A characterization of the scientific impact of Brazilian institutions

In this paper we studied the research activity of Brazilian Institutions for all sciences and also their performance in the area of physics between 1945 and December 2008. All the data come from the Web of Science database for this period. The analysis of the experimental data shows that, within a nonextensive thermostatistical formalism, the Tsallis \emph{q}-exponential distribution $N(c)$ can constitute a new characterization of the research impact for Brazilian Institutions. The data examined in the present survey can be fitted successfully by applying a universal curve namely, $N(c) \propto 1/[1+(q-1) c/T]^{\frac{1}{q-1}}$ with $q\simeq 4/3$ for {\it all} the available citations $c$, $T$ being an "effective temperature". The present analysis ultimately suggests that via the "effective temperature" $T$, we can provide a new performance metric for the impact level of the research activity in Brazil, taking into account the number of the publications and their citations. This new performance metric takes into account the "quantity" (number of publications) and the "quality" (number of citations) for different Brazilian Institutions. In addition we analyzed the research performance of Brazil to show how the scientific research activity changes with time, for instance between 1945 to 1985, then during the period 1986-1990, 1991-1995, and so on until the present. Finally, this work intends to show a new methodology that can be used to analyze and compare institutions within a given country.Comment: 7 pages, 5 figure

Homotheties and topology of tangent sphere bundles

We prove a Theorem on homotheties between two given tangent sphere bundles $S_rM$ of a Riemannian manifold $M,g$ of $\dim\geq 3$, assuming different variable radius functions $r$ and weighted Sasaki metrics induced by the conformal class of $g$. New examples are shown of manifolds with constant positive or with constant negative scalar curvature, which are not Einstein. Recalling results on the associated almost complex structure $I^G$ and symplectic structure ${\omega}^G$ on the manifold $TM$, generalizing the well-known structure of Sasaki by admitting weights and connections with torsion, we compute the Chern and the Stiefel-Whitney characteristic classes of the manifolds $TM$ and $S_rM$.Comment: 15 pages, to appear in Journal of Geometr

Are citations of scientific papers a case of nonextensivity ?

The distribution $N(x)$ of citations of scientific papers has recently been illustrated (on ISI and PRE data sets) and analyzed by Redner [Eur. Phys. J. B {\bf 4}, 131 (1998)]. To fit the data, a stretched exponential ($N(x) \propto \exp{-(x/x_0)^{\beta}}$) has been used with only partial success. The success is not complete because the data exhibit, for large citation count $x$, a power law (roughly $N(x) \propto x^{-3}$ for the ISI data), which, clearly, the stretched exponential does not reproduce. This fact is then attributed to a possibly different nature of rarely cited and largely cited papers. We show here that, within a nonextensive thermostatistical formalism, the same data can be quite satisfactorily fitted with a single curve (namely, $N(x) \propto 1/[1+(q-1) \lambda x]^{q/{q-1}}$ for the available values of $x$. This is consistent with the connection recently established by Denisov [Phys. Lett. A {\bf 235}, 447 (1997)] between this nonextensive formalism and the Zipf-Mandelbrot law. What the present analysis ultimately suggests is that, in contrast to Redner's conclusion, the phenomenon might essentially be one and the same along the entire range of the citation number $x$.Comment: Revtex,1 Figure postscript;[email protected]

O aplicativo computacional "Irrigafácil" implementado via web para o manejo de irrigação dos campos experimentais da Embrapa Milho e Sorgo.

bitstream/item/79197/1/ct-203.pd

Neutrino Telescopes as a Direct Probe of Supersymmetry Breaking

We consider supersymmetric models where the scale of supersymmetry breaking lies between 5 $\times 10^6$ GeV and 5 $\times 10^8$ GeV. In this class of theories, which includes models of gauge mediated supersymmetry breaking, the lightest supersymmetric particle is the gravitino. The next to lightest supersymmetric particle is typically a long lived charged slepton with a lifetime between a microsecond and a second, depending on its mass. Collisions of high energy neutrinos with nucleons in the earth can result in the production of a pair of these sleptons. Their very high boost means they typically decay outside the earth. We investigate the production of these particles by the diffuse flux of high energy neutrinos, and the potential for their observation in large ice or water Cerenkov detectors. The relatively small cross-section for the production of supersymmetric particles is partially compensated for by the very long range of heavy particles. The signal in the detector consists of two parallel charged tracks emerging from the earth about 100 meters apart, with very little background. A detailed calculation using the Waxman-Bahcall limit on the neutrino flux and realistic spectra shows that km$^3$ experiments could see as many as 4 events a year. We conclude that neutrino telescopes will complement collider searches in the determination of the supersymmetry breaking scale, and may even give the first evidence for supersymmetry at the weak scale.Comment: 4 pages, 3 figure