Numerical Integration of Nonlinear Wave Equations for General Relativity

A second-order numerical implementation is given for recently derived nonlinear wave equations for general relativity. The Gowdy T$^3$ cosmology is used as a test bed for studying the accuracy and convergence of simulations of one-dimensional nonlinear waves. The complete freedom in space-time slicing in the present formulation is exploited to compute in the Gowdy line-element. Second-order convergence is found by direct comparison of the results with either analytical solutions for polarized waves, or solutions obtained from Gowdy's reduced wave equations for the more general unpolarized waves. Some directions for extensions are discussed.Comment: 19 pages (LaTex), 3 figures (ps

Hadoop for EEG Storage and Processing: A Feasibility Study

Lots of heterogeneous complex data are collected for diagnosis purposes. Such data should be shared between all caregivers and, often at least partly automatically processed, due to its complexity, for its full potential to be harnessed. This paper is a feasibility study that assesses the potential of Hadoop as a medical data storage and processing platform using EEGs as example of medical data

Uniqueness in MHD in divergence form: right nullvectors and well-posedness

Magnetohydrodynamics in divergence form describes a hyperbolic system of covariant and constraint-free equations. It comprises a linear combination of an algebraic constraint and Faraday's equations. Here, we study the problem of well-posedness, and identify a preferred linear combination in this divergence formulation. The limit of weak magnetic fields shows the slow magnetosonic and Alfven waves to bifurcate from the contact discontinuity (entropy waves), while the fast magnetosonic wave is a regular perturbation of the hydrodynamical sound speed. These results are further reported as a starting point for characteristic based shock capturing schemes for simulations with ultra-relativistic shocks in magnetized relativistic fluids.Comment: To appear in J Math Phy

Meloidogyne duytsi n. sp. (Nematoda : Heteroderidae), a root-knot nematode from Dutch coastal foredunes

Un nématode galligène, #Meloidogyne duytsi n. sp., parasitant #Elymus farctus (Viv.) Melderis croissant sur les avant-dunes côtières hollandaises, est décrit et illustré. Cette nouvelle espèce est caractérisée par : femelle ayant un stylet long de 13,3 micromètres, légèrement incurvé dorasalement, boutons basaux grands et transversalement ovoïdes, bien séparés de la hampe ; empreinte périnéale asymétrique avec arche dorsale relativement basse, stries épaisses et lignes latérales indistinctes ; queue pointue. Mâle : région céphalique haute et séparée du reste du corps ; disque labial légèrement proéminent ; secteurs latéraux labiaux réduits ; queue conique à extrémité arrondie. Juvéniles de deuxième stade : longueur moyenne de 424 mircomètres ; hémizonide antéieur au pore excréteur ; queue longue de 70,4 micromètres, effilée, légèrement incurvée ventralement à partie hylaine terminale distincte et longue de 11,3 micromètres. Un profil nouveau pour la malate deshydrogénase et une bande estérasique de type lent ont été détectés. #M. duytsi n. sp. a également été collecté en mélange avec #M. maritima Jepson, 1987 sur #Ammophila areanaria$ (L.) Link. (Résumé d'auteur

Focusing Light through Random Photonic Media by Binary Amplitude Modulation

We study the focusing of light through random photonic materials using wavefront shaping. We explore a novel approach namely binary amplitude modulation. To this end, the light incident to a random photonic medium is spatially divided into a number of segments. We identify the segments that give rise to fields that are out of phase with the total field at the intended focus and assign these a zero amplitude, whereas the remaining segments maintain their original amplitude. Using 812 independently controlled segments of light, we find the intensity at the target to be 75 +/- 6 times enhanced over the average intensity behind the sample. We experimentally demonstrate focusing of light through random photonic media using both an amplitude only mode liquid crystal spatial light modulator and a MEMS-based spatial light modulator. Our use of Micro Electro-Mechanical System (MEMS)-based digital micromirror devices for the control of the incident light field opens an avenue to high speed implementations of wavefront shaping

Exploiting speckle correlations to improve the resolution of wide-field fluorescence microscopy

Fluorescence microscopy is indispensable in nanoscience and biological sciences. The versatility of labeling target structures with fluorescent dyes permits to visualize structure and function at a subcellular resolution with a wide field of view. Due to the diffraction limit, conventional optical microscopes are limited to resolving structures larger than 200 nm. The resolution can be enhanced by near-field and far-field super-resolution microscopy methods. Near-field methods typically have a limited field of view and far-field methods are limited by the involved conventional optics. Here, we introduce a combined high-resolution and wide-field fluorescence microscopy method that improves the resolution of a conventional optical microscope by exploiting correlations in speckle illumination through a randomly scattering high-index medium: Speckle correlation resolution enhancement (SCORE). As a test, we collect two-dimensional fluorescence images of 100-nm diameter dye-doped nanospheres. We demonstrate a deconvolved resolution of 130 nm with a field of view of 10 x 10 \text{\mu m}^2

Scattering Lens Resolves sub-100 nm Structures with Visible Light

The smallest structures that conventional lenses are able to optically resolve are of the order of 200 nm. We introduce a new type of lens that exploits multiple scattering of light to generate a scanning nano-sized optical focus. With an experimental realization of this lens in gallium phosphide we have succeeded to image gold nanoparticles at 97 nm optical resolution. Our work is the first lens that provides a resolution in the nanometer regime at visible wavelengths.Comment: 4 pages, 3 figure

Non-Imaging Speckle Interferometry forHigh Speed Nanometer-Scale Position Detection

We experimentally demonstrate a non-imaging approach to displacement measurement for complex scattering materials. By spatially controlling the wave front of the light that incidents on the material we concentrate the scattered light in a focus on a designated position. This wave front acts as an unique optical fingerprint that enables precise position detection of the illuminated material by simply measuring the intensity in the focus. By combining two optical fingerprints we demonstrate position detection along one dimension with a displacement resolution of 2.1 nm. As our approach does not require an image of the scattered field, it is possible to employ fast non-imaging detectors to enable high-speed position detection of scattering materials.Comment: 4 pages, 3 figure

Photovoltaic's silica-rich waste sludge as supplementary cementitious materials (SCM)

Waste sludge, a solid recovered from wastewater of photovoltaic-industries, composes of agglomerates of nano-particles like SiO2 and CaCO3. This sludge deflocculates in aqueous solutions into nano-particles smaller than 1000 nm. Thus, this sludge is potentially hazardous waste when is improperly dumped. Due to its high content of amorphous SiO2, this sludge has a potential use as supplementary cementitious material (SCM) in concrete. In this study the main properties of three different samples of photovoltaic silica-rich waste sludge (nSS) were physically and chemically characterized. The characterization techniques included: scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), nitrogen physical adsorption isotherm (BET, t-plot and BJH methods), density by Helium pycnometry, particle size distribution determined by laser light scattering (LLS) and dynamic light scattering (DLS). The effects on the hydration kinetics of cement pastes by the addition of nSS in the designed slurries were determined using an isothermal calorimeter. Finally, the compressive strength tests of standard mortars with 7% of cement replacement were performed to determine the puzzolanic activity of the waste nano-silica sludge. The results demonstrate the nSS can be utilized as SCM to replace portion of cement in mortars, thereby decreasing the CO2 footprint and the environmental impact of concrete