다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Physical, chemical and electrochemical properties of pure and doped ceria

Plasma-surface modification (PSM) is an effective and economical surface treatment technique for many materials and of growing interests in biomedical engineering This article reviews the various common plasma techniques and experimental methods as applied to biomedical materials research, such as plasma sputtering and etching, plasma implantation, plasma deposition, plasma polymerization, laser plasma deposition, plasma spraying, and so on The unique advantage of plasma modification is that the surface properties and biocompatibility can be enhanced selectively while the bulk attributes of the materials remain unchanged Existing materials can, thus, be used and needs for new classes of materials may be obviated thereby shortening the time to develop novel and better biomedical devices Recent work has spurred a number of very interesting applications in the biomedical field This review article concentrates upon the current status of these techniques, new applications, and achievements pertaining to biomedical materials research Examples described include hard tissue replacements, blood contacting prostheses, ophthalmic devices, and other products

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Plasma-surface modification of biomaterials

DNA sequencing with chain terminating inhibitors

: High purity submicron powders were sintered in a single mode cylindrical cavity applicator CMPR-250 operating at 2.45 GHz in the TMO12 mode. The alumina powders could be sintered from an initial green density of 60 % to a final density close to theoretical. Rapid heating rates at very low power level were achieved. Uniform microstructure and relatively small grain size in the microwave sintered alumina were evident. The initial results of this study demonstrate the potential applicability of a single mode applicator for sintering alumina ceramics.

Microwave Sintering of Alumina Ceramics in a Single Mode Applicator

This paper describes the method of producing plasma sprayed coatings of hydroxy apatite (HA) on metallic substrates of Ti-6Al-4V. Hydroxy apatite is a material which has similar composition to that of the mineral phase of the human bone. Poor mechanical properties however inhibits its use in the load bearing applications. The powders prepared in our laboratory are sprayed using a plasma spray torch operating in ambient. The deposited coatings are charaterized by X-ray diffraction and found to retain HA in the coatings as per requirements.

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Plasma sprayed hydroxy apatite coatings

A single wire-arc-plasma spray torch has been used to develop metal coatings on carbon and alumina substrates under argon atmosphere for various applications. Nickel coatings of around 1 mm thickness have been deposited on selected area (60 mm × 200 mm on each side) of large size carbon blocks by intermittent arc spraying and cooling to reduce thermal stresses and possibility of coating de-lamination from the base substrate. The same process is also used for depositing about 3 mm thick nickel metal coatings (8 mm dia. × 40 mm long) on alumina tubes for developing electrical feed throughs. The nickel coated alumina tubes were tested for the vacuum compatibility of the coated material with the base tube. The coated assemblies could withstand vacuum of the order of 1 × 10− 6 Torr and the leak rate was found to be less than 1 × 10− 9 Std. cc/s for Helium gas, indicating excellent bonding of the coated metal with alumina ceramics and no connected open porosity in the coatings. X-ray diffraction studies were conducted for identifying the phases and the optical microscope with image analysis technique was used for studying the microstructure and porosity in the coatings.

Development and characterization of single wire-arc-plasma sprayed coatings of nickel on carbon blocks and alumina tube substrates

Diamond like carbon (DLC) coatings were deposited on silicon substrates by microwave electron cyclotron resonance (ECR) plasma CVD process using plasma of Ar and CH 4 gases under the influence of negative d.c. self bias generated on the substrates by application of RF (13·56 MHz) power. The negative bias voltage was varied from −60 V to −150 V during deposition of DLC films on Si substrate. Detailed X-ray reflectivity (XRR) study was carried out to find out film properties like surface roughness, thickness and density of the films as a function of variation of negative bias voltage. The study shows that the DLC films constituted of composite layer i.e. the upper sub surface layer followed by denser bottom layer representing the bulk of the film. The upper layer is relatively thinner as compared to the bottom layer. The XRR study was an attempt to substantiate the sub-plantation model for DLC film growth.

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X-ray reflectivity study of bias graded diamond like carbon film synthesized by ECR plasma

Thermal, optical and electrical properties of the Agx(Ge28Sb12Se60)100x system (for x = 0 to 20) are systematically studied using various characterization techniques. In the present study, we have shown the reproducibility of the current results with the previously published literature and several novel results are also presented. The impedance data for the understanding of electrical properties of the materials has been analyzed using the random-walk (RW) model. We observed that, Ag playing two different concentration dependent roles i.e. above and below the 5% of Ag concentration, which is confirmed by the Raman analysis. The anomalous behaviors of electrical conductivity, optical and thermal properties with increasing Ag concentrations are explained by the role of Ag in the structural modification. We compared the diffusion coefficient (D), obtained from the RW model analysis with the experimental data(obtained from tracer diffusion) and found diffusion coefficient (D), obtained from the RW model are in good agreement corresponded with the experimental values. We also found a major change in conductivity of insulating Ge28Sb12Se60 (~ 10-14 S·cm-1) to a fast ionic conductor for Ag15(Ge28Sb12Se60)85 (~ 10-6 S·cm-1), i.e., a nine orders of magnitude. We demonstrated that the random-walk model can replacea time consuming and expensive tracer diffusion method for the determination of D. The present article helps to understand the ion conduction mechanism in disordered / amorphous materials.

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Deepak Patil

Papers

Microwave Sintering of Alumina Ceramics in a Single Mode Applicator

Plasma sprayed hydroxy apatite coatings

Development and characterization of single wire-arc-plasma sprayed coatings of nickel on carbon blocks and alumina tube substrates

X-ray reflectivity study of bias graded diamond like carbon film synthesized by ECR plasma

Influence of Ag Doping on Physico-Chemical Properties of the Ge28Sb12Se60 Chalcogenide Glassy Matrix