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Molecular-weight size marker A molecular-weight size marker, also referred to as a protein ladder, DNA ladder, or RNA ladder, is a set of standards that are used to identify the approximate size of a molecule run on a gel during electrophoresis, using the principle that molecular weight is inversely proportional to migration rate through a gel matrix. Therefore, when used in gel electrophoresis, markers effectively provide a logarithmic scale by which to estimate the size of the other fragments (providing the fragment sizes of the marker are known). Protein, DNA, and RNA markers with pre-determined fragment sizes and concentrations are commercially available. These can be run in either agarose or polyacrylamide gels. The markers are loaded in lanes adjacent to sample lanes before the commencement of the run. Although the concept of molecular-weight markers has been retained, techniques of development have varied throughout the years. New inventions of molecular-weight markers are distributed in kits specific to the marker's type. An early problem in the development of markers was achieving high resolution throughout the entire length of the marker. Depending on the running conditions of gel electrophoresis, fragments may have been compressed, disrupting clarity. To address this issue, a kit for Southern Blot analysis was developed in 1990, providing the first marker to combine target DNA and probe DNA | https://en.wikipedia.org/wiki?curid=6563587 |
Molecular-weight size marker This technique took advantage of logarithmic spacing, and could be used to identify target bands ranging over a length of 20,000 nucleotides. There are two common methods in which to construct a DNA molecular-weight size marker. One such method employs the technique of partial ligation. DNA ligation is the process by which linear DNA pieces are connected to each other via covalent bonds; more specifically, these bonds are phosphodiester bonds. Here, a 100bp duplex DNA piece is partially ligated. The consequence of this is that dimers of 200bp, trimers of 300bp, tetramers of 400bp, pentamers of 500bp, etc. will form. Additionally, a portion of the 100bp dsDNA will remain. As a result, a DNA "ladder" composed of DNA pieces of known molecular mass is created on the gel. The second method employs the use of restriction enzymes and a recognized DNA sequence. The DNA is digested by a particular restriction enzyme, resulting in DNA pieces of varying molecular masses. One of the advantages of this method is that more marker can readily be created simply by digesting more of the known DNA. On the other hand, the size of the DNA pieces are based on the sites where the restriction enzyme cuts. This makes it more difficult to control the size of the fragments in the marker. More recently, another method for constructing DNA molecular-weight size markers is being employed by laboratories. This strategy involves the use of Polymerase Chain Reaction (PCR) | https://en.wikipedia.org/wiki?curid=6563587 |
Molecular-weight size marker This is achieved one or two ways: 1) a DNA target is amplified at the same time via primer sets, or 2) different DNA targets are amplified independently via particular primers. As with experimental samples, the conditions of the gel can affect the molecular-weight size marker that runs alongside them. Factors such as buffer, charge/voltage, and concentration of gel can affect the mobility and/or appearance of your marker/ladder/standard. These elements need to be taken into consideration when selecting a marker and when analyzing the final results on a gel. Previously, protein markers had been developed using a variety of whole proteins. The development of a kit including a molecular-weight size marker based on protein fragments began in 1993. This protein marker, composed of 49 different amino acid sequences, included multidomain proteins, and allowed for the analysis of proteins cleaved at different sites. Current technique improvements in protein markers involve the use of auto-development. The first auto-developed regularly-weight protein marker was invented in 2012. Similar to DNA markers, these markers are typically composed of purified proteins whose molecular masses are already known. The list below outlines some of the proteins, as well as the molecular mass, that are commonly used when constructing a protein marker. Molecular-weight size markers can be broken up into two categories: molecular weight markers vs. molecular ladder markers | https://en.wikipedia.org/wiki?curid=6563587 |
Molecular-weight size marker Markers are either stained or unstained, and depending on the circumstance, one may be more appropriate than another. Molecular-weight size markers can also be biochemically altered. The conjugation with biotin is the most common. Molecular-weight size markers are most commonly used in SDS-polyacrylamide gel electrophoresis and western blotting. With all the different types and uses of molecular-weight size markers, it is important to choose the appropriate protein standard. Besides the most common use, as a way to calculate the molecular weight of the samples, other uses include allowing visual evidence of protein migration and transfer efficiency and are sometimes even used for positive control. As with DNA electrophoresis, conditions such as buffers, charge/voltage, and concentration should be taken into account when selecting a protein marker. RNA ladders composed of RNA molecular-weight size markers were initially developed by using the synthetic circle method to produce different-sized markers. This technique was improved upon by inventor Eric T. Kool to use circular DNA vectors as a method for producing RNA molecular-weight size markers. As referred to as the rolling circle method, the improvements of this technique stems from its efficiency in synthesizing RNA oligonucleotides. From the circular DNA template, single-stranded RNA varying in length from 4-1500 bp can be produced without the need for primers and by recycling nucleotide triphosphate | https://en.wikipedia.org/wiki?curid=6563587 |
Molecular-weight size marker DNA can also be synthesized from the circular template, adding to this technique's versatility. In comparison to runoff transcription, the synthetic circle method produces RNA oligonucleotides without the runoff. In comparison to PCR, the synthetic circle method produces RNA oligonucleotides without the need for polymerase nor a thermal cycler. This method is also cost-efficient in its ability to synthesize grand amounts of product at a lower error rate than machine synthesizers. The RNA markers consist of RNA transcripts of various incrementing lengths. For example, the Lonza 0.5-9 kbp marker has bands marking 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, and 9 kilobase pairs. Markers are dissolved in a storage buffer, such as EDTA, and can have a shelf life of up to 2 years when stored at -80 °C. To use the marker, such as for northern blot analysis, it is first thawed, and then stained so that it is detectable on a gel electrophoresis. One of the most common dyes used for markers is ethidium bromide. The range of a particular marker refers to variety of bands it can map. A "high" range refers to relatively large fragments (measured in kb) while a "low" range refers to markers that distinguish between small fragments (measured in bp). Some markers can even be described as "ultra-low range", but even more precise is the microRNA marker. A microRNA marker can be used to measure RNA fragments within a dozen nucleotides, such as the 17-25 nt microRNA marker. At equivalent molecular weights, RNA will migrate faster than DNA | https://en.wikipedia.org/wiki?curid=6563587 |
Molecular-weight size marker However, both RNA and DNA have a negative linear slope between their migration distance and logarithmic molecular weight. That is, samples of less weight are able to migrate a greater distance. This relationship is a consideration when choosing RNA or DNA markers as a standard. When running RNA markers and RNA samples on a gel, it is important to prevent nuclease contamination, as RNA is very sensitive to ribonuclease (RNase) degradation through catalysis. Thus, all materials to be used in the procedure must be taken into consideration. Any glassware that is to come into contact with RNA should be pretreated with diethylpyrocarbonate (DEPC) and plastic materials should be disposable. One of the most common uses for molecular-weight size markers is in gel electrophoresis. The purpose of gel electrophoresis is to separate proteins by physical or chemical properties, which include charge, molecular size, and pH.< When separating based on size, the ideal method is SDS-PAGE or polyacrylamide gel electrophoresis and molecular-weight size markers are the appropriate standards to use. Gels can vary in size. The number of samples to be run will determine the appropriate gel size. All gels are divided into lanes that run parallel through the gel. Each lane will contain a specific sample. Typically, molecular-weight size standards are placed in an outer lane. If a gel has a particularly high number of lanes, then multiple ladders may be placed across the gel for higher clarity | https://en.wikipedia.org/wiki?curid=6563587 |
Molecular-weight size marker Proteins and standards are pipetted on the gel in appropriate lanes. Sodium dodecyl sulfate (SDS) interacts with proteins, denaturing them, and giving them a negative charge. Since all proteins have the same charge-to-mass ratio, protein mobility through the gel will solely be based on molecular weight. Once the electric field is turned on, protein migration will initiate. Upon completion, a detection mechanism such as western blotting can be used, which will reveal the presence of bands. Each band represents a specific protein. The distance of travel is solely based on molecular weight; therefore, the molecular weight of each protein can be determined by comparing the distance of an unknown protein to the standard of known molecular weight. Many kinds of molecular-weight size markers exist, and each possess unique characteristics, lending to their involvement in a number of biological techniques. Selection of a molecular-weight size marker depends upon the marker type (DNA, RNA, or protein) and the length range it offers (e.g. 1kb). Before selecting a molecular-weight size marker, it is important to become familiar with these characteristics and properties. In a particular instance one type may be more appropriate than another. Although specific markers can vary between protocols for a given technique, this section will outline general markers and their roles. The first type of molecular marker developed and run on gel electrophoresis were allozymes | https://en.wikipedia.org/wiki?curid=6563587 |
Molecular-weight size marker These markers are used for the detection of protein variation. The word "allozyme" (also known as "alloenzyme") comes from "allelic variants of enzymes." When run on a gel, proteins are separated by size and charge. Although allozymes may seem dated when compared to the other markers available, they are still used today, mainly due to their low cost. One major downside is that since there is only a limited amount available, specificity an issue. Although allozymes can detect variations in DNA, it is by an indirect method and not very accurate. DNA-based markers were developed in the 1960s. These markers are much more effective at distinguishing between DNA variants. Today these are the most commonly used markers. DNA-based markers work by surveying nucleotides, which can serve a variety of functions, such as detecting differences in nucleotides or even quantifying the number of mutations. The success of DNA based markers lead to the development of PCR. PCR (polymerase chain reaction) is a DNA amplification technique that can be applied to various types of fragments. Prior to this development, to amplify DNA, it had to be cloned or isolated. Shortly after the discovery of PCR came the idea of using PCR-based markers for gel electrophoresis. These type of markers are based on PCR primers and are categorized as DNA sequence polymorphism. Although technically speaking, DNA sequence polymorphism has been going on since the use of RFLP in the 1960s, the analysis has changed significantly over the years | https://en.wikipedia.org/wiki?curid=6563587 |
Molecular-weight size marker DNA sequence polymorphism uses older techniques like RFLP, but on a larger scale. Sequencing is much faster and more efficient. The analysis is automated, as it uses a technique known as shotgun sequencing. This high-throughput method is commonly used in population genetics. Carbohydrate markers are employed in a technique known as polysaccharide analysis by carbohydrate gel electrophoresis (PACE), which is a measurable separation technique. It allows for the analysis of enzyme hydrolysis products. It has been used in applications such as characterizing enzymes involved in hemicellulose degradation, determining the structure of hemicellulose polysaccharides, and analysis of enzymatic cleavage of cellulose products. PACE depends on derivitization, which is the conversion of a chemical compound into a derivative. Here monosaccharides, oligosaccharides, and polysaccharides are the compounds of interest. They are labeled at their reducing ends with a fluorescent label (i.e. a fluorophore). This derivitization with a fluorophore permits both separation on a gel under the desired circumstances and fluorescence imaging of the gel. In this case, a polyacrylamide gel is used. As with DNA, RNA, and protein electrophoresis, markers are run alongside the samples of interest in carbohydrate gel electrophoresis. The markers consist of oligosaccharides of known molecular weight | https://en.wikipedia.org/wiki?curid=6563587 |
Molecular-weight size marker Like the samples of interest, the marker is also derivitized with a fluorophore (usually with 8-aminonapthalene-1,3,6-trisulfonic acid (ANTS) or 2-aminoacridone). | https://en.wikipedia.org/wiki?curid=6563587 |
Maximum density The maximum density of a substance is the highest attainable density of the substance under given conditions. Almost all known substances undergo thermal expansion in response to heating, meaning that a given mass of substance contracts to a low volume at low temperatures, when little thermal energy is present. Substances, especially fluids in which intermolecular forces are weak, also undergo compression upon the application of pressure. Nearly all substances therefore reach a density maximum at very low temperatures and very high pressures, characteristic properties of the solid state of matter. An especially notable irregular maximum density is that of water, which reaches a density peak at . This has important ramifications in Earth's ecosystem. | https://en.wikipedia.org/wiki?curid=6565890 |
Amsterdam Diamond The is a black diamond weighing , and has 145 facets. It is in a pear shape, and cut from a rough. It was sold in 2001 for $US352,000, the highest price paid for a black diamond at auction. The diamond originated in Africa. | https://en.wikipedia.org/wiki?curid=6574118 |
Chang–Refsdal lens A is a point-mass gravitational lens (e.g. Black hole) perturbed by constant external shear. The name derives from Kyongae Chang and Sjur Refsdal who in 1979 published a paper in NATURE 282, 561. "Flux Variations of QSO Q0957+561 A,B and image splitting by stars Near the Light Path." The paper illustrated that stars could affect quasar image brightness. | https://en.wikipedia.org/wiki?curid=6574860 |
Gene delivery is the process of introducing foreign genetic material, such as DNA or RNA, into host cells. Genetic material must reach the nucleus of the host cell to induce gene expression. Successful gene delivery requires the foreign genetic material to remain stable within the host cell and can either integrate into the genome or replicate independently of it. This requires foreign DNA to be synthesized as part of a vector, which is designed to enter the desired host cell and deliver the transgene to that cell's genome. Vectors utilized as the method for gene delivery can be divided into two categories, recombinant viruses and synthetic vectors (viral and non-viral). In complex multicellular eukaryotes (more specifically Weissmanists), if the transgene is incorporated into the host's germline cells, the resulting host cell can pass the transgene to its progeny. If the transgene is incorporated into somatic cells, the transgene will stay with the somatic cell line, and thus its host organism. is a necessary step in gene therapy for the introduction or silencing of a gene to promote a therapeutic outcome in patients and also has applications in the genetic modification of crops. There are many different methods of gene delivery for various types of cells and tissues. Viral based vectors emerged in the 1980s as a tool for transgene expression. In 1983, Siegel described the use of viral vectors in plant transgene expression although viral manipulation via cDNA cloning was not yet available | https://en.wikipedia.org/wiki?curid=6599910 |
Gene delivery The first virus to be used as a vaccine vector was the vaccinia virus in 1984 as a way to protect chimpanzees against hepatitis B. Non-viral gene delivery was first reported on in 1943 by Avery et al. who showed cellular phenotype change via exogenous DNA exposure. There are a variety of methods available to deliver genes to host cells. When genes are delivered to bacteria or plants the process is called transformation and when it is used to deliver genes to animals it is called transfection. This is because transformation has a different meaning in relation to animals, indicating progression to a cancerous state. For some bacteria no external methods are need to introduce genes as they are naturally able to take up foreign DNA. Most cells require some sort of intervention to make the cell membrane permeable to DNA and allow the DNA to be stably inserted into the hosts genome. Chemical based methods of gene delivery can use natural or synthetic compounds to form particles that facilitate the transfer of genes into cells. These synthetic vectors have the ability to electrostatically bind DNA or RNA and compact the genetic information to accommodate larger genetic transfers. Chemical vectors usually enter cells by endocytosis and can protect genetic material from degradation. One of the simplest method involves altering the environment of the cell and then stressing it by giving it a heat shock | https://en.wikipedia.org/wiki?curid=6599910 |
Gene delivery Typically the cells are incubated in a solution containing divalent cations (often calcium chloride) under cold conditions, before being exposed to a heat pulse. Calcium chloride partially disrupts the cell membrane, which allows the recombinant DNA to enter the host cell. It is suggested that exposing the cells to divalent cations in cold condition may change or weaken the cell surface structure, making it more permeable to DNA. The heat-pulse is thought to create a thermal imbalance across the cell membrane, which forces the DNA to enter the cells through either cell pores or the damaged cell wall. Another simple methods involves using calcium phosphate to bind the DNA and then exposing it to cultured cells. The solution, along with the DNA, is encaspulated by the cells and a small amount of DNA can be integrated into the genome. Liposomes and polymers can be used as vectors to deliver DNA into cells. Positively charged liposomes bind with the negatively charged DNA, while polymers can be designed that interact with DNA. They form lipoplexes and polyplexes respectively, which are then up-taken by the cells. The two systems can also be combined. Polymer-based non-viral vectors uses polymers to interact with DNA and form polyplexes. The use of engineered inorganic and organic nanoparticles is another non-viral approach for gene delivery. Artificial gene delivery can be mediated by physical methods which uses force to introduce genetic material through the cell membrane | https://en.wikipedia.org/wiki?curid=6599910 |
Gene delivery Electroporation is a method of promoting competence. Cells are briefly shocked with an electric field of 10-20 kV/cm, which is thought to create holes in the cell membrane through which the plasmid DNA may enter. After the electric shock, the holes are rapidly closed by the cell's membrane-repair mechanisms. Another method used to transform plant cells is biolistics, where particles of gold or tungsten are coated with DNA and then shot into young plant cells or plant embryos. Some genetic material enters the cells and transforms them. This method can be used on plants that are not susceptible to "Agrobacterium" infection and also allows transformation of plant plastids. Plants cells can also be transformed using electroporation, which uses an electric shock to make the cell membrane permeable to plasmid DNA. Due to the damage caused to the cells and DNA the transformation efficiency of biolistics and electroporation is lower than agrobacterial transformation. Microinjection is where DNA is injected through the cell's nuclear envelope directly into the nucleus. Sonoporation uses sound waves create pores in a cell membrane to allow entry of genetic material. Photoporation is when laser pulses are used to create pores in a cell membrane to allow entry of genetic material. Magnetofection uses magnetic particles complexed with DNA and an external magnetic field concentrate nucleic acid particles into target cells. A hydrodynamic capillary effect can be used to manipulate cell permeability | https://en.wikipedia.org/wiki?curid=6599910 |
Gene delivery In plants the DNA is often inserted using "Agrobacterium"-mediated recombination, taking advantage of the "Agrobacterium"s T-DNA sequence that allows natural insertion of genetic material into plant cells. Plant tissue are cut into small pieces and soaked in a fluid containing suspended "Agrobacterium". The bacteria will attach to many of the plant cells exposed by the cuts. The bacteria uses conjugation to transfer a DNA segment called T-DNA from its plasmid into the plant. The transferred DNA is piloted to the plant cell nucleus and integrated into the host plants genomic DNA.The plasmid T-DNA is integrated semi-randomly into the genome of the host cell. By modifying the plasmid to express the gene of interest, researchers can insert their chosen gene stably into the plants genome. The only essential parts of the T-DNA are its two small (25 base pair) border repeats, at least one of which is needed for plant transformation. The genes to be introduced into the plant are cloned into a plant transformation vector that contains the T-DNA region of the plasmid. An alternative method is agroinfiltration. Virus mediated gene delivery utilizes the ability of a virus to inject its DNA inside a host cell and takes advantage of the virus' own ability to replicate and implement their own genetic material. Viral methods of gene delivery are more likely to induce an immune response, but they have high efficiency. Transduction is the process that describes virus-mediated insertion of DNA into the host cell | https://en.wikipedia.org/wiki?curid=6599910 |
Gene delivery Viruses are a particularly effective form of gene delivery because the structure of the virus prevents degradation via lysosomes of the DNA it is delivering to the nucleus of the host cell. In gene therapy a gene that is intended for delivery is packaged into a replication-deficient viral particle to form a viral vector. Viruses used for gene therapy to date include retrovirus, adenovirus, adeno-associated virus and herpes simplex virus. However, there are drawbacks to using viruses to deliver genes into cells. Viruses can only deliver very small pieces of DNA into the cells, it is labor-intensive and there are risks of random insertion sites, cytophathic effects and mutagenesis. Viral vector based gene delivery uses a viral vector to deliver genetic material to the host cell. This is done by using a virus that contains the desired gene and removing the part of the viruses genome that is infectious. Viruses are efficient at delivering genetic material to the host cell's nucleus, which is vital for replication. RNA-based viruses were developed because of the ability to transcribe directly from infectious RNA transcripts. RNA vectors are quickly expressed and expressed in the targeted form since no processing is required. Gene integration leads to long-term transgene expression but RNA-based delivery is usually transient and not permanent. Retroviral vectors include oncoretroviral, lentiviral and human foamy virus | https://en.wikipedia.org/wiki?curid=6599910 |
Gene delivery DNA-based viral vectors are usually longer lasting with the possibility of integrating into the genome. DNA-based viral vectors include Adenoviridae, adeno-associated virus and herpes simplex virus. Several of the methods used to facilitate gene delivery have applications for therapeutic purposes. Gene therapy utilizes gene delivery to deliver genetic material with the goal of treating a disease or condition in the cell. in therapeutic settings utilizes non-immunogenic vectors capable of cell specificity that can deliver an adequate amount of transgene expression to cause the desired effect. Advances in genomics have enabled a variety of new methods and gene targets to be identified for possible applications. DNA microarrays used in a variety of next-gen sequencing can identify thousands of genes simultaneously, with analytical software looking at gene expression patterns, and orthologous genes in model species to identify function. This has allowed a variety of possible vectors to be identified for use in gene therapy. As a method for creating a new class of vaccine, gene delivery has been utilized to generate a hybrid biosynthetic vector to deliver a possible vaccine. This vector overcomes traditional barriers to gene delivery by combining "E. coli" with a synthetic polymer to create a vector that maintains plasmid DNA while having an increased ability to avoid degradation by target cell lysosomes. | https://en.wikipedia.org/wiki?curid=6599910 |
Nikolay Zinin Nikolay Nikolaevich Zinin () (25 August 1812 in Shusha – 18 February 1880 in Saint Petersburg) was a Russian organic chemist. He studied at the University of Kazan where he graduated in mathematics but he started teaching chemistry in 1835. To improve his skills he was asked to study in Europe for some time, which he did between 1838 and 1841. He studied with Justus Liebig in Giessen, where he finished his research on the benzoin condensation, which was discovered by Liebig several years before. He presented his research results at the University of Saint Petersburg, where he received his Ph.D. He became Professor for Chemistry in the same year at the University of Kazan and left for the University of Saint Petersburg in 1847 where he also became a member of the St. Petersburg Academy of Sciences and first president of the Russian Physical and Chemical Society (1868–1877). In St. Petersburg, professor Zinin was a private teacher of chemistry to the young Alfred Nobel. He is known for the so-called Zinin reaction or Zinin reduction, in which nitro aromates like nitrobenzene are converted to amines by reduction with ammonium sulfides. In 1842 Zinin played an important role in identifying aniline. | https://en.wikipedia.org/wiki?curid=6600809 |
Partial specific volume The partial specific volume formula_1 express the variation of the extensive volume of a mixture in respect to composition of the masses. It is the partial derivative of volume with respect to the mass of the component of interest. where formula_3 is the partial specific volume of a component formula_4 defined as: The PSV is usually measured in milliLiters (mL) per gram (g), proteins > 30 kDa can be assumed to have a partial specific volume of 0.708 mL/g . Experimental determination is possible by measuring the natural frequency of a U-shaped tube filled successively with air, buffer and protein solution . The sum of partial specific volumes of a mixture or solution is an inverse of density of the mixture namely the specific volume of the mixture. | https://en.wikipedia.org/wiki?curid=6601335 |
Artemis Corona is a corona found in the Aphrodite Terra continent, on the planet Venus, at . Named after Artemis, the goddess of hunting, it is the largest corona on Venus, with a diameter of 2,600 kilometers. It is largely enclosed by the near circular Artemis Chasma - a circular belt of arc-shaped features believed to be largely of compressional origin. Artemis is an unusual feature on Venus as it has been interpreted to be the site of plate tectonics operating on a regional scale. There are grabens and compressional arcs which rise above the surrounding plains. As a whole, Artemis is not elevated like other coronae. Regions within Artemis are in fact some 4 km below the surrounding plains. The differences between the highest and the lowest point within Artemis are in the order of 7.5 km. The central rift region of Artemis has been interpreted as a spreading zone (Britomartis Chasma) which has been offset - with clear signs of strike-slip faulting offsetting the central rift zone. Retrograde subduction is interpreted to occur at the circular arc belts of Artemis Chasmata. | https://en.wikipedia.org/wiki?curid=6601628 |
Nightingale Corona is a corona found on the planet Venus. Latitude 63.6° North, Longitude 129.5° East. It has a diameter of 471 kilometers, and is the 35th largest corona on Venus. It is named for Florence Nightingale, an English nurse. Coronae are conventionally named for goddesses: however, when it was first discovered it was thought to be a crater, and named accordingly. It was 1983 when it was closely observed by the radar imaging equipment aboard the Venera 15 and Venera 16 spacecraft, that its true nature became apparent. Unlike the circular Aramaiti Corona, the Nightingale formation is more elliptical and irregular in shape. | https://en.wikipedia.org/wiki?curid=6602079 |
Ralph Molnar Ralph E. Molnar is a paleontologist who had been Curator of Mammals at the Queensland Museum and more recently associated with the Museum of Northern Arizona. He is also a research associate at the Texas natural Science Centre. He co-authored descriptions of the dinosaurs "Muttaburrasaurus", "Kakuru", "Minmi" and "Ozraptor", as well as the mammal "Steropodon". | https://en.wikipedia.org/wiki?curid=6604848 |
Palivizumab (brand name Synagis which is manufactured by MedImmune) is a monoclonal antibody produced by recombinant DNA technology. It is used in the prevention of respiratory syncytial virus (RSV) infections. It is recommended for infants that are high-risk because of prematurity or other medical problems such as congenital heart disease. is a humanized monoclonal antibody (IgG) directed against an epitope in the A antigenic site of the F protein of RSV. In two phase III clinical trials in the pediatric population, palivizumab reduced the risk of hospitalization due to RSV infection by 55% and 45%. is dosed once a month via intramuscular (IM) injection, to be administered throughout the duration of the RSV season. targets the fusion protein of RSV, inhibiting its entry into the cell and thereby preventing infection. was approved for medical use in 1998. is used to reduce the risk of respiratory syncytial virus in children at increased risk of severe disease. The American Academy of Pediatrics has published guidelines for the use of palivizumab. The most recent updates to these recommendations are based on new information regarding RSV seasonality, palivizumab pharmacokinetics, the incidence of bronchiolitis hospitalizations, the effect of gestational age and other risk factors on RSV hospitalization rates, the mortality of children hospitalized with RSV infection, the effect of prophylaxis on wheezing, and palivizumab-resistant RSV isolates. All infants younger than one year who were born at <29 weeks (i.e | https://en.wikipedia.org/wiki?curid=6609299 |
Palivizumab ≤28 weeks, 6 days) of gestation are recommended to use palivizumab. Infants younger than one year with bronchopulmonary dysplasia (i.e. who were born at <32 weeks gestation and required supplemental oxygen for the first 28 days after birth) and infants younger than two years with bronchopulmonary dysplasia who require medical therapy (e.g. supplemental oxygen, glucocorticoids, diuretics) within six months of the anticipated RSV season are recommended to use palivizumab as prophylaxis. Other potential target groups for palivizumab prophylaxis include: Decisions regarding palivizumab prophylaxis for children in these groups should be made on a case-by-case basis. use may cause side effects, which include, but are not limited to: Some more serious side effects include: | https://en.wikipedia.org/wiki?curid=6609299 |
Buffer P2 is a lysis buffer solution produced by Qiagen. It contains 1% sodium dodecyl sulfate (SDS) (w/v) to puncture holes in cellular membranes, and 200mM NaOH. It is used in conjunction with other resuspension buffers and lysis buffers to release DNA from cells, often as part of the alkaline lysis method of purifying plasmid DNA from bacterial cell culture. | https://en.wikipedia.org/wiki?curid=6611632 |
Island growth is a physical model of deposited film growth and chemical vapor deposition. When atoms are deposited slowly onto a flat surface, the first one undergoes a random walk on that surface. Eventually a second atom is deposited; in all likelihood it will eventually meet the first atom. Once the two atoms meet they may bond to form a particle with a higher mass and a lower random walk velocity. Because the bonded particles are now more stable and less mobile than before, they are called an "island." Subsequent atoms deposited on the substrate eventually meet and bond with the island, further increasing its size and stability. Eventually the island can grow to fill the entire substrate with a single large grain. The faster the atoms are deposited, the greater amount of atoms on the substrate before any large stable islands form. As these atoms meet, they will bond to their local neighbors before having the chance to migrate to a distant island. In this way a large number of separate islands are formed and can grow independently. Eventually the separate islands will grow to become separate grains in the final film. The island growth model is used to explain how fast deposition techniques (such as sputter deposition) can produce films with many randomly oriented grains, whereas slow deposition techniques (such as MBE) tend to produce larger grains with more uniform structure. Stranski–Krastanov growth | https://en.wikipedia.org/wiki?curid=6639797 |
National Museums of Kenya The (NMK) is a state corporation that manages museums, sites and monuments in Kenya. It carries out heritage research, and has expertise in subjects ranging from palaeontology, ethnography and biodiversity research and conservation. Its headquarters and the National Museum (Nairobi National Museum) are located on Museum Hill, near Uhuru Highway between Central Business District and Westlands in Nairobi. The National Museum of Kenya was founded by the East Africa Natural History Society (E.A.N.H.S.) in 1910; the Society's main goal has always been to conduct an ongoing critical scientific examination of the natural attributes of the East African habitat. The museum houses collections, and temporary and permanent exhibits. Today the National Museum of Kenya manages over 22 regional museums, many sites, and monuments across the country. The East Africa and Uganda Natural History Society was founded in 1910–11 by persons with an interest in nature in British East Africa. The group included two canons of the Church Missionary Society: The Rev. Harry Leakey (father of Louis Leakey) and The Rev. Kenneth St. Aubyn Rogers; some government officials: C. W. Hobley and John Ainsworth, doctors, dentists, big-game hunters and plantation owners. In 1911 they established the Natural History Museum and library with an honorary curator. Aladina Visram put up the money for a one-story, two-room building. In 1914 they could afford a paid curator. They brought in Arthur Loveridge, a herpetologist, who arrived in March 1914 | https://en.wikipedia.org/wiki?curid=6639878 |
National Museums of Kenya Loveridge concentrated on collections, with the members volunteering to contribute specimens, labour and funds. They also ran the museum while Loveridge fought for the British in German East Africa. He returned for a brief stay after the war, only to go to America, where he eventually became a Harvard University professor. The next curator was A. F. J. Gedye. The museum moved to a new building at the corner of Government Road and Kirk Road. Among the new volunteers for the society were Sir Robert Coryndon, Governor of Kenya. At his unexpected death in 1925, Lady Coryndon established the Coryndon Memorial Fund to build a better museum for the society in memory of her husband. The government offered matching funds for public donations and in 1928 construction began. The building was ready in 1929. Unfortunately no workrooms or storage space had been provided and therefore the Natural History Society declined to move in. The government then bought the old museum and the society used the money to add three rooms, gave its collections to the museum trustees, but retained the library. Everything was moved to the museum. Lady Coryndon donated Sir Robert's books to it. The museum was officially opened on 22 September 1930, as Coryndon Museum, with Victor Gurney Logan Van Someren, a member, as curator. He was given a house on the grounds. In 1930 Evelyn Molony, née Napier was appointed the Museum's first botanist after a grant was given to the Museum by Ernest Carr to fund her employment | https://en.wikipedia.org/wiki?curid=6639878 |
National Museums of Kenya During her tenure she established within the Museum a herbarium on East African plants as well as publishing a series of scientific papers on East African flora. The relationship between the museum trustees and the society became problematic, and as a result the two organisations appointed a committee including Sir Charles Belcher, a Kenyan jurist, to stabilise it. The committee turned everything over to the museum except for the library in exchange for annual payments for 15 years to the society. The museum now had a staff. Mary Leakey became part of it and then Louis Leakey, as unpaid curator, in 1941. He stepped in when Dr. van Someren resigned after the board (including Louis) refused to dismiss Peter Bally in a personality conflict. The museum was a center for Leakey operations. In 1945 Louis was hired as paid curator with a new house, as the old one had become run-down. He built up the exhibitions and opened them to Africans and Asians by lowering the admission fee. Until then the museum had been "for whites only." The museum was a base for Leakey operations until 1961, when Louis founded the Centre for Prehistory and Paleontology on the grounds nearby and moved himself and his collections to it. He resigned in favour of the next director, Robert Carcasson. Kenya became independent in 1963. The Coryndon Museum was renamed "National Museum" in 1964 and was included in a new system, the "National Museums of Kenya | https://en.wikipedia.org/wiki?curid=6639878 |
National Museums of Kenya " In 1967 Richard Leakey was having irreconcilable differences with Louis Leakey, his employer in the Centre, and decided to improve the National Museum. His main objection was that it had not been Kenyanized. He and supporters formed the Kenya Museum Associates, which obtained an observer's seat for Richard on the board from Carcasson in exchange for a 5000-pound contribution. Richard did not do much observing, as he departed for the first Omo expedition. The Kenya Museum Associates included Joel Ojal, the museum overseer in the government. On his return from Omo Richard gave his ideas for improvement directly to Joel, who asked the chairman, Sir Ferdinand Cavendish-Bentinck, to place Richard in a senior position and begin replacing the board with Kenyans of Kenyan extraction, as there were only two out of 16 in that category. The penalty for inaction would be removal of government funding. Richard was at first offered a part-time executive position, which he turned down. Over the next few months much of the board was replaced and in May 1968 the new board offered Richard a permanent post as administrative director, with Carcasson to be retained as scientific director. However, Carcasson resigned and Richard became director. This gallery contains artwork by Joy Adamson featuring various Kenyan communities in traditional attire. On 15 October 2005 Nairobi Museum Galleries closed until December 2007 for an extensive rebuilding program. This was the first major renovation of Nairobi Museum since 1930 | https://en.wikipedia.org/wiki?curid=6639878 |
National Museums of Kenya A new administration block and commercial center were built, and NMK's physical planning was improved. The Museum re-opened in June 2008. It houses both temporary and permanent exhibitions. Within the grounds are also the Nairobi Snake Park and the Botanic Garden and nature trail. The museum's commercial wing has restaurants and shops. Other museums, sites and monuments operated by the NMK, including eco-tourist attractions are: | https://en.wikipedia.org/wiki?curid=6639878 |
MRC (file format) MRC is a file format that has become industry standard in cryo-electron microscopy (cryoEM) and electron tomography (ET), where the result of the technique is a three-dimensional grid of voxels each with a value corresponding to electron density or electric potential. It was developed by the MRC (Medical Research Council, UK) Laboratory of Molecular Biology. In 2014, the format was standardised. The format specification is available on the CCP-EM website. The MRC format is supported by many of the software packages listed in . | https://en.wikipedia.org/wiki?curid=6641341 |
Chaos Canyon is the name of a cleft in a giant quartzite rockslide in the White Rocks National Recreation Area located in southcentral Vermont, USA. The rockslide was formed more than 10,000 years ago when the west slope of White Rocks Peak, part of the Green Mountain range, gave way due to intense frost action. The wooded canyon can be viewed from the White Rocks vista overlook off the WRNRA Ice Beds Trail. | https://en.wikipedia.org/wiki?curid=6658175 |
MIT Chemistry Department The Department of Chemistry at MIT is one of the top university faculties in the world. Research conducted covers the entire field of chemistry, ranging from organic chemistry and biological chemistry to physical chemistry, inorganic chemistry, environmental chemistry, materials science and nanoscience. The Department of Chemistry at MIT has been established since the Institute opened its doors in 1865. It started with two professors, Charles W. Eliot and Francis H. Storer, and a class of 15 students. In 1866, the department moved to its then new quarters in the basement of the Rogers Building in Boston. In 1907, MIT awarded its first Ph.D. to three students in the field of physical chemistry. The department has several Nobel Laureates among its faculty and alumni, including the following: | https://en.wikipedia.org/wiki?curid=6674690 |
Self-amplified spontaneous emission (SASE) is a process within a free-electron laser (FEL) by which a laser beam is created from a high-energy electron beam. The SASE process starts with an electron bunch being injected into an undulator, with a velocity close to the speed of light and a uniform density distribution within the bunch. In the undulator the electrons are wiggled and emit light characteristic of the undulator strength but within a certain energy bandwidth. The emitted photons travel slightly faster than the electrons and interact with them each undulator period. Depending on the phase to each other, electrons gain or lose energy (velocity), i.e. faster electrons catch up with slower ones. Thereby the electron bunch density is periodically modulated by the radiation which is called microbunching. The structured electron beam amplifies only certain photon energies at the cost of kinetic energy until the system goes into saturation. SASE energy spectra show a noise-like distribution of intense spikes on top of a lower-amplitude background. The micro-bunch structuring reduces the phase space available to the photons, thus they are also more likely to have a similar phase and the emitted beam is quasi-coherent. This concept has been demonstrated at the SPring-8 FEL SACLA in Japan, the Free electron LASer in Hamburg (FLASH) and the Linac Coherent Light Source (LCLS) at SLAC. | https://en.wikipedia.org/wiki?curid=6683877 |
Monoxide A monoxide is any oxide containing only one atom of oxygen. A well known monoxide is carbon monoxide; see carbon monoxide poisoning. The prefix mono (Greek for "one") is used in chemical nomenclature. In proper nomenclature, the prefix is not always used in compounds with one oxygen atom. Generally, when the oxygen is bonded to a nonmetal, the prefix mono is used. However when the oxygen atom bonds to a metal, the prefix is dropped. For instance, in the compound KO, potassium (K) is a metal and therefore its proper name is potassium oxide, rather than potassium monoxide. Among monoxides, carbon monoxide is neutral, germanium(II) oxide is distinctly acidic, and both tin(II) oxide lead(II) oxide are amphoteric. | https://en.wikipedia.org/wiki?curid=6684233 |
Accumulation zone On a glacier, the accumulation zone is the area above the firn line, where snowfall accumulates and exceeds the losses from ablation, (melting, evaporation, and sublimation). The annual equilibrium line separates the accumulation and ablation zone annually. The accumulation zone is also defined as the part of a glacier's surface, usually at higher elevations, on which there is net accumulation of snow, which subsequently turns into firn and then glacier ice. Part of the glacier where snow builds up and turns to ice moves outward from there. | https://en.wikipedia.org/wiki?curid=6687259 |
Weather Research and Forecasting Model The Weather Research and Forecasting (WRF) model is a numerical weather prediction (NWP) system designed to serve both atmospheric research and operational forecasting needs. NWP refers to the simulation and prediction of the atmosphere with a computer model, and WRF is a set of software for this. WRF features two dynamical (computational) cores (or "solvers"), a data assimilation system, and a software architecture allowing for parallel computation and system extensibility. The model serves a wide range of meteorological applications across scales ranging from meters to thousands of kilometers. The effort to develop WRF began in the latter part of the 1990s and was a collaborative partnership principally among the National Center for Atmospheric Research (NCAR), the National Oceanic and Atmospheric Administration (represented by the National Centers for Environmental Prediction (NCEP) and the (then) Forecast Systems Laboratory (FSL)), the Air Force Weather Agency (AFWA), the Naval Research Laboratory (NRL), the University of Oklahoma (OU), and the Federal Aviation Administration (FAA). The bulk of the work on the model has been performed or supported by NCAR, NOAA, and AFWA. WRF allows researchers to produce simulations reflecting either real data (observations, analyses) or idealized atmospheric conditions. WRF provides operational forecasting a flexible and robust platform, while offering advances in physics, numerics, and data assimilation contributed by the many research community developers | https://en.wikipedia.org/wiki?curid=6688567 |
Weather Research and Forecasting Model WRF is currently in operational use at NCEP and other forecasting centers internationally. WRF has grown to have a large worldwide community of users (over 30,000 registered users in over 150 countries), and workshops and tutorials are held each year at NCAR. WRF is used extensively for research and real-time forecasting throughout the world. WRF offers two dynamical solvers for its computation of the atmospheric governing equations, and the variants of the model are known as WRF-ARW (Advanced Research WRF) and WRF-NMM (nonhydrostatic mesoscale model). The Advanced Research WRF (ARW) is supported to the community by the NCAR Mesoscale and Microscale Meteorology Laboratory. The WRF-NMM solver variant was based on the Eta model, and later nonhydrostatic mesoscale model, developed at NCEP. The WRF-NMM (NMM) is supported to the community by the Developmental Testbed Center (DTC). The WRF serves as the basis for the RAP and HRRR models: high-resolution operational forecast models run regularly at NCEP. A version of WRF-NMM tailored for hurricane forecasting, HWRF (hurricane weather research and forecasting), became operational in 2007. In 2009, a polar optimized WRF was released through the Byrd Polar Research Center at the Ohio State University. | https://en.wikipedia.org/wiki?curid=6688567 |
NGC 1073 is a barred spiral galaxy in the constellation Cetus. It probably has an H II nucleus. is about 55 million light years from Earth. is about 80,000 light years across. can be viewed with a mid-sized telescope and is found in the Cetus constellation, also called the Sea Monster. is a barred spiral galaxy like the Milky Way; unlike the Milky Way, however, does not have well formed symmetrical arms and the center bar is larger. | https://en.wikipedia.org/wiki?curid=6694013 |
NGC 1087 is an intermediate spiral galaxy in Cetus. The central bar/core is very small with many irregular features in the surrounding disk of material. With the many strange features of NGC 1087, its true nature is still uncertain. It has an extremely small nucleus and a very short stellar bar. Unlike most barred galaxies, the bar apparently has some new star-formation taking place. There is a multiple spiral structure defined more by the dust lanes than by luminous matter. Overall, the disc has a very low surface brightness. Even though it appears close to another galaxy (NGC 1090), these two galaxies are not interacting and should be considered isolated from one another. NCG 1087 lies near the small M77 (NGC 1068) galaxy group that also includes NGC 936, NGC 1055, and NGC 1090. However, because of its distance, it probably is not an actual group member. Based on the published red shift, (Hubble Constant of 62 km/s per Mpc) a rough distance estimate for is 80 million light-years, with a diameter of about 86,800 light-years. The Type II Supernova 1995V is the only recorded supernova in NGC 1087. | https://en.wikipedia.org/wiki?curid=6694149 |
NGC 1234 is a peculiar barred spiral galaxy exhibiting a ring structure in the constellation Eridanus, discovered by Francis Preserved Leavenworth in 1886. | https://en.wikipedia.org/wiki?curid=6694969 |
Samuel Paul Welles ["Not to be confused with Samuel Gardner Welles"] (November 9, 1907 – August 6, 1997) was an American palaeontologist. Welles was a research associate at the Museum of Palaeontology, University of California, Berkeley. He took part in excavations at the Placerias Quarry in 1930 and the "Shonisaurus" discoveries of 1954 and later, in what is now the Berlin-Ichthyosaur State Park. He accumulated an extensive collection of fossils of marine reptiles, amphibians, and fish, as well as describing the dinosaur "Dilophosaurus" in 1954. | https://en.wikipedia.org/wiki?curid=6697379 |
Charles Lewis Camp (March 12, 1893 Jamestown, North Dakota – August 14, 1975 San Jose, California) was a palaeontologist and zoologist, working from the University of California, Berkeley. He took part in excavations at the 'Placerias Quarry', in 1930 and the forty "Shonisaurus" skeleton discoveries of the 1960s, in what is now the Berlin-Ichthyosaur State Park. Camp served as the third director of the University of California Museum of Paleontology from 1930 to 1949, and coincidentally as chair of the UC Berkeley Paleontology Department between 1939 and 1949. Camp named a number of species of marine reptiles such as "Shonisaurus" and "Plotosaurus", as well as the dinosaur "Segisaurus". Camp was also an important bibliographer and historian of Western America. This aspect of his career is represented most notably by two works. The first is his biography of American pioneer James Clyman, which Bernard De Voto called "one of the half-dozen classics in the field." The second work was the third edition of "The Plains and the Rockies," published in 1953, which Camp annotated heavily. He was the 1970 recipient of the California Historical Society's Henry Raup Wagner Memorial Award. Camp was one of the early members of the revived fraternal order "E Clampus Vitus" and was the Noble Grand Humbug of the Yerba Buena Lodge in 1938. The theropod "Camposaurus" was named in Camp's honour in 1998. | https://en.wikipedia.org/wiki?curid=6697522 |
Picamar is a colorless, hydrocarbon oil extracted from the creosote of beechwood tar with a peculiar odor and bitter taste. It consists of derivatives of pyrogallol. It was discovered by German chemist Karl von Reichenbach in the 1830s. | https://en.wikipedia.org/wiki?curid=6710047 |
Capnomor (from Greek "smoke" + part) is a colorless and limpid oil with a peculiar odor, extracted by distillation from beechwood tar. It was discovered in the 1830s by the German chemist Baron Karl von Reichenbach. | https://en.wikipedia.org/wiki?curid=6710186 |
Paibian The is the lowest stage of Furongian series of the Cambrian. It follows the Guzhangian (3rd series of the Cambrian) and is succeeded by the Jiangshanian stage. The base is defined as the first appearance of the trilobite "Glyptagnostus reticulatus" around million years ago. The top, or the base of the Jiangshanian is defined as the first appearance of the trilobite "Agnostotes orientalis" around million years ago. The name is derived from Paibi, a village in Hunan, China. The GSSP is defined in the "Paibi section" (Wuling Mountains, Huayuan County), an outcrop of the Huaqiao Formation. The base is the first occurrence of "Glyptagnostus reticulatus" which is 396 m above the base of the Huaqiao Formation at the type locality (). | https://en.wikipedia.org/wiki?curid=6711121 |
Alfred Merz (24 January 1880 in Perchtoldsdorf, Niederösterreich – 16 August 1925 in Buenos Aires) was an Austrian geographer, oceanographer and director of the Institute of Marine Science in Berlin. He died of pneumonia in Buenos Aires while on an expedition to survey the South Atlantic and is buried in Perchtoldsdorf. Merz Peninsula is named after him. | https://en.wikipedia.org/wiki?curid=6719777 |
Head (geology) Head describes deposits consisting of fragmented material which, following weathering, have moved downslope through a process of solifluction. The term has been used by British geologists since the middle of the 19th century to describe such material in a range of different settings from flat hilltops to the bottoms of valleys. Areas identified as head include deposits of aeolian origin such as blown sand and loess, slope deposits such as gelifluctates and solifluctates, and recently eroded soil material, called colluvium. With geologists becoming more interested in studying the near-surface environment and its related processes, the term head is becoming obsolete. A related term is 'combe (or coombe) rock', descriptive of a body of chalk and flint fragments contained within a mass of chalky earth typically found on the chalk downlands of south-east England and resulting from freeze-thaw processes. Where the mass is also soliflucted, it is considered a variety of head. Though its earliest use is attributed to De la Beche in 1839 he mentions that in 1837 Mr. Trevelyn of Guernsey observed “ a bed of disintegrated granite, about three feet thick, mixed with angular fragments, thus reminding us of the head of angular fragments so commonly seen in Cornwall and Devon.“ | https://en.wikipedia.org/wiki?curid=6729727 |
Phase offset modulation works by overlaying two instances of a periodic waveform on top of each other. (In software synthesis, the waveform is usually generated by using a lookup table.) The two instances of the waveform are kept slightly out of sync with each other, as one is further ahead or further behind in its cycle. The values of both of the waveforms are either multiplied together, or the value of one is subtracted from the other. This generates an entirely new waveform with a drastically different shape. For example, one sawtooth (ramp) wave subtracted from another will create a pulse wave, with the amount of offset (i.e. the difference between the two waveforms' starting points) dictating the duty cycle. If you slowly change the offset amount, you create pulse-width modulation. Using this technique, not only can a ramp wave create pulsewidth modulation, but any other waveform can achieve a comparable effect. | https://en.wikipedia.org/wiki?curid=6729866 |
Sue Tyler Friedman Medal The is awarded by the Geological Society of London for work on the history of geology. Established in 1987, it is named after the wife of academic journal editor and publisher Gerald M. Friedman, and was funded by a gift to the Geological Society by Friedman's company, Northeastern Science Foundation, of Troy, New York. Source: The Geological Society | https://en.wikipedia.org/wiki?curid=6734942 |
Kalliroscope A is an art device/technique based on rheoscopic fluids invented by artist Paul Matisse. | https://en.wikipedia.org/wiki?curid=6742937 |
Binding constant The binding constant, or association constant, is a special case of the equilibrium constant "K", and is the inverse of the dissociation constant. It is associated with the binding and unbinding reaction of receptor (R) and ligand (L) molecules, which is formalized as: The reaction is characterized by the on-rate constant "k" and the off-rate constant "k", which have units of M s and s, respectively. In equilibrium, the forward binding transition R + L → RL should be balanced by the backward unbinding transition RL → R + L. That is, where [R], [L] and [RL] represent the concentration of unbound free receptors, the concentration of unbound free ligand and the concentration of receptor-ligand complexes. The binding constant "K" is defined by An often considered quantity is the dissociation constant "K" ≡ , which has the unit of concentration, despite the fact that strictly speaking, all association constants are unitless values. The inclusion of units arises from the simplification that such constants are calculated solely from concentrations, which is not the case. Once chemical activity is factored into the correct form of the equation, a dimensionless value is obtained. For the binding of receptor and ligand molecules in solution, the molar Gibbs free energy Δ"G", or the binding affinity is related to the dissociation constant "K" via in which "R" is the ideal gas constant, "T" temperature and the standard reference concentration "c" = 1 mol/L. | https://en.wikipedia.org/wiki?curid=6747488 |
Spin spherical harmonics In quantum mechanics, spin spherical harmonics are spinors eigenstates of the total angular momentum operator squared: where . They are the natural spinorial analog of vector spherical harmonics. For spin-1/2 systems, they are given in matrix form by | https://en.wikipedia.org/wiki?curid=6750203 |
Camillo Acqua was an Italian entomologist, born 30 August 1863 at Velletri, Italy. He died 25 March 1936 at Ascoli Piceno. was Directeur de l’Instituto Bacologico (Institut for sericulture) at Portici (near Naples) then at Stazione Sperimentale di Gelsicoltura e Bachicoltura ( An Experimental station for the culture of the mulberry and silkworm breeding) at Ascoli Piceno. He wrote much on the subject of sericulture. His best known work is "Il bombice del Gelso:Nello stato normale e patologico nella tecnica dell'allevamento e della riproduzione"("Industria della preparazione del seme Bachi")-Enc. tela. Casa Ed. di Giuseppe Cesari. | https://en.wikipedia.org/wiki?curid=6750567 |
Landolt–Börnstein is a collection of property data in materials science and the closely related fields of chemistry, physics and engineering published by Springer Nature. On July 28, 1882, Dr. Hans Heinrich Landolt and Dr. Richard Börnstein, both professors at the "Landwirtschaftliche Hochschule" (Agricultural College) at Berlin, signed a contract with the publisher Ferdinand Springer on the publication of a collection of tables with physical-chemical data. The title of this book "Physikalisch-chemische Tabellen" (Physical-Chemical Tables) published in 1883 was soon forgotten. Owing to its success the data collection has been known for more than a hundred years by each scientist only as "The Landolt-Börnstein". 1250 copies of the 1st Edition were printed and sold. In 1894, the 2nd Edition was published, in 1905 the 3rd Edition, in 1912 the 4th Edition, and finally in 1923 the 5th Edition. Supplementary volumes of the latter were printed until as late as 1936. New Editions saw changes in large expansion of volumes, number of authors, updated structure, additional tables and coverage of new areas of physics and chemistry. The 5th Edition was eventually published in 1923, consisting of two volumes and comprising a total of 1,695 pages. Sixty three authors had contributed to it. The growth that had already been noticed in previous editions, continued. It was clear, that "another edition in approximately 10 years" was no solution. A complete conceptual change of the Landolt-Börnstein had thus become necessary | https://en.wikipedia.org/wiki?curid=6756239 |
Landolt–Börnstein For the meantime supplementary volumes in two-year intervals should be provided to fill in the blanks and add the latest data. The first supplementary volume of the 5th Edition was published in 1927, the second in 1931 and the third in 1935/36. The latter consisted of three sub-volumes with a total of 3,039 pages and contributions from 82 authors. The 6th Edition (1950) was published in line with the revised general frame. The basic idea was to have four volumes instead of one, each of which was to cover different fields of the Landolt-Börnstein under different editors. Each volume was given a detailed table of contents. Two major restrictions were also imposed. The author of a contribution was asked to choose a "Bestwert" (optimum value) from the mass of statements of an experimental value in the publications of different authors, or derive a "wahrscheinlichster Wert” (most possible value). The other change of importance was that not only diagrams became as important as tables, but that text also became necessary to explain the presented data. The New Series represents over 520 books published between 1961 and 2018 and includes more than 220,000 pages covering mechanical, optical, acoustical, thermal, spectroscopic, electrical and magnetic properties among others. The New Series offers critically evaluated data by over 1,000 expert authors and editors in materials science. books have gone through various digitization initiatives, from CD-ROM to FTP and PDF formats | https://en.wikipedia.org/wiki?curid=6756239 |
Landolt–Börnstein books content is now available on SpringerMaterials. | https://en.wikipedia.org/wiki?curid=6756239 |
Cyclopentadienyl anion In chemistry, the cyclopentadienyl anion or cyclopentadienide is an aromatic species with a formula of [CH] and abbreviated as Cp. Its name derives from the molecule cyclopentadiene. It is a regular pentagonal, planar, cyclic ion; as well, it has 6 π-electrons (4"n" + 2, where "n" = 1), which fulfills Hückel's rule of aromaticity. It can coordinate as a ligand to metal atoms. The structure shown is a composite of five resonance contributors in which each carbon atom carries part of the negative charge. Salts of the cyclopentadienyl anion can be stable, e.g., sodium cyclopentadienide. Coordination compounds of the cyclopentadienyl anion (not the cyclopentadienyl radical) are known as cyclopentadienyl complexes. Biscyclopentadienyl complexes are called metallocenes. | https://en.wikipedia.org/wiki?curid=6764693 |
Sarcotesta The sarcotesta is a fleshy seedcoat, a type of testa. Examples of seeds with a sarcotesta are pomegranate and some cycad seeds. The sarcotesta of pomegranate seeds consists of epidermal cells derived from the integument, and there are no arils on these seeds. | https://en.wikipedia.org/wiki?curid=6768840 |
Boriding Boriding, also called boronizing, is the process by which boron is added to a metal or alloy. It is a type of surface hardening. In this process boron atoms are diffused into the surface of a metal component. The resulting surface contains metal borides, such as iron borides, nickel borides, and cobalt borides, As pure materials, these borides have extremely high hardness and wear resistance. Their favorable properties are manifested even when they are a small fraction of the bulk solid. Boronized metal parts are extremely wear resistant and will often last two to five times longer than components treated with conventional heat treatments such as hardening, carburizing, nitriding, nitrocarburizing or induction hardening. Most borided steel surfaces will have iron boride layer hardnesses ranging from 1200-1600 HV. Nickel-based superalloys such as Inconel and Hastalloys will typically have nickel boride layer hardnesses of 1700-2300 HV. can be achieved in several ways, but commonly the metal piece is packed with a boriding mixture and heating at 900 °C. Typical boriding mixture consists of boron carbide powder diluted with other refractory materials. The process converts some of the Fe to iron boride, consisting of two phases: FeB concentrated near the surface, and diiron boride (FeB). Boride layer depths can range from 0.001 - 0.015 inch depending on base material selection and treatment. It is often used on steel, but is applicable to a variety of alloys and cermet materials | https://en.wikipedia.org/wiki?curid=6768880 |
Boriding A wide range of materials suitable for treatment including plain carbon steels, alloy steels, tool steels, nickel-based super alloys, cobalt alloys, and stellite. gives the material the following desirable properties: wear resistance, improved hardness (1300-2000HV is possible), thermal stability, resistance to corrosion by acids, reduced coefficient of friction, and increased galling/cold-welding resistance. It is possible to combine with other heat treatments such as carburizing, hardening or induction hardening to create deeper wear layers or high core hardness. | https://en.wikipedia.org/wiki?curid=6768880 |
Semi-synchronous orbit A semi-synchronous orbit is an orbit with a period equal to half the average rotational period of the body being orbited, and in the same direction as that body's rotation. For Earth, a semi-synchronous orbit is considered a medium Earth orbit, with a period of just under 12 hours. For circular Earth orbits, the altitude is approximately . Semi-synchronous orbits are typical for GPS satellites. | https://en.wikipedia.org/wiki?curid=6771843 |
Dynamic scattering mode George Heilmeier proposed the dynamic scattering effect which causes a strong scattering of light when the electric field applied to a special liquid crystal mixture exceeds a threshold value. A DSM cell requires the following ingredients: With no voltage applied the LC-cell with the homeotropically aligned LC is clear and transparent. With increasing voltage and current, the electric field is trying to align the long molecular axis of the LC perpendicular to the field while the ion transport through the layer has the tendency to align the LC perpendicular to the substrate plates. As a result, a striped repetitive pattern is generated in the cell, of which the building blocks are named "Williams domains". Upon further increase of the voltage this regular pattern is replaced by a turbulent state which is strongly scattering light. This effect belongs to the class of electro-hydrodynamic effects in LCs. Electro-optic displays can be realized with that effect in the transmissive and reflective mode of operation. The driving voltages required for light scattering are in the range of several ten volts and the non-trivial current is depending on the area of the activated segments. The DMS effect was thus not suited for battery powered electronic devices. | https://en.wikipedia.org/wiki?curid=6772817 |
Victor Meyer apparatus The is the standard laboratory method for determining the molecular weight of a volatile liquid. It was developed by Viktor Meyer, who spelled his name "Victor" in publications at the time of its development. In this method, a known mass of a volatile solid or liquid under examination is converted into its vapour form by heating in a Victor Meyer's tube. The vapour displaces its own volume of air. The volume of air displaced at experimental temperature and pressure is calculated. Then volume of air displaced at Standard Temperature and Pressure is calculated. Using this, mass of air displaced at 2.24x10m of vapour at STP is calculated. This value represents the molecular mass of the substance. The apparatus consists of an inner Victor Meyer's tube, lower end of which is in form of a bulb. The upper end of tube has a side tube that leads to a trough filled with water. The Victor Meyer's tube is surrounded by an outer jacket. In the outer jacket, a liquid is placed, which boils at a temperature at least 30K than the substance under examination. A small quantity of glass-wool or asbestos pad covers the lower end of the Victor Meyer's tube to prevent breakage, when a glass bottle containing the substance under examination is dropped to it The liquid in the outer jacket is heated until no more air escapes from the side tube. Then, a graduated tube filled with water is inverted over the side tube dipping in a trough filled with water | https://en.wikipedia.org/wiki?curid=6775491 |
Victor Meyer apparatus A small quantity of substance is weighed exactly in a small stoppered bottle and is dropped in the Victor Meyer's tube and sealed immediately. The bottle falls on the asbestos pad and its contents suddenly change into vapour, blows out the stopper and displaces an equal volume of air in graduated tube. The volume of air displaced is measured by taking the graduated tube out, closing its mouth with thumb and dipping in a jar filled with water. When water levels inside and outside the tube is equal, the volume of air displaced is noted. The atmospheric pressure and laboratory temperature are noted. Victor Meyer suggested the idea of determining the types of alcohol i.e. (primary, secondary or tertiary). In this method the sample alcohol is treated with PI to get the iodoalkane which is again treated with AgNO to get the nitroalkane. The nitroalkane is then treated with nitrous acid which is obtained by NaNO and HCl. The resulting solution is treated with KOH and the colour is observed. The red, blue and no colour indicates the primary, secondary and tertiary alcohol respectively. | https://en.wikipedia.org/wiki?curid=6775491 |
Sound particle In the context of particle displacement and velocity, a sound particle is an imaginary infinitesimal volume of a medium that shares the movement of the medium in response to the presence of sound at a specified point or in a specified region. Sound particles are not molecules in the physical or chemical sense; they do not have defined physical or chemical properties, or the temperature-dependent kinetic behaviour of ordinary molecules. Sound particles are, then, indefinitely small (small compared to the wavelength of sound) so that their movement truly represents the movement of the medium in their locality. They exist in the mind’s eye to enable this movement to be visualized and described quantitatively. Assuming the medium as a whole to be at rest, sound particles are imagined to vibrate about fixed points. | https://en.wikipedia.org/wiki?curid=6784042 |
Ab initio multiple spawning The ab initio multiple spawning, or AIMS, method is a time-dependent formulation of quantum chemistry. In AIMS, nuclear dynamics and electronic structure problems are solved simultaneously. Quantum mechanical effects in the nuclear dynamics are included, especially the nonadiabatic effects which are crucial in modeling dynamics on multiple electronic states. The AIMS method makes it possible to describe photochemistry from first principles molecular dynamics, with no empirical parameters. The method has been applied to two molecules of interest in organic photochemistry - ethylene and cyclobutene. The photodynamics of ethylene involves both covalent and ionic electronic excited states and the return to the ground state proceeds through a pyramidalized geometry. For the photoinduced ring opening of cyclobutene, is it shown that the disrotatory motion predicted by the Woodward–Hoffmann rules is established within the first 50 fs after optical excitation. The method was developed by chemistry professor Todd Martinez. | https://en.wikipedia.org/wiki?curid=6786507 |
Preferential concentration is the tendency of dense particles in a turbulent fluid to cluster in regions of high strain (low vorticity) due to their inertia. The extent by which particles cluster is determined by the Stokes number, defined as formula_1, where formula_2 and formula_3 are the timescales for the particle and fluid respectively; note that formula_4 and formula_5 are the mass densities of the fluid and the particle, respectively, formula_6 is the kinematic viscosity of the fluid, and formula_7 is the kinetic energy dissipation rate of the turbulence. Maximum preferential concentration occurs at formula_8. Particles with formula_9 follow fluid streamlines and particles with formula_10 do not respond significantly to the fluid within the times the fluid motions are coherent. Systems that can be strongly influenced by the dynamics of preferential concentration are aerosol production of fine powders, spray, emulsifier, and crystallization reactors, pneumatic devices, cloud droplet formation, aerosol transport in the upper atmosphere, and even planet formation from protoplanetary nebula. | https://en.wikipedia.org/wiki?curid=6804782 |
NGC 4696 is an elliptical galaxy. It lies around away in the constellation Centaurus. It is the brightest galaxy in the Centaurus Cluster, a large, rich cluster of galaxies in the constellation of the same name. The galaxy is surrounded by many dwarf elliptical galaxies also located within the cluster. There is believed to be a supermassive black hole at the center of the galaxy. | https://en.wikipedia.org/wiki?curid=6805312 |
Hydra Cluster The (or Abell 1060) is a galaxy cluster that contains 157 bright galaxies, appearing in the constellation Hydra. The cluster spans about ten million light-years and has an unusually high proportion of dark matter. The cluster is part of the Hydra-Centaurus Supercluster located 158 million light-years from Earth. The cluster's largest galaxies are elliptical galaxies NGC 3309 and NGC 3311 and the spiral galaxy NGC 3312 all having a diameter of about 150,000 light-years. In spite of a nearly circular appearance on the sky, there is evidence in the galaxy velocities for a clumpy, three-dimensional distribution. | https://en.wikipedia.org/wiki?curid=6805353 |
Chia-Hsiung Tze (often H.C. Tze) is a professor emeritus at Virginia Tech. He is a theoretical particle physicist focusing on group theory, string theory, supersymmetry, octonions and other topics in theoretical physics. He was a colleague of the Feza Gürsey. | https://en.wikipedia.org/wiki?curid=6811745 |
Defence Nuclear Material within the UK is defined as: | https://en.wikipedia.org/wiki?curid=6816424 |
Lee–Boot effect The is a phenomenon concerning the suppression or prolongation of oestrous cycles of mature female mice (and other rodents), when females are housed in groups and isolated from males. It is caused by the effects of an estrogen-dependent pheromone, possibly 2,5-dimethylpyrazine, which is released via the urine and acts on the vomeronasal organ of recipients. This pheromone lowers the concentration of luteinizing hormone and elevates prolactin levels, synchronising or stopping the recipient's cycle. This effect goes some way to explain why spontaneous pseudopregnancy can occur in mice. The same response is invoked from isolated females when brought into contact with urine-soaked bedding from other females' cages. The adrenal glands are required for production of the urine pheromone which is responsible for this effect. | https://en.wikipedia.org/wiki?curid=6828719 |
Donald McGillivray Donald John McGillivray (20 August 1935 – 17 August 2012) in New South Wales, Australia, usually known as D.J. McGillivray, was an Australian botanical taxonomist. He was trained in forestry, and became interested in plant taxonomy just before he transferred in 1964 to the National Herbarium of the Royal Botanic Gardens in Sydney, New South Wales. From 1969 to 1970, he was the Australian Botanical Liaison Officer at the Royal Botanic Gardens in Kew, London. McGillivray specialised in the "Grevillea" genus, and in 1993 published "Grevillea – Proteaceae: A Taxonomic Revision", a definitive scientific survey of the prolific Australian plant genus. | https://en.wikipedia.org/wiki?curid=6835753 |
Trou du Diable The (translated in English as Devil's Hole) is a cave situated in St-Casimir, in the province of Quebec, Canada. On the CanMatrix System (), you can find the on the map Grondines (031-I/9) at the coordinates 22207325. The is in fact a creek of which the last 980 meters are underground, which makes it the second longest in Quebec. It is tributary of the Rivière Ste-Anne, about four kilometers upstream of St-Casimir. Its highest point is 6.8 metres above the bottom of the cave, and at some places visitors have to crawl to move forward. | https://en.wikipedia.org/wiki?curid=6839196 |
Ternary complex A ternary complex is a protein complex containing three different molecules that are bound together. In structural biology, "ternary complex" can also be used to describe a crystal containing a protein with two small molecules bound, for example cofactor and substrate; or a complex formed between two proteins and a single substrate. In Immunology, "ternary complex" can refer to the MHC–peptide–T-cell-receptor complex formed when T cells recognize epitopes of an antigen. Some other example can be taken like ternary complex while eukaryotic translation, in which ternary complex is composed of eIF-3 & eIF-2 + Ribosome 40s subunit+ tRNAi. A ternary complex can be a complex formed between two substrate molecules and an enzyme. This is seen in multi-substrate enzyme-catalyzed reactions where two substrates and two products can be formed. The ternary complex is an intermediate between the product formation in this type of enzyme-catalyzed reactions. An example for a ternary complex is seen in random-order mechanism or a compulsory-order mechanism of enzyme catalysis for multi substrates. The term "ternary complex" can also refer to a polymer formed by electrostatic interactions. Trevor Palmer (Enzymes, 2nd edition) | https://en.wikipedia.org/wiki?curid=6847848 |
Kentucky Geological Survey The (KGS) is a department of the University of Kentucky that provides information on the geology of Kentucky. According to its website, the KGS "conducts research, collects data, and serves as the State's official archive for data on petroleum, coal, minerals, ground water, and topographic and geologic maps." | https://en.wikipedia.org/wiki?curid=6854196 |
Phenotype mixing is a form of interaction between two virus particles, each of which holds its own unique genetic material. The two particles "share" coat proteins, therefore each has a similar assortment of identifying surface proteins, while having different genetic material. In other words; nongenetic interaction in which virus particles released from a cell that is infected with two different viruses have components from both the infecting agents, but with a genome from one of them. | https://en.wikipedia.org/wiki?curid=6863192 |
NGC 2812 is a lenticular galaxy in the constellation Cancer. It was discovered by Albert Marth on February 17, 1865. | https://en.wikipedia.org/wiki?curid=6864576 |
Humeocline is a genus of plants in the sunflower family, endemic to Madagascar. There is only one known species, madagascariensis. | https://en.wikipedia.org/wiki?curid=6881442 |
Juliet Wege Juliet Ann Wege (born 1971 in Western Australia) is an Australian botanist. She graduated in 1992 and gained a PhD at The University of Western Australia in 1999. She currently works as a researcher at the Western Australian Herbarium run by Western Australia's Department of Environment and Conservation. Her main area of expertise is in taxonomy and study of the Stylidiaceae family of triggerplants. During 2005 and 2006 she was the Australian Botanical Liaison Officer at the Royal Botanic Gardens in London, England. | https://en.wikipedia.org/wiki?curid=6881549 |
Ahmad Parsa (1907 in Tafresh, Iran – July 4, 1997 in California) was an Iranian botanist. After obtaining his doctorate in France, he returned to Iran and became the first modern professor of Botany at Tehran in 1933. He helped establish a natural history museum with a herbarium in Tehran in 1954. He wrote eight volumes on the flora of Iran published between 1943 and 1959, in which he described over 250 new species. Dr. is survived by two daughters, and three sons. Flora Stay D.D.S., Vida Parsa, Cyrus Parsa, M.D., Kooros Parsa, M.D., and Dariush Parsa, M.D. | https://en.wikipedia.org/wiki?curid=6882912 |
Health Products and Food Branch The (HPFB) of Health Canada manages the health-related risks and benefits of health products and food by minimizing risk factors while maximizing the safety provided by the regulatory system. HPFB has seven operational Directorates with direct regulatory responsibilities: | https://en.wikipedia.org/wiki?curid=6886070 |
Emma Dean (crater) Emma Dean is a small impact crater in the Meridiani Planum extraterrestrial plain situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. This geological feature was visited by the "Opportunity" rover from sols 929 to 943. The much larger crater Victoria lies about 100m to the east. Emma Dean lies directly on top of the ejecta blanket from Victoria and could therefore expose material originating from deep inside Victoria. The crater is named after Emma Dean, John Wesley Powell's wife and one of the boats in Grand Canyon Powell expedition. | https://en.wikipedia.org/wiki?curid=6896320 |
Model spectrum A model spectrum is an artificial spectrum of a star made by recreating the absorption or emission features seen in the spectrum. A model spectrum will usually be of a specific spectral type of star. It may include other properties of the star, such as a surrounding nebula, presence or lack of an extended atmosphere, or a circumstellar dust disc. | https://en.wikipedia.org/wiki?curid=6897217 |
Arcturus moving group In astronomy, the or Arcturus stream is a moving group or stellar stream which includes the nearby bright star Arcturus. It comprises many stars which share similar proper motion and so appear to be physically associated. This group of stars is not in the plane of the Milky Way galaxy, and has been proposed as a remnant of an ancient dwarf satellite galaxy, long since disrupted and assimilated into the Milky Way. It consists of old stars deficient in heavy elements. However, Bensby and colleagues, in analysing chemical composition of F and G dwarf stars in the solar neighbourhood, found there was no difference in chemical makeup of stars from the stream, suggesting an intragalactic rather than extragalactic origin. One possibility is that the stream appeared in a manner similar to the Hercules group, which is hypothesized to have formed due to Outer Lindblad Resonance with the Galactic bar. However, it is unclear how this could produce an overdensity of stars in the thick disk. Research from the RAdial Velocity Experiment (RAVE) at the Australian Astronomical Observatory, headed by Quentin Parker, was the first to quantify the nature of the group, though astronomers had known of its existence for some time. It was first discovered in 1971. Other members include the red giant κ Gruis and the M-class stars 27 Cancri, Alpha Vulpeculae and RT Hydrae. | https://en.wikipedia.org/wiki?curid=6902178 |
PP-format The (Post Processing Format) is a proprietary file format for meteorological data developed by the Met Office, the United Kingdom's national weather service. Simulations of the weather are performed by the Met Office's Unified Model, which can be used for Numerical Weather Prediction or Climatology, and data is collected. This data is usually meteorological in nature and may include averaged data for parameters like global surface temperatures or accumulations of rainfall for locations inside the model, though the Unified Model is capable of outputting many sophisticated diagnostics to PP-format. These files are binary streams, structured in a proprietary file format which can then be processed and transformed into other, more portable, formats. The main reason for using such a format is to increase the rate at which data can be written from the model to disk, a major consideration when running a simulation that must be timely and efficient. | https://en.wikipedia.org/wiki?curid=6903681 |
Morainic drift is the movement of rock debris (talus) (see also Moraine) left by glaciers. | https://en.wikipedia.org/wiki?curid=6904118 |
Spur (botany) The botanical term “spur” is given to outgrowths of tissue on different plant organs. The most common usage of the term in botany refers to nectar spurs in flowers. | https://en.wikipedia.org/wiki?curid=6905141 |
Infrared cirrus are filamentary structures seen in space that emit infrared light. The name is given because the structures are cloud-like in appearance. These structures were first detected by the Infrared Astronomy Satellite at wavelengths of 60 and 100 micrometres. | https://en.wikipedia.org/wiki?curid=6905556 |
Westmorland Geological Society The is a body based in the Lake District region of the UK that aims to engage all those interested in geology, particularly in the southern Lakes. The Society was founded in 1973 and continues to hold a programme of lectures during the winter in Kendal and summer field excursions, looking at the field geology of the Lake District and beyond. | https://en.wikipedia.org/wiki?curid=6915490 |
Autoinoculation is derived from the Latin root words "autos" and "inoculate" that mean "self implanting" or "self infection" or "implanting something from oneself". can refer to both beneficial medical procedures (e.g. vaccination) as well as non-beneficial or harmful natural processes (e.g. infection or disease). One beneficial autoinoculation medical procedure is when cells are removed from a person's body, medically altered then reinserted ("implanted" or "infected") into the same organism or person again to achieve some diagnostic or treatment aim. For example, stem cell treatments involve the harvesting of stem cells from one's own bone marrow and reintroduction (autoinoculation) of those cells at a later date, sometimes after altering those stem cells. may also be used for the transplantation of a patient's own healthy bone marrow after recovering from a condition afflicting the tissue. can also refer to the process by which viruses reproduce themselves within an organism by implanting themselves in an organism's cells, altering the metabolism, DNA repair, and replication processes of those cells, using those processes to reproduce and transmit itself throughout the organism. For example, warts and Molluscum contagiosum can be spread by this method if wart tissue cells (skin cells altered by a papillomavirus) are mechanically transported to another part of the body | https://en.wikipedia.org/wiki?curid=6917217 |
Autoinoculation This transmission or autoinoculation of the wart can occur by mechanical touching of one part of the organism to another, friction that removes a portion of the infected cells to an external surface (or another organism) and then reintroduces those cells upon contact with the body elsewhere, or when wart cells or tissue are transported though the blood stream of an organism. | https://en.wikipedia.org/wiki?curid=6917217 |
Biological constraints are factors which make populations resistant to evolutionary change. One proposed definition of constraint is "A property of a trait that, although possibly adaptive in the environment in which it originally evolved, acts to place limits on the production of new phenotypic variants." Constraint has played an important role in the development of such ideas as homology and body plans. Any aspect of an organism that has not changed over a certain period of time could be considered to provide evidence for "constraint" of some sort. To make the concept more useful, it is therefore necessary to divide it into smaller units. First, one can consider the pattern of constraint as evidenced by phylogenetic analysis and the use of phylogenetic comparative methods; this is often termed phylogenetic inertia, or phylogenetic constraint. It refers to the tendency of related taxa sharing traits based on phylogeny. Charles Darwin spoke of this concept in his 1859 book "On the Origin of Species", as being "Unity of Type" and went on to explain the phenomenon as existing because organisms do not start over from scratch, but have characteristics that are built upon already existing ones that were inherited from their ancestors; and these characteristics likely limit the amount of evolution seen in that new taxa due to these constraints. If one sees particular features of organisms that have not changed over rather long periods of time (many generations), then this could suggest some constraint on their ability to change (evolve) | https://en.wikipedia.org/wiki?curid=6920635 |
Biological constraints However, it is not clear that mere documentation of lack of change in a particular character is good evidence for constraint in the sense of the character being unable to change. For example, long-term stabilizing selection related to stable environments might cause stasis. It has often been considered more fruitful, to consider constraint in its causal sense: what are the causes of lack of change? The most common explanation for biological constraint is that stabilizing selection acts on an organism to prevent it changing, for example, so that it can continue to function in a tightly-defined niche. This may be considered to be a form of external constraint, in the sense that the organism is constrained not by its makeup or genetics, but by its environment. The implication would be that if the population was in a new environment, its previously constrained features would potentially begin to evolve. Related to the idea of stabilizing selection is that of the requirement that organisms function adequately in their environment. Thus, where stabilizing selection acts because of the particular niche that is occupied, mechanical and physico-chemical constraints act in a more general manner. For example, the acceleration caused by gravity places constraints on the minimum bone density and strength for an animal of a particular size. Similarly, the properties of water mean that tissues must have certain osmotic properties in order to function properly | https://en.wikipedia.org/wiki?curid=6920635 |
Biological constraints Functional coupling takes the idea that organisms are integrated networks of functional interactions (for example, the vertebral column of vertebrates is involved in the muscle, nerve, and vascular systems as well as providing support and flexibility) and therefore cannot be radically altered without causing severe functional disruption. This may be viewed as one type of trade-off. As Rupert Riedl pointed out, this degree of functional constraint — or burden — generally varies according to position in the organism. Structures literally in the centre of the organism — such as the vertebral column — are often more burdened than those at the periphery, such as hair or toes. This class of constraint depends on certain types of phenotype not being produced by the genotype (compare stabilizing selection, where there is no constraint on what is produced, but rather on what is naturally selected). For example, for a highly homozygous organism, the degree of observed phenotypic variability in its descendants would be lower than those of a heterozygous one. Similarly, developmental systems may be highly canalised, to prevent the generation of certain types of variation. Although they are separate, the types of constraints discussed are nevertheless relatable to each other. In particular, stabilizing selection, mechanical, and physical constraints might lead through time to developmental integration and canalisation | https://en.wikipedia.org/wiki?curid=6920635 |
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