Probing the Pulsar Wind in the gamma-ray Binary System PSR B1259-63/SS 2883

The spectral energy distribution from the X-ray to the very high energy regime ($>100$ GeV) has been investigated for the $\gamma$-ray binary system PSR B1259-63/SS2883 as a function of orbital phase within the framework of a simple model of a pulsar wind nebula. The emission model is based on the synchrotron radiation process for the X-ray regime and the inverse Compton scattering process boosting stellar photons from the Be star companion to the very high energy (100GeV-TeV) regime. With this model, the observed temporal behavior can, in principle, be used to probe the pulsar wind properties at the shock as a function of the orbital phase. Due to theoretical uncertainties in the detailed microphysics of the acceleration process and the conversion of magnetic energy into particle kinetic energy, the observed X-ray data for the entire orbit are fit using two different methods.Comment: 46 pages, 16 figures, accepted for publication in Ap

Swelling Pressures of a Permian Clay

Civil Engineerin

Total delay optimization for column reduction multipliers considering non-uniform arrival times to the final adder

textColumn Reduction Multiplier techniques provide the fastest multiplier designs and involve three steps. First, a partial product array of terms is formed by logically ANDing each bit of the multiplier with each bit of the multiplicand. Second, adders or counters are used to reduce the number of terms in each bit column to a final two. This activity is commonly described as column reduction and occurs in multiple stages. Finally, some form of carry propagate adder (CPA) is applied to the final two terms in order to sum them to produce the final product of the multiplication. Since forming the partial products, in the first step, is simply forming an array of the logical AND's of two bits, there is little opportunity for delay improvement for the first step. There has been much work done in optimizing the reduction stages for column multipliers in the second reduction step. All of the reduction approaches of the second step result in non-uniform arrival times to the input of the final carry propagate adder in the final step. The designs for carry propagate adders have been done assuming that the input bits all have the same arrival time. It is not evident that the non-uniform arrival times from the columns impacts the performance of the multiplier. A thorough analysis of the several column reduction methods and the impact of carry propagate adder designs, along with the column reduction design step, to provide the fastest possible final results, for an array of multiplier widths has not been undertaken. This dissertation investigates the design impact of three carry propagate adders, with different performance attributes, on the final delay results for four column reduction multipliers and suggests general ways to optimize the total delay for the multipliers.Electrical and Computer Engineerin

Grazing Behaviour of Dorper Sheep and Farmed Goats and Their Implications for Natural Resource Management in Western NSW

The introduction of exotic herbivores into the semi-arid and arid zones of Australia resulted in dramatic change in the native vegetation (e.g. Noble and Tongway 1986; Friedel et al. 1990). Overgrazing and trampling reduced ground cover and changed species composition from dominance by perennial grasses and shrubs to dominance by annual species over extensive areas (e.g. Gunn 1986), or assisted the encroachment of woody species (Wilcox and Cunningham 1994). It is particularly in this context that the recent introduction of new sheep breeds, reputedly hardier than traditional Merinos, and the increasing trend to farming or re-domestication of feral goats, poses serious questions for the ecological sustainability of the region. This ongoing project aims to combine information from laboratory experiments, field studies and producer experience to develop practical management strategies that are supportive of regional and national ground cover targets aimed at reducing wind erosion and maintaining biodiversity values. We report the preliminary results and recommend management strategies

Fat-Soluble Vitamin and Micromineral Concentrations in Preruminant Dairy Calves Fed to Achieve Different Growth Rates

Effects of neonatal growth rate on plasma concentrations of fat-soluble vitamins, zinc, and copper in preruminant calves were evaluated. Calves were assigned to dietary treatments designed to achieve three targeted rates of gain [No-Growth (NG) = 0.0 kg/d, Low-Growth (LG) = 0.55 kg/d, or High-Growth (HG) = 1.2 kg/d] over a 7 wk period. MR intakes needed to achieve specified growthrates were estimated using the NRC Nutrient Requirements of Dairy Cattle calf model computer program. Calves were fed a 30% CP, 20% fat, MR reconstituted to 14% DM. Because vitamin levels in the MR were based on DM intake of HG calves, NG and LG calves were supplemented with additional vitamins once weekly to compensate for reduced MR consumption. Growth rates for NG (0.11 kg/d), LG (0.58 kg/d), and HG (1.16 kg/d) calves differed throughout the study. Although vitamins A and D, and Zn concentrations were unaffected by growth rate, their concentrations increased and Zn/Cu concentrations decreased with time. Throughout the study their concentrations remained within normal ranges for the preruminant calf. Vitamin E and copper were affected by growth rate. At wk 7, HG calves had lower vitamin E concentrations than LG and NG calves. Copper concentrations were greater for HG calves than LG and NG calves from wk 4 to wk 7. Copper and vitE concentrations, however, remained within ranges considered normal for preruminant calves. These results suggest that growth rate during the neonatal period influences vitE and Cu availabilit

Infrared analysis of dry-band flashover of silicone rubber insulators

Wetting of a pollution layer by mist or light rain is inhibited, in the case of silicone rubber (SiR) insulators, by the migration of hydrophobic polymeric chains from the insulator to the layer surface. However, recent laboratory fog-chamber tests have shown that a salt/kaolin layer applied to the surface of an 11kV SiR insulator can reduce the specific creepage distance (SCD) at flashover to as low as 16mm/kV. Even for larger values of SCD, potentially damaging partial arcs can arise along the insulator surface. It has been shown that some mitigation of partial-arc activity and an increase of flashover voltage can be achieved by appropriate texturing of the SiR insulator housing. The present paper describes additional infrared (IR) recording which accompanied these previous tests. Although a reduction of the flashover voltage in polluted environments is generally surmised to be the result of the formation of dry bands in a conducting moistened surface layer, no direct observations of dry bands appear to have been previously demonstrated in the laboratory. Such observations are described here, where details of dry-band location and growth are revealed by IR recording. Dry bands are shown by close-up visual photography to be invariably bridged by small streamer/spark discharges which maintain current continuity in the pollution layer. Local surface heating by these discharges are the probable cause of the delayed rewetting of the bands. Partial-arc channels that may result in flashover develop from and across the dry-band streamers. It has become clear that clean-fog testing with infrared recording and leakage current measurements provide new possibilities for the modeling of dry band discharges and improvement of insulator design

Inhibiting the Plasmodium eIF2α Kinase PK4 Prevents Artemisinin-Induced Latency

Artemisinin and its derivatives (ARTs) are frontline antimalarial drugs. However, ART monotherapy is associated with a high frequency of recrudescent infection, resulting in treatment failure. A subset of parasites is thought to undergo ART-induced latency, but the mechanisms remain unknown. Here, we report that ART treatment results in phosphorylation of the parasite eukaryotic initiation factor-2α (eIF2α), leading to repression of general translation and latency induction. Enhanced phosphorylated eIF2α correlates with high rates of recrudescence following ART, and inhibiting eIF2α dephosphorylation renders parasites less sensitive to ART treatment. ART-induced eIF2α phosphorylation is mediated by the Plasmodium eIF2α kinase, PK4. Overexpression of a PK4 dominant-negative or pharmacological inhibition of PK4 blocks parasites from entering latency and abolishes recrudescence after ART treatment of infected mice. These results show that translational control underlies ART-induced latency and that interference with this stress response may resolve the clinical problem of recrudescent infection