Radar Cross-section Measurement Techniques

Radar cross-section (RCS) is an important study parameter for defence applications specially dealing with airborne weapon system. The RCS parameter guides the detection range for a target and is therefore studied to understand the effectiveness of a weapon system. It is not only important to understand the RCS characteristics of a target but also to look into the diagnostic mode of study where factors contributing to a particular RCS values are studied. This further opens up subject like RCS suppression and stealth. The paper discusses the RCS principle, control, and need of measurements. Classification of RCS in terms of popular usage is explained with detailed theory of RF imaging and inverse synthetic aperture radar (ISAR). The various types of RCS measurement ranges are explained with brief discussion on outdoor RCS measurement range. The RCS calibration plays a critical role in referencing the measurement to absolute values and has been described.The RCS facility at Reseach Centre Imarat, Hyderabad, is explained with some details of different activities that are carried out including RAM evaluation, scale model testing, and diagnostic imaging.Defence Science Journal, 2010, 60(2), pp.204-212, DOI:http://dx.doi.org/10.14429/dsj.60.34

Heisenberg uniqueness pairs on the Euclidean spaces and the motion group

In this article, we consider Heisenberg uniqueness pairs corresponding to the exponential curve and surfaces, paraboloid, and sphere. Further, we look for analogous results related to the Heisenberg uniqueness pair on the Euclidean motion group and related product group

Heisenberg uniqueness pairs on the Euclidean spaces and the motion group

In this article, we consider Heisenberg uniqueness pairs corresponding to the exponential curve and surfaces, paraboloid, and sphere. Further, we look for analogous results related to the Heisenberg uniqueness pair on the Euclidean motion group and related product group

Immune-driven adaptation of hepatitis B virus genotype D involves preferential alteration in B-cell epitopes and replicative attenuation—an insight from human immunodeficiency virus/hepatitis B virus coinfection

AbstractAn important driving force behind the sequence diversity of hepatitis B virus (HBV) is viral adaptation to host immune responses. To gain an insight into the impact of host immunity on genetic diversification and properties of HBV, we characterized HBV of genotype D from treatment-naive hepatitis B e antigen-positive (EP) and hepatitis B e antigen-negative (EN) patients with chronic hepatitis B (CHB), where HBV is under stronger immune pressure, with that of HBV derived from human immunodeficiency virus (HIV)/HBV-coinfected individuals, where HIV infection has significantly weakened the immune system. Full-length sequence analysis showed that HBV heterogeneity was most extensive in EN-CHB followed by EP-CHB and HIV/HBV coinfection. The relative magnitude of non-synonymous changes within B-cell epitopes was greater than that in T-cell epitopes of HBV open reading frames (ORFs) in both EP-CHB and EN-CHB. Nine amino acid substitutions were identified in B-cell epitopes and one in a T-cell epitope of HBV in EN-CHB, most of which resulted in altered hydrophobicities, as determined using the Kyte and Doolittle method, relative to wild-type residues found in HBV from the HIV-positive group. Additionally, 19 substitutions occurred at significantly higher frequencies in non-epitope regions of HBV ORF-P in EN-CHB than HIV/HBV-coinfected patients. In vitro replication assay demonstrated that the substitutions, particularly in reverse transcriptase and RNaseH domains of ORF-P, resulted in a decline in replication capacity of HBV. Hence, our results indicate that HBV adapts to increasing immune pressure through preferential mutations in B-cell epitopes and by replicative attenuation. The viral epitopes linked to immune response identified in this study bear important implications for future HBV vaccine studies

Quantum corrections to the entropy of charged rotating black holes

Hawking radiation from a black hole can be viewed as quantum tunneling of particles through the event horizon. Using this approach we provide a general framework for studying corrections to the entropy of black holes beyond semiclassical approximations. Applying the properties of exact differentials for three variables to the first law thermodynamics, we study charged rotating black holes and explicitly work out the corrections to entropy and horizon area for the Kerr-Newman and charged rotating BTZ black holes. It is shown that the results for other geometries like the Schwarzschild, Reissner-Nordstr\"{o}m and anti-de Sitter Schwarzschild spacetimes follow easily

A novel realization of the Calogero-Moser scattering states as coherent states

A novel realization is provided for the scattering states of the $N$-particle Calogero-Moser Hamiltonian. They are explicitly shown to be the coherent states of the singular oscillators of the Calogero-Sutherland model. Our algebraic treatment is straightforwardly extendable to a large number of few and many-body interacting systems in one and higher dimensions.Comment: 9 pages, REVTe

In vivo Antidiabetic and Antioxidant Potential of Stephania hernandifolia in Streptozotocin-Induced-Diabetic Rats

Stephania hernandifolia (Menispermaceae) is a medicinal plant, used by herbalists for treating various diseases, one of which is diabetes mellitus, in Darjeeling. However, its antidiabetic activity has not been scientifically investigated so far. The aim of this study, therefore, is to investigate the antidiabetic and antioxidant potential of the powdered corm of Stephania hernandifolia. This was tested in normal and Streptozotocin (STZ)-induced diabetic rats, using oral administration of ethanol and an aqueous extract (400 mg/kg body weight) of Stephania hernandifolia corm. After the oral administration of water and ethanol extracts at doses of 400 mg/kg body weight, blood glucose levels were monitored at specific intervals and it was found that they were significant lowered. Glibenclamide was used as a standard drug at a dose of 0.25 mg/kg. The experimental data revealed that both extracts has significant antihyperglycemic and antioxidant activity in Streptozotocin-induced rats compared to the standard drug. The antioxidant activity in vitro was measured by means of the 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and Superoxide-free radical scavenging assay. Ascorbic acid, a natural antioxidant, was used as a control. The extracts of ethanol and aqueous were strongly scavenged DPPH radicals, with IC50 being 265.33 and 217.90 µg/ml, respectively. Although the extracts of ethanol and aqueous were moderately scavenged, the superoxide radical were with IC50 values of 526.87 and 440.89 µg/ml. The study revealed that the ethanolic extract exhibited more significant antidiabetic and antioxidant activity then the aqueous extract

A Unified Algebraic Approach to Few and Many-Body Correlated Systems

The present article is an extended version of the paper {\it Phys. Rev.} {\bf B 59}, R2490 (1999), where, we have established the equivalence of the Calogero-Sutherland model to decoupled oscillators. Here, we first employ the same approach for finding the eigenstates of a large class of Hamiltonians, dealing with correlated systems. A number of few and many-body interacting models are studied and the relationship between their respective Hilbert spaces, with that of oscillators, is found. This connection is then used to obtain the spectrum generating algebras for these systems and make an algebraic statement about correlated systems. The procedure to generate new solvable interacting models is outlined. We then point out the inadequacies of the present technique and make use of a novel method for solving linear differential equations to diagonalize the Sutherland model and establish a precise connection between this correlated system's wave functions, with those of the free particles on a circle. In the process, we obtain a new expression for the Jack polynomials. In two dimensions, we analyze the Hamiltonian having Laughlin wave function as the ground-state and point out the natural emergence of the underlying linear $W_{1+\infty}$ symmetry in this approach.Comment: 18 pages, Revtex format, To appear in Physical Review

The generalized second law of thermodynamics of the universe bounded by the event horizon and modified gravity theories

In this paper, we investigate the validity of the generalized second law of thermodynamics of the universe bounded by the event horizon. Here we consider homogeneous and isotropic model of the universe filled with perfect fluid in one case and in another case holographic model of the universe has been considered. In the third case the matter in the universe is taken in the form of non-interacting two fluid system as holographic dark energy and dust. Here we study the above cases in the Modified gravity, f(R) gravity.Comment: 9 page