440 research outputs found
A proposal of a Renormalization Group transformation
We propose a family of renormalization group transformations characterized by
free parameters that may be tuned in order to reduce the truncation effects. As
a check we test them in the three dimensional XY model. The Schwinger--Dyson
equations are used to study the renormalization group flow.Comment: Contribution to Lattice'94. uuencoded postscript fil
Finite-size scaling study of the d=4 site-diluted Ising
We study the four dimensional site-diluted Ising model using finite-size
scaling techniques. We explore the whole parameter space (density-coupling) in
order to determine the Universality Class of the transition line. Our data are
compatible with Mean Field behavior plus logarithmic corrections.Comment: Contribution to LATTICE 9
Changes in cannabinoid receptor binding and mRNA levels in several brain regions of aged rats
AbstractWe have recently found that cannabinoid receptor binding and gene expression markedly decreased in extrapyramidal structures of aged rats. The present study was designed to analyze the possible existence of similar aging-induced changes in cannabinoid receptor binding and gene expression in brain regions other than extrapyramidal areas, but that also contain a significant population of cannabinoid receptors, such as the cerebellum, hippocampal structures, limbic and hypothalamic nuclei, the cerebral cortex and others. To this end, we analyzed cannabinoid receptor binding, using autoradiography, and cannabinoid receptor mRNA levels, using in situ hybridization, in slide-mounted brain sections obtained from young (3 month old) and aged (>2 year old) rats. Results were as follows. In the cerebellum, aged rats exhibited a marked decrease in cannabinoid receptor binding in the molecular layer (−33.3%), although accompanied by no changes in mRNA levels in the granular layer. In the cerebral cortex, a small, although statistically significant, decrease in binding was found in the deep layer (VI) (−18.3%) of aged rats, whereas no changes were found in the superficial layer (I). As in the case of the cerebellum, mRNA levels did not change in the cerebral cortex layers (II–III and V–VI). The different regions of the Ammon’s horn of the hippocampus exhibited similar cannabinoid receptor binding levels in aged and young rats. Interestingly, mRNA levels decreased in aged rats to a small, but statistically significant, extent (CA1: −26.1%; CA2: −21.6%; CA3: −14.4%). This was also seen in another hippocampal structure, the dentate gyrus (−14.6%), although in this region binding levels increased in aged rats (+28.4%). Two hypothalamic structures, the arcuate nucleus and the ventromedial hypothalamic nucleus, exhibited decreased cannabinoid receptor binding in aged rats (−31.1% and −30.3%, respectively), but this was not seen in the medial preoptic area. This was accompanied by no changes in mRNA levels in the ventromedial hypothalamic nucleus. In the limbic structures, aged rats exhibited similar binding levels to young rats. This was seen in the nucleus accumbens, septum nuclei and basolateral amygdaloid nucleus. However, mRNA levels slightly decreased in the basolateral amygdaloid nucleus (−13.4%), whereas they were not altered in the septum nuclei. Finally, other brain structures, such as the central gray substance and the brainstem, exhibited similar binding levels in aged and young rats. However, it is important to note that mRNA levels increased significantly (+211.2%) in the brainstem of aged rats, an area where the levels of binding and mRNA were very low in young rats. This marked increase may be related to an increase in the presence of glial elements in this region, as revealed by the increase in the immunoreactivity for glial fibrillary acidic protein observed in the brainstem of aged rats as compared to young animals. In summary, senescence was associated with changes in cannabinoid receptors in the cerebellum, the cerebral cortex, limbic and hypothalamic structures, the hippocampus and other brain regions. However, the changes observed (i) were not as marked and relevant as those early reported in extrapyramidal areas, and (ii) exhibited regional differences that might be attributed to the different roles played by these receptors in each region. Of particular relevance by their magnitude were the aging-induced decrease in binding found in the cerebellum and the hypothalamus, and the increase in mRNA levels observed in the brainstem. The latter might be related to an increase in the presence of glial cells which might contain cannabinoid receptor mRNA
APE Results of Hadron Masses in Full QCD Simulations
We present numerical results obtained in full QCD with 2 flavors of Wilson
fermions. We discuss the relation between the phase of Polyakov loops and the
{\bf sea} quarks boundary conditions. We report preliminary results about the
HMC autocorrelation of the hadronic masses, on a lattice
volume, at with .Comment: 3 pages, compressed ps-file (uufiles), Contribution to Lattice 9
Investigaciones Sobre Programación del Riego en Limonero y Olivo Mediante Medidas Directas y Continuas del Estado Hídrico.
En el presente trabajo se realiza una revisión del estado actual de conocimientos sobre aspectos relativos
a la utilización de medidas continuas del estado hídrico del limonero y olivo para su utilización en la
programación del riego, abarcando, esencialmente, aspectos tales como la sensibilidad de distintos
indicadores del estado hídrico medidos de forma continua o discontinua en las plantas, su significado
fisiológico, la obtención de niveles de referencia de los indicadores y primeros resultados sobre
programación del riegoThe feasibility of irrigation scheduling in olive and lemon trees using continuously recorded plant-based
water stress indicators was studied. For this, the characteristics of different plant-based water stress
indicators (stem water potential, sap flow and trunk diameter fluctuations), their sensibility and limitations
for water stress diagnosis purposes was discussed. The ways in which data can be interpreted, and
protocols for irrigation scheduling was also described
The U(1)-Higgs Model: Critical Behaviour in the Confinig-Higgs region
We study numerically the critical properties of the U(1)-Higgs lattice model,
with fixed Higgs modulus, in the region of small gauge coupling where the Higgs
and Confining phases merge. We find evidence of a first order transition line
that ends in a second order point. By means of a rotation in parameter space we
introduce thermodynamic magnitudes and critical exponents in close resemblance
with simple models that show analogous critical behaviour. The measured data
allow us to fit the critical exponents finding values in agreement with the
mean field prediction. The location of the critical point and the slope of the
first order line are accurately given.Comment: 21 text pages. 12 postscript figures available on reques
The four dimensional site-diluted Ising model: a finite-size scaling study
Using finite-size scaling techniques, we study the critical properties of the
site-diluted Ising model in four dimensions. We carry out a high statistics
Monte Carlo simulation for several values of the dilution. The results support
the perturbative scenario: there is only the Ising fixed point with large
logarithmic scaling corrections. We obtain, using the Perturbative
Renormalization Group, functional forms for the scaling of several observables
that are in agreement with the numerical data.Comment: 30 pages, 8 postscript figure
Simulating spin systems on IANUS, an FPGA-based computer
We describe the hardwired implementation of algorithms for Monte Carlo
simulations of a large class of spin models. We have implemented these
algorithms as VHDL codes and we have mapped them onto a dedicated processor
based on a large FPGA device. The measured performance on one such processor is
comparable to O(100) carefully programmed high-end PCs: it turns out to be even
better for some selected spin models. We describe here codes that we are
currently executing on the IANUS massively parallel FPGA-based system.Comment: 19 pages, 8 figures; submitted to Computer Physics Communication
Efectos de una maratón en valores hematológicos
Introducción: La maratón lleva asociado un estrés fi siológico en el organismo, si bien existe carencia de información sobre cómo afecta a los parámetros sanguíneos en corredores populares y si existe relación con variables de rendimiento, entrenamiento y experiencia deportiva.
Propósito: Evaluar los cambios producidos en variables hematológicas en corredores populares tras participar en una maratón en ambiente caluroso. Un segundo objetivo fue analizar la relación entre la experiencia deportiva, el nivel de entrenamiento y el tiempo de carrera con los cambios hematológicos.
Métodos: Se extrajo sangre venosa a 41 maratonianos, 35 hombres y 6 mujeres, antes y después de una maratón. Su edad fue de 41,15+8,1 años, y entrenaban como media 55,917,12 kilómetros semanales. El tiempo en meta fue de 3:40:410:32:02.
Las muestras fueron medidas con analizadores bioquímicos estándar para determinar los valores de la serie roja y serie blanca
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