Interlayer couplings and the coexistence of antiferromagnetic and d-wave pairing order in multilayer cuprates

A more extended low density region of coexisting uniform antiferromagnetism and d-wave superconductivity has been reported in multilayer cuprates, when compared to single or bilayer cuprates. This coexistence could be due to the enhanced screening of random potential modulations in inner layers or to the interlayer Heisenberg and Josephson couplings. A theoretical analysis using a renormalized mean field theory, favors the former explanation. The potential for an improved determination of the antiferromagnetic and superconducting order parameters in an ideal single layer from zero field NMR and infrared Josephson plasma resonances in multilayer cuprates is discussed.Comment: 6 pages, 2 figure

Biomass Utilization Allocation in Biofuel Production: Model and Application

Various biomass sources can potentially be used for biofuel production, and many of these same biomass sources also have other uses. This raises an important question about biomass utilization allocation. We demonstrate an economic principle for biomass allocation by examining the profitability of woody biomass utilization in a simple two-product case. We then develop a mixed-integer programming model for allocating multiple biomass resources in the production of different biofuels and bioproducts. Our model combines biomass utilization allocation with biofuel supply chain optimization. The model is applied to solving the forest biomass utilization allocation problem for East Texas in the southern United States. We find that besides biofuel prices, production scale and CO2 offset credits also significantly affect biomass utilization allocation. Our findings validate our integrative model approach to addressing biomass allocation and provide useful implications for enhancing the efficient utilization of forest biomass. Keywords: forest biomass, biofuel supply chain, greenhouse gas offset, mathematical programming, southern United States. Received 10 October 2010, Revised 20 July 2012, Accepted 24 October 2012

Superconducting Pairing Symmetries in Anisotropic Triangular Quantum Antiferromagnets

Motivated by the recent discovery of a low temperature spin liquid phase in layered organic compound $\kappa$-(ET)$_2$Cu$_2$(CN)$_3$ which becomes a superconductor under pressure, we examine the phase transition of Mott insulating and superconducting (SC) states in a Hubbard-Heisenberg model on an anisotropic triangular lattice. We use a renormalized mean field theory to study the Gutzwiller projected BCS wavefucntions. The half filled electron system is a Mott insulator at large on-site repulsion $U$, and is a superconductor at a moderate $U$. The symmetry of the SC state depends on the anisotropy, and is gapful with $d_{x^2-y^2}+id_{xy}$ symmetry near the isotropic limit and is gapless with $d_{x^2-y^2}$ symmetry at small anisotropy ratio.Comment: 6 pages, 5 figure

Study of thermoelectric magnetohydrodynamic convection on solute redistribution during laser additive manufacturing

Melt pools formed in laser additive manufacturing (AM) are subject to large thermal gradients, resulting in the formation of thermoelectric currents due to the Seebeck effect. When in the presence of an external magnetic field, a Lorentz force is formed which drives fluid flow in the melt pool. This Thermoelectric Magnetohydrodynamics (TEMHD) phenomenon, can have a significant impact on the melt pool morphology and can alter the microstructural evolution of the solidification process. By coupling steady-state mesoscopic melt pool calculations to a microscopic solidification model, predictions of the resulting microstructure for multiple deposited layers have been obtained. The results indicate that the magnetic field can have a transformative effect on the microstructure and solute redistribution. This study highlights the theoretical potential for using magnetic fields as an additional control system to tailor AM microstructures

Thermoelectric magnetohydrodynamic control of melt pool dynamics and microstructure evolution in additive manufacturing

Large thermal gradients in the melt pool from rapid heating followed by rapid cooling in metal additive manufacturing generate large thermoelectric currents. Applying an external magnetic field to the process introduces fluid flow through thermoelectric magnetohydrodynamics. Convective transport of heat and mass can then modify the melt pool dynamics and alter microstructural evolution. As a novel technique, this shows great promise in controlling the process to improve quality and mitigate defect formation. However, there is very little knowledge within the scientific community on the fundamental principles of this physical phenomenon to support practical implementation. To address this multiphysics problem that couples the key phenomena of melting/solidification, electromagnetism, hydrodynamics, heat and mass transport, the lattice Boltzmann method for fluid dynamics was combined with a purpose-built code addressing solidification modelling and electromagnetics. The theoretical study presented here investigates the hydrodynamic mechanisms introduced by the magnetic field. The resulting steady-state solutions of modified melt pool shapes and thermal fields are then used to predict the microstructure evolution using a cellular automata based grain growth model. The results clearly demonstrate that the hydrodynamic mechanisms and, therefore, microstructure characteristics are strongly dependent on magnetic field orientation

Disease management strategies for Ascochyta blight of chickpea

Non-Peer ReviewedManagement of chickpea ascochyta blight is a difficult task that requires ongoing attention and utilization of all possible techniques. Starting with clean seed of a resistant cultivar is critical, but even with this sound foundation, fungicide application is often necessary. Optimizing fungicide application strategies in chickpea is essential to protect the crop while simultaneously keeping costs as low as possible. Field experiments showed that early application of fungicide is crucial, and often additional applications were necessary for effective disease management. Of the product sequences tested, those including two strobilurin applications and two other applications during the season gave superior disease control in several cases, but this did not always confer higher yields. Nozzle type had no effect on disease development or yield in any of the field site-years. Similarly in the laboratory study, nozzle types had no effect on the amount of spray coverage or the degree of spray penetration into the crop canopy. A similar laboratory study comparing carrier volumes showed that using a higher carrier volume (>100 L ha-1) improves penetration of a fern leaf-type canopy, but offered no benefit in a unifoliate canopy. In the field, increasing carrier volume did not improve disease control when disease pressure was low to moderate. In some cases under high disease pressure, higher carrier volumes were important for achieving disease control

Fungicide application timing for management of Ascochyta blight in chickpea

Non-Peer ReviewedAscochyta blight of chickpea [Ascochyta rabiei] is an extremely destructive disease capable of causing high yield and quality losses. The disease is widespread in chickpea growing areas of the prairies, and the pathogen can survive in crop debris for several years. Although partially resistant cultivars are available, the disease can still be devastating if weather conditions are favourable, making fungicides an important disease management tool. Trials investigating the effectiveness of different fungicide application timings and sequences were conducted on the desi cv. Myles and the kabuli cv. CDC Yuma at Saskatoon in 2003. The products used included Bravo 500, Headline, and Lance. The first application was made prior to flowering, when disease pressure was still extremely low. Additional applications were made at early flower, mid-flower, late flower or podding, with a maximum of three applications per treatment. In both cultivars, treatments without a pre-flower application of fungicide had higher disease severity and lower yields than treatments with a pre-flower application. Treatments without a pre-flower application that were sprayed three times were still inferior to treatments with a pre-flower application that were only sprayed twice. These results emphasize the need for early and frequent scouting for disease symptoms in chickpea to allow for early fungicide application if it is appropriate

In situ tropical peatland ire emission factors and their variability, as determined by field measurements in peninsula Malaysia

Fires in tropical peatlands account for >25% of estimated total greenhouse gas emissions from deforestation and degradation. Despite significant global and regional impacts, our understanding of specific gaseous fire emission factors (EFs) from tropical peat burning is limited to a handful of studies. Furthermore, there is substantial variability in EFs between sampled fires and/or studies. For example, methane EFs vary by 91% between studies. Here we present new fire EFs for the tropical peatland ecosystem; the first EFs measured for Malaysian peatlands, and only the second comprehensive study of EFs in this crucial environment. During August 2015 (under El Niño conditions) and July 2016, we embarked on field campaigns to measure gaseous emissions at multiple peatland fires burning on deforested land in Southeast Pahang (2015) and oil palm plantations in North Selangor (2016), Peninsula Malaysia. Gaseous emissions were measured using open-path Fourier transform infrared spectroscopy. The IR spectra were used to retrieve mole fractions of 12 different gases present within the smoke (including carbon dioxide and methane), and these measurements used to calculate EFs. Peat samples were taken at each burn site for physicochemical analysis and to explore possible relationships between specific physicochemical properties and fire EFs. Here we present the first evidence to indicate that substrate bulk density affects methane fire EFs reported here. This novel explanation of interplume, within-biome variability, should be considered by those undertaking greenhouse gas accounting and haze forecasting in this region and is of importance to peatland management, particularly with respect to artificial compaction