Iron-Magnesium Alloy Bioabsorbable Blood Stent

Bioabsorbable materials are fairly new and proper alloys for implantation in the body have not yet been established. There are a few polymers that have showed promise, but they do not provide the proper mechanical support that metal does. These materials would be used to create devices such as blood stents and orthopedic screws. Investigation into the properties of different alloys can help to establish a material that can be used for implanted devices that are only needed for a limited amount of time. In order to investigate these alloys many different experiments will to be run to test the different properties. This includes corrosion tests, and cytotoxicity tests. Corrosion will be tested by using potentiondynamic polarization tests to accelerate the rate of corrosion. Cytotoxicity tests will be performed by incubating the cells with the material for a certain period of time to establish that the material does not cause cell death. The corrosion test showed that the alloy that was cold worked had a reduced corrosion rate as compared to the samples that were quenched. The cytotoxicity tests are currently underway and it is hoped that they will show no decrease in cell death when compared to a control. Cold working and changing the microstructure appears to reduce the corrosion rate. More investigation into what properties influence the corrosion rate of materials is needed. The cytotoxicity will hopefully increase cell growth meaning that when implanted it will encourage recovery and reconstruction of the damaged area

Silver Oxide-Graphene Sensor for Hydrogen Peroxide

A nonenzymatic, amperometric sensor for Hydrogen Peroxide (H2O2) was designed by drop coating glassy carbon electrodes (GCEs) with Silver Oxide (Ag2O). Combining Ag2O with Graphene Oxide and a polymer, PEDOT, was also attempted in order to increase stability and electrochemical properties. Using metal oxides along with Graphene Oxide for sensors has been done quite a bit, but Ag2O itself has not been research extensively. So, in order to produce the best H2O2 sensor, the configuration of all components had to be optimized. Three different Ag2O particle shapes (Hexapod, Octahedra, and Cube) were synthesized and tested on the GCEs. The different shapes caused the particles to have different surface properties, so each sample performed differently. The coatings on the electrodes were characterized using UV–Vis spectroscopy, scanning electron microscopy, and x-ray diffraction. The electrochemical properties and sensing abilities of the electrodes were tested using cyclic voltammetry, electrochemical impedance spectroscopy, zeta potential, calibration curves, DC current response, and selectivity tests. The Ag2O by itself showed the best electrochemical properties and response to H2O2 as compared to the Ag2O with Graphene Oxide and PEDOT. Of the three Ag2O particle shapes, the Hexapod showed the best electrochemical properties and sensitivity, but the Cube showed the best stability. This sensor will push the limits of previous designs and introduce new uses of Ag2O. It will also provide a foundation for future studies of particle shapes in sensors

Case Study of a Water Tank Behaviour on an Improved Collapsible Soil

The geotechnical report performed for the design stage of a water tank revealed a soil profile consisting in a thick layer of collapsible/loessial soil. The paper firstly presents the complex characterization of the natural ground conditions before and after the soil cushion performance, during the water filling tests of the tank. Specific charts are presented to emphasize the physical and mechanical parameter differences of the natural and improved ground by the soil cushion. The prediction of the supplementary settlement profile on the construction site of the water tank has been performed due to a significant water leakage from the tank during the filling tests, and thus endangering the tank stability and serviceability. Charts presenting the soil-tank interaction during service are included together with settlement diagrams related to potential water leakage from the tank. The paper presents in the second part the stress and strain states that have been comparatively analyzed for various moistening hypotheses with different risk level, according to the settlement increase based on the up going of the moistening front

Post-growth annealing of GaMnAs under As capping - an alternative way to increase Tc

We demonstrate that in situ post-growth annealing of GaMnAs layers under As capping is adequate for achieving high Curie temperatures (Tc) in a similar way as ex situ annealing in air or in N2 atmosphere practiced earlier.Comment: 13 pages, 4 figure

Geometric construction of D-branes in WZW models

The geometric description of D-branes in WZW models is pushed forward. Our starting point is a gluing condition\, $J_{+}=FJ_-$ that matches the model's chiral currents at the worldsheet boundary through a linear map $F$ acting on the WZW Lie algebra. The equivalence of boundary and gluing conditions of this type is studied in detail. The analysis involves a thorough discussion of Frobenius integrability, shows that $F$ must be an isometry, and applies to both metrically degenerate and nondegenerate D-branes. The isometry $F$ need not be a Lie algebra automorphism nor constantly defined over the brane. This approach, when applied to isometries of the form $F=R$ with $R$ a constant Lie algebra automorphism, validates metrically degenerate $R$-twined conjugacy classes as D-branes. It also shows that no D-branes exist in semisimple WZW models for constant\, $F=-R$.Comment: 23 pages, discussion of limitations of the gluing condition approach adde

D-branes in the WZW model

It is stated in the literature that D-branes in the WZW-model associated with the gluing condition J = - \bar{J} along the boundary correspond to branes filling out the whole group volume. We show instead that the end-points of open strings are rather bound to stay on `integer' conjugacy classes. In the case of SU(2) level k WZW model we obtain k-1 two dimensional Euclidean D-branes and two D particles sitting at the points e and -e.Comment: 2 pages, LaTe

Self-compacting concrete: a comparison between the workability properties, density, porosity and mechanical properties

This paper highlights some connections between the workability properties of self-compacting concrete and the density of the concrete mass and between mechanical properties of compression strength and porosity of concrete samples investigated at 28 days of free curing. Also are presented properties of raw materials used in this study

Polymer concrete, correlations between properties

Has been adopted new method for determining the fluidity concrete with polymers. In the research were used three types of polymer: epoxy resin - at a rate of 10%; polyurethane - at a rate of 10% methylcellulose - at a rate of 0.6%. The experimental results showed that the same water/cement material behaves differently depending on the polymer used. Moreover, epoxy resin gives significant improvements in workability and strength. It was found that the polymer influence positively the mechanical properties and concrete workability. Were performed mycroscopical investigations on reinforced concrete structures

Properties of polymer modified concrete in fresh and hardened state

It was carried out a study on the properties of polymer modified concrete (PCM) in fresh and hardened state. It was used three types of polymers: epoxy resins, polyurethane and methylcellulose in different percentages and different water cement ratio. The main objectives was to improve workability and rheological behavior of these mixtures in fresh state and mechanical strength tests on hard concrete. Has been investigated the polymer influence on compression strength and flexural strength and analyzing the time evolution of these strengths and participation of polymer in the microstructure formation.This work was partly financed by the European Social Fund through the POSDRU/CPP107/DMI1.5/S/77497 Program for PhD. Studen

Special self-compacting concretes

The paper presents experimental investigations on the special self-compacting concretes, in different compositions. Also, in this paper highlights the influence of super plasticizers additives use upon the mechanical, structural and chemical properties of selfcompacting concretes improving. During these laboratory investigations were made samples of self-compacting concrete with diferente compositions, on which were performed workability and mechanical tests (compressive strength), as well as, structural attempts (microscopy, density, porosity tests)