Kaluza-Klein universe with cosmic strings and bulk viscosity in f(R,T) gravity     

D. R. K. Reddy  R. L. Naidu  K. Dasu Naidu  T. Ram Prasad 《Astrophysics and Space Science》2013,346(1):261-265

A five dimensional Kaluza-Klein cosmological model is considered in the frame work of f(R,T) gravity proposed by Harko et al. (Phys. Rev. D 84:024020, 2011) when the source for energy momentum tensor is a bulk viscous fluid containing one dimensional cosmic strings. A barotropic equation of state is assumed to get a determinate solution of the field equations. Also, the bulk viscous pressure is assumed to be proportional to the energy density. The physical behavior of the model is also discussed.  相似文献   

Modeling of the sea surface for daylight imagery studies     

Naidu  P.S. Reddy  Y.V. 《Oceanic Engineering, IEEE Journal of》1988,13(2):81-83

Plastic-coated paper is shown to possess reflectivity characteristics quite similar to those of the surface of water. This correspondence has been used with a conversion factor to model a sea surface by means of plastic-coated paper. Such a paper model is then suitably illuminated and photographed, yielding physically simulated daylight imagery of the sea surface under controlled conditions. A simple example of sinusoidal surface simulation is described  相似文献   

Forest cover and landuse mapping in Karbi Anglong and North Cachar Hills districts of assam using landsat MSS data     

PS Roy  KK Das  KSM Naidu 《Journal of the Indian Society of Remote Sensing》1991,19(2):113-123

Karbi Anglong and North Cachar Hills districts of Assam are endowed with rich and diverse vegetation resources. Increased human pressure due to shifting cultivation and raw material extraction for industrial purposes are heavily altering the forested landscape. The present study deals with mapping of forest types in the two districts using LANDSAT-MSS digital data. The maps thus generated provide spatial distribution of bioclimatic vegetation types. Supervised maximum likelihood classification has been performed using training sets collected during field work. The spectral behaviour of vegetation types have been studied for optimising classification scheme. The classification accuracy of classes mapped has been calculated.  相似文献   

Soil bacterial strains with heavy metal resistance and high potential in degrading diesel oil and <Emphasis Type="Italic">n</Emphasis>-alkanes     

K. Ramadass  M. Megharaj  K. Venkateswarlu  R. Naidu 《International Journal of Environmental Science and Technology》2016,13(12):2863-2874

Four bacterial strains, capable of degrading diesel oil, n-alkanes or hexadecane, were isolated from soils contaminated with petroleum oil and identified. Strains of Pseudomonas sp., Pseudomonas putida TPHK-1 and Pseudomonas aeruginosa TPHK-4, were more efficient in degrading high concentrations of the hydrocarbons than the other two strains, Stenotrophomonas maltophilia TPHK-2 and Acenitobacter sp. TPHK-3. P. putida TPHK-1 exhibited tolerance to very high concentrations of heavy metals such as cadmium, lead, zinc and copper. The innate ability of P. putida TPHK-1, as evidenced by the amplified genes alkB1 and alkB2 that encode alkane hydroxylases, and cat12o and cat23o coding for catechol dioxygenase, in degrading diesel oil in the presence of heavy metals is far greater than that of the strains reported in the literature. Heavy metal tolerance coupled with rapid degradation of hydrocarbons, even at high concentrations, suggests that P. putida TPHK-1 has a great potential in remediating soils contaminated with mixtures of hydrocarbons and heavy metals.  相似文献   

Closed form solution for a point force in a rotating stratified fluid     

L. V. K. V. Sarma  K. B. Naidu 《Pure and Applied Geophysics》1972,99(1):156-168

Summary The motion generated by an oscillatory point force in an inviscid incompressible rotating stratified fluid is studied, taking into account the effect of stratification on the inertia terms in the equations of motion. The solutions are obtained in closed form using Fourier transforms. The motion is axisymmetric (or not) according as the force acts along (or perpendicular to) the axis of rotation of the fluid. In the hyperbolic case, the motion is confined to the inner region of a cone with vertex at the origin. The solution when there is no rotation-no stratification-neither rotation nor stratification, is deduced and each case is found to differ from the case of rotating stratified fluid in many respects. The solution for a steady force is also deduced in the limit.  相似文献   

Organic carbon isotope ratios (δ13C) of Arctic Amerasian Continental shelf sediments     

A. S. Naidu  L. W. Cooper  B. P. Finney  R. W. Macdonald  C. Alexander  I. P. Semiletov 《International Journal of Earth Sciences》2000,89(3):522-532

Organic matter origins are inferred from carbon isotope ratios ('¹³C) in recent continental shelf sediments and major rivers from 465 locations from the north Bering-Chukchi-East Siberian-Beaufort Sea, Arctic Amerasia. Generally, there is a cross-shelf increase in '¹³C, which is due to progressive increased contribution seaward of marine-derived organic carbon to surface sediments. This conclusion is supported by the correlations between sediment '¹³C, OC/N, and '¹⁵N. The sources of total organic carbon (TOC) to the Amerasian margin sediments are primarily from marine water-column phytoplankton and terrigenous C₃ plants constituted of tundra taiga and angiosperms. In contrast to more temperate regions, the source of TOC from terrigenous C₄ and CAM plants to the study area is probably insignificant because these plants do not exist in the northern high latitudes. The input of carbon to the northern Alaskan shelf sediments from nearshore kelp community (Laminaria solidungula) is generally insignificant as indicated by the absence of high sediment '¹³C values (-16.5 to -13.6‰) which are typical of the macrophytes. Our study suggests that the isotopic composition of sediment TOC has potential application in reconstructing temporal changes in delivery and accumulation of organic matter resulting from glacial-interglacial changes in sea level and environments. Furthermore, recycling and advection of the extensive deposits of terrestrially derived organic matter from land, or the wide Amerasian margin, could be a mechanism for elevating total CO₂ and pCO₂ in the Arctic Basin halocline.  相似文献   

Influence of Geomagnetic Storms on Ionospheric F2-Layer at Low and Mid Latitudes in 300° E Meridian     

Peddi Naidu  P.  Latha  T. Madhavi  Devi  M. Indira 《Geomagnetism and Aeronomy》2019,59(8):995-1002

Geomagnetism and Aeronomy - The behaviour of the ionospheric F2-layer during geomagnetic storm is studied using the critical frequency parameter foF2. The magnetic storms of 2nd October 2013 and...  相似文献   

GIS Based Marine Platinum Exploration, Goodnews Bay Region, Southwest Alaska     

Thomas Oommen  Anupma Prakash  Debasmita Misra  Sathy Naidu  John J. Kelley  Sukumar Bandopadhyay 《Marine Georesources & Geotechnology》2008,26(1):1-18

Goodnews Bay, southwest Alaska, is known for platinum (Pt) reserve that extends offshore in the Bering Sea. To assess the nearshore placer potential we first collated marine Pt concentrations available since 1960 in a geographic information system (GIS) database. Subsequently, in 2005, we collected 23 pipe dredge sediment samples and 26 vibracores from unexplored sites and analyzed them for Pt. This sampling was supplemented by magnetic (Sea Spy) and seismic (side scan, geoacoustic and datasonic bubble pulser) surveys. Integrating results of geospatial analysis of Pt concentrations with geophysical analysis using GIS techniques led to delineate four locations encouraging for further Pt exploration. Of these, two locations fall close to paleochannels and drowned ultramafic source, while the other two coincide with high energy environments in the Goodnews Bay and close to the Carter Bay.  相似文献   

Five dimensional string cosmological models in a scalar-tensor theory of gravitation     

D. R. K. Reddy  R. L. Naidu 《Astrophysics and Space Science》2007,307(4):395-398

Five dimensional Kaluza-Klein space-time is considered in the presence of cosmic string source in the frame work of scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113, 467 (1985)). Exact cosmological models, which represent Nambu, Takabayasi and Reddy strings are presented. Some physical and kinematical properties of the models are also discussed.  相似文献   

A Cosmological Model with a Negative Constant Deceleration Parameter in Scale-Covariant Theory of Gravitation     

D. R. K. Reddy  R. L. Naidu  K. S. Adhav 《Astrophysics and Space Science》2007,307(4):365-367

An axially symmetric Bianchi type-I space-time is considered in the presence of perfect fluid source in the scale-covariant theory of gravitation formulated by Canuto et al. [1977a, Phys. Rev. Lett. 39, 429]. With the help of special law of variation for Hubble’s parameter proposed by Bermann [1983, Nuovo Cimento 74B, 182] a cosmological model with a negative constant declaration parameter is obtained in this theory. Some physical properties of the model are also discussed.  相似文献