Quasiparticle band structure of infinite hydrogen fluoride and hydrogen chloride chains

We study the quasiparticle band structure of isolated, infinite HF and HCl bent (zigzag) chains and examine the effect of the crystal field on the energy levels of the constituent monomers. The chains are one of the simplest but realistic models of the corresponding three-dimensional crystalline solids. To describe the isolated monomers and the chains, we set out from the Hartree-Fock approximation, harnessing the advanced Green's function methods "local molecular orbital algebraic diagrammatic construction" (ADC) scheme and "local crystal orbital ADC" (CO-ADC) in a strict second order approximation, ADC(2,2) and CO-ADC(2,2), respectively, to account for electron correlations. The configuration space of the periodic correlation calculations is found to converge rapidly only requiring nearest-neighbor contributions to be regarded. Although electron correlations cause a pronounced shift of the quasiparticle band structure of the chains with respect to the Hartree-Fock result, the bandwidth essentially remains unaltered in contrast to, e.g., covalently bound compounds.Comment: 11 pages, 6 figures, 6 tables, RevTeX4, corrected typoe

Electron correlations for ground state properties of group IV semiconductors

Valence energies for crystalline C, Si, Ge, and Sn with diamond structure have been determined using an ab-initio approach based on information from cluster calculations. Correlation contributions, in particular, have been evaluated in the coupled electron pair approximation (CEPA), by means of increments obtained for localized bond orbitals and for pairs and triples of such bonds. Combining these results with corresponding Hartree-Fock (HF) data, we recover about 95 % of the experimental cohesive energies. Lattice constants are overestimated at the HF level by about 1.5 %; correlation effects reduce these deviations to values which are within the error bounds of this method. A similar behavior is found for the bulk modulus: the HF values which are significantly too high are reduced by correlation effects to about 97 % of the experimental values.Comment: 22 pages, latex, 2 figure

Oscillatory Shear Flow-Induced Alignment of Lamellar Melts of Hydrogen-Bonded Comb Copolymer Supramolecules

In this work we present the orientational behavior of comb copolymer-like supramolecules P4VP(PDP)1.0, obtained by hydrogen bonding between poly(4-vinylpyridine) and pentadecylphenol, during large-amplitude oscillatory shear flow experiments over a broad range of frequencies (0.001-10 Hz). The alignment diagram, presenting the macroscopic alignment in T/TODT vs ω/ωc, contains three regions of parallel alignment separated by a region of perpendicular alignment. For our material, the order-disorder temperature TODT = 67 °C and ωc, the frequency above which the distortion of the chain conformation dominates the materials’ viscoelasticity, is around 0.1 Hz at 61 °C. For the first time flipping from a pure transverse alignment via biaxial transverse/perpendicular alignment to a perpendicular alignment as a function of the strain amplitude was found.

Step-Wise Computational Synthesis of Fullerene C60 derivatives. 1.Fluorinated Fullerenes C60F2k

The reactions of fullerene C60 with atomic fluorine have been studied by unrestricted broken spin-symmetry Hartree-Fock (UBS HF) approach implemented in semiempirical codes based on AM1 technique. The calculations were focused on a sequential addition of fluorine atom to the fullerene cage following indication of the cage atom highest chemical susceptibility that is calculated at each step. The effectively-non-paired-electron concept of the fullerene atoms chemical susceptibility lays the foundation of the suggested computational synthesis. The obtained results are analyzed from energetic, symmetry, and the composition abundance viewpoints. A good fitting of the data to experimental findings proves a creative role of the suggested synthesis methodology.Comment: 33 pages, 11 figures, 2 tables, 2 chart

Enhancing reductive cleavage of aromatic carboxamides

[GRAPHICS] A set of aromatic and especially heteroaromatic N-benzyl carboxamides, derived from naphthalene, pyridine, pyrazine, and quinoline, and the corresponding tert-butyl acylcarbamates have been synthesized and studied by cyclic voltammetry with respect to facilitated reduction. The latter undergo regiospecific cleavage of their C(O)-N bonds under very mild reductive conditions with formation of Boc-protected (benzyl)amine in most cases in nearly quantitative yields, Examples of preparative cleavage by controlled potential electrolysis, activated aluminum, and NaBH4 are given

Partial costs of global climate change adaptation for the supply of raw industrial and municipal water: a methodology and application

Despite growing recognition of the importance of climate change adaptation, few global estimates of the costs involved are available for the water supply sector. We present a methodology for estimating partial global and regional adaptation costs for raw industrial and domestic water supply, for a limited number of adaptation strategies, and apply the method using results of two climate models. In this paper, adaptation costs are defined as those for providing enough raw water to meet future industrial and municipal water demand, based on country-level demand projections to 2050. We first estimate costs for a baseline scenario excluding climate change, and then additional climate change adaptation costs. Increased demand is assumed to be met through a combination of increased reservoir yield and alternative backstop measures. Under such controversial measures, we project global adaptation costs of $12 bn p.a., with 83-90$73 bn p.a.), which supports the notion of mainstreaming climate change adaptation into broader policy aims. The method provides a tool for estimating broad costs at the global and regional scale; such information is of key importance in international negotiations. © 2010 IOP Publishing Ltd

Platelet monoamine oxidase activity predicts alcohol sensitivity and voluntary alcohol intake in rhesus monkeys

Platelet monoamine oxidase B (MAO-B) has been proposed to be a biological marker for the properties of monoamine systems, with low activity being associated with vulnerability for high scores on personality traits such as sensation seeking, monotony avoidance, and impulsiveness, as well as for vulnerability for alcoholism. In the present study, platelet MAO-B activity was analysed in 78 rhesus macaques, and its relation to voluntary alcohol intake and behaviours after intravenous alcohol administration was observed

Election proximity and representation focus in party-constrained environments

Do elected representatives have a time-constant representation focus or do they adapt their focus depending on election proximity? In this article, we examine these overlooked theoretical and empirical puzzles by looking at how reelection-seeking actors adapt their legislative behavior according to the electoral cycle. In parliamentary democracies, representatives need to serve two competing principals: their party and their district. Our analysis hinges on how representatives make a strategic use of parliamentary written questions in a highly party-constrained institutional context to heighten their reselection and reelection prospects. Using an original data set of over 32,000 parliamentary questions tabled by Portuguese representatives from 2005 to 2015, we examine how time interacts with two key explanatory elements: electoral vulnerability and party size. Results show that representation focus is not static over time and, in addition, that electoral vulnerability and party size shape strategic use of parliamentary questions