63 resultados para HYDROSTATIC PRESSURES


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El treballador públic és sotmès, des que comença la seva particular relació laboral, a un món fortament estructurat i amb una cultura, unes característiques i un tarannà propis i particulars. És en aquest procés que les forces socialitzadores del seu lloc de treball, juntament amb les del món exterior, el van formant com a treballador públic, fins al punt que es pot parlar del funcionari com d'una construcció. Això produeix una manera de veure i entendre el món laboral molt diferent de la que es té en l'empresa privada. Així, les aptituds, les actituds, les maneres de fer, les dèries i les manies només tenen sentit dins el seu entorn, que ell mateix comprèn com a totalment diferent. L'oposició com a ritual de pas, la socialització secundària, la percepció de l'alteritat, el qui és l'altre, el quan i el perquè, i els trets de la seva cultura - el temps, el treball, la normativa són algunes de les claus estudiades en aquest treball que ens ajuden a comprendre el perquè i el com d'aquesta construcció.

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Les zones europees d’alta muntanya, concretament les mediterrànies, han estat utilitzades des de temps remots per l’ésser humà, a través de l’aprofitament de boscos i prats mitjançant activitats com l’agricultura, la ramaderia, la silvicultura i la metal·lúrgia. Però, des de fa temps, amb l’abandonament de les àrees rurals, estem davant d’una falta de gestió dels boscos, degut a la pèrdua de les activitats tradicionals. L’objectiu d’aquest treball és el de determinar l’impacte provocat per les societats antigues sobre els boscos, amb la utilització del foc com a eina de gestió, així com l’anàlisi dels processos d’antropització de les zones de muntanya que utilitzaven aquest recurs. En aquest treball l’anàlisi de l’evolució del paisatge es fa mitjançant l’estudi de les comunitats vegetals històriques i la dinàmica d’incendis, a través de dues metodologies basades en testimonis sedimentaris: l’anàlisi de carbons i l’anàlisi del pol·len. El testimoni sedimentari ha estat extret de la torbera ombrotròfica de Montarenyo, situada a la vessant sud dels Pirineus, a la Vall de Cardós, al Pallars Sobirà. Aquestes dues disciplines han permès indagar en la geohistòria ambiental, per tal d’establir les relacions entre l’ambient i la societat. Els resultats mostren que el foc ha estat utilitzat per nombroses activitats, creant unes dinàmiques forestals característiques. El paisatge actual és conseqüència de les pressions que va haver de patir el bosc durant anys, unes pressions que, amb major o menor mesura han gestionat les masses forestals. Cal doncs conèixer quina ha estat la gestió històrica del bosc per entendre’n el seu estat actual i poder escollir la gestió més adequada per conservar-lo.

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En los últimos años la industria camaronera ha adquirido mucha importancia en Brasil y genera presiones sobre ecosistemas y comunidades tradicionales que viven en equilibrio con su entorno. En Cumbe, una comunidad tradicional del municipio de Aracati, Ceará, Brasil, el ecosistema que rodea a su población es el manglar. Debido a esta fuerte presión, tanto el manglar como los servicios ambientales que la población local se beneficia, están transformándose. En este trabajo, la población local de Cumbe identifica, valora y caracteriza los servicios ambientales que les proporciona el manglar dándole así una vital importancia, que puede servir de precedente para una posible protección. Por otra parte, se hace una aproximación en términos económicos de la pesca artesanal y las granjas de camarón para discutir a corto y a largo plazo cuál es el modelo más sostenible a seguir.

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En los últimos años la acuicultura de camarón se ha desarrollado como industria potencial en Brasil y sus actividades generan presiones sobre ecosistemas y comunidades tradicionales que viven en equilibrio con su entorno. En Cumbe, una comunidad tradicional del municipio de Aracati, Ceará, Brasil, el ecosistema que rodea a su población es el manglar. Debido a esta fuerte presión, tanto el manglar como los servicios ambientales de los que la población local se beneficia, están en peligro. Este estudio pretende evaluar las diferencias entre tres áreas de manglar que están afectadas en diferente grado por la presión de las industrias camaroneras. Se evalúan parámetros biológicos y la estructura de los manglares para observar las posibles diferencias y relacionarlas con las diferentes variables.

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We present an experimental and numerical study on the influence that particle aspect ratio has on the mechanical and structural properties of granular packings. For grains with maximal symmetry (squares), the stress propagation in the packing localizes forming chainlike forces analogous to the ones observed for spherical grains. This scenario can be understood in terms of stochastic models of aggregation and random multiplicative processes. As the grains elongate, the stress propagation is strongly affected. The interparticle normal force distribution tends toward a Gaussian, and, correspondingly, the force chains spread leading to a more uniform stress distribution reminiscent of the hydrostatic profiles known for standard liquids

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This paper explores the existence of negative peer-group pressures derived from the concentration of foreigners in French lower secondary schools. Using different dependent variables (number of years spent in lower secondary education, grades in 4th ‘and 3rd year and track election in upper secondary schooling) the analyses indicate that the much disputed existence of significant and negative effects of the concentration of foreign students in schools depends on the method used for the estimation. If we assume that the concentration of foreigners is a random and exogenous process, then the multivariate analyses confirm negative interactions. If, on the contrary, we question the assumption that this contextual information is not end the result of prior sorting mechanisms of individuals across social spaces, the concentration of foreigners has no statistical impact on attainment.

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We present a model of conglomeration motivated by technology synergies and strategic reductions in variable costs in the face of competitive pressures. The resulting firm integration is neither horizontal nor vertical but rather congeneric integration of firms in related industries. We endogenize the industrial conglomeration structure and examine the effects of competition between conglomerates, and between a conglomerate and independent firms. We show that there is an equilibrium synergy trap in which conglomerates are formed to exploit economies of scope, but resulting profits are lower than under the status quo. We also show that strategic firm integration can occur even in the presence of diseconomies of scope. The model helps to explain features of recent mergers and acquisitions experience.

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Immunity-related GTPases (IRG) play an important role in defense against intracellular pathogens. One member of this gene family in humans, IRGM, has been recently implicated as a risk factor for Crohn's disease. We analyzed the detailed structure of this gene family among primates and showed that most of the IRG gene cluster was deleted early in primate evolution, after the divergence of the anthropoids from prosimians ( about 50 million years ago). Comparative sequence analysis of New World and Old World monkey species shows that the single-copy IRGM gene became pseudogenized as a result of an Alu retrotransposition event in the anthropoid common ancestor that disrupted the open reading frame (ORF). We find that the ORF was reestablished as a part of a polymorphic stop codon in the common ancestor of humans and great apes. Expression analysis suggests that this change occurred in conjunction with the insertion of an endogenous retrovirus, which altered the transcription initiation, splicing, and expression profile of IRGM. These data argue that the gene became pseudogenized and was then resurrected through a series of complex structural events and suggest remarkable functional plasticity where alleles experience diverse evolutionary pressures over time. Such dynamism in structure and evolution may be critical for a gene family locked in an arms race with an ever-changing repertoire of intracellular parasites.

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The number of private gardens has increased in recent years, creating a more pleasant urban model, but not without having an environmental impact, including increased energy consumption, which is the focus of this study. The estimation of costs and energy consumption for the generic typology of private urban gardens is based on two simplifying assumptions: square geometry with surface areas from 25 to 500 m2 and hydraulic design with a single pipe. In total, eight sprinkler models have been considered, along with their possible working pressures, and 31 pumping units grouped into 5 series that adequately cover the range of required flow rates and pressures, resultin in 495 hydraulic designs repeated for two climatically different locations in the Spanish Mediterranean area (Girona and Elche). Mean total irrigation costs for the locality with lower water needs (Girona) and greater needs (Elche) were € 2,974 ha-¹ yr-¹ and € 3,383 ha-¹ yr-¹, respectively. Energy costs accounted for 11.4% of the total cost for the first location, and 23.0% for the second. While a suitable choice of the hydraulic elements of the setup is essential, as it may provide average energy savings of 77%, due to the low energy cost in relation to the cost of installation, the potential energy savings do not constitute a significant incentive for the irrigation system design. The low efficiency of the pumping units used in this type of garden is the biggest obstacle and constraint to achieving a high quality energy solution

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Catalan libraries find themselves stretched to their limits due to the conflict between the traditional model of preserving and conserving knowledge and the pressures created by the constant expansion of the collection. A solution can be found in weeding the collection. This article first explains the legal and reglamentary framework in which weeding should take place, followed by a proposed planning method that suggests different criteria to be applied. A description is provided of practical aspects of organising a project and of evaluating results. The article concludes with various alternatives for final disposal of the documents to be withdrawn definitively. A selective, annotated bibliography is included.

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The forced oscillation technique (FOT) is a method for non-invasively assessing respiratory mechanics that is applicable both in paralysed and non-paralysed patients. As the FOT requires a minimal modification of the conventional ventilation setting and does not interfere with the ventilation protocol, the technique is potentially useful to monitor patient mechanics during invasive and noninvasive ventilation. FOT allows the assessment of the respiratory system linearity by measuring resistance and reactance at different lung volumes or end-expiratory pressures. Moreover, FOT allows the physician to track the changes in patient mechanics along the ventilation cycle. Applying FOT at different frequencies may allow the physician to interpret patient mechanics in terms of models with pathophysiological interest. The current methodological and technical experience make possible the implementation of portable and compact computerised FOT systems specifically addressed to its application in the mechanical ventilation setting.

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Large phasic variations of respiratory mechanical impedance (Zrs) have been observed during induced expiratory flow limitation (EFL) (M. Vassiliou, R. Peslin, C. Saunier, and C. Duvivier. Eur. Respir. J. 9: 779-786, 1996). To clarify the meaning of Zrs during EFL, we have measured from 5 to 30 Hz the input impedance (Zin) of mechanical analogues of the respiratory system, including flow-limiting elements (FLE) made of easily collapsible rubber tubing. The pressures upstream (Pus) and downstream (Pds) from the FLE were controlled and systematically varied. Maximal flow (Vmax) increased linearly with Pus, was close to the value predicted from wave-speed theory, and was obtained for Pus-Pds of 4-6 hPa. The real part of Zin started increasing abruptly with flow (V) >85%Vmax and either further increased or suddenly decreased in the vicinity of V¿max. The imaginary part of Zin decreased markedly and suddenly above 95%Vmax. Similar variations of Zin during EFL were seen with an analogue that mimicked the changes of airway transmural pressure during breathing. After pressure andV measurements upstream and downstream from the FLE were combined, the latter was analyzed in terms of a serial (Zs) and a shunt (Zp) compartment. Zs was consistent with a large resistance and inertance, and Zp with a mainly elastic element having an elastance close to that of the tube walls. We conclude that Zrs data during EFL mainly reflect the properties of the FLE.

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El artículo describe los efectos de las aceleraciones positivas (+Gz) sobre el organismohumano. Se consideran los factores determinantes de las aceleraciones: intensidad, velocidad de comienzo, dirección y duración. La fisiopatología describe los factores hidrostáticos,hemodinámicos y de regulación refleja del aparato cardiocirculatorio. La exposición a +Gz produce reacciones adaptativas fisiológicas. Cuando éstas se superan, aparecen patologías de tipocardiocirculatorio, respiratorio, músculoesquelético, nervioso, sensorial,... Se describen los diferentes procedimientos y equipos específicos que protegen al piloto de los efectos de +Gz. Éstos incluyen las maniobras de contracción muscular, los trajes anti-G, los equipos de respiración a presión positiva, así como el entrenamiento en centrífuga.

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Nanocrystalline silicon layers have been obtained by thermal annealing of films sputtered in various hydrogen partial pressures. The as-deposited and crystallized films were investigated by infrared, Raman, x-ray diffraction, electron microscopy, and optical absorption techniques. The obtained data show evidence of a close correlation between the microstructure and properties of the processed material, and the hydrogen content in the as-grown deposit. The minimum stress deduced from Raman was found to correspond to the widest band gap and to a maximum hydrogen content in the basic unannealed sample. Such a structure relaxation seems to originate from the so-called "chemical annealing" thought to be due to Si-H2 species, as identified by infrared spectroscopy. The variation of the band gap has been interpreted in terms of the changes in the band tails associated with the disorder which would be induced by stress. Finally, the layers originally deposited with the highest hydrogen pressure show a lowest stress-which does not correlate with the hydrogen content and the optical band gap¿and some texturing. These features are likely related to the presence in these layers of a significant crystalline fraction already before annealing.

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[spa] En este artículo aplicamos un modelo input-output ampliado medioambientalmente para analizar un aspecto específico de la hipótesis de la curva de Kuznets ambiental. El propósito del estudio es analizar si las estructuras de consumo de los hogares con una mejor ‘posición económica’ pueden tener un efecto positivo para reducir las presiones medioambientales. Para ello combinamos información de diferentes bases de datos para analizar el impacto de la contaminación atmosférica del consumo de diferentes hogares españoles en el año 2000. Consideramos nueve gases, i.e. los seis gases de efecto invernadero (CO2, CH4, N2O, SF6, HFCs, y PFCs) y otros tres gases (SO2, NOx, y NH3). Clasificamos los hogares en quintiles de gasto per capita y quintiles de gasto equivalente. Los resultados obtenidos muestran que hay una relación positiva y elevada entre el nivel de gasto y las emisiones directas e indirectas generadas por el consumo de los hogares; sin embargo, las intensidades de emisión tienden a disminuir con el nivel de gasto para los diferentes gases, con la excepción de SF6, HFCs, y PFCs.