography | [
"Chemistry"
] | 275 | [
"Biochemistry stubs",
"Biochemistry journals",
"Biochemistry literature",
"Biochemistry journal stubs"
] |
11,763,521 | https://en.wikipedia.org/wiki/Nucleate%20boiling | In fluid thermodynamics, nucleate boiling is a type of boiling that takes place when the surface temperature is hotter than the saturated fluid temperature by a certain amount but where the heat flux is below the critical heat flux. For water, as shown in the graph below, nucleate boiling occurs when the surface temperature is higher than the saturation temperature () by between . The critical heat flux is the peak on the curve between nucleate boiling and transition boiling. The heat transfer from surface to liquid is greater than that in film boiling.
Nucleate boiling is common in electric kettles and is responsible for the noise that occurs before boiling occurs. It also occurs in water boilers where water is rapidly heated.
Mechanism
Two different regimes may be distinguished in the nucleate boiling range. When the temperature difference is between approximately above TS, isolated bubbles form at nucleation sites and separate from the surface. This separation induces considerable fluid mixing near the surface, substantially increasing the convective heat transfer coefficient and the heat flux. In this regime, most of the heat transfer is through direct transfer from the surface to the liquid in motion at the surface and not through the vapor bubbles rising from the surface.
Between above TS, a second flow regime may be observed. As more nucleation sites become active, increased bubble formation causes bubble interference and coalescence. In this region the vapor escapes as jets or columns which subsequently merge into plugs of vapor.
Interference between the densely populated bubbles inhibits the motion of liquid near the surface. This is observed on the graph as a change in the direction of the gradient of the curve or an inflection in the boiling curve. After this point, the heat transfer coefficient starts to reduce as the surface temperature is further increased although the product of the heat transfer coefficient and the temperature difference (the heat flux) is still increasing.
When the relative increase in the temperature difference is balanced by the relative reduction in the heat transfer coefficient, a maximum heat flux is achieved as observed by the peak in the graph. This is the critical heat flux. At this point in the maximum, considerable vapor is being formed, making it difficult for the liquid to continuously wet the surface to receive heat from the surface. This causes the heat flux to reduce after this point. At extremes, film boiling commonly known as the Leidenfrost effect is observed.
The process of forming steam bubbles within liquid in micro cavities adjacent to the wall if the wall temperature at the heat transfer surface rises above the saturation temperature while the bulk of the liquid (heat exchanger) is subcooled. The bubbles grow until they reach some critical size, at which point they separate from the wall and are carried into the main fluid stream. There the bubbles collapse because the temperature of bulk fluid is not as high as at the heat transfer surface, where the bubbles were created. This collapsing is also responsible for the sound a water kettle produces during heat up but before the temperature at which bulk boiling is reached.
Heat transfer and mass transfer during nucleate boiling has a significant effect on the heat transfer rate. This heat transfer process helps quickly and efficiently to carry away the energy created at the heat transfer surface and is therefore sometimes desirable—for example in nuclear power plants, where liquid is used as a coolant.
The effects of nucleate boiling take place at two locations:
the liquid-wall interface
the bubble-liquid interface
The nucleate boiling process has a complex nature. A limited number of experimental studies provided valuable insights into the boiling phenomena, however these studies provided often contradictory data due to internal recalculation (state of chaos in the fluid not applying to classical thermodynamic methods of calculation, therefore giving wrong return values) and have not provided conclusive findings yet to develop models and correlations. Nucleate boiling phenomenon still requires more understanding.
Boiling heat transfer correlations
The nucleate boiling regime is important to engineers because of the high heat fluxes possible with moderate temperature differences. The data can be correlated by an equation of the form
Where is the Nusselt number, defined as:
where:
is the total heat flux,
is the maximum bubble diameter as it leaves the surface,
is the excess temperature,
is the thermal conductivity of the liquid,
is the Prandtl number of the liquid,
is the bubble Reynolds number, where:
is the average mass velocity of the vapor leaving the surface
is the liquid viscosity.
Rohsenow has developed the first and most widely used correlation for nucleate boiling,
where:
is the specific heat of the liquid,
is the surface fluid combination and vary for various combinations of fluid and surface,
is the surface tension of the liquid-vapor interface.
The variable depends on the surface fluid combination and typically has a value of 1.0 or 1.7. For example, water and nickel have a of 0.006 and of 1.0.
Departure from nucleate boiling
If the heat flux of a boiling system is higher than the critical heat flux (CHF) of the system, the bulk fluid may boil, or in some cases, regions of the bulk fluid may boil where the fluid travels in small channels. Thus large bubbles form, sometimes blocking the passage of the fluid. This results in a departure from nucleate boiling (DNB) in which steam bubbles no longer break away from the solid surface of the channel, bubbles dominate the channel or surface, and the heat flux dramatically decreases. Vapor essentially insulates the bulk liquid from the hot surface.
During DNB, the surface temperature must therefore increase substantially above the bulk fluid temperature in order to maintain a high heat flux. Avoiding the CHF is an engineering problem in heat transfer applications, such as nuclear reactors, where fuel plates must not be allowed to overheat. DNB may be avoided in practice by increasing the pressure of the fluid, increasing its flow rate, or by utilizing a lower temperature bulk fluid which has a higher CHF. If the bulk fluid temperature is too low or the pressure of the fluid is too high, nucleate boiling is however not possible.
DNB is also known as transition boiling, unstable film boiling, and partial film boiling. For water boiling as shown on the graph, transition boiling occurs when the temperature difference between the surface and the boiling water is approximately above the TS. This corresponds to the high peak and the low peak on the boiling curve. The low point between transition boiling and film boiling is the Leidenfrost point.
During transition boiling of water, the bubble formation is so rapid that a vapor film or blanket begins to form at the surface. However, at any point on the surface, the conditions may oscillate between film and nucleate boiling, but the fraction of the total surface covered by the film increases with increasing temperature difference. As the thermal conductivity of the vapor is much less than that of the liquid, the convective heat transfer coefficient and the heat flux reduces with increasing temperature difference.
See also
Boiling
Cavitation
Chemical engineering
Fluid physics
Heat transfer
Leidenfrost effect
Sonoluminescence
References
Thermodynamic entropy
Nuclear technology
Cooling technology
Heat transfer
Transport phenomena | Nucleate boiling | [
"Physics",
"Chemistry",
"Engineering"
] | 1,453 | [
"Transport phenomena",
"Physical phenomena",
"Heat transfer",
"Physical quantities",
"Chemical engineering",
"Thermodynamic entropy",
"Nuclear technology",
"Entropy",
"Thermodynamics",
"Nuclear physics",
"Statistical mechanics"
] |
11,763,579 | https://en.wikipedia.org/wiki/Microvesicle | Microvesicles (ectosomes, or microparticles) are a type of extracellular vesicle (EV) that are released from the cell membrane. In multicellular organisms, microvesicles and other EVs are found both in tissues (in the interstitial space between cells) and in many types of body fluids. Delimited by a phospholipid bilayer, microvesicles can be as small as the smallest EVs (30 nm in diameter) or as large as 1000 nm. They are considered to be larger, on average, than intracellularly-generated EVs known as exosomes. Microvesicles play a role in intercellular communication and can transport molecules such as mRNA, miRNA, and proteins between cells.
Though initially dismissed as cellular debris, microvesicles may reflect the antigenic content of the cell of origin and have a role in cell signaling. Like other EVs, they have been implicated in numerous physiologic processes, including anti-tumor effects, tumor immune suppression, metastasis, tumor-stroma interactions, angiogenesis, and tissue regeneration. Microvesicles may also remove misfolded proteins, cytotoxic agents and metabolic waste from the cell. Changes in microvesicle levels may indicate diseases including cancer.
Formation and contents
Different cells can release microvesicles from the plasma membrane. Sources of microvesicles include megakaryocytes, blood platelets, monocytes, neutrophils, tumor cells and placenta.
Platelets play an important role in maintaining hemostasis: they promote thrombus growth, and thus they prevent loss of blood. Moreover, they enhance immune response, since they express the molecule CD154 (CD40L). Platelets are activated by inflammation, infection, or injury, and after their activation microvesicles containing CD154 are released from platelets. CD154 is a crucial molecule in the development of T cell-dependent humoral immune response. CD154 knockout mice are incapable of producing IgG, IgE, or IgA as a response to antigens. Microvesicles can also transfer prions and molecules CD41 and CXCR4.
Endothelial microparticles
Endothelial microparticles are small vesicles that are released from endothelial cells and can be found circulating in the blood.
The microparticle consists of a plasma membrane surrounding a small amount of cytosol. The membrane of the endothelial microparticle contains receptors and other cell surface molecules which enable the identification of the endothelial origin of the microparticle, and allow it to be distinguished from microparticles from other cells, such as platelets.
Although circulating endothelial microparticles can be found in the blood of normal individuals, increased numbers of circulating endothelial microparticles have been identified in individuals with certain diseases, including hypertension and cardiovascular disorders,
and pre-eclampsia and various forms of vasculitis. The endothelial microparticles in some of these disease states have been shown to have arrays of cell surface molecules reflecting a state of endothelial dysfunction. Therefore, endothelial microparticles may be useful as an indicator or index of the functional state of the endothelium in disease, and may potentially play key roles in the pathogenesis of certain diseases, including rheumatoid arthritis.
Endothelial microparticles have been found to prevent apoptosis in recipient cells by inhibiting the p38 pathway via inactivating mitogen-activated protein kinase (MKP)-1. Uptake of endothelial micoparticles is Annexin I/Phosphatidylserine receptor dependant.
Microparticles are derived from many other cell types.
Process of formation
Microvesicles and exosomes are formed and released by two slightly different mechanisms. These processes result in the release of intercellular signaling vesicles. Microvesicles are small, plasma membrane-derived particles that are released into the extracellular environment by the outward budding and fission of the plasma membrane. This budding process involves multiple signaling pathways including the elevation of intracellular calcium and reorganization of the cell's structural scaffolding. The formation and release of microvesicles involve contractile machinery that draws opposing membranes together before pinching off the membrane connection and launching the vesicle into the extracellular space.
Microvesicle budding takes place at unique locations on the cell membrane that are enriched with specific lipids and proteins reflecting their cellular origin. At these locations, proteins, lipids, and nucleic acids are selectively incorporated into microvesicles and released into the surrounding environment.
Exosomes are membrane-covered vesicles, formed intracellularly are considered to be smaller than 100 nm. In contrast to microvesicles, which are formed through a process of membrane budding, or exocytosis, exosomes are initially formed by endocytosis. Exosomes are formed by invagination within a cell to create an intracellular vesicle called an endosome, or an endocytic vesicle. In general, exosomes are formed by segregating the cargo (e.g., lipids, proteins, and nucleic acids) within the endosome. Once formed, the endosome combines with a structure known as a multivesicular body (MVB). The MVB containing segregated endosomes ultimately fuses with the plasma membrane, resulting in exocytosis of the exosomes.
Once formed, both microvesicles and exosomes (collectively called extracellular vesicles) circulate in the extracellular space near the site of release, where they can be taken up by other cells or gradually deteriorate. In addition, some vesicles migrate significant distances by diffusion, ultimately appearing in biological fluids such as cerebrospinal fluid, blood, and urine.
Mechanism of shedding
There are three mechanisms which lead to release of vesicles into the extracellular space. First of these mechanisms is exocytosis from multivesicular bodies and the formation of exosomes. Another mechanism is budding of microvesicles directly from a plasma membrane. And the last one is cell death leading to apoptotic blebbing. These are all energy-requiring processes.
Under physiologic conditions, the plasma membrane of cells has an asymmetric distribution of phospholipids. aminophospholipids, phosphatidylserine, and phosphatidylethanolamine are specifically sequestered in the inner leaflet of the membrane. The transbilayer lipid distribution is under the control of three phospholipidic pumps: an inward-directed pump, or flippase; an outward-directed pump, or floppase; and a lipid scramblase, responsible for non-specific redistribution of lipids across the membrane.
After cell stimulation, including apoptosis, a subsequent cytosolic Ca2+ increase promotes the loss of phospholipid asymmetry of the plasma membrane, subsequent phosphatidylserine exposure, and a transient phospholipidic imbalance between the external leaflet at the expense of the inner leaflet, leading to budding of the plasma membrane and microvesicle release.
Molecular contents
The lipid and protein content of microvesicles has been analyzed using various biochemical techniques. Microvesicles display a spectrum of enclosed molecules enclosed within the vesicles and their plasma membranes. Both the membrane molecular pattern and the internal contents of the vesicle depend on the cellular origin and the molecular processes triggering their formation. Because microvesicles are not intact cells, they do not contain mitochondria, Golgi, endoplasmic reticulum, or a nucleus with its associated DNA.
Microvesicle membranes consist mainly of membrane lipids and membrane proteins. Regardless of their cell type of origin, nearly all microvesicles contain proteins involved in membrane transport and fusion. They are surrounded by a phospholipid bilayer composed of several different lipid molecules. The protein content of each microvesicle reflects the origin of the cell from which it was released. For example, those released from antigen-presenting cells (APCs), such as B cells and dendritic cells, are enriched in proteins necessary for adaptive immunity, while microvesicles released from tumors contain proapoptotic molecules and oncogenic receptors (e.g. EGFR).
In addition to the proteins specific to the cell type of origin, some proteins are common to most microvesicles. For example, nearly all contain the cytoplasmic proteins tubulin, actin and actin-binding proteins, as well as many proteins involved in signal transduction, cell structure and motility, and transcription. Most microvesicles contain the so-called "heat-shock proteins" hsp70 and hsp90, which can facilitate interactions with cells of the immune system. Finally, tetraspanin proteins, including CD9, CD37, CD63 and CD81 are one of the most abundant protein families found in microvesicle membranes. Many of these proteins may be involved in the sorting and selection of specific cargos to be loaded into the lumen of the microvesicle or its membrane.
Other than lipids and proteins, microvesicles are enriched with nucleic acids (e.g., messenger RNA (mRNA) and microRNA (miRNA)). The identification of RNA molecules in microvesicles supports the hypothesis that they are a biological vehicle for the transfer of nucleic acids and subsequently modulate the target cell's protein synthesis. Messenger RNA transported from one cell to another through microvesicles can be translated into proteins, conferring new function to the target cell. The discovery that microvesicles may shuttle specific mRNA and miRNA suggests that this may be a new mechanism of genetic exchange between cells. Exosomes produced by cells exposed to oxidative stress can mediate protective signals, reducing oxidative stress in recipient cells, a process which is proposed to depend on exosomal RNA transfer. These RNAs are specifically targeted to microvesicles, in some cases containing detectable levels of RNA that is not found in significant amounts in the donor cell.
Because the specific proteins, mRNAs, and miRNAs in microvesicles are highly variable, it is likely that these molecules are specifically packaged into vesicles using an active sorting mechanism. At this point, it is unclear exactly which mechanisms are involved in packaging soluble proteins and nucleic acids into microvesicles.
Role on target cells
Once released from their cell of origin, microvesicles interact specifically with cells they recognize by binding to cell-type specific, membrane-bound receptors. Because microvesicles contain a variety of surface molecules, they provide a mechanism for engaging different cell receptors and exchanging material between cells. This interaction ultimately leads to fusion with the target cell and release of the vesicles' components, thereby transferring bioactive molecules, lipids, genetic material, and proteins. The transfer of microvesicle components includes specific mRNAs and proteins, contributing to the proteomic properties of target cells. microvesicles can also transfer miRNAs that are known to regulate gene expression by altering mRNA turnover.
Mechanisms of signaling
Degradation
In some cases, the degradation of microvesicles is necessary for the release of signaling molecules. During microvesicle production, the cell can concentrate and sort the signaling molecules which are released into the extracellular space upon microvesicle degradation. Dendritic cells, macrophage and microglia derived microvesicles contain proinflammatory cytokines and neurons and endothelial cells release growth factors using this mechanism of release.
Fusion
Proteins on the surface of the microvesicle will interact with specific molecules, such as integrin, on the surface of its target cell. Upon binding, the microvesicle can fuse with the plasma membrane. This results in the delivery of nucleotides and soluble proteins into the cytosol of the target cell as well as the integration of lipids and membrane proteins into its plasma membrane.
Internalization
Microvesicles can be endocytosed upon binding to their targets, allowing for additional steps of regulation by the target cell. The microvesicle may fuse, integrating lipids and membrane proteins into the endosome while releasing its contents into the cytoplasm. Alternatively, the endosome may mature into a lysosome causing the degradation of the microvesicle and its contents, in which case the signal is ignored.
Transcytosis
After internalization of microvesicle via endocytosis, the endosome may move across the cell and fuse with the plasma membrane, a process called transcytosis. This results in the ejection of the microvesicle back into the extracellular space or may result in the transportation of the microvesicle into a neighboring cell. This mechanism might explain the ability of microvesicle to cross biological barriers, such as the blood brain barrier, by moving from cell to cell.
Contact dependent signaling
In this form of signaling, the microvesicle does not fuse with the plasma membrane or engulfed by the target cell. Similar to the other mechanisms of signaling, the microvesicle has molecules on its surface that will interact specifically with its target cell. There are additional surface molecules, however, that can interact with receptor molecules which will interact with various signaling pathways. This mechanism of action can be used in processes such as antigen presentation, where MHC molecules on the surface of microvesicle can stimulate an immune response. Alternatively, there may be molecules on microvesicle surfaces that can recruit other proteins to form extracellular protein complexes that may be involved in signaling to the target cell.
Relevance in disease
Cancer
Promoting aggressive tumor phenotypes
The oncogenic receptor ECGFvIII, which is located in a specific type of aggressive glioma tumor, can be transferred to a non-aggressive population of tumor cells via microvesicles. After the oncogenic protein is transferred, the recipient cells become transformed and show characteristic changes in the expression levels of target genes. It is possible that transfer of other mutant oncogenes, such as HER2, may be a general mechanism by which malignant cells cause cancer growth at distant sites. Microvesicles from non-cancer cells can signal to cancer cells to become more aggressive. Upon exposure to microvesicles from tumor-associated macrophages, breast cancer cells become more invasive in vitro.
Promoting angiogenesis
Angiogenesis, which is essential for tumor survival and growth, occurs when endothelial cells proliferate to create a matrix of blood vessels that infiltrate the tumor, supplying the nutrients and oxygen necessary for tumor growth. A number of reports have demonstrated that tumor-associated microvesicles release proangiogenic factors that promote endothelial cell proliferation, angiogenesis, and tumor growth. Microvesicles shed by tumor cells and taken up by endothelial cells also facilitate angiogenic effects by transferring specific mRNAs and miRNAs.
Involvement in multidrug resistance
When anticancer drugs such as doxorubicin accumulate in microvesicles, the drug's cellular levels decrease. This can ultimately contribute to the process of drug resistance. Similar processes have been demonstrated in microvesicles released from cisplatin-insensitive cancer cells. Vesicles from these tumors contained nearly three times more cisplatin than those released from cisplatin-sensitive cells. For example, tumor cells can accumulate drugs into microvesicles. Subsequently, the drug-containing microvesicles are released from the cell into the extracellular environment, thereby mediating resistance to chemotherapeutic agents and resulting in significantly increased tumor growth, survival, and metastasis.
Interference with antitumor immunity
Microvesicles from various tumor types can express specific cell-surface molecules (e.g. FasL or CD95) that induce T-cell apoptosis and reduce the effectiveness of other immune cells. microvesicles released from lymphoblastoma cells express the immune-suppressing protein latent membrane protein-1 (LMP1), which inhibits T-cell proliferation and prevents the removal of circulating tumor cells (CTCs). As a consequence, tumor cells can turn off T-cell responses or eliminate the antitumor immune cells altogether by releasing microvesicles.
the combined use of microvesicles and 5-FU resulted in enhanced chemosensitivity of squamous cell carcinoma cells more than the use of either 5-FU or microvesicle alone
Impact on tumor metastasis
Degradation of the extracellular matrix is a critical step in promoting tumor growth and metastasis. Tumor-derived microvesicles often carry protein-degrading enzymes, including matrix metalloproteinase 2 (MMP-2), MMP-9, and urokinase-type plasminogen activator (uPA). By releasing these proteases, tumor cells can degrade the extracellular matrix and invade surrounding tissues. Likewise, inhibiting MMP-2, MMP-9, and uPA prevents microvesicles from facilitating tumor metastasis. Matrix digestion can also facilitate angiogenesis, which is important for tumor growth and is induced by the horizontal transfer of RNAs from microvesicles.
Cellular Origin of Microvesicles
The release of microvesicles has been shown from endothelial cells, vascular smooth muscle cells, platelets, white blood cells (e.g. leukocytes and lymphocytes), and red blood cells. Although some of these microvesicle populations occur in the blood of healthy individuals and patients, there are obvious changes in number, cellular origin, and composition in various disease states. It has become clear that microvesicles play important roles in regulating the cellular processes that lead to disease pathogenesis. Moreover, because microvesicles are released following apoptosis or cell activation, they have the potential to induce or amplify disease processes. Some of the inflammatory and pathological conditions that microvesicles are involved in include cardiovascular disease, hypertension, neurodegenerative disorders, diabetes, and rheumatic diseases.
Cardiovascular disease
Microvesicles are involved in cardiovascular disease initiation and progression. Microparticles derived from monocytes aggravate atherosclerosis by modulating inflammatory cells. Additionally, microvesicles can induce clotting by binding to clotting factors or by inducing the expression of clotting factors in other cells. Circulating microvesicles isolated from cardiac surgery patients were found to be thrombogenic in both in vitro assays and in rats. Microvesicles isolated from healthy individuals did not have the same effects and may actually have a role in reducing clotting. Tissue factor, an initiator of coagulation, is found in high levels within microvesicles, indicating their role in clotting. Renal mesangial cells exposed to high glucose media release microvesicles containing tissue factor, having an angiogenic effect on endothelial cells.
Inflammation
Microvesicles contain cytokines that can induce inflammation via numerous different pathways. These cells will then release more microvesicles, which have an additive effect. This can call neutrophils and leukocytes to the area, resulting in the aggregation of cells. However, microvesicles also seem to be involved in a normal physiological response to disease, as there are increased levels of microvesicles that result from pathology.
Neurological disorders
Microvesicles seem to be involved in a number of neurological diseases. Since they are involved in numerous vascular diseases and inflammation, strokes and multiple sclerosis seem to be other diseases for which microvesicles are involved. Circulating microvesicles seem to have an increased level of phosphorylated tau proteins during early stage Alzheimer's disease. Similarly, increased levels of CD133 are an indicator of epilepsy.
Clinical applications
Detection of cancer
Tumor-associated microvesicles are abundant in the blood, urine, and other body fluids of patients with cancer, and are likely involved in tumor progression. They offer a unique opportunity to noninvasively access the wealth of biological information related to their cells of origin. The quantity and molecular composition of microvesicles released from malignant cells varies considerably compared with those released from normal cells. Thus, the concentration of plasma microvesicles with molecular markers indicative of the disease state may be used as an informative blood-based biosignature for cancer. Microvesicles express many membrane-bound proteins, some of which can be used as tumor biomarkers. Several tumor markers accessible as proteins in blood or urine have been used to screen and diagnose various types of cancer. In general, tumor markers are produced either by the tumor itself or by the body in response to the presence of cancer or some inflammatory conditions. If a tumor marker level is higher than normal, the patient is examined more closely to look for cancer or other conditions. For example, CA19-9, CA-125, and CEA have been used to help diagnose pancreatic, ovarian, and gastrointestinal malignancies, respectively. However, although they have proven clinical utility, none of these tumor markers are highly sensitive or specific. Clinical research data suggest that tumor-specific markers exposed on microvesicles are useful as a clinical tool to diagnose and monitor disease. Research is also ongoing to determine if tumor-specific markers exposed on microvesicles are predictive for therapeutic response.
Evidence produced by independent research groups has demonstrated that microvesicles from the cells of healthy tissues, or selected miRNAs from these microvesicles, can be employed to reverse many tumors in pre-clinical cancer models, and may be used in combination with chemotherapy.
Conversely, microvesicles processed from a tumor cell are involved in the transport of cancer proteins and in delivering microRNA to the surrounding healthy tissue. It leads to a change of healthy cell phenotype and creates a tumor-friendly environment. Microvesicles play an important role in tumor angiogenesis and in the degradation of matrix due to the presence of metalloproteases, which facilitate metastasis. They are also involved in intensification of the function of regulatory T-lymphocytes and in the induction of apoptosis of cytotoxic T-lymphocytes, because microvesicles released from a tumor cell contain Fas ligand and TRAIL. They prevent differentiation of monocytes to dendritic cells.
Tumor microvesicles also carry tumor antigen, so they can be an instrument for developing tumor vaccines. Circulating miRNA and segments of DNA in all body fluids can be potential markers for tumor diagnostics.
Microvesicles and Rheumatoid arthritis
Rheumatoid arthritis is a chronic systemic autoimmune disease characterized by inflammation of joints. In the early stage there are abundant Th17 cells producing proinflammatory cytokines IL-17A, IL-17F, TNF, IL-21, and IL-22 in the synovial fluid. regulatory T-lymphocytes have a limited capability to control these cells. In the late stage, the extent of inflammation correlates with numbers of activated macrophages that contribute to joint inflammation and bone and cartilage destruction, because they have the ability to transform themselves into osteoclasts that destroy bone tissue. Synthesis of reactive oxygen species, proteases, and prostaglandins by neutrophils is increased. Activation of platelets via collagen receptor GPVI stimulates the release of microvesicles from platelet cytoplasmic membranes. These microparticles are detectable at a high level in synovial fluid, and they promote joint inflammation by transporting proinflammatory cytokine IL-1.
Biological markers for disease
In addition to detecting cancer, it is possible to use microvesicles as biological markers to give prognoses for various diseases. Many types of neurological diseases are associated with increased level of specific types of circulating microvesicles. For example, elevated levels of phosphorylated tau proteins can be used to diagnose patients in early stages of Alzheimer's. Additionally, it is possible to detect increased levels of CD133 in microvesicles of patients with epilepsy.
Mechanism for drug delivery
Circulating microvesicles may be useful for the delivery of drugs to very specific targets. Using electroporation or centrifugation to insert drugs into microvesicles targeting specific cells, it is possible to target the drug very efficiently. This targeting can help by reducing necessary doses as well as prevent off-target side effects. They can target anti-inflammatory drugs to specific tissues. Additionally, circulating microvesicles can bypass the blood–brain barrier and deliver their cargo to neurons while not having an effect on muscle cells. The blood-brain barrier is typically a difficult obstacle to overcome when designing drugs, and microvesicles may be a means of overcoming it. Current research is looking into efficiently creating microvesicles synthetically, or isolating them from patient or engineered cell lines.
Microvesicles used in therapeutic genome editing appoaches are sometimes called a “gesicle”, especially if used to package/deliver the Cas9 RNP complex.
See also
International Society for Extracellular Vesicles
Journal of Extracellular Vesicles
Exocytosis
Membrane vesicle trafficking
References
Further reading
External links
Vesiclepedia—A database of molecules identified in extracellular vesicles
ExoCarta—A database of molecules identified in exosomes
International Society for Extracellular Vesicles
Resource on the detection of circulating microvesicles
Cell biology
Vesicles
Medical diagnosis
Nanotechnology | Microvesicle | [
"Materials_science",
"Engineering",
"Biology"
] | 5,340 | [
"Nanotechnology",
"Cell biology",
"Materials science"
] |
11,764,175 | https://en.wikipedia.org/wiki/Journal%20of%20Applied%20Toxicology | The Journal of Applied Toxicology is a monthly peer-reviewed scientific journal published since 1981 by John Wiley & Sons. It covers all aspects of toxicology and publishes reviews and research articles on mechanistic, fundamental, and applied research relating to the toxicity of drugs and chemicals at the molecular, cellular, tissue, target organ, and whole body level, both in vivo (by all routes of exposure) and in vitro/ex vivo.
The current editor-in-chief is Philip W. Harvey (Covance Laboratories).
Most cited papers
The journal's three most-cited papers (>130 citations) are:
'Review of oximes available for treatment of nerve agent poisoning', Volume 14, Issue 5, Sep-Oct 1994, Pages: 317–331, Dawson RM
'Chronic effects on the respiratory-tract of hamsters, mice and rats after long-term inhalation of high-concentrations of filtered and unfiltered diesel-engine emissions', Volume 6, Issue 6, Dec 1986, Pages: 383–395, Heinrich U, Muhle H and Takenaka S, et al.
'Development of a reconstituted water medium and preliminary validation of the Frog Embryo Teratogenesis Assay Xenopus (FETAX)', Volume 7, Issue 4, Aug 1987, Pages: 237–244, Dawson DA and Bantle JA
Abstracting and indexing
The Journal of Applied Toxicology is abstracted and indexed in Chemical Abstracts Service, Scopus, and the Science Citation Index Expanded. The 2020 impact factor is 3.446. It is ranked 27th out of 87 journals in the category "Toxicology".
References
External links
Toxicology journals
Wiley (publisher) academic journals
Academic journals established in 1981
English-language journals
Monthly journals | Journal of Applied Toxicology | [
"Environmental_science"
] | 362 | [
"Toxicology journals",
"Toxicology"
] |
11,764,275 | https://en.wikipedia.org/wiki/Orgalim | Orgalim (derived originally from the French Organisme de Liaison des Industries Métalliques Européennes) represents Europe’s technology industries, consisting of 770,000 companies.
Orgalim is registered under the European Union Transparency Register operated jointly by the European Commission and the European Parliament – ID number: 20210641335-88.
History
Orgalim was formally created in late 1954, therefore pre-dating the official European Union project. Founding associations came from Austria, Belgium, France, West Germany, Italy, the Netherlands, Switzerland, the UK, Sweden, Finland, Denmark and Norway. Meetings and informal collaboration between industries had begun in 1948, and although initially created as an informal club without any financial demands, the organisation became increasingly structured and eventually developed a secretariat in the early 1950s. Various other engineering groups had been created at the same time as the European Coal and Steel Community developed, such as MEFTA and COLIME. Orgalim members decided in 1960 to incorporate the groups into Orgalim as working groups.
Overview
Orgalim is a European-level federation that engages with EU policymakers on behalf of its membership, speaking for 28 national industry associations and 20 European sector associations. Orgalim's advocacy work addresses a broad spectrum of policy and regulatory issues from digital transformation and trade to Internal Market and environment policies.
As part of its service, Orgalim publishes legal publications to provide companies with contractual solutions for business-to-business relations – with use cases ranging from product supply, product installation, repair and maintenance, to agency contracts and distributor abroad contracts.
Orgalim is a member of the Alliance for a Competitive European Industry (ACEI) and the European Forum for Manufacturing (EFM).
References
Manufacturing trade associations
Engineering organizations
European trade associations
International organisations based in Belgium
Lobbying organizations in Europe | Orgalim | [
"Engineering"
] | 368 | [
"nan"
] |
11,764,449 | https://en.wikipedia.org/wiki/Journal%20of%20Molecular%20Recognition | The Journal of Molecular Recognition is a monthly peer-reviewed scientific journal publishing original research papers, perspectives and reviews describing molecular recognition phenomena in biology. The current editor-in-chief is Rebecca C. Wade (Heidelberg Institute for Theoretical Studies and Heidelberg University). Marc H. V. van Regenmortel (École supérieure de biotechnologie Strasbourg) was the editor-in-chief from 1999 to 2023. The journal was established in 1988 with Irwin Chaiken as the founding editor and is published by John Wiley & Sons.
Abstracting and indexing
Journal of Molecular Recognition is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2020 impact factor of 2.137, ranking it 53rd out of 72 journals in the category "Biophysics" and 247th out of 297 journals in the category "Biochemistry & Molecular Biology".
Highest cited papers
According to the Web of Science, the most-cited articles of this journal are:
"'Automated docking of flexible ligands: Applications of AutoDock", Volume 9, Issue 1, Jan-Feb 1996, Pages: 1–5, Goodsell DS, Morris GM, Olson AJ.
"Improving biosensor analysis", Volume 12, Issue 5, Sep-Oct 1999, Pages: 279–284, Myszka DG.
"Reversible and irreversible immobilization of enzymes on Graphite Fibrils(TM)", Volume 9, Issue 5–6, Sep-Dec 1996, Pages: 383–388, Dong LW, Fischer AB, Lu M, et al.
"Isothermal titration calorimetry and differential scanning calorimetry as complementary tools to investigate the energetics of biomolecular recognition", Volume 12, Issue 1, Jan-Feb 1999, Pages: 3–18, Jelesarov I, Bosshard HR.
References
External links
Biochemistry journals
Wiley (publisher) academic journals
Academic journals established in 1988
English-language journals
Monthly journals | Journal of Molecular Recognition | [
"Chemistry"
] | 414 | [
"Biochemistry journals",
"Biochemistry literature"
] |
11,764,738 | https://en.wikipedia.org/wiki/Bonnet%27s%20theorem | In classical mechanics, Bonnet's theorem states that if n different force fields each produce the same geometric orbit (say, an ellipse of given dimensions) albeit with different speeds v1, v2,...,vn at a given point P, then the same orbit will be followed if the speed at point P equals
History
This theorem was first derived by Adrien-Marie Legendre in 1817, but it is named after Pierre Ossian Bonnet.
Derivation
The shape of an orbit is determined only by the centripetal forces at each point of the orbit, which are the forces acting perpendicular to the orbit. By contrast, forces along the orbit change only the speed, but not the direction, of the velocity.
Let the instantaneous radius of curvature at a point P on the orbit be denoted as R. For the kth force field that produces that orbit, the force normal to the orbit Fk must provide the centripetal force
Adding all these forces together yields the equation
Hence, the combined force-field produces the same orbit if the speed at a point P is set equal to
References
Classical mechanics | Bonnet's theorem | [
"Physics"
] | 228 | [
"Mechanics",
"Classical mechanics"
] |
11,764,750 | https://en.wikipedia.org/wiki/Point%20diffraction%20interferometer | A point diffraction interferometer (PDI) is a type of common-path interferometer. Unlike an amplitude-splitting interferometer, such as a Michelson interferometer, which separates out an unaberrated beam and interferes this with the test beam, a common-path interferometer generates its own reference beam. In PDI systems, the test and reference beams travel the same or almost the same path. This design makes the PDI extremely useful when environmental isolation is not possible or a reduction in the number of precision optics is required. The reference beam is created from a portion of the test beam by diffraction from a small pinhole in a semitransparent coating. The principle of a PDI is shown in Figure 1.
The device is similar to a spatial filter. Incident light is focused onto a semi-transparent mask (about 0.1% transmission). In the centre of the mask is a hole about the size of the Airy disc, and the beam is focused onto this hole with a Fourier-transforming lens. The zeroth order (the low frequencies in Fourier space) then passes through the hole and interferes with the rest of beam. The transmission and the hole size are selected to balance the intensities of the test and reference beams. The device is similar in operation to phase-contrast microscopy.
Development in PDI systems
PDI systems are valuable tool to measure absolute surface characteristics of an optical or reflective instruments non destructively. The common path design eliminates any need of having a reference optics, which are known to overlap the absolute surface form of a test object with its own surface form errors. This is a major disadvantage of a double path systems, such as Fizeau interferometers, as shown in Figure 2. Similarly the common path design is resistant to ambient disturbances.
The main criticisms of the original design are (1) that the required low-transmission reduces the efficiency, and (2) when the beam becomes too aberrated, the intensity on-axis is reduced, and less light is available for the reference beam, leading to a loss of fringe contrast. Lowered transmission was associated with lowered signal to noise ratio. These problems are largely overcome in the phase-shifting point diffraction interferometer designs, in which a grating or beamsplitter creates multiple, identical copies of the beam that is incident on an opaque mask. The test beam passes through a somewhat large hole or aperture in the membrane, without losses due to absorption; the reference beam is focused onto the pinhole for highest transmission. In the grating-based instance, phase-shifting is accomplished by translating the grating perpendicular to the rulings, while multiple images are recorded. The continued developments in phase shifting PDI have achieved accuracy orders of magnitude greater than standard Fizeau based systems.
Phase-shifting [see Interferometry] versions have been created to increase measurement resolution and efficiency. These include a diffraction grating interferometer by Kwon and the Phase-Shifting Point Diffraction Interferometer.
Types of phase-shifting PDI systems
Phase-shifting PDI with single pinhole
Gary Sommargren proposed a point diffraction interferometer design which directly followed from the basic design where parts of the diffracted wavefront was used for testing and the remaining part for detection as shown in Figure 3. This design was a major upgrade to existing systems. The scheme could accurately measure the optical surface with variations of 1 nm. The phase shifting was obtained by moving the test part with a piezo electric translation stage. An unwanted side effect of moving the test part is that the defocus also moves distorting the fringes. Another downsides of Sommargren's approach is that it produces low contrast fringes and an attempt to regulate the contrast also modifies the measured wavefront.
PDI systems using optical fibres
In this type of point diffraction interferometer the point source is a single mode fiber. The end face is narrowed down to resemble a cone and is covered with metallic film to reduce the light spill. Fibre is arranged so that they generate spherical waves for both testing and referencing. End of an optical fibre is known to generate spherical waves with an accuracy greater than . Although optical fibre based PDIs provide some advancement over the single pinhole based system, they are difficult to manufacture and align.
Two-beam phase-shifting PDI
Two-beam PDI provides a major advantage over other schemes by availing two independently steerable beams. Here, the test beam and reference beam are perpendicular to each other, where the intensity of reference can be regulated. Similarly, an arbitrary and stable phase shifts can be obtained relative to the test beam keeping the test part static. The scheme as shown in Figure 4 is easy to manufacture and provides user-friendly measuring conditions similar to Fizeau type interferometers. At the same time renders following additional benefits:
Absolute surface form of the test part.
High numerical aperture (NA = 0.55).
Clear fringe patterns of high contrast.
High accuracy of surface form testing (wavefront RMS error 0.125 nm).
Simple RMS repeatability 0.05 nm.
Can measure depolarising test parts.
The device is self-referencing, therefore it can be used in environments with a lot of vibrations or when no reference beam is available, such as in many adaptive optics and short-wavelength scenarios.
Applications of PDI
Interferometry has been used for various quantitative characterisation of optical systems indicating their overall performance. Traditionally, Fizeau interferometers have been used to detect optical or polished surface forms but new advances in precision manufacturing has allowed industrial point diffraction interferometry possible. PDI is especially suited for high resolution, high accuracy measurements in laboratory conditions to noisy factory floors. Lack of reference optics makes the method suitable to visualise absolute surface form of optical systems. Therefore, a PDI is uniquely suitable to verify the reference optics of other interferometers. It is also immensely useful in analysing optical assemblies used in Laser based systems. Characterising optics for UV lithography. Quality control of precision optics. Verifying the actual resolution of an optical assembly. Measuring the wavefront map produced by X-ray optics. PS-PDI can also be used to verify rated resolution of space optics before deployment.
See also
Interferometry
References
External links
Making sure the space camera is up for the job before deployment: A case study by the Interferometer manufacturer Difrotec OÜ.
Interferometers | Point diffraction interferometer | [
"Technology",
"Engineering"
] | 1,346 | [
"Interferometers",
"Measuring instruments"
] |
11,764,998 | https://en.wikipedia.org/wiki/Journal%20of%20Physical%20Organic%20Chemistry | The Journal of Physical Organic Chemistry is a monthly peer-reviewed scientific journal, published since 1988 by John Wiley & Sons. It covers research in physical organic chemistry in its broadest sense and is available both online and in print. The current editor-in-chief is Rik Tykwinski (University of Alberta).
Highest cited papers
According to Web of Science the three most cited papers in the journal are:
Chiappe C, Pieraccini D. Ionic liquids: solvent properties and organic reactivity, 18(4): 275–297, 2005
Carmichael AJ, Seddon KR. Polarity study of some 1-alkyl-3-methylimidazolium ambient-temperature ionic liquids with the solvatochromic dye, Nile Red, 13(10): 591–595, 2000
Matyjaszewski K, Ziegler MJ, Arehart SV, et al. Gradient copolymers by atom transfer radical copolymerization, 13(12): 775–786, 2000
Abstracting and indexing
The journal is indexed in Chemical Abstracts Service, Scopus, and Web of Science. According to the Journal Citation Reports, the journal has a 2021 impact factor of 2.155.
References
External links
Physical chemistry journals
Wiley (publisher) academic journals
English-language journals
Academic journals established in 1988
Monthly journals | Journal of Physical Organic Chemistry | [
"Chemistry"
] | 281 | [
"Physical chemistry journals",
"Physical chemistry stubs"
] |
11,765,713 | https://en.wikipedia.org/wiki/Joseph%20G.%20Davis | Joseph G. Davis (born 1953) is an Indian-born, Australian Information systems researcher, and Professor of Information Systems and Services, and Director of the Knowledge Discovery and Management Research Group (KDMRG) at the University of Sydney in Sydney, Australia. He is known for his work on decision support systems, ontologies, semantic technologies, and technological and organizational approaches to discovering and sharing knowledge in organizations.
Biography
Davis completed the first stage of education from St. Joseph's boys higher secondary school, Kozhikode. He completed his PhD at the University of Pittsburgh in 1986 under the supervision of William R. King. Prior to this, he earned his Masters at the Indian Institute of Management, Ahmedabad (IIMA), India, and Bachelor of Science (BSc) in Mathematics and Statistics at St. Joseph’s College, Devagiri, Calicut University as a National Science Talent Scholar.
He worked for four years in industry middle management roles in India before starting his PhD research. He has previously served in the Information Systems departments at Indiana University Bloomington, Indiana, United States, the University of Auckland, Auckland, New Zealand, and University of Wollongong, Wollongong, Australia.
Davis has held Visiting Professorships or Visiting Researcher positions at the University of Pittsburgh and Carnegie Mellon University in Pittsburgh, Syracuse University, Syracuse, Moscow State University, Moscow, and IBM Research Laboratories in Bangalore, India, and Newcastle University, Newcastle upon Tyne, UK.
At the School of Information Technologies, the University of Sydney, Davis was instrumental in launching the Knowledge Discovery and Management Research Group and starting the Master of Information Technology Management (MITM) course and revising the Information Systems major at the undergraduate level. He has served as the Associate Dean (International) in the Faculty of Engineering and Information Technologies at the University of Sydney from 2010 to 2013 and as Associate Head of School (of Information Technologies) from 2002 to 2007. He is also the theme leader for Service Computing at the Centre for Distributed and High Performance Computing at the University of Sydney.
Research
Davis’s research interests and contributions span knowledge management including ontologies, Knowledge Graphs, service computing, and crowdsourcing/human computation. His research has been funded by the Australian Research Council, Carnegie Bosch Institute, and the Cooperative Research Centre (CRC) for Smart Services, among others. He was a National Science Talent Scholar in Mathematics in India and was awarded the IBM Faculty Research Award in 2008.
Davis has published two books and over one hundred refereed research papers in these and related areas.
The research performed by his lab, KDMRG, spans knowledge discovery and management, ontologies, data mining, service computing and service systems, crowdsourcing and human computation, and Linked Open Data.
Publications
Books
Knowledge Management: Organizational and Technological Dimensions, Heidelberg: Springer Verlag, 2005 (edited book, with E. Subrahmanian and A. Westerberg)
Implementing Decision Support Systems: Methods, Techniques, and Tools, London: McGraw Hill, 2000 (with A. Srinivasan and D. Sundaram)
Selected Research Papers
Meymandpour, R., Davis, J. (2019). Measuring the diversity of recommendations: a preference-aware approach for evaluating and adjusting diversity. Knowledge and Information Systems, 2019, https://doi.org/10.1007/s10115-019-01371-0
Moghaddam, M., Davis, J. (2019). Simultaneous service selection for multiple composite service requests: A combinatorial auction approach. Decision Support Systems, 120(May 2019), 81-94. [More Information]
Renard, D., Davis, J. (2019). Social interdependence on crowdsourcing platforms [Forthcoming]. International Journal of Business Research, 103, 186-194
Meymandpour, R. and J. Davis, A Semantic Similarity Measure for Linked Data: An Information Content-Based Approach, Knowledge-Based Systems, October 2016.
JG. Davis, From Crowdsourcing to Crowdservicing, IEEE Internet Computing 15 (3), 92-94
JG Davis, E Subrahmanian, AW Westerberg, The “global” and the “local” in knowledge management, Journal of Knowledge Management, 2005.
H Lin, JG Davis, Computational and Crowdsourcing methods for Extracting Ontological Structures from Folksonomy, The Semantic Web: Research and Applications, 2010.
G Pandey, S Chawla, S Poon, B Arunasalam, JG Davis, Association Rule Networks: Definition and Applications, Statistical Analysis and Data Mining 1 (4), 260-279, 2009.
J. Davis and S. Ganeshan, Aversion to Loss and Information Overload, Research paper, Proceedings of the International Conference on Information Systems (ICIS2009), Phoenix AZ, December 15–18, 2009.
K de Souza, J Davis, S de Medeiros Evangelista, Aligning Ontologies, Evaluating Concept Similarities and Visualizing Results, Journal on Data Semantics V, 211-236, 2006
JG Davis, E Subrahmanian, S Konda, H Granger, M Collins, AW Westerberg, Creating Shared Information Spaces to support Collaborative Design Work, Information Systems Frontiers 3 (3), 377-392, 2001.
D. Batra, J.G. Davis. "Conceptual data modelling in database design: similarities and differences between expert and novice designers." International Journal of Man-Machine Studies 37 (1), 83-101 (1992)
Y. Zhou, J. Davis. "Open source software reliability model: an empirical approach." ACM SIGSOFT Software Engineering Notes 30 (4), 1-6 (2005)
B. Choi, S.K. Poon, J.G. Davis. "Effects of knowledge management strategy on organizational performance: a complementarity theory-based approach." Omega 36 (2), 235-251 (2008)
References
1943 births
Living people
Australian computer scientists
Information systems researchers | Joseph G. Davis | [
"Technology"
] | 1,243 | [
"Information systems",
"Information systems researchers"
] |
11,766,287 | https://en.wikipedia.org/wiki/Rhodolith | Rhodoliths (from Greek for red rocks) are colorful, unattached calcareous nodules, composed of crustose, benthic marine red algae that resemble coral. Rhodolith beds create biogenic habitat for diverse benthic communities. The rhodolithic growth habit has been attained by a number of unrelated coralline red algae, organisms that deposit calcium carbonate within their cell walls to form hard structures or nodules that resemble beds of coral.
Rhodoliths do not attach themselves to the rocky seabed. Rather, they roll like tumbleweeds along the seafloor until they become too large in size to be mobilised by the prevailing wave and current regime. They may then become incorporated into a semi-continuous algal mat or form an algal build-up. While corals are animals that are both autotrophic (photosynthesize via their symbionts) or heterotrophic (feeding on plankton), rhodoliths produce energy solely through photosynthesis (i.e. they can only grow and survive in the photic zone of the ocean).
Scientists believe rhodoliths have been present in the world's oceans since at least the Eocene epoch, some 55 million years ago.
Overview
Rhodoliths (including maërl) have been defined as calcareous nodules composed of more than 50% of coralline red algal material and consisting of one to several coralline species growing together.
Habitat
Rhodolith beds have been found throughout the world's oceans, including in the Arctic near Greenland, in waters off British Columbia, Canada, the Gulf of California, Mexico, the Mediterranean as off New Zealand and eastern Australia. Globally, rhodoliths fill an important niche in the marine ecosystem, serving as a transition habitat between rocky areas and barren, sandy areas. Rhodoliths provide a stable and three-dimensional habitat onto and into which a wide variety of species can attach, including other algae, commercial species such as clams and scallops, and true corals. Rhodoliths are resilient to a variety of environmental disturbances, but can be severely impacted by harvesting of commercial species. For these reasons, rhodolith beds deserve specific actions for monitoring and conservation. Rhodoliths come in many shapes, including laminar, branching and columnar growth forms. In shallow water and high-energy environments, rhodoliths are typically mounded, thick or unbranched; branching is also rarer in deeper water, and most profuse in tropical, mid-depth waters.
Geological significance
Rhodoliths are a common feature of modern and ancient carbonate shelves worldwide. Rhodolith communities contribute significantly to the global calcium carbonate budget, and fossil rhodoliths are commonly used to obtain paleoecologic and paleoclimatic information. Under the right circumstances, rhodoliths can be the main carbonate sediment producers, often forming rudstone or floatstone beds consisting of rhodoliths and their fragments in grainy matrix.
Climate change and the rhodolith holobiont
Rhodoliths are significant photosynthesizers, calcifiers, and ecosystem engineers, which raises an issue about how they might respond to ocean acidification.
Changes in ocean carbonate chemistry driven by increasing anthropogenic carbon dioxide emissions promotes ocean acidification. Increasing the ocean carbon dioxide uptake results in increases in pCO2 (the partial pressure of carbon dioxide in the ocean) as well as lower pH levels and a lower carbonate saturation in the seawater. These affect the calcification process. Organisms like rhodoliths accrete carbonate as part of their physical structure, since precipitating CaCO3 would be less efficient. Ocean acidification presents a threat by potentially affecting their growth and reproduction. Coralline algae are particularly sensitive to ocean acidification because they precipitate high magnesium-calcite carbonate skeletons, the most soluble form of CaCO3.
Calcification rates in coralline algae are thought to be directly related to their photosynthetic rates, but it is not clear how a high-CO2 environment might affect rhodoliths. Elevated CO2 levels might impair biomineralization due to decreased seawater carbonate () availability as pH falls, but photosynthesis could be promoted as the availability of bicarbonate () increases. This would result in a parabolic relationship between declining pH and coralline algal fitness, which could explain why varied responses to declining pH and elevated pCO2 have been recorded to date.
The widespread distribution of rhodoliths hints at the resilience of this algal group, which have persisted as chief components of benthic marine communities through considerable environment changes over geologic times.
In 2018 the first metagenomic analysis of live rhodoliths was published. Whole genome shotgun sequencing was performed on a variety of rhodolith bed constituents. This revealed a stable live rhodolith microbiome thriving under elevated pCO2 conditions, with positive physiological responses such as increased photosynthetic activity and no calcium carbonate biomass loss over time. However, the seawater column and coralline skeleton biofilms showed significant microbial shifts. These findings reinforce the existence of a close host-microbe functional entity, where the metabolic crosstalk within the rhodolith as a holobiont could be exerting reciprocal influence over the associated microbiome.
While the microbiome associated with live rhodoliths remained stable and resembled a healthy holobiont, the microbial community associated with the water column changed after exposure to elevated pCO2.
See also
Maerl
References
Other references
Riosmena-Rodríguez R, Nelson W and Aguirre J (Eds.) (2016) Rhodolith/Maërl Beds: A Global Perspective Springer. .
Red algae
Fossil algae
Extant Eocene first appearances | Rhodolith | [
"Biology"
] | 1,245 | [
"Red algae",
"Fossil algae",
"Algae"
] |
11,766,301 | https://en.wikipedia.org/wiki/X-Ray%20Spectrometry%20%28journal%29 | X-Ray Spectrometry is a bimonthly peer-reviewed scientific journal established in 1972 and published by John Wiley & Sons. It covers the theory and application of X-ray spectrometry. The current editor-in-chiefs are Johan Boman (University of Gothenburg) and Liqiang Luo (National Research Center of Geoanalysis).
Abstracting and indexing
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2020 impact factor of 1.488, ranking it 30th out of 43 journals in the category "Spectroscopy".
Notable articles
The highest-cited articles from this journal are:
References
External links
Spectroscopy journals
Wiley (publisher) academic journals
Academic journals established in 1972
English-language journals
Bimonthly journals
X-ray spectroscopy | X-Ray Spectrometry (journal) | [
"Physics",
"Chemistry",
"Astronomy"
] | 164 | [
"Spectroscopy stubs",
"Spectrum (physical sciences)",
"Astronomy stubs",
"Spectroscopy journals",
"X-ray spectroscopy",
"Molecular physics stubs",
"Spectroscopy",
"Physical chemistry stubs"
] |
11,766,346 | https://en.wikipedia.org/wiki/Intelligent%20vehicular%20ad%20hoc%20network |
Intelligent vehicular ad hoc networks (InVANETs) use WiFi IEEE 802.11p (WAVE standard) and effective communication between vehicles with dynamic mobility. Effective measures such as media communication between vehicles can be enabled as well methods to track automotive vehicles. InVANET is not foreseen to replace current mobile (cellular phone) communication standards.
"Older" designs within the IEEE 802.11 scope may refer just to IEEE 802.11b/g. More recent designs refer to the latest issues of IEEE 802.11p (WAVE, draft status). Due to inherent lag times, only the latter one in the IEEE 802.11 scope is capable of coping with the typical dynamics of vehicle operation.
Automotive vehicular information can be viewed on electronic maps using the Internet or specialized software. The advantage of WiFi based navigation system function is that it can effectively locate a vehicle which is inside big campuses like universities, airports, and tunnels.
InVANET can be used as part of automotive electronics, which has to identify an optimally minimal path for navigation with minimal traffic intensity. The system can also be used as a city guide to locate and identify landmarks in a new city.
Communication capabilities in vehicles are the basis of an envisioned InVANET or intelligent transportation systems (ITS). Vehicles are enabled to communicate among themselves (vehicle-to-vehicle, V2V) and via roadside access points (vehicle-to-roadside, V2R) also called as Road Side Units (RSUs). Vehicular communication is expected to contribute to safer and more efficient roads by providing timely information to drivers, and also to make travel more convenient. The integration of V2V and V2R communication is beneficial because V2R provides better service sparse networks and long-distance communication, whereas V2V enables direct communication for small to medium distances/areas and at locations where roadside access points are not available.
Providing vehicle–vehicle and vehicle–roadside communication can considerably improve traffic safety and comfort of driving and traveling. For communication in vehicular ad hoc networks, position-based routing has emerged as a promising candidate.
For Internet access, Mobile IPv6 is a widely accepted solution to provide session continuity and reachability to the Internet for mobile nodes. While integrated solutions for usage of Mobile IPv6 in (non-vehicular) mobile ad hoc networks exist, a solution has been proposed that, built upon a Mobile IPv6 proxy-based architecture, selects the optimal communication mode (direct in-vehicle, vehicle–vehicle, and vehicle–roadside communication) and provides dynamic switching between vehicle–vehicle and vehicle–roadside communication mode during a communication session in case that more than one communication mode is simultaneously available.
See also
Mobile ad hoc network
Vehicular ad hoc network
Simulation of VANETs
Wireless mesh network
Research fora
Google Groups – InADVENC
CiteULike reading group on VANET
References
Ad hoc network books:
Intelligent ad hoc vehicular network papers (Overview):
Intelligent ad hoc vehicular network architecture:
External links
IETF MANET group
A Middleware Architectural framework for Vehicular Safety over VANET (InVANET)
NIST MANET and Sensor Network Security project
Wireless Ad Hoc Networks Bibliography
Wireless networking | Intelligent vehicular ad hoc network | [
"Technology",
"Engineering"
] | 659 | [
"Wireless networking",
"Computer networks engineering"
] |
11,766,478 | https://en.wikipedia.org/wiki/Lactarius%20scrobiculatus | Lactarius scrobiculatus, commonly known as the scrobiculate milk cap, is a basidiomycete fungus, belonging to the genus Lactarius, whose members are called "milk caps." Taxonomy places this species into subgenus Piperites, section Zonarii, subsection Scrobiculati.
The distinctive fruiting bodies of this large fungus are locally common in forests throughout Europe and North America. It is regarded as inedible by some authors, but it is nevertheless eaten in parts of Europe.
Description
Lactarius scrobiculatus produces large agaricoid fruiting bodies which arise from soil. The cap has an eye-catching orange to yellow coloration and is covered with small scales arranged in indistinctive concentric rings. The surface is wet, glossy and slimy especially in wet weather. The cap may be wide, with a large diameter (about 15 cm in mature specimens), but with a depressed centre and slightly enrolled margin. The gills are crowded and coloured cream to yellow, with darker patches being present sometimes. When cut, the gills bleed copious amounts of a white to cream milk (latex), which soon darkens to yellow. The stem, in relation to the cap, is quite short and stubby, in addition to being hollow. The surface is cap-coloured but the presence of small pits, filled with fluid, is a key identifying feature. The spores are coloured creamy with an elliptical-globular shape.
When a small piece of flesh is chewed, it tastes bitter to acrid. So acrid, that a researcher reportedly developed a numbness in the mouth, having nibbled on a piece. It doesn't have any discernible smell.
There are several recognised varieties, including var. canadensis. var. montanus and var. pubescens.
Similar species
Similar species include Lactarius alnicola, L. controversus, L. plumbeus, L. repraesentaneus, and L. torminosus.
Distribution
Lactarius scrobiculatus is known to occur throughout Europe, and to a lesser extent North America where its occurrence is rare. It occurs primarily in coniferous and birch forests.
It forms mycorrhizal relationships and appears to prefer damp, shady and boggy areas. The fruiting bodies appear in troops, sometimes forming fairy rings and only rarely occur singly. The fruiting season of L. scrobiculatus is summer to autumn.
Edibility
Most authors consider Lactarius scrobiculatus inedible. It is collected and eaten in parts of eastern Europe and Russia after salting, pickling and thorough cooking. Consuming it irritates the gastrointestinal tract, causing symptoms of gastrointestinal syndrome. Careful preparation seeks to neutralise the acrid taste. This usually involves a process of boiling, during which the water is discarded. Further cooking and pickling may not eliminate the possibility of distressing symptoms.
See also
List of Lactarius species
References
scrobiculatus
Inedible fungi
Fungi described in 1772
Fungi of Europe
Fungi of North America
Fungus species | Lactarius scrobiculatus | [
"Biology"
] | 650 | [
"Fungi",
"Fungus species"
] |
11,766,544 | https://en.wikipedia.org/wiki/Journal%20of%20Raman%20Spectroscopy | The Journal of Raman Spectroscopy is a monthly peer-reviewed scientific journal covering all aspects of Raman spectroscopy, including Higher Order Processes, and Brillouin and Rayleigh scattering. It was established in 1973 and is published by John Wiley & Sons. The editor-in-chief is Laurence A. Nafie (Syracuse University).
Abstracting and indexing
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2020 impact factor of 3.133.
Notable papers
, the most cited papers published by the journal are:
References
External links
Spectroscopy journals
Wiley (publisher) academic journals
English-language journals
Academic journals established in 1973
Monthly journals
Raman spectroscopy | Journal of Raman Spectroscopy | [
"Physics",
"Chemistry"
] | 141 | [
"Spectroscopy",
"Spectrum (physical sciences)",
"Spectroscopy journals"
] |
11,766,887 | https://en.wikipedia.org/wiki/Curvature%20of%20a%20measure | In mathematics, the curvature of a measure defined on the Euclidean plane R2 is a quantification of how much the measure's "distribution of mass" is "curved". It is related to notions of curvature in geometry. In the form presented below, the concept was introduced in 1995 by the mathematician Mark S. Melnikov; accordingly, it may be referred to as the Melnikov curvature or Menger-Melnikov curvature. Melnikov and Verdera (1995) established a powerful connection between the curvature of measures and the Cauchy kernel.
Definition
Let μ be a Borel measure on the Euclidean plane R2. Given three (distinct) points x, y and z in R2, let R(x, y, z) be the radius of the Euclidean circle that joins all three of them, or +∞ if they are collinear. The Menger curvature c(x, y, z) is defined to be
with the natural convention that c(x, y, z) = 0 if x, y and z are collinear. It is also conventional to extend this definition by setting c(x, y, z) = 0 if any of the points x, y and z coincide. The Menger-Melnikov curvature c2(μ) of μ is defined to be
More generally, for α ≥ 0, define c2α(μ) by
One may also refer to the curvature of μ at a given point x:
in which case
Examples
The trivial measure has zero curvature.
A Dirac measure δa supported at any point a has zero curvature.
If μ is any measure whose support is contained within a Euclidean line L, then μ has zero curvature. For example, one-dimensional Lebesgue measure on any line (or line segment) has zero curvature.
The Lebesgue measure defined on all of R2 has infinite curvature.
If μ is the uniform one-dimensional Hausdorff measure on a circle Cr or radius r, then μ has curvature 1/r.
Relationship to the Cauchy kernel
In this section, R2 is thought of as the complex plane C. Melnikov and Verdera (1995) showed the precise relation of the boundedness of the Cauchy kernel to the curvature of measures. They proved that if there is some constant C0 such that
for all x in C and all r > 0, then there is another constant C, depending only on C0, such that
for all ε > 0. Here cε denotes a truncated version of the Menger-Melnikov curvature in which the integral is taken only over those points x, y and z such that
Similarly, denotes a truncated Cauchy integral operator: for a measure μ on C and a point z in C, define
where the integral is taken over those points ξ in C with
References
Curvature (mathematics)
Measure theory | Curvature of a measure | [
"Physics"
] | 578 | [
"Geometric measurement",
"Physical quantities",
"Curvature (mathematics)"
] |
11,767,273 | https://en.wikipedia.org/wiki/Water%20Lily%20Nebula | The Water Lily Nebula, in the southern constellation of Ara, is a pre-planetary nebula also known as IRAS 16594-4656, in the process of developing to a planetary nebula. It was discovered by Bruce Hrivnak and Sun Kwok in 1999. The Water Lily is one of the pre-planetary nebulae containing polycyclic aromatic hydrocarbons, organic hydrocarbons otherwise constituting the basis for life.
References
ESA press release
Sun Kwok's page on the object
Simbad entry
Protoplanetary nebulae
Ara (constellation) | Water Lily Nebula | [
"Astronomy"
] | 116 | [
"Constellations",
"Ara (constellation)"
] |
11,767,744 | https://en.wikipedia.org/wiki/Luteophanol | Luteophanol is a type of organic compound. There are variants labeled luteophanol A through luteophanol D. They contain the following common fragments with amphidinols:
Polyhydroxyl groups.
Two tetrahydropyran rings.
Luteophanols have demonstrated antibacterial properties, but unlike amphidinols, they do not show antifungal activity.
References
Y. Doi et al., "Luteophanol A, a New Polyhydroxyl Compound from Symbiotic Marine Dinoflagellate Amphidinium sp.", Journal of Organic Chemistry (1997)
Abstract of article on Luteophanol D
Ethers
Alkene derivatives
Tetrahydropyrans
Polyols | Luteophanol | [
"Chemistry"
] | 163 | [
"Organic compounds",
"Functional groups",
"Ethers"
] |
11,770,045 | https://en.wikipedia.org/wiki/Proven%20reserves | Proven reserves (also called measured reserves, 1P, and reserves) is a measure of fossil fuel energy reserves, such as oil and gas reserves and coal reserves. It is defined as the "quantity of energy sources estimated with reasonable certainty, from the analysis of geologic and engineering data, to be recoverable from well established or known reservoirs with the existing equipment and under the existing operating conditions." A reserve is considered proven if it is probable that at least 90% of the resource is recoverable by economically profitable means.
Operating conditions are taken into account when determining if a reserve is classified as proven. Operating conditions include operational break-even price, regulatory and contractual approvals, without which the reserve cannot be classified as proven. Price changes therefore can have a large impact on the classification of proven reserves. Regulatory and contractual conditions may change, and also affect the amount of proven reserves. If a reserve's resources can be recovered using current technology but is not economically profitable it is considered "technically recoverable" but cannot be considered a proven reserve. Reserves less than 90% recoverable but more than 50% are considered "probable reserves" and below 50% are "possible reserves".
Numbered terms
The engineering term P90 refers to 90 percent engineering probability, is a commonly accepted specific definition by Society of Petroleum Engineers, it does not take into account anything except technical concerns. Therefore, it is different from the business term which does take into account current break-even profitability, and regulatory and contractual approval, but is considered a very rough equivalent. The definition is certainly not universal. Energy Watch Group uses a different definition, P95.
More terms
Disregarding economics, the proper engineering term for the total technologically extractable amount is the Producible fraction, which is easily confused with the business term proven reserves. However, the purely engineering term is also misleading in that squeezing the last bits of fossil fuel out follows the diminishing returns and at some point is so costly that it becomes highly impractical, as seen on a bell curve, which is why measures like P90 and P95 were created. The term proven reserves is further subdivided into proved developed reserves and proved undeveloped reserves. Note that it does not include unproven reserves, which is broken down into probable reserves and possible reserves.
These reserve categories are totaled up by the measures 1P, 2P, and 3P, which are inclusive of all reserves types:
"1P reserves" = proven reserves (both proved developed reserves + proved undeveloped reserves).
"2P reserves" = 1P (proven reserves) + probable reserves, hence "proved AND probable."
"3P reserves" = the sum of 2P (proven reserves + probable reserves) + possible reserves, all 3Ps "proven AND probable AND possible."
New proven reserves are commonly added by new field discoveries. Reserves growth also commonly occurs in previously existing fields, as the characteristics of the reservoir become better understood, as fields are extended laterally, or new oil and gas reservoirs are found in existing fields. Reserve growth may also take place due to technological and economic changes.
Russian reserve categories
In Russia, reserves categories A, B, and C correspond roughly to developed producing reserves, undeveloped reserves with approved development, and discovered resources without a firm plan to develop yet. The designation ABC corresponds to estimated recoverable reserves.
Reserve evaluations, valuations and certifications
Oil companies employ specialist, independent, reserve valuation consultants - such as Gaffney, Cline & Associates, Sproule, Miller and Lents, Ltd., DeGolyer and MacNaughton, Ryder Scott, Netherland, Sewell & Associates Inc. (NSAI), Lloyd's Register (LR ), Evolution Resources, Cawley, Gillespie & Associates Inc. (CG&A) and others - to provide third party reports as part of Securities and Exchange Commission (SEC) SEC filings and SPE Petroleum Resources Management System (PRMS) for other Stockmarket listings. On December 30, 2009, recognising advances in exploration and valuation technology, the SEC allowed 2P probable and 3P possible reserves to be reported, along with 1P proved reserves, though oil companies also have to verify the independence of third party consultants. Since investors view 1P reserves with much greater importance than 2P or 3P reserves, oil companies seek to convert 2P and 3P reserves into 1P reserves.
See also
Estimated ultimate recovery
List of countries by proven oil reserves
Oil and gas reserves
List of countries by coal reserves
References
Energy development
Energy economics
Peak oil | Proven reserves | [
"Environmental_science"
] | 929 | [
"Energy economics",
"Environmental social science"
] |
11,770,934 | https://en.wikipedia.org/wiki/Chinese%20glazed%20roof%20tile | Glazed tiles () have been used in China since the Tang dynasty as a material for roofs. During the Song dynasty, the manufacture of glazed tiles were standardized in Li Jie's Architecture Standard. In the Ming dynasty and Qing dynasty, glazed tiles became ever more popular for top-tier buildings, including palace halls in the Forbidden City, and ceremonial temples (for example the Heavenly Temple).
There are two main types of Chinese glazed tiles: glazed tubular tile and glazed plate tile. Glazed tubular tiles (see monk and nun) are moulded into tube shape on a wooden mould, then cut into halves along their length, producing two tubular tiles, each semicircular in section. A tube-shaped clay mould can be cut into four equal parts, with a cross-section of a quarter of a circle, then glazed into a four-plate tile.
Glazed plate tiles are laid side by side across and overlapping each other. In the Song dynasty, the standard overlap was forty percent, which increased to seventy percent in the Qing dynasty. With the Song-style forty-percent overlap, it was not possible to have triple tile overlap, as there was a twenty-percent gap between the first plate tile and the third plate tile. Hence, if a crack developed in the second tile, water leakage was inevitable. On the other hand, with the Qing dynasty style seventy-percent overlapping, the first plate tile was overlapped seventy percent, forty percent, and ten percent by the second, third and fourth tiles, respectively; thus even if the second and the third tiles developed cracks, there would be no leakage.
Glazed tubular tiles used at the eave edge have an outer end made into a round shape top, often moulded with the pattern of a dragon. Eave-edge plate tiles have their outer edges decorated with triangles, to facilitate rain-shedding.
References
Building materials
Architecture in China
Chinese architectural history
Roof tiles | Chinese glazed roof tile | [
"Physics",
"Engineering"
] | 394 | [
"Building engineering",
"Architecture",
"Construction",
"Materials",
"Matter",
"Building materials"
] |
11,771,113 | https://en.wikipedia.org/wiki/Gauss%27s%20continued%20fraction | In complex analysis, Gauss's continued fraction is a particular class of continued fractions derived from hypergeometric functions. It was one of the first analytic continued fractions known to mathematics, and it can be used to represent several important elementary functions, as well as some of the more complicated transcendental functions.
History
Lambert published several examples of continued fractions in this form in 1768, and both Euler and Lagrange investigated similar constructions, but it was Carl Friedrich Gauss who utilized the algebra described in the next section to deduce the general form of this continued fraction, in 1813.
Although Gauss gave the form of this continued fraction, he did not give a proof of its convergence properties. Bernhard Riemann and L.W. Thomé obtained partial results, but the final word on the region in which this continued fraction converges was not given until 1901, by Edward Burr Van Vleck.
Derivation
Let be a sequence of analytic functions that obey the three-term recurrence relation
for all , where the are constants.
Then
Setting
So
Repeating this ad infinitum produces the continued fraction expression
In Gauss's continued fraction, the functions are hypergeometric functions of the form , , and , and the equations arise as identities between functions where the parameters differ by integer amounts. These identities can be proven in several ways, for example by expanding out the series and comparing coefficients, or by taking the derivative in several ways and eliminating it from the equations generated.
The series 0F1
The simplest case involves
Starting with the identity
we may take
giving
or
This expansion converges to the meromorphic function defined by the ratio of the two convergent series (provided, of course, that a is neither zero nor a negative integer).
The series 1F1
The next case involves
for which the two identities
are used alternately.
Let
etc.
This gives where , producing
or
Similarly
or
Since , setting a to 0 and replacing b + 1 with b in the first continued fraction gives a simplified special case:
The series 2F1
The final case involves
Again, two identities are used alternately.
These are essentially the same identity with a and b interchanged.
Let
etc.
This gives where , producing
or
Since , setting a to 0 and replacing c + 1 with c gives a simplified special case of the continued fraction:
Convergence properties
In this section, the cases where one or more of the parameters is a negative integer are excluded, since in these cases either the hypergeometric series are undefined or that they are polynomials so the continued fraction terminates. Other trivial exceptions are excluded as well.
In the cases and , the series converge everywhere so the fraction on the left hand side is a meromorphic function. The continued fractions on the right hand side will converge uniformly on any closed and bounded set that contains no poles of this function.
In the case , the radius of convergence of the series is 1 and the fraction on the left hand side is a meromorphic function within this circle. The continued fractions on the right hand side will converge to the function everywhere inside this circle.
Outside the circle, the continued fraction represents the analytic continuation of the function to the complex plane with the positive real axis, from to the point at infinity removed. In most cases is a branch point and the line from to positive infinity is a branch cut for this function. The continued fraction converges to a meromorphic function on this domain, and it converges uniformly on any closed and bounded subset of this domain that does not contain any poles.
Applications
The series 0F1
We have
so
This particular expansion is known as Lambert's continued fraction and dates back to 1768.
It easily follows that
The expansion of tanh can be used to prove that en is irrational for every non-zero integer n (which is alas not enough to prove that e is transcendental). The expansion of tan was used by both Lambert and Legendre to prove that π is irrational.
The Bessel function can be written
from which it follows
These formulas are also valid for every complex z.
The series 1F1
Since ,
With some manipulation, this can be used to prove the simple continued fraction representation of
e,
The error function erf (z), given by
can also be computed in terms of Kummer's hypergeometric function:
By applying the continued fraction of Gauss, a useful expansion valid for every complex number z can be obtained:
A similar argument can be made to derive continued fraction expansions for the Fresnel integrals, for the Dawson function, and for the incomplete gamma function. A simpler version of the argument yields two useful continued fraction expansions of the exponential function.
The series 2F1
From
It is easily shown that the Taylor series expansion of arctan z in a neighborhood of zero is given by
The continued fraction of Gauss can be applied to this identity, yielding the expansion
which converges to the principal branch of the inverse tangent function on the cut complex plane, with the cut extending along the imaginary axis from i to the point at infinity, and from −i to the point at infinity.
This particular continued fraction converges fairly quickly when z = 1, giving the value π/4 to seven decimal places by the ninth convergent. The corresponding series
converges much more slowly, with more than a million terms needed to yield seven decimal places of accuracy.
Variations of this argument can be used to produce continued fraction expansions for the natural logarithm, the arcsin function, and the generalized binomial series.
Notes
References
(This is a reprint of the volume originally published by D. Van Nostrand Company, Inc., in 1948.)
Continued fractions | Gauss's continued fraction | [
"Mathematics"
] | 1,151 | [
"Continued fractions",
"Number theory"
] |
2,160,442 | https://en.wikipedia.org/wiki/Rodomontade | Rodomontade () is a mass noun meaning boastful talk or behavior. The term is a reference to Rodomonte, a character in the Italian Renaissance epic poem Orlando innamorato and its sequel Orlando furioso.
Henry Fielding in History of Tom Jones writes, “In fact, the good squire was a little too apt to indulge that kind of pleasantry which is generally called rhodomontade. . .”
Examples of use
17th century
A 17th-century example of the term exists in Don Tomazo by Thomas Dangerfield, albeit with a slight alteration of spelling. As the titular protagonist heads towards Cairo with a number of stolen treasures, he is informed by an acquaintance that:
. . . he could, in that heathenish city, command a thousand pound – which was at that time no rodomontado, in regard the jewels were worth above four times the value.
18th century
In 1784, a tract of satirical but politically charged poetry of 94 pages was published in London, titled A Rodomontade of Politics: Or, a Series of Fables, with Notes Variorum; to be Continued Occasionally. The unnamed author describes literary rodomontade as "what is called a sketch or caracature in drawing", and proceeds to surreptitiously address his rodomontades to important political figures of the day, including Lord North, Edmund Burke, Richard Brinsley Sheridan, and William Pitt the Younger, whom were identified as being the subjects of these caracatures the very same year, in The English Review.
The German composer Georg Philipp Telemann composed a Suite in b minor (in German, h moll) for violin solo, strings and continuo (TWV 55: h4), which ends with a piece named "Rodomontade".
19th century
A 19th-century example of the use of the term can be found in The Adventures of Captain Bonneville by Washington Irving. Irving used it to describe the behavior of "free trappers", fur trappers who worked freelance and adopted the manner, habits, and dress of the Native Americans. When free trappers visited Bonneville's camp, he welcomed them and ordered grog for everyone:
They [the free trappers] pronounced the captain the finest fellow in the world, and his men all bon garçons, jovial lads, and swore they would pass the day with them. They did so, and a day it was, of boast, and swagger, and rodomontade.
Edgar Allan Poe's 1838 novel “The Narrative of Arthur Gordon Pym of Nantucket” includes the following description of a shipwreck survivor who upon seeing a possible rescuing vessel “danced about the deck like a madman, uttering the most extravagant rodomontades, intermingled with howls and imprecations...”.
Another 19th-century example can be found in Thomas Carlyle's 1829 essay Signs of the Times:
We have more Mathematics than ever; but less Mathesis. Archimedes and Plato could not have read the Mécanique Céleste; but neither would the whole French Institute see aught in that saying, "God geometrises!" but a sentimental rodomontade.
20th century
In the English translation of Natsume Soseki's novel, I am a Cat (1905-1906), when referring to the feline character Rickshaw Blacky: "Blacky, like all true braggarts, is somewhat weak in the head. As long as you purr and listen attentively, pretending to be impressed by his rhodomontade, he is a more or less manageable cat.”
"For surely, had Lucinda heard aught of the story of the duel, it would have been her first thing to speak of, not all this rhodomontade of silly necromancies." - from the novel An Affair of Dishonour (1910) by William De Morgan.
Rex Stout uses it in the second Nero Wolfe novel, "The League of Frightened Men" (1935), when Wolfe says, "If Mr. Chapin had ... restrained his impulse to rodomontade ..."
The word, with its alternative spelling (rhodomontade) is quoted in John Lukacs' book Five Days in London May 1940. While describing the tempestuous days of Churchill's first weeks in office, Lukacs quotes Alexander Cadogan, a bureaucrat with the Foreign Office, counselling Foreign Secretary Lord Halifax who was complaining that he could no longer work with Churchill. Cadogan said: Nonsense: his rhodomontades probably bore you as much as they do me, but don't do anything silly under the stress of that.
Julian Hawthorne employs the word twice in his posthumously published Memoirs, first to lambaste Amos Bronson Alcott, maintaining that he "couldn't write", and, "turned out a pretentious rodomontade of platitudes", and also to describe his 1864 initiation into the Harvard secret society The Dickey Club.
Hannah Arendt describes Adolf Eichmann's boasting as "sheer rodomontade" in Eichmann in Jerusalem:
"Bragging was the vice that was Eichmann's undoing. It was sheer rodomontade when he told his men during the last days of the war: 'I will jump into my grave laughing, because of the fact that I have the death of five million Jews...on my conscience gives me extraordinary satisfaction.' ... [For Eichmann to] claim the death of five million Jews, the approximate total of losses suffered from the combined efforts of all Nazi offices and authorities, was preposterous...."
The term was used in Desert Island Discs by the singer Morrissey when describing his own music.
Sir Anthony Parsons as UK Ambassador to the United Nations used the word during a speech on 22 May 1982 during a debate of the Security Council. He was describing the speeches of several other members including the USSR, Cuba and Panama during that day's debate on the Falklands War. He started the speech by saying:
"Obviously we expected other delegations to give bent to atrociously offensive, confused and ill-directed rodomontades against my country..."
William F. Buckley used the word in a May 29, 1995, column in the National Review entitled "What does Clinton have in mind? – Pres. Clinton's attack on conservative radio broadcasts"; Buckley, asking rhetorically whom Clinton was attacking, cited one theory:
The best those commentators could do who appeared on the MacNeil – Lehrer program was to quote an imprudent remark by Gordon Liddy, but what he said – that if any official came to his house to requisition his pistol, he'd better shoot straight – was more rodomontade than a call to arms or hatred.
William Makepeace Thackeray uses the word to describe a letter written by the eponymous hero of 'The Memoirs of Barry Lyndon, Esq.'.
The term was used by W. Somerset Maugham in 'Of Human Bondage' in Athelny's conversation, over tea, with his daughter's suitor.
'He (Athelny) addressed himself directly to his guest with a torrent of rhodomontade'.
Jane Austen in Northanger Abbey: 'mislead by the rodomontade of his friend to believe his father a man of substance and credit... (chapter 30)
Vladimir Nabokov criticized Fyodor Dostoevsky for his "gothic rodomontade".
Roy Jenkins in his biography of Churchill: '..., but also revealed a plain soldier's distaste for the publicity rodomontade which always attended Churchill, and maybe a touch of perverse jealousy too' (chapter 3, 1899–1935).
21st century
By poet Michael Rosen about Boris Johnson on Twitter 11 September 2022: 'Dear Mogg, My speech was by far and away the best. Only I have the sense of rhetoric and rodomontade fitting for such a solemn occasion. Lo, how the paltry ranks of squalid, time-serving weasels will regret they've lost a giant and won a flea. Ry vita brevis arse longa. Boris'
See also
Braggadocio (rap)
References
Narcissism
Morality
Rhetorical techniques | Rodomontade | [
"Biology"
] | 1,756 | [
"Behavior",
"Narcissism",
"Human behavior"
] |
2,160,470 | https://en.wikipedia.org/wiki/Inspur | Inspur Group is an information technology conglomerate in mainland China focusing on cloud computing, big data, key application hosts, servers, storage, artificial intelligence and ERP. On April 18, 2006, Inspur changed its English name from Langchao to Inspur. It is listed on the SSE, SZSE, and SEHK.
History
In 2005, Microsoft invested US$20 million in the company. Inspur announced several agreements with virtualization software developer VMware on research and development of cloud computing technologies and related products. In 2009, Inspur acquired the Xi'an-based research and development facilities of Qimonda AG for 30 million Chinese yuan (around US$4 million). The centre had been responsible for design and development of Qimonda's DRAM products.
In 2011, Shandong Inspur Software Co., Ltd., Inspur Electronic Information Co., Ltd. and Inspur (Shandong) Electronic Information Company, established a cloud computing joint venture, with each holding a third.
U.S. sanctions
In June 2020, the United States Department of Defense published a list of Chinese companies operating in the U.S. that have ties to the People's Liberation Army, which included Inspur. In November 2020, Donald Trump issued an executive order prohibiting any American company or individual from owning shares in companies that the U.S. Department of Defense has listed as having links to the People's Liberation Army.
In March 2023, the United States Department of Commerce added Inspur to the Bureau of Industry and Security's Entity List.
See also
Inspur Server Series
References
External links
Chinese brands
Companies based in Jinan
Companies established in 2000
Computer hardware companies
Multinational companies headquartered in China
Software companies of China
Defence companies of the People's Republic of China
2000 in Jinan | Inspur | [
"Technology"
] | 368 | [
"Computer hardware companies",
"Computers"
] |
2,160,844 | https://en.wikipedia.org/wiki/The%20Core%20Pocket%20Media%20Player | The Core Pocket Media Player (TCPMP) is a software media player which operates on portable devices and Windows-based PCs. It is discontinued, but still available from the official mirror site. Supported operating systems include Palm OS, Symbian OS, and Microsoft Windows, CE, and Mobile. It is also available on Microsoft's Zune HD via a hack called Liberate. TCPMP also has hardware accelerated playback for ATI and Intel 2700G mobiles, such as the Tapwave Zodiac and Dell Axim X50v/X51V.
Development of the free version of the software was discontinued by CoreCodec in favour of the commercially licensed CorePlayer, though TCPMP is still regarded as one of the more versatile media players for PocketPC and Palm OS mobile devices.
History
According to the CoreCodec.com website as of September 2002, the development team planned to continue development and releases of the open source version of the player "offsite"; this code would also be incorporated into the commercial player.
In 2004, on CoreCodec.org, the open source player was released as BetaPlayer 0.01a for Windows CE and Windows Mobile. It was renamed The Core Pocket Media Player in July 2005 upon its release for the Palm OS and Windows CE/Mobile operating systems.
A release of TCPMP for the Symbian OS has been remarked upon, but further information about it is available only in forums.
The TCPMP project page indicates that the development languages used were "assembly, C".
In 2006, CoreCodec Inc. discontinued development of TCPMP to focus on the commercial CorePlayer Platform.
Codecs
TCPMP supports many audio, video, and image formats, including AC3, HE-AAC (later removed), AMR, DivX, FLAC, H.263, H.264, JPEG, Monkey's Audio, MJPEG, MPEG-1, MP2, MP3, Musepack, MS-MPEG4-v3, PNG, Speex, TIFF, TTA, Vorbis, WAV, WavPack and XviD.
It supports many container formats, including 3GP, ASF, AVI, Matroska, MPEG, OGG, OGM and QuickTime.
On the Windows desktop platform, a third-party codec can support H.264, and a third-party plugin can support YouTube videos and other Flash video formats.
Reception
The program received consistently positive reviews for its performance, versatility, and functionality, with minor criticism of user interface issues. HPC:Factor magazine, in evaluating version 0.66, declared it "excellent" while noting a need for improvement in menu space usage, and the "complete lack of documentation."
Version 0.70 was described as "the best, free multimedia player for both the Pocket PC and the Palm OS platform" in Smartphone & Pocket PC magazine in November 2005.
The 2006 Treo Central review gave it a score of 4/5 for use on Palm OS-equipped Treo devices, with "a pretty cool and logical interface, albeit with some drawbacks", "supporting almost every video encapsulation known to humankind" without conversion prior to playback.
SmartDevice Central reviewed version 0.71 on the Palm Treo 700 in 2007, called it "impressive", and "a solid piece of software," while summarizing its user interface as resembling "a black-and-white Macintosh app from the late 1980s, it has absolutely no eye candy whatsoever."
After CoreCodec Inc. discontinued development of TCPMP in 2006, renamed it CorePlayer, and developed it for commercial sale, one review referred to the "quirky but rock solid TCPMP" as "bulletproof", compared to a very early version of the new player (later reviews mentioned no problems with stability).
See also
CorePlayer
References
External links
CoreCodec TCPMP Official website (at archive.org, dead download links)
CoreCodec TCPMP 0.72 RC1 mirror site (at archive.org). Last player under GPL and codecs
TCPMP 0.72 RC1 mirrored at videohelp.com (might not work on WM 6.1+)
Media players
Multimedia
Windows media players
Palm OS software
Pocket PC software
Symbian software
Windows Mobile Standard software
S60 (software platform) | The Core Pocket Media Player | [
"Technology"
] | 917 | [
"Multimedia"
] |
2,160,901 | https://en.wikipedia.org/wiki/Resentment | Resentment (also called ranklement or bitterness) is a complex, multilayered emotion that has been described as a mixture of disappointment, disgust and anger. Other psychologists consider it a mood or as a secondary emotion (including cognitive elements) that can be elicited in the face of insult or injury.
Inherent in resentment is a perception of unfairness (i.e. from trivial to very serious), and a generalized defense against unfair situations (e.g. relationships or unfavourable circumstances).
The word originates from French "ressentir", re-, intensive prefix, and sentir "to feel"; from the Latin "sentire". The English word has become synonymous with anger, spite, and holding a grudge.
Causes
Resentment can result from a variety of situations involving a perceived wrongdoing from an individual, which are often sparked by expressions of injustice or humiliation. Common sources of resentment include publicly humiliating incidents such as accepting negative treatment without voicing any protest; feeling like an object of regular discrimination or prejudice; envy/jealousy; feeling used or taken advantage of by others; and having achievements go unrecognized, while others succeed without working as hard. Resentment can also be generated by dyadic interactions, such as emotional rejection or denial by another person, deliberate embarrassment or belittling by another person, or ignorance, putting down, or scorn by another person.
Resentment can also develop, and be maintained by: focusing on past grievances (i.e. disturbing memories of hurtful experiences) continuously, or by trying to justify the emotion (i.e. with additional thoughts/feelings). Thus, resentment can occur as a result of the grief process and can be sustained by ruminating.
Function
Resentment has healthy and unhealthy aspects.
Alice MacLachlan writes "What we resent reveals what it is we value, and what we have come to expect (or hope) from others; it may also reveal to what we see ourselves as entitled {to}: that is, how our expectations of our surroundings are organized and measured." Indeed, she goes on to further write that only an amoral person (a person who didn't have values or concern for the well-being of self or others) could not experience resentment.
Resentment can also function to warn against further, future, harmful and unfair situations from occurring again (its focus is on the future). Resentment, used as a form of distrust, has a strong component of self-punishment: "the false appeal of self-punishment is that it seems to keep us safe from future hurt and disappointment", when in reality it is hurting the resenter more (i.e. how we mistreat or distrust others unrelated to the offense, ourselves, etc.).
Resentment has also been conceptualized as a form of protest: "More specifically, resentment protests a past action, that persists as a present threat". The 'present threat' being that the past harmful action(s), makes a claim: that you can be treated this way, or that such treatment is acceptable; It poses a threat, and in resenting it, you challenge that claim (i.e. protest). "Resentment affirms what the {offenders'} act denies"- its harmfulness and the victim's worth. Pamela Hieronymi claims the object of protest is the past event, rather than the offender of the event: claiming that resentment need not develop into malice or a desire for retribution (if resentment is focused on the past harmful situation or event, rather than the person who caused it).
Resentment, when it is unhealthy, can come in the form of: hostile anger with a retaliation motive (i.e. fantasizing about putting someone down, devaluing, or paying someone back for a perceived injury), time duration (which can go on for days, weeks, or even years), or when too many resentments are held; Thus, draining resources, creating stress, and draining positive emotions.
Physical expression
Unlike many emotions, resentment does not have physical tags exclusively related to it that telegraph when a person is feeling this emotion. However, physical expressions associated with related emotions such as anger and envy may be exhibited, such as furrowed brows or bared teeth.
Resentment can be self-diagnosed by looking for signs such as the need for emotion regulation, faking happiness while with a person to cover true feelings toward them, or speaking in a sarcastic or demeaning way to or about the person. It can also be diagnosed through the appearance of agitation- or dejection-related emotions, such as feeling inexplicably depressed or despondent, becoming angry for no apparent reason, or having nightmares or disturbing daydreams about a person.
Internal experience
Resentment is most powerful when it is felt toward someone whom the individual is close to or intimate with. To have an injury resulting in resentful feelings inflicted by a friend or loved one leaves the individual feeling betrayed as well as resentful, and these feelings can have deep effects.
Resentment can have a variety of negative results on the person experiencing it, including touchiness or edginess when thinking of the person resented, denial of anger or hatred against this person, and provocation or anger arousal when this person is recognized positively. It can also have more long-term effects, such as the development of a hostile, cynical, sarcastic attitude that may become a barrier against other healthy relationships; lack of personal and emotional growth; difficulty in self-disclosure; trouble trusting others; loss of self-confidence; and overcompensation.
Chronic resentment (i.e. for a prolonged period of time) can also lead to unhealthy symptoms, such as the constriction of nerve endings in one's muscles (causing chronic, low-grade muscle and back-pain). Such long-lasting resentment can also cause destruction of T cells (lowering the immune system), hypertension (which increases the threat of stroke and heart attack), cancer, (drug) addictions, depression, and shortened life span.
Coping
To further compound these negative effects, resentment often functions in a downward spiral. Resentful feelings cut off communication between the resentful person and the person they feel committed the wrong, and can result in future miscommunications and the development of further resentful feelings. Because of the consequences they carry, resentful feelings are dangerous to live with and need to be dealt with. Resentment is an obstacle to the restoration of equal moral relations among persons.
Resentment and spite also share a connection of self-harm, yet differ primarily in the way they are expressed. Resentment is unique in that it is almost exclusively internalized, where it can do further emotional and psychological damage but does not strongly impact the person resented. By contrast, spite is exclusively externalized, involving vindictive actions against a (perceived or actual) source of wrong. Spiteful actions can stem from resentful feelings, however.
Psychologist James J. Messina recommends five steps to facing and resolving resentful feelings: (1) Identify the source of the resentful feelings and what it is the person did to evoke these feelings; (2) develop a new way of looking at past, present and future life, including how resentment has affected life and how letting go of resentment can improve the future; (3) write a letter to the source of the resentment, listing offenses and explaining the circumstances, then forgive and let go of the offenses (but do not send the letter); (4) visualize a future without the negative impact of resentment; and (5) if resentful feelings still linger, return to Step 1 and begin again.
Post-traumatic embitterment disorder has been linked to resentment, in some cases.
Comparison with anger
Robert C. Solomon, a professor of philosophy at the University of Texas at Austin, places resentment on the same continuum as anger and contempt, and he argues that the differences between the three are that resentment is anger directed toward a higher-status individual; anger is directed toward an equal-status individual; and contempt is anger directed toward a lower-status individual.
Steven Stosny makes an analogy, distinguishing the functions of anger and resentment, as: anger being a fire-extinguisher meant to 'put-out' and prevent immediately harmful situations, from becoming more harmful, while resentment is more like a smoke-alarm: something that is always 'on' (and requires energy and emotions to sustain this alarm-system), and is meant to protect us if, just in case, someone or something harmful from past experience shows up. Resentment and anger differ primarily in the way they are externally expressed. Anger results in aggressive behavior, used to avert or deal with a threat, while resentment occurs once the injury has been dealt and is not expressed as aggressively or as openly.
Another differentiation between anger and resentment, is as follows: anger is about the immediate situation (to back off or submit), whereas resentment is a defensive way to mentally punish (or in the more extreme case, to devalue) yourself, or the remembered offender. Another differentiation is that
resentment is rarely (if ever) about a single specific stimulus: even after behavioural changes have been made (i.e. accountability has been addressed) or the stimulus is no longer present (i.e. situation is no longer encountered) resentment can still be present. Whereas anger is triggered by a specific stimulus, and usually reduces in intensity as the stimulus attenuates (or is no longer present).
Comparison with conviction
An important feature of acting on resentment is that it is against something (i.e. unfairness, injustice, abuse, situations that threaten values or well-being). Whereas, acting on conviction is for something (i.e. justice, well-being of self or others, or any other values held by an individual as important). The distinction is important, when acted upon, because while acting for one's deeper values creates actions consistent with one's values, acting against things (or people) one does not value does not necessarily lead to actions that are consistent with one's deeper values (i.e. retribution, murder). Self-reflection can help determine which of the two that one is acting on, by stating why the behavior is consistent with one's deeper values: if one's answer represents conviction, it will reflect one's deeper values; if it is resentful it will devalue someone or something.
Philosophical perspectives
Max Scheler considered resentment as the product of weakness and passivity.
Nietzsche saw resentment as an ignoble emotion underlying Rousseau-esque Romanticism - "for under all romanticism lie the grunting and greed of Rousseau's instinct for revenge".
Philosopher Robert C. Solomon wrote extensively on the emotion of resentment and its negative effects on those who experience it. Solomon describes resentment as the means by which man clings to his self-respect. He wrote that it is in this moment when humanity is at its lowest ebb.
Scheler was instrumental in Ressentiment thought.
Alcoholism and bigotry
Alcoholics Anonymous (AA) cites resentment as the number one offender, and one of the greatest threats to an alcoholic. The Twelve Steps of AA involve identifying and dealing with resentment as part of the path toward recovery, including acknowledging one's own role in resentment and praying for the resentment to be taken away. The inventory that AA suggests for processing resentments is to first inventory the resentment by identifying what person, institution, or principle one is angry at, then to identify why one is angry, what instincts of self are affected by the resentment. Finally, disregarding the other person involved entirely, the alcoholic looks for their own mistakes, where they are to blame and where they have been at fault: where has the alcoholic been selfish, self-seeking, dishonest, or frightened? After writing and sharing an inventory, unselfish, constructive action is taken.
Resentment can also play a role in racial and ethnic conflicts. Resentment is cited as having infected the structure of social value, and is thus a regular catalyst in conflicts sparked by inequality. It can also be one of the emotions experienced during class conflict, particularly by the oppressed social class.
Literary examples
The writer Norman Douglas confessed to a habit of borrowing money, like D. H. Lawrence; but unlike Lawrence, Douglas was able to hide "the primary reaction: resentfulness…. We object to being patronized; it makes us resentful".
Sociologist Zygmunt Bauman discusses resentment: "Both Nietzsche and Scheler point to ressentiment as a major obstacle to loving the Other as thyself. (While they wrote in German, they used the French term ressentiment, the complex meaning of which is less than perfectly conveyed by the more straightforward English term "resentment").
See also
References
Further reading
Hatred
Emotions
de:Aversion
fr:Ressentiment
ja:ルサンチマン
pl:Poczucie krzywdy | Resentment | [
"Biology"
] | 2,692 | [
"Hatred",
"Behavior",
"Aggression"
] |
2,160,932 | https://en.wikipedia.org/wiki/BS%205950 | BS 5950 is a withdrawn British Standard for the design, fabrication and erection of structural steelwork. It was written for use in the UK but can be used worldwide. It was superseded by BS EN 1993 and withdrawn on 30 March 2010.
It does not apply to bridges, which are covered by BS 5400. BS 5950 replaced BS 449, which used a permissible stress approach, and uses limit state design methods.
References
05950
Structural engineering standards | BS 5950 | [
"Engineering"
] | 95 | [
"Structural engineering",
"Structural engineering standards"
] |
2,161,236 | https://en.wikipedia.org/wiki/Cross%20Cave | Cross Cave (, ), also named Cold Cave under Cross Mountain (), is a cave in Slovenia's Lož Valley, in the area between the Lož Karst Field, Cerknica Karst Field, and Bloke Plateau. The cave is named after nearby Holy Cross Church in Podlož. The cave is particularly noted among Karst caves for its chain of over 45 subterranean lakes of emerald green water. Extremely slow-growing calcareous formations (up to 0.1 mm per year) and their fragility are the main obstacle to large-scale tourism in the cave and limit daily tourist visits to the flooded part of the cave to four people. As a result, the Cross Cave is among the best-preserved caves, opened to the public in Slovenia. The cave was prepared for visits in the 1950s by the Lož Valley Tourist Association. It was later managed by the Ljubljana Cave Research Society. Since the 1990s, it has been cared for by the Friends of Cross Cave Association ().
With 45 species of organisms, some not discovered until 2000, Cross Cave is the fourth-largest cave ecosystem in the world in terms of biodiversity. The cave was first documented in 1832, but the part of the cave that includes lakes and stream passages was first explored by Slovene cavers in 1926.
On January 6, 2024, five people were trapped in the cave due to high water levels caused by heavy rainfall. They were rescued on January 8, 2024.
Course
At Calvary (, the best-known symbol of Cross Cave), the cave splits into two branches: the Muds to the north and the Variegated Passage to the northeast. The passage through the Muds is more difficult, and so most visitors choose to continue through the Variegated Passage, which requires the use of small boats. Cross Cave continues into New Cross Cave (). In the direction from the entrance to the cave, the Variegated Passage is the left gallery of Cross Cave at the confluence with the Muds at Cavalry. The access requires the use of boats. Part of the way along the Variegated Passage is a side gallery named the Matjaž Passage (), and it contains several large columns. Continuing along the Variegated Passage, visitors enter the Crystal Mountain (), the largest room in the cave. They can climb a mountainous pile of collapsed rocks to a point well above the stream.
Archeological site
Cross Cave exhibits one of the largest deposits of cave bear skeletons in this part of Europe. Over two thousand cave bear bones have been found in the cave. In addition to the abundance of cave bear bones, ceramic and lyrical remains from the eneolithic period were discovered at the entrance of the cave at the beginning of the first lake.
Incident
On 6 January 2024 at 8:00 a.m., a group of three, together with a guide and a trainee guide, went on a tourist tour of the cave, although it was unsuitable for a visit at that time due to weather conditions. However, because they had not returned by the scheduled time of 3:00 p.m., other guides went to look for them. Because they were not found, the Cave Rescue Service (JRS) was activated at approximately 5:25 p.m.
At around 4:00 a.m., the rescuers found the missing persons at a location in a cave called Cross Mountain. They were found on a ledge elevated 10 m above the water level that always remains dry, located about 2 km from the entrance to the cave under Cross Mountain. All those trapped were safe and in good health. They were evacuated on the afternoon of 8 January.
References
External links
Cross Cave on Geopedia
Cross Cave. Official webpage.
Cross Cave. A map and a virtual panorama.
Limestone caves
Ecosystems
Show caves in Slovenia
Municipality of Bloke
Municipality of Cerknica
Municipality of Loška Dolina
Caves of Inner Carniola
Underground lakes | Cross Cave | [
"Biology"
] | 804 | [
"Symbiosis",
"Ecosystems"
] |
2,161,298 | https://en.wikipedia.org/wiki/Bioglass%2045S5 | Bioglass 45S5 or calcium sodium phosphosilicate, is a bioactive glass specifically composed of 45 wt% SiO2, 24.5 wt% CaO, 24.5 wt% Na2O, and 6.0 wt% P2O5. Typical applications of Bioglass 45S5 include: bone grafting biomaterials, repair of periodontal defects, cranial and maxillofacial repair, wound care, blood loss control, stimulation of vascular regeneration, and nerve repair.
The name "Bioglass" was trademarked by the University of Florida as a name for the original 45S5 composition. It should therefore only be used in reference to the 45S5 composition and not as a general term for bioactive glasses. Bioglass 45S5 is available commercially under the registered trade name NovaMin, which is owned by the pharmaceutical company GlaxoSmithKline. NovaMin is bioactive glass that has been ground into a fine particulate with a median size of less than 20 μm. It can reduce dentin hypersensitivity by blocking open dentinal tubules and by supplying calcium (Ca2+) and phosphate () ions to form hydroxycarbonate apatite (HCA), the principal mineral component of bone tissue in mammals. NovaMin is the active ingredient in Sensodyne "Repair & Protect" toothpaste, except when sold in the United States, containing stannous fluoride instead.
Characteristics
45S5 bioactive glass is white in color and is in powder form, with particulates with a median size of less than 20 μm. Its chemical composition by weight is: silica (SiO2) 43–47%, calcium oxide (CaO) 22.5–26.5%, phosphorus pentoxide (P2O5) 5–7% and sodium oxide (Na2O) 22.5–26.5%.
Glasses are non-crystalline disordered solids that are commonly composed of silica-based materials with other minor additives. Compared to soda-lime glass (commonly used, as in windows or bottles), Bioglass 45S5 contains less silica and higher amounts of calcium and phosphorus. The 45S5 name signifies glass with 45% by weight of SiO2 and 5:1 molar ratio of calcium to phosphorus. This high ratio of calcium to phosphorus promotes formation of apatite crystals; calcium and silica ions can act as crystallization nuclei. Lower Ca:P ratios do not bond to bone. Bioglass 45S5's specific composition is optimal in biomedical applications because of its similar composition to that of hydroxyapatite, the mineral component of bone. This similarity provides Bioglass 45S5's ability to be integrated with living bone.
This composition of bioactive glass is mechanically soft in comparison to other glasses. It can be machined, preferably with diamond tools, or ground to powder. Bioglass 45S5 has to be stored in a dry environment, as it readily absorbs moisture and reacts with it. Bioglass 45S5 is the first formulation of an artificial material that was found to chemically bond with bone, and its discovery led to a series of other bioactive glasses. One of its main medical advantages is its biocompatibility, seen in its ability to avoid an immune reaction and fibrous encapsulation. Its primary application is the repair of bone injuries or defects too large to be regenerated by the natural process.
History
Bioglass 45S5 is important to the field of biomimetic materials as one of the first completely synthetic materials that seamlessly bonds to bone. It was developed by Larry L. Hench in the late 1960s. The idea for the material came to him during a bus ride in 1967. While working as an assistant professor at the University of Florida, Hench decided to attend the U.S. Army Materials Research Conference held in Sagamore, New York, where he planned to talk about radiation resistant electronic materials. He began discussing his research with a fellow traveller on the bus, Colonel Klinker, who had recently returned to the United States after serving as an Army medical supply officer in Vietnam.
After listening to Hench's description of his research, the Colonel asked, “If you can make a material that will survive exposure to high energy radiation can you make a material that will survive exposure to the human body?” Klinker then went on to describe the amputations that he had witnessed in Vietnam, which resulted from the body's rejection of metal and plastic implants. Hench realized that there was a need for a novel material that could form a living bond with tissues in the body.
When Hench returned to Florida after the conference, he submitted a proposal to the U.S. Army Medical Research and Design Command. He received funding in 1968, and in November 1969 Hench began to synthesize small rectangles of what he called 45S5 glass. Ted Greenlee, Assistant Professor of Orthopaedic Surgery at the University of Florida, implanted them in rat femurs at the VA Hospital in Gainesville. Six weeks later, Greenlee called Hench asking, "Larry, what are those samples you gave me? They will not come out of the bone. I have pulled on them, I have pushed on them, I have cracked the bone and they are still bonded in place."
With this first successful experiment, Bioglass was born and the first compositions studied. Hench published his first paper on the subject in 1971 in the Journal of Biomedical Materials Research, and his lab continued to work on the project for the next 10 years with continued funding from the U.S. Army. By 2006, there were over 500 papers published on the topic of bioactive glasses from different laboratories and institutions around the world. The first successful surgical use of Bioglass 45S5 was in replacement of ossicles in the middle ear as a treatment of conductive hearing loss, and the material continues to be used in bone reconstruction applications today.
Other uses include cones for implantation into the jaw following a tooth extraction. Composite materials made of Bioglass 45S5 and patient's own bone can be used for bone reconstruction. Further research is being conducted for the development of new processing techniques to allow for more applications of Bioglass.
Applications
Bioglass 45S5 is used in jaw and orthopedics applications, in this way it dissolves and can stimulate the natural bone to repair itself. Bioactive glass offers good osteoconductivity and bioactivity, it can deliver cells and is biodegradable. This makes it an excellent candidate to be used in tissue engineering applications. Although this material is known to be brittle, it is still used extensively to enhance the growth of bone since new forms of bioactive glasses are based on borate and borosilicate compositions. Bioglass can also be doped with varying quantities of elements like copper, zinc, or strontium which can allow the growth and formation of healthy bone. The formation of neocartilage can also be induced with bioactive glass by using an in vitro culture of chondrocyte-seeded hydrogels and can serve as a subchondral substrate for tissue-engineered osteochondral constructs.
The borate-based bioactive glass has controllable degradation rates in order to match the rate at which actual bone is formed. Bone formation has been shown to enhance when using this type of material. When implanted into rabbit femurs, the 45S5 bioactive glass showed that it could induce bone proliferation at a much quicker rate than synthetic hydroxyapatite (HA). 45S5 glass can also be osteoconductive and osteoinductive because it allows for new bone growth along the bone-implant interface as well as within the bone-implant interface. Studies have been conducted to determine the process by which it can induce bone formation. It was shown that 45S5 glass degrades and releases sodium ions, as well as soluble silica, the combination of all these ions is said to produce new bone. Borate bioglass has proven that it can support cell proliferation and differentiation in vitro and in vivo. It also has shown that it is suitable to be used as a substrate for drug release when treating bone infection. However, there has been a concern as to whether or not the release of boron into a solution as borate ions will be toxic to the body. It has been shown that in static cell culture conditions, borate glasses were toxic to cells, but not in dynamic culture conditions.
Bioactive glass was applied to medical devices to help restore the hearing to a deaf patient using Bioglass 45S5 in 1984. The patient went deaf due to at ear infection that degraded two of the three bones in her middle ear. An implant was designed to replace the damaged bone and carry sound from the eardrum to the cochlea, restoring the patient's hearing. Before this material was available, plastics and metals would be used because they did not produce a reaction in the body; however, they eventually failed because tissue would grow around them after implantation. A prosthesis made up of Bioglass 45S5 was made to fit the patient and most of the prosthesis that were made were able to maintain functionality after 10 years. The Endosseous Ridge Maintenance Implant made of Bioglass 45S5 was another device that could be inserted into tooth extraction sites that would repair tooth roots and allow for a stable ridge for dentures.
Another area in which bioactive glass has been investigated to use is tooth enamel reconstruction, which has proven to be a difficult task in the field of dentistry. Enamel is made up of a very organized hierarchical microstructure of carbonated hydroxyapatite nanocrystals. It has been reported that Bioglass 45S5-phosphoric acid paste can be used to form an interaction layer that can obstruct dentinal tubule orifices and can therefore be useful in the treatment of dentin hypersensitivity lesions. This material in an aqueous environment could have an antibacterial property that is advantageous in periodontal surgical procedures. In a study done with 45S5 Bioglass, biofilms of Streptococcus sanguinis were grown on inactive glass particulates and the biofilm grown on the Bioglass was significantly lower than those that were on the inactive glass. It was concluded that Bioglass may reduce bacterial colonisation which could aid osseointegration. A highly effective antibacterial bioactive glass is S53P4, which has been reported to exhibit a high antimicrobial activity and did not seem to select for resistance in the microbial strains tested. Bioactive glasses that are sol-gel derived, such as CaPSiO and CaPSiO II, have also exhibited antibacterial properties. Studies done with S. epidermidis and E. coli cultured with bioactive glass have shown that the 45S5 bioactive glass have a very high antibacterial resistance. It was also observed in the experiment that there were needle-like bioglass debris which could have ruptured the cell walls of the bacteria and rendered them inactive.
GlaxoSmithKline is using this material as an active ingredient in toothpaste under the commercial name NovaMin, which can help repair tiny holes and decrease tooth sensitivity. More advanced fluoride-containing formulations of Bioglass have been developed, which provide stronger and longer-lasting protection against sensitivity. The inclusion of fluoride within the glass rather than as a soluble addition, such as the toothpaste BioMin, is claimed to optimise the rate of development of apatite, which shields the teeth from sensitivity for up to 12 hours.
Mechanism of action
When implanted, Bioglass 45S5 reacts with the surrounding physiological fluid, causing the formation of a hydroxyl carbonated apatite (HCA) layer at the material surface. The HCA layer has a similar composition to hydroxyapatite, the mineral phase of bone, a quality which allows for strong interaction and integration with bone. The process by which this reaction occurs can be separated into 12 steps. The first 5 steps are related to the Bioglass response to the environment within the body, and occur rapidly at the material surface over several hours. Reaction steps 6–10 detail the reaction of the body to the integration of the biomaterial, and the process of integration with bone. These stages occur over the scale of several weeks or months. The steps are separated as follows:
Alkali ions (such as Na+ and Ca2+) on the glass surface rapidly exchange with hydrogen ions or hydronium from surrounding bodily fluids. The reaction below shows this process, which causes hydrolysis of silica groups. As this occurs, the pH of the solution increases.
Si⎯O⎯Na+ + H+ + OH− → Si⎯OH+ + Na+ (aq) + OH−
Due to an increase in the hydroxyl (OH−) concentration at the surface (a result of step 1), a dissolution of the silica glass network occurs, seen by the breaking of Si⎯O⎯Si bonds. Soluble silica is transformed to the form of Si(OH)4 and silanols (Si⎯OH) creation occurs at the material surface. The reaction occurring in this stage is shown below:
Si⎯O⎯Si + H2O→ Si⎯OH + OH⎯Si
The silanol groups at the material surface condense and repolymerize to form a silica-gel layer at the surface of bioglass. As a result of the first steps, the surface contains very little alkali content. The condensation reaction is shown below:
Si⎯OH + Si⎯OH → Si⎯O⎯Si
Amorphous Ca2+ and gather at the silica-rich layer (created in step 3) from both the surrounding bodily fluid and the bulk of the Bioglass. This creates a layer composed primarily of CaO⎯P2O5 on top of the silica layer.
The CaO⎯P2O5 film created in step 4 incorporates OH− and from the bodily solution, causing it to crystallize. This layer is called a mixed carbonated hydroxyl apatite (HCA).
Growth factors adsorb (adsorption) to the surface of Bioglass due to its structural and chemical similarities to hydroxyapatite.
Adsorbed growth factors cause the activation of M2 macrophages. M2 macrophages tend to promote wound healing and initiate the migration of progenitor cells to an injury site. In contrast, M1 macrophages become activated when a non-biocompatible material is implanted, triggering an inflammatory response.
Triggered by M2 macrophage activation, mesenchymal stem cells and osteoprogenitor cells migrate to the Bioglass surface and attach to the HCA layer.
Stem cells and osteoprogenitor cells at the HCA surface differentiate to become osteogenic cells typically present in bone tissue, particularly osteoblasts.
The attached and differentiated osteoblasts generate and deposit extracellular matrix (ECM) components, primarily type I collagen, the main protein component of bone.
The collagen ECM becomes mineralized as normally occurs in native bone. Nanoscale hydroxyapatite crystals form a layered structure with the deposited collagen at the surface of the implant.
Following these reactions, bone growth continues as the newly recruited cells continue to function and facilitate tissue growth and repair. The Bioglass implant continues to degrade and be converted to new ECM material.
Manufacturing
There are two main manufacturing techniques that are used for the synthesis of bioglass. The first is melt quench synthesis, which is the conventional glassmaking technology used by Larry Hench when he first manufactured the material in 1969. This method includes melting a mixture of oxides such as SiO2, Na2O, CaO and P2O5 at high temperatures generally above 1100–1300 °C. Platinum or platinum alloy crucibles are used to avoid contamination, which would interfere with the product's chemical reactivity in organism. Annealing is a crucial step in forming bulk parts, due to high thermal expansion of the material. Heat treatment of Bioglass reduces the volatile alkali metal oxide content and precipitates apatite crystals in the glass matrix. However, the scaffolds that result from melt quench techniques are much less porous compared to other manufacturing methods, which may lead to defects in tissue integration when implanted in vivo.
The second method is sol-gel synthesis of Bioglass. This process is carried out at much lower temperatures than the traditional melting methods. It involves the creation of a solution (sol), which is composed of metal-organic and metal salt precursors. A gel is then formed through hydrolysis and condensation reactions, and it undergoes thermal treatment for drying, oxide formation, and organic removal. Because of the lower fabrication temperatures used in this method, there is a greater level of control on the composition and homogeneity of the product. In addition, sol-gel bioglasses have much higher porosity, which leads to a greater surface area and degree of integration in the body.
Newer methods include flame and microwave synthesis of Bioglass, which has been gaining attention in recent years. Flame synthesis works by baking the powders directly in a flame reactor. Microwave synthesis is a rapid and low-cost powder synthesis method in which precursors are dissolved in water, transferred to an ultrasonic bath, and irradiated.
Shortcomings
A setback to using Bioglass 45S5 is that it is difficult to process into porous 3D scaffolds. These porous scaffolds are usually prepared by sintering glass particles that are already formed into the 3D geometry and allowing them to bond to the particles into a strong glass phase made up of a network of pores. Since this particular type of bioglass cannot fully sinter by viscous flow above its Tg, and its Tg is close to the onset of crystallization, it is hard to sinter this material into a dense network.
45S5 glass also has a slow degradation and rate of conversion to an HA-like material. This setback makes it more difficult for the degradation rate of the scaffold to coincide with the rate of tissue formation. Another limitation is that the biological environment can be easily influenced by its degradation. Increases in the sodium and calcium ions and changing pH is due to its degradation. However, the roles of these ions and their toxicity to the body have not been fully researched.
Methods of improvement
Several studies have investigated methods to improve the mechanical strength and toughness of Bioglass 45S5. These include creating polymer–glass composites, which combine the bioactivity of Bioglass with the relative flexibility and wear resistance of different polymers. Another solution is coating a metallic implant with Bioglass, which takes advantage of the mechanical strength of the implant's bulk material while retaining bioactive effects at the surface. Some of the most notable modifications have used various forms of carbon to improve the properties of 45S5 glass.
For example, Touri et al. developed a method to incorporate carbon nanotubes (CNTs) into the structure without interfering with the material's bioactive properties. CNTs were chosen because of their large aspect ratio and high strength. By synthesizing Bioglass 45S5 on a CNT scaffold, the researchers were able to create a composite that more than doubled the compressive strength and the elastic modulus when compared to the pure glass.
Another study carried out by Li et al. looked into different properties, such as the fracture toughness and wear resistance of Bioglass 45S5. The authors loaded graphene nanoplatelets (GNP) into the glass structure through a spark plasma sintering method. Graphene was chosen because of its high specific surface area and strength, as well as its cytocompatibility and lack of interference with Bioglass 45S5's bioactivity. The composites that were created in this experiment achieved a fracture toughness of more than double the control. In addition, the tribological properties of the material were greatly improved.
See also
Mechanical properties of biomaterials
Synthesis of bioglass
References
Glass compositions
Biomaterials | Bioglass 45S5 | [
"Physics",
"Chemistry",
"Biology"
] | 4,174 | [
"Biomaterials",
"Glass chemistry",
"Glass compositions",
"Materials",
"Matter",
"Medical technology"
] |
2,161,429 | https://en.wikipedia.org/wiki/Eigenvalues%20and%20eigenvectors | In linear algebra, an eigenvector ( ) or characteristic vector is a vector that has its direction unchanged (or reversed) by a given linear transformation. More precisely, an eigenvector, , of a linear transformation, , is scaled by a constant factor, , when the linear transformation is applied to it: . The corresponding eigenvalue, characteristic value, or characteristic root is the multiplying factor (possibly negative).
Geometrically, vectors are multi-dimensional quantities with magnitude and direction, often pictured as arrows. A linear transformation rotates, stretches, or shears the vectors upon which it acts. Its eigenvectors are those vectors that are only stretched, with neither rotation nor shear. The corresponding eigenvalue is the factor by which an eigenvector is stretched or squished. If the eigenvalue is negative, the eigenvector's direction is reversed.
The eigenvectors and eigenvalues of a linear transformation serve to characterize it, and so they play important roles in all the areas where linear algebra is applied, from geology to quantum mechanics. In particular, it is often the case that a system is represented by a linear transformation whose outputs are fed as inputs to the same transformation (feedback). In such an application, the largest eigenvalue is of particular importance, because it governs the long-term behavior of the system after many applications of the linear transformation, and the associated eigenvector is the steady state of the system.
Definition
Consider an matrix and a nonzero vector of length If multiplying with (denoted by ) simply scales by a factor of , where is a scalar, then is called an eigenvector of , and is the corresponding eigenvalue. This relationship can be expressed as: .
There is a direct correspondence between n-by-n square matrices and linear transformations from an n-dimensional vector space into itself, given any basis of the vector space. Hence, in a finite-dimensional vector space, it is equivalent to define eigenvalues and eigenvectors using either the language of matrices, or the language of linear transformations.
The following section gives a more general viewpoint that also covers infinite-dimensional vector spaces.
Overview
Eigenvalues and eigenvectors feature prominently in the analysis of linear transformations. The prefix eigen- is adopted from the German word eigen (cognate with the English word own) for 'proper', 'characteristic', 'own'. Originally used to study principal axes of the rotational motion of rigid bodies, eigenvalues and eigenvectors have a wide range of applications, for example in stability analysis, vibration analysis, atomic orbitals, facial recognition, and matrix diagonalization.
In essence, an eigenvector v of a linear transformation T is a nonzero vector that, when T is applied to it, does not change direction. Applying T to the eigenvector only scales the eigenvector by the scalar value λ, called an eigenvalue. This condition can be written as the equation
referred to as the eigenvalue equation or eigenequation. In general, λ may be any scalar. For example, λ may be negative, in which case the eigenvector reverses direction as part of the scaling, or it may be zero or complex.
The example here, based on the Mona Lisa, provides a simple illustration. Each point on the painting can be represented as a vector pointing from the center of the painting to that point. The linear transformation in this example is called a shear mapping. Points in the top half are moved to the right, and points in the bottom half are moved to the left, proportional to how far they are from the horizontal axis that goes through the middle of the painting. The vectors pointing to each point in the original image are therefore tilted right or left, and made longer or shorter by the transformation. Points along the horizontal axis do not move at all when this transformation is applied. Therefore, any vector that points directly to the right or left with no vertical component is an eigenvector of this transformation, because the mapping does not change its direction. Moreover, these eigenvectors all have an eigenvalue equal to one, because the mapping does not change their length either.
Linear transformations can take many different forms, mapping vectors in a variety of vector spaces, so the eigenvectors can also take many forms. For example, the linear transformation could be a differential operator like , in which case the eigenvectors are functions called eigenfunctions that are scaled by that differential operator, such as
Alternatively, the linear transformation could take the form of an n by n matrix, in which case the eigenvectors are n by 1 matrices. If the linear transformation is expressed in the form of an n by n matrix A, then the eigenvalue equation for a linear transformation above can be rewritten as the matrix multiplication
where the eigenvector v is an n by 1 matrix. For a matrix, eigenvalues and eigenvectors can be used to decompose the matrix—for example by diagonalizing it.
Eigenvalues and eigenvectors give rise to many closely related mathematical concepts, and the prefix eigen- is applied liberally when naming them:
The set of all eigenvectors of a linear transformation, each paired with its corresponding eigenvalue, is called the eigensystem of that transformation.
The set of all eigenvectors of T corresponding to the same eigenvalue, together with the zero vector, is called an eigenspace, or the characteristic space of T associated with that eigenvalue.
If a set of eigenvectors of T forms a basis of the domain of T, then this basis is called an eigenbasis.
History
Eigenvalues are often introduced in the context of linear algebra or matrix theory. Historically, however, they arose in the study of quadratic forms and differential equations.
In the 18th century, Leonhard Euler studied the rotational motion of a rigid body, and discovered the importance of the principal axes. Joseph-Louis Lagrange realized that the principal axes are the eigenvectors of the inertia matrix.
In the early 19th century, Augustin-Louis Cauchy saw how their work could be used to classify the quadric surfaces, and generalized it to arbitrary dimensions. Cauchy also coined the term racine caractéristique (characteristic root), for what is now called eigenvalue; his term survives in characteristic equation.{{efn| Augustin Cauchy (1839) "Mémoire sur l'intégration des équations linéaires" (Memoir on the integration of linear equations), Comptes rendus, 8: 827–830, 845–865, 889–907, 931–937. From p. 827: ''"On sait d'ailleurs qu'en suivant la méthode de Lagrange, on obtient pour valeur générale de la variable prinicipale une fonction dans laquelle entrent avec la variable principale les racines d'une certaine équation que j'appellerai léquation caractéristique, le degré de cette équation étant précisément l'order de l'équation différentielle qu'il s'agit d'intégrer." (One knows, moreover, that by following Lagrange's method, one obtains for the general value of the principal variable a function in which there appear, together with the principal variable, the roots of a certain equation that I will call the "characteristic equation", the degree of this equation being precisely the order of the differential equation that must be integrated.)}}
Later, Joseph Fourier used the work of Lagrange and Pierre-Simon Laplace to solve the heat equation by separation of variables in his 1822 treatise The Analytic Theory of Heat (Théorie analytique de la chaleur). Charles-François Sturm elaborated on Fourier's ideas further, and brought them to the attention of Cauchy, who combined them with his own ideas and arrived at the fact that real symmetric matrices have real eigenvalues. This was extended by Charles Hermite in 1855 to what are now called Hermitian matrices.
Around the same time, Francesco Brioschi proved that the eigenvalues of orthogonal matrices lie on the unit circle, and Alfred Clebsch found the corresponding result for skew-symmetric matrices. Finally, Karl Weierstrass clarified an important aspect in the stability theory started by Laplace, by realizing that defective matrices can cause instability.
In the meantime, Joseph Liouville studied eigenvalue problems similar to those of Sturm; the discipline that grew out of their work is now called Sturm–Liouville theory. Schwarz studied the first eigenvalue of Laplace's equation on general domains towards the end of the 19th century, while Poincaré studied Poisson's equation a few years later.
At the start of the 20th century, David Hilbert studied the eigenvalues of integral operators by viewing the operators as infinite matrices. He was the first to use the German word eigen, which means "own", to denote eigenvalues and eigenvectors in 1904, though he may have been following a related usage by Hermann von Helmholtz. For some time, the standard term in English was "proper value", but the more distinctive term "eigenvalue" is the standard today.
The first numerical algorithm for computing eigenvalues and eigenvectors appeared in 1929, when Richard von Mises published the power method. One of the most popular methods today, the QR algorithm, was proposed independently by John G. F. Francis and Vera Kublanovskaya in 1961.
Eigenvalues and eigenvectors of matrices
Eigenvalues and eigenvectors are often introduced to students in the context of linear algebra courses focused on matrices.University of Michigan Mathematics (2016) Math Course Catalogue . Accessed on 2016-03-27.
Furthermore, linear transformations over a finite-dimensional vector space can be represented using matrices, which is especially common in numerical and computational applications.
Consider -dimensional vectors that are formed as a list of scalars, such as the three-dimensional vectors
These vectors are said to be scalar multiples of each other, or parallel or collinear, if there is a scalar such that
In this case, .
Now consider the linear transformation of -dimensional vectors defined by an by matrix ,
or
where, for each row,
If it occurs that and are scalar multiples, that is if
then is an eigenvector of the linear transformation and the scale factor is the eigenvalue corresponding to that eigenvector. Equation () is the eigenvalue equation for the matrix .
Equation () can be stated equivalently as
where is the by identity matrix and 0 is the zero vector.
Eigenvalues and the characteristic polynomial
Equation () has a nonzero solution v if and only if the determinant of the matrix is zero. Therefore, the eigenvalues of A are values of λ that satisfy the equation
Using the Leibniz formula for determinants, the left-hand side of equation () is a polynomial function of the variable λ and the degree of this polynomial is n, the order of the matrix A. Its coefficients depend on the entries of A, except that its term of degree n is always (−1)nλn. This polynomial is called the characteristic polynomial of A. Equation () is called the characteristic equation or the secular equation of A.
The fundamental theorem of algebra implies that the characteristic polynomial of an n-by-n matrix A, being a polynomial of degree n, can be factored into the product of n linear terms,
where each λi may be real but in general is a complex number. The numbers λ1, λ2, ..., λn, which may not all have distinct values, are roots of the polynomial and are the eigenvalues of A.
As a brief example, which is described in more detail in the examples section later, consider the matrix
Taking the determinant of , the characteristic polynomial of A is
Setting the characteristic polynomial equal to zero, it has roots at and , which are the two eigenvalues of A. The eigenvectors corresponding to each eigenvalue can be found by solving for the components of v in the equation In this example, the eigenvectors are any nonzero scalar multiples of
If the entries of the matrix A are all real numbers, then the coefficients of the characteristic polynomial will also be real numbers, but the eigenvalues may still have nonzero imaginary parts. The entries of the corresponding eigenvectors therefore may also have nonzero imaginary parts. Similarly, the eigenvalues may be irrational numbers even if all the entries of A are rational numbers or even if they are all integers. However, if the entries of A are all algebraic numbers, which include the rationals, the eigenvalues must also be algebraic numbers.
The non-real roots of a real polynomial with real coefficients can be grouped into pairs of complex conjugates, namely with the two members of each pair having imaginary parts that differ only in sign and the same real part. If the degree is odd, then by the intermediate value theorem at least one of the roots is real. Therefore, any real matrix with odd order has at least one real eigenvalue, whereas a real matrix with even order may not have any real eigenvalues. The eigenvectors associated with these complex eigenvalues are also complex and also appear in complex conjugate pairs.
Spectrum of a matrix
The spectrum of a matrix is the list of eigenvalues, repeated according to multiplicity; in an alternative notation the set of eigenvalues with their multiplicities.
An important quantity associated with the spectrum is the maximum absolute value of any eigenvalue. This is known as the spectral radius of the matrix.
Algebraic multiplicity
Let λi be an eigenvalue of an n by n matrix A. The algebraic multiplicity μA(λi) of the eigenvalue is its multiplicity as a root of the characteristic polynomial, that is, the largest integer k such that (λ − λi)k divides evenly that polynomial.
Suppose a matrix A has dimension n and d ≤ n distinct eigenvalues. Whereas equation () factors the characteristic polynomial of A into the product of n linear terms with some terms potentially repeating, the characteristic polynomial can also be written as the product of d terms each corresponding to a distinct eigenvalue and raised to the power of the algebraic multiplicity,
If d = n then the right-hand side is the product of n linear terms and this is the same as equation (). The size of each eigenvalue's algebraic multiplicity is related to the dimension n as
If μA(λi) = 1, then λi is said to be a simple eigenvalue. If μA(λi) equals the geometric multiplicity of λi, γA(λi), defined in the next section, then λi is said to be a semisimple eigenvalue.
Eigenspaces, geometric multiplicity, and the eigenbasis for matrices
Given a particular eigenvalue λ of the n by n matrix A, define the set E to be all vectors v that satisfy equation (),
On one hand, this set is precisely the kernel or nullspace of the matrix (A − λI). On the other hand, by definition, any nonzero vector that satisfies this condition is an eigenvector of A associated with λ. So, the set E is the union of the zero vector with the set of all eigenvectors of A associated with λ, and E equals the nullspace of (A − λI). E is called the eigenspace or characteristic space of A associated with λ. In general λ is a complex number and the eigenvectors are complex n by 1 matrices. A property of the nullspace is that it is a linear subspace, so E is a linear subspace of .
Because the eigenspace E is a linear subspace, it is closed under addition. That is, if two vectors u and v belong to the set E, written , then or equivalently . This can be checked using the distributive property of matrix multiplication. Similarly, because E is a linear subspace, it is closed under scalar multiplication. That is, if and α is a complex number, or equivalently . This can be checked by noting that multiplication of complex matrices by complex numbers is commutative. As long as u + v and αv are not zero, they are also eigenvectors of A associated with λ.
The dimension of the eigenspace E associated with λ, or equivalently the maximum number of linearly independent eigenvectors associated with λ, is referred to as the eigenvalue's geometric multiplicity . Because E is also the nullspace of (A − λI), the geometric multiplicity of λ is the dimension of the nullspace of (A − λI), also called the nullity of (A − λI), which relates to the dimension and rank of (A − λI) as
Because of the definition of eigenvalues and eigenvectors, an eigenvalue's geometric multiplicity must be at least one, that is, each eigenvalue has at least one associated eigenvector. Furthermore, an eigenvalue's geometric multiplicity cannot exceed its algebraic multiplicity. Additionally, recall that an eigenvalue's algebraic multiplicity cannot exceed n.
To prove the inequality , consider how the definition of geometric multiplicity implies the existence of orthonormal eigenvectors , such that . We can therefore find a (unitary) matrix whose first columns are these eigenvectors, and whose remaining columns can be any orthonormal set of vectors orthogonal to these eigenvectors of . Then has full rank and is therefore invertible. Evaluating , we get a matrix whose top left block is the diagonal matrix . This can be seen by evaluating what the left-hand side does to the first column basis vectors. By reorganizing and adding on both sides, we get since commutes with . In other words, is similar to , and . But from the definition of , we know that contains a factor , which means that the algebraic multiplicity of must satisfy .
Suppose has distinct eigenvalues , where the geometric multiplicity of is . The total geometric multiplicity of ,
is the dimension of the sum of all the eigenspaces of 's eigenvalues, or equivalently the maximum number of linearly independent eigenvectors of . If , then
The direct sum of the eigenspaces of all of 's eigenvalues is the entire vector space .
A basis of can be formed from linearly independent eigenvectors of ; such a basis is called an eigenbasis Any vector in can be written as a linear combination of eigenvectors of .
Additional properties
Let be an arbitrary matrix of complex numbers with eigenvalues . Each eigenvalue appears times in this list, where is the eigenvalue's algebraic multiplicity. The following are properties of this matrix and its eigenvalues:
The trace of , defined as the sum of its diagonal elements, is also the sum of all eigenvalues,
The determinant of is the product of all its eigenvalues,
The eigenvalues of the th power of ; i.e., the eigenvalues of , for any positive integer , are .
The matrix is invertible if and only if every eigenvalue is nonzero.
If is invertible, then the eigenvalues of are and each eigenvalue's geometric multiplicity coincides. Moreover, since the characteristic polynomial of the inverse is the reciprocal polynomial of the original, the eigenvalues share the same algebraic multiplicity.
If is equal to its conjugate transpose , or equivalently if is Hermitian, then every eigenvalue is real. The same is true of any symmetric real matrix.
If is not only Hermitian but also positive-definite, positive-semidefinite, negative-definite, or negative-semidefinite, then every eigenvalue is positive, non-negative, negative, or non-positive, respectively.
If is unitary, every eigenvalue has absolute value .
If is a matrix and are its eigenvalues, then the eigenvalues of matrix (where is the identity matrix) are . Moreover, if , the eigenvalues of are . More generally, for a polynomial the eigenvalues of matrix are .
Left and right eigenvectors
Many disciplines traditionally represent vectors as matrices with a single column rather than as matrices with a single row. For that reason, the word "eigenvector" in the context of matrices almost always refers to a right eigenvector, namely a column vector that right multiplies the matrix in the defining equation, equation (),
The eigenvalue and eigenvector problem can also be defined for row vectors that left multiply matrix . In this formulation, the defining equation is
where is a scalar and is a matrix. Any row vector satisfying this equation is called a left eigenvector of and is its associated eigenvalue. Taking the transpose of this equation,
Comparing this equation to equation (), it follows immediately that a left eigenvector of is the same as the transpose of a right eigenvector of , with the same eigenvalue. Furthermore, since the characteristic polynomial of is the same as the characteristic polynomial of , the left and right eigenvectors of are associated with the same eigenvalues.
Diagonalization and the eigendecomposition
Suppose the eigenvectors of A form a basis, or equivalently A has n linearly independent eigenvectors v1, v2, ..., vn with associated eigenvalues λ1, λ2, ..., λn. The eigenvalues need not be distinct. Define a square matrix Q whose columns are the n linearly independent eigenvectors of A,
Since each column of Q is an eigenvector of A, right multiplying A by Q scales each column of Q by its associated eigenvalue,
With this in mind, define a diagonal matrix Λ where each diagonal element Λii is the eigenvalue associated with the ith column of Q. Then
Because the columns of Q are linearly independent, Q is invertible. Right multiplying both sides of the equation by Q−1,
or by instead left multiplying both sides by Q−1,
A can therefore be decomposed into a matrix composed of its eigenvectors, a diagonal matrix with its eigenvalues along the diagonal, and the inverse of the matrix of eigenvectors. This is called the eigendecomposition and it is a similarity transformation. Such a matrix A is said to be similar to the diagonal matrix Λ or diagonalizable. The matrix Q is the change of basis matrix of the similarity transformation. Essentially, the matrices A and Λ represent the same linear transformation expressed in two different bases. The eigenvectors are used as the basis when representing the linear transformation as Λ.
Conversely, suppose a matrix A is diagonalizable. Let P be a non-singular square matrix such that P−1AP is some diagonal matrix D. Left multiplying both by P, . Each column of P must therefore be an eigenvector of A whose eigenvalue is the corresponding diagonal element of D. Since the columns of P must be linearly independent for P to be invertible, there exist n linearly independent eigenvectors of A. It then follows that the eigenvectors of A form a basis if and only if A is diagonalizable.
A matrix that is not diagonalizable is said to be defective. For defective matrices, the notion of eigenvectors generalizes to generalized eigenvectors and the diagonal matrix of eigenvalues generalizes to the Jordan normal form. Over an algebraically closed field, any matrix A has a Jordan normal form and therefore admits a basis of generalized eigenvectors and a decomposition into generalized eigenspaces.
Variational characterization
In the Hermitian case, eigenvalues can be given a variational characterization. The largest eigenvalue of is the maximum value of the quadratic form . A value of that realizes that maximum is an eigenvector.
Matrix examples
Two-dimensional matrix example
Consider the matrix
The figure on the right shows the effect of this transformation on point coordinates in the plane. The eigenvectors v of this transformation satisfy equation (), and the values of λ for which the determinant of the matrix (A − λI) equals zero are the eigenvalues.
Taking the determinant to find characteristic polynomial of A,
Setting the characteristic polynomial equal to zero, it has roots at and , which are the two eigenvalues of A.
For , equation () becomes,
Any nonzero vector with v1 = −v2 solves this equation. Therefore,
is an eigenvector of A corresponding to λ = 1, as is any scalar multiple of this vector.
For , equation () becomes
Any nonzero vector with v1 = v2 solves this equation. Therefore,
is an eigenvector of A corresponding to λ = 3, as is any scalar multiple of this vector.
Thus, the vectors vλ=1 and vλ=3 are eigenvectors of A associated with the eigenvalues and , respectively.
Three-dimensional matrix example
Consider the matrix
The characteristic polynomial of A is
The roots of the characteristic polynomial are 2, 1, and 11, which are the only three eigenvalues of A. These eigenvalues correspond to the eigenvectors and or any nonzero multiple thereof.
Three-dimensional matrix example with complex eigenvalues
Consider the cyclic permutation matrix
This matrix shifts the coordinates of the vector up by one position and moves the first coordinate to the bottom. Its characteristic polynomial is 1 − λ3, whose roots are
where is an imaginary unit with
For the real eigenvalue λ1 = 1, any vector with three equal nonzero entries is an eigenvector. For example,
For the complex conjugate pair of imaginary eigenvalues,
Then
and
Therefore, the other two eigenvectors of A are complex and are and with eigenvalues λ2 and λ3, respectively. The two complex eigenvectors also appear in a complex conjugate pair,
Diagonal matrix example
Matrices with entries only along the main diagonal are called diagonal matrices. The eigenvalues of a diagonal matrix are the diagonal elements themselves. Consider the matrix
The characteristic polynomial of A is
which has the roots , , and . These roots are the diagonal elements as well as the eigenvalues of A.
Each diagonal element corresponds to an eigenvector whose only nonzero component is in the same row as that diagonal element. In the example, the eigenvalues correspond to the eigenvectors,
respectively, as well as scalar multiples of these vectors.
Triangular matrix example
A matrix whose elements above the main diagonal are all zero is called a lower triangular matrix, while a matrix whose elements below the main diagonal are all zero is called an upper triangular matrix. As with diagonal matrices, the eigenvalues of triangular matrices are the elements of the main diagonal.
Consider the lower triangular matrix,
The characteristic polynomial of A is
which has the roots , , and . These roots are the diagonal elements as well as the eigenvalues of A.
These eigenvalues correspond to the eigenvectors,
respectively, as well as scalar multiples of these vectors.
Matrix with repeated eigenvalues example
As in the previous example, the lower triangular matrix
has a characteristic polynomial that is the product of its diagonal elements,
The roots of this polynomial, and hence the eigenvalues, are 2 and 3. The algebraic multiplicity of each eigenvalue is 2; in other words they are both double roots. The sum of the algebraic multiplicities of all distinct eigenvalues is μA = 4 = n, the order of the characteristic polynomial and the dimension of A.
On the other hand, the geometric multiplicity of the eigenvalue 2 is only 1, because its eigenspace is spanned by just one vector and is therefore 1-dimensional. Similarly, the geometric multiplicity of the eigenvalue 3 is 1 because its eigenspace is spanned by just one vector . The total geometric multiplicity γA is 2, which is the smallest it could be for a matrix with two distinct eigenvalues. Geometric multiplicities are defined in a later section.
Eigenvector-eigenvalue identity
For a Hermitian matrix, the norm squared of the jth component of a normalized eigenvector can be calculated using only the matrix eigenvalues and the eigenvalues of the corresponding minor matrix,
where is the submatrix formed by removing the jth row and column from the original matrix. This identity also extends to diagonalizable matrices, and has been rediscovered many times in the literature.
Eigenvalues and eigenfunctions of differential operators
The definitions of eigenvalue and eigenvectors of a linear transformation T remains valid even if the underlying vector space is an infinite-dimensional Hilbert or Banach space. A widely used class of linear transformations acting on infinite-dimensional spaces are the differential operators on function spaces. Let D be a linear differential operator on the space C∞ of infinitely differentiable real functions of a real argument t. The eigenvalue equation for D is the differential equation
The functions that satisfy this equation are eigenvectors of D and are commonly called eigenfunctions.
Derivative operator example
Consider the derivative operator with eigenvalue equation
This differential equation can be solved by multiplying both sides by dt/f(t) and integrating. Its solution, the exponential function
is the eigenfunction of the derivative operator. In this case the eigenfunction is itself a function of its associated eigenvalue. In particular, for λ = 0 the eigenfunction f(t) is a constant.
The main eigenfunction article gives other examples.
General definition
The concept of eigenvalues and eigenvectors extends naturally to arbitrary linear transformations on arbitrary vector spaces. Let V be any vector space over some field K of scalars, and let T be a linear transformation mapping V into V,
We say that a nonzero vector v ∈ V is an eigenvector of T if and only if there exists a scalar λ ∈ K such that
This equation is called the eigenvalue equation for T, and the scalar λ is the eigenvalue of T corresponding to the eigenvector v. T(v) is the result of applying the transformation T to the vector v, while λv is the product of the scalar λ with v.
Eigenspaces, geometric multiplicity, and the eigenbasis
Given an eigenvalue λ, consider the set
which is the union of the zero vector with the set of all eigenvectors associated with λ. E is called the eigenspace or characteristic space of T associated with λ.
By definition of a linear transformation,
for x, y ∈ V and α ∈ K. Therefore, if u and v are eigenvectors of T associated with eigenvalue λ, namely u, v ∈ E, then
So, both u + v and αv are either zero or eigenvectors of T associated with λ, namely u + v, αv ∈ E, and E is closed under addition and scalar multiplication. The eigenspace E associated with λ is therefore a linear subspace of V.
If that subspace has dimension 1, it is sometimes called an eigenline.
The geometric multiplicity γT(λ) of an eigenvalue λ is the dimension of the eigenspace associated with λ, i.e., the maximum number of linearly independent eigenvectors associated with that eigenvalue. By the definition of eigenvalues and eigenvectors, γT(λ) ≥ 1 because every eigenvalue has at least one eigenvector.
The eigenspaces of T always form a direct sum. As a consequence, eigenvectors of different eigenvalues are always linearly independent. Therefore, the sum of the dimensions of the eigenspaces cannot exceed the dimension n of the vector space on which T operates, and there cannot be more than n distinct eigenvalues.
Any subspace spanned by eigenvectors of T is an invariant subspace of T, and the restriction of T to such a subspace is diagonalizable. Moreover, if the entire vector space V can be spanned by the eigenvectors of T, or equivalently if the direct sum of the eigenspaces associated with all the eigenvalues of T is the entire vector space V, then a basis of V called an eigenbasis can be formed from linearly independent eigenvectors of T. When T admits an eigenbasis, T is diagonalizable.
Spectral theory
If λ is an eigenvalue of T, then the operator (T − λI) is not one-to-one, and therefore its inverse (T − λI)−1 does not exist. The converse is true for finite-dimensional vector spaces, but not for infinite-dimensional vector spaces. In general, the operator (T − λI) may not have an inverse even if λ is not an eigenvalue.
For this reason, in functional analysis eigenvalues can be generalized to the spectrum of a linear operator T as the set of all scalars λ for which the operator (T − λI) has no bounded inverse. The spectrum of an operator always contains all its eigenvalues but is not limited to them.
Associative algebras and representation theory
One can generalize the algebraic object that is acting on the vector space, replacing a single operator acting on a vector space with an algebra representation – an associative algebra acting on a module. The study of such actions is the field of representation theory.
The representation-theoretical concept of weight is an analog of eigenvalues, while weight vectors and weight spaces are the analogs of eigenvectors and eigenspaces, respectively.
Hecke eigensheaf is a tensor-multiple of itself and is considered in Langlands correspondence.
Dynamic equations
The simplest difference equations have the form
The solution of this equation for x in terms of t is found by using its characteristic equation
which can be found by stacking into matrix form a set of equations consisting of the above difference equation and the k – 1 equations giving a k-dimensional system of the first order in the stacked variable vector in terms of its once-lagged value, and taking the characteristic equation of this system's matrix. This equation gives k characteristic roots for use in the solution equation
A similar procedure is used for solving a differential equation of the form
Calculation
The calculation of eigenvalues and eigenvectors is a topic where theory, as presented in elementary linear algebra textbooks, is often very far from practice.
Classical method
The classical method is to first find the eigenvalues, and then calculate the eigenvectors for each eigenvalue. It is in several ways poorly suited for non-exact arithmetics such as floating-point.
Eigenvalues
The eigenvalues of a matrix can be determined by finding the roots of the characteristic polynomial. This is easy for matrices, but the difficulty increases rapidly with the size of the matrix.
In theory, the coefficients of the characteristic polynomial can be computed exactly, since they are sums of products of matrix elements; and there are algorithms that can find all the roots of a polynomial of arbitrary degree to any required accuracy. However, this approach is not viable in practice because the coefficients would be contaminated by unavoidable round-off errors, and the roots of a polynomial can be an extremely sensitive function of the coefficients (as exemplified by Wilkinson's polynomial). Even for matrices whose elements are integers the calculation becomes nontrivial, because the sums are very long; the constant term is the determinant, which for an matrix is a sum of different products.
Explicit algebraic formulas for the roots of a polynomial exist only if the degree is 4 or less. According to the Abel–Ruffini theorem there is no general, explicit and exact algebraic formula for the roots of a polynomial with degree 5 or more. (Generality matters because any polynomial with degree is the characteristic polynomial of some companion matrix of order .) Therefore, for matrices of order 5 or more, the eigenvalues and eigenvectors cannot be obtained by an explicit algebraic formula, and must therefore be computed by approximate numerical methods. Even the exact formula for the roots of a degree 3 polynomial is numerically impractical.
Eigenvectors
Once the (exact) value of an eigenvalue is known, the corresponding eigenvectors can be found by finding nonzero solutions of the eigenvalue equation, that becomes a system of linear equations with known coefficients. For example, once it is known that 6 is an eigenvalue of the matrix
we can find its eigenvectors by solving the equation , that is
This matrix equation is equivalent to two linear equations
that is
Both equations reduce to the single linear equation . Therefore, any vector of the form , for any nonzero real number , is an eigenvector of with eigenvalue .
The matrix above has another eigenvalue . A similar calculation shows that the corresponding eigenvectors are the nonzero solutions of , that is, any vector of the form , for any nonzero real number .
Simple iterative methods
The converse approach, of first seeking the eigenvectors and then determining each eigenvalue from its eigenvector, turns out to be far more tractable for computers. The easiest algorithm here consists of picking an arbitrary starting vector and then repeatedly multiplying it with the matrix (optionally normalizing the vector to keep its elements of reasonable size); this makes the vector converge towards an eigenvector. A variation is to instead multiply the vector by this causes it to converge to an eigenvector of the eigenvalue closest to
If is (a good approximation of) an eigenvector of , then the corresponding eigenvalue can be computed as
where denotes the conjugate transpose of .
Modern methods
Efficient, accurate methods to compute eigenvalues and eigenvectors of arbitrary matrices were not known until the QR algorithm was designed in 1961. Combining the Householder transformation with the LU decomposition results in an algorithm with better convergence than the QR algorithm. For large Hermitian sparse matrices, the Lanczos algorithm is one example of an efficient iterative method to compute eigenvalues and eigenvectors, among several other possibilities.
Most numeric methods that compute the eigenvalues of a matrix also determine a set of corresponding eigenvectors as a by-product of the computation, although sometimes implementors choose to discard the eigenvector information as soon as it is no longer needed.
Applications
Geometric transformations
Eigenvectors and eigenvalues can be useful for understanding linear transformations of geometric shapes.
The following table presents some example transformations in the plane along with their 2×2 matrices, eigenvalues, and eigenvectors.
The characteristic equation for a rotation is a quadratic equation with discriminant , which is a negative number whenever is not an integer multiple of 180°. Therefore, except for these special cases, the two eigenvalues are complex numbers, ; and all eigenvectors have non-real entries. Indeed, except for those special cases, a rotation changes the direction of every nonzero vector in the plane.
A linear transformation that takes a square to a rectangle of the same area (a squeeze mapping) has reciprocal eigenvalues.
Principal component analysis
The eigendecomposition of a symmetric positive semidefinite (PSD) matrix yields an orthogonal basis of eigenvectors, each of which has a nonnegative eigenvalue. The orthogonal decomposition of a PSD matrix is used in multivariate analysis, where the sample covariance matrices are PSD. This orthogonal decomposition is called principal component analysis (PCA) in statistics. PCA studies linear relations among variables. PCA is performed on the covariance matrix or the correlation matrix (in which each variable is scaled to have its sample variance equal to one). For the covariance or correlation matrix, the eigenvectors correspond to principal components and the eigenvalues to the variance explained by the principal components. Principal component analysis of the correlation matrix provides an orthogonal basis for the space of the observed data: In this basis, the largest eigenvalues correspond to the principal components that are associated with most of the covariability among a number of observed data.
Principal component analysis is used as a means of dimensionality reduction in the study of large data sets, such as those encountered in bioinformatics. In Q methodology, the eigenvalues of the correlation matrix determine the Q-methodologist's judgment of practical significance (which differs from the statistical significance of hypothesis testing; cf. criteria for determining the number of factors). More generally, principal component analysis can be used as a method of factor analysis in structural equation modeling.
Graphs
In spectral graph theory, an eigenvalue of a graph is defined as an eigenvalue of the graph's adjacency matrix , or (increasingly) of the graph's Laplacian matrix due to its discrete Laplace operator, which is either (sometimes called the combinatorial Laplacian) or (sometimes called the normalized Laplacian), where is a diagonal matrix with equal to the degree of vertex , and in , the th diagonal entry is . The th principal eigenvector of a graph is defined as either the eigenvector corresponding to the th largest or th smallest eigenvalue of the Laplacian. The first principal eigenvector of the graph is also referred to merely as the principal eigenvector.
The principal eigenvector is used to measure the centrality of its vertices. An example is Google's PageRank algorithm. The principal eigenvector of a modified adjacency matrix of the World Wide Web graph gives the page ranks as its components. This vector corresponds to the stationary distribution of the Markov chain represented by the row-normalized adjacency matrix; however, the adjacency matrix must first be modified to ensure a stationary distribution exists. The second smallest eigenvector can be used to partition the graph into clusters, via spectral clustering. Other methods are also available for clustering.
Markov chains
A Markov chain is represented by a matrix whose entries are the transition probabilities between states of a system. In particular the entries are non-negative, and every row of the matrix sums to one, being the sum of probabilities of transitions from one state to some other state of the system. The Perron–Frobenius theorem gives sufficient conditions for a Markov chain to have a unique dominant eigenvalue, which governs the convergence of the system to a steady state.
Vibration analysis
Eigenvalue problems occur naturally in the vibration analysis of mechanical structures with many degrees of freedom. The eigenvalues are the natural frequencies (or eigenfrequencies) of vibration, and the eigenvectors are the shapes of these vibrational modes. In particular, undamped vibration is governed by
or
That is, acceleration is proportional to position (i.e., we expect to be sinusoidal in time).
In dimensions, becomes a mass matrix and a stiffness matrix. Admissible solutions are then a linear combination of solutions to the generalized eigenvalue problem
where is the eigenvalue and is the (imaginary) angular frequency. The principal vibration modes are different from the principal compliance modes, which are the eigenvectors of alone. Furthermore, damped vibration, governed by
leads to a so-called quadratic eigenvalue problem,
This can be reduced to a generalized eigenvalue problem by algebraic manipulation at the cost of solving a larger system.
The orthogonality properties of the eigenvectors allows decoupling of the differential equations so that the system can be represented as linear summation of the eigenvectors. The eigenvalue problem of complex structures is often solved using finite element analysis, but neatly generalize the solution to scalar-valued vibration problems.
Tensor of moment of inertia
In mechanics, the eigenvectors of the moment of inertia tensor define the principal axes of a rigid body. The tensor of moment of inertia is a key quantity required to determine the rotation of a rigid body around its center of mass.
Stress tensor
In solid mechanics, the stress tensor is symmetric and so can be decomposed into a diagonal tensor with the eigenvalues on the diagonal and eigenvectors as a basis. Because it is diagonal, in this orientation, the stress tensor has no shear components; the components it does have are the principal components.
Schrödinger equation
An example of an eigenvalue equation where the transformation is represented in terms of a differential operator is the time-independent Schrödinger equation in quantum mechanics:
where , the Hamiltonian, is a second-order differential operator and , the wavefunction, is one of its eigenfunctions corresponding to the eigenvalue , interpreted as its energy.
However, in the case where one is interested only in the bound state solutions of the Schrödinger equation, one looks for within the space of square integrable functions. Since this space is a Hilbert space with a well-defined scalar product, one can introduce a basis set in which and can be represented as a one-dimensional array (i.e., a vector) and a matrix respectively. This allows one to represent the Schrödinger equation in a matrix form.
The bra–ket notation is often used in this context. A vector, which represents a state of the system, in the Hilbert space of square integrable functions is represented by . In this notation, the Schrödinger equation is:
where is an eigenstate of and represents the eigenvalue. is an observable self-adjoint operator, the infinite-dimensional analog of Hermitian matrices. As in the matrix case, in the equation above is understood to be the vector obtained by application of the transformation to .
Wave transport
Light, acoustic waves, and microwaves are randomly scattered numerous times when traversing a static disordered system. Even though multiple scattering repeatedly randomizes the waves, ultimately coherent wave transport through the system is a deterministic process which can be described by a field transmission matrix . The eigenvectors of the transmission operator form a set of disorder-specific input wavefronts which enable waves to couple into the disordered system's eigenchannels: the independent pathways waves can travel through the system. The eigenvalues, , of correspond to the intensity transmittance associated with each eigenchannel. One of the remarkable properties of the transmission operator of diffusive systems is their bimodal eigenvalue distribution with and . Furthermore, one of the striking properties of open eigenchannels, beyond the perfect transmittance, is the statistically robust spatial profile of the eigenchannels.
Molecular orbitals
In quantum mechanics, and in particular in atomic and molecular physics, within the Hartree–Fock theory, the atomic and molecular orbitals can be defined by the eigenvectors of the Fock operator. The corresponding eigenvalues are interpreted as ionization potentials via Koopmans' theorem. In this case, the term eigenvector is used in a somewhat more general meaning, since the Fock operator is explicitly dependent on the orbitals and their eigenvalues. Thus, if one wants to underline this aspect, one speaks of nonlinear eigenvalue problems. Such equations are usually solved by an iteration procedure, called in this case self-consistent field method. In quantum chemistry, one often represents the Hartree–Fock equation in a non-orthogonal basis set. This particular representation is a generalized eigenvalue problem called Roothaan equations.
Geology and glaciology
In geology, especially in the study of glacial till, eigenvectors and eigenvalues are used as a method by which a mass of information of a clast's fabric can be summarized in a 3-D space by six numbers. In the field, a geologist may collect such data for hundreds or thousands of clasts in a soil sample, which can be compared graphically or as a stereographic projection. Graphically, many geologists use a Tri-Plot (Sneed and Folk) diagram,. A stereographic projection projects 3-dimensional spaces onto a two-dimensional plane. A type of stereographic projection is Wulff Net, which is commonly used in crystallography to create stereograms.
The output for the orientation tensor is in the three orthogonal (perpendicular) axes of space. The three eigenvectors are ordered by their eigenvalues ;
then is the primary orientation/dip of clast, is the secondary and is the tertiary, in terms of strength. The clast orientation is defined as the direction of the eigenvector, on a compass rose of 360°. Dip is measured as the eigenvalue, the modulus of the tensor: this is valued from 0° (no dip) to 90° (vertical). The relative values of , , and are dictated by the nature of the sediment's fabric. If , the fabric is said to be isotropic. If , the fabric is said to be planar. If , the fabric is said to be linear.
Basic reproduction number
The basic reproduction number () is a fundamental number in the study of how infectious diseases spread. If one infectious person is put into a population of completely susceptible people, then is the average number of people that one typical infectious person will infect. The generation time of an infection is the time, , from one person becoming infected to the next person becoming infected. In a heterogeneous population, the next generation matrix defines how many people in the population will become infected after time has passed. The value is then the largest eigenvalue of the next generation matrix.
Eigenfaces
In image processing, processed images of faces can be seen as vectors whose components are the brightnesses of each pixel. The dimension of this vector space is the number of pixels. The eigenvectors of the covariance matrix associated with a large set of normalized pictures of faces are called eigenfaces; this is an example of principal component analysis. They are very useful for expressing any face image as a linear combination of some of them. In the facial recognition branch of biometrics, eigenfaces provide a means of applying data compression to faces for identification purposes. Research related to eigen vision systems determining hand gestures has also been made.
Similar to this concept, eigenvoices''' represent the general direction of variability in human pronunciations of a particular utterance, such as a word in a language. Based on a linear combination of such eigenvoices, a new voice pronunciation of the word can be constructed. These concepts have been found useful in automatic speech recognition systems for speaker adaptation.
See also
Antieigenvalue theory
Eigenoperator
Eigenplane
Eigenmoments
Eigenvalue algorithm
Quantum states
Jordan normal form
List of numerical-analysis software
Nonlinear eigenproblem
Normal eigenvalue
Quadratic eigenvalue problem
Singular value
Spectrum of a matrix
Notes
Citations
Sources
Further reading
External links
What are Eigen Values? – non-technical introduction from PhysLink.com's "Ask the Experts"
Eigen Values and Eigen Vectors Numerical Examples – Tutorial and Interactive Program from Revoledu.
Introduction to Eigen Vectors and Eigen Values – lecture from Khan Academy
Eigenvectors and eigenvalues | Essence of linear algebra, chapter 10 – A visual explanation with 3Blue1Brown
Matrix Eigenvectors Calculator from Symbolab (Click on the bottom right button of the 2×12 grid to select a matrix size. Select an size (for a square matrix), then fill out the entries numerically and click on the Go button. It can accept complex numbers as well.)
Theory
Computation of Eigenvalues
Numerical solution of eigenvalue problems Edited by Zhaojun Bai, James Demmel, Jack Dongarra, Axel Ruhe, and Henk van der Vorst
Abstract algebra
Linear algebra
Mathematical physics
Matrix theory
Singular value decomposition | Eigenvalues and eigenvectors | [
"Physics",
"Mathematics"
] | 11,215 | [
"Applied mathematics",
"Theoretical physics",
"Linear algebra",
"Abstract algebra",
"Mathematical physics",
"Algebra"
] |
2,161,447 | https://en.wikipedia.org/wiki/Terfenadine | Terfenadine is an antihistamine formerly used for the treatment of allergic conditions. It was brought to market by Hoechst Marion Roussel (now Sanofi) and was marketed under various brand names, including Seldane in the United States, Triludan in the United Kingdom, and Teldane in Australia. It was superseded by fexofenadine in the 1990s due to the risk of a particular type of disruption of the electrical rhythms of the heart (specifically cardiac arrhythmia caused by QT interval prolongation) and has been withdrawn from markets worldwide.
Pharmacology
Terfenadine acts as a peripherally-selective antihistamine, or antagonist of the histamine H1 receptor. It is a prodrug, generally completely metabolized to the active form fexofenadine in the liver by the enzyme cytochrome P450 3A4. Due to its near complete metabolism by the liver immediately after leaving the gut, terfenadine normally is not measurable in the plasma. Terfenadine itself, however, is cardiotoxic at higher doses, while its major active metabolite is not. Terfenadine, in addition to its antihistamine effects, also acts as a potassium channel blocker (Kv11.1 encoded by the gene hERG). Since its active metabolite is not a potassium channel blocker, no cardiotoxicity is associated with fexofenadine. Sudden toxicity is possible even after years of use without problems as a result of an interaction with other medications such as erythromycin, or foods such as grapefruit. The addition of, or a dosage increase in, these CYP3A4 inhibitors makes it harder for the body to metabolize and remove terfenadine. In larger plasma concentrations, it may lead to toxic effects on the heart's rhythm (e.g. ventricular tachycardia and torsades de pointes).
History
Terfenadine was synthesized by chemists at Richardson–Merrell in 1973 as a potential tranquilizer. However, it was found to be inactive for such purposes as it did not cross the blood–brain barrier or enter the central nervous system. Pharmacologist Richard Kinsolving noticed that terfenadine showed a structural resemblance to the antihistamine diphenhydramine, so terfenadine was tested as an antihistamine. It was found to be a non-sedating antihistamine and was the first such drug to be discovered.
In the United States, terfenadine as Seldane was brought to market in 1985 as the first non-sedating antihistamine for the treatment of allergic rhinitis. In June 1990, evidence of serious ventricular arrhythmias among those taking Seldane prompted the FDA to issue a report on the risk factors associated with concomitant use of the drug with macrolide antibiotics and ketoconazole. Two months later, the FDA required the manufacturer to send a letter to all physicians, alerting them to the problem; in July 1992, the existing precautions were elevated to a black box warning and the issue attracted mass media attention in reports that people with liver disease or who took ketoconazole, an antifungal agent, or the antibiotic erythromycin, could suffer cardiac arrhythmia if they also took Seldane.
In January 1997, the same month when the U.S. Food and Drug Administration (FDA) had earlier approved a generic version of Seldane made by IVAX Corporation of Miami, the FDA recommended terfenadine-containing drugs be removed from the market and physicians consider alternative medications for their patients. Seldane (and Seldane-D, terfenadine combined with the decongestant pseudoephedrine) were removed from the U.S. market by their manufacturer in late 1997 after the FDA approval of Allegra-D (fexofenadine/pseudoephedrine). Terfenadine-containing drugs were subsequently removed from the Canadian market in 1999, and are no longer available for prescription in the UK.
References
1985 introductions
Benzhydryl compounds
CYP2D6 inhibitors
German inventions
H1 receptor antagonists
Hepatotoxins
HERG blocker
Peripherally selective drugs
Piperidines
Prodrugs
Secondary alcohols
Withdrawn drugs | Terfenadine | [
"Chemistry"
] | 930 | [
"Chemicals in medicine",
"Withdrawn drugs",
"Drug safety",
"Prodrugs"
] |
2,161,528 | https://en.wikipedia.org/wiki/Yan%20tan%20tethera | Yan Tan Tethera or yan-tan-tethera is a sheep-counting system traditionally used by shepherds in Northern England and some other parts of Britain. The words are numbers taken from Brythonic Celtic languages such as Cumbric which had died out in most of Northern England by the sixth century, but they were commonly used for sheep counting and counting stitches in knitting until the Industrial Revolution, especially in the fells of the Lake District. Though most of these number systems fell out of use by the turn of the 20th century, some are still in use.
Origin and development
Sheep-counting systems ultimately derive from Brythonic Celtic languages, such as Cumbric; Tim Gay writes: “[Sheep-counting systems from all over the British Isles] all compared very closely to 18th-century Cornish and modern Welsh". It is impossible, given the corrupted form in which they have survived, to be sure of their exact origin. The counting systems have changed considerably over time. A particularly common tendency is for certain pairs of adjacent numbers to come to resemble each other by rhyme (notably the words for 1 and 2, 3 and 4, 6 and 7, or 8 and 9). Still, multiples of five tend to be fairly conservative; compare bumfit with Welsh , in contrast with standard English fifteen.
Use in sheep counting
Like most Celtic numbering systems, they tend to be vigesimal (based on the number twenty), but they usually lack words to describe quantities larger than twenty; this is not a limitation of either modernised decimal Celtic counting systems or the older ones. To count a large number of sheep, a shepherd would repeatedly count to twenty, placing a mark on the ground, or move a hand to another mark on a shepherd's crook, or drop a pebble into a pocket to represent each score (e.g. 5 score sheep = 100 sheep).
Importance of keeping count
In order to keep accurate records (e.g. of birth and death) and to be alert to instances of straying, shepherds must perform frequent head-counts of their flocks. Dating back at least to the medieval period, and continuing to the present in some areas like Slaidburn, farms were granted fell rights, allowing them access to common grazing land. To prevent overgrazing, it was vitally important for each farm to keep accurate, updated head-counts. Though fell rights are largely obsolete in modern agriculture except in upland areas, farms are often subsidised and taxed according to the quantity of their sheep. For this reason, accurate counts are still necessary, and must be performed frequently.
Generally, a count is the first action performed in the morning and the last action performed at night. A count is made after moving the sheep from one pasture to another, and after any operation involving the sheep, such as shearing, tagging, foot-trimming, mulesing, etc., although sheep are far less likely to stray while being moved in a group rather than when grazing at large on open ground.
Knitting
Their use is also attested in a "knitting song" known to be sung around the middle of the nineteenth century in Wensleydale, Yorkshire, beginning "yahn, tayhn, tether, mether, mimph".
Modern usage
The counting system has been used for products sold within Northern England, such as prints, beers, alcoholic sparkling water (hard seltzer in U.S.), and yarns, as well as in artistic works referencing the region, such as Harrison Birtwistle's 1986 opera Yan Tan Tethera.
Jake Thackray's song "Old Molly Metcalfe" from his 1972 album Bantam Cock uses the Swaledale "Yan Tan Tether Mether Pip" as a repeating lyrical theme.
Garth Nix used the counting system to name the seven Grotesques in his novel Grim Tuesday.
Yan or yen
The word yan or yen for 'one' in Cumbrian, Northumbrian, and some Yorkshire dialects generally represents a regular development in Northern English in which the Old English long vowel <ā> was broken into , and so on. This explains the shift to yan and ane from the Old English , which is itself derived from the Proto-Germanic . Another example of this development is the Northern English word for 'home', hame, which has forms such as hyem, yem and yam all deriving from the Old English .
Systems by region
Yorkshire and Lancashire
Lincolnshire, Derbyshire and County Durham
Southwest England
Cumberland, and Westmorland
Wilts, Scots, Lakes, Dales and Welsh
Note: Scots here means "Scots" not "Gaelic"
Numerals in Brythonic Celtic languages
See also
Counting-out game
References
Further reading
Rawnsley, Hardwicke Drummmond (1987) "Yan tyan tethera: counting sheep". Woolley: Fleece Press
External links
Breton numerals
Carol Justus's use of this numbering system to explain pre-decimal counting systems
The Sheep Counting Score – By Walter Skeat, 1910
Modern Welsh decimal system and older vigesimal system in full
Sheep farming in the United Kingdom
Languages of the United Kingdom
British English
Celtic words and phrases
English words and phrases
Numeral systems | Yan tan tethera | [
"Mathematics"
] | 1,079 | [
"Numeral systems",
"Mathematical objects",
"Numbers"
] |
2,161,573 | https://en.wikipedia.org/wiki/Pax%20Christi | Pax Christi International is an international Catholic peace movement. The Pax Christi International website declares its mission is "to transform a world shaken by violence, terrorism, deepening inequalities, and global insecurity".
History
Pax Christi (Latin for Peace of Christ) was established in France in March 1945 by Marthe Dortel-Claudot and Bishop Pierre-Marie Théas, after the Germans had been expelled from France but before the end of World War II in Europe. Both were French citizens interested in reconciliation between French and German citizens in the aftermath of the war.
Some of the first actions of Pax Christi were the organisation of kindness pilgrimages and other actions fostering reconciliation between France and Germany. Although Pax Christi initially began as a movement for French-German reconciliation, it expanded its focus and spread to other European countries in the 1950s. It grew as “a crusade of prayer for peace among all nations.”
Pax Christi was recognized as “the official international Catholic peace movement” by Pope Pius XII in 1952. It also has chapters in the United States. In the 1960s, it became involved in Mississippi in organizing economic boycotts of businesses that discriminated against blacks, in an effort to support protesters in the civil rights movement, who were trying to end discrimination in facilities and employment. It was active in Greenwood, Mississippi, among other places. In 1983, Pax Christi International was awarded the UNESCO Peace Education Prize. The Pax Christi network membership is made up of 18 national sections and 115 Member Organizations working in over 50 countries.
Peace work
Pax Christi focuses on human rights, human security, disarmament and demilitarisation, nonviolence, nuclear disarmament, extractives in Latin America, and a renewed peace process for Israel-Palestine. Since 1988, the organisation gives out the Pax Christi International Peace Award to peace organisations and peace activists around the world.
Organization
Pax Christi is made up of national sections of the movement, affiliated organizations and partner organizations. Its International Secretariat is in Brussels. Pax Christi has consultative status as a non-governmental organization at the United Nations.
International presidents
Maurice Feltin (1950–1965)
Bernard Alfrink (1965–1978)
Luigi Bettazzi (1978–1985)
Franz König (1985–1990)
Godfried Danneels (1990–1999)
Michel Sabbah (1999–2007)
In 2007, a co-presidency was created with a bishop and a lay woman.
Laurent Monsengwo (2007–2010)
Marie Dennis (2007–2019)
Kevin Dowling (C.SS.R.) (2010–2019)
Sr. Teresia Wamuyu Wachira, IBVM (2019–present)
Marc Stenger (2019–present)
See also
Catholic peace traditions
Religion and peacebuilding
Pope Paul VI Teacher of Peace Award
List of anti-war organizations
References
Further reading
External links
Pax Christi Peace Stories
Catholic Nonviolence Initiative
International Christian organizations
Peace organizations
Catholic lay organisations
Organizations established in 1945
Anti-nuclear organizations
International Campaign to Abolish Nuclear Weapons | Pax Christi | [
"Engineering"
] | 628 | [
"Nuclear organizations",
"Anti-nuclear organizations"
] |
2,161,644 | https://en.wikipedia.org/wiki/Rose%20oil | Rose oil (rose otto, attar of rose, attar of roses, or rose essence) is an essential oil that is extracted from the petals of various types of rose. Rose ottos are extracted through steam distillation, while rose absolutes are obtained through solvent extraction, the absolute being used more commonly in perfumery. The production technique originated in Greater Iran. Even with their high price and the advent of organic synthesis, rose oils are still perhaps the most widely used essential oil in perfumery.
R. damascena and R. centifolia
Two major species of rose are cultivated for the production of rose oil:
Rosa damascena production today is dominated by 3 producers account for over 70% of the Rose oil market share:
Bulgaria, sold as "Bulgarian Rose"
Turkey, sold as "Turkish Rose"
Saudi Arabia, sold as "Taif Rose"
It is also grown on a smaller scale in Afghanistan, Armenia, Azerbaijan, Bosnia, Croatia, Cyprus, Ethiopia, Georgia, Greece, Jordan, Lebanon, India, Iran, Iraq, Israel, Moldova, North Macedonia, Oman, Serbia, Syria, Tajikistan, Turkmenistan, Pakistan, Romania, Russia, Ukraine, United Arab Emirates and Yemen.
Rosa centifolia, the cabbage rose, which is more commonly grown in Morocco, Egypt and France.
Rosa damascena composition
Composition of rose oil and headspace vary, but the Rose international standard survey of 2003–2020 lists three components as the major components with a specific range specified in ISO 9842:2003.
Major rose components
Citronellol 20–34%
Geraniol 15–22%
Nonadecane 8–15%
Minor rose components
Heneicosane, eicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, nonacosane, dodecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nerol, linalool, phenyl ethyl alcohol, farnesol, α-pinene, β-pinene, α-terpinene, limonene, p-cymene, camphene, β-caryophyllene, neral,
geranyl acetate, neryl acetate, eugenol, methyl eugenol, benzaldehyde, benzyl alcohol, octane and tetradecanol.
Key rose components
β-damascenone (0.01–1.85%)
β-damascone (under 1%)
other damascones (under 1%)
beta-ionone (under 1%)
rose oxide (under 1%)
Beta-damascenone's presence is considered as the marker for the quality of rose oil.
Even though these compounds usually exist in less than 1% quantity of rose oil, they make up for slightly more than 90% of the odor content due to their low odor detection thresholds.
Rosa centifolia composition
Rosa centifolia does not have a rose oil because of the delicate nature of its petals. The Rosa centifolia absolute is composed of more than 50% phenylethyl alcohol and the rest of the composition resembles a Rosa damascena.
Production
Due to the labor-intensive production process and the low content of oil in the rose blooms, rose oil commands a very high price. Harvesting of flowers is done by hand in the morning before sunrise, and the material is distilled the same day.
There are three main methods of extracting the oil from the plant material:
Steam distillation, which produces an essential oil called rose otto or attar of roses.
Solvent extraction, which results in an absolute called rose absolute.
Supercritical carbon dioxide extraction, yielding a concrete that may be marketed as a concrete, absolute or extract.
Distillation
In the first part of the two-stage process of distillation, large stills – traditionally of copper – are filled with roses and water. The still is fired for 60–105 minutes. The vaporized water and rose oil exit the still and enter a condensing apparatus and are then collected in a flask. This distillation yields a very concentrated oil, direct oil, which makes up about 20% of the final product of the whole process. The water which condenses along with the oil is drained off and redistilled, cohobation, in order to obtain the water-soluble fractions of the rose oil such as phenethyl alcohol which are a vital component of the aroma and which make up the large bulk, 80%, of the oil.
The two oils are combined and make the final rose attar.
Rose attar is mobile in room temperature and is usually clear, light yellow in color. It will form white crystals at normal room temperature which disappear when the oil is gently warmed. It will tend to become more viscous at lower temperatures due to this crystallization of some of its components.
The essence has a very strong odor, but is pleasant when diluted and used for perfume. Attar of roses was once made in India, Persia, Syria, and the Ottoman Empire. The Rose Valley in Bulgaria, near the town of Kazanlak, is among the major producers of attar of roses in the world.
In India, Kannauj is an important city of fabrication of rose attar, Kannauj is nicknamed "The Grasse of the East" or "The Grasse of the Orient". Grasse (in France) is an important city of fabrication of rose fragrance.
Due to the heat required for distillation, some of the compounds extracted from the rose denature or break down chemically. As such, rose attar does not smell very similar to "fresh" roses.
The hydrosol portion of the distillate is known as rosewater. This inexpensive by-product is used widely as a food flavoring as well as in skin care.
Solvent extraction
In the solvent extraction method, the flowers are agitated in a vat with a solvent such as hexane, which draws out the aroma compounds as well as other soluble substances such as wax and pigments. The extract is subjected to vacuum processing which removes the solvent for re-use. The remaining waxy mass is known as a concrete. The concrete is then mixed with alcohol which dissolves the aromatic constituents, leaving behind the wax and other substances. The alcohol is low-pressure evaporated, leaving behind the finished absolute. The absolute may be further processed to remove any impurities that are still present from the solvent extraction.
Rose absolute is a deep reddish brown with no crystals. Due to the low temperatures in this process, the absolute may be more faithful to the scent of the fresh rose than the otto.
Carbon dioxide extraction
A third process, supercritical carbon dioxide extraction, combines the best aspects of the other two methods. When carbon dioxide is put under at least of pressure and at a temperature of at least (the critical point), it becomes a supercritical fluid with the permeation properties of a gas and the solvation properties of a liquid. (Under normal pressure changes directly from a solid to a gas in a process known as sublimation.) The supercritical fluid extracts the aromatics from the plant material.
Like solvent extraction, the extraction takes place at a low temperature, extracts a wide range of compounds rendering an essence more faithful to the original, and leaves the aromatics unaltered by heat. Because is gas at normal atmospheric pressure, it leaves no trace of itself in the final product. The equipment for extraction is expensive, which is reflected in the price of the essential oils obtained from the process.
Adulteration
It takes a large amount of rose petals to distill a small amount of essential oil. Depending on extraction method and plant species, the typical yield can be approximately 1:3,000. To mitigate the cost, most dealers cut rose oil with Citronellol, Geraniol, Geranium or Palmarosa (Cymbopogon martinii) essential oils, both of which are rich in Geraniol, the main constituent of rose oil. Some of these "rose oils" are up to 90% geranium or palmarosa to 10% rose. This is referred to as extending the rose fragrance. This may be done to compensate for chemotype, e.g. Bulgarian distilled rose oil is naturally low in phenylethanol, and Ukrainian or Russian rose oil is naturally high in phenylethanol. Pure rose oil should not be used directly on the skin, as it can cause allergic reactions such as red skin and spots.
Bulgarian rose oil
Bulgarian rose oil is generally characterized by the following qualities:
It differs to other rose oils in the quantitative content of its ingredients. About 283 components have been identified in the composition of Bulgarian rose oil. They are divided into two groups of substances:
odor carriers – represent the liquid part of the oil-eleoptene;
odor fixatives – hard at room temperature and odorless, but fix the odor and give it durability-stearoptene. Of the many components of eleoptene with a rosy odor are citronellol, geraniol, nerol, phenylethyl alcohol, but the typical rose odor is also formed by the presence of some characteristic molecules in trace amounts.
contains: ethanol (up to 3%), linalool (1 to 3%), phenethyl alcohol(up to 3%), citronellol (24 to 35%), nerol (5 to 12%), geraniol (13 to 22%), geranyl acetate (up to 1.5%), eugenol (up to 2.5%), methyl eugenol (up to 2%) and farnesol (at least 1.4%); hydrocarbons – C17 heptadecane (from 1 to 2.5%), C19 saturated hydrocarbon nonadecane CH3 (CH2) 17CH3 (from 8 to 15%), C19 unsaturated hydrocarbon with one or more double carbon bonds nonadecene CH3 (CH2) 16CH = CH2 from 2 to 5%), C21 heneicosane (from 3 to 5.5%) and C23 tricosane (from 0.5 to 1.5%).
It has a light yellow color with a greenish tinge;
It resembles almond oil in consistency;
It has a strong aroma and sharp balsamic taste;
It has an excellent combination of liquid and solid components.
References
External links
Essential oils
Roses
Flavors | Rose oil | [
"Chemistry"
] | 2,210 | [
"Essential oils",
"Natural products"
] |
2,161,709 | https://en.wikipedia.org/wiki/Padovan%20sequence | In number theory, the Padovan sequence is the sequence of integers P(n) defined by the initial values
and the recurrence relation
The first few values of P(n) are
1, 1, 1, 2, 2, 3, 4, 5, 7, 9, 12, 16, 21, 28, 37, 49, 65, 86, 114, 151, 200, 265, ...
The Padovan sequence is named after Richard Padovan who attributed its discovery to Dutch architect Hans van der Laan in his 1994 essay Dom. Hans van der Laan : Modern Primitive. The sequence was described by Ian Stewart in his Scientific American column Mathematical Recreations in June 1996. He also writes about it in one of his books, "Math Hysteria: Fun Games With Mathematics".
The above definition is the one given by Ian Stewart and by MathWorld. Other sources may start the sequence at a different place, in which case some of the identities in this article must be adjusted with appropriate offsets.
Recurrence relations
In the spiral, each triangle shares a side with two others giving a visual proof that
the Padovan sequence also satisfies the recurrence relation
Starting from this, the defining recurrence and other recurrences as they are discovered,
one can create an infinite number of further recurrences by repeatedly replacing by
The Perrin sequence satisfies the same recurrence relations as the Padovan sequence, although it has different initial values.
The Perrin sequence can be obtained from the Padovan sequence by the
following formula:
Extension to negative parameters
As with any sequence defined by a recurrence relation, Padovan numbers P(m) for m<0 can be defined by rewriting the recurrence relation as
Starting with m = −1 and working backwards, we extend P(m) to negative indices:
{| class="wikitable" style="text-align:right"
|-
| P−20
| P−19
| P−18
| P−17
| P−16
| P−15
| P−14
| P−13
| P−12
| P−11
| P−10
| P−9
| P−8
| P−7
| P−6
| P−5
| P−4
| P−3
| P−2
| P−1
| P0
| P1
| P2
|-
| 7
| −7
| 4
| 0
| −3
| 4
| −3
| 1
| 1
| −2
| 2
| −1
| 0
| 1
| −1
| 1
| 0
| 0
| 1
| 0
| 1
| 1
| 1
|-
|}
Sums of terms
The sum of the first n terms in the Padovan sequence is 2 less than P(n + 5), i.e.
Sums of alternate terms, sums of every third term and sums of every fifth term are also related to other terms in the sequence:
Sums involving products of terms in the Padovan sequence satisfy the following identities:
Other identities
The Padovan sequence also satisfies the identity
The Padovan sequence is related to sums of binomial coefficients by the following identity:
For example, for k = 12, the values for the pair (m, n) with 2m + n = 12 which give non-zero binomial coefficients are (6, 0), (5, 2) and (4, 4), and:
Binet-like formula
The Padovan sequence numbers can be written in terms of powers of the roots of the equation
This equation has 3 roots; one real root p (known as the plastic ratio) and two complex conjugate roots q and r. Given these three roots, the Padovan sequence can be expressed by a formula involving p, q and r :
where a, b and c are constants.
Since the absolute values of the complex roots q and r are both less than 1 (and hence p is a Pisot–Vijayaraghavan number), the powers of these roots approach 0 for large n, and tends to zero.
For all , P(n) is the integer closest to . Indeed, is the value of constant a above, while b and c are obtained by replacing p with q and r, respectively.
The ratio of successive terms in the Padovan sequence approaches p, which has a value of approximately 1.324718. This constant bears the same relationship to the Padovan sequence and the Perrin sequence as the golden ratio does to the Fibonacci sequence.
Combinatorial interpretations
P(n) is the number of ways of writing n + 2 as an ordered sum in which each term is either 2 or 3 (i.e. the number of compositions of n + 2 in which each term is either 2 or 3). For example, P(6) = 4, and there are 4 ways to write 8 as an ordered sum of 2s and 3s:
2 + 2 + 2 + 2 ; 2 + 3 + 3 ; 3 + 2 + 3 ; 3 + 3 + 2
The number of ways of writing n as an ordered sum in which no term is 2 is P(2n − 2). For example, P(6) = 4, and there are 4 ways to write 4 as an ordered sum in which no term is 2:
4 ; 1 + 3 ; 3 + 1 ; 1 + 1 + 1 + 1
The number of ways of writing n as a palindromic ordered sum in which no term is 2 is P(n). For example, P(6) = 4, and there are 4 ways to write 6 as a palindromic ordered sum in which no term is 2:
6 ; 3 + 3 ; 1 + 4 + 1 ; 1 + 1 + 1 + 1 + 1 + 1
The number of ways of writing n as an ordered sum in which each term is odd and greater than 1 is equal to P(n − 5). For example, P(6) = 4, and there are 4 ways to write 11 as an ordered sum in which each term is odd and greater than 1:
11 ; 5 + 3 + 3 ; 3 + 5 + 3 ; 3 + 3 + 5
The number of ways of writing n as an ordered sum in which each term is congruent to 2 mod 3 is equal to P(n − 4). For example, P(6) = 4, and there are 4 ways to write 10 as an ordered sum in which each term is congruent to 2 mod 3:
8 + 2 ; 2 + 8 ; 5 + 5 ; 2 + 2 + 2 + 2 + 2
Generating function
The generating function of the Padovan sequence is
This can be used to prove identities involving products of the Padovan sequence with geometric terms, such as:
Generalizations
In a similar way to the Fibonacci numbers that can be generalized to a set of polynomials
called the Fibonacci polynomials, the Padovan sequence numbers can be generalized to
yield the Padovan polynomials.
Padovan L-system
If we define the following simple grammar:
variables : A B C
constants : none
start : A
rules : (A → B), (B → C), (C → AB)
then this Lindenmayer system or L-system produces the following sequence of strings:
n = 0 : A
n = 1 : B
n = 2 : C
n = 3 : AB
n = 4 : BC
n = 5 : CAB
n = 6 : ABBC
n = 7 : BCCAB
n = 8 : CABABBC
and if we count the length of each string, we obtain the Padovan numbers:
1, 1, 1, 2, 2, 3, 4, 5, ...
Also, if you count the number of As, Bs and Cs in each string, then for the nth
string, you have P(n − 5) As, P(n − 3) Bs and P(n − 4) Cs. The count of BB pairs
and CC pairs are also Padovan numbers.
Cuboid spiral
A spiral can be formed based on connecting the corners of a set of 3-dimensional cuboids.
This is the Padovan cuboid spiral. Successive sides of this spiral have lengths that are
the Padovan numbers multiplied by the square root of 2.
Pascal's triangle
Erv Wilson in his paper The Scales of Mt. Meru observed certain diagonals in Pascal's triangle (see diagram) and drew them on paper in 1993. The Padovan numbers were discovered in 1994. Paul Barry (2004) observed that these diagonals generate the Padovan sequence by summing the diagonal numbers.
References
Ian Stewart, A Guide to Computer Dating (Feedback), Scientific American, Vol. 275, No. 5, November 1996, Pg. 118.
External links
A Padovan sequence calculator
Integer sequences
Recurrence relations | Padovan sequence | [
"Mathematics"
] | 1,844 | [
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2,161,878 | https://en.wikipedia.org/wiki/Protein%E2%80%93protein%20interaction | Protein–protein interactions (PPIs) are physical contacts of high specificity established between two or more protein molecules as a result of biochemical events steered by interactions that include electrostatic forces, hydrogen bonding and the hydrophobic effect. Many are physical contacts with molecular associations between chains that occur in a cell or in a living organism in a specific biomolecular context.
Proteins rarely act alone as their functions tend to be regulated. Many molecular processes within a cell are carried out by molecular machines that are built from numerous protein components organized by their PPIs. These physiological interactions make up the so-called interactomics of the organism, while aberrant PPIs are the basis of multiple aggregation-related diseases, such as Creutzfeldt–Jakob and Alzheimer's diseases.
PPIs have been studied with many methods and from different perspectives: biochemistry, quantum chemistry, molecular dynamics, signal transduction, among others. All this information enables the creation of large protein interaction networks – similar to metabolic or genetic/epigenetic networks – that empower the current knowledge on biochemical cascades and molecular etiology of disease, as well as the discovery of putative protein targets of therapeutic interest.
Examples
Electron transfer proteins
In many metabolic reactions, a protein that acts as an electron carrier binds to an enzyme that acts as its reductase. After it receives an electron, it dissociates and then binds to the next enzyme that acts as its oxidase (i.e. an acceptor of the electron). These interactions between proteins are dependent on highly specific binding between proteins to ensure efficient electron transfer. Examples: mitochondrial oxidative phosphorylation chain system components cytochrome c-reductase / cytochrome c / cytochrome c oxidase; microsomal and mitochondrial P450 systems.
In the case of the mitochondrial P450 systems, the specific residues involved in the binding of the electron transfer protein adrenodoxin to its reductase were identified as two basic Arg residues on the surface of the reductase and two acidic Asp residues on the adrenodoxin.
More recent work on the phylogeny of the reductase has shown that these residues involved in protein–protein interactions have been conserved throughout the evolution of this enzyme.
Signal transduction
The activity of the cell is regulated by extracellular signals. Signal propagation inside and/or along the interior of cells depends on PPIs between the various signaling molecules. The recruitment of signaling pathways through PPIs is called signal transduction and plays a fundamental role in many biological processes and in many diseases including Parkinson's disease and cancer.
Membrane transport
A protein may be carrying another protein (for example, from cytoplasm to nucleus or vice versa in the case of the nuclear pore importins).
Cell metabolism
In many biosynthetic processes enzymes interact with each other to produce small compounds or other macromolecules.
Muscle contraction
Physiology of muscle contraction involves several interactions. Myosin filaments act as molecular motors and by binding to actin enables filament sliding. Furthermore, members of the skeletal muscle lipid droplet-associated proteins family associate with other proteins, as activator of adipose triglyceride lipase and its coactivator comparative gene identification-58, to regulate lipolysis in skeletal muscle
Types
To describe the types of protein–protein interactions (PPIs) it is important to consider that proteins can interact in a "transient" way (to produce some specific effect in a short time, like signal transduction) or to interact with other proteins in a "stable" way to form complexes that become molecular machines within the living systems. A protein complex assembly can result in the formation of homo-oligomeric or hetero-oligomeric complexes. In addition to the conventional complexes, as enzyme-inhibitor and antibody-antigen, interactions can also be established between domain-domain and domain-peptide. Another important distinction to identify protein–protein interactions is the way they have been determined, since there are techniques that measure direct physical interactions between protein pairs, named “binary” methods, while there are other techniques that measure physical interactions among groups of proteins, without pairwise determination of protein partners, named “co-complex” methods.
Homo-oligomers vs. hetero-oligomers
Homo-oligomers are macromolecular complexes constituted by only one type of protein subunit. Protein subunits assembly is guided by the establishment of non-covalent interactions in the quaternary structure of the protein. Disruption of homo-oligomers in order to return to the initial individual monomers often requires denaturation of the complex. Several enzymes, carrier proteins, scaffolding proteins, and transcriptional regulatory factors carry out their functions as homo-oligomers.
Distinct protein subunits interact in hetero-oligomers, which are essential to control several cellular functions. The importance of the communication between heterologous proteins is even more evident during cell signaling events and such interactions are only possible due to structural domains within the proteins (as described below).
Stable interactions vs. transient interactions
Stable interactions involve proteins that interact for a long time, taking part of permanent complexes as subunits, in order to carry out functional roles. These are usually the case of homo-oligomers (e.g. cytochrome c), and some hetero-oligomeric proteins, as the subunits of ATPase. On the other hand, a protein may interact briefly and in a reversible manner with other proteins in only certain cellular contexts – cell type, cell cycle stage, external factors, presence of other binding proteins, etc. – as it happens with most of the proteins involved in biochemical cascades. These are called transient interactions. For example, some G protein–coupled receptors only transiently bind to Gi/o proteins when they are activated by extracellular ligands, while some Gq-coupled receptors, such as muscarinic receptor M3, pre-couple with Gq proteins prior to the receptor-ligand binding. Interactions between intrinsically disordered protein regions to globular protein domains (i.e. MoRFs) are transient interactions.
Covalent vs. non-covalent
Covalent interactions are those with the strongest association and are formed by disulphide bonds or electron sharing. While rare, these interactions are determinant in some posttranslational modifications, as ubiquitination and SUMOylation. Non-covalent bonds are usually established during transient interactions by the combination of weaker bonds, such as hydrogen bonds, ionic interactions, Van der Waals forces, or hydrophobic bonds.
Role of water
Water molecules play a significant role in the interactions between proteins. The crystal structures of complexes, obtained at high resolution from different but homologous proteins, have shown that some interface water molecules are conserved between homologous complexes. The majority of the interface water molecules make hydrogen bonds with both partners of each complex. Some interface amino acid residues or atomic groups of one protein partner engage in both direct and water mediated interactions with the other protein partner. Doubly indirect interactions, mediated by two water molecules, are more numerous in the homologous complexes of low affinity. Carefully conducted mutagenesis experiments, e.g. changing a tyrosine residue into a phenylalanine, have shown that water mediated interactions can contribute to the energy of interaction. Thus, water molecules may facilitate the interactions and cross-recognitions between proteins.
Structure
The molecular structures of many protein complexes have been unlocked by the technique of X-ray crystallography. The first structure to be solved by this method was that of sperm whale myoglobin by Sir John Cowdery Kendrew. In this technique the angles and intensities of a beam of X-rays diffracted by crystalline atoms are detected in a film, thus producing a three-dimensional picture of the density of electrons within the crystal.
Later, nuclear magnetic resonance also started to be applied with the aim of unravelling the molecular structure of protein complexes. One of the first examples was the structure of calmodulin-binding domains bound to calmodulin. This technique is based on the study of magnetic properties of atomic nuclei, thus determining physical and chemical properties of the correspondent atoms or the molecules. Nuclear magnetic resonance is advantageous for characterizing weak PPIs.
Protein-protein interaction domains
Some proteins have specific structural domains or sequence motifs that provide binding to other proteins. Here are some examples of such domains:
Src homology 2 (SH2) domain
SH2 domains are structurally composed by three-stranded twisted beta sheet sandwiched flanked by two alpha-helices. The existence of a deep binding pocket with high affinity for phosphotyrosine, but not for phosphoserine or phosphothreonine, is essential for the recognition of tyrosine phosphorylated proteins, mainly autophosphorylated growth factor receptors. Growth factor receptor binding proteins and phospholipase Cγ are examples of proteins that have SH2 domains.
Src homology 3 (SH3) domain
Structurally, SH3 domains are constituted by a beta barrel formed by two orthogonal beta sheets and three anti-parallel beta strands. These domains recognize proline enriched sequences, as polyproline type II helical structure (PXXP motifs) in cell signaling proteins like protein tyrosine kinases and the growth factor receptor bound protein 2 (Grb2).
Phosphotyrosine-binding (PTB) domain
PTB domains interact with sequences that contain a phosphotyrosine group. These domains can be found in the insulin receptor substrate.
LIM domain
LIM domains were initially identified in three homeodomain transcription factors (lin11, is11, and mec3). In addition to this homeodomain proteins and other proteins involved in development, LIM domains have also been identified in non-homeodomain proteins with relevant roles in cellular differentiation, association with cytoskeleton and senescence. These domains contain a tandem cysteine-rich Zn2+-finger motif and embrace the consensus sequence CX2CX16-23HX2CX2CX2CX16-21CX2C/H/D. LIM domains bind to PDZ domains, bHLH transcription factors, and other LIM domains.
Sterile alpha motif (SAM) domain
SAM domains are composed by five helices forming a compact package with a conserved hydrophobic core. These domains, which can be found in the Eph receptor and the stromal interaction molecule (STIM) for example, bind to non-SAM domain-containing proteins and they also appear to have the ability to bind RNA.
PDZ domain
PDZ domains were first identified in three guanylate kinases: PSD-95, DlgA and ZO-1. These domains recognize carboxy-terminal tri-peptide motifs (S/TXV), other PDZ domains or LIM domains and bind them through a short peptide sequence that has a C-terminal hydrophobic residue. Some of the proteins identified as having PDZ domains are scaffolding proteins or seem to be involved in ion receptor assembling and receptor-enzyme complexes formation.
FERM domain
FERM domains contain basic residues capable of binding PtdIns(4,5)P2. Talin and focal adhesion kinase (FAK) are two of the proteins that present FERM domains.
Calponin homology (CH) domain
CH domains are mainly present in cytoskeletal proteins as parvin.
Pleckstrin homology domain
Pleckstrin homology domains bind to phosphoinositides and acid domains in signaling proteins.
WW domain
WW domains bind to proline enriched sequences.
WSxWS motif
Found in cytokine receptors
Properties of the interface
The study of the molecular structure can give fine details about the interface that enables the interaction between proteins. When characterizing PPI interfaces it is important to take into account the type of complex.
Parameters evaluated include size (measured in absolute dimensions Å2 or in solvent-accessible surface area (SASA)), shape, complementarity between surfaces, residue interface propensities, hydrophobicity, segmentation and secondary structure, and conformational changes on complex formation.
The great majority of PPI interfaces reflects the composition of protein surfaces, rather than the protein cores, in spite of being frequently enriched in hydrophobic residues, particularly in aromatic residues. PPI interfaces are dynamic and frequently planar, although they can be globular and protruding as well. Based on three structures – insulin dimer, trypsin-pancreatic trypsin inhibitor complex, and oxyhaemoglobin – Cyrus Chothia and Joel Janin found that between 1,130 and 1,720 Å2 of surface area was removed from contact with water indicating that hydrophobicity is a major factor of stabilization of PPIs. Later studies refined the buried surface area of the majority of interactions to 1,600±350 Å2. However, much larger interaction interfaces were also observed and were associated with significant changes in conformation of one of the interaction partners. PPIs interfaces exhibit both shape and electrostatic complementarity.
Regulation
Protein concentration, which in turn are affected by expression levels and degradation rates;
Protein affinity for proteins or other binding ligands;
Ligands concentrations (substrates, ions, etc.);
Presence of other proteins, nucleic acids, and ions;
Electric fields around proteins.
Occurrence of covalent modifications;
Experimental methods
There are a multitude of methods to detect them. Each of the approaches has its own strengths and weaknesses, especially with regard to the sensitivity and specificity of the method. The most conventional and widely used high-throughput methods are yeast two-hybrid screening and affinity purification coupled to mass spectrometry.
Yeast two-hybrid screening
This system was firstly described in 1989 by Fields and Song using Saccharomyces cerevisiae as biological model. Yeast two hybrid allows the identification of pairwise PPIs (binary method) in vivo, in which the two proteins are tested for biophysically direct interaction. The Y2H is based on the functional reconstitution of the yeast transcription factor Gal4 and subsequent activation of a selective reporter such as His3. To test two proteins for interaction, two protein expression constructs are made: one protein (X) is fused to the Gal4 DNA-binding domain (DB) and a second protein (Y) is fused to the Gal4 activation domain (AD). In the assay, yeast cells are transformed with these constructs. Transcription of reporter genes does not occur unless bait (DB-X) and prey (AD-Y) interact with each other and form a functional Gal4 transcription factor. Thus, the interaction between proteins can be inferred by the presence of the products resultant of the reporter gene expression. In cases in which the reporter gene expresses enzymes that allow the yeast to synthesize essential amino acids or nucleotides, yeast growth under selective media conditions indicates that the two proteins tested are interacting. Recently, software to detect and prioritize protein interactions was published.
Despite its usefulness, the yeast two-hybrid system has limitations. It uses yeast as main host system, which can be a problem when studying proteins that contain mammalian-specific post-translational modifications. The number of PPIs identified is usually low because of a high false negative rate; and, understates membrane proteins, for example.
In initial studies that utilized Y2H, proper controls for false positives (e.g. when DB-X activates the reporter gene without the presence of AD-Y) were frequently not done, leading to a higher than normal false positive rate. An empirical framework must be implemented to control for these false positives. Limitations in lower coverage of membrane proteins have been overcoming by the emergence of yeast two-hybrid variants, such as the membrane yeast two-hybrid (MYTH) and the split-ubiquitin system, which are not limited to interactions that occur in the nucleus; and, the bacterial two-hybrid system, performed in bacteria;
Affinity purification coupled to mass spectrometry
Affinity purification coupled to mass spectrometry mostly detects stable interactions and thus better indicates functional in vivo PPIs. This method starts by purification of the tagged protein, which is expressed in the cell usually at in vivo concentrations, and its interacting proteins (affinity purification). One of the most advantageous and widely used methods to purify proteins with very low contaminating background is the tandem affinity purification, developed by Bertrand Seraphin and Matthias Mann and respective colleagues. PPIs can then be analysed by mass spectrometry using different methods: chemical incorporation, biological or metabolic incorporation (SILAC), and label-free methods. Furthermore, network theory has been used to study the whole set of identified protein–protein interactions in cells.
Nucleic acid programmable protein array (NAPPA)
This system was first developed by LaBaer and colleagues in 2004 by using in vitro transcription and translation system. They use DNA template encoding the gene of interest fused with GST protein, and it was immobilized in the solid surface. Anti-GST antibody and biotinylated plasmid DNA were bounded in aminopropyltriethoxysilane (APTES)-coated slide. BSA can improve the binding efficiency of DNA. Biotinylated plasmid DNA was bound by avidin. New protein was synthesized by using cell-free expression system i.e. rabbit reticulocyte lysate (RRL), and then the new protein was captured through anti-GST antibody bounded on the slide. To test protein–protein interaction, the targeted protein cDNA and query protein cDNA were immobilized in a same coated slide. By using in vitro transcription and translation system, targeted and query protein was synthesized by the same extract. The targeted protein was bound to array by antibody coated in the slide and query protein was used to probe the array. The query protein was tagged with hemagglutinin (HA) epitope. Thus, the interaction between the two proteins was visualized with the antibody against HA.
Intragenic complementation
When multiple copies of a polypeptide encoded by a gene form a complex, this protein structure is referred to as a multimer. When a multimer is formed from polypeptides produced by two different mutant alleles of a particular gene, the mixed multimer may exhibit greater functional activity than the unmixed multimers formed by each of the mutants alone. In such a case, the phenomenon is referred to as intragenic complementation (also called inter-allelic complementation). Intragenic complementation has been demonstrated in many different genes in a variety of organisms including the fungi Neurospora crassa, Saccharomyces cerevisiae and Schizosaccharomyces pombe; the bacterium Salmonella typhimurium; the virus bacteriophage T4, an RNA virus and humans. In such studies, numerous mutations defective in the same gene were often isolated and mapped in a linear order on the basis of recombination frequencies to form a genetic map of the gene. Separately, the mutants were tested in pairwise combinations to measure complementation. An analysis of the results from such studies led to the conclusion that intragenic complementation, in general, arises from the interaction of differently defective polypeptide monomers to form a multimer. Genes that encode multimer-forming polypeptides appear to be common. One interpretation of the data is that polypeptide monomers are often aligned in the multimer in such a way that mutant polypeptides defective at nearby sites in the genetic map tend to form a mixed multimer that functions poorly, whereas mutant polypeptides defective at distant sites tend to form a mixed multimer that functions more effectively. Direct interaction of two nascent proteins emerging from nearby ribosomes appears to be a general mechanism for homo-oligomer (multimer) formation. Hundreds of protein oligomers were identified that assemble in human cells by such an interaction. The most prevalent form of interaction is between the N-terminal regions of the interacting proteins. Dimer formation appears to be able to occur independently of dedicated assembly machines. The intermolecular forces likely responsible for self-recognition and multimer formation were discussed by Jehle.
Other potential methods
Diverse techniques to identify PPIs have been emerging along with technology progression. These include co-immunoprecipitation, protein microarrays, analytical ultracentrifugation, light scattering, fluorescence spectroscopy, luminescence-based mammalian interactome mapping (LUMIER), resonance-energy transfer systems, mammalian protein–protein interaction trap, electro-switchable biosurfaces, protein–fragment complementation assay, as well as real-time label-free measurements by surface plasmon resonance, and calorimetry.
Computational methods
Computational prediction of protein–protein interactions
The experimental detection and characterization of PPIs is labor-intensive and time-consuming. However, many PPIs can be also predicted computationally, usually using experimental data as a starting point. However, methods have also been developed that allow the prediction of PPI de novo, that is without prior evidence for these interactions.
Genomic context methods
The Rosetta Stone or Domain Fusion method is based on the hypothesis that interacting proteins are sometimes fused into a single protein in another genome. Therefore, we can predict if two proteins may be interacting by determining if they each have non-overlapping sequence similarity to a region of a single protein sequence in another genome.
The Conserved Neighborhood method is based on the hypothesis that if genes encoding two proteins are neighbors on a chromosome in many genomes, then they are likely functionally related (and possibly physically interacting).
The Phylogenetic Profile method is based on the hypothesis that if two or more proteins are concurrently present or absent across several genomes, then they are likely functionally related. Therefore, potentially interacting proteins can be identified by determining the presence or absence of genes across many genomes and selecting those genes which are always present or absent together.
Text mining methods
Publicly available information from biomedical documents is readily accessible through the internet and is becoming a powerful resource for collecting known protein–protein interactions (PPIs), PPI prediction and protein docking. Text mining is much less costly and time-consuming compared to other high-throughput techniques. Currently, text mining methods generally detect binary relations between interacting proteins from individual sentences using rule/pattern-based information extraction and machine learning approaches. A wide variety of text mining applications for PPI extraction and/or prediction are available for public use, as well as repositories which often store manually validated and/or computationally predicted PPIs. Text mining can be implemented in two stages: information retrieval, where texts containing names of either or both interacting proteins are retrieved and information extraction, where targeted information (interacting proteins, implicated residues, interaction types, etc.) is extracted.
There are also studies using phylogenetic profiling, basing their functionalities on the theory that proteins involved in common pathways co-evolve in a correlated fashion across species. Some more complex text mining methodologies use advanced Natural Language Processing (NLP) techniques and build knowledge networks (for example, considering gene names as nodes and verbs as edges). Other developments involve kernel methods to predict protein interactions.
Machine learning methods
Many computational methods have been suggested and reviewed for predicting protein–protein interactions. Prediction approaches can be grouped into categories based on predictive evidence: protein sequence, comparative genomics, protein domains, protein tertiary structure, and interaction network topology. The construction of a positive set (known interacting protein pairs) and a negative set (non-interacting protein pairs) is needed for the development of a computational prediction model. Prediction models using machine learning techniques can be broadly classified into two main groups: supervised and unsupervised, based on the labeling of input variables according to the expected outcome.
In 2005, integral membrane proteins of Saccharomyces cerevisiae were analyzed using the mating-based ubiquitin system (mbSUS). The system detects membrane proteins interactions with extracellular signaling proteins Of the 705 integral membrane proteins 1,985 different interactions were traced that involved 536 proteins. To sort and classify interactions a support vector machine was used to define high medium and low confidence interactions. The split-ubiquitin membrane yeast two-hybrid system uses transcriptional reporters to identify yeast transformants that encode pairs of interacting proteins.
In 2006, random forest, an example of a supervised technique, was found to be the most-effective machine learning method for protein interaction prediction. Such methods have been applied for discovering protein interactions on human interactome, specifically the interactome of Membrane proteins and the interactome of Schizophrenia-associated proteins.
As of 2020, a model using residue cluster classes (RCCs), constructed from the 3DID and Negatome databases, resulted in 96-99% correctly classified instances of protein–protein interactions. RCCs are a computational vector space that mimics protein fold space and includes all simultaneously contacted residue sets, which can be used to analyze protein structure-function relation and evolution.
Databases
Large scale identification of PPIs generated hundreds of thousands of interactions, which were collected together in specialized biological databases that are continuously updated in order to provide complete interactomes. The first of these databases was the Database of Interacting Proteins (DIP).
Primary databases collect information about published PPIs proven to exist via small-scale or large-scale experimental methods. Examples: DIP, Biomolecular Interaction Network Database (BIND), Biological General Repository for Interaction Datasets (BioGRID), Human Protein Reference Database (HPRD), IntAct Molecular Interaction Database, Molecular Interactions Database (MINT), MIPS Protein Interaction Resource on Yeast (MIPS-MPact), and MIPS Mammalian Protein–Protein Interaction Database (MIPS-MPPI).<
Meta-databases normally result from the integration of primary databases information, but can also collect some original data.
Prediction databases include many PPIs that are predicted using several techniques (main article). Examples: Human Protein–Protein Interaction Prediction Database (PIPs), Interlogous Interaction Database (I2D), Known and Predicted Protein–Protein Interactions (STRING-db), and Unified Human Interactive (UniHI).
The aforementioned computational methods all depend on source databases whose data can be extrapolated to predict novel protein–protein interactions. Coverage differs greatly between databases. In general, primary databases have the fewest total protein interactions recorded as they do not integrate data from multiple other databases, while prediction databases have the most because they include other forms of evidence in addition to experimental. For example, the primary database IntAct has 572,063 interactions, the meta-database APID has 678,000 interactions, and the predictive database STRING has 25,914,693 interactions. However, it is important to note that some of the interactions in the STRING database are only predicted by computational methods such as Genomic Context and not experimentally verified.
Interaction networks
Information found in PPIs databases supports the construction of interaction networks. Although the PPI network of a given query protein can be represented in textbooks, diagrams of whole cell PPIs are frankly complex and difficult to generate.
One example of a manually produced molecular interaction map is the Kurt Kohn's 1999 map of cell cycle control. Drawing on Kohn's map, Schwikowski et al. in 2000 published a paper on PPIs in yeast, linking 1,548 interacting proteins determined by two-hybrid screening. They used a layered graph drawing method to find an initial placement of the nodes and then improved the layout using a force-based algorithm.
Bioinformatic tools have been developed to simplify the difficult task of visualizing molecular interaction networks and complement them with other types of data. For instance, Cytoscape is an open-source software widely used and many plugins are currently available. Pajek software is advantageous for the visualization and analysis of very large networks.
Identification of functional modules in PPI networks is an important challenge in bioinformatics. Functional modules means a set of proteins that are highly connected to each other in PPI network. It is almost similar problem as community detection in social networks. There are some methods such as Jactive modules and MoBaS. Jactive modules integrate PPI network and gene expression data where as MoBaS integrate PPI network and Genome Wide association Studies.
protein–protein relationships are often the result of multiple types of interactions or are deduced from different approaches, including co-localization, direct interaction, suppressive genetic interaction, additive genetic interaction, physical association, and other associations.
Signed interaction networks
Protein–protein interactions often result in one of the interacting proteins either being 'activated' or 'repressed'. Such effects can be indicated in a PPI network by "signs" (e.g. "activation" or "inhibition"). Although such attributes have been added to networks for a long time, Vinayagam et al. (2014) coined the term Signed network for them. Signed networks are often expressed by labeling the interaction as either positive or negative. A positive interaction is one where the interaction results in one of the proteins being activated. Conversely, a negative interaction indicates that one of the proteins being inactivated.
Protein–protein interaction networks are often constructed as a result of lab experiments such as yeast two-hybrid screens or 'affinity purification and subsequent mass spectrometry techniques. However these methods do not provide the layer of information needed in order to determine what type of interaction is present in order to be able to attribute signs to the network diagrams.
RNA interference screens
RNA interference (RNAi) screens (repression of individual proteins between transcription and translation) are one method that can be utilized in the process of providing signs to the protein–protein interactions. Individual proteins are repressed and the resulting phenotypes are analyzed. A correlating phenotypic relationship (i.e. where the inhibition of either of two proteins results in the same phenotype) indicates a positive, or activating relationship. Phenotypes that do not correlate (i.e. where the inhibition of either of two proteins results in two different phenotypes) indicate a negative or inactivating relationship. If protein A is dependent on protein B for activation then the inhibition of either protein A or B will result in a cell losing the service that is provided by protein A and the phenotypes will be the same for the inhibition of either A or B. If, however, protein A is inactivated by protein B then the phenotypes will differ depending on which protein is inhibited (inhibit protein B and it can no longer inactivate protein A leaving A active however inactivate A and there is nothing for B to activate since A is inactive and the phenotype changes). Multiple RNAi screens need to be performed in order to reliably appoint a sign to a given protein–protein interaction. Vinayagam et al. who devised this technique state that a minimum of nine RNAi screens are required with confidence increasing as one carries out more screens.
As therapeutic targets
Modulation of PPI is challenging and is receiving increasing attention by the scientific community. Several properties of PPI such as allosteric sites and hotspots, have been incorporated into drug-design strategies. Nevertheless, very few PPIs are directly targeted by FDA-approved small-molecule PPI inhibitors, emphasizing a huge untapped opportunity for drug discovery.
In 2014, Amit Jaiswal and others were able to develop 30 peptides to inhibit recruitment of telomerase towards telomeres by utilizing protein–protein interaction studies. Arkin and others were able to develop antibody fragment-based inhibitors to regulate specific protein-protein interactions.
As the "modulation" of PPIs not only includes the inhibition, but also the stabilization of quaternary protein complexes, molecules with this mechanism of action (so called molecular glues) are also intensively studied.
Examples
Tirobifan, inhibitor of the glycoprotein IIb/IIIa, used as a cardiovascular drug
Maraviroc, inhibitor of the CCR5-gp120 interaction, used as anti-HIV drug.
AMG-176, AZD5991, S64315, inhibitors of myeloid cell leukemia 1 (Mcl-1) protein and its interactions
See also
Glycan-protein interactions
3did
Allostery
Biological network
Biological machines
DIMA (database)
Enzyme catalysis
HitPredict
Human interactome
IsoBase
Multiprotein complex
Protein domain dynamics
Protein flexibility
Protein structure
Protein–protein interaction prediction
Protein–protein interaction screening
Systems biology
References
Further reading
External links
Protein–Protein Interaction Databases
Library of Modulators of Protein–Protein Interactions (PPI)
Proteomics
Signal transduction
Biophysics
Biochemistry methods
Biotechnology
Quantum biochemistry
Protein–protein interaction assays
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"nan",
"Atomic",
"Neurochemistry",
... |
2,162,434 | https://en.wikipedia.org/wiki/Chris%20Pancratz | Christopher Michael Pancratz (October 31, 1950 - August 2, 2003) was the Chairman of the Executive Committee of the National Space Society. He died August 2, 2003, of cancer.
Pancratz also operated a health care industry consulting business in the Northern Virginia area called PAN Development Associates (PANDA), from the late 1990s until shortly before his death, in which he was CEO and principal consultant.
Pancratz was active in community service, and served on the board of trustees of the Jaycees.
"The loss of Chris Pancratz robs the NSS of a valuable resource-and individual who combined the qualities of understanding and enthusiastically supporting the exploration of space, plus personal energy and organizational drive."
– Hugh Downs, Chairman of the NSS Board of Governors
References
1950 births
2003 deaths
American health care businesspeople
Space advocates | Chris Pancratz | [
"Astronomy"
] | 173 | [
"Outer space stubs",
"Outer space",
"Astronomy stubs"
] |
2,162,538 | https://en.wikipedia.org/wiki/Genetic%20predisposition | A genetic predisposition is a genetic characteristic which influences the possible phenotypic development of an individual organism within a species or population under the influence of environmental conditions. In medicine, genetic susceptibility to a disease refers to a genetic predisposition to a health problem, which may eventually be triggered by particular environmental or lifestyle factors, such as tobacco smoking or diet. Genetic testing is able to identify individuals who are genetically predisposed to certain diseases.
Behavior
Predisposition is the capacity humans are born with to learn things such as language and concept of self. Negative environmental influences may block the predisposition (ability) one has to do some things. Behaviors displayed by animals can be influenced by genetic predispositions. Genetic predisposition towards certain human behaviors is scientifically investigated by attempts to identify patterns of human behavior that seem to be invariant over long periods of time and in very different cultures.
For example, philosopher Daniel Dennett has proposed that humans are genetically predisposed to have a theory of mind because there has been evolutionary selection for the human ability to adopt the intentional stance. The intentional stance is a useful behavioral strategy by which humans assume that others have minds like their own. This assumption allows one to predict the behavior of others based on personal knowledge.
In 1951, Hans Eysenck and Donald Prell published an experiment in which identical (monozygotic) and fraternal (dizygotic) twins, ages 11 and 12, were tested for neuroticism. It is described in detail in an article published in the Journal of Mental Science in which Eysenck and Prell concluded that, "The factor of neuroticism is not a statistical artifact, but constitutes a biological unit which is inherited as a whole....neurotic Genetic predisposition is to a large extent hereditarily determined."
E. O. Wilson's book on sociobiology and his book Consilience discuss the idea of genetic predisposition of behaviors.
The field of evolutionary psychology explores the idea that certain behaviors have been selected for during the course of evolution.
Genetic discrimination in health insurance in US
In the United States, the Genetic Information Nondiscrimination Act, which was signed into law by President George W. Bush on May 21, 2008, prohibits discrimination in employment and health insurance based on genetic information.
See also
Human nature
Nature versus nurture
Behavioral genetics
Predispositioning Theory
Psychiatric genetics
Gene-environment correlation
Eugenics
Eggshell skull
MODY
Allergy
Oncogene
Quantitative trait locus
Genetic privacy
References
The results of this survey are discussed here (January 20, 1998).
A summary of U.S.A. executive orders and proposed legislation is compiled by the National Center for Genome Resources.
The Intentional Stance (MIT Press; Reprint edition 1989) ()
External links
Genetic discrimination fact sheet from the National Human Genome Research Institute.
Genetics
Behavioural sciences | Genetic predisposition | [
"Biology"
] | 592 | [
"Behavioural sciences",
"Behavior",
"Genetics"
] |
2,162,651 | https://en.wikipedia.org/wiki/Japp%E2%80%93Klingemann%20reaction | The Japp–Klingemann reaction is a chemical reaction used to synthesize hydrazones from β-keto-acids (or β-keto-esters) and aryl diazonium salts. The reaction is named after the chemists Francis Robert Japp and Felix Klingemann.
The hydrazone products of the Japp–Klingemann reaction are most often used as intermediates in syntheses of more complex organic molecules. For example, a phenylhydrazone product can be heated in the presence of strong acid to produce an indole via the Fischer indole synthesis.
If there is a leaving group elsewhere in the Japp–Klingemann product, the hydrazone instead can cyclize at that site via a substitution reaction to give a pyrazole. This process is a key part of the synthesis of and related compounds:
Reaction mechanism
To illustrate the mechanism, the Japp-Klingemann ester variation will be considered. The first step is the deprotonation of the β-keto-ester. The nucleophilic addition of the enolate anion 2 to the diazonium salt produces the azo compound 3. Intermediate 3 has been isolated in rare cases. However, in most cases, the hydrolysis of intermediate 3 produces a tetrahedral intermediate 4, which quickly decomposes to release the carboxylic acid 6. After hydrogen exchange, the final hydrazone 7 is produced.
References
Substitution reactions
Name reactions | Japp–Klingemann reaction | [
"Chemistry"
] | 308 | [
"Coupling reactions",
"Name reactions",
"Organic reactions"
] |
2,162,692 | https://en.wikipedia.org/wiki/Rapid%20thermal%20processing | Rapid thermal processing (RTP) is a semiconductor manufacturing process which heats silicon wafers to temperatures exceeding 1,000°C for not more than a few seconds. During cooling wafer temperatures must be brought down slowly to prevent dislocations and wafer breakage due to thermal shock. Such rapid heating rates are often attained by high intensity lamps or lasers. These processes are used for a wide variety of applications in semiconductor manufacturing including dopant activation, thermal oxidation, metal reflow and chemical vapor deposition.
Temperature control
One of the key challenges in rapid thermal processing is accurate measurement and control of the wafer temperature. Monitoring the ambient with a thermocouple has only recently become feasible, in that the high temperature ramp rates prevent the wafer from coming to thermal equilibrium with the process chamber. One temperature control strategy involves in situ pyrometry to effect real time control. Used for melting iron for welding purposes.
Rapid thermal anneal
Rapid thermal anneal (RTA) in rapid thermal processing is a process used in semiconductor device fabrication which involves heating a single wafer at a time in order to affect its electrical properties. Unique heat treatments are designed for different effects. Wafers can be heated in order to activate dopants, change film-to-film or film-to-wafer substrate interfaces, densify deposited films, change states of grown films, repair damage from ion implantation, move dopants or drive dopants from one film into another or from a film into the wafer substrate.
Rapid thermal anneals are performed by equipment that heats a single wafer at a time using either lamp based heating, a hot chuck, or a hot plate that a wafer is brought near. Unlike furnace anneals they are of short duration, processing each wafer in several minutes.
To achieve short annealing times and quick throughput, sacrifices are made in temperature and process uniformity, temperature measurement and control, and wafer stress.
RTP-like processing has found applications in another rapidly growing field: solar cell fabrication. RTP-like processing, in which the semiconductor sample is heated by absorbing optical radiation, has come to be used for many solar cell fabrication steps, including phosphorus diffusion for N/P junction formation and impurity gettering, hydrogen diffusion for impurity and defect passivation, and formation of screen-printed contacts using Ag-ink for the front and Al-ink for back contacts, respectively.
See also
Tamman and Hüttig temperature
References
External links
IEEE RTP Conference Proceedings
RTP-Technology
Different Heating Systems with Microwaves/Plasma
Semiconductor device fabrication | Rapid thermal processing | [
"Materials_science"
] | 526 | [
"Semiconductor device fabrication",
"Microtechnology"
] |
2,162,720 | https://en.wikipedia.org/wiki/Hitachi%20Flora%20Prius | The Hitachi Flora Prius was a range of personal computers marketed in Japan by Hitachi, Ltd. during the late 1990s.
The Flora Prius was preinstalled with both Microsoft Windows 98 as well as BeOS. It did not, however, have a dual-boot option as Microsoft reminded Hitachi of the terms of the Windows OEM license. In effect, two thirds of the hard drive was hidden from the end-user, and a series of complicated manipulations was necessary to activate the BeOS partition.
Models
FLORA Prius 330J came in three models:
330N40JB: Base version with no LCD Screen
3304ST40JB: Included a 14.1-inch super TFT color LCD Display
3304ST40JBT: Included a 14.1-inch super TFT color LCD Display and WinTV Video capture board
Base specifications
CPU: Pentium II processor (400 MHz)
RAM: 64 MB SDRAM
Hard Drive: 6.4 GB (2 GB for Windows 98 and 4.6 GB for BeOS)
CD-ROM Drive: 24X speed max.
100BASE-TX/10BASE-10
References
Hitachi products
BeOS | Hitachi Flora Prius | [
"Technology"
] | 242 | [
"BeOS",
"Computing stubs",
"Computing platforms",
"Computer hardware stubs"
] |
2,162,735 | https://en.wikipedia.org/wiki/Textile%20manufacturing | Textile manufacturing or textile engineering is a major industry. It is largely based on the conversion of fibre into yarn, then yarn into fabric. These are then dyed or printed, fabricated into cloth which is then converted into useful goods such as clothing, household items, upholstery and various industrial products.
Different types of fibres are used to produce yarn. Cotton remains the most widely used and common natural fiber making up 90% of all-natural fibers used in the textile industry. People often use cotton clothing and accessories because of comfort, not limited to different weathers. There are many variable processes available at the spinning and fabric-forming stages coupled with the complexities of the finishing and colouration processes to the production of a wide range of products.
History
Textile manufacturing in the modern era is an evolved form of the art and craft industries. Until the 18th and 19th centuries, the textile industry was a household work. It became mechanised in the 18th and 19th centuries, and has continued to develop through science and technology since the twentieth century. Specifically, ancient civilizations in India, Egypt, China, sub-Saharan Africa, Eurasia, South America, and North and East Africa all had some forms of textile production. The first book about textile manufacturing is considered to be 'A Treatise on the Art of Weaving' by John Murphy.
Processing of cotton
Cotton is the world's most important natural fibre. In the year 2007, the global yield was 25 million tons from 35 million hectares cultivated in more than 50 countries.
There are six stages to the manufacturing of cotton textiles:
Cultivating and Harvesting
Preparatory Processes
Spinning
Weaving or Knitting
Finishing
Marketing
Cultivating and harvesting
Cotton is grown in locations with long, hot, dry summers with plenty of sunshine and low humidity. Indian cotton, Gossypium arboreum, is finer but the staple is only suitable for hand processing. American cotton, Gossypium hirsutum, produces the longer staple needed for mechanised textile production. The planting season is from September to mid-November, and the crop is harvested between March and June. The cotton bolls are harvested by stripper harvesters and spindle pickers that remove the entire boll from the plant. The cotton boll is the seed pod of the cotton plant; attached to each of the thousands of seeds are fibres about 2.5 cm long. There is a higher rate of cotton being produced compared to the actual workers needed to produce the material. In 2013 a cotton farmer in Mississippi, Bower Flowers, produced around 13,000 bales of cotton in that year alone. This amount of cotton could be used to produce up to 9.4 million T-shirts.
Ginning
The seed cotton goes into a cotton gin. The cotton gin separates seeds and removes the "trash" (dirt, stems and leaves) from the fibre. In a saw gin, circular saws grab the fibre and pull it through a grating that is too narrow for the seeds to pass. A roller gin is used with longer-staple cotton. Here, a leather roller captures the cotton. A knife blade, set close to the roller, detaches the seeds by drawing them through teeth in circular saws and revolving brushes which clean them away. The ginned cotton fibre, known as lint, is then compressed into bales which are about 1.5 m tall and weigh almost 220 kg. Only 33% of the crop is usable lint. Commercial cotton is graded and priced according to its quality; this broadly relates to the average length of the staple and the variety of the plant. Longer-staple cotton (2½ in to 1¼ in) is called Egyptian, medium staple (1¼ in to ¾ in) is called American upland, and short staple (less than ¾ in) is called Indian. The cotton seed is pressed into cooking oil. The husks and meal are processed into animal feed, and the stems into paper.
Preparatory processes – preparation of yarn
Ginning, bale-making and transportation
Ginning, bale-making and transportation are done in the country of origin.
Opening and cleaning
Cotton is shipped to mills in large 500-pound bales. When the cotton comes out of a bale, it is all packed together and still contains vegetable matter. The bale is broken open using a machine with large spikes, called an opener. To fluff up the cotton and remove the vegetable matter, the cotton is sent through a picker or a similar machine. In a picker, the cotton is beaten with a beater bar to loosen it up. It is then fed through various rollers, which serve to remove the vegetable matter. The cotton, aided by fans, then collects on a screen and gets fed through more rollers where it emerges as a continuous soft fleecy sheet, known as a lap.
Blending, mixing and scutching
Scutching refers to the process of cleaning cotton of its seeds and other impurities. The first scutching machine was invented in 1797, but did not come into further mainstream use until after 1808 or 1809, when it was introduced and used in Manchester, England. By 1816, it had become generally adopted. The scutching machine worked by passing the cotton through a pair of rollers, and then striking it with iron or steel bars called beater bars or beaters. The beaters, which turn very quickly, strike the cotton hard and knock the seeds out. This process is done over a series of parallel bars so as to allow the seeds to fall through. At the same time, air is blown across the bars, which carries the cotton into a cotton chamber.
Carding
In the carding process, the fibres are separated and then assembled into a loose strand (sliver or tow). The cotton comes off of the picking machine in laps, and is then taken to carding machines. The carders line up the fibres neatly to make them easier to spin. The carding machine consists mainly of one big roller with smaller ones surrounding it. All of the rollers are covered in small teeth, and as the cotton is moved forwards, the teeth get finer (i.e. closer together). The cotton leaves the carding machine in the form of a sliver: a large rope of fibres. In a wider sense, carding can refer to these four processes:
Willowing: loosening the fibres
Lapping: removing the dust to create a flat sheet or lap of cotton
Carding: combing the tangled lap into a thick rope of 1/2 inch in diameter, a sliver
Drawing: where a drawing frame combines 4 slivers into one, repeated for increased quality
Combing is optional, but is used to remove the shorter fibres, creating a stronger yarn.
Several slivers are combined. Each sliver will have thin and thick spots, and by combining several slivers together, a more consistent size can be reached. Since combining several slivers produces a very thick rope of cotton fibres, the slivers are separated into rovings. Generally speaking, for machine processing, a roving is about the width of a pencil. These rovings (or slubbings) are then what are used in the spinning process.
Spinning – yarn manufacture
Spinning
Most spinning today is done using break, or open-end spinning. This is a technique where the fibres are blown by air into a rotating drum, where they attach themselves to the tail of formed yarn that is continually being drawn out of the chamber. Other methods of break spinning use needles and electrostatic forces. This method has replaced the older methods of ring and mule spinning. It is also easily adapted for artificial fibres.
The spinning machines takes the roving, thins it and twists it, creating yarn which it winds onto a bobbin.
In mule spinning the roving is pulled off a bobbin and fed through rollers, which are feeding at several different speeds. This thins the roving at a consistent rate. If the roving was not a consistent size, then this step could cause a break in the yarn, or jam the machine. The yarn is twisted through the spinning of the bobbin as the carriage moves out, and is rolled onto a cylinder called a spindle, which then produces a cone-shaped bundle of fibres known as a "cop", as the carriage returns. Mule spinning produces a finer thread than ring spinning.
The mule was an intermittent process, as the frame advanced and returned a distance of five feet. It was the descendant of the 1779 Crompton device. It produces a softer, less twisted thread that was favoured for fine fabrics and wefts.
The ring was a descendant of the Arkwright Water frame of 1769. It was a continuous process, the yarn was coarser, had a greater twist and was stronger, thus suitable for use as warp thread. Ring spinning is slow due to the distance the thread must pass around the ring.
Sewing thread was made of several threads twisted together, or doubled.
Checking
This is the process where each of the bobbins is rewound to give a tighter bobbin.
Folding and twisting
Plying is done by pulling yarn from two or more bobbins and twisting it together, in a direction opposite to the one it was spun in. Depending on the weight desired, the cotton may or may not be plied, and the number of strands twisted together varies.
Gassing
Gassing is the process of passing yarn very rapidly through a series of Bunsen gas flames in a gassing frame, to burn off the projecting fibres and to make the thread round and smooth and bright. Only the better qualities of yarn are gassed, like the kinds used for voiles, poplins, venetians, gabardines, Egyptian cottons, etc. The thread loses around 5-8% of its weight if it's gassed. The gassed yarn is darker in shade afterwards, but should not be scorched.
Measurements
Cotton Counts: Refers to the thickness of the cotton yarn where 840 yards of yarns weighs . 10-count cotton means that of yarn weighs . This is coarser than 40-count cotton where 40x840 yards are needed. In the United Kingdom, counts from 10 to 40 are coarse (Oldham Counts), 40 to 80 are medium counts and above 80 is a fine count. In the United States ones, counts up to the 20s are coarse counts.
Hank: A length of 7 leas or 840 yards (the worsted hank is only 560 yd)
Thread: A length of 54 in (the circumference of a warp beam)
Bundle: Usually 10 lb
Lea: A length of 80 threads or 120 yards
Denier: this is an alternative method. It is defined as a number that is equivalent to the weight in grams of 9000m of a single yarn. 15 denier is finer than 30 denier.
Tex: is the weight in grams of 1 km of yarn.
Weaving
The weaving process uses a loom. The lengthwise threads are known as the warp, and the crosswise threads are known as the weft. The warp, which must be strong, needs to be presented to loom on a warp beam. The weft passes across the loom in a shuttle that carries the yarn on a pirn. These pirns are automatically changed by the loom. Thus, the yarn needs to be wrapped onto a beam, and onto pirns before weaving can commence.
Winding
After being spun and plied, the cotton thread is taken to a warping room where the winding machine takes the required length of yarn and winds it onto warpers' bobbins.
Warping or beaming
Racks of bobbins are set up to hold the thread while it is wound onto the warp beam of a loom. Because the thread is fine, often three of these would be combined to get the desired number of ends.
Sizing
A sizing machine is needed for strengthening the warp by adding starch, to reduce breakage.
Drawing in, Looming
The process of drawing each end of the warp separately through the dents of the reed and the eyes of the healds, in the order indicated by the draft.
Pirning (processing the weft)
A pirn-winding frame was used to transfer the weft from cheeses of yarn onto the pirns that would fit into the shuttle.
Weaving
At this point, the thread is woven. Depending on the era, one person could manage anywhere from 3 to 100 machines. In the mid-nineteenth century, four was the standard number. A skilled weaver in 1925 could run 6 Lancashire Looms. As time progressed, new mechanisms were added that stopped the loom any time something went wrong. The mechanisms checked for such things as broken warp or weft threads, the shuttle going straight across, and if the shuttle was empty. Forty of these Northrop Looms or automatic looms could be operated by one skilled worker.
The three primary movements of a loom are shedding, picking, and beating-up.
Shedding: The operation of dividing the warp into two lines so that the shuttle can pass between these lines. There are two general kinds of sheds: "open" and "closed." In an open shed, the warp threads are moved from one line to the other when the pattern requires it. In a closed shed, the warp threads are all placed level.
Picking: The operation of projecting the shuttle from side to side of the loom through the division in the warp threads. This is done by the overpick or underpick motions. The overpick is suitable for quick-running looms, whereas the underpick is best for heavy or slow looms.
Beating-up: The third primary movement of the loom when making cloth: the action of the reed as it drives each pick of weft to the fell of the cloth.
The Lancashire Loom was the first semi-automatic loom. Jacquard looms and Dobby looms are looms that have sophisticated methods of shedding. They may be separate looms or mechanisms added to a plain loom. A Northrop Loom was fully automatic and was mass-produced between 1909 and the mid-1960s. Modern looms run faster and do not use a shuttle: there are air jet looms, water jet looms, and rapier looms.
Measurements
Ends and Picks: Picks refer to the weft, ends refer to the warp. The coarseness of the cloth can be expressed as the number of picks and ends per quarter-inch square, or per inch square. Ends is always written first. For example: Heavy domestics are made from coarse yarns, such as 10's to 14's warp and weft, and about 48 ends and 52 picks.
Associated job titles
Associated job titles include piecer, scavenger, weaver, tackler, draw boy.
Issues
When a hand loom was located in the home, children helped with the weaving process from an early age. Piecing needs dexterity, and a child can be as productive as an adult. When weaving moved from the home to the mill, children were often allowed to help their older sisters, and laws had to be made to prevent child labour from becoming established. The working conditions of cotton production were often harsh, with long hours, low pay, and dangerous machinery. Children, above all, were also prone to physical abuse and often forced to work in unsanitary conditions. It should also be noted that Children who worked in handlooms often faced extreme poverty and were unable to obtain an education. The working conditions of cotton production were often harsh, with long hours, low pay, and dangerous machinery. Children, above all, were also prone to physical abuse and often forced to work in unsanitary conditions. It should also be noted that Children who worked in handlooms often faced extreme poverty and were unable to obtain an education.
Knitting – fabric manufacture
Knitting by machine is done in two different ways; warp and weft. Weft knitting (as seen in the pictures) is similar in method to hand knitting with stitches all connected to each other horizontally. Various weft machines can be configured to produce textiles from a single spool of yarn or multiple spools, depending on the size of the machine cylinder (in which the needles are bedded). In a warp knit, there are many pieces of yarn and there are vertical chains, zigzagged together by crossing the cotton yarn.
Warp knits do not stretch as much as a weft knits, and they are run-resistant. A weft knit is not run-resistant, but it has more stretch. This is especially true if spools of elastane are processed from separate spool containers and interwoven through the cylinder with cotton yarn, giving the finished product more flexibility and preventing it from having a 'baggy' appearance. The average t-shirt is a weft knit.
Finishing – processing of textiles
Finishing is a broad range of physical and chemical processes/treatments that complete one stage of textile manufacturing, sometimes in preparation for the next step. Finishing adds value to the product and makes it more attractive, useful and functional for the end-user. Fresh off the loom, cotton fabric not only contains impurities, including warp size, but it also requires further treatment to develop its full potential and to add to its value.
Desizing
Depending on the size that has been used, the cloth may be steeped in a dilute acid and then rinsed, or enzymes may be used to break down the size.
Scouring
Scouring is a chemical washing process carried out on cotton fabric to remove natural waxes and non-fibrous impurities (like the remains of seed fragments) from the fibres and any soiling or dirt that might remain. Scouring is usually carried out in iron vessels called kiers. The fabric is boiled in an alkali solution, which forms a soap with free fatty acids. A kier is usually enclosed, so the solution of sodium hydroxide can be boiled under pressure, excluding oxygen, which would degrade the cellulose in the fibre. If the appropriate reagents are used, scouring will also remove size from the fabric, although desizing often precedes scouring and is considered to be a separate process. Preparation and scouring are prerequisites to most of the other finishing processes. At this stage, even the most naturally white cotton fibres are yellowish, and bleaching is required.
Bleaching
Bleaching improves whiteness by removing natural colouration and whatever impurities remain in the cotton; the degree of bleaching is determined by the levels of whiteness and absorbency required of the fabric. Cotton, being a vegetable fibre, is bleached using an oxidizing agent, such as diluted sodium hypochlorite or diluted hydrogen peroxide. If the fabric is to be dyed a deep shade, then lower levels of bleaching are acceptable. However, for white bedding and for medical applications, the highest levels of whiteness and absorbency are essential.
Mercerising
A further possibility is mercerising, during which the fabric is treated with a caustic soda solution, to cause swelling of the fibres. This results in improved lustre, strength and dye affinity. Cotton is mercerised under tension, and all alkali must be washed out before the tension is released, or shrinkage will take place.
Many other chemical treatments may be applied to cotton fabrics to produce low flammability, crease-resistance and other qualities, but the four most important non-chemical finishing treatments are:
Singeing
Singeing is designed to burn off the surface fibres from the fabric to produce smoothness. The fabric passes over brushes to raise the fibres, then passes over a plate heated by gas flames.
Raising
During raising, the fabric surface is treated with sharp teeth to lift the surface fibres, thereby imparting downiness, softness and warmth, as in flannelette.
Calendering
Calendering is a process in which the fabric is passed between heated rollers to generate smooth, polished or embossed effects.
Shrinking (sanforising)
Sanforisation is a form of mechanical pre-shrinking, so that the fabric will shrink less upon laundering.
Dyeing
Dyeing is commonly carried out with an anionic direct dye by completely immersing the fabric (or yarn) in an aqueous dye bath according to a prescribed procedure. For improved fastness to washing, rubbing and light, further dyeing methods can be used. These require more complex chemistry during processing, and are thus more expensive to apply.
Printing
Printing is the application of colour in the form of a paste or ink to the surface of a fabric in a predetermined pattern. It can be described as a form of localised dyeing. Printing designs onto previously dyed fabric is also possible.
Economic, environmental and political consequences of cotton manufacture
Production of cotton requires arable land.
In addition, cotton is farmed intensively and uses large amounts of fertilizer and 25% of the world's insecticides. Native Indian varieties of cotton were rainwater fed, but modern hybrids used for the mills need irrigation, which spreads pests. The 5% of cotton-bearing land in India uses 55% of all pesticides used in India.
The consumption of energy in form of water and electricity is relatively high, especially in processes like washing, de-sizing, bleaching, rinsing, dyeing, printing, coating and finishing. Processing is time-consuming. The major portion of water in textile industry is used for wet processing of textile (70 per cent). Approximately 25 per cent of energy in the total textile production like fibre production, spinning, twisting, weaving, knitting, clothing manufacturing etc. is used in dyeing. About 34 per cent of energy is consumed in spinning, 23 per cent in weaving, 38 per cent in chemical wet processing and five per cent in miscellaneous processes. Power dominates consumption pattern in spinning and weaving, while thermal energy is the major factor for chemical wet processing.
Cotton acts as a carbon sink as it contains cellulose and this contains 44.44% carbon. However, due to carbon emissions from fertiliser application, use of mechanized tools to harvest the cotton and so forth cotton manufacture tends to emit more CO2 than is stored in the form of cellulose.
The growth of cotton is divided into two segments i.e. organic and genetically modified. Cotton crop provides livelihood to millions of people but its production is becoming expensive because of high water consumption, use of expensive pesticides, insecticides and fertiliser. Genetically modified products aim to increase disease resistance and reduce the water required. The organic sector in India was worth $583 million. Genetically modified cotton, in 2007, occupied 43% of cotton growing areas in India.
Before mechanisation, cotton was harvested manually by farmers in India and by African slaves in America. In 2012 Uzbekistan was a major exporter of cotton and uses manual labour during the harvest. Human rights groups have expressed concerns over healthcare professionals and children being forced to pick cotton.
There was a 1.5 million tonne cotton deficit in 2018 due to adverse weather conditions, limited water, and pest issues.
Processing of other vegetable fibres
Flax
Flax is a bast fibre, which means it comes in bundles under the bark of the Linum usitatissimum plant. The plant flowers and is harvested. It is subjected to retting, breaking, scutching, hackling or combing. It is then treated like cotton.
Jute
Jute is a bast fibre, which comes from the inner bark of the plants of the Corchorus genus. It is retted like flax, sundried and baled. When spinning a small amount of oil must be added to the fibre. It can be bleached and dyed. It was used for sacks and bags but is now used for the backing for carpets. Jute can be blended with other fibres to make composite fabrics and work continues in Bangladesh to refine the processes and extend the range of usage possible. In the 1970s, jute-cotton composite fabrics were known as jutton fabrics.
Hemp
Hemp is a bast fibre from the inner bark of Cannabis sativa. It is difficult to bleach, and is used for making cord and rope. It is subject to retting, separating and pounding
Other bast fibres
These bast fibres can also be used: kenaf, urena, ramie, nettle.
Other leaf fibres
Sisal is the main leaf fibre used; others are abacá and henequen.
Processing of wool and silk
Wool
Wool comes from domesticated sheep. It is used to create two kinds of yarn, woolens and worsteds. These are distinguished by the direction of the wool fibres in relation to the thread; woolens are perpendicularly arranged, allowing for fluffy yarns that trap air, while worsteds have parallel fibres, creating a strong and smooth yarn.
Modern sheep have uniform fleeces, while primitive and landrace sheep often have dual coats; a soft, short under layer and a hardier, coarser, and longer guard layer. These can be sorted to be processed separately, or spun together. The differing characteristics of each coat allows for very different yarn; the guard hairs can be used for durable outerwear, while the inner coat is what is traditionally used to produce the ultrafine wedding ring shawls across Europe. Spinning them together, like in lopi, produces a unique yarn that combines the strength of the guard hairs with the loft and softness of the undercoat.
Wool that has never been used is known as virgin wool and can be mixed with wool that has been recovered from rags. "Shoddy" is the term for recovered wool that is not matted, while "mungo" comes from felted wool. Extract is recovered chemically from mixed cotton/wool fabrics.
The fleece is shorn in one piece from the sheep. Ideally, the wool is cut as close to the skin as possible to maximise fibre length. Going over the same spot twice produces small fibres that will produce pills in finished fabric, something that skilled shearers are usually able to avoid. This is then skirted to remove the soiled wool from around the legs and anus, graded, and baled. Grading is done on quality as well as length of the fibres. Long wool fibres can be up to 15 in, but anything over 2.5 inches is suitable for combing into worsteds. Fibres less than that form short wool and are described as clothing or carding wool, and are best suited for the jumbled arrangement of woolens.
At the mill the wool is scoured in a detergent to remove grease (the yolk) and impurities. This is done mechanically in the opening machine. Vegetable matter can be removed chemically using sulphuric acid (carbonising). Washing uses a solution of soap and sodium carbonate. The wool is oiled before carding or combing.
Woollens: Fibre is prepared through carding, which arranged fibres perpendicular to the spun yarn. It can also use noils from the worsted combs, mungo, and shoddy.
Worsteds
Combing: Oiled slivers are wound into laps, and placed in the circular comber. The worsted yarn gathers together to form a top. The shorter fibres or noils remain behind and are removed with a knife.
Angora
Silk
The processes in silk production are similar to those of cotton but take account that reeled silk is a continuous fibre. The terms used are different.
Opening bales. Assorting skeins: where silk is sorted by colour, size and quality, scouring: where the silk is washed in water of 40 degrees for 12 hours to remove the natural gum, drying: either by steam heating or centrifuge, softening: by rubbing to remove any remaining hard spots.
Silk throwing (winding). The skeins are placed on a reel in a frame with many others. The silk is wound onto spools or bobbins.
Doubling and twisting. The silk is far too fine to be woven, so now it is doubled and twisted to make the warp, known as organzine, and the weft, known as tram. In organzine each single is given a few twists per inch (tpi), and combine with several other singles counter twisted hard at 10 to 14 tpi. In tram the two singles are doubled with each other with a light twist, 3 to 6 tpi. Sewing thread is two tram threads, hard twisted, and machine-twist is made of three hard-twisted tram threads. Tram for the crepe process is twisted at up to 80 tpi to make it 'kick up'.
Stretching. The thread is tested for consistent size. Any uneven thickness is stretched out. The resulting thread is reeled into containing 500 yd to 2500 yd. The skeins are about 50 inches in loop length.
Dyeing: the skeins are scoured again, and discoloration removed with a sulphur process. This weakens the silk. The skeins are now tinted or dyed. They are dried and rewound onto bobbins, spools and skeins. Looming, and the weaving process on power looms is the same as with cotton.
Weaving. The organzine is now warped. This is a similar process to in cotton. Firstly, thirty threads or so are wound onto a warping reel, and then using the warping reels, the threads are beamed. A thick layer of paper is laid between each layer on the beam to stop entangling.
Environmental consequences of wool and silk manufacture
Both wool and silk require farmland. Whereas silkworms require mulberry leaves, sheep eat grass, clover, forbs and other pasture plants. Sheep, like all ruminants emit via their digestive system. Also, their pastures may sometimes be fertilised which further increases emissions.
Processing of synthetic fibres
Synthetic fibres are the result of extensive development by scientists to improve upon the naturally occurring animal and plant fibres. In general, synthetic fibres are created by forcing, or extruding, fibre forming materials through holes (called spinnerets) into the air, thus forming a thread. Before synthetic fibres were developed, cellulose fibres were made from natural cellulose, which comes from plants.
The first artificial fibre, known as art silk from 1799 onwards, became known as viscose around 1894, and finally rayon in 1924. A similar product known as cellulose acetate was discovered in 1865. Rayon and acetate are both artificial fibres, but not truly synthetic, being made from wood. Although these artificial fibres were discovered in the mid-nineteenth century, successful modern manufacture began much later in the 1930s. Nylon, the first synthetic fibre, made its debut in the United States as a replacement for silk, and was used for parachutes and other military uses.
The techniques used to process these fibres in yarn are essentially the same as with natural fibres, modifications have to be made as these fibres are of great length, and have no texture such as the scales in cotton and wool that aid meshing.
Unlike natural fibres, produced by plants, animals or insects, synthetic fibres are made from fossil fuels, and thus require no farmland.
See also
Clothing technology
Dref Friction Spinning
Fashion design
Glossary of textile manufacturing
Textile from algae
Textile design
Timeline of clothing and textiles technology
Wet processing engineering
References
Bibliography
External links
Cotton Year Book 1910 (Textile Mercury) Descriptions and calculations for purchasing all cotton processing machines.
1921 John Hetherington & Sons Catalogue Descriptions and illustrations of principal machines.
Textile industry | Textile manufacturing | [
"Physics",
"Engineering"
] | 6,539 | [
"Applied and interdisciplinary physics",
"Textile engineering"
] |
2,163,161 | https://en.wikipedia.org/wiki/List%20of%20plant%20communities%20in%20the%20British%20National%20Vegetation%20Classification | The following is the list of the 286 plant communities which comprise the British National Vegetation Classification (NVC). These are grouped by major habitat category, as used in the five volumes of British Plant Communities, the standard work describing the NVC.
Woodland and scrub communities
The following 25 communities are described in Volume 1 of British Plant Communities. For an article summarising these communities see Woodland and scrub communities in the British National Vegetation Classification system.
W1 Salix cinerea - Galium palustre woodland
W2 Salix cinerea - Betula pubescens - Phragmites australis woodland
W3 Salix pentandra - Carex rostrata woodland
W4 Betula pubescens - Molinia caerulea woodland
W5 Alnus glutinosa - Carex paniculata woodland
W6 Alnus glutinosa - Urtica dioica woodland
W7 Alnus glutinosa - Fraxinus excelsior - Lysimachia nemorum woodland
W8 Fraxinus excelsior - Acer campestre - Mercurialis perennis woodland
W9 Fraxinus excelsior - Sorbus aucuparia - Mercurialis perennis woodland
W10 Quercus robur - Pteridium aquilinum - Rubus fruticosus woodland
W11 Quercus petraea - Betula pubescens - Oxalis acetosella woodland
W12 Fagus sylvatica - Mercurialis perennis woodland
W13 Taxus baccata woodland
W14 Fagus sylvatica - Rubus fruticosus woodland
W15 Fagus sylvatica - Deschampsia flexuosa woodland
W16 Quercus spp. - Betula spp. - Deschampsia flexuosa woodland
W17 Quercus petraea - Betula pubescens - Dicranum majus woodland
W18 Pinus sylvestris - Hylocomium splendens woodland
W19 Juniperus communis ssp. communis - Oxalis acetosella woodland
W20 Salix lapponum - Luzula sylvatica scrub
W21 Crataegus monogyna - Hedera helix scrub
W22 Prunus spinosa - Rubus fruticosus scrub
W23 Ulex europaeus - Rubus fruticosus scrub
W24 Rubus fruticosus - Holcus lanatus underscrub
W25 Pteridium aquilinum - Rubus fruticosus underscrub
Mires
The following 38 communities are described in Volume 2 of British Plant Communities. For an article summarising these communities see Mires in the British National Vegetation Classification system.
M1 Sphagnum auriculatum bog pool community
M2 Sphagnum cuspidatum/recurvum bog pool community
M3 Eriophorum angustifolium bog pool community
M4 Carex rostrata - Sphagnum recurvum mire
M5 Carex rostrata - Sphagnum squarrosum mire
M6 Carex echinata - Sphagnum recurva/auriculatum mire
M7 Carex curta - Sphagnum russowii mire
M8 Carex rostrata - Sphagnum warnstorfii mire
M9 Carex rostrata - Calligeron cuspidatum/giganteum mire
M10 Carex dioica - Pinguicula vulgaris mire Pinguiculo-Caricetum dioicae Jones 1973 emend.
M11 Carex demissa - Saxifraga aizoides mire Carici-Saxifragetum aizoidis McVean & Ratcliffe 1962 emend.
M12 Carex saxatilis mire Caricetum saxatilis McVean & Ratcliffe 1962
M13 Schoenus nigricans - Juncus subnodulosus mire Schoenetum nigricantis Koch 1926
M14 Schoneus nigricans - Narthecium ossifragum mire
M15 Scirpus cespitosus - Erica tetralix wet heath
M16 Erica tetralix - Sphagnum compactum wet heath Ericetum tetralicis Schwickerath 1933
M17 Scirpus cespitosus - Eriophorum vaginatum blanket mire
M18 Erica tetralix - Sphagnum papillosum raised and blanket mire
M19 Calluna vulgaris - Eriophorum vaginatum blanket mire
M20 Eriophorum vaginatum raised and blanket mire
M21 Narthecium ossifragum - Sphagnum papillosum valley mire Narthecio-Sphagnetum euatlanticum Duvigneaud 1949
M22 Juncus subnodulosus - Cirsium palustre fen-meadow
M23 Juncus effusus/acutiflorus - Galium palustre rush-pasture
M24 Molinia caerulea - Cirsium dissectum fen-meadow Cirsium-Molinietum caeruleae Sissingh & De Vries 1942 emend.
M25 Molinia caerulea - Potentilla erecta mire
M26 Molinia caerulea - Crepis paludosa mire
M27 Filipendula ulmaria - Angelica sylvestris mire
M28 Iris pseudacorus - Filipendula ulmaria mire Filipendulo-Iridetum pseudacori Adam 1976 emend.
M29 Hypericum elodes - Potamogeton polygonifolius soakway Hyperico-Potametum polygonifolii (Allorge 1921) Braun-Blanquet & Tüxen 1952
M30 Related vegetation of seasonally-inundated habitats Hydrocotyla-Baldellion Tüxen & Dierssen 1972
M31 Anthelia judacea - Sphagnum auriculatum spring Sphagno auriculati-Anthelietum judaceae Shimwell 1972
M32 Philonotis fontana - Saxifraga stellaris spring Philonoto-Saxifragetum stellaris Nordhagen 1943
M33 Pohlia wahlenbergii var. glacialis spring Pohlietum glacialis McVean & Ratcliffe 1962
M34 Carex demissa - Koenigia islandica flush
M35 Ranunculus omiophyllus - Montia fontana rill
M36 Lowland springs and streambanks of shaded situations Cardaminion (Maas 1959) Westhoff & den Held 1969
M37 Cratoneuron commutatum - Festuca rubra spring
M38 Cratoneuron commutatum - Carex nigra spring
Heaths
The following 22 communities are described in Volume 2 of British Plant Communities. For an article summarising these communities see Heaths in the British National Vegetation Classification system.
H1 Calluna vulgaris - Festuca ovina heath
H2 Calluna vulgaris - Ulex minor heath
H3 Ulex minor - Agrostis curtisii heath
H4 Ulex gallii - Agrostis curtisii heath
H5 Erica vagans - Schoenus nigricans heath
H6 Erica vagans - Ulex europaeus heath
H7 Calluna vulgaris - Scilla verna heath
H8 Calluna vulgaris - Ulex gallii heath
H9 Calluna vulgaris - Deschampsia flexuosa heath
H10 Calluna vulgaris - Erica cinerea heath
H11 Calluna vulgaris - Carex arenaris heath
H12 Calluna vulgaris - Vaccinium myrtillus heath
H13 Calluna vulgaris - Cladonia arbuscula heath
H14 Calluna vulgaris - Racomitrium lanuginosum heath
H15 Calluna vulgaris - Juniperus communis ssp. nana heath
H16 Calluna vulgaris - Arctostaphylos uva-ursi heath
H17 Calluna vulgaris - Arctostaphylos alpinus heath
H18 Vaccinium myrtillus - Deschampsia flexuosa heath
H19 Vaccinium myrtillus - Cladonia arbuscula heath
H20 Vaccinium myrtillus - Racomitrium lanuginosum heath
H21 Calluna vulgaris - Vaccinium myrtillus - Sphagnum capillifolium heath
H22 Vaccinium myrtillus - Rubus chamaemorus heath
Mesotrophic grasslands
The following 13 communities are described in Volume 3 of British Plant Communities. For an article summarising these communities see Mesotrophic grasslands in the British National Vegetation Classification system.
MG1 Arrhenatherum elatius grassland Arrhenatheretum elatioris Br.-Bl. 1919
MG2 Arrhenatherum elatius - Filipendula ulmaria tall-herb grassland Filipendulo-Arrhenatheretum elatioris Shimwell 1968a
MG3 Anthoxanthum odoratum - Geranium sylvaticum grassland
MG4 Alopecurus pratensis - Sanguisorba officinalis grassland
MG5 Cynosurus cristatus - Centaurea nigra grassland Centaureo-Cynosuretum cristati Br.-Bl. & Tx 1952
MG6 Lolium perenne - Cynosurus cristatus grassland Lolio-Cynosuretum cristati (Br.-Bl. & De Leeuw 1936) R. Tx 1937
MG7 Lolium perenne leys and related grasslands Lolio-Plantaginion Sissingh 1969 p.p.
MG8 Cynosurus cristatus - Caltha palustris grassland
MG9 Holcus lanatus - Deschampsia cespitosa grassland
MG10 Holcus lanatus - Juncus effusus rush-pasture Holco-Juncetum effusi Page 1980
MG11 Festuca rubra - Agrostis stolonifera - Potentilla anserina grassland
MG12 Festuca arundinacea grassland Potentillo-Festucetum arundinaceae Nordhagen 1940
MG13 Agrostis stolonifera - Alopecurus geniculatus grassland
MG14 Carex nigra - Agrostis stolonifera - Senecio aquaticus grassland
MG15 Alopecurus pratensis - Poa trivialis - Cardamine pratensis grassland
MG16 Agrostis stolonifera - Eleocharis palustris grassland
Calcicolous grasslands
The following 14 communities are described in Volume 3 of British Plant Communities. For an article summarising these communities see Calcicolous grasslands in the British National Vegetation Classification system.
CG1 Festuca ovina - Carlina vulgaris grassland
CG2 Festuca ovina - Avenula pratensis grassland
CG3 Bromus erectus grassland
CG4 Brachypodium pinnatum grassland
CG5 Bromus erectus - Brachypodium pinnatum grassland
CG6 Avenula pubescens grassland
CG7 Festuca ovina - Hieracium pilosella - Thymus praecox/pulegioides grassland
CG8 Sesleria albicans - Scabiosa columbaria grassland
CG9 Sesleria albicans - Galium sterneri grassland
CG10 Festuca ovina - Agrostis capillaris - Thymus praecox grassland
CG11 Festuca ovina - Agrostis capillaris - Alchemilla alpina grass-heath
CG12 Festuca ovina - Alchemilla alpina - Silene acaulis dwarf-herb community
CG13 Dryas octopetala - Carex flacca heath
CG14 Dryas octopetala - Silene acaulis ledge community
Calcifugous grasslands and montane communities
The following 21 communities are described in Volume 3 of British Plant Communities. For an article summarising these communities see Calcifugous grasslands and montane communities in the British National Vegetation Classification system.
U1 Festuca ovina - Agrostris capillaris - Rumex acetosella grassland
U2 Deschampsia flexuosa grassland
U3 Agrostis curtisii grassland
U4 Festuca ovina - Agrostris capillaris - Galium saxatile grassland
U5 Nardus stricta - Galium saxatile grassland
U6 Juncus squarrosus - Festuca ovina grassland
U7 Nardus stricta - Carex bigelowii grass-heath
U8 Carex bigelowii - Polytrichum alpinum sedge-heath
U9 Juncus trifidus - Racomitrium lanuginosum rush-heath
U10 Carex bigelowii - Racomitrium lanuginosum moss-heath
U11 Polytrichum sexangulare - Kiaeria starkei snow-bed
U12 Salix herbacea - Racomitrium heterostichum snow-bed
U13 Deschampsia cespitosa - Galium saxatile grassland
U14 Alchemilla alpina - Sibbaldia procumbens dwarf-herb community
U15 Saxifraga aizoides - Alchemilla glabra banks
U16 Luzula sylvatica - Vaccinium myrtillus tall-herb community
U17 Luzula sylvatica - Geum rivale tall-herb community
U18 Cryptogramma crispa - Athyrium distentifolium snow-bed
U19 Thelypteris limbosperma - Blechnum spicant community
U20 Pteridium aquilinum - Galium saxatile community
U21 Cryptogramma crispa - Deschampsia flexuosa community
Aquatic communities
The following 24 communities are described in Volume 4 of British Plant Communities. For an article summarising these communities see Aquatic communities in the British National Vegetation Classification system.
A1 Lemna gibba community Lemnetum gibbae Miyawaki & J. Tx. 1960
A2 Lemna minor community Lemnetum minoris Soó 1947
A3 Spirodela polyrhiza - Hydrocharis morsus-ranae community
A4 Hydrocharis morsus-ranae - Stratiotes aloides community
A5 Ceratophyllum demersum community Certaophylletum demersi Hild 1956
A6 Ceratophyllum submersum community Certaophylletum submersi Den Hartog & Segal 1964
A7 Nymphaea alba community Nymphaeetum albae Oberdorfer & Mitarb. 1967
A8 Nuphar lutea community
A9 Potamogeton natans community
A10 Polygonum amphibium community
A11 Potamogeton pectinatus - Myriophyllum spicatum community
A12 Potamogeton pectinatus community
A13 Potamogeton perfoliatus - Myriophyllum alterniflorum community
A14 Myriophyllum alterniflorum community Myriophylletum alterniflori
A15 Elodea canadensis community
A16 Callitriche stagnalis community
A17 Ranunculus penicillatus ssp. pseudofluitans community
A18 Ranunculus fluitans community Ranunculetum fluitantis Allorge 1922
A19 Ranunculus aquatilis community Ranunculetum aquatilis Géhu 1961
A20 Ranunculus peltatus community Ranunculetum peltati Sauer 1947
A21 Ranunculus baudotii community Ranunculetum baudotii Br.-Bl. 1952
A22 Littorella uniflora - Lobelia dortmanna community
A23 Isoetes lacustris/setacea community
A24 Juncus bulbosus community
Swamps and tall-herb fens
The following 28 communities are described in Volume 4 of British Plant Communities. For an article summarising these communities see Swamps and tall-herb fens in the British National Vegetation Classification system.
S1 Carex elata sedge-swamp Caricetum elatae Koch 1926
S2 Cladium mariscus swamp and sedge-beds Cladietum marisci Zobrist 1933 emend. Pfeiffer 1961
S3 Carex paniculata swamp Caricetum paniculatae Wangerin 1916
S4 Phragmites australis swamp and reed-beds Phragmitetum australis (Gams 1927) Schmale 1939
S5 Glyceria maxima swamp Glycerietum maximae (Nowinski 1928) Hueck 1931 emend. Krausch 1965
S6 Carex riparia swamp Caricetum ripariae Soó 1928
S7 Carex acutiformis swamp Caricetum acutiformis Sauer 1937
S8 Scirpus lacustris ssp. lacustris swamp Scirpetum lacustris (Allorge 1922) Chouard 1924
S9 Carex rostrata swamp Caricetum rostratae Rübel 1912
S10 Equisetum fluviatile swamp Equisetetum fluviatile Steffen 1931 emend. Wilczek 1935
S11 Carex vesicaria swamp Caricetum vesicariae Br.-Bl. & Denis 1926
S12 Typha latifolia swamp Typhetum latifoliae Soó 1927
S13 Typha angustifolia swamp Typhetum angustifoliae Soó 1927
S14 Sparganium erectum swamp Sparganietum erecti Roll 1938
S15 Acorus calamus swamp Acoretum calami Schulz 1941
S16 Sagittaria sagittifolia swamp
S17 Carex pseudocyperus swamp
S18 Carex otrubae swamp Caricetum otrubae Mirza 1978
S19 Eleocharis palustris swamp Eleocharitetum palustris Schennikow 1919
S20 Scirpus lacustris ssp. tabernaemontani swamp Scirpetum tabernaemontani Passarge 1964
S21 Scirpus maritimus swamp Scirpetum maritimi (Br.-Bl. 1931) R.Tx. 1937
S22 Glyceria fluitans water-margin vegetation Glycerietum fluitantis Wilczek 1935
S23 Other water-margin vegetation Glycerio-Sparganion Br.-Bl. & Sissingh apud Boer 1942 emend. Segal
S24 Phragmites australis - Peucedanum palustre tall-herb fen Peucedano-Phragmitetum australis Wheeler 1978 emend.
S25 Phragmites australis - Eupatorium cannabinum tall-herb fen
S26 Phragmites australis - Urtica dioica tall-herb fen
S27 Carex rostrata - Potentilla palustris tall-herb fen Potentillo-Caricetum rostratae Wheeler 1980a
S28 Phalaris arundinacea tall-herb fen Phalaridetum arundinaceae Libbert 1931
Salt-marsh communities
The following 28 communities are described in Volume 5 of British Plant Communities. For an article summarising these communities see Salt-marsh communities in the British National Vegetation Classification system.
SM1 Zostera communities Zosterion Christiansen 1934
SM2 Ruppia maritima salt-marsh community Ruppietum maritimae Hocquette 1927
SM3 Eleocharis parvula salt-marsh community Eleocharitetum parvulae (Preuss 1911/12) Gillner 1960
SM4 Spartina maritima salt-marsh community Spartinetum maritimae (Emb. & Regn. 1926) Corillion 1953
SM5 Spartina alterniflora salt-marsh community Spartinetum alterniflorae Corillion 1953
SM6 Spartina anglica salt-marsh community Spartinetum townsendii (Tansley 1939) Corillion 1953
SM7 Arthrocnemum perenne stands
SM8 Annual Salicornia salt-marsh community Salicornietum europaeae Warming 1906
SM9 Suaeda maritima salt-marsh community Suaedetum maritimae (Conrad 1935) Pignatti 1953
SM10 Transitional low-marsh vegetation with Puccinellia maritima, annual Salicornia species and Suaeda maritima
SM11 Aster tripolium var. discoideus salt-marsh community Asteretum tripolii Tansley 1939
SM12 Rayed Aster tripolium on salt-marshes
SM13 Puccinellia maritima salt-marsh community Puccinellietum maritimae (Warming 1906) Christiansen 1927
SM14 Halimione portaculoides salt-marsh community Halimionetum portulacoidis (Kuhnholtz-Lordat 1927) Des Abbayes & Corillion 1949
SM15 Juncus maritimus - Triglochin maritima salt-marsh community
SM16 Festuca rubra salt-marsh community Juncetum gerardi Warming 1906
SM17 Artemisia maritima salt-marsh community Artemisietum maritimae Hocquette 1927
SM18 Juncus maritimus salt-marsh community
SM19 Blysmus rufus salt-marsh community Blysmetum rufi (G.E. & G. Du Rietz 1925) Gillner 1960
SM20 Eleocharis uniglumis salt-marsh community Eleocharitetum uniglumis Nordhagen 1923
SM21 Suaeda vera - Limonium binervosum salt-marsh community
SM22 Halimione portulacoides - Frankenia laevis salt-marsh community Limonio vulgaris - Frankenietum laevis Géhu & Géhu-Franck 1975
SM23 Spergularia marina - Puccinellia distans salt-marsh community Puccinellietum distantis Feekes (1934) 1945
SM24 Elymus pycnanthus salt-marsh community Atriplici-Elymetum pycnanthi Beeftink & Westhoff 1962
SM25 Suaeda vera drift-line community Elymo pycnanthi - Suaedetum verae (Arènes 1933) Géhu 1975
SM26 Inula crithmoides on salt-marshes
SM27 Ephermeral salt-marsh vegetation with Sagina maritima Saginion maritimae Westhoff, van Leeuwen & Adriani 1962
SM28 Elymus repens salt-marsh community Elymetum repentis maritimum Nordhagen 1940
Shingle, strandline and sand-dune communities
The following 19 communities are described in Volume 5 of British Plant Communities. For an article summarising these communities see Shingle, strandline and sand-dune communities in the British National Vegetation Classification system.
SD1 Rumex crispus - Glaucium flavum shingle community
SD2 Honkenya peploides - Cakile maritima strandline community
SD3 Matricaria maritima - Galium aparine strandline community
SD4 Elymus farctus ssp. boreali-atlanticus foredune community
SD5 Leymus arenarius mobile dune community
SD6 Ammophila arenaria mobile dune community
SD7 Ammophila arenaria - Festuca rubra semi-fixed dune community
SD8 Festuca rubra - Galium verum fixed dune grassland
SD9 Ammophila arenaria - Arrhenatherum elatius dune grassland
SD10 Carex arenaria dune community
SD11 Carex arenaria - Cornicularia aculeata dune community
SD12 Carex arenaria - Festuca ovina - Agrostis capillaris dune grassland
SD13 Sagina nodosa - Bryum pseudotriquetrum dune-slack community
SD14 Salix repens - Campylium stellatum dune-slack community
SD15 Salix repens - Calliergon cuspidatum dune-slack community
SD16 Salix repens - Holcus lanatus dune-slack community
SD17 Potentilla anserina - Carex nigra dune-slack community
SD18 Hippophae rhamnoides dune scrub
SD19 Phleum arenarium - Arenaria serpyllifolia dune annual community Tortulo-Phleetum arenariae (Massart 1908) Br.-Bl. & de Leeuw 1936
Maritime cliff communities
The following 12 communities are described in Volume 5 of British Plant Communities. For an article summarising these communities see Maritime cliff communities in the British National Vegetation Classification system.
MC1 Crithmum maritimum - Spergularia rupicola maritime rock-crevice community Crithmo-Spergularietum rupicolae Géhu 1964
MC2 Armeria maritima - Ligusticum scoticum maritime rock-crevice community
MC3 Rhodiola rosea - Armeria maritima maritime cliff-ledge community
MC4 Brassica oleracea maritime cliff-ledge community
MC5 Armeria maritima - Cerastium diffusum ssp. diffusum maritime therophyte community
MC6 Atriplex prostrata - Beta vulgaris ssp. maritima sea-bird cliff community Atriplici-Betetum maritimae J.-M. & J. Géhu 1969
MC7 Stellaria media - Rumex acetosa sea-bird cliff community
MC8 Festuca rubra - Armeria maritima maritime grassland
MC9 Festuca rubra - Holcus lanatus maritime grassland
MC10 Festuca rubra - Plantago spp. maritime grassland
MC11 Festuca rubra - Daucus carota ssp. gummifer maritime grassland
MC12 Festuca rubra - Hyacinthoides non-scripta maritime bluebell community
Vegetation of open habitats
The following 42 communities are described in Volume 5 of British Plant Communities. For an article summarising these communities see Vegetation of open habitats in the British National Vegetation Classification system.
OV1 Viola arvensis - Aphanes microcarpa community
OV2 Briza minor - Silene gallica community
OV3 Papaver rhoeas - Viola arvensis community Papaveretum argemones (Libbert 1933) Kruseman & Vlieger 1939
OV4 Chrysanthemum segetum - Spergula arvensis community Spergulo-Chrysanthemetum segetum (Br.-Bl. & De Leeuw 1936) R. Tx. 1937
OV5 Digitaria ischaemum - Erodium cicutarium community
OV6 Cerastium glomeratum - Fumaria borealis ssp. boraei community
OV7 Veronica persica - Veronica polita community Veronico - Lamietum hybridi Kruseman & Vlieger 1939
OV8 Veronica persica - Alopecurus myosuroides community Alopecuro-Chamomilletum recutitae Wasscher 1941
OV9 Matricaria perforata - Stellaria media community
OV10 Poa annua - Senecio vulgaris community
OV11 Poa annua - Stachys arvensis community
OV12 Poa annua - Myosotis arvensis community
OV13 Stellaria media - Capsella bursa-pastoris community
OV14 Urtica urens - Lamium amplexicaule community
OV15 Anagallis arvensis - Veronica persica community Kickxietum spuriae Kruseman & Vlieger 1939
OV16 Papaver rhoeas - Silene noctiflora community Papaveri-Sileneetum noctiflori Wasscher 1941
OV17 Reseda lutea - Polygonum aviculare community Descurainio-Anchusetum arvensis Silverside 1977
OV18 Polygonum aviculare - Chamomilla suavolens community
OV19 Poa annua - Matricaria perforata community
OV20 Poa annua - Sagina procumbens community Sagino - Bryetum argentii Diemont, Sissingh & Westhoff 1940
OV21 Poa annua - Plantago major community
OV22 Poa annua - Taraxacum officinale community
OV23 Lolium perenne - Dactylis glomerata community
OV24 Urtica dioica - Galium aparine community
OV25 Urtica dioica - Cirsium arvense community
OV26 Epilobium hirsutum community
OV27 Epilobium angustifolium community
OV28 Agrostis stolonifera - Ranunculus repens community Agrostio - Ranunculetum repentis Oberdorfer et al. 1967
OV29 Alopecurus geniculatus - Rorippa palustris community Ranunculo - Alopecuretum geniculati R. Tx. (1937) 1950
OV30 Bidens tripartita - Polygonum amphibium community Polygono - Bidentetum tripartitae Lohmeyer in R. Tx. 1950
OV31 Rorippa palustris - Filaginella uliginosa community
OV32 Myosotis scorpioides - Ranunculus sceleratus community Ranunculetum scelerati R. Tx. 1950 ex Passarge 1959
OV33 Polygonum lapathifolium - Poa annua community
OV34 Allium schoenoprasum - Plantago maritima community
OV35 Lythrum portula - Ranunculus flammula community
OV36 Lythrum hyssopifolia - Juncus bufonius community
OV37 Festuca ovina - Minuartia verna community Minuartio-Thlaspietum alpestris Koch 1932
OV38 Gymnocarpium robertianum - Arrhenatherum elatius community Gymnocarpietum robertianae (Kuhn 1937) R. Tx. 1937
OV39 Asplenium trichomanes - Asplenium ruta-muraria community Asplenietum trichomano-rutae-murariae R. Tx. 1937
OV40 Asplenium viride - Cystopteris fragilis community Asplenio viridis-Cystopteridetum fragilis (Kuhn 1939) Oberdorfer 1977
OV41 Parietaria diffusa community Parietarietum judaicae (Arènes 1928) Oberdorfer 1977
OV42 Cymbalaria muralis community Cymbalarietum muralis Görs 1966
.
plant communities
.
National Vegetation Classification
British National Vegetation Classification | List of plant communities in the British National Vegetation Classification | [
"Biology"
] | 6,488 | [
"British National Vegetation Classification communities",
"British National Vegetation Classification"
] |
2,163,279 | https://en.wikipedia.org/wiki/Undulating%20number | In mathematics, an undulating number is a number that has the digit form ABABAB... when in the base 10 number system. It is sometimes restricted to non-trivial undulating numbers, which are required to have at least three digits and A ≠ B. The first few undulating numbers are:
101, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 343, 353, 363, 373, 383, 393, 404, 414, 424, 434, 454, 464, 474, 484, 494, ...
For the full sequence of undulating numbers, see .
Some larger undulating numbers are: 1010, 80808, 171717, 989898989.
Properties
There are infinitely many undulating numbers.
For any n ≥ 3, there are 9 × 9 = 81 non-trivial n-digit undulating numbers, since the first digit can have 9 values (it cannot be 0), and the second digit can have 9 values when it must be different from the first.
Every undulating number with even number of digits and at least four digits is composite, since: ABABAB...AB = 10101...01 × AB. For example, 171717 = 10101 × 17.
Undulating numbers with odd number of digits are palindromic. They can be prime, for example 151.
The undulating number ABAB...AB with n repetitions of AB can be expressed as AB × (102n − 1)/99. For example, 171717 = 17 × (106 − 1)/99.
The undulating number ABAB...ABA with n repetitions of AB followed by one A can be expressed as (AB × 102n+1 − BA)/99. For example, 989898989 = (98 × 109 − 89)/99
Undulating numbers can be generalized to other bases. If a number in base with even number of digits is undulating, in base it is a repdigit.
Undulating primes
An undulating prime is an undulating number that is also prime. In every base, all undulating primes having at least three digits have an odd number of digits and are palindromic primes. The undulating primes in base 10 are:
2, 3, 5, 7, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 131, 151, 181, 191, 313, 353, 373, 383, 727, 757, 787, 797, 919, 929, 18181, 32323, 35353, 72727, 74747, 78787, 94949, 95959, ...
References
External links
Base-dependent integer sequences | Undulating number | [
"Mathematics"
] | 647 | [
"Number theory stubs",
"Number theory"
] |
2,163,333 | https://en.wikipedia.org/wiki/M%C3%A9rida%20International%20Airport | Mérida International Airport (), officially (Manuel Crescencio Rejón International Airport) , is an international airport located in the Mexican city of Mérida. It serves as the primary international gateway to Mérida and the State of Yucatán, a popular tourist destination, offering flights to and from Mexico, the United States, Canada, Central America, and the Caribbean. The airport also accommodates facilities for the Mexican Airspace Navigation Services, and the Mexican Army, and supports various tourism, flight training, and general aviation activities. Additionally, it serves as a focus city for Viva.
The airport is named in honor of the jurist and politician Manuel Crescencio García Rejón, who was originally from Yucatán. It is operated by the Grupo Aeroportuario del Sureste (ASUR). The airport has become one of the fastest-growing airports in the country. In 2022, it handled 3,079,618 passengers, surpassing three million passengers in a calendar year for the first time; and in 2023, the number increased to 3,674,103 passengers. It also ranked as the eighth-busiest airport in terms of passengers and aircraft movements, and tenth for cargo.
History
The airport's history traces back to its inauguration in 1929 when Mexicana de Aviación introduced the Mérida-Campeche-Ciudad del Carmen-Minatitlán-Veracruz-Mexico City route, operated with a Ford Trimotor aircraft. In 1964, Mexicana de Aviación sold the airport to the Mexican government. A significant reconstruction of the airport was completed in 1968, replacing the previous facilities. During the 1960s, American Airlines provided service to the airport, making it one of the few airports, apart from Mexico City and Acapulco, to be served by a major airline.
During the 1990s, the airport became part of the Grupo Aeroportuario del Sureste, marking an important instance of a private concession within this group. This consortium encompasses various airports, including Cancún, Cozumel, Huatulco, Mérida, Minatitlán, Oaxaca, Tapachula, Villahermosa, and Veracruz. Throughout the years, it underwent several modifications and modernizations, notably in 1999, 2011, and 2021. The airport has welcomed distinguished political and religious figures, such as Pope John Paul II, as well as U.S. Presidents Bill Clinton and George W. Bush, and President of China, Xi Jinping.
Throughout its history, the airport has been serviced by a range of airlines, including Aero California, Aeromar, Aviateca, Blue Panorama Airlines, Cubana, Delta, Interjet, Mexicana, Neos, Pan Am, Lufthansa, TAR, and Tropic Air. From 1972 to 2005, it functioned as the primary hub for Aerocaribe and Aerocozumel, both subsidiaries of the former Mexicana. Between 1992 and 1995 it served as a hub for Aviacsa, and more recently, it was home to the regional airline Mayair.
Facilities
The airport is situated in the Mérida urban area, less than southwest of the city centre, at an elevation of above sea level. It features two runways: Runway 10/28, which is long, and Runway 18/36, which spans . Adjacent to the terminal, there is a commercial aviation apron capable of accommodating up to 11 narrow-body aircraft or a combination of 3 narrow-body and 3 wide-body aircraft. Additionally, a remote stand is available for 2 narrow-body aircraft. The airport has the capacity to service airplanes as large as Boeing 747s and 777s, although most daily flights involve smaller aircraft, with the most common being the Boeing 737 and Airbus A320. The airport can handle up to 30 operations per hour and operates around the clock.
Passenger terminal
The passenger terminal is a two-story structure. The ground floor comprises the main entrance, a check-in area, and the arrivals section, which includes customs and immigration facilities, along with baggage claim services. Additionally, car rental services, taxi stands, snack bars, and souvenir shops are available. The upper terminal floor hosts a security checkpoint and departure area, featuring a long departures concourse. Within this section, there are restaurants, food stands, duty-free shops, VIP lounges, and eleven gates (C1-11), with seven of them equipped with jet bridges.
In the vicinity of the terminal, various facilities are located, including civil aviation hangars, cargo and logistics companies, and cargo services. There is also a dedicated general aviation terminal that supports a range of activities, such as tourism, flight training, executive aviation, and general aviation.
Other facilities
The airport is home to the Mérida Area Control Center (ACC), one of four such centers in Mexico, alongside the Mexico City ACC, Monterrey ACC, and Mazatlán ACC. Operated by the Mexican Airspace Navigation Services (), Mérida ACC provides air traffic control services for aircraft operating within the Mérida Flight Data Region (FDRG), which encompasses the southeastern region of Mexico. This region shares its boundaries with six other Area Control Centers. To the west, it borders the Monterrey ACC and Mexico ACC, while to the north, it shares borders with the Houston ARTCC (KZHU), and to the east and south, it connects with the Havana ACC (MUFH) and the Central American ACC (MHTG), respectively.
Air Force Base No. 8 () (BAM-8) is located on the airport grounds, north of Runway 10/28. It serves as the home for Air Squadron 114, responsible for operating Cessna 182 aircraft. BAM-8 features two aprons, one spanning and another covering . In addition to these, it includes three hangars and various other facilities for accommodating Air Force personnel.
Airlines and destinations
Passenger
Viva flight to Tijuana makes a stopover in León/El Bajío.
Cargo
Destinations map
Statistics
Busiest routes
Accidents and incidents
On 9 April 1958, a Vickers Viscount of Cubana de Aviación was hijacked en route from José Martí International Airport, Havana, to Santa Clara Airport. The aircraft landed at Mérida-Rejón Airport, Mexico, where the hijack ended.
On 1 June 2023, an Aeromexico Boeing 737-8JP declared a Squawk 7700, a regulation for emergency on an aircraft. While en route to Mexico City, the aircraft, registered XA-PPP diverted back to Merida International Airport. The aircraft suffered an engine loss and safely landed with no deaths to the people on board.
See also
List of the busiest airports in Mexico
List of airports in Mexico
List of airports by ICAO code: M
List of busiest airports in North America
List of the busiest airports in Latin America
Transportation in Mexico
Tourism in Mexico
Grupo Aeroportuario Centro Norte
Area control center
List of area control centers
Flight information region
List of Mexican military installations
Mexican Air Force
References
External links
Official Website
Grupo Aeroportuario del Sureste
Merida International Airport
Mérida Airport information at Great Circle Mapper
Accident history for MID at Aviation Safety Network
Mexican Air Traffic Control Services
Servicios a la Navegación en el Espacio Aéreo Mexicano
Airports in Mexico
Airports in Yucatán
Mérida, Yucatán
Mexican Air Force bases
Mexican Air Force
Military installations of Mexico
Air traffic control centers
WAAS reference stations
Buildings and structures completed in 1929
1929 establishments in Mexico | Mérida International Airport | [
"Technology"
] | 1,518 | [
"Global Positioning System",
"WAAS reference stations"
] |
2,163,460 | https://en.wikipedia.org/wiki/Michel%20Virlogeux | Michel Virlogeux (born 1946, Vichy, Allier, Auvergne) is a French structural engineer and bridge specialist.
Career
Virlogeux graduated from the École Polytechnique in 1967 and from the École Nationale des Ponts et Chaussées in 1970. From 1970 to 1973 he served in Tunisia on road projects and at the same time gained his Engineering Doctorate from the Pierre et Marie Curie University (also known as "Paris 6"). In January 1974 he joined the Bridge Department of SETRA, the technical service of the French Highway Administration.
In 1980 he became Head of the Large Concrete Bridge Division, and in 1987 of the large Bridge Division, Steel and Concrete. During twenty years he designed more than 100 bridges, including the Normandy Bridge which held the world record for longest cable-stayed bridge for four years. In 1995 he left the French Administration and set up as independent consulting engineer; his major achievements include his participation in the construction of the 'Second Tagus Crossing', the Vasco da Gama Bridge in Lisbon, and the design of the Millau Viaduct in France. Several of his bridges have received architectural awards.
Since 1977, Virlogeux has been a part-time professor of structural analysis at the École Nationale des Ponts et Chaussées and at the Centre des Hautes Études de la Construction in Paris. He also has been very active in technical associations such as the French Association of Civil Engineering (AFGC), 1974–1995; the Fédération Internationale de Précontrainte (FIP) (President 1996); the Fédération Internationale du Béton (FIB); first President in 1998 after the merger with the Comité Européen du Béton (CEB).
Awards
A member of the International Association for Bridge and Structural Engineering (IABSE) since 1974, Virlogeux received the inaugural IABSE Prize in Venice in 1983.
He has received many other international awards, which include the 'Award of Excellence of the Engineering News Record' (1995), the 'Gold Medal of the Institution of Structural Engineers' (1979), the Gold Medal of the Institution of Civil Engineers (2005) the 'Gustave Magnel Medal' (1999) and the 'Fritz Leonhardt Prize' (also the first year that it was awarded). He is a member of the French Academy of Technology.
He received the 2003 IABSE Award of Merit in Structural Engineering in recognition of "his major contributions leading to very significant progress in the field of civil engineering, in particular through the development of external prestressing, landmark cable-stayed bridges and composite structures". The Award Presentation took place during the Opening of the IABSE Symposium 'Structures for High-Speed Railway Transportation', Antwerp, Belgium on 27 August 2003. The presentation was presented by Manabu Ito, President of IABSE.
In 2010 he was invited to deliver the MacMillan Memorial Lecture to the Institution of Engineers and Shipbuilders in Scotland. He chose the subject "The Design of Long Span Bridges".
He was appointed an International Fellow of the Royal Academy of Engineering in 2012 and Corresponding Fellow of the Royal Society of Edinburgh in 2013.
References
External links
Dr Michel Virlogeux, France IABSE biography
1946 births
Living people
IStructE Gold Medal winners
French bridge engineers
French civil engineers
Structural engineers
École Polytechnique alumni
École des Ponts ParisTech alumni
Corps des ponts
Viaduct engineers
Knights of the Legion of Honour | Michel Virlogeux | [
"Engineering"
] | 703 | [
"Structural engineering",
"Structural engineers"
] |
2,163,544 | https://en.wikipedia.org/wiki/Sieve%20%28category%20theory%29 | In category theory, a branch of mathematics, a sieve is a way of choosing arrows with a common codomain. It is a categorical analogue of a collection of open subsets of a fixed open set in topology. In a Grothendieck topology, certain sieves become categorical analogues of open covers in topology. Sieves were introduced by in order to reformulate the notion of a Grothendieck topology.
Definition
Let C be a category, and let c be an object of C. A sieve on c is a subfunctor of Hom(−, c), i.e., for all objects c′ of C, S(c′) ⊆ Hom(c′, c), and for all arrows f:c″→c′, S(f) is the restriction of Hom(f, c), the pullback by f (in the sense of precomposition, not of fiber products), to S(c′); see the next section, below.
Put another way, a sieve is a collection S of arrows with a common codomain that satisfies the condition, "If g:c′→c is an arrow in S, and if f:c″→c′ is any other arrow in C, then gf is in S." Consequently, sieves are similar to right ideals in ring theory or filters in order theory.
Pullback of sieves
The most common operation on a sieve is pullback. Pulling back a sieve S on c by an arrow f:c′→c gives a new sieve f*S on c′. This new sieve consists of all the arrows in S that factor through c′.
There are several equivalent ways of defining f*S. The simplest is:
For any object d of C, f*S(d) = { g:d→c′ | fg ∈ S(d)}
A more abstract formulation is:
f*S is the image of the fibered product S×Hom(−, c)Hom(−, c′) under the natural projection S×Hom(−, c)Hom(−, c′)→Hom(−, c′).
Here the map Hom(−, c′)→Hom(−, c) is Hom(−, f), the push forward by f.
The latter formulation suggests that we can also take the image of S×Hom(−, c)Hom(−, c′) under the natural map to Hom(−, c). This will be the image of f*S under composition with f. For each object d of C, this sieve will consist of all arrows fg, where g:d→c′ is an arrow of f*S(d). In other words, it consists of all arrows in S that can be factored through f.
If we denote by ∅c the empty sieve on c, that is, the sieve for which ∅(d) is always the empty set, then for any f:c′→c, f*∅c is ∅c′. Furthermore, f*Hom(−, c) = Hom(−, c′).
Properties of sieves
Let S and S′ be two sieves on c. We say that S ⊆ S′ if for all objects c′ of C, S(c′) ⊆ S′(c′). For all objects d of C, we define (S ∪ S′)(d) to be S(d) ∪ S′(d) and (S ∩ S′)(d) to be S(d) ∩ S′(d). We can clearly extend this definition to infinite unions and intersections as well.
If we define SieveC(c) (or Sieve(c) for short) to be the set of all sieves on c, then Sieve(c) becomes partially ordered under ⊆. It is easy to see from the definition that the union or intersection of any family of sieves on c is a sieve on c, so Sieve(c) is a complete lattice.
A Grothendieck topology is a collection of sieves subject to certain properties. These sieves are called covering sieves. The set of all covering sieves on an object c is a subset J(c) of Sieve(c). J(c) satisfies several properties in addition to those required by the definition:
If S and S′ are sieves on c, S ⊆ S′, and S ∈ J(c), then S′ ∈ J(c).
Finite intersections of elements of J(c) are in J(c).
Consequently, J(c) is also a distributive lattice, and it is cofinal in Sieve(c).
References
Category theory | Sieve (category theory) | [
"Mathematics"
] | 1,028 | [
"Functions and mappings",
"Mathematical structures",
"Mathematical objects",
"Fields of abstract algebra",
"Mathematical relations",
"Category theory"
] |
2,163,561 | https://en.wikipedia.org/wiki/Stable%20storage | Stable storage is a classification of computer data storage technology that guarantees atomicity for any given write operation and allows software to be written that is robust against some hardware and power failures. To be considered atomic, upon reading back a just written-to portion of the disk, the storage subsystem must return either the write data or the data that was on that portion of the disk before the write operations.
Most computer disk drives are not considered stable storage because they do not guarantee atomic write; an error could be returned upon subsequent read of the disk where it was just written to in lieu of either the new or prior data.
Implementation
Multiple techniques have been developed to achieve the atomic property from weakly atomic devices such as disks. Writing data to a disk in two places in a specific way is one technique and can be done by application software.
Most often though, stable storage functionality is achieved by mirroring data on separate disks via RAID technology (level 1 or greater). The RAID controller implements the disk writing algorithms that enable separate disks to act as stable storage.
The RAID technique is robust against some single disk failure in an array of disks whereas the software technique of writing to separate areas of the same disk only protects against some kinds of internal disk media failures such as bad sectors in single disk arrangements.
Computer data storage | Stable storage | [
"Technology"
] | 263 | [
"Computing stubs",
"Computer science",
"Computer science stubs"
] |
2,163,562 | https://en.wikipedia.org/wiki/Peaucellier%E2%80%93Lipkin%20linkage | The Peaucellier–Lipkin linkage (or Peaucellier–Lipkin cell, or Peaucellier–Lipkin inversor), invented in 1864, was the first true planar straight line mechanism – the first planar linkage capable of transforming rotary motion into perfect straight-line motion, and vice versa. It is named after Charles-Nicolas Peaucellier (1832–1913), a French army officer, and Yom Tov Lipman Lipkin (1846–1876), a Lithuanian Jew and son of the famed Rabbi Israel Salanter.
Until this invention, no planar method existed of converting exact straight-line motion to circular motion, without reference guideways. In 1864, all power came from steam engines, which had a piston moving in a straight-line up and down a cylinder. This piston needed to keep a good seal with the cylinder in order to retain the driving medium, and not lose energy efficiency due to leaks. The piston does this by remaining perpendicular to the axis of the cylinder, retaining its straight-line motion. Converting the straight-line motion of the piston into circular motion was of critical importance. Most, if not all, applications of these steam engines, were rotary.
The mathematics of the Peaucellier–Lipkin linkage is directly related to the inversion of a circle.
Earlier Sarrus linkage
There is an earlier straight-line mechanism, whose history is not well known, called the Sarrus linkage. This linkage predates the Peaucellier–Lipkin linkage by 11 years and consists of a series of hinged rectangular plates, two of which remain parallel but can be moved normally to each other. Sarrus' linkage is of a three-dimensional class sometimes known as a space crank, unlike the Peaucellier–Lipkin linkage which is a planar mechanism.
Geometry
In the geometric diagram of the apparatus, six bars of fixed length can be seen: , , , , , . The length of is equal to the length of , and the lengths of , , , and are all equal forming a rhombus. Also, point is fixed. Then, if point is constrained to move along a circle (for example, by attaching it to a bar with a length halfway between and ; path shown in red) which passes through , then point will necessarily have to move along a straight line (shown in blue). In contrast, if point were constrained to move along a line (not passing through ), then point would necessarily have to move along a circle (passing through ).
Mathematical proof of concept
Collinearity
First, it must be proven that points , , are collinear. This may be easily seen by observing that the linkage is mirror-symmetric about line , so point must fall on that line.
More formally, triangles and are congruent because side is congruent to itself, side is congruent to side , and side is congruent to side . Therefore, angles and are equal.
Next, triangles and are congruent, since sides and are congruent, side is congruent to itself, and sides and are congruent. Therefore, angles and are equal.
Finally, because they form a complete circle, we have
but, due to the congruences, and , thus
therefore points , , and are collinear.
Inverse points
Let point be the intersection of lines and . Then, since is a rhombus, is the midpoint of both line segments and . Therefore, length = length .
Triangle is congruent to triangle , because side is congruent to side , side is congruent to itself, and side is congruent to side . Therefore, angle = angle . But since , then , , and .
Let:
Then:
(due to the Pythagorean theorem)
(same expression expanded)
(Pythagorean theorem)
Since and are both fixed lengths, then the product of and is a constant:
and since points , , are collinear, then is the inverse of with respect to the circle with center and radius .
Inversive geometry
Thus, by the properties of inversive geometry, since the figure traced by point is the inverse of the figure traced by point , if traces a circle passing through the center of inversion , then is constrained to trace a straight line. But if traces a straight line not passing through , then must trace an arc of a circle passing through . Q.E.D.
A typical driver
Peaucellier–Lipkin linkages (PLLs) may have several inversions. A typical example is shown in the opposite figure, in which a rocker-slider four-bar serves as the input driver. To be precise, the slider acts as the input, which in turn drives the right grounded link of the PLL, thus driving the entire PLL.
Historical notes
Sylvester (Collected Works, Vol. 3, Paper 2) writes that when he showed a model to Kelvin, he “nursed it as if it had been his own child, and when a motion was made to relieve him of it, replied ‘No! I have not had nearly enough of it—it is the most beautiful thing I have ever seen in my life.’”
Cultural references
A monumental-scale sculpture implementing the linkage in illuminated struts is on permanent exhibition in Eindhoven, Netherlands. The artwork measures , weighs , and can be operated from a control panel accessible to the general public.
See also
Linkage (mechanical)
Straight line mechanism
References
Bibliography
— proof and discussion of Peaucellier–Lipkin linkage, mathematical and real-world mechanical models
(and references cited therein)
Hartenberg, R.S. & J. Denavit (1964) Kinematic synthesis of linkages, pp 181–5, New York: McGraw–Hill, weblink from Cornell University.
External links
How to Draw a Straight Line, online video clips of linkages with interactive applets.
How to Draw a Straight Line, historical discussion of linkage design
Interactive Java Applet with proof.
Java animated Peaucellier–Lipkin linkage
Jewish Encyclopedia article on Lippman Lipkin and his father Israel Salanter
Peaucellier Apparatus features an interactive applet
A simulation using the Molecular Workbench software
A related linkage called Hart's Inversor.
Modified Peaucellier robotic arm linkage (Vex Team 1508 video)
Linkages (mechanical)
Articles containing proofs
Linear motion
Straight line mechanisms | Peaucellier–Lipkin linkage | [
"Physics",
"Mathematics"
] | 1,341 | [
"Articles containing proofs",
"Physical phenomena",
"Motion (physics)",
"Linear motion"
] |
2,163,563 | https://en.wikipedia.org/wiki/Heat%20escape%20lessening%20position | The heat escape lessening position (HELP) is a human position to reduce heat loss while immersed in cold water.
Position
HELP is taught as part of the curriculum in Australia, North America, and Ireland for lifeguard and boating safety training. It involves positioning one's knees together and hugging them close to the chest using one's arms. Furthermore, groups of people can huddle together in this position to conserve body heat, offer moral support, and provide a larger target for rescuers.
The HELP is an attempt to reduce heat loss enough to lessen the effect of hypothermia. Hypothermia is a condition where bodily temperature drops too low to perform normal voluntary or involuntary functions. Cold water causes "immersion hypothermia", which can cause damage to extremities or the body's core, including unconsciousness or death.
The HELP reduces exposure of high heat loss areas of the body. Wearing a personal flotation device allows a person to draw their knees to their chest and arms to their sides, while still remaining able to breathe.
See also
Huddling
References
Survival skills
Human positions | Heat escape lessening position | [
"Biology"
] | 231 | [
"Behavior",
"Human positions",
"Human behavior"
] |
2,163,601 | https://en.wikipedia.org/wiki/Carbon%20monoxide%20%28data%20page%29 | This page provides supplementary chemical data on carbon monoxide.
Material safety data sheet
The handling of this chemical may incur notable safety precautions. It is highly recommended that you seek the material safety data sheet (MSDS) for this chemical from a reliable source such as SIRI, and follow its directions.
MSDS from Advanced Gas Technologies in the SDSdata.org database
Structure and properties
Thermodynamic properties
Spectral data
References
Chemical data pages
Carbon monoxide
Chemical data pages cleanup | Carbon monoxide (data page) | [
"Chemistry"
] | 98 | [
"Chemical data pages",
"nan"
] |
2,163,724 | https://en.wikipedia.org/wiki/Ground%20glass | Ground glass is glass whose surface has been ground to produce a flat but rough (matte) finish, in which the glass is in small sharp fragments.
Ground glass surfaces have many applications, ranging from ornamentation on windows and table glassware to scientific uses in optics and laboratory glassware.
Uses
Photography
In photography, a sheet of ground glass is used for the manual focusing in some still and movie cameras; the ground-glass viewer is inserted in the back of the camera, and the lens opened to its widest aperture. This projects the scene on the ground glass upside down. The photographer focuses and composes using this projected image, sometimes with the aid of a magnifying glass (or loupe). In order to see the image better, a dark cloth is used to block out light, whence came the image of the old-time photographer with his head stuck under a large black cloth.
A ground glass is also used in the reflex finder of an SLR or TLR camera.
In motion-picture cameras, the ground glass is a small, usually removable piece of transparent glass that sits between the rotary disc shutter and the viewfinder. The ground glass usually contains precise markings to show the camera operator the boundaries of the frame or the center reticle, or any other important information. Because the ground glass is positioned between the mirror shutter and the viewfinder, it does not interfere with the image reaching the film and is therefore not recorded over the final image, but rather serves as a reference for the camera operator.
Ground glasses commonly serve as a framing reference for a desired aspect ratio. Because most films shot with spherical lenses are shot full-frame and later masked during projection to a more widescreen aspect ratio, it is important not only for the operator to be able to see the boundaries of that aspect ratio, but also for the ground glass to be properly aligned in the camera so that the markings are an exact representation of the boundaries of the image recorded on film.
Lighting
Ground or frosted glass is widely used as a weather- and heat-proof light diffuser in ambient lighting, namely on glass covers or enclosures for lamp fixtures, and sometimes on incandescent bulbs. Its functions include reducing glare and preventing retinal damage by direct sight of the lamp filament. This hides unsightly details of the lamp and fixture without blocking its light, yielding a softer illumination without giving hard shadows.
Chemistry
Ground glass surfaces are often found on the glass equipment of chemical laboratories.
Glass flasks, stoppers, valves, funnels, and tubing are often connected together by ground glass joints, matching pairs of conical or spherical surfaces that have been ground to a precise shape.
Flasks and test tubes often have a small ground-glass label area on the side. (Pencil writing on ground glass is largely inert, rub-proof and waterproof, but can be easily erased.)
Technical optics
An optical microscope may include a ground- or frosted-glass diffuser to evenly illuminate the field behind the specimen. Microscope slides are often ground on the sides and beveled on the corners to soften the edges for safer handling.
Abrin
Popular belief for many centuries is that ground-up glass (i.e., glass broken into tiny fragments) can kill if swallowed. In fact, this is a myth, as it is largely ineffective.
The Guy de Maupassant short story "La Confession" concerns a jealous girl who poisons her older sister's suitor by inserting ground-up glass into cake.
The term ground-glass, as it relates to poisoning, is a corruption of grain d'église, the term given by the French in India to the seeds of the Jaquirity or Rosary Pea plant (Abrus precatorius). The seeds contain the extremely toxic lectin abrin, whose toxicity is over 30times that of ricin. These seeds have been used in India to kill cattle, and in homicides. Captain F. C. Briggs, adjutant to General Reginald Dyer, died of 'powdered glass' poisoning before he could give evidence to the Hunter Commission examining the Jallianwalla Bagh massacre.
See also
Focusing screen
Frosted glass
Ground glass hepatocyte
Ground glass joints
Ground-glass opacity
References
External links
Ground glasses available from Panavision
Ground glass focusing with the Speed Graphic
Ground Glass focusing screens available from hopfglass
Optical components
Photography equipment
Glass shaping
Glass types
Laboratory glassware | Ground glass | [
"Materials_science",
"Technology",
"Engineering"
] | 918 | [
"Glass engineering and science",
"Optical components",
"Components"
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2,163,963 | https://en.wikipedia.org/wiki/Air%20traffic%20control%20radar%20beacon%20system | The air traffic control radar beacon system (ATCRBS) is a system used in air traffic control (ATC) to enhance surveillance radar monitoring and separation of air traffic. It consists of a rotating ground antenna and transponders in aircraft. The ground antenna sweeps a narrow vertical beam of microwaves around the airspace. When the beam strikes an aircraft, the transponder transmits a return signal back giving information such as altitude and the Squawk Code, a four digit code assigned to each aircraft that enters a region. Information about this aircraft is then entered into the system and subsequently added to the controller's screen to display this information when queried. This information can include flight number designation and altitude of the aircraft. ATCRBS assists air traffic control (ATC) surveillance radars by acquiring information about the aircraft being monitored, and providing this information to the radar controllers. The controllers can use the information to identify radar returns from aircraft (known as targets) and to distinguish those returns from ground clutter.
Parts of the system
The system consists of transponders, installed in aircraft, and secondary surveillance radars (SSRs), installed at air traffic control facilities. The SSR is sometimes co-located with the primary surveillance radar, or PSR. These two radar systems work in conjunction to produce a synchronized surveillance picture. The SSR transmits interrogations and listens for any replies. Transponders that receive an interrogation decode it, decide whether to reply, and then respond with the requested information when appropriate. Note that in common informal usage, the term "SSR" is sometimes used to refer to the entire ATCRBS system, however this term (as found in technical publications) properly refers only to the ground radar itself.
Ground Interrogation Equipment
An ATC ground station consists of two radar systems and their associated support components. The most prominent component is the PSR. It is also referred to as skin paint radar because it shows not synthetic or alpha-numeric target symbols, but bright (or colored) blips or areas on the radar screen produced by the RF energy reflections from the target's "skin." This is a non-cooperative process, no additional avionic devices are needed. The radar detects and displays reflective objects within the radar's operating range. Weather radar data is displayed in skin paint mode. The primary surveillance radar is subject to the radar equation that says signal strength drops off as the fourth power of distance to the target. Objects detected using the PSR are known as primary targets.
The second system is the secondary surveillance radar, or SSR, which depends on a cooperating transponder installed on the aircraft being tracked. The transponder emits a signal when it is interrogated by the secondary radar. In a transponder based system signals drop off as the inverse square of the distance to the target, instead of the fourth power in primary radars. As a result, effective range is greatly increased for a given power level. The transponder can also send encoded information about the aircraft, such as identity and altitude.
The SSR is equipped with a main antenna, and an omnidirectional "Omni" antenna at many older sites. Newer antennas (as in the adjacent picture), are grouped as a left and right antenna, and each side connects to a hybrid device which combines the signals into sum and difference channels. Still other sites have both the sum and difference antenna, and an Omni antenna. Surveillance aircraft, e.g. AWACS, have only the sum and difference antennas, but can also be space stabilized by phase shifting the beam down or up when pitched or rolled. The SSR antenna is typically fitted to the PSR antenna, so they point in the same direction as the antennas rotate. The omnidirectional antenna is mounted near and high, usually on top of the radome if equipped. Mode-S interrogators require the sum and difference channels to provide the monopulse capability to measure the off-boresight angle of the transponder reply.
The SSR repetitively transmits interrogations as the rotating radar antenna scans the sky. The interrogation specifies what type of information a replying transponder should send by using a system of modes. There have been a number of modes used historically, but four are in common use today: mode 1, mode 2, mode 3/A, and mode C. Mode 1 is used to sort military targets during phases of a mission. Mode 2 is used to identify military aircraft missions. Mode 3/A is used to identify each aircraft in the radar's coverage area. Mode C is used to request/report an aircraft's altitude.
Two other modes, mode 4 and mode S, are not considered part of the ATCRBS system, but they use the same transmit and receive hardware. Mode 4 is used by military aircraft for the Identification Friend or Foe (IFF) system. Mode S is a discrete selective interrogation, rather than a general broadcast, that facilitates TCAS for civilian aircraft. Mode S transponders ignore interrogations not addressed with their unique identity code, reducing channel congestion. At a typical SSR radar installation, ATCRBS, IFF, and mode S interrogations will all be transmitted in an interlaced fashion. Some military facilities and/or aircraft will also utilize Mode S.
Returns from both radars at the ground station are transmitted to the ATC facility using a microwave link, a coaxial link, or (with newer radars) a digitizer and a modem. Once received at the ATC facility, a computer system known as a radar data processor associates the reply information with the proper primary target and displays it next to the target on the radar scope.
Airborne Transponder Equipment
The equipment installed in the aircraft is considerably simpler, consisting of the transponder itself, usually mounted in the instrument panel or avionics rack, and a small L band UHF antenna, mounted on the bottom of the fuselage. Many commercial aircraft also have an antenna on the top of the fuselage, and either or both antennas can be selected by the flight crew.
Typical installations also include an altitude encoder, which is a small device connected to both the transponder and the aircraft's static system. It provides the aircraft's pressure altitude to the transponder, so that it may relay the information to the ATC facility. The encoder uses 11 wires to pass altitude information to the transponder in the form of a Gillham Code, a modified binary Gray code.
The transponder has a small required set of controls and is simple to operate. It has a method to enter the four-digit transponder code, also known as a beacon code or squawk code, and a control to transmit an ident, which is done at the controller's request (see SPI pulse below). Transponders typically have 4 operating modes: Off, Standby, On (Mode-A), and Alt (Mode-C). On and Alt mode differ only in that the On mode inhibits transmitting any altitude information. Standby mode allows the unit to remain powered and warmed up but inhibits any replies, since the radar is used for searching the aircraft and exact location of aircraft.
Theory of operation
The steps involved in performing an ATCRBS interrogation are as follows: First, the ATCRBS interrogator periodically interrogates aircraft on a frequency of 1030 MHz. This is done through a rotating or scanning antenna at the radar's assigned Pulse Repetition Frequency (PRF). Interrogations are typically performed at 450 - 500 interrogations/second. Once an interrogation has been transmitted, it travels through space (at the speed of light) in the direction the antenna is pointing until an aircraft is reached.
When the aircraft receives the interrogation, the aircraft transponder will send a reply on 1090 MHz after a 3.0 μs delay indicating the requested information. The interrogator's processor will then decode the reply and identify the aircraft. The range of the aircraft is determined from the delay between the reply and the interrogation. The azimuth of the aircraft is determined from the direction the antenna is pointing when the first reply was received, until the last reply is received. This window of azimuth values is then divided by two to give the calculated "centroid" azimuth. The errors in this algorithm cause the aircraft to jitter across the controllers scope, and is referred to as "track jitter." The jitter problem makes software tracking algorithms problematic, and is the reason why monopulse was implemented.
The interrogation
Interrogations consist of three pulses, 0.8 μs in duration, referred to as P1, P2 and P3. The timing between pulses P1 and P3 determines the mode (or question) of the interrogation, and thus what the nature of the reply should be. P2 is used in side-lobe suppression, explained later.
Mode 3/A uses a P1 to P3 spacing of 8.0 μs, and is used to request the beacon code, which was assigned to the aircraft by the controller to identify it. Mode C uses a spacing of 21 μs, and requests the aircraft's pressure altitude, provided by the altitude encoder. Mode 2 uses a spacing of 5 μs and requests the aircraft to transmit its Military identification code. The latter is only assigned to Military aircraft and so only a small percentage of aircraft actually reply to a mode 2 interrogation.
The reply
Replies to interrogations consist of 15 time slots, each 1.45 μs in width, encoding 12 + 1 bits of information. The reply is encoded by the presence or absence of a 0.45 μs pulse in each slot. These are labeled as follows:
F1 C1 A1 C2 A2 C4 A4 X B1 D1 B2 D2 B4 D4 F2 SPI
The F1 and F2 pulses are framing pulses, and are always transmitted by the aircraft transponder. They are used by the interrogator to identify legitimate replies. These are spaced 20.3 μs apart.
The A4, A2, A1, B4, B2, B1, C4, C2, C1, D4, D2, D1 pulses constitute the "information" contained in the reply. These bits are used in different ways for each interrogation mode.
For mode A, each digit in the transponder code (A, B, C, or D) may be a number from zero to seven. These octal digits are transmitted as groups of three pulses each, the A slots reserved for the first digit, B for the second, and so on.
In a mode C reply, the altitude is encoded by a Gillham interface, Gillham code, which uses Gray code. The Gillham interface is capable of representing a wide range of altitudes, in increments. The altitude transmitted is pressure altitude, and corrected for altimeter setting at the ATC facility. If no encoder is attached, the transponder may optionally transmit only framing pulses (most modern transponders do).
In a mode 3 reply, the information is the same as a mode A reply in that there are 4 digits transmitted between 0 and 7. The term mode 3 is utilized by the military, whereas mode A is the civilian term.
The X bit is currently only used for test targets. This bit was originally transmitted by BOMARC missiles that were used as air-launched test targets. This bit may be used by drone aircraft.
The SPI pulse is positioned 4.35μs past the F2 pulse (3 time slots) and is used as a "Special Identification Pulse". The SPI pulse is turned on by the "identity control" on the transponder in the aircraft cockpit when requested by air traffic control. The air traffic controller can request the pilot to ident, and when the identity control is activated, the SPI bit will be added to the reply for about 20 seconds (two to four rotations of the interrogator antenna) thereby highlighting the track on the controllers display.
Side lobe suppression
The SSR's directional antenna is never perfect; inevitably it will "leak" lower levels of RF energy in off-axis directions. These are known as side lobes. When aircraft are close to the ground station, the side lobe signals are often strong enough to elicit a reply from their transponders when the antenna is not pointing at them. This can cause ghosting, where an aircraft's target may appear in more than one location on the radar scope. In extreme cases, an effect known as ring-around occurs, where the transponder replies to excess resulting in an arc or circle of replies centered on the radar site.
To combat these effects, side lobe suppression (SLS) is used. SLS employs a third pulse, P2, spaced 2μs after P1. This pulse is transmitted from the omnidirectional antenna (or the antenna difference channel) by the ground station, rather than from the directional antenna (or the sum channel). The power output from the omnidirectional antenna is calibrated so that, when received by an aircraft, the P2 pulse is stronger than either P1 or P3, except when the directional antenna is pointing directly at the aircraft. By comparing the relative strengths of P2 and P1, airborne transponders can determine whether or not the antenna is pointing at the aircraft when the interrogation was received. The power to the difference antenna pattern (for systems so equipped) is not adjusted from that of the P1 and P3 pulses. Algorithms are used in the ground receivers to delete replies on the edge of the two beam patterns.
To combat these effects more recently, side lobe suppression (SLS) is still used, but differently. The new and improved SLS employs a third pulse, spaced 2μs either before P3 (a new P2 position) or after P3 (which should be called P4 and appears in the Mode S radar and TCAS specifications). This pulse is transmitted from the directional antenna at the ground station, and the power output of this pulse is the same strength as the P1 and P3 pulses. The action to be taken is specified in the new and improved C74c as:
Any requirement at the transponder to detect and act upon a P2 pulse 2μs after P1 has been removed from the new and improved TSO C74c specification.
Most "modern" transponders (manufactured since 1973) have an "SLS" circuit which suppresses reply on receipt of any two pulses in any interrogation spaced 2.0 microseconds apart that are above the MTL Minimum Triggering Level threshold of the receiver amplitude discriminator (P1->P2 or P2->P3 or P3->P4). This approach was used to comply with the original C74c and but also complies with the provisions of the new and improved C74c.
The FAA refers to the non-responsiveness of new and improved TSO C74c compliant transponders to Mode S compatible radars and TCAS as "The Terra Problem", and has issued Airworthiness Directives (ADs) against various transponder manufacturers, over the years, at various times on no predictable schedule. The ghosting and ring around problems have recurred on the more modern radars.
To combat these effects most recently, great emphasis is placed upon software solutions. It is highly likely that one of those software algorithms was the proximate cause of a mid-air collision recently, as one airplane was reported at showing its altitude as the pre-flight paper filed flight plan, and not the altitude assigned by the ATC controller (see the reports and observations contained in the below reference ATC Controlled Airplane Passenger Study of how radar worked).
See the reference section below for errors in performance standards for ATCRBS transponders in the US.
See the reference section below for FAA Technician Study of in-situ transponders.
Radar display
The beacon code and altitude were historically displayed verbatim on the radar scope next to the target, however modernization has extended the radar data processor with a flight data processor, or FDP. The FDP automatically assigns beacon codes to flight plans, and when that beacon code is received from an aircraft, the computer can associate it with flight plan information to display immediately useful data, such as aircraft callsign, the aircraft's next navigational fix, assigned and current altitude, etc. near the target in a data block.
Although the ATCRBS does not display aircraft heading.
Mode S
Mode S, or mode select, despite also being called a mode, is actually a radically improved system intended to replace ATCRBS altogether. A few countries have mandated mode S, and many other countries, including the United States, have begun phasing out ATCRBS in favor of this system. Mode S is designed to be fully backward compatible with existing ATCRBS technology.
Mode S, despite being called a replacement transponder system for ATCRBS, is actually a data packet protocol which can be used to augment ATCRBS transponder positioning equipment (radar and TCAS).
One major improvement of Mode S is the ability to interrogate a single aircraft at a time. With old ATCRBS technology, all aircraft within the beam pattern of the interrogating station will reply. In an airspace with multiple interrogation stations, ATCRBS transponders in aircraft can be overwhelmed. By interrogating one aircraft at a time, workload on the aircraft transponder is greatly reduced.
The second major improvement is increased azimuth accuracy. With PSRs and old SSRs, azimuth of the aircraft is determined by the half split (centroid) method. The half split method is computed by recording the azimuth of the first and last replies from the aircraft, as the radar beam sweeps past its position. Then the midpoint between the start and stop azimuth is used for aircraft position. With MSSR (monopulse secondary surveillance radar) and Mode S, the radar can use the information of one reply to determine azimuth. This is calculated based on the RF phase of the aircraft reply, as determined by the sum and difference antenna elements, and is called monopulse. This monopulse method results in superior azimuth resolution, and removes target jitter from the display.
The Mode S system also includes a more robust communications protocol, for a wider variety of information exchange. this capability is becoming mandatory across Europe with some states already requiring its use.
Diversity Operations
Diversity Mode S transponders may be implemented for the purpose of improving air-to-air surveillance and communications. Such systems shall employ two antennas, one
mounted on the top and the other on the bottom of the aircraft. Appropriate switching and signal processing channels to select the best antenna on the basis of the characteristics of
the received interrogation signals shall also be provided. Such diversity systems, in their installed configuration, shall not result in degraded performance relative to that which would have been produced by a single system having a bottom-mounted antenna.
Frequency Congestion, FRUIT
Mode S was developed as a solution to frequency congestion on both the uplink and downlink frequencies (1030 and 1090 MHz). The high coverage of radar service available today means that some radar sites receive transponder replies from interrogations that were initiated by other nearby radar sites. This results in FRUIT, or False Replies Unsynchronous In Time, which is the reception of replies at a ground station that do not correspond with an interrogation. This problem has worsened with the increasing prevalence of technologies like TCAS, in which individual aircraft interrogate one another to avoid collisions.
Finally, technology improvements have made transponders increasingly affordable such that today almost all aircraft are equipped with them. As a result, the sheer number of aircraft replying to SSRs has increased. Defruiter circuitry clears FRUIT from the display.
Mode S as a Congestion Solution
Mode S attempts to reduce these problems by assigning aircraft a permanent mode S address, derived from the aircraft's internationally assigned registration number. It then provides a mechanism by which an aircraft can be selected, or interrogated such that no other aircraft reply.
The system also has provisions for transferring arbitrary data both to and from a transponder. This aspect of mode S makes it a building block for many other technologies, such as TCAS 2, Traffic Information Service (TIS), and Automatic Dependent Surveillance-Broadcast.
See also
Acronyms and abbreviations in avionics
References
The Story of Mode S: An Air Traffic Control Data Link Technology (12/15/2000) - Story of the development of Mode S at MIT's Lincoln Laboratory
EUROCONTROL Mode S & ACAS Programme - Home page for the European Mode S & ACAS implementation coordination program
FAA TSO C74c (2/20/1973) - Minimum performance standards for ATCRBS transponders in the US (Historical)
FAA Controller Study of how his radar works
More about "The Terra Problem" (Dead link 2016)
The Story of Mode S AIS-P: An Air Traffic Control Positioning Technology Augmentation - Story of the development of AIS-P at the TailLight Consortium
AlliedSignal Aerospace (1996) Bendix/King KT76A/78A ATCRBS Transponder Maintenance Manual. (Rev. 6) (Dead link 2016)
RTCA/DO-181C, June 12, 2001: "Minimum Operational Performance Standards for Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/MODE S) Airborne Equipment"
Further reading
(59 pages)
(5 pages)
(9 pages)
External links
"Avionics" a 1971 Flight article on the RRE system of 1963.
Avionics
radar beacon system
Radar | Air traffic control radar beacon system | [
"Technology"
] | 4,511 | [
"Avionics",
"Aircraft instruments"
] |
2,164,190 | https://en.wikipedia.org/wiki/Cellomics | Cellomics is the discipline of quantitative cell analysis using bioimaging methods and informatics with a workflow involving three major components: image acquisition, image analysis, and data visualization and management. These processes are generally automated. All three of these components depend on sophisticated software to acquire qualitative data, quantitative data, and the management of both images and data, respectively. Cellomics is also a trademarked term, which is often used interchangeably with high-content analysis (HCA) or high-content screening (HCS), but cellomics extends beyond HCA/HCS by incorporating sophisticated informatics tools.
History
HCS and the discipline of cellomics was pioneered by a once privately held company named Cellomics Inc., which commercialized instruments, software, and reagents to facilitate the study of cells in culture, and more specifically, their responses to potentially therapeutic drug-like molecules. In 2005, Cellomics was acquired by Fisher Scientific International, Inc., now Thermo Fisher Scientific, which develops cellomics-related products under its high content analysis product line.
Applications
Like many of the -omics, e.g., genomics and proteomics, applications have grown in depth and breadth over time. Currently there are over 40 different application areas that cellomics is used in, including the analysis of 3-D cell models, angiogenesis, and cell-signalling. Originally a tool used by the pharmaceutical industry for screening, cellomics has now expanded into academia to better understand cell function in the context of the cell. Cellomics is used in both academic and industrial life-science research in areas, such as cancer research, neuroscience research, drug discovery, consumer products safety, and toxicology; however, there are many more areas for which cellomics could provide a much deeper understanding of cellular function.
Image analysis
With HCA at its core, cellomics incorporates the flexibility of fluorescence microscopy, the automation and capacity of the plate reader, and flow cytometry’s multi-parametric analysis in order to extract data from single-cells or from a population of cells.
Once an image is acquired using high content technology hardware, cell data is extracted from that image using image analysis software. Single cell data or population data may be of interest, but for both, a series of steps is followed with varying degrees of user interaction depending on the application and the software being used. The first step is segmenting the cells in the image which provides the software algorithms with the information it needs for downstream processing of individual cell measurements. Next, a user must define the area(s) of interest based on a multitude of parameters, i.e., the area a user wants to measure. After the area of interest has been defined, measurements are collected. The measurements, oftentimes referred to as features, are dictated by the type of data desired from the sample. There are many mathematical algorithms powering all of these steps, and each image analysis software package provides its own level of openness to the mathematical algorithms being used.
Data management
Large numbers of images and amounts of data need to be managed when doing cellomics research. Data and image volumes can quickly range from 11MB to 1TB in less than a year, which is why cellomics uses the power of informatics to collect, organize, and archive all of this information. Secure and effective data mining requires the associated metadata to be captured and integrated into the data management model. Due to the critical nature of cellomics data management, implementing cellomics studies often requires inter-departmental cooperation between information technology and the life science research group leading the study.
References
Cell imaging
Omics | Cellomics | [
"Chemistry",
"Biology"
] | 742 | [
"Bioinformatics",
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"Cell imaging",
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2,164,351 | https://en.wikipedia.org/wiki/Phaedon%20Avouris | Phaedon Avouris (; born 1945) is a Greek chemical physicist and materials scientist. He is an IBM Fellow and was formerly the group leader for Nanometer Scale Science and Technology at the Thomas J. Watson Research Center in Yorktown Heights, New York. His group conducted early work on carbon nanotubes, including the production the first nanotube transistors.
He was born and raised in Athens, Greece. In 1968 he graduated with a BSc. in chemistry from the Aristotle University of Thessaloniki, Greece.
Awards and Honors
Phaedon Avouris was elected as member of the National Academy of Sciences in 2017, the American Academy of Arts and Sciences in 2003, the Academy of Athens, Greece (Corresponding member) in 2007, and the IBM Academy of Technology in 2004.
He was also appointed Fellow in the following scientific societies: the American Physical Society (APS) in 1987; Institute of Physics (U.K.) in 2004; Institute of Electronic and Electrical Engineers (IEEE) in 2014; American Association for the Advancement of Science (AAAS) in 1996; Materials Research Society (MRS) in 2011; American Vacuum Society (AVS) in 1997; World Technology Network (1999). For his work, Avouris has received many awards from diverse scientific institutions including:
Irving Langmuir Prize for Chemical Physics, American Physical Society, 2003
Medard W. Welch Award for Surface Science, American Vacuum Society, 1997
IEEE Nanotechnology Section, Nanotechnology Pioneer Award, 2010
Richard Feynman Prize for Nanotechnology, Foresight Institute, 1999
Julius Springer Prize for Applied Physics (with T. Heinz), 2008
MRS David Turnbull Lectureship, Materials Research Society, 2011
Richard E. Smalley Prize of the Electrochemical Society, 2009
H. Bloch Medal, Excellence of Research in Industry, Univ. of Chicago, 2015
IBM Exceptional Achievement Corporate Award, 2011
Outstanding Technical Achievement Awards, IBM Corporation, 1989, 1993, 2000, 2002, 2003, 2013, 2015
Honorary Doctorate, International Hellenic University, 2013
Distinguished Alumnus Award, Michigan State University, 2001
General References
Publications
LYO, I.-W.; AVOURIS, P. (1991-07-12). "Field-Induced Nanometer- to Atomic-Scale Manipulation of Silicon Surfaces with the STM". Science. 253 (5016): 173–176. doi:10.1126/science.253.5016.173. ISSN 0036-8075.
LYO, I.-W.; AVOURIS, P. (1991-07-12). "Field-Induced Nanometer- to Atomic-Scale Manipulation of Silicon Surfaces with the STM". Science. 253 (5016): 173–176. doi:10.1126/science.253.5016.173. ISSN 0036-8075. Field-Induced Nanometer- to Atomic-Scale Manipulation of Silicon Surfaces with the STM
I-W. Lyo and Ph. Avouris (1989). "Negative Differential Resistance on the Atomic Scale: Implications for Atomic Scale Devices". Science 245 (4924): 1369–1371. doi: 10.1126/science.245.4924.1369
Martel, R.; Schmidt, T.; Shea, H. R.; Hertel, T.; Avouris, Ph. (1998-10-21). "Single- and multi-wall carbon nanotube field-effect transistors". Applied Physics Letters. 73 (17): 2447–2449. doi:10.1063/1.122477. ISSN 0003-6951. Single- and multi-wall carbon nanotube field-effect transistors
Collins, P. G. (2001-04-27). "Engineering Carbon Nanotubes and Nanotube Circuits Using Electrical Breakdown". Science. 292 (5517): 706–709. doi:10.1126/science.1058782.
Martel, R.; Derycke, V.; Lavoie, C.; Appenzeller, J.; Chan, K. K.; Tersoff, J.; Avouris, Ph. (2001-12-03). "Ambipolar Electrical Transport in Semiconducting Single-Wall Carbon Nanotubes". Physical Review Letters. 87 (25): 256805. doi:10.1103/PhysRevLett.87.256805. ISSN 0031-9007
Wind, S. J.; Appenzeller, J.; Avouris, Ph. (2003-07-29). "Lateral Scaling in Carbon-Nanotube Field-Effect Transistors". Physical Review Letters. 91 (5): 058301.https://doi.org/10.1103%2FPhysRevLett.91.058301
Perebeinos, Vasili; Tersoff, J.; Avouris, Phaedon (2004-06-25). "Scaling of Excitons in Carbon Nanotubes". Physical Review Letters. 92 (25): 257402. Scaling of Excitons in Carbon Nanotubes
Chen, J., Perebeinos, V, Freitag, M., Tsang, J., Fu, Q., Liu, J., Avouris, P. (2005-11-18). "Bright Infrared Emission from Electrically Induced Excitons in Carbon Nanotubes". Science. 310 (5751): 1171–1174. ISSN 0036-8075. Bright Infrared Emission from Electrically Induced Excitons in Carbon Nanotubes
Chen, Z. (2006-03-24). "An Integrated Logic Circuit Assembled on a Single Carbon Nanotube". Science. 311 (5768): 1735–1735. ISSN 0036-8075. An Integrated Logic Circuit Assembled on a Single Carbon Nanotube
Chen, Zhihong; Lin, Yu-Ming; Rooks, Michael J.; Avouris, Phaedon (2007-12-01). "Graphene nano-ribbon electronics". Physica E: Low-dimensional Systems and Nanostructures. 40 (2): 228–232. ISSN 1386-9477. Graphene nano-ribbon electronics
Perebeinos, Vasili; Avouris, Phaedon (2008-07-30). "Phonon and Electronic Nonradiative Decay Mechanisms of Excitons in Carbon Nanotubes". Physical Review Letters. 101 (5): 057401. Phonon and Electronic Nonradiative Decay Mechanisms of Excitons in Carbon Nanotubes
Xia, Fengnian; Mueller, Thomas; Lin, Yu-ming; Valdes-Garcia, Alberto; Avouris, Phaedon (2009–12). "Ultrafast graphene photodetector". Nature Nanotechnology. 4 (12): 839–843. ISSN 1748–3395. Ultrafast graphene photodetector
Steiner, Mathias; Freitag, Marcus; Perebeinos, Vasili; Tsang, James C.; Small, Joshua P.; Kinoshita, Megumi; Yuan, Dongning; Liu, Jie; Avouris, Phaedon (2009-03-01). "Phonon populations and electrical power dissipation in carbon nanotube transistors". Nature Nanotechnology. 4 (5): 320–324. ISSN 1748–3387. Phonon populations and electrical power dissipation in carbon nanotube transistors
Mueller, Thomas; Xia, Fengnian; Avouris, Phaedon (2010–05). "Graphene photodetectors for high-speed optical communications". Nature Photonics. 4 (5): 297–301. ISSN 1749–4893. Graphene photodetectors for high-speed optical communications
Mueller, Thomas; Kinoshita, Megumi; Steiner, Mathias; Perebeinos, Vasili; Bol, Ageeth A.; Farmer, Damon B.; Avouris, Phaedon (2010–01). "Efficient narrow-band light emission from a single carbon nanotube p–n diode". Nature Nanotechnology. 5 (1): 27–31. ISSN 1748–3395. Efficient narrow-band light emission from a single carbon nanotube p–n diode
Xia, Fengnian; Farmer, Damon B.; Lin, Yu-ming; Avouris, Phaedon (2010-02-10). "Graphene Field-Effect Transistors with High On/Off Current Ratio and Large Transport Band Gap at Room Temperature". Nano Letters. 10 (2): 715–718. ISSN 1530–6984. Graphene Field-Effect Transistors with High On/Off Current Ratio and Large Transport Band Gap at Room Temperature
Lin, Y.-M.; Valdes-Garcia, A.; Han, S.-J.; Farmer, D. B.; Meric, I.; Sun, Y.; Wu, Y.; Dimitrakopoulos, C.; Grill, A.; Avouris, P.; Jenkins, K. A. (2011-06-10). "Wafer-Scale Graphene Integrated Circuit". Science. 332 (6035): 1294–1297. ISSN 0036-8075. Wafer-Scale Graphene Integrated Circuit
Wu, Yanqing; Lin, Yu-ming; Bol, Ageeth A.; Jenkins, Keith A.; Xia, Fengnian; Farmer, Damon B.; Zhu, Yu; Avouris, Phaedon (2011–04). "High-frequency, scaled graphene transistors on diamond-like carbon". Nature. 472 (7341): 74–78. ISSN 1476–4687. High-frequency, scaled graphene transistors on diamond-like carbon
Xia, Fengnian; Perebeinos, Vasili; Lin, Yu-ming; Wu, Yanqing; Avouris, Phaedon (2011–03). "The origins and limits of metal–graphene junction resistance". Nature Nanotechnology. 6 (3): 179–184. ISSN 1748–3395. The origins and limits of metal–graphene junction resistance
Engel, Michael; Steiner, Mathias; Lombardo, Antonio; Ferrari, Andrea C.; Löhneysen, Hilbert v; Avouris, Phaedon; Krupke, Ralph (2012-06-19). "Light–matter interaction in a microcavity-controlled graphene transistor". Nature Communications. 3 (1): 906. ISSN 2041-1723. PMC 3621428. PMID 22713748. Light–matter interaction in a microcavity-controlled graphene transistor
Yan, Hugen; Li, Xuesong; Chandra, Bhupesh; Tulevski, George; Wu, Yanqing; Freitag, Marcus; Zhu, Wenjuan; Avouris, Phaedon; Xia, Fengnian (2012–05). "Tunable infrared plasmonic devices using graphene/insulator stacks". Nature Nanotechnology. 7 (5): 330–334. ISSN 1748–3395. Tunable infrared plasmonic devices using graphene/insulator stacks
Freitag, Marcus; Low, Tony; Xia, Fengnian; Avouris, Phaedon (2012-12-16). "Photoconductivity of biased graphene". Nature Photonics. 7 (1): 53–59. ISSN 1749–4885. Photoconductivity of biased graphene
Yan, Hugen; Low, Tony; Zhu, Wenjuan; Wu, Yanqing; Freitag, Marcus; Li, Xuesong; Guinea, Francisco; Avouris, Phaedon; Xia, Fengnian (2013–05). "Damping pathways of mid-infrared plasmons in graphene nanostructures". Nature Photonics. 7 (5): 394–399. ISSN 1749–4893. Damping pathways of mid-infrared plasmons in graphene nanostructures
Low, T.; Perebeinos, V.; Tersoff, J.; Avouris, Ph. (2012-03-01). "Deformation and Scattering in Graphene over Substrate Steps". Physical Review Letters. 108 (9): 096601. Deformation and Scattering in Graphene over Substrate Steps
Freitag, Marcus; Low, Tony; Zhu, Wenjuan; Yan, Hugen; Xia, Fengnian; Avouris, Phaedon (2013-06-03). "Photocurrent in graphene harnessed by tunable intrinsic plasmons". Nature Communications. 4 (1): 1951. ISSN 2041-1723. Photocurrent in graphene harnessed by tunable intrinsic plasmons
Zhu, Wenjuan; Low, Tony; Lee, Yi-Hsien; Wang, Han; Farmer, Damon B.; Kong, Jing; Xia, Fengnian; Avouris, Phaedon (2014-01-17). "Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition". Nature Communications. 5 (1): 3087. doi:10.1038/ncomms4087. ISSN 2041-1723. Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition
Yan, Hugen; Low, Tony; Guinea, Francisco; Xia, Fengnian; Avouris, Phaedon (2014-08-13). "Tunable Phonon-Induced Transparency in Bilayer Graphene Nanoribbons". Nano Letters. 14 (8): 4581–4586. doi:10.1021/nl501628x. ISSN 1530–6984. Tunable Phonon-Induced Transparency in Bilayer Graphene Nanoribbons
Low, Tony; Guinea, Francisco; Yan, Hugen; Xia, Fengnian; Avouris, Phaedon (2014-03-18). "Novel Midinfrared Plasmonic Properties of Bilayer Graphene". Physical Review Letters. 112 (11): 116801. doi:10.1103/PhysRevLett.112.116801. Novel Midinfrared Plasmonic Properties of Bilayer Graphene
Koppens, F. H. L.; Mueller, T.; Avouris, Ph; Ferrari, A. C.; Vitiello, M. S.; Polini, M. (2014–10). "Photodetectors based on graphene, other two-dimensional materials and hybrid systems". Nature Nanotechnology. 9 (10): 780–793. doi:10.1038/nnano.2014.215. ISSN 1748–3395. Photodetectors based on graphene, other two-dimensional materials and hybrid systems
Farmer, Damon B.; Rodrigo, Daniel; Low, Tony; Avouris, Phaedon (2015-03-10). "Plasmon–Plasmon Hybridization and Bandwidth Enhancement in Nanostructured Graphene". Nano Letters. 15 (4): 2582–2587. doi:10.1021/acs.nanolett.5b00148. ISSN 1530–6984. Plasmon–Plasmon Hybridization and Bandwidth Enhancement in Nanostructured Graphene
Falk, Abram L.; Chiu, Kuan-Chang; Farmer, Damon B.; Cao, Qing; Tersoff, Jerry; Lee, Yi-Hsien; Avouris, Phaedon; Han, Shu-Jen (2017-06-22). "Coherent Plasmon and Phonon-Plasmon Resonances in Carbon Nanotubes". Physical Review Letters. 118 (25). doi:10.1103/physrevlett.118.257401. ISSN 0031-9007. Coherent Plasmon and Phonon-Plasmon Resonances in Carbon Nanotubes
Low, Tony; Chaves, Andrey; Caldwell, Joshua D.; Kumar, Anshuman; Fang, Nicholas X.; Avouris, Phaedon; Heinz, Tony F.; Guinea, Francisco; Martin-Moreno, Luis; Koppens, Frank (2017–02). "Polaritons in layered two-dimensional materials". Nature Materials. 16 (2): 182–194. doi:10.1038/nmat4792. ISSN 1476–4660. Polaritons in layered two-dimensional materials
Ho, Po-Hsun; Farmer, Damon B.; Tulevski, George S.; Han, Shu-Jen; Bishop, Douglas M.; Gignac, Lynne M.; Bucchignano, Jim; Avouris, Phaedon; Falk, Abram L. (2018-12-11). "Intrinsically ultrastrong plasmon–exciton interactions in crystallized films of carbon nanotubes". Proceedings of the National Academy of Sciences. 115 (50): 12662–12667. doi:10.1073/pnas.1816251115. ISSN 0027-8424. PMC 6294907. PMID 30459274.
Lee, In-Ho; Yoo, Daehan; Avouris, Phaedon; Low, Tony; Oh, Sang-Hyun (2019-02-11). "Graphene acoustic plasmon resonator for ultrasensitive infrared spectroscopy". Nature Nanotechnology. 14 (4): 313–319. doi:10.1038/s41565-019-0363-8. ISSN 1748–3387. Graphene acoustic plasmon resonator for ultrasensitive infrared spectroscopy
Lee, In-Ho; He, Mingze; Zhang, Xi; Luo, Yujie; Liu, Song; Edgar, James H.; Wang, Ke; Avouris, Phaedon; Low, Tony; Caldwell, Joshua D.; Oh, Sang-Hyun (2020-07-20). "Image polaritons in boron nitride for extreme polariton confinement with low losses". Nature Communications. 11 (1). doi:10.1038/s41467-020-17424-w. ISSN 2041-1723. Image polaritons in boron nitride for extreme polariton confinement with low losses
Avouris, Phaedon (1995-03-01). "Manipulation of Matter at the Atomic and Molecular Levels". Accounts of Chemical Research''. 28 (3): 95–102. doi:10.1021/ar00051a002. ISSN 0001-4842. Manipulation of Matter at the Atomic and Molecular Levels
References
External links
Nanometer Scale Science and Technology Group Homepage
Irving Langmuir Prize
Academy of Athens
Feynman Prize Recipients, Foresight Nanotech Institute
1945 births
Living people
Fellows of the American Academy of Arts and Sciences
Greek academics
Greek nanotechnologists
IBM Fellows
Michigan State University alumni
Aristotle University of Thessaloniki alumni
Corresponding Members of the Academy of Athens (modern) | Phaedon Avouris | [
"Chemistry",
"Materials_science"
] | 4,160 | [
"Nanotechnology",
"Nanotechnologists",
"Physical chemists"
] |
2,164,533 | https://en.wikipedia.org/wiki/Type%20B%20videotape | 1-inch Type B Helical Scan or SMPTE B is a reel-to-reel analog recording video tape format developed by the Bosch Fernseh division of Bosch in Germany in 1976. The magnetic tape format became the broadcasting standard in continental Europe, but adoption was limited in the United States and United Kingdom, where the Type C videotape format met with greater success.
Details
The tape speed allowed 96 minutes on a large reel (later 120 minutes), and used 2 record/playback (R/P) heads on the drum rotating at 9,000 RPM with a 190-degree wrap around a very small head drum, recording 52 video lines per head segment. A single video frame or field was recorded across 6 tracks in the tape. The format only allowed for play, rewind and fast forward. Video is recorded on an FM signal with a bandwidth of 5.5 MHz. Three longitudinal audio tracks are recorded on the tape as well: two audio and one Linear timecode (LTC) track. BCN 50 VTRs were used at the 1980 Summer Olympics in Moscow.
The format required an optional, and costly, digital framestore in addition to the normal analog timebase corrector to do any "trick-play" operations, such as slow motion/variable-speed playback, frame step play, and visible shuttle functions. This was because, unlike 1-inch type C which recorded one field per helical scan track on the tape, Type B segmented each field to 5 or 6 tracks per field according to whether it was a 525- (NTSC) or 625- (PAL) line machine.
The picture quality was excellent, and standard R/P machines, digital frame store machines, reel-to-reel portables, random access cart machines (for playback of short-form video material such as television commercials), and portable cart versions were marketed.
Echo Science Corporation, a United States company, made units like a BCN 1 for the U.S. military for a short time in the 1970s. Echo Science models were Pilot 1, Echo 460, Pilot 260.
Models introduced
BCR (BCR-40, BCR-50 and BCR-60) was a pre BCN VTR, made jointly with Philips, the large scanner made it not useful.
BCN-40 (1976, record unit with no TBC playback)
BCN-50 (1976, recorder with TBC playback)
BCN-20 (1976, one hour, portable with no TBC playback)
BCWQ ("L" Unit for BCN20/21, added TBC playback to the portable units)
Effects control option for digital framestore, for freeze frame, quad split and mirror effects (early digital Special effects).
BNC-51 (recorder with TBC playback, optional Slow motion and visible shuttle)
BCN-5 (26 pound, portable cart recorder, 40 min)
BCN-100 (random access 32 multicassette machine, up to 16 hours rec/playback-20 min per tape) Each unit had 3 tape desks with a 21 sec load time each cart. For on air playback and 3 deck editing system
BCN-52 (recorder with Digital TBC playback, with slow motion & visible shuttle)
BCN-21 (lightweight reel to reel portable with no TBC playback, first Composite material VTR)
BCN-53 (recorder with Digital TBC playback, with slow motion & visible shuttle)
HR-400: RCA also sold the BCN-50 as an HR-400.
Special BCN units
Ruxton Video in Burbank (1970–1980s) used modified BCNs for 24 Frame playback to TVs used on movie studio sets. Thus the TVs had no flicker when seen on film, due to the film-compatible frame rate. In 1981, Bill Hogan of Ruxton Ltd received an Academy Award for Technical Achievement for his 24frame TV work.
Image Transform in Universal City, co-founded by Ken Holland, in 1970, used specially modified BCNs to record 24-frame video also, but for their "Image Vision" system. The BCN would record and play back 24-frame video at 10 MHz bandwidth, with 655-line resolution. To record this the headwheel and capstan ran at twice normal speed. Modified 24 frame/s 10 MHz Bosch Fernseh KCK-40 professional video cameras were used on the set. This was a custom pre-HDTV video system. This Image Vision recording could then be recorded to film on a modified 3M Electron Beam film recorder (EBR). Image Transform had modified other gear for this process. The system was used to record "Monty Python Live at the Hollywood Bowl" in 1982. This was the first major use of early electronic cinema technology (using wideband high-resolution analog video technology, predating IT-based DI (digital intermediate) post production for film nowadays) using a film recorder for Film out. Electronovision was also a pre-process like Image Vision. Merlin Engineering also worked on the BCN's wide bandwidth, 10 MHz, BCN modification.
Bell and Howell (later Rank Video Services) used special BCNs for mass VHS duplication. These specially-modified BCN VTRs could play back movies at two times the normal speed. In addition, the sync signals were also at two times speed as well. For proper playback, the headwheel and capstan also ran at twice normal speed. Specially modified VHS recorders could record this video. In doing this, the duplication plant could output twice the product than normal videocassette duplicating systems.
Bell and Howell's Data Tape division in Pasadena, California modified BCNs to record high speed data for instrumentation purposes. These instrumentation recordings were mostly used by US government agencies, such as for NASA on the Space Shuttle. This unit could record data from up to 800 sensors.
Because of the small scanner, BCNs could record even at high g-forces. Hand picked BCN20 VTRs could record at low temperatures, down to -40 °C (-40 °F). This was done at the Olympic Winter Games in Lake Placid (1980) and in Sarajevo (1984).
Some users modified BCNs to fit 2-hour reels of tape on the BCN, so complete 2-hour movies could fit on one reel of tape. Bosch later made this a factory option, and was designated as BCN LP.
Bosch also offered SLP BCN, a "long-play" variant of the format. It moved the tape at 1/3 speed so that up to 6 hours could be recorded one reel. The unit has a special head wheel with azimuth head. This was mostly used for time zone tape delay by television networks. With a head wheel change and a switch the unit could be returned to normal play.
Between 1977 and 1980 the UK Independent Broadcasting Authority (IBA) experimented with a B format machine as part of their researches into digital video broadcasting standards. In April 1980 a machine was exhibited at a meeting of the EBU Technical Committee in London as part of a complete digital studio system based on a proposed video standard based on YUV 12.4.4. The machine is described in a paper in the IBA Technical Review of March 1982 which can be found here by scrolling down to the item IBA_TechnicalReviews1-24""
One of the first Digital SDTV VTRs was a non-production prototype BCN deck that could record and play back early type of CCIR 601 digital signals. These three Bosch VTRs paved the way for the later SMPTE D1 VTR standard. In 1985 and 1986 in a Rennes experimental digital studio in France, an experimental all-digital television center was made, it used the two all digital BCN units.
The BCH 1000 is an analog high-definition television VTR that records and playbacks HD-MAC at 50 frames per second, each at a resolution of 2048×1152. The BCH 1000 was used in the 1992 Summer Olympic Games in Barcelona and 1992 Winter Olympics in Albertville. It used 8 video heads to handle the increased bandwidth requirements of HD-MAC, due to its high resolution.
Specifications
1 Inch open reel to reel analog video system.
Video scanner rotation 9600 rpm, 150 rps.
52 horizontal lines per head.
Video FM signal at a bandwidth of 5,5 MHz
Three analog audio tracks: 2 audio tracks and 1 linear timecode track, 0.8mm wide - 30 mils
One analog control track 0.4mm wide - 15 mils, built into video scanner head.
Magnetic tape coating on the outside of the videotape reel.
Studio reel 96 minutes, later 120 minutes
Portable reel 60 minutes
Cart reel 20 minutes (BCN5 - BCN100)
Video scanner wrap 190 deg.
Video scanner dia. 50.3mm, 2 inches
Video track length 3.1 inches, 80mm
Video track gap 40 um, 1.5 mils
Tape speed 24 cm/sec - 9.5 ips.
Video head write speed: 24m /sec - 950 ips
Video track angle 14.3 deg.
Video track width 160 um - 6.3 mils
Two video record/play heads at 180 deg. (rotary transformer)
Two video erase head for insert edits at 180 deg. (rotary transformer)
Some BCN users
ABC-TV at MCF
AME – Hollywood, California
Aquarius Theater –Hollywood, California
Astin Moore – Los Angeles, California; see John Astin
ATC – Buenos Aires, Argentina
Audio Plus Video – Los Angeles, California and Northvale, New York
Australian Film & Television School – Sydney (now Australian Film, Television & Radio School)
Bell and Howell, (Rank Video Services) – Oak Brook, Illinois
Bell and Howell Data Tape – Pasadena, California
Cinema Video Processors – Chicago, Illinois
Channel 7 – Bangkok, Thailand
Complete Post – Hollywood, California
Cossey Studios – Santa Cruz, California
Dash Motorcars – Santa Cruz, California
DC Video – current user – Burbank, California
Doordarshan – Delhi, India
Editel – Hollywood, California
Eesti Televisioon
Glendale Studios (Outpost Video) – Glendale, California
Image Transform – Universal City, California
KCPT – Kansas City, Missouri
KPAZ-TV – Phoenix, Arizona
KTBN-TV – Costa Mesa, California
KTBO-TV – Oklahoma, Oklahoma
KTBW-TV – Tacoma, Washington
Laser Pacific – Hollywood, California
Leon Russell – Burbank, California and Tulsa, Oklahoma
4MC – Burbank, California
Measurement Analysis – Torrance, California
Merlin – Palo Alto, California
Modern Video Film – Hollywood, California
National Institutes of Health – Bethesda, Maryland
Oral Roberts University – Tulsa, Oklahoma
ORF-Austrian Broadcasting Corporation – Vienna, Austria
Premore (see Solo Cup Company) – Culver City, California
Ruxton – Burbank, California
Spin Physics – San Diego, California
Starfax – Burbank, California
STW Channel 9 – Perth, Western Australia
Technicolor – Newberry Park, California
The Video Tape Company – North Hollywood, California
The Videography Studios – West Los Angeles, California
TV2 in Framersheim, Germany
TV Bandeirantes – São Paulo, Brazil
Tyne Tees Television – Newcastle, United Kingdom (used the BCN100 cart system for commercial playout)
VDI – Hollywood, California
Video Business – New York, New York
Video Pack – New York, New York
Video Tape Company – Burbank, California
Vidtronics – Hollywood, California
WHFT-TV – Pembroke Park, Florida
WTVY – Dothan, Alabama
Yorkshire Television – Leeds, United Kingdom (used the BCN100 cart system for commercial playout)
ZDF – Mainz, Germany
See also
Ampex 2 inch helical VTR
D1
D6 HDTV VTR
Fernseh
1 inch type A videotape
1 inch type C videotape
IVC videotape format
VTR
References
External links
vtoldboys.com BCN Pictures
The history of television, 1942 to 2000, page 197, By Albert Abramson
DC Video BNC page, Current user
little-archives.net BCN Specs
youtube.com BCN studio demo
youtube.com BCN20 demo
youtube.com BCN 51 PAL studio demo
Videotape
Products introduced in 1976
Composite video formats
Television technology
Television terminology | Type B videotape | [
"Technology"
] | 2,540 | [
"Information and communications technology",
"Television technology"
] |
2,164,548 | https://en.wikipedia.org/wiki/Airport%20rail%20link | An airport rail link is a service providing passenger rail transport between an airport and a nearby city. Direct links operate straight from the airport terminal to the city, while other links require an intermediate use of a people mover or shuttle bus. Advantages for the passenger include faster travel times and easy connections with other public transport. Advantages for the airport include increased patronage and enhanced accessibility for staff. Additionally, authorities have benefitted from less highway congestion, less pollution, and more business opportunities.
History
Although airport rail links have been a popular solution in Europe and Japan for decades, only recently have links been constructed in North America, South America, Africa, Oceania, and the rest of Asia.
Some early examples of inter-city railway stations built to serve an airport include:
The first rapid transit station to connect with an airport was Berlin's U-Bahn U6 Paradestraße station which opened in 1927 as Flughafen () and was built to provide direct access to Berlin Tempelhof Airport. However, the connection was removed in 1937 and the preceding Platz der Luftbrücke station was instead granted the connection and remained so until Berlin Tempelhof Airport's closure in 2008.
Other early examples of rapid transit stations connecting with airports include Boston's MBTA Blue Line Airport station which opened in 1952 (rebuilt in 2004), and Cleveland's RTA Rapid Transit Red Line Cleveland Hopkins International Airport station which opened in 1968 (rebuilt in 1994). Boston's link requires a short shuttle bus transfer from the station to the airport terminal, whilst Cleveland's link is considered the first direct service in the Western Hemisphere.
Tokyo Monorail, which opened in 1964 as Japan's first airport rail link, had its original southern terminus underneath the old domestic terminal of Haneda Airport. When Haneda Airport was expanded onto landfill reclaimed from Tokyo Bay in the 1980s–2010s, the monorail was extended to the new terminals as well, with the original southern terminus later renamed as Tenkūbashi Station.
Connection types
High-speed rail and inter-city rail
A high-speed or inter-city service provides direct travel between an airport and its surrounding cities. This solution usually requires the building of new track, whether it is a newly built main line or a branch (spur) line. These services often have premium fares, lower frequencies (e.g. every 30 minutes) and luxury features (e.g. luggage racks, power outlets, Wi-Fi, bathrooms).
Integration with high-speed and inter-city services has produced alliances where airlines sell tickets that include the connecting rail service. Parts of Europe have seen integration of high-speed rail stations into airports, with domestic and international TGV services from Paris Charles de Gaulle Airport and ICE services from Frankfurt Airport. Because of this, some stations have received IATA codes.
Regional rail and commuter rail
A regional or commuter "airport express" service provides direct travel between an airport and its city centre. This solution is often used where the airport is outside the urban area and some way from the mass transit system but a direct downtown service is required. There are various ways this can be achieved: it may operate on a combination of existing or newly built mainline rail track using a dedicated fleet of rolling stock designed for airport service. Similarly to high-speed and inter-city services, these services often have premium fares, lower frequencies and luxury features.
Rapid transit and light rail
For airports built within or close to the city limits, extending rapid transit or light rail to the airport allows seamless transport to suburbs and full integration with other lines. These services usually have a higher frequency (e.g. every 5 minutes) but longer travel times due to the service making many intermediate stops between the airport and the city centre. Additionally, there may not be enough space for baggage commonly carried by airport-bound passengers. Luggage stowing facilities are not commonly found on rapid transit or light rail vehicles as their primary objective is to provide high-capacity service.
Rail to people mover
A hybrid solution adopted in some cities is a direct link to an airport railway station connected to a people mover. The passenger transfers from the railway station to the people mover which then completes the journey to the airport terminal. While this option is commonly chosen to reduce construction costs, it is only feasible when a rail line is near the airport. Some airports, such as San Francisco International Airport, are directly served by an airport rail link to some terminals but not others. In such cases, passengers using terminals that lack a direct connection must use a people mover to access their terminal. People movers typically also serve parking lots, airport hotels and off-site car rental facilities. People movers are seen to have a higher perceived quality compared to a shuttle bus.
Rail to shuttle bus
Another hybrid solution is a direct link to an airport railway station connected to a shuttle bus. The passenger transfers from the railway station to the shuttle bus which then completes the journey to the airport terminal. A shuttle bus requires no specialised infrastructure, and is often the preferred choice at smaller or low-cost airports. Shuttle buses may involve a wait for a transfer to the next stage of the journey and often suffer from lower perceived quality and market share compared to direct connections.
Current examples
High-speed rail and inter-city rail
Examples include Schipol Airport station to other Dutch cities, Zürich Flughafen station to other Swiss cities, and Daxing Airport station to other Chinese cities.
Regional rail and commuter rail
Examples include the Airport Rail Link between Suvarnabhumi Airport and Bangkok, the Narita Express between Narita International Airport and Tokyo, the Union Pearson Express between Toronto Pearson International Airport and Toronto, and the Leonardo Express between Leonardo da Vinci–Rome Fiumicino Airport and Rome.
Rapid transit and light rail
Examples include the East–West Line between Changi Airport station and Singapore, the Silver Line between Washington Dulles International Airport station and Washington, D.C., the Canada Line between YVR-Airport station and Vancouver, and the Orange Line between DFW Airport Terminal A station and Dallas.
Rail to people mover
Examples include Soekarno–Hatta International Airport via Soekarno–Hatta Airport Skytrain to/from SHIA station, London Luton Airport via Luton DART to/from Luton Airport Parkway station, and Paris Orly Airport via Orlyval to/from Antony station.
Rail to shuttle bus
Examples include Shijiazhuang Zhengding International Airport via shuttle bus to/from Zhengding Airport station, Salvador Bahia Airport via shuttle bus to/from Aeroporto station, and Milwaukee Mitchell International Airport via shuttle bus to/from Milwaukee Airport station.
See also
Air-rail alliance
Intermodal passenger transport
List of IATA-indexed railway stations
References
Rail link
Passenger rail transport | Airport rail link | [
"Engineering"
] | 1,370 | [
"Airport infrastructure",
"Aerospace engineering"
] |
2,164,583 | https://en.wikipedia.org/wiki/State%20Research%20Center%20of%20Virology%20and%20Biotechnology%20VECTOR | The State Research Center of Virology and Biotechnology VECTOR, also known as the Vector Institute (), is a biological research center in Koltsovo, Novosibirsk Oblast, Russia. It has research facilities and capabilities for all levels of biological hazard, CDC levels 1–4. It is one of two official repositories for the now-eradicated smallpox virus, and was part of the system of laboratories known as the Biopreparat.
The facility was upgraded and secured using modern cameras, motion sensors, fences and biohazard containment systems. Its relative seclusion makes security an easier task. Since its inception there has been an army regiment guarding the facility.
At least in Soviet times the facility was a nexus for biological warfare research (see Soviet biological weapons program), though the nature of any ongoing research in this area is uncertain.
As of April 2022 the Vector Institute is the Russian site for the WHO H5 Reference Laboratory Network, which responds "to the public health needs arising from avian influenza A (H5N1) infection in humans and influenza pandemic preparedness."
History
Organized in 1974, the center has a long history of virology, making impressive Soviet contribution to smallpox research. Genetic engineering projects included creation of viruses that manufacture toxins as well as research on bioregulators and various peptides that function in the nervous system. In the post-Soviet times the center made research and development contributions in many projects like a vaccine for Hepatitis A, influenza vaccines, vaccines for the Ebola virus, antiviral drugs with nucleotide analogs, test-systems for diagnostics of HIV and Hepatitis B and other development. It is one of the two laboratories worldwide that are authorized to keep smallpox.
COVID-19 vaccine development
In March 2020 it was reported that Russian scientists have begun to test vaccine prototypes for the new coronavirus disease (COVID-19), with the plan of presenting the most effective one in June, a laboratory chief at Vector Institute said. The prototypes have been created and the testing on animals began.
In July 2020, research by the centre found that the SARS-CoV-2 virus that causes COVID-19 can be killed in room temperature water within 72 hours, helping further research about the disease during the pandemic.
Tasks
The main tasks of the centre, according to VECTOR, are:
Basic research of causative agents of especially dangerous and socially important viral infections, and their genetic variability and diversity, pathogenesis of viral infections.
Ensuring constant readiness for implementing diagnostics of especially dangerous infectious agents.
The development and introduction into healthy practice of diagnostic curative and preventive medicines.
Post-graduate training, and scientific training of higher qualification in the field of Virology, molecular biology and biotechnology through graduate school and higher education.
Accidents
On 30 April 1988, a doctor died two weeks after accidentally pricking himself through two layers of rubber gloves with a needle contaminated with the Marburg virus.
In 2004, a researcher at VECTOR died after accidentally pricking herself with a needle contaminated with the Ebola virus.
On 17 September 2019, a gas explosion occurred at Vector. One worker suffered third-degree burns, and the blast blew out window panes. The lab has highly contagious forms of bird flu and strains of hepatitis. The explosion happened in a decontamination room that was being renovated by a contractor.
See also
Smallpox
Notes
Citations
External links
State Research Center of Virology and Biotechnology VECTOR homepage
About the center
NPO Vector at Globalsecurity.org
1974 establishments in the Soviet Union
Biological warfare facilities
Biosafety level 4 laboratories
COVID-19 vaccine producers
V
Medical research institutes in the Soviet Union
National public health agencies
Research institutes established in 1974
Soviet biological weapons program | State Research Center of Virology and Biotechnology VECTOR | [
"Biology"
] | 765 | [
"Biological warfare facilities",
"Biological warfare"
] |
2,164,610 | https://en.wikipedia.org/wiki/The%20Bottle%20Imp | "The Bottle Imp" is an 1891 short story by the Scottish author Robert Louis Stevenson usually found in the short story collection Island Nights' Entertainments. It was first published in the New York Herald (February–March 1891) and Black and White magazine (London, March–April 1891). In it, the protagonist buys a bottle with an imp inside that grants wishes. However, the bottle is cursed; if the holder dies bearing it, his or her soul is forfeit to hell.
Plot
Keawe, a poor Native Hawaiian, buys a strange unbreakable bottle from a sad, elderly gentleman who credits the bottle with his fortune. He promises that an imp residing in the bottle will also grant Keawe his every desire.
Of course, there is a catch. The bottle must be sold, for cash, at a loss, i.e. for less than its owner originally paid, and cannot be thrown or given away, or else it will magically return to him. All of these rules must be explained by each seller to each purchaser. If an owner of the bottle dies without having sold it in the prescribed manner, that person's soul will burn for eternity in Hell.
The bottle was said to have been brought to Earth by the Devil and first purchased by Prester John for millions; it was owned by Napoleon and Captain James Cook and accounted for their great successes. By the beginning of the story the price has diminished to fifty dollars.
Keawe buys the bottle and instantly tests it by wishing his money to be refunded, and by trying to sell it for more than he paid and abandoning it, to test if the story is true. When these all work as described, he realizes the bottle does indeed have unholy power. He wishes for his heart's desire: a big, fancy mansion on a landed estate, and finds his wish granted, but at a price: his beloved uncle and cousins have been killed in a boating accident, leaving Keawe sole heir to his uncle's fortune. Keawe is horrified, but uses the money to build his house. Having all he wants, and being happy, he explains the risks to a friend who buys the bottle from him.
Keawe lives a happy life, but there is something missing. Walking along the beach one night, he meets a beautiful woman, Kokua. They soon fall in love and become engaged. Keawe's happiness is shattered on the night of his betrothal, when he discovers that he has contracted the then-incurable disease of leprosy. He must give up his house and wife, and live in Kalaupapa—a remote community for lepers—unless he can recover the bottle and use it to cure himself.
Keawe begins this quest by attempting to track down the friend to whom he sold the bottle, but the friend has become suddenly wealthy and left Hawaii. Keawe traces the path of the bottle through many buyers and eventually finds a Haole in Honolulu. The man of European ancestry has both good and bad news for Keawe: (a) he owns the bottle and is very willing to sell, but (b) he had only paid two cents for it. Therefore, if Keawe buys it, he will not be able to resell it.
Keawe decides to buy the bottle anyway, for the price of one cent, and indeed cures himself. Now, however, he is understandably despondent: how can he possibly enjoy life, knowing his doom? His wife mistakes his depression for regret at their marriage, and asks for a divorce. Keawe confesses his secret to her.
His wife suggests they sail, with the bottle, to Tahiti; on that archipelago the colonists of French Polynesia use centimes, a coin worth one fifth of an American cent. This offers a potential recourse for Keawe.
When they arrive, however, the suspicious natives will not touch the cursed bottle. Kokua determines to make a supreme sacrifice to save her husband from his fate. Since, however, she knows he would never sell the bottle to her knowingly, Kokua is forced to bribe an old sailor to buy the bottle for four centimes, with the understanding that she will secretly buy it back for three. Now Kokua is happy, but she carries the curse.
Keawe discovers what his wife has done, and resolves to sacrifice himself for her in the same manner. He arranges for a brutish boatswain to buy the bottle for two centimes, promising he will buy it back for one, thus sealing his doom. However, the drunken sailor refuses to part with it, and is unafraid of the prospect of Hell. "I reckon I'm going anyway," he says.
Keawe returns to his wife, both of them free from the curse, and the reader is encouraged to believe that they live happily ever after.
Background
The theme of the bottle imp can be found in the German legend Spiritus familiaris by the Brothers Grimm as well. At the time of publication in 1891, the currency system of the Kingdom of Hawaii included cent coins that circulated at par with the U.S. penny.
The novel reflects Stevenson's impressions gained during his five-month visit of the Kingdom of Hawaii in 1889. Part of the storyline takes place in the little town Hoʻokena at the Kona coast of the island of Hawaii, which the author visited. In a scene which takes place in Honolulu Stevenson mentions Heinrich Berger, the bandmaster of the Royal Hawaiian Band. The name of Keawe's wife refers to the Hawaiian word kōkua, which means help. In 1889 Stevenson also visited the leper colony on the island of Molokaʻi and met Father Damien there. Therefore, he had a first-hand experience from the fate of lepers. Several times Stevenson uses the Hawaiian word Haole, which is the usual term for Caucasians, for example describing the last owner of the bottle.
The story could be considered as both a continuation of and a rather light-hearted counterpoint to the theme of selling one's soul to The Devil, manifested in the numerous depictions of Doctor Faust as well as in such stories as "The Devil and Tom Walker" by Washington Irving and "The Devil and Daniel Webster" by Stephen Vincent Benét.
Publication
"The Bottle Imp" was published in the missionary magazine O le sulu Samoa (The Samoan Torch) in 1891, with the title "O Le Tala I Le Fagu Aitu". According to Publishers Weekly and School Library Journal (both quoted by Amazon.com) "this tale was originally published, in Samoan, in 1891". The Locus Online Index to Science Fiction similarly states "The Stevenson story was first published in Samoan in 1891, appearing later that year in English." The Project Gutenberg text of the story has a note by Stevenson which says "...the tale has been designed and written for a Polynesian audience..." which also suggests initial publication in Polynesia, not in the United States.
Bottle Imp paradox
The premise of the story creates a logical paradox similar to the unexpected hanging paradox. Clearly no rational person would buy it for one cent as this would make it impossible for it to be sold at a loss. However, it follows that no rational person would buy it for two cents either if it is later to be sold only to a rational person for a loss. By backward induction, the bottle cannot be sold for any price in a perfectly rational world. And yet, the actions of the people in the story do not seem particularly unwise.
The story shows that the paradox could be resolved by the existence of certain characters:
Someone who loves the bottle's current owner enough to sacrifice their own soul for that person.
Someone who believes they are inevitably destined for Hell already.
Someone who believes there is someone else willing to make an irrational decision to purchase the bottle.
Since the exchange rates of different currencies can fluctuate with respect to one another, it is also possible that the value of the bottle could increase from one transaction to the next even if the stated price decreases. This leads to an endless staircase-type paradox which would make it possible, in theory, for the bottle to keep getting sold infinitely many times. However, this might be forbidden depending on how the bottle imp interprets the idea of "selling at a loss".
Adaptations
A silent film based on Stevenson's story was released in 1917. The screenplay was adapted by Charles Maigne. The film was directed by Marshall Neilan, and starred Sessue Hayakawa, Lehua Waipahu, H. Komshi, George Kuwa, Guy Oliver and James Neill.
The Witch's Tale, a horror anthology radio series, adapted the story as "The Wonderful Bottle" in 1934.
Käthe von Nagy starred in the German film Love, Death and the Devil (1934) and the French film The Devil in the Bottle (1935), both based on the story.
West German filmmakers the Diehl Brothers used the story as the basis for a feature film shot with a mixture of puppetry and live action, released in 1952 under the title Der Flaschenteufel.
An Italian TV adaptation, "Il diavolo nella bottiglia", aired on Rai 2 on 23 June 1981 as part of the horror anthology series I giochi del diavolo.
"The Imp in the Bottle" was episode number 143 of the CBS Radio Mystery Theater which aired in 1974.
The Devil Inside, an opera based on Stevenson's short story written by the novelist Louise Welsh and the composer Stuart MacRae, premiered at the Theatre Royal, Glasgow in January 2016. The opera was a co-production between Scottish Opera and Music Theatre Wales.
The story has inspired the trick-taking card game Bottle Imp, designed by Günter Cornett. It was first published in 1995 by Bambus Spieleverlag, and has been republished several times since under the name "Bottle Imp".
See also
Greater fool theory
Unexpected hanging paradox
References
External links
Short stories by Robert Louis Stevenson
1891 short stories
Gothic short stories
Media related to game theory
Native Hawaiian
Works originally published in the New York Herald
Hawaii in fiction
Short stories adapted into films
Cultural depictions of Napoleon
Cultural depictions of James Cook
Imps
fr:Veillées des Îles#La Bouteille endiablée | The Bottle Imp | [
"Mathematics"
] | 2,139 | [
"Game theory",
"Media related to game theory"
] |
2,164,726 | https://en.wikipedia.org/wiki/Hilbert%27s%20twelfth%20problem | Hilbert's twelfth problem is the extension of the Kronecker–Weber theorem on abelian extensions of the rational numbers, to any base number field. It is one of the 23 mathematical Hilbert problems and asks for analogues of the roots of unity that generate a whole family of further number fields, analogously to the cyclotomic fields and their subfields. Leopold Kronecker described the complex multiplication issue as his , or "dearest dream of his youth", so the problem is also known as Kronecker's Jugendtraum.
The classical theory of complex multiplication, now often known as the , does this for the case of any imaginary quadratic field, by using modular functions and elliptic functions chosen with a particular period lattice related to the field in question. Goro Shimura extended this to CM fields. In the special case of totally real fields, Samit Dasgupta and Mahesh Kakde provided a construction of the maximal abelian extension of totally real fields using the Brumer–Stark conjecture.
The general case of Hilbert's twelfth problem is still open.
Description of the problem
The fundamental problem of algebraic number theory is to describe the fields of algebraic numbers. The work of Galois made it clear that field extensions are controlled by certain groups, the Galois groups. The simplest situation, which is already at the boundary of what is well understood, is when the group in question is abelian. All quadratic extensions, obtained by adjoining the roots of a quadratic polynomial, are abelian, and their study was commenced by Gauss. Another type of abelian extension of the field Q of rational numbers is given by adjoining the nth roots of unity, resulting in the cyclotomic fields. Already Gauss had shown that, in fact, every quadratic field is contained in a larger cyclotomic field. The Kronecker–Weber theorem shows that any finite abelian extension of Q is contained in a cyclotomic field. Kronecker's (and Hilbert's) question addresses the situation of a more general algebraic number field K: what are the algebraic numbers necessary to construct all abelian extensions of K? The complete answer to this question has been completely worked out only when K is an imaginary quadratic field or its generalization, a CM-field.
Hilbert's original statement of his 12th problem is rather misleading: he seems to imply that the abelian extensions of imaginary quadratic fields are generated by special values of elliptic modular functions, which is not correct. (It is hard to tell exactly what Hilbert was saying, one problem being that he may have been using the term "elliptic function" to mean both the elliptic function ℘ and the elliptic modular function j.)
First it is also necessary to use roots of unity, though Hilbert may have implicitly meant to include these. More seriously, while values of elliptic modular functions generate the Hilbert class field, for more general abelian extensions one also needs to use values of elliptic functions. For example, the abelian extension is not generated by singular moduli and roots of unity.
One particularly appealing way to state the Kronecker–Weber theorem is by saying that the maximal abelian extension of Q can be obtained by adjoining the special values exp(2i/n) of the exponential function. Similarly, the theory of complex multiplication shows that the maximal abelian extension of Q(τ), where τ is an imaginary quadratic irrationality, can be obtained by adjoining the special values of ℘(τ,z) and j(τ) of modular functions j and elliptic functions ℘, and roots of unity, where τ is in the imaginary quadratic field and z represents a torsion point on the corresponding elliptic curve. One interpretation of Hilbert's twelfth problem asks to provide a suitable analogue of exponential, elliptic, or modular functions, whose special values would generate the maximal abelian extension Kab of a general number field K. In this form, it remains unsolved. A description of the field Kab was obtained in the class field theory, developed by Hilbert
himself, Emil Artin, and others in the first half of the 20th century. However the construction of Kab in class field theory involves first constructing larger non-abelian extensions using Kummer theory, and then cutting down to the abelian extensions, so does not really solve Hilbert's problem which asks for a more direct construction of the abelian extensions.
Modern developments
Developments since around 1960 have certainly contributed. Before that in his dissertation used Hilbert modular forms to study abelian extensions of real quadratic fields. Complex multiplication of abelian varieties was an area opened up by the work of Shimura and Taniyama. This gives rise to abelian extensions of CM-fields in general. The question of which extensions can be found is that of the Tate modules of such varieties, as Galois representations. Since this is the most accessible case of ℓ-adic cohomology, these representations have been studied in depth.
Robert Langlands argued in 1973 that the modern version of the should deal with Hasse–Weil zeta functions of Shimura varieties. While he envisaged a grandiose program that would take the subject much further, more than thirty years later serious doubts remain concerning its import for the question that Hilbert asked.
A separate development was Stark's conjecture (in the abelian rank-one case), which in contrast dealt directly with the question of finding particular units that generate abelian extensions of number fields and describe leading coefficients of Artin L-functions. In 2021, Dasgupta and Kakde announced a p-adic solution to finding the maximal abelian extension of totally real fields by proving the integral Gross–Stark conjecture for Brumer–Stark units.
Notes
References
Footnotes
Sources
Algebraic number theory
Conjectures
12 | Hilbert's twelfth problem | [
"Mathematics"
] | 1,187 | [
"Unsolved problems in mathematics",
"Hilbert's problems",
"Conjectures",
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2,164,886 | https://en.wikipedia.org/wiki/Homological%20mirror%20symmetry | Homological mirror symmetry is a mathematical conjecture made by Maxim Kontsevich. It seeks a systematic mathematical explanation for a phenomenon called mirror symmetry first observed by physicists studying string theory.
History
In an address to the 1994 International Congress of Mathematicians in Zürich, speculated that mirror symmetry for a pair of Calabi–Yau manifolds X and Y could be explained as an equivalence of a triangulated category constructed from the algebraic geometry of X (the derived category of coherent sheaves on X) and another triangulated category constructed from the symplectic geometry of Y (the derived Fukaya category).
Edward Witten originally described the topological twisting of the N=(2,2) supersymmetric field theory into what he called the A and B model topological string theories. These models concern maps from Riemann surfaces into a fixed target—usually a Calabi–Yau manifold. Most of the mathematical predictions of mirror symmetry are embedded in the physical equivalence of the A-model on Y with the B-model on its mirror X. When the Riemann surfaces have empty boundary, they represent the worldsheets of closed strings. To cover the case of open strings, one must introduce boundary conditions to preserve the supersymmetry. In the A-model, these boundary conditions come in the form of Lagrangian submanifolds of Y with some additional structure (often called a brane structure). In the B-model, the boundary conditions come in the form of holomorphic (or algebraic) submanifolds of X with holomorphic (or algebraic) vector bundles on them. These are the objects one uses to build the relevant categories. They are often called A and B branes respectively. Morphisms in the categories are given by the massless spectrum of open strings stretching between two branes.
The closed string A and B models only capture the so-called topological sector—a small portion of the full string theory. Similarly, the branes in these models are only topological approximations to the full dynamical objects that are D-branes. Even so, the mathematics resulting from this small piece of string theory has been both deep and difficult.
The School of Mathematics at the Institute for Advanced Study in Princeton devoted a whole year to Homological Mirror Symmetry during the 2016-17 academic year. Among the participants were Paul Seidel from MIT, Maxim Kontsevich from IHÉS, and Denis Auroux, from UC Berkeley.
Examples
Only in a few examples have mathematicians been able to verify the conjecture. In his seminal address, Kontsevich commented that the conjecture could be proved in the case of elliptic curves using theta functions. Following this route, Alexander Polishchuk and Eric Zaslow provided a proof of a version of the conjecture for elliptic curves. Kenji Fukaya was able to establish elements of the conjecture for abelian varieties. Later, Kontsevich and Yan Soibelman provided a proof of the majority of the conjecture for nonsingular torus bundles over affine manifolds using ideas from the SYZ conjecture. In 2003, Paul Seidel proved the conjecture in the case of the quartic surface. In 2002 explained SYZ conjecture in the context of Hitchin system and Langlands duality.
Hodge diamond
The dimensions hp,q of spaces of harmonic (p,q)-differential forms (equivalently, the cohomology, i.e., closed forms modulo exact forms) are conventionally arranged in a diamond shape called the Hodge diamond. These (p,q)-Betti numbers can be computed for complete intersections using a generating function described by Friedrich Hirzebruch. For a three-dimensional manifold, for example, the Hodge diamond has p and q ranging from 0 to 3:
Mirror symmetry translates the dimension number of the (p, q)-th differential form hp,q for the original manifold into hn-p,q of that for the counter pair manifold. Namely, for any Calabi–Yau manifold the Hodge diamond is unchanged by a rotation by π radians and the Hodge diamonds of mirror Calabi–Yau manifolds are related by a rotation by π/2 radians.
In the case of an elliptic curve, which is viewed as a 1-dimensional Calabi–Yau manifold, the Hodge diamond is especially simple: it is the following figure.
In the case of a K3 surface, which is viewed as 2-dimensional Calabi–Yau manifold, since the Betti numbers are {1, 0, 22, 0, 1}, their Hodge diamond is the following figure.
In the 3-dimensional case, usually called the Calabi–Yau manifold, a very interesting thing happens. There are sometimes mirror pairs, say M and W, that have symmetric Hodge diamonds with respect to each other along a diagonal line.
M'''s diamond:W's diamond:M and W'' correspond to A- and B-model in string theory. Mirror symmetry not only replaces the homological dimensions but also the symplectic structure and complex structure on the mirror pairs. That is the origin of homological mirror symmetry.
In 1990-1991, had a major impact not only on enumerative algebraic geometry but on the whole mathematics and motivated . The mirror pair of two quintic threefolds in this paper have the following Hodge diamonds.
See also
Mirror symmetry conjecture - more mathematically based article
Topological quantum field theory
Category theory
Floer homology
Fukaya category
Derived category
Quintic threefold
References
Differential geometry
Conjectures
Symmetry
Duality theories
String theory | Homological mirror symmetry | [
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2,164,907 | https://en.wikipedia.org/wiki/Polybutadiene | Polybutadiene [butadiene rubber, BR] is a synthetic rubber. It offers high elasticity, high resistance to wear, good strength even without fillers, and excellent abrasion resistance when filled and vulcanized. "Polybutadiene" is a collective name for homopolymers formed from the polymerization of the monomer 1,3-butadiene. The IUPAC refers to polybutadiene as "poly(buta-1,3-diene)". Historically, an early generation of synthetic polybutadiene rubber produced in Germany by Bayer using sodium as a catalyst was known as "Buna rubber". Polybutadiene is typically crosslinked with sulphur, however, it has also been shown that it can be UV cured when bis-benzophenone additives are incorporated into the formulation.
Polybutadiene rubber (BR) accounted for about 28% of total global consumption of synthetic rubbers in 2020, whereas styrene-butadiene rubber (SBR) was by far the most important grade (S-SBR 12%, E-SBR 27% of the entire synthetic rubber market). It is mainly used in the manufacture of tires, which consumes about 70% of the production. Another 25% is used as an additive to improve the toughness (impact resistance) of plastics such as polystyrene and acrylonitrile butadiene styrene (ABS). Polybutadiene is also used to manufacture golf balls, various elastic objects and to coat or encapsulate electronic assemblies, offering high electrical resistivity.
History
The Russian chemist Sergei Vasilyevich Lebedev was the first to polymerize butadiene in 1910. In 1926 he invented a process for manufacturing butadiene from ethanol, and in 1928, developed a method for producing polybutadiene using sodium as a catalyst.
The government of the Soviet Union strove to use polybutadiene as an alternative to natural rubber and built the first pilot plant in 1930, using ethanol produced from potatoes. The experiment was a success and in 1936 the Soviet Union built the world's first polybutadiene plant in which the butadiene was obtained from petroleum. By 1940, the Soviet Union was by far the largest producer of polybutadiene with 50,000 tons per year.
Following Lebedev's work, other industrialized countries such as Germany and the United States developed polybutadiene and SBR as an alternative to natural rubber.
In the mid-1950s there were major advances in the field of catalysts that led to the development of an improved versions of polybutadiene. The leading manufacturers of tires and some petrochemical companies began to build polybutadiene plants on all inhabited continents; the boom lasted until the 1973 oil crisis. Since then, the growth rate of the production has been more modest, focused mainly in the Far East.
In Germany, scientists from Bayer (at the time a part of the conglomerate IG Farben) reproduced Lebedev's processes of producing polybutadiene by using sodium as a catalyst. For this, they used the trade name Buna, derived from Bu for butadiene, Na for sodium (natrium in Latin, Natrium in German). They discovered that the addition of styrene to the process resulted in better properties, and thus opted for this route. They had invented styrene-butadiene, which was named Buna-S (S for styrene).
Although the Goodrich Corporation had successfully developed a process for producing polybutadiene in 1939, the U.S. federal government opted for the use of Buna-S to develop its synthetic-rubber industry after its entry into the World War II, using patents of IG Farben obtained via Standard Oil. Because of this, there was little industrial production of polybutadiene in America during this time.
After the war, the production of synthetic rubber was in decline due to the decrease in demand when natural rubber was readily available again. However, interest was renewed in the mid-1950s after the discovery of the Ziegler–Natta catalyst. This method proved to be much better for tire manufacturing than the old sodium polybutadiene. The following year, Firestone Tire and Rubber Company was first to produce low cis polybutadiene using butyllithium as a catalyst.
The relatively high production costs were a hindrance to commercial development until 1960 when production on a commercial scale began. Tire manufacturers like Goodyear Tire and Rubber Company and Goodrich were the first to produce plants for high cis polybutadiene, this was followed by oil companies like Shell and chemical manufacturers such as Bayer.
Initially, with plants built in the United States and France, Firestone enjoyed a monopoly on low cis polybutadiene, licensing it to plants in Japan and the United Kingdom. In 1965, the Japanese JSR Corporation developed its own low cis process and began licensing it during the next decade.
The 1973 oil crisis marked a halt to the growth of synthetic rubber production; the expansion of existing plants almost ceased for a few years. Since then, the construction of new plants has mainly taken place in industrializing countries in the Far East (such as South Korea, Taiwan, Thailand, and China), while Western countries have chosen to increase the capacity of existing plants.
In 1987, Bayer started to use neodymium-based catalysts to catalyze polybutadiene. Soon thereafter other manufacturers deployed related technologies such as EniChem (1993) and Petroflex (2002).
In the early 2000s, the synthetic rubber industry was once again hit by one of its periodic crises. The world's largest producer of polybutadiene, Bayer, went through major restructuring as it was troubled by financial losses; between 2002 and 2005 it closed its cobalt-polybutadiene plants in Sarnia (Canada) and Marl (Germany), transferring their production to neodymium plants in Port Jérôme (France) and Orange (USA). During the same time, the synthetic rubber business was transferred from Bayer to Lanxess, a company founded in 2004 when Bayer spun off its chemicals operations and parts of its polymer activities.
Polymerization of butadiene
1,3-Butadiene is an organic compound that is a simple conjugated diene hydrocarbon (dienes have two carbon-carbon double bonds). Polybutadiene forms by linking many 1,3-butadiene monomers to make a much longer polymer chain molecule. In terms of the connectivity of the polymer chain, butadiene can polymerize in three different ways, called cis, trans and vinyl. The cis and trans forms arise by connecting the butadiene molecules end-to-end, so-called 1,4-polymerisation. The properties of the resulting isomeric forms of polybutadiene differ. For example, "high cis"-polybutadiene has a high elasticity and is very popular, whereas the so-called "high trans" is a plastic crystal with few useful applications. The vinyl content of polybutadiene is typically no more than a few percent. In addition to these three kinds of connectivity, polybutadienes differ in terms of their branching and molecular weights.
The trans double bonds formed during polymerization allow the polymer chain to stay rather straight, allowing sections of polymer chains to align to form microcrystalline regions in the material. The cis double bonds cause a bend in the polymer chain, preventing polymer chains from aligning to form crystalline regions, which results in larger regions of amorphous polymer. It has been found that a substantial percentage of cis double bond configurations in the polymer will result in a material with flexible elastomer (rubber-like) qualities. In free radical polymerization, both cis and trans double bonds will form in percentages that depend on temperature. The catalysts influence the cis vs trans ratio.
Types
The catalyst used in the production significantly affects the type of polybutadiene product.
High cis polybutadiene
This type is characterized by a high proportion of cis (typically over 92%) and a small proportion of vinyl (less than 4%). It is manufactured using Ziegler–Natta catalysts based on transition metals. Depending on the metal used, the properties vary slightly.
Using cobalt gives branched molecules, resulting in a low viscosity material that is easy to use, but its mechanical strength is relatively low. Neodymium gives the most linear structure (and therefore higher mechanical strength) and a higher percentage of 98% cis. Other less-used catalysts include nickel and titanium.
Low cis polybutadiene
Using an alkyllithium (e.g. butyllithium) as the catalyst produces a polybutadiene called "low cis" which typically contains 36% cis, 54% trans and 10% vinyl.
Despite its high liquid-glass transition, low cis polybutadiene is used in tire manufacturing and is blended with other tire polymers, also it can be advantageously used as an additive in plastics due to its low contents of gels.
High vinyl polybutadiene
In 1980, researchers from the Japanese company, Zeon, discovered that high-vinyl polybutadiene (over 70%), despite having a high liquid-glass transition, could be advantageously used in combination with high cis in tires. This material is produced with an alkyllithium catalyst.
High trans polybutadiene
Polybutadiene can be produced with more than 90% trans using catalysts similar to those of high cis: neodymium, lanthanum, nickel. This material is a plastic crystal (i.e. not an elastomer) which melts at about 80 °C. It was formerly used for the outer layer of golf balls. Today it is only used industrially, but companies like Ube are investigating other possible applications.
Other
Metallocene polybutadiene
The use of metallocene catalysts to polymerize butadiene is being explored by Japanese researchers. The benefits seem to be a higher degree of control both in the distribution of molecular mass and the proportion of cis/trans/vinyl. As of 2006, no manufacturer produces "metallocene polybutadiene" on a commercial basis.
Copolymers
1,3-butadiene is normally copolymerized with other types of monomers such as styrene and acrylonitrile to form rubbers or plastics with various qualities. The most common form is styrene-butadiene copolymer, which is a commodity material for car tires. It is also used in block copolymers and tough thermoplastics such as ABS plastic. This way a copolymer material can be made with good stiffness, hardness, and toughness.
Because the chains have a double bond in each and every repeat unit, the material is sensitive to ozone cracking.
Production
The annual production of polybutadiene was 2.0 million tons in 2003. This makes it the second most produced synthetic rubber by volume, behind the styrene-butadiene rubber (SBR).
The production processes of high cis polybutadiene and low cis used to be quite different and were carried out in separate plants. Lately, the trend has changed to use a single plant to produce as many different types of rubber as possible, including, low cis polybutadiene, high cis (with neodymium used as a catalyst) and SBR.
Processing
Polybutadiene rubber is seldom used alone, but is instead mixed with other rubbers. Polybutadiene is difficult to band in a two roll mixing mill. Instead, a thin sheet of polybutadiene may be prepared and kept separate. Then, after proper mastication of natural rubber, the polybutadiene rubber may be added to the two roll mixing mill. A similar practice may be adopted, for example, if polybutadiene is to be mixed with Styrene Butadiene Rubber (SBR). *Polybutadiene rubber may be added with Styrene as an impact modifier. High dosages may affect clarity of Styrene.
In an internal mixer, natural rubber and/or styrene-butadiene rubber may be placed first, followed by polybutadiene.
The plasticity of polybutadiene is not reduced by excessive mastication.
Uses
The annual production of polybutadiene is 2.1 million tons (2000). This makes it the second most produced synthetic rubber by volume, behind styrene-butadiene rubber (SBR).
Tires
Polybutadiene is largely used in various parts of automobile tires; the manufacture of tires consumes about 70% of the world production of polybutadiene, with a majority of it being high cis. The polybutadiene is used primarily in the sidewall of truck tires, this helps to improve fatigue to failure life due to the continuous flexing during run. As a result, tires will not blow out in extreme service conditions. It is also used in the tread portion of giant truck tires to improve the abrasion, i.e. less wearing, and to run the tire comparatively cool, since the internal heat comes out quickly. Both parts are formed by extrusion.
Its main competitors in this application are styrene-butadiene rubber (SBR) and natural rubber. Polybutadiene has the advantage compared to SBR in its lower liquid-glass transition temperature, which gives it a high resistance to wear and a low rolling resistance. This gives the tires a long life and low fuel consumption. However, the lower transition temperature also lowers the friction on wet surfaces, which is why polybutadiene almost always is used in combination with any of the other two elastomers. About 1 kg of polybutadiene is used per tire in automobiles, and 3.3 kg in utility vehicles.
Plastics
About 25% of the produced polybutadiene is used to improve the mechanical properties of plastics, in particular of high-impact polystyrene (HIPS) and to a lesser extent acrylonitrile butadiene styrene (ABS). The addition of between 4 and 12% polybutadiene to polystyrene transforms it from a fragile and delicate material to a ductile and resistant one.
The quality of the process is more important in the use in plastics than in tires, especially when it comes to color and content of gels which have to be as low as possible. In addition, the products need to meet a list of health requirements due to its use in the food industry.
Golf balls
Most golf balls are made of an elastic core of polybutadiene surrounded by a layer of a harder material. Polybutadiene is preferred to other elastomers due to its high resilience.
The core of the balls are formed by compression molding with chemical reactions. First, polybutadiene is mixed with additives, then extruded, pressed using a calender and cut into pieces which are placed in a mold. The mold is subjected to high pressure and high temperature for about 30 minutes, enough time to vulcanize the material.
The golf ball production consumes about 20,000 tonnes of polybutadiene per year (1999).
Other uses
Polybutadiene rubber may be used in the inner tube of hoses for sandblasting, along with natural rubber, to increase resilience. This rubber can also be used in the cover of hoses, mainly pneumatic and water hoses.
Polybutadiene rubber can also be used in railway pads, bridge blocks, etc.
Polybutadiene rubber can be blended with nitrile rubber for easy processing. However large use may affect the oil resistance of nitrile rubber.
Polybutadiene is used in the manufacturing of the high-restitution toy Super Ball. Due to the high resilience property, 100% polybutadiene rubber based vulcanizate is used as crazy balls — i.e. a ball if dropped from 6th floor of a house will rebound up to 5½ to 6th floor (assuming no air resistance).
Polybutadiene is also used as binder in combination with an oxidizer and a fuel in various Solid Rocket Boosters such as Japan's H-IIB launch vehicle, and ESA's Ariane 5; commonly is employed as hydroxyl-terminated polybutadiene (HTPB) or carboxyl-terminated polybutadiene (CTPB).
See also
Ozone cracking
Polymer degradation
References
Bibliography
External links
Organic polymers
Elastomers
Thermoplastics
Polymers
Russian inventions | Polybutadiene | [
"Chemistry",
"Materials_science"
] | 3,522 | [
"Organic polymers",
"Synthetic materials",
"Elastomers",
"Organic compounds",
"Polymer chemistry",
"Polymers"
] |
2,164,976 | https://en.wikipedia.org/wiki/Dip-pen%20nanolithography | Dip pen nanolithography (DPN) is a scanning probe lithography technique where an atomic force microscope (AFM) tip is used to directly create patterns on a substrate. It can be done on a range of substances with a variety of inks. A common example of this technique is exemplified by the use of alkane thiolates to imprint onto a gold surface. This technique allows surface patterning on scales of under 100 nanometers. DPN is the nanotechnology analog of the dip pen (also called the quill pen), where the tip of an atomic force microscope cantilever acts as a "pen", which is coated with a chemical compound or mixture acting as an "ink", and put in contact with a substrate, the "paper".
DPN enables direct deposition of nanoscale materials onto a substrate in a flexible manner. Recent advances have demonstrated massively parallel patterning using two-dimensional arrays of 55,000 tips.
Applications of this technology currently range through chemistry, materials science, and the life sciences, and include such work as ultra high density biological nanoarrays, and additive photomask repair.
Development
The uncontrollable transfer of a molecular "ink" from a coated AFM tip to a substrate was first reported by Jaschke and Butt in 1995, but they erroneously concluded that alkanethiols could not be transferred to gold substrates to form stable nanostructures. A research group at Northwestern University, US led by Chad Mirkin independently studied the process and determined that under the appropriate conditions, molecules could be transferred to a wide variety of surfaces to create stable chemically-adsorbed monolayers in a high resolution lithographic process they termed "DPN". Mirkin and his coworkers hold the patents on this process, and the patterning technique has expanded to include liquid "inks". It is important to note that "liquid inks" are governed by a very different deposition mechanism when compared to "molecular inks".
Deposition materials
Molecular inks
Molecular inks are typically composed of small molecules that are coated onto a DPN tip and are delivered to the surface through a water meniscus. In order to coat the tips, one can either vapor coat the tip or dip the tips into a dilute solution containing the molecular ink. If one dip-coats the tips, the solvent must be removed prior to deposition. The deposition rate of a molecular ink is dependent on the diffusion rate of the molecule, which is different for each molecule. The size of the feature is controlled by the tip/surface dwell-time (ranging from milliseconds to seconds) and the size of the water meniscus, which is determined by the humidity conditions (assuming the tip's radius of curvature is much smaller than the meniscus).
Water meniscus mediated (exceptions do exist)
Nanoscale feature resolution (50 nm to 2000 nm)
No multiplexed depositions
Each molecular ink is limited to its corresponding substrate
Examples
Alkane thiols written to gold
Silanes (solid phase) written to glass or silicon
Liquid inks
Liquid inks can be any material that is liquid at deposition conditions. The liquid deposition properties are determined by the interactions between the liquid and the tip, the liquid and the surface, and the viscosity of the liquid itself. These interactions limit the minimum feature size of the liquid ink to about 1 micrometre, depending on the contact angle of the liquid. Higher viscosities offer greater control over feature size and are desirable. Unlike molecular inks, it is possible to perform multiplexed depositions using a carrier liquid. For example, using a viscous buffer, it is possible to directly deposit multiple proteins simultaneously.
1–10 micrometre feature resolution
Multiplexed depositions
Less restrictive ink/surface requirements
Direct deposition of high viscosity materials
Examples
Protein, peptide, and DNA patterning
Hydrogels
Sol gels
Conductive inks
Lipids
Silanes (liquid phase) written to glass or silicon
Applications
In order to define a good DPN application, it is important to understand what DPN can do that other techniques cannot. Direct-write techniques, like contact printing, can pattern multiple biological materials but it cannot create features with subcellular resolution. Many high-resolution lithography methods can pattern at sub-micrometre resolution, but these require high-cost equipment that were not designed for biomolecule deposition and cell culture. Microcontact printing can print biomolecules at ambient conditions, but it cannot pattern multiple materials with nanoscale registry.
Industrial applications
The following are some examples of how DPN is being applied to potential products.
Biosensor Functionalization – Directly place multiple capture domains on a single biosensor device
Nanoscale Sensor Fabrication – Small, high-value sensors that can detect multiple targets
Nanoscale Protein Chips – High-density protein arrays with increased sensitivity
Emerging applications
Cell engineering
DPN is emerging as a powerful research tool for manipulating cells at subcellular resolution
Stem cell differentiation
Subcellular drug delivery
Cell sorting
Surface gradients
Subcellular ECM protein patterns
Cell adhesion
Rapid prototyping
Plasmonics and Metamaterials
Cell and tissue screening
Properties
Direct write
DPN is a direct write technique so it can be used for top-down and bottom-up lithography applications. In top-down work, the tips are used to deliver an etch resist to a surface, which is followed by a standard etching process. In bottom-up applications, the material of interest is delivered directly to the surface via the tips.
Unique advantages
Directed Placement – Directly print various materials onto existing nano and microstructures with nanoscale registry
Direct Write – Maskless creation of arbitrary patterns with feature resolutions from as small as 50 nm and as large as 10 micrometres
Biocompatible – Subcellular to nanoscale resolution at ambient deposition conditions
Scalable – Force independent, allowing for parallel depositions
Thermal dip pen lithography
A heated probe tip version of Dip Pen Lithography has also been demonstrated, thermal Dip Pen Lithography (tDPL), to deposit nanoparticles. Semiconductor, magnetic, metallic, or optically active nanoparticles can be written to a substrate via this method. The particles are suspended in a Poly(methyl methacrylate) (PMMA) or equivalent polymer matrix, and heated by the probe tip until they begin to flow. The probe tip acts as a nano-pen, and can pattern nanoparticles into a programmed structure. Depending on the size of the nanoparticles, resolutions of 78–400 nm were attained. An O2 plasma etch can be used to remove the PMMA matrix, and in the case of Iron Oxide nanoparticles, further reduce the resolution of lines to 10 nm. Advantages unique to tDPL are that it is a maskless additive process that can achieve very narrow resolutions, it can also easily write many types of nanoparticles without requiring special solution preparation techniques. However there are limitations to this method. The nanoparticles must be smaller than the radius of gyration of the polymer, in the case of PMMA this is about 6 nm. Additionally, as nanoparticles increase in size viscosity increases, slowing the process. For a pure polymer deposition speeds of 200 μm/s are achievable. Adding nanoparticles reduces speeds to 2 μm/s, but is still faster than regular Dip Pen Lithography.
Beam pen lithography
A two dimensional array of (PDMS) deformable transparent pyramid shaped tips are coated with an opaque layer of metal. The metal is then removed from the very tip of the pyramid, leaving an aperture for light to pass through. The array is then scanned across a surface and light is directed to the base of each pyramid via a micromirror array, which funnels the light toward the tip. Depending on the distance between the tips and the surface, light interacts with the surface in a near-field or far-field fashion, allowing sub-diffraction scale features (100 nm features with 400 nm light) or larger features to be fabricated.
Common misconceptions
Direct comparisons to other techniques
The criticism most often directed at DPN is the patterning speed. The reason for this has more to do with how it is compared to other techniques rather than any inherent weaknesses. For example, the soft lithography method, microcontact printing (μCP), is the current standard for low cost, bench-top micro and nanoscale patterning, so it is easy to understand why DPN is compared directly to microcontact printing. The problem is that the comparisons are usually based upon applications that are strongly suited to μCP, instead of comparing them to some neutral application. μCP has the ability to pattern one material over a large area in a single stamping step, just as photolithography can pattern over a large area in a single exposure. Of course DPN is slow when it is compared to the strength of another technique. DPN is a maskless direct write technique that can be used to create multiple patterns of varying size, shape, and feature resolution, all on a single substrate. No one would try to apply microcontact printing to such a project because then it would never be worth the time and money required to fabricate each master stamp for each new pattern. Even if they did, microcontact printing would not be capable of aligning multiple materials from multiple stamps with nanoscale registry. The best way to understand this misconception is to think about the different ways to apply photolithography and e-beam lithography. No one would try to use e-beam to solve a photolithography problem and then claim e-beam to be "too slow". Directly compared to photolithography's large area patterning capabilities, e-beam lithography is slow and yet, e-beam instruments can be found in every lab and nanofab in the world. The reason for this is because e-beam has unique capabilities that cannot be matched by photolithography, just as DPN has unique capabilities that cannot be matched by microcontact printing.
Connection to atomic force microscopy
DPN evolved directly from AFM so it is not a surprise that people often assume that any commercial AFM can perform DPN experiments. In fact, DPN does not require an AFM, and an AFM does not necessarily have real DPN capabilities. There is an excellent analogy with scanning electron microscopy (SEM) and electron beam (E-beam) lithography. E-beam evolved directly from SEM technology and both use a focused electron beam, but it is not possible to perform modern E-beam lithography experiments on a SEM that lacks the proper lithography hardware and software components.
It is also important to consider one of the unique characteristics of DPN, namely its force independence. With virtually all ink/substrate combinations, the same feature size will be patterned no matter how hard the tip is pressing down against the surface. As long as robust SiN tips are used, there is no need for complicated feedback electronics, no need for lasers, no need for quad photo-diodes, and no need for an AFM.
See also
Nanolithography
References
Lithography (microfabrication)
Microtechnology
Scanning probe microscopy
Biological engineering
Tissue engineering | Dip-pen nanolithography | [
"Chemistry",
"Materials_science",
"Engineering",
"Biology"
] | 2,380 | [
"Biological engineering",
"Microtechnology",
"Cloning",
"Chemical engineering",
"Materials science",
"Tissue engineering",
"Scanning probe microscopy",
"Microscopy",
"Nanotechnology",
"Medical technology",
"Lithography (microfabrication)"
] |
2,165,091 | https://en.wikipedia.org/wiki/Emergency%20Response%20Guidebook | The Emergency Response Guidebook: A Guidebook for First Responders During the Initial Phase of a Dangerous Goods/Hazardous Materials Transportation Incident (ERG) is used by emergency response personnel (such as firefighters, paramedics and police officers) in Canada, Mexico, and the United States when responding to a transportation emergency involving hazardous materials. First responders in Argentina, Brazil, and Colombia have recently begun using the ERG as well. It is produced by the United States Department of Transportation's Pipeline and Hazardous Materials Safety Administration, Transport Canada, and the Secretariat of Communications and Transportation (Mexico).
History
The first iteration was published by the United States Department of Transportation (USDOT) in December 1973, as Emergency Services Guide for Selected Hazardous Materials. This first document was 63 pages long, containing information for only 29 chemicals. The next version, appeared in May 1976, as Hazardous Materials - Emergency Action Guide. A revised version would be released in January 1977, which added an image of the relevant, newly adopted hazardous material placards to each substance's entry. These early documents were very barebones, containing only 29 to 43 materials, mostly flammable substances, corrosives and toxic gases.
1980 saw the first year of the Emergency Response Guidebook in its modern form. The book grew significantly from 87 pages in prior editions, to just over 140 pages, introducing the color coded sections, alongside general guide pages that described the response to a wide number of similar substances, replacing the specific entries for individual substances. Placard charts for devising responses when the exact substances isn't known and Chemtrec as an advice resource would also make their first appearances in 1980. New editions would be published in 1984, 1987, 1990, 1993.
The 1996 edition would be a turning point, released as North American Emergency Response Guidebook, this edition would see formal involvement of Transport Canada (TC) and he Secretariat of Communications and Transportation (SCT) of Mexico for the first time, with their national emblems appearing alongside the USDOT logo and contact information in the rear of the book. This would also see the start of the four year refresh cycle. The book's title reverted to the previous Emergency Response Guidebook in the 2000 edition.
From the 2004 edition, information on responding to terrorism involving hazardous materials was included. 2004 would also mark the involvement of the Chemistry Information Center for Emergencies (CIQUIME) of Argentina assisting in development of the guidebook. New editions have been published in 2004, 2008, 2012, 2016, 2020, and most recently 2024.
Guidebook Contents
The Emergency Response Guide is intended to give first responders (firefighters, police officers) prompt advice during the initial stages of an emergency, such as a fire or chemical leak resulting from a transportation accident, such as a train derailment or crash involving a truck. It is primarily intended to respond to transportation accidents involving railroads, highways and pipelines. While it can be used with incidents involving aircraft, ships and permanent structures, the advice may not be suitable. First responders are expected to transition away from using the ERG as soon as possible, consulting better information sources, such as emergency response resources through the manufacturer or shipper, or emergency response organizations such as ChemTrec, Canutec, Cenacom, etc.
Since the 1980s, the ERG has used a layout that divides the book into six color-coded sections (white [uncolored], yellow, blue, orange, green, and a second white [uncolored]). The blue and yellow sections assist in connecting a substance to a specific "Guide" which provides appropriate response to the substance in question. The Orange Section, consists of 62 "Guides", that identify the primary hazards associated with the applicable general category of hazardous material and general guidance on how to respond to incidents involving that general category of hazardous material. Substances that are hazardous enough to demand a widespread evacuation, such as Chlorine, are listed in the Green Section. The white sections provide other information to support the guidebook, such as contact numbers for expert chemical information sources, glossary, decontamination and protective clothing.
The document is formally published in three languages: English, French, and Spanish. It has been translated in to a number of other languages by third parties, including Mandarin, German, Hebrew, Japanese, Portuguese, Korean, Hungarian, Polish, Turkish and Thai.
White Section (front)
The first section, with white page (uncolored) borders, provides the following:
Information regarding reading and understanding shipping documents
A flowchart for how to use the guidebook to respond to an incident
General guidance for responding to any hazardous material incident
Basic information on the hazard classification system and the associated placards/labels
Guide recommendations for situations where materials are unknown, and must be identified by:
placards,
rail cars
truck trailers
General safety precautions
Information on labels for Globally Harmonized System of Classification and Labelling of Chemicals
Hazard identification numbers, (Used in European & South American placards systems)
Specific guidance for incidents involving pipelines
Yellow Section
The second section, with yellow page borders, references the material in order of its assigned 4-digit UN/NA number (Called "ID No." in the ERG) and identifies the appropriate guide number to reference in the Orange Section and its official name per UN regulations. Chemical/biological warfare agents don't appear in this section, starting in the 2024 edition. Items highlighted in green in this section will have evacuation distances included in the Green Section.
Blue Section
The third section, with blue page borders, references the material in alphabetical order of its official name and identifies the appropriate guide number to reference in the Orange Section) and its 4-digit UN/NA number. Items highlighted in green in this section will also have evacuation distances included in the Green Section. As with the yellow section, chemical/biological warfare agents don't appear in this section, starting in the 2024 edition.
Orange Section
The fourth section, with orange page borders, includes the actual response guides. Each guide is broken into three primary sections: "Potential Hazards", "Public Safety", and "Emergency Response". Each of the 62 guides provides safety recommendations and directions on how to proceed during the initial response phase (first thirty minutes) of the incident. It includes "health" and "fire or explosion" potential hazard information (with the more dangerous hazard listed first). For example, "the material gives off irritating vapors, easily ignited by heat, reactive with water"; "highly toxic, may be fatal if inhaled, swallowed or absorbed through skin"; etc.
Next this section includes information for responders on appropriate protective clothing and possible evacuation information for either spill or fire is given. It also includes information on fighting fires (example, do not apply water to sodium), warnings for spills or leaks, and special directions for first aid (example, not to give mouth-to-mouth resuscitation if the materials are toxic).
There are two special guides in this section: "General First Aid", which provides basic first aid information when dealing with an individual exposed to a hazardous material, and doesn't correspond to a specific hazardous material, and is unnumbered. The other, is Guide #111 - Mixed Load/Unidentified Cargo, which is for use in situations where either multiple hazardous materials are involved, or even basic information is unavailable, such as when a railcar or truck is buried under vehicles/debris or obscured by fire or smoke.
Green Section
The fifth section, with green page borders, suggests initial evacuation or shelter in place distances (protective action distances) for spills of materials that are Toxic-by-Inhalation (TIH). These distances vary based on the size of the spill (small or large) and whether the incident occurs during the day or at night. Only materials that were highlighted in green in the Yellow and Blue Sections are included in the Green Section.
This section also includes information regarding toxic gases that are produced when certain materials are spilled in water (as identified previously in this section). Finally, this section includes some very specific evacuation details for six common materials.
White Section (back)
The sixth section, with white page (uncolored) borders, provides the following:
Additional instructions on how to use the guidebook
Information regarding protective clothing and equipment
Instructions on fire and spill control
Responding to lithium-ion battery and electric vehicle fires
BLEVE (boiling liquid expanding vapor explosion) safety precautions
Beginning with the 2004 edition, information specifically for hazardous materials being used for terrorism
Glossary of terms used in the ERG
Contact information for the various countries
See also
Dangerous goods
Emergency management
Wireless Information System for Emergency Responders
References
External links
Editions of the ERG
2024 Edition - Current Edition - (Archived)
2020 Edition - (Archived)
2016 Edition - (Archived)
2012 Edition - (Archived)
2008 Edition - (Archived)
2004 Edition - (Archived)
2000 Edition - At Internet Archive
1996 Edition - At Internet Archive
1993 Edition- At HathiTrust
1990 Edition - At HathiTrust
1984 Edition - At HathiTrust
1980 Edition - At HathiTrust
Emergency Action Guide for Selected Hazardous Materials - 1978 - At HathiTrust
Hazardous Materials - Emergency Action Guide - 1976 - At HathiTrust
Emergency Services Guide for Selected Hazardous Materials (1974) - At HathiTrust
Other links
- The United States Pipeline and Hazardous Materials Safety Administration
- Transport Canada webpage
1973 non-fiction books
1977 non-fiction books
1978 non-fiction books
1980 non-fiction books
1984 non-fiction books
1987 non-fiction books
1990 non-fiction books
1993 non-fiction books
1996 non-fiction books
2000 non-fiction books
2004 non-fiction books
2008 non-fiction books
2012 non-fiction books
2016 non-fiction books
2024 non-fiction books
Handbooks and manuals
Firefighting
Emergency management
Firefighting in the United States
Hazardous materials | Emergency Response Guidebook | [
"Physics",
"Chemistry",
"Technology"
] | 2,023 | [
"Materials",
"Hazardous materials",
"Matter"
] |
2,165,201 | https://en.wikipedia.org/wiki/Document%20Definition%20Markup%20Language | Document Definition Markup Language (DDML) is an XML schema language proposed in 1999 by various contributors from the xml-dev electronic mailing list. It was published only as a W3C Note, not a Recommendation, and never found favor with developers.
DDML began as XSchema, a reformulation of XML DTDs as full XML documents, so that elements and attributes, rather than declarations, could be used to describe a schema. As development continued, the name was changed to DDML, reflecting a shift away from the goal of replicating all DTD functionality, in order to concentrate on providing a robust framework for describing basic element/attribute hierarchy. DDML offered no datatypes or functionality beyond what DTDs already provided, so there was not much advantage to using DDML instead of DTDs. DDML did, however, inform the development of the next generation of XML-based schema languages, including the more successful XML Schema and RELAX NG.
External links
The DDML specification (W3C Note)
XML markup languages
XML-based standards
Computer-related introductions in 1999 | Document Definition Markup Language | [
"Technology"
] | 228 | [
"Computing stubs",
"Computer standards",
"XML-based standards",
"Computer network stubs"
] |
2,165,388 | https://en.wikipedia.org/wiki/Truth-value%20semantics | In formal semantics, truth-value semantics is an alternative to Tarskian semantics. It has been primarily championed by Ruth Barcan Marcus, H. Leblanc, and J. Michael Dunn and Nuel Belnap. It is also called the substitution interpretation (of the quantifiers) or substitutional quantification.
The idea of these semantics is that a universal (respectively, existential) quantifier may be read as a conjunction (respectively, disjunction) of formulas in which constants replace the variables in the scope of the quantifier. For example, may be read () where are individual constants replacing all occurrences of in .
The main difference between truth-value semantics and the standard semantics for predicate logic is that there are no domains for truth-value semantics. Only the truth clauses for atomic and for quantificational formulas differ from those of the standard semantics. Whereas in standard semantics atomic formulas like or are true if and only if (the referent of) is a member of the extension of the predicate , respectively, if and only if the pair is a member of the extension of , in truth-value semantics the truth-values of atomic formulas are basic. A universal (existential) formula is true if and only if all (some) ground substitution instances of the unquantified subformula are true. Compare this with the standard semantics, which says that a universal (existential) formula is true if and only if for all (some) members of the domain, the formula holds for all (some) of them; for example, is true (under an interpretation) if and only if for all in the domain , is true (where is the result of substituting for all occurrences of in ). (Here we are assuming that constants are names for themselves—i.e. they are also members of the domain.)
Truth-value semantics is not without its problems. First, the strong completeness theorem and compactness fail. To see this consider the set . Clearly the formula is a logical consequence of the set, but it is not a consequence of any finite subset of it (and hence it is not deducible from it). It follows immediately that both compactness and the strong completeness theorem fail for truth-value semantics. This is rectified by a modified definition of logical consequence as given in Dunn and Belnap 1968.
Another problem occurs in free logic. Consider a language with one individual constant that is nondesignating and a predicate standing for 'does not exist'. Then is false even though a substitution instance (in fact every such instance under this interpretation) of it is true. To solve this problem we simply add the proviso that an existentially quantified statement is true under an interpretation for at least one substitution instance in which the constant designates something that exists.
See also
Game semantics
Kripke semantics
Proof-theoretic semantics
Quasi-quotation
Truth-conditional semantics
References
Mathematical logic
Semantics | Truth-value semantics | [
"Mathematics"
] | 621 | [
"Mathematical logic"
] |
2,984,115 | https://en.wikipedia.org/wiki/Aminoglutethimide | Aminoglutethimide (AG), sold under the brand names Elipten, Cytadren, and Orimeten among others, is a medication which has been used in the treatment of seizures, Cushing's syndrome, breast cancer, and prostate cancer, among other indications. It has also been used by bodybuilders, athletes, and other men for muscle-building and performance- and physique-enhancing purposes. AG is taken by mouth three or four times per day.
Side effects of AG include lethargy, somnolence, dizziness, headache, appetite loss, skin rash, hypertension, liver damage, and adrenal insufficiency, among others. AG is both an anticonvulsant and a steroidogenesis inhibitor. In terms of the latter property, it inhibits enzymes such as cholesterol side-chain cleavage enzyme (CYP11A1, P450scc) and aromatase (CYP19A1), thereby inhibiting the conversion of cholesterol into steroid hormones and blocking the production of androgens, estrogens, and glucocorticoids, among other endogenous steroids. As such, AG is an aromatase inhibitor and adrenal steroidogenesis inhibitor, including both an androgen synthesis inhibitor and a corticosteroid synthesis inhibitor.
AG was introduced for medical use, as an anticonvulsant, in 1960. It was withdrawn in 1966 due to toxicity. Its steroidogenesis-inhibiting properties were discovered serendipitously and it was subsequently repurposed for use in the treatment of Cushing's syndrome, breast cancer, and prostate cancer from 1969 and thereafter. However, although used in the past, it has mostly been superseded by newer agents with better efficacy and lower toxicity such as ketoconazole, abiraterone acetate, and other aromatase inhibitors. It remains marketed only in a few countries.
Medical uses
AG is used as an anticonvulsant in the treatment of petit mal epilepsy and as a steroidogenesis inhibitor in the treatment of Cushing's syndrome, postmenopausal breast cancer, and prostate cancer. It is also used to treat secondary hyperaldosteronism, edema, adrenocortical carcinoma, and ectopic adrenocorticotropic hormone (ACTH) producing tumors. When used as a steroidogenesis inhibitor to treat breast cancer and prostate cancer, AG is given in combination with hydrocortisone, prednisone, or an equivalent corticosteroid to prevent adrenal insufficiency. AG is a second- or third-line choice in the treatment of hormone-sensitive metastatic breast cancer. While effective in the treatment of breast cancer in postmenopausal women, it is not effective in premenopausal women and is not an effective ovarian steroidogenesis inhibitor, probably because it is not a potent enough aromatase inhibitor. The medication is effective in the treatment of prostate cancer, but its effectiveness is low and inconsistent, likely due to its relatively weak steroidogenesis inhibition and poor pharmacokinetics. Nonetheless, AG was found to be non-significantly different in effectiveness from surgical adrenalectomy in terms of prostate cancer tumor regression. In any case, AG is not recommended as a first-line therapy in prostate cancer, but instead only as a second-line therapy. It has only rarely been used in the treatment of prostate cancer.
AG is used for adrenal steroidogenesis inhibition by mouth at a dosage of 250 mg three times per day (750 mg/day total) for the first 3 weeks of therapy and then increased to 250 mg four times per day (1,000 mg/day total) thereafter. It can be used at a dosage of up to 500 mg four times per day (2,000 mg/day). It is used as an aromatase inhibitor to inhibit peripheral estrogen production by mouth at a dosage of 125 mg twice per day (250 mg/day total), without significant suppression of adrenal steroidogenesis at this dosage. Maximal aromatase inhibition is said to occur between dosages of 250 to 500 mg per day. The side effects of AG are less frequent and severe at this dosage. However, they are still less when AG is combined with hydrocortisone, and so AG is generally combined with a corticosteroid even at this lower dosage. AG should only be used under close medical supervision and with laboratory tests including thyroid function, baseline hematological, serum glutamic-oxaloacetic transaminase, alkaline phosphatase, and bilirubin.
Ketoconazole can achieve similar decreases in steroid hormone levels as AG but is more effective in promoting tumor regression and is moderately less toxic in comparison. AG can still be a useful alternative in those who have failed or are unable to tolerate ketoconazole and other therapies however.
Available forms
AG is provided most commonly in the form of 250 mg tablets.
Non-medical uses
AG is used by bodybuilders, athletes, and other men to lower circulating levels of cortisol in the body and thereby prevent muscle loss. Cortisol is catabolic to protein in muscle and effective suppression of cortisol by AG at high doses can prevent muscle loss. It is usually used in combination with an anabolic steroid to avoid androgen deficiency. However, the usefulness of AG for such purposes has been questioned, with few users reportedly having positive comments about it, and the risks of AG are said to be high. In any case, AG is also used by bodybuilders and other men for its actions as an aromatase inhibitor in order to decrease estrogen levels. It is said to be useful for inhibiting the estrogenic side effects of certain anabolic steroids such as gynecomastia, increased water retention, and fat gain.
Contraindications
AG should not be used in people with known hypersensitivity to AG. It should not be used in women who are pregnant or breastfeeding. Other potential contraindications include chicken pox, shingles (herpes zoster), infection, kidney disease, liver disease, and hypothyroidism.
Side effects
AG has many side effects and is a relatively toxic medication, although its side effects are described as usually relatively mild. The side effects of AG include lethargy, fatigue, weakness, malaise, drowsiness, somnolence, depression, apathy, sleep disturbances, stomach discomfort, nausea, vomiting, ataxia, joint aches and pains, fever, skin rash, hypotension or hypertension, high cholesterol levels, virilization, hypothyroidism, thyroid abnormalities, elevated liver enzymes, jaundice, hepatotoxicity, weight gain, leg cramps, personality changes, blood dyscrasias, and adrenal insufficiency (e.g., hyponatremia, hypoglycemia, others). Lethargy is the most common side effect and has been found to occur in 31 to 70% of people treated with AG. It is the most common reason for discontinuation of AG. Skin rash and hypotension have both been observed in about 15% of people. At least one side effect will occur in 45 to 85% of people. Severe toxicity is seen in 10% of people, including circulatory collapse thought to be due to adrenal insufficiency. Hematological and bone marrow toxicity, including marked depression of white blood cell count, platelets, or both, occurs rarely, with an incidence of about 0.9%. It is usually seen within the first 7 weeks of treatment and resolves within 3 weeks following discontinuation. AG is discontinued in 5 to 10% of people due to intolerable side effects. The central nervous system side effects of AG are due to its nature as an anticonvulsant and relation to glutethimide.
Overdose
In the event of overdose of AG, drowsiness, nausea, vomiting, hypotension, and respiratory depression may occur. Medical attention should be sought urgently. Treatment of AG overdose can include gastric lavage to decrease absorption and dialysis to enhance elimination.
Interactions
AG has an interaction with all corticosteroids. It enhances the metabolism of dexamethasone, so hydrocortisone should be used instead. If the person is taking warfarin, the dosage of warfarin may need to be increased. Alcohol potentiates the central nervous system side effects of AG. Dosages of theophylline, digitoxin, and medroxyprogesterone acetate may need to be increased.
Pharmacology
Pharmacodynamics
AG is a potent and non-selective steroidogenesis inhibitor, acting as a reversible and competitive inhibitor of multiple steroidogenic enzymes, including:
Aromatase (CYP19A1) (600 nM). Inhibits the formation of the estrogens estradiol and estrone from testosterone and androstenedione, respectively.
Cholesterol side-chain cleavage enzyme (P450scc; CYP11A1) (~20,000 nM). Inhibits the conversion of cholesterol into pregnenolone and consequently decreases the synthesis of all steroid hormones including the progestogens, androgens, glucocorticoids, and mineralocorticoids, as well as neurosteroids.
21-Hydroxylase (CYP21A2). Prevents the conversion of progesterone and 17α-hydroxyprogesterone into 11-deoxycorticosterone and 11-deoxycortisol, respectively.
11β-Hydroxylase (CYP11B1). Prevents the conversion of 11-deoxycorticosterone and 11-deoxycortisol into corticosterone and cortisol, respectively.
Aldosterone synthase (18-hydroxylase; CYP11B2). Prevents the conversion of corticosterone into aldosterone.
As such, AG is an estrogen synthesis inhibitor and adrenal steroidogenesis inhibitor, including both an androgen synthesis inhibitor and a corticosteroid synthesis inhibitor. For these reasons, AG has functional antiestrogenic, antiandrogenic, antiglucocorticoid, and antimineralocorticoid actions. In terms of its actions as an adrenal steroidogenesis inhibitor, it is described as a form of reversible "medical adrenalectomy" or "chemical adrenalectomy". While AG inhibits all of the enzymes listed above, inhibition of P450scc is primarily responsible for its inhibition of adrenal steroidogenesis. In terms of adrenal androgens, AG has been shown to significantly suppress dehydroepiandrosterone sulfate, androstenedione, testosterone, and dihydrotestosterone levels in men. Although it is most potent in inhibiting aromatase among the enzymes it targets, AG is described nonetheless as a relatively weak aromatase inhibitor. In addition, it is described as a much more potent aromatase inhibitor than adrenal steroidogenesis inhibitor. AG can inhibit aromatase by 74 to 92% and decrease circulating estradiol levels by 58 to 76% in men and postmenopausal women. AG is not an effective ovarian steroidogenesis inhibitor in premenopausal women. However, interference with ovarian steroidogenesis by AG may in any case result in hyperandrogenism and virilization in premenopausal women.
Pharmacokinetics
With oral administration, the absorption of AG is rapid and complete. It is well-distributed throughout the body. In terms of metabolism, a portion of AG is acetylated in the liver. The biological half-life of AG is 12.5 hours. It is excreted in urine 34 to 54% unchanged.
Chemistry
AG is a nonsteroidal compound, specifically a glutarimide, and is a derivative of glutethimide. It is also known by its chemical names 2-(4-aminophenyl)-2-ethylglutarimide and 2-(aminophenyl)-3-ethylpiperidine-2,6-dione. Aside from glutethimide, AG is structurally related to rogletimide (pyridoglutethimide) and thalidomide, as well as amphenone B, metyrapone, and mitotane.
History
AG was introduced for medical use, as an anticonvulsant, in 1960. In 1963, it was reported that AG had induced symptoms of Addison's disease (adrenal insufficiency) in a young girl. Following additional reports, it was determined that AG acts as a steroidogenesis inhibitor. As such, the discovery of AG as a steroidogenesis inhibitor was serendipitous. The medication was withdrawn from the market in 1966 due to its adverse effects. The first report of AG in the treatment of breast cancer was published in 1969, and the first report of AG in the treatment of prostate cancer was published in 1974. The medication was one of the first adrenal steroidogenesis inhibitors as well as the first aromatase inhibitor to be discovered and used clinically, and led to the development of other aromatase inhibitors. Along with testolactone, it is described as a "first-generation" aromatase inhibitor. AG has largely been superseded by medications with better effectiveness and tolerability and reduced toxicity, such as ketoconazole, abiraterone acetate, and other aromatase inhibitors.
Society and culture
Generic names
Aminoglutethimide is the generic name of the drug and its , , and , while aminoglutéthimide is its and aminoglutetimide is its . It is also known by its developmental code names Ba 16038, Ciba 16038, and ND-1966.
Brand names
AG has been marketed under brand names including Elipten, Cytandren, and Orimeten. It has also been marketed under other brand names such as Aminoblastin, Rodazol, and Mamomit, among numerous others.
Availability
AG appears to remain marketed only in a few countries, which include China, Egypt, and Lithuania. Previously, AG was available very widely throughout the world, including in more than two dozen countries and under numerous brand names. Among other places, it was marketed in the United States, Canada, the United Kingdom, other European countries, Australia, New Zealand, South Africa, South America, Israel, Malaysia, and Hong Kong.
References
11β-Hydroxylase inhibitors
21-Hydroxylase inhibitors
Abandoned drugs
Aldosterone synthase inhibitors
Anticonvulsants
Antiglucocorticoids
Aromatase inhibitors
Cholesterol side-chain cleavage enzyme inhibitors
Glutarimides
Hepatotoxins
Hormonal antineoplastic drugs
Withdrawn drugs
4-Aminophenyl compounds | Aminoglutethimide | [
"Chemistry"
] | 3,215 | [
"Drug safety",
"Withdrawn drugs",
"Abandoned drugs"
] |
2,984,167 | https://en.wikipedia.org/wiki/Fixed-satellite%20service | Fixed-satellite service (FSS, or fixed-satellite radiocommunication service) is – according to article 1.21 of the International Telecommunication Union's (ITU) Radio Regulations (RR) – defined as A radiocommunication service between earth stations at given positions, when one or more satellites are used; the given position may be a specified fixed point or any fixed point within specified areas; in some cases this service includes satellite-to-satellite links, which may also be operated in the inter-satellite service; the fixed-satellite service may also include feeder links for other space radiocommunication services.
Classification
This radiocommunication service is classified in accordance with ITU Radio Regulations (article 1) as follows:
Fixed service (article 1.20)
Fixed-satellite service (article 1.21)
Inter-satellite service (article 1.22)
Earth exploration-satellite service (article 1.51)
Meteorological-satellite service (article 1.52)
Frequency allocation
The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (most recent version, Edition of 2020).
In order to improve harmonisation in spectrum utilisation, the majority of service-allocations stipulated in this document were incorporated in national Tables of Frequency Allocations and Utilisations which is within the responsibility of the appropriate national administration. The allocation might be primary, secondary, exclusive, and shared.
primary allocation: is indicated by writing in capital letters (see example below)
secondary allocation: is indicated by small letters
exclusive or shared utilization: is within the responsibility of administrations
Example of frequency allocation
Use in North America
FSS – is as well the official classification (used chiefly in North America) for geostationary communications satellites that provide broadcast feeds to television stations, radio stations and broadcast networks. FSSs also transmit information for telephony, telecommunications, and data communications.
References
Radiocommunication services ITU
Satellite broadcasting | Fixed-satellite service | [
"Engineering"
] | 395 | [
"Telecommunications engineering",
"Satellite broadcasting"
] |
2,984,191 | https://en.wikipedia.org/wiki/DFI | DFI (Diamond Flower Inc) is a Taiwanese industrial computer company with headquarters in Taipei. It designs, develops, manufactures, and sells industrial motherboard, industrial PCs, System-on-Module, industrial displays, and ODM/OEM services.
DFI was founded by Y.C Lu on July 14, 1981, developing and selling electronics components and add-on cards in the beginning. However, DFI switched to the production of motherboards after searching for potential markets and deciding to focus on the strengths of DFI. Targeting the new growing market in motherboard products, DFI announced the Patent License Agreement with Intel Corporation to build partnership with Intel in 1990 and has been developing and manufacturing motherboard products since 1992. With continuous dedication, DFI quickly gained a reputation in Asia-Pacific region after five years and was awarded Top 10 Motherboard Manufacturer in CRN Magazine from the year 1997 to 1999. Starting from 1998, DFI began to follow the strategies of Intel by releasing Intel 440BX series motherboards, 810 motherboards, and 810e motherboards to worldwide markets. Since its growing advances in manufacturing motherboards, DFI was awarded the Intel Global Demo Board manufacturer award in 1998 and 1999 respectively.
Catering to the growing market of high-end motherboards, DFI developed advanced overclocking motherboards, the LanParty series, which has proven to be a valuable segment for small powerful computers that meet the requirements of end users in the 2000s. DFI introduced the junior lineup (“JR”) with two products, p45 and 790gx, in the beginning, which has since been extended with Nvidia and X58 chipsets. There are other LanParty series like LT, DK(Dark), and Lanparty UT.
With blossoming business in the market, DFI went public and launched its initial public offering (IPO) on January 15, 2000. DFI has already gained a reputation from its motherboard products and hot-selling lineup, LanParty, at that time. And aside from developing LanParty consumer products, DFI started to develop ACP (Application Control Platform) businesses, mainly targeted at vertical applications in slot machine, POS, security system, and so on since 2002. In 2005, DFI gained over 50% revenues from this new business. With this successful transformation, industrial computer became the primary business of DFI. As of 2003, DFI's renowned overclocked gamer motherboard, LANPARTY NFII ULTRA, was awarded the Chief Editor Choice Award in PC Magazine and the Best Creativity Award in Tom's Hardware Guide.
Since DFI planned to focus on developing embedded system products, not only did they stop developing Consumer Product Line, but also started establishing embedded system developments and designs in 2011 to expand its industrial computer business.
History
1981–1991
In 1981, Y.C Lu founded DFI Electronics Components Inc. in Taipei, Taiwan; mainly supplying and exporting electronics components with $1 million in capital. During the first year, DFI earned a revenue of $30 million. In 1984, DFI established facility in Taipei and began manufacturing and selling computers and peripherals. When the capital increased up to $10 million, the Sales (Revenue) Growth Rate of DFI also increased to 300% and DFI successfully expanded its operations to the American regions as well as earning nearly $1 billion in revenues. In 1987, with the capital of $30 million, DFI started to establish facility in Hsi-Chih City, Taiwan. At the same time, DFI planned to stretch its product line into the European markets, starting with Germany and England. As of 1988, the facility relocated to Hsi-Chih City, which was the major facility of DFI. With the expansion of production line and the addition of Automatic Test Equipment (ATE), DFI not only upgraded the quality of products, but also released a handheld scanner. As of 1989, DFI added Computer Aided Design System (CAD) to its facility to manufacture more products like computer mouse, handheld scanner, personal computer, and add-on card, etc. In 1990, DFI announced its Patent License Agreement with Intel Corporation and became the first company with an assembly production line in America to enable technical support service in cooperation with Intel. DFI's capital increased to $196 million and expanded its facility to 1,900 square feet in 1991.
1992–2000
As of 1992, DFI introduced ICT and SMT devices into its facility to increase the manufacturing quality and efficiency. In 1993, DFI continually expanded the facility, which was located in Hsi-Chih City and was 2,300 square feet. DFI's business office and Research and Development Department moved to the facility and introduced Green PC with energy-efficiency design into the facility. As of 1994, DFI researched and developed CD-ROM, officially entered into multimedia system market. The revenue of the notebook increased to over $100 million and the overall revenue of 1994 increased by 25%, over $2 billion. As of 1996, DFI transformed the CD-ROM facility into an assembly system facility, designing and manufacturing the world's first 75MHZ system bus motherboard, which supported the CYRIX PR 200+CPU. In the meantime, DFI began establishing the third SMT assembly and adopted Siemens SIPLACE80S-15 high speed CNC machine to increase the production of motherboards to 40,000 pcs per month, as well as increasing the self-production to 120, 000 per month. After manufacturing 586 motherboards that supported dual CPU, DFI was dominant in the motherboard market and targeted developing countries, accommodating to Philips Asian marketing system. As of 1997, DFI expanded the facility in Hsi-Chih City for the third time, totaling the area to 2, 800 square feet. DFI also expanded 2 surface mount technology (SMT) high speed CNC machines to upgrade the production of motherboards to 180, 000 pcs per month. Devoted to developing Philips and Lemel assembly OEM business, DFI manufactured 10, 000 systems every month. At the same time, DFI established a third OEM assembly facility in Dongguan city, China and built a European branch office in Bremen, Germany in order to advance the quality of services in European regions. Being engaged in the server market, DFI got started in designing and developing motherboards that support SCSI onboard and Dual Pentium CPU in 1997. From the year of 1997 to 1999, DFI was awarded the Top 10 Motherboard Manufacturer in CRN (Computer Reseller New) Magazine, which had already gained attention by the worldwide market due to DFI's motherboards’ design and development. In April, 1998, DFI was preparing to apply for becoming a listed company at Taipei Exchange (TPEx) and TWSE. In the same year, DFI released Intel 440BX series motherboard, which was in line with Intel. The 810 motherboard of DFI was awarded the Demo Board amongst Intel Asia-Pacific region. In February, 1999, P5BV3＋motherboards was awarded the high performance Socket7 motherboard in Computer World Magazine in China. In early May of the same year, DFI launched 810 motherboard to the market, following the release of Intel and had already gone into mass production worldwide. The 810e motherboard was re-awarded Intel Global Demo Board and was launched to the market in September, 1999. DFI went public and launched its initial public offering (IPO) on 15, January, 2000. During the same year, DFI founded Diamond Flower H.T. Group (BVI) Inc.
2001–2005
In April 2001, DFI's facilities added the seventh SMT assembly line, increasing productivity to 30,000 pieces per month. As of 2002, DFI added the eighth SMT assembly line into factory. In the same year, DFI established worldwide office located in Tokyo, Japan, developing ACP (applied computing platform) businesses for vertical applications and starting to focus on high profit motherboards. In the same year, the local office in Europe relocated to Rotterdam-Hoogvliet in the Netherlands, setting a service center in Eastern Europe, Poland. In 2003, DFI's renowned gamer overclocking motherboard, LANPARTY NFII ULTRA, was awarded LANPARTY.com Highly Commended Prize, PC Professionell Magazine Extreme Award, Chief Editor Choice Award in PC Magazine and awarded the Best Creativity Award in Tom's Hardware Guild. In 2004, DFI launched a product line based on Intel® 940 Series Chipsets (code name: Calistoga), covering different form factors from COM Express Basic, G5C900-B, Mini-ITX motherboard, CT132-B, to ST100-G5C embedded system,. As of 2005, DFI's capital increased to NTD 1.097 billion, profiting in ACP (Applied Computing Platform) business and gained over 50% revue from this new business. Through this increasingly developed new business, industrial computer has become the major business of DFI. In 2005, DFI launched a product line based on Intel® 960 Series Chipsets (code name: Broadwater,) including different form factors such as microATX motherboard, G7B336-P, ATX motherboard, G7B630-B/N. DFI also launched the panel PC, FS200-BMX5, which was based on ARM Cortex-A8 Freescale i.MX53 processors.
2006–2010
As of 2006, GE became the vital investor of DFI, benefiting from a large amount of DFI's business as well as acquiring 100% equity of DFI-Japan. With the acquisition cost of NTD 24.55 million, it allowed DFI to completely devote itself to in-depth industrial computer market in Japan. In the following three years, the consolidated revenue growth rate in ACP (Applied Computing Platform) business increased over 51%. DFI then launched a product line based on
Intel 960 Series Chipsets (code name: Crestline), including different form factors consisting of SR100-L20C Mini-ITX motherboard and SR330-L microATX motherboard. In the same year, DFI also launched a product line based on Intel 945P Chipsets (code name: Lakeport), covering different form factors like G7L331-B microATX motherboard and LT600-D ATX motherboard. As of 2007, DFI's capital increased to NTD1.14 billion as well as a 65.77% equity of DFI-ITOX with acquisition cost of NTD 234 million. To guarantee exceptional quality and reliability of products under rigorous quality standards, DFI's products were approved by QC080000, WASO14001, and Green Partner certifications in 2007. DFI launched a product line based on Intel G41 Chipsets (code name: Eagle Lake), inclusive of EL109-N Mini-ITX motherboard, EL339-B microATX motherboard, and EL620-C ATX motherboard, as well as HNVR320-EL embedded system. In 2007, DFI also released a product line based on Intel Q35 Chipsets (code name: Bearlake), ranging from BL100-NE/PE Mini-ITX motherboard, to BL330-B microATX motherboard, to BL631-D ATX motherboard, As of 2008, DFI's capital increased to NTD 1.19 billion, acquiring 100% equity of YAN TONG TECHNOLOGYLTD with acquisition cost of NTD 187.26 million, as well as increasing the capital to DFI-Japan to JPY 280 million. In 2008, DFI released a product line based on Intel GM45 Chipsets (code name: Cantiga), ranging from CA900-B COM Express Basic, to small form factor CA230-BF Mini-DTX board, to CA101-D Mini-ITX motherboard, to CA331-P microATX motherboard. Furthermore, DFI launched a product series based on Intel Atom Processor Z500 series (code name: Silverthorne), offering from ML905-B11C/B16C COM Express, to small form factor ML936-B11C/B16C board, to CS910-ML embedded system. In the same year, DFI also kicked off a full range of product series which were based on Intel 945GSE Chipsets (code name: Navy Pier), covering from NP102-N16C Mini-ITX motherboard, to NP905-B16C COM Express Compact, to NP951-B16C small form factor 3.5" SBC, to ES122-NP embedded system. As of 2009, DFI's capital increased to NTD 1.21 billion. And DFI launched a lineup including PT330-DRM microATX motherboard, PT631-IPM ATX motherboard, and HNVR320-PT embedded system based on Intel Core/Intel Pentium Processors (code name: Piketon). In 2010, DFI's capital increased to NTD 1.202 billion. DFI also launched a product line including CP100-NRM Mini-ITX motherboard, CP330-NRM microATX motherboard, CP908-B COM Express Compact, and ST101-CP embedded system based on Intel Core/Intel® Celeron® Processors with Mobile Intel QM57 Chipset (code name: Calpella).
DFI also launched system-on-module Qseven, QB700-B + Q7951, which was powered by Intel Atom E600 series processors (code name: Queensbay). In the end of 2010, DFI launched LR100-N18D/S/M Mini-ITX motherboard, LR905-B18D/S/M COM Express, and EC200/210/220/221 embedded system, which were based on
Intel Atom® D525/D425 series processors (code name: Luna Pier).
2011–2018
In May 2011, DFI's process-on-order factory in China was transformed into Sole proprietorship, which was capitalized with US$2.5 million. To expand its industrial computer business, DFI established a system engineering department to fulfill highly dedicated researches and design developments for the future. In 2012, DFI launched a product line based on Intel Atom® Processor D2550/N2800 (code name: Cedar Trail), including Mini-ITX form factor motherboard CD101-N, COM Express Compact CD905-B, 3.5" SBC motherboard CD951, and embedded system DS910-CD. On June 4, 2014, DFI established Yan Ying Hao Trading Co. Ltd.in ShenZhen, and started to develop business in the China region. To accommodate increasing growth and expansion, DFI relocated its corporate headquarter to Farglory U-Town building in New Taipei City. In 2016, DFI has released Qualcomm-based motherboard and medical industrial computer that dedicate itself to various fields and expand its business with different platforms. DFI has joined Qisda/BenQ Group. In the second half year of 2018, DFI has added the new SMT line to the factory to scale up its facilities and production capability.
Popular products
As of 2012, DFI stopped consumer product line and no longer produced high-end gamer boards such as the LanParty series for end users
DFI-ACP
DFI is also manufacturing motherboards for various industrial purposes. DFI-ACP is a Wintel based platform provider for non-PC business, products range from board level, open frame, add-on boards to barebone systems.
References
1981 establishments in Taiwan
Companies established in 1981
Computer companies of Taiwan
Computer hardware companies
Computer systems companies
Motherboard companies
Electronics companies of Taiwan
Taiwanese brands
Manufacturing companies based in New Taipei | DFI | [
"Technology"
] | 3,367 | [
"Computer hardware companies",
"Computer systems companies",
"Computers",
"Computer systems"
] |
2,984,353 | https://en.wikipedia.org/wiki/251%20%28number%29 | 251 (two hundred [and] fifty-one) is the natural number between 250 and 252. It is also a prime number.
In mathematics
251 is:
a Sophie Germain prime.
the sum of three consecutive primes (79 + 83 + 89) and seven consecutive primes (23 + 29 + 31 + 37 + 41 + 43 + 47).
a Chen prime.
an Eisenstein prime with no imaginary part.
a de Polignac number, meaning that it is odd and cannot be formed by adding a power of two to a prime number.
the smallest number that can be formed in more than one way by summing three positive cubes:
Every 5 × 5 matrix has exactly 251 square submatrices.
References
Integers | 251 (number) | [
"Mathematics"
] | 151 | [
"Mathematical objects",
"Number stubs",
"Elementary mathematics",
"Integers",
"Numbers"
] |
2,984,446 | https://en.wikipedia.org/wiki/257%20%28number%29 | 257 (two hundred [and] fifty-seven) is the natural number following 256 and preceding 258.
257 is a prime number of the form specifically with n = 3, and therefore a Fermat prime. Thus, a regular polygon with 257 sides is constructible with compass and unmarked straightedge. It is currently the second largest known Fermat prime.
Analogously, 257 is the third Sierpinski prime of the first kind, of the form ➜ .
It is also
a balanced prime,
an irregular prime,
a prime that is one more than a square,
and a Jacobsthal–Lucas number.
Four-fold 257 is 1028, which is the prime index of the fifth Mersenne prime, 8191.
There are exactly 257 combinatorially distinct convex polyhedra with eight vertices (or polyhedral graphs with eight nodes).
References
Integers | 257 (number) | [
"Mathematics"
] | 180 | [
"Mathematical objects",
"Number stubs",
"Elementary mathematics",
"Integers",
"Numbers"
] |
2,984,476 | https://en.wikipedia.org/wiki/Kaup%E2%80%93Kupershmidt%20equation | The Kaup–Kupershmidt equation (named after David J. Kaup and Boris Abram Kupershmidt) is the nonlinear fifth-order partial differential equation
It is the first equation in a hierarchy of integrable equations with the Lax operator
.
It has properties similar (but not identical) to those of the better-known KdV hierarchy in which the Lax operator has order 2.
References
External links
Partial differential equations
Integrable systems | Kaup–Kupershmidt equation | [
"Physics",
"Mathematics"
] | 94 | [
"Integrable systems",
"Mathematical analysis",
"Theoretical physics",
"Mathematical analysis stubs"
] |
2,985,027 | https://en.wikipedia.org/wiki/SageTV | SageTV Media Center, now open source, was a proprietary, commercial DVR (Digital Video Recording) and HTPC (Home theater PC) software for Mac OS X, Windows and Linux. It requires that the host computer have a hardware-based TV tuner card. The SageTV software has an integrated Electronic Programming Guide (EPG) that is updated via the Internet. The program provides a television interface for DVR, music, and photos on Windows and Linux. SageTV Media Center typically records in standard MPEG2, making it possible to transfer recordings to laptops or other devices. It also has a built-in conversion feature to transcode files into other formats compatible with iPod, PSP, cell phones and other portable devices.
A "lite" version is commonly shipped as part of an OEM software bundle. Both the lite and regular versions offer a Java API.
SageTV Placeshifter allows the user to watch TV from any high speed internet connection, similar to the Slingbox. As of Version 6, the SageTV Placeshifter is available for Windows, Linux and Macintosh platforms. The SageTV Media Extender set-top allows other TVs to connect to SageTV over a home network. There is also the ability to use the Hauppauge MediaMVP with SageTV by purchasing a MediaMVP Client License.
On June 18, 2011, Jeffrey Kardatzke, CTO and founder of the company, announced in a SageTV forum post that his company had been acquired by Google. An official press release followed later the same day, and since then the SageTV products have no longer been available for purchase.
On March 9, 2015, Jeffrey Kardatzke announced that SageTV would be open-sourced "in the near future (i.e. months, not years)". Then a few months later, SageTV became open source, hosted on GitHub.
Google Fiber
After the acquisition of SageTV, LLC by Google, they began modifying and updating it to work with Google's upcoming Google Fiber TV service. SageTV v8 was the initial platform used for the Google Fiber Storage Box (DVR) and TV Box (Client). It has since been replaced with an in-house developed software.
SageTV Media Center for Linux
SageTV Media Center for Linux is compatible with most major Linux distributions. Information on a Gentoo distribution tuned for Media Center usage is available from the SageTV website. It runs on low cost PC and consumer electronics hardware including embedded processors (embedded only available for OEMs).
SageTV Studio
SageTV software also includes a SageTV Studio Development GUI that allows the customization of the user interface and development of add-ons. The company provides documentation so that these customizations can use a Java API. Built-in EPG support is available only for North America; however, the developer community has developed plug-ins that allow unsupported regions to access EPG info through sources such as XMLTV and ICETV in Australia. Additionally, there are IMDb and commercial skipping plugins.
Other PVR software
Comparison of PVR software packages
References
Digital video recorders
Discontinued Google acquisitions
Google acquisitions
Television placeshifting technology
Television technology | SageTV | [
"Technology"
] | 663 | [
"Information and communications technology",
"Recording devices",
"Television technology",
"Digital video recorders"
] |
2,985,223 | https://en.wikipedia.org/wiki/Apomorphine | Apomorphine, sold under the brand name Apokyn among others, is a type of aporphine having activity as a non-selective dopamine agonist which activates both D2-like and, to a much lesser extent, D1-like receptors. It also acts as an antagonist of 5-HT2 and α-adrenergic receptors with high affinity. The compound is an alkaloid belonging to nymphaea caerulea, or blue lotus, but is also historically known as a morphine decomposition product made by boiling morphine with concentrated acid, hence the -morphine suffix. Contrary to its name, apomorphine does not actually contain morphine or its skeleton, nor does it bind to opioid receptors. The apo- prefix relates to it being a morphine derivative ("[comes] from morphine").
Historically, apomorphine has been tried for a variety of uses, including as a way to relieve anxiety and craving in alcoholics, an emetic (to induce vomiting), for treating stereotypies (repeated behaviour) in farmyard animals, and more recently in treating erectile dysfunction. Currently, apomorphine is used in the treatment of Parkinson's disease. It is a potent emetic and should not be administered without an antiemetic such as domperidone. The emetic properties of apomorphine are exploited in veterinary medicine to induce therapeutic emesis in canines that have recently ingested toxic or foreign substances.
Apomorphine was also used as a private treatment of heroin addiction, a purpose for which it was championed by the author William S. Burroughs. Burroughs and others claimed that it was a "metabolic regulator" with a restorative dimension to a damaged or dysfunctional dopaminergic system. Despite anecdotal evidence that this offers a plausible route to an abstinence-based mode, no clinical trials have ever tested this hypothesis. A recent study indicates that apomorphine might be a suitable marker for assessing central dopamine system alterations associated with chronic heroin consumption. There is, however, no clinical evidence that apomorphine is an effective and safe treatment regimen for opiate addiction.
Medical uses
Apomorphine is used in advanced Parkinson's disease intermittent hypomobility ("off" episodes), where a decreased response to an anti-Parkinson drug such as L-DOPA causes muscle stiffness and loss of muscle control. While apomorphine can be used in combination with L-DOPA, the intention is usually to reduce the L-DOPA dosing, as by this stage the patient often has many of dyskinesias caused by L-DOPA and hypermobility periods. When an episode sets in, the apomorphine is injected subcutaneously or applied sublingually, and signs subside. It is used an average of three times a day. Some people use portable mini-pumps that continuously infuse them with apomorphine, allowing them to stay in the "on" state and using apomorphine as an effective monotherapy.
Contraindications
The main and absolute contraindication to using apomorphine is the concurrent use of adrenergic receptor antagonists; combined, they cause a severe drop in blood pressure and fainting. Alcohol causes an increased frequency of orthostatic hypotension (a sudden drop in blood pressure when getting up), and can also increase the chances of pneumonia and heart attacks. Dopamine antagonists, by their nature of competing for sites at dopamine receptors, reduce the effectiveness of the agonistic apomorphine.
IV administration of apomorphine is highly discouraged, as it can crystallize in the veins and create a blood clot (thrombus) and block a pulmonary artery (pulmonary embolism).
Side effects
Nausea and vomiting are common side effects when first beginning therapy with apomorphine; antiemetics such as trimethobenzamide or domperidone, dopamine antagonists, are often used while first starting apomorphine. Around 50% of people grow tolerant enough to apomorphine's emetic effects that they can discontinue the antiemetic.
Other side effects include orthostatic hypotension and resultant fainting, sleepiness, dizziness, runny nose, sweating, paleness, and flushing. More serious side effects include dyskinesias (especially when taking L-DOPA), fluid accumulation in the limbs (edema), suddenly falling asleep, confusion and hallucinations, increased heart rate and heart palpitations, and persistent erections (priapism). The priapism is caused by apomorphine increasing arterial blood supply to the penis. This side effect has been exploited in studies attempting to treat erectile dysfunction.
Pharmacology
Mechanism of action
Apomorphine's R-enantiomer is an agonist of both D1 and D2 dopamine receptors, with higher activity at D2. The members of the D2 subfamily, consisting of D2, D3, and D4 receptors, are inhibitory G protein–coupled receptors. The D4 receptor in particular is an important target in the signaling pathway, and is connected to several neurological disorders. Shortage or excess of dopamine can prevent proper function and signaling of these receptors leading to disease states.
Apomorphine improves motor function by activating dopamine receptors in the nigrostriatal pathway, the limbic system, the hypothalamus, and the pituitary gland. It also increases blood flow to the supplementary motor area and to the dorsolateral prefrontal cortex (stimulation of which has been found to reduce the tardive dyskinesia effects of L-DOPA). Parkinson's has also been found to have excess iron at the sites of neurodegeneration; both the (R)- and (S)-enantiomers of apomorphine are potent iron chelators and radical scavengers.
Apomorphine also decreases the breakdown of dopamine in the brain (though it inhibits its synthesis as well). It is an upregulator of certain neural growth factors, in particular NGF but not BDNF, epigenetic downregulation of which has been associated with addictive behaviour in rats.
Apomorphine causes vomiting by acting on dopamine receptors in the chemoreceptor trigger zone of the medulla; this activates the nearby vomiting center.
Pharmacokinetics
While apomorphine has lower bioavailability when taken orally, due to not being absorbed well in the GI tract and undergoing heavy first-pass metabolism, it has a bioavailability of 100% when given subcutaneously. It reaches peak plasma concentration in 10–60 minutes. Ten to twenty minutes after that, it reaches its peak concentration in the cerebrospinal fluid. Its lipophilic structure allows it to cross the blood–brain barrier.
Apomorphine possesses affinity for the following receptors (note that a higher Ki indicates a lower affinity):
It has a Ki of over 10,000 nM (and thus negligible affinity) for β-adrenergic, H1, and mACh.
Apomorphine has a high clearance rate (3–5 L/kg/hr) and is mainly metabolized and excreted by the liver. It is likely that while the cytochrome P450 system plays a minor role, most of apomorphine's metabolism happens via auto-oxidation, O-glucuronidation, O-methylation, N-demethylation, and sulfation. Only 3–4% of the apomorphine is excreted unchanged and into the urine. The half-life is 30–60 minutes, and the effects of the injection last for up to 90 minutes.
Toxicity depends on the route of administration; the LD50s in mice were 300 mg/kg for the oral route, 160 mg/kg for intraperitoneal, and 56 mg/kg intravenous.
Chemistry
Properties
Apomorphine has a catechol structure similar to that of dopamine.
Synthesis
Several techniques exist for the creation of apomorphine from morphine. In the past, morphine had been combined with hydrochloric acid at high temperatures (around 150 °C) to achieve a low yield of apomorphine, ranging anywhere from 0.6% to 46%.
More recent techniques create the apomorphine in a similar fashion, by heating it in the presence of any acid that will promote the essential dehydration rearrangement of morphine-type alkaloids, such as phosphoric acid. The method then deviates by including a water scavenger, which is essential to remove the water produced by the reaction that can react with the product and lead to decreased yield. The scavenger can be any reagent that will irreversibly react with water such as phthalic anhydride or titanium chloride. The temperature required for the reaction varies based upon choice of acid and water scavenger. The yield of this reaction is much higher: at least 55%.
History
The pharmacological effects of the naturally-occurring analog aporphine in the blue lotus (Nymphaea caerulea) were known to the ancient Egyptians and Mayans, with the plant featuring in tomb frescoes and associated with entheogenic rites. It is also observed in Egyptian erotic cartoons, suggesting that they were aware of its erectogenic properties.
The modern medical history of apomorphine begins with its synthesis by Arppe in 1845 from morphine and sulfuric acid, although it was named sulphomorphide at first. Matthiesen and Wright (1869) used hydrochloric acid instead of sulfuric acid in the process, naming the resulting compound apomorphine. Initial interest in the compound was as an emetic, tested and confirmed safe by London doctor Samuel Gee, and for the treatment of stereotypies in farmyard animals. Key to the use of apomorphine as a behavioural modifier was the research of Erich Harnack, whose experiments in rabbits (which do not vomit) demonstrated that apomorphine had powerful effects on the activity of rabbits, inducing licking, gnawing and in very high doses convulsions and death.
Treatment of alcoholism
Apomorphine was one of the earliest used pharmacotherapies for alcoholism. The Keeley Cure (1870s to 1900) contained apomorphine, among other ingredients, but the first medical reports of its use for more than pure emesis come from James Tompkins and Charles Douglas. Tompkins reported, after injection of 6.5 mg ("one tenth of a grain"):Douglas saw two purposes for apomorphine:This use of small, continuous doses (1/30th of a grain, or 2.16 mg by Douglas) of apomorphine to reduce alcoholic craving comes some time before Pavlov's discovery and publication of the idea of the "conditioned reflex" in 1903. This method was not limited to Douglas; the Irish doctor Francis Hare, who worked in a sanatorium outside London from 1905 onward, also used low-dose apomorphine as a treatment, describing it as "the most useful single drug in the therapeutics of inebriety". He wrote:He also noted there appeared to be a significant prejudice against the use of apomorphine, both from the associations of its name and doctors being reluctant to give hypodermic injections to alcoholics. In the US, the Harrison Narcotics Tax Act made working with any morphine derivatives extremely hard, despite apomorphine itself not being an opiate.
In the 1950s the neurotransmitter dopamine was discovered in the brain by Katharine Montagu, and characterised as a neurotransmitter a year later by Arvid Carlsson, for which he would be awarded the Nobel Prize. A. N. Ernst then discovered in 1965 that apomorphine was a powerful stimulant of dopamine receptors. This, along with the use of sublingual apomorphine tablets, led to a renewed interest in the use of apomorphine as a treatment for alcoholism. A series of studies of non-emetic apomorphine in the treatment of alcoholism were published, with mostly positive results. However, there was little clinical consequence.
Parkinson's disease
The use of apomorphine to treat "the shakes" was first suggested by Weil in France in 1884, although seemingly not pursued until 1951. Its clinical use was first reported in 1970 by Cotzias et al., although its emetic properties and short half-life made oral use impractical. A later study found that combining the drug with the antiemetic domperidone improved results significantly. The commercialization of apomorphine for Parkinson's disease followed its successful use in patients with refractory motor fluctuations using intermittent rescue injections and continuous infusions.
Aversion therapy
Aversion therapy in alcoholism had its roots in Russia in the early 1930s, with early papers by Pavlov, Galant and Sluchevsky and Friken, and would remain a strain in the Soviet treatment of alcoholism well into the 1980s. In the US a particularly notable devotee was Dr Voegtlin, who attempted aversion therapy using apomorphine in the mid to late 1930s. However, he found apomorphine less able to induce negative feelings in his subjects than the stronger and more unpleasant emetic emetine.
In the UK, however, the publication of J. Y. Dent's (who later went on to treat Burroughs) 1934 paper "Apomorphine in the treatment of Anxiety States" laid out the main method by which apomorphine would be used to treat alcoholism in Britain. His method in that paper is clearly influenced by the then-novel idea of aversion:However, even in 1934 he was suspicious of the idea that the treatment was pure conditioned reflex – "though vomiting is one of the ways that apomorphine relives the patient, I do not believe it to be its main therapeutic effect." – and by 1948 he wrote:This led to his development of lower-dose and non-aversive methods, which would inspire a positive trial of his method in Switzerland by Dr Harry Feldmann and later scientific testing in the 1970s, some time after his death. However, the use of apomorphine in aversion therapy had escaped alcoholism, with its use to treat homosexuality leading to the death of a British Army Captain Billy Clegg Hill in 1962, helping to cement its reputation as a dangerous drug used primarily in archaic behavioural therapies.
Opioid addiction
In his Deposition: Testimony Concerning a Sickness in the introduction to later editions of Naked Lunch (first published in 1959), William S. Burroughs wrote that apomorphine treatment was the only effective cure to opioid addiction he has encountered:
He goes on to lament the fact that as of his writing, little to no research has been done on apomorphine or variations of the drug to study its effects on curing addiction, and perhaps the possibility of retaining the positive effects while removing the side effect of vomiting.
Despite his claims throughout his life, Burroughs never really cured his addiction and was back to using opiates within years of his apomorphine "cure". However, he insisted on apomorphine's effectiveness in several works and interviews.
Society and culture
Apomorphine has a vital part in Agatha Christie's detective story Sad Cypress.
The 1965 Tuli Kupferberg song "Hallucination Horrors" recommends apomorphine at the end of each verse as a cure for hallucinations brought on by a humorous variety of intoxicants; the song was recorded by The Fugs and appears on the album Virgin Fugs.
Research
There is renewed interest in the use of apomorphine to treat addiction, in both smoking cessation and alcoholism. As the drug is known to be reasonably safe for use in humans, it is a viable target for repurposing.
Apomorphine has been researched as a possible treatment for erectile dysfunction and female hypoactive sexual desire disorder, though its efficacy has been limited. Nonetheless, it was under development as a treatment for erectile dysfunction by TAP Pharmaceuticals under the brand name Uprima. In 2000, TAP withdrew its new drug application after an FDA review panel raised questions about the drug's safety, due to many clinical trial subjects fainting after taking the drug.
Alzheimer's disease
Apomorphine is reported to be an inhibitor of amyloid beta protein fiber formation, whose presence is a hallmark of Alzheimer's disease, and a potential therapeutic under the amyloid hypothesis.
Alternative administration routes
Two routes of administration are currently clinically utilized: subcutaneous (either as intermittent injections or continuous infusion) and sublingual. Other non-invasive administration routes were investigated as a substitute for parenteral administration, reaching different preclinical and clinical stages. These include: peroral, nasal, pulmonary, transdermal, rectal, and buccal, as well as iontophoresis methods.
Veterinary use
Apomorphine is used to inducing vomiting in dogs after ingestion of various toxins or foreign bodies. It can be given subcutaneously, intramuscularly, intravenously, or, when a tablet is crushed, in the conjunctiva of the eye. The oral route is ineffective, as apomorphine cannot cross the blood–brain barrier fast enough, and blood levels don't reach a high enough concentration to stimulate the chemoreceptor trigger zone. It can remove around 40–60% of the contents in the stomach.
One of the reasons apomorphine is a preferred drug is its reversibility: in cases of prolonged vomiting, the apomorphine can be reversed with dopamine antagonists like the phenothiazines (for example, acepromazine). Giving apomorphine after giving acepromazine, however, will no longer stimulate vomiting, because apomorphine's target receptors are already occupied. An animal who undergoes severe respiratory depression due to apomorphine can be treated with naloxone.
Apomorphine does not work in cats, who have too few dopamine receptors.
Related compounds
Mdo-npa, the methylenedioxy analog of apomorphine, has greater bioavailability and a longer duration of action.
References
5-HT2A antagonists
5-HT2B antagonists
5-HT2C antagonists
Alpha blockers
Catechols
Dibenzoquinolines
D1-receptor agonists
D2-receptor agonists
D3 receptor agonists
D4 receptor agonists
D5 receptor agonists
Erectile dysfunction drugs
Sexual orientation and medicine
Emetics | Apomorphine | [
"Chemistry"
] | 4,000 | [
"Pharmacology",
"Alpha blockers"
] |
2,985,358 | https://en.wikipedia.org/wiki/Common%20tendinous%20ring | The common tendinous ring, also known as the annulus of Zinn or annular tendon, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. It is the common origin of the four recti muscles of the group of extraocular muscles.
It can be used to divide the regions of the superior orbital fissure.
The arteries surrounding the optic nerve form a vascular structure known as the circle of Zinn-Haller, or sometimes as the circle of Zinn.
The following structures pass through the tendinous ring (superior to inferior):
Superior division of the oculomotor nerve (CNIII)
Nasociliary nerve (branch of ophthalmic nerve)
Inferior division of the oculomotor nerve (CNIII)
Abducens nerve (CNVI)
Optic nerve
Parts
The common tendinous ring spans the superior orbital fissure and can be described as having two parts – an inferior tendon which gives origin to the inferior rectus muscle, and to part of the lateral rectus muscle; and a superior tendon which gives origin to the superior rectus muscle, and to part of the medial and lateral recti muscles.
Eponym
It is named for Johann Gottfried Zinn. It should not be confused with the zonule of Zinn, though it is named after the same person.
References
Histology
Human eye anatomy | Common tendinous ring | [
"Chemistry"
] | 293 | [
"Histology",
"Microscopy"
] |
2,985,420 | https://en.wikipedia.org/wiki/Japanese%20units%20of%20measurement | Traditional Japanese units of measurement or the shakkanhō () is the traditional system of measurement used by the people of the Japanese archipelago. It is largely based on the Chinese system, which spread to Japan and the rest of the Sinosphere in antiquity. It has remained mostly unaltered since the adoption of the measures of the Tang dynasty in 701. Following the 1868 Meiji Restoration, Imperial Japan adopted the metric system and defined the traditional units in metric terms on the basis of a prototype metre and kilogram. The present values of most Korean and Taiwanese units of measurement derive from these values as well.
For a time in the early 20th century, the traditional, metric, and English systems were all legal in Japan. Although commerce has since been legally restricted to using the metric system, the old system is still used in some instances. The old measures are common in carpentry and agriculture, with tools such as chisels, spatels, saws, and hammers manufactured in sun and bu sizes. Floorspace is expressed in terms of tatami mats, and land is sold on the basis of price in tsubo. Sake is sold in multiples of 1gō, with the most common bottle sizes being 4 (720 mL) or 10 (1.8 L, isshōbin).
History
Customary Japanese units are a local adaption of the traditional Chinese system, which was adopted at a very early date. They were imposed and adjusted at various times by local and imperial statutes. The details of the system have varied over time and location in Japan's history.
Japan signed the Treaty of the Metre in 1885, with its terms taking effect in 1886. It received its prototype metre and kilogram from the International Bureau of Weights and Measures in 1890. The next year, a weights and measurements law codified the Japanese system, taking its fundamental units to be the shaku and kan and deriving the others from them. The law codified the values of the traditional and metric units in terms of one another, but retained the traditional units as the formal standard and metric values as secondary.
In 1909, English units were also made legal within the Empire of Japan. Following World War I, the Ministry of Agriculture and Commerce established a Committee for Weights and Measures and Industrial Standards, part of whose remit was to investigate which of Japan's three legal systems should be adopted. Upon its advice, the Imperial Diet established the metric system as Japan's legal standard, effective 1 July 1924, with use of the other systems permitted as a transitional measure. The government and "leading industries" were to convert within the next decade, with others following in the decade after that. Public education—at the time compulsory through primary school—began to teach the metric system. Governmental agencies and the Japanese Weights and Measures Association undertook a gradual course of education and conversion but opposition became vehemently outspoken in the early 1930s. Nationalists decried the "foreign" system as harmful to Japanese pride, language, and culture, as well as restrictive to international trade. In 1933, the government pushed the deadline for the conversion of the first group of industries to 1939; the rest of the country was given until 1954. Emboldened, the nationalists succeeded in having an Investigating Committee for Weights and Measures Systems established. In 1938, it advised that the government should continue to employ the "Shaku–Kan" system alongside the metric one. The next year, the imperial ordinance concerning the transition to the metric system was formally revised, indefinitely exempting real estate and historical objects and treasures from any need for metric conversion. The deadline for compulsory conversion in all other fields was moved back to 31 December 1958.
Following its defeat in World War II, Japan was occupied by America and saw an expanded use of US customary units. Gasoline was sold by the gallon and cloth by the yard. The Diet revisited the nation's measurements and, with the occupation's approval, promulgated a Measurements Law in June 1951 that reaffirmed its intention to continue Japan's metrication, effective on the first day of 1959. An unofficial and ad hoc Metric System Promotion Committee was established by interested scholars, public servants, and businessmen in August 1955, undertaking a public awareness campaign and seeking to accomplish as much of the conversion ahead of schedule as possible. Its first success was the conversion of candy sales in Tokyo department stores from the momme to the gram in September 1956; others followed, with NHK taking the lead in media use.
With the majority of the public now exposed to it since childhood, the metric system became the sole legal measurement system in most fields of Japanese life on 1 January 1959. Redrafting of laws to use metric equivalents had already been accomplished, but conversion of the land registries required until 31 March 1966 to complete. Industry transitioned gradually at its own expense, with compliance sometimes being nominal, as in the case of screws becoming " screws". Since the original fines for noncompliance were around $140 and governmental agencies mostly preferred to wait for voluntary conversion, metric use by December 1959 was estimated at only 85%. Since research showed that individual Japanese did not intend to actually use the metric units when given other options, however, sale and verification of devices marked with non-metric units (such as rulers and tape measures noting shaku and sun) were criminalised after 1961.
Some use of the traditional units continues. Some Japanese describe their weight in terms of kan. Homes continue to be reckoned in terms of tsubo, even on the national census as late as 2005, although the practice was discontinued in 2010. English units continue to be employed in aviation, munitions, and various sports, including golf and baseball.
Length
The base unit of Japanese length is the shaku based upon the Chinese chi, with other units derived from it and changing over time based on its dimensions. The chi was originally a span taken from the end of the thumb to the tip of an outstretched middle finger, but which gradually increased in length to about , just a few centimetres longer than the size of a foot.
As in China and Korea, Japan employed different shaku for different purposes. The "carpentry" shaku (, kanejaku) was used for construction. It was a little longer in the 19th century prior to its metric redefinition. The "cloth" or "whale" shaku (, kujirajaku), named for tailors' and fabric merchants' baleen rulers, was longer and used in measuring cloth. (A longer unit of about 25cloth shaku was the tan.) Traditional Japanese clothing was reckoned using the "traditional clothing" shaku (, gofukujaku), about longer than the carpentry shaku. The Shōsōin in Nara has ivory 1-shaku rulers, the .
The Japanese ri is now much longer than the Chinese or Korean li, comprising 36 chō, 2160 ken, or 12,960shaku. A still longer unit was formerly standard in Ise on Honshu and throughout the 9 provinces of Kyushu, which comprised 50 chō, 3000 ken, or 18,000shaku. The imperial nautical mile of 6080feet (1853.19m) was also formerly used by the Japanese in maritime contexts as a "marine ri". A fourth and shorter ri of about 600m is still evident in some beach names. The "99-Ri" beach at Kujukuri is about 60 km. The "7-Ri" beach at Shichiri is 4.2 km long.
The traditional units are still used for construction materials in Japan. For example, plywood is usually manufactured in (about ) sheets known in the trade as , or 3 × 6 shaku. Each sheet is about the size of one tatami mat. The thicknesses of the sheets, however, are usually measured in millimetres. The names of these units also live in the name of the bamboo flute , literally "shaku eight", which measures one shaku and eight sun, and the Japanese version of the Tom Thumb story, , literally "one sun boy", as well as in many Japanese proverbs.
Area
The base unit of Japanese area is the tsubo, equivalent to a square ken or 36 square shaku. It is twice the size of the jō, the area of the Nagoya tatami mat. Both units are used informally in discussing real estate floorspace. Due to historical connections, the tsubo is still used as the official base unit of area in Taiwan.
In agricultural contexts, the tsubo is known as the bu. The larger units remain in common use by Japanese farmers when discussing the sizes of fields.
Volume
The base unit of Japanese volume is the shō, although the gō now sees more use since it is reckoned as the appropriate size of a serving of rice or sake. Sake and shochu are both commonly sold in large 1800mL bottles known as , literally "one shō bottle".
The koku is historically important: since it was reckoned as the amount of rice necessary to feed a person for a single year, it was used to compute agricultural output and official salaries. The koku of rice was sometimes reckoned as 3000"sacks". By the 1940s the shipping koku was of the shipping ton of 40 or 42cuft (i.e., ); the koku of timber was about 10cuft (); and the koku of fish, like many modern bushels, was no longer reckoned by volume but computed by weight (40kan). The shakujime of timber was about 12cuft () and the taba about 108ft³ ( or ).
Mass
The base unit of Japanese mass is the kan, although the momme is more common. It is a recognised unit in the international pearl industry. In English-speaking countries, momme is typically abbreviated as mo.
The Japanese form of the Chinese tael was the ryō (). It was customarily reckoned as around 4 or 10 momme but, because of its importance as a fundamental unit of the silver and gold bullion used as currency in medieval Japan, it varied over time and location from those notional values.
Imperial units
Imperial units are sometimes used in Japan. Feet and inches are used for most non-sport bicycles, whose tyre sizes follow a British system; for sizes of magnetic tape and many pieces of computer hardware; for photograph sizes; and for the sizes of electronic displays for electronic devices. Photographic prints, however, are usually rounded to the nearest millimetre and screens are not described in terms of inches but "type" (, gata). For instance, a television whose screen has a 17-inch diagonal is described as a "17-type" () and one with a 32-inch widescreen screen is called a "32-vista-type" ().
See also
Japanese numerals, counter words, currency, & clocks
Heavenly Stems & Earthly Branches
Units, Systems, & History of measurement
Chinese, Taiwanese, Hong Kong, Mongolian, Korean, & Vietnamese units of measurement
Metric system & Metrication
References
Notes
Citations
Bibliography
.
Iwata, Shigeo. "Weights and Measures in Japan" article in "Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures". Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures See Iwata's full table here: Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures
Gyllenbok, Jan. "Encyclopaedia of Historical Metrology, Weights and Measures", Vol 1. Encyclopaedia of Historical Metrology, Weights, and Measures
, reprinted by the Louisiana State University Press at Baton Rouge in 1991.
.
.
.
.
External links
Japanese Carpentry Museum
Japanese units
Convert traditional Japanese units to metric and imperial units (lengths, areas, volumes, weights) (sci.lang.Japan FAQ pages)
Japanese Measurement to Metric and Imperial Converter for Length/Distance, Area, Volume, Mass/Weight, and Rice Weights
Simple Japanese Traditional Area Units Converter
Simple Japanese Distance and Length Units Converter
Obsolete units of measurement
Systems of units
Units
Units
Units
Customary units of measurement
Units of measurement by country
Standards of Japan | Japanese units of measurement | [
"Mathematics"
] | 2,518 | [
"Obsolete units of measurement",
"Systems of units",
"Units of measurement by country",
"Quantity",
"Customary units of measurement",
"Units of measurement"
] |
2,985,434 | https://en.wikipedia.org/wiki/1-Click | 1-Click, also called one-click or one-click buying, is the technique of allowing customers to make purchases with the payment information needed to complete the purchase having been entered by the user previously. More particularly, it allows an online shopper using an Internet marketplace to purchase an item without having to use shopping cart software. Instead of manually inputting billing and shipping information for a purchase, a user can use one-click buying to use a predefined address and credit card number to purchase one or more items. Since the expiration of Amazon's patent, there has been an advent of checkout experience platforms, such as ShopPay, Simpler, PeachPay, Zplit, and Bolt which offer similar one-click checkout flows.
Patent
The United States Patent and Trademark Office (USPTO) issued a patent for this technique to Amazon.com in September 1999. Amazon.com also owns the "1-Click" trademark.
On May 12, 2006, the USPTO ordered a reexamination of the "One-Click" patent, based on a request filed by Peter Calveley. Calveley cited as prior art an earlier e-commerce patent and the Digicash electronic cash system.
On October 9, 2007, the USPTO issued an office action in the reexamination which confirmed the patentability of claims 6 to 10 of the patent. The patent examiner, however, rejected claims 1 to 5 and 11 to 26. In November 2007, Amazon responded by amending the broadest claims (1 and 11) to restrict them to a shopping cart model of commerce. They have also submitted several hundred references for the examiner to consider. In March 2010, the reexamined and amended patent was allowed.
Amazon's U.S. patent expired on September 11, 2017.
In Europe, a patent application on 1-Click ordering was filed with the European Patent Office (EPO) but was rejected by the EPO in 2007 due to obviousness; the decision was upheld in 2011.
A related gift-ordering patent was granted in 2003, but revoked in 2007 following an opposition.
In Canada, the Federal Court of Canada held that the One click patent could not be rejected as a pure business method since it had a physical effect. The Court remanded the application to the Canadian patent office for a reexamination.
Licensing
Apple Inc.
Amazon.com in 2000 licensed 1-Click ordering to Apple Computer (now Apple Inc.) for use on its online store. Apple subsequently added 1-Click ordering to the iTunes Store and iPhoto. Apple paid $1 million to license the patent.
Barnes & Noble
Amazon filed a patent infringement lawsuit in October 1999 in response to Barnes & Noble's offering a 1-Click ordering option called "Express Lane". After reviewing the evidence, a judge issued a preliminary injunction ordering Barnes & Noble to stop offering Express Lane until the case was settled. Barnes & Noble had developed a way to design around the patent by requiring shoppers to make a second click to confirm their purchase. The lawsuit was settled in 2002. The terms of the settlement, including whether or not Barnes & Noble took a license to the patent or paid any money to Amazon, were not disclosed.
In response to the lawsuit, the Free Software Foundation urged a boycott of Amazon.com. The boycott was lifted by GNU in September 2002.
References
Amazon (company)
Internet properties established in 1997
Internet terminology
Software features
Software patent law | 1-Click | [
"Technology"
] | 711 | [
"Computing terminology",
"Software features",
"Internet terminology"
] |
2,985,588 | https://en.wikipedia.org/wiki/GlueX | GlueX is a particle physics experiment located at the Thomas Jefferson National Accelerator Facility (JLab) accelerator in Newport News, Virginia. Its primary purpose is to better understand the nature of confinement in quantum chromodynamics (QCD) by identifying a spectrum of hybrid and exotic mesons generated by the excitation of the gluonic field binding the quarks. Such mesonic states are predicted to exist outside of the well-established quark model, but none have been definitively identified by previous experiments. A broad high-statistics survey of known light mesons up to and including the is also underway.
Experimental apparatus
The experiment uses photoproduction (that is, the scattering of a real photon on a nucleon) to produce mesonic states. Unlike previous similar experiments, it uses linearly polarized photons, which allows the analysis of accumulated events for certain polarization observables that are thought to make identification of exotic states feasible.
The GlueX detector was installed in the new Hall D (the fourth such hall at JLab) as part of the accelerator's upgrade to 12 GeV energy. GlueX began its first commissioning run in 2014, and first received 12 GeV electrons in 2015, the highest energy available at the CEBAF accelerator. Publication-quality physics data was accumulated during multi-weeks runs starting in 2016, continuing into 2023 and beyond.
The detector is based on a solenoidal hermetic detector optimized for tracking of charged particles (electron, pions, kaons, and protons) and detection of neutral particles (primarily photons). Figure 1 shows the detector.
GlueX uses the coherent bremsstrahlung technique to produce a linearly polarized photon beam. In order to reach the optimal photon energy near 9 GeV for this mapping of the exotic spectrum, 12 GeV electrons are required and are provided by the CEBAF accelerator at Jefferson Lab.
In 2018, improved kaon/pion separation capability will be established with the addition of a quartz-based differential Cherenkov light detector ("DIRC").
Program
The goal of the GlueX experiment is to search for and study hybrid mesons. Hybrid mesons, and in particular exotic hybrid mesons, provide the ideal laboratory for testing QCD in the confinement regime since these mesons explicitly manifest the gluonic degrees of freedom. Photoproduction is expected to be particularly effective in producing and identifying these states. At the same time these data will be used to study the spectrum of conventional mesons, including the poorly-understood excited vector mesons and strangeonium.
The search for new mesonic states requires very specialized analysis methods since such states are rare and must be established through their decay to lighter and longer-lived particles. By examining the energy and angular distributions of produced particles through partial wave analysis, the production and decay of all intermediate states can be reconstructed. The quantum numbers of the intermediate states can be established by this method. These quantum numbers include the spin angular momentum (J), parity (P), and charge conjugation parity (C). Many hybrid states are expected to have quantum number combinations that are the same as conventional quark-model mesons. But the quark model predicts precisely how many such states should exist, and it is expected that an "overpopulation" of certain combinations may herald hybrid states. That is, identified intermediate states with quantum numbers permitted by the quark model may be "hybrids" that contain gluonic excitation, and can be established as such if their number and pattern of mass distribution are not explained within the simple quark model. States with quantum numbers that are strictly forbidden by the naive quark model are said to be "exotic" and, if found experimentally, immediately demonstrate gluonic excitation.
A list of the scientific and technical papers resulting from the GlueX program is linked at the bottom of this article. The range of questions addressed is broad, as seen in the following list of topics of present and possible future runs:
Exploration of the light meson spectrum
Partial wave decomposition of various reaction channels to identify underlying mesonic structure
Threshold photoproduction of charm and the search for associated pentaquarks
High-statistics study of eta and eta' meson production, asymmetries, and decays
Photoproduction of baryon-antibaryon pairs
Search for photoproduced cascade resonances beyond the few well-known ones
Search for "leptophobic" states beyond the Standard Model
Eta meson decay width measurement via the Primakoff effect
Measurement of the polarizability of pions, as a test of low-energy QCD
Collaborating institutions
Cumulative since 2003.
Universities
Arizona State University - Tempe, AZ
Carnegie Mellon University - Pittsburgh, PA
Catholic University of America - Washington, DC
Christopher Newport University - Newport News, VA
Florida International University - Miami, FL
Florida State University - Tallahassee, FL
George Washington University - Washington, DC
Indiana University - Bloomington, IN
Massachusetts Institute of Technology - Cambridge, MA
Norfolk State University - Norfolk, VA
North Carolina A&T State - Greensboro, NC
Northwestern University - Chicago, IL
Old Dominion University - Norfolk, VA
Rensselaer Polytechnic Institute - Troy, NY
The College of William and Mary - Williamsburg, VA
Tomsk State University - Tomsk, Russia
Universidad Técnica Federico Santa María - Valparaíso, Chile
University of Athens - Athens, Greece
University of Connecticut - Storrs, CT
University of Glasgow - Glasgow, Scotland
University of North Carolina - Wilmington, NC
University of Massachusetts - Amherst, MA
University of Regina - Regina, Canada
University of Virginia - Charlottesville, VA
Wuhan University - Wuhan, China
Laboratories
Budker Institute of Nuclear Physics - Novosibirsk, Russia
GSI - Darmstadt, Germany
Institute for High Energy Physics - Protvino, Russia
Institute of High Energy Physics(IHEP) - Beijing, China
Nuclear Physics Institute, Moscow State University - Moscow, Russia
Thomas Jefferson National Accelerator Facility - Newport News, VA
Yerevan Physics Institute - Yerevan, Armenia
See also
Exotic meson
Glueball
Gluon
References
External links
A list of GlueX publications from INSPIRE-HEP
Official Hall-D web page at Jefferson Lab
GlueX.org: Collaboration website
GlueX experiment record on INSPIRE-HEP
Physics experiments
Particle experiments
Spectrometers | GlueX | [
"Physics",
"Chemistry"
] | 1,295 | [
"Spectrum (physical sciences)",
"Physics experiments",
"Experimental physics",
"Spectrometers",
"Spectroscopy"
] |
2,985,783 | https://en.wikipedia.org/wiki/Square-free%20element | In mathematics, a square-free element is an element r of a unique factorization domain R that is not divisible by a non-trivial square. This means that every s such that is a unit of R.
Alternate characterizations
Square-free elements may be also characterized using their prime decomposition. The unique factorization property means that a non-zero non-unit r can be represented as a product of prime elements
Then r is square-free if and only if the primes pi are pairwise non-associated (i.e. that it doesn't have two of the same prime as factors, which would make it divisible by a square number).
Examples
Common examples of square-free elements include square-free integers and square-free polynomials.
See also
Prime number
References
David Darling (2004) The Universal Book of Mathematics: From Abracadabra to Zeno's Paradoxes John Wiley & Sons
Baker, R. C. "The square-free divisor problem." The Quarterly Journal of Mathematics 45.3 (1994): 269-277.
Ring theory | Square-free element | [
"Mathematics"
] | 225 | [
"Fields of abstract algebra",
"Ring theory"
] |
2,985,811 | https://en.wikipedia.org/wiki/Signed%20measure | In mathematics, a signed measure is a generalization of the concept of (positive) measure by allowing the set function to take negative values, i.e., to acquire sign.
Definition
There are two slightly different concepts of a signed measure, depending on whether or not one allows it to take infinite values. Signed measures are usually only allowed to take finite real values, while some textbooks allow them to take infinite values. To avoid confusion, this article will call these two cases "finite signed measures" and "extended signed measures".
Given a measurable space (that is, a set with a σ-algebra on it), an extended signed measure is a set function
such that and is σ-additive – that is, it satisfies the equality
for any sequence of disjoint sets in
The series on the right must converge absolutely when the value of the left-hand side is finite. One consequence is that an extended signed measure can take or as a value, but not both. The expression is undefined and must be avoided.
A finite signed measure (a.k.a. real measure) is defined in the same way, except that it is only allowed to take real values. That is, it cannot take or
Finite signed measures form a real vector space, while extended signed measures do not because they are not closed under addition. On the other hand, measures are extended signed measures, but are not in general finite signed measures.
Examples
Consider a non-negative measure on the space (X, Σ) and a measurable function f: X → R such that
Then, a finite signed measure is given by
for all A in Σ.
This signed measure takes only finite values. To allow it to take +∞ as a value, one needs to replace the assumption about f being absolutely integrable with the more relaxed condition
where f−(x) = max(−f(x), 0) is the negative part of f.
Properties
What follows are two results which will imply that an extended signed measure is the difference of two non-negative measures, and a finite signed measure is the difference of two finite non-negative measures.
The Hahn decomposition theorem states that given a signed measure μ, there exist two measurable sets P and N such that:
P∪N = X and P∩N = ∅;
μ(E) ≥ 0 for each E in Σ such that E ⊆ P — in other words, P is a positive set;
μ(E) ≤ 0 for each E in Σ such that E ⊆ N — that is, N is a negative set.
Moreover, this decomposition is unique up to adding to/subtracting μ-null sets from P and N.
Consider then two non-negative measures μ+ and μ− defined by
and
for all measurable sets E, that is, E in Σ.
One can check that both μ+ and μ− are non-negative measures, with one taking only finite values, and are called the positive part and negative part of μ, respectively. One has that μ = μ+ − μ−. The measure |μ| = μ+ + μ− is called the variation of μ, and its maximum possible value, ||μ|| = |μ|(X), is called the total variation of μ.
This consequence of the Hahn decomposition theorem is called the Jordan decomposition. The measures μ+, μ− and |μ| are independent of the choice of P and N in the Hahn decomposition theorem.
The space of signed measures
The sum of two finite signed measures is a finite signed measure, as is the product of a finite signed measure by a real number – that is, they are closed under linear combinations. It follows that the set of finite signed measures on a measurable space (X, Σ) is a real vector space; this is in contrast to positive measures, which are only closed under conical combinations, and thus form a convex cone but not a vector space. Furthermore, the total variation defines a norm in respect to which the space of finite signed measures becomes a Banach space. This space has even more structure, in that it can be shown to be a Dedekind complete Banach lattice and in so doing the Radon–Nikodym theorem can be shown to be a special case of the Freudenthal spectral theorem.
If X is a compact separable space, then the space of finite signed Baire measures is the dual of the real Banach space of all continuous real-valued functions on X, by the Riesz–Markov–Kakutani representation theorem.
See also
Angular displacement
Complex measure
Spectral measure
Vector measure
Riesz–Markov–Kakutani representation theorem
Signed arc length
Signed area
Signed distance
Signed volume
Total variation
Notes
References
Integral calculus
Measures (measure theory)
Wikipedia articles incorporating text from PlanetMath
Sign (mathematics) | Signed measure | [
"Physics",
"Mathematics"
] | 987 | [
"Physical quantities",
"Calculus",
"Measures (measure theory)",
"Quantity",
"Sign (mathematics)",
"Mathematical objects",
"Size",
"Numbers",
"Integral calculus"
] |
2,985,858 | https://en.wikipedia.org/wiki/Hahn%20decomposition%20theorem | In mathematics, the Hahn decomposition theorem, named after the Austrian mathematician Hans Hahn, states that for any measurable space and any signed measure defined on the -algebra , there exist two -measurable sets, and , of such that:
and .
For every such that , one has , i.e., is a positive set for .
For every such that , one has , i.e., is a negative set for .
Moreover, this decomposition is essentially unique, meaning that for any other pair of -measurable subsets of fulfilling the three conditions above, the symmetric differences and are -null sets in the strong sense that every -measurable subset of them has zero measure. The pair is then called a Hahn decomposition of the signed measure .
Jordan measure decomposition
A consequence of the Hahn decomposition theorem is the , which states that every signed measure defined on has a unique decomposition into a difference of two positive measures, and , at least one of which is finite, such that for every -measurable subset and for every -measurable subset , for any Hahn decomposition of . We call and the positive and negative part of , respectively. The pair is called a Jordan decomposition (or sometimes Hahn–Jordan decomposition) of . The two measures can be defined as
for every and any Hahn decomposition of .
Note that the Jordan decomposition is unique, while the Hahn decomposition is only essentially unique.
The Jordan decomposition has the following corollary: Given a Jordan decomposition of a finite signed measure , one has
for any in . Furthermore, if for a pair of finite non-negative measures on , then
The last expression means that the Jordan decomposition is the minimal decomposition of into a difference of non-negative measures. This is the minimality property of the Jordan decomposition.
Proof of the Jordan decomposition: For an elementary proof of the existence, uniqueness, and minimality of the Jordan measure decomposition see Fischer (2012).
Proof of the Hahn decomposition theorem
Preparation: Assume that does not take the value (otherwise decompose according to ). As mentioned above, a negative set is a set such that for every -measurable subset .
Claim: Suppose that satisfies . Then there is a negative set such that .
Proof of the claim: Define . Inductively assume for that has been constructed. Let
denote the supremum of over all the -measurable subsets of . This supremum might a priori be infinite. As the empty set is a possible candidate for in the definition of , and as , we have . By the definition of , there then exists a -measurable subset satisfying
Set to finish the induction step. Finally, define
As the sets are disjoint subsets of , it follows from the sigma additivity of the signed measure that
This shows that . Assume were not a negative set. This means that there would exist a -measurable subset that satisfies . Then for every , so the series on the right would have to diverge to , implying that , which is a contradiction, since . Therefore, must be a negative set.
Construction of the decomposition: Set . Inductively, given , define
as the infimum of over all the -measurable subsets of . This infimum might a priori be . As is a possible candidate for in the definition of , and as , we have . Hence, there exists a -measurable subset such that
By the claim above, there is a negative set such that . Set to finish the induction step. Finally, define
As the sets are disjoint, we have for every -measurable subset that
by the sigma additivity of . In particular, this shows that is a negative set. Next, define . If were not a positive set, there would exist a -measurable subset with . Then for all and
which is not allowed for . Therefore, is a positive set.
Proof of the uniqueness statement:
Suppose that is another Hahn decomposition of . Then is a positive set and also a negative set. Therefore, every measurable subset of it has measure zero. The same applies to . As
this completes the proof. Q.E.D.
References
External links
Hahn decomposition theorem at PlanetMath.
Theorems in measure theory
Articles containing proofs | Hahn decomposition theorem | [
"Mathematics"
] | 861 | [
"Articles containing proofs",
"Theorems in mathematical analysis",
"Theorems in measure theory"
] |
2,986,034 | https://en.wikipedia.org/wiki/Character%20sum | In mathematics, a character sum is a sum of values of a Dirichlet character χ modulo N, taken over a given range of values of n. Such sums are basic in a number of questions, for example in the distribution of quadratic residues, and in particular in the classical question of finding an upper bound for the least quadratic non-residue modulo N. Character sums are often closely linked to exponential sums by the Gauss sums (this is like a finite Mellin transform).
Assume χ is a non-principal Dirichlet character to the modulus N.
Sums over ranges
The sum taken over all residue classes mod N is then zero. This means that the cases of interest will be sums over relatively short ranges, of length R < N say,
A fundamental improvement on the trivial estimate is the Pólya–Vinogradov inequality, established independently by George Pólya and I. M. Vinogradov in 1918, stating in big O notation that
Assuming the generalized Riemann hypothesis, Hugh Montgomery and R. C. Vaughan have shown that there is the further improvement
Summing polynomials
Another significant type of character sum is that formed by
for some function F, generally a polynomial. A classical result is the case of a quadratic, for example,
and χ a Legendre symbol. Here the sum can be evaluated (as −1), a result that is connected to the local zeta-function of a conic section.
More generally, such sums for the Jacobi symbol relate to local zeta-functions of elliptic curves and hyperelliptic curves; this means that by means of André Weil's results, for N = p a prime number, there are non-trivial bounds
The constant implicit in the notation is linear in the genus of the curve in question, and so (Legendre symbol or hyperelliptic case) can be taken as the degree of F. (More general results, for other values of N, can be obtained starting from there.)
Weil's results also led to the Burgess bound, applying to give non-trivial results beyond Pólya–Vinogradov, for R a power of N greater than 1/4.
Assume the modulus N is a prime.
for any integer r ≥ 3.
Notes
References
Further reading
External links
PlanetMath article on the Pólya–Vinogradov inequality
Analytic number theory | Character sum | [
"Mathematics"
] | 483 | [
"Analytic number theory",
"Number theory"
] |
2,986,091 | https://en.wikipedia.org/wiki/Alfred%20Young%20%28mathematician%29 | Alfred Young, FRS (16 April 1873 – 15 December 1940) was a British mathematician.
He was born in Widnes, Lancashire, England, and educated at Monkton Combe School in Somerset and Clare College, Cambridge, graduating BA as 10th Wrangler in 1895. He is known for his work in the area of group theory. Both Young diagrams and Young tableaux (which he introduced in 1900) are named after him.
Young was appointed to the position of lecturer at Selwyn College, Cambridge, in 1901, transferring to Clare College in 1905. In 1902 he collaborated with John Hilton Grace on the book The Algebra of Invariants.
In 1907 he married Edith Clara née Wilson. In 1908 he became an ordained clergyman, and in 1910 became parish priest at Birdbrook in Essex, a village 25 miles east of Cambridge. He lived there for the rest of his life, but in 1926 began lecturing once again at Cambridge.
Most of his long series of papers on invariant theory and the symmetric group were written while he was a clergyman.
See also
Hyperoctahedral group
Young's lattice
Young–Fibonacci lattice
Young symmetrizer
Representation theory of the symmetric group
References
Bibliography
19th-century English mathematicians
20th-century English mathematicians
1873 births
1940 deaths
People educated at Monkton Combe School
People from Widnes
Group theorists
Combinatorialists
Alumni of Clare College, Cambridge
Fellows of the Royal Society | Alfred Young (mathematician) | [
"Mathematics"
] | 287 | [
"Combinatorialists",
"Combinatorics"
] |
2,986,151 | https://en.wikipedia.org/wiki/Kodaira%20embedding%20theorem | In mathematics, the Kodaira embedding theorem characterises non-singular projective varieties, over the complex numbers, amongst compact Kähler manifolds. In effect it says precisely which complex manifolds are defined by homogeneous polynomials.
Kunihiko Kodaira's result is that for a compact Kähler manifold M, with a Hodge metric, meaning that the cohomology class in degree 2 defined by the Kähler form ω is an integral cohomology class, there is a complex-analytic embedding of M into complex projective space of some high enough dimension N.
The fact that M embeds as an algebraic variety follows from its compactness by Chow's theorem.
A Kähler manifold with a Hodge metric is occasionally called a Hodge manifold (named after W. V. D. Hodge), so Kodaira's results states that Hodge manifolds are projective.
The converse that projective manifolds are Hodge manifolds is more elementary and was already known.
Kodaira also proved (Kodaira 1963), by recourse to the classification of compact complex surfaces, that every compact Kähler surface is a deformation of a projective Kähler surface. This was later simplified by Buchdahl to remove reliance on the classification (Buchdahl 2008).
Kodaira embedding theorem
Let X be a compact Kähler manifold, and L a holomorphic line bundle on X. Then L is a positive line bundle if and only if there is a holomorphic embedding of X into some projective space such that for some m > 0.
See also
Fujita conjecture
Hodge structure
Moishezon manifold
References
A proof of the embedding theorem without the vanishing theorem (due to Simon Donaldson) appears in the lecture notes here.
Theorems in complex geometry
Theorems in algebraic geometry | Kodaira embedding theorem | [
"Mathematics"
] | 374 | [
"Theorems in algebraic geometry",
"Theorems in complex geometry",
"Theorems in geometry"
] |
2,986,194 | https://en.wikipedia.org/wiki/Rhamnose | Rhamnose (Rha, Rham) is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose predominantly occurs in nature in its L-form as L-rhamnose (6-deoxy-L-mannose). This is unusual, since most of the naturally occurring sugars are in D-form. Exceptions are the methyl pentoses L-fucose and L-rhamnose and the pentose L-arabinose. However, examples of naturally-occurring D-rhamnose include some species of bacteria, such as Pseudomonas aeruginosa and Helicobacter pylori.
Rhamnose can be isolated from buckthorn (Rhamnus), poison sumac, and plants in the genus Uncaria. Rhamnose is also produced by microalgae belonging to class Bacillariophyceae (diatoms).
Rhamnose is commonly bound to other sugars in nature. It is a common glycone component of glycosides from many plants. Rhamnose is also a component of the outer cell membrane of acid-fast bacteria in the Mycobacterium genus, which includes the organism that causes tuberculosis. Natural antibodies against L-rhamnose are present in human serum, and the majority of people seem to possess IgM, IgG or both of these types of immunoglobulins capable of binding this glycan.
An interesting particularity of rhamnose is the presence of formaldehyde production when reacted with periodates in the vicinal diol cleavage reaction, that makes it very useful to remove excess periodate in glycerol or other vicinal diol analysis, that would otherwise give colored blank issues.
See also
Galactose binding lectin domain, despite the name, often binds rhamnose
Alpha-L-rhamnosidase
Disaccharides:
Rutinose, rhamnose-glucose
Neohesperidose, rhamnose-glucose
Robinose, rhamnose-galactose
Polysaccharides:
Gellan gum -glucose-glucuronic acid-glucose-rhamnose-
Welan gum
Glycosides:
:Category:Rhamnosides
Echinacoside
Rhamnolipid
Verbascoside
References
Further reading
Deoxy sugars
Aldohexoses
Pyranoses | Rhamnose | [
"Chemistry"
] | 535 | [
"Deoxy sugars",
"Carbohydrates"
] |
2,986,221 | https://en.wikipedia.org/wiki/Soft%20goal | In connection with modeling languages and especially with goal-oriented modeling, a soft goal is an objective without clear-cut criteria. Soft goals can represent:
Non-functional requirements
Relations between non-functional requirements
Non-functional requirements (or quality attributes, qualities, or more colloquially "-ilities") are global qualities of a software system, such as flexibility, maintainability, usability, and so forth. Such requirements are usually stated only informally; and they are often controversial (i.e. management wants a secure system but staff desires user-friendliness). They are also often difficult to validate.
Why soft?
Normally a goal is a very strict and clear logical criterion. It is satisfied when all sub-goals are satisfied. But in non-functional requirements you often need more loosely defined criteria, like satisficeable or unsatisficeable. The term satisficing was first coined by Herbert Simon. Soft goals are goals that do not have a clear-cut criterion for their satisfaction: they are satisficed when there is sufficient positive and little negative evidence for this claim, while they are unsatisficeable in the opposite case.
Relations between soft goals
Decompositions
AND
OR
Contributions
Helps (+)
Hurts (-)
Makes (++)
Breaks (--)
Unknown
References
Further reading
From Object-Oriented to Goal-Oriented Requirements Analysis, Mylopoulos John, Chung Lawrence, Yu Eric
Software requirements | Soft goal | [
"Engineering"
] | 296 | [
"Software engineering",
"Software requirements"
] |
2,986,388 | https://en.wikipedia.org/wiki/Triphosphoric%20acid | Triphosphoric acid (also tripolyphosphoric acid), with formula H5P3O10, is a condensed form of phosphoric acid. In the family of phosphoric acids, it is the next polyphosphoric acid after pyrophosphoric acid, H4P2O7, also called diphosphoric acid.
Compounds such as ATP (adenosine triphosphate) are esters of triphosphoric acid.
Triphosphoric acid has not been obtained in crystalline form. The equilibrium mixture with an overall composition corresponding to H5P3O10 contains about 20% of triphosphoric acid. A solution of the pure species can be obtained by ion exchange of the sodium salt, sodium triphosphate, at 0 °C.
Triphosporic acid is a pentaprotic acid, meaning that it can release five protons in basic enough conditions. Sources differ on the corresponding pKa values:
1.0; 2.2; 2.3; 5.7; 8.5
1.0; 2.2; 2.3; 3.7; 8.5
small; small; 2.30; 6.50; 9.24
References
Phosphorus oxoacids
Phosphorus(V) compounds | Triphosphoric acid | [
"Chemistry"
] | 268 | [
"Inorganic compounds",
"Inorganic compound stubs"
] |
2,986,559 | https://en.wikipedia.org/wiki/SEQUAL%20framework | The SEQUAL framework is systems modelling reference model for evaluating the quality of models. The SEQUAL framework, which stands for "semiotic quality framework" is developed by John Krogstie and others since the 1990s.
The SEQUAL framework is a so-called "top-down quality framework", which is based on semiotic theory, such as the works of Charles W. Morris. Building on these theory it "defines several quality aspects based on relationships between a model, a body of knowledge, a domain, a modeling language, and the activities of learning, taking action, and modeling". Its usefulness, according to Mendling et al. (2006), was confirmed in a 2002 experiment by Moody et al.
History
The basic idea behind the SEQUAL framework is, that "conceptual models can be considered as sets of
statements in a language, and therefore can be evaluated in semiotic/linguistic terms". A first semiotic
framework for evaluating conceptual models was originally proposed by Lindland et al. in the 1994 article "Understanding quality in conceptual modeling". In its initial version, it considered three quality levels:
syntactic,
semantic, and
pragmatic quality
The framework was later extended, and called the SEQUAL framework by Krogstie et al. in the 1995 article "Defining quality aspects for conceptual models". in the 2002 article "Quality of interactive models" Krogstie & Jørgensen extended the initial framework adding
more levels of Stamper's semiotic ladder.
SEQUAL framework topics
Modeling is an integral part of many technical fields, including engineering, economics, and software engineering. In this context, a model is a formal representation of an organizational system, such as a business model or a formal description of software in UML.
Model activation
Model activation, according to John Krogstie (2006), is the process by which a model affects reality. Model activation involves actors interpreting the model and to some extent adjusting their behaviour accordingly. This process can be:
automated, where a software component interprets the model,
manual, where the model guides the actions of human actors, or
interactive, where prescribed aspects of the model are automatically interpreted and ambiguous parts are left to the users to resolve.
Sets in the Quality Framework
The Quality Framework works with a set of eight items:
A: Actors that develop or have to relate to (parts of) the model. Can be persons or tools.
L: What can be expressed in the modeling language
M: What is expressed in the model
D: What can be expressed about the domain (area of interest)
K: The explicit knowledge of the participating persons
I: What the persons in the audience interpret the model to say
T: What relevant tools interpret the model to say
G: The goals of the modeling
Physical quality
The three main aspects of physical quality are:
Externalization or the question "Is it possible to externalize knowledge by using the model language?",
Internalizability about model persistence and availability, and
Basically or the question "Is the model language able to express the model domain?"
Externalization is presenting the modeller's concept in some model form for others to make sense of it. Other people can have look on it and can discuss. How other people perceives the model is a matter of internalization. After perceiving the model in their own way they can discuss and change their mind accordingly. To make sense others, it is better to have some model language in common. Physical quality refers to the possibility of externalizing models by using model language that should be available and of course in persistence manner to be internalized by audiences.
How available is the model to audience? Availability depends on distributability, especially when members of the audience are geographically dispersed. Then, a model which is an electronically distributable format will be more easily distributed than one which must be printed on paper and sent by ordinary mail or fax. It may also matter exactly what is distributed, e.g. the model in an editable form or merely in an output format.
How persistent is the model, how protected is it against loss or damage? This also includes previous versions of the model, if these are relevant. E.g. for a model on disk, the physical quality will be higher if there is a backup copy, or even higher if this backup is on another disk whose failure is independent of the originals. Similarly, for models on paper, the amount and security of backup copies will be essential.
Empirical quality
To evaluate empirical quality, the model should be well externalized. Main aspects are:
Ergonomics,
readability,
layout, and
information theory.
Basically empirical quality is about the question "Is the model easily readable?". Empirical quality deals with the variety of elements distinguished, error frequencies when being written or read, coding (shapes of boxes) and ergonomics for Computer-Human Interaction for documentation and modeling-tools. Ergonomics is the study of workplace design and the physical and psychological impact it has on workers. This quality is related to readability and layout. There are different factors that have an important impact on visual emphasis like size, solidity, foreground/background differences, colour (red attracts the eye more than other colours), change (blinking or moving symbols attract attention), position and so on.
For graph aesthetics there may be different consideration(Battista, 1994, Tamassia, 1988) like angles between edges not be too small, minimize the number of bends along edges, minimize the number of crossings between edges, place nodes with high degree in the centre of the drawing, have symmetry of sons in hierarchies, have uniform density of nodes in the drawing, have verticality of hierarchical structures and so on.
Syntactical quality
Syntactic quality is the correspondence between the model M and the language extension L of the language in which the model is written. Three aspects here are:
Error detection: During a modeling session, some syntactical errors--- syntactic incompleteness --- should be allowed on a temporary basis. For instance, although the DFD language requires that all processes are linked to a flow, it is difficult to draw a process and a flow simultaneously. Syntactical completeness has to be checked upon user's request. So, in contrast to implicit checks where the tool is forcing the user to follow the language syntax, explicit check can only detect and report on existing errors. The user has to make the corrections.
Error correction: to replace a detected error with a correct statement
Semantic quality
What is expressed in the model?
The semantic goals of this framework are:
Validity; if all the statements in the model are correct and related to the problem. M\D = Ø
Completeness; if the model contains all relevant and correct statements to solve this problem. D\M = Ø
Perceived semantic quality
Perceived semantic quality is the relation between an actor's interpretation of a model and his/her knowledge of the domain.
Perceived validity I\K = Ø
Perceived completeness K\I = Ø
Pragmatic quality
Pragmatic quality is the correspondence between the model and people's interpretation of it. Comprehension is the only pragmatic goal in the framework. It is very important that people that read the model, understand it. No solution is good if no-one understands it. Pragmatic quality relates to the effect the model have on the participants and the world. Four aspects is treated specifically, that:
the human interpretation of the model is correct relative to what is meant.
the tool interpretation is correct relative to what is meant to be expressed in the model.
the participants learn based on the model.
the domain is changed (preferably in a positive direction relative to the goal of modeling).
Social quality
The goal for the social quality is agreement. Agreement about knowledge, interpretation and model. Agreement is achieved if perceived semantic quality and comprehension are achieved. There is relative agreement and absolute agreement. For the three agreement parts (knowledge, interpretation and model) we can define:
Relative agreement in the three above agreement types; all Knowledge, Interpretation and Model are consistent.
Absolute agreement in the three above agreement types; all Knowledge, Interpretation and Model are equal.
Knowledge quality
Degree of internalization of existing organizational reality.
Knowledge in domain is "complete": D\K = Ø.
Knowledge in domain is "valid": K\D = Ø.
Activities for improvement:
Stakeholder identification
Knowledge source identification
Research and investigation
Participant selection
Participant training
Problem definition
Language quality
To receive good language quality it is important that:
The language is appropriate to the domain.
The language is appropriate to the participants' knowledge of modeling languages
The language appropriate to express the knowledge of the participants
If the language quality is good, it will improve the participants' interpretation and other technical actors' interpretation.
For additional detail, see the quality of modelling languages
Organizational quality
The organizational quality of the model relates to:
That all statements in the model contribute to fulfilling the goals of modeling, or Organizational goal validity.
That all the goals of modeling are addressed through the model, or Organizational goal completeness.
Alternative quality framework
An alternative quality framework is the Guidelines of Modeling (GoM) based on general accounting principles. The framework "include the six principles of correctness, clarity, relevance, comparability, economic efficiency, and systematic design". It was operationalized for Event-driven Process Chains and also tested in experiments
Another alternative modelling process quality framework actually based on SEQUAL is the "Quality of Modelling" framework (QoMo). QoMo is still a "preliminary modelling process oriented, based on knowledge state transitions, cost of the activities bringing such transitions about, and a goal structure for activities-for-modelling. Such goals are directly linked to concepts of SEQUAL".
References
Further reading
John Krogstie (2012). "Model-Based Development and Evolution of Information Systems: A Quality Approach"
John Krogstie (2001). "A semiotic approach to quality in requirements specifications"
Conceptual modelling
Enterprise modelling | SEQUAL framework | [
"Engineering"
] | 2,042 | [
"Systems engineering",
"Enterprise modelling"
] |
2,986,564 | https://en.wikipedia.org/wiki/Product%20measure | In mathematics, given two measurable spaces and measures on them, one can obtain a product measurable space and a product measure on that space. Conceptually, this is similar to defining the Cartesian product of sets and the product topology of two topological spaces, except that there can be many natural choices for the product measure.
Let and be two measurable spaces, that is, and are sigma algebras on and respectively, and let and be measures on these spaces. Denote by the sigma algebra on the Cartesian product generated by subsets of the form , where and :
This sigma algebra is called the tensor-product σ-algebra on the product space.
A product measure
(also denoted by by many authors)
is defined to be a measure on the measurable space satisfying the property
.
(In multiplying measures, some of which are infinite, we define the product to be zero if any factor is zero.)
In fact, when the spaces are -finite, the product measure is uniquely defined, and for every measurable set E,
where and , which are both measurable sets.
The existence of this measure is guaranteed by the Hahn–Kolmogorov theorem. The uniqueness of product measure is guaranteed only in the case that both and are σ-finite.
The Borel measures on the Euclidean space Rn can be obtained as the product of n copies of Borel measures on the real line R.
Even if the two factors of the product space are complete measure spaces, the product space may not be. Consequently, the completion procedure is needed to extend the Borel measure into the Lebesgue measure, or to extend the product of two Lebesgue measures to give the Lebesgue measure on the product space.
The opposite construction to the formation of the product of two measures is disintegration, which in some sense "splits" a given measure into a family of measures that can be integrated to give the original measure.
Examples
Given two measure spaces, there is always a unique maximal product measure μmax on their product, with the property that if μmax(A) is finite for some measurable set A, then μmax(A) = μ(A) for any product measure μ. In particular its value on any measurable set is at least that of any other product measure. This is the measure produced by the Carathéodory extension theorem.
Sometimes there is also a unique minimal product measure μmin, given by μmin(S) = supA⊂S, μmax(A) finite μmax(A), where A and S are assumed to be measurable.
Here is an example where a product has more than one product measure. Take the product X×Y, where X is the unit interval with Lebesgue measure, and Y is the unit interval with counting measure and all sets are measurable. Then, for the minimal product measure the measure of a set is the sum of the measures of its horizontal sections, while for the maximal product measure a set has measure infinity unless it is contained in the union of a countable number of sets of the form A×B, where either A has Lebesgue measure 0 or B is a single point. (In this case the measure may be finite or infinite.) In particular, the diagonal has measure 0 for the minimal product measure and measure infinity for the maximal product measure.
See also
Fubini's theorem
References
Measures (measure theory)
Integral calculus | Product measure | [
"Physics",
"Mathematics"
] | 702 | [
"Physical quantities",
"Calculus",
"Measures (measure theory)",
"Quantity",
"Size",
"Integral calculus"
] |
2,986,645 | https://en.wikipedia.org/wiki/Non-functional%20requirements%20framework | NFR (Non-Functional Requirements) need a framework for compaction. The analysis begins with softgoals that represent NFR which stakeholders agree upon. Softgoals are goals that are hard to express, but tend to be global qualities of a software system. These could be usability, performance, security and flexibility in a given system. If the team starts collecting them it often finds a great many of them. In order to reduce the number to a manageable quantity, structuring is a valuable approach. There are several frameworks available that are useful as structure.
Structuring Non-functional requirements
The following frameworks are useful to serve as structure for NFRs:
1. Goal Modelling
The finalised softgoals are then usually decomposed and refined to uncover a tree structure of goals and subgoals for e.g. the flexibility softgoal. Once uncovering tree structures, one is bound to find interfering softgoals in different trees, e.g. security goals generally interferes with usability. These softgoal trees now form a softgoal graph structure. The final step in this analysis is to pick some particular leaf softgoals, so that all the root softgoals are satisfied.[1]
2. IVENA - Integrated Approach to Acquisition of NFR
The method has integrated a requirement tree. [2]
3. Context of an Organization
There are several models to describe the context of an organization such as Business Model Canvas, OrgManle [3], or others [4]. Those models are also a good framework to assign NFRs.
Measuring the Non-functional requirements
SNAP is the Software Non-functional Assessment Process. While Function Points measure the functional requirements by sizing the data flow through a software application, IFPUG's SNAP measures the non-functional requirements.
The SNAP model consists of four categories and fourteen sub-categories to measure the non-functional requirements. Non-functional requirement are mapped to the relevant sub-categories. Each sub-category is sized, and the size of a requirement is the sum of the sizes of its sub-categories.
The SNAP sizing process is very similar to the Function Point sizing process. Within the application boundary, non-functional requirements are associated with relevant categories and their sub-categories. Using a standardized set of basic criteria, each of the sub-categories is then sized according to its type and complexity; the size of such a requirement is the sum of the sizes of its sub-categories. These sizes are then totaled to give the measure of non-functional size of the software application.
Beta testing of the model shows that SNAP size has a strong correlation with the work effort required to develop the non-functional portion of the software application.
See also
SNAP Points
References
[1] Mylopoulos, Chung, and Yu: “From Object-oriented to Goal-oriented Requirements Analysis" Communications of the ACM, January 1999
[CACM.f.doc
[2] Götz, Rolf; Scharnweber, Heiko: "IVENA: Integriertes Vorgehen zur Erhebung nichtfunktionaler Anforderungen". https://www.pst.ifi.lmu.de/Lehre/WS0102/architektur/VL1/Ivena.pdf
[3] Teich, Irene: Tutorial PlanMan. Working paper Postbauer-Heng, Germany 2005. Available on Demand.
[4] Teich, Irene: Context of the organization-Models. Working paper Meschede, Germany 2020. Available on Demand.
Systems engineering
Software requirements | Non-functional requirements framework | [
"Engineering"
] | 750 | [
"Software engineering",
"Systems engineering",
"Software requirements"
] |
2,986,886 | https://en.wikipedia.org/wiki/Goal-oriented%20Requirements%20Language | Goal-oriented Requirements Language (GRL), an i*-based modeling language used in systems development, is designed to support goal-oriented modeling and reasoning about requirements especially the non-functional requirements
GRL topics
Concepts
Goal-oriented Requirements Language (GRL) allows to express conflict between goals and helps to make decisions that resolve conflicts. There are three main categories of concepts in GRL:
intentional elements,
intentional relationships and
actors.
They are called for intentional because they are used in models that primarily concerned with answering "why" question of requirements (for ex. why certain choices for behavior or structure were made, what alternatives exist and what is the reason for choosing of certain alternative.)
Intentional elements
Intentional elements are: goal, soft goal, task, belief and resource.
Goal is condition or situation that can be achieved or not. Goal is used to define the functional requirements of the system. In GRL notation goal is represented by a rounded rectangle with the goal name inside.
Task is used to represent different ways of how to accomplish goal. In GRL notation task is represented by hexagon with the task name inside.
Softgoal is used to define non-functional requirements. It’s usually a quality attribute of one of the intentional elements. In GRL notation softgoal is represented by irregular curvilinear shape with the softgoal name inside.
Resource is a physical or informational object that is available for use in the task. Resource is represented in GRL as a rectangle.
Belief is used to represent assumptions and relevant conditions. This construct is represented as ellipse in GRL notation.
Relationships
Intentional relationships are: means-ends, decomposition, contribution, correlation and dependency.
Means-ends relationship shows how the goal can be achieved. For example, it can be used to connect task to a goal.
Decomposition relationship is used to show the sub-components of a task.
Contribution relationship describes how one element influence another one. Often a weighted means-ends relationship for brevity. +ve and -ve contribution allows for defeasible reasoning by way of Defenders and Defeaters.
Correlation relationship describes side effects of existence of one element to others.
Dependency relationship describe interdependences between agents.
Actors
Actor is an active object that carries out actions to achieve the goal. In GRL notation actor is represented as a circle with the actor name inside.
Agent is a concrete actor, such as a human individual or machine.
Role can be taken to be an behavioral aspect assigned to either an Actor or an Agent.
GRL Tool Support
At present, GRL is supported by a general-purpose organization modelling tool - OME (Organization Modeling Environment). OME provides support to various modelling frameworks by loading the framework and its functional modules dynamically.
See also
Extended Enterprise Modeling Language
i*
References
External links
GRL - Goal-oriented Requirement Language University of Toronto, CANADA
Specification languages
Software requirements
de:User Requirements Notation#Goal-oriented Requirements Language (GRL) | Goal-oriented Requirements Language | [
"Engineering"
] | 608 | [
"Software engineering",
"Specification languages",
"Software requirements"
] |
2,986,919 | https://en.wikipedia.org/wiki/Direct-conversion%20receiver | A direct-conversion receiver (DCR), also known as a homodyne, synchrodyne, zero intermediate frequency or zero-IF receiver, is a radio receiver design that demodulates the incoming radio signal using synchronous detection driven by a local oscillator whose frequency is identical to, or very close to the carrier frequency of the intended signal. (This contrasts with the standard superheterodyne receiver, which uses an initial conversion to an intermediate frequency.)
The simplification of performing only a single frequency conversion reduces the basic circuit complexity but other issues arise, for instance, regarding dynamic range. In its original form it was unsuited to receiving AM and FM signals without implementing an elaborate phase locked loop. Although these and other technical challenges made this technique rather impractical around the time of its invention (1930s), current technology, and software radio in particular, have revived its use in certain areas including some consumer products.
Principle of operation
The conversion of the modulated signal to baseband is done in a single frequency conversion. This avoids the complexity of the superheterodyne's two (or more) frequency conversions, IF stage(s), and image rejection issues.
The received radio frequency signal is fed directly into a frequency mixer, just as in a superheterodyne receiver. However unlike the superheterodyne, the frequency of the local oscillator is not offset from, but identical to, the received signal's frequency. The result is a demodulated output just as would be obtained from a superheterodyne receiver using synchronous detection (a product detector) following an intermediate frequency (IF) stage.
Technical issues
To match the performance of the superheterodyne receiver, a number of the functions normally addressed by the IF stage must be accomplished at baseband. Since there is no high gain IF amplifier utilizing automatic gain control (AGC), the baseband output level may vary over a very wide range dependent on the received signal strength. This is one major technical challenge which limited the practicability of the design. Another issue is the inability of this design to implement envelope detection of AM signals. Thus direct demodulation of AM or FM signals (as used in broadcasting) requires phase locking the local oscillator to the carrier frequency, a much more demanding task compared to the more robust envelope detector or ratio detector at the output of an IF stage in a superheterodyne design. However this can be avoided in the case of a direct-conversion design using quadrature detection followed by digital signal processing. Using software radio techniques, the two quadrature outputs can be processed in order to perform any sort of demodulation and filtering on down-converted signals from frequencies close to the local oscillator frequency. The proliferation of digital hardware, along with refinements in the analog components involved in the frequency conversion to baseband, has thus made this simpler topology practical in many applications.
History and applications
The homodyne was developed in 1932 by a team of British scientists searching for a design to surpass the superheterodyne (two stage conversion model). The design was later renamed the "synchrodyne". Not only did it have superior performance due to the single conversion stage, but it also had reduced circuit complexity and power consumption. The design suffered from the thermal drift of the local oscillator which changed its frequency over time. To counteract this drift, the frequency of the local oscillator was compared with the broadcast input signal by a phase detector. This produced a correction voltage which would vary the local oscillator frequency keeping it in lock with the wanted signal. This type of feedback circuit evolved into what is now known as a phase-locked loop. While the method has existed for several decades, it had been difficult to implement due largely to component tolerances, which must be of small variation for this type of circuit to function successfully.
Advantages
Unwanted by-product beat signals from the mixing stage do not need any further processing, as they are completely rejected by use of a low-pass filter at the audio output stage. The receiver design has the additional advantage of high selectivity, and is therefore a precision demodulator. The design principles can be extended to permit separation of adjacent channel broadcast signals whose sidebands may overlap the wanted transmission. The design also improves the detection of pulse-modulated transmission mode signals.
Disadvantages
Signal leakage paths can occur in the receiver. The high audio frequency gain required can result in difficulty in rejecting mains hum. Local-oscillator energy can leak through the mixer stage to the antenna input and then reflect back into the mixer stage. The overall effect is that the local oscillator energy will self-mix and create a DC offset signal. The offset may be large enough to overload the baseband amplifiers and prevent receiving the wanted signal. There are design modifications that deal with this issue, but they add to the complexity of the receiver. The additional design complexity often outweighs the benefits of a direct-conversion receiver.
Modern usage
Wes Hayward and Dick Bingham's 1968 article brought new interest in direct-conversion designs.
The development of the integrated circuit and incorporation of complete phase-locked loop devices in low-cost IC packages made this design widely accepted. Usage is no longer limited to the reception of AM radio signals, but also finds use in processing more complex modulation methods. Direct-conversion receivers are now incorporated into many receiver applications, including cellphones, pagers, televisions, avionics, medical imaging apparatus and software-defined radio systems.
See also
Crystal radio
Harmonic mixer
Heterodyne
Heterodyne detection
Homodyne detection
IQ imbalance, a problem affecting direct-conversion receivers
Low IF receiver
Neutrodyne
Reflectional receiver
Regenerative radio receiver
Tuned radio frequency receiver
References
External links
The History of the Homodyne and Syncrodyne The Journal of the British Institution of Radio Engineers, April 1954
, "Wireless Signaling" (heterodyne principle) – 12 August 1902 - by Reginald Fessenden
Radio electronics
Receiver (radio) | Direct-conversion receiver | [
"Engineering"
] | 1,259 | [
"Radio electronics",
"Receiver (radio)"
] |
2,987,124 | https://en.wikipedia.org/wiki/Salt%20bridge%20%28protein%20and%20supramolecular%29 | In chemistry, a salt bridge is a combination of two non-covalent interactions: hydrogen bonding and ionic bonding (Figure 1). Ion pairing is one of the most important noncovalent forces in chemistry, in biological systems, in different materials and in many applications such as ion pair chromatography. It is a most commonly observed contribution to the stability to the entropically unfavorable folded conformation of proteins. Although non-covalent interactions are known to be relatively weak interactions, small stabilizing interactions can add up to make an important contribution to the overall stability of a conformer. Not only are salt bridges found in proteins, but they can also be found in supramolecular chemistry. The thermodynamics of each are explored through experimental procedures to access the free energy contribution of the salt bridge to the overall free energy of the state.
Salt bridges in chemical bonding
In water, formation of salt bridges or ion pairs is mostly driven by entropy, usually accompanied by unfavorable ΔH contributions on account of desolvation of the interacting ions upon association. Hydrogen bonds contribute to the stability of ion pairs with e.g. protonated ammonium ions, and with anions is formed by deprotonation as in the case of carboxylate, phosphate etc; then the association constants depend on the pH. Entropic driving forces for ion pairing (in absence of significant H-bonding contributions) are also found in methanol as solvent. In nonpolar solvents contact ion pairs with very high association constants are formed; in the gas phase the association energies of e.g. alkali halides reach up to 200 kJ/mol. The Bjerrum or the Fuoss equation describe ion pair association as function of the ion charges zA and zB and the dielectric constant ε of the medium; a corresponding plot of the stability ΔG vs. zAzB shows for over 200 ion pairs the expected linear correlation for a large variety of ions.
Inorganic as well as organic ions display at moderate ionic strength I similar salt bridge association ΔG values around 5 to 6 kJ/mol for a 1:1 combination of anion and cation, almost independent of the nature (size, polarizability etc) of the ions. The ΔG values are additive and approximately a linear function of the charges, the interaction of e.g. a doubly charged phosphate anion with a single charged ammonium cation accounts for about 2x5 = 10 kJ/mol. The ΔG values depend on the ionic strength I of the solution, as described by the Debye–Hückel equation, at zero ionic strength one observes ΔG = 8 kJ/mol. The stabilities of the alkali-ion pairs as function of the anion charge z by can be described by a more detailed equation.
Salt bridges found in proteins
The salt bridge most often arises from the anionic carboxylate (RCOO−) of either aspartic acid or glutamic acid and the cationic ammonium (RNH3+) from lysine or the guanidinium (RNHC(NH2)2+) of arginine (Figure 2). Although these are the most common, other residues with ionizable side chains such as histidine, tyrosine, and serine can also participate, depending on outside factors perturbing their pKa's. The distance between the residues participating in the salt bridge is also cited as being important. The N-O distance required is less than 4 Å (400 pm). Amino acids greater than this distance apart do not qualify as forming a salt bridge. Due to the numerous ionizable side chains of amino acids found throughout a protein, the pH at which a protein is placed is crucial to its stability.
Salt bridges found in protein - ligand complexes
Salt bridges also can form between a protein and small molecule ligands. Over 1100 unique protein-ligand complexes from the Protein Databank were found to form salt bridges with their protein targets, indicating that salt bridges are frequent in drug-protein interaction. These contain structures from different enzyme classes, including hydrolase, transferases, kinases, reductase, oxidoreductase, lyases, and G protein-coupled receptors (GPCRs).
Methods for quantifying salt bridge stability in proteins
The contribution of a salt bridge to the overall stability to the folded state of a protein can be assessed through thermodynamic data gathered from mutagenesis studies and nuclear magnetic resonance techniques. Using a mutated pseudo-wild-type protein specifically mutated to prevent precipitation at high pH, the salt bridge’s contribution to the overall free energy of the folded protein state can be determined by performing a point-mutation, altering and, consequently, breaking the salt bridge. For example, a salt bridge was identified to exist in the T4 lysozyme between aspartic acid (Asp) at residue 70 and a histidine (His) at residue 31 (Figure 3). Site-directed mutagenesis with asparagine (Asn) (Figure 4) was done obtaining three new mutants: Asp70Asn His31 (Mutant 1), Asp70 His31Asn (Mutant 2), and Asp70Asn His31Asn (Double Mutant).
Once the mutants have been established, two methods can be employed to calculate the free energy associated with a salt bridge. One method involves the observation of the melting temperature of the wild-type protein versus that of the three mutants. The denaturation can be monitored through a change in circular dichroism. A reduction in melting temperature indicates a reduction in stability. This is quantified through a method described by Becktel and Schellman where the free energy difference between the two is calculated through ΔTΔS. There are some issues with this calculation and can only be used with very accurate data. In the T4 lysozyme example, ΔS of the pseudo-wild-type had previously been reported at pH 5.5 so the midpoint temperature difference of 11 °C at this pH multiplied by the reported ΔS of 360 cal/(mol·K) (1.5 kJ/(mol·K)) yields a free energy change of about −4 kcal/mol (−17 kJ/mol). This value corresponds to the amount of free energy contributed to the stability of the protein by the salt bridge.
The second method utilizes nuclear magnetic resonance spectroscopy to calculate the free energy of the salt bridge. A titration is performed, while recording the chemical shift corresponding to the protons of the carbon adjacent to the carboxylate or ammonium group. The midpoint of the titration curve corresponds to the pKa, or the pH where the ratio of protonated: deprotonated molecules is 1:1. Continuing with the T4 lysozyme example, a titration curve is obtained through observation of a shift in the C2 proton of histidine 31 (Figure 5). Figure 5 shows the shift in the titration curve between the wild-type and the mutant in which Asp70 is Asn. The salt bridge formed is between the deprotonated Asp70 and protonated His31. This interaction causes the shift seen in His31’s pKa. In the unfolded wild-type protein, where the salt bridge is absent, His31 is reported to have a pKa of 6.8 in H2O buffers of moderate ionic strength. Figure 5 shows a pKa of the wild-type of 9.05. This difference in pKa is supported by the His31’s interaction with Asp70. To maintain the salt bridge, His31 will attempt to keep its proton as long as possible. When the salt bridge is disrupted, like in the mutant D70N, the pKa shifts back to a value of 6.9, much closer to that of His31 in the unfolded state.
The difference in pKa can be quantified to reflect the salt bridge’s contribution to free energy. Using Gibbs free energy:
ΔG = −RT ln(Keq), where R is the universal gas constant, T is the temperature in kelvins, and Keq is the equilibrium constant of a reaction in equilibrium. The deprotonation of His31 is an acid equilibrium reaction with a special Keq known as the acid dissociation constant, Ka: His31-H+ His31 + H+. The pKa is then related to Ka by the following: pKa = −log(Ka). Calculation of the free energy difference of the mutant and wild-type can now be done using the free energy equation, the definition of pKa, the observed pKa values, and the relationship between natural logarithms and logarithms. In the T4 lysozyme example, this approach yielded a calculated contribution of about 3 kcal/mol to the overall free energy. A similar approach can be taken with the other participant in the salt bridge, such as Asp70 in the T4 lysozyme example, by monitoring its shift in pKa after mutation of His31.
A word of caution when choosing the appropriate experiment involves the location of the salt bridge within the protein. The environment plays a large role in the interaction. At high ionic strengths, the salt bridge can be completely masked since an electrostatic interaction is involved. The His31-Asp70 salt bridge in T4 lysozyme was buried within the protein. Entropy plays a larger role in surface salt bridges where residues that normally have the ability to move are constricted by their electrostatic interaction and hydrogen bonding. This has been shown to decrease entropy enough to nearly erase the contribution of the interaction. Surface salt bridges can be studied similarly to that of buried salt bridges, employing double mutant cycles and NMR titrations. Although cases exist where buried salt bridges contribute to stability, like anything else, exceptions do exist and buried salt bridges can display a destabilizing effect. Also, surface salt bridges, under certain conditions, can display a stabilizing effect. The stabilizing or destabilizing effect must be assessed on a case by case basis and few blanket statements are able to be made.
Supramolecular chemistry
Supramolecular chemistry is a field concerned with non-covalent interactions between macromolecules. Salt bridges have been used by chemists within this field in both diverse and creative ways, including sensing of anions, the synthesis of molecular capsules and double helical polymers.
Anion complexation
Major contributions of supramolecular chemistry have been devoted to recognition and sensing of anions. Ion pairing is the most important driving force for anion complexation, but selectivity e.g. within the halide series has been achieved, mostly by hydrogen bonds contributions.
Molecular capsules
Molecular capsules are chemical scaffolds designed to capture and hold a guest molecule (see molecular encapsulation). Szumna and coworkers developed a novel molecular capsule with a chiral interior. This capsule is made of two halves, like a plastic easter egg (Figure 6). Salt bridge interactions between the two halves cause them to self-assemble in solution (Figure 7). They are stable even when heated to 60 °C.
Double helical polymers
Yashima and coworkers have used salt bridges to construct several polymers that adopt a double helix conformation much like DNA. In one example, they incorporated platinum to create a double helical metallopolymer. Starting from their monomer and platinum(II) biphenyl (Figure 8), their metallopolymer self assembles through a series of ligand exchange reactions. The two halves of the monomer are anchored together through the salt bridge between the deprotonated carboxylate and the protonated nitrogens.
References
Chemical bonding
Protein engineering | Salt bridge (protein and supramolecular) | [
"Physics",
"Chemistry",
"Materials_science"
] | 2,493 | [
"Chemical bonding",
"Condensed matter physics",
"nan"
] |
2,987,217 | https://en.wikipedia.org/wiki/Xenoserver | A XenoServer is a server that can safely execute foreign, potentially untrusted code. The XenoServer is developed collaboratively by Telekom Innovation Laboratories and Cambridge University and implemented using the Xen VMM.
The XenoServer platform is a network of XenoServers meant to support distributed code execution services.
The name comes from the Greek word ξένος, which can mean both "foreigner" and "guest", hence the notion of inviting foreign code to run on your server as a guest.
References
External links
Official site
Server hardware | Xenoserver | [
"Technology"
] | 118 | [
"Computing stubs",
"Computer hardware stubs"
] |
2,987,246 | https://en.wikipedia.org/wiki/Yojana | A yojana (Devanagari: योजन; Khmer language: យោជន៍; ; ) is a measure of distance that was used in ancient India, Cambodia, Thailand and Myanmar. Various textual sources from ancient India define Yojana as ranging from 3.5 to 15 km.
Edicts of Ashoka (3rd century BCE)
Ashoka, in his Major Rock Edict No.13, gives a distance of 600 yojanas between the Maurya empire, and "where the Yona king named Antiyoga (is ruling)", identified as King Antiochus II Theos, whose capital was Babylon. A range of estimates, for the length of a yojana, based on the ~2,000 km from Baghdad to Kandahar, on the eastern border of the empire, to the ~4,000 km to the Capital at Patna, have been offered by historians.
Yojana in geodesy
Hindu units of length
Units
In Hindu scriptures, Paramāṇu is the fundamental particle and smallest unit of length.
Variations in length
The length of the yojana varied over time and locale, its length has been estimated as:
- 14th-century mathematician Paramesvara.
- A. C. Bhaktivedanta Swami Prabhupada throughout his translations of the Bhagavata Purana.
to - From The Ancient Geography of India, 1871, Alexander Cunningham, estimated by comparison with Chinese units of length.
- 1997, Thompson, from dividing the earths diameter by the yojana circumferences offered In the Surya Siddhanta and Aryabhatiya (late 4th-century to 5th-century CE)
See also
Hindu cosmology
History of measurement systems in India
Hindu units of time
Palya
Rajju
List of numbers in Hindu scriptures
References
Notes
Sources
Further reading
The Artha Shaastra of Kautilya, Penguin Books
Valmiki Ramayana
Dictionary of Historical and Related Terms
Customary units in India
Hindu astronomy
Obsolete units of measurement
Units of length | Yojana | [
"Mathematics"
] | 408 | [
"Obsolete units of measurement",
"Quantity",
"Units of measurement",
"Units of length"
] |
2,987,342 | https://en.wikipedia.org/wiki/Venti%20%28software%29 | Venti is a network storage system that permanently stores data blocks. A 160-bit SHA-1 hash of the data (called score by Venti) acts as the address of the data. This enforces a write-once policy since no other data block can be found with the same address: the addresses of multiple writes of the same data are identical, so it is highly likely that duplicate data is easily identified and the data block is stored only once. Data blocks cannot be removed, making it ideal for permanent or backup storage. Venti is typically used with Fossil to provide a file system with permanent snapshots.
History
Venti was designed and implemented by Sean Quinlan and Sean Dorward at Bell Labs. It appeared in the Plan 9 distribution in 2002. Development has been continued by Russ Cox who has reimplemented most of the server, written a library for creating datastructures (files, directories and meta-data) to store in Venti and implemented optimizations. Venti is available both in the Plan 9 distribution and for many Unix-like operating systems as part of Plan 9 from User Space. Venti is included as part of Inferno with accompanying modules for access.
There is a Go set of programs to build your own Venti servers. Included are examples using different kinds of backend storage.
Details
Venti is a user space daemon. Clients connect to Venti over TCP and communicate using a simple RPC-protocol. The most important messages of the protocol are listed below. Note that there is no message to delete an address or modify data at a given address.
read(score, type), returns the data identified by score and type
write(data, type), stores data at the address calculated by SHA-1 hashing data, combined with type.
The data block stored by Venti must be greater than 512 bytes in length and smaller than 56 kilobytes. So, if a Venti user/client wants to store larger data blocks, it has to make a datastructure (which can be stored in Venti). For example, Fossil uses hash trees to store large files. Venti itself is not concerned with the contents of a data block; it does however store the type of a data block.
The design of Venti has the following consequences:
Since writes are permanent, the file system is append-only (which allows for a simple implementation with lower chance of data-destroying bugs); no file system fragmentation occurs.
Clients can verify the correctness of the server: the score of the returned data should be the same as the address requested. Since SHA-1 is a cryptographically secure hash, it is computationally infeasible to fabricate data.
Data cannot be overwritten. If an address is already present, the data is already present.
There is little need for user authentication: Data cannot be deleted, and can be read only if the score is known. The only potential problem is a user filling up the disks.
Data can be compressed without making the disk structure complicated.
The data blocks are stored on hard drives. The disks making up the available storage, typically a RAID, is called the data log. This data log is split up in smaller pieces called arenas, which are sized so they can be written to other media such as CD/DVD or magnetic tape. Another set of hard drives is used for the index, which maps scores to addresses in the data log. The data structure used for the index is a hash table with fixed-sized buckets. Venti relies on the scores to be randomly distributed so buckets do not fill up. Since each lookup costs one disk seek time, an index usually consists of multiple hard drives with low access time.
Usage
The Venti server may be used by clients in several ways. The Plan 9 operating system makes use of Venti for daily archival snapshots of the file system. These copies of the main filesystem can be mounted as a filetree of full copies organized by date. The utility programs 'vac' and 'unvac' can be used to store and retrieve data from a Venti server in the form of individual files or as a directory and its contents. 'Vacfs' allows browsing of the data associated with a vac score without full retrieval of all remotely stored data. Data and index scores can be duplicated between Venti servers using 'rdarena' and 'wrarena'. Plan 9 from Bell Labs, Plan 9 from User Space, Inferno and any other clients that implement the Venti protocol can all be used interchangeably to store and retrieve data.
Hash collisions
A basic principle of information theory is the pigeonhole principle, which states that if set A contains more values than set B, then for any function that maps A to B there will be members of B that are associated with more than one member of set A. In the case of Venti, the set of possible SHA-1 hashes is obviously smaller than the set of all possible blocks that could be stored in the filesystem, and thus a hash collision is possible.
The risk of accidental hash collision in a 160-bit hash is very small, even for exabytes of data. Historically, however, many hash functions become increasingly vulnerable to malicious hash collisions due to both cryptographic and computational advances.
Venti does not address the issue of hash collisions; as of this time, it is still computationally infeasible to find collisions in SHA-1, but it may become necessary for Venti to switch to a different hash function at some point in the future. On 23 February 2017, Google announced the SHAttered attack, in which they generated two different PDF files with the same SHA-1 hash in roughly 263.1 SHA-1 evaluations.
See also
Fossil - snapshot file system that uses Venti for permanent storage
Plan 9 from User Space
References
External links
Venti: a new approach to archival storage, paper describing Venti.
New Venti manual page (overview), section 7 venti manual page including general description and storage format.
New Venti manual page (server), section 8 venti server manual page.
New Venti manual page (tools), section 1 venti utilities manual page.
Go code for implementing clients and servers.
Venti module in Limbo for Inferno, kindly brought to life thanks to the Google Summer of Code.
2002 software
Plan 9 from Bell Labs | Venti (software) | [
"Technology"
] | 1,314 | [
"Plan 9 from Bell Labs",
"Computing platforms"
] |
2,987,351 | https://en.wikipedia.org/wiki/Felypressin | Felypressin is a non-catecholamine vasoconstrictor that is chemically related to vasopressin, the posterior pituitary hormone. It is added to some local anaesthetics such as prilocaine in a concentration of 0.03 IU/ml. Felypressin is a Vasopressin 1 agonist, and will thus have effects at all Arginine vasopressin receptor 1As. It will, however, have its main physiological effects on vascular SMC's due to the form in which it is administered.
V1 receptors are found in various sites around the body. The major points include the CNS, Liver, Anterior Pituitary, Muscle (both vascular and non-vascular smooth muscle), and Platelets (CLAMP).
Another example of a V1 agonist is terlipressin - which is used in oesophageal varices.
References
"Vasopressin analogues and treatments", Prof Buckingham, Imperial College School of Medicine (ICSM) - adapted by JHPatel
Vasoconstrictors
Peptides
Vasopressin receptor agonists | Felypressin | [
"Chemistry"
] | 245 | [
"Biomolecules by chemical classification",
"Peptides",
"Molecular biology"
] |
2,987,369 | https://en.wikipedia.org/wiki/Breech-lock | A breech-lock is a system for mounting camera lenses to camera bodies. The lens is attached to the camera by means of a rotating ring which is used to tighten the lens to the camera by friction.
Other methods for mounting a lens to a camera include bayonet mount or thread mounts. With breech-lock, the body of the lens does not rotate relative to the camera body, whereas with bayonet or screw mounts, the lens is rotated into place.
Breech-lock comes from the mechanisms that lock closed the breech of breech-loading firearms and artillery.
See also
Lens mount: for a list of camera lens mount systems, including several of the breech-lock type
References
Fasteners | Breech-lock | [
"Engineering"
] | 148 | [
"Construction",
"Fasteners"
] |
2,987,454 | https://en.wikipedia.org/wiki/Trachelium%20%28architecture%29 | Trachelium (from the for "neck") is the term in architecture given to the neck of the capital of the Doric and Ionic orders. In the Greek Doric capital it is the space between the annulets of the echinus and the grooves, which marked the junction of the shaft and capital.
In some early examples, as in the basilica and temple of Ceres at Paestum and the temple at Metapontum, it forms a sunk concave moulding, which by the French is called the gorge. In the Roman Doric and the Ionic orders the term is given by modern writers to the interval between the lowest moulding of the capital and the top of the astragal and annulet, which were termed the hypotrachelium.
References
Columns and entablature | Trachelium (architecture) | [
"Technology"
] | 171 | [
"Structural system",
"Columns and entablature"
] |
2,987,487 | https://en.wikipedia.org/wiki/Critical%20design | Critical design uses design fiction and speculative design proposals to challenge assumptions and conceptions about the role objects play in everyday life. Critical design plays a similar role to product design, but does not emphasize an object's commercial purpose or physical utility. It is mainly used to share a critical perspective or inspire debate, while increasing awareness of social, cultural, or ethical issues in the eyes of the public. Critical design was popularized by Anthony Dunne and Fiona Raby through their firm, Dunne & Raby.
Critical design can make aspects of the future physically present to provoke a reaction. "Critical design is critical thought translated into materiality. It is about thinking through design rather than through words and using the language and structure of design to engage people."
It may be conflated with the critical theory or the Frankfurt School, but it is not related.
Definition
A critical design object challenges an audience's preconceptions, provoking new ways of thinking about the object, its use, and the surrounding culture. Its adverse is affirmative design: design that reinforces the status quo. For a project to succeed in critical design, the viewer must be mentally engaged and willing to think beyond the expected and ordinary. Humor is important, but satire is not the goal.
Many practitioners of critical design have never heard of the term itself, and/or would describe their work differently. Referring to it as critical design simply garners more attention to it, and emphasizes that design has applications beyond problem solving.
It is more of an attitude than a style or movement; a position rather than a method. Critical design builds on this attitude by creatively critiquing concepts and ideologies using fabricated artifacts to embody commentaries around everything from consumer culture to the #MeToo Movement. Regardless of its processes, critical design is often discussed as a unique approach in Design Research, perhaps because of its focus on critiquing widely held social, cultural, and technical beliefs. The process of designing such an object, as well as the presentation and narrative around the object itself, allows for reflection on existing cultural values, morals, and practices. In making such an object, critical designers frequently employ classic design processes—research, user experience, iteration—while working to conceptualize scenarios intended to highlight social, cultural, or political paradigms. Design as societal critique is not a new idea.
History
Italian Radical Design of the 1960s and 70s was highly critical of prevailing social values and design ideologies.
The term "critical design" was first used in Anthony Dunne's book Hertzian Tales (1999) and further developed in Design Noir: The Secret Life of Electronic Objects (2001).
According to Sanders, critical design probes an "ambiguous stimuli that
designers send to people who then respond to them, providing insights for the design process." Uta Brandes identifies critical design as a discrete Design Research method and Bowen integrates it into human-centered design activities as a useful tool for stakeholders to critically think about possible futures.
FABRICA, a communication research center owned by Italian fashion giant Benetton Group, has been actively involved in producing provocative imagery and critical design projects. FABRICA's Visual Communication department, led by Omar Vulpinari, actively participates in critiquing social, political and environmental issues through global awareness campaigns for international magazines and organizations like UN-WHO. Several young artists who have produced critical design projects at FABRICA in recent years are Erik Ravello (Cuba), Yianni Hill (Australia), Marian Grabmayer (Austria), Priya Khatri (India), Andy Rementer (United States), and An Namyoung (South Korea).
Function
To attribute to design practice, critical design broadens the vision in design from traditional practice. It is no longer limited to highlighting the physical function in product design, though this causes some ambiguities in the discussion of critical design's function as it maintains in design area. Matt Malpass addresses Larry Ligo's classification of five different types of function: Structural articulation, Physical function, Psychological function, Social function, as well as Cultural-existential function in his article, with a further discussion of how Modernism leaves a narrower understanding of physical utility when we think about function, which leads to the ambiguity in critical design's function. As critical design focuses on present social, cultural, and ethical implications of design objects and practice, it mostly emphasizes on social and cultural impact from its function.
In addition, critical design objects have a lot of potential to contribute to testing ideas during the process of the development of new technology. As Dunne and Raby express their concerns about always lacking communication between the specialists and the general public to form a two-way discussion of new technology. It always limits to one-way flow from specialists to the public. Critical design provides a stage to give scenarios, completes the dialog between specialists and the general public and helps to collect feedback from the public for further refinements before the idea is going too far for any changes.
Critical play
Researcher Mary Flanagan wrote Critical Play:Radical Game Design in 2009, the same year that Lindsay Grace started the Critical Gameplay project. Grace's Critical Gameplay project is an internationally exhibited collection of video games that apply critical design. The games provoke questions about the way games are designed and played. The Critical Gameplay Game, Wait, was awarded the Games for Change hall of fame award for being one of the 5 most important games for social impact since 2003. The work has been shown at Electronic Language International Festival, Games, Learning & Society Conference, Conference on Human Factors in Computing Systems among other notable events.
Critiques
As critical design has gained mainstream exposure, the discipline has been itself criticized by some for dramatizing so-called 'dystopian scenarios,' which may, in fact, be reflective of real-life conditions in some places in the world. Some see critical design as rooted in the fears of a wealthy, urban, western population and failing to engage with existing social problems. As an example, a project titled Republic of Salivation, by designers Michael Burton and Michiko Nitta, featured as part of MoMA's Design and Violence series, portrays a society plagued by overpopulation and food scarcity which is reliant on heavily modified, government-provided, nutrient blocks. Certain media responses to the work, point to the "presumed naivety of the project," which presents a scenario that "might be dystopian to some, but in some other parts of the world it has been the reality for decades."
Critical acclaim
In recognition of their formalization of the field, Anthony Dunne and Fiona Raby were presented with the inaugural MIT Media Lab Award in June 2015 with director Joichi Ito pointing out that "[Dunne and Raby's] pioneering approach to critical design and its intersection with science, technology, art, and the humanities has changed the landscape of design education and practice worldwide."
Distinctions with Conceptual art
Conceptual art practice has a very similar role as critical design since both of them are sharing critical perspectives to the public and being commentators to issues, the public may get confused to understand these two different fields. However, Matt Malpass points out that the critical designer still applies the skills from the training and practice as designer but re-orientates these skills from a focus on practical ends to a focus on design work that functions symbolically, culturally, existentially, and discursively. Critical design objects are made precisely based on the design principles and carefully follow the design and design research process. Also, critical design objects always stay close to people's everyday life. They tend to be tested on real people and get feedback for further developments. Conceptual art usually associates with gallery spaces and mostly tends to apply the artistic media in the process.
See also
Social fiction
Design fiction
Critical making
Critical technical practice
Science fiction prototyping
Speculative design
Talk to Me (exhibition) (MoMA), 2011
References
Critical theory | Critical design | [
"Technology",
"Engineering"
] | 1,615 | [
"Critical design",
"Design"
] |
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