Physics

Interest to the passive Q-switching mode in lasers does not fade on decades. Manufacturing in the last time of new passive Q-switches (PS) of crystalline type allows one to realize this regime for lasers of the broad spectral range. This, in turn, demands to perfect the model describing this mode of oscillation. In particular, general formulas for output energy and giant pulse duration are recently generalized for the case of excited state (ES) absorption in PS with phototropic centers (PC). The aim of the present paper is further ...

Page 1. Electronic copy available at: http://ssrn.com/abstract=1837223 Inter-linkages between Stock Exchanges: A Study of BRIC Nations Gagan Deep Sharma BBSB Engineering College Fatehgarh Sahib Gurjit Singh BBSB Engineering College Fatehgarh Sahib ...

Structural defects present on chemical vapor deposition (CVD)-graphene are usually originated from growth stage and transfer process. Those limit the electronic transport properties of the graphene and degrade performance of related devices. Here we report that those inherent atomic defects could be selectively healed by simple vapor phase treatment performed in equipment conventionally used for atomic layer deposition (ALD). The unique chemistry of Al2O3 ALD facilitated selective depositions of AlxOy compounds on the defects, which was able to be readily probed and visualized using AFM imaging. The healing agent, AlxOy, was observed to bind tightly to the defects and lead to doping of the CVD-graphene, which were reflected in noticeable improvement in the electrical sheet resistance. In contrast with the chemically doped graphene, the ALD treated graphenes revealed notable long term stability under environmental conditions. Our approach promises selective healing of defects present...

ABSTRACTTo investigate the role of grain boundaries and other growth related microstructure in manganite films, a scanning tunneling microscope is used to simultaneously probe surface topography and local potential distribution under current flow at nanometer level in films of epitaxial thin films of La0.7Ca0.3MnO3 deposited on single crystal SrTiO3 and NdGaO3 substrate by laser ablation. We have studied two types of films strained and strain relaxed. Thin (50nm) films (strained due to lattice mismatch between substrate and the film) show step growth (unit cell steps) and have very smooth surfaces. Relatively thicker films (strain relaxed, thickness 200nm) do not have these step growths and show rather smooth well connected grains. Charge transport in these films is not uniform on the nanometer level and is accompanied by potential jumps at the internal surfaces. In particular scattering from grain boundaries results in large variations in the local potential resulting in fields as ...

... Resistivities of Nao.63WO3 and Nao.61Tao.lWo.903 single crystals (N~ Gayathri, private communication). x ~< 0.9. ... 200-5 0 0 0 5o 100 150 200 300 Temperature (K) Resistivities of polycrystalline LaNiO3 and Na0.9WO3 single crystal (N. Gayathri, private communication). ...

ABSTRACT Nanowires with high aspect ratio can become unstable due to Rayleigh-Plateau instability. The instability sets in below a certain minimum diameter when the force due to surface tension exceeds the limit that can lead to plastic flow as determined by the yield stress of the material of the wire. This minimum diameter is given dm ≈ 2sigmaS/sigmaY , where sigmaS is the surface tension and sigmaY is the Yield force. For Ag and Cu we estimate that dm ≈ 15nm. The Rayleigh instability (a classical mechanism) is severely modified by electronic shell effect contributions. It has been predicted recently that quantum-size effects arising from the electron confinement within the cross section of the wire can become an important factor as the wire is scaled down to atomic dimensions, in fact the Rayleigh instability could be completely suppressed for certain values of kF r0. Even for the stable wires, there are pockets of temperature where the wires are unstable. Low-frequency resistance fluctuation (noise) measurement is a very sensitive probe of such instabilities, which often may not be seen through other measurements. We have studied the low-frequency resistance fluctuations in the temperature range 77K to 400K in Ag and Cu nanowires of average diameter ≈ 15nm to 200nm. We identify a threshold temperature T* for the nanowires, below which the power spectral density SV(f) ~1/f. As the temperature is raised beyond T* there is onset of a new contribution to the power spectra. We link this observation to onset of Rayleigh instability expected in such long nanowires. T* ~ 220K for the 15nm Ag wire and ~ 260K for the 15nm Cu wire. We compare the results with a simple estimation of the fluctuation based on Rayleigh instability and find good agreement.

... KSS thanks DST, Government of India for financial support. MP thanks CSIR for research fellowship. AKR thanks DST and BRNS for sponsored projects. Authors thank Dr Barnali Ghosh and Sohini Kar for helping with the low field magnetic measurements. References ...

Rare earth manganites having perovskite structure are susceptible to lattice strain. So far most investigations have been done with hydrostatic pressure or biaxial strain. We have observed that hole doped rare-earth manganites, which are known to display colossal magnetoresistance (CMR) also show change in its resistance under the influence of uniaxial strain. We report the direct measurement of piezoresistive response of La0.67Ca0.33MnO3 (LCMO) and La0.67Sr0.33MnO3 (LSMO) of this manganite family. The measurements were carried out on nanostructured polycrystalline films of LCMO and LSMO grown on oxidized Si(100) substrates. The piezoresistance was measured by bending the Si cantilevers (on which the film is grown) in flexural mode both with compressive and tensile strain. At room temperature the gauge factor approximately 10-20 and it increases to a large value near metal-insulator transition temperature (Tp) where the resistivity shows a peak.

Artemisia annua is an important medicinal crop used for the production of the anti-malarial compound artemisinin. In order to assist in the production of affordable high quality artemisinin we have carried out an A. annua breeding programme aimed at improving artemisinin concentration and biomass. Here we report on a combining ability analysis of a diallel cross to identify robust parental lines for hybrid breeding. The parental lines were selected based on a range of phenotypic traits to encourage heterosis. The general combining ability (GCA) values for the diallel parental lines correlated to the positive alleles of quantitative trait loci (QTL) in the same parents indicating the presence of beneficial alleles that contribute to parental performance. Hybrids generated from crossing specific parental lines with good GCA were identified as having an increase in both artemisinin concentration and biomass when grown either in glasshouse or experimental field trials and compared to co...

High intensity focused ultrasound (HIFU) is a treatment modality for tissue ablation with an expanding range of indications. It is helpful to understand its basic principles, the physiological changes induced, and the pathophysiology of the patient groups undergoing HIFU. HIFU is usually performed in a radiology suite, and requires co-ordinated efforts between the radiologist/surgeon and anaesthetist during ablation therapy to enhance accuracy of treatment and patient safety. Planning of the equipment, ventilation strategies and drugs needed during the procedure would reduce potential anaesthetic and procedure-related complications.