1.55 µm InAs/GaAs Quantum Dots and High Repetition Rate Quantum Dot SESAM Mode-locked Laser

High pulse repetition rate (≥10 GHz) diode-pumped solid-state lasers, modelocked using semiconductor saturable absorber mirrors (SESAMs) are emerging as an enabling technology for high data rate coherent communication systems owing to their low noise and pulse-to-pulse optical phase-coherence. Quantum dot (QD) based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the development of an epitaxial process for the realization of high optical quality 1.55 µm In(Ga)As QDs on GaAs substrates, their incorporation into a SESAM, and the realization of the first 10 GHz repetition rate QD-SESAM modelocked laser at 1.55 µm, exhibiting ∼2 ps pulse width from an Er-doped glass oscillator (ERGO). With a high areal dot density and strong light emission, this QD structure is a very promising candidate for many other applications, such as laser diodes, optical amplifiers, non-linear and photonic crystal based devices

Crop Updates 2000 Cereals - part 4

This session covers twelve papers from different authors: BREEDING 1.Response to subsoil acidity of wheat genotypes differing in Al-tolerance, C. Tang, Z. Rengel, E. Diatloff and B. McGann, Soil Science and Plant Nutrition/CLIMA, University of Western Australia 2. Application of molecular markers in Barley Improvement, Mehmet Cakir1, Nick Galwey1 and David Poulsen2, 1Plant Sciences, Faculty of Agriculture, University of Western Australia, 2Queensland Department of Primary Industries, Hermitage Research Station, Queensland 3. Implementation of molecular markers for wheat improvement in the Western Region, M. Carter1, A. Briney1, R. Wilson2, R.H. Potter1 and M.G.K. Jones1, 1Western Australian State Agricultural Biotechnology Centre, Murdoch University, 2Crop Industries, Agriculture Western Australia 4. Performance in 1999 of recently released wheat varieties in Western Australia, Robin Wilson, Iain Barclay, Robyn McLean, Dean Diepeveen and Robert Loughman, Agriculture Western Australia ECONOMICS 5. Outlook for prices and implications for rotations, Ross Kingwell1 2, Michael O’Connell1, Simone Blennerhasset1 1Agriculture Western Australia, 2University of Western Australia 6. Price Risk Management and the Western Australian Grain Producer, Benjamin Michael Tiller, Muresk Institute of Agriculture FORECASTING 7. Can we forecast wheat yields in Western Australia, Senthold Asseng1, Holger Meinke2, and Bill Bowden3, 1CSIRO Plant Industry, 2 APSRU/DPI, 3Agriculture Western Australia ON FARM TESTING 8. On-farm testing, the quiet revolution continues, Jeff Russell1, Ivan Lee2 1Agriculture Western Australia, 2 Farmer Kunjin TopCrop group, Corrigin GRAIN STORAGE 9. CD-ROM tool for growers and advisers: Managing on-farm grain storage – effective practices for the delivery of quality assured products, Clare Johnson1, Chris Newman2 1Quality Wheat CRC Ltd, 2Production Resource Protection Services, Agriculture Western Australia 10. The Internet as a tool for managing grain insects, Robert Emery, Romolo Tassone and Ernestos Kostas, Agriculture Western Australia SUMMER CROPS AND WINDBREAK EFFECT ON YIELD 11. Summer crop Update and agronomic considerations, Graeme Ralph, Pioneer Hi-Bred Australia Pty Ltd 12. The effect of tree windbreaks on grain yield in the medium and low rainfall areas in Western Australia, Robert Sudmeyer, David Hall and Harvey Jones, Agriculture Western Australi

Optical Coherence Tomography in Parkinsonian Syndromes

BACKGROUND/OBJECTIVE: Parkinson's disease (PD) and the atypical parkinsonian syndromes multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) are movement disorders associated with degeneration of the central nervous system. Degeneration of the retina has not been systematically compared in these diseases. METHODS: This cross-sectional study used spectral-domain optical coherence tomography with manual segmentation to measure the peripapillar nerve fiber layer, the macular thickness, and the thickness of all retinal layers in foveal scans of 40 patients with PD, 19 with MSA, 10 with CBS, 15 with PSP, and 35 age- and sex-matched controls. RESULTS: The mean paramacular thickness and volume were reduced in PSP while the mean RNFL did not differ significantly between groups. In PSP patients, the complex of retinal ganglion cell- and inner plexiform layer and the outer nuclear layer was reduced. In PD, the inner nuclear layer was thicker than in controls, MSA and PSP. Using the ratio between the outer nuclear layer and the outer plexiform layer with a cut-off at 3.1 and the additional constraint that the inner nuclear layer be under 46 µm, we were able to differentiate PSP from PD in our patient sample with a sensitivity of 96% and a specificity of 70%. CONCLUSION: Different parkinsonian syndromes are associated with distinct changes in retinal morphology. These findings may serve to facilitate the differential diagnosis of parkinsonian syndromes and give insight into the degenerative processes of patients with atypical parkinsonian syndromes

Quantifying the response of crops to shelter in the agricultural regions of South Australia

Integrating belts of woody perennials into Australian farms is proposed as a method of enhancing crop productivity through shelter benefits while addressing natural resource management issues including groundwater recharge. This paper presents yield data from cereal and pulse crops collected from windbreak sites through the eastern agricultural districts of South Australia, using a harvester equipped with a yield monitor. The crop response followed the expected pattern of a competition zone of reduced yield of 1–4 tree heights (H) adjacent to the windbreak followed by a shelter benefit zone of unchanged or improved yield extending out to a maximum of 20H. The yield response in the sheltered benefit zone is +3.7% for all cereals (2.2H–9.7H) and is +14.0% for all pulse crops (1.7H–10.4H). Wheat and barley have similar results, with gains in the shelter benefit zones of 4.1% and 2.1%, respectively, with windbreak competition effects resulting in net yields of 3.0% for wheat and –1.1% for barley in the sheltered zones. Faba bean (Vicia faba) shows a strong consistent response to wind shelter, with a yield increase of 19.6% in the shelter benefit zone (1.5H–19.6H) and net gain of 19.1% in the sheltered zone (crop edge at 1.0H and extending to 19.6H). The response of cereals to sheltered effects varied across the years of the survey, with net positive results in 1997 (7.4%) and 1999 (7.5%) and close to zero in 1998 and 2000. A theoretical prediction of potential crop yield based on climate for the years of the survey showed that 1997 and 1999 had lower yield potential than 2000 and 1998. This suggests that the climatic conditions occurring during the growing season also influence crop shelter responses. Where cereals are the predominant crop the net yield returns from windbreaks would be small, even if root pruning could be successfully undertaken.M. R. Bennell and A. P. Verbyl

Effect of artificial wind shelters on the growth and yield of rainfed crops

There is great interest in quantifying and understanding how shelter modifies crop growth and development under Australian conditions. Small constructed enclosures (shelters) can consistently reduce wind speed, allowing experiments to be run with replicated sheltered and unsheltered treatments in close proximity. The aim of this study was to quantify the effect on microclimate of consistently reducing wind speed by 70% and explain the consequences for dryland wheat (Triticum aestivum), lupin (Lupinus angustifolius) and mungbean (Vigna radiata) growth and development, at sites in Queensland, Victoria and Western Australia. Crops were grown inside and outside of artificial shelters, 10 by 10 m and extending 1 m above the crop canopy throughout the growing season. Mean daily air and soil temperatures and atmospheric vapour pressure inside the shelters were largely similar to unsheltered conditions. However, clear diurnal trends were evident; daily maximum temperature and vapour pressure deficit (VPD) were increased in shelter when crops were establishing or senescing. When leaf area index (LAI) was reduced in the shelters, soil temperature was greater than in the open, however when LAI was increased in the shelters, soil temperature was less than in the open. Grain yield in shelters ranged between 78 and 120% of unsheltered yield, depending on seasonal conditions and crop species; the mean yield for all sites, crops and years was 99% of unsheltered yield. In the absence of waterlogging, sheltered crops tended to develop more leaf area than unsheltered crops, with an increase in the ratio of leaf area to above-ground biomass. This greater leaf area did not increase soil water use. While LAI was increased by shelter, only 2 of the 6 sheltered crops that were not waterlogged yielded significantly more grain than the unsheltered crops. This may be because the sheltered crops experienced greater maximum temperatures and VPD during anthesis and grain filling than unsheltered crops. Also, net photosynthesis may not have increased in the shelters after canopy closure (LAI>3–4). Lupins, which developed more leaf area inside shelters, may have experienced strong competition for assimilates between developing branches, flowers and fruit. When rainfall was above average and the soil became waterlogged for part of the growing season, grain yield was reduced inside the shelters. Reduced evaporation inside the shelters may have extended the duration and severity of waterlogging and increased stresses on sheltered plants when potential yield was being set. The reductions in wind speed achieved inside the artificial shelters were greater than those likely in conventional tree windbreak systems. Analysis of crop growth illustrated that microclimate modification at this high level of shelter can be both beneficial and harmful, depending on the crop species and climatic conditions during the growing season

The Australian National Windbreaks Program: overview and summary of results

This overview paper presents a description of the National Windbreaks Program (NWP) — its objectives, the main methods used to achieve these objectives and a summary of the key results. It draws these from the individual papers appearing in this special issue, which provide detailed descriptions and discussion about the specific research sites and research methods used, in addition to interpreting and discussing the results. The key findings were the following: (i) Two broad areas of crop and pasture response can be identified downwind of a porous windbreak: a zone of reduced yield associated with competition with the windbreak trees that extended from 1 H to 3 H, where H is the windbreak height, and a zone of unchanged or slightly increased yield stretching downwind to 10 H or 20 H. (ii) Averaged over the paddock, yield gains due to the effect of shelter on microclimate were smaller than expected — especially for cereals. Yield simulations conducted using the APSIM model and 20 years of historical climate data confirmed this result for longer periods and for other crop growing regions in Australia. Larger yield gains were simulated at locations where the latter part of the growing season was characterised by high atmospheric demand and a depleted soil water store. (iii) Economic analyses that account for the costs of establishing windbreaks, losses due to competition and yield gains as a result of shelter found that windbreaks will either lead to a small financial gain or be cost neutral. (iv) Part of the reason for the relatively small changes in yield measured at the field sites was the variable wind climate which meant that the crop was only sheltered for a small proportion of the growing season. In much of southern Australia, where the day-to-day and seasonal variability in wind direction is large, additional windbreaks planted around the paddock perimeter or as closely-spaced rows within the paddock will be needed to provide more consistent levels of shelter. (v) Protection from infrequent, high magnitude wind events that cause plant damage and soil erosion was observed to lead to the largest yield gains. The main forms of direct damage were sandblasting, which either buries or removes seedlings from the soil or damages the leaves and stems, and direct leaf tearing and stripping. (vi) A corollary to these findings is the differing effect that porous windbreaks have on the air temperature and humidity compared to wind. While winds are reduced in strength in a zone that extends from 5 H upwind to at least 25 H downwind of the windbreak, the effects of shelter on temperature and humidity are smaller and restricted mainly to the quiet zone. This means that fewer windbreaks are required to achieve reductions in wind damage than for altering the microclimate. (vii) The wind tunnel experiments illustrate the important aspects of windbreak structure that determine the airflow downwind, and subsequent microclimate changes, in winds oriented both perpendicular and obliquely to porous windbreaks. These results enable a series of guidelines to be forwarded for designing windbreaks for Australian agricultural systems.H. A. Cleugh, R. Prinsley, P. R. Bird, S. J. Brooks, P. S. Carberry, M. C. Crawford, T. T. Jackson, H. Meinke, S. J. Mylius, I. K. Nuberg, R. A. Sudmeyer and A. J. Wrigh