How to achieve full electrification: Lessons from Latin America

Electricity coverage in Latin America has increased substantially in recent decades, rising from 50% of the population in 1970 to more than 95% in 2015. Growth, however, slowed in the 1990s as many countries experienced difficulties in extending their networks further, in particular to serve those living in isolated and rural areas. In spite of this, the process of electrification was not interrupted and at the beginning of the 2010s decade most countries in the region were able to provide access to electricity to almost all of their populations. In this paper, we examine the main strategies used in Latin America to increase coverage and argue that only a combination of policy efforts has made it possible to achieve the current situation. We also examine the remaining obstacles, at policy and institutional levels, to achieving full coverage

Non-volatility of ferroelectric SBT thin fims, at 75ºC

[ES] El estudio de la no volatilidad de una memoria FeRAM de tantalato de bismuto y estroncio, SrBi2Ta2O9 (SBT) en condiciones reales de uso, requiere la caracterización ferroeléctrica del material en forma de lámina delgada a temperaturas por encima del ambiente. Para ello se han depositado láminas de SBT mediante un método sol-gel, sobre substratos de Pt/TiO2/SiO2/Si(100), seleccionándose condensadores de área 5.10-4 cm-2. Basándonos en las medidas de la variación de la polarización con el tiempo (retención) realizadas a temperatura ambiente y a 75ºC, analizamos la viabilidad del material como una FeRAM en condiciones reales de uso.[EN] The study of the non-volatility of Strontium bismuth tantalate SrBi2Ta2O9 (SBT) FeRAM memory, at real operating conditions, requires the ferroelectric characterisation of the material, as a thin film, above the room temperature.As a result, it has been deposited SBT films by the sol-gel method, onto Pt/TiO2/SiO2/Si (100) substrates, using capacitors of 5 x 10–4 cm-2 .In this work, we analysed the viability of this material as a FeRAM memory in real operating conditions, as a result of the variation of the polarisation measurements with time (retention), performed at room temperature and 75ºC.Este trabajo ha sido realizado con el apoyo del proyecto de la CICYT MAT98-1068.Peer reviewe

Superintegrability and higher order polynomial algebras II

In an earlier article, we presented a method to obtain integrals of motion and polynomial algebras for a class of two-dimensional superintegrable systems from creation and annihilation operators. We discuss the general case and present its polynomial algebra. We will show how this polynomial algebra can be directly realized as a deformed oscillator algebra. This particular algebraic structure allows to find the unitary representations and the corresponding energy spectrum. We apply this construction to a family of caged anisotropic oscillators. The method can be used to generate new superintegrable systems with higher order integrals. We obtain new superintegrable systems involving the fourth Painleve transcendent and present their integrals of motion and polynomial algebras.Comment: 11 page

Structure of a bacterial type IV secretion core complex at subnanometre resolution

Type IV secretion (T4S) systems are able to transport DNAs and/or proteins through the membranes of bacteria. They form large multiprotein complexes consisting of 12 proteins termed VirB1-11 and VirD4. VirB7, 9 and 10 assemble into a 1.07 MegaDalton membrane-spanning core complex (CC), around which all other components assemble. This complex is made of two parts, the O-layer inserted in the outer membrane and the I-layer inserted in the inner membrane. While the structure of the O-layer has been solved by X-ray crystallography, there is no detailed structural information on the I-layer. Using high-resolution cryo-electron microscopy and molecular modelling combined with biochemical approaches, we determined the I-layer structure and located its various components in the electron density. Our results provide new structural insights on the CC, from which the essential features of T4S system mechanisms can be derived

Nitrogen-doped carbon nanodots deposited on titania nanoparticles: unconventional near-infrared active photocatalysts for cancer therapy

Cancer represents a major public health issue and a primary cause of death for the mankind and the search for alternative cancer treatments that assist or alleviate the drawbacks of current cancer therapies remains imperative. Nanocatalytic medicine represents a new discipline that aims at exploiting the unique response of heterogeneous catalysts exposed to unconventional conditions such as those encountered in the tumor microenvironment (TME). Photo-triggered cancer therapies using light-activable catalytic materiales can stimulate and activate multiple biological processes and represent a very promising field of study. Herein, we evaluate the use of carbon nanodots with different composition (CNDs) retrieved by laser pyrolysis as potential near-infrared (NIR) photosensitizers able to activate P25 semiconductor nanostructured photocatalysts. We describe the enhanced photocatalytic response towards glucose conversion and reactive oxygen species (ROS) generation upon irradiation with NIR-LEDs when CNDs doped with heteroatoms were tested. The most active photocatalysts were evaluated in the presence of cancer cells and revealed a promising photodynamic effect under NIR irradiation. This work represents one of the scarce examples of a conventional inorganic photocatalyst containing TiO2 that is translated into a biomedical application with a successful outcome

Tropical Grass Growth Functions Modeling by Using Nonlinear Mixed Models

Nonlinear Growth curves are used for modeling plant physiological variables. These models are preferable because the polynomial coefficients of the equations have a biological significance. The response variables of the curves occurs commonly with repeated measurements over time and measurements are on different environments. The traditional statistical analysis does not include a repeated measures approach, which can lead to improper estimation of the error terms. It is important to study the growth of tropical grass (Da Silva and Carvalho 2005)

Intertwining symmetry algebras of quantum superintegrable systems on the hyperboloid

A class of quantum superintegrable Hamiltonians defined on a two-dimensional hyperboloid is considered together with a set of intertwining operators connecting them. It is shown that such intertwining operators close a su(2,1) Lie algebra and determine the Hamiltonians through the Casimir operators. By means of discrete symmetries a broader set of operators is obtained closing a so(4,2) algebra. The physical states corresponding to the discrete spectrum of bound states as well as the degeneration are characterized in terms of unitary representations of su(2,1) and so(4,2).Comment: 11 pages, 5 figure