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Biomedical subjects

J Melbin

Publications and source records attributed to J Melbin.

At least 37 records · Page 2Linked to original sources
PubMed1976

On a non linear describing function for bio-data.

The behaviour and handling of a flexible three variable--parameter function is presented, which is suitable for unbiased regression analysis. The function is defined by an intercept, a slope or coefficient and an exponent on the independent variable. Analog and digital problems and solutions are defined. Handling is simple and the program is run without operator intervention. The range of curves include linear, convex, concave and asymptotic forms and can be extended to include sigmoid and parabolic forms. Some application results are presented for different situations.

Computers↗
PubMed1975

Three dimensional laminar flow in distorting, axisymmetric, axially varying vessels.

Three dimensional laminar, viscid flow is developed for Newtonian fluids which provides absolute values for axial, radial and tangential velocity fields everywhere if the dimensions of the vessel are known and two simultaneous axial velocities e.g. on and off the central axis in the same plane, and the central axis velocity gradient are measured. In addition, normal and shear stresses are determinable. The equation set satisfies gemoetric and other known flow limiting conditions such as no slip at surfaces etc. and are amenable for inclusion in general, dynamic flow expressions. Alternatively they may be used alone for certain problems involving gradients and secondary flows. A range of illustrations are shown for a distorting vessel with elliptic cross-section and small axial taper (analogous to the pulmonary trunk during ejection).

Mathematics↗
PubMed1975

A new method for fabrication of latex cuffs.

A new and simple method is presented that is suitable for the fabrication of inflatable cuffs for any gross vascular size. The method lends itself to mass production which is particularly useful for the fabrication of small cuffs. The procedure generally consists of spraying latex on a rotating cylinder in two separable layers. An activating tube is inserted between the layers and the edges sealed. Outward expansion is prevented by means of a suitable backing material.

Methods↗
PubMedDate not supplied

Stress reduction by geometric compliance matching at vascular graft anastomoses.

An analysis is presented of stresses developed with different junctional configurations of end-to-end vascular graft anastomoses with severe compliance mismatch. Junctions of circular transverse sections and junctions by bias cuts (beveled ends) are compared with an anastomosis of a graft constructed with an elliptical transverse section and a bevel end cut vessel. This latter substitutes midwall inextensional deformations for extensional deformations that occur with the former, conventional configurations. Applications to end-to-side anastomoses are also discussed. A range of parameters are considered: i.e., vascular wall thickness/radius ratios between 0.1 and 0.5, locations from the anastomotic plane between 1/2 and 3/2 times the vascular wall thickness, host vessel axial stretch by external forces between 0 and 15%, maximal vascular circumferential stretch distal from the anastomosis between 0 and 25%, and perimeter locations at the anastomotic junction between 0 degree and 90 degrees. The graft constructed with an elliptic cross-section developed peak stresses that are orders of magnitude lower than those developed with conventional configurations. The introduction of matching geometric compliance that dominates at the anastomotic junction minimizes consequences of material mismatch between graft and vessel and has the potential to reduce suture line stress greatly. This analysis may suggest designs for experimental studies to confirm relationships between neointimal hyperplasia and suture line stress levels, and provide a relatively simple solution for reduction of such stresses at the anastomotic junction. Choices may be permitted of graft materials with optimal surface properties despite less favorable elastic properties.

Anastomosis, Surgical↗