42 results on '"Narayana, P A"'
Search Results
2. Analytical Bit-Error Model of NAND Flash Memories for Dosimetry Application
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Maryla Wasiolek, Narayana P. Bhat, Biswajit Ray, Preeti Kumari, Khalid Hattar, and Umeshwarnath Surendranathan
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Nuclear and High Energy Physics ,Flash (photography) ,Bit (horse) ,Nuclear Energy and Engineering ,business.industry ,Computer science ,NAND gate ,Dosimetry ,Electrical and Electronic Engineering ,business ,Computer hardware - Published
- 2022
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3. Mixed convection instability in a viscosity stratified flow in a vertical channel
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Ankush, Narayana, P. A. L., and Sahu, K. C.
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Fluid Dynamics (physics.flu-dyn) ,FOS: Physical sciences ,Physics - Fluid Dynamics - Abstract
The present study examines the linear instability characteristics of double-diffusive mixed convective flow in a vertical channel with viscosity stratification. The viscosity of the fluid is modelled as an exponential function of temperature and concentration, with an activation energy parameter determining its sensitivity to temperature variation. Three scenarios are considered: buoyancy force due to thermal diffusion only, buoyancy force due to temperature and solute acting in the same direction, and buoyancy force due to temperature and solute acting in opposite directions. A generalized eigenvalue problem is derived and solved numerically for linear stability analysis via the Chebyshev spectral collocation method. Results indicate that higher values of the activation energy parameter lead to increased flow stability. Additionally, when both buoyant forces act in opposite directions, the Schmidt number has both stabilizing and destabilizing effects across the range of activation energy parameters, similar to the case of pure thermal diffusion. Furthermore, the solutal-buoyancy-opposed base flow is found to be the most stable, while the solutal-buoyancy-assisted base flow is the least stable. As expected, an increase in Reynolds number is shown to decrease the critical Rayleigh number., Comment: 10 pages, 9 figures, Physics of Fluids
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- 2023
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4. Radiation-Induced Error Mitigation by Read-Retry Technique for MLC 3-D NAND Flash Memory
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Maryla Wasiolek, Biswajit Ray, Narayana P. Bhat, Umeshwarnath Surendranathan, Khalid Hattar, and Preeti Kumari
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Nuclear and High Energy Physics ,Hardware_MEMORYSTRUCTURES ,010308 nuclear & particles physics ,business.industry ,Computer science ,Nand flash memory ,Error mitigation ,NAND gate ,Radiation induced ,Chip ,01 natural sciences ,Non-volatile memory ,Nuclear Energy and Engineering ,Logic gate ,0103 physical sciences ,Electrical and Electronic Engineering ,business ,Error detection and correction ,Computer hardware - Abstract
In this article, we have evaluated the Read-Retry (RR) functionality of the 3-D NAND chip of multilevel-cell (MLC) configuration after total ionization dose (TID) exposure. The RR function is typically offered in the high-density state-of-the-art NAND memory chips to recover data once the default memory read method fails to correct data with error correction codes (ECCs). In this work, we have applied the RR method on the irradiated 3-D NAND chip that was exposed with a Co-60 gamma-ray source for TID up to 50 krad (Si). Based on our experimental evaluation results, we have proposed an algorithm to efficiently implement the RR method to extend the radiation tolerance of the NAND memory chip. Our experimental evaluation shows that the RR method coupled with ECC can ensure data integrity of MLC 3-D NAND for TID up to 50 krad (Si).
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- 2021
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5. SARS-CoV-2 infects adipose tissue in a fat depot- and viral lineage-dependent manner
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Tatiana Dandolini Saccon, Felippe Mousovich-Neto, Raissa Guimarães Ludwig, Victor Corasolla Carregari, Ana Beatriz dos Anjos Souza, Amanda Stephane Cruz dos Passos, Matheus Cavalheiro Martini, Priscilla Paschoal Barbosa, Gabriela Fabiano de Souza, Stéfanie Primon Muraro, Julia Forato, Mariene Ribeiro Amorim, Rafael Elias Marques, Flavio Protasio Veras, Ester Barreto, Tiago Tomazini Gonçalves, Isadora Marques Paiva, Narayana P. B. Fazolini, Carolina Mie Kawagosi Onodera, Ronaldo Bragança Martins Junior, Paulo Henrique Cavalcanti de Araújo, Sabrina Setembre Batah, Rosa Maria Mendes Viana, Danilo Machado de Melo, Alexandre Todorovic Fabro, Eurico Arruda, Fernando Queiroz Cunha, Thiago Mattar Cunha, Marco Antônio M. Pretti, Bradley Joseph Smith, Henrique Marques-Souza, Thiago L. Knittel, Gabriel Palermo Ruiz, Gerson S. Profeta, Tereza Cristina Minto Fontes-Cal, Mariana Boroni, Marco Aurélio Ramirez Vinolo, Alessandro S. Farias, Pedro Manoel M. Moraes-Vieira, Joyce Maria Annichino Bizzacchi, Tambet Teesalu, Felipe David Mendonça Chaim, Everton Cazzo, Elinton Adami Chaim, José Luiz Proença-Módena, Daniel Martins-de-Souza, Mariana Kiomy Osako, Luiz Osório Leiria, and Marcelo A. Mori
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Multidisciplinary ,Adipose Tissue ,SARS-CoV-2 ,General Physics and Astronomy ,COVID-19 ,Cytokines ,Humans ,General Chemistry ,Angiotensin-Converting Enzyme 2 ,General Biochemistry, Genetics and Molecular Biology - Abstract
Visceral adiposity is a risk factor for severe COVID-19, and a link between adipose tissue infection and disease progression has been proposed. Here we demonstrate that SARS-CoV-2 infects human adipose tissue and undergoes productive infection in fat cells. However, susceptibility to infection and the cellular response depends on the anatomical origin of the cells and the viral lineage. Visceral fat cells express more ACE2 and are more susceptible to SARS-CoV-2 infection than their subcutaneous counterparts. SARS-CoV-2 infection leads to inhibition of lipolysis in subcutaneous fat cells, while in visceral fat cells, it results in higher expression of pro-inflammatory cytokines. Viral load and cellular response are attenuated when visceral fat cells are infected with the SARS-CoV-2 gamma variant. A similar degree of cell death occurs 4-days after SARS-CoV-2 infection, regardless of the cell origin or viral lineage. Hence, SARS-CoV-2 infects human fat cells, replicating and altering cell function and viability in a depot- and viral lineage-dependent fashion.
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- 2022
6. Fermi-GBM Observations of GRB 210812A: Signatures of a Million Solar Mass Gravitational Lens
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Narayana P. Bhat, Nissim Illich Fraija, Péter Veres, and S. Lesage
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Solar mass ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,law.invention ,Lens (optics) ,Supernova ,Gravitational lens ,Spitzer Space Telescope ,Space and Planetary Science ,law ,Gamma-ray burst ,Astrophysics - High Energy Astrophysical Phenomena ,Fermi Gamma-ray Space Telescope - Abstract
Observing gravitationally lensed objects in the time domain is difficult, and well-observed time-varying sources are rare. Lensed gamma-ray bursts (GRBs) offer improved timing precision to this class of objects complementing observations of quasars and supernovae. The rate of lensed GRBs is highly uncertain, approximately 1 in 1000. The Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-ray Space Telescope has observed more than 3000 GRBs making it an ideal instrument to uncover lensed bursts. Here we present observations of GRB 210812A showing two emission episodes, separated by 33.3 s, and with flux ratio of about 4.5. An exhaustive temporal and spectral analysis shows that the two emission episodes have the same pulse and spectral shape, which poses challenges to GRB models. We report multiple lines of evidence for a gravitational lens origin. In particular, modeling the lightcurve using nested sampling we uncover strong evidence in favor of the lensing scenario. Assuming a point mass lens, the mass of the lensing object is about 1 million solar masses. High-resolution radio imaging is needed for future lens candidates to derive tighter constraints., 13 pages, 8 figures, AAS journals accepted (ApJL)
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- 2021
7. Lipid droplets: platforms with multiple functions in cancer hallmarks
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Patrícia T. Bozza, João P. B. Viola, André L S Cruz, Ester A. Barreto, and Narayana P. B. Fazolini
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Cancer Research ,Immunology ,Review Article ,Cellular and Molecular Neuroscience ,Lipid droplet ,Neoplasms ,Organelle ,Tumor Microenvironment ,Animals ,Humans ,lcsh:QH573-671 ,Cell Proliferation ,Inflammation ,Cell Death ,Chemistry ,Cell growth ,lcsh:Cytology ,Lipid metabolism ,Cell Biology ,Lipid Droplets ,Lipids ,Cancer metabolism ,Cell biology ,Cell Transformation, Neoplastic ,Cytoplasm ,Neoplastic Stem Cells ,Tumor Hypoxia ,lipids (amino acids, peptides, and proteins) ,Signal transduction ,Inflammation Mediators ,Energy Metabolism ,Intracellular ,Biogenesis ,Signal Transduction - Abstract
Lipid droplets (also known as lipid bodies) are lipid-rich, cytoplasmic organelles that play important roles in cell signaling, lipid metabolism, membrane trafficking, and the production of inflammatory mediators. Lipid droplet biogenesis is a regulated process, and accumulation of these organelles within leukocytes, epithelial cells, hepatocytes, and other nonadipocyte cells is a frequently observed phenotype in several physiologic or pathogenic situations and is thoroughly described during inflammatory conditions. Moreover, in recent years, several studies have described an increase in intracellular lipid accumulation in different neoplastic processes, although it is not clear whether lipid droplet accumulation is directly involved in the establishment of these different types of malignancies. This review discusses current evidence related to the biogenesis, composition and functions of lipid droplets related to the hallmarks of cancer: inflammation, cell metabolism, increased proliferation, escape from cell death, and hypoxia. Moreover, the potential of lipid droplets as markers of disease and targets for novel anti-inflammatory and antineoplastic therapies will be discussed.
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- 2020
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8. Design and Analysis of Latentheat Storage Based Solar Thermal Energy Conversion Cycle
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Tjprc and P. Badari Narayana, P. Badari Narayana
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Fluid Flow and Transfer Processes ,Materials science ,Solar thermal energy ,Mechanical Engineering ,Nuclear engineering ,Aerospace Engineering - Published
- 2020
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9. Nature of Senescence in Six Popular Rice Varieties of Andhra Pradesh
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Venkata Narayana. P Venkata Narayana. P and Tjprc
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Senescence ,business.industry ,Biology ,business ,Biotechnology - Published
- 2018
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10. A Cosmological Fireball with Thirty-Percent Gamma-Ray Radiative Efficiency
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A. J. Castro-Tirado, Narayana P. Bhat, Bing Zhang, Liang Li, Asaf Pe'er, Felix Ryde, David Alexander Kann, K. L. Page, Sylvain Guiriec, Yu Wang, Peter Vereš, and Magnus Axelsson
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Physics ,Radiative efficiency ,Astrophysics::High Energy Astrophysical Phenomena ,Gamma ray ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics - Abstract
Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. The composition of the jets is, however, subject to debate\cite{Peer2015,Zhang2018}. Whereas the traditional model invokes a relativistic matter-dominated fireball with a bright photosphere emission component\cite{Meszaros2000}, the lack of the detection of such a component in some GRBs\cite{Abdo2009} has led to the conclusion that GRB jets may be Poynting-flux-dominated\cite{Zhang2009}. Furthermore, how efficiently the jet converts its energy to radiation is poorly constrained. A definitive diagnosis of the GRB jet composition and measurement of GRB radiative efficiency requires high-quality prompt emission and afterglow data, which has not been possible with the sparse observations in the past. Here we report a comprehensive temporal and spectral analysis of the TeV-emitting bright GRB 190114C. Its fluence is one of the highest of all GRBs detected so far, which allows us to perform a high-significance study on the prompt emission spectral properties and their variations down to a very short timescale of about 0.1 s. We identify a clear thermal component during the first two prompt emission episodes, which is fully consistent with the prediction of the fireball photosphere model. The third episode of the prompt emission is consistent with synchrotron radiation from the deceleration of the fireball. This allows us to directly dissect the fireball energy budget in a parameter-independent manner\cite{Zhang2021} and robustly measure a nearly $30\%$ radiative efficiency for this GRB. The afterglow microphysics parameters can be also well constrained from the data. GRB 190114C, therefore, exhibits the evolution of a textbook-version relativistic fireball, suggesting that fireballs can indeed power at least some GRBs with high efficiency.
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- 2021
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11. Wear behavior and Microstructural Characterization of AA7075/MWCNT Surface Composites fabricated through Friction Stir Processing
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Syed Azeem Pasha, Ravinder Reddy P, and Laxmi Narayana P
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0209 industrial biotechnology ,020901 industrial engineering & automation ,Friction stir processing ,Materials science ,02 engineering and technology ,Composite material ,021001 nanoscience & nanotechnology ,0210 nano-technology ,Characterization (materials science) - Published
- 2017
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12. Rab7 controls lipid droplet-phagosome association during mycobacterial infection
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Jens Rietdorf, Heloisa D'Avila, Clarissa M. Maya-Monteiro, Patrícia T. Bozza, Natalia R. Roque, Narayana P. B. Fazolini, Silvia L. Lage, Rossana C. N. Melo, and Roberta Navarro
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0301 basic medicine ,Male ,03 medical and health sciences ,Mice ,0302 clinical medicine ,Immune system ,Lipid droplet ,Phagosomes ,Organelle ,Animals ,Molecular Biology ,Phagosome ,Mycobacterium Infections ,Chemistry ,Intracellular parasite ,rab7 GTP-Binding Proteins ,Cell Biology ,Lipid signaling ,Lipid Droplets ,Mycobacterium tuberculosis ,Cell biology ,Mice, Inbred C57BL ,030104 developmental biology ,rab GTP-Binding Proteins ,Female ,Rab ,Signal transduction ,030215 immunology - Abstract
Lipid droplets (LDs) are organelles that have multiple roles in inflammatory and infectious diseases. LD act as essential platforms for immunometabolic regulation, including as sites for lipid storage and metabolism, inflammatory lipid mediator production, and signaling pathway compartmentalization. Accumulating evidence indicates that intracellular pathogens may exploit host LDs as source of nutrients and as part of their strategy to promote immune evasion. Notably, numerous studies have demonstrated the interaction between LDs and pathogen-containing phagosomes. However, the mechanism involved in this phenomenon remains elusive. Here, we observed LDs and PLIN2 surrounding M. bovis BCG-containing phagosomes, which included observations of a bacillus cell surrounded by lipid content inside a phagosome and LAM from mycobacteria co-localizing with LDs; these results were suggestive of exchange of contents between these compartments. By using beads coated with M.tb lipids, we demonstrated that LD-phagosome associations are regulated through the mycobacterial cell wall components LAM and PIM. In addition, we demonstrated that Rab7 and RILP, but not Rab5, localizes to LDs of infected macrophages and observed the presence of Rab7 at the site of interaction with an infected phagosome. Moreover, treatment of macrophages with the Rab7 inhibitor CID1067700 significantly inhibited the association between LDs and LAM-coated beads. Altogether, our data demonstrate that LD-phagosome interactions are controlled by mycobacterial cell wall components and Rab7, which enables the exchange of contents between LDs and phagosomes and may represent a fundamental aspect of bacterial pathogenesis and immune evasion.
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- 2019
13. A COMPARISON OF TWO DIFFERENT DOSES OF DEXMEDETOMIDINE INFUSION DURING MAINTENANCE OF GENERAL ANAESTHESIA IN PATIENTS UNDERGOING SPINE SURGERIES, FUNCTIONAL ENDOSCOPIC SINUS SURGERY AND MIDDLE EAR SURGERIES
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Shankara Narayana P, Aiyappa D. S, Anish N. G. Sharma, M Nazim, Bijay M, and Ganapathi P
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medicine.medical_specialty ,lcsh:R5-130.5 ,business.industry ,Functional endoscopic sinus surgery ,Surgery ,medicine.anatomical_structure ,Anesthesia ,Middle ear ,Medicine ,Hemodynamic Parameters ,In patient ,General anaesthesia ,Dexmedetomidine ,business ,lcsh:General works ,medicine.drug - Abstract
BACKGROUND This study is undertaken to compare the hemodynamic effects and reduction in the doses of volatile anaesthetics and muscle relaxants using two different doses of dexmedetomidine infusion during maintenance of anaesthesia in spine, functional endoscopic sinus surgery and middle ear surgeries. METHODS Sixty patients are randomly divided into 2 groups of 30 each. After shifting to the operation theatre baseline vitals were recorded. Anesthesia induced with thiopentone sodium and intubation done with the help of succinylcholine and maintained with oxygen, nitrous oxide and isoflurane. After 1 min of intubation, maintenance infusion of dexmedetomidine (0.4 mcg/kg/hr and 0.7 mcg/kg/hr for patients allotted in 2 separate groups) was started and stopped 15 min before end of surgery. Hemodynamic parameters and any reduction in the doses of volatile anaesthetics and muscle relaxants was noted. RESULTS Dexmedetomidine infusion (0.4 mcg/kg/hr and 0.7 mcg/kg/hr) in both groups reduced the requirements of muscle relaxants and volatile anaesthetics. Hemodynamic stability was better in the group receiving 0.4 mcg/kg/hr. Patients receiving 0.7 mcg/kg/hr had higher incidence of hypotension, bradycardia and delayed emergence from anaesthesia. CONCLUSION Dexmedetomidine infusion at 0.4 mcg/kg/hr during maintenance of anaesthesia in spine surgery, FESS and middle ear surgery would be good option to reduce the requirements of volatile anaesthetics, muscle relaxants and for better hemodynamic stability. OBJECTIVE OF STUDY: Primary Objective To compare and evaluate the hemodynamic effects and reduction in requirements of volatile anaesthetics and muscle relaxants with two different doses of dexmedetomidine infusion during maintenance of general anaesthesia in patients undergoing spine, FESS and middle ear surgeries.
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- 2016
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14. Cross-linking of poly (vinyl alcohol) films under acidic and thermal stress
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George Crull, Ipsit Kundu, Balvinder S. Vig, Varia Sailesh Amilal, Salil D. Desai, Hemant Bhutani, Narayana P. Swamy, Ravi P. Shah, Chiranjeevi Venkatesh, Sridhar Desikan, Sherif Badawy, Duohai Pan, and Junshu Zhao
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Vinyl alcohol ,Materials science ,Polymers ,Pharmaceutical Science ,Ether ,Hydrochloric acid ,02 engineering and technology ,engineering.material ,030226 pharmacology & pharmacy ,Excipients ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Coating ,Dissolution ,chemistry.chemical_classification ,Aqueous solution ,Polymer ,021001 nanoscience & nanotechnology ,Acid strength ,chemistry ,Chemical engineering ,Polyvinyl Alcohol ,engineering ,0210 nano-technology ,Tablets - Abstract
Poly (vinyl alcohol), PVA, a commonly used excipient to coat tablets, forms insoluble films in the presence of acids and thermal stress. This may lead to drug products failing to meet dissolution specifications over time. Studies were conducted to understand the effect of acid strength, processing conditions, and storage stress on the mechanism of insoluble film formation using PVA and OpadryⓇ II as model systems. Aqueous cast films, prepared by incorporating hydrochloric acid (HCl) into the coating solutions or exposing pre-cast "as is" films to HCl vapors, were used as surrogates to develop analytical methods. To understand effect of acid and processing on coatings, acidified OpadryⓇ II was spray coated onto inert cores under "wet" or "dry" conditions. Samples stored at 50-60 °C were analyzed for film disintegration to understand physical/chemical changes in the polymer. Rate and extent of insoluble films formation was dependent on the acid concentration and thermal stress. Analysis of the films indicated significant de-acetylation and ether bond formation in insoluble aqueous cast films. In contrast, acidified coated films showed only ether bond formation, which increased on stress, forming insoluble films. The reduction in the time to form insoluble films for "wet" versus "dry" coated films was rationalized by considering effect of coating, drying, and storage on the microstructure of acidified PVA and ether bond propagation. The results highlight the need to develop an in-depth understanding of the design space for PVA coated products and storage conditions in presence of acids.
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- 2020
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15. Leptin activation of mTOR pathway in intestinal epithelial cell triggers lipid droplet formation, cytokine production and increased cell proliferation
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João P. B. Viola, Patrícia T. Bozza, Narayana P. B. Fazolini, André L S Cruz, Clarissa M. Maya-Monteiro, and Miriam B. F. Werneck
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Leptin ,lipid droplets ,Adipose tissue ,Inflammation ,Biology ,Cell Line ,Report ,Lipid droplet ,medicine ,Animals ,Obesity ,Intestinal Mucosa ,Molecular Biology ,Protein kinase B ,PI3K/AKT/mTOR pathway ,Cell Proliferation ,rapamycin ,TOR Serine-Threonine Kinases ,Cell Cycle ,RPTOR ,Epithelial Cells ,Lipid metabolism ,Cell Biology ,Lipid Metabolism ,Rats ,Cell biology ,Biochemistry ,Cyclooxygenase 2 ,Enzyme Induction ,mTOR ,Cytokines ,medicine.symptom ,Signal Transduction ,Developmental Biology - Abstract
Accumulating evidence suggests that obesity and enhanced inflammatory reactions are predisposing conditions for developing colon cancer. Obesity is associated with high levels of circulating leptin. Leptin is an adipocytokine that is secreted by adipose tissue and modulates immune response and inflammation. Lipid droplets (LD) are organelles involved in lipid metabolism and production of inflammatory mediators, and increased numbers of LD were observed in human colon cancer. Leptin induces the formation of LD in macrophages in a PI3K/mTOR pathway-dependent manner. Moreover, the mTOR is a serine/threonine kinase that plays a key role in cellular growth and is frequently altered in tumors. We therefore investigated the role of leptin in the modulation of mTOR pathway and regulation of lipid metabolism and inflammatory phenotype in intestinal epithelial cells (IEC-6 cells). We show that leptin promotes a dose- and time-dependent enhancement of LD formation. The biogenesis of LD was accompanied by enhanced CXCL1/CINC-1, CCL2/MCP-1 and TGF-β production and increased COX-2 expression in these cells. We demonstrated that leptin-induced increased phosphorylation of STAT3 and AKT and a dose and time-dependent mTORC activation with enhanced phosphorilation of the downstream protein P70S6K protein. Pre-treatment with rapamycin significantly inhibited leptin effects in LD formation, COX-2 and TGF-β production in IEC-6 cells. Moreover, leptin was able to stimulate the proliferation of epithelial cells on a mTOR-dependent manner. We conclude that leptin regulates lipid metabolism, cytokine production and proliferation of intestinal cells through a mechanism largely dependent on activation of the mTOR pathway, thus suggesting that leptin-induced mTOR activation may contribute to the obesity-related enhanced susceptibility to colon carcinoma.
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- 2015
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16. Analytical modeling of pulse-pileup distortion using the true pulse shape; applications to Fermi-GBM
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Narayana P. Bhat, Valerie Connaughton, Michael S. Briggs, and Vandiver Chaplin
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Nuclear and High Energy Physics ,Physics - Instrumentation and Detectors ,Photon ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Photon energy ,High Energy Physics - Experiment ,High Energy Physics - Experiment (hep-ex) ,Optics ,Distortion ,Nuclear Experiment (nucl-ex) ,Nuclear Experiment ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,Instrumentation ,Physics ,business.industry ,Detector ,Instrumentation and Detectors (physics.ins-det) ,Physics - Medical Physics ,Pulse shaping ,Photon counting ,Pulse (physics) ,Medical Physics (physics.med-ph) ,Astrophysics - Instrumentation and Methods for Astrophysics ,business ,Fermi Gamma-ray Space Telescope - Abstract
Pulse-pileup affects most photon counting systems and occurs when photon detections occur faster than the detector's registration and recovery time. At high input rates, shaped pulses interfere and the source spectrum, as well as intensity information, get distorted. For instruments using bipolar pulse shaping there are two aspects to consider: `peak' and `tail' pileup effects, which raise and lower the measured energy, respectively. Peak effects have been extensively modeled in the past. Tail effects have garnered less attention due to the increased complexity: bipolar tails mean the tail pulse-height measurement depends on events in more than one time interval. We leverage previous work to derive an accurate, semi-analytical prediction for peak and tail pileup, up to high orders. We use the true pulse shape from the detectors of the Fermi Gamma-ray Burst Monitor. The measured spectrum is calculated by writing exposure time as a state-space expansion of overlapping pileup states and is valid up to very high rates. This expansion models losses due to fixed and extendable deadtime by averaging overlap configurations. Additionally, the model correctly predicts energy-dependent losses due to tail subtraction (sub-threshold) effects. We discuss pileup losses in terms of the true rate of photon detections versus the recorded count rate., Comment: Journal article; 24 pages and 21 figures. Accepted to Nuclear Instruments and Methods in Physics Research, A
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- 2013
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17. Role of Catalyst on the Formation of Resorcinol-Furfural Based Carbon Aerogels and Its Physical Properties
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P.A. Abraham, Narayana P. R. Panicker, Nimai Chand Pramanik, Karumully S. Rejitha, and Kollanoor S. Jacob
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Materials science ,Supercritical drying ,Inorganic chemistry ,chemistry.chemical_element ,General Medicine ,Resorcinol ,Furfural ,Catalysis ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Polymerization ,Carbon ,Pyrolysis ,BET theory - Abstract
Carbon aerogels (CAG) were synthesized by the pyrolysis of resorcinol-furfural based organic aerogels, derived from sol-gel polymerization of resorcinol and furfural using different catalysts followed by supercritical drying of as-prepared gels. Different catalysts viz. hydrochloric acid (HA), acetic acid (AcH) and hexamethylenetetramine (HMTA) of different concentrations were used for this purpose in order to study the role of different catalysts and the effect of R/C ratio (reactant to catalyst molar ratio) on the formation of organic gel monolith and their physical properties were investigated. Aerogels were thoroughly characterized by using CHN, FTIR, TG-DSC, XRD and SEM. A considerable reduction of gelation time and the formation of relatively denser organic gel were observed in the case of HMTA, which indicated the dual role (catalyst & cross-linking agent) of HMTA during the polymerization/polycondensation of resorcinol and furfural. Carbon aerogels obtained by using different catalysts showed BET surface area, average pore size, total pore volumes in the range of 438 496 m2/g, 17.9 22.4 ? and 0.20 0.27 cm3/g, respectively. The SEM images and results revealed the presence of different morphologies of carbon aerogels, obtained by using different catalysts. The HMTA catalyzed samples were found to have highest surface area with particles in smaller in size and well interconnected 3D carbon network.
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- 2013
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18. APPLICATION OF POPULATION BALANCE MODEL TO COMBINED ATOMIZATION AND EVAPORATION PROCESSES IN DENSE SPRAYS
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Mahesh V. Panchagnula, Narayana P. Rayapati, and John Peddieson
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Materials science ,Continuum mechanics ,Population balance model ,General Chemical Engineering ,Evaporation ,Mechanics ,Computational fluid dynamics ,Atomization process ,Atomization ,Physical application ,Non-dimensional parameters ,Population balance modeling ,Sauter mean diameter (SMD) ,Drops ,Multiphase model ,Population balances ,Secondary atomization - Abstract
Droplet atomization and evaporation in dense sprays is relevant to several physical applications. We report a population balance model wherein these processes are handled simultaneously. The model is implemented in an Eulerian-Eulerian multiphase framework wherein the drop phase is itself modeled as multiple continua. The continuum model of the drop phase allows us to incorporate a stress field which naturally arises in a collision dominated dense spray. The utility of the model is first demonstrated on a uniform flow evaporator, wherein the mean droplet surface area is shown to exhibit a similarity scaling in terms of a nondimensional parameter that characterizes the competition between atomization and evaporation. The model is then generalized to a computational fluid dynamics (CFD) situation wherein a plug flow atomizer/evaporator is studied. The continuous variation of Sauter mean diameter (SMD) in the flow is presented wherein atomization processes cause the SMD to decrease while evaporation processes cause the SMD to locally increase. This is due to the preferential disappearance of the smaller size drops. Finally, the utility of the model for studying dense droplet ensemble atomization, evaporation, and combustion is discussed. � 2013 by Begell House, Inc.
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- 2013
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19. Temporal Decomposition Studies of GRB Lightcurves
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Narayana P. Bhat
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Scale (ratio) ,Astrophysics::High Energy Astrophysical Phenomena ,General Engineering ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Light curve ,Pulse (physics) ,Lorentz factor ,symbols.namesake ,Spectral evolution ,Space and Planetary Science ,Rise time ,symbols ,Astrophysics - High Energy Astrophysical Phenomena ,Gamma-ray burst - Abstract
Gamma-ray bursts (GRB) are extremely energetic events and produce highly diverse light curves. Light curves are believed to be resulting from internal shocks reflecting the activities of the GRB central engine. Hence their temporal studies can potentially lead to the understanding of the GRB central engine and its evolution. The light curve variability time scale is an interesting parameter which most models attribute to a physical origin e.g., central engine activity, clumpy circumburst medium, or relativistic turbulence. We develop a statistical method to estimate the GRB minimum variability time scale (MVT) for long and short GRBs detected by GBM. We find that the MVT of short bursts is distinctly shorter than that for long GRBs supprting the possibility of a more compact central engine of the former. We find that MVT estimated by this method is consistent with the shortest rise time of the fitted pulses. Hence we use the fitted pulse rise times to study the evolution of burst variability time scale. Variability time is in turn related to the minimum bulk Lorentz factor. Using this we relate the GRB spectral evolution to the evolution of the variability time scale. %Gamma-ray burst (GRB) light curves are believed to result from internal shocks reflecting the activities of the GRB central engine. %Hence their temporal deconvolution studies can potentially lead to the understanding of the evolution of the minimum variability %time scales which in turn is related to the minimum bulk Lorentz factor. We relate the GRB spectral evolution to the evolution of the %minimum variability time scale., Comment: 5 pages 6 figures. Presented at GRB2012 at Marbella, Spain
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- 2013
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20. Palladium-α-lipoic acid complex attenuates alloxan-induced hyperglycemia and enhances the declined blood antioxidant status in diabetic rats
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Kainoor K Janardhanan, T.A. Ajith, Chirakkal V. Krishnan, and Narayana P. Sudheesh
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chemistry.chemical_classification ,medicine.medical_specialty ,Reactive oxygen species ,Antioxidant ,biology ,business.industry ,Endocrinology, Diabetes and Metabolism ,medicine.medical_treatment ,Glutathione peroxidase ,Glutathione ,medicine.disease ,Superoxide dismutase ,chemistry.chemical_compound ,Lipoic acid ,Endocrinology ,chemistry ,Diabetes mellitus ,Alloxan ,Internal medicine ,medicine ,biology.protein ,business - Abstract
Background: Palladium α-lipoic acid (Pd-LA) complex has unique electronic and redox properties that appear to be the key to its physiological effectiveness. A proprietary liquid blend containing Pd-LA as the major component was demonstrated to be effective in improving the activities of mitochondrial enzymes in aged rats. Methods: The Pd-LA complex was evaluated for its hypoglycemic effect against the alloxan-induced diabetic model, as well as in the oral glucose tolerance test in rats. The in vitro free radical scavenging activity of Pd-LA was also determined. Results: Administration of Pd-LA (0.5 mL/kg; equivalent to 3.8 mg complexed α-lipoic acid/kg, p.o.) daily for 5 days to alloxan-induced diabetic animals significantly reduced the blood glucose level (P
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- 2011
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21. Ganoderma lucidum protects liver mitochondrial oxidative stress and improves the activity of electron transport chain in carbon tetrachloride intoxicated rats
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John Mathew, T.A. Ajith, Narayana P. Sudheesh, Kainoor K Janardhanan, and Nalin Nima
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chemistry.chemical_classification ,Reactive oxygen species ,Hepatology ,Respiratory chain complex ,CCL4 ,Mitochondrion ,Pharmacology ,medicine.disease_cause ,chemistry.chemical_compound ,Infectious Diseases ,chemistry ,Biochemistry ,Apoptosis ,Carbon tetrachloride ,medicine ,Alkaline phosphatase ,Oxidative stress - Abstract
Aim: Liver injuries induced by carbon tetrachloride (CCl4) cause mitochondrial stress and disruption of membrane potential resulting in apoptosis. In this study, we evaluated the effects of Ganoderma lucidum against CCl4 (1:5 v/v in paraffin oil, 1.5 mL/kg, i.p) induced deterioration of the activities of mitochondrial enzymes and electron transport chain complexes in the liver mitochondria. Methods: Ganoderma lucidum (100 and 250 mg/kg) was administered once daily for 15 days prior to the CCl4 administration. α-Tocopherol (100 mg/kg, p.o.) was used as the standard. Hepatic damage was assessed by determining the activities of serum transaminases (SGPT and SGOT) and alkaline phosphatase (ALP), 24 h after CCl4 injection. The activities of mitochondrial dehydrogenases as well as mitochondrial complexes I, II, III, and IV were evaluated. Results: Activities of SGPT, SGOT and ALP were significantly (P
- Published
- 2011
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22. Randomized Trial of Oral Teriflunomide for Relapsing Multiple Sclerosis
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Paul, O'Connor, Wolinsky, Jerry S., Christian, Confavreux, Giancarlo, Comi, Ludwig, Kappos, Olsson, Tomas P., Hadj, Benzerdjeb, Philippe, Truffinet, Lin, Wang, Aaron, Miller, Temso Trial Group Reingold, Freedman Ms S., Cutter, G., Antel, J., Barkhof, F., Maddrey, W., Ravnborg, M., Schenker, S., O'Connor, P., Wolinsky, J. S., Confavreux, C., Comi, G., Kappos, L., Olsson, T. P., Miller, A., Freedman, Mark S., Narayana, P. A., Nelson, F., Vainrub, I., Datta, S., He, R., Gates, B., Ton, K., Wamil, B., Truffinet, P., Igau, B., Nicolas, V., Notelet, L., Payrard, S., Wijnand, P., Devore, S., H. H., Li, Osho, T., Wang, L., Wei, L., Dukovic, D., Ling, Y., Benzerdjeb, H., Mednikova, Z., Trabelsi, N., Musset, M., Merrill, D., Turpault, S., Williams, B., Nortmeyer, H., Kirst, E., Witthaus, E., Chen, S., Maida, E., Auff, E., Fazekas, F., Berger, T., Bhan, V., Bouchard, J. P., Duquette, P., Freedman, M., Grand'Maison, F., Kremenchutzky, M., Bourque, C., Marrie, R. A., Melanson, M., Patry, D., Oger, J., Stefanelli, M., Jacques, F., Venegas, P., Miranda, M., Barrientos, N., Tenhamm, E., Gloger, S., Rohde, G., Mares, J., Frederiksen, J., Stenager, E., Haldre, S., Gross Paju, K., Elovaara, I., Sumelahti, M. L., Erälinna, J. P., Farkkila, M., Harno, H., Reunanen, M., Jolma, T., Camu, W., Clavelou, P., Magy, L., Debouverie, M., Edan, G., Lebrun Frenay, C., Moreau, T., Pelletier, J., Roullet, E., Alamowitch, S., Clanet, M., Hautecoeur, P., Damier, P., Rumbach, L., Chan, A., Schimrigk, S., Haas, J., Lensch, E., Diener, H., Limmroth, V., Anders, D., Berghoff, M., Oschmann, P., Stangel, M., Frese, A., Kiefer, R., Marziniak, M., Zettl, U., Stark, E., Jendroska, K., Reifschneider, G., Amato, M. P., Cosi, V., Gallo, P., Gasperini, Claudio, Ghezzi, A., Trojano, M., Pozzilli, Carlo, Montanari, E., Zwanikken, C. P., Jongen, P. J., Van Munster, E. T., Hupperts, R. M., Anten, B., Sanders, E. A., Celius, E., Hovdal, H., Krogseth, S. B., Kozubski, W., Kwiecinski, H., Czlonkowska, A., Stelmasiak, Z., Selmaj, K., Hasiec, T., Fryze, W., Drozdowski, W., Kochanowicz, J., Cunha, L., De Sa, J., Sena, A. H., Odinak, M., Skoromets, A., Gusev, E., Boiko, A., Lashch, N., Stolyarov, I., Belova, A., Malkova, N., Doronin, B., Yakupov, E., Brundin, L., Hillert, J., Karabudak, R., Irkec, C., Idiman, E., Turan, O., Efendi, H., Gedizlioglu, M., Buchakchyyska, N., Goloborodko, A., Ipatov, A., Kobets, S., Lebedynets, V., Moskovko, S., Sanotskyy, Y., Smolanka, V., Yavorskaya, V., Bates, D., Evangelou, N., Hawkins, C., Mclean, B., O'Riordan, J., Price, S., Turner, B., Barnes, D., Zajicek, J., Honeycutt, W., Khan, O., Spikol, L., Stevens, J., Klinische Neurowetenschappen, and RS: MHeNs School for Mental Health and Neuroscience
- Subjects
medicine.medical_specialty ,biology ,Nausea ,business.industry ,Incidence (epidemiology) ,Placebo-controlled study ,General Medicine ,Placebo ,Gastroenterology ,Surgery ,chemistry.chemical_compound ,Alanine transaminase ,chemistry ,Internal medicine ,Relative risk ,Teriflunomide ,medicine ,biology.protein ,medicine.symptom ,business ,Leflunomide ,medicine.drug - Abstract
Teriflunomide reduced the annualized relapse rate (0.54 for placebo vs. 0.37 for teri flunomide at either 7 or 14 mg), with relative risk reductions of 31.2% and 31.5%, respectively (P
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- 2011
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23. Analytical solutions for particulate pipe flows with fragmentation, evaporation, and diffusion
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Srimani Bhamidipati, Mahesh V. Panchagnula, Narayana P. Rayapati, and John Peddieson
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Materials science ,Evaporation ,education ,Rotational symmetry ,Thermodynamics ,Aerosol flow ,Analytical solutions ,Thermal diffusivity ,Spray ,Diffusion ,Physics::Fluid Dynamics ,Fragmentation (mass spectrometry) ,Fragmentation ,General Materials Science ,Atmospheric movements ,Physics::Atmospheric and Oceanic Physics ,Civil and Structural Engineering ,Circular pipe ,Pipe ,Pipe flow ,Multiphase transport ,Size dependent ,Mechanical Engineering ,Mechanics ,Particulates ,Condensed Matter Physics ,Atomization ,Aerosol ,Diffusivities ,Mechanics of Materials ,Axisymmetric ,Fragmentation process ,Population balances - Abstract
We report an analytical solution to a problem of steady axisymmetric fragmentation and evaporation in a circular pipe using a multiphase transport approach including diffusion. We show specific examples of the applicability of this solution to the problem of an aerosol flow in a pipe undergoing evaporation and fragmentation involving size dependent diffusivity. The early part of the subsequent discussion will be carried out in the context of fragmentation only. A methodology to treat evaporation as an equivalent fragmentation process will then be utilized. � 2010 Elsevier Ltd. All rights reserved.
- Published
- 2010
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24. F 1s spectroscopy and ionic fragmentation of trifluoropropyne
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Narayana P. Appathurai, Liu Yang, Samuel O. Odoh, Yongheng Fan, and John J. Neville
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Chemistry ,Organic Chemistry ,Ionic bonding ,General Chemistry ,Photoionization ,Catalysis ,Ion ,Fragmentation (mass spectrometry) ,Excited state ,Ionization ,Physics::Atomic and Molecular Clusters ,Molecular orbital ,Atomic physics ,Spectroscopy - Abstract
The F 1s excitation spectroscopy and ionic fragmentation of 3,3,3-trifluoro-1-propyne have been studied using synchrotron radiation and ion time-of-flight mass spectrometry. The total ion yield spectrum and photoionization branching ratios in the vicinity of the F 1s ionization threshold are reported. Core excited state calculations using the static exchange approximation are used to aid in the interpretation of the experimental results. The F 1s excitation spectrum consists of a number of broad overlapping bands below threshold, attributed to excitations to mixed σ*(C-F)/π*(C-C) molecular orbitals and unresolved Rydberg states, and a continuum shape resonance 12.5 eV above threshold. Ionic fragmentation following F 1s excitation or ionization results overwhelmingly in singly charged ionic fragments, primarily via cleavage of bonds to the fluorinated carbon atom adjacent to the core-excited atom.Key words: F 1s excitation, XANES, photoelectron-photoion coincidence, ionic fragmentation, static exchange approximation.
- Published
- 2008
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25. Which $E_{\rm peak}$? - The Characteristic Energy of Gamma-Ray Burst Spectra
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Narayana P. Bhat, Adam Goldstein, M. Stanbro, Robert D. Preece, Dylan Blalock, and Jon Hakkila
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Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Spectral line ,Space and Planetary Science ,0103 physical sciences ,Astrophysics - High Energy Astrophysical Phenomena ,Gamma-ray burst ,010303 astronomy & astrophysics ,Characteristic energy - Abstract
A characteristic energy of individual gamma-ray burst (GRB) spectra can in most cases be determined from the peak energy of the energy density spectra ($\nu{\cal F}_{\nu}$), called '$E_{\rm peak}$'. Distributions of $E_{\rm peak}$ have been compiled for time-resolved spectra from bright GRBs, and also time-averaged spectra and peak flux spectra for nearly every burst observed by CGRO-BATSE and Fermi-GBM. Even when determined by an instrument with a broad energy band, such as GBM (8 keV to 40 MeV), the distributions themselves peak at around 240 keV in the observer's frame, with a spread of roughly a decade in energy. $E_{\rm peak}$ can have considerable evolution (sometimes greater than one decade) within any given burst, as amply demonstrated by single pulses in GRB110721A and GRB130427A. Meanwhile, several luminosity or energy relations have been proposed to correlate with either the time-integrated or peak flux $E_{\rm peak}$. Thus, when discussing correlations with $E_{\rm peak}$, the question arises, "Which $E_{\rm peak}$?". A single burst may be characterized by any one of a number of values for $E_{\rm peak}$ that are associated with it. Using a single pulse simulation model with spectral evolution as a proxy for the type of spectral evolution observed in many bursts, we investigate how the time-averaged $E_{\rm peak}$ emerges from the spectral evolution within a single pulse, how this average naturally correlates with the peak flux derived $E_{\rm peak}$ in a burst and how the distribution in $E_{\rm peak}$ values from many bursts derives its surprisingly narrow width., Comment: 49 pages, 15 figures, 3 tables; accepted for publication in The Astrophysical Journal (version 2: prettified 2-column format; content unchanged)
- Published
- 2016
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26. Measurements of Gamma-Ray Bursts with GLAST
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A. von Kienlin, Narayana P. Bhat, Robert B. Wilson, Valerie Connaughton, Helmut Steinle, G. G. Lichti, Michael S. Briggs, Chryssa Kouveliotou, Charles A. Meegan, W. S. Paciesas, R. M. Kippen, Roland Diehl, Gerald J. Fishman, Jochen Greiner, and Robert D. Preece
- Subjects
Physics ,Spacecraft ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,law.invention ,Telescope ,Spitzer Space Telescope ,Space and Planetary Science ,law ,Satellite ,Detection rate ,Gamma-ray burst ,business ,Fermi Gamma-ray Space Telescope - Abstract
The next large NASA mission in the field of γ-ray astronomy is the Gamma-Ray Large Area Space Telescope (GLAST), which is scheduled for a launch end of 2007. This satellite consists of the main instrument LAT (Large-Area Telescope) which is sensitive in the energy range between 10 MeV and 300$>>300 GeV, and a secondary instrument, the Gamma-Ray Burst Monitor (GBM), sensitive from 10 keV to 30 MeV. This omnidirectional monitor is an important instrument for γ-ray burst (GRB) science with GLAST, as it provides the link between the majority of the γ-ray busts emitting at lower energies and the high-energy events of γ-ray bursts and other transients. It will also serve as a trigger to increase the detection rate of γ-ray burst with the LAT. The GBM will provide real-time burst locations over a wide field-of-view (FoV) with sufficient accuracy to repoint the whole GLAST spacecraft. Time-resolved spectra of bursts recorded with LAT and the burst monitor will allow the investigation of the relation between the keV and the MeV–GeV emission from GRBs over seven decades in energy and will provide new insights into the physics of GRBs in general. In addition, the excellent localization of GRBs by the LAT will stimulate follow-up observations at other wavelengths which may yield clues about the nature of the burst sources.
- Published
- 2006
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27. Mining Positive and Negative Association Rules Using CoherentApproach
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Duggirala, Rakesh and Narayana, P.
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FOS: Computer and information sciences ,97Pxx ,Computer Science - Databases ,Databases (cs.DB) - Abstract
In the data mining field, association rules are discovered having domain knowledge specified as a minimum support threshold. The accuracy in setting up this threshold directly influences the number and the quality of association rules discovered. Typically, before association rules are mined, a user needs to determine a support threshold in order to obtain only the frequent item sets. Having users to determine a support threshold attracts a number of issues. We propose an association rule mining framework that does not require a per-set support threshold. Often, the number of association rules, even though large in number, misses some interesting rules and the rules quality necessitates further analysis. As a result, decision making using these rules could lead to risky actions., IJCTT-2013
- Published
- 2013
28. Palladium-α-lipoic acid complex attenuates alloxan-induced hyperglycemia and enhances the declined blood antioxidant status in diabetic rats
- Author
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Narayana P, Sudheesh, Thekuttuparambil A, Ajith, Kainoor K, Janardhanan, and Chirakkal V, Krishnan
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Blood Glucose ,Male ,Glutathione Peroxidase ,Thioctic Acid ,Superoxide Dismutase ,Rats, Inbred Strains ,Catalase ,Glutathione ,Antioxidants ,Diabetes Mellitus, Experimental ,Rats ,Alloxan ,Animals ,Palladium - Abstract
Palladium α-lipoic acid (Pd-LA) complex has unique electronic and redox properties that appear to be the key to its physiological effectiveness. A proprietary liquid blend containing Pd-LA as the major component was demonstrated to be effective in improving the activities of mitochondrial enzymes in aged rats.The Pd-LA complex was evaluated for its hypoglycemic effect against the alloxan-induced diabetic model, as well as in the oral glucose tolerance test in rats. The in vitro free radical scavenging activity of Pd-LA was also determined.Administration of Pd-LA (0.5 mL/kg; equivalent to 3.8 mg complexed α-lipoic acid/kg, p.o.) daily for 5 days to alloxan-induced diabetic animals significantly reduced the blood glucose level (P0.05). The blood antioxidant status in the diabetic animals was significantly improved by the treatment of Pd-LA (P0.05). Similarly, Pd-LA showed significant in vitro antioxidant activity in a concentration-dependent manner.Results of the study conclude that the Pd-LA complex is effective in lowering the blood glucose level and enhancing the declined antioxidant status in diabetic animals. Significant finding(s) of the study include: (i) Pd-LA significantly increased the tolerance of glucose and was also effective in ameliorating hyperglycemia induced by alloxan; (ii) Pd-LA significantly enhanced the activities of blood superoxide dismutase, catalase, glutathione peroxidase and level of glutathione in diabetic animals; and (iii) Pd-LA showed significant in vitro antioxidant activity. This study adds: The therapeutic efficiency of Pd-LA is demonstrated against declined antioxidant status as well as hyperglycemia associated with diabetes.
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- 2011
29. Eulerian multiphase population balance model of atomizing, swirling flows
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Mahesh V. Panchagnula, John Peddieson, Steven Smith, John Short, and Narayana P. Rayapati
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Materials science ,Computer simulation ,Meteorology ,Population balance model ,Drop (liquid) ,lcsh:Mechanical engineering and machinery ,lcsh:Motor vehicles. Aeronautics. Astronautics ,Multiphase flow ,General Physics and Astronomy ,Energy Engineering and Power Technology ,Experimental data ,Eulerian path ,Mechanics ,Phase doppler ,Physics::Fluid Dynamics ,symbols.namesake ,Automotive Engineering ,symbols ,Airblast atomizer ,Drop size ,Drop size distribution ,Eulerian ,Experimental measurements ,Model prediction ,Multi-phase flow models ,Phase Doppler particle analyzer ,Population balance models ,Quantitative agreement ,Relative contribution ,Secondary atomization ,Spray drops ,Atomization ,Drops ,Population statistics ,Size determination ,Size distribution ,Swirling flow ,Two phase flow ,lcsh:TJ1-1570 ,Particle size ,lcsh:TL1-4050 - Abstract
An Eulerian/Eulerian multiphase flow model coupled with a population balance model is used as the basis for numerical simulation of atomization in swirling flows. The objective of this exercise is to develop a methodology capable of predicting the local point-wise drop size distribution in a spray, such as would be measured by the Phase Doppler Particle Analyzer (PDA). Model predictions are compared to experimental measurements of particle size distributions in an air-blast atomizer spray to demonstrate good qualitative and quantitative agreement. It is observed that the dependence of velocity on drop size inherent in a multiphase description of the drop cloud appears necessary to capture some features of the experimental data. Using this model, we demonstrate the relative contributions of secondary atomization and transport to the variation observed in the downstream spray drop size distribution.
- Published
- 2011
30. Analytical solutions for convective fragmentation
- Author
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John Peddieson, Srimani Bhamidipati, Mahesh V. Panchagnula, and Narayana P. Rayapati
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Convection ,Rotational symmetry ,Analytical solutions ,Population balance models ,Pipe flow ,Physics::Fluid Dynamics ,Gas carriers ,Fragmentation (mass spectrometry) ,Fragmentation ,Liquid drop ,General Materials Science ,Nuclear Experiment ,Civil and Structural Engineering ,Physics ,Axisymmetric jet ,Turbulence ,Mechanical Engineering ,Multiphase flow ,Liquids ,Mechanics ,Condensed Matter Physics ,Grinding ,Atomization ,Classical mechanics ,Mechanics of Materials ,Axisymmetric ,Flow problems ,Drops ,Non-homogeneous - Abstract
Fragmentation of liquid drops occurs in many processes involving convection of dispersions of liquid drops in liquid or gas carrier phases. Such fragmentation is often spatially nonhomogeneous (due, for example, to turbulence induced fragmentation). Recent work has studied a class of pipe flow problems involving convective fragmentation. In the present paper we generalize a version of the problem discussed above to allow for unsteady two-dimensional axisymmetric convective fragmentation and report a corresponding analytical solution. We connect our analytical solution to the grinding solution of Reid (1965) and demonstrate its applicability by applying it to a problem of a pulsating convective fragmentation in an unsteady axisymmetric jet, with the fragmentation characteristics being spatially dependent. � 2010 Elsevier Ltd. All rights reserved.
- Published
- 2010
31. Free radical scavenging and mitochondrial antioxidant activities of Reishi- Ganoderma lucidum (Curt: Fr) P. Karst and Arogyapacha-Trichopus zeylanicus Gaertn extracts
- Author
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Elizabeth Cherian, Kainoor K Janardhanan, George Patani, and Narayana P. Sudheesh
- Subjects
Antioxidant ,Physiology ,DPPH ,medicine.medical_treatment ,Mitochondria, Liver ,Antioxidants ,Lipid peroxidation ,Mice ,chemistry.chemical_compound ,Drug Discovery ,medicine ,Animals ,Dioscoreaceae ,Pharmacology ,ABTS ,Dose-Response Relationship, Drug ,Traditional medicine ,biology ,Super oxide dismutase ,Plant Extracts ,Superoxide Dismutase ,Ganoderma ,Free Radical Scavengers ,General Medicine ,Glutathione ,Catalase ,Malondialdehyde ,biology.organism_classification ,chemistry ,Trichopus zeylanicus ,Lipid Peroxidation - Abstract
Endogenous damage to mitochondrial DNA by free radicals is believed to be a major contributory factor to aging. The current study examined the effects of the extracts of two important anti-fatigue and rejuvenating medicinal herbs Ganoderma lucidum and Trichopus zeylanicus for their free-radical scavenging property and for their effects on liver mitochondrial antioxidant activity in aged mice. Both extracts were administrated orally to aged BALB/c mice at doses of 50 and 250 mg/kg body weight for 15 days. Super oxide dismutase (SOD) and catalase (CAT) activity and levels of reduced glutathione (GSH) and lipid peroxidation as equivalents of malondialdehyde (MDA) formed were determined. Groups of young mice and aged mice (more than 15 months old) were taken as controls. Both G. lucidum and T. zeylanicus extracts increased antioxidant status in liver mitochondria of aged mice compared with the aged control. Higher levels of GSH, increased activity of SOD and CAT, and decreased level of MDA in both treated groups compared with the controls were evident. Both extracts possessed significant 2,2-diphenyl-1-picrylhydrazil (DPPH), 2, 2'-azinobis (3-ethylbenzothiazolin-6-sulphonic acid) (ABTS) radical scavenging activities and ferric reducing antioxidant power (FRAP). The DPPH, ABTS, and FRAP activities were higher in G. lucidum extract than in T. zeylanicus. G. lucidum extract also showed superoxide and hydroxyl radical scavenging activities. T. zeylanicus had significantly higher lipid peroxidation inhibiting activity than G. lucidum. Thus, we conclude that the antioxidative effect of the G. lucidum extract was higher than that of T. zeylanicus. Our findings suggest a potential therapeutic efficacy of G. lucidum extract to protect against aging and to a certain extent against age-related degenerative diseases.
- Published
- 2009
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32. Free Convective Transport In Porous Media With Emphasis On Second Order Effects
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Narayana, P. Anantha Lakshmi
- Subjects
Porous Media ,Free Convective Transport - Published
- 2007
33. Modified lateral thoracodorsal flap: a way out of a difficult problem
- Author
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Fabio N. Silva, Carlos L. Collado, André R. Monte, Ronaldo Pontes, Gisela Hobson Pontes, and Narayana P. Serpa
- Subjects
medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,Mammaplasty ,Carcinoma ,Breast Neoplasms ,Silicone implant ,Middle Aged ,medicine.disease ,Surgical Flaps ,Surgery ,Plastic surgery ,Breast cancer ,Otorhinolaryngology ,medicine ,Humans ,Female ,Breast reconstruction ,business ,Mastectomy ,Reduction (orthopedic surgery) - Abstract
Breast deformities, often attributable to surgical mutilations as a result of mammary carcinoma treatment, still are a challenge to plastic surgeons. Interesting alternatives for the frequently used musculocutaneous flaps are local flaps such as the lateral thoracodorsal flap developed by Holmstrom in 1986. This flap is simple to raise and involves no sacrifice of important muscular structures. This report aims to demonstrate the use of the modified lateral thoracodorsal flap in an immediate mammary reconstruction for a patient who refused any other scar. A case report describes a patient presenting with breast cancer after reduction mammaplasty who was treated with a skin-sparing mastectomy and immediate reconstruction. Satisfactory defect correction was accomplished with adequate silicone implant covering and a natural ptotic breast shape. The versatility of this flap and its simple execution make it an important option for diverse breast reconstruction situations. The lateral thoracodorsal flap provides aesthetic results similar to those with other reconstruction methods, but without major complexity. The authors believe that it could be an interesting tool for the treatment of a breast anomaly.
- Published
- 2006
34. Energy Water Nexus - Community institution models: a co-management solution?
- Author
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Sinha, S., Narayana, P., Ahsan, U.A., and Scott, C.
- Published
- 2004
35. The GLAST Burst Monitor
- Author
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Michael S. Briggs, Charles A. Meegan, Roland Diehl, Narayana P. Bhat, G. G. Lichti, Robert D. Preece, Valerie Connaughton, Andrew S. Hoover, William S. Paciesas, Andreas von Kienlin, Chryssa Kouveliotou, Volker Schoenfelder, Helmut Steinle, R. Marc Kippen, Gerald J. Fishman, Jochen Greiner, and Robert B. Wilson
- Subjects
Physics ,Spacecraft ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astrophysics ,law.invention ,Telescope ,law ,Detection rate ,business - Abstract
The next large NASA mission in the field of gamma-ray astronomy, GLAST, is scheduled for launch in 2007. Aside from the main instrument LAT (Large-Area Telescope), a gamma-ray telescope for the energy range between 20 MeV and > 100 GeV, a secondary instrument, the GLAST burst monitor (GBM), is foreseen. With this monitor one of the key scientific objectives of the mission, the determination of the high-energy behaviour of gamma-ray bursts and transients can be ensured. Its task is to increase the detection rate of gamma-ray bursts for the LAT and to extend the energy range to lower energies (from ~10 keV to \~30 MeV). It will provide real-time burst locations over a wide FoV with sufficient accuracy to allow repointing the GLAST spacecraft. Time-resolved spectra of many bursts recorded with LAT and the burst monitor will allow the investigation of the relation between the keV and the MeV-GeV emission from GRBs over unprecedented seven decades of energy. This will help to advance our understanding of the mechanisms by which gamma-rays are generated in gamma-ray bursts., 8 pages, 7 figures, to appear in SPIE conference proceedings vol 5488, "UV-Gamma Ray Space Telescope Systems," Glasgow UK, 21-24 June 2004
- Published
- 2004
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36. Finite element simulation of transient laminar flow past a circular cylinder and two cylinders in tandem
- Author
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B.S.V. Patnaik, Narayana, P. A. A., and Seetharamu, K. N.
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Finite element method ,Wakes ,Unsteady eddy patterns ,Velocity ,Richardson number ,Computer simulation ,Computational fluid dynamics ,Vortex shedding ,Laminar flow ,Drag ,Flow patterns ,Reynolds number ,Buoyancy ,Transient laminar flow ,Cylinders (shapes) ,Karman vortex ,Average drag coefficient ,Numerical particle release ,Velocity correction method ,Streakline patterns ,Flow visualization ,Root mean square lift coefficients ,Strouhal number - Abstract
Flow past an isolated circular cylinder and two cylinders in tandem is numerically simulated, under the influence of buoyancy aiding and opposing the flow. A modified velocity correction method is employed, which has second order accuracy in both space and time. The influence of buoyancy on the temporal fluid flow patterns is investigated, with respect to streamlines, isotherms and streaklines. Comparisons are made with respect to mean center line velocities, drag coefficients, Strouhal number and streakline patterns. Degeneration of naturally occurring Karman vortex street into a twin eddy pattern is noticed in the Reynolds number (Re) range of 41-200, under buoyancy aided convection. On the contrary, buoyancy opposed convection could trigger vortex shedding even at a low Re range of 20-40, where only twin eddies are found in the natural wake. Temporal evolution of unsteady eddy patterns is visualized by means of numerical particle release (NPR). Zones of vortex shedding and twin vortices are demarcated on a plot of Richardson number against Strouhal number. Root mean square (RMS) lift coefficients (CL,RMS) and average drag coefficient are obtained as a function of Richardson number (Ri).
- Published
- 2000
37. Comparative study of convolution, superposition, and fast superposition algorithms in conventional radiotherapy, three-dimensional conformal radiotherapy, and intensity modulated radiotherapy techniques for various sites, done on CMS XIO planning system
- Author
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KR Muralidhar, Narayana P Murthy, Alluri Krishnam Raju, and Nvnm Sresty
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Biophysics ,conformity index ,Convolution ,Algorithm ,Conformity index ,Superposition principle ,Conventional radiotherapy ,otorhinolaryngologic diseases ,Dosimetry ,Original Article ,Radiology, Nuclear Medicine and imaging ,Intensity modulated radiotherapy ,treatment planning system ,Three dimensional conformal radiotherapy ,homogenity index ,Radiation treatment planning ,Mathematics - Abstract
The aim of this study is to compare the dosimetry results that are obtained by using Convolution, Superposition and Fast Superposition algorithms in Conventional Radiotherapy, Three-Dimensional Conformal Radiotherapy (3D-CRT), and Intensity Modulated Radiotherapy (IMRT) for different sites, and to study the suitability of algorithms with respect to site and technique. For each of the Conventional, 3D-CRT, and IMRT techniques, four different sites, namely, Lung, Esophagus, Prostate, and Hypopharynx were analyzed. Treatment plans were created using 6MV Photon beam quality using the CMS XiO (Computerized Medical System, St.Louis, MO) treatment planning system. The maximum percentage of variation recorded between algorithms was 3.7% in case of Ca.Lung, for the IMRT Technique. Statistical analysis was performed by comparing the mean relative difference, Conformity Index, and Homogeneity Index for target structures. The fast superposition algorithm showed excellent results for lung and esophagus cases for all techniques. For the prostate, the superposition algorithm showed better results in all techniques. In the conventional case of the hypopharynx, the convolution algorithm was good. In case of Ca. Lung, Ca Prostate, Ca Esophagus, and Ca Hypopharynx, OARs got more doses with the superposition algorithm; this progressively decreased for fast superposition and convolution algorithms, respectively. According to this study the dosimetric results using different algorithms led to significant variation and therefore care had to be taken while evaluating treatment plans. The choice of a dose calculation algorithm may in certain cases even influence clinical results.
- Published
- 2009
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38. BATSE observations of the very intense gamma-ray burst GRB 930131
- Author
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Robert D. Preece, Michael S. Briggs, W. S. Paciesas, Geoffrey N. Pendleton, Charles A. Meegan, Jay P. Norris, Chryssa Kouveliotou, Bonnard J. Teegarden, Gerald J. Fishman, John M. Horack, David L. Band, Narayana P. Bhat, Jim Matteson, and D. M. Palmer
- Subjects
Physics ,Range (particle radiation) ,Spectral index ,Photon ,Astrophysics::High Energy Astrophysical Phenomena ,Flux ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Power law ,Space and Planetary Science ,Temporal resolution ,Energetic Gamma Ray Experiment Telescope ,Gamma-ray burst - Abstract
Burst and Transient Source Experiment (BATSE) observed its most intense gamma-ray burst on 1993 January 31. The event reached count rates is approximately greater than 2 x 10(exp 6) counts/s with most of the flux emitted in an extremely short (is approximately less than 0.1 s) interval followed by a long tail, lasting about 50 s. Most of this initial pulse was recorded by our instrument with unique, very high temporal resolution (1 ms). We were thus able to show large changes in spectral hardness on 2 ms timescales throughout this initial complex. Photons as low as 25 keV and extending up to greater than 4 MeV in energy were recorded by BATSE during this first interval. The burst spectrum is best fitted by a broken power law with a break energy of 170 +/- 27 keV. The low-energy spectral index is -1.30 +/- 0.05, while a softer spectral index of -1.9 fits the spectrum between 170 keV and 2 MeV. Our data provide the only low-energy spectrum for this event; the combination of our spectrum with the one reported for GRB 930131 by the Energetic Gamma Ray Experiment Telescope (EGRET) group extends the total energy spectrum of a GRB for the first time over five decades, up to the GeV range.
- Published
- 1994
- Full Text
- View/download PDF
39. Identification of two classes of gamma-ray bursts
- Author
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Michael S. Briggs, Thomas M. Koshut, Narayana P. Bhat, William S. Paciesas, G. N. Pendleton, Chryssa Kouveliotou, Gerald J. Fishman, and Charles A. Meegan
- Subjects
Physics ,Swift Gamma-Ray Burst Mission ,Astrophysics::High Energy Astrophysical Phenomena ,GRB 050509B ,media_common.quotation_subject ,GRB 130427A ,Astronomy ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,GRB 050709 ,Bimodality ,Identification (information) ,Space and Planetary Science ,Sky ,Gamma-ray burst ,media_common - Abstract
We have studied the duration distribution of the gamma-ray bursts of the first BATSE catalog. We find a bimodality in the distribution, which separates GRBs into two classes: short events (less than 2 s) and longer ones (more than 2 s). Both sets are distributed isotropically and inhomogeneously in the sky. We find that their durations are anticorrelated with their spectral hardness ratios: short GRBs are predominantly harder, and longer ones tend to be softer. Our results provide a first GRB classification scheme based on a combination of the GRB temporal and spectral properties.
- Published
- 1993
- Full Text
- View/download PDF
40. Natural convection through an annular vertical cylindrical porous medium
- Author
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Badruddin, I. A., Zainal Alimuddin Zainal Alauddin, Aswatha Narayana, P. A., and Seetharamu, K. N.
41. Electrochemical determination of 3,5-dinitrobenzoic acid in the presence and absence of CTAB at multi-walled carbon nanotubes modified glassy carbon electrode: A voltammetric study
- Author
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Venkataprasad, G., Reddy, T. M., Shaikshavali Petnikota, Gopal, P., and Narayana, P. V.
42. Optimal torque control strategy for a variable speed wind turbine
- Author
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Lakshmi Narayana, P., Srinivasa Yadlapati, and Pidikiti, T.
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