Two methods for voltage sag source location

This paper presents and compares two approaches to estimate the origin (upstream or downstream) of voltage sag registered in distribution substations. The first approach is based on the application of a single rule dealing with features extracted from the impedances during the fault whereas the second method exploit the variability of waveforms from an statistical point of view. Both approaches have been tested with voltage sags registered in distribution substations and advantages, drawbacks and comparative results are presented

Antifungal activity of extracts from Atacama Desert fungi againstParacoccidioides brasiliensis and identification ofAspergillus felis as a promising source of natural bioactive compounds

Fungi of the genus Paracoccidioides are responsible for paracoccidioidomycosis. The occurrence of drug toxicity and relapse in this disease justify the development of new antifungal agents. Compounds extracted from fungal extract have showing antifungal activity. Extracts of 78 fungi isolated from rocks of the Atacama Desert were tested in a microdilution assay against Paracoccidioides brasiliensis Pb18. Approximately 18% (5) of the extracts showed minimum inhibitory concentration (MIC) values≤ 125.0 ��g/mL. Among these, extract from the fungus UFMGCB 8030 demonstrated the best results, with an MIC of 15.6 ��g/mL. This isolate was identified as Aspergillus felis (by macro and micromorphologies, and internal transcribed spacer, β-tubulin, and ribosomal polymerase II gene analyses) and was grown in five different culture media and extracted with various solvents to optimise its antifungal activity. Potato dextrose agar culture and dichloromethane extraction resulted in an MIC of 1.9 ��g/mL against P. brasiliensis and did not show cytotoxicity at the concentrations tested in normal mammalian cell (Vero). This extract was subjected to bioassay-guided fractionation using analytical C18RP-high-performance liquid chromatography (HPLC) and an antifungal assay using P. brasiliensis. Analysis of the active fractions by HPLC-high resolution mass spectrometry allowed us to identify the antifungal agents present in the A. felis extracts cytochalasins. These results reveal the potential of A. felis as a producer of bioactive compounds with antifungal activity.

Fracture imaging within a granitic rock aquifer using multiple-offset single-hole and cross-hole GPR reflection data

The sparsely spaced highly permeable fractures of the granitic rock aquifer at Stang-er-Brune (Brittany, France) form a well-connected fracture network of high permeability but unknown geometry. Previous work based on optical and acoustic logging together with single-hole and cross-hole flowmeter data acquired in 3 neighbouring boreholes (70-100 m deep) has identified the most important permeable fractures crossing the boreholes and their hydraulic connections. To constrain possible flow paths by estimating the geometries of known and previously unknown fractures, we have acquired, processed and interpreted multifold, single- and cross-hole GPR data using 100 and 250 MHz antennas. The GPR data processing scheme consisting of timezero corrections, scaling, bandpass filtering and F-X deconvolution, eigenvector filtering, muting, pre-stack Kirchhoff depth migration and stacking was used to differentiate fluid-filled fracture reflections from source generated noise. The final stacked and pre-stack depth-migrated GPR sections provide high-resolution images of individual fractures (dipping 30-90��) in the surroundings (2-20 m for the 100 MHz antennas; 2-12 m for the 250 MHz antennas) of each borehole in a 2D plane projection that are of superior quality to those obtained from single-offset sections. Most fractures previously identified from hydraulic testing can be correlated to reflections in the single-hole data. Several previously unknown major near vertical fractures have also been identified away from the boreholes.

Identification of potential rockfall source areas at a regional scale using a DEM-based geomorphometric analysis

The availability of high resolution Digital Elevation Models (DEM) at a regional scale enables the analysis of topography with high levels of detail. Hence, a DEM-based geomorphometric approach becomes more accurate for detecting potential rockfall sources. Potential rockfall source areas are identified according to the slope angle distribution deduced from high resolution DEM crossed with other information extracted from geological and topographic maps in GIS format. The slope angle distribution can be decomposed in several Gaussian distributions that can be considered as characteristic of morphological units: rock cliffs, steep slopes, footslopes and plains. A terrain is considered as potential rockfall sources when their slope angles lie over an angle threshold, which is defined where the Gaussian distribution of the morphological unit "Rock cliffs" become dominant over the one of "Steep slopes". In addition to this analysis, the cliff outcrops indicated by the topographic maps were added. They contain however "flat areas", so that only the slope angles values above the mode of the Gaussian distribution of the morphological unit "Steep slopes" were considered. An application of this method is presented over the entire Canton of Vaud (3200 km2), Switzerland. The results were compared with rockfall sources observed on the field and orthophotos analysis in order to validate the method. Finally, the influence of the cell size of the DEM is inspected by applying the methodology over six different DEM resolutions.

Investigation and monitoring of rock slope instabilities in Norway by terrestrial laser scanning

Long-range Terrestrial Laser Scanning (TLS) is widely used in studies on rock slope instabilities. TLS point clouds allow the creation of high-resolution digital elevation models for detailed mapping of landslide morphologies and the measurement of the orientation of main discontinuities. Multi-temporal TLS datasets enable the quantification of slope displacements and rockfall volumes. We present three case studies using TLS for the investigation and monitoring of rock slope instabilities in Norway: 1) the analysis of 3D displacement of the Oksfjellet rock slope failure (Troms, northern Norway); 2) the detection and quantification of rockfalls along the sliding surfaces and at the front of the Kvitfjellet rock slope instability (M��re og Romsdal, western Norway); 3) the analysis of discontinuities and rotational movements of an unstable block at Stampa (Sogn og Fjordane, western Norway). These case studies highlight the possibilities but also limitations of TLS in investigating and monitoring unstable rock slopes.

Financial Markets and Real Ecinomy: Four Essays in International Trade

Financial markets play an important role in an economy performing various functions like mobilizing and pooling savings, producing information about investment opportunities, screening and monitoring investments, implementation of corporate governance, diversification and management of risk. These functions influence saving rates, investment decisions, technological innovation and, therefore, have important implications for welfare. In my PhD dissertation I examine the interplay of financial and product markets by looking at different channels through which financial markets may influence an economy.My dissertation consists of four chapters. The first chapter is a co-authored work with Martin Strieborny, a PhD student from the University of Lausanne. The second chapter is a co-authored work with Melise Jaud, a PhD student from the Paris School of Economics. The third chapter is co-authored with both Melise Jaud and Martin Strieborny. The last chapter of my PhD dissertation is a single author paper.Chapter 1 of my PhD thesis analyzes the effect of financial development on growth of contract intensive industries. These industries intensively use intermediate inputs that neither can be sold on organized exchange, nor are reference-priced (Levchenko, 2007; Nunn, 2007). A typical example of a contract intensive industry would be an industry where an upstream supplier has to make investments in order to customize a product for needs of a downstream buyer. After the investment is made and the product is adjusted, the buyer may refuse to meet a commitment and trigger ex post renegotiation. Since the product is customized to the buyer's needs, the supplier cannot sell the product to a different buyer at the original price. This is referred in the literature as the holdup problem. As a consequence, the individually rational suppliers will underinvest into relationship-specific assets, hurting the downstream firms with negative consequences for aggregate growth. The standard way to mitigate the hold up problem is to write a binding contract and to rely on the legal enforcement by the state. However, even the most effective contract enforcement might fail to protect the supplier in tough times when the buyer lacks a reliable source of external financing. This suggests the potential role of financial intermediaries, banks in particular, in mitigating the incomplete contract problem. First, financial products like letters of credit and letters of guarantee can substantially decrease a risk and transaction costs of parties. Second, a bank loan can serve as a signal about a buyer's true financial situation, an upstream firm will be more willing undertake relationship-specific investment knowing that the business partner is creditworthy and will abstain from myopic behavior (Fama, 1985; von Thadden, 1995). Therefore, a well-developed financial (especially banking) system should disproportionately benefit contract intensive industries.The empirical test confirms this hypothesis. Indeed, contract intensive industries seem to grow faster in countries with a well developed financial system. Furthermore, this effect comes from a more developed banking sector rather than from a deeper stock market. These results are reaffirmed examining the effect of US bank deregulation on the growth of contract intensive industries in different states. Beyond an overall pro-growth effect, the bank deregulation seems to disproportionately benefit the industries requiring relationship-specific investments from their suppliers.Chapter 2 of my PhD focuses on the role of the financial sector in promoting exports of developing countries. In particular, it investigates how credit constraints affect the ability of firms operating in agri-food sectors of developing countries to keep exporting to foreign markets.Trade in high-value agri-food products from developing countries has expanded enormously over the last two decades offering opportunities for development. However, trade in agri-food is governed by a growing array of standards. Sanitary and Phytosanitary standards (SPS) and technical regulations impose additional sunk, fixed and operating costs along the firms' export life. Such costs may be detrimental to firms' survival, "pricing out" producers that cannot comply. The existence of these costs suggests a potential role of credit constraints in shaping the duration of trade relationships on foreign markets. A well-developed financial system provides the funds to exporters necessary to adjust production processes in order to meet quality and quantity requirements in foreign markets and to maintain long-standing trade relationships. The products with higher needs for financing should benefit the most from a well functioning financial system. This differential effect calls for a difference-in-difference approach initially proposed by Rajan and Zingales (1998). As a proxy for demand for financing of agri-food products, the sanitary risk index developed by Jaud et al. (2009) is used. The empirical literature on standards and norms show high costs of compliance, both variable and fixed, for high-value food products (Garcia-Martinez and Poole, 2004; Maskus et al., 2005). The sanitary risk index reflects the propensity of products to fail health and safety controls on the European Union (EU) market. Given the high costs of compliance, the sanitary risk index captures the demand for external financing to comply with such regulations.The prediction is empirically tested examining the export survival of different agri-food products from firms operating in Ghana, Mali, Malawi, Senegal and Tanzania. The results suggest that agri-food products that require more financing to keep up with food safety regulation of the destination market, indeed sustain longer in foreign market, when they are exported from countries with better developed financial markets.Chapter 3 analyzes the link between financial markets and efficiency of resource allocation in an economy. Producing and exporting products inconsistent with a country's factor endowments constitutes a serious misallocation of funds, which undermines competitiveness of the economy and inhibits its long term growth. In this chapter, inefficient exporting patterns are analyzed through the lens of the agency theories from the corporate finance literature. Managers may pursue projects with negative net present values because their perquisites or even their job might depend on them. Exporting activities are particularly prone to this problem. Business related to foreign markets involves both high levels of additional spending and strong incentives for managers to overinvest. Rational managers might have incentives to push for exports that use country's scarce factors which is suboptimal from a social point of view. Export subsidies might further skew the incentives towards inefficient exporting. Management can divert the export subsidies into investments promoting inefficient exporting.Corporate finance literature stresses the disciplining role of outside debt in counteracting the internal pressures to divert such "free cash flow" into unprofitable investments. Managers can lose both their reputation and the control of "their" firm if the unpaid external debt triggers a bankruptcy procedure. The threat of possible failure to satisfy debt service payments pushes the managers toward an efficient use of available resources (Jensen, 1986; Stulz, 1990; Hart and Moore, 1995). The main sources of debt financing in the most countries are banks. The disciplining role of banks might be especially important in the countries suffering from insufficient judicial quality. Banks, in pursuing their rights, rely on comparatively simple legal interventions that can be implemented even by mediocre courts. In addition to their disciplining role, banks can promote efficient exporting patterns in a more direct way by relaxing credit constraints of producers, through screening, identifying and investing in the most profitable investment projects. Therefore, a well-developed domestic financial system, and particular banking system, would help to push a country's exports towards products congruent with its comparative advantage.This prediction is tested looking at the survival of different product categories exported to US market. Products are identified according to the Euclidian distance between their revealed factor intensity and the country's factor endowments. The results suggest that products suffering from a comparative disadvantage (labour-intensive products from capital-abundant countries) survive less on the competitive US market. This pattern is stronger if the exporting country has a well-developed banking system. Thus, a strong banking sector promotes exports consistent with a country comparative advantage.Chapter 4 of my PhD thesis further examines the role of financial markets in fostering efficient resource allocation in an economy. In particular, the allocative efficiency hypothesis is investigated in the context of equity market liberalization.Many empirical studies document a positive and significant effect of financial liberalization on growth (Levchenko et al. 2009; Quinn and Toyoda 2009; Bekaert et al., 2005). However, the decrease in the cost of capital and the associated growth in investment appears rather modest in comparison to the large GDP growth effect (Bekaert and Harvey, 2005; Henry, 2000, 2003). Therefore, financial liberalization may have a positive impact on growth through its effect on the allocation of funds across firms and sectors.Free access to international capital markets allows the largest and most profitable domestic firms to borrow funds in foreign markets (Rajan and Zingales, 2003). As domestic banks loose some of their best clients, they reoptimize their lending practices seeking new clients among small and younger industrial firms. These firms are likely to be more risky than large and established companies. Screening of customers becomes prevalent as the return to screening rises. Banks, ceteris paribus, tend to focus on firms operating in comparative-advantage sectors because they are better risks. Firms in comparative-disadvantage sectors finding it harder to finance their entry into or survival in export markets either exit or refrain from entering export markets. On aggregate, one should therefore expect to see less entry, more exit, and shorter survival on export markets in those sectors after financial liberalization.The paper investigates the effect of financial liberalization on a country's export pattern by comparing the dynamics of entry and exit of different products in a country export portfolio before and after financial liberalization.The results suggest that products that lie far from the country's comparative advantage set tend to disappear relatively faster from the country's export portfolio following the liberalization of financial markets. In other words, financial liberalization tends to rebalance the composition of a country's export portfolio towards the products that intensively use the economy's abundant factors.

Country portfolios and the Solow-model

This paper shows that an open economy Solow model provides a good description of international investment positions in industrialized countries. More than half of the variation of net foreign assets in the 1990's can be attributed to cross country differences in the savings rate, population and productivity growth. Furthermore, these factors seem to be an important channel through which output and wealth affect international investment positions. We interpret this funding as evidence that decreasing returns are an important source of international capital movements. The savings rate (andpopulation growth) influence the composition of country portfolios through their downward (upward) pressure on the marginal productivity of capital.

Estudo de caso: o uso da l��ngua portuguesa por jovens provindos de outros pa��ses no dom��nio privado, p��blico e educativo

A aflu��ncia de imigrantes a Portugal, nas ��ltimas tr��s d��cadas transformou radicalmente todo o tecido social portugu��s, caracterizando-se hoje pela sua heterogeneidade. At�� ao in��cio da d��cada de 90 do s��culo XX, os fluxos migrat��rios provinham essencialmente dos Pa��ses de L��ngua Oficial Portuguesa, com maior incid��ncia de Cabo Verde, Brasil e Angola. �� nessa d��cada que se registam movimentos bastante significativos de imigrantes provenientes da Europa Central e Oriental, principalmente da Ucr��nia, R��ssia, Rom��nia e Mold��via, assim como da ��sia, destacando-se os naturais da China, ��ndia, Paquist��o e das antigas rep��blicas sovi��ticas. De acordo com a an��lise apresentada pelo Instituto Nacional de Estat��stica em Dezembro de 2006, residiam de forma legal em Portugal 329 898 cidad��os de nacionalidade estrangeira, sendo as maiores comunidades de Cabo Verde (57 349), Brasil (41 728) e Angola (28 854). A sociedade portuguesa do s��culo XXI, distancia-se cada vez mais do conceito de monolinguismo, tal como se evidencia no Projecto Gulbenkian ���Diversidade Lingu��stica na Escola Portuguesa���, que, segundo o estudo feito, onze por cento dos alunos residentes na ��rea da Grande Lisboa nasceram fora de Portugal e t��m como l��nguas maternas cinquenta e oito idiomas. �� urgente uma interven����o diferente no que corresponde a esta nova realidade lingu��stica em Portugal e sobretudo no que concerne �� integra����o do ���outro���, reconhecendo e respeitando as v��rias l��nguas maternas e culturas, como tamb��m a sua preserva����o a fim de possibilitar o desenvolvimento ��ntegro e harmonioso da identidade. A heterogeneidade da actual sociedade portuguesa imp��e um olhar atento para com esta nova realidade no pa��s, sobretudo em muitas das escolas onde a par do uso da l��ngua portuguesa outras l��nguas s��o tamb��m usadas como forma de comunica����o entre os mesmos pares, situa����o esta perfeitamente desajustada da realidade escolar madeirense Estudo de caso: O uso da L��ngua Portuguesa por jovens oriundos de outros pa��ses nos dom��nios privado, p��blico e educativo. 10 de in��cios da d��cada de 90 do s��culo XX, �� excep����o dos alunos provenientes da Venezuela, os denominados luso-descendentes. A escola mudara, tudo se alterara, havia que tentar perceber o que estava a ocorrer, um novo Mundo ���invadira��� as turmas, prontas a aprender, a saber, a descobrir. Era preciso preencher o sil��ncio expectante. Aprender uma nova l��ngua, a portuguesa, decorrente da obrigatoriedade impl��cita de tratar-se da l��ngua oficial, obrigava a repensar o ensino, a continuamente desvendar novos caminhos possibilitadores de encontro entre a l��ngua materna e a segunda, de reencontro com a identidade lingu��stica e cultural que n��o se quer perdidas, s�� tornado poss��vel na diferen��a. A par de uma escola que se apresentava de forma diferente, cuja interven����o teria de ser oposta �� de ent��o, uma vez que a aprendizagem do portugu��s era feita como l��ngua segunda (L2), muitas foram e s��o as inquieta����es, um turbilh��o de interroga����es decorriam deste contacto constante de uma l��ngua que se diz minha, fonte de partilha com outros jovens. O uso da l��ngua portuguesa confinar-se-�� unicamente �� escola com os professores e colegas ou despoletar�� curiosidades, vontades, interesses, motivados por objectivos confinados ao percurso e �� hist��ria humana? Muitas s��o as interroga����es que ocorrem, muitos s��o tamb��m os momentos de sabedoria m��tua de l��nguas e pa��ses a desvendar num cont��nuo ininterrupto e �� essa constante procura que determina a busca de respostas. Entre muitas interroga����es uma afigurava-se de forma latente, qui���� fonte de resposta para outras interroga����es inerentes �� l��ngua portuguesa como l��ngua segunda. A sua utiliza����o por parte dos alunos de outras nacionalidades nos dom��nios privado, p��blico e educativo engloba dom��nios diversos capazes de informar acerca do uso dessa mesma l��ngua. Importa no entanto refor��ar que estes alunos constituem um grupo heterog��neo sob diversos pontos de vista: et��rio, lingu��stico e cultural. Do ponto de vista lingu��stico a popula����o que tem o portugu��s como l��ngua segunda abrange alunos falantes de diferentes l��nguas maternas, umas mais pr��ximas, outras mais afastadas do portugu��s, propiciando diferentes graus de transfer��ncia de conhecimentos lingu��sticos e de experi��ncias comunicativas, como tamb��m em diferentes est��dios de aquisi����o e que fora da escola o usam em maior ou menor n��mero de contextos e com um grau de frequ��ncia desigual. Estudo de caso: O uso da L��ngua Portuguesa por jovens oriundos de outros pa��ses nos dom��nios privado, p��blico e educativo. 11 Disp��em tamb��m de diferentes capacidades individuais para discriminar, segmentar e produzir sequ��ncias lingu��sticas. J�� do ponto de vista cultural apresentam diferentes h��bitos de aprendizagem, bem como diferentes representa����es e expectativas face �� escola. Todos estes factores determinar��o ritmos de progress��o distintos no que respeita �� aprendizagem do portugu��s como l��ngua segunda. As oportunidades de aprendizagem e de uso que cada indiv��duo tem ao longo da vida, determinantes no processo de aquisi����o, desenvolvimento e aprendizagem de uma l��ngua, variam bastante de indiv��duo para indiv��duo. Os alunos podem viver num mesmo contexto no entanto raz��es variad��ssimas determinar��o diferentes oportunidades de aprendizagem e de uso. Viver-se num contexto de imers��o n��o �� suficiente para que todos tenham o mesmo grau de exposi����o a material lingu��stico rico e variado da L2. Essas oportunidades tamb��m se relacionam com a dist��ncia lingu��stica entre l��ngua primeira (L1) e a l��ngua segunda, quanto mais afastadas s��o as duas l��nguas mais os falantes da L2 se refugiam na sua l��ngua materna, assim como tamb��m se associam aos h��bitos culturais da comunidade e da fam��lia.

Estudo de caso : o uso da l��ngua portuguesa por jovens provindos de outros pa��ses no dom��nio privado, p��blico e educativo

A aflu��ncia de imigrantes a Portugal, nas ��ltimas tr��s d��cadas transformou radicalmente todo o tecido social portugu��s, caracterizando-se hoje pela sua heterogeneidade. At�� ao in��cio da d��cada de 90 do s��culo XX, os fluxos migrat��rios provinham essencialmente dos Pa��ses de L��ngua Oficial Portuguesa, com maior incid��ncia de Cabo Verde, Brasil e Angola. �� nessa d��cada que se registam movimentos bastante significativos de imigrantes provenientes da Europa Central e Oriental, principalmente da Ucr��nia, R��ssia, Rom��nia e Mold��via, assim como da ��sia, destacando-se os naturais da China, ��ndia, Paquist��o e das antigas rep��blicas sovi��ticas. De acordo com a an��lise apresentada pelo Instituto Nacional de Estat��stica em Dezembro de 2006, residiam de forma legal em Portugal 329 898 cidad��os de nacionalidade estrangeira, sendo as maiores comunidades de Cabo Verde (57 349), Brasil (41 728) e Angola (28 854). A sociedade portuguesa do s��culo XXI, distancia-se cada vez mais do conceito de monolinguismo, tal como se evidencia no Projecto Gulbenkian ���Diversidade Lingu��stica na Escola Portuguesa���, que, segundo o estudo feito, onze por cento dos alunos residentes na ��rea da Grande Lisboa nasceram fora de Portugal e t��m como l��nguas maternas cinquenta e oito idiomas. �� urgente uma interven����o diferente no que corresponde a esta nova realidade lingu��stica em Portugal e sobretudo no que concerne �� integra����o do ���outro���, reconhecendo e respeitando as v��rias l��nguas maternas e culturas, como tamb��m a sua preserva����o a fim de possibilitar o desenvolvimento ��ntegro e harmonioso da identidade. A heterogeneidade da actual sociedade portuguesa imp��e um olhar atento para com esta nova realidade no pa��s, sobretudo em muitas das escolas onde a par do uso da l��ngua portuguesa outras l��nguas s��o tamb��m usadas como forma de comunica����o entre os mesmos pares, situa����o esta perfeitamente desajustada da realidade escolar madeirense Estudo de caso: O uso da L��ngua Portuguesa por jovens oriundos de outros pa��ses nos dom��nios privado, p��blico e educativo. 10 de in��cios da d��cada de 90 do s��culo XX, �� excep����o dos alunos provenientes da Venezuela, os denominados luso-descendentes. A escola mudara, tudo se alterara, havia que tentar perceber o que estava a ocorrer, um novo Mundo ���invadira��� as turmas, prontas a aprender, a saber, a descobrir. Era preciso preencher o sil��ncio expectante. Aprender uma nova l��ngua, a portuguesa, decorrente da obrigatoriedade impl��cita de tratar-se da l��ngua oficial, obrigava a repensar o ensino, a continuamente desvendar novos caminhos possibilitadores de encontro entre a l��ngua materna e a segunda, de reencontro com a identidade lingu��stica e cultural que n��o se quer perdidas, s�� tornado poss��vel na diferen��a. A par de uma escola que se apresentava de forma diferente, cuja interven����o teria de ser oposta �� de ent��o, uma vez que a aprendizagem do portugu��s era feita como l��ngua segunda (L2), muitas foram e s��o as inquieta����es, um turbilh��o de interroga����es decorriam deste contacto constante de uma l��ngua que se diz minha, fonte de partilha com outros jovens. O uso da l��ngua portuguesa confinar-se-�� unicamente �� escola com os professores e colegas ou despoletar�� curiosidades, vontades, interesses, motivados por objectivos confinados ao percurso e �� hist��ria humana? Muitas s��o as interroga����es que ocorrem, muitos s��o tamb��m os momentos de sabedoria m��tua de l��nguas e pa��ses a desvendar num cont��nuo ininterrupto e �� essa constante procura que determina a busca de respostas. Entre muitas interroga����es uma afigurava-se de forma latente, qui���� fonte de resposta para outras interroga����es inerentes �� l��ngua portuguesa como l��ngua segunda. A sua utiliza����o por parte dos alunos de outras nacionalidades nos dom��nios privado, p��blico e educativo engloba dom��nios diversos capazes de informar acerca do uso dessa mesma l��ngua. Importa no entanto refor��ar que estes alunos constituem um grupo heterog��neo sob diversos pontos de vista: et��rio, lingu��stico e cultural. Do ponto de vista lingu��stico a popula����o que tem o portugu��s como l��ngua segunda abrange alunos falantes de diferentes l��nguas maternas, umas mais pr��ximas, outras mais afastadas do portugu��s, propiciando diferentes graus de transfer��ncia de conhecimentos lingu��sticos e de experi��ncias comunicativas, como tamb��m em diferentes est��dios de aquisi����o e que fora da escola o usam em maior ou menor n��mero de contextos e com um grau de frequ��ncia desigual. Estudo de caso: O uso da L��ngua Portuguesa por jovens oriundos de outros pa��ses nos dom��nios privado, p��blico e educativo. 11 Disp��em tamb��m de diferentes capacidades individuais para discriminar, segmentar e produzir sequ��ncias lingu��sticas. J�� do ponto de vista cultural apresentam diferentes h��bitos de aprendizagem, bem como diferentes representa����es e expectativas face �� escola. Todos estes factores determinar��o ritmos de progress��o distintos no que respeita �� aprendizagem do portugu��s como l��ngua segunda. As oportunidades de aprendizagem e de uso que cada indiv��duo tem ao longo da vida, determinantes no processo de aquisi����o, desenvolvimento e aprendizagem de uma l��ngua, variam bastante de indiv��duo para indiv��duo. Os alunos podem viver num mesmo contexto no entanto raz��es variad��ssimas determinar��o diferentes oportunidades de aprendizagem e de uso. Viver-se num contexto de imers��o n��o �� suficiente para que todos tenham o mesmo grau de exposi����o a material lingu��stico rico e variado da L2. Essas oportunidades tamb��m se relacionam com a dist��ncia lingu��stica entre l��ngua primeira (L1) e a l��ngua segunda, quanto mais afastadas s��o as duas l��nguas mais os falantes da L2 se refugiam na sua l��ngua materna, assim como tamb��m se associam aos h��bitos culturais da comunidade e da fam��lia.

Biosphere/lithosphere interface : microbially-mediated CaCO3 precipitation in hypersaline and freshwater environments

Abstract: Microbial mats very efficiently cycle elements, such as C, 0, N, S and H, which makes them key players of redox processes at the biosphere-lithosphere interface. They are characterized by high metabolic activities and high turnover rates (production and consumption) of biomass, which mainly consists of cell material and of extracellular organic matter (EOM). The EOM forms a matrix, embedding the microbial cells and fulfilling various functions within the microbial mat, including: mat attachment to surfaces; creation of micro-domains within the mat; physical stabilization under hy- drodynamic stress and the protection of the cells in multiple other stress conditions. EOM mainly consists of polysaccharides, amino acids, and a variety of chemical func-tional groups {e.g., -C00H, - SH -OH). These groups strongly bind cations such as Ca2+ and Mg2+ and thus exert a strong control on carbonate mineral formation within the microbial mat. A feedback mechanism between community metabolisms, their prod��ucts, and the surrounding physicochemical microenvironment thus influences the de��gree of carbonate saturation favoring either carbonate precipitation or dissolution. We investigated the driving forces and mechanisms of microbialite formation in the Sari ne River, FR, Switzerland, the hypersaline lake, Big Pond, Bahamas and in labo��ratory experiments. The two fundamentally different natural systems allowed us to compare the geochemical conditions and microbial metabolisms, necessary for car��bonate formation in microbial mats. Although carbonates are oversaturated in both environments, precipitation does not occur on physicochemical substrates (i.e. out��side the microbial mats). In the Sarine a high crystal nucleation threshold exceeds the carbonate saturation, despite the high carbonate alkalinity in the water column. Cyanobacterial photosynthesis strongly locally enhances the carbonate alkalinity, whereas the EOM attract and immobilize calcium, which increases the saturation state and finally leads to carbonate precipitation within the EOM (in this case the cyanobacterial sheath) as nucleation template. In Big Pond, the presence of calcium- chelating anions (i.e. sulfate) and EOM, as well as the presence of magnesium, lowers the calcium activity in the water column and mat, and thus inhibits carbonate pre��cipitation. Coupled with other heterotrophic metabolisms, sulfate reduction uses the EOM as carbon source, degrading it. The resulting EOM consumption creates alkalin��ity, releases calcium and consumes sulfate in mat-micro domains, which leads to the formation of carbonate layers at the top of the microbial mat. R��sum��: Interface biosph��re/lithosph��re: m��diation microbienne de la pr��cipitation de CaC03 dans des environnements en eaux douces et hypersalines Les tapis microbiens engendrent une circulation tr��s efficace des ��l��ments, tels que C, 0, N, S et H, ce qui en fait des acteurs cl�� pour les processus d'oxydor��duction �� l'inter��face biosph��re-lithosph��re. Ils sont caract��ris��s par des taux ��lev��s d'activit�� m��ta��bolique, ainsi que par la production et la consommation de biomasse, principalement constitu��e de cellules microbiennes et de mati��re organique extracellulaire (MOE). Dans un tapis microbien, les cellules microbiennes sont envelopp��es par une matrice de MOE qui a diff��rentes fonctions dont l'attachement du tapis aux surfaces, la cr��a��tion de micro-domaines dans le tapis, la stabilisation physique en situation de stress hydrodynamique, et la protection des cellules dans de multiples autres conditions de stress. La MOE se compose principalement de polysaccharides, d'acides amin��s, et d'une vari��t�� de groupes fonctionnels chimiques (par exemple, COOH, -SH et -OH). Ces groupes se lient fortement aux cations, tels que Ca2+ et Mg2+, et exercent ainsi un contr��le fort sur la formation de CaC03 dans le tapis microbien. Un m��canisme de r��troaction, entre les m��tabolismes de la communaut�� microbienne, leurs produits, et le microenvironnement physico-chimique, influence le degr�� de saturation de car��bonate, favorisant soit leur pr��cipitation, soit leur dissolution. Nous avons ��tudi�� le moteur et les m��canismes de min��ralisation dans des tapis de la Sarine, FR, Suisse et du lac hypersalin, Big Pond, aux Bahamas, ainsi que durant des exp��riences en laboratoire. Les deux syst��mes naturels, fondamentalement dif��f��rents, nous ont permis de comparer les conditions g��ochimiques et les m��tabolis��mes n��cessaires �� la formation des carbonates dans des tapis microbiens. Bien que les carbonates soient sursatur��s dans les deux environnements, la pr��cipitation ne se produit pas sur des substrats physico-chimiques (en dehors du tapis microbien). Dans la Sarine, malgr�� un taux d'alcalinit�� ��lev��, les valeurs de seuil pour la nucl��a- tion de carbonates sont plus hautes que la saturation du carbonate. La photosynth��se cyanobact��rienne augmente localement l'alcalinit��, alors que la MOE attire et immo��bilise le calcium, ce qui augmente l'��tat de saturation et conduit finalement �� la pr����cipitation des carbonates, en utilisant la MOE comme substrat de nucl��ation. �� Big Pond, la pr��sence de ch��lateurs de calcium, notamment les anions (p.ex. le sulfate) et la MOE, ainsi que la pr��sence de magn��sium, r��duit l'activit�� du calcium et inhibe en cons��quence la pr��cipitation des carbonates. Coupl��e avec d'autres m��tabolismes h��t��rotrophes, la r��duction des sulfates utilise la MOE comme source de carbone, en la d��gradant. Cette consommation de MOE cr��e l'alcalinit��, consomme des sulfates et lib��re du calcium dans des micro-domaines, conduisant �� la formation de couches de carbonates dans le haut du tapis microbien.

Kinematic reduction of reaction-diffusion fronts with multiplicative noise. Derivation of stochastic sharp-interface equations

We study the dynamics of generic reaction-diffusion fronts, including pulses and chemical waves, in the presence of multiplicative noise. We discuss the connection between the reaction-diffusion Langevin-like field equations and the kinematic (eikonal) description in terms of a stochastic moving-boundary or sharp-interface approximation. We find that the effective noise is additive and we relate its strength to the noise parameters in the original field equations, to first order in noise strength, but including a partial resummation to all orders which captures the singular dependence on the microscopic cutoff associated with the spatial correlation of the noise. This dependence is essential for a quantitative and qualitative understanding of fluctuating fronts, affecting both scaling properties and nonuniversal quantities. Our results predict phenomena such as the shift of the transition point between the pushed and pulled regimes of front propagation, in terms of the noise parameters, and the corresponding transition to a non-Kardar-Parisi-Zhang universality class. We assess the quantitative validity of the results in several examples including equilibrium fluctuations and kinetic roughening. We also predict and observe a noise-induced pushed-pulled transition. The analytical predictions are successfully tested against rigorous results and show excellent agreement with numerical simulations of reaction-diffusion field equations with multiplicative noise.

Heat pulse line-source method to determine thermal conductivity of consolidated rocks

An instrument designed to measure thermal conductivity of consolidated rocks, dry or saturated, using a transient method is presented. The instrument measures relative values of the thermal conductivity, and it needs calibration to obtain absolute values. The device can be used as heat pulse line source and as continuous heat line source. Two parameters to determine thermal conductivity are proposed: TMAX, in heat pulse line source, and SLOPE, in continuous heat line source. Its performance is better, and the operation simpler, in heat pulse line-source mode with a measuring time of 170 s and a reproducibility better than 2.5%. The sample preparation is very simple on both modes. The performance has been tested with a set of ten rocks with thermal conductivity values between 1.4 and 5.2 W m��1 K��1 which covers the usual range for consolidated rocks.

Phosphorus extracted by ion exchange resins and mehlich-1 from oxisols (latosols) treated with different phosphorus rates and sources for varied soil-source contact periods

Despite the large number of studies addressing the quantification of phosphorus (P) availability by different extraction methods, many questions remain unanswered. The aim of this paper was to compare the effectiveness of the extractors Mehlich-1, Anionic Resin (AR) and Mixed Resin (MR), to determine the availability of P under different experimental conditions. The laboratory study was arranged in randomized blocks in a [(3 x 3 x 2) + 3] x 4 factorial design, with four replications, testing the response of three soils with different texture: a very clayey Red Latosol (LV), a sandy clay loam Red Yellow Latosol (LVA), and a sandy loam Yellow Latosol (LA), to three sources (triple superphosphate, reactive phosphate rock from Gafsa-Tunisia; and natural phosphate from Arax��-Minas Gerais) at two P rates (75 and 150 mg dm-3), plus three control treatments (each soil without P application) after four contact periods (15, 30, 60, and 120 days) of the P sources with soil. The soil acidity of LV and LVA was adjusted by raising base saturation to 60 % with the application of CaCO3 and MgCO3 at a 4:1 molar ratio (LA required no correction). These samples were maintained at field moisture capacity for 30 days. After the contact periods, the samples were collected to quantify the available P concentrations by the three extractants. In general, all three indicated that the available P-content in soils was reduced after longer contact periods with the P sources. Of the three sources, this reduction was most pronounced for triple superphosphate, intermediate for reactive phosphate, while Arax�� phosphate was least sensitive to the effect of time. It was observed that AR extracted lower P levels from all three soils when the sources were phosphate rocks, while MR extracted values close to Mehlich-1 in LV (clay) and LVA (medium texture) for reactive phosphate. For Arax�� phosphate, much higher P values were determined by Mehlich-1 than by the resins, because of the acidity of the extractor. For triple superphosphate, both resins extracted higher P levels than Mehlich-1, due to the consumption of this extractor, particularly when used for LV and LVA.

The database search problem: a question of rational decision making

This paper applies probability and decision theory in the graphical interface of an influence diagram to study the formal requirements of rationality which justify the individualization of a person found through a database search. The decision-theoretic part of the analysis studies the parameters that a rational decision maker would use to individualize the selected person. The modeling part (in the form of an influence diagram) clarifies the relationships between this decision and the ingredients that make up the database search problem, i.e., the results of the database search and the different pairs of propositions describing whether an individual is at the source of the crime stain. These analyses evaluate the desirability associated with the decision of 'individualizing' (and 'not individualizing'). They point out that this decision is a function of (i) the probability that the individual in question is, in fact, at the source of the crime stain (i.e., the state of nature), and (ii) the decision maker's preferences among the possible consequences of the decision (i.e., the decision maker's loss function). We discuss the relevance and argumentative implications of these insights with respect to recent comments in specialized literature, which suggest points of view that are opposed to the results of our study.