Reliability training

Discussed here is failure physics, the study of how products, hardware, software, and systems fail and what can be done about it. The intent is to impart useful information, to extend the limits of production capability, and to assist in achieving low cost reliable products. A review of reliability for the years 1940 to 2000 is given. Next, a review of mathematics is given as well as a description of what elements contribute to product failures. Basic reliability theory and the disciplines that allow us to control and eliminate failures are elucidated

Heavy metal removal from aqueous solutions by sorption using natural clays from Burkina Faso

The acid-base properties of two raw and purified mixed clays from Burkina Faso were studied, as well as their potential to remove copper(II), lead(II) and chromium(III), and thereby their ability to be used to purify water from heavy metals. The purification procedure of the clays involved removal of carbonates, iron oxides and organic matter. A determination of the elemental composition of the mixed clays revealed the presence of aluminum, iron and silicon as main constituents. The high alkaline pH in one of the samples is attributable to the presence of carbonate in the raw clay. The point of zero charge (pHpzc) values of the clays, as determined by potentiometric titrations, were 6.79 and 9.52 for the raw clays, while after purification they were 6.87 and 6.76, respectively. Metal adsorption to the clay surfaces started at pH values below pHpzc, strongly indicating formation of inner-sphere complexes. With contact time of 48 h, complete removal of copper(II) was achieved at pH 8 for all samples. More than 90% of the lead(II) removal was attributed to adsorption while for chromium(III), it was 85%. Adsorption to organic matter and iron oxides, and precipitation of metal hydroxides gave significant contributions to the removal of metal ions in aqueous systems.Key words: Mixed clays, potentiometric titration, heavy metals, pHpzc

Theory of electronic transport through a triple quantum dot in the presence of magnetic field

Theory of electronic transport through a triangular triple quantum dot subject to a perpendicular magnetic field is developed using a tight binding model. We show that magnetic field allows to engineer degeneracies in the triple quantum dot energy spectrum. The degeneracies lead to zero electronic transmission and sharp dips in the current whenever a pair of degenerate states lies between the chemical potential of the two leads. These dips can occur with a periodicity of one flux quantum if only two levels contribute to the current or with half flux quantum if the three levels of the triple dot contribute. The effect of strong bias voltage and different lead-to-dot connections on Aharonov-Bohm oscillations in the conductance is also discussed

How Metal/Insulator Interfaces Enable the Enhancement of the Hydrogen Evolution Reaction Kinetics in Two Ways

Laterally nanostructured surfaces give rise to a new dimension of understanding and improving electrochemical reactions. In this study, we present a peculiar mechanism appearing at a metal/insulator interface, which can significantly enhance the Hydrogen Evolution Reaction (HER) from water reduction by altering the local reaction conditions in two ways: facilitated adsorption of hydrogen on the metal catalyst surface and improved transfer of ions through the double layer. The mechanism is uncovered using electrodes consisting of well-defined nanometer-sized metal arrays (Au, Cu, Pt) embedded in an insulator layer (silicon nitride), varying various parameters of both the electrode (size of the metal patches, catalyst material) and the electrolyte (cationic species, cation concentration, pH). In addition, simulations of the electrochemical double layer are carried out, which support the elaborated mechanism. Knowledge of this mechanism will enable new design principles for novel composite electrocatalytic systems

Computational model for the Oak Ridge National Laboratory (ORNL) Bulk Shielding Reactor (BSR)

A procedure is outlined for formulating an accurate neutronics computational model of the ORNL-BSR. Results to data are presented and discussed

Development of a stochastic computational fluid dynamics approach for offshore wind farms

In this paper, a method for stochastic analysis of an offshore wind farm using computational fluid dynamics (CFD) is proposed. An existing offshore wind farm is modelled using a steady-state CFD solver at several deterministic input ranges and an approximation model is trained on the CFD results. The approximation model is then used in a Monte-Carlo analysis to build joint probability distributions for values of interest within the wind farm. The results are compared with real measurements obtained from the existing wind farm to quantify the accuracy of the predictions. It is shown that this method works well for the relatively simple problem considered in this study and has potential to be used in more complex situations where an existing analytical method is either insufficient or unable to make a good prediction

Differential maturation and subcellular localization of severe acute respiratory syndrome coronavirus surface proteins S, M and E

Post-translational modifications and correct subcellular localization of viral structural proteins are prerequisites for assembly and budding of enveloped viruses. Coronaviruses, like the severe acute respiratory syndrome-associated virus (SARS-CoV), bud from the endoplasmic reticulum-Golgi intermediate compartment. In this study, the subcellular distribution and maturation of SARS-CoV surface proteins S, M and E were analysed by using C-terminally tagged proteins. As early as 30 min post-entry into the endoplasmic reticulum, high-mannosylated S assembles into trimers prior to acquisition of complex N-glycans in the Golgi. Like S, M acquires high-mannose N-glycans that are subsequently modified into complex N-glycans in the Golgi. The N-glycosylation profile and the absence of O-glycosylation on M protein relate SARS-CoV to the previously described group 1 and 3 coronaviruses. Immunofluorescence analysis shows that S is detected in several compartments along the secretory pathway from the endoplasmic reticulum to the plasma membrane while M predominantly localizes in the Golgi, where it accumulates, and in trafficking vesicles. The E protein is not glycosylated. Pulse-chase labelling and confocal microscopy in the presence of protein translation inhibitor cycloheximide revealed that the E protein has a short half-life of 30 min. E protein is found in bright perinuclear patches colocalizing with endoplasmic reticulum markers. In conclusion, SARS-CoV surface proteins S, M and E show differential subcellular localizations when expressed alone suggesting that additional cellular or viral factors might be required for coordinated trafficking to the virus assembly site in the endoplasmic reticulum-Golgi intermediate compartment. © 2005 SGM.postprin

PEG Branched Polymer for Functionalization of Nanomaterials with Ultralong Blood Circulation

Nanomaterials have been actively pursued for biological and medical applications in recent years. Here, we report the synthesis of several new poly(ethylene glycol) grafted branched-polymers for functionalization of various nanomaterials including carbon nanotubes, gold nanoparticles (NP) and gold nanorods (NRs), affording high aqueous solubility and stability for these materials. We synthesize different surfactant polymers based upon poly-(g-glutamic acid) (gPGA) and poly(maleic anhydride-alt-1-octadecene) (PMHC18). We use the abundant free carboxylic acid groups of gPGA for attaching lipophilic species such as pyrene or phospholipid, which bind to nanomaterials via robust physisorption. Additionally, the remaining carboxylic acids on gPGA or the amine-reactive anhydrides of PMHC18 are then PEGylated, providing extended hydrophilic groups, affording polymeric amphiphiles. We show that single-walled carbon nanotubes (SWNTs), Au NPs and NRs functionalized by the polymers exhibit high stability in aqueous solutions at different pHs, at elevated temperatures and in serum. Morever, the polymer-coated SWNTs exhibit remarkably long blood circulation (t1/2 22.1 h) upon intravenous injection into mice, far exceeding the previous record of 5.4 h. The ultra-long blood circulation time suggests greatly delayed clearance of nanomaterials by the reticuloendothelial system (RES) of mice, a highly desired property for in vivo applications of nanomaterials, including imaging and drug delivery

Chiral Transparency

Color transparency is the vanishing of initial and final state interactions, predicted by QCD to occur in high momentum transfer quasielastic nuclear reactions. For specific reactions involving nucleons, the initial and final state interactions are expected to be dominated by exchanges of pions. We argue that these interactions are also suppressed in high momentum transfer nuclear quasielastic reactions; this is ``chiral transparency". We show that studies of the $e ^3He \to e'\Delta^{++} nn$ reaction could reveal the influence of chiral transparency.Comment: 20 pages, three figures available by fax from [email protected]; submitted to Phys. Rev.

Design of Cationic Multi-Walled Carbon Nanotubes as Efficient siRNA Vectors for Lung Cancer Xenograft Eradication

Polo-Like Kinase (PLK1) has been identified as a potential target in cancer gene therapy via chemical or genetic inhibitory approaches. The biomedical applications of chemically functionalized carbon nanotubes (f-CNTs) in cancer therapy have been studied due to their ability to efficiently deliver siRNA intracellularly. In this study, we established the capacity of cationic MWNT-NH3+ to deliver the apoptotic siRNA against PLK1 (siPLK1) in Calu6 tumor xenografts by direct intratumoural injections. A direct comparison with cationic liposomes was made. This study validates the PLK1 gene as a potential target in cancer gene therapy including lung cancer, as demonstrated by the therapeutic efficacy of siPLK1:MWNT-NH3+ complexes and their ability to significantly improve animal survival. Biological analysis of the siPLK1:MWNT-NH3+ treated tumors by RT-PCR and Western blot, in addition to TUNEL staining confirmed the biological functionality of the siRNA intratumourally, suggesting that tumor eradication was due to PLK1 knockdown. Furthermore, by using a fluorescently labelled, non-coding siRNA sequence complexed with MWNT-NH3+, we established for the first time that the improved therapeutic efficacy observed in f-CNT-based siRNA delivery is directly proportional to the enhanced siRNA retention in the solid tumor and subsequent uptake by tumor cells after local administration in vivo