Coherent Diffraction Imaging of Single 95nm Nanowires

Photonic or electronic confinement effects in nanostructures become significant when one of their dimension is in the 5-300 nm range. Improving their development requires the ability to study their structure - shape, strain field, interdiffusion maps - using novel techniques. We have used coherent diffraction imaging to record the 3-dimensionnal scattered intensity of single silicon nanowires with a lateral size smaller than 100 nm. We show that this intensity can be used to recover the hexagonal shape of the nanowire with a 28nm resolution. The article also discusses limits of the method in terms of radiation damage.Comment: 5 pages, 5 figure

Clathrin-dependent endocytosis of membrane-bound RANKL in differentiated osteoclasts

Bone is continuously repaired and remodelled through well-coordinated activity of osteoblasts that form new bone and osteoclasts, which resorb it. Osteoblasts synthesize and secrete two key molecules that are important for osteoclast differentiation, namely the ligand for the receptor of activator of nuclear factor κB (RANKL) and its decoy receptor osteoprotegerin (OPG). Active membrane transport is a typical feature of the resorbing osteoclast during bone resorption. Normally, one resorption cycle takes several hours as observed by monitoring actin ring formation and consequent disappearance in vitro. During these cyclic changes, the cytoskeleton undergoes remarkable dynamic rearrangement. Active cells show a continuous process of exocytosis that plays an essential role in transport of membrane components, soluble molecules and receptor-mediated ligands thus allowing them to communicate with the environment. The processes that govern intracellular transport and trafficking in mature osteoclasts are poorly known. The principal methodological problem that have made these studies difficult is a physiological culture of osteoclasts that permit observing the vesicle apparatus in conditions similar to the in vivo conditions. In the present study we have used a number of morphological approaches to characterize the composition, formation and the endocytic and biosynthetic pathways that play roles in dynamics of differentiation of mature bone resorbing cells using a tri-dimensional system of physiologic coculture

Nonlinear dynamics of Bose-condensed gases by means of a low- to high-density variational approach

We propose a versatile variational method to investigate the spatio-temporal dynamics of one-dimensional magnetically-trapped Bose-condensed gases. To this end we employ a \emph{q}-Gaussian trial wave-function that interpolates between the low- and the high-density limit of the ground state of a Bose-condensed gas. Our main result consists of reducing the Gross-Pitaevskii equation, a nonlinear partial differential equation describing the T=0 dynamics of the condensate, to a set of only three equations: \emph{two coupled nonlinear ordinary differential equations} describing the phase and the curvature of the wave-function and \emph{a separate algebraic equation} yielding the generalized width. Our equations recover those of the usual Gaussian variational approach (in the low-density regime), and the hydrodynamic equations that describe the high-density regime. Finally, we show a detailed comparison between the numerical results of our equations and those of the original Gross-Pitaevskii equation.Comment: 11 pages, 12 figures, submitted to Phys. Rev. A, January 200

TLR7/8 agonist induces a post-entry SAMHD1-independent block to HIV-1 infection of monocytes

Additional file 6. Recombinant IL-1β does not block HIV infection in PBMC. Two additional donors similar to Fig. 4e are shown. PBMC from 2 healthy donors were treated with 100 U/mL IFNα, 10 μM R848 or 0.1, 1, 10 or 100 ng/mL IL-1μ for 24 h. The cells were then infected with HIV1 or HIV1 X+ luciferase reporter virus and infectivity was measured 72 h post-infection by luciferase assay

Nonresonant microwave absorption in epitaxial La-Sr-Mn-O films and its relation to colossal magnetoresistance

We study magnetic-field-dependent nonresonant microwave absorption and dispersion in thin La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ films and show that it originates from the colossal magnetoresistance. We develop the model for magnetoresistance of a thin ferromagnetic film in oblique magnetic field. The model accounts fairly well for our experimental findings, as well as for results of other researchers. We demonstrate that nonresonant microwave absorption is a powerful technique that allows contactless measurement of magnetic properties of thin films, including magnetoresistance, anisotropy field and coercive field.Comment: 20 pages, 11 figure

Local tetragonal distortion in La_{0.7}Sr_{0.3}MnO_3 strained thin films probed by x-ray absorption spectroscopy

We report on an angular resolved X-ray Absorption Spectroscopy study of $La_{0.7}Sr_{0.3}MnO_{3}$ thin films epitaxially grown by pulsed laser deposition on slightly mismatched substrates which induce tensile or compressive strains. XANES spectra give evidence of tetragonal distortion within the $MnO_{6}$ octahedra, with opposite directions for tensile and compressive strains. Quantitative analysis has been done and a model of tetragonal distortion reflecting the strain has been established. EXAFS data collected in plane for tensile substrate confirm the change in the $Mn-O$ average bond distance and the increase of $Mn-Mn$ length matching with the enlargement of the cell parameter. From these results we conclude that there is no significant change in the $Mn-O-Mn$ angle. Our observations conflict with the scenarios which this angle is the main driving parameter in the sensitivity of manganite films properties to external strains and suggest that the distortion within the octahedra plays a key role in the modification of the transport and magnetic properties.Comment: 8 pages, 6 figure

Analysis of strain and stacking faults in single nanowires using Bragg coherent diffraction imaging

Coherent diffraction imaging (CDI) on Bragg reflections is a promising technique for the study of three-dimensional (3D) composition and strain fields in nanostructures, which can be recovered directly from the coherent diffraction data recorded on single objects. In this article we report results obtained for single homogeneous and heterogeneous nanowires with a diameter smaller than 100 nm, for which we used CDI to retrieve information about deformation and faults existing in these wires. The article also discusses the influence of stacking faults, which can create artefacts during the reconstruction of the nanowire shape and deformation.Comment: 18 pages, 6 figures Submitted to New Journal of Physic

High frequency magnetic oscillations of the organic metal θ\theta-(ET)4_4ZnBr4_4(C6_6H4_4Cl2_2) in pulsed magnetic field of up to 81 T

De Haas-van Alphen oscillations of the organic metal $\theta$-(ET)$_4$ZnBr$_4$(C$_6$H$_4$Cl$_2$) are studied in pulsed magnetic fields up to 81 T. The long decay time of the pulse allows determining reliable field-dependent amplitudes of Fourier components with frequencies up to several kiloteslas. The Fourier spectrum is in agreement with the model of a linear chain of coupled orbits. In this model, all the observed frequencies are linear combinations of the frequency linked to the basic orbit $\alpha$ and to the magnetic-breakdown orbit $\beta$.Comment: 6 pages, 4 figure

The impact of acute calcium intake on bone turnover markers during a training day in elite male rowers

Introduction: While an acute exercise session typically increases bone turnover markers (BTM), the impact of subsequent sessions and the interaction with pre-exercise calcium intake remains unclear despite the application to the ‘real life’ training of many competitive athletes. Methods: Using a randomized crossover design, elite male rowers (n = 16) completed two trials, a week apart, consisting of two 90-minute rowing ergometer sessions (Ex1, Ex2) separated by 150 minutes. Prior to each trial, participants consumed a high (CAL: ~1000 mg) or isocaloric low (CON: \u3c 10 mg) calcium meal. Biochemical markers including parathyroid hormone: PTH; serum ionised calcium (iCa) and bone turnover markers (C-terminal telopeptide of type I collagen: β-CTX-I; osteocalcin: OC) were monitored from baseline to 3 hours post Ex2. Results: While each session caused perturbances of serum iCa, CAL maintained calcium concentrations above those of CON for most time points, 4.5 and 2.4 % higher post EX1 and EX2 respectively. The decrease in iCa in CON was associated with an elevation of blood PTH (p \u3c 0.05) and β-CTX-I (p \u3c 0.0001) over this period of repeated training sessions and their recovery, particularly during and after Ex2. Pre-exercise intake of calcium-rich foods lowered BTM over the course of a day with several training sessions. Conclusions: Pre-exercise intake of a calcium-rich meal prior to training sessions undertaken within the same day had a cumulative and prolonged effect on the stabilisation of blood iCa during exercise. In turn, this reduced the post-exercise PTH response, potentially attenuating the increase in markers of bone resorption. Such practical strategies may be integrated into the athlete’s overall sports nutrition plan, with the potential to safeguard long term bone health and reduce the risk of bone stress injuries

Superfluid Dynamics of a Bose-Einstein Condensate in a Periodic Potential

We investigate the superfluid properties of a Bose-Einstein condensate (BEC) trapped in a one dimensional periodic potential. We study, both analytically (in the tight binding limit) and numerically, the Bloch chemical potential, the Bloch energy and the Bogoliubov dispersion relation, and we introduce {\it two} different, density dependent, effective masses and group velocities. The Bogoliubov spectrum predicts the existence of sound waves, and the arising of energetic and dynamical instabilities at critical values of the BEC quasi-momentum which dramatically affect its coherence properties. We investigate the dependence of the dipole and Bloch oscillation frequencies in terms of an effective mass averaged over the density of the condensate. We illustrate our results with several animations obtained solving numerically the time-dependent Gross-Pitaevskii equation.Comment: 13 pages, 7 figures, movies and published paper available at http://www.iop.org/EJ/abstract/1367-2630/5/1/11