Ordered OLPS and CF Nth numerators

Definitions, theorems and examples are established for a general model of Laurent polynomial spaces and ordered orthogonal Laurent polynomial sequences, ordered with respect to ordered bases and orthogonal with respect to inner products ·=L°⊙ decomposed into transition functional ⊙ and strong moment functional, or, more generally, sample functional L couplings. Under this formulation that is shown to subsume those in the existing literature, new fundamental results are produced, including necessary and sufficient conditions for ordered OLPS to be sequences of nth numerators of continued fractions, in contrast to the classical result concerning nth denominators which is shown to hold only in special cases.     

New combining rules for rare gas van der waals parameters

New combining rules are proposed for the well depth, ?, and interaction distance, σ, describing nonbonded interatomic forces for rare gas pair interactions. Concepts underlying current combining rules applied in simulations of macromolecular and polymer systems are shown to be incompatible with experimental data on the rare gases. The current combining rules are compared with the new results using the experimental data. Mathematical properties of combining rules are considered, and it is shown how to reduce combining rule formulas from a two-parameter to a single-parameter problem. It is also shown how to graphically analyze combining rules against experimental data. We demonstrate using this analysis technique that the rare gas potentials do not obey a single combining rule for the ? parameter but do follow a single combining rule for the σ parameter. Finally, we demonstrate that a combining rule using both ? and ω can be used to predict the ? parameters for the mixed rare gas pairs. © John Wiley & Sons, Inc.     

Testing shelled corn for aflatoxin, Part III: evaluating the performance of aflatoxin sampling plans

The effects of changes in sample size and/or sample acceptance level on the performance of aflatoxin sampling plans for shelled corn were investigated. Six sampling plans were evaluated for a range of sample sizes and sample acceptance levels. For a given sample size, decreasing the sample acceptance level decreases the percentage of lots accepted while increasing the percentage of lots rejected at all aflatoxin concentrations, and decreases the average aflatoxin concentration in lots accepted and lots rejected. For a given sample size where the sample acceptance level decreases relative to a fixed regulatory guideline, the number of false positives increases and the number of false negatives decreases. For a given sample size where the sample acceptance level increases relative to a fixed regulatory guideline, the number of false positives decreases and the number of false negatives increases. For a given sample acceptance level, increasing the sample size increases the percentage of lots accepted at concentrations below the regulatory guideline while increasing the percentage of lots rejected at concentrations above the regulatory guideline, and decreases the average aflatoxin concentration in the lots accepted while increasing the average aflatoxin concentration in the rejected lots. For a given sample acceptance level that equals the regulatory guideline, increasing the sample size decreases misclassification of lots, both false positives and false negatives.     

Analysis of some metabolites of T-2 toxin, diacetoxyscirpenol and deoxynivalenol by thermospray high-performance liquid chromatography-mass spectrometry

Detection and identification of mycotoxin metabolites is a very challenging task. In order to achieve adequate sensitivity and specificity an analytical technique must overcome serious matrix interferences. Gas chromatography-mass spectrometry (GC-MS) which has the sensitivity and specificity to detect and identify mycotoxin metabolites requires hydrolysis of conjugated metabolites as well as derivatization. Thermospray high-performance liquid chromatography-mass spectrometry (HPLC-MS) offers the sensitivity, specificity, and structural information to detect and identify some mycotoxin metabolites in fecal and urine samples without derivatization. The mycotoxins evaluated in this study include deoxynivalenol (DON), T-2 toxin, and diacetoxyscirpenol. The de-epoxy and hydroxy metabolites of each toxin and the glucuronide conjugate of DON were isolated, extracted, and analyzed to detect their occurrence in animals. The thermospray mass spectra of the toxins showed an [M + H]+ ion and numerous structurally significant fragment ions in the positive ion detection mode. Negative ion detection exhibited primarily [M + acetate]- cluster ions with less fragmentation than observed by positive ion detection. The operation of the interface in the filament-on mode greatly increased the sensitivity in both positive and negative ion detection mode. Detection limits of 50-500 pg injected on column are obtained for these toxins and their metabolites using multiple ion detection. The urine and fecal extracts from rats, hens, and cows did not interfere with the HPLC-MS analysis for the specific metabolites or the glucuronide conjugate.     

Derivation of class II force fields. VIII. Derivation of a general quantum mechanical force field for organic compounds

A class II valence force field covering a broad range of organic molecules has been derived employing ab initio quantum mechanical "observables." The procedure includes selecting representative molecules and molecular structures, and systematically sampling their energy surfaces as described by energies and energy first and second derivatives with respect to molecular deformations. In this article the procedure for fitting the force field parameters to these energies and energy derivatives is briefly reviewed. The application of the methodology to the derivation of a class II quantum mechanical force field (QMFF) for 32 organic functional groups is then described. A training set of 400 molecules spanning the 32 functional groups was used to parameterize the force field. The molecular families comprising the functional groups and, within each family, the torsional angles used to sample different conformers, are described. The number of stationary points (equilibria and transition states) for these molecules is given for each functional group. This set contains 1324 stationary structures, with 718 minimum energy structures and 606 transition states. The quality of the fit to the quantum data is gauged based on the deviations between the ab initio and force field energies and energy derivatives. The accuracy with which the QMFF reproduces the ab initio molecular bond lengths, bond angles, torsional angles, vibrational frequencies, and conformational energies is then given for each functional group. Consistently good accuracy is found for these computed properties for the various types of molecules. This demonstrates that the methodology is broadly applicable for the derivation of force field parameters across widely differing types of molecular structures. Copyright 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1782-1800, 2001     

Preface

In life sciences,molecules are categorized into biological macromolecules(protein,DNA,RNA etc.)and small molecules(neurotransmitters,vitamins,drugs,natural products,water etc.).The main methodology of chemistry for life sciences is using chemical techniques and tools to explore and manipulate the functions of biological macromolecules.This methodology can be traced back to W hler’s synthesis of urea from"inorganic"compounds in 1828.Today,we realize that chemistry can advance a molecular understanding of biology,and the harnessing of biology can advance chemical knowledge as well[1–4].Chemicals are widely used as probes to investigate biological functions[5–7].     

Flow Compactifications of Nondiscrete Monoids, Idempotents and Hindman's Theorem

We describe the extension of the multiplication on a not-necessarily-discrete topological monoid to its flow compactification. We offer two applications. The first is a nondiscrete version of Hindman's Theorem, and the second is a characterization of the projective minimal and elementary flows in terms of idempotents of the flow compactification of the monoid.     

Warm plasma dispersion relation of the fast Alfven wave forasymmetrical heating current drive

Experimental observation of current drive by asymmetrical heating of ions in the Texas Tech Tokamak suggests that penetration of the fast Alfven wave near the fundamental ion-cyclotron resonance is restricted. A numerical study of the warm plasma dispersion relation near the ion-cyclotron resonance does indeed show this effect. The data reveal that, as the wave approaches the resonant layer from the high or low field side of the torus, it first passes through a region where asymmetrical heating takes place and the wave energy is absorbed by ions moving with high velocity parallel to the magnetic field     

Density functional studies of molecular structures of N-methyl formamide, N,N-dimethyl formamide, and N,N-dimethyl acetamide

Density functional theory was applied to the calculation of molecular structures of N-methyl formamide (NMF), N,N-dimethyl formamide (DMF), and N,N-dimethyl acetamide (DMA). DFT calculations on NMF, DMF, and DMA were performed using a combination of the local functional of Vosko, Wilk, and Nusair (VWN) with the nonlocal exchange functional of Becke and the nonlocal correlational functional of Lee, Yang, and Parr (BLYP). The adiabatic connection method (ACM) of Becke has also been used, for the first time, for the calculation of molecular structures of NMF, DMF, and DMA. The calculated molecular structures are in excellent agreement with the experimental geometries of NMF and DMA derived from gas-phase electron-diffraction studies. Sparse experimental data on the gas-phase geometry of DMF reported in the literature compares well with the DFT results on DMF. DFT emerges as a powerful method to calculate molecular structures.     

Links between microscopic and macroscopic fluid mechanics

The microscopic and macroscopic versions of fluid mechanics differ qualitatively. Microscopic particles obey time-reversible ordinary differential equations. The resulting particle trajectories {q(t)} may be time-averaged or ensemble-averaged so as to generate field quantities corresponding to macroscopic variables. On the other hand, the macroscopic continuum fields described by fluid mechanics follow irreversible partial differential equations. Smooth particle methods bridge the gap separating these two views of fluids by solving the macroscopic field equations with particle dynamics that resemble molecular dynamics. Recently, nonlinear dynamics have provided some useful tools for understanding the relationship between the microscopic and macroscopic points of view. Chaos and fractals play key roles in this new understanding. Non-equilibrium phase-space averages look very different from their equilibrium counterparts. Away from equilibrium the smooth phase-space distributions are replaced by fractional-dimensional singular distributions that exhibit time irreversibility.