A methodological framework to determine optimum durations for the construction of soil water characteristic curves using centrifugation

peer-reviewedDuring laboratory assessment of the soil water characteristic curve (SWCC), determining equilibrium at various pressures is challenging. This study establishes a methodological framework to identify appropriate experimental duration at each pressure step for the construction of SWCCs via centrifugation. Three common temporal approaches to equilibrium – 24-, 48- and 72-h – are examined, for a grassland and arable soil. The framework highlights the differences in equilibrium duration between the two soils. For both soils, the 24-h treatment significantly overestimated saturation. For the arable site, no significant difference was observed between the 48- and 72-h treatments. Hence, a 48-h treatment was sufficient to determine ‘effective equilibrium’. For the grassland site, the 48- and 72-h treatments differed significantly. This highlights that a more prolonged duration is necessary for some soils to conclusively determine that effective equilibrium has been reached. This framework can be applied to other soils to determine the optimum centrifuge durations for SWCC construction.Teagasc Walsh Fellowship Programm

Forum on Samir Gandesha - Johan Hartle (eds.), "Aesthetic Marx"

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Acetic Acid Bacteria: Physiology and Carbon Sources Oxidation

Acetic acid bacteria (AAB) are obligately aerobic bacteria within the family Acetobacteraceae, widespread in sugary, acidic and alcoholic niches. They are known for their ability to partially oxidise a variety of carbohydrates and to release the corresponding metabolites (aldehydes, ketones and organic acids) into the media. Since a long time they are used to perform specific oxidation reactions through processes called “oxidative fermentations”, especially in vinegar production. In the last decades physiology of AAB have been widely studied because of their role in food production, where they act as beneficial or spoiling organisms, and in biotechnological industry, where their oxidation machinery is exploited to produce a number of compounds such as l-ascorbic acid, dihydroxyacetone, gluconic acid and cellulose. The present review aims to provide an overview of AAB physiology focusing carbon sources oxidation and main products of their metabolism

Progress Towards High Performance, Steady-state Spherical Torus

Research on the Spherical Torus (or Spherical Tokamak) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect-ratio devices, such as the conventional tokamak. The Spherical Tours (ST) experiments are being conducted in various U.S. research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium-size ST research facilities: Pegasus at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the U.S., an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high-performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (B), noninductive sustainment, ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values bT of up to 35% with the near unity central betaT have been obtained. NSTX will be exploring advanced regimes where bT up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for noninductive sustainment in NSTX is the high beta-poloidal regime, where discharges with a high noninductive fraction ({approx}60% bootstrap current + neutral-beam-injected current drive) were sustained over the resistive skin time. Research on radio-frequency-based heating and current drive utilizing HHFW (High Harmonic Fast Wave) and EBW (Electron Bernstein Wave) is also pursued on NSTX, Pegasus, and CDX-U. For noninductive start-up, the Coaxial Helicity Injection (CHI), developed in HIT/HIT-II, has been adopted on NSTX to test the method up to Ip {approx} 500 kA. In parallel, start-up using radio-frequency current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor

The effect of soil moisture deficit on the susceptibility of soil to compaction as a result of vehicle traffic

Soil compaction negatively affects soil productivity, fertilizer use efficiency and water infiltration. The extent of compaction is dependant on soil strength, which is influenced by the soil moisture content. The purpose of this study was to determine the extent of soil compaction (measured by changes in soil bulk density and shear strength) and soil deformation incurred due to a single pass of a tractor and a fully loaded slurry tanker over grassland soils at a range of soil moisture deficits (SMD). The study should identify threshold values of SMD at which adverse soil compaction becomes significant for the soil-crop system. These values may be incorporated into the forecasting and decision making process for slurry spreading. SMD was used as a proxy for volumetric water content. Treatments of a single pass by a Landini Vision 105 tractor and a loaded 7.2 m³ single axle slurry tanker (total weight of c. 18 tonnes) were conducted on well, moderate and poorly drained grassland soils at forecasted SMD of 0, 5, 10 and 20 mm. The moderately drained soil was classified as a loam, while the well and poorly drained sites were classified as sandy loams. Changes in soil bulk density and torsional shear strength were used as indicators of compaction, with rut profile measurements taken to measure the extent of surface deformation, which is often the most visible indicator of compaction on the soil surface. Grass yields were measured at 30 and 60 days subsequent to trafficking. Results showed that SMD at the time of traffic had an effect on the changes in bulk density, shear strength and the extent of soil rutting following wheel traffic. Preliminary results indicate that higher SMD at the time of trafficking resulted in smaller changes to soil characteristics and more rapid recovery from surface deformation than when trafficking occurred at lower SMD. Trafficking at an SMD of 20 mm led to mean increases in soil bulk density of 8% and formation of ruts with cross sectional areas in the range of 29.4 cm² to 98.3 cm². Trafficking at 0 SMD (field capacity) led to mean increases in bulk density of 15% and the formation of rut profiles in the range of 91.6 cm² to 197.9 cm². These preliminary results indicate that forecasted SMD provides a valuable tool to determine the suitability of the soil for supporting farm vehicle operations such as slurry spreading. This study is still ongoing, with more detailed results and analysis to be forthcoming