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are controlled by the interfaces between minerals and their environment. The atomic-scale structure and chemical properties of mineral–solution interfaces are studied using in situ synchrotron X-ray techniques such as X-ray reflectivity, X-ray standing waves, and X-ray absorption spectroscopy as well as scanning probe ...	{ "page_id": 68513, "title": "Surface science" }
torr) partial pressure of a contaminant and standard temperature, it only takes on the order of 1 second to cover a surface with a one-to-one monolayer of contaminant to surface atoms, so much lower pressures are needed for measurements. This is found by an order of magnitude estimate for the (number) specific surface ...	{ "page_id": 68513, "title": "Surface science" }
the size, shape, and orientation of nanoparticles on surfaces. The crystal structure and texture of thin films can be investigated using grazing-incidence X-ray diffraction (GIXD, GIXRD). X-ray photoelectron spectroscopy (XPS) is a standard tool for measuring the chemical states of surface species and for detecting the...	{ "page_id": 68513, "title": "Surface science" }
Heterogeneous gold catalysis refers to the use of elemental gold as a heterogeneous catalyst. As in most heterogeneous catalysis, the metal is typically supported on metal oxide. Furthermore, as seen in other heterogeneous catalysts, activity increases with a decreasing diameter of supported gold clusters. Several indu...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
cost is affected by only ~1%. Therefore, green gold catalysis is considered valuable. The price fluctuation in gold has later led to cease the operations based on their use in catalytic converters. Very recently, there has been a lot of developments in gold catalysis for the synthesis of organic molecules including the...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
hydroxide supports such as Be(OH)2, Mg(OH)2, and La(OH)3, with gold clusters of < 1.5 nm in diameter constitute highly active catalysts for CO oxidation at 200 K (-73 °C). By means of techniques such as HR-TEM and EXAFS, it has been proven that the activity of these catalysts is due exclusively to clusters with 13 atom...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
suggests that the mechanism above 333 K takes place on the gold surfaces. By contrast, at 300 K (27 °C), the reaction rate per surface Au atom is inversely proportional to particle diameter, while the rate per perimeter interface does not depend on particle size. Hence, CO oxidation occurs on the perimeter sites at roo...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
H2. It involves the reaction of carbon monoxide and water (syngas) to form hydrogen and carbon dioxide as a byproduct. In many catalytic reaction schemes, one of the elementary reactions is the oxidation of CO with an adsorbed oxygen species. Gold catalysts have been proposed as an alternative for water gas shift at lo...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
°C). The reaction took place in the gas phase. Furthermore, using mesoporous titanosilicate supports (Ti-MCM-41 and Ti-MCM-48), gold catalysts provided > 90% selectivity at ~ 7% propylene conversion, 40% H2 efficiency, and 433 K (160 °C). The active species in these catalysts were identified to be hemispherical gold na...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
K (200 °C). However, the rate of hydrogen activation increases for Au nanoparticles. Notwithstanding its poor activity, nano-sized gold immobilized in various supports has been found to provide a good selectivity in hydrogenation reactions. One of the early studies (1966) of hydrogenation on supported, highly dispersed...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
bond untouched. In the hydrogenation of crotonaldehyde to crotyl alcohol, 80% selectivity was attained at 5-10% conversion and 523 K (250 °C) on Au/ZrO2 and Au/ZnO. The selectivity increased along with Au particle size in the range of ~2 to ~5 nm. Other instances of this reaction include acrolein, citral, benzal aceton...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
~100% selective to p-chloroaniline. In a mechanistic study of hydrogenation of nitrobenzenes with Pt-Au/TiO2, the dissociation of H2 was identified as rate-controlling, hence the incorporation of Pt, an efficient hydrogenation metal, highly improved catalytic activity. Dihydrogen dissociated on Pt and the nitroaromatic...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
the thickness of the deposited particles was decreased below three atomic layers. The two-layer thick supported gold clusters were also shown to be exceptionally active for CO combustion, based on which it was concluded that quantum-size effects inducing a metal-insulator transition play a key role in enhancing the cat...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
of gold clusters, the size-dependency of the d-band width as well as the 5 d 3 / 2 - d 5 / 2 {\displaystyle 5d_{3/2}{\text{-}}d_{5/2}} spin-orbit splitting has been studied from the viewpoint of catalytic activity. As the size of the gold clusters is decreased below 150 atoms (diameter ca. 2.5 nm), rapid drops in both ...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
This is further coupled with the local shift of the d-band center of the unsaturated Au atoms towards energies closer to the Fermi level, which in accordance with the d-band model results in increased substrate-adsorbate interaction and lowering of the adsorption-dissociation energy barriers. Lopez et al. calculated th...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
antibonding 2 π ∗ {\displaystyle 2\pi ^{*}} orbital of oxygen interacts with the metal d-band. As the antibonding orbital is occupied, the O-O bond is significantly weakened and stretched, i.e. activated. In gas-phase model studies, the formation of activated super-oxo species O2− is found to correlate with the size-de...	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
sites where it reacts with O2 to form adsorbed hydroxyl (OH) and hydroperoxo (OOH) species. The reaction of these intermediates with adsorbed CO is very rapid, and results in the efficient formation of CO2 with concomitant recovery of the water molecule. == See also == == References ==	{ "page_id": 57084837, "title": "Heterogeneous gold catalysis" }
Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface. Examples include macroscopic phenomena that can be very obvious, like corrosion, and subtler effects associated with heterogeneous catalysis, where t...	{ "page_id": 68518, "title": "Chemisorption" }
If it loses enough momentum through an inelastic collision, then it "sticks" onto the surface, forming a precursor state bonded to the surface by weak forces, similar to physisorption. The particle diffuses on the surface until it finds a deep chemisorption potential well. Then it reacts with the surface or simply deso...	{ "page_id": 68518, "title": "Chemisorption" }
i } ) = E e l ( { R i } ) + V ion-ion ( { R i } ) {\displaystyle E(\{R_{i}\})=E_{el}(\{R_{i}\})+V_{\text{ion-ion}}(\{R_{i}\})} where E e l {\displaystyle E_{el}} is the energy eigenvalue of the Schrödinger equation for the electronic degrees of freedom and V i o n − i o n {\displaystyle V_{ion-ion}} is the ion interact...	{ "page_id": 68518, "title": "Chemisorption" }
into a precursor state. The molecule then diffuses across the surface to the chemisorption sites. They break the molecular bond in favor of new bonds to the surface. The energy to overcome the activation potential of dissociation usually comes from translational energy and vibrational energy. An example is the hydrogen...	{ "page_id": 68518, "title": "Chemisorption" }
cis-3-Hexenal, also known as (Z)-3-hexenal and leaf aldehyde, is an organic compound with the formula CH3CH2CH=CHCH2CHO. It is classified as an unsaturated aldehyde. It is a colorless liquid and an aroma compound with an intense odor of freshly cut grass and leaves. == Occurrence == It is one of the major volatile comp...	{ "page_id": 1641386, "title": "Cis-3-Hexenal" }
The molecular formula C10H6O2 (molar mass: 158.15 g/mol, exact mass: 158.0368 u) may refer to: Naphthoquinone 1,2-Naphthoquinone 1,4-Naphthoquinone	{ "page_id": 23661478, "title": "C10H6O2" }
Jüri Kärner (25 April 1940 – 25 September 2010) was an Estonian biologist. 1988-1993 he was the rector of Tartu University. Awards: 1997: Order of the National Coat of Arms, III class. == References ==	{ "page_id": 68225964, "title": "Jüri Kärner" }
Dexbrompheniramine is an antihistamine with anticholinergic properties used to treat allergic conditions such as hay fever or urticaria. It is the pharmacologically active dextrorotatory isomer of brompheniramine. It was formerly marketed in combination with pseudoephedrine under the name Drixoral in the US and Canada....	{ "page_id": 5114795, "title": "Dexbrompheniramine" }
AlvaDesc is a commercial software application for the calculation and analysis of molecular descriptors, fingerprints, and structural patterns. Developed by Alvascience, alvaDesc is used in cheminformatics and quantitative structure–activity relationship (QSAR) modeling to numerically describe molecular structures, aid...	{ "page_id": 78908332, "title": "AlvaDesc" }
The strong CP problem is a question in particle physics, which brings up the following quandary: why does quantum chromodynamics (QCD) seem to preserve CP-symmetry? In particle physics, CP stands for the combination of C-symmetry (charge conjugation symmetry) and P-symmetry (parity symmetry). According to the current m...	{ "page_id": 986029, "title": "Strong CP problem" }
− 1 4 F μ ν F μ ν + θ g 2 32 π 2 F μ ν F ~ μ ν + ψ ¯ ( i γ μ D μ − m e i θ ′ γ 5 ) ψ . {\displaystyle {\mathcal {L}}=-{\frac {1}{4}}F_{\mu \nu }F^{\mu \nu }+\theta {\frac {g^{2}}{32\pi ^{2}}}F_{\mu \nu }{\tilde {F}}^{\mu \nu }+{\bar {\psi }}(i\gamma ^{\mu }D_{\mu }-me^{i\theta '\gamma _{5}})\psi .} The first and third ...	{ "page_id": 986029, "title": "Strong CP problem" }
α ) + ( θ + α ) = θ ′ + θ {\displaystyle \theta '+\theta \rightarrow (\theta '-\alpha )+(\theta +\alpha )=\theta '+\theta } remains unchanged. For example, the CP violation due to the mass term can be eliminated by picking α = θ ′ {\displaystyle \alpha =\theta '} , but then all the CP violation goes to the θ-term which...	{ "page_id": 986029, "title": "Strong CP problem" }
the strong CP problem. == Proposed solutions == The strong CP problem is solved automatically if one of the quarks is massless. In that case one can perform a set of chiral transformations on all the massive quark fields to get rid of their complex mass phases and then perform another chiral transformation on the massl...	{ "page_id": 986029, "title": "Strong CP problem" }
5-Formiminotetrahydrofolate is an intermediate in the catabolism of histidine. It is produced by glutamate formimidoyltransferase and then converted into 5,10-methenyltetrahydrofolate by formiminotransferase cyclodeaminase. == References ==	{ "page_id": 11471795, "title": "5-Formiminotetrahydrofolate" }
Glycomimetic is a term used to refer to molecules that have structures similar to carbohydrates, but with some variation. This will normally result in modified biological properties. == Introduction == Often, modification of the structure will take place around the glycosidic linkage. Replacement of one or other of the...	{ "page_id": 32967604, "title": "Glycomimetic" }
groups. Substitution by CF2 rather than methylene has been explored in efforts to address this and come up with better mimetics while still retaining the hydrolytic stability gained by the modification. == Examples of commercially relevant glycomimetic molecules == === Tamiflu === Tamiflu is a carbocyclic mimic of the ...	{ "page_id": 32967604, "title": "Glycomimetic" }
Repulsive guidance molecules (RGMs) are members of a three gene family (in vertebrates) composed of RGMa, RGMb, and RGMc (also called hemojuvelin). RGMa has been implicated to play an important role in the developing brain and in the scar tissue that forms after a brain injury. For example, RGMa helps guide retinal gan...	{ "page_id": 18156469, "title": "Repulsive guidance molecule" }
Inverse vulcanization is a process that produces polysulfide polymers, which also contain some organic linkers. In contrast, sulfur vulcanization produces material that is predominantly organic but has a small percentage of polysulfide crosslinks. == Synthesis == Like Thiokols and sulfur-vulcanization, inverse vulcaniz...	{ "page_id": 59050931, "title": "Inverse vulcanization" }
shown by thermogravimetric analysis (TGA), the copolymer thermal stability increases with the amount of added crosslinker; however, all the tested compositions degrade above 222 °C. Copolymer behavior included that, the glass-transition temperature depends upon the composition and crosslinking species. For given comono...	{ "page_id": 59050931, "title": "Inverse vulcanization" }
these electrochemical devices, again providing high stability over their cycles. In order to overcome the disadvantages related to the materials' low electrical conductivity (1015–1016 Ω·cm), researchers have started to add special carbon-based particles to increase electron transport inside the copolymer. Furthermore,...	{ "page_id": 59050931, "title": "Inverse vulcanization" }
that can function as high performance electrodes for Li-S batteries". 15 April 2013.	{ "page_id": 59050931, "title": "Inverse vulcanization" }
Amidosulfites are chemical compounds containing the group =NS(O)O-. Substituents can attach two bonds to the nitrogen and one to the oxygen. These have the form RR'NS(O)OR" compounds can be a zwitterion with a positive charge on the nitrogen, and a negative charge on the oxygen, which then has no group attached. These ...	{ "page_id": 56429493, "title": "Amidosulfite" }
The Chemical Structure Association Trust (CSA Trust) is an internationally recognized, registered charity which promotes education, research and development in the field of storage, processing and retrieval of information about chemical structures, reactions and compounds. Since 2003 it has incorporated the activities ...	{ "page_id": 12782519, "title": "CSA Trust" }
the Trust. Bursaries, which are also for specific purposes, are age-neutral and requests follow the same procedure as that for the Grant applications and will be evaluated against the same criteria. The awarding of Bursaries in any given year will be determined by the availability of funds. == See also == Cheminformati...	{ "page_id": 12782519, "title": "CSA Trust" }
The molecular formula C10H9N (molar mass: 143.19 g/mol, exact mass: 143.0735 u) may refer to: Benzazepine Lepidine, or 4-methylquinoline 1-Naphthylamine 2-Naphthylamine Quinaldine	{ "page_id": 23661497, "title": "C10H9N" }
Sodium hydrogenoxalate or sodium hydrogen oxalate is a chemical compound with the chemical formula NaHC2O4. It is an ionic compound. It is a sodium salt of oxalic acid H2C2O4. It is an acidic salt, because it consists of sodium cations Na+ and hydrogen oxalate anions HC2O−4 or HO−C(=O)−CO−2, in which only one acidic hy...	{ "page_id": 58461116, "title": "Sodium hydrogenoxalate" }
of oxalic acid and other oxalate or hydrogenoxalate salts, which can follow ingestion or absorption through the skin. The toxic effects include necrosis of tissues due to sequestration of calcium ions Ca2+, and the formation of poorly soluble calcium oxalate stones in the kidneys that can obstruct the kidney tubules. =...	{ "page_id": 58461116, "title": "Sodium hydrogenoxalate" }
SeaSeep is a combination of 2D seismic data (a group of seismic lines acquired individually, as opposed to multiple closely space lines1), high resolution multibeam sonar which is an evolutionary advanced form of side-scan sonar, navigated piston coring (one of the more common sea floor sampling methods2), heat flow sa...	{ "page_id": 15600576, "title": "SeaSeep" }
seep mapping and core geochemistry by Texas A&M University's Geochemical & Environmental Research Group8 and later TDI Brooks9 demonstrated thermogenic charge in deepwater Angola and deepwater Nigeria leading to an aggressive exploration program by a number of oil companies and subsequent discoveries. The emphasis on, ...	{ "page_id": 15600576, "title": "SeaSeep" }
Soil gases (soil atmosphere) are the gases found in the air space between soil components. The spaces between the solid soil particles, if they do not contain water, are filled with air. The primary soil gases are nitrogen, carbon dioxide and oxygen. Oxygen is critical because it allows for respiration of both plant ro...	{ "page_id": 22940609, "title": "Soil gas" }
the kinetic theory of gases, and there is also collision between molecules – a random walk process. In soil, a concentration gradient causes net movement of molecules from high concentration to low concentration, which gives the movement of gas by diffusion. Numerically, it is explained by the Fick's law of diffusion. ...	{ "page_id": 22940609, "title": "Soil gas" }
refers to the limited release of hydrocarbons on the soil surface and can be used to look for petroleum deposits based on the assumption that hydrocarbons vertically migrate to the soil surface in small quantities. Migration of soil gases, specifically radon, can also be examined as earthquake precursors. Furthermore, ...	{ "page_id": 22940609, "title": "Soil gas" }
The School of Life Sciences at the University of Dundee conducts research into the molecular and cellular mechanisms underlying human health and disease. == History == Life Sciences research at the university began within the Department of Physiology. Following a campaign by Robert P. Cook who was a lecturer in Physiol...	{ "page_id": 59182018, "title": "School of Life Sciences (University of Dundee)" }
in the research with several key appointments. As part of the fundraising efforts for this building, Sir Philip Cohen received a donation from Sir Sean Connery that came from part of his salary for his role in the 1991 film Robin Hood Prince of Thieves. A room in the building was named in his honour. The building origi...	{ "page_id": 59182018, "title": "School of Life Sciences (University of Dundee)" }
was named Director of Research and Dean of Life Sciences (Research). The college comprised the following research divisions: Biological Chemistry and Molecular Biology; Cell Biology and Immunology; Gene Regulation and Expression; Cell and Developmental Biology; Molecular Physiology; Environmental and Applied Biology; M...	{ "page_id": 59182018, "title": "School of Life Sciences (University of Dundee)" }
== Reputation == In 2003, an international survey of life scientists by the journal The Scientist named the School the third-best place to work outside the US. In 2011, the College of Life Sciences won the award for the 'Greatest delivery of impact' from the Biotechnology and Biological Sciences Research Council (BBSRC...	{ "page_id": 59182018, "title": "School of Life Sciences (University of Dundee)" }
Athena SWAN === The school was awarded in October 2018 a Silver Athena SWAN award under the extended charter. == Notable alumni == Through its many incarnations over the years, many notable scientists have conducted research in Dundee. Notable faculty alumni include (dates in brackets refer to their time as faculty res...	{ "page_id": 59182018, "title": "School of Life Sciences (University of Dundee)" }
In theoretical physics, fine-tuning is the process in which parameters of a model must be adjusted very precisely in order to fit with certain observations. Theories requiring fine-tuning are regarded as problematic in the absence of a known mechanism to explain why the parameters happen to have precisely the observed ...	{ "page_id": 986051, "title": "Fine-tuning (physics)" }
fine-tuning was traditionally measured by ad hoc fine-tuning measures, such as the Barbieri-Giudice-Ellis measure, over the past decade many scientists recognized that fine-tuning arguments were a specific application of Bayesian statistics. == See also == Anthropic principle Fine-tuned universe Hierarchy problem Stron...	{ "page_id": 986051, "title": "Fine-tuning (physics)" }
Counterimmunoelectrophoresis is a laboratory technique used to evaluate the binding of an antibody to its antigen, it is similar to immunodiffusion, but with the addition of an applied electrical field across the diffusion medium, usually an agar or polyacrylamide gel. The effect is rapid migration of the antibody and ...	{ "page_id": 8850372, "title": "Counterimmunoelectrophoresis" }
The molecular formula C22H27N3O (molar mass: 349.4713 g/mol) may refer to: AL-LAD, or 6-allyl-6-nor-LSD CYP-LAD CUMYL-PINACA, also known as SGT-24	{ "page_id": 61017029, "title": "C22H27N3O" }
The molecular formula C23H27N3O2 (molar mass: 377.48 g/mol, exact mass: 377.2103 u) may refer to: CUMYL-THPINACA (SGT-42) Morazone	{ "page_id": 61017030, "title": "C23H27N3O2" }
The Radiological Research Accelerator Facility (RARAF), located on the Columbia University Nevis Laboratories campus in Irvington, New York is a National Institute of Biomedical Imaging and Bioengineering biotechnology resource center (P41) specializing in microbeam technology. The facility is currently built around a ...	{ "page_id": 27397063, "title": "RARAF" }
developing and improving microbeam technologies. Developments focus on adding and improving imaging techniques to the existing microbeam. Neutron and x-ray microbeams are also in development. Some examples of microbeam developments are listed below. === Microbeam lens === In order to focus charged particles in the RARA...	{ "page_id": 27397063, "title": "RARAF" }
of the stage—dramatically reducing the irradiation time. === X-ray microbeam === The RARAF microbeam is adding an x-ray microbeam using characteristic Kα x rays from Ti. The x rays will be generated using an electrostatic lens system to focus protons onto a thick Ti target. The x rays generated are demagnified using a ...	{ "page_id": 27397063, "title": "RARAF" }
living organisms, have become more common. == Applications of Microfluidics == RARAF is developing various microfluidic devices which add to the irradiation capabilities of the facility. The precision control and manipulation of fluids and biological materials afforded by microfluidics are ideal to interface with the m...	{ "page_id": 27397063, "title": "RARAF" }
Research Experience for Undergraduates program. In addition, RARAF has become a de facto training center for developers of new microbeams. A virtual microbeam training course, complete with videos and handouts, is also available online. == References ==	{ "page_id": 27397063, "title": "RARAF" }
The molecular formula C23H46N6O13 (molar mass: 614.64 g/mol, exact mass: 614.3123 u) may refer to: Neomycin	{ "page_id": 23661513, "title": "C23H46N6O13" }
Policy gradient methods are a class of reinforcement learning algorithms. Policy gradient methods are a sub-class of policy optimization methods. Unlike value-based methods which learn a value function to derive a policy, policy optimization methods directly learn a policy function π {\displaystyle \pi } that selects a...	{ "page_id": 53349322, "title": "Policy gradient method" }
policy gradient is defined as ∇ θ J ( θ ) {\displaystyle \nabla _{\theta }J(\theta )} . Different policy gradient methods stochastically estimate the policy gradient in different ways. The goal of any policy gradient method is to iteratively maximize J ( θ ) {\displaystyle J(\theta )} by gradient ascent. Since the key ...	{ "page_id": 53349322, "title": "Policy gradient method" }
t , n ) ∑ τ ∈ t : T ( γ τ R τ , n ) ] {\displaystyle \nabla _{\theta }J(\theta )\approx {\frac {1}{N}}\sum _{n=1}^{N}\left[\sum _{t\in 0:T}\nabla _{\theta }\ln \pi _{\theta }(A_{t,n}\mid S_{t,n})\sum _{\tau \in t:T}(\gamma ^{\tau }R_{\tau ,n})\right]} where the index n {\displaystyle n} ranges over N {\displaystyle N} ...	{ "page_id": 53349322, "title": "Policy gradient method" }
{\displaystyle \alpha _{i}} is the learning rate at update step i {\displaystyle i} . == Variance reduction == REINFORCE is an on-policy algorithm, meaning that the trajectories used for the update must be sampled from the current policy π θ {\displaystyle \pi _{\theta }} . This can lead to high variance in the updates...	{ "page_id": 53349322, "title": "Policy gradient method" }
special case where b i ≡ 0 {\displaystyle b_{i}\equiv 0} . === Actor-critic methods === If b i {\textstyle b_{i}} is chosen well, such that b i ( S t ) ≈ ∑ τ ∈ t : T ( γ τ R τ ) = γ τ V π θ i ( S t ) {\textstyle b_{i}(S_{t})\approx \sum _{\tau \in t:T}(\gamma ^{\tau }R_{\tau })=\gamma ^{\tau }V^{\pi _{\theta _{i}}}(S_{...	{ "page_id": 53349322, "title": "Policy gradient method" }
∑ 0 ≤ t ≤ T γ t ∇ θ ln ⁡ π θ ( A t \| S t ) ⋅ Q π θ ( S t , A t ) \| S 0 = s 0 ] {\displaystyle \nabla _{\theta }J(\theta )=E_{\pi _{\theta }}\left[\sum _{0\leq t\leq T}\gamma ^{t}\nabla _{\theta }\ln \pi _{\theta }(A_{t}\|S_{t})\cdot Q^{\pi _{\theta }}(S_{t},A_{t}){\Big \|}S_{0}=s_{0}\right]} by a similar argument using t...	{ "page_id": 53349322, "title": "Policy gradient method" }
: never used. γ t ∑ t ≤ τ ≤ T ( γ τ − t R τ ) {\textstyle \gamma ^{t}\sum _{t\leq \tau \leq T}(\gamma ^{\tau -t}R_{\tau })} : used by the REINFORCE algorithm. γ t ∑ t ≤ τ ≤ T ( γ τ − t R τ ) − b ( S t ) {\textstyle \gamma ^{t}\sum _{t\leq \tau \leq T}(\gamma ^{\tau -t}R_{\tau })-b(S_{t})} : used by the REINFORCE with b...	{ "page_id": 53349322, "title": "Policy gradient method" }
− V π θ ( S t ) ) {\textstyle \gamma ^{t}\sum _{n=1}^{\infty }{\frac {\lambda ^{n-1}}{1-\lambda }}\cdot \left(\sum _{k=0}^{n-1}\gamma ^{k}R_{t+k}+\gamma ^{n}V^{\pi _{\theta }}(S_{t+n})-V^{\pi _{\theta }}(S_{t})\right)} : TD(λ) learning, also known as GAE (generalized advantage estimate). This is obtained by an exponent...	{ "page_id": 53349322, "title": "Policy gradient method" }
{\displaystyle {\begin{cases}\max _{\theta _{i+1}}J(\theta _{i})+(\theta _{i+1}-\theta _{i})^{T}\nabla _{\theta }J(\theta _{i})\\{\bar {D}}_{KL}(\pi _{\theta _{i+1}}\\|\pi _{\theta _{i}})\leq \epsilon \end{cases}}} where the KL divergence between two policies is averaged over the state distribution under policy π θ i {\...	{ "page_id": 53349322, "title": "Policy gradient method" }
) − 1 ∇ θ J ( θ i ) {\displaystyle \theta _{i+1}=\theta _{i}+\alpha F(\theta _{i})^{-1}\nabla _{\theta }J(\theta _{i})} The step size α {\displaystyle \alpha } is typically adjusted to maintain the KL constraint, with α ≈ 2 ϵ ( ∇ θ J ( θ i ) ) T F ( θ i ) − 1 ∇ θ J ( θ i ) {\textstyle \alpha \approx {\sqrt {\frac {2\ep...	{ "page_id": 53349322, "title": "Policy gradient method" }
( s , a ) ] {\displaystyle L(\theta ,\theta _{i})=\mathbb {E} _{s,a\sim \pi _{\theta _{i}}}\left[{\frac {\pi _{\theta }(a\|s)}{\pi _{\theta _{i}}(a\|s)}}A^{\pi _{\theta _{i}}}(s,a)\right]} is the surrogate advantage, measuring the performance of π θ {\displaystyle \pi _{\theta }} relative to the old policy π θ i {\displa...	{ "page_id": 53349322, "title": "Policy gradient method" }
However, when θ ≠ θ i {\displaystyle \theta \neq \theta _{i}} , this is not necessarily true. Thus it is a "surrogate" of the real objective. As with natural policy gradient, for small policy updates, TRPO approximates the surrogate advantage and KL divergence using Taylor expansions around θ t {\displaystyle \theta _{...	{ "page_id": 53349322, "title": "Policy gradient method" }
following test-solutions θ i + 1 = θ i + 2 ϵ x T F x x , θ i + α 2 ϵ x T F x x , θ i + α 2 2 ϵ x T F x x , … {\displaystyle \theta _{i+1}=\theta _{i}+{\sqrt {\frac {2\epsilon }{x^{T}Fx}}}x,\;\theta _{i}+\alpha {\sqrt {\frac {2\epsilon }{x^{T}Fx}}}x,\;\theta _{i}+\alpha ^{2}{\sqrt {\frac {2\epsilon }{x^{T}Fx}}}x,\;\dots...	{ "page_id": 53349322, "title": "Policy gradient method" }
) , 1 + ϵ ) A π θ t ( s , a ) if A π θ t ( s , a ) > 0 max ( π θ ( a \| s ) π θ t ( a \| s ) , 1 − ϵ ) A π θ t ( s , a ) if A π θ t ( s , a ) < 0 ] {\displaystyle \max _{\theta }\mathbb {E} _{s,a\sim \pi _{\theta _{t}}}\left[{\begin{cases}\min \left({\frac {\pi _{\theta }(a\|s)}{\pi _{\theta _{t}}(a\|s)}},1+\epsilon \right...	{ "page_id": 53349322, "title": "Policy gradient method" }
same batch of data. It would initialize θ = θ t {\displaystyle \theta =\theta _{t}} , then repeatedly apply gradient descent (such as the Adam optimizer) to update θ {\displaystyle \theta } until the surrogate advantage has stabilized. It would then assign θ t + 1 {\displaystyle \theta _{t+1}} to θ {\displaystyle \thet...	{ "page_id": 53349322, "title": "Policy gradient method" }
This has been used in training reasoning language models with reinforcement learning from human feedback. The KL divergence penalty term can be estimated with lower variance using the equivalent form (see f-divergence for details): − β E s , a ∼ π θ t [ log ⁡ ( π θ ( a \| s ) π ref ( a \| s ) ) + π ref ( a \| s ) π θ ( a ...	{ "page_id": 53349322, "title": "Policy gradient method" }
A π θ t ( s , a i ) if A π θ t ( s , a i ) > 0 max ( π θ ( a i \| s ) π θ t ( a i \| s ) , 1 − ϵ ) A π θ t ( s , a i ) if A π θ t ( s , a i ) < 0 ] {\displaystyle \max _{\theta }{\frac {1}{G}}\sum _{i=1}^{G}\mathbb {E} _{(s,a_{1},\dots ,a_{G})\sim \pi _{\theta _{t}}}\left[{\begin{cases}\min \left({\frac {\pi _{\theta }(a...	{ "page_id": 53349322, "title": "Policy gradient method" }
Lilian (2018-04-08). "Policy Gradient Algorithms". lilianweng.github.io. Retrieved 2025-01-25. "Vanilla Policy Gradient — Spinning Up documentation". spinningup.openai.com. Retrieved 2025-01-25.	{ "page_id": 53349322, "title": "Policy gradient method" }
Intramolecular aglycon delivery is a synthetic strategy for the construction of glycans. This approach is generally used for the formation of difficult glycosidic linkages. == Introduction == Glycosylation reactions are very important reactions in carbohydrate chemistry, leading to the synthesis of oligosaccharides, pr...	{ "page_id": 22416330, "title": "Intramolecular aglycon delivery" }
transformed into an enol ether by the Tebbe reagent (Cp2Ti=CH2), and then the glycosyl acceptor is tethered to the enol ether under acid-catalysed conditions to generate a mixed acetal. In a subsequent step, the β-mannoside is formed upon activation of the anomeric leaving group (Y), followed by work up. ==== Iodonium ...	{ "page_id": 22416330, "title": "Intramolecular aglycon delivery" }
oxidative tethering to para-alkoxybenzyl ethers ==== This is a modification of the method of oxidative tethering to a para-methoxybenzyl ether. The difference here is that the para-alkoxybenzyl group is attached to a solid support; the β-mannoside product is released into the solution phase in the last step, while the ...	{ "page_id": 22416330, "title": "Intramolecular aglycon delivery" }
Combustion analysis is a method used in both organic chemistry and analytical chemistry to determine the elemental composition (more precisely empirical formula) of a pure organic compound by combusting the sample under conditions where the resulting combustion products can be quantitatively analyzed. Once the number o...	{ "page_id": 3738572, "title": "Combustion analysis" }
known amount of sample gives the empirical formula. For every hydrogen atom in the compound 1/2 equivalent of water is produced, and for every carbon atom in the compound 1 equivalent of carbon dioxide is produced. Nowadays, modern instruments are sufficiently automated to be able to do these analyses routinely. Sample...	{ "page_id": 3738572, "title": "Combustion analysis" }
Western equine encephalitis virus is the causative agent of the relatively uncommon viral disease Western equine encephalitis (WEE). An alphavirus of the family Togaviridae, the WEE virus is an arbovirus (arthropod-borne virus) transmitted by mosquitoes of the genera Culex and Culiseta. WEE is a recombinant virus betwe...	{ "page_id": 7539661, "title": "Western equine encephalitis virus" }
from necropsies of horses that had been dead for some time and needed samples from an animal in the earlier stages of disease. When the team heard of a horse that appeared to have encephalitis, its owner threatened to shoot the scientists. However Meyer was able to convince the farmer's wife that the horse was dying an...	{ "page_id": 7539661, "title": "Western equine encephalitis virus" }
In astrophysics, the Eddington number, NEdd, is the number of protons in the observable universe. Eddington originally calculated it as about 1.57×1079; current estimates make it approximately 1080. The term is named for British astrophysicist Arthur Eddington, who in 1940 was the first to propose a value of NEdd and t...	{ "page_id": 461770, "title": "Eddington number" }
mathematical relationship between α and NEdd. On possible roles for NEdd in contemporary cosmology, especially its connection with large number coincidences, see Barrow (2002) (easier) and Barrow & Tipler (1986, pp. 224–231) (harder). == See also == Eddington–Dirac number The Sand Reckoner Universe == References == == ...	{ "page_id": 461770, "title": "Eddington number" }
In applied statistics, the Morris method for global sensitivity analysis is a so-called one-factor-at-a-time method, meaning that in each run only one input parameter is given a new value. It facilitates a global sensitivity analysis by making a number r {\displaystyle r} of local changes at different points x ( 1 → r ...	{ "page_id": 33557455, "title": "Morris method" }
out. When the goal is to rank factors in order of importance by making use of a single sensitivity measure, scientific advice is to use μ ∗ {\displaystyle \mu } , which by making use of the absolute value, avoids the occurrence of effects of opposite signs. In Revised Morris method μ ∗ {\displaystyle \mu } is used to...	{ "page_id": 33557455, "title": "Morris method" }
assumptions about the model, such as for instance additivity or monotonicity of the model input-output relationship. The Morris method is simple to understand and implement, and its results are easily interpreted. Furthermore, it is economic in the sense that it requires a number of model evaluations that is linear in ...	{ "page_id": 33557455, "title": "Morris method" }
In planetary science, any material that has a relatively high equilibrium condensation temperature is called refractory. The opposite of refractory is volatile. The refractory group includes elements and compounds like metals and silicates (commonly termed rocks) which make up the bulk of the mass of the terrestrial pl...	{ "page_id": 19074000, "title": "Refractory (planetary science)" }
Glycopolymer is a synthetic polymer with pendant carbohydrates. Glycopolymers play an important role in many biological recognition events such as cell–cell adhesion, the development of new tissues and the infectious behavior of virus and bacteria. They have high potential in targeted drug delivery, tissue engineering ...	{ "page_id": 31394768, "title": "Glycopolymer" }
The Doebner reaction is the chemical reaction of an aniline with an aldehyde and pyruvic acid to form quinoline-4-carboxylic acids. The reaction serves as an alternative to the Pfitzinger reaction. == Reaction mechanism == The reaction mechanism is not exactly known; two proposals are presented here. One possibility is...	{ "page_id": 13503440, "title": "Doebner reaction" }
Quantum machine learning is the integration of quantum algorithms within machine learning programs. The most common use of the term refers to machine learning algorithms for the analysis of classical data executed on a quantum computer, i.e. quantum-enhanced machine learning. While machine learning algorithms are used ...	{ "page_id": 44108758, "title": "Quantum machine learning" }
result of the quantum computation is read out by measuring the quantum system. For example, the outcome of the measurement of a qubit reveals the result of a binary classification task. While many proposals of quantum machine learning algorithms are still purely theoretical and require a full-scale universal quantum co...	{ "page_id": 44108758, "title": "Quantum machine learning" }

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