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Faradaic loss is only one form of energy loss in an electrochemical system. Another is overpotential, the difference between the theoretical and actual electrode voltages needed to drive the reaction at the desired rate. Even a rechargeable battery with 100% faradaic efficiency requires charging at a higher voltage than it produces during discharge, so its overall energy efficiency is the product of voltage efficiency and faradaic efficiency. Voltage efficiencies below 100% reflect the thermodynamic irreversibility of every real-world chemical reaction. | 0 | Theoretical and Fundamental Chemistry |
Lucy Pevensie, a pivotal character in C. S. Lewiss Chronicles of Narnia, was, as Queen Lucy in The Lion, the Witch and the Wardrobe', gifted a bottle of magical cordial by Father Christmas along with her dagger, prior to the Battle of Beruna. The cordial was said to be made from the juice of Fire-Flowers that grew in the mountains of the sun, with a single drop curing almost any illness or injury, bringing people back from the brink of death in some cases. The use of the word "cordial" by the author was archaic even at the time.
Miruvor (cordial of Imladris) J.R.R. Tolkien, Fellowship of the Ring. | 1 | Applied and Interdisciplinary Chemistry |
Depending on the location of the application and machinability, there exist different kinds of mounts for attaching pneumatic cylinders: | 1 | Applied and Interdisciplinary Chemistry |
The total radiated power is
where (the velocity of the particle divided by the speed of light), is the Lorentz factor, is the vacuum permittivity, signifies a time derivative of and is the charge of the particle.
In the case where velocity is parallel to acceleration (i.e., linear motion), the expression reduces to
where is the acceleration. For the case of acceleration perpendicular to the velocity (), for example in synchrotrons, the total power is
Power radiated in the two limiting cases is proportional to or . Since , we see that for particles with the same energy the total radiated power goes as or , which accounts for why electrons lose energy to bremsstrahlung radiation much more rapidly than heavier charged particles (e.g., muons, protons, alpha particles). This is the reason a TeV energy electron-positron collider (such as the proposed International Linear Collider) cannot use a circular tunnel (requiring constant acceleration), while a proton-proton collider (such as the Large Hadron Collider) can utilize a circular tunnel. The electrons lose energy due to bremsstrahlung at a rate times higher than protons do. | 0 | Theoretical and Fundamental Chemistry |
In spherical coordinates ( r , θ , φ ), r is the radial distance from the origin, θ is the zenith angle and φ is the azimuthal angle. In axisymmetric flow, with θ = 0 the rotational symmetry axis, the quantities describing the flow are again independent of the azimuth φ. The flow velocity components u and u are related to the Stokes stream function through:
Again, the azimuthal velocity component u is not a function of the Stokes stream function ψ. The volume flux through a stream tube, bounded by a surface of constant ψ, equals 2π ψ, as before. | 1 | Applied and Interdisciplinary Chemistry |
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. | 1 | Applied and Interdisciplinary Chemistry |
Pressure jump is a technique used in the study of chemical kinetics. It involves making rapid changes to the pressure of an experimental system and observing the return to equilibrium or steady state. This allows the study of the shift in equilibrium of reactions that equilibrate in periods between milliseconds to hours (or longer), these changes often being observed using absorption spectroscopy, or fluorescence spectroscopy though other spectroscopic techniques such as CD, FTIR or NMR can also be used.
Historically, pressure jumps were limited to one direction. Most commonly fast drops in pressure were achieved by using a quick release valve or a fast burst membrane. Modern equipment can achieve pressure changes in both directions using either double reservoir arrangements (good for large changes in pressure) or pistons operated by piezoelectric actuators (often faster than valve based approaches). Ultra fast pressure drops can be achieved using electrically disintegrated burst membranes. The ability to automatically repeat measurements and average the results is useful since the reaction amplitudes are often small.
The fractional extent of the reaction (i.e. the percentage change in concentration of a measurable species) depends on the molar volume change (ΔV°) between the reactants and products and the equilibrium position. If K is the equilibrium constant and P is the pressure then the volume change is given by:
where R is the universal gas constant and T is the absolute temperature. The volume change can thus be understood to be the pressure dependency of the change in Gibbs free energy associated with the reaction.
When a single step in a reaction is perturbed in a pressure jump experiment, the reaction follows a single exponential decay function with the reciprocal time constant (1/τ) equal to the sum of the forward and reverse intrinsic rate constants. In more complex reaction networks, when multiple reaction steps are perturbed, then the reciprocal time constants are given by the eigenvalues of the characteristic rate equations. The ability to observe intermediate steps in a reaction pathway is one of the attractive features of this technology. | 0 | Theoretical and Fundamental Chemistry |
Excited-state absorption (ESA) occurs when the pump beam sends an electron into an excited state, then the probe beam sends the electron into a higher excited state. This differs from TPA primarily in the timescale over which it occurs. Since an electron can remain in an excited state for a period of nanoseconds, thus requiring longer pulse durations than TPA. | 0 | Theoretical and Fundamental Chemistry |
Stagnation temperature can be derived from the First Law of Thermodynamics. Applying the Steady Flow Energy Equation
and ignoring the work, heat and gravitational potential energy terms, we have:
where:
: mass-specific stagnation (or total) enthalpy at a stagnation point
: mass-specific static enthalpy at the point of interest along the stagnation streamline
: velocity at the point of interest along the stagnation streamline
Substituting for enthalpy by assuming a constant specific heat capacity at constant pressure () we have:
or
where:
: specific heat capacity at constant pressure
: stagnation (or total) temperature at a stagnation point
: temperature (or static temperature) at the point of interest along the stagnation streamline
: velocity at the point of interest along the stagnation streamline
: Mach number at the point of interest along the stagnation streamline
: Ratio of Specific Heats (), ~1.4 for air at ~300 K | 1 | Applied and Interdisciplinary Chemistry |
The journal is abstracted and indexed in MEDLINE and Analytical Abstracts. According to the Journal Citation Reports, the journal has a 2022 impact factor of 4.2. | 0 | Theoretical and Fundamental Chemistry |
Applying 2-D potential flow, if an airfoil with a sharp trailing edge begins to move with an angle of attack through air, the two stagnation points are initially located on the underside near the leading edge and on the topside near the trailing edge, just as with the cylinder. As the air passing the underside of the airfoil reaches the trailing edge it must flow around the trailing edge and along the topside of the airfoil toward the stagnation point on the topside of the airfoil. Vortex flow occurs at the trailing edge and, because the radius of the sharp trailing edge is zero, the speed of the air around the trailing edge should be infinitely fast. Though real fluids cannot move at infinite speed, they can move very fast. The high airspeed around the trailing edge causes strong viscous forces to act on the air adjacent to the trailing edge of the airfoil and the result is that a strong vortex accumulates on the topside of the airfoil, near the trailing edge. As the airfoil begins to move it carries this vortex, known as the starting vortex, along with it. Pioneering aerodynamicists were able to photograph starting vortices in liquids to confirm their existence.
The vorticity in the starting vortex is matched by the vorticity in the bound vortex in the airfoil, in accordance with Kelvin's circulation theorem. As the vorticity in the starting vortex progressively increases the vorticity in the bound vortex also progressively increases and causes the flow over the topside of the airfoil to increase in speed. The starting vortex is soon cast off the airfoil and is left behind, spinning in the air where the airfoil left it. The stagnation point on the topside of the airfoil then moves until it reaches the trailing edge. The starting vortex eventually dissipates due to viscous forces.
As the airfoil continues on its way, there is a stagnation point at the trailing edge. The flow over the topside conforms to the upper surface of the airfoil. The flow over both the topside and the underside join up at the trailing edge and leave the airfoil travelling parallel to one another. This is known as the Kutta condition.
When an airfoil is moving with an angle of attack, the starting vortex has been cast off and the Kutta condition has become established, there is a finite circulation of the air around the airfoil. The airfoil is generating lift, and the magnitude of the lift is given by the Kutta–Joukowski theorem.
One of the consequences of the Kutta condition is that the airflow over the topside of the airfoil travels much faster than the airflow under the underside. A parcel of air which approaches the airfoil along the stagnation streamline is cleaved in two at the stagnation point, one half traveling over the topside and the other half traveling along the underside. The flow over the topside is so much faster than the flow along the underside that these two halves never meet again. They do not even re-join in the wake long after the airfoil has passed. There is a popular fallacy called the equal transit-time fallacy that claims the two halves rejoin at the trailing edge of the airfoil. This has been understood as a fallacy since Martin Kutta's discovery.
Whenever the speed or angle of attack of an airfoil changes there is a weak starting vortex which begins to form, either above or below the trailing edge. This weak starting vortex causes the Kutta condition to be re-established for the new speed or angle of attack. As a result, the circulation around the airfoil changes and so too does the lift in response to the changed speed or angle of attack.<Ref name=clancy/>
The Kutta condition gives some insight into why airfoils have sharp trailing edges, even though this is undesirable from structural and manufacturing viewpoints.
In irrotational, inviscid, incompressible flow (potential flow) over an airfoil, the Kutta condition can be implemented by calculating the stream function over the airfoil surface.
The same Kutta condition implementation method is also used for solving two dimensional subsonic (subcritical) inviscid steady compressible flows over isolated airfoils.
The viscous correction for the Kutta condition can be found in some of the recent studies. | 1 | Applied and Interdisciplinary Chemistry |
The Young–Dupré equation (Thomas Young 1805, Lewis Dupré 1855) dictates that neither γ nor γ can be larger than the sum of the other two surface energies. The consequence of this restriction is the prediction of complete wetting when γ > γ + γ and zero wetting when γ > γ + γ. The lack of a solution to the Young–Dupré equation is an indicator that there is no equilibrium configuration with a contact angle between 0 and 180° for those situations.
A useful parameter for gauging wetting is the spreading parameter S,
When S > 0, the liquid wets the surface completely (complete wetting).
When S < 0, partial wetting occurs.
Combining the spreading parameter definition with the Young relation yields the Young–Dupré equation:
which only has physical solutions for θ when S < 0. | 0 | Theoretical and Fundamental Chemistry |
It is estimated that approximately half of all proteins contain a metal. In another estimate, about one quarter to one third of all proteins are proposed to require metals to carry out their functions. Thus, metalloproteins have many different functions in cells, such as storage and transport of proteins, enzymes and signal transduction proteins, or infectious diseases. The abundance of metal binding proteins may be inherent to the amino acids that proteins use, as even artificial proteins without evolutionary history will readily bind metals.
Most metals in the human body are bound to proteins. For instance, the relatively high concentration of iron in the human body is mostly due to the iron in hemoglobin. | 1 | Applied and Interdisciplinary Chemistry |
If the reduced masses and momenta of the colliding system are , and , before and after the collision respectively, the differential cross section is given by
where the on-shell matrix is defined by
in terms of the S-matrix. Here is the Dirac delta function. The computation of the S-matrix is the main goal of the scattering theory. | 0 | Theoretical and Fundamental Chemistry |
In tissues, many different cell types interact with one another. In the brain, for example, neurons, astrocytes, and oligodendrocytes (specialized cells of the neural tissue, each with specific functions) interact with one another as well as with cells that comprise blood vessels. All these different cell types may interact with all others by the production of ligands that may activate receptors on the cell surface of other cell types. Understanding the way these different cell types interact with one another will allow to predict ways of activating eNSCs. For example, because eNSCs are found in close proximity with blood vessels, it has been hypothesized that signals (e.g., ligands) from cells comprising the blood vessel act on receptors found on the cell surface of eNSCs.
Endogenous neural stem cells are often in close physical proximity to blood vessels. Signals from blood vessels regulate their interaction with stem cells and contribute to the cytoarchitecture of the tissue. The STAT3-Ser/Hes3 signaling axis operating in Hes3+ cells is a convergence point for several of these signals (e.g. Delta4, Angiopoietin 2). Hes3, in turn, by regulating the expression of Shh and potentially other factors, can also exert an effect on blood vessels and other cells comprising their microenvironment. | 1 | Applied and Interdisciplinary Chemistry |
Boundary layer separation can occur for internal flows. It can result from such causes such as a rapidly expanding duct of pipe. Separation occurs due to an adverse pressure gradient encountered as the flow expands, causing an extended region of separated flow. The part of the flow that separates the recirculating flow and the flow through the central region of the duct is called the dividing streamline. The point where the dividing streamline attaches to the wall again is called the reattachment point. As the flow goes farther downstream it eventually achieves an equilibrium state and has no reverse flow. | 1 | Applied and Interdisciplinary Chemistry |
Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term as light-induced damage to PSII. In living organisms, photoinhibited PSII centres are continuously repaired via degradation and synthesis of the D1 protein of the photosynthetic reaction center of PSII. Photoinhibition is also used in a wider sense, as dynamic photoinhibition, to describe all reactions that decrease the efficiency of photosynthesis when plants are exposed to light. | 0 | Theoretical and Fundamental Chemistry |
* In 2013, six months prior to opening, the East Span of the Oakland Bay Bridge failed during testing. Catastrophic failures occurred in shear bolts in the span, after only two weeks of service, with the failure attributed to embrittlement (see details above).
* In the City of London, 122 Leadenhall Street, generally known as the Cheesegrater, suffered from hydrogen embrittlement in steel bolts, with three bolts failing in 2014 and 2015. Most of the 3,000 bolts were replaced at a cost of £6m. | 0 | Theoretical and Fundamental Chemistry |
Woods metal, also known as Lipowitzs alloy or by the commercial names Cerrobend, Bendalloy, Pewtalloy and MCP 158, is a metal alloy that is useful for soldering and making custom metal parts, but its vapor is toxic to touch or breathe. The alloy is named for Barnabas Wood, who invented and patented the alloy in 1860. It is a eutectic, fusible alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by mass. It has a melting point of approximately . | 1 | Applied and Interdisciplinary Chemistry |
# Substrate for deubiquitinylating enzyme activity assays.
# Identification/confirmation of enzyme deubiquitinylation activity.
# Investigation of deconjugating enzyme substrate specificity in comparison with alternative UBL-AMC substrates (e.g. NEDD8-AMC) | 1 | Applied and Interdisciplinary Chemistry |
The symbol of a space group is defined by combining the uppercase letter describing the lattice type with symbols specifying the symmetry elements. The symmetry elements are ordered the same way as in the symbol of corresponding point group (the group that is obtained if one removes all translational components from the space group). The symbols for symmetry elements are more diverse, because in addition to rotations axes and mirror planes, space group may contain more complex symmetry elements – screw axes (combination of rotation and translation) and glide planes (combination of mirror reflection and translation). As a result, many different space groups can correspond to the same point group. For example, choosing different lattice types and glide planes one can generate 28 different space groups from point group mmm, e.g. Pmmm, Pnnn, Pccm, Pban, Cmcm, Ibam, Fmmm, Fddd, and so on. In some cases, a space group is generated when translations are simply added to a point group. In other cases there is no point around which the point group applies. The notation is somewhat ambiguous, without a table giving more information. For example, space groups I23 and I23 (nos. 197 and 199) both contain two-fold rotational axes as well as two-fold screw axes. In the first, the two-fold axes intersect the three-fold axes, whereas in the second they do not. | 0 | Theoretical and Fundamental Chemistry |
The genetic code within living organisms can potentially be co-opted to store information. Furthermore synthetic biology can be used to engineer cells with "molecular recorders" to allow the storage and retrieval of information stored in the cell's genetic material. CRISPR gene editing can also be used to insert artificial DNA sequences into the genome of the cell. For encoding developmental lineage data (molecular flight recorder), roughly 30 trillion cell nuclei per mouse * 60 recording sites per nucleus * 7-15 bits per site yields about 2 TeraBytes per mouse written (but only very selectively read). | 1 | Applied and Interdisciplinary Chemistry |
In physics, tunnel ionization is a process in which electrons in an atom (or a molecule) tunnel through the potential barrier and escape from the atom (or molecule). In an intense electric field, the potential barrier of an atom (molecule) is distorted drastically. Therefore, as the length of the barrier that electrons have to pass decreases, the electrons can escape from the atom's potential more easily. Tunneling ionization is a quantum mechanical phenomenon since in the classical picture an electron does not have sufficient energy to overcome the potential barrier of the atom.
When the atom is in a DC external field, the Coulomb potential barrier is lowered and the electron has an increased, non-zero probability of tunnelling through the potential barrier. In the case of an alternating electric field, the direction of the electric field reverses after the half period of the field. The ionized electron may come back to its parent ion. The electron may recombine with the nucleus (nuclei) and its kinetic energy is released as light (high harmonic generation). If the recombination does not occur, further ionization may proceed by collision between high-energy electrons and a parent atom (molecule). This process is known as non-sequential ionization. | 0 | Theoretical and Fundamental Chemistry |
The velocity vector of the fluid may be written in terms of the stream function as
The stream function in a Stokes flow problem, satisfies the biharmonic equation. By regarding the -plane as the complex plane, the problem may be dealt with using methods of complex analysis. In this approach, is either the real or imaginary part of
Here , where is the imaginary unit, , and are holomorphic functions outside of the disk. We will take the real part without loss of generality.
Now the function , defined by is introduced. can be written as , or (using the Wirtinger derivatives).
This is calculated to be equal to
Without loss of generality, the disk may be assumed to be the unit disk, consisting of all complex numbers z of absolute value smaller or equal to 1.
The boundary conditions are:
whenever ,
and by representing the functions as Laurent series:
the first condition implies for all .
Using the polar form of results in .
After deriving the series form of u, substituting this into it along with , and changing some indices, the second boundary condition translates to
Since the complex trigonometric functions compose a linearly independent set, it follows that all coefficients in the series are zero.
Examining these conditions for every after taking into account the condition at infinity shows that and are necessarily of the form
where is an imaginary number (opposite to its own complex conjugate), and and are complex numbers. Substituting this into gives the result that globally, compelling both and to be zero. Therefore, there can be no motion – the only solution is that the cylinder is at rest relative to all points of the fluid. | 1 | Applied and Interdisciplinary Chemistry |
Neuromodulators may alter the output of a physiological system by acting on the associated inputs (for instance, central pattern generators). However, modeling work suggests that this alone is insufficient, because the neuromuscular transformation from neural input to muscular output may be tuned for particular ranges of input. Stern et al. (2007) suggest that neuromodulators must act not only on the input system but must change the transformation itself to produce the proper contractions of muscles as output. | 1 | Applied and Interdisciplinary Chemistry |
The extracellular polymeric substance(EPS) matrix is a very important part of the aerobic granular system because it aggregates the microorganism. EPS brings structural stability to the AGS which promotes microbial aggregation. Many researchers use fluorophores and confocal laser scanning microscopes to observe microbial cells in order to determine the stability of the AGS. | 1 | Applied and Interdisciplinary Chemistry |
When exposure to a carcinogenic substance is suspected, the cause/effect relationship on any given case can never be ascertained. Lung cancer occurs spontaneously, and there is no difference between a "natural" cancer and another one caused by radon (or smoking). Furthermore, it takes years for a cancer to develop, so that determining the past exposure of a case is usually very approximative. The health effect of radon can only be demonstrated through theory and statistical observation.
The study design for epidemiological methods may be of three kinds:
* The best proofs come from observations of cohorts (predetermined populations with known exposures and exhaustive follow-up), such as those on miners, or on Hiroshima and Nagasaki survivors. Such studies are efficient, but very costly when the population needs to be a large one. Such studies can only be used when the effect is strong enough, hence, for high exposures.
* Alternate proofs are case-control studies (the environment factors of a "case" population is individually determined, and compared to that of a "control″ population, to see what the difference might have been, and which factors may be significant), like the ones that have been used to demonstrate the link between lung cancer and smoking. Such studies can identify key factors when the signal/noise ratio is strong enough, but are very sensitive to selection bias, and prone to the existence of confounding factors.
* Lastly, ecological studies may be used (where the global environment variables and their global effect on two different populations are compared). Such studies are "cheap and dirty": they can be easily conducted on very large populations (the whole USA, in Dr Cohen's study), but are prone to the existence of confounding factors, and exposed to the ecological fallacy problem.
Furthermore, theory and observation must confirm each other for a relationship to be accepted as fully proven. Even when a statistical link between factor and effect appears significant, it must be backed by a theoretical explanation; and a theory is not accepted as factual unless confirmed by observations. | 1 | Applied and Interdisciplinary Chemistry |
The C–H···O interaction was discovered in 1937 by Samuel Glasstone. Glasstone studied properties of mixtures of acetone with different halogenated derivatives of hydrocarbons and realized that dipole moments of these mixtures differ from dipole moments of pure substances. He explained this by establishing the concept of C–H···O interactions. The first crystallographic analysis of C-H ⋯O hydrogen bonds were published by June Sutor in 1962. | 0 | Theoretical and Fundamental Chemistry |
The first experiment to achieve controlled thermonuclear fusion was accomplished using Scylla I at LANL in 1958. Scylla I was a θ-pinch machine, with a cylinder full of deuterium. Electric current shot down the sides of the cylinder. The current made magnetic fields that pinched the plasma, raising temperatures to 15 million degrees Celsius, for long enough that atoms fused and produced neutrons. The Sherwood program sponsored a series of Scylla machines at Los Alamos. The program began with 5 researchers and $100,000 in US funding in January 1952. By 1965, a total of $21 million had been spent. The θ-pinch approach was abandoned after calculations showed it could not scale up to produce a reactor. | 0 | Theoretical and Fundamental Chemistry |
Most of the dose is due to the decay of the polonium (Po) and lead (Pb) daughters of Rn. By controlling exposure to the daughters the radioactive dose to the skin and lungs can be reduced by at least 90%. This can be done by wearing a dust mask, and wearing a suit to cover the entire body. Note that exposure to smoke at the same time as radon and radon daughters will increase the harmful effect of the radon. In uranium miners radon has been found to be more carcinogenic in smokers than in non-smokers. | 0 | Theoretical and Fundamental Chemistry |
Thiosulfate is an acceptable common name (but used almost always); functional replacement IUPAC name is sulfurothioate; the systematic additive IUPAC name is trioxidosulfidosulfate(2−) or trioxido-1κO-disulfate(S—S)(2−). The external sulfur atom has a valence of 2 while the central sulfur atom has a valence of 6. The oxygen atoms have a valence of 2.
Thiosulfate also refers to the esters of thiosulfuric acid, e.g. O,S-dimethyl thiosulfate . Such species are rare. | 1 | Applied and Interdisciplinary Chemistry |
Indium gallium arsenide (InGaAs) is a compound III-V semiconductor. It can be applied in two ways for use in TPVs. When lattice-matched to an InP substrate, InGaAs has a bandgap of 0.74 eV, no better than GaSb. Devices of this configuration have been produced with a fill factor of 69% and an efficiency of 15%. However, to absorb higher wavelength photons, the bandgap may be engineered by changing the ratio of In to Ga. The range of bandgaps for this system is from about 0.4 to 1.4 eV. However, these different structures cause strain with the InP substrate. This can be controlled with graded layers of InGaAs with different compositions. This was done to develop of device with a quantum efficiency of 68% and a fill factor of 68%, grown by MBE. This device had a bandgap of 0.55 eV, achieved in the compound InGaAs. It is a well-developed material. InGaAs can be made to lattice match perfectly with Ge resulting in low defect densities. Ge as a substrate is a significant advantage over more expensive or harder-to-produce substrates. | 0 | Theoretical and Fundamental Chemistry |
PG5 has a molecular mass of about 200 MDa or 200,000,000 g/mol. It has roughly 20 million atoms and a diameter of roughly 10 nm. Its length is up to a few micrometers. It is similar in size to a tobacco mosaic virus with comparable length and diameter. PG5 was shown to be resistant against attempts to flatten its structure. | 0 | Theoretical and Fundamental Chemistry |
If we introduce a large number of particles with uniformly distributed impact parameters, the rate at which they exit the system is known as the decay rate. We can calculate the decay rate by simulating the system over many trials and forming a histogram of the delay time, T. For the GR system, it is easy to see that the delay time and the length of the particle trajectory are equivalent but for a multiplication coefficient. A typical choice for the impact parameter is the y-coordinate, while the trajectory angle is kept constant at zero degrees—horizontal. Meanwhile, we say that the particle has "exited the system" once it passes a border some arbitrary, but sufficiently large, distance from the centre of the system.
We expect the number of particles remaining in the system, N(T), to vary as:
Thus the decay rate, , is given as:
where n is the total number of particles.
Figure 3 shows a plot of the path-length versus the number of particles for a simulation of one million (1e6) particles started with random impact parameter, b. A fitted straight line of negative slope, is overlaid. The path-length, s, is equivalent to the decay time, T, provided we scale the (constant) speed appropriately.
Note that an exponential decay rate is a property specifically of hyperbolic chaotic scattering. Non-hyperbolic scatterers may have an arithmetic decay rate. | 0 | Theoretical and Fundamental Chemistry |
Plaque hybridization is a technique used in Molecular biology for the identification of recombinant phages.
The procedure can also be used for the detection of differentially represented repetitive DNA.
The technique (similar to colony hybridization) involves hybridizing isolated phage DNA to a label probe for the gene of study. This is followed by autoradiography to detect the position of the label.
The plaque hybridization procedure has some advantages over colony hybridization due to the smaller and well defined area of the filter to which the DNA binds. | 1 | Applied and Interdisciplinary Chemistry |
Sabatier is best known for the Sabatier process and his works such as La Catalyse en Chimie Organique (Catalysis in organic chemistry) which was published in 1913. He won the Nobel Prize in Chemistry jointly with fellow Frenchman Victor Grignard in 1912. He is also known for the Sabatier principle of catalysis.
The reduction of carbon dioxide using hydrogen at high temperature and pressure is another use of nickel catalyst to produce methane.
:∆H = −165.0 kJ/mol
:(some initial energy/heat is required to start the reaction) | 0 | Theoretical and Fundamental Chemistry |
As a base, pyridine can be used as the Karl Fischer reagent, but it is usually replaced by alternatives with a more pleasant odor, such as imidazole.
Pyridinium chlorochromate, pyridinium dichromate, and the Collins reagent (the complex of chromium(VI) oxide) are used for the oxidation of alcohols. | 0 | Theoretical and Fundamental Chemistry |
At first, the study of biometals was referred to as bioinorganic chemistry. Each branch of bioinorganic chemistry studied separate, particular sub-fields of the subject. However, this led to an isolated view of each particular aspect in a biological system. This view was revised into a holistic approach of biometals in metallomics.
Metal ions in biology were studied in various specializations. In nutrition, it was to define the essentials for life; in toxicology, to define how the adverse effects of certain metal ions in biological systems and in pharmacology for their therapeutic effects. In each field, at first, they were studied and separated on a basis of concentration. In low amounts, metal ions in a biological system could perform at their optimal functionality whereas in higher concentrations, metal ions can prove fatal to biological systems. However, the concentration gradients were proved to be arbitrary as low concentrations of non-essential metals (like lithium or helium) in essential metals (like sodium or potassium) can cause an adverse effect in biological systems and vice versa.
Investigations into biometals and their effects date back to the 19th century and even further back to the 18th century with the identification of iron in blood. Zinc was identified to be essential in fungal growth of yeast as shown by Jules Raulin in 1869 yet no proof for the need of zinc in human cells was shown until the late 1930s where its presence was demonstrated in carbonic anhydrase and the 1960s where it was identified as a necessary element for humans. Since then, understanding of zinc in human biology has advanced to the point that it is considered as important as iron. Modern advancements in analytical technology have made it clear the importance of biometals in signalling pathways and the initial thoughts on the chemical basis of life. | 1 | Applied and Interdisciplinary Chemistry |
*Demonstration model heat engines have been built which use nitinol wire to produce mechanical energy from hot and cold heat sources. A prototype commercial engine developed in the 1970s by engineer Ridgway Banks at Lawrence Berkeley National Laboratory, was named the Banks Engine.
*Nitinol is also popular in extremely resilient glasses frames. It is also used in some mechanical watch springs.
*Boeing engineers successfully flight-tested SMA-actuated morphing chevrons on the Boeing 777-300ER Quiet Technology Demonstrator 2.
*The Ford Motor Company has registered a US patent for what it calls a "bicycle derailleur apparatus for controlling bicycle speed". Filed on 22 April 2019, the patent depicts a front derailleur for a bicycle, devoid of cables, instead using two nitinol wires to provide the movement needed to shift gears.
*It can be used as a temperature control system; as it changes shape, it can activate a switch or a variable resistor to control the temperature.
*It has been used in cell-phone technology as a retractable antenna, or microphone boom, due to its highly flexible and mechanical memory nature.
*It is used to make certain surgical implants, such as the SmartToe.
*It is used in some novelty products, such as self-bending spoons which can be used by amateur and stage magicians to demonstrate "psychic" powers or as a practical joke, as the spoon will bend itself when used to stir tea, coffee, or any other warm liquid.
*It can also be used as wires which are used to locate and mark breast tumours so that the following surgery can be more exact.
*Due to the high damping capacity of superelastic nitinol, it is also used as a golf club insert.
*Nickel titanium can be used to make the underwires for underwire bras.
*It is used in the neckbands of several headphones due to its superelasticity and durability.
*It is being increasingly used for wire stemmed fishing floats due to its superelasticity. | 1 | Applied and Interdisciplinary Chemistry |
Irving Langmuir accurately described the geometric structure of a monolayer film on water in 1917, work for which he would be later awarded the Nobel prize in chemistry. The evaporation suppressing properties of these materials were first reported by Rideal in the 1920s In the 1940s Langmuir and Schaefer quantified the evaporation resistance and its dependence on temperature. This work was extended by Archer and La Mer in the following decade, who observed a dependence on surface pressure, chain length, monolayer phase, subphase composition and surface temperature. Large scale field trials were being conducted at this time in Australia by Mansfield He reported that the results seen in the laboratory setting could not be replicated in real world conditions, with dust and wind being cited as adversely affecting evaporation suppressing performance.
In later decades, research efforts focussed on multicomponent monolayer materials such as hexadecanol + octadecanol, altering the number of carbons in the aliphatic chain, and later on, the addition of polymerised surfactants to increase monolayer stability.
Better monolayer materials are required as are better methods of monolayer distribution methods, although no resolution of these difficulties presently exists.
Despite research in this area for most of the 20th century, no durable, effective and inexpensive product has come to market. Recently, advances in experimental and modelling techniques have increased the understanding of these materials. | 0 | Theoretical and Fundamental Chemistry |
* Favorskii rearrangement of α-haloketones in presence of base
* Baeyer–Villiger oxidation of ketones with peroxides
* Pinner reaction of nitriles with an alcohol
* Nucleophilic abstraction of a metal–acyl complex
*Hydrolysis of orthoesters in aqueous acid
*Cellulolysis via esterification
* Ozonolysis of alkenes using a work up in the presence of hydrochloric acid and various alcohols.
* Anodic oxidation of methyl ketones leading to methyl esters.
* Interesterification exchanges the fatty acid groups of different esters. | 0 | Theoretical and Fundamental Chemistry |
Yuan Chengye (; 1924–2018) was a Chinese organic chemist.
Yuan was born in Shangyu, Zhejiang province in 1924. He graduated from National College of Pharmacy (now China Pharmaceutical University) in 1948 and received Degree for Candidate for D.Sc from All-Union Research Institute of Pharmaceutical Chemistry, Moscow in 1955. He worked at the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences after returning to China. He led a research team for nuclear fuel extractants since 1958. In 1997, he was elected an academician of the Chinese Academy of Sciences. He died on 9 January 2018. | 0 | Theoretical and Fundamental Chemistry |
Shock is an abrupt discontinuity in the flow field and it occurs in flows when the local flow speed exceeds the local sound speed. More specifically, it is a flow whose Mach number exceeds 1. | 1 | Applied and Interdisciplinary Chemistry |
In DNA, regulation of gene expression normally happens at the level of RNA biosynthesis (transcription). It is accomplished through the sequence-specific binding of proteins (transcription factors) that activate or inhibit transcription. Transcription factors may act as activators, repressors, or both. Repressors often act by preventing RNA polymerase from forming a productive complex with the transcriptional initiation region (promoter), while activators facilitate formation of a productive complex. Furthermore, DNA motifs have been shown to be predictive of epigenomic modifications, suggesting that transcription factors play a role in regulating the epigenome.
In RNA, regulation may occur at the level of protein biosynthesis (translation), RNA cleavage, RNA splicing, or transcriptional termination. Regulatory sequences are frequently associated with messenger RNA (mRNA) molecules, where they are used to control mRNA biogenesis or translation. A variety of biological molecules may bind to the RNA to accomplish this regulation, including proteins (e.g., translational repressors and splicing factors), other RNA molecules (e.g., miRNA) and small molecules, in the case of riboswitches. | 1 | Applied and Interdisciplinary Chemistry |
Jack Richard Norton (born May 5, 1945) is an American organometallic chemist and Professor at Columbia University. His research has focused on the studying the reactivity and properties of transition metal hydrides. He coauthored the textbook "Principles and Applications of Organotransition Metal Chemistry." | 0 | Theoretical and Fundamental Chemistry |
By the first law of thermodynamics, the excitation driving electron generation in both photo- and phonovoltaic cells, i.e., the photon or phonon, must have more energy than the semiconductor band gap. For a PV cell, many materials are available with a band gap () well matched to the solar photon spectrum, like Silicon or Gallium Arsenide. For a pV cell, however, no current semiconducting materials have a band gap smaller than the energy of their most energetic (optical) phonon modes (). Thus, novel materials are required with both energetic optical phonon modes ( meV, e.g., graphene, diamond, or boron nitride) and a small band gap (, e.g., graphene).
By the second law of thermodynamics, the excitation must be "hotter" than the cell for power generation to occur. In a PV, the light comes from an outside source, for example, the sun, which is nearly 6000 kelvins, whereas the PV is around 300 kelvins. Thus, the second law is satisfied and energy conversion is possible. However, the crystal vibrations driving power generation in a pV are intrinsic to the material itself. As such, they can not be imported from an outside source like the sun, but must instead be excited by some other process until they are hotter than the cell. The temperature of the optical phonon population is calculated by comparing the number of optical phonon to the number expected at a given temperature, which comes from the Bose–Einstein statistics. | 0 | Theoretical and Fundamental Chemistry |
Surface flow wetlands, also known as free water surface constructed wetlands, can be used for tertiary treatment or polishing of effluent from wastewater treatment plants. They are also suitable to treat stormwater drainage.
Surface flow constructed wetlands always have horizontal flow of wastewater across the roots of the plants, rather than vertical flow. They require a relatively large area to purify water compared to subsurface flow constructed wetlands and may have increased smell and lower performance in winter.
Surface flow wetlands have a similar appearance to ponds for wastewater treatment (such as "waste stabilization ponds") but are in the technical literature not classified as ponds.
Pathogens are destroyed by natural decay, predation from higher organisms, sedimentation and UV irradiation since the water is exposed to direct sunlight. The soil layer below the water is anaerobic but the roots of the plants release oxygen around them, this allows complex biological and chemical reactions.
Surface flow wetlands can be supported by a wide variety of soil types including bay mud and other silty clays.
Plants such as water hyacinth (Eichhornia crassipes) and Pontederia spp. are used worldwide (although Typha and Phragmites are highly invasive).
However, surface flow constructed wetlands may encourage mosquito breeding. They may also have high algae production that lowers the effluent quality and due to open water surface mosquitos and odours, it is more difficult to integrate them in an urban neighbourhood. | 1 | Applied and Interdisciplinary Chemistry |
Examples of other type of method of the magnetic particle capturing device are as follows.
* Pen type capture
* Tube type capture | 1 | Applied and Interdisciplinary Chemistry |
While a reaction may exhibit one set of kinetic behavior at early conversion, that behavior may change due to:
* changes in catalyst resting state influenced by changing substrate concentrations
* multiple or changing mechanisms influenced by substrate or product concentrations
* catalyst activation (an initiation period)
* product inhibition
* irreversible (or reversible) catalyst death
In the case of saturation kinetics described above, provided that [A] is not present in a large excess relative to [B], saturation conditions will only apply at the beginning of the reaction. As the substrate is consumed, the concentration decreases and eventually [A] is no longer sufficient to completely overwhelm [Cat]. This is manifested by a gradual change in rate from 0-order to some higher (i.e. 1st, 2nd, etc.) order in [A]. This can also be described as a change in catalyst resting state from the bound form to the unbound form over the course of the reaction.
In addition to simply slowing the reaction, a change in catalyst resting state over the course of the reaction may result in competing paths or processes. Multiple mechanisms may be present to access the product, in which case the order in catalyst or substrate may change depending on the conditions or point in the reaction. A particularly useful probe for changes in reaction mechanism involves examination of the normalized reaction rate vs. catalyst loading at multiple, fixed conversion points. Note that the normalized reaction rate:
:k =
adjusts for the consumption of substrate over the course of the reaction, so only rate changes due to catalyst loading will be observed. A linear dependence on catalyst loading for a given conversion is indicative of a first order dependence on catalyst at that conversion, and one can similarly imagine the non-linear plots resulting from higher order dependence. Changes in the linearity or non-linearity from one set of conversion points to another are indicative of changes in the dependence on catalyst over the course of the reaction. Conversely, changes in the linearity or non-linearity of regions of the plot conserved over multiple conversion points (i.e. at 30, 50, and 70%) are indicative of a change in the dependence on catalyst based on the absolute catalyst concentration.
Catalyst interactions with multiple components of a reaction mixture can lead to a complex kinetic dependence. While off-cycle catalyst-substrate or catalyst-product interactions are generally considered "poisonous" to the system (certainly the case in the event of irreversible complexation) cases do exist in which the off-cycle species actually protects the catalyst from permanent deactivation.
In either case, it is often essential to understand the role of the catalyst resting state. | 0 | Theoretical and Fundamental Chemistry |
Metals, under the right conditions, burn in a process similar to the combustion of wood or gasoline. In fact, rust is the result of oxidation of steel or iron at very slow rates. A thermite reaction results when the correct mixtures of metallic fuels combine and ignite. Ignition itself requires extremely high temperatures.
Ignition of a thermite reaction normally requires a sparkler or easily obtainable magnesium ribbon, but may require persistent efforts, as ignition can be unreliable and unpredictable. These temperatures cannot be reached with conventional black powder fuses, nitrocellulose rods, detonators, pyrotechnic initiators, or other common igniting substances. Even when the thermite is hot enough to glow bright red, it does not ignite, as it has a very high ignition temperature. Starting the reaction is possible using a propane torch if done correctly.
Often, strips of magnesium metal are used as fuses. Because metals burn without releasing cooling gases, they can potentially burn at extremely high temperatures. Reactive metals such as magnesium can easily reach temperatures sufficiently high for thermite ignition. Magnesium ignition remains popular among amateur thermite users, mainly because it can be easily obtained, but a piece of the burning strip can fall off into the mixture, resulting in premature ignition.
The reaction between potassium permanganate and glycerol or ethylene glycol is used as an alternative to the magnesium method. When these two substances mix, a spontaneous reaction begins, slowly increasing the temperature of the mixture until it produces flames. The heat released by the oxidation of glycerine is sufficient to initiate a thermite reaction.
Apart from magnesium ignition, some amateurs also choose to use sparklers to ignite the thermite mixture. These reach the necessary temperatures and provide enough time before the burning point reaches the sample. This can be a dangerous method, as the iron sparks, like the magnesium strips, burn at thousands of degrees and can ignite the thermite, though the sparkler itself is not in contact with it. This is especially dangerous with finely powdered thermite.
Match heads burn hot enough to ignite thermite. Use of match heads enveloped with aluminium foil and a sufficiently long viscofuse/electric match leading to the match heads is possible.
Similarly, finely powdered thermite can be ignited by a flint spark lighter, as the sparks are burning metal (in this case, the highly reactive rare-earth metals lanthanum and cerium). Therefore, it is unsafe to strike a lighter close to thermite. | 0 | Theoretical and Fundamental Chemistry |
Soils represent a short to long-term carbon storage medium, and contain more carbon than all terrestrial vegetation and the atmosphere combined. Plant litter and other biomass including charcoal accumulates as organic matter in soils, and is degraded by chemical weathering and biological degradation. More recalcitrant organic carbon polymers such as cellulose, hemi-cellulose, lignin, aliphatic compounds, waxes and terpenoids are collectively retained as humus.
Organic matter tends to accumulate in litter and soils of colder regions such as the boreal forests of North America and the Taiga of Russia. Leaf litter and humus are rapidly oxidized and poorly retained in sub-tropical and tropical climate conditions due to high temperatures and extensive leaching by rainfall. Areas where shifting cultivation or slash and burn agriculture are practiced are generally only fertile for two to three years before they are abandoned. These tropical jungles are similar to coral reefs in that they are highly efficient at conserving and circulating necessary nutrients, which explains their lushness in a nutrient desert.
Grasslands contribute to soil organic matter, stored mainly in their extensive fibrous root mats. Due in part to the climatic conditions of these regions (e.g. cooler temperatures and semi-arid to arid conditions), these soils can accumulate significant quantities of organic matter. This can vary based on rainfall, the length of the winter season, and the frequency of naturally occurring lightning-induced grass-fires. While these fires release carbon dioxide, they improve the quality of the grasslands overall, in turn increasing the amount of carbon retained in the humic material. They also deposit carbon directly to the soil in the form of biochar that does not significantly degrade back to carbon dioxide.
Wetlands are a natural carbon sink, however climate change can cause these biomes to turn into a carbon source. The high temperature and low water resulted from climate change causes the wetland to transform into a carbon source. This can be seen in peatbogs which are a type of wetland. They undergoes slow anaerobic decomposition below the surface. This process is slow enough that in many cases the bog grows rapidly and fixes more carbon from the atmosphere than is released. Over time, the peat grows deeper. Peat bogs hold approximately one-quarter of the carbon stored in land plants and soils. | 0 | Theoretical and Fundamental Chemistry |
The polymerase chain reaction (PCR) is a biochemistry and molecular biology technique for isolating and exponentially amplifying a fragment of DNA, via enzymatic replication, without using a living organism. It enables the detection of specific strands of DNA by making millions of copies of a target genetic sequence. The target sequence is essentially photocopied at an exponential rate, and simple visualisation techniques can make the millions of copies easy to see.
The method works by pairing the targeted genetic sequence with custom designed complementary bits of DNA called primers. In the presence of the target sequence, the primers match with it and trigger a chain reaction. DNA replication enzymes use the primers as docking points and start doubling the target sequences. The process is repeated over and over again by sequential heating and cooling until doubling and redoubling has multiplied the target sequence several million-fold. The millions of identical fragments are then purified in a slab of gel, dyed, and can be seen with UV light. It is not prone to contamination. Irrespective of the variety of methods used for DNA analysis, only PCR in its different formats has been widely applied in GMO detection/analysis and generally accepted for regulatory compliance purposes. Detection methods based on DNA rely on the complementarity of two strands of DNA double helix that hybridize in a sequence-specific manner. The DNA of GMO consists of several elements that govern its functioning. The elements are promoter sequence, structural gene and stop sequence for the gene. | 1 | Applied and Interdisciplinary Chemistry |
In 1944, Lewis Ferry Moody plotted the Darcy–Weisbach friction factor against Reynolds number Re for various values of relative roughness ε / D.
This chart became commonly known as the Moody chart or Moody diagram.
It adapts the work of Hunter Rouse
but uses the more practical choice of coordinates employed by R. J. S. Pigott, whose work was based upon an analysis of some 10,000 experiments from various sources.
Measurements of fluid flow in artificially roughened pipes by J. Nikuradse were at the time too recent to include in Pigott's chart.
The chart's purpose was to provide a graphical representation of the function of C. F. Colebrook in collaboration with C. M. White, which provided a practical form of transition curve to bridge the transition zone between smooth and rough pipes, the region of incomplete turbulence. | 1 | Applied and Interdisciplinary Chemistry |
In mainland China, modafinil is strictly controlled like other stimulants such as amphetamines and methylphenidate. It is classified as Class I psychotropic drug. This classification means that modafinil is considered to have a high potential for abuse and dependence, and is therefore subject to strict regulation and control. As a result, modafinil is only available by prescription and cannot be purchased over the counter. In order to obtain a prescription for modafinil, a patient must have a valid medical reason for using the drug, such as narcolepsy or sleep apnea. Additionally, the prescription must be written by a licensed physician and filled at a licensed pharmacy. The use of modafinil for non-medical purposes, such as with the aim to improve cognitive performance or to stay awake for long periods of time, is strictly prohibited and can result in legal consequences. | 0 | Theoretical and Fundamental Chemistry |
GFP can be used to analyse the colocalization of proteins. This is achieved by "splitting" the protein into two fragments which are able to self-assemble, and then fusing each of these to the two proteins of interest. Alone, these incomplete GFP fragments are unable to fluoresce. However, if the two proteins of interest colocalize, then the two GFP fragments assemble together to form a GFP-like structure which is able to fluoresce. Therefore, by measuring the level of fluorescence it is possible to determine whether the two proteins of interest colocalize. | 1 | Applied and Interdisciplinary Chemistry |
Magnetic gradiometers are pairs of magnetometers with their sensors separated, usually horizontally, by a fixed distance. The readings are subtracted to measure the difference between the sensed magnetic fields, which gives the field gradients caused by magnetic anomalies. This is one way of compensating both for the variability in time of the Earth's magnetic field and for other sources of electromagnetic interference, thus allowing for more sensitive detection of anomalies. Because nearly equal values are being subtracted, the noise performance requirements for the magnetometers is more extreme.
Gradiometers enhance shallow magnetic anomalies and are thus good for archaeological and site investigation work. They are also good for real-time work such as unexploded ordnance (UXO) location. It is twice as efficient to run a base station and use two (or more) mobile sensors to read parallel lines simultaneously (assuming data is stored and post-processed). In this manner, both along-line and cross-line gradients can be calculated. | 0 | Theoretical and Fundamental Chemistry |
For Stirling engines, the Schmidt number is related to the specific power.
Gustav Schmidt of the German Polytechnic Institute of Prague published an analysis in 1871 for the now-famous closed-form solution for an idealized isothermal Stirling engine model.
where:
* is the Schmidt number
* is the heat transferred into the working fluid
* is the mean pressure of the working fluid
* is the volume swept by the piston. | 1 | Applied and Interdisciplinary Chemistry |
The main function of chemokines is to manage the migration of leukocytes (homing) in the respective anatomical locations in inflammatory and homeostatic processes.
Basal: homeostatic chemokines are basal produced in the thymus and lymphoid tissues. Their homeostatic function in homing is best exemplified by the chemokines CCL19 and CCL21 (expressed within lymph nodes and on lymphatic endothelial cells) and their receptor CCR7 (expressed on cells destined for homing in cells to these organs). Using these ligands is possible routing antigen-presenting cells (APC) to lymph nodes during the adaptive immune response. Among other homeostatic chemokine receptors include: CCR9, CCR10, and CXCR5, which are important as part of the cell addresses for tissue-specific homing of leukocytes. CCR9 supports the migration of leukocytes into the intestine, CCR10 to the skin and CXCR5 supports the migration of B-cell to follicles of lymph nodes. As well CXCL12 (SDF-1) constitutively produced in the bone marrow promotes proliferation of progenitor B cells in the bone marrow microenvironment.
Inflammatory: inflammatory chemokines are produced in high concentrations during infection or injury and determine the migration of inflammatory leukocytes into the damaged area. Typical inflammatory chemokines include: CCL2, CCL3 and CCL5, CXCL1, CXCL2 and CXCL8. A typical example is CXCL-8, which acts as a chemoattractant for neutrophils. In contrast to the homeostatic chemokine receptors, there is significant promiscuity (redundancy) associated with binding receptor and inflammatory chemokines. This often complicates research on receptor-specific therapeutics in this area. | 1 | Applied and Interdisciplinary Chemistry |
In medicinal chemistry, parallel artificial membrane permeability assay (PAMPA) is a method which determines the permeability of substances from a donor compartment, through a lipid-infused artificial membrane into an acceptor compartment. A multi-well microtitre plate is used for the donor and a membrane/acceptor compartment is placed on top; the whole assembly is commonly referred to as a “sandwich”. At the beginning of the test, the drug is added to the donor compartment, and the acceptor compartment is drug-free. After an incubation period which may include stirring, the sandwich is separated and the amount of drug is measured in each compartment. Mass balance allows calculation of drug that remains in the membrane. | 1 | Applied and Interdisciplinary Chemistry |
20 mEq (781 mg) potassium from potassium gluconate (4680 mg), or potassium citrate (2040 mg), mixed a half-cup (1.12 dL) water, taken two to four times a day, may be used on daily basis. | 1 | Applied and Interdisciplinary Chemistry |
Initially used to approximate chemical reaction rates, models of isotope fractionation are used throughout the physical sciences. In chemistry, the Urey–Bigeleisen–Mayer equation has been used to predict equilibrium isotope effects and interpret the distributions of isotopes and isotopologues within systems, especially as deviations from their natural abundance. The model is also used to explain isotopic shifts in spectroscopy, such as those from nuclear field effects or mass independent effects. In biochemistry, it is used to model enzymatic kinetic isotope effects. Simulation testing in computational systems biology often uses the Bigeleisen–Mayer model as a baseline in the development of more complex models of biological systems. Isotope fractionation modeling is a critical component of isotope geochemistry and can be used to reconstruct past Earth environments as well as examine surface processes. | 0 | Theoretical and Fundamental Chemistry |
Gamma-ray radiography systems capable of scanning trucks usually use cobalt-60 or caesium-137 as a radioactive source and a vertical tower of gamma detectors. This gamma camera is able to produce one column of an image. The horizontal dimension of the image is produced by moving either the truck or the scanning hardware. The cobalt-60 units use gamma photons with a mean energy 1.25 MeV, which can penetrate up to 15–18 cm of steel. The systems provide good quality images which can be used for identifying cargo and comparing it with the manifest, in an attempt to detect anomalies. It can also identify high-density regions too thick to penetrate, which would be the most likely to hide nuclear threats. | 0 | Theoretical and Fundamental Chemistry |
In the United States, overall availability of IVF in 2005 was 2.5 IVF physicians per 100,000 population, and utilisation was 236 IVF cycles per 100,000. 126 procedures are performed per million people per year. Utilisation highly increases with availability and IVF insurance coverage, and to a significant extent also with percentage of single persons and median income. In the US, an average cycle, from egg retrieval to embryo implantation, costs $12,400, and insurance companies that do cover treatment, even partially, usually cap the number of cycles they pay for. As of 2015, more than 1 million babies had been born utilising IVF technologies.
In the US, nineteen states have laws requiring insurance coverage for infertility treatment, and thirteen of those specifically include IVF. These states that mandate IVF coverage are: Arkansas, California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Louisiana, Maryland, Massachusetts, Montana, New Hampshire, New Jersey, New York, Ohio, Rhode Island, Texas, Utah, and West Virginia. These laws differ by state but many require an egg be fertilised with sperm from a spouse and that in order to be covered you must show you cannot become pregnant through penile-vaginal sex. These requirements are not possible for a same-sex couple to meet. No state Medicaid program, however, covers for IVF according to a 2020 report.
Many fertility clinics in the United States limit the upper age at which people are eligible for IVF to 50 or 55 years. These cut-offs make it difficult for people older than fifty-five to utilise the procedure. | 1 | Applied and Interdisciplinary Chemistry |
Carboxypeptidase E is found in all species of vertebrates that have been examined, and is also present in many other organisms that have been studied (nematode, sea slug). Carboxypeptidase E is not found in the fruit fly (Drosophila), and another enzyme (presumably carboxypeptidase D) fills in for carboxypeptidase E in this organism. In humans, CPE is encoded by the CPE gene. | 1 | Applied and Interdisciplinary Chemistry |
In statistical mechanics, the radial distribution function, (or pair correlation function) in a system of particles (atoms, molecules, colloids, etc.), describes how density varies as a function of distance from a reference particle.
If a given particle is taken to be at the origin O, and if is the average number density of particles, then the local time-averaged density at a distance from O is . This simplified definition holds for a homogeneous and isotropic system. A more general case will be considered below.
In simplest terms it is a measure of the probability of finding a particle at a distance of away from a given reference particle, relative to that for an ideal gas. The general algorithm involves determining how many particles are within a distance of and away from a particle. This general theme is depicted to the right, where the red particle is our reference particle, and blue particles are those whose centers are within the circular shell, dotted in orange.
The radial distribution function is usually determined by calculating the distance between all particle pairs and binning them into a histogram. The histogram is then normalized with respect to an ideal gas, where particle histograms are completely uncorrelated. For three dimensions, this normalization is the number density of the system multiplied by the volume of the spherical shell, which symbolically can be expressed as .
Given a potential energy function, the radial distribution function can be computed either via computer simulation methods like the Monte Carlo method, or via the Ornstein–Zernike equation, using approximative closure relations like the Percus–Yevick approximation or the Hypernetted Chain Theory. It can also be determined experimentally, by radiation scattering techniques or by direct visualization for large enough (micrometer-sized) particles via traditional or confocal microscopy.
The radial distribution function is of fundamental importance since it can be used, using the Kirkwood–Buff solution theory, to link the microscopic details to macroscopic properties. Moreover, by the reversion of the Kirkwood-Buff theory, it is possible to attain the microscopic details of the radial distribution function from the macroscopic properties. The radial distribution function may also be inverted to predict the potential energy function using the Ornstein-Zernike equation or structure-optimized potential refinement. | 0 | Theoretical and Fundamental Chemistry |
Ge-V can be created during the diamond growth, or by ion implantation and subsequent annealing at 800 °C. The former way results in lower lattice strain, as revealed by the spread in the position and width of the Ge-V ZPL. | 0 | Theoretical and Fundamental Chemistry |
Ionophores are widely used in cell physiology experiments and biotechnology as these compounds can effectively perturb gradients of ions across biological membranes and thus they can modulate or enhance the role of key ions in the cell. Many ionophores have shown antibacterial and antifungal activities. Some of them also act against insects, pests and parasites. Some ionophores have been introduced into medicinal products for dermatological and veterinary use. A large amount of research has been directed toward investigating novel antiviral, anti-inflammatory, anti-tumor, antioxidant and neuroprotective properties of different ionophores.
Chloroquine is an antimalarial and antiamebic drug. It is also used in the management of rheumatoid arthritis and lupus erythematosus. Pyrithione is used as an anti-dandruff agent in medicated shampoos for seborrheic dermatitis. It also serves as an anti-fouling agent in paints to cover and protect surfaces against mildew and algae. Clioquinol and PBT2 are 8-hydroxyquinoline derivatives. Clioquinol has antiprotozoal and topical antifungal properties, however its use as an antiprotozoal agent has widely restricted because of neurotoxic concerns. Clioquinol and PBT2 are currently being studied for neurodegenerative diseases, such as Alzheimers disease, Huntingtons disease and Parkinson's disease. Gramicidin is used in throat lozenges and has been used to treat infected wounds. Epigallocatechin gallate is used in many dietary supplements and has shown slight cholesterol-lowering effects. Quercetin has a bitter flavor and is used as a food additive and in dietary supplements. Hinokitiol (ß-thujaplicin) is used in commercial products for skin, hair and oral care, insect repellents and deodorants. It is also used as a food additive, shelf-life extending agent in food packaging, and wood preservative in timber treatment.
Polyene antimycotics, such as nystatin, natamycin and amphotericin B, are a subgroup of macrolides and are widely used antifungal and antileishmanial medications. These drugs act as ionophores by binding to ergosterol in the fungal cell membrane and making it leaky and permeable for K and Na ions, as a result contributing to fungal cell death.
Carboxylic ionophores, i.e. monensin, lasalocid, salinomycin, narasin, maduramicin, semduramycin and laidlomycin, are marketed globally and widely used as anticoccidial feed additives to prevent and treat coccidiosis in poultry. Some of these compounds have also been used as growth and production promoters in certain ruminants, such as cattle, and chickens, however this use has been mainly restricted because of safety issues.
Zinc ionophores have been shown to inhibit replication of various viruses in vitro, including coxsackievirus, equine arteritis virus, coronavirus, HCV, HSV, HCoV-229E, HIV, mengovirus, MERS-CoV, rhinovirus, SARS-CoV-1, Zika virus. | 0 | Theoretical and Fundamental Chemistry |
Cost of the sequestration (not including capture and transport) varies but is below US$10 per tonne in some cases where onshore storage is available. For example Carbfix cost is around US$25 per tonne of CO. A 2020 report estimated sequestration in forests (so including capture) at US$35 for small quantities to US$280 per tonne for 10% of the total required to keep to 1.5 C warming. But there is risk of forest fires releasing the carbon. | 0 | Theoretical and Fundamental Chemistry |
The chief advantage over direct amperometry is that the magnitude of the measured current is of interest only as an indicator. Thus, factors that are of critical importance to quantitative amperometry, such as the surface area of the working electrode, completely disappear from amperometric titrations.
The chief advantage over other types of titration is the selectivity offered by the electrode potential, as well as by the choice of titrant. For instance, lead ion is reduced at a potential of -0.60 V (relative to the saturated calomel electrode), while zinc ions are not; this allows the determination of lead in the presence of zinc. Clearly this advantage depends entirely on the other species present in the sample. | 0 | Theoretical and Fundamental Chemistry |
The discovery of proton and neutron demonstrated that an atom was divisible; this rendered Lavoisier's definition of a chemical element obsolete. A chemical element is defined today as a species of atoms with a consistent number of protons and that number is now known to be precisely the atomic number of an element. The discovery also explained the mechanism of several types of radioactive decay, such as alpha decay.
Eventually, it was proposed that protons and neutrons were made of even smaller particles called quarks; their discovery explained the transmutation of neutrons into protons in beta decay. | 1 | Applied and Interdisciplinary Chemistry |
Silyl enol ethers are generally prepared by reacting an enolizable carbonyl compound with a silyl electrophile and a base, or just reacting an enolate with a silyl electrophile. Since silyl electrophiles are hard and silicon-oxygen bonds are very strong, the oxygen (of the carbonyl compound or enolate) acts as the nucleophile to form a Si-O single bond.
The most commonly used silyl electrophile is trimethylsilyl chloride. To increase the rate of reaction, trimethylsilyl triflate may also be used in the place of trimethylsilyl chloride as a more electrophilic substrate.
When using an unsymmetrical enolizable carbonyl compound as a substrate, the choice of reaction conditions can help control whether the kinetic or thermodynamic silyl enol ether is preferentially formed. For instance, when using lithium diisopropylamide (LDA), a strong and sterically hindered base, at low temperature (e.g., -78°C), the kinetic silyl enol ether (with a less substituted double bond) preferentially forms due to sterics. When using triethylamine, a weak base, the thermodynamic silyl enol ether (with a more substituted double bond) is preferred.
Alternatively, a rather exotic way of generating silyl enol ethers is via the Brook rearrangement of appropriate substrates. | 0 | Theoretical and Fundamental Chemistry |
Substituted phenethylamines are a chemical class of organic compounds based upon the phenethylamine structure; the class is composed of all the derivative compounds of phenethylamine which can be formed by replacing, or substituting, one or more hydrogen atoms in the phenethylamine core structure with substituents.
Many substituted phenethylamines are psychoactive drugs, which belong to a variety of different drug classes, including central nervous system stimulants (e.g., amphetamine), hallucinogens (e.g., 2,5-dimethoxy-4-methylamphetamine), entactogens (e.g., 3,4-methylenedioxyamphetamine), appetite suppressants (e.g. phentermine), nasal decongestants and bronchodilators (e.g., pseudoephedrine), antidepressants (e.g. bupropion), antiparkinson agents (e.g., selegiline), and vasopressors (e.g., ephedrine), among others. Many of these psychoactive compounds exert their pharmacological effects primarily by modulating monoamine neurotransmitter systems; however, there is no mechanism of action or biological target that is common to all members of this subclass.
Numerous endogenous compounds – including hormones, monoamine neurotransmitters, and many trace amines (e.g., dopamine, norepinephrine, adrenaline, tyramine, and others) – are substituted phenethylamines. Dopamine
is simply phenethylamine with a hydroxyl group attached to the 3 and 4 position of the benzene ring. Several notable recreational drugs, such as MDMA (ecstasy), methamphetamine, and cathinones, are also members of the class. All of the substituted amphetamines are phenethylamines, as well.
Pharmaceutical drugs that are substituted phenethylamines include phenelzine, phenformin, and fanetizole, among many others. | 1 | Applied and Interdisciplinary Chemistry |
To date, many studies have been conducted on the benefits of selenium intake in reducing the risk of cancer incidence at the nutritional level, indicating that likely selenium functions as an immunostimulator, i.e. reversing the immunosuppression in tumour microenvironment towards antitumour immunity by activating immune cells (e.g. M1 macrophages and CD8+ T-lymphocytes, the elevated number of neutrophils and activated cytotoxic NK cells) and releasing pro-inflammatory cytokines such as IFNγ and TNFα. | 1 | Applied and Interdisciplinary Chemistry |
Sternhell began his career as a research chemist in private industry with Monsanto in 1953. Two years later, he was appointed a senior research officer at CSIRO and remained in that position until 1964. Sternhell was a senior lecturer in the Department of Organic Chemistry at the University of Sydney, from 1964 until 1967. He spent a further ten years as a reader in organic chemistry at the University of Sydney before being appointed Professor of Organic Chemistry. He was an Emeritus Professor from 1999. In 1991–92, he was chairman of the Australian Research Council Chemical Sciences Panel. | 0 | Theoretical and Fundamental Chemistry |
Absorption of light and energy transfer (or conversion) involves colored molecules that can transfer electromagnetic energy, commonly in the form of a laser light source, to other molecules in another form of energy, such as thermal or electrical. These laser addressable colorants, also called near-infrared absorbers, are used in thermal energy conversion, photosensitisation of chemical reactions and the selective absorption of light. Applications areas include optical data storage, as organic photoconductors, as sensitisers in photomedicine, such as photodynamic therapy and photothermal therapy in the treatment of cancer, in photodiagnosis and phototheranostics, and in the photoinactivation of microbes, blood and insects. The absorption of natural sunlight by chromic materials/chromophores is exploited in solar cells for the production of electrical energy via solar cells, using both inorganic photovoltaics and organic materials (organic photovoltaics) and dye sensitized solar cells (DSSCs), and also in the production of useful chemicals via artificial photosynthesis. A developing area is the conversion of light into kinetic energy, often described under the generic term of lightdriven molecular machines. | 0 | Theoretical and Fundamental Chemistry |
Deuterium is one of only five stable nuclides with an odd number of protons and an odd number of neutrons. (H, Li, B, N, Ta; the long-lived radionuclides K, V, La, Lu also occur naturally.) Most odd-odd nuclei are unstable with respect to beta decay, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects. Deuterium, however, benefits from having its proton and neutron coupled to a spin-1 state, which gives a stronger nuclear attraction; the corresponding spin-1 state does not exist in the two-neutron or two-proton system, due to the Pauli exclusion principle which would require one or the other identical particle with the same spin to have some other different quantum number, such as orbital angular momentum. But orbital angular momentum of either particle gives a lower binding energy for the system, primarily due to increasing distance of the particles in the steep gradient of the nuclear force. In both cases, this causes the diproton and dineutron nucleus to be unstable.
The proton and neutron making up deuterium can be dissociated through neutral current interactions with neutrinos. The cross section for this interaction is comparatively large, and deuterium was successfully used as a neutrino target in the Sudbury Neutrino Observatory experiment.
Diatomic deuterium (D or H) has ortho and para nuclear spin isomers like diatomic hydrogen, but with differences in the number and population of spin states and rotational levels, which occur because the deuteron is a boson with nuclear spin equal to one. | 0 | Theoretical and Fundamental Chemistry |
Fougèrite is a relatively recently described naturally occurring green rust mineral. It is the archetype of the fougèrite group in the larger hydrotalcite supergroup of naturally occurring layered double hydroxides. The structure is based on brucite-like layers containing Fe and Fe cations, O and OH anions, with loosely bound [CO] groups and HO molecules between the layers. Fougèrite crystallizes in trigonal system. The ideal formula for fougèrite is [FeFe(OH)][CO]·3HO. Higher degrees of oxidation produce the other members of the fougèrite group, namely trébeurdenite, [FeFeO(OH)][CO]·3HO and mössbauerite, [FeO(OH)][CO]·3HO.
Fougèrite was first found in forested soils near Fougères, Brittany, France, and recognised as a valid mineral species by the International Mineralogical Association in 2002. It is blue-green to bluish-gray in colour, and resembles clay minerals in habit, forming hexagonal platelets of submicron diameter. In this environment, it is intimately intergrown with trébeurdenite, to give varying overall ratios of Fe:Fe. The existence of two intergrown fixed-composition phases has been demonstrated by Mössbauer spectroscopy. The mineral is unstable in air, and decomposes by oxidation, dehydration and decarbonation, to ferrihydrite, and ultimately to lepidocrocite or goethite, FeO(OH). | 1 | Applied and Interdisciplinary Chemistry |
In Cartesian coordinates the advection operator is
where is the velocity field, and is the del operator (note that Cartesian coordinates are used here).
The advection equation for a conserved quantity described by a scalar field is expressed mathematically by a continuity equation:
where is the divergence operator and again is the velocity vector field. Frequently, it is assumed that the flow is incompressible, that is, the velocity field satisfies
In this case, is said to be solenoidal. If this is so, the above equation can be rewritten as
In particular, if the flow is steady, then
which shows that is constant along a streamline.
If a vector quantity (such as a magnetic field) is being advected by the solenoidal velocity field , the advection equation above becomes:
Here, is a vector field instead of the scalar field . | 1 | Applied and Interdisciplinary Chemistry |
Desorption is a physical process that can be very useful for several applications. In this section two applications of thermal desorption are explained. One of them is actually a technique of thermal desorption, temperature programmed desorption, rather than an application itself, but it has plenty of very important applications. The other one is the application of thermal desorption with the aim of reducing pollution. | 0 | Theoretical and Fundamental Chemistry |
There is currently no evidence supporting targeted temperature management use in humans and clinical trials have not been completed. Most of the data concerning hypothermia's effectiveness in treating stroke is limited to animal studies. These studies have focused primarily on ischemic stroke as opposed to hemorrhagic stroke, as hypothermia is associated with a lower clotting threshold. In these animal studies, hypothermia was represented an effective neuroprotectant. The use of hypothermia to control intracranial pressure (ICP) after an ischemic stroke was found to be both safe and practical. | 1 | Applied and Interdisciplinary Chemistry |
In 2008, Hunter married Rosaleen Theresa McHugh. Together they have three children; two sons and one daughter. | 0 | Theoretical and Fundamental Chemistry |
Femtochemistry has been used to show the time-resolved electronic stages of bromine dissociation. When dissociated by a 400 nm laser pulse, electrons completely localize onto individual atoms after 140 fs, with Br atoms separated by 6.0 Å after 160 fs. | 0 | Theoretical and Fundamental Chemistry |
VitaminD (ergocalciferol) and vitaminD (cholecalciferol) share a similar mechanism of action as outlined above. Metabolites produced by vitamin D are named with an er- or ergo- prefix to differentiate them from the D-based counterparts (sometimes with a chole- prefix).
* Metabolites produced from vitaminD tend to bind less well to the vitamin D-binding protein.
* VitaminD can alternatively be hydroxylated to calcifediol by sterol 27-hydroxylase (CYP27A1), but vitaminD cannot.
* Ergocalciferol can be directly hydroxylated at position 24 by CYP27A1. This hydroxylation also leads to a greater degree of inactivation: the activity of calcitriol decreases to 60% of original after 24-hydroxylation, whereas ercalcitriol undergoes a 10-fold decrease in activity on conversion to ercalcitetrol.
It is disputed whether these differences lead to a measurable drop in efficacy (see ). | 1 | Applied and Interdisciplinary Chemistry |
Imines are widely used as intermediates in the synthesis of heterocycles.
*Aromatic imines react with an enol ether to a quinoline in the Povarov reaction.
*Imines react, thermally, with ketenes in [2+2] cycloadditions to form β-lactams in the Staudinger synthesis. Several variants have been described.
*Imine react with dienes in the Imine Diels-Alder reaction to a tetrahydropyridine.
*tosylimines react with α,β-unsaturated carbonyl compound to give allylic amines in the Aza-Baylis–Hillman reaction. | 0 | Theoretical and Fundamental Chemistry |
In gene therapy, gene delivery vectors, such as viruses, can be imaged according either to their particle biodistribution or their transduction pattern. The former means labeling the viruses with a contrast agent, being visible in some imaging modality, such as MRI or SPECT/PET and latter means visualising the marker gene of gene delivery vector to be visible by the means of immunohistochemical methods, optical imaging or even by PCR. Non-invasive imaging has gained popularity as the imaging equipment has become available for research use from clinics.
For example, avidin-displaying baculoviruses could be imaged in rat brain by coating them with biotinylated iron particles, rendering them visible in MR imaging. The biodistribution of the iron-virus particles was seen to concentrate on the choroid plexus cells of lateral ventricles. | 1 | Applied and Interdisciplinary Chemistry |
Butterfly wings also exhibit anisotropic self-cleaning, superhydrophobic properties. The butterfly wings exhibit anisotropy on a one dimensional level, compared to the other biological materials, which exhibited the anisotropy on a two dimensional level. Butterfly wings are composed of overlapping layers of scales, that have the best self-cleaning properties in the radial directions. This anisotropic interface my prove important for fluid controllable interfaces. Alumina layers patterned from the original butterfly wing have been used to mimic the structure and properties of the butterfly wings. Additionally, butterfly wing mimetic structures have used to fabricate anatase titania photoanodes. Butterfly wing structures have also been made using layer-by-layer sol-gel-based deposition and soft lithography molding. | 0 | Theoretical and Fundamental Chemistry |
The Sod shock tube problem, named after Gary A. Sod, is a common test for the accuracy of computational fluid codes, like Riemann solvers, and was heavily investigated by Sod in 1978.
The test consists of a one-dimensional Riemann problem with the following parameters, for left and right states of an ideal gas.
where
::* is the density
::* is the pressure
::* is the velocity
The time evolution of this problem can be described by solving the Euler equations,
which leads to three characteristics, describing the propagation speed of the
various regions of the system. Namely the rarefaction wave, the contact discontinuity and
the shock discontinuity.
If this is solved numerically, one can test against the analytical solution,
and get information how well a code captures and resolves shocks and contact discontinuities
and reproduce the correct density profile of the rarefaction wave. | 1 | Applied and Interdisciplinary Chemistry |
Men have a V̇O max that is 26% higher (6.6 mL/(kg·min)) than women for treadmill and 37.9% higher (7.6 mL/(kg·min)) than women for cycle ergometer on average. V̇O max is on average 22% higher (4.5 mL/(kg·min)) when measured using a cycle ergometer compared with a treadmill. | 1 | Applied and Interdisciplinary Chemistry |
Liquid ammonia will dissolve all of the alkali metals and other electropositive metals such as Ca, Sr, Ba, Eu, and Yb (also Mg using an electrolytic process), giving characteristic blue solutions. For alkali metals in liquid ammonia, the solution is blue when dilute and copper-colored when more concentrated (> 3 molar). These solutions conduct electricity. The blue colour of the solution is due to ammoniated electrons, which absorb energy in the visible region of light. The diffusivity of the solvated electron in liquid ammonia can be determined using potential-step chronoamperometry.
Solvated electrons in ammonia are the anions of salts called electrides.
:Na + 6 NH → [Na(NH)] + e
The reaction is reversible: evaporation of the ammonia solution produces a film of metallic sodium. | 0 | Theoretical and Fundamental Chemistry |
The Platinum-Cobalt Scale (Pt/Co scale or Apha-Hazen Scale ) is a color scale that was introduced in 1892 by chemist Allen Hazen (1869–1930). The index was developed as a way to evaluate pollution levels in waste water. It has since expanded to a common method of comparison of the intensity of yellow-tinted samples. It is specific to the color yellow and is based on dilutions of a 500 ppm platinum cobalt solution. The colour produced by one milligram of platinum cobalt dissolved in one liter of water is fixed as one unit of colour in platinum-cobalt scale. The ASTM has detailed description and procedures in ASTM Designation D1209, "Standard Test Method for Color of Clear Liquids (Platinum-Cobalt Scale)".
Colour may be reported on a water quality report using this scale. | 1 | Applied and Interdisciplinary Chemistry |
Electrocoagulation ("electro", meaning to apply an electrical charge to water, and "coagulation", meaning the process of changing the particle surface charge, allowing suspended matter to form an agglomeration) is an advanced and economical water treatment technology. It effectively removes suspended solids to sub-micrometre levels, breaks emulsions such as oil and grease or latex, and oxidizes and eradicates heavy metals from water without the use of filters or the addition of separation chemicals
A wide range of wastewater treatment techniques are known, which includes biological processes for nitrification, denitrification and phosphorus removal, as well as a range of physico-chemical processes that require chemical addition. The commonly used physico-chemical treatment processes are filtration, air stripping, ion exchange, chemical precipitation, chemical oxidation, carbon adsorption, ultrafiltration (UF), reverse osmosis (RO), electrodialysis, volatilization, and gas stripping. | 1 | Applied and Interdisciplinary Chemistry |
In the late 1990s it was discovered that very distant supernovae were dimmer than expected suggesting that the universes expansion was accelerating rather than slowing down. This revived discussion that Einsteins cosmological constant, long disregarded by physicists as being equal to zero, was in fact some small positive value. This would indicate empty space exerted some form of negative pressure or energy.
There is no natural candidate for what might cause what has been called dark energy but the current best guess is that it is the zero-point energy of the vacuum. One difficulty with this assumption is that the zero-point energy of the vacuum is absurdly large compared to the observed cosmological constant. This issue, called the cosmological constant problem, is one of the greatest unsolved mysteries in physics.
The European Space Agencys Euclid telescope, launched on 1 July 2023, will map galaxies up to 10 billion light years away. By seeing how dark energy influences their arrangement and shape, the mission will allow scientists to see if the strength of dark energy has changed. If dark energy is found to vary throughout time it would indicate it is due to quintessence, where observed acceleration is due to the energy of a scalar field, rather than the cosmological constant. No evidence of quintessence is yet available, but it has not been ruled out either. It generally predicts a slightly slower acceleration of the expansion of the universe than the cosmological constant. Some scientists think that the best evidence for quintessence would come from violations of Einsteins equivalence principle and variation of the fundamental constants in space or time. Scalar fields are predicted by the Standard Model of particle physics and string theory, but an analogous problem to the cosmological constant problem (or the problem of constructing models of cosmological inflation) occurs: renormalization theory predicts that scalar fields should acquire large masses again due to zero-point energy. | 0 | Theoretical and Fundamental Chemistry |
2,2,2-Trichloroethoxycarbonyl (Troc) group is largely used as a protecting group for amines in organic synthesis. | 0 | Theoretical and Fundamental Chemistry |
Also known as the two-site Langmuir equation. This equation describes the adsorption of one adsorbate to two or more distinct types of adsorption sites. Each binding site can be described with its own Langmuir expression, as long as the adsorption at each binding site type is independent from the rest.
where
: – total amount adsorbed at a given adsorbate concentration,
: – maximum capacity of site type 1,
: – maximum capacity of site type 2,
: – equilibrium (affinity) constant of site type 1,
: – equilibrium (affinity) constant of site type 2,
: – adsorbate activity in solution at equilibrium
This equation works well for adsorption of some drug molecules to activated carbon in which some adsorbate molecules interact with hydrogen bonding while others interact with a different part of the surface by hydrophobic interactions (hydrophobic effect). The equation was modified to account for the hydrophobic effect (also known as entropy-driven adsorption):
The hydrophobic effect is independent of concentration, since Therefore, the capacity of the adsorbent for hydrophobic interactions can obtained from fitting to experimental data. The entropy-driven adsorption originates from the restriction of translational motion of bulk water molecules by the adsorbate, which is alleviated upon adsorption. | 0 | Theoretical and Fundamental Chemistry |
From the contamination of the sediment, more of the ecosystem is affected. Organisms in the sediment are now exposed to the new chemicals. Organisms are then ingested by fish and other aquatic animals. These animals now contain concentrations of hazardous chemicals which were secreted from the creosote. Other issues with ecosystems include bioaccumulation. Bioaccumulation occurs when high levels of chemicals are passed to aquatic life near the creosote pilings. Mollusks and other smaller crustaceans are at higher risk because they are directly attached to the surface of wood pilings that are filled with creosote preservative. Studies show that mollusks in these environments take on high concentrations of chemical compounds which will then be transferred through the ecosystem's food chain. Bioaccumulation contributes to the higher concentrations of chemicals within the organisms in the aquatic ecosystems. | 0 | Theoretical and Fundamental Chemistry |
The Fourier-domain version of the a/LCI system uses a superluminescent diode (SLD) with a fiber-coupled output as the light source. A fiber splitter separates the signal path at 90% intensity and the reference path at 10%.
The light from the SLD passes through an optical isolator and subsequently a polarization controller. It has been shown that control of light polarization is important for maximizing optical signal and comparing angular scattering with the Mie scattering model. A polarization-maintaining fiber is used to carry the illumination light to the sample. A second polarization controller is similarly used to control the polarization of the light passing through the reference path.
The output of the fiber on the right is collimated using lens L1 and illuminates the tissue. But because the delivery fiber is offset from the optical axis of the lens, the beam is delivered to the sample at an oblique angle. Backscattered light is then collimated by the same lens and collected by the fiber bundle. The fibers are one focal length from the lens, and the sample is one focal length on the other side. This configuration captures light from the maximum range of angles and minimizes light noise due to specular reflections.
At the distal end of the fiber bundle, light from each fiber is imaged onto the spectrometer. Light from the sample and reference arms are mixed by a beamsplitting cube (BS), and are incident on the entrance slit of an imaging spectrometer. Data from the imaging spectrometer are transferred to a computer via USB interface for signal processing and display of results. The computer also provides control of the imaging spectrometer. | 0 | Theoretical and Fundamental Chemistry |
Microelectrophoresis is a method of studying electrophoresis of various dispersed particles using optical microscopy. This method provides image of moving particles, which is its unique advantage. e.g. observation of RBCs, neutrophiles and bacteria. This type of electrophoresis is carried out in a closed medium with critical observations made by focusing and adjusting the lens of the microscope.
Complexity of this method is associated with electro-osmosis generated by electric field influence on the double layers of the sample cell walls. In the usually used closed cells, this creates Poiseuille type back flow, leading to parabolic velocity profile. There are two stationary layers, where fluid does not move. Position of these stationary layer regarding cell walls depends on the cell geometry. It is possible to focus microscope on this stationary layers and observe particles motion not affected with electro-osmosis.
The second complexity comes from necessity of diluting sample, if it was initially concentrated. Concentration must be sufficiently low for observing individual particles.
Measurement in the low polar fluids present additional problems. These systems have low electrical conductivity and low dielectric permittivity. Electrophoretic mobility is low and this requires high electric field, by factor 10 and higher.
Details of this method are presented in IUPAC Technical Report prepared by a group of most known world experts on the electrokinetic phenomena. | 0 | Theoretical and Fundamental Chemistry |
Sodium hydroxide can be used for the base-driven hydrolysis of esters (also called saponification), amides and alkyl halides. However, the limited solubility of sodium hydroxide in organic solvents means that the more soluble potassium hydroxide (KOH) is often preferred. Touching a sodium hydroxide solution with bare hands, while not recommended, produces a slippery feeling. This happens because oils on the skin such as sebum are converted to soap.
Despite solubility in propylene glycol it is unlikely to replace water in saponification due to propylene glycol's primary reaction with fat before reaction between sodium hydroxide and fat. | 0 | Theoretical and Fundamental Chemistry |
A response is observed in humans where elevated PFOS levels were significantly associated with elevated total cholesterol and LDL cholesterol, highlighting significantly reduced PPAR expression and alluding to PPAR independent pathways predominating over lipid metabolism in humans compared to rodents. | 0 | Theoretical and Fundamental Chemistry |
Humphry Davy was an English chemist and a professor of chemistry at the Londons Royal Institution in the early 1800s. There he performed experiments that cast doubt upon some of Lavoisiers key ideas such as the acidity of oxygen and the idea of a caloric element. Davy was able to show that acidity was not due to the presence of oxygen using muriatic acid (hydrochloric acid) as proof. He also proved that the compound oxymuriatic acid contained no oxygen and was instead an element, which he named chlorine. Through his use of electric batteries at the Royal Institution Davy first isolated chlorine, followed by the isolation of elemental iodine in 1813. Using the batteries Davy was also able to isolate the elements sodium and potassium. From these experiments Davy concluded that the forces that join chemical elements together must be electrical in nature. Davy also opposed the idea that caloric was an immaterial fluid, arguing instead that heat was a type of motion. | 1 | Applied and Interdisciplinary Chemistry |
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