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Search Results: 1 - 10 of 1507 matches for " Jayaraman Srinivasan "
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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.
Quantitative Characterization of Glycan-Receptor Binding of H9N2 Influenza A Virus Hemagglutinin
Karunya Srinivasan, Rahul Raman, Akila Jayaraman, Karthik Viswanathan, Ram Sasisekharan
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0059550
Abstract: Avian influenza subtypes such as H5, H7 and H9 are yet to adapt to the human host so as to establish airborne transmission between humans. However, lab-generated reassorted viruses possessing hemagglutinin (HA) and neuraminidase (NA) genes from an avian H9 isolate and other genes from a human-adapted (H3 or H1) subtype acquired two amino acid changes in HA and a single amino acid change in NA that confer respiratory droplet transmission in ferrets. We previously demonstrated for human-adapted H1, H2 and H3 subtypes that quantitative binding affinity of their HA to α2→6 sialylated glycan receptors correlates with respiratory droplet transmissibility of the virus in ferrets. Such a relationship remains to be established for H9 HA. In this study, we performed a quantitative biochemical characterization of glycan receptor binding properties of wild-type and mutant forms of representative H9 HAs that were previously used in context of reassorted viruses in ferret transmission studies. We demonstrate here that distinct molecular interactions in the glycan receptor-binding site of different H9 HAs affect the glycan-binding specificity and affinity. Further we show that α2→6 glycan receptor-binding affinity of a mutant H9 HA carrying Thr-189→Ala amino acid change correlates with the respiratory droplet transmission in ferrets conferred by this change. Our findings contribute to a framework for monitoring the evolution of H9 HA by understanding effects of molecular changes in HA on glycan receptor-binding properties.
Quantitative Description of Glycan-Receptor Binding of Influenza A Virus H7 Hemagglutinin
Karunya Srinivasan, Rahul Raman, Akila Jayaraman, Karthik Viswanathan, Ram Sasisekharan
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0049597
Abstract: In the context of recently emerged novel influenza strains through reassortment, avian influenza subtypes such as H5N1, H7N7, H7N2, H7N3 and H9N2 pose a constant threat in terms of their adaptation to the human host. Among these subtypes, it was recently demonstrated that mutations in H5 and H9 hemagglutinin (HA) in the context of lab-generated reassorted viruses conferred aerosol transmissibility in ferrets (a property shared by human adapted viruses). We previously demonstrated that the quantitative binding affinity of HA to α2→6 sialylated glycans (human receptors) is one of the important factors governing human adaptation of HA. Although the H7 subtype has infected humans causing varied clinical outcomes from mild conjunctivitis to severe respiratory illnesses, it is not clear where the HA of these subtypes stand in regard to human adaptation since its binding affinity to glycan receptors has not yet been quantified. In this study, we have quantitatively characterized the glycan receptor-binding specificity of HAs from representative strains of Eurasian (H7N7) and North American (H7N2) lineages that have caused human infection. Furthermore, we have demonstrated for the first time that two specific mutations; Gln226→Leu and Gly228→Ser in glycan receptor-binding site of H7 HA substantially increase its binding affinity to human receptor. Our findings contribute to a framework for monitoring the evolution of H7 HA to be able to adapt to human host.
Oil Price and Economic Growth in Small Pacific Island Countries  [PDF]
T. K. Jayaraman, Evan Lau
Modern Economy (ME) , 2011, DOI: 10.4236/me.2011.22020
Abstract: Among the 14 Pacific Island countries (PICs), only Papua New Guinea has fossil fuel resources. None of the remaining 13 PICs has any energy sources. Consequently, all the 13 PICs are totally dependent on oil imports for their economic activities. Recent surges and volatility in oil prices have had serious economic re-percussions on economic growth. Since PICs have limited foreign exchange earning capacities, as they have very narrow range of exports and are highly dependent on foreign aid, high oil prices in recent months have seriously tested their economic resilience. This paper applies the recently developed panel analysis procedures to five major PICs, namely Fiji, Samoa, Solomon islands, Tonga and Vanuatu with a view to assess the impact of oil price on economic growth. The findings are that oil price, economic growth and international reserve are cointegrated. The study findings are that although in the long run there is no long run causality relationship between these variables, in the short run the causality linkage runs from oil prices and interna-tional reserve to economic growth. The paper concludes with a brief discussion on policy options.
Urban and Rural HIV Estimates among Adult Population (15 - 49 Years) in Selected States of India Using Spectrum Data  [PDF]
Lincoln Priyadarshi Choudhury, Jayaraman Prabakaran
World Journal of AIDS (WJA) , 2015, DOI: 10.4236/wja.2015.53026
Abstract: HIV estimation has become a standard tool for understanding the epidemic. Although the majority of India’s population lives in rural areas, to date, an exploration of the urban and rural HIV epidemic has not been undertaken. The objective of this study is to develop HIV estimation based on urban and rural adult populations in selected states of India to understand the difference in HIV related indices geographically. Ten states were selected based on HIV prevalence levels-Andhra Pradesh, Tamil Nadu, Karnataka, Maharashtra, Manipur, and Nagaland, Mizoram, Punjab, Odisha and Jharkhand. Spectrum, version 4.53 beta 19, was used. Data files of Indian national estimation, 2010-11 which included population, HIV Sentinel Surveillance, Integrated Bio Behavioral Assessment and program coverage data, were used and alterations made wherever necessary. The urban and rural sub epidemic structures and their subpopulations were separately configured in the Estimation projection package and curve fitting done. Outputs for each state were separately analyzed. Findings show that HIV prevalence is lower in urban than rural areas in Tamil Nadu and Maharashtra; in Karnataka there is no difference in HIV prevalence in the urban and rural populations; and in the remaining seven states urban HIV prevalence is higher as compared to rural HIV prevalence. In the states of Andhra Pradesh, Tamil Nadu, Maharashtra, Odisha and Punjab, the number of people living with HIV, new HIV infections and deaths among people living with HIV is higher in the rural than in the urban population. An early and lower peak in HIV prevalence and incidence in the urban population was seen in Andhra Pradesh, Tamil Nadu, Karnataka and Naga-land, while in Maharashtra the rural peak was earlier and higher. Mizoram shows an earlier and lower peak in the rural population while Manipur shows an earlier and higher urban peak. In Odisha, the epidemic peaked earlier and was lower in the rural than the urban population. HIV prevalence in the urban population in Punjab was still peaking while HIV incidence was earlier and lower in the rural population. In Jharkhand, both urban and rural HIV prevalence and incidence are still increasing. Our findings indicate lower levels of HIV prevalence and incidence in the urban population as compared to the rural populations in Maharashtra and Tamil Nadu. In the remaining eight states, urban prevalence and incidence are higher than their rural counterparts. Future estimations of the HIV epidemic in the country need to adopt a similar approach to inform the design of appropriate
Clusters of CDK2, CCND1, and CMYC genes involved in cancers: Acute Lymphocytic Leukemia (ALL) as a model
A Jayaraman
Biology and Medicine , 2012,
Abstract: Cancer is not a single disease but it involves changes in multifunctional genes, the causes for these changes remain less understood. It is now becoming clear that multiple genes orchestrate to turn on the carcinogenesis process. These genes involve several signaling pathways which then characterize uncontrolled cell divisions. Our aim was to study cell cycle genes CDK2, CCND1, and c-MYC to determine their clustering in the evolutionary pathway and to understand their diversions leading to continued cell division processes. Since Acute Lymphoblastic Leukemia (ALL)is the most prevalent form of cancer in children we took this as a model for analyzing the role of these genes in theleukemia process. The prevalence/spread of these genes was found to be very limited in the animal kingdom; hencethe question is whether this may be due to the fact that during evolution in time there could have been loss of some functions or mutations in these genes which relates to the switch function of these genes. Alternatively, have they evolved in a way which we are unable to trace due to limited methodology? Further, with the results analyzed so far we can imagine that these species in which we found the presence of these genes across the animal kingdom could have had cancer like diseases during their lifetime. We conclude that each of these genes formed several clusters which were typical of their role/functions in ALL.
The interaction of p53 and MDM2 genes in cancers, in silico studies and phylogenetic analysis
A. Jayaraman
Biology and Medicine , 2011,
Abstract: The normal cell cycle process is a crucial process and is generally mediated by a number of regulatory genes. One ofthe most important regulators is the tumor suppressor p53, which in turn is regulated by MDM2 gene. The expressionof p53 and MDM2 is found to be frequently altered in many cancers and metastasis/ relapses .This is the first reportto look at the evolutionary history of these genes to decipher the role of these genes in the tumorigenesis processusing in silico methods. We also found that they showed high degree of sequence similarity across the mammalianspecies, indicating that these species probably share parallel cancer causing mechanisms. Their individual unrootedphylogenetic tree formed 5 clusters each; however, p53 gene was found in a large number of species whereasMDM2 was found in smaller number of species. The role of MDM2 is therefore limited and occurs in fewer speciesacross the mammalian species. It is evident that these molecules play an important role in the cancer process,perhaps responsible for relapses and hence need to be explored further as therapeutic targets. Such studies that arebased on evidence from paleontology and genetics suggest that mechanisms of cancer are embedded deeplythroughout evolution. Understanding the phylogenetic evolution of these genes could help in furthering our knowledgeon the mechanisms involved in cancer.
Modeling of the Dissolved Oxygen in a River with Storage Zone on the Banks  [PDF]
Nitash Kaushik, Babita Tyagi, Girija Jayaraman
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.37103
Abstract: The prediction of water quality in terms of variables like dissolved oxygen (DO), biochemical oxygen demand (BOD), pH value, total dissolved solids (TDS) and salinity etc. is useful for evaluating the use of water for various related purposes. The widely used Streeter and Phelps models for computing biochemical oxygen demand and its impact on dissolved oxygen do not account for the settleable component of BOD and related implications. The model also does not account for the impact of storage zone on the stream’s DO. In the present work an attempt is made to develop a model which simultaneously accounts for the settleable component of BOD and the effect of storage zones onriver’s DO. An application of the model to real field data suggests that the cumulative impact of settleable BOD and presence of storage zone in the river is to shift the critical deficit closer to the point source and magnify its amount.
Trace Level Gas Sensing Characteristics of Nano-Crystalline Silver Decamolybdate  [PDF]
Sunasira Misra, Venkataraman Jayaraman, Thiagarajan Gnanasekaran
Soft Nanoscience Letters (SNL) , 2013, DOI: 10.4236/snl.2013.34A011
Abstract: A soft-chemical method has been developed for the synthesis of nano-crystalline powders of silver decamolybdate. Gas sensing characteristics of this composition both in porous pellet and thin film configurations were investigated. The compound Ag6Mo10O33 was found to sense selectively ammonia at 503 K. Above 503 K it has significant cross sensitivity to petroleum gas (PG). Spin coated thin films exhibited selective sensing towards PG.
Effects of Aluminum Particle Size, Galinstan Content and Reaction Temperature on Hydrogen Generation Rate Using Activated Aluminum and Water  [PDF]
Kandasamy Jayaraman, Christian Chauveau, Iskender G?kalp
Energy and Power Engineering (EPE) , 2015, DOI: 10.4236/epe.2015.79041
Abstract: Aluminum, in its normal passive oxidized state, does not react with water. In this work, aluminum activation is carried out using liquid metal eutectics Ga-In-Sn-Zn (60:25:10:5). Subsequently, the reaction with water of activated aluminum to produce hydrogen has been examined. The effects of aluminum particle size, liquid eutectics content, and reaction temperature on hydrogen production rates are investigated. The liquid eutectics interaction with aluminum is discussed and the mechanisms of liquid eutectics penetration within the Al particles have been investigated. The specific surface area of the Al particles, the mass ratio of Al to eutectics content and the reaction temperature were found to determine the hydrogen production rate and yield. It is observed that micro-aluminum particles of ~30 μm size display lower reaction rates and hydrogen yields than ~350 μm size particles.
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