Gravitational deflection of light in the Schwarzschild -de Sitter space time

Recent studies suggest that the cosmological constant affects the gravitational bending of photons although the orbital equation for light in Schwarzschild-de Sitter space time is free from cosmological constant. Here we argued that the very notion of cosmological constant independency of photon orbit in the Schwarzschild-de Sitter space time is not proper. Consequently the cosmological constant has some clear contribution to the deflection angle of light rays. We stressed the importance of the study of photon trajectories from the reference objects in bending calculation, particularly for asymptotically non-flat space-time. When such an aspect is taken in to consideration the contribution of cosmological constant to the effective bending is found to depend on the distances of the source and the reference objects.Comment: 5 pages, no figur

Strong field gravitational lensing in scalar tensor theories

Strong field gravitational lensing in the Brans-Dicke theory has been studied. The deflection angle for photons passing very close to the photon sphere is estimated for the static spherically symmetric space-time of the theory and the position and magnification of the relativistic images are obtained. Modeling the super massive central object of the galaxy by the Brans-Dicke space-time, numerical values of different strong lensing observable are estimated. It is found that against the expectation there is no significant scalar field effect in the strong field observable lensing parameters. This observation raises question on the potentiality of the strong field lensing to discriminate different gravitational theories.Comment: 20 pages, accepted in Class. Quantum Grav., final versio

On static spherically symmetric solutions of the vacuum Brans-Dicke theory

It is shown that among the four classes of the static spherically symmetric solution of the vacuum Brans-Dicke theory of gravity only two are really independent. Further by matching exterior and interior (due to physically reasonable spherically symmetric matter source) scalar fields it is found that only Brans class I solution with certain restriction on solution parameters may represent exterior metric for a nonsingular massive object. The physical viability of the black hole nature of the solution is investigated. It is concluded that no physical black hole solution different from the Schwarzschild black hole is available in the Brans-Dicke theory.Comment: 15 pages, To be published in Gen. Rel. and Grav, typos in references correcte

Study on parameters of severity in Dengue infection with both NS1 Antigen and Dengue IgM reactive on the same day, in a tertiary care hospital, Kolkata

Background: Dengue, an important arboviral disease in the tropics manifests with severe thrombocytopenia and deranged liver function. Detection of both NS1 antigen and Dengue IgM on the same day, during the first few days of fever increases the Dengue diagnostic severity. Therefore this study was conducted to study the changes in platelet count and level of hepatic enzymes along with other biochemical and haematological parameters to predict the severity of Dengue infection in these cases.Methods: This prospective study was conducted in the Department of Microbiology, NRS Medical College and Hospital, Kolkata from July 2018 to January 2019 for the simultaneous detection of NS1 antigen and Dengue IgM on the same day of febrile hospitalized patients in the age group of 13 to 60 years. The platelet count and hepatic enzymes along with other biochemical and haematological parameters were evaluated for these patients.Results: Of the total 284 blood samples received, 91 patients were Reactive to both NS1 antigen and Dengue IgM on the same day. Their mean age was 34 years, with male preponderance and maximum reactive on the 5th day of fever. Mean platelet count was 50,000 / mcL, SGOT and SGPT levels were raised with a mean of 215.60 units/litre and 152.7 unit/litre respectively.Conclusion: Presence of both NS1 antigen and Dengue IgM on the same day, associated with thrombocytopenia and deranged liver functions are important parameters for predicting disease severity and play a major role in determining the clinical outcome

Bacteriocin production by clinical isolates of ‘Non fermenting Gram negative bacilli’- a ray of hope in the post antibiotic era

Background: Bacteriocins are a kind of ribosomal synthesized antimicrobial peptides produced by bacteria, during their growth, triggered by competition for space and scarce resources. Non fermenting Gram negative bacilli (NFGNB), which have pivotal role in causing health care associated infection (HAI) need to establish themselves in the hospital environment pushing aside existing flora and do so probably by bacteriocin production.Objective:Present study was undertaken to explore bacteriocin production ability of Pseudomonas aeruginosa and Acinetobacter baumannii and their range of action on other bacteria.Setting and design: A prospective observational study.Material and methods:Fifty MDR-NFGNB isolates were tested for phenotypic detection of bacteriocin production against commonly encountered indicator hospital strains and control strains following some modification of Gratia and Fredericq’s method.Results: All 27 (100%) Pseudomonas aeruginosa isolates, produced bacteriocin active against Escherichia coli and Klebsiella pneumoniae, 26(96.2%) and 21(77.7%) acted on Proteus mirabilis and Enterococcus faecalis respectively. Out of 23 Acinetobacter baumannii, 20(86.9%), 15(65.2%), 15(65.2%) and 12(52.1%) produced bacteriocin active against Enterococcus faecalis, Escherichia coli, Coagulase negative Staphylococcus species (CoNS) and Klebsiella pneumonia respectively. Bacteriocin produced by A baumannii had similar effect on both Gram positive and Gram negative bacteria.Conclusion: The antibacterial spectra of these bacteriocins raise a hope of using these peptides therapeutically in post-antibiotic era

Differential transmission of the molecular signature of RBSP3, LIMD1 and CDC25A in basal/ parabasal versus spinous of normal epithelium during head and neck tumorigenesis: A mechanistic study

<div><p>Head and neck squamous cell carcinoma (HNSCC) is a global disease and mortality burden, necessitating the elucidation of its molecular progression for effective disease management. The study aims to understand the molecular profile of three candidate cell cycle regulatory genes, RBSP3, LIMD1 and CDC25A in the basal/ parabasal versus spinous layer of normal oral epithelium and during head and neck tumorigenesis. Immunohistochemical expression and promoter methylation was used to determine the molecular signature in normal oral epithelium. The mechanism of alteration transmission of this profile during tumorigenesis was then explored through additional deletion and mutation in HPV/ tobacco etiological groups, followed byclinico-pathological correlation. In basal/parabasal layer, the molecular signature of the genes was low protein expression/ high promoter methylation of RBSP3, high expression/ low methylation of LIMD1 and high expression of CDC25A. Dysplastic epithelium maintained the signature of RBSP3 through high methylation/ additional deletion with loss of the signatures of LIMD1 and CDC25A via deletion/ additional methylation. Similarly, maintenance and / or loss of signature in invasive tumors was by recurrent deletion/ methylation. Thus, differential patterns of alteration of the genes might be pre-requisite for the development of dysplastic and invasive lesions. Etiological factors played a key role in promoting genetic alterations and determining prognosis. Tobacco negative HNSCC patients had significantly lower alterations of LIMD1 and CDC25A, along with better survival among tobacco negative/ HPV positive patients. Our data suggests the necessity for perturbation of normal molecular profile of RBSP3, LIMD1 and CDC25A in conjunction with etiological factors for head and neck tumorigenesis, implying their diagnostic and prognostic significance.</p></div