A cobalt complex of a microbial arene oxidation product

ABSTRACT: We report the first synthesis of a cobalt Cp diene complex wherein the diene is derived by microbial dearomatising dihydroxylation of an aromatic ring. The complex has been characterised crystallographically and its structure is compared to that of an uncomplexed diene precursor.     

Sharp convex Lorentz–Sobolev inequalities

New sharp Lorentz–Sobolev inequalities are obtained by convexifying level sets in Lorentz integrals via the L ^p Minkowski problem. New L ^p isocapacitary and isoperimetric inequalities are proved for Lipschitz star bodies. It is shown that the sharp convex Lorentz–Sobolev inequalities are analytic analogues of isocapacitary and isoperimetric inequalities.     

Multireference coupled-cluster theory: the easy way

The multi-ionization equation-of-motion coupled-cluster (CC) method is developed for multireference (MR) problems. It is operationally single reference, depending upon a formal matrix diagonalization step to define the coefficients in the wavefunction in an unbiased way that allows for important MR character. The method is illustrated for the autoisomerization of cyclobutadiene, which has a very large multireference effect and compared to other MR-CC results. The newly implemented methods are also used to obtain the vertical double ionization (DI) potentials of several small molecules (H(2)O, CO, C(2)H(2), C(2)H(4)). Also, the performance of the new methods is analyzed by plotting the potential energy curve for twisted ethylene as a function of a dihedral angle between two methylenes. Evaluation of the total molecular energy via MR-DI-CC calculations makes it possible to avoid an unphysical cusp.     

The start-to-end chemometric image processing of 2D thin-layer videoscans

The purpose of the research was to recommend a unified procedure of image preprocessing of 2D thin layer videoscans for further supervised or unsupervised chemometric analysis. All work was done with open source software. The videoscans saved as JPG files underwent the following procedures: denoising using a median filter, baseline removal with the rollerball algorithm and nonlinear warping using spline functions. The application of the proposed procedure enabled filtration of random difference between images (background intensity changes and spatial differences of the spots location). After the preprocessing only spot intensities have an influence on the performed PCA or other techniques. The proposed technique was successfully applied to recognize the differences between three Carex species from the 2D videoscans of the extracts. The proposed solution may be of value for the any chemometric task--both unsupervised and supervised.     

Vibrational transitions of the 7LiH+ ion calculated without the Born-Oppenheimer approximation and with leading relativistic corrections

We recently presented very accurate calculations of the fundamental vibrational frequency of the (7)LiH(+) and (3)He(4)He(+) ions [Stanke et al. Phys. Rev. A 79, 060501(R) (2009)] performed without the Born-Oppenheimer approximation and included leading relativistic corrections. The accuracy of those calculations was estimated to be of the order of 0.06 cm(-1). In the present work we extend the calculations to the remaining pure vibrational states of (7)LiH(+) and similarly accurate results are generated. They may lead to the experimental search for still unidentified lines corresponding to those transitions.     

Chemoselective and enantioselective analysis of proteinogenic amino acids utilizing N-derivatization and 1-D enantioselective anion-exchange chromatography in combination with tandem mass spectrometric detection

D-Amino acid analysis in biological samples still poses a challenge to analytical chemists. In higher developed species trace amounts of d-amino acids have to be detected in vast excesses of the corresponding L-enantiomers. This method utilizes an easy-to-carry-out derivatization step on the amino group with an iron ferrocenyl propionate hydroxy succinimide ester followed by one-dimensional enantioselective anion exchange chromatography with cinchona alkaloid based chiral stationary phases (CSPs). MS detection is carried out in the highly sensitive SRM (selected reaction monitoring) mode, which allows a chemoselective differentiation of amino acid derivatives as well as their enantioselective separation in one step. Application of this method allows LOD (limits of detection) in the low μmol L(-1) range and baseline enantioseparation for all proteinogenic amino acids except for Pro, Arg and His. The D-enantiomers of isomeric Leu and Ile were separated chromatographically and pose an example for the complementary selectivities of LC and MS. A successful application of this procedure to unprocessed human urine indicated the eligibility to analyse biological samples.     

String modular phases in Calabi–Yau families

We investigate the structure of singular Calabi–Yau varieties in moduli spaces that contain a Brieskorn–Pham point. Our main tool is a construction of families of deformed motives over the parameter space. We analyze these motives for general fibers and explicitly compute the L$L$-series for singular fibers for several families. We find that the resulting motivic L$L$-functions agree with the L$L$-series of modular forms whose weight depends both on the rank of the motive and the degree of the degeneration of the variety. Surprisingly, these motivic L$L$-functions are identical in several cases to L$L$-series derived from weighted Fermat hypersurfaces. This shows that singular Calabi–Yau spaces of non-conifold type can admit a string worldsheet interpretation, much like rational theories, and that the corresponding irrational conformal field theories inherit information from the Gepner conformal field theory of the weighted Fermat fiber of the family. These results suggest that phase transitions via non-conifold configurations are physically plausible. In the case of severe degenerations we find a dimensional transmutation of the motives. This suggests further that singular configurations with non-conifold singularities may facilitate transitions between Calabi–Yau varieties of different dimensions.     

Surface molecular imprinted layer-by-layer film attached to a porous membrane for selective filtration

A surface molecular imprinted layer-by-layer (SMILbL) film was fabricated on a polyethersulfone (PES) porous membrane substrate for selective filtration of cations and anions. The LbL deposition procedure and the ultraviolet (UV) cross-linking of the modified membrane were monitored by attenuated total reflection-infrared (ATR-IR) spectra. The SMILbL-PES membrane with 4.5 bilayers of diazoresin (DAR)/poly(acrylic acid) complexed with 5,10,15,20-tetrakis(4-(trimethylammonio)-phenyl)-21H,23H-porphyrin tetratosylate (PAA-Por(4+)) effectively reduced the permeation velocity of Por(4+) after washing the Por(4+) template out. In comparison to a control film DAR/PAA-modified PES membrane (ConLbL-PES) in a dialysis experiment, the SMILbL-PES membrane exhibited better selectivity for permeation of 5,10,15,20-tetraphenyl-21H,23H-porphine-p,p',p″,p?-tetrasulfonic acid tetrasodium hydrate (Por(4-)) against permeation of Por(4+). In pressure-driven transport experiments, the SMILbL-PES membrane showed a much longer blocking time for Por(4+) than for Por(4-), indicating the selective loading of Por(4+) into the SMILbL film. The surface charge of the SMILbL-PES membrane after Por(4+) loading was higher than that of other membranes, resulting in an enhanced rejection ability of the SMILbL-PES membrane to Por(4+) caused by Coulomb repulsion. A possible mechanism was proposed as follows. The binding sites generated through imprinting in the SMILbL-PES membrane enable loading of a larger amount of Por(4+). The stronger repulsion between Por(4+) and the SMILbL film may cause the main contribution to the selective rejection of Por(4+). It can be easily imagined that this concept can be extended to the construction of composite membranes from other imprinting systems.     

Preparation of ultrathin coating layers using surface modified silica nanoparticles

Silica nanoparticles are used in various applications including catalysts, paints and coatings. To reach an optimal performance via stability and functionality, in most cases, the surface properties of the particles are altered using complex procedures. Here we describe a simple method for surface modification of silica nanoparticles (SNP) using sequential adsorption of oppositely charged components. First, the SNPs were made cationic by adsorption of a cationic polyelectrolyte. Poly(allylamine hydrochloride) (PAH) and polyethyleneimine (PEI) were chosen as polycations to investigate the difference between a linear and a branched polyelectrolyte. Next, the dispersion of cationic SNPs was combined with an anionic alkyl ketene dimer (AKD) emulsion. Using this approach cationic, hydrophobic silica particle dispersions were produced. Dynamic light scattering, contact angle measurements and atomic force microscopy (AFM) were used for analyzing the particle and coating layer properties. The chosen polyelectrolyte affected the structure of the dispersion. The layer build-up was studied in detail using a quartz crystal microbalance with dissipation monitoring (QCM-D). The adsorption and layer properties of the cationic polyelectrolytes adsorbed on silica as well as the affinity of AKD to this layer were explored. The application possibilities of the modified particle dispersions were demonstrated by preparing paper and silica surfaces with tailored properties, such as elevated surface hydrophobicity, using an ultrathin coating layer.     

TLC-Densitometric Determination of Tenoxicam and Its Degradation Products in Pharmaceutical Preparations and after Hydrolysis in Solutions

JPC – Journal of Planar Chromatography – Modern TLC - A direct, rapid, and sensitive thin-layer chromatography (TLC) method with densitometric detection was developed and validated for...