Durability of Fe-Co thin films on Ti-6Al-4V

The durability of Fe-Co thin films bonded on Ti-6Al-4V was studied as a function of layer thickness at ambient temperature. Interface toughness of the thin films was characterized by indentation and analyzed using an interface fracture model. The critical stresses for interface debonding and the fatigue life response of Ti-6Al-4V with and without Fe-Co thin films were evaluated by three-point bend fatigue at a stress ratio R of 0.1. The results indicated that the critical stress for interface debonding increased with decreasing layer thickness according to a critical energy release rate criterion. The Fe-Co thin films did not alter the fatigue life of the Ti-6Al-4V substrate. The presence of microcracks and interface debonds in the thin films did not affect the functionality of the sensor to detect strain via the inverse magneto-elastic effect. The overall durability of the films was in the range needed for practical application of the film as an embedded sensor.     

IL-12, but not IFN-gamma, plays a major role in sustaining the chronic phase of colitis in IL-10-deficient mice

IL-10-deficient (IL-10(-/-)) mice develop chronic enterocolitis mediated by CD4+ Th1 cells producing IFN-gamma. Because IL-12 can promote Th1 development and IFN-gamma production, the ability of neutralizing anti-IL-12 mAb to modulate colitis in IL-10(-/-) mice was investigated. Anti-IL-12 mAb treatment completely prevented disease development in young IL-10(-/-) mice. Treatment of adult mice resulted in significant amelioration of established disease accompanied by reduced numbers of mesenteric lymph node and colonic CD4+ T cells and of mesenteric lymph node T cells spontaneously producing IFN-gamma. In contrast, anti-IFN-gamma mAb had minimal effect on disease reversal, despite a significant preventative effect in young mice. These findings suggested that IL-12 sustains colitis by supporting the expansion of differentiated Th1 cells that mediate disease independently of their IFN-gamma production. This conclusion was supported by the finding that anti-IL-12 mAb greatly diminished the ability of a limited number of CD4+ T cells expressing high levels of CD45RB from diseased IL-10(-/-) mice to expand and cause colitis in recombination-activating gene-2(-/-) recipients, while anti-IFN-gamma mAb had no effect. Furthermore, IL-12 could support pathogenic IL-10(-/-) T cells stimulated in vitro in the absence of IL-2. While these studies show that IL-12 plays an important role in sustaining activated Th1 cells during the chronic phase of disease, the inability of anti-IL-12 mAb to abolish established colitis or completely prevent disease transfer by Thl cells suggests that additional factors contribute to disease maintenance.     

Statistics for estimating the population average of a Lifshitz–Slyozov–Wagner (LSW) distribution

A generic version of the Lifshitz–Slyozov–Wagner (LSW) distribution is introduced. Using this generic form, a maximum likelihood (ML) estimator for the population average has been developed. The statistical properties of the estimates obtained by the ML method, as well as the conventional sample average method, have been assessed by Monte Carlo simulations for seven sample sizes ranging from 10 to 1000. Results showed that (i) both estimators yield practically unbiased results, (ii) the standard deviation of estimates obtained by the ML method is significantly less than that of the sample averages, (iii) the distribution of estimates is neither normal, lognormal nor 2-parameter Weibull. Percentage points of the distribution of estimates for both methods have been developed. The use of these points for calculating confidence limits for the population average of the LSW distribution is demonstrated by examples in this article.     

Recovery and fractionation of phosphorus retained by lightweight expanded shale and masonry sand used as media in subsurface flow treatment wetlands

Most subsurface flow treatment wetlands, also known as reed bed or root zone systems, use sand or gravel substrates to reduce organics, solids, and nutrients in septic tank effluents. Phosphorus (P) retention in these systems is highly variable and few studies have identified the fate of retained P. In this study, two substrates, expanded shale and masonry sand, were used as filter media in five subsurface flow pilot-scale wetlands (2.7 m3). After 1 year of operation, we estimated the annual rate of P sorption by taking the difference between total P (TP) of substrate in the pilot cells and TP of substrate not exposed to wastewater (control). Means and standard deviations of TP retained by expanded shale were 349 +/- 171 mg kg(-1), respectively. For a substrate depth of 0.9 m, aerial P retention by shale was 201 +/- 98.6 g of P m(-2) year(-1), respectively. Masonry sand retained an insignificant quantity of wastewater P (11.9 +/- 21.8 mg kg(-1)) and on occasion exported P. Substrate samples were also sequentially fractionated into labile P, microbial P, (Fe + Al) P, humic P, (Ca + Mg) P, and residual P. In expanded shale samples, the greatest increase in P was in the relatively permanent form of (Fe + Al) P (108 mg kg(-1)), followed by labile P (46.7 mg kg(-1)) and humic P (39.8 mg kg(-1)). In masonry sand, there was an increase in labile P (9.71 mg kg(-1)). Results suggest that sand is a poor candidate for long-term P storage, but its efficiency is similar to that reported for many sand, gravel, and rock systems. By contrast, expanded shale and similar products with high hydraulic conductivity and P sorption capacity could greatly improve performance of P retention in constructed wetlands.     

On estimating Weibull modulus by the linear regression method

Statistical models were developed to estimate the bias of the shape parameter of a 2-parameter Weibull distribution where the shape parameter was estimated using a linear regression. These models were formulated for 27 sample sizes from 5 to 100 and for 35 probability estimators, , by varying “a” and “b”. In each simulation, 20,000 trials were used. From these models, a class of unbiased estimators were developed for each sample size. The standard deviation and coefficient of variation of these estimators were compared to the bias of the estimators. The standard deviation increased while the coefficient of variation decreased with increasing bias of the shape parameter. Also, the Anderson–Darling statistics was used to determine that the normal, log-normal, 3-parameter Weibull, and 3-parameter log-Weibull distributions did not provide good fit to the estimator of the shape parameter.