Raman Spectra and Solvent-Solute Interaction of Mercury(II)-Thiocyanate Complexes in Some Aprotic Donor Solvents

Raman spectra of the species Hg(SCN)₂, [Hg(SCN)₃], and [Hg(SCN)₄]^2- in solution of ten aprotic donor solvents have been investigated in the region of the Hg-S vibration. Observed frequency values of measured band of Hg(SCN)₂ and [Hg(SCN)₃] in different solutions correlate well with donor strength of the solvents. There is a linearity between Hg-S frequency decreasing and increasing of the interaction of the solvent molecules with the mercury (II) ion in the thiocyanate complexes. No significant frequency changes have be found for [Hg(SCN)₄]^2-. Evidence based on the frequency shifts and depolarization ratios in various solvents supports the view that the Hg(SCN)₂ in solution undergos departure from linearity as a result of increasing solvent coordination to the mercury (II) ion. Almost constant frequencies of Hg-S vibration of [Hg(SCN)₄]^2- in all investigated solvents suggest a regular tetrahedral structure of the ion in solution having much larger radius than corresponding HgX₄ (X=Cl,Br,I) ions.     

Effects of screening on quark-antiquark cross sections in quark-gluon plasma

Lowest-order cross sections for qq? production and annihilation can be approximately corrected for higher-order QCD effects by using a corrective K-factor. For energies where quark masses cannot be ignored, the K-factor is dominated by the wave function distortion arising from the initialor final-state interaction between the quark and the antiquark. We evaluate this K-factor for qq? production and annihilation in a quark-gluon plasma by taking into account the effects of Debye screening through a color-Yukawa potential. We present the corrective K-factor as a function of dimensionless parameters which may find applications in other systems involving attractive or repulsive Yukawa interactions. Prominent peaks of the K-factor occur for an attractive q-q? color-Yukawa interaction with Debye screening lengths of 0.835 and 3.23 times the Bohr radius, corresponding to two lowest s-wave qq? bound states moving into the continuum to become qq? resonances as the Debye screening length decreases. These resonances, especially the cc? and the bb? resonances, may be utilized to study the quark-gluon plasma by examining the systematics of the temperature dependence of heavy-quark pair production just above the threshold.     

Γ-convergence for one-dimensional Ginzburg-Landau functional with generalized Lipschitz penalizing term

We use the approach developed in the paper G. Alberti, S. Muller: A new approach to variational problems with multiple scales, Comm. Pure Appl. Math. 54 , 761-825 (2001) to obtain Γ-convergence for a class of Ginzburg-Landau functionals I^ε(v), where v = v(s) is appropriate Sobolev function. We generalize results from the paper A. Raguž: Relaxation of Ginzburg-Landau functional with 1-Lipschitz penalizing term in one dimension by Young measures on micropatterns, Asymptotic Anal. 41 ( 3,4 ), 331-361 (2005), where original functional was penalized by 1-Lipschitz function g = g(s). In this note we prove Γ-convergence when g = g(s, v(s), v′(s)) under suitable growth conditions imposed on g. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Separation of brombuterol enantiomers in capillary electrophoresis with cyclodextrin‐type chiral selectors and investigation of structure of selector‐selectand complexes using nuclear magnetic resonance spectroscopy

The major goal of this study was to determine the affinity pattern of brombuterol (BB) enantiomers toward various cyclodextrins (CD) and to evaluate the potential of NMR spectroscopy for understanding fine mechanisms of interactions between CDs and BB enantiomers. Separation of BB enantiomers was performed in a fused‐silica capillary using a phosphate buffer, pH 2.5, at the room temperature in the normal polarity mode. It was shown once again that CE in combination with NMR spectroscopy represents a very sensitive tool for studies of affinity patterns and structure of CD complexes with chiral guests. Although opposite affinity patterns of BB enantiomers were observed toward native β‐ and γ‐CDs, no significant differences between the structures of the complexes of these two CDs with BB were detected by NMR spectroscopy. In contrary to this, the opposite affinity pattern of BB enantiomers toward β‐CD and its two sulfated derivatives, heptakis (2,3‐O‐diacetyl‐6‐sulfo)‐β‐CD (HDAS‐β‐CD) and heptakis (2‐O‐methyl‐3,6‐di‐O‐sulfo)‐β‐CD (HMDS‐β‐CD) was associated with major differences in the structure of the complexes. In addition, it was shown again that HMDS‐β‐CD provides separation of enantiomers without formation of inclusion‐type complex with the chiral analyte.     

Calorimetric study of phase transitions in a liquid-crystal-based microemulsion

A lyotropic inverse micelle phase composed of water, thermotropic liquid-crystal octylcyanobiphenyl (8CB), and surfactant (DDAB) was studied by using high-resolution calorimetry on several mixtures with 3%, 8%, and 15% micelle concentration. Calorimetric results show strong depression of the isotropic to nematic (I-N) phase-transition temperature. Broad heat-capacity anomalies show the existence of a wide coexistence range of isotropic, nematic, and smectic-A phases, which mimics the behavior of a new nearly stable thermodynamic phase. An observation of the rather sharp almost bulklike nematic to smectic-A (N-A) transition at low-temperatures indicates that our heat capacity results are consistent with the phase separation scenario in which significant number of micelles is expelled during I-N conversion leaving almost pure nematic phase at lower temperatures. It was found that micelles get almost completely remixed on heating the mixture back to the isotropic phase.     

A facile one-pot highly chemo- and regioselective synthesis of the novel heterocyclic system indolo[1,2-c]azolo[1,5-a]quinazoline-8,10-dione

A series of novel indolo[1,2-c]azolo[1,5-a]quinazoline-8,10-diones was obtained by a multi-component reaction between cyclic 1,3-diketones, α-aminoazoles, and glyoxal. The unexpected cyclization process was established by NMR spectroscopy and X-ray diffraction measurements.