Probing the gluon density of the proton in the exclusive photoproduction of vector mesons at the LHC: A phenomenological analysis

The current uncertainty on the gluon density extracted from the global parton analysis is large in the kinematical range of small values of the Bjorken - $x$ variable and low values of the hard scale $Q^2$. An alternative to reduces this uncertainty is the analysis of the exclusive vector meson photoproduction in photon - hadron and hadron - hadron collisions. This process offers a unique opportunity to constrain the gluon density of the proton, since its cross section is proportional to the gluon density squared. In this paper we consider current parametrizations for the gluon distribution and estimate the exclusive vector meson photoproduction cross section at HERA and LHC using the leading logarithmic formalism. We perform a fit of the normalization of the $\gamma h$ cross section and the value of the hard scale for the process and demonstrate that the current LHCb experimental data are better described by models that assume a slow increasing of the gluon distribution at small - $x$ and low $Q^2$.Comment: 8 pages, 6 figures, 1 table. Version published in European Physical Journal

Phase Transition in a Stochastic Forest Fire Model and Effects of the Definition of Neighbourhood

We present results on a stochastic forest fire model, where the influence of the neighbour trees is treated in a more realistic way than usual and the definition of neighbourhood can be tuned by an additional parameter. This model exhibits a surprisingly sharp phase transition which can be shifted by redefinition of neighbourhood. The results can also be interpreted in terms of disease-spreading and are quite unsettling from the epidemologist's point of view, since variation of one crucial parameter only by a few percent can result in the change from endemic to epidemic behaviour.Comment: 23 pages, 13 figure

Predatory lizards perceive plant-derived volatile odorants

Many lizards are olfactory foragers and prey upon herbivorous arthropods, yet their responses to common herbivore-associated plant volatiles remain unknown. As such, their role in mediating plant indirect defenses also remains largely obscured. In this paper, we use a cotton-swab odor presentation assay to ask whether lizards respond to two arthropod-associated plant-derived volatile compounds: 2-(E)-hexenal and hexanoic acid. We studied the response of two lizard species, Sceloporus virgatusand Aspidoscelis exsanguis, because they differ substantially in their foraging behavior. We found that the actively foraging A. exsanguisresponded strongly to hexanoic acid, whereas the ambush foraging S. virgatus responded to 2-(E)-hexenal—an herbivore-associated plant volatile involved in indirect defense against herbivores. These findings indicate that S. virgatus may contribute to plant indirect defense and that a species\u27 response to specific odorants is linked with foraging mode. Future studies can elucidate how lizards use various compounds to locate prey and how these responses impact plant-herbivore interactions

Consequências genéticas da regeneração natural de espécies arbóreas em área antrópica, AC, Brasil.

O cedro (Cedrela odorata L.) e o ipê-amarelo (Tabebuia serratifolia Nichols.) são espécies arbóreas tropicais economicamente valiosas e que têm sido ameaçadas pela exploração madeireira predatória e pela fragmentação florestal. Ambas apresentam dispersão anemocórica e regeneram naturalmente em áreas de pastagem. Esse estudo comparou, para as duas espécies, a diversidade genética de indivíduos estabelecidos em pastagem e em floresta. Trinta indivíduos de ipê-amarelo foram genotipados com cinco locos isoenzimáticos e 54 de cedro, com quatro locos microssatélites. A diversidade genética foi elevada nas duas subpopulações. Para ipê-amarelo, a diversidade genética foi maior na pastagem. Para cedro, observou-se perda de alelos na pastagem (Â = 11,75 alelos/loco) em comparação à floresta (Â = 14,50). Além disso, 31% dos alelos de cedro foram exclusivos da floresta. Não houve divergência genética entre as subpopulações de ipê-amarelo, porém, para cedro, houve divergência significativa, embora baixa (2,2%). Os resultados mostraram que, para as duas espécies, a subpopulação da pastagem não passou por um gargalo genético severo. A colonização de áreas antrópicas mostrou-se eficiente, mas há necessidade de fluxo gênico contínuo, por sucessivas gerações, entre as áreas para restabelecer (cedro) e manter (ipê) os níveis de diversidade genética observados na área de vegetação primária

Scientific Performance of the ISDC Quick Look Analysis

The INTEGRAL Science Data Centre (ISDC) routinely monitors the Near Real Time data (NRT) from the INTEGRAL satellite. A first scientific analysis is made in order to check for the detection of new, transient or highly variable sources in the data. Of primary importance for this work is the Interactive Quick Look Analysis (IQLA), which produces JEM-X and ISGRI images and monitors them for interesting astrophysical eventsComment: 4 pages, 3 figures. Proceedings of 5th INTEGRAL Workshop: The INTEGRAL Universe, Munich, 16-20 February 2004. Accepted for publication in European Space Agency Special Publication 552. See paper for institute affiliation

METHODOLOGY FOR AUTOMOTIVE AIR-CONDITIONING CONTROL OPTIMIZATION USING ARTIFICIAL NEURAL NETWORKS

The transient nature of automotive air conditioning systems control is generally achieved through proportional–integral–derivative controllers (PID’s) parameters tunning. Due to the vast database available from decades of automotive manufacturers design and expertise, Artificial Neural Networks (ANN) might be able to identify underlying patterns to predict and properly tune the air-conditioning PID control systems under different thermal requirements. Recently, advances in computational capability have enabled compact embarked systems to rapidly solve complex, multi-variable sets of equations, thus allowing for ANN to promptly calculate tunning parameters and act upon PID controllers. As any new application, technical literature is still scarce. On this research, a coupled PID and 6-layers perceptron ANN system was devised, programmed and used to simulate how an air-conditioning system performance can be optimized through proportional–integral–derivative controllers tuning. This proposed setup response was then compared to a conventional heuristic PID tunning method (Ziegler Nichols) to demonstrate how ANN’s can more rapidly stabilize the system output