Periodic orbit effects on conductance peak heights in a chaotic quantum dot

We study the effects of short-time classical dynamics on the distribution of Coulomb blockade peak heights in a chaotic quantum dot. The location of one or both leads relative to the short unstable orbits, as well as relative to the symmetry lines, can have large effects on the moments and on the head and tail of the conductance distribution. We study these effects analytically as a function of the stability exponent of the orbits involved, and also numerically using the stadium billiard as a model. The predicted behavior is robust, depending only on the short-time behavior of the many-body quantum system, and consequently insensitive to moderate-sized perturbations.Comment: 14 pages, including 6 figure

Use of social media in higher education: a new teaching competence arises

[ES] El presente trabajo se centra en la contextualización y el empleo de los medios sociales, así como de sus aplicaciones y herramientas colaborativas, por parte de los docentes en el Espacio Europeo de la Educación Superior (EEES). Los mecanismos que ofrecen estos medios de comunicación social permiten a sus usuarios establecer nuevas estrategias basadas en la colaboración y en la comunicación multidireccional, que resultaban impensables hace unos años. La aportación principal de estos medios son sus funcionalidades, a saber: interrelación de sus usuarios en tiempo real y diferido; colaboración eliminando las distancias; afiliación; divulgación y valoración de trabajos científicos; entre otras. A lo largo de estas páginas se incide en la capacidad de aprovechar al máximo las formas de comunicación e interacción que ofrecen estos medios al profesorado. Tal es su impacto, que se plantea como objeto de la cuestión que aquí nos ocupa, si el dominio de los medios sociales puede ser considerado como una nueva competencia docente con entidad propia. La utilización adecuada de estos medios responde a una nueva organización social basada en la colaboración y el compromiso. La formación de los docentes en esta competencia podría resultar, en breve, una prioridad que permita a las universidades afrontar con garantías los retos presentes y futuros del dinámico y cambiante contexto del EEES. En conclusión, las dimensiones pedagógicas e investigadoras del docente universitario en la sociedad cognitiva se encuentran en constante evolución, en relación directa con el desarrollo vertiginoso de los medios sociales.[EN] This paper focuses on the context and the use of social media and its applications and collaborative tools by teachers in the European Higher Education Area (EHEA). Mechanisms offered by these media allow users to establish new strategies based on collaboration and communication in multiple directions that were unthinkable a few years ago. The main contributions of these media are its features, namely: interconnection of its users in real time and deferred; collaboration eliminating distances, membership, outreach and assessment of scientific works, among others. Throughout these pages affects the ability to make the most of the forms of communication and interaction offered by these means to teachers. Such is its impact, which arises as an object of the question that concerns us here, if the domain of social media can be considered as a new teacher competence in its own right. Proper use of these media reflects a new social organization based on cooperation and compromise. The training of teachers in this competition can be, in short, a priority that allows universities successfully tackle the current and future challenges of the dynamic and changing context of the EHEA. In conclusion, teaching and research dimensions of university teachers in the learning society are constantly evolving, directly related to the rapid development of social media.De-Juanas Oliva, A.; Diestro Fernández, A. (2012). Empleo de los medios sociales en educación superior: una nueva competencia docente en ciernes. REDU. Revista de Docencia Universitaria. 10(2):365-379. https://doi.org/10.4995/redu.2012.6113OJS365379102Aced, C. (2009). Redes Sociales. Palp: Barcelona.Beltrán, J.A. y Pérez, L.F. (2005). "El profesor universitario desde la perspectiva de los alumnos". Revista de Psicología y Educación, 1 (1), 79-114.Bradley, A.J. y McDonald, M.P. (2012). La organización Social: convertir en resultados las oportunidades de las redes sociales. Barcelona: Profit.Cano, E. (2007). Las competencias de los docentes. En A. López (Coord.), El desarrollo de Competencias docentes en la formación del profesorado, pp.33-60. Madrid: MEC.Caurcel, M.J. y Morales, J. (2008). La enseñanza y el aprendizaje en la Universidad. En A. Rodríguez, M.J. Caurcel y A.M. Ramos (Coords.), Didáctica en el Espacio Europeo de Educación Superior: Guías de trabajo autónomo, pp.47-72. Madrid: EOS.De-Juanas, A. (2010). Contemplando Bolonia: una década de acontecimientos en la formación del Espacio Europeo de Educación Superior. Foro de educación, 12, 69-91.De-Juanas, A., García, J. y Diestro, A. (2010). Análisis de las ventajas del uso pedagógico de las redes sociales de Internet. XV Congreso Internacional de tecnologías para la Educación y el Conocimiento: redes sociales para el aprendizaje, Madrid, UNED, 3 de junio.Esteban, R.M. y Menjívar, S.V. (Coords.) (2011). Una mirada internacional a las competencias docentes universitarias. Barcelona: Octaedro.Esteve Mon, F.M. y Gisbert Cervera, M. (2011). El nuevo paradigma de aprendizaje y las nuevas tecnologías. Revista de Docencia Universitaria. REDU. Monográfico: El espacio europeo de educación superior. Hacia dónde va la Universidad Europea?. 9 (3), 55-73. Recuperado el 20 de marzo de 2012 en http://redaberta.usc.es/reduGallego, M., Larriba, I.J. y Fernández, L. (2011). Sinergias entre las redes sociales y la comunidad de investigadores. En J. Sampedro, A. Ferro, J. Coterón (Coords.), Redes de investigación en Ciencias del Deporte, pp. 149-164.Giles, J. (2005). Special Report Internet encyclopaedias go head to head. Nature, 438, 900-901.Kaplan A.M., Haenlein M. (2010). Users of the world, unite! The challenges and opportunities of social media. Business Horizons, 53 (1), 59-68.Kluemper, D. H., Rosen, P. A., & Mossholder, K. W. (en prensa). Social networking websites, personality ratings, and the organizational context: More than meets the eye? Journal of Applied Social Psychology.Perrenaud, P. (2004). Diez nuevas competencias para enseñar. Barcelona: Graó.Michavila, F. (2011). Bolonia en crisis. Revista de Docencia Universitaria, REDU. Monográfico: El espacio europeo de educación superior. Hacia dónde va la Universidad Europea?. 9 (3), 15-27. Recuperado el 20 de marzo de 2012 en http://redaberta.usc.es/reduRubia, B. (2010). La implicación de las nuevas tecnologías en el aprendizaje colaborativo. Tendencias pedagógicas, 16, 89-106.Toffler, A. (1990). El Cambio de Poder. Barcelona: Ed. Plaza & Janes.Valcárcel, M. (2003). La Preparación del Profesorado universitario español para la Convergencia Europea en Educación Superior. Informe de investigación. Recuperado el 21 de septiembre de 2009 desde http://www.etsit.upv.es/paeees/pdf/PRY_MECD _PDI_EEES.pdfValle, J. M. (2010). La política educativa de la Unión Europea en el laberinto del Minotauro. Foro de educación, 12, 7-23.Zabalza, M.A. (2002). La enseñanza universitaria: el escenario y sus protagonistas. Madrid: Narcea.Zabalza, M.A. (2003). Las competencias docentes del profesorado universitario. Calidad y desarrollo profesional. Madrid: Narcea.Zabalza M.A. (2011). Prólogo. En R. Mª. Esteban y S.V. Menjívar (Coords.), Una mirada internacional a las competencias docentes universitarias, pp. 13-16. Barcelona: Octaedro

Environmentally-determined production frontiers and lease utilization in Virginia\u27s eastern oyster aquaculture industry

During the last decade, oyster aquaculture has rebounded in Virginia and has been associated with an increase in subaqueous leased area. Production levels remain historically low, however, and many leases are thought to be underutilized. This study uses a novel approach leveraging high-resolution environmental data to evaluate lease utilization and identify constraints on aquaculture development. Stochastic Frontier Analysis (SFA) and Data Envelopment Analysis (DEA) were used to define environmentally-determined production frontiers, i.e. production possibilities based on empirical observations of aquaculture production, available space, and environmental conditions. Both methods estimated Lease Capacity Utilization (LCU, from 0 to 1) for leases producing oysters with intensive culture methods from 2007 to 2016. Models revealed significant heterogeneity in lease utilization and mean LCU scores of 0.25 (DEA) and 0.27 (SFA), which suggests many leases could scale up production or reduce the size of their lease to more efficiently utilize ambient environmental conditions (i.e., achieve scores closer to 1). Capacity underutilization arising from characteristics of the leaseholder and surrounding spatial environment were quantified and indicated efficiency gains for horizontally integrated leaseholders, though also suggested leases in more populated areas were less efficiently used, possibly due to increased use conflicts. These results highlight potential externalities and tradeoffs associated with aquaculture development and can inform the design of more efficient aquaculture leasing systems

Hamiltonization of Nonholonomic Systems and the Inverse Problem of the Calculus of Variations

We introduce a method which allows one to recover the equations of motion of a class of nonholonomic systems by finding instead an unconstrained Hamiltonian system on the full phase space, and to restrict the resulting canonical equations to an appropriate submanifold of phase space. We focus first on the Lagrangian picture of the method and deduce the corresponding Hamiltonian from the Legendre transformation. We illustrate the method with several examples and we discuss its relationship to the Pontryagin maximum principle.Comment: 23 pages, accepted for publication in Rep. Math. Phy

Likely locations of sea turtle stranding mortality using experimentally-calibrated, time and space-specific drift models

This is an accepted manuscript of the published article. Sea turtle stranding events provide an opportunity to study drivers of mortality, but causes of strandings are poorly understood. A general turtle carcass oceanographic drift model was developed to estimate likely mortality locations from coastal sea turtle stranding records. Key model advancements include realistic direct wind forcing on carcasses, temperature driven carcass decomposition and the development of mortality location predictions for individual strandings. We applied this model to 2009-2014 stranding events within the Chesapeake Bay, Virginia. Predicted origin of vessel strike strandings were compared to commercial vessel data, and potential hazardous turtle-vessel interactions were identified in the southeastern Bay and James River. Commercial fishing activity of gear types with known sea turtle interactions were compared to predicted mortality locations for stranded turtles with suggested fisheries-induced mortality. Probable mortality locations for these strandings varied seasonally, with two distinct areas in the southwest and southeast portions of the lower Bay. Spatial overlap was noted between potential mortality locations and gillnet, seine, pot, and pound net fisheries, providing important information for focusing future research on mitigating conflict between sea turtles and human activities. Our ability to quantitatively assess spatial and temporal overlap between sea turtle mortality and human uses of the habitat were hindered by the low resolution of human use datasets, especially those for recreational vessel and commercial fishing gear distributions. This study highlights the importance of addressing these data gaps and provides a meaningful conservation tool that can be applied to stranding data of sea turtles and other marine megafauna worldwide

Consequences of drift and carcass decomposition for estimating sea turtle mortality hotspots

Sea turtle strandings provide important mortality information, yet knowledge of turtle carcass at-sea drift and decomposition characteristics are needed to better understand and manage where these mortalities occur. We used empirical sea turtle carcass decomposition and drift experiments in the Chesapeake Bay, Virginia, USA to estimate probable carcass oceanic drift times and quantify the impact of direct wind forcing on carcass drift. Based on the time period during which free-floating turtle carcasses tethered nearshore were buoyant, we determined that oceanic drift duration of turtle carcasses was highly dependent on water temperature and varied from 2 to 15 days during typical late spring to early fall Bay water conditions. The importance of direct wind forcing for turtle carcass drift was assessed based on track divergence rates from multiple simultaneous deployments of three types of surface drifters: bucket drifters, artificial turtles and turtle carcass drifters. Turtle drift along-wind leeway was found to vary from 1 to 4% of wind speed, representing an added drift velocity of approximately 0.03–0.1 m/s for typical Bay wind conditions. This is comparable to current speeds in the Bay (0.1–0.2 m/s), suggesting wind is important for carcass drift. Estimated carcass drift parameters were integrated into a Chesapeake Bay oceanographic drift model to predict carcass drift to terrestrial stranding locations. Increased drift duration (e.g., due to low temperatures) increases mean distance between expected mortality events and stranding locations, as well as decreases overall likelihood of retention in the Bay. Probable mortality hotspots for the peak month of strandings (June) were identified off coastal southeastern Virginia and within the lower Bay, including the Bay mouth and lower James River. Overall, results support that sea turtle drift time is quite variable, and varies greatly depending on water and air temperature as well as oceanic conditions. Knowledge of these parameters will improve our ability to interpret stranding events around the globe

Mathematical methods and models for radiation carcinogenesis studies

Research on radiation carcinogenesis requires a twofold approach. Studies of primary molecular lesions and subsequent cytogenetic changes are essential, but they cannot at present provide numerical estimates of the risk of small doses of ionizing radiations. Such estimates require extrapolations from dose, time, and age dependences of tumor rates observed in animal studies and epidemiological investigations, and they necessitate the use of statistical methods that correct for competing risks. A brief survey is given of the historical roots of such methods, of the basic concepts and quantities which are required, and of the maximum likelihood estimates which can be derived for right censored and double censored data. Non-parametric and parametric models for the analysis of tumor rates and their time and dose dependences are explained

Medium-chain triglyceride supplementation may increase working memory in older adults: A pilot study

Poster presentatio

Coupled-channel effective field theory and proton-7^7Li scattering

We apply the renormalisation group (RG) to analyse scattering by short-range forces in systems with coupled channels. For two S-wave channels, we find three fixed points, corresponding to systems with zero, one or two bound or virtual states at threshold. We use the RG to determine the power countings for the resulting effective field theories. In the case of a single low-energy state, the resulting theory takes the form of an effective-range expansion in the strongly interacting channel. We also extend the analysis to include the effects of the Coulomb interaction between charged particles. The approach is then applied to the coupled $p+{^7}$Li and $n+{^7}$Be channels which couple to a $J^P=2^-$ state of $^8$Be very close to the $n+{^7}$Be threshold. At next-to-leading order, we are able to get a good description of the $p+{^7}$Li phase shift and the ${^7}$Be(n,p)${^7}$Li cross section using four parameters. Fits at one order higher are similarly good but the available data are not sufficient to determine all five parameters uniquely.Comment: 22 pages, 2 figures, RevTeX4, typos corrected, accepted for publication in European Physical Journal

Quantum carpet interferometry for trapped atomic Bose-Einstein condensates

We propose an ``interferometric'' scheme for Bose-Einstein condensates using near-field diffraction. The scheme is based on the phenomenon of intermode traces or quantum carpets; we show how it may be used in the detection of weak forces.Comment: 4 figures. Submitted to Phys. Rev.