Measurement of the top quark pair production cross section in pp collisions at s=7TeV in dilepton final states with ATLAS

A measurement of the production cross section of top quark pairs ($t\overline{t}$) in proton–proton collisions at a center-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider is reported. Candidate events are selected in the dilepton topology with large missing transverse energy and at least two jets. Using a data sample corresponding to an integrated luminosity of $35{\mathrm{pb}}^{?1}$, a $t\overline{t}$ production cross section ${\sigma }_{t\overline{t}}=177\pm 20(\text{stat.})\pm 14(\text{syst.})\pm 7(\text{lum.})\text{pb}$ is measured for an assumed top quark mass of $m_t=172.5\text{GeV}$. A second measurement requiring at least one jet identified as coming from a b quark yields a comparable result, demonstrating that the dilepton final states are consistent with being accompanied by b-quark jets. These measurements are in good agreement with Standard Model predictions.     

Transient resonance Raman and density functional theory investigation of the ultraviolet photolysis of dibromoacetonitrile in the solution phase

Ultraviolet photolysis of dibromoacetonitrile in cyclohexane solution was investigated using transient resonance Raman spectroscopy. The experimental Raman vibrational frequencies were compared to those predicted from density functional theory calculations for several probable photoproduct species. Our results indicate that significant amounts of the Br–NCCHBr adduct is produced on the nanosecond time scale. We briefly discuss the probable mechanisms of formation of the Br–NCCHBr species and implications for using substituted dihaloalkanes as carbenoid agents in cyclopropanation reactions.     

Synthesis and in vitro activity of a non-epimerizable analog of the angiotensin-converting enzyme inhibitor A58365A

The 3-methyl-substituted analog (±)-3 of the angiotensin converting enzyme inhibitor A58365A (1) was synthesized from lactone 4 and amino acid ester 16, via key intermediates 18, 19 and 21a,b. Compound (±)-3 was found to possess powerful ACE inhibitory activity (IC₅₀ = ca 500 nM), as judged by in vitro tests against porcine kidney ACE, under conditions in which the commercial drug captopril has IC₅₀ = 280 nM.     

The muon anomalous magnetic moment from a generic charged Higgs with SUSY

We study the contribution of a generic charged Higgs (H⁺) to the muon anomalous magnetic moment a_μ with the SUSY soft breaking parameters. We find out that the deviation between the experimental data and the predicted SM value on a_μ can be explained by the two-loop charged Higgs diagrams even with m_H⁺∼400 GeV.     

Ionic and electronic conductivity of Yb2+xTi2−xO7−x/2 materials

Bulk and grain boundary conductivities of Yb_2+xTi_2−xO_7−x/2 (x = 0, 0.1, 0.18 and 0.29) materials were studied by impedance spectroscopy in the range 300–900 °C in air. Ionic and electronic conductivities were separated by both ion blocking Hebb–Wagner measurements and total conductivity measurements as a function of oxygen partial pressure in the temperature range 700–1000 °C. The oxygen partial pressure dependence of the total conductivity shows that these materials are nearly pure ionic conductors in air and that the ionic conductivity decreases for Yb-rich compositions. This was interpreted as a predominant effect of a decrease in mobility of ionic charge carriers, opposing the expected increase in concentration of oxygen vacancies with increasing Yb content. The studied materials become mixed conductors under typical fuel conditions, except possibly at temperatures below about 700 °C. Yb-excess slightly suppresses the electronic conductivity.     

Dynamics of solitary waves over an erodible surface

In this paper, we propose a new approach in the study of the dynamics of solitary waves over an erodible surface consisting of non-cohesive particles transported by a constant unidirectional fluid. Using the multiple scale perturbation method, we show that the system can be described by the Kadomtsev–Petviashvili equation. The solution presented here shows that this mathematical model can be used to explain the dynamical behaviour of sand dunes in the desert.     

Laying the groundwork for proteomics: Mass spectrometry from 1958 to 1988

The development of mass spectrometric methodologies for the sequencing of peptides and proteins are recounted. Early strategies for the determination of very large proteins based on a combination of nucleotide sequencing and mass spectrometric amino acid sequencing are described and their historical significance to the new field of proteomics is outlined.     

Resolving Atomic-Scale Defects in Conjugated Polymers On-Surfaces

Atomic scale defects significantly affect the mechanical, electronic, and optical properties of π-conjugated polymers. Here, isolated atomic-scale defects are deliberately introduced into a prototypical anthracene-ethynylene π-conjugated polymer, and its local density of states is carefully examined on the atomic scale to show how individual defects modify the inherent electronic and magnetic properties of this one-dimensional systems. Scanning tunneling and atomic force microscopy experiments, supplemented with density functional theory calculations, reveal the existence of a sharp electronic resonance at the Fermi energy around certain defects, which is associated with the formation of a local magnetic moment accompanied by substantial mitigation of the mobility of charge carriers. While defects in traditionally synthesized polymers lead to arbitrary conformations, the presented results clearly reflect the preferential formation of low dimensional defects at specific polymer sites, which may introduce the possibility of engineering macroscopic defects in surface-synthesized conjugated polymers.