206 research outputs found
Follajes comercializados en dos mercados de flores del altiplano central mexicano
Los tradicionales mercados de flores Xochiquetzal del municipio de Tenancingo, Estado de México y Jamaica en el Distrito Federal, son importantes en la comercialización de especies de follajes, de los cuales se desconoce su filiación taxonómica, por lo que resulta relevante realizar su inventario. Para ello, se visitaron ambos mercados para la adquisición de las especies, y su posterior herborización e identificación taxonómica en el herbario de la facultad de Ciencias Agrícolas de la Universidad Autónoma del Estado de México. Adicionalmente se obtuvo información complementaria de cada una de ellas a través de encuestas aplicadas. Con los datos obtenidos se realizó el inventario y el catálogo de follajes de ambos mercados.Los resultados obtenidos muestran que el número de especies comercializadas en los dos mercados es de 87 especies, las cuales pertenecen a 57 géneros y 38 familias. El mayor número de especies de follajes se comercializan en forma de manojo (43%) y el menor número corresponde a racimos de frutos (3%); el mayor número de especies de follajes se comercializan en el mercado de Jamaica (71%) y sólo el 13% en el mercado de Tenancingo. La familia Araceae muestra un mayor número de especies de follajes (10%). Estos datos se deben a que sus especies tienen inflorescencias muy llamativas y que tienen una larga vida en florero. La información recopilada en el catálogo servirá de difusión y apoyo para establecer estrategias de conservación y uso sustentable de las especies comercializadas en los mercados, objeto de estudio
Cultivo en maceta de Iris xiphium L. (Iris de Holanda) con diferentes concentraciones de humus de lombriz y sus lixiviados
Se evaluaron tres variedades de Iris xiphium L. cultivadas en maceta en cuatro proporciones de humus de lombriz y se aplicaron los lixiviados diluidos como bioabono foliar. El experimento se realizó en un diseño completamente al azar con arreglo trifactorial y se midieron ocho variables: longitud de tallo (LT), longitud de botón (LB), longitud de flor (LF), diámetro de botón (DB), diámetro de flor (DF), biomasa (B), área foliar (AF) y días de cosecha (DDC). Los resultados indicaron que la variedad Telstar resultó ser la más precoz. El mejor tratamiento en dicha variedad para las variables LT, LB, B, DF y DDC correspondió a la proporción 30/70 (% lombrihumus / % suelo) y la dilución 1:10 de lixiviado; el segundo mejor tratamiento fue en la variedad Discovery en la proporción 40/60 (%lombrihumus / %suelo) y dilución 1:10 de lixiviado para las variables LT, AF y B. El presente trabajo aporta nueva información en cuanto al uso de sustratos y abono foliar orgánicos para el manejo sustentable, con bajo impacto ambiental, en cultivos florícolas
Realistic D-Brane Models on Warped Throats: Fluxes, Hierarchies and Moduli Stabilization
We describe the construction of string theory models with semirealistic
spectrum in a sector of (anti) D3-branes located at an orbifold singularity at
the bottom of a highly warped throat geometry, which is a generalisation of the
Klebanov-Strassler deformed conifold. These models realise the Randall-Sundrum
proposal to naturally generate the Planck/electroweak hierarchy in a concrete
string theory embedding, and yielding interesting chiral open string spectra.
We describe examples with Standard Model gauge group (or left-right symmetric
extensions) and three families of SM fermions, with correct quantum numbers
including hypercharge. The dilaton and complex structure moduli of the geometry
are stabilised by the 3-form fluxes required to build the throat. We describe
diverse issues concerning the stabilisation of geometric Kahler moduli, like
blow-up modes of the orbifold singularities, via D term potentials and gauge
theory non-perturbative effects, like gaugino condensation. This local
geometry, once embedded in a full compactification, could give rise to models
with all moduli stabilised, and with the potential to lead to de Sitter vacua.
Issues of gauge unification, proton stability, supersymmetry breaking and
Yukawa couplings are also discussed.Comment: 46 pages, 13 figures (figures 3 and 13 corrected
Sistema de medida de iluminación urbana basado en GPS
La presente ponencia consistiría en la descripción de una herramienta para la
elaboración y evaluación de mapas de niveles de iluminación a escala de población.
Describe el desarrollo de un sistema de medición y análisis de los niveles de
iluminación de las vías públicas de un ayuntamiento, de forma que pueda evaluarse a
través de una medida directa el nivel de servicio de una instalación de alumbrado.
Medir y evaluar el estado actual, examinar la mejora tras la realización de operaciones
de mantenimiento (cambios masivos de lámpara, limpieza de luminarias, etc.), valorar
el exceso o la falta de luz en determinadas zonas, de forma que puedan establecerse
políticas de actuación más ajustadas a las necesidades reales de los usuarios y
entornos de la instalación
La herramienta descrita consta de dos partes, una para realizar medidas de
iluminancia en vías urbanas y otra para procesar, elaborar y evaluar mapas de
iluminancias medias a partir de las medidas realizadas.
El sistema encargado de tomar las medidas está formado por un ordenador conectado
a un GPS y a un luxómetro, todo ello integrado en un vehículo.Postprint (published version
D-brane instantons and the effective field theory of flux compactifications
We provide a description of the effects of fluxes on euclidean D-brane
instantons purely in terms of the 4d effective action. The effect corresponds
to the dressing of the effective non-perturbative 4d effective vertex with 4d
flux superpotential interactions, generated when the moduli fields made massive
by the flux are integrated out. The description in terms of effective field
theory allows a unified description of non-perturbative effects in all flux
compactifications of a given underlying fluxless model, globally in the moduli
space of the latter. It also allows us to describe explicitly the effects on
D-brane instantons of fluxes with no microscopic description, like
non-geometric fluxes. At the more formal level, the description has interesting
connections with the bulk-boundary map of open-closed two-dimensional
topological string theory, and with the \NN=1 special geometry.Comment: 33 page
Progress in D-brane model building
The state of the art in D-brane model building is briefly reviewed, focusing
on recent achievements in the construction of D=4 N = 1 type II string vacua
with semi-realistic gauge sectors. Such progress relies on a better
understanding of the spectrum of BPS D-branes, the effective field theory
obtained from them and the explicit construction of vacua. We first consider
D-branes in standard Calabi-Yau compactifications, and then the more involved
case of compactifications with fluxes. We discuss how the non-trivial interplay
between D-branes and fluxes modifies the previous model-building rules, as well
as provides new possibilities to connect string theory to particle physics.Comment: Using w-art.cls, 27 pages, 6 figures. Based on a talk given at the
RTN `Constituents, Fundamental Forces and Symmetries of the Universe'
Workshop and Midterm meeting in Napoli, October 2006. v2: typos corrected and
references adde
Recommended from our members
Comparative design study of a diesel exhaust gas heat exchanger for truck applications with conventional and state of the art heat transfer enhancements
The exhaust gas of heavy duty diesel engines can provide an important heat source that may be used in a number of ways to provide additional power and improve overall engine efficiency. The sizing of a heat exchanger that can manage the heat load and still be of reasonable size and weight without excessive pressure drop is of significant importance especially for truck applications. This is the subject of the present work. To approach the problem, a total of five different configurations are investigated and a comparison of conventional and state of the art heat transfer enhancement technologies is included. Two groups of configurations are examined: (a) a classical shell and tube heat exchanger using staggered cross-flow tube bundles with smooth circular tubes, finned tubes and tubes with dimpled surfaces and (b) a cross-flow plate heat exchanger, initially with finned surfaces on the exhaust gas side and then with 10 ppi and 40 ppi metal foam material substituting for the fins. Calculations were performed, using established heat exchanger design methodologies and recently published data from the literature to size the aforementioned configurations. The solutions provided reduce the overall heat exchanger size, with the plate and fin type consisting of plain fins presenting the minimum pressure drop (up to 98% reduction compared to the other configurations), and the 40 ppi metal foam being the most compact in terms of size and weight. Durability of the solutions is another issue which will be examined in a future investigation. However, coupling of the exhaust heat exchanger after a particulate trap appears to be the most promising solution to avoid clogging from soot accumulation
Nonsupersymmetric Brane/Antibrane Configurations in Type IIA and M Theory
We study metastable nonsupersymmetric configurations in type IIA string
theory, obtained by suspending D4-branes and anti-D4-branes between
holomorphically curved NS5's, which are related to those of hep-th/0610249 by
T-duality. When the numbers of branes and antibranes are the same, we are able
to obtain an exact M theory lift which can be used to reliably describe the
vacuum configuration as a curved NS5 with dissolved RR flux for g_s<<1 and as a
curved M5 for g_s>>1. When our weakly coupled description is reliable, it is
related by T-duality to the deformed IIB geometry with flux of hep-th/0610249
with moduli exactly minimizing the potential derived therein using special
geometry. Moreover, we can use a direct analysis of the action to argue that
this agreement must also hold for the more general brane/antibrane
configurations of hep-th/0610249. On the other hand, when our strongly coupled
description is reliable, the M5 wraps a nonholomorphic minimal area curve that
can exhibit quite different properties, suggesting that the residual structure
remaining after spontaneous breaking of supersymmetry at tree level can be
further broken by the effects of string interactions. Finally, we discuss the
boundary condition issues raised in hep-th/0608157 for nonsupersymmetric IIA
configurations, their implications for our setup, and their realization on the
type IIB side.Comment: 84 pages (57 pages + 4 appendices), 18 figure
D-brane Instantons as Gauge Instantons in Orientifolds of Chiral Quiver Theories
Systems of D3-branes at orientifold singularities can receive
non-perturbative D-brane instanton corrections, inducing field theory operators
in the 4d effective theory. In certain non-chiral examples, these systems have
been realized as the infrared endpoint of a Seiberg duality cascade, in which
the D-brane instanton effects arise from strong gauge theory dynamics. We
present the first UV duality cascade completion of chiral D3-brane theories, in
which the D-brane instantons arise from gauge theory dynamics. Chiral examples
are interesting because the instanton fermion zero mode sector is topologically
protected, and therefore lead to more robust setups. As an application of our
results, we provide a UV completion of certain D-brane orientifold systems
recently claimed to produce conformal field theories with conformal invariance
broken only by D-brane instantons.Comment: 50 pages, 32 figures. v2: version published in JHEP with references
adde
- …