A Berger type normal holonomy theorem for complex submanifolds

We prove a kind of Berger-Simons' Theorem for the normal holonomy group of a complex submanifold of the projective spac

La aplicación de las IDEs en la enseñanza en ingeniería

Las Infraestructuras de Datos Espaciales (IDEs) cada vez más cobran relevancia como recurso docente en la enseñanza en carreras técnicas. Las IDEs permiten a los estudiantes acceder vía Web a información geográfica que les es de utilidad en el desarrollo de supuestos prácticos, así como refuerza sus habilidades. Tras la publicación de la Directiva Europea INSPIRE es obligatoria su instalación. Ello ha supuesto un desafío en la formación de personal especializado en temática. Dada las características de la información a la que se refiere, el desarrollo de recursos didácticos para introducir esta formación en carreras técnicas se considera crucial. En el presente trabajo, se desarrolla una experiencia piloto que expone las fortalezas y debilidades de su utilización como recurso docente

Interaction signatures and non-Gaussian photon states from a strongly driven atomic ensemble coupled to a nanophotonic waveguide

We study theoretically a laser-driven one-dimensional chain of atoms interfaced with the guided optical modes of a nanophotonic waveguide. The period of the chain and the orientation of the laser field can be chosen such that emission occurs predominantly into a single guided mode. We find that the fluorescence excitation line shape changes as the number of atoms is increased, eventually undergoing a splitting that provides evidence for the waveguide-mediated all-to-all interactions. Remarkably, in the regime of strong driving the light emitted into the waveguide is nonclassical with a significant negativity of the associated Wigner function. We show that both the emission properties and the non-Gaussian character of the light are robust against voids in the atom chain, enabling the experimental study of these effects with present-day technology. Our results offer a route towards novel types of fiber-coupled quantum light sources and an interesting perspective for probing the physics of interacting atomic ensembles through light

DISTRIBUCIÓN POBLACIONAL Y ABUNDANCIA DE LOS PECES ENDÉMICOS DE LA LLANURA DE RIOVERDE, S.L.P., MÉXICO

In the Rioverde plain, San Luis Potosí, México, there are wetlands distributed in five natural spring systems, in addition to the green river itself, with endemic fishes. A study was developed to locate new reservoirs for endemic fish, in addition to confirming the presence of each species, estimating their abundance and possible threats. The localization of reservoirs was done through a visual analysis in ArcGIS 9.2, of the panchromatic band of the SPOT satellite. The presence and abundance of species was determined through direct observation while diving. The records showed 14 species of fish, of which five are endemic to the plain, two more to the region, two are native but not endemic, and five introduced. The endemic fish, Tampichthys mandibularis and Ataeniobius toweri, showed greater distribution with high abundance in some systems, and medium to scarce in others. The species Cualac tessellatus was not found in system one or in the Río Verde, although in the others it was abundant. Herichthys labridens and H. bartoni were found in all the systems, except the Río Verde; the first was abundant and the second scarce. Poecilia mexicana is distributed broadly and abundantly, while Gambusia panuco and P. latipunctata were only found in system four. T. dichromus was found in system five with medium abundance. Astyanax mexicanus and Oreochromis sp. were found in all the systems and were the only species in the Río Verde. The presence of Ictalurus mexicanus was confirmed in systems three and four, and I. furcatus in the latter. Endemic species were confirmed in three new systems of natural springs (1, 2 and 3), mitigating the risk of extinction. Studies about distribution, possible threats and management plans that guarantee viability in the long-term of the species and their habitats are necessary.En la llanura de Rioverde, San Luis Potosí, México, existen humedales distribuidos en cinco sistemas de manantiales con sus respectivos arroyos, además del propio Río Verde con especies de peces endémicos. Se desarrolló un estudio para localizar nuevos reservorios para peces endémicos, además de confirmar la presencia de cada especie, estimar su abundancia y posibles amenazas. La localización de reservorios se realizó mediante análisis visual en ArcGIS 9.2, de la banda pancromática del satélite SPOT. La presencia y abundancia de especies se realizó por observación directa mediante buceo libre. Los registros evidenciaron 14 especies de peces, de las cuales cinco son endémicas de la llanura, dos más de la región, dos nativos no endémicos y cinco introducidas. Los endemismos Tampichthys mandibularis y Ataeniobius toweri mostraron mayor distribución con abundancia alta en algunos sistemas, y media o escasa en otros. La especie Cualac tessellatus no se encontró en el sistema uno ni en el Río Verde, en los demás fue abundante. Herichthys labridens y H. bartoni se registraron en todos los sistemas, exceptuando el Río Verde; el primero abundante y el segundo escaso. Poecilia mexicana está de manera amplia y abundante, mientras que Gambusia panuco y P. latipunctata sólo se encontraron en el sistema cuatro. T. dichromus se encontró en el sistema cinco con abundancia media. Astyanax mexicanus y Oreochromis sp. se registraron en todos los sistemas y fueron las únicas especies en el Río Verde. La presencia de Ictalurus mexicanus fue confirmada en los sistemas tres y cuatro, e, I. furcatus en este último. Se confirmaron especies endémicas en tres nuevos sistemas de manantiales (1, 2 y 3) que atenúa el riesgo de extinción. Se requieren estudios de distribución, posibles amenazas y planes de manejo que garanticen viabilidad a largo plazo de las especies y su hábitat

Stability of relative equilibria with singular momentum values in simple mechanical systems

A method for testing $G_\mu$-stability of relative equilibria in Hamiltonian systems of the form "kinetic + potential energy" is presented. This method extends the Reduced Energy-Momentum Method of Simo et al. to the case of non-free group actions and singular momentum values. A normal form for the symplectic matrix at a relative equilibrium is also obtained.Comment: Partially rewritten. Some mistakes fixed. Exposition improve

Teaching through Learning Analytics: Predicting Student Learning Profiles in a Physics Course at a Higher Education Institution

Learning Analytics (LA) is increasingly used in Education to set prediction models from artificial intelligence to determine learning profiles. This study aims to determine to what extent K-nearest neighbor and random forest algorithms could become a useful tool for improving the teaching-learning process and reducing academic failure in two Physics courses at the Technological Institute of Monterrey, México (n = 268). A quasi-experimental and mixed method approach was conducted. The main results showed significant differences between the first and second term evaluations in the two groups. One of the main findings of the study is that the predictions were not very accurate for each student in the first term evaluation. However, the predictions became more accurate as the algorithm was fed with larger datasets from the second term evaluation. This result indicates how predictive algorithms based on decision trees, can offer a close approximation to the academic performance that will occur in the class, and this information could be use along with the personal impressions coming from the teacher

Universal time-evolution of a Rydberg lattice gas with perfect blockade

We investigate the dynamics of a strongly interacting spin system that is motivated by current experimental realizations of strongly interacting Rydberg gases in lattices. In particular we are interested in the temporal evolution of quantities such as the density of Rydberg atoms and density-density correlations when the system is initialized in a fully polarized state without Rydberg excitations. We show that in the thermodynamic limit the expectation values of these observables converge at least logarithmically to universal functions and outline a method to obtain these functions. We prove that a finite one-dimensional system follows this universal behavior up to a given time. The length of this universal time period depends on the actual system size. This shows that already the study of small systems allows to make precise predictions about the thermodynamic limit provided that the observation time is sufficiently short. We discuss this for various observables and for systems with different dimensions, interaction ranges and boundary conditions.Comment: 16 pages, 3 figure

Pâturage: une alternative pour la cultures d’orge à faible rendement

An experiment was performed to evaluate the nutritive value of vitreous-grain barley grazed by sheep (instantaneous stocking rate of 66 sheep/ha). Available biomass (2353 kg dry matter (DM)/ha, on average) was determined at the beginning of the experimental period, which lasted for three consecutive weeks, and barley heads, leaves and stems were separated for quantification. Important amounts of Wimmera ryegrass (Lolium rigidum) were also found. Diet selection, intake and digestibility were estimated using the nalkanes technique. Rumen fermentation characteristics and in situ degradation parameters were obtained from rumen cannulated animals. Transit kinetics of barley heads, leaves and stems was also assessed. The proportion of barley heads in the diet consumed was high (0.53 on average) and varied along the grazing period (0.30 in the first, 0.64 in the second and 0.65 in the third week). Wimmera ryegrass was highly selected during the first week of the experimental period (0.7) and much lesser afterwards (0.35). Estimated total DM intake was low (428, 376 and 657 g/day for weeks 1, 2 and 3, respectively), and chan ged with the botanical composition of the paddock and biomass availability. Average DM digestibility of the diet consumed was also low (56%) and decreased as the grazing period advanced (67%, 55% and 47% for weeks 1, 2 and 3, respectively). Rumen pH was, on average, 6.6, whereas ammonia concentration reached a value of 93 mg/l. Proportions of acetic (0.65), propionic (0.15) and butyric (0.15) acids were representative of a rumen environment driven by fibre fermentation. Effective DM degradability of barley heads, leaves and stems was, on average, 81%, 66% and 55%, respectively.Un essai a été mené pour évaluer la valeur nutritive de l’orge en stade de grain vitreux pâturé par les ovins (taux de charge animale instantanée de 66 brebis/ha). La biomasse disponible (2353 kilogrammes de matière sèche (MS)/ha, en moyenne) a été déterminée au début de la période expérimentale, qui a duré trois semaines consécutives, et les épis, les feuilles et les tiges de l’orge ont été séparés pour leur quantification. Des quantités importantes d’ivraie raide (Lolium rigidum) ont été également rencontrées. Le choix alimentaire, les quantités ingérées et la digestibilité du régime ont été estimés en utilisant la technique des nalcanes. Les caractéristiques de fermentation ruminale et les paramètres de dégradation in situ ont été obtenues en utilisant des animaux canulés dans le rumen. La cinétique de passage des épis, des feuilles et des tiges d’orge a été également évaluée. La proportion des épis d’orge dans le régime consommé était élevée (0,53 en moyenne) et variait le long de la période de pâturage (0,30, 0,64 et 0,65 pendant la première, la deuxième et la troisième semaine respectivement). L’ivraie raide a été fortement choisie pendant la première semaine de la période expérimentale (0,7) et beaucoup moins après (0,35). Les quantités ingérées estimées de MS étaient faibles (428, 376 et 657 g/j pendant la 1ère, 2ème et 3ème semaine, respectivement), et changeaient avec la composition botanique et la disponibilité de la biomasse. La digestibilité moyenne de MS du régime consommé était également faible (56%) et diminuait avec la progression de la période du pâturage (67%, 55% et 47% durant la 1ère, 2ème et 3ème semaine, respectivement). Le pH ruminal était, en moyenne, de 6,6, tandis que la concentration en ammoniaque atteignait une valeur 93 de mg/l. Les proportions d’acide acétique (0,65), propionique (0,15) et butyrique (0,15) étaient représentatives d’un milieu ruminal propice d’une fermentation cellulolytique. La dégradabilité effective de la MS des épis, des feuilles et des tiges d‘orge était, en moyenne, 81%, 66% et 55%, respectivement