14,472 research outputs found
Static inverters which sum a plurality of waves Patent
Describing static inverter with single or multiple phase outpu
Winter wheat: A model for the simulation of growth and yield in winter wheat
The basic ideas and constructs for a general physical/physiological process level winter wheat simulation model are documented. It is a materials balance model which calculates daily increments of photosynthate production and respiratory losses in the crop canopy. The partitioning of the resulting dry matter to the active growing tissues in the plant each day, transpiration and the uptake of nitrogen from the soil profile are simulated. It incorporates the RHIZOS model which simulates, in two dimensions, the movement of water, roots, and soluble nutrients through the soil profile. It records the time of initiation of each of the plant organs. These phenological events are calculated from temperature functions with delays resulting from physiological stress. Stress is defined mathematically as an imbalance in the metabolite supply; demand ratio. Physiological stress is also the basis for the calculation of rates of tiller and floret abortion. Thus, tillering and head differentiation are modeled as the resulants of the two processes, morphogenesis and abortion, which may be occurring simulaneously
Towards the graviton from spinfoams: higher order corrections in the 3d toy model
We consider the recent calculation gr-qc/0508124 of the graviton propagator
in the spinfoam formalism. Within the 3d toy model introduced in gr-qc/0512102,
we test how the spinfoam formalism can be used to construct the perturbative
expansion of graviton amplitudes. Although the 3d graviton is a pure gauge, one
can choose to work in a gauge where it is not zero and thus reproduce the
structure of the 4d perturbative calculations. We compute explicitly the next
to leading and next to next to leading orders, corresponding to one-loop and
two-loop corrections. We show that while the first arises entirely from the
expansion of the Regge action around the flat background, the latter receives
contributions from the microscopic, non Regge-like, quantum geometry.
Surprisingly, this new contribution reduces the magnitude of the next to next
to leading order. It thus appears that the spinfoam formalism is likely to
substantially modify the conventional perturbative expansion at higher orders.
This result supports the interest in this approach. We then address a number
of open issues in the rest of the paper. First, we discuss the boundary state
ansatz, which is a key ingredient in the whole construction. We propose a way
to enhance the ansatz in order to make the edge lengths and dihedral angles
conjugate variables in a mathematically well-defined way. Second, we show that
the leading order is stable against different choices of the face weights of
the spinfoam model; the next to leading order, on the other hand, is changed in
a simple way, and we show that the topological face weight minimizes it.
Finally, we extend the leading order result to the case of a regular, but not
equilateral, tetrahedron.Comment: 24 pages, many figure
Liminality, the Australian State and Asian Nurse Immigrants
Over the last two decades the flow of Asians to Australia through legitimate immigration programs has accelerated. This is particularly the case for Asian nurses coming from countries that were once subjected to European colonisation. The difficulties encountered by nurses from Asian countries mirror those of earlier waves of migrants. These include navigating the language and differences in cultural mores, values, and beliefs, along with the loneliness that may come from leaving strong family ties at home. While racism has been evident for all earlier waves of migrants, Asians face an additional hurdle linked to the uneasy relationship Australians and the Australian state has with Asia. Australia is geographically in Asia, but culturally Anglo and European. The impact this might have on the working relationships of Asian and Australian born registered nurses is significant given the nature of their work in caring for the sick and elderly. This liminal relationship between the Australian state and Asians provides a theoretical insight into the particular difficulties experienced by Asian nurses and the integration programs that might assist them and their Australian colleagues to develop cohesive working relationships
Environmental characteristics of black crappie (\u3ci\u3ePomoxis nigromaculatus\u3c/i\u3e) nesting sites in two South Dakota waters
A biotelemetry study was undertaken during spring 1995 to identify black crappie (Pomoxis nigromaculatus) nesting sites in two South Dakota water bodies. Individually coded ultrasonic transmitters were implanted into the body cavity of 15 adult male black crappie in each water body prior to spawning. Available habitat characteristics were recorded at 75 randomly selected sites within each water body, and habitat characteristics at nesting sites were recorded for each male black crappie believed to be nesting. Of the habitat characteristics analyzed, only substrate firmness did not differ (P=0.79) between water bodies. In Richmond Lake, black crappie selected nesting sites with live cattails (Typha spp.) that were protected from prevailing south winds. In Brant Lake, black crappie selected nest sites with vegetation (usually woody debris) and silty substrate that had warmer water and were protected from wind and waves. It appeared that black crappie nested in the most protected areas available
Developing enterprise culture in a northern educational authority in the UK: involving trainee teachers in learning-orientated evaluation
In this paper we discuss our use of innovative methods - at least in the context of regeneration evaluation - to help evaluate an enterprise project in northern England, paying particular attention to the involvement of trainee teachers. We discuss the methods used and critically appraise the methods and methodology, present some emerging findings from the trainee teachers strand and conclude by discussing the place of what might be termed 'learning-orientated evaluation' in relation to the currently dominant output-focussed evaluation paradigm.</p
Dynamic stability of crack fronts: Out-of-plane corrugations
The dynamics and stability of brittle cracks are not yet fully understood.
Here we use the Willis-Movchan 3D linear perturbation formalism [J. Mech. Phys.
Solids {\bf 45}, 591 (1997)] to study the out-of-plane stability of planar
crack fronts in the framework of linear elastic fracture mechanics. We discuss
a minimal scenario in which linearly unstable crack front corrugations might
emerge above a critical front propagation speed. We calculate this speed as a
function of Poisson's ratio and show that corrugations propagate along the
crack front at nearly the Rayleigh wave-speed. Finally, we hypothesize about a
possible relation between such corrugations and the long-standing problem of
crack branching.Comment: 5 pages, 2 figures + supplementary informatio
Synthesis of Diarylheptanoid Scaffolds Inspired by Calyxins I and J
γ,δ-Unsaturated
alcohols are prepared efficiently in
two steps from <i>o</i>-hydroxycinnamaldehyde. The TMSOTf-mediated
reaction of the γ,δ-unsaturated alcohols with aldehydes
creates two oxygen heterocycles and three new stereocenters in a single
pot. The approach is versatile, and by varying the boronic acid, Grignard
reagent, and aldehyde, different substituents may be introduced, while
use of a chiral base in the conjugate addition gives enantioenriched
products
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