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Search Results: 1 - 10 of 329230 matches for " Dipanjan S. Roy "
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Inferring network properties of cortical neurons with synaptic coupling and parameter dispersion
Dipanjan Roy,Viktor Jirsa
Frontiers in Computational Neuroscience , 2013, DOI: 10.3389/fncom.2013.00020
Abstract: Computational models at different space-time scales allow us to understand the fundamental mechanisms that govern neural processes and relate uniquely these processes to neuroscience data. In this work, we propose a novel neurocomputational unit (a mesoscopic model which tell us about the interaction between local cortical nodes in a large scale neural mass model) of bursters that qualitatively captures the complex dynamics exhibited by a full network of parabolic bursting neurons. We observe that the temporal dynamics and fluctuation of mean synaptic action term exhibits a high degree of correlation with the spike/burst activity of our population. With heterogeneity in the applied drive and mean synaptic coupling derived from fast excitatory synapse approximations we observe long term behavior in our population dynamics such as partial oscillations, incoherence, and synchrony. In order to understand the origin of multistability at the population level as a function of mean synaptic coupling and heterogeneity in the firing rate threshold we employ a simple generative model for parabolic bursting recently proposed by Ghosh et al. (2009). Further, we use here a mean coupling formulated for fast spiking neurons for our analysis of generic model. Stability analysis of this mean field network allow us to identify all the relevant network states found in the detailed biophysical model. We derive here analytically several boundary solutions, a result which holds for any number of spikes per burst. These findings illustrate the role of oscillations occurring at slow time scales (bursts) on the global behavior of the network.
Dynamic Patterns of Circulating Seasonal and Pandemic A(H1N1)pdm09 Influenza Viruses From 2007–2010 in and around Delhi, India
Shobha Broor, Anand Krishnan, Dipanjan S. Roy, Shivram Dhakad, Samander Kaushik, Muneer A. Mir, Yashpal Singh, Ann Moen, Mandeep Chadha, Akhilesh C. Mishra, Renu B. Lal
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029129
Abstract: Influenza surveillance was carried out in a subset of patients with influenza-like illness (ILI) presenting at an Employee Health Clinic (EHS) at All India Institute of Medical Sciences (AIIMS), New Delhi (urban) and pediatric out patients department of civil hospital at Ballabhgarh (peri-urban), under the Comprehensive Rural Health Services Project (CRHSP) of AIIMS, in Delhi region from January 2007 to December 2010. Of the 3264 samples tested, 541 (17%) were positive for influenza viruses, of which 221 (41%) were pandemic Influenza A(H1N1)pdm09, 168 (31%) were seasonal influenza A, and 152 (28%) were influenza B. While the Influenza viruses were detected year-round, their types/subtypes varied remarkably. While there was an equal distribution of seasonal A(H1N1) and influenza B in 2007, predominance of influenza B was observed in 2008. At the beginning of 2009, circulation of influenza A(H3N2) viruses was observed, followed later by emergence of Influenza A(H1N1)pdm09 with co-circulation of influenza B viruses. Influenza B was dominant subtype in early 2010, with second wave of Influenza A(H1N1)pdm09 in August-September, 2010. With the exception of pandemic H1N1 emergence in 2009, the peaks of influenza activity coincided primarily with monsoon season, followed by minor peak in winter at both urban and rural sites. Age group analysis of influenza positivity revealed that the percent positivity of Influenza A(H1N1)pdm09 influenza virus was highest in >5–18 years age groups (OR 2.5; CI = 1.2–5.0; p = 0.009) when compared to seasonal influenza. Phylogenetic analysis of Influenza A(H1N1)pdm09 from urban and rural sites did not reveal any major divergence from other Indian strains or viruses circulating worldwide. Continued surveillance globally will help define regional differences in influenza seasonality, as well as, to determine optimal periods to implement influenza vaccination programs among priority populations.
Low frequency radio-FIR correlation in normal galaxies at ~1 kpc scales
Aritra Basu,Subhashis Roy,Dipanjan Mitra
Physics , 2012, DOI: 10.1088/0004-637X/756/2/141
Abstract: We study the radio--FIR correlation between the nonthermal (synchrotron) radio continuum emission at \lambda 90 cm (333 MHz) and the far infrared emission due to cool (~20 K) dust at \lambda 70\mu m in spatially resolved normal galaxies at scales of ~1 kpc. The slope of the radio--FIR correlation significantly differs between the arm and interarm regions. However, this change is not evident at a lower wavelength of \lambda 20 cm (1.4 GHz). We find the slope of the correlation in the arm to be 0.8 \pm 0.12 and we use this to determine the coupling between equipartition magnetic field (B_{eq}) and gas density (\rho_{gas}) as B_{eq} \propto \rho_{gas}^{0.51 \pm 0.12}. This is close to what is predicted by MHD simulations of turbulent ISM, provided the same region produces both the radio and far infrared emission. We argue that at 1 kpc scales this condition is satisfied for radio emission at 1.4 GHz and may not be satisfied at 333 MHz. Change of slope observed in the interarm region could be caused by propagation of low energy (~1.5 GeV) and long lived (~ 10^8 yr) cosmic ray electrons at 333 MHz.
Non tuberculous mycobacteria and toxoplasma co-infection of the central nervous system in a patient with AIDS
Sardar, Partha;Bandyopadhyay, Dipanjan;Roy, Deeptarka;Guha, Pradipta;Guha, Goutam;Banerjee, Amit Kumar;
Brazilian Journal of Infectious Diseases , 2009, DOI: 10.1590/S1413-86702009000600011
Abstract: new-onset seizures are frequent manifestations in patients infected with human immunodeficiency virus (hiv). we describe the clinical and radiological findings in an 25yr old aids patient presenting with new onset seizures as the primary manifestation of cerebral toxoplasmosis and non tuberculous mycobacterial [ntm] co-infection. cranial computed tomography showed a subtle ventricular dilatation whereas magnetic resonance imaging disclosed prominent temporal horn. toxoplasma tachyzoites and rapidly growing mycobacteria were recovered from csf. seizures were complex partial in nature and refractory to antiepileptic therapy.
Multiorgan involvement due to cytomegalovirus infection in AIDS
Majumder, Shounak;Mandal, Sanjay K.;Bandyopadhyay, Dipanjan;Chowdhury, Subhasis Roy;Chakraborty, Partha P.;K., Mitra;
Brazilian Journal of Infectious Diseases , 2007, DOI: 10.1590/S1413-86702007000100039
Abstract: cytomegalovirus (cmv) infection is a relatively late complication of aids. like other viruses contributing to co-morbidity of hiv infection, cytomegalovirus has the propensity to cause multiorgan involvement. we report the case of a 34-year-old seropositive man who presented with bilateral lower limb weakness and symptomatic pallor. he was already on antiretroviral drugs for a month prior to presentation. detailed clinical examination and laboratory investigations revealed cytomegalovirus polyradiculoneuropathy associated with bone marrow dysplasia. dysplasia of haematopoeitic cell lines occurs in 30% to 70% of hiv infected patients, and is often indistinguishable from myelodysplastic syndrome. however, in our case, the bone marrow picture reverted back to normal with treatment of the cmv infection, pointing to a possible role of cmv as the causative agent of bone marrow dysplasia. moreover, cmv has been incriminated as a pathogen producing the immune reconstitution inflammatory syndrome. the onset of the disease in our case one month after initiation of haart strongly raises the possibility of this being a case of cmv related iris. this is the first reported case where iris has presented with cmv polyradiculoneuropathy and bone marrow dysplasia. we would like to highlight that in today's era of hiv care, clinicians should be aware of the possibility of multiorgan involvement by cmv, for appropriate management of this disease in the background of aids.
Therapeutic evaluation of Ivermectin Pour on against tick infestation in dogs
S. Roy and M. Roy
Veterinary World , 2010,
Abstract: Study was conducted on 20 dogs of different breeds and age, of Bhilai area naturally infested with Rhipicephalus Sanguineus ticks. Dogs with moderate to severe tick infestations were treated with ivermectin pour on @ 1ml/10kg body weight. In the present study ivermectin pour on was found to be 100 percent effective against naturally occurring tick infestation in dogs. [Vet. World 2010; 3(3.000): 113-114]
Carbonic Anhydrase III S-Glutathionylation Is Necessary for Anti-Oxidant Activity  [PDF]
P. Roy, M. Ireland, S. Roy, J. Craft, C. Bartholomew
Yangtze Medicine (YM) , 2018, DOI: 10.4236/ym.2018.24026
Abstract: Carbonic anhydrase isozyme CA3 protects cells against oxidative stress. Ectopic expression of murine Ca3, but not Ca2, protects proto-oncogene Evi1 expressing Rat1 fibroblast cells (ca3low) against hydrogen peroxide (H2O2) induced stress. Ca3 is S-glutathionylated via glutathione adducts with cysteines 181 and 186. Substitution of both Ca3 cysteines with serine fails to protect cells from oxidative stress. Insertion of cysteine at 181 and 186 in Ca2 is insufficient for conferring efficient anti-oxidant activity. This shows for the first time that S-glutathionylation of cys181 and cys186 residues is required for Ca3 anti-oxidant activity but that additional factors are also required.
Effect of administration of tamoxifen citrate on xanthine oxidase activity of liver during 3-methylcholanthrene induced carcinogenesis in female albino mice
S Roy
Biology and Medicine , 2012,
Abstract: Tamoxifen citrate, the non-steroidal anti-estrogen and the first selective estrogen receptor modulator is the treatment of choice for patients with all stages of estrogen receptor positive breast cancer. Although Cytochrome P-450s (CYP) are well known to be responsible for much of its metabolism, fragmentary studies have been carried out to analyze the activity of xanthine oxidase, a non-CYP drug metabolizing enzyme, in tamoxifen metabolism. So, the present investigation is aimed to ascertain the effect of tablet and nano-formulation of tamoxifen on xanthine oxidase expression during 3-methylcholanthrene-induced carcinogenesis. It is found that oral administration of tamoxifen in both the formulations significantly (p < 0.01) decreases the xanthine oxidaseactivity in liver tissue of female mice. We speculate our results to be beneficial for the better understanding of drug metabolism and intensity, which in turn will pave the way for new and efficient nano-formulations of drug coming into therapeutic use.
Planck Scale Physics, Pregeometry and the Notion of Time
S. Roy
Physics , 2003,
Abstract: Recent progress in quantum gravity and string theory has raised interest among scientists to whether or not nature behaves discretely at the Planck scale. There are two attitudes twoards this discretenes i.e. top-down and bottom-up approach. We have followed up the bottom-up approach. Here we have tried to describe how macroscopic space-time or its underlying mesoscopic substratum emerges from a more fundamental concept. The very concept of space-time, causality may not be valid beyond Planck scale. We have introduced the concept of generalised time within the framework of Sheaf Cohomology where the physical time emrges around and above Planck scale. The possible physical amd metaphysical implications are discussed.
Observations that can unravel the coherent radio emission mechanism in pulsars
Dipanjan Mitra
Physics , 2013,
Abstract: Searching for the physical mechanism that can excite the coherent radio emission in pulsars is still an enigmatic problem. A wealth of high quality observations exist, which over the years have been instrumental in putting stringent constraints to pulsar emission models. In this article we will discuss the observational results that strongly suggests that pulsar radio emission is excited by coherent curvature radiation. We will also mention issues that remain to be resolved.
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