An Elastic Analysis of a Plated Bone to Determine Fracture Gap Motion

An elastic analysis to determine fracture gap motions occurring in the osteotomized and plated canine femur was performed using the finite element program NASTRAN. The femur was idealized as a hollow right cylinder, and transverse anisotropy was assumed for the elastic properties of the bone. A 3-D 360 degree model consisting of 224 isoparametric quadrilateral hexahedral and 11 beam elements was created. A range of plate stiffnesses was tested by varying the modulus of elasticity of the plate from 207 GPa to 1 GPA. Moments were applied in the plane of the plate, about the axis of the plate, and in the plane of the screws. Results showed that, for plates of typical geometry and elastic modulus under 10 GPa, the contribution to fracture gap motion occurring due to deformation in the bone was negligible compared to that contribution from deformation in the plate

A STUDY OF THE FORMING OF ZIRCALOY-2 HEMISPHERES BY POWER SPINNING

S>Twelve Zircaloy-2 sheets, with thicknesses between 1/8and 5/16-in., were formed into 15-in.-diameter hemispheres by power spinning in an effort to determine the feasibility of using such a method to fabricate core vessels for the Homogeneous Reactor Project (HRP). The fabrication of an entire hemisphere as a unit is of interest because it would reduce the number of welds required to form a vessel. This in turn, would reduce the chance of weld contami nation and consequent impairment of corrosion resistance and mechanical properties. A number of difficulties such as laps and earing, were encountered but were overcome by modifications of the procedure. The maximum percentage of reduction in shell thickness was between 30 and 40%. The springback on the equatorial radius increased with thickness from 0.040 to 0.175 in., whereas the diametral ellipticity varies between 0.016 and 0.100 in. Three complete spheres were welded in a vacuum chamber using a technique developed by the vendor. Although the welding was not quite of HRP quality, it demonstrated that the spun shells could be assembled into vessels. (auth

Influence of Spin Wave Excitations on the Ferromagnetic Phase Diagram in the Hubbard-Model

The subject of the present paper is the theoretical description of collective electronic excitations, i.e. spin waves, in the Hubbard-model. Starting with the widely used Random-Phase-Approximation, which combines Hartree-Fock theory with the summation of the two-particle ladder, we extend the theory to a more sophisticated single particle approximation, namely the Spectral-Density-Ansatz. Doing so we have to introduce a `screened` Coulomb-interaction rather than the bare Hubbard-interaction in order to obtain physically reasonable spinwave dispersions. The discussion following the technical procedure shows that comparison of standard RPA with our new approximation reduces the occurrence of a ferromagnetic phase further with respect to the phase-diagrams delivered by the single particle theories.Comment: 8 pages, 9 figures, RevTex4, accepted for publication in Phys. Rev.

Elevating crop disease resistance with cloned genes

Essentially all plant species exhibit heritable genetic variation for resistance to a variety of plant diseases caused by fungi, bacteria, oomycetes or viruses. Disease losses in crop monocultures are already significant, and would be greater but for applications of disease-controlling agrichemicals. For sustainable intensification of crop production, we argue that disease control should as far as possible be achieved using genetics rather than using costly recurrent chemical sprays. The latter imply CO2 emissions from diesel fuel and potential soil compaction from tractor journeys. Great progress has been made in the past 25 years in our understanding of the molecular basis of plant disease resistance mechanisms, and of how pathogens circumvent them. These insights can inform more sophisticated approaches to elevating disease resistance in crops that help us tip the evolutionary balance in favour of the crop and away from the pathogen. We illustrate this theme with an account of a genetically modified (GM) blight-resistant potato trial in Norwich, using the Rpi-vnt1.1 gene isolated from a wild relative of potato, Solanum venturii, and introduced by GM methods into the potato variety Desiree

Comparisons between placing and broadcasting of nitrogen, phosphorus and potassium fertilizers for potatoes, peas, beans, kale and maize

RESP-398

Placement of fertilizers for row crops

RESP-323

Nitrogen fertilizers for spring barley and wheat

RESP-396

The value of nitrophosphate for spring-sown cereals

RESP-354

Field experiments on phosphate fertilizers. A joint investigation

RESP-412