Capsule thickness

The gelatin capsule delays work slowly in cold weather and will pot work at or below 32 F. Capsule thickness also affects delay time. In water at 77 F.. a delay time of approximately 20 minutes can be expected, while the same type of capeule in concentrated sulfuric acid at 77 F. will give a delay time of approximately one hour. At a temperature of 50 F., the same type of capsule will give a 6 to 8 hour delay time in water and about 24 bouts delay time in concentrated sulfuric acid. Delay times become less accurate at lower temperatures. 

The spray head configuration is an interesting aspect of EHDA. The nozzle varies from a simple hypodermic needle of different diameters to highly technologically advanced multiplex nozzles (Figure 22.8). The coaxial needle shown increases the number of centered nozzles to four and is mainly used to fabricate multilayer spheres. In coaxial setups, the most commonly used is the coaxial two-capillary nozzle used to fabricate core-shell spheres (capsules). The inner needle is supplied by a solution of active substance and the outer needle is filled with shell material.In this process, parameters are used as adjusting switches to control the diameter of the capsules, thickness of the shell, and number of inner cores. The two solvents used in the coaxial setup are immiscible and wettable, and the inner one has a higher surface tension. 

Mechanical factors and edge effects may modify the response to a biomaterial. Implant motion or micromotion can lead to variations in the fibrous capsule thickness and the composition of the fibrous capsule and the interfacial foreign body reaction. Edges and sharp changes in surface features may lead to a variation in fibrous capsule thickness and the presence of variable concentrations of chronic inflammatory cells, i.e., monocytes and lymphocytes. 

We observed that all the devices were separated from neighbouring bone by a fibrous capsule with an average thickness of 292 pm. This is probably due to the material itself, since the fibrous capsule was obvious both in actuators and static devices, with no statistical significant differeiKes in capsule thickness between the two groups (289.59 131.20 pm in actuated films vs 293.93 84.79 pm). It would be mandatory to develop and test a material with improved biocompatibility to evaluate accurately the bone material interface. 

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