9,881 research outputs found
Directed Random Walk on the Lattices of Genus Two
The object of the present investigation is an ensemble of self-avoiding and
directed graphs belonging to eight-branching Cayley tree (Bethe lattice)
generated by the Fucsian group of a Riemann surface of genus two and embedded
in the Pincar\'e unit disk. We consider two-parametric lattices and calculate
the multifractal scaling exponents for the moments of the graph lengths
distribution as functions of these parameters. We show the results of numerical
and statistical computations, where the latter are based on a random walk
model.Comment: 17 pages, 8 figure
Casimir interaction at liquid nitrogen temperature: Comparison between experiment and theory
We have measured the normalized gradient of the Casimir force between
Au-coated surfaces of the sphere and the plate and equivalent Casimir pressure
between two parallel Au plates at T=77K. These measurements have been performed
by means of dynamic force microscope adapted for operating at low temperatures
in the frequency shift technique. It was shown that the measurement results at
T=77K are in a very good agreement with those at T=300K and with computations
at T=77K using both theoretical approaches to the thermal Casimir force
proposed in the literature. No thermal effect in the Casimir pressure was
observed in the limit of experimental errors with the increase of temperature
from T=77K to T=300K. Taking this into account, we have discussed the possible
role of patch potentials in the comparison between measured and calculated
Casimir pressures.Comment: 18 pages, 8 figures, to appear in Phys. Rev.
Fitoplancton en costas occidentales de Baja California en dos temporadas distintas de 1998
Phytoplankton was studied in two different seasons of 1998 (March-April and December), during two cruises along the western coasts of Baja California, in three zones. Two different protocols for obtaining and studying phytoplankton were followed. In the March-April season, phytoplankton had relatively low species richness and was dominated in cell density (up to 93%) by coccolithophorids (mainly Emiliania huxleyi), together with nanoplanktonic centric and pennate diatoms, with abundances ranging from 5.4 103 to 1.2 105 cells L-1. In December, phytoplankton had higher species richness and was represented by larger, chain-forming diatom species, such as Pseudonitzschia delicatissima and P. pungens, which were widespread and numerically significant. There was a relative scarcity of coccolithophorids and thecate dinoflagellates, and densities were between 7 102 and 1.4 106 cells L-1. Hydrographic and oceanographic conditions in March-April were influenced by the occurrence of El Niño and the phytoplankton structure was found to be modified accordingly, with nanoplanktonic coccolithophorids and diatoms being significant contributors to the total abundance. In contrast, post-upwelling conditions might have favoured relatively high densities of Pseudonitzschia and other diatoms in December, 1998. Coccolithophorids have not been previously regarded as important contributors to the phytoplankton abundances in Baja California.Se estudió el fitoplancton en dos temporadas diferentes de 1998 (marzo-abril y diciembre), durante dos cruceros en tres zonas de las costas de Baja California. Se siguieron dos protocolos distintos para obtener y estudiar el fitoplancton. En marzo-abril, el fitoplancton tuvo una riqueza de especies baja y estuvo dominado en densidades celulares (de hasta 93%) por cocolitofóridos (principalmente Emiliania huxleyi), junto con diatomeas centrales y pennales nanoplanctónicas, con abundancias desde 5.4 103 to 1.2 105 cells L-1. Para diciembre, el fitoplancton incrementó la riqueza de especies y estuvo representado por diatomeas más grandes, formadoras de cadenas, que se distribuyeron ampliamente y fueron numéricamente importantes, como: Pseudonitzschia delicatissima y P. pungens, con relativa escasez de cocolitofóridos y dinoflagelados tecados, con densidades entre 7 102 and 1.4 106 cells L-1. Las condiciones oceanográficas en marzo-abril indicaron la presencia de El Niño y los resultados mostraron una estructura de fitoplancton modificada por ello, con una contribución importante de cocolitofóridos y diatomeas nanoplanctónicas a la abundancia total. En cambio, en diciembre, las condiciones de post-surgencia pudieron haber favorecido las relativas altas densidades de especies de Pseudonitzschia y otras diatomeas. Los cocolitofóridos no habÃan sido documentados previamente como contribuyentes importantes a la abundancia fitoplanctónica en Baja California
Programa de capacitación en el tema de violencia doméstica. Dirigido a estudiantes de la XLVI promoción de aspirantes al cargo de agentes de la PolicÃa Nacional
Objetivo General :
Conocer y profundizar en los orÃgenes, desarrollo y consecuencias de la violencia doméstica con el fin de contar con las herramientas para prevenir, detectar, orientar y atender de manera oportuna y eficaz a los involucrados en esta problemática y brindarles alternativas viables que le faciliten la búsqueda de un apoyo psicosocial y legal a su problema.
Objetivo EspecÃficos :
< Mejorar el conocimiento de la realidad de la violencia doméstica y profundizar en sus causas, Desde las diferentes disciplinas en las que se pueda intervenir tanto en la prevención como en el tratamiento
< Dotar de herramientas adecuadas en materia de prevención, tratamiento y seguimiento a las unidades policiales que deben atender la problemática de la violencia doméstica para mejorar el abordaje policial en estos casos
< Reconocer e identificar las situaciones de malos tratos en el ámbito familiar, detallando la actuación policial adecuada con respecto a las vÃctimas de violencia doméstica
< Reconocer los factores relacionados y los modelos explicativos de la violencia doméstica
< Reconocer en una vÃctima de violencia doméstica las consecuencias psicológicas de la misma
Experimental procedures for precision measurements of the Casimir force with an Atomic Force Microscope
Experimental methods and procedures required for precision measurements of
the Casimir force are presented. In particular, the best practices for
obtaining stable cantilevers, calibration of the cantilever, correction of
thermal and mechanical drift, measuring the contact separation, sphere radius
and the roughness are discussed.Comment: 14 pages, 7 figure
COmplexome Profiling ALignment (COPAL) reveals remodeling of mitochondrial protein complexes in Barth syndrome
Item does not contain fulltextMOTIVATION: Complexome profiling combines native gel electrophoresis with mass spectrometry to obtain the inventory, composition and abundance of multiprotein assemblies in an organelle. Applying complexome profiling to determine the effect of a mutation on protein complexes requires separating technical and biological variations from the variations caused by that mutation. RESULTS: We have developed the COmplexome Profiling ALignment (COPAL) tool that aligns multiple complexome profiles with each other. It includes the abundance profiles of all proteins on two gels, using a multi-dimensional implementation of the dynamic time warping algorithm to align the gels. Subsequent progressive alignment allows us to align multiple profiles with each other. We tested COPAL on complexome profiles from control mitochondria and from Barth syndrome (BTHS) mitochondria, which have a mutation in tafazzin gene that is involved in remodeling the inner mitochondrial membrane phospholipid cardiolipin. By comparing the variation between BTHS mitochondria and controls with the variation among either, we assessed the effects of BTHS on the abundance profiles of individual proteins. Combining those profiles with gene set enrichment analysis allows detecting significantly affected protein complexes. Most of the significantly affected protein complexes are located in the inner mitochondrial membrane (mitochondrial contact site and cristae organizing system, prohibitins), or are attached to it (the large ribosomal subunit). AVAILABILITY AND IMPLEMENTATION: COPAL is written in python and is available from http://github.com/cmbi/copal. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online
Gradient of the Casimir force between Au surfaces of a sphere and a plate measured using atomic force microscope in a frequency shift technique
We present measurement results for the gradient of the Casimir force between
an Au-coated sphere and an Au-coated plate obtained by means of an atomic force
microscope operated in a frequency shift technique. This experiment was
performed at a pressure of 3x10^{-8} Torr with hollow glass sphere of 41.3 mcm
radius. Special attention is paid to electrostatic calibrations including the
problem of electrostatic patches. All calibration parameters are shown to be
separation-independent after the corrections for mechanical drift are included.
The gradient of the Casimir force was measured in two ways with applied
compensating voltage to the plate and with different applied voltages and
subsequent subtraction of electric forces. The obtained mean gradients are
shown to be in mutual agreement and in agreement with previous experiments
performed using a micromachined oscillator. The obtained data are compared with
theoretical predictions of the Lifshitz theory including corrections beyond the
proximity force approximation. An independent comparison with no fitting
parameters demonstrated that the Drude model approach is excluded by the data
at a 67% confidence level over the separation region from 235 to 420 nm. The
theoretical approach using the generalized plasma-like model is shown to be
consistent with the data over the entire measurement range. Corrections due to
the nonlinearity of oscillator are calculated and the application region of the
linear regime is determined. A conclusion is made that the results of several
performed experiments call for a thorough analysis of the basics of the theory
of dispersion forces.Comment: 35 pages, 14 figures, 1 table; to appear in Phys. Rev.
Autonomous surveillance robots: a decision-making framework for networked multiagent systems
This article proposes an architecture for an intelligent surveillance system, where the aim is to mitigate the burden on humans in conventional surveillance systems by incorporating intelligent interfaces, computer vision, and autonomous mobile robots. Central to the intelligent surveillance system is the application of research into planning and decision making in this novel context. In this article, we describe the robot surveillance decision problem and explain how the integration of components in our system supports fully automated decision making. Several concrete scenarios deployed in real surveillance environments exemplify both the flexibility of our system to experiment with different representations and algorithms and the portability of our system into a variety of problem contexts. Moreover, these scenarios demonstrate how planning enables robots to effectively balance surveillance objectives, autonomously performing the job of human patrols and responders.This work was partially supported by the Portuguese Fundação para a Ciência e a Tecnologia (FCT), through strategic funding for Institute for Systems and Robotics/Laboratory for Robotics and Engineering Systems (ISR/LARSyS) under grant PEst-OE/EEI/LA0021/2013 and through the Carnegie Mellon Portugal Program under grant CMU-PT/SIA/0023/2009. This study also received national funds through the FCT, with reference UID/CEC/S0021/2013, and through grant FCT UID/EEA/50009/2013 of ISR/LARSyS
Magnetocaloric effect and magnetic cooling near a field-induced quantum-critical point
The presence of a quantum critical point (QCP) can significantly affect the
thermodynamic properties of a material at finite temperatures T. This is
reflected, e.g., in the entropy landscape S(T, r) in the vicinity of a QCP,
yielding particularly strong variations for varying the tuning parameter r such
as pressure or magnetic field B. Here we report on the determination of the
critical enhancement of near a B-induced QCP via
absolute measurements of the magnetocaloric effect (MCE), , and demonstrate that the accumulation of entropy around the QCP can be
used for efficient low-temperature magnetic cooling. Our proof of principle is
based on measurements and theoretical calculations of the MCE and the cooling
performance for a Cu-containing coordination polymer, which is a very
good realization of a spin-1/2 antiferromagnetic Heisenberg chain - one of the
simplest quantum-critical systems.Comment: 21 pages, 4 figure
Experimental approaches to the difference in the Casimir force through the varying optical properties of boundary surface
We propose two novel experiments on the measurement of the Casimir force
acting between a gold coated sphere and semiconductor plates with markedly
different charge carrier densities. In the first of these experiments a
patterned Si plate is used which consists of two sections of different dopant
densities and oscillates in the horizontal direction below a sphere. The
measurement scheme in this experiment is differential, i.e., allows the direct
high-precision measurement of the difference of the Casimir forces between the
sphere and sections of the patterned plate or the difference of the equivalent
pressures between Au and patterned parallel plates with static and dynamic
techniques, respectively. The second experiment proposes to measure the Casimir
force between the same sphere and a VO film which undergoes the
insulator-metal phase transition with the increase of temperature. We report
the present status of the interferometer based variable temperature apparatus
developed to perform both experiments and present the first results on the
calibration and sensitivity. The magnitudes of the Casimir forces and pressures
in the experimental configurations are calculated using different theoretical
approaches to the description of optical and conductivity properties of
semiconductors at low frequencies proposed in the literature. It is shown that
the suggested experiments will aid in the resolution of theoretical problems
arising in the application of the Lifshitz theory at nonzero temperature to
real materials. They will also open new opportunities in nanotechnology.Comment: 23 pages of the text, 2 tables, and captions of 12 figures (to appear
in Phys. Rev. A
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