Conductance fluctuations at the integer quantum Hall plateau transition

We study numerically conductance fluctuations near the integer quantum Hall effect plateau transition. The system is presumed to be in a mesoscopic regime, with phase coherence length comparable to the system size. We focus on a two-terminal conductance G for square samples, considering both periodic and open boundary conditions transverse to the current. At the plateau transition, G is broadly distributed, with a distribution function close to uniform on the interval between zero and one in units of e^2/h. Our results are consistent with a recent experiment by Cobden and Kogan on a mesoscopic quantum Hall effect sample.Comment: minor changes, 5 pages LaTex, 7 postscript figures included using epsf; to be published Phys. Rev. B 55 (1997

Criticality in the two-dimensional random-bond Ising model

The two-dimensional (2D) random-bond Ising model has a novel multicritical point on the ferromagnetic to paramagnetic phase boundary. This random phase transition is one of the simplest examples of a 2D critical point occurring at both finite temperatures and disorder strength. We study the associated critical properties, by mapping the random 2D Ising model onto a network model. The model closely resembles network models of quantum Hall plateau transitions, but has different symmetries. Numerical transfer matrix calculations enable us to obtain estimates for the critical exponents at the random Ising phase transition. The values are consistent with recent estimates obtained from high-temperature series.Comment: minor changes, 7 pages LaTex, 8 postscript figures included using epsf; to be published Phys. Rev. B 55 (1997

Risk Assessment to the Health of Amazonian Indigenous For the Consumption of Fish, Meat of Hunts and Vegetables Containing Metylmercury

This study was to evaluate the exposure to methylmercury (HgMe) and the potential health risk of Tupari Indians through the consumption of their main foods. Were collection of samples of plant foods and muscle tissue from different species of fish and wild animals consumed in three villages of the Rio Branco Indigenous Land in Rondônia, in the Brazilian Amazon. The HgMe was measured in an atomic fluorescence spectrophotometer with gas chromatography. The statistical treatment of the data was performed by software R. Of the six different plant species, only sweet potato (Ipomoea batatas) had mean concentrations of HgMe above the limit of detection of the analytical technique for the three villages. There was a significant difference in the levels of HgMe between the species of wild animals and fish belonging to the same alimentary habit. Carnivores presented higher levels of HgMe than those obtained for non-predators, both for fish and for wild animals. The results of the assessment of the potential risk to indigenous health indicated a total HgMe of the weekly ingestion rate (WIR) of between 8.4 and 15.0 μg / kg of body weight for the villages evaluated, extrapolating all reference doses ( RfD) regarding for the Provisional Tolerable Weekly Intake (PTWI). The risk quotients (RQ) varied from 5.3 to 21.4, considerably exceeding the limit (RQ ≤ 1), which allows to consider the impossibility of toxic effects of HgMe. The fishes accounted for the highest percentage of WIR of HgMe for all villages, with an emphasis on predatory species. Considering the nutritional value of fish meat, it is suggested the continuity of the consumption of this meat in the villages with preference for non-carnivores

Altered Neurocircuitry in the Dopamine Transporter Knockout Mouse Brain

The plasma membrane transporters for the monoamine neurotransmitters dopamine, serotonin, and norepinephrine modulate the dynamics of these monoamine neurotransmitters. Thus, activity of these transporters has significant consequences for monoamine activity throughout the brain and for a number of neurological and psychiatric disorders. Gene knockout (KO) mice that reduce or eliminate expression of each of these monoamine transporters have provided a wealth of new information about the function of these proteins at molecular, physiological and behavioral levels. In the present work we use the unique properties of magnetic resonance imaging (MRI) to probe the effects of altered dopaminergic dynamics on meso-scale neuronal circuitry and overall brain morphology, since changes at these levels of organization might help to account for some of the extensive pharmacological and behavioral differences observed in dopamine transporter (DAT) KO mice. Despite the smaller size of these animals, voxel-wise statistical comparison of high resolution structural MR images indicated little morphological change as a consequence of DAT KO. Likewise, proton magnetic resonance spectra recorded in the striatum indicated no significant changes in detectable metabolite concentrations between DAT KO and wild-type (WT) mice. In contrast, alterations in the circuitry from the prefrontal cortex to the mesocortical limbic system, an important brain component intimately tied to function of mesolimbic/mesocortical dopamine reward pathways, were revealed by manganese-enhanced MRI (MEMRI). Analysis of co-registered MEMRI images taken over the 26 hours after introduction of Mn^(2+) into the prefrontal cortex indicated that DAT KO mice have a truncated Mn^(2+) distribution within this circuitry with little accumulation beyond the thalamus or contralateral to the injection site. By contrast, WT littermates exhibit Mn^(2+) transport into more posterior midbrain nuclei and contralateral mesolimbic structures at 26 hr post-injection. Thus, DAT KO mice appear, at this level of anatomic resolution, to have preserved cortico-striatal-thalamic connectivity but diminished robustness of reward-modulating circuitry distal to the thalamus. This is in contradistinction to the state of this circuitry in serotonin transporter KO mice where we observed more robust connectivity in more posterior brain regions using methods identical to those employed here

The COMPASS Experiment at CERN

The COMPASS experiment makes use of the CERN SPS high-intensitymuon and hadron beams for the investigation of the nucleon spin structure and the spectroscopy of hadrons. One or more outgoing particles are detected in coincidence with the incoming muon or hadron. A large polarized target inside a superconducting solenoid is used for the measurements with the muon beam. Outgoing particles are detected by a two-stage, large angle and large momentum range spectrometer. The setup is built using several types of tracking detectors, according to the expected incident rate, required space resolution and the solid angle to be covered. Particle identification is achieved using a RICH counter and both hadron and electromagnetic calorimeters. The setup has been successfully operated from 2002 onwards using a muon beam. Data with a hadron beam were also collected in 2004. This article describes the main features and performances of the spectrometer in 2004; a short summary of the 2006 upgrade is also given.Comment: 84 papes, 74 figure

Interactions of Cathinone NPS with Human Transporters and Receptors in Transfected Cells

Pharmacological assays carried out in transfected cells have been very useful for describing the mechanism of action of cathinone new psychoactive substances (NPS). These in vitro characterizations provide fast and reliable information on psychoactive substances soon after they emerge for recreational use. Well-investigated comparator compounds, such as methamphetamine, 3,4-methylenedioxymethamphetamine, cocaine, and lysergic acid diethylamide, should always be included in the characterization to enhance the translation of the in vitro data into clinically useful information. We classified cathinone NPS according to their pharmacology at monoamine transporters and receptors. Cathinone NPS are monoamine uptake inhibitors and most induce transporter-mediated monoamine efflux with weak to no activity at pre- or postsynaptic receptors. Cathinones with a nitrogen-containing pyrrolidine ring emerged as NPS that are extremely potent transporter inhibitors but not monoamine releasers. Cathinones exhibit clinically relevant differences in relative potencies at serotonin vs. dopamine transporters. Additionally, cathinone NPS have more dopaminergic vs. serotonergic properties compared with their non-β-keto amphetamine analogs, suggesting more stimulant and reinforcing properties. In conclusion, in vitro pharmacological assays in heterologous expression systems help to predict the psychoactive and toxicological effects of NPS

Diagnóstico de las asimetrías faciales y dentales

ABSTRACT: Craniofacial asymmetries are a characteristic of the human species as long as they are within reasonable limits. The asymmetries can be of dental, skeletal, functional origin or a combination of these. Likewise, there are diverse etiologic factors such as the genetic ones, the environmental ones and the functional ones that should be understood in order to achieve a good diagnosis and in this way focus on an appropriate treatment plan. The purpose of this article is to integrate the general knowledge of transversal problems focused on the diagnosis, evaluating the different etiologic factors, the prevalence and the clinical and radiographic characteristics of the dental, skeletal and functional asymmetries.RESUMEN: Las asimetrías craneofaciales son un rasgo característico de la especie humana mientras se encuentren dentro de límites razonables. Las asimetrías pueden ser de origen dental, esquelético y funcional o una combinación de éstas. Así mismo existen diversos factores etiológicos como son los genéticos, los ambientales y los funcionales que deben ser bien comprendidos para lograr un buen diagnóstico y de esta forma enfocar un adecuado plan de tratamiento. Este artículo tiene como propósito integrar un conocimiento general de los problemas transversales enfocado hacia el diagnóstico, evaluando los diferentes factores etiológicos, la prevalencia, y las características clínicas y radiográficas de las asimetrías dentales, esqueléticas y funcionales

FAK Is a Critical Regulator of Neuroblastoma Liver Metastasis

Neuroblastomas express increased levels of gastrin-releasing peptide receptor (GRP-R). However, the exact molecular mechanisms involved in GRP-R-mediated cell signaling in neuroblastoma growth and metastasis are unknown. Here, we report that focal adhesion kinase (FAK), as a critical downstream target of GRP-R, is an important regulator of neuroblastoma tumorigenicity. We found that FAK expression correlates with GRP-R expression in human neuroblastoma sections and cell lines. GRP-R overexpression in SK-N-SH cells increased FAK, integrin α3 and β1 expressions and cell migration. These cells demonstrated flatter cell morphology with broad lamellae, in which intense FAK expression was localized to the leading edges of lamellipodia. Interestingly, FAK activation was, in part, dependent on integrin α3 and β1 expression. Conversely, GRP-R silencing decreased FAK as well as Mycn levels in BE(2)-C cells, which displayed a denser cellular morphology. Importantly, rescue experiments in GRP-R silenced BE(2)-C cells showed FAK overexpression significantly enhanced cell viability and soft agar colony formation; similarly, FAK overexpression in SK-N-SH cells also resulted in increased cell growth. These effects were reversed in FAK silenced BE(2)-C cells in vitro as well as in vivo. Moreover, we evaluated the effect of FAK inhibition in vivo. FAK inhibitor (Y15) suppressed GRP-induced neuroblastoma growth and metastasis. Our results indicate that FAK is a critical downstream regulator of GRP-R, which mediates tumorigenesis and metastasis in neuroblastoma

Linking Remotely Sensed Carbon and Water Use Efficiencies with In Situ Soil Properties

The capacity of terrestrial ecosystems to sequester carbon dioxide (CO2 ) from the atmosphere is expected to be altered by climate change and CO2 fertilization, but this projection is limited by our understanding of how the soil system interacts with plants. Understanding the soil–vegetation interactions is essential to assess the magnitude and response of terrestrial ecosystems to the changing climate. Here, we used soil profile and satellite data to explore the role that soil properties play in regulating water and carbon use by plants. Data obtained for 19 terrestrial ecosystem sites in a warm temperate and humid climate were used to investigate the relationship between remotely sensed data and soil physical and chemical properties. Classification and regression tree results showed that in situ soil carbon isotope (δ 13C), and soil order were significant predictors (r2 = 0.39, mean absolute error (MAE) = 0 of 0.175 gC/KgH2O) of remotely sensed water use efficiency (WUE) based on the Moderate Resolution Imaging Spectroradiometer (MODIS). Soil extractable calcium (Ca), and land cover type were significant predictors of remotely sensed carbon use efficiency (CUE) based on MODIS and Landsat data-(r2 = 0.64–0.78, MAE = 0.04–0.06). We used gross primary productivity (GPP) derived from solar-induced fluorescence (SIF) data, based on the Orbiting Carbon Observatory-2 (OCO-2), to calculate WUE and CUE (referred to as WUESIF and CUESIF, respectively) for our study sites. The regression tree analysis revealed that soil organic matter and soil extractable magnesium (Mg), δ 13C, and soil silt content were the important predictors of both WUESIF (r2 = 0.19, MAE = 0.64 gC/KgH2O) and CUESIF (r2 = 0.45, MAE = 0.1), respectively. Our results revealed the importance of soil extractable Ca, soil carbon (S13C is a facet of soil carbon content), and soil organic matter predicting CUE and WUE. Insights gained from this study highlighted the importance of biotic and abiotic factors regulating plant and soil interactions. These types of data are timely and critical for accurate predictions of how terrestrial ecosystems respond to climate change

Development and validation of the Spanish short version of the Work Design Questionnaire (WDQ-S)

[eng] Job transformation is changing work characteristics at a fast pace. This makes work design matter more than ever before. The Work Design Questionnaire (WDQ) is a powerful measurement of current work characteristics that can be used when (re)designing work to be safe, healthy, and motivating. However, its length represents a relevant challenge to its application. This study aims to validate a short version of the WDQ (WDQ-S) for Spanish-speaking countries. Through a two-waves longitudinal design, the WDQ-S was validated in a sample of 653 workers from 27 Spanish companies. Results confirmed the hierarchical factor structure, which comprised four general and nine specific dimensions, good internal consistency, and acceptable levels of convergent and discriminant validity. Hierarchical regression analyses showed predictive and incremental validity on job satisfaction and performance. The main limitation is that the WDQ-S was not tested against the original version, instead test-retest reliability was performed. Future research should replicate these findings in other samples, validate this scale in other languages and expand research with other outcomes. This study is relevant to industrial and occupational ergonomics as it provides a useful tool for designing healthy, productive, and sustainable workplaces