1,792 research outputs found
An Unbiased Survey for Outflows in the W3 and W5 Star-Formation Regions
During their birth all stars undergo periods of copious mass loss, frequently
characterized by the occurrence of bipolar outflows. These outflows are
believed to play a fundamental role in the star formation process. However the
exact outflow generating method is obscure at present. To elucidate this
problem we are investigating whether the flow properties are correlated over
the entire protostellar mass spectrum. Progress in this area requires that we
assemble a statistically valid sample of high-mass outflow systems. This is
necessary since existing catalogues of such objects are heterogeneous and
statistically incomplete.Comment: 2 pages, 1 figure, uses newpasp.sty. To appear in "Hot Star Workshop
III: The Earliest Phases of Massive Star Birth" (ed. P.A. Crowther
Scaling state of dry two-dimensional froths: universal angle deviations and structure
We characterize the late-time scaling state of dry, coarsening,
two-dimensional froths using a detailed, force-based vertex model. We find that
the slow evolution of bubbles leads to systematic deviations from 120degree
angles at three-fold vertices in the froth, with an amplitude proportional to
the vertex speed, v ~ sqrt(t), but with a side-number dependence that is
independent of time. We also find that a significant number of T1
side-switching processes occur for macroscopic bubbles in the scaling state,
though most bubble annihilations involve four-sided bubbles at microscopic
scales.Comment: 7 pages, 7 figure
On the frontline: the ‘gatekeeper' in statutory homelessness services.
In light of earlier findings linking resource shortages to the practise of illegitimate gatekeeping in statutory frontline homelessness services, this article draws on an implementation literature to revisit this topic following the recent economic downturn and related political austerity agenda. Following previous research, it was found that unlawful gatekeeping was practised chiefly in response to resource scarcity, alongside related pressures due to higher level performance measures. However, its use was also found, albeit to a lesser extent, to be due to miscomprehension around relevant legislation and the influence of individual or peer-level values. Overall, the findings provided a strong indication that illegitimate gatekeeping has worsened in the current climate due in large part to the twofold challenge of diminishing resources, alongside an increase in service users
Short-term effects of deep ploughing on soil C stocks following renewal of a dairy pasture in New Zealand
In New Zealand’s high producing permanent pastures the topsoil constitutes a large reservoir of soil organic carbon (SOC), which shows a marked stratification with depth. As consequence, sub-surface layers can contain 10 times less carbon than the surface soil. In permanent pastures with high carbon inputs, the formation and decomposition of these surface SOC stocks are often at equilibrium and C storage shows little change over time. Pastoral based dairy systems utilising ryegrass plus clover cultivars require renewal every 7-10 years to avoid reversion to less productive grasses. This may involve spring cultivation (either no-till, shallow till or full cultivation), summer forage cropping and autumn re-grassing. It has been hypothesised that SOC stocks can be increased by inverting the soil profile at pasture renewal through infrequent (once in 25-30 years) deep mouldboard ploughing (up to 30 cm depth). Increased C sequestration occurs when the new grass quickly rebuilds SOC stocks in the new topsoil (exposed low C sub-soil) at a rate faster than the decomposition of SOC in the rich former topsoil transferred to depth (now below 15 cm). However, benefits form accelerated C storage may be offset if crop and pasture production is adversely affected by the ploughing event (e.g., as result of compaction or excessive drainage). Hence, the aim of this work was to assess the short-term effects of infrequent inversion tillage of long-term New Zealand pastoral-based dairy soils under summer crop management and autumn re-grassing. An imperfectly drained Typic Fragiaqualf under dairy grazing was deep ploughed (approx. 25 cm) and re-sown with turnip in October 2016; other treatments included were shallow (< 10 cm) cultivation and no-till. The site was core sampled (0-40 cm) before cultivation and after 5 months of turnip growth to assess changes in SOC. Plant growth, herbage quality, and nutrient leaching were monitored during the 5-month period; root growth was assessed at the end of the crop rotation. Full cultivation transferred SOC below 10 cm depth, as expected. Soil bulk density decreased whereas root mass increased (10-20 cm depth; P < 0.05) under deep cultivation only. Besides, losses of mineral N were attenuated under deep tillage, resulting in a relative increase in crop yield. The potential for infrequent inversion tillage increasing soil C sequestration as a greenhouse gas (GHG) mitigation tool is currently being tested at other sites in New Zealand
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