Potential function of the internal rotation of a methacrolein molecule in the ground (<Emphasis Type="Italic">S</Emphasis> <Subscript>0</Subscript>) electronic state

The structural parameters of s-trans- and s-cis-isomers of a methacrolein molecule in the ground (S₀) electronic state are determined by means of MP2 method with the cc-pVTZ basis set. Kinematic factor F(φ) is expanded in a Fourier series. The potential function of internal rotation (PFIR) of methacrolein in this state is built using experimental frequencies of transitions of the torsional vibration of both isomers, obtained from an analysis of the vibrational structure of the high-resolution UV spectrum with allowance for the geometry and difference between the energy (ΔH) of the isomers. It is shown that the V_n parameters of the potential function of internal rotation of the molecule, built using the frequencies of the transition of the torsional vibrations of s-trans- and s-cis-isomers of the methacrolein molecule, determined from vibrational structure of the high-resolution UV spectrum and the FTIR spectrum, are close.     

DISTINGUISHED PRE-NICHOLS ALGEBRAS

We formally define and study the distinguished pre-Nichols algebra \( \tilde{B} \)(V) of a braided vector space of diagonal type V with finite-dimensional Nichols algebra B(V). The algebra \( \tilde{B} \)(V) is presented by fewer relations than B(V), so it is intermediate between the tensor algebra T(V) and B(V). Prominent examples of distinguished pre-Nichols algebras are the positive parts of quantized enveloping (super)algebras and their multiparametric versions. We prove that these algebras give rise to new examples of Noetherian pointed Hopf algebras of finite Gelfand-Kirillov dimension. We investigate the kernel (in the sense of Hopf algebras) of the projection from \( \tilde{B} \)(V) to B(V), generalizing results of De Concini and Procesi on quantum groups at roots of unity.     

Molecular Modeling of the 1,1-Cyclopropane- and 1,1-Cyclobutanedicarboxamide Systems. Insights into the Self-Assembly of Diamide Diacids in Water

Modeling of the following compounds bis-(N--amido-L-phenylalaninyl)-1,1-cyclopropane dicarboxylate, 3, and bis-(N--amido-L-phenylalaninyl)-1,1-cyclobutane dicarboxylate, 4, were undertaken. The study involved construction and optimization of the precursory 1,1-dicarboxaldehydes and continued stepwise via the 1,1-dicarboxamides, the bis-N-(methyl)dicarboxamides, the bis(N--amidoglycinyl) dicarboxylates, the bis(N--amido-L-alaninyl) dicarboxylates and onto the targeted bis(N--amido-L-phenylalaninyl) dicarboxylates. Using the X-ray crystal structure of 4 (i.e., 4X) as a guide, we found that our approach was not able to reproduce the packable conformer of 4, via the computational methods employed. Nevertheless, an enhanced understanding of the intramolecular hydrogen bonding patterns available to these systems was obtained from IR and VT-NMR studies. In summary, the conformational preferences found in the 1,1-disubstituted cycloalkanes (3 and 4) direct their respective self-assembly processes by controlling the orientation of their amide NH populations.     

Quantum-mechanical calculations of the structure and vibrational spectra of CH<Subscript>3−<Emphasis Type="Italic">n</Emphasis></Subscript>Cl<Subscript>n</Subscript>SiF<Subscript>3</Subscript> (<Emphasis Type="Italic">n</Emphasis> = 0–3) substituted methylsilanes

Quantum-mechanical calculations of the optimized structures, barriers to internal rotation about the Si-C bond, harmonic force fields, and vibrational frequencies of CCH₃SiF₃, CH₂ClSiF₃, CHCl₂SiF₃, and CCl₃SiF₃ were performed using the Hartree-Fock approximation and density functional theory at the MP2/6-31G*, B3LYP/6-31G*, B3LYP/6-311++G**, B3LYP/aug-cc-pVDZ, and B3LYP/aug-cc-pVTZ levels. A new interpretation of the infrared absorption and Raman spectra of the compounds was suggested on the basis of the theoretical results     

Advancements in internationally accepted standards for radiation processing

Three subcommittees of the American Society for Testing and Materials (ASTM) are developing standards on various aspects of radiation processing. Subcommittee E10.01 “Dosimetry for Radiation Processing” has published 9 standards on how to select and calibrate dosimeters, where to put them, how many to use, and how to use individual types of dosimeter systems. The group is also developing standards on how to use gamma, electron beam, and x-ray facilities for radiation processing, and a standard on how to treat dose uncertainties. Efforts are underway to promote inclusion of these standards into procedures now being developed by government agencies and by international groups such as the United Nations' International Consultative Group on Food Irradiation (ICGFI) in order to harmonize regulations and help avoid trade barriers.

Subcommittee F10.10 “Food Processing and Packaging” has completed standards on good irradiation practices for meat and poultry and for fresh fruits, and is developing similar standards for the irradiation of seafood and spices. These food-related standards are based on practices previously published by ICGFI.

Subcommittee E10.07 on “Radiation Dosimetry for Radiation Effects on Materials and Devices” principally develops standards for determining doses for radiation hardness testing of electronics. Some, including their standards on the Fricke and TLD dosimetry systems are equally useful in other radiation processing applications.     

Shadows Of Mapping Class Groups: Capturing Convex Cocompactness

We strengthen the analogy between convex cocompact Kleinian groups and convex cocompact subgroups of the mapping class group of a surface in the sense of B. Farb and L. Mosher. Received: August 2006, Accepted: January 2007, Revision: February 2007     

Ab initio prediction of the low-temperature phase diagrams in the systems KBr-NaBr, KX-RbX, and LiX-RbX (X=Cl,Br)

The authors have calculated the low-temperature phase diagrams for the ternary alkali halides KBr-NaBr, KX-RbX, and LiX-RbX (X=Cl,Br) systems on the ab initio level without any recourse to experimental information. Via global exploration of the enthalpy landscapes for many different compositions in these systems, candidates for both ordered stoichiometric modifications and crystalline solid solution phases have been identified. Next, their free enthalpies were computed on ab initio level, and the respective low-temperature phase diagram has been derived. They find miscibility gaps in the systems KBr-NaBr and KX-RbX (X=Cl,Br), while in LiX-RbX (X=Cl,Br) only crystalline ordered phases should be present, in agreement with available experimental data. Furthermore, they predict several new thermodynamically stable and metastable phases in these systems.