3,249 research outputs found
Cosmological Bianchi Class A models in S\'aez-Ballester theory
We use the S\'aez-Ballester (SB) theory on anisotropic Bianchi Class A
cosmological model, with barotropic fluid and cosmological constant, using the
Hamilton or Hamilton-Jacobi approach. Contrary to claims in the specialized
literature, it is shown that the S\'aez-Ballester theory cannot provide a
realistic solution to the dark matter problem of Cosmology for the dust epoch,
without a fine tunning because the contribution of the scalar field in this
theory is equivalent to a stiff fluid (as can be seen from the energy--momentum
tensor for the scalar field), that evolves in a different way as the dust
component. To have similar contributions of the scalar component and the dust
component implies that their past values were fine tunned. So, we
reinterpreting this null result as an indication that dark matter plays a
central role in the formation of structures and galaxy evolution, having
measureable effects in the cosmic microwave bound radiation, and than this
formalism yield to this epoch as primigenius results. We do the mention that
this formalism was used recently in the so called K-essence theory applied to
dark energy problem, in place to the dark matter problem. Also, we include a
quantization procedure of the theory which can be simplified by reinterpreting
the theory in the Einstein frame, where the scalar field can be interpreted as
part of the matter content of the theory, and exact solutions to the
Wheeler-DeWitt equation are found, employing the Bianchi Class A cosmological
models.Comment: 24 pages; ISBN: 978-953-307-626-3, InTec
Risk of Upper Gastrointestinal Bleeding in a Cohort of New Users of Low-Dose ASA for Secondary Prevention of Cardiovascular Outcomes
The Health Improvement Network UK primary care database was used to identify a cohort of 38 077 individuals aged 50–84 years with a first prescription of low-dose acetylsalicylic acid (ASA; 75–300 mg/day) for secondary prevention of cardiovascular or cerebrovascular events during 2000–2007. From this cohort, 169 incident cases of upper gastrointestinal bleeding (UGIB) were identified. Controls with no UGIB (n = 2000) were frequency-matched to the cases by age, sex, and follow-up time. A nested case–control analysis was performed to determine risk factors associated with UGIB. The incidence of UGIB was 1.1 per 1000 person-years (95% CI, 1.0–1.3). Low-dose ASA users with a history of peptic ulcer disease had an increased risk of UGIB compared with those without (Relative Risk [RR], 4.59; 95% CI, 2.87–7.33). Concomitant use of ASA and clopidogrel (RR, 1.61; 95% CI, 0.85–3.05) or non-steroidal anti-inflammatory drugs (NSAIDs; RR, 2.92; 95% CI, 1.77–4.82) conferred an increased risk of UGIB compared with ASA monotherapy. Discontinuation of ASA therapy (RR: 0.71, 95% CI, 0.42–1.20) and PPI co-treatment given since the start of ASA therapy (RR, 0.56; 95% CI, 0.33–0.96) were associated with a reduced risk of UGIB. In conclusion, in a cohort of individuals receiving low-dose ASA for secondary prevention of cardiovascular or cerebrovascular events, patients with a history of peptic ulcer disease, or who were receiving clopidogrel or NSAIDs had an increased risk of UGIB. The prescription of PPI therapy at the initiation of low-dose ASA reduced the risk of UGIB by almost half
Nuevas metodologías docentes para la enseñanza de estructuras aeronáuticas.
La asignatura “Estructuras Aeronáuticas” está orientada a completar los conocimientos del análisis de estructuras del futuro ingeniero aeronáutico. La organización y programación de la asignatura está pensada para transmitir los conocimientos necesarios para el cálculo de estructuras laminares mediante métodos clásicos y modernos, como el basado en el Análisis con Elementos Finitos (AEF), de manera que el alumno posea una perspectiva amplia de la problemática asociada al diseño de estructuras laminares como las que integran una aeronave. Ello se lleva a cabo mediante clases teóricas, clases de problemas, clases prácticas de estructuras por ordenador y trabajos prácticos. En este trabajo se presentan nuevas metodologías docentes implementadas e introducidas en el esquema docente de dicha asignatura con objeto de satisfacer las líneas prioritarias del Plan Propio de la Universidad de Sevilla sobre metodologías docentes. De esta forma se llevan a cabo diferentes frentes de actuación: estudio y experimentación de nuevas metodologías didácticas como la enseñanza virtual, usando plataformas virtuales tipo WebCT, la elaboración de clases por transparencias PowerPoint y animaciones a partir de material específico, y la promoción del trabajo en equipo mediante la realización de un proyecto en grupo de AEF de un ala de una aeronave de recreo. El modelado mediante elementos finitos se realizará empleando el software comercial NASTRAN ® y PATRAN ® , de extensa aplicación en el sector aeronáutico
Risk of myocardial infarction and overall mortality in survivors of venous thromboembolism
<p>Abstract</p> <p>Background</p> <p>Venous thromboembolism (VTE) and thromboembolic arterial diseases are usually considered to be distinct entities, but there is evidence to suggest that these disorders may be linked. The aim of this study was to determine whether a diagnosis of VTE increases the long-term risk of myocardial infarction (MI).</p> <p>Methods</p> <p>The incidence rate (IR) and relative risk (RR) of MI in a cohort of patients with a diagnosis of VTE (n = 4890) compared with that of a control cohort without prior VTE (n = 43 382) were evaluated in the UK General Practice Research Database (GPRD). Death during follow-up was also determined. Patients were followed for up to 8 years (mean of 3 years).</p> <p>Results</p> <p>The IR of MI per 1000 person-years was 4.1 (95% CI: 3.1–5.3) for the VTE cohort and 3.5 (95% CI: 3.2–3.8) for the control cohort. The IR of MI was highest in the first year after the VTE episode, but overall differences between the two cohorts were not significant (RR of MI associated with VTE: 1.2; 95% CI: 0.9–1.6). The risk of death was higher in the VTE cohort than the control cohort, even after adjustment for cancer, heart failure and ischaemic heart disease (RR: 2.4; 95% CI: 2.2–2.6), particularly during the first year after VTE (RR: 3.8; 95% CI: 3.4–4.3).</p> <p>Conclusion</p> <p>A VTE episode does not significantly increase the risk of MI, but does increase the risk of death, particularly in the first year following VTE diagnosis.</p
Innovación y mejora docente en el ámbito de la enseñanza de estructuras metálicas.
La asignatura “Estructuras Metálicas” está orientada a completar los conocimientos del análisis de estructuras del futuro ingeniero industrial con su aplicación práctica al diseño de estructuras metálicas. La organización y programación de la asignatura está pensada para transmitir los conocimientos necesarios para el cálculo de elementos estructurales simples, de manera que el alumno posea una perspectiva amplia de la problemática asociada al diseño de estructuras metálicas complejas. Ello se lleva a cabo mediante clases teóricas, clases de problemas, clases prácticas de estructuras por ordenador, prácticas de laboratorio, y trabajos prácticos. Este trabajo presenta nuevas metodologías docentes, de acuerdo con las líneas prioritarias del Plan Propio de la Universidad de Sevilla, para mejorar los diferentes frentes de docencia que la asignatura posee. Para ello se profundiza en el estudio y experimentación de nuevas metodologías didácticas como la enseñanza virtual, usando plataformas virtuales tipo WebCT, la elaboración de clases por transparencias PowerPoint y animaciones numéricas realizadas mediante elementos finitos, todo ello basadas en la normativa vigente actual y bibliografía referente actualizada. Además se fomenta el trabajo en equipo mediante la realización de prácticas de campo y un proyecto en grupo, y se desarrollan nuevas prácticas de laboratorio y actividades de manera que el alumno contemple la visión práctica de los conocimientos adquiridos
Puf3p, a Pumilio family RNA binding protein, localizes to mitochondria and regulates mitochondrial biogenesis and motility in budding yeast
Puf3p binds preferentially to messenger RNAs (mRNAs) for nuclear-encoded mitochondrial proteins. We find that Puf3p localizes to the cytosolic face of the mitochondrial outer membrane. Overexpression of PUF3 results in reduced mitochondrial respiratory activity and reduced levels of Pet123p, a protein encoded by a Puf3p-binding mRNA. Puf3p levels are reduced during the diauxic shift and growth on a nonfermentable carbon source, conditions that stimulate mitochondrial biogenesis. These findings support a role for Puf3p in mitochondrial biogenesis through effects on mRNA interactions. In addition, Puf3p links the mitochore, a complex required for mitochondrial–cytoskeletal interactions, to the Arp2/3 complex, the force generator for actin-dependent, bud-directed mitochondrial movement. Puf3p, the mitochore, and the Arp2/3 complex coimmunoprecipitate and have two-hybrid interactions. Moreover, deletion of PUF3 results in reduced interaction between the mitochore and the Arp2/3 complex and defects in mitochondrial morphology and motility similar to those observed in Arp2/3 complex mutants. Thus, Puf3p is a mitochondrial protein that contributes to the biogenesis and motility of the organelle
Synthesis, characterization, bioactivity and biocompatibility of nanostructured materials based on the wollastonite-poly(ethylmethacrylate-co-vinylpyrrolidone) system
Composite materials are very promising biomaterials
for hard tissue augmentation. The approach assayed
in this work involves the manufacturing of a composite
made of a bioactive ceramic, natural wollastonite (W) and a
nanostructured copolymer of ethylmethacrylate (EMA) and
vinylpyrrolidone (VP) to yield a bioresorbable and biocompatible
VP–EMA copolymer. A bulk polymerization was
induced thermally at 508C, using 1 wt % azobis(isobutyronitrile)
(AIBN) as free-radical initiator. Structural characterization,
compressive strength, flexural strength (FS), degradation,
bioactivity, and biocompatibility were evaluated in
specimens with a 60/40 VP/EMA ratio and ceramic content
in the range 0–60%. A good integration between phases
was achieved. Greater compression and FS, in comparison
with the pure copolymer specimens was obtained only
when the ceramic load got up to 60% of the total weight.
The soaking in NaCl solution resulted in the initial swelling
of the specimens tested. The maximum swelling was
reached after 2–3 h of immersion and it was significantly
greater for lower ceramic loads. This result makes the polymer
component the main responsible for the interactions
with the media. After soaking in SBF, microdomains segregation
can be observed in the polymer component that can
be related with a dramatic difference in the reactivity of
both monomers in free radical polymerization, whereas the
formation of an apatite-like layer on the W surfaces can be
observed. Biocompatibility in vitro studies showed the absence
of cytotoxicity of all formulations. The cells were able
to adhere on the polystyrene negative control and on specimens
containing 60 wt % wollastonite forming a monolayer
and showing a normal morphology. However, a low cellular
growth was observed. 2008 Wiley Periodicals, Inc.
J Biomed Mater Res 88A: 53–64, 2009Peer reviewe
Determinación del hábitat potencialmente utilizable por la especie Salmo trutta en un tramo del río Lozoya, España
En el presente trabajo se efectua la estimacion del habitat potencialrnente utilizable (HPU) y del caudal que lo maximiza para los estadios de vida adulto, juvenil, alevin y freza de la especie Salmo trutta (trucha comun), especie muy apreciada en la pesca deportiva y para el consumo humane Para tal fin, de acuerdo con la Metodologia IFIM (Instream Flow Incremental Methodology), se efectuo la simulacion del habitat fisico fluvial de un tramo de 609 m del rio Lozoya (Madrid, Espana) utilizando un modelo bidimensional de la hidrodinamica, un modelo para la simulacion del habitat y los modelos de preferencia de habitat de la especie antes mencionada. Los modelos fueron alimentados con informacion hidraulica, geomorfologica, biologica y de caracteristicas especificas del habitat obtenidas en campo. Los valores del habitat potencialrnente utilizable (HPU) obtenidos para los cuatro estadios de desarrollo de la especie Salmo trutta permitieron determinar que el caudal de 1.97 m3/s maximiza el HPU para sus estadios de vida adulto, juvenil y freza, y que el caudal de 1.08 m3/s maximiza el habitat potencialrnente utilizable para su estadio de desarrollo alevin. Las curvas caudal-habitat potencialrnente utilizable obtenidas en el presente trabajo constituyen informacion valiosa para los usuarios y los gestores de los recursos fluviales del rio Lozoya, con miras a establecer un regimen de caudales ecologicos que permita conservar el ecosistema correspondiente y, en caso necesario, evaluar los impactos relacionados con posibles modificaciones del regimen de caudales
Unleashing the Potential of LTE for Next Generation Railway Communications
[Abstract]: In an increasingly demanding marketplace that will put great strain on railway services, research on broadband wireless communication must continue to strive for improvement. Based on the mature narrowband GSM technology, Global System for Mobile Communications-Railways (GSM-R) has been deployed both for operational and voice communications. Although GSM-R fulfills the requirements of current railway services, it imposes limited capacity and high costs that restrict enhancements of operational efficiency, passenger security and transport quality. 4G LongTerm Evolution (LTE) is expected to be the natural successor of GSM-R not only for its technical advantages and increasing performance, but also due to the current evolution of general-purpose communication systems. This paper examines the key features of LTE as well as its technical ability to support both the migration of current railway services and the provisioning of future ones
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