Universidade Federal de Minas Gerais

About: Universidade Federal de Minas Gerais is a education organization based out in Belo Horizonte, Minas Gerais, Brazil. It is known for research contribution in the topics: Population & Immune system. The organization has 41631 authors who have published 75688 publications receiving 1249905 citations.

Raman spectroscopy of graphene and carbon nanotubes

Abstract: This paper reviews progress that has been made in the use of Raman spectroscopy to study graphene and carbon nanotubes These are two nanostructured forms of sp2 carbon materials that are of major current interest These nanostructured materials have attracted particular attention because of their simplicity, small physical size and the exciting new science they have introduced This review focuses on each of these materials systems individually and comparatively as prototype examples of nanostructured materials In particular, this paper discusses the power of Raman spectroscopy as a probe and a characterization tool for sp2 carbon materials, with particular emphasis given to the field of photophysics Some coverage is also given to the close relatives of these sp2 carbon materials, namely graphite, a three-dimensional (3D) material based on the AB stacking of individual graphene layers, and carbon nanoribbons, which are one-dimensional (1D) planar structures, where the width of the ribbon is on the nano

Comparative genomics of trypanosomatid parasitic protozoa.

Abstract: A comparison of gene content and genome architecture of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major, three related pathogens with different life cycles and disease pathology, revealed a conserved core proteome of about 6200 genes in large syntenic polycistronic gene clusters. Many species-specific genes, especially large surface antigen families, occur at nonsyntenic chromosome-internal and subtelomeric regions. Retroelements, structural RNAs, and gene family expansion are often associated with syntenic discontinuities that-along with gene divergence, acquisition and loss, and rearrangement within the syntenic regions-have shaped the genomes of each parasite. Contrary to recent reports, our analyses reveal no evidence that these species are descended from an ancestor that contained a photosynthetic endosymbiont.

A brief survey of web data extraction tools

Abstract: In the last few years, several works in the literature have addressed the problem of data extraction from Web pages. The importance of this problem derives from the fact that, once extracted, the data can be handled in a way similar to instances of a traditional database. The approaches proposed in the literature to address the problem of Web data extraction use techniques borrowed from areas such as natural language processing, languages and grammars, machine learning, information retrieval, databases, and ontologies. As a consequence, they present very distinct features and capabilities which make a direct comparison difficult to be done. In this paper, we propose a taxonomy for characterizing Web data extraction fools, briefly survey major Web data extraction tools described in the literature, and provide a qualitative analysis of them. Hopefully, this work will stimulate other studies aimed at a more comprehensive analysis of data extraction approaches and tools for Web data.

Wet periods in northeastern Brazil over the past 210 kyr linked to distant climate anomalies

Abstract: The tropics are the main source of the atmosphere's sensible and latent heat, and water vapour, and are therefore important for reconstructions of past climate1. But long, accurately dated records of southern tropical palaeoclimate, which would allow the establishment of climatic connections to distant regions, have not been available. Here we present a 210,000-year (210-kyr) record of wet periods in tropical northeastern Brazil—a region that is currently semi-arid. The record is obtained from speleothems and travertine deposits that are accurately dated using the U/Th method. We find wet periods that are synchronous with periods of weak East Asian summer monsoons2, cold periods in Greenland3, Heinrich events in the North Atlantic4 and periods of decreased river runoff to the Cariaco basin5. We infer that the wet periods may be explained with a southward displacement of the Intertropical Convergence Zone. This widespread synchroneity of climate anomalies suggests a relatively rapid global reorganization of the ocean–atmosphere system. We conclude that the wet periods probably affected rainforest distribution, as plant fossils show that forest expansion occurred during these intermittent wet intervals, and opened a forest corridor6,7,8 between the Amazonian and Atlantic rainforests.

Cryptographic distinguishability measures for quantum-mechanical states

Abstract: This paper, mostly expository in nature, surveys four measures of distinguishability for quantum-mechanical states. This is done from the point of view of the cryptographer with a particular eye on applications in quantum cryptography. Each of the measures considered is rooted in an analogous classical measure of distinguishability for probability distributions: namely, the probability of an identification error, the Kolmogorov distance, the Bhattacharyya coefficient, and the Shannon (1948) distinguishability (as defined through mutual information). These measures have a long history of use in statistical pattern recognition and classical cryptography. We obtain several inequalities that relate the quantum distinguishability measures to each other, one of which may be crucial for proving the security of quantum cryptographic key distribution. In another vein, these measures and their connecting inequalities are used to define a single notion of cryptographic exponential indistinguishability for two families of quantum states. This is a tool that may prove useful in the analysis of various quantum-cryptographic protocols.