The structures of vanadium oxide cluster-ethene complexes. A combined IR multiple photon dissociation spectroscopy and DFT calculation study

Infrared spectra of complexes of small vanadium oxide clusters with ethene are determined using infrared multiple photon dissociation (IR-MPD) spectroscopy in the range of 550-1850 cm-1. The structures of the complexes have been identified by comparison of the experimental spectra with the harmonic vibrational frequencies and corresponding IR intensities of possible isomers calculated with DFT methods. We find that the ethene molecule binds directly to a vanadium atom in the cluster, although this it is not in all cases the most stable arrangement.     

Some notes on the threshold graphs

In this paper we consider threshold graphs (also called nested split graphs) and investigate some invariants of these graphs which can be of interest in bounding the largest eigenvalue of some graph spectra.     

Statistical investigations of some element distributions in healthy and pathologically altered human colon mucosa

In this paper data are presented concerning the distribution of Cr, Sb, Sc, Fe, Co, and Zn in HCM, of patients with histopathologically and clinically verified findings: Healthy—N; Colitis Chronica-CCh; Colitis Ulcerosa-CU; Adenoma Tubulare-AT; Adenocarcinoma-ACa. The data are presented on the basis of the contents of elements (C_E parameter expressed in nkg/g of lyophilized HCM) obtained by INAA and calculated by computer programs, with statistical parameters (n, XBAR, XMIN-XMAX, R, V, SE and SDEV). The values of C_E parameters of elements found in all diagnostic groups (decreasing order) are also presented. The minimal \(\bar C_E \) parameters for all elements except Zn are found in diagnostic groups AT and ACa. The maximal differences of \(\bar C_E \) parameters in DS-decreasing orders are found for Sb (78.89%) and the minimal for Zn (18.89%).     

Strings, world-sheet covariant quantization and Bohmian mechanics

The covariant canonical method of quantization based on the De Donder–Weyl covariant canonical formalism is used to formulate a world-sheet covariant quantization of bosonic strings. To provide the consistency with the standard non-covariant canonical quantization, it is necessary to adopt a Bohmian deterministic hidden-variable equation of motion. In this way, string theory suggests a solution to the problem of measurement in quantum mechanics. PACS 11.25.-w; 04.60.Ds; 03.65.Ta     

Two-dimensional on- and off-resonance nutation FFT/MEM NQR spectroscopy

The new two-dimensional nuclear quadrupole resonance experiments based on the principle of nutation spectroscopy, which can be used to determine the asymmetry parameter, and thus the full quadrupolar tensor of spin-3/2 nuclei at zero applied magnetic field are discussed. The problems of reconstructing 2D-nutation NQR spectra using conventional methods and the advantages of using implementation of the maximum entropy method (MEM) are analyzed. Use of the MEM in 2D-NQR spectroscopy can lead to sensitivity improvement, reduction of instrumental artifacts and truncation errors, shortened data acquisition times and automatic suppression of noise, while at the same time increasing the resolution. The possibilities of off-resonance irradiation in nutation experiments are demonstrated experimentally and theoretically. It is shown that the off-resonance nutation spectroscopy is a useful extension of the conventional on-resonance experiments thus facilitating the determination of asymmetry parameters in multiple spectrum. The methods have been successfully demonstrated for the³⁵Cl on-and off-resonance 2D-nutation spectra in polycrystalline 2,4,6-trichloro-1,3,5-triazine.     

Solvent and structural effects on the kinetics of the reactions of 2‐substituted cyclohex‐1‐enylcarboxylic and 2‐substituted benzoic acids with diazodiphenylmethane

The rate constants for the reaction of 2‐methyl‐cyclohex‐1‐enylcarboxylic, 2‐phenylcyclohex‐1‐enylcarboxylic, and 2‐methylbenzoic and 2‐phenylbenzoic acids with diazodiphenyl‐methane were determined in 14 various solvents at 30°C. To explain the kinetic results through solvent effects, the second‐order rate constants of the examined acids were correlated using the Kamlet–Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis, and the solvent effects on the reaction rates were analyzed in terms of initial and transition state contributions. The quantitative relationship between the molecular structure and the chemical reactivity has been discussed, as well as the effect of geometry on the reactivity of the examined molecules. The geometric data of all the examined compounds corresponding to the energy minima in solvent, simulated as dielectric continuum, obtained using semiempirical MNDO‐PM3 energy calculations. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 664–671, 2007     

Validation of an HPLC Method for the Determination of Valdecoxib and its Degradation Product: a Mixture of α- and β-n-Lactosyl Sulfonamide Anomers

An HPLC method has been developed for the separation of valdecoxib and a degradation product consisting of α and β-N-lactosyl sulfonamide, i.e. α and β anomers (SC-77852). Best results were achieved with a Chromolith Performance RP-18e column (100 mm × 4.6 mm), macropore size 2 μm, mesopore size 13 nm, with an eluent of methanol:water containing a 1% solution of TEA (36:64 v/v), pH 7.4 (adjusted with 85% orthophosphoric acid), at 22 °C. Detection was at 220 nm. The method was validated for its selectivity, linearity, precision (repeatability) and robustness. Quantitation and detection limits were determined for both valdecoxib and SC-77852. Method robustness was further evaluated by performing 2³ full factorial design experiments. The final step, optimisation of the variables, was performed using response surface design. The validated method was used for assay of valdecoxib and SC-77852 in Bextra^® film-coated tablets.