5,677 research outputs found
Method and apparatus for fabricating improved solar cell modules
A method and apparatus for fabricating an improved solar cell module is described. The apparatus includes a supply drum for feeding a flexible strip having etched electrical circuitry deposited on it a supply drum for feeding into overlying engagement with the flexible strip a flexible tape having a pair of exposed tacky surfaces, and a plurality of rams for receiving and depositing a plurality of solar cells in side-by-side relation on an exposed tacky surface of the tape in electrical contacting engagement with the etched circuitry
Completion Report: Pesticide and Nitrate Monitoring Results for Craighead, Mississippi, and Poinsett Counties, Arkansas: Phase II
Because of the concern for potential contamination of ground water by agricultural chemicals, 38 wells drilled in the Mississippi River Valley alluvial aquifer in Mississippi County and the eastern parts of Craighead and Poinsett Counties, Arkansas were analyzed for pesticides and nitrate. The pesticide, fluometuron, was detected in one sample at a concentration of 0.5 mg/L. Bentazon was detected in three samples at concentrations of 2.5, 0.3, and 0.3 mg/L. The occurrences of the pesticides appear to represent isolated incidents rather than a widespread aquifer contamination. All detections were below health and safety standards. Nitrate is present in several wells at concentrations above 0.15 mg/L, one of which exceeded the EPA established maximum contaminant level for drinking water of 10 milligrams per liter as nitrogen. Except for two wells nitrate and iron are not present together at concentrations above 0.15 mg!L. This is probably due to microbially mediated reactions. Nitrate concentrations above 0.15 mg/L is only present in wells that are less than 60 feet deep and near permeable soils. Iron is present in wells that are not near permeable soils or wells that are greater than 40 feet deep, and may exceed 1 mg/L in some cases
Structure of the two-boundary XXZ model with non-diagonal boundary terms
We study the integrable XXZ model with general non-diagonal boundary terms at
both ends. The Hamiltonian is considered in terms of a two boundary extension
of the Temperley-Lieb algebra.
We use a basis that diagonalizes a conserved charge in the one-boundary case.
The action of the second boundary generator on this space is computed. For the
L-site chain and generic values of the parameters we have an irreducible space
of dimension 2^L. However at certain critical points there exists a smaller
irreducible subspace that is invariant under the action of all the bulk and
boundary generators. These are precisely the points at which Bethe Ansatz
equations have been formulated. We compute the dimension of the invariant
subspace at each critical point and show that it agrees with the splitting of
eigenvalues, found numerically, between the two Bethe Ansatz equations.Comment: 9 pages Latex. Minor correction
Equivalences between spin models induced by defects
The spectrum of integrable spin chains are shown to be independent of the
ordering of their spins. As an application we introduce defects (local spin
inhomogeneities in homogenous chains) in two-boundary spin systems and, by
changing their locations, we show the spectral equivalence of different
boundary conditions. In particular we relate certain nondiagonal boundary
conditions to diagonal ones.Comment: 14 pages, 16 figures, LaTeX, Extended versio
Instability driven fragmentation of nanoscale fractal islands
Formation and evolution of fragmentation instabilities in fractal islands,
obtained by deposition of silver clusters on graphite, are studied. The
fragmentation dynamics and subsequent relaxation to the equilibrium shapes are
controlled by the deposition conditions and cluster composition. Sharing common
features with other materials' breakup phenomena, the fragmentation instability
is governed by the length-to-width ratio of the fractal arms.Comment: 5 pages, 3 figures, Physical Review Letters in pres
Metagenetic analysis of patterns of distribution and diversity of marine meiobenthic eukaryotes
AimMeiofaunal communities that inhabit the marine benthos offer unique opportunities to simultaneously study the macroecology of numerous phyla that exhibit different life-history strategies. Here, we ask: (1) if the macroecology of meiobenthic communities is explained mainly by dispersal constraints or by environmental conditions; and (2) if levels of meiofaunal diversity surpass existing estimates based on morphological taxonomy. LocationUK and mainland European coast. MethodsNext-generation sequencing techniques (NGS; Roche 454 FLX platform) using 18S nuclear small subunit ribosomal DNA (rDNA) gene. Pyrosequences were analysed using AmpliconNoise followed by chimera removal using Perseus. ResultsRarefaction curves revealed that sampling saturation was only reached at 15% of sites, highlighting that the bulk of meiofaunal diversity is yet to be discovered. Overall, 1353 OTUs were recovered and assigned to 23 different phyla. The majority of sampled sites had c. 60-70 unique operational taxonomic units (OTUs) per site, indicating high levels of beta diversity. The environmental parameters that best explained community structure were seawater temperature, geographical distance and sediment size, but most of the variability (R-2=70%-80%) remains unexplained. Main conclusionsHigh percentages of endemic OTUs suggest that meiobenthic community composition is partly niche-driven, as observed in larger organisms, but also shares macroecological features of microorganisms by showing high levels of cosmopolitanism (albeit on a much smaller scale). Meiobenthic communities exhibited patterns of isolation by distance as well as associations between niche, latitude and temperature, indicating that meiobenthic communities result from a combination of niche assembly and dispersal processes. Conversely, isolation-by-distance patterns were not identified in the featured protists, suggesting that animals and protists adhere to radically different macroecological processes, linked to life-history strategies.Natural Environment Research Council (NERC) [NE/E001505/1, NE/F001266/1, MGF-167]; Portuguese Foundation for Science and Technology (FCT) [SFRH/BD/27413/2006, SFRH/BPD/80447/2014]; EPSRC [EP/H003851/1]; BBSRC CASE studentship; Unilever; Biotechnology and Biological Sciences Research Council [987347]; Engineering and Physical Sciences Research Council [EP/H003851/1]; Natural Environment Research Council [NE/F001290/1, NE/F001266/1, NE/E001505/1, NBAF010002]info:eu-repo/semantics/publishedVersio
Anti-Lu14: A Lutheran Antibody Defining the Product of an Allele at the Lu8 Blood Group Locus 1
A ‘new’ Lutheran-related antibody, named anti-Lu14, reacts with approximately 2.4% of random bloods. Red cells of the rare Lu:-8 phenotype are Lu:14. The data indicate, with a high probability, that the Lu 14 antigen is a product of an allele of Lu 8 and that Lu 14 and Lu 8 comprise a third pair of alleles at the Lutheran locus. Red cells of the original Sw (a+) propositus are Lu:14. By coincidence, he has inherited two low-incidence genes. This observation may explain the discrepancy in different families concerning a possible relationship between Sw a and Lutheran. Pedigree information now suggests that Sw a is not a Lutheran gene.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75055/1/j.1423-0410.1977.tb00632.x.pd
Changing shapes in the nanoworld
What are the mechanisms leading to the shape relaxation of three dimensional
crystallites ? Kinetic Monte Carlo simulations of fcc clusters show that the
usual theories of equilibration, via atomic surface diffusion driven by
curvature, are verified only at high temperatures. Below the roughening
temperature, the relaxation is much slower, kinetics being governed by the
nucleation of a critical germ on a facet. We show that the energy barrier for
this step linearly increases with the size of the crystallite, leading to an
exponential dependence of the relaxation time.Comment: 4 pages, 5 figures. Accepted by Phys Rev Let
X-Atlas: An Online Archive of Chandra's Stellar High Energy Transmission Gratings Observations
The high-resolution X-ray spectroscopy made possible by the 1999 deployment
of the Chandra X-ray Observatory has revolutionized our understanding of
stellar X-ray emission. Many puzzles remain, though, particularly regarding the
mechanisms of X-ray emission from OB stars. Although numerous individual stars
have been observed in high-resolution, realizing the full scientific potential
of these observations will necessitate studying the high-resolution Chandra
dataset as a whole. To facilitate the rapid comparison and characterization of
stellar spectra, we have compiled a uniformly processed database of all stars
observed with the Chandra High Energy Transmission Grating (HETG). This
database, known as X-Atlas, is accessible through a web interface with
searching, data retrieval, and interactive plotting capabilities. For each
target, X-Atlas also features predictions of the low-resolution ACIS spectra
convolved from the HETG data for comparison with stellar sources in archival
ACIS images. Preliminary analyses of the hardness ratios, quantiles, and
spectral fits derived from the predicted ACIS spectra reveal systematic
differences between the high-mass and low-mass stars in the atlas and offer
evidence for at least two distinct classes of high-mass stars. A high degree of
X-ray variability is also seen in both high and low-mass stars, including
Capella, long thought to exhibit minimal variability. X-Atlas contains over 130
observations of approximately 25 high-mass stars and 40 low-mass stars and will
be updated as additional stellar HETG observations become public. The atlas has
recently expanded to non-stellar point sources, and Low Energy Transmission
Grating (LETG) observations are currently being added as well
Exact solution of the open XXZ chain with general integrable boundary terms at roots of unity
We propose a Bethe-Ansatz-type solution of the open spin-1/2 integrable XXZ
quantum spin chain with general integrable boundary terms and bulk anisotropy
values i \pi/(p+1), where p is a positive integer. All six boundary parameters
are arbitrary, and need not satisfy any constraint. The solution is in terms of
generalized T - Q equations, having more than one Q function. We find numerical
evidence that this solution gives the complete set of 2^N transfer matrix
eigenvalues, where N is the number of spins.Comment: 22 page
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