Simulation of Concrete Paving Operations on Interstate-74

The objective of this paper was to study and optimize the concrete paving operations taking place in the reconstruction project of Interstate-74 using computer simulation. To achieve this objective, field data were collected during construction, and were then used to determine adequate probabilistic density functions for the activities’ duration and to test a developed simulation model. Upon testing, the developed model was used to study the impacts of resources on the flow of operations and on the cost effectiveness of the construction process. In general, application of simulation methods to concrete paving operations was successful and its accuracy was acceptable as compared to field measurements. Based on the results of a sensitivity analysis of the critical resources, multiple factors were considered in the decision-making process to ensure that all aspects of the operation are evaluated. This includes total operation time, productivity, costs of the operation, average truck delay, and idle times for the paver and the spreader. For the conditions pertinent to this construction site, ten trucks, one paver and one spreader, and three finishing and plastic-covering crews are recommended. Using this set of resources would result in a prompt and effective execution of the operation. Practical implementation and limitations of the developed model in similar construction operations is discussed.     

A novel,fast and accurate chemiluminescence method for measuring lipoxidation in almonds and almond-based products during processing and storage

An analytical method for investigating lipoxidation processes based on soft extraction and chemiluminescence (CL) detection methods was developed and tested on almond and almond-derived foodstuffs. The TBARS method, which detects any carbonyls generated by lipoxidation, was used for comparative purposes. When developing the present method, the classical chloroform–methanol procedure was first used to extract the CL reacting substances initially generated, and solubilizing agents were then screened for optimal extraction. In the detection stage, cytochrome C was used as a reference substance for screening the CL signal enhancers. The method presented here was based on an extraction step with a dimethylsulfoxide/Gum Arabic mixture, and hemin was used to enhance the luminescence signal. This method accurately detects the lipoxidation processes triggered by the physical and chemical treatments of all kinds which are applied during almond processing. The simultaneous use of the present method and the TBARS method gave a broader picture of the chemical interactions involved, including the lipoxidation process.     

Comparison of electrothermal and hydride generation atomic absorption spectrometry for the determination of total arsenic in broiler chicken

The purpose of this study was to estimate total arsenic concentration in different tissues (leg, breast, liver and heart) of broiler chicken by hydride generation atomic absorption spectrometry (HGAAS) and graphite furnace atomic absorption spectrometry (GFAAS), prior to microwave assisted acid digestion. The accuracy of the techniques was evaluated by using certified reference material DORM-2. The percentage recoveries of total As were observed as 100.6% and 99.4% for HGAAS and GFAAS, respectively. The precision of the techniques, expressed as relative standard deviation, was observed as 1.71% and 4.18% for HGAAS and GFAAS measurements, respectively. The limits of detection for HGAAS and GFAAS were 0.025 μg/g and 0.052 μg/g, respectively. The concentrations of total arsenic in different tissues of broiler chicken were found in the range of 2.19–5.28, 2.15–5.22, 2.97–7.17 and 2.68–6.36 μg/g for leg, breast, liver and heart tissues, respectively. At a mean level of chicken consumption (60 g/person/day), people may ingest in the range of 72.0–85.1 μg arsenic/person/day from chicken alone.     

Effects of light,temperature and water activity on the kinetics of lipoxidation in almond-based products

Lipoxidation in almond-derived products was investigated using the chemiluminescence (CL) and thiobarbituric acid-reactive substances (TBARS) methods to detect the first and later reaction products, respectively. The effects of light during storage at 5 °C, 22 °C and 40 °C were studied, as well as the effects of combined heat/water activity treatments in the 60–120 °C and 0.38–0.72 range. During storage, light was found to enhance the CL and TBARS values, and specific responses were observed in almond paste and the final Calisson product. During the heating of almond paste, as the initial water activity (a_w) increased, the CL rate constants increased during heating to 60 °C and 80 °C, but interestingly, these values decreased during further heating to 120 °C, whereas the maximum TBARS rate constants occurred at a_w 0.57 at all the heating temperatures tested. The activation energies, based on the CL and TBARS values, decreased specifically when the a_w increased from 0.38 to 0.72, giving overall values ranging from110 kJ mol⁻¹ to 60 kJ mol⁻¹. Likewise, in the same water activity range, the temperature-dependent rate constant enhancing factor (Q₁₀) decreased from 3.3 to 1.6.     

Efficient three-dimensional Delaunay triangulation with automatic point creation and imposed boundary constraints

A method is described which constructs three-dimensional unstructured tetrahedral meshes using the Delaunay triangulation criterion. Several automatic point creation techniques will be highlighted and an algorithm will be presented which can ensure that, given an initial surface triangulation which bounds a domain, a valid boundary conforming assembly of tetrahedra will be produced. Statistics of measures of grid quality are presented for several grids. The efficiency of the proposed procedure reduces the computer time for the generation of realistic unstructured tetrahedral grids to the order of minutes on workstations of modest computational capabilities.     

Synthesis and evaluation of morpholinoalkyl ester prodrugs of indomethacin and naproxen

Morpholinoalkyl esters (HCl salts) of naproxen 1 and indomethacin 3 were synthesized and evaluated in vitro and in vivo for their potential use as prodrugs for oral delivery. Prodrugs were freely soluble in simulated gastric fluid (SGF) and pH 7.4 phosphate buffer and showed a minimum of a 2000-fold increase in solubility over the parent drugs. All prodrugs were more lipophilic than parent drugs as indicated by n-octanol/pH 7.4 buffer partition coefficients but less lipophilic in terms of n-octanol/SGF partition coefficients. Potentiometrically determined pKa's for prodrugs were in the range of 6.89 to 8.62 at 25 degrees C. All prodrugs were quantitatively hydrolyzed to their respective parent drugs by enzymatic and/or by chemical means. An increase in carbon chain length rendered the prodrugs more stable at pH 7.4 but less stable in SGF. The esters were generally found to be hydrolyzed rapidly in rat plasma at 37 degrees C, the half-lives being in the range of 1.2-31.0 min. Based on in vitro results, prodrugs 2c and 4c were chosen to evaluate solid-state stability, in vivo bioavailability, and ulcerogenicity. At elevated temperatures, the solid-state decomposition of 2c and 4c followed biphasic kinetics, with rapid decomposition occurring initially. The prodrugs were 30-36% more bioavailable orally than the parent drugs following a single equimolar solution dose in rats. Prodrugs 2c and 4c were significantly less irritating to gastric mucosa than parent drugs following single-dose and chronic oral administration in rats.     

Formulation of electric-field integral equation without use of differential operator

We derive a new formulation of the electric-field integral equation for the surface current density on an infinitely long conducting strip, with a TE incident field. The formulation avoids the use of a differential operator, allows numerical solution using pulse basis functions and point matching, and is applicable to any two-dimensional scatterer. Our approach is readily extendable to three-dimensional problems.     

Fluorescent lipids of bovine brain white matter

Two fluorescent lipids were isolated from a chloroform-methanol (2∶1 v/v) extract of bovine brain white matter by two-step preparative thin layer chromatography on Silica Gel G. The first step was performed with chloroform-diethyl ether-acetic acid (70∶30∶1 v/v) as developing solvent and revealed a single fluorescent band below the solvent front. The band was scraped off, and the lipid was eluted in chloroform and reapplied to Silica Gel G plates. In the second step, benzene-methanol-ethyl acetate (85∶10∶5 v/v) as developing solvent revealed two fluoresent bands (A and B) with R_f values of 0.72 and 0.65. The lipids were eluted and the UV and visible absorption spectra were measured in heptane, as were the excitation and fluorescence spectra. Sulfuric acid absorption spectra (2 and 24 hr treatment at 22 C) as well as the resulting excitation and fluorescence spectra were also determined. The fluorescent lipids reacted positively in a number of nonspecific color tests for steroids, but the chemical nature of these minor components of the neutral lipid fraction remains to be established.     

Methane oxidative coupling over bismuth oxychloride-lithium carbonate-magnesia systems

The conversion of methane, the selectivity to C₂ hydrocarbons, and, particularly, the ethene-to-ethane ratio are much higher over BiOCl-Li₂CO₃-MgO than those over pure BiOCl and BiOCl-MgO. In addition, they remain almost the same over a period of 5 h for the former system, but decline significantly for the other two systems (BiOCl and 10% BiOCl-MgO). The XPS investigations provide some insight about the processes responsible for this behavior, indicating that not only Cl but also Bi is likely to play a role.