213 research outputs found
Economic evaluation of the effect of selected crop practices on nonagricultural uses of water
Cropping systems may have an unfavorable influence on the quality of nearby surface water. In this study, linear programming methods were used to assess the impact of improvements in certain water quality characteristics on economically optimal crop systems. Thus, the effect of crop practices on water quality is analyzed indirectly by assuming that farmers would alter their cropping practices in the most economical way in order to conform to various water-quality constraints. A 1,200-acre watershed was used to illustrate the procedure. Sediment entering the reservoir was treated as a variable constraint on maximization of farm income. Requiring successively lower amounts of sediment to enter the reservoir caused farm income to decrease at an increasing rate. The analysis was enlarged to include a constraint on nitrate in the leachate below the root zone. This phase of the analysis also included a charge for removing at least some of the sediment entering the reservoir. As the nitrate limit on the leachate was lowered, farm income decreased at an increasing rate. The requirement of removal of the sediment by itself had little or no effect on the nitrate concentration in the leachate. Extensions of the procedure for use in other situations are suggested.U.S. Geological SurveyU.S. Department of the InteriorOpe
Desperately Seeking Chiral Fermions
Chiral fermions can (presumably) be constructed by introducing two
regulators, one for the gauge fields (e.g. a lattice), and another for the
fermion functional integrals in a fixed (regulated) gauge field. This talk
discusses cutoff effects arising from the regulator of the fermions.Comment: 4 pages, contribution to Lattice '95 Postscript at
http://www-theory.fnal.gov/people/ask/TeX/lat95/chiral.p
Properties of the Fixed Point Lattice Dirac Operator in the Schwinger Model
We present a numerical study of the properties of the Fixed Point lattice
Dirac operator in the Schwinger model. We verify the theoretical bounds on the
spectrum, the existence of exact zero modes with definite chirality, and the
Index Theorem. We show by explicit computation that it is possible to find an
accurate approximation to the Fixed Point Dirac operator containing only very
local couplings.Comment: 38 pages, LaTeX, 3 figures, uses style [epsfig], a few comments and
relevant references adde
Quenched Lattice QCD with Domain Wall Fermions and the Chiral Limit
Quenched QCD simulations on three volumes, , and
and three couplings, , 5.85 and 6.0 using domain
wall fermions provide a consistent picture of quenched QCD. We demonstrate that
the small induced effects of chiral symmetry breaking inherent in this
formulation can be described by a residual mass (\mres) whose size decreases
as the separation between the domain walls () is increased. However, at
stronger couplings much larger values of are required to achieve a given
physical value of \mres. For and , we find
\mres/m_s=0.033(3), while for , and ,
\mres/m_s=0.074(5), where is the strange quark mass. These values are
significantly smaller than those obtained from a more naive determination in
our earlier studies. Important effects of topological near zero modes which
should afflict an accurate quenched calculation are easily visible in both the
chiral condensate and the pion propagator. These effects can be controlled by
working at an appropriately large volume. A non-linear behavior of in
the limit of small quark mass suggests the presence of additional infrared
subtlety in the quenched approximation. Good scaling is seen both in masses and
in over our entire range, with inverse lattice spacing varying between
1 and 2 GeV.Comment: 91 pages, 34 figure
Scintillation Counters for the D0 Muon Upgrade
We present the results of an upgrade to the D0 muon system. Scintillating
counters have been added to the existing central D0 muon system to provide
rejection for cosmic ray muons and out-of-time background, and to provide
additional fast timing information for muons in an upgraded Tevatron.
Performance and results from the 1994-1996 Tevatron run are presented.Comment: 30 pages, 25 postscript figure
Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV
We report the results of a study of color coherence effects in ppbar
collisions based on data collected by the D0 detector during the 1994-1995 run
of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8
TeV. Initial-to-final state color interference effects are studied by examining
particle distribution patterns in events with a W boson and at least one jet.
The data are compared to Monte Carlo simulations with different color coherence
implementations and to an analytic modified-leading-logarithm perturbative
calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters
Probing stress and fracture mechanism in encapsulated thin silicon solar cells by synchrotron X-ray microdiffraction
Thin (<150 ”m) silicon solar cell technology is attractive due to the significant cost reduction associated with it. Consequently, fracture mechanisms in the thin silicon solar cells during soldering and lamination need to be fully understood quantitatively in order to enable photovoltaics (PV) systems implementation in both manufacturing and field operations. Synchrotron X-ray Microdiffraction (”SXRD) has proven to be a very effective means to quantitatively probe the mechanical stress which is the driving force of the fracture mechanisms (initiation, propagation, and propensity) in the thin silicon solar cells, especially when they are already encapsulated. In this article, we present the first ever stress examination in encapsulated thin silicon solar cells and show how nominally the same silicon solar cells encapsulated by different polymer encapsulants could have very different residual stresses after the lamination process. It is then not difficult to see how the earlier observation, as reported by Sander et al. (2013) [1], of very different fracture rates within the same silicon solar cells encapsulated by different Ethylene Vinyl Acetate (EVA) materials could come about. The complete second degree tensor components of the residual stress of the silicon solar cells after lamination process are also reported in this paper signifying the full and unique capabilities of the Synchrotron X-Ray Microdiffraction technique not only for measuring residual stress but also for measuring other potential mechanical damage within thin silicon solar cells
Spectroscopic target selection for the Sloan Digital Sky Survey: The luminous red galaxy sample
We describe the target selection and resulting properties of a spectroscopic sample of luminous red galaxies (LRGs) from the imaging data of the Sloan Digital Sky Survey (SDSS). These galaxies are selected on the basis of color and magnitude to yield a sample of luminous intrinsically red galaxies that extends fainter and farther than the main flux-limited portion of the SDSS galaxy spectroscopic sample. The sample is designed to impose a passively evolving luminosity and rest-frame color cut to a redshift of 0.38. Additional, yet more luminous red galaxies are included to a redshift of âŒ0.5. Approximately 12 of these galaxies per square degree are targeted for spectroscopy, so the sample will number over 100,000 with the full survey. SDSS commissioning data indicate that the algorithm efficiently selects luminous (M*g â - 21.4) red galaxies, that the spectroscopic success rate is very high, and that the resulting set of galaxies is approximately volume limited out to z = 0.38. When the SDSS is complete, the LRG spectroscopic sample will fill over 1 h-3 Gpc3 with an approximately homogeneous population of galaxies and will therefore be well suited to studies of large-scale structure and clusters out to z = 0.5
Loss-of-function mutations in UDP-Glucose 6-Dehydrogenase cause recessive developmental epileptic encephalopathy
Developmental epileptic encephalopathies are devastating disorders characterized by intractable epileptic seizures and developmental delay. Here, we report an allelic series of germline recessive mutations in UGDH in 36 cases from 25 families presenting with epileptic encephalopathy with developmental delay and hypotonia. UGDH encodes an oxidoreductase that converts UDP-glucose to UDP-glucuronic acid, a key component of specific proteoglycans and glycolipids. Consistent with being loss-of-function alleles, we show using patientsâ primary fibroblasts and biochemical assays, that these mutations either impair UGDH stability, oligomerization, or enzymatic activity. In vitro, patient-derived cerebral organoids are smaller with a reduced number of proliferating neuronal progenitors while mutant ugdh zebrafish do not phenocopy the human disease. Our study defines UGDH as a key player for the production of extracellular matrix components that are essential for human brain development. Based on the incidence of variants observed, UGDH mutations are likely to be a frequent cause of recessive epileptic encephalopathy
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