Development of an apparatus for obtaining molecular beams in the energy range from 2 to 200 eV

The formation and detection of molecular beams obtained by charge exchange from a low-energy ion source is discussed. Dispersion in energy of the ion source was measured and problems concerning detection of neutral beams were studied. Various methods were used, specifically secondary electron emissivity of a metallic surface and ionization of a gas target with a low ionization voltage. The intensities of neutral beams as low as 10 eV are measured by a tubular electron multiplier and a lock-in amplifier

A statistical approach for predicting grassland degradation in disturbance-driven landscapes

Maintaining a land base that supports safe and realistic training operations is a significant challenge for military land managers which can be informed by frequent monitoring of land condition in relation to management practices. This study explores the relationship between fire and trends in tallgrass prairie vegetation at military and non -military sites in the Kansas Flint Hills. The response variable was the longterm linear trend (2001-2010) of surface greenness measured by MODIS NDVI using BFAST time series trend analysis. Explanatory variables included fire regime (frequency and seasonality) and spatial strata based on existing management unit boundaries. Several non-spatial generalized linear models (GLM) were computed to explain trends by fire regime and/or stratification. Spatialized versions of the GLMs were also constructed. For non-spatial models at the military site, fire regime explained little (4%) of the observed surface greenness trend compared to strata alone (7% - 26%). The non-spatial and spatial models for the non -military site performed better for each explanatory variable and combination tested with fire regime. Existing stratifications contained much of the spatial structure in model residuals. Fire had only a marginal effect on surface greenness trends at the military site despite the use of burning as a grassland management tool. Interestingly, fire explained more of the trend at the nonmilitary site and models including strata improved explanatory power. Analysis of spatial model predictors based on management unit stratification suggested ways to reduce the number of strata while achieving similar performance and may benefit managers of other public areas lacking sound data regarding land usage

In Practice: Teaching Environmental American Studies in a Time of Crisis: Decarbonizing the US History Survey: The Case of “Postwar Affluence”

I have been thinking a lot about environmental pedagogy in American studies, especially since I started teaching a third-year interdisciplinary course, Climate Change & Culture Wars, which focusses on the post-1970s US. I wanted to know more about how others are approaching the topic as we face up to looming climate and ecological collapse. University teachers and learners across disciplines are reckoning with it, but what's going on in American studies in Britain, and what can we learn from each other and from teachers elsewhere? How is the crisis impacting on the framing of our disciplinary fields and how are we incorporating its intellectual and practical demands into pedagogic spaces and syllabi

Nuclear Interactions of 400 GeV Protons in Emulsion

We report on 400 GeV proton-emulsion nucleus reactions and compare the results to hadron-nucleus reactions at smaller energies. In particular we present results on the emission of fast target protons (essentially grey track particles) and on their correlation with the number of collisions inside the nucleus, ν, with the number of charged evaporated particles (essentially black track particles) and with the number of pions produced (essentially shower particles). We observe that the main features of the 200¿400 GeV data are very similar. However, we find that the mean shower-particle multiplicity at 400 GeV is essentially higher than expected from the simple independent particle model prediction 〈ns〉 = 〈nch〉[1 + 0.5(〈ν〉 − 1)]. The shower particle multiplicities do not seem to follow a target mass dependence of the form 〈ns〉 = 〈nch〉 Aα with α = 0.14 or α = 0.19 as has been suggested in the literature. The pseudo-rapidity distribution shows limiting target and projectile fragmentation. The shower-particle multiplicity in the ¿central region¿ increases linearity with 〈ν〉 but faster than 0.5〈ν〉 times the corresponding multiplicity in pp reactions

Synthesis, characterization and antibacterial activity studies of new 2‑pyrral‑L‑amino acid Schif base palladium (II) complexes.

Three new 2-pyrral amino acid Schif base palladium (II) complexes were synthesized, characterized and their activity against six bacterial species was investigated. The ligands: Potassium 2-pyrrolidine-L-methioninate (L1), Potassium 2-pyrrolidine-L-histidinate (L2) and Potassium 2-pyrrolidine-L-tryptophanate (L3) were synthesized and reacted with dichloro(1,5- cyclooctadiene)palladium(II) to form new palladium (II) complexes C1, C2 and C3, respectively. 1 NMR, FTIR, UV–Vis,elemental analysis and conductivity measurements were used to characterize the products. The antibacterial activities of the compounds were evaluated against Gram-positive Staphylococcus aureus (S. aureus, ATCC 25923), methicillin-resistant Staphylococcus aureus (MRSA, ATCC 33591), Staphylococcus epidermidis (S. epidermidis, ATCC 12228) and Streptococcus pyogenes (S. pyogenes, ATCC 19615) and, gram-negative Pseudomonas aeruginosa (P. aeruginosa, ATCC 27853) and Klebsiella pneumoniae (K. pneumoniae, ATCC 13883) using the agar well difusion assay and microtitre plate serial dilution method. The palladium complexes were active against the selected bacteria with the imidazole ring containing complex C2 and indole heterocyclic ring containing complex C3 showing the highest activity

Vitesses et répartition spatiale des molécules « réfléchies» après impact sur une surface d'aluminium d'un jet moléculaire d'argon de haute énergie

The velocity measurement and the determination of the spatial distribution of " reflected " molecules after impact on a solid surface have been made experimentally. This experimental research has been carried out with a high energy molecular beam of argon impinging on a smooth surface of aluminium with an incidence angle of 60°. The energy of the argon molecules is about 2 100 eV. For this research, we have used an apparatus named " molecular gun ". With this apparatus, by charge exchange, we can obtain molecular beams having an energy that ranges from 50 to 5 000 eV and having an intensity from 10^11 to 5 x 10^13 molecules/cm3/s. We determine the flight time of the molecules with a special sampling apparatus to measure the velocity of impinging or reflected molecules. The error in the determination of the velocity curve distribution of incident molecules is about 1 %, For the " reflected " molecules, the précision is not so good ; it is of the order of a few per cent. The velocity measurement of " reflected " molecules shows that their speed dispersion is larger than that of incident molecules. The mean quadratic velocity v of " reflected" molecules is similar to U, the speed of impinging molecules. The ratio v/U varies in relation to the angle of the reflected direction and otherwise with the azimuthal angle of the plane of measurement. The ratio decreases when the reflected angle varies from 80° to — 80° and when the azimuthal angle increases. When we know the velocity of the " reflected " molecules, we can define exactly the spatial distribution of these molecules. The scattering pattern is elliptical and not circular as is predicted by the Knudsen law.La mesure des vitesses et la détermination de la répartition spatiale des molécules réfléchies, après impact sur une surface solide, ont été effectuées expérimentalement. Cette étude expérimentale a eu lieu dans le cas de jets moléculaires d'argon d'énergie voisine de 2 100 eV heurtant sous une incidence de 60° une surface polie constituée par de l'aluminium industriel. Pour cette étude on a utilisé un appareil appelé « canon moléculaire » et qui permet d'obtenir des jets moléculaires d'énergie comprise entre 50 et 5 000 eV, et des intensités comprises entre 10^11 et 5 × 10^13 molécules/cm2/s. Les vitesses des molécules incidentes ou réfléchies sont mesurées grâce à une méthode de temps de vol et en utilisant un appareil spécial d'échantillonnage. La courbe des vitesses incidentes est déterminée à 1 % près. Celle des molécules réfléchies est déterminée avec une précision plus faible, de l'ordre de quelques pour cent. Les résultats des mesures montrent que la vitesse v des molécules réfléchies a une dispersion beaucoup plus grande que celle, U, des molécules incidentes et que, d'autre part, la vitesse quadratique moyenne v est du même ordre de grandeur que U. Le rapport v/Uvarie en fonction de l'angle de la direction d'observation et d'autre part de l'angle azimutal du plan qui la contient. Ce rapport décroît lorsque l'angle d'observation varie de + 80° à — 80° et lorsque l'angle azimutal croît. Connaissant les vitesses des molécules réfléchies on peut déterminer la répartition spatiale exacte de ces molécules. Cette répartition montre qu'en coordonnées polaires la courbe représentative n'est pas un cercle tangent à la surface mais s'apparente à une ellipse dont le grand axe est voisin de la direction de réflexion spéculaire

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