227 research outputs found
First-order symmetrizable hyperbolic formulations of Einstein's equations including lapse and shift as dynamical fields
First-order hyperbolic systems are promising as a basis for numerical
integration of Einstein's equations. In previous work, the lapse and shift have
typically not been considered part of the hyperbolic system and have been
prescribed independently. This can be expensive computationally, especially if
the prescription involves solving elliptic equations. Therefore, including the
lapse and shift in the hyperbolic system could be advantageous for numerical
work. In this paper, two first-order symmetrizable hyperbolic systems are
presented that include the lapse and shift as dynamical fields and have only
physical characteristic speeds.Comment: 11 page
DIANA Scheduling Hierarchies for Optimizing Bulk Job Scheduling
The use of meta-schedulers for resource management in large-scale distributed
systems often leads to a hierarchy of schedulers. In this paper, we discuss why
existing meta-scheduling hierarchies are sometimes not sufficient for Grid
systems due to their inability to re-organise jobs already scheduled locally.
Such a job re-organisation is required to adapt to evolving loads which are
common in heavily used Grid infrastructures. We propose a peer-to-peer
scheduling model and evaluate it using case studies and mathematical modelling.
We detail the DIANA (Data Intensive and Network Aware) scheduling algorithm and
its queue management system for coping with the load distribution and for
supporting bulk job scheduling. We demonstrate that such a system is beneficial
for dynamic, distributed and self-organizing resource management and can assist
in optimizing load or job distribution in complex Grid infrastructures.Comment: 8 pages, 9 figures. Presented at the 2nd IEEE Int Conference on
eScience & Grid Computing. Amsterdam Netherlands, December 200
Highly efficient potentiometric glucose biosensor based on functionalized InN quantum dots
We present a fast, highly sensitive, and efficient potentiometric glucose biosensor based on functionalized InN quantum-dots (QDs). The InN QDs are grown by molecular beam epitaxy. The InN QDs are bio-chemically functionalized through physical adsorption of glucose oxidase (GOD). GOD enzyme-coated InN QDs based biosensor exhibits excellent linear glucose concentration dependent electrochemical response against an Ag/AgCl reference electrode over a wide logarithmic glucose concentration range (1âĂâ10â5 M to 1âĂâ10â2 M) with a high sensitivity of 80âmV/decade. It exhibits a fast response time of less than 2âs with good stability and reusability and shows negligible response to common interferents such as ascorbic acid and uric acid. The fabricated biosensor has full potential to be an attractive candidate for blood sugar concentration detection in clinical diagnoses
Single nanowire-based UV photodetectors for fast switching
Relatively long (30 ”m) high quality ZnO nanowires (NWs) were grown by the vapor-liquid-solid (VLS) technique. Schottky diodes of single NW were fabricated by putting single ZnO NW across Au and Pt electrodes. A device with ohmic contacts at both the sides was also fabricated for comparison. The current-voltage (I-V) measurements for the Schottky diode show clear rectifying behavior and no reverse breakdown was seen down to -5 V. High current was observed in the forward bias and the device was found to be stable up to 12 V applied bias. The Schottky barrier device shows more sensitivity, lower dark current, and much faster switching under pulsed UV illumination. Desorption and re-adsorption of much smaller number of oxygen ions at the Schottky junction effectively alters the barrier height resulting in a faster response even for very long NWs. The NW was treated with oxygen plasma to improve the switching. The photodetector shows high stability, reversibility, and sensitivity to UV light. The results imply that single ZnO NW Schottky diode is a promising candidate for fabricating UV photodetectors
Time-symmetric initial data for binary black holes in numerical relativity
We look for physically realistic initial data in numerical relativity which
are in agreement with post-Newtonian approximations. We propose a particular
solution of the time-symmetric constraint equation, appropriate to two
momentarily static black holes, in the form of a conformal decomposition of the
spatial metric. This solution is isometric to the post-Newtonian metric up to
the 2PN order. It represents a non-linear deformation of the solution of Brill
and Lindquist, i.e. an asymptotically flat region is connected to two
asymptotically flat (in a certain weak sense) sheets, that are the images of
the two singularities through appropriate inversion transformations. The total
ADM mass M as well as the individual masses m_1 and m_2 (when they exist) are
computed by surface integrals performed at infinity. Using second order
perturbation theory on the Brill-Lindquist background, we prove that the
binary's interacting mass-energy M-m_1-m_2 is well-defined at the 2PN order and
in agreement with the known post-Newtonian result.Comment: 27 pages, to appear in Phys. Rev.
Dynamical Gauge Conditions for the Einstein Evolution Equations
The Einstein evolution equations have been written in a number of symmetric
hyperbolic forms when the gauge fields--the densitized lapse and the shift--are
taken to be fixed functions of the coordinates. Extended systems of evolution
equations are constructed here by adding the gauge degrees of freedom to the
set of dynamical fields, thus forming symmetric hyperbolic systems for the
combined evolution of the gravitational and the gauge fields. The associated
characteristic speeds can be made causal (i.e. less than or equal to the speed
of light) by adjusting 14 free parameters in these new systems. And 21
additional free parameters are available, for example to optimize the stability
of numerical evolutions. The gauge evolution equations in these systems are
generalizations of the ``K-driver'' and ``Gamma-driver'' conditions that have
been used with some success in numerical black hole evolutions.Comment: New appendix on constraint evolution adde
Immunoparesis defined by heavy plus light chain suppression is a novel marker of long-term outcomes in cardiac AL amyloidosis
Cardiac involvement and presenting dFLC (difference between involved and uninvolved free light chains) are independent predictors of outcome in systemic AL amyloidosis. These markers have limited prognostic utility in patients surviving the initial months following diagnosis. Here we assessed immunoparesis, as determined by novel heavy+light chain (HLC) immunoassays, as a prognostic marker for survival in AL amyloidosis. HLC measurements identified immunoparesis of at least one immunoglobulin (Ig) isotype in 145 (85%) patients; and severe immunoparesis (â„2 Ig isotypes suppressed by >50% below normal levels) in 29 (17%) patients. Median overall survival (OS) on intention to treat (ITT) analysis was 26·2 months. In the ITT cohort, dFLC >180 mg/l was associated with shorter OS (P = 0·05); whereas HLC immunoparesis was not prognostic. On a landmark analysis of 127 patients alive at 6 months, presenting dFLC was not prognostic for OS (P = 0·33) and severe HLC immunoparesis trended towards poorer survival (20·2 vs. 42·8 months; P = 0·09). In the subset of patients with cardiac involvement, severe HLC immunoparesis conferred very poor outcome (median OS 8·8 vs. 29·9 months, P = 0·007). In conclusion, severe HLC immunoparesis is an independent marker of long-term poor prognosis in AL patients with cardiac involvement. The pathophysiological significance of this observation needs further study
From Geometry to Numerics: interdisciplinary aspects in mathematical and numerical relativity
This article reviews some aspects in the current relationship between
mathematical and numerical General Relativity. Focus is placed on the
description of isolated systems, with a particular emphasis on recent
developments in the study of black holes. Ideas concerning asymptotic flatness,
the initial value problem, the constraint equations, evolution formalisms,
geometric inequalities and quasi-local black hole horizons are discussed on the
light of the interaction between numerical and mathematical relativists.Comment: Topical review commissioned by Classical and Quantum Gravity.
Discussion inspired by the workshop "From Geometry to Numerics" (Paris, 20-24
November, 2006), part of the "General Relativity Trimester" at the Institut
Henri Poincare (Fall 2006). Comments and references added. Typos corrected.
Submitted to Classical and Quantum Gravit
Risk factors of gallbladder cancer in Karachi-a case-control study
<p>Abstract</p> <p>Background</p> <p>Gallbladder carcinoma (GC) is a relatively rare malignancy worldwide but is the second commonest gastrointestinal cancer in Pakistani women. Gallstones have a positive association with GC but other factors also influence in causation.</p> <p>Methods</p> <p>This is a retrospective case control study over a period of 19 years. The cases (Group A) were patients with histopathological proven carcinoma gallbladder (N = 60) and controls were patients with cholelithiasis but no carcinoma gallbladder on histopathology (N = 120). Multivariate regression analysis was done to calculate the odds ratio, 95% confidence interval and P-Value. A positive relationship was found between size of stone > 1 cm, solitary stone, age > 55 years and multi-parity in women.</p> <p>Results</p> <p>There were 60 patients in Group A and 120 patients in Group B. mean age of diagnosis in Group A patients was 57 ± 2.4 years while mean age of diagnosis in Group B patients was 48 ± 1.35 years. Sixty seven percent of cancer group patients were female as compared to 78% females in non-cancer group. In Group A, 69% of female patients were multiparous (parity of more than 5) while 43% of group B patients were multiparous. For body mass index (BMI), both groups were not very different in our study population i.e. around 78% patients in each group has BMI of more than 23 Kg/m2. In Group A, 37% (n = 22) have solitary stones as compared to 15% (n = 18) in group B. similarly Group A patients has larger stone size as compared to Group B i.e.59% (n = 36) patients in Group A have stones of more than 1 cm when compared to 35% (n = 41) patients in Group B. After using multivariate regression analysis, age more than 55 years (OR - 7.27, p value- < 0.001), solitary stone (OR - 3.33, p value - 0.002) and stone of more than 1 cm (OR - 2.73, p value - 0.004) were found to be independent risk factors for development of gallbladder cancer.</p> <p>Conclusion</p> <p>Most of the patients (78%) with GC were female, and the statistically significant risk factors were older age, solitary stones and stones size more than one centimeter. A case can be made for prophylactic cholecystectomy in such a high risk group. However a population based study is required to calculate the true incidence of GC in Karachi and a prospective multi center study is needed to produce strong evidence for screening and prophylactic cholecystectomy.</p> <p>Trial Registration</p> <p>As this was a retrospective review of medical records, as per institution policy, its gives waiver from any registration (ethical/trial).</p
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