Psychophysical evidence for two routes to suppression before binocular summation of signals in human vision

Visual mechanisms in primary visual cortex are suppressed by the superposition of gratings perpendicular to their preferred orientations. A clear picture of this process is needed to (i) inform functional architecture of image-processing models, (ii) identify the pathways available to support binocular rivalry, and (iii) generally advance our understanding of early vision. Here we use monoptic sine-wave gratings and cross-orientation masking (XOM) to reveal two cross-oriented suppressive pathways in humans, both of which occur before full binocular summation of signals. One is a within-eye (ipsiocular) pathway that is spatially broadband, immune to contrast adaptation and has a suppressive weight that tends to decrease with stimulus duration. The other pathway operates between the eyes (interocular), is spatially tuned, desensitizes with contrast adaptation and has a suppressive weight that increases with stimulus duration. When cross-oriented masks are presented to both eyes, masking is enhanced or diminished for conditions in which either ipsiocular or interocular pathways dominate masking, respectively. We propose that ipsiocular suppression precedes the influence of interocular suppression and tentatively associate the two effects with the lateral geniculate nucleus (or retina) and the visual cortex respectively. The interocular route is a good candidate for the initial pathway involved in binocular rivalry and predicts that interocular cross-orientation suppression should be found in cortical cells with predominantly ipsiocular drive

Apparent vernalization requirement of high yielding spring wheat

Non-Peer ReviewedControlled environment studies have demonstrated that the high yield potential of certain spring wheat (Triticum aestivum L.) cultivars may result from a moderate vernalization requirement. The objective of this study was to determine whether apparent vernalization responses of cultivars could be detected when comparing the development of early and late-seeded crops. The effect of delayed seeding on 9 or 10 spring wheat cultivars was studied at Saskatoon over a period of four years. Within years, the earliest and latest dates of seeding differed by a minimum of 22 days. Vernalization effects were apparent in 1983 and 1986 but not in 1985 and 1987. In 1983 and 1986 Growing Degree Day accumulation 14 days after seeding (GDD14) averaged 44 for the earliest date of seeding compared to 120 GDD or more for the later seeding dates. However, the GDD14 for the earliest date of seeding was 121 in 1985 and 134 in 1987. Apparent vernalization effects were manifested by higher main stem leaf number, increased spikelet production and delayed spike emergence. Cultivars were ranked in the following order for apparent vernalization sensitivity: Fielder = Pitic 62 > HY402 > HY320 > Genesis > HY912 > Leader > Glenlea > Neepawa > Katepwa > Siete Cerros > Potam. Fielder had the greatest vernalization requirement and Potam the least. On average, delayed seeding resulted in increased grain yields, but this observation was not consistent over years

Optimizing nitrogen fertilizer response by winter wheat and rye

Non-Peer ReviewedSouthwestern Alberta has been the traditional winter wheat production area in western Canada. In recent years, the adoption of a practical snow management system, which utilizes no-till seeding into standing stubble immediately after harvest of the previous crop, has resulted in an extension of this production area to include most of the western Canadian prairies. Winter rye is also adapted to the no-till production system developed for winter wheat. Most stubble fields are deficient in available soil nitrogen (N) with the result that N fertilizer is a major input cost in the production of no-till winter wheat and rye. This report summarizes the N response observed in 40 winter wheat and 20 winter rye trials representing a broad range of soil types and environments in western Canada. Nitrogen fertilizer did not have a significant influence on heading date, maturity, hectoliter weight or kernel size in most trials. Where a significant N response was detected, maximum differences were a one and two day delay in heading, a two and nine day delay in maturity, a three and three kg reduction in hectoliter weight, and a seven and nine mg reduction in seed size for wheat and rye, respectively. A significant N response was observed more frequently for height. In this instance, the response was not directional and increases up to 25 and eight cm and reductions to nine and nine cm were observed with increased N for wheat and rye, respectively. The Gompertz equation provided the most complete description of the relationship between protein concentration and total plant-available N. Predicted grain protein concentration from this equation explained 98 and 93 percent of the variability in actual grain protein concentration for wheat and rye, respectively. The N response curves for protein concentration were similar for winter wheat and rye. After an initial lag, protein concentration increased rapidly, and then tailed off at high N levels. An inverse polynomial function was employed to describe grain and protein yield response to N fertilizer. Predicted yields from these equations explained 96 and 88 percent of the variability in actual grain yield and 94 and 89 percent of the variability in actual protein yield for wheat and rye, respectively. Winter rye demonstrated a greater N use efficiency and yield potential than winter wheat. There was a large interdependence of N response and environmental conditions, especially moisture supply, in determining yield in these trials

Factors affecting performance of different pedigreed seedlots of Harrington barley and Katepwa wheat

Non-Peer Reviewe

Pedestrian Solution of the Two-Dimensional Ising Model

The partition function of the two-dimensional Ising model with zero magnetic field on a square lattice with m x n sites wrapped on a torus is computed within the transfer matrix formalism in an explicit step-by-step approach inspired by Kaufman's work. However, working with two commuting representations of the complex rotation group SO(2n,C) helps us avoid a number of unnecessary complications. We find all eigenvalues of the transfer matrix and therefore the partition function in a straightforward way.Comment: 10 pages, 2 figures; eqs. (101) and (102) corrected, files for fig. 2 fixed, minor beautification

Salt tolerance in barley

Non-Peer Reviewe

Integrated radwaste treatment system lessons learned from 2{1/2} years of operation

The Integrated Radwaste Treatment System (IRTS) at the West Valley Demonstration Project (WVDP) is a pretreatment scheme to reduce the amount of salts in the high-level radioactive waste (vitrification) stream. Following removal of cesium-137 (Cs-137) by ion-exchange in the Supernatant Treatment System (STS), the radioactive waste liquid is volume-reduced by evaporation. Trace amounts of Cs-137 in the resulting distillate are removed by ion-exchange, then the distillate is discharged to the existing plant water treatment system. The concentrated product, 37 to 41 percent solids by weight, is encapsulated in cement producing a stable, low-level waste form. The Integrated Radwaste Treatment System (IRTS) operated in this mode from May 1988 through November 1990, decontaminating 450,000 gallons of high-level waste liquid; evaporating and encapsulating the resulting concentrates into 10,393 71-gallon square drums. A number of process changes and variations from the original operating plan were required to increase the system flow rate and minimize waste volumes. This report provides a summary of work performed to operate the IRTS, including system descriptions, process highlights, and lessons learned

The Lazarus project: A pragmatic approach to binary black hole evolutions

We present a detailed description of techniques developed to combine 3D numerical simulations and, subsequently, a single black hole close-limit approximation. This method has made it possible to compute the first complete waveforms covering the post-orbital dynamics of a binary black hole system with the numerical simulation covering the essential non-linear interaction before the close limit becomes applicable for the late time dynamics. To determine when close-limit perturbation theory is applicable we apply a combination of invariant a priori estimates and a posteriori consistency checks of the robustness of our results against exchange of linear and non-linear treatments near the interface. Once the numerically modeled binary system reaches a regime that can be treated as perturbations of the Kerr spacetime, we must approximately relate the numerical coordinates to the perturbative background coordinates. We also perform a rotation of a numerically defined tetrad to asymptotically reproduce the tetrad required in the perturbative treatment. We can then produce numerical Cauchy data for the close-limit evolution in the form of the Weyl scalar $\psi_4$ and its time derivative $\partial_t\psi_4$ with both objects being first order coordinate and tetrad invariant. The Teukolsky equation in Boyer-Lindquist coordinates is adopted to further continue the evolution. To illustrate the application of these techniques we evolve a single Kerr hole and compute the spurious radiation as a measure of the error of the whole procedure. We also briefly discuss the extension of the project to make use of improved full numerical evolutions and outline the approach to a full understanding of astrophysical black hole binary systems which we can now pursue.Comment: New typos found in the version appeared in PRD. (Mostly found and collected by Bernard Kelly

Resummation of Nonalternating Divergent Perturbative Expansions

A method for the resummation of nonalternating divergent perturbation series is described. The procedure constitutes a generalization of the Borel-Pad\'{e} method. Of crucial importance is a special integration contour in the complex plane. Nonperturbative imaginary contributions can be inferred from the purely real perturbative coefficients. A connection is drawn from the quantum field theoretic problem of resummation to divergent perturbative expansions in other areas of physics.Comment: 5 pages, LaTeX, 2 tables, 1 figure; discussion of the Carleman criterion added; version to appear in Phys. Rev.

Analysis of the genome sequence of an alpaca coronavirus

AbstractCoronaviral infection of New World camelids was first identified in 1998 in llamas and alpacas with severe diarrhea. In order to understand this infection, one of the coronavirus isolates was sequenced and analyzed. It has a genome of 31,076 nt including the poly A tail at the 3′ end. This virus designated as ACoV-00-1381 (ACoV) encodes all 10 open reading frames (ORFs) characteristic of Group 2 bovine coronavirus (BCoV). Phylogenetic analysis showed that the ACoV genome is clustered closely (>99.5% identity) with two BCoV strains, ENT and LUN, and was also closely related to other BCoV strains (Mebus, Quebec, DB2), a human corona virus (strain 043) (>96%), and porcine hemagglutinating encephalomyelitis virus (>93% identity). A total of 145 point mutations and one nucleotide deletion were found relative to the BCoV ENT. Most of the ORFs were highly conserved; however, the predicted spike protein (S) has 9 and 12 amino acid differences from BCoV LUN and ENT, respectively, and shows a higher relative number of changes than the other proteins. Phylogenetic analysis suggests that ACoV shares the same ancestor as BCoV ENT and LUN