205 research outputs found
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
Stochastic vs. deterministic magnetic coding in designed cylindrical nanowires for 3D magnetic networks
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