Dynamics of a Charged Particle Around a Slowly Rotating Kerr Black Hole Immersed in Magnetic Field

The dynamics of a charged particle moving around a slowly rotating Kerr black hole in the presence of an external magnetic field is investigated. We are interested to explore the conditions under which the charged particle can escape from the gravitational field of the black hole after colliding with another particle. The escape velocity of the charged particle in the innermost stable circular orbit is calculated. The effective potential and escape velocity of the charged particle with angular momentum in the presence of magnetic field is analyzed. This work serves as an extension of a preceding paper dealing with the Schwarzschild black hole [Zahrani {\it et al}, Phys. Rev. D 87, 084043 (2013)].Comment: 20 pages, 12 figure

Dynamics of Particles Around a Schwarzschild-like Black Hole in the Presence of Quintessence and Magnetic Field

We investigate the dynamics of a neutral and a charged particle around a static and spherically symmetric black hole in the presence of quintessence matter and external magnetic field. We explore the conditions under which the particle moving around the black hole could escape to infinity after colliding with another particle. The innermost stable circular orbit (ISCO) for the particles are studied in detail. Mainly the dependence of ISCO on dark energy and on the presence of external magnetic field in the vicinity of black hole is discussed. By using the Lyapunov exponent, we compare the stabilities of the orbits of the particles in the presence and absence of dark energy and magnetic field. The expressions for the center of mass energies of the colliding particles near the horizon of the black hole are derived. The effective force on the particles due to dark energy and magnetic field in the vicinity of black hole is also discussed.Comment: 25 pages, 17 figures, accepted for publication in the European Physical Journal

Strong Gravitational Lensing by Kiselev Black Hole

We investigate the gravitational lensing scenario due to Schwarzschild-like black hole surrounded by quintessence (Kiselev black hole). We work for the special case of Kiselev black hole where we take the state parameter $w_{q}=-\frac{2}{3}$. For the detailed derivation and analysis of the bending angle involved in the deflection of light, we discuss three special cases of Kiselev black hole: non-extreme, extreme and naked singularity. We also calculate the approximate bending angle and compare it with exact bending angle. We found the relation of bending angles in the decreasing order as: naked singularity, extreme Kiselev black hole, non-extreme Kiselev black hole and Schwarzschild black hole. In the weak field approximation, we compute the position and total magnification of relativistic images as well

Modifiable Factors Associated with Intracerbral Hemorrhage

Background and Purpose:  The purpose of the study was to evaluate modifiable factors causing intracerebral hemorrhage in our set up. Material and Method:  This prospective descriptive study was done at King Edward Medical University/ Mayo Hospital, Lahore from January 2009 to August 2010. Patients of spontaneous intracerebral hemorrhage admitted through emergency department were included. After history and examination, diagnosis of ICH was made on CT brain without contrast in all cases. Further evaluation was done by platelet count, INR, LFTs, renal function tests and CT angiogram brain. Modifiable factors studied were hypertension, coagulopathy and drugs. Only patients of negative CT angiogram were included in the study. Results:  Age range of patients was 11 to 85 years. Male were more than female i.e. 24 (54.5%). Maximum patients i.e. 10 (22.5%) had ICH in 7th decade. Maximum patient had uncontrolled hypertension as the cause of intracerebral hemorrhage i.e. 31 (70.5%). It was followed by coagulopathy and smoking i.e. 4(9.9%). Dengue fever was present 2 (4.5%) cases and both had low platelet count. Conclusion:  Hypertension is the commonest modifiable risk factor for ICH, affecting middle aged and elderly persons. All modifiable factors especially hypertension needs extensive public awareness programs to decrease mortality and morbidity related to ICH

Generalized Second Law of Thermodynamics for FRW Cosmology with Power-Law Entropy Correction

In this work, we have considered the power law correction of entropy on the horizon. If the flat FRW Universe is filled with the n components fluid with interactions, the GSL of thermodynamics for apparent and event horizons have been investigated for equilibrium and non-equilibrium cases. If we consider a small perturbation around the de Sitter space-time, the general conditions of the validity of GSL have been found. Also if a phantom dominated Universe has a polelike type scale factor, the validity of GSL has also been analyzed. Further we have obtained constraints on the power-law parameter {\alpha} in the phantom and quintessence dominated regimes. Finally we obtain conditions under which GSL breaks down in a cosmological background.Comment: 10 page

Pattern of Presentation of Spinal Dysraphism

Objective:  To assess the pattern of presentation of spinal dysraphism and compare with already available data on the subject. Design:  Prospective study. Material and Method:  This prospective study was done in the department of Neurosurgery, King Edward Medi-cal University (KEMU) Lahore, Pakistan from January 2008 to December 2009. Cases of spinal dysraphism admitted and managed in the department during this period were included in the study.  Results:  Total patients admitted with spinal dysraphism during this period were 56. Of them, spina bifida aperta were 42 (75%) and occulta were 14 (25%). Age range of patients of spinal dysraphism was from 1 day to 27 years. Male to female ratio was 1.5 : 1. All the patients of spina bifida aperta had myelomeningocele i.e. 42 (75%). Of them maximum patients had myelomeningocele at lumbosacral region i.e. 18 (42%) followed by lumbar area i.e. 11 (26%). No patients had cervical spina bifida aperta. Hydrocephalus was present in 32 (76%) patient. Of 56 cases of spinal dysraphism, 14 (25%) had spina bifida occulta. Among spina bifida occulta, lipo-myelomeningocele and congenital dermal sinus were 5 (9%) each while 4 (7%) patients had meningocele. All patients had x-ray spine of the affected region. All patients of spina bifida occulta had MRI brain and whole spine.  Conclusion:  All patients of spina bifida aperta presented with myelomeningocele, commonest at lumbosacral area. Age at presentation was relatively late.  Of spina bifida occulta, Lipomyelomeningocele and congenital der-mal sinus were unusually equal. Meningocele was relative less

Aspergillosis of the Sphenoid Sinus with the Involvement of the Clivus

Introduction: Fungal infections of the nose and paranasal sinuses are frequent in this part of the world. One aspect of the increased frequency is the improved clinical, radiological and pathological diagnostic methods that are now available. Aspergillus is the commonest infecting fungus of the nose and the paranasal sinus1 . It is mainly a saprophytic spore producing fungus and can cause invasive and non-invasive infections. The initial report of fungal paranasal infection largely dealt with immunocompromised individuals as distinct from the allergic fungal infection. Aspergillosis confined to the sphenoid sinus is uncommon with only 34 cases having been reported in the literature2,3. These were mostly seen in immunosuppressed patients. Isolated sphenoid sinusitis is uncommon and that due to fungal infection is rare4 . We report the case of aspergillosis of the sphenoid siiius where disease had extended into the upper part of the clivus bone

Particle Dynamics Around Weakly Magnetized Reissner-Nordstr\"{o}m Black Hole

Considering the geometry of Reissner-Nordstr\"{o}m (RN) black hole immersed in magnetic field we have studied the dynamics of neutral and charged particles. A collision of particles in the inner stable circular orbit is considered and the conditions for the escape of colliding particles from the vicinity of black hole are given. The trajectories of the escaping particle are discussed. Also the velocity required for this escape is calculated. It is observed that there are more than one stable regions if magnetic field is present in the accretion disk of black hole so the stability of ISCO increases in the presence of magnetic field. Effect of magnetic field on the angular motion of neutral and charged particles is observed graphically.Comment: 16 pages, 16 figures, version accepted for publication in 'Advances in High Energy Physics