Strong color fields and heavy flavor production

The clustering of color sources provides a natural framework for soft partonic interactions producing strong color fields. We study the consequences of these color fields in the production of heavy flavor and the behavior of the nuclear modification factor.Comment: 11 pages, 7 figures, to appear in Physical Review

Evaluation of artificial feeds for shrimp (Penaeus monodon) production in brackishwater ponds

Abstract only.The experiment was conducted in fifteen 500-m2 brackishwater ponds to determine the response of Penaeus monodon juveniles fed with various artificial diets. Five treatments with three replicates each were: two commercial feeds containing 45% and 40% crude protein (treatments I and II), two experimental diets formulated to contain 35% crude protein (treatments III and IV) and control, without feeding (treatment V). Shrimp were fed twice daily at feeding rates based on shrimp consumption. Highest mean harvest weight was attained in treatment I (23.47 g) > III (19.25 g) > II (18.86 g) > IV (11.29 g) > V (9.27 g). Statistical analysis showed that differences in growth were significant at 5% probability level. However, growth in treatments I, II and III are comparable, also growth in treatments II, III and IV. Growth in treatments I, II, III and IV was significantly different from treatment V. Highest mean survival was attained in treatment III (91.82%) > I (88.93%) > II (86.95%) > IV (83.62%) V (82.62%). Statistical analysis showed no significant differences among treatments at 5% probability level. Projecting on a hectare basis, mean yield for each treatment was: I (628.37 kg) > II (496.35 kg) per crop in 120 days culture. Good yield was attributed to provision of formulated feeds, use of pumps in addition to tidal change for water exchange and control of predators, and pest eradication through proper pond preparation

Absolute single photoionization cross-sections of Br3+: Experiment and theory

Absolute single photoionization cross section measurements for Br3+ ions are reported in the photon energy range 44.79-59.54 eV at a photon energy resolution of 21 ±3 meV. Measurements were performed at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged-beams technique. Numerous resonance features in the experimental spectrum are assigned and their energies and quantum defect values are tabulated. The cross-section measurements are also compared with Breit-Pauli R-matrix calculations with suitable agreement over the photon energy range investigated. Analysis of the measured spectrum including Rydberg resonance series identifications produced a new emperical determination of the ionizational potential of Br3+ of 46.977 ± 0.050 eV, which is 805 meV lower than the most recently published value of 47.782 eV. This disparity between our determination and the earlier published value is similar to an 843 meV shift in the accepted ionization potential published for iso-electronic Se2+ as part of this same research program

Eutrofització dels rius d'Andorra

8 páginas, 4 figures.An analysis of the phosphorus increase in the watersheds of Andorra as a result of the increase of human population in the river banks is made. The greater concentrations in phosphorus are found in relation to the increase of population and also in some sampling stations in the highlands of this country. In high altitude the phosphorus concentrations are related to hotel and sport facilities. Also the influence of water catchements to power works are analized. In August the major stream, the Valira river, is dried in this catchement process in station 22 and until the time of return of water (station 14) the main river receives only wastewaters of two villages and water of minor tributaires. This means a great increase in the phosphorus concentration in waters in stations 15 and 16 (figs. 1 and 2). A modification in the composition of animal communities can be stated examining the macrofauna, especially insects, of river stones. There is a relationship between phosphorus concentration and the modification of communities. As a result of human population increase the lower part of Andorra is higly enriched in nutrients in August, especially in phosporus. A great quantity of phosphorus, estimated between 4 and 8 MT/month, leaves the Valira river in the sampling station 1.Peer reviewe

Atomic Processes in Planetary Nebulae and H II Regions

Spectroscopic studies of Planetary Nebulae (PNe) and H {\sc ii} regions have driven much development in atomic physics. In the last few years the combination of a generation of powerful observatories, the development of ever more sophisticated spectral modeling codes, and large efforts on mass production of high quality atomic data have led to important progress in our understanding of the atomic spectra of such astronomical objects. In this paper I review such progress, including evaluations of atomic data by comparisons with nebular spectra, detection of spectral lines from most iron-peak elements and n-capture elements, observations of hyperfine emission lines and analysis of isotopic abundances, fluorescent processes, and new techniques for diagnosing physical conditions based on recombination spectra. The review is directed toward atomic physicists and spectroscopists trying to establish the current status of the atomic data and models and to know the main standing issues.Comment: 9 pages, 1 figur

Cellular and Molecular Mechanisms of Pain

The nervous system detects and interprets a wide range of thermal and mechanical stimuli, as well as environmental and endogenous chemical irritants. When intense, these stimuli generate acute pain, and in the setting of persistent injury, both peripheral and central nervous system components of the pain transmission pathway exhibit tremendous plasticity, enhancing pain signals and producing hypersensitivity. When plasticity facilitates protective reflexes, it can be beneficial, but when the changes persist, a chronic pain condition may result. Genetic, electrophysiological, and pharmacological studies are elucidating the molecular mechanisms that underlie detection, coding, and modulation of noxious stimuli that generate pain

Extensão Supersimétrica do Modelo BF bidimensional e a quantização de laços.

Um dos grandes desafios da física nos últimos cinquenta anos tem sido a conciliação da Mecânica Quântica com a Relatividade Geral, numa teoria Quântica da Gravitação. Teoria que até hoje não foi encontrada, de forma concreta, devido a sua complexidade, sobretudo quando tratamos sistemas gravitação-matéria, e a falta de tecnologias que possam nos dar evidências experimentais. Mas, existem muitos modelos teóricos que procuram explicar esta teoria, entre os quais temos a Gravitação Quântica de Laços. Para entender e simplificar as dificuldades teoricas da Gravitação Quântica de Laços em 3+1 dimensões, estudamos modelos de dimensões mais baixas. Partindo do modelo topológico BF, discutimos nesta tese sistemas gravitação-matéria do espaço-tempo bidimensional, a través de extensões supersimétricas N = 1. Discutimos dois modelos: 1.) Num primeiro modelo, o grupo de calibre da teoria é dado pelo supergrupo super (anti-)de Sitter, S(A)dS, que é a extensão supersimétrica N = 1 do grupo de calibre (A)dS, a qual possue três geradores bosônicos e dois geradores fermiônicos. 2.) No segundo modelo acoplamos matéria, sendo guiados pela existência de uma supersimétria rígida (estudamos especificamente a gravitação num espaço Riemanniano com constante cosmológica positiva), onde os campos do modelo BF usual são expressos em termos de supercampos, como grupo de calibre sendo uma supersimetrização de SU(2). Neste caso particular quantizamos o modelo extendendo as técnicas usadas na Gravitação Quântica de Laços. Em ambos casos, discutimos a estrutura canônica do modelo, mostramos que a Hamiltoniana do modelo é completamente vinculada, bem como construimos quantidades invariantes de calibre (observáveis de Dirac)

Elliptic flow from color strings

It is shown that the elliptic flow can be successfully described in the color string picture with fusion and percolation provided anisotropy of particle emission from the fused string is taken into account. Two possible sources of this anisotropy are considered, propagation of the string in the transverse plane and quenching of produced particles in the strong color field of the string. Calculations show that the second source gives an overwhelming contribution to the flow at accessible energies.Comment: 23 pages, 11 figure

Chemical Abundances from the Continuum

The calculation of solar absolute fluxes in the near-UV is revisited, discussing in some detail recent updates in theoretical calculations of bound-free opacity from metals. Modest changes in the abundances of elements such as Mg and the iron-peak elements have a significant impact on the atmospheric structure, and therefore self-consistent calculations are necessary. With small adjustments to the solar photospheric composition, we are able to reproduce fairly well the observed solar fluxes between 200 and 270 nm, and between 300 and 420 nm, but find too much absorption in the 270-290 nm window. A comparison between our reference 1D model and a 3D time-dependent hydrodynamical simulation indicates that the continuum flux is only weakly sensitive to 3D effects, with corrections reaching <10% in the near-UV, and <2% in the optical.Comment: 10 pages, 5 figures, to appear in the proceedings of the conference A Stellar Journey, a symposium in celebration of Bengt Gustafsson's 65th birthday, June 23-27, 2008, Uppsal