Linear constraints from generally covariant systems with quadratic constraints

How to make compatible both boundary and gauge conditions for generally covariant theories using the gauge symmetry generated by first class constraints is studied. This approach employs finite gauge transformations in contrast with previous works which use infinitesimal ones. Two kinds of variational principles are taken into account; the first one features non-gauge-invariant actions whereas the second includes fully gauge-invariant actions. Furthermore, it is shown that it is possible to rewrite fully gauge-invariant actions featuring first class constraints quadratic in the momenta into first class constraints linear in the momenta (and homogeneous in some cases) due to the full gauge invariance of their actions. This shows that the gauge symmetry present in generally covariant theories having first class constraints quadratic in the momenta is not of a different kind with respect to the one of theories with first class constraints linear in the momenta if fully gauge-invariant actions are taken into account for the former theories. These ideas are implemented for the parametrized relativistic free particle, parametrized harmonic oscillator, and the SL(2,R) model.Comment: Latex file, revtex4, 18 pages, no figures. This version includes the corrections to many misprints of v1 and also the ones of the published version. The conceptual and technical parts of the paper are not altere

Immirzi Ambiguity in the Kinematics of Quantum General Relativity

The Immirzi ambiguity arises in loop quantum gravity when geometric operators are represented in terms of different connections that are related by means of an extended Wick transform. We analyze the action of this transform in gravity coupled with matter fields and discuss its analogy with the Wick rotation on which the Thiemann transform between Euclidean and Lorentzian gravity is based. In addition, we prove that the effect of this extended Wick transform is equivalent to a constant scale transformation as far as the symplectic structure and kinematical constraints are concerned. This equivalence is broken in the dynamical evolution. Our results are applied to the discussion of the black hole entropy in the limit of large horizon areas. We first argue that, since the entropy calculation is performed for horizons of fixed constant area, one might in principle choose an Immirzi parameter that depends on this quantity. This would spoil the linearity with the area in the entropy formula. We then show that the Immirzi parameter appears as a constant scaling in all the steps where dynamical information plays a relevant role in the entropy calculation. This fact, together with the kinematical equivalence of the Immirzi ambiguity with a change of scale, is used to preclude the potential non-linearity of the entropy on physical grounds.Comment: very minor stylistic changes, version published in Phys. Rev.

Loop quantum gravity and light propagation

Within loop quantum gravity we construct a coarse-grained approximation for the Einstein-Maxwell theory that yields effective Maxwell equations in flat spacetime comprising Planck scale corrections. The corresponding Hamiltonian is defined as the expectation value of the electromagnetic term in the Einstein-Maxwell Hamiltonian constraint, regularized a la Thiemann, with respect to a would-be semiclassical state. The resulting energy dispersion relations entail Planck scale corrections to those in flat spacetime. Both the helicity dependent contribution of Gambini and Pullin [GP] and, for a value of a parameter of our approximation, that of Ellis et. al. [ELLISETAL] are recovered. The electric/magnetic asymmetry in the regularization procedure yields nonlinearities only in the magnetic sector which are briefly discussed. Observations of cosmological Gamma Ray Bursts might eventually lead to the needed accuracy to study some of these quantum gravity effects.Comment: Latex, 45 pages, shorter abstract, additional reference

Validation of Picture Free and Cued Selective Reminding Test for Illiteracy in Lima, Peru

Dementia in Latin America is a crucial public health problem. Identifying brief cognitive screening (BCS) tools for the primary care setting is crucial, particularly for illiterate individuals. We evaluated tool performance characteristics and validated the free and total recall sections of the Free and Cued Selective Reminding Test-Picture version (FCSRT-Picture) to discriminate between 63 patients with early Alzheimer?s disease dementia (ADD), 60 amnestic mild cognitive impairment (aMCI) and 64 cognitively healthy Peruvian individuals with illiteracy from an urban area. Clinical, functional, and cognitive assessments were performed. FCSRT-Picture performance was assessed using receiver operating characteristic curve analyses. The mean ± standard deviation scores were 7.7 ± 1.0 in ADD, 11.8 ± 1.6 in aMCI, and 29.5 ± 1.8 in controls. The FCSRT-Picture had better performance characteristics for distinguishing controls from aMCI compared with several other BCS tools, but similar characteristics between controls and early ADD. The FCSRT-Picture is a reliable BCS tool for illiteracy in Peru

1873-1874, End of a Century?: Time and Space in Valera's Pepita Jiménez, Ros de Olano's Jornadas de retorno, and Alarcón's El sombrero de tres picos and La Alpujarra

This article argues for the existence of a literature of the first Spanish Republic in the early 1870s. Valera's Pepita Jimenez makes sense in relation to this literature, rather than in comparison with 'Realism'. The literature of the first republic is distinguished by two facets: an ongoing dialogue with Ros de Olano's experiments in simultaneous compression and extension of form; and a belief that the nineteenth-century revolutionary spirit of the age has reached a critical end point, and needs reinvention that leads to Restoration politics

PARTNeR, a Radio Astronomy experience for students

PARTNeR is the acronym for Academic Project with the NASA Radio Telescope at Robledo. The 34-m antenna in Robledo de Chavela is used by high schools, universities and amateur astronomers to learn about radioastronomy, physics and to get interested in science. The main project we develop is the observations of radio-bursts in X-ray binaries.
The high-school teachers joining our program take a training course to learn the basis of radioastronomy. Some practical lessons to teach the children the physical fundamentals of radioastronomy are also given to them.
The operational phase of the project started in 2004, and 25 high schools, 5 universities and 4 societies of amateur astronomers have been involved in the project

Left ventricle postinfarction pseudoaneurysm: Anatomical forms and surgical management

Introduction: Left Ventricle Postinfarction Pseudoaneurysm (LVPS)—false aneurysm occurs after a free-wall rupture contained by the adjacent pericardium. LVPS lacks the normal structure of the ventricular wall and disrupts the normal chamber anatomy. However, the natural history, clinical presentation and surgical outcome are still unclear. For that reason, it is necessary to describe the most relevant anatomical characteristics of LVPS and the appropriate surgical strategies currently applied. Methods: We reviewed the anatomical characteristics of several patients diagnosed of LVPS and the surgical technique performed. In this work two different anatomical types of LVPS are described in detail, with the surgical and structural implications for left ventricle reconstruction. Results: There are two different anatomical forms of LVPS: 1) Typical pseudoaneurysm, with a small gateway neck between the Left Ventricle and the false aneurysm chamber (Figure 1(A)); 2) Atypical pseudoaneurysm, in which the anatomical defect is bigger, without well-defined edges, extends over a large segment of infarcted and thinned myocardial tissue. In both cases, the therapeuticstargets and the surgical techniques used were directed to restore the normal geometry ofLeft Ventricle, keeping the optimal mitral valve function. Conclusions: The surgical key-step is to preserve or to remodel the ventricular chamber anatomy. This fact restores the ventricular geometry, not only removing the wall discontinuity that generated the pseudoaneurysm. Nevertheless, final prognosis depends on the underlying ischemic cardiomyopathy and mechanical complications, such us mitral regurgitation or ventricular septal defect.No data (2014)UE

Immunocytochemical developmental patterns of the thoracolumbar sympathetic chain in the chick and a comparison with its adrenal counterpart

The immunocytochemical development of the thoracolumbar sympathetic ganglion and its adrenal counterpart was studied in the chick from days 3.5 to 12 of incubation, using antibodies to 17 separate antigens, including antibodies to pan-neuroendocrine markers, catecholamine-synthesizing and proprotein-processing enzymes, and neuropeptides. Some of the antigens studied (Go protein-a subunit, thyrosine hydroxylase, and galanin) were strongly expressed from the first days of development, whereas others (chromogranin-A, chromogranin-B, 7B2 protein, and somatostatin) showed a diverse immunoreactive expression at different stages. Three different patterns were found in the development of both adrenal medulla and thoracolumbar sympathetic ganglion. In the first (chromogranin-A and B, Go protein-a subunit, tyrosine hydroxylase, HNK-1, and galanin), virtually all medullary and thoracolumbar sympathetic ganglion cells were strongly immunostained from day 4 onward. Except for HNK-1, chromogranin-A and B, there was a steady increase in immunoreactive cells for all the remaining antigens up to day 12. In the second (7B2 protein, proprotein convertase 2, and secretogranin II), full antigenic expression was reached in medullary and thoracolumbar sympathetic ganglion cells by day 10. In the third pattern (proprotein convertase 3, somatostatin, dopamine-ß-hydroxylase, neuron-specific enolase, vasoactive intestinal polypeptide, and met-enkephalin), differences in immunoreactivity were observed between the medullary and thoracolumbar sympathetic ganglion cells

Flow cytometric identification and enumeration of photosynthetic sulfur bacteria and potential for ecophysiological studies at the single-cell level

17 páginas, 9 figuras, 2 tablas.We show the potential of flow cytometry as a fast tool for population identification and enumeration of photosynthetic sulfur bacteria. Purple (PSB) and green sulfur bacteria (GSB) oxidize hydrogen sulfide to elemental sulfur that can act as storage compound to be further oxidized to sulfate generating the reducing power required for growth. Both groups have different elemental sulfur allocation strategies: whereas PSB store elemental sulfur as intracellular inclusions, GSB allocate sulfur globules externally. We used well-characterized laboratory strains and complex natural photosynthetic populations developing in a sharply stratified meromictic lake to show that PSB and GSB could be detected, differentiated and enumerated in unstained samples using a blue laser-based flow cytometer. Variations in cell-specific pigment content and the dynamics of sulfur accumulation, both intra- and extracellularly, were also detected in flow cytometric plots as sulfur accumulation changed the light scatter characteristics of the cells. These data were used to show the potential for studies on the metabolic status and the rate of activity at the single-cell level. Flow cytometric identification and enumeration resulted in faster and more precise analyses than previous approaches, and may open the door to more complex ecophysiological experiments with photosynthetic sulfur bacteria in mixed cultures and natural environments.This work was financed by the coordinated project VIARC Grant No. REN2003-08333 to E.O.C. and C.M.B. and MicroDiff and Modivus Grants REN2001-2120/MAR and CTM2005-04795/MAR to J.M.G. from the Spanish Ministerio de Educación y Ciencia (MEC). We thank J. Mas for support and lab facilities at the Department of Genetics and Microbiology, Autonomous University of Barcelona. E.O.C. benefits from the Program Ramon y Cajal of the Spanish MEC and FEDER.Peer reviewe