466 research outputs found
A multistage linear array assignment problem
The implementation of certain algorithms on parallel processing computing architectures can involve partitioning contiguous elements into a fixed number of groups, each of which is to be handled by a single processor. It is desired to find an assignment of elements to processors that minimizes the sum of the maximum workloads experienced at each stage. This problem can be viewed as a multi-objective network optimization problem. Polynomially-bounded algorithms are developed for the case of two stages, whereas the associated decision problem (for an arbitrary number of stages) is shown to be NP-complete. Heuristic procedures are therefore proposed and analyzed for the general problem. Computational experience with one of the exact problems, incorporating certain pruning rules, is presented with one of the exact problems. Empirical results also demonstrate that one of the heuristic procedures is especially effective in practice
Effect of temperature, rainfall and planting date on aflatoxin and fumonisin contamination in commercial Bt and non-Bt corn hybrids in Arkansas
Corn (maize, Zea mays) is susceptible to contamination with aflatoxins, fumonisins and other mycotoxins, particularly in the southeastern USA. In principle, mycotoxin contamination could be reduced in commercial corn hybrids with shorter growing seasons by planting at dates which minimize plant stress during the critical kernel-filling period. To evaluate this strategy, commercial Bt and non-Bt hybrids were planted in Arkansas in mid-April and early May of 2002, 2004 and 2005. The mid-April planting date resulted in lower aflatoxin contamination in harvested corn each yr and in significantly less frequent contamination above a regulatory action level in 2005 and overall than did the early-May planting date in both Bt and non-Bt corn. The mid-April planting date resulted in significantly lower total fumonisin contamination in harvested corn and in less frequent contamination above a regulatory advisory level than the early May planting date in 2 of 3 yr and overall in both Bt and non-Bt corn. All fumonisin subtypes studied were reduced. Frequent co-occurrence of aflatoxin and fumonisin was observed. Fumonisin levels averaged lower in Bt hybrids than in non-Bt hybrids at all plantings. Reduced aflatoxin and fumonisin contamination with mid-April planting could not be explained by any measure of heat stress during the kernel-filling period.Le maĂŻs (Zea mays) est sensible Ă la contamination par les aflatoxines, les fumonisines et d'autres mycotoxines, surtout dans le sud-est des Ătats-Unis. En principe, la contamination par les mycotoxines pourrait ĂȘtre diminuĂ©e chez les hybrides commerciaux de maĂŻs par des saisons de croissance plus courtes en plantant Ă des dates qui minimisent le stress sur les plantes au moment de la pĂ©riode critique du remplissage des grains. Pour Ă©valuer cette stratĂ©gie, des hybrides commerciaux Bt et non Bt ont Ă©tĂ© semĂ©s en Arkansas de la mi-avril au dĂ©but de mai 2002, 2004 et 2005. Pour toutes les annĂ©es, tant pour le maĂŻs Bt que le non Bt, le grain issu des semis de la mi-avril Ă©tait moins contaminĂ© aux aflatoxines que celui semĂ© au dĂ©but de mai. De mĂȘme, la contamination supĂ©rieure aux niveaux lĂ©galement acceptĂ©s a Ă©tĂ© moindre en 2005 et dans l'ensemble pour les semis de la mi-avril. Avec les semis de la mi-avril, il y avait significativement moins de contamination par les fumonisines dans le grain rĂ©coltĂ© et moins de contamination supĂ©rieure aux niveaux lĂ©galement acceptĂ©s qu'avec les semis du dĂ©but de mai pour deux des trois annĂ©es et dans l'ensemble, tant pour le maĂŻs Bt que celui non Bt. La quantitĂ© de tous les sous-types de fumonisines Ă©tudiĂ©s a Ă©tĂ© diminuĂ©e. La prĂ©sence simultanĂ©e d'aflatoxines et de fumonisines a frĂ©quemment Ă©tĂ© observĂ©e. Pour tous les semis, les quantitĂ©s de fumonisines des hybrides Bt ont Ă©tĂ© infĂ©rieures en moyenne Ă celles des hybrides non Bt. Les moindres contaminations par les aflatoxines et les fumonisines avec les semis de la mi-avril n'ont pu ĂȘtre expliquĂ©es par aucune des mesures du stress causĂ© par la chaleur lors de la pĂ©riode du remplissage des grains
What is the probability of connecting two points ?
The two-terminal reliability, known as the pair connectedness or connectivity
function in percolation theory, may actually be expressed as a product of
transfer matrices in which the probability of operation of each link and site
is exactly taken into account. When link and site probabilities are and
, it obeys an asymptotic power-law behavior, for which the scaling factor
is the transfer matrix's eigenvalue of largest modulus. The location of the
complex zeros of the two-terminal reliability polynomial exhibits structural
transitions as .Comment: a few critical polynomials are at the end of the .tex source fil
Hospital fall prevention: a systematic review of implementation, components, adherence, and effectiveness.
ObjectivesTo systematically document the implementation, components, comparators, adherence, and effectiveness of published fall prevention approaches in U.S. acute care hospitals.DesignSystematic review. Studies were identified through existing reviews, searching five electronic databases, screening reference lists, and contacting topic experts for studies published through August 2011.SettingU.S. acute care hospitals.ParticipantsStudies reporting in-hospital falls for intervention groups and concurrent (e.g., controlled trials) or historic comparators (e.g., before-after studies).InterventionFall prevention interventions.MeasurementsIncidence rate ratios (IRR, ratio of fall rate postintervention or treatment group to the fall rate preintervention or control group) and ratings of study details.ResultsFifty-nine studies met inclusion criteria. Implementation strategies were sparsely documented (17% not at all) and included staff education, establishing committees, seeking leadership support, and occasionally continuous quality improvement techniques. Most interventions (81%) included multiple components (e.g., risk assessments (often not validated), visual risk alerts, patient education, care rounds, bed-exit alarms, and postfall evaluations). Fifty-four percent did not report on fall prevention measures applied in the comparison group, and 39% neither reported fidelity data nor described adherence strategies such as regular audits and feedback to ensure completion of care processes. Only 45% of concurrent and 15% of historic control studies reported sufficient data to compare fall rates. The pooled postintervention incidence rate ratio (IRR) was 0.77 (95% confidence interval = 0.52-1.12, P = .17; eight studies; I(2) : 94%). Meta-regressions showed no systematic association between implementation intensity, intervention complexity, comparator information, or adherence levels and IRR.ConclusionPromising approaches exist, but better reporting of outcomes, implementation, adherence, intervention components, and comparison group information is necessary to establish evidence on how hospitals can successfully prevent falls
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Analysis of a SBLOCA initiated by an ATWS event
The response of a four-loop Westinghouse pressurized water reactor to SBLOCAs initiated as a result of an anticipated transient without scram (ATWS) has been analyzed using the RELAP5 computer code. The ATWS is initiated by a loss-of-feedwater, and the small breaks were due to either one or three stuck-open safety valves or reactor coolant pump seal failure. For the cases analyzed, the results show that a LOF-ATWS followed by a SBLOCA does not have more safety significance than that found when each accident is analyzed independently of one another
Dust and gas in luminous infrared galaxies - results from SCUBA observations
We present new data taken at 850 m with SCUBA at the JCMT for a sample
of 19 luminous infrared galaxies. Fourteen galaxies were detected. We have used
these data, together with fluxes at 25, 60 and 100 m from IRAS, to model
the dust emission. We find that the emission from most galaxies can be
described by an optically thin, single temperature dust model with an exponent
of the dust extinction coefficient () of
. A lower is required to model the dust
emission from two of the galaxies, Arp 220 and NGC 4418. We discuss various
possibilities for this difference and conclude that the most likely is a high
dust opacity. In addition, we compare the molecular gas mass derived from the
dust emission, , with the molecular gas mass derived from the CO
emission, , and find that is on average a factor 3 higher than
.Comment: 10 pages, 6 figures, latex, with MN-macros, accepted by MNRAS -
revised version (changed flux values for some galaxies
A Chromosome-Length Reference Genome for the Endangered Pacific Pocket Mouse Reveals Recent Inbreeding in a Historically Large Population
High-quality reference genomes are fundamental tools for understanding population history, and can provide estimates of genetic and demographic parameters relevant to the conservation of biodiversity. The federally endangered Pacific pocket mouse (PPM), which persists in three small, isolated populations in southern California, is a promising model for studying how demographic history shapes genetic diversity, and how diversity in turn may influence extinction risk. To facilitate these studies in PPM, we combined PacBio HiFi long reads with Omni-C and Hi-C data to generate a de novo genome assembly, and annotated the genome using RNAseq. The assembly comprised 28 chromosome-length scaffolds (N50â=â72.6â
MB) and the complete mitochondrial genome, and included a long heterochromatic region on chromosome 18 not represented in the previously available short-read assembly. Heterozygosity was highly variable across the genome of the reference individual, with 18% of windows falling in runs of homozygosity (ROH) >1â
MB, and nearly 9% in tracts spanning >5â
MB. Yet outside of ROH, heterozygosity was relatively high (0.0027), and historical Ne estimates were large. These patterns of genetic variation suggest recent inbreeding in a formerly large population. Currently the most contiguous assembly for a heteromyid rodent, this reference genome provides insight into the past and recent demographic history of the population, and will be a critical tool for management and future studies of outbreeding depression, inbreeding depression, and genetic load
Near-infrared line imaging of the starburst galaxies NGC 520, NGC 1614 and NGC 7714
We present high spatial resolution (0.6 arcsec) near-infrared broad-band JHK
images and Br_gamma 2.1661 micron and H_2 1-0 S(1) 2.122 micron emission line
images of the nuclear regions in the interacting starburst galaxies NGC 520,
NGC 1614 and NGC 7714. The near-infrared emission line and radio morphologies
are in general agreement, although there are differences in details. In NGC
1614, we detect a nuclear double structure in Br_gamma, in agreement with the
radio double structure. We derive average extinctions of A(K) = 0.41 and A(K) =
0.18 toward the nuclear regions of NGC 1614 and NGC 7714, respectively. For NGC
520, the extinction is much higher, A(K) = 1.2 - 1.6. The observed H_2/Br_gamma
ratios indicate that the main excitation mechanism of the molecular gas is
fluorescence by intense UV radiation from clusters of hot young stars, while
shock excitation can be ruled out.
The starburst regions in all galaxies exhibit small Br_gamma equivalent
widths. Assuming a constant star formation model, even with a lowered upper
mass cutoff of M_u = 30 M_o, results in rather old ages (10 - 40 Myr), in
disagreement with the clumpy near-infrared morphologies. We prefer a model of
an instantaneous burst of star formation with M_u = 100 M_o, occurring 6 - 7
Myr ago, in agreement with previous determinations and with the detection of
W-R features in NGC 1614 and NGC 7714. Finally, we note a possible systematic
difference in the amount of hot molecular gas between starburst and Seyfert
galaxies.Comment: 13 pages, A&A, accepte
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