Azreg-Ainou M.,Baskent University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013
Null geodesics of normal and phantom Einstein-Maxwell-dilaton black holes are determined analytically by the Weierstrass elliptic functions. The black hole parameters other than the mass enter, with the appropriate signs, the formula for the angle of deflection to the second order in the inverse of the impact parameter allowing for the identification of the nature of matter (phantom or normal). Such identification is also possible via the time delay formula and observation of relativistic images. Scattering experiences may favor black holes of Einstein-anti-Maxwell-dilatonic theory for their high relative discrepancy with respect to the Schwarzschild value. For the cases we restrict ourselves to, phantom black holes are characterized by the absence of many-world and two-world null geodesics. © 2013 American Physical Society.
Gulec A.T.,Baskent University
Journal of the European Academy of Dermatology and Venereology | Year: 2012
Background Botulinum toxin A (BTX-A) is an effective and safe treatment modality for primary axillary hyperhidrosis. However, some patients experience considerable pain during injections. Design Dilution of botulinum toxin A in lidocaine vs. in normal saline for the treatment of primary axillary hyperhidrosis: a double-blind, randomized, comparative preliminary study. Objective The aim of this study was to compare the efficacy, safety and pain tolerance of lidocaine-diluted BTX-A vs. saline-diluted BTX-A for the treatment of axillary hyperhidrosis. Methods Eight patients were injected with 50 U of BTX-A diluted in 0.5 mL of saline and 1 mL of 2% lidocaine into one axilla and 50 U of BTX-A diluted in 1.5 mL of saline into the other axilla in a randomized fashion. The pain associated with the injections were self-assessed by the subjects using a 100-mm visual analogue scale (VAS). Results Lidocaine-diluted BTX-A and saline-diluted BTX-A were similarly effective regarding the reduction in sweat production, the onset of sweat cessation and the duration of hypo/anhidrosis. Nevertheless, the pain VAS score during the injections was significantly lower in the axilla treated with lidocaine-diluted BTX-A than the one treated with saline-diluted toxin. Limitations Preliminary study due to relatively small sample size. Conclusion Botulinum toxin A diluted in lidocaine causes significantly less pain than BTX-A diluted in saline, whereas it is is equally effective and safe as the latter one in treating axillary hyperhidrosis. Therefore, we suggest that lidocaine-diluted BTX-A may be a better treatment option for the patients with primary axillary hyperhidrosis. © 2011 The Author. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.
Pinarci E.Y.,Baskent University
Journal of Cataract and Refractive Surgery | Year: 2012
Purpose: To assess the results of posterior neodymium:YAG (Nd:YAG) laser capsulotomy in patients with late postoperative capsular block syndrome (CBS) with decreased vision because of posterior capsule opacification (PCO). Setting: Baskent University Hospital, Department of Ophthalmology, Ankara, Turkey. Design: Case-control study. Methods: Patients with CBS who had phacoemulsification and foldable hydrophilic or hydrophobic acrylic intraocular lens implantation with continuous curvilinear capsulorhexis were retrospectively reviewed. Transparent to slight milky fluid had collected in the capsular bag. Capsular block syndrome was undiagnosed before the PCO developed. The CBS was treated with Nd:YAG laser capsulotomy, after which the change in refraction, corrected distance visual acuity (CDVA), intraocular pressure (IOP), complications, and inflammation rate were evaluated. Follow-up examinations were at 1 day, 1 week, and 1 and 6 months. Results: The mean time between cataract surgery and laser capsulotomy was 48 months ± 10.27 (SD) (range 28 to 66 months). The Nd:YAG capsulotomy was successful in all eyes. Capsulotomy did not change the refraction in 14 eyes (93.3%). One patient (6.6%) had a change of +0.75 diopter. After capsulotomy, the logMAR CDVA improved in 13 cases (mean 0.26 ± 0.18; range 0.0 to 0.7) and did not change in 2 cases. There were no complications, inflammation, or significant IOP changes. Conclusions: Neodymium:YAG laser capsulotomy in patients with PCO associated with late CBS increased visual acuity without a significant change in refraction or IOP. Capsular block syndrome may be asymptomatic and remain undiagnosed for a long time after cataract surgery before PCO develops. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. © 2012 ASCRS and ESCRS.
Azreg-Ainou M.,Baskent University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015
The early literature on black hole thermodynamics ignored the P-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-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 -Λ/8π 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 8πTtt. 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 Teffμν but not with the linear component of the electromagnetic field. Using the field equations Gμν=8πTeffμν, 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. © 2015 American Physical Society.
Mizuno H.,Juntendo University |
Tobita M.,Japan Self Defense Force Hospital Yokosuka |
Uysal A.C.,Baskent University
Stem Cells | Year: 2012
The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs offers a paradigm shift that may provide alternative therapeutic solutions for a number of diseases. The use of either embryonic stem cells (ESCs) or induced pluripotent stem cells in clinical situations is limited due to cell regulations and to technical and ethical considerations involved in the genetic manipulation of human ESCs, even though these cells are, theoretically, highly beneficial. Mesenchymal stem cells seem to be an ideal population of stem cells for practical regenerative medicine, because they are not subjected to the same restrictions. In particular, large number of adipose-derived stem cells (ASCs) can be easily harvested from adipose tissue. Furthermore, recent basic research and preclinical studies have revealed that the use of ASCs in regenerative medicine is not limited to mesodermal tissue but extends to both ectodermal and endodermal tissues and organs, although ASCs originate from mesodermal lineages. Based on this background knowledge, the primary purpose of this concise review is to summarize and describe the underlying biology of ASCs and their proliferation and differentiation capacities, together with current preclinical and clinical data from a variety of medical fields regarding the use of ASCs in regenerative medicine. In addition, future directions for ASCs in terms of cell-based therapies and regenerative medicine are discussed. © AlphaMed Press.
Aktas A.,Baskent University
Seminars in Nuclear Medicine | Year: 2014
The best option for the treatment of end-stage renal disease is kidney transplantation. Prompt diagnosis and management of early posttransplantation complications is of utmost importance for graft survival. Biochemical markers, allograft biopsies, and imaging modalities are used for the timely recognition and management of graft dysfunction. Among several other factors, improvements in imaging modalities have been regarded as one of the factors contributing to increased short-term graft survival. Each imaging procedure has its own unique contribution to the evaluation of renal transplant dysfunction. In the era of multimodality imaging and emerging clinical considerations for the improvement of graft survival, evaluating an imaging modality in its own right may not be relevant and may fall short of expectation. Recognized as being mainly a functional imaging procedure, radionuclide imaging provides valuable information on renal function that cannot be obtained with other imaging modalities. For evaluating and establishing the current place, indications, and potential applications of radionuclide renal transplant imaging, a classification of renal allograft complications based on renal allograft dysfunction is essential. The major factor affecting long-term graft loss is chronic allograft nephropathy. Its association with early posttransplantation delayed graft function and repeated acute rejection episodes is well documented. Long-term graft survival rate have not improve significantly over the years. Imaging procedures are most commonly performed during the early period after transplantation. There seems to be a need for performing more frequent late posttransplantation imaging for the evaluation of acute allograft dysfunction, subclinical pathology, and chronic allograft changes; for understanding their contribution to patient management; and for identification of pathophysiological mechanisms leading to proteinuria and hypertension. With its unique advantage of relating perfusion to function, the potential for radionuclide imaging to replace late protocol biopsies needs to be investigated. © 2014 Elsevier Inc.
Ic Y.T.,Baskent University
Robotics and Computer-Integrated Manufacturing | Year: 2012
The selection of Computer-Integrated Manufacturing (CIM) technologies becomes more complex as the decision makers in the manufacturing organization have to assess a wide range of alternatives based on a set of attributes. Although, a lot of Multi-Attribute Decision-Making (MADM) methods are available to deal with selection applications, this paper aims to explore the applicability of an integrated TOPSIS and DoE method to solve different CIM selection problems in real-time industrial applications. Four CIM selection problems, which include selection of (a) an industrial robot, (b) a rapid prototyping process, (c) a CNC machine tool and (d) plant layout design, are considered in this paper. TOPSIS method and Design of Experiment (DoE) are used together to identify critical selection attributes and their interactions of all these cases by fitting a polynomial to the experimental data in a multiple linear regression analysis. This mathematical model development process involves TOPSIS experiments with the model. The regression meta-model greatly reduced the cost, time and amount of the calculation step in application the TOPSIS model. Application results were validated and shown that they provide good approximations to four decision making problems results in the literature. © 2011 Elsevier Ltd. All rights reserved.
Karakayali F.Y.,Baskent University
World Journal of Gastroenterology | Year: 2014
Acute pancreatitis is one of the most common gastrointestinal disorders worldwide. It requires acute hospitalization, with a reported annual incidence of 13 to 45 cases per 100000 persons. In severe cases there is persistent organ failure and a mortality rate of 15% to 30%, whereas mortality of mild pancreatitis is only 0% to 1%. Treatment principles of necrotizing pancreatitis and the role of surgery are still controversial. Despite surgery being effective for infected pancreatic necrosis, it carries the risk of long-term endocrine and exocrine deficiency and a morbidity and mortality rate of between 10% to 40%. Considering high morbidity and mortality rates of operative necrosectomy, minimally invasive strategies are being explored by gastrointestinal surgeons, radiologists, and gastroenterologists. Since 1999, several other minimally invasive surgical, endoscopic, and radiologic approaches to drain and debride pancreatic necrosis have been described. In patients who do not improve after technically adequate drainage, necrosectomy should be performed. When minimal invasive management is unsuccessful or necrosis has spread to locations not accessible by endoscopy, open abdominal surgery is recommended. Additionally, surgery is recognized as a major determinant of outcomes for acute pancreatitis, and there is general agreement that patients should undergo surgery in the late phase of the disease. It is important to consider multidisciplinary management, considering the clinical situation and the comorbidity of the patient, as well as the surgeons experience. © 2014 Baishideng Publishing Group Inc. All rights reserved.
Azreg-Ainou M.,Baskent University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014
We drop the complexification procedure from the Newman-Janis algorithm and introduce more physical arguments and symmetry properties, and we show how one can generate regular and singular rotating black hole and non-black-hole solutions in Boyer-Lindquist coordinates. We focus on generic rotating regular black holes and show that they are regular on the Kerr-like ring, but physical entities are undefined there. We show that rotating regular black holes have much smaller electric charges, and, with increasing charge, they turn into regular non-black-hole solutions well before their Kerr-Newman counterparts become naked singularities. No causality violations occur in the region inside a rotating regular black hole. The separability of the Hamilton-Jacobi equation for neutral particles is also carried out in the generic case, and the innermost boundaries of circular orbits for particles are briefly discussed. Other, but special, properties pertaining to the rotating regular counterpart of the Ayón-Beato-García regular static black hole are also investigated. © 2014 American Physical Society.
Azreg-Ainou M.,Baskent University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014
Using a new metric for generating rotating solutions, we derive in a general fashion the solution of an imperfect fluid and that of its conformal homolog. We discuss the conditions that the stress-energy tensors and invariant scalars be regular. On classical physical grounds, it is stressed that conformal fluids used as cores for static or rotating solutions are exempt from any malicious behavior in that they are finite and defined everywhere. © 2014 The Author.