Role of oxygen vacancies in the magnetic and dielectric properties of the high-dielectric-constant system CaCu3Ti4O12: An electron-spin resonance study

We report experiments of electron spin resonance (ESR) of Cu2+ in polycrystalline samples of CaCu3Ti4O12 post-annealed in different atmospheres. After being synthesized by solid state reaction, pellets of CaCu3Ti4O12 were annealed for 24 h at 1000 degrees C under air, Ar or O-2. Our temperature dependent ESR data revealed for all samples nearly temperature independent g value (2.15(1)) and linewidth for T > T-N approximate to 25 K. However, the values of ESR linewidth are strongly affected by the oxygen content in the sample. For instance, argon post-annealed samples show a much larger linewidth than the O-2 or air post-annealed samples. We attribute this broadening to an increase of the dipolar homogeneous broadening of the Cu2+ ESR lines due to the presence of oxygen vacancies which induce an S=1/2 spin inside the TiO6 octahedra. Correlation between a systematic dependence of the ESR linewidth on the oxygen content and the high dielectric constant of these materials is addressed. Also, ESR, magnetic susceptibility, and specific heat data for a single crystal of CaCu3Ti4O12 and for polycrystals of CdCu3Ti4O12 are reported.

Magnetic field dependence of the magnetic susceptibility and the specific heat of the doped plasticized polyaniline (PANI-DB3EPSA)0.5

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

Translating conduction-electron spin-resonance lines into lorentzian lines

The Dysonian line in the limit d < or ∼ δ, where d is the thickness and 6 the skin depth, was fitted to a combination of absorption and dispersion Lorentzian lines. This procedure allows one to determine not only microwave conductivity from the Dysonian line but also the true g value, linewidth, and paramagnetic susceptibility by the measurement of five parameters of the ESR absorption-derivative Dysonian line. ©1990 Academic Press, inc.

Electric and magnetic properties of polymer electrolyte/carbon black composites

Measurements of 1H Nuclear Magnetic Resonance (NMR) relaxation times, Electron Paramagnetic Resonance (EPR) and AC Impedance Spectroscopy (IS) are reported for composites based on PEO8:LiClO4 and carbon black (CB), prepared by two methods: solvent and fusion processing. Three nuclear relaxation processes were identified for 1H nuclei: (i) belonging to the polymer chains in the amorphous phase, loosely bound to the CB particles, whose dynamics is almost the same as for unfilled polymer, (ii) belonging to the polymer chains which are tightly attached to the CB particles, and (iii) belonging to the crystalline phase in the loose polymer chain. The paramagnetic electronic susceptibility of the composite samples, measured by EPR, was interpreted by assuming a contribution of localized spin states that follow a Curie law, and a Pauli-like contribution of delocalized spins. A significant change of the EPR linewidth was observed at 40 K, which is the temperature where the Curie and Pauli susceptibilities equally contribute to the paramagnetic electronic susceptibility. The electrical properties are very sensitive to the preparation methods of the composites, which conditions the interaction between carbon particle-carbon particle and carbon particle-polymer chain. Classical statistic models to describe the conductivity in these media were not satisfactory. © 1998 Published by Elsevier Science B.V. All rights reserved.

Changes in the distribution of income and the New Economic Model in Jamaica

Includes bibliography

Global economic developments, 1999

Includes bibliography

Capital flows to Latin America: second quarter 2003

Includes bibliography

Capital flows to Latin America: third quarter 2003

Includes bibliography

Capital flows to Latin America: fourth quarter 2003

Includes bibliography

A representação social e a territorialização da reforma agrária no espaço urbano a partir do Programa de Aquisição de Alimentos

Pós-graduação em Geografia - IGCE

The employment situation in Latin America and the Caribbean: Advances and challenges in measuring decent work

At 6.4%, the unemployment rate for the Latin American and Caribbean region overall was the lowest for the past few decades, down from 6.7% in 2011. This is significant, in view of the difficult employment situation prevailing in other world regions. Labour market indicators improved despite modest growth of just 3.0% in the region’s economy. Even with sharply rising labour market participation, the number of urban unemployed fell by around 400,000, on the back of relatively strong job creation. Nevertheless, around 15 million are still jobless in the region. Other highlights of 2012 labour market performance were that the gender gaps in labour market participation, unemployment and employment narrowed, albeit slightly; formal employment increased; the hourly underemployment rate declined; and average wages rose. This rendering was obviously not homogenous across the region. Labour market indicators worsened again in the Caribbean countries, for example, reflecting the sluggish performance of their economies. The sustainability of recent labour market progress is also a cause for concern. Most of the new jobs in the region were created as part of a self-perpetuating cycle in which new jobs and higher real wages (and greater access to credit) have boosted household purchasing power and so pushed up domestic demand. Much of this demand is for non-tradable goods and services (and imports), which has stimulated expansion of the tertiary sector and hence its demand for labour, and many of the new jobs have therefore arisen in these sectors of the economy. This dynamic certainly has positive implications in terms of labour and distribution, but the concern is whether it is sustainable in a context of still relatively low investment (even after some recent gains) which is, moreover, not structured in a manner conducive to diversifying production. Doubt hangs over the future growth of production capacity in the region, given the enormous challenges facing the region in terms of innovation, education quality, infrastructure and productivity. As vigorous job creation has driven progress in reducing unemployment, attention has turned once again to the characteristics of that employment. Awareness exists in the region that economic growth is essential, but not in itself sufficient to generate more and better jobs. For some time, ILO has been drawing attention to the fact that it is not enough to create any sort of employment. The concept of decent work, as proposed by ILO, emphasized the need for quality jobs which enshrine respect for fundamental rights at work. The United Nations General Assembly endorsed this notion and incorporated it into the targets set in the framework of the Millennium Development Goals. This eighth issue of the ECLAC/ILO publication “The employment situation in Latin America and the Caribbean” examines how the concept of decent work has evolved in the region, progress in measuring it and the challenges involved in building a system of decent work indicators, 14 years after the concept was first proposed. Although the concept of decent work has been accompanied since the outset by the challenge of measurement, its first objective was to generate a discussion on the best achievable labour practices in each country. Accordingly, rather than defining a universal threshold of what could be considered decent work —regarding which developed countries might have almost reached the target before starting, while poor countries could be left hopelessly behind— ILO called upon the countries to define their own criteria and measurements for promoting decent work policies. As a result, there is no shared set of variables for measuring decent work applicable to all countries. The suggestion is, instead, that countries move forward with measuring decent work on the basis of their own priorities, using the information they have available now and in the future. However, this strategy of progressing according to the data available in each country tends to complicate statistical comparison between them. So, once the countries have developed their respective systems of decent work indicators, it will be also be important to work towards harmonizing them. ECLAC and ILO are available to provide technical support to this end. With respect to 2013, there is cautious optimism regarding the performance of the region’s labour markets. If projections of a slight uptick —to 3.5%— in the region’s economic growth in 2013 are borne out, labour indicators should continue to gradually improve. This will bring new increases in real wages and a slight drop of up to 0.2 percentage points in the region’s unemployment rate, reflecting a fresh rise in the regional employment rate and slower growth in labour market participation.

Horizons 2030: Equality at the centre of sustainable development. Summary

The world is living a change of era. The 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals represent the international community’s response to the economic, distributive and environmental imbalances built up under the prevailing development pattern. This document, presented by the Economic Commission for Latin America and the Caribbean (ECLAC) to its member States at its thirty-sixth session, provides an analytical complement to the 2030 Agenda from a structuralist perspective and from the point of view of the Latin American and Caribbean countries. The proposals made here stem from the need to achieve progressive structural change in order to incorporate more knowledge into production, ensure social inclusion and combat the negative impacts of climate change. The reflections and proposals for advancing towards a new development pattern are geared to achieving equality and environmental sustainability. In these proposals, the creation of global and regional public goods and the corresponding domestic policies form the core for expanding the structuralist tradition towards a global Keynesianism and a development strategy centred around an environmental big push.

Horizons 2030: Equality at the centre of sustainable development

The world is living a change of era. The 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals represent the international community’s response to the economic, distributive and environmental imbalances built up under the prevailing development pattern. This document, presented by the Economic Commission for Latin America and the Caribbean (ECLAC) to its member States at its thirty-sixth session, provides an analytical complement to the 2030 Agenda from a structuralist perspective and from the point of view of the Latin American and Caribbean countries. The proposals made here stem from the need to achieve progressive structural change in order to incorporate more knowledge into production, ensure social inclusion and combat the negative impacts of climate change. The reflections and proposals for advancing towards a new development pattern are geared to achieving equality and environmental sustainability. In these proposals, the creation of global and regional public goods and the corresponding domestic policies form the core for expanding the structuralist tradition towards a global Keynesianism and a development strategy centred around an environmental big push.

Random laser action from flexible biocellulose-based device

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Silk fibroin biopolymer films as efficient hosts for DFB laser operation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)