Plasma jets driven by ultraintense-laser interaction with thin foils

Experimental evidence of plasma jets ejected from the rear side of thin solid targets irradiated by ultraintense (>10(19) W cm(-2)) laser pulses is presented. The jets, detected by transverse interferometric measurements with high spatial and temporal resolutions, show collimated expansion lasting for several hundreds of picoseconds and have substantially steep density gradients at their periphery. The role played by radiation pressure of the laser in the jet formation process is highlighted analytically and by extensive two-dimensional particle-in-cell simulations.     

First-principles study of defect-induced magnetism in carbon

We have studied the role of defects on the magnetic properties of carbon materials using first-principles density functional methods. We show that, while the total magnetization decreases both for diamond and graphite with increase in vacancy density, the magnetization decreases more rapidly for graphitic structures. The presence of nitrogen nearby a vacancy is shown to produce larger macroscopic magnetic signals as compared to a standalone carbon vacancy. The results indicate the possibility of tuning magnetization in carbon by controlled defect generation and doping.     

Potential-screening on atomic wavelengths

In this article, we review or report recent works on atomic wavelengths in screening environments. We mainly review recent works on the transition, tune-out and magic wavelengths with Coulomb and screened Coulomb potentials. We also present our investigation on tune-out and magic wavelengths for two-electron Yukawa atoms. The various transition wavelengths for two-electron systems with and without screening environments are also presented.     

Acquisition Time for Ground-to-Satellite Optical Communication System in Weak Atmospheric Turbulence with Spatial Diversity

Abstract

In this article, various issues involved in a ground-to-satellite optical communication link (i.e., acquisition time, uncertainty area, and channel noise) are discussed. Acquisition time of a free-space optical link is evaluated for coherent (sub-carrier BPSK and QPSK) and non-coherent (OOK and -PPM) modulation schemes over weak turbulent channel with transmit diversity. In the analysis, both uncorrelated and correlated beams are considered. It is seen that an increase in transmit diversity order helps to improve the acquisition time, irrespective of turbulence strength in the atmosphere. At high correlation, a marginal change in acquisition time is observed with the increase in diversity order.     

Bound states and resonance states of the plasma-embedded tdμ and ddμ molecular ions

We have investigated the bound states and resonance states of plasma-embedded tdμ and ddμ molecular ions using accurate correlated basis functions. The plasma effect has been taken care of by considering the Debye shielding approach of plasma modeling which admits a variety of plasma conditions. The density of resonance states are calculated using the stabilization method. The ground and excited states energies, and the S-wave resonance energies of tdμ and ddμ molecular ions immersed in plasmas are reported for various shielding parameters, along with the 1S and 2S threshold energies of the tμ and dμ atoms.     

Quality Related Safety Evaluation of a South African Traditional Formulation (PHELA®) as Novel Anti-Biofilm Candidate

A South African traditional formulation, PHELA^®, is consumed by the traditional people for severe chest problems with coughing, diarrhea, oral ulcers etc. The present study focused on establishing the anti-infective properties of a safe and standardized poly-herbal formulation through a series of criteria and specifications.     

Nucleation of microcracks during dislocation interactions in a Ti<Subscript>3</Subscript>Al single crystal

Reactions between superdislocations involved in deformation in the basal, prismatic, and type-I and II pyramidal planes in single-crystal Ti₃Al are considered. The types of dislocation interactions are established that result in the formation dislocation barriers (microcrack nuclei). The force and energy conditions for microcracks to arise are found. The interaction between a and 2c + a superdislocations results in microcracks with the plane of opening lying in basal and pyramidal planes; the interaction of 2c + a superdislocations in different pyramidal planes results in the formation of microcracks in prismatic and pyramidal planes; and the interaction of a superdislocations in basal and/or pyramidal planes does not cause the formation of dislocation barriers. The types of microcracks are classified in terms of the orientation of deformation axes of single crystals, and the regions of the stereographic triangle are determined characterized by a preferential type of crack opening.     

Kinetics of Early Decomposition Stages in Diluted bcc Fe–Сu–Ni–Al Alloy: MC+MD Simulation

Physics of the Solid State - A combined approach including the Monte Carlo and molecular-dynamics simulation, decomposition kinetics and segregation formation in the multicomponent low-alloy...     

Essential Amino Acid–Enabled Lead Bromide Perovskite Nanocrystals with High Stability

This work reports the first synthesis of MAPbBr₃ perovskite nanocrystals (PNCs) using amino acids as the ligand with excellent optical properties. A variety of amino acids are used to optimize the luminescence properties. A mechanochemical approach has taken lead over conventional colloidal chemistry during synthesis. All morphological and optical studies are performed to characterize the synthesized perovskite nanoparticles. Later, stability studies are investigated through thermogravimetric analysis, temperature‐dependent photoluminescence, time‐dependent X‐ray diffraction, as well as X‐ray photoelectron spectroscopy. In an application, interestingly, these perovskites show high luminescence upon scratching on flexible conducting plates and on plain paper surface. These results suggest that the amino acid–ligated perovskite nanocrystals can be potential materials for optoelectronic application including light‐emitting diodes and imaging.     

On further application of r as a metric for validation of QSAR models

Validation is a crucial aspect for quantitative structure–activity relationship (QSAR) model development. External validation is considered, in general, as the most conclusive proof of predictive capacity of a QSAR model. In the absence of truly external data set, external validation is usually performed on test set compounds, which are members of the original data set but not used in model development exercise. In the case of small data sets, QSAR researchers experience problem in model development due to the fact that the developed models may be less reliable on account of the small number of training set compounds and such models may also show poor external predictability because the models may not have captured all necessary features required for the particular structure–activity relationships. The present paper attempts to show that ‘true r_(LOO)’ statistic calculated based on the model derived from the undivided data set with application of variable selection strategy at each cycle of leave‐one‐out (LOO) validation may reflect external validation characteristics of the developed model thus obviating the requirement of splitting of the data set into training and test sets. This approach may be helpful in the case of small data sets as it uses all available data for model development and validation thus making the resulting model more reliable. Copyright © 2009 John Wiley & Sons, Ltd.