Flexural Behaviour of Stay-In-Place PVC Encased Reinforced Concrete Walls with Various Panel Types

The use of stay-in-place (SIP) formwork has become an increasingly popular tool for concrete structures, providing advantages in construction scheduling and labour reduction. Stay-in-place formwork made of strong materials such as fibre reinforced polymer (FRP) and steel have proven to supplement and even replace reinforcement in concrete elements. The use of polyvinyl chloride (PVC) SIP formwork has also been explored. Current research suggests that PVC provides an enhancement to reinforced concrete strength and ductility. The research herein outlines tests on reinforced concrete walls with a compressive strength 25MPa, utilizing two types of PVC panels; flat or hollow, in order to further understand the polymer’s contribution to flexural resistance. The PVC forming system consisted of panels on the tension and compression faces with evenly spaced connectors securing the faces of the wall. Variables studied included concrete core thickness (152 mm, 178 mm, and 203 mm), reinforcing ratio (3-10M bars or 3-15M bars), and panel type (hollow or flat). The walls were tested in four point bending. The concrete control walls failed due to steel yielding followed by concrete crushing. The failure of the flat panel encased walls was dependent on the reinforcing ratio. Wall reinforced with 10M bars and encased with flat panels failed due to steel yielding followed by concrete crushing, PVC buckling, and PVC rupture while walls with 15M bars did not experience PVC rupture. Finally the failure for walls encased in hollow panels was due to steel yielding, followed by concrete crushing and PVC buckling. The hollow panel encased specimens also experienced slip of the panels on the tensile face. The PVC encasement enhanced the yield load, ultimate load, ductility, and toughness of the concrete walls. For flat panel encased walls, the average improvement at yield and ultimate loads were 21% and 27% respectively. Hollow panel encased walls recorded average yield and ultimate load improvements of 8% and 27% respectively. Flat panel encased walls improved ductility by an average of 71% and toughness by 122%. Hollow panel encased walls improved ductility by an average of 29% and toughness by 70%. Concrete cores were taken from the tested PVC encased specimens and compressive strength was found to be the same as the control walls. An analytical model was developed to estimate the yield and ultimate load of PVC encased concrete walls. Calculated yield loads were in good agreement with the experimental data, with an average error of 8% for the control walls and 6% for the PVC encased walls. In addition, calculated ultimate (peak) loads showed good correlation with the experimental data. The average error for the control, flat panel and hollow panel encased walls were 3%, 3% and 8% respectively. Calculated and experimental PVC tensile strain values were in good correlation at ultimate load conditions. The average error for the calculated PVC tensile strain was 21%. With the proposed model providing results in good agreement with the test data, other PVC encased wall cross-sections were explored. An “optimized” panel layout was proposed that utilized flat panels on the compression side of the wall and hollow panels on the tension side. This configuration of panels resulted in the greatest estimated improvement at both yield and ultimate load levels

Studies of Diffuse Interstellar Bands. V. Pairwise Correlations of Eight Strong DIBs and Neutral Hydrogen, Molecular Hydrogen, and Color Excess

We establish correlations between equivalent widths of eight diffuse interstellar bands (DIBs), and examine their correlations with atomic hydrogen, molecular hydrogen, and EB-V . The DIBs are centered at \lambda\lambda 5780.5, 6204.5, 6283.8, 6196.0, 6613.6, 5705.1, 5797.1, and 5487.7, in decreasing order of Pearson\^as correlation coefficient with N(H) (here defined as the column density of neutral hydrogen), ranging from 0.96 to 0.82. We find the equivalent width of \lambda 5780.5 is better correlated with column densities of H than with E(B-V) or H2, confirming earlier results based on smaller datasets. We show the same is true for six of the seven other DIBs presented here. Despite this similarity, the eight strong DIBs chosen are not well enough correlated with each other to suggest they come from the same carrier. We further conclude that these eight DIBs are more likely to be associated with H than with H2, and hence are not preferentially located in the densest, most UV shielded parts of interstellar clouds. We suggest they arise from different molecules found in diffuse H regions with very little H (molecular fraction f<0.01). Of the 133 stars with available data in our study, there are three with significantly weaker \lambda 5780.5 than our mean H-5780.5 relationship, all of which are in regions of high radiation fields, as previously noted by Herbig. The correlations will be useful in deriving interstellar parameters when direct methods are not available. For instance, with care, the value of N(H) can be derived from W{\lambda}(5780.5).Comment: Accepted for publication in The Astrophysical Journal; 37 pages, 11 figures, 6 table

Faint High Latitude Carbon Stars Discovered by the Sloan Digital Sky Survey: Methods and Initial Results

We report the discovery of 39 Faint High Latitude Carbon Stars (FHLCs) from Sloan Digital Sky Survey commissioning data. The objects, each selected photometrically and verified spectroscopically, range over 16.6 < r* < 20.0, and show a diversity of temperatures as judged by both colors and NaD line strengths. At the completion of the Sloan Survey, there will be many hundred homogeneously selected and observed FHLCs in this sample. We present proper motion measures for each object, indicating that the sample is a mixture of extremely distant (>100 kpc) halo giant stars, useful for constraining halo dynamics, plus members of the recently-recognized exotic class of very nearby dwarf carbon (dC) stars. Motions, and thus dC classification, are inferred for 40-50 percent of the sample, depending on the level of statistical significance invoked. The new list of dC stars presented here, although selected from only a small fraction of the final SDSS, doubles the number of such objects found by all previous methods. (Abstract abridged).Comment: Accepted for publication in The Astronomical Journal, Vol. 124, Sep. 2002, 40 pages, 7 figures, AASTeX v5.

Low serum magnesium and 1-year mortality in alcohol withdrawal syndrome

Background: In 2014, the WHO reported that 6% of all deaths were attributable to excess alcohol consumption. The aim of the present study was to examine the relationship between serum magnesium concentrations and mortality in patients with alcohol withdrawal syndrome (AWS). Materials and methods: A retrospective review of 700 patients with documented evidence of previous AWS indicating a requirement for benzodiazepine prophylaxis or evidence of alcohol withdrawal syndrome between November 2014 and March 2015. Results: Of 380 patients included in the sample analysis, 64 (17%) were dead at 1 year following the time of treatment for AWS. The majority of patients had been prescribed thiamine (77%) and a proton pump inhibitor (66%). In contrast, the majority of patients had low circulating magnesium concentrations (2 (P  50 years (OR 3.37, 95% CI 1.52-7.48, P 2 (OR 3.10, 95% CI 1.38-6.94, P < 0.01) and magnesium < 0.75 mmol/L (OR 4.11, 95% CI 1.3-12.8, P < 0.05) remained independently associated with death at 1 year. Conclusion: Overall, 1-year mortality was significantly higher among those patients who were magnesium deficient (<0.75 mmol/L) when compared to those who were replete (≥0.75 mmol/L; P < 0.001)

A Cautionary Tale: MARVELS Brown Dwarf Candidate Reveals Itself To Be A Very Long Period, Highly Eccentric Spectroscopic Stellar Binary

We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R ~ <30,000), this particular stellar binary mimics a single-lined binary with an RV signal that would be induced by a brown dwarf companion (Msin(i)~50 M_Jup) to a solar-type primary. At least three properties of this system allow it to masquerade as a single star with a very low-mass companion: its large eccentricity (e~0.8), its relatively long period (P~238 days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight (omega~189 degrees). As a result of these properties, for ~95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding on the apparently single-lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit (e~0.3). Only during the ~5% of the orbit near periastron passage does the true, double-lined nature and large RV amplitude of ~15 km/s reveal itself. The discovery of this binary system is an important lesson for RV surveys searching for substellar companions; at a given resolution and observing cadence, a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters. Finally, for surveys like MARVELS that lack the resolution for a useful line bisector analysis, it is imperative to monitor the peak of the cross-correlation function for suspicious changes in width or shape, so that such false positives can be flagged during the candidate vetting process.Comment: 16 pages, 11 figures, 6 table