Clumps of material orbiting a black hole and the QPOs

Clumps of material orbiting a black hole may be disturbed, somewhat like comets in the Kuiper belt, to relatively small periastron orbits. Each periastron passage changes the orbital parameters in such a way that the orbit becomes more and more eccentric and the angular momentum approaches the critical value for tidal capture. When this value is reached, the body is suddenly caught by the relativistic potential to the last periastron (occurring at two Schwarzschild radii for a non rotating black hole). In this process the transfer of orbital into internal energy heats the body before it makes a few more turns toward the horizon of the black hole. Because of strong relativistic effects this last bright message from the object is seen as a quasi-periodic flare. Assuming that a black hole may be fed by a large number of such small debris we calculate light curves expected from such events. We investigate the resemblance of the Fourier spectra of such light curves with those of observed QPOs.Comment: 3 pages, 6 figure

Do flares in Sagittarius A* reflect the last stage of tidal capture?

In recent years the case for the presence of 3-4 10^6 M_sun black hole in our Galactic Center has gained strength from results of stellar dynamics observations and from the detection of several rapid X-ray and IR flares observed in the Sagittarius A* from 2000 to 2004. Here we explore the idea that such flares are produced when the central black hole tidally captures and disrupts a small body - e.g. a comet or an asteroid.Comment: 6 pages, 9 figures, acknowledgments added, to appear in the Proceedings of the Albert Einstein's Century International Conference, Paris 200

Cross-Border Investment, Conflict of Laws, and the Privatization of Securities Law

The rapid acceleration of transnational investing is occurring in an environment in which emerging markets, and foreign interest in these markets, are exploding. The issues involved with cross-border investment, conflict of laws and the privatization of securities law are examined

Quantification of the early pupillary dilation kinetic to assess rod and cone activity.

Rods, cones and melanopsin contribute in various proportions, depending on the stimulus light, to the pupil light response. This study used a first derivative analysis to focus on the quantification of the dynamics of pupillary dilation that immediately follows light-induced pupilloconstriction in order to identify novel parameters that reflect rod and cone activity. In 18 healthy adults, the pupil response to a 1 s blue light stimulus ranging from - 6.0 to 2.65 log cd/m <sup>2</sup> in dark-adapted conditions and to a 1 s blue light stimulus (2.65 log cd/m <sup>2</sup> ) in light-adapted conditions was recorded on a customized pupillometer. Three derivative parameters which describe the 2.75 s following the light onset were quantified: dAMP (maximal amplitude of the positive peak), dLAT (latency of the positive peak), dAUC (area under the curve of the positive peak). We found that dAMP and dAUC but not dLAT have graded responses over a range of light intensities. The maximal positive value of dAMP, representing maximal rate of change of early pupillary dilation phase, occurs at - 1.0 log cd/m <sup>2</sup> and this stimulus intensity appears useful for activating rods and cones. From - 0.5 log cd/m <sup>2</sup> to brighter intensities dAMP and dAUC progressively decrease, reaching negligible values at 2.65 log cd/m <sup>2</sup> indicative of a melanopsin-driven pupil response that masks the contribution from rods and cones to the early phase of pupillary dilation

Compression and strength behaviour of viscose/polypropylene nonwoven fabrics

Compression and strength properties of viscose/polypropylene nonwoven fabrics has been studied. Compressionbehavior of the nonwoven samples (sample compressibility, sample thickness loss & sample compressive resilience) havebeen analyzed considering the magnitude of applied pressure, fabric weight, fabric thickness, and the porosity of thesamples. Based on the calculated porosity of the samples, pore compression behavior (pore compressibility, porosity loss &pore compressive resilience) are determined. Equations for the determination of pore compressibility, porosity loss, and porecompressive resilience, are established. Tensile strength and elongation as well as bursting strength and ball traverseelongation are also determined. The results show that the sample compression behavior as well as pore compressionbehavior depend on the magnitude of applied pressure. At the high level of applied pressure, a sample with highercompressibility has the lower sample compressive resilience. Differences in pore compressibility and porosity loss betweeninvestigated samples have also been registered, except in pore compressive resilience. Sample with the higher fabric weight,higher thickness, and lower porosity shows the lower sample compressibility, pore compressibility, sample thickness loss,porosity loss, and tensile elongation, but the higher tensile strength, bursting strength, and ball traverse elongation

Design of Proportional-Resonant Control for Current Harmonic Compliance in Electric Railway Power Systems

This paper presents the process of designing proportional-resonant controller for a four-quadrant rectifier in electric railway traction system. In the context of ever-stricter power quality and electromagnetic compatibility standards in electric railway power systems, developers of electric locomotives need to adapt with new ways to comply. This paper develops on the process of designing a four-quadrant rectifier proportional-resonant control for mitigation of low frequency current harmonic distortion, a novel method in the field of railway EMC. The control parameters are determined through analytical modeling of the rectifier through transfer functions. For the purpose of studying the harmonic distortion mitigation effects, only the current control loop was modeled and designed. The modeling starts with simplification of the model via large-signal modeling of the power converter. The parameters of the circuit then were used to develop the transfer functions, and select the appropriate parameter values of the current loop plant. The control loop and parameters were evaluated on test locomotive to validate the control, with results confirming the improved impact on the electromagnetic compatibility and conformity to regulation

Paramagnetic Meissner Effect in Multiply-Connected Superconductors

We have measured a paramagnetic Meissner effect in Nb-Al2O3-Nb Josephson junction arrays using a scanning SQUID microscope. The arrays exhibit diamagnetism for some cooling fields and paramagnetism for other cooling fields. The measured mean magnetization is always less than 0.3 flux quantum (in terms of flux per unit cell of the array) for the range of cooling fields investigated. We demonstrate that a new model of magnetic screening, valid for multiply-connected superconductors, reproduces all of the essential features of paramagnetism that we observe and that no exotic mechanism, such as d-wave superconductivity, is needed for paramagnetism.Comment: 4 pages, 3 figures, LaTe

Fracture mechanics of laser sintered cracked polyamide for a new method to induce cracks by additive manufacturing

This paper presents an experimental investigation on specimens manufactured by Selective Laser Sintering (SLS), with the purposes of giving designers advice when designing 3D printed parts, and laying the basis for a step forward in the field of fracture mechanics of 3D complex parts. The aim is to investigate the effect of building direction in Polyamide (PA) 3D printed samples and to assess whether a crack can be initiated directly from the sintering process for fracture mechanics study purposes. Six different configurations of Mode I Compact Tension (CT) specimens were manufactured and tested; the experiments were monitored by Digital Image Correlation (DIC) and fractured surfaces were analyzed using microscopy. Results showed that samples with better mechanical performance are those in which all the layers contain a portion of the crack. On the other hand, those with layers parallel to the crack plan offer a preferential pathway for the crack to propagate. DIC and fractography investigations showed that, under certain conditions, small-radius geometries, or too-close surfaces may glue depending on printer resolution. Experiments also showed that SLS is capable of printing specimens with internal cracks that can be used to study fracture mechanics of complex parts or parts with internal cracks

Determination of Rod and Cone Influence to the Early and Late Dynamic of the Pupillary Light Response.

PURPOSE: This study aims to identify which aspects of the pupil light reflex are most influenced by rods and cones independently by analyzing pupil recordings from different mouse models of photoreceptor deficiency. METHODS: One-month-old wild type (WT), rodless (Rho-/-), coneless (Cnga3-/-), or photoreceptor less (Cnga3-/-; Rho-/- or Gnat1-/-) mice were subjected to brief red and blue light stimuli of increasing intensity. To describe the initial dynamic response to light, the maximal pupillary constriction amplitudes and the derivative curve of the first 3 seconds were determined. To estimate the postillumination phase, the constriction amplitude at 9.5 seconds after light termination was related to the maximal constriction amplitude. RESULTS: Rho-/- mice showed decreased constriction amplitude but more prolonged pupilloconstriction to all blue and red light stimuli compared to wild type mice. Cnga3-/- mice had constriction amplitudes similar to WT however following maximal constriction, the early and rapid dilation to low intensity blue light was decreased. To high intensity blue light, the Cnga3-/- mice demonstrated marked prolongation of the pupillary constriction. Cnga3-/-; Rho-/- mice had no pupil response to red light of low and medium intensity. CONCLUSIONS: From specific gene defective mouse models which selectively voided the rod or cone function, we determined that mouse rod photoreceptors are highly contributing to the pupil response to blue light stimuli but also to low and medium red stimuli. We also observed that cone cells mainly drive the partial rapid dilation of the initial response to low blue light stimuli. Thus photoreceptor dysfunction can be derived from chromatic pupillometry in mouse models