Xi and AntiXi production in Pb+Pb collisions at 40 AGeV at CERN SPS

First results on the production of Xi and AntiXi hyperons in Pb+Pb interactions at 40 AGeV are presented. The AntiXi/Xi ratio at midrapidity is studied as a function of collision centrality. The ratio shows no significant centrality dependence within statistical errors; it ranges from 0.07 to 0.15. The AntiXi/Xi ratio for central Pb+Pb collisions increases strongly with the collision energy.Comment: 6 pages, 6 figures, proceedings of SQM03, to be published in Journal of Physics G; V2: changes in table 1 and figure

Identification of a cell population model for algae growth processes

The growth process of a Chlamydomonas reinhardtii cell population is modelled with experimental data obtained in a batch reactor. To describe the growth process of this culture, the Droop model, extended by cell population balance model, is considered. On the basis of available measurements and the mathematical model, an optimization problem is defined in order to determine the kinetic parameter values for the growth functions of the Droop model and the cell division parameters of the cell population balance model

FunGrim: a symbolic library for special functions

We present the Mathematical Functions Grimoire (FunGrim), a website and database of formulas and theorems for special functions. We also discuss the symbolic computation library used as the backend and main development tool for FunGrim, and the Grim formula language used in these projects to represent mathematical content semantically

Evaluation of pelleting diets to broilers

The processing of diets means change the structure of an ingredient in natural state to achieve the maximum potential nutrition, to improve the performance of animals. The more processing plants used in animal feed are the expansion, extrusion, and mainly the pelleting. The process of pellet is an agglomeration of particles ground of an ingredient or a mixture of ingredients, through mechanical processes in combination with humidity, pressure and heat, occurring any changes in the structure of food. Among the key processes operated by industry, the pelleting is the most used. Literature reviews shows, the main benefits of pelleting are to improve the digestibility of nutrients, increasing the feed intake, decreasing the use energy of maintenance, reduce the waste of feed for poultry and reduce contamination by microorganisms in the diet. The disadvantages are involved mainly with the high cost of equipments, increase use of electrical energy, carcasses more fat and increase mortality. However, a badly pelleting or badly managed by the factory as far as poultry houses, can cause to damage to the increase in the concentration of disaggregate particles (fines). When there is a concentration of fines high, the benefits of pelleting are equalized with relation the mashed diets, making the process of pelleting infeasible.  Processar um alimento significa alterar a estrutura dos ingredientes em seu estado natural para alcançar o seu máximo potencial nutricional, objetivando melhorar o desempenho dos animais. Os processamentos mais utilizados nas fábricas de rações são a expansão, a extrusão, e principalmente a peletização. O processo de peletização consiste em uma aglomeração de partículas moídas de um ingrediente ou de uma mistura de ingredientes, por meio de processos mecânicos em combinação com umidade, pressão e calor, fazendo com que ocorram mudanças na estrutura dos alimentos. Na literatura, as principais vantagens da peletização são de melhorar a digestibilidade de nutrientes, aumentar o consumo de ração, reduzir o gasto de energia de mantença, diminuir o desperdício da ração pelas aves e reduzir a contaminação por microorganismos na ração. As desvantagens estariam envolvidas principalmente com o alto custo dos equipamentos, maior gasto de energia elétrica, carcaças com maior teor de gordura e maior taxa de mortalidade. Porém, uma ração mal peletizada ou mal manejada da indústria até o aviário, pode acarretar em prejuízos devido ao aumento da concentração de partículas desagregadas (finos). Quando existe uma concentração de finos elevada, os benefícios da peletização são igualados em relação às dietas fareladas, tornando o processo de peletização inviável.

The Shape and Figure Rotation of NGC 2915's Dark Halo

NGC 2915 is a blue compact dwarf galaxy with a very extended HI disk showing a short central bar and extended spiral arms, both reaching far beyond the optical component. We use Tremaine & Weinberg (1984) method to measure the pattern speed of the bar from HI radio synthesis data. Our measurements yield a pattern speed of 0.21+/-0.06 km/s/arcsec (8.0+/-2.4 km/s/kpc for D=5.3 Mpc), in disagreement with the general view that corotation in barred disks lies just outside the end of the bar, but consistent with recent models of barred galaxies with dense dark matter halos. Our adopted bar semi-length puts corotation at more than 1.7 bar radii. The existence of the pattern is also problematic. Because NGC 2915 is isolated, interactions cannot account for the structure observed in the HI disk. We also demonstrate that the low observed disk surface density and the location of the pseudo-rings make it unlikely that swing amplification or bar-driven spiral arms could explain the bar and spiral pattern. Based on the similarity of the dark matter and HI surface density profiles, we discuss the possibility of dark matter distributed in a disk and following closely the HI distribution. The disk then becomes unstable and can naturally form a bar and spiral pattern. However, this explanation is hard to reconcile with some properties of NGC 2915. We also consider the effect of a massive and extended triaxial dark matter halo with a rotating figure. The existence of such halos is supported by CDM simulations showing strongly triaxial dark halos with slow figure rotation. The observed structure of the HI disk can then arise through forcing by the rotating triaxial figure. We associate the measured pattern speed in NGC 2915 with the figure rotation of its dark halo.Comment: 37 pages, including 8 figures and 2 tables (AASTeX, aaspp4.sty). Fig.1 and 2 available as jpg. Accepted for publication in The Astronomical Journal. Online manuscript with PostScript figures available at: http://www.strw.leidenuniv.nl/~bureau/pub_list.htm

Determination of phthalates in water using fiber introduction mass spectrometry

Fiber introduction mass spectrometry (FIMS) - a direct coupling of SPME and MS - using selective ion monitoring (SIM) was used to detect and quantify dimethylphthalate (DMP), diethylphthalate (DEP) and dipropylphthalate (DPP) in mineral water. In FIMS, a chromatographic silicone septum is the only barrier between ambient and the high-vacuum mass spectrometer, permitting direct introduction of the SPME fiber into the ionization region of the equipment. After their thermal desorption and ionization and dissociation, the extracted phthalates are detected and quantitated by MS. Three types of SPME fibers were screened for best analyte sorption/desorption behaviors: 100 mum polydimethylsiloxane ( PDMS), 65 mum polydimethylsiloxane/divinylbenzene (PDMS/DVB) and 65 mum Carbowax/divinylbenzene (CW/DVB). The PDMS/DVB and CW/DVB fibers were then evaluated for precision, and quantitative figures of merit were assessed for extractions using the PDMS/DVB fiber, which displayed the best overall performance. FIMS with the PDMS/DVB fiber allows simple extraction and MS detection and quantitation of DMP in water with good linearity and precision, and at concentrations as low as 3.6 mug L-1. The LD and LQ of FIMS are below the maximum phthalate concentration allowed by the USEPA for drinking water ( 6 mug L-1).130218819