Effect of moisture on and kinetic features of the ultrafiltration rate of dialysis membrane.
The kinetic features of ultrafiltration of cellulose dialysis membrane stored under various humidity and temperature conditions were studied to obtain basic information of shelf-life characteristics of dialyzers. The ultrafiltration rate (UFR) decreased with time and the UFR-time curve suggested that the UFR would approach a certain equilibrium value. This phenomenon could be simulated well by the following equation: UFR = a.b.t/(1 + a.t) + c, where a, b, and c are constants and t is time. The effect of moisture adsorption onto the membrane on the UFR is discussed. A hypothesis is that in the amorphous region of cellulose, adsorbed water molecules would serve as molecular crosslinks through hydrogen bonding, and as this would reduce size of fine pores in the amorphous region, the UFR decreases.
Properties of hydrated cellulose membranes for hemodialysis after storage and radiation sterilization
The problem of the influence of long-term storage of hydrated cellulose membranes for hemodialysis on their functional properties and also on the changes of their properties on radiation sterilization has arisen in connection with the need to establish guarantees for the storage life of membranes before using them in single-use dialyzers. There is also the need to determine guarantees for the storage lives of the dialyzers themselves which are sterilized by the radiation method. In the latter case the membrane is subjected to y-ster ~, ilization and subsequent storage directly in hermetically sealed single-use dialyzers.
Damage initiation and propagation in composite shells subjected to impact
Abstract The paper investigates the impact-induced damage initiation and propagation for laminated composite shells under low-velocity impact. A three-dimensional eight-node non-conforming element is described to analyze interlaminar stress distribution, and progressive failure. The damage analysis is performed by using Tsai–Wu quadratic failure criterion, Tsai’s damage modes and an additional delamination formula at all Gaussian points. The damage modes considered are matrix cracking, fiber breakage and delamination. The progressive failure is expressed by reducing stiffness of the material at all failed Gaussian points. Special attention is centered on curved laminates. Impact energy threshold for the onset of damage and transient damage size are predicted for composite shells. The analyses of the flat and curved laminates are compared for discussing their different damage mechanism. In addition, the influence of the stacking sequence, the thickness and the radius of curvature on damage behavior of composite shells are studied.