摘要:

AbstractIncidental polarized light microscopy can be used for the optical analysis of crystal phases with similar anisotropic behavior or preferred textures in polished sections. In this method, the vibration mode of the reflected light is determined by remarkable interference colors in the microscope using a compensator plate. The application of this method for the analysis of dental materials is demonstrated with amalgams and gold‐reduced alloys. As a prerequisite, a modified procedure for preparing suitable polished sections of inhomogenous materials is described. Employing this optical and a crystallographic computing method, more detailed information about the way of element replacement in the course of the chemical reaction can be obtained. The results of these investigations also warrant the assumption that coherent crystal intergrowth which prefers low indicated and closely packed lattice directions, gives rise to a good adhesive strength of the bonding in the allo

ISSN:0021-9304    

DOI:10.1002/jbm.820190403

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThirty‐seven types of catheters made from plastics including silicone rubber, polyvinylchloride, polyethylene, and polyurethane were tested for thrombogenesis in the cephalic vein of sheep. The range in the mass of thrombus on the catheters at autopsy 9 days after insertion was 20‐fold. There was considerable variation when catheters made from the same types of plastic were compared, but polyethylene catheters tended to be more thrombogenic than other types. Scanning electron microscopy (SEM) revealed a variety of surfaces ranging from very smooth to very rough. Roughness was frequently associated with the presence of radioopaque particles which in several catheters were concentrated into radio‐opaque tracer strips. Within types of plastics, catheters with rougher surfaces were usually more thrombogenic than those with smooth sur

ISSN:0021-9304    

DOI:10.1002/jbm.820190404

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractFilms were prepared by reaction of HEMA monomer with the crosslinking agent ethyleneglycol dimethacrylate (EGDMA) at crosslinking ratios,X, of 0.005, 0.01, 0.0128, 0.025, and 0.050 mol EGDMA/mol HEMA in the presence of 40 wt. % water at 60°C for 12 h. These membranes were subsequently swollen in water at 37°C and their structure analyzed using a modified Gaussian distribution equation of equilibrium swelling. The calculated values ofMcvaried between 800 and 3700 daltons, which corresponded to a correlation length of the mesh size ζ of 16.2 to 35.6 Å. The structural analysis and diffusive studies of PHEMA membranes indicate that the recent determinations ofMcfor PHEMA by Migliaresiet al.(C. Migliaresi, L. Nicodemo, L. Nicolais, and P. Passerini), “Physical characterization of PHEMA gels,”J. Biomed. Mater. Res.,15, 307 (1981) and others are not accurate. The methods presented can also be used for analysis of any highly crosslinked polymer network produced by simultaneous polymerization and crosslinking re

ISSN:0021-9304    

DOI:10.1002/jbm.820190405

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA segment of silk polyfilament suture [No. 2‐0(USP)], ca. 10 cm long, was coated with a thin membrane (2–6 μm) of chitosan,N‐acetylchitosan, orN‐hexanoylchitosan. The suture was directly inserted into the lumen of dog's peripheral veins. Thein vivoblood compatibility of these membranes was macroscopically determined from the blood coagulum formed on the membrane surface at 2 h. An intense thick blood coagulum formed on the chitosan membrane surface and a thin blood coagulum formed onN‐acetylchitosan membrane surface, but no blood coagulum formed onN‐hexanoylchitosan memb

ISSN:0021-9304    

DOI:10.1002/jbm.820190406

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractHeparin immobilization chemistry using alkyl spacer arms was adapted to optimize yield on polyurethane (PU) surfaces. The resultant biological activity of immobilized heparin (HI) was examinedin vitroandin vivo, and compared with a heparin releasing (HR) system. Immobilized heparin retained its ability to bind and inactivate thrombin and Factor Xa; nonspecific coagulation factor binding was insignificant. Such activity cannot be attributed to the leakage of improperly bound heparin. Immobilized heparin–polurethane catheters implanted in canine femoral and jugular veins for 1 h periods exhibited significant reduction in thrombus formation compared with untreated PU contralateral controls. Polyurethane catheters coated with a 9% heparin dispersion in PU (HR) system provided even greater improvement in antithrombogenicit

ISSN:0021-9304    

DOI:10.1002/jbm.820190407

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractPoly(ε‐caprolactone) [PEC], a biodegradable aliphatic polyester, undergoes a two‐stage degradation process: The first lengthy phase involves nonenzymatic hydrolytic cleavage of ester groups, the second phase beginning when the polymer is more highly crystalline, and of low molecular weight. The cellular events of the second phase were examined by implanting gelatin capsules containing 25 mg of low molecular weight (Mn3000) PEC powders, 106 to 500 μm, in rats. PEC fragments ultimately were degraded in phagosomes of macrophages and giant cells, the process requiring less than 13 days for completion at some sites. PEC was also identified within fibroblasts. These studies support the intracellular degradation of PEC as the principal pathway of degradation once the molecular weight of the aged polymer is reduced to 3000 or

ISSN:0021-9304    

DOI:10.1002/jbm.820190408

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractMatrices composed of ethylene‐vinyl acetate copolymer (EVAc) have been used for controlled delivery of macromolecular bioactive agents. Three EVAc samples of differentmolecular weight(MW) were selected from solution fractionated samples. The polymer MW is a sensitive factor in affecting the release rate of bovine serum albumin (BSA); the higher the MW of EVAc, the slower the release rate. Depending on the degree of hydrophilicity of the device, the relatively hydrophilic drug particles would cause various degrees of swelling pressure upon water uptake. The relatively hydrophobic EVAc carrier would impose different degrees of restrictive force as determined by polymer MW. The interaction between the restrictive force of the carrier and the swelling pressure of the drug particles is a key factor in affecting the drug release kinetics. As a result, the selection of the polymer carrier can be used to affect the kinetics of a controlled release devic

ISSN:0021-9304    

DOI:10.1002/jbm.820190409

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820190410

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820190411

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY

ISSN:0021-9304    

DOI:10.1002/jbm.820190402

出版商:John Wiley&Sons, Inc.    

年代:1985

数据来源: WILEY