Cultivar considerations and pod sealants for straight-combining canola in Saskatchewan

Non-Peer ReviewedWhile the recommended and preferred harvest practice in western Canada is to swath canola (Brassica napus L.), there is appreciable interest in straight-combining this crop. In a recent study, five cultivars were harvested according to one of four harvest treatments and evaluated for seed yield, yield loss due to shattering, percent green seed and seed size. The cultivars included four B. napus hybrids and an open-pollinated canola quality B. juncea variety. Harvest strategies were swathed, straight-combined without a pod sealant, straight-combined with Pod Ceal DC® and straight-combined with Pod-Stik®. While average yields ranged from 894-3066 kg ha-1, cultivar rankings for yield were generally consistent across sites. Seed yields were equal when averaged across harvest treatments and sites, but swathed yields differed from straight-combined yields 50% of the time for individual sites. At two sites, straight-combining produced 142-370 kg ha-1 higher yields than swathing while, when harvest was delayed due to unfavourable weather, swathed yields were 276-413 kg ha-1 higher. A 217 kg ha-1 yield increase occurred with pod sealants at one site, but there were no differences amongst the two products and pod sealants did not affect yields of straight-combined canola at the remaining seven sites. Pod sealants did not have a measurable effect on shattering losses, even under high shattering conditions. In contrast, cultivar effects on seed loss were generally significant with losses from one of the napus cultivars being particular and consistently low, especially when overall shattering losses were high. On average, losses for all cultivars were 4% of the total yield when harvest was completed reasonably close to the optimal stage. Straight-combining resulted in a small but significant increase in percent green seed and seed size but pod sealants did not affect seed quality in any cases. In conclusion, straight-combining can be a viable alternative to swathing, but substantial yield losses may occur if harvest is delayed too long. Important varietal differences in shattering losses were detected and cultivar selection appears to be a factor of greater importance than pod sealants for growers planning to straight-combine canola

A photometric study of the young open cluster NGC 1220

We present UBV CCD observations obtained in the field of the northern open cluster NGC 1220, for which little information is available. We provide also BV CCD photometry of a field 5$^{\prime}$ northward of NGC 1220 to take into account field star contamination. We argue that NGC 1220 is a young compact open cluster, for which we estimate a core radius in the range $1.5-2.0$ arcmin. We identify 26 likely candidate members with spectral type earlier than $A5$, down to $V_o$=15.00 mag on the basis of the position in the two-colour Diagram and in the Colour Magnitude Diagrams (CMDs). By analyzing the distribution of these stars in the colour-colour and CMDs, we find that NGC 1220 has a reddening E$(B-V)=0.70\pm0.15$ mag, is placed $1800\pm200$ pc distant from the Sun, and has an age of about 60 Myrs. The cluster turns out to be located about 120 pc above the Galactic plane, relatively high with respect to its age.Comment: 7 pages, 8 eps figures, accepted for publication in A&

The cytoplasm of living cells: A functional mixture of thousands of components

Inside every living cell is the cytoplasm: a fluid mixture of thousands of different macromolecules, predominantly proteins. This mixture is where most of the biochemistry occurs that enables living cells to function, and it is perhaps the most complex liquid on earth. Here we take an inventory of what is actually in this mixture. Recent genome-sequencing work has given us for the first time at least some information on all of these thousands of components. Having done so we consider two physical phenomena in the cytoplasm: diffusion and possible phase separation. Diffusion is slower in the highly crowded cytoplasm than in dilute solution. Reasonable estimates of this slowdown can be obtained and their consequences explored, for example, monomer-dimer equilibria are established approximately twenty times slower than in a dilute solution. Phase separation in all except exceptional cells appears not to be a problem, despite the high density and so strong protein-protein interactions present. We suggest that this may be partially a byproduct of the evolution of other properties, and partially a result of the huge number of components present.Comment: 11 pages, 1 figure, 1 tabl

Collisional kinetics of non-uniform electric field, low-pressure, direct-current discharges in H2_{2}

A model of the collisional kinetics of energetic hydrogen atoms, molecules, and ions in pure H$_2$ discharges is used to predict H$_\alpha$ emission profiles and spatial distributions of emission from the cathode regions of low-pressure, weakly-ionized discharges for comparison with a wide variety of experiments. Positive and negative ion energy distributions are also predicted. The model developed for spatially uniform electric fields and current densities less than $10^{-3}$ A/m$^2$ is extended to non-uniform electric fields, current densities of $10^{3}$ A/m$^2$, and electric field to gas density ratios $E/N = 1.3$ MTd at 0.002 to 5 Torr pressure. (1 Td = $10^{-21}$ V m$^2$ and 1 Torr = 133 Pa) The observed far-wing Doppler broadening and spatial distribution of the H$_\alpha$ emission is consistent with reactions among H$^+$, H$_2^+$, H$_3^+$, and H$^-H$ ions, fast H atoms, and fast H$_2$ molecules, and with reflection, excitation, and attachment to fast H atoms at surfaces. The H$_\alpha$ excitation and H$^-$ formation occur principally by collisions of fast H, fast H$_2$, and H$^+$ with H$_2$. Simplifications include using a one-dimensional geometry, a multi-beam transport model, and the average cathode-fall electric field. The H$_\alpha$ emission is linear with current density over eight orders of magnitude. The calculated ion energy distributions agree satisfactorily with experiment for H$_2^+$ and H$_3^+$, but are only in qualitative agreement for H$^+$ and H$^-$. The experiments successfully modeled range from short-gap, parallel-plane glow discharges to beam-like, electrostatic-confinement discharges.Comment: Submitted to Plasmas Sources Science and Technology 8/18/201

Numerical simulation of unconstrained cyclotron resonant maser emission

When a mainly rectilinear electron beam is subject to significant magnetic compression, conservation of magnetic moment results in the formation of a horseshoe shaped velocity distribution. It has been shown that such a distribution is unstable to cyclotron emission and may be responsible for the generation of Auroral Kilometric Radiation (AKR) an intense rf emission sourced at high altitudes in the terrestrial auroral magnetosphere. PiC code simulations have been undertaken to investigate the dynamics of the cyclotron emission process in the absence of cavity boundaries with particular consideration of the spatial growth rate, spectral output and rf conversion efficiency. Computations reveal that a well-defined cyclotron emission process occurs albeit with a low spatial growth rate compared to waveguide bounded simulations. The rf output is near perpendicular to the electron beam with a slight backward-wave character reflected in the spectral output with a well defined peak at 2.68GHz, just below the relativistic electron cyclotron frequency. The corresponding rf conversion efficiency of 1.1% is comparable to waveguide bounded simulations and consistent with the predictions of kinetic theory that suggest efficient, spectrally well defined radiation emission can be obtained from an electron horseshoe distribution in the absence of radiation boundaries.Publisher PD

Optimizing N fertilizer rates for seed yield in Camelina sativa and Brassica carinata

Non-Peer Reviewe

Optimizing nitrogen rates in Camelina sativa

Non-Peer ReviewedCamelina is a new oilseed crop to western Canada with potential applications in cosmetics, human nutrition, and biofuel. Nitrogen recommendations for camelina production in Western Canada aren’t available. Field studies were conducted in 2008 and 2009 for 10 site years at locations in western Canada to determine the effect of nitrogen rate on seed yield. Depending on the experiment, nitrogen rates ranged from 0 to 200 kg ha-1. The join point (N rate at which yields plateau) for camelina were 111 to 116 kg ha-1, which is similar to other Brassica oilseed species

Experiment and simulations of kinetic instabilities in mirror-confined ECR discharge plasma

Non-Maxwellian electron distribution functions give rise to a rich variety of kinetic instabilities, such as streaming instability, Weibel instability, and electrostatic and electromagnetic cyclotron instabilities. Electron ring-like distributions are ubiquitous in space plasmas and also occur in mirror-confined plasma where the loss-cone cuts a 'hole' in the distribution function. We report recent observations and simulations of instabilities in mirror-confined ECR discharge plasma [1], where excitation on harmonics and half-harmonics of the electron cyclotron frequency have been observed. The relevance to space plasma are also discussed where similar observations by satellites are common [2,3]. Theory and simulations show that electrostatic instabilities take place where two electron Bernstein modes merge [4]. Electromagnetic Vlasov simulations also show the coupling between electrostatic and electromagnetic electron Bernstein modes leading to instabilities near cyclotron harmonics

Microwave emission due to kinetic instabilities in an over-dense mirror-confined plasma

The kinetic instabilities of a microwave plasma confined in an open magnetic trap are relevant to understanding various types of radio emission in space plasma, for example, in the magnetospheres of the Earth and the planets, the Sun, and certain types of stars. The high efficiency of the kinetic wave generation mechanism is due to the low group velocity of plasma waves (in comparison with electromagnetic waves), which ensures they enjoy an extended interaction time with nonequilibrium particles resulting in a high integral gain. Emission from the plasma is observed due to various mechanisms for the transformation of plasma waves into electromagnetic waves, for example, as a result of scattering by thermal ions. In view of the universality of the physical mechanisms of radiation generation, essential aspects of natural systems can be reproduced in laboratory magnetic traps under controlled and reproducible conditions. Hitherto the excitation of plasma waves in open magnetic traps has been carried out with the use of electron beams. The technique reported here exploits a plasma generated by irradiating a mirror confined plasma using mm-waves from a gyrotron under electron-cyclotron resonance conditions, a technique also potentially of interest for technological applications. In such a discharge, a two-component plasma is created with a dense cold (background) fraction with an isotropic particle velocity distribution and a less dense high-energy fraction of nonequilibrium electrons with an anisotropic distribution function. In these experiments, bursts of powerful electromagnetic radiation at a frequency close to the upper hybrid resonance and to the second harmonic of the electron gyrofrequency were observed for the first time, accompanied by synchronous precipitation of fast electrons from the trap. The observed bursts were associated with the instability of plasma waves under conditions of a double plasma resonance, with subsequent transformation of the plasma waves into electromagnetic waves. This poster focuses on a theoretical and experimental study of wave generation in a dense magnetoactive plasma at the harmonics of the electron gyrofrequency. In the experiments at the IAP RAS, a detailed study of the fine structure of dynamic spectra using ultra-wideband oscilloscopes with a bandwidth of up to 59 GHz is reported. Theoretical and numerical analysis at relevant plasma parameters is underway at the University of Strathclyde. Comparison of experimental and theoretical data will lead to an understanding of the mechanisms of electromagnetic radiation generation in magnetic traps and the features of the radio emission spectra observed in natural conditions

Network metrics can guide nearly-optimal management of invasive species at large scales

Invasive species harm biodiversity and ecosystem services, with global economic costs of invasions exceeding $40 billion annually. Widespread invasions are a particular challenge because they involve large spatial scales with many interacting components. In these contexts, typical optimization-based approaches to management may fail due to computational or data constraints. Here we evaluate an alternative solution that leverages network science, representing the invasion as occurring across a network of connected sites and using network metrics to prioritize sites for intervention. Such heuristic network-guided methods require less data and are less computationally intensive than optimization methods, yet network-guided approaches have not been bench-marked against optimal solutions for real-world invasive species management problems. We provide the first comparison of the performance of network-guided management relative to optimal solutions for invasive species, examining the placement of watercraft inspection stations for preventing spread of invasive zebra mussels through recreational boat movement within 58 Minnesota counties in the United States. To additionally test the promise of network-based approaches in limited data contexts, we evaluate their performance when using only partial data on network structure and invaded status. Metric-based approaches can achieve a median of 100% of optimal performance with full data. Even with partial data, 80% of optimal performance is achievable. Finally, we show that performance of metric-guided management improves for counties with denser and larger networks, suggesting this approach is viable for large-scale invasions. Together, our results suggest network metrics are a promising approach to guiding management actions for large-scale invasions.Comment: 29 pages, 8 figures, 3 table