Alcohol simulations

Random-oriented powder fixed by frozen alcohol (simulating the ideal polycrystalline sample). 

Ultraviolet spectroscopy is applicable to the determination of phenolic antioxidants in aqueous and alcoholic simulant liquids and also to one of the fatty simulants, liquid paraffin, recommended by the British Plastics Federation (BPF). Full details of the procedure, which is capable of determining down to 1-2 ppm of Santonox R in the simulent liquids, is given next. With the exception of the 5% citric acid simulent, errors are generally of the order of less than 10% of the determined concentration. Typical recoveries of Santonox R in the 5% citric acid extractant were between 15% of the expected result. 

Because alcohol intoxication may be simulated by many pathologic conditions, including diabetic acidosis, the postconvulsive depression of epilepsy, uremia, head injuries, and poisonings by any other central nervous depressant and some stimulants (280), a diagnosis of acute alcoholism should not be made casually chemical testing of blood, urine, or expired air is always desirable. 

U Ryde. Molecular dynamics simulations of alcohol dehydrogenase with a four- or five-coordinate catalytic zinc ion. Proteins 21 40-56, 1995. 

The program will be demonstrated with poly(vinyl alcohol) for tacticity analysis and with copolymer vinylidene chloride isobutylene for monomer sequence analysis. Peak assignments in C-13 spectra were obtained independently by two-dimensional NMR techniques. In some cases, assignments have been extended to longer sequences and confirmed via simulation of the experimental data. Experimental and "best-fit" simulated spectra will be compared. 

From the nitrile. By refluxing a mixture of the aromatic nitrile (with —CN group in side chain) with alcohol and concentrated sulphuric acid simul taneous hydrolysis and esterification occurs, for example ... 

Results of parameter optimization and MD simulations of small model compounds have been published, including alcohols [63], alkanes [63], aromatic [64] and heteroaromatic [209] compounds and liquid amides [65], Studies of ions in aqueous solution were also performed [61, 88] and results from an MD simulation on a DPPC lipid monolayer have been reported (Harder, MacKerell, Roux, submitted). Notable from the monolayer study was the reproduction of the dipole potential across the monolayer, a value that cannot be reproduced using non-polarizable models. This exciting, unforeseen observation points to the types of results that may be obtained from polarizable macromolecular force fields that are not accessible to the present additive models. 

Gao JL, Habibollazadeh D, Shao L (1995) A polarizable intermolecular potential function for simulation of liquid alcohols. J Phys Chem 99(44) 16460-16467... 

When ethanol was used to extract the dye, the efficiency increased to 0.71% the rationale is the higher solubility of the sensitizer in alcohol and minor association which favors a more homogeneous distribution of the anthocyanins on the Ti02 surface. However, exposure to simulated sunlight (AM = 1.5,100 mWcm 2) caused a significant decrease in efficiency after 3h, probably because alcohol favors the photocatalytic decomposition of anthocyanin. 

Using the Onsager model, the function Av-l(t) can be calculated for all time domains of dielectric relaxation of solvents measured experimentally for commonly used liquids (see, for example, [39]). Such simulations, for example, give for alcohols, at least, three different time components of spectral shift during relaxation, which are due to appropriate time domains of solvents relaxation. 

Mentus S, Maroncelli M (1998) Solvation and the excited-state tautomerization of 7-azaindole and 1-azacarbazole computer simulations in water and alcohol solvents. J Phys Chem A 102 3860-3876... 

Schulten and coworkers coupled SMD [23] simulations with the Jarzynski identity [102] to derive the free energy profile for glycerol conduction in the facilitator GlpF, a channel that allows the selective passage of water and small, linear alcohols,... 

A continuous cross-flow filtration process has been utilized to investigate the effectiveness in the separation of nano sized (3-5 nm) iron-based catalyst particles from simulated Fischer-Tropsch (FT) catalyst/wax slurry in a pilot-scale slurry bubble column reactor (SBCR). A prototype stainless steel cross-flow filtration module (nominal pore opening of 0.1 pm) was used. A series of cross-flow filtration experiments were initiated to study the effect of mono-olefins and aliphatic alcohol on the filtration flux and membrane performance. 1-hexadecene and 1-dodecanol were doped into activated iron catalyst slurry (with Polywax 500 and 655 as simulated FT wax) to evaluate the effect of their presence on filtration performance. The 1-hexadecene concentrations were varied from 5 to 25 wt% and 1-dodecanol concentrations were varied from 6 to 17 wt% to simulate a range of FT reactor slurries reported in literature. The addition of 1-dodecanol was found to decrease the permeation rate, while the addition of 1-hexadecene was found to have an insignificant or no effect on the permeation rate. 

The objective of the present study is to develop a cross-flow filtration module operated under low transmembrane pressure drop that can result in high permeate flux, and also to demonstrate the efficient use of such a module to continuously separate wax from ultrafine iron catalyst particles from simulated FTS catalyst/ wax slurry products from an SBCR pilot plant unit. An important goal of this research was to monitor and record cross-flow flux measurements over a longterm time-on-stream (TOS) period (500+ h). Two types (active and passive) of permeate flux maintenance procedures were developed and tested during this study. Depending on the efficiency of different flux maintenance or filter media cleaning procedures employed over the long-term test to stabilize the flux over time, the most efficient procedure can be selected for further development and cost optimization. The effect of mono-olefins and aliphatic alcohols on permeate flux and on the efficiency of the filter membrane for catalyst/wax separation was also studied. 

Polywax 500 and 655 (polyethylene fraction with average molecular weights of 500 and 655, respectively), purchased from Baker Petrolite, Inc., was used to prepare simulated FT wax (i.e., solvent) for the evaluation of flltration performance with and without the presence of aliphatic alcohol and mono-olefin in the FT wax. 1-dodecanol (ACS reagent, > 98%, Sigma-Aldrich, Inc.) and 1-hexadecene (GC standard grade reagent, > 99.8%, Sigma-Aldrich, Inc.) were used as model... 

M. Nagaoka, K. Suenobu, and T. Yamabe, On the hydronium ion cataylsed mechanism in vinyl alcohol-aldehyde isomerization Ab initio molecular orbital theory and Monte Carlo simulation, J. Am. Chem. Soc. 119 8023 (1997). 

The OPLS parameters (charges and Lennard-Jones terms) were obtained primarily via Monte Carlo simulations with particular emphasis on reproducing the experimental densities and heats of vaporization of liquids. Those simulations were performed iteratively as part of the parametrization, so better agreement with experiment is obtained than in previous studies where the simulations were usually carried out after the parametrization. Once the OPLS parametrization was completed, further simulations were also performed in order to test the new set of parameters in the calculation of other thermodynamic and structural properties of the system, besides its density and its heat of vaporization. Parameters have now been generated, among others, for water, alkanes, alkenes, alcohols, amides, alkyl chlorides, amines, carboxylic esters and acids, various sulfur and nitrogen compounds, and nitriles. A protein force field has been established as well. 

After this brief characterisation of reversibility, we may use the example of esterification to consider next the question how the limitation of the reaction is to be explained. To the extent that acid and alcohol interact, and their reaction products, ester and water, are formed, the reverse reaction (ester + water = acid + alcohol) also gains in extent. A point is eventually reached at which just as many molecules of add and alcohol react to form ester as molecules of ester and water are decomposed to form acid and alcohol. The two reactions balance each other, and it would seem as if the reacting system had come to a state of rest. But this apparent rest is simulated by the fact that, in unit time, equal numbers of ester molecules are formed and decomposed. A state of equilibrium has been attained, and, as the above considerations indicate, this state would also have been reached had the reaction proceeded at the outset from the opposite side between equimolecular amounts of ester and water. In the latter case the hydrolysis of the ester would likewise have been balanced sooner or later, according to the conditions prevailing, by the opposing esterification—in this case when 33-3 per cent of the ester had been decomposed. The equilibrium is therefore the same, no matter from which side it is approached on this depends its exact experimental investigation, both here and in many other reactions. 

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