Coupled-states statistical investigation of vibrational and rotational relaxation of OH(2pi) by collisions with atomic hydrogen

We report state-to-state cross sections and thermal rate constants for vibrational and rotational relaxation of OH(2pi) by collision with H atoms. The cross sections are calculated by the coupled-states (CS) statistical method including the full open-shell character of the OH + H system. Four potential energy surfaces (PESs) ((1,3)A' and (1,3)A') describe the interaction of OH(X2pi) with H atoms. Of these, three are repulsive, and one (1A') correlates with the deep H2O well. Consequently, rotationally and ro-vibrationally inelastic scattering of OH in collisions with H can occur by scattering on the repulsive PESs, in a manner similar to the inelastic scattering of OH by noble gas atoms, or by collisions which enter the H2O well and then reemerge. At 300 K, we predict large (approximately 1 x 10(-10) cm3 molecule(-1) s(-1)) vibrational relaxation rates out of both v = 2 and v = 1, comparable to earlier experimental observations. This anomalously fast relaxation results from capture into the H2O complex. There exists a significant propensity toward formation of OH in the pi(A') lambda-doublet level. We also report state-resolved cross sections and rate constants for rotational excitation within the OH v = 0 manifold. Collisional excitation from the F1 to the F2 spin-orbit manifold leads to an inverted lambda-doublet population.     

Typing of unknown microorganisms based on quantitative analysis of fatty acids by mass spectrometry and hierarchical clustering

Rapid identification of unknown microorganisms of clinical and agricultural importance is not only critical for accurate diagnosis of infections but also essential for appropriate and prompt treatment. We describe here a rapid method for microorganisms typing based on quantitative analysis of fatty acids by iFAT approach (Isotope-coded Fatty Acid Transmethylation). In this work, lyophilized cell lysates were directly mixed with 0.5M NaOH solution in d3-methanol and n-hexane. After 1 min of ultrasonication, the top n-hexane layer was combined with a mixture of standard d0-methanol derived fatty acid methylesters with known concentration. Measurement of intensity ratios of d3/d0 labeled fragment ion and molecular ion pairs at the corresponding target fatty acids provides a quantitative basis for hierarchical clustering. In the resultant dendrogram, the Euclidean distance between unknown species and known species quantitatively reveals their differences or shared similarities in fatty acid related pathways. It is of particular interest to apply this method for typing fungal species because fungi has distinguished lipid biosynthetic pathways that have been targeted for lots of drugs or fungicides compared with bacteria and animals. The proposed method has no dependence on the availability of genome or proteome databases. Therefore, it is can be applicable for a broad range of unknown microorganisms or mutant species.     

A Numerical Method for Evaluating Delay to a Customer in a Time-Inhomogeneous,Single Server Queue with Batch Arrivals

Using the method of discrete time analysis, a numerical method is developed for evaluating the distribution of the delay encountered by a customer in a time-inhomogeneous, single server queue with batch arrivals.     

Crystal structure and nonlinear optical properties of the K2UO2(SO4)2 · 2H2O compound at 293 K

Single crystals of potassium uranyl sulfate are grown, and their atomic structure is determined using X-ray diffraction analysis. The compound crystallizes in the orthorhombic crystal system with space group Pna2₁ [a = 13.773(4) Å, b = 7.288(2) Å, c = 11.556(4) Å, R ₁ = 0.033, wR ₂ = 0.0892 for 2630 reflections with I > 2σ(I)]. The crystal structure of the K₂UO₂(SO₄)₂ · 2H₂O compound is built up of two-dimensional infinite, negatively charged layers of the composition [UO₂(SO₄)₂·H₂O] _2∞ ^δ? ], which are linked together through the K⁺ ions. The specific features of the atomic arrangement in the structure of this compound are analyzed, and the second harmonic generation of laser radiation is investigated.     

Comparison of high-performance liquid chromatography of cyclotriphosphazene derivatives with one or two equivalent stereogenic centres

High-performance liquid chromatographic (HPLC) methods have been developed for investigating the stereogenic properties of two analogous series of dibenzylamino derivatives of cyclotriphosphazene containing either one or two equivalent stereogenic centres. Separation of the enantiomers of all the racemic compounds has been investigated by chiral HPLC using Whelk-01 and Chiralcel OD columns. In all cases, conditions for separation of enantiomers have been found using a Whelk-01 column with different ratios of tetrahydrofuran in n-hexane as the mobile phase. It is found that both the separation factor (alpha) and resolution factor (R(S)) of molecules with two equivalent stereogenic centres are greater than those for analogues with only one centre.     

Removal of Th(IV) ions from aqueous solution using bi-functionalized algae-yeast biosorbent

Composites could be more effective adsorbents than inorganic and organic components individually. In the present study, the red macro marine algae, Jania Rubens and yeast, Saccharomyces cerevisiae immobilized on silica gel were used as a constituent of bi-functionalized biosorbent to remove thorium ions from aqueous solution. Optimum biosorption conditions were determined as a function of pH, initial Th(IV) concentration, contact time, temperature, volume/mass ratio and co-ion effect. The morphological analysis of the biocomposite was performed by the scanning electron microscopy and functional groups in the biosorbent were determined by FT-IR spectroscopy. In order to find the adsorption characteristics, Langmuir, Freundlich, and Dubinin–Radushkevich adsorption isotherms were applied to the adsorption data. The data were well described by Langmuir adsorption isotherms while the fit of Freundlich adsorption isotherms and Dubinin–Radushkevich equation to adsorption data was poor. Using the equilibrium constant value obtained at different temperature, the thermodynamics properties of the biosorption (ΔG°, ΔH° and ΔS°) were also determined. The results show that biosorption of Th(IV) ions onto biocomposite was exothermic nature, spontaneous and more favorable at lower temperature under examined conditions.     

On approximating higher order MAPs with MAPs of order two

We show that the autocorrelation sequence of interarrival times for a Markovian arrival process (MAP) of order two is geometric. We determine the set of feasible values for the autocorrelation decay parameter and the first two or three moments of the interarrival time distribution. A method is derived for matching these parameters to a MAP of order two and some numerical examples are included to illustrate approximating higher dimensional MAPs by two dimensional ones. The numerical examples have helped us pose important questions regarding the significance of correlation in a MAP of order two when it is used as input to a queueing model.     

Synthesis and non-aqueous medium titrations of some new 4-benzylidenamino-4,5-dihydro-1H-1,2,4-triazol-5-one derivatives

The synthesis of 3-alkyl(aryl)-4-(3-ethoxy-4-hydroxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones 3 from the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones 2 with 3-ethoxy-4-hydroxybenzaldehyde is described.The acetylation and methylation reactions of the compounds 3 giving compounds of type 4 and 5, respectively, were investigated. The newly synthesized compounds were characterized using elemental analyses and IR, (1)H-NMR, (13)C-NMR and UV spectral data.In addition, to investigate the effects of solvents and molecular structure upon acidity,compounds 3 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, acetonitrile and N,N-dimethylformamide). The half-neutralization potential values and the corresponding pKa values were determined for all cases.     

Synthesis of some new five membered heterocycles,a facile synthesis of oxazolidinones

The synthesis and structural properties of two kinds of thiosemicarbazide derivatives ( 2a‐c and 3a‐c ) and one kind of semicarbazide derivatives ( 4a, 4b ) have been described. These compounds were synthesized by treating 2‐(4‐amino‐3‐alkyl‐5‐oxo‐4,5‐dihydro‐1H‐1,2,4‐triazol‐1‐yl)acetohydrazides ( 1a‐c ) with benzyl isothiocyanate, 3‐florophenyl isothiocyanate and benzylisocyanate, respectively. The synthesis of 4‐amino‐3‐alkyl‐1‐[(4‐alkyl‐5‐mercapto(or 5‐oxo)‐4H‐1,2,4‐triazol‐3‐yl)methyl]‐4,5‐dihydro‐1H‐1,2,4‐triazol‐5‐ones ( 5a‐c, 6a‐c and 7 ) have been performed from the reaction with sodium hydroxide. On the other hand, the acidic treatment of compounds 2b, 3b and 4b has afforded 4‐amino‐3‐(4‐chlorobenzyl)‐1‐[(5‐alkylamino‐1,3,4‐thidazol(or 1,3,4‐oxazol)‐2‐yl)methyl]‐4,5‐dihydro‐1H‐1,2,4‐triazol‐5‐ones ( 8, 9 and 10 ). The condensation of thiosemi(or semi)carbazide derivatives ( 2a‐c, 3c and 4b ) with 4‐chlorophenacylbromide have resulted in the formation of 2‐[4‐amino‐3‐alkyl‐5‐oxo‐4,5‐dihydro‐1H‐1,2,4‐triazol‐1‐yl]‐N′‐(3,4‐dialkyl‐1,3‐thiazol(or oxazol)‐2(3H)‐yliden]acetohydrazides ( 11a‐c, 12, 13 ), while their condensation with chloroacetic acid has produced 2‐[4‐amino‐3‐alkyl‐5‐oxo‐4,5‐dihydro‐1H‐1,2,4‐triazol‐1‐yl]‐N′‐[3‐(3‐alkyl)]‐4‐oxo‐1,3‐thiazolidin(or oxazolidin)‐2‐yliden}acetohydrazides ( 14, 15 and 16 ). The spectral data and elemental analyses have support the proposed structures.     

Axially chiral 2-arylimino-3-aryl-thiazolidine-4-one derivatives: enantiomeric separation and determination of racemization barriers by chiral HPLC

Axially chiral 2-arylimino-3-aryl-thiazolidine-4-ones have been synthesized as racemic mixtures, and each mixture with the exception of 2-(o-chlorophenyl)imino-3-(o-chlorophenyl)-thiazolidine-4-one has been converted to the corresponding 5-benzylidene-2-arylimino-3-aryl-thiazolidine-4-one racemates by reaction with benzaldehyde. The thermally interconvertible enantiomers of each compound have been obtained by enantioselective HPLC separation on columns Chiralpak AD-H and Chiralcel OD-H, and the barriers to racemization have been found to be 98.1-114.1 kJ/mol. The barriers determined were compared to those of structurally related compounds to provide evidence for the stereochemistry of the aryl imino bond.