Responses of grain yield, biomass and harvest index and their rates of genetic progress to nitrogen availability in ten winter wheat varieties.

peer-reviewedIncreased yields in winter wheat cultivars have been found to be largely attributable to improved partitioning of biomass to the grain, i.e., higher harvest index. However, there is a biological upper limit to harvest index and therefore breeders need to exploit increased biomass production as the mechanism by which yields are increased. Evidence for improved biomass was sought in experiments conducted over three years (1994 to 1996), at the Plant Testing Station, Crossnacreevy, near Belfast, with 10 varieties of winter wheat introduced over the period 1977 to 1991. Variation in grain yield was more strongly associated with variation in biomass (an increase of 0.78 t/ha in grain yield at 85% dry matter (DM) per 1t/ha increase in biomass at 100% DM; R2 = 0.71) than in harvest index (an increase of 0.1t/ha at 85% DM per percentage point increase in harvest index; R2 = 0.36). When age (= year of first harvest in UK National List trials) of the varieties was taken into account, yield (0.037 t ha−y−; R2 = 0.42) and biomass (0.034 t ha−y−; R2 = 0.31), but not harvest index (0.34%/year; R2 = 0.001), increased as year increased. Genetic gain in yield was smaller without fertiliser N (0.021 t ha−y−; R2 = 0.21) and at 40 kg ha N (0.025 t ha−y−; R2 =0.25) than at 215–250 kg/ha N (0.065 t ha−y−; R2 = 0.39). Theoretically, if the maximum biomass (18.60 t/ha for Rialto), could have been combined with the maximum harvest index (55.3%) in Riband, yield would potentially have been increased by 2.5 t/ha compared with yields for either variety.Advice and guidance from Dr. Sally Watson, Biometrics Branch, Agri-Food and Biosciences Institute is appreciated

Electronic marketplace-to-marketplace alliances: emerging trends and strategic rationales

The electronic marketplace domain has recently witnessed the joining together of a number of previously independent marketplaces and the formation of collaborative alliances between others. This study seeks to determine the nature or type of cooperative arrangements or alliances that are currently being forged between electronic marketplaces, and the strategic rationale that is leading to this observed alliance formation. The findings of the study are based upon an examination of statements made to the press by marketplaces undertaking strategic alliances. This published data was supplemented with face-to-face interviews with managers at three relevant electronic marketplaces. Three distinct types of alliance are observed; the merger between previously separate marketplaces, the acquisition of one marketplace by another and the formation of an interoperability agreement between two marketplaces. Three rationales for alliance formation were observed: an increase in the number of buyers or suppliers in a given market sector that can access the marketplace (an increase in scale of operations), an increase in the breadth or depth of services that are offered to users of the marketplace (an increase in the scope of operations) and providing the ability to exchange information across multiple tiers of a supply chain. A broader discussion of the findings is given and suggestions for further research are made

Database Analysis to Support Nutrient Criteria Development (Phase II)

The intent of this publication of the Arkansas Water Resources Center is to provide a location whereby a final report on water research to a funding agency can be archived. The Texas Commission on Environmental Quality (TCEQ) contracted with University of Arkansas researchers for a multiple year project titled “Database Analysis to Support Nutrient Criteria Development”. This publication covers the second of three phases of that project and has maintained the original format of the report as submitted to TCEQ. This report can be cited either as an AWRC publication (see below) or directly as the final report to TCEQ

Mechanical Treatment and Burning for High Quality Range Forage

Annual yields of western wheatgrass and total vegetation were increased on a clayey range site following mechanical treatment. More important to the range manager, year t o year variability in forage production was reduced, since soil moisture is stabilized. Yields of Japanese brome, an annual grass, increased from the second through the fourth growing seasons after treatment. Three consecutive years of abundant fall precipitation beginning in 1980 probably triggered seed germination of this invader plant. Prescribed burning of the mechanical range treatments drastically reduced production of Japanese brome and increased forage quality. Both quantity and quality of western wheatgrass increased after burning. Prescribed burning did not negatively impact yields of total vegetation. Reducing the yield of an undesirable species such as Japanese brome causes an increase in percentage composition, if not the yield, of desirables such as western wheatgrass. Therefore, range condition percentage and carrying capacity should be higher. Further prescribed burning research in South Dakota would appear to be important since the cost of this practice is relatively low compared with most, if not all, other range improvement practices

Factors Affecting Yield and Quality of Oats.

End of Project ReportQuality evaluation of oats relies primarily on hectolitre weight and, while it is an important characteristic, work carried out at Oak Park and elsewhere has shown that it does not accurately measure grain quality. Consequently, the selection of oat lots and varieties which have a high milling value has been limited, as present techniques fail to accurately determine the characteristics most closely related to milling quality. In this regard the kernel content and the ease of husk removal, termed the hullability, are the most important. This study has developed a new test for assessing oat kernel content, which is more rapid and cheaper than techniques currently available. Despite its obvious importance, oat hullability has not been assessed to date in quality evaluation due to the absence of a test procedure. However, this obstacle has now been overcome. The results of this work also provide a much better understanding of how hullability of individual varieties can be assessed, as well as investigating how this could be manipulated at field level. Using the methods developed, the selection of varieties with enhanced processing characteristics can now be carried out more precisely for Irish conditions. The field trials conducted to evaluate the effect of agronomic practices on quality indicated that the effect of factors such as nitrogen rate and seed rate was small in comparison to variety, which had the largest and most consistent effect. The variation in quality could not be completely explained by variation in the panicle characteristics studied. Increasing the nitrogen rate increased yield with the optimum being 160 kg N/ha in 1998 and 1999. However, lodging became a very significant factor at nitrogen rates above 100 kg N/ha in 1998, although it did not occur in 1999. This work supports the current Teagasc nitrogen recommendations for oats where levels of 110-140 kg N/ha (Soil Index 1) are advised

Magnetic polarons in weakly doped high-Tc superconductors

We consider a spin Hamiltonian describing $d$-$d$ exchange interactions between localized spins $d$ of a finite antiferromagnet as well as $p$-$d$ interactions between a conducting hole ($p$) and localized spins. The spin Hamiltonian is solved numerically with use of Lanczos method of diagonalization. We conclude that $p$-$d$ exchange interaction leads to localization of magnetic polarons. Quantum fluctuations of the antiferromagnet strengthen this effect and make the formation of polarons localized in one site possible even for weak $p$-$d$ coupling. Total energy calculations, including the kinetic energy, do not change essentially the phase diagram of magnetic polarons formation. For parameters reasonable for high-$T_c$ superconductors either a polaron localized on one lattice cell or a small ferron can form. For reasonable values of the dielectric function and $p$-$d$ coupling, the contributions of magnetic and phonon terms in the formation of a polaron in weakly doped high-$T_c$ materials are comparable.Comment: revised, revtex-4, 12 pages 8 eps figure

Direct observation by resonant tunneling of the B^+ level in a delta-doped silicon barrier

We observe a resonance in the conductance of silicon tunneling devices with a delta-doped barrier. The position of the resonance indicates that it arises from tunneling through the B^+ state of the boron atoms of the delta-layer. Since the emitter Fermi level in our devices is a field-independent reference energy, we are able to directly observe the diamagnetic shift of the B^+ level. This is contrary to the situation in magneto-optical spectroscopy, where the shift is absorbed in the measured ionization energy.Comment: submitted to PR

Magnifying Grains of Sand, Seeds, and Blades of Grass: Optical Effects in Robert Grosseteste’s De iride (On the Rainbow) (circa 1228–1230)

In his treatise On the Rainbow (De iride), composed nearly four hundred years before the first known telescope, the English polymath Robert Grosseteste identified three striking optical effects: distant objects can be rendered close by; close-by large objects can be rendered small; and distant small objects can be rendered large. In the context of the history of optics, the first effect is especially striking. Grosseteste did not give details of the mechanisms underlying these effects but did mention the passage of rays through refraction in “diaphanous” or transparent bodies. While making no final claim that Grosseteste himself necessarily knew of or used lenses, this essay examines the coherence between the three optical effects described in Grosseteste’s treatise and two candidate proposals for the deployment of a single convex lens. A convex lens, deployed in different ways, is shown to produce all three of Grosseteste’s optical effects, in a manner strikingly aligned with the language that he uses to distinguish changes in the location and size of objects. The implications of this coherence for interpretations of On the Rainbow are discussed throughout the essay

Coulomb gap in a model with finite charge transfer energy

The Coulomb gap in a donor-acceptor model with finite charge transfer energy $\Delta$ describing the electronic system on the dielectric side of the metal-insulator transition is investigated by means of computer simulations on two- and three-dimensional finite samples with a random distribution of equal amounts of donor and acceptor sites. Rigorous relations reflecting the symmetry of the model presented with respect to the exchange of donors and acceptors are derived. In the immediate neighborhood of the Fermi energy $\mu$ the the density of one-electron excitations $g(\epsilon)$ is determined solely by finite size effects and $g(\epsilon)$ further away from $\mu$ is described by an asymmetric power law with a non-universal exponent, depending on the parameter $\Delta$.Comment: 10 pages, 6 figures, submitted to Phys. Rev.

The Sachs-Wolfe Effect: Gauge Independence and a General Expression

In this paper we address two points concerning the Sachs-Wolfe effect: (i) the gauge independence of the observable temperature anisotropy, and (ii) a gauge-invariant expression of the effect considering the most general situation of hydrodynamic perturbations. The first result follows because the gauge transformation of the temperature fluctuation at the observation event only contributes to the isotropic temperature change which, in practice, is absorbed into the definition of the background temperature. Thus, we proceed without fixing the gauge condition, and express the Sachs-Wolfe effect using the gauge-invariant variables.Comment: 5 pages, closer to published versio