Mechanical properties at room temperature of an Al-Zn-Mg-Cu alloy processed by equal channel angular pressing

Tensile tests were conducted to evaluate the influence of equal-channel angular pressing (ECAP) on the mechanical properties at room temperature of overaged Al 7075-O alloy. ECAP processing was performed using route B_C at different temperatures and number of passes, i.e. different processing severity conditions. The maximum load (F_max) recorded during the last pass of each ECAP path considered in this study is a very good estimation of the processing severity. The mechanical properties were studied in terms of the balance between tensile strength and ductility. In the processed Al 7075-O alloy, the grain size was reduced down to ∼150 nm. Consequently, tensile testing at room temperature revealed a significant increase in the maximum tensile strength after ECAP with respect to the as start material. In the present study, as the processing severity increases with the number of ECAP passes or with the decrease in processing temperature, there is a consistent trend of increment in ultimate tensile strength with minor decrease in uniform plastic elongation respect to the first ECAP pass at room temperature. This is in contrast to the behaviour after more severe plastic deformation conditions, where an increase in strength together with a strong decrease in elongation would be expected.     

Influence of total solids concentration on membrane permeability in a submerged hollow-fibre anaerobic membrane bioreactor

The main aim of this work was to study the influence of the mixed liquor total solids (MLTS) concentration on membrane permeability (K(20)) in a submerged anaerobic membrane bioreactor (SAnMBR) pilot plant, which is equipped with industrial hollow-fibre membranes and treats urban wastewater. This pilot plant was operated at 33 °C and 70 days of SRT. Two different transmembrane fluxes (13.3 and 10 LMH) were tested with a gas sparging intensity of 0.23 Nm(3) m(-2)h(-1) (measured as Specific Gas Demand referred to membrane area). A linear dependence of K(20) on MLTS concentration was observed within a range of MLTS concentration from 13 to 32 g L(-1) and J(20) of 10 LMH. K(20) was maintained at sustainable values (about 100 LMH bar(-1)) even at high MLTS concentrations (up to 20 g L(-1)). In addition, several short-tests were carried out when the membranes were operated at high MLTS concentrations in order to assess the effect of the physical cleaning strategies (relaxation and back-flush) on membrane performance. It was observed that, with the applied gas sparging intensity, the duration of the relaxation stage did not critically affect the membrane performance. On the other hand, the required back-flush frequency was considerably affected by the MLTS concentration.     

Fuzzy rule extraction by bacterial memetic algorithms

In our previous papers, fuzzy model identification methods were discussed. The bacterial evolutionary algorithm for extracting fuzzy rule base from a training set was presented. The Levenberg–Marquardt method was also proposed for determining membership functions in fuzzy systems. The combination of the evolutionary and the gradient‐based learning techniques is usually called memetic algorithm. In this paper, a new kind of memetic algorithm, the bacterial memetic algorithm, is introduced for fuzzy rule extraction. The paper presents how the bacterial evolutionary algorithm can be improved with the Levenberg–Marquardt technique. © 2009 Wiley Periodicals, Inc.     

Sterols and Stanols in Foods and Dietary Supplements Containing Added Phytosterols: A Collaborative Study

An international, multilaboratory collaborative study was carried out to evaluate the performance of Official Method Ce 12‐16 of the American Oil Chemists’ Society (AOCS) for the determination of plant sterols and stanols, collectively referred to as phytosterols, in foods and dietary supplements containing added phytosterols and in the phytosterol food additive concentrates used to prepare such products. AOCS Official Method Ce 12‐16 involves the extraction of free sterols/stanols and saponified steryl/stanol esters followed by the gas chromatographic separation and flame ionization detection of phytosterol trimethylsilyl ether derivatives. A total of 14 laboratories from six countries successfully completed the analysis of collaborative samples of foods (e.g., baked goods, beverages, margarines; n = 9), dietary supplements (n = 5), and phytosterol concentrates (n = 4). Study results for the contents of total phytosterols (weight/weight) were 0.19–8.4% for foods, 8.7–49% for dietary supplements, and 57–97% for concentrates. AOCS Official Method Ce 12‐16 showed acceptable performance for total and individual phytosterols, indicating that this method was suitable for the determination of added phytosterols in a wide variety of market products and concentrates. AOCS Official Method Ce 12‐16 is appropriate for the determination of the five major phytosterols (i.e., campesterol, stigmasterol, β‐sitosterol, campestanol, and sitostanol) that are the subject of the United States Food and Drug Administration's health claim for phytosterols and the reduced risk of coronary heart disease.     

Paternal Exercise Improves the Metabolic Health of Offspring via Epigenetic Modulation of the Germline

Background/Aims: Epigenetic regulation is considered the main molecular mechanism underlying the developmental origin of health and disease’s (DOHAD) hypothesis. Previous studies that have investigated the role of paternal exercise on the metabolic health of the offspring did not control for the amount and intensity of the training or possible effects of adaptation to exercise and produced conflicting results regarding the benefits of parental exercise to the next generation. We employed a precisely regulated exercise regimen to study the transgenerational inheritance of improved metabolic health. Methods: We subjected male mice to a well-controlled exercise -training program to investigate the effects of paternal exercise on glucose tolerance and insulin sensitivity in their adult progeny. To investigate the molecular mechanisms of epigenetic inheritance, we determined chromatin markers in the skeletal muscle of the offspring and the paternal sperm. Results: Offspring of trained male mice exhibited improved glucose homeostasis and insulin sensitivity. Paternal exercise modulated the DNA methylation profile of PI3Kca and the imprinted H19/Igf2 locus at specific differentially methylated regions (DMRs) in the skeletal muscle of the offspring, which affected their gene expression. Remarkably, a similar DNA methylation profile at the PI3Kca, H19, and Igf2 genes was present in the progenitor sperm indicating that exercise-induced epigenetic changes that occurred during germ cell development contributed to transgenerational transmission. Conclusion: Paternal exercise might be considered as a strategy that could promote metabolic health in the offspring as the benefits can be inherited transgenerationally.     

Lowering the temperature for high strain rate superplasticity in an Al–Mg–Zn–Cu alloy via cooled friction stir processing

An Al–Zn–Mg–Cu alloy was friction stir processed over two kinds of backing anvils, at two different cooling rates. A finer grain size, 0.3 vs 0.5 μm, was obtained by processing at the highest cooling rate. Both materials showed superplastic behavior with a maximum elongation to fracture of about 510%. Grain boundary sliding was the operative deformation mechanism. Furthermore, the finer grain size material showed high strain rate superplasticity, at 10⁻² s⁻¹, at lower temperatures, as low as 250 °C.     

Flame hydrolysis deposition of glass on silicon for the integration of optical and microfluidic devices

Flame hydrolysis deposition (FHD) of glasses has previously found applications in the telecommunications industry. This paper shows how the technology can be used to deposit silica with different refractive indices and thereby produce low-loss planar waveguides for use in analytical applications. We also show that the glasses can be patterned using a new reactive ion etch and sealed using a modification of anodic bonding, such that the resulting microstructures can be readily incorporated within a lithographically defined "chip", integrating both optical and fluidic circuitry on the same device. In the example described in this paper, waveguides, analytical microtiter chambers and fluidic capillary channels, with the necessary high aspect ratio features (and with depths up to 40 microm) were all produced in glass, using the appropriate deposition and etching technologies. The performance of the chip was assessed in the framework of a low-volume fluorescence assay, using waveguides to address miniaturized microtiter chambers with volumes of 230 and 570 pL. Devices featuring different optical detection configurations, including both in-line and orthogonal waveguide geometries, were fabricated. In the optimal configuration, the experimental detection limit was determined as ca. 20 pM (equivalent to 10 zmol) of a cyanine fluorophore, Cy5. The applicability of the device as a biochip platform was further illustrated by analytical measurements on fluorescently labeled oligodeoxynucleotides.     

Effect of acidic pH on the structure and lipid binding properties of porcine surfactant protein A. Potential role of acidification along its exocytic pathway

Pulmonary surfactant protein A (SP-A) is synthesized by type II cells and stored intracellularly in secretory granules (lamellar bodies) together with surfactant lipids and hydrophobic surfactant proteins B and C (SP-B and SP-C). We asked whether the progressive decrease in pH along the exocytic pathway could influence the secondary structure and lipid binding and aggregation properties of porcine SP-A. Conformational analysis from CD spectra of SP-A at various pH values indicated that the percentage of alpha-helix progressively decreased and that of beta-sheet increased as the pH was reduced. The protein underwent a marked self-aggregation at mildly acidic pH in the presence of Ca2+, conditions thought to resemble those existing in the trans-Golgi network. Protein aggregation was greater as the pH was reduced. We also found that both neutral and acidic vesicles either with or without SP-B or SP-C bound to SP-A at acidic pH as demonstrated by co-migration during centrifugation. However, the binding of acidic but not neutral vesicles to SP-A led to 1) a striking change in the CD spectra of the protein, which was interpreted as a decrease of the level of SP-A self-aggregation, and 2) a protection of the protein from endoproteinase Glu-C degradation at pH 4.5. SP-A massively aggregated acidic vesicles but poorly aggregated neutral vesicles at acidic pH. Aggregation of dipalmitoylphosphatidylcholine (DPPC) vesicles either with or without SP-B and/or SP-C strongly depended on pH, being progressively decreased as the pH was reduced and markedly increased when pH was shifted back to 7.0. At the pH of lamellar bodies, SP-A-induced aggregation of DPPC vesicles containing SP-B or a mixture of SP-B and SP-C was very low, although SP-A bound to these vesicles. These results indicate that 1) DPPC binding and DPPC aggregation are different phenomena that probably have different SP-A structural requirements and 2) aggregation of membranes induced by SP-A at acidic pH is critically dependent on the presence of acidic phospholipids, which affect protein structure, probably preventing the formation of large aggregates of protein.     

Denuded zones, diffusional creep, and grain boundary sliding

The appearance of denuded zones following low stress creep in particle-containing crystalline materials is both a microstructural prediction and observation often cited as irrefutable evidence for the Nabarro-Herring (N-H) mechanism of diffusional creep. The denuded zones are predicted to be at grain boundaries that are orthogonal to the direction of the applied stress. Furthermore, their dimensions should account for the accumulated plastic flow. In the present article, the evidence for such denuded zones is critically examined. These zones have been observed during creep of magnesium, aluminum, and nickel-base alloys. The investigation casts serious doubts on the apparently compelling evidence for the link between denuded zones and diffusional creep. Specifically, denuded zones are clearly observed under conditions that are explicitly not diffusional creep. Additionally, the denuded zones are often found in directions that are not orthogonal to the applied stress. Other mechanisms that can account for the observations of denuded zones are discussed. It is proposed that grain boundary sliding accommodated by slip is the rate-controlling process in the stress range where denuded zones have been observed. It is likely that the denuded zones are created by dissolution of precipitates at grain boundaries that are simultaneously sliding and migrating during creep. This article is based on a presentation made in the workshop entitled “Mechanisms of Elevated Temperature Plasticity and Fracture,” which was held June 27–29, 2001, in Dan Diego, CA, concurrent with the 2001 Joint Applied Mechanics and Materials Summer Conference. The workshop was sponsored by Basic Energy Sciences of the United States Department of Energy.