976 resultados para nucleon-nucleon cross sections


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The air fluorescence detector of the Pierre Auger Observatory is designed to perforin calorimetric measurements of extensive air showers created by Cosmic rays of above 10(18) eV. To correct these measurements for the effects introduced by atmospheric fluctuations, the Observatory contains a group Of monitoring instruments to record atmospheric conditions across the detector site, ail area exceeding 3000 km(2). The atmospheric data are used extensively in the reconstruction of air showers, and are particularly important for the correct determination of shower energies and the depths of shower maxima. This paper contains a summary of the molecular and aerosol conditions measured at the Pierre Auger Observatory since the start of regular operations in 2004, and includes a discussion of the impact of these measurements oil air shower reconstructions. Between 10(18) and 10(20) eV, the systematic Uncertainties due to all atmospheric effects increase from 4% to 8% in measurements of shower energy, and 4 g cm(-2) to 8 g cm(-2) in measurements of the shower maximum. (C) 2010 Elsevier B.V. All rights reserved.

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Two-photon absorption induced polymerization provides a powerful method for the fabrication of intricate three-dimensional microstructures. Recently, Lucirin TPO-L was shown to be a photoinitiator with several advantageous properties for two-photon induced polymerization. Here we measure the two-photon absorption cross-section spectrum of Lucirin TPO-L, which presents a maximum of 1.2 GM at 610 nm. Despite its small two-photon absorption cross-section, it is possible to fabricate excellent microstructures by two-photon polymerization due to the high polymerization quantum yield of Lucirin TPO-L. These results indicate that optimization of the two-photon absorption cross-section is not the only material parameter to be considered when searching for new photoinitiators for microfabrication via two-photon absorption.

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The use of roll-formed products in automotive, furniture, buildings etc. increases every year due to the low part-production cost and the complicated cross-sections that can be produced. The limitation with roll-forming until recent years is that one could only produce profiles with a constant cross-section in the longitudinal direction. About eight years ago ORTIC AB [1] developed a machine in which it was possible to produce profiles with a variable width (“3D roll-forming”) for the building industry. Experimental equipment was recently built for research and prototyping of profiles with variable cross-section in both width and depth for the automotive industry. The objective with the current study is to investigate the new tooling concept that makes it possible to roll-form hat-profiles, made of ultra high strength steel, with variable cross-section in depth and width. The result shows that it is possible to produce 3D roll-formed profiles with close tolerances.

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One of the first questions to consider when designing a new roll forming line is the number of forming steps required to produce a profile. The number depends on material properties, the cross-section geometry and tolerance requirements, but the tool designer also wants to minimize the number of forming steps in order to reduce the investment costs for the customer. There are several computer aided engineering systems on the market that can assist the tool designing process. These include more or less simple formulas to predict deformation during forming as well as the number of forming steps. In recent years it has also become possible to use finite element analysis for the design of roll forming processes. The objective of the work presented in this thesis was to answer the following question: How should the roll forming process be designed for complex geometries and/or high strength steels? The work approach included both literature studies as well as experimental and modelling work. The experimental part gave direct insight into the process and was also used to develop and validate models of the process. Starting with simple geometries and standard steels the work progressed to more complex profiles of variable depth and width, made of high strength steels. The results obtained are published in seven papers appended to this thesis. In the first study (see paper 1) a finite element model for investigating the roll forming of a U-profile was built. It was used to investigate the effect on longitudinal peak membrane strain and deformation length when yield strength increases, see paper 2 and 3. The simulations showed that the peak strain decreases whereas the deformation length increases when the yield strength increases. The studies described in paper 4 and 5 measured roll load, roll torque, springback and strain history during the U-profile forming process. The measurement results were used to validate the finite element model in paper 1. The results presented in paper 6 shows that the formability of stainless steel (e.g. AISI 301), that in the cold rolled condition has a large martensite fraction, can be substantially increased by heating the bending zone. The heated area will then become austenitic and ductile before the roll forming. Thanks to the phenomenon of strain induced martensite formation, the steel will regain the martensite content and its strength during the subsequent plastic straining. Finally, a new tooling concept for profiles with variable cross-sections is presented in paper 7. The overall conclusions of the present work are that today, it is possible to successfully develop profiles of complex geometries (3D roll forming) in high strength steels and that finite element simulation can be a useful tool in the design of the roll forming process.

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O objetivo do trabalho é investigar a relação de longo prazo entre capital e inovação, utilizando técnicas econométricas mais recentes, com dados em painel. Diversos testes alternativos de cointegração foram utilizados, como testes com coeficientes comuns e idiossincráticos entre os cross-sections (testes de Pedroni, de Kao e de Fischer), e testes onde a hipótese de cointegração é nula (teste de McCoskey e Kao), incluindo testes com quebras estruturais (teste de Westerlund). As conclusões principais são a evidência forte de que estoque de capital humano afeta de forma significativa o número de inovações. Tabém foram encontradas evidências de que a hierarquia de educação importe para o aumento de inovações.

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This study uses a new data set of crime ratesfor a large sample of countriesfor the period 1970- 1994, based on information from the United Nations World Crime Surveys, to ana/yze the determinants ofnational homicide and robbery rates. A simple model of the incentives to commit crimes is proposed, which explicit/y considers possible causes of the persistence of crime over time (criminal inertia). Several econometric mode/s are estimated, attempting to capture the . determinonts of crime rates across countries and over time. The empirical mode/s are first run for cross-sections and then applie'd to panel data. The former focus on erplanatory variables that do not change markedly over time, while the panel data techniques consider both the eflect of the business cyc1e (i.e., GDP growth rate) on the crime rate and criminal inertia (accountedfor by the inclusion of the /agged crime rate as an explanatory variable). The panel data techniques a/so consider country-specific eflects, the joint endogeneity of some of the erplanatory variables, and lhe existence of some types of measurement e"ors aJjlicting the crime data. The results showthat increases in income inequality raise crime rates, dete"ence eflects are significant, crime tends to be counter-cyclical, and criminal inertia is significant even after controlling for other potential determinants of homicide and robbery rates.

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This paper examines the evolution of wage inequality in Brazil in the 1980s and 1990s . It tries to investigate the role played by changing economic returns to education and to experience over this period together with the evolution of within-group inequality. It applies a quantile regression approach on grouped data to the Brazilian case. Results using repeated cross-sections of a Brazilian annual household survey indicate that : i) Male wage dispersion remained basically constant overall in the 1980's and 1990' s but has increased substantially within education and age groups. ii) Returns to experience increased significantly over this period, with the rise concentrated on the iliterate/primary school group iii) Returns to college education have risen over time, whereas return to intermediate and high-school education have fallen iv) The apparent rise in within-group inequality seems to be the result of a fall in real wages, since the difference in wage leveIs has dec1ined substantially over the period, especially within the high-educated sample. v) Returns to experience rise with education. vi) Returns to education rise over the life-cycle. vii) Wage inequality increases over the life-cycle. The next step i~ this research will try to conciliate all these stylised facts.

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Estuaries are environments prone to the input of chemical pollutants of various kinds and origins, including polycyclic aromatic hydrocarbons (PAHs). Anthropogenic PAHs may have two possible sources: pyrolytic (with four or more aromatic rings and low degree of alkylation) and petrogenic (with two and three aromatic rings and high degree of alkylation). This study aimed to evaluate the levels, distribution and possible sources of polycyclic aromatic hydrocarbons in the estuary of the Potengi river, Natal, Brazil. Samples of bottom sediments were collected in the final 12 km of the estuary until its mouth to the sea, where the urbanization of the Great Natal is more concentrated. Sampling was performed on 12 cross sections, with three stations each, totaling 36 samples, identified as T1 to T36. The non alkylated and alkylated PAHs were analyzed by gas chromatography coupled to mass spectrometry (GC / MS). PAHs were detected in all 36 stations with total concentration on each varying 174-109407 ng g-1. These values are comparable to those of several estuarine regions worldwide with high anthropogenic influence, suggesting the record of diffuse contamination installed in the estuary. PAHs profiles were similar for most stations. In 32 of the 36 stations, low molecular weight PAHs (with 2 and 3 ring: naphthalene, phenanthrene and their alkylated homologues) prevailed, which ranged from 54% to 100% of the total PAH, indicating that leaks, spills and combustion fuels are the dominant source of PAH pollution in the estuary. The level of contamination by PAHs in most stations suggests that there is potential risk of occasional adverse biological effects, but in some stations adverse impacts on the biota may occur frequently. The diagnostic ratios could differentiate sources of PAHs in sediments of the estuary, which were divided into three groups: petrogenic, pyrolytic and mixing of sources. The urban concentration of the Great Natal and the various industrial activities associated with it can be blamed as potential sources of PAHs in bottom sediments of the estuary studied. The data presented highlight the need to control the causes of existing pollution in the estuary

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The Potengi river estuary is located in the region of Natal (RN, Brazil), comprising a population of approximately 1,000,000 inhabitants. Besides the dominant urban presence, the estuary has fragments of mangrove forest. The objective of this study is to determine the aliphatic hydrocarbons found in the bottom sediments of this estuary, identifying their levels, distribution and their possible origins through the diagnostic rates, indexes and results comparisons with the local anthropic and natural characteristics. The samples were obtained according to a plan that allowed sampling of the estuary up to 12 km upstream from it as mounth. 36 stations were selected, grouped into 12 cross sections through the course of the river and spaced on average by 1 km. Each section consisted of three stations: the right margin, the deepest point and the left margin. The hydrocarbon n-alkanes from C10 to C36, the isoprenoids pristane and phytane, the unresolved complex mixture (UCM) and the total resolved hydrocarbons were analyzed by gas chromatography. N-alkanes, pristane, phytane and UCM were detected only at some stations. In the other, the concentration was below the detection limit defined by the analytical method (0.1 mg / kg), preventing them from being analyzed to determine the origin of the material found. By using different parameters, the results show that the estuary receives both the input of petrogenic hydrocarbons, but also of biogenic hydrocarbons, featuring a mixture of sources and relatively impacted portions. Based on the characteristics and activities found in the region, it is possible to affirm that petrogenic sources related to oil products enter the estuary via urban runoff or boats traffic, boat washing and fueling. Turning to the biogenic source, the predominant origin was terrestrial, characterized by vascular plants, indicating contribution of mangrove vegetation. It was evident the presence of, at specific points in the estuary, hydrocarbon pollution, and, therefore is recommended the adoption of actions aimed at interrupting or, at least, mitigating the sources potentially capable of damp petrogenic hydrocarbons in the estuary studied.

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A seringueira é uma planta de fácil reconhecimento por ser lenhosa, de porte mediano a grande, que apresenta um padrão característico de desfolha e reenfolhamento e, sobretudo, pela produção de látex. O objetivo do trabalho foi efetuar um estudo anatômico e morfológico foliar, comparando os clones RRIM 600 e GT 1 de seringueira &91;Hevea brasiliensis (Wild. ex Adr. de Juss.) Muell.- Arg&93;, desenvolvidos sob as mesmas condições edáficas e climáticas, para obtenção de informações que possam fornecer subsídios para correlações com dados fisiológicos e também diferenciar os clones em relação ao conteúdo de fibras, espessamento de tecidos do parênquima paliçádico e do parênquima lacunoso, caracterização anatômica do pecíolo, número e tamanho de estômatos e fornecer dados referentes a morfologia foliolar. Foram realizadas secções transversais na região do mesófilo, nervura central e pecíolo, seguindo-se os métodos usuais de preparação de lâminas permanentes. Foram realizadas análises biométricas de extensões de tecidos dos parênquimas paliçádico e lacunoso e contagem do número de células do parênquima lacunoso. Paralelamente foram realizadas análises biométricas para aferições de estômatos. Não houve diferenças para a altura das células epidérmicas, altura e número de camadas do parênquima lacunoso e para o comprimento e para a maior largura do limbo foliolar. Porém houve variação para a espessura das células do parênquima paliçádico, sendo que GT 1 apresentou maior espessura em relação a RRIM 600. GT1 apresentou maior número de estômatos em relação a RRIM 600, porém com menor tamanho. GT1 apresentou maior diâmetro da nervura central da folha e do pecíolo e maior quantidade de fibras de esclerênquima que RRIM 600.

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The objective of this study was to evaluate the influence of methods of preparation in postharvest conservation of minimally processed products of cactus pear fruits. Ripe cactus pear fruits orange-fleshed, from a commercial orchard in the region of Valinhos, SP, Brazil, were used. After selection, the fruits were washed and the surface sanitized with a solution of dichloro s. triazinatriona sodium dihydrate (Sumaveg (R)) 200 mg 100g(-1) of free chlorine for 5 minutes. Fruits were then stored at 12 degrees C for 12 hours before processing. The first process was the removal of the shell and ends. Then, the fruits were cut longitudinally into two halves, peeled and sliced in 2 cm thick cross-sections. The whole fruit, halves and slices were packaged in polyethylene terephthalate containers (Neoforma (R) N-94). These units were stored at 3 degrees C for 16 days and analyses were performed every 4 days. The weight loss, the content of soluble solids (SS), the titratable acidity (TA), the ratio (SS / TA) and the ascorbic acid content were evaluated and the sensory analysis of products was performed. Whole fruits were preferred concerning the purchase intent and showed better results regarding the content of soluble solids, titratable acidity, soluble solids / titratable acidity and ascorbic acid content. The highest weight loss was observed in slices.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Urban growth of metropolitan areas has produced impacts of considerable importance on environment and water resources. Such impacts are in general associated with human activities, such as basin area uncontrolled development. In this context, Pitimbu river watershed, located at Natal metropolitan area, has been affected by uncontrolled development caused by urban expansion. Indeed, such effects have been reflected on water quantity and quality, which may produce social consequences. Pitimbu river is an important water supplier for human consumption, actually supplying a 2600 m3/h water discharge. This study aims to analyze the qualitative and quantitative aspects of water and sediment on Pitimbu river lowland portion. For this purpose, physical-chemical water properties were analyzed, and sediment macro invertebrates benthonic were monitored in two cross sections in a period between November 8th, 2007 and October 3rd, 2008. Monitoring methodology consisted of water and sediment sampling for laboratory analysis. Water quality analysis included Dissolved Oxygen, Oxygen Biochemical Demand, Nitrate, pH and Alkalinity, Suspended and Total Solids. The analysis of heavy metals in the sediment included Cadmium, Cobalt, Copper, Chrome, Silver and Nickel. Dry season water discharge data were measured and used to adjust recession function parameters, whose values reveal quick recession and strong river-aquifer unconfined interaction. Water quality analysis revealed the absence of degradation by organic composites. However, DO and BOD levels indicate that more consistent results could be provided if sampling time interval were reduced. Biomonitoring showed signs of aquatic ecosystem degradation by the absence of sensitive and abundance of resistant benthic organisms. Obtained results demonstrate the urgent need of effective management measures to provide environmental protection. The increase of environmental degradation will certainly make impracticable the use of water for human consumption

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This work reports on the two-photon absorption (2PA) cross-section for bis (n-butylimido) perylene (BuPTCD), bis (benzimidazo) perylene (AzoPTCD), bis (benzimidazo) thioperylene (Monothio BZP), bis (phenethylimido) perylene (PhPTCD), bis (benzylimido) perylene (BePTCD) and n-pentylimido-benzimidazo perylene (PAzoPTCD) solutions measured using the Z-scan technique with femtosecond laser pulses at 775 nm. All perylene derivatives studied present large 2PA cross-sections, only comparable to the best ones reported in the literature. The experimental 2PA cross-sections obtained for each PTCD compound are in good agreement with a simplified sum-over-state calculation. The results of the present work indicates perylene derivatives as promising materials for two-photon applications. (C) 2003 Elsevier B.V. B.V. All rights reserved.

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This work presents a boundary element formulation for the analysis of building floor slabs, without beams, in which columns are coupled with the plate. An alternative formulation of boundary element method is presented, which considers three nodal displacements values (w, partial derivativew/partial derivativen and partial derivativew/partial derivatives) for the nodes at the boundary of the plate. In this formulation three boundary equations are written for all nodes at the boundary and in the domain of the plate. As the nodes of the column-plate connections are also represented by three nodal values, all these structural elements can be easily coupled. It is supposed that the cross-sections of the columns remain flat after the deflection and consequently the assumption of linear variation of the stress in the plate-column contact surface is also valid. (C) 2003 Elsevier B.V. Ltd. All rights reserved.