The structure of 2R-(3′S-benzyloxy-5′S-hydroxy-2′R-hydroxymethyl-1′-oxacyclohexan-6′S-yl)-propionic acid-1,5′-lactone,C16H20O5

The title compound is C₁₆H₂₀O₅, MW=292.3, orthorhombic,P2₁2₁2₁,a=9.741(2),b=29.391(7),c=5.354(1) Å from diffractometer measurements,V=1532.8 ų,Z=4,D _c =1.267 g cm^?3,D _o =1.271 g cm^?3 (ether/1,1,2,2-tetrabromoethane), λ(Mo Kα)=0.71069 Å,F(000)=624,μ=1.02 cm^?1, crystal dimensions 0.23×0.23×0.40 mm,R=0.049 for 1164 observed reflections. The molecule contains a possibly significant asymmetric ether linkage between the oxacyclohexane ring and the highly anisotropic benzyl ring. The packing consists of zigzagged chains parallel to thea-axis formed by hydrogen bonds. The chains are separated by van der Waals contacts.     

Effects of the juxtaposition of carbonaceous slit pores on the overall transport behavior of adsorbed fluids

It is a common approximation in the modeling of adsorption in microporous carbons to treat the pores as slit pores, whose walls are considered to consist of an infinite number of graphitic layers. In practice, such an approximation is appropriate as long as the number of graphitic layers in the wall is greater than three. However, it is understood that pore walls in microporous carbons commonly consist of three or fewer layers. As well as affecting the solid--fluid interaction within a pore, such narrow walls permit the interaction of fluid molecules through the wall, with consequences for the adsorption characteristics. We consider the effect that a distributed pore-wall thickness model can have on transport properties. At low density we find that the only significant deviation in the transport properties from the infinite pore-wall thickness model occurs in pores with single-layer walls. For a model of activated carbons with a distribution of pore widths and pore-wall thicknesses, the transport properties are generally insensitive to the effects of finite walls, in terms of both the solid-fluid interaction within a pore and fluid-fluid interaction through the pore walls.     

Calculation of the deuteron quadrupole relaxation rate in a mixture of water and dimethyl sulfoxide

An approach is presented that allows NMR relaxation rates to be determined for a complex mixture, and it is applied to a dimethyl sulfoxide/water solution. This approach is novel for such systems, having only been used for simple systems such as atomic liquids or atomic ions in liquids until now. It involves use of a predetermined, quantum mechanical, multidimensional property surface in a simulation. The results are used in conjunction with the simulated rotational correlation time to calculate the deuteron quadrupole coupling constant (DQCC), in an analogous approach to the one used by experimentalists, and to examine the surprising experimental findings for the composition dependence of the DQCC in the dimethyl sulfoxide/water mixture. Experiments have suggested that the DQCC for a mixture of 5% dimethyl sulfoxide in water is close to the DQCC of ice, whereas its value increases to a value close to the gas value with further dilution.(1) The results are further critically analyzed using combinations of different experimental and theoretical results from the literature.     

The diels-alder chemistry of 1-vinyl-2-pyridones

The Diels-Alder chemistry of a series of 1-vinyl-2-pyridones using a variety of dienophilic species including dimethyl acetylenedicarboxylate, benzyne, maleic anhydride and methyl vinyl ketone has been explored in order to determine the generality of this method for generation of N-vinylisoquinuclidines. In general, the cycloaddition reactions lead to modestly high yeilds of the azabicyclooctane products. In the course of these studies, we noted that retro-Diels-Alder reactions of N-vinylisoquinuclidienones lead to generation of N-vinylisocyanates and a benzene fragment while the corresponding mono-unsaturated isoquinuclidenones form the corresponding pyridones by elimination of an ethylene unit. Lastly, the regio- and stereochemical courses for the π2+ π4 addition reactions of methyl vinyl ketone and 1-vinyl-2-pyridones were investigated. The major products from these reactions appear to result from reaction pathways predicted to be of low energy using first-order molecular orbital methods.     

Supercritical fluid chromatographic analysis for on-line monitoring of hexane removal from soybean oil miscella using liquid carbon dioxide

Liquid carbon dioxide (L-CO2) can be used to separate hexane from hexane/soybean oil (SBO) mixtures (i.e., miscella). An on-line supercritical fluid chromatographic (SFC) method was developed to monitor this separation. L-CO2 (25 degrees C and 9.31 MPa) was passed through 50 mL of a 25% (w/w) hexane miscella and then directed on-line through a SFC injector. After passing 300-L expanded CO2, the hexane concentrations in the L-CO2 were 0.05% and 0.04% for n-hexane and isohexane, respectively and the residual hexane concentrations in the SBO were 3.8 and 3.3 ppm, respectively. This technique provided real time on-line monitoring of the hexane separation process.     

Temporal asymmetry of fluctuations in nonequilibrium steady states: links with correlation functions and nonlinear response

The presence of temporal asymmetries in fluctuation paths of nonequilibrium systems has recently been confirmed numerically in nonequilibrium molecular dynamics simulations of particular deterministic systems. Here we show that this is a common feature of homogeneously driven and thermostatted, reversible, deterministic, chaotic, nonequilibrium systems of interacting particles. This is done by expressing fluctuation paths as correlation functions. The theoretical arguments look rather general, and we expect them to easily extend to other forms of driving and thermostats. The emergence of asymmetry is also justified using the transient time correlation function expression of nonlinear response theory. Numerical simulations are used to verify our arguments.     

A sensitive high-throughput HPLC assay for simultaneous determination of everolimus and clobetasol propionate

A novel sensitive high-throughput high-performance liquid chromatography assay is developed and validated for the simultaneous determination of everolimus and clobetasol propionate in pharmaceutical formulations. The chromatographic separation is achieved on a Zorbax Eclipse XDB-C18 reversed-phase column using a gradient elution, with solvent A: ammonium acetate (pH 6.8; 0.01 M) and solvent B: acetonitrile. The mean recovery ranges from 95.1% to 100.0% for clobetasol propionate and from 97.9% to 103.7% for everolimus. The limit of quantitation for each analyte is 0.02 microg/mL. The percent relative standard deviations are less than 3% for intra- and inter-day analyses. The proposed method can be used for the routine quality control of everolimus and clobetasol propionate in complex pharmaceutical formulations, especially the drug-delivery systems with a low total drug-load.     

Statistical Measures for the Computer-Aided Diagnosis of Mammographic Masses

Abstract

We propose statistical measures for finding masses in mammograms. The measures are based on fitting broken line regressions to local intensity plots of the images. The method is illustrated on a small database of mammograms that have been read by a radiologist and confirmed by operative data. This work illustrates some of the statistical challenges in working with large diagnostic images     

DNA cleavage by the photolysis of cyclopentadienyl metal complexes: mechanistic studies and sequence selectivity of strand scission by CpW(CO)3CH3

[Reaction: see text]. The photolysis of CpW(CO)3Me has been shown to produce methyl radicals and to cleave DNA in a single-stranded manner, and preliminary evidence implicated a carbon-centered radical in this process. In this work, the mechanism of strand scission in this reaction was determined to occur by hydrogen atom abstraction from the 4'- and 5'-positions of the deoxyribose moiety of the backbone of DNA. Additionally, in a side reaction that does not lead to frank strand scission, all four bases of DNA are methylated under these conditions; however, none of these base or backbone modifications lead to the formation of abasic sites.     

Posets with interval upper bound graphs

Competition graphs of transitive acyclic digraphs are strict upper bound graphs. This paper characterizes those posets, which can be considered transitive acyclic digraphs, which have upper bound graphs that are interval graphs. The results proved here may shed some light on the open question of those digraphs which have interval competition graphs.This material is taken from Chapter 3 of my (maiden name Diny) PhD Dissertation.