Microchemical composition and cell dimensions of mullites from refractory-grade South American bauxites

Two different types of mullite could be determined in differently coloured fragments of South American bauxites: − Mullites, occuring in light bauxite fragments with low impurity contents (Σ wt % (Fe₂O₃ + TiO₂) 2.5), and cell dimensions close to that of 3/2 mullite, the b parameter being slightly shorter. − Mullites, occurring in grey to dark grey, and in brown bauxite fragments, with high impurity contents (Σ wt % (Fe₂O₃ + TiO₂) 4,0) and a and c cell dimensions close to those of 2/1 mullite. The b constant of these mullites is slightly expanded with respect to impurity free mullites. Increasing impurity contents in mullite are linearly correlated with a b expansion. The expansion was structurally explained with a substitution of Al³⁺ by Fe³⁺ and Ti⁴⁺ at octahedral lattice sites, which causes stretching of the AlO₆ octahedra along to the elastic Al₁---D_D bond in mullites which is 30° to either side of b. The substitution-produced expansion is superimposed by an expansion due to the change of the structural state of mullite from the 3/2 to the 2/1 type. The greatest variation in any cell parameter with the change of the structural state is the a constant.     

A stochastic local search algorithm for constrained continuous global optimization

This paper presents a new stochastic local search algorithm known as feasible–infeasible search procedure (FISP) for constrained continuous global optimization. The proposed procedure uses metaheuristic strategies for combinatorial optimization as well as combined strategies for exploring continuous spaces, which are applied to an efficient process in increasingly refined neighborhoods of current points. We show effectiveness and efficiency of the proposed procedure on a standard set of 13 well‐known test problems. Furthermore, we compare the performance of FISP with SNOPT (sparse nonlinear optimizer) and with few successful existing stochastic algorithms on the same set of test problems.     

In situ laser heating and radial synchrotron x-ray diffraction in a diamond anvil cell

We report a first combination of diamond anvil cell radial x-ray diffraction with in situ laser heating. The laser-heating setup of ALS beamline 12.2.2 was modified to allow one-sided heating of a sample in a diamond anvil cell with an 80 W yttrium lithium fluoride laser while probing the sample with radial x-ray diffraction. The diamond anvil cell is placed with its compressional axis vertical, and perpendicular to the beam. The laser beam is focused onto the sample from the top while the sample is probed with hard x-rays through an x-ray transparent boron-epoxy gasket. The temperature response of preferred orientation of (Fe,Mg)O is probed as a test experiment. Recrystallization was observed above 1500 K, accompanied by a decrease in stress.     

Brazilian scientific production in science education

In the present study we analyzed the Brazilian scientific production in the area of science education. The study was structured on: data by research groups registered in Conselho Nacional de Desenvolvimento Científico e Tecnológico; analysis of the post-graduate strictu sensu programs; analysis of theses and dissertations linked to post-graduate programs; and papers in international databases. Our research was conducted strictly via world wide web, from December 2009 to September 2010. It was found that both number of research groups, researchers, post-graduate programs, thesis, dissertations and papers presented a marked increase, especially in the last decade (from 2000 onwards). The major research centers were found to be located in public universities from Brazilian southeast and south regions. However, it was observed a tendency of decentralization, due to a recent investment in new public universities in the other Brazilian regions. So, this study sought to present an overview of the scientific production about science education and we expect that this information can help to expand the vision about the development of this research area in Brazil.     

Pt-Ru-TiO2 photoelectrocatalysts for methanol oxidation

Novel photoelectrocatalysts composed of PtRuTiO₂/C are prepared by the polymeric precursor method and are characterized by scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy and cyclic voltammetry. The onset potential for methanol oxidation is similar (0.3 V vs. RHE) for all of the photoelectrocatalyst layers investigated, although the peak current density is dependent on the layer composition. Irradiation of UV light on the photoelectrocatalyst surfaces enhances the chronoamperometric responses up to 18%, which clearly demonstrates a synergistic effect between the photo- and electrocatalysts. The comparison between all the layers prepared indicates that there is an appropriate ratio of metallic nanoparticles and TiO₂ to obtain the best performance of these photoelectroactive layers. These results demonstrate that methanol oxidation is achieved by electro- and photocatalysis using a simple and affordable method. This procedure can be conveniently exploited to enhance the response of direct methanol fuel cell electrodes.     

Harnessing the base-pushout effect for ESD protection in bipolar and BiCMOS technologies

The impact of the base-pushout or Kirk-effect on the ESD characteristic of modern radio frequency (RF) NPN transistors is investigated. Due to the RF NPNs selectively implanted collector the onset of base-pushout is shifted to ESD relevant current levels, expressing itself in a characteristically high-ohmic breakdown mode after first snapback and a non-thermal second snapback, the so-called current mode snapback. Concepts to exploit the base-pushout effect for improved RF protection schemes are presented.     

Endotoxins affect diverse biological activity of chitosans in matters of hemocompatibility and cytocompatibility

Chitosan is used in several pharmaceutical and medical applications, owing to its good cytocompatibility and hemocompatibility. However, there are conflicting reports regarding the biological activities of chitosan with some studies reporting anti-inflammatory properties while others report pro-inflammatory properties. In this regards we analyzed the endotoxin content in five different chitosans and examined these chitosans with their different deacetylation degrees for their hemocompatibility and cytocompatibility. Therefore, we incubated primary human endothelial cells or whole blood with different chitosan concentrations and studied the protein and mRNA expression of different inflammatory markers or cytokines. Our data indicate a correlation of the endotoxin content and cytokine up-regulation in whole blood for Poly-Morpho-Nuclear (PMN)-Elastase, soluble terminal complement complex SC5b-9, complement component C5/C5a, granulocyte colony-stimulating factor, Interleukin-8 (IL), IL-10, IL-13, IL-17E, Il-32α and monocyte chemotactic protein-1. In contrast, the incubation of low endotoxin containing chitosans with primary endothelial cells resulted in increased expression of E-selectin, intercellular adhesion molecule-1, vascular cell adhesion protein-1, IL-1β, IL-6 and IL-8 in endothelial cells. We suggest that the endotoxin content in chitosan plays a major role in the biological activity of chitosan. Therefore, we strongly recommend analysis of the endotoxin concentration in chitosan, before further determining if it has pro- or anti-inflammatory properties or if it is applicable for pharmaceutical and medical fields.     

Corrosion of experimental magnesium alloys in blood and PBS: A gravimetric and microscopic evaluation

Corrosion tests for medical materials are often performed in simulated body fluids (SBF). When SBF are used for corrosion measurement, the open question is, how well they match the conditions in the human body. The aim of the study was to compare the corrosion behaviour of different experimental magnesium alloys in human whole blood and PBS^minus (phosphate buffered saline w/o Ca and Mg) as a simulated body fluid by gravimetric weight measurements and microscopic evaluation. Eight different experimental magnesium alloys, containing neither Mn nor other additives, were manufactured. With these alloys, a static immersion test in PBS^minus and a dynamic test using the Chandler-loop model with human whole blood over 6 h were performed. During the static immersion test, the samples were weighed every hour. During the dynamic test, the specimens were weighed before and after the 6 h incubation period in the Chandler-loop. From both tests, the total mass change was calculated for each alloy and the values were compared. Additionally, microscopic pictures from the samples were taken at the end of the test period. All alloys showed different corrosion behaviour in both tests, especially the alloys with high aluminium content, MgAl9 and MgAl9Zn1. Generally, alloys in PBS showed a weight gain due to generation of a microscopically visible corrosion layer, while in the blood test system a more or less distinct weight loss was observed. When alloys are ranked according to corrosion susceptibility, the results differ also between the test systems. The MgAl9 alloy, showing the most pronounced corrosion in PBS, was one of the least corroding alloys under simulated in vivo conditions in blood. Thus, the ranking concerning clinical suitability of the magnesium alloys tested in this study is different, depending on the used electrolyte and the kind of method. For a possible clinical use, the alloy MgAl9Zn1 might be preferable for further investigations.     

Superparamagnetic Twist‐Type Actuators with Shape‐Independent Magnetic Properties and Surface Functionalization for Advanced Biomedical Applications

Directed nanoparticle self‐organization and two‐photon polymerization are combined to enable three‐dimensional soft‐magnetic microactuators with complex shapes and shape‐independent magnetic properties. Based on the proposed approach, single and double twist‐type swimming microrobots with programmed magnetic anisotropy are demonstrated, and their swimming properties in DI‐water are characterized. The fabricated devices are actuated using weak rotating magnetic fields and are capable of performing wobble‐free corkscrew propulsion. Single twist‐type actuators possess an increase in surface area in excess of 150% over helical actuators with similar feature size without compromising the forward velocity of over one body length per second. A generic and facile combination of glycine grafting and subsequent protein immobilization exploits the actuator's increased surface area, providing for a swimming microrobotic platform with enhanced load capacity desirable for future biomedical applications. Successful surface modification is confirmed by FITC fluorescence.