Electron-positron pair creation in the superposition of two oscillating electric field pulses with largely different frequency, duration and relative positioning

Production of electron-positron pairs in two oscillating strong electric field pulses with largely different frequencies and durations is considered. In a first scenario, the influence of a low-frequency background field on pair production by a short main pulse of high frequency is analyzed. The background field is shown to cause characteristic modifications of the momentum spectra of created particles which, in turn, may be used for imaging of the background pulse. In a second scenario, an ultrashort, relatively weak assisting pulse is superimposed onto a strong main pulse. By studying the dependence of the pair production on the field parameters it is shown that duration and relative position of the ultrashort pulse modify the momentum spectra of produced particles in a distinctive way. Both scenarios enable, moreover, to extract partial information about the time periods when pairs with certain momenta are produced predominantly.Comment: 10 pages, 9 figure

Trastorno por déficit de atención e hiperactividad dual en niños y adolescentes internados en un centro para el tratamiento de adicciones

Introducción: El trastorno por déficit de atención e hiperactividad es el trastorno psiquiátrico más frecuente en la edad escolar y múltiples estudios han evidenciado que es un factor de riesgo independiente para desarrollar abuso o dependencia de sustancias. El objetivo principal de este trabajo es determinar la frecuencia de este trastorno y otros trastornos externalizantes en niños y adolescentes internados en un centro de referencia, así como el impacto de estas patologías en la escolarización, inicio precoz del consumo de sustancias, caracterización de las conductas adictivas y perfil de los pacientes. Sujetos y métodos: Se analizaron las historias clínicas de la totalidad de niños y adolescentes internados en un centro de referencia durante los meses de junio y julio de 2013, todos ellos con el diagnóstico de trastorno por uso de sustancias. Se realizaron entrevistas estructuradas para los diagnósticos de déficit de atención e hiperactividad y otros trastornos externalizantes. Resultados: Se determinó la presencia de comorbilidad con déficit de atención e hiperactividad en el 40% de los pacientes y de comorbilidad con trastorno disocial en 95% de los pacientes. Los pacientes con déficit de atención e hiperactividad presentaron mayores dificultades en la escolarización y en el inicio precoz en el uso de sustancias. Conclusión: el trastorno por déficit de atención e hiperactividad es frecuentemente minimizado en sus síntomas y sobre todo en las posibles consecuencias negativas para el paciente; si su diagnóstico no se realiza a tiempo, no será posible un buen abordaje terapéutico del niño y adolescente

On the connection between Hamilton and Lagrange formalism in Quantum Field Theory

The connection between the Hamilton and the standard Lagrange formalism is established for a generic Quantum Field Theory with vanishing vacuum expectation values of the fundamental fields. The Effective Actions in both formalisms are the same if and only if the fundamental fields and the momentum fields are related by the stationarity condition. These momentum fields in general differ from the canonical fields as defined via the Effective Action. By means of functional methods a systematic procedure is presented to identify the full correlation functions, which depend on the momentum fields, as functionals of those usually appearing in the standard Lagrange formalism. Whereas Lagrange correlation functions can be decomposed into tree diagrams the decomposition of Hamilton correlation functions involves loop corrections similar to those arising in n-particle effective actions. To demonstrate the method we derive for theories with linearized interactions the propagators of composite auxiliary fields and the ones of the fundamental degrees of freedom. The formalism is then utilized in the case of Coulomb gauge Yang-Mills theory for which the relations between the two-point correlation functions of the transversal and longitudinal components of the conjugate momentum to the ones of the gauge field are given.Comment: 25 pages, 24 figures, revised and extended version with an explicit application of the formalism to Coulomb gauge QC

Digital skills, methodology and evaluation in teacher trainers

La competencia digital forma parte de las competencias que caracterizan el actual perfil profesional del docente de educación superior. Así, este artículo aborda el desarrollo de las habilidades digitales de los docentes de una escuela profesional de Educación de una Universidad privada. Para ello, se utiliza el Cuestionario de Competencia digital docente de Tourón, que consta de 54 ítems distribuidos en cinco dimensiones: Alfabetización Informática, Comunicación y Colaboración, Creación de Contenidos digitales, Seguridad y Resolución de Problemas; y el Cuestionario de Evaluación de la Metodología docente y Evaluativa (CEMEdEPU) validado por gargallo, que evalúa los modelos de metodología docente: el modelo centrado en la enseñanza y el modelo centrado en los fundamentos de aprendizaje y habilidades de los profesores universitarios. Los resultados muestran que los profesores conocen y utilizan sus habilidades digitales por encima de la media. En cuanto a la Metodología docente, encontramos un mayor avance del modelo centrado en el aprendizaje que del modelo centrado en la enseñanza; y en cuanto a las habilidades de enseñanza, las habilidades de planificación y gestión de la instrucción están mejor desarrolladas que las habilidades de interacción y evaluacióndigital competence is part of the competencies that characterize the current professional profile of higher education teachers. Thus, this article addresses the development of digital skills of teachers of a professional school of Education of a private university. for this, the Tourón Teaching digital Competence Questionnaire is used, which consists of 54 items distributed in five dimensions: Computer Literacy, Communication and Collaboration, Creation of digital Content, Security and Problem Solving; and the Evaluation and Teaching Methodology Evaluation Questionnaire (CEMEdEPU) validated by gargallo, which evaluates the teaching methodology models: the model focused on teaching and the model focused on the fundamentals of learning and skills of university professors. The results show that teachers know and use their digital skills above average. Regarding the Teaching Methodology, we found a greater advance of the model centered on learning than the model centered on teaching; and in terms of teaching skills, instructional planning and management skills are better developed than interaction and assessment skill

Reproductive biology of the nonnative oyster, Crassostrea gigas (Thunber, 1793) as a key for its successful spread along the rocky shores of Northern Patagonia, Argentina

Crassostrea gigas was introduced in Anegada Bay (North Patagonia, Argentina), in 1981 for aquaculture purposes. The species has, since established in the field, covered all available hard substrata in the bay and gradually expanded south along the coast of the neighboring province of Río Negro, 90 km away from its original introduction site. Our work focused on the reproductive dynamics of the species at the introduction site, with emphasis on the thermal thresholds needed for each stage of gonad development. During early spring, the oysters in Anegada Bay go through active gonad proliferation. Maturity extends mainly from October to January. The first spawning occurs in November, when seawater temperature exceeds 17°C, and peaks from December to February, when seawater temperature lies in the range ot 19–21.5°C. The timing of gonad development is size dependent. Larger (≥70 mm) and medium-size oysters begin spawning first, whereas small oysters ( 17°C), and spawning only occurs in those sites where this threshold is reached.Versión del editor

ALP production through non-linear Compton scattering in intense fields

23 pages, 14 figuresWe derive production yields for massive pseudo-scalar and scalar axion-like-particles (ALPs), through non-linear Compton scattering of an electron in the background of low- and high-intensity electromagnetic fields. In particular, we focus on electromagnetic fields from Gaussian plane wave laser pulses. A detailed study of the angular distributions and effects of the scalar and pseudo-scalar masses is presented. It is shown that ultra-relativistic seed electrons can be used to produce scalars and pseudo-scalars with masses up to the order of the electron mass. We briefly discuss future applications of this work towards lab-based searches for light beyond-the-Standard-Model particles

Boost operators in Coulomb-gauge QCD: the pion form factor and Fock expansions in phi radiative decays

In this article we rederive the Boost operators in Coulomb-Gauge Yang-Mills theory employing the path-integral formalism and write down the complete operators for QCD. We immediately apply them to note that what are usually called the pion square, quartic... charge radii, defined from derivatives of the pion form factor at zero squared momentum transfer, are completely blurred out by relativistic and interaction corrections, so that it is not clear at all how to interpret these quantities in terms of the pion charge distribution. The form factor therefore measures matrix elements of powers of the QCD boost and Moeller operators, weighted by the charge density in the target's rest frame. In addition we remark that the decomposition of the eta' wavefunction in quarkonium, gluonium, ... components attempted by the KLOE collaboration combining data from phi radiative decays, requires corrections due to the velocity of the final state meson recoiling against a photon. This will be especially important if such decompositions are to be attempted with data from J/psi decays.Comment: 14 pages, 4 figure