The effect of a polypropylene skin on the structure and properties of PE/PP dual layer pressure pipe

A new and growing family of polyethylene (PE)‐based pressure pipes have a polypropylene (PP) skin. The effect of the PP skin on the structure and properties of the core PE pipe was investigated by comparing the skinned pipe with an uncoated pipe made from the same PE material and with the same dimensions. The annealing effect introduced by the skin changed the PE core pipe density profile across the wall thickness, increasing density in the PE core pipe near to its outer surface. The density at the bore of the coated and the uncoated pipe was similar. The melting temperature and enthalpy of melting data from DSC agreed with the density profile results. The melting temperature of PE core pipe material close to the PP skin increased with increasing skin thickness. Residual stress assessment indicated that, as the PP skin thickness increased, the PE core pipe had a lower level of overall residual stress in the hoop direction. Long‐term hydrostatic strength (LTHS) tests were carried out and showed a higher strength for the coated pipe than the uncoated one. The observed structural changes have been used to explain the relative strength of these two PE pipes. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

The Crosstalk of Adipose-Derived Stem Cells (ADSC), Oxidative Stress,and Inflammation in Protective and Adaptive Responses

The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs is a major goal in repair medicine. Stem cells are classified by their potential to differentiate into functional cells. Compared with other sources, adipose-derived stem cells (ADSCs) have the advantage of being abundant and easy to obtain. ADSCs are considered to be tools for replacing, repairing, and regenerating dead or damaged cells. The capacity of ADSCs to maintain their properties depends on the balance of complex signals in their microenvironment. Their properties and the associated outcomes are in part regulated by reactive oxygen species, which mediate the oxidation-reduction state of cells as a secondary messenger. ADSC therapy has demonstrated beneficial effects, suggesting that secreted factors may provide protection. There is evidence that ADSCs secrete a number of cytokines, growth factors, and antioxidant factors into their microenvironment, thus regulating intracellular signaling pathways in neighboring cells. In this review, we introduce the roles of ADSCs in the protection of cells by modulating inflammation and immunity, and we develop their potential therapeutic properties.     

Fecal bile acid excretion and composition in response to changes in dietary wheat bran,fat and calcium in the rat

The effect and possible interactive influence of different dietary amounts of wheat bran, fat and calcium on the fecal excretion, concentration and composition of bile acids was studied in Fischer-344 rats. The fecal bile acids were analyzed using gas-liquid chromatography. Dietary wheat bran increased both total bile acid excretion and fecal weight without changes in fecal bile acid concentration. The proportion of fecal hyodeoxycholic acid decreased with increasing dietary fiber, whereas that of lithocholic and deoxycholic acids increased significantly with fiber intake. The percent content of fecal chenodeoxycholic acid did not change. Increasing dietary fat led to an increase in bile acid excretion without changes in either fecal weight or bile acid concentration. In contrast, the level of dietary calcium did not affect the total excretion of bile acids. However, since calcium increased the fecal weight, it consequently diluted bile acids and decreased their fecal concentration. Dietary fat and calcium had no influence on fecal bile acid composition. There were no interactive effects of wheat bran, fat and calcium on fecal bile acids. The finding in this study that dietary fiber, fat and calcium induce significant changes in fecal bile acids may be of relevance to the potential of bile acids to promote carcinogenesis.     

Influence of Thermal Conductivity and Fracture Toughness on the Thermal Shock Resistance of Alumina—Silicon–Carbide–Whisker Composites

The thermal shock resistance (indentation–quench method), fracture toughness, and thermal conductivity of three alumina–silicon–carbide–whisker composites and alumina have been investigated. A new procedure for the evaluation of thermal conductivity data is suggested, and higher room-temperature thermal conductivity than that reported in the literature is determined for silicon carbide whiskers. The ranking of the materials according to thermal shock resistance is consistent with the ranking according to fracture toughness but disagrees with the ranking according to thermal conductivity. This finding supports the analytically obtained result that, in defining thermal shock resistance, fracture toughness is more important than thermal conductivity.     

Properties and Use of the Shewhart Method and Its Followers

Abstract

After the Shewhart method was suggested for industrial applications, other applications, such as surveillance for bioterrorism and financial transactions, came into focus. Other methods for surveillance have also followed. The relation between the Shewhart method and the followers is examined. A uniform presentation of methods, by expressions of likelihood ratios, facilitates the comparisons between methods. The situations for which the Shewhart method has optimality properties are thus determined. The uses of the Shewhart method and its followers for complicated situations are reviewed.     

Fate of fertilizer 15N in intensive ridge cultivation with plastic mulching under a monsoon climate

Reducing nitrogen (N) leaching to groundwater requires an improved understanding of the effect of microtopography on N fate. Because of the heterogeneity between positions, ridge tilled fields, frequently used in intensive agriculture, should be treated as two distinct management units. In this study, we measured N dynamics in plastic-mulched ridges and bare furrows with the goal of developing more sustainable agricultural practices with optimal gains, namely crop production versus limited impacts on water quality. We investigated: (1) biomass production; (2) crop N uptake; (3) N retention in soil; and (4) N leaching using ¹⁵N fertilizer in a radish crop. Broadcast mineral N fertilizer application prior to planting resulted in high total leaching losses (of up to 390 N kg ha^?1). The application of plastic mulch in combination with local fertilizer management did not help to reduce N leaching. At all fertilizer N rates, the mean NO₃ ^? concentrations in seepage water were found to be above the WHO drinking water standard of 50 mg NO₃ ^? l^?1. To reduce NO₃ ^? leaching, we recommend: (1) decreasing the fertilizer N rates to a maximum of 150 kg N ha^?1; (2) applying fertilizer N in 3–4 split applications according to the plant’s N needs; (3) applying fertilizer N to the ridges (after their formation) to avoid losses from the furrows; and (4) increasing the soil organic matter content to enhance the water and nutrient retention by covering the furrows with plant residues.     

Effects of dietary α-linolenic acid on the conversion and oxidation of13C-α-linolenic acid

The effects of a diet rich in α-linolenic acid vs. one rich in oleic acid on the oxidation of uniformly labeled¹³C-α-linolenic acid and its conversion into longer-chain polyunsaturates (LCP) were investigatedin vivo in healthy human subjects. Volunteers received a diet rich in oleic acid (n=5) or a diet rich in α-linolenic acid (n=7; 8.3 g/d) for 6 wk before and during the study. After 6 wk, subjects were given 45 mg of¹³C-α-linolenic acid dissolved in olive oil. Blood samples were collected att=0, 5, 11, 24, 96, and 336 h. Breath was sampled and CO₂ production was measured each hour for the first 12 h. The mean (±SEM) maximal absolute amount of¹³C-eicosapentaenoic acid (EPA) in plasma total lipids was 0.04 ±0.01 mg in the α-linolenic acid group, which was significantly lower (P=0.01) than the amount of 0.12±0.03 mg¹³C-EPA in the oleic acid group. Amounts of¹³C-docosapentaenoic acid (DPA) and¹³C-docosahexaenoic acid (DHA) tended to be lower as well. The mean proportion of labeled α-linolenic acid (ALA) recovered as¹³CO₂ in breath after 12 h was 20.4% in the ALA and 15.7% in the oleic acid group, which was not significantly different (P=0.12). The cumulative recovery of¹³C from¹³C-ALA in breath during the first 12 h was negatively correlated with the maximal amounts of plasma¹³C-EPA (r=−0.58,P=0.047) and¹³C-DPA (r=−0.63,P=0.027), but not of¹³C-DHA (r=−0.49,P=0.108). In conclusion, conversion of¹³C-ALA into its LCP may be decreased on diets rich in ALA, while oxidation of¹³C-ALA is negatively correlated with its conversion into LCP. In a few pilot samples, low¹³C enrichments of n−3 LCP were observed in a diet rich in EPA/DHA as compared to oleic acid.     

Calcium carbonate and ammonium polyphosphate flame retardant additives formulated to protect ethylene vinyl acetate copolymer against fire: Hydrated or carbonated calcium?

In this study, the effect of the chemical nature of different calcium (Ca)-based minerals as flame retardant additives in combination with ammonium polyphosphate (APP), in 1:1 proportions, on the flame retardancy behavior and performance of ethylene vinyl acetate copolymer was discussed. Combining APP with partly and completely hydrated calcium oxide led to superior flame-retardant function detected in mass loss calorimeter measurements with respect to the corresponding system containing carbonated calcium. This privileged character was attributed to the higher reactivity of hydrated Ca-based fillers toward APP in comparison with Ca carbonate, which induced the formation of an intumescent residue. The difference between reactivity potential of hydrated and dry Ca was demonstrated by the newly formed thermally stable species, and further evidenced by thermogravimetric analysis performed on APP/fillers blends. Moreover, the presence of more crystalline domains in the Ca/phosphorus-based compounds was evidenced by XRD analysis of the mass loss calorimeter test residues. The results of this work highlight the role of blend additive systems on the performance of flame retardancy of polymer materials.