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Biomedical subjects

D Annis

Publications and source records attributed to D Annis.

7 recordsLinked to original sources
PubMed1992

Evaluation of soft tissue response to a poly(urethane urea).

Variations in the performance of vascular prostheses constructed of polyurethanes, and some evidence which suggested that these variations could be due not to the properties of the polymer itself, but to differences in the cellular response to the various microstructures of porous polyurethanes require investigation. Experiments were performed to evaluate quantitatively the extent of the cell behaviour adjacent to a series of polyurethane samples. It was shown that, with Biomer, a polyurethane urea, the profile of cell behaviour as a function of distance from the implant surface and of time following implantation, the response of cells in general and macrophages in particular, varied considerably with different internal microstructure. This supports the suggestion that the cellular response to different structures and susceptibility to degradation are related.

Animals↗
PubMed1990

Effect of compliance mismatch on flow disturbances in a model of an arterial graft replacement.

Flow disturbances in a model of an interposition graft in an arterial segment were measured using an ultrasound Doppler velocimeter. The effect of the degree of compliance mismatch between a stiff' graft' and compliant 'arterial' segments was investigated. In steady flow, disturbances were detected when the compliance ratio (stiff to compliant segments) was less than or equal to 0.1 and the Reynolds number greater than or equal to 2200. A recirculation zone just downstream of the distal anastomosis was observed at a Reynolds number greater than or equal to 2400. Disturbances were also measured under pulsatile flow which consisted of a time-varying component superimposed on a steady flow component. The time-varying flow component was either quasiphysiological or sinusoidal in shape. The Reynolds number was 500 but the frequency parameter varied from 4.2 to 8.5. Significant disturbances were observed for conduits with compliance ratio less than or equal to 0.19. The disturbance intensity tended to increase as the compliance ratio decreased and the frequency parameter increased. The magnitude of the disturbance was also greater with the quasiphysiological than the sinusoidal input flow waveform.

Arteries↗
PubMed1977

Ultrasonic scanning of the thyroid gland as a guide to the treatment of the clinically solitary nodule.

This study examines the diagnostic accuracy of ultrasonic scanning in the recognition of multinodular goitre in 87 patients referred for examination who were thought by the referring clinician to have a single nodule in the thyroid gland. Twenty-five were found to have multinodular glands, 23 of which were correctly identified by ultrasound. Of those who had truly solitary nodules, ultrasonic scanning enabled us to identify all 23 who had cystic lesions and 35 out of the 39 who had predominantly solid lesions. The clinical significance of these observations in the management of patients with so-called 'single nodules' is discussed.

Adolescent↗