474 research outputs found
High-performance model reduction procedures in multiscale simulations
Technological progress and discovery and mastery of increasingly sophisticated
structural materials have been inexorably tied together since the dawn
of history. In the present era — the so-called Space Age —-, the prevailing
trend is to design and create new materials, or improved existing ones, by
meticulously altering and controlling structural features that span across all
types of length scales: the ultimate aim is to achieve macroscopic proper-
ties (yield strength, ductility, toughness, fatigue limit . . . ) tailored to given
practical applications. Research efforts in this aspect range in complexity
from the creation of structures at the scale of single atoms and molecules —
the realm of nanotechnology —, to the more mundane, to the average civil
and mechanical engineers, development of structural materials by changing
the composition, distribution, size and topology of their constituents at the
microscopic/mesoscopic level (composite materials and porous metals, for
instance)
Lista actualizada y estado de conservación de los mamíferos del Parque Nacional el Chico, Hidalgo, México. 563-583.
We present a check-list of mammals of El Chico National Park based in field surveys realized between years 2004 to 2008. The mammals identificated were 30 species and 11 are recorded for the first time in the park: Glaucomys volans, Peromyscus melanotis, Reithrodontomys megalotis, R. sumichrasti, Spilogale gracilis, Cryptotis mexicana, Sorex saussurei, Dermanura azteca, Corynorhinus towsendii, Eptesicus fuscus, Lasiurus cinereus, Myotis californicus y M. velifer. The most abundant species belonged to Rodentia and Carnivora. Threatened species account for 16.67 % of the richness (C. mexicana, S. saussurei, Sciurus oculatus, G. volans y Corynorhinus mexicanus). Mammals in this park are threatened by human settlements and excessive tourism. El Chico National Park is important for conservation and management of mammals as 23.8% of the mammalian diversity of the State of Hidalgo.Se presenta la lista actualizada de los mamíferos del Parque Nacional El Chico con base en el trabajo de campo realizado entre los años 2004 y 2006. Se identificaron 30 especies, 13 de ellas se registran por primera vez en el parque: Glaucomys volans, Peromyscus melanotis, Reithrodontomys megalotis, R. sumichrasti, Spilogale gracilis, Cryptotis mexicana, Sorex saussurei, Dermanura azteca, Corynorhinus towsendii, Eptesicus fuscus, Lasiurus cinereus, Myotis californicus y M. velifer. El orden mejor representado, con 10 especies (33.33 %) fue Rodentia, seguido por Carnivora con ocho especies (26.67 %). El 16.67 % de las especies están consideradas en estado de conservación delicado (C. mexicana, S. saussurei, Sciurus oculatus, G. volans y Corynorhinus mexicanus). Localmente las amenazas para la mastofauna son consecuencia de los asentamientos humanos y el turismo descontrolado. El Chico es importante para la conservación y manejo de los mamíferos de Hidalgo, porque en el habita el 23.8 % de la mastofauna estatal, no obstante su reducida extensión territorial (2,739 ha)
The Zero-Removing Property and Lagrange-Type Interpolation Series
The classical Kramer sampling theorem, which provides a method for obtaining orthogonal sampling formulas, can be formulated in a more general nonorthogonal setting. In this setting, a challenging problem is to characterize the situations when the obtained nonorthogonal sampling formulas can be expressed as Lagrange-type interpolation series. In this article a necessary and sufficient condition is given in terms of the zero removing property. Roughly speaking, this property concerns the stability of the sampled functions on removing a finite number of their zeros
Top quark effects in composite vector pair production at the LHC
In the context of a strongly coupled Electroweak Symmetry Breaking, composite
light scalar singlet and composite triplet of heavy vectors may arise from an
unspecified strong dynamics and the interactions among themselves and with the
Standard Model gauge bosons and fermions can be described by a Effective Chiral Lagrangian. In this framework, the
production of the and final states at the LHC by
gluon fusion mechanism is studied in the region of parameter space consistent
with the unitarity constraints in the elastic channel of longitudinal gauge
boson scattering and in the inelastic scattering of two longitudinal Standard
Model gauge bosons into Standard Model fermions pairs. The expected rates of
same-sign di-lepton and tri-lepton events from the decay of the
final state are computed and their corresponding backgrounds are estimated. It
is of remarkable relevance that the final state can only be
produced at the LHC via gluon fusion mechanism since this state is absent in
the Drell-Yan process. It is also found that the final state
production cross section via gluon fusion mechanism is comparable with the
Drell-Yan production cross section. The comparison of the
and total cross sections will be crucial for
distinguishing the different models since the vector pair production is
sensitive to many couplings. This will also be useful to determine if the heavy
vectors are only composite vectors or are gauge vectors of a spontaneously
broken gauge symmetry.Comment: 18 pages, 5 tables, 6 figures. Missing figures added. Matches
published versio
Regime mapping and the role of the intermediate region in wall-coated microreactors
Operation of a wall-coated microreactor can occur in several mass transfer-reaction regimes. We define these regimes analytically in several planes of a multi-parametric map, taking into account the different degrees of concentration profile development, as well as the influence of non-unity orders of reaction and reactant inhibition in the kinetic law. It was found that the regions where conversion can be calculated from simplified mass transfer models are not discriminated by common results for entrance-length. We also illustrate the trade-offs that exist across this operating map concerning the catalyst design (costs associated with loading and volume) and overall system performance (evaluated in terms of reactant conversion, flow efficiency and microreactor effectiveness). It is shown that under certain conditions, the existence of moderate mass transfer resistance can be advantageous (even if internal limitations cannot be avoided), clarifying the role of the intermediate transport-reaction region
Pharmacological analysis of the increases in heart rate and diastolic blood pressure produced by (S)-isometheptene and (R)-isometheptene in pithed rats
Background: Isometheptene is a sympathomimetic drug effective in acute migraine treatment. It is composed of two enantiomers with diverse pharmacological properties. This study investigated in pithed rats the cardiovascular effects of (S)- isometheptene and (R)-isometheptene, and the pharmacological profile of the more potent enantiomer. Methods: The effects of i.v. bolus injections (0.03, 0.1, 0.3, 1 and 3 mg/kg) of isometheptene racemate, (S)-isometheptene or (R)-isometheptene on heart rate and blood pressure were analyzed in control experiments. The enantiomer producing more pronounced tachycardic and/or vasopressor responses was further analyzed in rats receiving i.v. injections of prazosin (0.1 mg/kg), rauwolscine (0.3 mg/kg), propranolol (1 mg/kg) or intraperitoneal reserpine (5 mg/kg, -24 h). Results: Compared to (R)-isometheptene, (S)-isometheptene produced greater vasopressor responses, whilst both compounds equipotently increased heart rate. The tachycardic responses to (S)-isometheptene were abolished after propranolol, but remained unaffected by the other antagonists. In contrast, the vasopressor responses to (S)-isometheptene were practically abolished after prazosin. Interestingly, after reserpine, the tachycardic responses to (S)-isometheptene were abolished, whereas its vasopressor responses were attenuated and subsequently abolished by prazosin. Conclusions: The different cardiovascular effects of the isometheptene enantiomers are probably due to differences in their mechanism of action, namely: (i) a mixed sympathomimetic action for (S)-isometheptene (a tyramine-like action and a direct stimulation of α1-adrenoceptors); and (ii) exclusively a tyramine like action for (R)-isometheptene. Thus, (R)-isometheptene may represent a superior therapeutic benefit as an antimigraine agent
Chronic lymphocytic leukemia patients with IGH translocations are characterized by a distinct genetic landscape with prognostic implications
Chromosome 14q32 rearrangements/translocations involving the immunoglobulin heavy chain (IGH) are rarely detected in chronic lymphocytic leukemia (CLL). The prognostic significance of the IGH translocation is controversial and its mutational profile remains unknown. Here, we present for the first time a comprehensive next-generation sequencing (NGS) analysis of 46 CLL patients with IGH rearrangement (IGHR-CLLs) and we demonstrate that IGHR-CLLs have a distinct mutational profile with recurrent mutations in NOTCH1, IGLL5, POT1, BCL2, FBXW7, ZMYM3, MGA, BRAF and HIST1H1E genes. Interestingly, BCL2 and FBXW7 mutations were significantly associated with this subgroup and almost half of BCL2, IGLL5 and HISTH1E mutations reported were previously identified in non-Hodgkin lymphomas. Notably, IGH/BCL2 rearrangements were associated with a lower mutation frequency and carried BCL2 and IGLL5 mutations, while the other IGHR-CLLs had mutations in genes related to poor prognosis (NOTCH1, SF3B1 and TP53) and shorter time to first treatment (TFT). Moreover, IGHR-CLLs patients showed a shorter TFT than CLL patients carrying 13q-, normal fluorescence in situ hybridization (FISH) and +12 CLL, being this prognosis particularly poor when NOTCH1, SF3B1, TP53, BIRC3 and BRAF were also mutated. The presence of these mutations not only was an independent risk factor within IGHR-CLLs, but also refined the prognosis of low-risk cytogenetic patients (13q-/normal FISH). Hence, our study demonstrates that IGHR-CLLs have a distinct mutational profile from the majority of CLLs and highlights the relevance of incorporating NGS and the status of IGH by FISH analysis to refine the risk-stratification CLL model
Study of Bc --> J/psi pi, etac pi decays with perturbative QCD approach
The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD
approach. It is found that form factors and branching ratios are sensitive to
the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of
the charmonium wave functions for Coulomb potential and harmonic oscillator
potential, respectively, f_J/psi and f_etac are the decay constants of the
J/psi and etac mesons, respectively. The large branching ratios and the clear
signals of the final states make the Bc --> J/psi pi, etac pi decays to be the
prospective channels for measurements at the hadron collidersComment: 21 pages, revtex
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