Microwave spectrum,centrifugal distortion,substitution structure,and dipole moment of sulfine,CH2SO

The microwave spectrum of the reactive species sulfine (CH₂SO) has been studied. Assignments of 86 transitions of the ground vibrational state normal isotopic species, with J up to 60, have allowed a thorough centrifugal distortion analysis. With planarity implied by the I_c-I_a-I_b value of 0.1333 amu $\text{A}\text{?}{}^2$, spectral assignments of seven other isotopic modifications have resulted in the following substitution bond lengths and angles: CH_syn = 1.085 Å, CH_anti = 1.077 Å, CS = 1.610 Å, SO = 1.469 Å, ?HCH = 121.86^°, ?SCH_syn = 122.51^°, ?SCH_anti = 115.63^°, and ?CSO = 122.51^°. From Stark effect measurements of the normal and d₂ species, the dipole moment has been determined to be 2.994 D, oriented 25.50° relative to the SO bond and 9.61° relative to the normal species “a” axis. At an initial pressure of 30 mTorr in a clean brass waveguide, the lifetime of sulfine at 25°C is ～30 min.     

Analysis of IAEA environmental samples for plutonium and uranium by ICP/MS in support of international safeguards

A method for the separation and determination of total and isotopic uranium and plutonium by ICP/MS was developed for IAEA samples on cellulose-based media. Preparation of the IAEA samples involved a series of redox chemistries and separations using TRU® resin (Eichrom). The sample introduction system, an APEX nebulizer (Elemental Scientific, Inc.), provided enhanced nebulization for a several-fold increase in sensitivity and reduction in background. Application of mass bias (ALPHA) correction factors greatly improved the precision of the data. By combining the enhancements of chemical separation, instrumentation and data processing, detection levels for uranium and plutonium approached high attogram levels.     

Molecular modeling based approach to potent P2-P4 macrocyclic inhibitors of hepatitis C NS3/4A protease

Molecular modeling of inhibitor bound full length HCV NS3/4A protease structures proved to be a valuable tool in the design of a new series of potent NS3 protease inhibitors. Optimization of initial compounds provided 25a. The in vitro activity and selectivity as well as the rat pharmacokinetic profile of 25a compare favorably with the data for other NS3/4A protease inhibitors currently in clinical development for the treatment of HCV.     

Prediction of activation energies for aromatic oxidation by cytochrome P450

We have estimated the activation energy for aromatic oxidation by compound I in cytochrome P450 for a diverse set of 17 substrates using state-of-the-art density functional theory (B3LYP) with large basis sets. The activation energies vary from 60 to 87 kJ/mol. We then test if these results can be reproduced by computationally less demanding methods. The best methods (a B3LYP calculation of the activation energy of a methoxy-radical model or a partial least-squares model of the semiempirical AM1 bond dissociation energies and spin densities of the tetrahedral intermediate for both a hydroxyl-cation and a hydroxyl-radical model) give correlations with r(2) of 0.8 and mean absolute deviations of 3 kJ/mol. Finally, we apply these simpler methods on several sets of reactions for which experimental data are available and show that we can predict the reactive sites by combining calculations of the activation energies with the solvent-accessible surface area of each site.     

Multifractal analysis of divergence points of deformed measure theoretical Birkhoff averages. IV: Divergence points and packing dimension

During the past 10 years multifractal analysis has received an enormous interest. For a sequence n(φn) of functions on a metric space X, multifractal analysis refers to the study of the Hausdorff and/or packing dimension of the level sets(1) of the limit function limnφn. However, recently a more general notion of multifractal analysis, focusing not only on points x for which the limit limnφn(x) exists, has emerged and attracted considerable interest. Namely, for a sequence n(xn) in a metric space X, we let A(xn) denote the set of accumulation points of the sequence n(xn). The problem of computing that the Hausdorff dimension of the set of points x for which the set of accumulation points of the sequence (φnn(x)) equals a given set C, i.e. computing the Hausdorff dimension of the set(2){x∈X|A(φn(x))=C} has recently attracted considerable interest and a number of interesting results have been obtained. However, almost nothing is known about the packing dimension of sets of this type except for a few special cases investigated in [I.S. Baek, L. Olsen, N. Snigireva, Divergence points of self-similar measures and packing dimension, Adv. Math. 214 (2007) 267–287]. The purpose of this paper is to compute the packing dimension of those sets for a very general class of maps φn, including many examples that have been studied previously, cf. Theorem 3.1 and Corollary 3.2. Surprisingly, in many cases, the packing dimension and the Hausdorff dimension of the sets in (2) do not coincide. This is in sharp contrast to well-known results in multifractal analysis saying that the Hausdorff and packing dimensions of the sets in (1) coincide.