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Search Results: 1 - 10 of 161 matches for " Duvvuri SUBBARAO "
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Journal of Engineering Science and Technology , 2008,
Abstract: Gas to particle mass transfer coefficient in risers was observed to increase with gas velocity, decrease with solid circulation rate and decrease with particle size. A model to explain gas to particle mass transfer in risers is developed considering that particles move as clusters. The model equations compare well with the available experimental observations on gas to particle mass transfer coefficients in risers.
Correlation between Fischer-Tropsch catalytic activity and composition of catalysts
Sardar Ali, Noor Mohd Zabidi, Duvvuri Subbarao
Chemistry Central Journal , 2011, DOI: 10.1186/1752-153x-5-68
Abstract: H2-TPR analysis of cobalt catalyst indicated three temperature regions at 506°C (low), 650°C (medium) and 731°C (high). The incorporation of iron up to 30% into cobalt catalysts increased the reduction, CO chemisorption and number of cobalt active sites of the catalyst while an opposite trend was observed for the iron-riched bimetallic catalysts. The CO conversion was 6.3% and 4.6%, over the monometallic cobalt and iron catalysts, respectively. Bimetallic catalysts enhanced the CO conversion. Amongst the catalysts studied, bimetallic catalyst with the composition of 70Co30Fe showed the highest CO conversion (8.1%) while exhibiting the same product selectivity as that of monometallic Co catalyst. Monometallic iron catalyst showed the lowest selectivity for C5+ hydrocarbons (1.6%).Fischer-Tropsch synthesis (FTS) is a process which deals with the conversion of syngas derived from coal, biomass and natural gas into hydrocarbons consisting of paraffins, olefins, alcohols and aldehydes with a high cetane number and is environmentally friendly [1]. Due to limited petroleum reserves and environmental restrictions, Fischer-Tropsch synthesis (FTS) is gaining more attention nowadays than ever. FTS is considered as a surface-catalyzed polymerization reaction. During this process, CO is adsorbed on the surface of the transition metal and hydrogenated producing CHx monomers which consequently propagate to produce hydrocarbons and oxygenates with a broad range of functionalities and chain lengths [2].All the group VIII elements show considerable activity for this process. Among them Co, Fe and Ru present the highest activity [3]. Due to high activity for Fischer-Tropsch synthesis, high selectivity to linear products, more stability towards deactivation, low activity towards water-gas shift (WGS) reaction and low cost compared to Ru, cobalt-based catalysts are the preferred catalyst for Fischer-Tropsch synthesis [4,5]. In order to enhance the catalytic activity and stability, diffe
Effect of Loading on the Physicochemical Properties of Alumina Supported Co/Mo Bimetallic Nanocatalysts
Sardar Ali,Noor Asmawati Mohd Zabidi,Duvvuri Subbarao
Journal of Applied Sciences , 2011,
Abstract: The present research deals with the synthesis of cobalt bimetallic Co/Mo nanocatalysts supported on alumina. The nanocatalysts were prepared by wet impregnation method. The samples were characterized in terms of reducibility, dispersion and particle size using Temperature Programmed Reduction (TPR), Transmission Electron Microscopy (TEM) and BET-surface area analysis. H2-TPR analysis of Co/Al2O3 indicated three temperature regions at 380C (low temperature), 680C (medium temperature) and 900C (high temperature). The incorporation of molybdenum into cobalt nanocatalysts shifted the reduction temperatures towards higher temperature but the percentage of species being reduced at low temperature increased also incorporation of molybdenum reduce the crystallinity but decreased the metal particle size of the catalysts. Increasing metal loading from 5 to 10 %wt increased the reducibility of bimetallic nanocatalysts.
Effect of niobium promoter on iron-based catalyst for Fischer-Tropsch reaction
Sardar ALI,Noor Asmawati MOHD ZABIDI,Duvvuri SUBBARAO,
Sardar ALI
,Noor Asmawati MOHD ZABIDI,Duvvuri SUBBARAO

燃料化学学报 , 2012,
Abstract: Niobium-promoted Fe/CNTs catalysts were prepared using a wet impregnation method.Samples were characterized by nitrogen adsorption,H2-TPR,TPD,XRD and TEM.The Fischer-Tropsch Synthesis(FTS) was carried out in a fixed-bed microreactor at 220 ℃,1 atm and H2/CO=2 for 5 h.Addition of niobium into Fe/CNTs increased the dispersion,decreased the average size of iron oxide nanoparticles and the catalyst reducibility.Niobium-promoted Fe catalyst resulted in appreciable increase in the selectivity of C5+ hydrocarbons and suppressed methane formation.These effects were more pronounced for the 0.04%Nb/Fe/CNTs catalyst,compared to those observed from other niobium compositions.The 0.04%Nb/Fe/CNTs catalyst enhanced the C5+ hydrocarbons selectivity by a factor of 67.5% and reduced the methane selectivity by a factor of 59.2%.
P53 pseudogene: potential role in heat shock induced apoptosis in a rat histiocytoma  [PDF]
Amere Subbarao Sreedhar
Health (Health) , 2010, DOI: 10.4236/health.2010.29156
Abstract: The p53 tumor suppressor gene is either non- functional or highly and frequently mutated in majority of cancers. In our study towards understanding cellular adaptations to stress using a rat histiocytic tumor model, we have identified mis-sense mutation in p53 that led to premature termination of translation at the carboxyl-termi- nus. Further, the cDNA isolated from heat stre- ssed cells producing two amplicons with cDNA specific primers (N-terminus) suggested occurrence of possible pseudogene(s). A comparative analysis between different tumor cell lines of rat origin and rat genomic DNA using p53 gene specific primers resulted in the amplification of a processed pseudogene and its positive interaction with wild type p53 probe on Southern blot analysis. The genomic DNA sequence analysis, and sequence comparison with cDNA discovered that the processed pseudogene lacks DNA binding domain and nuclear localization signal, however, contains the ribosomal entry and stop signals. Rat genome BLAST analysis of the pesudogene suggested chromosome-18 localization which was in addition to 14, 13, 10, 9 localization of the cDNA. In the interest of unraveling hidden dimensions of p53 tumor suppressor gene, our study explores the probability of p53 functional pseudogenes in rat histiocytoma.
Single Crystal X-Ray Diffraction Studies on Magnetic Yb5Co4Ge10  [PDF]
Udumula Subbarao, Sebastian C. Peter
Advances in Materials Physics and Chemistry (AMPC) , 2013, DOI: 10.4236/ampc.2013.31A008

The high quality single crystals of Yb5Co4Ge10 have been grown by the indium metal flux method and characterized by means of single crystal X-ray diffraction data. Yb5Co4Ge10 crystallizes in the Sc5Co4Si10 structure type, tetragonal space group P4/mbm and lattice constants are a = b = 12.6369(18) ? and c = 4.1378(8) ?. Crystal structure of Yb5Co4Ge10 composed of three-dimensional [Co4Ge12

Information and communication technology developments in asthma management: A systematic review
Duvvuri Venkata Rama,Jianhong Wu
Indian Journal of Medical Sciences , 2007,
Abstract: This review aims to explain the progress of information and communication technology (ICT) applications in asthma management. Appropriate literature was printed out from the bibliographic databases and library source using relevant key phrases of ICT and asthma. The ICT developments from simple to complex modules to augment the conventional methods of asthma care with a caution of excessive reliance upon technology were discussed. However, it should be noted ICTs are for maximizing the human clinician′s own ability to receive and process information as well as providing unique opportunities for patients, physicians, pharmacists and researchers.
Skeletal Dysplasia (Non - Sclerosing dysplasias – Part II)
K Subbarao
Nepalese Journal of Radiology , 2014, DOI: 10.3126/njr.v4i1.11364
Abstract: DOI: http://dx.doi.org/10.3126/njr.v4i1.11364 Nepalese Journal of Radiology, Vol.4(1) 2014: 1-11
Anisotropic Inflation and the Origin of Four Large Dimensions
C. Armendariz-Picon,Vikram Duvvuri
Physics , 2003, DOI: 10.1088/0264-9381/21/8/007
Abstract: In the context of (4+d)-dimensional general relativity, we propose an inflationary scenario wherein 3 spatial dimensions grow large, while d extra dimensions remain small. Our model requires that a self-interacting d-form acquire a vacuum expectation value along the extra dimensions. This causes 3 spatial dimensions to inflate, whilst keeping the size of the extra dimensions nearly constant. We do not require an additional stabilization mechanism for the radion, as stable solutions exist for flat, and for negatively curved compact extra dimensions. From a four-dimensional perspective, the radion does not couple to the inflaton; and, the small amplitude of the CMB temperature anisotropies arises from an exponential suppression of fluctuations, due to the higher-dimensional origin of the inflaton. The mechanism triggering the end of inflation is responsible, both, for heating the universe, and for avoiding violations of the equivalence principle due to coupling between the radion and matter.
The role of cellular immunity in Influenza H1N1 population dynamics
Duvvuri Venkata R,Heffernan Jane M,Moghadas Seyed M,Duvvuri Bhargavi
BMC Infectious Diseases , 2012, DOI: 10.1186/1471-2334-12-329
Abstract: Background Pre-existing cellular immunity has been recognized as one of the key factors in determining the outcome of influenza infection by reducing the likelihood of clinical disease and mitigates illness. Whether, and to what extent, the effect of this self-protective mechanism can be captured in the population dynamics of an influenza epidemic has not been addressed. Methods We applied previous findings regarding T-cell cross-reactivity between the 2009 pandemic H1N1 strain and seasonal H1N1 strains to investigate the possible changes in the magnitude and peak time of the epidemic. Continuous Monte-Carlo Markov Chain (MCMC) model was employed to simulate the role of pre-existing immunity on the dynamical behavior of epidemic peak. Results From the MCMC model simulations, we observed that, as the size of subpopulation with partially effective pre-existing immunity increases, the mean magnitude of the epidemic peak decreases, while the mean time to reach the peak increases. However, the corresponding ranges of these variations are relatively small. Conclusions Our study concludes that the effective role of pre-existing immunity in alleviating disease outcomes (e.g., hospitalization) of novel influenza virus remains largely undetectable in population dynamics of an epidemic. The model outcome suggests that rapid clinical investigations on T-cell assays remain crucial for determining the protection level conferred by pre-existing cellular responses in the face of an emerging influenza virus.
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