2,047 research outputs found
The Effect of Nitrogen Rates and Plant Density on Grain Yield Components and Persistence in Intermediate Wheatgrass (\u3ci\u3eThinopyrum intermedium\u3c/i\u3e) and Mountain Rye (\u3ci\u3eSecale strictum\u3c/i\u3e)
Intermediate wheatgrass (IWG; Thinopyrum intermedium) and Mountain Rye (Mtn Rye; Secale strictum) have potential for release as dual-purpose (grazing and grain production) perennial grains in Australia due to their superior longevity compared to hybrid perennial wheats. Initially developed as perennial forage grasses, few management guidelines exist to inform agronomic practices to maximise grain yields and profitability in Australian environments. An experiment was established in 2020 to examine the effect of plant density and nitrogen rates on grain yield components. The experiment compared the two species (IWG, Mtn Rye) sown at three plant densities (50, 100 and 200 plants/m2) with three nitrogen rates (0, 100, 200 kg/ha N). Overall, in the first year of production, Mtn Rye had higher grain yields than Kernza although yield decreased with increasing N rates. With further selection for floret fertility and seed size, Mtn Rye could prove a successful candidate for a perennial grain crop in Australia
Casimir force between sharp-shaped conductors
Casimir forces between conductors at the sub-micron scale cannot be ignored
in the design and operation of micro-electromechanical (MEM) devices. However,
these forces depend non-trivially on geometry, and existing formulae and
approximations cannot deal with realistic micro-machinery components with sharp
edges and tips. Here, we employ a novel approach to electromagnetic scattering,
appropriate to perfect conductors with sharp edges and tips, specifically to
wedges and cones. The interaction of these objects with a metal plate (and
among themselves) is then computed systematically by a multiple-scattering
series. For the wedge, we obtain analytical expressions for the interaction
with a plate, as functions of opening angle and tilt, which should provide a
particularly useful tool for the design of MEMs. Our result for the Casimir
interactions between conducting cones and plates applies directly to the force
on the tip of a scanning tunneling probe; the unexpectedly large temperature
dependence of the force in these configurations should attract immediate
experimental interest
Stable suspension and dispersion-induced transitions from repulsive Casimir forces between fluid-separated eccentric cylinders
Using an exact numerical method for finite nonplanar objects, we demonstrate
a stable mechanical suspension of a silica cylinder within a metallic cylinder
separated by ethanol, via a repulsive Casimir force between the silica and the
metal. We investigate cylinders with both circular and square cross sections,
and show that the latter exhibit a stable orientation as well as a stable
position, via a method to compute Casimir torques for finite objects.
Furthermore, the stable orientation of the square cylinder is shown to undergo
an unusual 45 degrees transition as a function of the separation lengthscale,
which is explained as a consequence of material dispersion.Comment: Published in Physical Review Letters. Vol. 101, page, 190404 (2008
Towards improved socio-economic assessments of ocean acidificationās impacts
Ocean acidification is increasingly recognized as a component of global change that could have a wide range of impacts on marine organisms, the ecosystems they live in, and the goods and services they provide humankind. Assessment of these potential socio-economic impacts requires integrated efforts between biologists, chemists, oceanographers, economists and social scientists. But because ocean acidification is a new research area, significant knowledge gaps are preventing economists from estimating its welfare impacts. For instance, economic data on the impact of ocean acidification on significant markets such as fisheries, aquaculture and tourism are very limited (if not non-existent), and non-market valuation studies on this topic are not yet available. Our paper summarizes the current understanding of future OA impacts and sets out what further information is required for economists to assess socio-economic impacts of ocean acidification. Our aim is to provide clear directions for multidisciplinary collaborative research
Entrepreneurial ecosystems, agency and regional development: Emergence and new path creation in the Cardiff city region
This paper addresses the process of entrepreneurial ecosystem emergence in regions and the mechanisms through which new industrial paths are created. It focuses on the context of a relatively weak economic region and develops a mode of analysis that considers the role of human agency within the emergence of entrepreneurial ecosystems. This analysis addresses the case study of the Cardiff city region in the United Kingdom. It indicates that the revitalisation of lagging regions through an entrepreneurial ecosystem approach is likely to be contingent upon a number of important components: (1) access to potential entrepreneurial agency, (2) the engagement of āenlightenedā local political agency and (3) the formation of a collective agency across entrepreneurial and political agents as well as other relevant stakeholders. The emergence of collective agency in the city region is found to have led to new policies, networks and entrepreneurial support within the high-tech industry, coupled with the development of new industrial paths and improved economic conditions. The paper argues that adopting an agency-based approach to analysing entrepreneurial emergence highlights the importance of key human actors in such emergence. It is concluded that lagging regions can trigger a process of development through new path creation stemming from the emergence of an entrepreneurial ecosystem
The first massive compact companion in a wide orbit around a hot subdwarf star
We report the discovery of the first hot subdwarf B (sdB) star with a massive
compact companion in a wide () binary system. It was
discovered based on an astrometric binary solution provided by the Gaia mission
Data Release 3. We performed detailed analyses of the spectral energy
distribution (SED) as well as spectroscopic follow-up observations and confirm
the nature of the visible component as a sdB star. The companion is invisible
despite of its high mass of .
A main sequence star of this mass would significantly contribute to the SED and
can be excluded. The companion must be a compact object, either a massive white
dwarf or a neutron star. Stable Roche lobe overflow to the companion likely led
to the stripping of a red giant and the formation of the sdB, the hot and
exposed helium core of the giant. Based on very preliminary data, we estimate
that of the sdBs might be formed through this new channel. This
binary might also be the prototype for a new progenitor class of supernovae
type Ia, which has been predicted by theory.Comment: 11 pages, accepted for publication in A&
Measurements of the Casimir-Lifshitz force in fluids: the effect of electrostatic forces and Debye screening
In this work, we present detailed measurements of the Casimir-Lifshitz force
between two gold surfaces (a sphere and a plate) immersed in ethanol and study
the effect of residual electrostatic forces, which are dominated by static
fields within the apparatus and can be reduced with proper shielding.
Electrostatic forces are further reduced by Debye screening through the
addition of salt ions to the liquid. Additionally, the salt leads to a
reduction of the Casimir-Lifshitz force by screening the zero-frequency
contribution to the force; however, the effect is small between gold surfaces
at the measured separations and within experimental error. An improved
calibration procedure is described and compared to previous methods. Finally,
the experimental results are compared to Lifshitz's theory and found to be
consistent for the materials used in the experiment.Comment: 11 figures. PRA in pres
Impact of Deep Water Formation on Antarctic Circumpolar Transport During Gateway Opening
Ambiguity over the Eocene opening times of the Tasman Gateway and Drake Passage makes it difficult to determine the initiation time of the Antarctic Circumpolar Current. If the Tasman Gateway opened later than Drake Passage, then Australia may have prevented the proto-ACC from forming. Recent modeling results have shown that only a relatively weak circumpolar transport results under Eocene surface forcing. This leads to warm and buoyant coastal water around Antarctica, which may impede the formation of deep waters and convective processes. This suggests that a change in deep water formation might be required to increase the density contrast across the Southern Ocean and increase circumpolar transport. Here we use a simple reduced gravity model with two basins, to represent the Atlantic and the Pacific. This fixes the density difference between surface and deep water and allows us to isolate the impact of deep water formation on circumpolar transport. With no obstacle on the southern boundary the circumpolar current increases its transport from 82.3 to 270.0Ā Sv with deep water formation. Placing an Antipodean landmass on the southern boundary reduces this transport as the landmass increases in size. However, circumpolar flow north of this landmass remains a possibility even without deep water formation. Weak circumpolar transport continues until the basin is completely blocked by the Antipodes. When the Antipodes is instead allowed to split from the southern boundary, circumpolar transport recovers to its unobstructed value. Flow rapidly switches to south of the Antipodes when the gateway is narrow
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