Software utilizing Imhoff cone volumes to estimate furrow-irrigation erosion

Data analysis required for furrow-irrigation induced erosion research is greatly facilitated with the aid of computational software. Several programs have been developed at Kimberly, Idaho, that compute infiltration, runoff and sediment loss from the following inputs: inflow and runoff rates, sediment concentration in runoff determined by Imhoff cones, sampling times, furrow spacing, and row length. We found that more than one program type was required to meet various user needs. Two PC-based programs are presented for intense furrow monitoring, one employs spreadsheet software and the other is a PASCAL program. They produce accurate estimates and display output in formats suited to quantitative evaluation or for further data reductions needed in research applications. An HP-IIC hand calculator program provides coarse diagnostic information that can easily he used by farm advisors to assess potential severity of furrow erosion in farmer's fields. The software have been extensively tested and are reliable. They can be used to quantify any component of runoff removal

Estimating polyacrylamide concentration in irrigation water

One practice used to control irrigation-induced erosion amends irrigation furrow inflows with water-soluble, anionic polyacrylamide (PAM) at low concentrations (0.25-10 mg L-1). Researchers wish to determine the fate of PAM, once added to furrow water streams. We developed and tested an instrumented flocculation test for quantifying PAM concentration in irrigation water. A kaolinite mineral standard is mixed with a PAM-amended water sample, agitated, then placed in a spectrophotometer. The PAM concentration in the suspension was correlated with settling-related transmittance changes. One highly correlated (r 0.91-0.98) parameter, the time needed to initiate suspension clearing (clarity-shift inflection, CS1), was used as the procedure endpoint. The procedure was sensitive to variations in the amount of kaolinite added, and sample volume, water salinity, and original sediment content. A 10% change in these factors altered measured CSIs by 10 to 50%. The sediment affected CSI by increasing the sample's dissolved organic C concentration. The procedure detected as little as 0.1 mg PAM dissolved in irrigation water; in samples containing >4 mt. settled sediment per liter, the PAM detection limit was approximately 0.25 mg L-`. Precision ranged from ±0.06 to 0.11 mg L-1 for 0 to 2.5 mg L-1 PAM and ±0.39 to 0.86 mg L-1 for 2.5 to 10.0 mg L-1 PAM. The PAM concentration in runoff from irrigated furrows equaled that of the inflow stream after 3 b continuous treatment at 10 mg L-1. The CSI test provides a simple and accurate method of determining polyacrylamide in surface waters

Scanning electron micrographs of polyacrylamide-treated soil in irrigation furrows

Polyacrylamide (PAM) is used at rates of i to 2 kg ha per irrigation on a half million hectares of United States irrigated farmland to prevent 94% of irrigation-induced erosion and to enhance infiltration by 15% to 50% on medium to fine-textured soils. The polyacrylamides used for this application are large (12 to 15 megagrams per mole), water-soluble anion molecules applied in the irrigation stream. Erosion prevention has been shown to result from stabilized soil structure in the i to 5 mm veneer of surface soil that regulates infiltration, runoff, and sediment loss on water application. We hypothesized that this could be confirmed from scanning electron micrographs (SEMs) of PAM-treated soil. Both untreated and PAM-treated soils form surface seals in irrigation furrows, but the stable surface structure of PAM-treated furrows is more pervious. This is thought to result from a greater number of continuous unblocked pores at the soil-water interface. SEMs of PAM-treated and untreated soil microstructures are presented from thin surface samples of Portneuf silt loam, collected from furrows immediately following an irrigation, and freeze-dried. SEMs of PAM-treated soil showed net or web-like microstructural surface coatings about 1um thick on soil mineral particles, giving a glue-like porous appearance. Individual strands of PAM were about 0.2 in diameter. Strands of PAM aggregated the soil by ensnaring and bridging mineral particles while untreated soil had poorly aggregated, unconnected particles. Thus, microstructural differences between PAM-treated and untreated soil from irrigation furrows were consistent with erosion and infiltration results

Weed seed transport and weed establishment as affected by polyacrylamide in furrow-irrigated corn

Polyacrylamide (PAM) has been used successfully to reduce erosion and increase infiltration on nearly a half million hectares of United States irrigated farmland. PAM is a potent and environmentally safe flocculent that greatly accelerates separation of suspended solids from water. It also improves particle cohesion, stabilizing soil structure. We hypothesized that in irrigation furrows, PAM prevents loss of weed seed and might affect weed establishment and management practices. We grew corn (Zea mays L.) in plots without herbicides, or that were treated with either Eradicane ® (EPTC + dichlormid) or Dual ® II (S-Metolachlor) and irrigated in furrows that had either no PAM, or that were treated either with 10 g m- 3 (io kg ML-1 or 10 ppm) dissolved PAM during water advance, or with PAM applied as a powder patch at the furrow head. As in previous studies, erosion was greatly reduced with PAM and infiltration was increased. PAM use also reduced runoff loss of weed seeds (barnyardgrass, kochia, redroot pigweed, common lambsquarters, and hairy nightshade) 62% to 90%. Interactions of herbicide treatments and PAM on erosion, infiltration, and weed seed loss were related to the mulching effect of weed vegetation. PAM is an effective and environmentally safe means of reducing weed seed distribution in furrow irrigation water while simultaneously reducing erosion and increasing infiltration in weed-free crop production

On spin chains and field theories

We point out that the existence of global symmetries in a field theory is not an essential ingredient in its relation with an integrable model. We describe an obvious construction which, given an integrable spin chain, yields a field theory whose 1-loop scale transformations are generated by the spin chain Hamiltonian. We also identify a necessary condition for a given field theory to be related to an integrable spin chain. As an example, we describe an anisotropic and parity-breaking generalization of the XXZ Heisenberg spin chain and its associated field theory. The system has no nonabelian global symmetries and generally does not admit a supersymmetric extension without the introduction of more propagating bosonic fields. For the case of a 2-state chain we find the spectrum and the eigenstates. For certain values of its coupling constants the field theory associated to this general type of chain is the bosonic sector of the Leigh-Strassler deformation of N=4 SYM theory.Comment: 22 pages, Latex; v2. typos correcte

Soil water measurements relevant to agronomic and environmental functions of chemically treated soil

Modern agricultural, turf, and landscape management routinely apply and depend upon chemical applications to optimize system function for specific outcomes. The effectiveness of these applied chemicals to achieve desired outcomes usually depends upon their interaction with and transport by water. To fully and accurately assess the role of water as a chemical delivery and activation system requires a good understanding of how the applied chemicals, soil, and water interact, the scale at which a phenomenon is important, the nature of soil variability, and which of the three dominant soil water properties ?content, movement, or potential energy? is most suited to assessing water’s role. The science of this assessment process is extensive and its literature is voluminous. For the uninitiated, however, it is worth being aware at least of the basics of soil water assessment and where some of the pitfalls lie. This presentation describes soil as a three-phase system ?solids, liquid, and gases? and highlights some of the key measurements and measurement considerations necessary to appropriately characterize treatment efficacy for specific, and especially, non-intuitive effects. The presentation cannot be comprehensive or substitute for requisite university-level courses in soil physics and soil chemistry, but can, perhaps, alert applicators to situations and considerations that demand more than mere cursory assessment for proper evaluation and interpretation

Direct observation of transverse and vortex metastable magnetic domains in cylindrical nanowires

We present experimental evidence of transverse magnetic domains, previously observed only in nanostrips, in CoNi cylindrical nanowires with designed crystal symmetry and tailored magnetic anisotropy. The transverse domains are found together with more conventional vortex domains along the same cylindrical nanowire, denoting a bistable system with similar energies. The surface and the inner magnetization distribution in both types of domains are analyzed by photoemission electron microscopy with x-ray magnetic circular dichroism contrast, and hysteresis loop in individual nanowires are measured by magneto-optical Kerr effect. These experimental data are understood and compared with complementary micromagnetic simulations

Domain wall propagation and pinning induced by current pulses in cylindrical modulated nanowires

The future developments in 3D magnetic nanotechnology require the control of domain wall dynamics by means of current pulses. While this has been extensively studied in 2D magnetic strips (planar nanowires), few reports on this exist in cylindrical geometry, where Bloch point domain walls are expected to have intriguing properties. Here, we report an investigation on cylindrical magnetic Ni nanowires with geometrical notches. An experimental work based on synchrotron X-ray magnetic circular dichroism (XMCD) combined with photoemission electron microscopy (PEEM) indicates that large current densities induce domain wall nucleation, while smaller currents move domain walls preferably antiparallel to the current direction. In the region where no pinning centers are present, we found a domain wall velocity of about 1 km s. Thermal modelling indicates that large current densities temporarily raise the temperature in the nanowire above the Curie temperature, leading to nucleation of domain walls during the system cooling. Micromagnetic modelling with a spin-torque effect shows that for intermediate current densities, Bloch point domain walls with chirality parallel to the Oersted field propagate antiparallel to the current direction. In other cases, domain walls can be bounced from the notches and/or get pinned outside their positions. We thus found that current is not only responsible for domain wall propagation, but also is a source of pinning due to the Oersted field action.Grants PID2019-108075RB-C31 funded by the Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033 and S2018/NMT-4321 NANOMAGCOST-CM funded by the Government of Madrid Region, Spain. We acknowledge the service from the MiNa Laboratory at IMN and the funding from CM (project SpaceTec, S2013/ICE2822), MINECO (project CSIC13-4E-1794), and EU (FEDER, FSE).Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d3nr00455

Detecting a stochastic gravitational wave background with the Laser Interferometer Space Antenna

The random superposition of many weak sources will produce a stochastic background of gravitational waves that may dominate the response of the LISA (Laser Interferometer Space Antenna) gravitational wave observatory. Unless something can be done to distinguish between a stochastic background and detector noise, the two will combine to form an effective noise floor for the detector. Two methods have been proposed to solve this problem. The first is to cross-correlate the output of two independent interferometers. The second is an ingenious scheme for monitoring the instrument noise by operating LISA as a Sagnac interferometer. Here we derive the optimal orbital alignment for cross-correlating a pair of LISA detectors, and provide the first analytic derivation of the Sagnac sensitivity curve.Comment: 9 pages, 11 figures. Significant changes to the noise estimate