Effect of built-in-polarization field on mean free path of phonons in binary nitrides

In this paper, the built-in-polarization field effect on mean free path of acoustic phonons in bulk wurtzite binary nitrides (GaN, AlN) has been theoretically investigated. Due to the modification of elastic constant of the material by the effect of polarization field, there is a corresponding enhancement in group velocity and Debye frequency of phonons. The scattering rate of phonons also affected by this field, as it is a function of velocity or/and Debye frequency. The result shows that polarization field suppresses various scattering rates as well as combined scattering rate of phonons. This implies an increased combined relaxation time of phonons. Hence, the mean free path of phonons increases. Thus, phonons travel freely for a longer distance between two successive scatterings. It is found that, the mean free path of low frequency phonons is longer than that of the high frequency phonons. It indicates that, the low frequency phonons are significantly affected by the built-in-polarization field. This can enhance thermal transport properties of the material, when built-in-polarization field taken into account. It may be a method to control the thermal transport properties of such materials by the application of electric field in a desired way, which can be considered in addressing thermal management issues in nitride based optoelectronic devices to minimize self-heating effects

Transverse currents in spin transistors

In a variety of systems such as topological insulators and spin-orbit coupled materials, it is known that Hall conductance arises due to an in-plane Zeeman field. This effect known as planar Hall effect is rooted in spin-orbit coupling of the system. A spin transistor put forward by Datta and Das on the other hand consists of ferromagnetic leads connected to spin-orbit coupled central region and its conductance can be controlled by tuning the strength of spin-orbit coupling. We find that transverse currents also appear in Datta-Das transistors made by connecting two two-dimensional ferromagnetic reservoirs to a central spin-orbit coupled two-dimensional electron gas. We find that the spin transistor exhibits a nonzero transverse conductivity which depends on the direction of polarization in ferromagnets and the location where it is measured. We study the conductivities for the system with finite and infinite widths. The conductivities exhibit Fabry-P\'erot type oscillations as the length of the spin-orbit coupled regions is varied. Interestingly, even in the limit when longitudinal conductivity is made zero by cutting off the junction between central spin-orbit coupled region and the ferromagnetic lead on one side (right), the transverse conductivities remain nonzero in the regions that are on the left side of the cut-off junction.Comment: 7 pages, 7 captioned figure

CHEMICAL COMPOSITION, ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES OF ESSENTIAL OIL FROM LIME BASIL (OCIMUM AMERICANUM): A POTENT SOURCE FOR NATURAL ANTIOXIDANT

Objective: GC and GC MS based analysis of the essential oil from leaf samples of Ocimum americanum were done. The essential oil composition, In vitro antioxidant and antimicrobial activity of the essential oil of O. americanum were evaluated in this research to explore its potential for future use. Methods: The component identification was achieved by the GC–MS analysis. Radical-scavenging activities of the plant essential oil were determined by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) activity. Antimicrobial activity of the essential oil was done using standard pathogenic strains in disc diffusion method. Results: GC and GC/MS analysis of the plant essential oil resulted in the identification of 19 compounds representing 100% of the oil. Citral (47.18%) and β - citral (36.57%) were the two major constituents. The essential oil subjected to analysis of its antioxidant activity using 2, 2- diphenyl-1-1picrylhydrazyl (DPPH) showed higher activity as compared to the standard. The oil was also screened for its antimicrobial activity and the inhibition was recorded against pathogenic microorganisms. Conclusion: Both the antimicrobial and anti oxidant activity of Ocimum americanum showed its potential for further use as natural antioxidant and preservative. Essential oil from the medicinal plants is one of the promising natural compounds for preparation of safer antimicrobial and antioxidant agent. Antioxidants conventionally used in food industries are obtained by chemical synthesis, but their use, reserved for certain categories of food is regulated by dose limits. Leaves of Ocimum americanum L. contain citral rich essential oil which is a potent source for natural antioxidants and biologically active compounds

COMPARISION OF SEDATIVE EFFECT OF DEXMEDETOMIDINE/ XYLAZINE IN COMBINATION WITH BUTORPHANOL-MIDAZOLAM AS PREANAESTHETIC TO KETAMINE ANAESTHESIA FOR OVARIOHYSTERECTOMY IN DOGS

The research was conducted in 12 female dogs undergoing elective ovariohysterectomy. They were divided into two groups of six animals each to evaluate and compare sedative effect in Group-I atropine- meloxicam - dexmedetomidine - butorphanol - midazolam - ketamine and Group-II atropine- meloxicam - xylazine - butorphanol - midazolam - ketamine anaesthetic combination. Maintenance of anaesthesia was done by ketamine in both the groups. Anaesthetic combinations were evaluated by clinical and physiological observations. Adequate muscle relaxation, sedation and analgesia necessary for surgical intervention were achieved along with smooth and uneventful recovery of the patients. Onset of sedation and induction time were quicker in Group-I. Physiological parameters fluctuated within the normal limits. Both anaesthetic protocols in the present study provided satisfactory surgical plane of anaesthesia in dogs. But dexmedetomidine may be preferred over xylazine in the anaesthetic regimen of atropine-meloxicam-butorphanolmidazolam-ketamine for elective ovariohysterectomy in dogs

Effect of Piezoelectric Polarization on Phonon group velocity in Wurtzite Nitrides

We have investigated the effect of piezoelectric (PZ) polarization property on group velocity of phonons in binary as well as in ternary wurtzite nitrides. It is found that with the presence of PZ polarization property, the phonon group velocity is modified. The change in phonon group velocity due to PZ polarization effect directly depends on piezoelectric tensor value. Using different piezoelectric tensor values recommended by different workers in the literature, percent change in group velocities of phonons has been estimated. The Debye temperatures and frequencies of binary nitrides GaN, AlN and InN are also calculated using the modified group velocities. For ternary nitrides AlxGa(1-x)N, InxGa(1-x)N and InxAl(1-x)N, the phonon group velocities have been calculated as a functions of composition. A small positive bowing is observed in phonon group velocities of ternary alloys. Percent variations in phonon group velocities are also calculated for a straightforward comparison among ternary nitrides. The results are expected to show a change in phonon relaxation rates and thermal conductivity of III-nitrides when piezoelectric polarization property is taken into account.Comment: 05 figures; Journal of Material science, 201

Global burden and strength of evidence for 88 risk factors in 204 countries and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

Background: Understanding the health consequences associated with exposure to risk factors is necessary to inform public health policy and practice. To systematically quantify the contributions of risk factor exposures to specific health outcomes, the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 aims to provide comprehensive estimates of exposure levels, relative health risks, and attributable burden of disease for 88 risk factors in 204 countries and territories and 811 subnational locations, from 1990 to 2021. Methods: The GBD 2021 risk factor analysis used data from 54 561 total distinct sources to produce epidemiological estimates for 88 risk factors and their associated health outcomes for a total of 631 risk–outcome pairs. Pairs were included on the basis of data-driven determination of a risk–outcome association. Age-sex-location-year-specific estimates were generated at global, regional, and national levels. Our approach followed the comparative risk assessment framework predicated on a causal web of hierarchically organised, potentially combinative, modifiable risks. Relative risks (RRs) of a given outcome occurring as a function of risk factor exposure were estimated separately for each risk–outcome pair, and summary exposure values (SEVs), representing risk-weighted exposure prevalence, and theoretical minimum risk exposure levels (TMRELs) were estimated for each risk factor. These estimates were used to calculate the population attributable fraction (PAF; ie, the proportional change in health risk that would occur if exposure to a risk factor were reduced to the TMREL). The product of PAFs and disease burden associated with a given outcome, measured in disability-adjusted life-years (DALYs), yielded measures of attributable burden (ie, the proportion of total disease burden attributable to a particular risk factor or combination of risk factors). Adjustments for mediation were applied to account for relationships involving risk factors that act indirectly on outcomes via intermediate risks. Attributable burden estimates were stratified by Socio-demographic Index (SDI) quintile and presented as counts, age-standardised rates, and rankings. To complement estimates of RR and attributable burden, newly developed burden of proof risk function (BPRF) methods were applied to yield supplementary, conservative interpretations of risk–outcome associations based on the consistency of underlying evidence, accounting for unexplained heterogeneity between input data from different studies. Estimates reported represent the mean value across 500 draws from the estimate's distribution, with 95% uncertainty intervals (UIs) calculated as the 2·5th and 97·5th percentile values across the draws. Findings: Among the specific risk factors analysed for this study, particulate matter air pollution was the leading contributor to the global disease burden in 2021, contributing 8·0% (95% UI 6·7–9·4) of total DALYs, followed by high systolic blood pressure (SBP; 7·8% [6·4–9·2]), smoking (5·7% [4·7–6·8]), low birthweight and short gestation (5·6% [4·8–6·3]), and high fasting plasma glucose (FPG; 5·4% [4·8–6·0]). For younger demographics (ie, those aged 0–4 years and 5–14 years), risks such as low birthweight and short gestation and unsafe water, sanitation, and handwashing (WaSH) were among the leading risk factors, while for older age groups, metabolic risks such as high SBP, high body-mass index (BMI), high FPG, and high LDL cholesterol had a greater impact. From 2000 to 2021, there was an observable shift in global health challenges, marked by a decline in the number of all-age DALYs broadly attributable to behavioural risks (decrease of 20·7% [13·9–27·7]) and environmental and occupational risks (decrease of 22·0% [15·5–28·8]), coupled with a 49·4% (42·3–56·9) increase in DALYs attributable to metabolic risks, all reflecting ageing populations and changing lifestyles on a global scale. Age-standardised global DALY rates attributable to high BMI and high FPG rose considerably (15·7% [9·9–21·7] for high BMI and 7·9% [3·3–12·9] for high FPG) over this period, with exposure to these risks increasing annually at rates of 1·8% (1·6–1·9) for high BMI and 1·3% (1·1–1·5) for high FPG. By contrast, the global risk-attributable burden and exposure to many other risk factors declined, notably for risks such as child growth failure and unsafe water source, with age-standardised attributable DALYs decreasing by 71·5% (64·4–78·8) for child growth failure and 66·3% (60·2–72·0) for unsafe water source. We separated risk factors into three groups according to trajectory over time: those with a decreasing attributable burden, due largely to declining risk exposure (eg, diet high in trans-fat and household air pollution) but also to proportionally smaller child and youth populations (eg, child and maternal malnutrition); those for which the burden increased moderately in spite of declining risk exposure, due largely to population ageing (eg, smoking); and those for which the burden increased considerably due to both increasing risk exposure and population ageing (eg, ambient particulate matter air pollution, high BMI, high FPG, and high SBP). Interpretation: Substantial progress has been made in reducing the global disease burden attributable to a range of risk factors, particularly those related to maternal and child health, WaSH, and household air pollution. Maintaining efforts to minimise the impact of these risk factors, especially in low SDI locations, is necessary to sustain progress. Successes in moderating the smoking-related burden by reducing risk exposure highlight the need to advance policies that reduce exposure to other leading risk factors such as ambient particulate matter air pollution and high SBP. Troubling increases in high FPG, high BMI, and other risk factors related to obesity and metabolic syndrome indicate an urgent need to identify and implement interventions

Effect of built-in-polarization field on mean free path of phonons in binary nitrides

179-186In this paper, the built-in-polarization field effect on mean free path of acoustic phonons in bulk wurtzite binary nitrides (GaN, AlN) has been theoretically investigated. Due to the modification of elastic constant of the material by the effect of polarization field, there is a corresponding enhancement in group velocity and Debye frequency of phonons. The scattering rate of phonons also affected by this field, as it is a function of velocity or/and Debye frequency. The result shows that polarization field suppresses various scattering rates as well as combined scattering rate of phonons. This implies an increased combined relaxation time of phonons. Hence, the mean free path of phonons increases. Thus, phonons travel freely for a longer distance between two successive scatterings. It is found that, the mean free path of low frequency phonons is longer than that of the high frequency phonons. It indicates that, the low frequency phonons are significantly affected by the built-in-polarization field. This can enhance thermal transport properties of the material, when built-in-polarization field taken into account. It may be a method to control the thermal transport properties of such materials by the application of electric field in a desired way, which can be considered in addressing thermal management issues in nitride based optoelectronic devices to minimize self-heating effects

Characterization of purified α-amylase produced by Aspergillus terreus NCFT 4269.10 using pearl millet as substrate ABOUT THE AUTHORS

Abstract: α-amylase was produced by Aspergillus terreus NCFT 4269.10 using both liquid static surface (LSSF) and solid-state fermentation using pearl millet residues as substrate. The maximum production of α-amylase was noticed at 30°C incubated for 96h. The crude α-amylase was purified to electrophoretic homogeneity and characterized. Characterization of amylase confirmed that the purified α-amylase was found to be most stable at pH 5.0, 60°C temperature, and a substrate concentration of 1.25%. The enzyme was active for 40 min at 70°C with an optimum enzyme-substrate reaction time of 60 min. Amylase was compatible with all detergents tested having highest activity with Surf excel followed by Henko and Ariel. SDS and Tween 20 reduced the activity. Among the metal ions tested, the maximum α-amylase activity was attained in the presence of Ca 2+ , followed by Mg 2+ and Mn 2+ . The activity of α-amylase was not considerably affected in the presence of ethylenediaminetetraacetic acid and Triton X-100. Amylase activity was accelerated in the presence of sodium lauryl sulfate and phenylmethylsulfonyl fluoride did not significantly (or slightly) affect the activity and stability. Tween 20, urea (5%), and the reducing agent, β-mercaptoethanol significantly inhibited the activity of α-amylase. Owin

Effects of Mimosa pudica L. leaves extract on anxiety, depression and memory

Objective: The present study was carried out to investigate the neuropharmacological activities of ethyl acetate extract of Mimosa pudica (EAMP) leaves on anxiety, depression and memory in a mouse model. Materials and Methods: Anti-anxiety potential of EAMP was evaluated by elevated plus maze (EPM), light-dark box (LDB) and social interaction (SI) tests in mice.Anti-depressant potential of EAMP was evaluated by forced swimming (FST), tail suspension (TST), and open field tests (OFT). The behavioral findings were further corroborated with estimation of neurotransmitters and their metabolites from mouse brain homogenate. Effect on learning and memory was evaluated by EPM, passive avoidance (PA) tests. Further, it was confirmed with assessment of acetylcholinesterase and caspase-3 activity in brain homogenate. Results: EAMP showed significant anti-anxiety activity by increasing the time spent in open arm of EPM, light box of LDB. Social interaction time was increased significantly (

Characterization of biotechnologically relevant extracellular lipase produced by Aspergillus terreus NCFT 4269.10

Abstract Enzyme production by Aspergillus terreus NCFT 4269.10 was studied under liquid static surface and solid-state fermentation using mustard oil cake as a substrate. The maximum lipase biosynthesis was observed after incubation at 30 °C for 96 h. Among the domestic oils tested, the maximum lipase biosynthesis was achieved using palm oil. The crude lipase was purified 2.56-fold to electrophoretic homogeneity, with a yield of 8.44%, and the protein had a molecular weight of 46.3 kDa as determined by SDS-PAGE. Enzyme characterization confirmed that the purified lipase was most active at pH 6.0, temperature of 50 °C, and substrate concentration of 1.5%. The enzyme was thermostable at 60 °C for 1 h, and the optimum enzyme–substrate reaction time was 30 min. Sodium dodecyl sulfate and commercial detergents did not significantly affect lipase activity during 30-min incubation at 30 °C. Among the metal ions tested, the maximum lipase activity was attained in the presence of Zn2+, followed by Mg2+ and Fe2+. Lipase activity was not significantly affected in the presence of ethylenediaminetetraacetic acid, sodium lauryl sulfate and Triton X-100. Phenylmethylsulfonyl fluoride (1 mM) and the reducing, β-mercaptoethanol significantly inhibited lipase activity. The remarkable stability in the presence of detergents, additives, inhibitors and metal ions makes this lipase unique and a potential candidate for significant biotechnological exploitation