The palaeoceanography of the Leeuwin Current : implications for a future world

Long-term progressive changes of the Leeuwin Current are linked to plate and ocean basin ‘geography’ and Cenozoic global climates and palaeoceanography. Suggestions of the presence of a proto-Leeuwin Current as early as late Middle to Late Eocene times (c. 35–42 Ma) cannot be verified by the fossil record of the western margin of Australia. “Leeuwin Current style” circulation around Australia was certainly established by the early Oligocene, in response to palaeogeographic changes in the Tasman Strait. This, followed by tectonic eorganisation of the Indonesian Archipelago throughout the Miocene, provided a palaeogeographic setting, which by the Pliocene was essentially that of today. The subsequent history of the Leeuwin Current comprises climatically-induced changes operating over orbital and sub-orbital temporal scales. Specifically, the advent of Pleistocene-style climates, especially over the last 800 000 years, and their associated interglacial – glacial states provide the two end-member climate-ocean states that have characterised Leeuwin Current activity during that time. Indications of the nature of these contrasting states is provided by: (i) the Last Interglacial (c. 125 Ka) during which sea level was higher by some +4 m, and with higher sea surface temperatures (SSTs) clearly indicating a more ‘active’ Leeuwin Current; and (ii) the Last Glacial Maximum (21 Ka), during which sea level wassome 130 m lower than today, resulting in massive shelf extensions along the coast of Western Australia, ccompanied by reduced Indonesian Throughflow, lower low latitude SSTs and changes in the Western Pacific Warm Water Pool, and with these changes, possibly reduced Leeuwin Current activity. Sub-orbital scale luctuations in current strength are driven by global climate change associated with El Niño – La Niña events as well as regional climatic changes driven by volcanism. These forcing mechanisms operate at time scales well within the reach of human experience, and provide important comparative data for predicting the response of the Leeuwin Current to climate change predicted for this century. Studies of the impact of changes in the vigour of the Leeuwin Current on shallow marine communities are in their infancy. Coupling climate models with geological analogues provide important research agenda for predicting the trajectory of future changes to the Leeuwin Current and their impacts on the marine biota of coastal Western Australia

Fluorescent probes of the orientation of myosin regulatory light chains in relaxed, rigor, and contracting muscle.

The orientation of the light-chain region of myosin heads in relaxed, rigor, and isometrically contracting fibers from rabbit psoas muscle was studied by fluorescence polarization. Cysteine 108 of chicken gizzard myosin regulatory light chain (cgRLC) was covalently modified with iodoacetamidotetramethylrhodamine (iodo-ATR). Native RLC of single glycerinated muscle fibers was exchanged for labeled cgRLC in a low [Mg2+] rigor solution at 30 degrees C. Troponin and troponin C removed in this procedure were replaced. RLC exchange had little effect on active force production. X-ray diffraction showed normal structure in rigor after RLC exchange, but loss of axial and helical order in relaxation. In isolated myofibrils labeled cgRLC was confined to the regions of the sarcomere containing myosin heads. The ATR dipoles showed a preference for orientations perpendicular to the fiber axis, combined with limited nanosecond rotational motion, in all conditions studied. The perpendicular orientation preference was more marked in rigor than in either relaxation or active contraction. Stretching relaxed fibers to sarcomere length 4 microns to eliminate overlap between actin- and myosin-containing filaments had little effect on the orientation preference. There was no change in orientation preference when fibers were put into rigor at sarcomere length 4.0 microns. Qualitatively similar results were obtained with ATR-labeled rabbit skeletal RLC

New polyimide polymer has excellent processing characterisitcs with improved thermo-oxidative and hydrolytic stabilities

Polyimide P10P and its processing technique apply to most high temperature plastic products, devices and castings. Prepolymer, when used as varnish, impregnates fibers directly and is able to be processed into advanced composities. Material may also be used as molding powder and adhesive