Geometric Bounds in Spherically Symmetric General Relativity

We exploit an arbitrary extrinsic time foliation of spacetime to solve the constraints in spherically symmetric general relativity. Among such foliations there is a one parameter family, linear and homogeneous in the extrinsic curvature, which permit the momentum constraint to be solved exactly. This family includes, as special cases, the extrinsic time gauges that have been exploited in the past. These foliations have the property that the extrinsic curvature is spacelike with respect to the the spherically symmetric superspace metric. What is remarkable is that the linearity can be relaxed at no essential extra cost which permits us to isolate a large non - pathological dense subset of all extrinsic time foliations. We identify properties of solutions which are independent of the particular foliation within this subset. When the geometry is regular, we can place spatially invariant numerical bounds on the values of both the spatial and the temporal gradients of the scalar areal radius, $R$. These bounds are entirely independent of the particular gauge and of the magnitude of the sources. When singularities occur, we demonstrate that the geometry behaves in a universal way in the neighborhood of the singularity.Comment: 16 pages, revtex, submitted to Phys. Rev.

Directivity enhancement and deflection of the beam emitted from a photonic crystal waveguide via defect coupling

Cataloged from PDF version of article.We experimentally and numerically investigate the spatial distribution of the emission from a photonic crystal waveguide, coupled with defects, that are located at the output edge. Two defects that are located symmetrically enhance the directivity of the beam compared to that of a plain waveguide, as was reported in recently conducted theoretical work. We further demonstrate that a single defect deflects of the beam. By choosing the defect resonance that is close to the edge of the pass band of the waveguide, where the group velocity of the beam within the waveguide is slow, a significant amount of deflection can be achieved. (c) 2007 Optical Society of Americ

Covariant perturbations of domain walls in curved spacetime

A manifestly covariant equation is derived to describe the perturbations in a domain wall on a given background spacetime. This generalizes recent work on domain walls in Minkowski space and introduces a framework for examining the stability of relativistic bubbles in curved spacetimes.Comment: 15 pages,ICN-UNAM-93-0

Effects of Age and Comorbidities on Intensive Care and 1-year Mortality after HeartMate 3 Implantation

Background: The use of left ventricular assist devices (LVAD) has been rapidly increasing in older people over the past two decades due to their availability as destination therapy. This study aimed to assess the effect of age and comorbidities on the intensive care unit (ICU) and 1-year mortality after HeartMate 3 LVAD implantation. Methods: From 2016 to 2023, all consecutive adult patients implanted with HeartMate 3 LVAD in our tertiary referral center were enrolled in the study. Patients were stratified according to their age at implantation into Group-1 (&lt;45 years), Group-2 (46–64 years), and Group-3 (&gt;65 years). The effect of age and comorbidities on ICU and 1-year mortality were assessed. Results: In total, 135 patients were included (mean age 54±13 years, 79% males). Baseline vital signs, comorbidities, and hemodynamic support were not different between age groups. The older population had significantly lower eGFR (p=0.025), ischemic cardiac diseases as the underlying heart problem (p&lt;0.001), and LVAD as destination therapy (p&lt;0.001). The mortality rate at the ICU and at one year were 90% and 83%, respectively. The median age of the patients who died in the ICU was significantly higher than 63 [56–65] years versus 57 years [49–62, p=0.034). However, age lost its significance with logistic regression analysis. Having a recent major myocardial infarct, high preoperative leukocyte count, and cardiopulmonary bypass time were independent risk factors for ICU mortality. On the other hand, age was an independent risk factor for one-year mortality. Conclusion: Older age predicts increased one-year but not ICU mortality after HeartMate 3 LVAD implantation, while recent major myocardial infarction, high preoperative leukocyte count, and longer cardiopulmonary bypass time were independent risk factors for ICU mortality. Careful patient selection is critical to optimize outcomes after HeartMate 3 LVAD implantation.</p

Observation of negative refraction and negative phase velocity in left-handed metamaterials

Cataloged from PDF version of article.We report the transmission characteristics of a two-dimensional (2D) composite metamaterial (CMM) structure in free space. At the frequencies where left-handed transmission takes place, we experimentally confirmed that the CMM structure has effective negative refractive index. Phase shift between consecutive numbers of layers of CMM is measured and phase velocity is shown to be negative at the relevant frequency range. Refractive index values obtained from the refraction experiments and the phase measurements are in good agreement. (C) 2005 American Institute of Physics

Hamilton's equations for a fluid membrane: axial symmetry

Consider a homogenous fluid membrane, or vesicle, described by the Helfrich-Canham energy, quadratic in the mean curvature. When the membrane is axially symmetric, this energy can be viewed as an `action' describing the motion of a particle; the contours of equilibrium geometries are identified with particle trajectories. A novel Hamiltonian formulation of the problem is presented which exhibits the following two features: {\it (i)} the second derivatives appearing in the action through the mean curvature are accommodated in a natural phase space; {\it (ii)} the intrinsic freedom associated with the choice of evolution parameter along the contour is preserved. As a result, the phase space involves momenta conjugate not only to the particle position but also to its velocity, and there are constraints on the phase space variables. This formulation provides the groundwork for a field theoretical generalization to arbitrary configurations, with the particle replaced by a loop in space.Comment: 11 page

Modelovanje pražnjenja creva evropskog brancina dicentrarachus labrax l.

Digestion physiology of an animal is important since it is essential source of information for aquaculture and also it helps to outline the rule of such animal in the aquatic food web. Especially it is vital for the management issues of the living resources concerning multispecies VPA. Bearing in mind, sea bass is a one of the most important sea fish having high salinity and temperature tolerance and commercial value not only in Turkey, but in the European countries as well. It has growing culturing potential in Turkey and Europe, but not much detailed studies concerned feeding and digestion physiology have been performed yet. In this study, digestion physiology; gastric emptying in Dicentrarchus labrax force fed on artificial (formulated) food will be investigated. Factors affecting gastric emptying rate (GER) and time (GET) in sea bass will be studied. An attempt will also be made to model GER and GET in sea bass. Food consumption and feeding periodicity and return of appetite of sea bass will also be worked out

The Constraints in Spherically Symmetric General Relativity II --- Identifying the Configuration Space: A Moment of Time Symmetry

We continue our investigation of the configuration space of general relativity begun in I (gr-qc/9411009). Here we examine the Hamiltonian constraint when the spatial geometry is momentarily static (MS). We show that MS configurations satisfy both the positive quasi-local mass (QLM) theorem and its converse. We derive an analytical expression for the spatial metric in the neighborhood of a generic singularity. The corresponding curvature singularity shows up in the traceless component of the Ricci tensor. We show that if the energy density of matter is monotonically decreasing, the geometry cannot be singular. A supermetric on the configuration space which distinguishes between singular geometries and non-singular ones is constructed explicitly. Global necessary and sufficient criteria for the formation of trapped surfaces and singularities are framed in terms of inequalities which relate appropriate measures of the material energy content on a given support to a measure of its volume. The strength of these inequalities is gauged by exploiting the exactly solvable piece-wise constant density star as a template.Comment: 50 pages, Plain Tex, 1 figure available from the authors

Note on flat foliations of spherically symmetric spacetimes

It is known that spherically symmetric spacetimes admit flat spacelike foliations. We point out a simple method of seeing this result via the Hamiltonian constraints of general relativity. The method yields explicit formulas for the extrinsic curvatures of the slicings.Comment: 4 pages, to appear in PRD, reference added, typos correcte