Fourier‐Transform Rheology of Unvulcanized,Carbon Black Filled Styrene Butadiene Rubber

Rubber materials filled with reinforcing fillers display nonlinear rheological behavior at small strain amplitudes below γ₀ < 0.1. Nevertheless, rheological data are analyzed mostly in terms of linear parameters, such as shear moduli (G′, G″), which loose their physical meaning in the nonlinear regime. In this work styrene butadiene rubber filled with carbon black (CB) under large amplitude oscillatory shear (LAOS) is analyzed in terms of the nonlinear parameter I_3/1. Three different CB grades are used and the filler load is varied between 0 and 70 phr. It is found that I_3/1(φ) is most sensitive to changes of the total accessible filler surface area at low strain amplitudes (γ₀ = 0.32). The addition of up to 70 phr CB leads to an increase of I_3/1(φ) by a factor of more than ten. The influence of the measurement temperature on I_3/1 is pronounced for CB levels above the percolation threshold.

     

An efficient algorithm for computing the transmission through highly conducting thin sheild in TLM

This paper presents a new method in TLM for very efficient computation of highly conducting thin shielding walls. Firstly, the impulse response of a finite conducting sheet is computed analytically via inverse Laplace transform. Subsequently, a recursive convolution integral is formulated with the analytical impulse response. This allows a very efficient and accurate calculation of the diffusion process through imperfectly conducting walls.     

Microbial and chemical assessment of regions within New Orleans, LA impacted by Hurricane Katrina

The city of New Orleans, LA was severely impacted by flooding and wind damage following landfall of Hurricane Katrina in August 2005. The city's drinking water infrastructure was severely compromised and massive amounts of sediment were redeposited throughout the flooded region. Thousands of homes were water-damaged resulting in the rapid growth of mold. In September and October 2005 a convenience sample of selected homes, tap water, surface water, and sediment within New Orleans was assessed for mold contamination, microbial contamination, and heavy metal concentrations. At selected sites, indoor mold spore concentrations were compared to outdoor concentrations. The purpose of this study was to conduct a baseline environmental assessment in an effort to identify public health threats caused by wind and flood damage. Surface waters contained high concentrations of bacterial indicators whereas no bacteria were detected in tap water, even from taps containing no chlorine residual. Sediment samples contained concentrations of lead and arsenic similarto pre-Katrina concentrations. Outdoor total spore (sp) concentrations ranged from >6500 to 84 713 sp/m(3). Indoor concentrations ranged from 6142 to 735 123 sp/m(3). For the 13 locations with matched indoor/ outdoor samples, the mean indoor/outdoor spore ratio was 4.11 (ranging from 0.27 to >11.44). Inside 5 of the 13 homes, total spore counts/m(3) exceeded 100 000, with measurements in the moldiest home exceeding 700 000 sp/ m(3). In conclusion, surface waters had high concentrations of bacterial contamination but no bacterial indicators were present in tap water. Sediment samples did not have appreciable increases in lead or arsenic. Flooded homes, however, contained substantial concentrations of mold which could present a public health exposure route to individuals repopulating and restoring the City of New Orleans.     

Evaluation of the furosine and homoarginine methods for determining reactive lysine in rumen-undegraded protein

Three samples of soybean meal (SBM), 3 samples of expeller SBM (SoyPlus, West Central Cooperative, Ralston, IA), 5 samples of distillers dried grains with solubles (DDGS), and 5 samples of fish meal were used to evaluate the furosine and homoarginine procedures to estimate reactive Lys in the rumen-undegraded protein fraction (RUP-Lys). One sample each of SBM, expeller SBM, and DDGS were subjected to additional heat treatment in the lab to ensure there was a wide range in reactive RUP-Lys content among the samples. Furosine is a secondary product of the initial stages of the Maillard reaction and can be used to calculate blocked Lys. Homoarginine is formed via the reaction of reactive Lys with O-methylisourea and can be used to calculate the concentration of reactive Lys. In previous experiments, each sample was ruminally incubated in situ for 16 h, and standardized RUP-Lys digestibility of the samples was determined in cecectomized roosters. All rumen-undegraded residue (RUR) samples were analyzed for furosine and Lys; however, only 9 of the 16 samples contained furosine, and only the 4 unheated DDGS samples contained appreciable amounts of furosine. Blocked RUP-Lys was calculated from the furosine and Lys concentrations of the RUR. Both the intact feed and RUR samples were evaluated using the homoarginine method. All samples were incubated with an O-methylisourea/BaOH solution for 72 h and analyzed for Lys and homoarginine concentrations. Reactive Lys concentrations of the intact feeds and RUR were calculated. Results of the experiment indicate that blocked RUP-Lys determined via the furosine method was negatively correlated with standardized RUP-Lys digestibility, and reactive RUP-Lys determined via the guanidination method was positively correlated with standardized RUP-Lys digestibility. Reactive Lys concentrations of the intact samples were also highly correlated with RUP-Lys digestibility. In conclusion, the furosine assay is useful in predicting RUP-Lys digestibility of DDGS samples, and the guanidination procedure can be used to predict RUP-Lys digestibility of SBM, expeller SBM, DDGS, and fish meal samples.     

Benchmark results on the linearized equations of motion of an uncontrolled bicycle

In this paper we present the linearized equations of motion for a bicycle as, a benchmark The results obtained by pencil-and-paper and two programs are compaied The bicycle model we consider here consists of four rigid bodies, viz a rear frame, a front frame being the front fork and handlebar assembly, a rear wheel and a fiont wheel, which are connected by revolute joints The contact between the knife-edge wheels and the flat level surface is modelled by holonomic constiaints in the normal direction and by non-holonomic constraints in the longitudinal and lateral direction The rider is rigidly attached to the rear frame with hands free from the handlebar This system has three degrees of freedom, the roll, the steer, and the forward speed For the benchmark we consider the linearized equations for small perturbations of the upright steady forward motion The entries of the matrices of these equations form the basis for comparison Three diffrent kinds of methods to obtain the results are compared pencil-and-paper, the numeric multibody dynamics program SPACAR, and the symbolic software system AutoSim Because the results of the three methods are the same within the machine round-off error, we assume that the results are correct and can be used as a bicycle dynamics benchmark     

Interplay between Endothelin and Erythropoietin in Astroglia: The Role in Protection against Hypoxia

We show that, under in vitro conditions, the vulnerability of astroglia to hypoxia is reflected by alterations in endothelin (ET)-1 release and capacity of erythropoietin (EPO) to regulate ET-1 levels. Exposure of cells to 24 h hypoxia did not induce changes in ET-1 release, while 48–72 h hypoxia resulted in increase of ET-1 release from astrocytes that could be abolished by EPO. The endothelin receptor type A (ETA) antagonist BQ123 increased extracellular levels of ET-1 in human fetal astroglial cell line (SV-FHAS). The survival and proliferation of rat primary astrocytes, neural precursors, and neurons upon hypoxic conditions were increased upon administration of BQ123. Hypoxic injury and aging affected the interaction between the EPO and ET systems. Under hypoxia EPO decreased ET-1 release from astrocytes, while ETA receptor blockade enhanced the expression of EPO mRNA and EPO receptor in culture-aged rat astroglia. The blockade of ETA receptor can increase the availability of ET-1 to the ETB receptor and can potentiate the neuroprotective effects of EPO. Thus, the new therapeutic use of combined administration of EPO and ETA receptor antagonists during hypoxia-associated neurodegenerative disorders of the central nervous system (CNS) can be suggested.     

Cross-Sectional Associations of Food Consumption with Plasma Fatty Acid Composition and Estimated Desaturase Activities in Finnish Children

Plasma fatty acid (FA) composition is known to be an indicator of dietary fat quality, but the associations of other dietary factors with plasma FA composition remain unknown in children. We investigated the cross-sectional associations of food consumption with the proportions of FA and estimated desaturase activities in plasma cholesteryl esters (CE) and phospholipids (PL) among children. The subjects were a population sample of 423 children aged 6–8 years examined at baseline of The Physical Activity and Nutrition in Children (PANIC) Study. We assessed food consumption by food records and plasma FA composition by gas chromatography. We used linear regression models adjusted for age, sex, physical activity and total energy intake to analyze the associations. A higher consumption of vegetable oil-based margarine (fat 60–80 %) was associated with a higher proportion of linoleic and α-linolenic acids in plasma CE and PL. A higher consumption of high-fiber grain products was related to a lower proportion of oleic acid in CE and PL. The consumption of candy was directly associated with the proportion of palmitoleic and oleic acid in plasma CE. The consumption of vegetable oil-based margarine was inversely associated with estimated stearoyl-CoA-desaturase activity in plasma CE and PL and the consumption of candy was directly related to it in plasma CE. The results of our study suggest that plasma FA composition is not only a biomarker for dietary fat quality but also reflects the consumption of high-fiber grain products and foods high in sugar among children.     

Contents of Volume 8 (2002)

Volume Contents

Contents of Volume 8 (2002)