Geometry of the quantum complex projective spaceCP q (N)

We study the constraints from theb→sγ decay in the parameter space of effective supergravities from orbifold string theory and with minimal supesymmetric particle content. Both the general dilaton-dominated universal scenario as well as a non-universal scenario for the soft terms are investigated. It is found that the recently reported CLEO upper and lower bounds constrain the parameter space of the models under scrutiny. In particular we find constraints on the values of the parameter tanβ and the gluino masses. In this class of string scenarios the negative sign of the Higgs mixing parameterμ, is phenomenologically preferred.     

DESIRS: a state‐of‐the‐art VUV beamline featuring high resolution and variable polarization for spectroscopy and dichroism at SOLEIL

DESIRS is a new undulator‐based VUV beamline on the 2.75 GeV storage ring SOLEIL (France) optimized for gas‐phase studies of molecular and electronic structures, reactivity and polarization‐dependent photodynamics on model or actual systems encountered in the universe, atmosphere and biosphere. It is equipped with two dedicated endstations: a VUV Fourier‐transform spectrometer (FTS) for ultra‐high‐resolution absorption spectroscopy (resolving power up to 10⁶) and an electron/ion imaging coincidence spectrometer. The photon characteristics necessary to fulfill its scientific mission are: high flux in the 5–40 eV range, high spectral purity, high resolution, and variable and well calibrated polarizations. The photon source is a 10 m‐long pure electromagnetic variable‐polarization undulator producing light from the very near UV up to 40 eV on the fundamental emission with tailored elliptical polarization allowing fully calibrated quasi‐perfect horizontal, vertical and circular polarizations, as measured with an in situ VUV polarimeter with absolute polarization rates close to unity, to be obtained at the sample location. The optical design includes a beam waist allowing the implementation of a gas filter to suppress the undulator high harmonics. This harmonic‐free radiation can be steered toward the FTS for absorption experiments, or go through a highly efficient pre‐focusing optical system, based on a toroidal mirror and a reflective corrector plate similar to a Schmidt plate. The synchrotron radiation then enters a 6.65 m Eagle off‐plane normal‐incidence monochromator equipped with four gratings with different groove densities, from 200 to 4300 lines mm^?1, allowing the flux‐to‐resolution trade‐off to be smoothly adjusted. The measured ultimate instrumental resolving powers are 124000 (174 µeV) around 21 eV and 250000 (54 µeV) around 13 eV, while the typical measured flux is in the 10¹⁰–10¹¹ photons s^?1 range in a 1/50000 bandwidth, and 10¹²–10¹³ photons s^?1 in a 1/1000 bandwidth, which is very satisfactory although slightly below optical simulations. All of these features make DESIRS a state‐of‐the‐art VUV beamline for spectroscopy and dichroism open to a broad scientific community.     

Design principles and error analysis for reduced-shear plate-bending finite elements

Summary. In this paper, we consider the problem of designing plate-bending elements which are free of shear locking. This phenomenon is known to afflict several elements for the Reissner-Mindlin plate model when the thickness of the plate is small, due to the inability of the approximating subspaces to satisfy the Kirchhoff constraint. To avoid locking, a “reduction operator” is often applied to the stress, to modify the variational formulation and reduce the effect of this constraint. We investigate the conditions required on such reduction operators to ensure that the approximability and consistency errors are of the right order. A set of sufficient conditions is presented, under which optimal errors can be obtained – these are derived directly, without transforming the problem via a Hemholtz decomposition, or considering it as a mixed method. Our analysis explicitly takes into account boundary layers and their resolution, and we prove, via an asymptotic analysis, that convergence of the finite element approximations will occur uniformly as , even on quasiuniform meshes. The analysis is carried out in the case of a free boundary, where the boundary layer is known to be strong. We also propose and analyze a simple post-processing scheme for the shear stress. Our general theory is used to analyze the well-known MITC elements for the Reissner-Mindlin plate. As we show, the theory makes it possible to analyze both straight and curved elements. We also analyze some other elements. Received June 19, 1995     

Enclosing a Set of Objects by Two Minimum Area Rectangles

In this paper, we face the problem of computing an enclosing pair of axis-parallel rectangles of a set of polygonal objects in the plane, serving as a simple container. We propose anO(nα(n)log n) worst-case time algorithm, where α( ) is the inverse Ackermann's function, for finding, given a setMof points, segments and polygons defined bynvertices, a pair of axis-parallel rectangles (s, t) such thats∪tencloses all objects inMand area(s)+area(t) is minimum. The algorithm works inO(nα(n) log log n) worst-case space. Moreover, we prove an Ω(n log n) lower bound for the one-dimensional version of the problem. We also show that for the special case of enclosing a set of polygons with axis-parallel sides, our algorithm runs in optimal worst-case timeO(n log n), using worst-case spaceO(n log log n).     

Laser speckle decorrelation in NDT

The random noise of the laser speckle field which develops at the focusing plane of an imaging system, is, by now, efficiently used in several interferometric techniques as an information carrier of the macroscopic wavefront distortion induced by the surface displacement field of the object under investigation. The actual noise in this kind of techniques is represented by the speckle decorrelation at the image plane — i.e. the destruction of the carrier — which may be caused by the modification of the texture surface (e.g. by yielding under a severe stress state), but it is inherently produced by the same displacement field under measurement. In the paper the phenomenon of laser speckle decorrelation is numerically simulated and experimentally investigated with the aim of estimating its sensitivity to local deformation and assessing a possible field of application. Satisfactory results in the field of NDT of multilayer fiber-reinforced composites were obtained by reducing the diaphragm of the lens to increase the sensitivity of the imaging system to speckle decorrelation induced by local deformation; unfortunately this simple approach requires a considerable amount of laser power for illuminating the object. Different aperture shapes were therefore numerically simulated which provided improved efficiency and sensitivity and whereby a semi-quantitative analysis of the displacement field could be experimented.     

Nonlinear behavior of vocal fold vibration: The role of coupling between the vocal folds

Coupling between the vocal folds is one of the nonlinear mechanisms allowing regulation and synchronization of mucosal vibration. The purpose of this study was to establish that modulations such as diplophonia and abnormalities observed in vocal signals that may be observed in some cases of laryngeal pathology can be considered as nonlinear behavior due to the persistence of some physical interaction (coupling). An experimental model using excised porcine larynx was designed to create tension asymmetry between the vocal folds and to obtain vocal signals with modulations. Signals were analyzed by spectral analysis and the phase portrait method. Results were compared with computer-generated synthetic signals corresponding to nonlinear combinations of sinusoid signals. Under these conditions, evidence of nonlinear behavior was detected in 85% of experimental signals. These findings were interpreted as a demonstration of vocal fold interaction. Based on these findings, the authors conclude that (1) coupling must be taken into account in physical models of laryngeal physiology, and that (2) methods of nonlinear dynamics may be used for objective voice analysis.     

Development of Aptamer Beacons for Rapid Presumptive Detection of <Emphasis Type="Italic">Bacillus</Emphasis> Spores

A library of 92 DNA aptamer sequences was developed against Bacillus anthracis (nonpathogenic Sterne strain) spores and anthrose sugar immobilized on magnetic beads. The selected DNA sequences were studied for similarities and potential binding pockets between the B. anthracis spore and anthrose aptamers. Several recurring loop structures were identified and tested for their potential to act as aptamer beacons when labeled with TYE 665 dye on their 5′ ends and Iowa Black quencher on their 3′ ends. Of these candidate sequences, two beacons designated BAS-6F and BAS-6R emerged which gave strong fluorescence responses at high spore concentrations (greater than 30,000 spores/ml). These aptamer beacons also detect B. cereus and B. thuringiensis spores with greater fluorescence intensity, but do not strongly detect vegetative cells from an array of other bacterial species. BAS-6F and 6R are also not capable of detecting pure anthrose, thereby probably ruling that epitope out as a spore surface target for these particular beacons. While not extremely sensitive, the BAS-6F and 6R aptamer beacons are potentially valuable for rapid presumptive detection of anthrax or Bacillus spores in suspect powders or bioterrorist activity where spore concentrations are anticipated to be high. The sequence similarities of these beacons to other published Bacillus spore aptamers are also discussed.     

Numerical modeling of transient two-dimensional viscoelastic waves

This paper deals with the numerical modeling of transient mechanical waves in linear viscoelastic solids. Dissipation mechanisms are described using the generalized Zener model. No time convolutions are required thanks to the introduction of memory variables that satisfy local-in-time differential equations. By appropriately choosing the relaxation parameters, it is possible to accurately describe a large range of materials, such as solids with constant quality factors. The evolution equations satisfied by the velocity, the stress, and the memory variables are written in the form of a first-order system of PDEs with a source term. This system is solved by splitting it into two parts: the propagative part is discretized explicitly, using a fourth-order ADER scheme on a Cartesian grid, and the diffusive part is then solved exactly. Jump conditions along the interfaces are discretized by applying an immersed interface method. Numerical experiments of wave propagation in viscoelastic and fluid media show the efficiency of this numerical modeling for dealing with challenging problems, such as multiple scattering configurations.     

Dark matter results from 100 live days of XENON100 data

We present results from the direct search for dark matter with the XENON100 detector, installed underground at the Laboratori Nazionali del Gran Sasso of INFN, Italy. XENON100 is a two-phase time-projection chamber with a 62 kg liquid xenon target. Interaction vertex reconstruction in three dimensions with millimeter precision allows the selection of only the innermost 48 kg as the ultralow background fiducial target. In 100.9 live days of data, acquired between January and June 2010, no evidence for dark matter is found. Three candidate events were observed in the signal region with an expected background of (1.8 ± 0.6) events. This leads to the most stringent limit on dark matter interactions today, excluding spin-independent elastic weakly interacting massive particle (WIMP) nucleon scattering cross sections above 7.0 × 10(-45) cm(2) for a WIMP mass of 50 GeV/c(2) at 90% confidence level.