Inverse Compton e-p pair cascade model for the gamma-ray production in massive binary LSI +61^o 303

We apply an inverse Compton $e^\pm$ pair cascade model for $\gamma$-ray production in massive binary system LSI +61$^{\rm o}$ 303 assuming that electrons are accelerated already inside the inner part of the jet launched by the compact object. $\gamma$-ray spectra, affected by the cascade process, and lower energy spectra, from the synchrotron cooling of the highest energy electrons in the jet, are calculated as a function of the phase of this binary system. $\gamma$-ray spectra expected in such model have different shape than that ones produced by electrons in the jet directly to observer. Moreover, the model predicts clear anti-correlation between $\gamma$-ray fluxes in the GeV (1-10 GeV) and TeV ($>200$ GeV) energy ranges with the peak of the TeV emission at the phase $\sim$0.5 (the peak half width ranges between the phases $\sim$0.4-0.9 for the inclination of the binary system equal to $60^{\rm o}$, and $\sim$0.4-0.1 for $30^{\rm o}$). The fine features of TeV $\gamma$-ray emission (fluxes and spectral shapes) as a function of the phase of the binary system are consistent with recent observations reported by the MAGIC collaboration. Future simultaneous observations in the GeV energies (by the GLAST and AGILE telescopes) and in the TeV energies (by the MAGIC and VERITAS telescopes) should test other predictions of the considered model supporting or disproving the hypothersis of acceleration of electrons already in the inner part of the microquasar jets.Comment: 8 pages, 4 figures, version accepted to MNRA

High energy processes in microquasars

Microquasars are X-ray binary stars with the capability to generate relativisticjets. It is expected that microquasars are gamma-ray sources, because of the analogy with quasars and because the theoretical models predict emission at such energy range. In addition, from observational arguments, there are two microquasars that appear as the possible counterparts for two unidentified high-energy gamma-ray sources.Comment: Universitat de Barcelona, Departament d'Astronomia i Meteorologia, 12 pages, 5 figures. Invited talk presented at the International Symposium "High-Energy Gamma-Ray Astronomy", 26-30 July 2004, Heidelberg (Germany). To be published by AIP Proceedings Serie

A parasitic copepod, Perulernaea gamitanae gen. et sp. nov. (Cyclopoida: Lernaeidae), from the nasal fossae of a Peruvian Amazon food fish

The female of Perulernaea gamitanae gen. et sp. nov. (Copepoda: Cyclopoida: Lernaeidae) is described from the nasal fossae of an important food fish, Colossoma macropomum (CUVIER), collected in the Peruvian Amazon near lquitos. The new genus differs from others in the family by having blunt head anchors, a well defined slender "neck", a fusiform hindbody, uropods, four pairs of well separated legs, genital pores which are post-equatorial in the hindbody and multiseriate egg sacs. The host is one of the largest freshwater fish of the Amazon region and is of considerable economic importance

Chiral Ladders and the Edges of Chern Insulators

The realization and detection of topological phases with ultracold atomic gases is at the frontier of current theoretical and experimental research. Here, we identify cold atoms in optical ladders subjected to synthetic magnetic fields as readily realizable bridges between one-dimensional spin-orbit (time reversal) topological insulators and two-dimensional Chern insulators. We reveal three instances of their promising potential: i) they realize spin-orbit coupling, with the left-right leg degree of freedom playing the role of an effective spin, ii) their energy bands and eigenstates exactly reproduce the topological chiral edge modes of two-dimensional Chern insulators, and iii) they can be tailored to realize a topological phase transition from a trivial to a topological insulating phase. We propose realistic schemes to observe the chiral and topological properties of ladder systems with current optical lattice-based experiments. Our findings open a door to the exploration of the physics of the edges of Chern insulators and to the realization of spin-orbit coupling and topological superfluid phases with ultracold atomic gases.Comment: 6 pages, 6 figure

Chilean EFL teachers`perceptions of their working condition in the private, semi -private and public school systems

Tesis (Profesor de Inglés para la Enseñanza Básica y Media y al grado académico de Licenciado en Educación)This study followed a quantitative survey research design. The main purpose of the research was to explore Chilean English teachers’ perceptions of their working conditions, and compare the perceptions of teachers from the public, semi-private and private school systems. The data was collected by applying a questionnaire, a technique used in quantitative research. Sixty three teachers from forty six schools of the three educational sectors polled, answered the questionnaire using a 5-point Likert scale in order to express their perceptions regarding their working conditions. In the analysis process, the information collected was presented descriptively. In general, the participants showed positive perceptions concerning school environment and school support from their school authorities, but negative perceptions regarding salary, workload, time for non-instructional activities and society perceptions toward their profession.El presente estudio utilizó el diseño de encuesta cuantitativa. El propósito principal de nuestra investigación fue explorar las percepciones de los profesores de inglés chilenos acerca de sus condiciones laborales, y comparar estas percepciones de los profesores del sistema público, subvencionado y privado de la educación. La información fue recopilada a través de la aplicación de un cuestionario; técnica usada en el método cuantitativo de investigación. Sesenta y tres profesores de cuarenta y seis colegios de los tres sectores educacionales: público, subvencionado y privado, contestaron la encuesta usando la escala Likert del 1 al 5, de manera de obtener sus percepciones acerca de sus condiciones laborales. En el proceso de análisis, la información recolectada fue presentada descriptivamente. De manera general, los participantes demostraron percepciones positivas de acuerdo al clima laboral y el apoyo de las autoridades de los colegios; sin embargo, las percepciones fueron negativas acerca de su salario, carga laboral, tiempo para actividades extra curriculares y las percepciones de la sociedad acerca de la profesión docente

The timing of capacity expansion investments in oligopoly under demand uncertainty

Since a flexibility value emerges in waiting to expand capacity, the impact of demand uncertainty in an oligopolistic industry leads to capacity expansion timing. The creation of growth opportunities is then the outcome of expanding capacity at optimal times. However, in our model different capacity size competitors interact not affecting each others, because assessing the impact of demand uncertainty on capacity expansion projects takes them to set up independently their optimal capacity expansion timing schedules. In equilibrium no firm expands capacity more often than any other. Under demand uncertainty simultaneity in capacity expansions is the only possible Markov Perfect Equilibrium