On the Equation of State of Nuclear Matter in 158A GeV Pb+Pb Collisions

Within a hydrodynamical approach we investigate the sensitivity of single inclusive momentum spectra of hadrons in 158A GeV Pb+Pb collisions to three different equations of state of nuclear matter. Two of the equations of state are based on lattice QCD results and include a phase transition to a quark-gluon plasma. The third equation of state has been extracted from the microscopic transport code RQMD under the assumption of complete local thermalization. All three equations of state provide reasonable fits to data taken by the NA44 and NA49 Collaborations. The initial conditions before the evolution of the fireballs and the space-time evolution pictures differ dramatically for the three equations of state when the same freeze-out temperature is used in all calculations. However, the softest of the equations of state results in transverse mass spectra that are too steep in the central rapidity region. We conclude that the transverse particle momenta are determined by the effective softness of the equation of state during the fireball expansion.Comment: 4 pages, including 4 figures and 2 tables. For a PostScript file of the manuscript, you can also goto http://t2.lanl.gov/schlei/eprint.htm

Microscopic study of freeze-out in relativistic heavy ion collisions at SPS energies

The freeze-out conditions in the light (S+S) and heavy (Pb+Pb) colliding systems of heavy nuclei at 160 AGeV/$c$ are analyzed within the microscopic Quark Gluon String Model (QGSM). We found that even for the most heavy systems particle emission takes place from the whole space-time domain available for the system evolution, but not from the thin ''freeze-out hypersurface", adopted in fluid dynamical models. Pions are continuously emitted from the whole volume of the reaction and reflect the main trends of the system evolution. Nucleons in Pb+Pb collisions initially come from the surface region. For both systems there is a separation of the elastic and inelastic freeze-out. The mesons with large transverse momenta, $p_t$, are predominantly produced at the early stages of the reaction. The low $p_t$-component is populated by mesons coming mainly from the decay of resonances. This explains naturally the decreasing source sizes with increasing $p_t$, observed in HBT interferometry. Comparison with S+S and Au+Au systems at 11.6 AGeV/$c$ is also presented.Comment: REVTEX, 26 pages incl. 9 figures and 2 tables, to be published in the Physical Review

Pion and thermal photon spectra as a possible signal for a phase transition

We calculate thermal photon and neutral pion spectra in ultrarelativistic heavy-ion collisions in the framework of three-fluid hydrodynamics. Both spectra are quite sensitive to the equation of state used. In particular, within our model, recent data for $S+Au$ at $200$ AGeV can only be understood if a scenario with a phase transition (possibly to a quark-gluon plasma) is assumed. Results for $Au+Au$ at $11$ AGeV and $Pb+Pb$ at $160$ AGeV are also presented.Comment: 14 pages, 5 figures separate

Catalytic living ring-opening metathesis polymerization

In living ring-opening metathesis polymerization (ROMP), a transition-metal–carbene complex polymerizes ring-strained olefins with very good control of the molecular weight of the resulting polymers. Because one molecule of the initiator is required for each polymer chain, however, this type of polymerization is expensive for widespread use. We have now designed a chain-transfer agent (CTA) capable of reducing the required amount of metal complex while still maintaining full control over the living polymerization process. This new method introduces a degenerative transfer process to ROMP. We demonstrate that substituted cyclohexene rings are good CTAs, and thereby preserve the ‘living’ character of the polymerization using catalytic quantities of the metal complex. The resulting polymers show characteristics of a living polymerization, namely narrow molecular-weight distribution, controlled molecular weights and block copolymer formation. This new technique provides access to well- defined polymers for industrial, biomedical and academic use at a fraction of the current costs and significantly reduced levels of residual ruthenium catalyst

Flavor Production in Pb(160AGeV) on Pb Collisions: Effect of Color Ropes and Hadronic Rescattering

Collective interactions in the preequilibrium quark matter and hadronic resonance gas stage of ultrarelativistic nucleus-nucleus collisions are studied in the framework of the the transport theoretical approach RQMD. The paper reviews string fusion into color ropes and hadronic rescattering which serve as models for these interactions. Hadron production in central Pb(160AGeV) on Pb collisions has been calculated. The changes of the final flavor composition are more pronounced than in previous RQMD studies of light ion induced reactions at 200AGeV. The ratio of created quark pairs $s\bar{s}$/($u\bar{u}$+$d\bar{d}$) is enhanced by a factor of 2.4 in comparison to $pp$ results. Color rope formation increases the initially produced antibaryons to 3 times the value in the `NN mode', but only one quarter of the produced antibaryons survives because of subsequent strong absorption. The differences in the final particle composition for Pb on Pb collisions compared to S induced reactions are attributed to the hadronic resonance gas stage which is baryon-richer and lasts longer.Comment: 60 pages + 11 postscript figures (uuencoded and included

Characterization of microbial communities of biofilters by phospholipid fatty acid analysis and rRNA targeted oligonucleotide probes

The microbial community of a biofilter for waste gas treatment of an animal rendering plant was characterized by the analyses of the phospholipid fatty acids (PLFAs) of the filter material. For these analyses five samples of one filter were taken in intervals between one and two months. The main components of the PLFA profiles were straight chain saturated, monounsaturated and cyclopropyl fatty acids. Terminally branched and 10-methyl branched fatty acids were present in minor amounts. The structure and succession of the microbial community was interpreted by the presence and quantitative changes of diagnostic fatty acids. The stability of diagnostic fatty acids in relation to varying incubation parameters was tested for a number of bacterial isolates from biofilters representing different phylogenetic branches. For two samples, the data from the PLFA-analyses were compared with data obtained by hybridization with fluorescently labeled, rRNA-targeted oligonucleotide probes specific for the alpha-, beta- and gamma-subclass of the Proteobacteria, the Actinobacteria (Firmicutes with high G+C content) and the Firmicutes with low G+C content. These data indicated a dominating number of Proteobacteria (54% and 35% of DAPI-stained cells), in which the gamma-Proteobacteria represented the main fraction. Actinobacteria were detected in minor amounts, the number of Firmicutes with low G+C content was near the detection limit of the method. About half of the cells detected with a probe specific fur Bacteria did not hybridize with the probes specific for the alpha-, beta- and gamma subclass of the Pruteobacteria and the two subgroups of the Firmicutes. The results of both methods, the fluorescence in situ hybridization (FISH) and the PLFA analyses corresponded well and were best suited to confirm and complement each other

Anuros e lagartos associados a bromélias em um fragmento de Mata Atlântica no Estado de Pernambuco, Nordeste brasileiro

The Atlantic Forest is distinguished by its great diversity of organisms, high rate of endemism and for being one of the most threatened natural environments on the planet. Among the universe of organisms that inhabit this biome, we highlight the herpetofauna because of its high microenvironmental specificity and the Bromeliaceae for providing a natural microenvironment which can be used by several species, including frogs and lizards. This study aimed to record the richness, abundance, temporal and spatial distribution and specificity of frogs and lizards related to the bromeliad species found in the Estação Ecológica do Tapacurá, na Atlantic Forest fragment in Pernambucano. The bromeliads were visited weekly, and sampled twice during the day (morning and evening) during the rainy (April-June) and dry seasons (September-November 2008), with limited effort of 80 bromeliads per day, 40 per each day period, totaling 1.600 bromeliads analyzed, 800 per season. All plants were investigated by direct observation, manipulation of the leaves and, 3 per turn, by removing the plant. In addition to the registration of herpetofauna they were recorded species of bromeliads, their position on the leaf (base, middle, center) and in part of the leaf (proximal, medial, distal) where the specimens were. The animals were classified according to the use of bromeliads. We recorded 10 representatives of herpetofauna (9 frogs and 1 lizard) occupying two species of bromeliads: Portea leptantha and Hohenbergia hamageana. Six species (Dendropsophus elegans, Hypsiboas albomarginatus, Scinax eurydice, S. x-signatus, Elachistocleis ovalis and Bogertia lutzae) were considered bromelicolous and four (Ischnocnema ramagii, Dendropsophus decipiens, Scinax auratus and S. pachycrus) bromelicolous behavior. The animals were recorded mainly in the dry season, which was expected, since in this season bromeliads are one of the few reserves of water in the Atlantic Forests; in relation to day periods, the records were more frequent during the day of the dry season, without differences in the rainy season. In general the community analyzed showed no preference between the two species of bromeliads studied, although the species S. pachycrus has been found more in P. leptantha. The frogs used mainly the proximal portions of the leaves of the middle and the center of the bromeliads, mainly due to the microenvironment formed by the armpits and the central tank. The method of withdrawal of bromeliads was not effective, simply by direct observation and manipulation of the leaves to expose the armpits.A Mata Atlântica destaca-se por apresentar grande diversidade de organismos, alta taxa de endemismo e por ser um dos ambientes naturais mais ameaçados do planeta. Dentre o universo de organismos que habitam este bioma, destacam-se a herpetofauna, por possuir alta especificidade microambiental, e as Bromeliaceae, por oferecerem um microambiente singular que pode ser utilizado por várias espécies, como anuros e lagartos. Este trabalho objetivou registrar a riqueza, abundância, distribuição temporal e espacial e a especificidade dos anuros e lagartos em relação às espécies de bromélias encontradas na Estação Ecológica do Tapacurá, fragmento de Mata Atlântica pernambucano. As bromélias foram visitadas semanalmente, sendo amostradas duas vezes por dia (manhã e noite) durante a estação chuvosa (abril a junho) e seca (setembro a novembro) de 2008, com esforço limitado a 80 bromélias por dia, 40 por turno, totalizando 1.600 bromélias analisadas, 800 por estação. Todas as plantas foram investigadas por observação direta, manipulação das folhas e três por turno pela remoção da planta. Paralelamente ao registro da herpetofauna, foram registradas espécies de bromélias, posição da folha (base, meio, centro) e parte da folha (proximal, medial, distal) onde se encontravam espécimes. Os animais foram classificados de acordo com o uso das bromélias. Foram registrados 10 representantes da herpetofauna (9 anuros e 1 lagarto) ocupando duas espécies de bromélias: Portea leptantha e Hohenbergia hamageana. Seis espécies (Dendropsophus elegans, Hypsiboas albomarginatus, Scinax eurydice, S. x-signatus, Elachistocleis ovalis e Bogertia lutzae) foram consideradas bromelícolas eventuais e quatro (Ischnocnema ramagii, Dendropsophus decipiens, Scinax auratus e S. pachycrus) bromelícolas habituais. Os animais foram registrados predominantemente na estação seca, fato esperado, já que nesta estação as bromélias representam uma das poucas reservas de água em Matas Atlânticas Estacionárias. Com relação aos períodos do dia, os registros foram mais freqüentes no período diurno da estação seca, sem diferenças na estação chuvosa. No geral, a comunidade analisada mostrou-se sem preferência entre as duas espécies de bromélias estudadas, embora S. pachycrus tenha sido mais encontrada em P. leptantha. Os anuros utilizaram principalmente as porções proximais das folhas do meio e do centro das bromélias, devido principalmente ao microambiente formado pelas axilas e pelo tanque central. O método de retirada das bromélias não se mostrou eficaz, bastando a observação direta e manipulação das folhas para exposição das axilas