Anomalous temperature dependence of the quadrupole coupling frequency of a lattice defect trapped to111In in Pt

The quadrupole coupling frequency of an¹¹¹In-defect bound state in Pt with ω₀(295 K) = 200 Mrad/s was measured over the range 4 – 300 K using perturbed angular correlations. The temperature dependence exhibited positive curvature, unlike the T^3/2 dependence observed in noncubic metals, and was fitted using a model which assumed that the temperature dependence was caused by vibrations of a resonant mode in the probe-defect complex.     

Vibrational stretch—bend coupling and the adiabatic approximation

Two different adiabatic methods are applied to the calculation of energy levels for a two-dimensional system modeling an anharmonic XH stretch and an associated harmonic bend coupled through centrifugal stretching. The two methods are compared in their ability to yield accurate eigenvalues for the first several overtones and combination bands, and are both shown to be easily extendible to handle cases of Fermi resonance.     

On asymptotic expansions in nonlinear,singularly perturbed difference equations ∗

The present paper deals with the problem of constructing and proving asymptotic expansions for nonlinear, singularly perturbed difference equations. New methods for the construction of asymptotic expansions are presented and compared with well-known ones. For the proof of their validity, fundamental principles for the treatment of nonlinear singular perturbation problems are applied, based on the concepts of e-stability, formal asymptotic expansions, matching and asymptotic expansions. The results are derived from a general theory of asymptotic expansions of nonlinear operator equations that has been developed recently by the author.     

Biosynthesis of pentangular polyphenols: deductions from the benastatin and griseorhodin pathways

The benastatins, pradimicins, fredericamycins, and members of the griseorhodin/rubromycin family represent a structurally and functionally diverse group of long-chain polyphenols from actinomycetes. Comparison of their biosynthetic gene clusters (ben, prm, fdm, grh, rub) revealed that all loci harbor genes coding for a similar, yet uncharacterized, type of ketoreductases. In a phylogenetic survey of representative KRs involved in type II PKS systems, we found that it is generally possible to deduce the KR regiospecificity (C-9, C-15, C17) from the amino acid sequence and thus to predict the nature of the aromatic polyketide (e.g., angucycline, anthracycline, benzoisochromanequinones). We hypothezised that the new clade of KRs is characteristic for biosynthesis of polyphenols with an extended angular architecture we termed "pentangular". To test this hypothesis, we demonstrated the biogenetic relationship between benastatin and the structurally unrelated spiro ketal griseorhodin by generating a mutant producing collinone, a pentangular pathway intermediate. The benastatin pathway served as a model to characterize the KR. Gene inactivation of benL resulted in the formation of a series of 19-hydroxy benastatin and bequinostatin derivatives (e.g., benastatin K and benastatin L). These results clearly showed that BenL functions as a C-19 KR in pentangular pathways.     

Linoleic Acid Isomerase from <Emphasis Type="Italic">Propionibacterium acnes</Emphasis>: Purification,Characterization, Molecular Cloning,and Heterologous Expression

Propionibacterium acnes strain ATCC 6919 catalyzes the isomerization of the double bond at the C9 position in linoleic acid (c9,c12, 18:2) to form t10,c12 conjugated linoleic acid (CLA, 18:2). CLA has significant health benefits in animal and human. The linoleic acid C9 isomerase was purified to an apparent homogeneity by successive chromatography on diethylaminoethyl (DEAE) anion exchange, hydrophobic interaction, and chromatofocusing columns. Two degenerated oligonucleotide primers were synthesized according to the N-terminal peptide sequence to clone, by polymerase chain reaction (PCR), a short nucleotide sequence (62 bp) of the isomerase gene. The linoleic acid isomerase gene (lai) was subsequently cloned by inverse PCR. The amino acid sequence deduced from the lai coding sequence predicts a protein of 424 amino acid residues (48 kDa), excluding the N-terminal methionine, which was absent in the polypeptide purified from the native host. The isomerase shares no significant sequence homology to other enzymes except a flavin-binding domain in the N-terminal region. The recombinant isomerase purified from Escherichia coli showed a typical ultraviolet spectrum for FAD-bound proteins. The recombinant enzyme produced a single isomer of t10,c12-CLA from linoleic acid, as demonstrated by gas chromatography and gas chromatography-mass spectrum analysis. The recombinant isomerase protein was expressed at high levels in E. coli, but it was almost totally sequestered in inclusion bodies. The level of active isomerase was increased 376-fold by medium and process optimization in bench-scale fermentors.     

Comment on: “Lorentz violation in high-energy ions” by Santosh Devasia

In an article “Lorentz violation in high-energy ions” by S. Devasia published in this Journal [EPJ C 69, 343 (2010)], our recent Doppler shift experiments on fast ion beams are reanalyzed. Contrary to our analysis, Devasia concludes that our results provide an “indication of Lorentz violation”. We argue that this conclusion is based on a fundamental misunderstanding of our experimental scheme and reiterate that our results are in excellent agreement with Special Relativity.     

Simulation of round jets with nozzle-dependent inflow conditions using the k−ε turbulence model

In view of the “round jet initial condition anomaly”, discussed in literature, we investigate the effect of inflow conditions resulting from the use of different nozzle geometries to form the jet. RANS simulations in the framework of OpenFOAM using the k − ε turbulence model are performed. As the standard model coefficient C_ε1 = 1.44 is known to overpredict spreading rates for round jets, a value of C_ε1 = 1.6 was recommended for this case already in the 1970's. While this works well for jets issuing from long pipes, it does not give satisfactory results for other nozzle geometries. To overcome this deficiency while keeping the k − ε model, we suggest modified coefficients C_ε1 based on profiles of mean flow and turbulence at the nozzle exit. We determine optimal values of C_ε1 for three different nozzle geometries, and test them at various Reynolds numbers. Good agreement with experimental data is obtained. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Evidence of an isomeric pair in furan...HCl: Fourier transform infrared spectroscopy and ab initio calculations

For the first time the coexistence of a sigma- and a pi-complex in the C(4)H(4)O:HCl system has been observed, in the same supersonic expansion of a molecular jet seeded with argon (or helium) or in a flow-cooled cell at 240 K. This is an exception to the third of the Legon-Miller rules which claims the sigma-structure to be the only one to exist. On the grounds of energetic considerations and band contour simulations, two observed bands at 2787.7 and 2795.5 cm(-1) of the nu(s) HCl stretching frequency are assigned to the two complexes, recorded as Fourier transform infrared spectra with a resolution between 0.2 and 0.5 cm(-1). Complementary calculations show that the use of the standard second-order Moller-Plesset perturbation theory may be erroneous for such a complex, due of the overestimation of the dispersion contribution with respect to the electrostatic term. It is finally established that only a balanced version of the second-order Moller-Plesset perturbation method, spin-component scaled-MP2, or a higher level of theory like a coupled-cluster approach, can provide a reliable energetic analysis for this complex.