Hydrogen absorption properties of carbon supported Pd–Ni nanoalloys

Carbon supported Pd–Ni nanoalloys with well controlled composition and particle size distribution were synthesized by incipient wetness impregnation method. The Pd-rich nanoalloys (10 and 20 Ni at.%) form a hydride phase at atmospheric pressure and ambient temperature whereas, no hydride formation is observed for higher Ni content (30 at%), as determined by Pressure-Composition-Isotherms and in situ X-ray diffraction. Significant thermodynamic changes for hydride forming Pd–Ni nanoalloys are noticed as compared to pure Pd, in agreement with the bulk counterparts: the enthalpy of the hydride formation of Pd–Ni nanoalloys decreases by increasing the Ni content. These thermodynamic changes are not related to downsizing of particles but rather to an alloying effect. The solely effects of particle downsizing are the sloping and the shortening of the plateau observed in the PCI curves.     

Development of piezoelectric actuators for active X-ray optics

Piezoelectric actuators are widely utilised in adaptive optics to enable mirrors having an actively controlled reflective surface for the purpose of the wavefront correction by reducing the effects of rapidly changing optical distortion. Two new prototype adaptive X-ray optical systems are under development with the aim of approaching the fundamental diffraction limit. One proposed technology is microstructured optical arrays (MOAs) involving two or four piezoelectric strips bonded to a silicon wafer to produce a micro-focused X-ray source for biological applications, and which uses grazing incidence reflection through consecutive aligned arrays of channels obtained using deep silicon etching. Another technology is large scale optics which uses a thin shell mirror bonded with 20?C40 piezoelectric actuators for the next generation of X-ray telescopes with an aim to achieve a resolution greater than that currently available by Chandra (0.5"). PZT-based piezoelectric actuators are being developed in this programme according to the design and implementation of the proposed mirror and array structures. Viscous plastic processing is chosen for the preparation of the materials system, which is subsequently formed and shaped into the suitable configurations. Precise controls on the thickness, surface finish and the curvature are the key factors to delivering satisfactory actuators. Unimorph type piezoelectric actuators have been proposed for the applications and results are presented regarding the fabrication and characterisation of such piezo-actuators, as well as the related design concepts and comparison to modelling work.     

Surface properties and blood compatibility of some aliphatic/aromatic polyimide blends

Two binary polyimide (PI) blends having a common monomer, diamine and dianhydride, were prepared. The first system was composed of PIs obtained from an alicyclic and flexible dianhydride, namely 5‐(2,5‐dioxotetrahydrofurfuryl)‐3‐methyl‐3‐cyclohexene‐1,2‐dicarboxylic acid anhydride (DOCDA) and two aromatic diamines, 4,4′‐oxydianiline (ODA) and p‐phenylenediamine (PPD), respectively. In the second system, ODA was combined with DOCDA and (hexafluoroisopropyldiene)diphtalic dianhydride (6FDA). Incorporation of aliphatic and asymmetric DOCDA moieties, hexafluoropropyldiene groups and ether linkages in the molecular structure of PI blends, poly(DOCDA/PPD)/poly(DOCDA‐ODA) and poly(6FDA‐ODA)/poly(DOCDA‐ODA) influenced the surface tension parameters, surface and interfacial free energy, and the work of spreading of water, maintaining the surface hydrophobic characteristics of both systems. In addition, it has been found out that surface hydrophobicity and surface roughness are properties that can be correlated with the red blood cells and platelets compatibility. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

An insight on the effect of rubbing textile fiber on morphology of some semi-alicyclic polyimides for liquid crystal orientation

Two semi-alicyclic PIs were prepared from bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BOCA) and the aromatic diamines: 4,4′-oxydianiline (ODA) or 4-(4-{[4-(4-aminophenoxy)phenyl]sulfonyl}phenoxy)aniline (pBAPS). The obtained films are transparent in visible domain, having a cut-off wavelength of 294 nm for poly(BOCA–ODA) and 264 nm for poly(BOCA– p BAPS), respectively. Atomic force microscopy images indicate a better surface organization after rubbing with cotton velvet (V_C) comparatively with cellulose diacetate (V_CD). Contact angle measurements reveal a slight increase of hydrophobicity after patterning as a result of dipolar forces intensification and geometrical constraints of the macromolecular chains. The alignment properties of both PIs, tested with N-(4-methoxybenzylidene)-4-butylaniline, are more obviously for processing with V_C. Also, the contrast between the dark and bright states is higher for poly(BOCA– p BAPS)/V_C comparatively with poly(BOCA–ODA)/V_CD, since its larger surface malleability generates deeper microgrooves.     

In vitro assessment of tooth color changes due to orthodontic treatment using knowledge discovery methods

Esthetic dentistry imposes several demands on the artistic abilities of the dentist, and knowledge of the underlying scientific principles of tooth color is considered to be essential by Sikri. The supervised classification methods, such as the artificial neural networks, the support vector machines, and also the Bayesian classifier, and the feature selection methods, such as decision trees, genetic algorithms and neural networks, as well as independent component analysis combined with least square support vector machines, were applied successfully in the medical field but were less implemented in the dental analysis domain. This study was conducted on extracted premolars from people who required orthodontic treatment. Data gathering was done using spectrophotometric recordings of tooth color parameters before and after accelerated bleaching, staining, and control procedures on extracted teeth on which was simulated orthodontic treatment. Comparison between data mining techniques and classical statistical interpretation of data was done. The results demonstrated the usefulness of these innovating data assessment techniques in the dental field.     

Surface topography effect on fibroblasts population on epiclon-based polyimide films

A polyimide based on alicyclic units, such as epiclon (5-(2,5-dioxotetrahydrofurfuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride), was investigated from the point of view of its surface features to check their suitability for cell culture applications. Atomic force microscopy data revealed fractal and isotropic surfaces with nanoscale roughness and peaks placed at much smaller distances comparing to the cell size scale, favoring a good compatibility of the synthesized material with the biological medium, particularly after plasma treatment. Surface tension properties were determined in order to evaluate the interactions at the bio-interface affecting the adherence behavior of cell-binding proteins to the sample surface. In vitro experiments regarding the cytocompatibility and population tendency reveal that polyimide allows cells to adhere and to proliferate onto the surface. These tests indicate that the studied epiclon-based polyimide is not cytotoxic and can be recommended as good candidate for cell culture substrate in tissue engineering, especially after plasma treatment.     

Electrochemical and Antibacterial Performance of CoCrMo Alloy Coated with Hydroxyapatite or Silver Nanoparticles

This paper presents a comparative study of antimicrobial and electrochemical performance of CoCrMo alloy surface treated with hydroxyapatite coating or silver nanoparticles (nAg) in the presence/absence of albumin addition. Nanoparticles dimension was quantified using dynamic light scattering. Antibacterial activity was evaluated by a spread plate method, while electrochemical characterization of CoCrMo samples coated and uncoated was studied by open circuit potential and cyclic polarization experiments. Furthermore, all surface coatings characterization was investigated by transmission electron microscopy, scanning electron spectroscopy, and energy-dispersive x-ray spectroscopy. The highest corrosion rate in simulated body solution (SBF) is for untreated CoCrMo alloy, and the lowest value is for CoCrMo alloy treated with nAg after addition in SBF of 80 g/L albumin. Only the surface treated with nAg has antibacterial effect.     

Multi-objective energy aware multiprocessor scheduling using bat intelligence

In this paper, a new heuristic called bat intelligence (BI) is introduced for solving energy aware multiprocessor scheduling problems. Bat intelligence is a novel optimization method that models prey hunting behaviors of bats. Bat intelligence and genetic algorithm (GA) are used to solve single-objective multiprocessor scheduling problem using, makespan, tardiness, and energy consumption as objective functions. Bat intelligence shows considerable improvement in terms of solution quality when compared with GA. Different combinations of these objectives are used to solve bi-objective multiprocessor scheduling problems, (makespan vs. energy, and also tardiness vs. energy). Tri-objective multiprocessor scheduling problem is also presented at the end. To generate desirable efficient alternatives, a Normalized Weighted Additive Utility Function is used. Simulation shows that BI identifies a set of efficient solutions that correspond to the assigned weights. The computational simulation also shows conflicting relationships between makespan and energy, and also between tardiness and energy.