Effects of subgrid scale and combustion modelling on flame structure of a turbulent premixed flame within LES and tabulated chemistry framework

The effects of combustion and SubGrid Scale (SGS) modelling on the overall flame characteristics of a turbulent premixed flame are investigated. This is achieved in terms of mean flow statistics, variances and flame surfaces. In particular, the chemical flame structure is analysed and compared. The Artificially Thickened Flame (ATF) approach coupled with the Flamelet Generated Manifolds (FGMs) and Filtered TAbulated Chemistry for LES (F-TACLES) approaches are used for this investigation. A Germano like procedure for dynamical calculation of SGS wrinkling is used which ensures the conservation of the total flame surface for both models. It turns out that using the dynamic SGS wrinkling model improves the results. Although the results of both combustion models in terms of statistics, mean and variances show very good agreement, the resolved flame surfaces hide different dynamic behaviour.     

Contribution by Lazare and Sadi Carnot to the caloric theory of heat and its inspirative role in thermodynamics

The works of Lazare and Sadi Carnots are reviewed emphasizing their contribution to the caloric theory of heat, which is consequently analyzed in terms of an alternative thermodynamic approach. In the framework of the caloric theory the elementary derivation of the efficiency of real heat engines, η_K=1−tr(T ₂/T ₁), is given which is a direct consequence of linearity of Fourier’s law of heat transfer.     

Ultra-high-performance liquid chromatography fingerprinting method for chemical screening of metabolites in cultivation broth

A fingerprinting method for chemical screening of microbial metabolites, potential antibiotics, in spent cultivation broths is described. The method is based on high-throughput ultra-high-performance liquid chromatography (UHPLC) separation with UV detection (photodiode array detector). Thirteen antibiotic standards and four cultivation broths were used for the method development. The comparison of ten liquid–liquid and solid phase extraction protocols for sample clean-up and pre-concentration revealed that Oasis HLB C18 sorbent gives the best recoveries. The Acquity BEH C18 chromatographic column was chosen for the samples separation with respect to its universality, selectivity, efficiency and robustness. The method is presented by two 3D fingerprints for every sample that was obtained under different, acidic and alkaline, UHPLC conditions. The acidic mobile phase consisted of 0.5% phosphoric acid with methanol and the alkaline mobile phase of 1 mM ammonium formate, pH 9 with acetonitrile. Each pair of 3D fingerprints includes the following physico-chemical information: polarity (retention time), presence and characterization of chromophores (UV spectra), compound concentration (detector response), and acid–base properties (influence of different pH of the aqueous parts of mobile phases on retention times). The sample extraction and method validation were assessed with relative standard deviation (RSD) of 0.5, 5.0 and 20.0% for retention times, peak areas and minor compound peak areas, respectively.     

K^{-} nuclear quasi-bound states in a chirally motivated coupled-channel approach

K ^?? nuclear optical potentials are constructed from in-medium ${\bar K}N$ scattering amplitudes within a chirally motivated coupled-channel model. The strong energy and density dependence of the scattering amplitudes at and below threshold leads to K ^?? potential depths ?Re $V_{K^-}(\rho_0) \approx 80 -100$ ?MeV. Self consistent calculations of K ^?? nuclear quasi-bound states are discussed.     

Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, and trimethylstannyl derivatives of 3,3-dimethylcyclopropene VII. 3,3-Dimethyl-1-(trimethylstannyl) cyclopropene

The quantum mechanical force fields (QMFF's) of 3,3-dimethyl-1-(tert-butyl)cyclopropene (I), 3,3-dimethyl-1-(trimethylsilyl)cyclopropene (II), 3,3-dimethyl-1-(trimethylgermyl)cyclopropene (III), and 3,3-dimethyl-1-(trimethylstannyl)cyclopropene (IV) were calculated at the HF/3-21G*//HF/3-21G* level. The set of scale factors for the correction of HF/3-21G*//HF/3-21G* QMFF of II was determined using its well-characterised vibrational spectrum. Transferral of the set of scale factors obtained for II to the QMFF's of I, III and IV and calculation of the fundamental frequencies resulted in good agreement between the calculated and previously assigned experimental frequencies of III. This again demonstrates the feasibility of transferral of a set of scale factors obtained for the correction of the QMFF of a molecule to others containing heteroatoms from the same column of the Mendeleyev Periodic Table. Thus the calculations performed permitted the accurate assignment of the fundamental vibrational frequencies in the experimental IR spectrum of IV. The vibrational frequencies of 3,3-dimethyl-1-(tert-butyl)cyclopropene (I) were also calculated from the HF/6-31G*//HF/6-31G* QMFF, scaled by the set of scale factors used previously for the HF/6-31G*//HF/6-31G* QMFF's of II and III. Regularities in the trends of some vibrational frequencies with increasing atomic number of the heteroatom are observed.     

Steepest Descent on Real Flag Manifolds

Real flag manifolds are the isotropy orbits of noncompact symmetricspaces G/K. Any such manifold M is acted on transitively bythe (noncompact) Lie group G, and it is embedded in euclideanspace as a taut submanifold. The aim of this paper is to showthat the gradient flow of any height function is a one-parametersubgroup of G, where the gradient is defined with respect toa suitable homogeneous metric s on M; this generalizes the Kählermetric on adjoint orbits (the so-called complex flag manifolds).2000 Mathematics Subject Classification 53C30, 53C35.     

Influence of solvent on the ortho substituent effect in the alkaline hydrolysis of phenyl esters of substituted benzoic acids

The second‐order rate constants k (dm³ mol^?1 s^?1) for the alkaline hydrolysis of phenyl esters of meta‐, para‐ and ortho‐substituted benzoic acids in aqueous 5.3 M NaClO₄ and 1.0 M Bu₄NBr were measured by UV/Vis spectrophotometry at 25 °C. The variations in the ortho inductive, ortho resonance, as well as meta and para polar effects with solvent parameters were studied using data for the alkaline hydrolysis of phenyl esters of substituted benzoic acids in various media. The dependence of the ortho substituent effect on solvent can be precisely described with the following equation: Δlog k_ortho = log k_ortho ? log k_H = 0.059 + 2.19σ_I + 0.304σ°_R + 2.79E ? 0.016ΔEσ_I ? 0.085ΔEσ°_R, where ΔE is the solvent electrophilicity, ΔE = E_S ? E_H2O, characterizing the hydrogen‐bond donating power of the solvent. The increase in the meta and para polar substituent effects with decrease in the solvent hydrogen‐bond donor capacity (electrophilicity) was approximately to the same extent (?0.068ΔEσ°_m,p) as the resonance term for the ortho substituents. The steric term of ortho substituents was independent of the solvent parameters. The variations in the ortho inductive, ortho resonance, as well as meta and para polar substituent effects with the solvent electrophilicity were to the same extent as in phenyl benzoates containing the substituents in the phenyl part. The substituent effects in the alkaline hydrolysis of ethyl benzoates appeared to vary with the solvent electrophilicity nearly to the same extent as in the alkaline hydrolysis of substituted phenyl esters of benzoic acids. Copyright © 2009 John Wiley & Sons, Ltd.