All existing transistors are based on the use of semiconductor junctions formed by introducing dopant atoms into the semiconductor material. As the distance between junctions in modern devices drops below 10 nm, extraordinarily high doping concentration gradients become necessary. Because of the laws of diffusion and the statistical nature of the distribution of the doping atoms, such junctions represent an increasingly difficult fabrication challenge for the semiconductor industry. Here, we propose and demonstrate a new type of transistor in which there are no junctions and no doping concentration gradients. These devices have full CMOS functionality and are made using silicon nanowires. They have near-ideal subthreshold slope, extremely low leakage currents, and less degradation of mobility with gate voltage and temperature than classical transistors.

Ocean colour data from the NASA Seaviewing Wide Field-of-view Sensor (SeaWiFS) was used to estimate chlorophyll a concentration around New Zealand on a monthly basis between September 1997 and May 2000. The performance of the SeaWiFS chlorophyll a algorithm (OC4v4) was investigated by comparing in situ measurements of the underwater light field with measurements of phytoplankton pigment concentration by High Performance Liquid Chromatography. The algorithm performed well for chlorophyll a concentrations below 0.6 mg m-3 but overestimated by a factor of two or more at higher concentrations. The average chlorophyll a concentration for New Zealand Exclusive Economic Zone was calculated as an indication of the overall productivity of the region and varied between 0.26 and 0.43 mg m-3 with no obvious relationship to the Southern Oscillation Index. New †

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Accurate estimation of the greenhouse gas (GHG) mitigation potential of bioenergy crops requires the integration of a significant component of spatially varying information. In particular, crop yield and soil carbon (C) stocks are variables which are generally soil type and climate dependent. Since gaseous emissions from soil C depend on current C stocks, which in turn are related to previous land management it is important to consider both previous and proposed future land use in any C accounting assessment. We have conducted a spatially explicit study for England and Wales, coupling empirical yield maps with the RothC soil C turnover model to simulate soil C dynamics. We estimate soil C changes under proposed planting of four bioenergy crops, Miscanthus (Miscanthus  giganteus), short rotation coppice (SRC) poplar (Populus trichocarpa Torr. & Gray  P. trichocarpa, var. Trichobel), winter wheat, and oilseed rape. This is then related to the former land use -arable, pasture, or forest/seminatural, and the outputs are then assessed in the context of a life cycle analysis (LCA) for each crop. By offsetting emissions from management under the previous land use, and considering fossil fuel C displaced, the GHG balance is estimated for each of the 12 land use change transitions associated with replacing arable, grassland, or forest/seminatural land, with each of the four bioenergy crops. Miscanthus and SRC are likely to have a mostly beneficial impact in reducing GHG emissions, while oilseed rape and winter wheat have either a net GHG cost, or only a marginal benefit. Previous land use is important and can make the difference between the bioenergy crop being beneficial or worse than the existing land use in terms of GHG balance.

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