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58,264,058 | https://en.wikipedia.org/wiki/Measurable%20acting%20group | In mathematics, a measurable acting group is a special group that acts on some space in a way that is compatible with structures of measure theory. Measurable acting groups are found in the intersection of measure theory and group theory, two sub-disciplines of mathematics. Measurable acting groups are the basis for the study of invariant measures in abstract settings, most famously the Haar measure, and the study of stationary random measures.
Definition
Let be a measurable group, where denotes the -algebra on and the group law. Let further be a measurable space and let be the product -algebra of the -algebras and .
Let act on with group action
If is a measurable function from to , then it is called a measurable group action. In this case, the group is said to act measurably on .
Example: Measurable groups as measurable acting groups
One special case of measurable acting groups are measurable groups themselves. If , and the group action is the group law, then a measurable group is a group , acting measurably on .
References
Group theory
Measure theory | Measurable acting group | [
"Mathematics"
] | 223 | [
"Group theory",
"Fields of abstract algebra"
] |
58,264,540 | https://en.wikipedia.org/wiki/Heok%20Hee%20Ng | Heok Hee Ng is a Singaporean ichthyologist and researcher of biodiversity at the Lee Kong Chian Natural History Museum of the National University of Singapore. He specialises in Asian catfish systematics with particular focus on sisoroid catfishes. As of 2018, Ng authored 14 species of Siluriformes
Publications
Ng has (co-)authored many publications.
See Wikispecies below.
Taxon described by him
See :Category:Taxa named by Heok Hee Ng
References
External links
Living people
Taxon authorities
Singaporean ichthyologists
Year of birth missing (living people) | Heok Hee Ng | [
"Biology"
] | 118 | [
"Taxon authorities",
"Taxonomy (biology)"
] |
56,530,120 | https://en.wikipedia.org/wiki/Jean%20Cerf | Jean Cerf (born 1928) is a French mathematician, specializing in topology.
Education and career
Jean Cerf was born in Strasbourg, France, in 1928. He studied at the École Normale Supérieure, graduating in sciences in 1947. After passing his agrégation in mathematics in 1950, he obtained a doctorate with thesis supervised by Henri Cartan. Cerf became a maître de conférences at the University of Lille and was later appointed a professor at the University of Paris XI. He was also a director of research at CNRS.
Cerf's research deals with differential topology, cobordism, and symplectic topology. In 1966 he was an Invited Speaker at the ICM in Moscow. In 1968 Cerf proved that every orientation-preserving diffeomorphism of is isotopic to the identity. In 1970 Cerf proved the pseudo-isotopy theory for simply connected manifolds. In 1970 he was awarded the prix Servant, together with Bernard Malgrange and André Néron (for independent work). 1971 he was the president of the Société Mathématique de France.
Selected publications
" Groupes d'automorphismes et groupes de difféomorphismes des variétés compactes de dimension 3." Bull. Soc. Math. France 87 (1959): 319–329.
"Topologie de certains espaces de plongements." Bull. Soc. Math. France 89, no. 196 (1961): 227–380.
"Théorèmes de fibration des espaces de plongements. Applications." Séminaire Henri Cartan 15 (1962): 1–13.
"Travaux de Smale sur la structure des variétés." Seminaire Bourbaki 7 (1962): 113–128.
"La nullité de Γ4, généralisation du théorème de Schönflies pour S2." In Sur les difféomorphismes de la sphère de dimension trois (Γ4= O), pp. 1–10. Springer, Berlin, Heidelberg, 1968.
"La stratification naturelle des espaces de fonctions différentiables réelles et le théoreme de la pseudo-isotopie." Publications Mathématiques de l'Institut des Hautes Études Scientifiques 39, no. 1 (1970): 7–170.
References
1928 births
Living people
20th-century French mathematicians
21st-century French mathematicians
École Normale Supérieure alumni
Academic staff of the University of Paris
Topologists
Academic staff of the Lille University of Science and Technology | Jean Cerf | [
"Mathematics"
] | 538 | [
"Topologists",
"Topology"
] |
56,530,524 | https://en.wikipedia.org/wiki/Apama%20%28software%29 | Apama is a complex event processing (CEP) and event stream processing (ESP) engine, developed by Software AG. Apama serves as a platform for performing streaming analytics over a range of high volume/low latency inputs and applications, such as IoT devices, financial exchanges, fraud detection, social media and similar.
History
Apama Ltd. was founded in 1999 by Dr John Bates, Dr Giles Nelson and Dr Mohamad Afshar, who met while undertaking research at the Cambridge University Department of Computer Science and Technology. It was acquired by Progress Software for $25 million in 2005. In 2013, Software AG acquired it from Progress for an undisclosed amount.
See also
Complex event processing (CEP) - A related technology for building and managing event-driven information systems.
Data Stream Management System (DSMS) - A type of software system for managing and querying data streams
Event correlation
Event-driven architecture — (EDA) is a software architecture pattern promoting the production, detection, consumption of, and reaction to events.
Event stream processing — (ESP) is a related technology that focuses on processing streams of related data.
Operational intelligence — Both CEP and ESP are technologies that underpin operational intelligence.
Pattern matching
Real-time business intelligence — Business Intelligence is the application of knowledge derived from CEP system
References
Events (computing) | Apama (software) | [
"Technology"
] | 275 | [
"Information systems",
"Events (computing)"
] |
56,531,421 | https://en.wikipedia.org/wiki/Temporal%20light%20artefacts | Temporal light artefacts (TLAs) are undesired effects in the visual perception of a human observer induced by temporal light modulations. Two well-known examples of such unwanted effects are flicker and stroboscopic effect. Flicker is a directly visible light modulation at relatively low frequencies (< 80 Hz) and small intensity modulation levels. Stroboscopic effect may become visible for a person when a moving object is illuminated by modulated light at somewhat higher frequencies (>80 Hz) and larger intensity variations.
Relevance
Various scientific committees have assessed the potential health, performance and safety-related aspects resulting from temporal light modulations. TLAs must be limited to certain levels to avoid annoyance due to the direct visibility by humans and to prevent potential health issues. After longer exposure, TLAs may reduce task performance and cause fatigue. Possible health effects for specific persons are photosensitive epileptic seizure, migraine and aggravation of autistic behavior. The incorrect perception of the motion of an object due to stroboscopic effect may be unacceptable in working environments with fast moving or rotating machinery.
Types
TLAs are generally unwanted effects that may be perceived by humans due to the fact that the light output of a lighting equipment varies with time. Different TLA phenomena, the associated terms and definitions and their visibility aspects are given in a technical note of CIE; see CIE TN 006:2016. In CIE TN 006:2016 three types of TLAs are distinguished:
Flicker refers to unacceptable (irritating) light variation of a light source that is perceived by an average person, either directly or via a reflecting surface ;
Stroboscopic effect is an unwanted effect which may become visible for an average person when a moving or rotating object is illuminated by a time-modulated light source;
Phantom array (or ghosting) may be perceived by an average person when making an eye saccade over a small light source having a periodic fluctuation, the light source is then perceived as a series of spatially extended light spots.
Further background and explanations on the different TLA phenomena are given in a recorded webinar "Is it all just flicker?". Models for the visibility of flicker and stroboscopic effect from the temporal behavior of luminous output of LEDs are in the doctoral thesis of Perz.
Root causes
The root cause of TLAs is the variation of the light intensity of lighting equipment. Important factors that can contribute and that determine the magnitude and type of light modulation of lighting equipment are:
Light source technology: LEDs do not intrinsically produce temporal modulation; they just reproduce the input current waveform very well, and any ripple in the current waveform is reproduced by a light ripple because LEDs have a fast response; therefore compared to conventional lighting technologies (incandescent, fluorescent), for LED lighting more variety in the TLA properties is seen.
Power source technology (driver, electrical ballast): Many types and topologies of LED drivers and electrical ballasts are applied; simpler electronics and limited or no buffer capacitors often result in larger residual current ripple and thus larger temporal light modulation.
Light regulation: Dimming technologies of either externally applied dimmers (incompatible dimmers) or internal light-level regulators may have a large impact.; the level of temporal light modulation generally increases at lower light levels.
Mains voltage fluctuations: Electrical mains voltage variations are caused by switching or varying loads of electrical apparatus connected to the mains network, or may be intentionally applied e.g. for power-line communication.
Visible light communication technologies: Intentional temporal light modulations like LiFi can be applied, e.g. for communication purposes; these additional TLMs may give rise to unwanted TLAs.
Metrics
Several simple metrics such as Modulation Depth, Flicker Index and Flicker Percentage are often used to assess the acceptability of flicker. None of these metrics are suitable to objectively assess the visibility and acceptability of TLAs by humans. Human perception of TLAs is impacted by various factors: modulation depth, frequency, wave shape and duty cycle.
More advanced metrics have been developed and validated to objectively assess the visibility of TLAs:
for flicker, the short-term flicker indicator PstLM,
for stroboscopic effect, the stroboscopic effect visibility measure SVM.
For flicker also two alternative measures are derived to measure its visibility, the Flicker Visibility Measure FVM and the Time domain Flicker Visibility Measure TFVM.
NOTE - The application of the SVM-metric is limited for human perception of stroboscopic effect in normal application environments (residential, office) where the speed of movement of persons and/or objects is limited. For phantom array effect no metric has been defined yet.
Measurement methods
Standardised test and measurement methods
Measurement of PstLM, and optionally testing effect of mains voltage fluctuations or dimming: see IEC TR 61547-1, edition 3;
Measurement of SVM, and optionally testing effect of dimming: see IEC TR 63158;
TLA: Test Methods and Guidance for Acceptance Criteria, see NEMA 77-2017;
Guidance on the measurement of temporal light modulation of light sources and lighting systems: see CIE TN 012
Recommended limits
Recommended limits for the TLA phenomena flicker and stroboscopic effect are in NEMA 77-2017 publication.
Improper use of cameras for TLA assessment
If smart-phone phone cameras, video cameras or film cameras are used in presence of temporally modulated light, a variety of artefacts may be seen on the picture or on the recording, e.g. vertical or horizontal banding with varying brightness (this category of unwanted effects is temporal light interference - TLI). However, the type of artefact depends very much on the camera technology and camera settings. Different camera's will show different artefacts depending on type of shutter, picture frame rate and on the mitigation measures taken in the camera. Apart from the possible variety of effects that can be seen, there is also a difference between what people perceive directly compared to what people perceive via a camera and display or monitor. Hence, usage of common cameras is not a valid and objective means to assess the potential TLA from lighting equipment.
See also
Temporal light effects
Temporal light interference
Flicker (light)
Stroboscopic effect (lighting)
Stroboscopic effect
References
Further reading
LightingEurope TLA position paper, LightingEurope Position Paper on Flicker and Stroboscopic Effect (Temporal Light Artefacts), September 2016;
NEMA TLA position paper, Temporal Light Artifacts (Flicker and Stroboscopic Effects), 15 June 2015;
ZVEI information paper, Temporal Light Artefacts – TLA, March 2017 (in German and English);
CIE Technical Note CIE TN 008:2017, Final Report CIE Stakeholder Workshop for Temporal Light Modulation Standards for Lighting Systems.
Lighting
Optical illusions | Temporal light artefacts | [
"Physics"
] | 1,402 | [
"Optical phenomena",
"Physical phenomena",
"Optical illusions"
] |
56,531,645 | https://en.wikipedia.org/wiki/Medullary%20thymic%20epithelial%20cells | Medullary thymic epithelial cells (mTECs) represent a unique stromal cell population of the thymus which plays an essential role in the establishment of central tolerance. Therefore, mTECs rank among cells relevant for the development of functional mammal immune system.
T cell precursors rise in bone marrow and migrate through the bloodstream to the thymus for further development. During their maturation in the thymus, they undergo a process called V(D)J recombination which conducts the development of T cell receptors (TCRs). The mechanism of this stochastic process enables on one hand the generation of vast repertoire of TCRs, however, on the other hand causes also origin of so called "autoreactive T cells" which recognize self antigens via their TCRs. Autoreactive T cells must be eliminated from the body or skewed into the T Regulatory cells (TRegs) lineage to prevent manifestations of autoimmunity. mTECs possess the ability to deal with these autoreactive clones via mediation of the processes of central tolerance, namely clonal deletion or T regulatory cells selection, respectively.
N.B.: All the below cited references utilized mouse as a model organism.
Self-antigens generation and presentation
In 1989, two scientific groups came up with the hypothesis that the thymus expresses genes which are in the periphery, strictly expressed by specific tissues (e.g.: Insulin produced by β cells of the pancreas) to subsequently present these so-called "tissue-restricted antigens" (TRAs) from almost all parts of the body to developing T cells in order to test which TCRs recognize self-tissues and can be therefore harmful to the body. It was found, after more than a decade, that this phenomenon is managed specifically by mTECs in the thymus and was named Promiscuous gene expression (PGE).
Autoimmune regulator
Aire is a protein called autoimmune regulator (Aire) which is also specifically expressed by mTECs. and its expression is completely dependent on NF- kappa B signaling pathway. Aire recognizes target genes of TRAs via specific methylation marks and requires about 50 partner molecules for activation of their expression. Moreover, Aire-dependent activation of TRA genes expression is accompanied by formation of DNA double-strand breaks. which probably results in very short lifespan of mTECs between 2–3 days
Mutations of Aire gene in human cause a rare autoimmune disorder called Autoimmune Polyendocrinopathy Candidiasis Ectodermal Distrophy (APECED)., which usually manifests in combination with other autoimmune diseases e.g.: diabetes mellitus type 1. Dysfunction of murine Aire gene results in comparable scenario and therefore mouse is used as the model organism for investigation of APECED.
mTECs in numbers
mTECs as a population are capable to express more than 19000 genes (about 80% of mouse genome) among which approximately 4000 belong to Aire-dependent TRAs. It is important to emphasize that single mTEC expresses about 150 Aire-dependent TRAs and approximately 600 Aire-independent TRAs, indicating that other still unknown PGE regulators exist. Indeed, another protein called Fezf2 was suggested to be the second regulator of PGE.
It was shown that each mTEC expresses stochastically 1-3% of TRA pool. However, more recent studies discovered stable co-expression patterns between TRA genes which are localized in close proximity, suggesting "order in this stochastic process".
Tissues protection against autoreactive T cells
T cell precursors extravasate from the bloodstream in cortico-medullary junction and they first migrate to the thymic cortex, where they undergo construction of TCRs and subsequently a process called T cell positive selection which is mediated by mTEC-related cells: cortical thymic epithelial cells (cTECs). This process verifies, whether newly generated TCRs are functional. About 90% of T cells displays badly rearranged TCRs, they cannot reach the positive selection and they die by neglect in the cortex. The rest starts to express CCR7, which is a receptor for mTEC-generated chemokine CCL21, and migrate after concentration gradient to the thymic medulla to encounter mTECs.
Two modes of central tolerance
mTECs are not only mediators of PGE and "factories of TRAs". They also express high levels of MHC II and costimulatory molecules CD80/CD86 and rank among efficient antigen-presenting cells (APCs). Moreover, they utilize macroautophagy to load self antigens on MHCII molecules. Thus, mTECs are capable to present self-generated TRAs on their MHC molecules to select potential autoreactive T cells. It was published that mTECs mediate clonal deletion (recessive tolerance), via presentation of TRAs, which leads to the apoptosis of autoreactive T cells, as well as they are competent to skew autoreactive T cells into TRegs, also through the presentation of TRAs, which then migrate to the periphery to protect tissues against autoreactive T cells that occasionally avoid selection processes in the thymus (dominant tolerance).
How mTECs discriminate between these two modes of tolerance? It was shown that prospective TRegs interact with presented TRAs with lower affinity than those which are clonally deleted. Furthermore, it was also revealed that specific TRAs skew autoreactive T cells into TRegs with much higher efficiency than they do in the case of clonal deletion.
Antigen transfer in the thymus
mTECs form rare population which is composed of approximately 100000 cells per thymus of 2-week-old mice. Thus, there is low probability of encounter between autoreactive T cell and mTEC. Unidirectional antigen transfer from mTECs to thymic dendritic cells (DCs), which itself can't express TRAs, extends the network of TRA presentation, enables TRA processing by different microenvironments and increases the probability of encounter between autoreactive T cell and its appropriate self-antigen. Moreover, DCs competently induce both recessive and dominant tolerance as well as mTECs.
In contrast, another seminal study reveals that mTECs itself suffice to establish both recessive and dominant tolerance without help of additional APCs.
Development
Subsets
mTEC population is not homogenous and basically could be subdivided into more numerous population of mTECs which express low number of MHCII and CD80/CD86, namely mTECsLo and smaller population of mTECsHi which express higher amounts of these molecules. PGE regulator Aire is expressed only by part of mTECsHi. However, this claim does not mean that mTECsLo don't contribute to PGE, mTECsHi, especially that expressing Aire, are just much more efficient in this process.
There is evidence that mTECsLo serve as precursors of mTECsHi in the embryonic thymus Nevertheless, situation changes after birth, where only part of mTECsLo pool represents immature mTECsHi reservoir and another part is constituted by mature mTECs which are specialized for expression of chemokine CCL21, discussed above. Further subset of mTECsLo pool is formed by terminally differentiated cells called Post- Aire mTECs which already downregulated the expression of Aire, MHCII and CD80/CD86.
mTECs can develop into Thymic mimetic cells, which combine the mTEC identity with lineage specific transcription factors. These cells exhibit the phenotype of differentiated peripheral cells and produce their corresponding TRAs. The most famous example is Hassall's corpuscles.
Progenitor cells
TECs (mTECs and cTECs) originate from the third pharyngeal pouch which is a product of endoderm. Their common origin points to the fact that both mTECs and cTECs rise from one bipotent progenitor. This notion was confirmed by several studies of embryonic thymus. and was further developed by finding that these bipotent progenitors express cTEC markers. Nevertheless, another sources document existence of mTEC unipotent progenitors that express claudin 3 and 4 (Cld3/4). These two opposite findings were interfaced by observation of unipotent mTEC progenitors in the postnatal thymus that previously expressed cTEC markers and concurrently express Cld3/4. On the other hand, several other studies describe appearance of bipotent progenitors in postnatal thymus. Thus, embryonic as well as postnatal thymus might shelter both bipotent TEC or unipotent mTEC progenitors.
Similarly to Aire expression, mTECs development is highly dependent on NF- kappa B signaling pathway.
References
Immunology
Thymus
Epithelial cells | Medullary thymic epithelial cells | [
"Biology"
] | 1,894 | [
"Immunology"
] |
56,533,153 | https://en.wikipedia.org/wiki/TCMTB | (Benzothiazol-2-ylthio)methyl thiocyanate (TCMTB) is a chemical compound classified as a benzothiazole.
Properties
TCMTB is an oily, flammable, red to brown liquid with a pungent odor that is very slightly soluble in water. It decomposes on heating producing hydrogen cyanide, sulfur oxides, and nitrogen oxides. The degradation products are 2-mercaptobenzothiazole (2-MBT) and 2-benzothiazolesulfonic acid.
Uses
TCMTB is used as wideband microbicide, paint fungicide, and paint gallicide. The active substance approved in 1980 in the United States. It is used, for example, in leather preservation, for the protection of paper products, in wood preservatives, and against germs in industrial water.
In the US, TCMTB is used as a fungicide for seed dressing in cereals, safflower, cotton and sugar beet.
It is also used when dealing with fungal problems when extracting hydrocarbons via fracking.
Approval
TCMTB is not an authorized plant protection product in the European Union.
In Germany, Austria and Switzerland, no plant protection products containing this active substance are authorized.
TCMTB contributes to health problems in tannery workers as it is a potential carcinogen, and is a hepatotoxin. It is also a skin sensitizer, and may cause contact dermatitis in those exposed to the poisonous compound. Hence, it is mainly used in developing countries.
References
Benzothiazoles
Thioethers
Thiocyanates
Biocides
Fungicides | TCMTB | [
"Chemistry",
"Biology",
"Environmental_science"
] | 357 | [
"Fungicides",
"Toxicology",
"Functional groups",
"Thiocyanates",
"Biocides"
] |
56,533,582 | https://en.wikipedia.org/wiki/Project%20Andrea | Project Andrea () is the code name of an effort by the military dictatorship of Augusto Pinochet to manufacture sarin gas for use as a weapon against its opponents.
The Lo Curro house
At the beginning of the period of the Military Regime, an electronic and chemical warfare laboratory was installed in the house of Michael Townley and Mariana Callejas in , located at Via Naranja 4925, Vitacura, Chile. The government of Augusto Pinochet had given them that house – three floors, almost 1,000 square meters of building and 5,000 of land – located in the upper part of Santiago, in return for services rendered to the Dirección de Inteligencia Nacional (DINA).
Legally it was not theirs, as it had been acquired by then Army Major Raúl Iturriaga and a DINA lawyer who died in strange circumstances in 1976 under a false identity.
The idea was for it to serve as housing for the married agents and their children, but mainly – because it was not an unconditional gift – for the barracks to operate there, from which subsequent terrorist operations abroad would be prepared. In the DINA this barracks house was called Quetropillán. It had two permanent agents, who served as drivers and assistants, and a secretary, who kept the accounts and assisted the homeowner in administrative tasks. In addition, the team included a gardener, a cook, and two chemists: Francisco Oyarzún and Eugenio Berríos, alias Hermes. The latter two spent the day locked in a laboratory, experimenting with the lethality of sarin gas on mice and rabbits.
Victims
The sarin gas was first manufactured by the DINA in Santiago, and then began to be made in Colonia Dignidad, with its logistical support. It was exported and used to assassinate opponents of the regime both in Chile and abroad. The victims presented the symptoms of a heart attack.
First tests
Sarin manufactured in Chile was used for the first time by Michael Townley against two Peruvian citizens. Townley revealed to Judge Alejandro Madrid that in Chile not only real estate conservator Renato León Zenteno (1976) and Army corporal and DINA agent Manuel Leyton (1977) were murdered with sarin, but also other people whose deaths were made to appear as suicides or strange deaths. Some of these people, according to Townley, were involved in the storage and transport of containers of sarin in the 1970s and early 1980s. One of them would be a doctor or assistant who participated in the autopsies of Renato Zenteno and Corporal Leyton.
Carlos Osorio
Townley told the judge that the Protocol Director of the Chilean Ministry of Foreign Affairs, Carlos Guillermo Osorio, had not committed suicide – as was officially announced in October 1977 – but had been killed. Osorio was in charge of granting passports with false identities so that Army officers – among them, Armando Fernández Larios – could travel to the United States to prepare the attack against Orlando Letelier and two others (Rolando Mosqueira and René Riveros), to try to mislead American intelligence about the authorship of the attack and cover for the DINA. The sources maintain that Townley affirmed that Osorio was another victim of sarin, even though he had been shot once in the head.
Carmelo Soria
Eugenio Berríos played a role in the death of Carmelo Soria, a CEPAL official who was kidnapped by a DINA operative in July 1976 and taken to Townley's house in Lo Curro. There, in the Berríos laboratory, Soria was administered sarin gas, according to the investigation, and was then tortured until his spine was broken. Later, his body was found in a car in the .
This gas was probably used to murder the journalist , who in June 1975 was found dead in circumstances not entirely clear, in the room he occupied in Paris, where he worked at the newspaper L'Humanité. In 1990, the journalist Edwin Harrington published in the magazine Nueva Voz that Lira was murdered by the DINA as part of a plan called Operation France after the arrival in the French capital of "Bernardo Conrads Salazar, identity card No. 4.152.556-6, official of the security service of the dictatorship." Harrington, who cited an FBI report as one of his main sources, argued that Lira's death may have been triggered by sarin gas, which Townley carried on his travels in a bottle of Chanel perfume.
Another suspicious death was that of Alfred Schaak, a representative of Paul Schäfer in Germany in charge of arms trafficking. In 1985, two couples who fled from Colonia Dignidad publicly denounced Schäfer's pedophilia. It seems that Schaak then wanted to denounce the arms trade. To prevent this, Winfried Schmidtke and Helmut Seelbach, who were received at the airport by Schaak, who was in perfect health, would have traveled from Dignidad to Germany. A few days later, in October, Schaak died suddenly. Dr. Hartmut Hopp went immediately to Germany and brought the body of Schaak to Chile. In the assembly of settlers he said that Schaak had died of fever and that in his will he left his property to the Colony. At the same time they reported – ten months after the fact – the escape of the couples, adding that their complaints in Germany had done them great harm.
The subsequent condemnation of Schäfer does not include sarin gas production in Colonia Dignidad, the , nor the Monte Maravilla forced labor camp that the colony maintained, since Judge Jorge Zepeda Arancibia did not include these charges in the ruling that sentenced him to a minimum term of seven years of imprisonment for infraction of the Law on Arms Control.
Simón Bolívar de La Reina barracks
Alexei Jaccard, age 25, was arrested in Buenos Aires on 16 May 1977, along with two other communist militants, by agents of the Argentine dictatorship and the DINA. At that time all traces of them were lost. Despite the efforts made by his family to learn his whereabouts, both in Argentina and in Chile, they only turned up false leads. This changed when three agents, who did not lose their memory or declare themselves insane as their former boss Augusto Pinochet had, gave the judiciary unequivocal information about what happened with Jaccard and the two militants, Ricardo Ramírez Herrera and Héctor Velásquez Mardones. The testimonies coincide in that the three detainees, from Buenos Aires, were taken to the La Reina barracks by "Don Jaime" (alias of Captain Germán Barriga, who committed suicide in 2005) and his agents of Dolphin Group, an elite squad that operated inside the . The director of the DINA, Manuel Contreras, always stated in private and in public that Jaccard, Herrera, and Velásquez were arrested by Argentine intelligence, which had made them disappear by throwing their bodies into the Río de la Plata. But the former agents Eduardo Oyarce Riquelme, Héctor Valdebenito Araya, and Guillermo Ferrán Martínez, all prosecuted for the crimes committed in Simón Bolívar, deny that version, and confirm the passage of Jaccard and his companions through that barracks. Former agent Oyarce recalls another relevant piece of information:
Judicial aspects
On 23 July 2007, Judge Alejandro Madrid undertook "two resolutions that mark milestones in the trials for human rights violations" and that are related to the Andrea Project: "He affirmed that the murder of the ex-Army corporal Manuel Leyton was carried out using sarin gas, and prosecuted thirteen former DINA agents for this crime. He proceeded to prosecute the former Army auditor, Fernando Torres Silva, for conspiracy in the case of the murder with the chemical that produced the poisonous element in the security services, Eugenio Berríos."
FBI investigation
The FBI has evidence confirming that Augusto Pinochet accumulated large amounts of poison gas, according to Saul Landau, the US investigator for the Orlando Letelier murder. The FBI investigated the sarin, and its conclusions were condensed in a report indicating that it was manufactured in an amount sufficient to kill the entire Peruvian Army twice over.
Book La danza de los cuervos
In 2012, Javier Rebolledo published La danza de los cuervos (The Dance of the Crows), a book describing the atrocities committed in the Simón Bolívar barracks. He then premiered the movie El Mocito, in which the experiences of a boy who worked in the Simón Bolívar House of Extermination are related. It details the torture and suffering of the political abductees, and mention is made of the use of sarin gas to exterminate the prisoners.
See also
Operation Condor
Project Coast
Notes
References
1976 in Chile
Colonia Dignidad
Dirección de Inteligencia Nacional
Enforced disappearances in Chile
Military operations involving chemical weapons
Political repression in Chile during the military government (1973–1990)
Political scandals in Chile
Terrorism in Chile
Chemical weapons by country | Project Andrea | [
"Chemistry"
] | 1,860 | [
"Military operations involving chemical weapons",
"Chemical weapons by country",
"Chemical weapons"
] |
56,536,030 | https://en.wikipedia.org/wiki/Webduino | The BPI Bit (also referred to as BPI:bit, stylised as webduino:bit) is an ESP32 with Xtensa 32bit LX6 single/dual-core processor based embedded system
The board is and has an ESP32 module with Xtensa 32bit LX6 single/dual-core processor, with a capacity of up to 600DMIPS, with a built-in 448KB ROM and 520 KB SRAM accelerometer and magnetometer sensors, 2.4G WiFi, Bluetooth and USB connectivity, a display consisting of 25 light-emitting diodes, two programmable buttons, and can be powered by either USB or an external battery pack. The device inputs and outputs are through five ring connectors that are part of the 23-pin edge connector.
BPI:bit provides a wide range of onboard resources, supports photosensitive sensor, digital triaxial sensor, digital compass, temperature sensor interface. Webduino:bit have 25 intelligent control LED light source that the control circuit and RGB chip are integrated in a package of 5050 components. Cascading port transmission signal by single line. Each pixel of the three primary color can achieve 256 brightness display, completed 16777216 color full color display, and scan frequency not less than 400 Hz/s.
BPI:bit use MPU9250 on board, MPU-9250 is a multi-chip module (MCM) consisting of two dies integrated into a single QFN package. One die houses the 3-Axis gyroscope and the 3-Axis accelerometer. The other die houses the AK8963 3-Axis magnetometer from Asahi Kasei Microdevices Corporation. Hence, the MPU-9250 is a 9-axis MotionTracking device that combines a 3-axis gyroscope, 3-axis accelerometer, 3-axis magnetometer and a Digital Motion Processor™ (DMP) all in a small 3x3x1mm package available as a pin-compatible upgrade from the MPU-6515. With its dedicated I2C sensor bus, the MPU-9250directly provides complete 9-axis MotionFusion™ output. The MPU-9250 MotionTracking device, with its 9-axis integration, on-chip MotionFusion™, and runtime calibration firmware, enables manufacturers to eliminate the costly and complex selection, qualification, and system level integration of discrete devices, guaranteeing optimal motion performance for consumers. MPU-9250 is also designed to interface with multiple non-inertial digital sensors, such as pressure sensors, on its auxiliary I²C port.
BPI:bit interface：
BPI:bit for arduino Source code on GitHub: https://github.com/BPI-STEAM
BPI:bit for webduino source code on GitHub: https://github.com/webduinoio
BPI:bit wiki page : http://wiki.banana-pi.org/BPI-Bit
BPI:UNO32 for Webduino & Arduino
The BPI:UNO32 (also referred to as BPI UNO32, stylised as BPI-UNO32), BPI-UNO32 uses the ESP-WROOM-32 of espressif company as MCU. ESP32 is a single-chip solution integrating 2.4 GHz Wi-Fi and Bluetooth dual mode. The 40 nanometer technology of TSMC has the best power consumption, RF performance, stability, versatility and reliability. It can deal with various application scenarios.
Two separate controlled CPU cores, the main frequency can be up to 240 MHz, 448KB ROM, 520KB SRAM.
BPI-UNO32 The appearance size is fully matched with Arduino UNO R3
BPI:UNO32 for arduino Source code on GitHub: https://github.com/BPI-STEAM
BPI-UNO32 BPI wik page : http://wiki.banana-pi.org/BPI-UNO32
BPI:Smart for Webduino & Arduino
The BPI:Smart (also referred to as BPI-Smart, stylised as Webduino Smart), it use ESP8266 design, Webduino official support it. also can support Arduino.
BPI:Smart Board dimensions: 3 cm in length, 2.5 cm in width, 1.3 cm in height, and a weight of 85 grams. Digital pins: 0, 2, 4, 5, 14, and 16. PWM pins: 12, 13, 15. Analog Pin: AD (A0). Other pins: TX, RX, 3.3V, VCC, RST, and GRD.
BPI:Smart has a photocell sensor, an RGB LED, and a micro switch button on board. The photocell is connected to the AD pin, and the RGB (Red, Geen, Blue) LED is connected to pins 15, 12, and 13 respectively (The LED is a common cathode, whereas most of the examples on this site use common anode RGB LED.) And the micro switch button is connected to pin 4. Please take note when you use these pins.
BPI-smart BPI wiki page ： http://wiki.banana-pi.org/BPI-Smart
Arduino
Physical computing | Webduino | [
"Engineering"
] | 1,170 | [
"Physical computing",
"Robotics engineering"
] |
56,536,405 | https://en.wikipedia.org/wiki/Jean-Pierre%20Verdet | Jean-Pierre Verdet (born 1932) is a French astronomer, historian of astronomy and mathematician.
Biography
Jean-Pierre Verdet is a Bachelor of Mathematics. Doctor of Science at Paris Diderot University (1975). In 1963, he entered the Paris Observatory, where, after studying the solar corona, he inaugurated infrared astronomy in France, then studied the radiation of the planets in this wavelength domain. He later became head of the Department of spherical astronomy at Paris Observatory. He has regularly taught the MAS of celestial mechanics at the Observatory, a higher education institution which is authorized to issue doctorates.
He left the Observatory in 1976, he devoted half of his activity to the history of ancient astronomy with the multidisciplinary team he had assembled at the Observatory, to translate Latin, Greek and Arabic astronomical texts. In the field of history of astronomy, in addition to scholarly works, he has authored many books for general public, especially for youth. He was a member of Pierre Marchand’s team that helped to create Gallimard Jeunesse. He wrote (1987), a heavily illustrated pocket book for Gallimard’s encyclopaedic collection "Découvertes", which has been translated into fourteen languages, including English. He has published more than 30 books at Gallimard.
In 1991, he collaborated in the astronomical organisation , with Daniel Kunth and Hubert Reeves on a TV show at France 2. The show lasted 4 hours.
In 2016, the Budget Prize of Académie des Inscriptions et Belles-Lettres was awarded to Michel-Pierre Lerner, and Jean-Pierre Verdet for their 3-volume critical works of Nicolaus Copernicus’ De revolutionibus orbium coelestium.
For this same publication, which is the first critical work of De revolutionibus orbium coelestium translated into French with commentaries, the Alexandre Koyré Medal 2015 of the International Academy of the History of Science was awarded to this team work.
Selected bibliography
The Air Around Us, Moonlight Publishing, 1986
Le ciel, ordre et désordre, collection « Découvertes Gallimard » (nº 26), série Sciences et techniques. Éditions Gallimard, 1987, new edition in 2001
UK edition – The Sky: Order and Chaos, ‘New Horizons’ series. Thames & Hudson, 1992
US edition – The Sky: Mystery, Magic, and Myth, "Abrams Discoveries" series. Harry N. Abrams, 1992
The Earth and Sky, Scholastic, 1992
Earth, Sky and Beyond: A Journey Through Space, Dutton Juvenile, 1995
Penser l’univers, collection « Découvertes Gallimard Texto » (nº 2). Éditions Gallimard, 1998
Collective work
Nicolaus Copernicus, translated by J-P Verdet and others, De revolutionibus orbium coelestium / Des révolutions des orbes célestes, Les Belles Lettres, 2015
References
1932 births
20th-century French astronomers
Historians of astronomy
French non-fiction writers
Living people | Jean-Pierre Verdet | [
"Astronomy"
] | 620 | [
"People associated with astronomy",
"Historians of astronomy",
"History of astronomy"
] |
56,537,774 | https://en.wikipedia.org/wiki/Stephen%20Baker%20%28animal%20behaviorist%29 | Stephen Baker (April 17, 1921, Vienna, Austria-September 13, 2004, Manhattan, New York City) was an animal behaviorist, advertising executive, author and humorist of Austrian origin. He came with his mother and brothers Thomas and Peter from Hungary, April 2, 1940 aboard the S.S. Vulcanin from Italy. In December 1940 he made a Declaration of Intention to become a U.S. citizen at the District Court of Pottawatomie County, Shawnee, Oklahoma. He was a student at the Jewish Teachers Seminary, New York.
He had been born Stefan Bacher in Vienna, Baker, both artist and writer, created the "Let your fingers do the walking" ad campaign for the AT&T Yellow Pages as art director for the advertising agency Cunningham & Walsh.
Baker wrote 22 books on various topics, from "The Systematic Approach to Advertising Creativity" and "Advertising Layout and Art Direction," to "How to Look like Somebody in Business without Being Anybody," "How to Get a Job without Asking for It" and "I Hate Meetings."
"How to Live with a Neurotic Dog", published in 1960, sold more than 200,000 copies.
Other works include "How to Live with a Neurotic Cat" and "How to Play Golf in the Low 120's".
References
1921 births
2004 deaths
Ethologists
Austrian male writers
Austrian humorists
20th-century American zoologists
Austrian emigrants to the United States | Stephen Baker (animal behaviorist) | [
"Biology"
] | 302 | [
"Ethology",
"Behavior",
"Ethologists"
] |
56,538,024 | https://en.wikipedia.org/wiki/Columbia%20Data%20Center | Columbia Data Center is Microsoft's data center in Quincy, Washington. Property at Quincy was purchased in 2006; the building opened in April, 2007; and the data center reached operational status in May, 2007. It was said to be the largest data center in the world as of 2015. The company located there due to low land costs, abundant data fiber, and extremely low cost electricity provided by Grant County PUD for as little as 1.9 or 2.5 cents per kilowatt-hour. Building began with a facility in 2006 and several expansions followed, occupying with of floorspace in two buildings on a complex by 2016.
The data center consumed 30 to 50 megawatts in 2012 and employs 50 people.
References
Buildings and structures in Grant County, Washington
Data centers
Microsoft buildings and structures
2007 establishments in Washington (state)
Infrastructure completed in 2007 | Columbia Data Center | [
"Technology"
] | 174 | [
"Data centers",
"Computers"
] |
56,538,986 | https://en.wikipedia.org/wiki/Ssm%20spooky%20toxin | Spooky toxin (SsTx) is a small peptide neurotoxin. It is found in the venom of Chinese red-headed centipedes (Scolopendra subspinipes mutilans), also known as golden head centipedes. It is originally composed of 76 amino acids (sequence: MEKKIIFLVFLVAL
LALPGFISTEVIKK
DTPYKKRKFPYKSEC
LKACATSFTG
GDESRIQEGKPG
FFKCTCYFTTG, disulfide bonds Cys43-Cys69,
Cys47-Cys71), with a molecular weight of 6017.5 daltons, but loses the first 23 residues and becomes 53 residues long (sequence
EVIKKDTPYKKRKFPYKSECLKACATSFTGGDESRIQEGKPFGFKCTCYFTTG, disulfide bonds Cys20-Cys46, Cys24-Cys48). SsTx is currently thought to be unique to Scolopendra subspinipes mutilans.
By blocking KCNQ channels (preventing potassium from flowing into and out of cells) SsTx disrupts cardiovascular, respiratory, muscular, and nervous systems; where snake venoms typically only affect circulatory or nervous systems, and venom from spiders, scorpions, and snails typically only target nervous systems. This allows for golden headed centipedes to target larger prey up to 15 times their size.
Applications
The venom of the Scolopendra subspinipes mutilans is already being widely used as a traditional medicine in Asian countries. Claimed medicinal uses include antimicrobial, antibacterial, and anticancer.
See also
Charybdotoxin
References
Centipede toxins
Neurotoxins
Ion channel toxins
Potassium channel blockers
Protein toxins | Ssm spooky toxin | [
"Chemistry"
] | 386 | [
"Neurochemistry",
"Protein toxins",
"Neurotoxins",
"Toxins by chemical classification"
] |
64,936,230 | https://en.wikipedia.org/wiki/Ghost%20Gunner | Ghost Gunner is an American desktop CNC mill manufactured in Austin, Texas. It specializes in the making of firearms as well as finishing 0%–80% receivers. It was launched in October 2014 by Cody Wilson and the founders of Defense Distributed.
History
Ghost Gunner began as a limited series of CNC mills produced by Defense Distributed in a crowdfunding sale to its mailing list in October 2014. Spring 2015 shipments sold out almost immediately, and its first media reviewer noted the machine "...worked so well that it may signal a new era in the gun control debate, one where the barrier to legally building an untraceable, durable, and deadly semiautomatic rifle has reached an unprecedented low point in cost and skill."
Products
Since 2014, Ghost Gunner has issued 3 generations of its CNC mill, with the latest being the Ghost Gunner 3. The second version, named Ghost Gunner 2, is open-source hardware, allowing third party manufacturers to sell their own versions.
, Ghost Gunner had sold over 6,000 units worldwide. The most recent version of the Ghost Gunner accepts "Zero Percent Receivers," solid blocks of aluminum that are milled into a partial lower receiver of an AR-15 style rifle. These are in contrast to the 80 percent receivers first released with the Ghost Gunner.
Political controversy
Ghost Gunner is cited by politicians and the media as the most popular machine tool used to produce ghost guns.
In May 2024, San Diego County, joined by The Giffords Law Center, brought suit against Ghost Gunner in California state court arguing that it violated a state law "blocking gun-making milling machines" in developing and selling the Coast Runner CNC.
References
External links
Ghost Gunner and "zero percent" Receivers
Companies established in 2014
Firearm construction
Numerical control
Open-source hardware | Ghost Gunner | [
"Engineering"
] | 363 | [
"Firearm construction",
"Mechanical engineering"
] |
64,946,153 | https://en.wikipedia.org/wiki/LASCNN%20algorithm | In graph theory, LASCNN is a Localized Algorithm for Segregation of Critical/Non-critical Nodes The algorithm works on the principle of distinguishing between critical and non-critical nodes for network connectivity based on limited topology information. The algorithm finds the critical nodes with partial information within a few hops.
This algorithm can distinguish the critical nodes of the network with high precision, indeed, accuracy can reach 100% when identifying non-critical nodes. The performance of LASCNN is scalable and quite competitive compared to other schemes.
Pseudocode
The LASCNN algorithm establishes a -hop neighbor list and a duplicate free pair wise connection list based on -hop information. If the neighbors stay connected then the node is non-critical.
Function LASCNN(MAHSN)
For ∀ A ∈ MAHSN
If (A->ConnList.getSize() == 1) then
A->SetNonCritical() = LEAF
Else
Continue = TRUE
While (Continue == TRUE)
Continue = FALSE
For ∀ ActiveConn ∈ ConnList
If (A∉ActiveConn) then
If (A->ConnNeighbors.getSize() == 0)
A->ConnNeighbors.add(ActiveConn)
Continue = TRUE
else
If (ActiveConn ∩ ConnNeighbors == TRUE)
ActiveConn ∪ ConnNeighbors
Continue = TRUE
Endif
Endif
Endif
End For
End While
Endif
If (A->ConnNeighbors.getSize() < A->Neighbors.getSize())
A->SetCritical() = TRUE
else
A->SetNonCritical() = INTERMEDIATE
Endif
End For
End Function
Implementation
The Critical Nodes application is a Free Open-Source implementation for the LASCNN algorithm. The application was developed in 2013 using Programming Without Coding Technology software.
See also
Connectivity (graph theory)
Dynamic connectivity
Strength of a graph
Cheeger constant (graph theory)
Critical point (network science)
Depth-first search
Breadth-first search
References
External links
Critical Nodes application
Networks
Network theory
Graph algorithms | LASCNN algorithm | [
"Mathematics"
] | 431 | [
"Network theory",
"Mathematical relations",
"Graph theory"
] |
64,946,914 | https://en.wikipedia.org/wiki/Jocic%20reaction | In organic chemistry, the Jocic reaction, also called the Jocic–Reeve reaction (named after Zivojin Jocic and Wilkins Reeve) is a name reaction that generates α-substituted carboxylic acids from trichloromethylcarbinols and corresponding nucleophiles in the presence of sodium hydroxide. The reaction involves nucleophilic displacement of the hydroxyl group in a 1,1,1-trichloro-2-hydroxyalkyl structure with concomitant conversion of the trichloromethyl portion to a carboxylic acid or other acyl group.
The key stages of the reaction involve an SN2 reaction, where the nucleophile displaces the oxygen with geometric inversion.
Mechanism
The reaction mechanism involves an epoxide intermediate that undergoes an SN2 reaction by the nucleophile. As a result of this mechanistic aspect, the reaction can easily occur on secondary or tertiary positions, and chiral products can be made by using chiral alcohol substrates. The reaction is one stage of the Corey–Link reaction, the Bargellini reaction, and other processes for synthesizing α-amino acids and related structures. Using hydride as the nucleophile, which also reduces the carbonyl of the product, allows this sequence to be used as a homologation reaction for primary alcohols.
Scope
Examples of this reaction include: Generation of α-azidocarboxylic acids with the use of sodium azide as the nucleophile in DME with the presence of sodium hydroxide.Conversion of aldehydes to homoelongated carboxylic acids, by first reacting with trichloromethide to form a trichloromethylcarbinol, then undergoing a Jocic reaction with either sodium borohydride or sodium phenylseleno(triethoxy)borate as the nucleophile in sodium hydroxide. This reaction can be followed by the introduction of an amine, to form the corresponding homoelongated amides.
References
Name reactions
Substitution reactions | Jocic reaction | [
"Chemistry"
] | 448 | [
"Name reactions"
] |
64,949,119 | https://en.wikipedia.org/wiki/Sandra%20Mitchell%20Hedetniemi | Sandra Lee "Sandee" Mitchell Hedetniemi (; born July 5, 1949) is an American mathematician and computer scientist, known for her research in graph theory and algorithms on graphs. She is a professor of computer science at Clemson University.
Education and career
Hedetniemi majored in applied mathematics at Centre College in Kentucky, graduating in 1971. She completed a Ph.D. in computer science in 1977 at the University of Virginia under the supervision of Stephen T. Hedetniemi. Her dissertation was Algorithms on Trees and Maximal Outerplanar Graphs: Design, Complexity Analysis, and Data Structures Study.
She joined the University of Louisville faculty as an instructor in applied mathematics and computer science 1973, and became an assistant professor there in 1975. She moved to the department of computer and information science at the University of Oregon in 1978, and was given tenure there in 1981. In 1982 she moved again to Clemson University, taking a half-time position as an associate professor of computer science, and she was promoted to full professor in 1994.
Personal life
Hedetniemi is originally from Louisville, Kentucky; her father, Wilber A. Mitchell, was a US Navy veteran, psychiatrist, and hospital administrator. She married Stephen T. Hedetniemi, her former advisor, in 1979, when both were faculty members at the University of Oregon.
References
External links
Home page
1949 births
Living people
Scientists from Louisville, Kentucky
American computer scientists
American women computer scientists
20th-century American mathematicians
21st-century American mathematicians
Graph theorists
Centre College alumni
University of Virginia alumni
University of Louisville faculty
University of Oregon faculty
Clemson University faculty
Mathematicians from South Carolina
20th-century American women mathematicians
21st-century American women mathematicians | Sandra Mitchell Hedetniemi | [
"Mathematics"
] | 347 | [
"Mathematical relations",
"Graph theory",
"Graph theorists"
] |
64,951,967 | https://en.wikipedia.org/wiki/Lectures%20in%20Geometric%20Combinatorics | Lectures in Geometric Combinatorics is a textbook on polyhedral combinatorics. It was written by Rekha R. Thomas, based on a course given by Thomas at the 2004 Park City Mathematics Institute, and published by the American Mathematical Society and Institute for Advanced Study in 2006, as volume 33 of their Student Mathematical Library book series.
Topics
The 14 chapters of the book can be grouped into two parts, with the first 2/3 of the book concerning the combinatorial properties of convex polytopes and the remainder connecting these topics to abstract algebra.
The topics covered include Schlegel diagrams and Gale diagrams, irrational polytopes, point set triangulations, regular triangulations and their polyhedral representation by secondary polytopes, the permutohedron as an example of a secondary polytope, Gröbner bases, toric ideals, and toric varieties, and the connections between Gröbner bases of toric ideals and regular triangulations of points.
Audience and reception
Although originally presented as an advanced undergraduate course, the book is also suitable for graduate students and for researchers interested in beginning work in this area. It requires only an undergraduate level of background material in mathematics (particularly linear algebra), and includes exercises making it suitable as a textbook. Reviewers Miklós Bóna and Alexander Zvonkin suggest it as a "quick introduction" to its topics, after which other books on the same topics can provide greater depth.
See also
List of books about polyhedra
References
Polyhedral combinatorics
Mathematics textbooks
2006 non-fiction books
Books of lectures | Lectures in Geometric Combinatorics | [
"Mathematics"
] | 324 | [
"Polyhedral combinatorics",
"Combinatorics"
] |
64,952,415 | https://en.wikipedia.org/wiki/Pharmacovigilance%20Programme%20of%20India | The Pharmacovigilance Programme of India (PvPI) is an Indian government organization which identifies and responds to drug safety problems. Its activities include receiving reports of adverse drug events and taking necessary action to remedy problems. The Central Drugs Standard Control Organisation established the program in July 2010 with All India Institute of Medical Sciences, New Delhi as the National Coordination Centre, which later shifted to Indian Pharmacopoeia Commission in Ghaziabad on 15 April 2011.
History
Many developed countries set up their pharmacovigilance programs following the Thalidomide scandal in the 1960s. India set up its program in the 1980s. This general concept of drug safety monitoring went through different forms, but the Central Drugs Standard Control Organisation established the present Pharmacovigilance Program of India in 2010. Now the program is well integrated with government legislation, a regulator as leader, and a research center as part of the Indian Pharmacopoeia Commission.
Activities
As of 2018 there were 250 centers around India capable of responding to reports of serious adverse reactions. One of the challenges of the organization is training doctors and hospitals to report adverse drug reactions when patients have them. The Pharmacovigilance Program makes these reports itself, but ideally, such reports could originate from any clinic. The Pharmacovigilance Programme seeks to encourage a culture and social expectation of reporting drug problems.
One of the successes of the program was detecting adverse effects of people in India using carbamazepine. While this drug is safer among people native to the Europe, people of South Asia have different genetics and are more likely to experience problems when using it. Other countries could not have been able to detect this problem, and the Pharmacovigilance Programme's detection of it was a success story.
Collaboration
The establishment of the Pharmacovigilance Program made India a more attractive international destination for foreign companies to bring clinical trials research. Understanding the quality of India's pharmacovigilance programme is key to international researchers conducting trials in India.
The program collaborates both in India and internationally with the World Health Organization on projects for safe medication. As a collaborating center, the Pharmacovigilance Programme assists the WHO in developing international policy for other countries to manage their own drug safety programs.
While the United States and Europe have pharmacovigilance systems which are developed well in some ways, the Indian programme has more and specialized expertise to apply for the unique circumstances of India. The Pharmaceutical industry in India produces more drugs than any other national industry. Because of the large amount of drugs and the many countries which import them, the Indian program monitors in some ways more than anywhere else.
References
External links
Drug safety
Pharmaceuticals policy
Medical and health organisations based in India
National agencies for drug regulation
Regulators of biotechnology products
Regulatory agencies of India
Ministry of Health and Family Welfare | Pharmacovigilance Programme of India | [
"Chemistry",
"Biology"
] | 581 | [
"Biotechnology products",
"Regulation of biotechnologies",
"National agencies for drug regulation",
"Regulators of biotechnology products",
"Drug safety"
] |
64,953,991 | https://en.wikipedia.org/wiki/KissAnime | KissAnime was an anime-focused file streaming website that hosted links and embedded videos, allowing users to stream or download movies and TV shows illegally for free. It was a sister site to a related manga viewing website, KissManga. KissAnime was described as "one of the world’s biggest streaming anime websites". TorrentFreak reported that the sites had audiences of millions and that, for a time, KissAnime was "the most visited pirate site in the world".
History
In mid-2017 the site was a target of a subpoena by US company Funimation Global Group, which described its actions as aimed at "someone... disseminating infringing content on a MASSIVE scale, for profit."
In December 2018, the site was blocked in Australia. It was also blocked in India in July 2020, along with other pirate streaming and torrent websites, after a decision by the Delhi High Court in favour of the plaintiff, Disney India. The court order provided for "dynamic" blocking meaning that Disney could ask for further bans on websites violating copyrights other than the ones in the order.
The website, as well as KissManga, was shut down on 14 August 2020 (the .com website had been registered in 2012 and a more recent .ru domain in 2016), and it has been suggested this was done due to copyright complaints, and the threat of the new, stricter Japanese laws on online piracy.
Reactions
The site has been criticized for its copyright infringement and occasionally for advertisements that contained malware, but it has been praised for popularizing anime and manga, and for providing access to content that is not legally available in certain areas, particularly in parts of Europe, Southeast Asia and India.
Its main site, KissAnime.ru, was shut down on 14 August 2020. One commentator noted that "fans are furious" as "in many countries they really have nowhere to go" for the kind of content that was hosted on the site. Another commentator has described the outcome as both "a major strike to media piracy [and] a blow to the history of anime", noting that the website has also been an archive of rare titles, such as the 1993 original video animation, Battle Angel. Many of the works that have been available on the website can be considered lost, as not only are many titles not distributed legally in many countries, but in some cases, they are only available on physical media, which is subject to degradation over time, and are not possible to legally stream anywhere in the world.
See also
References
Anime and manga websites
File sharing communities
Defunct websites
Internet properties disestablished in 2020
Internet properties established in 2012
Internet censorship in India
Internet services shut down by a legal challenge | KissAnime | [
"Technology"
] | 557 | [
"File sharing communities",
"Computing websites"
] |
64,956,453 | https://en.wikipedia.org/wiki/Leavitt%20path%20algebra | In mathematics, a Leavitt path algebra is a universal algebra constructed from a directed graph. Leavitt path algebras generalize Leavitt algebras and may be considered as algebraic analogues of graph C*-algebras.
History
Leavitt path algebras were simultaneously introduced in 2005 by Gene Abrams and Gonzalo Aranda Pino as well as by Pere Ara, María Moreno, and Enrique Pardo, with neither of the two groups aware of the other's work. Leavitt path algebras have been investigated by dozens of mathematicians since their introduction, and in 2020 Leavitt path algebras were added to the Mathematics Subject Classification with code 16S88 under the general discipline of Associative Rings and Algebras.
The basic reference is the book Leavitt Path Algebras.
Graph terminology
The theory of Leavitt path algebras uses terminology for graphs similar to that of C*-algebraists, which differs slightly from that used by graph theorists. The term graph is typically taken to mean a directed graph consisting of a countable set of vertices , a countable set of edges , and maps identifying the range and source of each edge, respectively. A vertex is called a sink when ; i.e., there are no edges in with source . A vertex is called an infinite emitter when is infinite; i.e., there are infinitely many edges in with source . A vertex is called a singular vertex if it is either a sink or an infinite emitter, and a vertex is called a regular vertex if it is not a singular vertex. Note that a vertex is regular if and only if the number of edges in with source is finite and nonzero. A graph is called row-finite if it has no infinite emitters; i.e., if every vertex is either a regular vertex or a sink.
A path is a finite sequence of edges with for all . An infinite path is a countably infinite sequence of edges with for all . A cycle is a path with , and an exit for a cycle is an edge such that and for some . A cycle is called a simple cycle if for all .
The following are two important graph conditions that arise in the study of Leavitt path algebras.
Condition (L): Every cycle in the graph has an exit.
Condition (K): There is no vertex in the graph that is on exactly one simple cycle. Equivalently, a graph satisfies Condition (K) if and only if each vertex in the graph is either on no cycles or on two or more simple cycles.
The Cuntz–Krieger relations and the universal property
Fix a field . A Cuntz–Krieger -family is a collection in a -algebra such that the following three relations (called the Cuntz–Krieger relations) are satisfied:
(CK0) for all ,
(CK1) for all ,
(CK2) whenever is a regular vertex, and
(CK3) for all .
The Leavitt path algebra corresponding to , denoted by , is defined to be the -algebra generated by a Cuntz–Krieger -family that is universal in the sense that whenever is a Cuntz–Krieger -family in a -algebra there exists a -algebra homomorphism with for all , for all , and for all .
We define for , and for a path we define and . Using the Cuntz–Krieger relations, one can show that
Thus a typical element of has the form for scalars and paths in . If is a field with an involution (e.g., when ), then one can define a *-operation on by that makes into a *-algebra.
Moreover, one can show that for any graph , the Leavitt path algebra is isomorphic to a dense *-subalgebra of the graph C*-algebra .
Examples
Leavitt path algebras has been computed for many graphs, and the following table shows some particular graphs and their Leavitt path algebras. We use the convention that a double arrow drawn from one vertex to another and labeled indicates that there are a countably infinite number of edges from the first vertex to the second.
Correspondence between graph and algebraic properties
As with graph C*-algebras, graph-theoretic properties of correspond to algebraic properties of . Interestingly, it is often the case that the graph properties of that are equivalent to an algebraic property of are the same graph properties of that are equivalent to corresponding C*-algebraic property of , and moreover, many of the properties for are independent of the field .
The following table provides a short list of some of the more well-known equivalences. The reader may wish to compare this table with the corresponding table for graph C*-algebras.
The grading
For a path we let denote the length of . For each integer we define . One can show that this defines a -grading on the Leavitt path algebra and that with being the component of homogeneous elements of degree . It is important to note that the grading depends on the choice of the generating Cuntz-Krieger -family . The grading on the Leavitt path algebra is the algebraic analogue of the gauge action on the graph C*-algebra , and it is a fundamental tool in analyzing the structure of .
The uniqueness theorems
There are two well-known uniqueness theorems for Leavitt path algebras: the graded uniqueness theorem and the Cuntz-Krieger uniqueness theorem. These are analogous, respectively, to the gauge-invariant uniqueness theorem and Cuntz-Krieger uniqueness theorem for graph C*-algebras. Formal statements of the uniqueness theorems are as follows:
The Graded Uniqueness Theorem: Fix a field . Let be a graph, and let be the associated Leavitt path algebra. If is a graded -algebra and is a graded algebra homomorphism with for all , then is injective.
The Cuntz-Krieger Uniqueness Theorem: Fix a field . Let be a graph satisfying Condition (L), and let be the associated Leavitt path algebra. If is a -algebra and is an algebra homomorphism with for all , then is injective.
Ideal structure
We use the term ideal to mean "two-sided ideal" in our Leavitt path algebras. The ideal structure of can be determined from . A subset of vertices is called hereditary if for all , implies . A hereditary subset is called saturated if whenever is a regular vertex with , then . The saturated hereditary subsets of are partially ordered by inclusion, and they form a lattice with meet and join defined to be the smallest saturated hereditary subset containing .
If is a saturated hereditary subset, is defined to be two-sided ideal in generated by . A two-sided ideal of is called a graded ideal if the has a -grading and for all . The graded ideals are partially ordered by inclusion and form a lattice with meet and joint defined to be the ideal generated by . For any saturated hereditary subset , the ideal is graded.
The following theorem describes how graded ideals of correspond to saturated hereditary subsets of .
Theorem: Fix a field , and let be a row-finite graph. Then the following hold:
The function is a lattice isomorphism from the lattice of saturated hereditary subsets of onto the lattice of graded ideals of with inverse given by .
For any saturated hereditary subset , the quotient is -isomorphic to , where is the subgraph of with vertex set and edge set .
For any saturated hereditary subset , the ideal is Morita equivalent to , where is the subgraph of with vertex set and edge set .
If satisfies Condition (K), then every ideal of is graded, and the ideals of are in one-to-one correspondence with the saturated hereditary subsets of .
References
Algebras
Ring theory | Leavitt path algebra | [
"Mathematics"
] | 1,599 | [
"Mathematical structures",
"Algebras",
"Ring theory",
"Fields of abstract algebra",
"Algebraic structures"
] |
64,958,336 | https://en.wikipedia.org/wiki/Henry%20Vernon%20Wong | Henry Vernon Wong is a Jamaican-American physicist known for his work in plasma physics. He is professor emeritus at the University of Texas, Austin.
Career
Wong's early education was at Cornwall College in Montego Bay, Jamaica. He won a Jamaica Scholarship to the University of the West Indies, graduating with a B.Sc. in physics in 1961. He obtained his D.Phil. in Nuclear physics from Wadham College, Oxford in 1964. Wong remained at Oxford during 1964–1965 as a postdoctoral scholar. In 1965, he was the recipient of a CIBA Fellowship to continue his research at the International Centre for Theoretical Physics in Trieste, Italy. The following year he joined the Laboratoria Gas Ionizzati in Rome. In 1967, Wong joined the Fusion Research Center (FRC) of the University of Texas at Austin as a research scientist.
Awards and honors
In 1961, Wong was awarded a Rhodes Scholarship to Wadham College, Oxford
In 1988, He was elected fellow of the American Physical Society.
Selected publications
Wong, H. Vernon. "Stability of Bernstein‐Greene‐Kruskal Wave with Small Fraction of Trapped Electrons" The Physics of Fluids 15, 632 (1972); DOI:10.1063/1.1693958
Wong, H. Vernon. "Sideband instabilities in free electron lasers" Physics of Fluids B: Plasma Physics, 2 1635 (1990). DOI:10.1063/1.859489
Wong, H. Vernon. "Particle canonical variables and guiding center Hamiltonian up to second order in the Larmor radius" Physics of Plasmas 7, 73 (2000). DOI:10.1063/1.873782
Wong, H. Vernon. "Nonlinear finite-Larmor-radius drift-kinetic equation" Physics of Plasmas 12, 112305 (2005). DOI:10.1063/1.2116867
References
University of the West Indies alumni
Alumni of the University of Oxford
Alumni of Wadham College, Oxford
Living people
20th-century American physicists
21st-century American physicists
Jamaican scientists
Jamaican Rhodes Scholars
Plasma physicists
Fellows of the American Physical Society
University of Texas at Austin faculty
1938 births
Cornwall College, Jamaica alumni | Henry Vernon Wong | [
"Physics"
] | 457 | [
"Plasma physicists",
"Plasma physics"
] |
64,958,354 | https://en.wikipedia.org/wiki/Satellize | Satellize (formerly known as Exseed Space) is the first private Indian company to have a satellite in space. In December 2018, their first satellite was launched into space via SpaceX. They launched their second satellite, AISAT (called ExseedSat-2) for a customer, AMSAT (Radio Amateur Satellite Corporation) India on board the fourth stage of the PSLV-C45.
Exseed Innovations was started in 2017 by Mahesh Murthy, Asshar Farhan, and Kris Nair in Hyderabad. Its focus is on "assembly, integration, testing and operation of satellites" and seeks to "democratize space exploration".
See also
List of private spaceflight companies
Pixxel
Skyroot Aerospace
References
Private spaceflight companies
Space programme of India
Indian private spaceflight companies
Indian companies established in 2018
2018 establishments in Maharashtra
Companies based in Mumbai | Satellize | [
"Astronomy"
] | 180 | [
"Outer space stubs",
"Outer space",
"Astronomy stubs"
] |
64,958,765 | https://en.wikipedia.org/wiki/SPT0418-47 | SPT0418-47 is a gravitationally lensed, high-redshift, dusty star-forming galaxy, discovered with the South Pole Telescope. Observations with NASA's James Webb Space Telescope (JWST) have revealed the presence of a companion galaxy, which may indicate that SPT0418-47 is a merging system of galaxies.
In June 2023 detection of organic molecules in SPT0418-47 using the Webb telescope was announced.
References
Galaxies
Horologium (constellation)
Galaxies discovered in 2020 | SPT0418-47 | [
"Astronomy"
] | 112 | [
"Constellations",
"Horologium (constellation)"
] |
64,958,837 | https://en.wikipedia.org/wiki/Ultragraph%20C%2A-algebra | In mathematics, an ultragraph C*-algebra is a universal C*-algebra generated by partial isometries on a collection of Hilbert spaces constructed from ultragraphs.pp. 6-7. These C*-algebras were created in order to simultaneously generalize the classes of graph C*-algebras and Exel–Laca algebras, giving a unified framework for studying these objects. This is because every graph can be encoded as an ultragraph, and similarly, every infinite graph giving an Exel-Laca algebras can also be encoded as an ultragraph.
Definitions
Ultragraphs
An ultragraph consists of a set of vertices , a set of edges , a source map , and a range map taking values in the power set collection of nonempty subsets of the vertex set. A directed graph is the special case of an ultragraph in which the range of each edge is a singleton, and ultragraphs may be thought of as generalized directed graph in which each edges starts at a single vertex and points to a nonempty subset of vertices.
Example
An easy way to visualize an ultragraph is to consider a directed graph with a set of labelled vertices, where each label corresponds to a subset in the image of an element of the range map. For example, given an ultragraph with vertices and edge labels, with source an range mapscan be visualized as the image on the right.
Ultragraph algebras
Given an ultragraph , we define to be the smallest subset of containing the singleton sets , containing the range sets , and closed under intersections, unions, and relative complements. A Cuntz–Krieger -family is a collection of projections together with a collection of partial isometries with mutually orthogonal ranges satisfying
, , for all ,
for all ,
whenever is a vertex that emits a finite number of edges, and
for all .
The ultragraph C*-algebra is the universal C*-algebra generated by a Cuntz–Krieger -family.
Properties
Every graph C*-algebra is seen to be an ultragraph algebra by simply considering the graph as a special case of an ultragraph, and realizing that is the collection of all finite subsets of and for each . Every Exel–Laca algebras is also an ultragraph C*-algebra: If is an infinite square matrix with index set and entries in , one can define an ultragraph by , , , and . It can be shown that is isomorphic to the Exel–Laca algebra .
Ultragraph C*-algebras are useful tools for studying both graph C*-algebras and Exel–Laca algebras. Among other benefits, modeling an Exel–Laca algebra as ultragraph C*-algebra allows one to use the ultragraph as a tool to study the associated C*-algebras, thereby providing the option to use graph-theoretic techniques, rather than matrix techniques, when studying the Exel–Laca algebra. Ultragraph C*-algebras have been used to show that every simple AF-algebra is isomorphic to either a graph C*-algebra or an Exel–Laca algebra. They have also been used to prove that every AF-algebra with no (nonzero) finite-dimensional quotient is isomorphic to an Exel–Laca algebra.
While the classes of graph C*-algebras, Exel–Laca algebras, and ultragraph C*-algebras each contain C*-algebras not isomorphic to any C*-algebra in the other two classes, the three classes have been shown to coincide up to Morita equivalence.
See also
Leavitt path algebra
Exel–Laca algebras
Infinite matrix
Infinite graph
Notes
C*-algebras
Graph theory | Ultragraph C*-algebra | [
"Mathematics"
] | 770 | [
"Discrete mathematics",
"Mathematical relations",
"Graph theory",
"Combinatorics"
] |
64,959,394 | https://en.wikipedia.org/wiki/Energy%20diplomacy | Energy diplomacy is a form of diplomacy, and a subfield of international relations. It is closely related to its principal, foreign policy, and to overall national security, specifically energy security. Energy diplomacy began in the first half of the twentieth century and emerged as a term during the second oil crisis as a means of describing OPEC's actions. It has since mainly focused on the securitization of energy supplies, primarily fossil fuels, but also nuclear energy and increasingly sustainable energy, on a country or bloc basis.
Background
Energy diplomacy emerged as a term during the second oil crisis as a means of describing OPEC's actions and of characterizing the quest for the United States to secure energy independence and the Cold War relationship between Russia and satellite states regarding oil and gas exports. Since the oil crises, energy diplomacy has mainly focused on the securitization of energy supplies on a country or bloc basis and on the foreign policy to obtain that energy security.
Ontological relationship with national security, foreign policy, and energy security
Foreign politics has been around for thousands of years of our civilization, while energy has only entered in the last 150 years. However, in that period foreign policy and energy have had an increasing number of overlapping and interconnected elements. Foreign policy in its own part is closely linked and dependent on the concept of national security. National security is a principle of actions governing relations of one state with others based on geography, external threats and other national security challenges, of which energy is one.
The three concepts, national security, foreign policy and energy security are ontologically structured, where national security is the most general concept, foreign policy is one level lower covering the international aspect of national security risks, and the lowest on the scale is energy diplomacy. Foreign policy is linked to national security as it is the tool which implements overall national security. National security also has a direct link to energy diplomacy. National security denotes the capability of a nation to overcome its internal and external multi-dimensional threats by balancing all instruments of state policy through governance. It aims to protect national independence, security and territorial, political and economic integrity, dealing with a large number of national security risks.
Energy is one of the fundamental items on the national security agenda. National security that deals with such external issues and risks is applied and implemented by government departments for external relations. Implementation of the national security strategy involving external factors and international issues is carried out through foreign policy instruments, namely international relations and diplomacy. Energy diplomacy specifically focuses on external energy relations. Despite the ontological hierarchy of the three concepts, it is a recurring theme for them to continuously intersect in practical diplomatic life and the geopolitical reality.
History
The beginning of the 20th century was the early era of energy diplomacy, which was largely marked by corporate players. Such diplomacy was dominated by the corporations that produced and distributed fossil fuel, rather than sovereign governments, as in the case of Royal Dutch Shell and Standard Oil. National security on a national level as a concept in its own right had not yet been formulated, but the energy issues were increasing in importance. Carving up the global oil reserves and markets was carried out persistently, alike during the 1908 negotiations between Royal Dutch Shell head Deterding and the US Standard Oil director Teagle; or on the occasion of signing the US “As-Is” Pool Association agreement in 1928. The corporations were competing and racing over privileges, quotas and allocations. The governments were not too far behind, supporting them and often facilitating the race, but the influential corporations dominantly shaped the industry and foreign policy.
The Post World War II era experienced fall of empires, rise of colonies, global shifts in geopolitical influence of UK, US, Russia and others. It is the OPEC that has succeeded in the 1960s and 1970s to gain ground in relation to the international oil corporations, nationalizing and regaining control over the national fossil fuel resources in several large producing countries. The oil shocks after WWII were the ones that greatly contributed to the growth of security concerns and diplomatic efforts in the energy sphere. The most important occurrences were the Suez Crisis of 1956-1957 and the OPEC oil embargo of 1973–1974. Whole economies were brought near to a standstill, escalating energy issues as top security concerns.
Soon came other disruptions, albeit smaller, caused by the Iranian revolution of 1979, the Iran-Iraq War of 1980 followed by the first Persian Gulf War in 1990–1991. Turbulences on the oil market that disturbed and endangered economies were also caused by the 2003 Iraq invasion, oil price spike of 2007-2008, Russian Ukrainian gas dispute in 2009, and others including smaller disruptions. Oil passages are still a global security concern as 40% of all oil transits via four conduits of the straits of Hormuz, Malacca, Bab-el-Mandeb and the Suez Canal. International Energy Agency (IEA) expects that these quantities will rise from 40% to 60% by 2030. Any longer interruption would cause another large-scale economic downfall.
Therefore, energy diplomacy has entered the domain of foreign policy through the national security passageway. Numerous grave national and international risks associated with energy security and energy diplomacy have paved this way and assured that energy is viewed and judged as a security concern, so it acquired all the features of a security issue, and is constantly monitored for level of risk, potential prevention or intervention in the diplomatic field.
Next to the security path, energy concerns have entered foreign policy considerations via another path, the economy. A valid example is Australia, which has in 2018 decided to form a new policy body titled energy diplomacy. Australia, being by far the largest global exporter of coal, has only been mildly affected by the shifts on the market and geopolitics of energy, so its security risk concerning energy has not been very high.
The rise of energy risks and main issues
Energy diplomacy is a growing diplomatic field, aimed at providing energy security. Energy has entered the sphere of diplomacy and foreign policy as a result of its rising impact on national security and economy. Energy, the ability to do any work, powers the economy. Its uninterrupted flow, inward for importing countries, and outward for exporting, must be secured at all times. Until the last few decades of the 20th century the question of energy was not treated as a matter of such urgency nor geopolitics. The availability, affordability and supply were not a security issue. The industrial production and consumption capacities were smaller, and movement of energy was generally safe and dependable. Throughout the industrial revolution the increasing need for energy grew at a remarkable pace, spiraling in the 20th century. Only in the last 50 years, between 1971 and 2017 world total primary energy supply grew by more than 250% from 5, 519 Mtoe to 13, 972 Mtoe. Energy use worldwide is yet to grow by one-third until 2040.
The changed situation generated a series of factors that required energy security and energy diplomacy to be elevated onto the national security agenda. National security departments worldwide closely monitor the severe escalation of energy use. The modern consumer and the contemporary economy have gradually grown to critically depend on energy. Hence, economy and energy have become inseparable concepts. Energy has become a synonym for the economy and power, and not having enough of it became a concern of the utmost national security. Access to energy resources has decided on war outcomes, security of supply shaped national and international agendas, oil and gas producing countries organized together into coalitions, tapping into the newly discovered energy resources to back their political and geopolitical goals. Oil and gas companies became some of the most influential organizations in the global business and power-influencing arena. Oil price volatility caused by oil shocks spelled economic fortunes or disasters for many participants in the international arena affecting national and geopolitical strategies. The economic consequences were considerable, so energy had to be included on the list of security and foreign policy issues of states.
Nature of energy diplomacy
Energy diplomacy refers to diplomatic activities designed to enhance access to energy resources and markets. It is a system of influencing the policies, resolutions and conduct of foreign governments and other international factors by means of diplomatic dialogue, negotiation, lobbying, advocacy and other peaceful methods. The general relationship between foreign policy and energy diplomacy is conceptually one of principal and agent. Foreign policy sets the goals and overall political strategy while energy diplomacy is a mechanism for achieving the goals. Energy diplomacy is an instrument of foreign policy. The purpose of energy diplomacy is to safeguard economic and energy security. Energy diplomacy channels economic and trade relations of a state with other states and organizations safeguarding Energy security through availability, reliability and affordability.
Diplomatic efforts aimed at providing energy security grew in importance and complexity. It matured and spun off from general foreign policy and public diplomacy into a separate diplomatic niche field, energy diplomacy, mostly after the 1970s oil crises. This diplomatic activity has several other popular names like "geopetroleum politics", or "petro–politics" (Dorraj and Currier, 2011), or pipeline diplomacy (Aalto, 2008), but it mostly covers the same field. Energy diplomacy has developed its own programs, goals, instruments, tactics and action plans, such as the European Union Energy Diplomacy Action Plan.
Thus, at the institutional level, energy diplomacy typically focuses on such topics as targets and guidelines; regulations and energy saving; the development of nuclear energy; research and development and demonstration; oil sharing; energy transportation; energy exploration; energy early warning and response; and, in the context of global warming, energy sustainability and energy transition for hydrocarbon exporting states. Commercial energy diplomacy, a hybrid of commercial diplomacy and energy diplomacy, involves political support for foreign-investing energy businesses.
Energy diplomacy employs foreign policy methods to ensure a steady flow of energy and security of energy supplies. Energy producing and energy consuming countries apply them differently. Energy producing states mostly focus on using energy diplomacy to expand their exports and presence on the global markets. The example is the energy diplomacy of an exporting state, Russia, who aims to secure access to buyers for oil and gas. It is similar with the energy diplomacy of the Organization of the Petroleum Exporting Countries (OPEC), whose focus is similarly export and keeping external demand. Energy consuming and importing states apply energy diplomacy to secure energy supplies and steady inflow, like China's oil diplomacy in Africa or more recently, with Iran. There are also hybrid strategies, which are retained by states that are both large consumers and producers; such are India and the United States.
Energy diplomacy and the energy transition
Although the integration of energy diplomacy into foreign policy for some states has been security and the others economy, the energy transition is reshaping those dynamics so that questions of security and economy will follow a new geopolitical reality. The dynamics of the relationship with foreign policy and national security is thus undergoing a fundamental change—energy transition. Providing energy security has traditionally included several key notions: availability, reliability and affordability, but in the past two decades another crucial aspect is added – environmental sustainability and transition to low carbon energy.
This has initiated a huge shift in how energy is perceived, its toll on the environment and it prompted policies to curb climate change. It was spearheaded by policy makers in the EU. With the proliferation of more renewable energy in the energy mix, like solar, tidal, energy efficiency, wind or water, the geography of resources will not be limited to only a few resource rich countries, but much more evenly spread throughout the world. The way national energy risks are perceived is gradually changing, as energy availability will be significantly improved and more prevalent all over the planet. The energy transition into low carbon energy is already shaping the dynamic relationship of geopolitics, national security strategies, foreign policies and energy diplomacy. Various scholars argue that renewable energy may cause more small-scale conflicts but reduce the risk of large conflicts between states.
Energy diplomacy by country or bloc
Arab states of the Persian Gulf
Hydrocarbon exporting states in the Persian Gulf, such as those of the Gulf Cooperation Council, traditionally reliant on oil export and often members of OPEC, are increasingly seeking bilateral relations which enable their ability to conduct an energy transition from fossil fuels to energy sustainability, including renewable energy and nuclear power.
Australia
Australia is considered an energy superpower. Its energy diplomacy focuses primarily on promoting fossil fuels, primarily coal, and securing export markets for them.
European Union
While the European Union's internal energy policy may be seen as an example of energy diplomacy between the member states, the European Union has been developing external energy policy over the past two decades, via its EU Energy Diplomacy Action Plan, most notably with regard to Russia, Africa, and Eurasia, including across the Caspian basin.
People's Republic of China
The country on which much of the energy diplomacy literature has focused is China, due to its management of its fundamental energy insecurity, for instance in the relationship between national and corporate interests, as in its gas supply and infrastructure. China faces an energy supply deficit by 2030, and its energy diplomacy is guided by the strategic need to secure sufficient gas and oil supplies by this time. Given this situation, it first aggressively attempted application of the 'Beijing Consensus' to other countries via energy diplomacy, such as the BRICS bloc countries.
China's energy diplomacy has covered a plethora of countries, such as, in the early years, Turkey, and in later years the Middle East and North Africa, with special regard to the Iran and Saudi Arabia conflict, where China's role in peace-building came under scrutiny. China's energy diplomacy with South American countries such as Brazil is an issue, as is its relationship with Russia, which can be examined at the levels of personalism and institutionalism.
At the heart of China's energy diplomacy as regards the West and indeed the world is the issue of whether China's struggle for energy security will result in energy diplomacy behavior normalization through economic interdependence or whether China will continue to practice resource neo-mercantilism and power politics. Global energy governance institutions such as the International Energy Agency continue to look for responsible domestic energy governance from China, while China has switched attention from trying to impose its leadership on BRICS to developing its own "Silk Road Economic Belt", in part via the Shanghai Cooperation Organisation, as a means to obtain energy imports.
Russia
Russian energy diplomacy is mainly focused on its relationship with Europe, especially over natural gas supply, including across Eurasia, and Russia has combined energy supply with cyber and maritime power as policy instruments. Russia also pursues nuclear energy diplomacy, for instance with Finland and Hungary, via Rosatom.
United States
United States (US) energy diplomacy has consistently focused on oil, and more recently on the oil and gas boom, and is coordinated by the Bureau of Energy Resources at the Department of State. Its commercial energy diplomacy interests extend widely, beyond the traditional Middle East oil exporters to Central Asian countries such as Kazakhstan. Historically, the US has exported nuclear energy reactors, by building on its Atoms for Peace program exporting research reactors.
See also
1973 oil crisis
1979 oil crisis
2000s energy crisis
Energy policy
Energy security
Energy superpower
Gulf War
International Energy Agency
ITER
OPEC
Suez crisis
Commercial diplomacy
Medical diplomacy
Public diplomacy
Defence diplomacy
References
Further reading
Abelson, P.H. (1976), Energy diplomacy. Science, 192(4238), 429.
Chi Zhang (2016), The Domestic Dynamics Of China's Energy Diplomacy, World Scientific Publishing Co.
Maness, R., Valeriano, B. (2015), Russia's Coercive Diplomacy: Energy, Cyber, and Maritime Policy as New Sources of Power, Palgrave Macmillan.
External links
United Nations Sustainable Energy Diplomacy (page)
International relations
Types of diplomacy
Petroleum politics
Energy security
Energy treaties | Energy diplomacy | [
"Chemistry"
] | 3,206 | [
"Petroleum",
"Petroleum politics"
] |
64,959,915 | https://en.wikipedia.org/wiki/DNA%20end%20resection | DNA end resection, also called 5′–3′ degradation, is a biochemical process where the blunt end of a section of double-stranded DNA (dsDNA) is modified by cutting away some nucleotides from the 5' end to produce a 3' single-stranded sequence. The presence of a section of single-stranded DNA (ssDNA) allows the broken end of the DNA to line up accurately with a matching sequence, so that it can be accurately repaired.Double-strand breaks (DSBs) can occur at any phase of the cell cycle causing DNA end resection and repair activities to take place, but they are also normal intermediates in mitosis recombination. Furthermore, the natural ends of the linear chromosomes resemble DSBs, and although DNA breaks can cause damage to the integrity of genomic DNA, the natural ends are packed into complex specialized DNA protective packages called telomeres that prevent DNA repair activities. Telomeres and mitotic DSBs have different functionality, but both experience the same 5′–3′ degradation process.
Background
A double-strand break is a kind of DNA damage in which both strands in the double helix are severed. DSBs only occur during DNA replication of the cell cycle. Furthermore, DSBs can lead to genome rearrangements and instability. Cases where two complementary strands are linked at the point of the DSB have potential to be catastrophic, such that the cell will not be able to complete mitosis when it next divides, and will either die or, in rare cases, undergo chromosomal loss, duplications, and even mutations. Three mechanisms exist to repair DSBs: non-homologous end joining (NHEJ), microhomology-mediated end joining (MMEJ), and homologous recombination HR. Of these, only NHEJ does not rely on DNA end resection.
Mechanism
Accurate repair of DSBs are essential in the upkeep of genome integrity. From the three mechanisms that exists to repair DSBs, NHEJ and HR repair mechanisms are the dominant pathways. Several highly conservative proteins trigger the DNA Damage Checkpoint for detection of DSBs ensuing repair by either NHEJ or HR repair pathways. NHEJ mechanism functions in ligating two different DSBs with high fidelity, while HR relies on a homologous template to repair DSB ends.
DNA end resection in the HR pathway only occurs at two specific phases: S and G2 phases. Since HR pathway requires sister chromatids for activation, this event only happens in the G2 and S phases of the cell cycle during replication. DSBs that have not begun DNA end resection can be ligated by NHEJ pathway, but resection of a few nucleotides inhibits the NHEJ pathway and commits' DNA repair by the HR pathway. The NHEJ pathway is involved throughout the cell cycle, but it is critical to DNA repair during the G1 phase. In G1 phase there is no sister chromatids to repair DSBs via the HR pathway making the NHEJ pathway a critical repair mechanism.
Before resection can take place, the break needs to be detected. In animals, this detection is done by PARP1; similar systems exist in other eukaryotes: in plants, PARP2 seems to play this role. PARP binding then recruits the MRN complex to the breakage site. This is a highly conserved complex consisting of Mre11, Rad50 and NBS1 (known as Nibrin in mammals, or Xrs2 in yeast, where this complex is called the MRX complex).
Before resection can start, CtBP1-interacting protein (CtIP) needs to bind to the MRN complex so that the first phase of resection can begin, namely short-range end resection. After phosphorylated CtIP binds, the Mre11 subunit is able to cut the 5'-terminated strand endonucleolytically, probably about 300 base pairs from the end, and then acts as a 3'→5' exonuclease to strip away the end of the 5' strand.
Resection of telomere DSBs
Linear chromosomes are packed into complex specialized DNA protective packages called telomeres. The structure of telomeres is highly conserve and is organized in multiple short tandem DNA repeats. Telomeres and DSBs have different functionality, such that telomeres prevent DNA repair activities. During telomeric DNA replication in the S/G2 and G1 phases of the cell cycle, the 3' lagging strand leaves a short overhang called a G-tail. Telomeric DNA ends at the 3' G tail end because the 3' lagging strand extends without its complementary 5' C leading strand. The G tail provide a major function to telomeric DNA such that the G tails control telomere homeostasis.
Telomeres in G1 phase
In the G1 phase of the cell cycle, the telomere-associated proteins RIF1, RIF2, and RAP2 bind to telomeric DNA and prevent access to the MRX complex. Such process in S. Cerevisiae for example is negatively regulated by this activity. The MRX complex and the Ku complex bind simultaneously and independently to DSBs ends. In the presence of the telomere-associated proteins, MRX fails to bind to the DSB ends while the Ku complex binds to DSB ends. The bound Ku complex to the DSB ends protect the telomeres from nucleolytic degradation by exo1. This results in an inhibition of telomerase elongation at the DSB ends and prevents further telomere action at the G1 phase of the cell cycle.
Telomeres in the late S/G2 phase
In the late S/G2 phase of the cell cycle, the telomere-associated proteins RIF1, RIF2, and RAP2 exhibit their inhibitory effect by binding to telomeric DNA. In the Late S/G2 phase, the protein kinase CDK1 (cyclin-dependent) promotes telomeric resection. This control is exerted by cyclin-dependent kinases, which phosphorylate parts of the resection machinery. This process alleviates the inhibitory effect of the telomere-associated proteins, and allows Cdc13 (a binding protein on both the lagging strand, and leading strand) to cover telomeric DNA. The binding of cdc13 to DNA suppresses DNA damage checkpoint and allows resection to occur while allowing for telomerase elongation at the DSB ends.
Resection of mitotic DSBs
One of the important regulatory controls in mitotic cells is deciding which specific DSB repair pathway to take. Once a DSB is detected, the highly conserved complexes are recruited by the DNA ends. If the cell is in the G1 phase of the cell cycle, the complex Ku prevents resection to occur and triggers the NHEJ pathway factors. DSBs in the NHEJ pathway are ligated, a step in the NHEJ pathway that requires DNA ligase activity of Dnl4-Lif1/XRCC4 heterodimer and the Nej1/XLF protein. This process results in error-prone religation of DSB ends at the G1 phase of the cell cycle.
If the cells are in S/G2 phase, mitotic DSBs are controlled through Cdk1 activity and involves phosphorylation of Sae2 Ser267. After phosphorylation occurs by Cdk1, MRX complex binds to dsDNA ends and generates short ssDNA that stretches in the 5' direction. The 5' ssDNA continues resection by the activity of the helicase enzyme, Sgs1 enzyme, and the nucleases Exo1 and Dna2. Involvement of Sae2 Sar267 in DSB processing is highly conserved throughout eukaryotes, such that the Sae2 along with the MRX complex are involved in two major functions: single-strand annealing, and processing of hairpin DNA structures. Like all ssDNA in the nucleus, the resected region is first coated by Replication protein A (RPA) complex, but RPA is then replaced with RAD51 to form a nucleoprotein filament which can take part in the search for a matching region, allowing HR to take place. The 3' ssDNA coated by a RPA promotes the recruitment of Mec1. Mec1 further phosphorylates Sae2 along with cdk1. The resulting phosphorylation by Sae2 by Mec1 helps increase the effect of resection and this in turn leads to the DNA damage checkpoint activation.
Regulators
The pathway of choice in DNA repair is highly regulated to guarantee that cells in the S/G2 and G1 phase use the appropriate mechanism. Regulators in both the NHEJ and HR pathway mediate the appropriate DNA repair response pathway. Furthermore, recent studies into DNA repair show that regulation of DNA end resection is governed by the activity of cdk1 in the cell replication cycle.
NHEJ pathway
DNA end resection is key in determining the correct pathway in NHEJ. For NHEJ pathway to occur, positive regulators such as the Ku and MRX complex mediate recruitment of other NHEJ-associated proteins such as Tel1, Lif1, Dnl4, and Nej1. Since NHEJ does not rely on end resection, NHEJ could only happen in the G1 phase of the cell cycle. Both Ku and NHEJ-associated proteins prevent initiation of resection.
Resection ensures that DSBs are not repaired by NHEJ (which joins broken DNA ends together without ensuring that they match), but rather by methods based on homology (matching DNA sequences). Cyclin-dependent protein kinase such as cdk1 in yeast serves as a negative regulator of the NHEJ pathway. Any activity associated with the presence of cyclin dependent protein kinases inhibit the NHEJ pathway
Positive regulators
The presence of a ssDNA allows the broken end of the DNA to line up accurately with a matching sequence, so that it can be accurately repaired. For HR pathway to occur in the S and G2 phases of the cell cycle, availability of a sister chromatid is required. 5′–3′ resection automatically links a DSB to the HR pathway. Cyclin-dependent protein kinase such as cdk1 serve as a positive regulator of the HR pathway. This positive regulator promotes 5′–3′ nucleolytic degradation of DNA ends. Along with cdk1, the MRX complex, B1 cyclin, and Spo11-induced DSBs serve as a positive regulators to the HR pathway.
See also
Exonuclease
Double-strand breaks
Blunt ends
Non-homologous end joining
Nucleotide
Cell cycle
Telomere
NHEJ
Homologous Recombination
Microhomology-mediated end joining
References
DNA repair | DNA end resection | [
"Biology"
] | 2,277 | [
"Molecular genetics",
"DNA repair",
"Cellular processes"
] |
64,960,944 | https://en.wikipedia.org/wiki/Universal%20causation | Universal causation is the proposition that everything in the universe has a cause and is thus an effect of that cause. This means that if a given event occurs, then this is the result of a previous, related event. If an object is in a certain state, then it is in that state as a result of another object interacting with it previously.
The idea of universal causation is formulated in western philosophy similarly for ages, however the formulations contain some profound differences in methodology and philosophical assumptions.
Examples:
In contrast, Bertrand Russell argued (in 1912) that the law of causation as usually stated by philosophers is false and is not used in sciences (maybe with exception of their infancy). However his position on universal causation evolved and "was not as naive as it may have appeared". In 1927 Russell writes that the notion of universal causation marks the beginnings of science and philosophy.
Philosophers who do believe in exception-less, universal, fundamental laws of nature are in recent times more often referred to as "fundamentalists", however these who present "anti-laws" efforts (for instance showing that in many cases laws of sciences are ceteris paribus laws) "pluralists" are in the minority.
As axioms of causality
According to William Whewell (hypothetico-deductivist view) the concept of universal causation depends on three axioms:
Nothing takes place without a cause.
The magnitude of an effect is proportional to the magnitude of its cause.
To every action there is an equal and opposed reaction.
Whewell writes that the first axiom is so clear that it requires no proof if only the idea of cause is understood.
Example
Example for the axiom: if a baseball is moving through the air, it must be moving this way because of a previous interaction with another object, such as being hit by a baseball bat.
Criticism
An epistemological axiom is a self-evident truth. Thus the "Axiom of Causality" claims to be a universal rule that is so obvious that it does not need to be proved to be accepted. Even among epistemologists, the existence of such a rule is controversial.
As Law of Universal Causation or Principle of Universal Causation (PUC)
John Stuart Mill describes the Law of Universal Causation in following way:
Contrary to hypothetico-deductivists Mill focuses on inductive reasoning and observations in framing of the Law of Universal Causation i.e. uses basic features of experimental methods and convinces, after critical analysis, that this law is proved by induction better than any other of subordinate generalizations.
Also popular proof and answer to skepticism (for instance that of David Hume) is that PUC has been true in so many cases, that (using basic inductivist scientific method enumerative inductive reasoning) it is reasonable to say that it is true in every case, moreover counter-example i.e. event that does not have a cause is hard to conceive.
Criticism
Modern version of law of universal causation is connected with Newtonian physics, but is also criticized for instance by David Hume who presents skeptical reductionist view on causality. Since then his view on the concept of causality is often predominating (see Causality, After the Middle Ages). Kant answered to Hume in many aspects, defending the a priority of universal causation.
In 2017 book Robert C. Koons & Timothy Pickavance point out four objections to Universal Causation:
If we additionally assume mereological universalism, universal causation doesn't exclude self-causation, which is controversial.
Pluralized causal principle - there are pluralized versions of universal causation, that allow exceptions to the principle.
Robert K. Meyer's causal chain principle, uses set theory axioms, assumes that something must cause itself in set of causes and so universal causation doesn't exclude self-causation.
Against infinite regress.
Spontaneity
One implication of Universal Causation is that if a phenomenon appears to occur without any observable external cause, the cause must be internal.
Variation
Another implication of the Universal Causation is that all change in the universe is a result of the continual application of physical laws.
Determinism
If all events are cause and effect relationships that follow universal rules, then all events—past, present and future—are theoretically determinate.
First Cause and possible exceptions
If all effects are the result of previous causes, then the cause of a given effect must itself be the effect of a previous cause, which itself is the effect of a previous cause, and so on, forming an infinite logical chain of events that can have no beginning (see: Cyclic model), however usually it is assumed that there is one (see: Big Bang, the religious belief in Creationism or pseudo-scientific idea of Intelligent design).
Exception for the Universal Causation - First Cause is sometimes pointed out to be logically necessary for it to not contradict itself. Infinite chain of events is hard to conceive in finite world. The answer is looped chain of events. But this is also questioned as the whole loop would have no cause. However it can not be ruled out that the Universe is infinite in time or can expand infinitly.
Other exceptions are pointed out - only every of the following things are caused:
contingent and unnecessary,
causable,
that have beginning,
finite.
See also
Principle of sufficient reason
Trademark argument
Causal adequacy principle
Causality principle
References
External links
Causality
Philosophy of physics
Philosophy of science
Metaphysical principles | Universal causation | [
"Physics"
] | 1,162 | [
"Philosophy of physics",
"Applied and interdisciplinary physics"
] |
64,961,918 | https://en.wikipedia.org/wiki/Quasitrace | In mathematics, especially functional analysis, a quasitrace is a not necessarily additive tracial functional on a C*-algebra. An additive quasitrace is called a trace. It is a major open problem if every quasitrace is a trace.
Definition
A quasitrace on a C*-algebra A is a map such that:
is homogeneous:
for every and .
is tracial:
for every .
is additive on commuting elements:
for every that satisfy .
and such that for each the induced map
has the same properties.
A quasitrace is:
bounded if
normalized if
lower semicontinuous if
is closed for each .
Variants
A 1-quasitrace is a map that is just homogeneous, tracial and additive on commuting elements, but does not necessarily extend to such a map on matrix algebras over A. If a 1-quasitrace extends to the matrix algebra , then it is called a n-quasitrace. There are examples of 1-quasitraces that are not 2-quasitraces. One can show that every 2-quasitrace is automatically a n-quasitrace for every . Sometimes in the literature, a quasitrace means a 1-quasitrace and a 2-quasitrace means a quasitrace.
Properties
A quasitrace that is additive on all elements is called a trace.
Uffe Haagerup showed that every quasitrace on a unital, exact C*-algebra is additive and thus a trace. The article of Haagerup was circulated as handwritten notes in 1991 and remained unpublished until 2014. Blanchard and Kirchberg removed the assumption of unitality in Haagerup's result. As of today (August 2020) it remains an open problem if every quasitrace is additive.
Joachim Cuntz showed that a simple, unital C*-algebra is stably finite if and only if it admits a dimension function. A simple, unital C*-algebra is stably finite if and only if it admits a normalized quasitrace. An important consequence is that every simple, unital, stably finite, exact C*-algebra admits a tracial state.
Every quasitrace on a von Neumann algebra is a trace.
Notes
References
Functional analysis | Quasitrace | [
"Mathematics"
] | 471 | [
"Functional analysis",
"Functions and mappings",
"Mathematical relations",
"Mathematical objects"
] |
70,707,994 | https://en.wikipedia.org/wiki/H3T11P | H3T11P is an epigenetic modification to the DNA packaging protein histone H3. It is a mark that indicates the phosphorylation the 11th threonine residue of the histone H3 protein.
Histone H3 phosphorylation at threonine 11 establishes a unique chromatin mark for transcriptional control. The levels of phosphorylated H3T11 are higher in prostate carcinomas as measured by Gleason scores.
H3T11P is a biomarker for aging and nutritional stress. Under stress, the Sch9 and CK2 kinases work together to regulate H3T11P. By changing dietary stress responses, H3pT11 mutants were able to extend their chronological longevity.
Nomenclature
The name of this modification indicates the protein phosphorylation of threonine 11 on histone H3 protein subunit:
Serine/threonine/tyrosine phosphorylation
The addition of a negatively charged phosphate group can lead to major changes in protein structure, leading to the well-characterized role of phosphorylation in controlling protein function. It is not clear what structural implications histone phosphorylation has, but histone phosphorylation has clear functions as a post-translational modification.
Clinical effect of modification
Protein-kinase-C-related kinase 1 (PRK1) phosphorylates histone H3 at threonine 11 when ligand-dependent recruitment to androgen receptor target genes occurs. The levels of PRK1 and phosphorylated H3T11 are higher in prostate carcinomas as measured by Gleason scores. PRK1 inhibition inhibits AR-induced tumor cell proliferation, making it a potential therapeutic target. The androgen receptor functions as a transcription factor in the genesis and progression of prostate cancer.
H3T11P is a biomarker for aging and nutritional stress. Under stress, the Sch9 and CK2 kinases work together to regulate H3T11P. By changing dietary stress responses, H3T11P mutants were able to extend their chronological longevity. The phosphorylation of H3T11 by Sch9 and CK2 links a nutritional stress response to chromatin in the regulation of lifespan. Loss of H3T11P prolongs lifespan by altering the stress response at an early stage.
Histone modifications
The genomic DNA of eukaryotic cells is wrapped around special protein molecules known as histones. The complexes formed by the looping of the DNA are known as chromatin.
Post-translational modification of histones such as histone phosphorylation has been shown to modify the chromatin structure by changing protein:DNA or protein:protein interactions. Histone post-translational modifications modify the chromatin structure. The most commonly associated histone phosphorylation occurs during cellular responses to DNA damage, when phosphorylated histone H2A separates large chromatin domains around the site of DNA breakage. Researchers investigated whether modifications of histones directly impact RNA polymerase II directed transcription. Researchers choose proteins that are known to modify histones to test their effects on transcription, and found that the stress-induced kinase, MSK1, inhibits RNA synthesis. Inhibition of transcription by MSK1 was most sensitive when the template was in chromatin, since DNA templates not in chromatin were resistant to the effects of MSK1. It was shown that MSK1 phosphorylated histone H2A on serine 1, and mutation of serine 1 to alanine blocked the inhibition of transcription by MSK1. Thus results suggested that the acetylation of histones can stimulate transcription by suppressing an inhibitory phosphorylation by a kinase as MSK1.
Mechanism and function of modification
Phosphorylation introduces a charged and hydrophilic group in the side chain of amino acids, possibly changing a protein's structure by altering interactions with nearby amino acids. Some proteins such as p53 contain multiple phosphorylation sites, facilitating complex, multi-level regulation. Because of the ease with which proteins can be phosphorylated and dephosphorylated, this type of modification is a flexible mechanism for cells to respond to external signals and environmental conditions.
Kinases phosphorylate proteins and phosphatases dephosphorylate proteins. Many enzymes and receptors are switched "on" or "off" by phosphorylation and dephosphorylation. Reversible phosphorylation results in a conformational change in the structure in many enzymes and receptors, causing them to become activated or deactivated. Phosphorylation usually occurs on serine, threonine, tyrosine and histidine residues in eukaryotic proteins. Histidine phosphorylation of eukaryotic proteins appears to be much more frequent than tyrosine phosphorylation. In prokaryotic proteins phosphorylation occurs on the serine, threonine, tyrosine, histidine or arginine or lysine residues. The addition of a phosphate (PO43-) molecule to a non-polar R group of an amino acid residue can turn a hydrophobic portion of a protein into a polar and extremely hydrophilic portion of a molecule. In this way protein dynamics can induce a conformational change in the structure of the protein via long-range allostery with other hydrophobic and hydrophilic residues in the protein.
Epigenetic implications
The post-translational modification of histone tails by either histone-modifying complexes or chromatin remodeling complexes is interpreted by the cell and leads to complex, combinatorial transcriptional output. It is thought that a histone code dictates the expression of genes by a complex interaction between the histones in a particular region. The current understanding and interpretation of histones comes from two large scale projects: ENCODE and the Epigenomic roadmap. The purpose of the epigenomic study was to investigate epigenetic changes across the entire genome. This led to chromatin states, which define genomic regions by grouping different proteins and/or histone modifications together.
Chromatin states were investigated in Drosophila cells by looking at the binding location of proteins in the genome. Use of ChIP-sequencing revealed regions in the genome characterized by different banding. Different developmental stages were profiled in Drosophila as well, an emphasis was placed on histone modification relevance. A look in to the data obtained led to the definition of chromatin states based on histone modifications. Certain modifications were mapped and enrichment was seen to localize in certain genomic regions.
The human genome is annotated with chromatin states. These annotated states can be used as new ways to annotate a genome independently of the underlying genome sequence. This independence from the DNA sequence enforces the epigenetic nature of histone modifications. Chromatin states are also useful in identifying regulatory elements that have no defined sequence, such as enhancers. This additional level of annotation allows for a deeper understanding of cell specific gene regulation.
Methods
The histone mark can be detected in a variety of ways:
1. Chromatin Immunoprecipitation Sequencing (ChIP-sequencing) measures the amount of DNA enrichment once bound to a targeted protein and immunoprecipitated. It results in good optimization and is used in vivo to reveal DNA-protein binding occurring in cells. ChIP-Seq can be used to identify and quantify various DNA fragments for different histone modifications along a genomic region.
2. Micrococcal Nuclease sequencing (MNase-seq) is used to investigate regions that are bound by well-positioned nucleosomes. Use of the micrococcal nuclease enzyme is employed to identify nucleosome positioning. Well-positioned nucleosomes are seen to have enrichment of sequences.
3. Assay for transposase accessible chromatin sequencing (ATAC-seq) is used to look in to regions that are nucleosome free (open chromatin). It uses hyperactive Tn5 transposon to highlight nucleosome localisation.
References
Epigenetics
Post-translational modification | H3T11P | [
"Chemistry"
] | 1,754 | [
"Post-translational modification",
"Gene expression",
"Biochemical reactions"
] |
70,708,060 | https://en.wikipedia.org/wiki/Controversies%20surrounding%20Uber | Uber, officially Uber Technologies Inc., has been the subject of controversies. Like other ridesharing companies, the company classifies its drivers as gig workers/independent contractors. This has become the subject of legal action in several jurisdictions. The company has disrupted taxicab businesses and allegedly caused an increase in traffic congestion. Ridesharing companies are regulated in many jurisdictions and the Uber platform is not available in several countries where the company is not able or willing to comply with local regulations. Other controversies involving Uber include various unethical practices such as aggressive lobbying and ignoring and evading local regulations. Many of these were revealed by a leak of documents showing controversial activity between 2013 and 2017 under the leadership of Travis Kalanick.
Ignoring and evading local regulations
Uber has been criticized for its strategy of generally commencing operations in a city without regard for local regulations. If faced with regulatory opposition, Uber called for public support for its service and mounted a political campaign, supported by lobbying, to change regulations. Uber argued that it is "a technology company" and not a taxi company, and therefore it was not subject to regulations affecting taxi companies. Uber's strategy was generally to "seek forgiveness rather than permission". In 2014, with regards to airport pickups without a permit in California, drivers were actually told to ignore local regulations and that the company would pay for any citations. Uber's response to California Assembly Bill 5 (2019), whereby it announced that it would not comply with the law, then engaged lobbyists and mounted an expensive public opinion campaign to overturn it via a ballot, was cited as an example of this policy.
More than 124,000 Uber documents covering the five-year period from 2012 to 2017 when Uber was run by its co-founder Travis Kalanick were leaked by Mark MacGann, a lobbyist who "led Uber's efforts to win over governments across Europe, the Middle East and Africa", to The Guardian newspaper and first printed on 10 July 2022 by its Sunday sister The Observer. The documents revealed attempts to lobby Joe Biden, Olaf Scholz and George Osborne; how Emmanuel Macron secretly aided Uber lobbying in France, and use of a kill switch during police raids to conceal data. Travis Kalanick dismissed concerns from other executives that sending Uber drivers to a protest in France put them at risk of violence from angry opponents in the taxi industry, saying "I think it's worth it, violence guarantees success".
Legal action from taxi companies
Taxi companies sued Uber in numerous American cities, alleging that Uber's policy of violating taxi regulations was a form of unfair competition or a violation of antitrust law. Although some courts did find that Uber intentionally violated the taxi rules, Uber prevailed in every case, including the only case to proceed to trial. However, Uber agreed a $178 million payout in a similar class action lawsuit in Australia. The suit was filed by 8000 taxi drivers who claimed that Uber's entry into the Australian market resulted in major financial losses for them.
Greyball
In March 2017, an investigation by The New York Times revealed that Uber developed a software tool called "Greyball" to avoid giving rides to known law enforcement officers in areas where its service was illegal such as in Portland, Oregon, Australia, South Korea, and China. The tool identified government officials using geofencing, mining credit card databases, identifying devices, and searches of social media. While at first, Uber stated that it only used the tool to identify riders that violated its terms of service, after investigations by Portland, Oregon, and the United States Department of Justice, Uber admitted to using the tool to skirt local regulations and promised not to use the tool for that purpose. The use of Greyball in London was cited by Transport for London as one of the reasons for its decision not to renew Uber's private hire operator licence in September 2017.
Through the use of Greyball, Uber was capable of targeting selected individuals, for example local police, with a fake version of the app that displayed fake cars that would never arrive if contacted. This was developed with the intention of evading the law where the company's practices had been deemed illegal. Greyball was deployed in countries including Belgium, the Netherlands, Germany, Spain and Denmark, with the knowledge of senior management such as Kalanick and Pierre-Dimitri Gore-Coty. Uber said that it stopped using the app in 2017.
Kill switch
A January 2018 report by Bloomberg News stated that Uber routinely used a kill switch, codenamed "Ripley", that locked, powered off and changed passwords on staff computers when those offices were subjected to government raids. Uber allegedly used this button at least 24 times, from spring 2015 until late 2016. The existence of the kill switch was confirmed in documents leaked in 2022.
When Uber offices were raided by police or regulatory agencies, the "kill switch" of which was not used until the very moment, was used to cut access to the data systems. This technique was used in France, the Netherlands, Belgium, India, Hungary and Romania. For example, it was reported that when the French competition regulator, the DGCCRF, raided Uber's offices in Paris, de Kievit asked an engineer in Denmark to "please kill access now". Similar procedures were used in Brussels and Amsterdam to prevent police accessing evidence. In the Netherlands, de Kievit was taken into custody and fined EUR750 for "non-compliance with an official order".
The company claims the kill switches were not intended to obstruct justice, but rather to protect IP, customer privacy, and due process. It further claimed no data was permanently deleted, and was available for authorities to obtain later.
Attempts to sabotage competitors
In 2014, Uber employees were caught ordering and then quickly cancelling rides on competing services Lyft and Gett, in an attempt to disrupt these services. In 2014, Uber was also accused of recruiting people to use competing services for the sole purpose of recruiting their drivers to Uber, at which point the recruiter would receive a commission. Uber denied that it had any involvement with the cancellation of orders or the recruitment efforts.
Wage disputes
In January 2017, Uber agreed to pay $20 million to the Federal Trade Commission to resolve allegations of having misled drivers about potential earnings.
In 2017, a class action lawsuit was filed on behalf of thousands of Uber drivers, alleging that Uber’s “upfront prices” policy did not provide drivers with the 80% of fares to which they were entitled. The lawsuit was settled for $345,622, with each driver in the class getting at least $20.
In May 2017, after the New York Taxi Workers Alliance (NYTWA) filed a class-action lawsuit in federal court in New York, Uber admitted to underpaying New York City drivers tens of millions of dollars over 2.5 years by calculating driver commissions on a net amount. Uber agreed to pay the amounts owed plus interest.
Boycott in the US
In late January 2017, GrabYourWallet advised to boycott Uber because the company did not join protests against Executive Order 13769, while Travis Kalanick, then CEO of Uber, was a member of Donald Trump's "business advisory council" and GrabYourWallet was advising boycotts of businesses with ties to Trump. Approximately 200,000 users deleted the Uber mobile app. On February 2, 2017, Kalanick resigned from the council, which disbanded in August 2017.
Sexual harassment
On February 19, 2017, former Uber engineer Susan Fowler published on her website that she was propositioned for sex by a manager and subsequently threatened with termination of employment by another manager if she continued to report the incident. Kalanick was alleged to have been aware of the complaint. On February 27, 2017, Amit Singhal, Uber's Senior Vice President of Engineering, was forced to resign after he failed to disclose a sexual harassment claim against him that occurred while he served as Vice President of Google Search. After investigations led by former attorney general Eric Holder and Arianna Huffington, a member of Uber's board of directors, in June 2017, Uber fired over 20 employees. Kalanick took an indefinite leave of absence but, under pressure from investors, he resigned as CEO a week later. Also departing the company in June 2017 was Emil Michael, a senior vice president who suggested that Uber hire a team of opposition researchers and journalists, with a million-dollar budget, to "dig up dirt" on the personal lives and backgrounds of media figures who reported negatively about Uber, specifically targeting Sarah Lacy, editor of PandoDaily, who, in an article published in October 2014, accused Uber of sexism and misogyny in its advertising. In August 2018, Uber agreed to pay a total of $7 million to settle claims of gender discrimination, harassment, and hostile work environment, with 480 employees and former employees receiving $10,700 each and 56 of those employees and former employees receiving an additional $33,900 each. In December 2019, Kalanick resigned from the board of directors of the company and sold his shares.
God view and privacy concerns
In November 2014, then U.S. Senator Al Franken, Chairman of the United States Senate Judiciary Subcommittee on Privacy, Technology and the Law, expressed concerns regarding ride sharing privacy, specifically Uber's "God View", whereby the whereabouts of specific customers, including journalists and politicians, are able to be tracked by Uber insiders. In December 2014, in response to Franken, Uber implemented restrictions on that function.
In 2012, an Uber employee tracked the frequency of probable one-night stands in six U.S. cities by day and neighborhood, by correlating late-night and next-day trips. The blog posting coined the term "ride of glory" for the Uber equivalent of a walk of shame.
Delayed disclosure of data breaches
On February 27, 2015, Uber admitted that it had suffered a data breach more than nine months prior. Names and license plate information from approximately 50,000 drivers were inadvertently disclosed. Uber discovered this leak in September 2014, but waited more than five months to notify the affected individuals.
An announcement in November 2017 revealed that in 2016, a separate data breach had disclosed the personal information of 600,000 drivers and 57 million customers. This data included names, email addresses, phone numbers, and drivers' license information. Hackers used employees' usernames and passwords that had been compromised in previous breaches (a "credential stuffing" method) to gain access to a private GitHub repository used by Uber's developers. The hackers located credentials for the company's Amazon Web Services datastore in the repository files, and were able to obtain access to the account records of users and drivers, as well as other data contained in over 100 Amazon S3 buckets. Uber paid a $100,000 ransom to the hackers on the promise they would delete the stolen data. Uber was subsequently criticized for concealing this data breach. Khosrowshahi publicly apologized. In September 2018, in the largest multi-state settlement of a data breach, Uber paid $148 million to the Federal Trade Commission, admitted that its claim that internal access to consumers' personal information was closely monitored on an ongoing basis was false, and stated that it had failed to live up to its promise to provide reasonable security for consumer data. Also in November 2018, Uber's British divisions were fined £385,000 (reduced to £308,000) by the Information Commissioner's Office.
In 2020, the US Department of Justice announced criminal charges against former Chief Security Officer Joe Sullivan for obstruction of justice. The criminal complaint said Sullivan arranged, with Kalanick's knowledge, to pay a ransom for the 2016 breach as a "bug bounty" to conceal its true nature, and for the hackers to falsify non-disclosure agreements to say they had not obtained any data.
Tax evasion
In November 2017, the Paradise Papers, a set of confidential electronic documents relating to offshore investment, revealed that Uber is one of many corporations that used an offshore company to minimize taxes.
London-based executive Fraser Robinson was asked to move to Amsterdam to persuade UK tax collectors that the company was not partly managed in the UK. (Under UK law, being partly managed in the UK, for example by having senior executives in London, would make a company taxable in the UK.) He refused to move, possibly for family reasons, and stepped down.
Discrimination against a blind customer
In April 2021, an arbitrator ruled against Uber in a case involving Lisa Irving, a blind American customer with a guide dog who was denied rides on 14 separate occasions. Uber was ordered to pay US$1.1 million, reflecting $324,000 in damages and more than $800,000 in attorney fees and court costs.
Court of Amsterdam case on 'robo-firings'
In April 2021, the court of Amsterdam ruled that Uber has to reinstate and pay compensation to six drivers that were allegedly automatically terminated solely due to algorithms, which is in violation of Article 22 of GDPR, which relates to automated decisions causing "legal or significant impact". Uber challenged the ruling, claiming it was not aware of the case and that the judgement was brought by default without the company ever being notified; however, the decision was upheld.
Racial discrimination
In October 2020, a class action lawsuit was filed on behalf of all non-White drivers, alleging there was racial discrimination in how it uses passengers’ reviews to evaluate drivers. Driver evaluation relies on Uber's star rating system, which the lawsuit says disproportionately leads to the firing of people who are not white or who speak with accents. The case argues that "Uber’s reliance on customer ratings to determine driver termination constitutes race discrimination, as it is widely recognized that customer evaluations of workers are frequently racially biased." The lawsuit was dismissed in August 2021 due to lack of evidence to prove that the rating system has a racially disparate impact and that Uber intentionally discriminated against the lead plaintiff. However, the judge acknowledged the plausibility of the case and granted permission to file a new complaint.
In October 2021, Uber was sued in London over allegations that its facial recognition system is not able to effectively identify people with darker skin and has precluded some people from using the platform, thereby discriminating against people of color.
Passenger safety
On 5 December 2014, a passenger was assaulted in an Uber cab by its driver in New Delhi. Following this, Uber was temporarily withdrawn and then forced to manage operations through an Indian subsidiary. Uber also ran into disputes with the Reserve Bank of India, the Income Tax department and consumer courts. Following this, a 'kill switch' was used to prevent Indian authorities accessing evidence. Uber Manager Rob van der Woude described the system in an e-mail - "what we did in India is have the city team be as cooperative as possible and have [Uber] BV take the heat. E.g. Whenever the local team was called to provide the information, we shut them down from the system making it practically impossible for them to give out any info despite their willingness to do so. At the same time we kept directing the authorities to talk to [Uber] BV representatives instead." In another mail, Allen Penn, Uber's Asia head, told employees "we will generally stall, be unresponsive, and often say no to what they want. This is how we operate and it’s nearly always the best". The Indian Express also found that in most Uber cabs, safety features mandated by the Delhi Government, such as a panic button, were not present or did not work.
Driver safety
In one exchange, Kalanick was quoted as saying that sending Uber drivers to a protest in France was "worth it", despite the risk of violence from angry taxi drivers. Warned that "extreme right thugs" had infiltrated the protest and were "spoiling for a fight", he was quoted as saying that "violence guarantee[s] success".
The Washington Post reported that the documents, together with interviews with Uber drivers, showed that Uber knowingly created working conditions that resulted in its drivers barely scraping by, and created a system that rewarded drivers for taking routes and schedules that put them at risk of harm in violence-plagued areas.
Arbitration agreements and class action waivers
Uber's arbitration clause and class action waiver in its driver and rider terms of service, which requires that both the rider/driver and Uber waive their rights file a lawsuit in court against the company, has come under significant scrutiny by the Pennsylvania Superior Court. Uber's arbitration clause was found to be in violation of the Pennsylvania state Constitution numerous times between 2022 and 2023. The Superior Court of Pennsylvania, an appellate court in the state, ruled in a 2023 lawsuit against the company by Shannon and Keith Chilutti that the right to a jury trial is enshrined deeply in the state constitution, and any waiver of it must be placed in bold text at the top of a contract. According to Bloomberg Law correspondent Chris Marr, the Chilutti ruling places Pennsylvania as having one of the strongest protections against arbitration clauses.
Judge Daniel D. McCaffery, in a 2-1 majority with judge Alice Beck Dubow concurring, ruled that even though a Ninth Circuit ruling in Berman v. Freedom Financial Network, which itself found that "browsewrap" agreements are enforceable where there is conspicuous notice provided by one party to the other as well as an action required to assert agreement, would find that Uber's agreement is conscionable, Pennsylvania's constitution requires a more stringent set of procedures in order to make clear to all parties there is an "unambiguous manifestation of assent to arbitration", which was failed to be provided to the Chilutti's. The dissenting judge, Victor P. Stabile, rejected McCaffery's assessment on procedural grounds, writing that the appealed trial court's order to compel arbitration was not the final ruling in the case.
Lawyers for Uber, which included attorneys from law firms Morgan Lewis & Bockius and Vaughan Baio & Partners, did not comment to Bloomberg law, though an attorney for the Chiluttis from Messa & Associates P.C, Joseph L. Messa Jr., commended the Superior Court's ruling and its broad implication for Pennsylvania businesses. Messa blasted the concept of arbitration agreements in his praise for the court, arguing that he can’t think of any other constitutional right you give up by clicking an agreement to purchase a service".
References
External links
Uber Files at the ICIJ
Uber
Uber | Controversies surrounding Uber | [
"Technology"
] | 3,807 | [
"Criticisms of software and websites"
] |
70,709,995 | https://en.wikipedia.org/wiki/Laboulbenia%20slackensis | Laboulbenia slackensis is a microscopic fungus found on Carabidae arthropods. Like all fungi found in the Laboulbeniomycetes class, L. slackensis is an obligate ectoparasite and lives its entire life cycle on one host. It is differentiated from other related species based on host preference, and is studied as an example of speciation due to ecological niche preference.
Habitat and distribution
L. slackensis spends its entire life cycle confined to one host. Its preferred host species is the beetle Pogonus chalceus. The optimal habitat of the beetle is salt marshes, although they have been found in a variety of habitats. High levels of humidity are associated with larger populations of the fungus. Specimens have been collected from all over the world, including Japan, the Netherlands, Finland, and Belgium.
Morphology
The fungus forms microscopic thalli around 1mm in length. It is a perithecial ascomycete, with one perithecium on each thallus. Ascus development and ascospore formation within the perithecium have never been observed. Mature ascospores are two-celled and are tapered on both ends. The coating of the ascospore is sticky to ensure attachment to a new host. The fungus attaches itself to the host integument via the foot cell. Each thallus also includes several appendages, which develop into reproductive structures such as a trichogyne and an antheridium. Thalli do not appear to cause damage to the host, although large numbers of thalli can reduce host fitness and cause death. It is morphologically similar to many Laboulbeniomycetes and is often differentiated solely based on host preference.
Transmission
Thalli typically develop over the course of three weeks, although a maximum life cycle of 10 weeks has been observed. Only a sexual reproductive cycle has been observed. Transmission largely occurs through direct transmission when an infected host comes into contact with another suitable host. The ascospores form thread-like structures which aid in adherence to a new host. Within beetle populations, similar infection sizes are reached on each host. This is thought to occur due to unidirectional spore transmission balancing out infection sizes between hosts. Auto-infection of the same host is negligible unless large populations of the fungus are present on the infected beetle. Populations of the fungus are linked to host populations, with solitary beetles supporting smaller numbers of thalli.
Although the fungus is univorous in nature, laboratory conditions can cause successful artificial transmissions to 19 other carabid species. Ecological conditions, such as soil composition and humidity, must be kept as close to natural conditions as possible to support infection on hosts other than P. chalceus.
Nutrition
It is unclear how the fungus feeds from the host. Possible mechanisms for feeding include water and nutrient absorption through the thalli or uptake of waxy lipids produced by the host.
Speciation
Sister species, such as Laboulbenia littoralis, are often found on other host species in the same habitat. Speciation was caused due to ecological separation due to host preference and environmental conditions.
The close relationship between the fungi and its host may have led to co-evolution and an evolutionary arms race between the two species. One example of this may be the lack of haustoria in L. slackensis. The lack of haustoria allows for the fungus to go unrecognized by the host until the thalli mature.
Morphological constructs have been proved to be an unreliable way to determine species. Genetic sequencing studies have begun on related species in this genus, although the practicality remains limited due to the difficulties of collecting enough molecular samples.
See also
Laboulbenia quarantenae
References
Laboulbeniaceae
Fungus species | Laboulbenia slackensis | [
"Biology"
] | 777 | [
"Fungi",
"Fungus species"
] |
70,710,332 | https://en.wikipedia.org/wiki/LO%20Pegasi | LO Pegasi is a single star in the northern constellation of Pegasus that has been the subject of numerous scientific studies. LO Pegasi, abbreviated LO Peg, is the variable star designation. It is too faint to be viewed with the naked eye, having an apparent visual magnitude that ranges from 9.04 down to 9.27. Based on parallax measurements, LO Peg is located at a distance of 79 light years from the Sun. It is a member of the young AB Doradus moving group, and is drifting closer with a radial velocity of −23 km/s.
This is a K-type main-sequence star with a stellar classification of K3Vke, where the 'k' suffix indicates interstellar absorption lines and 'e' means there are emission lines in the spectrum. It became of interest to astronomers when significant X-ray emission was detected from this star in 1994. R. D. Jeffries and associates reported flare activity based on a rotationally-broadened hydrogen α emission line and found the star varied in brightness.
LO Peg is an ultrafast rotator, completing a full rotation every . It is classified as a BY Draconis variable that is magnetically active and has star spots. The combination of non-uniform surface brightness and rotation makes it appear to vary in luminosity. Up to 25.7% of the surface is covered in spots. Long term changes in periodicity suggest activity cycles, similar to the solar cycle, with periods of approximately 3 and 7.4 years. The element lithium has been detected in its atmosphere, whose abundance, in combination with the star's rapid rotation, indicates this is a young star with an age of no more than a few hundred million years.
See also
References
Further reading
K-type main-sequence stars
BY Draconis variables
Emission-line stars
Pegasus (constellation)
Durchmusterung objects
Gliese and GJ objects
106231
Pegasi, LO | LO Pegasi | [
"Astronomy"
] | 396 | [
"Pegasus (constellation)",
"Constellations"
] |
70,711,754 | https://en.wikipedia.org/wiki/Lasiobolus%20lasioboloides | Lasiobolus lasioboloides is a species of coprophilous fungus in the family Ascodesmidaceae. It grows on the dung of sheep.
References
External links
Fungi described in 1885
Fungi of Europe
Fungi of Greece
Pezizales
Fungus species | Lasiobolus lasioboloides | [
"Biology"
] | 55 | [
"Fungi",
"Fungus species"
] |
70,712,764 | https://en.wikipedia.org/wiki/Zwackhiomyces%20sipmanii | Zwackhiomyces sipmanii is a species of lichenicolous fungus in the family Xanthopyreniaceae. Found in the boreal ecosystem of north-eastern Russia, it was formally described as a new species in 2009 by Paul Diederich and Mikhail Zhurbenko. The type specimen was collected in the Magadan Region of Eastern Siberia at an altitude of ; here, on a south-exposed slope with steppe-like vegetation, the fungus was found growing on the lichen Phaeorrhiza sareptana var. sphaerocarpa. It is only known from the type locality. The species epithet honours Dutch lichenologist Harrie Sipman, "on the occasion of his 64th birthday".
References
Xanthopyreniaceae
Fungi described in 2009
Fungi of Europe
Lichenicolous fungi
Taxa named by Mikhail Petrovich Zhurbenko
Taxa named by Paul Diederich
Fungus species | Zwackhiomyces sipmanii | [
"Biology"
] | 191 | [
"Fungi",
"Fungus species"
] |
70,713,128 | https://en.wikipedia.org/wiki/Ilie%20Popa%20%28mathematician%29 | Ilie Popa (July 20, 1907 – July 26, 1983) was a Romanian mathematician and Head of the Mathematical Analysis Department at the University of Iași. He is known for his contributions to differential geometry, mathematical analysis, and the history of mathematics.
Born in Iași, he attended the Costache Negruzzi High School in his native city. In 1927 he enrolled at the University of Iași, graduating in 1931. Upon graduation, he became an assistant professor at the Faculty of Science of the University of Iași and began his research activity under the guidance of his advisor, Alexander Myller. In 1932 Popa published his first papers (in differential geometry), in collaboration with . He obtained his Ph.D. in 1934 with thesis Contributions to Centro-Affine Differential Geometry, in which he pursued research themes of his two mentors, Myller and Octav Mayer. In 1936, the Romanian Academy awarded him a two-year scholarship to pursue his postdoctoral studies in Italy and Germany; during this period, he visited Enrico Bompiani at Sapienza University of Rome and Wilhelm Blaschke at the University of Hamburg. While away, he was promoted to associate professor in the Department of Higher Algebra at the University of Iași. After a brief stint in 1942 at the Gheorghe Asachi Technical University of Iași, he returned to the University of Iași as Professor. In 1948 he became the Head of the Mathematical Analysis Department, a position that he held until his retirement in 1973. From 1944 to 1945 and again from 1965 to 1971 he was pro-rector of the university.
References
1907 births
1983 deaths
Scientists from Iași
Alexandru Ioan Cuza University alumni
Academic staff of Alexandru Ioan Cuza University
Romanian mathematicians
Historians of mathematics
Differential geometers
Mathematical analysts | Ilie Popa (mathematician) | [
"Mathematics"
] | 369 | [
"Mathematical analysis",
"Mathematical analysts"
] |
70,714,167 | https://en.wikipedia.org/wiki/Spicamycin | Spicamycin is an antibiotic with the molecular formula C30H51N7O7 which is produced by the bacterium Streptomyces alanosinicus. Spicamycin also shows antitumor activity.
References
Further reading
Antibiotics
Purines
Amides
Heptoses | Spicamycin | [
"Chemistry",
"Biology"
] | 61 | [
"Biocides",
"Biotechnology products",
"Functional groups",
"Organic compounds",
"Antibiotics",
"Amides",
"Organic compound stubs",
"Organic chemistry stubs"
] |
70,714,339 | https://en.wikipedia.org/wiki/Spur%20%28chemistry%29 | A spur or track in radiation chemistry is a region of high concentration of chemical products after ionizing radiation passes through. The spur model, proposed by Samuel and Magee in 1953, describes the kinetic behavior of reaction spurs involving one type of radicals in a diffusion-driven environment. The spurs from gamma rays or X-rays are considered to be spherical, while those from alpha particles are cylindrical, also called tracks.
See also
Linear energy transfer
Radiobiology
References
Nuclear chemistry
Reaction mechanisms | Spur (chemistry) | [
"Physics",
"Chemistry"
] | 96 | [
"Reaction mechanisms",
"Nuclear chemistry",
"Nuclear chemistry stubs",
"Physical organic chemistry",
"Nuclear physics",
"nan",
"Chemical kinetics"
] |
70,714,373 | https://en.wikipedia.org/wiki/John%20L.%20Magee%20%28chemist%29 | John Lafayette Magee (October 28, 1914 – December 16, 2005) was an American chemist known for his work on kinetic models of radiation chemistry, especially the Samuel-Magee model for describing radiolysis in solution.
Education and career
Magee obtained his A.B. at Mississippi College in 1935, M.S. at Vanderbilt University in 1936, and his Ph.D. in chemistry at University of Wisconsin in 1939, under the supervision of Farrington Daniels. He then worked with Henry Eyring at Princeton University during his postdoctoral research. Between 1943 and 1946, he worked at the Los Alamos National Laboratory on the Manhattan Project. Afterwards, he moved to Argonne National Laboratory. In 1948, he joined the Department of Chemistry at University of Notre Dame at the invitation of Milton Burton and became a full professor in 1953. He became the director of the Radiation Laboratory at Notre Dame between 1971 and 1975. He moved to Lawrence Berkeley National Laboratory afterwards, conducting research on the biological effects of ionizing radiation. He retired from Berkeley in 1986.
Magee was elected president of the Radiation Research Society for the year 1967, and he became a fellow of the American Physical Society in 1976.
Bibliography
Paper series
Reviews
Books
See also
Milton Burton
Spur (chemistry)
References
20th-century American chemists
Mississippi College alumni
Vanderbilt University alumni
University of Wisconsin–Madison alumni
Princeton University faculty
Los Alamos National Laboratory personnel
Manhattan Project people
Argonne National Laboratory people
University of Notre Dame faculty
1914 births
2005 deaths
Radiobiologists
Theoretical chemists
Fellows of the American Physical Society
Lawrence Berkeley National Laboratory people
People from Franklinton, Louisiana | John L. Magee (chemist) | [
"Chemistry"
] | 323 | [
"Theoretical chemists",
"American theoretical chemists"
] |
70,714,912 | https://en.wikipedia.org/wiki/Yosef%20Shenberger | Yosef Shenberger (, also Schenberger; 191213 June 1982) was an Israeli architect. He designed many public buildings in the newly independent State of Israel including yeshivas, synagogues, hospitals and nursing homes, many of them in Jerusalem. Among his more notable projects are Mayanei Hayeshua Medical Center in Bnei Brak and, along with , the new campus of Shaare Zedek Medical Center in Jerusalem. He was involved in the restoration of many ancient ruins and religious sites, including the Kfar Bar'am synagogue, Western Wall Plaza and the Cave of the Patriarchs in Hebron.
Early life
Yosef Shenberger was born in Frankfurt, Germany to Yehuda, a member of the Orthodox Jewish community founded by Samson Raphael Hirsch.
Career
As a result of Adolf Hitler's rise to power, Shenberger emigrated to Mandatory Palestine in 1935, where he found work as an architect at Ma'atz, the Public Works Department of the Ministry of Transportation, which ultimately became the National Roads Company of Israel. In the 1940s, he designed the dormitory of the Mekor Haim yeshiva, and an industrial complex
in Tel Arza on behalf of (not to be confused with Poalei Agudat YisraelPAI) a Haredi workers' organisation.
After the State of Israel was established in 1948, Shenberger served as deputy director of the Jerusalem Development Department at the Jewish Agency. After 1950, he started to work as an independent architect in Jerusalem, and became a member of the Planning and Construction Committee of the Jerusalem Municipality. In 1963, he was a panel member on the committee in charge of the competition to procure a design for the Jerusalem Municipality building. He designed Mayanei Hayeshua Medical Center in Bnei Brak and, along with , the new campus of Shaare Zedek Medical Center in Jerusalem.
In 1954, Shenberger was on the panel that was tasked with selecting which exhibits would be shown at an applied arts exhibition in Italy. It was the first time that Israel had been invited to participate in such a venue. In 1959, he was involved in a project to establish sebils (water fountains) for the Arab sector at Abu Ghosh, Tayibe and Meron. At a press conference together with Zev Vilnay that announced the initiative, Shenberger said that he had previously renovated a dilapidated sebil that had been established by Suleiman the Magnificent on Mount Zion.
In 1970, Shenberger took on his friend as a colleague and business partner.
Synagogues and yeshivas
Shenberger was well-versed in the principles of synagogue building, and designed many of them, including those of Lavi and Shluhot—two religious kibbutzim. The latter was built to the width instead of to the depth, as is more typical, in order to allow the hazzan's voice to reach every congregant. At a symposium held in December 1966 at the Jerusalem branch of the Association of Engineers in Israel, Shenberger advocated for an institute dedicated to the study of synagogues. Deriving inspiration from ancient ruins in Dura-Europos and Kfar Bar'am, he articulated his preference for adding stained glass and other decorative elements to synagogues, in contrast to others who saw these things as distractions for worshipers. He believed that a minimum of 300 square metres was a requirement for the main hall in order to accommodate a congregation comfortably.
Shenberger designed many Israeli yeshivas during the 1960s, including the Tchebin yeshiva (Kokhav MiYaakov) in Tel Arza, Kol Torah in Bayit VeGan, Grodno yeshiva in Ashdod, Ofakim yeshiva and Midreshet Noam seminary in Pardes Hanna. He carried out all of his plans according to the instructions of senior rabbis. Among them were his mentor Shlomo Zalman Auerbach, Yitzchok Zev Soloveitchik, Dov Berish Weidenfeld, and Sholom Noach Berezovsky. As an example of this fealty, when Shenberger wanted to design the Grodno yeshiva as an octagon because the building was situated on a street not in alignment with the direction of prayer to Jerusalem, he first asked Yosef Shlomo Kahaneman whether this was allowed. Later, Kahaneman had a dream wherein he was told to look up the Noda BiYehuda. Upon waking up, he found that this exact scenario was discussed in the book; and while it was technically permitted, it was not advisable, so the progressive idea was scuttled.
According to HaTzofe, Shenberger had connections with Neturei Karta, a Haredi anti-Zionist group.
Antiquities
Shenberger was deeply interested in the design and artistry of ancient ruins. He was impressed with the frescos and carvings unearthed at the Dura-Europos synagogue. From his restorative work carried out at heritage sites all over Israel, including the Kfar Bar'am synagogue, he noted the ancient builders' usage of decorative elements and local materials, such as mosaics, and integrated some of these ideas into his own plans. In 1956, he won a competition to renovate the tomb of Rabbi Shimon Bar Yochai in Meron.
In 1964, Shenberger's expertise was sought at the Safed cemetery, where the chevra kadisha (burial society) members were having a difficult time reaching the new section due to the sloping terrain. He drafted a plan for an earthen ramp that would straddle the mountain, in this way granting easier access. However, a clerk in the technical department of the mayor's office scuttled the plan in favor of a bridge, under the rationalisation that the ramp would be washed away in the first rain. After work got underway, and after an investment of IL50,000, it was determined that the bridge could not be made wide enough for a pickup truck (12 metres) while still remaining stable. When Shenberger was called back, he declared that the bridge was useless and should be dismantled. Subsequently, he tried to use what he could of the half-completed bridge, with a suggestion that stone arches be looked into as a way to mask the ugly cement pillars used. When the city went ahead and started building the first arch, a very annoyed Shenberger said, "I only made a suggestion that requires intense scrutiny and you already come and build again on your own?"
After the Six Day War, Shenberger was tasked with planning the grounds of both the Cave of the Patriarchs and Rachel's Tomb. In his capacity as advisor to the Ministry of Religious Affairs, he was the architect in charge of directing the initial planning work on the Western Wall Plaza, supervising the work of Shlomo Aronson and Arthur Kutcher. In February 1970, he gave a guided tour of the Western Wall Tunnel to the Knesset's legislative committee. One of the Knesset members was so impressed with Shenberger's knowledge, that he joked that if ever the architect needed a new job, he would be well-suited to be a tour guide.
Personal life and legacy
Shenberger was an Orthodox Jew. During his later years, he lived in the Jewish Quarter of Jerusalem until his death in 1982. He was buried in the Mount of Olives Jewish Cemetery. His daughter Rachel (19422019) was married to , a rosh yeshiva (dean) of Kol Torah, one of the yeshivas that Shenberger designed.
The Jerusalem Municipality named a street after Shenberger in the Ramot neighborhood.
Published works
Mikvaot, combines historical, halakhic and technical knowledge of mikvaot (ritual baths) suitable for both architects and poskim. (1974)
References
External links
Mikvaot, digital version on Daat website (1974)
Blog roll featuring various projects of Yosef Shenberger, Back Window. Michael Jacobson blog (in Hebrew)
1912 births
1982 deaths
20th-century Israeli architects
Architects from Frankfurt
Architects from Mandatory Palestine
Architecture writers
Ashkenazi Jews in Mandatory Palestine
German Ashkenazi Jews
Israeli Ashkenazi Jews
Israeli Orthodox Jews
Jewish emigrants from Nazi Germany to Mandatory Palestine
Preservationist architects | Yosef Shenberger | [
"Engineering"
] | 1,677 | [
"Architecture writers",
"Architecture"
] |
70,715,388 | https://en.wikipedia.org/wiki/Sykes%20Smelt%20Mill | Sykes Smelt Mill was a mediaeval mill located between Sykes and Hareden in Bowland Forest High, Lancashire, England. It stood on the banks of Langden Brook.
A "Smelt Mill Clough", but not the mill itself, appears on the 1841 tithe map for the Upper Division of the Trough of Bowland. The site is now believed to be occupied by a group of small buildings, known as "Smelt Mill Cottages", one of which is the home of Bowland Pennine Mountain Rescue Team. One of the buildings sits on an old foundation.
There is some evidence that smelting was being done in the early 17th century, during which period Bevis Bulmer was working at the King's Silver Mines on Brunghill Moor, near Newton-in-Bowland. It is possible that Bulmer also worked at Sykes mill (or nearby Ashnott) under a "blanket lease" held by the Society of Mines Royal. It is not known whether Bulmer had a smelt mill on his mines, but in 1630 Charles Coare, from Bashall Eaves, was the smelter at Thievley Mine.
References
Industrial buildings in England
Buildings and structures in Ribble Valley
Smelting | Sykes Smelt Mill | [
"Chemistry"
] | 255 | [
"Metallurgical processes",
"Smelting"
] |
70,716,297 | https://en.wikipedia.org/wiki/Spatial%20anxiety | Spatial anxiety (sometimes also referred to as spatial orientation discomfort) is a sense of anxiety an individual experiences while processing environmental information contained in one's geographical space (in the sense of Montello's classification of space), with the purpose of navigation and orientation through that space (usually unfamiliar, or very little known). Spatial anxiety is also linked to the feeling of stress regarding the anticipation of a spatial-content related performance task (such as mental rotation, spatial perception, spatial visualisation, object location memory, dynamic spatial ability). Particular cases of spatial anxiety can result in a more severe form of distress, as in agoraphobia.
Classification
It is still investigated whether spatial anxiety would be considered as one solid, concrete ("unitary") construct (including the experiences of anxiety due to any spatial task), or whether it could be considered to be a "multifactorial construct" (including various subcomponents), attributing the experience of anxiety to several aspects. Evidence has shown that spatial anxiety seems to be a "multifactorial construct" that entails two components; that of anxiety regarding navigation and that of anxiety regarding the demand of rotation and visualization skills.
Gender and further individual differences
Gender differences appear to be one of the most prominent differences in spatial anxiety as well as in navigational strategies. Evidence show higher levels of spatial anxiety in women, who tend to choose route strategies, as opposed to men, who tend to choose orientation strategies (a fact which, in turn, has been found to be negatively related to spatial anxiety).
Spatial anxiety levels also seem to vary across different age groups. Evidence has shown spatial anxiety to appear also, early on, during the elementary school years, with anxiety varying in level and tending to be stable; with minimum fluctuations, across life span.
Measuring instruments
There are two primary ways of measuring spatial anxiety. One of them is Lawton's Spatial Anxiety Scale, which was dominant during its era of creation. The other is the Child Spatial Anxiety Questionnaire, which was first one to assess spatial anxiety levels related to other spatial abilities other than navigation and map reading.
Lawton's Spatial Anxiety Scale
The scale measures the degree of anxiety regarding the individual's experience and performance, in tasks assessing one's information processing related to the environment; such as way-finding and navigation.
In total there are eight statements. Some examples are "leaving a store that you have been to for the first time and deciding which way to turn to get to a destination" and "finding your way around in an unfamiliar mall". The rating takes place on a 5-point scale, expressing the degree of anxiety with a continuum from "not at all" to "very much".
Child Spatial Anxiety Questionnaire
The Child Spatial Anxiety Questionnaire was designed for young children and attempts to assess anxiety related to a wider (than usually) range of spatial abilities. Children are asked to report the level of anxiety they feel while in particular spatial abilities-demanding situations. In total it includes eight situations. Some examples are: "how do you feel being asked to say which direction is right or left?", "how do you feel when you are asked to point to a certain place on a map, like this one?", "how do you feel when you have to solve a maze like this in one minute?".
In the original version, the rating takes place on a 3-point scale which includes three different faces; each facial expression, representing a different emotional state (getting from "calm", to "somewhat nervous", to "very nervous"). The revised version assessment takes place on a 5-point scale, with two more facial expressions added.
Cognitive maps in individuals with spatial anxiety
Self-reported spatial anxiety is negatively correlated with performance in spatial tasks, both small-scale – as assessing mental rotation, spatial visualization; and large scale – as environment learning, with participants scoring higher in spatial anxiety scale showing lowered performance. Spatial anxiety is also negatively correlated navigation proficiency ratings on the self-reported sense of direction measures, as well as orientation (map based) and route (egocentric) strategies. Additionally, as anxiety has been shown to influence performance on tasks that utilize working memory resources, working memory is bound to be affected by spatial anxiety, especially visuo-spatial working memory.
There has been evidence demonstrating the negative relationship between spatial anxiety and environmental learning ability. For example, spatial anxiety is found to induce more errors in directional pointing tasks. In an experiment where participants were required to use directional instructions to move a toy car in a virtual three-dimensional environment, those with higher reported spatial anxiety performed with less accuracy. As spatial anxiety increases, pointing accuracy decreases, and navigation errors increase significantly.. This effect has been also shown in patients with cognitive impairment. Early detection might therefore allow for timely therapeutical intervention, e.g., in Alzheimer's disease
Moreover, spatial anxiety has been shown to relate to gender differences in spatial abilities. Generally, women report higher levels of spatial anxiety than men. The use of orientation (based on map view) strategies in indoor or/and outdoor environment can be associated with lower levels of spatial anxiety. Women tend to report using route strategies more than orientation strategies, whereas men report the opposite. Spatial anxiety also contributes to gender differences in environment learning. Recent findings in university students indicate that men rely more than women upon distal gradient cues that provide information on both orientation and direction (i.e., hill lines) whereas women depend upon proximal pinpoint (i.e., landmark) cues more than other cue types when identifying a visual scene. The addition of an exogenous stressor would differentially alter the impact of spatial anxiety on performance in men and women by producing a higher perception of stress in women than males, which results in decreasing performance in females. The findings suggest that gender differences in distal gradient and new cue perception varied based on stress condition.
Some studies have discovered that acute stress can reduce memory for spatial locations, and people reporting difficulties in memorizing landmarks and directions when they are displaced also report higher levels of spatial anxiety. In addition, it has been demonstrated that people with Agoraphobia Disorder have reduced visuo-spatial working memory when they are required to process multiple spatial elements simultaneously. Specifically, in tasks where they were required to navigate using the landmarks independent of themselves (allocentric coordinates), visuo-spatial working memory deficits were shown to hinder their performance.
Bilateral vestibulopathy can cause higher levels of spatial anxiety, potentially related to hippocampal atrophy. Overall, the role of the vestibular system on spatial anxiety is not yet fully understood, but vestibular function plays a relevant role in emotion processing and the development of (vertigo-related) anxiety, as well as in spatial perception.
Possible explanations for the negative correlation between spatial anxiety and the ability to form cognitive map include: individuals lacking sense of their own position with respect to the external environment are more likely to get anxious when faced with unplanned navigation, and the anxiety about becoming lost itself may reduce the ability to attend to cues necessary for way-finding strategizing.
The influence of spatial anxiety can be counteracted by positive beliefs, such as spatial self-efficacy and confidence (i.e. as the belief that one will do well in cognitive tasks). For example, it has been demonstrated that confidence was a predictive factor for accuracy in mental rotation tasks, with participants being more accurate when they were more confident. When this factor was manipulated, the performance was significantly affected. Furthermore, having more self-perception of spatial self-efficacy has a positive role in supporting environment learning beyond the role of gender.
See also
Spatial cognition
Agoraphobia
Navigation
Sex differences in psychology
References
External links
Child Spatial Anxiety Questionnaire (CSAQ) (northwestern.edu)
SpatialAnxietyQuestionnaire A sample of the CSAQ's items
Anxiety
Spatial cognition
Navigation
Orientation (geometry)
Agoraphobia | Spatial anxiety | [
"Physics",
"Mathematics"
] | 1,630 | [
"Topology",
"Space",
"Spatial cognition",
"Geometry",
"Spacetime",
"Orientation (geometry)"
] |
70,717,136 | https://en.wikipedia.org/wiki/Heat%20content%20%28fuel%29 | In the U.S. energy industry, heat content is the amount of heat energy that will be released by combustion of a unit quantity of a fuel or by transformation of another energy form. For example, fossil fuels are rated by heat content, with a distinction made between gross heat content (which includes heat energy used to vaporize moisture in the fuel) and net heat content (which excludes heat energy used to vaporize moisture in the fuel.) The term is also sometimes applied to other energy forms, such as heat content of a kilowatt-hour of electricity or a pound of steam.
References
Energy | Heat content (fuel) | [
"Physics"
] | 125 | [
"Energy (physics)",
"Energy",
"Physical quantities"
] |
70,717,230 | https://en.wikipedia.org/wiki/Sclerococcum%20sipmanii | Sclerococcum sipmanii is a rare species of lichenicolous fungus in the family Dactylosporaceae. Found in Malaysia, it was formally described as a new species in 2015 by Belgian mycologist Paul Diederich. The type specimen was found on the southern slope of Mount Kinabalu (Kota Belud, Sabah) at an altitude of ; here, in a mossy forest on a mountain ridge, it was found growing on the lichen Anomomorpha cf. roseola. The fungus forms black, convex, rounded typically measuring 100–200 μm in diameter; the fungus does not otherwise cause visible damage to the host lichen. Sclerococcum sipmanii is only known to occur at the type locality. The species epithet honours Dutch lichenologist Harrie Sipman, one of the collectors of the type.
References
Lecanorales
Fungi described in 2015
Lichenicolous fungi
Taxa named by Paul Diederich
Fungus species | Sclerococcum sipmanii | [
"Biology"
] | 204 | [
"Fungi",
"Fungus species"
] |
70,717,277 | https://en.wikipedia.org/wiki/Porous%20carbon | Porous carbons (PCs) are versatile materials with a wide range of applications, including sensors, actuators, thermal insulation, and energy conversion. Some examples of PCs are graphene and carbon nanotube-based aerogel. Physical properties that make PCs unique are their low density, high conductivity, mechanical flexibility, and stability in extreme environments.
Mechanical properties
To ensure durability of PCs, mechanical properties are important to study. Elaborate efforts have been made for studying compressive brittleness of porous carbon materials. In 1999, Iizuka, et al. studied the mechanical properties of wood ceramics, a type of porous carbon material. Stable medium-density fiber was used as the base material of wood ceramics and phenol resin was impregnated into the board. Starting at 300 °C, Young's modulus and the compressive strength first decreased with increasing temperature, but at 500 °C the strength increases sharply until it reaches 800 °C and plateaus. The effects of temperature were due to microstructural changes in the resin during carbonization. Effects of impregnates phenol resin at 800 °C were also investigated. Results showed that Young's modulus increased with phenol resin impregnation (Figure 1). The maximum Young's modulus was 5 MPa and the maximum compressive strength was 80 MPa. Wall-bending mechanical test were also performed and it was found that cell wall is breakage was correlated to relative density on compressive strength and Young's modulus.
Another type of compressive porous carbon consisting of cellulose and graphene aerogels was studied by Mi, et al. Modified cellulose/graphene aerogels (MCGA) was synthesized via bidirectional freeze drying and grafting of long carbon chains through chemical vapor deposition (Figure 2). The final product had a bulk density of 5.9 mg/cm3 and surface area of 47.3 m2/g with flexible cellulose nanofibril and stiff graphene components. After optimizing the concentration of graphene oxide concentration and anisotropic porous structure, tensile tests were performed. It was found that MGCA could recover 99.8% and 96.3% when compressed to 60% and 90% strain, respectively. SEM images showed that due to its unique structure, MCGA pore walls were able to wrinkle and fold during compression. Another unique characteristic of this material is its absorption capacity of 80-197 times its weight towards hydrophobic compounds, such as oils and chemical solvents.
On the contrary, less effort has been made to study the stretchability of porous carbons. Gao, et al. synthesized a long-range lamellar scaffold composed of chitosan and graphene oxide via bidirectional freezing, freeze drying, and annealing. The result is a material with density of 11 mg cm−3 and porosity of about 99.4%. Various tensile tests were conducted, and it was found that carbon spring could revert to its original shape upon 80% compression strain and -60% stretching strain with a Poisson's ratio between 0.05 and 0.1. The narrow hysteresis loop of the stress-strain curve indicates a low energy dissipation (energy loss coefficient of about 0.2) because of its negligible interior friction, localized buckling, or cracks during deformation processes. The stretchable mechanical properties of this material allow for great candidates for vibrational and magnetism sensors.
References
Allotropes of carbon
Foams | Porous carbon | [
"Chemistry"
] | 741 | [
"Foams",
"Allotropes of carbon",
"Allotropes"
] |
70,717,503 | https://en.wikipedia.org/wiki/Jennifer%20Park%20Stout | Jennifer Park Stout (born in 1976 as Park Ji-young; ) is an American diplomat and policy expert known for being the Deputy Assistant Secretary for East Asian and Pacific Affairs during the Obama administration.
Early life and education
Stout was born in Washington D.C.; she is the great-granddaughter of Park Eun-sik. She has a B.A. from James Madison University and an M.A. in International Affairs from the Elliott School of International Affairs at George Washington University. She is married and has two children and lives in Virginia.
Career
Stout has served as senior advisor and director of Senate affairs in the Bureau of Legislative Affairs at the State Department. She worked on Capitol Hill for 11 years, as a legislative aide to then-senator Joe Biden on the Senate Foreign Relations Committee (1998), with Senator Patrick Leahy on the Senate Committee on Appropriations, and also as foreign-policy advisor to Senator Jim Webb, and Representative Jim Moran.
She was chief of staff to Under Secretary of State for Public Diplomacy and Public Affairs Richard Stengel. Before that, she was special assistant to the president in the White House Office of Legislative Affairs. From 2010 to 2012, she served as deputy assistant secretary in the East Asian and Pacific Affairs Bureau at the State Department. After that job she served as vice president of international government relations for MetLife from 2012 to 2013. In March 2015 she was appointed to be deputy chief of staff to Secretary of State John Kerry.
In 2017 she was hired by Snap, Inc. to be their head of global public policy; in 2021 she was listed as their vice-president of global public policy and head of their Washington, DC office. She served on the board of governors of the East-West Center from 2018 through 2021.
References
1976 births
Living people
21st-century American diplomats
21st-century American women
American people of Korean descent
Snap Inc.
People from Washington, D.C. | Jennifer Park Stout | [
"Technology"
] | 388 | [
"Instant messaging",
"Snap Inc."
] |
70,717,643 | https://en.wikipedia.org/wiki/Puccinia%20myrsiphylli | Puccinia myrsiphylli is a rust fungus in the genus Puccinia, family Pucciniaceae, and is native to South Africa. It has been tested, introduced, and targeted in Australia and New Zealand as an effective biocontrol agent for Asparagus asparagoides, also known as bridal creeper.
Taxonomy
Puccinia myrsiphylli was initially described by Felix von Thümen in 1877. Ethel M. Doidge noted Paul Sydow's 1884 monograph as a resource for this species. P. myrsiphylli was described further in 1926. Later, in 1932, Doidge made an entry describing each section starting with: “[Aecidia],” “Uredo-sori hypophyllous,” and “Teleuto-sori”. She ends this entry by writing, “I have not seen the aecidia.” P. myrsiphylli is in the family Pucciniaceae, and the host-substratum are leaves that are alive from Myrsiphyllum falciforme.
Description
Puccinia myrsiphylli is a rust fungus with the following characteristics: “Uredospores ellipsoid or sub-globose, pale yellow 30-40 x 26-30 μ; epispore hyaline, about 1.5 μ thick, closely and finely echinulate and with 4-5 scattered germ pores…Teleutospores oblong, cuneate or clavate, apex rounded, acuminate or truncate, usually attenuate at the base, usually gently constricted at the septum, light brown, darker at the apex, 43-70 x 17-28 μ; epispore smooth, about 1.5 μ thick, thickened at the apex (up to 7 μ); germ pores obscure, pedicel short, fragile, hyaline or tinged with brown."
The rust fungus shows up in early to late autumn with little, orange structures on the top of the leaves of the A. Asparagoides, and looking like warts. This is the spermagonia and pycnia stage of the disease cycle. Next, there are aecia, which take the form of cup-shapes and are also orange, but they are on the under side of the leaves. The aecia produce aeciospores, and lead to uredinia. Uredinia and telia are on the under side of the leaves, but also on stems. The uredeina are also orange and in the shape of pustules, while the telia are a brown-black color, but also in the shape of pustules. The uredinia produce urediniospores, which are dispersed by the wind. Telia occur several weeks later. Then the telia produce thick-walled resting spores called teliospores.
P. myrsiphylli is likely macrocyclic because it includes all five spores stages. It is also likely autoecious because field reports show that pycnia, aecia, uredinia, and telia of P. myrsiphylli were found on A. asparagoides. No other host plants outside of A. asparagoides are required for P. myrsiphylli to complete its life cycle. The researchers in this study found dormant teliospores on extremely diseased cladodes and stems around spring/early summer time in the winter/rainfall region. This suggests that the fungus survives the dry summer months on debris, when above-ground biomass of host plants have stopped growing. It is the thick-walled teliospores that make sure the rust can survive when bridal creeper deteriorates during the summer. P. myrsipjylli recycles each 3–4 weeks during the summer.
P. myrsiphylli has two natural enemies: Cecidomyiidae larva and Eudarluca caricis. However, these two enemies do not look like they have a major impact on P. myrsiphylli.
Distribution and habitat
Puccinia myrsiphylli is found in Eastern Cape Province in South Africa. P. myrsiphylli was present in South Africa in winter regions, aseasonal regions, and summer rainfall regions in all regions where there is widespread A. asparagoides. In southern Africa, the occurrence of P. myrsiphylli was dependent on the existence of living foliage of its host plant and season of rainfall. P. myrsiphylli is a very flexible pathogen, as shown by its ability to distribute widely throughout many different South African climate regions. It can also survive harsh, dry conditions without its host. P. myrsiphylli can be found in South Africa, Australia, and New Zealand.
Biological control agent
Surveys identified Puccinia myrsiphylli as a possible biological control agent for A. asparagoides, which is also called bridal creeper. Bridal creeper is originally from southern Africa, and has been in Australia since 1871. Surveys were conducted in South Africa to find out if P. myrsiphylli would be able to spread as a possible biological control for A. asparagoides. Specificity information was also gathered because safety is a key criterion for introduction of a biological control agent into a different country. A study showed that it had a limited host range, which supported the introduction of the rust into Australia. In 2000, P. myrsiphylli was approved for introduction into Australia (Kleinjan et al., 2004). Conservationists see bridal creeper in areas of native vegetation as a threat, and had approved it as a target of biological control.
In New South Wales, Australia, P. myrsiphylli has been monitored, and there is reason for optimism that it is affecting the growth of A. asparagoides. From July 2000 to November 2001, the rust was monitored at three places in New South Wales: Scheyville National Park near Windsor, Eurobodalla National Park near Moruya, and Bar Beach near Narooma. The monitoring showed that the epidemic could have a heavy and detrimental impact on A. asparagoides. However, the spread was up to 30 m in the first four months after the release, which is relatively slow. A glasshouse experiment was also done. The result was that in the infected plant, the number of tubers, rhizome length, and shoot mass decreased by 60%. P. myrsiphylli builds up resistance and oversummering inoculum which allows it to survive the harsh, dry summer and to return for the next growing season.
The rust fungus Puccinia myrsiphylli requires 8 hours or more of the leaf being wet in order to infect bridal creeper. Between 16 and 20 degrees Celsius is the optimal infection temperature. However, infection is totally stopped at 25 degrees Celsius. In tests, P. myrsiphylli only develops successfully on A. asparagoides. Every other species tested were unaffected or very resistant to the rust. For P. myrsiphylli to be effective, it needs to attack the bridal creeper's root system because 90% of bridal creeper's biomass is below-ground rhizomes and tubers. The way P. myrsiphylli works is by infecting leaves and stems, which cause heavy defoliation of bridal creeper plants. It limits the nutrients and water available for the host plant's production of vegetation and reproduction. P. myrsiphylli also reduces the photosynthetic surface, which destroys leaf tissue. The rust destroys the capacities of A. asparagoides in 20 weeks. Morin believes it will likely take several years for P. myrsiphylli to decrease the biomass below ground.
P. myrsiphylli has gone above and beyond expectations, because it did not die and recolonized at specific places in between seasons. The rust is particularly effective in coastal areas, where conditions are ripe for epidemic growth. Those who use, develop, and manage land in Australia have excitedly used P. myrsiphylli at more than 2,500 locations around Australia. Combining P. myrsiphylli with another biological control agent, a leafhopper, Zygina sp., acted together to lessen the growth of rhizome length and number and biomass of tubers in A. asparagoides. In addition, a long-term 7-year study has shown decreases in seedling, shoot numbers, and above-ground biomass of A. asparagoides across all sites that were observed (using the biological control agents of the leafhopper and P. myrsiphylli). Some sites recorded greater declines in A. asparagoides on trellises than others due to varying climate and leafhopper factors. Due to the expansive nature of the study, scientists feel confident that the biocontrol agents of leafhopper and Puccinia myrsiphylli played a role in the decline of A. asparagoides.
After P. myrsiphylli was introduced in Australia, it was also detected in New Zealand. New Zealand is also trying to find ways to deal with undesirable weeds. Invasive exotic weeds have a negative impact on production and biodiversity. Puccinia myrsiphylli has spread across bridal creeper's range in northern New Zealand. It as an effective biocontrol agent in New Zealand. P. myrsiphylli is seen as a high quality example of effective biological control in New Zealand's 90-year history of weed biocontrol studies. P. myrsiphylli is likely effective by itself, but it has also been tested with other fungal pathogens. For example, it has been tested with Colletotrichum Gloeosporioides. In that test C. Gloeosporioides was only mildly effective on its own. This illustrates that P. myrsiphylli is seen as the most impactful biological control agent in this situation. The Environmental Risk Management Authority of New Zealand was attempting to “de-new” the classification of Puccinia myrsiphylli, which would allow those who use, develop, and manage land in Australia to manipulate P. myrsiphylli for even greater biocontrol effectiveness.
References
myrsiphylli
Biological pest control agents
Fungi described in 1877
Fungi of Africa
Fungus species | Puccinia myrsiphylli | [
"Biology"
] | 2,208 | [
"Fungi",
"Fungus species"
] |
70,717,881 | https://en.wikipedia.org/wiki/Terpene%20synthase | Terpene synthases include:
β-farnesene synthase
(3R,6E)-nerolidol synthase
(-)-α-pinene synthase
(E)-β-ocimene synthase
These synthases' structures may include:
Terpene synthase N terminal domain
Terpene synthase C terminal domain
Biosynthesis | Terpene synthase | [
"Chemistry"
] | 81 | [
"Biomolecules by chemical classification",
"Natural products",
"Organic compounds",
"Biosynthesis",
"Chemical synthesis",
"Terpenes and terpenoids",
"Metabolism"
] |
70,718,467 | https://en.wikipedia.org/wiki/Rhizophagus%20clarus | Rhizophagus clarus (previously known as Glomus clarum) is an arbuscular mycorrhizal fungus in the family Glomeraceae. The species has been shown to improve nutrient absorption and growth in several agricultural crops but is not typically applied commercially.
Distribution and conservation
Rhizophagus clarus is widely distributed and found worldwide. The species is proposed to be at the level of Least Concern on the IUCN Red List due to its global distribution.
Spores and morphology
The spores of Rhizophagus clarus vary in color from white to yellow-brown. They naturally vary in size from 100 to 260 μm and are globose to subglobose in shape. The spores are larger than the spores of other species in the genus Rhizophagus. The spores are composed of an outer mucilaginous layer which thickens as they mature.
Rhizophagus clarus is composed of extraradical hyphae that extend past the rhizosphere soil zone, and intraradical hyphae that inhabit the host plant's roots.
Ecology
Rhizophagus clarus is a biotrophic mutualist fungus that exchanges soil nutrients with its host plant for photoassimilates.
Rhizophagus clarus is able to form a symbiotic relationship with a wide variety of plant hosts, some of which include:
Strawberry (Fragaria x ananasa Duch.)
Maize (Zea mays)
Soybean (Glycine max)
Cotton (Gossypium hirsutum)
Spearmint (Mentha crispa)
Tomato (Solanum lycopersicum)
Genome
Rhizophagus clarus has a relatively small number of genes coding for cell wall degrading enzymes because the species is mutualistic and not pathogenic. Effector molecules secreted by the fungus affect plant signaling and immune function to promote fungal colonization. Hyphal anastomosis is common in colonies of Rhizophagus clarus and allows for horizontal gene transfer and increased variation in genotypes.
References
Glomerales
Fungus species | Rhizophagus clarus | [
"Biology"
] | 444 | [
"Fungi",
"Fungus species"
] |
70,718,499 | https://en.wikipedia.org/wiki/Angzarr | Angzarr () is the name of a ghost character-like Unicode symbol of unknown origin and unknown meaning. It was added to Unicode 3.2, but the symbol has been present in works prior to its release. The name is from an abbreviation of its ISO 9573-13 name, "Angle with Down Zig-zag Arrow", also reflected in its Unicode name, "Right Angle with Downwards Zigzag Arrow". Its HTML entity reference, originally defined in ISO 9573-13, is .
History
The earliest known use of the symbol is found in a 1963 Monotype typeset catalog of arrow characters; it does not appear in an earlier 1954 edition of the same catalog. Monotype listed the symbol as matrix serial number S9576. A later 1972 Monotype catalog, for mathematical characters, listed it under another serial number, S16139; the reason for the redundant serial number is unclear. It is unknown why Monotype added the character, or what purpose it was intended to serve, although much of Monotype's character repertoire for movable type originated from customer requests, including corporate logos.
In 1988, the International Organization for Standardization added the symbol to its Standard Generalized Markup Language (SGML) definition, apparently pulling it from the Monotype character set. The STIX Fonts project adopted the Angzarr symbol from the ISO's SGML characters.
In March 2000, the Angzarr symbol reached wide distribution when the Unicode Project proposed adding it to the Unicode Standard. The symbol appeared in the ISO publication Proposal for Encoding Additional Mathematical Symbols, although the symbol has no specific purpose.
The lack of meaning associated with the Angzarr symbol gained notoriety in 2022 when a blog post was published on its unknown origins. The blog was updated in 2023, confirming the appearance of Angzarr in a 1972 Monotype typeset catalogue with a scan of the page, and in 2024, confirming its appearance in earlier Monotype catalogues.
See also
List of Unicode characters
Arrow (symbol)
References
Unicode
Symbols
Symbols introduced in 1963 | Angzarr | [
"Astronomy",
"Mathematics"
] | 425 | [
"Astronomical coordinate systems",
"Horizontal coordinate system",
"Symbols"
] |
70,718,546 | https://en.wikipedia.org/wiki/Delphinella%20polyspora | Delphinella polyspora is a species of fungus in the family Dothioraceae. It is known to grow on the pedicels and fruit of Kalmia procumbens and on Rhododendron indicum.
References
External links
Fungi described in 1962
Fungi of Argentina
Fungi of Brazil
Fungi of Iceland
Dothideales
Fungus species | Delphinella polyspora | [
"Biology"
] | 72 | [
"Fungi",
"Fungus species"
] |
70,719,258 | https://en.wikipedia.org/wiki/YF-102%20%28rocket%20engine%29 | The YF-102 is a Chinese liquid rocket engine burning LOX and kerosene in a gas generator cycle. It is manufactured by the AALPT based on the experience of previous kerolox engines, and using 3D printing technology and is capable of multiple restarts. It is used in Tianlong-2 launch vehicle developed by Space Pioneer.
History
The engine was revealed in 2021 without a target launch vehicle. In its presentation video, it was shown in a five engine configuration on a 3.35m diameter first stage and as a single engine on the second stage. As of October 2021, it was in an advanced state of development, with six fully assembled prototypes some of which had achieved over 200 seconds of test firing. It was stated that it could be ready by 2022. A reusable version, YF-102R could be ready by 2026 according to the manufacturer.
In 2023, Space Pioneer, a Chinese private aerospace startup used YF-102 engines to power its Tianlong-2 Rocket. Tianlong-2 is a medium-sized, 3-stage rocket powered by RP-1 and liquid oxygen, with a payload capability of 2 tonnes to LEO and 1.5 tonnes to SSO. Each of the stages of the Tianlong-2 rocket is equipped with a YF-102 gas generator engine, which develops 85 tons of thrust. The three first-stage YF-102 were arranged in a triangular arrangement.
See also
YF-100 – First stage Chinese rocket engine which is a previous kerolox engine from the manufacturer.
YF-115 – Upper stage Chinese rocket engine which is a previous kerolox engine from the manufacturer.
References
Rocket engines of China
Rocket engines using kerosene propellant
Rocket engines using the expander cycle | YF-102 (rocket engine) | [
"Astronomy"
] | 364 | [
"Rocketry stubs",
"Astronomy stubs"
] |
70,719,921 | https://en.wikipedia.org/wiki/Cuphophyllus%20lacmus | Cuphophyllus lacmus is a species of agaric (gilled mushroom) in the family Hygrophoraceae. It has been given the recommended English name of grey waxcap. The species has a European distribution, occurring mainly in agriculturally unimproved grassland. Threats to its habitat have resulted in the species being assessed as globally "vulnerable" on the IUCN Red List of Threatened Species.
Taxonomy
The species was first described from Denmark in 1803 by naturalist Heinrich Schumacher as Agaricus lacmus. It was transferred to the genus Cuphophyllus by the French mycologist Marcel Bon in 1985.
Recent molecular research, based on cladistic analysis of DNA sequences, has confirmed that Cuphophyllus lacmus is a distinct species, but within a group (including Cuphophyllus subviolaceus) that requires further research.
Description
Basidiocarps are agaricoid, up to 70mm (5 in) tall, the cap hemispherical at first, becoming broadly convex to flat when expanded, up to 60mm (3 in) across. The cap surface is smooth, slightly greasy when damp, grey to bluish grey. The lamellae (gills) are waxy, thick, decurrent (running down the stipe), pale to dark grey. The stipe (stem) is smooth, white, lacking a ring. The spore print is white, the spores (under a microscope) smooth, inamyloid, ellipsoid, c. 7 to 8 by 4.5 to 6 μm.
Similar species
The Yellow Foot Waxcap Cuphophyllus flavipes and the Scandinavian Cuphophyllus flavipesoides are superficially similar, but in both species the lower part of the stipe is flushed yellow. Cuphophyllus subviolaceus, long considered a synonym of C. lacmus, has been shown to be a distinct species occurring in both Europe and North America, but further research is required to distinguish it morphologically.
Distribution and habitat
The Grey Waxcap is widespread but generally rare throughout Europe. It is also known from Greenland. Like most other European waxcaps, Cuphophyllus lacmus occurs in old, agriculturally unimproved, short-sward grassland (pastures and lawns).
Recent research suggests waxcaps are neither mycorrhizal nor saprotrophic but may be associated with mosses.
Conservation
Cuphophyllus lacmus is typical of waxcap grasslands, a declining habitat due to changing agricultural practices. As a result, the species is of global conservation concern and is listed as "vulnerable" on the IUCN Red List of Threatened Species. Cuphophyllus lacmus also appears on the official or provisional national red lists of threatened fungi in several European countries, including Croatia, Czech Republic, Denmark, Finland, Germany, Norway, and Sweden.
See also
List of fungi by conservation status
References
Fungi of Europe
Hygrophoraceae
Fungi described in 1803
Fungus species | Cuphophyllus lacmus | [
"Biology"
] | 614 | [
"Fungi",
"Fungus species"
] |
70,720,177 | https://en.wikipedia.org/wiki/Sclerococcum%20aptrootii | Sclerococcum aptrootii is a species of lichenicolous fungus in the family Dactylosporaceae. Found in Puerto Rico, it was formally described as a new species in 2015 by Belgian mycologist Paul Diederich. The type specimen was collected in Maricao State Forest north of Sabana Grande (Mayagüez), at an altitude of ; here, in a low mountain forest, it was found growing on the lichen Fissurina dumastii. It is only known to occur at the type locality. The fungus forms black, rounded sporodochia that measure 50–100 μm in diameter; it does not otherwise damage the host. The species epithet honours Dutch lichenologist André Aptroot, who collected the type in 1989.
References
Lecanorales
Fungi described in 2015
Fungi of the Caribbean
Lichenicolous fungi
Taxa named by Paul Diederich
Fungus species | Sclerococcum aptrootii | [
"Biology"
] | 191 | [
"Fungi",
"Fungus species"
] |
70,720,486 | https://en.wikipedia.org/wiki/Robin%20F.%20C.%20Farrow | Robin F. C. Farrow is a crystallographer. Farrow, an employee of IBM at the time, was elected a fellow of the American Physical Society in 1998, "[f]or pioneering the development of molecular beam epitaxy to grow and study epitaxial semiconductors, metastable phases, dielectrics, magnetic elements and alloys."
References
Living people
IBM people
Year of birth missing (living people)
20th-century American physicists
American crystallographers
21st-century American physicists
Fellows of the American Physical Society
Place of birth missing (living people) | Robin F. C. Farrow | [
"Chemistry",
"Materials_science"
] | 124 | [
"Crystallography stubs",
"Materials science stubs",
"Crystallography"
] |
70,720,694 | https://en.wikipedia.org/wiki/Sebacina%20sparassoidea | Sebacina sparassoidea, the white coral jelly fungus, is a species of fungus in the family Sebacinaceae. Its coral-like basidiocarps (fruit bodies) are typically a yellowish off-white and have a gelatinous and elastic texture. Found in eastern North America, in humid environments amongst rotting logs of deciduous trees, particularly oaks, it is often observed growing throughout the months of August to September.
Taxonomy
The white coral jelly fungus was first described in 1873 by British mycologist Miles Joseph Berkeley as a variety, var. reticulatum, of Corticium tremellinum. In 1908 it was raised to species level and placed in the genus Tremella, as Tremella reticulata, by American mycologist William Gilson Farlow. In 2003 British mycologist Peter Roberts re-examined the species and transferred it to the genus Sebacina. Since a different species (Sebacina reticulata Pat.) already existed with the species epithet reticulata, the new combination in Sebacina was applied to the earliest available synonym, as Sebacina sparassoidea.
Description
Fruit bodies of the white coral jelly fungus are composed of multiple, erect, coalescing, hollow lobes or branches arising from a central point. Such structures are roughly 3 to 20 cm in diameter and 3 to 12 cm tall. The associated spore print is white. Microscopically, the hyphae lack clamp connections. Basidia are septate. Basidiospores are ellipsoid, 9–13 × 6–7 μm.
Edibility
Sources disagree about edibility. However it is never considered dangerous, nor is it of exceptional culinary use.
References
Sebacinales
Fungus species | Sebacina sparassoidea | [
"Biology"
] | 364 | [
"Fungi",
"Fungus species"
] |
70,720,766 | https://en.wikipedia.org/wiki/Exobasidium%20camelliae | Exobasidium camelliae is a phytopathagenic fungus that infects ornamental shrubs of the Camellia genus. It absorbs nutrients from the host through its haustoria and causes the leaves of the host plant to be thicker and lighter green than usual. It forms a hymenium between cells four to six layers above the lower epidermis which is subsequently sloughed off to reveal its basidia.
Morphology
Mycelium
The hyphae of E. camelliae grow in the intercellular spaces of the host plant’s cells.The hyphae are thick walled and septate. The septa can be either true septa or pseudosepta. True septa are single small pores between cells which have pore plugs that control the flow of material through the fungus. Pseuduosepta are single large pores that allow the movement of larger materials and organelles through the fungus. Pseudosepta do not have pore plugs and form through the invagination of entire lateral walls. In contrast to other basidiomycetes, E. Camelliae do not form clamp connections.
Haustoria
The haustoria of E. camelliae are projections into host cells walls with slender, branched, fingerlike lobes. A collar of host cell wall material remains at each lobe’s entry point into the cell, and host cells can synthesize cell wall material to surround the lobes as a form of protection. The haustoria contain inclusion bodies which appear in the extracellular space between the lobe’s plasma membrane and cell wall. These inclusion bodies give rise to the haustorial cap which acts as a barrier between the lobes and the hyphae. While the lobes contain similar cytoplasmic material to the hyphae, they do not contain nuclei.
Reproductive structures
While the intercellular hyphae mostly grow between the second or third layer of cells above the lower epidermis, the hymenial layer is formed between cells four to six layers above the lower epidermis. As the hymenium forms and expands, the lower layers of the leaf’s cells slough off to reveal the basidia. This mechanism is unique to E. camelliae, other species in the genus expose their basidia by growing their hymenium through the epidermis and cuticle of the host cells.
E. camelliae lack a thick walled spore suitable for long term survival, which suggests the fungus survives between growing seasons by living dormant in host buds. When germinating, basidiospores form germ tubes that produce conidia. Conidia can also directly bud off of basidiospores.
Parasitic effects
E. camelliae is a biotroph that lives in between host cells and absorbs nutrients through haustoria. Macroscopically, the infection turns the host’s leaves a light green shade and causes a thickening of the host’s leaves up to three to five times their original size. Inside the leaf, the cells are undifferentiated and disorderly. These effects may be caused by the fungus’ production of indoleacetic acid. Besides the leaf, hyphae are also present in the cortex and the apical meristem of infected shoots. These projections cause the cortex to be enlarged and the growth of hyphae in leaf primordia. While most infected shoots produce leaves that are fully affected by the fungus, leaves can be locally infected.
E. camelliae has also been observed to infect the fruit tissue of C. japonica. The infected fruits have swollen tissue and are covered in a white colored hymenium when the exocarp sloughs off.
Symbiosis with Cladosporium species
Species of the Cladosporium genus have been observed to grow on the hymenium of E. camelliae. The Cladiosporium grow on top of the exposed basidia, lysing the cells and inducing the release of their contents. This is in contrast to other Cladiosporium relationships where the parasite grows inside the cells of their host. It is still unclear whether this is a parasitic, comensalistic, or mutualistic relationship.
References
Fungal plant pathogens and diseases
Fungi described in 1896
Exobasidium camelliae
Fungus species | Exobasidium camelliae | [
"Biology"
] | 889 | [
"Fungi",
"Fungus species"
] |
70,721,274 | https://en.wikipedia.org/wiki/Phenelfamycin%20E | Phenelfamycin E is an elfamycin-type antibiotic with the molecular formula C65H95ON21. Phenelfamycin E is only used for research Phenelfamycin E is produced by Streptomyces bacteria.
References
Antibiotics
Tetrasaccharides
Amides
Tetrahydropyrans
Pyrrolidines
Methoxy compounds
Carboxylic acids
Phenyl alkanoic acids | Phenelfamycin E | [
"Chemistry",
"Biology"
] | 93 | [
"Biotechnology products",
"Biocides",
"Carboxylic acids",
"Functional groups",
"Antibiotics",
"Amides"
] |
70,721,338 | https://en.wikipedia.org/wiki/List%20of%20world%20regions%20by%20life%20expectancy | This is a list of world regions by life expectancy.
United Nations (2023)
Estimation of the analytical agency of the UN.
UN: Estimate of life expectancy for various ages in 2023
UN: Change of life expectancy from 2019 to 2023
List by the World Bank Group (2022)
Estimation of the World Bank Group for 2022. The values in the World Bank Group tables are rounded. All calculations are based on raw data, so due to the nuances of rounding, in some places illusory inconsistencies of indicators arose, with a size of 0.01 year.
In 2014, some of the world's leading countries had a local peak in life expectancy, so this year is chosen for comparison with 2019 and 2022.
List by World Health Organization (2019)
Estimation of the World Health Organization for 2019.
Charts
See also
List of countries by life expectancy
References
world
World | List of world regions by life expectancy | [
"Biology"
] | 188 | [
"Senescence",
"Life expectancy"
] |
61,321,571 | https://en.wikipedia.org/wiki/Free%20and%20Open%20Source%20Software%20Conference%20India | The Free and Open Source Software Conference India (FossCon India) is planned to be an annual, three days conference for the discussion and promotion of the Free and open-source software.
History
Locations
Belagavi, India - Started in 2019
Keynote Speakers
See also
References
External links
FOSSCON INDIA
Fosscon India Facebook
Fosscon India (@fosscon) Instagram
Free-software conferences
Academic conferences
International conferences in India | Free and Open Source Software Conference India | [
"Technology"
] | 89 | [
"Computing stubs",
"Computer conference stubs"
] |
61,321,852 | https://en.wikipedia.org/wiki/Enik%C5%91%20Kubinyi | Eniko Kubinyi (born 1 August 1976) is a Hungarian biologist, professor and head of department at the Department of Ethology, ELTE Eotvos Lorand University, who studies dog behaviour, cognition, ageing, and the relationship between dogs and humans. She is the principal investigator of the Senior Family Dog Project, the MTA-ELTE Lendület/Momentum Companion Animal Research Group, and the Canine Brain and Tissue Bank.
In 2012, she appeared on the Horizon (BBC TV series) programme The Secret Life of the Dog, where she presented their research on hand-rearing wolves and comparing the behaviour of wolves and dogs. Kubinyi has received several awards for his work, including APA Comparative Psychology Award in 2004 and the L'Oréal-UNESCO Award For Women in Science in 2018. She is a fellow of the Young Academy of Europe and a founding member of the Hungarian Young Academy.
Bibliography
Books
Author of 10 chapters The Dog - A Natural History
References
External links
Young Academy of Europe
Eotvos Lorand University profile
Academic staff of Eötvös Loránd University
Ethologists
Hungarian biologists
Living people
1976 births | Enikő Kubinyi | [
"Biology"
] | 236 | [
"Ethology",
"Behavior",
"Ethologists"
] |
61,322,759 | https://en.wikipedia.org/wiki/BW284C51 | BW284C51 is a selective acetylcholinesterase inhibitor. It is also a nicotinic antagonist.
See also
Cholinesterase inhibitor
Nicotinic antagonist
References
Acetylcholinesterase inhibitors
Quaternary ammonium compounds
Ketones
Allyl compounds
Bromides
Bisquaternary anticholinesterases | BW284C51 | [
"Chemistry"
] | 70 | [
"Pharmacology",
"Ketones",
"Functional groups",
"Medicinal chemistry stubs",
"Salts",
"Bromides",
"Pharmacology stubs"
] |
61,323,423 | https://en.wikipedia.org/wiki/Hawkes%20process | In probability theory and statistics, a Hawkes process, named after Alan G. Hawkes, is a kind of self-exciting point process. It has arrivals at times where the infinitesimal probability of an arrival during the time interval is
The function is the intensity of an underlying Poisson process. The first arrival occurs at time and immediately after that, the intensity becomes , and at the time of the second arrival the intensity jumps to and so on.
During the time interval , the process is the sum of independent processes with intensities The arrivals in the process whose intensity is are the "daughters" of the arrival at time The integral is the average number of daughters of each arrival and is called the branching ratio. Thus viewing some arrivals as descendants of earlier arrivals, we have a Galton–Watson branching process. The number of such descendants is finite with probability 1 if branching ratio is 1 or less. If the branching ratio is more than 1, then each arrival has positive probability of having infinitely many descendants.
Applications
Hawkes processes are used for statistical modeling of events in mathematical finance, epidemiology, earthquake seismology, and other fields in which a random event exhibits self-exciting behavior.
See also
Point process
Self-oscillation
References
Further reading
Stochastic processes
Point processes
Mathematical finance | Hawkes process | [
"Mathematics"
] | 264 | [
"Point processes",
"Point (geometry)",
"Mathematical finance",
"Applied mathematics"
] |
61,323,434 | https://en.wikipedia.org/wiki/Micro-atmosphere%20method | The micro-atmosphere method is an antimicrobial sensitivity testing method involving the use of potentially bacteriostatic or fungicidal compounds which are obtained from the volatile oils of plants, such as citronella grass. This method involves the use of essential oils, a growth medium, a selection of bacterial or fungal cultures, and an incubator.
Method
In this microbiological procedure, theoretically, the antibacterial or anti-fungal activity of the volatile oils from a chosen plant may be tested against a selection of gram-positive and gram-negative bacteria or a species of fungus. The growth of the bacteria or fungi are then monitored on a timely basis to measure the bacteriostatic or anti-fungal activity of the volatile oils. In some cases, a complete inhibition of growth for the bacteria tested can be observed.
Dilution of essential oils
Before it can be tested, the essential oils are first diluted to produce solutions of varying concentrations. In this way, the minimum inhibitory concentration can be calculated to obtain the most cost-effective antimicrobial agent.
Antibacterial activity
Until recently, the antibacterial activity of essential oils has been primarily evaluated through direct contact methods between the pathogen and the antimicrobial agent through diffusion and dilution methods, however the role of essential oils in the vapour phase as antimicrobial agents is gaining increasing significance.
This method was developed on the premise that essential oil vapours exert critical biological activity. These methods offer rapid screening protocols for the antimicrobial assessment of plant essential oils. It has been suggested that essential oils in the vapour phase possess the greatest degree of antimicrobial activity since the active constituents are highly volatile in nature and thus, the vapour is therefore the contributing attribute for its biological activity. Each individual constituent has differing volatility, therefore when the mixtures are introduced into a free, non-saturated state in a closed micro-environment; the volatile constituents begin to disperse at differing rates in the vapour phase within the headspace according to their degree of volatility until they reach equilibrium.
Preliminary research involving the essential oils of citronella yielded promising results when tested against a selection of Gram-positive bacteria and Gram-negative bacteria. The use of such extracts can be explored especially in the development of cost-effective treatments of respiratory illness, specifically of those caused by bacterial or fungal infection. Preliminary tests exhibit complete inhibition of the growth of certain bacterial strains.
Anti-fungal activity
In a separate research, the micro-atmosphere method was used to investigate the anti-fungal efficacy of the essential oils from the cinnamon, a plant belonging to the genus Cinnamomum.
The procedure was employed to ensure that the active films, the material containing the active compound, does not come into direct contact to the tested fungal suspension.
The micro-atmosphere method was performed, in order to evaluate the indirect effects of active films against P. digitatum. Addition of 0.5% cinnamon essential oil, led to 12% inhibition of fungal growth. Higher anti-fungal effects were obtained by adding higher amounts of the essential oil. An inhibition of fungal growth between 28% and 50% were observed for the films incorporated with 1.5% and 3% essential oil, respectively.
In this particular research, the potential anti-fungal agent was subjected to both disk diffusion test and the micro-atmosphere method for comparison and to get an idea of how the active compound may be utilized. The active compound exhibited higher anti-fungal effects in the disc diffusion test compared to the micro-atmosphere assays. This could be attributed to the fact that in the disc diffusion test, both direct contact and migration of active compounds from the film to the outside induced the observed antimicrobial effects. On the other hand, only the migration of the volatile compounds to the headspace, may cause the anti-fungal effect in the micro-atmosphere method.
References
Antimicrobials
Pharmacology | Micro-atmosphere method | [
"Chemistry",
"Biology"
] | 809 | [
"Pharmacology",
"Biocides",
"Antimicrobials",
"Medicinal chemistry"
] |
61,324,337 | https://en.wikipedia.org/wiki/Applied%20category%20theory | Applied category theory is an academic discipline in which methods from category theory are used to study other fields including but not limited to computer science, physics (in particular quantum mechanics), natural language processing, control theory, probability theory and causality. The application of category theory in these domains can take different forms. In some cases the formalization of the domain into the language of category theory is the goal, the idea here being that this would elucidate the important structure and properties of the domain. In other cases the formalization is used to leverage the power of abstraction in order to prove new results about the field.
List of applied category theorists
Samson Abramsky
John C. Baez
Bob Coecke
Joachim Lambek
Valeria de Paiva
Gordon Plotkin
Dana Scott
David Spivak
See also
Categorical quantum mechanics
ZX-calculus
DisCoCat
Petri net
Univalent foundations
String diagrams
External links
Journals:
Compositionality
Conferences:
Applied category theory
Symposium on Compositional Structures (SYCO)
Books:
Picturing Quantum Processes
Categories for Quantum Theory
An Invitation to Applied Category Theory (preprint)
Category Theory for the Sciences (preprint)
Institutes:
the Quantum Group at the University of Oxford
TallCat, a research group at Tallinn University of Technology
Topos Institute
Cybercat Institute
Software:
DisCoPy, a Python toolkit for computing with string diagrams
CatLab.jl, a framework for applied category theory in the Julia language
CQL, a query language based on Kan extensions
Companies:
Conexus AI, a data integration company
Symbolica, a machine learning company
Mascots:
Gremlin-Morgoth
References
Category theory | Applied category theory | [
"Mathematics"
] | 330 | [
"Functions and mappings",
"Mathematical structures",
"Category theory stubs",
"Mathematical objects",
"Fields of abstract algebra",
"Mathematical relations",
"Category theory"
] |
61,324,498 | https://en.wikipedia.org/wiki/H2N | {{DISPLAYTITLE:H2N}}
The molecular formula H2N may refer to:
Amino group ()
Amino radical ()
Azanide ()
Nitrenium ion (), or aminylium ion
H2N may also refer to the Zoom H2n Handy Recorder | H2N | [
"Chemistry"
] | 62 | [
"Isomerism",
"Set index articles on molecular formulas"
] |
61,324,726 | https://en.wikipedia.org/wiki/Go%20back%20to%20where%20you%20came%20from | "Go back to where you came from" is a racist or xenophobic epithet which is used in many countries, and it is mainly used to target actual immigrants and falsely presumed immigrants.
In contemporary United States, it is directed often at Asian and Hispanic Americans, and sometimes African, Arab, Jewish, and Slavic Americans. It has even been directed towards Indigenous Americans in the US. There is also a common variant of the phrase that has been popularized by the Ku Klux Klan: "Go back to your country." It was originally used in the US by White Anglo-Saxon Protestants and targeted at other European immigrants, such as Irish, Italians, Poles, and Jews.
The phrase was popularized during World War I and World War II in relation to German Americans, who were subject to suspicion, discrimination, and violence. The term is often accompanied with an erroneous assumption of the target's origin; for example, Hispanic and Latino Americans may be told to "Go back to Mexico" even if they aren't Mexican. The message conveys a sense that the person is "not supposed to be there, or that it isn't their place." The speaker is presumed to be a "real" American, but the target of the remark is not.
Such phrases are deemed by the United States federal government and the court system to be discriminatory in the workplace. Their use has been accepted as evidence of workplace discrimination in cases brought before the Equal Employment Opportunity Commission (EEOC), a federal government agency that "enforces federal law to make sure employees are not discriminated against for their gender, sex, national origin or age." EEOC documents specifically cite the use of the comment "Go back to where you came from," as the example of unlawful workplace conduct by co-workers and supervisors, along with the use of "insults, taunting, or ethnic epithets, such as making fun of a person's accent," deemed to be "harassment based on national origin."
Background
The Equal Employment Opportunity Commission (EEOC) is a federal government agency that "enforces federal law to make sure employees are not discriminated against for their gender, sex, national origin or age".
EEOC documents defining "harassment based on national origin" specifically cite the use of the comment "Go back to where you came from", as the example of "unlawful" workplace conduct by co-workers and supervisors if its use is creates an "intimidating, hostile, or offensive working environment, interfere[s] with work performance, or negatively affect[s] job opportunities". Other "illegal" workplace behavior includes the use of "insults, taunting, or ethnic epithets, such as making fun of a person's accent".
According to a July 20, 2019, CNN article, the United States Equal Employment Opportunity Commission has used phrases, such as, "Go back to where you came from" as evidence of workplace discrimination.
Examples
According to an August 31, 2003, Houston Chronicle article, a car salesman of East Indian descent who was Muslim had been hired at a Texas car dealership in May 2001. He began to be subjected to taunts by his co-workers including "go back where you came from" post 9/11. He filed a complaint with the EEOC in 2003 after he was fired from the dealership in 2002. According to CNN, in rendering their decision to side with the EEOC case on behalf of the salesman and against the car dealership accused of creating a "hostile work environment based on ... national origin and religion", the United States Court of Appeals for the Fifth Circuit "cited the example" several times of the repeated use of the phrase "just go back where [he] came from". By 2003, allegedly as part of the post-9/11 backlash, over 943 discrimination complaints were filed to the EEOC leading to over 115 lawsuits.
On July 14, 2019, former President Donald Trump used the phrase to refer to four American congresswomen of color in a tweet, stating "Why don't they go back and help fix the totally broken and crime infested places from which they came...", even though three of the four are native-born Americans. The tweet drew controversy due to Donald Trump's history of racially-charged comments. According to CNN legal analyst Laura Coates, the statement, "although obviously racist to the public," may not be unlawful, because EEOC guidelines only apply to work environments and "the United States Congress and its members do not work for the President." In response to Trump's tweet, The New York Times invited readers to comment. They received accounts from 16,000 readers of their "experiences of being told to 'go back'."
Global usage
Europe
Numerous articles which are related to racism in Europe cite the use of the phrase and its variations in many European countries. In 2009, a nurse who worked in a Södertälje Hospital in Sweden complained to management about the way the staff treated patients who had immigrant backgrounds, citing examples of verbal harassment such as "go back to Arabia". The nurse lost his job.
In 2008 Greenlanders where forced to flee Gellerupparken after having been subjected to racist persecution from Arab and Somali residents for years. Chants like "Fuck home to Greenland, this is our Gellerup" was reported as being common, along with being shot at with fireworks by Arab youth.
Incidents of verbal harassment based on ethnicity in Italy include the 2018 beating of a 19-year-old man from Senegal, who had requested political asylum and was working as a server in Palermo. He was attacked by three Sicilian men and told to "Go back to your country, dirty nigger". Their actions were denounced by Monsignor Michele Pennisi, the Archbishop of Monreale, who expressed the "strongest condemnation of this act of racism, of xenophobia" that does not reflect the "attitude of Christians and of many men of good will in Sicily".
On 28 January 2020, André Ventura, leader of the Portuguese political party Chega, provoked an outcry in Parliament by saying that black Joacine Katar Moreira, a Guinea-Bissau-born Assembly member who wanted museum items from Portugal's former colonies to be returned, should be "sent back to her country of origin. It would be a lot better for everyone".
Africa
The phrase was used during the 2015 South African xenophobic riots, in which immigrants—including African expatriates from other African countries—were blamed for the high unemployment rate of South Africans. The Los Angeles Times said that South Africa's high unemployment rate has been the catalyst for violent attacks in South Africa against migrants from India, Pakistan, Bangladesh, and African countries who are blamed for "stealing jobs and undercutting small businesses owned by South Africans". There was a wave of xenophobic killings in South Africa in 2008, in which 62 people were killed.
Asia
In Malaysia, parliament members sometimes told politicians of Chinese descent to "balik Cina" (go back to China), especially if they are members of DAP.
Oceania
In 2015, New Zealand First Ron Mark told National MP Melissa Lee to "go back to Korea" in parliament.
In September 2022, One Nation Senator Pauline Hanson tweeted that Greens senator Mehreen Faruqi should "piss off back to Pakistan". This came after Faruqi was slammed over a controversial and "appalling" tweet about Elizabeth II after her death.
Israel/Palestine conflict
The phrase "Jews/Israelis go back to Europe" has been used in anti-Israel protests during the Israel–Hamas war. Jo-Ann Mort of The Guardian pointed out the irony in the phrase as the majority of the Jewish population in Israel are the children or grandchildren of those who made aliyah to Israel, namely from Europe and the MENA region. In addition, Mizrahi Jews (who lived in the Middle East and North Africa before the establishment of the state) outnumber Ashkenazi Jews in Israel. There are also Indian Jews and Ethiopian Jews in Israel, none of which ever lived in Europe. And Jews as a whole originated in the Land of Israel, not Europe, where they were long regarded as the non-European other.
See also
Pendatang asing – Malay term which means "foreign visitor", it is also used as a pejorative term for non-Bumiputera Malays.
Perpetual foreigner, a pejorative term for people who are not considered citizens of a particular country even though they were born in it, the use of this term has disproportionately affected Asian Americans.
Remigration – far-right political concept of forcibly returning immigrants to their place of ethnic origin
Rootless cosmopolitan – Soviet antisemitic slur
Notes
References
Further reading
Aftermath of the September 11 attacks
Anti-immigration politics in the United States
Harassment and bullying
Bullying in the United States
Ethnic and racial stereotypes in the United States
Ethnic supremacy
Equal Employment Opportunity Commission
Far-right politics in the United States
Freedom of speech
Hate speech
Linguistic controversies
Political terminology
Race legislation in the United States
Racism
Racism in the United States
Right-wing politics in the United States
United States administrative law
White supremacy in the United States
Xenophobia | Go back to where you came from | [
"Biology"
] | 1,906 | [
"Harassment and bullying",
"Behavior",
"Aggression"
] |
61,325,757 | https://en.wikipedia.org/wiki/Kolmogorov%20Medal | The Kolmogorov Medal is a prize awarded to distinguished researchers with life-long contributions to one of the fields initiated by Andrey Kolmogorov.
The Kolmogorov Medal was first awarded in 2003 to celebrate 100 years since the birth of Kolmogorov. The recipient is invited to deliver a lecture at the Centre for Reliable Machine Learning of Royal Holloway, University of London. Early lectures were published in The Computer Journal.
Recipients
The following people have received the Kolmogorov Medal:
Publications
See also
List of mathematics awards
References
Mathematics awards | Kolmogorov Medal | [
"Technology"
] | 112 | [
"Science and technology awards",
"Mathematics awards"
] |
61,325,885 | https://en.wikipedia.org/wiki/PURB%20%28cryptography%29 | In cryptography, a padded uniform random blob or PURB is a discipline for encrypted data formats designed to minimize unintended information leakage either from its encryption format metadata or from its total length.
Properties of PURBs
When properly created, a PURB's content is indistinguishable from a uniform random bit string to any observer without a relevant decryption key. A PURB therefore leaks no information through headers or other cleartext metadata associated with the encrypted data format. This leakage minimization "hygiene" practice contrasts with traditional encrypted data formats such as Pretty Good Privacy, which include cleartext metadata encoding information such as the application that created the data, the data format version, the number of recipients the data is encrypted for, the identities or public keys of the recipients, and the ciphers or suites that were used to encrypt the data. While such encryption metadata was considered non-sensitive when these encrypted formats were designed, modern attack techniques have found numerous ways to employ such incidentally-leaked metadata in facilitating attacks, such as by identifying data encrypted with weak ciphers or obsolete algorithms, fingerprinting applications to track users or identify software versions with known vulnerabilities, or traffic analysis techniques such as identifying all users, groups, and associated public keys involved in a conversation from an encrypted message observed between only two of them.
In addition, a PURB is padded to a constrained set of possible lengths, in order to minimize the amount of information the encrypted data could potentially leak to observers via its total length. Without padding, encrypted objects such as files or bit strings up to bits in length can leak up to bits of information to an observer - namely the number of bits required to represent the length exactly. A PURB is padded to a length representable in a floating point number whose mantissa is no longer (i.e., contains no more significant bits) than its exponent. This constraint limits the maximum amount of information a PURB's total length can leak to bits, a significant asymptotic reduction and the best achievable in general for variable-length encrypted formats whose multiplicative overhead is limited to a constant factor of the unpadded payload size. This asymptotic leakage is the same as one would obtain by padding encrypted objects to a power of some base, such as to a power of two. Allowing some significant mantissa bits in the length's representation rather than just an exponent, however, significantly reduces the overhead of padding. For example, padding to the next power of two can impose up to 100% overhead by nearly doubling the object's size, while a PURB's padding imposes overhead of at most 12% for small strings and decreasing gradually (to 6%, 3%, etc.) as objects get larger.
Experimental evidence indicate that on data sets comprising objects such as files, software packages, and online videos, leaving objects unpadded or padding to a constant block size often leaves them uniquely identifiable by total length alone. Padding objects to a power of two or to a PURB length, in contrast, ensures that most objects are indistinguishable from at least some other objects and thus have a nontrivial anonymity set.
Encoding and decoding PURBs
Because a PURB is a discipline for designing encrypted formats and not a particular encrypted format, there is no single prescribed method for encoding or decoding PURBs. Applications may use any encryption and encoding scheme provided it produces a bit string that appears uniformly random to an observer without an appropriate key, provided the appropriate hardness assumptions are satisfied of course, and provided the PURB is padded to one of the allowed lengths. Correctly-encoded PURBs therefore do not identify the application that created them in their ciphertext. A decoding application, therefore, cannot readily tell before decryption whether a PURB was encrypted for that application or its user, other than by trying to decrypt it with any available decryption keys.
Encoding and decoding a PURB presents technical efficiency challenges, in that traditional parsing techniques are not applicable because a PURB by definition has no metadata markers that a traditional parser could use to discern the PURB's structure before decrypting it. Instead, a PURB must be decrypted first obliviously to its internal structure, and then parsed only after the decoder has used an appropriate decryption key to find a suitable cryptographic entrypoint into the PURB.
Encoding and decoding PURBs intended to be decrypted by several different recipients, public keys, and/or ciphers presents the additional technical challenge that each recipient must find a different entrypoint at a distinct location in the PURB non-overlapping with those of the other recipients, but the PURB presents no cleartext metadata indicating the positions of those entrypoints or even the total number of them. The paper that proposed PURBs also included algorithms for encrypting objects to multiple recipients using multiple cipher suites. With these algorithms, recipients can find their respective entrypoints into the PURB with only a logarithmic number of trial decryptions using symmetric-key cryptography and only one expensive public-key operation per cipher suite.
A third technical challenge is representing the public-key cryptographic material that needs to be encoded into each entrypoint in a PURB, such as the ephemeral Diffie-Hellman public key a recipient needs to derive the shared secret, in an encoding indistinguishable from uniformly random bits. Because the standard encodings of elliptic-curve points are readily distinguishable from random bits, for example, special indistinguishable encoding algorithms must be used for this purpose, such as Elligator and its successors.
Tradeoffs and limitations
The primary privacy advantage that PURBs offer is a strong assurance that correctly-encrypted data leaks nothing incidental via internal metadata that observers might readily use to identify weaknesses in the data or software used to produce it, or to fingerprint the application or user that created the PURB. This privacy advantage can translate into a security benefit for data encrypted with weak or obsolete ciphers, or by software with known vulnerabilities that an attacker might exploit based on trivially-observable information gleaned from cleartext metadata.
A primary disadvantage of the PURB encryption discipline is the complexity of encoding and decoding, because the decoder cannot rely on conventional parsing techniques before decryption. A secondary disadvantage is the overhead that padding adds, although the padding scheme proposed for PURBs incurs at most only a few percent overhead for objects of significant size.
The Padme padding proposed in the PURB paper only creates files of specific very distinct sizes. Thus, an encrypted file may often be identified as PURB encrypted with high confidence, as the probability of any other file having exactly one of those padded sizes is very low. Another padding problem occurs with very short messages, where the padding does not effectively hide the size of the content.
One critique of incurring the complexity and overhead costs of PURB encryption is that the context in which a PURB is stored or transmitted may often leak metadata about the encrypted content anyway, and such metadata is outside of the encryption format's purview or control and thus cannot be addressed by the encryption format alone. For example, an application's or user's choice of filename and directory in which to store a PURB on disk may indicate allow an observer to infer the application that likely created it and to what purpose, even if the PURB's data content itself does not. Similarly, encrypting an E-mail's body as a PURB instead of with traditional PGP or S/MIME format may eliminate the encryption format's metadata leakage, but cannot prevent information leakage from the cleartext E-mail headers, or from the endpoint hosts and E-mail servers involved in the exchange. Nevertheless, separate but complementary disciplines are typically available to limit such contextual metadata leakage, such as appropriate file naming conventions or use of pseudonymous E-mail addresses for sensitive communications.
References
Cryptography
Padding algorithms | PURB (cryptography) | [
"Mathematics",
"Engineering"
] | 1,753 | [
"Applied mathematics",
"Cryptography",
"Cybersecurity engineering"
] |
61,327,033 | https://en.wikipedia.org/wiki/Britta%20Nestler | Britta Nestler (born 1972) is a German materials scientist at the Karlsruhe Institute of Technology. Her research involves the development of software to simulate the formation of microstructures in advanced materials for which experimental studies would be too expensive or difficult.
Nestler did her undergraduate and graduate studies in mathematics and physics at RWTH Aachen University. She joined the Karlsruhe University of Applied Sciences in 2001 and moved to the Karlsruhe Institute of Technology in 2009.
In 2017, the Deutsche Forschungsgemeinschaft awarded to her the Gottfried Wilhelm Leibniz Prize "for her significant, internationally recognised research in computer-assisted materials research and the development of new material models with multiscale and multiphysical approaches".
References
External links
Home page
1972 births
Living people
German materials scientists
Women materials scientists and engineers
RWTH Aachen University alumni
Academic staff of the Karlsruhe Institute of Technology
Recipients of the Cross of the Order of Merit of the Federal Republic of Germany | Britta Nestler | [
"Materials_science",
"Technology"
] | 192 | [
"Women materials scientists and engineers",
"Materials scientists and engineers",
"Women in science and technology"
] |
61,327,141 | https://en.wikipedia.org/wiki/Cell%20Proliferation%20%28journal%29 | Cell Proliferation is a monthly open-access online-only scientific journal covering cell biology. It was established in 1968 as Cell and Tissue Kinetics, obtaining its current title in 1991. It is published by John Wiley & Sons and the editor-in-chief is Q. Zhou (Chinese Academy of Sciences). According to the Journal Citation Reports, the journal has a 2021 impact factor of 8.755, ranking it 42nd out of 194 journals in the category "Cell Biology".
References
External links
Molecular and cellular biology journals
Academic journals established in 1968
Wiley (publisher) academic journals
English-language journals
Monthly journals
Online-only journals
Open access journals | Cell Proliferation (journal) | [
"Chemistry"
] | 131 | [
"Molecular and cellular biology journals",
"Molecular biology"
] |
61,328,143 | https://en.wikipedia.org/wiki/Performance%20and%20modelling%20of%20AC%20transmission | Performance modelling is the abstraction of a real system into a simplified representation to enable the prediction of performance. The creation of a model can provide insight into how a proposed or actual system will or does work. This can, however, point towards different things to people belonging to different fields of work.
Performance modelling has many benefits, which includes:
Relatively inexpensive prediction of future performance.
A clearer understanding of a system's performance characteristics.
Additionally it may include, a mechanism for risk management and reduction with design support for future projects.
A model will often be created specifically so that it can be interpreted by a software tool that simulates the system's behaviour, based on the information contained in the performance model. Such tools provide further insight into the system's behaviour and can be used to identify bottlenecks or hot spots where the design is inadequate. Solutions to the problems identified might involve the provision of more physical resources or change in the structure of the design.
Performance modelling is found helpful, in case of:
Estimating the performance of a new system.
Estimating the impact on the performance of an existing system when a new system is interacting with it.
Estimating the impact of a change of workload or input on an existing system.
Modelling of a transmission line is done to analyse its performance and characteristics. The gathered information vis simulating the model can be used to reduce losses or to compensate these losses. Moreover, it gives more insight into the working of transmission lines and helps to find a way to improve the overall transmission efficiency with minimum cost.
Overview
Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation and is different from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. The interconnected network which facilitates this movement is known as a transmission line. A transmission line is a set of electrical conductors carrying an electrical signal from one place to another. Coaxial cable and twisted pair cable are examples. The transmission line is capable of transmitting electrical power from one place to another. In many electric circuits, the length of the wires connecting the components can, for the most part, be ignored. That is, the voltage on the wire at a given time can be assumed to be the same at all points. However, when the voltage changes in a time interval comparable to the time it takes for the signal to travel down the wire, the length becomes important and the wire must be treated as a transmission line. Stated another way, the length of the wire is important when the signal includes frequency components with corresponding wavelengths comparable to or less than the length of the wire. So far transmission lines are categorized and defined in many ways. Few approaches to modelling have also being done by different methods. Most of them are mathematical and assumed circuit-based models.
Transmission can be of two types :
HVDC Transmission (High Voltage Direct Current transmission)
HVAC Transmission (High Voltage Alternating Current Transmission)
HVDC transmission
High-voltage direct current (HVDC) is used to transmit large amounts of power over long distances or for interconnections between asynchronous grids. When electrical energy is to be transmitted over very long distances, the power lost in AC transmission becomes appreciable and it is less expensive to use direct current instead of alternating current. For a very long transmission line, these lower losses (and reduced construction cost of a DC line) can offset the additional cost of the required converter stations at each end.In DC transmission line, the mercury arc rectifier converts the alternating current into the DC. The DC transmission line transmits the bulk power over long distance. At the consumer ends the thyratron converts the DC into the AC.
HVAC transmission
The AC transmission line is used for transmitting the bulk of the power generation end to the consumer end. The power is generated in the generating station. The transmission line transmits the power from generation to the consumer end. High-voltage power transmission allows for lesser resistive losses over long distances in the wiring. This efficiency of high voltage transmission allows for the transmission of a larger proportion of the generated power to the substations and in turn to the loads, translating to operational cost savings. The power is transmitted from one end to another with the help of step-up and step down transformer. Most transmission lines are high-voltage three-phase alternating current (AC), although single phase AC is sometimes used in railway electrification systems. Electricity is transmitted at high voltages (115 kV or above) to reduce the energy loss which occurs in long-distance transmission.
Power is usually transmitted through overhead power lines. Underground power transmission has a significantly higher installation cost and greater operational limitations, but reduced maintenance costs. Underground transmission is sometimes used in urban areas or environmentally sensitive locations.
Terminologies
Lossless line
The lossless line approximation is the least accurate model; it is often used on short lines when the inductance of the line is much greater than its resistance. For this approximation, the voltage and current are identical at the sending and receiving ends.
The characteristic impedance is purely real, which means resistive for that impedance, and it is often called surge impedance for a lossless line. When a lossless line is terminated by surge impedance, there is no voltage drop. Though the phase angles of voltage and current are rotated, the magnitudes of voltage and current remain constant along the length of the line. For load > SIL, the voltage will drop from sending end and the line will “consume” VARs. For load < SIL, the voltage will increase from sending end, and the line will generate VARs.
Power factor
In electrical engineering, the power factor of an AC electrical power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit, and is a dimensionless number in the closed interval of −1 to 1.
A power factor of less than one indicates the voltage and current are not in phase, reducing the instantaneous product of the two. A negative power factor occurs when the device (which is normally the load) generates power, which then flows back towards the source.
Real power is the instantaneous product of voltage and current and represents the capacity of the electricity for performing work.
Apparent power is the average product of current and voltage. Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power may be greater than the real power(pf ≤0.5).
In an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred. The higher currents increase energy loss in the distribution system and require larger wires and other equipment. Because of the costs of larger equipment and wasted energy, electrical utilities will usually charge a higher cost to industrial or commercial customers where there is a low power factor.
Surge impedance
The characteristic impedance or surge impedance (usually written Z0) of a uniform transmission line is the ratio of the amplitudes of voltage and current of a single wave propagating along the line; that is, a wave travelling in one direction in the absence of reflections in the other direction. Alternatively and equivalently it can be defined as the input impedance of a transmission line when its length is infinite. Characteristic impedance is determined by the geometry and materials of the transmission line and, for a uniform line, is not dependent on its length. The SI unit of characteristic impedance is Ohm (Ώ)
Surge impedance determines the loading capability of the line and reflection coefficient of the current or voltage propagating waves.
Where,
Z0 = Characteristic Impedance of the Line
L = Inductance per unit length of the Line
C = Capacitance per unit length of the Line
Line parameters
The transmission line has mainly four parameters, resistance, inductance, and capacitance and shunt conductance. These parameters are uniformly distributed along the line. Hence, it is also called the distributed parameter of the transmission line.
Ferranti Effect
In electrical engineering, the Ferranti effect is the increase in voltage occurring at the receiving end of a very long (> 200 km) AC electric power transmission line, relative to the voltage at the sending end, when the load is very small, or no load is connected. It can be stated as a factor, or as a percent increase:.
The capacitive line charging current produces a voltage drop across the line inductance that is in-phase with the sending-end voltage, assuming negligible line resistance. Therefore, both line inductance and capacitance are responsible for this phenomenon. This can be analysed by considering the line as a transmission line where the source impedance is lower than the load impedance (unterminated). The effect is similar to an electrically short version of the quarter-wave impedance transformer, but with smaller voltage transformation.
The Ferranti effect is more pronounced the longer the line and the higher the voltage applied. The relative voltage rise is proportional to the square of the line length and the square of frequency.
The Ferranti effect is much more pronounced in underground cables, even in short lengths, because of their high capacitance per unit length, and lower electrical impedance.
Corona discharge
A corona discharge is an electrical discharge brought on by the ionization of a fluid such as air surrounding a conductor that is electrically charged. Spontaneous corona discharges occur naturally in high-voltage systems unless care is taken to limit the electric field strength. A corona will occur when the strength of the electric field (potential gradient) around a conductor is high enough to form a conductive region, but not high enough to cause electrical breakdown or arcing to nearby objects. It is often seen as a bluish (or another colour) glow in the air adjacent to pointed metal conductors carrying high voltages and emits light by the same property as a gas discharge lamp.
In many high voltage applications, the corona is an unwanted side effect. Corona discharge from high voltage electric power transmission lines constitutes an economically significant waste of energy. Corona discharges are suppressed by improved insulation, corona rings, and making high voltage electrodes in smooth rounded shapes.
ABCD parameters
A, B, C, D are the constants also known as the transmission parameters or chain parameters. These parameters are used for the analysis of an electrical network. It is also used for determining the performance of input, output voltage and current of the transmission network.
Propagation constant
The propagation constant of the sinusoidal electromagnetic wave is a measure of the change undergone by the amplitude and phase of the wave as it propagates in a given direction. The quantity being measured can be the voltage, the current in a circuit, or a field vector such as electric field strength or flux density. The propagation constant itself measures the change per unit length, but it is otherwise dimensionless. In the context of two-port networks and their cascades, propagation constant measures the change undergone by the source quantity as it propagates from one port to the next.
Attenuation constant
The real part of the propagation constant is the attenuation constant and is denoted by Greek lowercase letter α (alpha). It causes signal amplitude to decrease along a transmission line.
Phase constant
The imaginary part of the propagation constant is the phase constant and is denoted by Greek lowercase letter β (beta). It causes the signal phase to shift along a transmission line. Generally denoted in radians per meter (rad/m).
The propagation constant is denoted by Greek lowercase letter γ (gamma), and γ = α + jβ
Voltage Regulation
Voltage regulation is a measure of the change in the voltage magnitude between the sending and receiving end of a component, such as a transmission or distribution line. It is given in percentage for different lines.
Mathematically, voltage regulation is given by,
Line parameters of AC transmission
The AC transmission has four line parameters, these are the series resistance & inductance, and shunt capacitance and
admittance. These parameters are responsible
for distinct behavior of voltage and current waveforms along the
transmission line. Line parameters are generally represented in their
respective units per Km of length in transmission lines. So these parameters depend upon the geometric alignment of transmission
lines (no of conductors used, shape of conductors, physical spacing
between conductors and height above the ground etc.). These parameters
are independent of current and voltage of any of the sending or
receiving ends.
Series resistance
Definition
The electrical resistance of an object is property of a substance due to which it restricts the flow of electric current due to a potential difference in its two ends. The inverse quantity is , and is the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with the notion of mechanical friction. The SI unit of electrical resistance is the ohm (Ω), while electrical conductance is measured in siemens (S).
Characteristics
The resistance of an object depends in large part on the material it is made of—objects made of electrical insulators like rubber tend to have very high resistance and low conductivity, while objects made of electrical conductors like metals tend to have very low resistance and high conductivity. This material dependence is quantified by resistivity or conductivity. However, resistance and conductance are extensive rather than bulk properties, meaning that they also depend on the size and shape of an object. For example, a wire's resistance is higher if it is long and thin, and lower if it is short and thick. All objects show some resistance, except for superconductors, which have a resistance of zero.
The resistance (R) of an object is defined as the ratio of voltage across it (V) to current through it (I), while the conductance (G) is the inverse:
For a wide variety of materials and conditions, V and I are directly proportional to each other, and therefore R and G are constants (although they will depend on the size and shape of the object, the material it is made of, and other factors like temperature or strain). This proportionality is called Ohm's law, and materials that satisfy it are called ohmic materials. In other cases, such as a transformer, diode or battery, V and I are not directly proportional. The ratio V/I is sometimes still useful, and is referred to as a "chordal resistance" or "static resistance", since it corresponds to the inverse slope of a chord between the origin and an I–V curve. In other situations, the derivative may be most useful; this is called the "differential resistance".
Transmission lines, as they consist of conducting wires of very long length, have an electrical resistance that can't be neglected at all.
Series inductance
Definition
When current flows within a conductor, magnetic flux is set up. With the variation of current in the conductor, the number of lines of flux also changes, and an emf is induced in it (Faraday's Law). This induced emf is represented by the parameter known as inductance. It is customary to use the symbol L for inductance, in honour of the physicist Heinrich Lenz.
In the SI system, the unit of inductance is the henry (H), which is the amount of inductance which causes a voltage of 1 volt when the current is changing at a rate of one ampere per second. It is named for Joseph Henry, who discovered inductance independently of Faraday.
Types of inductance
The flux linking with the conductor consists of two parts, namely, the internal flux and the external flux :
The internal flux is induced due to the current flow in the conductor.
The external flux produced around the conductor is due to its current and the current of the other conductors place around it. The total inductance of the conductor is determined by the calculation of the internal and external flux.
Characteristics
The transmission line wiring is also inductive in nature and, the inductance of a single circuit line can be given mathematically by :
Where,
D is the physical spacing between the conductors.
is the radius of the fictitious conductor having no internal flux linkages but with the same inductace as the original conductor of radius r. A quantity of (=0.7788 appx.) is multiplied with the actual radius of conductor in order to account for the internal flux linkages(applicable to solid round conductors only).
is the permeability of free space and .
For transposed lines with two or more phases, the inductance between any two lines can be calculated using :
.
Where, is the geometric mean distance in between the conductors.
If the lines are not properly transposed, the inductances become unequal and contain imaginary terms due to mutual inductances. In case of proper transposition, all the conductors occupy the available positions equal distance and thus the imaginary terms are cancelled out. And all the line inductances become equal.
Shunt capacitance
Definition
Capacitance is the ratio of the change in an electric charge in a system to the corresponding change in its electric potential. The capacitance is a function only of the geometry of the design (e.g. area of the plates and the distance between them) and the permittivity of the dielectric material between the plates of the capacitor. For many dielectric materials, the permittivity and thus the capacitance is independent of the potential difference between the conductors and the total charge on them.
The SI unit of capacitance is the farad (symbol: F), named after the English physicist Michael Faraday. A 1 farad capacitor, when charged with 1 coulomb of electrical charge, has a potential difference of 1 volt between its plates. The reciprocal of capacitance is called elastance.
Types of capacitance
There are two closely related notions of capacitance self-capacitance and mutual capacitance :
For an isolated conductor, there exists a property called self-capacitance, which is the amount of electric charge that must be added to an isolated conductor to raise its electric potential by one unit (i.e. one volt, in most measurement systems). The reference point for this potential is a theoretical hollow conducting sphere, of infinite radius, with the conductor centered inside this sphere. Any object that can be electrically charged exhibits self-capacitance. A material with a large self-capacitance holds a more electric charge at a given voltage than one with low self-capacitance.
The notion of mutual capacitance is particularly important for understanding the operations of the capacitor, one of the three elementary linear electronic components (along with resistors and inductors).In electrical circuits, the term capacitance is usually a shorthand for the mutual capacitance between two adjacent conductors, such as the two plates of a capacitor.
Characteristics
Transmission line conductors constitute a capacitor between them, exhibiting mutual capacitance. The conductors of the transmission line act as a parallel plate of the capacitor and the air is just like a dielectric medium between them. The capacitance of a line gives rise to the leading current between the conductors. It depends on the length of the conductor. The capacitance of the line is proportional to the length of the transmission line. Their effect is negligible on the performance of lines with a short length and low voltage. In the case of high voltage and long lines, it is considered as one of the most important parameters. The shunt capacitance of the line is responsible for Ferranti effect.
The capacitance of a single phase transmission line can be given mathematically by :
Where,
D is the physical spacing between the conductors.
r is the radius of each conductor.
is the permittivity of air and
For lines with two or more phases, the capacitance between any two lines can be calculated using :
Where, is the geometric mean distance of the conductors.
The effect of self-capacitance, on a transmission line, is generally neglected because the conductors are not isolated and thus there exists no detectable self-capacitance.
Shunt admittance
Definition
In electrical engineering, admittance is a measure of how easily a circuit or device will allow a current to flow. It is defined as the reciprocal of impedance. The SI unit of admittance is the siemens (symbol S); the older, synonymous unit is mho, and its symbol is ℧ (an upside-down uppercase omega Ω). Oliver Heaviside coined the term admittance in December 1887.
Admittance is defined as
where
Y is the admittance, measured in siemens
Z is the impedance, measured in ohms
Characteristics
Resistance is a measure of the opposition of a circuit to the flow of a steady current, while impedance takes into account not only the resistance but also dynamic effects (known as reactance). Likewise, admittance is not only a measure of the ease with which a steady current can flow but also the dynamic effects of the material's susceptance to polarization:
where
is the admittance, measured in siemens.
is the conductance, measured in siemens.
is the susceptance, measured in siemens.
The dynamic effects of the material's susceptance relate to the universal dielectric response, the power-law scaling of a system's admittance with frequency under alternating current conditions.
In the context of electrical modelling of transmission lines, shunt components that provide paths of least resistance in certain models are generally specified in terms of their admittance. Transmission lines can span hundreds of kilometres, over which the line's capacitance can affect voltage levels. For short length transmission line analysis, this capacitance can be ignored and shunt components are not necessary for the model. Lines with more length, contain a shunt admittance governed by
where
Y – total shunt admittance
y – shunt admittance per unit length
l – length of the line
C – capacitance of the line
Modelling of transmission lines
Two port networks
A two-port network (a kind of four-terminal network or quadripole) is an electrical network (circuit) or device with two pairs of terminals to connect to external circuits. Two terminals constitute a port if the currents applied to them satisfy the essential requirement known as the port condition: the electric current entering one terminal must equal the current emerging from the other terminal on the same port. The ports constitute interfaces where the network connects to other networks, the points where signals are applied or outputs are taken. In a two-port network, often port 1 is considered the input port and port 2 is considered the output port.
The two-port network model is used in mathematical circuit analysis techniques to isolate portions of larger circuits. A two-port network is regarded as a "black box" with its properties specified by a matrix of numbers. This allows the response of the network to signals applied to the ports to be calculated easily, without solving for all the internal voltages and currents in the network. It also allows similar circuits or devices to be compared easily. For example, transistors are often regarded as two-ports, characterized by their h-parameters (see below) which are listed by the manufacturer. Any linear circuit with four terminals can be regarded as a two-port network provided that it does not contain an independent source and satisfies the port conditions.
Transmission matrix and ABCD parameters
Oftentimes, we are only interested in the terminal characteristics of the transmission line, which are the voltage and current at the sending and receiving ends, for performance analysis of the line. The transmission line itself is then modelled as a "black box" and a 2 by 2 transmission matrix is used to model its behaviour, as follows
Derivation
This equation in matrix form, consists of two individual equations as stated below:
Where,
is the sending end voltage
is the receiving end voltage
is the sending end current
is the receiving end current
Now, if we apply open circuit at the receiving end, the effective load current will be zero (i.e. IR = 0)
1.
So, the parameter A is the ratio of sending end voltage to receiving end voltage, thus called the voltage ratio. Being the ratio of two same quantities, the parameter A is unitless.
2.
So, the parameter C is the ratio of sending end current to receiving end voltage, thus called the transfer admittance and the unit of C is Mho ().
Now, if we apply short circuit at the receiving end, the effective receiving end voltage will be zero (i.e. VR = 0)
1.
So, the parameter B is the ratio of sending end voltage to receiving end current, thus called the transfer impedance and the unit of C is Ohm (Ω).
2.
So, the parameter D is the ratio of sending end current to receiving end current, thus called the current ratio. Being the ratio of two same quantities, the parameter D is unitless.
ABCD parameter values
To summarize, ABCD Parameters for a two port(four terminal) passive, linear and bilateral network is given as :
Properties
The line is assumed to be a reciprocal, symmetrical network, meaning that the receiving and sending labels can be switched with no consequence. The transmission matrix T also has the following properties:
The A, B, C and D constants are complex numbers due to the complex values of transmission parameters. And because of the complex nature, they are represented as Vectors in the Complex Plane (phasors).
(Condition for reciprocity)
(condition for symmetry)
The parameters A, B, C, and D differ depending on how the desired model handles the line's resistance (R), inductance (L), capacitance (C), and shunt (parallel, leak) conductance G. The four main models are the short line approximation, the medium line approximation, the long line approximation (with distributed parameters), and the lossless line. In all models described, a capital letter such as R refers to the total quantity summed over the line and a lowercase letter such as r refers to the per-unit-length quantity.
Classification of AC transmission line
Classification overview
The AC transmission line has resistance R, inductance L, capacitance C and the shunt or leakage conductance G. These parameters along with the load and the transmission line determines the performance of the line. The term performance means the sending end voltage, sending
end currents, sending end factor, power loss in the line, efficiency of the transmission line, regulate and limit of power flow during efficiency and transmission, regulation and limits of power during the steady-state and transient condition. AC transmission line is
generally categorized into three classes
Short Transmission Line (line length ≤ 60 km)
Medium Transmission Line (80 km ≤ Line length ≤ 250 km)
Long Transmission Line (Line length ≥ 250 km)
The classification of the transmission line depends on the frequency of power transfer and is an assumption made for ease of calculation of line performance parameters and its losses. And because this, the range of length for the categorization of a transmission line is not rigid. The ranges of length may vary (a little), and all of them are valid in their areas of approximation.
Basis of classification
Derivation of voltage\current wavelength
Current and voltage propagate in a transmission line with a speed equal to the speed of light (c) i.e. appx. and the frequency (f) of voltage or current is 50 Hz ( although in the America and parts of Asia it is typically 60 Hz)
Therefore, wavelength (λ) can be calculated as below :
or,
or,
Reason behind classification
A transmission line with 60 km of length is very very small( times) when compared with wavelength i.e. 6000 km. Up to 240 km ( times of wavelength) (250 km is taken for easy remembering) length of the line, current or voltage waveform is so small that it can be approximated to a straight line for all practical purposes. For line length of about 240 km parameters are assumed to be lumped (though practically these parameters are always distributed). Therefore, the response of transmission line for a length up to 250 km can be considered linear and hence the equivalent circuit of the line can be approximated to a linear circuit.
But if the length of the line is more than 250 km say 400 km i.e. times of wavelength, then the waveform of current or voltage can not be considered linear and therefore we need to use integration for the analysis of these lines.
For the lines of up to 60 km of length is so short, that the effect of shunt parameters are nearly undetectable throughout the line. And hence, these linear lines are categorized as Short Transmission Lines.
For the lines of effective length in between 60 km to 250 km, the effect of shunt parameters can not be neglected. And hence, they are assumed as lumped either at the middle of the line (a nominal T representation) or at the two ends of the line (a nominal Π representation). These linear lines are categorized as Medium Transmission Lines
For transmission lines of effective length above 250 km, the equivalent circuit can not be considered as linear. The parameters are distributed and rigorous calculations are required for performance analysis. These non-linear lines are categorized as Long Transmission Lines.
Short transmission line
The transmission lines which have a length less than 60 km are generally referred to as short transmission lines. For its short length, parameters like electrical resistance, impedance and inductance of these short lines are assumed to be lumped. The shunt capacitance for a short line is almost negligible and thus, are not taken into account (or assumed to be zero).
Derivation of ABCD parameter values
Now, if the impedance per km for an l km of line is, and the sending end & receiving end voltages make an angle of & respectively, with the receiving end current. Then, the total impedance of the line will be,
The sending end voltage and current for this approximation are given by :
In this, the sending and receiving end voltages are denoted by and respectively. Also the currents and are entering and leaving the network respectively.
So, by considering the equivalent circuit model for the short transmission line, the transmission matrix can be obtained as follows:
Therefore, the ABCD parameters are given by :
A = D =1, B = Z Ω and C = 0
Medium transmission line
The transmission line having its effective length more than 80 km but less than 250 km is generally referred to as a medium transmission line. Due to the line length being considerably high, shunt capacitance along with admittance Y of the network does play a role in calculating the effective circuit parameters, unlike in the case of short transmission lines. For this reason, the modelling of a medium length transmission line is done using lumped shunt admittance along with the lumped impedance in series to the circuit.
Counterintuitive behaviours of medium-length transmission lines:
voltage rise at no load or small current (Ferranti effect)
receiving-end current can exceed sending-end current
These lumped parameters of a medium length transmission line can be represented using two different models, namely :
Nominal Π representation
In case of a nominal Π representation, the total lumped shunt admittance is divided into 2 equal halves, and each half with value Y ⁄ 2 is placed at both the sending & receiving end, while the entire circuit impedance is lumped in between the two halves. The circuit, so formed resembles the symbol of pi (Π), hence is known as the nominal Π (or Π network representation) of a medium transmission line. It is mainly used for determining the general circuit parameters and performing load flow analysis.
Derivation of ABCD parameter values
Applying KCL at the two shunt ends, we get
In this,
The sending and receiving end voltages are denoted by and respectively. Also the currents and are entering and leaving the network respectively.
are the currents through the shunt capacitances at the sending and receiving end respectively whereas is the current through the series impedance.
Again,
or,
So, by substituting we get :
or,
The equation obtained thus, eq() & () can be written into matrix form as follows :
so, the ABCD parameters are :
A = D = per unit
B =Z Ω
C =
Nominal T representation
In the nominal T model of a medium transmission line, the net series impedance is divided into two halves and placed on either side of the lumped shunt admittance i.e. placed in the middle. The circuit so formed resembles the symbol of a capital T or star(Y), and hence is known as the nominal T network of a medium length transmission line.
derivation of ABCD parameter values
The application of KCL at the juncture(the neutral point for Y connection) gives,
The above equation can be rearranged as,
Here, the sending and receiving end voltages are denoted by and respectively. Also the currents and are entering and leaving the network respectively
Now, for the receiving end current, we can write :
By rearranging the equation and replacing the value of with the derived value, we get :
Now, the sending end current can be written as:
Replacing the value of in the above equation :
The equation obtained thus, eq.() & eq.() can be written into matrix form as follows :
So, the ABCD parameters are :
A = D = per unit
B =
C =
Long Transmission Line
A transmission line having a length more than 250 km is considered as a long transmission line. Unlike short and medium lines the line parameters of long transmission line are assumed to be distributed at each point of line uniformly. Thus modelling of a long line is somewhat difficult. But a few approaches can be made based on the length and values of line parameters. For a long transmission line, it is considered that the line may be divided into various sections, and each section consists of inductance, capacitance, resistance and conductance, as shown in the RLC (resistance and inductance in series, with shunt capacitance) cascade model.
Derivation of ABCD parameter values
Cascaded Model approach
Considering a bit smaller part of a long transmission line having length dx situated at a distance x from the receiving end. The series impedance of the line is represented by zdx and ydx is the shunt impedance of the line. Due to charging current and corona loss, the current is not uniform along the line. Voltage is also different in different parts of the line because of inductive reactance.
Where,
z – series impedance per unit length, per phase
y – shunt admittance per unit length, per phase to neutral
Again, as
Now for the current through the strip, applying KCL we get,
The second term of the above equation is the product of two small quantities and therefore can be neglected.
For we have,
Taking the derivative concerning x of both sides, we get
Substitution in the above equation results
The roots of the above equation are located at .
Hence the solution is of the form,
Taking derivative with respect to x we get,
Combining these two we have,
The following two quantities are defined as,
, which is called the characteristic impedance
, which is called the propagation constant
Then the previous equations can be written in terms of the characteristic impedance and propagation constant as,
Now, at we have, and
Therefore, by putting at eq.() & eq.() we get,
Solving eq.() & eq.() we get the following values for :
Also, for , we have and .
Therefore, by replacing x by l we get,
Where,
is called incident voltage wave
is called reflected voltage wave
We can rewrite the eq.() & eq.() as,
So, by considering the corresponding analogy for long transmission line, the obtained equations i.e. eq.() eq.() can be written into matrix form as follows:
The ABCD parameters are given by :
A = D =
B =
C =
Π Representation approach
Like the medium transmission line, the long line can also be approximated into an equivalent Π representation. In the Π-equivalent of a long transmission line, the series impedance is denoted by Z′ while the shunt admittance is denoted by Y′.
So, the ABCD parameters of this long line can be defined like medium transmission line as :
A = D = per unit
B = Z′ Ω
C =
Comparing it with the ABCD parameters of cascaded long transmission model, we can write :
or,
Where Z(= zl), is the total impedance of the line.
By rearranging the above equation,
or,
This can be further reduced to,
where Y(= yl) is called the total admittance of the line.
Now, if the line length(l) is small, .
Now, if the line length (l) is small, it is found that Z = Z′ and Y = Y′.
This refers that if the line length(l) is small, the nominal-π representation incorporating the assumption of lumped parameters can be befitting. But if the length of the line(l) exceeds a certain boundary(near about 240 to 250) the nominal-π representation becomes erroneous and can not be used further, for performance analysis.
Travelling waves
Travelling waves are the current and voltage waves that create a disturbance and moves along the transmission line from the sending end of a transmission line to the other end at a constant speed. The travelling wave plays a major role in knowing the voltages and currents at all the points in the power system. These waves also help in designing the insulators, protective equipment, the insulation of the terminal equipment, and overall insulation coordination.
When the switch is closed at the transmission line's starting end, the voltage will not appear instantaneously at the other end. This is caused by the transient behaviour of inductor and capacitors that are present in the transmission line. The transmission lines may not have physical inductor and capacitor elements but the effects of inductance and capacitance exist in a line. Therefore, when the switch is closed the voltage will build up gradually over the line conductors. This phenomenon is usually called as the voltage wave is travelling from the transmission line's sending end to the other end. And similarly, the gradual charging of the capacitances happens due to the associated current wave.
If the switch is closed at any instant of time, the voltage at load does not appear instantly. The 1st section will charge first and then it will charge the next section. Until and unless a section gets charged the successive section will not be charged .thus this process is a gradual one. It can be realized such that several water tanks are placed connectively and water flows from the 1st tank to the last tank.
See also
Electric power transmission
Dynamic demand (electric power)
Demand response
List of energy storage projects
Traction power network
Backfeeding
Conductor marking lights
Double-circuit transmission line
Electromagnetic Transients Program (EMTP)
Flexible AC transmission system (FACTS)
Geomagnetically induced current, (GIC)
Grid-tied electrical system
List of high voltage underground and submarine cables
Load profile
Power line communications (PLC)
Power system simulation
Radio frequency power transmission
Wheeling (electric power transmission)
References
Further reading
Grigsby, L. L., et al. The Electric Power Engineering Handbook. USA: CRC Press. (2001).
The Physics of Everyday Stuff - Transmission Lines
Electrical engineering
Electric power transmission
Scientific modelling
Power engineering | Performance and modelling of AC transmission | [
"Engineering"
] | 8,207 | [
"Power engineering",
"Electrical engineering",
"Energy engineering"
] |
61,328,640 | https://en.wikipedia.org/wiki/Difluorosilane | Difluorosilane is a gaseous chemical compound with formula SiH2F2. It can be considered as a derivative of silane with two hydrogen atoms replaced with fluorine.
Production
Difluorosilane can be made by fluorinating dichlorosilane with antimony trifluoride.
3 SiH2Cl2 + 2 SbF3 → 3 SiH2F2 + 2 SbCl3
Some is also made in a reaction of silicon tetrafluoride with hydrogen
SiF4 + 2 H2 → SiH2F2 + 2 HF
Traces of difluorosilane are made when coal is burnt.
Properties
Difluorosilane is a gas with boiling point −77.8 °C, and a freezing point of −122 °C. It has no colour. The silicon–fluorine bond length in difluorosilane is 1.358 Å which is greater than that in fluorosilane but less than the length in trifluorosilane.
Reactions
In an electric discharge, hydrogen atoms are preferentially removed from the molecule and SiHF2SiHF2 is formed along with hydrogen.
2 SiH2F2 → SiHF2SiHF2 + H2
At elevated temperatures, difluorosilane can disproportionate by swapping hydrogen and fluorine atoms between molecules to form fluorosilane and trifluorosilane.
Use
Difluorosilane is used in dental varnish in order to prevent tooth cavities.
Difluorosilane is also used in chemical vapour deposition to deposit silicon nitride films.
References
Fluorine compounds
Silicon compounds
Gases | Difluorosilane | [
"Physics",
"Chemistry"
] | 362 | [
"Statistical mechanics",
"Gases",
"Phases of matter",
"Matter"
] |
61,328,950 | https://en.wikipedia.org/wiki/Boron%20monohydride | Borane(1), boron monohydride, hydridoboron or borylene is the molecule with the formula BH. It exists as a gas but rapidly degrades when condensed. By contrast, the cluster B12H122- (dodecaborate), which has very similar empirical formula, forms robust salts.
Formation
Boron monohydride can be formed from borane carbonyl exposed to ultraviolet light. BH3CO → BH + CH2O
Boron monohydride is formed when boron compounds are heated to a high temperature in the presence of hydrogen.
Boron monohydride is formed when the boron anion B− reacts with a hydrogen ion H+. It is also formed when atomic boron reacts with hydrogen. B + H2 → BH + H. There is too much energy in the reaction for BH2 to be stable.
Boron monohydride probably exists in sunspots, but as of 2008 has not been detected.
Properties
The ionization potential is around 9.77 eV. The dissociation energy for the ground state molecule is 81.5 kcal/mol. The electron affinity is roughly 0.3 eV, and the HB− ion is formed.
The dipole moment of the molecule in its ground state is 1.27 debye and for the first excited electronic state A1Π is 0.58 debye.
The spectrum of boron monohydride includes a molecular band for the lowest electronic transition X1Σ+ → A1Π with a band head at 433.1 nm (for 0→0) and 437.1 (for 0→1) The spectrum contains P, Q, and R branches.
Although BH is a closed shell molecule, it is paramagnetic independent of temperature.
Reactions
Boron monohydride is unstable in bulk and disappears quickly on a timescale of 20 ns when at a pressure of 20 Torr.
Boron monohydride reacts with oxygen, probably forming HBO. Boron monohydride shows no reaction with methane, but reacts with propane to give C3H7BH2. With nitric oxide (NO) it probably yields HBO and HBNO. Boron monohydride appears to add onto double bonds in unsaturated organic compounds. It also reacts with water.
Boron monohydride can take on the form of solid poly-borane(1) which spontaneously inflames in air.
Solid BH is predicted to take on an Ibam phase at pressures over 50 GPa and then become a metallic P6/mmm phase over 168 GPa.
Ions
Both a cation and a dication are known. The dication HB2+ can be supported by a σ-donating ligand framework with two links. The dianion can also be stabilized by an amine.
References
Boranes
Free radicals
Diatomic molecules | Boron monohydride | [
"Physics",
"Chemistry",
"Biology"
] | 615 | [
"Molecules",
"Free radicals",
"Senescence",
"Biomolecules",
"Diatomic molecules",
"Matter"
] |
61,329,044 | https://en.wikipedia.org/wiki/K.%20Radway%20Allen%20Award | The K. Radway Allen Award is the highest honour awarded by the Australian Society for Fish Biology. It recognises individuals who have made an "outstanding contribution in fish or fisheries science." The award, inaugurated in 1995, is named for New Zealand fisheries biologist Kenneth Radway Allen.
Although the process of the award is annual, it is not necessarily awarded every year. Between 1995 and 2013, the K. Radway Allen Award was given every two to four years; since 2013, it has been awarded annually. Recipients need not be a member of the Australian Society for Fish Biology, although most of their research must have been undertaken in Australia.
K. Radway Allen
Kenneth Radway Allen (1911 – 2008) was a New Zealand fisheries biologist. After a MSc from Cambridge University, Allen arrived in New Zealand and worked for many years at what was to become the Department of Scientific and Industrial Research. In 1972, he moved to Cronulla, south of Sydney, New South Wales, to become head of the CSIRO Division of Fisheries and Oceanography, where he worked until he retired.
Recipients
The K. Radway Allen Award was first awarded in 1995, to researcher Peter C. Young. As of July 2020, 14 researchers have received the honour.
See also
List of biology awards
References
Australian science and technology awards
Biology awards
Awards established in 1995
1995 establishments in Australia | K. Radway Allen Award | [
"Technology"
] | 282 | [
"Science and technology awards",
"Biology awards"
] |
67,795,589 | https://en.wikipedia.org/wiki/Nandrolone%20nonanoate | Nandrolone nonanoate, also known as nandrolone pelargonate or as 19-nortestosterone 17β-nonanoate, is an androgen and anabolic steroid and an androgen ester—specifically, the C17β nonanoate (pelargonate) ester of nandrolone (19-nortestosterone)—which was studied but was never marketed.
References
Abandoned drugs
Alkene derivatives
Anabolic–androgenic steroids
Enones
Nonanoate esters
Nandrolone esters
Progestogens | Nandrolone nonanoate | [
"Chemistry"
] | 119 | [
"Drug safety",
"Abandoned drugs"
] |
67,795,795 | https://en.wikipedia.org/wiki/Judith%20Ann%20McKenzie | Judith Ann McKenzie (May 4, 1942 – August 11, 2023) was an American biogeochemist known for her research on past climate change, chemical cycles in sediments, and geobiology.
Education and career
McKenzie had an M.S. in chemistry from the University of Colorado, Boulder (1970), studied at Scripps Institution of Oceanography, and earned her Ph.D. from the Institute of Geology at ETH Zurich (1976). McKenzie remained at ETH as a postdoc until moving to the University of Florida Gainesville in 1985 where she was promoted to tenured professor in 1987. She returned to ETH Zurich and was appointed full professor in 1996 and later retired at the end of September 2007.
McKenzie served as president of the International Association of Sedimentologists (2002–2006) and the Geochemical Society (2002–2003). McKenzie has also worked within the International Ocean Drilling Program (IODP), specially within the Swiss contribution to the project and from 2006 to 2008 she presented lectures on the deep biosphere in the distinguished lecture series of the European Consortium for Ocean Research Drilling.
In a 2011 interview conducted by the European Association of Geochemistry, McKenzie reflected on her career arc from her Ph.D. research on the chemistry of dolomites in Abu Dhabi to the research of her final postdoc on the geobiology of the dolomites in the same area. During the interview she noted this shift from focusing solely on the geology of rocks to an additional consideration of the biology of the rocks is reflected in the shift of the community at large.
McKenzie has enabled the ability of students to participate in field work through establishing summer schools within the International Association of Sedimentologists and by establishing the Judith McKenzie field work award for graduate students using funds from the Emile Argand Award she received in 2016. McKenzie received multiple awards (details below) and has shared insight on how to improve the diversity of award winners within geosciences.
Research
McKenzie's research used the sedimentary record to define past climates and change over time. This research partially relies on quantifying stable isotopes of dolomite in Abu Dhabi sabkhas and evaporites in Sicily. She has also examined the impact of biological activity on the carbon and nitrogen isotopic ratio in sediments. Cindy Lee, McKenzie, and Michael Sturm used stable isotopes to examine fluxes in particulate matter in a Swiss lake. In the same lake David Hollander and McKenzie examined the fractionation of carbon isotopes as a potential measure of the past atmospheric carbon dioxide concentrations.
McKenzie's work on the 'dolomite problem', an enigma whereby the past prevalence of dolomite is higher than what is found in modern environments, has recently revealed that dolomite is precipitated by bacteria living under anoxic conditions which was first observed in the laboratory with sulfate-reducing Desulfovibrio, and subsequently with microbes isolated from a coastal lagoon in Brazil and in the coastal sabkha of Abu Dhabi.
Later life and death
McKenzie retired as a full Professor of Earth System Sciences at ETH Zurich in 2007.
Judith Ann McKenzie died on August 11, 2023, at the age of 81.
Awards
Fellow, American Geophysical Union (1999)
Rachel Carson Award, American Geophysical Union (2003)
Jean Baptiste Lamarck Medal, European Geosciences Union (2006)
Member, Royal Danish Academy of Sciences and Letters (2006)
Gustav Steinmann Medal,German Geological Society-Geological Association (2008)
Honorary Member, International Association of Sedimentologists (2015)
Emile Argand Award, International Union of Geological Sciences (2016)
William H. Twenhofel Medal, Society for Sedimentary Geology (2017)
References
External links
April 11, 2011
1942 births
2023 deaths
University of Colorado Boulder alumni
Scripps Institution of Oceanography alumni
Academic staff of ETH Zurich
American women geologists
American geologists
Biogeochemists
Scientists from Pittsburgh
21st-century American women scientists
Presidents of the Geochemical Society
ETH Zurich alumni | Judith Ann McKenzie | [
"Chemistry"
] | 818 | [
"Geochemists",
"Presidents of the Geochemical Society",
"Biogeochemistry",
"Biogeochemists"
] |
67,795,808 | https://en.wikipedia.org/wiki/Aleksandr%20Kharkevich | Aleksandr Aleksandrovich Kharkevich (; 3 February, 1904 – 30 March, 1965) was a specialist in radio engineering, electronics, acoustics and instrumentation. He was a corresponding member in 1960 and an academician in 1964 of the Academy of Sciences of the Soviet Union.
Biography
He was born in 1904 in Saint Petersburg. From 1922 to 1930 he studied at the Saint Petersburg Electrotechnical University. He began his career in 1924 as a battery laboratory fitter, later as an intern, technician and supervisor at the plant. The first of his scientific and engineering was instrument engineering. He created a number of original designs of devices, many of which were kept in Soviet industry as universally recognized examples for many years. He also successfully developed a number of issues of spectral theory, the theory of nonlinear oscillations, and parametric phenomena.
In 1938 he is already a doctor of technical sciences and professor. At this time he gets a chair at the St. Petersburg State University of Telecommunications, where he works until 1941. In 1948 he was elected a corresponding member of the Academy of Sciences of the Ukrainian SSR.
In the early 1950s, he moved to Moscow and, combining several disparate groups, created the Institute for Information Transmission Problems of the Academy of Sciences of the Soviet Union. On December 17, 1956, A. A. Kharkevich gave a speech stating that "considering the set and value of communication problems, it is time to create Institute for Telecommunications in USSR Academy of Sciences, which has already been decided in principle, but is delayed for technical reasons". He headed this institute until his death. In 2004 the institute was named after A. A. Kharkevich.
In 1962, he published an article in the journal "Communist" about a computer network for processing information and control of the economy. In fact, he proposed to make a network like the modern Internet for the needs of algorithmic governance.
In his later years, A. A. Kharkevich focused on the development of information theory and cybernetics. He died on March 30, 1965, in Moscow. He is buried at Novodevichy Cemetery.
Awards
He was awarded the Order of Lenin and the Order of the Red Banner of Labour.
Bibliography
A. A. Kharkevich published more than 100 scientific works and 12 books, many of which have had several editions and translated into several foreign countries (USA, France, Poland, China).
References
1904 births
1965 deaths
Academic staff of Lviv Polytechnic
Full Members of the USSR Academy of Sciences
Saint Petersburg Electrotechnical University alumni
Recipients of the Order of Lenin
Recipients of the Order of the Red Banner of Labour
Acousticians
Cyberneticists
Electrical engineering academics
Government by algorithm
Internet theorists
Russian information theorists
Soviet engineers
Burials at Novodevichy Cemetery | Aleksandr Kharkevich | [
"Engineering"
] | 563 | [
"Government by algorithm",
"Automation"
] |
67,798,185 | https://en.wikipedia.org/wiki/Zero-knowledge%20service | In cloud computing, the term zero-knowledge (or occasionally no-knowledge or zero access) refers to an online service that stores, transfers or manipulates data in a way that maintains a high level of confidentiality, where the data is only accessible to the data's owner (the client), and not to the service provider. This is achieved by encrypting the raw data at the client's side or end-to-end (in case there is more than one client), without disclosing the password to the service provider. This means that neither the service provider, nor any third party that might intercept the data, can decrypt and access the data without prior permission, allowing the client a higher degree of privacy than would otherwise be possible. In addition, zero-knowledge services often strive to hold as little metadata as possible, holding only that data that is functionally needed by the service.
The term "zero-knowledge" was popularized by backup service SpiderOak, which later switched to using the term "no knowledge" to avoid confusion with the computer science concept of zero-knowledge proof.
Disadvantages
Most cloud storage services keep a copy of the client's password on their servers, allowing clients who have lost their passwords to retrieve and decrypt their data using alternative means of authentication; but since zero-knowledge services do not store copies of clients' passwords, if a client loses their password then their data cannot be decrypted, making it practically unrecoverable.
Most cloud storage services are also able to furnish access requests from law enforcement agencies for similar reasons; zero-knowledge services, however, are unable to do so, since their systems are designed to make clients' data inaccessible without the client's explicit cooperation.
References
Privacy
Computer security
Backup software
Secure communication
Internet terminology | Zero-knowledge service | [
"Technology"
] | 374 | [
"Computing terminology",
"Internet terminology"
] |
67,801,265 | https://en.wikipedia.org/wiki/Guilded | Guilded is a VoIP, instant messaging, and digital distribution platform designed by Guilded Inc. and was bought by Roblox Corporation on August 16, 2021 for $90M. Guilded is based in San Francisco. Users communicate with voice calls, video calls, text messaging, media and files in private chats or as part of communities called "servers". Guilded was founded by Eli Brown, a former Facebook and Xbox employee. Guilded is available on Windows, Linux, macOS, Android, and iOS.
Guilded is a main competitor of Discord and primarily focuses on video game communities, such as those focused on competitive gaming and esports. It provides features intended for video gaming clans, such as scheduling tools and integrated calendars. Guilded is developed by Guilded, Inc. which has been an independent product group of the Roblox Corporation since August 16, 2021.
On May 31, 2024, Roblox Corporation announced that all current accounts must have a Roblox account linked before July 15, 2024 to continue using their Guilded account, while new users will only have the option to sign up with Roblox.
On October 12, 2024, Guilded restricted access to users from Russia due to Guilded having the fear that it would be blocked in the country.
References
2017 software
Android (operating system) software
Freeware
IOS software
Instant messaging clients for Linux
Instant messaging clients
Internet properties established in 2017
MacOS instant messaging clients
Proprietary cross-platform software
Proprietary freeware for Linux
Voice over IP clients for Linux
Windows instant messaging clients | Guilded | [
"Technology"
] | 320 | [
"Instant messaging",
"Instant messaging clients"
] |
67,802,155 | https://en.wikipedia.org/wiki/NGC%203426 | NGC 3426 is a lenticular galaxy located in the constellation Leo. It was discovered on March 23, 1887, by the astronomer Lewis A. Swift.
One supernova has been observed in NGC 3426: SN2019ape (typeIc, mag. 18.6).
See also
List of NGC objects (3001–4000)
References
External links
Leo (constellation)
3426
Lenticular galaxies
032577
Discoveries by Lewis Swift
18870323
+03-28-020
05975 | NGC 3426 | [
"Astronomy"
] | 106 | [
"Leo (constellation)",
"Constellations"
] |
67,803,756 | https://en.wikipedia.org/wiki/Guluronic%20acid | Guluronic acid is a uronic acid monosaccharide that may be derived from gulose. -Guluronic acid is a C-3 epimer of -galacturonic acid and a C-5 epimer of -mannuronic acid. Along with -mannuronic acid, -guluronic acid is a component of alginic acid, a polysaccharide found in brown algae. α-L-Guluronic acid has been found to bind divalent metal ions (such as calcium and strontium) through the carboxylate moiety and through the axial-equatorial-axial arrangement of hydroxyl groups found around the ring.
References
Uronic acids | Guluronic acid | [
"Chemistry"
] | 154 | [
"Organic compounds",
"Organic compound stubs",
"Organic chemistry stubs"
] |
67,805,066 | https://en.wikipedia.org/wiki/Mannuronic%20acid | Mannuronic acid is a uronic acid monosaccharide that can be derived from mannose. Along with -guluronic acid, -mannuronic acid is a component of alginic acid, a polysaccharide found predominantly in brown algae. Mannuronic acid is also incorporated into some bacterial capsular polysaccharides.
References
Uronic acids | Mannuronic acid | [
"Chemistry"
] | 81 | [
"Organic compounds",
"Organic compound stubs",
"Organic chemistry stubs"
] |
67,805,310 | https://en.wikipedia.org/wiki/Andreaea%20nivalis | Andreaea nivalis, commonly known as snow rock-moss, is a species of moss in the Andreaea family found in Alaska, California, Oregon, Washington, Greenland, Spain, Japan, Russia and Poland. It is black and reddish, dioicous, and grows on wet, acidic rocks. It is threatened by droughts and global warming, and is a near-threatened species on the IUCN red list.
Description
Andreaea nivalis was first described in 1811. It is black and reddish, and grows in dense cushions. Its leaves can be secund to falcate-secund, meaning they can be sickle-shaped, and curved towards one side. They are mostly subulate, meaning they are awl-shaped. The leaves are mainly falcate-secund when dry. When moist, they are more spread out than when dry. The leaves have a strong costa, and they can have a width of or more, and a length of or more. Andreaea nivalis has sharp laminal papillae on its dorsal side, which almost reach to its base, and a very short fruit stalk. Unlike other mosses in its species, which have six-valved capsules, Andreaea nivalis can have capsules with two or four valves. There is always one capsule on each fruiting plant.
Distribution
Andreaea nivalis grows on wet acidic rocks, outcrops, and rocky areas, at medium to high elevations. It can be found in Greenland, Japan, Spain, Alaska, California, Oregon, and Washington. It has also been found in Poland and Spain. It is native to North America, Alaska, the UK, and Norway.
Reproduction
Andreaea nivalis is dioicous, which means its gametophytes only produce either sperm or eggs. Its perichaetial leaves, which enclose the moss's archegonia, reach to the top of the moss's capsules.
Conservation
Andreaea nivalis is near threatened on the IUCN red list. The main threats to this species are drought and global warming. Its population is currently decreasing. The IUCN has recommended land and water protection to conserve this species, and says that research is needed to monitor Andreaea nivalis's population trends.
References
External links
Information about Andreaea nivalis at a USDA website
Andreaeaceae
Plants described in 1811
Lithophytes
Near threatened biota of Europe
Taxa named by William Jackson Hooker | Andreaea nivalis | [
"Biology"
] | 507 | [
"Lithophytes",
"Plants"
] |
67,805,514 | https://en.wikipedia.org/wiki/NGC%20807 | NGC 807 is an elliptical galaxy located in the constellation Triangulum. It is listed as part of the New General Catalogue (NGC) of astronomical objects. It was discovered by the astronomer William Herschel on September 11, 1784.
One supernova has been observed in NGC 807: SN 2023abnb (type Ia, mag. 16.2).
References
Elliptical galaxies
0807
Triangulum
007934 | NGC 807 | [
"Astronomy"
] | 90 | [
"Triangulum",
"Constellations"
] |
67,805,581 | https://en.wikipedia.org/wiki/Eddy%20saturation%20and%20eddy%20compensation | Eddy saturation and eddy compensation are phenomena found in the Southern Ocean. Both are limiting processes where eddy activity increases due to the momentum of strong westerlies, and hence do not enhance their respective mean currents. Where eddy saturations impacts the Antarctic Circumpolar Current (ACC), eddy compensation influences the associated Meridional Overturning Circulation (MOC).
In recent decades wind stresses in the Southern Ocean have increased partly due to greenhouse gases and ozone depletion in the stratosphere. Because the ACC and MOC play an important role in the global climate; affecting the stratification of the ocean, uptake of heat, carbon dioxide and other passive tracers. Addressing how these increased zonal winds affect the MOC and the ACC will help understand whether the uptakes will change in the future, which could have serious impact on the carbon cycle. This remains an important and critical research topic.
Formation of eddies and overturning response
Dynamics in the Southern Ocean are dominated by two cells with opposing rotation, each is forced by surface buoyancy fluxes. Via isopycnals, tracers are transferred from the deep to the surface. Isopycnal slopes are key for determining the depth of the global Pycnocline, and where water mass outcrops are. Therefore, isopycnals play an important role in the interaction with the atmosphere. In the Southeren Ocean it is thought that isopycnals are steepened by wind forcing and baroclinic eddies are acting to flatten the isopycnals.
The westerly winds (), which make the ACC flow eastward, induce a clockwise rotating Eulerian meridional circulation () via Ekman dynamics, which is also known as the Deacon cell. This circulation acts to overturn isopycnals enhance the buoyance forcing and therefore increase the mean flow.
Although the ACC is very close to a geostrophic balance, when frontal jets reach a velocity that is high enough geostrophic turbulence (i.e. chaotic motion of fluids that are near to a state of hydrostatic balance and geostrophic balance) arises. Due to this geostrophic turbulence, potential energy stored in the fronts of jet streams is converted into eddy kinetic energy (EKE), which finally leads to the formation of mesoscale eddies. The surface EKE has increased in the recent decades, as proven by satellite altimetry. The relation between the increased wind stress and EKE is assumed to be near-linear, which explains the limited sensitivity of the ACC transport.
In areas where stratification is very weak the formation of eddies is often associated with barotropic instabilities. Where stratification is more substantial, baroclinic instabilities (misalignment of isobars and isopycnals) are the mean cause of the formation of eddies. Eddies have the tendency to flatten isopycnals (surfaces of equal buoyancy), which slow down the mean flow . Due to these instabilities a counterclockwise rotating eddy-induced circulation () is formed, which partially counteracts the Eulerian meridional circulation.
The balance between the two overturning circulations determines the residual overturning, . This residual flow () is assumed to be directed along mean buoyance surfaces in the interior but to have a diapycnal component in the mixed later.
Eddy saturation
The Southern Ocean contains a system of ocean currents, which together forms the Antarctic Circumpolar Current (ACC). These ocean currents are subject to strong westerly winds jointly responsible for driving the zonal transport of the ACC. In recent decades a positive trend in SAM index (Southern Annular Mode) is seen, which measures the zonal pressure difference between the latitudes of 40S and 65S, showing us that the zonal winds have increased in the Southern Ocean. Studies indicate that the zonal Ekman transport in the ACC is relatively insensitive to the increasing changes in wind stress. This behaviour can also be seen in the change in isopycnal slopes (surfaces of equal buoyancy), which show limited response despite intensification of western winds. Therefore, the increased momentum (due to enhanced wind stress) is diverted into the oceanic mesoscale and transferred to the bottom of the ocean instead of the horizontal mean flow. This flattens isopycnals (reduces buoyancy forcing) and therefore slows down the mean flow. This phenomenon is known as eddy saturation.
Eddy compensation
Alongside the ACC there is also the associated Meridional Overturning Circulation (MOC), which is also mainly driven by wind forcing. The insensitivity of the mean current to the accelerating wind forcing can also be seen in the MOC. This near independence of the MOC to the increase of wind stress is referred to as eddy compensation. There would be perfect eddy compensation when the Ekman transport would be balanced by eddy-induced transport.
There is a widespread belief that the sensitivities of the transport in the ACC and MOC are dynamically linked. However, note that eddy saturation and eddy compensation are distinct dynamical mechanisms. Occurrence of one does not necessarily entail the occurrence of the other. It is hypothesized that dearth of a dynamical link between eddy saturation and eddy compensation is a consequence of the depth dependence (cancellation between the Eulerian circulation and eddy-induced circulation). Currently it is assumed that the ACC is fully eddy saturated, but only partially eddy compensated. The degree to which there is eddy compensation in the Southern Ocean is currently unknown.
Models and sensitivity
Eddy permitting and eddy resolving models are used to examine the effect of eddy saturation and eddy compensation in the ACC. In these models resolution is of great importance. Ocean observations do not have a high enough resolution to fully estimate the degree of eddy saturation and eddy compensation. Idealized studies show that the MOC response is more sensitive to model resolution than the ACC transport. A general conclusion in such numerical models is that southward eddy transport in combination with enhanced westerlies results in an increase in EKE.
References
See also
Currents of the Southern Ocean
Physical oceanography
Fluid dynamics
Water waves | Eddy saturation and eddy compensation | [
"Physics",
"Chemistry",
"Engineering"
] | 1,299 | [
"Physical phenomena",
"Applied and interdisciplinary physics",
"Water waves",
"Chemical engineering",
"Waves",
"Physical oceanography",
"Piping",
"Fluid dynamics"
] |
67,805,862 | https://en.wikipedia.org/wiki/Aleksei%20Markushevich | Aleksei Ivanovich Markushevich (; , Petrozavodsk – 7 June 1979, Moscow) was a Soviet mathematician, mathematical educator, and historian of mathematics. He is known for the Farrell–Markushevich theorem.
Biography
Markushevich's father worked as a junior architect for the Olonets provincial government. In 1916 the family moved to Semipalatinsk, where he graduated from secondary school in 1924. In 1925 he matriculated at the First Central Asian State University (now the National University of Uzbekistan). There in 1930 he graduated and was admitted to the correspondence course (education by mail) of the graduate school. In autumn 1931 he became a graduate student in the Research Institute of Mechanics and Mathematics, Moscow State University. There he received in 1934 his Aspirantur (similar to a PhD) under the supervision of Mikhail Lavrentyev, became at the beginning of 1935 a senior researcher, and became in 1938 an associate professor. At Moscow State University, Markushevich received in 1944 his Russian Doctor of Sciences degree (habilitation) and in 1946 became a full professor, retaining that academic position until his death.
Markushevich was elected in 1945 a corresponding member and in 1950 a full member of Академии педагогических наук РСФСР (Academy of Pedagogical Sciences, Russian Soviet Federative Socialist Republic). For that academy he served as vice-president from 1950 to 1958 and again from 1964 to 1967. From 1958 to 1964 he was the primary deputy minister of education of the Russian Soviet Federative Socialist Republic.
In Академии педагогических наук СССР (Academy of Pedagogical Sciences of the USSR), he was elected a full member in 1967 and served as its vice-president from 1967 to 1975.
In 1978 he was an Invited Speaker at the International Congress of Mathematicians (ICM) in Helsinki.
The last years of his life were overshadowed by a scandal related to the theft of medieval European manuscripts from Российский государственный архив древних актов, РГАДА / RGADA (Russian State Archives of Ancient Documents; investigations revealed that the main buyer of the stolen documents was Markushevich.
He was buried in Moscow at the Kuntsevo Cemetery (section 10).
Mathematical research
Markushevich's mathematical research deals mainly with complex analysis, conformal mapping, and approximation theory. He published a series of papers on approximation, interpolation, and completeness; the papers contributed to the pioneering methods of functional analysis, in particular the theory of linear spaces, which began to be widely used in the theory of analytic functions.
Book publishing activities
He was head of the editorial office of mathematics of the Soviet Издательство технико-теоретической литературы (Publishing House of Technical and Theoretical Literature) from 1934 to 1937 and again from 1943 to 1947.
He initiated and participated in the publication of the series of books (Popular Lectures on Mathematics) published in 62 volumes from 1950 to 1992 and the series of books Библиотека учителя (Teacher's Library).
From 1951 to 1952 and from 1963 to 1966, he was among the initiators and editors of Энциклопедия элементарной математики (Encyclopedia of Elementary Mathematics).
Markushevich was keenly interested in the history of books. Beginning in the 1940s he collected old books of historical interest. In 1976, he donated his collection of incunables to the State Library of the USSR named after V.I. Lenin.
Educational reform
During the 1960s and 1970s Markushevich was a leading supporter of reforming the teaching of mathematics in Soviet schools. In the 1960s, he took part in the creation of new school textbooks on mathematics, developed the pedagogical theory of school textbooks, and worked on improving the training of school mathematics teachers. He was the chair of the joint commission of the Academy of Sciences of the Soviet Union and the Academy of Pedagogical Sciences of the USSR, which determined the content of education in secondary schools.
Selected publications
Articles
Die Arbeiten von C. F. Gauß über Funktionentheorie. (The works of C. F. Gauss on complex analysis) In: Hans Reichardt (ed.): C. F. Gauss. Gedenkband anlässlich des 100. Todestages am 23. Februar 1955. Teubner, Leipzig 1957, pp. 151–182.
A. N. Kolmogorov, A. P. Yushkevich (eds.), B. L. Laptev, B. A. Rosenfel'd, A. I. Markushevich: Mathematics of the 19th Century. Geometry, analytic function theory. Birkhäuser, Basel 1996. Markushevich contributed the section Analytic Function Theory.
Books
Theory of Analytic Functions. Hindustan Publishing Co., Delhi, 1963. (translation of 1961 Russian edition, revised from the 1944 Russian edition)
Skizzen zur Geschichte der analytischen Funktionen (Sketches on the history of analytic functions) (= Hochschulbücher für Mathematik. vol. 16). Deutscher Verlag der Wissenschaften, Berlin 1955.
Theory of functions of a complex variable. 3 vols. Prentice-Hall, 1965–1967
(1 volume abridgment of the 3 volumes translated by Richard A. Silverman)
Entire Functions. American Elsevier, 1966, 105 pages (translated from the 1965 Russian edition); (ebook)
The Remarkable Sine Functions. American Elsevier, 1966 (translated from 1965 Russian edition); (ebook)
(ebook translated from the 1979 Russian edition by G. Bluher)
References
External links
1908 births
1979 deaths
20th-century Russian mathematicians
People from Petrozavodsk
People from Petrozavodsky Uyezd
Academic staff of Moscow State University
Academicians of the RSFSR Academy of Pedagogical Sciences
Academicians of the USSR Academy of Pedagogical Sciences
Moscow State University alumni
National University of Uzbekistan alumni
Communist Party of the Soviet Union members
Members of the Supreme Soviet of the Russian Soviet Federative Socialist Republic, 1959–1963
Members of the Supreme Soviet of the Russian Soviet Federative Socialist Republic, 1963–1967
Recipients of the Order of Lenin
Recipients of the Order of the Red Banner of Labour
Complex analysts
Historians of mathematics
Mathematical analysts
Russian bibliophiles
Russian book and manuscript collectors
Soviet mathematicians
Burials at Kuntsevo Cemetery | Aleksei Markushevich | [
"Mathematics"
] | 1,451 | [
"Mathematical analysis",
"Mathematical analysts"
] |
76,547,127 | https://en.wikipedia.org/wiki/WonderFest | WonderFest is an American fan convention focusing on science fiction and horror, held annually since 1992 after two years as a predecessor event. "One of the biggest hobby events in the country," it takes place in Louisville, Kentucky, and is the site of the annual presentation of the Rondo Hatton Classic Horror Awards.
History
WonderFest originated in 1990 as the hobbyist club The Scale Figure Modelers Society's Louisville Plastic Kit & Toy Show, held at a Ramada Inn hotel. The club had been founded the year before by Irwin Severs and Larry Johnson. In 1992, the convention changed its name to WonderFest, and was held at a larger venue. Four years later, it relocated to its current home, the hotel Crowne Plaza, formerly Executive West. The convention formally split off from the hobbyist club after the 1997 show. The edition originally scheduled for May 30–31, 2020, and then October 24–25, 200, was canceled because of the COVID-19 pandemic.
Guests throughout the years have included filmmakers / TV producers Joe Dante, D. C. Fontana, Nicholas Meyer, Greg Nicotero, and George A. Romero, genre-film actors and actresses Dirk Benedict, Martine Beswick, Veronica and Angela Cartwright, Joanna Cassidy, Yvonne Craig, Claudia Christian, Denise Crosby, Sybil Danning, Keir Dullea, Anne Francis, Marta Kristen, Gary Lockwood, Kevin McCarthy, Lee Meriwether, Caroline Munro, Robert Picardo, Linnea Quigley, and Brinke Stevens, special effects artists Ray Harryhausen, Tom Savini, and Chris Walas, comics and children's-book writers / artists Frank Cho, Basil Gogos, Joe Jusko, Michael Kaluta, Mark Schultz, William Stout, and Bernie Wrightson, and horror scions Sara Karloff and Vanessa Harryhausen. It also features cosplayers.
Events there include the annual presentation of the Rondo Hatton Classic Horror Awards and the WonderFest Model Contest, hosted by Amazing Figure Modeler magazine. Charitable outreach has included raffles to benefit the Pediatric AIDS Foundation and the WHAS Crusade for Children.
In 2014, three Louisville, Kentucky-based podcasters attempted to set a Guinness World Record at WonderFest for the Longest Uninterrupted Webcast (now called now Longest Audio-Only Live Stream), Tower of Technobabble, to raise money for a local animal organization's spay and neuter program. They set the then-record of 41 hours.
The CEO as of 2004 was Dave Hodge. As of 2022, its CEO was Melina Angstrom.
References
External links
1990 establishments in Kentucky
Annual events in Kentucky
Science fiction conventions in the United States
Conventions in Kentucky
Recurring events established in 1990
Scale modeling
Multigenre conventions
Events in Louisville, Kentucky | WonderFest | [
"Physics"
] | 575 | [
"Scale modeling"
] |
76,547,408 | https://en.wikipedia.org/wiki/KPZ%20fixed%20point | In probability theory, the KPZ fixed point is a Markov field and conjectured to be a universal limit of a wide range of stochastic models forming the universality class of a non-linear stochastic partial differential equation called the KPZ equation. Even though the universality class was already introduced in 1986 with the KPZ equation itself, the KPZ fixed point was not concretely specified until 2021 when mathematicians Konstantin Matetski, Jeremy Quastel and Daniel Remenik gave an explicit description of the transition probabilities in terms of Fredholm determinants.
Introduction
All models in the KPZ class have in common, that they have a fluctuating height function or some analogue function, that can be thought of as a function, that models the growth of the model by time. The KPZ equation itself is also a member of this class and the canonical model of modelling random interface growth. The strong KPZ universality conjecture conjectures that all models in the KPZ universality class converge under a specific scaling of the height function to the KPZ fixed point and only depend on the initial condition.
Matetski-Quastel-Remenik constructed the KPZ fixed point for the -dimensional KPZ universality class (i.e. one space and one time dimension) on the polish space of upper semicontinous functions (UC) with the topology of local UC convergence. They did this by studying a particular model of the KPZ universality class the TASEP („Totally Asymmetric Simple Exclusion Process“) with general initial conditions and the random walk of its associated height function. They achieved this by rewriting the biorthogonal function of the correlation kernel, that appears in the Fredholm determinant formula for the multi-point distribution of the particles in the Weyl chamber. Then they showed convergence to the fixed point.
KPZ fixed point
Let denote a height function of some probabilistic model with denoting space-time. So far only the case for , also noted as , was deeply studied, therefore we fix this dimension for the rest of the article. In the KPZ universality class exist two equilibrium points or fixed points, the trivial Edwards-Wilkinson (EW) fixed point and the non-trivial KPZ fixed point. The KPZ equation connects them together.
The KPZ fixed point is rather defined as a height function and not as a particular model with a height function.
KPZ fixed point
The KPZ fixed point is a Markov process, such that the n-point distribution for and can be represented as
where and is a trace class operator called the extended Brownian scattering operator and the subscript means that the process in starts.
KPZ universality conjectures
The KPZ conjecture conjectures that the height function of all models in the KPZ universality at time fluctuate around the mean with an order of and the spacial correlation of the fluctuation is of order . This motivates the so-called 1:2:3 scaling which is the characteristic scaling for the KPZ fixed point. The EW fixed point has also a scaling the 1:2:4 scaling. The fixed points are invariant under their associated scaling.
1:2:3 scaling
The 1:2:3 scaling of a height function is for
where 1:3 and 2:3 stand for the proportions of the exponents and is just a constant.
Strong conjecture
The strong conjecture says, that all models in the KPZ universality class converge under 1:2:3 scaling of the height function if their initial conditions also converge, i.e.
with initial condition
where are constants depending on the model.
Weak conjecture
If we remove the growth term in the KPZ equation, we get
which converges under the 1:2:4 scaling
to the EW fixed point. The weak conjecture says now, that the KPZ equation is the only Heteroclinic orbit between the KPZ and EW fixed point.
Airy process
If one fixes the time dimension and looks at the limit
then one gets the Airy process which also occurs in the theory of random matrices.
References
Stochastic processes
Statistical mechanics
Fixed points (mathematics) | KPZ fixed point | [
"Physics",
"Mathematics"
] | 887 | [
"Mathematical analysis",
"Fixed points (mathematics)",
"Topology",
"Statistical mechanics",
"Dynamical systems"
] |
76,547,413 | https://en.wikipedia.org/wiki/Eclipses%20in%20mythology%20and%20culture | Eclipses of the Sun and of the Moon have been described by nearly every culture. In cultures without an astronomical explanation, eclipses were often attributed to supernatural causes or regarded as bad omens.
Religious and cultural practices
While solar and lunar eclipses are today understood astronomically as one celestial body shadowing another, their appearance from Earth does not intuitively belie a similar cause for each. Mark Littmann, Fred Espenak, and Ken Willcox classified solar eclipse mythologies into four distinct genres:
A celestial being (usually a monster) attempts to destroy the Sun.
The Sun fights with its lover the Moon.
The Sun and Moon make love and discreetly hide themselves in darkness.
The Sun god grows angry, sad, sick, or neglectful.
Abrahamic religions
Judaism
In the Talmud, solar eclipses are described as ill omens and several events in the Hebrew Bible are said to have occurred during eclipses. Judaism at large has been accepting of the modern astronomical explanation of eclipses and today many rabbis consider eclipses to be reminders of divinity and a time for prayer and introspection.
Christianity
The periodicity of lunar eclipses been deduced by Neo-Babylonian astronomers in the sixth century BCE and the periodicity of solar eclipses was deduced in first century BCE by Greek astronomers, who developed the Antikythera mechanism and had understood the Sun, Moon, and Earth to be spherical celestial bodies since Aristotle. The astronomical understanding of eclipses was thus well understood in the Ancient Near East in which Christianity developed. The New Testament describes the sky as darkening for hours during the crucifixion of Jesus. As the event's lengthy duration and occurrence on the day of a full moon made it clear to contemporary believers that it could not be an eclipse, early Christians interpreted this as an omen and sign of Jesus's divinity. In 12th-century Christian Europe, eclipses were thus connected to earthly rule, where the deaths of Charlemagne and Henry I were preceded by solar and lunar eclipses. Saints were often also connected with eclipses, with a solar eclipse at their death a sign of their holiness. Christian eschatology makes mention of eclipse-like phenomena, where Revelation 6:12 describes how "the sun became black as sackcloth, the full moon became like blood." A minority of modern Christians believe eclipses to portend the Second Coming.
Islam
Astronomy in the medieval Islamic world was well-developed, and contributions included Al-Ḥajjāj ibn Yūsuf ibn Maṭar's translation of Ptolemy's Almagest, in which he corrected Ptolemy's method for predicting eclipses. Theologically, the Quran explicitly rejects notions of the sun and moon's divinity:
In one hadith, Muhammad objects to followers' treatment of an eclipse as an omen and states that eclipses have no bearing on earthly life and death:
Because Muhammad instructed his followers to pray during eclipses as reminders of God's power, many Muslims today consider it sunnah to conduct a special prayer during solar eclipses, known as . With modern eclipse prediction techniques, Muslim congregations today announce solar eclipse prayers in advance as Islam places a great theological weight on communal prayer.
Classical Greco-Roman mythology
Plutarch associated the birth of Romulus, his foundation of Rome, and his death with three solar eclipses. Scholars have attempted to substantiate these mythological claims by through modern astronomical computation, and have not been able to find eclipses on the dates traditionally given for these events.
Hindu mythology
According to Hindu mythology, solar and lunar eclipses, known in Sanskrit as (), occur when the celestial gods Rahu and Ketu swallow the Sun and Moon respectively.
Hindus generally believe that a is a bad omen, and is considered the best time to chanting mantras that ward against evil. Fasting is practiced for up to six hours before an eclipse. Food is often prepared only after the passing of the eclipse, and conventions regarding consuming meals at given hours in the context of the event are prescribed in the Kurma Purana. During an eclipse, Hindus are considered unclean. They bathe and offer prayers to ancestors. Pilgrimage sites situated adjacent to a river throng with devotees during the onset of a in some regions. Pregnant women are considered to be especially at risk to the effects of an eclipse and are expected to adhere more strictly to rituals to prevent birth deformities in their children. It is regarded to be a bad omen to be born during an eclipse, and Brahmins are often called upon to ritually bless such babies.
Native American traditions
The Indigenous peoples of the Americas have very diverse cultural practices and beliefs about eclipses.
Maya
Since the sixteenth century, Western scholars have been interested in "eclipse glyphs" recorded by the Maya civilization in the Dresden Codex, thought by historians to be predictions of solar and lunar eclipses. As there is no evidence for Maya understanding of heliocentrism or celestial orbits, it is likely that such eclipse predictions were made entirely from observed periodicity. However, some scholars argue that the glyphs in the Mayan codices refer to skies darkened from heavy rainfall, and not to eclipses.
Aztec
In Aztec mythology, solar eclipses occurred when the jaguar god Tepēyōllōtl consumed the sun and threatened to swallow it completely, according to Eduard Seler's analysis of the Codex Vaticanus B. A 16th century passage from the Florentine Codex gives an account of a solar eclipse:
There is no record of lunar eclipses in Aztec mythology or recordkeeping, as noted by an observer who wrote in the Codex Telleriano-Remensis about a lunar eclipse in 1510. The Aztec records of solar eclipses, when present, are tied directly to historic events; it is likely that they chose to record such events only when they coincided with social or political events.
Navajo
Navajo people consider the time during an eclipse to be a sacred moment of renewal, and refrain from all activities including eating and drinking. During an eclipse, the Sun or Moon is believed to be dying and reborn. Members of the nation should be silent in prayer and it is considered forbidden to look anywhere except down on the ground. Before modern eclipse prediction methods, Navajo people believed they could predict oncoming eclipses through their traditional songs. During the solar eclipse of October 14, 2023, the offices of the Navajo Nation, including its parks, were closed out of reverence for the eclipse.
Hopi
The Hopi people, whose reservation is an enclave of the Navajo Nation, consider eclipses to be a time of ceremony.
New religious movements
Some New Age and Wicca practitioners view solar and lunar eclipses as important spiritual events. As decentralized religious practices, there are no set prescribed rituals and adherents are free to explore their own exercises, which can include crystal charging, imbuing water with energy, and tarot card reading. For some Wicca practitioners, the spiritual nature of the solar eclipse of August 21, 2017 was an opportunity for political activism, casting spells against the administration of Donald Trump.
Norse mythology
According to Norse mythology, a wolf named Fenrir lives in constant pursuit of the Sun. When Fenrir consumes the Sun, the end times events of Ragnarök will ensue. Historians consider it likely that the Golden Horns of Gallehus artifacts, which contain eschatological iconography, were made in response a lunar eclipse of November 4, 412 and a solar eclipse of April 16, 413.
Other Norse tribes believe that there are two wolves named Sköll and Hati that are in pursuit of the Sun and the Moon, known by the names of Sol and Mani, and that an eclipse occurs when one of the wolves successfully eats either the Sun or the Moon.
West African mythology
The Fon people believe that the creator god Mawu-Lisa divided into a Sun god Lisa and Moon god Mawu. Eclipses are seen as the two gods engaging in intercourse. The Jukun people explained eclipses as the Sun catching the Moon, and would beat drums to make the Sun release its hold on the Moon.
Modern secular practices
Eclipse chasing
A dedicated group of eclipse chasers have pursued the observation of solar eclipses when they occur around Earth. A person who chases eclipses is known as an umbraphile, meaning shadow lover. Umbraphiles travel for eclipses and use various tools to help view the Sun including solar viewing glasses, also known as eclipse glasses, as well as telescopes.
Educational outreach
Solar and lunar eclipses are often used by educational institutions as events for public outreach about astronomy. Lunar eclipses, which are visible by about half the planet at once, are relatively small-scale events for individual organizations and simple to plan for. In areas with extreme levels of light pollution, stargazing may be impossible and so educational stargazing is necessarily restricted to lunar eclipses. By studying lunar phases and eclipses, students can learn about the sizes and relative distances between the Sun, Earth, and Moon.
Solar eclipses happen at midday in narrow visibility bands, which allows educational organizations to plan daytime outreach events that will naturally reach large crowds. Astronomy educators often feel an obligation to ensure eclipse viewers use solar viewing glasses, and utilize outreach events to distribute glasses and encourage compliance. Where both a total and annular solar eclipse can be seen in relatively quick succession, outreach events can discuss the effect of the elliptical shapes of the Earth and Moon's orbits on the magnitude of eclipse. As solar eclipses trace indiscriminately across swaths of continents, rural and impoverished areas in their path can benefit from greater attention paid to educating on astronomy and science in the area.
Eclipses have also been opportunities for citizen science. As brief but geographically diverse events, it is difficult to organize traditional experiments across the entire viewing area. Crowd-sourced experiments have included a test of radio wave propagation, plant and animal reactions, and air temperature measurements.
Civic events
Solar eclipses are best visible in a narrow band across the planet, which places a significant logistical burden on organizations and towns in the path of totality. Southern Illinois University Carbondale found themselves at the center of the solar eclipse of August 21, 2017, for which the university had to spend three years planning for the anticipated 30,000 additional visitors on what was originally scheduled as new-student move-in day. Traffic congestion before and after a solar eclipse can be severe, with crowds numbering in the hundreds of thousands filling highways and spilling off into secondary roadways.
Eclipses are opportunities for large civic gatherings outside the educational sphere. For the solar eclipse of April 8, 2024, a rural portion of Texas had planned to hold a multi-day music and arts festival. During the solar eclipse of August 21, 2017, U.S. President Donald Trump made an appearance outside the White House visible to onlookers from across the South Lawn to view the eclipse.
See also
Notes
References
Historic primary sources
Books and academic journals
Newspapers and magazines
Web sources
Eclipses
Sun in culture
Comparative mythology
Mythological archetypes
Astrological aspects
Astronomical events
Earth phenomena | Eclipses in mythology and culture | [
"Physics",
"Astronomy"
] | 2,247 | [
"Physical phenomena",
"Astronomical events",
"Earth phenomena",
"Eclipses"
] |
76,548,512 | https://en.wikipedia.org/wiki/Chloroflexus%20aggregans | Chloroflexus aggregans is a bacterium from the genus Chloroflexus which has been isolated from hot springs in Japan.
Etymology
The Chloroflexus aggregans name origins from aggregate forming strains indicative of a new species from the Chloroflexus genus. The naming of the C. aggregans comes from the visible aggregates formed by the species.
Discovery and isolation
In 1995, Satoshi Hanada, Akira Hiraishi, Keizo Shimada, and Katsumi Matsuura discovered a new strain of the Chloroflexus genus, named as the Chloroflexus aggregans. The researchers discovered two strains of this bacterial species: MD-66T and YI-9. The "T" in MD-66T represents the type strain. The former, MD-66T strain, was discovered from the Meotobuchi hot spring while the YI-9 strain was from the Yufuin hot spring.
Phylogenetics
Phylogenetically, Chloroflexus bacteria are very distinct from green sulfur bacteria but are still taxonomic relatives. Thus, there is some overlap between these groups. For instance, the light harvesting systems responsible for photosynthesis in both groups rely on bacteriochlorophyll pigments. Currently, the molecular phylogenetic data remains unknown for most Chloroflexus strains. Moreover, Chloroflexus strains have not yet been isolated in axenic cultures—meaning, strains that are able to be grown in the absence of other types of species. Currently, the closest known relative to C. aggregans is C. aurantiacus.
Morphology
The naming of the C. aggregans comes from the visible aggregates formed by the species. At first, the researchers classified these microbes as the C. aurantiacus species because they had a similar morphological appearance. In addition, they had a high degree of genetic similarity. However, C. aggregans''' production of mat-like aggregates when cultured in the researchers' lab suggested that it was a different species than C. aurantiacus, resulting in the discovery of a new species.
Genomics
Phenotypically, the species resembles the Chloroflexus aurantiacus bacteria. Genotypically, the species' 16S rRNA sequences are 92.8% similar to C. aurantiacus. Its genome is 4.7 Megabases (Mb).
Metabolism Chloroflexus aggregans have an extremely versatile mixotrophic metabolism. This is an advantage for their environment, since the microbial mats they inhabit have constantly fluctuating conditions that follow a general daily cycle. During the daytime, when light is abundant, it is their main energy source and C. aggregans exhibit photoautotrophy, photomixotrophy, and photoheterotrophy. They perform photosynthesis through the use of their chlorosomes, which are large pigment-containing complexes that can harvest light. During the afternoon, when there is less light and lower oxygen concentrations in the microbial mats, the bacteria switch to chemoheterophy and use oxygen as their final electron acceptor (O2 respiration). At night, when light is not available and the microbial mats are anaerobic, the bacteria continue to exhibit a chemoheterotrophic metabolism, but it is instead based on fermentation. Finally to complete their daily metabolic cycle, C. aggregans vertically migrate to the surface of their microbial mats, which are microaerobic, in the early morning. Here, they switch to chemoautotrophy based on O2 respiration. When exhibiting heterotrophy, C. aggregans can utilize a diverse range of organic substrates as their carbon source, but grow optimally when either yeast extract or Casamino Acids are used.
Ecology
Currently, C. aggregans are known to reside in microbial mats in freshwater hot springs, living closely associated with other microorganisms in multilayered sheets. Specifically, they have been discovered and sampled from these hot springs in Japan. They coexist with filamentous, unicellular cyanobacteria in these mats. When exhibiting a heterotrophic metabolism, C. aggregans rely on organic substrates excreted from these cyanobacterial neighbors to obtain carbon for biosynthesis. To occupy these hot springs, C. aggregans are thermophiles and isolated cultures have been shown to exhibit optimal growth between . They are filamentous, meaning the cells grow into long rods that only divide terminally, forming unbranched, multicellular filaments. Uniquely, these long filaments of C. aggregans then associate into dense, mat-like aggregates, setting the bacteria apart from other species of Chloroflexus. Evolution of photosynthesis
16S rRNA data has shown that bacterial species within the Chloroflexus genus are among the earliest bacteria that were able to perform photosynthesis. However, much still remains unknown about Chloroflexus aggregans and its complete genome has yet to be fully sequenced. Thus, continued study of this organism could be important to help elucidate the origins of photosynthesis in bacteria. In addition, studying the broader evolutionary relationships of C. aggregans to other groups of early photosynthetic bacteria could help scientists build a phylogenetic tree of these related phyla, deducing their evolutionary order. For instance, a study comparing the signature sequences in highly conserved proteins of photosynthetic bacteria found that organisms in the genus Chloroflexus'' evolved before cyanobacteria. Resolving these phylogenies could further help scientists understand how photosynthesis developed. Today, this process sustains almost all life on Earth by providing oxygen to the atmosphere and energy for organisms in higher trophic levels. Therefore, it is highly valuable to study how this process first arose.
References
External links
LPSN
Type strain of Chloroflexus aggregans at BacDive - the Bacterial Diversity Metadatabase
Thermophiles
Chloroflexota | Chloroflexus aggregans | [
"Biology"
] | 1,317 | [
"Bacteria stubs",
"Bacteria"
] |
76,548,847 | https://en.wikipedia.org/wiki/Fervidicoccus | Fervidicoccus fontis is an extremophilic, coccus-shaped archaeaon known for thriving in high-temperature environments. It was discovered in Russia's Uzon Caldera and exhibits anaerobic, organotrophic metabolism, primarily fermenting organic compounds such as peptides and yeast extract. F. fontis is genetically distinct, sharing no more than 89% of its genetic material with its closest relatives. It is the sole species within the order Fervidicoccales and genus Fervidicoccus, although ongoing research suggests potential new species. It plays a significant role in biotechnological applications due to its lipid-hydrolyzing capabilities, contributing to industries ranging from wastewater treatment to pharmaceuticals.
Scientific Classification
Taxonomy
F. fontis belongs to the Archaea domain and falls within the Crenarchaeota phylum. Organisms within this phylum are known for their extremophilic nature, enabling them to survive in severe environments such as extreme heat, cold, or acidity. The class Thermoprotei includes thermophiles, among which F. fontis is a notable example. Thermophiles are characterized by their ability to survive in environments with high temperatures, with optimal growth at a temperature range of . Typically, thermophilic organisms are found in terrestrial and marine springs situated in volcanic areas or close to hydrothermal vents. F. fontis is classified within the order Fervidicoccales, the family Fervidicoccaceae, and the genus Fervidicoccus. The strains Kam940T and 1507b were isolated and used to identify the organism, leading to the creation of a new genus and species. Currently, F. fontis is the only species identified within the order Fervidicoccales. However, strain Kam1884, isolated from Uzon Caldera, displays about 96% similarity in the 16S RNA sequence to F. fontis Kam940T, indicating a possible new species within the Fervidicoccus genus.
Relatives
Phylogenetic trees were constructed to explore the evolutionary relationships of F. fontis, revealing its unique phylogenetic position while also illustrating its proximity to certain other species. This analysis combined sequencing data from 30 ribosomal proteins, the alpha and beta components of RNA polymerase, and 23S rRNA genes. F. fontis is genetically distinct within the Thermoprotei class, sharing less than 89% genetic identity with its members, which establishes it as the only known species within the Fervidicoccales order. This distinctness underscores its relatively distant evolutionary connections within the Thermoprotei class. However, notable relatives include Ignisphaera aggregans, Caldisphaera lagunensis, Acidilobus saccharovorans, and Desulfurococcus kamchatkensis. F. fontis is distinguished from its relatives due to its unique set of traits, including at least 25% unique protein-encoding genes and an absence of extracellular hydrolases, with the exception of proteases.
Discovery and isolation
The discovery of F. fontis was initiated through a prepared anaerobic basal medium, aimed at fostering the growth of microorganisms in extreme environments. Samples were collected from thermal springs within Russia's Uzon Caldera. The medium in which the samples were obtained had a pH adjusted to 6.0-6.5 and included 1 mg of resazurin, 1mL of trace element and vitamin solutions, and 0.2 g of yeast extract. This was then transferred into tubes which were sealed with butyl rubber stoppers to maintain an anaerobic environment of 80% N2 and 20% CO2. The method for isolating strains Kam940T and Kam 1507b involved the incubation of a 10% inoculum, sourced from a blend of sediment and water at . This incubation also included the addition of chitin or β-keratin as polymeric substrates at a 2 g l−1 concentration. Kam940T was isolated in a basal medium with peptone with 1.5% agar, whereas Kam1507b was obtained through serial dilution in a medium enriched with peptone. Within 3–5 days, this approach successfully isolated organisms with coccoid cells, marking the discovery of unique Fervidicoccus strains: Kam940T and Kam1507b. The purity of these isolated strains was confirmed through phase-contrast microscopy, which revealed that the strains consisted entirely of single cocci cells, ultimately demonstrating effective isolation and the discovery of a new species.
Morphology
F. fontis is characterized by its coccus-shaped cellular morphology and lack of motility due to its absence of a flagellum. Its cell envelope consists of a cell membrane formed by a layer of protein subunits. The dimensions of these cells can vary, with their lengths and widths ranging between 1-3 μm.
Metabolism
F. fontis, an obligate anaerobic organotroph, primarily derives its energy from the fermentation of various organic compounds. It uses metabolites such as beef extract, peptone, and yeast extract for fermentation purposes, growing to densities greater than 107 cells mL−1. F. fontis shows optimal growth when cultivated with peptides and 20 mg/L yeast extract between 65 °C and 70 °C and a pH of 5.5-6.0. Additionally, F. fontis is capable of reducing sulfur to H2S. The genome of F. fontis encodes 45 peptidases that facilitate protein and peptide hydrolysis as well as amino acid catabolism, which are essential processes for the transport of oligopeptides and free amino acids into cells. Pyruvate catabolism is also assumed to be present as an intermediate product from alanine metabolism. Pyruvate-ferredoxin oxidoreductase facilitates the production of acetyl-CoA, CO2, and reduced ferredoxin. Subsequently, acetyl-CoA is transformed into acetate, generating ATP in a reaction carried out by acetyl-CoA synthetases. Despite its metabolic versatility, F. fontis lacks complete pathways for carbohydrate catabolism. This is evidenced by the lack of genes typically found in organisms capable of breaking down carbohydrates, such as glycoside hydrolases, polysaccharide lyases, or carbohydrate esterases.
Genomics
The chromosome of F. fontis is circular, as determined through comprehensive genome sequencing and analysis, and confirmed by polymerase chain reaction (PCR) verification of regions with insertion sequence elements. It consists of 1,319,216 base pairs with a 37.5% average of G and C content. Its genome includes a duplicate of the 16S-23S rRNA operon, as well as a distinct 5S rRNA gene. Across the genome, there are 42 tRNA genes, nine of which include introns. Through similarity searches and coding potential predictions, 1,385 potential protein-coding genes were identified, with an average length of 829 nucleotides per gene. This ultimately resulted in an 87.1% protein-coding genes coverage of the entire F. fontis genome.
Ecology
The F. fontis Kam940T and Kam1507b strains were derived from areas with temperatures ranging from and pH levels of 6.5 and 6.3, respectively. Further analysis using Denaturing gradient gel electrophoresis (DGGE) identified Fervidicoccaceae in enrichment cultures from Uzon Caldera, demonstrating their ability to grow at high temperatures () and a pH range of 6.4–7.0 on various polymeric substrates. Sampling of environmental DNA uncovered the presence of Fervidicoccaceae in various hot springs around the world. These findings show that the 16S ribosomal RNA sequences of these organisms share a 94-95% 16S similarity to that of F. fontis, indicating F. fontis'''s widespread distribution and ecological adaptability.
Significance
The demand for new lipases and lipid-consuming microorganisms is growing, presenting a challenge for biotechnology and microbiology. F. fontis has the capability to hydrolyze lipid substrates; therefore, it finds application in various industries such as wastewater treatment, the creation of refined products like pharmaceuticals, esters, and amino acids, as well as in the manufacture of biodiesel, biopolymers, cleaning products, cosmetics, paper, leather, and food products. The difficulty in isolating and sustaining pure archaeal cultures has constrained scientific knowledge of these microorganisms, as previously, only Thermococcus sibiricus was recognized for its lipid growth capabilities. Therefore, this new finding broadens the understanding of the ecological capabilities of the Fervidicoccus genus. F. fontis, with its small genome size compared to many other free-living thermophiles, may share ecological niches with other thermophilic bacteria and outcompete them, suggesting that it may be advantageous in competitive environments. F. fontis may also have antioxidant capabilities due to the presence of superoxide reductase, which can reduce oxidative damage and potentially decrease disease risk, highlighting its medical importance. The presence of a superoxide reductase gene in F. fontis'' highlights its function in superoxide detoxification, further contributing to antioxidant defense mechanisms.
References
Thermoproteota
Bacteria described in 2010
Anaerobes | Fervidicoccus | [
"Biology"
] | 2,006 | [
"Bacteria",
"Anaerobes"
] |
76,549,012 | https://en.wikipedia.org/wiki/Sichere%20Inter-Netzwerk%20Architektur | Sichere Inter-Netzwerk Architektur (SINA) is a cryptographic system developed by and a product of the Bundesamt für Sicherheit in der Informationstechnik, an arm of the German government. It also has the anglicized name Secure Inter-Network Architecture. As of April 2024 the cryptosystem was employed by "many European governments for transmitting classified information".
History
SINA came to prominence in March 2023 when it was divulged in a court warrant for the arrest of the Austrian intelligence officer Egisto Ott, who has a relationship with Wirecard fraudster Jan Marsalek, that a SINA laptop was handed to the Russian secret services, specifically the Lubyanka Building office of the FSB.
The Austrian authorities report that Ott received €20,000 for the laptop from Marsalek.
References
Cryptographic software
Communications in Germany
Federal Ministry of the Interior (Germany)
German history stubs | Sichere Inter-Netzwerk Architektur | [
"Mathematics"
] | 204 | [
"Cryptographic software",
"Mathematical software"
] |
76,551,613 | https://en.wikipedia.org/wiki/Cytonuclear%20discordance | Cytonuclear discordance describes the discrepancy in phylogenetic relationships using mitochondrial DNA (mtDNA) versus nuclear genes (or nuclear DNA, nDNA). In other words, mitochondrial and nuclear gene sequences may lead to different, if not contradictory, phylogenetic trees that show the relationships among species. In theory, nuclear DNA and mtDNA sequences should lead to similar phylogenetic tree topologies among species but this is often not the case.
Other terms for the concept are Nuclear-mitochondrial discordance or mito-nuclear discordance.
Examples
An example are Australian rock-wallabies (Petrogale) in which several species form a monophyletic group with nDNA genes, but not with mtDNA. This cytonuclear discordance involves at least four operational taxonomic units (OTUs) across four species.
Another example is the relationship among grasshoppers (Orthoptera). Phylogenies based on complete mitogenomes recovered some species as para- or polyphyletic. By contrast, a phylogeny based on nuclear genes derived from transcriptomic data retrieved all species as monophyletic clusters.
Many other taxonomic groups display cytonuclear discordance, e.g. Burmese pythons or vipers of the genus Cerastes.
References
Mitochondrial genetics
Phylogenetics | Cytonuclear discordance | [
"Biology"
] | 276 | [
"Bioinformatics",
"Phylogenetics",
"Taxonomy (biology)"
] |
76,554,532 | https://en.wikipedia.org/wiki/Gertrud%20Zwicknagl | Gertrud Zwicknagl is a retired German solid-state physicist whose research involved the development of renormalized band theory for intermetallic solids and its application to the theory of superconductors and heavy fermion materials, as well as the study of heavy quasiparticles in uranium compounds. Formerly a professor of physics at the Technical University of Braunschweig, she retired in 2020.
Education and career
After studying physics as an undergraduate at Ludwig Maximilian University of Munich from 1970 to 1975, Zwicknagl continued her studies at the University of Cologne, earning a doctorate (Dr. rer. nat.) in 1979.
She became a researcher at KFA Jülich (now the Forschungszentrum Jülich) from 1976 to 1980, at the Max Planck Institute for Solid State Research in Stuttgart from 1980 to 1986, at the Laboratory of Atomic and Solid State Physics at Cornell University in the US from 1983 to 1984, and at the Institute of Solid State Physics at the Technische Universität Darmstadt from 1986 to 1991. While at Darmstadt she completed a habilitation in 1991.
She returned to the Max Planck Institute for Solid State Research as a senior researcher in 1991, and moved to the Max Planck Institute for the Physics of Complex Systems in Dresden in 1996. In 1998 she took a professorship at the Technical University of Braunschweig, from which she retired in 2020.
Recognition
Zwicknagl was the 1993 recipient of the Walter Schottky Prize of the German Physical Society.
She was named a Fellow of the American Physical Society (APS) in 2023, after a nomination from the APS Division of Condensed Matter Physics, "for original and paramount contributions to the theory of emergent solid-state materials, in particular, for groundbreaking advances toward the quantitative microscopic understanding of strongly correlated systems on the basis of their atomistic and electronic structure".
References
External links
Interview with Zwicknagl (in German), German Physical Society
Year of birth missing (living people)
Living people
German physicists
German women physicists
Condensed matter physicists
Ludwig Maximilian University of Munich alumni
University of Cologne alumni
Academic staff of the Technical University of Braunschweig
Fellows of the American Physical Society | Gertrud Zwicknagl | [
"Physics",
"Materials_science"
] | 451 | [
"Condensed matter physicists",
"Condensed matter physics"
] |
76,554,816 | https://en.wikipedia.org/wiki/Sponge%20microbiomes | Sponge microbiomes are diverse communities of microorganisms in symbiotic association with marine sponges as their hosts. These microorganisms include bacteria, archaea, fungi, viruses, among others. The sponges have the ability to filter seawater and recycle nutrients while providing a safe habitat to many microorganisms, which provide the sponge host with fixed nitrogen and carbon, and stimulates the immune system. Together, a sponge and its microbiome form a holobiont, with a single sponge often containing more than 40 bacterial phyla, making sponge microbial environments a diverse and dense community. Furthermore, individual holobionts work hand in hand with other near holobionts becoming a nested ecosystem, affecting the environment at multiple scales.
Composition
Microbiome species diversity
Microbial composition in sponges can differ based on the amount of light the microbes have access to. The outer layer of sponge, which is exposed to light, is usually inhabited by photosynthetically active microorganisms, such as Cyanobacteria, whereas the inner portion of the sponge is dominated by heterotrophic microbes. Shallow-water sponges in particular form complex host-microbe relationships within the marine ecosystem, with over 40 bacterial phyla identifiable on a sponge individual. Deep-sea sponge microbes are less diverse overall, but have more varied compositions between individual sponge organisms. Although there are common microorganism species shared by both shallow-water sponges and deep-sea sponges, many microbial species differ between the two sponges. For example, Chloroflexota was found in higher abundance in deep-sea sponges compared to shallow ones.
Sponges can be classified as High Microbial Abundance (HMA) sponges and Low Microbial Abundance (LMA) sponges based on the density of microorganisms they host. HMA sponges are specifically characterized by their capacity to support a 1010 cells per gram of sponge tissue, whereas LMA sponges are defined by a much lower density of 106 cells per gram of sponge tissue. In HMA sponges, up to one third of the overall sponge biomass can be microbial biomass. Chloroflexota, Gammaproteobacteria, and Alphaproteobacteria are phyla and subphyla that have been reported to characterize HMA species. The HMA sponge communities were found to be complex, and are dominated by Proteobacteria, Cyanobacteria, Bacteroidetes, Acidobacteria, and Planctomycetes in the samples from Montgri Coast (northwest Mediterranean Sea). In contrast, LMA sponge communities have restricted the number of microbe species, including Proteobacteria and Cyanobacteria.
Symbiont acquisition
Sponge-specific symbionts are hypothesized to have begun their association with sponges as long as 600 million years ago, but there are several hypotheses as to how the microbes colonized and continued to inhabit sponges. The most evidenced hypothesis of sponge-specific symbionts says that sponges were colonized prior to sponge speciation, during the Precambrian period. This colonization is thought to have been maintained throughout the years by vertical transmission, which resulted in microbial species diverging alongside sponge species. Support for this hypothesis comes from the presence of fatty acids within sponges that are not present within the surrounding environment. These fatty acids are of microbial origin and appear within many different sponge species that share neither location nor ancestry, indicating that the microbial producers of these fatty acids colonized sponges before the sponge species differentiated. However, this hypothesis is still only a hypothesis, and it requires more evidence before it (or other hypotheses of microbe acquisition) can be confirmed.
Ecological functions
Carbon metabolism
Marine sponges are commonly heterotrophic, getting their carbon from dissolved organic material or consumption of microorganisms. However, transfer of organic carbon from the microbiome to the sponge host has been demonstrated in several sponge species. This is most often observed in tropical sponges that carry dense communities of photosynthetic cyanobacteria, which use sunlight and oxygen to produce organic carbon. Some of that organic carbon is then provided to the sponge, largely in the form of glycerol. Sponges that live in high-light, low-nutrient locations such as tropical reefs rely heavily on organic carbon produced by their symbiotic cyanobacteria, and in some cases have been observed to gain more than 50% of their required energy from this carbon transfer. Alternately, sponges living in areas with less available light and higher nutrients (such as areas with higher water turbidity) demonstrate less association with cyanobacteria and less reliance on photosynthesis-derived organic carbon.
A more unusual form of carbon exchange utilizing methane has been observed in carnivorous deep-sea sponges (family Cladorhizidae) living near hydrothermal vents. The level of methanol dehydrogenase present within the sponge tissues indicates that these sponges are host to methanotrophic bacteria, which thrive off of methane gas from nearby hydrothermal vents. Instead of extracellular nutrient transfer (such as with photosynthetic cyanobacteria), most sponge cells are able to phagocytose old or dying bacterial cells, which are then used by the sponge as a source of organic carbon. Cladorhiza species are thought to benefit quite significantly from this symbiosis, as large sponge size and high sponge abundance is correlated with the methane flow of the most active hydrothermal vents, and Cladorhiza species are much less abundant away from the vents.
Nitrogen metabolism
Symbiotic microbes may assist sponges in the acquisition of organic nitrogen in two ways: nitrogen fixation and ammonia oxidation.
Symbiosis with nitrogen-fixing bacteria has been identified in several families of marine sponges through measurement of nitrogenase activity and is particularly beneficial for sponges in low-nitrogen waters, where fixed nitrogen is in very high demand. The symbiotic bacteria pull molecular nitrogen from the atmosphere and convert it into ammonia, nitrate, and other organic nitrogen-containing compounds that can then be utilized by the sponges.
Many sponge species are inhabited by ammonia-oxidizing bacteria or archaea, making ammonia oxidation one of the best-studied symbiotic functions of the sponge microbiome. Symbiotic microbes use ammonium released by the sponges as a byproduct of digestion to fuel ammonia and nitrate oxidation, thus providing more fixed nitrogen for the sponges to use. Sponges’ mechanism of pumping water through their tissues can result in deoxygenated zones, which could allow for microbial denitrification and anaerobic ammonia oxidation to occur. This is supported by the greater presence of genes related to denitrification and ammonia oxidation in sponge microbial communities than in surrounding free-living microbes. However, these communities do not have as many genes for nitric oxide reduction, which may lead to harmful buildup of nitric oxide in sponge tissues. At least one bacterial species (Candidatus Methylomirabilis oxyfera) has been identified in the sponge microbiome as being able to convert nitric oxide directly to oxygen and nitrogen gas, which could alleviate the buildup of nitric oxide and assist with oxygenating inner sponge tissues.
Sulfur metabolism
Unlike carbon and nitrogen metabolism, wherein organic carbon and nitrogen are transferred between sponges and resident microbes, sulfur metabolism within the sponge microbiome only involves the microbiota. The sponge acts as the environment in which sulfur-reducing and sulfur-oxidizing microbes carry out a sulfur cycle. This cycling likely takes place within the anaerobic zones of the sponge, as sulfur reduction is an anaerobic process. Accumulation of hydrogen sulfide – which is produced as a byproduct by sulfur-reducing bacteria and is toxic to sponges – is likely prevented by the presence of sulfur-oxidizing bacteria within the sponge microbiota. Current research suggests that sulfur-oxidizing bacteria may also allow sponges to root in sulfur-rich sediments that would otherwise be uninhabitable.
Synthesis of B Vitamins
B vitamins are an important resource for sponge cell metabolism. Sponges cannot synthesize their own B vitamins and so have no way to acquire these vitamins except through filter-feeding. Therefore, association with a B vitamin synthesizing microbe is favorable for the sponge host and may increase the stability of that microbe's presence in the sponge's microbiome. Through the analysis of transporters from symbionts and microbial phyla, six B vitamins have been detected to have come from sponge microbiomes: thiamine (vitamin B1), riboflavin (vitamin B2), pyridoxine (vitamin B6), biotin (vitamin B7), and cobalamin (B12).
References
Wikipedia Student Program
Sponge biology
Microbiomes
Marine microorganisms | Sponge microbiomes | [
"Biology",
"Environmental_science"
] | 1,887 | [
"Microbiomes",
"Environmental microbiology",
"Marine microorganisms",
"Microorganisms"
] |
76,554,949 | https://en.wikipedia.org/wiki/Young%20function | In mathematics, certain functions useful in functional analysis are called Young functions.
A function is a Young function, if it is convex, even, lower semicontinuous, and non-trivial, in the sense that it is not the zero function , and it is not the convex dual of the zero function
A Young function is finite iff it does not take value .
The convex dual of a Young function is denoted .
A Young function is strict iff both and are finite. That is,
The inverse of a Young function is
The definition of Young functions is not fully standardized, but the above definition is usually used. Different authors disagree about certain corner cases. For example, the zero function might be counted as "trivial Young function". Some authors (such as Krasnosel'skii and Rutickii) also require
References
Léonard, Christian. "Orlicz spaces." (2007).
. Gives another definition of Young's function.
In the book, a slight strengthening of Young functions is studied as "N-functions".
Harmonic analysis
Real analysis
Banach spaces | Young function | [
"Mathematics"
] | 221 | [
"Mathematical analysis",
"Mathematical analysis stubs"
] |
76,555,624 | https://en.wikipedia.org/wiki/Yang%20Hao%20%28engineer%29 | Yang Hao is a British Chinese electronic engineer, academic, and author most known for his research in wireless connectivity and metamaterials. He is the holder of the QinetiQ/Royal Academy of Engineering (RAE) Research Chair, and serves as the Director of both the EPSRC Research Centre on Future Wireless Connectivity and the EPSRC Centre for Transformation Optics and Metamaterials. He is also a Professor of Antennas and Electromagnetics, and Deputy Vice Principal for Strategic Research at Queen Mary University of London (QMUL). He is a Co-Founder and Director of AOTOMAT, and co-founded a satellite communication company called Isotropic Systems.
Hao has authored/edited two books titled, FDTD Modeling of Metamaterials: Theory and Applications and Antennas and Propagation for dy-Centric Wireless Communications. He has been the recipient of the BAE Systems Chairman's Silver Award, the Royal Society Wolfson Research Merit Award, the IET AF Harvey Research Prize, and the EurAAP Antenna Award.
Hao became a Fellow of the ERA Foundation in 2007, the IET in 2010, the IEEE in 2013, and the Royal Academy of Engineering (RAEng) in 2020. He served as Editor-in-Chief for IEEE Antennas and Wireless Propagation Letters, and founded an open-access journal, EPJ Applied Metamaterials, where he serves as Editor-in-Chief, while also serving as Vice President of the Publication Committee for IEEE Antennas and Propagation Society. He is a member of the Fellowship Committee, Research Committee, and Enterprise Hub for the RAEng as well.
Education and early career
Hao earned his Ph.D. from the Centre for Communications Research (CCR) at the University of Bristol in 1998. Following this, he worked as a postdoctoral research fellow in the School of Electrical and Electronic Engineering at University of Birmingham, from 1998 to 2000. In May 2000, he joined the Antenna and Electromagnetics Group in the School of Electronic Engineering and Computer Science at QMUL, initially as a lecturer, advancing to Reader in 2005, and eventually becoming a Professor in 2007.
Career
Hao's research focuses on wireless communication, metamaterials, antennas, terahertz technology, and adaptive systems. He has headed projects such as the EPSRC/QinetiQ DREAM Prosperity Partnership, the EPSRC QUEST Programme Grant, and ANIMATE project. In his role as QinetiQ/Royal Academy of Engineering Research Chair, he has contributed to the advancement of wireless technology, while also co-founding Isotropic Systems (All.Space) to apply research in satellite communication. Additionally, he served on the EPSRC SAT (Strategic Advisory Team), emphasizing the importance of ICT, electronics, and manufacturing, and holds positions on the management boards of the AI for Science and Government program at the Alan Turing Institute, and the Cambridge Graphene Centre, as well as on the boards of the European School of Antenna Excellence, Virtual Institute for Artificial Electromagnetic Materials and Metamaterials, Metamorphose VI AISBL, and International Advisory Committee (IAC) of the Comin Labs.
Hao has held roles such as Deputy Vice Principal for Strategic Research at QMUL since 2021, and Dean for Research at the Faculty of Science and Engineering from 2018 to 2021. He has also been an Elected University Council Member and Governance Committee Member since 2021.
Research
Hao developed integrated antenna solutions using novel materials for security, aerospace, and healthcare, such as lens antennas for satellite communications and supply chain establishment. He co-developed stable active non-Foster metamaterial for small antennas and coined the term "body-centric wireless communications," which involves integrating wearable and implantable sensors. His early research in metamaterials, transformation optics, and AI-driven robotics for precise wave control has impacted electromagnetic devices and medical communication technology. This work has been featured by media outlets such as CNN, Telegraph, Financial Times, and IEEE Spectrum.
Body-centric wireless communications and wearable antennas
In 2003, Hao and his colleague conducted research, becoming the first to explore the characterization of the human body as a communication medium. Their work revealed that radio signals travelling across the body's surface experience considerable signal loss and variations in propagation time, known as dispersion. He noted that antennas placed on the body suffer from decreased efficiency, altered radiation patterns, and impedance fluctuations. To address these challenges, his focus shifted towards using surface and creeping waves for on-body communication among sensors. Concurrently, he developed a theoretical framework for modeling these waves in the presence of the human body and proceeded to design antennas tailored for reliable on-body communication, utilizing precise and realistic models.
In addition to on-body channel modelling studies, Hao pioneered the exploration of on-body antennas across frequencies ranging from 10 MHz to 100 GHz. His research laid the foundation for designing low-profile antennas capable of reliably facilitating on-body communications, and engineered various body-worn antennas featuring spatial diversity at UHF/VHF and UWB frequencies. In particular, antennas operating at 60GHz and 94GHz were developed to support on/off-body communications, particularly in defense and healthcare sectors. Throughout his research journey, he has developed RF modeling methods tailored for body-centric wireless communication. He integrated Huygens' principle into FDTD algorithms for precise analysis of on-body radio propagation, and while emphasizing the significance of human-specific modelling, devised commercial tools for designing wearable and implantable sensors.
Metamaterials and transformation optics
To support his efforts in antenna design, Hao pioneered the development of a set of computational tools in 2005 for modelling microwave metamaterials. He also explored the properties of a hyperbolic wire medium lens, which contributed to the reduction in mass, footprint, and profile of reconfigurable intelligent surfaces (RIS). His work on metamaterials and transformational optics, published in leading journals such as Physics Review Letters, Nature Communications, and IEEE Transactions, focused on applications to antennas and propagation. Notably, in 2018, his collaborative research introduced an approach to antenna design utilizing transformation optics. He demonstrated the feasibility of manufacturing satellite antennas in various shapes using flat surfaces and thin nanomaterial layers via 3D printing, offering cost-effective, compact, and resilient designs. In 2009, he developed a manufacturing process for free-formed 3D woodpile structures operating at sub-THz frequencies, initially utilized for concealed weapon detection and later realized through 3D additive manufacturing.
Antenna design and integration of emerging technologies
Hao's later work has focused on innovating antenna design, materials science, and integrating emerging technologies like machine learning into electromagnetics. He introduced a concept involving hyperuniform disordered antenna arrays and metasurfaces to enhance spectral and spatial performance. Employing Natural Language Processing (NLP) tools, he applied machine learning techniques to forecast trends in antennas and propagation research using vast unstructured data. Additionally, in two journal papers published in Advanced Science and npj Computational Materials, he applied unsupervised deep learning to identify disordered material signatures in perovskites, facilitating predictions on crystal symmetry and phase transitions, and introduced a graph-based machine learning model to analyze material properties, advancing computational materials for antenna applications.
Awards and honours
2005 – CRUCIBLE Award, NESTA
2010 – Fellow, IET
2013 – Fellow, IEEE
2013 – AF Harvey Research Prize, IET
2013-2017 – Wolfson Research Merit Award, Royal Society
2014 – Chairman’s Silver Award, BAE Systems
2020 – Fellow, RAEng
2024 – EurAAP Antenna Award, European Association of Antennas and Propagation (EurAAP)
2024 - Fred W. Ellersick Prize, The IEEE Communications Society
2024 – John Kraus Antenna Award, the IEEE Antennas and Propagation Society
Bibliography
Books
FDTD Modeling of Metamaterials: Theory and Applications (2008) ISBN 9781596931602
Antennas and Propagation for Body-Centric Wireless Communications (2012) ISBN 9781608073764
Selected articles
Hall, P. S., & Hao, Y. (2006, November). Antennas and propagation for body centric communications. In 2006 First European Conference on Antennas and Propagation (pp. 1-7). IEEE.
Hao, Y., Alomainy, A., & Zhao, Y. (2006). Antenna design and propagation measurements and modelling for UWB wireless BAN. Ultra‐Wideband, 331-359.
Hao, Y., & Foster, R. (2008). Wireless body sensor networks for health-monitoring applications. Physiological measurement, 29(11), R27.
Argyropoulos, C., Zhao, Y., Kallos, E., & Hao, Y. (2010). Finite-Difference Time-Domain Modeling of Electromagnetic Cloaks. Metamaterials: Theory, Design, and Applications, 115-153.
Pan, C., Ren, H., Wang, K., Kolb, J. F., Elkashlan, M., Chen, M., ... & Hanzo, L. (2021). Reconfigurable intelligent surfaces for 6G systems: Principles, applications, and research directions. IEEE Communications Magazine, 59(6), 14-20.
References
Living people
Scientific journal editors
Year of birth missing (living people)
Alumni of the University of Bristol
Academics of Queen Mary University of London
Fellows of the IEEE
Fellows of the Royal Academy of Engineering
Fellows of the Institution of Engineering and Technology
British electrical engineers
British electronics engineers
British academics
British writers
Shandong University alumni | Yang Hao (engineer) | [
"Engineering"
] | 1,973 | [
"Institution of Engineering and Technology",
"Fellows of the Institution of Engineering and Technology"
] |
76,555,802 | https://en.wikipedia.org/wiki/Cobalt%28II%29%20perchlorate | Cobalt(II) perchlorate is an inorganic chemical compound with the formula Co(ClO4)2·nH2O (n = 0,6). The pink anhydrous and red hexahydrate forms are both hygroscopic solids.
Preparation and reactions
Cobalt(II) perchlorate hexahydrate is produced by reacting cobalt metal or cobalt(II) carbonate with perchloric acid, followed by the evaporation of the solution:
CoCO3 + 2 HClO4 → Co(ClO4)2 + H2O + CO2
The anhydrous form cannot be produced from the hexahydrate by heating, as it instead decomposes to cobalt(II,III) oxide at 170 °C. Instead, anhydrous cobalt(II) perchlorate is produced from the reaction of dichlorine hexoxide and cobalt(II) chloride, followed by heating in a vacuum at 75 °C.
Structure
The anhydrous form consists of octahedral Co(ClO4)6 centers, with tridentate perchlorate ligands. On the other hand, the orthorhombic hexahydrate consists of isolated [Co(H2O)6]2+ octahedrons and perchlorate anions with lattice constants a = 7.76 Å, b = 13.44 Å and c = 5.20 Å. The hexahydrate undergoes phase transitions at low temperatures.
References
Cobalt(II) compounds
Perchlorates | Cobalt(II) perchlorate | [
"Chemistry"
] | 321 | [
"Perchlorates",
"Salts"
] |
76,556,199 | https://en.wikipedia.org/wiki/Urinary%20anti-infective%20agent | Urinary anti-infective agent, also known as urinary antiseptic, is medication that can eliminate microorganisms causing urinary tract infection (UTI). UTI can be categorized into two primary types: cystitis, which refers to lower urinary tract or bladder infection, and pyelonephritis, which indicates upper urinary tract or kidney infection.
Escherichia coli (E. Coli) is the predominant microbial trigger of UTIs, accounting for 75% to 95% of reported cases. Other pathogens such as Proteus mirabilis, Klebsiella pneumoniae, and Staphylococcus saprophyticus can also cause UTIs.
The use of antimicrobial therapy to treat UTIs started in the 20th century. Nitrofurantoin, trimethoprim-sulfamethoxazole (TMP/SMX), fosfomycin, and pivmecillinam are currently the first-line agents for empiric therapy of simple cystitis. On the other hand, the choice of empiric antimicrobial therapy for pyelonephritis depends on the severity of illness, specific host factors, and the presence of resistant bacteria. Ceftriaxone is often considered for parenteral treatment, while oral or parenteral fluoroquinolones, such as levofloxacin and ciprofloxacin, are suitable alternatives for treating pyelonephritis.
Antimicrobial therapy should be tailored to the individual, considering factors like the severity of illness, specific host factors, and pathogen resistance in the local community.
Types of urinary anti-infective agent
Urinary antiseptics are medications that target bacteria in the urinary tract. They can be divided into two groups: bactericidal agents, and bacteriostatic agents. These antiseptics help prevent infections by effectively eliminating UTI symptoms through their action on microorganisms.
Urinary bactericidal agents
Nitrofurantoin
Nitrofurantoin is regarded as the first-line agent for simple cystitis, with an efficacy rate ranging from 88% to 92%. It can also be a prophylactic agent to prevent long-term UTIs. This antibacterial medication is effective against both gram-positive and gram-negative bacteria. Nitrofurantoin exhibits its bactericidal activity through various mechanisms, including inhibiting ribosomal translation, causing bacterial DNA damage and interfering with the citric acid cycle. However, the specific role of each mechanism remains to be further explored.
When nitrofurantoin is metabolized, it converts into a reactive intermediate that attacks bacterial ribosomes, inhibiting bacterial protein synthesis. This medication is typically taken orally and has minimal systemic absorption, reducing potential side effects. Common adverse reactions associated with nitrofurantoin include brown urine discoloration, nausea, vomiting, loss of appetite, rash, and peripheral neuropathy.
Fosfomycin
Fosfomycin is a phosphonic acid bactericidal agent. It is commonly used as the first-line treatment for acute simple cystitis, demonstrating a 91% cure rate. It is administered orally as a single dose; In more complicated UTIs, the dose is adjusted to be repeated every three days to achieve successful eradication.
The bactericidal effect of fosfomycin is attributed to its capability to inhibit bacterial wall synthesis by inactivating an enzyme called pyruvyl transferase, which is responsible for microbial cell wall synthesis. Fosfomycin acts against gram-positive and gram-negative bacteria. Administration of fosfomycin may lead to side effects such as headache, dizziness, nausea, vomiting, and abdominal cramps.
Beta-lactam antibiotics
Beta-lactam antibiotics are often considered as a second-line option for treating UTIs due to their lower effectiveness compared to other antibiotics and their potential adverse effects. Commonly used beta-lactam antibiotics for UTIs include cephalosporins and penicillin. By binding to penicillin-binding proteins through their beta-lactam rings, beta-lactam antibiotics disrupt the normal function of these proteins, inhibiting bacterial cell wall synthesis, ultimately resulting in cell death.
Cephalosporins are a subclass of beta-lactam family with broad-spectrum activity against gram-positive and gram-negative bacteria. They are categorized into five generations. First and third-generation cephalosporins, like cefalexin and ceftriaxone, are more commonly used in clinical practice. Common adverse effects associated with cephalosporins include hypersensitivity, rash, anaphylaxis, and seizures.
Penicillin is another widely used subclass that effectively targets various bacteria. However, it is not regarded as the first-line treatment for uncomplicated cystitis because of the high prevalence of penicillin-resistant E. coli strains. Within the penicillin class, pivmecillinam is considered the first-line empiric treatment for acute cystitis due to its wide spectrum of activity against gram-negative bacteria and its specific efficacy in the urinary tract. It has consistently demonstrated a high cure rate of over 85% for UTIs and a low resistance rate among E. coli strains. Amoxicillin-clavulanate combination, which enhances the effectiveness of amoxicillin, is often used as an alternative for cystitis treatment when other options cannot be used.
Fluoroquinolones
Fluoroquinolones are a class of antimicrobial agents known for their high efficacy and broad spectrum activity against aerobic gram-positive and gram-negative bacteria. These potent antibiotics exert their bactericidal effects by selectively inhibiting the activity of type II DNA topoisomerases, which effectively halt the replication of bacterial DNA, leading to bacterial death.
Among the fluoroquinolones, ciprofloxacin and levofloxacin are used more frequently for the treatment of UTIs. These agents are well-absorbed orally and achieve significant concentrations in urine and various tissues. However, fluoroquinolones administration carries risk of GI symptoms, confusion, hypersensitivity, tendinopathy, and neuropathy. Additionally, the extensive use of fluoroquinolones has contributed to the prevalence of antimicrobial resistance in some areas. As a result, fluoroquinolones are generally reserved for more serious UTIs or when there are no better anti urinary-infective agent options.
Bacterial static agent
Sulfonamide
Sulfonamide is a bacteriostatic agent that competitively inhibits the bacterial enzyme dihydropteroate synthase. By acting as a substrate analog of para-aminobenzoic acid, sulfonamide inhibits folic acid production. TMP/SMX is a combination of two antibacterial agents that work synergistically to combat a wide range of urinary tract pathogens. TMP/SMX is commonly used due to its ability to achieve high concentrations in urinary tract tissues and urine. This antibiotic combination demonstrates notable efficacy in both the treatment and prophylaxis of recurrent urinary tract infections. Common adverse effects include nausea, vomiting, rash,pruritus, and photosensitivity.
Renal dysfunction
Kidney disease can affect drug elimination, absorption, and distribution in the body, leading to altered serum drug concentrations. This can increase the risk of drug toxicity or suboptimal therapeutic effects. As a result, dosage adjustments are necessary for patients who fail to achieve the desired therapeutic serum drug levels.
Management
The choice of urinary anti-infective agents for patients with renal dysfunction is generally similar to that for individuals with normal kidney function. However, in cases where the patient's glomerular filtration rate (GFR) decreases to less than 20 mL/min, drug dosages adjustment is necessary because achieving the desired therapeutic serum drug levels becomes challenging in such patients.
Medication safety
Some drugs need to be used with caution in patients with renal dysfunction. The use of nitrofurantoin is contraindicated in patients with an estimated GFR of less than 30 mL/min/1.73m2 as drug accumulation can lead to increased side effects and impaired recovery of the urinary tract, increasing the risk of treatment failure. The use of TMP/SMX also raises concerns in patients with kidney disease. In patients with creatinine clearance less than 50 mL/min, the urine concentrations of SMX may decrease to subtherapeutic levels. Therefore, in patients with low creatinine clearance, it is recommended to prescribe a reduced dosage of TMP alone.
Pregnancy
Pregnant women with UTIs are at a higher risk of experiencing recurrent bacteriuria and developing pyelonephritis compared to non-pregnant individuals. Untreated UTIs during pregnancy can lead to adverse outcomes, including preterm birth and low birth weight infants.
Management
Antimicrobial treatment should be adjusted for UTIs in pregnant women to avoid potential side effects brought to fetus. For acute cystitis and pyelonephritis in pregnant women, empiric antibiotic treatment is often initiated. Commonly used antibiotics for uncomplicated cystitis include amoxicillin-clavulanate and fosfomycin, while parenteral beta-lactams are preferred for acute pyelonephritis. These options are chosen because they are considered safer in pregnancy and have a relatively broad spectrum of activity. Typically, an antimicrobial course of five to seven days is given. This duration is chosen to minimize fetal exposure to antimicrobials while ensuring optimal treatment outcomes.
Medication safety
The type of urinary anti-infective agents should be carefully chosen for pregnant women with UTIs due to the potential impact on fetal development. Penicillins, cephalosporins, and fosfomycin are safe options during pregnancy. Nitrofurantoin is typically avoided during the first trimester due to uncertain associations with congenital anomalies. TMP/SMX should also be avoided as it may be associated with impaired folate metabolism, which increases the risk of neural tube defects. However, when all alternative antibiotics are contraindicated, nitrofurantoin and TMP/SMX become the last resort at the expense of the fetus. Fluoroquinolones should be avoided during pregnancy as they are associated with bone and cartilage toxicity in developing fetuses.
Pediatrics
Urinary tract infection in pediatric patients is a significant clinical issue, affecting approximately 7% of fevered infants and children. If left untreated, the infection can ascend from the bladder to the kidneys, resulting in acute pyelonephritis, which leads to hypertension, kidney scarring, and end-stage kidney disease.
Management
The choice of urinary anti-infective agents used in pediatric patients and the duration of therapy depend on the types of UTIs they are suffering from. It is important to note that the dosage of antibiotics used in children is typically weight-dependent. Generally, oral or parenteral cephalosporins are recommended as the first-line agent for children older than two months. Second-line therapy should be considered for patients who have poor response to first-line treatment. Alternative choices include amoxicillin-clavulanate, nitrofurantoin, TMP/SMX, and ciprofloxacin.
For the treatment of simple cystitis in children, a five-day oral course of cephalexin is the preferred choice. As for children with suspected pyelonephritis, a ten-day treatment regimen is recommended. In such cases, a third-generation cephalosporin, such as cefdinir, is suggested as an appropriate option. If second-line therapy is initiated in pediatric patients with suspected pyelonephritis, ciprofloxacin should be the preferred option among the four alternatives. Nitrofurantoin may not be adequate in treating upper urinary tract infections, while TMP/SMX and amoxicillin-clavulanate should be used with caution due to the risk of kidney scarring in these patients.
Medication safety
The choice of urinary anti-infective agents in pediatric patients may differ from that in adults due to the potential harm they can cause to children. For example, the systemic use of fluoroquinolones is not appropriate in pediatric patients due to the potential risk of musculoskeletal toxicity.
History
The discovery of antimicrobial agents contributed significantly to UTI management during the 20th century. Nitrofurantoin emerged as the first practical and safe urinary antimicrobial agent, but it was with limited spectrum of activity. Subsequently, in the 1970s, beta-lactam antibiotics and TMP/SMX became available for UTI therapy. Antimicrobial resistance was developed to these agents due to their widespread and extensive usage, which restricted their clinical efficacy in UTI management. Fluoroquinolones emerged during the 1980s and were recommended as an alternative when resistance to TMP/SMX reaches 10% or higher. The evolving landscape of drug resistance will continue to influence the development and application of antimicrobial agents in UTI therapy.
See also
UTI vaccine
Uromune
Methenamine
LACTIN-V
TOL-463
References
External links
Medicine
Infection-control measures
Urologic procedures
Urology
Medical treatments
Bactericides
Antiseptics | Urinary anti-infective agent | [
"Biology"
] | 2,863 | [
"Bactericides",
"Biocides",
"Medicine"
] |
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