Small x divergences in a heavy quark-antiquark state

With the current state of similarity renormalisation group approach to light-front QCD, it is possible to address with a degree of generality the issue of light-cone zero modes. We find, contrary to earlier results in a less general framework, that infrared divergences associated with the zero modes do not cancel out in a color singlet heavy quark-antiquark states, except for the lowest order in the nonrelativistic expansion.Comment: 3 pgs. Talk, originally entitled "Die Hard with Vengence", presented at the Int. Light-Cone Workshop "Light-Cone Physics: Particles and Strings", Trento 200

A comparison of production processes for OER

In most cases the initial production and publication of OER is undertaken by a University and funded through a special project with grants from external bodies. In this phase, OER are developed both from scratch or derived from existing Higher Education courses. After this project phase, the ongoing development and publication of OER continues and the question of the management and upgrading of the OER comes into focus. The costs of producing and upgrading OER are an important factor in devising a sustainable process. Therefore, it is necessary to develop an efficient process for the continuing production, publication and maintenance of OER. To learn more about influencing factors of production process efficiency we have compared the production processes of two institutions, the Open University UK (OU-UK) and the Open Universiteit Netherlands (OU-NL), both in the initial project phase (OpenLearn for OU-UK and OpenER for OU-NL) and the post initial phase. We aim to identify the differences and commonalities and the influence of these on the efficiency of the production processes. The main difference between the two Universities is the adoption of state-of-the-art (XML) standard to deliver to different channels at OU-UK. At OU-NL this adoption has just started. Valuable lessons learned in the project phase for the post initial phase are clear specification of requirements for selection of an open course and utilization of technologies already being used for regular materials production. Both institutions firstly drew upon the existing expertise and capabilities for educational resource production being used for regular courses. But rather than strictly follow exactly the same process and possibly compromise the more mission critical development of resources for students both institutions chose to experiment or adapt this process to help provide lessons that might be taken back into regular materials production. Once these lessons and experiences had been gained both open universities sought to reduce the costs of dealing with legacy or de novo educational resources by integrating identification, production and publication within the regular curriculum and course development processes

Learning and Teaching Online: Structuring Computer-Mediated Communication Systems to Support Interaction at a Distance

The aim of this thesis is to investigate the effects and benefits of different ways of structuring conferences in Computer Mediated Communication (CMC) environments for learning. To this end, the thesis uses two studies of a conventional distance learning course in undergraduate computer science which was supplemented with a structured CMC environment. The research was undertaken over a period of twenty months. Tile first theme of the thesis is an investigation of the possibilities of using conference structures to improve navigation and organisation. The second theme of the thesis investigates the likely benefits of such structuring. Categorical analysis was used to find out the extent to which this structure was beneficial to students. The effects and benefits of various CMC structures were assessed through analysis of data collected using a variety of techniques- observation, user opinions, and interpretation of naturally occurring online interactions. Categorical analysis was undertaken with rich data on actual behaviour obtained from online conferences and compared with students' perceptions gathered through open responses in interviews and questionnaires. The categorical analysis used an approach influenced by grounded theory. The pilot study revealed the need for a new staff role to support the structured CMC. This role, called the Interactive Media Facilitator (IMF), was created during the course of the study to design the CMC structure and monitor activity within the structure. A conceptual framework consisting of a three-dimensional taxonomy was created and used to guide the IMF in the development of the broad conference structure in the main study. The framework was also used to organise the fine detail of the different discussion areas within the CMC structure. This taxonomy, developed from elements of online interaction types found in the CMC literature, is a generalisable framework, applicable in a distance learning context to any electronically supplemented course

Quarkonia in Hamiltonian Light-Front QCD

A constituent parton picture of hadrons with logarithmic confinement naturally arises in weak coupling light-front QCD. Confinement provides a mass gap that allows the constituent picture to emerge. The effective renormalized Hamiltonian is computed to ${\cal O}(g^2)$, and used to study charmonium and bottomonium. Radial and angular excitations can be used to fix the coupling $\alpha$, the quark mass $M$, and the cutoff $\Lambda$. The resultant hyperfine structure is very close to experiment.Comment: 9 pages, 1 latex figure included in the text. Published version (much more reader-friendly); corrected error in self-energ

Small x divergences in the Similarity RG approach to LF QCD

We study small x divergences in boost invariant similarity renormalization group approach to light-front QCD in a heavy quark-antiquark state. With the boost invariance maintained, the infrared divergences do not cancel out in the physical states, contrary to previous studies where boost invariance was violated by a choice of a renormalization scale. This may be an indication that the zero mode, or nontrivial light-cone vacuum structure, might be important for recovering full Lorentz invariance.Comment: 23 pgs, 1 fig. Revised for publication: typos corrected, improved discussion of regularizatio

The new dynamics of scientific knowledge and their impact on Psychology in Latin America

Este trabajo analiza las diversas transformaciones que se registraron en las nuevas formas de producción de conocimiento científico durante las últimas décadas con el objetivo de identificar las repercusiones en el terreno específico de la psicología en América Latina. En primer lugar, se revisan diferentes posiciones teóricas provenientes del campo de la sociología de la ciencia que dan cuenta de los cambios producidos en el contexto de la investigación científica en el mundo. Luego, se realiza un análisis retrospectivo del desarrollo de la psicología en América Latina con especial cobertura de los tópicos que reconocen modificaciones sustanciales: publicaciones científicas, formación de investigadores, agendas de investigación, entre otros. En su conjunto, se plantea que las diversas transformaciones operadas en el campo del conocimiento científico en los últimos tiempos han tenido su correlato en el desarrollo de la psicología en América Latina a través de la modificación de sus prácticas, temas y dinámicas de producción y circulación de conocimiento.This paper analyzes the various transformations that took place in the new ways to produce scientific knowledge in the last decades, with the purpose of identifying their repercussions on the specific field of Psychology in Latin America. First, we review the different theoretical stances emerging from the Sociology of Science field, which provide an account of the changes that took place in the context of scientific research around the world. Then, we perform a retrospective analysis of the evolution of Psychology in Latin America, with emphasis on topics that underwent substantial changes, such as scientific publications, research education, research agendas, etc. Taking them as a whole, we propose that the various transformations that take place in the field of scientific knowledge in recent times relate to the development of Psychology in Latin America because it modified the practice, the topics and the dynamics of production and dissemination of knowledge.Fil: Gallegos de San Vicente, Miguel Omar. Universidad Nacional de Rosario. Facultad de Psicologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Berra, Martina Paula. Universidad Nacional de Rosario. Facultad de Psicologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Benito, Ezequiel. Universidad Maimonides; ArgentinaFil: López López, Wilson. Pontificia Universidad Javeriana; Colombi

Note on restoring manifest rotational symmetry in hyperfine and fine structure in light-front QED

We study the part of the renormalized, cutoff QED light-front Hamiltonian that does not change particle number. The Hamiltonian contains interactions that must be treated in second-order bound state perturbation theory to obtain hyperfine structure. We show that a simple unitary transformation leads directly to the familiar Breit-Fermi spin-spin and tensor interactions, which can be treated in degenerate first-order bound-state perturbation theory, thus simplifying analytic light-front QED calculations. To the order in momenta we need to consider, this transformation is equivalent to a Melosh rotation. We also study how the similarity transformation affects spin-orbit interactions.Comment: 17 pages, latex fil

(S)norlaudanosoline synthase. the first enzyme in the benzylisoquinoline biosynthetic pathway

1. introduction Isoquinoline alkaloids form the largest group of alkaloids in the plant kingdom. Numerous publications deal with aspects of the biosynthesis of these compounds in vivo [ 11, while isoquinoline biosynthesis at the cell-free level had hardly been touched [Z]. The initial reaction in isoquinoline biosynthesis has long [3] been assumed to be a condensation of two aromatic units, both derived from tyrosine, namely dopamine and 3,4-d~ydroxyphenylacet~dehyde [4]. This scheme was later modified [5] where it was reported that condensation of dopamine with 3,4-dihydroxyphenylpyruvate would lead to an amino acid, norlaudanosoline-l-carboxylic acid, which in turn, by decarboxylation, would yield norlaudanosoline

Initial bound state studies in light-front QCD

We present the first numerical QCD bound state calculation based on a renormalization group-improved light-front Hamiltonian formalism. The QCD Hamiltonian is determined to second order in the coupling, and it includes two-body confining interactions. We make a momentum expansion, obtaining an equal-time-like Schrodinger equation. This is solved for quark-antiquark constituent states, and we obtain a set of self-consistent parameters by fitting B meson spectra.Comment: 38 pages, latex, 5 latex figures include

Mississippian lamprophyre dikes in western Sierras Pampeanas, Argentina: Evidence of transtensional tectonics along the SW margin of Gondwana

In the Famatina range, Sierras Pampeanas of Argentina (SW Gondwana), subvertical calc-alkaline lamprophyric dike swarms crop out through >300 km. The dikes cut Ordovician units with a prominent NW-SE trending and are covered by continental sedimentary successions of Pennsylvanian to Permian age. The dikes show a strong structural control associated with Riedel fault systems. Detailed field analysis suggested a ∼N-S opening direction oblique to the attitude of dike walls and a left-lateral transtensional tectonics during the emplacement. 40Ar/39Ar geochronology of a lamprophyric sample defined a crystallization age (plateau; whole rock) of 357.1 ± 7.1 Ma (MSWD = 2.3). Coetaneous ductile zones with dominant strike-slip motion, documented along western Argentina for >600 km, suggest a regional event in SW Gondwana during the Mississippian. We propose that this deformation was the result of the counterclockwise fast rotation of Gondwana between 365 and 345 Ma, when the Famatina range and western Argentina occupied a sub-polar position. A transform margin along SW Gondwana better explains our (and others) data rather than a subduction margin. This scenario is also consistent with the occurrence of A-type granites and normal-fault basins within the foreland as well as bimodal volcanics.Fil: Martina, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Canelo, Horacio Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Davila, Federico Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: de Hollanda, María Helena M.. Universidade de Sao Paulo; BrasilFil: Teixeira, Wilson. Universidade de Sao Paulo; Brasi