Landform evolution in the headwaters area of Araguaia river (Mato Grosso and Goiás states, Brazil).

Editors: Francisco Gutiérrez, Mateo Gutiérrez, Gloria Desir, Jesús Guerrero, Pedro Lucha, Cinta Marín, José María García-Ruiz

Interaction of surface acoustic waves with a two-dimensional electron gas in the presence of spin splitting of the Landau bands

The absorption and variation of the velocity of a surface acoustic wave of frequency $f$= 30 MHz interacting with two-dimensional electrons are investigated in GaAs/AlGaAs heterostructures with an electron density $n=(1.3 - 2.8) \times 10^{11} cm^{-2}$ at $T$=1.5 - 4.2 K in magnetic fields up to 7 T. Characteristic features associated with spin splitting of the Landau level are observed. The effective g factor and the width of the spin-split Landau bands are determined: $g^* \simeq 5$ and $A$=0.6 meV. The greater width of the orbital-split Landau bands (2 meV) relative to the spin-split bands is attributed to different shielding of the random fluctuation potential of charged impurities by 2D electrons. The mechanisms of the nonlinearities manifested in the dependence of the absorption and the velocity increment of the SAW on the SAW power in the presence of spin splitting of the Landau levels are investigated.Comment: Revtex 5 pages + 5 EPS Figures, v.2 - minor corrections in text and pic

Electron localization in sound absorption oscillations in the quantum Hall effect regime

The absorption coefficient for surface acoustic waves in a piezoelectric insulator in contact with a GaAs/AlGaAs heterostructure (with two-dimensional electron mobility $\mu= 1.3\times 10^5 cm^2/V\cdot s)$ at T=4.2K) via a small gap has been investigated experimentally as a function of the frequency of the wave, the width of the vacuum gap, the magnetic field, and the temperature. The magnetic field and frequency dependencies of the high-frequency conductivity (in the region 30-210 MHz) are calculated and analyzed. The experimental results can be explained if it assumed that there exists a fluctuation potential in which current carrier localization occurs. The absorption of the surface acoustic waves in an interaction with two-dimensional electrons localized in the energy "tails" of Landau levels is discussed.Comment: RevTeX 6 pages+6 EPS pic

Project-based, collaborative, algorithmic robotics for high school students: Programming self-driving race cars at MIT

We describe the pedagogy behind the MIT Beaver Works Summer Institute Robotics Program, a new high-school STEM program in robotics. The program utilizes state-of-the-art sensors and embedded computers for mobile robotics. These components are carried on an exciting 1/10-scale race-car platform. The program has three salient, distinguishing features: (i) it focuses on robotics software systems: the students design and build robotics software towards real-world applications, without being distracted by hardware issues; (ii) it champions project-based learning: the students learn through weekly project assignments and a final course challenge; (iii) the learning is implemented in a collaborative fashion: the students learn the basics of collaboration and technical communication in lectures, and they work in teams to design and implement their software systems. The program was offered as a four-week residential program at MIT in the summer of 2016. In this paper, we provide the details of this new program, its teaching objectives, and its results. We also briefly discuss future directions and opportunities

Personalized treatment of asthma: the importance of sex and gender differences

An individual's sex (nominally 'male' or 'female', based on biological attributes) and gender (a complex term, referring to socially constructed roles, behaviors, and expressions of identity) influences the clinical course of asthma in several ways. The physiological development of the lungs and effects of sex hormones may explain why more boys have asthma than girls, and post-puberty, more women have asthma than men. Female sex hormones have an impact throughout the lifespan and are associated with poor asthma control. Gender may influence exposure to asthma triggers, and sex and gender can influence the prevalence of comorbidities and interactions with healthcare professionals (HCPs). Despite widely reported sex and gender-based differences in asthma and asthma management, these issues are frequently not considered by HCPs. There is also inconsistency around use of 'sex' and 'gender' in scientific discourse, and research is needed to better define sex and gender-based differences and how they might interact to influence asthma outcomes. This review outlines the impact an individual's sex and gender can have on the pathogenesis, clinical course, diagnosis, treatment, and management of asthma

Orbital-based Scenario for Magnetic Structure of Neptunium Compounds

In order to understand a crucial role of orbital degree of freedom in the magnetic structure of recently synthesized neptunium compounds NpTGa_5 (T=Fe, Co, and Ni), we propose to discuss the magnetic phase of an effective two-orbital model, which has been constructed based on a j-j coupling scheme to explain the magnetic structure of uranium compounds UTGa_5. By analyzing the model with the use of numerical technique such as exact diagonalization, we obtain the phase diagram including several kinds of magnetic states. An orbital-based scenario is discussed to understand the change in the magnetic structure among C-, A-, and G-type antiferromagnetic phases, experimentally observed in NpFeGa_5, NpCoGa_5, and NpNiGa_5.Comment: 18 pages, 8 figures, to appear in New Journal of Physic

Symposium on Obesity and Asthma-November 2006

L’asthme et l’obésité sont fréquemment associés et l’obésité est considérée comme un facteur impliqué tant dans l’augmentation de la sévérité que dans le développement de l’asthme. Ce document est un compte-rendu des présentations effectuées dans le cadre d’un symposium du Réseau en santé respiratoire du Fonds de la recherche en santé du Québec qui a eu lieu à Montréal le 2 novembre 2006, en collaboration avec le McGill University – Strauss Severe Asthma Program, l’Université Laval (Québec) et l’Université de Montréal. Au cours de cette rencontre, divers aspects de la relation entre obésité et asthme ont été abordés, en regard des modèles animaux, des influences génétiques, hormonales et physiologiques, de l’influence des comorbidités (ex : syndrome d’apnée du sommeil), de l’épidémiologie, des aspects cliniques et psychologiques et, enfin, du traitement de l’asthme chez la personne obèse.Asthma and obesity are frequently associated, and obesity has been considered a factor contributing to both an increase in severity of asthma and to its development. The present document summarizes the proceedings of a symposium held in Montreal, Quebec, on November 2, 2006, under the auspices of the Réseau en santé respiratoire du Fonds de la recherche en santé du Québec in collaboration with the McGill University - Strauss Severe Asthma Program, Université Laval (Quebec City) and Université de Montréal. It includes an overview of the various aspects of the relationships between asthma and obesity with regard to animal models; genetic, hormonal and physiological determinants; influence of comorbidities (eg, sleep apnea syndrome); epidemiology; clinical and psychological features; and management of asthma in the obese population

How much do health care providers value a community-based asthma care program? – a survey to collect their opinions on the utilities of and barriers to its uptake

<p>Abstract</p> <p>Background</p> <p>A comprehensive asthma care program (ACP) based on Canadian Asthma Consensus Guidelines was implemented in 8 primary care sites in Ontario, Canada. A survey was distributed to health care providers' (HCPs) to collect their opinions on the utilities of and barriers to the uptake of the ACP.</p> <p>Methods</p> <p>A 39-item self-administered survey was mailed to 184 HCPs and support staff involved in delivering the ACP at the end of implementation. The items were presented in mixed formats with most items requiring responses on a five-point Likert scale. Distributions of responses were analyzed and compared across types of HCPs and sites.</p> <p>Results</p> <p>Of the 184 surveys distributed, 108 (59%) were returned, and of that, 83 were completed by HCPs who had clinical contact with the patients. Overall, 95% of the HCPs considered the ACP useful for improving asthma care management. Most HCPs favored using the asthma care map (72%), believed it decreased uncertainties and variations in patient management (91%), and considered it a convenient and reliable source of information (86%). The most commonly reported barrier was time required to complete the asthma care map. Over half of the HCPs reported challenges to using spirometry, while almost 40% identified barriers to using the asthma action plan.</p> <p>Conclusion</p> <p>Contrary to the notion that physicians believe that guidelines foster cookbook medicine, our study showed that HCPs believed that the ACP offered an effective and reliable approach for enhancing asthma care and management in primary care.</p