Simultaneous calculation of the helical pitch and the twist elastic constant in chiral liquid crystals from intermolecular torques

We present a molecular simulation method that yields simultaneously the equilibrium pitch wave number q and the twist elastic constant K2 of a chiral nematic liquid crystal by sampling the torque density. A simulation of an untwisted system in periodic boundary conditions gives the product K2q; a further simulation with a uniform twist applied provides enough information to separately determine the two factors. We test our new method for a model potential, comparing the results with K2q from a thermodynamic integration route, and with K2 from an order fluctuation analysis. We also present a thermodynamic perturbation theory analysis valid in the limit of weak chirality

Determination of some dominant parameters of the global dynamic sea surface topography from GEOS-3 altimetry

The 1977 altimetry data bank is analyzed for the geometrical shape of the sea surface expressed as surface spherical harmonics after referral to the higher reference model defined by GEM 9. The resulting determination is expressed as quasi-stationary dynamic SST. Solutions are obtained from different sets of long arcs in the GEOS-3 altimeter data bank as well as from sub-sets related to the September 1975 and March 1976 equinoxes assembled with a view to minimizing seasonal effects. The results are compared with equivalent parameters obtained from the hydrostatic analysis of sporadic temperature, pressure and salinity measurements of the oceans and the known major steady state current systems with comparable wavelengths. The most clearly defined parameter (the zonal harmonic of degree 2) is obtained with an uncertainty of + or - 6 cm. The preferred numerical value is smaller than the oceanographic value due to the effect of the correction for the permanent earth tide. Similar precision is achieved for the zonal harmonic of degree 3. The precision obtained for the fourth degree zonal harmonic reflects more closely the accuracy expected from the level of noise in the orbital solutions

Screening properties of Gaussian electrolyte models, with application to dissipative particle dynamics

We investigate the screening properties of Gaussian charge models of electrolyte solutions by analysing the asymptotic behaviour of the pair distribution functions. We use a combination of Monte-Carlo simulations with the hyper-netted chain integral equation closure, and the random phase approximation, to establish the conditions under which a screening length is well defined and the extent to which it matches the expected Debye length. For practical applications, for example in dissipative particle dynamics, we are able to summarise our results in succinct rules-of-thumb which can be used for mesoscale modeling of electrolyte solutions. We thereby establish a solid foundation for future work, such as the systematic incorporation of specific ion effects.Comment: 9 pages, 9 figures, 1 table, RevTeX4-

Comparison of impact results for several polymeric composites over a wide range of low impact velocities

Static indentation, falling weight, and ballistic impact tests were conducted in clamped plates made of AS4/3501-6 and IM7/8551-7 prepreg tape. The transversely isotropic plates were nominally 7-mm thick. Pendulum and ballistic tests were also conducted on simply supported plates braided with Celion 12000 fibers and 3501-6 epoxy. The 20 degree braided plates were about 5-mm thick. The impactors had spherical or hemispherical shapes with a 12.7 mm diameter. Residual compression strength and damage size were measured. For a given kinetic energy, damage size was least for IM7/8551-7 and greatest for the braided material. Strengths varied inversely with damage size. For a given damage size, strength loss as a fraction of original strength was least for the braided material and greatest for AS4/3501-6 and IM7/8551-7. Strength loss for IM7/8551-7 and AS4/3501-6 was nearly equal. No significant differences were noticed between damage sizes and residual compression strengths for the static indentation, falling weight, and ballistic tests of AS4/3501-6 and IM7/8551-7. For the braided material, sizes of damage were significantly less and compression strengths were significantly more for the falling weight tests than for the ballistic tests

Conscious monitoring and control (reinvestment) in surgical performance under pressure.

Research on intraoperative stressors has focused on external factors without considering individual differences in the ability to cope with stress. One individual difference that is implicated in adverse effects of stress on performance is "reinvestment," the propensity for conscious monitoring and control of movements. The aim of this study was to examine the impact of reinvestment on laparoscopic performance under time pressure

Magneto-Transport in the Two-Dimensional Lorentz Gas

We consider the two-dimensional Lorentz gas with Poisson distributed hard disk scatterers and a constant magnetic field perpendicular to the plane of motion. The velocity autocorrelation is computed numerically over the full range of densities and magnetic fields with particular attention to the percolation threshold between hopping transport and pure edge currents. The Ohmic and Hall conductance are compared with mode-coupling theory and a recent generalized kinetic equation valid for low densities and small fields. We argue that the long time tail as $t^{-2}$ persists for non-zero magnetic field.Comment: 7 pages, 14 figures. Uses RevTeX and epsfig.sty. Submitted to Physical Review

Grazing Evaluation of Big Bluestems Bred for Improved Forage Yield and Digestibility

Two big bluestem (Andropogon gerardii Vitman) strains (Pawnee C3 and Kaw C3) developed by three breeding cycles for increased forage yield and in vitro dry matter digestibility (IVDMD) were compared with the base populations of \u27Pawnee\u27 and \u27Kaw\u27 in a 3-yr grazing trial. Pastures were seeded in May 1998 near Mead, NE. Experimental units were three 0.4-ha pastures of each strain or cultivar in a randomized complete block design. Pastures were burned and fertilized with ammonium nitrate at 112 kg N ha-1 in the spring of 2000, 2001, and 2002 before grazing. Each pasture was continuously stocked with three crossbred yearling steers (Bos taurus) (380 +/- 38 kg) in mid-June 2000, 2001, and 2002 to provide a stock density of 7.5 steers ha-1. Pawnee C3 and Kaw C3 produced 16 and 7% more average daily gain (ADG), respectively, than the base populations during the 3-yr study. Additionally, Pawnee C3 and Kaw C3 produced 14 and 5% more total body weight (BW) gain ha-1, respectively, than the base populations. Pawnee C3 ADG was 1.30 kg hd-1 and produced greater than 455 kg total BW gain ha-1 during a drought period in eastern Nebraska. Pawnee C3 pastures produced more available forage with higher IVDMD, cell soluble, cell wall digestibility, and lower lignin concentration than forages from Pawnee pastures. Kaw C3 pastures differed from Kaw pastures by producing forage with greater crude protein concentration. These results demonstrate the productivity of big bluestem pastures in the eastern Great Plains and document the positive livestock response to moderate increases in forage IVDMD. The strains bred for increased yield and IVDMD provided as much as 26% more total BW gain ha-1 at no additional cost. Pawnee C3 was released as the cultivar Bonanza and Kaw C3 was released as \u27Goldmine\u27

Grazing Evaluation of Big Bluestems Bred for Improved Forage Yield and Digestibility

Two big bluestem (Andropogon gerardii Vitman) strains (Pawnee C3 and Kaw C3) developed by three breeding cycles for increased forage yield and in vitro dry matter digestibility (IVDMD) were compared with the base populations of \u27Pawnee\u27 and \u27Kaw\u27 in a 3-yr grazing trial. Pastures were seeded in May 1998 near Mead, NE. Experimental units were three 0.4-ha pastures of each strain or cultivar in a randomized complete block design. Pastures were burned and fertilized with ammonium nitrate at 112 kg N ha-1 in the spring of 2000, 2001, and 2002 before grazing. Each pasture was continuously stocked with three crossbred yearling steers (Bos taurus) (380 +/- 38 kg) in mid-June 2000, 2001, and 2002 to provide a stock density of 7.5 steers ha-1. Pawnee C3 and Kaw C3 produced 16 and 7% more average daily gain (ADG), respectively, than the base populations during the 3-yr study. Additionally, Pawnee C3 and Kaw C3 produced 14 and 5% more total body weight (BW) gain ha-1, respectively, than the base populations. Pawnee C3 ADG was 1.30 kg hd-1 and produced greater than 455 kg total BW gain ha-1 during a drought period in eastern Nebraska. Pawnee C3 pastures produced more available forage with higher IVDMD, cell soluble, cell wall digestibility, and lower lignin concentration than forages from Pawnee pastures. Kaw C3 pastures differed from Kaw pastures by producing forage with greater crude protein concentration. These results demonstrate the productivity of big bluestem pastures in the eastern Great Plains and document the positive livestock response to moderate increases in forage IVDMD. The strains bred for increased yield and IVDMD provided as much as 26% more total BW gain ha-1 at no additional cost. Pawnee C3 was released as the cultivar Bonanza and Kaw C3 was released as \u27Goldmine\u27