Topology of the polarization field in ferroelectric nanowires from first principles

The behaviour of the cross-sectional polarization field is explored for thin nanowires of barium titanate from first-principles calculations. Topological defects of different winding numbers have been obtained, beyond the known textures in ferroelectric nanostructures. They result from the inward accommodation of the polarization patterns imposed at the surface of the wire by surface and edge effects. Close to a topological defect the polarization field orients out of the basal plane in some cases, maintaining a close to constant magnitude, whereas it virtually vanishes in other cases.Comment: 4 pages, 3 figure

In vitro and in vivo effects of salbutamol on neutrophil function in acute lung injury

Background: Intravenous salbutamol (albuterol) reduces lung water in patients with the acute respiratory distress syndrome (ARDS). Experimental data show that it also reduces pulmonary neutrophil accumulation or activation and inflammation in ARDS. Aim: To investigate the effects of salbutamol on neutrophil function. Methods: The in vitro effects of salbutamol on neutrophil function were determined. Blood and bronchoalveolar lavage (BAL) fluid were collected from 35 patients with acute lung injury (ALI)/ARDS, 14 patients at risk from ARDS and 7 ventilated controls at baseline and after 4 days’ treatment with placebo or salbutamol (ALI/ARDS group). Alveolar–capillary permeability was measured in vivo by thermodilution (PiCCO). Neutrophil activation, adhesion molecule expression and inflammatory cytokines were measured. Results: In vitro, physiological concentrations of salbutamol had no effect on neutrophil chemotaxis, viability or apoptosis. Patients with ALI/ARDS showed increased neutrophil activation and adhesion molecule expression compared with at risk-patients and ventilated controls. There were associations between alveolar– capillary permeability and BAL myeloperoxidase (r = 0.4, p = 0.038) and BAL interleukin 8 (r = 0.38, p = 0.033). In patients with ALI/ARDS, salbutamol increased numbers of circulating neutrophils but had no effect on alveolar neutrophils. Conclusion: At the onset of ALI/ARDS, there is increased neutrophil recruitment and activation. Physiological concentrations of salbutamol did not alter neutrophil chemotaxis, viability or apoptosis in vitro. In vivo, salbutamol increased circulating neutrophils, but had no effect on alveolar neutrophils or on neutrophil activation. These data suggest that the beneficial effects of salbutamol in reducing lung water are unrelated to modulation of neutrophil-dependent inflammatory pathways

Measurements of the semileptonic decays B[overbar]→Dℓν[overbar] and B[overbar]→D^*ℓν[overbar] using a global fit to DXℓν[overbar] final states

Semileptonic B[overbar] decays to DXℓν[overbar](ℓ=e or μ) are selected by reconstructing D^0ℓ and D^+ℓ combinations from a sample of 230×10^6 Υ(4S)→BB[overbar] decays recorded with the BABAR detector at the PEP-II e^+e^- collider at SLAC. A global fit to these samples in a three-dimensional space of kinematic variables is used to determine the branching fractions B(B^-→D^0ℓν[overbar])=(2.34±0.03±0.13)% and B(B^-→D^(*0)ℓν[overbar])=(5.40±0.02±0.21)% where the errors are statistical and systematic, respectively. The fit also determines form-factor parameters in a parametrization based on heavy quark effective theory, resulting in ρ_D^2=1.20±0.04±0.07 for B[overbar]→Dℓν[overbar] and ρ_(D*)^2=1.22±0.02±0.07 for B[overbar]→D^*ℓν[overbar]. These values are used to obtain the product of the Cabibbo-Kobayashi-Maskawa matrix element |V_(cb)| times the form factor at the zero recoil point for both B[overbar]→Dℓν[overbar] decays, G(1)|V_(cb)|=(43.1±0.8±2.3)×10^(-3), and for B[overbar]→D^*ℓν[overbar] decays, F(1)|V_(cb)|=(35.9±0.2±1.2)×10^(-3)

Bifurcation Boundary Conditions for Switching DC-DC Converters Under Constant On-Time Control

Sampled-data analysis and harmonic balance analysis are applied to analyze switching DC-DC converters under constant on-time control. Design-oriented boundary conditions for the period-doubling bifurcation and the saddle-node bifurcation are derived. The required ramp slope to avoid the bifurcations and the assigned pole locations associated with the ramp are also derived. The derived boundary conditions are more general and accurate than those recently obtained. Those recently obtained boundary conditions become special cases under the general modeling approach presented in this paper. Different analyses give different perspectives on the system dynamics and complement each other. Under the sampled-data analysis, the boundary conditions are expressed in terms of signal slopes and the ramp slope. Under the harmonic balance analysis, the boundary conditions are expressed in terms of signal harmonics. The derived boundary conditions are useful for a designer to design a converter to avoid the occurrence of the period-doubling bifurcation and the saddle-node bifurcation.Comment: Submitted to International Journal of Circuit Theory and Applications on August 10, 2011; Manuscript ID: CTA-11-016

Measurement of time-dependent CP asymmetry in B^0→K_S^0π^0γ decays

We measure the time-dependent CP asymmetry in B^0→K_S^0π^0γ decays for two regions of K_S^0-π^0 invariant mass, m(KS0π0), using the final BABAR data set of 467×10^6 BB pairs collected at the PEP-II e^+e^- collider at SLAC. We find 339±24 B^0→K^(*0)γ candidates and measure S_(K*γ)=-0.03±0.29±0.03 and C_(K*_γ)=-0.14±0.16±0.03. In the range 1.1<m(K_S^0π^0)<1.8  GeV/c^2 we find 133±20 B^0→K_S^0π^0γ candidates and measure S_(KS^0π^0γ)=-0.78±0.59±0.09 and C_(KS^0π^0γ)=-0.36±0.33±0.04. The uncertainties are statistical and systematic, respectively

Border ownership selectivity in human early visual cortex and its modulation by attention

Natural images are usually cluttered because objects occlude one another. A critical aspect of recognizing these visual objects is to identify the borders between image regions that belong to different objects. However, the neural coding of border ownership in human visual cortex is largely unknown. In this study, we designed two simple but compelling stimuli in which a slight change of contextual information could induce a dramatic change of border ownership. Using functional MRI adaptation, we found that border ownership selectivity in V2 was robust and reliable across subjects, and it was largely dependent on attention. Our study provides the first human evidence that V2 is a critical area for the processing of border ownership and that this processing depends on the modulation from higher-level cortical areas. Copyright © 2009 Society for Neuroscience

Measurement of branching fractions of B decays to K_1(1270)π and K_1(1400)π and determination of the CKM angle α from B^0→a_1(1260)^±π^∓

We report measurements of the branching fractions of neutral and charged B meson decays to final states containing a K_1(1270) or K_1(1400) meson and a charged pion. The data, collected with the BABAR detector at the SLAC National Accelerator Laboratory, correspond to 454×10^6 BB̅ pairs produced in e^+e^- annihilation. We measure the branching fractions B(B^0→K_1(1270)^+π-+K_1(1400)^+π-)=3.1_(-0.7)^(+0.8)×10^(-5) and B(B^+→K_1(1270)^0π^++K_1(1400)^0π^+)=2.9_(-1.7)^(+2.9)×10^(-5) (<8.2×10^(-5) at 90% confidence level), where the errors are statistical and systematic combined. The B^0 decay mode is observed with a significance of 7.5σ, while a significance of 3.2σ is obtained for the B^+ decay mode. Based on these results, we estimate the weak phase α=(79±7±11)° from the time-dependent CP asymmetries in B^0→a1(1260)^±π^∓ decays