381 research outputs found
Construction time and cost control using the IBM Project Management System/360
The object of this investigation was to determine the advantages or disadvantages involved in the use of the IBM Project Management system/360 as a time and cost control tool as compared to the methods presently used by construction contractors in the small to medium size range.
The methods used by three construction contractors were investigated in order to acquire a sample of methods presently used.
It was determined from the investigation that a number of advantages could be obtained which would provide better control of a construction project.
It was also decided that a detailed investigation concerning the cost of installing and using the system must be made in order to determine the feasibility of using the system --Abstract, page ii
Nocturnal sleep, daytime sleepiness, and quality of life in stable patients on hemodialysis
BACKGROUND: Although considerable progress has been made in the treatment of chronic kidney disease, compromised quality of life continues to be a significant problem for patients receiving hemodialysis (HD). However, in spite of the high prevalence of sleep complaints and disorders in this population, the relationship between these problems and quality of life remains to be well characterized. Thus, we studied a sample of stable HD patients to explore relationships between quality of life and both subjective and objective measures of nocturnal sleep and daytime sleepiness METHODS: The sample included forty-six HD patients, 24 men and 22 women, with a mean age of 51.6 (10.8) years. Subjects underwent one night of polysomnography followed the next morning by a Multiple Sleep Latency Test (MSLT), an objective measure of daytime sleepiness. Subjects also completed: 1) a brief nocturnal sleep questionnaire; 2) the Epworth Sleepiness Scale; and, 3) the Quality of Life Index (QLI, Dialysis Version) which provides an overall QLI score and four subscale scores for Health & Functioning (H&F), Social & Economic (S&E), Psychological & Spiritual (P&S), and Family (F). (The range of scores is 0 to 30 with higher scores indicating better quality of life.) RESULTS: The mean (standard deviation; SD) of the overall QLI was 22.8 (4.0). The mean (SD) of the four subscales were as follows: H&F – 21.1 (4.7); S&E – 22.0 (4.8); P&S – 24.5 (4.4); and, F – 26.8 (3.5). H&F (r(s )= -0.326, p = 0.013) and F (r(s )= -0.248, p = 0.048) subscale scores were negatively correlated with periodic limb movement index but not other polysomnographic measures. The H&F subscale score were positively correlated with nocturnal sleep latency (r(s )= 0.248, p = 0.048) while the H&F (r(s )= 0.278, p = 0.030) and total QLI (r(s )= 0.263, p = 0.038) scores were positively associated with MSLT scores. Both of these latter findings indicate that higher life quality is associated with lower sleepiness levels. ESS scores were unrelated to overall QLI scores or the subscale scores. Subjective reports of difficulty falling asleep and waking up too early were significantly correlated with all four subscale scores and overall QLI. Feeling rested in the morning was positively associated with S&E, P&S, and Total QLI scores. CONCLUSION: Selected measures of both poor nocturnal sleep and increased daytime sleepiness are associated with decreased quality of life in HD patients, underscoring the importance of recognizing and treating these patients' sleep problems
Probing the Circumgalactic Medium at High-Redshift Using Composite BOSS Spectra of Strong Lyman-alpha Forest Absorbers
We present composite spectra constructed from a sample of 242,150 Lyman-alpha
(Lya) forest absorbers at redshifts 2.4<z<3.1 identified in quasar spectra from
the Baryon Oscillation Spectroscopic Survey (BOSS) as part of Data Release 9 of
the Sloan Digital Sky Survey III. We select forest absorbers by their flux in
bins 138 km/s wide (approximately the size of the BOSS resolution element). We
split these absorbers into five samples spanning the range of flux -0.05 <
F<0.45. Tests on a smaller sample of high-resolution spectra show that our
three strongest absorption bins would probe circumgalactic regions (projected
separation < 300 proper kpc and |Delta v| < 300km/s) in about 60% of cases for
very high signal-to-noise ratio. Within this subset, weakening Lya absorption
is associated with decreasing purity of circumgalactic selection once BOSS
noise is included. Our weaker two Lya absorption samples are dominated by the
intergalactic medium.
We present composite spectra of these samples and a catalogue of measured
absorption features from HI and 13 metal ionization species, all of which we
make available to the community. We compare measurements of seven Lyman series
transitions in our composite spectra to single line models and obtain further
constraints from their associated excess Lyman limit opacity. This analysis
provides results consistent with column densities over the range 14.4 <~ Log
(N_HI) <~ 16.45. We compare our measurements of metal absorption to a variety
of simple single-line, single-phase models for a preliminary interpretation.
Our results imply clumping on scales down to ~30 pc and near-solar
metallicities in the circumgalactic samples, while high-ionization metal
absorption consistent with typical IGM densities and metallicities is visible
in all samples.Comment: 23 pages, 15 figures, 5 tables, link to downloadable data included.
Accepted by MNRAS 2014 March 20. New sections 3.4 and 6.1 limiting the
occurrence and impact of Lyman limit system
Spatial patterns of soil nitrification and nitrate export from forested headwaters in the northeastern United States
Nitrogen export from small forested watersheds is known to be affected by N deposition but with high regional variability. We studied 10 headwater catchments in the northeastern United States across a gradient of N deposition (5.4 - 9.4 kg ha-1 yr-1) to determine if soil nitrification rates could explain differences in stream water NO 3- export. Average annual export of two years (October 2002 through September 2004) varied from 0.1 kg NO3--N ha-1 yr-1 at Cone Pond watershed in New Hampshire to 5.1 kg ha-1 yr-1 at Buck Creek South in the western Adirondack Mountains of New York. Potential net nitrification rates and relative nitrification (fraction of inorganic N as NO3-) were measured in Oa or A soil horizons at 21-130 sampling points throughout each watershed. Stream NO3- export was positively related to nitrification rates (r2 = 0.34, p = 0.04) and the relative nitrification (r2 = 0.37, p = 0.04). These relationships were much improved by restricting consideration to the 6 watersheds with a higher number of rate measurements (59-130) taken in transects parallel to the streams (r 2 of 0.84 and 0.70 for the nitrification rate and relative nitrification, respectively). Potential nitrification rates were also a better predictor of NO3- export when data were limited to either the 6 sampling points closest to the watershed outlet (r2 = 0.75) or sampling points \u3c250 m from the watershed outlet (r2 = 0.68). The basal area of conifer species at the sampling plots was negatively related to NO3- export. These spatial relationships found here suggest a strong influence of near-stream and near-watershed-outlet soils on measured stream NO3- export. Copyright 2012 by the American Geophysical Union
Emissions from Trucks using Fischer-Tropsch Diesel Fuel
The Fischer-Tropsch (F-T) catalytic conversion process can be used to synthesize diesel fuels from a variety of feedstocks, including coal, natural gas and biomass. Synthetic diesel fuels can have very low sulfur and aromatic content, and excellent autoignition characteristics. Moreover, Fischer-Tropsch diesel fuels may also be economically competitive with California B- diesel fuel if produced in large volumes. overview of Fischer-Tropsch diesel fuel production and engine emissions testing is presented. Previous engine laboratory tests indicate that F-T diesel is a promising alternative fuel because it can be used in unmodified diesel engines, and substantial exhaust emissions reductions can be realized. The authors have performed preliminary tests to assess the real-world performance of F-T diesel fuels in heavy-duty trucks. Seven White-GMC Class 8 trucks equipped with Caterpillar 10.3 liter engines were tested using F-T diesel fuel. Vehicle emissions tests were performed using West Virginia University's unique transportable chassis dynamometer. The trucks were found to perform adequately on neat F-T diesel fuel. Compared to a California diesel fuel baseline, neat F-T diesel fuel emitted about 12% lower oxides of nitrogen (NOx) and 24% lower particulate matter over a five-mile driving cycle
Baryon Acoustic Oscillations in the Ly{\alpha} forest of BOSS DR11 quasars
We report a detection of the baryon acoustic oscillation (BAO) feature in the
flux-correlation function of the Ly{\alpha} forest of high-redshift quasars
with a statistical significance of five standard deviations. The study uses
137,562 quasars in the redshift range from the Data Release
11 (DR11) of the Baryon Oscillation Spectroscopic Survey (BOSS) of SDSS-III.
This sample contains three times the number of quasars used in previous
studies. The measured position of the BAO peak determines the angular distance,
and expansion rate, , both on a scale set by the sound
horizon at the drag epoch, . We find
and
where . The optimal
combination, is determined with a precision of
. For the value , consistent with the CMB power
spectrum measured by Planck, we find
and . Tests with mock
catalogs and variations of our analysis procedure have revealed no systematic
uncertainties comparable to our statistical errors. Our results agree with the
previously reported BAO measurement at the same redshift using the
quasar-Ly{\alpha} forest cross-correlation. The auto-correlation and
cross-correlation approaches are complementary because of the quite different
impact of redshift-space distortion on the two measurements. The combined
constraints from the two correlation functions imply values of and
that are, respectively, 7% low and 7% high compared to the
predictions of a flat CDM cosmological model with the best-fit Planck
parameters. With our estimated statistical errors, the significance of this
discrepancy is .Comment: Accepted for publication in A&A. 17 pages, 18 figure
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