RESUMO
E896 has measured Lambda production in 11.6A GeV/c Au-Au collisions over virtually the whole rapidity phase space. The midrapidity p(t) distributions have been measured for the first time at this energy and appear to indicate that the Lambda hyperons have different freeze-out conditions than protons. A comparison with the relativistic quantum molecular dynamics model shows that while there is good shape agreement at high rapidity the model predicts significantly different slopes of the m(t) spectra at midrapidity. The data, where overlap occurs, are consistent with previously reported measurements.
RESUMO
Visual system anomalies in albino mammals are generally seen to be caused by a lack of retinal pigment and misrouting of retinofugal optic fibers. This study shows that the central visual system of white zebra finches is physiologically different from normally colored (wild type) birds, although the eye pigmentation and the retinofugal projection appear to be normal. Ipsilaterally evoked potentials in our white birds are enhanced in comparison to wild type birds, whereas in albino mammals the ipsilateral component of visually evoked potentials is reduced. Picrotoxin-induced blockade of inhibitory synapses in the ectostriatum reveals remarkable differences between wild type and white zebra finches. In wild type zebra finches, a significant shift of ipsilateral to contralateral stimulus response ratios is observed. However, there is no detectable shift in the white morph. The data suggest that inhibition of ipsilateral stimulus processing, as observed in wild type zebra finches, is significantly reduced in the white morph. Our results indicate that the effects observed in white zebra finches cannot be explained by the theories that have been developed for albinotic animals. We assume that in white zebra finches a genetic defect, which causes the white plumage, is coupled with the demonstrated deviations of inhibitory mechanisms in the central visual system.
Assuntos
Aves/genética , Dominância Cerebral/genética , Plumas , Transmissão Sináptica/genética , Visão Ocular/genética , Vias Visuais/fisiologia , Animais , Mapeamento Encefálico , Dominância Cerebral/fisiologia , Potenciais Evocados Visuais/genética , Potenciais Evocados Visuais/fisiologia , Genes Recessivos/genética , Fenótipo , Retina/anatomia & histologia , Retina/fisiologia , Especificidade da Espécie , Transmissão Sináptica/fisiologia , Visão Ocular/fisiologia , Vias Visuais/anatomia & histologiaRESUMO
The Transport Collaboration, consisting of researchers from institutions in France, Germany, Italy and the USA, has established a program to make new measurements of nuclear interaction cross sections for heavy projectiles (Z > or = 2) in targets of liquid H2, He and heavier materials. Such cross sections directly affect calculations of galactic and solar cosmic ray transport through matter and are needed for accurate radiation hazard assessment. To date, the collaboration has obtained data using the LBL Bevalac HISS facility with 20 projectiles from 4He to 58Ni in the energy range 393-910 MeV/nucleon. Preliminary results from the analysis of these data are presented here and compared to other measurements and to cross section prediction formulae.
Assuntos
Radiação Cósmica , Bases de Dados Factuais , Física Nuclear , Aceleradores de Partículas , França , Alemanha , Cooperação Internacional , Itália , Espectrometria de Massas , Radiação Ionizante , Estados UnidosRESUMO
Anatomical data suggest that visual information from the thalamofugal pathway contributes to visual processing in the tectofugal pathway. We addressed the question of the functionality of anatomically described connections to the visual system of a laterally eyed bird, the zebra finch. The study shows the contribution of visual wulst efferents, to visual processing in the ectostriatum by recordings of visually evoked slow field potentials. Suppression of visual wulst activity resulted in a selective reduction of distinct potential components in contralaterally evoked slow field potentials. A clear reduction was observed in the maximum amplitude of short latency components in the negative wave. Long latency components of the negative wave and the entire positive wave of the contralaterally flash evoked potentials were almost abolished. Ipsilateral visual evoked potentials (VEPs) were not significantly affected. Cooling and spreading depression of the optic tectum resulted in a uniform amplitude reduction of the negative wave. The positive wave was almost abolished. Ipsilateral VEPs disappeared completely during suppression of optic tectum activity. The results showed that the visual wulst has a significant, most likely facilitatory, influence on the processing of contralateral visual information in the ectostriatum. Ipsilateral stimulus processing was partly independent from visual wulst activity. A model for thalamo- and tectofugal connectivity in the ectostriatum is suggested.
