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Search Results: 1 - 10 of 223920 matches for " Shyamal R. Polaki "
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Evolution and defect analysis of vertical graphene nanosheets
Subrata Ghosh,K. Ganesan,Shyamal R. Polaki,T. R. Ravindran,Nanda Gopala Krishna,M. Kamruddin,A. K. Tyagi
Physics , 2014, DOI: 10.1002/jrs.4530
Abstract: We report catalyst-free direct synthesis of vertical graphene nanosheets (VGNs) on SiO2/Si and quartz substrates using microwave electron cyclotron resonance - plasma enhanced chemical vapor deposition. The evolution of VGNs is studied systematically at different growth stages. Raman analysis as a function of growth time reveals that two different disorder-induced competing mechanisms contributing to the defect band intensity. The VGNs grown on SiO2/Si substrates predominantly consists of both vacancy-like and hopping defects. On the other hand, the VGNs grown on quartz substrates contain mainly boundary-like defects. XPS studies also corroborate Raman analysis in terms of defect density and vacancy-like defects for the VGNs grown on SiO2/Si substrates. Moreover, the grown VGNs exhibit a high optical transmittance from 95 to 78 % at 550 nm and the sheet resistance varies from 30 to 2.17 kohms/square depending on growth time.
Formation of isolated islands by size-selected copper nanocluster deposition
Shyamal Mondal,B. Satpati,S. R. Bhattacharyya
Physics , 2013,
Abstract: Deposition of size-selected metal nanoclusters on a substrate with very low kinetic energy helps to keep the clusters intact with respect to their shape and size as compared to clusters in ight condition. Here we report formation of isolated monodispersed islands of copper of desired size on carbon film by deposition of size selected copper clusters (~ 3 nm) in soft-landing method. Copper clusters were produced by a magnetron based gas aggregation type source equipped with a quardrupole mass filter (QMF) to select size of clusters before landing. Transmission Electron Microscopy (TEM) study shows that diffusion of islands is very low.
Oblique Angle Deposition of HfO2 Thin Films: Investigation of Elastic and Micro Structural Properties
R B Tokas,S Jena,P Sarkar,Shyam polaki,S Thakur,S Basu,N K Sahoo
Physics , 2014,
Abstract: Oblique angle deposition of oxides is being famous for fabricating inhomogeneous thin films with variation of refractive index along thickness in a functional form. Inhomogeneous layers play a key role in the development of rugate interference devices for photo-physical applications. Such obliquely deposited thin films show high porosity which is a critical issue related to their mechanical and environmental stability. Hence, it is important to investigate elastic properties of such film in addition to optical properties. Using atomic force acoustic microscopy, we report indentation modulus of HfO2 thin films deposited at angles 80, 68, 57, 40 and 0 degree with normal to substrate plane on Si (100) substrate. Such films were measured to have indentation modulus of 42 GPa for extreme obliquely deposited film and indentation modulus increases with decrease in angle to become highest with a value of 221 GPa for normally deposited films. We also report microstructural properties and density of films measured by FESEM and grazing angle X-ray reflectometer respectively. Both indentation modulus and density depict a parabolic decreasing behavior with angle of deposition. Variation of density is again confirmed by FESEM cross-sectional morphology of such films.
The factorial structure of self-reported androgen-promoted physiological traits  [PDF]
Lee Ellis, Shyamal Das
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.210144
Abstract: Androgens make major contributions to average sex differences in anatomy, physiology, and behavior. Despite having established their crucial role in sexual differentiation, much remains to be learned about how androgens coordinate their influences. The present study was undertaken to shed light on androgenic effects on the body using self-reported survey data. We analyzed the ratings provided by over 11,000 college students on the magnitude of eleven traits that previous research has shown to be influenced by testosterone or other androgens. Predictably, the average values for all eleven traits were significantly greater in males than in females. Nevertheless, when data were analyzed separately according to sex of the respondents, some of the traits failed to positively correlate with one another, suggesting that not all an-drogen-influenced traits differentiate in a simple fashion. Factor analysis of these eleven traits by sex reinforced this view by identifying four factors. In men, the primary factor loaded most heavily on: masculine body build, masculine mannerisms, overall physical strength, upper body strength, and lower body strength. The primary factor for women was limited to: upper body strength, lower body strength, and overall physical strength. In both sexes, the primary factor was interpreted as reflecting the influence of perinatal and post-pubertal testosterone exposure. The other three factors may reflect the effects of other androgens (e.g., androstenediol), or the influence of female hormones such as estradiol. Findings were discussed in terms of future use of self-reported physiological measures for assessing androgenic effects on the human body.
Phase analysis of circadian-related genes in two tissues
Delong Liu, Shyamal D Peddada, Leping Li, Clarice R Weinberg
BMC Bioinformatics , 2006, DOI: 10.1186/1471-2105-7-87
Abstract: We propose a set of techniques from circular statistics to analyze phase angles of circadian-related genes in two tissues. We first estimate the phases of a cycling gene separately in each tissue, which are then used to estimate the paired angular difference of the phase angles of the gene in the two tissues. These differences are modeled as a mixture of two von Mises distributions which enables us to cluster genes into two groups; one group having synchronized transcripts with the same phase in the two tissues, the other containing transcripts with a discrepancy in phase between the two tissues. For each cluster of genes we assess the association of phases across the tissue types using circular-circular regression. We also develop a bootstrap methodology based on a circular-circular regression model to evaluate the improvement in fit provided by allowing two components versus a one-component von-Mises model.We applied our proposed methodologies to the circadian-related genes common to heart and liver tissues in Storch et al. [2], and found that an estimated 80% of circadian-related transcripts common to heart and liver tissues were synchronized in phase, and the other 20% of transcripts were lagged about 8 hours in liver relative to heart. The bootstrap p-value for being one cluster is 0.063, which suggests the possibility of two clusters. Our methodologies can be extended to analyze peak expression times of circadian-related genes across more than two tissues, for example, kidney, heart, liver, and the suprachiasmatic nuclei (SCN) of the hypothalamus.Circadian rhythms (or the biologic clocks that control them) have stimulated interest in recent years due to their importance in orchestrating physiological behavior, biological processes, and adaptability of biological systems to changes in environment [1-3]. Many circadian-related genes have been explored using high-throughput DNA microarray technology [1-3]. These studies also have stimulated efforts to apply and d
Using Citizens to Do Science Versus Citizens as Scientists
Shyamal Lakshminarayanan
Ecology and Society , 2007,
A study of anthropometric profile of indian inter-university male cricketers
Journal of Human Sport and Exercise , 2011,
Abstract: The purpose of this study was of two-fold, firstly, to evaluate the anthropometric profile of Indian inter-university cricketers and, secondly, to search the correlations among the anthropometric characteristics studied (if any). To serve this purpose, twelve anthropometric characteristics were taken on purposively selected 98 Indian inter-university (nine Indian universities) male cricketers aged 16-25 years (mean 21.03 years, ± 1.72) participated in the competitions organized in Guru Nanak Dev University, Amritsar, Punjab, India. An adequate number of controls (n = 99, mean age 21.50 years, ± 1.13) were also collected from the same place for comparisons. The findings of the present study indicated statistically significant differences (p≤ 0.05 - 0.000) in weight, BMI, thigh length, total leg length, calf and hip circumferences, percent body fat and back strength between cricketers and controls. Also, significantly positive correlations (p≤ 0.05 - 0.01) were noted among the linear measurements, viz. height, thigh length, lower leg length; and the circumferential measurements, viz. mid thigh circumference, hip circumference and calf circumference in Indian inter-university male cricketers.
Collapse of a Bose gas: kinetic approach
Shyamal Biswas
Physics , 2008, DOI: 10.1007/s12043-012-0317-2
Abstract: We have analytically explored temperature dependence of critical number of particles for the collapse of a harmonically trapped attractively interacting Bose gas below the condensation point by introducing a kinetic approach within the Hartree-Fock approximation. The temperature dependence obtained by this easy approach is consisted with that obtained from the scaling theory.
More Accurate Theory for Bose-Einstein Condensation Fraction
Shyamal Biswas
Physics , 2007, DOI: 10.1016/j.physleta.2007.10.009
Abstract: In the thermodynamic limit the ratio of system size to thermal de Broglie wavelength tends to infinity and the volume per particle of the system is constant. Our familiar Bose-Einstein statistics is absolutely valid in the thermodynamic limit. For finite thermodynamical system this ratio as well as the number of particles is much greater than 1. However, according to the experimental setup of Bose-Einstein condensation of harmonically trapped Bose gas of alkali atoms this ratio near the condensation temperature($T_c$) typically is $\sim 32$ and at ultralow temperatures well below $T_c$ a large fraction of particles come down to the single particle ground state, and this ratio becomes comparable to 1. We justify the finite size as well as ultralow temperature correction to Bose-Einstein statistics. From this corrected statistics we plot condensation fraction versus temperature graph. This theoretical plot satisfies well with the experimental plot(A. Griesmaier et al..,Phys.Rev.Lett. {\bf{{94}}}{(2005){160401}}).
Finite Size Effect on Bose-Einstein Condensation
Shyamal Biswas
Physics , 2006,
Abstract: We show various aspects of finite size effects on Bose-Einstein condensation(BEC). In the first section we introduce very briefly the BEC of harmonically trapped ideal Bose gas. In the second section we theoretically argued that Bose-Einstein(B-E) statistics needs a correction for finite system at ultralow temperatures. As a corrected statistics we introduced a Tsallis type of generalized B-E statistics. The condensate fraction calculated with this generalized B-E statistics, is satisfied well with the experimental result. In the third section we show how to apply the scaling theory in an inhomogeneous system like harmonically trapped Bose condensate at finite temperatures. We calculate the temperature dependence of the critical number of particles by a scaling theory within the Hartree-Fock approximation and find that there is a dramatic increase in the critical number of particles as the condensation point is approached. Our results support the experimental result which was obtained well below the condensation temperature. In the fourth section we concentrate on the thermodynamic Casimir force on the Bose-Einstein condensate. We explored the temperature dependence of the Casimir force.
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