Dust accretion in binary systems: implications for planets and transition discs

The presence of planets in binary systems poses interesting problems for planet formation theories, both in cases where planets must have formed in very compact discs around the individual stars and where they are located near the edge of the stable circumbinary region, where in situ formation is challenging. Dust dynamics is expected to play an important role in such systems, since dust trapping at the inner edge of circumbinary discs could aid in situ formation, but would simultaneously starve the circumstellar discs of the solid material needed to form planets. Here we investigate the dynamics of dust in binary systems using smoothed particle hydrodynamics. We find that all our simulations tend towards dust trapping in the circumbinary disc, but the time-scale on which trapping begins depends on binary mass ratio (q) and eccentricity as well as the angular momentum of the infalling material. For q ≳ 0.1, we find that dust can initially accrete on to the circumstellar discs, but as the circumbinary cavity grows in radius, dust eventually becomes trapped in the circumbinary disc. For q = 0.01, we find that increasing the binary eccentricity increases the time required for dust trapping to begin. However, even this longer time-scale is likely to be shorter than the planet formation time-scale in the inner disc and is insufficient to explain the observed pre-transitional discs. This indicates that increase in companion eccentricity alone is not enough to allow significant transfer of solids from the outer to the inner disc

Sheep Updates 2007 - part 1

This session covers six papers from different authors: PLENARY 1. Life beyond the farmgate - the meat perspective, Richard Gunner – Principal:- Richard Gunner’s Fine Meats 2. Do you need to worry about climate change?, Anthony Clark, Centre for Resource and Environmental Studies, Australian National University and Bureau of Rural Sciences. 3. Ruminant nutrition panel session - The impact of nutrition on animal health and welfare, Kevin Bell, School of Veterinary and Biomedical Studies, Murdoch University 4. Ruminant nutrition panel session - Pasture/animal interactions, Hugh Dove, Chief Research Scientist, CSIRO Plant Industry 5. Precision Cattle Breeding for the 21st Century, H.M. Burrow, Cooperative Research Centre for Beef Genetic Technologies 6. Profitable PerenialsTM for Australian Livestock Industries, Kevin Goss, CEO Designate, Future Farm Industries CRC, University of Western Australi

Ceratoscopelus maderensis : pecular sound-scattering layer identified with this myctophid fish

Reprint. Science, vol. 160, no. 3831, 1968, pp. 991-993. Originally issued as Reference No. 68-58, series later renamed WHOI-.A sound- scattering layer, composed of discrete hyperbolic echo-sequences and apparently restricted to the Slope Water region of the western North Atlantic, has been identified from the Deep Submergence Research Vehicle ALVIN with schools of the myctophid fish Ceratoscopelus maderensis. By diving into the layer and using ALVIN's echo-ranging sonar, we approached and visually identified the sound scatterers. The number of echo sequences observed with the surface echo-sounder (1 /23. 76 x 105 cubic meters of water) checked roughly with the number of sonar targets observed from the submarine (1/7. 45 x 105 cubic meters) . The fish schools appeared to be 5 to 10 meters thick, 10 to 100 meters in diameter, and on centers 100 to 200 meters apart. Density within schools was estimated at 10 to 15 fish per cubic meter.Supported in part by contracts Nonr-3484(00) and Nonr-4029(00) and by NSF grant GB-4431

P3-[2-(4-hydroxyphenyl)-2-oxo]ethyl ATP for the Rapid Activation of the Na+,K+-ATPase

This is the published version, also available here: http://dx.doi.org/10.1016/S0006-3495(00)76387-9.P3-[2-(4-hydroxyphenyl)-2-oxo]ethyl ATP (pHP-caged ATP) has been investigated for its application as a phototrigger for the rapid activation of electrogenic ion pumps. The yield of ATP after irradiation with a XeCl excimer laser (λ = 308 nm) was determined at pH 6.0–7.5. For comparison, the photolytic yields of P3-[1-(2-nitrophenyl)]ethyl ATP (NPE-caged ATP) and P3-[1,2-diphenyl-2-oxo]ethyl ATP (desyl-caged ATP) were also measured. It was shown that at λ = 308 nm pHP-caged ATP is superior to the other caged ATP derivatives investigated in terms of yield of ATP after irradiation. Using time-resolved single-wavelength IR spectroscopy, we determined a lower limit of 106 s−1 for the rate constant of release of ATP from pHP-caged ATP at pH 7.0. Like NPE-caged ATP, pHP-caged ATP and desyl-caged ATP bind to the Na+,K+-ATPase and act as competitive inhibitors of ATPase function. Using pHP-caged ATP, we investigated the charge translocation kinetics of the Na+,K+-ATPase at pH 6.2–7.4. The kinetic parameters obtained from the electrical measurements are compared to those obtained with a technique that does not require caged ATP, namely parallel stopped-flow experiments using the voltage-sensitive dye RH421. It is shown that the two techniques yield identical results, provided the inhibitory properties of the caged compound are taken into account. Our results demonstrate that under physiological (pH 7.0) and slightly basic (pH 7.5) or acidic (pH 6.0) conditions, pHP-caged ATP is a rapid, effective, and biocompatible phototrigger for ATP-driven biological systems