232 research outputs found
Multiconfigurational second-order perturbation study of the decomposition of the radical anion of nitromethane
The doublet potential energy surfaces involved in the decomposition of the nitromethane radical anion (CH3NO2−) have been studied by using the multistate extension of the multiconfigurational second-order perturbation method (MS-CASPT2) in conjunction with large atomic natural orbital-type basis sets. A very low energy barrier is found for the decomposition reaction: CH3NO2−→[CH3NO2]−→CH3+NO2−. No evidence has been obtained on the existence of an isomerization channel leading to the initial formation of the methylnitrite anion (CH3ONO−) which, in a subsequent reaction, would yield nitric oxide (NO). In contrast, it is suggested that NO is formed through the bimolecular reaction: CH3+NO2−→[CH3O-N-O]−→CH3O−+NO. In particular, the CASSCF/MS-CASPT2 results indicate that the methylnitrite radical anion CH3ONO− does not represent a minimum energy structure, as concluded by using density functional theory (DFT) methodologies. The inverse symmetry breaking effect present in DFT is demonstrated to be responsible for such erroneous [email protected]
Morphological variation of Astyanax species, subgenus Zygogaster (Teleostei, Characidae)
Astyanax es un género diverso de peces neotropicales, cuyas especies habitan gran variedad de ambientes acuáticos. La situación taxonómica de los subgéneros y de sus especies, no difiere de la problemática que presenta el género Astyanax. Basándonos en 354 individuos, se analizó la variación morfológica de cuatro especies del subgénero Zygogaster (A. atratoensis, A. caucanus, A. filiferus y A. magdalenae) mediante un análisis morfogeométrico comparado con dos especies del grupo hermano Poecilurichthys (A. orthodus y A. superbus). El ACP (Análisis de Componentes Principales) y AVC (Análisis de Variables Canónicas) evidenciaron afinidad morfológica entre los subgéneros e indicaron varianza en la profundidad del cuerpo, tendencia anterior del origen de la aleta dorsal y mancha humeral, depresión sobre la superficie dorsal del cráneo, y desplazamiento ventral de la orbita y el hocico. La variación entre las especies indicó aislamiento del tercer infraorbital del preopérculo y protrusión del extremo ventral del maxilar. La variación en estas estructuras evidencia especiación adaptativa como posible alternativa a la especiación por aislamiento geográfico.
Palabras clave: Astyanax, Characido, MorfogeometrÃa, Disparidad, Colombia.Astyanax es un género diverso de peces neotropicales, cuyas especies habitan gran variedad de ambientes acuáticos. La situación taxonómica de los subgéneros y de sus especies, no difiere de la problemática que presenta el género Astyanax. Basándonos en 354 individuos, se analizó la variación morfológica de cuatro especies del subgénero Zygogaster (A. atratoensis, A. caucanus, A. filiferus y A. magdalenae) mediante un análisis morfogeométrico comparado con dos especies del grupo hermano Poecilurichthys (A. orthodus y A. superbus). El ACP (Análisis de Componentes Principales) y AVC (Análisis de Variables Canónicas) evidenciaron afinidad morfológica entre los subgéneros e indicaron varianza en la profundidad del cuerpo, tendencia anterior del origen de la aleta dorsal y mancha humeral, depresión sobre la superficie dorsal del cráneo, y desplazamiento ventral de la orbita y el hocico. La variación entre las especies indicó aislamiento del tercer infraorbital del preopérculo y protrusión del extremo ventral del maxilar. La variación en estas estructuras evidencia especiación adaptativa como posible alternativa a la especiación por aislamiento geográfico.
Palabras clave: Astyanax, Characido, MorfogeometrÃa, Disparidad, Colombia.The diverse Neotropical fish genus Astyanax inhabits a variety of aquatic environments. As with other species in this genus, the taxonomic status and phylogenetic relationships of species of this subgenus remain largely undetermined. Based on 354 individuals, we analyzed the morphological variation of four species of the subgenus Zygogaster (A. atratoensis, A. caucanus, A. filiferus, and A. magdalenae) using procrustes analysis and compared findings with two species of the sister group: subgenus Poecilurichthys (A. orthodus y A. superbus). The PCA (Principal Component Analysis) and CVA (Canonical Variates Analysis) showed morphological affinity between the subgenera and indicated variance in body depth, anterior trend of dorsal fin origin and humeral spot, depression on the dorsal surface of the skull, and ventral displacement of the orbit and snout. The variation in these structures may provide evidence supporting adaptive speciation as an alternative to speciation driven by geographical isolation.
Key words: Astyanax, Characid fish, Morphogeometry, Disparity, Colombia
Variación morfológica de las especies de Astyanax, subgénero Zygogaster (Teleostei, Characidae)
Morphological variation of Astyanax species, subgenus Zygogaster (Teleostei, Characidae)
The diverse Neotropical fish genus Astyanax inhabits a variety of aquatic environments. As with other species in this genus, the taxonomic status and phylogenetic relationships of species of this subgenus remain largely undetermined. Based on 354 individuals, we analyzed the morphological variation of four species of the subgenus Zygogaster (A. atratoensis, A. caucanus, A. filiferus, and A. magdalenae) using procrustes analysis and compared findings with two species of the sister group: subgenus Poecilurichthys (A. orthodus and A. superbus). The PCA (Principal Component Analysis) and CVA (Canonical Variates Analysis) showed morphological affinity between the subgenera and indicated variance in body depth, anterior trend of dorsal fin origin and humeral spot, depression on the dorsal surface of the skull, and ventral displacement of the orbit and snout. The variation in these structures may provide evidence supporting adaptive speciation as an alternative to speciation driven by geographical isolation
Vacuum local and global electromagnetic self-energies for a point-like and an extended field source
We consider the electric and magnetic energy densities (or equivalently field
fluctuations) in the space around a point-like field source in its ground
state, after having subtracted the spatially uniform zero-point energy terms,
and discuss the problem of their singular behavior at the source's position. We
show that the assumption of a point-like source leads, for a simple Hamiltonian
model of the interaction of the source with the electromagnetic radiation
field, to a divergence of the renormalized electric and magnetic energy density
at the position of the source. We analyze in detail the mathematical structure
of such singularity in terms of a delta function and its derivatives. We also
show that an appropriate consideration of these singular terms solves an
apparent inconsistency between the total field energy and the space integral of
its density. Thus the finite field energy stored in these singular terms gives
an important contribution to the self-energy of the source. We then consider
the case of an extended source, smeared out over a finite volume and described
by an appropriate form factor. We show that in this case all divergences in
local quantities such as the electric and the magnetic energy density, as well
as any inconsistency between global and space-integrated local self-energies,
disappear.Comment: 8 pages. The final publication is available at link.springer.co
Ruteo de vehÃculos escolares: caso de estudio de la Universidad Autónoma de Coahuila
En este trabajo se proponen un conjunto de nuevas rutas de transporte para dar servicio a la comunidad estudiantil actual del Campus Arteaga de la Universidad Autónoma de Coahuila atendiendo a la dispersidad de los estudiantes en la zona metropolitana de Saltillo. Se analiza un caso de estudio con la información de una Facultad, considerando 380 estudiantes y 46 paradas correspondientes a las colonias de Saltillo. El problema se formula matemáticamente como un modelo lineal entero mixto, el cual es resuelto a través de un optimizador comercial. Con el modelo sólo es posible resolver a optimalidad instancias de 10 paradas y 50 estudiantes, por lo que se diseñó un algoritmo heurístico constructivo híbrido basado en el algoritmo de Clarke y Wright, en donde la factibilidad de una solución se verifica al resolver una versión simplificada del modelo matemático. Se implementan dos estrategias para reducir el tiempo de cómputo del algoritmo heurístico y se reportan las nuevas rutas propuestas, así como algunas recomendaciones para facilitar la construcción de las instancias del problema
Multiconfigurational second-order perturbation study of the decomposition of the radical anion of nitromethane
Parámetros genéticos para producción de leche de ganado Holstein en dos modalidades de control de producción
Variance components and genetic parameters were estimated for total milk production at first lactation (MP1), milkyield adjusted to 305 d and adult equivalent at the first lactation (MP1std), total milk production of the first fivelactations (MP5) and milk yield adjusted to 305 d and mature equivalent of the first five lactations (MP5std). Thedatabases of the Mexican Holstein Association (MHA, n= 43,668) and of the National Bank of Dairy Information(NBDI, n= 120,217) were used. Variances were estimated by REML, using a simple animal model for MP1 and MP1stdand a repeatability animal model for MP5 and MP5std. Heritability estimates ranged from low to moderate for thefirst lactation (0.17 ± 0.009 to 0.49 ± 0.019) and for the first five lactations (0.16 ± 0.006 to 0.41 ± 0.004). Therepeatabilities for MP5 and MP5std ranged from 0.32 ± 0.002 to 0.41 ± 0.004. The inclusion of information of theNBDI on the national evaluations made possible the incorporation of production data that had not been taken intoconsideration before. This inclusion not only improved the accuracy of sire breeding values  for milk production, butalso allowed the prediction of breeding values of more foreign and domestic animals with progeny in Mexico.Se estimaron componentes de varianza y parámetros genéticos para producción de leche total a la primera lactancia (PL1), producción de leche ajustada a 305 dÃas y a equivalente adulto de la primera lactancia (PL1std), producción de leche total de las cinco primeras lactancias (PL5) y producción de leche ajustada a 305 dÃas y a equivalente adulto de las primeras 5 lactancias (PL5std). Se utilizaron las bases de datos de la Asociación Holstein de México (AHM; n= 43,668) y del Banco Nacional de Información Lechera (BNIL; n= 120,217). Las varianzas fueron estimadas mediante REML, utilizando un modelo animal simple para PL1 y PL1std y un modelo animal de repetibilidad para PL5 y PL5std. Las heredabilidades estimadas fueron desde bajas a moderadas para la primera lactancia (0.17 ± 0.009 a 0.49 ± 0.019) y para las primeras cinco lactancias (0.16 ± 0.006 a 0.41 ± 0.004). Las repetibilidades para PL5 y PL5std tuvieron un rango de 0.32 ± 0.002 a 0.41 ± 0.004. La inclusión de la información del BNIL en las evaluaciones genéticas permitió incorporar datos de producción que no se estaban tomando en cuenta. Esto no solamente mejoró la precisión de los valores genéticos de los sementales para producción de leche, sino que también permitió la predicción de los valores genéticos de animales nacionales y extranjeros con progenies en México
Parámetros genéticos para producción de leche de ganado Holstein en dos modalidades de control de producción
Variance components and genetic parameters were estimated for total milk production at first lactation (MP1), milkyield adjusted to 305 d and adult equivalent at the first lactation (MP1std), total milk production of the first fivelactations (MP5) and milk yield adjusted to 305 d and mature equivalent of the first five lactations (MP5std). Thedatabases of the Mexican Holstein Association (MHA, n= 43,668) and of the National Bank of Dairy Information(NBDI, n= 120,217) were used. Variances were estimated by REML, using a simple animal model for MP1 and MP1stdand a repeatability animal model for MP5 and MP5std. Heritability estimates ranged from low to moderate for thefirst lactation (0.17 ± 0.009 to 0.49 ± 0.019) and for the first five lactations (0.16 ± 0.006 to 0.41 ± 0.004). Therepeatabilities for MP5 and MP5std ranged from 0.32 ± 0.002 to 0.41 ± 0.004. The inclusion of information of theNBDI on the national evaluations made possible the incorporation of production data that had not been taken intoconsideration before. This inclusion not only improved the accuracy of sire breeding values  for milk production, butalso allowed the prediction of breeding values of more foreign and domestic animals with progeny in Mexico.Se estimaron componentes de varianza y parámetros genéticos para producción de leche total a la primera lactancia (PL1), producción de leche ajustada a 305 dÃas y a equivalente adulto de la primera lactancia (PL1std), producción de leche total de las cinco primeras lactancias (PL5) y producción de leche ajustada a 305 dÃas y a equivalente adulto de las primeras 5 lactancias (PL5std). Se utilizaron las bases de datos de la Asociación Holstein de México (AHM; n= 43,668) y del Banco Nacional de Información Lechera (BNIL; n= 120,217). Las varianzas fueron estimadas mediante REML, utilizando un modelo animal simple para PL1 y PL1std y un modelo animal de repetibilidad para PL5 y PL5std. Las heredabilidades estimadas fueron desde bajas a moderadas para la primera lactancia (0.17 ± 0.009 a 0.49 ± 0.019) y para las primeras cinco lactancias (0.16 ± 0.006 a 0.41 ± 0.004). Las repetibilidades para PL5 y PL5std tuvieron un rango de 0.32 ± 0.002 a 0.41 ± 0.004. La inclusión de la información del BNIL en las evaluaciones genéticas permitió incorporar datos de producción que no se estaban tomando en cuenta. Esto no solamente mejoró la precisión de los valores genéticos de los sementales para producción de leche, sino que también permitió la predicción de los valores genéticos de animales nacionales y extranjeros con progenies en México
Dengue virus infection of blood-brain barrier cells: consequences of severe disease
More than 500 million people worldwide are infected each year by any of the four-dengue virus (DENV) serotypes. The clinical spectrum caused during these infections is wide and some patients may develop neurological alterations during or after the infection, which could be explained by the cryptic neurotropic and neurovirulent features of flaviviruses like DENV. Using in vivo and in vitro models, researchers have demonstrated that DENV can affect the cells from the blood–brain barrier (BBB) in several ways, which could result in brain tissue damage, neuronal loss, glial activation, tissue inflammation and hemorrhages. The latter suggests that BBB may be compromised during infection; however, it is not clear whether the damage is due to the infection per se or to the local and/or systemic inflammatory response established or activated by the BBB cells. Similarly, the kinetics and cascade of events that trigger tissue damage, and the cells that initiate it, are unknown. This review presents evidence of the BBB cell infection with DENV and the response established toward it by these cells; it also describes the consequences of this response on the nervous tissue, compares these evidence with the one reported with neurotropic viruses of the Flaviviridae family, and shows the complexity and unpredictability of dengue and the neurological alterations induced by it. Clinical evidence and in vitro and in vivo models suggest that this virus uses the bloodstream to enter nerve tissue where it infects the different cells of the neurovascular unit. Each of the cell populations respond individually and collectively and control infection and inflammation, in other cases this response exacerbates the damage leaving irreversible sequelae or causing death. This information will allow us to understand more about the complex disease known as dengue, and its impact on a specialized and delicate tissue like is the nervous tissue
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