971 resultados para Polímers -- Proves


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Este artículo muestra una variedad de posibles soluciones ante las dificultades que los científicos sociales pueden encontrarse en la investigación cuantitativa con poblaciones elusivas. Estas dificultades son de dos tipos: epistemológicas y técnicas. Desde el punto de vista epistemológico, se subraya la necesidad de adaptación de la investigación a las características de la población objeto de estudio, pues la elusividad de la población no puede considerarse un obstáculo insalvable. Esta flexibilidad se muestra más constructiva, en términos de consecución de objetivos de investigación, que un posicionamiento más rígido o tradicional, más apegado a modelos preestablecidos. Desde el punto de vista técnico, se muestran las soluciones ante cada dificultad encontrada en el curso de un estudio de caso: la población turístico-residencial del destino Costa Blanca en el Levante español. Estas soluciones se demuestran, finalmente, como adecuadas al contrastar los resultados con encuestas oficiales tipo panel realizadas de forma tradicional en origen.

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Este documento es un artículo inédito que ha sido aceptado para su publicación. Como un servicio a sus autores y lectores, Alternativas. Cuadernos de trabajo social proporciona online esta edición preliminar. El manuscrito puede sufrir alteraciones tras la edición y corrección de pruebas, antes de su publicación definitiva. Los posibles cambios no afectarán en ningún caso a la información contenida en esta hoja, ni a lo esencial del contenido del artículo.

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Dissertação apresentada à Escola Superior de Tecnologia do Instituto Politécnico de Castelo Branco para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Desenvolvimento de Software e Sistemas Interactivos, realizada sob a orientação científica da categoria profissional do orientador Doutor Eurico Ribeiro Lopes, do Instituto Politécnico de Castelo Branco.

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Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2014

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Countries can make a clean exit from financial assistance, or enter a new programme or a precautionary programme, depending on the sustainability of their public debt and their vulnerability to shocks. Ireland made a clean exit in December 2013, supported by significant budgetary and current-account adjustment and signs of economic recovery. But Irish debt sustainability is not guaranteed and prudence will be needed to avoid future difficulties. A clean exit for Portugal is not recommended when its programme ends in May 2014, because compared to Ireland it faces higher interest rates, has poorer growth prospects and has probably less ability to generate a consistently high primary surplus. A precautionary arrangement would be advisable. In case debt sustainability proves difficult to achieve later, some form of debt restructuring may prove necessary. It is unlikely that Greece will be able to exit its programme in December 2014. A third programme should be put in place to take Greece out of the market until 2030, accompanied by enhanced budgetary and structural reform commitments by Greece, a European boost to economic growth in the euro-area periphery and willingness on the part of lenders to reduce loan charges below their borrowing costs, should public debt levels prove unsustainable despite Greece meeting the loan conditions. Even assuming all goes well, the three countries will be subject to enhanced post-pro-gramme surveillance for decades. Managing such long-term relationships will be a key challenge.

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Gazprom is determined to continue its efforts to build the South Stream gas pipeline regardless of the slump on the European gas market and the fact that there is sufficient capacity already in the existing transport infrastructure. The official inauguration of the maritime section of South Stream was held on 7 December this year, but the construction itself will commence in 2014. The agreements concluded so far, both intergovernmental and between corporations, are necessary for the launch of the construction of the new pipeline, but still do not guarantee that the project will be completed on time. First of all, some legal problems have yet to be resolved, such as the evaluation of the compliance of the planned actions with the ‘third energy package’ or the fact that ecological surveys required under European law need to be carried out. Secondly, given the present situation on the European gas market and medium-term forecasts, the high cost of implementation of this project and the maintenance expenses of existing pipelines – which are not being used to full capacity – the new project seems to be unfeasible. However, Gazprom’s determination in its efforts to build the pipeline proves that Russia is ready to take a high economic risk to maintain its dominant position on the European gas supply market; it will restrict the possibilities of alternative infrastructural projects being implemented (above all, the EU’s Southern Corridor) and use the construction of new pipelines as an instrument of political pressure on the present transit countries (especially Ukraine).

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In its attempts to catch up with the global trend, Russia began granting development assistance in 2004. From the onset of Russia’s commitment, the aid delivered has increased fivefold and reached approximately US$ 500 million in 2010. Russian aid, albeit distributed nearly exclusively via international organisations, has been granted above all to members of the Commonwealth of Independent States (CIS). In recent months work on the establishment of the Russian development assistance system has been accelerated (a national strategy is being prepared and a specialised agency is to be established). This move proves that the Kremlin attaches weight to activity in this area which is an element of soft power politics, the foundations of which Moscow is currently attempting to lay. In its commitment to development co-operation Russia has sought on the one hand to increase its prestige on the international stage and on the other hand to gain another instrument of exerting its ascendancy in the CIS. The scale of aid and the way of delivering it have not made Russia an important global actor. Over the last five years Russia increased the funding allocated to development assistance several times, however, compared to other donors its aid does not appear impressive. The resources dedicated to this end stand at a mere 0.035% of Russian GDP. Unlike other non-Western superpowers such as China or India, Russia is not a competitor for Western countries in this area on the global scale. Nevertheless, within the CIS, Russia’s aid is building the country’s position as a donor. The long-term results of this aid are however being counteracted by the fact that Russia is expecting measurable and direct political and economic benefits in return. Although this policy helps Moscow achieve its objectives in the CIS, it does not develop Russian potential in the sphere of soft power or create a positive image of the country.

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Tensions over Iran’s nuclear programme have risen considerably in recent months. This has been visible in numerous threats of – and much speculation about – an imminent Israeli (and US) attack on Iran’s nuclear installations. In this context, the support for the attacks that the countries of the South Caucasus (and Azerbaijan in particular) could provide has been the subject of lively debate, as has been the prospect of a Russian political and military offensive in the Caucasus in response to the attacks on Iran. It seems that the ongoing war campaign in the media has been aimed primarily at putting pressure on Iran and the international community to find a political solution to the Iranian problem. This also applies to the Caucasus’s involvement in the campaign. Given the outcome of the Istanbul round of talks on a political solution to the Iranian issue (14 April), which warrants moderate optimism, the threat of a conflict now appears more distant and this also indirectly proves the effectiveness of the campaign. The war of nerves with Iran, however, is already now actually affecting the stability of the Southern Caucasus. While it seems that Azerbaijan is not Israel’s partner in the preparations to attacks, and that there is no real link between the Iranian problem and the ongoing and planned movements of Russian troops in the Caucasus, the tensions between Iran and Azerbaijan are indeed high. Moreover, the global image of the Caucasus is deteriorating, the USA’s position in the region is becoming more complicated, and Russia’s room for manoeuvre is expanding.

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Fifty radiolarian events of early Pleistocene and Neogene age were identified in an E-W transect of equatorial DSDP sites, extending from the Gulf of Panama to the western Pacific and eastern Indian Oceans. Our objective was to document the degree of synchroneity or time-transgressiveness of stratigraphically-useful datum levels from this geologic time interval. We restricted our study to low latitudes within which morphological variations of individual taxa are minimal, the total assemblage diversity remains high, and stratigraphic continuity is well-documented by an independent set of criteria. Each of the five sites chosen (503, 573, 289/586, 214) was calibrated to an "absolute" time scale, using a multiple of planktonic foraminiferal, nannofossil, and diatom datum levels which have been independently correlated to the paleomagnetic polarity time scale in piston core material. With these correlations we have assigned "absolute" ages to each radiolarian event, with a precision of 0.1-0.2 m.y. and an accuracy of 0.2-0.4 m.y. On this basis we have classified each of the events as either: (a) synchronous (range of ages <0.4 m.y.); (b) time-transgressive (i.e., range of ages >1.0 m.y.); and (c) not resolvable (range of ages 0.4-1.0 m.y.). Our results show that, among the synchronous datum levels, a large majority (15 out of 19) are last occurrences. Among those events which are clearly time-transgressive, most are first appearances (10 out of 13). In many instances taxa appear to evolve first in the Indian Ocean, and subsequently in the western and eastern Pacific Ocean. This pattern is particularly unexpected in view of the strong east-to-west zonal flow in equatorial latitudes. Three of the time-transgressive events have been used to define zonal boundaries: the first appearances of Spongaster pentas, Diartus hughesi, and D. petterssoni. Our results suggest that biostratigraphic non-synchroneity may be substantial (i.e., greater than 1 m.y.) within a given latitudinal zone; one would expect this effect to be even more pronounced across oceanographic and climatic gradients. We anticipate that the extent of diachroneity may be comparable for diatom, foraminiferal, and nannofossil datum levels as well. If this proves true, global "time scales" may need to be re-formulated on the basis of a smaller number of demonstrably synchronous events.

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The North Sea autumn-spawning herring (Clupea harengus) stock consists of a set of different spawning components. The dynamics of the entire stock have been well characterized, but although time-series of larval abundance indices are available for the individual components, study of the dynamics at the component level has historically been hampered by missing observations and high sampling noise. A simple state-space statistical model is developed that is robust to these problems, gives a good fit to the data, and proves capable of both handling and predicting missing observations well. Furthermore, the sum of the fitted abundance indices across all components proves an excellent proxy for the biomass of the total stock, even though the model utilizes information at the individual-component level. The Orkney-Shetland component appears to have recovered faster from historic depletion events than the other components, whereas the Downs component has been the slowest. These differences give rise to changes in stock composition, which are shown to vary widely within a relatively short time. The modelling framework provides a valuable tool for studying and monitoring the dynamics of the individual components of the North Sea herring stock.

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Drill core recovered at Ocean Drilling Program Site 808 (Leg 131) proves that the wedge of trench sediment within the central region of the Nankai Trough comprises approximately 600 m of hemipelagic mud, sandy turbidites, and silty turbidites. The stratigraphic succession thickens and coarsens upward, with hemipelagic muds and volcanic-ash layers of the Shikoku Basin overlain by silty and sandy trench-wedge deposits. Past investigations of clay mineralogy and sand petrography within this region have led to the hypothesis that most of the detritus in the Nankai Trough was derived from the Izu-Honshu collision zone and transported southwestward via axial turbidity currents. Shipboard analyses of paleocurrent indicators, on the other hand, show that most of the ripple cross-laminae within silty turbidites of the outer marginal trench-wedge facies are inclined to the north and northwest; thus, many of the turbidity currents reflected off the seaward slope of the trench rather than moving straight down the trench axis. Shore-based analyses of detrital clay minerals demonstrate that the hemipelagic muds and matrix materials within sandy and silty turbidites are all enriched in illite; chlorite is the second-most abundant clay mineral, followed by smectite. In general, the relative mineral percentages change relatively little as a function of depth, and the hemipelagic clay-mineral population is virtually identical to the turbidite-matrix population. Comparisons between different size fractions (<2 µm and 2-6 µm) show modest amounts of mineral partitioning, with chlorite content increasing in the coarser fraction and smectite increasing in the finer fraction. Values of illite crystallinity index are consistent with conditions of advanced anchimetamorphism and epimetamorphism within the source region. Of the three mica polytypes detected, the 2M1 variety dominates over the 1M and 1Md polytypes; these data are consistent with values of illite crystallinity. Measurements of mica bo lattice spacing show that the detrital illite particles were eroded from a zone of intermediate-pressure metamorphism. Collectively, these data provide an excellent match with the lithologic and metamorphic character of the Izu-Honshu collision zone. Data from Leg 131, therefore, confirm the earlier interpretations of detrital provenance. The regional pattern of sediment dispersal is dominated by a combination of southwest-directed axial turbidity currents, radial expansion of the axial flows, oblique movement of suspended clouds onto and beyond the seaward slope of the Nankai Trough, and flow reflection back toward the trench axis.

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A careful comparison is made between the most detailed records of sea level over the last glacial cycle, and two high-quality oxygen isotope records. One is a high-resolution benthonic record that contains superb detail but proves to record temperature change as well as ice volume; the other is a planktonic record from the west equatorial Pacific where the temperature effect may be minimal but where high resolution is not available. A combined record is generated which may be a better approximation to ice volume than was previously available. This approach cannot yet be applied to the whole Pleistocene. However, comparison of glacial extremes suggests that glacial extremes of stages 12 and 16 significantly exceeded the last glacial maximum as regards ice volume and hence as regards sea level lowering. Interglacial stages 7, 13, 15, 17 and 19 did not attain Holocene oxygen isotope values; possibly the sea did not reach its present level. It is unlikely that sea level was glacio-eustatically higher than present by more than a few metres during any interglacial of the past 2.5 million years.

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Experimental evidence is presented which proves that voids formed during diffusion in brass are heterogeneously nucleated. The nuclei appear to be oxide particles, probably ZnO. When these are removed by re-melting, voids practically do not form upon subsequent dezincification. Brass which had been freed of void nucleation catalysts exhibited a considerably reduced tendency for grain boundary cracking during creep, and increased stress-rupture life.

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The role of several theoretical factors in determining the demand of US banks for borrowed reserves from the Fed is empirically investigated. The main objective is to isolate the candidate(s) most likely responsible for the recent observed phenomenon of banks reluctance to borrow from the Fed, particularly since the mid-1980s. The results indicate that the declining number of banks due to mergers and consolidations holds much of the weight for explaining the weakened demand for borrowed reserves since the mid-1980s. Consistent evidence is found suggesting that US banks may have been unlawfully exploiting the discount window service for profit-taking purposes. This finding proves credible and suggests the need for further loan scrutiny at the Federal discount window.

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The ability to interpret collected data across international mental health communities often proves to be difficult. The following paper reports on the use and appropriateness of focus group methodology in helping to Clarify issues that could help substantiate data collection and comparison across different cultures and regions. Field tests of the focus group methodology were undertaken in different regions and this paper describes an overview of the final field test in Sofia, Bulgaria. The findings and experiences with utilizing this methodology were incorporated in subsequent data collections.