Foam Cover Research Articles

Measurement of 2,4-Toluenediamine in Urine and Serum Samples from Women with Même or Replicon Breast Implants

The objective of this matched case-control study was to determine whether women with Même or Replicon polyurethane-covered silicone breast implants are exposed to clinically significant levels of free 2,4-TDA from biodegradation of the polyurethane foam. Urine and serum samples were obtained from 61 patients with Même or Replicon breast implants and 61 controls on two separate occasions separated by 10 +/- 3 days. Free TDA was analyzed by gas chromatography combined with negative chemical ionization mass spectrometry with lower limit of quantitation in both urine and serum of 10 pg/ml. The results were correlated with the length of time since implantation. No patients or controls had detectable free 2,4-TDA in their sera. Thirty patients had quantifiable levels of free 2,4-TDA, and 18 had detectable levels in their urine. Controls had no quantifiable levels, but 7 subjects had detectable levels. The biodegradative half-life of the polyurethane foam was estimated to be 2 years. A risk assessment using the cancer potency estimate calculated by the FDA from rat data and the National Academy of Sciences methodology provided a theoretical lifetime risk of approximately one in one million. It was concluded that the polyurethane foam cover on the Même and Replicon breast implants biodegrades. The risk assessment of approximately one in one million derived from this study strengthens earlier conclusions by the Health Protection Branch (Canada) that there is no significant risk of cancer from exposure to the 2,4-TDA formed from this biodegradation.

Application of foam insulation for remediation of degraded permafrost

The factors involved in the use of urea foam to maintain permafrost are considered. A survey of the literature on forming and applying urea foams has been made. A simplified analysis of urea foam conductivity in the moisture content range from 0 to 500% is presented. A program for long-term field observations of foam cover and the temperature regime of permafrost is described. Techniques for the application of urea foams cover in north-western Siberia are discussed. The preliminary results of field observations in the summer period are presented.

Polyurethane-Covered Mammary Prosthesis: A Nine Year Follow-Up Assessment

We have examined ten tissue capsules from patients ranging from five months to nine years of mammary implantation. Contrary to published reports of polyurethane foam "fragmentation" or "disappearance" in the capsules evaluated, the polyurethane foam was still present and embedded in the surrounding tissue capsule. The foam was nearly always invisible by gross observation, or manual palpation. Only after enzymatic digestion of the tissue capsule did the foam become clearly visible as continuous sheets. ESCA analyses show that explanted foams are devoid of nitrogen peaks. Only carbon, oxygen and silicone signals are observed. The same foams do show nitrogen peaks (due to urethane linkages) when probed by FTIR. Since ESCA only analyzes the first 40-50 Angstroms of a surface, we believe that a "protective coating" composed of soft segments has formed. Beneath this "coating" the original polyurethane composition is still present as evidenced by FTIR analysis. Three possible explanations are advanced: (1) The surface hydrolysis, which takes place within the soft segment of the polyurethane polymer, results in the formation of oligomer(s). These oligomers, devoid of urethane linkages, appear to protect the polymer from further bioresorption, by significantly retarding the rate of additional surface hydrolysis. (2) Chain cleavage occurs in the soft segment producing a hydrophilic polyester chain end which orients into the interfacial area. These chain ends then produce a skin effect which increases the distance from the surface to the hard segments, or urethane-containing linkages. (3) Macromolecular motion in the soft segment phases of the polymer could be reorienting under the influence of the in vivo environment, thus producing a surface layer or "coating" which is predominantly soft segment in composition. Regardless of which of the three hypotheses proves to be most plausible, we interpret the data as showing that the polyurethane foam cover undergoes very slow bioresorption, even after 9 years of human implantation. The data further suggests that the in vivo surface of the polyurethane foam cover is biocompatible and interfacial interactions with inflammatory cells are downregulated or reduced because of the apparent biocompatibility of the material.

泡被覆による融雪制御の研究 Ｉ 屋外実験における効果と問題点

泡被覆による融雪制御の研究 Ｉ 屋外実験における効果と問題点

The effect of oceanic whitecaps and foams on pulse‐limited radar altimeters

Based on electromagnetic field theory of stratified media, the microwave reflectivity of a sea surface covered by whitecaps and foams at 13.9 GHz was computed. The computed results show that the reflectivity declines with increasing thickness of foams. The reflectivity of the sea surface without any whitecaps or foams is 0.6066 (20°C, S∶35‰), but it will be less than 0.15 when the thickness of foam cover is more than 0.3 cm. While gathering the data of whitecap and foam coverage in situ and reviewing whitecapping models, it can be shown that the effect of oceanic whitecaps and foams on the measured results of a pulse‐limited radar altimeter working at high frequencies will not be negligible in high sea state conditions.

Experimental investigation of noise radiation from a circular plate covered by polyurethane foam

An experimental investigation of the noise reduction achieved by covering a thin circular plate is reported. The plate boundary was unconstrained. One side of the plate was covered by sound-absorbing material so that noise radiation from the other side for different configurations of foam cover was measured and compared with the noise level obtained without any foam cover. It has been shown that substantial noise reduction can be achieved if a specific foam cover is used.

Removing 99.99998% of oil aerosols from compressed air and other gases

AbstractThe oil and water particulates in compressed air and other gases are present as sprays, mists, fogs, smoke, fumes and vapors. The best method found to date for removing the oil and water contaminants from compressed air is a combination of direct impaction, inertial compaction, diffusion (Brownian motion) and coalescence, the latter being the main method of removing them. Baffles, centrifugal flow and flow directional changes of the air stream are helpful in causing coalescence and impingement. Flowing the air through porous media also is effective. The best way to coalesce liquid particulates from compressed air is to control the air flow and velocity as it passes through a fibrous bed that has predetermined porosity and which has minute strands and permanent electrostatic charges. An element designed with a prefilter with tiny pores in a cloth‐like layer such as silicon‐treated borosilicate enhances coalescing of the liquids. The air passageway between the random microfibers of inert strands located in the next layer through which air travels, and at right angles to the air stream, is very small. he strands must also be very fine (0.5 μ mean diameter). Because of the smaller open area and the smaller diameter of the fibers, this material is more effective as a coalescer of liquid droplets from 5 μ in size down to 0.01 μ in size. This structure also removes small solid particulates by diffusion (Brownian motion) and direct or inertial impaction. As long as air is flowing this design results in an almost continuous film of liquid on the outer layer. Ordinarily excessive air velocities in an element of this kind will cause subdivision of coalesced droplets. An outer cover of a material like a soft plastic, porous foam traps the coalesced film of liquid something like a sponge sleeve would “soak” liquids off a wetted outer cylinder wall. By gravity the liquids migrate down within the foam cover, dropping off the bottom of it and into the sump, out of the gas system.