Simulations of quantum dynamics with fermionic phase-space representations using numerical matrix factorizations as stochastic gauges

The Gaussian phase-space representation can be used to implement quantum dynamics for fermionic particles numerically. To improve numerical results, we explore the use of dynamical diffusion gauges in such implementations. This is achieved by benchmarking quantum dynamics of few-body systems against independent exact solutions. A diffusion gauge is implemented here as a so-called noise-matrix, which satisfies a matrix equation defined by the corresponding Fokker--Planck equation of the phase-space representation. For the physical systems with fermionic particles considered here, the numerical evaluation of the new diffusion gauges allows us to double the practical simulation time, compared with hitherto known analytic noise-matrices. This development may have far reaching consequences for future quantum dynamical simulations of many-body systems

Sowing date effects on timing of growth stages, yield and oil content of potential biodiesel crops

Oilseed rape (Brassica napus) is the major temperate crop producing biodiesel. Management of nitrogen applications and monitoring of pests and diseases in oilseed crops overseas relies heavily on correct identification of crop growth stages. In New Zealand, other crops besides oilseed rape are being trialled for biodiesel production including brown mustard (Brassica juncea) and camelina or false flax (Camelina sativa), which also belongs to the Crucifereae family. Together with yield evaluation this study was designed to investigate whether growth stages for oilseed rape were similar to these other potential biodiesel crops. The times from emergence to stem elongation, 50% flowering and final harvest were recorded in the 2010-11 season across four sowings dates on three species in a trial at Lincoln University near Christchurch, New Zealand. All species took different periods of time to reach the four growth stages measured. The time to reach a certain growth stage varied considerably more in the two autumn sowings, but much less in the spring sowings for all species. Oilseed rape out yielded the other crop species at all sowings in seed yield and oil content, but took longer to reach full maturity. Oilseed rape yielded an average of 2.4 t seed/ha with 42% oil content. Brown mustard and camelina yielded an average just over 1 t seed/ha, with 30 and 35% oil content respectively

Sonication assisted gold deposition on multiwall carbon nanotubes

Gold was successfully deposited on multiwall carbon nanotubes (MWNTs). It was achieved by applying a gold colloid stabilised by [tetrakis(hydroxymethyl)phosphonium chloride] (THPC) surfactant and ultrasonic irradiation during preparation. By controlling the quantity of gold and optimising sonication time up to 50 wt% gold could be deposited on MWNTs. (C) 2003 Elsevier Science B.V. All rights reserved.status: publishe