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T Niemelä

Publications and source records attributed to T Niemelä.

6 recordsLinked to original sources
PubMed2006

Manufacturing, mechanical characterization, and in vitro performance of bioactive glass 13-93 fibers.

Fibers were manufactured from the bioactive glass 13-93 by melt spinning. The fibers were further characterized by measuring their tensile and flexural strength, and their in vitro performance was characterized by immersing them in simulated body fluid, which analyzed changes in their mass, their flexural strength, and surface reactions. The strength of glass fibers is highly dependent on fiber diameter, test method, and possible surface flaws, for example, cracks due to abrasion. In this study, the thinnest fibers (diameter between 24 and 33 microm) possessed the highest average tensile strength of 861 MPa. The flexural strength was initially 1353.5 MPa and it remained at that level for 2 weeks. The Weibull modulus for both tensile and flexural strength values was initially about 2.1. The flexural strength started to decrease and was only approximately 20% of the initial strength after 5 weeks. During the weeks 5-40, only a slight decrease was detected. The flexural modulus decreased steadily from 68 to 40 GPa during this period. The weight of the samples initially decreased due to leaching of ions and further started to increase due to precipitation of calcium phosphate on the fiber surfaces. The mass change of the bioactive glass fibers was dependent on the surface area rather than initial weight of the sample. The compositional analysis of the fiber surface after 24 h and 5 weeks immersion did confirm the initial leaching of ions and later the precipitation of a calcium phosphate layer on the bioactive glass 13-93 fiber surface in vitro.

Biocompatible Materials↗
PubMed2004

Self-reinforced composites of bioabsorbable polymer and bioactive glass with different bioactive glass contents. Part I: Initial mechanical properties and bioactivity.

Spherical bioactive glass 13-93 particles, with a particle size distribution of 50-125 microm, were combined with bioabsorbable poly-L,DL-lactide 70/30 using twin-screw extrusion. The composite rods containing 0, 20, 30, 40 and 50 wt% of bioactive glass were further self-reinforced by drawing to a diameter of approximately 3 mm. The bioactive glass spheres were well dispersed and the open pores were formed on the composite surface during drawing. The initial mechanical properties were studied. The addition of bioactive glass reduced the bending strength, bending modulus, shear strength, compression strength and torsion strength of poly-L,DL-lactide. However, the strain at maximum bending load increased in self-reinforced composites. Initially brittle composites became ductile in self-reinforcing. The bioactivity was studied in phosphate buffered saline for up to 12 days. The formation of calcium phosphate precipitation was followed using scanning electron microscopy and energy dispersive X-ray analysis. Results showed that the bioactive glass addition affected the initial mechanical properties and bioactivity of the composites. It was concluded that the optimal bioactive glass content depends on the applications of the composites.

Biocompatible Materials↗
PubMed1975

Tracheostomy in children.

Tracheostomies were performed on 47 children, using the flap technique. Thirteen patients (28%) died of their basic disease and two (4%) died of complications resulting from the tracheostomy. Decannulation was difficult in four patients, and there was one case each of bleeding, infection, and tracheocutaneous fistula. Thus, the primary complication rate was 19%, including the two deaths. Clinical reexamination with tracheography was made on 20 patients after a follow-up period varying from four to ten years (average, eight years). One small stenotic ring in the area of the distal end of the cannula site and two slight depressions in the tracheal forewall were found. According to these results, the flap technique, if properly performed, is safe also in children.

Child↗
PubMed1975

Epidemiological markers for Pseudomonas aeruginosa. 5. Subdivision by interative numerical analysis of isolates according to lysotypes.

A computer-based numerical approach to the allocation of Pseudomonas aeruginosa bacteriphage patterns has been presented. This rendered a usefule identification of similar phage types. The grouping had epidemiological relevance. Grouping of phage typing patterns of P. aeruginosa by numerical analysis showed that the patterns of related isolations may differ in one strong lysotype reaction, occasionally even in more reactions. Thus parallels previous findings which have been based on studies of the reproducibility of the method and evaluations of differences in epidemiologically related strains from the same sources.

Bacteriophage Typing↗