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Notes: Epitaxial growth techniques are used to impose in-plane magnetocrystalline anisotropy on a spin-polarized tunneling configuration. A Cu(100) buffer layer grown on a Si(100) substrate stabilizes epitaxial face-centered-cubic cobalt as one of the ferromagnetic electrodes. The negative magnetocrystalline constant of this metastable phase favors easy axes along Co 〈110〉 and, due to the single crystal nature of this layer, the coercivity is more than an order of magnitude larger than in the polycrystalline layers which form the second electrode. Our approach provides a way to access the high degree of spin polarization characteristic of the 3d transition metals. © 1999 American Institute of Physics.

Notes: We report an in situ study of the molecular-beam epitaxy growth and annealing of Cu(001) films grown on hydrogen-terminated Si(001) substrates, resulting in a promising approach to achieve smooth epitaxial morphology. Using correlated reflection high-energy electron diffraction and scanning tunneling microscopy data, we find a temperature interval below the onset of silicide formation where a dramatic smoothening of the epitaxial Cu surfaces occurs. Our measurements indicate that a reduction in roughness is possible in this regime because the annealing is controlled by lateral diffusion kinetics. © 2000 American Institute of Physics.

Notes: Monte Carlo calculations have been performed on two nominally athermal polymer/solvent mixtures to test molecular theories of mixing properties for these systems. We first used the incremental chemical potential concept to derive an equation of state in the spirit of the generalized Flory dimer theory, without resorting to the concept of excluded volume. The resulting generalized Flory dimer-like theory and a related model, statistical associating fluid theory, were tested against simulation results for the excess volume, excess Gibbs free energy and component activity coefficients. Good agreement was obtained between the statistical associating fluid theory and computer simulations for all properties studied. The generalized Flory dimer theory, when applied self-consistently, was also able to provide quantitative predictions for the thermodynamic properties of these mixtures. An important result that emerges from our calculations is that these polymer solutions behave ideally when examined on the basis of a "Flory-like'' reference state augmented by density effects. This asserts that the effects of molecular size disparity on system thermodynamics are properly captured by this approach. By contrast, the incompressible Flory approach fails to capture the dependence of activity coefficients on composition. © 1995 American Institute of Physics.

Notes: Summary. The relative susceptibility of six commercial sugarcane varieties to diuron previously described was confirmed in a second similar experiment. A significant correlation was found between the susceptibility of these varieties to 10 kg/ha diuron and their rooting characteristics. The more susceptible varieties were found to produce larger sett-roots and smaller shoot-roots, both of which also tended to be more easily injured by diuron. The root injury appeared as‘burnt’root tips resulting from contact with the layer of soil treated by the herbicide. The roots of tolerant varieties seemed to be immune to such injury and continued growing after penetrating the contaminated soil layers. Retarded plant growth appeared to result from the root injury.Uptake of diuron through shoot-roots of the susceptible variety F 156 resulted in 68·5% growth retardation. This damage was reduced by 15·5% if the plants were allowed to develop sett-roots from two-bud cutting. Death of the plant resulted when both root systems received the same dose of herbicide.

Notes: Summary. Six sugarcane varieties, N: Co 310, F146, F148, F152, F153 and F156, were Found in a field trial to differ in their tolerance to pre-emergence diuron with units of susceptibility of 100, 1·57, 1·20, 1·60, 11·30 and 8·07, and to pre-emergence atrazine of 0·75, 0·97, 0·59, 1·44, 2·42 and 0·78 respectively. Relative tolerance was assessed by subjecting each variety to seven rates of the herbicides in geometric series and calculating the F values for monthly measurements of the cane plants through the growing seasons of both the autumn-planting and ratoon crops. Units of susceptibility of each variety were obtained by transforming each mean F value into a proportion of the value for the standard variety N: Co 310. Any residual effect of the pre-emergence herbicides even at 20 kg/ha a.i. on cane plants was found to be small and insignificant after ploughing field ridges 5 months from cane-planting. With diuron, increasing the rate up to 10 kg/ha began to cause a significant reduction of sugar yield per hectare of cane, while atrazine gave such a reduction only with 20 kg/ha.Détermination de la résistance variétale de la canne à sucre à l'éigard du diuron et de l'atrazine appliqués en pré-levéeRésumé. Six variétés de canne à sucre, N:Co 310, F146, F148, F152, F153 et F156, ont manifesté dans un essai au champ des differences de résistance au diuron en pré-levée, avec des mesures de sensibilité de 1,00, 1,57, 1,20, 1,60, 11,30 et 8,07; pour l'atrazine en pré-levée, 0,75, 0,97, 0,59, 1,44, 2,42 et 0,78 respectivement. Une résistance relative fut établie en soumettant chaque variétéà sept doses des herbicides en progression géométrique et en calculant les valeurs de F pour des mensurations mensuelles des plantes de canne, durant la saison de croissance, à la fois pour les plantations d'automne et les repousses de cannes après recépage. Des unités dc sensibilité pour chaque variété furent obtenues en transformant chaque valeur moyenne de F en une proportion de la valeur pour la variety standard N:Co 310. L'effet résiduel des herbicides appliqués en pré-levée, même à 20 kg/ha (m.a.) sur les piantes de cannes fut faible et non significatif apres labour des billons à 5 mois de la plantation des cannes. Avec le diuron l'aecroissement de la dose jusqu’à 10 kg/ha provoqua un commencement de réduction significative de rendement en sucre par hectare, alors que l'atrazine provoqua une telle reduction seulement avec 20 kg/ha.Bestimmung der unterschiedlichen Toleranz von Zuckerrohrsorten gegenüber Diuron und Atrazin bei VorauflaufbehandlungZusammenfassung. Im Feldversuch wurde gefunden, dass die sechs Zuckerrohrsorten N: Co 310, F 146, F 148. F 152, F 153 und F 156 sich bei Vorauflaufbehandlung in ihrer Toleranz gegenüber Diuron und Atrazin unterscheiden. Die Suszeptibilitätseinheiten waren für Diuron 1,00, 1,57, 1,20, 1,60, 11,30 und 8,07, für Atrazin 0,75, 0,97, 0,59, 1,44, 2,42 und 0,78. Die Ermittlung der relativen Toleranz erfolgte, indem jede Sorte mit sieben Aufwandmengen der Herbizide in geometrischer Reihe behandelt wurde und die F-Werte für die monatlichen Messungen der Zuckerrohrpfianzen während der Vegetationsperiode berechnet wurden. Die Messungen erfolgten sowohl an im Herbst gepflanztem Zuckerrohr als auch an Wurzelschossen. Die Einheiten der Suszeptibilität für jede Sorte wurden durch Umformung eines jeden mittleren F-Wertes in einen auf die Standardsorte N: Co 310 bezogenen Relativwert erhalten. Die Wirkung von Rücks-tänden der Vorauflaufherbizide auf die Zuckerrohrpflanzen war selbst bei 20 kg/ha Wirkstoff nach Furchenpflügen 5 Monate nach der Auspflanzung gering und nicht signifikant.Diuron begann eine signifikante Minderung des Zuckerertrages pro Hektar hervorzurufen, wenn die Aufwandmenge bis auf 10 kg/ha gesteigert wurde, wahrend Atrazin erst bei 20 kg/ha eine solche Ertragsminderung verursachte.