Başkent University

About: Başkent University is a education organization based out in Ankara, Turkey. It is known for research contribution in the topics: Transplantation & Population. The organization has 4652 authors who have published 10380 publications receiving 143117 citations. The organization is also known as: Başkent Üniversitesi.

Black hole thermodynamics: No inconsistency via the inclusion of the missing P − V terms

Abstract: The early literature on black hole thermodynamics ignored the $P\text{\ensuremath{-}}V$ term associated with the existence of a fundamental physical constant in the black hole solution. The inclusion of this constant in the first law becomes inconsistent with the Smarr relation. Once the missing $P\text{\ensuremath{-}}V$ term is introduced, it becomes customary to introduce it only in problems where there is a negative cosmological constant. This practice is inherited from cosmological approaches which consider the quantity $\ensuremath{-}\mathrm{\ensuremath{\Lambda}}/8\ensuremath{\pi}$ as the constant pressure due to a cosmological fluid. However, the notions of pressure and thermodynamic volume in black hole thermodynamics are very different from their counterparts in classical thermodynamics. From this point of view, there is a priori no compelling reason to not extend this notion of pressure and associate a partial pressure with each ``external'' density ${8\ensuremath{\pi}{T}_{t}}^{t}$. In this work, we associate a partial pressure with a variable mass parameter as well as with each $tt$ component of the effective stress-energy tensor ${{T}_{\mathrm{eff}\ensuremath{\mu}}}^{\ensuremath{ u}}$ but not with the linear component of the electromagnetic field. Using the field equations ${{G}_{\ensuremath{\mu}}}^{\ensuremath{ u}}=8\ensuremath{\pi}{{T}_{\mathrm{eff}\ensuremath{\mu}}}^{\ensuremath{ u}}$, we derive universal expressions for the enthalpy, internal energy, free energies, thermodynamic volume, equation of state, law of corresponding states, criticality, and critical exponents of static (nonrotating) charged black holes, with possibly a variable mass parameter, whether they are solutions to the Einstein field equations or not. We extend the derivation to the case where the black hole is immersed in the field of a quintessence force and to the multiforce case. Many applications and extensions are considered, including applications to regular black holes derived in previous and present work. No inconsistency has been noticed in their thermodynamics.

Percutaneous Therapy of Ureteral Obstructions and Leak After Renal Transplantation: Long-Term Results

Abstract: The purpose of this study was to evaluate the long-term outcome of percutaneous therapy of ureteral complications after renal transplantation. Between January 2000 and June 2006 we percutaneously treated 26 renal transplant patients with ureteral obstruction (n=19) and leak (n=7). Obstructions were classified as early ( 2 months). Patients with leak were treated with nephro-ureteral catheter placement and subsequent double-J stenting. Balloon dilatation, stent placement, and basket extraction were used to treat ureteral obstructions. Patients were followed with ultrasonography. No major procedure-related complication occurred. The mean follow-up time was 34.3 months (range: 6 to 74 months). Initial clinical success was achieved in all 19 patients with obstruction and 6 of 7 patients with leak. Four of 9 early obstructions and 4 of 10 late obstructions recurred during the follow-up. All recurrences were initially managed again with percutaneous methods, including cutting balloon technique and metallic stent placement. Although there was no recurrence in patients with successfully treated leak, stricture was seen at the previous leak site in two patients. These strictures were also successfully managed percutaneously. We conclude that in the treatment of ureteral obstruction and leak following renal transplantation, percutaneous therapy is an effective alternative to surgery. However, further interventions are usually needed to maintain long-term patency.

Vascular endothelial function and plasma homocysteine levels in Behcet's disease

Abstract: The purpose of the present study was to test endothelial function and to determine if plasma homocysteine levels are associated with endothelial injury in patients with Behcet's disease (BD). Flow-mediated dilation in patients with BD was smaller than that of control subjects (p = 0.001), and mean plasma homocysteine levels in patients with BD were significantly higher (p = 0.0001). On regression analysis, only mean plasma homocysteine concentration was independently related to flow-mediated dilation (F = 5.7, p = 0.001).