Vortex-glass transition in superconducting Nb/Cu superlattices

Nb/Cu superconducting superlattices have been fabricated by dc magnetron sputtering. This system shows a vortex glass transition with critical exponents similar to high temperatures superconductors exponents. The transition dymensionality is governed by the superconducting coupling regime. The vortex glass transition shows a pure two dimensional behavior in decoupled superlattices and a quasi-two dimensional behavior in the superlattice coupling regime.Comment: 9 pages, 3 figure

Analysis of SPDEs Arising in Path Sampling Part I: The Gaussian Case

In many applications it is important to be able to sample paths of SDEs conditional on observations of various kinds. This paper studies SPDEs which solve such sampling problems. The SPDE may be viewed as an infinite dimensional analogue of the Langevin SDE used in finite dimensional sampling. Here the theory is developed for conditioned Gaussian processes for which the resulting SPDE is linear. Applications include the Kalman-Bucy filter/smoother. A companion paper studies the nonlinear case, building on the linear analysis provided here

Optical-fiber source of polarization-entangled photon pairs in the 1550nm telecom band

We present a fiber based source of polarization-entangled photon pairs that is well suited for quantum communication applications in the 1550nm band of standard fiber-optic telecommunications. Polarization entanglement is created by pumping a nonlinear-fiber Sagnac interferometer with two time-delayed orthogonally-polarized pump pulses and subsequently removing the time distinguishability by passing the parametrically scattered signal-idler photon pairs through a piece of birefringent fiber. Coincidence detection of the signal-idler photons yields biphoton interference with visibility greater than 90%, while no interference is observed in direct detection of either the signal or the idler photons. All four Bell states can be prepared with our setup and we demonstrate violations of CHSH form of Bell's inequalities by up to 10 standard deviations of measurement uncertainty.Comment: 12 pages, 4 figures, to be submitted to Phys. Rev. Lett. See also paper QTuB4 in QELS'03 Technical Digest (OSA, Washington, D.C., 2003). This is a more complete versio

Uso de hidroponia em cereais de inverno.

bitstream/CNPT-2010/40688/1/p-do70.pd

Aluminium-oxide wires for superconducting high kinetic inductance circuits

We investigate thin films of conducting aluminium-oxide, also known as granular aluminium, as a material for superconducting high quality, high kinetic inductance circuits. The films are deposited by an optimised reactive DC magnetron sputter process and characterised using microwave measurement techniques at milli-Kelvin temperatures. We show that, by precise control of the reactive sputter conditions, a high room temperature sheet resistance and therefore high kinetic inductance at low temperatures can be obtained. For a coplanar waveguide resonator with 1.5\,k$\Omega$ sheet resistance and a kinetic inductance fraction close to unity, we measure a quality factor in the order of 700\,000 at 20\,mK. Furthermore, we observe a sheet resistance reduction by gentle heat treatment in air. This behaviour is exploited to study the kinetic inductance change using the microwave response of a coplanar wave guide resonator. We find the correlation between the kinetic inductance and the sheet resistance to be in good agreement with theoretical expectations.Comment: 16 pages, 7 figure

Common beans in Africa and their constraints

Beans are grown in Africa in a wide range of environments, mainly in the cool highlands of central and tropical eastern Africa, leading to a diversity of cropping systems and agronomic constraints to production. Beans are cultivated for large-scale production or home consumption either in monoculture or in association. The main constraints to production are poor agronomic practices, soil infertility, lack of improved cv., water stress, weed competition, and diseases and pests. Main diseases affecting bean crops in Africa include viral diseases (BCMV, SBMV, BGMV, and BYMV), bacterial diseases (bacterial wilt and bacterial brown spot), and fungal diseases (angular leaf spot, anthracnose, rust, Ascochyta blight, and floury leaf spot). Suggestions for disease management are given, highlighting the use of integrated control. Estimates of annual production per region and crop losses due to pathogens are given in table form. (CIAT)El frijol se cultiva en Africa en un amplio rango de ambientes, principalmente en las areas montanosas templadas de las regiones central y oriental tropical de Africa, lo cual supone diversos sistemas de cultivo y limitaciones agronomicas a la produccion. El frijol se cultiva para produccion en gran escala o para consumo domestico, sea en monocultivo o en asociacion. Las principales limitaciones a la produccion son practicas agronomicas inadecuadas, infertilidad del suelo, falta de cv. mejorados, estres hidrico, competencia de malezas y plagas y enfermedades. Las principales enfermedades que afectan el cultivo del frijol en Africa son las de tipo viral (BCMV, SBMV, BGMV y BYMV), las bacterianas (anublo bacteriano y mancha parda bacteriana) y las fungicas (mancha angular, antracnosis, roya, anublo por Ascochyta y mancha harinosa). Se dan sugerencias para manejo de enfermedades, destacando el uso de control integrado. Se incluyen en forma de tabla estimativos de produccion anual por region y perdidas de cosecha por patogenos. (CIAT

Parallel Algorithm and Dynamic Exponent for Diffusion-limited Aggregation

A parallel algorithm for ``diffusion-limited aggregation'' (DLA) is described and analyzed from the perspective of computational complexity. The dynamic exponent z of the algorithm is defined with respect to the probabilistic parallel random-access machine (PRAM) model of parallel computation according to $T \sim L^{z}$, where L is the cluster size, T is the running time, and the algorithm uses a number of processors polynomial in L\@. It is argued that z=D-D_2/2, where D is the fractal dimension and D_2 is the second generalized dimension. Simulations of DLA are carried out to measure D_2 and to test scaling assumptions employed in the complexity analysis of the parallel algorithm. It is plausible that the parallel algorithm attains the minimum possible value of the dynamic exponent in which case z characterizes the intrinsic history dependence of DLA.Comment: 24 pages Revtex and 2 figures. A major improvement to the algorithm and smaller dynamic exponent in this versio