Near-Perfect Correlation of the Resistance Components of Mesoscopic Samples at the Quantum Hall Regime

We study the four-terminal resistance fluctuations of mesoscopic samples near the transition between the $\nu=2$ and the $\nu=1$ quantum Hall states. We observe near-perfect correlations between the fluctuations of the longitudinal and Hall components of the resistance. These correlated fluctuations appear in a magnetic-field range for which the two-terminal resistance of the samples is quantized. We discuss these findings in light of edge-state transport models of the quantum Hall effect. We also show that our results lead to an ambiguity in the determination of the width of quantum Hall transitions.Comment: As publishe

Lagged and instantaneous dynamical influences related to brain structural connectivity

Contemporary neuroimaging methods can shed light on the basis of human neural and cognitive specializations, with important implications for neuroscience and medicine. Different MRI acquisitions provide different brain networks at the macroscale; whilst diffusion-weighted MRI (dMRI) provides a structural connectivity (SC) coincident with the bundles of parallel fibers between brain areas, functional MRI (fMRI) accounts for the variations in the blood-oxygenation-level-dependent T2* signal, providing functional connectivity (FC).Understanding the precise relation between FC and SC, that is, between brain dynamics and structure, is still a challenge for neuroscience. To investigate this problem, we acquired data at rest and built the corresponding SC (with matrix elements corresponding to the fiber number between brain areas) to be compared with FC connectivity matrices obtained by 3 different methods: directed dependencies by an exploratory version of structural equation modeling (eSEM), linear correlations (C) and partial correlations (PC). We also considered the possibility of using lagged correlations in time series; so, we compared a lagged version of eSEM and Granger causality (GC). Our results were two-fold: firstly, eSEM performance in correlating with SC was comparable to those obtained from C and PC, but eSEM (not C nor PC) provides information about directionality of the functional interactions. Second, interactions on a time scale much smaller than the sampling time, captured by instantaneous connectivity methods, are much more related to SC than slow directed influences captured by the lagged analysis. Indeed the performance in correlating with SC was much worse for GC and for the lagged version of eSEM. We expect these results to supply further insights to the interplay between SC and functional patterns, an important issue in the study of brain physiology and function.Comment: Accepted and published in Frontiers in Psychology in its current form. 27 pages, 1 table, 5 figures, 2 suppl. figure

Historia y noticias del culto a la Virgen en el antiguo reino de León

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201

Measurement of Length and Position with Frequency Combs

We show two different absolute distance measurement methods with micrometer accuracy based on frequency combs, and we discuss possible applications. Using a mode- locked laser and MEMS-based tracking optics, we measure the 3D position of a retroreflector within 10 ms and with a 24 μm volumetric accuracy. We also investigate modulator-based combs and show that they enable highly sensitive surface topography measurements with microsecond acquisition times and micrometer precision. Moreover, the potential for photonic integration of frequency comb sources is explored

Localization properties of a one-dimensional tight-binding model with non-random long-range inter-site interactions

We perform both analytical and numerical studies of the one-dimensional tight-binding Hamiltonian with stochastic uncorrelated on-site energies and non-fluctuating long-range hopping integrals . It was argued recently [A. Rodriguez at al., J. Phys. A: Math. Gen. 33, L161 (2000)] that this model reveals a localization-delocalization transition with respect to the disorder magnitude provided . The transition occurs at one of the band edges (the upper one for and the lower one for). The states at the other band edge are always localized, which hints on the existence of a single mobility edge. We analyze the mobility edge and show that, although the number of delocalized states tends to infinity, they form a set of null measure in the thermodynamic limit, i.e. the mobility edge tends to the band edge. The critical magnitude of disorder for the band edge states is computed versus the interaction exponent by making use of the conjecture on the universality of the normalized participation number distribution at transition.Comment: 7 pages, 6 postscript figures, uses revtex

Aplicabilidad de las zeolitas como regulador de fraguado

El presente trabajo propone sustituir la proporción que corresponde al yeso en un cemento pórtland por zeolita natural, a fin de regular el fraguado de la pasta en condiciones más o menos similares a las ordinarias, y obtener igualmente resistencias mecánicas aceptables. Los criterios seguidos en esta investigación tienen su base en la propiedad de las zeolitas como intercambiadores iónicos, mediante la cual pueden saturarse de agua rápidamente, controlando la humedad de la pasta, y neutralizando así la reacción del C3A con el Ca(OH)2; de este modo, “ralentizan” el fraguado durante un período de tiempo lo suficientemente adecuado como para facilitar la hidratación óptima de los silicatos, principalmente los bicálcicos, con la formación de variedades secundarias más estables, como la tobermorita. Las resistencias mecánicas obtenidas en esta investigación alcanzaron los 59,3 Mpa a los 28 días. Asimismo, los ensayos para la determinación de los tiempos de inicio y final de fraguado arrojaron resultados de 95 y 135 minutos, respectivamente, mientras que la expansión resultó igual a cero en todos los casos. Palabras claves: zeolitas, yeso, fraguado, cemento, resistencia ABSTRACT This work proposes to substitute the proportion of gypsum on cement by natural zeolite, in order to regulate the forged of the mortar under conditions more or less similar to the ordinary ones, and to obtain high mechanical strength. The approaches used in this investigation have been focused on the zeolites property as ion-exchanger, by means of which it can be quickly saturated itself with water, controlling the humidity inside mortar, and neutralizing the reaction of both, the C3A and Ca(OH)2; this way, zeolites diminishes the forged speed during an appropriate time in which it allows the complete hydrate of the silicates, mainly the belite, with the formation of secondary more stable varieties, as tobermorite. The mechanical strength obtained in this investigation reached 59,3 Mpa at 28 days. Also, the tests for the determination of the times of starting-final forged have reported results of 95 and 135 minutes, while the volume stability was similar to zero in all the cases. Key words: zeolites, gypsum, forged, cement, strengt

Geographic Inequalities in All-Cause Mortality in Japan: Compositional or Contextual?

Background: A recent study from Japan suggested that geographic inequalities in all-cause premature adult mortality have increased since 1995 in both sexes even after adjusting for individual age and occupation in 47 prefectures. Such variations can arise from compositional effects as well as contextual effects. In this study, we sought to further examine the emerging geographic inequalities in all-cause mortality, by exploring the relative contribution of composition and context in each prefecture. Methods We used the 2005 vital statistics and census data among those aged 25 or older. The total number of decedents was 524,785 men and 455,863 women. We estimated gender-specific two-level logistic regression to model mortality risk as a function of age, occupation, and residence in 47 prefectures. Prefecture-level variance was used as an estimate of geographic inequalities in mortality, and prefectures were ranked by odds ratios (ORs), with the reference being the grand mean of all prefectures (value = 1). Results: Overall, the degree of geographic inequalities was more pronounced when we did not account for the composition (i.e., age and occupation) in each prefecture. Even after adjusting for the composition, however, substantial differences remained in mortality risk across prefectures with ORs ranging from 0.870 (Okinawa) to 1.190 (Aomori) for men and from 0.864 (Shimane) to 1.132 (Aichi) for women. In some prefectures (e.g., Aomori), adjustment for composition showed little change in ORs, while we observed substantial attenuation in ORs in other prefectures (e.g., Akita). We also observed qualitative changes in some prefectures (e.g., Tokyo). No clear associations were observed between prefecture-level socioeconomic status variables and the risk of mortality in either sex. Conclusions: Geographic disparities in mortality across prefectures are quite substantial and cannot be fully explained by differences in population composition. The relative contribution of composition and context to health inequalities considerably vary across prefectures