TRANSPORT IN A BILAYER SYSTEM AT HIGH LANDAU FILLING FACTOR

We have studied Shubnikov de Haas oscillations and the quantum Hall effect in GaAs-double well structures in tilted magnetic fields. We found strong magnetoresistance oscillations as a function of an in-plane magnetic field B(parallel to) at nu = 4N + 3 and nu = 4N + 1 filling factors. At low perpendicular magnetic field B(perpendicular to), the amplitude of the conventional Shubnikov-de Haas (SdH) oscillations also exhibits B(parallel to)-periodic dependence at fixed values of B(perpendicular to). We interpret the observed oscillations as a manifestation of the interference between cyclotron orbits in different quantum wells.

Nd and Pb isotope signatures on the Southeastern South American upper margin: Implications for sediment transport and source rocks

Neodymium and lead isotope values in sediment samples were used to interpret sediment transport and source rocks on the Southeastern South American upper margin. The sediments of the Argentinian margin exhibit an average epsilon(Nd) value of -1.9, indicating the influence of the Andean rocks as sediment sources. Sediments from the Rio de La Plata estuary show an average epsilon(Nd) value of -9.6 which is similar to that of the Southern Brazilian Upper Margin. Finally, sediments of Southeastern Brazil, which are associated with the transport of the Brazil Current exhibit an average epsilon(Nd) of -13.0. The Pb isotope signatures also confirm the differentiation of source rocks in the sedimentation of the study area. In addition, Pb isotopes helped to establish the extent of the influence of the Rio de La Plata on the sedimentation of the Southern Brazilian margin. In terms of Pb isotopes the sediments from the Rio de La Plata estuary and Southern Brazil are more radiogenic than those of Southeastem Brazil and the Argentinian margin. (c) 2007 Elsevier B.V. All rights reserved.

Russian Arctic Ports : Problems with the development and management of tourist flows

The potential changes to the territory of the Russian Arctic open up unique possibilities for the development of tourism. More favourable transport opportunities along the Northern Sea Route (NSR) create opportunities for tourism development based on the utilisation of the extensive areas of sea shores and river basins. A major challenge for the Russian Arctic sea and river ports is their strong cargo transport orientation originated by natural resource extraction industries. A careful assessment of the prospects of current and future tourism development is presented here based on the development of regions located along the shores of the Arctic ocean (including Murmansk and Arkhangelsk oblast, Nenets Autonomous okrug (AO), Yamal-Nenets AO, Taymyr AO, Republic of Sakha, Chykotsky AO). An evaluation of the present development of tourism in maritime cities suggests that a considerable qualitative and quantitative increase of tourism activities organised by domestic tourism firms is made virtually impossible. There are several factors contributing to this. The previously established Soviet system of state support for the investments into the port facilities as well as the sea fleet were not effectively replaced by creation of new structures. The necessary investments for reconstruction could be contributed by the federal government but the priorities are not set towards the increased passenger transportation. Having in mind, increased environmental pressures in this highly sensitive area it is especially vital to establish a well-functioning monitoring and rescue system in the situation of ever increasing risks which come not only from the increased transports along the NSR, but also from the exploitation of the offshore oil and gas reserves in the Arctic seas. The capacity and knowledge established in Nordic countries (Norway, Finland) concerning cruise tourism should not be underestimated and the already functioning cooperation in Barents Region should expand towards this particular segment of the tourism industry. The current stage of economic development in Russia makes it clear that tourism development is not able to compete with the well-needed increase in the cargo transportation, which means that Russia’s fleet is going to be utilised by other industries. However, opening up this area to both local and international visitors could contribute to the economic prosperity of these remote areas and if carefully managed could sustain already existing maritime cities along the shores of the Arctic Ocean.

Calibration Strategies Designed For Long Term Sediment Transport Modelling

The presented work deals with the calibration of a 2D numerical model for the simulation of long term bed load transport. A settled basin along an alpine stream was used as a case study. The focus is to parameterise the used multi fractional transport model such that a dynamically balanced behavior regarding erosion and deposition is reached. The used 2D hydrodynamic model utilizes a multi-fraction multi-layer approach to simulate morphological changes and bed load transport. The mass balancing is performed between three layers: a top mixing layer, an intermediate subsurface layer and a bottom layer. Using this approach bears computational limitations in calibration. Due to the high computational demands, the type of calibration strategy is not only crucial for the result, but as well for the time required for calibration. Brute force methods such as Monte Carlo type methods may require a too large number of model runs. All here tested calibration strategies used multiple model runs utilising the parameterization and/or results from previous run. One concept was to reset to initial bed elevations after each run, allowing the resorting process to convert to stable conditions. As an alternative or in combination, the roughness was adapted, based on resulting nodal grading curves, from the previous run. Since the adaptations are a spatial process, the whole model domain is subdivided in homogeneous sections regarding hydraulics and morphological behaviour. For a faster optimization, the adaptation of the parameters is made section wise. Additionally, a systematic variation was done, considering results from previous runs and the interaction between sections. The used approach can be considered as similar to evolutionary type calibration approaches, but using analytical links instead of random parameter changes.

Numerical Simulation Of Sediment Transport And Bedmorphology Around A Hydraulic Structure On A River

Scour around hydraulic structures is a critical problem in hydraulic engineering. Under prediction of scour depth may lead to costly failures of the structure, while over prediction might result in unnecessary costs. Unfortunately, up-to-date empirical scour prediction formulas are based on laboratory experiments that are not always able to reproduce field conditions due to complicated geometry of rivers and temporal and spatial scales of a physical model. However, computational fluid dynamics (CFD) tools can perform using real field dimensions and operating conditions to predict sediment scour around hydraulic structures. In Korea, after completing the Four Major Rivers Restoration Project, several new weirs have been built across Han, Nakdong, Geum and Yeongsan Rivers. Consequently, sediment deposition and bed erosion around such structures have became a major issue in these four rivers. In this study, an application of an open source CFD software package, the TELEMAC-MASCARET, to simulate sediment transport and bed morphology around Gangjeong weir, which is the largest multipurpose weir built on Nakdong River. A real bathymetry of the river and a geometry of the weir have been implemented into the numerical model. The numerical simulation is carried out with a real hydrograph at the upstream boundary. The bedmorphology obtained from the numerical results has been validated against field observation data, and a maximum of simulated scour depth is compared with the results obtained by empirical formulas of Hoffmans. Agreement between numerical computations, observed data and empirical formulas is judged to be satisfactory on all major comparisons. The outcome of this study does not only point out the locations where deposition and erosion might take place depending on the weir gate operation, but also analyzes the mechanism of formation and evolution of scour holes after the weir gates.

Beyond sea, sun and fun in Rio de Janeiro: understanding exchange students motivations and interests

O objetivo deste estudo é compreender o que leva estudantes de intercâmbio ao Rio de Janeiro, quais são suas motivações e interesses que influenciam na escolha dessa cidade, um destino pouco tradicional para intercâmbios, que recebe um crescente número de intercambistas de países desenvolvidos. Também apresentamos uma discussão mais ampla sobre a educação internacional do século 21, posicionando programas de intercâmbio como uma das possíveis iniciativas para a internacionalização de instituições de ensino superior. Para responder essa questão, 20 estudantes de 11 países foram entrevistados. Os resultados indicam que existe muito mais no Rio de Janeiro além do sol e das belas praias. Há uma grande variedade de interesses que explicam porque estudantes de intercâmbio escolhem esse destino. O clichê sobre sol, praia e carnaval se manifestou em diversas respostas, no entanto, nunca como principal fator. Intercambistas se interessam pela cidade por diversos motivos além das atrações turísticas, como aprender português, melhorar o currículo e estar em uma economia emergente. Recomendações para a internacionalização de instituições de educação e uma agenda de pesquisa para o desenvolvimento desse tópico são apresentadas na parte final.

Transport stress in matrinxa, Brycon cephalus (Teleostei : Characidae), at different densities

Matrinxa, Brycon cephalus, is a native teleost fish from the Amazon Basin, and is of economic importance for cultivation for food and sport in Brazil. Mortality losses due to handling and transport of this stenohaline freshwater species are common. The effects of transportation at different densities on the biochemical stress responses of matrinxa (mean weight 1 kg) were examined. Fish were subjected to three different transport densities (100, 200, and 300 kg m(-3)) for four h in water with added salt (0.6%). The fish were bled at departure (baseline level), arrival (immediately after transportation) and at 24 and 96 h after arrival (recovery period). Blood glucose, cortisol, sodium, chloride, potassium and ammonia were used as stress bioindicators. No mortality was observed and no alterations in plasma cortisol were registered. However, blood glucose and ammonia levels increased and serum sodium and plasma chloride decreased on arrival for the fish transported at the highest densities. These stress responses were transient and the concentrations returned to baseline levels within 24 h. This study showed that matrinxa can be transported at densities as high as those tested in the present study, at least under the conditions employed in this study. A recovery period of at least 24 h is strongly recommended.

Bridging infrastructural gaps in Central America: prospects and potential for maritime transport

Includes bibliography

Landlocked countries in South America: transport system challenges

Includes bibliography

The economic costs associated with landlocked status

Two Latin American republics, Bolivia and Paraguay, lack sovereign access to ocean ports. Their landlocked status effectively forces them to export and import products through borders with neighbouring countries; for this purpose, they frequently use land transport modes which are intrinsically more costly than ocean transport. However, being distant from ocean ports is an attribute not only of landlocked countries; but also of states or provinces, such as Mato Grosso, in Brazil, or Tucumán, in Argentina, which belong to countries with direct access to the sea. If perfect political and economic integration were to be achieved in the region, the distances and topographic accidents between points such as La Paz, Bolivia, and Arica, Chile, or Asunción, Paraguay and Paranaguá, Brazil, would remain unchanged. What would disappear would be the delays at border crossings and their related costs. For the two landlocked countries, border expenses, although significant, are a relatively small fraction of the cost of the land segments of international transport. More important for these countries, are the dependency of infrastructure services and the institutional framework of the transit countries for the transport of their external trade.

Third ordinary meeting of the conference of South American ministers of transport, communications and public works

The third ordinary meeting of the Conference of South American Ministers of Transport, Communications and Public Works was held from 6 to 8 November 1996 in Montevideo, Uruguay. Representatives of Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay and Venezuela took part. Representatives of the following organizations were present as observers: the Latin American and Caribbean Federation of National Associations of Cargo Agents, the Latin American Railways Association, the Latin American Association for Automated Highway Transport, the Inter-American Development Bank, the Economic Commission for Latin America and the Caribbean (ECLAC), the United Nations Conference on Trade and Development (UNCTAD), the International Road Federation/German Agency for Technical Cooperation (IRF/GTZ); and other representatives from both the private and public sectors.

Integrated transport systems in Latin America and the Caribbean: converging initiatives

The year 1998 is shaping up to be a year of grand regional initiatives focusing on the setting up of regional integrated transport systems. The past six months have seen intense activity in Latin America and the Caribbean. It would seem that the public and private sectors have agreed to launch converging initiatives, each from its own perspectives. In Central America, a multimodal transport project is already under way, while a new transport master plan put forward by the Permanent Secretariat of the General Treaty on Central American Economic Integration (SIECA) is being prepared; in South America, the Latin American Integration Association (LAIA) and Latin American Railways Association (ALAF) have launched a prefeasability study concerning a plan for the sustainable development of transport; the second Summit of the Americas adopted a plan of action that now takes in the work of the Executive Committee of the Western Hemisphere Transport Initiative; and the private sector also held its regional meeting in São Paulo, Brazil, with Intermodal 98, the fourth in a series. These initiatives are taking shape around similar lines of thought and action; their backgrounds are similar, and they tend towards the same goal: taking action in the immediate environment with a view to expanding linkages with the global economy. The background is the observation that after several years of growth, transport infrastructure, equipment and services appear unable to satisfy the growing demand of international trade in the region. The goal is to implement the requisite reforms in the transport sector so as to meet the challenges posed by global competition. This issue of the Bulletin is devoted to news about recent initiatives and possible future developments.

Road maintenance and international competitiveness

The present and subsequent editions of the Bulletin will deal with the issue of road maintenance, its close connection with transport costs and its impact upon the international competitiveness of the countries of Latin America and the Caribbean. When roads are in poor condition, vehicle operating costs increase by 30 to 50% or even more. Autonomous, adequate and regular funding contributes to effective road maintenance and, consequently, to reducing vehicle operating costs.

Facilitation of international trade in goods

The FAL Bulletin is reverting to its original concept, that is, facilitation of trade in the broad sense. In the context of ECLAC, this is a topic covered by the International Trade Unit in the International Trade and Development Finance Division, to which the Transport Unit also belonged until it was incorporated into the Natural Resources and Infrastructure Division in April 1999.In an effort at inter-divisional cooperation starting with this issue, the International Trade Unit will be responsible for preparing four articles per year on trade facilitation for the FAL Bulletin. These are certain to be of great interest not only to those of our readers concerned with multi-modal ocean transport and customs procedures but also to those with links to the broader issue of promoting foreign trade in the region.