Thin Flexible Membrane Research Articles

MODIFIED BLISTER TESTS FOR EVALUATION OF THIN FLEXIBLE MEMBRANE ADHESION ON RIGID SUBSTRATE

The blister test geometry commonly used for the measurement of interfacial work of adhesion W has been re-examined and new fracture mechanics analyses are given for thin flexible membranes on rigid substrates in which the stretching deformations are predominant. Two loading configurations are considered. (1) The blister is pressurized under an internal expansion of a fixed mass of working gas. Here stable crack propagation and multiple measurements per specimen are allowed. (2) The blister is loaded by a shaft at its apex, which also gives stable interface crack propagation. The fracture mechanics analyses are verified with simple experiments using sticky tapes on an aluminium plate based on these two test methods. Additional shaft-loaded blister experiments of nylon 6 films on surface treated aluminium substrates have also been studied and compared to the double cantilever geometry.

Talc Deposition in Skin and Tissues Surrounding Silicone Gel-Containing Prosthetic Devices

Periprosthetic capsule formation is the most common cause of morbidity associated with silicone gel-filled breast implants. All implant recipients develop capsules. However, the extent of capsule formation varies greatly among patients, ranging from a thin flexible membrane to a constrictive inelastic band of sclerotic collagen. Although silicone gel bleed has been proposed as the most likely cause of excessive capsular sclerosis, liquid silicone did not induce fibrosis in early clinical trials. Because many implant modifications have been introduced since the original studies were performed, a more plausible explanation for excess capsular sclerosis is the inadvertent introduction of a fibrogenic contaminant. The skin and periprosthetic tissues removed from 41 women during implant revision surgery were examined for the presence of foreign substances that might contribute to capsular sclerosis. Tissue was examined histologically with and without polarizing filters and with scanning electron microscopy equipped for energy-dispersive x-ray analysis. A high incidence of talc was found within the skin and tissues adjacent to silicone-containing breast prostheses. Birefringent talc crystals, identified in 71% of the patients, were observed within nodular granulomas and perivascular histiocytes. Two specimens containing talc crystals were analyzed by energy-dispersive roentgenographic analysis, which confirmed the identity of the crystalline material as talc. Among 10 capsules examined by direct immunofluorescence, there was no evidence of immune complex deposition. The high incidence of talc deposition in the skin and tissues surrounding silicone implants suggests that talc either is introduced at the time of implant surgery (possibly in association with the silicone elastomer bag, tissue sizers, or surgical gloves) or is released into the tissues as a silicone gel contaminant during gel bleed. Talc, a known sclerosing agent, may contribute to periprosthetic fibrosclerosis.

Talc deposition in skin and tissues surrounding silicone gel-containing prosthetic devices

<h3>Background and Design:</h3> Periprosthetic capsule formation is the most common cause of morbidity associated with silicone gel-filled breast implants. All implant recipients develop capsules. However, the extent of capsule formation varies greatly among patients, ranging from a thin flexible membrane to a constrictive inelastic band of sclerotic collagen. Although silicone gel bleed has been proposed as the most likely cause of excessive capsular sclerosis, liquid silicone did not induce fibrosis in early clinical trials. Because many implant modifications have been introduced since the original studies were performed, a more plausible explanation for excess capsular sclerosis is the inadvertent introduction of a fibrogenic contaminant. The skin and periprosthetic tissues removed from 41 women during implant revision surgery were examined for the presence of foreign substances that might contribute to capsular sclerosis. Tissue was examined histologically with and without polarizing filters and with scanning electron microscopy equipped for energy-dispersive x-ray analysis. <h3>Results:</h3> A high incidence of talc was found within the skin and tissues adjacent to silicone-containing breast prostheses. Birefringent talc crystals, identified in 71% of the patients, were observed within nodular granulomas and perivascular histiocytes. Two specimens containing talc crystals were analyzed by energy-dispersive roentgenographic analysis, which confirmed the identity of the crystalline material as talc. Among 10 capsules examined by direct immunofluorescence, there was no evidence of immune complex deposition. <h3>Conclusions:</h3> The high incidence of talc deposition in the skin and tissues surrounding silicone implants suggests that talc either is introduced at the time of implant surgery (possibly in association with the silicone elastomer bag, tissue sizers, or surgical gloves) or is released into the tissues as a silicone gel contaminant during gel bleed. Talc, a known sclerosing agent, may contribute to periprosthetic fibrosclerosis. (Arch Dermatol. 1994;130:48-53)

Scanning electron microscopy of egg hatching of Anopheles albimanus (Diptera: Culicidae).

Scanning electron and light microscopic observations showed that egg hatching in Anopheles albimanus Wiedemann is aided by a chisel-shaped spine. This hatching tooth is surrounded by a thin flexible membrane fixed to a groove in the head of the larvae. Increased intracranial pressure may force the spine against the egg shell until a fissure is produced. Further opening of the egg is achieved by movements of the head and the entire body of the larva.

Entropy-driven expansion of electric double layer repulsion between highly flexible membranes

Most formulations of electric double layer interactions between charged surfaces in electrolyte solutions are essentially “hard—smooth” surface theories. However, there are many situations where the surfaces are “soft” and extremely flexible. In these systems, thermal fluctuations “roughen” the surface topography which augments double layer interactions through direct geometric effects and subtle entropy—driven renormalization. The effects of entropy confinement lead to diminished attraction and expansion of the underlying repulsion to distances much larger than given by the exponential decay. With a self-consistent field approximation, the osmotic equilibrium of a condensed-multilayer assembly of thin flexible membranes has been analyzed to obtain universal predictions for the interaction pressure between layers stabilized by a “bare” exponential repulsion. The results demonstrate a continuous crossover from the direct exponential force to a steric pressure which decays as an inverse-cube law.

The chemistry of natural enzyme-induced cross-links of proteins

The cross-linking of protein molecules to form stable supramolecular aggregates capable of acting as protective and supporting structures is a common feature of organisms coping with the stresses of life. These new polymeric forms range from thick rigid structures to thin flexible membranes. The formation of such cross-links must be carefully controlled since more or less than optimal cross-linking could lead to malfunction or even death of the organism. The chemistry of the amino acids converted or directly involved in the formation of these cross-links is complex and a range of new amino acids has been identified. Di- and tri-tyrosines are formed by the action of peroxidases, quinones by catechol oxidases,γ glutamyl lysine iso-peptide bonds by glutamyl transferase and a complex series of lysine- aldehyde derived cross-links induced by lysyl oxidase. These cross-linking mechanisms provide an insight into the complex changes in tissue function during growth of the organism and their effects on the properties of foods.

Two-dimensional analysis of two-file flow of red cells along capillaries

The effect of a tank-treading motion of the red cell membrane on a staggered “zipper”-type red cell flow in capillaries is examined, using a two-dimensional theoretical model. An approximately triangular cell with a thin flexible membrane enclosing a viscous fluid is adopted as a model of the red cell. The motion of model red cells arranged periodically along a two-dimensional channel in an idealized zipper-type arrangement is analyzed numerically by a finite element method applied to the Stokes equations for the flow both inside and outside the model cells. It is shown that, if the viscosity ratio of the internal fluid to the suspending fluid is lower than a critical value, there exists a stable zipper-type arrangement of cells. In that arrangement, the cells remain stationary relative to each other with the membrane tank-treading. In contrast, inhibiting tank-treading by increasing the viscosity ratio above the critical value induces a cyclic oscillatory motion of red cells. The critical viscosity ratio increases if the channel is narrowed or if the spacing between cells is reduced. The present results suggest that the membrane tank-treading tends to stabilize zipper-type arrangements of red cells in capillaries at high hematocrit.

Transmission and Reflection Characteristics of Waves Over a Submerged Flexible Mound

A new type of submeged structure called “Flexible Mound” is proposed, which consists of a thin flexible membrane filled with water. A numerical analysis based on the linear potential theory is carr...

Treatment of Primary Hypogonadism in Men by the Transdermal Administration of Testosterone*

We tested the efficacy of a thin flexible testosterone-impregnated membrane applied to the scrotum for the long term treatment of male hypogonadism. Ten men with primary hypogonadism were treated for 3 months (2 men) or 13 months (8 men). Serum testosterone concentrations increased in all 10 men, to within the normal range in 8. Serum dihydrotestosterone concentrations increased to supranormal values in all of the men, decreased to the normal range in 6, indicating the biological effectiveness of the testosterone in those subjects. Two men whose serum LH concentrations did not fall to normal had small or distorted scrotal surfaces. Seven of the 8 men whose serum testosterone concentrations became normal said that their hypogonadal symptoms were corrected by this treatment. We conclude that the transdermal administration of testosterone is an effective means of treating the majority of hypogonadal men who have a normal scrotum.

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Moiré interferometry strain measurements in elastic thin membranes

The strain in thin flexible membranes representing human skin has been studied using moiré interferometry. A method of using a flexible coating of photographic emulsion was developed. The equations for use in differential interferometry were also derived for very large deformations. The method was applied to two types of cases: rectangular membranes subjected to a uniform axial strain, and membranes containing strain concentrators that represent bandages placed on the surface of the skin. Results for the former case were within 3% of exact results, while results near the concentrator indicate strain concentration factors ranging from -1.25 to 1.75.