Global Modeling of Spur Formation in Spiral Galaxies

We investigate the formation of substructure in spiral galaxies using global MHD simulations, including gas self-gravity. Our models extend previous local models by Kim and Ostriker (2002) by including the full effects of curvilinear coordinates, a realistic log-spiral perturbation, self-gravitational contribution from 5 radial wavelengths of the spiral shock, and variation of density and epicyclic frequency with radius. We show that with realistic Toomre Q values, self-gravity and galactic differential rotation produce filamentary gaseous structures with kpc-scale separations, regardless of the strength -- or even presence -- of a stellar spiral potential. However, the growth of sheared features distinctly associated with the spiral arms, described as spurs or feathers in optical and IR observations of many spiral galaxies, requires a sufficiently strong spiral potential in self gravitating models. Unlike independently-growing ''background'' filaments, the orientation of arm spurs depends on galactic location. Inside corotation, spurs emanate outward, on the convex side of the arm; outside corotation, spurs grow inward, on the concave side of the arm. Based on spacing, orientation, and the relation to arm clumps, it is possible to distinguish ''true spurs'' that originate as instabilities in the spiral arms from independently growing ''background'' filaments. Our models also suggest that magnetic fields are important in preserving grand design spiral structure when gas in the arms fragments via self-gravity into GMCs.Comment: 36 pages, 17 figures, Accepted for publication in ApJ. PDF version with high resolution figures available at http://www.astro.umd.edu/~shetty/Research

Interaction Between Motor Domains Can Explain the Complex Dynamics of Heterodimeric Kinesins

Motor proteins are active enzyme molecules that play a crucial role in many biological processes. They transform the chemical energy into the mechanical work and move unidirectionally along rigid cytoskeleton filaments. Single-molecule experiments suggest that motor proteins, consisting of two motor domains, move in a hand-over-hand mechanism when each subunit changes between trailing and leading positions in alternating steps, and these subunits do not interact with each other. However, recent experiments on heterodimeric kinesins suggest that the motion of motor domains is not independent, but rather strongly coupled and coordinated, although the mechanism of these interactions are not known. We propose a simple discrete stochastic model to describe the dynamics of homodimeric and heterodimeric two-headed motor proteins. It is argued that interactions between motor domains modify free energy landscapes of each motor subunit, and motor proteins still move via the hand-over-hand mechanism but with different transitions rates. Our calculations of biophysical properties agree with experimental observations. Several ways to test the theoretical model are proposed.Comment: To appear in New J. Phy

A comparative study of the antidepressant effect of ondansetron and granisetron on Albino mice

Background: Ondansetron and granisetron are selective 5-HT receptor antagonists used as antiemetics. The present study as aimed at comparing the antidepressant activity of ondansetron and granisetron in animal experimental models.Methods: The study was done after obtaining approval from the institutional animal ethical committee of JJM Medical college, Davangere and CPCSEA. A total of 24 mice of either sex and of weight between 20-40g were included in the study. The antidepressant activity of ondansetron and granisetron was evaluated in mice using forced swim test model (FST) and tail suspension test model (TST). In both the experimental models animals were divided into 4 groups and received the following drugs- Group 1 (control) - normal saline 10mg/kg i.p, Group 2 (standard)-fluoxetine 10mg/kg i.p, Group 3(test drug 1), ondansetron 2mg/kg i.p, Group 4 (test drug 2)- granisetron 0.5mg/kg i.p. The duration of immobility was noted and compared amongst the 4 groups in both the models 60 min after drug administration. The observations were analysed using ANOVA (one way) and post hoc Tukey’s test.Results: The test drugs showed significant reduction in duration of immobility in both the models. In FST and TST models, granisetron (0.5mg/kg i.p) showed a significant reduction in immobility period of 10.33 sec and 67 secs respectively when compared to ondansetron (2mg/kg i.p) and the standard drug fluoxetine (10mg/kg i.p).Conclusions: The results of study suggest that granisetron may be useful as a potential candidate for treatment of depression. Hence further animal studies with different model for depression and clinical studies should be conducted in order to choose the better drug for treatment PONV which is often associated with depression

Evaluation of Effect of Melatonin on Hematological Parameters in Patients of Periodontitis

Introduction: Considering the immunity enhancing property of melatonin, a study on the evaluation of the effect of melatonin on the hematological parameters in patients suffering from Periodontitis.  Methods: This study was conducted in the Department of Periodontics, Rural Dental College, Loni. Patients of chronic Periodontitis, of age between 18 to 65 years of either gender ready to give informed consent to participate in the study were included. Postoperative patients, patients having night duties, drivers and those using heavy machinery, pregnant women, lactating mothers, patients with any clinically significant systemic disease and patients on any other drugs were excluded from the study. Patients were divided into two Groups. Group B received scaling and root planning (SRP) and melatonin 3 mg per day were compared to Group A which received SRP only. The Total Leukocyte count, Differential Leukocyte count and Erythrocyte sedimentation rate of each patient was studied at a baseline, 1st (30 days) visit, 2nd (60 days) visit and 3rd (90 days) visit. Results: Both the groups consisted of 80 subjects each. Group A consisted of 71.25% male and 28.75% female patients. There were 56.25% male and 43.75% female patients in Group B. With respect to visit 3, the TLC was statistically lower in Group B. The neutrophil count of Group B was significantly lower during visit 3 as compared to Group A. The lymphocyte count of Group B was significantly lower than that of Group A during the visit 1, and also significantly higher during visit 3 on comparison with Group A. There was no statistically significant difference in the groups with respect to eosinophil and basophil count. The Monocyte count of Group B was statistically lower when compared to that of Group A. There was no statistically significant difference between ESR of Group A & Group B.  Conclusions: It can be concluded that melatonin has a positive effect on TLC and differential count of patients of periodontitis, conferring a new facet to the management of periodontitis and an attempt to impede the disease progression. Keywords: Melatonin; Hematological parameters; Periodontitis; Total Leukocyte count; Differential Leukocyte count; Erythrocyte sedimentation rate; Scaling and Root Planning

Evaluation of Effect of Melatonin on Hematological Parameters in Patients of Periodontitis

Introduction: Considering the immunity enhancing property of melatonin, a study on the evaluation of the effect of melatonin on the hematological parameters in patients suffering from Periodontitis.  Methods: This study was conducted in the Department of Periodontics, Rural Dental College, Loni. Patients of chronic Periodontitis, of age between 18 to 65 years of either gender ready to give informed consent to participate in the study were included. Postoperative patients, patients having night duties, drivers and those using heavy machinery, pregnant women, lactating mothers, patients with any clinically significant systemic disease and patients on any other drugs were excluded from the study. Patients were divided into two Groups. Group B received scaling and root planning (SRP) and melatonin 3 mg per day were compared to Group A which received SRP only. The Total Leukocyte count, Differential Leukocyte count and Erythrocyte sedimentation rate of each patient was studied at a baseline, 1st (30 days) visit, 2nd (60 days) visit and 3rd (90 days) visit. Results: Both the groups consisted of 80 subjects each. Group A consisted of 71.25% male and 28.75% female patients. There were 56.25% male and 43.75% female patients in Group B. With respect to visit 3, the TLC was statistically lower in Group B. The neutrophil count of Group B was significantly lower during visit 3 as compared to Group A. The lymphocyte count of Group B was significantly lower than that of Group A during the visit 1, and also significantly higher during visit 3 on comparison with Group A. There was no statistically significant difference in the groups with respect to eosinophil and basophil count. The Monocyte count of Group B was statistically lower when compared to that of Group A. There was no statistically significant difference between ESR of Group A & Group B.  Conclusions: It can be concluded that melatonin has a positive effect on TLC and differential count of patients of periodontitis, conferring a new facet to the management of periodontitis and an attempt to impede the disease progression. Keywords: Melatonin; Hematological parameters; Periodontitis; Total Leukocyte count; Differential Leukocyte count; Erythrocyte sedimentation rate; Scaling and Root Planning

Evaluation of antioxidant potential of melatonin in periodontitis: a prospective clinic-biochemical study

Background: The present study was done with an objective to evaluate the effect of melatonin as an antioxidant in patients suffering from periodontitis.Methods: This study was conducted in the Department of Periodontics, Rural Dental College, Loni. Patients of chronic periodontitis, of age between 18 to 65 years of either gender ready to give informed consent to participate in the study were included. Postoperative patients, patients having night duties, drivers and those using heavy machinery, pregnant women, lactating mothers, patients with any clinically significant systemic disease and patients on any other drugs were excluded from the study. Patients were divided into three Groups. Group A included patients who underwent SRP (Scaling and Root Planning) alone, Group B included patients who underwent SRP & supplemented with Vitamin E 200 IU daily at night for 4 weeks. Group C included patients who underwent SRP & supplemented with tablet melatonin 3 mg daily at night for 4 weeks. Estimation of Malondialdehyde (MDA) for serum lipid peroxidation8, Superoxide dismutase (SOD) and Glutathione peroxidase (GPx) was done on day 0, day 30, day 60 and day 90.Results: A total 240 patients were enrolled in the study. It was demonstrated that there was considerable oxidative stress in periodontitis patients, as established by high serum MDA levels, which was reduced significantly by melatonin reflecting its antioxidant potential. Pretreatment levels of SOD and GPx also were low, which were improved with the treatment of melatonin far better than with vitamin E.Conclusions: Melatonin acts as an antioxidant in the patients of periodontitis which has positive effect on biochemical parameters of periodontitis, conferring a new facet to the management of periodontitis and an attempt to impede the disease progression

Study of Properties of Al LM-25/SIC fabricated by using Stir Casting Method and Wear Analysis by RSM

Aluminum MMC’s are widely used in various applications because of their higher mechanical and physical properties when compared with their base Al alloy. This paper focuses on the change in mechanical properties of various Al/SiC composites fabricated by using stir casting method. Effect of SiC reinforcement in different Al alloys on mechanical properties like hardness, tensile strength, wear test, percentage elongation, residual stress measurements are discussed in detail. For this purpose various reinforcement of SiC with 0,4,8 percent weight and different particle sizes are considered along with Al alloys. Variations in process parameters of stir casting are also made and taken into consideration

Evaluation of antioxidant potential of melatonin in periodontitis with a focus on vitamin C

Background: The present study was done with an objective to evaluate the effect of melatonin as an antioxidant, with a focus on vitamin C, in patients suffering from periodontitis.Methods: This study was conducted jointly in the Department of Periodontics, Rural Dental College, and Department of Pharmacology, PIMS, Loni. Patients suffering from chronic periodontitis, of age between 18 to 65 years of either gender were included in the study, after obtaining a written informed consent. Patients were divided into three Groups. Group A included patients who underwent scaling and root planning (SRP) alone, Group B included patients who underwent SRP and supplemented with vitamin E 200 IU daily at night for 4 weeks. Group C included patients who underwent SRP and supplemented with tablet melatonin 3 mg daily at night for 4 weeks. Estimation of vitamin C was done on day 0, day 30, day 60 and day 90.Results: A total 240 patients were enrolled in the study, 80 in each group. Statistical analysis was done using ‘Z’ test of difference between two sample means for comparison of vitamin C among the three groups. It was observed that, there was a highly significant increase in mean values of vitamin C in group C when compared with group A and group B at 1st, 2nd and 3rd visits (p<0.01).Conclusions: Melatonin acts as an antioxidant in the patients of periodontitis which has positive effect on biochemical parameters of periodontitis, conferring a new facet to the management of periodontitis and an attempt to impede the disease progression

Exact ground state and kink-like excitations of a two dimensional Heisenberg antiferromagnet

A rare example of a two dimensional Heisenberg model with an exact dimerized ground state is presented. This model, which can be regarded as a variation on the kagome lattice, has several features of interest: it has a highly (but not macroscopically) degenerate ground state; it is closely related to spin chains studied by earlier authors; in particular, it is probably the first genuinely two-dimensional quantum system to exhibit domain-wall-like ``kink'' excitations normally found only in one-dimensional systems. In some limits it decouples into non-interacting chains, purely dynamically and not because of weakening of interchain couplings: indeed, paradoxically, this happens in the limit of strong coupling of the chains.Comment: 4 pages, revtex, 5 figures included via epsfi