There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

http://sistemas.eel.usp.br/docentes/arquivos/2166002/1234Nb/Geetha-review2009.pdf

Ti based biomaterials, the ultimate choice for orthopaedic implants – A review

Titanium alloys for biomedical applications

OBJECTIVE To establish an indirect immunofluorescent test so as to improve the sensitivity and specificity of examination of antibodies to beta(2)-glycoprotein METHODS Full-length beta(2)GP cDNA was obtained from human hepatocellular cancer cell line HepG2 by RT-PCR and cloned into the mammalian expression vector pEGFP-C1 The recombinant plasmid pEGFP-beta(2)GP was transfected into HEp-2 cells RT-PCR, immunoblotting (IBT), confocal fluorescence microscopy, and indirect immunofluorescent test (IIF) were used to confirm the expression, localization, and antigenicity of fusion protein of green fluorescent protein (GFP) Serum specimens from 19 patients suspected as with secondary antiphospholipid syndrome (APS), 1 patient diagnosed as with primary APS, and 10 normal persons were detected with IIF-IgG-beta(2)GP1, ELISA-IgG-ACL, and ELISA-IgG-beta(2)GP I simultaneously RESULTS (1) The HEp-beta(2)GP I cells thus obtained retained their ability of expression of beta(2)GP-I-GFP for more than ten generations This beta(2)GP-I-GFP showed the antigenicity of beta(2)GP-I with a characteristic feature (2) Seven of the 20 serum specimens from APS patients showed characteristic immunofluorescent pattern No serum specimen from normal persons showed immunofluorescent staining The comparison of results of the three methods showed that the concordance between IIF-IgG-beta(2)GP I and ELISA-IgG-beta(2)GP I was the most perfect (Kappa = 0886) (3) HEp-beta(2)GP I retained the immunofluorescent property of HEp-2 cell CONCLUSION As a new kind of substrate of IIF, beta(2)GP I transfectant can be used to detect anti-beta(2)GP-I antibodies Transfeted HEp-2 cells keep the immunofluorescent property of HEp-2 cells in IFANA test and can be used as substrate for routine IFANA detection

[Expression of fusion proteins in beta(2)GP I gene-transfected HEp-2 cells and its clinical application].

Thermohydrogen processing is a technique in which hydrogen is used as a temporary alloying element in titanium alloys to control the microstructure and improve the final mechanical properties. Thermohydrogen processing can also be used to enhance the processability/fabricability of titanium products including sintering, compaction, machining, and hot working (forging, rolling, superplastic forming, etc.). In the case of near net shapes, such as castings and powder metallurgy products, thermohydrogen processing is the only method available for significant microstructural modifications and consequent enhancement in mechanical properties. This paper reviews the status of the methods and applications of thermohydrogen processing to titanium alloys. Principles of thermohydrogen processing, based on the hydrogen induced alterations of the phase compositions and the kinetics of phase reactions in hydrogenated titanium alloys, are overviewed. Stable and metastable phase diagrams of several titanium alloys...

Hydrogen as a temporary alloying element in titanium alloys: thermohydrogen processing

Microstructures, phases, and phase transformations in Ti-6Al-4V alloy specimens containing 0, 10, 20, and 30 at. pct hydrogen were investigated using optical microscopy (OM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and microhardness testing. Alloying with hydrogen was achieved by holding the specimens in a pure hydrogen atmosphere of different pressures at 780 °C for 24 hours. The phases present in the temperature range of 20 °C to 1000 °C were determined by microstructural characterization of the specimens quenched from different temperatures. Increasing the hydrogen addition from 0 to 30 at. pct lowered the beta-transus temperature of the alloy from 1005 °C to 815 °C, significantly slowed down the kinetics of the beta-to-alpha transformation, and led to formation of an orthorhombic martensite instead of the hexagonal martensite found in quenched specimens containing 0 pct H. A hydride phase was detected in specimens containing 20 and 30 at. pct hydrogen. The time-temperature-transformation (TTT) diagrams for beta-phase decomposition were determined at different hydrogen concentrations. The nose temperature for the beginning of the transformation decreased from 725 °C to 580 °C, and the nose time increased from 12 seconds to 42 minutes when the hydrogen concentration was increased from 0 to 30 at. pct.

Phase transformations in Ti-6Al-4V-xH alloys

The kinetics of martensite decomposition in hydrogenated Ti–6Al–4V alloy samples was studied. To produce the martensite structure, the samples containing 0, 10, 20 and 30 at.% H were annealed in the β phase field and water quenched. Optical microscopy, transmission electron microscopy, X-ray diffraction analysis and microhardness testing techniques were utilized to study the phases and phase transformations and to obtain time–temperature-transformation (TTT) diagrams for the martensite decomposition. The martensite structure of the hydrogenated samples consisted of a mixture of hexagonal close packed (hcp) α′ and orthorhombic α″ martensites. The amount of the orthorhombic α″ martensite increased from 0 to ∼80 vol.% when the hydrogen content of the alloy was increased from 0 to 30 at.%. During aging at temperatures below the β transus temperature and above the martensite start temperature (Ms), the martensite structure transformed into a mixture of hexagonal close-packed (hcp) α and body-centered-cubic (bcc) β phases. At aging temperatures below the Ms, on the other hand, the martensite first transformed partially into a metastable β phase, and then equilibrium α and β phases were formed. On quenching after aging, in both these cases, the β transformed into martensite plus residual β, with the amount of the latter increasing with an increase in the hydrogen concentration and a decrease in the aging temperature. Hydrogen additions lowered the Ms of the Ti–6Al–4V alloy, and for samples containing 30 at.% H the Ms was below 500 °C. In the alloys containing 20 and 30 at.% H, a hydride phase was also detected. Complete decomposition of the martensite structure in the samples containing 30 at.% H and aged at 530 °C resulted in a fine and homogenous equiaxed microstructure consisting of a mixture of α, β and hydride phases. The nose temperature for the start of the martensite decomposition decreased from 800 to 625 °C when the hydrogen concentration increased from 0 to 30 at.%. The nose time for the start of the martensite decomposition increased from 6 s to 10 min when the hydrogen concentration increased from 0 to 10 at.% and did not change significantly with further increase in the hydrogen concentration.

Kinetics of martensite decomposition in Ti /6Al /4V /xH alloys

This investigation has shown that the strength of low-modulus metastable beta-titanium alloys can be increased by increasing their oxygen content and/or aging. Yield strength as high as 1,288 MPa along with reasonable ductility was obtained by aging Ti-35Nb-7Zr-5Ta-0.7O at 482°C for 8 h. Strengthening of these alloys is discussed in terms of ω-and α-phase precipitates.

/pdf/high-strength-metastable-beta-titanium-alloys-for-biomedical-2by6f3u610.pdf

Javaid Qazi

Papers

Titanium alloys for biomedical applications

Hydrogen as a temporary alloying element in titanium alloys: thermohydrogen processing

Phase transformations in Ti-6Al-4V-xH alloys

Kinetics of martensite decomposition in Ti /6Al /4V /xH alloys

High-strength metastable beta-titanium alloys for biomedical applications