Amrit Baral - Academia.edu (original) (raw)

Papers by Amrit Baral

Physical Review Letters, 2013

Motivated by the recent controversy about the importance of spin-flip scattering for ultrafast de... more Motivated by the recent controversy about the importance of spin-flip scattering for ultrafast demagnetization in ferromagnets, we study the spin-dependent electron dynamics based on a dynamical Elliott-Yafet mechanism. The key improvement to earlier approaches is the use of a modified Stoner model with a dynamic exchange splitting between majority and minority bands. In the framework of our microscopic model, we find a novel feedback effect between the time-dependent exchange splitting and the spin-flip scattering. This feedback effect allows us to reproduce important properties of the demagnetization dynamics quantitatively. Our results demonstrate that in general Elliott-Yafet spin-flip scattering needs to be taken into account to obtain a microscopic picture of demagnetization dynamics.

Physical Review B, 2013

ABSTRACT Using time- and angle-resolved two-photon photoemission spectroscopy, we investigate the... more ABSTRACT Using time- and angle-resolved two-photon photoemission spectroscopy, we investigate the energy- and momentum-dependent ultrafast electron dynamics in the Rashba spin-split quantum-well nanofilm Bi/Cu(111). We find an expected increase of electron lifetimes towards the band bottom due to a competition of intra- and interband scattering processes. In addition, we find an unexpected peculiar decrease of the lifetimes around the intersection of the split bands. We compare the experimental results with calculated lifetimes due to electron-electron scattering in a model system of a 2D electron gas including a Rashba interaction term and an effective statically screened Coulomb interaction. Although the Rashba model reproduces the increase of lifetimes towards the band bottom well, there is no indication of the experimentally observed decrease around the intersection point in this simple model system. To investigate spin-orbit coupling effects, beyond those contained in a pure Rashba model, we introduce a phenomenological k-dependent spin mixing that leads to a “spin hot spot.” It is shown that such a mixing would strongly increase the electron-electron scattering rate around the band intersection and thus improves the agreement with experiment.

Molecular Cytogenetics, 2014

Molecular BioSystems, 2013

G-quadruplex biology gained interest based on evidence supporting its widespread role as elements... more G-quadruplex biology gained interest based on evidence supporting its widespread role as elements that can control or modulate gene regulation. This followed initial prediction based on computational analysis that found prevalence of quadruplex motifs in promoters of many bacterial and other organisms. In parallel, further evidence was found indicating the function of quadruplex motifs in replication, recombination and also DNA repair. In this review, we summarize recent findings that provide a new perspective by introducing quadruplex motifs in roles that support involvement during epigenetic events, in determining evolutionary selection and as possible determinants of quantitative expression traits (eQTL) across populations.

Journal of the …, 2002

Long term stability of photosensitivity versus time in indium (III) sulfide thin films thermally ... more Long term stability of photosensitivity versus time in indium (III) sulfide thin films thermally vacuum evaporated onto photocell-patterned printed circuit boards varies sensitively with several factors including contact metal type, contact metal diffusion and electromigration into the semiconductor, doping, and encapsulation method. Because of the significant photoconductivity and relative low toxicity and environmental impact of this compound semiconductor, it is important to better characterize these dependences toward commercial applications. We willreport on measurements of photoconductivity vs. time as functions of such factors and evolving methods to stabilize this photoconductivity.

International Journal of Power and Energy Conversion, 2013

ABSTRACT To improve the reliability and quality of electric power systems, preventive diagnosis a... more ABSTRACT To improve the reliability and quality of electric power systems, preventive diagnosis and regular maintenance of high voltage capacitors are required. Dielectric response measurements in both time domain and frequency domain are potential tools for assessing the condition of dielectric of high voltage capacitors. Modern measurements in time domain include polarisation and depolarisation current (PDC) and recovery voltage (RV) measurements, whereas frequency domain measurements include dielectric dissipation factor (DDF) measurements. To understand the physical behaviour due to the effect of moisture and aging, a detailed analysis of dielectric test results is required. In this paper, a detailed equivalent circuit model of the insulation system in high voltage capacitors has been given. The values of the parameter of the circuit model have been calculated from the dielectric test results. Correlation between the physical condition of the insulation and the equivalent model parameters are also presented in this paper.

Indian Journal of Nephrology, 2012

Atheroembolic renal disease is characterized by renal failure secondary to occlusion of renal vas... more Atheroembolic renal disease is characterized by renal failure secondary to occlusion of renal vasculature by cholesterol containing atheromatous plaques. Clinical presentations of this disease entity are myriad, with limited therapeutic options and unfavorable outcomes. This report describes an elderly male patient with peripheral vascular disease who developed acute renal failure during hospital admission for rectal bleed, and was diagnosed with atheroembolic renal disease on renal biopsy. The patient was managed with pulse steroid therapy and had a favorable outcome.

Experimental Parasitology, 1992

amazonensis infection: A comparison of in vivo leishmanicidal mechanisms between immunized and na... more amazonensis infection: A comparison of in vivo leishmanicidal mechanisms between immunized and naive infected BALBlc mice. Experimental Parasitology 74, 169-176. In vitro studies have shown that both macrophage activation and destruction of parasitized macrophages lead to leishmania destruction. The relative role played by such mechanisms in vivo have not been properly evaluated. We took advantage of the model of intravenous immunization with solubilized leishmanial antigen which renders partially resistant the otherwise highly susceptible BALB/c mice to address this issue avoiding the interference of different genetic backgrounds. Leishmania destruction occurred in three situations: destruction of the parasitized macrophage, which were in close contact with lymphocytes or eosinophils; extracellular damage, always surrounded by small foci of granulocytes; and parasite damage inside activated macrophages. Destruction of the parasitized macrophages was frequently seen in immunized and protected animals. Our observations suggest that destruction of parasite-loaded macrophages is an important mechanism of host protection in experimental cutaneous leishmaniasis. 0 19% Academic PESS, IX.

Power Systems, 2009. …, 2009

... logic. Advantages of VAR compensation employing SCADA is reported by Thomas B.Girotti et.al [... more ... logic. Advantages of VAR compensation employing SCADA is reported by Thomas B.Girotti et.al [8] where real time data are in use instead of traditional time control, where an elaborate platform for installation will be required. ...

Bulletin of Materials Science

Double perovskite polycrystalline single phase and dense Sr 2 SbMnO 6 (SSM) ceramics, fabricated ... more Double perovskite polycrystalline single phase and dense Sr 2 SbMnO 6 (SSM) ceramics, fabricated using the nanocrystalline powders synthesized by molten salt method, exhibited high dielectric constant with low dielectric loss as compared to that of SSM ceramics obtained from the powders prepared by solid-state synthesis method. The dielectric data obtained over a wide frequency (100 Hz-1 MHz) and temperature (190 K-300 K) ranges exhibited distinct relaxations owing to both the grain and grain boundary. The dielectric dispersion was modeled using the Cole-Cole equation consisting of two separate relaxation terms corresponding to the grain and grain boundary. The grain and grain boundary relaxations observed in the Nyquist plots (Z and Z) were modeled by an equivalent circuit consisting of two parallel RC circuits connected in series with each other. A careful analysis of both the impedance (Z vs ω ω ω) and modulus (M vs ω ω ω) behaviour corroborated the conclusions drawn from the dielectric data.

Biomass and Bioenergy, 2004

... The amount of carbon stock in litter including slash and soil is highly variable and site spe... more ... The amount of carbon stock in litter including slash and soil is highly variable and site specific. There are conflicting findings regarding the carbon sequestration in soil. ... [15]. The carbon content in soil and litter is difficult to include in an accounting system. ...

Environmental Technology, 2001

Lignite based granular activated carbon of 20x30 mesh size was used to investigate the extent of ... more Lignite based granular activated carbon of 20x30 mesh size was used to investigate the extent of bioregeneration of phenol and 2,4-DCP in a batch system. The adsorption isotherm fits very well with the Freundlich isotherm and it is apparent that 2,4-DCP is more adsorbable than phenol. The degree of reversible adsorption for phenol and 2,4-DCP were 32.9 and 10.6 %, respectively. The low percentages of their reversibility meant that the adsorption phenomena of both phenol and 2,4-DCP were not fully physicosorption. The microorganisms can regenerate 31.4% (21.2 mg g(-1)) of GAC loaded with phenol and 14.3% (24.8 mg g(-1)) of GAC loaded with 2,4-DCP over a period of 7-10 days. The bioregeneration of phenols closely followed the first order kinetics with the rate constant of 0.046 day(-1) at initial phenol concentration of 100 mg l(-1) and biomass concentration of 20 mg l(-1) MLVSS. The rate constant was 0.021 day(-1) at initial 2,4-DCP concentration of 200 mg l(-1) and 200 mg l(-1) MLVS...

Archives of Environmental Contamination and Toxicology, 2006

This study evaluated aquatic toxicities of chromium and chromium-containing laboratory samples re... more This study evaluated aquatic toxicities of chromium and chromium-containing laboratory samples representative of effluents from chromium electroplating industries, and compared the aquatic environmental risks of hexavalent and trivalent chromium electroplating operations. Trivalent chromium electroplating has emerged as an acceptable alternative to hazardous hexavalent chromium electroplating. This process substitution has reduced the human health impact in the workplace and minimized the production of hazardous sludge regulated under the Resource Conservation and Recovery Act (RCRA). The thrust behind this research was to investigate whether trivalent chromium electroplating operations have lower adverse impacts on standardized toxicity test organisms. Ceriodaphnia dubia and Pimephales promelas were used to investigate toxicities of trivalent chromium (Cr (III)), hexavalent chromium (Cr (VI)), and industrial effluents. In agreement with previous studies, Cr (III) was found to be le...

This paper advances the scope of life cycle analysis by considering resource qualities and integr... more This paper advances the scope of life cycle analysis by considering resource qualities and integration of materials and energy to offer complementary insight to existing process LCA studies of biofuels. Resource qualities were partially accounted for by introducing ecological cumulative exergy analysis (ECEC). Integration of materials and energy of ecological goods and services was achieved via ECEC and industrial cumulative exergy consumption (ICEC) which facilitates comparison of disparate units (mass and energy) on a common thermodynamic unit. Four categories of metrics were developed from hybrid ecological life cycle assessment (Eco-LCA): (1) disaggregated metrics, (2) return on investment (ROI) metrics,(3) renewability metrics, and (4) efficiency metrics to elicit complementary insight. Results indicate that biofuelscorn ethanol and biodiesel-consume less non-renewable ICEC per km than gasoline and diesel, however, number of non-renewable resources consumed more by biofuels relative to petroleumbased fuels is higher. Exergetic efficiencies (km/ICEC) and returns on exergy investment (rEx) are lower for biofuels implying that biofuels consume more materials and fuels combined to produce 1Joule of exergy output. Improving photosynthetic efficiency and minimization of soil erosion and water consumption may enhance exergetic efficiencies of biofuels. ICEC analysis shows that contribution of non-fuel materials is appreciable relative to fossil fuels and electricity for biofuels. Low yield ratios of biofuels indicate that more resources from the economy are needed to process freely available low quality sunlight into high quality bioenergy suggesting they may not be energetically competitive with gasoline/diesel. Unlike well-to-wheel exergetic efficiencies (km/ICEC), ecological efficiencies (km/ECEC) obtained by adjusting the quality aspect of exergy are higher for corn ethanol and biodiesel implying that they do not depend on as high quality resources as gasoline/diesel. Better ecological efficiencies but lower yield ratios, energy and exergy returns on investment present us with a unique trade-off as we move down the emergy hierarchy to tap in low quality sunlight for liquid fuel production.