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73,967,005 | https://en.wikipedia.org/wiki/Matsaev%27s%20theorem | Matsaev's theorem is a theorem from complex analysis, which characterizes the order and type of an entire function.
The theorem was proven in 1960 by Vladimir Igorevich Matsaev.
Matsaev's theorem
Let with be an entire function which is bounded from below as follows
where
and
Then is of order and has finite type.
References
Theorems in complex analysis | Matsaev's theorem | [
"Mathematics"
] | 77 | [
"Theorems in mathematical analysis",
"Theorems in complex analysis"
] |
73,971,166 | https://en.wikipedia.org/wiki/Third%20medium%20contact%20method | The third medium contact (TMC) is an implicit formulation used in contact mechanics. Contacting bodies are embedded in a highly compliant medium (the third medium), which becomes increasingly stiff under compression. The stiffening of the third medium allows tractions to be transferred between the contacting bodies when the third medium between the bodies is compressed. In itself, the method is inexact; however, in contrast to most other contact methods, the third medium approach is continuous and differentiable, which makes it applicable to applications such as topology optimization.
History
The method was first proposed in 2013 by , Jörg Schröder, and Alexander Schwarz, where a St. Venant-Kirchhoff material was used to model the third medium. This approach required explicit treatment of surface normals and continued to be used until 2017, when Bog et al. simplified the method by applying a Hencky material with the inherent property of becoming rigid under ultimate compression. This property made the explicit treatment of surface normals redundant, transforming the third medium contact method into a fully implicit method, contrasting with the more widely used Mortar methods or Penalty methods. However, at this stage, the third medium contact method could only handle very small degrees of sliding, and a friction model for TMC had yet to be developed. The rising popularity of Mortar methods, which emerged in the same period with a rigorous mathematical foundation and rapid development and adoption, overshadowed the TMC method. Consequently, TMC was abandoned at an early stage and remained largely unknown in contact mechanics.
In 2021, the method was revived when Gore Lukas Bluhm, Ole Sigmund, and Konstantinos Poulios rediscovered it, realizing that a highly compliant void material could transfer forces in a topology optimization setting. Bluhm et al. added a new regularization to stabilize the third medium, enabling the method to contact problems involving moderate sliding and thus making it practically applicable. The use of TMC in topology optimization was refined in subsequent work and applied to more complex problems.
In 2024, Frederiksen et al. proposed a crystal plasticity-inspired scheme to include friction. This involved adding a term to the material model to contribute to high shear stresses in the contact interface, along with a plastic slip scheme to release shear stresses and accommodate sliding. During the same period, new regularization methods were proposed, and the method was extended to thermal contact by Dalklint et al. and utilized for pneumatic actuation by Faltus et al.
Principles
Material model
TMC relies on a material model for the third medium, which stiffens under compression. The most commonly applied material models are of a neo-Hookean type, characterized by a strain energy density function:
,
where is the bulk modulus, is the shear modulus, and is the deformation gradient tensor of the displacement field .
As the current material volume approaches zero, this material model exhibits the characteristic of becoming infinitely stiff. Consequently, when the third medium is compressed, its volume remains positive and finite. This ensures that if two solids are embedded in a third medium with significantly lower bulk and shear moduli, the third medium can still transfer substantial forces to deform the solids when sufficiently compressed, as its stiffness becomes comparable to that of the embedded solids.
Regularization
While the neo-Hookean material model can be stable for contact without sliding, sliding often leads to instability. To address this, regularization techniques are applied to the strain energy density function.
Regularization is typically achieved by adding a regularization term to the strain energy density function of the material model. A common approach is the HuHu regularization, expressed as:
,
where represents the augmented strain energy density of the third medium, is the regularization term representing the inner product of the spatial Hessian of by itself, and is the underlying strain energy density of the third medium, e.g. a neo-Hookean solid or another hyperelastic material.
The HuHu regularization was the first regularization method specifically developed for TMC. A subsequent refinement is known as the HuHu-LuLu regularization, expressed as:
,
where is the Laplacian of the displacement field , and is the trace of the identity matrix corresponding to the problem's dimension (2D or 3D). The LuLu term is designed to mitigate the penalization of bending and quadratic compression deformations while maintaining the penalization of excessive skew deformations, thus preserving the stabilizing properties of the HuHu regularization. This reduced penalization on bending deformations enhances the accuracy of modeling curved contacts, particularly beneficial when using coarse finite element meshes. Similarly, the reduced penalization on quadratic compression is advantageous in topology optimization applications, where finite elements with varying material densities undergo non-uniform compression.
An alternative and more complex regularization approach involves penalizing volume change and rotations, initially proposed by Faltus et al. This approach requires further extension to 3D applications. A later improvement by Wriggers et al. directly utilizes the rotation tensor instead of the approximation used in .
Friction
The integration of friction into the TMC method represents a significant advancement in simulating realistic contact conditions, addressing the previous limitations in replicating real-world scenarios. Currently, there is only one approach available for adding friction. This approach introduces shear stress to the contact and releases it through plastic slip if the contact is sliding.
When a neo-Hookean material model is used to represent the third medium, it exhibits much greater stiffness in compression compared to shear during contact. To address this and provide shear resistance, an anisotropic term is incorporated into the neo-Hookean material model. This modification rapidly builds up shear stress in compressed regions of the third medium, which is crucial for accurately modeling frictional contact.
In this formulation, the extended strain energy density expression with the added shear term is:
,
where:
is a scaling parameter,
is a unit vector parallel to the direction of sliding,
is a unit vector perpendicular to the contact interface, and
is the right Cauchy-Green tensor of the elastic deformation.
The shear extension works by penalising the contribution in associated with shear in the slip direction .
To release the shear stresses at the onset of sliding, a framework inspired by crystal plasticity is employed. This includes a yield criterion specifically designed to replicate the effects of Coulomb friction. This framework allows the model to simulate the onset of sliding when the shear stress, provided by the added anisotropic term, exceeds a certain threshold, effectively mimicking real-world frictional behavior. The yield criterion, based on the Coulomb friction model, determines when sliding occurs, initiating once the shear stress surpasses a critical value.
Applications
TMC is widely used in computational mechanics and topology optimization due to its ability to model contact mechanics in a differentiable and fully implicit manner. One of the key advantages of TMC is that it eliminates the need to explicitly define surfaces and contact pairs, thereby simplifying the modeling process.
In topology optimization, TMC ensures that sensitivities are properly handled, enabling gradient-based optimization approaches to converge effectively and produce designs with internal contact. Notable designs achieved through this approach include compliant mechanisms such as hooks, bending mechanisms, and self-contacting springs. The design of metamaterials is a common application for topology optimization, where TMC has expanded the range of possible designs. Additionally, soft springs and pneumatically activated systems, which are useful in the design of soft robots, have been modeled using TMC.
TMC has also been extended to applications involving frictional contact and thermo-mechanical coupling. These advancements enhance the method’s utility in modeling real-world mechanical interfaces.
See also
Contact mechanics
Hyperelastic materials
Topology optimization
References
Engineering
Mechanical engineering
Contact mechanics
Friction
Solid mechanics | Third medium contact method | [
"Physics",
"Chemistry",
"Engineering"
] | 1,583 | [
"Mechanical phenomena",
"Solid mechanics",
"Physical phenomena",
"Friction",
"Physical quantities",
"Force",
"Applied and interdisciplinary physics",
"Surface science",
"Mechanics",
"Mechanical engineering"
] |
73,971,837 | https://en.wikipedia.org/wiki/Erwin-F%C3%A9lix%20Lewy-Bertaut | Erwin-Félix Lewy-Bertaut (9 February 1913 – 6 November 2003), also known separately as Erwin Lewy, Félix Bertaut, and E. F. Bertaut, or Erwin Félix Lewy-Bertaut, was a German-born French materials scientist who led a former life as a law school student in Nazi Germany. He was renowned internationally for his work in magnetic crystallography, X-ray diffraction, and neutron scattering. He was a research director at CNRS, a member of the French Academy of Sciences and played an important role in the creation of Institut Laue–Langevin, a leading neutron research facility in the world.
Biography
Lewy-Bertaut was born with the name Erwin Lewy to Jewish parents in Leobschütz of Silesia (then in Germany). The year 1930 marked a significant shift as his mother passed away, prompting their entire family's relocation to Gleiwitz amidst an era of economic turmoil and the ascent of Nazism. Following this, in 1931, Lewy embarked on his legal studies first at the University of Freiburg and subsequently in University of Breslau (now Wrocław). As Hitler's ascendancy to power unfurled in Germany, instituting a "numerus clausus" that effectively precluded Jewish individuals from university access, Lewy-Bertaut left for Bordeaux, France. There, the Rothschild Foundation awarded him a scholarship, facilitating his enrollment at the University of Bordeaux, where Lewy-Bertaut studied chemical engineering, physics, and mathematics. After graduation, Lewy-Bertaut undertook roles as a mathematics and German tutor and acquired French citizenship in 1936. In 1938, Lewy-Bertaut worked as an engineer at Institut du pin and joined the French army as a military volunteer near Bordeaux. At the onset of the conflict in 1940, Colonel Faure entrusted him with the military records of a missing soldier, Félix Bertaut, and he adopted this name permanently.
Lewy-Bertaut worked as a chemical engineer between 1941 and 1943 to enhance the durability of bicycle brakes crafted from agglomerated cork. To elude police inspections and evade mandatory labor service, he went to Paris, where he collaborated with Marcel Mathieu at the Laboratoire Central des Poudres. Subsequently, he partnered with Emmanuel Grison, who tutored him in the utilization of the International Tables for Crystallography. Regrettably, a bicycle registration check by the police led to his summons to the Paris Prefecture. Lewy-Bertaut moved to Grenoble in the Italian-occupied zone to meet Louis Néel, who was temporarily withdrawn from the University of Strasbourg and has founded the Laboratoire d'Electrostatique et de Physique du Métal (LEPM, now Institut Néel) in 1946, which was the first CNRS laboratory outside the Paris region. Lewy-Bertaut also took over Erwin Lewy's qualifications in 1946 and obtained a research grant from the CNRS under his wartime identity, "Félix Bertaut". Lewy-Bertaut eventually finished his thesis under Louis Néel in 1953 and André Guinier was also an examiner. His thesis involves X-ray diffraction studies of powder granulometry, which later became known as the Bertaut-Warren-Averbach method. Immediately after his thesis, Lewy-Bertaut started establishing his group at the LEPM that formed the basis of the X-ray department to carry out research in cristallography, along with Francis Forrat and Professor René Pauthenet, distinguished themselves with their work on garnet ferrites, from which the theory of antiferromagnetism and ferrimagnetism was built up.
In 1949, Lewy-Bertaut read a one-page publication by Clifford G. Shull and J. Samuel Smart, which recovered the magnetic structure of MnO from neutron diffraction and validated Louis Néel's work on antiferromagnetism. In 1953, Lewy-Bertaut secured a Fulbright grant to visit Raymond Pepinski's laboratory at State College, Pennsylvania and accessed the neutron diffraction facilities at the Brookhaven National Laboratory, where he acquainted himself with neutron experiments under the guidance of Lester Corliss and Julius Hastings. Upon returning to Grenoble, Lewy-Bertaut was placed in charge of the development of the military facility Polygone d'Artillerie (now Polygone Scientifique) into a neutron research center, which later became the Institut Laue-Langevin, an international research facility collaboratively funded by the French and German governmental agencies. Lewy-Bertaut was CNRS research director in 1956 and the scientific director of CNRS in 1961.
Research
Lewy-Bertaut made an enormous contributions to magnetic and neutron crystallography, including the use of group theory in describing magnetic structures. When the International Union of Crystallography (IUCr) decided to finalize the volume on the symmetry of space groups in the International Tables of Crystallography, he was a member of the ad hoc committee and contributed in particular to the definition of magnetic groups. He used the symmetry of crystals to propose all possible magnetic structures. This "Bertaut method" was very useful for complex structures. Lewy-Bertaut also developed what is known as structure factor algebra and solved the structure of complex compounds such as the non-stoichiometric pyrrhotite.
Honors and distinctions
Lewy-Bertaut was a member of the IUCr executive committee between 1975 and 1981. He was co-founder of its "Neutron Diffraction" commission and co-founder and chairman of its "International Tables" and "Charge, Spin and Momentum Density" commissions. He was the IUCr representative on the Solid State Commission of the International Union of Pure and Applied Physics (IUPAP) between 1966 and 1972 and was secretary and then chairman of the Solid State Physics Section. He was editor or co-editor of numerous scientific journals. From 1958 to 1982, he was scientific advisor to various institutes, including the Commissariat à l'Energie Atomique (CEA), CNRS, ILL, and the Max Planck Institute for Metal Research in Stuttgart.
Lewy-Bertaut received the CNRS Silver Medal in 1959. He received the Knight of the Legion of Honour and Commander of the National Order of Merit. In 1979, Lewy-Bertaut was elected a full member of the Académie des Sciences. In 1986, Lewy-Bertaut received the Gregori Aminoff Prize from the Royal Swedish Academy of Sciences.
Further reading
Erwin Félix Lewy-Bertaut, Notice nécrologique de l’Académie des Sciences, J. Villain (2004).
La vie et l'oeuvre scientifique d’Erwin Félix Lewy-Bertaut, Séance publique Académie des Sciences du 8 novembre 2005, J-Cl. Pecker (2005)
Journée Scientifique « E.F. BERTAUT » May 2006, CNRS-Polygone, Grenoble.
References
1913 births
2003 deaths
Crystallographers
20th-century French physicists
Members of the French Academy of Sciences
University of Bordeaux alumni
University of Breslau alumni
Grenoble Alpes University alumni
Research directors of the French National Centre for Scientific Research
French National Centre for Scientific Research scientists
Recipients of the Legion of Honour
People from Głubczyce
Fellows of the American Physical Society | Erwin-Félix Lewy-Bertaut | [
"Chemistry",
"Materials_science"
] | 1,561 | [
"Crystallographers",
"Crystallography"
] |
73,972,756 | https://en.wikipedia.org/wiki/Universal%20International%20Shared%20Cost%20Number | Universal International Shared Cost Number (UISCN) is part of the E.164 telephone numbering space that includes international telephone numbers where the call costs are split between the caller and the called. An international shared-cost number allows the calling party to make the call at national rates, since the costs of any international routing will be borne by the called party.
The International Telecommunication Union (ITU) has allocated the country code 808 to this service.
As of 2023, the only companies that had requested UISCN number allocation were Swisscom (Switzerland), SMSRelay (Switzerland, now defunct) and Mr Next Id (now DTMS; Germany).
See also
Shared-cost service
List of country calling codes
References
International telecommunications
Telephone numbers
Further reading | Universal International Shared Cost Number | [
"Mathematics"
] | 154 | [
"Mathematical objects",
"Numbers",
"Telephone numbers"
] |
73,973,823 | https://en.wikipedia.org/wiki/HD%20170384 | HD 170384, also known as HR 6931 or rarely 11 G. Coronae Australis, is a solitary white-hued star located in the southern constellation Corona Australis. It has an apparent magnitude of 6.02, making it barely visible to the naked eye, even under ideal conditions. The object is located relatively close at a distance of 229.1 light-years based on Gaia DR3 parallax measurements and it is drifting closer with a heliocentric radial velocity of . At its current distance, HD 170384's brightness is diminished by interstellar extinction of 0.28 magnitudes and it has an absolute magnitude of +1.86.
This object has a stellar classification of A3 V, indicating that it is an ordinary A-type main-sequence star. It has double the Sun's mass and 1.91 times the radius of the Sun. It radiates 16.7 times the luminosity of the Sun from its photosphere at an effective temperature of . HD 170384 has a near solar metallicity at [Fe/H] = −0.01 (97% solar) and it is estimated to be 544 million years old, having completed 45% of its main sequence lifetime. Like many hot stars HD 170384 spins rapidly, having a projected rotational velocity of and an estimated rotation period of 19.2 hours.
References
A-type main-sequence stars
Corona Australis
Coronae Australis, 11
CD-41 12871
170384
090759
6931 | HD 170384 | [
"Astronomy"
] | 322 | [
"Corona Australis",
"Constellations"
] |
73,975,599 | https://en.wikipedia.org/wiki/Lyngbyastatins | Lyngbyastatins 1 and 3 are cytotoxic cyclic depsipeptides that possess antiproliferative activity against human cancer cell lines. These compounds, first isolated from the extract of a Lyngbya majuscula/Schizothrix calcicola assemblage and from L. majuscula Harvey ex Gomont (Oscillatoriaceae) strains, respectively, target the actin cytoskeleton of eukaryotic cells.
Biosynthesis
Lyngbyastatins 1 and 3 are encoded for by a 52 kb biosynthetic gene cluster (BGC) containing one polyketide synthase (PKS)/non-ribosomal peptide synthetase (NRPS) hybrid (LbnA), four NRPSs (LbnB-D, LbnF), and one PKS (LbnE).
Biosynthesis commences with PKS activity — thiolation of propanoic (Lyngbyastatin 1) or butyric (Lyngbyastatin 3) acid and subsequent loading onto the ketosynthase (KS) of LbnA. An acyl unit from malonyl CoA is then coupled onto the initial substrate via an acyltransferase (AT) and then methylated at the alpha carbon through a C-methyltransferase (CMT) before an aminotransferase (AmT) conducts a transamination of the initial substrate carbonyl. The latter half of LbnA follows traditional NRPS activity containing condensation (C), adenylation (A), and thiolation (T) domains to couple 2-hydroxy-3-methylvaleric acid, which is believed to be formed from the 2-oxo analog through PKS ketoreductase (KR) activity.
LbnB, a traditional NRPS, adds glycine into the growing thioester by its amino group. LbnC is another traditional NRPS that adds L-leucine and glycine, respectively, except the L-leucine domain possesses an active N-methyltransferase (NMT) domain that methylates the nitrogen of L-leucine.
NRPS LbnD then adds L-valine, L-tyrosine, and L or D-valine, respectively to the growing molecule. PKS LbnE couples an acyl unit from malonyl-CoA onto the C-terminus of the valine residue before a C-methyltransferase methylates the carbon alpha to the thioester twice to produce a quaternary alpha carbon.
NRPS LbnF completes the biosynthesis by coupling L-alanine before the thioesterase (TE) domain conducts a head-to-tail cyclization to produce the final depsipeptide products.
References
Depsipeptides | Lyngbyastatins | [
"Chemistry",
"Biology"
] | 611 | [
"Biochemistry stubs",
"Biotechnology stubs",
"Biochemistry"
] |
69,500,010 | https://en.wikipedia.org/wiki/Puerto%20Mosquito | The Puerto Mosquito Bioluminescent Bay (), or Mosquito Bio Bay, is a bay in the island of Vieques famous for its bioluminescence produced by the dinoflagellate Pyrodinium bahamense, which glows blue when agitated. This species of phytoplankton is found in bays in the Virgin Islands, Puerto Rico and The Bahamas.
History
According to legend, Puerto Mosquito is named after the Mosquito, the name of one of pirate Roberto Cofresí's ships. The bio bay was proclaimed a National Natural Landmark in 1980.
Bioluminescence
Bioluminescence is produced by the dinoflagellate Pyrodinium bahamense, which glows blue when agitated. Although the phytoplankton responsible for the phenomenon of bioluminescence is found throughout the Antilles, Puerto Mosquito is one of the seven year-round bioluminescent bays in the Caribbean. The bioluminescence is the product of a number of factors: the water conditions and ecosystem created by the surrounding mangrove forest (mostly Rhizophora mangle), the complete lack of modern development in the lagoon, the temperature of the water and the depth of the bay.
Recreation
The bright blue hues produced by the microorganisms during nights of very little moonlight or new moon attracts tourists to the bio bay. It is one of the three bio bays in Puerto Rico; the other two are Laguna Grande in Fajardo and La Parguera in Lajas. The bay and its surrounding mangrove forest are protected by the Vieques Bioluminescent Bay Natural Reserve and no swimming is allowed. Guided tours allow visitors to kayak in the bay and observe the bioluminescence. The bio bay is located near the beach community of Esperanza, between the barrios of Puerto Ferro and Puerto Real in Vieques, Puerto Rico.
Gallery
See also
La Parguera Nature Reserve
List of National Natural Landmarks in Puerto Rico
References
External links
Bahía Mosquito "Bahía Bioluminiscente", Vieques, Puerto Rico (Spanish)
Mosquito Bioluminescent Bay|Vieques (English)
IUCN Category III
Vieques, Puerto Rico
National Natural Landmarks in Puerto Rico
Bays of Puerto Rico
Tourist attractions in Puerto Rico
Bioluminescence
1980 establishments in Puerto Rico
Protected areas established in 1980 | Puerto Mosquito | [
"Chemistry",
"Biology"
] | 477 | [
"Biochemistry",
"Luminescence",
"Bioluminescence"
] |
69,500,966 | https://en.wikipedia.org/wiki/Rainwater%20management | Rainwater management is a series of countermeasures to reduce runoff volume and improve water quality by replicating the natural hydrology and water balance of a site, with consideration of rainwater harvesting, urban flood management and rainwater runoff pollution control.
The continuous growth of human populations and the consequent growing need for drinking water is a global problem. Rainwater is an important source of drinking water, and as a free source of water, considerable quantities can be collected from roof catchments and other surface areas for various uses. Due to water shortages, rainfall events and flooding, attention has been given to rainwater management. Rainwater management re-conceptualizes urban rainwater, transforming it from a community risk to a resource for urban development, a good rainwater management is important for the design of sanitation systems and the environment, nowadays different methods of rainwater management have been developed, including reduction of impervious surfaces, separation of rainwater and sanitary sewers, collection and reuse of rainwater, and Low-impact development (LID).
Components
Rainwater harvesting and use
Rainwater harvesting (RWH) is the process of collecting and storing rainwater rather than letting it run off. Rainwater harvesting systems are increasingly becoming an integral part of the sustainable rainwater management "toolkit" and are widely used in homes, home-scale projects, schools and hospitals for a variety of purposes including watering gardens, livestock, irrigation, home use with proper treatment and home heating. For households it is effective in reducing electricity and greenhouse gas emissions and providing domestic water; for urban agriculture, it is effective in reducing rainwater runoff and related issues; and for industry, it provides sustainability of facilities and low financial resource utilization.
Rainwater harvested from roof structures or other compact surfaces is discharged through drains into storage tank, processed by treatment systems and then deployed in use facilities to complete the beneficial use of rainwater. Rainwater so treated is mainly used for irrigation, washing, laundry, and in some countries it is also considered as drinking water after the necessary purification.
Urban flood management
Urban flood management has now become one of the highest priorities in urban development, Urban flooding has a major impact on both public transportation systems and supply chains and is an important topic in rainwater management
Gray-green infrastructure
The use of combined sewer systems to treat excess rainwater runoff is common in older urban areas. The Combined Sewer System (CSS) collects rainwater runoff, domestic sewage and industrial wastewater into a single pipe. Combined sewer overflows (CSOs) occur when untreated wastewater is discharged to surface water beyond its hydraulic capacity, when this occurs, untreated rainwater and wastewater are discharged directly into nearby streams, rivers and other water bodies. Combined sewer overflows (CSOs) contain untreated or partially treated human and industrial waste, toxic materials and debris, and rainwater. a problem that is currently a key challenge for rainwater management and can lead to public health incidents. Gray-green infrastructure is the key technology to solve this problem and is the core technology of the currently introduced "sponge city". The implementation of gray infrastructure, such as upgrading drainage networks, storage facilities or pumping stations with large diameter pipes, is critical to drain rainwater from urban catchments, while most green infrastructure handles the storage and infiltration of rainwater and drainage of gray infrastructure
Constructed wetlands
Constructed wetlands for sewer overflows treatment are currently an effective and less costly option to prevent untreated wastewater from overflowing from polluted natural water bodies, and constructed wetlands that act as retention ponds during the rainy season can collect and treat rainwater due to their natural purification function, and produce high quality water for reuse after treatment by constructed wetlands with aeration system and soils infiltration system.
Separate sewer systems
The conversion of Combined Sewer System (CSS) to separate sewer systems with retention ponds will not only increase rainwater drainage and reduce the potential for urban flooding, but their own retention ponds will also retain pollutants, thereby reducing or preventing unnecessary pollution of a single receiving waters.
Land use
The ratio of pervious to impervious surfaces is important in flood management. Building vegetated spaces, such as parks integrated with urban facilities, can increase the amount of pervious area. For new and redevelopment projects, reduce the amount of impervious surfaces, such as buildings, roads, parking lots, and other structures.
Low-impact development (LID)
Low-impact development (LID) refers to systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to protect water quality and associated aquatic habitat. Low-impact development (LID) practices provide more sustainable solutions than traditional piping and storm ponds in rainwater management. The sustainability of LID practices is achieved primarily through the use of porous pavement, bioretention, green roofs, rainwater harvesting, and other rainwater management strategies. Bioretention can effectively retain large amounts of runoff, porous pavement can effectively infiltrate rainwater runoff, and green roofs can retain rainwater under a variety of climatic conditions. These methods create and restore green space and reduce the impact of built-up areas at the site and regional scales, promoting the natural flow of water within an ecosystem or watershed. Applied over a wide range of scales, LID can maintain or restore the hydrologic and ecological functions of a watershed.
Rainwater management in agriculture
Applying rainwater management, surface runoff can be collected and stored in hand-dug farm ponds. To enhance irrigation in dry conditions, earthen ridges were constructed to collect and prevent rainwater from flowing down the hillsides and slopes. Even during periods of low rainfall, enough water can be collected for crop growth. Rainwater management can increase the productivity of smallholder farmers in arid environments. Productivity of rainfed agriculture is improved through supplemental irrigation, especially when combined with soil fertility management.
Tools
Rainwater management as a means of multi-stage control and improvement of rainwater systems needs to go through multiple steps of analysis and design, and in the new era of Low-impact development, rainwater management has become more than just a task for engineers, rainwater management projects have tended to become Integrated project delivery (IPD), designers need to consider rainwater management issues at a much earlier stage to avoid The development and use of software such as Rainwater+ is now helping designers to implement rainwater management at the design stage, its more intuitive GUI and simple workflow ensures that designers with little to no experience in hydrology can use Rainwater+, which will reduce later building construction conflicts to facilitate communication between all parties and improve construction quality.
Terminologies
Low impact development (LID)
The term Low-impact development is commonly used in North America and New Zealand, and was first used in the United States by Barlow et al.
Water sensitive urban design (WSUD)
Water sensitive urban design (WSUD) is a concept widely accepted and partially acted on throughout Australia's federal and state governments.
Integrated urban water management (IUWM)
IUWM derives from the broader term, Integrated Water Management, which involves the integrated management of all parts of the water cycle within a watershed.
Sustainable urban drainage systems (SUDS)
SUDS established in a similar but separate design manual that includes Scotland and Northern Ireland as well as England and Wales, SUDS consists of a range of techniques and technologies based on the concept of replicating the natural, pre-development drainage of the site as closely as possible, culminating in a management system.
Best management practices
Best management practices are structural, vegetative or managerial practices used to treat, prevent or reduce water pollution. Structural BMPs. Extended Detention Ponds.
See also
Integrated urban water management
Urban flooding
Constructed wetlands
Low-impact development
Water-sensitive urban design
Sponge city
References
Civil engineering
Rainwater harvesting
Water management | Rainwater management | [
"Engineering"
] | 1,592 | [
"Construction",
"Civil engineering"
] |
69,503,348 | https://en.wikipedia.org/wiki/Middle%20ear%20implant | A middle ear implant is a hearing device that is surgically implanted into the middle ear. They help people with conductive, sensorineural or mixed hearing loss to hear.
Middle ear implants work by improving the conduction of sound vibrations from the middle ear to the inner ear. There are two types of middle ear devices: active and passive. Active middle ear implants (AMEI) consist of an external audio processor and an internal implant, which actively vibrates the structures of the middle ear. Passive middle ear implants (PMEIs) are sometimes known as ossicular replacement prostheses, TORPs or PORPs. They replace damaged or missing parts of the middle ear, creating a bridge between the outer ear and the inner ear, so that sound vibrations can be conducted through the middle ear and on to the cochlea. Unlike AMEIs, PMEIs contain no electronics and are not powered by an external source.
PMEIs are the usual first-line surgical treatment for conductive hearing loss, due to their lack of external components and cost-effectiveness. However, each patient is assessed individually as to whether an AMEI or PMEI would bring more benefit. This is especially true if the patient has already had several surgeries with PMEIs.
Active middle ear implant
Parts
An active middle ear implant (AMEI) has two parts: an internal implant and an external audio processor. The microphone of the audio processor picks up sounds from the environment. The processor then converts these acoustic signals into digital signals and sends them to the implant through the skin. The implant sends the signals to the Floating Mass Transducer (FMT): a small vibratory part that is surgically fixed either on one of the three ossicles or against the round window of the cochlea. The FMT vibrates and sends sound vibrations to the cochlea. The cochlea converts these vibrations into nerve signals and sends them to the brain, where they are interpreted as sound.
Indications
AMEIs are intended for patients with mild-to-severe sensorineural hearing loss, as well as those with conductive or mixed hearing loss. They can be used by adults and children over the age of 5.
Sensorineural hearing loss
An AMEI can be beneficial for patients with mild-to-severe sensorineural hearing loss who have an intact ossicular chain and healthy middle ear, but who either cannot wear hearing aids or who do not get sufficient benefit from them. Reasons for not being able to wear hearing aids include earmold allergies, skin problems, narrow, collapsed or closed ear canals, or malformed ears. In cases of sensorineural hearing loss, the FMT is usually attached to the incus.
Conductive or mixed hearing loss
An AMEI is also indicated for patients with conductive or mixed hearing loss with bone conduction thresholds from 45 dB in the low frequencies to 65 dB in the high frequencies. In these cases, the FMT can be coupled to various parts of the middle ear, depending on the patient's pathology:
The oval window, causing stimulation of the cochlea in patients without an ossicular chain.
The round window, causing reverse stimulation of the cochlea in patients without an ossicular chain.
The mobile stapes in patients with absence or fixation of other ossicles, usually in cases of chronic otitis media or malformations.
Efficacy
AMEIs have been shown by several studies to be equal or superior to both hearing aids and bone conduction implants. Lee et al used the PBmax test to study speech intelligibility in patients before and after receiving an AMEI. All patients had used hearing aids pre-implantation. The researchers found that speech intelligibility improved with the AMEI, particularly in patients with a down-sloping hearing loss. These findings were supported by Iwasaki et al, who found that both speech intelligibility and quality of life improved after implantation with an AMEI, applied to the round window.
AMEIs can also offer improved hearing performance over bone conduction implants for patients with mixed hearing loss. Mojallal et al found that patients whose mixed hearing loss was treated with an AMEI experienced both better word recognition and speech understanding in noise than those who received a bone conduction implant, providing that their bone conduction pure-tone average (0.5 to 4 kHz) was poorer than 35 dB HL.
Passive middle ear implant
Parts
Passive middle ear implants (PMEI) are ossicular replacement prostheses designed to replace some or all of the ossicular chain in the middle ear. They create a bridge between the outer ear and the inner ear, so that sound vibrations can be conducted through the middle ear and on to the cochlea
There are two types of PMEIs: tympanoplasty implants and stapes implants. Tympanoplasty implants (also known as PORPs or TORPs) are suitable for patients with a mobile stapes footplate, ie. a stapes footplate that moves in the normal way. Either a partial or a total tympanoplasty implant can be used, depending on the condition of the stapes. If the stapes is fixed and cannot transfer vibrations to the inner ear, then a stapes implant would be used.
PMEIs are made from different materials including titanium, teflon, hydroxylapatite, platinum, and nitinol, all of which are suitable for use within the human body. Titanium implants can safely undergo MRIs of up to 7.0 Tesla.
Indications
Tympanoplasty implant
The tympanoplasty implant is indicated in cases of congenital or acquired defects of the ossicular chain, due to e.g.:
Chronic otitis media
Traumatic injury
Malformation
Cholesteatoma
It can also be used to treat patients with inadequate conductive hearing from previous middle ear surgery.
Stapes implant
The stapesplasty prosthesis is indicated in cases of congenital or acquired defects of the stapes due to e.g.:
Otosclerosis
Congenital fixation of the stapes
Traumatic injury
Malformation of the ossicular chain/middle ear
It can also be used to treat patients with inadequate conductive hearing from previous stapes surgery.
See also
Ossicular replacement prosthesis
References
Medical technology | Middle ear implant | [
"Biology"
] | 1,310 | [
"Medical technology"
] |
69,506,742 | https://en.wikipedia.org/wiki/Hycean%20planet | A hycean planet ( ) is a hypothetical type of exoplanet that features a liquid water ocean underneath a hydrogen-rich atmosphere. The term hycean is a portmanteau of hydrogen and ocean.
Definition
A hycean planet is a hypothetical type of planet with liquid water oceans under a hydrogen atmosphere. The presence of extraterrestrial liquid water makes hycean planets regarded as promising candidates for planetary habitability. They are usually considered to be larger and more massive than Earth. As of 2023, there are no confirmed hycean planets, but the Kepler mission detected many candidates.
History
The term "hycean planet" was coined in 2021 by a team of exoplanet researchers at the University of Cambridge, as a portmanteau of "hydrogen" and "ocean," used to describe planets that are thought to have large oceans and hydrogen-rich atmospheres. Hycean planets are thought to be common around red dwarf stars, and are considered to be a promising place to search for life beyond Earth. The term was first used in a paper published in The Astrophysical Journal on August 31, 2021.
Life on hycean planets would probably be entirely aquatic. Their water-rich compositions imply that they can have larger sizes than comparable non-hycean planets, thus making detection of biosignatures easier. Hycean worlds could be investigated for biosignatures by terrestrial telescopes and space telescopes like the James Webb Space Telescope (JWST). In 2023, the JWST investigated K2-18b and found evidence for both a hycean atmosphere and the presence of dimethyl sulfide ─ a potential biosignature.
Properties
Hycean planets could be considerably larger than previous estimates for habitable planets, with radii reaching () and masses of (). Moreover, the habitable zone of such planets could be considerably larger than that of Earth-like planets. The planetary equilibrium temperature can reach for planets orbiting late M-dwarfs. However, mass and radius do not by themselves inform the composition of a planet, as bodies with identical mass and radius can have distinct compositions: A given planet may thus be either a hycean planet or a super-Earth.
Such planets can have many distinct atmospheric compositions and internal structures. Also possible are tidally locked "dark hycean" planets (habitable only on the side of permanent night) or "cold hycean" planets (with negligible irradiation, being kept warm by the greenhouse effect). Dark hycean worlds can form when the atmosphere does not effectively transport heat from the permanent day side to the permanent night side, thus the night side has temperate temperatures while the day side is too hot for life. Cold hycean planets may exist even in the absence of stars, e.g. rogue planets.
Although the presence of water may help them be habitable planets, their habitability may be limited by a possible runaway greenhouse effect. Hydrogen reacts differently to starlight's wavelengths than do heavier gases like nitrogen and oxygen. If the planet orbits a sun-like star at one Astronomical unit (AU), the temperature would be so high that the oceans would boil and water would become vapor. Current calculations locate the habitable zone where water would remain liquid at 1.6 AU, if the atmospheric pressure is similar to Earth's, or at 3.85 AU if it is the more likely tenfold to twentyfold pressure. All current hycean planet candidates are located within the area where oceans would boil, and are thus unlikely to have actual oceans of liquid water. Another limiting factor is that X-ray and UV radiation from the star (especially active stars) can destroy the water molecules.
Features
They are regarded to be covered in oceans.
They have hydrogen-rich atmospheres. The atmospheres on hycean planets are thought to be made up of hydrogen, helium, and water vapor.
Dark hycean planets thought to be common around red dwarf stars. Red dwarf stars are the most common type of star in the Milky Way galaxy.
They are considered to be a promising place to search for life beyond Earth. Hycean planets have the ingredients that is necessary for life, including liquid water, energy, and organic molecules.
Their atmospheres may have less methane and ammonia than comparable non-hycean Neptune-like planets, if they have water oceans.
They might have a much higher free energy availability for their ecosystems than Earth.
Hycean planets may be capable of supporting extraterrestrial life, despite their properties differing drastically from Earth's. Astronomers plan to use telescopes like the James Webb Space Telescope to search for hycean planets and to learn more about their potential for habitability.
Candidates
K2-18b
One such candidate planet is K2-18b, which orbits a faint star with a period of about 33 days. This candidate planet could have liquid water, containing a considerable high amount of hydrogen gas in its atmosphere, and is far enough from its star, such that it resides within its star's habitable zone. Such candidate planets can be studied for biomarkers.
In 2023, the James Webb Space Telescope detected carbon dioxide and methane in the atmosphere of K2-18b, but it did not detect large amounts of ammonia. This supports the hypothesis that K2-18b could indeed have a water ocean. The same observations also suggest that K2-18b's atmosphere might contain dimethyl sulfide, a compound associated with life on Earth, although this has yet to be confirmed. Another possibility is that K2-18b is a lava world with a hydrogen atmosphere.
Other candidates
K2-3b, a potential Dark hycean planet but may be too hot.
K2-3c but may be too hot.
Kepler-138d
LTT 1445 A b but may be too hot and too water-poor.
TOI-732 c but may be too hot.
TOI-1266 c but may be too hot.
TOI-175 d but may be too hot.
TOI-2136 b
TOI-270 c, a potential Dark hycean planet but may be too hot.
TOI-270 d but may be too hot.
TOI-776 b, a potential Dark hycean planet but may be too hot.
TOI-776 c but may be too hot.
See also
Hot Neptune
Exoplanet
Ocean world
References
Sources
External links
Types of planet
Hypothetical astronomical objects
Extraterrestrial water
2021 neologisms
2021 in science | Hycean planet | [
"Astronomy"
] | 1,349 | [
"Astronomical hypotheses",
"Hypothetical astronomical objects",
"Astronomical myths",
"Astronomical objects"
] |
69,509,977 | https://en.wikipedia.org/wiki/Neodymium%20phosphide | Neodymium phosphide is an inorganic compound of neodymium and phosphorus with the chemical formula NdP.
Preparation
Neodymium phosphide can be obtained by reacting neodymium and phosphorus in a stoichiometric ratio:
4Nd + P4 -> 4NdP
Physical properties
Neodymium phosphide forms cubic crystals, space group Fmm, cell parameters a = 0.5838 nm, Z = 4.
Uses
The compound is a semiconductor used in high power, high frequency applications, and in laser diodes.
References
Phosphides
Neodymium(III) compounds
Semiconductors
Rock salt crystal structure | Neodymium phosphide | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 132 | [
"Electrical resistance and conductance",
"Physical quantities",
"Semiconductors",
"Materials",
"Electronic engineering",
"Condensed matter physics",
"Solid state engineering",
"Matter"
] |
68,194,734 | https://en.wikipedia.org/wiki/Corepresentations%20of%20unitary%20and%20antiunitary%20groups | In quantum mechanics, symmetry operations are of importance in giving information about solutions to a system. Typically these operations form a mathematical group, such as the rotation group SO(3) for spherically symmetric potentials. The representation theory of these groups leads to irreducible representations, which for SO(3) gives the angular momentum ket vectors of the system.
Standard representation theory uses linear operators. However, some operators of physical importance such as time reversal are antilinear, and including these in the symmetry group leads to groups including both unitary and antiunitary operators.
This article is about corepresentation theory, the equivalent of representation theory for these groups. It is mainly used in the theoretical study of magnetic structure but is also relevant to particle physics due to CPT symmetry. It gives basic results, the relation to ordinary representation theory and some references to applications.
Corepresentations of unitary/antiunitary groups
Eugene Wigner showed that a symmetry operation S of a Hamiltonian is represented in quantum mechanics either by a unitary operator, S = U, or an antiunitary one, S = UK where U is unitary, and K denotes complex conjugation. Antiunitary operators arise in quantum mechanics due to the time reversal operator
If the set of symmetry operations (both unitary and antiunitary) forms a group, then it is commonly known as a magnetic group and many of these are described in magnetic space groups.
A group of unitary operators may be represented by a group representation. Due to the presence of antiunitary operators this must be replaced by Wigner's corepresentation theory.
Definition
Let G be a group with a subgroup H of index 2. A corepresentation is a homomorphism into a group of operators over a vector space over the complex numbers where for all u in H the image of u is a linear operator and for all a in the coset G-H the image of a is antilinear (where '*' means complex conjugation):
Properties
As this is a homomorphism
Reducibility
Two corepresentations are equivalent if there is a matrix V
Just like representations, a corepresentation is reducible if there is a proper subspace invariant under the operations of the corepresentation. If the corepresentation is given by matrices, it is reducible if it is equivalent to a corepresentation with each matrix in block diagonal form.
If the corepresentation is not reducible, then it is irreducible.
Schur's lemma
Schur's lemma for irreducible representations over the complex numbers states that if a matrix commutes with all matrices of the representation then it is a (complex) multiple of the identity matrix, that is, the set of commuting matrices is isomorphic to the complex numbers . The equivalent of Schur's lemma for irreducible corepresentations is that the set of commuting matrices is isomorphic to , or the quaternions . Using the intertwining number over the real numbers, this may be expressed as an intertwining number of 1, 2 or 4.
Relation to representations of the linear subgroup
Typically, irreducible corepresentations are related to the irreducible representations of the linear subgroup H. Let be an irreducible (ordinary) representation of he linear subgroup H. Form the sum over all the antilinear operators of the square of the character of each of these operators:
and set for an arbitrary element .
There are three cases, distinguished by the character test eq 7.3.51 of Cracknell and Bradley.
Type(a) If S = |H| (the intertwining number is one) then D is an irreducible corepresentation of the same dimension as with
Type(b) S = -|H| (the intertwining number is four) then D is an irreducible representation formed from two 'copies' of
Type(c) If S = 0 (the intertwining number is two), then D is an irreducible corepresentation formed from two inequivalent representations and where
Cracknell and Bradley show how to use these to construct corepresentations for the magnetic point groups, while Cracknell and Wong give more explicit tables for the double magnetic groups.
Character theory of corepresentations
Standard representation theory for finite groups has a square character table with row and column orthogonality properties. With a slightly different definition of conjugacy classes and use of the intertwining number, a square character table with similar orthogonality properties also exists for the corepresentations of finite magnetic groups.
Based on this character table, a character theory mirroring that of representation theory has been developed.
See also
References
Representation theory of groups
Quantum mechanics | Corepresentations of unitary and antiunitary groups | [
"Physics"
] | 979 | [
"Theoretical physics",
"Quantum mechanics"
] |
76,995,097 | https://en.wikipedia.org/wiki/4D%20N%20%3D%201%20supergravity | In supersymmetry, 4D supergravity is the theory of supergravity in four dimensions with a single supercharge. It contains exactly one supergravity multiplet, consisting of a graviton and a gravitino, but can also have an arbitrary number of chiral and vector supermultiplets, with supersymmetry imposing stringent constraints on how these can interact. The theory is primarily determined by three functions, those being the Kähler potential, the superpotential, and the gauge kinetic matrix. Many of its properties are strongly linked to the geometry associated to the scalar fields in the chiral multiplets. After the simplest form of this supergravity was first discovered, a theory involving only the supergravity multiplet, the following years saw an effort to incorporate different matter multiplets, with the general action being derived in 1982 by Eugène Cremmer, Sergio Ferrara, Luciano Girardello, and Antonie Van Proeyen.
This theory plays an important role in many Beyond the Standard Model scenarios. Notably, many four-dimensional models derived from string theory are of this type, with supersymmetry providing crucial control over the compactification procedure. The absence of low-energy supersymmetry in our universe requires that supersymmetry is broken at some scale. Supergravity provides new mechanisms for supersymmetry breaking that are absent in global supersymmetry, such as gravity mediation. Another useful feature is the presence of no-scale models, which have numerous applications in cosmology.
History
Supergravity was first discovered in 1976 in the form of pure 4D supergravity. This was a theory of only the graviton and its superpartner, the gravitino. The first extension to also couple matter fields to the theory was acquired by adding Maxwell and Yang–Mills fields. Adding chiral multiplets proved harder, but the first step was to successfully add a single massless chiral multiplet in 1977. This was then extended the next year to adding more chiral multiplets in the form of the non-linear sigma model. All these theories were constructed using the iterative Noether method, which does not lend itself towards deriving more general matter coupled actions due to being very tedious.
The development of tensor calculus techniques allowed for the construction of supergravity actions more efficiently. Using this formalism, the general four-dimensional matter-coupled supergravity action was constructed in 1982 by Eugène Cremmer, Sergio Ferrara, Luciano Girardello, and Antonie Van Proeyen. It was also derived by Jonathan Bagger shortly after using superspace techniques, with this work highlighting important geometric features of the theory. Around this time two other features of the models were identified. These are the Kähler–Hodge structure present in theory and the presence and importance of no-scale models.
Overview
The particle content of a general four-dimensional supergravity consists of a single supergravity multiplet and an arbitrary number of chiral multiplets and gauge multiplets. The supergravity multiplet contains the spin-2 graviton describing fluctuations in the spacetime metric , along with a spin-3/2 Majorana gravitino , where the spinor index is often left implicit. The chiral multiplets , indexed by lower-case Latin indices , each consist of a scalar and its Majorana superpartner . Similarly, the gauge multiplets consist of a Yang–Mills gauge field and its Majorana superpartner the gaugino , with these multiplets indexed by capital Latin letters .
One of the most important structures of the theory is the scalar manifold, which is the field space manifold whose coordinates are the scalars. Global supersymmetry implies that this manifold must be a special type of complex manifold known as a Kähler manifold. Local supersymmetry of supergravity further restricts its form to be that of a Kähler–Hodge manifold.
The theory is primarily described by three arbitrary functions of the scalar fields, the first being the Kähler potential which fixes the metric on the scalar manifold. The second is the superpotential, which is an arbitrary holomorphic function that fixes a number of aspects of the action such as the scalar field F-term potential along with the fermion mass terms and Yukawa couplings. Lastly, there is the gauge kinetic matrix whose components are holomorphic functions determining, among other aspects, the gauge kinetic term, the theta term, and the D-term potential.
Additionally, the supergravity may be gauged or ungauged. In ungauged supergravity, any gauge transformations present can only act on abelian gauge fields. Meanwhile, a gauged supergravity can be acquired from an ungauged one by gauging some of its global symmetries, which can cause the scalars or fermions to also transform under gauge transformations and result in non-abelian gauge fields. Besides local supersymmetry transformations, local Lorentz transformations, and gauge transformations, the action must also be invariant under Kähler transformations , where is an arbitrary holomorphic function of the scalar fields.
Construction
Historically, the first approach to constructing supergravity theories was the iterative Noether formalism which uses a globally supersymmetric theory as a starting point. Its Lagrangian is then coupled to pure supergravity through the term which couples the gravitino to the supercurrent of the original theory, with everything also Lorentz covariantized to make it valid in curved spacetime. This candidate theory is then varied with respect to local supersymmetry transformations yielding some nonvanishing part. The Lagrangian is then modified by adding to it new terms that cancel this variation, at the expense of introducing new nonvanishing variations. More terms are the introduced to cancel these, and the procedure is repeated until the Lagrangian is fully invariant.
Since the Noether formalism proved to be very tedious and inefficient, more efficient construction techniques were developed. The first formalism that successfully constructed the general matter-coupled 4D supergravity theory was the tensor calculus formalism. Another early approach was the superspace approach which generalizes the notion of superspace to a curved superspace whose tangent space at each point behaves like the traditional flat superspace from global supersymmetry. The general invariant action can then be constructed in terms of the superfields, which can then be expanded in terms of the component fields to give the component form of the supergravity action.
Another approach is the superconformal tensor calculus approach which uses conformal symmetry as a tool to construct supergravity actions that do not themselves have any conformal symmetry. This is done by first constructing a gauge theory using the superconformal algebra. This theory contains extra fields and symmetries, but they can be eliminated using constraints or through gauge fixing to yield Poincaré supergravity without conformal symmetry.
The superconformal and superspace ideas have also been combined into a number of different supergravity conformal superspace formulations. The direct generalization of the original on-shell superspace approach is the Grimm–Wess–Zumino formalism formulated in 1979. There is also the superspace formalism proposed by Paul Howe in 1981. Lastly, the conformal superspace approach formulated in 2010 has the convenient property that any other formulation of conformal supergravity is either equivalent to it or can otherwise be obtained from a partial gauge fixing.
Symmetries
Scalar manifold and Kähler transformations
Supergravity often uses Majorana spinor notation over that of Weyl spinors since four-component notation is easier to use in curved spacetime. Weyl spinors can be acquired as projections of a Majorana spinor , with the left and right handed Weyl spinors denoted by .
Complex scalars in the chiral multiplets act as coordinates on a complex manifold in the sense of the nonlinear sigma model, known as the scalar manifold. In supersymmetric theories these manifolds are imprinted with additional geometric constraints arising from the supersymmetry transformations. In supergravity this manifold may be compact or noncompact, while for supergravities it is necessarily noncompact.
Global supersymmetry already restricts the manifold to be a Kähler manifolds. These are a type of complex manifold, which roughly speaking are manifolds that look locally like and whose transition maps are holomorphic functions. Complex manifolds are also Hermitian manifolds if they admit a well-defined metric whose only nonvanishing components are the components, where the bar over the index denotes the conjugate coordinate . More generally, a bar over scalars denotes complex conjugation while for spinors it denotes an adjoint spinor. Kähler manifolds are Hermitian manifolds that admit a two-form called a Kähler form
that is closed . A property of these manifolds is that their metric can be written in terms of the derivatives of a scalar function , where the is known as the Kähler potential. Here denotes a derivative with respect to . This potential corresponding to a particular metric is not unique and can be changed by the addition of the real part of a holomorphic function in what are known as Kähler transformations
Since this does not change the scalar manifold, supersymmetric actions must be invariant under such transformations.
While in global supersymmetry, fields and the superpotential transform trivially under Kähler transformations, in supergravity they are charged under the Kähler transformations as
where is the Majorana spinor supersymmetry transformation parameter. These transformation rules impose further restrictions on the geometry of the scalar manifold. Since the superpotential transforms by a prefactor, this implies that the scalar manifold must globally admit a consistent line bundle. The fermions meanwhile transform by a complex phase, which implies that the scalar manifold must also admit an associated principal bundle. The nondynamical connection corresponding to this principal bundle is given by
with this satisfying , where is the Kähler form. Here are holomorphic functions associated to the gauge sector, described below. This condition means that the scalar manifold in four-dimensional supergravity must be of a type which can admit a connection whose field strength is equal to the Kähler form. Such manifolds are known as Kähler–Hodge manifolds. In terms of characteristic classes, this condition translates to the requirement that where is the first Chern class of the line bundle, while is the cohomology class of the Kähler form.
An implication of the presence of an associated principal bundle on the Kähler–Hodge manifold is that its field strength must be quantized on any topologically non-trivial two-sphere of the scalar manifold, analogous to the Dirac quantization condition for magnetic monopoles. This arises due to the cocycle condition, which is the consistency of the connection across different coordinate patches. This can have various implications for the resulting physics, such as on an scalar manifold, it results in the quantization of Newton's constant.
Global symmetries of ungauged supergravity
Global symmetries in ungauged supergravity fall roughly into three classes; they are subgroups of the scalar manifold isometry group, they are rotations among the gauge fields, or they are the R-symmetry group. The exact global symmetry group depends on the details of the theory, such as the particular superpotential and gauge kinetic function, which provide additional constraints on the symmetry group.
The global symmetry group of a supergravity with abelian vector multiplets and chiral multiplets must be a subgroup of . Here is the isometry group of the scalar manifold, is the set of symmetries acting only on the vector fields, and is the R-symmetry group, with this surviving as a global symmetry only in theories with a vanishing superpotential. When the gauge kinetic matrix is a function of scalars, then the isometry group decomposes into , where the first group acts only on the scalars leaving the vectors unchanged, while the second simultaneously transforms both the scalars and vectors. These simultaneous transformations are not conventional symmetries of the action, rather they are duality transformations that leave the equations of motion and Bianchi identity unchanged, similar to the Montonen–Olive duality.
Global symmetries acting on scalars can only be subgroups of the isometry group of the scalar manifold since the transformations must preserves the scalar metric. Infinitesimal isometry transformations are described by Killing vectors , which are vectors satisfying the Killing equation , where is the Lie derivative along the direction of the Killing vector. They act on the scalars as and are the generators for the isometry algebra, satisfying the structure equation
Since the scalar manifold is a complex manifold, Killing vectors corresponding to symmetries of this manifold must also preserve the complex structure , which implies that they must be holomorphic . Therefore, the gauge group must be a subgroup of the group formed by holomorphic Killing vectors, not merely a subgroup of the isometry group. For Kähler manifolds, this condition additionally implies that there exists a set of holomorphic functions known as Killing prepotentials which satisfy , where is the interior product. The Killing prepotentials can be explicitly written in terms of the Kähler potential
where the holomorphic functions are the Kähler transformations that undo the isometry transformation, defined by
The prepotential must also satisfy a consistency condition known as the equivariance condition
where are the structure constants of the gauge algebra.
An additional restriction on global symmetries of scalars is that the superpotential must be invariant up to the same Kähler transformation that leaves the Kähler potential invariant, which imposes the condition that the only admissible superpotentials are ones satisfying
Global symmetries involving scalars present in the gauge kinetic matrix still act on the scalar fields as isometry transformations, but now these transformations change the gauge kinetic matrix. To leave the theory invariant under a scalar isometry transformation requires a compensating transformation on the vectors. These vector transformations can be expressed as transformations on the electric field strength tensors and their dual magnetic counterpart defined from the equation of motion
Writing the field strengths and dual field strengths in a single vector allows the most general transformations to be written as where the generators of these transformation are given by
Demanding that the equations of motion and Bianchi identities are unchanged restricts the transformations to be a subgroup of the symplectic group . The exact generators depend on the particular gauge kinetic matrix, with them
fixing the coefficients determining . Transformations involving , are non-perturbative symmetries that do not leave the action invariant since they map the electric field strength into the magnetic field strength. Rather, these are duality transformations that are only symmetries at the level of the equations of motion, related to the electromagnetic duality. Meanwhile, transformations with are known as generalized Peccei–Quinn shifts and they only leave the action invariant up to total derivatives. Global symmetries involving only vectors are transformations that map the field strength tensor into itself and generally belong to .
Gauge symmetry
In an ungauged supergravity, gauge symmetry only consists of abelian transformations of the gauge fields , with no other fields being gauged.
Meanwhile, gauged supergravity gauges some of the global symmetries of the ungauged theory. Since the global symmetries are strongly limited by the details of the theory present, such as the scalar manifold, the scalar potential, and the gauge kinetic matrix, the available gauge groups are likewise limited.
Gauged supergravity is invariant under the gauge transformations with gauge parameter given by
Here are the generators of the gauged algebra while are defined as the compensating Kähler transformations needed to restore the Kähler potential to its original form after performing scalar field isometry transformations, with their imaginary components fixed by the equivariance condition. Whenever a subgroup is gauged, as occurs when R-symmetry is gauged, this does not fix , with these terms then referred to as Fayet–Iliopoulos terms.
Covariant derivatives
Supergravity has a number of distinct symmetries, all of which require their own covariant derivatives. The standard Lorentz covariant derivative on curved spacetime is denoted by , with this being trivial for scalar fields, while for fermionic fields it can be written using the spin connection as
Scalars transform nontrivially only under scalar coordinate transformations and gauge transformations, so their covariant derivative is given by
where are the holomorphic Killing vectors corresponding to the gauged isometry subgroup of the scalar manifold. A hat above a derivative indicates that it is covariant with respect to gauge transformations. Meanwhile, the superpotential only transforms nontrivially under Kähler transformations and so has a covariant derivative given by
where is a derivative with respect to .
The various covariant derivatives associated to the fermions depend upon which symmetries the fermions are charged under. The gravitino transforms under both Lorentz and Kähler transformation, while the gaugino additionally also transforms under gauge transformations. The chiralino transforms under all these as well as transforming as a vector under scalar field redefinitions. Therefore, their covariant derivatives are given by
Here is the Christoffel symbol of the scalar manifold, while are the structure constants of the Lie algebra associated to the gauge group. Lastly, is the connection on the scalar manifold, with its explicit form given in terms of the Kähler potential described previously.
R-symmetry
R-symmetry of superalgebras is a global symmetry acting only on fermions, transforming them by a phase
This is identical to the way that a constant Kähler transformation acts on fermions, differing from such transformations only in that it does not additionally transform the superpotential. Since Kähler transformations are necessarily symmetries of supergravity, R-symmetry is only a symmetry of supergravity when these two coincide, which only occurs for a vanishing superpotential.
Whenever R-symmetry is a global symmetry of the ungauged theory, it can be gauged to construct a gauged supergravity, which does not necessarily require gauging any chiral scalars. The simplest example of such a supergravity is Freedman's gauged supergravity which only has a single vector used to gauge R-symmetry and whose bosonic action is equivalent to an Einstein–Maxwell–de Sitter theory.
4D N = 1 supergravity Lagrangian
The Lagrangian for 4D supergravity with an arbitrary number of chiral and vector supermultiplets can be split up as
Besides being invariant under local supersymmetry transformations, this Lagrangian also is Lorentz invariant, gauge invariant, and Kähler transformation invariant, with covariant derivatives being covariant under these. The three main functions determining the structure of the Lagrangian are the superpotential, the Kähler potential, and the gauge kinetic matrix.
Kinetic and theta terms
The first term in the Lagrangian consists of all the kinetic terms of the fields
The first line is the kinetic action for the supergravity multiplet, made up of the Einstein–Hilbert action and the covariantized Rarita–Schwinger action; this line is the covariant generalization of the pure supergravity action. The formalism used for describing gravity is the vielbein formalism, where is the vielbein while is the spin-connection. Additionally, and is the four-dimensional Planck mass.
The second line consists of the kinetic terms for the chiral multiplets, with its overall form determined by the scalar manifold metric which itself is fully fixed by the Kähler potential . The third line has the kinetic terms for the gauge multiplets, with their behaviour fixed by the real part of the gauge kinetic matrix. The holomorphic gauge kinetic matrix must have a positive definite real part to have kinetic terms with the correct sign. The slash on the covariant derivatives corresponds to the Feynman slash notation , while are the field strengths of the gauge fields .
The gauge sector also introduces a theta-like term
with this being a total derivative whenever the imaginary part of the gauge kinetic matrix is a constant, in which case it does not contribute to the classical equations of motion.
Mass and interaction terms
The supergravity action has a set of mass-like bilinear terms for its fermions given by
The D-terms are defined as
where are the holomorphic Killing prepotentials and is the holomorphic superpotential. The first line in the Lagrangian is the mass-like term for the gravitino while the remaining two lines are the mass terms for the chiralini and gluini along with bilinear mixing terms for these. These terms determine the masses of the fermions since evaluating the Lagrangian in a vacuum state with constant scalar fields reduces the Lagrangian to a set of fermion bilinears with numerical prefactors. This can be written as a matrix, with the eigenvalues of this mass matrix being the masses of the fermions in the mass basis. The mass eigenstates are in general linear combinations of the chiralini and gaugini fermions.
The next term in the Lagrangian is the supergravity generalization of a similar term found in the corresponding globally supersymmetric action that describes mixing between the gauge boson, a chiralino, and the gaugino. In the supergravity Lagrangian it is given by
Supercurrent terms
The supercurrent terms describe the coupling of the gravitino to generalizations of the chiral and gauge supercurrents from global supersymmetry as
where
These are the supercurrents of the chiral sector and of the gauge sector modified appropriately to be covariant under the symmetries of the supergravity action. They provide additional bilinear terms between the gravitino and the other fermions that need to be accounted for when going into the mass basis.
The presence of terms coupling the gravitino to the supercurrents of the global theory is a generic feature of supergravity theories since the gravitino acts as the gauge field for local supersymmetry. This is analogous to the case of gauge theories more generally, where gauge fields couple to the current associated to the symmetry that has been gauged. For example, quantum electrodynamics consists of the Maxwell action and the Dirac action, together with a coupling between the photon and the current , with this usually being absorbed into the definition of the fermion covariant derivative.
Scalar potential
The potential term in the Lagrangian describes the scalar potential as
where the first term is known as the F-term, and is a generalization of the potential arising from the chiral multiplets in global supersymmetry, together with a new negative gravitational contribution proportional to . The second term is called the D-term and is also found in a similar form in global supersymmetry, with it arising from the gauge sector.
The Kähler potential and the superpotential are not independent in supergravity since Kähler transformations allow for the shifting of terms between them. The two functions can instead be packaged into an invariant function known as the Kähler invariant function
The Lagrangian can be written in terms of this function as
Four-fermion terms
Finally, there are the four-fermion interaction terms. These are given by
Here is the scalar manifold Riemann tensor, while is the supergravity four-gravitino interaction term
that arises in the second-order action of pure supergravity after the torsion tensor has been substituted into the first-order action.
Properties
Supersymmetry transformation rules
The supersymmetry transformation rules, up to three-fermion terms which are unimportant for most applications, are given by
where
are known as fermionic shifts. It is a general feature of supergravity theories that fermionic shifts fix the form of the potential. In this case they can be used to express the potential as
showing that the fermionic shifts from the matter fields gives a positive-definite contribution, while the gravitino gives a negative definite contribution.
Spontaneous symmetry breaking
A vacuum state used in many applications of supergravity is that of a maximally symmetric spacetime with no fermionic condensate. The case when fermionic condensates are present can be dealt with similarly by instead considering the effective field theory below the condensation scale where the condensate is now described by the presence of another scalar field. There are three types of maximally symmetric spacetimes, those being de Sitter, Minkowski, and anti-de Sitter spacetimes, with these distinguished by the sign of the cosmological constant, which in supergravity at the classical level is equivalent to the sign of the scalar potential.
Supersymmetry is preserved if all supersymmetric variations of fermionic fields vanish in the vacuum state. Since the maximally symmetric spacetime under consideration has a constant scalar field and a vanishing gauge field, the variation of the chiralini and gluini imply that . This is equivalently to the condition that . From the form of the scalar potential it follows that one can only have a supersymmetric vacuum if . Additionally, supersymmetric Minkowski spacetime occurs if and only if the superpotential also vanishes . However, having a Minkowski or an anti-de Sitter solution does not necessarily imply that the vacuum is supersymmetric. An important feature of supersymmetic solutions in anti-de Sitter spacetime is that they satisfy the Breitenlohner–Freedman bound and are therefore stable with respect to fluctuations of the scalar fields, a feature that is present in other supergravity theories as well.
Supergravity provides a useful mechanism for spontaneous symmetry breaking of supersymmetry known as gravity mediation. This setup has a hidden and an observable sector that have no renormalizable couplings between them, meaning that they fully decouple from each other in the global supersymmetry limit. In this scenario, supersymmetry breaking occurs in the hidden sector, with this transmitted to the observable sector only through nonrenormalizable terms, resulting in soft supersymmetry breaking in the visible sector, meaning that no quadratic divergences are introduced. One of the earliest and simplest models of gravity mediation is the Polonyi model. Other notable spontaneous symmetry breaking mechanism are anomaly mediation and gauge mediation, in which the tree-level soft terms generated from gravity mediation are themselves subdominant.
Super-Higgs mechanism
The supercurrent Lagrangian terms consists in part of bilinear fermion terms mixing the gravitino with the other fermions. These terms can be expressed as
where is the supergravity generalization of the global supersymmetry goldstino field
This field transforms under supersymmetry transformations as , where is the positive part of the scalar potential. When supersymmetry is spontaneously broken , then one can always choose a gauge where , in which case the terms mixing the gravitino with the other fermions drops out. The only remaining fermion bilinear term involving the gravitino is the quadratic gravitino term in . When the final spacetime is Minkowski spacetime, this bilinear term corresponds to a mass for the gravitino with a value of
An implication of this procedure when calculating the mass of the remaining fermions is that the gauge fixing transformation for the goldstino leads to additional shift contributions to the mass matrix for the chiral and gauge fermions, which have to be included.
Mass sum rules
The supertrace sum of the squares of the mass matrix eigenvalues gives valuable information about the mass spectra of particles in supergravity. The general formula is most compactly written in the superspace formalism, but in the special case of a vanishing cosmological constant, a trivial gauge kinetic matrix , and chiral multiplets, it is given by
which is the supergravity generalization of the corresponding result in global supersymmetry. One important implication is that generically scalars have masses of order of the gravitino mass while fermionic masses can remain small.
No-scale models
No-scale models are models with a vanishing F-term, achieved by picking a Kähler potential and superpotential such that
When D-terms for gauge multiplets are ignored, this gives rise to the vanishing of the classical potential, which is said to have flat directions for all values of the scalar field. Additionally, supersymmetry is formally broken, indicated by a non-vanishing but undetermined mass of the gravitino. When moving beyond the classical level, quantum corrections come in to break this degeneracy, fixing the mass of the gravitino. The tree-level flat directions are useful in pheonomenological applications of supergravity in cosmology where even after lifting the flat directions, the slope is usually relatively small, a feature useful for building inflationary potentials. No-scale models also commonly occur in string theory compactifications.
Quantum effects
Quantizing supergravity introduces additional subtleties. In particular, for supergravity to be consistent as a quantum theory, new constraints come in such as anomaly cancellation conditions and black hole charge quantization. Quantum effects can also play an important role in many scenarios where they can contribute dominant effects, such as when quantum contributions lift flat directions. The nonrenormalizability of four-dimensional supergravity also implies that it should be seen as an effective field theory of some UV theory.
Quantum gravity is expected to have no exact global symmetries, which forbids constant Fayet–Iliopoulos terms as these can only arise if there are exact unbroken global symmetries. This is seen in string theory compactifications, which can at most produce field dependent Fayet–Iliopoulos terms associated to Stueckelberg masses for gauged symmetries.
Related theories
A globally supersymmetric 4D theory can be acquired from its supergravity generalization through the decoupling of gravity by rescaling the gravitino and taking the Planck mass to infinity . The pure supergravity theory is meanwhile acquired by having no chiral or gauge multiplets. Additionally, a more general version of 4D supergravity exists that also includes Chern–Simon terms.
Unlike in global supersymmetry, where all extended supersymmetry models can be constructed as special cases of the theory, extended supergravity models are not merely special cases of the theory. For example, in supergravity the relevant scalar manifold must be a quaternionic Kähler manifold. But since these manifolds are not themselves Kähler manifolds, they cannot occur as special cases of the supergravity scalar manifold.
Four-dimensional supergravity plays a significant role in Beyond the Standard Model physics, being especially relevant in string theory, where it is the resulting effective theory in many compactifications. For example, since compactification on a 6-dimensional Calabi–Yau manifold breaks 3/4ths of the initial supersymmetry, compactification of heterotic strings on such manifolds gives an supergravity, while the compactification of type II string theories gives an supergravity. But if the type II theories are instead compactified on a Calabi–Yau orientifold, which breaks even more of the supersymmetry, the result is also an supergravity. Similarly, compactification of M-theory on a manifold also results in an supergravity. In all these theories, the particular properties of the resulting supergravity theory such as the Kähler potential and the superpotential are fixed by the geometry of the compact manifold.
Notes
References
Supersymmetric quantum field theory
Theories of gravity | 4D N = 1 supergravity | [
"Physics"
] | 6,713 | [
"Supersymmetric quantum field theory",
"Theoretical physics",
"Theories of gravity",
"Supersymmetry",
"Symmetry"
] |
76,995,631 | https://en.wikipedia.org/wiki/TensorFloat-32 | TensorFloat-32 or TF32 is a numeric floating point format designed for Tensor Core running on certain Nvidia GPUs.
Format
The binary format is:
1 sign bit
8 exponent bits
10 fraction bits (also called mantissa, or precision bits)
The total 19 bits fits within a double word (32 bits), and while it lacks precision compared with a normal 32 bit IEEE 754 floating point number, provides much faster computation, up to 8 times on a A100 (compared to a V100 using FP32).
See also
IEEE 754
References
External links
Computer arithmetic
IEEE standards
Floating point types
Binary arithmetic | TensorFloat-32 | [
"Mathematics",
"Technology"
] | 132 | [
"Computer standards",
"Computer arithmetic",
"Arithmetic",
"Binary arithmetic",
"IEEE standards"
] |
76,998,123 | https://en.wikipedia.org/wiki/Nion%20%28company%29 | Nion was a manufacturer of scanning transmission electron microscopes (STEMs) based in Kirkland, Washington State, USA.
History
Nion Co. was founded in 1997 in Washington State, USA, by Ondrej Krivanek and Niklas Dellby, with a mission to design and build advanced instruments for electron microscopy. Prior to founding Nion, Krivanek and Dellby built a working proof-of-principle aberration corrector for a STEM, in Cambridge UK. Following this success, Philip Batson of IBM TJ Watson Research Center asked them to build an aberration corrector for his STEM. Krivanek was a research professor at University of Washington at the time, and he and Dellby decided to start Nion Co. and build a redesigned corrector. The new corrector was delivered to IBM in June 2020, and demonstrated direct sub-Å resolution. Nion went on to supply the scientific community with correctors for 100 and 300 kV dedicated STEMs made by Vacuum Generators. Nion's 2004 Science article demonstrated 0.78 Å resolution and led to wide acceptance of aberration correction as the best way to achieve high spatial resolution in electron microscopy.
It soon became clear that a new, higher stability electron microscope was needed, built from the ground up so that resolutions of 0.5 Ångstroms and below could be reached. Nion developed such an instrument as its next project: a 100 kV aberration corrected, high-stability electron microscope called UltraSTEM, with resolution capability well below one Angstrom. The first deliveries of this instrument took place in 2008, to Cornell University and the SuperSTEM Daresbury Laboratory. A 200 kV version of this microscope was delivered to the Orsay STEM laboratory near Paris in 2010 and many other labs since. It is able to reach 0.5 Å resolution.
Nion went on to develop a monochromated STEM, with the first delivery to Arizona State University in 2013 and subsequent deliveries to Rutgers University, Daresbury SuperSTEM, and many other laboratories in the USA, Canada, Europe and China. In 2014, the ASU and Rutgers monochromatic STEMs showed that phonons could be detected with high spatial resolution in an electron microscope by ultra-high energy resolution electron energy loss spectroscopy (EELS). In 2018, Nion introduced a new EELS spectrometer, which improved the EELS resolution to 3 meV, and allowed the vibrations of single atoms to be studied.
Other innovations introduced by Nion and the ongoing operation under the Bruker umbrella include X-ray spectroscopy with single-atom sensitivity, imaging samples in a contamination-free ultra-high vacuum (UHV) environment, atomic resolution secondary electron imaging (SEI) of surfaces of samples held in UHV, and stable imaging at temperatures <10 K.
Awards
In 2020, co-founder of Nion, Ondrej Krivanek, shared the Kavli Prize for Nanoscience for work creating the first aberration-corrected scanning transmission electron microscope with resolution below one ångstrom (0.1 nanometers).
Acquisition
In January 2024, Nion was acquired by Bruker, which moved Bruker into the manufacture of electron microscopes.
References
Crystallography
Electron microscopy
Electron beam
Materials science | Nion (company) | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 671 | [
"Electron",
"Electron microscopy",
"Applied and interdisciplinary physics",
"Electron beam",
"Materials science",
"Crystallography",
"Condensed matter physics",
"nan",
"Microscopy"
] |
77,002,430 | https://en.wikipedia.org/wiki/Aza-Wittig%20reaction | The Aza-Wittig reaction or is a chemical reaction of a carbonyl group with an aza-ylide, also known as an iminophosphorane (). Aza-Wittig reactions are most commonly used to convert aldehydes and ketones to the corresponding imines. The conversion has also been practiced in an intramolecular sense, which is commonly used in the synthesis of N-heterocyclic compounds.
Reaction mechanism
The mechanism of the aza-Wittig reaction is analogous to that of the Wittig reaction, with the Wittig reagent replaced by an iminophosphorane.
In some cases, the iminophosphorane is not isolated but generated in situ. In this manifestation, the phosphine, carbonyl, and organic azide are combined
Scope and limitations
Besides preparing imines from aldehydes and ketones, the aza-Wittig-reaction can also convert carbon dioxide to isocyanates, carbon disulfide to organic thiocyanates, and isocyanates to carbodiimides.
There exists solid-supported modifications of the reaction.
Similar to the Wittig reaction, the reaction suffers from issues with triphenylphosphine oxide by-product removal. Such an issue is mitigated via catalytic aza-Wittig-reactions, some of which entail elements other than phosphorus, like arsenic and tellurium.
History
The reagent for the aza-Wittig reaction, iminophosphorane, was discovered in 1919 by Hermann Staudinger. The reaction itself was discovered thirty years later.
Examples
An example of the aza-Wittig-reaction being utilized in organic synthesis is the synthesis of (–)-benzomalvin A. Two intramolecular aza-Wittig-reactions were used to construct the seven-membered ring and the six-membered ring in the molecule's skeleton.
See also
Staudinger reaction
Schiff base
Wittig reaction
Imine
References
External links
Wittig reaction in Organic Syntheses, Coll. Vol. 10, p. 703 (2004); Vol. 75, p. 153 (1998). (Article)
Wittig reaction in Organic Syntheses, Coll. Vol. 5, p. 361 (1973); Vol. 45, p. 33 (1965). (Article)
Name reactions | Aza-Wittig reaction | [
"Chemistry"
] | 518 | [
"Name reactions"
] |
77,002,567 | https://en.wikipedia.org/wiki/Landau%E2%80%93de%20Gennes%20theory | In physics, Landau–de Gennes theory describes the NI transition, i.e., phase transition between nematic liquid crystals and isotropic liquids, which is based on the classical Landau's theory and was developed by Pierre-Gilles de Gennes in 1969. The phenomonological theory uses the tensor as an order parameter in expanding the free energy density.
Mathematical description
The NI transition is a first-order phase transition, albeit it is very weak. The order parameter is the tensor, which is symmetric, traceless, second-order tensor and vanishes in the isotropic liquid phase. We shall consider a uniaxial tensor, which is defined by
where is the scalar order parameter and is the director. The tensor is zero in the isotropic liquid phase since the scalar order parameter is zero, but becomes non-zero in the nematic phase.
Near the NI transition, the (Helmholtz or Gibbs) free energy density is expanded about as
or more compactly
Further, we can expand , and with being three positive constants. Now substituting the tensor results in
This is minimized when
The two required solutions of this equation are
The NI transition temperature is not simply equal to (which would be the case in second-order phase transition), but is given by
is the scalar order parameter at the transition.
References
Soft matter
Phase transitions
Liquid crystals | Landau–de Gennes theory | [
"Physics",
"Chemistry",
"Materials_science"
] | 284 | [
"Physical phenomena",
"Phase transitions",
"Soft matter",
"Phases of matter",
"Critical phenomena",
"Condensed matter physics",
"Statistical mechanics",
"Matter"
] |
77,005,027 | https://en.wikipedia.org/wiki/Bearing%20compass | A bearing compass, is a nautical instrument used to determine the bearing of observed objects. (Bearing: angle formed by the north and the visual to a certain object in the sea or ashore). Used in navigation to determine the angle between the direction of an object and the magnetic north or, indirectly relative to another reference point. Provides the absolute bearing, which is the clockwise angle between magnetic north or true north and the object. For example, an object to the east would have an absolute bearing of 90º, if it is relative to the magnetic north than it is called magnetic bearing. It is commonly used by geologists and surveyors to obtain precise bearings on the ground.
Sailors use successive demarcations of fixed reference points along with simple geometric techniques to determine their position, course and speed. In addition, making successive demarcations of other vessels, together with simple geometry techniques, can help the navigator to determine if there is a risk of collision and to decide what measures should be taken to avoid the danger.
Description
All hand compasses can be used to take bearings, but what distinguishes the bearing compass from the rest is the fact that it has some type of optics to allow viewing "at the same time" the compass marks and the observed target. The simplest and most common type of hand compass has a horizontal compass rose and an observation device: a pinnule, alidade or viewfinder that allows the user to observe the target and then by "changing view", read the angle formed by the target's direction and the one marked by the compass with respect to the magnetic north. More complex prismatic versions, such as SUUNTO compasses (see first photograph), use an optical system to display the bearing marks through an ocular while pointing to the target.
Monocular Bearing Compass
There are also some models of monoculars/binoculars, with electric lighting or without, which by means of an hybrid optical system (some of them electronic-digital) allow the bearing marks to be viewed at the same time as the object is observed through its optical system.
Types
Monocular with zoom: this type has variable magnification, allowing the observation of objects at a wide range of distances, with the possibility to zoom in, adjusting the magnification to particular needs..
Monocular with rangefinder: this type also includes a reticle to estimate distances
Characteristics
Magnification: Compass monoculars are produced with different magnifications. For example, the model 8x25 monocular means that has a magnification x8, making the image twice bigger than a model 4x25 monocular
Diameter of the outer lens: The diameter of the front lens influences the amount of light that enters into the lens. For example, an 8x42 monocular with a 42mm front lens diameter, it's almost twice more luminous than a 8x25 with a 25mm front lens diameter
See also
Compass
Adrianov compass
Astrocompass
Geological compass
Grid compass
Hand compass
History of the compass
Marine sandglass
Prismatic compass
Qibla compass
References
Bibliography
Avery, T.E., Burkhart, H.E., Forest Measurements, 5th ed. New York:McGraw-Hill (2002)
Johnson, Mark, The Ultimate Desert Handbook: A Manual for Desert Hikers, Campers, and Travelers, McGraw-Hill Professional (2003), , 9780071393034
Mooers Jr., Robert L. Finding Your Way In The Outdoors, Outdoor Life Press (1972),
Rutstrum, The Wilderness Route Finder, University of Minnesota Press (2000),
External links
historytoday.com
Forest modelling
Navigational equipment
Hiking equipment
Orientation (geometry)
Measuring instruments
Orienteering | Bearing compass | [
"Physics",
"Mathematics",
"Technology",
"Engineering"
] | 754 | [
"Measuring instruments",
"Topology",
"Space",
"Geometry",
"Spacetime",
"Orientation (geometry)"
] |
77,007,034 | https://en.wikipedia.org/wiki/International%20Journal%20of%20RF%20and%20Microwave%20Computer-Aided%20Engineering | International Journal of RF and Microwave Computer-Aided Engineering is a peer-reviewed scientific journal, covering computer-aided design methodologies for radio-frequency and microwave engineering. Established in 1991 and originally published by Wiley, it was transferred to its subsidiary Hindawi in 2023, adopting an open access model. The journal was previously known as International Journal of Microwave and Millimeter-Wave Computer-Aided Engineering until 1998.
Abstracting and indexing
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2022 impact factor of 1.7.
References
External links
Electromagnetism journals
Wiley (publisher) academic journals
Hindawi Publishing Corporation academic journals
Academic journals established in 1991
Electrical and electronic engineering journals
Computational modeling journals | International Journal of RF and Microwave Computer-Aided Engineering | [
"Engineering"
] | 153 | [
"Electrical engineering",
"Electronic engineering",
"Electrical and electronic engineering journals"
] |
77,008,021 | https://en.wikipedia.org/wiki/Karen%20Livesey | Karen L. Livesey is an Australian physicist, who is an associate professor at the University of Newcastle. She was named a "Superstar of STEM" by Science Technology Australia, in the 2023–2024 cohort.
Education
Livesey was the first in her family to complete high school and went on to study physics at the University of Western Australia, where she was awarded a Bachelor of Science in 2004, and earned her PhD in 2010.
Career
Livesey worked at the University of Colorado at Colorado Springs from 2012 to 2020, achieving the rank of associate professor. In 2020, during the COVID-19 pandemic, Livesey moved with her family to Newcastle, NSW, Australia. She is now an associate professor of physics at the University of Newcastle and also is an Associate Investigator at the ARC Centre of Excellence in Future Low Energy Electronic Technologies.
Publications
Livesey has over 970 citations, and an H index of 16, as at May 2024, according to Google Scholar. Select publications include:
KL Livesey, S Ruta, NR Anderson, D Baldomir, RW Chantrell, D Serantes, (2018) Beyond the blocking model to fit nanoparticle ZFC/FC magnetisation curves. Scientific Reports 8 (1), 11166.
KL Livesey, RL Stamps (2010) High-frequency susceptibility of a weak ferromagnet with magnetostrictive magnetoelectric coupling: Using heterostructures to tailor electromagnon frequencies. Physical Review B 81 (9), 094405.
Media
She published a physics paper, to the Journal of Magnetism and Magnetic Materials, where all four authors were women.
Awards
2023 – Australian Awards for University Teaching Citation for Outstanding Contributions to Student Learning, "For development of engaging, contemporary physics curricula and resources that excite students about their studies and prepare them with skills for modern careers", Universities Australia.
2023 – Community Engagement Excellence Award, College of Engineering Science and Environment, the University of Newcastle.
2023 – Superstar of STEM, Science and Technology Australia.
2023 – Women in Physics Lecturer, Australian Institute of Physics.
2019 – Emmy Noether Visiting Fellow, Perimeter Institute for Theoretical Physics.
2016 – Europhysics Letters Distinguished Referee, European Physical Society.
References
External links
UWA - Magnetoelectric coupling
Womens Agenda - Superstars of STEM
Living people
Theoretical physicists
University of Western Australia alumni
Australian women scientists
Australian women physicists
Year of birth missing (living people) | Karen Livesey | [
"Physics"
] | 513 | [
"Theoretical physics",
"Theoretical physicists"
] |
66,682,314 | https://en.wikipedia.org/wiki/Cadogan%E2%80%93Sundberg%20indole%20synthesis | The Cadogan–Sundberg indole synthesis, or simply Cadogan indole synthesis, is a name reaction in organic chemistry that allows for the generation of indoles from o-nitrostyrenes with the use of trialkyl phosphites, such as triethyl phosphite.
Mechanism
o-nitrostyrene first reacts with triethyl phosphite, and the nitro group is converted to a nitroso group. The nitroso group then reacts with the alkene, and N-hydroxylindole is formed, which reacts again with triethyl phosphite to form the indole.
Application
The Cadogan–Sundberg indole synthesis has been used as an intermediate step in the total synthesis of Tjipanazole E, transforming 2-[trans-2-[5-Chloro-2-nitrophenyl)vinyl]-5-chloro-1H-indole to 5,5’-Dichloro-2,2’-biindole.
References
Indole forming reactions
Carbon-heteroatom bond forming reactions
Name reactions | Cadogan–Sundberg indole synthesis | [
"Chemistry"
] | 240 | [
"Name reactions",
"Carbon-heteroatom bond forming reactions",
"Ring forming reactions",
"Organic reactions"
] |
65,416,418 | https://en.wikipedia.org/wiki/Chance-constrained%20portfolio%20selection | Chance-constrained portfolio selection is an approach to portfolio selection under loss aversion.
The formulation assumes that (i) investor's preferences are representable by the expected utility of final wealth, and that (ii) they require that the probability of their final wealth falling below a survival or safety level must to be acceptably low.
The chance-constrained portfolio problem is then to find:
Max wjE(Xj), subject to Pr( wjXj < s) ≤ , wj = 1, wj ≥ 0 for all j,
where s is the survival level and is the admissible probability of ruin; w is the weight and x is the value of the jth asset to be included in the portfolio.
The original implementation is based on the seminal work of Abraham Charnes and William W. Cooper on chance constrained programming in 1959,
and was first applied to finance by Bertil Naslund and Andrew B. Whinston in 1962
and in 1969 by N. H. Agnew, et al.
For fixed the chance-constrained portfolio problem represents lexicographic preferences and is an implementation of capital asset pricing under loss aversion.
In general though, it is observed that no utility function can represent the preference ordering of chance-constrained programming because a fixed does not admit compensation for a small increase in by any increase in expected wealth.
For a comparison to mean-variance and safety-first portfolio problems, see; for a survey of solution methods here, see; for a discussion of the risk aversion properties of chance-constrained portfolio selection, see.
See also
Capital asset pricing model
Expected utility theory
Kelly criterion
Lexicographic preferences
Loss aversion
Portfolio optimization
Post modern portfolio theory
Roy's safety-first criterion
Stochastic programming
References
Portfolio theories
Stochastic optimization
Financial economics
Actuarial science | Chance-constrained portfolio selection | [
"Mathematics"
] | 371 | [
"Applied mathematics",
"Actuarial science"
] |
65,426,689 | https://en.wikipedia.org/wiki/NPZ%20model | An NPZ model is the most basic abstract representation, expressed as a mathematical model, of a pelagic ecosystem which examines the interrelationships between quantities of nutrients, phytoplankton and zooplankton as time-varying states which depend only on the relative concentrations of the various states at the given time.
One goal in pelagic ecology is to understand the interactions among available nutrients (i.e. the essential resource base), phytoplankton and zooplankton. The most basic models to shed light on this goal are called nutrient-phytoplankton-zooplankton (NPZ) models. These models are a subset of Ecosystem models.
Example
An unrealistic but instructive example of an NPZ model is provided in Franks et al. (1986) (FWF-NPZ model). It is a system of ordinary differential equations that examines the time evolution of dissolved and assimilated nutrients in an ideal upper water column consisting of three state variables corresponding to amounts of nutrients (N), phytoplankton (P) and zooplankton (Z). This closed system model is shown in the figure to the right which also shows the "flow" directions of each state quantity.
These interactions, assumed to be spatial homogeneous (and thus is termed a "zero-dimensional" model) are described in general terms as follows
This NPZ model can now be cast as a system of first order differential equations:
where the parameters and variables are defined in the table below along with nominal values for a "standard environment"
An example of a 60 day sequence for the values shown is depicted in the figure to the right. Each state is color coded (Nutrient – black, Phytoplankton – green and Zooplankton – blue). Note that the initial nutrient concentration is rapidly consumed resulting in a phytoplankton bloom until the zooplankton begin aggressive grazing around day 10. Eventually both populations drop to a very low level and a high nutrient concentration remains. In the next section more sophistication is applied to the model in order to increase realism.
More Sophisticated NPZ Models
The Franks et al. (1986) work has inspired significant analysis from other researchers but is overly simplistic to capture the complexity of actual pelagic communities. A more realistic NPZ model would simulate control of primary production by incorporating mechanisms to simulate seasonally varying sunlight and decreasing illumination with depth. Evans and Parslow (1985) developed an NPZ model which includes these mechanisms and forms the basis of the following example (see also Denman and Pena (1999)).
A 200 day sequence resulting from this configuration of the FWF-NPZ model is shown in the figure to the right. Each state is color coded (Nutrient – black, Phytoplankton – green and Zooplankton – blue). Several interesting features in the model output are easily observed. First, a spring bloom occurs in the first 20 days or so, where the high nutrient concentrations are consumed by the phytoplankton causing an inverse relationship which is halted by a rise in zooplankton concentration eventually settling into a sustained steady-state solution for the remainder of the summer. Another bloom, not as pronounced as in the spring, occurs in the fall with a remixing of nutrients into the water column.
References
Ecosystems
Oceanography
Marine biology
Planktology
Zoology | NPZ model | [
"Physics",
"Biology",
"Environmental_science"
] | 715 | [
"Hydrology",
"Symbiosis",
"Applied and interdisciplinary physics",
"Oceanography",
"Marine biology",
"Zoology",
"Ecosystems"
] |
65,426,864 | https://en.wikipedia.org/wiki/X-ray%20birefringence%20imaging | X‑ray birefringence imaging (XBI) can be considered the X‑ray analogue of the polarizing optical microscope. XBI uses linearly polarized X-rays with an energy tuned to an elemental absorption edge. The tuned X-rays interact solely with the absorbing element, thus allowing the local anisotropy of the bonding environment of the X‑ray absorbing element to be studied. Due to the requirement of linearly polarized tunable X-rays a synchrotron source is necessary. Interaction with the bonding environment of the selected element in the sample changes the incident X-ray polarization plane. A polarization analyzer is used to diffract the rotated component of the polarization plane to an area detector. The greater the vertical component of the polarization plane the greater the intensity observed on the detector. In this way, it is possible to study the distribution of bond environments containing the X-ray absorbing element in a spatially resolved manner.
The XBI technique has been shown to be a sensitive method for spatially resolved mapping of the local orientational properties of anisotropic materials. In the case of organic materials, the technique may be applied to study the orientational properties of individual molecules and/or bonds (most applications of the technique so far have focused on studies of orientational ordering of C–Br bonds, from XBI measurements carried out using incident linearly polarized X-rays tuned to the bromine K-edge). Applications of the technique have included the study of changes in molecular orientations associated with order-disorder phase transitions in solids and characterization of phase transitions in liquid crystalline materials. XBI can also be exploited for spatially resolved analysis of orientationally distinct domains in materials, giving information the sizes of domains, the orientational relationships between domains, and the nature of domain boundaries.
References
X-ray crystallography
Laboratory techniques
Microscopy | X-ray birefringence imaging | [
"Chemistry",
"Materials_science"
] | 387 | [
"X-ray crystallography",
"Crystallography",
"nan",
"Microscopy"
] |
71,037,565 | https://en.wikipedia.org/wiki/Oligoclonal%20antibody | Oligoclonal antibodies are an emerging immunological treatment relying on the combinatory use of several monoclonal antibodies (mAb) in one single drug. The composition can be made of mAb targeting different epitopes of a same protein (homo-combination) or mAb targeting different proteins (hetero-combination). It mimicks the natural polyclonal humoral immunological response to get better efficiency of the treatment. This strategy is most efficient in infections and in cancer treatment as it allow to overcome acquired resistance by pathogens and the plasticity of cancers.
History
Oligoclonal antibody treatment is a part of the serotherapy strategy (or antiserum).
19th century: Serotherapy was initiated thanks to Shibasaburo Kitasato and Emil von Behring in Germany, and Emile Roux in France. It is the administration of animal or human serum that was previously exposed to a pathogen and thus contains antibodies against it and will help the patient to fight infection.
1975 and 1986: First mAb was produced by hybridomas technique and then fully licensed. It was great progress since it allows targeting of specific epitope that can be shared among several diseases.
1982: Combination of two antibodies to enhance the immune response against viruses.
2000's: Several research teams came up with the idea of combining antibodies against different epitopes of the same receptor in cancer treatment. Particularly in anti-EGFR, anti-HER2 or anti-cMET combinations.
2010: Combination of two antibodies against immune control checkpoint to enhance cytotoxic T lymphocytes response and inhibit regulatory T lymphocytes suppressive effect on the immune response.
2012: First oligoclonal antibody combination was approved for use. It is composed of trastuzumab and pertuzumab both targeting HER-2 in breast cancer.
Numerous studies on animal models or in clinical trials are currently ongoing for treatment of infections and cancers.
Infectious diseases treatment
In infection oligoclonal treatment may be used to directly target the pathogen (e.g. surface marker on viruses or bacterias) or to neutralize toxins (e.g. botulinum neurotoxins, Clostridioides difficile toxins).
Many pathogens show increasing resistance to currently available drugs, especially antibiotics. This is particularly true for bacteria, but they harbor many membrane surface markers that can be targeted by antibodies. Oligoclonal treatment is recognized to have the potential to address this issue by aiming for multiple surface proteins and still can bind to proteins after mutation even if the affinity is lowered. However, most of these treatments are still in the stage of clinical trials.
Oncologic treatment
In cancer treatment, several targets and strategies can be used:
Targeting cancer cell markers (e.g. mutated EGFR, HER2): it raises antibody-dependent cell-mediated cytotoxicity (ADCC) response against tumor cells.
Targeting secreted signaling proteins of tumoral environment (e.g. VEGF neutralization) : limiting tumor environment, for example blocking angiogenesis.
Targeting immune cells regulation checkpoints : inhibition of T regulatory cells downregulatory effects (e.g. using antagonist against CTLA-4) , activation of cytotoxic T cells (e.g. using antagonist against PD-1). The goal is to activate the immune cells by lifting self-tolerance checkpoints that are restraining T cells to attack tumor cells.
Today, more than 300 antibody combinations are undergoing phase II or phase III clinical trials for various targets and cancer types (both solid and liquid). Most of them are targeting immune checkpoints (CTLA-4, PD1/PD-L1, ...). The only oligoclonal antibody treatment against immune checkpoint currently approved is the cocktail of nivolumab (anti-PD1 antibody) and ipilimumab (anti-CTLA-4 antibody). It is used to treat melanomas, low-risk renal cancer and colorectal cancer. This combination is also on phase III clinical trial to be used to treat non-small lung cancer, it shows good efficacy.
Treatments on non-small lung cancer have shown higher efficiency on patient with tumors of heavy mutational background. This underlines the potential of oligoclonal treatments to tackle cancer plasticity.
See also
Monoclonal antibody
Polyclonal antibodies
Immunotherapy
References
Immunology
.
Therapeutic antibodies | Oligoclonal antibody | [
"Biology"
] | 923 | [
"Immunology"
] |
71,038,216 | https://en.wikipedia.org/wiki/Puncture%20%28topology%29 | In topology, puncturing a manifold is removing a finite set of points from that manifold. The set of points can be small as a single point. In this case, the manifold is known as once-punctured. With the removal of a second point, it becomes twice-punctured, and so on.
Examples of punctured manifolds include the open disk (which is a sphere with a single puncture), the cylinder (which is a sphere with two punctures), and the Möbius strip (which is a projective plane with a single puncture).
References
Bibliography
Topology | Puncture (topology) | [
"Physics",
"Mathematics"
] | 125 | [
"Topology stubs",
"Topology",
"Space",
"Geometry",
"Spacetime"
] |
63,883,551 | https://en.wikipedia.org/wiki/Xenopus%20egg%20extract | Xenopus egg extract is a lysate that is prepared by crushing the eggs of the African clawed frog Xenopus laevis. It offers a powerful cell-free (or in vitro) system for studying various cell biological processes, including cell cycle progression, nuclear transport, DNA replication and chromosome segregation. It is also called Xenopus egg cell-free system or Xenopus egg cell-free extract.
History
The first frog egg extract was reported in 1983 by Lohka and Masui. This pioneering work used eggs of the Northern leopard frog Rana pipiens to prepare an extract. Later, the same procedure was applied to eggs of Xenopus laevis, becoming popular for studying cell cycle progression and cell cycle-dependent cellular events. Extracts derived from eggs of the Japanese common toad Bufo japonicus or of the Western clawed frog Xenopus tropicalis have also been reported.
Basics of extract preparation
The cell cycle of unfertilized eggs of X. laevis is arrested highly synchronously at metaphase of meiosis II. Upon fertilization, the metaphase arrest is released by the action of Ca2+ ions released from the endoplasmic reticulum, thereby initiating early embryonic cell cycles that alternates S phase (DNA replication) and M phase (mitosis).
M phase extract
Unfertilized eggs in a buffer containing the Ca2+ chelator EGTA (ethylene glycol tetraacetic acid) are packed into a centrifuge tube. After removing excess buffer, the eggs are crushed by centrifugation (~10,000 g). A soluble fraction that appears between the lipid cap and the yolk is called an M phase extract. This extract contains a high level of cyclin B-Cdk1. When demembranated sperm nuclei are incubated with this extract, it undergoes a series of structural changes and is eventually converted into a set of M phase chromosomes with bipolar spindles.
Interphase (S phase) extract
Different types of egg extracts
Cycling extract
High-speed supernatant (HSS)
Nucleoplasmic extract (NPE)
Discoveries made using egg extracts
Purification of M-phase promoting factor (MPF)
Elucidation of the role of synthesis and degradation of cyclin B in cell cycle progression
Discovery that degradation of a protein(s) other than cyclin B is necessary for initiating chromosome segregation
Discovery of a mechanism of spindle assembly that depends on chromatin, but not centrosomes
Proposal of a DNA replication licensing system and identification of its responsible factor
Identification of importin α/β responsible for nuclear transport
Discovery of the condensin complex essential for mitotic chromosome assembly
Identification of the cohesin complex essential for sister chromatid cohesion
More recently, the egg extracts have been used to study reprogramming of differentiated nuclei, physical properties of spindles and nuclei, and theoretical understanding of cell cycle control.
See also
Yoshio Masui
cell cycle
Cdk1
cyclin
DNA replication
nuclear transport
spindle apparatus
condensin
cohesin
References
Cell cycle
Mitosis
DNA replication | Xenopus egg extract | [
"Biology"
] | 652 | [
"Genetics techniques",
"DNA replication",
"Molecular genetics",
"Cellular processes",
"Cell cycle",
"Mitosis"
] |
63,886,215 | https://en.wikipedia.org/wiki/Polymer-protein%20hybrid | Polymer-protein hybrids are a class of nanostructure composed of protein-polymer conjugates (i.e. complexes composed of one protein attached to one or more polymer chains). The protein component generally gives the advantages of biocompatibility and biodegradability, as many proteins are produced naturally by the body and are therefore well tolerated and metabolized. Although proteins are used as targeted therapy drugs, the main limitations—the lack of stability and insufficient circulation times still remain. Therefore, protein-polymer conjugates have been investigated to further enhance pharmacologic behavior and stability. By adjusting the chemical structure of the protein-polymer conjugates, polymer-protein particles with unique structures and functions, such as stimulus responsiveness, enrichment in specific tissue types, and enzyme activity, can be synthesized. Polymer-protein particles have been the focus of much research recently because they possess potential uses including bioseparations, imaging, biosensing, gene and drug delivery.
Types
Single chain protein-polymer hybrids
Attaching a single polymer chain to a specific site away from the active center of the protein has less impact on protein activity compared with random attachments. In practice, attaching a single polymer chain can be used to adjust chemical properties of the therapeutic protein. For example, conjugation of a single chain of the hydrophilic polyethylene glycol (PEG) can increase the hydrodynamic radius of the protein conjugate by 5-10 fold. Attachment to PEG was mainly achieved by covalent conjugation via the grafting to strategy, targeting chemo-selective anchor groups. Other polymers, such as oligosaccharides and polypeptides, offer different properties to the enzymes attached to them.
Stimuli responsive hybrids
Heat
Researchers conjugated the thermo-responsive polymer poly(N-isopropylacrylamide) (pNIPAm) with the biotin-recognizing protein streptavidin close to its recognition site. At temperatures above the lower critical solution temperature (LCST), the polymer collapses and blocks the binding site, thus reversibly preventing biotin from binding to streptavidin. By copolymerization with two different thermosensitive polymers poly(sulfobetaine methacrylamide) (pSBAm) and pNIPAm together, researchers can control enzyme activity in a small temperature window.
Light
((N,N'-dimethylacrylamide)-co-4-phenylazophenyl acrylate) at the active site of endoglycanase creates a photoswitchable protein hybrid. The resulting hybrid catalyzes the hydrolysis of glycoside when irradiated by 350 nm UV light, but turns inactive under 420 nm visible light depending on the conformation of the conjugated polymer.
Polymer shell protein core
A polymer shell is formed by conjugation of multiple molecules of polymers onto the protein core. The polymer shell can either protect the protein core from unwanted degradation or create desired interactive sites for guest molecules. The first generation of polymer shell protein core structures mainly used of Polyethylene glycol (PEG) chains to increase the hydrodynamic radius and reduce immune response to proteins. However, the PEG shell can reduce protein activity in the inner core. More advanced designs use biodegradable linkers to achieve programmed release of the protein core in specific tissues. Several therapeutic designs with biodegradable PEG shells are already being developed in vivo.
Direct conjugation of polymers ("grafting to" strategy) can efficiently construct a polymer shell with diverse polymer types, however, it has low polymer density, especially with large polymers. In contrast, "grafting from" strategy allows the formation of a dense and uniform polymer shell. The protein core can also function as a carrier for other therapeutic molecules, such as plasmid DNA.
Dendrite polymer shells have a high volume to molecular weight ratio compared with traditional polymer shells. Using branched carbohydrates can give unique biological properties while maintaining molecular definition.
Non-covalent conjugation
Although covalent conjugation has been the dominant strategy for constructing polymer-protein hybrids, noncovalent chemistry can add another level of complexity and provides the opportunity to create higher-ordered structures. Specifically, self-assembly by non-covalent interactions is progressing rapidly. Supramolecular self-assembly can create nanoparticles, vesicles/micelles, protein cages, etc. Metal-binding interactions, host-guest, and boronic acid-based chemistries are widely studied as non-covalent conjugation methods to create polymer-protein hybrids.
Polymer-Streptavidin system
Streptavidin is a protein purified from the bacterium Streptomyces avidinii, which has a high affinity for biotin. By covalently linking streptavidin and polymers, well defined supramolecular constructs can be created due to the high specificity of
Streptavidin for both biotin and its analogues.
Building upon the covalent core shell strategy, several polymer–streptavidin systems have been developed for affinity separation, bio-sensors and diagnostic applications due to the robust binding conditions and stability of the protein.
Streptavidin can be used as a macro-initiator for in situ ATRP, through grafting from strategy, a stoichiometrically well defined polymer-protein conjugate can be synthesized. Polymer streptavidin systems can also be empowered to cross the cellular membrane by conjugating with cell penetrating molecules such as peptides and membrane disturbing polymers.
Polymer streptavidin systems can also be modulated to respond to certain environmental changes such as pH. By incorporating pH responsive poly(propylacrylic acid) (PPAAc) into the system, tumor cell suppressor p53 and cytochrome C can be delivered into cancer cells efficiently.
For biomolecules that are not hampered by the biotin-streptavidin interaction, iminobiotin, an analogue of biotin, has been applied as a pH-sensitive linker that allows the controlled and reversible assembly and intracellular release of cargo molecules in acidic intracellular compartments.
Protein-polymer hybrid supramolecular structures
Polymer-protein conjugates can also form a higher ordered supramolecular structure via self-assembly of amphiphilic polymers into micelles and microcapsules, which is one of the most promising strategies to generate drug delivery systems. Such systems have the innate advantage of rapid preparation, a high drug loading capacity, ease of surface decoration, and the potential to be stimuli responsive.
Micelles
Micelles refers to a type of supramolecular structure consisting of amphiphilic molecules self-assemblies, usually hollow centered. Researchers successfully conjugated a diblock copolymer site specifically onto GFP, the resulting amphiphilic polymer-protein conjugate is capable of reversible self-assembly into micelles.
In addition to retaining the native globular shape of proteins, the polypeptide backbone of denatured proteins can also be utilized to be conjugated with hydrophilic polymer chains to generate higher ordered structure through hydrophobic interactions. For example, nanoconjugates of poly-ethylene glycol(PEG) and denatured bovine serum albumin(BSA) will spontaneously self-assemble into a micellar structure, whose protein core can adsorb high numbers of hydrophobic drugs.
Nanoparticles
An efficient way to synthesize protein-polymer hybrid nanoparticles is to take advantage of photoinitiated reversible addition−fragmentation chain transfer (RAFT) polymerization-induced self-assembly(PISA) by using multi-RAFT modified bovine serum albumin (BSA) as a macromolecular chain transfer agent. RAFT mediated growth of the PHPMA chains will graft from the BSA-RAFT, and increase the hydrophobicity of the star BSA−PHPMA conjugates. At the critical aggregation concentration, they form nanoparticles due to the hydrophobic interactions. The resulting nanoparticles show excellent encapsulation capability for both hydrophobic and hydrophilic molecules, such as cancer drugs and DNA.
A rather easy method to prepare protein-polymer hybrid nanoparticles is nanoprecipitation. Spherical nanoparticles composed of BSA-PMMA with diameters of around 100 nm were obtained and the water insoluble chemotherapeutic drug camptothecin was encapsulated within the hydrophobic core consisting of PMMA. Such protein-polymer hybrid nanoparticles possess tunable sizes and surface charges, have attractive bio-compatibilities and allow efficient cell uptake. Camptothecin-encapsulated BSA-PMMA nanoparticles revealed enhanced anti-tumor activity both in vitro and in animals.
Beyond the nanoscale, protein-polymer conjugate could also be used as building blocks for constructing more complicated structures such as microcapsules through hydrophobic interactions. By performing pickering emulsion technique to process BSA–pNIPAm nanoconjugates into hollowed microcapsules consisting of a closely packed monolayer of conjugated protein–polymer building blocks (named proteinosomes). These proteinosomes exhibit protocellular properties such as guest molecule encapsulation, selective permeability, controllable mobilization, gene-directed protein synthesis and membrane-gated internalized enzyme catalysis.
Based on the above-mentioned method, a multi responsive microcapsule has been synthesized by incorporating photoswitchable spiropyran units and the thermoresponsive monomer N-isopropylacrylamide into the membrane. Stimuli responsive membrane exhibited advantages in the capture and release of different-molecular-weight products by opening and closing the photoresponsive spiropyran ligands, under body temperature, room temperature, UV, redox.
Another effective way to modulate the permeability of microcapsules was based on a self-sacrificing strategy. By selectively using lysozyme and BSA as building blocks as well as self-sacrificing components, the corresponding pores could be generated in the membrane, and then the permeability of the generated microcapsules could be increased from10 kDa to 22 kDa and then to 71 kDa. By loading FITC-Lys (14 kDa), RBITCdextran (70 kDa) and DNA (90 kDa) into the microcapsules, a programmed release of the encapsulants from low molecular weight to high molecular weight was realized.
Using similar strategy, pH-sensitive protein-polymer microcapsules were developed. Both doxycycline (DOX) and folic acid were incorporated onto the surface of protein covalently. The very low toxicity of polymer-protein nanoconjugates effectively avoided the high toxicity of DOX, which is expected to not only reduce toxic side effects, but also improve anticancer efficiency in vitro examinations.
Protein Nanocages
Protein nanocages are natural nanocarriers composed of protein subunits with a porous structure. They benefit from monodispersity, intrinsic high stability for protection of internalized drugs from enzymatic degradation and controllable assembly for cargo loading and release.
However, their application might be blocked by immunogenicity, broad biodistribution and significant function and property variations. The incorporation of polymer chains by performing in situ ATRP on the outer surface of or inside the protein nanocages can be an effective way to mitigate those drawbacks. For example, increased loading density of cargo molecules and enhanced stability of the cage assembly can be obtained via internal ATRP inside the cavity of the virus capsid.
Beyond virus type particles, large multimeric proteins such as the iron storage protein ferritin have emerged as attractive tools to be used as well-defined nano-containers. Using a grafting from strategy, polymers can be introduced to ferritin in a highly regular fashion for precise spatial control. These polymer–ferritin constructs exhibited protease resistance, enabling longer retention time within the bloodstream while reducing possible antibody interactions.
Properties
Polymer-Protein nanoparticles not only contain the traditional properties of nanoparticles, but also have their own unique properties based on the properties of specific proteins. Because they are proteinaceous, they have high biocompatibility, biodegradability and biofunctionality. Protein-polymer bioconjugates which is the building block of Polymer-Protein hybrids exhibit a unique array of properties such as: light-switching effects, acoustic signal capture, thermal energy transfer, and magnetic signal response.
Synthesis
Synthesis of Polymer-Protein hybrids
Generally, Polymer-Protein hybrids can be synthesized by interfacial self-assembly of protein–polymer conjugates in emulsions.
Grafting to
Grafting to approach which is the most common and straightforward methodology refers to directly attaching the synthetic polymers to the target protein. This technique can be engineered for site-specific or random conjugation and, when compared to other conjugation methods, provides simple and thorough characterization of polymer before conjugation. And when using this method, the protein remains unaffected by polymerization methods.
Grafting from
As shown in the figure, a protein is firstly conjugated with the initiator and the polymer chain then grows from the protein core in a controlled manner via living polymerization. Likewise, to the earlier discussed methods, grafting from approach can be designed for site-specific or random attachment.
Grafting through
Not like the grafting from and grafting to approach which can conjugate several polymers onto one protein core, the grafting through approach enables several proteins to connect to one polymer chain due to the multivalent nature of protein.
Application
Thermoresponsive protein–polymer particles
Thermoresponsive conjugates have been exploited for the subsequent separation of proteins from a complex mixture. This method has been utilized to purify polyclonal antibodies in serum samples. This method of purification is rapid, sensitive, inexpensive and could be used to purify various types of antibodies.
Thermoresponsive conjugates can also be exploited to mediate bioactivity. One of the utilities of the method is demonstrated temperature control of biotin binding and release. Biotin binding was observed below the LCST, while above the LCST the conjugates aggregated, and the biotin binding affinity was reduced by ~20%. By changing the temperature, the recovery of the biotinylated molecules can be achieved.
Protein–polymer particles designed for drug delivery
The absorption of proteins for particles in physiological fluids can greatly affect the subsequent medical performance of particles in vivo. Nonspecific protein adsorption can be controlled in vivo by modifying the nanoparticle surface with a non-toxic, biocompatible protein possessing tolerable antigenic properties such as albumin.
The high recognition ability of proteins can enable high delivery efficiency. Protein-polymer particles have potential to deliver drugs to specific regions of the body using the inherent biorecognition property at the protein interface. Additionally, in some cases the presentation of specific proteins on nanoparticle surfaces can be useful for aiding passage through impermeable biological barriers.
Particles designed for other biomedical and biotechnology applications
Nanoreactors
Enzyme-catalyzed reactions can be performed at higher temperatures using enzyme-immobilized nanoparticles, in which the presence of multiple proteins at the nanoparticle surface facilitates the retention of water molecules limiting the denaturation of the attached proteins. After modification with poly(amide), protein activity could remain unchanged over 500 min at 50 °C, while the half-life time of the native lipase at 50 °C is only 30 min in aqueous solution. Immobilized enzymes on nanoparticles can significantly improve the efficiency of enzyme reactions by increasing tolerance to a wider range of experimental conditions without significantly reducing biological activity. Besides, polymer-protein particles are reported to control the activity of proteins and compartmentalize different enzymes to perform multi-step reactions.
Protein purification and separation
By immobilizing proteins to polymer nanoparticles or polymer/inorganic hybrid nanoparticles (such as polymer-stabilized iron oxide nanoparticles), proteins or their affinity ligands can be separated from complex solutions by applying magnetic fields or centrifugation. Lipase attached to iron oxide nanoparticles maintained 85% biological activity after 30 reaction and separation cycles.
As the appropriate target is combined with magnetic nanoparticles, the selected target can be magnetically separated directly from natural biological fluids, which offers a fast, gentle, extensible, and easy to automate separation technique. The simplicity of magnetic separation has been applied in a number of disciplines, including mineral processing wastewater treatment, molecular biology, cell sorting, and clinical diagnostics.
Protocells
Microcapsules termed protocells prepared by polymer-protein hybrids are the hotspot of the research area recently, enabling various functions such as bioreactors, cascade system and multiresponsive membranes, etc.
References
Nanomaterials
Pharmacology | Polymer-protein hybrid | [
"Chemistry",
"Materials_science"
] | 3,603 | [
"Pharmacology",
"Nanotechnology",
"Medicinal chemistry",
"Nanomaterials"
] |
63,892,796 | https://en.wikipedia.org/wiki/Lutetium%20%28177Lu%29%20chloride | {{DISPLAYTITLE:Lutetium (177Lu) chloride}}
Lutetium (177Lu) chloride is a radioactive compound used for the radiolabeling of pharmaceutical molecules, aimed either as an anti-cancer therapy or for scintigraphy (medical imaging). It is an isotopomer of lutetium(III) chloride containing the radioactive isotope 177Lu, which undergoes beta decay with a half-life of 6.64 days.
Medical uses
Lutetium (177Lu) chloride is a radiopharmaceutical precursor and is not intended for direct use in patients. It is used for the radiolabeling of carrier molecules specifically developed for reaching certain target tissues or organs in the body. The molecules labeled in this way are used as cancer therapeutics or for scintigraphy, a form of medical imaging. 177Lu has been used with both small molecule therapeutic agents (such as 177Lu-DOTATATE) and antibodies for targeted cancer therapy
Contraindications
Medicines radiolabeled with lutetium (177Lu) chloride must not be used in women unless pregnancy has been ruled out.
Adverse effects
The most common side effects are anaemia (low red blood cell counts), thrombocytopenia (low blood platelet counts), leucopenia (low white blood cell counts), lymphopenia (low levels of lymphocytes, a particular type of white blood cell), nausea (feeling sick), vomiting and mild and temporary hair loss.
Society and culture
Legal status
Lutetium (177Lu) chloride (Lumark) was approved for use in the European Union in June 2015. Lutetium (177Lu) chloride (EndolucinBeta) was approved for use in the European Union in July 2016.
In July 2022, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Illuzyce, a radiopharmaceutical precursor. Illuzyce is not intended for direct use in patients and must be used only for the radiolabelling of carrier medicines that have been specifically developed and authorized for radiolabelling with lutetium (177Lu) chloride. The applicant for this medicinal product is Billev Pharma ApS. Illuzyce was approved for medical use in the European Union in September 2022.
In September 2024, the CHMP adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Theralugand, a radiopharmaceutical precursor. Theralugand is not intended for direct use in patients and must be used only for the radiolabelling of carrier medicines that have been specifically developed and authorized for radiolabelling with lutetium (177Lu) chloride. The applicant for this medicinal product is Eckert & Ziegler Radiopharma GmbH.
References
Radiopharmaceuticals
Lutetium compounds
Chlorides
Orphan drugs | Lutetium (177Lu) chloride | [
"Chemistry"
] | 619 | [
"Chlorides",
"Medicinal radiochemistry",
"Inorganic compounds",
"Salts",
"Radiopharmaceuticals",
"Chemicals in medicine"
] |
63,892,807 | https://en.wikipedia.org/wiki/Lutetium%20%28177Lu%29%20oxodotreotide | {{DISPLAYTITLE:Lutetium (177Lu) oxodotreotide}}
Lutetium (177Lu) oxodotreotide (INN) or 177Lu dotatate, brand name Lutathera, is a chelated complex of a radioisotope of the element lutetium with dotatate, used in peptide receptor radionuclide therapy. Specifically, it is used in the treatment of cancers which express somatostatin receptors. It is a radiolabeled somatostatin analog.
Alternatives to 177Lu-dotatate include yttrium-90 dotatate or DOTATOC. The longer range of the beta particles emitted by 90Y, which deliver the therapeutic effect, may make it more suitable for large tumors with 177Lu reserved for smaller volumes
The US Food and Drug Administration (FDA) considers 177Lu dotatate to be a first-in-class medication.
Medical uses
In the US, 177Lu dotatate is indicated for the treatment of somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors (GEP-NETs), including foregut, midgut, and hindgut neuroendocrine tumors in adults.
In the EU, lutetium (177Lu) oxodotreotide is indicated for the treatment of unresectable or metastatic, progressive, well differentiated (G1 and G2), somatostatin receptor positive gastroenteropancreatic neuroendocrine tumours (GEP-NETs) in adults.
Adverse effects
The therapeutic effect of 177Lu derives from the ionizing beta radiation it emits, however this can also be harmful to healthy tissue and organs. The kidneys are particularly at risk as they help to remove 177Lu dotatate from the body. To protect them, an amino acid solution (arginine/lysine) is administered by slow infusion, starting before the radioactive administration and normally continuing for several hours afterwards.
History
The European Commission approved lutetium (177Lu) oxodotreotide (brand name Lutathera) "for the treatment of unresectable or metastatic, progressive, well differentiated (G1 and G2), somatostatin receptor positive gastroenteropancreatic neuroendocrine tumours (GEP-NETs) in adults" in September 2017.
177Lu dotatate was approved in the United States for the treatment of SSTR positive gastroenteropancreatic neuroendocrine tumors (GEP-NETs), including foregut, midgut and hindgut neuroendocrine tumors in adults, in January 2018. This was the first time a radiopharmaceutical had been approved for the treatment of GEP-NETs in the United States.
The US Food and Drug Administration (FDA) approved 177Lu dotatate based primarily on evidence from one clinical trial, NETTER-1 of 229 participants with somatostatin-receptor positive midgut GEP-NETs. Enrolled participants had tumors which could not be surgically removed and were worsening while receiving treatment with octreotide.
Participants were randomly assigned to receive either 177Lu dotatate with long-acting octreotide or long-acting octreotide, at a higher dose, alone. 177Lu dotatate was injected through the vein and long-acting octreotide was injected in the muscle. Both, participants and health care providers knew which treatment was given. The benefit of 177Lu dotatate was evaluated by measuring the length of time that tumors did not grow after treatment and compared it to the control group (progression free survival).
The FDA considered additional data from a second study based on data from 1,214 participants with somatostatin receptor-positive tumors, including GEP-NETS, who received 177Lu dotatate at a single site in the Netherlands, Erasmus MC. All participants received 177Lu dotatate with octreotide. Participants and health care providers knew which treatment was given. The benefit of 177Lu dotatate was evaluated by measuring if and how much the tumor size changed during treatment (the overall response rate). Complete or partial tumor shrinkage was reported in 16 percent of a subset of 360 participants with GEP-NETs who were evaluated for response by the FDA. Participants initially enrolled in the study received 177Lu dotatate as part of an expanded access program.
The FDA granted the application for 177Lu dotatate priority review and orphan drug designations. The FDA granted the approval of Lutathera to Advanced Accelerator Applications.
In April 2024, the FDA approved 177Lu dotatate for the treatment of children aged 12 years and older with somatostatin receptor-positive (SSTR)-positive gastroenteropancreatic neuroendocrine tumors (GEP-NETs), including foregut, midgut, and hindgut neuroendocrine tumors. It was approved for adults in 2018. This is the first FDA approval of a radioactive drug, or radiopharmaceutical, for children aged twelve years of age and older with SSTR-positive gastroenteropancreatic neuroendocrine tumors.
Approval for children aged 12 years and older was based on pharmacokinetic, dosimetry, and safety data from NETTER-P (NCT04711135), an ongoing, international, multi-center, open-label, single-arm study of lutetium Lu 177 dotatate in adolescents with locally advanced/inoperable or metastatic SSTR-positive gastroenteropancreatic neuroendocrine tumors or pheochromocytoma/paraganglioma. Approval was also based on the extrapolation of efficacy outcomes observed in NETTER-1 (NCT01578239), a randomized, multicenter, open-label, active-controlled trial in 229 participants with locally advanced/inoperable or metastatic SSTR-positive midgut carcinoid tumors, which supported the original approval of lutetium Lu 177 dotatate in adults.
Safety was evaluated in nine pediatric participants in NETTER-P, including four participants with gastroenteropancreatic neuroendocrine tumors. The major outcome measures were absorbed radiation doses in target organs and incidence of adverse reactions after the first treatment cycle. Additional outcome measures included short-term adverse reactions following treatment with lutetium Lu 177 dotatate. The adverse reaction profile observed in NETTER-P was similar to that observed in adults.
References
Chelating agents
Lutetium complexes
Macrocycles
Orphan drugs
Radiopharmaceuticals | Lutetium (177Lu) oxodotreotide | [
"Chemistry"
] | 1,387 | [
"Medicinal radiochemistry",
"Organic compounds",
"Radiopharmaceuticals",
"Macrocycles",
"Chelating agents",
"Chemicals in medicine",
"Process chemicals"
] |
72,545,562 | https://en.wikipedia.org/wiki/Hafnium%28III%29%20iodide | Hafnium(III) iodide is an inorganic compound of hafnium and iodine with the formula Hf I3. It is a black solid.
Preparation
Like other group 4 trihalides, hafnium(III) iodide can be prepared from hafnium(IV) iodide by high-temperature reduction with hafnium metal, although incomplete reaction and contamination of the product with excess metal often occurs.
3 Hf I4 + Hf → 4 Hf I3
Other metals can be used as the reducing agent, for example aluminium. The product is often nonstoichiometric, with the compositions Hf I3.2–3.3 and Hf I3.0–3.5 reported.
Structure and bonding
Hafnium(III) iodide adopts the same crystal structure as zirconium(III) iodide. This is very similar to the β-TiCl3 structure. The structure is based on hexagonal close packing of iodide ions with one third of the octahedral interstices occupied by Hf3+ ions. It consists of parallel chains of face-sharing {HfI6} octahedra.
Hafnium(III) iodide has a lower magnetic moment than is expected for the d1 metal ion Hf3+, indicating non-negligible Hf–Hf bonding. The Hf–Hf separation was originally reported to be 3.295 Å, but a subsequent study of nonstoichiometric hafnium(III) iodide indicated a lower symmetry structure.
Reactivity
Like the chloride and bromide, hafnium(III) iodide is a powerful enough reducing agent to reduce water and therefore does not have any aqueous chemistry.
References
Hafnium compounds
Iodides
Metal halides | Hafnium(III) iodide | [
"Chemistry"
] | 383 | [
"Inorganic compounds",
"Metal halides",
"Salts"
] |
72,547,151 | https://en.wikipedia.org/wiki/Microsoft%20Autofill | Microsoft Autofill is a password manager developed by Microsoft. It supports multiple platforms such as Android, iOS, and Google Chrome or other Chromium-based web browsers. It is a part of Microsoft Authenticator app in Android and iOS, and a browser extension on Google Chrome. It stores users' passwords under the user's Microsoft Account. It can import passwords from Chrome and some popular password managers or from a CSV file. In Microsoft Authenticator app, it requires multi-factor authentication to sign in which provides an additional layer of security. The passwords are encrypted both on the device and the cloud.
Features
Multi-factor authentication (through Microsoft Authenticator mobile app)
Import from competitors
Export to CSV file
Save credit card information
Security
The Microsoft Authenticator app requires biometric or device passcode as extra security. The passwords on the device are encrypted, and encryption/decryption keys are not stored and are always generated when needed. Passwords are decrypted only when a user wants to see the password or the password is filled out automatically. Passwords are synced over an SSL-protected HTTPS connection.
Retirement
It will be replaced by Microsoft Wallet on 14 December 2024.
See also
Autofill
List of Microsoft software
References
External links
Chrome Web Store
Password managers
Cryptographic software
2021 software
Google Chrome extensions
Proprietary cross-platform software | Microsoft Autofill | [
"Mathematics"
] | 285 | [
"Cryptographic software",
"Mathematical software"
] |
72,551,201 | https://en.wikipedia.org/wiki/HD%20168592 | HD 168592, also designated as HR 6862 or rarely 7 G. Coronae Australis, is a solitary star located in the southern constellation Corona Australis. It is faintly visible to the naked eye as an orange-hued star with an apparent magnitude of 5.07. Gaia DR3 parallax measurements place it at a distance of 490 light years and is currently receding with a heliocentric radial velocity of . At its current distance, HD 168592's brightness is diminished by 0.38 magnitudes due to interstellar dust. It has an absolute magnitude of −0.76.
HD 168592 has a stellar classification of K4/5 III, indicating that it is an evolved K-type star with the characteristics of a K4 and K5 giant star. It has a comparable mass to the Sun but the star has expanded to 43.6 times the Sun's radius. It radiates 666 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of . HD 168592 is slightly metal deficient with an iron abundance 26% below solar levels. The star spins slowly, as is common for giant stars, with a projected rotational velocity of .
References
K-type giants
Corona Australis
Coronae Australis, 7
CD-38 12729
168592
090037
6862 | HD 168592 | [
"Astronomy"
] | 287 | [
"Corona Australis",
"Constellations"
] |
72,557,046 | https://en.wikipedia.org/wiki/1985%20Karlskoga%20gas%20leak | On 10 January 1985, a gas leak occurred at Björkborn, Karlskoga Municipality, Sweden, when a chemical plant spewed sulfuric acid gas over Karlskoga. The incident forced 300 people to evacuate and injured 20 people.
Accident
On Thursday, January 10, 1985, at 7:30 PM local time, a gas leak was detected at the Björkborn Industrial Zone. The site is situated just northeast of Björkborn Manor.
The gas container stopped leaking by 3 AM local time still the gas had reacted with the fog. Thus, resulting in an almost opaque-like fog covering the town of Karlskoga.
Response
Schools and workplaces were closed, requiring all 36,000 inhabitants to remain inside their homes. Traffic on the European Route E18 came to a halt, and daily activities were put on hold, all in response to the gas leak.
In addition, approximately 20 people sought treatment at an emergency clinic set up at a local school, treating chest pains and coughing.
See also
Bofors
References
External links
Gas leak report at the Swedish Civil Contingencies Agency
1985 in Sweden
History of Karlskoga
Chemical disasters
Man-made disasters in Sweden
Bofors | 1985 Karlskoga gas leak | [
"Chemistry"
] | 244 | [
"Chemical accident",
"Chemical disasters"
] |
75,374,898 | https://en.wikipedia.org/wiki/InsideWood | InsideWood is an online resource and database for wood anatomy, serving as a reference, research, and teaching tool. Wood anatomy is a sub-area within the discipline of wood science. This freely accessible database is purely scientific and noncommercial. It was created by NC State University Libraries in 2004, using funds from NC State University and the National Science Foundation, with the donation of wood anatomy materials by several international researchers and members of the IAWA, mostly botanists, biologists and wood scientists.
Contents
The database contains categorized anatomical descriptions of wood based on the IAWA List of Microscopic Features for Hardwood and Softwood Identification, complemented by a comprehensive set of photomicrographs. As of November 2023, the database contained thousands of wood anatomical descriptions and nearly 66,000 photomicrographs of contemporary woods, along with more than 1,600 descriptions and 2,000 images of fossil woods. Its coverage is worldwide.
Hosted by North Carolina State University Libraries, this digital collection encompasses CITES-listed timber species and other endangered woody plants. Its significance lies in aiding wood identification through a multi-entry key, enabling searches based on the presence or absence of IAWA features. Additionally, it functions as a virtual reference collection, allowing users to retrieve descriptions and images by searching scientific or common names, or other relevant keywords. The whole database contains materials from over 10,000 woody species and 200 plant families.
Initiator for this wood anatomy database has been the American botanist and wood scientist Elisabeth Wheeler.
The database contains two distinctive menus for specific anatomical features of modern wood species:
Softwoods
Hardwoods
Identifying wood holds significance across several domains and is of critical importance for commercial, forensic, archaeological, and paleontological applications. Also, timber identification provides new tools needed for the tracking of illegal logging and transportation. Wood identification is also important from an economic point of view.
References
External links
InsideWood
Inside Wood – A Web resource for hardwood anatomy by Elisabeth Wheeler
Facebook
Wood sciences
Biological databases | InsideWood | [
"Materials_science",
"Engineering",
"Biology"
] | 401 | [
"Wood sciences",
"Bioinformatics",
"Biological databases",
"Materials science"
] |
75,381,527 | https://en.wikipedia.org/wiki/Egan%20conjecture | In geometry, the Egan conjecture gives a sufficient and necessary condition for the radii of two spheres and the distance of their centers, so that a simplex exists, which is completely contained inside the larger sphere and completely encloses the smaller sphere. The conjecture generalizes an equality discovered by William Chapple (and later independently by Leonhard Euler), which is a special case of Poncelet's closure theorem, as well as the Grace–Danielsson inequality in one dimension higher.
The conjecture was proposed in 2014 by the Australian mathematician and science-fiction author Greg Egan. The "sufficient" part was proved in 2018, and the "necessary" part was proved in 2023.
Basics
For an arbitrary triangle (-simplex), the radius of its inscribed circle, the radius of its circumcircle and the distance of their centers are related through Euler's theorem in geometry:
,
which was published by William Chapple in 1746 and by Leonhard Euler in 1765.
For two spheres (-spheres) with respective radii and , fulfilling , there exists a (non-regular) tetrahedron (-simplex), which is completely contained inside the larger sphere and completely encloses the smaller sphere, if and only if the distance of their centers fulfills the Grace–Danielsson inequality:
.
This result was independently proven by John Hilton Grace in 1917 and G. Danielsson in 1949. A connection of the inequality with quantum information theory was described by Anthony Milne.
Conjecture
Consider -dimensional euclidean space for . For two -spheres with respective radii and , fulfilling , there exists a -simplex, which is completely contained inside the larger sphere and completely encloses the smaller sphere, if and only if the distance of their centers fulfills:
.
The conjecture was proposed by Greg Egan in 2014.
For the case , where the inequality reduces to , the conjecture is true as well, but trivial. A -sphere is just composed of two points and a -simplex is just a closed interval. The desired -simplex of two given -spheres can simply be chosen as the closed interval between the two points of the larger sphere, which contains the smaller sphere if and only if it contains both of its points with respective distance and from the center of the larger sphere, hence if and only if the above inequality is satisfied.
Status
Greg Egan showed that the condition is sufficient in comments on a blog post by John Baez in 2014. The comments were lost in a rearrangement of the website, but the central parts were copied into the original blog post. Further comments by Greg Egan on 16 April 2018 concern the search for a generalized conjecture involving ellipsoids. Sergei Drozdov published a paper on ArXiv showing that the condition is also necessary in October 2023.
References
Conjectures that have been proved
Geometry | Egan conjecture | [
"Mathematics"
] | 584 | [
"Mathematical theorems",
"Mathematical problems",
"Geometry",
"Conjectures that have been proved"
] |
75,383,618 | https://en.wikipedia.org/wiki/Summation%20theorems%20%28biochemistry%29 | In metabolic control analysis, a variety of theorems have been discovered and discussed in the literature. The most well known of these are flux and concentration control coefficient summation relationships. These theorems are the result of the stoichiometric structure and mass conservation properties of biochemical networks. Equivalent theorems have not been found, for example, in electrical or economic systems.
The summation of the flux and concentration control coefficients were discovered independently by the Kacser/Burns group and the Heinrich/Rapoport group in the early 1970s and late 1960s.
If we define the control coefficients using enzyme concentration, then the summation theorems are written as:
However these theorems depend on the assumption that reaction rates are proportional to enzyme concentration. An alternative way to write the theorems is to use control coefficients that are defined with respect to the local rates which is therefore independent of how rates respond to changes in enzyme concentration:
Although originally derived for simple linear chains of enzyme catalyzed reactions, it became apparent that the theorems applied to pathways of any structure including pathways with complex regulation involving feedback control.
Derivation
There are different ways to derive the summation theorems. One is analytical and rigorous using a combination of linear algebra and calculus. The other is less rigorous, but more operational and intuitive. The latter derivation is shown here.
Consider the two-step pathway:
where and are fixed species so that the system can achieve a steady-state.
Let the pathway be at steady-state and imagine increasing the concentration of enzyme, , catalyzing the first step, , by an amount, . The effect of this is to increase the steady-state levels of S and flux, J. Let us now increase the level of by such that the change in S is restored to the original value it had at steady-state.
The net effect of these two changes is by definition, .
There are two ways to look at this thought experiment, from the perspective of the system and from the perspective of local changes. For the system we can compute the overall change in flux or species concentration by adding the two control coefficient terms, thus:
We can also look at what is happening locally at every reaction step for which there will be two: one for , and another for . Since the thought experiment guarantees that , the local equations are quite simple:
where the terms are the elasticities. However, because the enzyme elasticity is equal to one, these reduce to:
Because the pathway is linear, at steady-state, . We can substitute these expressions into the system equations to give:
Note that at steady state the change in and must be the same, therefore .
Setting , we can rewrite the above equations as:
We then conclude through cancelation of since , that:
Interpretation
The summation theorems can be interpreted in various ways. The first is that the influence enzymes have over steady-state fluxes and concentrations is not necessarily concentrated at one location. In the past, control of a pathway was considered to be located at one point only, called the master reaction or rate limiting step. The summation theorem suggests this does not necessarily have to be the case.
The flux summation theorem also suggests that there is a total amount of flux control in a pathway such that if one step gains control another step most lose control.
Although flux control is shared, this doesn't imply that control is evenly distributed. For a large network, the average flux control will, according to the flux summation theorem, be equal to , that is a small number. In order for a biological cell to have any appreciable control over a pathway via changes in gene expression, some concentration of flux control at a small number of sites will be necessary. For example, in mammalian cancer cell lines, it has been shown that flux control is concentrated at four sites: glucose import, hexokinase, phosphofructokinase, and lactate export.
Moreover, Kacser and Burns suggested that since the flux–enzyme relationship is somewhat hyperbolic, and that for most enzymes, the wild-type diploid level of enzyme activity occurs where the curve is reaching a point in the curve where changes have little effect, then since a heterozygote of the wild-type with a null mutant will have half the enzyme activity it will not exhibit a noticeably reduced flux. Therefore, the wild type appears dominant and the mutant recessive because of the system characteristics of a metabolic pathway. Although originally suggested by Sewall Wright, the development of metabolic control analysis put the idea on a more sound theoretical footing. The flux summation theorem in particular is consistent with the flux summation theorem for large systems. Not all dominance properties can be explained in this way but it does offers an explanation for dominance at least at the metabolic level.
Concentration summation theorem
In contrast to the flux summation theorem, the concentration summation theorem sums to zero. The implications of this are that some enzymes will cause a given metabolite to increase while others, in order to satisfy the summation to zero, must cause the same metabolite to decrease. This is particularly noticeable in a linear chain of enzyme reactions where, given a metabolite located in the center of the pathway, an increase in expression of any enzyme upstream of the metabolite will cause the metabolite to increase in concentration. In contrast, an increase in expression of any enzyme downstream of the metabolite will cause the given metabolite to decrease in concentration.
See also
Control coefficient (biochemistry)
Elasticity coefficient
Metabolic control analysis
References
Biochemistry methods
Metabolism
Mathematical and theoretical biology
Systems biology | Summation theorems (biochemistry) | [
"Chemistry",
"Mathematics",
"Biology"
] | 1,134 | [
"Biochemistry methods",
"Mathematical and theoretical biology",
"Applied mathematics",
"Cellular processes",
"Biochemistry",
"Metabolism",
"Systems biology"
] |
68,200,658 | https://en.wikipedia.org/wiki/Containerization%20%28computing%29 | In software engineering, containerization is operating-system–level virtualization or application-level virtualization over multiple network resources so that software applications can run in isolated user spaces called containers in any cloud or non-cloud environment, regardless of type or vendor. The term "container" is overloaded, and it is important to ensure that the intended definition aligns with the audience's understanding.
Usage
Each container is basically a fully functional and portable cloud or non-cloud computing environment surrounding the application and keeping it independent of other environments running in parallel. Individually, each container simulates a different software application and runs isolated processes by bundling related configuration files, libraries and dependencies. But, collectively, multiple containers share a common operating system kernel (OS).
In recent times, containerization technology has been widely adopted by cloud computing platforms like Amazon Web Services, Microsoft Azure, Google Cloud Platform, and IBM Cloud. Containerization has also been pursued by the U.S. Department of Defense as a way of more rapidly developing and fielding software updates, with first application in its F-22 air superiority fighter.
Types of containers
OS containers
Application containers
Security issues
Because of the shared OS, security threats can affect the whole containerized system.
In containerized environments, security scanners generally protect the OS, but not the application containers, which adds unwanted vulnerability.
Container management, orchestration, clustering
Container orchestration or container management is mostly used in the context of application containers. Implementations providing such orchestration include Kubernetes and Docker swarm.
Container cluster management
Container clusters need to be managed. This includes functionality to create a cluster, to upgrade the software or repair it, balance the load between existing instances, scale by starting or stopping instances to adapt to the number of users, to log activities and monitor produced logs or the application itself by querying sensors. Open-source implementations of such software include OKD and Rancher. Quite a number of companies provide container cluster management as a managed service, like Alibaba, Amazon, Google, Microsoft.
See also
Docker (software)
Kubernetes
Open Container Initiative
Virtual machines
Further reading
Journal articles
Books
Gabriel N. Schenker, Hideto Saito, Hui-Chuan Chloe Lee, Ke-Jou Carol Hsu, (2019) Getting Started with Containerization: Reduce the operational burden on your system by automating and managing your containers, Packt Publishing,
Jeeva S. Chelladhurai, Vinod Singh, Pethuru Raj (2014), Learning Docker, Packt Publishing,
References
Cloud computing | Containerization (computing) | [
"Engineering"
] | 523 | [
"Software engineering",
"Software engineering stubs"
] |
68,205,243 | https://en.wikipedia.org/wiki/Fossil%20Fuel%20Non-Proliferation%20Treaty%20Initiative | The Fossil Fuel Non-Proliferation Treaty Initiative is a diplomatic and civil society campaign to create a treaty to stop fossil fuel exploration and expansion and phase-out existing production in line with the targets of the Paris Climate Agreement, while supporting a just transition to renewable energy.
The call for a treaty was first endorsed by the Pacific Island nations of Vanuatu and Tuvalu and to date, has the support of 13 national governments, the World Health Organization, the European Parliament, Nobel laureates, academics, researchers, activists, and a growing list of governments (municipal, subnational, national), and individual Parliamentarians.
The program includes the creation of a standalone Global Registry of Fossil Fuels to ensure transparency and accountability of production and reserves.
History
In 2015, Pacific Island leaders issued the "Suva Declaration On Climate Change" during the Pacific Islands Development Forum in Suva, Fiji. They called for "the implementation of an international moratorium on the development and expansion of fossil fuel extracting industries, particularly the construction of new coal mines, as an urgent step towards de-carbonising the global economy." The next year, in 2016, 14 Pacific Island nations continued to discuss the world's first "treaty" that would ban new coal mining and embrace the 1.5 °C goal set at the recent Paris climate talks.
In August 2017, a group of academics, activists, and analysts issued the Lofoten Declaration which stressed that climate policy and governance required a managed decline of fossil fuel production. The international manifesto called for fossil fuel divestment and phase-out of use with a just transition to a low-carbon economy. The declaration received the support of 744 organizations, spanning 76 countries and helped mobilize efforts for a global treaty on fossil fuel production. The government of Norway divested from exploration and production shortly afterward.
At the closing of United Nations Climate Change Conference, on 17 November 2017, the Democratic Republic of Ethiopia made a final statement on behalf of Least Developed Countries (LDC), which they stressed the need for "an increase in ambition by all countries to put us on track to limit the global temperature increase to 1.5 °C by strengthening our national contributions, managing a phase-out of fossil fuels, promoting renewable energy and implementing the most ambitious climate action."
A year later, on 23 October 2018, Peter Newell and Andrew Simms, academics at the University of Sussex, wrote an op-ed in The Guardian that renewed these public calls for a "treaty": This time they presented the treaty idea as a "Fossil Fuel Non-Proliferation Treaty." While the Intergovernmental Panel on Climate Change (IPCC) advised reducing carbon emissions 45% by 2030 to hold global temperature rise below 1.5 °C, global demand for coal, oil and gas has continued to grow. Newell and Simms noted that fossil fuels accounted for 81% of energy use in 2018 with forecasts, including those by the International Energy Agency, anticipating greater demand in future decades. As a historical precedent for a fossil fuel non-proliferation treaty, Newell and Simms cited the Toronto Conference on the Changing Atmosphere in 1988, where the threat of "climatic upheaval" was compared "second only to nuclear war"—a sentiment endorsed at the time by the CIA, MI5, United Nations. In 2019 and 2020, Newell and Simms continued to write and publish on the Treaty in non-specialist news and academic journals.
Launch
The Fossil Fuel Non-Proliferation Treaty Initiative officially launched at Climate Week NYC on September 25, 2020, at an event called "International Cooperation to Align Fossil Fuel Production with a 1.5°C World."
Tzeporah Berman, a Canadian environmental activist, was named the chair of the Treaty Initiative, and Alex Rafalowicz, the director of the Treaty Initiative. Berman has argued that by "explicitly addressing the supply side of the climate crisis, the Fossil Fuel Non-Proliferation Treaty offers a way for countries to shift course." Berman has since argued that the Treaty would be a more genuine and realistic way to achieve the goals of the Paris Agreement than the "net zero" approach which, she claimed, is "delusional and based on bad science." As Rafalowicz has put it, the "Treaty aims to be a complementary mechanism to the Paris Agreement by directly addressing the fossil fuel industry and putting the just transition at its core." "The hope many academics, researchers, and activists have is that an international agreement to prevent the expansion of fossil fuels, to manage a fair global phase-out, and to guide a just transition could be used to preserve a planet that can support human life." "The Treaty aims to be a complementary mechanism to the Paris Agreement by directly addressing the fossil fuel industry and putting the just transition at its core," according to Rafalowicz.
Letter to World Leaders
On 21 April 2021, the Treaty Initiative coordinated a letter signed by 100 Nobel laureates, including scientists, peace makers, writers, and the Dalai Lama, urging world leaders "to take concrete steps to phase out fossil fuels in order to prevent catastrophic climate change."
The open letter referenced the importance of both the United Nations Framework Convention on Climate Change and the 2015 Paris Agreement which aims to limit global warming to "well below" 2 °C and, ideally, restrict any rise to 1.5 °C, compared to pre-industrial levels. It noted that failure to meet the 1.5 °C target would risk "pushing the world towards catastrophic global warming." It also added that the Paris Agreement makes no mention of oil, gas or coal. The letter highlighted a report from the United Nations Environment Programme, stating that "120% more coal, oil, and gas will be produced by 2030 than is consistent with limiting warming to 1.5°C."
The letter concluded that the expansion of the fossil fuel industry "is unconscionable ... The fossil fuel system is global and requires a global solution—a solution the Leaders' Climate Summit must work towards. And the first step is to keep fossil fuels in the ground."
The open letter, published a day before U.S. President Joe Biden hosted the virtual 2021 Leaders' Climate Summit with leaders from various countries, described the burning of fossil fuels as "by far the major contributor to climate change."
Alongside the Dalai Lama, signatories to the letter included Jody Williams, the International Campaign to Ban Landmines' founding coordinator; the economist Christopher Pissarides; Shirin Ebadi, the first female judge in Iran; and former Colombian President Juan Manuel Santos. Other names included Liberian peace activist and advocate for women's rights, Leymah Gbowee, and Wole Soyinka, the Nigerian playwright, novelist and poet.
Global registry of fossil fuels
In February 2021, Carbon Tracker, a UK-based think tank, and Global Energy Monitor, a US-based research organization, announced the creation of an independent and standalone Global Registry of Fossil Fuels. The Registry is supported by the Treaty as an important step in ensuring transparency and accountability in fossil fuel production and reserves.
Mark Campanale, the founder and executive director of Carbon Tracker, wrote in the Financial Times that the registry "will allow governments, investors, researchers and civil society organisations, including the public, to assess the amount of embedded CO2 in coal, oil and gas projects globally. It will be a standalone tool and can provide a model for a potential UN-hosted registry."
At the 2021 United Nations Climate Change Conference, Ted Nace, executive director of Global Energy Monitor, said "The development of this dataset is the first step in a virtuous circle of transparency. The more the inventory of carbon in the ground advances, the more useful it will become and the greater the pressure on countries and companies for full transparency."
Prospective Role in International Agreements
On Jan 31, 2023, journalist Gaye Taylor reported that, "ten years after Ecuador abandoned efforts to get the international community to pay it not to drill for oil in a corner of Yasuní National Park, one of the most biodiverse places on Earth, the cash-strapped country’s decision to double down on fossil exploration is signalling the need for a global fossil fuel non-proliferation agreement." A reassessment of that abandoned Yasuní-ITT Initiative points to the broader issue of how the Fossil Fuel Non-proliferation Treaty could be built and implemented as an international agreement and a compliance mechanism for a more fair fossil fuel phase-out.
United Nations Climate Change Conferences
2021
On 11 November, at the 2021 United Nations Climate Change Conference, "a group of young climate activists delivered a sharp rebuke to delegates at the COP26 climate summit...demanding that a fossil fuel non-proliferation treaty be put in place and calling out global leaders for their continued closeness to the coal, oil and gas industries...The activists did not mince their words when they took over the stage at the Glasgow conference, pointing out the absurdity of the fact that the very mentioning of "fossil fuels" in the meeting's agreement has become a sticking point. No COP agreement has ever mentioned fossil fuels as the main driver of the climate crisis.... The youth and the leaders of the Fridays for Future group [had] joined the already established Fossil Fuel Non-Proliferation Treaty Initiative, a network of civil society organizations pushing for a speedy and just phaseout of fossil fuels."
2022
At the 2022 United Nations Climate Change Conference, Vanuatu and Tuvalu became the first countries to endorse a fossil fuel non proliferation treaty. Tuvalu's Prime Minister Kausea Natano in his speech stated “We all know that the leading cause of climate crisis is fossil fuels”, “ we have joined Vanuatu and other nations calling for a fossil fuels non-proliferation treaty… It’s getting too hot and there is very (little) time to slow and reverse the increasing temperature. Therefore, it is essential to prioritize fast acting strategies that avoids the most warming.”
2023
At the 2023 United Nations Climate Change Conference, Palau, Colombia, and Samoa all formally endorsed the treaty. On the 1 December, over 100 cities and subnational governments voiced their support for the treaty.
Endorsements
As of February 11, 2022, the initiative "has been supported by 101 Nobel Laureates, 2,600 academics, 170 parliamentarians, hundreds of prominent youth leaders, a growing group of faith leaders, and more than 1,300 civil society organisations, including Catalyst 2030, Limaatzuster, Citizens' Climate Europe, Both Ends and Fridays for Future Leeuwarden."
On July 21, 2022, the treaty was endorsed by the Vatican. On September 14, 2022, the World Health Organization, along with nearly 200 other health organizations endorsed the treaty. On October 20, 2022, the European Parliament endorsed the initiative.
As of December 2, 2023, 95 cities and subnational governments have either formally endorsed the Fossil Fuel Non-Proliferation Treaty or signed the Mayors Declaration.
Scientists and academics
As of September 14, 2021, the Fossil Fuel Non-Proliferation Treaty Initiative has received the endorsement of 2,185 scientists and researchers from 81 countries.
Cities
See also SAFE Cities.
Sub-national regional governments
National governments
Multi-National Organizations
International Organizations
See also
Powering Past Coal Alliance
Fossil fuel phase-out
Special Report on Global Warming of 1.5 °C
Treaty on the Non-Proliferation of Nuclear Weapons
Stand.earth
Global Covenant of Mayors for Climate and Energy
References
External links
Fossil Fuel Non-Proliferation Treaty Initiative - Official website
Research and Publications associated with the Fossil Fuel Non-Proliferation Treaty Initiative
Legislators, Parliamentarians and other individual elected officials call for a fossil fuel free future (also under "About" at the Fossil Fuel Non-Proliferation Treaty Initiative website)
International climate change organizations
Proposed treaties
14th Dalai Lama
Climate change mitigation
Climate change policy
Emissions reduction
Energy policy
Open environmental policy proposals | Fossil Fuel Non-Proliferation Treaty Initiative | [
"Chemistry",
"Environmental_science"
] | 2,424 | [
"Greenhouse gases",
"Environmental social science",
"Energy policy",
"Emissions reduction"
] |
68,209,537 | https://en.wikipedia.org/wiki/DMG-PEG%202000 | DMG-PEG 2000 is a synthetic lipid formed by the PEGylation of myristoyl diglyceride. It is used to manufacture lipid nanoparticles that are used in mRNA vaccines, and in particular forms part of the drug delivery system for the Moderna COVID-19 vaccine.
See also
Moderna COVID-19 vaccine nanoparticle ingredients
Distearoylphosphatidylcholine
SM-102
Cholesterol
References
Excipients
Polyethers
Polymers | DMG-PEG 2000 | [
"Chemistry",
"Materials_science"
] | 107 | [
"Polymers",
"Polymer chemistry"
] |
78,346,509 | https://en.wikipedia.org/wiki/Dicke%20state | In quantum optics and quantum information, a Dicke state is a quantum state defined by Robert H. Dicke in connection to spontaneous radiation processes taking place in an ensemble of two-state atoms. A Dicke state is the simultaneous eigenstate of the angular momentum operators and
Dicke states have recently been realized with photons with up to six particles and cold atoms of more than thousands of particles. They are highly entangled, and in quantum metrology they lead to the maximal Heisenberg scaling of the precision of parameter estimation.
Defining equations
Dicke states are defined in a system of spin- particles as the simultaneous eigenstates of the angular momentum operators and by the equations
and
Here, is a label used to distinguish several states orthogonal to each other, for which the two eigenvalues are the same.
It is worth to consider the case, namely an -qubit system. For , Dicke states are symmetric. In this case, we do not need the additional parameter , since for a given there is only a single simultaneous eigenstate of and .
It is also common to use for the characterization of these states the quantity . They can be written as
where is the number of 1's, and the summation is over all distinct permutations.
A W-state is given as
and it equals the Dicke state .
The entanglement properties of symmetric Dicke states have been studied extensively.
Symmetric Dicke states of spin- particles can easily be mapped to symmetric Dicke states of spin-1/2 particles.
The case of i.e., the case of non-symmetric Dicke states in multi-qubit systems is more complicated. In this case, the simultaneous eigenstates are denoted by , and we need now the label to dinstinguish several eigenstates with the same eigenvalues orthogonal to each other. These states can also be obtained expclicitly.
Fidelity
In an experiment, determining the fidelity with respect to pure quantum states is not an easy task in general. However, for states in the symmetric (bosonic subspace) the necessary measuement effort increases only polinomially with the number of particles. For instance, for qubits it is upper bounded by local measurement settings, which is known from the theory of Permutationally invariant quantum state tomography. It is also a valid bound for measuring the fidelity with respect to symmetric Dicke states.
For the 4-qubit case, 7 local measurement settings is sufficient, while for the 6-qubit case 21 local measuementy settings is sufficient.
Entanglement properties of Dicke states
When a Dicke states has been prepared in an experiment, it is important to verify that the state has been prepared with a good quality. Apart from obtaining the fidelity, a usual goal is to show that the quantum state was highly entangled.
If for a quantum state the fidelity with respect to W-states
holds then the quantum state is genuine multipartite entangled. This means that all the particles are entangled with each other, and the quantum state
cannot be put together with entangled quantum states of smaller units by trivial operations such as making a tensor product and mixing.
Note that the bound is approaching 1 for a large , which can make experiments with large systems difficult.
For the symmetric Dicke state , if for the fidelity of a quantum state
holds then the quantum state is genuine multipartite entangled. Now the bound approaches 1/2 for large , which makes experiments for detecting genuine multipartite entanglement feasible even for a large .
Unlike in the case of GHZ states, the entanglement of Dicke states can be detected by measuring collective observables. It is also possible to detect multipartite entanglement or entanglement depth of such states based on collective measurements. Finally, there are efficient methods to detect multipartite entanglement of noisey Dicke states based on their density matrix.
Quantum metrological properties
For an -qubit quantum state,
holds for where are the components of the collective angular momentum
and are the Pauli spin matrices.
Here, denotes the quantum Fisher information characterizing how well the state
can be used to estimate the parameter in the unitary dynamics
For separable states the bound discovered by Pezze and Smerzi
holds, which is relevant for linear interferometers, a very large class of interferometers used in experiments. For the Dicke state
holds, which corresponds to a quadratic scaling in the particle number, that is, a Heisenberg scaling.
Such Dicke states also saturate the relation
which is valid for any quantum state.
Greenberger-Horne-Zeilinger (GHZ) states also saturate this relation.
Experiments with Dicke states
W-states of three qubits have been created in photons.
Symmetric Dicke states have been created in a four and a six-qubit photonic experiment in which genuine four- and six-paricle entanglement, respectively, has been demonstrated.
They have also been prepared in a Bose-Einstein condensate with thousands of atoms.
Dicke states have also been used for quantum metrology in cold gasses and photonic systems. In these experiments it has been demonstrated that the experimentally created Dicke states outperform separable states in metrology.
Multipartite entanglement and the depth of entanglement has been detected in Dicke states in an ensemble of cold atoms.
Bipartite entanglement and Einstein-Podolsky-Rosen (EPR) steering has been detected in Dicke states of an ensemble of thousands of cold atoms.
See also
Bell state
Graph state
Cluster state
Optical cluster state
Greenberger-Horne-Zeilinger (GHZ) state
Dicke model
Jaynes–Cummings model
References
Quantum information science
Quantum states | Dicke state | [
"Physics"
] | 1,196 | [
"Quantum states",
"Quantum mechanics"
] |
78,351,617 | https://en.wikipedia.org/wiki/Jorge%20Kurchan | Jorge Kurchan (born September 4, 1959) is an Argentine-Italian statistical physicist. He is currently Director of Exceptional Class Research at the French National Centre for Scientific Research (CNRS). His primary areas of study include statistical physics, non-equilibrium thermodynamics, and complex systems. Kurchans research often explores topics such as glassy dynamics, stochastic processes, and the behavior of disordered systems, focusing on understanding the fundamental principles underlying the statistical mechanics of complex and out-of-equilibrium systems.
Education and Career
Kurchan was born in Buenos Aires, Argentina. He completed his master's degree in 1985 and his Ph.D. in 1989, both in physics at the University of Buenos Aires under Daniel R. Bes. He conducted postdoctoral research at the Weizmann Institute of Science in 1990 in the group of Eytan Domany and at the Sapienza University of Rome from 1991 to 1994. Kurchan joined École normale supérieure de Lyon as an associate researcher. In 1996, he became a CNRS research director at ESPCI ParisTech's physics and mechanics lab. He served as Deputy Director of the Henri Poincaré Institute from 2010 to 2013 and as Director of the Statistical Physics Laboratory at École normale supérieure in Paris from 2014 to 2018. Kurchan co-edited Europhysics Letters from 2002 to 2005 and currently edits Journal of Statistical Physics (2003–2014, 2018–present) and SciPost (2018–present).
Recognition
Kurchan received the Prix Paul Langevin in 2002 from the Société Française de Physique. He received the Prix Servant de la Academie des Sciences from the French Academy of Sciences in 2005. He is selected to receive the 2025 Lars Onsager Prize from the American Physical Society.
Bibliography
Books
Selected publications
Analytic solution of out-of-equilibrium mean field glass dynamics, and its relation to the phase-space landscape (with L. Cugliandolo)
Identification of an effective temperature in out-of-equilibrium systems (with L. Cugliandolo and L. Peliti)
High-dimensional geometry and slow dynamics (with L. Laloux)
The first fluctuation theorem for stochastic dynamics
Quantum fluctuation theorem and discussion of the measurement protocol
Uncovering of hidden non-abelian symmetries in interacting particle systems and their relation to duality, along with the quantum extension of duality (with C. Giardinà, R. Frassek, F. Redig, and K. Vafayi)
Analytic solution of liquid and glass dynamics in large dimensions (with T. Maimbourg and F. Zamponi)
The "full" Eigenstate Thermalization Hypothesis (with L. Foini)
Eigenstate Thermalization Hypothesis and Free Probability (with L. Foini and S. Pappalardi)
References
1959 births
Living people
Argentine physicists
21st-century Italian physicists
20th-century Italian physicists
Statistical physicists
University of Buenos Aires alumni
Research directors of the French National Centre for Scientific Research
Academic staff of the École Normale Supérieure
People from Buenos Aires
Thermodynamicists | Jorge Kurchan | [
"Physics",
"Chemistry"
] | 651 | [
"Statistical physicists",
"Statistical mechanics",
"Thermodynamics",
"Thermodynamicists"
] |
78,353,280 | https://en.wikipedia.org/wiki/Julio%20M.%20Ottino | Julio M. Ottino is a chemical engineer known for his research in fluid dynamics, chaos and mixing, and complex systems. He is also an artist, author, and educator. He is currently the Distinguished Robert R. McCormick Institute Professor and Walter P. Murphy Professor of Chemical and Biological Engineering at Northwestern University and is also a professor of management and organizations in the Kellogg School of Management. He previously served as the dean of the McCormick School of Engineering and Applied Science at Northwestern University from 2005-2023.
Early life and education
Ottino was born in La Plata, Argentina. Growing up with twin interests in art and science, he received a degree in chemical engineering from the National University of La Plata in 1974. After this, while drafted as an officer in the Argentinean Navy, he mounted a solo art exhibit. Immediately after finishing a two-year term in the Navy, he got married and moved to the United States for graduate school in chemical engineering at the University of Minnesota, where he received his PhD in 1979.
Career
After his PhD, Ottino held faculty positions at University of Massachusetts, Amherst and held visiting appointments at Caltech, Stanford, and the University of Minnesota before joining Northwestern in 1991. He was chair of Northwestern’s Department of Chemical Engineering from 1992 to 2000 and was founder and co-director of NICO, the Northwestern Institute for Complex Systems. In 2005, he became dean of Northwestern’s McCormick School of Engineering. As dean, he developed the whole-brain engineering approach to research and education, integrating both left-brain analysis and right brain creativity through design, entrepreneurship, and leadership and personal development. He created university-wide centers and initiatives, including the Segal Design Institute and the Farley Center for Entrepreneurship and Innovation.
In education, he launched several new master’s degrees programs in analytics, artificial intelligence, robotics, and energy and sustainability. At the undergraduate level, he made the first-year Design Thinking and Communication course a centerpiece of the engineering education experience. He was instrumental in developing several cross-school initiatives, including the NUvention series of courses, which brought together university-wide multidisciplinary teams to create and launch startups, and the Bay Area Immersion program, which educates students at the intersection of design, technology, and digital media.
He was also instrumental in developing more education and programming at the intersection of fine arts. With the Block Museum, he developed the Artist-at-Large and the Art + Engineering program. He partnered with the Art Institute of Chicago to facilitate the creation of the Center for Scientific Studies in the Arts and to create joint courses such as "Data as Art."
During his tenure, applications to the engineering school quadrupled, and research funding doubled. In 2017, he was awarded the Bernard M. Gordon Prize for Innovation in Engineering and Technology Education from the National Academy of Engineering for developing and implementing whole-brain engineering.
In 2022, his book The Nexus: Augmented Thinking for a Complex World – The New Convergence of Art, Technology, and Science, co-authored with Bruce Mau, was published by MIT Press.
Research
Ottino's experimental and theoretical work in chemical engineering connected the fields of chaos and fluid mixing. For the first 10 years of his career, Ottino's principal focus was on fluid mixing. He established the scientific basis of mixing and developed mathematical frameworks that showed flows can produce stretching and folding that creates chaotic motion and effective mixing. He has extended this foundational knowledge to applications including microfluidics, materials processing, and CO2 capture. Recently, Ottino turned his attention to the mixing and segregation of granular materials, exploiting the mathematics of piecewise isometries.
His research has been featured in articles and on the covers of Nature, Science, Scientific American, the Proceedings of the National Academy of Sciences of the USA and other publications and has impacted fields such as complex systems, microfluidics, geophysical sciences, and nonlinear dynamics and chaos. He has directed more than 65 PhD theses and is the author of nearly 250 papers and three books.
Awards and honors
43rd Annual Michelson Memorial Lecture (2024)
Fellow, American Institute for Medical and Biological Engineering (2024)
Member, National Academy of Sciences (2022)
Founders Award, American Institute of Chemical Engineers (2018)
Bernard M. Gordon Prize for Innovation in Engineering and Technology Education, National Academy of Engineering (2017)
Fellow, American Institute of Chemical Engineers (2013)
Fluid Dynamics Prize, American Physical Society (2008)
"One Hundred Engineers of the Modern Era," American Institute of Chemical Engineers (2008)
Member, American Academy of Arts and Sciences (2003)
Ernest W. Thiele Award (AIChE, Chicago section) (2002)
William H. Walker Award, American Institute of Chemical Engineers (2001)
John S. Guggenheim Fellowship (2001)
Member, National Academy of Engineering (1997)
Fellow, American Association for the Advancement of Science (1996)
Alpha Chi Sigma Award, American Institute of Chemical Engineers (1994)
Fellow, American Physical Society, Division of Fluid Dynamics (1993)
Presidential Young Investigator Award (NSF) (1984)
Bibliography
The Kinematics of Mixing: Stretching, Chaos, and Transport, Cambridge University Press, Cambridge, England 1989 (xiv, 364 pp., illus., + plates), reprinted 1990, 1997; 2004.
Mathematical Foundations of Mixing: The Linked Twist Map as a Paradigm in Applications – Micro to Macro, Fluids to Solids, Cambridge University Press, Cambridge, England, 2006. Rob Sturman, Julio M. Ottino, and Stephen Wiggins.
The Nexus: Augmented Thinking for a Complex World – The New Convergence of Art, Technology, and Science, MIT Press 2022. Julio Mario Ottino with Bruce Mau.
External links
www.juliomarioottino.com
https://jmo-research.northwestern.edu
References
Living people
Chemical engineers
Year of birth missing (living people) | Julio M. Ottino | [
"Chemistry",
"Engineering"
] | 1,205 | [
"Chemical engineering",
"Chemical engineers"
] |
66,707,540 | https://en.wikipedia.org/wiki/Higher%20gauge%20theory | In mathematical physics higher gauge theory is the general study of counterparts of gauge theory that involve higher-degree differential forms instead of the traditional connection forms of gauge theories.
Frameworks for higher gauge theory
There are several distinct frameworks within which higher gauge theories have been developed. Alvarez et al. extend the notion of integrability to higher dimensions in the context of geometric field theories. Several works of John Baez, Urs Schreiber and coauthors have developed higher gauge theories heavily based on category theory. Arthur Parzygnat has a detailed development of this framework. An alternative approach, motivated by the goal of constructing geometry over spaces of paths and higher-dimensional objects, has been developed by Saikat Chatterjee, Amitabha Lahiri, and Ambar N. Sengupta.
The mathematical framework for traditional gauge theory places the gauge potential as a 1-form on a principal bundle over spacetime. Higher gauge theories provide geometric and category-theoretic, especially higher category theoretic, frameworks for field theories that involve multiple higher differential forms.
See also
Gauge theory
Introduction to gauge theory
Gauge group (mathematics)
Yang–Mills theory
Yang–Mills equations
References
Differential geometry
Mathematical physics | Higher gauge theory | [
"Physics",
"Mathematics"
] | 246 | [
"Applied mathematics",
"Theoretical physics",
"Mathematical physics"
] |
66,709,348 | https://en.wikipedia.org/wiki/British%20Columbia%20Shore%20Station%20Oceanographic%20Program | The British Columbia Shore Station Oceanographic Program is a sea surface temperature and salinity monitoring program on the Canadian coast of the northeast Pacific Ocean. The program is administered by Fisheries and Oceans Canada, and regroups 12 lighthouse stations in British Columbia. Most lighthouses are staffed by the Department of Fisheries and Oceans, but some have independent contractors instead.
The practice of recording ocean water temperature and salinity levels in the area was initiated in 1914 at the Pacific Biological Station in Nanaimo. Data is collected daily around the time of the daytime high tide. The methodology of the sampling was originally designed by oceanographer John P. Tully, and was never modified in order to maintain the homogeneity of the data. The program expanded to 12 stations in the 1930s. Over time, more stations joined the programs while others stopped reporting. Currently, twelve stations remain in the program.
Data from the Amphitrite point and Kains island lightstations, which started reporting in the mid-1930s, show an increase in coastal water temperatures of 0.08 °C per decade. On the other hand, data from the Entrance Island station, which started reporting around the same time, show an increase in coastal water temperatures of 0.15°C per decade. These trends are a result of anthropogenic climate change.
The stations currently being monitored as part of the program are:
See also
Oceanography
CCGS John P. Tully
List of lighthouses in British Columbia
References
Oceanography
Fisheries and Oceans Canada | British Columbia Shore Station Oceanographic Program | [
"Physics",
"Environmental_science"
] | 302 | [
"Oceanography",
"Hydrology",
"Applied and interdisciplinary physics"
] |
69,519,758 | https://en.wikipedia.org/wiki/Niobium%20phosphide | Niobium phosphide is an inorganic compound of niobium and phosphorus with the chemical formula NbP.
Synthesis
Sintering powdered niobium and phosphorus:
4Nb + P4 -> 4NbP
Physical properties
The compound is a unique material combining topological and conventional electronic phases. Its superfast electrons demonstrate extremely large magnetoresistance, so NbP may be suitable for use in new electronic components.
Niobium phosphide forms dark gray crystals of the tetragonal system, space group , cell parameters , , .
It does not dissolve in water.
Niobium phosphide, like tantalum arsenide TaAs, is a topological Weyl semimetal.
Uses
The compound is a semiconductor used in high power, high frequency applications and in laser diodes.
References
Phosphides
Niobium(III) compounds
Semiconductors | Niobium phosphide | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 183 | [
"Electrical resistance and conductance",
"Physical quantities",
"Semiconductors",
"Materials",
"Electronic engineering",
"Condensed matter physics",
"Solid state engineering",
"Matter"
] |
69,520,552 | https://en.wikipedia.org/wiki/Polarization%20gradient%20cooling | Polarization gradient cooling (PG cooling), or Sisyphus cooling, is a technique in laser cooling of atoms by dampening the motion of the trapped particles via photon momentum. It was proposed to explain the experimental observation of cooling below the Doppler limit observed in cesium atom-related laser cooling experiments in 1985. Shortly after the theory was introduced, experiments were performed that verified the theoretical predictions. While Doppler cooling allows atoms to be cooled to hundreds of microkelvin, PG cooling allows atoms to be cooled to a few microkelvin or less.
True to its name, PG cooling involves the use of a polarization gradient typically generated by the superposition of two counter propagating beams of light with orthogonal polarizations. This creates a gradient where the polarization varies in space, with the gradient depending on which type of polarization is used. Orthogonal linear polarizations (the lin⊥lin configuration) results in the polarization varying between linear and circular polarization in the range of half a wavelength. However, if orthogonal circular polarizations (the σ+σ− configuration) are used, the result is a linear polarization that rotates along the axis of propagation. Both configurations can be used for cooling and yield similar results, however, the physical mechanisms involved are very different. For the lin⊥lin case, the polarization gradient causes periodic light shifts in Zeeman sublevels of the atomic ground state that allows for a Sisyphus effect to occur. In the σ+-σ− configuration, the rotating polarization creates a motion-induced population imbalance in the Zeeman sublevels of the atomic ground state, resulting in an imbalance in the radiation pressure that opposes the motion of the atom. Both configurations achieve sub-Doppler cooling and instead reach the recoil limit. While the limit of PG cooling is lower than that of Doppler cooling, the capture range of PG cooling is lower and thus an atomic gas must be pre-cooled before PG cooling.
Observation of Cooling Below the Doppler Limit
When laser cooling of atoms was first proposed in 1975, the only cooling mechanism considered was Doppler cooling. As such the limit on the temperature was predicted to be the Doppler limit:
Here kb is the Boltzmann constant, T is the temperature of the atoms, and Γ is the inverse of the excited state's radiative lifetime.
Early experiments seemed to be in agreement with this limit, and it was understood to be the main method of laser cooling atoms. However, in 1988 experiments began to report temperatures below the Doppler limit. These observations would take the theory of PG cooling to explain.
Theory
There are two different configurations that form polarization gradients: lin⊥lin and σ+σ−. Both configurations provide cooling, but the type of polarization gradient and the physical mechanism for cooling are different between the two.
The lin⊥lin Configuration (Gradient of Ellipticity)
In the lin⊥lin configuration cooling is achieved via a Sisyphus effect. Consider two counterpropagating electromagnetic plane waves with equal amplitude and orthogonal linear polarizations and , where k is the wavenumber . The superposition of and is given as:
Introducing a new pair of coordinates and the field can be written as:
The polarization of the total field changes with z. For example: we see that at the field is linearly polarized along , at the field has left circular polarization, at the field is linearly polarized along , at the field has right circular polarization, and at the field is again linearly polarized along .
Consider an atom interacting with the field detuned below the transition from atomic states and (). The variation of the polarization along z results in a variation in the light shifts of the atomic Zeeman sublevels with z. The Clebsch-Gordan coefficient connecting the state to the state is 3 times larger than connecting the state to the state. Thus for polarization the light shift is three times larger for the state than for the state. The situation is reversed for polarization, with the light shift being three times larger for the state than the state. When the polarization is linear, there is no difference in the light shifts between the two states. Thus the energies of the states will oscillate in z with period .
As an atom moves along z, it will be optically pumped to the state with the largest negative light shift. However, the optical pumping process takes some finite time . For field wavenumber k and atomic velocity v such that , the atom will travel mostly uphill as it moves along z before being pumped back down to the lowest state. In this velocity range, the atom travels more uphill than downhill and gradually loses kinetic energy, lowering its temperature. This is called the Sisyphus effect after the mythological Greek character. Note that this initial condition for velocity requires the atom to be cooled already, for example through Doppler cooling.
The σ+σ− Configuration (Pure Rotation of Polarization)
Representing the total electric field as , we can make the argument that the positive-frequency component is expressed as , where and ' are polarization vectors along some axes. In this case, we consider the Cartesian coordinate system for familiarity. Then, we consider the case where we have two opposing circular polarizations, or:
Where and are the amplitudes of the polarization vectors across the x- and y-axis, respectively. Substituted into our positive-frequency electric field expression, we note:
Where we utilize Euler's identity to simplify the polarization vectors and ' into the following forms:
This results in a total electric field that is elliptically polarized. It falls from elliptical polarization that when one vector moves along the propagation axis, the axes of the ellipse rotate accordingly an angle -kz. This preserves the elliptical polarization of the total electric field regardless of the position along the propagation axis.
As a result, there is no Sisyphus effect. The rotating polarization instead leads to motion-induced population imbalances in the Zeeman levels that cause imbalances in radiation pressure leading to a damping of the atomic motion. These population imbalances are only present for states with or higher.
Consider two EM waves detuned from an atomic transition with equal amplitudes. Now, consider an atom moving along the z-axis with some velocity v. The atom sees the polarization rotating with a frequency of . In the rotating frame, the polarization is fixed, however, there is an inertial field due to the frame rotating. This inertial term appears in the Hamiltonian as follows.
Here we see the inertial term looks like a magnetic field along with an amplitude such that the Larmor precession frequency is equal to rotation frequency in the lab frame. For small v, this term in Hamiltonian can be treated using perturbation theory.
Choosing the polarization in the rotating frame to be fixed along , the unperturbed atomic eigenstates are the eigenstates of . The rotating term in the Hamiltonian causes perturbations in the atomic eigenstates such that the Zeeman sublevels become contaminated by each other. For the is light shifted more than the states. Thus, the steady state population of the is higher than that of the other states. The populations are equal for the states. Thus, states are balanced with . However, when we change basis, we see that populations are not balanced in the z-basis and there is a non-zero value of proportional to the atom's velocity:
Where is the light shift for the state. There is a motion induced population imbalance in the Zeeman sublevels in the z basis. For red detuned light, is negative, and thus there will be a higher population in the state when the atom is moving to the right (positive velocity) and a higher population in the state when the atom is moving to the left (negative velocity). From the Clebsch-Gordan coefficients, we see that the state has a six times greater probability of absorbing a photon moving to the left than a photon moving to the right. The opposite is true for the state. When the atom moves to the right it is more likely to absorb a photon moving to the left and likewise when the atom moves to the left it is more likely to absorb a photon moving to the right. Thus, there is an unbalanced radiation pressure when the atom moves which dampens the motion of the atom, lowering its velocity and therefore its temperature by virtue of the kinetic theory.
Note the similarity to Doppler cooling in the unbalanced radiation pressures due to the atomic motion. The unbalanced pressure in PG cooling is not due to a Doppler shift but an induced population imbalance. Doppler cooling depends on the parameter where is the scattering rate, whereas PG cooling depends on . At low intensity, , indicating PG cooling works at lower atomic velocities and temperatures than Doppler Cooling.
Limits and Scaling
Both methods of PG cooling surpass the Doppler limit and instead are limited by the one-photon recoil limit:
Where M is the atomic mass.
For a given detuning and Rabi frequency , dependent on the light intensity, both configurations display a similar scaling at low intensity () and large detuning ():
Where is a dimensionless constant dependent on the configuration and atomic species. See ref for a full derivation of these results.
Therefore, in order to reduce the temperature, it is advised to have the Rabi frequency be substantially larger than the detuning (i.e. the detuning should be minimized).
Experiment
PG cooling is typically performed using a 3D optical setup with three pairs of perpendicular laser beams with an atomic ensemble in the center. Each beam is prepared with an orthogonal polarization to its counterpropagating beam. The laser frequency detuned from a selected transition between the ground and excited states of the atom. Since the cooling processes rely on multiple transitions between ground and excited states, care must be taken such that the atomic state does not fall out of these two states. This is done by using a second, "repumping", laser to pump any atoms that fall out back into the ground state of the transition. For example: in cesium cooling experiments, the cooling laser is typically chosen to be detuned from the to transition and a repumping laser tuned to the to transition is also used to prevent the Cs atoms from being pumped into the state.
The atoms must be cooled before the PG cooling, this can be done using the same setup via Doppler cooling. If the atoms are precooled with Doppler cooling, the laser intensity must be lowered and the detuning increased for PG cooling to be achieved.
The atomic temperature can be measured using the time of flight (ToF) technique. In this technique, the laser beams are suddenly turned off and the atomic ensemble is allowed to expand. After a set time delay t, a probe beam is turned on to image the ensemble and obtain the spatial extent of the ensemble at time t. By imaging the ensemble at several time delays, the rate of expansion is found. By measuring the rate of expansion of the ensemble the velocity distribution is measured and from this, the temperature is inferred.
An important theoretical result is that in the regime where PG cooling functions, the temperature only depends on the ratio of to and that the cooling approaches the recoil limit. These predictions were confirmed experimentally in 1990 when W.D. Phillips et al. observed such scaling in their cesium atoms as well as a temperature of 2.5K, 12 times the recoil temperature of 0.198K for the D2 line of cesium used in the experiment.
Modern Research
Recently, PG cooling has been important in research topics such as Bose-Einstein condensates, optical dipole traps, and integrated photonics. As an important aspect of atom trapping, there is substantial interest in achieving PG cooling for 3D magneto-optical traps. However, such traps typically require large volumes due to necessitating the use of multiple collimated lasers within an atomic vacuum cell. Thus, there is an active research scene in PICMOTs, or photonic integrated circuit magneto-optical traps. One proposed avenue through which such small form factors can be achieved is via metasurfaces for devices orders of magnitude smaller. If this were to be successful, PG cooling could be achieved at a much smaller form factor than currently possible, and deployed in the use of PICMOTs for higher levels of system integration, reduced optical losses, and compact magnetic field generation.
With regards to optical dipole traps, it was recently shown that PG cooling operating under the σ+σ− configuration is able to probe an optical trap's trapping field (i.e. the dependency of the cooling limit of its polarization). Currently, the efficiency of such an idea is vastly unexplored by literature and thus provides a promising field of interest for further research.
References
Quantum optics
Atomic, molecular, and optical physics
Doppler effects
Photonics | Polarization gradient cooling | [
"Physics",
"Chemistry"
] | 2,679 | [
"Physical phenomena",
"Quantum optics",
"Quantum mechanics",
"Astrophysics",
" molecular",
"Atomic",
"Doppler effects",
" and optical physics"
] |
77,009,362 | https://en.wikipedia.org/wiki/Fusion%20Engineering%20and%20Design | Fusion Engineering and Design is a peer-reviewed scientific journal, published monthly by Elsevier. Established under the name Nuclear Engineering and Design/Fusion in 1984 and retitled to its current name in 1987, it covers research on fusion power and plasma science. Its editors-in-chief are Seungyon Cho (Korea Institute of Fusion Energy) and Rudolf Neu (Max Planck Institute for Plasma Physics).
Abstracting and indexing
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2023 impact factor of 1.9.
References
External links
English-language journals
Academic journals established in 1984
Monthly journals
Plasma science journals
Engineering journals
Elsevier academic journals
Fusion power | Fusion Engineering and Design | [
"Physics",
"Chemistry"
] | 142 | [
"Nuclear fusion",
"Plasma science journals",
"Fusion power",
"Plasma physics"
] |
77,010,060 | https://en.wikipedia.org/wiki/International%20Journal%20of%20Circuit%20Theory%20and%20Applications | International Journal of Circuit Theory and Applications is a peer-reviewed scientific journal, published monthly by Wiley. It covers research on circuit theory and its applications on engineering problems, with a focus on electrical engineering. Its editor-in-chief is Ahmed El Wakil (University of Sharjah).
Abstracting and indexing
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2023 impact factor of 1.8.
References
External links
Electrical and electronic engineering journals
Monthly journals
English-language journals
Computational modeling journals
Wiley (publisher) academic journals
Academic journals established in 1973 | International Journal of Circuit Theory and Applications | [
"Engineering"
] | 124 | [
"Electrical engineering",
"Electronic engineering",
"Electrical and electronic engineering journals"
] |
77,010,482 | https://en.wikipedia.org/wiki/IEEE%20Electron%20Device%20Letters | IEEE Electron Device Letters is a peer-reviewed scientific journal published monthly by the IEEE. It was founded in 1980 by IEEE Electron Devices Society. The journal covers the advances in electron and ion integrated circuit devices. Its editor-in-chief is Sayeef Salahuddin (University of California, Berkeley).
According to the Journal Citation Reports, the journal has a 2023 impact factor of 4.1.
References
External links
Electron Device Letters, IEEE
Electrical and electronic engineering journals
Academic journals established in 1980
Semiconductor journals
English-language journals
Monthly journals | IEEE Electron Device Letters | [
"Engineering"
] | 110 | [
"Electrical engineering",
"Electronic engineering",
"Electrical and electronic engineering journals"
] |
77,012,880 | https://en.wikipedia.org/wiki/IEEE%20Transactions%20on%20Nanotechnology | IEEE Transactions on Nanotechnology is a peer-reviewed scientific journal published by IEEE. Sponsored by IEEE Nanotechnology Council, the journal covers physical basis and engineering applications in nanotechnology. Its editor-in-chief is Sorin Coțofană (Delft University of Technology).
According to the Journal Citation Reports, the journal has a 2023 impact factor of 2.1.
References
External links
Nanotechnology, IEEE Transactions on
Academic journals established in 2002
English-language journals
Nanotechnology journals | IEEE Transactions on Nanotechnology | [
"Materials_science"
] | 103 | [
"Nanotechnology journals",
"Materials science journals"
] |
77,018,809 | https://en.wikipedia.org/wiki/Transition%20metal%20complexes%20of%20phosphine%20oxides | Transition metal complexes of phosphine oxides are coordination complex containing one or more phosphine oxide ligands. Many phosphine oxides exist and most behave as hard Lewis bases. Almost invariably, phosphine oxides bind metals by formation of M-O bonds.
Structure
The structure of the phosphine oxide is not strongly perturbed by coordination. The geometry at phosphorus remains tetrahedral. The P-O distance elongates by ca. 2%. In triphenylphosphine oxide, the P-O distance is 1.48 Å. In NiCl2[OP(C6H5)3]2, the distance is 1.51 Å (see figure). A similar elongation of the P-O bond is seen in cis-WCl4(OPPh3)2. The trend is consistent with the stabilization of the ionic resonance structure upon complexation.
Examples
Typically, complexes are derived from hard metal centers. Examples include cis-WCl4(OPPh3)2 and NbOCl3(OPPh3)2 Trialkylphosphine oxides are more basic (better ligands) than triarylphosphine oxides. One such complex is FeCl2(OPMe3)2 (Me = CH3).
Synthesis and reactions
Most complexes of phosphine oxides are prepared by treatment of a labile metal complex with preformed phosphine oxide. In some cases, the phosphine oxide is unintentionally generated by air-oxidation of the parent phosphine ligand.
Since phosphine oxides are weak Lewis bases, they are readily displaced from their metal complexes. This behavior has led to investigation of mixed phosphine-phosphine oxide ligands, which exhibit hemilability. Typical phosphine-phosphine oxide ligands are Ph2P(CH2)nP(O)Ph2 (Ph = C6H5) derived from bis(diphenylphosphino)ethane (n = 2) and bis(diphenylphosphino)methane (n = 1).
In one case, coordination of the oxide of dppe to W(0) results in deoxygenation, giving an oxotungsten complex of dppe.
Secondary phosphine oxides as ligands
Secondary phosphine oxides have the formula R2P(O)H. They tautomerize to small amounts of the hydroxy tautomer R2P-OH. Regardless, the hydroxy tautomer forms a wide variety of complexes with transition metals. In contrast to O-bonded phosphine oxide ligands, the P-bonded phosphine oxides are strong field ligands. These ligands, which tend to engage in intramolecular hydrogen bonds. Illustrative is the complex derived from dimethylphosphine oxide, (Me = CH3).
The pattern also applies to several phosphorus compounds including phosphorous acid, which forms complexes as P(OH)3. The complex platinum pop is one example.
The Kläui ligand is the anion {(C5H5)Co[(CH3O)2PO]3}−. It is derived from the trimethylphosphite ligand by dealkylation. In this case the "ligand" is a complex of cobalt that also binds to other metals in a tridentate manner.
References
Coordination chemistry
Coordination complexes
Ligands | Transition metal complexes of phosphine oxides | [
"Chemistry"
] | 717 | [
"Ligands",
"Coordination chemistry",
"Coordination complexes"
] |
77,019,650 | https://en.wikipedia.org/wiki/IEEE%20Transactions%20on%20Power%20Electronics | IEEE Transactions on Power Electronics is a peer-reviewed scientific journal published monthly by the IEEE. Sponsored by the IEEE Power Electronics Society, the journal covers advances in device, circuit or system issues in power electronics. Its editor-in-chief is Yaow-Ming Chen (National Taiwan University).
According to the Journal Citation Reports, the journal has a 2023 impact factor of 6.6.
References
External links
Power Electronics, IEEE Transactions on
Academic journals established in 1986
English-language journals
Monthly journals
Power electronics | IEEE Transactions on Power Electronics | [
"Engineering"
] | 103 | [
"Electronic engineering",
"Power electronics"
] |
63,900,356 | https://en.wikipedia.org/wiki/DFTB | The Density Functional Based Tight Binding method is an approximation to density functional theory, which reduces the Kohn-Sham equations to a form of tight binding related to the Harris functional. The original approximation limits interactions to a non-self-consistent two center hamiltonian between confined atomic states. In the late 1990s a second-order expansion of the Kohn-Sham energy enabled a charge self-consistent treatment of systems where Mulliken charges of the atoms are solved self-consistently. This expansion has been continued to the 3rd order in charge fluctuations and with respect to spin fluctuations.
Unlike empirical tight binding the (single particle) wavefunction of the resulting system is available, since the integrals used to produce the matrix elements are calculated using a set of atomic basis functions.
References
Electronic structure methods
Electronic band structures
Quantum chemistry
Theoretical chemistry | DFTB | [
"Physics",
"Chemistry",
"Materials_science"
] | 166 | [
"Electron",
"Quantum chemistry stubs",
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... |
71,057,533 | https://en.wikipedia.org/wiki/Jabsco%20pump | A Jabsco pump, neoprene vane pump or self-priming neoprene vane pump, is a type of pump typically used for liquid handling. They are mainly used when water or other liquids must be pumped. In this type of pump, the fluid is sucked continuously, with a capacity depending on the size of the pump and the speed of rotation of the neoprene impeller.
Description
It consists of a cylindrical compartment with a false deflector that turns it into an oval. Inside the cylinder rotates an impeller with radial neoprene blades, whose turning movement ensures the formation of variable volume chambers with the compartment wall. Since the impeller is in a non-central position, the formation of chambers (delimited by the impeller blades) of variable volume occurs, between which the fluid passes, which the blades suck from the inlet hole and push towards the hole. exit.
History
The first self-priming neoprene vane pumps date back to a 1953 patent issued to Jabsco. The US patent USA no. 422,191 for a "self-priming neoprene pump." In 1982 another patent was granted to Jabsco UK (1982-12-23, Priority to GB08205279A) extending the number of blades of the neoprene impeller to 16.
Marine engines
The unique shape of the neoprene impeller rotating inside the oval cavity makes this pump completely self-priming and can automatically pump the water needed to cool a boat's engine, even if the pump is mounted above the water level, as a vacuum is created in the unit that sucks water from any level and from environments as varied as they can be: the sea, a lake or a stream.
Drinking water
The neoprene blade unit can be used with any potable water storage tank as it applies a pressure to the water distribution circuit equivalent to the strong depression with which it sucks water from the tank and no pressure tank or air compressor system are needed. The system is easy to install and If instant hot water is needed, simply connect the vane pump outlet to a water heater.
References
Bibliography
External links
Pumps
Watercraft components | Jabsco pump | [
"Physics",
"Chemistry"
] | 446 | [
"Pumps",
"Hydraulics",
"Physical systems",
"Turbomachinery"
] |
72,560,422 | https://en.wikipedia.org/wiki/Erin%20S.%20Baker | Erin Shammel Baker is an American bioanalytical chemist specializing in developing ion mobility-mass spectrometry hybrid instruments for biological and environmental applications. Baker is an expert in the research of perfluoroalkyl and polyfluoroalkyl substances analysis.
Early life and education
Baker grew up on a cattle ranch in Montana, US. Her interests in chemistry stemmed from a determination to understand the arsenic and cyanide pollution from gold mines that affected animals on her family's ranch and local wildlife. She obtained a bachelor of science in chemistry, with a minor in mathematics from Montana State University in 2001, where she conducted research using ion mobility spectrometry in Eric Grimsrud's laboratory. She continued with research in ion mobility spectrometry in graduate school, and received a PhD in chemistry under the direction of Michael T. Bowers from University of California, Santa Barbara in 2005.
Career
After graduation, Baker did post-doctoral research in Richard D. Smiths' laboratory at Pacific Northwest National Laboratory (PNNL), and was later promoted to senior research scientist. In 2018, she began her academic career at North Carolina State University as associate professor, and moved to University of North Carolina at Chapel Hill in 2022.
The scope of Baker's research involves both developing high throughput ion mobility–mass spectrometry (IMS–MS) systems and using these hybrid instruments to study biological and environmental systems. She was one of five researchers from the PNNL Interactive Omics Group who worked on the Structures for lossless ion manipulations (SLIM). The group received the R&D 100 Award for their effort on SLIM in 2017. She was also part of the PNNL team who helped with the commercialization of the Agilent 6560 Ion Mobility Quadrupole Time-of-Flight (IM–QTOF) Liquid Chromatography–Mass Spectrometer system. She is an expert in the research of perfluoroalkyl and polyfluoroalkyl substances (PFAS) analysis. She is the director of the Core of Advanced Platform Technologies Used for Remediation and Exploration (CAPTURE), the analytical branch of the PFAS Superfund Research Centre. She is named one of the "Worldwide Water Warriors" in 2017.
Baker served as a member-at-large for education for the American Society for Mass Spectrometry from 2019 to 2020. She serves on the editorial board of Journal of the American Society for Mass Spectrometry, Journal of Proteome Research, International Journal of Mass Spectrometry, and Scientific Reports.
Awards
2024 The Analytical Scientist The Power List - Instrumental Innovators
2023 The Analytical Scientist The Power List - Innovators and Trailblazers
2022 American Society for Mass Spectrometry Biemann Medal
2022 International Mass Spectrometry Foundation Curt Brunnée Award
2021–2022 North Carolina State University Faculty Scholar
2021 The Analytical Scientist The Power List
2021 North Carolina State University Impact Scholars
2019 The Analytical Scientist The Power List
2017 Women Chemists Committee of the American Chemical Society Rising Star Award
References
Living people
Year of birth missing (living people)
Mass spectrometrists
American women chemists
21st-century American chemists
Montana State University alumni
University of California, Santa Barbara alumni
University of North Carolina at Chapel Hill faculty
21st-century American women scientists
American women academics
Chemists from Montana | Erin S. Baker | [
"Physics",
"Chemistry"
] | 702 | [
"Biochemists",
"Mass spectrometry",
"Spectrum (physical sciences)",
"Mass spectrometrists"
] |
73,980,675 | https://en.wikipedia.org/wiki/Price%20of%20anarchy%20in%20congestion%20games | The Price of Anarchy (PoA) is a concept in game theory and mechanism design that measures how the social welfare of a system degrades due to selfish behavior of its agents. It has been studied extensively in various contexts, particularly in congestion games (CG).
Example
The inefficiency of congestion games was first illustrated by Pigou in 1920, using the following simple congestion game. Suppose there are two roads that lead from point A to point B:
Road 1 is wide but slow. Using this road, it takes 1 minute to get from A to B, regardless of how many drivers use it.
Road 2 is fast but narrow, so it becomes congested and slower as more drivers use it. If x drivers use the road, it takes them x/1000 minutes to get from A to B.
Suppose there are 1000 drivers who need to go from A to B. Each driver wants to minimize his own delay, but the government would like to minimize the total delay (the sum of delays of all drivers).
First, let us compute the minimum possible delay. Suppose x drivers go to road 2 and 1000 − x go to road 1. Then, the total delay is x2/1000+(1000 − x). This is minimized when x ≈ 500, that is, 500 drivers go to road 2 and the other 500 to road 1; the total delay is 500×1/2 + 500×1 ≈ 750 minutes.
For every single driver, the delay is always smaller when driving through road 2, as x/1000 < 1. This means that choosing road 2 is a dominant strategy. So in "anarchy" (that is, without central planning), all drivers choose road 2, their delay is 1 minute, and the total delay is 1000 minutes. The problem is that each agent minimizes his own delay, but ignores the cost imposed by his own actions on the delay of others; there is a negative externality which leads to an inefficient outcome.
In this example, selfish routing leads to a total delay that is 4/3 times higher than the optimum, so the price of anarchy is 4/3. In general, the price of anarchy may differ based on the type of congestion game, the structure of the network, and the delay functions. Various authors have computed upper and lower bounds on the PoA in various congestion games.
Effect of delay functions
To illustrate the effect of the delay functions on PoA, consider a variant of the above example in which the delay in road 1 is still 1 minute, but the delay in road 2 when x drivers use it is , for some d>1.
The minimum possible delay is attained when the number of drivers going to road 2 is . As , this number approaches 1000, so drivers go to road 2, where . The total delay is , which approaches 0 as .
However, for every single driver in road 1, it is still worthwhile to move to road 2. Therefore, in anarchy, all drivers go to road 2, and the delay is minutes.
Therefore, the price of anarchy approaches infinity as .
Definitions
A congestion game (CG) is defined by a set of resources. For example, in a road network, each road is an individual resource. For each
resource, there is a delay function (aka cost function). The function maps the amount of congestion in the resource (e.g. the number of drivers choosing to use the road) to the delay experienced by each player using it. The total cost of a player is the total delay in all the resources he chooses. Each player chooses a strategy in order to minimize his own cost.
A Nash equilibirum is a situation in which no player can improve his delay by unilaterally changing his choice. The price of anarchy (PoA) is the ratio between the largest delay in Nash equilibrium, and the smallest possible delay overall. The price of stability (PoS) is the ratio between the smallest delay in Nash equilibrium (that is: the best possible equilibrium), and the smallest possible delay overall. The PoA and PoS can also be computed with respect to other equilibrium concepts, such as mixed equilibrium or correlated equilibrium.
There are several main classes of congestion games:
In atomic CGs, there are finitely many players, and each player chooses a single path (- a single subset of the resources). Atomic congestion games have two variants:
In unweighted CGs, each player contributes the same amount 1 to the congestion of the resources he uses. Hence, the congestion in each resource is simply the number of players choosing this resource.
In weighted CGs, each player i has a different weight wi. For example, in road networks, the weight of a driver can be equal to the length of his car. The congestion in each resource is the sum of weights of all players choosing this resource.
In nonatomic CGs, the number of players approaches infinity, which means that the contribution of each single player to the congestion is negligible. The players are represented by a continuous amount. Pigou's example (illustrated above) was actually originally stated as a nonatomic game. Suppose the delay through road 1 is 1. There is 1 continuous unit of players. The minimum total delay is attained when 1/2 of the players go to road 1 and 1/2 of the go to road 2; the total delay is than 1*1/2+1/2*1/2 = 3/4. However, for each single player, the delay is always smaller through road 2, so in Nash equilibrium, the total delay is 1*1=1.
In splittable CGs, there are finitely many players, each player has a weight, and each player may split his weight among several paths (- several subsets of resources).
Another classification of CGs is based on the sets of strategies available to the players:
In symmetric CGs, all players have the same set of possible strategies, as in Pigou's example above.
In asymmetric CGs, different players may have different sets of possible strategies, such as drivers with different source and destination locations.
Moreover:
In singleton CGs, every strategy of every player is a singleton set. That is: each players chooses a single resource.
In network CGs, there is an underlying graph, and every strategy of every player is a simple path in the graph. If the CG is symmetric, then all players have the same source and destination; if it is asymmetric, then different players may have different sources or destinations.
Atomic congestion games
Christodoulou and Koutsoupias analyzed atomic unweighted CGs. They proved that the PoA when all delay functions are linear is exactly 2.5 (that is: the PoA is always at most 2.5, and in some cases it is exactly 2.5). They also gave upper and lower bounds for PoA when the delay functions are polynomials of bounded degree. In another paper, Christodoulou and Koutsoupias analyzed the PoS of atomic unweighted congestion games with linear delay functions. They proved that the PoS is at most 1.6, and showed an example in which the PoS is 1.577. They also showed that the PoA of correlated equilibria in this case is exactly 2.5 for unweighted games and exactly 2.618 for weighed games.
Awerbuch, Azar and Epstein analyzed analyzed atomic weighted CGs. They proved that the PoA when all delay functions are linear is exactly 2.618. They also showed that, when the delay functions are polynomials of degree d, the PoA is in .
, Dumrauf, Gairing, Monien and Schoppmann computed the exact PoA for atomic CGs, for delay functions that are polynomials of degree at most d:
For unweighted games, the PoA is , where is the unique nonnegative real solution to . Note that is the Golden ratio, and grows like . So the PoA is in .
For weighted games, the PoA is , where . Asymptotically, this still grows like .
The same bounds hold whenever no player can improve his expected cost by a unilateral deviation. Therefore, the worst-case PoA are the same with respect to pure Nash equilibrium, mixed Nash equilibrium, correlated equilibrium and coarse-correlated equilibrium. Moreover, the bounds hold for unweighted and weighted network congestion games.
Bhawalkar, Gairing and Roughgarden analyze weighed CGs, and show how to compute the PoA for any class of cost functions (not necessarily polynomial). They also show that, under mild conditions on the allowable delay functions, the PoA with respect to pure Nash equilibria, mixed Nash equilibria, correlated equilibria and coarse correlated equilibria are always equal. They also show that, with polynomial cost functions, the worst-case PoA is attained on a simple network, consisting only of a set of parallel edges. They also show that the PoA of symmetric unweighted congestion games is always equal to the asymmetric ones.
Further results
De-Jong and Uetz study sequential CGs, in which players pick their strategies sequentially rather than simultaneously. They analyze the PoA of subgame perfect equilibrium. They show that the sequential PoA with affine cost functions is exactly 1.5 for two players and ≈2.13 for three players, and at least 2.46 for four players. For singleton congestion games with affine cost functions, when there are n players, the sequential PoA is at most n-1; when , the sequential PoA is at least 2+1/e ≈ 2.37. For symmetric singleton atomic congestion games with affine cost functions, the sequential PoA is exactly 4/3.
Fotakis studies the PoA of CGs with linearly-independent paths, which is an extension of the setting of parallel links.
Law, Huang and Liu study the PoA of CGs in cognitive radio networks.
Gairing, Burkhard and Karsten study the PoA of CGs with player-specific linear delay functions.
Mlichtaich analyzes the effect of network topology on the efficiency of PNE in atomic CGs:
A graph G guarantees that every PNE is Pareto-efficient, iff three simple "forbidden networks" are not embedded in G.
A graph G guarantees that Braess's paradox does not occur, iff it is a series-parallel graph.
PoA of nonatomic congestion games
Roughgarden and Tardos analyzed nonatomic CGs. They showed that, when the delay functions are polynomials of degree at most d, the PoA is in , which is substantially smaller than the PoA of atomic games. In particular, when d=1, the PoA is 4/3; this shows that Pigou's simple example is the worst case for linear delay functions.
Chau and Sim extend the results of Roughgarden and Tardos by (1) considering symmetric cost maps and (2) incorporating elastic demands.
Correa, Schulz and Stier-Moses present a short, geometric proof to the results on PoA for nonatomic CGs. They also give stronger bounds on the PoA when equilibrium costs are within reasonable limits of the fixed costs.
Blum, Even-Dar and Ligett showed that all these PoA bounds apply under relatively weak behavioral assumptions: it is sufficient that all users achieve vanishing average regret over repeated plays of the game.
A useful concept in the analysis of PoA is smoothness. A delay function d is called -smooth if for all , . If the delay is smooth, is a Nash equilibrium, and is an optimal allocation, then . In other words, the price of anarchy is .
Mlichtaich analyzed singleton nonatomic CGs, with the following additional characteristics:
The utility of each player is composed of two parts: a player-specific value, minus a resource-specific delay. Formally, if player i chooses resource e, then , where is the intrinsic value i assigns to e.
The delay functions are strictly increasing.
The marginal social cost of congestion in any resource e (defined as the derivative ) is strictly-increasing.
In such games, the equilibrium payoffs are always unique and Pareto-efficient, but may not maximize the sum of utilities. Moreover:
If there are at least three resources, the equilibrium maximizes the sum (that is, PoS=PoA=1) iff the delay functions are logarithmic. For non-logarithmic delay functions, there are always fixed utilities or costs for which no equilibrium maximizes the sum of utilities (PoS>1, which implies PoA>1). When there are only two resources, the class of delay functions for which PoA=1 is somewhat larger.
If the delay functions are not “too” convex, then it is possible to maximize the sum of utilities using a negotiation process, and there is an explicit formula which specifies the share of the maximum aggregate utility that should be allocated to each group of players.
PoA of splittable congestion games
Roughgarden and Schoppmann analyzed splittable congestion games. They showed that, when the delay functions are polynomials of degree at most d, the PoA is in . In particular, when d=1, the PoA is at most 3/2. The PoA for splittable games is smaller than for atomic games, but larger than nonatomic games. For example:
When d=1, the PoA is 1.333 for nonatomic games, 1.5 for splittable games and 2.5 for atomic games;
When d=8, the PoA is 3.081 for nonatomic games, 512 for splittable games, and 1,101,126 for atomic games.
PoA with altruistic players
The basic CG model assumes that players are selfish - they care only about their own payoff. In fact, players may be altruistic and care about the social cost too. This can be modeled by assuming that the actual cost of each player is a weighted average of his own delay and the total delay. Altruism may have surprising effects on the system efficiency:
In atomic CGs, in general, even partial altruism may harm the overall efficiency. However, in the special case of symmetric load-balancing games, optimal efficiency can be attained by balancing selfishness and altruism.
In atomic CGs and cost sharing games, the robust PoA worsens with increasing altruism, whereas for valid utility games, it is not affected by altruism. But in general nonatomic CGs with uniform altruism, the PoA improves with increasing altruism. For atomic and nonatomic singleton CGs, there are bounds on the pure PoA that improve with the average altruism.
There are other papers studying the effect of altruism on the PoA. An alternative way to measure the effect of altruism on efficiency is via comparative statics: in a single game (not necessarily worst-case one), how does increasing the altruism coefficient affect the social cost? For some classes of CGs, the effect of altruism on efficiency may be negative.
See also
Congestion pricing - a tax that aims to increase the efficiency in congested networks.
Externality - a general discussion of the inefficiency caused by selfish behaviour.
References
Inefficiency in game theory | Price of anarchy in congestion games | [
"Mathematics"
] | 3,202 | [
"Game theory",
"Inefficiency in game theory"
] |
73,981,008 | https://en.wikipedia.org/wiki/Switched%20reluctance%20linear%20motor | Switched reluctance linear motors (SRLMs) (also known as linear switched reluctance motors (LSRMs), variable reluctance linear motor or switched reluctance linear machines) are a type of electric machines called linear motors which work based on the principle of a varying magnetic reluctance for force generation. The system can be used in reversed mode and then is called Switched Reluctance Linear Generator. The SRLMs consist of two parts: the active part or primary part and the passive or secondary. The active part contains the windings and defines two main types of LSRMs: transverse and longitudinal. It is longitudinal when the plane that contains the flux lines is parallel to the line of movement and transverse when it is perpendicular. Other classifications are considering the windings totally concentrated in one coil per phase or partially concentrated in two poles per phase (i.e., single-sided) or four poles per phase (double-sided). Switched Reluctance motors have been used extensively in clocks and phonograph turntables before, but nowadays, with the rising emphasis on energy efficiency, SR motors are taking more prominent roles in appliances, industrial uses, and commercial and vehicular applications and they are getting traction in the linear applications due to their simplicity, robustness, economic rationality, and high fault tolerance ability as compared with the Linear Synchronous and Linear Induction motors. The SRLM has been researched widely and there are applications of SRLMs and generators for example in wave energy conversion or hyperloop ultra high speed transportation system. One of the main advantages of the SRLM is that it does not require the use of permanent magnets, which are considered a scarce material, so it enables it to be deployed over long distances.
History
The first switched reluctance motor was invented all in 1838 by W. H. Taylor in the United States and was initially designed to propel locomotives. Then, in the 1920s, the synchronous reluctance motor was invented. These use a specially designed cageless rotor, eliminating rotor losses, with a magnetic field being generated inside the motor, which is guided through low reluctance paths. The field is rotated, which in turn pulls the rotor around to generate torque. The switched reluctance motor initially suffered from a lack of effective speed control. It was not until the 1970s, with the emergence of fast-switching electronics within variable speed drives (VSDs), that the synchronous reluctance motor was able to finally come into its own and reach performances comparable to that of conventional induction and permanent magnet motors.
The first switched reluctance linear motor ideas date back to the 1970s. In 1973, inventors Hi D Chai and Joseph P Pawletko from International Business Machines Corp patent a "Variable reluctance linear stepper motor". Then a linear stepper motor of the variable reluctance type was for serial printer applications. In 1977 J.W. Finch researcher on the Linear Vernier Reluctance Stepper Motor to replace a mechanical conveyor for a trolley. In 1988-89, Takamaya developed a linear motor based on the principle of variable reluctance. Patent proposals emerge in 1995, where inventors Matsukawa Koji and Saito Jin from Matsushita Electric Works Ltd (Panasonic Electric Works) in relation to an automatic door opening-closing device to reduce the ripple of the driving force.
In the XXIst century, the SRLM technology has been validated in on-site pilot projects like the SeaTitan, developed by the Spanish company Wedge Global and thanks to the research carried out by researchers at CIEMAT with a laboratory in Spain to validate the technology.
Working principle
A SRLM operates based on magnetic reluctance torque/force principle, which is proportional to current or flux density squared, inveresely proportional to gap length squared, this is why the airgap needs to be as small as possible. Stator windings currents are switched on and off to change the magnetic circuit formed by the rotor and the stator. A stator pole is energized by turning on its phase current. When there is no alignment between stator and rotor poles, the magnetic reluctance of the motor is high. Hence, the rotor tends to align with the energized stator poles which minimizes the reluctance of the magnetic circuit. The commutation of the stator windings should be precisely timed to ensure that a stator pole is energizing when a rotor pole is approaching. An encoder or a Hall effect sensor can be used to get the position feedback required to control the commutation. This is different from the Lorentz force where force is proportional to current and flux density.
Applications
The SRLM is particularly suitable for conveyor operation, since its method of operation is such that no relative motion is required for force to be produced. This contrasts with, for example, the linear induction motor, which depends on relative motion between the magnetic field and the conductors in which current is induced for force to be produced. This means that a reluctance motor can be designed to hold indefinitely, if required, at any particular position, before moving on to the next fixed position.
References
Electric motors
Magnetic propulsion devices | Switched reluctance linear motor | [
"Technology",
"Engineering"
] | 1,038 | [
"Electrical engineering",
"Engines",
"Electric motors"
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73,989,969 | https://en.wikipedia.org/wiki/Moser%27s%20trick | In differential geometry, a branch of mathematics, the Moser's trick (or Moser's argument) is a method to relate two differential forms and on a smooth manifold by a diffeomorphism such that , provided that one can find a family of vector fields satisfying a certain ODE.
More generally, the argument holds for a family and produce an entire isotopy such that .
It was originally given by Jürgen Moser in 1965 to check when two volume forms are equivalent, but its main applications are in symplectic geometry. It is the standard argument for the modern proof of Darboux's theorem, as well as for the proof of Darboux-Weinstein theorem and other normal form results.
General statement
Let be a family of differential forms on a compact manifold . If the ODE admits a solution , then there exists a family of diffeomorphisms of such that and .
In particular, there is a diffeomorphism such that .
Proof
The trick consists in viewing as the flows of a time-dependent vector field, i.e. of a smooth family of vector fields on . Using the definition of flow, i.e. for every , one obtains from the chain rule that By hypothesis, one can always find such that , hence their flows satisfies . In particular, as is compact, this flows exists at .
Application to volume forms
Let be two volume forms on a compact -dimensional manifold . Then there exists a diffeomorphism of such that if and only if .
Proof
One implication holds by the invariance of the integral by diffeomorphisms: .
For the converse, we apply Moser's trick to the family of volume forms . Since , the de Rham cohomology class vanishes, as a consequence of Poincaré duality and the de Rham theorem. Then for some , hence . By Moser's trick, it is enough to solve the following ODE, where we used the Cartan's magic formula, and the fact that is a top-degree form:However, since is a volume form, i.e. , given one can always find such that .
Application to symplectic structures
In the context of symplectic geometry, the Moser's trick is often presented in the following form.Let be a family of symplectic forms on such that , for . Then there exists a family of diffeomorphisms of such that and .
Proof
In order to apply Moser's trick, we need to solve the following ODE
where we used the hypothesis, the Cartan's magic formula, and the fact that is closed. However, since is non-degenerate, i.e. , given one can always find such that .
Corollary
Given two symplectic structures and on such that for some point , there are two neighbourhoods and of and a diffeomorphism such that and .This follows by noticing that, by Poincaré lemma, the difference is locally for some ; then, shrinking further the neighbourhoods, the result above applied to the family of symplectic structures yields the diffeomorphism .
Darboux theorem for symplectic structures
The Darboux's theorem for symplectic structures states that any point in a given symplectic manifold admits a local coordinate chart such thatWhile the original proof by Darboux required a more general statement for 1-forms, Moser's trick provides a straightforward proof. Indeed, choosing any symplectic basis of the symplectic vector space , one can always find local coordinates such that . Then it is enough to apply the corollary of Moser's trick discussed above to and , and consider the new coordinates .
Application: Moser stability theorem
Moser himself provided an application of his argument for the stability of symplectic structures, which is known now as Moser stability theorem.Let a family of symplectic form on which are cohomologous, i.e. the deRham cohomology class does not depend on . Then there exists a family of diffeomorphisms of such that and .
Proof
It is enough to check that ; then the proof follows from the previous application of Moser's trick to symplectic structures. By the cohomologous hypothesis, is an exact form, so that also its derivative is exact for every . The actual proof that this can be done in a smooth way, i.e. that for a smooth family of functions , requires some algebraic topology. One option is to prove it by induction, using Mayer-Vietoris sequences; another is to choose a Riemannian metric and employ Hodge theory.
References
Symplectic geometry
Theorems in differential geometry | Moser's trick | [
"Mathematics"
] | 976 | [
"Theorems in differential geometry",
"Theorems in geometry"
] |
68,212,199 | https://en.wikipedia.org/wiki/Vision%20transformer | A vision transformer (ViT) is a transformer designed for computer vision. A ViT decomposes an input image into a series of patches (rather than text into tokens), serializes each patch into a vector, and maps it to a smaller dimension with a single matrix multiplication. These vector embeddings are then processed by a transformer encoder as if they were token embeddings.
ViTs were designed as alternatives to convolutional neural networks (CNNs) in computer vision applications. They have different inductive biases, training stability, and data efficiency. Compared to CNNs, ViTs are less data efficient, but have higher capacity. Some of the largest modern computer vision models are ViTs, such as one with 22B parameters. In 2024, a 113 billion-parameter ViT model was proposed (the largest ViT to date) for weather and climate prediction, and trained on the Frontier supercomputer with a throughput of 1.6 exaFLOPs.
Subsequent to its publication, many variants were proposed, with hybrid architectures with both features of ViTs and CNNs. ViTs have found application in image recognition, image segmentation, and autonomous driving.
History
Transformers were introduced in Attention Is All You Need (2017), and have found widespread use in natural language processing. A 2019 paper applied ideas from the Transformer to computer vision. Specifically, they started with a ResNet, a standard convolutional neural network used for computer vision, and replaced all convolutional kernels by the self-attention mechanism found in a Transformer. It resulted in superior performance. However, it is not a Vision Transformer.
In 2020, an encoder-only Transformer was adapted for computer vision, yielding the ViT, which reached state of the art in image classification, overcoming the previous dominance of CNN. The masked autoencoder (2022) extended ViT to work with unsupervised training. The vision transformer and the masked autoencoder, in turn, stimulated new developments in convolutional neural networks.
Subsequently, there was cross-fertilization between the previous CNN approach and the ViT approach.
In 2021, some important variants of the Vision Transformers were proposed. These variants are mainly intended to be more efficient, more accurate or better suited to a specific domain. Two studies improved efficiency and robustness of ViT by adding a CNN as a preprocessor. The Swin Transformer achieved state-of-the-art results on some object detection datasets such as COCO, by using convolution-like sliding windows of attention mechanism, and the pyramid process in classical computer vision.
Overview
The basic architecture, used by the original 2020 paper, is as follows. In summary, it is a BERT-like encoder-only Transformer.
The input image is of type , where are height, width, channel (RGB). It is then split into square-shaped patches of type .
For each patch, the patch is pushed through a linear operator, to obtain a vector ("patch embedding"). The position of the patch is also transformed into a vector by "position encoding". The two vectors are added, then pushed through several Transformer encoders.
The attention mechanism in a ViT repeatedly transforms representation vectors of image patches, incorporating more and more semantic relations between image patches in an image. This is analogous to how in natural language processing, as representation vectors flow through a transformer, they incorporate more and more semantic relations between words, from syntax to semantics.
The above architecture turns an image into a sequence of vector representations. To use these for downstream applications, an additional head needs to be trained to interpret them.
For example, to use it for classification, one can add a shallow MLP on top of it that outputs a probability distribution over classes. The original paper uses a linear-GeLU-linear-softmax network.
Variants
Original ViT
The original ViT was an encoder-only Transformer supervise-trained to predict the image label from the patches of the image. As in the case of BERT, it uses a special token <CLS> in the input side, and the corresponding output vector is used as the only input of the final output MLP head. The special token is an architectural hack to allow the model to compress all information relevant for predicting the image label into one vector.
Transformers found their initial applications in natural language processing tasks, as demonstrated by language models such as BERT and GPT-3. By contrast the typical image processing system uses a convolutional neural network (CNN). Well-known projects include Xception, ResNet, EfficientNet, DenseNet, and Inception.
Transformers measure the relationships between pairs of input tokens (words in the case of text strings), termed attention. The cost is quadratic in the number of tokens. For images, the basic unit of analysis is the pixel. However, computing relationships for every pixel pair in a typical image is prohibitive in terms of memory and computation. Instead, ViT computes relationships among pixels in various small sections of the image (e.g., 16x16 pixels), at a drastically reduced cost. The sections (with positional embeddings) are placed in a sequence. The embeddings are learnable vectors. Each section is arranged into a linear sequence and multiplied by the embedding matrix. The result, with the position embedding is fed to the transformer.
Architectural improvements
Pooling
After the ViT processes an image, it produces some embedding vectors. These must be converted to a single class probability prediction by some kind of network. In the original ViT and Masked Autoencoder, they used a dummy [CLS] token , in emulation of the BERT language model. The output at [CLS] is the classification token, which is then processed by a LayerNorm-feedforward-softmax module into a probability distribution.
Global average pooling (GAP) does not use the dummy token, but simply takes the average of all output tokens as the classification token. It was mentioned in the original ViT as being equally good.
Multihead attention pooling (MAP) applies a multiheaded attention block to pooling. Specifically, it takes as input a list of vectors , which might be thought of as the output vectors of a layer of a ViT. The output from MAP is , where is a trainable query vector, and is the matrix with rows being . This was first proposed in the Set Transformer architecture.
Later papers demonstrated that GAP and MAP both perform better than BERT-like pooling. A variant of MAP was proposed as class attention, which applies MAP, then feedforward, then MAP again.
Re-attention was proposed to allow training deep ViT. It changes the multiheaded attention module.
Masked Autoencoder
The Masked Autoencoder took inspiration from denoising autoencoders and context encoders. It has two ViTs put end-to-end. The first one ("encoder") takes in image patches with positional encoding, and outputs vectors representing each patch. The second one (called "decoder", even though it is still an encoder-only Transformer) takes in vectors with positional encoding and outputs image patches again. During training, both the encoder and the decoder ViTs are used. During inference, only the encoder ViT is used.
During training, each image is cut into patches, and with their positional embeddings added. Of these, only 25% of the patches are selected. The encoder ViT processes the selected patches. No mask tokens are used. Then, mask tokens are added back in, and positional embeddings added again. These are processed by the decoder ViT, which outputs a reconstruction of the full image. The loss is the total mean-squared loss in pixel-space for all masked patches (reconstruction loss is not computed for non-masked patches).
A similar architecture was BERT ViT (BEiT), published concurrently.
DINO
Like the Masked Autoencoder, the DINO (self-distillation with no labels) method is a way to train a ViT by self-supervision. DINO is a form of teacher-student self-distillation. In DINO, the student is the model itself, and the teacher is an exponential average of the student's past states. The method is similar to previous works like momentum contrast and bootstrap your own latent (BYOL).
The loss function used in DINO is the cross-entropy loss between the output of the teacher network () and the output of the student network (). The teacher network is an exponentially decaying average of the student network's past parameters: . The inputs to the networks are two different crops of the same image, represented as and , where is the original image. The loss function is written asOne issue is that the network can "collapse" by always outputting the same value (), regardless of the input. To prevent this collapse, DINO employs two strategies:
Sharpening: The teacher network's output is sharpened using a softmax function with a lower temperature. This makes the teacher more "confident" in its predictions, forcing the student to learn more meaningful representations to match the teacher's sharpened output.
Centering: The teacher network's output is centered by averaging it with its previous outputs. This prevents the teacher from becoming biased towards any particular output value, encouraging the student to learn a more diverse set of features.
In January 2024, Meta AI Research released an updated version called DINOv2 with improvements in architecture, loss function, and optimization technique. It was trained on a larger and more diverse dataset. The features learned by DINOv2 were more transferable, meaning it had better performance in downstream tasks.
Swin Transformer
The Swin Transformer ("Shifted windows") took inspiration from standard CNNs:
Instead of performing self-attention over the entire sequence of tokens, one for each patch, it performs "shifted window based" self-attention, which means only performing attention over square-shaped blocks of patches. One block of patches is analogous to the receptive field of one convolution.
After every few attention blocks, there is a "merge layer", which merges neighboring 2x2 tokens into a single token. This is analogous to pooling (by 2x2 convolution kernels, with stride 2). Merging means concatenation followed by multiplication with a matrix.
It is improved by Swin Transformer V2, which modifies upon the ViT by a different attention mechanism:
LayerNorm immediately after each attention and feedforward layer ("res-post-norm");
scaled cosine attention to replace the original dot product attention;
log-spaced continuous relative position bias, which allows transfer learning across different window resolutions.
TimeSformer
The TimeSformer was designed for video understanding tasks, and it applied a factorized self-attention, similar to the factorized convolution kernels found in the Inception CNN architecture. Schematically, it divides a video into frames, and each frame into a square grid of patches (same as ViT). Let each patch coordinate be denoted by , denoting horizontal, vertical, and time.
A space attention layer is a self-attention layer where each query patch attends to only the key and value patches such that .
A time attention layer is where the requirement is instead.
The TimeSformer also considered other attention layer designs, such as the "height attention layer" where the requirement is . However, they found empirically that the best design interleaves one space attention layer and one time attention layer.
ViT-VQGAN
In ViT-VQGAN, there are two ViT encoders and a discriminator. One encodes 8x8 patches of an image into a list of vectors, one for each patch. The vectors can only come from a discrete set of "codebook", as in vector quantization. Another encodes the quantized vectors back to image patches. The training objective attempts to make the reconstruction image (the output image) faithful to the input image. The discriminator (usually a convolutional network, but other networks are allowed) attempts to decide if an image is an original real image, or a reconstructed image by the ViT.
The idea is essentially the same as vector quantized variational autoencoder (VQVAE) plus generative adversarial network (GAN).
After such a ViT-VQGAN is trained, it can be used to code an arbitrary image into a list of symbols, and code an arbitrary list of symbols into an image. The list of symbols can be used to train into a standard autoregressive transformer (like GPT), for autoregressively generating an image. Further, one can take a list of caption-image pairs, convert the images into strings of symbols, and train a standard GPT-style transformer. Then at test time, one can just give an image caption, and have it autoregressively generate the image. This is the structure of Google Parti.
Others
Other examples include the visual transformer, CoAtNet, CvT, the data-efficient ViT (DeiT), etc.
In the Transformer in Transformer architecture, each layer applies a vision Transformer layer on each image patch embedding, add back the resulting tokens to the embedding, then applies another vision Transformer layer.
Comparison with CNNs
Typically, ViT uses patch sizes larger than standard CNN kernels (3x3 to 7x7). ViT is more sensitive to the choice of the optimizer, hyperparameters, and network depth. Preprocessing with a layer of smaller-size, overlapping (stride < size) convolutional filters helps with performance and stability.
This different behavior seems to derive from the different inductive biases they possess.
CNN applies the same set of filters for processing the entire image. This allows them to be more data efficient and less sensitive to local perturbations. ViT applies self-attention, allowing them to easily capture long-range relationships between patches. They also require more data to train, but they can ingest more training data compared to CNN, which might not improve after training on a large enough training dataset. ViT also appears more robust to input image distortions such as adversarial patches or permutations.
Applications
ViT have been used in many Computer Vision tasks with excellent results and in some cases even state-of-the-art. Image Classification, Object Detection, Video Deepfake Detection, Image segmentation, Anomaly detection, Image Synthesis, Cluster analysis, Autonomous Driving.
ViT had been used for image generation as backbones for GAN and for diffusion models (diffusion transformer, or DiT).
DINO has been demonstrated to learn useful representations for clustering images and exploring morphological profiles on biological datasets, such as images generated with the Cell Painting assay.
See also
Transformer (machine learning model)
Attention (machine learning)
Perceiver
Deep learning
PyTorch
TensorFlow
References
Further reading
Neural network architectures
Computer vision
Artificial neural networks
Image processing | Vision transformer | [
"Engineering"
] | 3,205 | [
"Artificial intelligence engineering",
"Packaging machinery",
"Computer vision"
] |
75,388,505 | https://en.wikipedia.org/wiki/Quantum%20Cheshire%20cat | In quantum mechanics, the quantum Cheshire cat is a quantum phenomena that suggests that a particle's physical properties can take a different trajectory from that of the particle itself. The name makes reference to the Cheshire Cat from Lewis Carroll's Alice's Adventures in Wonderland, a feline character which could disappear leaving only its grin behind. The effect was originally proposed by Yakir Aharonov, Daniel Rohrlich, Sandu Popescu and Paul Skrzypczyk in 2012.
In classical physics, physical properties cannot be detached from the object associated to it. If a magnet follows a given trajectory in space and time, its magnetic moment follows it through the same trajectory. However, in quantum mechanics, particles can be in a quantum superposition of more than one trajectory previous to measurement. The quantum Cheshire experiments suggests that previous to a measurement, a particle may take two paths, but the property of the particle, like the spin of a massive particle or the polarization of a light beam, travels only through one of the paths, while the particle takes the opposite path. The conclusion is only obtained from an analysis of weak measurements, which consist in interpreting the particle history previous to measurement by studying quantum systems in the presence of small disturbances.
Experimental demonstration of the quantum Cheshire cat have already been claimed in different systems, including photons and neutrons. The effect has been suggested as a probe to study properties of massive particles by detaching it from its magnetic moment in order to shield them from electromagnetic disturbances. A dynamical quantum Cheshire cat has also been proposed as a counterfactual quantum communication protocol.
Example of the experiment
Neutrons are uncharged subatomic particles that have a magnetic moment, with two possible projections on any given axis.
A beam of neutrons, with all with their magnetic moments aligned to the right, enters a Mach–Zehnder interferometer coming from the left-to-right. The neutrons can exit the interferometer into a right port, where a detector of neutrons with right magnetic moment is located, or upwards into a dark port with no detector (see picture).
The neutrons enter the interferometer and reach a beam splitter. Each neutron that passes through, enters into a quantum superposition state of two different paths, namely A and B. This initial state is referred to as the preselected state. As the neutrons travel the different paths, their wave functions reunites at a second beam splitter, causing interference. If there is nothing in the path of the neutrons, every neutron exits to the interferometer moving to the right and activates the detector. No neutron escapes upwards into the dark port due to destructive interference.
One can add different components and filters in one of the paths. By adding a filter that flips the magnetic moment of the neutron in path B (lower branch), it leads to a new superposition state: neutron taking path A with a magnetic moment pointing right, plus the neutron taking path B with the magnetic moment flipped pointing to the left. This state is called a postselected state. As the states cannot longer interfere coherently due to this modification, the neutrons can exit through the two ports, either to the right reaching the detector or exiting towards the dark port.
In this configuration, if the detector clicks, it is only because the neutrons had a magnetic moment oriented in to the right. By means of this postselection, it can be confidently stated that the neutron that reached the detector passed through path A, which is the only path to contains neutron magnetic moments oriented to the right. This effect can be easily demonstrated by putting a thin absorber of neutrons in the path. By placing the absorber in path B, the rate of neutrons that are detected remains constant. However, when the absorber is positioned in path A, the detection rate decreases, providing evidence that detected neutrons in the postselected state travel only through path A.
If a magnetic field is applied perpendicular to the plane of the interferometer and localized in either path A or path B, the number of neutrons that are detected changes, as the magnetic fields makes the neutrons precess and alters the probabilities of being measured. Additionally, measuring the magnetism and the trajectory (with an absorber) at the same time is not possible without also disrupting the quantum state.
The quantum Cheshire cat appears in the weak limit of the interaction. When a sufficiently small magnetic field is applied to path A, there is no impact on the measurement. In contrast, if the magnetic field is applied to path B, the detection rate diminishes, demonstrating that the neutrons magnetism, perpendicular to the plane of the interferometer, predominantly resided in path B. We can do the same with a thin absorber, showing that only the neutrons that are detected are all from path A. This experiment effectively separated the "cat", representing the neutron, from its "grin", symbolizing its magnetic moment out of the plane.
General description
Consider a particle with a two-level property that can be either or , this can be for example the horizontal and vertical polarization of a photon or the spin projection of a spin-1/2 particle as in the previous example with the neutrons. One of these two polarization states (let's say ) is chosen and the particle is then prepared to be in the following superposition:
where and are two possible orthogonal trajectories of the particle. The state is called the preselected state.
A filter is added in path of the particle in order to flip its polarization from to , such that it ends up in the state
such state indicates that if the particle is measured to be in state , the particle took path ; analogously, if the particle is measured to be in state , the particle took path . The state is called the postselected state.
Using postselection techniques, the particle is measured in order to detect the overlap between the preselected state and postselected state. If there are no disturbances, the preselected and postselected states produce the same results 1/4 of time.
Weak measurements
We define the weak value of an operator given by
where is the preselected state and the postselected state. This calculation can be thought as the contribution of a given interaction up to linear order.
For the system, one considers two projectors operators given by
and
which measure if the particle is on either path or , respectively.
Additionally, an out-of the-plane polarization operator is defined as
this operator can be thought as a measure of angular momentum in the system. Outside the weak limit, the interaction related to this operator tends to make the polarization precess between and .
Performing the following weak measurements on the positions with and , one obtains the following
,
These weak values indicate that if the path is slightly perturbed, then the measurement is perturbed. While if instead path is perturbed this does not affect the measurement.
We also consider weak measurements on the out-of the-plane polarization in each of the paths, such that
These values indicate that if the polarization is slightly modified in path , then the results are slightly modified too. However, if the polarization is perturbed in path there is no correction to the intensity measured (in the weak limit).
These 4 weak values lead to the quantum Cheshire cat conclusion.
Interpretations and criticism
The proposal of quantum Cheshire cat has received some criticism. Popescu, one of the authors of the original paper, acknowledged it was not well received by all of the referees who first reviewed the original work.
As the quantum Cheshire cat effect is subjected to analysis of the trajectory before measurement, its conclusion depends on the interpretation of quantum mechanics, which is still an open problem in physics. Some authors reach different conclusions for this effect or disregard the effect completely. It has been suggested that the quantum Cheshire cat is just an apparent paradox raising from misinterpreting wave interference. Other authors consider that it can be reproduced classically.
The experimental results depend on the postselection and analysis of the data. It has been suggested that the weak value cannot be interpreted as a real property of the system, but as an optimal estimate of the corresponding observable, given that the postselection is successful. Aephraim M. Steinberg, notes that the experiment with neutrons does not prove that any single neutron took a different path than its magnetic moments; but shows only that the measured neutrons behaved this way on average. It has also been argued that even if the weak values were measured in the neutron Cheshire cat experiment, they do not imply that a particle and one of its properties have been disembodied due to unavoidable quadratic interactions in the experiment. This last point was acknowledged by A. Matzkin, one of the coauthors of the neutron experiment paper.
References
Quantum mechanics
Physics experiments
Quantum measurement | Quantum Cheshire cat | [
"Physics"
] | 1,834 | [
"Physics experiments",
"Theoretical physics",
"Quantum mechanics",
"Quantum measurement",
"Experimental physics"
] |
75,391,238 | https://en.wikipedia.org/wiki/Pelacarsen | Pelacarsen is an antisense therapy that is designed to reduce Lipoprotein(a) concentrations in people with high levels of the lipoprotein and who are at risk of cardiovascular disease. It was developed by Ionis Pharmaceuticals and Novartis.
References
Antisense RNA
Drugs developed by Novartis | Pelacarsen | [
"Chemistry"
] | 68 | [
"Pharmacology",
"Pharmacology stubs",
"Medicinal chemistry stubs"
] |
75,395,346 | https://en.wikipedia.org/wiki/Dynamic%20toroidal%20dipole | In classical electrodynamics, the dynamic toroidal dipole arises from time-dependent currents flowing along the poloidal direction on the surface of a torus. In relativistic quantum mechanics, spin contributions to the toroidal dipole needs to be taken into account. Toroidal dipole moments are odd under parity and time-reversal symmetries. Dynamic toroidal dipole is distinguished from the static toroidal dipole introduced by Zeldovich in 1957 under the name of static anapole.
The dynamic toroidal multipoles were theoretically introduced in the 1970s in the context of a complete multipole expansion in electrodynamics and their radiation properties were studied in a series of theoretical works. The experimental study of dynamic toroidal multipoles, however, became possible only with advances in artificial electromagnetic materials (metamaterials), leading to the first experimental observation of the toroidal dipole, in 2010 in an array of microwave resonators with elements of toroidal symmetry.
The far-field radiation properties of the dynamic toroidal dipole are identical to those of the conventional electric dipole. Hence combining a dynamic toroidal dipole with an electric dipole can result in a non-radiating charge-current configuration (termed dynamic anapole), in which the electromagnetic fields vanish outside the source, whereas the vector potential persists. Non-radiating anapoles were observed experimentally for the first time in 2013 as peak of transmission of structured matter at microwave frequencies and in 2015 at optical wavelengths in nanoparticles. Electrodynamics of dynamic toroidal dipole and anapoles is now massively influencing research in metamaterials, nanoparticles, plasmonics, sensors, lasers and spectroscopy
Note: The terminology of dynamic "electric" and "magnetic" toroidal multipoles has also been introduced. The latter is already part of the standard multipole expansion in the form of the mean square radii of the magnetic multipoles.
See also
Multipole expansion
Toroidal moment
References
Electrodynamics
Moment (physics) | Dynamic toroidal dipole | [
"Physics",
"Mathematics"
] | 423 | [
"Physical quantities",
"Quantity",
"Electrodynamics",
"Moment (physics)",
"Dynamical systems"
] |
75,395,638 | https://en.wikipedia.org/wiki/Quantum%20mechanics%20of%20nuclear%20magnetic%20resonance%20%28NMR%29%20spectroscopy | Nuclear magnetic resonance (NMR) spectroscopy uses the intrinsic magnetic moment that arises from the spin angular momentum of a spin-active nucleus. If the element of interest has a nuclear spin that is not 0, the nucleus may exist in different spin angular momentum states, where the energy of these states can be affected by an external magnetic field. For a spin, l = ½ nucleus two energy levels may be considered: spin up and spin down, depending on how the spin aligns with the external magnetic field. It is important to remember that, in the presence of an external magnetic field, individual nuclei may have random orientations other than up and down. However, the sample's bulk magnetization, that is, the sum of the total magnetic moments will determine the strength of the NMR signal. In addition, the energy of the applied radio frequency used in NMR must be consistent with the energy difference between the spin states.
Hamiltonian (Ĥ)
The Hamiltonian operator / function represents the energy operator. The spin Hamiltonian for a nuclear spin under an applied magnetic field (B0) is,
In classical mechanics, the Hamiltonian H(q, p) is expressed as:
H(q, p) = T(p) + V(q)
where:
q : Generalized coordinates (position variables).
p : Generalized momenta (momentum variables).
T(p) : Kinetic energy (often depends on p ).
V(q) : Potential energy (depends on q ).
Ĥone spin = -γB0ÎZ
Where γ is the gyro-magnetic ratio and ÎZ is the z-component of the nuclear spin angular momentum.
The energy of the nuclear spin level is given by this Hamiltonian operator, since we know the eigenvalue for ψ. We will first determine the energy of states and subsequently convert it to frequency units since in NMR, energy is expressed in frequency units is more common.
Eigenvalues of nuclear spin angular momentum
The equation of the Hamiltonian contains an angular momentum operator. So it will be easy if we find the eigenvalues of the angular momentum operator first and then substitute it into the Hamiltonian. For a spin half nucleus there are two eigenfunctions for ÎZ.
Let m = +1/2 and m = -1/2 and eigenfunctions are,
ÎZ ψm = mħψm Eigenvalues and Hamiltonian
Applying the equation of nuclear spin angular momentum (ÎZ ψm) to one spin Hamiltonian (Ĥone spin) will give,Ĥone spin ψm = -mħγB0ψmFrom this, eigenvalue is,Em = -mħγB0In frequency units,Em = -mγB0/2π Hz
Introducing Larmor frequency (v0), Em = mv0 Hz
Hence the Hamiltonian in frequency units, Ĥone spin = v0ÎZ
Examples
1. Nucleus with Spin I= 1/2
Eigenvalues of ÎZ:
m_I \hbar, \quad m_I = \pm \frac{1}{2}.
Two spins without coupling
If there are two spin states, then we have to change the Hamiltonian in such a way that it accommodates both the spin states.
Ĥtwo spins, no coupling = v0,1Î1Z + v0,2Î2Z
v0,1 is the Larmor frequency of first spin and v0,2 is the Larmor frequency of second spin. Similarly Î1Z is the z-component of angular momentum operator of first spin and Î2Z is the z-component of angular momentum operator of first spin. Here in this case coupling is not considered.
Here while considering the wave function we have to look into both spin states of both spin 1 and 2. The spin up state is represented by α and spin down is β. The wave functions hence will have four combinations as below.
ψα,1 ψα,2 = αα ψα,1 ψβ,2 = αβ ψβ,1 ψα,2 = βα ψβ,1 ψβ,2 = ββ
Applying these combinations into the two spin Hamiltonian above will give the eigenvalue which is the energy state. This is tabulated below.
In general, the energy level (eigenvalue) can be written as;
Em = m1v0,1 + m2v0,2
Eigenvalues of coupled spins
To consider coupling of spin 1 and 2 a coupling constant (J) and corresponding coupling term is introduced in the Hamiltonian:
Ĥtwo spins = v0,1Î1Z + v0,2Î2Z + J12Î1ZÎ2Z
Applying the wave functions in this Hamiltonian gives the eigenvalues as tabulated below.
Selection rule and transitions
When two spins couple each other, the Hamiltonian operator will be,
Ĥtwo spins = v0,1Î1Z + v0,2Î2Z + J12Î1ZÎ2Z
The eigenvalue,
Em = m1v0,1 + m2v0,2 + m1m2 J12
The selection rule for allowed transition is + or -1. Here we are considering homonuclear protons. Thus their αβ and βα states will have the same energy. The transition energy can be calculated by reducing the energy (eigenvalue) of the upper state from the lower state. The transition energy in frequency units is tabulated below.
The transitions given in the above table is represented in the figure below:
Relevance in Nuclear Magnetic Resonance (NMR):
In NMR, the nuclear spin angular momentum interacts with an external magnetic field. The splitting of energy levels due to mI (known as Zeeman splitting) forms the basis of NMR spectroscopy.
The transitions between these quantised levels are detected as resonance frequencies.
References
Nuclear magnetic resonance spectroscopy | Quantum mechanics of nuclear magnetic resonance (NMR) spectroscopy | [
"Physics",
"Chemistry"
] | 1,226 | [
"Nuclear magnetic resonance",
"Spectroscopy",
"Spectrum (physical sciences)",
"Nuclear magnetic resonance spectroscopy"
] |
75,398,609 | https://en.wikipedia.org/wiki/Connectivity%20theorems | The stoichiometric structure and mass-conservation properties of biochemical pathways gives rise to a series of theorems or relationships between the control coefficients and the control coefficients and elasticities. There are a large number of such relationships depending on the pathway configuration (e.g. linear, branched or cyclic) which have been documented and discovered by various authors. The term theorem has been used to describe these relationships because they can be proved in terms of more elementary concepts. The operational proofs in particular are of this nature.
The most well known of these theorems are the summation theorems for the control coefficients and the connectivity theorems which relate control coefficients to the elasticities. The focus of this page are the connectivity theorems.
When deriving the summation theorems, a thought experiment was conducted that involved manipulating enzyme activities such that concentrations were unaffected but fluxes changed. The connectivity theorems use the opposite thought experiment, that is enzyme activities are changed such that concentrations change but fluxes are unchanged. This is an important observation that highlights the orthogonal nature of these two sets of theorem.
As with the summation theorems, the connectivity theorems can also be proved using more rigorous mathematical approaches involving calculus and linear algebra. Here the more intuitive and operational proofs will be used to prove the connectivity theorems.
Statement of the connectivity theorems
Two basic sets of theorems exists, one for flux and another for concentrations. The concentration connectivity theorems are divided again depending on whether the system species is different from the local species .
Proof
The operational proof for the flux connectivity theorem relies on making perturbations to enzyme levels such that the pathway flux is unchanged but a single metabolite level is changed. This can be illustrated with the following pathway:
Let us make a change to the rate through by increasing the concentration of enzyme . Assume is increased by an amount, . This will result in a change to the steady-state of the pathway. The concentrations of , and the flux, through the pathway will increase, and the concentration of will decrease because it is upstream of the disturbance.
Impose a second change to the pathway such that the flux, is restored to what it was before the original change. Since the flux increased when was changed, the flux can be decreased by decreasing one of the other enzyme levels. If the concentration of is decreased, this will reduce the flux. Decreasing will also cause the concentration of to further increase. However, and will change in the opposite direction compared to when was increased.
When is sufficiently changed so that the flux is restored to its original value, the concentrations of and will also be restored to their original values. It is only that will differ. This is true because the flux through is now the same as it was originally (since we’ve restored the flux), and has not been manipulated in anyway. This means that the concentration of and all
species upstream of must be the same as they were before the modulations occurred. The same arguments apply to and all species downstream of .
The net result is that has been increased by resulting a change in flux of . The concentration of was decreased such that the flux was restored to it original value, . In the process, changed by but neither or . In fact no other species in the entire system has changed other than .
This thought experiment can be expressed mathematically as follows. The system equations in terms of the flux control coefficients can be written as:
There are only two terms because only and were changed.
The local change at each step can be written for and in terms of elasticities:
Note that won't necessarily equal and by construction both rates, and showed no change. Also by construction only changed.
The local equation can be rearranged as:
The right-hand sides can be inserted into the system equation the change in flux:
Therefore:
However, by construction of the perturbations, does not equal zero, hence we arrive at the connectivity theorem:
The operational method can also be used for systems where a given metabolite can influence multiple steps. This would apply to cases such as branched systems or systems with negative feedback loops.
The same approach can be used to derive the concentration connectivity theorems except one can consider either the case that focuses on a single species or a second case where the system equation is written to consider the effect on a distance species.
Interpretation
The flux control coefficient connectivity theorem is the easiest to understand. Starting with a simple two step pathway:
where and are fixed species so that the pathway can reach a steady-state. and are the reaction rates for the first and second steps.
We can write the flux connectivity theorem for this simple system as follows:
where is the elasticity of the first step with respect to the species and is the elasticity of the second step with respect to the species . It is easier to interpret the equation with a slight rearrangement to the following form:
The equation indicates that the ratio of the flux control coefficients is inversely proportional to the elasticities. That is, a high flux control coefficient on step one is associated with a low elasticity and vice versa. Likewise a high value for the flux control coefficient on step two is associated with a low elasticity .
This can be explained as follows: If is high (in absolute terms, since it is negative) then a change at will be resisted by the elasticity, hence the flux control coefficient on step one will be low.
See also
Branched pathways
Control coefficient (biochemistry)
Elasticity coefficient
Metabolic control analysis
Summation theorems (biochemistry)
References
Biochemistry methods
Metabolism
Mathematical and theoretical biology
Systems biology | Connectivity theorems | [
"Chemistry",
"Mathematics",
"Biology"
] | 1,125 | [
"Biochemistry methods",
"Mathematical and theoretical biology",
"Applied mathematics",
"Cellular processes",
"Biochemistry",
"Metabolism",
"Systems biology"
] |
75,400,017 | https://en.wikipedia.org/wiki/Foscarbidopa/foslevodopa | Foscarbidopa/foslevodopa, sold under the brand name Vyalev among others, is a fixed-dose combination medication used for the treatment of Parkinson's disease. It is a fixed-dose combination of foscarbidopa, an aromatic amino acid decarboxylation inhibitor and prodrug for carbidopa; and foslevodopa, an aromatic amino acid and prodrug for levodopa that was developed by AbbVie. Its structure is identical to carbidopa/levodopa except for the replacement of a hydroxyl on each molecule with a phosphate group, similar to the antiepileptic prodrug fosphenytoin as it relates to phenytoin.
The combination was refused approval by the US Food and Drug Administration (FDA) in 2023. It was approved for medical use in Canada in May 2023, in Australia in March 2024, and in the United States in October 2024.
Produodopa uses a pump to steadily release foscarbidopa/foslevodopa into the bloodstream round-the-clock. It is available via the UK National Health Service since February 2024.
Medical uses
The combination of foscarbidopa and foslevodopa is indicated for the treatment of motor fluctuations in adults with advanced Parkinson's disease.
Side effects
The most common adverse reactions include infusion/catheter site reactions, infusion/catheter site infections, hallucinations, and dyskinesia.
References
Aromatic L-amino acid decarboxylase inhibitors
Antiparkinsonian agents
Combination drugs
Dopamine agonists
Drugs developed by AbbVie
Monoamine precursors
Prodrugs | Foscarbidopa/foslevodopa | [
"Chemistry"
] | 360 | [
"Chemicals in medicine",
"Prodrugs"
] |
75,400,032 | https://en.wikipedia.org/wiki/C24H32O3 | {{DISPLAYTITLE:C24H32O3}}
The molecular formula C24H32O3 may refer to:
Caleicine
1,2-Didehydro-3-oxo-THCO | C24H32O3 | [
"Chemistry"
] | 48 | [
"Isomerism",
"Set index articles on molecular formulas"
] |
66,713,788 | https://en.wikipedia.org/wiki/Kenneth%20Henderson%20Jack | Kenneth Henderson Jack FRS (12 October 1918—28 January 2013) was a British chemist whose career involved the application of X-ray crystallography to the field of materials science.
Biography
Kenneth Henderson Jack was born on 12 October 1918 at his grandmother's flat in Coburg Street, North Shields. He was the eldest of three sons of John Henderson Jack, mariner, and Emily (née Cozens). He attended King Edward's Primary School and then Tynemouth Municipal High School. He gained a scholarship place to study chemistry at Armstrong College (later part of the Newcastle Colleges of Durham University). Jack graduated with first-class honours in chemistry and came top of his year. After a brief spell in teaching – a requirement of his scholarship – he was directed into war work at the Chemical Defence Research Establishment, Sutton Oak, before the Professor of Inorganic and Physical Chemistry, H. L. Riley brought him back to Newcastle in October 1941.
Riley led a group involved with the Ministry of Supply on armour-plated steel. Jack's work in this field came to the notice of Sir Charles Goodeve, the first director of the British Iron and Steel Research Association (BISRA), who appointed him as a Senior Scientific Officer in 1945. After a year at Newcastle, Jack moved to Cambridge for three years, to work on crystallography in W H Taylor's group with Peter Hirsch.He worked for a PhD while at Cambridge and was awarded the degree in 1949. He then returned to Newcastle as a lecturer in inorganic chemistry, while continuing his work in interstitial alloys.
In 1951 Jack was invited to give a paper at the Pittsburgh Diffraction Conference. While there he helped pay his way by giving lectures at various institutions, one of which was Westinghouse Electric Corporation. Over lunch he was told by the research director, Clarence Zener, to send for his wife and children and come to work at Westinghouse. On 11 August he and his family arrived in New York on the Mauretania, and Jack started at the 500-strong research facility, in charge of the X-ray lab. The facility was upgraded with new equipment, some of which he helped build. Although he was offered several jobs in Pittsburgh, Kenneth Jack and his family decided to return to England. They sailed from Montreal on the Empress of Scotland on 28 August 1953, bound for Liverpool.
Back at Newcastle Jack worked on developing his powder diffraction techniques. He enjoyed his teaching and research, but could gain no promotion or salary increase. After several unsuccessful applications for professorships he accepted a position in 1957 at Thermal Syndicate Limited. He had less freedom than in academia, and was required to focus on the needs of the business. He and his team developed a way ok making a much-improved version of the firm's main product: a fused quartz with the brand name Spectrosil. The new Spectrosil® WF “had outstanding optical transmission as well as a very low impurity content and found important applications in the production of optical fibres for telecommunications”.
But Newcastle beckoned again. The professor of metallurgy at Jing's College asked Kenneth Jack, in 1963, if he was interested in a recently established readership there. The outcome, in the following year, was Jack's appointment with a Personal Chair in Applied Crystal Chemistry, at what was now the University of Newcastle upon Tyne, now more usually Newcastle University. His lines of research includes a focus on silicon nitride () and its development into more complex Si-Al-O-N structures; the discovery of Guinier–Preston (GP) zones in Fe-Mo-N. The latter led to funding in 1970 from the Wolfson Foundation for a transmission electron microscope and additional staff.
The work of the growing Wolfson group “became better and better known [and] there were many invitations to give lectures overseas in Europe, the USA, Japan, India, Pakistan and China. Ken’s seven-week visit to India and Pakistan in early 1981 was particularly memorable. ”. He coined the term “sialon” to describe the Si-Al-O-N complexes. Other universities and the Joseph Lucas Group Research Centre became interested, and the Lucas group trademarked some of them Syalon®.
Jack “received many honours, prizes and awards throughout his career. In 1980 he was elected a Fellow of the Royal Society and in 1996 he was made an honorary professor at Swansea University. He was appointed OBE in 1997 and, a decade later, was made a distinguished life member of the American Ceramic Society”.
Kenneth Jack retired from the University of Newcastle in 1984.
Family
Kenneth Henderson Jack married Alfreda Hughes, whom he had known since childhood, in 1942. They had two children: David Hughes born in 1944, and Stephen in 1950.
David Jack studied metallurgy at Cambridge, where he gained a PhD. He spent 1969–1970 as an ICI postdoctoral fellow in his father's research group at Newcastle, before being appointed Lecturer in the Metallurgy Department at Leeds University. In 1981 he took up a research manager position in Coventry with the Swedish industrial group Sandvik. From 1997 he worked for the Japanese machine tool company Yamazaki Mazak, retiring in 2009. He then oversaw which has its European HQ and factory in Worcester, UK, ultimately becoming responsible for its total European business. (Memoir) to retirement in 2009. He then presided over the opening of the company's new $17-million European Technology Centre in Worcester; it opened on 24 November 2009.
Freda Jack died suddenly in 1974 from a cerebral aneurysm. Kenneth developed health problems around 2007, and died in hospital on 28 January 2013. He was survived by his two sons.
References
1918 births
Fellows of the Royal Society
British chemists
X-ray crystallography
Officers of the Order of the British Empire
2013 deaths | Kenneth Henderson Jack | [
"Chemistry",
"Materials_science"
] | 1,195 | [
"X-ray crystallography",
"Crystallography"
] |
66,718,077 | https://en.wikipedia.org/wiki/Vitaly%20Khlopin | Vitaly Grigorievich Khlopin (Russian:Вита́лий Григо́рьевич Хло́пин) (January 1890 - 10 July 1950) was a Russian and Soviet scientist- radiochemist, professor, academician of the USSR Academy of Sciences (1939), Hero of Socialist Labour (1949), and director of the Radium Institute of the USSR Academy of Sciences (1939-1950). He was one of the founders of Soviet radiochemistry and radium industry, received the first domestic radium preparations (1921), one of the founders of the Radium Institute and leading participants in the atomic project and founder of the school of Soviet radiochemists.
Biography
He was born on January 14 (26), 1890 in Perm, in the family of a doctor Grigory Vitalievich Khlopin (1863-1929). From 1905 the Khlopins lived in St. Petersburg.
Brief chronology of his life path:
1897 - began studying at a private men's school in Yuriev;
1908 - graduated from the 12th St. Petersburg Gymnasium;
1911 - graduated from the chemistry department of the University of Göttingen.
1911—1913 - at the St. Petersburg Clinical Institute of the Grand Duchess Helena Pavlovna he taught practical sessions on chemical methods of sanitary analyses;
1912 - graduated with a first degree diploma from the Faculty of Physics and Mathematics of St. Petersburg University in chemistry;
1912-1917 - remained at the University at the Department of General Chemistry as an assistant, where under the guidance of L. A. Chugaev he was being prepared for teaching (the first work with L. A. Chugaev on the synthesis of complex compounds of platonitrite with dithioethers);
1913-1916 - engaged in experimental research in the chemistry of platinum compounds and analysis of rare elements;
1914, 1915 - laboratory assistant at the Petrograd Central City Chemical Laboratory;
1915 - at the suggestion of Academician V.I. Vernadsky he started working in the Radiological Laboratory of the Academy of Sciences (organized in the autumn of 1911 in the former studio of A.I. Quindzhi on Vasilievsky Island) as a specialist in chemistry (until 1921);
1915, 1916 - at the suggestion of the Chemical Committee at the State Academy of Sciences, conducts experimental work on obtaining products of military-chemical importance (some asphyxiants) and on developing methods for obtaining pure platinum from Russian raw materials, and on behalf of the Central Laboratory of the Central Laboratory of the Navy Department participates in the development of a method for obtaining sodium azide;
Autumn 1916 - the Military Chemical Committee sent as a specialist in chemistry as the head of sanitary and evacuation part in the "Urmiyskaya Expedition for the survey of boron-acid springs of the Kara region and the Urmiysky lake area";
1916 - member of the Commission for the Study of the Natural Productive Forces of Russia (CNPF);
1917 - until the liquidation of the Committee for Military Labor Assistance - secretary of its Chemical Division and chairman of the Commission on Luminous Compounds; in October participated in the work of the Congress on Technical Defense of the State; assistant at the Department of General Chemistry I of Petrograd University (until 1924);
1918-1919 - in summer he was elected Commissioner of the Board formed under the NPFR for the organization of the first Radium Plant in Russia. V. G. Khlopin was entrusted with the general management of issues related to the chemical and administrative side of the case; in December he was elected as a representative of CNPF to the Council of the Radium Association; from January 1919 he was a member of the Council of the Chemical Division of the Russian Technical Society; from July 1918 to September 1919 he was a member of the Council of the Platinum Institute;
1918-1934 - member of the editorial board of the Chemical-Technical Publishing House, later transformed into the publishing house Chemteoret;
1920 - elected Professor of the Department of General Chemistry at the Ural State University (unable to travel to the Urals, he was forced to give up his position);
1921 - on December 1, V. G. Khlopin obtained the first highly active preparations of domestic radium;
1922-1934 - Head of the gas department of NPFR, - Geochemical Institute of the USSR Academy of Sciences (Leningrad);
1922 - began research at the Radium Institute in Petrograd (Leningrad);
1922-1935 - deputy director and head of the chemical department; from 1924 (simultaneously at the Leningrad University) he headed the gas department of the Geochemical Institute of the USSR Academy of Sciences and the Helium Laboratory of the Soyuzgaz Trust;
1924 - V. G. Khlopin suggested the idea that the process of fractional crystallization is caused by the distribution of matter between two immiscible phases (crystals and saturated solution) - the law of microcomponent distribution between liquid and solid phases (Khlopin's law); since summer he has been holding meetings with students of the Physics and Mathematics Faculty of Moscow State University;
1924-1930 - associate professor at Leningrad State University;
1924-1933 - member of the Scientific and Technical Council on Helium at the Helium Committee of the Supreme Council of National Economy; took an active part in the search and study of helium deposits and the development of analytical methods for determining helium;
1925 - at the IV Mendeleev Congress made a report on "Achievements in the field of radioactive substances in the USSR"; scientific trip to Germany;
1928-1934 - member of the Committee for the Chemicalization of the National Economy under the Council of People's Commissars of the USSR (hereinafter - under the Presidium of the USSR State Planning Committee);
1929, 1930 - Head of hydrochemical works of the Alagez Party of the USSR Academy of Sciences;
1930-1936 - permanent consultant on radium industry at the plant "Rare Elements" (existed until 1931, since 1931 Giredmet was established on its basis) of Soyuzredmet (then Glavredmet);
1931, 1932 - Scientific Director of the Geochemical Institute of the USSR Academy of Sciences;
1933 - Corresponding Member of the USSR Academy of Sciences; member of the Scientific and Technical Council on Helium at the USSR State Planning Committee;
1933-1938 - consultant of the laboratory of the Soyuzgaz Trust, later Heliogazrazvedka (Leningrad);
1934-1937 - professor at the Leningrad State University;
1935 - approved by the Presidium of the USSR Academy of Sciences with the degree of Chemistry Philosophy Doctor;
1936-1946 - Director of the Radium Institute of the USSR Academy of Sciences (Leningrad);
1937 - pays much attention to the study of the chemical nature of products of artificial decay of uranium and thorium, which became possible due to irradiation of their preparations at the cyclotron launched at the Radium Institute - the first in Europe;
1938 - consultant to the State Institute of Rare and Minor Metals of the People's Commissariat for Rare and Minor Metals (Moscow);
1939 - full member of the USSR Academy of Sciences;
1940 - Chairman of the Committee on Uranium Problem at the Presidium of the USSR Academy of Sciences;
1941, 1942 - in evacuation in Kazan, directed the activities of the Radium Institute; Deputy Chairman of the USSR Academy of Sciences Commission for Mobilization of Volga Region Resources; Deputy Academician-Secretary of the Chemical Department of the USSR Academy of Sciences;
1943 - Stalin Prize of the third degree for the development of a method of industrial production of radium;
1945 - in Leningrad University V. G. Khlopin headed the first in the USSR chair of radiochemistry, where he gave the first in the Soviet Union course of lectures on radioactivity - the training of a new generation of radiochemists for research organizations and nuclear industry began;
1947 - V. G. Khlopin and E. K. Gerling developed a new method for determining geologic age by xenon accumulated during spontaneous uranium fission.
He died on July 10, 1950, and was buried in Leningrad, on the Necropolis of the Masters of Arts of the Alexander Nevsky Lavra[14].
Family
Father - Grigory Vitalievich Khlopin (1863-1929).
Mother - Ekaterina Alexandrovna, née Kavaderova (1865-1945) - a graduate of the Higher Women's Courses in St. Petersburg (verbal-historical and physical-mathematical faculties), was engaged in journalism. (at the time of G. V. Khlopin's exile to the Urals in 1886), from 1905, when the Khlopins lived already in St. Petersburg, Ekaterina Alexandrovna was engaged in charity work. She died on the road during the re-evacuation of the State Radium University from Kazan to Leningrad.
Brother - Nikolai Grigorievich Khlopin, a histologist.
Khlopin was first married to Nadezhda Pavlovna Annenkova (daughter of the Narodovtsy P. S. Annenkov[clarification]).
A daughter (born 1913), whom they baptized in a church in Kuokkala.
In 1920 he married Maria Alexandrovna Pasvik.
Scientific works
V. G. Khlopin began his independent scientific activity as a student in 1911 - in his father's laboratory at the Clinical Institute he carried out work, the results of which were published in the article "On the formation of oxidants in the air under the action of ultraviolet rays".
In these studies V. G. Khlopin first proved the formation in atmospheric air under the action of ultraviolet rays not only hydrogen peroxide and ozone, but also nitrogen oxides, the latter statement began a long discussion that lasted until 1931, when D. Vorländer () proved the correctness of the observations of V. G. Khlopin.
The circle of V. G. Khlopin's interests is not strictly confined to any one area. It is determined by the school, which he passed under the guidance of L. A. Chugaev and V. I. Vernadsky, respectively - in general chemistry and geochemistry, which, in turn, allowed V. G. Khlopin to develop his own scientific direction - to create the first domestic school of radiochemists.
Working with L. A. Chugaev
At the initial stage of his research activity (1911-1917), V. G. Khlopin was mainly concerned with problems related to inorganic and analytical chemistry. In 1913, together with L. A. Chugaev, he worked on the synthesis of complex compounds of platonitrite with dithioethers. Of his further works, especially important are those aimed at the development of a new method for the preparation of various derivatives of univalent nickel, and the creation of a device for determining the solubility of compounds at different temperatures.
To the most interesting works of this period belongs the discovery of hydroxopentamine series of complex compounds of platinum made in 1915 by L. A. Chugaev and V. G. Khlopin; curiously, but methodologically, from the point of view of the theory of cognition, it is quite natural that historically it was made somewhat earlier than the discovery by L. A. Chugaev and N. A. Vladimirov of the pentamine series, later called Chugaev's salts.
Two works hold a special place in this period of V. G. Khlopin's scientific work:
1. The action of hydrosulfur sodium salt on metallic selenium and tellurium, leading to the development of a convenient method of obtaining sodium telluride and selenide and a convenient synthesis of organic compounds of tellurium and selenium (1914),
2. On the action of hydrosulfurosodium salt on nickel salts in the presence of nitrous sodium salt. The work led to the synthesis of univalent nickel derivatives (1915), which were much later (in 1925) obtained in Germany by S. Mansho and co-workers by the action of carbon monoxide and nitric oxide on nickel salts.
Here, at the same department, already in the First World War, on the assignment of the Chemical Committee of the Main Artillery Department, V.G. Khlopin performed his first technological work - he developed a method of obtaining pure platinum from Russian raw materials. The importance of this work was due to the sharp reduction of imports. His participation in several expeditions aimed at identifying Russia's natural resources was subordinated to the solution of the same problems. He wrote reviews on rare elements: boron, lithium, rubidium, cesium and zirconium.
At V. I. Vernadsky’s laboratory
All of V.G. Khlopin's further scientific activity was predetermined by this meeting. In the laboratory founded by Vladimir Ivanovich Vernadsky, a systematic study of radioactive minerals and rocks was carried out, the search for which in Russia was carried out by expeditions, also organized on his initiative. V. I. Vernadsky was the first Russian scientist who realized the importance of the discovery of radioactivity: "...For us it is not completely indifferent at all how radioactive minerals of Russia will be studied... Now, when mankind is entering a new age of radiant - atomic energy, we, and not others, should know, should find out what the soil of our native country holds in this respect".
In 1909 V. I. Vernadsky headed the research of radioactivity phenomena in Russia, under his chairmanship the Radium Commission was organized - all the works were united under the auspices of the Academy of Sciences, the Radiological Laboratory was founded, since 1914 the publication of the "Proceedings of the Radium Expedition of the Academy of Sciences" was started. In the mentioned speech V. I. Vernadsky notes the specific features of the new direction of scientific research: "This discovery has produced a huge revolution in the scientific outlook, caused the creation of a new science, different from physics and chemistry - the doctrine of radioactivity, put before life and technology practical tasks of a completely new kind...".
In 1915, V. I. Vernadsky attracted V. G. Khlopin to work in the Radiological Laboratory. V. G. Khlopin was destined to become the first, and for many years - the leading specialist in the new discipline. But research in the field of radioactivity, study of new radioactive elements already discovered in Russia at that time was still in the state of initial organizational period - there were no domestic radium preparations for laboratory experiments; however, deposits of minerals and ores - raw materials for consistent development of scientific work in this direction, systematic study of radioactive minerals - were already known. The leading experts of the profile - Professors K. A. Nenadkevich and A. E. Fersman - were invited to participate in the present work.
In the context of mastering the fundamental areas of activity, which for V.G. Khlopin became his life's work, he develops research of scientific and applied aspects, including methods of geochemistry of radioactive elements and noble gases, analytical chemistry and thermodynamics; at the same time, the scientist develops an independent direction, which gave the preconditions for the formation of a scientific school. By the early 1920s, four main lines had emerged, which in turn led to the establishment of an independent school:
1. radium technology;
2. chemistry of radioelements and applied radiochemistry;
3. geochemistry of radioelements and noble gases;
4.analytical chemistry.
First trial radium plant
In 1917, the purely scientific interest in the study of radium was replaced by the practical need to use it for military purposes - the military department and defense organizations received information that radium was used for the production of light compounds. The necessity of radium extraction from domestic raw materials became urgent. A large batch of radium-containing ore from the Tyuya-Muyun deposit was stored in the warehouse of a private commercial firm "Fergana Society for Rare Metals Mining". This organization, due to the lack of specialists-radiochemists in Russia, was preparing the raw material for shipment to Germany for technological extraction of the final product from it, but the war and then the February Revolution of 1917 prevented this.
The Congress for the Technical Defense of the State in October 1917 decided to organize a special radium plant under the direct control of the Academy of Sciences, but the October Socialist Revolution again removed this issue from the queue. In January 1918 V. G. Khlopin published an article "A Few Words on the Application of Radioactive Elements in Military Technology and on the Possible Future of the Radium Industry in Russia", in which he characterized the importance and prospective use of radium for military-strategic purposes. In the spring of the same year, the Presidium of the All-Russian Council of National Economy (RCNE) decided to sequester radioactive raw materials belonging to the "Fergana Society"; in April, the Chemical Department of the RCNE, headed by Prof. L. Ya. Karpov, entrusted the Academy of Sciences with the mission of organizing a plant for radium extraction from domestic uranium-vanadium ores and ensuring scientific control over production; at a meeting of specialists convened on 12 April by the Commission for the Study of the Natural Productive Forces of Russia (NPFR), headed by N. S. Kovalev. С. Kurnakov, V. G. Khlopin and L. I. Bogoyavlensky it was reported on the results of the work undertaken to obtain radium from the available raw materials; in July 1918 a special Commission, the Technical Council or later the Board for the organization of a radium plant at the Academy of Sciences was elected, which decided to organize a research laboratory, a special Radium Department (under the Commission) headed by V. I. Vernadsky was established under the chairmanship of A. E. Fersman, senior mineralogist of the Academy of Sciences, professor of the Higher Women's Courses. The secretary of the department, a specialist of the Radium Laboratory of the Academy, an assistant of the Department of General Chemistry of the Petrograd University, 28-year-old V. G. Khlopin, was appointed its commissioner for the organization of the radium plant. His thorough theoretical training and mastery of the methods of fine chemical analysis, his ability to solve practical problems effectively, and his experience in expeditions fully justified his involvement in such a responsible business. L. N. Bogoyavlensky, a specialist on this subject, was invited as the head of the plant.
"October 28, 1918.Uralsovnarkhoz (Perm), Usolsk executive committee, Management of Berezniki soda plant. «I order the Berezniki plant to immediately begin work on the organization of a radium plant according to the resolution of the Vysovnarkhoz. The necessary funds have been allocated by the Council of People's Commissars. The work should be carried out under the direction and responsibility of chemical engineer Bogoyavlensky, to whom I propose to render full assistance. Chairman of the Council of People 's Commissars Lenin»".
Lenin V. I. Complete Collected Works, vol. 50, p. 375.
In 1918, all radioactive residues that were in Petrograd were evacuated inland - first to the Berezniki soda plant in Perm province, and in May 1920, already by the new plant manager I. Ya. Bashilov, - to the Bondyuzhsky chemical plant of Khimosnov (now Khimzavod named after L. Y. Karpov in Mendeleevsk), where only in the fall of 1920 it became possible to put into operation a temporary pilot plant for radium extraction.
Radioactive substances technology
V. G. Khlopin developed a method of mechanical enrichment to improve the quality of raw barium-radium sulfates rich in silica (together with engineer S. P. Alexandrov). Later, the scientist transformed the Curie-Debierne method of conversion of sulfates into carbonates under the condition of saturation of sulfates with silica - through the combination of soda with caustic soda (together with P. A. Volkov).
On the basis of theoretical assumptions, V. G. Khlopin proposed several methods of fractional crystallization of barium-radium salts, excluding evaporation of solutions - by increasing the concentration of the same ion in the cold: fractional precipitation of chlorides with hydrochloric acid (1921), fractional precipitation of bromides (together with M. A. Pasvik, 1923), fractional precipitation of nitrates (with P. I. Tolmachev, with A. P. Ratner, 1924-1930). A. Pasvik, 1923), fractional precipitation of nitrates (with P. I. Tolmachev, with A. P. Ratner, 1924-1930), fractional precipitation of chromates (M. S. Merkulova), fractional precipitation of chlorides with zinc chloride (I. Y. Bashilov and Y. S. Vilnyansky, 1926).
In 1924, V. G. Khlopin created a general theory of the fractional crystallization process, which greatly facilitated the calculation of the technological process in general and the development of the required apparatus for its implementation in particular. A number of versions of the conventional crystallization scheme were hereby based on calculations used in plant practice. Later this theory was applied and developed in the All-Russian Research Institute of Chemical Reagents and Particularly Pure Chemicals for obtaining chemically pure substances by recrystallization.
Chemistry of radio elements and applied radiochemistry
In this field, V. G. Khlopin and his colleagues and students (M. S. Merkulova, V. I. Grebenshchikov and others) developed a methodology for studying the process of isomorphous coprecipitation of microcomponents and ways to achieve equilibrium in the solid phase-solution system, - the influence of many factors on this process was established and the hypothesis of V. G. Khlopin (1924) about the subordination of the process of fractional crystallization to the law of substance distribution between two immiscible phases was proved (Khlopin's law). The possibility of using the method of isomorphic co-crystallization not only for the isolation of radioactive elements, but also for the study of their state in liquid and solid phases - for determining their valence was shown. V. G. Khlopin and A. G. Samartseva established the existence of compounds of divalent and hexavalent polonium by this method. The process of adsorption of crystalline precipitates by the surface was also studied, - the distribution between the gas phase and crystalline precipitate, as well as between the salt melt and the solid phase.
Thus, in this section, V. G. Khlopin's studies address the following key issues:
1. conditions for achieving true (thermodynamic) microcomponent equilibrium between the crystalline solid phase and solution;
2. the use of radioelements as indicators in determining the mechanism of isomorphic substitution of dissociated ions;
3. application of general laws of isomorphous substitution for development of a method for fixation of chemical compounds present in extremely small proportions and unstable in the solid phase, establishment of their valence and chemical type, - for revealing new chemical equilibria both in the solid phase and in solution;
4. conditions of adsorption equilibrium between solid crystalline phase and solution.
Thermodynamic equilibrium of microcomponent
It has been rigorously experimentally established that:
a) When a true (thermodynamic) equilibrium is reached between a crystalline solid phase (electrolyte) and a solution, the microcomponent present in the solution and isomorphic with the solid phase is distributed between the two immiscible solvents according to the Berthelot-Nernst law and at that in all known cases in its simple form: Ск/Ср=К or
where x is the amount of microcomponent transferred into crystals, a is the total amount of microcomponent, y and b are the corresponding values for macrocomponent.
b) The mechanism responsible for achieving true equilibrium between the crystalline phase and the solution is reduced to the process of multiple recrystallization of the solid phase, that replaces in the considered case practically absent under ordinary conditions the diffusion process in the solid state. Recrystallization at submicroscopic sizes of crystals proceeds extremely fast, thus in crystallization from supersaturated solutions recrystallization and establishment of equilibrium are finished at the stage when crystallites are small enough.
c) In the case of slow crystallization not from supersaturated solutions, but from saturated ones, in particular, due to slow evaporation, the true equilibrium between crystals and solution is not observed, and the distribution of the microcomponent between the solid phase and solution proceeds in this case according to the logarithmic law of Goskins and Derner, developed on the basis of the idea of continuous ion exchange between the faces of the growing crystal and the solution
Here, as above: a is the total amount of microcomponent, x is the amount of microcomponent transferred to the solid phase, b is the total amount of macrocomponent, y is the amount of macrocomponent transferred to the solid phase.
d) An abrupt change in the value of D with a change in temparature or in the composition of the liquid phase is an indicator of the occurrence of a new chemical equilibrium in solution or in the solid phase.
The case of distribution of the microcomponent between the crystalline solid phase and the solution (according to the Berthelot-Nernst or Goskins and Derner law) can serve as evidence for the formation between the microcomponent and the anion or cation of the solid phase of compounds crystallizing isomorphically with the solid phase.
Radioactive elements as indicators
Radioactive elements (Ra and RaD) were used by V. G. Khlopin and B. A. Nikitin as indicators in determining the nature of a new kind of mixed Gramm crystals. These studies showed a fundamental difference between true mixed crystals in the spirit of Eilhard Mitscherlich, when the substitution of one component for another is expressed in the form of ion for ion, or atom for atom, molecule for molecule, and mixed crystals of a new kind, in which such a simple substitution is impossible, and proceeds by means of very small sizes of the ready sections of the crystal lattice of each component. Scientists have shown that mixed crystals of a new kind fundamentally differ from true mixed crystals by the presence of a low miscibility limit - they are not formed at low concentration of one of the components at all. In this case, they are similar to anomalous mixed crystals (as shown experimentally by V. G. Khlopin and M. A. Tolstaya), and relate to the latter approximately as a colloidal solution with suspension. These works (on the structure and properties of mixed crystals of a new kind and anomalous mixed crystals) led V. G. Khlopin to the idea of the need to classify isomorphic bodies not by considering the structure of isomorphic mixtures in static equilibrium (as it was done, for example, by V. G. Goldschmidt and his school), but according to the methods of substitution of components - taking into account the dynamics of the formation of an isomorphic mixture. In this case, all isomorphic bodies are strictly divided into two groups according to the method of substitution:
(a) Isomorphic compounds in the spirit of E. Mitscherlich, truly isomorphic. Substitution in the formation of mixed crystals by such compounds occurs according to the first principle: ion on ion, etc. The above distribution laws apply to such crystals. Such compounds have similar chemical composition and molecular structure.
(b) All other isomorphic compounds, when the formation of mixed crystals is conditioned by the second principle: substitution of sites from the unit cell or close to them (mixed crystals of a new kind or isomorphic of the 2nd kind according to W.G. Goldschmidt), up to microscopic - anomalous mixed crystals such as FeCl2 — NH4Cl, Ba(NO3)2, Pb(NO2)2, methylene blue K2SO4 - Ponsorot, etc., showing heterogeneity).
3.Thanks to the works discussed in the previous two paragraphs, V. G. Khlopin was able to present in a new form the law of E. Mitscherlich, which makes it possible to judge the composition and molecular structure of unknown compounds on the basis of their formation of isomorphous mixtures with compounds whose composition and molecular structure are known. V.G. Khlopin proposed the method of isomorphous co-crystallization from solutions for fixation of weightless and unstable chemical compounds and determination of their composition. The method made it possible to discover and determine the composition of individual compounds of divalent and hexavalent polonium (V. G. Khlopin and A. G. Samartseva).
4. Studying adsorption of isomorphous ions on the surface of crystalline precipitates, V. G. Khlopin showed that adsorption equilibrium is established in 20–30 minutes; adsorption of isomorphous ions does not depend on the charge of the adsorber surface when its solubility does not change. Correctly reproducible results of adsorption study and full reversibility of this process are achieved only if the adsorber surface remains unchanged throughout the experiment - if the adsorber solubility remains unchanged; in case of changes in the liquid phase composition or under other additional conditions, when the adsorber solubility changes, adsorption acquires a more complex character, which is accompanied by co-crystallization distorting the results. Studying the adsorption kinetics, a similar phenomenon was encountered by L. Imre. V. G. Khlopin gave a formula for determining the surface of crystalline precipitates by adsorption of an isomorphic ion on them and experimentally confirmed its applicability (V. G. Khlopin, M. S. Merkulova).
Geochemistry of radioelements and noble gases
In this field, the following directions were developed in V. G. Khlopin's works:
1. radioelements migration, in particular - relatively short-lived in the Earth's crust;
2. study of radium-mesothorium containing waters;
3. Determination of geologic age on the basis of radioactive data;
4. distribution of helium and argon in natural gases of the country;
5. effects of natural waters in geochemistry of noble gases;
6. distribution of boron in natural waters.
Radioelements migration
The scientist was the first to draw attention to the special importance of studying the migration of relatively short-lived radioelements in the Earth's crust for solving general geological and geochemical problems (1926). V. G. Khlopin pointed out a number of questions of these disciplines, which imply solution by the proposed methods: determination of sequence in geological and geochemical processes, determination of absolute age of relatively young and very young geological formations, and a number of other thematic areas. Migrations of uranium and radium were subjected to experimental study.
Radioactive water studies
Extensive studies relating to the establishment of the presence of radium, uranium, and decay products of the thorium series in natural brines of the Soviet Union were carried out under the direction of V. G. Khlopin; numerous expeditions revealed a new form of accumulation in nature of radium and its isotopes in brine waters of the Na, Ca, and Cl types. The following of his students and colleagues participated in these studies: V. I. Baranov, L. V. Komlev, M. S. Merkulov, B. A. Nikitin, V. P. Savchenko, A. G. Samartseva, N. V. Tageev, and others.
Determination of geologic age by radiometric method
These works concern, on the one hand, consideration of the basics of the method and analysis of the nature of errors, and, on the other hand, experimental determination of the age of uranites from different pegmatite veins both by the uranium/lead ratio and by Lan's oxygen method, which was developed and refined in the works of V.G. Khlopin. The scientist supervised research in this direction in the Radium Institute - on helium and lead methods, which gave the determination of the geologic age of some formations. The work (with E. K. Gerling and E. M. Ioffe) on helium migration from minerals and rocks and the influence of the gas phase on this process should be attributed to this cycle.
Helium and argon distribution in natural gases of the USSR
V. G. Khlopin began to study the distribution of helium in freely emitting gases of the country in 1922-1923. In 1924, he and A. I. Lakashuk discovered helium in the gases of the Novouzensky district of Saratov province; and in the period from 1924 to 1936, V. G. Khlopin and his students (E. K. Gerling, G. M. Ermolina, B. A. Nikitin, I. E. Starik, P. I. Tolmachev, and others) analyzed many samples of natural gases and created a distribution map based on the data. For the first time a new type of gas jets in the Kokand area, called "air jets" and characteristic of wide mountain basins (1936), was identified.
Natural waters and geochemistry of noble gases
The works of the present direction were a direct consequence of the previous section, on the basis of which V.G. Khlopin came to the concept of continuous gas exchange between inner and outer gas atmospheres, about the role of natural waters, in a particular case - in the exchange of noble gases (excluding helium) between outer air and underground atmospheres. In accordance with these ideas in underground gas atmospheres there is a gradual enrichment of argon, krypton and xenon, - depletion of neon in relation to their content in the air. Relation
in underground atmospheres is greater than in air. It has been found that gases dissolved in the lower layers of deep natural reservoirs are sharply enriched with heavy noble gases.
Boron in natural waters
The beginning of this direction of geochemistry was the work on boron-acid springs in northwestern Persia and Transcaucasia; later these studies were extended to other areas of the USSR. It was found that boron is a typical element in the waters of oil-bearing areas, enriched in them. V.G. Khlopin also for the first time noted the need for prospecting boron-acid compounds in the Embinsky and Gurievsky counties of the Ural region, where much later the Inderskoye field was discovered.
Analytical chemistry
V. G. Khlopin’s work in this area concerns gas, volumetric, gravimetric and colorimetric analysis.
Gas analysis. V. G. Khlopin developed instruments for rapid assessment of the amount of helium and neon in gas mixtures (V. G. Khlopin, E. K. Gerling, 1932). These devices have simplified the analysis of noble gases so much that they have made it possible to include it in the general method of gas analysis.
Volumetric analysis. For the first time in the USSR, V. G. Khlopin introduced the method of differential reduction and differential oxidation with the simultaneous determination of several cations in a mixture (1922) and experimentally mastered the simultaneous determination of vanadium, iron and uranium - volumetric methods for the determination of vanadium and uranium were proposed.
Gravimetric analysis. V. G. Khlopin developed a quantitative method for separating tetravalent uranium in the form UF4NH4F1/2H2O from hexavalent uranium and trivalent and divalent iron.
Colorimetric analysis. Scientists have proposed a method for determining small amounts of iridium in the presence of platinum.
Under the leadership of V.G. Khlopin, several methods of analysis were also developed: a volumetric method for determining small amounts of boron, a volumetric method for determining SO4^2- and Mg^2+, gravimetric methods for determining uranium, a colorimetric method for determining fluorine, and others.
The Uranium Problem and the Atomic Project
In the process of studying natural radioactivity - studying the radiation of radioactive elements and radioactive transformations, new natural radioactive elements were discovered, systematized in radioactive groups - uranium and thorium, which include the third, so-called actinium family - actinides (this name was proposed by S. A. Shchukarev). F.Soddy's discovery of the law of radioactive displacements made it possible to assume that the final stable decay products of elements of all three families are three isotopes of the same element - lead.
The Bohr model of the atom is based on the study of natural radioactivity, which showed the complexity of the structure of the atom, the decay of which produces atoms of other elements, which is accompanied by three types of radiation: α, β и γ.
The neutron-proton theory of the structure of the atomic nucleus owes its origin to the discovery of new elementary particles that make up the nucleus: the neutron (10n) and the proton (11p), which became possible by the artificial splitting of the atom under the influence of α-particles (1919): 147N+42He→178O+11H, accompanied by the release of a proton (soon experiments were carried out with a number of other light elements).
Further fundamental research in this area showed that in light elements the number of neutrons in the nucleus is equal to the number of protons; and as we move to heavy elements, neutrons begin to dominate over protons, and the nuclei become unstable - they become radioactive.
As part of the atomic project, he was a member of the technical council and was responsible for the activities of the radium institute. Through the efforts of V.G. Khlopin and the First Secretary of the Leningrad Regional Committee and City Committee of the All-Union Communist Party of Bolsheviks, Alexey Kuznetsov, the Radium Institute received additional premises. The decision to allocate space was made by the Special Committee in November 1945, carried out by the chairmen of the Operations Bureau of the Council of People's Commissars of the RSFSR A. N. Kosygin and the representative of the State Planning Committee in the Special Committee N. A. Borisov.
Pedagogical, administrative, social and editorial activities
After graduating from St. Petersburg University, V. G. Khlopin was left at the department of Professor L. A. Chugaev, but while still a student, in 1911 he conducted a workshop on the chemical methods of sanitary analyzes with doctors at the St. Petersburg Clinical Institute, and continued this course of practical training in 1912 and 1913.
From 1917 to 1924, V. G. Khlopin served as an assistant in the department of general chemistry at the university, and from 1924, as an assistant professor, he began teaching a special course on radioactivity and the chemistry of radioelements - the first in the USSR; since brief and incomplete data and summaries existed only in foreign literature, this course was completely developed by V. G. Khlopin, who taught it until 1930, and resumed in 1934 as a professor, teaching it until 1935. In the spring of 1945, the scientist organized and headed the department of radiochemistry at Leningrad University.
Developed by V. G. Khlopin in collaboration with B. A. Nikitin and A. P. Ratner, a course of lectures on radiochemistry formed the basis of an extensive monograph on the chemistry of radioactive substances.
V. G. Khlopin took an active part in the work of the Russian Physical-Chemical Society, and after the latter was transformed into the All-Union Chemical Society, he was a member of the Council of the Leningrad branch of the organization, and later was its chairman.
At the Academy of Sciences, V. G. Khlopin was a member of the Analytical Commission, the Commission on Isotopes, and the Commission for the Development of the Scientific Heritage of D. I. Mendeleev. From 1941 to 1945, V. G. Khlopin, as Deputy Academician-Secretary, did a lot of work in the Department of Chemical Sciences of the USSR Academy of Sciences. During the Eastern Front (World War II), V. G. Khlopin served as deputy chairman of the Commission for the Mobilization of Resources of the Volga and Kama Region and chairman of its chemical section.
For many years he was a member of the Editorial Council of the Chemical-Technical Publishing House (Khimteoret). The scientist was the executive editor of the journal Uspekhi Khimii and was on the editorial boards of the journals: “Reports of the USSR Academy of Sciences”, “Izvestia of the USSR Academy of Sciences (Department of Chemical Sciences)”, “Journal of General Chemistry” and “Journal of Physical Chemistry”.
Vitaly Grigorievich Khlopin trained students in all the most important areas of scientific activity, many of whom became not only independent scientific researchers, but also the creators of their own scientific directions and schools.
Awards and scientific recognition
Hero of Socialist Labor (10/29/1949);
three Orders of Lenin (10.6.1945; 21.3.1947; 29.10.1949);
Stalin Prize of the third degree (1943) - for the development of a method for the industrial production of radiothorium
Stalin Prize of the first degree (1946) - for scientific research in the field of chemistry of radioactive substances, the results of which are presented in the articles: “Radioactive methods for determining the absolute surface of crystalline suspensions”, “Adsorption of radium on lead sulfate”, “Transformation of elements and the periodic law” (1939 —1944)
Stalin Prize, first degree (10/29/1949) - scientific director of the development of the technological process for separating plutonium from uranium metal at plant "B"
Small Prize of D. I. Mendeleev for work on radium (1924);
Honored Scientist of the RSFSR (1940);
The first Mendeleev's reader (1941).
Addresses in St. Petersburg
1922-1941, 1945-1950 - Roentgen street, 3;
1922-1941, 1945-1950 - Kamennoostrovsky Avenue, 23;
1908-1941, 1945-1949 - Universitetskaya embankment, 7;
1913-1941 - Bolshaya Zelenina street, 13;
1945-1950 - Lesnoy Avenue, 61 (House of Specialists).
Memory
The following were named after V. G. Khlopin:
By resolution of the Presidium of the USSR Academy of Sciences, the Radium Institute was named after V. G. Khlopin (1950).
The V. G. Khlopin Prize was established for the best work in the field of radiochemistry (1950).
Since 1970, the Radium Institute has held Khlopin readings on radiochemistry and the chemistry of rare elements.
Khlopin Street - in the Kalininsky district since 1972, from Polytechnicheskaya to Gzhatskaya streets.
Radium Institute named after. V. G. Khlopin - 2nd Murinsky Avenue, building 28;
Radium Institute named after. V. G. Khlopin (historical building) - Roentgen Street, building 1 (for more information about this building, see the article Roentgen Street).
Memorial plaques
Memorial plaque on the building of the Radium Institute
A memorial plaque was installed on the building at 3 Roentgen Street in 1952 (architect Z. M. Vilensky).
A memorial plaque was installed on the building at 23 Kamennoostrovsky Prospekt in 1990 (sculptor E. N. Rotanov, architect S. L. Mikhailov).
In 1996, a memorial plaque was installed on the building at 7 Universitetskaya embankment with erroneous dates in the text: “In this building, from 1908 to 1949, the outstanding scientist, organizer of the nuclear industry, founder of the Department of Radiochemistry V. G. Khlopin studied and worked.” (In 1941-1945 he was evacuated to Kazan.)
In the 1950s, a memorial plaque was installed on the house at 61 Lesnoy Avenue with the text: “The outstanding Russian chemist Vitaly Grigorievich Khlopin lived in this house from 1945 to 1950.”
References
Soviet chemists
1890 births
1950 deaths
Nuclear chemists
Full Members of the USSR Academy of Sciences | Vitaly Khlopin | [
"Chemistry"
] | 9,595 | [
"Nuclear chemists"
] |
69,531,997 | https://en.wikipedia.org/wiki/Magnetic%20skyrmionium | In magnetic systems, excitations can be found that are characterized by the orientation of the local magnetic moments of atomic cores. A magnetic skyrmionium is a ring-shaped topological spin texture and is closely related to the magnetic skyrmion.
Topological charge
The topological charge can be defined as follows.
With this definition, the topological charge of a skyrmion can be calculated to be ±1. A magnetic skyrmionium is a topological quasi particle that is composed of a superposition of two magnetic skyrmions of opposite topological charge adding up to zero total topological charge. On this basis one can view the core of a skyrmionium as a skyrmion (yellow central disk in figure) with opposite charge compared to a bigger skyrmion (green disk) in which it is situated.
Different to magnetic skyrmions, that experience a transverse deflection under current driven motion known as the skyrmion Hall effect (similar to the Hall effect), magnetic skyrmioniums are expected to move parallel to electrical-drive currents. The current-driven motion of magnetic excitations is one example of the direct link between topological charge and a physical observable.
Theoretical predictions
Skyrmioniums have been the subject of numerous theoretical investigations. Besides theoretical predictions concerning the existence of skyrmioniums such as in the 2D Janus mono layer CrGe(Se,Te)3, a lot of research concentrated on their manipulation by electrical currents, spin currents or spin waves. So far, there is only little experimental evidence for the existence of magnetic skyrmioniums. One example is the observation of skyrmionium in a NiFe-CrSb2Te3 hetero-structure.
Potential applications
Magnetic excitations such as skyrmions or skyrmioniums are potential building blocks of next generation spintronic devices, which enable for instance neuromorphic computing.
References
Quasiparticles
Magnetism | Magnetic skyrmionium | [
"Physics",
"Materials_science"
] | 392 | [
"Quasiparticles",
"Subatomic particles",
"Condensed matter physics",
"Matter"
] |
69,533,402 | https://en.wikipedia.org/wiki/Anthony%20Kelly%20%28materials%20scientist%29 | Anthony Kelly CBE FRS (25 January 1929 — 3 June 2014) was a British materials scientist.
He joined the Crystallography Research Group in the Cavendish Laboratory in 1950, after completing his physics undergraduate degree at the University of Reading. In the 50s, he held positions at the University of Illinois, the University of Birmingham, and Northwestern University, before returning to Cambridge in 1959 as lecturer in the department of metallurgy.
In 1967, he moved to the National Physical Laboratory, where he worked first in the Division of Inorganic and Metallic Structure, and then in the Materials Group as deputy director. Whilst still involved with NPL, he served an extensive period as Vice Chancellor of the University of Surrey from 1975 to 1994. He returned to Cambridge in 1994 as a distinguished research fellow in the Department of Materials Science.
He was elected Fellow of the Royal Society in 1973, Fellow of the Royal Academy of Engineering in 1979.
References
1929 births
2014 deaths
Academics of the University of Cambridge
Alumni of the University of Reading
Fellows of the Royal Society
Fellows of the Royal Academy of Engineering
Materials scientists and engineers
People associated with the University of Surrey | Anthony Kelly (materials scientist) | [
"Materials_science",
"Engineering"
] | 225 | [
"Materials scientists and engineers",
"Materials science"
] |
69,536,196 | https://en.wikipedia.org/wiki/Julia%20Rice | Julia Elizabeth Rice (born 1960) is a British-American computational chemist who works for IBM Research at their Almaden Research Center in San Jose California. Her work their involves the study of nonlinear optics in the simulation of organic molecules, the development of the Mulliken software package for quantum chemistry, the management of scientific data, and connections to statistical mechanics.
Education and career
Rice was born on 10 July 1960 in Cambridge, England. She earned a bachelor's degree in mathematics and chemistry from Royal Holloway, University of London in 1981, winning the Martin Holloway Prize as that year's best honours finalist in her subject. She completed her Ph.D. in theoretical chemistry at the University of Cambridge in 1985, under the supervision of Nicholas C. Handy.
After postdoctoral research with Henry F. Schaefer III at the University of California, Berkeley, and a year as a research fellow of Newnham College, Cambridge, she joined IBM Research in 1988.
Recognition
In 2001 Rice was named a Fellow of the American Physical Society (APS), after a nomination from the APS Division of Computational Physics, "for pioneering the development of efficient algorithms for the analytic derivative method with electron correlation, and for the calculation of frequency dependent polarizabilities with accuracy comparable to experiment". She was elected to the IBM Academy of Technology in 2003, and is a member of the International Academy of Quantum Molecular Science.
References
External links
1960 births
Living people
British chemists
British women chemists
American chemists
American women chemists
Computational chemists
Alumni of Royal Holloway, University of London
Alumni of the University of Cambridge
Fellows of the American Physical Society
Members of the International Academy of Quantum Molecular Science | Julia Rice | [
"Chemistry"
] | 335 | [
"Computational chemistry",
"Theoretical chemists",
"Computational chemists"
] |
65,435,579 | https://en.wikipedia.org/wiki/Eran%20Rabani | Eran Rabani (Hebrew: ערן רבני) is an Israeli theoretical chemist. He is a professor of chemistry at the University of California, Berkeley, holding the Glenn T. Seaborg Chair in Physical Chemistry, and at the Tel Aviv University. Rabani serves as the director of The Sackler Center for Computational Molecular and Materials Science, and as a faculty scientist at the Lawrence Berkeley National Laboratory.
Education
Rabani received his B.Sc. in chemistry from the Hebrew University of Jerusalem in 1991. Under the supervision of Raphael David Levine, Rabani studied molecular Rydberg states, completing his PhD. in 1996. Having completed his post-doctoral fellowship at Columbia University in 1999 he joined the faculty of the School of Chemistry at the Tel Aviv University.
Career
Rabani's interest in the theory of nanomaterials rose during his post-doctoral stay in the group of Bruce J. Berne at Columbia University, studying the electronic properties of cadmium selenide nanocrystals. This work included the first application of the filter-diagonalization method for the study of electronic structure, as well as the first quantitative study interactions between nanocrystals. Later early work in Rabani's independent career included further the study of the latter, the highlight of which is the theoretical study of drying-induced self-assembly of nanocrystals.
Starting in 2012, Rabani has been working extensively with Roi Baer (Hebrew University of Jerusalem) and Daniel Neuhauser (University of California, Los Angeles) on applying stochastic methods for the study of the electronic structure of large systems, such as nanocrystals, including stochastic formulations of the random-phase approximation, second order Møller–Plesset perturbation theory and density functional theory. Such methods have allowed the calculation of GW self-energies of 10,000 electrons-large systems with linear scaling.
Rabani became a full professor at Tel Aviv University in 2008. In 2014 he joined the faculty of the department of chemistry at University of California, Berkeley and later the faculty of the Lawrence Berkeley National Laboratory in 2015. Rabani has held various positions, including serving as the Vice President for Research and Development at Tel Aviv University, where today he is the director of The Sackler Center for Computational Molecular and Materials Science. In 2015 Rabani joined the editorial board of the American Chemical Society journal Nano Letters as an associate editor.
Rabani has an h-index of 47 as of 2020, having published more than 230 papers which were cited more than 8600 times. Among his doctoral students throughout the years is Oded Hod, a faculty member at Tel Aviv University.
Awards
Source:
Visiting Miller Research Professorship, University of California, Berkeley 2010
Marie Curie IOF, 2010 - 2013
J.T. Oden Faculty Fellow, University of Texas, Austin 2009
Invited Professorship, Ecole Normale Superieure, Paris 2008 - 2009
The Michael Bruno memorial award, Yad Hanadiv, 2006
ICS Prize for Excellent Young Chemists, Israel Chemical Society, 2003
The Friedenberg Foundation Award, Israel Science Foundation, 2002
The Bergmann Memorial Research Award, United States-Israel Binational Science Foundation, 2000
The Yigal Alon Fellowship, The Israeli Council of Higher Education, 1999 - 2002
The Fulbright Postdoctoral Fellowship, 1997
The Rothschild Postdoctoral Fellowship, Yad Hanadiv, 1996
Community activity
Rabani served as a council member and the vice mayor of Har Adar between the years 2008–2010.
References
Israeli chemists
Hebrew University of Jerusalem alumni
Israeli nanotechnologists
Jewish scientists
Living people
Jewish chemists
1967 births
Academic staff of Tel Aviv University
Theoretical chemists
UC Berkeley College of Chemistry faculty | Eran Rabani | [
"Chemistry"
] | 762 | [
"Quantum chemistry",
"Theoretical chemistry",
"Theoretical chemists",
"Physical chemists"
] |
65,436,967 | https://en.wikipedia.org/wiki/Transition%20metal%20chloride%20complex | In chemistry, a transition metal chloride complex is a coordination complex that consists of a transition metal coordinated to one or more chloride ligand. The class of complexes is extensive.
Bonding
Halides are X-type ligands in coordination chemistry. They are both σ- and π-donors. Chloride is commonly found as both a terminal ligand and a bridging ligand. The halide ligands are weak field ligands. Due to a smaller crystal field splitting energy, the homoleptic halide complexes of the first transition series are all high spin. Only [CrCl6]3− is exchange inert.
Homoleptic metal halide complexes are known with several stoichiometries, but the main ones are the hexahalometallates and the tetrahalometallates. The hexahalides adopt octahedral coordination geometry, whereas the tetrahalides are usually tetrahedral. Square planar tetrahalides are known for Pd(II), Pt(II), and Au(III). Examples with 2- and 3-coordination are common for Au(I), Cu(I), and Ag(I).
Due to the presence of filled pπ orbitals, halide ligands on transition metals are able to reinforce π-backbonding onto a π-acid. They are also known to labilize cis-ligands.
Homoleptic complexes
Homoleptic complexes (complexes with only chloride ligands) are often common reagents. Almost all examples are anions.
1st row
2nd row
Some homoleptic complexes of the second row transition metals feature metal-metal bonds.
3rd row
Heteroleptic complexes
Heteroleptic complexes containing chloride are numerous. Most hydrated metal halides are members of this class. Hexamminecobalt(III) chloride and Cisplatin (cis-Pt(NH3)2Cl2) are prominent examples of metal-ammine-chlorides.
Hydrates
As indicated in the table below, many hydrates of metal chlorides are molecular complexes. These compounds are often important commercial sources of transition metal chlorides. Several hydrated metal chlorides are not molecular and thus are not included in this tabulation. For example the dihydrates of manganese(II) chloride, nickel(II) chloride, copper(II) chloride, iron(II) chloride, and cobalt(II) chloride are coordination polymers.
Adducts
Metal chlorides form adducts with ethers to give transition metal ether complexes.
References
Coordination chemistry
Coordination complexes
Inorganic compounds | Transition metal chloride complex | [
"Chemistry"
] | 527 | [
"Inorganic compounds",
"Coordination complexes",
"Coordination chemistry",
"Salts",
"Metal halides"
] |
78,358,012 | https://en.wikipedia.org/wiki/Isotryptamine | Isotryptamine, also known as 2-(1-indolyl)ethylamine, is a chemical compound and positional isomer of tryptamine (2-(3-indolyl)ethylamine).
A variety of isotryptamine derivatives, or substituted isotryptamines, have been developed, including serotonergic psychedelics and psychoplastogens like 6-MeO-isoDMT; non-hallucinogenic psychoplastogens like isoDMT, 5-MeO-isoDMT, and AAZ-A-154 (DLX-001); serotonin 5-HT2C receptor agonists like (S)-5,6-difluoro-isoAMT, Ro60-0175 ((S)-5-fluoro-6-chloro-isoAMT), and PNU-181731; serotonin 5-HT6 receptor modulators; and dual monoamine releasing agents and serotonin receptor agonists like isoAMT (PAL-569).
References
Serotonin receptor modulators | Isotryptamine | [
"Chemistry"
] | 244 | [
"Organic compounds",
"Organic compound stubs",
"Organic chemistry stubs"
] |
78,359,137 | https://en.wikipedia.org/wiki/Bioliteracy | Bioliteracy is the ability to understand and engage with biological topics. The concept is used particularly in the contexts of biotechnology and biodiversity.
Description
In the biotechnology context, bioliteracy is considered important for promoting the biotechnology industry and the development of biological engineering products. It has also been defined as "the concept of imbuing people, personnel, or teams with an understanding of and comfort with biology and biotechnology." The use in the context of biodiversity is somewhat distinct, focusing on improving awareness of different organisms with the goal of conservation.
Citizen science initiatives, such as iNaturalist, are considered effective ways to increase bioliteracy, engaging students with the direct observation of nature.
References
Biology
Biotechnology
Biodiversity
Biology terminology
Biological engineering
Literacy
Conservation biology | Bioliteracy | [
"Engineering",
"Biology"
] | 152 | [
"Biological engineering",
"Biotechnology",
"nan",
"Biodiversity",
"Conservation biology"
] |
78,360,430 | https://en.wikipedia.org/wiki/Protactinyl%20nitrate | Protactinyl nitrate, protactinium(V) oxynitrate, or erroneously known as protactinium nitrate, is a radioactive chemical compound with the formula PaO(NO3)3·xH2O (1.5 ≤ x ≤ 4). It is a white solid that readily hydrolyzes to protactinium(V) oxide in moist air. This compound is a common commercial source of protactinium.
Preparation and decomposition
Protactinyl nitrate was first prepared in 1966 by reacting protactinium(V) chloride or protactinium(V) bromide with fuming nitric acid. Lower concentrations of nitric acid cannot be used, due to the hydrolysis of the compound.
Protactinyl nitrate decomposes at 400 °C to protactinium(V) oxide.
References
Protactinium compounds
Nitrates | Protactinyl nitrate | [
"Chemistry"
] | 187 | [
"Oxidizing agents",
"Nitrates",
"Salts"
] |
78,360,967 | https://en.wikipedia.org/wiki/Dibromo%20neopentyl%20glycol%20diglycidyl%20ether | Dibromo neopentyl glycol diglycidyl ether is a brominated version of neopentyl glycol diglycidyl ether. It is an aliphatic organic chemical in the glycidyl ether family that is used in epoxy resin formulations. It has the molecular formula C11H18Br2O4
Synthesis
The usual method of synthesis is to take brominated neopentyl glycol and react with epichlorohydrin using Lewis acid catalysis to form the halohydrin. This species is then reacted with sodium hydroxide to form the diglycidyl ether.
Uses
A key use of the material is reducing the viscosity of epoxy resins. As an epoxy modifier it is classed as a reactive diluent, which may then be formulated into CASE applications (coatings, adhesives, sealants, and elastomers and composite materials). As it is an organobromine compound it is used to improve the Flame retardant properties of materials. Flame retardant coatings including powder coatings maybe produced.
Toxicity
There is a trend to try and formulate away from brominated species in general because of the toxicity of the smoke produced when heated.
Further reading
References
Reactive diluents
Bromine compounds
Glycidyl ethers
Flame retardants | Dibromo neopentyl glycol diglycidyl ether | [
"Chemistry"
] | 291 | [] |
78,365,422 | https://en.wikipedia.org/wiki/Mapping%20space | In mathematics, especially in algebraic topology, the mapping space between two spaces is the space of all the (continuous) maps between them.
Viewing the set of all the maps as a space is useful because that allows for topological considerations. For example, a curve in the mapping space is exactly a homotopy.
Topologies
A mapping space can be equipped with several topologies. A common one is the compact-open topology. Typically, there is then the adjoint relation
and thus is an analog of the Hom functor. (For pathological spaces, this relation may fail.)
Smooth mappings
For manifolds , there is the subspace that consists of all the -smooth maps from to . It can be equipped with the weak or strong topology.
A basic approximation theorem says that is dense in for .
References
Hirsch, Morris, Differential Topology, Springer (1997),
Algebraic topology | Mapping space | [
"Mathematics"
] | 181 | [
"Topology stubs",
"Fields of abstract algebra",
"Topology",
"Algebraic topology"
] |
78,369,920 | https://en.wikipedia.org/wiki/Gruppentheorie%20und%20Quantenmechanik | Gruppentheorie und Quantenmechanik, or The Theory of Groups and Quantum Mechanics, is a textbook written by Hermann Weyl about the mathematical study of symmetry, group theory, and how to apply it to quantum physics. Weyl expanded on ideas he published in a 1927 paper, basing the text on lectures he gave at ETH Zurich during the 1927–28 academic year. The first edition was published by in Leipzig in 1928; a second edition followed in 1931, which was translated into English by Howard P. Robertson. Dover Publications issued a reprint of this translation in 1950.
John Archibald Wheeler wrote of learning quantum mechanics from Weyl's book, "His style is that of a smiling figure on horseback, cutting a clean way through, on a beautiful path, with a swift bright sword." Edward Condon called the text "authoritative". Julian Schwinger said of it, "I read and re-read that book, each time progressing a little farther, but I cannot say that I ever – not even to this day – fully mastered it." The book was one of the first works to give a quantitative statement of the uncertainty principle, which Werner Heisenberg had previously introduced in a less precise way. Weyl credited the idea to Wolfgang Pauli. (Robertson, who later translated Weyl's book into English, cited the argument Weyl gave as the basis for his own generalization of the uncertainty principle to arbitrary noncommuting observables.) Moreover, it contains an early description of density matrices and quantum entanglement, and it uses what quantum information theory would later call the Weyl–Heisenberg group to give a finite-dimensional version of the canonical commutation relation.
Weyl noted that Paul Dirac's relativistic quantum mechanics implied that the electron should have a positively charged anti-particle. The only known particle with a positive charge was the proton, but Weyl was convinced that the anti-electron had to have the same mass as the electron, and physicists had already established that protons are much more massive than electrons. Weyl wrote, "I fear that the clouds hanging over this part of the subject will roll together to form a new crisis in quantum physics." The discrepancy was resolved in 1932 with the discovery of the positron.
References
External links
1950 edition at the Internet Archive (registration required)
Hermann Weyl and the Application of Group Theory to Quantum Mechanics by George Mackey
1928 non-fiction books
1931 non-fiction books
Group theory
Mathematics textbooks
Physics textbooks
Quantum mechanics
German-language non-fiction books
Translations into English | Gruppentheorie und Quantenmechanik | [
"Physics",
"Mathematics"
] | 539 | [
"Group theory",
"Fields of abstract algebra",
"Quantum mechanics",
"Works about quantum mechanics"
] |
63,909,474 | https://en.wikipedia.org/wiki/TEM-function | In petroleum engineering, TEM (true effective mobility), also called TEM-function is a criterion to characterize dynamic two-phase flow characteristics of rocks (or dynamic rock quality). TEM is a function of relative permeability, porosity, absolute permeability and fluid viscosity, and can be determined for each fluid phase separately. TEM-function has been derived from Darcy's law for multiphase flow.
in which is the absolute permeability, is the relative permeability, φ is the porosity, and μ is the fluid viscosity.
Rocks with better fluid dynamics (i.e., experiencing a lower pressure drop in conducting a fluid phase) have higher TEM versus saturation curves. Rocks with lower TEM versus saturation curves resemble low quality systems.
TEM-function in analyzing relative permeability data is analogous with Leverett J-function in analyzing capillary pressure data. Furthermore, TEM-function in two-phase flow systems is an extension of RQI (rock quality index) for single-phase systems.
Also, TEM-function can be used for averaging relative permeability curves (for each fluid phase separately, i.e., water, oil, gas, ).
See also
Lak wettability index
USBM wettability index
References
Petroleum engineering | TEM-function | [
"Chemistry",
"Engineering"
] | 278 | [
"Petroleum engineering",
"Energy engineering",
"Fluid dynamics stubs",
"Fluid dynamics"
] |
63,910,051 | https://en.wikipedia.org/wiki/Glycan-protein%20interactions | Glycan-Protein interactions represent a class of biomolecular interactions that occur between free or protein-bound glycans and their cognate binding partners. Intramolecular glycan-protein (protein-glycan) interactions occur between glycans and proteins that they are covalently attached to. Together with protein-protein interactions, they form a mechanistic basis for many essential cell processes, especially for cell-cell interactions and host-cell interactions. For instance, SARS-CoV-2, the causative agent of COVID-19, employs its extensively glycosylated spike (S) protein to bind to the ACE2 receptor, allowing it to enter host cells. The spike protein is a trimeric structure, with each subunit containing 22 N-glycosylation sites, making it an attractive target for vaccine search.
Glycosylation, i.e., the addition of glycans (a generic name for monosaccharides and oligosaccharides) to a protein, is one of the major post-translational modification of proteins contributing to the enormous biological complexity of life. Indeed, three different hexoses could theoretically produce from 1056 to 27,648 unique trisaccharides in contrast to only 6 peptides or oligonucleotides formed from 3 amino acids or 3 nucleotides respectively. In contrast to template-driven protein biosynthesis, the "language" of glycosylation is still unknown, making glycobiology a hot topic of current research given their prevalence in living organisms.
The study of glycan-protein interactions provides insight into the mechanisms of cell-signaling and allows to create better-diagnosing tools for many diseases, including cancer. Indeed, there are no known types of cancer that do not involve erratic patterns of protein glycosylation.
Thermodynamics of Binding
The binding of glycan-binding proteins (GBPs) to glycans could be modeled with simple equilibrium. Denoting glycans as and proteins as :
With an associated equilibrium constant of
Which is rearranged to give dissociation constant following biochemical conventions:
Given that many GBPs exhibit multivalency, this model may be expanded to account for multiple equilibria:
Denoting cumulative equilibrium of binding with ligands as
With corresponding equilibrium constant:
And writing material balance for protein ( denotes the total concentration of protein):
Expressing the terms through an equilibrium constant, a final result is found:
The concentration of free protein is, thus:
If , i.e. there is only one carbohydrate receptor domain, the equation reduces to
With increasing the concentration of free protein decreases; hence, the apparent decreases too.
Binding with aromatic rings
The chemical intuition suggests that the glycan-binding sites may be enriched in polar amino acid residues that form non-covalent interactions, such as hydrogen bonds, with polar carbohydrates. Indeed, a statistical analysis of carbohydrate-binding pockets shows that aspartic acid and asparagine residues are present twice as often as would be predicted by chance. Surprisingly, there is an even stronger preference for aromatic amino acids: tryptophan has a 9-fold increase in prevalence, tyrosine a 3-fold one, and histidine a 2-fold increase. It has been shown that the underlying force is the interaction between the aromatic system and the in carbohydrate as shown in Figure 1. The interaction is identified if the °, the distance (distance from to ) is less than 4.5Å.
Effects of stereochemistry
This interaction strongly depends on the stereochemistry of the carbohydrate molecule. For example, consider the top () and bottom () faces of -D-Glucose and -D-Galactose. It has been shown that a single change in the stereochemistry at C4 carbon shifts preference for aromatic residues from side (2.7 fold preference for glucose) to the side (14 fold preference for galactose).
Effects of electronics
The comparison of electrostatic surface potentials (ESPs) of aromatic rings in tryptophan, tyrosine, phenylalanine, and histidine suggests that electronic effects also play a role in the binding to glycans (see Figure 2). After normalizing the electron densities for surface area, the tryptophan still remains the most electron rich acceptor of interactions, suggesting a possible reason for its 9-fold prevalence in carbohydrate binding pockets. Overall, the electrostatic potential maps follow the prevalence trend of Trp >> Tyr > (Phe) > His.
Carbohydrate-binding partners
There are many proteins capable of binding to glycans, including lectins, antibodies, microbial adhesins, viral agglutinins, etc.
Lectins
Lectins is a generic name for proteins with carbohydrate-recognizing domains (CRD). Although it became almost synonymous with glycan-binding proteins, it does not include antibodies which also belong to the class.
Lectins found in plants and fungi cells have been extensively used in research as a tool to detect, purify, and analyze glycans. However, useful lectins usually have sub-optimal specificities. For instance, Ulex europaeus agglutinin-1 (UEA-1), a plant-extracted lectin capable of binding to human blood type O antigen, can also bind to unrelated glycans such as 2'-fucosyllactose, GalNAcα1-4(Fucα1-2)Galβ1-4GlcNAc, and Lewis-Y antigen.
Antibodies
Although antibodies exhibit nanomolar affinities toward protein antigens, the specificity against glycans is very limited. In fact, available antibodies may bind only <4% of the 7000 mammalian glycan antigens; moreover, most of those antibodies have low affinity and exhibit cross-reactivity.
Lambodies
In contrast with jawed vertebrates whose immunity is based on variable, diverse, and joining gene segments (VDJs) of immunoglobulins, the jawless invertebrates, such as lamprey and hagfish, create a receptor diversity by somatic DNA rearrangement of leucine-rich repeat (LRR) modules that are incorporate in *vlr* genes (variable leukocyte receptors). Those LRR form 3D structures resembling curved solenoids that selectively bind specific glycans.
A study from University of Maryland has shown that lamprey antibodies (lambodies) could selectively bind to tumor-associated carbohydrate antigens (such as Tn and TF) at nanomolar affinities. The T-nouvelle antigen (Tn) and TF are present in proteins in as much as 90% of different cancer cells after post-translational modification, whereas in healthy cells those antigens are much more complex. A selection of lambodies that could bind to aGPA, a human erythrocyte membrane glycoprotein that is covered with 16 TF moieties, through magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS) has yielded a leucine-rich lambody VLRB.aGPA.23. This lambody selectively stained (over healthy samples) cells from 14 different types of adenocarcinomas: bladder, esophagus, ovary, tongue, cheek, cervix, liver, nose, nasopharynx, greater omentum, colon, breast, larynx, and lung. Moreover, patients whose tissues stained positive with VLRB.aGPA.23 had a significantly smaller survival rate.
A close look at the crystal structure of VLRB.aGPA.23 reveals a tryptophan residue at position 187 right over the carbohydrate binding pocket.
Multivalency in structure
Many glycan binding proteins (GBPs) are oligomeric and typically contain multiple sites for glycan binding (also called carbohydrate-recognition domains). The ability to form multivalent protein-ligand interactions significantly enhances the strength of binding: while values for individual CRD-glycan interactions may be in the mM range, the overall affinity of GBP towards glycans may reach nanomolar or even picomolar ranges. The overall strength of interactions is described as avidity (in contrast with an affinity which describes single equilibrium). Sometimes the avidity is also called an apparent to emphasize the non-equilibrium nature of the interaction.
Common oligomerization structures of lectins are shown below. For example, galectins are usually observed as dimers, while intelectins form trimers and pentraxins assemble into pentamers. Larger structures, like hexameric Reg proteins, may assemble into membrane penetrating pores. Collectins may form even more bizarre complexes: bouquets of trimers or even cruciform-like structures (e.g. in SP-D).
Current Research
Given the importance of glycan-protein interactions, there is an ongoing research dedicated to the a) creation of new tools to detect glycan-protein interactions and b) using those tools to decipher the so-called sugar code.
Glycan Arrays
One of the most widely used tools for probing glycan-protein interactions is glycan arrays. A glycan array usually is an NHS- or epoxy-activated glass slides on which various glycans were printed using robotic printing. These commercially available arrays may contain up to 600 different glycans, specificity of which has been extensively studied.
Glycan-protein interactions may be detected by testing proteins of interest (or libraries of those) that bear fluorescent tags. The structure of the glycan-binding protein may be deciphered by several analytical methods based on mass-spectrometry, including MALDI-MS, LC-MS, tandem MS-MS, and/or 2D NMR.
Bioinformatics driven research
Computational methods have been applied to search for parameters (e.g. residue propensity, hydrophobicity, planarity) that could distinguish glycan-binding proteins from other surface patches. For example, a model trained on 19 non-homologous carbohydrate binding structures was able to predict carbohydrate-binding domains (CRDs) with an accuracy of 65% for non-enzymatic structures and 87% for enzymatic ones. Further studies have employed calculations of Van der Waals energies of protein-probe interactions and amino acid propensities to identify CRDs with 98% specificity at 73% sensitivity. More recent methods can predict CRDs even from protein sequences, by comparing the sequence with those for which structures are already known.
Sugar code
In contrast with protein studies, where a primary protein structure is unambiguously defined by the sequence of nucleotides (the genetic code), the glycobiology still cannot explain how a certain "message" is encoded using carbohydrates or how it is "read" and "translated" by other biological entities.
An interdisciplinary effort, combining chemistry, biology, and biochemistry, studies glycan-protein interactions to see how different sequences of carbohydrates initiate different cellular responses.
See also
Protein-protein interactions
Glycobiology
References
Glycoproteins
Monosaccharides
Oligosaccharides
Glycobiology
Protein–protein interaction assays | Glycan-protein interactions | [
"Chemistry",
"Biology"
] | 2,429 | [
"Biochemistry methods",
"Protein–protein interaction assays",
"Carbohydrates",
"Biochemistry",
"Monosaccharides",
"Oligosaccharides",
"Glycoproteins",
"Glycobiology"
] |
63,912,994 | https://en.wikipedia.org/wiki/Isoquinoline%20alkaloids | Isoquinoline alkaloids are natural products of the group of alkaloids, which are chemically derived from isoquinoline. They form the largest group among the alkaloids.
Isoquinoline alkaloids can be further classified based on their different chemical basic structures. The most common structural types are the benzylisoquinolines and the aporphines. According to current knowledge, a total of about 2500 isoquinoline alkaloids are known nowadays, which are mainly formed by plants.
Known examples
Occurrence in nature
The isoquinoline alkaloids are primarily formed in the plant families of Papaveraceae, Berberidaceae, Menispermaceae, Fumariaceae and Ranunculaceae.
The opium poppy, which belongs to the Papavaraceae family, is of great interest, since the isoquinoline alkaloids morphine, codeine, papaverine, noscapine and thebaine can be found in its latex. In addition to the opium poppy, there are other poppy plants, such as the celandine, in which isoquinoline alkaloids are found. Their latex contains berberine, which also occurs in other plant families, such as the Berberidaceae. An example of the Berberidaceae with the ingredient berberine is Berberis vulgaris.
The alkaloid tubocurarin is found in the hairy cartilage tree. There the Tubocurarin is extracted from the bark and roots.
Biological effect
In general, isoquinoline alkaloids can have different effects. The opium alkaloids may have sedative, psychotropic or analgesic properties. Morphine and codeine are indeed used as analgesics.
Papaverine, in contrast, has an antispasmodic effect if it comes from smooth muscles, as is the case in humans in the gastrointestinal tract or blood vessels. This is why it is used as an antispasmodic.
Tubocurarin impairs the transmission of stimuli in the nervous system, so that paralysis may occur in the affected organism.
References | Isoquinoline alkaloids | [
"Chemistry"
] | 440 | [
"Isoquinoline alkaloids",
"Alkaloids by chemical classification"
] |
63,915,831 | https://en.wikipedia.org/wiki/Ester%20H.%20Segal | Ester H. Segal is an Israeli nanotechnology researcher and professor in the Department of Biotechnology and Food Engineering at the Technion - Israel Institute of Technology, where she heads the Laboratory for Multifunctional Nanomaterials. She is also affiliated with the Russell Berrie Nanotechnology Institute at the Technion - Israel Institute of Technology. Segal is a specialist in porous silicon nanomaterials, as well as nanocomposite materials for active packaging technologies to extend the shelf life of food.
Education
Segal received her bachelor of science degree in chemical engineering from the Technion - Israel Institute of Technology in 1997. She earned her master of science degree and PhD from the Technion in polymer science.
Research and career
Segal competed her graduate research with Moshe Narkis at the Technion - Israel Institute of Technology, where she developed electrically conductive polymer systems and their application as sensors for volatile organic compounds. After completing her PhD in 2004, Segal was awarded the Rothschild Postdoctoral Fellowship and joined the group of Michael J. Sailor at the Department of Chemistry and Biochemistry at the University of California, San Diego from 2004 to 2007. There, she developed porous silicon nanomaterials for drug delivery and optical biosensing purposes. In 2007, She returned to Israel and joined the Department of Biotechnology and Food Engineering at the Technion - Israel Institute of Technology to begin her own research lab. She was promoted to full professor in 2020.
Her research lab focuses on coupling materials science with chemistry and biotechnology to address problems in food technology and medicine. Specific areas include optical biosensing, silicon-based therapeutics, silicon-polymer hybrids, and food packaging technologies.
Optical biosensors
Fabry-Perot interferometers
Using electrochemical etched mesoporous silicon, Segal's research group has developed label-free, optical sensors by means of Fabry-Perot interferometry. These sensors, containing pores between 10 and 100 nm detect analytes such as proteins, DNA, whole bacteria cells, amphipathic molecules on lipid bilayers, organophosphorus compounds, heavy metal ions, and proteolytic products from enzymatic activity. Some of these sensors have been integrated with isotachophoresis and/or engineered with specific surface functions (e.g. attached proteins, enzymes, aptamers, and antimicrobial peptides) to enhance the limits of detection for analytes. She has helped engineer hybrid porous silicon materials for sensing purposes, including carbon dot-infused silicon transducers, hydrogel-confined silicon substrates, and polymer-silicon hybrids.
Diffraction gratings
Segal's research group engineered microstructured silicon optical sensors for the detection of microorganisms, including bacteria and fungi, in clinical samples and food. The microstructured substrates serve as reflective diffraction gratings for label-free measurements of refractive index. Her group (in collaboration with the Department of Urology at the Bnai Zion hospital and Ha'Emek Medical Center) developed a means of rapid antimicrobial susceptibility testing for clinical samples.
Porous silicon therapeutics
Segal and her research team engineered porous silicon carriers containing nerve growth factor for delivery to the brain in Alzheimer's models, in addition to carriers of anti-cancer drugs to diseased tissue and bone morphogenetic protein 2. She also demonstrated the delivery of anti-cancer drugs captured in silicon microparticles with a pneumatic capillary gene gun. She has studied the kinetics and degradation of porous silicon therapeutics in disease models, finding that porous silicon materials tend to degrade at faster rates in diseased tissue environments compared to healthy tissue.
Food packaging technologies
Some of Segal's research focuses on development of technologies for active packaging of food usually through the incorporation of polymers, nanomaterials, and essential oils. These materials have antimicrobial properties, allowing them to preserve food for longer times, and reduce food waste.
Professional activities
2019 ACS Advances in Measurement Science Lectureship Award for her work on photonic crystal sensing.
2019 Lady Globes named her one of Israel's top 50 most influential women.
2017 Discovery Award for Team Prismatix (part of UK Longitude Prize Contest) antimicrobial resistance testing technology
2016 Hershel Rich Innovation Award
2016 Daniel Shiran Memorial Research Prize for outstanding research in biomedicine
2015 Yanai Prize for Excellence in Academic Education
2014 Henry Taub Award for Academic Excellence
Entrepreneurship
Segal serves as the CTO to BactuSense Technologies Ltd and was the project coordinator of Nanopak, an EU-funded project that developed food packaging products in order to extend the shelf life of food.
Personal life
Segal is a cancer survivor, married, and has two children.
References
Year of birth missing (living people)
Living people
Technion – Israel Institute of Technology alumni
Academic staff of Technion – Israel Institute of Technology
Israeli nanotechnologists
Israeli women engineers
Israeli chemical engineers
Polymer scientists and engineers
21st-century Israeli women scientists | Ester H. Segal | [
"Chemistry",
"Materials_science"
] | 1,047 | [
"Polymer scientists and engineers",
"Physical chemists",
"Polymer chemistry"
] |
63,917,263 | https://en.wikipedia.org/wiki/Human-to-human%20transmission | Human-to-human transmission (HHT) is an epidemiologic vector, especially in case the disease is borne by individuals known as superspreaders. In these cases, the basic reproduction number of the virus, which is the average number of additional people that a single case will infect without any preventative measures, can be as high as 203.9. Interhuman transmission is a synonym for HHT.
The World Health Organization designation of a pandemic hinges on the demonstrable fact that there is sustained HHT in two regions of the world.
Synopsis
Relevant microbes may be viruses, bacteria, or fungi, and they may be spread through breathing, talking, coughing, sneezing, spraying of liquids, toilet flushing or any activities which generate aerosol particles or droplets or generate fomites, such as raising of dust.
Transfer efficiency depends not only on surface, but also on pathogen type. For example, avian influenza survives on both porous and non-porous materials for 144 hours.
The microbes may also be transmitted by poor use of cutlery or improper sanitation of dishes or bedlinen. Particularly problematic are toilet practices, which lead to the fecal–oral route. STDs are by definition spread through this vector.
List of HHT diseases
Examples of some HHT diseases are listed below.
measles: vaccine available
mumps: vaccine available
chicken pox: vaccine available
small pox
bubonic plague: slim non-nil risk
pneumonic plague: 1910-11 Manchurian plague
tuberculosis
Norovirus
monkeypox
SARS-CoV-1
SARS-CoV-2: vaccine available
MERS
Avian flu
Sexually transmitted infections (STIs) or sexually transmitted diseases (STDs):
Syphilis, aka French pox
References
Sources
Epidemiology
Parasitology
Infectious diseases
Sanitation
Hygiene
Global health
Epidemics | Human-to-human transmission | [
"Environmental_science"
] | 390 | [
"Epidemiology",
"Environmental social science"
] |
63,918,169 | https://en.wikipedia.org/wiki/Semiconductor%20saturable-absorber%20mirror | Semiconductor saturable-absorber mirrors (SESAMs) are a type of saturable absorber used in mode locking lasers.
Semiconductor saturable absorbers were used for laser mode-locking as early as 1974 when p-type germanium was used to mode lock a laser which generated pulses of around 500 picoseconds. Modern SESAMs are III-V semiconductor single quantum well (SQW) or multiple quantum wells grown on semiconductor distributed Bragg reflectors (DBRs). They were initially used in a Resonant Pulse Modelocking (RPM) scheme as starting mechanisms for Ti:Sapphire lasers which employed KLM as a fast saturable absorber. RPM is another coupled-cavity mode-locking technique. Different from APM lasers which employ non-resonant Kerr-type phase nonlinearity for pulse shortening, RPM employs the amplitude nonlinearity provided by the resonant band filling effects of semiconductors. SESAMs were soon developed into intracavity saturable absorber devices because of more inherent simplicity with this structure. Since then, the use of SESAMs has enabled the pulse durations, average powers, pulse energies and repetition rates of ultra-fast solid-state lasers to be improved by several orders of magnitude. Average power of 60W and repetition rate up to 160 GHz were obtained. By using SESAM-assisted KLM, sub-six-femtosecond pulses directly from a Ti: Sapphire oscillator were achieved.
Ursula Keller invented and demonstrated the semiconductor saturable absorber mirror (SESAM) which demonstrated the first passively mode-locked diode-pumped solid-state laser in 1992. "For almost two decades since then, her group at ETH Zurich has continued to define and push the frontier in ultrafast solid-state lasers both with detailed theoretical models and with world-leading experimental results, demonstrating orders of magnitude improvement in key features such as pulse duration, energy, and repetition rate. She also helped to spearhead industrial transfer of this technology. Today most ultrashort lasers are based on SESAM modelocking, with important industrial applications ranging from optical communication, precision measurements, microscopy, ophthalmology, and micromachining."
A major advantage SESAMs have over other saturable absorber techniques is that absorber parameters can be easily controlled over a wide range of values. For example, saturation fluence can be controlled by varying the reflectivity of the top reflector while modulation depth and recovery time can be tailored by changing the low temperature growing conditions for the absorber layers. This freedom of design has further extended the application of SESAMs into modelocking of fiber lasers where a relatively high modulation depth is needed to ensure self-starting and operation stability. Fiber lasers working at 1 μm and 1.5 μm were successfully demonstrated.
References
Nonlinear optics
Optical devices | Semiconductor saturable-absorber mirror | [
"Materials_science",
"Engineering"
] | 583 | [
"Glass engineering and science",
"Optical devices"
] |
63,919,427 | https://en.wikipedia.org/wiki/Holmium%28III%29%20fluoride | Holmium(III) fluoride is an inorganic compound with a chemical formula of HoF3.
Preparation
Holmium(III) fluoride can be produced by reacting holmium oxide and ammonium fluoride, then crystallising it from the ammonium salt formed in solution:
It can also be prepared by directly reacting holmium with fluorine:
Properties
Holmium(III) fluoride is a yellowish powder that is insoluble in water. It has an orthorhombic crystal system (corresponding to β-YF3) with the space group Pnma (space group no. 62). However, there is also a trigonal low-temperature form of the lanthanum(III) fluoride type.
References
Holmium compounds
Fluorides
Lanthanide halides | Holmium(III) fluoride | [
"Chemistry"
] | 168 | [
"Fluorides",
"Salts"
] |
77,030,087 | https://en.wikipedia.org/wiki/Wladyslaw%20Opechowski | Wladyslaw Opechowski (Polish: Władysław Opęchowski, 10 March 1911 – 27 September 1993) was a Polish and Canadian theoretical physicist. He is known for the work on the quantum theory of magnetism and group-theoretic classification of magnetic structures, which led to the Opechowski–Guccione convention in magnetic space groups.
Education and career
Opechowski was born in Warsaw as the son of Edward Opechowski, an electrical engineer, and Wanda Pelz, a social activist. He studied mathematics and physics at the University of Warsaw from 1931 to 1935. In 1935, he completed a research internship in France at the University of Paris and in the Netherlands, where he was an assistant for Hans Kramers and later studied under Adriaan Fokker and Léon Rosenfeld. After returning to Poland in 1937, he became an assistant of Czesław Białobrzeski at the Department of Theoretical Physics of the University of Warsaw, and also started teaching at the university. Opechowski moved to Leiden University in 1939 and remained working there until 1945. This was followed by another research position at the Philips Natuurkundig Laboratorium from 1945 to 1948 in Eindhoven.
Opechowski emigrated to Vancouver, Canada in September 1948 and became a professor of physics at the University of British Columbia and remained there for the rest of his career. After retiring in 1976, he continued to work there as an emeritus professor.
Honors and awards
Opechowski served as the Lorentz chair and delivered the invited lecture at Leiden University from 1964 to 1965. He became a member of the Royal Society of Canada since 1960. He received an honorary doctorate from the University of Wroclaw in 1973. He received the Marian Smoluchowski Medal from the Polish Physical Society in 1982.
Bibliography
References
1911 births
1993 deaths
University of Warsaw alumni
Academic staff of the University of Warsaw
People from Warsaw
Polish physicists
Theoretical physicists
Condensed matter physicists
Crystallographers
Academic staff of the University of British Columbia
Philips employees | Wladyslaw Opechowski | [
"Physics",
"Chemistry",
"Materials_science"
] | 416 | [
"Condensed matter physicists",
"Theoretical physics",
"Crystallography",
"Condensed matter physics",
"Crystallographers",
"Theoretical physicists"
] |
77,037,673 | https://en.wikipedia.org/wiki/Energy%20signature | In mechanical engineering, energy signatures (also called change-point regression models) relate energy demand of buildings to climatic variables, typically ambient temperature. Also other climatic variables such as heating or cooling degree days are used. In most cases, heating or cooling building energy demand is analysed through energy signatures, but also hot water or electricity demand is considered.
Energy signatures make a simplified assumption of a linear relationship between a building's energy demand and temperature. This assumption allows for balancing accuracy with computation time, as the estimation of energy demand through energy signatures is considerably faster than using building performance simulation software. A crucial advantage of applying energy signatures is that no detailed information on the geometrical, construction, and operational characteristics of buildings needs to be available.
References
Energy
Building
Heating, ventilation, and air conditioning
Temperature | Energy signature | [
"Physics",
"Chemistry",
"Engineering"
] | 161 | [
"Thermodynamics stubs",
"Scalar physical quantities",
"Temperature",
"Thermodynamic properties",
"Physical quantities",
"Building",
"SI base quantities",
"Intensive quantities",
"Construction",
"Energy (physics)",
"Energy",
"Thermodynamics",
"Wikipedia categories named after physical quantit... |
66,742,046 | https://en.wikipedia.org/wiki/Gravitational%20decoherence | Gravitational decoherence is a term for hypothetical mechanisms by which gravitation can act on quantum mechanical systems to produce decoherence. Advocates of gravitational decoherence include Frigyes Károlyházy, Roger Penrose and Lajos Diósi.
A number of experiments have been proposed to test the gravitational decoherence hypothesis.
Dmitriy Podolskiy and Robert Lanza have argued that gravitational decoherence may explain the existence of the arrow of time.
See also
Penrose interpretation
Diósi–Penrose model
Objective-collapse theory
Quantum gravity
References
Quantum mechanics
Quantum gravity | Gravitational decoherence | [
"Physics"
] | 119 | [
"Theoretical physics",
"Unsolved problems in physics",
"Quantum mechanics",
"Quantum gravity",
"Physics beyond the Standard Model",
"Quantum physics stubs"
] |
75,406,231 | https://en.wikipedia.org/wiki/Amaterasu%20particle | The Amaterasu particle, named after the sun goddess in Japanese mythology, was an unexpected ultra-high-energy cosmic ray detected in 2021 and later identified in 2023, using the Telescope Array Project observatory in Utah, United States. It had an energy exceeding 240 exa-electronvolts (EeV) and was inferred through the two dozen particles it sent toward ground detectors. This single particle appears to have emerged, inexplicably, from the Local Void, an empty area of space bordering the Milky Way galaxy. The single subatomic particle held energy roughly equivalent to a brick dropping to the ground from waist height.
According to study leader, Associate Professor Toshihiro Fujii from Osaka Metropolitan University, "No promising astronomical object matching the direction from which the cosmic ray arrived has been identified, suggesting possibilities of unknown astronomical phenomena and novel physical origins beyond the Standard Model."
Previously reported extremely high-energy cosmic ray events include a 320 EeV particle in 1991 (Oh-My-God particle), a 213 EeV particle in 1993 and a 280 EeV particle in 2001. This makes the Amaterasu particle the third most powerful cosmic ray to have been detected.
See also
Greisen–Zatsepin–Kuzmin limit
References
Cosmic rays
2021 in science
2021 in Utah
Individual particles | Amaterasu particle | [
"Physics",
"Astronomy"
] | 269 | [
"Physical phenomena",
"Astronomy stubs",
"Astrophysics",
"Radiation",
"Cosmic rays"
] |
75,409,524 | https://en.wikipedia.org/wiki/Betatron%20oscillations | Betatron oscillations are the fast transverse oscillations of a charged particle in various focusing systems: linear accelerators, storage rings, transfer channels. Oscillations are usually considered as a small deviations from the ideal reference orbit and determined by transverse forces of focusing elements i.e. depending on transverse deviation value: quadrupole magnets, electrostatic lenses, RF-fields. This transverse motion is the subject of study of electron optics. Betatron oscillations were firstly studied by D.W. Kerst and R. Serber in 1941 while commissioning the fist betatron. The fundamental study of betatron oscillations was carried out by Ernest Courant, Milton S.Livingston and Hartland Snyder that lead to the revolution in high energy accelerators design by applying strong focusing principle.
Hill's equations
To hold particles of the beam inside the vacuum chamber of accelerator or transfer channel magnetic or electrostatic elements are used. The guiding field of dipole magnets sets the reference orbit of the beam while focusing magnets with field linearly depending on transverse coordinate returns the particles with small deviations forcing them to oscillate stably around reference orbit. For any orbit one can set locally the co-propagating with the reference particle Frenet–Serret coordinate system. Assuming small deviations of the particle in all directions and after linearization of all the fields one will come to the linear equations of motion which are a pair of Hill equations:
Here , are periodic functions in a case of cyclic accelerator such as betatron or synchrotron. is a gradient of magnetic field. Prime means derivative over s, path along the beam trajectory. The product of guiding field over curvature radius is magnetic rigidity, which is via Lorentz force strictly related to the momentum , where is a particle charge.
As the equation of transverse motion independent from each other they can be solved separately. For one dimensional motion the solution of Hill equation is a quasi-periodical oscillation. It can be written as , where is Twiss beta-function, is a betatron phase advance and is an invariant amplitude known as Courant-Snyder invariant.
References
Literature
Accelerator physics | Betatron oscillations | [
"Physics"
] | 449 | [
"Accelerator physics",
"Applied and interdisciplinary physics",
"Experimental physics"
] |
75,415,269 | https://en.wikipedia.org/wiki/JNJ-54175446 | JNJ-54175446 is an investigational P2X7 receptor antagonist developed by Janssen Pharmaceuticals. It is hoped that the drug can reduce neuroinflammation and therefore treat psychiatric disorders such as major depressive disorder.
See also
JNJ-55308942
References
Drugs developed by Johnson & Johnson
Receptor antagonists
Purines
Triazolopyridines
Chloroarenes
Fluoroarenes
Trifluoromethyl compounds
Small-molecule drugs
Experimental antidepressants | JNJ-54175446 | [
"Chemistry"
] | 107 | [
"Neurochemistry",
"Receptor antagonists"
] |
69,540,685 | https://en.wikipedia.org/wiki/ChoKyun%20Rha | ChoKyun Rha (October 5, 1933 – March 2, 2021) was a Korean-born American food technologist, inventor, and professor of biomaterials science and engineering at the Massachusetts Institute of Technology (MIT). She was the first Asian woman awarded tenure at MIT.
Early life
ChoKyun Rha was born in Seoul, the daughter of SaeJin Rha and Young Soon Choi Rha. Her father was a physician and dean of the medical school at Seoul National University. She moved to the United States in 1956, and attended Miami University in Ohio, before enrolling at MIT as an undergraduate. She finished a bachelor's degree in 1962, with a senior thesis on the storage of dried scallions. She stayed at MIT to earn master's degrees in 1964 and 1966, and completed a doctoral degree in 1967, with a dissertation titled "Thermal Sterilization of Flexibly Packaged Foods".
Career
Rha was a professor of biomaterials science and engineering at MIT, until her retirement in 2006. In 1980, she became the first Asian woman to earn tenure at MIT. She helped establish Genzyme, a biotechnology firm, and founded and directed the Malaysia-MIT Biotechnology Partnership Program. She endowed a professorship in industrial biotechnology at MIT. She was a co-founder of Women’s World Banking, a microfinancing program.
Rha's research focused on biochemistry and biotechnology for food and other applications. Her work was published in academic journalist including Journal of Food Science, Nature Biotechnology, Applied Microbiology and Biotechnology, Bioresource Technology, Biotechnology Letters, and British Journal of Nutrition. She earned her first of several patents in 1988, with a process for encapsulation. As part of her work in Malaysia, she developed several patented products derived from palm oil.
Publications
"Evaluation of cheese texture" (1978, with Cho Lee and Em Imoto)
"Microstructure of soybean protein aggregates and its relation to the physical and textural properties of the curd" (1978, with Cho Lee)
"Single-Cell Protein: Engineering, Economics, and Utilization in Foods" (1980, with C. L. Cooney and S. R. Tannenbaum)
"Improved detergent-based recovery of polyhydroxyalkanoates (PHAs)" (2011, with Yung-Han Yang, Christopher Brigham, Laura Willis, and Anthony Sinskey)
Theory, Determination and Control of Physical Properties of Food Materials (book edited by Rha, 2012)
Characterization of chitosan film" (2012, with Carlos A. Kienzle-Sterzer and Dolores Rodriguez Sanchez)
"Characterization of an extracellular lipase and its chaperone from Ralstonia eutropha H16" (2013, with Jingnan Lu, Christopher Brigham, and Anthony Sinskey)
Personal life
ChoKyun Rha married fellow MIT professor Anthony Sinskey, and the couple frequently collaborated on research. She had two sons, Tong-ik Lee Sinskey and Taeminn Song, both of whom graduated from MIT. Rha died in 2021, in Boston, aged 87 years.
References
1933 births
2021 deaths
Academics from Seoul
South Korean emigrants to the United States
American women scientists
Massachusetts Institute of Technology faculty
Massachusetts Institute of Technology alumni
Food technology
Biotechnologists | ChoKyun Rha | [
"Biology"
] | 680 | [
"Biotechnologists"
] |
69,543,788 | https://en.wikipedia.org/wiki/FAM151A | Family with sequence similarity 151 member A (abbreviated FAM151A) is a protein that in humans is encoded by the FAM151A gene. The protein is a transmembrane protein expressed in the kidney tubules, and is an ortholog of menorin, a protein involved in neuron development in nematodes.
Gene
The FAM151A gene contains 8 exons and is located on the minus strand of chromosome 1 at 1p32.3, spanning approximately 14 kbp. The last exon contains approximately half of the coding sequence, and overlaps with the 3' UTR of gene ACOT11. No alternative splicings of FAM151A are known.
Expression
The mRNA transcript of FAM151A is expressed in the kidney, small intestine, and liver, while the FAM151A protein is only expressed in kidney tubules.
Protein
The FAM151A protein contains three known domains, one transmembrane domain and two domains of unknown function DUF2181. DUF2181 is a member of the GDPD/PLCD superfamily, which are known to hydrolyze glycerophosphodiester bonds. The second DUF2181 of FAM151A is hypothesized to be nonfunctional through homology analysis. The molecular weight of FAM151A is known to be approximately 95 kDa.
Evolutionary history
Orthologs of FAM151A
FAM151A has direct orthologs in chimpanzee, mouse, zebrafish, and other members of the clade Eumetazoa that diverged from humans up to around 700 million years ago. However, FAM151A does not have any known orthologs in birds.
Protein family FAM151/Menorin
FAM151A has one known paralog in humans, FAM151B, which contains only the first DUF2181 and no transmembrane region. In mammals, both FAM151A and FAM151B are homologs of the C. elegans menorin gene, involved in dendrite branching.
Clinical significance
FAM151A contains an SNP, rs11206394, that is a significant predictor of colorectal cancer. The SNP is a missense mutation that occurs in the region of the second DUF2181 of FAM151A that overlaps with the 3' UTR of ACOT11. Individuals with both copies of the minor allele have been observed to have the odds of cancer decreased between 11% and 59%.
References
Proteins
Genes
Uncharacterized proteins | FAM151A | [
"Chemistry",
"Biology"
] | 568 | [
"Biomolecules by chemical classification",
"Uncharacterized proteins",
"Protein classification",
"Molecular biology",
"Proteins"
] |
69,543,970 | https://en.wikipedia.org/wiki/Somatrogon | Somatrogon, sold under the brand name Ngenla, is a medication for the treatment of growth hormone deficiency. Somatrogon is a glycosylated protein constructed from human growth hormone and a small part of human chorionic gonadotropin which is appended to both the N-terminal and C-terminal. Somatrogon is a human growth hormone analog.
The most common side effects include reactions at the site of injection, headache, and fever.
Somatrogon was approved for medical use in Australia in November 2021, in the European Union in February 2022, and in the United States in June 2023.
Medical uses
Somatrogon is indicated for the treatment of children who have growth failure due to inadequate secretion of endogenous growth hormone.
History
The US Food and Drug Administration (FDA) approved somatrogon based on one clinical trial (NCT02968004) of 224 children with growth hormone deficiency and short stature. The trial was conducted at 84 sites in 24 countries including Argentina, Australia, Bulgaria, Belarus, Canada, Colombia, Germany, Georgia, Greece, India, Israel, Italy, Mexico, New Zealand, Poland, South Korea, Russia, Spain, Taiwan, Turkey, Ukraine, the United Kingdom, Vietnam, and the United States. This trial was used to assess efficacy and safety. The benefits and side effects were evaluated in a clinical trial. Children aged 3 to 12 years old were assigned at random to weekly somatrogon or another daily approved growth hormone for 52 weeks.
Society and culture
Legal status
In December 2021, the Committee for Medicinal Products for Human Use of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Ngenla, intended for the treatment of growth hormone deficiency in children and adolescents from three years of age. The applicant for this medicinal product is Pfizer Europe MA EEIG. Somatrogon was approved for medical use in the European Union in February 2022.
Names
Somatrogon is the international nonproprietary name.
References
Further reading
Growth factors
Orphan drugs
Drugs developed by Pfizer | Somatrogon | [
"Chemistry"
] | 443 | [
"Growth factors",
"Signal transduction"
] |
69,551,321 | https://en.wikipedia.org/wiki/Transition%20metal%20azide%20complex | Transition metal azide complexes are coordination complexes containing one or more azide (N3−) ligands. In addition to coordination complexes, this article summarizes homoleptic transition metal azides, which are often coordination polymers.
Structure and bonding
Azide is a pseudohalide but more nucleophilic than chloride, as reflected by the higher pKa of hydrazoic acid (4.6) vs hydrochloric acid (-5.9). As a monodentate ligand, azide binds through one of the two terminal nitrogen atoms, i.e. M-N=N=N. The N3 unit is linear or nearly so. The M-N-N angles are quite bent. Azide functions as a bridging ligand via two bonding modes. Commonly the metals share the same nitrogen ("N-diazonium" mode). Less common is the motif M-N=N=N-M, illustrated by [Cu(N3)(PPh3)2]2.
General synthetic methods
Traditionally, metal azide complexes are prepared by salt metathesis, e.g. the reaction of metal chlorides with sodium azide. In some cases, trimethylsilyl azide is employed as the azide source. Another popular route include acid-base reactions hydrazoic acid HN3 and either hydrido or lewis base complexes. Still other methods rely on halide-azide exchange with trimethylsilyl azide SiMe3N3 with the metal fluorides as incomplete halide/azide exchange is often seen when using the chloride derivatives.
Homoleptic complexes
Many homoleptic complexes (with only one kind of ligand) are known. Coordination numbers range from 2 (e.g., [Au(N3)2]−) to 7 (e.g., [W(N3)7]−). Many homoleptic complexes are octahedral anions of the type [M(N3)6]n-:
dianions for tetravalent metals V, Pt, Ti, Zr, Hf
trianions for trivalent metals Cr, Fe, Ru, Rh, Ir
tetraanions for the divalent Ni
For some metals, homoleptic complexes exist in two oxidation states: [Au(N3)2]− vs [Au(N3)4]− and [Pt(N3)6]2- vs [Pt(N3)4]2-.
Binary azide compounds can take on several structures including discrete compounds, or one- two, and three-dimensional nets, leading some to dub them as "polyazides". Reactivity studies of azide compounds are relatively limited due to how sensitive they can be.
Group 3
Neutral unsolvated group 3 polyazide is only known for divalent europium(II) compound, Eu(N3)2. Attempts to react lanthanide hydroxides with HN3 result in their basic azides, Ln(OH)(N3)2 or Ln(OH)2N3.
Group 4
Group 4 polyazides of the formula M(N3)4 are predicted to have linear or near linear M-N-N angles unlike their main group counterparts which are predicted to have bent M-N-N angles. This couldn’t be proved in the case of Ti(N3)4, owing to difficulty in crystallization. However, incorporation of large spacer counterions or N-donor adducts makes the compounds far easier to work with. In the cases of [PPh4]2[M(N3)6] (M=Ti, Zr, Hf), only the axial ligands exhibit near linear M-N-N angles whereas the equatorial ligands are closer to bent angles. This deviation in theory is also seen in the N-donor adducts.
The main hypothesis given for why these compounds do not have linear M-N-N angles despite theoretical calculations is that these adducts are not tetrahedral. In the homoleptic tetrahedral compounds, the nitrogen closest to the (+IV) metal center is positioned in such a way that the three valence electron pairs can donate to the vacant d orbitals on the metal and therefore the azido can act as a tridentate donor ligand in which case the expected coordination would be linear. Since the adduct compounds are not tetrahedral, the azido group can only act as a monodentate donor with two sterically active electron pairs which result in a bent M-N-N bond angles.
Group 5
The neutral binary V(IV) azide as well as V(III), V(IV), and V(V) azido ions are known. Similar to the neutral Ti(IV) azide, V(N3)4 is difficult to study due to high shock and temperature instability. However, [V(N3)6]2- paired with a large, inert counterion is relatively stable and crystalizeses as a near perfect octahedral. In contrast to V(IV), the neutral binary V(V) could not be synthesized and attempts result in the reduction of V(V) to V(IV) with the elimination of N2 gas. Fortunately, the oxidation potentials of anions are lower than that of their parent compounds so [V(N3)6]− can be formed. Unlike [V(N3)6]2-, [V(N3)6]− is highly shock sensitive and distorted from octahedral symmetry with three long and three short M-N bonds in mer positions.
The neutral binary Nb(N3)5 and Ta(N3)5 also exist, and the acetonitrile adducts of these compounds contain a nearly linear azido trans to the coordinating acetonitrile. They represent the first evidence of linear M-N-N bonding. The corresponding anions [Nb(N3)6]−, [Nb(N3)7]2-, [Ta(N3)6]−, and [Ta(N3)7]2- are known and accordingly are much less shock sensitive. The structure of the hexaazido monoanions are similar to other heptaazido monoanions with bent azido ligands despite being predicted to have perfect S6 symmetry in the gas phase for [Nb(N3)6]. The heptaazido dianions possess monocapped triangular-prismatic 1/4/2 structures unlike the actinide trianion [U(N3)7]3- which crystallizes as a monocapped octahedron or pentagonal bipyramid. Several N-donor adducts are known to exist as well. Reactions of the neutral binary NbF5 and TaF5 in the presence of Me3SiN3 with N-donors containing small bite angles such as 2,2’-bipyridine or 1,10-phenanthroline result in self ionization products of the type [M(N3)4L2]+[M(N3)6]− (L= N-donor) whereas N-donors containing large bite angles such as 3,3’-bipryidine or 4,4’-bipyridine produces the neutral pentaazide adducts M(N3)5•L (L=N-donor).
Group 6
Both Mo(N3)6 and W(N3)6 have been synthesized, and W(N3)6 is stable enough to grow single crystals. Contrary to group 4 and group 5 binary azido compounds, the anionic [Mo(N3)7]− and [W(N3)7]− are less stable and more sensitive to handle than their neutral parent compounds. Upon warming solutions of the heptaazido anions in either MeCN or SO2 to room temperature, the tetraazido nitrido ions [NMo(N3)4]− and [NW(N3)4]− are formed with elimination of N2.
Group 7
The first Mn polyazide compound was prepared by Wöhler et al. in 1917 by reaction of MnCO3 with HN3 to form Mn(N3)2. Many divalent Mn azide salts have been synthesized. 1D chains are formed when 2,2’-bipyridine, a bidentate ligand, is used as the counter ion in the reaction between Mn(ClO4)2 • 6H2O and excess NaN3. This results in a chain with alternating EE and EO bridges which predictably gives alternating antiferromagnetic-ferromagnetic coupling. Another 2D structure is accessed via the reaction of (PPh4)2MnCl2 with AgN3 to form the [PPh4]2[Mn(N3)4].
The first example of a 3D azido compound was [N(CH3)4][Mn(N3)3]. This compound has a pseudo-perovskite structure with [N(CH3)4]+ ions in the cavities between the Mn centers. The azido moieties are arranged in an EE fashion, and indeed, this compound exhibits the expected antiferromagnetic behavior. The cesium analogue Cs[Mn(N3)3] is synthesized in a similar manner. For each 6 coordinate Mn, four of the azido linkages are EE and two are EO instead of all six being EE. This arrangement results in a honeycomb-like shape and a rare example of alternating ferro-antiferromagnetic interactions in 3D solid.
Examples of manganese azido compounds in higher oxidation states are rare. The triazide acetonitrile adduct can be prepared using the fluoride exchange route to give Mn(N3)3CN as a dark red shock sensitive compound. Upon addition of PPh4N3 the compound disproportionates into an insensitive mixture of [PPh4]2[Mn(N3)2] and [PPh4]2[Mn(N3)6]. The Mn(IV) salt can be prepared on its own by using Cs2MnF6 as the starting material to give the highly explosive Cs2[Mn(N3)6].
Group 8
Pentaazidoiron (III) ion [Fe(N3)5]2- can be made by treating iron(III) salts with sodium azide. An iron azide reagent can be generated in situ. NaN3 and iron (III) sulfate Fe2(SO4)3 are combined in methanol and added to an organoborane followed by slow addition of 30% hydrogen peroxide, presumably forming Fe(N3)3. When combined with alkenes, the equivalent of hydrogen azide add in an anti-Markovnikov fashion.
[n-Bu4N]3[Ru(N3)6] is prepared by treating K2[RuIVCl6] with NaN3. N2 gas is liberated in this reaction, which involves reduction of Ru(IV) to Ru(III).
Group 9
Tetraazido cobalt(II) compounds have been isolated as both the tetraphenylphosphonium and tetraphenylarsonium salts from solutions of cobalt sulfate with a 15 time sexcess of NaN3 to yield [Ph4P]2[Co(N3)4] and [Ph4As]2[Co(N3)4] respectively. The autooxidation of solutions of [Co(N3)4]2- can be used as a colorimetric spot test for the presence of sulfite ions.
Tetrabutylammonium salts of rhodium(III) and iridium(III) azides are known and are prepared by reacting a large excess of NaN3 in an aqueous solution with the corresponding Na3[MCl6] • 12H2O metal chloride salt to form [n-Bu4N]3[Rh(N3)6] and [n-Bu4N]3[Ir(N3)6].
Group 10
The binary nickel azide Ni(N3)2 has been prepared by distilling HN3 onto nickel carbonate. Samples of Ni(N3)2 decompose upon heating .
[Pd(N3)4]2- anions are square planar and the degree of interaction between the anion and its corresponding cation can be determined by the amount of deviation in the torsion angles from the ideal geometry. Various platinates [Pt(N3)4]2- and [Pt(N3)6]4- are known and are prepared from Pt chloride salts with NaN3. Pt(II) salts tend to be far less stable than the Pt(IV) versions, and they either decompose fairly rapidly upon standing or explode. Their sensitivity in part has been explained by poor crystal packing.
Group 11
Both copper(I) and copper(II) azides are known. The binary copper(I) azide, CuN3, which is white, is a one-dimensional polymer. Molecular Copper (II) azides include salts of [Cu(N3)4]2- and [Cu(N3)6]2-. {[Cu(N3)3]−}n forms 1D chains wherein octahedral Cu(II) centers are linked by both EE and EO bridging azides. All copper azides are explosive but their sensitivities vary widely from the parent azides CuN3 and Cu(N3)2 which are extremely sensitive to the ions paired with large countercations that are practically insensitive.
Silver (I) azide is a well known explosive compound and has been demonstrated to form a 2D coordination polymer with square planar Ag+ ions surrounded by azido ligands in an EE fashion. Slow ramping of temperature from 150 °C to 251 °C results in melting and slow decomposition but rapid heating to 300 °C results in an explosion.
Gold(III) azide is known as the tetraethylammonium salt [Et4N][Au(N3)4] and also adopts a square planar structure. However unlike the silver azide, the gold azide is not stable at room temperature and will decompose after a few days and its metal azide bonds have significant covalent character.
Group 12
While Zn(N3)2 has been known since the late 1890s, solvent free Zn(N3)2 was isolated for the first time in 2016 from a dry ethereal solution of HN3 and Et2Zn in n-hexane. Zn(N3)2 crystallizes in three different polymorphs α-Zn(N3)2 and the labile β-Zn(N3)2 and γ-Zn(N3)2 forms.
The first mercury (I) azide was realized by Curtius in 1890 by combining aqueous mercury(I) salts with alkali metal azides and by combining HN3 with elemental mercury to produce Hg2(N3)2. Both mercury (I) and mercury(II) azides can be easily prepared by mixing the respective mercury nitrates with sodium azide in aqueous solution at roomtemperature. The mercury (II) azide Hg(N3)2 exists in two polymorphs α-Hg(N3)2 and β-Hg(N3)2. The β form is very labile and quickly turns into the α polymorphs at room temperature. However, the β polymorph can prepared in analogy to β-Pb(N3)2 by slow diffusion of aqueous NaN3 into a solution of Hg(NO3)2 separated by a layer of aqueous NaNO3, but crystals nearly always explode during formation leading to a mixture of α and β polymorphs.
Binary cadmium azide Cd(N3)2 can be prepared from CdCO3 and aqueous HN3. However, it is structural unrelated to the mercury or zinc anaolgues and is based on repeat units of Cd2(N3)10 double octahedrals.
Mixed ligand complexes
Azide forms myriad mixed ligand complexes. Examples include Zn(N3)2(NH3)2 and (C5H5)2Ti(N3)2.
Reactions
A characteristic reaction of azide complexes and compounds) is degradation via loss of nitrogen gas. The stoichiometry for a diazide compound is:
The process often occurs explosively.
Azide ligands are react with nitrosonium to give nitrous oxide. This reaction is used to generate coordinatively unsaturated complexes.
[Co(NH3)5N3]2+ + NO+ + H2O → [Co(NH3)5(H2O)]3+ + N2O + N2
This approach was used to prepare the previously elusive dicationic complex pentamminecobalt(III) perchlorate, .
See also
Main group azido compounds
References
Ligands
Azides | Transition metal azide complex | [
"Chemistry"
] | 3,663 | [
"Explosive chemicals",
"Azides",
"Ligands",
"Coordination chemistry"
] |
72,572,231 | https://en.wikipedia.org/wiki/Equinoctial%20hours | An equinoctial hour is one of the 24 equal parts of the full day (which includes daytime and nighttime).
Its length, unlike the temporal hour, does not vary with the season, but is constant. The measurement of the full day with equinoctial hours of equal length was first used about 2,400 years ago in Babylonia to make astronomical observations comparable regardless of the season. Our present hour is an equinoctial hour, freed only from its seasonal variation and from the small error due to some uniform Earth rotation, and realized by modern technical means (atomic clock, satellite and VLBI-Astrometry).
When the temporal hour was used, the daytime and nighttime, whose lengths vary greatly throughout the year, were each divided into 12 hours. This corresponded to the earlier sentiment and custom of not grouping the night with the daytime.
The name equinoctial hours refers to the fact that the temporal hours of the daytime (daylight hours) and those of the night are of equal length at each of the equinoxes.
History
Equinoctial hours () are found, in distinction to the , the 'unequal' hours, at least in Ancient Greece.
Geminos of Rhodes reported the observation of Pytheas of Massalia that the duration of the night depended on the geographical latitude of the place in question. However, it is not clear from his explanations whether he meant equal or equinoctial hours. Otto Neugebauer cites this account as the oldest testimony to the concept of hour (¹ra) as a defined measure of time.
The Babylonian calendar knew no division of the day into 24 time units, so Ancient Egyptian influence for this system can be considered probable. The period of its origin can be dated to the 4th century BC, since Pytheas of Massalia refers to the terminus G¨j perÐodoj introduced by Eudoxus of Cnidus.
The use of equinoctial hours was already familiar in the work of Hipparchus of Nicaea. In the appendix to his commentary on Aratos of Soloi and Eudoxos of Knidos, he uses the well-known 24-hour circles and names stars whose rises are separated from each other by about one equinoctial hour in certain seasons.
With the invention of the Stroke clock, for the first time one could read equinoctial hours mechanically without having to perform astronomical calculations. A mechanical clock displaying the previously used temporal hours would be very costly, but occasionally its construction was nevertheless attempted. Equinoctial hours are first attested in conjunction with striking clocks in Padua in 1344, in Genoa in 1353, and in Bologna in 1356. Subsequently, striking clocks came into use throughout Europe.
Equal hours in ancient Egypt
In Ancient Egypt, the earliest use of equal hours is attested by an inscription from the time of Amenophis I around 1525 BC. The use of water clocks allowed individual units of hours; for example, for the division of Decan star intervals, where fractions of hours were also taken into account.
Ten equivalent hours were used for the time between two sunrises.
Equal hours in Babylonia
The temporal hour was unknown to the Babylonians until the third century BC. However, attempts have been made to establish a second ideal calendar with seasonal hours alongside the astronomical system of equivalent hours. Bartel Leendert van der Waerden analyzed the "Babylonian system of the ideal calendar" in 1974:
Neugebauer reiterated this finding in 1975 as an important feature which distinguishes it from the later Greek temporal hours. The durations of the daytime and nighttime were measured by Babylonian astronomers with a gnomon and a water clock further in BERU as well as UŠ. The time periods were divided into equivalent time units with respect to celestial observation. The use of a gnomon together with a water clock is already documented in the MUL.APIN-cuneiform tablets around 700 BC.
From their contents it is clear that the values for the duration of the light day and night were recorded during four colures aligned with the longest and shortest days of the year. The records have gnomon tables, but they are preserved only for specific dates in the Hebrew calendar: the 15th of Nisan and the 15th of Tammuz. The tables for the 15th Tishrei and the 15th Tevet were at the beginning of the broken away second column. The gnomon tables are written in the form that the length of the gnomon corresponds to a Mesopotamian cubit, which measured between 40 and 50 cm.
A 24-hour day contained twelve Dannas, which in turn, taking into account the Babylonian model of the mean sun, comprised twelve equinoctial units, each lasting 120 minutes The equivalent hours had the Sumerian System of the distance covered on foot in broad daylight as a basis. The unit of measurement, which has a distance of about 10 km as a computational value, is also erroneously called "double hour" in modern literature.
See also
Epic of Gilgamesh
Hour
Literature
Friedrich Karl Ginzel: Handbuch der mathematischen und technischen Chronologie, Vol. 1 - Zeitrechnung der Babylonier, Ägypter, Mohammedaner, Perser, Inder, Südostasiaten, Chinesen, Japaner und Zentralamerikaner -, Deutsche Buch-Ex- und Import, Leipzig 1958 (Reprint Leipzig 1906)
Richard Anthony Parker: Egyptian Astronomy, Astrology and calendrical reckoning In: Charles-Coulson Gillispie: Dictionary of scientific Biography - American Council of Learned Societies - Vol. 15, Supplement 1 (Roger Adams, Ludwik Zejszner: Topical essays), Scribner, New York 1978, ISBN 0-684-14779-3, pp. 706–727.
François Thureau-Dangin: Itanerare - Babylonische Doppelstunde -. In: Dietz Otto Edzard: Reallexikon der Assyriologie und vorderasiatischen Archäologie. Vol. 5: Ia to Kizzuwatna, de Gruyter, Berlin 1980, ISBN 3-11-007192-4, p. 218.
François Thureau-Dangin: Rituels Accadiens Leroux, Paris 1921, p. 133.
Wolfgang Fels: Marcus Manilus: Astronomica - (Latin–German. published by Reclam, Stuttgart 1990, ISBN 3-15-008634-5.
Friedrich-Karl Ginzel: Handbuch der mathematischen und technischen Chronologie II - Das Zeitrechnungswesen der Völker: Zeitrechnung der Juden, der Naturvölker, der Römer und Griechen sowie Nachträge zum 1. Bande. Deutscher Buch-Ex- und Import, Leipzig 1958 (Reprint of first edition Leipzig 1911).
Otto Neugebauer: A history of ancient mathematical astronomy. Studies in the history of mathematics and physical sciences, Vols. 1–3. Springer, Berlin 2006, ISBN 3-540-06995-X (Reprint of 1975 Berlin edition).
References
External links
Die Aequinoctialstunden (German language site)
Timekeeping
Babylonia
Sumer
History of timekeeping
Equinoxes | Equinoctial hours | [
"Physics",
"Astronomy"
] | 1,531 | [
"Time in astronomy",
"Physical quantities",
"Time",
"Timekeeping",
"Equinoxes",
"Spacetime"
] |
72,573,008 | https://en.wikipedia.org/wiki/Marsh%20terrace | A marsh terrace is an artificially created berm that is built in a wetland to prevent erosion, reduce wave energy, and improve habitat for wildlife. Marsh terracing is most common throughout the upper Gulf Coast of the United States, where it is used to prevent coastal erosion, with 980 linear km (609 mi) having been built in Texas and Louisiana alone in the thirty years to 2020. The terraces catch sediment from rivers which is then colonized by plants to form marshland.
Construction and design
The design of marsh terraces depends on the local conditions such as wave strength and wind speed. There are several commonly used patterns, including chevrons (duck wings), straight lines, and square grids. Chevrons are the most effective pattern as wind can blow from any direction but there will still be calm water on at least one side of the chevron.
One thing that must be considered is the type of soil, as some are more vulnerable to erosion than others. Soils heavy with clay and silt are more resistant than soils primarily composed of organic matter.
Terraces are often built in shallow coastal ponds that may have been former marshland that has eroded away over time. Large berms, usually two to five meters in width, are built with material that is either dredged at the site or brought in as fill from inland. The berms themselves are often only a meter in height above sea level which allows it to be occasionally inundated with water and create the proper coastal plant community.
Marshland terraces are a relatively new construction, so far has only been extensively used in the Gulf Coast of the United States. They were first built at the Sabine National Wildlife Refuge in 1990. In 2021, a plan to create marsh terraces in Virginia's Back Bay National Wildlife Refuge has been approved. This will be the first project of its kind to be done in the Mid-Atlantic region.
Results
Being only constructed recently, there have not been a lot of published studies on the effects of marsh terracing. However, the existing results are promising. The terraces have a higher sediment accumulation rate compared to erosion, and are able to reduce wave strength by an average of 45%. The calmer waters allows sediment to settle which then promotes the growth of seagrasses which further hold down the sediment with their roots. Additionally, the terraces have been found to provide habitat for marsh wildlife such as seabirds and fish.
References
Ecological restoration
Environmental engineering
Hydrology
Land reclamation | Marsh terrace | [
"Chemistry",
"Engineering",
"Environmental_science"
] | 498 | [
"Hydrology",
"Ecological restoration",
"Chemical engineering",
"Civil engineering",
"Environmental engineering"
] |
72,577,761 | https://en.wikipedia.org/wiki/Clinical%20data%20standards | Clinical data standards are used to store and communicate information related to healthcare so that its meaning is unambiguous. They are used in clinical practice, in activity analysis and finding, and in research and development.
There are many existing and proposed standards and many bodies working in this field.
In addition to standards specific to the clinical domain health informatics relies on other standards that are lower in the communications stack, and on many standards from metrology.
Clinical data standards and interoperability
Interoperability between disparate clinical information systems requires common data standards or mapping of every transaction.
However common data standards alone will not provide interoperability, and the other requirements are identified in "How Standards will Support Interoperability" from the Faculty of Clinical Informatics and "Interoperability is more than technology: The role of culture and leadership in joined-up care" from the King's Fund
Barriers to development and use
Barriers to the widespread adoption of effective data standards include:
inconsistency in and poor understanding of the concepts and language used in clinical practice, for example compared to those in chemistry or accounting
rival systems of standards
the cost of implementation or change to better standards
avoidance of commercial competition.
Existing and proposed clinical data standards
Integrating the Healthcare Enterprise
Omaha System
SNOMED
SNOMED CT
ASC X12 (EDI) – transaction protocols used for transmitting patient data. Popular in the United States for transmission of billing data.
CEN's TC/251 provides EHR standards in Europe including:
EN 13606, communication standards for EHR information
CONTSYS (EN 13940), supports continuity of care record standardization.
HISA (EN 12967), a services standard for inter-system communication in a clinical information environment.
Continuity of Care Record – ASTM International Continuity of Care Record standard
DICOM – an international communications protocol standard for representing and transmitting radiology (and other) image-based data, sponsored by NEMA (National Electrical Manufacturers Association)
HL7 (HL7v2, C-CDA) – a standardized messaging and text communications protocol between hospital and physician record systems, and between practice management systems
Fast Healthcare Interoperability Resources (FHIR) – a modernized proposal from HL7 designed to provide open, granular access to medical information
ISO – ISO TC 215 provides international technical specifications for EHRs. ISO 18308 describes EHR architectures
xDT – a family of data exchange formats for medical purposes that is used in the German public health system.
openEHR: an open community developed specification for a shared health record with web-based content developed online by experts. Strong multilingual capability.
Virtual Medical Record: HL7's proposed model for interfacing with clinical decision support systems.
SMART (Substitutable Medical Apps, reusable technologies): an open platform specification to provide a standard base for healthcare applications.
Sentinel Common Data Model: Initially started as Mini-Sentinel in 2008. Use by the Sentinel Initiative of the USA's Food and Drug Administration.
OMOP Common Data Model: model that defines how electronic health record data, medical billing data or other healthcare data from multiple institutions can be harmonized and queried in unified way. It is maintained by Observational Health Data Sciences and Informatics consortium.
PCORNet Common Data Model: First defined in 2014 and used by PCORI and People-Centered Research Foundation.
Virtual Data Warehouse: First defined in 2006 by HMO Research Network. Since 2015, by Health Care System Research Network.
Previous standards, projects and bodies
Health Metrics Network
Read code
ASTM E1238
Bodies working in the field
Health Level Seven International
International Health Terminology Standards Development Organisation
Professional Record Standards Body
NHS England, which provides a Data Standards Directory
References
Health informatics | Clinical data standards | [
"Biology"
] | 761 | [
"Health informatics",
"Medical technology"
] |
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