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Search Results: 1 - 10 of 1548 matches for " Samrat Chatterjee "
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Evaluation of impression smears in the diagnosis of fungal keratitis
Chatterjee Samrat
Indian Journal of Ophthalmology , 2007,
Unraveling the Design Principle for Motif Organization in Signaling Networks
Samrat Chatterjee, Dhiraj Kumar
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0028606
Abstract: Cellular signaling networks display complex architecture. Defining the design principle of this architecture is crucial for our understanding of various biological processes. Using a mathematical model for three-node feed-forward loops, we identify that the organization of motifs in specific manner within the network serves as an important regulator of signal processing. Further, incorporating a systemic stochastic perturbation to the model we could propose a possible design principle, for higher-order organization of motifs into larger networks in order to achieve specific biological output. The design principle was then verified in a large, complex human cancer signaling network. Further analysis permitted us to classify signaling nodes of the network into robust and vulnerable nodes as a result of higher order motif organization. We show that distribution of these nodes within the network at strategic locations then provides for the range of features displayed by the signaling network.
"String of Pearls" following Nd:YAG laser posterior capsulotomy
Chatterjee Samrat,Garg Prashant
Indian Journal of Ophthalmology , 2002,
Abstract: Posterior capsular re-opacification can occur following Nd-YAG capsulotomy. This necessitates multiple capsulotomies with its potential complications. We report one such case and discuss possible predisposing factors and preventive measures for this condition
Fungal keratitis in Lattice dystrophy
Chatterjee Samrat,Agrawal Deepshikha
Indian Journal of Ophthalmology , 2010,
Abstract: We report a case of fungal keratitis occurring in a patient with lattice dystrophy. A 57-year-old farmer presented with a corneal ulcer following probable entry of paddy husk in the right eye, of one month duration. Corneal scraping revealed pigmented fungal filaments while culture grew Alternaria alternata. Treatment with 5% natamycin eye drops and 1% atropine healed the infection in four weeks. We would like to draw attention to the fact that the cornea in lattice dystrophy is prone to frequent erosions and is a compromised epithelial barrier to invasion by microorganisms. Patients must be made aware of this fact and should seek attention at the earliest following any trivial trauma. Management of minor corneal abrasions in them should be directed at healing the epithelium with adequate lubricants and preventing infection with topical antibiotic prophylaxis.
Defining the antigen receptor-dependent regulatory network that induces arrest of cycling immature B-lymphocytes
Mohammad Jamal, Srikanth Ravichandran, Noor Jailkhani, Samrat Chatterjee, Raina Dua, Kanury VS Rao
BMC Systems Biology , 2010, DOI: 10.1186/1752-0509-4-169
Abstract: Here we employed a systems biology approach that combined extensive experimentation with in silico methodologies to chart the network of receptor-activated pathways that mediated the arrest of immature B cells in the G1 phase of the cell cycle. Interestingly, we found that only a sparse network of signaling intermediates was recruited upon engagement of the antigen receptor. This then led to the activation of a restricted subset of transcription factors, with the consequent induction of genes primarily involved in the cell death pathway. Subsequent experiments revealed that the weak initiation of intracellular signaling pathways derived from desensitization of the receptor-proximal protein tyrosine kinase Lyn, to receptor-dependent activation. Intriguingly, the desensitization was a result of the constitutive activation of this kinase in unstimulated cells, which was likely maintained through a regulatory feedback loop involving the p38 MAP kinase. The high basal activity then attenuated the ability of the antigen receptor to recruit Lyn, and thereby also the downstream signaling intermediates. Finally, integration of these results into a mathematical model provided further substantiation to the novel finding that the ground state of the intracellular signaling machinery constitutes an important determinant of the outcome of receptor-induced cellular responses.Our results identify the global events leading to the G1 arrest and subsequent apoptosis in immature B cells upon receptor activation.Cellular responses to environmental cues are mediated through activation of the signal transduction machinery. This machinery is best represented as a complex network that, in turn, governs the decision-making capabilities of the cell [1,2]. Engagement of a cell surface receptor induces activation of signal transduction cascades that involve a series of phosphorylation/dephosphorylation events. These phosphorylation-dependent signaling events eventually transduce signal to trans
Cosine Modulated Non-Uniform Filter Banks  [PDF]
Jyotsna Ogale, Samrat Ashok
Journal of Signal and Information Processing (JSIP) , 2011, DOI: 10.4236/jsip.2011.23024
Abstract: Traditional designs for non-uniform filter bank (NUFB) are usually complex; involve complicated nonlinear optimization with a large number of parameters and lack of linear phase ([LP) property. In this paper, we describe a simple design method for multirate near perfect reconstruction (NPR) cosine modulated filter banks with non-uniform frequency spacing and linear phase property that involves optimization of only single parameter. It is derived from the uniform cosine modulated filter bank (CMFB) by merging some relevant band pass filters. The design procedure and the structure of the uniform CMFB are mostly preserved in the non-uniform implementation. Compared to other design methods our method provides very good design and converges very rapidly but the method is applicable, only if the upper band edge frequency of each non-uniform filter is an integral multiple of the bandwidth of the corresponding band. The design examples are presented to show the superiority of the proposed method over existing one.
The impact of upper tropospheric friction and Gill-type heating on the location and strength of the Tropical Easterly Jet: Idealized physics in a dry Atmospheric General Circulation Model
Samrat Rao
Physics , 2015,
Abstract: An atmospheric general circulation model (AGCM) with idealized and complete physics has been used to evaluate the Tropical Easterly Jet (TEJ) jet. In idealized physics, the role of upper tropospheric friction has been found to be important in getting realistic upper tropospheric zonal wind patterns in response to heating. In idealized physics, the location and strength of the TEJ as a response to Gill heating has been studied. Though the Gill model is considered to be widely successful in capturing the lower tropospheric response, it is found to be inadequate in explaining the location and strength of the upper level TEJ. Heating from the Gill model and realistic upper tropospheric friction does not lead to the formation of a TEJ.
Pathogenicity of Mycobacterium tuberculosis Is Expressed by Regulating Metabolic Thresholds of the Host Macrophage
Parul Mehrotra equal contributor,Shilpa V. Jamwal equal contributor,Najmuddin Saquib,Neeraj Sinha,Zaved Siddiqui,Venkatasamy Manivel,Samrat Chatterjee,Kanury V. S. Rao
PLOS Pathogens , 2014, DOI: doi/10.1371/journal.ppat.1004265
Abstract: The success of Mycobacterium tuberculosis as a pathogen derives from its facile adaptation to the intracellular milieu of human macrophages. To explore this process, we asked whether adaptation also required interference with the metabolic machinery of the host cell. Temporal profiling of the metabolic flux, in cells infected with differently virulent mycobacterial strains, confirmed that this was indeed the case. Subsequent analysis identified the core subset of host reactions that were targeted. It also elucidated that the goal of regulation was to integrate pathways facilitating macrophage survival, with those promoting mycobacterial sustenance. Intriguingly, this synthesis then provided an axis where both host- and pathogen-derived factors converged to define determinants of pathogenicity. Consequently, whereas the requirement for macrophage survival sensitized TB susceptibility to the glycemic status of the individual, mediation by pathogen ensured that the virulence properties of the infecting strain also contributed towards the resulting pathology.
The impact of latent heating on the location, strength and structure of the Tropical Easterly Jet in the Community Atmosphere Model, version 3.1: Aqua-planet simulations
Samrat Rao,Jayaraman Srinivasan
Physics , 2015,
Abstract: The Tropical Easterly Jet (TEJ) is a prominent atmospheric circulation feature observed during the Asian Summer Monsoon (ASM). The simulation of TEJ by the Community Atmosphere Model, version 3.1 (CAM-3.1) has been discussed in detail. Although the simulated TEJ replicates many observed features of the jet, the jet maximum is located too far to the west when compared to observation. Orography has minimal impact on the simulated TEJ hence indicating that latent heating is the crucial parameter. A series of aqua-planet experiments with increasing complexity was undertaken to understand the reasons for the extreme westward shift of the TEJ. The aqua-planet simulations show that a single heat source in the deep tropics is inadequate to explain the structure of the observed TEJ. Equatorial heating is necessary to impart a baroclinic structure and a realistic meridional structure. Jet zonal wind speeds are directly related to the magnitude of deep tropical heating. The location of peak zonal wind is influenced by off-equatorial heating which is closest to it. Hence the presence of excess rainfall in Saudi Arabia has been shown to be the primary reason for the extreme westward shift of the TEJ maximum.
The Impact of Orography and Latent Heating on the Location of the Tropical Easterly Jet
Samrat Rao,J. Srinivasan
Physics , 2013,
Abstract: The Tropical Easterly Jet (TEJ) is a prominent atmospheric circulation feature observed during the Asian Summer Monsoon. It is generally assumed that Tibet is an essential ingredient in determining the location of the TEJ. However studies have also suggested the importance of latent heating in determining the jet location. The relative importance of Tibetan orography and latent heating is explored through simulations with a general circulation model. The simulation of TEJ by the Community Atmosphere Model, version 3.1 (CAM-3.1) has been discussed in detail. Although the simulated TEJ replicated many observed features of the jet, the jet maximum was located too far to the west when compared to observation. The precipitation in the control simulation was high to the west of India and this caused the TEJ to shift westwards by approximately the same amount. Orography was found to have minimal impact on the simulated TEJ hence indicating that latent heating is the crucial parameter. The primacy of latent heating in determining the jet location was confirmed by additional simulations where the simulated precipitation was brought closer to observations. This made the TEJ to also shift to the correct position.
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