Assessment of fiber arrangement and contiguity in composite materials by image analysis

The overall objective of this research was to correlate the processing—fiber arrangement—properties relationships of composites. In order to do this, an experimental technique to quantitatively characterize the fiber arrangement was developed. Using this technique, the compression molded graphite/epoxy composites, CMC, were found to have a standard deviation of fiber spacing of about twice the value of those from the simulated random composites, SRC. The standard deviation of fiber volume fraction for CMC was about 4 times the value of SRC. In other words, the fibers in this laboratory CMC were poorly distributed relative to SRC.     

Early Osteogenic Marker Expression in hMSCs Cultured onto Acid Etching-Derived Micro- and Nanotopography 3D-Printed Titanium Surfaces

Polyetheretherketone (PEEK) titanium composite (PTC) is a novel interbody fusion device that combines a PEEK core with titanium alloy (Ti6Al4V) endplates. The present study aimed to investigate the in vitro biological reactivity of human bone-marrow-derived mesenchymal stem cells (hBM-MSCs) to micro- and nanotopographies produced by an acid-etching process on the surface of 3D-printed PTC endplates. Optical profilometer and scanning electron microscopy were used to assess the surface roughness and identify the nano-features of etched or unetched PTC endplates, respectively. The viability, morphology and the expression of specific osteogenic markers were examined after 7 days of culture in the seeded cells. Haralick texture analysis was carried out on the unseeded endplates to correlate surface texture features to the biological data. The acid-etching process modified the surface roughness of the 3D-printed PTC endplates, creating micro- and nano-scale structures that significantly contributed to sustaining the viability of hBM-MSCs and triggering the expression of early osteogenic markers, such as alkaline phosphatase activity and bone-ECM protein production. Finally, the topography of 3D-printed PTC endplates influenced Haralick’s features, which in turn correlated with the expression of two osteogenic markers, osteopontin and osteocalcin. Overall, these data demonstrate that the acid-etching process of PTC endplates created a favourable environment for osteogenic differentiation of hBM-MSCs and may potentially have clinical benefit.     

THE RELEASE OF STRAIN IN GLASS*

Measurements of strain release¹ showed that check results were obtained only when the previous history of the samples was the same. Moreover, it was found that the release of strain was more rapid at first than could be accounted for by the equation of Adams and Williamson. This paper discusscs the effect of previous history on the measurements, describes an improved device for loading the specimens, and suggests a logarithmic equation which, in general, fits the observations better than that of Adams and Williamson. Tests of the equation are made both on data obtained from the modified apparatus described and on the data of Adams and Williamson. It is indicated that the Adams and Williamson equation gives too long an annealing time at higher temperatures and too short an annealing time at lower temperatures. It appears that the rate of release of strain depends on some power of the strain which varies from unity at high temperatures where the glass is a viscous fluid to a higher power at low temperatures where the release of strain is elastico-viscous in character. With a siugle specimen at any fixed temperature in the annealing range, however, it appears that the release of strain in various parts of the specimen takes place at a rate which is proportional to the strain, but that the rate undergoes continual change with time.     

STUDIES OF THE CHANGES IN THE VISCOSITY OF CLAY SLIPS AND GLAZE SUSPENSIONS ON AGING AND BY TREATMENT WITH ELECTROLYTES1

The rate and extent of the spontaneous thinning out of clay slips and glaze suspensions were measured; the effects of electrolytes on the viscosities of slips and glazes after aging until minimum viscosity was reached were investigated; measurements of the rate and extent of the spontaneous thinning of a glaze after treatment with electrolytes were made; and further experiments hearing on spontaneous thinning were conducted, such as heating the slip or glaze and the application of the colorimetric method in determining P_H, etc.     

Frequency Stability of an Implantable Pressure Telemetry Capsule

An implantable pressure telemetry capsule was developed to permit monitoring cuff pressure in an artificial urethral sphincter during chronic conditions. Following implantation, the baseline frequency of the capsule was observed to increase by nearly 2 percent. A series of experiments was then conducted to determine whether this increase was caused by the temperature rise after implant, by fluid migration through the Silastic diaphragm, or by permeation of water vapor through the epoxy encapsulating the electronics. Elevated temperatures accounted for 84.5 percent of the frequency increase, migration through the diaphragm 11.85 percent of the total, and water permeation through the epoxy 3.65 percent.