Evidence of the dominant production mechanism of ammonia in a hydrogen plasma with parts per million of nitrogen

Absolute ground state atomic hydrogen densities were measured, by the utilization of two-photon absorption laser induced fluorescence, in a low-pressure electron cyclotron resonance plasma as a function of nitrogen admixtures - 0 to 5000 ppm. At nitrogen admixtures of 1500 ppm and higher, the spectral distribution of the fluorescence changes from a single Gaussian to a double Gaussian distribution; this is due to a separate, nascent contribution arising from the photolysis of an ammonia molecule. At nitrogen admixtures of 5000 ppm, the nascent contribution becomes the dominant contribution at all investigated pressures. Thermal loading experiments were conducted by heating the chamber walls to different temperatures; this showed a decrease in the nascent contributions with increasing temperature. This is explained by considering how the temperature influences recombination coefficients, and from which, it can be stated that the Langmuir-Hinshelwood recombination mechanism is dominant over the Eley-Rideal mechanism

TAU-PAIR PRODUCTION VIA PHOTON-PHOTON COLLISIONS AT LEP

We point out that the cross-section for the process $e^+ e^- \to e^+ e^- \tau^+ \tau^-$ at LEP is large enough to allow for a study of the anomalous electromagnetic couplings of the $\tau$ lepton. We show that the present bounds on the magnetic dipole moment can be improved and that competitive bounds can be obtained for the electric dipole moment using the data taken from 1992 to 1994. Finally, we briefly discuss the improvements that can be obtained at LEP II.Comment: 9 pages, latex, 2 figure

Search for TeV Strings and New Phenomena in Bhabha Scattering at LEP2

A combined analysis of the data on Bhabha scattering at centre-of-mass energies 183 and 189 GeV from the LEP experiments ALEPH, L3 and OPAL is performed to search for effects of TeV strings in quantum gravity models with large extra dimensions. No statistically significant deviations from the Standard Model expectations are observed and lower limit on the string scale M_S = 0.631 TeV at 95 % confidence level is derived. The data are used to set lower limits on the scale of contact interactions ranging from 4.2 to 16.2 TeV depending on the model. In a complementary analysis we derive an upper limit on the electron size of 2.8 x 10^{-19} m at 95 % confidence level.Comment: 10 pages, 1 table, 3 figure

Origem, disseminação, morfologia e fenologia.

Origem e disseminação; Morfologia: Semente, Talo e coroa, Folha, Flor, Desenvolvimento floral e polinização, Fruto; Fenologi

Can We Observe Weak Anomalous Couplings of Heavy Quarks Through Three Jet Events?

The rates and corresponding jet distributions for the decay $Z\to b\bar bg$ and the process $e^+e^-\to t\bar tg$ may be sensitive to anomalous dipole-like couplings of heavy quarks to the photon and $Z$. In the $b$-quark case, after updating our previous analysis on the constraints imposed by current experiments on $Zb\bar b$ anomalous couplings, we show that the variation of these couplings within their presently allowed ranges leads to rather minor modifications to the Standard Model expectations for $Z\to b\bar bg$ observables. In the $t$-quark case, significant deviations from the Standard Model predictions for $t\bar tg$ production at the Next Linear Collider are possible.Comment: 26 pages with 9 embedded figures; gzipped, uuencoded postscript file. To obtain a copy of this paper send e-mail to [email protected]

Superação de dormência em sementes de Paspalum dilatatum Poir biótipo virasoro pelo uso de ácido sulfúrico.

Esse trabalho tem por objetivo avaliar a superação de dormência pela escarificação química utilizando ácido sulfúrico em diferentes tempos de exposição.Claudia Cristina Gulias Gomes, editora técnica

Avaliação de genótipos de Dactylis glomerata na região da Campanha gaúcha.

A espécie Dactylis glomerata é uma gramínea forrageira de crescimento cespitoso e hibernal sendo uma alternativa interessante para períodos de escassez alimentar dos rebanhos Sul-brasileiros por apresentar elevada produção de forragem e de boa qualidade nos meses de outono e inverno.Claudia Cristina Gulias Gomes, editora técnica

Avaliação de genótipos de aveia preta na Região da Campanha gaúcha.

Objetivo de avaliar a produção de matéria seca de diferentes linhagens de aveia preta (Avena strigosa Schreb), a fim de identificar genótipos promissores para melhoramento genético e prever futuro lançamento de cultivares no mercado.Zootec

Efeito de regimes de cortes sob a produção de sementes de trigo duplo propósito no sul do RS.

Número especial. Trabalho 438. Edição dos Resumos do 19º Congresso Brasileiro de Sementes, Foz do Iguaçu, set. 2015