The Effects of Inter-particle Attractions on Colloidal Sedimentation

We use a mesoscopic simulation technique to study the effect of short-ranged inter-particle attraction on the steady-state sedimentation of colloidal suspensions. Attractions increase the average sedimentation velocity $v_s$ compared to the pure hard-sphere case, and for strong enough attractions, a non-monotonic dependence on the packing fraction $\phi$ with a maximum velocity at intermediate $\phi$ is observed. Attractions also strongly enhance hydrodynamic velocity fluctuations, which show a pronounced maximum size as a function of $\phi$. These results are linked to a complex interplay between hydrodynamics and the formation and break-up of transient many-particle clusters.Comment: 4 pages 4 figure

Studies in physiological undernourishment in sheep

1. An examination of changes in weight and body composition in a flock of free -grazing Scottish Blackface ewes indicated that, during the greater part of pregnancy, these ewes were undernourished and catabolizing considerable amounts of body tissue.2. The nutritional states of ewes from two differently managed Scottish Blackface flocks were characterized during late pregnancy in terms of circulating concentrations of plasma free fatty acids and ketones. Marked undernourishment was evident in both situations.3. Data collected in a variety of situations supported the hypothesis that the severity of undernourishment during late pregnancy is determined principally by foetal weight and the level of food intake. Within a group of pregnant ewes with comparable intakes, the general degree of undernourishment is dependent on the level of intake, and the relative severity of undernourishment in individual animals is determined by differences in foetal weight.4. The use of certain biochemical parameters as indices of undernourishment was examined in ewes with artificially induced hypoglycaemia. It was concluded that nutritional state is best characterized in terms of that parameter which shows the greatest response per unit change in either nutrient intake or nutrient requirement.5. Biochemical parameters were used to control the nutritional states of individual animals in an experiment on the effects of undernourishment during pregnancy on lamb birth- weight. The results of this experiment indicated that the undernourishment occurring in free- grazing hill ewes during late pregnancy was likely to reduce the birth - weight of single lambs by 10%, and that of twins by 25%.6. The additional energy requirements during pregnancy were estimated to be 100g digestible organic matter per kg foetus

Multiplicity at the Stellar/Substellar Boundary in Upper Scorpius

We present the results of a high-resolution imaging survey of 12 brown dwarfs and very low mass stars in the closest (~145 pc) young (~5 Myr) OB association, Upper Scorpius. We obtained images with the Advanced Camera for Surveys/High Resolution Camera on HST through the F555W (V), F775W (i'), and F850LP (z') filters. This survey discovered three new binary systems, including one marginally resolved pair with a projected separation of only 4.9 AU, resulting in an observed binary fraction of 25+/-14% at separations >4 AU. After correcting for detection biases assuming a uniform distribution of mass ratios for q>0.6, the estimated binary fraction is 33+/-17%. The binary fraction is consistent with that inferred for higher-mass stars in Upper Sco, but the separation and mass ratio distributions appear to be different. All three low-mass binary systems in Upper Sco are tight (<18 AU) and of similar mass (q>0.6), consistent with expectations based on previous multiplicity studies of brown dwarfs and very low mass stars in the field and in open clusters. The implication is that the distinct separation and mass ratio distributions of low-mass systems are set in the formation process or at very young ages, rather than by dynamical disruption of wide systems at ages >5 Myr. Finally, we combine the survey detection limits with the models of Burrows et al. (1997) to show that there are no planets or very low-mass brown dwarfs with masses >10 M_J at projected separations >20 AU, or masses >5 M_J at projected separations >40 AU orbiting any of the low-mass (0.04-0.10 M_sun) objects in our sample.Comment: Accepted for publication in ApJ; 10 pages, 4 figures in emulateapj forma

Phase Stability and Segregation in Alloy 22 Base Metal and Weldments

The current design of the waste disposal containers relies heavily on encasement in a multi-layered container, featuring a corrosion barrier of Alloy 22, a Ni-Cr-Mo-W based alloy with excellent corrosion resistance over a wide range of conditions. The fundamental concern from the perspective of the Yucca Mountain Project, however, is the inherent uncertainty in the (very) long-term stability of the base metal and welds. Should the properties of the selected materials change over the long service life of the waste packages, it is conceivable that the desired performance characteristics (such as corrosion reistance) will become compromised, leading to premature failure of the system. To address this, we will study the phase stability and solute segregation characteristics of Alloy 22 base metal and welds. A better understanding of the underlying microstructural evolution tendencies, and their connections with corrosion behavior will (in turn) produce a higher confidence in the extrapolated behavior of the container materials over time periods that are not feasibly tested in a laboratory. Additionally, the knowledge gained here may potentially lead to cost savings through development of safe and realistic design constraints and model assumptions throughout the entire disposal system

Potential for increasing producers' income from wool, fibre and pelts in Central Asia

The systems of livestock production, marketing and research have been profoundly transformed by recent policies in Central Asia since the break up of the Soviet Union. Decollectivisation of state farms has transferred livestock ownership to new private farming units. These receive little or no state support for inputs, or for processing and selling livestock products. Most livestock-keeping families have much-reduced incomes compared to the Soviet period. Live animal sales now constitute the main subsistence income for such families, but may be unsustainable for the majority of families who own small numbers of animals. Poverty is particularly prevalent in the more remote areas distant from urban markets

The Model Underlying SIMSOC

http://deepblue.lib.umich.edu/bitstream/2027.42/50927/1/152.pd

Dominance modification

Dominance modificatio

A Long-Lived Accretion Disk Around a Lithium-Depleted Binary T Tauri Star

We present a high dispersion optical spectrum of St 34 and identify the system as a spectroscopic binary with components of similar luminosity and temperature (both M3+/-0.5). Based on kinematics, signatures of accretion, and location on an H-R diagram, we conclude that St 34 is a classical T Tauri star belonging to the Taurus-Auriga T Association. Surprisingly, however, neither component of the binary shows LiI 6708 A, absorption, the most universally accepted criterion for establishing stellar youth. In this uniquely known instance, the accretion disk appears to have survived longer than the lithium depletion timescale. We speculate that the long-lived accretion disk is a consequence of the sub-AU separation companion tidally inhibiting, though not preventing, circumstellar accretion. Comparisons with pre-main sequence evolutionary models imply, for each component of St 34, a mass of 0.37+/-0.08 Msun and an isochronal age of 8+/-3 Myr, which is much younger than the predicted lithium depletion timescale of ~ 25 Myr. Although a distance 38% closer than that of Taurus-Auriga or a hotter temperature scale could reconcile this discrepancy at 21-25 Myr, similar discrepancies in other systems and the implications of an extremely old accreting Taurus-Auriga member suggest instead a possible problem with evolutionary models. Regardless, the older age implied by St 34's depleted lithium abundance is the first compelling evidence for a substantial age spread in this region. Additionally, since St 34's coeval co-members with early M spectral types would likewise fail the lithium test for youth, current membership lists may be incomplete.Comment: 4 pages, including 2 figures. Accepted for publication in ApJ Let

Remote sensing applications in forestry. The development of an earth resources information system using aerial photographs and digital computers photographs and digital computers

Remote aerial sensing and automatic mapping for forest resources information syste