Fast, Accurate and Robust Adaptive Finite Difference Methods for Fractional Diffusion Equations: The Size of the Timesteps does Matter

The computation time required by standard finite difference methods with fixed timesteps for solving fractional diffusion equations is usually very large because the number of operations required to find the solution scales as the square of the number of timesteps. Besides, the solutions of these problems usually involve markedly different time scales, which leads to quite inhomogeneous numerical errors. A natural way to address these difficulties is by resorting to adaptive numerical methods where the size of the timesteps is chosen according to the behaviour of the solution. A key feature of these methods is then the efficiency of the adaptive algorithm employed to dynamically set the size of every timestep. Here we discuss two adaptive methods based on the step-doubling technique. These methods are, in many cases, immensely faster than the corresponding standard method with fixed timesteps and they allow a tolerance level to be set for the numerical errors that turns out to be a good indicator of the actual errors

Blocked algorithms for the reduction to Hessenberg-triangular form revisited

We present two variants of Moler and Stewart's algorithm for reducing a matrix pair to Hessenberg-triangular (HT) form with increased data locality in the access to the matrices. In one of these variants, a careful reorganization and accumulation of Givens rotations enables the use of efficient level 3 BLAS. Experimental results on four different architectures, representative of current high performance processors, compare the performances of the new variants with those of the implementation of Moler and Stewart's algorithm in subroutine DGGHRD from LAPACK, Dackland and Kågström's two-stage algorithm for the HT form, and a modified version of the latter which requires considerably less flop

Measuring Thickness and Pretilt in Reflective Vertically Aligned Nematic Liquid Crystal Displays

Pretilt angle is a parameter of the utmost importance in the ultimate performance of vertically-aligned negative nematic LC displays. When these devices work in reflective mode, as is the LCOS microdisplays, accurate measurement of pretilt angles becomes a difficult problem, since usual experimental setups based on retardation of the polarization components of the impinging light are proportional to the product effective birefringence (neff - no) times thickness, and any attempt to separate these variables is cancelled out by symmetry. This work shows a relatively simple method capable of separating both variables. An experimental setup specifically aimed at vertically aligned reflective cells has been prepared. At the same time, a simulation model has been developed taking into account the properties of actual reflective displays. Comparison between experimental and theoretical results shows some discrepancies that can be explained assuming that the LC profile contains a residual twist. Including that twist in the model, an excellent agreement between theory and experiment has been achieved. Matching of simulations and measurements yields to the separate determination of pretilt angle and thickness and gives good estimates for the residual twist angle

Control System for the LEDA 6.7-MeV Proton Beam Halo Experiment

Measurement of high-power proton beam-halo formation is the ongoing scientific experiment for the Low Energy Demonstration Accelerator (LEDA) facility. To attain this measurement goal, a 52-magnet beam line containing several types of beam diagnostic instrumentation is being installed. The Experimental Physics and Industrial Control System (EPICS) and commercial software applications are presently being integrated to provide a real-time, synchronous data acquisition and control system. This system is comprised of magnet control, vacuum control, motor control, data acquisition, and data analysis. Unique requirements led to the development and integration of customized software and hardware. EPICS real-time databases, Interactive Data Language (IDL) programs, LabVIEW Virtual Instruments (VI), and State Notation Language (SNL) sequences are hosted on VXI, PC, and UNIX-based platforms which interact using the EPICS Channel Access (CA) communication protocol. Acquisition and control hardware technology ranges from DSP-based diagnostic instrumentation to the PLC-controlled vacuum system. This paper describes the control system hardware and software design, and implementation.Comment: LINAC2000 Conference, 4 pg

X-ray Over-Luminous Elliptical Galaxies: A New Class of Mass Concentrations in the Universe?

We detect four isolated, X-ray over-luminous (Lx>2e43 [h/0.5]**-2 erg/s) elliptical galaxies (OLEGs) in our 160 square degree ROSAT PSPC survey. The extent of their X-ray emission, total X-ray luminosity, total mass, and mass of the hot gas in these systems correspond to poor clusters, and the optical luminosity of the central galaxies (M_R<-22.5 + 5 lg h) is comparable to that of cluster cDs. However, there are no detectable fainter galaxy concentrations around the central elliptical. The mass-to-light ratio within the radius of detectable X-ray emission is in the range 250-450 Msun/Lsun, which is 2-3 times higher than typically found in clusters or groups. These objects can be the result of galaxy merging within a group. However, their high M/L values are difficult to explain in this scenario. OLEGs must have been undisturbed for a very long time, which makes them the ultimate examples of systmes in hydrostatic equilibrium. The number density of OLEGs is n=2.4(+3.1-1.2}x10**-7 (h/0.5)**-3 Mpc**-3 at the 90% confidence. They comprise 20% of all clusters and groups of comparable X-ray luminosity, and nearly all galaxies brighter than M_R=-22.5. The estimated contirubution of OLEGs to the total mass density in the Universe is close to that of T>7 keV clusters.Comment: 4 pages, 2 figures, uses emulateapj.sty, submitted to ApJ Letter

Antiherpes simplex virus type 2 activity of the antimicrobial peptide subtilosin

In the present study we evaluated the antiviral activity of subtilosin, a cyclical peptide isolated from Bacillus amyloliquefaciens, against herpes simplex virus type 2 (HSV-2) in cell cultures and we investigated subtilosin mode of action. We determined, using a virus yield inhibition assay, that non cytotoxic concentrations of subtilosin inhibit HSV-2 replication in Vero cell cultures. Subtilosin strongly inhibited extracellular and total virus production even when it was added at 8 h post-infection indicating that not only virus release but also viral particle formation is impeded by the antiviral peptide. Although viral glycoprotein gD level of expression is not affected by the bacteriocin, an altered pattern of gD intracellular localization was detected by immunofluorescence assay in subtilosin treated culture. On the other hand, at high concentrations subtilosin displays virucidal action.Fil: Quintana, Verónica Mara. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica. Laboratorio de Virología; ArgentinaFil: Torres, Nicolás. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica. Laboratorio de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Wachsman, Mónica B.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica. Laboratorio de Virología; ArgentinaFil: Sinko, Patrick J.. State University of New Jersey; Estados UnidosFil: Castilla, Viviana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica. Laboratorio de Virología; ArgentinaFil: Chikindas, Michael. State University of New Jersey; Estados Unido

Fractura de piso orbitario en un jugador de béisbol

Presentamos un caso de un paciente, jugador de béisbol que sufrió una fractura de piso orbitario al recibir un golpe directo (blowout) con un bate que se le escapó a otro jugador, esta fractura fue reparada con un bloque de Hidroxiapatita Porosa HAP -200 .Una vez reconstruido el defecto óseo, el paciente volvió a su vida normal y comenzó de nuevo a jugar béisbol, debido a que desaparecieron la diplopía y el enoftalmo, por lo que tuvo una completa rehabilitación estética y funcional. En los exámenes radiográficos postoperatorios se observó una excelente reconstrucción del piso de la orbita y una osteointegegración del material implantológicoWe attend one patient, baseball player that suffer floor orbital fracture when he received hit in his eye (blowout) during practice baseball. He was operating and repaired this fracture with Porous Hidroxyapatite HAP-200.After operation he returned to play baseball because disappear the signs and symptoms (diplopia and enophthalmo).The radiography study showed excellent result after one yea