511 research outputs found
Bimodal Distribution of Sulfuric Acid Aerosols in the Upper Haze of Venus
The upper haze (UH) of Venus is variable on the order of days and it is
populated by two particle modes. We use a 1D microphysics and vertical
transport model based on the Community Aerosol and Radiation Model for
Atmospheres to evaluate whether interaction of upwelled cloud particles and
sulfuric acid particles nucleated in situ on meteoric dust are able to generate
the two size modes and whether their observed variability are due to cloud top
vertical transient winds. Nucleation of photochemically produced sulfuric acid
onto polysulfur condensation nuclei generates mode 1 cloud droplets that then
diffuse upwards into the UH. Droplets generated in the UH from nucleation of
sulfuric acid onto meteoric dust coagulate with the upwelled cloud particles
and cannot reproduce the observed bimodal size distribution. The mass transport
enabled by cloud top transient winds are able to generate a bimodal size
distribution in a time scale consistent with observations. Sedimentation and
convection in the middle and lower clouds causes the formation of large mode 2
and mode 3 particles. Evaporation of these particles below the clouds creates a
local sulfuric acid vapor maximum that causes upwelling of sulfuric acid back
into the clouds. If the polysulfur condensation nuclei are small and their
production rate is high, coagulation of small droplets onto larger droplets in
the middle cloud may result in sulfuric acid "rain" below the clouds once every
few Earth months. Reduction of the polysulfur condensation nuclei production
rate destroys this oscillation and reduces the mode 1 particle abundance in the
middle cloud by two orders of magnitude, though it better reproduces the
sulfur-to-sulfuric-acid mass ratio in the cloud and haze droplets. In general
we find satisfactory agreement between our results and observations, though
improvements could be made by incorporating sulfur microphysics.Comment: 62 pages, 18 figures, 1 table. Accepted for publication in Icaru
Evidence review of the impact of the ESF on those furthest from the labour market 2007 - 2013
Small Satellite Launch to LEO:A Review of Current and Future Launch Systems
As minaturisation of ever improving enabling technologies increase the capabilities of small satellites, the issue of commercially affordable access to Earth orbit becomes more significant. Whilst the current practice of multiple manifesting is dominant, the emergence of new small launch vehicles may instigate a transition to the dedicated launch of these small satellites. A brief review of the current range of launch vehicles is presented and available small satellite launch market projections briefly examined. The small launch vehicles currently in development are also outlined and their potential to drive the future small satellite launch market discussed
Sustainable control of grapevine powdery mildew (Uncinula necator Schweinitz Burrill) in vineyards in South Australia.
Grapevine powdery mildew, caused by the fungus Uncinula necator Schweinitz Burrill, is a major disease affecting grape yield and quality worldwide. In conventional vineyards, the disease is controlled mainly by regular applications of sulphur and synthetic fungicides, such as demethylation inhibiting fungicides (DMIs), and in organic agriculture by sulphur and canola-based oils. The impending restrictions on the use of sulphur in organic viticulture, the development of resistance to DMls in Australia and elsewhere, and the demand for residue-free grapes create a need for effective alternatives to sulphur and synthetic chemicals. This research has identified potential replacements for synthetic fungicides and sulphur in the control of powdery mildew, such as milk, whey, bicarbonates and canola oil-based sprays.
A series of greenhouse experiments was conducted to evaluate 34 potential novel materials and biological agents for efficacy in controlling powdery mildew. The most effective treatments applied were Bacillus subtilis (which reduced disease by 94% compared to the untreated control), Synertrol Horti-Oil® (a canola oil-based product, 92%), milk (70%), whey (64%) and Ecocarb® (potassium bicarbonate, 58%). Milk and whey provided increased control of powdery mildew as the concentration increased. The efficacy of milk tended to decrease as the fat content of the milk was reduced.
The materials that were most promising in the greenhouse were then assessed in field trials in commercial vineyards. Applications of milk, whey and mixtures of a canola oil-based product and potassium bicarbonate, applied at rates of 300 L/ha to 1000 L/ha depending on canopy development, reduced the severity of powdery mildew. The severity of powdery mildew on vines sprayed with a 1:10 dilution of milk, 45 g/L whey powder and mixed programs was not significantly different from that on vines sprayed with sulphur (wettable powder, 3 g/L). However, the relative control of powdery mildew by the test materials in field trials was highly dependent on the degree of coverage of the plant surface achieved. In vineyards where coverage was compromised, the degree of control of powdery mildew was reduced, often to commercially unacceptable levels.
Electron spin resonance (ESR) and scanning electron microscopy (SEM) were used to investigate the possible mode or modes of action of milk and whey in the control of powdery mildew. The ESR experiments showed that production of oxygen radicals by various components of milk in natural light was associated with reduced severity of powdery mildew. SEM images showed that milk and whey caused the hyphae of U necator to collapse and damaged conidia within 24 h of treatment. Hydrogen peroxide, applied as a source of free radicals, also caused collapse of the hyphae of U necator within 24 h but did not damage conidia, and appeared to stimulate germination. Lactoferrin (an antimicrobial component of milk) ruptured conidia, but damage to hyphae was not evident in lactoferrin-treated samples until 48 h after treatment. The results suggested that fats, free radical production along with the action of lactoferrin, and possibly other proteins, are associated with the control of powdery mildew by milk.
Novel soft fungicides, such as milk and oil plus bicarbonate mixtures, were effective alternatives to sulphur and synthetic fungicides in certain South Australian conditions. Biological agents (including B. subtilis, which was highly effective in greenhouse experiments) did not provide acceptable control of powdery mildew in the vineyard.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture and Wine, 200
Ethnic minority customers of the Pensions, Disability and Carers Service: an evidence review.
The aim of this project was to review and synthesise available evidence that could
throw light on: why Black and Minority Ethnic (BME) customers are less satisfied
with the Pension, Disability and Carers Service (PDCS); why BME individuals eligible
for the PDCS benefits are less likely to apply for them; what interventions might
be successful at raising levels of take-up and satisfaction with PDCS services; and
what important gaps exist in research evidence to answer these questions
CYTOTAXONOMIC STUDIES IN THE SECTION ANNUl OF SENECIO
PhDSeneclo scualidus, a Mediterranean endemic, became
established in Britain about 180 years ago, where it is
now common and widespread.
S. saualidus is represented in Sicily by two distinct
taxa: the lowland S. chrysanthemif'olius, and the montane
S aetnensis. On the basis of their distinctiveness these
taxa are retained as separate species. Where these two
species meet they form hybrid swarms, and bipolar
introgression occurs. The British S.s pualidiis is
morphologically intermediate between the two Sicilian species,
but its autonomy and circumscribed morphology indicate that
it should be treated as a distinct species of hybrid origin.
In Britain, , squalidus (2n = 20) hybridises with
S. vular1s and S. viscosus (both 2n = 1+0). Both triploid
hybrids are very highly sterile.
A ligulate variety of S. vulgaris shows a close
geographical and historical correlation with the spread of
S. scualidus in Britain, and indicates introgresslon into
S. vulgaris from S. squalidus. The rare occurrence of
segregating fertile hybrid material supports this hypothesis.
- Experiments snow that introgresslon can occur via the
rare seed set by the triploid F1 S. saualldus X S, viscosus
at the more or less pentaploid level (2n = 1+7 - 50).
Subsequent generations from these pentaplolds tend towards
the teraploid level and increasing fertility. This may be
analogous to the method of introgression Into S. vularis.
S. cambrensis, an allohexaploid (2n = 60) from
S vulgaris X S. squalidus, has arisen in Britain, probably
within the last 50 years, and is still restricted to north
Wales and Cheshire. This species Is now segregating into
ligulate and eligulate races
- …