High Quality Electron Bunches up to 1 GeV from Laser Wakefield Acceleration at LBNL

Experiments at the LOASIS laboratory of LBNL havedemonstrated production of 100 MeV to 1 GeV electron bunches with lowenergy spread and low divergence from laser wakefield acceleration. Theradiation pressure of a 10 TW laser pulse, guided over 10 diffractionranges by a few-mm long plasma density channel, was used to drive anintense plasma wave (wakefield), producing electron bunches with energieson the order of 100 MeV and acceleration gradients on the order of 100GV/m. Beam energy was increased from 100 MeV to 1 GeV by using a few-cmlong guiding channel at lower density, driven by a 40 TW laser,demonstrating the anticipated scaling to higher beam energies. Particlesimulations indicate that the low energy spread beams were produced fromself-trapped electrons through the interplay of trapping, loading, anddephasing. Other experiments and simulations are also underway to controlinjection of particles into the wake, and hence improve beam quality andstability further

Effects of light and temperature on the photosynthesis of seagrasses, epiphytes and macroalgae and implications for management of the Albany harbours

A technique is descn"bed for measuring the metabolic response of 'whole plants' of seagrasses to different light intensities and water temperatures

Effects of light and temperature on the photosynthesis of temperate meadow-forming seagrasses in Western Australia

A technique is described for measuring the metabolic response of seagrasses to different light intensities and water temperatures in the laboratory. The observed depth distribution of the seagrass species can be related to their light requirements and metabolic rates. The photosynthetic efficiency and maximum photosynthetic rates of Amphibolis griffithii (Black) den Hartog were significantly higher than those of Posidonia sinuosa Cambridge & Kuo and Posidonia australis Hook.f. The optimum temperature range for net photosynthesis of Posidonia sinuosa was 18–23°C and photoinhibition occurred at relatively low temperature and high light intensity. Maximum gross photosynthetic rates of P. sinuosa in an attenuated light regime simulating that experienced by plants in the field were higher than in a uniform light field. The respiration rates of the leaves were four to seven times higher than those of the root/rhizome component in the Posidonia species. There was no evidence for physiological adaptation to low light environments, using P. sinuosa from different depths and with different epiphyte loadings

Amyloid arthropathy in haemodialysed patients.

SIR, Two recent letters to the editor in the Annals' about our paper on amyloid arthropathy in patients undergoing haemodialysis3 have suggested that the finding of amyloid in the synovial tissue or fluid, or both, of these patients could be interpreted as an epiphenomenon related mainly to aging and osteoarthritis..