“Parametric Study of the Effects of Water to Cementitious Materials Ratio and Cementitious Materials Content on the Durability Properties of High Performance Concrete

This study takes a detailed look at the factors that affect the durability of concrete and how they can be applied to the development of a useful performance specification and help to extend the life of bridge decks and other concrete structures exposed to the elements of nature. A series of fifteen mixes (with varying cement contents and water/cement ratios) were performed in order to determine exactly which of these factors have a significant effect on the durability of a concrete mix. Controlling the water/cement ratio is necessary in order to control strength and permeability. Cement content was found to have little bearing on strength while the amount of cement affected the shrinkage significantly. Shrinkage is also dramatically affected by the amount of water in the mix. The results of the mixes were then used to develop a new specification for a bridge deck mix that will potentially improve the lifespan of bridge decks. Prescriptive versus performance specifications were also explored with the benefits and deficiencies of each form of specification looked at in detail

Pre- and postprocessing techniques for determining goodness of computational meshes

Research in error estimation, mesh conditioning, and solution enhancement for finite element, finite difference, and finite volume methods has been incorporated into AUDITOR, a modern, user-friendly code, which operates on 2D and 3D unstructured neutral files to improve the accuracy and reliability of computational results. Residual error estimation capabilities provide local and global estimates of solution error in the energy norm. Higher order results for derived quantities may be extracted from initial solutions. Within the X-MOTIF graphical user interface, extensive visualization capabilities support critical evaluation of results in linear elasticity, steady state heat transfer, and both compressible and incompressible fluid dynamics

An Assessment of the Use of Structural Deformation as a Method of Determining Area of Fire Origin

Current methodologies of origin investigation have yet to include the structural deformations seen in steel buildings as a viable indicator of the area of origin of a given fire. As many steel structures are of relatively large size, it is often difficult to determine the area of origin using the typical dig and sift methods advocated in NFPA 921, especially if the extent of the fire was large and there were no witnesses as to the origin of the fire. As has been investigated for years, the performance of steel is highly affected by the application of heat. The science of predicting the deformations of steel members is such that an investigator may be able to “reverse engineer” the fire to get an idea of its relative growth rate and length of combustion even if it is not possible to compute a heat release rate curve. The information derived from careful analysis of the deformations may also yield valuable input for use in computer fire modeling. Using several example cases, this paper explores the methodology that can be applied in order to use the structural deformations as a viable tool to determine the point of origin of large, single story steel framed structures

Age Dating of a High-Redshift QSO B1422+231 at Z=3.62 and its Cosmological Implications

The observed Fe II(UV+optical)/Mg II lambda lambda 2796,2804 flux ratio from a gravitationally lensed quasar B1422+231 at z=3.62 is interpreted in terms of detailed modeling of photoionization and chemical enrichment in the broad-line region (BLR) of the host galaxy. The delayed iron enrichment by Type Ia supernovae is used as a cosmic clock. Our standard model, which matches the Fe II/Mg II ratio, requires the age of 1.5 Gyr for B1422+231 with a lower bound of 1.3 Gyr, which exceeds the expansion age of the Einstein-de Sitter Omega_0=1 universe at a redshift of 3.62 for any value of the Hubble constant in the currently accepted range, H_0=60-80 km,s^{-1},Mpc^{-1}. This problem of an age discrepancy at z=3.62 can be unraveled in a low-density Omega_0<0.2 universe, either with or without a cosmological constant, depending on the allowable redshift range of galaxy formation. However, whether the cosmological constant is a required option in modern cosmology awaits a thorough understanding of line transfer processes in the BLRs.Comment: 7 pages including 3 figures, to appear in ApJ Letter

Z decay into two massless gauge bosons in a magnetic field

An investigation of the processes Z to gluon-gluon and Z to photon-photon in a background magnetic field is presented. For homogeneous fields corrections to the charged fermion propagator can be calculated in leading orders of the magnetic field. This work examines the first order contributions of the corrected propagator to decays that are otherwise zero. Results of the decay rates for varying field strengths are included.Comment: 14 pages, 2 figures, needs RevTeX4; typos corrected, appendix added, references added, format changed to preprint mod

The influence of meal frequency and timing on health in humans: The role of fasting

The influence of meal frequency and timing on health and disease has been a topic of interest for many years. While epidemiological evidence indicates an association between higher meal frequencies and lower disease risk, experimental trials have shown conflicting results. Furthermore, recent prospective research has demonstrated a significant increase in disease risk with a high meal frequency (6 meals/day) as compared to a low meal frequency (1-2 meals/day). Apart from meal frequency and timing we also have to consider breakfast consumption and the distribution of daily energy intake, caloric restriction, and night-time eating. A central role in this complex scenario is played by the fasting period length between two meals. The physiological underpinning of these interconnected variables may be through internal circadian clocks, and food consumption that is asynchronous with natural circadian rhythms may exert adverse health effects and increase disease risk. Additionally, alterations in meal frequency and meal timing have the potential to influence energy and macronutrient intake.A regular meal pattern including breakfast consumption, consuming a higher proportion of energy early in the day, reduced meal frequency (i.e., 2-3 meals/day), and regular fasting periods may provide physiological benefits such as reduced inflammation, improved circadian rhythmicity, increased autophagy and stress resistance, and modulation of the gut microbiot

Decoupling 802.11B From the Partition Table in Erasure Coding

Many cyberneticists would agree that, had it not been for extensible epistemologies, the evaluation of superblocks might never have occurred. In this paper, authors disprove the improvement of context-free grammar, demonstrates the technical importance of distributed systems. In our research, we concentrate our efforts on showing that IPv4 and erasure coding are never incompatible

Halos of Spiral Galaxies. III. Metallicity Distributions

(Abriged) We report results of a campaign to image the stellar populations in the halos of highly inclined spiral galaxies, with the fields roughly 10 kpc (projected) from the nuclei. We use the F814W (I) and F606W (V) filters in the Wide Field Planetary Camera 2, on board the Hubble Space telescope. Extended halo populations are detected in all galaxies. The color-magnitude diagrams appear to be completely dominated by giant-branch stars, with no evidence for the presence of young stellar populations in any of the fields. We find that the metallicity distribution functions are dominated by metal-rich populations, with a tail extending toward the metal poor end. To first order, the overall shapes of the metallicity distribution functions are similar to what is predicted by simple, single-component model of chemical evolution with the effective yields increasing with galaxy luminosity. However, metallicity distributions significantly narrower than the simple model are observed for a few of the most luminous galaxies in the sample. It appears clear that more luminous spiral galaxies also have more metal-rich stellar halos. The increasingly significant departures from the closed-box model for the more luminous galaxies indicate that a parameter in addition to a single yield is required to describe chemical evolution. This parameter, which could be related to gas infall or outflow either in situ or in progenitor dwarf galaxies that later merge to form the stellar halo, tends to act to make the metallicity distributions narrower at high metallicity.Comment: 20 pages, 8 figures (ApJ, in press

Differential Effects of Oral vs. Intravenous Fluid Administration on Bioelectrical Impedance During Dehydration Induced by Exercise and Heat

There is continued debate regarding optimal evaluation of hydration. Bioimpedance analysis has been utilized to evaluate hydration status, but there is limited information regarding the ability of this technology to detect physiological changes occurring during acute dehydration. PURPOSE: To evaluate whether bioimpedance spectroscopy (BIS) detects changes in bioelectrical resistance (R) in response to dehydration induced by exercising in the heat, assess whether these changes are related to body mass changes, and determine if the route of fluid administration during the dehydration protocol influences these observations. METHODS: Twelve males (mean ± SD; age: 28.6 ± 12.4 y; body mass: 74.7 ± 7.9 kg; height: 179.4 ± 7.0 cm; VO2max: 49.8 ± 6.6 mL/kg/min) completed two randomized experimental trials, each consisting of 90 minutes of continuous cycling exercise at 55% VO2maxfollowed by a 12 km time trial in the heat (ambient temperature: 34.9 ± 0.6 °C; relative humidity: 30.3 ± 0.9 %; wind speed: 3.4 mile×h-1). During each trial, fluid was administered either orally (DRINK) or intravenously (IV). During the DRINK trial, participants drank 25 mL of water every 5 minutes. During the IV trial, participants received 25 mL of isotonic saline solution through their IV catheter every 5 minutes. Nude body mass and BIS data were collected before and after trials to assess hydration status. Data were analyzed using Pearson’s correlations and paired t-tests with p-values corrected via false discovery rate. RESULTS: Body mass decreased, without differences between conditions (IV: -2.3 ± 0.5%; DRINK: -2.4 ± 0.9%; p=0.85). However, significant differences were observed for changes in predicted R at zero frequency (R0; IV: -3.6 ± 4.6%; DRINK: 1.3 ± 5.6%; p=0.02) and R at 50 kHz (R50; IV: -3.2 ± 4.1%; DRINK: -0.2 ± 4.1%; p=0.04), without differences in predicted R at infinite frequency (R∞; IV: -2.4 ± 6.1%; DRINK: -1.1 ± 3.7%; p=0.45). In the IV condition, significant correlations between body mass changes and R changes were observed for R0 (r=-0.80; p=0.002), R50 (r=-0.85; p\u3c0.001), and R∞ (r=-0.84; p\u3c0.001); however, no correlations were observed in the DRINK condition (r=-0.06 to 0.13; p≥0.69 for each). CONCLUSION: Differences between oral and intravenous fluid administration were seemingly detected by bioelectrical resistance at low-to-moderate, but not high, frequencies. With intravenous administration, negative correlations between changes in body mass and changes in R at all frequencies were observed, unlike with oral fluid administration. These findings suggest a potential sensitivity of bioimpedance technologies for monitoring intravenous fluid administration in the context of acute dehydration. However, additional investigation is needed to confirm their utility during distinct fluid loss scenarios and to confirm if these technologies are useful in the context of oral intake of fluids varying in composition

Evolution of the Luminosity Density in the Universe: Implications for the Nonzero Cosmological Constant

We show that evolution of the luminosity density of galaxies in the universe provides a powerful test for the geometry of the universe. Using reasonable galaxy evolution models of population synthesis which reproduce the colors of local galaxies of various morphological types, we have calculated the luminosity density of galaxies as a function of redshift $z$. Comparison of the result with recent measurements by the Canada-France Redshift Survey in three wavebands of 2800{\AA}, 4400{\AA}, and 1 micron at z<1 indicates that the \Lambda-dominated flat universe with \lambda_0 \sim 0.8 is favored, and the lower limit on \lambda_0 yields 0.37 (99% C.L.) or 0.53 (95% C.L.) if \Omega_0+\lambda_0=1. The Einstein-de Sitter universe with (\Omega_0, \lambda_0)=(1, 0) and the low-density open universe with (0.2, 0) are however ruled out with 99.86% C.L. and 98.6% C.L., respectively. The confidence levels quoted apply unless the standard assumptions on galaxy evolution are drastically violated. We have also calculated a global star formation rate in the universe to be compared with the observed rate beyond z \sim 2. We find from this comparison that spiral galaxies are formed from material accretion over an extended period of a few Gyrs, while elliptical galaxies are formed from initial star burst at z >~ 5 supplying enough amount of metals and ionizing photons in the intergalactic medium.Comment: 11 pages including 3 figures, LaTeX, uses AASTeX. To Appear in ApJ Letter