Comparison of size-resolved PM elements measured using aluminum foil and Teflon impaction substrates: Implications for ultrafine particle source apportionment and future sampling networks in California.

Measurement networks for ultrafine particulate matter (PM0.1) have been limited by the high costs for equipment, supplies, and labor associated with the need to collect PM0.1 samples on multiple substrates for full chemical analysis. Here we explore whether a single cascade impactor loaded with aluminum foil substrates is sufficient for PM0.1 source apportionment calculations in order to reduce those costs. An extraction method previously designed to measure elements on Teflon substrates was modified to accommodate features of aluminum foil substrates. Regression analysis between co-located aluminum foil and Teflon substrates in the particle diameter range 0.1-1.8 µm showed good agreement (R > 0.7) for 18 elements. Regression in the diameter range 0.1-0.18 µm (quasi-ultrafine particulate matter) was used to characterize the uncertainty introduced by the aluminum foil extraction method for the elements Li, K, V, Br, Rb, Mo, Cd, Sn, Sb, and Ba. This uncertainty was used to generate 30 simulated aluminum foil PM0.1 datasets at each of three sites, followed by source apportionment analysis using Positive Matrix Factorization (PMF). At two of the three sites, the PM0.1 source contributions calculated using aluminum foil substrates alone were almost identical to the PMF results from combined aluminum foil and Teflon substrates. The PM0.1 source contributions calculated using aluminum foil substrates at the third site were closer to the results from a previous Chemical Mass Balance (CMB) study than to the PMF results from the combined aluminum foil and Teflon substrates, possibly because the CMB study also relied exclusively on samples collected using aluminum foil substrates. The success of the PM0.1 source apportionment approach using aluminum foil substrates in a single cascade impactor provides a viable method for reducing costs in PM0.1 sampling networks by 40-47%. Similar results may be achievable at locations outside of California.

Study of the temperature effect on the surface area of model organic molecules, the dispersive surface energy and the surface properties of solids by inverse gas chromatography.

This paper demonstrated the non-validity of Schultz et al. method by proving that the surface areas of n-alkanes and polar molecules strongly depend of the temperature. Consequently, the results of surface properties obtained by this method are inaccurate. Inverse gas chromatography (IGC) at infinite dilution and the dynamic contact angle (DCA) technique were used on the polytetrafluoroethylene (PTFE) fibers. DCA measurements led to the determination of the surface energy γs(T) of PTFE fibers as a function of the temperature T (Relation 6). The variations of the surface areas of n-alkanes and polar molecules versus the temperature were determined by studying the same PTFE fibers by IGC at infinite dilution. We proved that the product of the surface area a(T, Cn) (in Å2) of an alkane by the dispersive component of the surface energyγsd(T)of the solid is constant at any temperature: [Formula: see text] , where b(Cn) is a constant only depending on the carbon atom number n of n-alkane Cn. An analytical relation of the surface area of n-alkanes as a function of the temperature was obtained (equation 18). Our results highlighted the failure of Dorris-Gray method that was largely used to determine γsd of solids. This method considered the surface area a-CH2- of methylene group equal to 6 Å2 and constant for any used temperature. The obtained results proved the non-validity of Dorris-Gray method and gave the expression of a-CH2- as a function of the temperature T (Equation 20) proved the non-validity of Dorris-Gray method. The calculations of the thermal expansion coefficients of the surface area a and radius R represented by the respective derivatives da/dT and dR/dT, showed their important variations as a function of the temperature. The general expression of the surface area aX(T) of polar molecules was given as a function of the temperature (Expression 48). The large effect of the temperature on surface areas and radii of molecules was highlighted, except for toluene. The surface area of toluene was proved to remain constant whatever the temperature. Our results showed, in general, non-linear variations of the radius rX(T) of polar molecules adsorbed on PTFE fibers. However, except for chloroform, dichloromethane and diethyl ether where their thermal expansion coefficient depends on the temperature, the linearity of rX(T) was verified in the temperature interval [293 K, 353 K].

Improved recovery of Listeria monocytogenes from stainless steel and polytetrafluoroethylene surfaces using air/water ablation.

AIMS: To develop a gentle ablation technique to recover Listeria monocytogenes biofilms from stainless steel (SS) and polytetrafluoroethylene (PTFE) surfaces by using compressed air and water injection. METHODS AND RESULTS: Biofilms were grown for 4, 24 and 48 h or 7 days and a compressed air and water flow at 2, 3 and 4 bars was applied for cell removal. Collected cells were quantified for total/dead by staining with SYTO 9/PI double staining and cultivable populations were determined by plating onto brain heart infusion (BHI) agar, while coupon surfaces also were stained with DAPI to quantify in situ the remaining cells. The recovery efficiency was compared to that of conventional swabbing. Results showed that the air/water ablation is able to collect up to 98·6% of cells from SS surfaces while swabbing only recovered 11·2% of biofilm. Moreover, air/water ablation recovered 99·9% of cells from PTFE surfaces. CONCLUSIONS: The high recovery rate achieved by this technique, along with the fact that cells were able to retain membrane integrity and cultivability, indicate that this device is suitable for the gentle recovery of viable L. monocytogenes biofilm cells. SIGNIFICANCE AND IMPACT OF THE STUDY: This work presents a highly efficient technique to remove, collect and quantify L. monocytogenes from surfaces commonly used in the food industry, which can thus serve as an important aid in verifying cleaning and sanitation as well as in reducing the likelihood of cross-contamination events.

Properties and water sorption characteristics of spaghetti prepared using various dies.

Spaghetti was prepared using dies made of different materials. The surface was observed using digital and optical microscopes, and was rougher for the spaghettis prepared using the Teflon, polypropylene, polycarbonate, aluminum, and bronze dies in this order. The extrusion velocity when passing through the die was faster, the bulk density was higher, and the rupture strength was greater for the spaghetti having the smoother surface. The die material did not affect the gelatinization temperature. The water sorption curves in boiling water containing 0.5% (w/v) sodium chloride were also observed. The curves were expressed by an equation of the hyperbolic type except for the early stage of sorption in order to estimate the equilibrium amount of water sorbed based on the bone-dry sample. The momentarily-sorbed amount of water, which is a hypothetical quantity to characterize the initial water intake, was estimated by fitting the experimental points within 60 s. The amount was higher for the spaghetti having the rougher surface.

Retrospective exposure assessment of perfluorooctanoic acid serum concentrations at a fluoropolymer manufacturing plant.

Perfluorooctanoic acid (PFOA) is a suspect human carcinogen, causes neonatal loss, liver enlargement, and a variety of tumors in rodents, and has been associated with increased cholesterol levels in humans. Mortality analyses of worker cohorts have not been conclusive or consistent. As part of a series of epidemiologic studies of workers in a West Virginia plant that manufactures fluoropolymers, estimates of serum PFOA for the worker cohort were developed for the period of 1950-2004. An existing database of 2125 worker biomarker measurements of serum PFOA was used to model retrospective exposures. Historical PFOA serum levels for eight job category/job group combinations were modeled using linear mixed models to account for repeated measures, along with exposure determinants such as cumulative years worked in potentially exposed jobs, the amount of C8 used or emitted by the plant over time, as well as a four-knot restricted cubic spline function to reflect the influence of process changes over calendar time on exposure. The modeled biomarker levels matched well with measured levels, including those collected independently as part of a community study of PFOA levels (Spearman correlations of 0.8 for internal data comparisons and 0.6 for external data comparisons). These annualized PFOA serum estimates will be used in a series of morbidity and mortality studies of this worker cohort.

Potable water recovery from As, U, and F contaminated ground waters by direct contact membrane distillation process.

In this study, the feasibility of the direct contact membrane distillation (DCMD) process to recover arsenic, uranium and fluoride contaminated saline ground waters was investigated. Two types of membranes (polypropylene, PP; and polytetrafluoroethylene, PTFE) were tested to compare the permeate production rates and contaminant removal efficiencies. Several experiments were conducted to study the effect of salts, arsenic, fluoride and uranium concentrations (synthetic brackish water with salts: 1000-10,000 ppm; arsenic and uranium: 10-400 ppb; fluoride: 1-30 ppm) on the desalination efficiency. The effect of process variables such as feed flow rate, feed temperature and pore size was studied. The experimental results proved that the DCMD process is able to achieve over 99% rejection of the salts, arsenic, fluoride and uranium contaminants and produced a high quality permeate suitable for many beneficial uses. The ability to utilize the low grade heat sources makes the DCMD process a viable option to recover potable water from a variety of impaired ground waters.

A method of identification of abnormal glow curves in individual monitoring using CaSO4:Dy teflon TLD and hot gas reader.

In the present study, a method of identifying abnormal glow curves to electronically screen the glow curves of TL readout is presented. The method is based on the fact that the shape of an abnormal glow curve differs from the shape of a normal one. A few criteria for defining the normal shape of glow curves are arrived at by analysing the glow curves of dosemeters exposed to various doses in laboratory conditions and read at different elapsed time post irradiation. About 300 glow curves of dosemeters used for monthly monitoring were analysed as per these criteria and the effectiveness of the method is observed for total counts as low as 150 µSv equivalent.

Prospective histologic evaluation of intra-abdominal prosthetics four months after implantation in a rabbit model.

BACKGROUND: Placement of an intraperitoneal prosthetic is required for laparoscopic ventral hernia repair. The biocompatibility of these prosthetics determines the host's inflammatory response, scar plate formation, tissue ingrowth, and subsequent mesh performance, including prosthetic compliance and prevention of hernia recurrence. We evaluated the host response to intraperitoneal placement of several prosthetics currently used in clinical practice. METHODS: A 4-cm x 4-cm piece of mesh was implanted on intact peritoneum in New Zealand white rabbits. The mesh types included expanded polytetrafluoroethylene (ePTFE) (DualMesh), ePTFE and polypropylene (Composix, heavyweight polypropylene), polypropylene and oxidized regenerated cellulose (Proceed, midweight polypropylene), and polypropylene (Marlex, heavyweight polypropylene). At four months, standard hematoxylin and eosin and Milligan's trichrome stains of the mesh-tissue interaction were analyzed by three observers blinded to the mesh types. Each specimen was evaluated for scar plate formation, inflammatory response, and tissue ingrowth. Each of these three categories was graded on a standard scale of 1-4 (1 = normal tissue and 4 = severe inflammatory response). The scores were analyzed using Wilcoxon rank sum test with p < 0.05 as significant. RESULTS: Ten samples of each mesh type were evaluated. There was no difference in tissue incorporation between the groups. The mean scar plate formation was greater in the heavyweight polypropylene meshes than for DualMesh (p = 0.04). With Proceed, the reduction in scar plate formation compared with that for Composix and Marlex approached statistical significance (p = 0.07). The mean number of inflammatory cells was greater around the ePTFE when compared with the midweight polypropylene (p = 0.02) but equal to the other meshes. CONCLUSIONS: The four prosthetic materials evaluated in this study demonstrate comparable host biocompatibility as evidenced by the tissue ingrowth. Scar plate formation around DualMesh was significantly less than that around Composix and Marlex. Interestingly, more inflammatory cells were noted surrounding the DualMesh which was equal to that of the heavyweight meshes. Proceed, a midweight polypropylene mesh, has the potential for improved patient tolerance compared to heavyweight polypropylene meshes based on its favorable histologic findings.

In vitro bioactivity of MOEP grafted ePTFE membranes for craniofacial applications.

The bioactivity of three methacryloyloxyethyl phosphate (MOEP) grafted expanded polytetrafluoroethylene (ePTFE) membranes with varying surface coverage as well as unmodified ePTFE was investigated through a series of in vitro tests: calcium phosphate (CaP) growth in simulated body fluid (SBF), serum protein adsorption, and a morphology and attachment study of human osteoblast-like SaOS-2 cells. The graft copolymers were prepared by means of gamma irradiation induced grafting and displayed various surface morphologies and wettabilities depending on the grafting conditions used. Unmodified ePTFE did not induce nucleation of CaP minerals, whereas all the grafted membranes revealed the growth of CaP minerals after 7 days immersion in SBF. The sample with lowest surface grafting yield (24% coverage), a smooth graft morphology and relatively high hydrophobicity (theta(adv) = 120 degrees, theta(rec) = 80 degrees) showed carbonated hydroxyapatite growth covering the surface. On the other hand, the samples with high surface grafting yield (76% and 100%), a globular graft morphology and hydrophilic surfaces (theta(adv) = 60 degrees and 80 degrees, theta(rec) = 25 degrees and 15 degrees, respectively) exhibited irregular growth of non-apatitic CaP minerals. Irreversibly adsorbed protein measured after a 1h immersion in serum solution was quantified by the amount of nitrogen on the surface using XPS, as well as by weight increase. All grafted membranes adsorbed 3-6 times more protein than the unmodified membrane. The sample with the highest surface coverage adsorbed the most protein. Osteoblast-like SaOS-2 cells cultured for 3 h revealed significantly higher levels of cell attachment on all grafted membranes compared to unmodified ePTFE. Although the morphology of the cells was heterogeneous, in general, the higher grafted surfaces showed a much better cell morphology than both the low surface-grafted and the control unmodified sample. The suite of in vitro tests confirms that a judicious choice of grafted monomer such as the phosphate-containing methacrylate monomer (MOEP) significantly improves the bioactivity of ePTFE in vitro.

Infrared and Raman microspectroscopy of foreign materials in tissue specimens.

Infrared and Raman spectra of materials found in tissue specimens submitted for histopathologic diagnosis have been recorded. These foreign materials range in size from approximately 5 to 50 microm, and the vibrational spectra have been used to identify them. Examples include cholesterol and polytetrafluoroethylene (PTFE) in an implant case, polyethylene terephthalate (PET) and polyacrylonitrile (PAN) in a pilonidal cyst, and carbenicillin in a skin biopsy. In some instances, either the infrared or Raman spectra were sufficient to make a definitive identification, while in other cases both were necessary. Because some of the samples fluoresced with visible excitation at 532 nm, FT-Raman spectra with 1064-nm excitation were also recorded. The flexibility of sampling for vibrational microspectroscopy and the value of the recorded data in assisting pathologists render medical diagnoses in the examples cited and other cases are discussed.

Capillary gas chromatographic assay of residual methenamine hippurate in equipment cleaning validation swabs.

A capillary gas chromatographic method is described for the determination of methenamine hippurate residue in swabs collected from manufacturing equipment surfaces. Any residual methenamine hippurate remaining on process equipment after cleaning is removed by swabbing with one wet polyester Absorbond swab (4" x 4") pre-moistened with water followed by a dry Absorbond swab. The residual methenamine hippurate is chromatographed on a 30 x 0.32 mm (i.d.) Supelcowax-10 capillary column of 0.25-micron film thickness. The amount of residual methenamine hippurate is determined by comparing the ratio of methenamine hippurate peak area response to that of p-cresol (internal standard) obtained for the sample to a linear calibration curve obtained for a series of standard solutions. The method is demonstrated to be sufficiently linear, accurate, precise, sensitive and rugged for the determination of low levels of methenamine hippurate on equipment surfaces. Using this method, the mean recovery of methenamine hippurate from spiked Absorbond swab samples contained in high density polyethylene bottles was 105.2%, with a relative standard deviation (RSD) of +/- 7.1% (n = 25). The mean recoveries of methenamine hippurate from spiked test plates for '180 Grit' Stainless Steel, Teflon and WARCO White (neoprene and PVC) gasket material were 77.2, 96.1 and 50.6%, with RSDs of +/- 9.4 (n = 25), +/- 4.3 (n = 25) and +/- 36% (n = 20), respectively. Recovery correction factors have been incorporated into the method. The method was successfully applied to the assay of actual equipment cleaning validation swab samples. Stability studies demonstrate that methenamine hippurate is not very stable on the equipment surfaces or in the swabs. It is recommended that the surfaces be swabbed immediately after cleaning and the swabs analyzed within 24 h after sample collection. The results demonstrate that in order to fully validate the cleaning procedures, it is not only necessary to investigate the recovery of the drug from equipment surfaces and swabs but also that the stability of the drug on the surfaces and swabs be determined.

[Studies on the bottles of mineral water and the foreign plastic like substances].

The containers of mineral water and the foreign plastic substances which were found in the mineral water were investigated. Most of plastic bottles were made of polyethylene terephthalate (PET) and the caps were made of polypropylene (PP), polyethylene (PE) or aluminum. PE liners were attached to some caps. Most of the foreign plastic substances were PET while others were PE, PP, Teflon and rubber. Some bottles had a scratch on the top inside. The origin of most PET fragments was presumed to be scraped off the bottles by the lowering of the injection nozzle during the water filling process. The sources of the other substances were also determined.

Endoscopic treatment of reflux: experimental study and review of Teflon and collagen.

Endoscopic correction of vesicoureteric reflux in children has been performed in several hundred cases with the use of Teflon or cross-linked bovine collagen. The main criticism to this simple procedure is the potential migration of Teflon particles and the local pathological reaction. An experimental study was performed in 20 rabbits injected with Teflon or collagen in the bladder submucosa. A pathological examination of the bladder, lymph nodes, liver, lungs and brain was performed several months after the experiment to study the migration and the local reaction. There is no local granulomatous reaction with collagen while a local granulomatous reaction is found in the site of injection of Teflon and in 1 locoregional lymph node. The colonization of collagen by histiocytes increases with time. No distant granulomatous reaction was noted with both injections on histological examination. A mineralogic technique was applied after homogenisation of the lungs and brain to further investigate the distant migration problem. Rare particles of Teflon were observed in the lungs but not in the brain. The pathological significance of these particles remains unclear, but calls for research for different injection materials.

Fourier transform infrared microscopic identification of foreign materials in tissue sections.

Fourier-transform infrared microspectroscopy was used to identify polymeric microparticles, such as polyethylene, polysulfone, polytetrafluoroethylene, polyurethane, silicon-based, and nylon-based plastics, in tissue sections. Foreign particles as small as 30 microns in diameter were identified. In addition to being a nondestructive technique, infrared microscopy allows for more precise structural identification of polymeric materials than do X-ray or scanning electron microscopy.

Induction of connective tissue by various alloplastic materials: an experimental study in rats.

The capacity of three alloplastic implant materials to induce connective tissue was tested on the backs of 19 rats. A standardized viscous sponge served as control material. The commercial implant materials studied were carbon fibre and polypropylene ligament prostheses and a sponge composite of polytetrafluorethylene polymer and graphite fibre. Quantitative biochemical analyses (DNA, RNA, hydroxyproline and hexosamines) were done at 3 and 10 d, and 3, 6 and 9 wk post-operatively. Histological studies were done at 3, 6 and 9 wk. During the follow-up all the materials, when implanted subcutaneously, showed some capacity to induce ingrowth of granulation tissue. However, according to both quantitative chemical analyses and histological studies, the inductive capacity was greatest in the control sponge and in the polypropylene ligament prosthesis. In contrast, chemical analyses showed that the amount of granulation tissue developing during the follow-up was least in the rats with carbon fibre ligament implants.

[Analysis of arterial microporous teflon prosthesis following surgical excision]. / Analyse de prothèses artérielles en téflon microporeux après exérèse chirurgicale.

Twenty-one prosthetic explants were analysed after being surgically excised from 19 patients whose average age at implantation was 54.8 years. The arterial prosthesis was implanted 19 times for an advanced arteriopathy (stage III and stage IV) and twice for a stage II. The average time that the implants were in place was 14.8 months (with extremes of 19 days and 4 years). Surgical reintervention was caused by thrombosis (18 cases), infection (twice) and one case of degeneration of the prosthesis. The explanted prostheses displayed an irregular capsule, an uneven filling of the wall and a fibrous proliferation adhering to the internal surface. The role of the latter appeared essential to the prevention of the invasion of the prosthesis wall by fibrous tissues. The destruction of the structure of the microporous teflon is also prevented. Furthermore, this prosthesis seemed adversely affected when creased by flexion: the reduction in the caliber of the internal lumen caused thrombosis and a detachment of the external capsule. When such a material is implanted, everything must be done to prevent twisting or damaging the prostheses.

A study of the reaction of human tissue to proplast.

The femoral stems of Thompson prostheses coated with a polytetrafluoroethylene/carbon fiber composite (proplast) were studied using conventional histological examination, scanning electron microscopy and electron probe microanalysis in "successful" firm implants and in a "loose" clinically unsuccessful implant. Ingrowth was found throughout the coatings of the successful prostheses. In the most firmly fixed prosthesis the ingrowth consisted of fibrous tissue with abundant giant cells; however, no bone ingrowth was detected. There was less composite pore infilling in the unsuccessful implant. From both clinical, radiological and the studies described above, it is concluded that fibrous tissue ingrowth was a secondary stabilizing phenomenon in the proplast-coated prostheses studied.