8,369 research outputs found
The effect of substituted benzene dicarboxylic acid linkers on the optical band gap energy and magnetic coupling in manganese trimer metal organic frameworks
We have systematically studied a series of eight metal-organic frameworks (MOFs) in which the secondary building unit is a manganese trimer cluster, and the linkers are differently substituted benzene dicarboxylic acids (BDC). The optical band gap energy of the compounds vary from 2.62 eV to 3.57 eV, and theoretical studies find that different functional groups result in new states in the conduction band, which lie in the gap and lower the optical band gap energy. The optical absorption between the filled Mn 3d states and the ligands is weak due to minimal overlap of the states, and the measured optical band gap energy is due to transitions on the BDC linker. The Mn atoms in the MOFs have local moments of 5 mu B, and selected MOFs are found to be antiferromagnetic, with weak coupling between the cluster units, and paramagnetic above 10 K
Transient Free Convection in a Vertical Channel with Variable Temperature and Mass Diffusion
Effects of thermal radiation and constant mass diffusion on the transient laminar free convective flow in a vertical channel with have been analyzed. The exact solutions of the governing equations have been obtained by using the Laplace transform technique. The influences of the parameters on the velocity field, temperature distribution, concentration in the fluid, shear stress, rate of heat and mass transfers have been presented either graphically . It is seen that the velocity and temperature fields decrease with an increase in radiation parameter. On the other hand, the rate of heat transfer at the plate  decreases with an increase in either radiation parameter or Prandtl number. Further, the shear stress at the plate  increases with an increase in either radiation parameter or thermal Grashof number or mass Grashof number. Keywords: MHD flow, Transient Free convection, thermal Grashof number, mass Grashof number, thermal radiation, Heat transfer, and Mass transfer
Rolling tachyon solution of two-dimensional string theory
We consider a classical (string) field theory of matrix model which was
developed earlier in hep-th/9207011 and subsequent papers. This is a
noncommutative field theory where the noncommutativity parameter is the string
coupling . We construct a classical solution of this field theory and show
that it describes the complete time history of the recently found rolling
tachyon on an unstable D0 brane.Comment: 19 pages, 2 figures, minor changes in text and additional references,
correction of decay time (version to appear in JHEP.
Evolution of microstructure in spray formed Alâ18%Si alloy
Spray atomization and deposition process has emerged as an alternative to ingot and powder metallurgy routes. In the present investigation, we study the microstructural control during spray deposition of hypereutectic AlâSi alloy, employing different nozzle to substrate distances. Spray deposition is carried out using convergentâdivergent close-coupled nozzle design at deposition distances of 200, 300, 450, and 550 mm. Microstructural characterization of oversprayed powders as well as spray formed deposits was performed. Microstructural features obtained at smaller deposition distance consist of co-existing primary Si phase and needle like eutectic Si. Dendrites of α-Al phase are observed indicating a large undercooling of the liquid pool prior to solidification. A large number of pre-solidified particles with very fine microstructure, embedded in a relatively coarse region, typically characterize those evolved at large deposition distances. However, at intermediate deposition distances, uniform and refined primary Si phases, 3â8 ÎŒm size, are observed. An undercooling effect is manifested in both the spray deposits as well as powder particles. These microstructural features have been discussed in light of a proposed model, which describes the presence of two layers (1) solidification layer and (2) interaction layer in the liquid pool
Impact of continuous mechanical harvesting on leaf leatheriness and possible alleviation measures
Mechanization in plucking has become imperative to improve the profitability and efficiency in tea industry. Continuous shear harvesting of tea shoots creates a stress on plant thereby changing the texture of the crop shoots termed as âleaf leatherinessâ. Objective of the study was to generate data on the formation of leaf leatheriness due to continuous shear harvesting and to propose the remedial measures. A factorial block design experiment was conducted with a âChineryâ clone UPASI-9. Results indicated that continuous shear harvesting for a period of six months resulted in the accumulation of total wax content when compared to the hand plucked crop shoots which contributed to the leatheriness of crop shoots. Significant increase in the banji content in the harvest was also noticed due to continuous shear harvesting. Foliar applied chemicals influenced the reduction in banji shoots in the shear harvested treatments. Among the foliar applied treatments, reduction in the total wax content in the continuously shear harvested plots was obtained by the foliar application of KNO3 (2%) + Urea (1%) followed by KNO3 (2%) and Ca(NO3)2 (2%) when compared with control. Study concluded that foliar application of KNO3 (2%) alone or in combination with Urea (1%) is beneficial in alleviating the leaf leatheriness caused due to continuous shear harvesting without deterioration of quality characteristics with a prophylactic effect to improve the yield of tea plants
Study on prediction of type 2 diabetes mellitus in undergraduate MBBS students: a cross-section study in a tertiary health center, Kolkata
Background: Diabetes, is now a leading cause of morbidity and mortality worldwide. Prevalence of type-2 diabetes in children and adolescents is rapidly increasing worldwide. Adolescence and early youth period has pivotal importance for young people with diabetes risk when they usually start learning about how to take responsibility. With this background, present study was done to find out the proportion of various risk factors and future risk of developing diabetes among MBBS undergraduates in Kolkata.Methods: This study was a cross-sectional institution based study done from 1st June to 18th June 2017. Data was collected by interviewing each respondent with the help of structured pre-designed pre-tested schedule, after which clinical examination for height, weight, waist and hip circumference, blood pressure and RBS were done. Out of 150 undergraduates, 130 agreed to participate. Data was analysed with R software.Results: Mean age of the students was 20.45years. 48.5% of them were either overweight or obese. Nearly half of them had waist circumference and waist hip ratio in risk group. Only 65 were normotensive and 7 had high random blood sugar (â„140 mg/dl). 6 students were in high risk group according to both IDRS (â„60) and ADA (â„5) risk score. 66 students were in moderate risk (30-50) group as per IDRS risk score.Conclusions: The simple and cost-effective IDRS could serve as a screening tool health worker to identify at risk individuals at the earliest and enable primary prevention by encouraging these students to modify their life-style
Oxidative stress in diabetic patients with retinopathy
Background: Diabetes mellitus (DM) is known to induce oxidative stress along with deranging various metabolisms; one of the late complications of diabetes mellitus is diabetic retinopathy, which is a leading cause of acquired blindness. Poor glycemic control and oxidative stress have been attributed to the development of complications like diabetic retinopathy. The aim of this study was to analyze and correlate oxidative stress marker, Malondialdehyde (MDA), and antioxidants (erythrocyte glutathione, vitamin C) along with glycosylated hemoglobin (HbA1c) and fasting blood sugar (FBS) in diabetic patients with and without retinopathy.Materials and Methods: The study population comprised of 50 type 2 diabetics with retinopathy as Group 1 (G1) and 50 type 2 diabetics without retinopathy as Group 2 (G2) in the age group 40-70 years as patients, and 50 ageand gender-matched healthy individuals as controls, Group 3 (G3). FBS, HbA1c MDA, glutathione in erythrocytes, and vitamin C were assayed. Results were analyzed using SPSS 11.0, MannâWhitney U-test, and Pearson correlation coefficient.Results: Mean FBS (mg/dl) were 194.04 ± 48.52 (G1), 181.24 ± 50.05 (G2), and 92.20 ± 9.19 (G3) (P < 0.001). Mean values of MDA were 6.65 ± 0.30 (G1), 4.63 ± 0.56 (G2), and 3.90 ± 0.34 (G3) (P < 0.001). The mean reduced glutathione (GSH) levels were (mg/g of Hb) 6.10 ± 1.41 (G1), 6.44 ± 1.53 (G2), and 13.09 ± 2.49 (G3) (P < 0.001). The mean vitamin C levels (mg/dl) were 0.70 ± 0.24 (G1), 0.87 ± 0.29 (G2), and 1.25 ± 0.27 (G3) (P < 0.001).Conclusion: Estimation of HbA1c, MDA, GSH in erythrocytes, and vitamin C levels can contribute to determine the extent of oxidative stress in diabetes and help in effective control and prevention of the onset and progression of diabetic retinopathy.Keywords: Diabetic retinopathy, glycosylated hemoglobin, malondialdehyde, reduced glutathione, vitamin
Extraction of parton distributions from lattice QCD
We review the calculation of moments of both the polarized and unpolarized
parton distribution functions of the nucleon in lattice QCD, and in particular
their extrapolation to the physical region. We also discuss the reconstruction
of the x dependence of the valence quark distributions in the nucleon from a
finite number of lattice moments.Comment: 17 pages, 7 figures, mini-review prepared for Mod. Phys. Lett.
Wave Motion due to a Ring Source in Two Superposed Fluids Covered by a Thin Elastic Plate
The problem of wave generation by a horizontal ring of wave sources of the same time-dependent strength present in any one layer of a two-layer fluid is investigated here. The upper fluid is of finite height above the interface and is covered by a floating thin infinite elastic plate (modeling a thin sheet of ice) while the lower fluid extends infinitely downwards. Assuming linear theory, the problem is formulated as an initial value problem and the Laplace transform in time is employed to solve it. For time-harmonic source strength, the asymptotic representations of the potential functions describing the motion in the two layers for large time and distance are derived. In these representations, the two different coefficients for each of the surface and interface wave modes have the same numerical values although it has not been possible to prove their equivalence analytically. This shows that the steady-state analysis of the potential functions produces outgoing progressive waves at the surface and at the interface. The forms of the surface and interface waves are depicted graphically for different values of the flexural rigidity of the elastic plate and the ring source being submerged in the lower or upper layer
- âŠ