Bosonic Monocluster Expansion

We compute Green's functions of a Bosonic field theory with cutoffs by means of a “minimal” expansion which in a single move, interpolating a generalized propagator, performs the usual tasks of the cluster and Mayer expansion. In this way it allows a direct construction of the infinite volume or thermodynamic limit and it brings constructive Bosonic expansions closer to constructive Fermionic expansions and to perturbation theory. Received: 18 May 2000 / Accepted: 21 March 2001     

Fluorescent probes for detection of amphiphilic polymer hydrophobic microdomains: A comparative study between pyrene and molecular rotors

 Cationic amphiphilic polymers (e.g. polyvinylpyridinium bromides and polyvinylimidazo-lium bromides) adopt a compact coiled form in aqueous solutions. In the case of former polymers, the resulting hydrophobic microdomains are evidenced only by fluorescence spectroscopy if a molecular rotor (DMAC) is used as a fluorescent probe, while the behaviour of the latter can be studied in aqueous solution by using both types of fluorescent probes, i.e., pyrene and the molecular rotor. The purpose of the present investigation deals with a comparative study between the magnitude of the local viscosity and the polarity of the hydrophobic microdomains generated by poly(3-hexadecyl-1-vinylimidazolium bromide) in an aqueous medium using pyrene and DMAC as fluorescent probes. Moreover, the results are compared with the data obtained with micelles of conventional surfactants such as the homopolymer repetitive unit model and CTAB. Received: 3 June 1996 Accepted: 29 September 1996     

Coumarin-based D–π–A dyes for efficient DSSCs: DFT and TD-DFT study of the π-spacers influence on photovoltaic properties

Research on Chemical Intermediates - A series of D–π–A architectures dyes with Coumarin-based derivatives as difluorenylaminocoumarin (DF) and diphenylaminocoumarin (DP) have been...     

New materials based on thiazolothiazole and thiophene candidates for optoelectronic device applications: theoretical investigations

We report theoretical analysis on the geometries and electronic properties of new conjugated compounds based on thiazolothiazole synthesized by Ando et al. (Synth. Met., 156:327 [13]). The theoretical ground-state geometry and electronic structure of the studied molecules were investigated by the density functional theory (DFT) method at Becke’s three-parameter functional and Lee–Yang–Parr functional (B3LYP) level with 6-31G(d,p) basis set. The effects of the ring structure and the substituents on the geometries and electronic properties of these materials are discussed to investigate the relationship between molecular structure and optoelectronic properties. This investigation was used to drive further syntheses towards compounds more useful as active optoelectronic materials. Theoretical knowledge of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the components is basic in studying organic solar cells, so the HOMO, LUMO, and gap energy V _oc (open-circuit voltage) of the studied compounds are calculated and discussed. These properties suggest these materials as good candidates for use in organic dye-sensitized solar cells.     

Electronic structure and thermochemistry for monocarbides MC,MC+ and MC− (M=Zn,Cd, Hg): CCSD(T) and DFT works

In this work, the ab-initio coupled cluster CCSD(T) method and the B3LYP, BP91W and CAM-B3LYP functional of DFT method in conjunction with the aug-cc-pVTZ-PP basis have been applied to study the group 12 monocarbides MC, MC⁺ and MC^?. The potential energy curves (PECs) for the three electronic states ³Σ^?, ⁵Σ^? and ¹Δ of the MC and the two states ²∑^- and ⁴∑^- for the MC⁺ cations and MC^? anions have been investigated. In addition, Bond distance Re, transition energy Te, vibrational frequency ω_e, ionization energy IE, electron affinity EA, dipole moment μ, dissociation energy D₀ and heat formation ΔH°f₀/ΔH°f₂₉₈, were determined for each species. The analysis of the dissociation energy for ZnC, CdC and HgC shows the decrease in the stability of the monocarbides from Zn to Hg. For ΔH°f₀/ΔH°f₂₉₈ values of MC, which are not known experimentally or theoretically, we recommend the following CCSD(T) predictions of ZnC, CdC and HgC: 181.3/178.54, 180.65/178.4 and 175.35/174.71 kcal/mol respectively. Comparing the three functionals with the CCSD(T) results, the CAM-B3LYP functional shows excellent predictive agreement for the various properties of the group 12 monocarbides.     

Search for the scalar top quark in pp collisions at square root[s] = 1.8 TeV

We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses.     

Search for heavy particles decaying into electron-positron pairs in pp collisions

We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.     

Search for a standard model Higgs boson in the H→ZZ→ℓ(+)ℓ(-)νν decay channel with the ATLAS detector

A search for a heavy standard model Higgs boson decaying via H→ZZ→→?(+)?(-)νν, where ?=e, μ, is presented. It is based on proton-proton collision data at √s=7 TeV, collected by the ATLAS experiment at the LHC in the first half of 2011 and corresponding to an integrated luminosity of 1.04 fb(-1). The data are compared to the expected standard model backgrounds. The data and the background expectations are found to be in agreement and upper limits are placed on the Higgs boson production cross section over the entire mass window considered; in particular, the production of a standard model Higgs boson is excluded in the region 340相似文献   

A critique on the structural analysis of lignins and application of novel tandem mass spectrometric strategies to determine lignin sequencing

This review is devoted to the application of MS using soft ionization methods with a special emphasis on electrospray ionization, atmospheric pressure photoionization and matrix‐assisted laser desorption/ionization MS and tandem MS (MS/MS) for the elucidation of the chemical structure of native and modified lignins. We describe and critically evaluate how these soft ionization methods have contributed to the present‐day knowledge of the structure of lignins. Herein, we will introduce new nomenclature concerning the chemical state of lignins, namely, virgin released lignins (VRLs) and processed modified lignins (PML). VRLs are obtained by liberation of lignins through degradation of vegetable matter by either chemical hydrolysis and/or enzymatic hydrolysis. PMLs are produced by subjecting the VRL to a series of further chemical transformations and purifications that are likely to alter their original chemical structures. We are proposing that native lignin polymers, present in the lignocellulosic biomass, are not made of macromolecules linked to cellulose fibres as has been frequently reported. Instead, we propose that the lignins are composed of vast series of linear related oligomers, having different lengths that are covalently linked in a criss‐cross pattern to cellulose and hemicellulose fibres forming the network of vegetal matter. Consequently, structural elucidation of VRLs, which presumably have not been purified and processed by any other type of additional chemical treatment and purification, may reflect the structure of the native lignin. In this review, we present an introduction to a MS/MS top–down concept of lignin sequencing and how this technique may be used to address the challenge of characterizing the structure of VRLs. Finally, we offer the case that although lignins have been reported to have very high or high molecular weights, they might not exist on the basis that such polymers have never been identified by the mild ionizing techniques used in modern MS. Copyright © 2015 John Wiley & Sons, Ltd.