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72,203,783 | https://en.wikipedia.org/wiki/Arnold%20conjecture | The Arnold conjecture, named after mathematician Vladimir Arnold, is a mathematical conjecture in the field of symplectic geometry, a branch of differential geometry.
Strong Arnold conjecture
Let be a closed (compact without boundary) symplectic manifold. For any smooth function , the symplectic form induces a Hamiltonian vector field on defined by the formula
The function is called a Hamiltonian function.
Suppose there is a smooth 1-parameter family of Hamiltonian functions , . This family induces a 1-parameter family of Hamiltonian vector fields on . The family of vector fields integrates to a 1-parameter family of diffeomorphisms . Each individual is a called a Hamiltonian diffeomorphism of .
The strong Arnold conjecture states that the number of fixed points of a Hamiltonian diffeomorphism of is greater than or equal to the number of critical points of a smooth function on .
Weak Arnold conjecture
Let be a closed symplectic manifold. A Hamiltonian diffeomorphism is called nondegenerate if its graph intersects the diagonal of transversely. For nondegenerate Hamiltonian diffeomorphisms, one variant of the Arnold conjecture says that the number of fixed points is at least equal to the minimal number of critical points of a Morse function on , called the Morse number of .
In view of the Morse inequality, the Morse number is greater than or equal to the sum of Betti numbers over a field , namely . The weak Arnold conjecture says that
for a nondegenerate Hamiltonian diffeomorphism.
Arnold–Givental conjecture
The Arnold–Givental conjecture, named after Vladimir Arnold and Alexander Givental, gives a lower bound on the number of intersection points of two Lagrangian submanifolds and in terms of the Betti numbers of , given that intersects transversally and is Hamiltonian isotopic to .
Let be a compact -dimensional symplectic manifold, let be a compact Lagrangian submanifold of , and let be an anti-symplectic involution, that is, a diffeomorphism such that and , whose fixed point set is .
Let , be a smooth family of Hamiltonian functions on . This family generates a 1-parameter family of diffeomorphisms by flowing along the Hamiltonian vector field associated to . The Arnold–Givental conjecture states that if intersects transversely with , then
.
Status
The Arnold–Givental conjecture has been proved for several special cases.
Givental proved it for .
Yong-Geun Oh proved it for real forms of compact Hermitian spaces with suitable assumptions on the Maslov indices.
Lazzarini proved it for negative monotone case under suitable assumptions on the minimal Maslov number.
Kenji Fukaya, Yong-Geun Oh, Hiroshi Ohta, and Kaoru Ono proved it for semi-positive.
Urs Frauenfelder proved it in the case when is a certain symplectic reduction, using gauged Floer theory.
See also
Symplectomorphism#Arnold conjecture
Floer homology
Spectral invariants
Conley–Zehnder theorem
References
Citations
Bibliography
.
.
Conjectures
Symplectic geometry
Hamiltonian mechanics
Unsolved problems in mathematics | Arnold conjecture | [
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72,205,317 | https://en.wikipedia.org/wiki/N-Heterocyclic%20carbene%20boryl%20anion | An N-heterocyclic carbene boryl anion is an isoelectronic structure of an N-heterocyclic carbene (NHC), where the carbene carbon is replaced with a boron atom that has a -1 charge. NHC boryl anions have a planar geometry, and the boron atom is considered to be sp2-hybridized. They serve as extremely strong bases, as they are very nucleophilic. They also have a very strong trans influence, due to the σ-donation coming from the boron atom. NHC boryl anions have stronger electron-releasing character when compared to normal NHCs. These characteristics make NHC boryl anions key ligands in many applications, such as polycyclic aromatic hydrocarbons, and more commonly low oxidation state main group element bonding.
Synthesis
Ever since the first crystalline carbene structure was isolated by Arduengo ins 1990, tuning different properties of NHCs has been a popular area of study in main group chemistry. The first NHC boryl anion was synthesized by Segawa in 2006. The precursor to the complex was first synthesized by a diimine reduction by magnesium followed by a reaction with BBr3. The final complex was synthesized through cleavage on a boron-bromide bond in a bromo-diazaborole complex by lithium naphthalenide. This reaction made a boryllithium complex, where the boron atom shows strong structural similarity to a free boryl anion. These similarities show that boron has the anionic -1 charge and is recognized as an isoelectronic compound to a singlet carbene. The key to this synthesis was bulky R substituents on the nitrogen which prevented dimerization, something that is common in boron chemistry. These bulky substituents and low temperatures provided successful isolation of the species.
Differing Boryllithium Backbones
After the first synthesis of the NHC boryl anion, Segawa continued to synthesize other NHC boryl anions by switching the backbones of the complexes. In 2008, it was found that by using the same reducing conditions as the first boryl anions, many other NHC boryl anions could be synthesized.
The "Naked" Boryl Anion
A "naked" boryl anion, in which there is no cation near the -1 boron, can be synthesized through an amide metathesis reaction. What is formed is a borylpotassium dimer, in which the K+ ions interact weakly with both the carbons on the substituents on the nitrogens and also the boron centers. The K-B bond distances are >3.1 Å, which is much greater than the sum of the covalent radii. Additionally, the N-B-N bond angle is very close to the calculated gas-phase anion, leading to the conclusion that the boryl anion is as "free" as possible.
Reactivity
NHC boryl ligands tend to be strong σ donors but π acceptors.
Bonding with Group 1 and 2 Elements
When the NHC boryl anion is in the form of a boryllithium salt, it has displayed reactivity with CO, one of the most important building blocks in the industrial field. The complex goes through an insertion reaction, where the CO is inserted into the B-Li bond to make a short-lived intermediate species. This reaction shows promising applications in carbonylative coupling reactions, where CO insertion is necessary.
In 2007, the first B-Mg single bond was synthesized using an NHC boryl anion as the ligand. The B-Mg bonds are slightly longer than the sum of the covalent radii, but this has been attributed to weakened Coulombic interaction due to coordination of the solvent, which was THF in this experiment. This solvent interaction also affects the geometry of the molecule, as the crystal structure shows that the Mg atom has a distorted sp3-hybridized center. However, the results show that the Mg-B bond has ionic character and can be considered a single bond. Another Mg-B bond was synthesized by reacting the NHC boryl anion with a Mg compound in a 2:1 ratio. This Mg atom also had a distorted tetrahedral coordination, which was also attributed to the coordination of the solvent (THF).
The first Be-B bond was reported in 2014, however this bond showed more covalent character, rather than the ionic bond that was reported in the Mg analogue of this complex. This complex was formed by reacting two equivalents of the NHC boryl anion with BeCl2 using benzene as the solvent. In 2020, however, a very interesting reaction between the NHC boryl anion and Be was reported. In this case, the boryl anion was reacted with a Be complex, and rather than forming a bond to, and receiving σ-donation from the boron atom, it reacted with one of the carbons in the backbone of the anion. Although the mechanism of this reaction is unclear, it is believed that one of the backbone protons becomes deprotonated, allowing the Be to bind to the positively charged carbons. This compound is extremely stable even at room temperature, and more studies are being completed to further understand the mechanism of this reaction.
Bonding with Main Group Elements
The NHC boryl anion has also been used to achieve B=B double bonds, but in a tetraborane species rather than the diborane molecule. For this synthesis, an extra boron atom was added to the NHC boryl anion, and then was reduced, forcing dimerization between the molecules and allowing for a H-bridged tetraborane species to occur. Although the complex is H-bridged, the inner B-B bond distance lies between reported double and triple bond lengths. Additionally, the NPA charges on the central B-B moiety are negative, showing that the boryl anions donate electron density, leading to the conclusion that a B=B double bond is occurring.
With specific reaction conditions, a disilane single or double bond can be achieved using the NHC boryl anion. To make a Si-Si single bond, a NHC boryl silane compound is reduced by KC8 in DME solvent. To make a Si-Si double bond, a slightly different NHC boryl silane compound is reduced in KC8 in THF solvent.
Additionally, a dianionic disilyne (Si-Si triple bond) was reported in the form of a Mg complex. Two equivalents of a NHC boryl silane compound is reduced with Mg in THF, leading to a Mg-Si-Si three-membered ring. The boryl anion groups are arranged in a cis formation, and the Si atoms have planar geometry. Additionally, the Si-Si bond length is calculated to be the sum of the covalent radii for a double bond, and the NPA charges show dianionic character on the Si atoms.
Bonding with Transition Metals
NHC boryl anions have also been investigated for their ability to activate C-H bonds and hydroboration activity, two things that were previously thought to only be completed by transition metal systems. Anionic boryl ligands can covalently bond to transition metals, which is different than how it bonds to main group elements (ionically). These boryl ligands σ-bond but also are able to receive π-back donation into the vacant pz orbital that the boron has. It is said that boryl ligands, like NHC boryl anions, are the most effective ligand in controlling reactivity.
Many transition metal boryl complexes have been synthesized, including silver, gold, copper, and zinc. These complexes give insight into potential intermediates of transition metal catalyst reactions, and provide potential starting materials for both organic and inorganic synthetic chemistry.
Group 12 metal bonding has almost exclusively had the metals in the +1-oxidation state, but NHC boryl anions have helped synthesize group 12 M-M bonds in the 0-oxidation state. Group 12 metals take part in very weak bonding in the 0-oxidation state due to the filled valence d-orbitals, when the metals have NHC boryl anion ligands, they are able to bond in the 0-oxidation state because of the increase electron density that is donated by the ligand. These molecules are synthesized by first have m-terphenyls as the ligands on the metal, and then an isolobal exchange occurs, placing the boryl ligands onto the metal and allowing for the metal to be in the 0-oxidation state.
Polycyclic Aromatic Hydrocarbons
One of the most exciting applications for NHC boryl anions are their place in polycyclic aromatic hydrocarbons, or PAHs. PAHs are normally defined as a molecule that has two or more benzenoid rings and contain no other elements except hydrogen and carbon. They are highly fluorescent, and are naturally found in crude oil and other petrochemical products. It has been shown that replacing the end carbons with a B-N moiety expands the family of PAHs and can serve as functional materials.
Placing boron into PAHs is known to improve and diversity the optoelectronic properties by reducing the LUMO energy level. This lowering of the LUMO energy increases acceptor ability by lowering the energy needed for absorption and emission. The fused NHC boryl anion units add an element of bifunctionality and induce π-conjugation because of the empty pz orbital. The absorption and emission qualities of these molecules are very interesting. PAHs that have a pyrene core all fluoresce blue light under UV light, but their smaller and more planar counterparts had a variety of colors that are emitted. This change in color is attributed to the NHC boryl anion rings contributing more to the smaller PAHs, whereas in the pyrene core there is less effect coming from the boron ligand. These planar NHC boryl anion molecules are very promising in their application to functional materials because they emit light in the near-IR region.
References
Boron heterocycles
Anions
Nitrogen heterocycles
Pentacyclic compounds | N-Heterocyclic carbene boryl anion | [
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72,211,204 | https://en.wikipedia.org/wiki/Transformer%20ratio%20arm%20bridge | The transformer ratio arm bridge or TRA bridge is a type of bridge circuit for measuring electronic components, using a.c. It can be designed to work in terms of either impedance or admittance. It can be used on resistors, capacitors and inductors, measuring minor as well as major terms, e.g. series resistance in capacitors. It is probably the most accurate type of bridge available, being capable of the precision needed, for example, when checking secondary component standards against national standards.
Like all bridges, the TRA bridge involves comparing an unknown component against a standard. Like all a.c. bridges, it requires a signal source and a null detector. The accuracy of this class of bridge depends on the ratio of the turns on one or more transformers. A notable advantage is that normal stray capacitance across the transformer, including lead capacitance, may affect the sensitivity of the bridge but does not affect its measuring accuracy.
History
The invention of the TRA bridge is credited to Alan Blumlein in his UK patent 323037 (published 1929), and this class of bridge is sometimes known as a Blumlein bridge, although links to earlier types of bridge can be seen. Blumlein's first patent was for a capacitance-measuring bridge: Fig. 1 is redrawn from one of the diagrams in the patent.
Subsequently the ratio arm principle was applied more generally, to other classes of electronic components and at frequencies up to r.f., and with many variations in how the unknown component was connected to the transformer or transformers.
Blumlein himself was responsible for several further related patents. He made his first bridge while employed by the British company Standard Telephones and Cables, which did not manufacture test instruments. TRA bridges have since been made by many specialist manufacturers, including Boonton, ESI (formerly Brown Engineering and BECO), General Radio, Marconi Instruments, H. W. Sullivan (now part of Megger) and Wayne Kerr.
Principle
One possible configuration using two transformers is shown in Fig. 2. (The two transformers allow both the signal source and the null detector to be isolated from the measured component.) The unknown and the standard are both driven by T1, feeding currents to the primary of T2. Because of the winding sense of the two halves of the T2 primary, these currents are in antiphase.
If and have the same value and are fed from the same tap on T1, the antiphase currents cancel out perfectly and the null detector will show balance. When and are unequal, balance can be approached by connecting to a different tap on the T1 secondary. An exact balance may be achieved by using two or more standards connected to suitable taps.
Fig. 2 shows and as single components. Fig. 3 shows separate standards for conductance and susceptance , allowing minor as well as major terms of to be resolved. The standards are shown as variable components connected to fixed taps on the T1 secondary, but bridges can equally be made with fixed standards connected to variable taps.
The unknown component too may be connected to a tap part-way along the T1 secondary. Also the numbers of turns on the two arms of the T1 secondary are not necessarily equal, and likewise those on the T2 primary. Combinations of these various options offer great flexibility of construction, allowing measurements over a wide range of values while using only a small number of standards – essentially one per significant figure of the resistance or conductance value and one per significant figure of the reactance or susceptance value.
In Fig. 3, at balance
The bridge may be balanced (nulled) by manual switching of the standards, but "autobalance" bridges, in which the switching is wholly or partially automated, are also made.
Detailed example
The operation of a universal TRA bridge is best explained on the basis of an actual product, the Wayne Kerr B221 bridge, dating from the 1950s. It used valve (vacuum tube) technology. The following description is simplified.
The bridge is based on two transformers (Fig. 4): T1 is described as the voltage transformer, and is driven by the signal source in the usual way. T2, the "current transformer", compares the two arms of the circuit – for the unknown and the various standards – and drives the null detector, which takes the form of a phase-sensitive detector with adjustable sensitivity, feeding two magic eyes. (Later versions of the instrument, with transistorised circuitry, used a moving-coil meter as the display for the null detector.)
Taps at 1, 10, 100 and 1000 turns are shown on the T1 secondary and on T2 primary P2a. Four-way selector switches are shown, but the tap selections are actually combined on a single switch to give seven measuring ranges. Full-scale limits at full accuracy (specified as ±0.1%) are 100 MΩ, 11.1 pF and 10 kH for the least sensitive range, and 100 Ω, 11.1 μF and 10 mH for the most sensitive range. Each range can be extended in the direction of higher resistance, higher inductance or lower capacitance at reduced accuracy. The voltage applied by T1 to is about 30 V r.m.s. on the least sensitive range, 30 mV on the two most sensitive.
The most significant figures of the major and minor components of are obtained by switching the resistance standard Rs1 and the capacitance standard Cs1 to one of taps 0 to 10 on the secondary of T1. The second significant figures are obtained by switching Rs2 and Cs2 in the same way. Continuous ("vernier") fine adjustment to give third and fourth significant figures is provided by Rs3 and Cs3. Rs3 and Cs3 are shown connected to tap 10 on T1, but in practice these two standards may be connected to any convenient tap, as appropriate to their values.
Primary P2b on T2 provides 100-turn taps of both polarities. Switching the capacitance standards between the positive and negative taps selects between capacitance measurements and inductance measurements. Similarly the polarity of the resistance standard can be reversed, so that measurements can be made in all four quadrants.
Besides the main balance controls described above, the front panel of the instrument has zero adjustments for both resistance and capacitance. The inductive elements of the wire-wound resistance standards are compensated by trimming capacitors. All these and other trimming components are omitted in Fig. 4.
This bridge measures conductance and susceptance in parallel. The susceptance reading is displayed as capacitance, and inductance must be calculated as a reciprocal using
To simplify the arithmetic, the bridge operates at 1592 Hz so that ω2 is 108 s−2. The readings can be converted to resistance and capacitance in series. On the most sensitive ranges, readings must be adjusted to take account of lead resistance and inductance.
The external link allows two-, three- or four-terminal measurements to be made. Besides conventional component measurements, the bridge can also be used to measure attenuator performance, transformer turns ratio and the effectiveness of transformer screening. Subject to conditions, in-situ (in-circuit) measurement of a component is possible. With additional external components, capacitors with a polarising voltage or inductors with a standing direct current can be measured.
An optional low-impedance adaptor extends the measuring range downwards by another four orders of magnitude, giving full-scale readings down to 10 mΩ, 5 F and 1 μH at ±1% basic accuracy.
See also
Capacitance meter
LCR meter
References
Further reading
Henry P. Hall, A History of Impedance Measurements, based on a draft for an unpublished book.
Electrical meters
Bridge circuits
Measuring instruments
English inventions
Impedance measurements
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72,213,808 | https://en.wikipedia.org/wiki/Isotopocule | Isotopocules are isotopically substituted molecules, which differ only in their isotopic composition or their isotopes' intramolecular position. "Isotopocule" is also an umbrella term for the more specific terms "isotopologue" and "isotopomer", coined by Jan Kaiser and Thomas Röckmann in 2008.
References
Isotopes
Physical chemistry | Isotopocule | [
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73,622,656 | https://en.wikipedia.org/wiki/Laser-assisted%20drug%20delivery | Laser-assisted drug delivery (LADD) is a drug delivery technique commonly used in the dermatology field that involves lasers. As skin acts as a protective barrier to the environment, the absorption of topical products through the epidermis is limited; thus, different drug delivery modalities have been employed to improve the efficacy of these treatments. The use of lasers in LADD has been shown to enhance the penetration of drugs transdermal, leading to a higher absorption rate, limited systemic effects, and reduced duration of treatment. Although this technique has evolved in the past decade due to its efficacy through scientific research and clinical practice, there remain some limitations regarding the safety aspect that needs to be taken into consideration.
Transdermal drug delivery
The skin barrier
Skin is the largest organ in the human body that acts as the primary protective barrier against the external environment. It provides protection against ultraviolet light, trauma, pathogens, microorganisms, and toxins, sensory perception, temperature regulation, and immunity. There are primarily three layers of skin, which include the outer epidermis, followed by the dermis and subcutaneous tissue, or hypodermis. Skin is used as the target for drug delivery as it is a convenient route of drug administration, and the large area allows for different placements on the skin for transdermal delivery
Transdermal delivery
Transdermal delivery is a non-invasive method commonly assisted in transporting topical products into intact and healthy skin. The substances initially penetrate through the stratum corneum, which is the outermost layer of the epidermis, then diffuse into the deeper epidermis and dermis layers for a systemic effect. Although transdermal drug delivery presents several advantages as compared to other conventional modalities such as oral and parenteral routes, the complexity of the skin barrier limits the methodology to reach its full potential.
Improvement in transdermal delivery
Various technologies have been developed to enhance the permeability of transdermal drugs, which can be divided into passive or chemical and active or physical methods. The passive approach involves the optimization of drug and vehicle interaction that could modify the stratum corneum structure or the addition of penetration enhancers for better absorption rates. Some of the limitations of this approach include lag time in drug release, low efficiency, and skin irritation. The active approach involves ultrasound, electrical stimulation, thermal approach, and mechanical approach. These techniques facilitate the transportation of drugs by using energy as a driving force. Within the thermal approach, laser-assisted drug delivery is a common and effective method that has been used to increase the efficiency of transdermal drug delivery by selectively destroying the chromophores of interest using light waves.
Specifications for using LADD
Lasers
There are different types of lasers used in LADD, and they can be categorized into four main groups: (1) fully ablative lasers, (2) ablative fractional lasers (AFL), (3) non-ablative fractional lasers (NAFL), and (4) non-ablative dermal remodeling lasers. Common fully ablative lasers, including carbon dioxide (CO₂, wavelength peak 10,600 nm) and erbium-doped yttrium aluminum garnet (Er:YAG, wavelength peak 2940 nm), target water as their chromophore where all water-containing tissues within the epidermis are ablated. With its high wavelength peak, CO₂ laser has a high absorption rate of water and adipose tissues; whereas the wavelength of Er:YAG allows for the precise ablation of water and minimizes heat generation. The mechanism of AFL is similar to fully ablative lasers but when used fractionally, they create multiple vertical columns on the skin surface, which are also called microscopic treatment zones (MTZ) and allow for a more quantitatively controllable usage in LADD. NAFL are also fractionated lasers that produce MTZ, but as they are non-ablative, there is no ablation of the epidermis and instead, they use light energy to damage the dermis layer. Non-ablative dermal remodeling lasers include all types of lasers with a chromophore that is different from water as used in the previous groups. Common lasers within this group are neodymium-doped YAG laser (Nd: YAG, wavelength peak 1064 nm and 1320 nm), pulsed dye laser (wavelength ranges from 585 to 600 nm), and intense pulsed laser (IPL, wavelength ranges from 500 to 1200 nm). In general, with its high efficiency and rapid recovery time, AFL is the more common modality used for LADD, especially in the dermatology field.
Drugs
Lipophilic substances have shown to have a greater ability to cross the epidermis, thus, the efficiency of LADD is more remarkable when using hydrophilic substances. Liquid and gel formulations of drugs also are proven to cross the channels created from the fractional lasers more easily as compared to oily formulations such as creams or ointments. Common drugs used in LAPP include but are not limited to 5-aminolaevulinic (5-ALA), 5-aminolevulinate (MAL), methotrexate (MTX), imiquimod, 5-fluorouracil (5-FU), timolol, triamcinolone acetonide (TAC), bimatoprost, tretinoin, pimecrolimus, poly-L-lactic acid (PLLA), analgesics, minoxidil (MXD), diphencyprone (DPCP), vitamin C, small interfering RNA (siRNA), vaccine, and antibodies.
Patients
The efficiency of LADD with the selected laser settings is dependent upon the different characteristics associated with individual patients. The dermatological condition, the properties of the skin, and the surface area are taken into consideration to determine the eligibility of the patients for certain lasers and provide optimal treatments for each patient. For example, hydrated skin has a higher affinity for absorption of oily substances; skin atrophy that is associated with solar elastosis is more likely to produce pathological scarring under high laser intensity; hair areas have a higher absorption rate; older patients are more prone to adverse effects such as atrophy, erosion, ulceration, and will require longer recovery time. Not all patients are candidates for LADD as this method is intensified as compared to conventional topical treatment.
Pre-clinical application
A vast majority of pre-clinical work on LADD focuses on AFL based on its translational characteristics in clinical settings. These studies utilized mostly either porcine or murine skin as their disease model.
Porcine skin
Within the dermatology field, porcine skin has been used as a disease model for testing the efficacy of LADD in vivo. Haedersdal et al. pre-treated porcine skin with CO2-AFL before the application of MAL photodynamic therapy (PDT), creating single MTZs that increased porphyrin fluorescence uniformly up to 1.5 mm from the ablated channels. This demonstrated that for MAL, pre-treatment of AFL with MTZs spacing at 3-mm intervals, covering less than 1% surface of the area, was useful for the entire lesion. Similarly, Bachhav et al. showed that the increased numbers of MTZs from Er:YAG laser did not affect the absorption of lidocaine into either the epidermis or dermis, and thus, higher fluences of laser were not proportionally correlated to the absorption rate. AFL pre-treatment of porcine skin also has also shown to enhance the delivery of MAL at deeper layers of the skin, increase surface fluorescence from MAL as compared to non-AFL pre-treated skin, and induce higher fluorescence of 5-ALA as compared to MAL for deeper structure.
Murine skin
Besides porcine skin, murine skin has also been used for testing the efficacy of LADD. A study performed on murine skin has shown that the penetration of 5-FU through skin increased 36 to 133-fold after pre-treatment with fully ablative Q-switched ruby, CO2, or Er:YAG lasers. Likewise, delivery of imiquimod in both murine and porcine skin increased up to 65-fold and 127-fold, after one and four passes of low-fluence fractional Er:YAG laser, respectively. As a result, with LADD, a dose of 0.4% imiquimod was equivalent to a topically applied dose of 5% imiquimod, which implied that a lower dosage of drug could be used with similar clinical outcomes. Besides topical drugs, Chen et al. showed that the treatment of fractional CO2 on murine skin increased 8- to 15-fold the delivery of ovalbumin vaccine, along with an enhanced production of ovalbumin specific antibodies at 2 weeks.
Clinical application
LADD has been implemented in clinical practice to support the absorption of topical agents into the skin, representative drugs include 5-ALA, MAL, 5-FU, corticosteroid, vitamin, and lidocaine.
Photodynamic therapy
LADD has been used in adjunction to photodynamic therapy (PDT) as a pre-treatment, which has shown to enhance the absorption of these drugs into the skin. 5-ALA and MAL are common photosensitizers that are used in PDT to treat different skin diseases such as actinic keratoses (AK), Bowen’s disease, and superficial cell carcinoma.
5-ALA
Lim et al. (2014) utilized nonablative fractional laser Er:YAG to pre-treat twelve treatment areas on the back of 10 healthy males, followed by the incubation of 5-ALA. The results showed that pre-treated areas had higher level of porphyrin fluorescence as compared to non-pretreated areas, which indicated that LADD enhanced 5-ALA skin penetration. In another study, Jang et al. (2013) pre-treated 29 AK patients with an ablative CO2 fractional laser, followed by 5-ALA-PDT treatment with varying incubation times. The pre-treatment of laser showed improvement of clinical outcomes even with the short incubation time, with 70.6% of the AK lesions had a complete clinical response to PDT.
MAL
In a randomized study, Choi et al. used both conventional MAL-PDT and a combination of AFL (Er:YAG) and MAL-PDT to treat 93 AK patients. The group treated with a combination of LADD and PDT showed higher clinical response rate of 91.7% as compared to conventional MAL-PDT group with clinical response rate of 65.6% after three months, and results were persistent after a twelve-month follow-up. In another randomized study with 21 patients with Bowen’s disease, the clearance rate of the lesions after 3 months was higher with pre-treatment of one session of ablative fractional Er:YAG followed by MAL-PDT (93.8%) as compared to two sessions of conventional MAL-PDT (73.1%), and with lower recurrence rates (6.7% versus 31.6%).
5-FU
5-FU is a common drug which is used to treat cancer and certain skin diseases, such as AK and certain types of nonmelanoma skin cancers. In a case study of 28 patients, including 16 superficial basal cell carcinomas and 14 squamous cell carcinomas in situ, pre-treatment of a single pass of CO2-AFL followed by a single application of 5-FU showed histological clearance of 100% squamous cell carcinomas in situ and 71% of the superficial basal cell carcinomas. In a case report study, a patient with multiple Bowen’s disease lesions was selected for a half-side study, one was treated with Er:YAG laser followed by a topical treatment of 5-FU and the other was treated with only 5-FU cream. The legions treated with LADD showed accelerated clinical and histologic response as compared to conventional 5-FU, with no recurrences of lesions after 9 months. In another study, Wenande et al. (2021) showed that CO2-AFL enhanced the efficiency of cisplatin and 5-FU treatment for 20 patients with basal cell carcinoma, with 94.7% patients showed clinical clearance.
Corticosteroid
Triamcinolone acetonide (TAC) is a common corticosteroid used as a therapeutic strategy for hypertrophic scars and keloids. In a case study, Waibel et al. used CO2-AFL to assist topical TAC delivery to treat 15 patients with hypertrophic and restrictive cutaneous scars. The results showed that significant improvement of the scars was observed after 6 months, with the most impacts on texture. Similarly, in a pilot study, either CO2-AFL or radiofrequency was used in adjunction with ultrasound-assisted TAC to treat alopecia areata, a disease associated with hair loss. All patients showed complete response after the treatment and specifically, the use of LADD with CO2-AFL showed complete response of patients after a single session as compared to a required of three and six sessions for radiofrequency.
Vitamin
Vitamin C and E are important substances that show antioxidant effects against UV radiation. Transdermal delivery after topical application of these vitamins has been facilitated with LADD. Lee et al. (2003) showed that the application of either nonablative fractional Er:YAG or CO2 lasers improved the transdermal penetration of vitamin C significantly. In a split face comparison study regarding UV-induced skin aging, Trelles et al. treated 14 patients with conventional CO2-AFL on one side and CO2-AFL along with the application of vitamin C and E on the other side. As a result, the combination of LADD and vitamins demonstrated a 79% reduction in fine lines as compared to a 69% reduction for AFL-treated side without the delivery of vitamins.
Lidocaine
Local anesthesia is used widely for dermatological surgeries via topical products or injections. As topical agents have a long incubation time for drug penetration and injections are associated with pain, LADD has been applied to the field for advancing the efficacy of anesthesia. Lidocaine is a local anesthetic cream used to prevent and treat pain. Increase dermal absorption and transdermal bioavailability of lidocaine were seen when using in conjunction with LADD, specifically AFL. Yun et al. demonstrated that 5% lidocaine cream applied after Er:YAG-AFL for a full resurfacing procedure showed significant lower pain score after the first pass of resurfacing, but there were only half of the patients were able to tolerate the second pass. Nevertheless, this indicated that LADD showed an enhancement of lidocaine penetration through the stratum corneum. Similarly, in a double-blind randomized controlled trial with 320 healthy volunteers, the patients were either pre-treated with Er:YAG-AFL followed by 4% lidocaine or treated with topical 4% lidocaine alone before cannulation. The results showed a 62% reduction in pain with the use of LADD as compared to conventional topical lidocaine.
Safety and adverse events
When applying LADD in clinical settings, safety is an imperative factor that needs to be considered. As mentioned above, there are different lasers with distinct properties that could be implemented for patients. However, radiation of any type will damage human tissue to some extent. Some potential adverse events that are laser-induced include erythema, edema, scabbing, blistering, and pigmentary changes, especially at higher intensity and densities. Regarding intralesional therapies for scarring, telangiectasia, hypopigmentation, and skin atrophy have been observed in multiple studies as side effects of LADD. In LADD application for management of pigmentary condition, there are some pigment-related adverse effects such as worsening of melasma, and hyperpigmentation in vitiligo. While LADD improves the dermal infiltration of different medications, the skin also has heightened local reaction when exposed to the substances and external environment. In several studies about AFL-assisted delivery of MAL-photodynamic therapy, there are intensified local cutaneous responses, including burning sensation, pain, edema, pruritus, purpura, and transient pigmentary changes. Furthermore, exposing the underlying dermis and vasculature to the outside environment also increases the risk of infection. AFL-assisted delivery of 5-FU, steroids, and MAL have shown elevated bacterial infections. In general, most LADD safety concerns are related to local reactions similar to that of laser therapy, and are generally well-tolerated with some exceptions.
Future direction
Current studies support the use of LADD in adjunction with topical products in treating dermatological diseases, but these studies are limited in sample size and lack of long-term follow-up outcomes. Larger randomized controlled trials with a wide variety of topical drugs are required to validate the efficacy and side effects of LADD before this technique could be employed as a standard of treatment. Besides its application in drug delivery, the prospect of using LADD to improve the transdermal delivery of vaccines, promote wound healing, correct genetic sequence, and as a complement to inflammatory dermatoses and cosmetic indications is being investigated
References
Drug delivery devices | Laser-assisted drug delivery | [
"Chemistry"
] | 3,668 | [
"Pharmacology",
"Drug delivery devices"
] |
73,624,176 | https://en.wikipedia.org/wiki/Europium%28III%29%20phosphate | Europium(III) phosphate is one of the phosphates of europium, with the chemical formula of EuPO4. Other phosphates include europium(II) phosphate (Eu3(PO4)2) and europium(II,III) phosphate (Eu3Eu(PO4)3).
Preparation
Europium phosphate can be produced by the sol-gel method of europium(III) oxide. First, europium(III) oxide was dissolved in an equimolar amount of nitric acid, and then an excess of 10% phosphoric acid was added. The process also requires the addition of ammonia to adjust the pH to 4 and form a gel, which is then washed with water and heated to 1200 °C for a day.
Properties
Europium(III) phosphate is isotypic to CePO4 and crystallizes in the monazite structure type, in the space group P21/n (no. 14, position 2) with the lattice parameters a = 668.13(10), b = 686.18(9), c = 634.91(8) pm and β = 103.96(1)° with four formula units per unit cell. Its heat capacity is 111.5 J·K−1·mol−1 at 298.15 K, and its bulk modulus is 159(2) GPa.
References
Europium(III) compounds
Phosphates | Europium(III) phosphate | [
"Chemistry"
] | 304 | [
"Phosphates",
"Salts"
] |
73,627,447 | https://en.wikipedia.org/wiki/Introduction%20to%20Elementary%20Particles%20%28book%29 | Introduction to Elementary Particles, by David Griffiths, is an introductory textbook that describes an accessible "coherent and unified theoretical structure" of particle physics, appropriate for advanced undergraduate physics students. It was originally published in 1987, and the second revised and enlarged edition was published 2008.
Content (2nd edition)
Table of contents
History and Overview
Chapter 1: Historical Introduction to the Elementary Particles
Chapter 2: Elementary Particle Dynamics
Chapter 3: Relative Kinematics
Chapter 4: Symmetries
Chapter 5: Bound States
Quantitative Formulation of Particle Dynamics
Chapter 6: The Feynman Calculus
Chapter 7: Quantum Electrodynamics
Chapter 8: Electrodynamics of Quarks and Hadrons
Chapter 9: Quantum Chromodynamics
Chapter 10: Weak Interactions
Chapter 11: Gauge Theories
Appendices
Appendix A: The Dirac Delta Function
Appendix B: Decay Rates and Cross Sections
Appendix C: Pauli and Dirac Matrices
Appendix D: Feynman Rules
New content in the second addition includes "neutrino oscillations and prospects for physics beyond the Standard Model".
Reception
The first edition, reviewed by Gerald Intermann, earned praise for its "good use of examples as a means of discussing in detail useful problem-solving techniques that other texts leave for the student to discover."
Acknowledging it as a "a well-established textbook", an IAEA review said the second edition "...strikes a balance between quantitative rigor and intuitive understanding, using a lively, informal style... The first chapter provides a detailed historical introduction to the subject, while subsequent chapters offer a quantitative presentation of the Standard Model. A simplified introduction to the Feynman rules, based on a 'toy' model, helps readers learn the calculational techniques without the complications of spin. It is followed by accessible treatments of quantum electrodynamics, the strong and weak interactions, and gauge theories."
The Times Higher Education review said, "The first edition of this textbook was notable for providing a clear and logical overview of particle physics that was at the right level for advanced undergraduates... The contents of this revised edition are largely similar to those contained in the first edition and changes reflect the development of the subject in the intervening 20 years. As a result, some discussions have now been tightened or removed, and chapters describing neutrino oscillations and contemporary theoretical developments have been added." The review concluded, "Reading any section will always yield insights, and you can't go wrong with Griffiths as a guide. Who is it for? Advanced undergraduates, postgraduates, lecturers and anyone in the field of experimental particle physics."
Publication history
References
External links
, Preface | Physics Audio Books, video (4:11 minutes)
Physics textbooks
Quantum mechanics
1987 non-fiction books
2005 non-fiction books
2004 non-fiction books
Undergraduate education
Wiley (publisher) | Introduction to Elementary Particles (book) | [
"Physics"
] | 575 | [
"Quantum mechanics",
"Works about quantum mechanics"
] |
73,627,835 | https://en.wikipedia.org/wiki/Neodymium%28II%29%20hydride | Neodymium dihydride is an inorganic compound, with the chemical formula of NdH2, although it is an electride, and it is actually composed of Nd3+(e−)(H−)2. It is ferromagnetic.
Chemical properties
Neodymium dihydride reacts with lithium borohydride to obtain neodymium tetraboride:
NdH2 + 4 LiBH4 → NdB4 + 4 LiH + 7 H2↑
See also
Europium hydride
Ytterbium hydride
References
External reading
Struss, Arthur W.; Corbett, John D. Reaction of hydrogen with metallic and reduced halides. The requirement of delocalized electrons for reaction. Inorganic Chemistry, 1978. 17(4): 965-9. DOI:10.1021/ic50182a034
Neodymium(II) compounds
Metal hydrides
Ferromagnetic materials | Neodymium(II) hydride | [
"Physics",
"Chemistry"
] | 204 | [
"Electron",
"Inorganic compounds",
"Electrides",
"Ferromagnetic materials",
"Salts",
"Reducing agents",
"Materials",
"Metal hydrides",
"Matter"
] |
73,636,178 | https://en.wikipedia.org/wiki/Modifiable%20temporal%20unit%20problem | The Modified Temporal Unit Problem (MTUP) is a source of statistical bias that occurs in time series and spatial analysis when using temporal data that has been aggregated into temporal units. In such cases, choosing a temporal unit (e.g., days, months, years) can affect the analysis results and lead to inconsistencies or errors in statistical hypothesis testing.
Background
The MTUP is closely related to the modifiable areal unit problem or MAUP, in that they both relate to the scale of analysis and the issue of choosing an appropriate analysis. While the MAUP refers to the choice of spatial enumeration units, the MTUP arises because different temporal units have different properties and characteristics, such as the number of periods they contain or the amount of detail they provide. For example, daily sales data for a product can be aggregated into weekly, monthly, or yearly sales data. In this case, using monthly data instead of daily data can result in losing important information about the timing of events, and using yearly data can obscure short-term trends and patterns. However, the daily data in the example may have too much noise, temporal autocorrelation, or be inconsistent with other datasets. With only daily data, conducting an analysis accurately at the hourly rate would not be possible. In addition, the Modifiable Temporal Unit Problem can also arise when the time units are irregular or when the data is missing for some periods. In such cases, the choice of the time unit can affect the amount of missing data, which can impact the accuracy of the analysis and forecasting.
Overall, the Modifiable Temporal Unit Problem highlights the importance of carefully considering the time unit when analyzing and forecasting time series data. It is often necessary to try different time units and evaluate the results to determine the most appropriate choice.
Temporal autocorrelation
Temporal autocorrelation refers to the degree of correlation or similarity between values of a variable at different time points. It examines how a variable's past values are related to its current values over a sequence of time intervals. High temporal autocorrelation implies that past observations influence future observations, while low autocorrelation suggests that current values are independent of past values. This concept is often used in time series analysis to understand patterns, trends, and dependencies within a time-ordered dataset, helping to make predictions and infer the underlying dynamics of a system over time. By adjusting the temporal unit used to bin the data in the analysis, temporal autocorrelation can be addressed.
Implications
Crime
The impact of MTUP on crime analysis can be significant, as it can affect the accuracy and reliability of crime data and its conclusions about crime patterns and trends. For example, suppose the temporal unit of analysis is changed from days to weeks. In that case, the number of reported crimes may decrease or increase, even if the underlying pattern remains constant. This can lead to incorrect conclusions about the effectiveness of crime prevention strategies or the overall level of crime in a given area.
Food accessibility
The MTUP can also have an impact on food accessibility. This issue arises when the temporal unit of analysis is changed, leading to changes in the patterns and trends observed in food accessibility data. For example, if food accessibility data is analyzed from different years or aggregated differently, then the results of a study are likely to be impacted. This can affect our understanding of the availability of food in different areas over time, and can result in incorrect or incomplete conclusions about food accessibility.
Epidemiology
The MTUP can affect our understanding of the incidence and prevalence of diseases or health outcomes in different populations over time, resulting in incorrect or incomplete conclusions about the public health situation. The timeframe chosen for collecting and analyzing public health data is something that needs to be considered by researchers.
Suggested solutions
To address the MTUP, it is important to consider the temporal resolution of the data and choose the most appropriate temporal unit based on the research question and the goals of the analysis. In some cases, it may be necessary to aggregate or interpolate the data to a consistent temporal unit. Additionally, it may be helpful to use multiple temporal units or to present results for different temporal units to demonstrate the sensitivity of the results to the choice of temporal unit.
See also
Arbia's law of geography
Boundary problem (spatial analysis)
Coastline paradox
Concepts and Techniques in Modern Geography
Chronology
Ecological fallacy
Facility location problem
Geographic information systems
Historical GIS
Neighborhood effect averaging problem
Torsten Hägerstrand
Spatial epidemiology
Technical geography
Time geography
Timestamp
Tobler's first law of geography
Tobler's second law of geography
Uncertain geographic context problem
References
Bias
Geographic information systems
Problems in spatial analysis | Modifiable temporal unit problem | [
"Technology"
] | 951 | [
"Information systems",
"Geographic information systems"
] |
59,912,350 | https://en.wikipedia.org/wiki/Polysuccinimide | Polysuccinimide (PSI), also known as polyanhydroaspartic acid or polyaspartimide, is formed during the thermal polycondensation of aspartic acid and is the simplest polyimide. Polysuccinimide is insoluble in water, but soluble in some aprotic dipolar solvents. Its reactive nature makes polysuccinimide a versatile starting material for functional polymers made from renewable resources.
The name is derived from the salt of succinic acid, the structurally related succinate.
Production
The production of polysuccinimide was reported by Hugo Schiff as early as 1897. When dry aspartic acid was heated for about 20 hours at 190 °C to 200 °C, a colorless product was obtained. Above 200 °C, a weak yellowing occurs, the yield was almost quantitative.
In the experiments by Hugo Schiff, oligomers and low-molecular polymers were formed in a solid state reaction by polycondensation upon water elimination. This is generally the case in the absence of strong acids, which suppress the thermal decomposition of free amino end groups and thus chain interruption reactions. The formation of the polyimide polysuccinimide can be followed by the intensive absorption band in the infrared spectrum at 1714 cm−1. Many process variants described in the patent literature yield besides a relatively low degree of polymerization often branched and yellow to brown discolored products.
Recent work has focused on increasing the molar mass and achieving a linear chain structure while avoiding decomposition reactions. With a simple "oven process" in which a mixture or paste of crystalline aspartic acid and concentrated phosphoric acid or polyphosphoric acid in a thin layer is heated to 200 °C for 2 to 4 hours, polysuccinimide is produced with molar masses in the range of 30,000 g/mol and cream white shade. The implementation of the polycondensation in several steps (precondensation, comminution, postcondensation), with other dehydrating substances (for example zeolites, triphenyl phosphite) or in the presence of solvents (for example propylene carbonate) provides higher molecular weight products with molar masses in the range of 10,000 to 200,000 g/mol. However, the patent literature does not address the polymer morphology, in particular the degree of branching.
A recent patent describes the simple preparation of high molecular weight, virtually colorless and linear, unbranched polysuccinimide. For this purpose, aspartic acid, which is present as crystalline zwitterion and practically water-insoluble, is firstly dissolved with an aqueous, volatile acid (preferably hydrochloric acid) and mixed with phosphoric acid as condensing agent. The resulting homogeneous solution is evaporated at 120 °C and the resulting glassy mass is then polycondensed at 180 °C to 200 °C for at least one hour. The phosphoric acid is washed out and the dried polysuccinimide is converted by mild alkaline hydrolysis into water-soluble polyaspartic acid; the molar mass of which can be determined by gel permeation chromatography. The process provides reproducible polysuccinimide with molar masses above 100,000 g/mol.
Synthetic routes for polysuccinimides based on maleic acid monoammonium salt, maleic anhydride and ammonia or based on the intermediately formed maleic acid monoamide achieved only low molar masses of a few 1,000 g/mol and yielded colored products. The same was the case for "green" process variants in supercritical carbon dioxide and while avoiding mineral acids as catalysts.
Due to the lower cost of maleic anhydride and ammonia, starting materials produced from fossil raw materials, no L-aspartic acid (of biogenic origin) is used in the production of the commercial product Baypure® polysuccinimide either.
Properties
Polysuccinimide is produced as an odourless, non-hygroscopic, cream-white to brown powder which is soluble in aprotic dipolar solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, triethylene glycol or mesitylene/sulfolane mixtures. Polysuccinimide hydrolyses in water only very slowly. In diluted alkaline media (e.g. 1M sodium hydroxide solution), hydrolysis takes place in α- and β-position of the succinimide (2,5-pyrrolidinedione) ring structures and racemization follows at the chiral center of the aspartic acid, yielding the water-soluble sodium salt of the poly(α, β)-DL-aspartic acid. The α form is formed to approx. 30%, the β form to approx. 70% in random arrangement along the polymer chain.
In more basic solutions or with longer reaction times, the amide linkages in the polymer chain are attacked upon degradation of the molar mass. The presence of amide bonds makes the polyaspartic acid obtained in the hydrolysis relatively biodegradable (about 70% in wastewater), even of initially highly crosslinked polysuccinimides.
Use
The polysuccinimide developed by Bayer AG and marketed by Lanxess AG under the brand name Baypure® DSP with an average molecular weight of 4,400 g/mol is partially hydrolyzed even at slightly elevated pH values and is thus swellable in highly crosslinked form or water-soluble in linear form. The copoly-(succinimide-aspartic acid) formed by partial hydrolysis and especially polyaspartic acid (trade name Baypure® DS 100) produced by partial hydrolysis is suitable as a long-lasting inhibitor against limescale deposition in water treatment and applications in the oil and mining industries, and as a setting retarder for cement in the construction industry. Patent literature mentions polysuccinimide applications as chelating agents, inhibitors against scale formation, dispersant, humectants, and fertilizer additives.
The opening of the pyrrolidinedione ring structures in polysuccinimide via aminolysis with ammonia water (containgin NH4OH) produces poly-(α, β)-DL-asparagine, with hydrazine poly-(α, β)-DL-aspartylhydrazide (PAHy) and with functional amines, e.g. ethanolamine poly-(α), β)-DL-2-hydroxyethylaspartate (PHEA). PHEA can be used a plasma expander with good biocompatibility and biodegradability, high water solubility at low manufacturing costs and was investigated more intensive as a potential drug carrier) in medical applications.
Cross-linked poly(α, β)-DL aspartic acid sodium salt, which is the commercially most interesting polysuccinimide derivative, has been extensively tested for its suitability as a biodegradable superabsorbent compared to the non-biodegradable standard cross-linked sodium polyacrylate. The results obtained have not yet led to the use of crosslinked polyaspartic acid in large-volume applications for superabsorbents (e.g. baby diapers).
References
Polymers
Succinimides | Polysuccinimide | [
"Chemistry",
"Materials_science"
] | 1,594 | [
"Polymers",
"Polymer chemistry"
] |
59,915,725 | https://en.wikipedia.org/wiki/Behrend%20sequence | In number theory, a Behrend sequence is an integer sequence whose multiples include almost all integers. The sequences are named after Felix Behrend.
Definition
If is a sequence of integers greater than one, and if denotes the set of positive integer multiples of members of , then is a Behrend sequence if has natural density one. This means that the proportion of the integers from 1 to that belong to converges, in the limit of large , to one.
Examples
The prime numbers form a Behrend sequence, because every integer greater than one is a multiple of a prime number. More generally, a subsequence of the prime numbers forms a Behrend sequence if and only if the sum of reciprocals of diverges.
The semiprimes, the products of two prime numbers, also form a Behrend sequence. The only integers that are not multiples of a semiprime are the prime powers. But as the prime powers have density zero, their complement, the multiples of the semiprimes, have density one.
History
The problem of characterizing these sequence was described as "very difficult" by Paul Erdős in 1979.
These sequences were named "Behrend sequences" in 1990 by Richard R. Hall, with a definition using logarithmic density in place of natural density. Hall chose their name in honor of Felix Behrend, who proved that for a Behrend sequence , the sum of reciprocals of must diverge. Later, Hall and Gérald Tenenbaum used natural density to define Behrend sequences in place of logarithmic density. This variation in definitions makes no difference in which sequences are Behrend sequences, because the Davenport–Erdős theorem shows that, for sets of multiples, having natural density one and having logarithmic density one are equivalent.
Derived sequences
When is a Behrend sequence, one may derive another Behrend sequence by omitting from any finite number of elements.
Every Behrend sequence may be decomposed into the disjoint union of infinitely many Behrend sequences.
References
Integer sequences | Behrend sequence | [
"Mathematics"
] | 435 | [
"Sequences and series",
"Integer sequences",
"Mathematical structures",
"Recreational mathematics",
"Mathematical objects",
"Combinatorics",
"Numbers",
"Number theory"
] |
59,915,731 | https://en.wikipedia.org/wiki/Davenport%E2%80%93Erd%C5%91s%20theorem | In number theory, the Davenport–Erdős theorem states that, for sets of multiples of integers, several different notions of density are equivalent.
Let be a sequence of positive integers. Then the multiples of are another set that can be defined as the set of numbers formed by multiplying members of by arbitrary positive integers.
According to the Davenport–Erdős theorem, for a set , the following notions of density are equivalent, in the sense that they all produce the same number as each other for the density of :
The lower natural density, the inferior limit as goes to infinity of the proportion of members of in the interval .
The logarithmic density or multiplicative density, the weighted proportion of members of in the interval , again in the limit, where the weight of an element is .
The sequential density, defined as the limit (as goes to infinity) of the densities of the sets of multiples of the first elements of . As these sets can be decomposed into finitely many disjoint arithmetic progressions, their densities are well defined without resort to limits.
However, there exist sequences and their sets of multiples for which the upper natural density (taken using the superior limit in place of the inferior limit) differs from the lower density, and for which the natural density itself (the limit of the same sequence of values) does not exist.
The theorem is named after Harold Davenport and Paul Erdős, who published it in 1936. Their original proof used the Hardy–Littlewood tauberian theorem; later, they published another, elementary proof.
See also
Behrend sequence, a sequence for which the density described by this theorem is one
References
Theorems in number theory | Davenport–Erdős theorem | [
"Mathematics"
] | 348 | [
"Mathematical theorems",
"Theorems in number theory",
"Mathematical problems",
"Number theory"
] |
64,964,188 | https://en.wikipedia.org/wiki/Jani%20Ingram | Jani Ingram is a professor of chemistry and biochemistry at Northern Arizona University. Ingram researches the chemistry and health impacts of environmental pollutants, especially uranium and arsenic. Ingram is a member of the Navajo tribe, and the Naneesht’ezhi clan. She leads the Bridging Arizona Native American Students to Bachelor's Degrees (NIH Bridges to Baccalaureate) program and the Native American Cancer Prevention Program. She promotes educational and professional opportunities for Native American students in chemistry through a number of initiatives and for this work was awarded the 2018 American Chemical Society Award for Encouraging Disadvantaged Students into Careers in the Chemical Sciences.
Education
Ingram began her academic studies at Yavapai Community College in Arizona where she earned an associate's degree. She subsequently studied at New Mexico State University and earned a bachelor's degree in chemistry. Her Ph.D. is in chemistry from the University of Arizona.
Career and research
Ingram's research areas are analytical chemistry and environmental chemistry. She specializes on environmental uranium and arsenic contamination and how they effect the food chain and water supplies of the Navajo nation. She also researches traditional Navajo food ingredients and their health benefits, for example juniper ash as a calcium source. In light of the COVID-19 pandemic, her research laboratory repurposed their facilities to produce hand sanitizer which was donated to the Navajo Nation.
References
Northern Arizona University faculty
Navajo scientists
Yavapai College alumni
New Mexico State University alumni
University of Arizona alumni
Analytical chemists
American women biochemists
21st-century American women scientists
Native American women scientists
21st-century Native American scientists
21st-century Native American women
Living people
Year of birth missing (living people)
Chemists from Arizona | Jani Ingram | [
"Chemistry"
] | 340 | [
"Analytical chemists"
] |
64,971,289 | https://en.wikipedia.org/wiki/Katja%20Loos | Katja Loos is professor at the Zernike Institute for Advanced Materials of the University of Groningen, The Netherlands holding the chair of Macromolecular Chemistry and New Polymeric Materials.
She currently serves as the President of the European Polymer Federation (EPF).
Biography
Katja Loos studied chemistry at the Johannes Gutenberg Universität in Mainz, Germany and graduated in 1996. During her graduate studies she focused her studies on Organic Chemistry and Polymer Chemistry. In 1992 and 1993 she was an international exchange student at the University of Massachusetts in Amherst, USA.
In 2001, she received her PhD in Macromolecular Chemistry from the University of Bayreuth, Germany. Her thesis was focused on hybrid materials bearing amylose using enzymatic polymerizations. During her PhD research she worked in 1997 as an international exchange researcher at the Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
In 2001, she received a Feodor Lynen research fellowship of the Alexander von Humboldt Foundation to conduct postdoctoral research at the Polytechnic University in Brooklyn, NY, USA, where she worked on fundamentals of self-assembled monolayers and immobilization supports for biocatalysts.
In 2003, she started an independent research group at the University of Groningen, the Netherlands.
Katja Loos worked as guest professor at the Technical University of Catalonia, Barcelona, Spain in 2006 and at the Technical University Dresden, Germany in 2016.
Research
The research of Loos is focused on enzymatic polymerization, especially the biocatalytic synthesis of saccharides, polyamides and furan based polymers, as well as the synthesis and self-assembly of block copolymers using supramolecular motifs and containing ferroelectric blocks.
Loos published over 270 scholarly peer-reviewed publications, various patents and book chapters. Her publications frequently get included in special themed collections of scientific journals like “Women in Polymer Science” from Wiley en “Women at the Forefront of Chemistry” of the American Chemical Society
She is the editor of the only currently available textbook in the field of Enzymatic Polymerizations.
She is editor of the scientific journal Polymer and guest-edited special issues of various scientific journals.
Since 2017 she is a member of the board of the Zernike Institute for Advanced Materials of the University of Groningen. She serves as the vice-chair of the program council Chemistry of Advanced Materials of ChemistryNL, a member of the board of the MaterialenNL Platform and is a member of the board of the Dutch national postgraduate research school Polymer Technology Netherlands (PTN).
Katja Loos is the national representative of the Netherlands to the European Polymer Federation (EPF).
In addition to her research, Katja Loos advocates for diversity in science and open access publishing
Awards and honours
Katja Loos was awarded two travel scholarships of the German Academic Exchange Service (DAAD) for research stays at the University of Massachusetts in Amherst, USA, in 1992 and 1993 and at Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil, in 1997.
In 2001, she received a Feodor Lynen Fellowship award of the Alexander von Humboldt Foundation to conduct her postdoctoral research.
The Netherlands Organisation for Scientific Research (NWO) awarded her a VIDI innovational research grant in 2009 and a VICI innovational research grant in 2014
In 2016 the Technical University Dresden and the German Research Council (DFG) within the scope of its excellency initiative awarded her the Eleonore Trefftz guest professorship.
The Alexander von Humboldt Foundation awarded Katja Loos in 2019 the Friedrich Wilhelm Bessel Research Award.
In 2019, she was named "Topper of the year" by Science Guide.
She is one of the recipients of the IUPAC 2021 Distinguished Women in Chemistry or Chemical Engineering award.
In 2022 she won the Team Science Award of the Dutch Research Council (NWO) with her research group HyBRit.
In 2023 she received the title of Knight of the Order of the Netherlands Lion, the prestigious Dutch order of chivalry founded by King William I in 1815.
Katja Loos is a Fellow of the Dutch Polymer Institute (DPI) and the Royal Society of Chemistry (FRSC)
References
External links
Website research group
Information on university website
Profile on NARCIS
Profile on AcademiaNet
External links
1971 births
Living people
Academic staff of the University of Groningen
21st-century Dutch chemists
21st-century German chemists
Johannes Gutenberg University Mainz alumni
University of Bayreuth alumni
21st-century Dutch inventors
Women inventors
Scientists from Frankfurt
Polymer scientists and engineers
Polytechnic Institute of New York University alumni
21st-century Dutch women scientists | Katja Loos | [
"Chemistry",
"Materials_science"
] | 952 | [
"Polymer scientists and engineers",
"Physical chemists",
"Polymer chemistry"
] |
61,334,503 | https://en.wikipedia.org/wiki/I.%20I.%20Rabi%20Prize | The I. I. Rabi Prize in Atomic, Molecular, and Optical Physics is given by the American Physical Society to recognize outstanding work by mid-career researchers in the field of atomic, molecular, and optical physics. The award was endowed in 1989 in honor of the physicist I. I. Rabi and has been awarded biannually since 1991.
The prize citation reads:
Recipients
Source:
1991 Chris H. Greene: "For his many contributions to atomic and molecular theory including studies of resonance vibronic processes, multiple electron excitations, photo-absorption in external fields, and threshold effects of long range forces."
1993 Timothy E. Chupp: "For his contributions to the development of high density polarized noble gases by spin exchange with optically pumped alkali atoms and in particular for his leadership and use of polarized 3He as a target for fundamental experiments in nuclear physics."
1995 Randall G. Hulet: "For his contributions to a broad range of important problems in atomic and optical physics including cavity quantum electrodynamics, quantum jumps, ion storage, and laser cooling of atoms. In the latter field, in particular for his demonstration of multiphoton cooling involving Doppleron resonances in neutral Lithium and his collision experiments with cooled Lithium vapor."
1997 Eric Allin Cornell and Wolfgang Ketterle: "For achieving Bose-Einstein condensation of an atomic gas, for creating techniques for studying the Bose condensate, and for measuring the physical properties of the weakly interacting atomic Bose gas."
1999 Mark G. Raizen: "For his pioneering advances in the experimental study of atom optics, and especially for the insightful connections he has developed between this discipline and studies of chaotic dynamics, condensed matter physics, and dissipative quantum systems."
2001 Christopher Monroe: "For his pivotal experiments that implemented quantum logic using trapped atomic ions, and for his fundamental studies of coherence and decoherence in entangled quantum systems."
2003 Mark A. Kasevich: "For developing atom interferometer inertial sensors with unprecedented precision, and for pioneering studies of Bose-Einstein condensates, especially the achievement of non-classical spin states and the demonstration of a mode-locked atom laser."
2005 Deborah Jin:
2007 Jun Ye: "For advances in precision measurement, including techniques for stabilizing and measuring optical frequencies, controlling the phase of femtosecond laser pulses, and measuring molecular transitions."
2009 Mikhail Lukin: "For pioneering theoretical and experimental work at the interface between quantum optics, quantum information processing, and the quantum many body problem."
2011 Cheng Chin: "For pioneering work in strongly interacting Fermi gas and few body physics including the discovery of the Effimov effect."
2013 Markus Greiner: "For seminal contributions to the field of ultracold atoms, including the observation of the superfluid-to-Mott-insulator transition, the study of the BEC-BCS cross over for fermions, and the development of imaging techniques for atoms in optical lattices with single-atom resolution"
2015 Ian Spielman: "For the development of quantum simulations using ultra-cold atoms, creation of synthetic electromagnetic fields, demonstration of synthetic spinorbit coupling, and applications to studying new physical systems."
2017 Martin Zwierlein: "For seminal studies of ultracold Fermi gases, including precision measurements of the equation of state, the observation of superfluidity, solitons, vortices, and polarons, the realization of a microscope for fermions in a lattice; and the production of chemically stable polar molecules."
2019 Kang-Kuen Ni: "For seminal work on ultracold molecules, including original contributions to the understanding of chemical reactions in the quantum regime, deterministic creation of individual molecules with optical tweezers, and development of novel, high-precision techniques to interrogate and control the complete set of internal molecular resources."
2021 Monika Schleier-Smith: "For seminal work in quantum optics and for discoveries at the intersection of AMO, condensed matter, and quantum information, including original contributions to spin squeezing in optical cavities, engineering long-range interactions for quantum simulations, and metrology, and for theoretical development of a measurement protocol related to the scrambling of quantum information."
2023 Adam M. Kaufman: "For seminal developments in optical tweezer arrays and clocks based on alkaline earth atoms, with applications to metrology and quantum information processing."
See also
List of physics awards
Arthur L. Schawlow Prize in Laser Science
Norman F. Ramsey Prize in Atomic, Molecular and Optical Physics, and in Precision Tests of Fundamental Laws and Symmetries
References
External links
I.I. Rabi Prize in Atomic, Molecular, and Optical Physics (official site)
Awards of the American Physical Society
Atomic physics
Atomic, molecular, and optical physics | I. I. Rabi Prize | [
"Physics",
"Chemistry"
] | 1,006 | [
"Quantum mechanics",
"Atomic physics",
" molecular",
"Atomic",
" and optical physics"
] |
67,807,247 | https://en.wikipedia.org/wiki/Construction%20and%20Engineering%20Forces | The Construction and Engineering Forces (), also known as the Corps of Engineers, is a combat engineer branch of the Mongolian Armed Forces that specializes in military construction and civil works. They also construct defensive positions, serve as military engineering, sappers, and detect mines. They have played a leading role in Armed Forces peacekeeping missions and have successfully participated in UN peacekeeping operations and joint international training exercises.
History
Imperial era
The origin and development of the engineering army dates back to the era of the Mongol Empire. Engineers in the Mongol Army utilized unconventional techniques to win battles against enemies. Genghis Khan frequently utilized Chinese and Muslim engineers during the Khwarezmian campaign and the Sieges of Fancheng and Xiangyang.
Communist era
At the end of 1927, the 1st Cavalry Corps was entrenched as the main fighting force of the Mongolian People's Revolutionary Party, and in 1928, the first “Breakdown and Repair Sapper Branch” was established. This was the first construction army to be established in the Mongolian People's Republic. In 1947, the Military Construction Command was established, with more than 10 units. At its peak, there were 23 military construction units, totaling around 20,000 soldiers and 56,000 officers. Beginning in 1963, large-scale construction work operated as a military affair under the responsibility of the Mongolian People's Army. On January 8, 1964, the Council of Ministers established the General Construction Military Agency under the Ministry of People's Military Affairs. A large number of construction military units were established over the course of the decades that followed. Prior to the 1990s, military construction units contributed 70-80 percent of the country's construction. Five construction units were involved in the construction of Erdenet, which was established in 1974. Construction units were also responsible for developing the cities of Choibalsan and Darkhan. Between 1970 and 1990, the construction army commissioned 300-500 facilities a year.
Modern era
Work to create a new construction and engineering army began in 2010, and throughout the decade, the Ministry of Defense and the General Staff established six civil engineering units in the 2010s. In October 2019, the Cabinet announced that it would make some amendments to the Law on the Armed Forces on the expansion of military construction and engineering units of the Armed Forces into an independent military branch. In April 2020, the Minister of Defense, Nyamaagiin Enkhbold submitted a draft law on amendments to the Law on Armed Forces to the Speaker of the State Great Khural, providing for the creation of a "Civil Engineering Army" in the armed forces.
Units
339th Civil Engineering Unit (Bayankhongor Province)
014 Construction Unit
See also
United States Army Corps of Engineers
Russian Engineer Troops
Construction Troops (Bulgaria)
References
Military units and formations of Mongolia
Civil engineering organizations
Engineering units and formations
Military units and formations established in 2020
Construction in Asia
Construction organizations | Construction and Engineering Forces | [
"Engineering"
] | 579 | [
"Construction organizations",
"Civil engineering organizations",
"Engineering units and formations",
"Construction",
"Military engineering",
"Civil engineering"
] |
67,809,195 | https://en.wikipedia.org/wiki/Fischer%20carbene | A Fischer carbene is a type of transition metal carbene complex, which is an organometallic compound containing a divalent organic ligand. In a Fischer carbene, the carbene ligand is a σ-donor π-acceptor ligand. Because π-backdonation from the metal centre is generally weak, the carbene carbon is electrophilic.
Fischer carbenes are named for Ernst Otto Fischer.
Structure
A metal carbene complex could be considered a Fischer carbene when the carbene is in singlet state. Delocalization of the lone pair from the substituent on carbene carbon raises the energy of pz orbital, thus forcing the two of electrons of carbene stay as an electron pair. Bonding between carbene and the metal centre involves a strong σ donation from sp2 orbital to an empty d orbital on metal centre and a weak π back donation from the metal centre to the empty pz orbital. Because the π donation is weak, the carbene carbon is electrophilic in nature.
Because of this bonding property, Fischer carbenes often feature:
low oxidation state metal center
middle and late transition metals Fe(0), Mo(0), Cr(0)
π-acceptor metal ligands
π-donor substituents on the carbene atom such as alkoxy and alkylated amino groups.
Preparation
The most common strategy to prepare a Fischer carbene is reaction between a metal carbonyl complex with organolithium compounds. The corresponding lithium enolate-like structure is highly stabilized, and thus, needs to be quenched by a highly electrophilic alkylating reagent such as Meerwein's salt. Alkylation with MeI could be done with a phase transfer system. Alternatively, the lithium cation could be exchanged with a tetraalkylammonium cation to give a more reactive enolate. This tetraalkylammonium salt could be acylated to give a highly electrophilic mixed anhydride-like Fischer carbene which could undergo nucleophilic substitution with alcohol.
Fischer carbenes with an α-hydrogen are prepared by reaction of a metal carbonyl anion with a formamide. Treating the intermediate with excess amount of trimethylsilyl chloride yields this particular group of Fischer carbene complex.
Elaboration of Fischer carbenes
With a suitable hydride abstracting reagent, such as the trityl cation, the hydride on alkyl ligand of a metal complex could be abstracted to form a Fischer carbene.
Decarbonylation from an unstabilized metal carbenoid
In 2021, Alvarez et al reported that a Fischer carbene could be effectively prepared from a decarbonylative process of a metal carbenoid derived from a stabilized diazo compound.
Reactivity
Carbonyl-like reactivity
The carbene carbon of a Fischer carbene is electrophilic in nature. Thus, Fischer carbenes exhibit similar reactivity compared to carbonyl compounds. Many of the reactions can be understood by using the carboxylic equivalent structure such as transesterification, Michael addition, and aldol reaction. The Cr(CO)5 moiety is a strong electron withdrawing group making the α-proton highly acidic. A methoxy chromium carbene with a methyl side chain has a pKa of 12.5 in aqueous acetonitrile (1:1 volume ratio). For comparison, methyl acetate has a pKa of 25.6, demonstrating the strong electron withdrawing nature of the Cr(CO)5 moiety.
The strong electron withdrawing nature of Fischer carbenes is also reflected in many reactions. For instance, the Diels–Alder reaction between methyl acrylate and isoprene is completed in 7 days at room temperature with low para-meta selectivity. On the other hand, the Fischer carbene counterpart finished in 3 hours at room temperature with much higher para-meta selectivity.
Urotropin, a weak nucleophile, could participate in a Michael addition to an alkynyl Fischer carbene, giving an interesting double addition product.
The enolate-like structure, obtaining by deprotonation of Fischer carbene, could be alkylated. However, because the carbanion is highly stabilized, a reactive alkylating reagent, such as methyl fluorosulfonate ("magic methyl" reagent) or methyl bromoacetate is needed.
Aldol condensation of Fischer carbenes could be achieved by using much weaker bases compared to its carbonyl counterpart, such as triethylamine.
Demetallation
Fischer carbenes could be oxidized to the corresponding carbonyl compounds using mild oxidants such as ceric ammonium nitrate (CAN).
If the side chain of Fischer carbene bears an α-proton, it could be reversibly deprotonated with a weak base such as pyridine. This facilitates formation of chromium hydride species, which can undergo reductive elimination to give a cis-enol ether.
Photochemical properties of Fischer carbenes
The UV-Vis spectrum of a Fischer carbene shows a metal-to-ligand charge transfer band in the near ultraviolet. On the one hand, this excitation promotes an electron from a metal centered orbital to a ligand centered orbital, making the carbene carbon more electron rich. On the other hand, the metal centre, already electron poor because of the carbonyl ligands, becomes more electron poor, facilitating migratory insertion to the CO ligand. This migratory insertion gives a chromium metallacyclopropanone, which is a resonance form of the metallated ketene. With ketene reactivity, the species could be trapped by several nucleophiles such as alcohols and amines, or could react in [2+2] cycloaddition with alkenes, imines, or aldehyde yielding the corresponding cyclobutane, β-lactam, and β-lactone adducts.
See also
Wulff–Dötz reaction
References
Carbenes
Organometallic compounds | Fischer carbene | [
"Chemistry"
] | 1,307 | [
"Inorganic compounds",
"Organometallic compounds",
"Organic compounds",
"Carbenes",
"Organometallic chemistry"
] |
67,812,278 | https://en.wikipedia.org/wiki/Diffblue | Diffblue Ltd is a spin-out from University of Oxford whose Cover product uses AI to automatically write unit tests for Java code. It is similar to GitHub Copilot in that it uses AI to write code, but differs in that it writes code fully autonomously vs. providing code suggestions for humans to review and edit. Diffblue was founded by Daniel Kroening and Peter Schrammel in 2016, and Mathew Lodge became CEO in July 2019
In 2017, Diffblue raised £17.3 million in Series A funding led by Goldman Sachs and Oxford Sciences Innovation. In 2020, Diffblue released a freeware version, Cover Community Edition. It can be used by both open source and commercial organisations. Diffblue raised $7m in January 2022 in a round led by venture capitalist IP Group, and a further $8m in November 2022 in a round led by AlbionVC.
Diffblue customers include Goldman Sachs, S&P Global, Citi, JP Morgan and AWS.
References
Software testing | Diffblue | [
"Engineering"
] | 219 | [
"Software engineering",
"Software testing"
] |
67,819,114 | https://en.wikipedia.org/wiki/R-16661 | R-16661 is an extremely toxic organophosphate insecticide. With an oral LD50 of 0.1 mg/kg in mice and rats, R-16661 is about 10 times more toxic than aldicarb, the most toxic carbamate insecticide.
See also
Aldicarb
Paraoxon
References
Organophosphate insecticides
Acetylcholinesterase inhibitors
Oxazolidines
Methyl esters
Phosphoramidothioates | R-16661 | [
"Chemistry"
] | 99 | [
"Phosphoramidothioates",
"Functional groups"
] |
67,819,316 | https://en.wikipedia.org/wiki/Tetramethylammonium%20perchlorate | Tetramethylammonium perchlorate is a perchlorate salt with a condensed formula [N(CH3)4]+ClO4−.
Preparation
Tetramethylammonium perchlorate can be produced by mixing cold, dilute perchloric acid with cold tetramethylammonium hydroxide, the reaction will lead to a white precipitation.
Uses
The perchlorate is used as an intermediate in organic synthesis, in chromatography and as a supporting electrolyte in electrochemistry. Along with trimethylammonium perchlorate, it was investigated as a component in composite propellants during the Cold War, but without much success.
References
Further reading
Hofmann, K. A.; Roth, R.; Hobold, K.; Metzler, A. Relationship between the Constitution and Behavior towards Water of Ammonium Oxonium Perchlorates. Berichte der Deutschen Chemischen Gesellschaft, 1911. 43: 2624-2630.
Perchlorates
Tetramethylammonium salts | Tetramethylammonium perchlorate | [
"Chemistry"
] | 218 | [
"Inorganic compounds",
"Perchlorates",
"Inorganic compound stubs",
"Salts"
] |
63,498,084 | https://en.wikipedia.org/wiki/Heinrich%20M%C3%BCckter | Heinrich Mückter (14 June 1914 – 22 May 1987) was a German medical doctor, pharmacologist and chemist.
World War II
During the Nazi occupation of Poland, Mückter was deputy director of the Kraków Institute for Typhus and Virus Research. Mückter and his colleagues repeatedly experimented on concentration camp prisoners in Buchenwald. Many prisoners died as a result of the experiments.
Accused by Polish war crimes prosecutors of conducting medical experiments on concentration camp prisoners and Nazi forced labourers, Mückter escaped arrest and fled back to Germany.
Invention of thalidomide
In 1946 Mückter became Head of Research at the Grünenthal pharmaceutical company, where he further developed the infamous drug thalidomide which had been synthesized in 1952 by Chemical Industry Basel. Aggressively-marketed as an over-the-counter sleeping pill and remedy for morning sickness in pregnancy, thalidomide was first made available on 1 October 1957, and it became the second best-selling medication in Germany after Bayer Aspirin. Thalidomide was eventually found to cause miscarriages, severe birth defects in babies whose mothers had taken the medication while pregnant, and severe nerve damage.
In January 1968, Mückter was put on trial along with other Grünenthal employees. The trial ended abruptly in April 1970 with a settlement.
Mückter was never charged in relation to his role in experiments on concentration camp prisoners, nor his role in the thalidomide scandal. He died on 22 May 1987.
References
1914 births
1987 deaths
German pharmacologists
20th-century German chemists | Heinrich Mückter | [
"Chemistry"
] | 323 | [
"Pharmacology",
"Pharmacology stubs",
"Medicinal chemistry stubs"
] |
63,498,181 | https://en.wikipedia.org/wiki/Adawro%20exclosure | Adawro is an exclosure located in the Dogu'a Tembien woreda of the Tigray Region in Ethiopia. The area has been protected by the local community since 1994.
Environmental characteristics
Average slope gradient: 70%
Aspect: the exclosure is oriented towards the northeast
Minimum altitude: 2635 metres
Maximum altitude: 2705 metres
Lithology: Basalt
Management
As a general rule, cattle ranging and wood harvesting are not allowed. The grasses are harvested once yearly and taken to the homesteads of the village to feed livestock. Physical soil and water conservation has been implemented to enhance infiltration, and vegetation growth.
Benefits for the community
Setting aside such areas fits with the long-term vision of the communities were hiza’iti lands are set aside for use by the future generations. It has also direct benefits for the community:
improved infiltration
improved ground water availability
honey production
climate ameliorator (temperature, moisture)
carbon sequestration, dominantly sequestered in the soil, and additionally in the woody vegetation)
Water conservation
In the Adawro exclosure, more than 800 precise measurements were done in 2003 and 2004, using five runoff plots, where the volume of runoff was measured daily. The rock type (basalt), slope gradient and slope aspect were the same, the only difference was the land management and vegetation density. Whereas in degraded rangeland, 11.4% of the rainfall flows directly away to the river (runoff coefficient), this happens only for 2.5% of the rain in a recent exclosure and 3.2% in a eucalyptus forest.
In 2003, the soils of the then young exclosure could hold 280 litres of water per m³, similar to the adjacent rangeland.
Improved ecosystem
With vegetation growth, biodiversity in this exclosure has strongly improved: there is more varied vegetation and wildlife.
Trees
The main tree species found in the exclosure are:
Flat top acacia (Acacia abyssinica, renamed as Vachellia abyssinica)
Golden wattle (Acacia saligna)
Rumex nervosus, a woody sorrel species
Aloe macrocarpa
Soils
Main soil type in the exclosure are Phaeozems, formed in sediment that has been trapped by the vegetation of the exclosure, and as a remnant of the original situation before deforestation. Remarkably, also in the well-protected eucalypt plantation there is some undergrowth and soil development.
References
External links
Link For Forestry Projects
Exclosures of Tigray Region
1999 establishments in Ethiopia
Land management
Environmental conservation
Environmentalism in Ethiopia
Emissions reduction
Dogu'a Tembien | Adawro exclosure | [
"Chemistry"
] | 551 | [
"Greenhouse gases",
"Emissions reduction"
] |
63,498,200 | https://en.wikipedia.org/wiki/List%20of%20World%27s%20Fair%20architecture | This is a list of buildings and structures built for World's Fairs.
Officially recognized exhibitions
Architecture built for world's fairs recognized by the Bureau International des Expositions.
London Great Exhibition 1851
The Crystal Palace
Paris Exposition Universelle 1855
Palais de l'Industrie
Théâtre du Rond-Point
London International Exhibition 1862
The Exhibition Building of 1862
Paris Exposition Universelle 1867
Palais du Champ de Mars
Vienna World's Fair 1873
Rotunda
Philadelphia Centennial Exposition 1876
Main Exhibition Building
Paris Exposition Universelle 1878
Palais du Trocadéro
Melbourne International Exhibition 1880
Royal Exhibition Building
Barcelona Universal Exposition 1888
Parc de la Ciutadella
Paris Exposition Universelle 1889
Eiffel Tower
Galerie des machines
Chicago World's Columbian Exposition 1893
White City
Brussels International Exposition 1897
Palace of the Colonies
Paris Exposition Universelle 1900
Grand Palais
Petit Palais
Liège International 1905
Palais des beaux-arts de Liège
San Francisco Panama–Pacific International Exposition 1915
Tower of Jewels
Palace of Fine Arts
Barcelona International Exposition 1929
Palau Nacional
Barcelona Pavilion
Estadi Olímpic Lluís Companys
Poble Espanyol
Teatre Grec
Magic Fountain of Montjuïc
Paris Exposition Internationale des Arts et Techniques dans la Vie Moderne 1937
Palais de Chaillot
New York World's Fair 1939
1939 New York World's Fair pavilions and attractions
Trylon and Perisphere
Brussels Expo 58
Atomium
Philips Pavilion
Seattle Century 21 Exposition 1962
Seattle Center
Seattle Center Monorail
Space Needle
Montreal Expo 67
Expo 67 pavilions
Habitat 67
San Antonio HemisFair '68
Tower of the Americas
Others
Porto International Exhibition 1867
Palácio de Cristal
Sydney International Exhibition 1879
Garden Palace
Adelaide Jubilee International Exhibition 1887
Jubilee Exhibition Building
Hanoi Exhibition 1902
Grand Palais
Colonial Exhibition of Semarang 1914
Aceh Museum
Paris Colonial Exposition 1931
Palais de la Porte Dorée
Pagode de Vincennes
Glasgow Empire Exhibition 1938
Tait Tower
New York World's Fair 1964
1964 New York World's Fair pavilions
New York City Pavilion
New York Hall of Science
New York State Pavilion
Terrace on the Park
Wisconsin Pavilion
Unisphere
References
Architecture
World's Fair
Architecture | List of World's Fair architecture | [
"Engineering"
] | 415 | [
"Architecture lists",
"Architecture"
] |
63,498,286 | https://en.wikipedia.org/wiki/Calconcarboxylic%20acid | Calconcarboxylic acid (IUPAC name 3-hydroxy-4-[(2-hydroxy-4-sulfonaphthalen-1-yl)diazenyl]naphthalene-2-carboxylic acid; commonly called Patton and Reeder's Indicator) is an azo dye that is used as an indicator for complexometric titrations of calcium with ethylenediaminetetraacetic acid (EDTA) in the presence of magnesium. Structurally, it is similar to eriochrome blue black R, which is obtained from calconcarboxylic acid by decarboxylation and reaction with sodium hydroxide.
Properties
Calconcarboxlic acid is soluble in water and a variety of other solvents, including sodium hydroxide, ethanol and methanol. It has a violet colour in dissolved form in ethanol. The melting point of calconcarboxylic acid is at approximately 300 °C, where it undergoes thermal decomposition.
Background
Though the determination of calcium and magnesium by complexometric titration with standard solutions of disodium dihydrogen tetraacetate, utilising Eriochrome Black T as indicator is widely accepted and quite adequately understood, it, like other complexometric titration methods, suffers from the limitations of having an indistinct endpoint (where a photometric titrator is needed to provide acceptable accuracy) and/or having to separate the metals before titration can occur. Calconcarboxylic acid was thus adopted as a superior alternative due to its ability to give a good and visual endpoint and its rapid performance even with the presence of magnesium.
Synthesis
As described by James Patton and Wendell Reeder in 1956, calconcarboxylic acid can be synthesised by coupling diazotized 1-amino-2-naphthol-4-sulfonic acid with 2-hydroxy-3-napthoic acid.
Applications
Calconcarboxylic acid is used for the determination of calcium ion concentration by complexometric titration. Free calconcarboxylic acid is blue colour, but changes to pink/red when it forms a complex with calcium ions. EDTA forms a more stable complex with calcium than calconcarboxylic acid does, so addition of EDTA to the Ca–calconcarboxylic acid complex causes formation of Ca-EDTA instead, leading to reversion to the blue colour of free calconcarboxylic acid.
For the complexometric titration, the indicator is first added to the titrant containing the calcium ions to form the calcium ion-indicator complex (Ca-PR) with a pink/red colour. This is then titrated against a standard solution of EDTA. The endpoint can be observed when the indicator produces a sharp, stable colour change from wine red to pure blue, which occurs at pH values between 12 and 14, this indicates the endpoint of the titration, as the Ca-PR complexes have been completely replaced by the Ca-EDTA complexes and hence the PR indicator reverts to its blue colour.
The reaction can be given by:
Ca-PR + EDTA4- → PR + [Ca-EDTA]2-
The Patton-Reeder Indicator is often used here in the form of a triturate.
This method of complexometric titration is dependent on the pH of the solution being sufficiently high to ensure that magnesium ions precipitate as magnesium hydroxide before the PR indicator is added to prevent interference with the results, as if magnesium were present, the EDTA would also form complexes with it. Concentrated sodium hydroxide or potassium hydroxide is usually added to the solution to this end.
The accuracy of this method may also be affected by the presence of metal ions such as copper, iron, cobalt, zinc or manganese in sufficiently high concentrations.
References
Azo dyes
Chemistry
Carboxylic acids
Sulfonic acids | Calconcarboxylic acid | [
"Chemistry"
] | 823 | [
"Carboxylic acids",
"Functional groups",
"Sulfonic acids"
] |
63,506,979 | https://en.wikipedia.org/wiki/Ganpat%20Patel | Ganpat Patel (born 1945 or 1946), also known as Pat Patel, is an Indian-American scientist and philanthropist. He is the founder of Charokee International and was President and CEO before retiring in 2004.
Patel is the President and Pado-in-Chief of Ganpat University located in the Mehsana district of North Gujarat.
Patel is also advisor in fotonVR and chairman in Guniguru.
Patel was honored with the Padma Shri award in the literature and education category.
Early life and education
Ganpat Patel is the son of Iswarbhai Patel and Menaben Patel. He was born in the village of Bhunav in Mehsana, Gujarat in 1945 or 1946. He received a bachelor of science degree in electrical engineering from California State Polytechnic University, in Pomona in 1969 and a master's degree, also in electrical engineering, from UCLA in 1973.
Career
Patel got his first job in an aviation industry company Lockheed Martin but he lost this job soon due to a recession in the aviation sector. He was lucky to get the immediate job offer from Abbott Laboratories in Culver City of Los Angeles in 1971. There after he also got an opportunity in Burroughs Computer and he acquired many useful skills which gave a great push to the tenets of entrepreneurship in him. In 1978, Shri Patel, with the help of his wife, founded Cherokee International, Inc., a power supply company. Cherokee secured relationships with businesses like IBM, CISCO, Motorola, and Hewlett Packard and opened manufacturing facilities in the United States, India, Belgium, and Mexico. Patel retired from his professional career in 2004.
Personal life
His wife, Majnu Patel, is a social worker and philanthropic. She runs a sainik school for girls in her name "Smt M.G. Patel Sainik School for Girls" in North Gujarat, India and making sure that 400+ girls get their schooling education every year through this military school. She does philanthropic work with the help of her husband Ganpat Patel and her family.
Supported by his wife Smt Manjuben and motivated by his three daughters, Rita, Anita and Asha as well as his seven grandchildren, Patel has started a “सेवा यज्ञ” social upliftment through education and established various institutions in India which can impart quality learning to Indian students.
Awards and honors
References
External links
1940s births
Living people
Gujarati people
Indian billionaires
Businesspeople from Los Angeles
Electric power
University and college founders
Indian electrical engineers
Indian philanthropists
Indian emigrants to the United States
American people of Indian descent
American people of Gujarati descent
California State Polytechnic University, Pomona alumni
American billionaires
American electrical engineers
American philanthropists | Ganpat Patel | [
"Physics",
"Engineering"
] | 542 | [
"Power (physics)",
"Electrical engineering",
"Electric power",
"Physical quantities"
] |
69,216,364 | https://en.wikipedia.org/wiki/Daniel%20Deocampo | Daniel Michael Deocampo is an American geologist, geochemist, and academic administrator. He was an associate dean and professor of geosciences at Georgia State University. Deocampo pleaded guilty to possession of child pornography on November 3, 2021.
Early life and education
Deocampo was born to Helen Deocampo and cardiologist Paulino D. Deocampo of Holmdel Township, New Jersey. He completed a B.S. in geological sciences in 1994 at Tufts University. He earned a M.S. (1997) and Ph.D. (2001) in geological sciences at Rutgers University. His dissertation was titled Geochemistry and Sedimentology of Modern East African Wetlands and a Pleistocene Paleo-Wetland at Olduvai Gorge, Tanzania. His doctoral advisor was Gail Ashley.
He completed a postdoctoral fellowship at the National Museum of Natural History in 2001. In 2002, he was a postdoctoral research hydrologist in the water resources division of the United States Geological Survey in Reston, Virginia. He completed a postdoctoral fellowship at the Natural History Museum, London in 2003.
Career
Deocampo joined the faculty at Georgia State University (GSU) in 2008 as an assistant professor. He became full professor of geosciences in 2016. Deocampo served as the GSU College of Arts and Sciences Associate Dean for Research, Innovation, and Graduate Studies from 2019 to 2021.
In 2014, Deocampo was elected fellow of the Geological Society of America.
Personal life
The Federal Bureau of Investigation (FBI) and GSU Cyber Security identified Deocampo as the individual who had accessed multiple websites containing child pornography (or had links to other websites containing child pornography) from campus in November and December 2020. GSU Cyber Security also advised the FBI that Deocampo routinely accessed the university’s network from home. Based on that information, FBI determined that Deocampo was also accessing websites containing child pornography from his home on several days in late December 2020 and early January 2021. On January 6, 2021, the FBI executed search warrants at Deocampo's residence, as well as his GSU office and lab space. As a result of the search, agents recovered an Apple laptop belonging to Deocampo that contained more than 4,000 files of child pornography, including approximately 190 videos. On November 3, 2021, he pleaded guilty to possession of child pornography. On February 23, 2022, Deocampo was sentenced to 32 months in prison, 10 years of supervised probation, and a $10,100 special assessment.
References
External links
Living people
Year of birth missing (living people)
Place of birth missing (living people)
People from Avondale Estates, Georgia
21st-century American geologists
American geochemists
Fellows of the Geological Society of America
Tufts University School of Arts and Sciences alumni
Rutgers University alumni
Georgia State University faculty
American university and college faculty deans | Daniel Deocampo | [
"Chemistry"
] | 598 | [
"Geochemists",
"American geochemists"
] |
69,224,614 | https://en.wikipedia.org/wiki/Hazardous%20substances%20in%20cultural%20heritage%20collections | Cultural heritage collections contain many materials known to be hazardous to the environment and to human health. Some hazardous substances may be an integral part of the object (such as a toxic paint pigment or a naturally radioactive mineral sample), applied as a treatment after the object was made (such as a pesticide) or the result of material degradation (such as the exudation of plasticiser from polyvinyl chloride). The toxicity of such objects in heritage collections can also determine their historic and scientific value. Consequently, management of these materials within collecting organisations can be complex in terms of health and safety.
These substances represent a hazard for people working with or using affected collections items as well as acting as a record of the use of these materials over time. Disposal or removal of hazardous substances from cultural collections can be expensive and logistically challenging.
Many of the hazardous substances found in cultural heritage collections may also be classified as Dangerous Goods or Scheduled Poisons and subject to strict regulations concerning their sale, storage, labelling, handling, transport, display and disposal.
Asbestos
Asbestos was used widely as a fire-proof or fire-suppressing agent, in scientific, industrial and domestic appliances, clothing, and tools. Asbestos can also be found mixed with cements and resins and woven into fabrics. Asbestos-containing mineral samples may be present in natural history collections. The safe management of asbestos is highly regulated in most countries, e.g. the UK Control of Asbestos Regulations 2012.
Corrosives
Acids and alkalis can be found in industrial chemicals (e.g. photographic developing agents), as the preservative used for fluid-preserved natural history specimens (formalin) and in batteries.
Heavy metals (lead, mercury, arsenic, etc.)
Lead is a soft, malleable metal that has been used for a variety of purposes throughout history: as food additives, paint pigments, or solder, and to make pewter drinking vessels and lead toys.
Mercury can be found in scientific equipment such as thermometers, and as a residue on animal skins, furs, and hats where it was used in the preparation process. Mercuric chloride was also used as a pesticide or biocide.
Arsenic and mercury are a common hazardous substance found in historic dress and textile collections from the 18th and 19th centuries as it was used in textile dyes e.g. Scheele’s Green a yellow-green pigment, and textile manufacture, hat making.
Mould and micro-organisms
Mould and micro-organisms (e.g. bacteria) may be present on the surface of collection objects, particularly those that have been stored in warm and damp conditions.
Paints, pigments and dyes
Many toxic pigments and other paint ingredients have been used, many since antiquity. Toxic pigments include lead, mercury, cadmium, cobalt, antimony and arsenic.
Pesticides and herbicides
Museum collections can contain samples of actual pesticides and herbicides (such as mercuric chloride, paradichlorobenzene and DDT) as well as artefacts that have been treated with pesticides to prevent infestations by museum personnel and field collectors especially over the 18th century to the end of the 20th century as "[…] such treatments were traditionally thought to be part of general collections maintenance."
The latter can prevent access to collection items unless the chemical residues can be removed or safely managed, as there are also human health implications associated with most pesticides.
Once a commonplace treatment for objects made of organic materials (e.g. animal and insect specimens, woollen clothing, objects containing plant fibres, fur and feathers), use of pesticides has substantially diminished with the development of integrated pest management as a collection management strategy.
Naphthalene is one of the most commonly encountered pesticide residues found on museum collections. As a volatile substance, it can sublimate and recrystallise on surfaces nearby.
Mercury-based pesticides (such as mercuric chloride) can release mercury vapour, which can contaminate other collection objects and surfaces nearby. Monitoring vapour levels has shown that venting closed storage cabinets before use lowers airborne concentration limits to safe limits. Other mitigation strategies include enclosing affected collection objects inside enclosures made from gas vapour barriers and using vented cabinets instead of sealed cabinets for storage.
Plastics and plasticisers
Some deteriorating plastics may generate acidic byproducts (such as acetic acid from cellulose acetate film or nitric acid from cellulose nitrate film), which pose risk to those handling affected objects. Others leach plasticisers, such as the phthalates released from polyvinyl chloride or biphenyl A (BPA).
Pharmaceuticals, poisons and drugs
Many museums contain collections of old medicines and poisons, containing substances which - though once intended to heal - may contains substances hazardous to humans and to the environment. For these reasons pharmacy and prescription-only medicines in museum collections may be subject to local regulations for storage and display.
Radiation
Radioactive minerals may be found in mineralogy, palaeontology, and maritime collections, in radioactive paints on watch faces and aircraft dials, in medical and analytical equipment. Radiation in museum collections must usually be strictly controlled in accordance with local regulations.
Solvents and chemicals
A variety of chemicals can be found in cultural heritage collections, including oxidising agents, flammable and combustible liquids, and other solvents with known toxic, carcinogenic or other health effects. Ethanol and formalin are used to preserve specimens in natural history collections. Petroleum products may be found in industrial heritage collections. Organic solvents may also be found within cosmetics, medicines, and photographic processing chemicals.
Zoonotics
Zoonotic diseases (those transmitted from animals to humans) may be present in natural history specimens or museum objects made with unprocessed animal products.
Further reading
Profiling Hazardous Substances in the Museum Victoria State Collection
References
Hazardous materials
Cultural heritage conservation | Hazardous substances in cultural heritage collections | [
"Physics",
"Chemistry",
"Technology"
] | 1,215 | [
"Materials",
"Hazardous materials",
"Matter"
] |
69,227,378 | https://en.wikipedia.org/wiki/Mercedes-Benz%20M142%20engine | The Mercedes-Benz M142 engine is a naturally-aspirated, 3.2-liter to 3.4-liter, straight-6, internal combustion piston engine, designed, developed and produced by Mercedes-Benz; between 1937 and 1942.
Applications
Mercedes-Benz W142
Mercedes-Benz 320A
References
Mercedes-Benz engines
Straight-six engines
Engines by model
Gasoline engines by model | Mercedes-Benz M142 engine | [
"Technology"
] | 81 | [
"Engines",
"Engines by model"
] |
69,227,698 | https://en.wikipedia.org/wiki/Totally%20implantable%20cochlear%20implant | A totally implantable cochlear implant (TICI) is a new type of cochlear implant and is currently in development. Unlike a conventional cochlear implant, which has both an internal component (the implant) and an external component (the audio processor), all the components of the TICI - including the microphone and battery - are implanted under the skin. This makes the TICI completely invisible from the outside.
The TICI is currently in the clinical feasibility study stage of development. The first patient in Europe was implanted with a TICI in September 2020 as part of a clinical trial.
Parts
The TICI contains the same internal components as a conventional cochlear implant: the magnet, antenna coil, electronics and the electrode array, however will also include the features of an audio processor including an implanted rechargeable battery and microphone. The TICI components may be integrated into a single case, the so-called monobody design, or the various components may be attached to one another by connectors, thereby allowing replacement of each of the several modules in case of failure.
Some external hardware will still be required. The internal battery is charged transcutaneously using an external charger, for example while the user sleeps at night. A remote control or app may also be needed in order to switch the implant on and off, adjust the microphone sensitivity and indicate the battery status, among other functions.
Benefits
A totally implantable — and therefore “invisible” — cochlear implant is seen as a benefit to users, particularly those who feel self-conscious about wearing visible hearing devices.
In addition, as the TICI has no external components, it is less susceptible to small breakages from knocks and falls. The lack of external parts also means that they cannot be mislaid – a common problem with pediatric users.
A TICI can function while showering, swimming, and during many types of vigorous physical activity. This allows the user to hear while carrying out these activities.
References
Biomedical engineering
Medical devices | Totally implantable cochlear implant | [
"Engineering",
"Biology"
] | 414 | [
"Biological engineering",
"Medical technology",
"Medical devices",
"Biomedical engineering"
] |
70,721,631 | https://en.wikipedia.org/wiki/Activated%20protein%20C%E2%80%93protein%20C%20inhibitor | Activated protein C–protein C inhibitor (APC-PCI) is a complex of activated protein C (APC) and protein C inhibitor (PCI). It has been measured in coagulation testing to evaluate coagulation, thrombosis, and other cardiovascular complications. It is a marker of thrombin generation and indicates hypercoagulability. The half-life of APC-PCI is either 40 minutes or 140minutes.
Ethinylestradiol-containing birth control pills have been found to increase levels of APC-PCI to a similar degree as thrombin–antithrombin complex (TAT) and to a greater extent than D-dimer. However, only APC-PCI was able to differentiate between a second- and third-generation birth control pill.
Another complex related to APC-PCI is the activated protein C–α1-antitrypsin (APCAT) complex.
References
Coagulation system
Protein complexes | Activated protein C–protein C inhibitor | [
"Chemistry",
"Biology"
] | 209 | [
"Biochemistry stubs",
"Biotechnology stubs",
"Biochemistry"
] |
70,728,366 | https://en.wikipedia.org/wiki/Morphism%20of%20finite%20type | In commutative algebra, given a homomorphism of commutative rings, is called an -algebra of finite type if is a finitely generated as an -algebra. It is much stronger for to be a finite -algebra, which means that is finitely generated as an -module. For example, for any commutative ring and natural number , the polynomial ring is an -algebra of finite type, but it is not a finite -algebra unless = 0 or = 0. Another example of a finite-type homomorphism that is not finite is .
The analogous notion in terms of schemes is: a morphism of schemes is of finite type if has a covering by affine open subschemes such that has a finite covering by affine open subschemes of with an -algebra of finite type. One also says that is of finite type over .
For example, for any natural number and field , affine -space and projective -space over are of finite type over (that is, over ), while they are not finite over unless = 0. More generally, any quasi-projective scheme over is of finite type over .
The Noether normalization lemma says, in geometric terms, that every affine scheme of finite type over a field has a finite surjective morphism to affine space over , where is the dimension of . Likewise, every projective scheme over a field has a finite surjective morphism to projective space , where is the dimension of .
References
Algebraic geometry
Morphisms | Morphism of finite type | [
"Mathematics"
] | 312 | [
"Functions and mappings",
"Mathematical structures",
"Mathematical objects",
"Fields of abstract algebra",
"Category theory",
"Mathematical relations",
"Algebraic geometry",
"Morphisms"
] |
70,730,802 | https://en.wikipedia.org/wiki/Nickel%28II%29%20perchlorate | Nickel(II) perchlorate is a collection of inorganic compounds with the chemical formula of . Its colors of these solids vary with the degree of hydration. For example, the hydrate forms cyan crystals, the pentahydrate forms green crystals, but the hexahydrate (Ni(ClO4)2·6H2O) forms blue crystals. Nickel(II) perchlorate hexahydrate is highly soluble in water and soluble in some polar organic solvents.
Preparation
Aqueous solutions of nickel(II) perchlorate can be obtained by treating nickel(II) hydroxide, nickel(II) chloride or nickel(II) carbonate with perchloric acid.
Ni(OH)2 + 2HClO4 + 4H2O → Ni(ClO4)2·6H2O
Two hydrates have been characterized by X-ray crystallography: the hexahydrate and the octahydrate. Several other hydrates are mentioned including the pentahydrate, which is claimed to crystallize at room temperature, the nonahydrate, which is claimed to crystallize at −21.3 °C, a tetrahydrate, and a monohydrate.
The yellow anhydrous product is obtained by treating nickel(II) chloride with chlorine trioxide. As deduced by X-ray crystallography, Ni resides in a distorted octahedral environment and the perchlorate ligands bridge between the Ni(II) centers.
Applications
Nickel(II) perchlorates has few practical uses.
Other compounds
Ni(ClO4)2 also forms some compounds with NH3, such as Ni(ClO4)2·6NH3 which is a light purple crystal.
Ni(ClO4)2 also forms some compounds with N2H4, including Ni(ClO4)2·2N2H4 as a light positive solid or Ni(ClO4)2·5N2H4 which are purple crystals.
Ni(ClO4)2 forms compounds with CO(NH2)2, like Ni(ClO4)2·6CO(NH2)2 which is a yellow-green solid.
Ni(ClO4)2 forms compounds with CON3H5, for example Ni(ClO4)2·3CON3H5 which is a blue solid.
Ni(ClO4)2 forms compounds with CON4H6, such as Ni(ClO4)2·3CON4H6 which is an explosive blue crystal with a bulk density of 0.95 g/cm³.
Ni(ClO4)2 can also form compounds with CS(NH2)2, such as Ni(ClO4)2·6CS(NH2)2 which is a pale green solid.
Ni(ClO4)2 also forms some compounds with CSN3H5, such as Ni(ClO4)2·2CSN3H5·3H2O which is a blue paramagnetic crystal or Ni(ClO4)2·3CSN3H5·2H2O which is a dark positive crystal.
Ni(ClO4)2 also forms some compounds with pyridine.
Further reading
See also
Nickel
Perchloric acid
References
Oxidizing agents
Nickel compounds
Perchlorates | Nickel(II) perchlorate | [
"Chemistry"
] | 707 | [
"Perchlorates",
"Redox",
"Oxidizing agents",
"Salts"
] |
70,730,840 | https://en.wikipedia.org/wiki/Salbostatin | Salbostatin is an antibiotic and trehalase inhibitor with the molecular formula C13H23O8. Salbostatin is produced by the bacterium Streptomyces albus.
See also
Pseudouridimycin
References
Further reading
Salbostatin
Polyols
Secondary amines
Amino sugars | Salbostatin | [
"Chemistry",
"Biology"
] | 65 | [
"Amino sugars",
"Carbohydrates",
"Biotechnology products",
"Organic compounds",
"Antibiotics",
"Biocides",
"Organic compound stubs",
"Organic chemistry stubs"
] |
70,734,221 | https://en.wikipedia.org/wiki/Institut%20f%C3%BCr%20Kunststoffverarbeitung | The Institut für Kunststoffverarbeitung in Industrie und Handwerk (IKV), the Institute for Plastics Processing in Industry and Trade at the Rheinisch-Westfälische Technische Hochschule Aachen, Germany, is a teaching and research institute for the study of plastics technology. It stands for practice-oriented research, innovation and technology transfer. The focus of the IKV is the integrative view of product development in the material, construction and processing sectors, in particular in plastics and rubber. The sponsor is a non-profit association that currently includes around 300 companies from the plastics industry worldwide (as of December 2018) and through which the institute maintains a close connection between industry and science. In addition, the IKV is a member of the (AiF).
The institute was founded in 1950 and, with around 350 employees, has become Europe's largest research and training institute in the field of plastics technology. The first head of the institute was , followed in 1959 by Alfred Hermann Henning. From 1965 to 1988 headed the institute, followed by until his retirement in 2011. Since 2011, the current head of the institute, and at the same time managing director of the association, is . He also holds the Chair for within the Faculty of Mechanical Engineering at RWTH Aachen University.
Tasks
The tasks of the institute are:
scientific and practice-oriented research in the field of plastics technology
the training of students to become qualified junior staff for the plastics industry
the training of practitioners in the craft industry in the field of plastics technology
Structure
The scientific departments injection molding/PUR technology, extrusion and further processing, molded part design/materials engineering and fibre-reinforced plastics are the operative units of the institute. The (KAP) (English: Center for Plastics Analysis and Testing) at the IKV supports and advises scientific departments and is available as a service for the industry to solve problems. The training and education department is responsible nationwide for technology transfer to the skilled trades sector.
Since 1960, the institute has been cooperating with the (GFA, English: commercial development agency) in the training center of the (HWK), which served and was certified as a training center for plastics technology for both the IKV and the (DVS) and the (DVGW). On the initiative of the incumbent HWK President , this was transferred in 1983 to the (BGE) in Aachen's Tempelhofer Straße.
Currently, about 130 employees including some 80 scientists are working at the IKV in research, development and training. They are supported by about 220 student assistants. In addition to the tasks mentioned above, one of the goals of the IKV is to provide the industry with solutions to practical problems. Individual projects, but also those within the framework of often lead to high-quality product ideas and developments, which, in the sense of the desired technology transfer, benefit not only larger, but foremost small and medium-sized enterprises.
References
External links
Website of the Institute for Plastics Processing
Research institutes in Germany
Research institutes established in 1950
Plastics industry
Plastics applications
Materials science
Engineering disciplines | Institut für Kunststoffverarbeitung | [
"Physics",
"Materials_science",
"Engineering"
] | 637 | [
"Applied and interdisciplinary physics",
"Materials science",
"nan"
] |
70,735,144 | https://en.wikipedia.org/wiki/Vanessa%20Wood | Vanessa Claire Wood (born 25 February 1983) is an American engineer who is a professor at the ETH Zurich. She holds a chair in Materials and Device Engineering and serves as Vice President of Knowledge Transfer and Corporate Relations.
Early life and education
Wood earned her bachelor's degree in physics at Yale University. She moved to Massachusetts Institute of Technology for her graduate studies, where studied electrical engineering. She remained at MIT for graduate research, where she researched quantum dots in metal oxide structures with Vladimir Bulimic. Her research developed strategies to integrate colloidal quantum dots in optoelectronic devices. She created three light-emitting diodes where air-stable metal oxides were used to surround the quantum dot active layers. This can improve the shelf-life and luminance of the light-emitting diodes. She also demonstrated the world's first inorganic quantum dot displays incorporating metal oxide charge transport layers. After earning her doctorate, she worked for a short while as a postdoctoral research with Yet-Ming Chiang. She focused on lithium-ion battery flow cells.
Research and career
In 2011, Wood joined the faculty at ETH Zurich. Her research considered lithium-ion batteries, and how electrode microstructure impacts battery efficiency. She created a new analytical method which can be used to monitor battery electrodes during the manufacturing process. She was awarded a European Research Council starting grant to develop quantitative metrologie to guide lithium-ion battery manufacturing.
Wood founded the spin-off company Battrion in 2015. Battrion looks to improve charging speed of high energy density lithium ion cells through the development of innovative fabrication strategies. She was made full Professor in 2019.
In 2021, Wood was made the Vice President for Knowledge Transfer and Corporate Relations at ETH Zurich. She was appointed Meeting Chair of the Materials Research Society 2022 Spring Meeting.
Awards and honors
2014 BASF Science Prize in Electrochemistry
2018 MRS Outstanding Early-Career Investigator Award
Selected publications
References
1983 births
Living people
Yale College alumni
Massachusetts Institute of Technology alumni
American engineers
American women scientists
Academic staff of ETH Zurich
Materials scientists and engineers | Vanessa Wood | [
"Materials_science",
"Engineering"
] | 424 | [
"Materials scientists and engineers",
"Materials science"
] |
76,564,180 | https://en.wikipedia.org/wiki/Sulfurospirillum | Sulfurospirillum (/ˌsʌlfɜːroʊspɪˈrɪlʌm/ SULF-ur-oh-spə-RIHL-um) is a genus of the gram-negative, aerotolerant, rod-shaped bacteria in the family Campylobactaeraceae.
Details
Many species are microaerophillic, and are thus found in soil, groundwater, the deep sea, marine surface sediments, tube worm guts, and polluted environments. Many species can grow on toxic compounds such as arsenate and selenate, and in fact flourish in contaminated sites. The Sulfurospirillum genus contains the only species on the planet that can respire organohalides. No species in the Sulfurospirillum genus have been found to be pathogenic thus far.
References
Bacteria genera
Campylobacterota
Environmental microbiology | Sulfurospirillum | [
"Environmental_science"
] | 169 | [
"Environmental microbiology"
] |
76,571,911 | https://en.wikipedia.org/wiki/Pnictogen%20bond | In chemistry, a pnictogen bond (PnB) is a non-covalent interaction, occurring where there is a net attractive force between an electrophilic region on a 'donor' pnictogen atom (Pn) in a molecule, and a nucleophilic region on an 'acceptor' atom, which may be in the same or another molecule. Closely related to halogen and chalcogen bonding, pnictogen bonds are a form of non-covalent interaction which can be considered in terms of charge-transfer and electrostatic interactions.
Physical origins
Pnictogen bonds typically demonstrate directionality, with the interaction forming either on a linear projection to the R–Pn bond (a σ-hole) or in a plane perpendicular to the three coplanar R–Pn bonds (a π-hole). In such cases, polarisation of the pnictogen atom by an electron-withdrawing substituent, results in an anisotropic electron distribution in the Pn atom affording a directional electropositive region, resulting in an attractive electrostatic interaction. As the polarisability of an atom increases upon descending the periodic table, pnictogen bond strengths typically increase upon descending pnictogen group, both as a result of increased poliarisation resulting in a greater electrostatic contribution to bonding, but also through increased dispersion interactions between the heavier PnB donor and the PnB acceptor atom.
Contributions to pnictogen bonding interactions can also arise through charge transfer interactions, in which a lone pair on the pnictogen bond acceptor are donated into a σ*-orbital on the pnictogen atom. Despite the charge transfer interaction, pnictogen bond interactions are non-covalent interactions, with X···Y bond lengths shorter than the sum of the van der Waals radii, but significantly longer than the sum of the covalent radii.
Applications
The directionality of σ-hole interactions, including PnB interactions, has resulted in their exploitation within the field of supramolecular chemistry, incorporating PnB donor systems into a range of systems exploiting the formation of weak intermolecular interactions for a range of applications.
Organocatalysis
PnB donors have been demonstrated to be capable of functioning as Lewis acidic catalysts. The first reported PnB catalysis cam in 2018 when PnB interactions were demonstrated to be potent catalysts for the Reissert reaction. Given their intermediate position in the main group of the periodic table, PnB catalysis may be appealing due to a balance between steric repulsion and polarisability factors.
Anion recognition
As for halogen and chalocogen bonding interactions, the σ-hole interactions in PnB hosts have been exploited for anion binding and recognition, with a report in 2022 exploiting a series of triaryl antinomy and bismuth receptors for binding of halide anions. The reported systems demonstrated selectivity for chloride from other halies and over the binding of oxoanions, in contrast to trends observed for hydrogen bonding systems, suggesting PnB interactions may have advantages in selective halide anion sensing over hydrogen bonding systems.
Transmembrane transport
PnB systems have also been shown to be capable of transmembrane anion transport, in which lipophilic organopnictogen compounds bind an anion through PnB interactions, enabling transport. The redox activity of main group systems enables the tuning of transport, in which 'on/off' switchable behaviour is enabled between an inactive carrier and an reduced carrier. Park and Gabbaï have demonstrated such a system, in which reduction of an adjacent sulfonium enables the transmembrane transport of anions by an antimony transporter.
References
See also
Sigma hole interactions
Non-covalent interactions
Chemical bonding
Intermolecular forces | Pnictogen bond | [
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"Materials_science",
"Engineering"
] | 804 | [
"Molecular physics",
"Materials science",
"Intermolecular forces",
"Condensed matter physics",
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78,001,026 | https://en.wikipedia.org/wiki/Universal%20multiport%20interferometer | In quantum mechanics, a universal multiport interferometer (or universal modal unitary) is an optical device capable of imposing general unitary transformations in the modal space of single photons or electromagnetic waves.
Classically, a mode of the electromagnetic (EM) field is defined as a normalized solution to Maxwell's equations in vacuum. In general, a mode of the EM field is represented by a vector field that varies both in space and in time. In optics, the allowed (optical) modes are restricted by the boundary conditions imposed by the system in which they exist (e.g., in an optical fiber or an optical cavity) and are thus solutions to the Helmholtz equation. For example, the Hermite-Gauss optical modes are typically used to describe beams produced in spherical mirror cavities.
To continue, a set of orthonormal modes forms an orthonormal basis which spans a modal space, or Hilbert space. The transformation from one modal basis to another is described by a rotation which, in quantum mechanics, is the action of a unitary operator (e.g., the transformation of Hermite-Gauss optical modes to Laguerre-Gauss optical modes). It has been shown that any discrete modal unitary operator can be realized using successive beam splitters and phase-shifters applied to an optical beam array. The Reck scheme provides an algorithmic approach to designing an experimental setup that uses such beam splitters and phase-shifters to implement any modal unitary transformation. The beam splitters and phase-shifters are arranged in a triangular interferometric mesh. Today, such setups are commonly referred to as universal multiport interferometers or universal modal unitaries.
The transformation of a given optical mode into another, more desired optical mode has direct applications to quantum information, optical networking, and photonic computing. The first experimental realization of the Reck scheme was in 2015 by Carolan et al. who used it to implement various linear optical (LO) quantum computing protocols such as heralded quantum logic gates and performing various boson sampling experiments.
Overview
In general, fully determining any -dimensional unitary requires specifying independent real parameters. For the simple case of transforming a two-beam array, a universal modal unitary can be implemented using a variable beam splitter and three phase-shifters. In 1994, Michael Reck and Anton Zeilinger generalized this well-known approach by proving that variable beam splitters and phase-shifters, when arranged in an interferometric mesh with arms, can be used to impose any (discrete) unitary mode transformation. Using their deterministic algorithm to decompose a given unitary into a triangular network of these two optical elements, it is possible to experimentally realize a discrete universal unitary, specifically for mode transformations. The resulting device is commonly referred to as a universal multiport interferometer.
In 2016, Clements et al. introduced a variation of Reck and Zeilinger's decomposition, again using beam splitters and phase shifters, but arranged in a symmetrically-crossing network as opposed to a triangular network. Importantly, this variation has a smaller optical depth - the longest path through the interferometric mesh - and thus experiences lower propagation losses.
The two aforementioned methods are strictly different from the universal unitary decomposition commonly used in quantum computing. That is, the universal gate, whereby any -qubit gate can be realized by a circuit of single qubit gates and CNOT gates. The classical analog of such universality is the idea that an arbitrary Boolean function can be realized using a combination of NOT gates and any one of the two-bit gates (e.g. AND, OR).
Mathematical framework
According to the Davenport rotation theorem, any three-dimensional rotation can be decomposed into three elemental rotations about non-orthogonal axes. The axes may be associated with a fixed coordinate system (i.e., extrinsic rotations) or with a rotating coordinate system (i.e., intrinsic rotations), but those associated with the first and third rotations must be in the plane orthogonal to those associated with the second rotation. If the axes associated with the first and third rotations are perpendicular to one another, the Davenport generalized rotations are called Tait-Bryan rotations. However, if the axes associated with the first and third rotations overlap, they are called Euler rotations.
Mathematically, the three composed rotations are represented by a non-commutative product of three matrices. They are non-commutative as the order in which the rotations are applied affects the resulting orientation of the subject.
The elemental rotations each occur within a two-dimensional subspace of the higher-dimensional Euclidean space. In numerical linear algebra, rotations of this type are commonly described by the Givens rotation matrix. They were introduced in the 1950s by Wallace Givens and are used to implement rotations within a plane spanned by two coordinate axes.
Unitary operators are generalizations of the rotation of Euclidean vectors, and thus one can think of constructing a discrete unitary operator in a similar manner to that described by the Davenport rotation theorem. If one can build a tunable device capable of implementing the Givens rotation to a set of optical modes , then perhaps a chain of such devices could be used to implement any unitary mode transformation . Therefore, the experimental realization of such a Givens rotation device and the proof of its functionality represents a possible method for designing a universal unitary.
Givens rotation
A Givens rotation is a well-known operation in linear algebra that performs a rotation in a two-dimensional subspace of a higher-dimensional space. Mathematically, it the Givens rotation has the following matrix representation:where denote the rows in which the rotation terms appear. The left multiplication of on another matrix results in only rows and of being affected. The effect of the Givens operation thus reduces to the transformation of two input amplitudes, and (where and are elements of the - and -th rows of , respectively), into the new amplitudes, and , as follows:The Givens rotation can be used to zero out a specific element of a vector (e.g., making ) or systematically triangularize a matrix, making it essential for linear algebra algorithms like matrix factorization and solving systems of equations.
This is the same matrix that defines the Jacobi rotation, but the choice of angle differs by a factor of approximately 2.
Experimental motivation
In 1986, Mirsalehi et al. proposed a lossless integrated-optical implementation of a Givens rotation device using diffraction from a thick electro-optic grating and phase modulators to perform the necessary operations for efficient and high-speed data processing.
The proposed device operates with two coherent, monochromatic input waves representing amplitudes and . The phase modulators adjust the relative phase of these inputs, while the diffraction grating computes the sine and cosine components. The outputs and are coherently combined to produce the desired rotation.
The input and output light signals are guided in waveguides. The use of z-cut lithium niobate waveguides ensures low-loss and high-speed operation.
A thick diffraction grating modulated by a voltage generates the sine and cosine multiplications naturally. The input wave amplitudes and are processed through the grating to produce transmitted, , and diffracted, , components.
Electro-optic phase shifters adjust the phases of the optical waves to ensure coherent addition and subtraction, corresponding to the operations required for the rotation matrix.
The final implementation achieves the desired outputs:Mirsalehi et al. proposed using such a Givens device as a building block in lattice filters and wavefront processors. With this in mind, it was already known that such interferometric meshes could perform useful operations, but it was not until nearly a decade later, when Reck et al. published their work that these meshes were shown to implement a universal unitary.
Reck and Zeilinger Scheme
Reck et al. showed that a triangular arrangement of beam splitters and phase-shifters could be systematically programmed, using a straightforward analytical approach, to implement any unitary transformation across a set of optical channels. The notation below is from the second-quantization formulation of quantum optics. In particular, the creation operator represents the addition of a photon to a specific plane wave mode .
Phase-shifters
A phase-shifter adds a phase to the state of a photon passing through it. In terms of creation operators, it performs the following transformation:
The same phase can be achieved by propagating through a material with linear refractive index and thickness , where:
Beam splitters
A beam splitter mixes two input modes and , producing two output modes and . The transformations are given by:The universal unitary for beam transformations is more commonly written in the following form:which is a combination of the modified Givens rotation matrix seen above and three phase-shifters, namely , , and . The transmittance of the beam splitter appears in the matrix as . These are the four free parameters which must be set to fully characterize the unitary matrix (as expected, ). The third phase-shifter, , represents a global offset which can usually be neglected in most practical applications, though it does play an important role when considering geometric phase.
In the notation of Reck et al., the beam transformation is written as,where the missing free parameters are accounted for in a new matrix which will be introduced below.
Algorithm
The objective is to determine the set of matrices such that:where and are the port numbers in the triangular mesh. The matrix is a modified Givens rotation matrix.
Step 1: Initial multiplication
Multiply from the right by a succession of matrices for . This is where the matrix is an -dimensional identity matrix with the elements and replaced by the corresponding beam transformation matrix elements. Hence, it represents a modified Givens rotation matrix.
By the properties of the Givens rotation matrix, and in can be chosen such that, upon multiplication with , the resulting matrix element at vanishes. Changing the index and performing another multiplication with specially chosen values of and , the resulting matrix element at vanishes. Repeating successive multiplications until the index is reached will result in the last row vanishing (expect the on-diagonal element which remains 1). Due to the unitarity of each transformation, the rightmost column will also vanish (again, expect the on-diagonal element which remains 1). This step reduces the effective dimension of to .Step 2: Recursive multiplication
Multiply the reduced matrix from the right by a succession of matrices for . Following the same thought-process as in step 1, this will result in the second-to-last row vanishing and by unitarity, the second-to-rightmost column vanishing (except for the on-diagonal element). The resulting reduced matrix is of the following form:Repeating this step in a recursive fashion until the matrix multiplication involves will result in a transformed diagonal matrix. Notice that the elements along the diagonal have modulus of unity.
Step 3: Recovering the unitary
The final step is to separate the unitary from the successive transformations. This is accomplished by multiplying the transformed diagonal matrix by another diagonal matrix whose elements are also modulus of unity such that the outcome is the identity matrix:In practice, represents a set of phase shifters that compensate for the phases appearing along the diagonal of the transformed matrix.
By the properties of the identity matrix, the product of the final transformed matrix and represents the inverse of ,
Experimental implementation
The experimental setup predicted by the Reck algorithm is described entirely by Each matrix in this product has an experimental counterpart. That is, each matrix represents the beam transformation and thus can be implemented by an individual beam splitter, and the diagonal matrix can be realized by an additional set of phase-shifters.
The maximum number of beam splitters needed for a general is . Since each beam splitter has two free parameters, that is free parameters in addition to the free parameters from . This corresponds to a total of free parameters that must be controlled, as expected.
According to Reck et al., the practical implementation of this scheme is a triangular array of beam splitters and phase-shifters. This is where each beam splitter has an associated phase-shifter at one of its input ports. In addition, phase-shifters are placed at each of the final output ports of the multiport interferometer to perform final phase corrections.
This interferometric mesh essentially contains individual interferometers that all require phase stability. This represents the main challenge to experimentally implementing the Reck scheme in free-space.
Applications
In 2015, Jacques Carolan, Jeremy O'Brien, Anthony Laing, and colleagues experimentally implemented, for the first time, the Reck scheme for the purpose of demonstrating various linear optical (LO) quantum computing protocols. Their device utilized the Reck scheme, but had two key differences:
Their device was implemented in integrated optics and thus did not rely on the free-space propagation of light between the interferometers in the mesh.
Instead of using variable transmittivity () beam splitters at each node of the interferometric mesh, they used Mach-Zehnder interferometers containing tunable phase shifters.
The consequence of the first difference is that their device did not require extremely precise or tedious phase stabilization techniques. The consequence of the second difference is that their device was entirely controlled by phase and not a combination of phase and variable transmittivity.
In particular, their reprogrammable device functioned as a universal six-port interferometer and thus a universal unitary in the modal space spanned by up to six optical modes. It consisted of 15 Mach-Zehnder interferometers and a total of 30 thermo-optic phase shifters. Their measurements were performed using a 12-single-photon detector system.
They used their device to realize a controlled-NOT quantum logic gate and performed full quantum process tomography finding a process fidelity of and an average gate fidelity of . In addition, they implemented 100 Haar random unitaries with an average fidelity of , and six-dimensional complex Hadamard matrices. Finally, they demonstrated the use of their device in performing Boson sampling with six-photon verification tests.
The implementation of the Reck scheme in this form has been highly influential in the field of optics and photonic computing. They have since been used to demonstrate quantum walks, generate entangled qutrit states, and implement the Fast Fourier transform algorithm. In addition, they have been made in ultraviolet-written silica-on-silicon chips.
See also
Unitary operator
Unitary transformation
Universal quantum gate
Givens rotation
Interferometry
References
Further reading
Reck, M., Zeilinger, A., Bernstein, H. J., & Bertani, P. (1994). Experimental Realization of Any Discrete Unitary Operator (Vol. 73, Issue 1).
Clements, W. R., Humphreys, P. C., Metcalf, B. J., Kolthammer, W. S., & Walsmley, I. A. (2016). Optimal design for universal multiport interferometers. Optica, 3(12), 1460. https://doi.org/10.1364/optica.3.001460
Barnett, S. M. (2014). Quantum Information. Oxford University Press.
Nielsen, M. A., & Chuang, I. L. (2010). Introduction to quantum mechanics. In Quantum Computation and Quantum Information: 10th Anniversary Edition (pp. 60–119). chapter 2, Cambridge: Cambridge University Press.
External links
How to build any discrete unitary operator in your laboratory (https://opg.optica.org/abstract.cfm?uri=eqec-1994-QTuC6)
Interferometers | Universal multiport interferometer | [
"Technology",
"Engineering"
] | 3,261 | [
"Interferometers",
"Measuring instruments"
] |
78,001,798 | https://en.wikipedia.org/wiki/N-Acetylputrescine | N-Acetylputrescine (NacPut), also known as monoacetylputrescine, is an endogenous metabolite of putrescine and a precursor and metabolic intermediate in the biosynthesis of γ-aminobutyric acid (GABA) from putrescine.
The metabolic pathway is specifically putrescine into N-acetylputrescine by putrescine acetyltransferase (PAT), N-acetylputrescine into N-acetyl-γ-aminobutyraldehyde (N-acetyl-GABAL or N-acetyl-GABA aldehyde) by monoamine oxidase B (MAO-B), N-acetyl-GABAL into N-acetyl-γ-aminobutyric acid (N-acetyl-GABA) by aldehyde dehydrogenase (ALDH), and N-acetyl-GABA into GABA by an unknown deacetylase enzyme. This pathway is a minor alternative pathway to the major and primary pathway in which GABA is synthesized from glutamate. There is also another alternative pathway in which putrescine is converted into GABA with γ-aminobutyraldehyde (GABAL or GABA aldehyde) as an intermediate instead. It has been estimated that about 2 to 3% of GABA is synthesized from putrescine in the mouse brain, whereas in the case of the rat brain, the amount was negligible.
In 2021, it was discovered that MAO-B does not mediate dopamine catabolism in the rodent striatum but instead participates in striatal GABA synthesis and that synthesized GABA in turn inhibits dopaminergic neurons in this brain area. It has been found that MAO-B, via the putrescine pathway, importantly mediates GABA synthesis in astrocytes in various brain areas, including in the hippocampus, cerebellum, striatum, cerebral cortex, and substantia nigra pars compacta (SNpc). These findings may warrant a rethinking of the actions of MAO-B inhibitors in the treatment of Parkinson's disease.
References
1,4-Butanediyl compounds
Acetyl compounds
Diamines
GABA analogues
Neurotransmitter precursors
Prodrugs | N-Acetylputrescine | [
"Chemistry",
"Biology"
] | 512 | [
"Biotechnology stubs",
"Prodrugs",
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"Biochemistry",
"Chemicals in medicine"
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78,001,957 | https://en.wikipedia.org/wiki/N-Acetyl-%CE%B3-aminobutyric%20acid | N-Acetyl-γ-aminobutyric acid (N-acetyl-GABA), also known as N-acetyl-4-aminobutyric acid, is a metabolic intermediate in the biosynthesis of γ-aminobutyric acid (GABA) from putrescine. Other intermediates in this pathway include N-acetylputrescine and N-acetyl-γ-aminobutyraldehyde (N-acetyl-GABAL or N-acetyl-GABA aldehyde). Enzymes mediating the transformations in this pathway include putrescine acetyltransferase (PAT), monoamine oxidase B (MAO-B), aldehyde dehydrogenase (ALDH), and an unknown deacetylase enzyme. The pathway is a minor pathway in GABA synthesis compared to the main pathway in which GABA is synthesized from glutamate. However, the pathway has been found to have an important physiological role in the brain, for instance in the production of GABA in the striatum and resultant inhibition of dopaminergic neurons in this brain area.
References
Acetamides
GABA analogues
Gamma-Amino acids
Neurotransmitter precursors
Prodrugs | N-Acetyl-γ-aminobutyric acid | [
"Chemistry",
"Biology"
] | 275 | [
"Biotechnology stubs",
"Prodrugs",
"Biochemistry stubs",
"Biochemistry",
"Chemicals in medicine"
] |
78,002,065 | https://en.wikipedia.org/wiki/4-Acetamidobutanal | 4-Acetamidobutanal, also known as N-acetyl-γ-aminobutyraldehyde, N-acetyl-GABAL, or N-acetyl-GABA aldehyde, is a metabolic intermediate in the biosynthesis of γ-aminobutyric acid (GABA) from putrescine. Other intermediates in this pathway include N-acetylputrescine and N-acetyl-γ-aminobutyric acid (N-acetyl-GABA). Enzymes mediating the transformations in this pathway include putrescine acetyltransferase (PAT), monoamine oxidase B (MAO-B), aldehyde dehydrogenase (ALDH), and an unknown deacetylase enzyme. The pathway is a minor pathway in GABA synthesis compared to the main pathway in which GABA is synthesized from glutamate. However, the pathway has been found to have an important physiological role in the brain, for instance in the production of GABA in the striatum and resultant inhibition of dopaminergic neurons in this brain area.
References
Acetyl compounds
Aldehydes
Amines
GABA analogues
Neurotransmitter precursors
Prodrugs | 4-Acetamidobutanal | [
"Chemistry"
] | 273 | [
"Functional groups",
"Prodrugs",
"Chemicals in medicine",
"Amines",
"Bases (chemistry)"
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75,002,510 | https://en.wikipedia.org/wiki/Fractional%20Chern%20insulator | Fractional Chern insulators (FCIs) are lattice generalizations of the fractional quantum Hall effect that have been studied theoretically since 1993 and have been studied more intensely since early 2010.
They were first predicted to exist in topological flat bands carrying Chern numbers. They can appear in topologically non-trivial band structures even in the absence of the large magnetic fields needed for the fractional quantum Hall effect. In principle, they can also occur in partially filled bands with trivial band structures if the inter-electron interaction is unusual. They promise physical realizations at lower magnetic fields, higher temperatures, and with shorter characteristic length scales compared to their continuum counterparts.
FCIs were initially studied by adding electron-electron interactions to a fractionally filled Chern insulator, in one-body models where the Chern band is quasi-flat,
at zero magnetic field. The FCIs exhibit a fractional quantized Hall conductance.
Prior work and experiments with finite magnetic fields
In works predating the theoretical studies of FCIs, the analogue of the Laughlin state was demonstrated in Hofstadter-type models. The essential features of the topology of single-particle states in such models still stems from the presence of a magnetic field. Nevertheless, it was shown that in the presence of a lattice, fractional quantum Hall states can retain their topological character, in the form of fractional Chern numbers. Chern Insulators - single-particle states exhibiting an integer anomalous quantized Hall effect at zero field - have been theoretically proposed.
Fractionally filling such states, in the presence of repulsive interactions, can lead to the zero-field Fractional Chern Insulator. These FCIs are sometimes not connected to the Fractional Quantum Hall Effect in Landau Levels. This is the case in bands with Chern number ,
and are therefore a new type of states inherent to such lattice models. They have been explored with respect to their quasi-charge excitations, non-Abelian states and the physics of twist defects,
which may be conceptually interesting for topological quantum computing.
Experimentally, Chern insulators have been realized without a magnetic field.
FCIs have been claimed to be realized experimentally in van der Waals heterostructures, but with an external magnetic field of order and, more recently, FCIs in a band have been claimed to be observed in twisted bilayer graphene close to the magic angle, yet again requiring a magnetic field, of order 5 T in order to "smoothen" out the Berry curvature of the bands.
These states have been called FCIs due to their link to lattice physics -- either in Hofstadter bands or in the moiré structure, but still required nonzero-magnetic field for their stabilization.
Zero field fractional Chern insulators
The prerequisite of zero field fractional Chern insulator is magnetism. The best way to have magnetism is to have exchange interaction that simultaneously polarize the spin. This phenomenon in twisted MoTe2 in both integer and fractional states was first observed by a University of Washington group.
In 2023 a series of groups have reported FCIs at zero magnetic field
in twisted samples. The University of Washington group first identified fractional Chern number of , and state with trion emission sensing. This is followed by the Cornell group who performed thermodynamic measurement on and state. These samples, where the moiré bands are valley-spin locked, undergo a spin-polarization transition which gives rise to a Chern insulator state at integer filling of the moiré bands. Upon fractional filling at and , a gapped state develops with a fractional slope in the Streda formula, a hallmark of an FCI. These fractional states are identical to the predicted zero magnetic field FCIs. After the optical sensing measurement, University of Washington group first reported transport `smoking-gun` evidence of fractional quantum anomalous Hall effect that should be exhibited by a zero-field fractional Chern insulator at , and . They also identified a possible composite Fermi liquid at that mimics the half filled Landau level for 2D electron gas. The and states are also partially repeated by the Shanghai group, while the quantization is not as good.
The full matching of FCI physics in , using the single particle model proposed in, to experiments still holds intriguing and unresolved mysteries. These were only partially theoretically addressed,
where the issues of model parameters, sample magnetization, and the appearance of some FCI states (at filling and ) but the absence of others (so far at filling at ) are partially addressed.
References
Correlated electrons
Quantum phases | Fractional Chern insulator | [
"Physics",
"Chemistry",
"Materials_science"
] | 949 | [
"Quantum phases",
"Phases of matter",
"Quantum mechanics",
"Condensed matter physics",
"Correlated electrons",
"Matter"
] |
75,004,059 | https://en.wikipedia.org/wiki/Susana%20F.%20Huelga | Susana F. Huelga is a Spanish physicist, and Professor at the Institute of Theoretical Physics of Ulm University.
She is notable for her contributions to the field of quantum information theory. These include quantum metrology in the presence of Markovian and non-Markovian environments, the theory of open quantum systems, numerical methods for their description in the presence of structured environments, the characterization, quantification and detection of non-Markovianity and fundamental contributions to quantum effects in biological systems.
Education
She obtained her MSc in 1990 and her Doctorate in 1995 in physics from the Universidad de Oviedo, where she worked with Miguel Ferrero and Emilio Santos. Her thesis, Optical experiments for the study of fundamental quantum properties consisted of two parts, each proposing an optical experiment. The first part is a proposal for an experiment to test "Bell's inequality capable of closing the existing exits in the atomic cascade experiments already carried out". The second part is a proposal for the contrast of the Leggett–Garg inequality in an experiment.
Career
After finishing her doctorate she spent a postdoc at the Clarendon Laboratory of Oxford University 1996 - 1997 and held a position as Profesor Titular at Universidad de Oviedo. She joined the Faculty of the Department of Physics, Astronomy and Mathematics of the University of Hertfordshire as a Lecturer in 2000 and Reader in 2008. In October 2009 she accepted a Professorship at the Institute of Theoretical Physics of the Universität Ulm where she is still working.
Personal
She is married to physicist Martin Bodo Plenio.
References
External links
at the Institute of Theoretical Physics of Ulm University
Spanish physicists
Living people
21st-century women physicists
Quantum physicists
Year of birth missing (living people) | Susana F. Huelga | [
"Physics"
] | 351 | [
"Quantum physicists",
"Quantum mechanics"
] |
72,220,556 | https://en.wikipedia.org/wiki/Maia%20Vergniory | Maia Garcia Vergniory is a Spanish computational physicist who is a group leader at the Max Planck Institute for Chemical Physics of Solids. Her work in topological quantum chemistry investigates the phases of topological materials. She was elected Fellow of the American Physical Society in 2022.
Early life and education
Vergniory was born in Getxo. She was a doctoral researcher at the University of the Basque Country. Her research considered many-body effects on the interactions between excited electronic states and the mobile ions on surfaces. She started working on topological materials in 2012.
Research and career
Vergniory worked as a research fellow at the Ikerbasque and the Donostia International Physics Center. She studied novel materials and computational strategies to realise new condensed matter systems.
Verginory became interested in the design of new topological materials with optimised functional properties. Topological materials are insulators in the bulk but conductive on their surfaces. The conducting channels that facilitate current flow are robust and independent of size.
Vergniory studied the Inorganic Crystal Structure Database to identify topologically nontrivial materials. She designed a computational effort to simulate real materials and determine whether or not they showed topological properties. This included complex theoretical analysis that could classify topological phases, and information from materials scientists on whether materials were suitable or not. Vergniory uses her supercomputers to perform her calculations ab initio. In an interview with Physics World, Verginory said that she had been surprised by how many materials she identified with topological properties. As an output of this work, the high-order topological insulator Bi4Br4 was synthesised and studied experimentally. She showed that if it was possible to identify the symmetry of the crystalline symmetry of a material, she could easily anticipate the behaviour of the charge. She has since started investigating organic materials. She believes that topological crystals with a chiral structure will display several exotic physical phenomena.
Awards and honours
2017 L'Oréal-UNESCO For Women in Science Award
2022 Elected a Fellow of the American Physical Society
Selected publications
References
People from Getxo
Living people
University of the Basque Country alumni
Fellows of the American Physical Society
Spanish women chemists
Year of birth missing (living people)
Computational chemists
Materials scientists and engineers
Max Planck Institutes researchers
Condensed matter physicists
Basque people
21st-century chemists
21st-century Spanish physicists
Grenoble Alpes University alumni
Academic staff of the University of the Basque Country
21st-century Spanish women scientists | Maia Vergniory | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 502 | [
"Condensed matter physicists",
"Materials science",
"Computational chemists",
"Computational chemistry",
"Theoretical chemists",
"Condensed matter physics",
"Materials scientists and engineers"
] |
72,221,650 | https://en.wikipedia.org/wiki/Hantao%20Ji | Hantao Ji is a professor of astrophysical sciences at Princeton University. He received the John Dawson Award in 2002 for his work on magnetic reconnection. He is also a fellow of the American Physical Society.
References
Plasma physicists
Year of birth missing (living people)
Living people | Hantao Ji | [
"Physics"
] | 58 | [
"Plasma physicists",
"Plasma physics"
] |
72,230,055 | https://en.wikipedia.org/wiki/Neoproterozoic%20oxygenation%20event | The Neoproterozoic Oxygenation Event (NOE), also called the Second Great Oxidation Event, was a geologic time interval between around 850 and 540 million years ago during the Neoproterozoic era, which saw a very significant increase in oxygen levels in Earth's atmosphere and oceans. Taking place after the end to the Boring Billion, an euxinic period of extremely low atmospheric oxygen spanning from the Statherian period of the Paleoproterozoic era to the Tonian period of the Neoproterozoic era, the NOE was the second major increase in atmospheric and oceanic oxygen concentration on Earth, though it was not as prominent as the Great Oxidation Event (GOE) of the Neoarchean-Paleoproterozoic boundary. Unlike the GOE, it is unclear whether the NOE was a synchronous, global event or a series of asynchronous, regional oxygenation intervals with unrelated causes.
Evidence for oxygenation
Carbon isotopes
Beginning around 850 Mya to around 720 Mya, a time interval roughly corresponding to the Late Tonian, between the end of the Boring Billion and the onset of the Cryogenian “Snowball Earth”, marine deposits record a very significant positive carbon isotope excursion. These elevated δ13C values are believed to be linked to an evolutionary radiation of eukaryotic plankton and enhanced organic burial, which in turn indicate a spike in oxygen production during this interval. Further positive carbon isotope excursions occurred during the Cryogenian. Although several negative carbon isotope excursions, associated with warming events, are known from the Late Tonian all the way up to the Proterozoic-Phanerozoic boundary, the carbon isotope record nonetheless maintains a noticeable positive trend throughout the Neoproterozoic.
Nitrogen isotopes
δ15N data from 750 to 580 million year-old marine sediments hailing from four different Neoproterozoic basins show similar nitrogen isotope ratios to modern oceans, with a mode of +4% and a range from -4% to +11%. No significant change is observed across the Cryogenian-Ediacaran boundary, implying that oxygen was already ubiquitous in the global ocean as early as 750 Mya, during the Tonian period.
Sulfur isotopes
Seawater sulfate δ34S values, which saw a gradual increase over most of the Neoproterozoic punctuated by major drops during glaciations, show a significant positive excursion during the Ediacaran, with a corresponding decrease in pyritic δ34S. High fractionation rates between sulfte and sulfide indicate an increase in the availability of sulfate in the water column, which in turn is indicative of increased reaction of pyrite with oxygen. In addition, genetic evidence points to the occurrence of a radiation of non-photosynthetic sulfide-reducing bacteria during the Neoproterozoic. Through bacterial sulfur disproportionation, such bacteria further deplete marine sulfide of heavier sulfur isotopes. Because such bacteria require significant amounts of oxygen to survive, an oxygenation event during the Neoproterozoic raising oxygen concentrations to over 5-18% of modern levels is believed to have been a necessary prerequisite for the diversification of these microorganisms.
Strontium isotopes
δ13C can reliably indicate changes in net primary productivity and oxygenation if the rates of weathering into the oceans and carbon dioxide outgassing remain constant or increase, since a decrease in either of these could cause a positive δ13C excursion through continued preferential biological consumption of carbon-12 by existing communities while the supply of available carbon decreased, without indicating an increase in primary productivity and oxygen production. The ratio of strontium-87 to strontium-86 is used as a determinant of the relative contribution of continental weathering to the ocean's nutrient supply; an increase in this ratio, as observed throughout the Neoproterozoic and into the Cambrian until reaching a peak at the end of the Cambrian, suggests a rise in continental weathering and bolsters evidence from carbon isotope ratios for high oxygenation in this interval of time.
Chromium isotopes
Surface oxidation of Cr(III) to Cr(VI) causes isotopic fractionation of chromium; Cr(VI), typically present in the environment as either chromate or dichromate, has elevated values of δ53Cr, or the ratio of chromium-53 to chromium-52, whereas bacterial reduction of Cr(VI) to Cr(III) is associated with negative chromium isotope excursions. Following the riverine transport of oxidised chromium into the ocean, the reaction reducing Cr(VI) back into Cr(III) and subsequently oxidising ferrous iron into ferric iron is highly efficient at sequestering Cr(VI), as is the precipitation of Cr(III) with ferric oxyhydroxide, meaning that chemically precipitated chromium isotope ratios in sediments abundant in ferric iron accurately reflect seawater chromium isotope ratios at the time of deposition. Because efficient oxidation of Cr(III) to Cr(VI) is only possible in the presence of the catalyst manganese dioxide, which is only stable and abundant at high oxygen fugacities, a positive excursion of δ53Cr indicates an increase in atmospheric oxygen concentrations. Banded iron formations (BIFs) deposited during the Neoproterozoic consistently display highly positive δ53Cr values, from 0.9% to 4.9%, demonstrating the era's oxygenation of the atmosphere. Oxidative chromium cycling began approximately 0.8 Ga, indicating that oxygen level rise began well before the Cryogenian glaciations. Chromium isotopes also show that during the Cryogenian interglacial interval, between the Sturtian and Marinoan glaciations, oxygenation of the ocean and atmosphere was slow and subdued; this interval marked a lull in the NOE.
Molybdenum isotopes
δ98Mo values were slightly higher during the Late Ediacaran than in the Cryogenian or the Early and Middle Ediacaran. This isotopic proxy indicates the level of oxygenation of the Late Ediacaran ocean was comparable to that of Mesozoic oceanic anoxic events.
Uranium isotopes
The very low values of δ238U, commonly used as an isotopic measurement of changes in seawater oxygenation, during much of the Neoproterozoic have been interpreted to reflect progressive oxygenation punctuated by temporary, transient expansions of anoxic and euxinic waters. During the Early Ediacaran, the shift in uranium isotopes occurred in tandem with enrichment in light carbon isotopes.
Causes
Increase in nitrogen fixation
During the Boring Billion, open ocean productivity was very low compared to the Neoproterozoic and Phanerozoic as a result of the absence of planktonic nitrogen-fixing bacteria. The evolution and radiation of nitrogen-fixing bacteria and non-nitrogen-fixing picocyanobacteria capable of occupying marine planktonic niches and consequent changes to the nitrogen cycle during the Cryogenian are believed to be a culprit behind the rapid oxygenation of and removal of carbon dioxide from the atmosphere, which also helps explain the development of extremely severe glaciations that characterised this period of the Neoproterozoic.
Increase in day length
The slowdown of the Earth's rotation and corresponding increase in day length has been suggested as a possible cause of the NOE on the basis of experimental findings that cyanobacterial productivity is higher during longer periods of uninterrupted daylight compared to shorter periods more frequently interrupted by darkness.
Organic carbon burial
The Neoproterozoic saw organic carbon burial occur in large lakes with anoxic bottom waters on a massive scale. As carbon was locked away in sedimentary rock, it was unable to be oxidised, permitting a buildup of atmospheric oxygen.
Phosphorus removal
The increasing diversity of eukaryotes has been proposed as a cause of increased deep ocean oxygenation by means of phosphorus removal from the deep ocean. The evolution of large multicellular organisms led to increased amounts of organic matters sinking to the seafloor (marine snow). This, combined with the evolution of benthic filter feeders (e.g. choanoflagellates and primitive poriferans such as Otavia), is believed to have shifted oxygen demand further down in the water column, which would result in a positive feedback loop wherein phosphorus was removed from the ocean, which reduced productivity and decreased oxygen demand, which in turn led to increasing oxygenation of deep ocean water. Increasingly well oxygenated oceans enabled further eukaryotic dispersal, which likely acted as a positive feedback loop that accelerated oxygenation.
Consequences
Glaciation
The rapid increase in organic carbon sequestration as a result of the increased rates of global photosynthesis by both cyanobacteria and eukaryotic photoautotrophs (green and red algae), occurring in conjunction with an increase in silicate weathering of continental flood basalts resulting from the breakup of the supercontinent Rodinia, is believed to have been a trigger of the Sturtian and Marinoan glaciations during the Cryogenian, the middle period of the Neoproterozoic.
Biological diversity
During the Tonian, very early multicellular organisms may have evolved and diversified in oxygen "oases" in the deep oceans, which acted as cradles in these early stages of eukaryote evolution. However, the persistence of anoxia and euxinia over the late Tonian despite some increases in oxygen content meant eukaryotic diversity overall remained low. Over the course of the Ediacaran period, the oceans gradually became better oxygenated, with the time interval immediately after the Gaskiers Glaciation displaying evidence of significantly increasing marine oxygen content. The rapid diversification of multicellular life during this geologic period has been attributed by some authors to an increase in oxygen content, enabling the iconic oxygen-consuming multicellular eukaryotes of the Ediacaran biota to become ubiquitous and widespread. Initially restricted to deeper, colder waters that possessed the most dissolved oxygen, metazoan life gradually expanded into warmer zones of the ocean as global oxygen levels rose.
See also
Great Oxidation Event
Avalon explosion
Cambrian explosion
Silurian-Devonian Terrestrial Revolution
References
Neoproterozoic events
Origin of life
Oxygen
Events in the geological history of Earth
Evolution of the biosphere
Meteorological hypotheses | Neoproterozoic oxygenation event | [
"Biology"
] | 2,189 | [
"Biological hypotheses",
"Evolution of the biosphere",
"Origin of life"
] |
72,230,901 | https://en.wikipedia.org/wiki/Miyake%20event | A Miyake event is an observed sharp enhancement of the production of cosmogenic isotopes by cosmic rays. It can be marked by a spike in the concentration of radioactive carbon isotope in tree rings, as well as and in ice cores, which are all independently dated. At present, five significant events are known (7176 BCE, 5259 BCE, 664-663 BCE (historically referred to as 660 BCE), 774 CE, 993 CE) for which the spike in is quite remarkable, i.e. above 1% rise over a period of two years, and four more events (12,350BCE, 5410 BCE, 1052 CE, 1279 CE) need independent confirmation. It is not known how often Miyake events occur, but from the available data it is estimated to be every 400 to 2,400 years.
There is strong evidence that Miyake events are caused by extreme solar particle events and they are likely related to super-flares discovered on solar-like stars. Although Miyake events are based on extreme year-to-year rises of concentration, the duration of the periods over which the levels increase or stay at high levels is longer than one year. However, a universal cause and origin of all the events is not yet established in science, and some of the events may be caused by other phenomena coming from outer space (such as a gamma-ray burst).
A recently reported sharp spike in that occurred between 12,350 and 12,349BCE may represent the largest known Miyake event. This event was identified during a study conducted by an international team of researchers who measured radiocarbon levels in ancient trees recovered from the eroded banks of the Drouzet River, near Gap, France, in the Southern French Alps. According to the initial study the new event is roughly twice the size of the Δ increase for more recent 774CE and 993CE events, but the strength of the corresponding solar storm is not yet assessed. However, the newly discovered 12,350 BCE event has not yet been independently confirmed in wood from other regions, nor it is reliably supported by a clear corresponding spike in other isotopes (such as beryllium-10) that are usually used in combination for absolute radiometric dating.
A Miyake event occurring in modern conditions might have significant impacts on global technological infrastructure such as satellites, telecommunications, and power grids.
Discovery
The events are named after the Japanese physicist Fusa Miyake who, as a doctoral student, was the first one to identify these radiocarbon spikes and published the results with co-authors in 2012 in the journal Nature. The investigation at that time found a strong increase in the annual rings of Japanese cedars for the years 774/775. The event of 775 was independently discovered, using the low-resolution IntCal data.
In 2013, Miyake and co-authors published the discovery of another similar radiocarbon spike in the years 993/994. In December 2013, Miyake received her Doctor of Science degree from Nagoya University.
Time benchmark
After a Miyake event is well-studied and confirmed, it can serve as a reference time benchmark, a "year-stamp", enabling more precise dating of historical buildings, objects, and events. Six diverse historical occurrences, from archaeological sites to natural disasters, have thus been dated to a specific year, using Miyake events as benchmarks and counting tree rings. For example, wooden construction elements from the Viking archaeological site at L'Anse aux Meadows in Newfoundland were dated by identifying the spike of 993 CE in a sequence of tree-rings, which showed that the wood is from a tree felled in 1021 CE, thus definitely confirming Viking presence in the Americas at least before 1021 CE. Another study performed on the tree-rings of wooden building remains from the
Neolithic waterlogged site of Dispilio in north-western Greece, identified the Miyake event of 5259 BC, thus for a first time absolutely dating a Neolithic site in Europe from the 6th millennium BC to a single calendar year.
See also
Carrington Event
Coronal mass ejection
Dendrochronology
Geomagnetic storm
Solar storm
References
External links
Researchers succeed for first time in accurately dating a 7,000-year-old prehistoric settlement using cosmic rays – May 21, 2024 – University of Bern
Geomagnetic storms
Astrophysics
Geophysics
Stratigraphy
Dating methods | Miyake event | [
"Physics",
"Astronomy"
] | 917 | [
"Astronomical sub-disciplines",
"Applied and interdisciplinary physics",
"Astrophysics",
"Geophysics"
] |
67,834,439 | https://en.wikipedia.org/wiki/Trimeric%20intracellular%20cation-selective%20channel | The trimeric intracellular cation-selective channels or TRIC proteins are a group of homo-trimeric cation channel proteins of ~300 residues in the ER membrane. There are two known TRIC proteins, TRIC-A and TRIC-B.
Channel function
TRICs are permeable to both Na+ and K+ but not divalent cations like Ca2+. They exhibit marked voltage-dependence, becoming more open when the cytosol is more positively charged than the ER lumen.
TRIC-A
TRIC-A is predominantly expressed in excitable tissues including brain and skeletal muscle. TRIC-A activity is thought to support RyR1-mediated efflux of Ca2+ ions from the sarcoplasmic reticulum into the cytosol.
TRIC-B
K+ flux into the ER through TRIC-B is thought to support IP3-induced efflux of Ca2+ ions through IP3-gated Ca2+ channels in the ER membrane.
Clinical significance
TRIC-A has been implicated in the regulation of arterial blood pressure through regulating the excitability of vascular smooth muscle cells. Several single-nucleotide polymorphisms (SNPs) in close proximity to the TRIC-A locus and, in future, may serve as an important biomarker in the diagnosis of essential hypertension
Null mutations in TMEM38B encoding TRIC-B are an uncommon but relatively severe cause of autosomal recessive osteogenesis imperfecta or "brittle bone disease".
References
Proteins | Trimeric intracellular cation-selective channel | [
"Chemistry"
] | 325 | [
"Biomolecules by chemical classification",
"Proteins",
"Molecular biology"
] |
67,838,357 | https://en.wikipedia.org/wiki/Attosecond%20chronoscopy | Attosecond chronoscopy are measurement techniques for attosecond-scale delays of atomic and molecular single photon processes like photoemission and photoionization. Ionization-delay measurements in atomic targets provide information about the timing of the photoelectric effect, resonances, electron correlations, and transport.
Attosecond chronoscopy deals with the time-resolved observation of ultrafast electronic processes of quantum physics of matter with applications to atoms, molecules. and solids. Typical time scales covered range from attoseconds (10−18 sec.) to femtoseconds (10−15 sec.). Realtime observations of such processes became possible with the availability of well-controlled subfemtosecond laser pulses. Chronoscopy can provide information complementary to that accessible through conventional spectroscopy. While spectroscopy aims at characterizing processes through measurements with the highest possible energy resolution but without time resolution, chronoscopy attempts to capture dynamical aspects of quantum dynamics through high time resolution but with only limited energy resolution. Important applications are non-stationary and decaying states, quantum transport and charge migration, irreversible processes (the "Arrow of time") and the loss of phase information called decoherence of a quantum system due to its interaction with the environment.
See also
Attophysics
Bibliography
Time-resolved spectroscopy
Atomic physics
Molecular physics | Attosecond chronoscopy | [
"Physics",
"Chemistry"
] | 288 | [
" and optical physics stubs",
"Molecular physics",
"Spectrum (physical sciences)",
"Quantum mechanics",
"Time-resolved spectroscopy",
"Atomic physics",
" molecular",
"nan",
"Atomic",
"Molecular physics stubs",
"Spectroscopy",
"Physical chemistry stubs",
" and optical physics"
] |
63,508,559 | https://en.wikipedia.org/wiki/Chair%20tiling | In geometry, a chair tiling (or L tiling) is a nonperiodic substitution tiling created from L-tromino prototiles. These prototiles are examples of rep-tiles and so an iterative process of decomposing the L tiles into smaller copies and then rescaling them to their original size can be used to cover patches of the plane. Chair tilings do not possess translational symmetry, i.e., they are examples of nonperiodic tilings, but the chair tiles are not aperiodic tiles since they are not forced to tile nonperiodically by themselves. The trilobite and cross tiles are aperiodic tiles that enforce the chair tiling substitution structure and these tiles have been modified to a simple aperiodic set of tiles using matching rules enforcing the same structure. Barge et al. have computed the Čech cohomology of the chair tiling and it has been shown that chair tilings can also be obtained via a cut-and-project scheme.
References
External links
Tilings Encyclopedia, Chair
Aperiodic tilings | Chair tiling | [
"Physics",
"Mathematics"
] | 228 | [
"Tessellation",
"Geometry",
"Geometry stubs",
"Aperiodic tilings",
"Symmetry"
] |
63,513,617 | https://en.wikipedia.org/wiki/Pioneering%20Women%20in%20American%20Mathematics | Pioneering Women in American Mathematics: The Pre-1940 PhD's is a book on women in mathematics. It was written by Judy Green and Jeanne LaDuke, based on a long study beginning in 1978, and was published in 2009 by the American Mathematical Society and London Mathematical Society as volume 34 in their joint History of Mathematics series. Unlike many previous works on the topic, it aims at encyclopedic coverage of women in mathematics in the pre-World War II United States, rather than focusing only on the biographies of individual women or on collecting stories of only the most famous women in mathematics. The Basic Library List Committee of the Mathematical Association of America has strongly recommended its inclusion in undergraduate mathematics libraries.
Topics
The first part of the book discusses the institutions that granted doctorates to women in mathematics before 1940, and the milieu in which they operated, including typical practices of the time of that demanded that women resign on marriage, that forbade institutions from hiring wives or other relatives of their male faculty, or in some cases prevented women who had done all the work for a graduate degree from being granted one. It also discusses the patterns the authors' found in these women's lives, including the discovery that their life expectancies were higher than typical for their time. Its eight chapters include material on the family background of the subjects, their undergraduate and graduate education, hiring and careers, and their contributions to mathematics.
The second part of the book provides biographical profiles of every woman that the authors could identify as having earned a doctorate in mathematics in the US before 1940, as well as four American women who earned doctorates abroad, giving 228 in all. The typical biography in this section is approximately 2/3 of a page to a page in length, with information drawn from reference works, review journals, and archival material as well as interviews with the subjects still living at the time of the study. The 1940 cutoff for the biographies in the book represents both a time of "a precipitous drop in enrollment" for women in mathematics, and the starting time for two previous studies on women in mathematics and science by Margaret A. M. Murray and Margaret W. Rossiter. The rate of doctorates given to women in the period covered by the book, approximately 14%, would not be reached again until the 1980s.
A companion web site provides additional information on the subjects of the book, and can be considered as a third and "potentially most valuable" section of the book itself.
Audience and reception
This book is readable by a general audience, but reviewer Charles Ashbacher writes that "only people deeply interested in the history of mathematics, particularly in the role of women, will find it a critical read", and suggests that the second half should be used as reference material rather than reading it through. Reviewer Amy Shell-Gellasch agrees, writing "It is intended as a reference, not necessarily as a book to sit down and read." Reviewer Silke Göbel adds that, beyond mathematics, the book will also be of interests to sociologists.
Ashbacher rates the book as "an excellent resource for information in this area". Despite calling it "a labor of love" and "an important contribution", Shell-Gellasch writes that she was "disappointed by the lack of references" in the book, although significantly more references can be found in the companion web site. In contrast, reviewer Andrea Blunck calls the book "really fascinating", writing that she was "surprised to learn how numerous" these women were, "and how different yet how similar their lives and careers were". And reviewer Margaret A. M. Murray calls the book "spectacular" and "a stunning historical achievement", writing that because of it "we now know more about this first cohort of American women mathematicians than we know about any cohort of mathematicians, male or female."
Notable mentions
Mary Nicholas Arnoldy
Grace Hopper
M. Henrietta Reilly
References
External links
Additional Material for the Book, American Mathematical Society
Women in mathematics
Biographies and autobiographies of mathematicians
2009 non-fiction books | Pioneering Women in American Mathematics | [
"Technology"
] | 827 | [
"Women in science and technology",
"Women in mathematics"
] |
58,296,164 | https://en.wikipedia.org/wiki/Arterial%20spin%20labelling | Arterial spin labeling (ASL), also known as arterial spin tagging, is a magnetic resonance imaging technique used to quantify cerebral blood perfusion by labelling blood water as it flows throughout the brain. ASL specifically refers to magnetic labeling of arterial blood below or in the imaging slab, without the need of gadolinium contrast. A number of ASL schemes are possible, the simplest being flow alternating inversion recovery (FAIR) which requires two acquisitions of identical parameters with the exception of the out-of-slice saturation; the difference in the two images is theoretically only from inflowing spins, and may be considered a 'perfusion map'.
The ASL technique was developed by John S. Leigh Jr, John A. Detre, Donald S. Williams, and Alan P. Koretsky in 1992.
Physics
Arterial spin labeling utilizes the water molecules circulating with the brain, and using a radiofrequency pulse, tracks the blood water as it circulates throughout the brain. After a period of time in microseconds (enough to allow the blood to circulate through the brain), a 'label' image is captured. A 'control' image is also acquired before the labeling of the blood water. A subtraction technique gives a measurement of perfusion. In order to increase SNR, collections of control and label images can be averaged. There are also other specifications in the MRI that can increase SNR, like the amount of head coils of the MRI, or a stronger field strength (3 T is standard, but 1.5 T is satisfactory). In order to properly scale the perfusion values into cerebral blood flow units (CBF, ml/100g/1 min), a separate proton density map with the same parameters (but longer TR to fully relax the blood spins) is recommended to be acquired as well. Alternatively, the average control image can be used to generate CBF, which is the case for Phillips pCASL readouts. Usually background suppression is also applied to increase the SNR. Due to the different variations of each implementations, it is recommended that a large multi-scanner study should design a protocol minimizing the variety of readout methods used by each scanner.
One study has shown that although there are voxel differences when different readout methods are used, average gray matter CBF are still comparable. Differences in SNR are apparent when each voxel compared, but collectively are negligible.
Continuous arterial spin labelling
In continuous arterial spin labeling (CASL), the blood water is inverted as it flows through the brain in one plane. CASL is characterized by one single long pulse (around 1–3) seconds. This may be disadvantageous for certain scanners that are not designed to maintain a radiofrequency pulse that long, and therefore would require adjustments to a RF amplifier. This is rectified in pseudo-continuous arterial spin labeling (pCASL), where a single long pulse is replaced with multiple (up to a thousand) millisecond pulses. This leads to a higher labelling efficiency. pCASL is the preferred implementation of ASL. There are different readout modules for pCASL, depending on the scanner used, with 2D pCASL usually being implemented for all scanners and 3D pCASL stack of spirals implemented in GE scanners.
Pulsed arterial spin labelling
In pulse arterial spin labeling (PASL), blood water is inverted as it passes through a labeling slab (of 15 to 20 cm) instead of a plane. There are different variations of this implementations, including EPISTAR and PICORE and PULSAR. Most scanners have been designed to have PASL work out-of-the-box for research use.
Velocity selective arterial spin labelling
Velocity selective arterial spin labeling is a strategy that still requires validation. Velocity selective arterial spin labeling is advantageous in a population where blood flow may be impeded (e.g. stroke), because the labeling occurs closer to the capillaries. This allows the post labeling decay to be shorter.
Diffusion prepared pseudocontinuous arterial spin labelling (DP-pCASL)
Diffusion-prepared pseudocontinuous ASL (DP-pCASL) is a more recent ASL variant sequence that magnetically labels water molecules and measures their movement across the blood-brain barrier complex, which allows for the calculation of the water exchange rate (kw). kw is used as a surrogate for BBB function and permeability. Water exchange across the BBB is mediated by a number of processes, including passive diffusion, active co-transport through the endothelial membrane, and predominantly by facilitated diffusion through the dedicated water channel aquaporin-4 (AQP4). Several studies have investigated the use of DP-pCASL in cerebrovascular diseases, including acute ischemic stroke, CADASIL, hereditary cerebral small vessel disease as well as in animal models.
Analysis of ASL images
ASL maps can mainly be analyzed using the same tools to analyze fMRI and VBM. Many ASL-specific toolboxes have been developed to assist in ASL analysis, such as BASIL (Bayesian inference for arterial spin labelling MRI), part of the FSL neuroimaging package and also Ze Wang's ASL toolbox (using MATLAB) to assist in the subtraction and averaging of the tagged/control pairs. A visual quality check is often needed to make sure that the perfusion map is valid (such as correct registration, or correct segmentation of non-cerebral materials such as the dura mater). A whole brain/voxel-wise approach can be analyzed by registering the ASL map into MNI space for group comparisons. A region of interest approach can be analyzed by registering the ASL map into a selected cluster, or an atlas, like a standard (such as the Harvard-Oxford Cortical atlas) or an individual atlas developed by software like FreeSurfer. The recommended procedure of ASL registration for voxel-wise analysis is to register the perfusion map to a gray matter segmentation of each individual in a non-rigid procedure.
Gray matter often requires more oxygenation and is the source of more brain activity compared to white matter. Therefore, gray matter CBF is often higher than white matter CBF. The single value of gray matter CBF is often isolated in order to give a broad overview of CBF differences. Gray matter and white matter CBF can be localized using atlases or Freesurfer.
ASL functional connectivity can be designed with parameters conducive to a long scan time. Studies have suggested that ASL complement resting state fMRI findings well but can differentiate between resting brain networks (such as the default mode network) less.
Comparison with fMRI
Functional MRI (fMRI) has been the modality of choice to visualize brain activity, and takes advantages of a range of techniques that can be used to interpret it. However, the signal that fMRI is acquiring is BOLD signal, which does not directly correlate with blood flow. Cerebral blood flow on the other hand does, allowing for cardiovascular disease (CVD) and inflammatory risk factor analysis, and disorders (such as schizophrenia and bipolar disorder) that have comorbid effects with CVD. ASL imaging can be a useful tool to complement fMRI and vice versa.
Clinical use
In cerebral infarction, the penumbra has decreased perfusion. Besides acute and chronic neurovascular diseases, the value of ASL has been demonstrated in brain tumors, epilepsy and neurodegenerative disease, such as Alzheimer's disease, frontotemporal dementia and Parkinson disease. Additionally, DP-pCASL has promising potential for assessing blood-brain barrier integrity in patients with ischemic stroke.
Although the primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, ASL is another method of obtaining contrast.
There have been research to apply ASL to renal imaging, pancreas imaging, and placenta imaging. A challenge to these sort of non-cerebral perfusion is motion due to breathing. Additionally, there is a lot less development on the segmentation of theses specific organs, so the studies are relatively small scale.
Safety
ASL is in general a safe technique, although injuries may occur as a result of failed safety procedures or human error like other MRI techniques.
ASL, like other MRI modalities generate a fair amount of acoustic noise during the scan, so earplugs are advised.
References
External links
mriquestions.com
Neuroimaging
Nuclear magnetic resonance
Imaging
Magnetic resonance imaging
Scientific techniques | Arterial spin labelling | [
"Physics",
"Chemistry"
] | 1,785 | [
"Nuclear magnetic resonance",
"Magnetic resonance imaging",
"Nuclear physics"
] |
58,296,445 | https://en.wikipedia.org/wiki/Piezoelectric%20microelectromechanical%20systems | A piezoelectric microelectromechanical system (piezoMEMS) is a miniature or microscopic device that uses piezoelectricity to generate motion and carry out its tasks. It is a microelectromechanical system that takes advantage of an electrical potential that appears under mechanical stress. PiezoMEMS can be found in a variety of applications, such as switches, inkjet printer heads, sensors, micropumps, and energy harvesters.
Development
Interest in piezoMEMS technology began around the early 1990s as scientists explored alternatives to electrostatic actuation in radio frequency (RF) microelectromechanical systems (MEMS). For RF MEMS, electrostatic actuation specialized high voltage charge pump circuits due to small electrode gap spacing and large driving voltages. In contrast, piezoelectric actuation allowed for high sensitivity as well as low voltage and power consumption as low as a few millivolts. It also had the ability to close large vertical gaps while still allowing for low microsecond operating speeds. Lead zirconate titanate (PZT), in particular, offered the most promise as a piezoelectric material because of its high piezoelectric coefficient, tunable dielectric constant, and electromechanical coupling coefficient. PiezoMEMS have been applied to various different technologies from switches to sensors, and further research have led to the creation of piezoelectric thin films, which aided in the realization of highly integrated piezoMEMS devices.
The first reported piezoelectrically actuated RF MEMS switch was developed by scientists at the LG Electronics Institute of Technology in Seoul, South Korea in 2005. The researchers designed and actualized a RF MEMS switch with a piezoelectric cantilever actuator that had an operation voltage of 2.5 volts.
In 2017, researchers from the U.S. Army Research Laboratory (ARL) evaluated the radiation effects in the piezoelectric response of PZT thin films for the first time. They determined that PZT exhibited a degree of radiation hardness that could be further extended by using conductive oxide electrodes instead of traditional platinum electrodes. Gamma radiation tests have also shown that actuated devices such as switches, resonators, and inertial devices could benefit from the radiation tolerance of PZT, suggesting the possibility that actuators and sensors can be integrated into platforms evaluating nuclear material and reduce human exposure to radiation.
This experiment was part of a decades-long research investment effort at ARL to improve the use of PZT thin film technology for piezoMEMS. Other piezoMEMS-related work included developing a piezoelectric microphone based on PZT thin films, creating new integrated surface micromachining processes for RF MEMS to incorporate thin film PZT actuators, providing the first experimental demonstration of monolithically integrated piezoMEMS RF switches with contour mode filters, and demonstrating the feasibility of vibrational energy harvesting using thin film PZT MEMS. In their work, researchers from ARL have also increased the overall electromechanical response of PZT thin films by 15-30% by incorporating iridium oxide electrode materials.
Design
There exists three primary approaches to realizing PiezoMEMS devices:
The additive approach: The piezoelectric thin films are deposited on silicon substrates with layers of insulating and conducting material followed by surface or silicon bulk micromachining.
The subtractive approach: Single crystal or polycrystalline piezoelectrics and piezoceramics are subjected to direct bulk micromachining and then electrodes.
The integrative approach: Micromachined structures are integrated in silicon or piezoelectrics by using bonding techniques on bulk piezoelectric or silicon substrates.
PiezoMEMS use two principal crystal structures, the wurtzite and perovskite structures.
Challenges
PiezoMEMS still face many difficulties that impede its ability to be successfully commercialized. For instance, the success of depositing uniform films of piezoelectrics still depend heavily on the use of appropriate layers of proper nucleation and film growth. As a result, extensive device-specific development efforts are needed to create a proper sensor structure. In addition, researchers continue to search for ways to reduce and control the material and sensor drift and aging characteristics of thin film piezoelectric materials. Deposition techniques to create thin films with properties approaching those of bulk materials remain in development and in need of improvement. Furthermore, the chemistry and etching characteristics of most piezoelectric materials remain very slow.
References
Mechanical engineering
Electrical engineering
Microtechnology
Microelectronic and microelectromechanical systems
Transducers
Electrical phenomena
Energy harvesting | Piezoelectric microelectromechanical systems | [
"Physics",
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"Microtechnology",
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"Microelectronic and microelectromechanical systems"
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58,297,950 | https://en.wikipedia.org/wiki/Pauline%20Harrison | Pauline May Harrison (née Cowan, 24 August 1926 – 28 May 2024) was a British protein crystallographer and professor emeritus at the University of Sheffield. She gained her chemistry degree from Somerville College, Oxford in 1948, followed by a DPhil in X-ray crystallography in 1952 supervised by Dorothy Hodgkin. After three years at King's College London (contemporary with Rosalind Franklin) she moved to the University of Sheffield in 1955 as a demonstrator in the Biochemistry department (now Molecular Biology and Biotechnology), obtaining an MRC grant to study the iron storage protein Ferritin, publishing preliminary X-ray diffraction data in the 1st volume of the Journal of Molecular Biology in 1959. The molecule which became her life's work. In 1978, she was awarded a personal chair and retired in 1991. In 2001 she was appointed a CBE for services to higher education.
Personal life and death
Harrison was the daughter of botanists Adeline May Organe and John Macqueen Cowan, Assistant Keeper of the Royal Botanic Garden, Edinburgh. She was married to Royden Harrison, also a lecturer at Sheffield and a figure in the Labour movement until his death in 2002. Harrison was an alumna of St. Trinnean's School.
Harrison died on 28 May 2024, at the age of 97.
References
1926 births
2024 deaths
Alumni of Somerville College, Oxford
British biochemists
British crystallographers
Academics of the University of Sheffield
English biophysicists
X-ray crystallography
British women biologists
British women chemists
20th-century British women scientists
20th-century British scientists
21st-century British women scientists
21st-century British scientists | Pauline Harrison | [
"Chemistry",
"Materials_science"
] | 345 | [
"X-ray crystallography",
"Crystallography"
] |
58,300,295 | https://en.wikipedia.org/wiki/Structural%20support | A structural support is a part of a building or structure that provides the necessary stiffness and strength in order to resist the internal forces (vertical forces of gravity and lateral forces due to wind and earthquakes) and guide them safely to the ground. External loads (actions of other bodies) that act on buildings cause internal forces (forces and couples by the rest of the structure) in building support structures. Supports can be either at the end or at any intermediate point along a structural member or a constituent part of a building and they are referred to as connections, joints or restraints.
Building support structures, no matter what materials are used, have to give accurate and safe results. A structure depends less on the weight and stiffness of a material and more on its geometry for stability. Whatever the condition is, a specific rigidity is necessary for connection designs. The support connection type has effects on the load bearing capacity of each element, which makes up a structural system. Each support condition influences the behaviour of the elements and therefore, the system. Structures can be either Horizontal-span support systems (floor and roof structures) or Vertical building structure systems (walls, frames, cores, etc.)
Structure
Structure is necessary for buildings but architecture, as an idea, does not require structure. Every building has both load-bearing structures and non-load bearing portions. Structural members form systems and transfer the loads that are acting upon the structural systems, through a series of elements to the ground. Building Structure Elements include Line (beams, columns, cables, frames or arches, space frames, surface elements (walls, slab or shells) and Freeform.
The structure's functional requirements will narrow the possible forms that one can consider. Other factors such as the availability of materials, foundation conditions, the aesthetic requirements and economic limitations also play important roles in establishing the structural form. Structural systems or all their members and parts are considered to be in equilibrium if the systems are initially at rest and remain at rest when a system of forces and couples acts on them. They are not aspects of a model that should be guessed. To be able to analyze a structure, it is necessary to be clear about the forces that can be quite complicated.
There are two types of forces, External Forces which are the actions of other bodies on the structure under consideration and Internal Forces which the rest of the structure exert on a member or portion of the structure as forces and couples. A little deflection or play is required for a structure to protect other surrounding materials from those forces.
Support structure
There are five basic idealized support structure types, categorized by the types of deflection they constrain: roller, pinned, fixed, hanger and simple support.
Roller supports
A roller support allows thermal expansion and contraction of the span and prevents damage on other structural members such as a pinned support. The typical application of roller supports is in large bridges. In civil engineering, roller supports can be seen at one end of a bridge.
A roller support cannot prevent translational movements in horizontal or lateral directions and any rotational movement but prevents vertical translations. Its reaction force is a single linear force perpendicular to, and away from, the surface (upward or downward). This support type is assumed to be capable of resisting normal displacement.
It can be rubber bearings, rocker or a set of gears allowing a limited amount of lateral movement. A structure on roller skates, for example, remains in place as long as it must only support itself. As soon as lateral load pushes on the structure, a structure on roller skates will roll away in response to the force.
Pinned support
A pinned support attaches the only web of a beam to a girder called a shear connection. The support can exert a force on a member acting in any direction and prevent translational movements, or relative displacement of the member-ends in all directions but cannot prevent any rotational movements. Its reaction forces are single linear forces of unknown direction or horizontal and vertical forces which are components of the single force of unknown direction.
A pinned support is just like a human elbow. It can be extended and flexed (rotation), but you cannot move your forearm left to right (translation).
One benefit of pinned supports is not having internal moment forces and only their axial force playing a big role in designing them. However, a single pinned support cannot completely restrain a structure. At least two supports are needed to resist the moment. Applying in trusses is one frequent way we can use this support.
Fixed support
Rigid or fixed supports maintain the angular relationship between the joined elements and provide both force and moment resistance. It exerts forces acting in any direction and prevents all translational movements (horizontal and vertical) as well as all rotational movements of a member. These supports’ reaction forces are horizontal and vertical components of a linear resultant; a moment. It is a rigid type of support or connection. The application of the fixed support is beneficial when we can only use single support, and people most widely used this type as the only support for a cantilever. They are common in beam-to-column connections of moment-resisting steel frames and beam, column and slab connections in concrete frames.
Hanger support
A hanger support only exerts a force and prevents a member from acting or translating away in the direction of the hanger. However, this support cannot prevent translational movement in all directions and any rotational movement. This is one of the simplest structural forms in which the elements are in pure tension. Structures of this type range from simple guyed or stayed structures to large cable-supported bridge and roof systems.
Simple support
A simple support is basically where the structural member rests on an external structure as in two concrete blocks holding a resting plank of wood on their tops. This support is similar to roller support in a sense that restrains vertical forces but not horizontal forces. Therefore, it is not widely used in real life structures unless the engineer can be sure that the member will not translate.
Varieties of support
See also
Bracket (architecture)
References
Nl:Oplegging
Civil engineering | Structural support | [
"Engineering"
] | 1,222 | [
"Construction",
"Civil engineering"
] |
59,931,116 | https://en.wikipedia.org/wiki/Pillow-plate%20heat%20exchanger | Pillow-plate heat exchangers are a class of fully welded heat exchanger design, which exhibit a wavy, “pillow-shaped” surface formed by an inflation process. Compared to more conventional equipment, such as shell and tube and plate and frame heat exchangers, pillow plates are a quite young technology. Due to their geometric flexibility, they are used as well as “plate-type” heat exchangers and as jackets for cooling or heating of vessels. Pillow plate equipment is currently experiencing increased attention and implementation in process industry.
Construction
Pillow plates are manufactured by an inflation process, where two thin metal sheets are spot-welded to each other over the entire surface by laser or resistance welding. The sides of the plates are sealed by seam welding, other than the connecting ports. Finally, the gap between the thin metal sheets is pressurized by a hydraulic fluid causing a plastic forming of the plates, which eventually leads to their characteristic wavy surface.
In principle, there are two different types of pillow plates: single-embossed and double-embossed. The former commonly form the double walls of jacketed vessels, while the latter are assembled to a stack (bank) to manufacture pillow plate heat exchangers. Single-embossed pillow plates are formed when the base plate is significantly thicker than the top plate. The thinner top plate deforms, while the base plate remains plane.
Furthermore, pillow plates are commonly equipped with “baffle” seam weldings, which offer a targeted flow guidance in the pillow plate channels in cases, where flow distribution or fluid velocity might be an issue. A method for obtaining flow guidance by baffles in the channels between adjacent pillow plates in pillow plate heat exchangers, has recently been proposed in.
Due to their construction, pillow plates are hermetically sealed, they have a high structural stability and their manufacturing is mostly automated and highly flexible. Pillow plates can be operated at pressures > 100 MPa and temperatures of up to 800 °C.
Application
The application of pillow plates is very extensive, due to their favorable properties such as high geometric flexibility and good adaptivity to almost every process. Their implementation depends on their underlying construction, i.e. pillow plate banks or pillow plate jacketed tanks. The relatively flat external surface is easy to clean and suitable for high fouling or sanitary applications, but the internal surface has fine seams around each spot weld and is not easy to clean, therefore the internal surface is only suitable for non-fouling fluids like water, steam or refrigerants.
Pillow plate banks (heat exchangers)
Pillow plate banks are typically used in applications involving liquid-liquid, gas-liquid, high viscosity or dirty media, low pressure loss requirements, condensation (e.g. top condensers), falling film evaporation (e.g. paper & pulp industry), reboilers, water chilling, drying of solids, flake ice generation (food industry) and more. They are also commonly used as immersion chillers (e.g. in electroplating), where the banks are immersed directly into the tank. Banks can be constructed to allow the individual plates to be separated from the stack, allowing easy cleaning or maintenance.
Pillow plate jacketed tanks
The most extensive application of pillow plates to date is with jacketed vessels, because of their flexibility, full surface area coverage for heat transfer, low fluid hold-up, favorable manufacturing costs & time, and easy cleaning, especially in sterile applications. The tanks can be equipped with multiple jackets over its surface, including also the tank bottom, e.g. conical or dished, and can include additional cylindrical shells inside the tank. Typical areas of implementation of pillow plate jacketed tanks are in food and beverage industry and in chemical and pharmaceutical industry. These jackets are also referred to as "dimple jackets".
Other
Due to their geometrical flexibility, pillow plates can be customized/adapted to almost any geometry to offer targeted heat transfer where it is needed. Some examples are cooling of pipes in thermal processes or even battery packs and electric motors for electric vehicles in automotive industry.
Know-how and research on pillow plates
In contrast to more conventional heat exchangers, knowledge of thermohydraulic performance of pillow plates and experience with their design is limited. To overcome this bottleneck efforts are currently being made to develop commercial software tools. A rough overview of state-of-the-art on pillow plates can be found in.
Research on pillow plates can be subdivided into three main categories: geometrical analysis, analysis of fluid flow and heat transfer in pillow plates and analysis of fluid flow and heat transfer in the gap between adjacent pillow plates.
Geometrical analysis
Methods for the calculation of surface area, fluid hold-up volume, cross-sectional area and hydraulic diameter, needed in thermohydraulic calculations, have been proposed in. The mentioned geometrical parameters were determined using Finite Element Analysis (FEM), which imitates the inflation process during manufacturing of pillow plates. Moreover, theoretical burst pressures of pillow plates, could be estimated with FEM.
Fluid flow and heat transfer in pillow plates (inner channels)
The complex wavy geometry in pillow plate channels promotes fluid mixing, which leads to favorable heat transfer rates but is also unfavorable for pressure loss (formation of recirculation regions in the wake of welding spots). Information on fluid flow and heat transfer in pillow plates is available in, while correlations for the calculation of Darcy-Friction-Factor and Nusselt number in pillow plates over a wide range of geometrical parameters variations and process conditions is found in.
Fluid flow and heat transfer in the gap between adjacent pillow plates (outer channels)
Similar to the inner channels of pillow plates, the channels formed between adjacent pillow plates (outer channels) are also wavy and promote fluid mixing, which is in turn favorable for heat transfer rates. However, pressure loss in the outer channels is significantly lower than in the inner ones because of the absence of welding spots, which act as obstacles for the flow (flow around welding spots). Information on fluid flow and heat transfer in the outer channels of pillow plate heat exchangers is available in.
Falling film flow over the surface of pillow plates
The reliable design of condensers, falling film evaporators and water chillers requires detailed knowledge of fluid dynamics and heat transfer of the falling liquid film over the surface of the pillow plates.
References
Heat exchangers | Pillow-plate heat exchanger | [
"Chemistry",
"Engineering"
] | 1,307 | [
"Chemical equipment",
"Heat exchangers"
] |
64,989,681 | https://en.wikipedia.org/wiki/Aboso%20Glass%20Factory | Aboso Glass Factory is a glass company located in Aboso, a town near Tarkwa, which is the capital of Wassa West District, in the Western Region of Ghana.
Controversy
The situation surrounding the Aboso Glass Factory highlights ongoing tensions regarding resource management and community involvement. The opposition by the youth to Linkin Birds Company accessing scraps from the factory suggests concerns about transparency, equitable benefits for locals, or potential environmental impacts.
Such disputes are common when decisions about local resources are made without sufficient community engagement, particularly when those resources hold economic or historical significance. GIHOC Distilleries Company, as a key stakeholder, might need to work closely with the community to address these concerns and ensure that any agreements are fair and mutually beneficial.
In a phone interview, Maxwell Kofi Jumah, Managing Director of GIHOC Distilleries Company, explained that the directive originated from a new investor and assured that only the scraps would be removed, with nothing else taken out.
The community, however, disputes this claim, stating that scraps are still being taken away. They allege that roofing sheets from the building have also been removed, and transformers powering the factory have been dismantled.
History
The Aboso Glass Factory set up by Kwame Nkrumah in 1966, was a major manufacturer and supplier of bottles for the beverage industry, among many other products. Most of the employees were residents from Aboso and other neighbouring communities. The company was renamed as Tropical Glass Factory when it was handed over to Gilchrist Olympio. However due to financial constraints, the company collapsed. In 2003, Aboso Glass Factory was placed on a divestiture listing, after ECG ceased power supply for their works. The government in 2017 has announced plans of restoring the company to its former glory with the help of some investors. In 2019, GIHOC Distilleries Company Limited declared a takeover of the Aboso Glass Factory. Aboso youth in the Prestea Huni Valley Municipality of the Western Region to hit the streets if there are no signs of revising glass factory.
References
Glassmaking companies
Ghanaian brands
Western Region (Ghana)
1966 establishments in Ghana | Aboso Glass Factory | [
"Materials_science",
"Engineering"
] | 443 | [
"Glass engineering and science",
"Glassmaking companies",
"Engineering companies"
] |
64,991,255 | https://en.wikipedia.org/wiki/List%20of%20inflammatory%20disorders |
Nervous system
CNS
Encephalitis
Myelitis
Meningitis
Arachnoiditis
PNS
Neuritis
eye
Dacryoadenitis
Scleritis
Episcleritis
Keratitis
Retinitis
Chorioretinitis
Blepharitis
Conjunctivitis
Uveitis
ear
Otitis externa
Otitis media
Labyrinthitis
Mastoiditis
Cardiovascular system
Carditis
Endocarditis
Myocarditis
Pericarditis
Vasculitis
Arteritis
Phlebitis
Capillaritis
Respiratory system
upper
Sinusitis
Rhinitis
Pharyngitis
Laryngitis
lower
Tracheitis
Bronchitis
Bronchiolitis
Pneumonitis
Pleuritis
Mediastinitis
Digestion system
Mouth
Stomatitis
Gingivitis
Gingivostomatitis
Glossitis
Tonsillitis
Sialadenitis/Parotitis
Cheilitis
Pulpitis
Gnathitis
Gastrointestinal tract
Esophagitis
Gastritis
Gastroenteritis
Enteritis
Colitis
Enterocolitis
Duodenitis
Ileitis
Caecitis
Appendicitis
Proctitis
Accessory digestive organs
Hepatitis
Ascending cholangitis
Cholecystitis
Pancreatitis
Peritonitis
Integumentary system
Dermatitis
Folliculitis
Cellulitis
Hidradenitis
Musculoskeletal system
Arthritis
Dermatomyositis
soft tissue
Myositis
Synovitis/Tenosynovitis
Bursitis
Enthesitis
Fasciitis
Capsulitis
Epicondylitis
Tendinitis
Panniculitis
Osteochondritis: Osteitis/Osteomyelitis
Spondylitis
Periostitis
Chondritis
Urinary system
Nephritis
Glomerulonephritis
Pyelonephritis
Ureteritis
Cystitis
Urethritis
Reproductive system
Female
Oophoritis
Salpingitis
Endometritis
Parametritis
Cervicitis
Vaginitis
Vulvitis
Mastitis
Male
Orchitis
Epididymitis
Prostatitis
Seminal vesiculitis
Balanitis
Posthitis
Balanoposthitis
Pregnancy/newborn
Chorioamnionitis
Funisitis
Omphalitis
Endocrine system
Insulitis
Hypophysitis
Thyroiditis
Parathyroiditis
Adrenalitis
Lymphatic system
Lymphangitis
Lymphadenitis
Physiology
Inflammations | List of inflammatory disorders | [
"Biology"
] | 500 | [
"Physiology"
] |
56,553,704 | https://en.wikipedia.org/wiki/Lachancea%20thermotolerans | Lachancea thermotolerans is a species of yeast.
Taxonomy
L. thermotolerans is the type species of the genus Lachancea. The species has previously been known as Kluyveromyces thermotolerans and Zygosaccharomyces thermotolerans, which is the name by which it was first described in 1932.
Habitat and ecology
L. thermotolerans is widely distributed and occurs in diverse environments, both natural and man-made. It has been isolated from locations around the world. The species is commonly associated with fruit and with insects such as fruit flies that feed on fruit. In some cases, it has been identified as one of several species found in naturally fermented foods.
Uses
L. thermotolerans is unusual among yeasts in its ability to produce lactic acid through fermentation. This property has prompted study of L. thermotolerans in the production of wine and beer, both of which are traditionally produced using Saccharomyces yeasts. In winemaking, L. thermotolerans and other yeast species have been studied for the effects of their metabolites on the flavor profile of wines. Systems including L. thermotolerans in co-fermentation with wine yeast or in place of lactic acid bacteria have been described as an alternative to traditional malolactic fermentation. L. thermotolerans has been sold commercially on its own and in a yeast blend. In beer brewing, L. thermotolerans has been considered as a method for producing sour beer. It has been observed that this kind of yeast ferments at low temperatures (17 °C) as well as at high temperatures (27 °C) and with SO2 doses of 25 mg/L and 75 mg/L with an ethanol yield between 7-11% vol. Sequential inoculations (binary) and sequential co-inoculations (ternary) with different non-Saccharomyces, including L. thermotolerans, have also been studied, resulting in very significant synergies and inhibitions in lactic acid production.
References
Yeasts
Fungi described in 2003
Wine chemistry
Yeasts used in brewing
Fungus species | Lachancea thermotolerans | [
"Chemistry",
"Biology"
] | 466 | [
"Fungi",
"Fungus species",
"Yeasts",
"Alcohol chemistry",
"Wine chemistry"
] |
56,556,160 | https://en.wikipedia.org/wiki/PLEKHG2 | Pleckstrin homology domain containing, family G member 2 (PLEKHG2) is a protein that in humans is encoded by the PLEKHG2 gene. It is sometimes written as ARHGEF42, FLJ00018.
The PLEKHG2 protein is a huge protein of about 1300 amino acids, 130 kDa and has a Dbl homology (DH) domain and a pleckstrin homology (PH) domain near the N terminus of its structure. The DH domain is a domain responsible for guanine nucleotide exchange activity that converts GDP on the Rho family Small GTPase (RhoGTPase) to GTP, and PLEKHG2 having this domain also acts as a Rho-specific guanine nucleotide exchange factor (RhoGEF).
Activation of RhoGTPase reconstitute the actin cytoskeleton and changes the cell morphology, so PLEKHG2 might be contributes to cell motility and neuronal network development of neurons via RhoGTPase and actin remodeling (see later).
Cloning
Recombinant BXH2 and AKXD inbred mice mutated by retroviral transduction are known to develop myeloid leukemia, B cell and T cell leukemia at high frequency.
In 2002, Himmel et al., used this model of acute myelogenous leukemia and showed that a novel Dbl family guanine nucleotide exchange factor gene is contained downstream of the retroviral uptake site called Evi24. They named this gene Clg. Hemmel and colleagues cloned Clg and showed homology with PLEKHG2 contained in human chromosome 19 chromosome 19q13.1 region. From these observations they pointed out association with acute myeloid leukemia.
Functions
In a paper published by Hemmel et al., in 2002, they showed that a construct containing a DH-PH domain of Clg promotes guanine nucleotide exchange of Cdc42 but does not promote guanine nucleotide exchange of Rac1 or RhoA. In addition, DH-PH domains or full-length Clg were introduced into NIH3T3 cells and transformation occurred.
Later, Ueda and his colleagues introduced the expression construct of full-length human PLEKHG2 into HEK 293 cells. In this cell the Gβγ subunit of the trimeric G protein were interacted with PLEKHG2 directly. Ueda and colleagues also showed that PLEKHG2 were activated by Gbg and PLEKHG2 activates Rac1, Cdc42 of RhoGTPase and contributes to cell morphological change.
In 2013, Runne et al., showed that PLEKHG2 is elevated in several leukemia cell lines, including Jurkat T cells. In addition, they showed that GPCR signal-dependent activation of Rac and Cdc42 regulates the chemotaxis of lymphocytes via actin polymerization. From this observation PLEKHG2 was considered to an important regulator of cell motility.
Furthermore, in recent years, it has become clear that PLEKHG2 undergoes regulation through modification such as phosphorylation and interaction with other proteins by various intracellular signals (see the section on interaction / protein modification). However, the function in vivo is still unclear.
Disease related with PLEKHG2
In 2016, Edvardson et al., identified homozygosity for Arg204Trp mutation in the PLEKHG2 gene in the patients with dystonia or postnatal microcephaly.
Interactions
PLEKHG2 is known to interacted with the following proteins.
・Gβγ
・β-actin
・Four and a Half LIM domain1 (FHL1)
・Gαs
protein modification
It is known that PLEKHG2 undergoes modification such as phosphorylation by the following signals.
・SRC
・EGFR
References
Genes
Proteins | PLEKHG2 | [
"Chemistry"
] | 825 | [
"Biomolecules by chemical classification",
"Proteins",
"Molecular biology"
] |
69,232,129 | https://en.wikipedia.org/wiki/Xcel-Arc | Xcel-Arc is a New Zealand-based welding company that is owned by Esseti NZ Ltd. It was founded in 1994, providing welding machines across New Zealand. Today, it is one of the primary welding companies of New Zealand.
The company is headquartered in Palmerston North, Wellington, New Zealand.
History
The Xcel-Arc Welding NZ was founded in 1994 in New Zealand. It provides plasma cutters, TIG-welding, MIG, Arc welding machines, machine trolleys, and protective gear.
Xcel-Arc manufactures machines that comply Australian-New Zealand market standards AS/NZS60974-1 and EN 50199.
References
External links
Xcel-Arc Welding NZ
Welding
Companies based in Wellington | Xcel-Arc | [
"Engineering"
] | 150 | [
"Welding",
"Mechanical engineering"
] |
69,232,536 | https://en.wikipedia.org/wiki/Intelligent%20automation | Intelligent automation (IA), or alternately intelligent process automation, is a software term that refers to a combination of artificial intelligence (AI) and robotic process automation (RPA). Companies use intelligent automation to cut costs and streamline tasks by using artificial-intelligence-powered robotic software to mitigate repetitive tasks. As it accumulates data, the system learns in an effort to improve its efficiency. Intelligent automation applications consist of but are not limited to, pattern analysis, data assembly, and classification. The term is similar to hyperautomation, a concept identified by research group Gartner as being one of the top technology trends of 2020.
Technology
Intelligent automation applies the assembly line concept of breaking tasks into repetitive steps to improve business processes. Rather than having humans do each step, intelligent automation can replace steps with an intelligent software robot or bot, improving efficiency.
Applications
The technology is used to process unstructured content. Common real-world applications include self-driving cars, self-checkouts at grocery stores, smart home assistants, and appliances. Businesses can apply data and machine learning to build predictive analytics that react to consumer behavior changes, or to implement RPA to improve manufacturing floor operations.
For example, the technology has also been used to automate the workflow behind distributing Covid-19 vaccines. Data provided by hospital systems’ electronic health records can be processed to identify and educate patients, and schedule vaccinations.
Intelligent Automation can provide real-time insights on profitability and efficiency. However in an April 2022 survey by Alchemmy, despite three quarters of businesses acknowledging the importance of Artificial Intelligence to their future development, just a quarter of business leaders (25%) considered Intelligent Automation a “game changer” in understanding current performance. 42% of CTOs see “shortage of talent” as the main obstacle to implementing Intelligent Automation in their business, while 36% of CEOs see ‘upskilling and professional development of existing workforce’ as the most significant adoption barrier.
IA is becoming increasingly accessible for firms of all sizes. With this in mind, it is expected to continue to grow rapidly in all industries. This technology has the potential to change the workforce. As it advances, it will be able to perform increasingly complex and difficult tasks. In addition, this may expose certain workforce issues as well as change how tasks are allocated.
Benefits
Streamline Processes
Repetitive manual tasks can put a strain on the workforce, these tasks can be automated to allow the workforce to work on more important matters that require human cognition. Intelligent automation can also be used to mitigate tasks with human error which in turn increases proficiency. This allows the opportunity for firms to scale production without the traditional negative consequences such as reduced quality or increased risk.
Customer Service Improvement
Customers service can be improved drastically, this allows for a competitive advantage for the firm. IA utilizing chat features allows for instant curated responses to customers. In addition, it can give updates to customers, make appointments, manage calls, and personalize campaigns.
Flexibility
Due to the wide range of applications, IA is useful across a variety of fields, technologies, projects and industries. In addition, IA can be integrated with current automated systems in place. This allows for optimized systems unique to each firm to best fit their individual needs.
Capabilities
Cognitive automation: Employs AI techniques to assist humans in decision-making and task completion
Natural language processing: Allows computers to automate knowledge work
Business process management: Enhances the consistency and agility of corporate operations
Process mining: Applies data mining methods to discover, analyze, and improve business processes
Intelligent document processing: Utilizes OCR and other advanced technologies to extract data from documents and convert it into structured, usable data
Computer vision: Allows computers to extract information from digital images, videos, and other visual inputs
Integration automation: Establishes a unified platform with automated workflows that integrate data, applications, and devices.
See also
Robotic process automation
Artificial intelligence
Automation
References
&
Business software
Automation software
Information economy
Machine learning | Intelligent automation | [
"Engineering"
] | 800 | [
"Machine learning",
"Automation",
"Control engineering",
"Automation software",
"Artificial intelligence engineering"
] |
69,240,781 | https://en.wikipedia.org/wiki/Jennifer%20Van%20Eyk | Jennifer Eileen Van Eyk is the Erika Glazer Chair in Women's Heart Health, the Director of Advanced Clinical Biosystems Institute in the Department of Biomedical Sciences, the Director of Basic Science Research in the Women's Heart Center, a Professor in Medicine and in Biomedical Sciences at Cedars-Sinai. She is a renowned scientist in the field of clinical proteomics.
Early life and education
Jennifer E. Van Eyk was born in Northern Ontario, Canada. She obtained a bachelor of science in biology and chemistry from the University of Waterloo in 1982. She received a PhD in biochemistry under the direction of Robert S. Hodges from University of Alberta in 1991. She conducted post-doctoral research at University of Heidelberg, University of Alberta, and University of Illinois at Chicago with R. John Solaro.
Career
Van Eyk began her academic career in 1996 as an assistant professor in the Department of Physiology at Queen's University, Kingston, Canada, and she was promoted to associate professor and received tenure in 2001. She then left Canada to join Johns Hopkins University as the Director of the Proteomics Innovation Center in Heart Failure in 2003, and later Cedars-Sinai in 2014.
Van Eyk is a member-at-large and a council member of Human Proteome Organization, and the president of US Human Proteome Organization. She was a technical briefs editor at Proteomics. She served on the editorial board of Proteomics: clinical application and Journal of Physiology and Circulation Research. She currently serves on the editorial board of Clinical Proteomics. She is a Fellow of the International Society for Heart Research. and is a Fellow of the American Heart Association.
Research
She is an international leading scientist in clinical proteomics. She is the founding director of Cedars-Sinai Advanced Clinical Biosystems Research Institute, whose motto is “from discovery to patient care”.
She is co-editor of Clinical Proteomics: From Diagnosis to Therapy, an essential, important and impressive book in clinical proteomics and translational medicine.
Her list of publications: https://www.ncbi.nlm.nih.gov/sites/myncbi/1VsYqQYH8535l/bibliography/48183272/public/.
Awards
2024 The Analytical Scientist Power List, Human Health Heroes
2024 The Karger Medal, Barnett Institute of Chemical & Biological Analysis, NorthWestern University
2024 Richard Simpson Lecturer Award, Australian Proteomics Society
2024 U.S. Human Proteome Organization Catherine E. Costello Award for Exemplary Achievements in Proteomics
2023 The International Society of Heart Research, International President’s Lecture Award
2023 The Analytical Scientist Power List - Leaders and Advocates
2022 The Association for Mass Spectrometry and Advances in Clinical Lab (MSACL)Distinguished Contribution Award
2021 The Analytical Scientist Power List
2020 The Analytical Scientist Power List
2019 Human Proteome Organization Distinguished Achievement in Proteomic Sciences Award
2019 US Human Proteome Organization The Donald F. Hunt Distinguished Contribution in Proteomics award
2019 Canadian National Proteomics Network The Tony Pawson Proteomics Award
2017 The Analytical Scientist Power List: Top 10 Omics Explorers
2015 Human Proteome Organization Clinical & Translational Proteomics Award
2014 American Heart Association Council on Genomic and Precision Medicine Medal of Honor
2013 American Heart Association Council on Genomic and Precision Medicine Distinguished Achievement Award
Recent Patents
Role of citrullination in diagnosing diseases (2021) US 11,105,817 B2
Biomarkers of myocardial injury (2021) US 11,041,865 B2
Correlated peptides for quantitative mass spectrometry (2019) US 10,352,942 B2
Citrullinated proteins: a post-translated modification of myocardial proteins as marker of physiological and pathological disease (2019) US 10,309,974 B2
Diagnostic assay for Alzheimer's disease (2017) US 9,678,086 B2
References
Living people
University of Alberta alumni
Mass spectrometrists
Canadian women scientists
Cedars-Sinai Medical Center
Year of birth missing (living people)
Proteomics
Proteomics journals
Proteomics organizations
Canadian physiologists
Cardiovascular physiology
Cardiovascular researchers
American Heart Association
American scientists | Jennifer Van Eyk | [
"Physics",
"Chemistry"
] | 870 | [
"Biochemists",
"Mass spectrometry",
"Spectrum (physical sciences)",
"Mass spectrometrists"
] |
69,242,552 | https://en.wikipedia.org/wiki/Polyfluoroalkoxyaluminates | Polyfluoroalkoxyaluminates (PFAA) are weakly coordinating anions many of which are of the form [Al(ORF)4]−. Most PFAA's possesses an Al(III) center coordinated by four −ORF (RF = -CPh(CF3)2 (hfpp), -CH(CF3)2 (hfip), -C(CH3)(CF3)2 (hftb), -C(CF3)3 (pftb)) ligands, giving the anion an overall -1 charge. The most weakly coordinating PFAA is an aluminate dimer, [F{Al(Opftb)3}2]−, which possess a bridging fluoride between two Al(III) centers. The first PFAA, [Al(Ohfpp)4]−, was synthesized in 1996 by Steven Strauss, and several other analogs have since been synthesized, including [Al(Ohfip)4]−, [Al(Ohftb)4]−, and [Al(Opftb)4]− by Ingo Krossing in 2001. These chemically inert and very weakly coordinating ions have been used to stabilize unusual cations, isolate reactive species, and synthesize strong Brønsted acids.
Synthesis
Work by Strauss demonstrated that the synthesis of Li+[Al(Ohfpp)4]− could be achieved from the reaction of lithium aluminum hydride and HOhfpp. Analogous metal PFAA salts (MPFAA's) were later synthesized by Krossing using a similar synthetic pathway. LiAlH4 + 4HOR_{F} -> LiAl(OR_{F})4 + 4H2 Reaction of lithium aluminum hydride with four equivalents of polyfluoroalcohol overnight in refluxing toluene yields the desired PFAA's . The colorless products can be precipitated from toluene in high yields on multi-gram scales by cooling at -20 °C for an hour. It can be furthered purified by sublimation.
Cation exchange and reactivity
Metal exchange
While Li+[Al(Ohfpp)4]− is readily soluble in hydrocarbon solvents, presumably due to aryl substituents, Li+[Al(Ohfip)4]−, Li+[Al(Ohftb)4]−, and Li+[Al(Opftb)4]− are only sparingly soluble in common organic solvents including dichloromethane (DCM), toluene, and hexane. Their silver analogs are much more soluble however, making AgPFAA's more desirable reagents for liquid phase reactivity.LiAl(OR_{F})4 + AgF -> AgAl(OR_{F})4 +LiF
Ag+[Al(Ohfip)4]−, Ag+[Al(Ohftb)4]−, and Ag+[Al(Opftb)4]− can be synthesized via salt metathesis reactions; ultrasonication of a suspension of Li+[PFAA]− and an excess of AgF at 40 °C for 12 hours produces the final colorless products in high yields on multigram scales. Analogous M+[Al(Opftb)4]−, M = Na, K, Rb, Cs, salts can also be prepared via the same synthetic route, from the metathesis reactions of Li+[Al(Opftb)4]− with the corresponding MCl salt.
Brønsted acid chemistry
Strong Brønsted acids, [H(OEt2)2]+[Al(Opftb)4]− and [H(THF)2]+[Al(Opftb)4]− , can be prepared via the reaction of Li+[Al(Opftb)4]− with two equivalents of Lewis base, Et2O or THF, and strong acid, HX (X = Cl, Br). [H(OEt2)2]+[Al(Opftb)4]− is isolable as a white powder sensitive to air and water and stable at moderately high temperatures. [H(THF)2]+[Al(Opftb)4]− can be isolated as a crystalline solid from a brown oily reside, presumably containing polymerized THF products formed upon addition of strong acid.
Li+[Al(OR_{F})4]- + 2B + HX -> [H(B)2]+[Al(OR_{F})4]- + LiX
Ab initio calculations and crystallographic structural analysis of [H(OEt2)2]+[Al(Opftb)4]− indicate potential unequal sharing of the proton between the two diethyl ether molecules, and the authors propose a solid state structure in which [H(OEt2)2]+ is described as a diethyl ether molecule acting as a hydrogen bond acceptor from an ethanol molecule which stabilizes an ethyl cation as a Lewis base in one resonance structure.
Nitrosonium exchange
Nitrosonium salts, NO+[Al(Ohfpp)4]− and NO+[Al(Opftb)4]−, can be prepared via an exchange reaction of the respective lithium salt with nitrosonium hexafluoroantimonate.
Li+[Al(OR_{F})4]- + NO+[SbF6]- -> NO+[Al(OR_{F})4]- + Li+[SbF6]-
The NO+[Al(Opftb)4]− salt can be obtained in much higher yields than the analogous hfpp salt and can be used to oxidize several transition metal and main group element complexes.
Cation stabilization
Transition metal complexes
Manganese(V) nitrosyl cation
The first metal nitrosyl cation was prepared using the PFAA's [Al(Opftb)4]− and [F{Al(Opftb)3}2]− as stabilizing anions. Ultraviolet radiation of Mn2(CO)10 under a NO(g) atmosphere yields Mn(CO)(NO)3. Further oxidation of this complex is achieved through reaction with both NO+[PFAA]−'s to yield Mn(NO)4+[PFAA]− 's as deep red solids that are stable for months under an inert atmosphere. The Mn(NO)4+ cation is tetrahedral and linear NO− ligand in both salts indicate 3 electron donation to the Mn(V) metal center. Rigorous tetrahedral geometry of the Mn(NO)4+[F{Al(Opftb)3}2]− salt indicates a pseudo-gas phase environment about the cation due to the weakly coordinating behavior of the anionic PFAA.
Chromium(I) carbonyl radical cation
Synthesis of the chromium(I) homoleptic radical cation, [Cr(CO)6]•+, is achieved by use of PFAA's [Al(Opftb)4]− and [F{Al(Opftb)3}2]− as stabilizing anions. Oxidation of Cr(CO)6 by NO+[PFAA]−'s under cold vacuum for short reaction times yields the kinetic product [Cr(CO)6]•+[PFAA]− as a pale yellow crystalline solid. Oxidation in a closed room temperature vessel for long reaction times yields the thermodynamic product [Cr(CO)5(NO)]+[PFAA]− as an orange crystalline solid. Assignment of the thermodynamic and kinetic products was further supported by ab initio calculations. Fluctional Jahn-Teller distortions at room temperature are indicated by the presence of a broad band in the Raman spectra of these compounds.
Cobalt(I) sandwich complex
Cationic cobalt(I) sandwich complexes of the form Co(arene)2+[PFAA]- can be prepared via two synthetic routes (arene = mesitylene, benzene, fluorobenzene, o-difluorobenzene & PFAA = [Al(Opftb)4]− and [F{Al(Opftb)3}2]−). Reaction of Co(CO)5+[PFAA]− with arene yields the cobalt(I) sandwich complex stabilized by a PFAA anion. Additionally, the oxidation of Co2(CO)8 with Ag+[PFAA]− and arene yields the cobalt(I) sandwich complex stabilized by a PFAA anion and produces silver metal and gaseous carbon monoxide. Structural analysis of Co(I)bz2+[Al{OC(CF3)}4]− reveals the sandwich complex is slightly staggered, twisted 6° from an eclipsed confirmation. 3° bending of C-H bonds towards the cobalt center yields D6 symmetry. The cobalt sandwich complex can be used as a precursor to synthesize Co(PtBu3)2 upon ligand substitution.
Nickel(I) complexes
Oxidation of Ni(COD)2 with Ag+[Al(Opftb)4]− yields Ni(COD)2+[Al(Opftb)4]− as an orange crystalline solid. In the solid phase the material is stable to air and moisture, but is sensitive to diatomic oxygen in solution. EPR analysis reveals that 90% of the unpaired electron spin density is located on the nickel center. This nickel salt serves as synthetically feasible precursor to a series of nickel(I) arene and phosphine cations stabilized by PFAA's. Reactions of Ni(COD)2+[Al(Opftb)4]− with mesitylene, benzene, or hexamethyl benzene results in substitution of one COD ligand. Arene ligand exchange results in partial electron spin delocalization onto the aromatic arene ligand, with 84-87% of the unpaired electron spin density located on the nickel center. Reactions of Ni(COD)2+[Al(Opftb)4]− with phosphines results in complete ligand substitution and dissociation of COD. Addition of chelating phosphines, 1,3-bis(diphenylphosphino)propane (dppp) and 1,2-bis(diphenylphosphino)propane (dppe) yields four coordinate distorted tetrahedral nickel cations. Addition of triphenylphosphine yields a three coordinate trigonal planar cation. Addition of bulky tri-tert-butylphosphine yields a two coordinate linear cation.
Main group element complexes
AlCp2+
Reaction of AlCp3 with the strong Brønsted acid, [H(OEt2)2]+[Al(Opftb)4]−, yields [AlCp2]+[Al(Opftb)4]− as colorless solid as well as [AlCp2•2Et2O]+[Al(Opftb)4]−. The former complex exhibits nearly identical bonding to its analog AlCp*2+ while the Cp substituents in the later compound exhibit η1 bonding due to two diethyl ether substituents bound to the aluminum center.
Gallium(I) olefin complex
The first main-group homoleptic olefin compound isolable in bulk was synthesized using a stabilizing PFAA counter ion. [Ga(PhF)2]+[Al(Opftb)4]− can be prepared via the oxidation of Ga by Ag+[Al(Opftb)4]− in the presence of fluorobenzene. Fluorobenzene ligands can then be displaced by COD to produce [Ga(COD)2]+[Al(Opftb)4]−. AIM analysis of the compound reveals minimal back bonding to the olefin double bonds, characterizing the ligand-Ga interactions as primarily electrostatic. The gallium salt serves as a precursor to gallium phosphine complexes, as addition of triphenylphosphine yields [Ga(PPh3)2]+[Al(Opftb)4]−.
Germyl cation
Halide abstraction from BrGeR3 (R = [C6H3(OtBu)2]3) using Ag+[Al(Opftb)4]- yields the germyl cation Ge[C6H3(OtBu)2]3+, stabilized by bulky ligands and a weakly coordinating PFAA anion. The aryl substituents are oriented in a paddlewheel confirmation about the germanium center and possess shortened Ge-C bonds due to partial double bonding character. Due to the weakly coordinating nature of the PFAA anion, solid state structure of the salt reveals no ion-ion contacts between the germyl cation and the PFAA, giving rise to a very electrophilic germanium species.
Tin(II) dications
Various tin(II) dications can be synthesized with PFAA's as counterions. [Sn(MeCN)6]2+[Al(Opftb)4]2− can be prepared via the oxidation of tin metal with NO+[Al(Opftb)4]−. Addition of pyrazine to this complex results in ligand substitution to produce [Sn(pyz)2(MeCN)4]2+, while addition of triphenylphosphine produces [Sn(PPh3)2(MeCN)4]2+•MeCN. The salt, Sn(dmap)42+[Al(Opftb)4]2− is prepared by a different synthetic route. Halide abstraction of SnCpCl by Li+[Al(Opftb)4]− yields [SnCp]+ which produces Sn(dmap)42+ upon addition of dmap. Sn(dmap)42+ adopts a see-saw geometry with dmap ligands stabilizing a Sn(II) center.
P9+
The cationic P9+ cluster can be isolated from the oxidation of P4 by NO+[Al(Opftb)4]−. In the multistep reaction, [P4NO]+ is a proposed intermediate from analysis of collision-induced dissociation (CID) experiments. Complex coupling present in the 31P NMR spectra of P9+ allowed for the determination of its structure.
Applications
Ionic liquids
Due to low polarizability, large charge delocalization, and high conformational flexibility, PFAA salts are potentially useful ionic liquids. Several PFAA salts, including those of [Al(Ohfip)4]−, possess melting points as low as 273 K or colder. Walden Plots, which are created by plotting the logarithm of conductivity against the logarithm of inverse viscosity, indicate that several [Al(Ohfip)4]− ionic liquids are potentially better than the best commercially available ionic liquids. Better ionic liquids are defined to have high conductivities and high viscosities.
See also
Non-coordinating anions
Ionic liquids
References
Wikipedia Student Program
Aluminates
Alkoxy groups
Perfluorinated compounds | Polyfluoroalkoxyaluminates | [
"Chemistry"
] | 3,325 | [
"Substituents",
"Alkoxy groups",
"Functional groups"
] |
66,310,978 | https://en.wikipedia.org/wiki/7255%20aluminium%20alloy | 7255 aluminium alloy is a wrought alloy with high zinc weight percentage (from 7.8 to 8.4%). It also contains magnesium, copper.
Chemical composition
Properties
References
Aluminium alloy table
Aluminium–zinc alloys | 7255 aluminium alloy | [
"Chemistry"
] | 45 | [
"Alloys",
"Aluminium alloys"
] |
66,311,080 | https://en.wikipedia.org/wiki/7475%20aluminium%20alloy | 7475 aluminum alloy (Adirium) is a wrought alloy with high zinc weight percentage. It also contains magnesium, silicon and chromium.
7475 alloy can not be welded. It has more spring back because of its strength. It has high machinability.
Chemical composition
Properties
Applications
Shell casings
Aircraft
References
External links
https://www.suppliersonline.com/propertypages/7475.asp
https://www.suppliersonline.com/propertypages/7475.asp
https://www.makeitfrom.com/material-properties/7475-AlZn5.5MgCuA-Aluminum
https://www.efunda.com/Materials/alloys/aluminum/show_aluminum.cfm?ID=AA_7475&show_prop=all&Page_Title=AA%207475
Aluminium alloys
Aluminium–zinc alloys | 7475 aluminium alloy | [
"Chemistry"
] | 193 | [
"Alloys",
"Aluminium alloys"
] |
66,313,605 | https://en.wikipedia.org/wiki/Diiodine%20oxide | Diiodine oxide, also known as iodo hypoiodite, is an oxide of iodine that is equivalent to an acid anhydride of hypoiodous acid. This substance is unstable and it is very difficult to isolate.
Preparation
Diiodine oxide can be prepared by reacting iodine with potassium iodate (KIO3) in 96% sulfuric acid and then extracting it into chlorinated solvents.
Reactions
Diiodine oxide reacts with water to form hypoiodous acid:
References
Iodine compounds
Oxides | Diiodine oxide | [
"Chemistry"
] | 116 | [
"Oxides",
"Salts"
] |
66,317,881 | https://en.wikipedia.org/wiki/Martin%20Gouterman | Martin Paul Gouterman (December 26, 1931 – February 22, 2020) was an American chemist who was a professor of chemistry at the University of Washington. He is remembered for his seminal work on the optical spectra porphyrins, for which he developed a simple model generally referred to as Gouterman's four-orbital model.
Early life and education
Gouterman was born in Philadelphia, the only child to Bernard and Melba Buxbaum Gouterman. He attended Philadelphia Central High School and graduated in 1949. Gouterman was an undergraduate student at the University of Chicago, where originally he majored in piano performance but eventually studied physics. He stayed at Chicago for his doctoral research, where he started studying porphyrins.
Research and career
After graduating, Gouterman was appointed to the faculty at Harvard University where he worked as a postdoctoral researcher with William Moffitt. Shortly after Gouterman arrived, Moffitt died of a heart attack during a squash game. Gouterman was quickly promoted to assistant professor, and spent his time using quantum chemical calculations to understand the photophysical properties of porphyrins. He primarily made use of the Hückel molecular orbital method to interrogate their optical spectra. Gouterman's molecular models, which included symmetry arguments and configuration interactions, were able to predict the intensity differences between the absorption bands of porphyrins. The so-called four-orbit model incorporates two, almost degenerate highest occupied molecular orbitals and two degenerate lowest unoccupied molecular orbitals. The Soret and Q-bands that are visible in porphyrin spectra are the result of transitions from between these four orbitals.
Gouterman moved to the University of Washington in 1966, where he worked until his retirement. In Seattle, Gouterman continued to study the optical properties of porphyrins. He described how the chemical structures of porphyrins determine whether the spectral shape was 'normal', hyper- and hypso-. For example, the UV-Visible absorption spectra of hyper porphyrins contain red-shifted peaks and extra bands due to ligand-to-metal charge transfer (LMCT) transitions. Amongst the complicated structures analysed by Gouterman were cytochrome P450–carbon monoxide complexes, whose electronic spectra included a split Soret band due to LMCT transitions.
Awards and honors
Elected Fellow of the American Physical Society
University of Washington Minority Science and Engineering Program Faculty Excellence Award
Creativity Certificate Award, Porphyrin Chemistry Community
Selected publications
Personal life
Gouterman was a community organiser and activist. He campaigned to end the Vietnam War.
In his early career Gouterman was not open about his sexuality. He came out as gay at around age 35 after he moved to Seattle. There he became an activist for gay rights and co-founded the Dorian Society.
He also worked with the New Jewish Agenda and International Jewish Peace Union to promote Israeli-Palestinian peace.
In the early 1980s, Gouterman acted as a sperm donor and helped a lesbian couple have a son.Through mutual acquaintances, he discovered the identity of his son and thereafter enjoyed a close relationship with him.
In the last years of his life, Gouterman suffered from Alzheimer's disease.
References
American LGBTQ scientists
Scientists from Philadelphia
Chemists from Pennsylvania
1931 births
2020 deaths
American organic chemists
Computational chemists
University of Chicago alumni
University of Washington faculty
Fellows of the American Physical Society | Martin Gouterman | [
"Chemistry"
] | 706 | [
"Organic chemists",
"American organic chemists"
] |
66,323,417 | https://en.wikipedia.org/wiki/Transition%20metal%20dithiocarbamate%20complexes | Transition metal dithiocarbamate complexes are coordination complexes containing one or more dithiocarbamate ligand, which are typically abbreviated R2dtc−. Many complexes are known. Several homoleptic derivatives have the formula M(R2dtc)n where n = 2 and 3.
Ligand characteristics
Dithiocarbamates are anions. Because of the pi-donor properties of the amino substituent, the two sulfur centers show enhanced basicity. This situation is represented by the zwitterionic resonance structure that depicts a positive charge on N and negative charges on both sulfurs. This N to C pi-bonding results in partial double bond character. Consequently, barriers to rotational about this bond are elevated. Another consequence of their high basicity, dithiocarbamates often stabilize complexes in uncharacteristically high oxidation state (e.g., Fe(IV), Co(IV), Ni(III), Cu(III)).
Dithiocarbamate salts are easily synthesized. Many primary and secondary amines react with carbon disulfide and sodium hydroxide to form dithiocarbamate salts:
R2NH + CS2 + NaOH → R2NCS2−Na+ + H2O
A wide variety of secondary amines give the corresponding dtc ligand. Popular amines include dimethylamine (Me2NH), diethylamine (Et2NH), and pyrrolidine ((CH2)4NH).
Related ligands
Dithiocarbamates are classified as derivatives of dithiocarbamic acid. Their properties as ligands resemble the conjugate bases of many related "1,1-dithioacids":
Xanthates, ROCS2−
Dithiophosphates, (RO)2PS2−
Dithiocarboxylates, RCS2−
Synthetic methods
Commonly, metal dithiocarbamates are prepared by salt metathesis reactions using alkali metal dithiocarbamates:
NiCl2 + 2NaS2CNMe2 → Ni(S2CNMe2)2 + 2NaCl
In some cases, the dithiocarbamate serves as a reductant, followed by its complexation.
A complementary method entails oxidative addition of thiuram disulfides to low-valent metal complexes:
Mo(CO)6 + 2[S2CNMe2]2 → Mo(S2CNMe2)4 + 6CO
Metal amido complexes, such as tetrakis(dimethylamido)titanium, react with carbon disulfide:
Ti(NMe2)4 + 4CS2 → Ti(S2CNMe2)4
Homoleptic complexes
Bis complexes
nickel bis(dimethyldithiocarbamate), palladium bis(dimethyldithiocarbamate), platinum bis(dimethyldithiocarbamate), all square-planar complexes
copper bis(diethyldithiocarbamate), a square-planar complex
Tris complexes
vanadium tris(diethyldithiocarbamate), an octahedral complex
chromium tris(diethylditiocarbamate), an octahedral complex
manganese tris(dimthylthtiocarbamate), an octahedral complex
iron tris(diethyldithiocarbamate), ruthenium tris(diethyldithiocarbamate), osmium tris(diethyldithiocarbamate), all octahedral complexes
cobalt tris(diethyldithiocarbamate), rhodium tris(diethyldithiocarbamate), iridium tris(diethyldithiocarbamate), all octahedral complexes
Tetrakis complexes
titanium tetrakis(dimethyldithiocarbamate)
molybdenum tetrakis(diethyldithiocarbamate)
Dimetallic complexes
iron bis(diethyldithiocarbamate), pentacoordinate Fe dimer
zinc bis(dimethyldithiocarbamate), pentacoordinate Zn dimer
dicobalt pentakis(diethyldithiocarbamate) cation, with a pair of octahedral Co(III) centers
diruthenium pentakis(diethyldithiocarbamate) cation, with a pair of octahedral Ru(III) centers, two isomers
Reactions
Dithiocarbamate complexes do not undergo characteristic reactions. They can be removed from complexes by oxidation, as illustrated by the iodination of the iron tris(diethyldithiocarbamate):
They degrade to metal sulfides upon heating.
Applications
Dtc complexes find several applications:
herbicides in the form of the iron and zinc derivatives Ferbam and Zineb, respectively
vulcanization accelerators, zinc bis(dimethyldithiocarbamate).
medicine, iron tris(dimethyldithiocarbamate) as a nitric oxide scavenger.
lubricants. Metal thiocarbamates are also used in metal-to-metal lubrication proposes, mainly as an anti-oxidation or anti-extreme pressure (EP) additive. 1-2% of such compounds can be added to internal combustion engine lubricant to increase extreme pressure performance in high operational temperatures.
References
Dithiocarbamates | Transition metal dithiocarbamate complexes | [
"Chemistry"
] | 1,152 | [
"Dithiocarbamates",
"Functional groups"
] |
73,644,559 | https://en.wikipedia.org/wiki/James%20Busfield | James Busfield is a Queen Mary University of London professor, and head of the United Kingdom's largest research group in the area of Soft Matter.
Education
Busfield completed an MA in Engineering Science at the University of Oxford in 1989. In 2000, he completed a doctoral degree in materials science at Queen Mary University of London under advisor Alan G. Thomas. He made influential studies of ceramic foams and of the electrical and mechanical behavior of filled rubbers. He has chaired the 2003 European Conference on Constitutive Models for Rubber, together with Alan Muhr.
Awards and recognition
2009 - National Teaching Fellowship
2009 - Colwyn Medal from the IOM3
2010 - Sparks–Thomas award from the ACS Rubber Division.
2020 - Fellow of the Royal Academy of Engineering
2021 - George Stafford Whitby Award by the ACS Rubber Division
Notable students
Lewis Tunnicliffe
References
Polymer scientists and engineers
Living people
Year of birth missing (living people)
Academics of Queen Mary University of London
British physical chemists
21st-century British chemists
Alumni of the University of Oxford
Alumni of Queen Mary University of London
Fellows of the Royal Academy of Engineering | James Busfield | [
"Chemistry",
"Materials_science"
] | 227 | [
"Polymer scientists and engineers",
"Physical chemists",
"Polymer chemistry"
] |
70,738,617 | https://en.wikipedia.org/wiki/Target-mediated%20drug%20disposition | Target-mediated drug disposition (TMDD) is the process in which a drug binds with high affinity to its pharmacological target (for example, a receptor) to such an extent that this affects its pharmacokinetic characteristics. Various drug classes can exhibit TMDD, most often these are large compounds (biologics such as antibodies, cytokines or growth factors) but also smaller compounds can exhibit TMDD (such as warfarin).
A typical TMDD pattern of antibodies displays non-linear clearance and can be seen at concentration ranges that are usually defined as 'mid-to-low'. In this concentration range, the target is partly saturated.
References
Pharmacokinetics
Medicinal chemistry | Target-mediated drug disposition | [
"Chemistry",
"Biology"
] | 152 | [
"Pharmacology",
"Pharmacokinetics",
"Medicinal chemistry stubs",
"Medicinal chemistry",
"nan",
"Biochemistry",
"Pharmacology stubs"
] |
70,740,162 | https://en.wikipedia.org/wiki/Wyss%20Institute%20for%20Biologically%20Inspired%20Engineering | The Wyss Institute for Biologically Inspired Engineering (pronounced "veese") is a cross-disciplinary research institute at Harvard University focused on bridging the gap between academia and industry (translational medicine) by drawing inspiration from nature's design principles to solve challenges in health care and the environment. It is focused on the field of biologically inspired engineering to be distinct from bioengineering and biomedical engineering. The institute also has a focus on applications, intellectual property generation, and commercialization.
The Wyss Institute is located in Boston's Longwood Medical Area and has 375 full-time staff. The Wyss is organized around eight focus areas, each of which integrate faculty, postdocs, fellows, and staff scientists. The focus areas are bioinspired therapeutics & diagnostics, diagnostics accelerator, immuno-materials, living cellular devices, molecular robotics, 3D organ engineering, predictive bioanalytics and synthetic biology.
History
In 2005, Harvard University established a faculty working group to envision the future of bioengineering. The group was called the Harvard Institute for Biologically Inspired Engineering (HIBIE), with the committee focused on synthetic biology, living materials, and biological control. HIBIE was co-chaired by Harvard professors Donald E. Ingber and David J. Mooney. In January 2009, institute was reformed into the Wyss Institute upon receiving a $125 million gift from Hansjörg Wyss. Ingber became the founding director of the Wyss Institute and David Mooney became a founding Core Faculty member, along with Professors Joanna Aizenberg, David A. Edwards, Kit Parker, George M. Whitesides, George Church, Ary Goldberger, William Shih, Robert Wood, James J. Collins, L. Mahadevan, Radhika Nagpal, and Pamela Silver.
In 2013, Hansjörg Wyss gave another $125 million to Harvard University, doubling his initial gift. The funding was used to further the institute's interdisciplinary research, which includes DNA engineering, cleaning toxins from blood, vibrating insoles to help older adults maintain balance, and a melanoma cancer vaccine. In 2019, Hansjörg Wyss donated a third gift of $131 million to the Wyss Institute. In 2020, the Wyss Institute and Northpond Ventures, a Maryland-based venture capital firm, created the Laboratory for Bioengineering Research and Innovation at the Wyss Institute. The $12 million funding supports research related to RNA therapies, genome engineering, and new drug delivery methods.
Within its first ten years, the institute also spun out 29 startup companies to commercialize Wyss Institute developments.
Scientific developments
The institute was originally founded with fourteen faculty from Harvard University. The institute had around 40 scientists and engineers as a part of the Advanced Technology Team organized around six technology platforms and two cross-platform initiatives across the fields of adaptive material technologies, bioinspired soft robotics, biomimetic microsystems, immuno-materials, living cellular devices, molecular robotics, synthetic biology, and 3D organ engineering. The Wyss Institute has been responsible for a number of scientific developments and spinoffs.
In 2010, Donald Ingber pioneered the first 3D organ-on-a-chip that mimics a human lung. Following the lung-on-a-chip, the team built a kidney-on-a-chip and an intestine-on-a-chip. In 2014, Emulate spun out to make organ chips commercially available for other scientists to use for disease modeling and drug testing, including those at Johnson & Johnson, Merck, Takeda, Roche, and Cedars-Sinai Medical Center.
In 2013, Conor Walsh developed a soft exosuit that uses textiles and cables to replicate leg muscles, which can help a healthy wearer not fatigue as quickly and help people with physical disabilities restore their muscles and increase mobility. In 2016, ReWalk robotics licensed the exosuit technology for the treatment of stroke, Multiple Sclerosis (MS), and mobility limitations. In 2019, ReWalk received clearance from the FDA to sell their ReStore soft exosuit for rehabilitation of stroke survivors.
In 2013, David Mooney and the Dana-Farber Cancer Institute began a Phase I clinical trial for an implantable cancer vaccine. In 2018, Swiss pharmaceutical company Novartis licensed the technology. Mooney also developed injectable versions of their cancer vaccine.
In 2014, Jennifer A. Lewis developed inks and a process to 3D bioprint organs that could be suitable for human transplants. In 2022, Trestle Biotherapeutics licensed technology to develop 3D bioprinted kidney tissue from Harvard University.
In 2014, James J. Collins and MIT developed an inexpensive diagnostic that consists of cellular "machinery" (proteins, nucleic acids and ribosomes) freeze-dried on paper. The team tested their diagnostic with Ebola virus and in 2016 they tested it with the Zika virus. In 2021, the technology was licensed to Sherlock Biosciences.
In 2015, Donald Ingber engineered a blood protein that binds to more than 90 sepsis-causing pathogens, including bacteria, fungi, viruses, and parasites. The technology was licensed by BOA Biomedical and approved in 2021 by the FDA to conduct human clinical trials.
In 2015, Conor Walsh developed is a soft robotic grip glove to restore mobility for people with impaired hand function. In 2021, Imago Rehab spun out to develop the soft robotic glove for stroke rehabilitation.
In 2017 David J. Mooney, inspired by the sticky properties of Arion subfuscus slug secretions, developed a non-toxic hydrogel adhesive that sticks to wet surfaces and stretches, making it ideal for use within the body.
In 2019, George Church published research on combination gene therapy to treat multiple age-related diseases in mice, including diabetes, heart disease and kidney disease. The team founded Rejuvenate Bio to further develop the technology to treat age-related diseases in dogs.
In 2019, George Church's lab developed a machine-learning approach to make more efficient adeno-associated viruses (AAVs), which are delivery vehicles for gene therapies. This team spun out Dyno Therapeutics to continue developing enhanced AAVs. Dyno Therapeutics has partnerships with pharmaceutical companies Novartis, Sarepta Therapeutics, and Roche. In 2021, Dyno Therapeutics raised a $100 million Series A.
In 2020, Michael Levin and Josh Bongard developed new synthetic lifeform called Xenobots made from skin cells and heart muscle cells from the African clawed frog (Xenopus laevis). The scientists use an AI program to design the Xenobots to carry out desired functions, learning how cells cooperate to build complex bodies during morphogenesis and about regenerative medicine more broadly.
In 2021, Jennifer A. Lewis and Massachusetts Eye and Ear hospital developed PhonoGraft, a 3D-printed regenerative eardrum graft. The team launched a startup company that was acquired by Desktop Health, a subsidiary of Desktop Metal.
In 2021, Pamela Silver engineered bacteria to feed off of greenhouse gasses to then produce fats similar to animal and vegetable fats, as well as polymers similar to those made from petrochemicals.
Response to COVID
During the COVID-19 pandemic, the Wyss Institute was engaged in several notable efforts. This included the development of a diagnostic face mask that can detect SARS-CoV-2 RNA in the wearer's breath, and the application of the eRapid technology to detect the nucleic acids of the genome of SARS-CoV-2. The technology would be licensed by Antisoma Therapeutics as a point-of-care diagnostic test for COVID-19. The identification of undocumented nucleic acid contamination during routine experiments, which inadvertently caused false positives for COVID-19, led to the development of new safety protocols to protect researchers and ensure data integrity. New nasal swabs that could be manufactured quickly and more easily which launched the startup Rhinostics. Use of computational approaches and organ-chips to repurpose FDA-approved drugs like Amodiaquine to prevent or treat COVID-19.
See also
Bioinspiration
Wyss Center for Bio and Neuroengineering in Switzerland
References
External links
Official website
2009 establishments in Massachusetts
Biotechnology organizations
Engineering research institutes
Harvard University research institutes
Independent research institutes
Medical research institutes in Massachusetts
Laboratories in the United States
Multidisciplinary research institutes
Organizations established in 2009
Science and technology in Massachusetts | Wyss Institute for Biologically Inspired Engineering | [
"Engineering",
"Biology"
] | 1,765 | [
"Biotechnology organizations",
"Engineering research institutes"
] |
70,746,711 | https://en.wikipedia.org/wiki/Su-Huai%20Wei | Su-Huai Wei () is a Chinese computational physicist.
Wei earned a bachelor's of science degree in physics from Fudan University in 1981, and moved to the United States to pursue graduate study in the subject. After he completed his doctorate at the College of William & Mary in 1985, Wei became a postdoctoral researcher at the National Renewable Energy Laboratory. He remained on the NREL staff until returning to China for a post at the Computational Science Research Center. In 1998, while affiliated with NREL, Wei was elected a fellow of the American Physical Society "[f]or contributions to the understanding of electronic structures and stabilities of compounds, alloys, interfaces, superlattices and impurities using first-principles calculations and for development of the methods for such calculations."
References
Computational physicists
Living people
Year of birth missing (living people)
Fellows of the American Physical Society
College of William & Mary alumni
Chinese expatriates in the United States
21st-century Chinese physicists
20th-century Chinese physicists | Su-Huai Wei | [
"Physics"
] | 207 | [
"Computational physicists",
"Computational physics"
] |
70,749,968 | https://en.wikipedia.org/wiki/Bis%282-methoxyethyl%29%20phthalate | Bis(2-methoxyethyl) phthalate, also commonly di(2-methoxyethyl) phthalate (DMEP), is a phthalate ester baring 2-methoxyethanol groups. Historically it was used as a plasticizer in cellulose acetate plastics, it is now largely banned owing to concerns over its effects to human health.
References
Phthalate esters
Ethers
Methoxy compounds | Bis(2-methoxyethyl) phthalate | [
"Chemistry"
] | 99 | [
"Organic compounds",
"Functional groups",
"Ethers"
] |
72,235,151 | https://en.wikipedia.org/wiki/Phylogenetic%20reconciliation | In phylogenetics, reconciliation is an approach to connect the history of two or more coevolving biological entities. The general idea of reconciliation is that a phylogenetic tree representing the evolution of an entity (e.g. homologous genes or symbionts) can be drawn within another phylogenetic tree representing an encompassing entity (respectively, species, hosts) to reveal their interdependence and the evolutionary events that have marked their shared history. The development of reconciliation approaches started in the 1980s, mainly to depict the coevolution of a gene and a genome, and of a host and a symbiont, which can be mutualist, commensalist or parasitic. It has also been used for example to detect horizontal gene transfer, or understand the dynamics of genome evolution.
Phylogenetic reconciliation can account for a diversity of evolutionary trajectories of what makes life's history, intertwined with each other at all scales that can be considered, from molecules to populations or cultures. A recent avatar of the importance of interactions between levels of organization is the holobiont concept, where a macro-organism is seen as a complex partnership of diverse species. Modeling the evolution of such complex entities is one of the challenging and exciting direction of current research on reconciliation.
Phylogenetic trees as nested structures
Phylogenetic trees are intertwined at all levels of organization, integrating conflicts and dependencies within and between levels. Macro-organism populations migrate between continents, their microbe symbionts switch between populations, the genes of their symbionts transfer between microbe species, and domains are exchanged between genes.
This list of organization levels is not representative or exhaustive, but gives a view of levels where reconciliation methods have been used.
As a generic method, reconciliation could take into account numerous other levels. For instance, it could consider the syntenic organization of genes, the interacting history of transposable elements and species, the evolution of a protein complex across species. The scale of evolutionary events considered can go from population events such as geographical diversification to nucleotids levels one inside genes, including for instance chromosome levels events inside genomes such as whole genome duplication.
Phylogenies have been used for representing the diversification of life at many levels of organization: macro-organisms, their cells throughout development, micro-organisms through marker genes, chromosomes, proteins, protein domains, and can also be helpful to understand the evolution of human culture elements such as languages or fairy tales.
At each of these levels, phylogenetic trees describe different stories made of specific diversification events, which may or may not be shared among levels. Yet because they are structurally nested (similar to matryoshka dolls) or functionally dependent, the evolution at a particular level is bound to those at other levels.
Phylogenetic reconciliation is the identification of the links between levels through the comparison of at least two associated trees. Originally developed for two trees, reconciliations for more than two levels have been recently constructed (see section Explicit modeling of three or more levels). As such, reconciliation provides evolutionary scenarios that reveal conflict and cooperation among evolving entities. These links may be unintuitive, for instance, genes present in the same genome may show uncorrelated evolutionary histories while some genes present in the genome of a symbiont may show a strong coevolution signal with the host phylogeny. Hence, reconciliation can be a useful tool to understand the constraints and evolutionary strategies underlying the assemblage that forms a holobiont.
Because all levels essentially deal with the same object, a phylogenetic tree, the same models of reconciliation—in particular those based on duplication-transfer-loss events, which are central to this article—can be transposed, with slight modifications, to any pair of connected levels: an "inner", "lower", or "associate" entity (e.g. gene, symbiont species, population) evolves inside an "upper", or "host" one (respectively species, host, or geographical area).
The upper and lower entities are partially bound to the same history, leading to similarities in their phylogenetic trees, but the associations can change over time, become more or less strict or switch to other partners.
History
The principle of phylogenetic reconciliation was introduced in 1979 to account for differences between genes and species-level phylogenies. In a parsimonious setting, two evolutionary events, gene duplication and gene loss were invoked to explain the discrepancies between a gene tree and a species tree. It also described a score on gene trees knowing the species tree and an aligned sequence by using the number of gene duplication, loss, and nucleotide replacement for the evolution of the aligned sequence, an approach still central today with new models of reconciliation and phylogeny inference.
The term reconciliation has been used by Wayne Maddison in 1997, as a reverse concept of "phylogenetic discord" resulting from gene level evolutionary events.
Reconciliation was then developed jointly for the coevolution of host and symbiont and the geographic diversification of species. In both settings, it was important to model a horizontal event that implied parallel branches of the host tree: host switch for host and symbiont and species dispersion from one area to another in biogeography. Unlike for genes and genomes, the coevolution of host and symbiont and the explanation of species diversification by geography are not always the null hypothesis. A visual depiction of the two phylogenies in a tanglegram can help assess such coevolution, although it has no statistical obvious interpretation.
Character methods, such as Brooks Parsimony Analysis, were proposed to test coevolution and reconstruct scenarios of coevolution. In these methods, one of the trees is forgotten except for its leaves, which are then used as a character evolving on the second tree.
First models for reconciliation, taking explicitly into account the two topologies and using a mechanistic event-based approach, were proposed for host and symbiont and biogeography. Debates followed, as the methods were not yet completely sound but integrated useful information in a new framework.
Costs for each event and a dynamic programming technique considering all pairs of host and symbiont nodes were then introduced into a host and symbiont approach, both of which still underlie most of the current reconciliation methods for host and symbiont as well as for species and genes.
Reconciliation returned to the framework it was introduced in, gene and species. After character models were considered for horizontal gene transfer, a new reconciliation model, following and improving the dynamic programming approach presented for host and symbiont, effectively introduced horizontal gene transfer to gene and species reconciliation on top of the duplication and loss model.
The progressive development of phylogenetic reconciliation was thus possible through exchanges between multiple research communities studying phylogenies at the host and symbiont, gene and species, or biogeography levels. This story and its modern developments have been reviewed several times, generally focusing on specific pairs of levels, with a few exceptions. New developments start to bring the different frameworks together with new integrative models.
Pocket Gophers and their chewing lices: a classical example
Pocket gophers (Geomyidae) and their chewing lice (Trichodectidae) form a well studied system of host and symbiont coevolution. The phylogeny of host and symbiont and the matching of the leaves of their trees are depicted on the left. For the host, O. stands for Orthogeomys, G. for Geomys and T. for Thomomys; for the symbiont, G. stands for Geomydoecus and T. for Thomoydoecus.
Reconciling the two trees means giving a scenario with evolutionary events and matching on the ancestral nodes depicting the coevolution of the two trees. The events considered in this system are the events of the DTL model: duplication, transfer (or host switch), loss, and cospeciation, the null event of coevolution.
Two scenarios were proposed in two studies, using two different frameworks which could be deemed as pre-dynamic programming DTL reconciliation.
In modern DTL reconciliation frameworks, costs are assigned to events. The two scenarios were then shown to correspond to maximum parsimonious reconciliation with different cost assignments.
The scenario A uses 6 cospeciations, 2 duplications, 3 losses and 2 host switches to reconcile the two trees, while scenario B uses 5 cospeciations, 3 duplications, 3 losses and 2 host switches. The cost of a scenario is the sum of the cost of its events. For instance, with a cost of 0 for cospeciation, 2 for duplication, 1 for loss and 3 for host switch, scenario A has a cost of and scenario B of , and so according to a parsimonious principle, scenario A would be deemed more likely (scenario A stays more likely as long as the cost of cospeciation is less than the cost of duplication).
Development of Phylogenetic Reconciliation Models
Models and methods used today in phylogeny are the result of several decades of research, made progressively complex, driven by the nature of the data and the quest for biological realism on one side, and the limits and progresses of mathematical and algorithmic methods on the other.
Pre-reconciliation models: characters on trees
Character methods can be used when there is no tree available for one of the levels, but only values for a character at the leaves of a phylogenetic tree for the other level. A model defines the events of character value change, their rate, probabilities or costs. For instance, the character can be the presence of a host on a symbiont tree, the geographical region on a species tree, the number of genes on a genome tree, or nucleotides in a sequence.
Such methods thus aim at reconstructing ancestral characters at internal nodes of the tree.
Although these methods have produced results on genome evolution, the utility of a second tree appears with very simple examples. If a symbiont has recently acquired the ability to spread in a group of species and thus it is present in most of them, character methods will wrongly indicate that the common ancestor of the hosts already had the symbiont. In contrast, a comparison of the symbiont and host trees would show discrepancies revealing horizontal transfers.
The origins of reconciliation: the Duplication Loss model and the Lowest Common Ancestor mapping
Duplication and loss were invoked first to explain the presence of multiple copies of a gene in a genome or its absence in certain species. It is possible with those two events to reconcile any two trees, i.e. to map the nodes and branches of the lower and upper trees, or equivalently to give a list of evolutionary events explaining the discrepancies between the upper tree and the lower tree.
A most parsimonious Duplication and Loss (DL) reconciliation is computed through the Lowest Common Ancestor (LCA) mapping: proceeding from the leaves to the root, each internal node is mapped to the lowest common ancestor of the mapping of its two children.
A Markovian model for reconciliation
The LCA mapping in the DL model follows a parsimony principle: no event should be invoked if it is not necessary. However the use of this principle is debated, and it is commonly admitted that it is more accurate in molecular evolution to fit a probabilistic model as a random walk, which does not necessarily produce parsimonious scenarios.
A birth and death Markovian model is such a model that can generate a lower tree "inside" a fixed upper one from root to leaves.
Statistical inference provides a framework to find most likely scenarios, and in that case, a maximum likelihood reconciliation of two trees is also a parsimonious one. In addition, it is possible with such a framework to sample scenarios, or integrate over several possible scenarios in order to test different hypotheses, for example to explore the space of lower trees. Moreover, probabilistic models can be integrated into larger models, as probabilities simply multiply when assuming independence, for instance combining sequence evolution and DL reconciliation.
Introducing horizontal transfer
Host switch, i.e. inheritance of a symbiont from a kin lineage, is a crucial event in the evolution of parasitic or symbiotic relationships between species. This horizontal transfer also models migration events in biogeography and became of interest for the reconciliation of gene and species trees when it appeared that many discrepancies could not simply be explained by duplication and loss and that horizontal gene transfer (HGT) was a major evolutionary process in micro-organisms evolution.
This switching, or horizontal transfer, pattern can also model admixture or introgression.
It is considered in character methods, without information from the symbiont phylogeny.
On top of the DL model, horizontal transfer enables new and very different reconciliation scenarios.
The simple yet powerful dynamic programming approach
The LCA reconciliation method yields a unique solution, which has been shown to be optimal for the problem of minimizing the weighted number of events, whatever the relative weights of duplication and loss. In contrast, with Duplication, horizontal Transfer and Loss (DTL), there can be several equally parsimonious reconciliations. For instance, a succession of duplications and losses can be replaced by a single transfer. One of the first ideas to define a computational problem and approach a resolution was, in a host/symbiont framework, to maximize the number of co-speciations with a heuristic algorithm.
Another solution is to give relative costs to the events and find a scenario that minimizes the sum of the costs of its events.
In the probabilistic model frameworks, the equivalent task consists of assigning rates or probabilities to events and search for maximum likelihood scenarios, or sample scenarios according to their likelihood. All these problems are solved with a dynamic programming approach. This dynamic programming method involves traversing the two trees in a postorder.
Proceeding from the leaves and then going up in the two trees, for each couple of internal nodes (one for each tree), the cost of a most parsimonious DTL reconciliation is computed.
In a parsimony framework, costs of reconciling a lower subtree rooted at with an upper subtree rooted at is initialized for the leaves with their matching:
And then inductively, denoting the children of the children of the costs associated with speciation, duplication, horizontal transfer and loss, respectively (with often fixed to 0),
The costs and , because they do not depend on , can be computed once for all , hence achieving quadratic complexity to compute for all couples of and . The cost of losses only appears in association with other events because in parsimony, a loss can always be associated with the preceding event in the tree.
The induction behind the use of dynamic programming is based on always progressing in the trees toward the roots. However some combinations of events that can happen consecutively can make this induction ill-defined.
One such combination consists of a transfer followed immediately by a loss in the donor lineage (TL). Restricting the use of this TL event repairs the induction. With an unlimited use, it is necessary to use or add other known methods to solve systems of equations like fixed point methods, or numerical solving of differential equations. In 2016, only two out of seven of the most commonly used parsimony reconciliation programs did handle TL events, although their consideration can drastically change the result of a reconciliation.
Unlike LCA mapping, DTL reconciliation typically yields several scenarios of minimal cost, in some cases an exponential number. The strength of the dynamic programming approach is that it enables to compute a minimum cost of coevolution of the input upper and lower tree in quadratic time, and to get a most parsimonious scenario through backtracking.
It can also be transposed to a probabilistic framework to compute the likelihood of coevolution and get a most likely reconciliation, replacing costs with rates, minimums by sums and sums by products.
Moreover, through multiple backtracks, the approach is suitable for enumerating all parsimonious solutions or to sample scenarios, optimal and sub-optimal, according to their likelihood.
Estimation of event costs and rates
Dynamic programming per se is only a partial solution and does not solve several problems raised by reconciliation.
Defining a most parsimonious DTL reconciliation requires assigning costs to the different kinds of events (D, T and L). Different cost assignments can yield different reconciliation scenarios, so there is a need for a way to choose those costs.
There is a diversity of approaches to do so. CoRe-PA explores in a recursive manner the space of cost vectors, searching for a good matching with the event frequencies in reconciliations.
ALE uses the same idea in a probabilistic framework to estimate the event rates by maximum likelihood.
Alternatively, COALA is a preprocess using approximate Bayesian computation with sequential Monte Carlo: simulation and statistic rejection or acceptance of parameters with successive refinement.
In the parsimony framework, it is also possible to divide the space of possible event costs into areas of costs which lead to the same Pareto optimal solution.
Pareto optimal reconciliations are such that no other reconciliation has a strictly inferior cost for one type of event (duplication, transfer or loss), and less or equal for the others.
It is possible as well to rely on external considerations in order to choose the event costs. For example, the software Angst chooses the costs that minimize the variation of genome size, in number of genes, between parent and children species.
The problem of temporal feasibility
The dynamic programming method works for dated (internal nodes are totally ordered) or undated upper trees. However, with undated trees, there is a temporal feasibility issue. Indeed, a horizontal transfer implies that the donor and the receiver are contemporaneous, therefore implying a time constraint on the tree. In consequence, two horizontal transfers may be incompatible, because they imply contradicting time constraints.
The dynamic programming approach can not easily check for such incompatibilities. If the upper tree is undated, finding a temporally feasible most parsimonious reconciliation is NP-hard. It is fixed parameter tractable, which means that there are algorithms running in time bounded by an exponential of the number of transfers in the output scenarios.
Some solutions imply integer linear programming or branch and bound exploration.
If the upper tree is dated, then there is no incompatibility issue because horizontal transfers can be constrained to never go backward in time. Finding a coherent optimal reconciliation is then solved in polynomial time or with a speed-up in RASCAL, by testing only a fraction of node mappings.
Most of the software taking undated trees does not look for temporal feasibility, except Jane, which explores the space of total orders via a genetic algorithm, or, in a post process, Notung, and Eucalypt, which searches inside the set of optimal solutions for time consistent ones.
Other methods work as supplementary layers to reconciliations, correcting reconciliations or returning a subset of feasible transfers, which can be used to date a species tree.
Expanding phylogenies: Transfers from the dead
In phylogenetics in general, it is important to keep in mind that the extant and ancestral species that are represented in any phylogeny are only a sparse sample of the species that currently exist or ever have existed. This is why one can safely assume that all transfers that can be detected using phylogenetic methods have originated in lineages that are, strictly speaking, absent from a studied phylogeny. Accounting for extinct or unsampled biodiversity in phylogenetic studies can give a better understanding of these processes. Originally, DTL reconciliation methods did not recognize this phenomenon and only allowed for transfer between contemporaneous branches of the tree, hence ignoring most plausible solutions. However, methods working on undated upper trees can be seen as implicitly handling the unknown diversity by allowing transfers "to the future" from the point of view of one phylogeny, that is, the donor is more ancient than the recipient. A transfer to the future can be translated into a speciation to unknown species, followed by a transfer from unknown species.
ALE in its dated version explicitly takes the unknown diversity into account by adding a Moran process of speciation/extinctions of species to the dated birth/death model of gene evolution.
Transfers from the dead are also handled in a parsimonious setting by Tera and ecceTERA, showing that considering these transfers improves the capacity to reconstruct gene trees using reconciliation, and with a more explicit model and in a probabilistic setting, in ALE undated.
The specificity of biogeography: a tree like structure for the "evolution" of areas
In biogeography, some applications of reconciliation approaches consider as an upper tree an area cladogram with defined ancestral nodes. For instance, the root can be Pangaea and the nodes contemporary continents. Sometimes, internal nodes are not ancestral areas but the unions of the areas of their children, to account for the possibility of species evolving along the lower tree to inhabit one or several areas. In this case, the evolutionary events are migration, where one species colonizes a new area, allopatric speciation, or vicariance, equivalent to co-speciation in host/symbiont comparisons.
Even though this approach does not always give a tree (if the unions AB and BC of leaves A, B, C exist, a child can have several parents), and this structure is not associated with time (it is possible for a species to go from A to AB by migration, as well as from AB to A by extinction), reconciliation methods—with events and dynamic programming—can infer evolutionary scenarios between the upper geographical structure and the lower species tree. Diva and Lagrange are two reconciliation models constructing such a tree-like structure and then applying reconciliation, the first with a parsimony principle, the second in a probabilistic framework. Additionally, BioGeoBEARS is a biogeography inference package that reimplemented DIVA and Lagrange models and allows for new options, like distant dependent transfers and discussion on statistical model selection.
Graphical output
With two trees and multiple evolutionary events linking them to represent, viewing reconciled trees is a challenging but necessary question in order to make reconciliation studies more accessible. Some reconciliation software include annotation of the evolutionary events on the lower trees, while others, and specific packages, in DL or DTL, trace the lower tree embedded in the upper one. One difficulty in this regard is the variety of output formats for the different reconciliation software. A common standard, recphyloxml, has been established and endorsed by part of the community, and a viewer is available, able to display reconciliation in multi level systems.
Addressing Additional Practical Considerations
Applying DTL reconciliation to biological data raises several problems related to uncertainty and confidence levels of input and output. Concerning the output, the uncertainty of the answer calls for an exploration of the whole solution space. Concerning the input, phylogenetic reconciliation has to handle uncertainties in the resolution or rooting of the upper or lower trees, or even to propose roots or resolutions according to their confidence.
Exploring the space of reconciliations
Dynamic programming makes it possible to sample reconciliations, uniformly among optimal ones or according to their likelihood.
It is also possible to enumerate them in time proportional to the number of solutions, a number which can quickly become intractable (even only for optimal ones). Finding and presenting structure among the multitude of possible reconciliations has been at the center of recent methodological developments, especially for host and symbiont aimed methods. Several works have focused on representing a set of reconciliations in a compact way, from a uniform sample of optimal ones or by constructing a graph summarizing the optimal solutions. This can be achieved by giving support values to specific events based on all optimal (or suboptimal) reconciliations, or with the use of a consensus reconciled tree. In a DL model, it is possible to define a median reconciliation, based on shared events and to compute it in polynomial time.
EMPRess can group similar reconciliations through clustering, with all pairwise distance between reconciliations computable in polynomial time (independently of the number of most parsimonious reconciliations). With the same aim, Capybara defines equivalence classes among reconciliations, efficiently computing representatives for all classes, and outputs with linear delay a given number of reconciliations (first optimal ones, then sub optimal).
The space of most parsimonious reconciliation can be expanded or reduced when increasing or decreasing horizontal transfer allowed distance, which is easily done by dynamic programming.
Inferring phylogenetic trees with reconciliation
Reconciliation and input uncertainty
Reconciliation works with two fixed trees, a lower and an upper, both assumed correct and rooted. However, those trees are not first hand data.
The most frequently used data for phylogenetics consists in aligned nucleotidic or proteic sequences.
Extracting DNA, sequencing, assembling and annotating genomes, recognizing homology relationships among genes and producing multiple alignments for phylogenetic reconstruction are all complex processes where errors can ultimately affect the reconstructed tree.
Any topology or rooting error can be misinterpreted and cause systematic bias. For instance, in DL reconciliations, errors on the lower tree bias the reconciliation toward more duplication events closer to the root and more losses closer to the leaves.
On the other hand, reconciliation, as a macro evolutionary model, can work as a supplementary layer to the micro evolutionary model of sequence evolution, resolving polytomies (nodes with more than two children) or rooting trees, or be intertwined with it through integrative models in order to get better phylogenies.
Most of the works in this direction focus on gene/species reconciliations, nevertheless some first steps have been made in host/symbiont, such as considering unrooted symbiont trees or dealing with polytomies in Jane.
Exploring the space of lower trees with reconciliation
Reconciliation can easily take unrooted lower trees as input, which is a frequently used feature because trees inferred from molecular data are typically unrooted. It is possible to test all possible roots, or a thoughtful triple traversal of the unrooted tree allows to do it without additional time complexity. In a duplication-loss model, the set of roots minimizing the costs are found close to one another, forming a "plateau", a property which does not generalize to DTL.
Reconciliation can also take as input non binary trees, that is, with internal nodes with more than two children. Such trees can be obtained for example by contracting branches with low statistical support. Inferring a binary tree from a non binary tree according to reconciliation scores is solved in DL with efficient methods. In DTL, the problem is NP hard. Heuristics and exact fixed parameter tractable algorithms are possible solutions.
Another way to handle uncertainty in lower trees is to take as input a sample of alternative lower trees instead of a single one. For example, in the paper that gave reconciliation its name, it was proposed to consider all most likely lower trees, and choose from these trees the best one according to their DL costs, a principle also used by TreeFix-DTL.
The sample of lower trees can similarly reflect their likelihood according to the aligned sequences, as obtained from Bayesian Markov chain Monte Carlo methods as implemented for example in Phylobayes. AngST, ALE and ecceTERA use "amalgamation", an extension of the DTL dynamic programming that is able to efficiently traverse a set of alternative lower trees instead of a single tree.
A local search in the space of lower trees guided by a joint likelihood, on the one hand from multiple sequence alignments and on the other hand from reconciliation with the upper tree, is achieved in Phyldog with a DL model and in GeneRax with DTL. In a DL model with sequence evolution and relaxed molecular clock, the lower tree space can be explored with an MCMC. MowgliNNI can modify the input gene tree at poorly supported nodes to increase DTL score, while TreeSolve resolves the multifurcations added by collapsing poorly supported nodes.
Finally, integrative models—mixing sequence evolution and reconciliation—can compute a joint likelihood via dynamic programming (for both reconciliation and gene sequences evolution), use Markov chain Monte Carlo to include molecular clock to estimate branch lengths, in a DL model or with a relaxed molecular clock, and in a DTL model. These models have been applied in gene/species frameworks, not yet in host/symbiont or biogeography contexts.
Inferring upper trees using reconciliation
Inferring an upper tree from a set of lower trees is a long-standing question related to the supertree problem. It is particularly interesting in the case of gene/species reconciliation where many (typically thousands of) gene trees are available from complete genome sequences. Supertree methods attempt to assemble a species tree based on sets of trees which may differ in terms of contemporary species sets and topology, but usually without consideration for the biological process explaining these differences. However, some supertree approaches are statistically consistent for the reconstruction of the species tree if the gene trees are simulated under a DL model. This means that if the number of input lower trees generated from the true upper tree via the DL model grows toward infinity, given that there are no additional errors, the output upper tree converges almost surely to the true one. This has been shown in the case of a quartet distance, and with a generalised Robinson Foulds multicopy distance, with better running time but assuming gene trees do not contain bipartitions contradicting the species tree, which seems rare under a DL model.
Reconciliation can also be used for the inference of upper trees. This is a computationally hard problem: already resolving polytomies in a non binary upper tree with a binary lower one—minimizing a DL reconciliation score—is NP-hard. In particular, reconstructing the species tree giving the best DL cost for several gene trees is NP-hard and 2-approximable. It is called the Gene Duplication problem or more generally Gene Tree parsimony. The problem was seen as a way to detect paralogy to get better species tree reconstruction. It is NP-hard, with interesting results on the problem complexity and the behaviour of the model with different input size, structure and ILS presence. Multiple solutions exists, with ILP or heuristics, and with the possibility of a deep coalescence score.
ODTL takes as input gene trees and searches a maximum likelihood species tree according to a DTL model, with a hill-climbing search. The approach produces a species tree with internal nodes ordered in time, ensuring a time compatibility for the scenarios of transfer among lower trees {link section|The problem of temporal feasibility}.
Addressing a more general problem, Phyldog searches for the maximum likelihood species tree, gene trees and DL parameters from multiple family alignments via multiple rounds of local search. It thus performs the exploration of both upper and lower trees at the same time. MixTreEM presents a faster solution.
Limits of the two-level DTL model
A limit to dynamic programming: non independent evolution of children lineages
The dynamic programming framework, like usual birth and death models, works under the hypothesis of independent evolution of children lineages in the lower tree. However, this hypothesis does not hold if the model is complemented with several other documented evolutionary events, such as horizontal transfer with replacement of a homologous gene in the recipient lineage, or gene conversion. Horizontal transfer with replacement is usually modeled by a rearrangement of the upper tree, called Subtree Prune and Regraft (SPR). Reconciling under SPR is NP-hard, even in dated trees, and fixed-parameter tractable regarding the output size.
Another way to model and infer replacing horizontal transfers is through maximum agreement forest, where branches are cut in the lower and upper trees in order to get two identical (or statistically indistinguishable) upper and lower forests. The problem is NP-hard, but several approximations have been proposed.
Replacing transfers can be considered on top of the DL model. In the same vein, gene conversion can be seen as a "replacing duplication". In this latter case, a polynomial algorithm which does not use dynamic programming and is an extension of the LCA method can find all optimal solutions, including gene conversions.
Integrating population levels: failure to diverge and Incomplete Lineage Sorting
In host/symbiont frameworks, a single symbiont species is sometimes associated to several host species. This means that while a speciation or diversification has been observed in the host, the populations are indistinguishable in the symbiont.
This is handled for example by additional polytomies in the symbiont tree, possibly leading to intractable inference problems, because polytomies need to be resolved.
It is also modeled by an additional evolutionary event "failure to diverge" (Jane, Amocoala).
Failure to diverge can be a way to allow "free" host switch in a population, a flow of symbionts between closely related hosts.
Following that vision, host switch allowed only for close hosts is considered in Eucalypt. This idea of horizontal flow between close populations can also be applied to gene/species frameworks, with a definition of species based on a gradient of gene flow between populations.
Failure to diverge is one way of introducing population dynamics in reconciliation, a framework mainly adapted to the multi-species level, where populations are supposed to be well differentiated. There are other population phenomena that limit this framework, one of them being deep coalescence of lineages, leading to Incomplete Lineage Sorting (ILS), which is not handled by the DTL model. The multi species coalescent is a classical model of allele evolution along a species tree, with birth of alleles
and sorting of alleles at speciations, that takes into account population sizes and naturally encompasses ILS.
In a reconciliation context, several attempts have been made in order to account for ILS without the complex integration of a population model. For example, ILS can be seen as a possible evolutionary pattern for the gene tree. In that case, children lineages are not independent of one another, leading to intractability results. ILS alone can be handled with LCA, but ILS + DL reconciliation is NP hard, even without transfers.
Notung handles ILS by collapsing short branches of the species tree in polytomies and allowing ILS as a free diversification of gene trees on those polytomies. ecceTERA binds the maximum size of connected parts of the species tree where ILS can happen, proposing a fixed parameter tractable algorithm in that parameter.
ILS and DL can be considered on an upper network instead of a tree. This models in particular introgression, with the possibility to estimate model parameters.
More integrative reconciliation models accounting for ILS have been proposed, including both DL and multispecies coalescent, with DLCoal. It is a probabilistic model with a parsimony translation, proposing two sequential LCA-type heuristics handled via an intermediate locus tree between gene and species.
However, outside of the gene/species reconciliation framework, ILS seems, for no particular reason, never considered in host/symbiont, nor in biogeography.
Cophylogeny with more than two levels
A striking aspect of reconciliation is the common methodology handling different levels of organization: it is used for comparing domain and protein trees, gene and species trees, hosts and symbiont trees, population and geographic trees. However, now that scientists tend to consider that multi-level models of biological functioning bring a novel and game changing view of organisms and their environment, the question is how to use reconciliation to bring phylogenetics to this holobiont era.
Coevolution of entities at different scales of evolution is at the basis of the holobiont idea: macro-organisms, micro-organisms and their genes all have a different history bound to a common functioning in a single ecosystem. Biological systems like the entanglement of host, symbionts and their genes imply functional and evolutionary dependencies between more than two levels.
Examples of multi level systems with complex evolutionary inter-dependencies
Genes coevolving beyond genome boundaries
The holobiont concept stresses the possibility of genes from different genomes to cooperate and coevolve. For instance, certain genes in a symbiont genome may provide a function to its host, like the production of a vital compound absent from available feeding sources. An iconic example is the case for blood-feeding or sap-feeding insects, which often depend on one or several bacterial symbionts to thrive on a resource that is abundant in sugar, but lacks essential amino-acids or vitamins. Another example is the association of Fabaceae with nitrogen-fixing bacteria. The compound beneficiary to the host is typically produced by a set of genes encoded in the symbiont genome, which throughout evolution, may be transferred to other symbionts, and/or in and out of the host genome. Reconciliation methods have the potential to reveal evolutionary links between portions of genomes from different species. A search for coevolving genes beyond the boundaries of the genomes in which they are encoded would highlight the basis for the association of organisms in the holobiont.
Horizontal gene transfer routes depend on multiple levels
In intracellular mutualistic symbiont insect systems, multiple occurrences of horizontal gene transfers have been identified, whether from host to symbiont, symbiont to host or symbiont to symbiont.
Transfers of endosymbiont genes involved in nutrition pathways beneficiary to the insect host have been shown to occur preferentially if the donor and recipient lineages share the same host. This is also the case in insects with bacterial symbionts providing defensive protein or in obligate leaf nodule bacterial symbionts associated with plants. In the human host, gene transfer has been shown to occur preferentially among symbionts hosted in the same organs.
A review of horizontal gene transfers in host/symbiont systems stresses the importance of supporting HGTs with multiple evidence. Notably it is argued that transfers should be considered better supported when involving symbionts sharing a habitat, a geographical area, or the same host. One should, however, keep in mind that most of the diversity of hosts and symbionts is unknown and that transfers may have occurred in unsampled closely related species, hosts or symbionts.
The idea that gene transfer in symbionts is constrained by the host can also be used to investigate the host's phylogenetic history. For instance, based on phylogeographical studies, it is now accepted that the bacterium Helicobacter pylori has been associated with human populations since the origins of the human species. An analysis of the genomes of Helicobacter pylori in Europe suggests that they are issued from a recombination between African and Asian Helicobacter pylori. This strongly implies early contacts between the corresponding human populations.
Similarly, an analysis of HGTs in coronaviruses from different mammalian species using reconciliation methods has revealed frequent contact between viral lineages, which can be interpreted as frequent host switches.
Cultural evolution
The evolution of elements of human culture, for instance languages and folktales, in association with human population genetics, has been studied using concepts from phylogenetics. Although reconciliation has never been used in this framework, some of these studies encompass multiple levels of organization, each represented by a tree or the evolution of a character, with a focus on the coevolution of these levels.
Language trees can be compared with population trees in order to reveal vertically transmitted folktales, via a character model on this language tree. Variants in each folktale's family, languages, genetic diversity, populations and geography can be compared two by two, to link folktale diversification with languages on one side and with geography on the other side. As in genetics with symbionts sharing host promoting HGTs, linguistic barriers can foreclose the transmission of folktales or language elements.
Investigating three-level systems using two-level reconciliation
Multi level reconciliation is not as developed as two-level reconciliation. One way to approach the evolutionary dependencies between more than two levels of organization is to try to use available standard two-level methods to give a first insight into a biological system's complexity.
Multi-gene events: implicit consideration of an intermediate level
At the gene/species tree level, one typically deals with many different gene trees. In this case, the hypothesis that different gene families evolve independently is made implicitly. However, this does not need to be the case. For instance, duplication, transfer and loss can occur for segments of a genome spanning an arbitrary number of contiguous genes. It is possible to consider such multi-gene events using an intermediate guide for lower trees inside the upper one. For instance, one can compute the joint likelihood of multiple gene tree reconciliations with a dated species tree with duplication, loss and whole genome duplication or in a parsimonious setting, and one definition of the problem is NP-hard. Similarly, the DL framework can be enriched with duplication and loss of chromosome segments instead of a single gene. However, DL reconciliation becomes intractable with that new possibility.
The link between two consecutive genes can also be modeled as an evolving character, subject to gain, loss, origination, breakage, duplication and transfer. The evolution of this link appears as an additional level to species and gene trees, partly constrained by the gene/species tree reconciliation, partly evolving on its own, according to genome organization. It thus models the synteny, or proximity between genes. At another scale, it can as well model the evolution of two domains belonging to a protein.
The detection of "highways of transfers", the preferential acquisition of groups of genes from a specific donor, is another example of non-independence of gene histories. Similarly, multi-gene transfers can be detected. It has also led to methodological developments such as reconciliations using phylogenetic networks, seen as a tree augmented with transfer edges, which can be used to constrain transfers in a DTL model. Networks can also be used to model introgression and incomplete lineage sorting.
Detecting coevolution in multiple pairs of levels
It is a central question to understand the evolution of a holobiont to know what the levels are that coevolve with each other, for instance between host species, host genes, symbionts and symbiont genes. It is possible to approach the multiple inter-dependencies between all levels of evolution by multiple pairwise comparisons of two evolving entities.
Reconciliation of host and symbiont on one side and geography and symbiont on the other can also help to identify patterns of diversification of host and symbiont that reflect either coevolution or patterns that can be explained by a common geographical diversification.
Similarly, a study used reconciliation methods to differentiate the effect of diet evolution and phylogenetic inertia on the composition of mammalian gut microbiomes. By reconstructing ancestral diets and microbiome composition onto a mammalian phylogeny, the study revealed that both effects contribute but at different time scales.
Explicit modeling of three or more levels
In a model of a multi-level system as host/symbiont/genes, horizontal gene transfers should be more likely between two symbionts of a same host. This is invisible to a two-level gene tree/species tree or host/symbiont reconciliation: in some cases, looking at any combination of two levels can lead to missing an evolutionary scenario which can only be the most likely if the information from the three trees is considered together.
Trying to face the limitation of these uses of standard two-level reconciliations with systems involving inter-dependencies at multiple levels, a methodological effort has been undertaken in the last decade to construct and use multi-level models. This requires the identification of at least one "intermediate" level between the upper and the lower one.
Pre-reconciliation: characters onto reconciled trees
A first step towards integrated three-level models is to consider phylogenetic trees at two levels and another level represented only with characters at the leaves of one of the trees.
For instance, a reconciliation of host and symbiont phylogenies can be informed by geographic data. Ancestral geographic locations of host and symbiont species obtained through a character inference method can then be used to constrain the host/symbiont reconciliation: ancestral hosts and symbionts can only be associated if they belong to the same geographical location.
At another scale, the evolution at the sub-gene level can be approached with a character method. Here, parts of genes (e.g. the sequence coding for protein domains) is reconciled according to a DL model with a species tree, and the genes they belong to are mentioned as characters of these parts. Ancestral genes are then reconstructed a posteriori via merge and splits of gene parts.
Two-level reconciliations informed by a third level
As pointed out by several studies mentioned in , an upper level can inform a reconciliation between an intermediate and lower one, notably for horizontal transfers.
Three-level models can take into account these assumptions to guide reconciliations between an intermediate tree and lower levels with the knowledge of an upper tree. The model can for example give higher likelihoods to reconciliation scenarios where horizontal gene transfers happen between entities sharing the same habitat. This has been achieved for the first time with DTL gene/species reconciliations nested with a DTL gene domain and gene reconciliation. Different costs for inter and intra transfers depend on whether or not transfers happen between genes of the same genomes.
Note that this model explicitly considers three levels and three trees, but does not yet define a real three-level reconciliation, with a likelihood or score associated. It relies on a sequential operation, where the second reconciliation is informed by the result of the first one.
The reconciliation problem in multi-level models
The next step is to define the score of a reconciliation consisting of three nested trees and to compute, given the three trees, three-level reconciliations according to their score. It has been achieved with a species/gene/domain system, where genes evolve within the species tree with a DL model and domains evolve within the gene/species system with a DTL model, forbidding domain transfers between genes of two different species. Inference involves candidate scenarios with joint scores. Computing the minimum score scenario is NP-hard, but dynamic programming or integer linear programming can offer heuristics. Variations of the problem considering multiple domains are available, and so is a simulation framework.
Inferring the intermediate tree using models of 3-level lower/intermediate/upper reconciliation
Just like two-level reconciliation can be used to improve lower or upper phylogenies, or to help constructing them from aligned sequences, joint reconciliation models can be used in the same manner.
In this vein, a coupled gene/species DL, domain gene DL and gene sequence evolution model in a Bayesian framework improves the reconstruction of gene trees.
Software
Multiple pieces of software have been developed to implement the various models of reconciliation. The following table does not aim for exhaustiveness but presents a number of software tools aimed at reconciling trees to infer reconciliation scenarios or for related usage, such as correcting or inferring trees, or testing coevolution.
The levels of interest section details the levels for which the software was implemented, even though it is entirely possible, for instance, to use a software made for species and gene reconciliation to reconcile host and symbionts. Parsimony or probability is the underlying model that is used for the reconciliation.
References
External links
Phylogenetics
Evolutionary biology
NP-complete problems | Phylogenetic reconciliation | [
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"Biology"
] | 9,960 | [
"Evolutionary biology",
"Taxonomy (biology)",
"Computational problems",
"Bioinformatics",
"Phylogenetics",
"Mathematical problems",
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72,238,792 | https://en.wikipedia.org/wiki/Hunt%20effect%20%28color%29 | The Hunt effect or Luminance-on-colorfulness effect comprises an increase in colorfulness of a color with increasing luminance. The effect was first described by RWG Hunt in 1952.
Hunt noted that this effect occurs at low luminance levels. At higher luminance, he noted a hue shift of colors to be more blue with higher luminance, which is now known as the Bezold–Brücke effect. The Hunt effect is related to the Helmholtz–Kohlrausch effect, where a saturated stimulus is seen to be brighter than less saturated or achromatic stimuli.
See also
Opponent process
Purkinje shift
Abney effect
References
Color appearance phenomena | Hunt effect (color) | [
"Physics"
] | 144 | [
"Optical phenomena",
"Physical phenomena",
"Color appearance phenomena"
] |
72,242,728 | https://en.wikipedia.org/wiki/DREAM%20Challenges | DREAM Challenges (Dialogue for Reverse Engineering Assessment and Methods) is a non-profit initiative for advancing biomedical and systems biology research via crowd-sourced competitions. Started in 2006, DREAM challenges collaborate with Sage Bionetworks to provide a platform for competitions run on the Synapse platform. Over 60 DREAM challenges have been conducted over the span of over 15 years.
Overview
DREAM Challenges were founded in 2006 by Gustavo Stolovizky from IBM Research and Andrea Califano from Columbia University. Current chair of the DREAM organization is Paul Boutros from University of California. Further organization spans emeritus chairs Justin Guinney and Gustavo Stolovizky, and multiple DREAM directors.
Individual challenges focus on tackling a specific biomedical research question, typically narrowed down to a specific disease. A prominent disease focus has been on oncology, with multiple past challenges focused on breast cancer, acute myeloid leukemia, and prostate cancer or similar diseases. The data involved in an individual challenge reflects the disease context; while cancers typically involve data such as mutations in the human genome, gene expression and gene networks in transcriptomics, and large scale proteomics, newer challenges have shifted towards single cell sequencing technologies as well as emerging gut microbiome related research questions, thus reflecting trends in the wider research community.
Motivation for DREAM Challenges is that via crowd-sourcing data to a larger audience via competitions, better models and insight is gained than if the analysis was conducted by a single entity. Past competitions have been published in such scientific venues as the flagship journals of the Nature Portfolio and PLOS publishing groups. Results of DREAM challenges are announced via web platforms, and the top performing participants are invited to present their results in the annual RECOMB/ISCB Conferences with RSG/DREAM organized by the ISCB.
While DREAM Challenges have emphasized open science and data, in order to mitigate issues rising from highly sensitive data such as genomics in patient cohorts, "model to data" approaches have been adopted. In such challenges participants submit their models via containers such as Docker or Singularity. This allows retaining confidentiality of the original data as these containers are then run by the organizers on the confidential data. This differs from the more traditional open data model, where participants submit predictions directly based on the provided open data.
Challenge organization
DREAM challenge comprises a core DREAM/Sage Bionetworks organization group as well as an extended scientific expert group, who may have contributed to creation and conception of the challenge or by providing key data. Additionally, new DREAM challenges may be proposed by the wider research community. Pharmaceutical companies or other private entities may also be involved in DREAM challenges, for example in providing data.
Challenge structure
Timelines for key stages (such as introduction webinars, model submission deadlines, and final deadline for participation) are provided in advance. After the winners are announced, organizers start collaborating with the top performing participants to conduct post hoc analyses for a publication describing key findings from the competition.
Challenges may be split into sub-challenges, each addressing a different subtopic within the research question. For example, regarding cancer treatment efficacy predictions, these may be separate predictions for progression-free survival, overall survival, best overall response according to RECIST, or exact time until event (progression or death).
Participation
During DREAM challenges, participants typically build models on provided data, and submit predictions or models that are then validated on held-out data by the organizers. While DREAM challenges avoid leaking validation data to participants, there are typically mid-challenge submission leaderboards available to assist participants in evaluating their performance on a sub-sampled or scrambled dataset.
DREAM challenges are free for participants. During the open phase anybody can register via Synapse to participate either individually or as a team. A person may only register once and may not use any aliases.
There are some exceptions, which disqualify an individual from participating, for example:
Person has privileged access to the data for the particular challenge, thus providing them with an unfair advantage.
Person has been caught or is under suspicion of cheating or abusing previous DREAM Challenges.
Person is a minor (under age 18 or the age of majority in jurisdiction of residence). This may be alleviated via parental consent.
See also
List of crowdsourcing projects
Critical Assessment of Function Annotation (CAFA)
Critical Assessment of Genome Interpretation (CAGI)
Critical Assessment of Prediction of Interactions (CAPRI)
Critical Assessment of protein Structure Prediction (CASP)
Kaggle
References
Applied machine learning
Bioinformatics
Computer science competitions
Crowdsourcing
Forecasting competitions
Molecular modelling
Programming contests | DREAM Challenges | [
"Chemistry",
"Engineering",
"Biology"
] | 925 | [
"Biological engineering",
"Molecular physics",
"Bioinformatics",
"Molecular modelling",
"Theoretical chemistry"
] |
72,243,076 | https://en.wikipedia.org/wiki/Glossary%20of%20cellular%20and%20molecular%20biology%20%28M%E2%80%93Z%29 | This glossary of cellular and molecular biology is a list of definitions of terms and concepts commonly used in the study of cell biology, molecular biology, and related disciplines, including molecular genetics, biochemistry, and microbiology. It is split across two articles:
Glossary of cellular and molecular biology (0–L) lists terms beginning with numbers and those beginning with the letters A through L.
Glossary of cellular and molecular biology (M–Z) (this page) lists terms beginning with the letters M through Z.
This glossary is intended as introductory material for novices (for more specific and technical detail, see the article corresponding to each term). It has been designed as a companion to Glossary of genetics and evolutionary biology, which contains many overlapping and related terms; other related glossaries include Glossary of virology and Glossary of chemistry.
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
See also
Introduction to genetics
Outline of genetics
Outline of cell biology
Glossary of biology
Glossary of chemistry
Glossary of genetics and evolutionary biology
References
Further reading
External links
National Human Genome Research Institute (NHGRI) Talking Glossary of Genomic and Genetic Terms
Interactive, labeled animal cell from SwissBioPics
Glossary
Genetics
Molecular-biology-related lists
Wikipedia glossaries using description lists | Glossary of cellular and molecular biology (M–Z) | [
"Chemistry",
"Biology"
] | 264 | [
"Glossaries of biology",
"Molecular-biology-related lists",
"Genetics",
"Molecular biology"
] |
72,243,857 | https://en.wikipedia.org/wiki/FinVect | In the mathematical field of category theory, FinVect (or FdVect) is the category whose objects are all finite-dimensional vector spaces and whose morphisms are all linear maps between them.
Properties
FinVect has two monoidal products:
the direct sum of vector spaces, which is both a categorical product and a coproduct,
the tensor product, which makes FinVect a compact closed category.
Examples
Tensor networks are string diagrams interpreted in FinVect.
Group representations are functors from groups, seen as one-object categories, into FinVect.
DisCoCat models are monoidal functors from a pregroup grammar to FinVect.
See also
FinSet
ZX-calculus
category of modules
References
Categories in category theory
Dimension | FinVect | [
"Physics",
"Mathematics"
] | 156 | [
"Geometric measurement",
"Mathematical structures",
"Physical quantities",
"Vector spaces",
"Space (mathematics)",
"Categories in category theory",
"Category theory",
"Theory of relativity",
"Dimension"
] |
72,244,439 | https://en.wikipedia.org/wiki/Deutschlandticket | The () often shorted to the D-Ticket, also known as the 49-Euro-Ticket, is a subscription public transport ticket for all local public transport, valid in the whole of Germany, that costs 49 euros per month. The Scholz cabinet introduced it in May 2023 as a permanent successor to the 9-Euro-Ticket which had been offered in Summer 2022. The German federation () and the federal states () initially participate in the financing with 1.5 billion euros per year until 2025.
At the beginning of January 2025, the price of the ticket was raised to 58 per month.
Ticket conditions
Validity
The ticket is valid on all local and regional buses, trams, metros, S-Bahn trains, and local and regional trains (RB/RE) across the whole of Germany, except on few RE trains operated by DB Fernverkehr.
It is usually valid on international eligible trains from/to end stations in a neighbour country, if operated by a German operator. Deutschlandticket holders can also go to a number of border tariff stations outside Germany using their passes including; Tønder () in Denmark, Wissembourg (Gare de Wissembourg) in France, Hengelo (over Oldenzaal), and Venlo in the Netherlands, Basel in Switzerland and Świnoujście () in Poland.
It is not valid on most of the long-distance trains (such as Intercity Express (ICE), Intercity (IC) and Eurocity (EC) trains operated by Deutsche Bahn) and on long-distance bus coaches (such as those operated by Flixbus). There are exceptions for long-distance trains, which are co-financed by cities and states.
The ticket is only valid for transportation in second class. Often it is possible to buy upgrades to first class (if available) from the concerned operator. Children under 6 years old travel for free, while older children need their own ticket. The Deutschlandticket does not include transportation for pets or for bicycles in cases where they require a separate ticket.
Sales
The Deutschlandticket was originally sold as a monthly subscription at a cost of 49 Euros per month which increased to 58 Euros in January 2025. The ticket is valid for a calendar month, and is automatically renewed, with payment taken by SEPA direct debit from the user's bank account or by credit card. The subscription can be cancelled by the 10th day of each month. Users wishing to purchase a new subscription for the current month on the 11th day of the month or later must pay for at least the current and the following calendar month. The mo.pla app allows users to cancel their Deutschlandticket subscription up to the second-last day of the month.
The Deutschlandticket is sold by participating local transit authorities. It is issued as a digital ticket via mobile apps offered by local transit authorities. It can also be issued on a chip smartcard using the "eTicket Deutschland" standard. Employers can subsidise the ticket for their employees, and university students can upgrade their "Semesterticket" to a Deutschlandticket. Some communities have additionally subsidised the ticket for those on low income, senior citizens and apprentices. The city of Tübingen has gone as far as subsidising the ticket for every resident, so they can get it for 34 euros per month. The local council in the city of Stuttgart has offered the Deutschlandticket to its employees as an employee benefit.
The BahnCard 100, a rail card offered by Deutsche Bahn allowing unlimited travel on its trains, includes a Deutschlandticket at no additional charge.
History
After the start of the Russian invasion of Ukraine, energy prices in Germany rose significantly. In response, the government introduced the heavily subsidized 9-Euro-Ticket, which allowed unlimited use of public local transportation across Germany at a cost of 9 euros per calendar month. It was available for June, July, and August 2022. After the end of this 3-month period, politicians called for a permanent successor ticket that would offer similar simplicity, though there was debate about the price.
At the end of November 2022, transport ministers reaffirmed their commitment to the monthly ticket for 49 euros, and it was planned to start in April 2023, as a start in January was considered too early for implementation. The start was delayed further by one month as there was opposition from the local and regional transportation services like the Munich MVV that wanted more funding from the federal and the state governments.
On 31 March 2023, the Bundesrat approved the bill passed by the Bundestag for a nationwide ticket for local and regional public transportation at a monthly price of 49 euros. The monthly tickets started in May 2023, but could only be purchased by subscription. There are no paper tickets for the subscription – with the possible exception at the start-up phase; the users have to authenticate digitally (either via smartphone app or chip card).
The ticket price is to be adjusted to inflation each year, although the 49 euro price is intended to be fixed for at least the first two years of operation of the ticket.
On 31 July, three months after the introduction of the Deutschlandticket, the transport ministry reported that 11 million people subscribed to the ticket, with 5 million being existing subscribers to monthly transport passes, 5 million new subscribers from existing public transport ticket holders and one million new users of public transport. On 13 September, the Hamburg transport agency reported that it had sold over a million subscriptions.
Since the summer of 2023, Federal Transport Minister Volker Wissing (FDP) had argued with the federal states about the financing of the ticket. The financing of the ticket is unclear. Both sides have so far contributed 1.5 billion euros annually. If there is not enough money, the federal and state governments currently share the additional costs. The federal government rejects further financial commitments from 2024.
At the beginning of December 2023, the Stendal district decided that the ticket will no longer be valid on its buses from January 1, 2024. This would have meant that the Deutschlandticket would no longer be valid across the board. However, the district council reverted its decision two weeks later and the Deutschlandticket remains a valid ticket in the Stendal district.
Interest outside Germany
Due to the popularity and interest in the Deutschlandticket in Germany, other countries expressed interest in introducing a similar scheme in their country.
Portugal
On 30 June 2023, influenced by Deutschlandticket, the eco-socialist LIVRE party proposed a monthly rail pass for the regional trains by the state-owned rail operator Comboios de Portugal in the country's annual budget. The proposal passed in parliament, and the Portuguese government said it was introducing a 49 euros per month regional rail pass called the Passe Ferroviário Nacional (National Train Pass) from 1 August 2023. It would allow unlimited travel on all regional trains, known as comboios regionais apart from the tourist trains like the , and suburban rail services in Lisbon, Porto and Coimbra.
Critics have said that due to the rules and exclusions of the pass, there are virtually no regional rail services in the middle of the country and frequent strikes by rail workers make the pass worthless.
France
On 9 June 2023, German federal transport minister Volker Wissing said in an interview with Berliner Morgenpost, that he was talking to his French counterpart Clément Beaune about the scheme in a meeting between the two ministers during a discussion about a Franco-German student travel scheme.
In an interview with French YouTuber Hugo Travers on 4 September 2023, French president Emmanuel Macron said his government is looking at a French equivalent of the Deutschlandticket. Later that week on 7 September, on France 2's breakfast programme Télématin, Beaune said the transport ministry was provisionally working on a similar scheme called "Pass Rail" which would come in the summer of 2024. The ticket would allow unlimited travel throughout France on the country's regional trains, the TERs and the regular Intercités for 49 euros per month. Beaune said the government was talking to local authorities about including local bus and trams as well.
Reactions to the proposal were mixed, with the region of Grand Est being supportive of the idea, while the region of Hauts-de-France was critical particularly over costs, pointing out that the region already subsidises its TER to the tune of 530 million euros. The president of the Île-de-France region Valérie Pécresse said in an interview on France 3 Paris Île-de-France, that the costs for such a scheme would be around 1.8 billion euros for the region, making it unaffordable. Wissing has said he would like to interlink the two schemes, so that persons could use either pass in each other's countries.
On 27 September, Beaune and the presidents of all regions came together in Saint-Malo to begin discussions on financing such a scheme, together with general rail finance such as track fees and rolling stock. It is hoped that such a subscription would be available by the summer of 2024.
United Kingdom
A report produced for Greenpeace by the Greengauge 21 think tank suggested that a similar scheme might increase usage of UK train routes and reduce the climate impact of fossil fuel powered vehicles. The Department for Transport responded to the report by stating that the UK Government has no plans to implement a similar scheme at the present time.
See also
Klimaticket in Austria
365-Euro-Ticket in Vienna
External links
Federal government's information on the Deutschlandticket
Deutsche Bahn's page on the Deutschlandticket
Rhein-Main-Verkehrsverbund's page on the Deutschlandticket
References
2022 in politics
Emissions reduction
Euro
Fare collection systems in Germany
Public transport in Germany
Scholz cabinet
Public transport tickets
Environmental policies approved in 2023 | Deutschlandticket | [
"Chemistry"
] | 2,025 | [
"Greenhouse gases",
"Emissions reduction"
] |
63,520,272 | https://en.wikipedia.org/wiki/David%20Hodgkiss | David Michael William Hodgkiss (June 1948 – 29 March 2020) was a British businessman, and Chairman of Lancashire County Cricket Club between April 2017 and March 2020.
He was Chief Executive of structural steel contractor William Hare Group, a business founded by his grandfather. Hodgkiss's 2014 OBE was awarded for services to manufacturing and export at William Hare.
Hodgkiss served over twenty years at Lancashire County Cricket Club as Committee Member , Treasurer , Vice-Chairman and Chairman , being instrumental in completing a £60 million redevelopment of the Club's Old Trafford Cricket Ground.
He died age 71 in March 2020 after catching COVID-19. The England Cricket Team took to the field against the West Indies at Emirates Old Trafford wearing black armbands in his honour. Farokh Engineer lauded Hodgkiss as the best and the most popular Chairman Lancashire County Cricket Club ever had.
References
1948 births
2020 deaths
Deaths from the COVID-19 pandemic in England
British chief executives
Lancashire County Cricket Club
Officers of the Order of the British Empire
20th-century British businesspeople
21st-century British businesspeople
Alumni of the University of Liverpool
Structural steel | David Hodgkiss | [
"Engineering"
] | 240 | [
"Structural engineering",
"Structural steel"
] |
63,523,688 | https://en.wikipedia.org/wiki/Italian%20Medicines%20Agency | The Italian Medicines Agency (Agenzia italiana del farmaco, AIFA) is the public institution responsible for the regulatory activity of pharmaceuticals in Italy.
See also
European Medicines Agency
Istituto Superiore di Sanità
External links
Medical and health organisations based in Italy
National agencies for drug regulation
Drugs in Italy
Regulators of biotechnology products
Regulation in Italy | Italian Medicines Agency | [
"Chemistry",
"Biology"
] | 69 | [
"Pharmacology",
"Biotechnology products",
"Regulation of biotechnologies",
"National agencies for drug regulation",
"Drug safety",
"Medicinal chemistry stubs",
"Regulators of biotechnology products",
"Pharmacology stubs"
] |
76,599,128 | https://en.wikipedia.org/wiki/Agglomerate%20%28steel%20industry%29 | Agglomerate is a material composed of iron oxides and gangue, roasted and sintered in an agglomeration plant. This product is obtained by burning coal previously mixed with iron ore and oxides. This conditioning of iron ore optimizes its use in the blast furnace.
History
The advantages of agglomeration were identified very early on, but the processes used at the time were not continuous. The primitive method, which consisted of a grindstone grate, was abandoned towards the end of the 19th century because it was too fuel-intensive. Shaft furnaces then replaced them, their much higher efficiency being due both to the confinement of the reaction and to counter-current operation (the solids sink and the gases rise).
In these furnaces, iron ores were roasted to obtain the opposite result to the one we're looking for now: in 1895, roasting was carried out at low temperatures to avoid aggregation, and to obtain friable ore.
At the time, ore roasting furnaces were tanks inspired by blast furnaces and lime kilns, and were not very productive tools. Around 1910, the Greenawald process, which automated the principle3, saw some development, enabling the production of 300,000 tonnes a year.
In June 1906, A.S. Dwight and R. L. Lloyd built the first agglomerating machine on a chain (also known as a grate), which began agglomerating copper and lead ores. The first agglomeration line for iron ores was built in 1910 in Birdsboro, Pennsylvania.
It took some thirty years for the sintering of ores on chains to become widespread in the steel industry. Whereas before the Second World War, it was mainly used for reconditioning ore fines, after 1945 it became widespread for processing raw ores. Today, it plays an essential role in the blending of different ores and, above all, in the incorporation of mineral wastes of varying iron content. This recycling role improves profitability and limits the amount of waste generated by steel complexes, which generate numerous iron-rich residues (slag, sludge, dust, etc.).
Interests and limitations
Interests
Chipboard is a product optimized for use in blast furnaces. To do so, it must meet several conditions:
be composed of a gangue of oxides which, combined with the ash from coke combustion (essentially silica), will give rise to a fusible slag which is both reactive towards impurities (in particular the sulfur provided by the coke), not very aggressive towards the refractories lining the blast furnace and of a quality suitable for its use;
Ensure a precise particle size, generally between 20 and 80 mm (pieces that are too small clog up the furnace, and pieces that are too large take too long to transform in the core);
maintain permeability to reducing gases at the highest possible temperatures;
low-temperature endothermic reactions that can be carried out more economically outside a blast furnace. These are essentially drying, calcination of the gangue (decarbonisation of limestone and dehydration of clay or gypsum), and reduction reactions. The agglomerate then becomes, at equal weight, richer in iron than the ore.
over oxidize iron oxides, Fe2O3 being better reduced by the carbon monoxide present in the blast furnace than less oxidized compounds, especially Fe3O4.
Another advantage is the elimination of undesirable elements: the chain agglomeration process eliminates 80-95% of the sulfur present in the ore and its additives. It's also a way of getting rid of zinc, the element that "poisons" blast furnaces, as its vaporization temperature of 907°C corresponds to that of a well-conducted roast.
Limitations
On the other hand, agglomerate is an abrasive product that damages blast furnace vessels, especially if these are not designed for absorber, and is above all fragile. Repeated handling degrades its grain size and generates fines, making it unsuitable for packaging at sites far from blast furnaces: pellets are therefore preferable. Cold resistance, particularly to crushing, can be improved by increasing the energy input during sintering.
Improving mechanical strength also improves the performance of agglomerates in the processes that use them. The reduction of hematite (Fe2O3) to magnetite (Fe3O4) creates internal stresses. However, in addition to increasing the cost of agglomerate production, reducibility deteriorates when mechanical strength is sought.
Composition
Agglomerates are generally classified as acidic or basic. The complete basicity index ic is calculated by the following ratio of mass concentrations:
It is often simplified by simply calculating a simplified basicity index noted i (or sometimes ia), equal to the ratio CaO / SiO2. An agglomerate with an index ic of less than 1 is said to be acidic; above 1, it is generally said to be basic; equal to 1, it is said to be self-melting (ic=1 being equivalent to ia=1.40). Before the 1950s, agglomerates with an ic value of less than 0.5 were in the majority. Then, when it was realized that agglomerate could incorporate limestone, which was then charged into the blast furnace separately, basic indices became widespread: in 1965, indices below 0.5 represented less than 15% of the tonnage of agglomerate produced, while basic agglomerates accounted for 45%.
Again, we find the relationship: k being an empirically determined constant (sometimes equal, for simplicity, to 1). Iron reduction is, in itself, favored by a basic environment, and peaks at 2<ib<2.5. It is also in this range that mechanical strength is best (and also, the slag's fusibility is the worst, which complicates its removal from the blast furnace). Above an ib value of 2.6, the proportion of molten agglomerate increases, clogging the pores and slowing down chemical reactions between gases and oxides. As for acid agglomerates with an ib index of less than 1, softening begins as soon as only around 15% of the ore has been reduced.
The optimum basicity index is therefore determined according to the ore used, the technical characteristics of the blast furnace, the intended use of the cast iron and the desired qualities. For example:
Cast irons made from Minette (ore) and intended for refining using the Thomas process had basicities of i=1.35 (a complete index I=1), which was a compromise between low-temperature viscosity (which requires an acidic slag) and desulfurization (favored by a basic slag);
plants for which sulfur-rich cast iron is not a problem adopt a more acidic agglomerate: with i= 0.9 to 1.0. This favors silicon reduction but can result in very high sulfur contents, from 0.1 to 0.25%;
the production of ferromanganese in the blast furnace requires a high manganese yield and therefore high basicities, up to i = 1.7 or 1.8 (bearing in mind that in this particular case, the index corresponds to !). Meltability is a secondary consideration in this case, as slag temperatures can reach 1,650°C (instead of 1,450°C - 1,550°C in the production of cast irons for refining).
See also
Speiss
Sinter plant
Agglomerate
Pellet (steel industry)
References
Bibliography
Notes
Metallurgy
Minerals
Steel industry | Agglomerate (steel industry) | [
"Chemistry",
"Materials_science",
"Engineering"
] | 1,602 | [
"Metallurgy",
"Materials science",
"nan"
] |
76,599,574 | https://en.wikipedia.org/wiki/RG/RGG%20motif | The arginine-glycine or arginine-glycine-glycine (RG/RGG) motif is a repeating amino acid sequence motif commonly found in RNA-binding proteins (RBPs). RGG regions in proteins are defined as two or more RG/RGG sequences within a stretch of 30 amino acids. Initially named the RGG box, it confers a protein with the ability to bind double-stranded mRNA molecules. The RGG motif has been observed in proteins from at least 12 animal species, including humans.
Biochemical function
RGG motifs are primarily involved in mediating protein-RNA interactions. Positive charges from arginine residues promote electrostatic interactions with mRNA molecules. The composition and structure of the arginine side chain may also allow for specific interactions with other molecules as opposed to the other positively charged amino acids, lysine and histidine. Glycine residues add flexibility to the peptide structure and promote their tendency to form intrinsically disordered regions. The RGG motif can also drive liquid-lipid phase separation of proteins inside cells as well as in vitro.
Synthetic uses
Researchers have pursued creating condensates with novel functions for use in cellular and metabolic engineering. Synthetically designed proteins containing repeating RGG motifs have been used to form droplets with tunable properties in cells and in vitro.
Notable RGG-containing proteins
RGG motif-containing proteins are the second most abundant group of RBPs in the human genome. They are involved in various RNA metabolism, export, and translation functions.
Sbp1
Npl3
Ded1
FMR1
FUS
Laf-1
References
Bioinformatics | RG/RGG motif | [
"Engineering",
"Biology"
] | 339 | [
"Bioinformatics",
"Biological engineering"
] |
67,841,351 | https://en.wikipedia.org/wiki/Dibutylmagnesium | Dibutylmagnesium is an organometallic chemical compound of magnesium. Its chemical formula is . Dibutylmagnesium is a chemical compound from the group of organomagnesium compounds. The pure substance is a waxy solid. Commercially, it is marketed as solution in heptane.
Synthesis
Dibutylmagnesium can be obtained by reaction of butyllithium with magnesium butylchloride and subsequent addition of magnesium 2-ethylhexanoate. The compound can also be prepared by hydrogenation of magnesium, followed by reaction with 1-butene. It is also possible to prepare dibutylmagnesium using 2-chlorobutane, magnesium powder, and n-butyllithium.
Use
Dibutylmagnesium is used as a convenient reagent for the preparation of organomagnesium compounds.
References
Magnesium compounds
Organomagnesium compounds
Butyl compounds
Pyrophoric materials | Dibutylmagnesium | [
"Chemistry",
"Technology"
] | 208 | [
"Organomagnesium compounds",
"Reagents for organic chemistry"
] |
58,307,276 | https://en.wikipedia.org/wiki/Quantum%20dimer%20magnet | In condensed matter physics, the quantum dimer magnet state is one in which quantum spins in a magnetic structure entangle to form a singlet state. These entangled spins act as bosons and their excited states (triplons) can undergo Bose-Einstein condensation (BEC). The quantum dimer system was originally proposed by Matsubara and Matsuda as a mapping of the lattice Bose gas to the quantum antiferromagnet. Quantum dimer magnets are often confused as valence bond solids; however, a valence bond solid requires the breaking of translational symmetry and the dimerizing of spins. In contrast, quantum dimer magnets exist in crystal structures where the translational symmetry is inherently broken. There are two types of quantum dimer models: the XXZ model and the weakly-coupled dimer model. The main difference is the regime in which BEC can occur. For the XXZ model (commonly referred to as the magnon BEC), the BEC occurs upon cooling without a magnetic field and manifests itself as a symmetric dome in the field versus temperature phase diagram centered about H = 0. The weakly-coupled dimer model does not magnetically order in zero magnetic field, but instead orders upon the closing of the spin gap, where the BEC regime begins and is a dome centered at non-zero field.
Quantum dimer systems are considered to be of interest due to their relatively simple interactions and their BEC state is of interest as a novel playground for testing BEC physics. In addition, the BEC state of the quantum dimer magnet is thought to be a spin superfluid which could allow for the transfer of spin information over long distances without loss.
Bose-Einstein condensation in the weakly-coupled dimer model
The Bose-Einstein condensation in quantum dimer systems is, at its essence, a field-induced magnetically ordered state that comes about from the Zeeman splitting of the triplet states. The bosons of the Bose-Einstein condensate can be thought of as the component of the spin parallel to the applied magnetic field, reaching a maximum when the spins become polarized by the field. The difference between the Bose-Einstein condensation and a typical ordered state is the spontaneous breaking of the spin's U(1) symmetry (i.e. the circular symmetry transverse to an applied magnetic field). This spontaneous symmetry breaking gives rise to a Goldstone boson that is measureable via a inelastic neutron scattering (amongst other techniques).
References
Condensed matter physics | Quantum dimer magnet | [
"Physics",
"Chemistry",
"Materials_science",
"Engineering"
] | 524 | [
"Phases of matter",
"Condensed matter physics",
"Matter",
"Materials science"
] |
65,005,031 | https://en.wikipedia.org/wiki/Glyceryl%20octyl%20ascorbic%20acid | Glyceryl octyl ascorbic acid (GO-VC) is an amphipathic derivative of vitamin C consisting of two ether linkages: a 1-octyl at position 2 and a glycerin at position 3. The chemical name is 2-glyceryl-3-octyl ascorbic acid. The isomer in which these two groups are swapped (2-octyl-3-glyceryl ascorbic acid, OG-VC) is also known.
It is considered as a new stable amphipathic in the field of aesthetic medicine.
Overview
Vitamin C is rapidly converted to ascorbic acid radicals by UV rays, which causes cytotoxicity and sunburn, but GO-VC improves the stability of conventional vitamin C derivatives, and thus eliminates the problems of these prooxidants. Water-soluble vitamin C derivatives, such as sodium ascorbyl phosphate (APS), which have been used since the 1990s, have a problem of drying the skin in order to the sebum suppression effect. On the other hand, GO-VC has a high moisturizing power due to the binding of glycerin and can prevent the dryness of the skin. In addition, GO-VC has a sterilizing activity of octanol, so it has a sterilizing activity against many bacteria.
GO-VC is also used for wound healing and wrinkle prevention because it has a proliferative effect on fibroblasts and a promoting effect on type I collagen production. GO-VC has a stronger melanin production inhibitory effect than arbutin, which is used as a whitening agent, and it was confirmed in clinical trials that even low concentrations of 0.01 to 0.1% (by weight) are effective against acne redness and pigmentation.
The water-soluble vitamin C derivatives such as ascorbic acid 2-glucoside and APPS (trisodium ascorbyl palmitate) can not add to water-soluble polymer gels commonly used in cosmetics such as carboxy vinyl polymer and sodium polyacrylate. This is because the viscosity changes, causing precipitation. On the other hand, GO-VC can be dispersed in water-soluble polymer gel transparently and uniformly or can be stably dissolved for a long time.
The fat-soluble vitamin C derivatives such as ascorbyl tetrahexyl decanoate (VC-IP) are almost insoluble in water, making it difficult to mix in water-soluble formulations such as lotions without the use of surfactants. Fat-soluble vitamin C derivatives causes lipid oxidation problems when lipids are released, and the color of the formulation tends to change. GO-VC can solve these problems almost completely.
GO-VC is well absorbed percutaneously due to its amphiphilic nature, and because it is negatively charged rather than completely non-ionic, it can facilitate percutaneous absorption with an iontophoresis device. In addition, GO-VC is amphipathic but does not have a lipid group, so there are few skin toxicity problems due to lipid peroxidation, and it does not have the sticky feeling of conventional vitamin C derivatives and has a good feel.
Stability
When the aqueous solution containing vitamin C and GO-VC was stored at 50 °C for 90 days, the vitamin C residual amount decreased to less than 30% in 30 days, whereas the residual amount of GO-VC was 90% or more. Moreover, after 90 days, 80% or more of GO-VC was confirmed to remain.
It is considered that these high stability are due to the two most reactive hydroxyl groups of vitamin C being capped by glycerin and octanol at the same time. Because the viscosity is stable in the preparation containing GO-VC and the polymer gel too, and it can be kept in a transparent state for a long period of time. Therefore, GO-VC can be added to many preparations such as lotions, creams, serums and gels.
Acne
It was reported that GO-VC is effective against post-inflammatory hyperpigmentation (PIH), post-inflammatory erythema (PIE), and atrophic scar (AS), which are important complications in acne. It applied a complex vitamin C derivative lotion containing GO-VC to each of 10 patients with acne twice on the right side twice a day for 3 months, and confirmed the left side without application and its effect. It was reported that there was a marked improvement in PIH, PIE, and AS on the only right side applying lotion containing GO-VC after 3 months.
Pigmentation
Many phenolic compounds, which are conventional whitening agents, react with tyrosinase to induce melanocyte-specific cytotoxicity, and thus there was a risk of developing vitiligo. GO-VC reduced the intracellular melanin content of B16 melanoma cells. GO-VC's pigmentation inhibitory mechanism is shown to act through a novel melanogenesis inhibitory system that does not depend on tyrosinase activity inhibition, indicating that it is a safe and effective pigmentation inhibitor with low risk of vitiligo. GO-VC showed a remarkable effect in an actual pigmentation suppression clinical study, and a gel preparation containing 0.1% GO-VC was applied twice a day in the morning and evening on the entire face after 13 female subjects aged 39.8 years on average. As a result of a 1-5 month study, GO-VC significantly improved post-inflammatory pigmentation. It is reported that GO-VC also showed a clear improvement in pigmentation caused by metal allergy, which was not very effective when applied with hydroquinone.
Skin pore related diseases
Since conventional water-soluble vitamin C does not easily penetrate the skin barrier, an amphipathic vitamin C derivative was developed to improve this. However, since lipids such as palmitic acid were chemical modified to vitamin C derivatives in the past, exposure to ultraviolet light generated free fatty acids, raising concerns about lipid peroxidation. It was thought that GO-VC could avoid the problem of lipid peroxidation because GO-VC is amphipathic with octanol instead of lipid. The effect of 0.05% gel of GO-VC was investigated on skin pore related diseases. As a result, it was confirmed that there were no side effects and the number of abnormal pores decreased to 70% or less within 1 to 2 months after application.
References
Organic acids
3-Hydroxypropenals
Glycerol ethers
Lactones | Glyceryl octyl ascorbic acid | [
"Chemistry"
] | 1,394 | [
"Organic acids",
"Acids",
"Organic compounds"
] |
59,941,251 | https://en.wikipedia.org/wiki/Cysteine-rich%20protein | Cysteine-rich proteins (CRP, cysteine-rich peptide or disulphide-rich peptide) are small proteins that contain a large number of cysteines. These cysteines either cross-link to form disulphide bonds, or bind metal ions by chelation, stabilising the protein's tertiary structure. CRPs include a highly conserved secretion peptide signal at the N-terminus and a cysteine-rich region at the C-terminus.
Structure
Disulphides
In an oxidising environment cysteines cross-link to form disulphide bonds. CRPs that form these typically have an even number of cysteines.
Metal binding
Cysteines can coordinate one or more metal ions by forming a chelation complex around them.
Functions in plants
CRPs are numerous in plants, with 756 CRP-encoding genes in the Arabidopsis thaliana genome. Several CRPs bind known receptors, but most CRP signaling mechanisms and protein interactions are uncharacterized. Characterized CRPs function as short-range intercellular signals during processes such as plant defense, bacterial symbiosis, stomatal patterning, fertilization, vegetative tissue development, and seed development.
Many CRPs function in plant defense. Defensins, a major class of CRP with an eight-cysteine motif forming four disulfide bridges, are involved in pathogen response. Other putative antimicrobial CRPs include lipid transfer proteins, thionins, knottins, heveins, and snakins. Additionally, some CRPs have allergenic, ɑ-amylase inhibitory, or protease inhibitory functions that deter herbivores.
In plant reproduction, CRPs are involved in pollen tube growth and guidance and early embryo patterning, in addition to other functions. Among those involved in pollen tube attraction are the LUREs, a group of ovular pollen-tube attractants in Arabidopsis thaliana and Torenia fournieri that preferentially attract conspecific pollen, and STIG1, a CRP expressed in the stigma of Solanum lycopersicum that interacts with the pollen-specific receptor PRK2. In early embryo development, CRPs such as ESF1 are necessary for suspensor development and normal seed morphology.
References
Proteins
Sulfides
Protein classification
Cysteine-rich proteins | Cysteine-rich protein | [
"Chemistry",
"Biology"
] | 504 | [
"Biomolecules by chemical classification",
"Protein classification",
"Cysteine-rich proteins",
"Molecular biology",
"Proteins"
] |
59,941,638 | https://en.wikipedia.org/wiki/Metal-binding%20protein | Metal-binding proteins are proteins or protein domains that chelate a metal ion.
Binding of metal ions via chelation is usually achieved via histidines or cysteines. In some cases this is a necessary part of their folding and maintenance of a tertiary structure. Alternatively, a metal-binding protein may maintain its structure without the metal (apo form) and bind it as a ligand (e.g. as part of metal homeostasis). In other cases a coordinated metal cofactor is used in the active site of an enzyme to assist catalysis.
Histidine-rich metal-binding proteins
Poly-histidine tags (of six or more consecutive His residues) are utilized for protein purification by binding to columns with nickel or cobalt, with micromolar affinity. Natural poly-histidine peptides, found in the venom of the viper Atheris squamigera have been shown to bind Zn(2+), Ni(2+) and Cu(2+) and affect the function of venom metalloproteases. Furthermore, histidine-rich low-complexity regions are found in metal-binding and especially nickel-cobalt binding proteins. These histidine-rich low complexity regions have an average length of 36 residues, of which 53% histidine, 23% aspartate, 9% glutamate. Intriguingly, structured domains with metal binding properties also have very similar frequencies of these amino acids that are involved in the coordination of the metal. Accordingly, it has been hypothesized that these metal-binding structured domains could have originated and evolved/optimized from metal-binding low-complexity protein regions of similar amino acid content.
References
Proteins | Metal-binding protein | [
"Chemistry"
] | 356 | [
"Biomolecules by chemical classification",
"Proteins",
"Molecular biology"
] |
59,953,471 | https://en.wikipedia.org/wiki/DNA-templated%20organic%20synthesis | DNA‐templated organic synthesis (DTS) is a way to control the reactivity of synthetic molecules by using nature's molarity‐based approach. Historically, DTS was used as a model of prebiotic nucleic acid replication. Now however, it is capable of translating DNA sequences into complex small‐molecule and polymer products of multistep organic synthesis.
Base Editors
The DNA base editors, developed at Harvard University under David Liu, allow altering the genomic structure of DNA. The base editors include BE3, BE4 and ABE7.
BE3 and its later version, BE4 allow to change the nucleobase C to T and nucleobase G to A. ABE7 allows to change A-T base pairs into G-C base pairs. The system works by rearranging the atoms in the target base pair and then tricking cells into fixing the other DNA strand to make the change permanent.
References
Biological engineering
Biotechnology
Genome editing
Molecular biology | DNA-templated organic synthesis | [
"Chemistry",
"Engineering",
"Biology"
] | 199 | [
"Genetics techniques",
"Biological engineering",
"Bioengineering stubs",
"Genome editing",
"Biotechnology stubs",
"Genetic engineering",
"Biotechnology",
"nan",
"Molecular biology",
"Biochemistry"
] |
59,957,256 | https://en.wikipedia.org/wiki/Dibutylchloromethyltin%20chloride | Dibutylchloromethyltin chloride (DBCT) is a toxic organotin compound. It is a potent and irreversible ATP synthase inhibitor. DBCT is a volatile liquid with powerful vesicant effects.
See also
Tributyltin chloride
Oligomycin
References
ATP synthase inhibitors
Organotin compounds
Organochlorides
Blister agents
Tin(IV) compounds | Dibutylchloromethyltin chloride | [
"Chemistry"
] | 85 | [
"Blister agents",
"Chemical weapons",
"Organic compounds",
"Organic compound stubs",
"Organic chemistry stubs"
] |
59,959,559 | https://en.wikipedia.org/wiki/Technology-critical%20element | A technology-critical element (TCE) is a chemical element that is a critical raw material for modern and emerging technologies, resulting in a striking increase in their usage. Similar terms include critical elements, critical materials, energy-critical elements and elements of security.
Many advanced engineering applications, such as clean-energy production, communications and computing, use emergent technologies that utilize numerous chemical elements.
In 2013, the U.S. Department of Energy (DOE) created the Critical Materials Institute to address the issue. In 2015, the European COST Action TD1407 created a network of scientists working and interested on TCEs, from an environmental perspective to potential human health threats.
A study estimated losses of 61 metals to help the development of circular economy strategies, showing that usespans of, often scarce, tech-critical metals are short.
List of technology-critical elements
The set of elements usually considered as TCEs vary depending on the source, but they usually include:
Seventeen rare-earth elements
The six platinum-group elements
Twelve assorted elements
Elements such as oxygen, silicon, and aluminum (among others) are also vital for electronics, but are not included in these lists due to their widespread abundance.
Applications of technology-critical elements
TCEs have a variety of engineering applications in fields such as energy storage, electronics, telecommunication, and transportation. These elements are utilized in cellular phones, batteries, solar panel(s), electric motor(s), and fiber-optic cables. Emerging technologies also incorporate TCEs. Most notably, TCEs are used in the data networking of smart devices tied to the Internet of Things (IoT) and automation.
Environmental considerations
The extraction and processing of TCEs may cause adverse environmental impacts. The reliance on TCEs and critical metals like cobalt can run the risk of the “green curse,” or using certain metals in green technologies whose mining may be damaging to the environment.
The clearing of soil and deforestation that is involved with mining can impact the surrounding biodiversity through land degradation and habitat loss. Acid mine drainage can kill surrounding aquatic life and harm ecosystems. Mining activities and leaching of TCEs can pose significant hazards to human health. Wastewater produced by the processing of TCEs can contaminate groundwater and streams. Toxic dust containing concentrations of metals and other chemicals can be released into the air and surrounding bodies of water.
Deforestation caused by mining results in the release of stored carbon from the ground to the atmosphere in the form of carbon dioxide (CO2).
See also
Conflict resource
List of elements facing shortage
Rare-earth element
Strategic material
Renewable energy#Conservation areas, recycling and rare-earth elements
References
Sets of chemical elements
Scarcity
History of technology
Natural materials
Minerals | Technology-critical element | [
"Physics",
"Technology"
] | 543 | [
"Natural materials",
"Science and technology studies",
"Materials",
"History of technology",
"History of science and technology",
"Matter"
] |
66,326,711 | https://en.wikipedia.org/wiki/Adams%20resolution | In mathematics, specifically algebraic topology, there is a resolution analogous to free resolutions of spectra yielding a tool for constructing the Adams spectral sequence. Essentially, the idea is to take a connective spectrum of finite type and iteratively resolve with other spectra that are in the homotopy kernel of a map resolving the cohomology classes in using Eilenberg–MacLane spectra.
This construction can be generalized using a spectrum , such as the Brown–Peterson spectrum , or the complex cobordism spectrum , and is used in the construction of the Adams–Novikov spectral sequencepg 49.
Construction
The mod Adams resolution for a spectrum is a certain "chain-complex" of spectra induced from recursively looking at the fibers of maps into generalized Eilenberg–Maclane spectra giving generators for the cohomology of resolved spectrapg 43. By this, we start by considering the mapwhere is an Eilenberg–Maclane spectrum representing the generators of , so it is of the formwhere indexes a basis of , and the map comes from the properties of Eilenberg–Maclane spectra. Then, we can take the homotopy fiber of this map (which acts as a homotopy kernel) to get a space . Note, we now set and . Then, we can form a commutative diagramwhere the horizontal map is the fiber map. Recursively iterating through this construction yields a commutative diagramgiving the collection . This meansis the homotopy fiber of and comes from the universal properties of the homotopy fiber.
Resolution of cohomology of a spectrum
Now, we can use the Adams resolution to construct a free -resolution of the cohomology of a spectrum . From the Adams resolution, there are short exact sequenceswhich can be strung together to form a long exact sequencegiving a free resolution of as an -module.
E*-Adams resolution
Because there are technical difficulties with studying the cohomology ring in generalpg 280, we restrict to the case of considering the homology coalgebra (of co-operations). Note for the case , is the dual Steenrod algebra. Since is an -comodule, we can form the bigraded groupwhich contains the -page of the Adams–Novikov spectral sequence for satisfying a list of technical conditionspg 50. To get this page, we must construct the -Adams resolutionpg 49, which is somewhat analogous to the cohomological resolution above. We say a diagram of the formwhere the vertical arrows is an -Adams resolution if
is the homotopy fiber of
is a retract of , hence is a monomorphism. By retract, we mean there is a map such that
is a retract of
if , otherwise it is
Although this seems like a long laundry list of properties, they are very important in the construction of the spectral sequence. In addition, the retract properties affect the structure of construction of the -Adams resolution since we no longer need to take a wedge sum of spectra for every generator.
Construction for ring spectra
The construction of the -Adams resolution is rather simple to state in comparison to the previous resolution for any associative, commutative, connective ring spectrum satisfying some additional hypotheses. These include being flat over , on being an isomorphism, and with being finitely generated for which the unique ring mapextends maximally.
If we setand letbe the canonical map, we can setNote that is a retract of from its ring spectrum structure, hence is a retract of , and similarly, is a retract of . In additionwhich gives the desired terms from the flatness.
Relation to cobar complex
It turns out the -term of the associated Adams–Novikov spectral sequence is then cobar complex .
See also
Adams spectral sequence
Adams–Novikov spectral sequence
Eilenberg–Maclane spectrum
Hopf algebroid
References
Algebraic topology
Homological algebra
Topology | Adams resolution | [
"Physics",
"Mathematics"
] | 824 | [
"Mathematical structures",
"Algebraic topology",
"Fields of abstract algebra",
"Topology",
"Space",
"Category theory",
"Geometry",
"Spacetime",
"Homological algebra"
] |
66,333,418 | https://en.wikipedia.org/wiki/Satellite%20dispenser | A satellite dispenser is a space tug usually released from the upper stage (sometimes called kick stage) of a rocket and designed to fly small secondary payloads to their desired location before deploying them.
Project West Ford launched 480,000,000 needles in space in 1961 and 1963 using a dispenser.
The company Moog Inc. launched a satellite dispenser on a Falcon 9 rocket on 14 July 2014, placing 6 Orbcomm satellites in orbit.
SHERPA is a satellite dispenser first launched on 3 December 2018 on a rideshare mission called SSO-A: SmallSat Express. The two SHERPA dispensers placed 64 satellites, after separating from the Falcon 9 Block 5 rocket once it entered a polar Sun-synchronous orbit around 575 kilometers above Earth.
Canisterized Satellite Dispenser is a satellite dispenser created by Planetary Systems Corp, launched on 17 April 2019 with the Cygnus NG-11 mission.
ION CubeSat Carrier is a satellite dispenser launched on 3 September 2020 on a Vega rocket, mission Vega flight VV16, and carried 12 SuperDove satellites from Planet Labs.
The company Launcher is developing an orbital transfer vehicle named Orbiter which will be able to carry up to 90U of cubesats or other smallsats.
See also
KickSat
Space tug
Notes | Satellite dispenser | [
"Astronomy"
] | 286 | [
"Astronomy stubs",
"Spacecraft stubs"
] |
78,006,261 | https://en.wikipedia.org/wiki/Semorinemab | Semorinemab (, ; developmental code names MTAU-9937A, RG-6100, RO-7105705) is a monoclonal antibody against tau which was under development for the treatment of Alzheimer's disease but was discontinued. It binds to the N-terminus of all six isoforms of tau. The drug was ineffective in the treatment of Alzheimer's disease in two phase 2 clinical trials. Clinical development of semorinemab for Alzheimer's disease was discontinued in February 2024.
References
External links
Semorinemab - AlzForum
Abandoned drugs
Experimental drugs for Alzheimer's disease
Experimental monoclonal antibodies | Semorinemab | [
"Chemistry"
] | 135 | [
"Drug safety",
"Abandoned drugs"
] |
78,006,672 | https://en.wikipedia.org/wiki/Dosage%20%28pharmacology%29 | In pharmacology and medicine, dosage refers to the prescribed regimen for administering a medication or substance, encompassing the amount, frequency, and duration of use. It is distinct from dose, which denotes a single, specific quantity of a drug or substance given at one time. Dosage typically includes information on the number of doses, intervals between administrations, and the overall treatment period. For example, a dosage might be described as "200 mg twice daily for two weeks," where 200 mg represents the individual dose, twice daily indicates the frequency, and two weeks specifies the duration of treatment.
References
Medication pharmacology | Dosage (pharmacology) | [
"Chemistry"
] | 129 | [
"Pharmacology",
"Pharmacology stubs",
"Medicinal chemistry stubs"
] |
78,008,724 | https://en.wikipedia.org/wiki/C18H18N4O2 | {{DISPLAYTITLE:C18H18N4O2}}
The molecular formula C18H18N4O2 may refer to:
Armesocarb
Mesocarb | C18H18N4O2 | [
"Chemistry"
] | 41 | [
"Isomerism",
"Set index articles on molecular formulas"
] |
78,010,827 | https://en.wikipedia.org/wiki/Stephan%20Roche | Stephan S. Roche is a Catalan theoretician studying quantum transport theory in condensed matter, spin transport physics and devices simulation. Roche has been a Catalan Institution for Research and Advanced Studies research professor since 2009 and the head of the theoretical & computational nanoscience Group at the Catalan Institute of Nanoscience and Nanotechnology.
Roche works in the fields of theoretical and computational nanoscience, with expertise in quantum transport physics in Dirac materials (graphene & topological insulators) and 2D materials-based van der Waals heterostructures. He made contributions of charge, thermal and spin transport phenomena in complex and disordered condensed matter. He also works on the development of linear scaling quantum transport approaches, methods which are now connected with Artificial Intelligence methods.
Research and career
S. Roche has co-authored around 270 journal papers.
He has been the Editor-in-Chief of J. Phys. Materials (IOP) since 2018 and the main organiser of the conference series GRAPHENE 20XX (www.grapheneconf.com) and, since 2011, QUANTUM MATTER 20XX (www.quantumconf.eu)
Awards and honours
Friedrich Wilhelm Bessel Award (Alexander Von-Humboldt Foundation, Germany) – 2009.
Selected publications
References
Nanotechnologists
Spanish physicists
Condensed matter physicists
Year of birth missing (living people)
Living people | Stephan Roche | [
"Physics",
"Materials_science"
] | 278 | [
"Nanotechnology",
"Condensed matter physicists",
"Condensed matter physics",
"Nanotechnologists"
] |
78,013,417 | https://en.wikipedia.org/wiki/Ammonium%20hexachloroplumbate | Ammonium hexachloroplumbate is an inorganic chemical compound with the chemical formula .
Synthesis
Adding ammonium chloride to a solution of lead(IV) tetraacetate in concentrated hydrochloric acid.
Physical properties
Ammonium hexachloroplumbate forms yellow crystals of cubic system.
The compound is slightly soluble in cold water and decomposes in hot water.
Chemical properties
When added to cold concentrated sulphuric acid, the compound decomposes, yielding :
The compound chlorinates tetraorganolead and hexaorganodilead compounds.
References
Chloro complexes
Ammonium compounds
Chlorometallates | Ammonium hexachloroplumbate | [
"Chemistry"
] | 135 | [
"Ammonium compounds",
"Salts"
] |
78,024,047 | https://en.wikipedia.org/wiki/Hezbollah%20tunnels | Hezbollah's underground tunnels (or Hezbollah Tunnels Network or Hezbollah's Underground Facilities, ) refer to a network of underground passages used by Hezbollah, primarily in southern Lebanon, along the Lebanon-Israel border. These tunnels are often used for military purposes, such as smuggling weapons, storing supplies, and allowing fighters to move discreetly. The tunnels have been a significant concern for Israel, which views them as a direct security threat. The presence of tunnels near the so-called blue line, as well as incursions into Lebanese territory by other countries, constitute a violation of UN Resolution 1701, such violations contribute to the ongoing tensions between Israel and Hezbollah.
History
Nicholas Blanford, a Beirut-based Hezbollah expert considers that Hezbollah's tunnel networks began in the mid-1980s after the 1982 Lebanon War resulting from the invasion of Lebanon by Israel that led to the creation of the Hezbollah. These tunnels were used shortly after launching its own military operations against the occupation state in the 1990s. However, the investment in tunnel construction has been increased since the early 2000s, due partially to the armed conflict with the South Lebanon Army and military operations against Israeli military posts in occupied Lebanese territory, and particularly since the 2006 Lebanon War. Israel has conducted operations to locate and destroy these tunnels, viewing them as a significant threat to its security.
Operation Northern Shield
In December 2018, Israel launched "Operation Northern Shield" to detect and destroy the tunnels. In recent years, the Israeli Defense Forces (IDF) claimed to have found and destroyed several tunnels crossing the border from Lebanon into Israel.
UN involvement
With the resolution 1701 of the Security Council agreed in 2006, the blue line was used to monitor the withdrawal of Israeli forces from southern Lebanon and the activities of armed groups. The resolution states that the area must be free of arms and armed personnel except for the Lebanese armed forces and UN peacekeepers, and no foreign forces can be present in Lebanon without the consent of its government. The United Nations Interim Force in Lebanon (UNIFIL) is responsible for ensuring compliance by all parties with this resolution and has reported violations of resolution UN 1701 by both sides, Israel and Hezbollah, according to the Security Council reports.
The UNIFIL was able to confirm the existence of only three of the tunnels that were reported by IDF. UNIFIL also confirmed that an old concrete factory in Kfar Kela had an opening to the tunnel, which crossed the Blue Line.
Purposes
These tunnels serve various purposes, including:
Military Operations: They allow Hezbollah fighters to move undetected and launch surprise attacks against Israeli forces.
Smuggling: The tunnels are used for smuggling weapons and supplies, often circumventing Israeli surveillance.
Shelter: They provide protection for fighters during airstrikes or ground operations.
Logistics: The network facilitates communication and transportation of goods and personnel.
See also
United Nations Interim Force in Lebanon
Hezbollah
South Lebanon conflict (1985–2000)
Israeli occupation of Southern Lebanon
References
Tunnel warfare
Hezbollah–Israel conflict
Israel–Lebanon border
Tunnels in Lebanon | Hezbollah tunnels | [
"Engineering"
] | 599 | [
"Military engineering",
"Tunnel warfare"
] |
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