559 research outputs found
Influence of soil acidity on barley production.
A soil survey of 38 sites in barley growing areas of Western Australia was carried out in 1984. It was found that 53% of topsoils surveyed had a pH less than 5.5, acid enough to suspect barley yields might be affected. In 1985 an extensive field trial proqramme was established at 9 sites. The sites were selected from the 1984 survey and they varied in their level of acidity from mild to severe. 85NA, 85NA2, 85NA5, 85NA4, 85NA3, 85KA3, 85KA4, 85KA5, 85KA6, 83N046
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Influence of fluoride on the mineralization of collagen via the polymer-induced liquid-precursor (PILP) process.
ObjectiveThe polymer-induced liquid-precursor (PILP) mineralization process has been shown to remineralize artificial dentin lesions to levels consistent with those of native dentin. However, nanoindentation revealed that the moduli of those remineralized lesions were only ∼50% that of native dentin. We hypothesize that this may be due to the PILP process having been previously optimized to obtain high amounts (∼70wt%) of intrafibrillar crystals, but without sufficient interfibrillar mineral, another significant component of dentin.MethodsFluoride was added to the PILP-mineralization of collagen from rat tail tendon at varying concentrations to determine if a better balance of intra- versus inter-fibrillar mineralization could be obtained, as determined by electron microscopy. Nanoindentation was used to determine if fluoridated apatite could improve the mechanical properties of the composites.ResultsFluoride was successfully incorporated into the PILP-mineralization of rat tail tendon and resulted in collagen-mineral composite systems with the mineral phase of hydroxyapatite containing various levels of fluoridation. As the fluoride concentration increased, the crystals became larger and more rod-like, with an increasing tendency to form on the fibril surfaces rather than the interior. Nanomechanical testing of the mineralized tendons revealed that fluoride addition did not increase modulus over PILP mineralization alone. This likely resulted from the separated nature of collagen fibrils that comprise tendon, which does not provide lateral reinforcement and therefore may not be suited for the compressive loads of nanoindentation.SignificanceThis work contributes to the development of minimally invasive approaches to caries treatment by determining if collagen can be functionally mineralized
ADOPT: a tool for predicting adoption of agricultural innovations
A wealth of evidence exists about the adoption of new practices and technologies in agriculture but there does not appear to have been any attempt to simplify this vast body of research knowledge into a model to make quantitative predictions across a broad range of contexts. This is despite increasing demand from research, development and extension agencies for estimates of likely extent of adoption and the likely timeframes for project impacts. This paper reports on the reasoning underpinning the development of ADOPT (Adoption and Diffusion Outcome Prediction Tool). The tool has been designed to: 1) predict an innovation‘s likely peak extent of adoption and likely time for reaching that peak; 2) encourage users to consider the influence of a structured set of factors affecting adoption; and 3) engage R, D & E managers and practitioners by making adoptability knowledge and considerations more transparent and understandable. The tool is structured around four aspects of adoption: 1) characteristics of the innovation, 2) characteristics of the population, 3) actual advantage of using the innovation, and 4) learning of the actual advantage of the innovation. The conceptual framework used for developing ADOPT is described.Adoption, Diffusion, Prediction, Research and Development/Tech Change/Emerging Technologies,
Negative effective permeability and left-handed materials at optical frequencies
We present here the design of nano-inclusions made of properly arranged
collections of plasmonic metallic nano-particles that may exhibit a resonant
magnetic dipole collective response in the visible domain. When such inclusions
are embedded in a host medium, they may provide metamaterials with negative
effective permeability at optical frequencies. We also show how the same
inclusions may provide resonant electric dipole response and, when combining
the two effects at the same frequencies, lefthanded materials with both
negative effective permittivity and permeability may be synthesized in the
optical domain with potential applications for imaging and nano-optics
applications.Comment: 11 pages, 6 figures; modified the format, added a figur
Cut-wire-pair structures as two-dimensional magnetic metamaterials
We study numerically and experimentally magnetic metamaterials based on
cut-wire pairs instead of split-ring resonators. The cut-wire pair planar
structure is extended in order to create a truly two-dimensional metamaterial
suitable for scaling to optical frequencies. We fabricate the cut-wire
metamaterial operating at microwave frequencies with lattice spacing around 10%
of the free-space wavelength, and find good agreement with direct numerical
simulations. Unlike the structures based on split-ring resonators, the
nearest-neighbor coupling in cut-wire pairs can result in a magnetic stop-band
with propagation in the transverse direction
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THE ADAPTIVE RESPONSE AND PROTECTION AGAINST HERITABLE MUTATIONS AND FETAL MALFORMATION
There are a number of studies that show radiation can cause heritable mutations in the offspring of irradiated organisms. These “germ-line mutations” have been shown to occur in unique sequences of DNA called “minisatellite loci”. The high frequencies of spontaneous and induced mutations at minisatellite loci allow mutation induction to be measured at low doses of exposure in a small population, making minisatellite mutation a powerful tool to investigate radiation-induced heritable mutations. However, the biological significance of these mutations is uncertain, and their relationship to health risk or population fitness is unknown. We have adopted this mutation assay to study the role of adaptive response in protecting mice against radiation-induced heritable defects. We have shown that male mice, adapted to radiation with a low dose priming exposure, do not pass on mutations to their offspring caused by a subsequent large radiation exposure to the adapted males. This presentation and paper provide a general overview of radiationinduced mutations in offspring and explain the effect of low dose exposures and the adaptive response on these mutations. It is also known that exposure of pregnant females to high doses of radiation can cause death or malformation (teratogenesis) in developing fetuses. Malformation can only occur during a specialized stage of organ formation known as organogenesis. Studies in rodents show that radiation-induced fetal death and malformation can be significantly reduced when a pregnant female is exposed to a prior low dose of ionizing radiation. The mechanism of this protective effect, through an adaptive response, depends on the stage of organogenesis when the low dose exposures are delivered. To better understand this process, we have investigated the role of an important gene known as p53. Therefore, this report will also discuss fetal effects of ionizing radiation and explain the critical stages of development when fetuses are at risk. Research will be explained that investigates the biological and genetic systems (p53) that protect the developing fetus and discuss the role of low dose radiation adaptive response in these processes
A polarized beam splitter using an anisotropic medium slab
The propagation of electromagnetic waves in the anisotropic medium with a
single-sheeted hyperboloid dispersion relation is investigated. It is found
that in such an anisotropic medium E- and H-polarized waves have the same
dispersion relation, while E- and H-polarized waves exhibit opposite amphoteric
refraction characteristics. E- (or H-) polarized waves are positively refracted
whereas H- (or E-) polarized waves are negatively refracted at the interface
associated with the anisotropic medium. By suitably using the properties of
anomalous refraction in the anisotropic medium it is possible to realize a very
simple and very efficient beam splitter to route the light. It is shown that
the splitting angle and the splitting distance between E- and H- polarized beam
is the function of anisotropic parameters, incident angle and slab thickness.Comment: 14 pages, 6 figure
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