Spin dynamics of electrons in the first excited subband of a high-mobility low-density two-dimensional electron system

We report on time-resolved Kerr rotation measurements of spin coherence of electrons in the first excited subband of a high-mobility low-density two-dimensional electron system in a GaAs/Al0.35Ga0.65As heterostructure. While the transverse spin lifetime (T-2(*)) of electrons decreases monotonically with increasing magnetic field, it has a nonmonotonic dependence on the temperature and reaches a peak value of 596 ps at 36 K, indicating the effect of intersubband electron-electron scattering on the electron-spin relaxation.

High-mobility Ga-polarity GaN achieved by NH3-MBE

GaN epilayers were grown on (0001) sapphire substrates by NH3-MBE and RF-MBE (radio frequency plasma). The polarities of the epilayers were investigated by in-situ RHEED, chemical solution etching and AFM surface examination. By using a RF-MBE grown GaN layer as template to deposit GaN epilayer by NH3-MBE method, we found that not only Ga-polarity GaN films were repeatedly obtained, but also the electron mobility of these Ga-polarity films was significantly improved with a best value of 290 cm(2)/V.s at room temperature. Experimental results show it is an easy and stable way for growth of high quality Ga-polarity GaN films.

Capillary electrochromatography for separation of peptides driven with electrophoretic mobility on monolithic column

A mode of capillary electrochromatography for separation of ionic compounds driven by electrophoretic mobility on a neutrally hydrophobic monolithic column was developed. The monolithic column was prepared from the in situ copolymerization of lauryl methacrylate and ethylene dimethacrylate to form a C-12 hydrophobic stationary phase. It was found that EOF in this hydrophobic monolithic column was very poor, even the pH value of mobile phase at 8.0. The peptides at acidic buffer were separated on the basis of their differences in electrophoretic mobility and hydrophobic interaction with the stationary phase; therefore, different separation selectivity can be obtained in CEC from that in capillary zone electrophoresis (CZE). Separation of peptides has been realized with high column efficiency (up to 150 000 plates/meter) and good reproducibility (migration time with RSD < 0.5%), and all of the peptides, including some basic peptides, showed good peak symmetry. Effects of the mobile phase compositions on the retention of peptides at low pH have been investigated in a hydrophobic capillary monolithic column. The significant difference in selectivity of peptides in CZE and CEC has been observed. Some peptide isomers that cannot be separated by CZE have been successfully separated on the capillary monolithic column in this mode with the same buffer used.

Single-Element and Competitive Metal Mobility Measured with Column Infiltration and Batch Tests

The distribution coefficient, K-d, is often used to quantify heavy metal mobility in soils. Batch sorption or column infiltration tests may be used to measure K-d. The latter are closer to natural soil conditions, but are difficult to conduct in clays. This difficulty can be overcome by using a laboratory centrifuge. An acceleration of 2600 gravities was applied to columns of London Clay, an Eocene clay sub-stratum, and Cu, Ni, and Zn mobility was measured in centrifuge infiltration tests, both as single elements and in dual competition. Single-element K-d values were also obtained from batch sorption tests, and the results from the two techniques were compared. It was found that K-d values obtained by batch tests vary considerably depending on the metal concentration, while infiltration tests provided a single K-d value for each metal. This was typically in the lower end of the range of the batch test K-d values. For both tests, the order of mobility was Ni > Zn > Cu. Metals became more mobile in competition than when in single-element systems: Ni K-d decreased 3.3 times and Zn K-d 3.4 times when they competed with Cu, while Cu decreased only 1.2 times when in competition with either Ni or Zn. Our study showed that competitive sorption between metals increases the mobility of those metals less strongly bound more than it increases the mobility of more strongly bound metals.

Considering daily mobility in contextual studies of social inequalities in health : conceptual and empirical insights

Les études sur les milieux de vie et la santé ont traditionnellement porté sur le seul quartier de résidence. Des critiques ont été émises à cet égard, soulignant le fait que la mobilité quotidienne des individus n’était pas prise en compte et que l’accent mis sur le quartier de résidence se faisait au détriment d’autres milieux de vie où les individus passent du temps, c’est-à-dire leur espace d’activité. Bien que la mobilité quotidienne fasse l’objet d’un intérêt croissant en santé publique, peu d’études se sont intéressé aux inégalités sociales de santé. Ceci, même en dépit du fait que différents groupes sociaux n’ont pas nécessairement la même capacité à accéder à des milieux favorables pour la santé. Le lien entre les inégalités en matière de mobilité et les inégalités sociales de santé mérite d’être exploré. Dans cette thèse, je développe d'abord une proposition conceptuelle qui ancre la mobilité quotidienne dans le concept de potentiel de mobilité. Le potentiel de mobilité englobe les opportunités et les lieux que les individus peuvent choisir d’accéder en convertissant leur potentiel en mobilité réalisée. Le potentiel de mobilité est façonné par des caractéristiques individuelles (ex. le revenu) et géographiques (ex. la proximité des transports en commun), ainsi que par des règles régissant l’accès à certaines ressources et à certains lieux (ex. le droit). Ces caractéristiques et règles sont inégalement distribuées entre les groupes sociaux. Des inégalités sociales en matière de mobilité réalisée peuvent donc en découler, autant en termes de l'ampleur de la mobilité spatiale que des expositions contextuelles rencontrées dans l'espace d'activité. Je discute de différents processus par lesquels les inégalités en matière de mobilité réalisée peuvent mener à des inégalités sociales de santé. Par exemple, les groupes défavorisés sont plus susceptibles de vivre et de mener des activités dans des milieux défavorisés, comparativement à leurs homologues plus riches, ce qui pourrait contribuer aux différences de santé entre ces groupes. Cette proposition conceptuelle est mise à l’épreuve dans deux études empiriques. Les données de la première vague de collecte de l’étude Interdisciplinaire sur les inégalités sociales de santé (ISIS) menée à Montréal, Canada (2011-2012) ont été analysées. Dans cette étude, 2 093 jeunes adultes (18-25 ans) ont rempli un questionnaire et fourni des informations socio-démographiques, sur leur consommation de tabac et sur leurs lieux d’activités. Leur statut socio-économique a été opérationnalisé à l’aide de leur plus haut niveau d'éducation atteint. Les lieux de résidence et d'activité ont servi à créer des zones tampons de 500 mètres à partir du réseau routier. Des mesures de défavorisation et de disponibilité des détaillants de produits du tabac ont été agrégées au sein des ces zones tampons. Dans une première étude empirique je compare l'exposition à la défavorisation dans le quartier résidentiel et celle dans l'espace d’activité non-résidentiel entre les plus et les moins éduqués. J’identifie également des variables individuelles et du quartier de résidence associées au niveau de défavorisation mesuré dans l’espace d’activité. Les résultats démontrent qu’il y a un gradient social dans l’exposition à la défavorisation résidentielle et dans l’espace d’activité : elle augmente à mesure que le niveau d’éducation diminue. Chez les moins éduqués les écarts dans l’exposition à la défavorisation sont plus marquées dans l’espace d’activité que dans le quartier de résidence, alors que chez les moyennement éduqués, elle diminuent. Un niveau inférieur d'éducation, l'âge croissant, le fait d’être ni aux études, ni à l’emploi, ainsi que la défavorisation résidentielle sont positivement corrélés à la défavorisation dans l’espace d’activité. Dans la seconde étude empirique j'étudie l'association entre le tabagisme et deux expositions contextuelles (la défavorisation et la disponibilité de détaillants de tabac) mesurées dans le quartier de résidence et dans l’espace d’activité non-résidentiel. J'évalue si les inégalités sociales dans ces expositions contribuent à expliquer les inégalités sociales dans le tabagisme. J’observe que les jeunes dont les activités quotidiennes ont lieu dans des milieux défavorisés sont plus susceptibles de fumer. La présence de détaillants de tabac dans le quartier de résidence et dans l’espace d’activité est aussi associée à la probabilité de fumer, alors que le fait de vivre dans un quartier caractérisé par une forte défavorisation protège du tabagisme. En revanche, aucune des variables contextuelles n’affectent de manière significative l’association entre le niveau d’éducation et le tabagisme. Les résultats de cette thèse soulignent l’importance de considérer non seulement le quartier de résidence, mais aussi les lieux où les gens mènent leurs activités quotidiennes, pour comprendre le lien entre le contexte et les inégalités sociales de santé. En discussion, j’élabore sur l’idée de reconnaître la mobilité quotidienne comme facteur de différenciation sociale chez les jeunes adultes. En outre, je conclus que l’identification de facteurs favorisant ou contraignant la mobilité quotidienne des individus est nécessaire afin: 1 ) d’acquérir une meilleure compréhension de la façon dont les inégalités sociales en matière de mobilité (potentielle et réalisée) surviennent et influencent la santé et 2) d’identifier des cibles d’intervention en santé publique visant à créer des environnements sains et équitables.

Conformations of poly{G}-poly{C} π stacks with high hole mobility

Charge transfer properties of DNA depend strongly on the π stack conformation. In the present paper, we identify conformations of homogeneous poly-{G}-poly-{C} stacks that should exhibit high charge mobility. Two different computational approaches were applied. First, we calculated the electronic coupling squared, V2, between adjacent base pairs for all 1 ps snapshots extracted from 15 ns molecular dynamics trajectory of the duplex G15. The average value of the coupling squared 〈 V2 〉 is found to be 0.0065 eV2. Then we analyze the base-pair and step parameters of the configurations in which V2 is at least an order of magnitude larger than 〈 V2 〉. To obtain more consistent data, ∼65 000 configurations of the (G:C)2 stack were built using systematic screening of the step parameters shift, slide, and twist. We show that undertwisted structures (twist<20°) are of special interest, because the π stack conformations with strong electronic couplings are found for a wide range of slide and shift. Although effective hole transfer can also occur in configurations with twist=30° and 35°, large mutual displacements of neighboring base pairs are required for that. Overtwisted conformation (twist38°) seems to be of limited interest in the context of effective hole transfer. The results may be helpful in the search for DNA based elements for nanoelectronics

Current account and capital mobility hypothesis: Evidence from the G-7

This paper investigates an intertemporal optimization model in order to analyze the current account of the G-7 countries, measured as the present value of the future changes in net output. The study compares observed and forecasted series, generated by the model, using Campbell & Shiller’s (1987) methodology. In the estimation process, the countries are considered separately (with OLS technique) as well as jointly (SURE approach), to capture contemporaneous correlations of the shocks in net output. The paper also proposes a note on Granger causality and its implications to the optimal current account. The empirical results are sensitive to the technique adopted in the estimation process and suggest a rejection of the model in the G-7 countries, except for the USA and Japan, according to some papers presented in the literature.

The value of local partners in Brazil: the effects of ownership clusters and business group membership on firm value in emerging markets

Este estudo analisa como a classe de acionistas afeta o valor das empresas brasileiras listadas na bolsa de valores no ponto de vista da governança corporativa. O trabalho examina a interação entre o valor das empresas e cinco tipos de concentrações acionárias comumente presente em mercados emergentes: famílias, agentes públicos, investidores estrangeiros, executivos e investidores financeiros nacionais. A análise empírica demonstra que o mix e a concentração de participação acionária afeta significativamente o valor das empresas. Utilizando uma compilação única de dados em painel de 2004 a 2008, a presente pesquisa também desenvolve hipóteses sobre o efeito da participação em grupos econômicos para o valor das empresas. A investigação encontra evidências de que, apesar de sua importância para o desenvolvimento de empresas brasileiras, o capital familiar, instituições públicas, e investidores estrangeiros estão cedendo lugar a monitores mais especializados e menos concentrados, como executivos e instituições financeiras nacionais. Estes resultados indicam que a governança corporativa no Brasil pode estar alcançando níveis de maturidade mais elevados. Adicionalmente, apesar de não haver indicação da existência de correlação entre a participação em grupos econômicos e o valor das empresas, os resultados indicam que a presença de um tipo específico de acionista em uma empresa do grupo facilita investimentos futuros desta classe de acionista em outras empresas do mesmo grupo, sinalizando que os interesses acionários são provavelmente perpetuados dentro de uma mesma rede de empresas. Finalmente, a pesquisa demonstra que enquanto o capital familiar prefere investir em empresas com ativa mobilidade do capital, investidores internacionais e instituições públicas procuram investimentos em equity com menor mobilidade de capital, o que lhes garante mais transparência com relação ao uso dos recursos e fundos das empresas.

Citizens and the future of multilateralism in a polycentric world at 2030: the perspectives of emerging countries for the trading system: the impasse of WTO, the trends of mega agreements, the logic of value chains and the advent of consumers concerns on international trade

A new paradigm is modeling the World: evolutionary innovations in all fronts, new information technologies, huge mobility of capital, use of risky financial tools, globalization of production, new emerging powers and the impact of consumer concerns on governmental policies. These phenomena are shaping the World and forcing the advent of a new World Order in the Multilateral Monetary, Financial, and Trading System. The effects of this new paradigm are also transforming global governance. The political and economic orders established after the World War and centered on the multilateral model of UN, IMF, World Bank, and the GATT, leaded by the developed countries, are facing significant challenges. The rise of China and emerging countries shifted the old model to a polycentric World, where the governance of these organizations are threatened by emerging countries demanding a bigger participation in the role and decision boards of these international bodies. As a consequence, multilateralism is being confronted by polycentrism. Negotiations for a more representative voting process and the pressure for new rules to cope with the new demands are paralyzing important decisions. This scenario is affecting seriously not only the Monetary and Financial Systems but also the Multilateral Trading System. International trade is facing some significant challenges: a serious deadlock to conclude the last round of the multilateral negotiation at the WTO, the fragmentation of trade rules by the multiplication of preferential and mega agreements, the arrival of a new model of global production and trade leaded by global value chains that is threatening the old trade order, and the imposition of new sets of regulations by private bodies commanded by transnationals to support global value chains and non-governmental organizations to reflect the concerns of consumers in the North based on their precautionary attitude about sustainability of products made in the World. The lack of any multilateral order in this new regulation is creating a big cacophony of rules and developing a new regulatory war of the Global North against the Global South. The objective of this paper is to explore how these challenges are affecting the Tradinge System and how it can evolve to manage these new trends.

The international mobility of talent and its impact on global development: an overview

Includes bibliography

Employment and structural mobility. Revisiting a Prebischian theme

Includes bibliography

Benchmarking sustainable urban mobility: The case of Curitiba, Brazil

Transportation planning is currently being confronted with a broader planning view, which is given by the concept of mobility. The Index of Sustainable Urban Mobility (I_SUM) is among the tools developed for supporting this new concept implementation. It is a tool to assess the current mobility conditions of any city, which can also be applied for policy formulation. This study focus on the application of I_SUM in the city of Curitiba, Brazil. Considering that the city is known worldwide as a reference of successful urban and transportation planning, the index application must confirm it. An additional objective of the study was to evaluate the index itself, or the subjacent assessment method and reference values. A global I_SUM value of 0.747 confirmed that the city has indeed very positive characteristics regarding sustainable mobility policies. However, some deficiencies were also detected, particularly with respect to non-motorized transport modes. The application has also served to show that a few I_SUM indicators were not able to capture some of the positive aspects of the city, what may suggest the need of changes in their formulation. Finally, the index application in parts of the city suggests that the city provides fair and equitable mobility conditions to all citizens throughout the city. This is certainly a good attribute for becoming a benchmark of sustainable mobility, even if it is not yet the ideal model. (C) 2012 Elsevier Ltd. All rights reserved.

Assessing urban mobility through participatory scenario building and combined utility-regret assessment

La planificación de la movilidad sostenible urbana es una tarea compleja que implica un alto grado de incertidumbre debido al horizonte de planificación a largo plazo, la amplia gama de paquetes de políticas posibles, la necesidad de una aplicación efectiva y eficiente, la gran escala geográfica, la necesidad de considerar objetivos económicos, sociales y ambientales, y la respuesta del viajero a los diferentes cursos de acción y su aceptabilidad política (Shiftan et al., 2003). Además, con las tendencias inevitables en motorización y urbanización, la demanda de terrenos y recursos de movilidad en las ciudades está aumentando dramáticamente. Como consecuencia de ello, los problemas de congestión de tráfico, deterioro ambiental, contaminación del aire, consumo de energía, desigualdades en la comunidad, etc. se hacen más y más críticos para la sociedad. Esta situación no es estable a largo plazo. Para enfrentarse a estos desafíos y conseguir un desarrollo sostenible, es necesario considerar una estrategia de planificación urbana a largo plazo, que aborde las necesarias implicaciones potencialmente importantes. Esta tesis contribuye a las herramientas de evaluación a largo plazo de la movilidad urbana estableciendo una metodología innovadora para el análisis y optimización de dos tipos de medidas de gestión de la demanda del transporte (TDM). La metodología nueva realizado se basa en la flexibilización de la toma de decisiones basadas en utilidad, integrando diversos mecanismos de decisión contrariedad‐anticipada y combinados utilidad‐contrariedad en un marco integral de planificación del transporte. La metodología propuesta incluye dos aspectos principales: 1) La construcción de escenarios con una o varias medidas TDM usando el método de encuesta que incorpora la teoría “regret”. La construcción de escenarios para este trabajo se hace para considerar específicamente la implementación de cada medida TDM en el marco temporal y marco espacial. Al final, se construyen 13 escenarios TDM en términos del más deseable, el más posible y el de menor grado de “regret” como resultado de una encuesta en dos rondas a expertos en el tema. 2) A continuación se procede al desarrollo de un marco de evaluación estratégica, basado en un Análisis Multicriterio de Toma de Decisiones (Multicriteria Decision Analysis, MCDA) y en un modelo “regret”. Este marco de evaluación se utiliza para comparar la contribución de los distintos escenarios TDM a la movilidad sostenible y para determinar el mejor escenario utilizando no sólo el valor objetivo de utilidad objetivo obtenido en el análisis orientado a utilidad MCDA, sino también el valor de “regret” que se calcula por medio del modelo “regret” MCDA. La función objetivo del MCDA se integra en un modelo de interacción de uso del suelo y transporte que se usa para optimizar y evaluar los impactos a largo plazo de los escenarios TDM previamente construidos. Un modelo de “regret”, llamado “referencedependent regret model (RDRM)” (modelo de contrariedad dependiente de referencias), se ha adaptado para analizar la contribución de cada escenario TDM desde un punto de vista subjetivo. La validación de la metodología se realiza mediante su aplicación a un caso de estudio en la provincia de Madrid. La metodología propuesta define pues un procedimiento técnico detallado para la evaluación de los impactos estratégicos de la aplicación de medidas de gestión de la demanda en el transporte, que se considera que constituye una herramienta de planificación útil, transparente y flexible, tanto para los planificadores como para los responsables de la gestión del transporte. Planning sustainable urban mobility is a complex task involving a high degree of uncertainty due to the long‐term planning horizon, the wide spectrum of potential policy packages, the need for effective and efficient implementation, the large geographical scale, the necessity to consider economic, social, and environmental goals, and the traveller’s response to the various action courses and their political acceptability (Shiftan et al., 2003). Moreover, with the inevitable trends on motorisation and urbanisation, the demand for land and mobility in cities is growing dramatically. Consequently, the problems of traffic congestion, environmental deterioration, air pollution, energy consumption, and community inequity etc., are becoming more and more critical for the society (EU, 2011). Certainly, this course is not sustainable in the long term. To address this challenge and achieve sustainable development, a long‐term perspective strategic urban plan, with its potentially important implications, should be established. This thesis contributes on assessing long‐term urban mobility by establishing an innovative methodology for optimizing and evaluating two types of transport demand management measures (TDM). The new methodology aims at relaxing the utility‐based decision‐making assumption by embedding anticipated‐regret and combined utilityregret decision mechanisms in an integrated transport planning framework. The proposed methodology includes two major aspects: 1) Construction of policy scenarios within a single measure or combined TDM policy‐packages using the survey method incorporating the regret theory. The purpose of building the TDM scenarios in this work is to address the specific implementation in terms of time frame and geographic scale for each TDM measure. Finally, 13 TDM scenarios are built in terms of the most desirable, the most expected and the least regret choice by means of the two‐round Delphi based survey. 2) Development of the combined utility‐regret analysis framework based on multicriteria decision analysis (MCDA). This assessment framework is used to compare the contribution of the TDM scenario towards sustainable mobility and to determine the best scenario considering not only the objective utility value obtained from the utilitybased MCDA, but also a regret value that is calculated via a regret‐based MCDA. The objective function of the utility‐based MCDA is integrated in a land use and transport interaction model and is used for optimizing and assessing the long term impacts of the constructed TDM scenarios. A regret based model, called referente dependent regret model (RDRM) is adapted to analyse the contribution of each TDM scenario in terms of a subjective point of view. The suggested methodology is implemented and validated in the case of Madrid. It defines a comprehensive technical procedure for assessing strategic effects of transport demand management measures, which can be useful, transparent and flexible planning tool both for planners and decision‐makers.

Patterns of prehistoric human mobility in Polynesia indicated by mtDNA from the Pacific rat

Human settlement of Polynesia was a major event in world prehistory. Despite the vastness of the distances covered, research suggests that prehistoric Polynesian populations maintained spheres of continuing interaction for at least some period of time in some regions. A low level of genetic variation in ancestral Polynesian populations, genetic admixture (both prehistoric and post-European contact), and severe population crashes resulting from introduction of European diseases make it difficult to trace prehistoric human mobility in the region by using only human genetic and morphological markers. We focus instead on an animal that accompanied the ancestral Polynesians on their voyages. DNA phylogenies derived from mitochondrial control-region sequences of Pacific rats (Rattus exulans) from east Polynesia are presented. A range of specific hypotheses regarding the degree of interaction within Polynesia are tested. These include the issues of multiple contacts between central east Polynesia and the geographically distinct archipelagos of New Zealand and Hawaii. Results are inconsistent with models of Pacific settlement involving substantial isolation after colonization and confirm the value of genetic studies on commensal species for elucidating the history of human settlement.

Identifying mobility in populations with mixed marine/terrestrial diets : strontium isotope analysis of skeletal material from a passage grave in Resmo, Öland, Sweden

Strontium isotope analysis of skeletal material as a means to reconstruct prehistoric residential patterns has previously mainly been applied to populations with terrestrial diets. Here we present a model for populations with mixed marine/terrestrial diets, which is based on two-component mixing of strontium isotopes. Applying this model, we can estimate the original strontium isotope value of the terrestrial component of the diet. Accordingly it is possible to identify non-local individuals even if they had a mixed marine/terrestrial diet. The model is applied to tooth enamel samples representing nine individuals recovered from a passage grave in Resmo, on the island of Öland in the Baltic Sea, where at least five non-local individuals, representing at least two different geographical regions of origin, were identified. Non-local individuals were more frequent during the Bronze Age than during previous phases.