470 research outputs found
Qué se puede decir de la equidad de género en las carreras de Ciencias, IngenierÃa y Matemáticas en Colombia. Resultados del proyecto Iris
En este trabajo presentamos algunas consideraciones en torno a los resultados del proyecto IRIS para Colombia. Discutimos los resultados relacionados con el género a partir de la necesidad de entender el concepto de identidad más allá de la diferencia entre chicos y chicas y explorando lo que es común a los jóvenes con identidades cientÃficas que deciden, a pesar de lo poco atractivo que resulta para los demás jóvenes, estudiar una carrera relacionada con ciencias, tecnologÃa o matemáticas (CTM)
Functional approach to quantum friction: effective action and dissipative force
We study the Casimir friction due to the relative, uniform, lateral motion of
two parallel semitransparent mirrors coupled to a vacuum real scalar field,
. We follow a functional approach, whereby nonlocal terms in the action
for , concentrated on the mirrors' locii, appear after functional
integration of the microscopic degrees of freedom. This action for ,
which incorporates the relevant properties of the mirrors, is then used as the
starting point for two complementary evaluations: Firstly, we calculate the {
in-out} effective action for the system, which develops an imaginary part,
hence a non-vanishing probability for the decay (because of friction) of the
initial vacuum state. Secondly, we evaluate another observable: the vacuum
expectation value of the frictional force, using the { in-in} or Closed Time
Path formalism. Explicit results are presented for zero-width mirrors and
half-spaces, in a model where the microscopic degrees of freedom at the mirrors
are a set of identical quantum harmonic oscillators, linearly coupled to $\phi
Inter-annual variability of the Pelagic-Benthic coupling in the upwelling system off central Chile
International audienceThe coastal region of central Chile (36° S) is one of the most productive coastal systems, characterized by a marked seasonality in the upwelling regime, that brings subsurface waters rich in nutrient and poor in oxygen (ESSW) into the euphotic zone. This oceanographic condition depends basically on the equatorward wind strength and is modified on different time scales, with the El Niño-Southern Oscillation (ENSO) phenomenon as the main source of interannual variability in the Pacific Ocean. Here we present an effort to integrate physical and biogeochemical variability associated with in situ information and experiments at coastal stations off central Chile (36° S) in order to improve the knowledge on the pelagic-benthic coupling in this upwelling system during the warm ENSO phase or El Niño. Carbon fluxes exported from the water column to the sediments and the ammonium exchange across the sediment-water interface are discussed together with oceanographic and benthic conditions. All measurements and estimations were carried out from May 1997 until April 2001 at two stations, one located inside Concepción Bay (~28 m depth), and the other on the continental shelf at ~36° S (~88 m depth). The results show that the pelagic and benthic systems are strongly coupled off central Chile (36° S). Oceanographic variability associated with upwelling events (seasonal scale) and an El Niño event (interannual scale) was observed. The carbon fluxes exported to the sediments, the benthic conditions (i.e., quantity and quality of the sediment organic matter), and the ammonium exchange across the sediment-water interface, responded to the seasonal regime of upwelling during non El Niño years as well as to the ENSO related oceanographic variability
La oferta académica de posgrados en comunicación en México, Centroamérica y el Caribe: una expansión asimétrica y desarticulada
En este informe se presentan los datos sistematizados y contextualizados disponibles en 2011 para elaborar un diagnóstico actualizado de la oferta educativa de nivel de posgrado en el campo de la comunicación en la región norte de América Latina, comprendida por México, Guatemala, El Salvador, Honduras, Nicaragua (aunque en este paÃs no se localizó ningún programa), Costa Rica, Panamá, Cuba, Puerto Rico y República Dominicana.ITESO, A.C
Electronic and Geometric Corrugation of Periodically Rippled, Self-nanostructured Graphene Epitaxially Grown on Ru(0001)
Graphene epitaxially grown on Ru(0001) displays a remarkably ordered pattern
of hills and valleys in Scanning Tunneling Microscopy (STM) images. To which
extent the observed "ripples" are structural or electronic in origin have been
much disputed recently. A combination of ultrahigh resolution STM images and
Helium Atom diffraction data shows that i) the graphene lattice is rotated with
respect to the lattice of Ru and ii) the structural corrugation as determined
from He diffraction is substantially smaller (0.015 nm) than predicted (0.15
nm) or reported from X-Ray Diffraction or Low Energy Electron Diffraction. The
electronic corrugation, on the contrary, is strong enough to invert the
contrast between hills and valleys above +2.6 V as new, spatially localized
electronic states enter the energy window of the STM. The large electronic
corrugation results in a nanostructured periodic landscape of electron and
holes pockets.Comment: 16 pages, 6 figure
Desarrollo larvario de Pilumnoides hassleri (Decapoda: Brachyura: Pilumnoididae) cultivado en laboratorio, con una revisión de la sistematica de Pilumnoididae utilizando caracteres larvarios
The genus Pilumnoides is an interesting taxon because its systematic position, based on adult characters, remains unclear. These xanthoid crabs have been related to the Carpiliidae, Goneplacidae and Eriphioidea. P. hassleri A. Milne Edwards, 1880 lives in Brazilian, Uruguayan and Argentinian coasts as far south as the Magellan Strait (southwestern Atlantic). Larvae of P. hassleri from females collected in the harbour of Mar del Plata were reared in the laboratory from zoea I to megalopa and the first larval stage, and described. The species passed through 5 zoeal stages and a megalopa. Larval characters were compared with the previous description of larvae from the southeastern Pacific species P. perlatus and with species of Carpilius, Goneplax and Eriphia in order to review the relationships between these taxa.El género Pilumnoides es un taxón interesante dado que su posición sistemática, basada en caracteres adultos, permanece poco clara. Estos cangrejos xantoideos han sido relacionados con las familias Carpiliidae, Goneplacidae y Eriphioidea. P. hassleri A. Milne Edwards, 1880 vive en las costas de Brasil, Uruguay y Argentina hasta el Estrecho de Magallanes (Atlántico Sudoccidental). Se cultivaron larvas de P. hassleri, provenientes de hembras colectadas en el puerto de Mar del Plata, desde la zoea Ihasta la megalopa y el primer estadio de cangrejo, y posteriormente se describieron. La especie pasa por 5 estadios de zoea y una megalopa. Las caracterÃsticas larvarias se compararon con descripciones previas de larvas de P. perlatus del PacÃfico Suroriental, y con especies de Carpilius, Goneplax y Eriphia con el objetivo de rever las relaciones entre estos taxa
Diacritical study of light, electrons, and sound scattering by particles and holes
We discuss the differences and similarities in the interaction of scalar and
vector wave-fields with particles and holes. Analytical results are provided
for the transmission of isolated and arrayed small holes as well as surface
modes in hole arrays for light, electrons, and sound. In contrast to the
optical case, small-hole arrays in perforated perfect screens cannot produce
acoustic or electronic surface-bound states. However, unlike electrons and
light, sound is transmitted through individual holes approximately in
proportion to their area, regardless their size. We discuss these issues with a
systematic analysis that allows exploring both common properties and unique
behavior in wave phenomena for different material realizations.Comment: 3 figure
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