We have carried out magneto-absorption and magneto-photoluminescence experiments on micelle-suspended single-walled carbon nanotubes in magnetic fields up to 45 T. Chirality-assigned spectral peaks ...exhibit significant changes with increasing magnetic field, which can be quantitatively explained in terms of the theoretically predicted splittings and redshifts of the band edge due to the Aharonov–Bohm effect combined with the magnetic-field-induced alignment of the nanotubes.
The fabrication of reliable InP-based Geiger- mode avalanche photodiodes are described. Devices passivated with polyimide coated with silicon nitride have not degraded even while aging under more ...strenuous conditions than those used in fielded systems.
(1) Growth and nutrient relations of Carex aquatilis were examined in the field and in glasshouse-grown plants from five polygon microhabitats in wet meadow tundra at Barrow, Alaska. These habitats ...can occur within 1 m of each other, and differ greatly in soil moisture, availability of N and P and thaw depth. (2) Field-grown plants from these microhabitats differed between populations in above-ground weight per tiller, leaf-production rate, root:leaf weight ratio, rate of uptake of32P, and concentration of sugar, N and P in roots and rhizomes. Tissue concentrations of N and P were correlated with corresponding availability in the soil but not with plant size. There was a moderate positive correlation between soil moisture and plant size. (3) Carex aquatilis populations grown in the glasshouse with either no addition or moderate addition of phosphate showed no significant differences in plant size, but large differences in tissue-nutrient concentrations,32P-uptake kinetics and responsiveness to phosphorus availability. A strong effect of phosphorus stress on nitrogen and potassium metabolism was observed. Responsiveness of32P-uptake kinetics to changed conditions was inversely related to the degree of responsiveness in growth rate and mineral accumulation in the tissues. (4) These ecotypic differences among populations of Carex aquatilis are remarkable in view of the extreme rarity of reproduction by seed in the field, and the close proximity of the populations.
A model that simulates carbon (C) and nitrogen (N) cycles in terrestrial ecosystems is developed. The model is based on the principle that the responses of terrestrial ecosystems to changes in CO2, ...climate, and N deposition will encompass enzymatic responses, shifts in tissue stoichiometry, changes in biomass allocation among plant tissues, altered rates of soil organic matter turnover and N mineralization, and ultimately a redistribution of C and N between vegetation and soils. The model is a highly aggregated, process-based, biogeochemical model designed to examine changes in the fluxes and allocation of C and N among foliage, fine roots, stems, and soils in response to changes in atmospheric CO2 concentration, temperature, soil water, irradiance, and inorganic nitrogen inputs. We use the model to explore how changes in CO2 concentration, temperature, and N inputs affect carbon storage in two ecosystems: arctic tundra and temperate hardwood forest. The qualitative responses of the two ecosystems were similar. Quantitative differences are attributed to the initial distribution of C and N between vegetation and soils, to the amounts of woody tissue in the two ecosystems, and to their relative degree of N limitation. We conclude with a critical analysis of the model's strengths and weaknesses, and discuss possible future directions.
We report on \(J/\psi\) production from asymmetric Cu+Au heavy-ion collisions at \(\sqrt{s_{_{NN}}}\)=200 GeV at the Relativistic Heavy Ion Collider at both forward (Cu-going direction) and backward ...(Au-going direction) rapidities. The nuclear modification of \(J/\psi\) yields in Cu\(+\)Au collisions in the Au-going direction is found to be comparable to that in Au\(+\)Au collisions when plotted as a function of the number of participating nucleons. In the Cu-going direction, \(J/\psi\) production shows a stronger suppression. This difference is comparable in magnitude and has the same sign as the difference expected from shadowing effects due to stronger low-\(x\) gluon suppression in the larger Au nucleus. The relative suppression is opposite to that expected from hot nuclear matter dissociation, since a higher energy density is expected in the Au-going direction.
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