Novel electrical switching behaviour and logic in carbon nanotube Y-junctions

Carbon-nanotube-based electronics offers significant potential as a nanoscale alternative to silicon-based devices for molecular electronics technologies. Here, we show evidence for a dramatic electrical switching behaviour in a Y-junction carbon-nanotube morphology. We observe an abrupt modulation of the current from an on- to an off-state, presumably mediated by defects and the topology of the junction. The mutual interaction of the electron currents in the three branches of the Y-junction is shown to be the basis for a potentially new logic device. This is the first time that such switching and logic functionalities have been experimentally demonstrated in Y-junction nanotubes without the need for an external gate. A class of nanoelectronic architecture and functionality, which extends well beyond conventional field-effect transistor technologies, is now possible.     

Higher US crop prices trigger little area expansion so marginal land for biofuel crops is limited

By expanding energy biomass production on marginal lands that are not currently used for crops, food prices increase and indirect climate change effects can be mitigated. Studies of the availability of marginal lands for dedicated bioenergy crops have focused on biophysical land traits, ignoring the human role in decisions to convert marginal land to bioenergy crops. Recent history offers insights about farmer willingness to put non-crop land into crop production. The 2006–09 leap in field crop prices and the attendant 64% gain in typical profitability led to only a 2% increase in crop planted area, mostly in the prairie states. At this rate, a doubling of expected profitability from biomass crops would expand cropland supply by only 3.2%. Yet targets for cellulosic ethanol production in the US Energy Independence and Security Act imply boosting US planted area by 10% or more with perennial biomass crops. Given landowner reluctance to expand crop area with familiar crops in the short run, large scale expansion of the area in dedicated bioenergy crops will likely be difficult and costly to achieve.     

Mass transfer of chlorobenzene in concentrated sulfuric acid

Mass transfer of chlorobenzene in sulfuric acid is very important in the nitration of chlorobenzene by mixed acid. This article presents the determination of mass transfer coefficient at high-concentrations of sulfuric acid at 298 K and 313 K at 2π rad/s and 4π rad/s impeller speeds. The experiments were carried out under flat-interface conditions in an unbaffled glass reactor of 10 cm diameter and 1 dm³ capacity. A glass stirrer with two paddle-type impellers was employed for stirring. The upper paddle stirred the organic phase and the lower paddle stirred the aqueous phase. High mass transfer coefficients were obtained at high-concentrations of sulfuric acid. Dynamic light scattering of the aqueous phase revealed that a dispersion of chlorobenzene spontaneously formed in sulfuric acid, which is believed to be the main factor behind the high mass transfer coefficient. NMR analysis of the aqueous phase showed that no chemical reaction occurred at 298 K and 313 K, but some amount of 4-chlorobenzenesulfonic acid formed at 323 K. The high mass transfer coefficient is expected to result in high yield of chloronitrobenzenes at moderate temperatures and low stirring speeds.     

Nutritional factors and colon cancer

During the last 2 decades, substantial progress has been made in understanding the relationship between dietary constituents and the development of colon cancer in man. Unlike studies of cancer among smokers and nonsmokers, nutritional epidemiologic studies are confronted with the inherent difficulty of assessing reasonably precise exposures. The lack of consistency between international correlation studies and case‐control studies does not necessarily negate a dietary etiology of colon cancer because these inconsistencies may have arisen, at least in part, from methodological limitations. Some of these deficiencies in epidemiological studies of diet and cancer have been corrected; recent case‐control studies demonstrated that high dietary fat is a risk factor for colon cancer development and that an overall increase in intake of foods high in fiber might decrease the risk for colon cancer. The results of epidemiologic studies may be assumed to present conservative estimates of the true risk for cancer associated with diet. The populations with high incidences of colon cancer are characterized by high consumption of dietary fat, which may be a risk factor in the absence of factors that are protective, such as whole‐grain cereals and of other high fiber. Laboratory‐animal model studies have shown that certain dietary lipids and fibers influence tumorigenesis in the colon. The data of metabolic epidemiological and laboratory‐animal model studies are sufficiently convincing with respect to the enhancement of colon cancer by type of fat and protection by certain dietary fibers.