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Notes: Using an ac Bridge technique, the resistance of thin-film (500 nm thick) Al and AlCu(5%) conductor stripes was monitored during high direct current density (1×106 A cm−2) stressing. The resistance was found to increase approximately linearly with time during stressing with a rate that was thermally activated. Surprisingly the activation energy varied considerably between nominally identical samples. After 3 h of stressing, the current was turned off and an exponential decay in the resistance was observed with a time constant of several hours. The decay was also thermally activated with an energy that varied from film to film. Both results suggest that the activation energy for resistance change during electrical stress can be significantly different in nominally identical films.

Notes: The activation energy for electromigration failure was determined for Al-4% Cu conductor stripes covered with polyimide. The activation energy was measured to be 0.88 eV, which is substantially higher than that measured previously for similar systems under glass. The difference in the activation energies is attributed to the possible presence of hydrogen in the Al–Cu grain boundaries.

Notes: A model was constructed for electromigration failure where both Fickian diffusion and mass transport due to the electromigration driving force are considered concurrently. The solution to the resulting diffusion equation yields a current exponent of 2 and an activation energy consistent with grain-boundary self-diffusion. A modification of the standard median time to failure equation first proposed by Black is suggested.

Notes: A scanning microscope stage has been developed for use at cryogenic temperatures. The stage uses a piezoelectric driving element and circular flexure hinges to achieve a slow scan travel of greater than 10 μm and a near-resonance travel of 100 μm while immersed in liquid helium at 4.2 K. The scanner has been operated inside a pressure cell in a dilution refrigerator, where it dissipates less than 150 μW of heat at 100 mK.

Notes: The room temperature coadsorption of CO and low coverages of K on Ni(110) has been studied with LEED, thermal desorption spectroscopy, and high resolution electron energy loss spectroscopy (HREELS). The results indicate that two distinct CO species coexist on the surface. A strongly perturbed species is observed that exhibits behavior commonly attributed to alkali-promoted surfaces: a higher thermal desorption temperature and a lower C–O stretch frequency of 1660 cm−1. A very weakly perturbed species is observed that behaves in nearly identical fashion to CO adsorbed on the clean surface. We propose that the appearance of the distinct alkali-promoted species in HREELS is the result of the formation of ordered surface structures of fixed alkali:CO stoichiometry, and suggest that this relationship may be a general one.

Notes: Abstract While citrus rootstocks differ in capacity for sodium and chloride ion exclusion, citrus scion species also vary in foliar sensitivity to NaCl salinisation. Of two common scions, ‘Lisbon’ lemon appears more sensitive, whereas ‘Valencia’ orange in less sensitive to leaf salt. In an attempt to explain this difference. ‘Valencia’ orange (Citrus sinensis [L.] Osbeck) and ‘Prior Lisbon’ lemon (Citrus limon [L.] Burm. F.) were budded to rootstocks known to differ in their ability to exclude sodium ions viz, the strong excluder Trifoliata (Poncirus trifoliata [L.] Raf.), and the weaker excluder Troyer citrange (C. sinensis×P. trifoliata); neither rootstock shows strong exclusion of chloride ions. Budded trees were held under a photosynthetic photon flux density of 450 μmol m 2 S 1 and watered with nutrient solution containing either 0 or 50 mol m 3 NaCl. Growth and photosynthetic responses were measured over 58 d following onset of salinization: salinity effects on leaf gas exchange were studied in relation to changes in leaf water status, compatible solutes and foliar content of sodium and chloride ions, over that same period.Once root-zone salinization began to influence leaf solutes (day 30 onwards), lemon showed a steeper increase in leaf chloride than occurred for orange. Although rootstock differences were without effect on this ingress of chloride ions for either scion, sodium ions were excluded from both scions to a larger extent by Trifoliata than by Troyer citrange.Carbon dioxide assimilation of scion foliage was reduced earlier and to a much larger extent by rootzone salinization in lemon than in orange. Furthermore, comparisons of CO2 assimilation in relation to leaf tissue solutes between scions (on either rootstock) showed stronger responses for both sodium and chloride ions in lemon than in orange. Faster ingress of chloride into lemon leaves was identified as the crucial factor which predisposed towards expression of that contrast between scions.Although contrasts between scions in photosynthetic responses to salinization matched a faster ingress of chloride into lemon than into orange leaves, the sharper photosynthetic response of ‘Prior Lisbon’ lemon to salinity was not solely attributable to higher concentrations of chloride ions (cell sap basis). A difference between species in subcellular compartmentation of the chloride ion under saline conditions was invoked.

Notes: : Four alternate schemes often used to deal with a water shortage are: physical rationing, lifeline with increasing block rates, rationing with resale, and pure price rationing. Each of these are analyzed using a supply-demand framework. The theoretical results are applied to a representative California water district and the welfare loss is calculated for a hypothetical 20 percent reduction in water supply for six different income classes. We find that reliance on schemes using the price mechanism in one form or another is clearly superior, in terms of welfare loss, as a means of dealing with a water shortage.