2,868 research outputs found

    A study of the effect of projectile orientation on the results of ballistic impact tests as described in the EASA CS-25 regulations for fuel tank access covers

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    This paper presents the results of an investigation of the ballistic limits and failure modes of AA2024-T351 sheets impacted with cubical projectiles. The experiment/test setup was based on EASA CS-25 regulations for fuel tank access covers. The effect of cube orientation on the ballistic limit and failure modes was considered in detail. A 25% variation in ballistic limit was observed with the lowest ballistic limit (202 m/s) observed for the cubical projectile edge impacted on the target. In the cube face impacts, the ballistic limit was higher (223 m/s), and the highest ballistic limit (254 m/s) was observed for the corner impact. The observed differences in the ballistic limit were due to differences in failure mechanism, which resulted in different localised deformations near the projectile impact point, but also led to differences in global dishing deformation

    Hipotiroidismo subclínico y factores de riesgo cardiovascular

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    Objetivo: Conocer la prevalencia del hipotiroidismo subclínico en la población general de un centro de salud urbano y describir las características clínicas y factores de riesgo cardiovascular de los pacientes con hipotiroidismo subclínico. Métodos: Se realizó un estudio observacional descriptivo, transversal, retrospectivo, revisando las historias clínicas de los pacientes incluidos en la muestra desde junio de 2005 hasta julio de 2007. Se analizaron las siguientes variables; Datos generales: edad y sexo. Antecedentes familiares: patología tiroidea y otras enfermedades. Antecedentes personales: cardiovasculares, pulmonares, enfermedades autoinmunes, alteraciones gineco-obstétricas, diabetes, hipertensión (HT), dislipemia, obesidad, alteraciones psiquiátricas y hematológicas. Datos de laboratorio: niveles de TSH, niveles de T4 libre,presencia de anticuerpos antiperoxidasa, niveles de colesterol total y sus fracciones. Resultados: La prevalencia de la muestra de 100 pacientes recogida durante 8 meses fue de 3,8% de la población general mayor de 14 años, de la cual 79 eran mujeres y 21 eran hombres. El 13% eran diabéticos tipo 2, 23% tenían HT y un 40% tenían dislipemia. Sobrepeso y obesidad estaban presentes en un 26%. El nivel medio de TSH fue 6.92 ± 2,29 U/ml y el nivel medio de T4 libre fue 1,16 ± 0,16 ng/ml. Conclusiones: La prevalencia del hipotiroidismo subclínico fue 3,8%. sobre todo en mujeres con una edad media de 46 años. La incidencia de factores de riesgo cardiovascular en los sujetos estudiados es mayor en DM (13%), similar a la población general en cuanto a la dislipemia (40%) y obesidad (20%) y menor en HTA (23%). En nuestro estudio no se observa una pauta común en el manejo del hipotiroidismo subclínico, siendo necesaria la implementación y promoción de guías de actuación en Atención PrimariaObjective: To determine the prevalence of subclinical hypothyroidism in the general population of an urban health center and describe the clinical characteristics and cardiovascular risk factors in patients with subclinical hypothyroidism. Methods: An observational study, retrospective, reviewing the medical histories of patients sampled from June 2005 until July 2007. We analyzed the following variables; facts: age and sex. Family history thyroid disease and other diseases. Personal history: cardiovascular pulmonary autoimmune, alterations gynecology obstetric diabetes, hypertension (HT) dislipemia, obesity, psychiatric alterations and haematological. Laboratory data: novel TSH, free T4, antiperoxidase antibodies, total cholesterol and its fractions. Results: The prevalence of the sample of 100 patients collected over 8 months was 3.8% in the general population over 14 years, of which 79 were women and 21 were men. 13% were type 2 diabetics, 23% had HT and 40% had dyslipidemia. Overweight and obesity were present in 26%. The average level of TSH was 6.92 ± 2.29 U/ml and the average level of free T4 was 1.16 ± 0.16 ng/ml. Conclusions: Prevalence subclinical hypothyroidism was 3.8%. especially in women with a mean age of 46. The incidence of cardiovascular risk factors in the subjects studied is higher in DM (13%), similar to general population in terms of dyslipidemia (40%) and obesity (23%) and lowest in hypertension (23%). In our study we observed a common pattern in the management of subclinical hypothyroidism, requiring the implementation and promotion of practice guidelines in primary car

    Factores del retardo de consolidación en fracturas de antebrazo pediátricas

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    El objetivo de este estudio es determinar factores para el retardo de curación en fracturas pediátricas diafisarias de antebrazo. Presentamos un estudio caso-control de todas las fracturas pediáticas de antebrazo tratadas en el Hospital Universitario Miguel Servet, desde 2003 hasta 2009, y que presentaron retardo de consolidación, con un seguimiento mínimo de 12 meses. Los criterios de exclusión fueron fractura-luxación, infección, osteosíntesis insuficiente, fractura en tallo verde, abierta, patológica y asociada a fractura de cabeza radial, así como pacientes sin el seguimiento mínimo establecido. El cálculo estadístico incluyó análisis de regresión lineal bivariante y multivariante. Resultados: Durante este periodo se trataron 441 fracturas de antebrazo completas, de ambos huesos: 14 de ellas (3.2%) sufrieron retardo de consolidación; y 63 controles cumplieron los criterios de inclusión y fueron seleccionados aleatoriamente. El análisis bivariante mostró diferencias significativas entre los grupos "retardo de consolidación" y "control" en edad, necesidad de tratamiento quirúrgico, reducción abierta frente a cerrada y tiempo hasta retirada del material. Si embargo, la reducción abierta de la fractura, más frecuente en el grupo "retardo de consolidación", fue la única variable que permaneció asociada en el análisis multivariante. Conclusiones: El factor predictivo más importante para el retardo de consolidación en fracturas pediátricas de antebrazo es la reducción abierta.The aim of this study was to assess predictive factors for delayed healing in forearm paediatric fractures. This is a case-control study of all paediatric shaft fractures of forearm presenting delayed union in follow-up period of 12 months or more, from 2003 through 2009, treated in Miguel Servet University Hospital. Exclusion criteria were fracture-dislocations, infection, suboptimal osteosynthesis, greenstick, open, pathologic and associated radial head fractures, as well as patients without stablished period of follow up. Statistical assessment included bivariant and multivariant linear regression analysis. Results: During the study period 441 complete both-bone forearm fractures were treated: 14 of them (3.2%) were identified as suffering delayed union; and 63 controls fulfilling inclusion criteria were randomly selected. Bivariant analysis showed significant differences between "delayed union" and "control" groups in age, need of surgical treatment, open versus closed reduction and mean time to hardware removal. However, open reduction of the fracture, more frequent in the "delayed union" group, was the only variable which remained associated in the multivariant analysis. Conclusions: The strongest predictor of union delay in paediatric forearm fractures is open reduction

    Preferential oxidation of CO in excess of H2 on Pt/CeO2–Nb2O5 catalysts

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    A series of CeO2–Nb2O5 mixed oxides with different Nb content, as well as the pure oxides, have been synthesized by co-precipitation with excess urea. These materials have been used as supports for platinum catalysts, with [Pt(NH3)4](NO3)2 as precursor. Both supports and catalysts have been characterized by several techniques: N2 physisorption at 77 K, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, UV–vis spectroscopy, scanning electron microscopy, transmission electron microscopy, temperature-programmed reduction and temperature-programmed desorption (CO and H2), and their catalytic behaviour has been determined in the PROX reaction, both with an ideal gas mixture (CO, O2 and H2) and in simulated reformate gas containing CO2 and H2O. Raman spectroscopy analysis has shown the likely substitution of some Ce4+ cations by Nb5+ to some extent in supports with low niobium contents. Moreover, the presence of Nb in the supports hinders their ability to adsorb CO and to oxidize it to CO2. However, an improvement of the catalytic activity for CO oxidation is obtained by adding Nb to the support, although the Pt/Nb2O5 catalyst shows very low activity. The best results are found with the Pt/0.7CeO2–0.3Nb2O5 catalyst, which shows a high CO conversion (85%) and a high yield (around 0.6) after a reduction treatment at 523 K. The effect of the presence of CO2 and H2O in the feed has also been determined.The authors gratefully acknowledge the financial sup-port from the MINECO (Spain, Project MAT2010-21147) and Generalitat Valenciana (PROMETEO/2009/002–FEDER and PROMETEOII/2014/004–FEDER). EVRF thanks the MINECO for his Ramón y Cajal Fellowship RYC-2012-11427. EOJ thanks the CNPq – Brazil for her grant

    Influence of the metal precursor on the catalytic behavior of Pt/Ceria catalysts in the preferential oxidation of CO in the presence of H2 (PROX)

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    The effect of the metal precursor (presence or absence of chlorine) on the preferential oxidation of CO in the presence of H2 over Pt/CeO2 catalysts has been studied. The catalysts are prepared using (Pt(NH3)4)(NO3)2 and H2PtCl6, as precursors, in order to ascertain the effect of the chlorine species on the chemical properties of the support and on the catalytic behavior of these systems in the PROX reaction. The results show that chloride species exert an important effect on the redox properties of the oxide support due to surface chlorination. Consequently, the chlorinated catalyst exhibits a poorer catalytic activity at low temperatures compared with the chlorine-free catalyst, and this is accompanied by a higher selectivity to CO2 even at high reaction temperatures. It is proposed that the CO oxidation mechanism follows different pathways on each catalyst.The authors gratefully acknowledge financial support from Ministerio de Ciencia e Innovación (Project MAT2010-21147) and Generalitat Valenciana (PROMETEO/2009/002 – FEDER and PROMETEOII/2014/004) (Spain). EOJ thanks the CNPq – Brazil for her grant

    La molibdenita, nueva especie mineral en "Mina Berta", San Cugat del Vallés, Barcelona

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    Mediante difracción de rayos X se identifica la molibdenita. Esta especie mineral no había sido citada por ningún autor.Se realiza igualmente el estudio espectrográfico por fluorescenciade rayos X

    Methodological approaches to determining the marine radiocarbon reservoir effect

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    The marine radiocarbon reservoir effect is an offset in 14C age between contemporaneous organisms from the terrestrial environment and organisms that derive their carbon from the marine environment. Quantification of this effect is of crucial importance for correct calibration of the <sup>14</sup>C ages of marine-influenced samples to the calendrical timescale. This is fundamental to the construction of archaeological and palaeoenvironmental chronologies when such samples are employed in <sup>14</sup>C analysis. Quantitative measurements of temporal variations in regional marine reservoir ages also have the potential to be used as a measure of process changes within Earth surface systems, due to their link with climatic and oceanic changes. The various approaches to quantification of the marine radiocarbon reservoir effect are assessed, focusing particularly on the North Atlantic Ocean. Currently, the global average marine reservoir age of surface waters, R(t), is c. 400 radiocarbon years; however, regional values deviate from this as a function of climate and oceanic circulation systems. These local deviations from R(t) are expressed as +R values. Hence, polar waters exhibit greater reservoir ages (δR = c. +400 to +800 <sup>14</sup>C y) than equatorial waters (δR = c. 0 <sup>14</sup>C y). Observed temporal variations in δR appear to reflect climatic and oceanographic changes. We assess three approaches to quantification of marine reservoir effects using known age samples (from museum collections), tephra isochrones (present onshore/offshore) and paired marine/terrestrial samples (from the same context in, for example, archaeological sites). The strengths and limitations of these approaches are evaluated using examples from the North Atlantic region. It is proposed that, with a suitable protocol, accelerator mass spectrometry (AMS) measurements on paired, short-lived, single entity marine and terrestrial samples from archaeological deposits is the most promising approach to constraining changes over at least the last 5 ky BP

    Observation of an Excited Bc+ State

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    Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date
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