Categorical models for equivariant classifying spaces

Starting categorically, we give simple and precise models of equivariant classifying spaces. We need these models for work in progress in equivariant infinite loop space theory and equivariant algebraic K-theory, but the models are of independent interest in equivariant bundle theory and especially equivariant covering space theory.Comment: 29 pages. Revised version, to appear in AGT. Considerable changes of notation and organization and other changes aimed at making the paper more user friendl

A Growing Hole in the Safety Net: Physician Charity Care Declines Again

Examines reasons for the decline in the number of physicians providing free or reduced cost health care in proportion to the number of uninsured Americans, in the last decade. Includes implications related to the decline in access to medical care

Vibrational effects in laser driven molecular wires

The influence of an electron-vibrational coupling on the laser control of electron transport through a molecular wire that is attached to several electronic leads is investigated. These molecular vibrational modes induce an effective electron-electron interaction. In the regime where the wire electrons couple weakly to both the external leads and the vibrational modes, we derive within a Hartree-Fock approximation a nonlinear set of quantum kinetic equations. The quantum kinetic theory is then used to evaluate the laser driven, time-averaged electron current through the wire-leads contacts. This novel formalism is applied to two archetypical situations in the presence of electron-vibrational effects, namely, (i) the generation of a ratchet or pump current in a symmetrical molecule by a harmonic mixing field and (ii) the laser switching of the current through the molecule.Comment: 12 pages, 7 figures, RevTeX4 require

The user structure in Brazil's tropical rain forest

This paper presents quantitative evidence on the relationship between forest conversion and the productivity of agropastoral activities in the Legal Amazon. The extraction of timber products such as wood, fuelwood and charcoal is related to the process of agropastoral expansion in this region with the aim of providing physical coefficients to define intersectoral connections in Brazil's economy. The paper is organized as follows. Section I makes a geographical characterization of the original vegetation types of the region according to its principal geopolitical subdivisions. Section II presents evidence on deforestation rates and gross areas affected. Section III describes the principal sources of deforestation. Section IV describes sectoral activities and land occupation patterns distinguishing between forested and non-forested areas. Section V analyses major determinants of productivity in agropastoral activities following this broad vegetation distinction. Section VI provides gross estimates of wood removal associated with agropastoral expansion, and compares this with wood and fuel production figures. Conclusions are presented in Section VII.

Equivariant infinite loop space theory, I. The space level story

We rework and generalize equivariant infinite loop space theory, which shows how to construct G-spectra from G-spaces with suitable structure. There is a naive version which gives naive G-spectra for any topological group G, but our focus is on the construction of genuine G-spectra when G is finite. We give new information about the Segal and operadic equivariant infinite loop space machines, supplying many details that are missing from the literature, and we prove by direct comparison that the two machines give equivalent output when fed equivalent input. The proof of the corresponding nonequivariant uniqueness theorem, due to May and Thomason, works for naive G-spectra for general G but fails hopelessly for genuine G-spectra when G is finite. Even in the nonequivariant case, our comparison theorem is considerably more precise, giving a direct point-set level comparison. We have taken the opportunity to update this general area, equivariant and nonequivariant, giving many new proofs, filling in some gaps, and giving some corrections to results in the literature.Comment: 94 page

A More Student Centred Approach to Cambridge Proficiency

Este artículo propone desarrollar una actitud más activa y eficaz en la preparación de los alumnos, incluidos los más jóvenes, para exámenes como el de Cambridge Proficiency. Se describen varias actividades prácticas, algunas de las cuales se pueden también emplear con los alumnos de nivel Cambridge First Certifícate o Certifícate in Advanced English. Estas actividades consisten en: - Estudio exhaustivo por parte de los alumos de las respuestas correctas y las punctuaciones ofrecidas por UCLES (Universidad de Cambridge) en anteriores exámenes. - Colaboración más intensa entre los alumnos para trabajar juntos en clase. - Enseñar a los alumnos a elaborar preguntas como las que fíguran en los exámenes de Cambridge. - Simulación de exámenes orales. Los alumnos de nivel mas avanzado entrevistan a los de nivel mas bajo, puntuándolos como en el examen de Proficiency o First Certifícate. - Asimismo se comentan los resultados de estas técnicas con alumnos españoles

A More Student Centred Approach to Cambridge Proficiency

Este artículo propone desarrollar una actitud más activa y eficaz en la preparación de los alumnos, incluidos los más jóvenes, para exámenes como el de Cambridge Proficiency. Se describen varias actividades prácticas, algunas de las cuales se pueden también emplear con los alumnos de nivel Cambridge First Certifícate o Certifícate in Advanced English. Estas actividades consisten en: - Estudio exhaustivo por parte de los alumos de las respuestas correctas y las punctuaciones ofrecidas por UCLES (Universidad de Cambridge) en anteriores exámenes. - Colaboración más intensa entre los alumnos para trabajar juntos en clase. - Enseñar a los alumnos a elaborar preguntas como las que fíguran en los exámenes de Cambridge. - Simulación de exámenes orales. Los alumnos de nivel mas avanzado entrevistan a los de nivel mas bajo, puntuándolos como en el examen de Proficiency o First Certifícate. - Asimismo se comentan los resultados de estas técnicas con alumnos españoles

Energy based method for numerical fatigue analysis of multidirectional carbon fibre reinforced plastics

This paper describes experiments on multiaxial fibre reinforced plastic laminates, which were performed to obtain calibration data for numerical fatigue analyses. For this purpose, fatigue tests of laminates with multidirectional layers subjected to constant amplitude and block loading (0 <= R<1 or R<1) were analysed. The presented simulation results display the fatigue behaviour of carbon fibre reinforced plastics for unidirectional loading conditions and a selected laminate