23 research outputs found
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PIXE pollution studies across Europe
We collected vegetation and soil samples from various locations along a route covering Eastern and Western Europe. We measured the level of elemental pollution in different places uniformly spread across the continent to determine which of them may have common sources. To achieve these objectives, samples were collected along the main roads from Romania to Portugal and analyzed using in-air PEE (Particle-Induced X-ray Emission)
Enhanced biocompatibility of GPC by MeV ion bombardment
2005 MRS Spring Meeting -- 28 March 2005 through 1 April 2005 -- San Francisco, CA -- 69749Glassy Polymeric Carbon (GPC) is completely biocompatible and is widely used as a material for artificial heart valves and in other biomedical applications. Although it is ideally suited for fluid flow in the blood stream, collagenous tissue that normally forms around the moving parts of a GPC heart valve sometimes loses adhesion and creates embolisms downstream. We have shown that moderate fluence of MeV ions, especially oxygen ions, increases the surface roughness of GPC on a scale appropriate for enhancing tissue adhesion. Silver ion implantation is shown to inhibit cell growth on GPC. Ion bombardment also increases the surface hardness of GPC, already an extremely hard material. In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that MeV ion bombardment can favorably influence the surface of GPC for biomedical applications. © 2005 Materials Research Society
Studying the destruction of various fluoropolymers caused by y-irradiation and MeV protons
While fluoropolymers are normally used as anti-adherent coating, they are intensely investigated for potential use in various radiation dosimeter applications as well as space technology. In order to understand the discrepancy between high chemical and thermal stability and low radiation stability of various fluoropolymers, we are bombarding them with 1 MeV protons to fluences up to 2*10^15 protons/cm^2 as well as subjected some of them to у-irradiation by dose of 10 kGy. During bombardment we are monitoring the emission of chemical species with a residual gas analyzer (RGA). у - irradiated samples were tested by Radio thermoluminescence (RTL) method. The results we present here are a good indicator that material damage happens much earlier than 2*10^15 protons/cm^2 and that further work should be addressed at much smaller exposures. RTL also can be used at small doses of Irradiation (10-30 kGy). The thermomechanical curve (TMC) of radiation-free polyvlnyledenefluoride (PVDF) is characteristic for topologlcally di-block amorphous polymer of quasi-crossing structure. In the temperature range of from 173 К up to 228 К polymer is vitrified. The vitrification temperature of PVDF is 228 K. All molecular-relaxation and quantitative characteristics of PVDF were determined before and after its Irradiation by protons. Protons caused significant changes in PVDF. From di-block amorphous it transformed in to amorphous-crystalline structure. An appreciable influence of dose at proton irradiation of polymer was revealed both on topological level and on molecular-relaxation one
Studying the destruction of various fluoropolymers caused by y-irradiation and MeV protons
While fluoropolymers are normally used as anti-adherent coating, they are intensely investigated for potential use in various radiation dosimeter applications as well as space technology. In order to understand the discrepancy between high chemical and thermal stability and low radiation stability of various fluoropolymers, we are bombarding them with 1 MeV protons to fluences up to 2*10^15 protons/cm^2 as well as subjected some of them to у-irradiation by dose of 10 kGy. During bombardment we are monitoring the emission of chemical species with a residual gas analyzer (RGA). у - irradiated samples were tested by Radio thermoluminescence (RTL) method. The results we present here are a good indicator that material damage happens much earlier than 2*10^15 protons/cm^2 and that further work should be addressed at much smaller exposures. RTL also can be used at small doses of Irradiation (10-30 kGy). The thermomechanical curve (TMC) of radiation-free polyvlnyledenefluoride (PVDF) is characteristic for topologlcally di-block amorphous polymer of quasi-crossing structure. In the temperature range of from 173 К up to 228 К polymer is vitrified. The vitrification temperature of PVDF is 228 K. All molecular-relaxation and quantitative characteristics of PVDF were determined before and after its Irradiation by protons. Protons caused significant changes in PVDF. From di-block amorphous it transformed in to amorphous-crystalline structure. An appreciable influence of dose at proton irradiation of polymer was revealed both on topological level and on molecular-relaxation one
Enhanced biocompatibility of GPC by silver ion implantation
2005 MRS Fall Meeting -- 28 November 2005 through 2 December 2005 -- Boston, MA -- 69769Biocompatible Glassy Polymeric Carbon (GPC) is used for artificial heart valves and in other biomedical applications. Although it is ideally suited for implants in the blood stream, tissue that normally forms around the moving parts of a GPC heart valve sometimes loses adhesion and creates embolisms downstream. Here we compare silver ion implantation and silver deposition, each of which strongly inhibits cell attachment on GPC. Inhibition of cell adhesion is a desirable improvement to current GPC cardiac implants. In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that traces of silver can favorably influence the surface of GPC for biomedical applications. © 2006 Materials Research Society
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KeV Ion Beam Induced Surface Modification of SiC Hydrogen Sensor
Silicon carbide, a wide-bandgap semiconductor, is currently used to fabricate an efficient high temperature hydrogen sensor. When a palladium coating is applied on the exposed surface of silicon carbide, the chemical reaction between palladium and hydrogen produces a detectable change in the surface chemical potential. Rather than applying a palladium film, we have implanted palladium ions into the silicon face of 6H, n-type Sic samples. The implantation energies and fluences, as well as the results obtained by monitoring the current through the sample in the presence of hydrogen are included in this paper