Maximizing pre-harvest sprouting in white- and red-seeded wheat

Non-Peer ReviewedSeed dormancy is the main factor responsible for conferring pre-harvest sprouting tolerance to wheat grain. Recently, five common wheat germplasm lines (W98616, Line 211, CDC EMDR-4, CDC EMDR-9, and CDC EMDR-14) with deep seed dormancy levels and differing genetic backgrounds were released by the Crop Development Centre, University of Saskatchewan. The objective of this presentation is to give an overview of (1) the five CDC germplasm lines, (2) the two dormancy breaking methods that effectively overcome the deep seed dormancy levels in the five CDC germplasm lines, and (3) how the two dormancy breaking method can be used by breeders to improve sprouting tolerance within their breeding programs using the five CDC germplasm lines

Isolation distances for minimizing out-crossing in spring wheat

Non-Peer ReviewedCurrently recommended isolation distances of three or 10 m for pedigreed seed production of spring wheat (Triticum aestivum L.) may not be sufficient for cultivars with high out-crossing (OC) rates. The detection of higher than expected OC rates in wheat has directed this research to reassess currently recommended minimum isolation distances. The objective of this study was to determine if increased isolation distances are needed for cultivars that exhibit higher than normal levels of out-crossing. In each of two years, OC rates were determined for four Canadian spring wheat cultivars at each of 15 distances (0-33 m) from a blue aleurone pollen source. Cultivars were grown in rows perpendicular to the pollinator block to the north, south, west, & east. Target rows were replicated four times within each direction. Out-crossing in ‘Katepwa’ & ‘Biggar’ was not detected beyond three meters. Cultivars ‘Roblin’ & ‘Oslo’ exhibited higher than normal OC at distances of up to 27m. For Roblin & Oslo, an isolation distance of 30m is recommended to mitigate OC-derived off-types in the subsequent generation of pedigreed seed

Skin effect as a probe of transport regimes in Weyl semimetals

We study the propagation of an oscillatory electromagnetic field inside a Weyl semimetal. In conventional conductors, the motion of the charge carriers in the skin layer near the surface can be diffusive, ballistic, or hydrodynamic. We show that the presence of chiral anomalies, intrinsic to the massless Weyl particles, leads to a hitherto neglected nonlocal regime that can separate the normal and viscous skin effects. We propose to use this regime as a diagnostic of the presence of chiral anomalies in optical conductivity measurements. These results are obtained from a generalized kinetic theory that includes various relaxation mechanisms, allowing us to investigate different transport regimes of Weyl semimetals

Influence of local fullerene orientation on the electronic properties of A3C60 compounds

We have investigated sodium containing fullerene superconductors Na2AC60, A = Cs, Rb, and K, by Na-23 nuclear magnetic resonance (NMR) spectroscopy at 7.5 T in the temperature range of 10 to 400 K. Despite the structural differences from the Rb3C60 class of fullerene superconductors, in these compounds the NMR line of the tetrahedrally coordinated alkali nuclei also splits into two lines (T and T') at low temperature. In Na2CsC60 the splitting occurs at 170 K; in the quenched cubic phase of Na2RbC60 and Na2KC60 we observe split lines at 80 K. Detailed investigations of the spectrum, spin-spin and spin-lattice relaxation as well as spin-echo double resonance (SEDOR) in Na2CsC60 we show that these two different tetrahedral sites are mixed on a microscopic scale. The T and T' sites differ in the orientation of first-neighbor C60 molecules. We present evidence that the orientations of neighboring molecules are uncorrelated. Thermally activated molecular reorientations cause an exchange between the T and T' sites and motional narrowing at high temperature. We infer the same activation energy, 3300 K, in the temperature range 125 to 300 K. The spin lattice relaxation rate is the same for T and T' down to 125 K but different below. Both the spin-lattice relaxation rate and Knight shift are strongly temperature dependent in the whole range investigated. We interpret this temperature variation by the effect of phonon excitations involving the rigid librational motion of the C60 molecules. By extending the understanding of the structure and molecular dynamics of C60 superconductors, these results may help in clarifying the effects of the structure on the superconducting properties.Comment: 13 pages, 10 figures, submitted to PR

Seed dormancy and germination in three annual canarygrass (Phalaris canariensis L.) cultivars relative to spring wheat (Triticum aestivum L.)

Non-Peer ReviewedSeed dormancy in annual canarygrass may lead to unsatisfactory germination in seed tests. The objectives of this study were (i) to quantify the levels of seed dormancy in three morphologically diverse annual canarygrass cultivars (‘Keet’, ‘CDC Maria’, & ‘CY 184’) relative to spring wheat & (ii) to determine the effectiveness of three treatments (GA3, KNO3, & chilling) & two temperature regimes (15/25°C & 15°C) in promoting germination of dormant annual canarygrass seeds. The hard red spring wheat cultivar ‘Katepwa’ control was included as a representative of a cereal crop that has been extensively characterized with regards to seed dormancy. In 1998 & 1999, the four cultivars were grown at Saskatoon, Canada. At maturity, panicles & spikes were hand harvested & stored at –20°C. Four replications of 50 seeds per cultivar were used in each experiment. Three experiments were conducted: (i) seeds were germinated at 10, 15, 20, & 25°C for one week, (ii) seeds were stored at 24°C for zero to eight weeks prior to germination at 22°C for one week, & (iii) seeds were treated with GA3, KNO3, & chilling prior to germination at 15/25°C (16/8h) or 15°C for two weeks. For experiment one & three, a split-plot analysis was used to analyze arc sin transformed percentage germination data. Average percentage germination data in experiment two were tested to be significantly different from 98% germination (P=0.05) based on one-tailed t-tests. Annual canarygrass developed deeper dormancy than the wheat cultivar in both years, particularly when germinated at 20 & 25°C. The highest percentage germination was observed at 15°C. Two (1998) & four weeks (1999) of storage at 24°C were required to overcome dormancy in annual canarygrass. Pre-chilling or KNO3 treatment prior to germination at 15/25°C (16/8h in darkness) resulted in average germination levels of 94% (1998) & 66% (1999). Potassium nitrate treatment prior to incubation at 15°C in darkness was the most effective method of promoting germination in dormant seeds, resulting in 99% (1998) & 97% (1999) germination. Thus, we recommend the use of the latter method, instead of the former or currently recommended method (pre-chilling or KNO3 treatment prior to germination at 15/25°C [16/8h] in darkness), for testing germination levels of dormant seed of annual canarygrass

Coefficient stability of operator–difference schemes

A priori estimates expressing continuous dependence of the solution of a first order evolutionary equation in Hubert space on initial condition, right hand side and operator perturbations are obtained in time–integral norms. Analogous results hold for corresponding finite difference schemes. Operatorinių-diferencialinių schemų koeficientis stabilumas Santrauka Darbe tiriamas pirmosios eiles nestacionariu diferencialiniu lygčiu, apibrežtu Huberto erdvese, stabilumas pradines salygos, laisvuju nariu ir operatoriaus koeficientu atžvilgiu. Stabilumo iverčiai irodomi integralinese laiko atžvilgiu normose. Analogiški rezultatai gauti ir baigtiniu skirtumu schemoms. Irodyti stipraus stabilumo iverčiai, kai modifikuojami lygties operatorius ir pradine salyga. Teoriniai rezultatai pritaikyti vienmačiam šilumos laidumo uždaviniui ir ji aproksimuojančiai baigtiniu skirtumu schemai. First Published Online: 14 Oct 201

Обобщение теоремы Лакса–Рябенького–Филиппова на нелинейные задачи

In this paper, Lax’s equivalence theorem, which states that stability is a necessary and sufficient condition for its convergence in the presence of an approximation of a difference scheme, is generalized to abstract nonlinear difference problems with operators acting in finite dimensional Banach spaces. In contrast to linear finite-difference methods, such a criterion in the nonlinear case can be established only for unconditionally stable computational methods, when the corresponding a priori estimates take place for sufficiently small |h| ≤ h0. In this case, the value of h0 depends both on the consistency of discrete and continuous norms in Banach spaces, and on the magnitude of the perturbation of the input data of the problem. The proven convergence criterion is used to study the stability of difference schemes approximating quasilinear parabolic equations with nonlinearities of unbounded growth with respect to the initial data.Теорема эквивалентности Лакса, утверждающая, что при наличии аппроксимации разностной схемы устойчивость является необходимым и достаточным условием ее сходимости, обобщается на абстрактные нелинейные разностные задачи с операторами, действующими в конечномерных банаховых пространствах. В отличие от линейных конечно-разностных методов, такой критерий в нелинейном случае удается установить лишь для безусловно устойчивых вычислительных методов, когда соответствующие априорные оценки имеют место при достаточно малом |h| ≤ h0. При этом величина h0 зависит как от согласованности дискретных и непрерывных норм в банаховых пространствах, так и от величины возмущения входных данных задачи. Доказанный критерий сходимости применяется для исследования устойчивости по начальным данным разностных схем, аппроксимирующих квазилинейные параболические уравнения с нелинейностями неограниченного роста

Difference schemes of high order accuracy for mathematical physics problems in arbitrary domains

In the present paper the difference schemes of high order accuracy for two‐dimensional equations of mathematical physics in an arbitrary domain are constructed. The computational domain is covered by a uniform rectangular grid. The second order accuracy of local approximation by spatial variables is achieved near‐boundary nodes. No increase of a standard grid scheme template is required. A priori estimates of the stability are obtained. Didelio tikslumo baigtinių skirtumų schemos Santrauka Darbe nagrinejami matematines fizikos uždaviniai, kai apibrežimo srities kontūras yra bet kokia glodi uždara kreive. Ši sritis pakeičiama tolygiu stačiakampiu tinklu. Panaudojant specialias aproksimavimo formules ir pasienio taškuose aproksimacijos paklaidos eile yra antroji. Svarbi naujojo algoritmo savybe yra tai, kad visuose taškuose naudojamas toks pat diskrečiojo tinklo šablonas. Irodomi aprioriniai stabilumo iverčiai ir ivertinamas diskrečiojo sprendinio konvergavimo greitis. Pateikti skaičiavimo eksperimento, kuriame naujoji schema palyginama su dviem kitomis žinomomis baigtiniu skirtumu schemomis, rezultatai. First Published Online: 14 Oct 201

Applying Fishers' Ecological Knowledge to Construct Past and Future Lobster Stocks in the Juan Fernández Archipelago, Chile

Over-exploited fisheries are a common feature of the modern world and a range of solutions including area closures (marine reserves; MRs), effort reduction, gear changes, ecosystem-based management, incentives and co-management have been suggested as techniques to rebuild over-fished populations. Historic accounts of lobster (Jasus frontalis) on the Chilean Juan Fernández Archipelago indicate a high abundance at all depths (intertidal to approximately 165 m), but presently lobsters are found almost exclusively in deeper regions of their natural distribution. Fishers' ecological knowledge (FEK) tells a story of serial depletion in lobster abundance at fishing grounds located closest to the fishing port with an associated decline in catch per unit effort (CPUE) throughout recent history. We have re-constructed baselines of lobster biomass throughout human history on the archipelago using historic data, the fishery catch record and FEK to permit examination of the potential effects of MRs, effort reduction and co-management (stewardship of catch) to restore stocks. We employed a bioeconomic model using FEK, fishery catch and effort data, underwater survey information, predicted population growth and response to MR protection (no-take) to explore different management strategies and their trade-offs to restore stocks and improve catches. Our findings indicate that increased stewardship of catch coupled with 30% area closure (MR) provides the best option to reconstruct historic baselines. Based on model predictions, continued exploitation under the current management scheme is highly influenced by annual fluctuations and unsustainable. We propose a community-based co-management program to implement a MR in order to rebuild the lobster population while also providing conservation protection for marine species endemic to the Archipelago