Evidence of microscopic effects in fragment mass distribution in heavy ion induced fusion-fission reactions

Our measurements of variances ($\sigma_{m}^2$) in mass distributions of fission fragments from fusion-fission reactions of light projectiles (C, O and F) on deformed thorium targets exhibit a sharp anomalous increase with energy near the Coulomb barrier, in contrast to the smooth variation of $\sigma_{m}^2$ for the spherical bismuth target. This departure from expectation based on a statistical description is explained in terms of microscopic effects arising from the orientational dependence in the case of deformed thorium targets.Comment: Replaced with revised version, to appear in Phys. Lett.

On the role of pressure anisotropy for relativistic stars admitting conformal motion

We investigate the spacetime of anisotropic stars admitting conformal motion. The Einstein field equations are solved using different ansatz of the surface tension. In this investigation, we study two cases in details with the anisotropy as: [1] $p_t = n p_r$ [2] $p_t - p_r = \frac{1}{8 \pi}(\frac{c_1}{r^2} + c_2)$ where, n, $c_1$ and $c_2$ are arbitrary constants. The solutions yield expressions of the physical quantities like pressure gradients and the mass.Comment: 21 pages, accepted for publication in 'Astrophysics and Space Science

Gravitational Collapse: Expanding and Collapsing Regions

We investigate the expanding and collapsing regions by taking two well-known spherically symmetric spacetimes. For this purpose, the general formalism is developed by using Israel junction conditions for arbitrary spacetimes. This has been used to obtain the surface energy density and the tangential pressure. The minimal pressure provides the gateway to explore the expanding and collapsing regions. We take Minkowski and Kantowski-Sachs spacetimes and use the general formulation to investigate the expanding and collapsing regions of the shell.Comment: 12 pages, 4 figures, accepted for publication in Gen. Relativ. Gra

Cervical lymph node metastasis in squamous cell carcinoma of the buccal mucosa:a retrospective study on pattern of involvement and clinical analysis

The study was performed with an aim to map the pattern of metastasis of squamous cell carcinomas of buccal mucosa to various cervical lymph node levels and analyze its correlation with primary tumor size and histo-pathological grading. 254 patients with squamous cell carcinoma of the buccal mucosa treated with surgery first approach were analyzed retrospectively. The tumor size was noted from pre-operative CT Scans and were divided into early and advanced tumors. The resected specimen was studied to note the histo-pathological grading of the squamous cell carcinoma and the metastatic deposits at various lymph node levels. Out of 254 patients (149 females, 105 males), 145 patients showed histo-pathologically proven metastatic deposits in one or more lymph nodes out of which there were 56 patients showing occult metastasis. 78/145 patients showed metastatic involvement of level IB and/or IA lymph nodes, 31 showed involvement of level II and/or I lymph nodes, 27 showed involvement of level III with or without involvement of level I and II and 9 showed metastasis to level IV and V lymph nodes with or without level I, II or III lymph nodes. Cervical lymph node metastasis had statistically significant association with tumor size with advanced tumors showing worse pattern of metastatic spread beyond level I and II lymph nodes. As the degree of differentiation of squamous cell carcinoma reduced, they were more prone for cervical metastasis with moderately and poorly differentiated squamous cell carcinoma showing higher involvement of level III, IV and V lymph nodes. The majority of buccal mucosa cases showed metastasis to level I, II and III lymph nodes out of which level IB and/or IA was most frequently involved. Metastasis to level IV and V lymph nodes was rare and was seen especially in patients with advanced primary tumor and poor histo-pathologic differentiation

Nature of singularity formed by the gravitational collapse in Husain space-time with electromagnetic field and scalar field

In this work, we have investigated the outcome of gravitational collapse in Husain space-time in the presence of electro-magnetic and a scalar field with potential. In order to study the nature of the singularity, global behavior of radial null geodesics have been taken into account. The nature of singularities formed has been thoroughly studied for all possible variations of the parameters. These choices of parameters has been presented in tabular form in various dimensions. It is seen that irrespective of whatever values of the parameters chosen, the collapse always results in a naked singularity in all dimensions. There is less possibility of formation of a black hole. Hence this work is a significant counterexample of the cosmic censorship hypothesis.Comment: 9 pages, 19 figure

Strong Gravitational Lensing in a Charged Squashed Kaluza- Klein Black hole

In this paper we investigate the strong gravitational lensing in a charged squashed Kaluza-Klein black hole. We suppose that the supermassive black hole in the galaxy center can be considered by a charged squashed Kaluza-Klein black hole and then we study the strong gravitational lensing theory and estimate the numerical values for parameters and observables of it. We explore the effects of the scale of extra dimension $\rho_0$ and the charge of black hole $\rho_q$ on these parameters and observables.Comment: 17 pages, 10 figure

Goos-H\"{a}nchen-like shifts for Dirac fermions in monolayer graphene barrier

We investigate the Goos-H\"{a}nchen-like shifts for Dirac fermions in transmission through a monolayer graphene barrier. The lateral shifts, as the functions of the barrier's width and the incidence angle, can be negative and positive in Klein tunneling and classical motion, respectively. Due to their relations to the transmission gap, the lateral shifts can be enhanced by the transmission resonances when the incidence angle is less than the critical angle for total reflection, while their magnitudes become only the order of Fermi wavelength when the incidence angle is larger than the critical angle. These tunable beam shifts can also be modulated by the height of potential barrier and the induced gap, which gives rise to the applications in graphene-based devices.Comment: 5 pages, 5 figure

Gravitational collapse of a Hagedorn fluid in Vaidya geometry

The gravitational collapse of a high-density null charged matter fluid, satisfying the Hagedorn equation of state, is considered in the framework of the Vaidya geometry. The general solution of the gravitational field equations can be obtained in an exact parametric form. The conditions for the formation of a naked singularity, as a result of the collapse of the compact object, are also investigated. For an appropriate choice of the arbitrary integration functions the null radial outgoing geodesic, originating from the shell focussing central singularity, admits one or more positive roots. Hence a collapsing Hagedorn fluid could end either as a black hole, or as a naked singularity. A possible astrophysical application of the model, to describe the energy source of gamma-ray bursts, is also considered.Comment: 14 pages, 2 figures, to appear in Phys. Rev.

TeV-Scale Horizontal Symmetry and the Slepton Mass Problem of Anomaly Mediation

We propose a new scenario for solving the tachyonic slepton mass problem of anomaly mediated supersymmetry breaking models with a non-Abelian horizontal gauge symmetry broken at the TeV scale. A specific model based on SU(3)_{H} horizontal symmetry is presented wherein the sleptons receive positive mass-squared from the asymptotically free SU(3)_{H} gauge sector. Approximate global symmetries present in the model strongly suppress flavor changing processes induced by the horizontal vector gauge bosons. The model predicts m_{h} < 120 GeV for the lightest Higgs boson mass, tan{beta} nearly equal to 4, and M_V = 1-4 TeV for the SU(3)_{H} gauge boson masses. The lightest SUSY particle is found to be the neutral Wino, which is a candidate for cold dark matter.Comment: 25 pages in LaTeX, 2 eps figure