4,817 research outputs found
Solar radiation force modeling for TDRS orbit determination
The relative orbit determination accuracies resulting from several TDRS models are evaluated. These models include spherical, single-plate, and restricted two-plate models. The plate models can be adjusted in both area and reflectivity through differential correction. The restricted two-plate model has an Earth-pointing plate and a solar plate; the orientation of the solar plate is restricted to rotation about an axis perpendicular to the satellite's orbital plane
EC64-210 Swine Ration Suggestions
Extension 64-210 is about rationing for swine. The publication includes information about sources of protein, supplements, and parakeratosis
Principal scientific results of the Surveyor 3 Mission
The fine lunar surface material at the Surveyor 3 landing site has about 3 à 10^3-dyne/cm^2 cohesion, 35° angle of internal friction, 3 à 10^5-dyne/cm^2 static bearing capacity. A small rock withstood a local pressure of 2 à 10^7 dynes/cm^2. Soil strength and density increase significantly at depths of a few centimeters. Exposed surface has a considerably higher albedo than the material just below it. The photometric function changed when the surface was slightly compressed. Fine surface material appears to be gradually moving downslope
Principal science results from Surveyor 5
The area of Mare Tranquillitatis in which Surveyor 5 landed appears to be similar to sites in Oceanus Procellarum. The gross elemental composition of the surface material and its response to a magnet are similar to those of a basalt. The debris layer appears to consist of aggregates of the order of 1 cm in diameter consisting of fine grains and set in a matrix of less-coherent fine grains (most of them 2 to 60 ÎŒ in diameter) mixed with some rocky fragments 1 mm and larger. The static bearing strength is less than 10^4 dynes/cm^2 for the upper few millimeters and averages approximately 3 Ă 10^5 dynes/cm^2 for the upper few centimeters. The evidence suggests that chemical differentiation has occurred in the moon, probably owing to internal heat sources; this is consistent with the hypothesis that the maria are basaltic volcanic flows
A refined, controlled 16S rRNA gene sequencing approach reveals limited detection of cerebrospinal fluid microbiota in children with bacterial meningitis
Advances in both laboratory and computational components of high-throughput 16S amplicon sequencing (16S HTS) have markedly increased its sensitivity and specificity. Additionally, these refinements have better delineated the limits of sensitivity, and contributions of contamination to these limits, for 16S HTS that are particularly relevant for samples with low bacterial loads, such as human cerebrospinal fluid (CSF). The objectives of this work were to (i) optimize the performance of 16S HTS in CSF samples with low bacterial loads by defining and addressing potential sources of error, and (ii) perform refined 16S HTS on CSF samples from children diagnosed with bacterial meningitis and compare results with those from microbiological cultures. Several bench and computational approaches were taken to address potential sources of error for low bacterial load samples. We compared DNA yields and sequencing results after applying three different DNA extraction approaches to an artificially constructed mock-bacterial community. We also compared two postsequencing computational contaminant removal strategies, decontam R and full contaminant sequence removal. All three extraction techniques followed by decontam R yielded similar results for the mock community. We then applied these methods to 22 CSF samples from children diagnosed with meningitis, which has low bacterial loads relative to other clinical infection samples. The refined 16S HTS pipelines identified the cultured bacterial genus as the dominant organism for only 3 of these samples. We found that all three DNA extraction techniques followed by decontam R generated similar DNA yields for mock communities at the low bacterial loads representative of CSF samples. However, the limits of detection imposed by reagent contaminants and methodologic bias precluded the accurate detection of bacteria in CSF from children with culture-confirmed meningitis using these approaches, despite rigorous controls and sophisticated computational approaches. Although we did not find current DNA-based diagnostics to be useful for pediatric meningitis samples, the utility of these methods for CSF shunt infection remains undefined. Future advances in sample processing methods to minimize or eliminate contamination will be required to improve the sensitivity and specificity of these methods for pediatric meningitis
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The characterization of Vicker`s microhardness indentations and pile-up profiles as a strain-hardening microprobe
Microhardness measurements have long been used to examine strength properties and changes in strength properties in metals, for example, as induced by irradiation. Microhardness affords a relatively simple test that can be applied to very small volumes of material. Microhardness is nominally related to the flow stress of the material at a fixed level of plastic strain. Further, the geometry of the pile-up of material around the indentation is related to the strain-hardening behavior of a material; steeper pile-ups correspond to smaller strain-hardening rates. In this study the relationship between pile-up profiles and strain hardening is examined using both experimental and analytical methods. Vickers microhardness tests have been performed on a variety of metal alloys including low alloy, high Cr and austenitic stainless steels. The pile-up topology around the indentations has been quantified using confocal microscopy techniques. In addition, the indentation and pile-up geometry has been simulated using finite element method techniques. These results have been used to develop an improved quantification of the relationship between the pile-up geometry and the strain-hardening constitutive behavior of the test material
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale XXIV: The Calibration of Tully-Fisher Relations and the Value of the Hubble Constant
This paper presents the calibration of BVRIH$ Tully-Fisher relations based on
Cepheid distances to 21 galaxies within 25 Mpc, and 23 clusters within 10,000
km/s. These relations have been applied to several distant cluster surveys in
order to derive a value for the Hubble constant, H0, mainly concentrating on an
I-band all-sky survey by Giovanelli and collaborators which consisted of total
I magnitudes and 50% linewidth data for ~550 galaxies in 16 clusters. For
comparison, we also derive the values of H0 using surveys in B-band and V-band
by Bothun and collaborators, and in H-band by Aaronson and collaborators.
Careful comparisons with various other databases from literature suggest that
the H-band data, whose magnitudes are isophotal magnitudes extrapolated from
aperture magnitudes rather than total magnitudes, are subject to systematic
uncertainties. Taking a weighted average of the estimates of Hubble constants
from four surveys, we obtain H0 = 71 +- 4 (random) +- 7 (systematic) km/s/Mpc.
We have also investigated how various systematic uncertainties affect the value
of H0 such as the internal extinction correction method used, Tully-Fisher
slopes and shapes, a possible metallicity dependence of the Cepheid
period-luminosity relation and cluster population incompleteness bias.Comment: 34 pages, 13 figure
CNVassoc: Association analysis of CNV data using R
Background: Copy number variants (CNV) are a potentially important component of the genetic contribution to
risk of common complex diseases. Analysis of the association between CNVs and disease requires that uncertainty
in CNV copy-number calls, which can be substantial, be taken into account; failure to consider this uncertainty can
lead to biased results. Therefore, there is a need to develop and use appropriate statistical tools. To address this
issue, we have developed CNVassoc, an R package for carrying out association analysis of common copy number
variants in population-based studies. This package includes functions for testing for association with different
classes of response variables (e.g. class status, censored data, counts) under a series of study designs (case-control,
cohort, etc) and inheritance models, adjusting for covariates. The package includes functions for inferring copy
number (CNV genotype calling), but can also accept copy number data generated by other algorithms (e.g.
CANARY, CGHcall, IMPUTE).
Results: Here we present a new R package, CNVassoc, that can deal with different types of CNV arising from
different platforms such as MLPA o aCGH. Through a real data example we illustrate that our method is able to
incorporate uncertainty in the association process. We also show how our package can also be useful when
analyzing imputed data when analyzing imputed SNPs. Through a simulation study we show that CNVassoc
outperforms CNVtools in terms of computing time as well as in convergence failure rate.
Conclusions: We provide a package that outperforms the existing ones in terms of modelling flexibility, power,
convergence rate, ease of covariate adjustment, and requirements for sample size and signal quality. Therefore, we
offer CNVassoc as a method for routine use in CNV association studiesThis work has been supported by the Spanish Ministry of
Science and Innovation (MTM2008-02457 to JRG, BIO2009-12458 to RD-U
and statistical genetics network MTM2010-09526-E (subprograma MTM) to
JRG, IS, GL and RD-U). GL is supported by the Juan de la Cierva Program of
the Spanish Ministry of Science and Innovation
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