Photochemical reaction channels of OCS with Cl2, ICl, or IBr isolated together in an argon matrix: isolation of syn-iodocarbonylsulfenyl bromide

The photolytically induced reactions of a dihalogen XY (= Cl2, ICl, or IBr) with OCS isolated together in an Ar matrix at about 15 K lead to different photoproducts depending on the natures of X and Y. In addition to the known species ClCO*, OCCl2, syn-ClC(O)SCl, syn-ClC(O)SSCl, IC(O)Cl, IC(O)Br, and syn-BrC(O)SBr, syn-iodocarbonylsulfenyl bromide, syn-IC(O)SBr, has thus been identified for the first time as a photoproduct of the reactions involving IBr. The first product to be formed in the reactions with Cl2 or ICl is the ClCO* radical which reacts subsequently with halogen or sulfur atoms or other matrix guests to give the corresponding carbonyl dihalide (OCCl2 and IC(O)Cl), syn-ClC(O)SCl or syn-ClC(O)SSCl. The analogous reaction with IBr affords syn-BrC(O)SBr, IC(O)Br, and syn-IC(O)SBr. The changes have been followed, the products characterized experimentally by IR measurements, and the spectra analyzed in the light of the results of appropriate theoretical calculations.     

Extremal solutions for a nonlinear impulsive differential equations with multi-orders fractional derivatives

In this paper, by employing the lower and upper solutions method, we give an existence theorem for the extremal solutions for a nonlinear impulsive differential equations with multi-orders fractional derivatives and integral boundary conditions. A new comparison result is also established.     

Computational study and analysis of the kinetic isotope effects of the rearrangement of cis-bicyclo[4.2.0]oct-7-ene to cis,cis-cycloocta-1,3-diene

[reaction: see text] On the basis of KIE experiments, the ring opening of cis-bicyclo[4.2.0.]oct-7-ene has been suggested as an anti-Woodward-Hoffmann reaction candidate. We hereby report the results of a high-level computational study of the alternate reaction pathways which proves that the energy profiles show a clear preference for the conrotatory (W-H allowed) ring opening followed by double-bond isomerization. Computed KIE values for the aforementioned mechanism are in good agreement with the experimental values.     

Exchangeable claim sizes in a compound Poisson‐type process

When dealing with risk models the typical assumption of independence among claim size distributions is not always satisfied. Here we consider the case when the claim sizes are exchangeable and study the implications when constructing aggregated claims through compound Poisson‐type processes. In particular, exchangeability is achieved through conditional independence, using parametric and nonparametric measures for the conditioning distribution. Bayes' theorem is employed to ensure an arbitrary but fixed marginal distribution for the claim sizes. A full Bayesian analysis of the proposed model is illustrated with a panel‐type data set coming from a Medical Expenditure Panel Survey (MEPS). Copyright © 2009 John Wiley & Sons, Ltd.     

Proposed interpretation of the transverse magnetic field dependence of the melting temperature T m(B) of a two-dimensional one-component plasma driven by logarithmic interactions

We propose an approximate scaling property of the classical partition function of a two-dimenisional one-component plasma in a high magnetic field based on the molecular dynamics simulations of dubey and Gumbs     

Closed Prime Ideals in Algebras with Semiprime Multiplication Algebra

Let A be an algebra whose multiplication algebra M(A) is semiprime. We prove that, except in an exceptional case, the proper closed prime ideals of A are the maximal closed ideals of A, for the closure operations π and ?. In fact, these sets agree for both closures. The same can be said in M(A) for the closure operations π and ?′. Moreover, we establish the relationships between the proper closed prime ideals of A and the ones of the algebras M(A),U and A/U, for a given ideal U of A.     

Measuring the transition between nonhyperbolic and hyperbolic regimes in open Hamiltonian systems

Nonlinear Dynamics - We show that the presence of KAM islands in nonhyperbolic chaotic scattering has deep implications on the unpredictability of open Hamiltonian systems. When the energy of the...     

Rapid enantiomeric excess and concentration determination using simple racemic metal complexes

Racemic-metal complexes were used to determine identity, enantiomeric excess, and concentration of chiral diamines using metal-to-ligand charge transfer bands in circular dichroism spectroscopy. It takes under just 2 min per sample to determine [G]t and %R with tolerable errors (19% and 4%, respectively). The simplicity of the achiral receptors employed confers to this technique great potential for high-throughput screening.     

Solution structures of chemoenzymatically synthesized heparin and its precursors

We report the first chemoenzymatic synthesis of the stable isotope-enriched heparin from a uniformly labeled [(13)C,(15)N]N-acetylheparosan (-GlcA(1,4)GlcNAc-) prepared from E. coli K5. Glycosaminoglycan (GAG) precursors and heparin were formed from N-acetylheparosan by the following steps: chemical N-deacetylation and N-sulfonation leading to N-sulfoheparosan (-GlcA(1,4)GlcNS-); enzyme-catalyzed C5-epimerization and 2-O-sulfonation leading to undersulfated heparin (-IdoA2S(1,4)GlcNS-); enzymatic 6-O-sulfonation leading to the heparin backbone (-IdoA2S(1,4)GlcNS6S-); and selective enzymatic 3-O-sulfonation leading to the anticoagulant heparin, containing the GlcNS6S3S residue. Heteronuclear, multidimensional nuclear magnetic resonance spectroscopy was employed to analyze the chemical composition and solution structure of [(13)C,(15)N]N-acetylheparosan, precursors, and heparin. Isotopic enrichment was found to provide well-resolved (13)C spectra with the high sensitivity required for conformational studies of these biomolecules. Stable isotope-labeled heparin was indistinguishable from heparin derived from animal tissues and is a novel reagent for studying the interaction of heparin with proteins.