Quartz Glass Fiber Research Articles

Investigation of filtration artifacts when sampling ambient particulate matter for mutagen assay

An ultra-high volume ambient particulate sampler capable of collecting four identical samples was used to investigate filtration artifacts which may affect mutagen assays. During five sampling episodes variables employed included filter material (glass, quartz, Teflon and Teflon-impregnated glass fiber), sampling interval (3–12 h) and the re-exposure to varying concentrations of gaseous pollutants. Filters were extracted with an equi-volume mixture of dichloromethane, toluene and methanol and extracts subjected to Salmonella /mammalian microsome mutagenicity testing employing strain TA98. From this somewhat limited data set, no large differences were observed which could be attributed to filtration artifacts.

Direct and indirect mutagenic effects of extracts from particles emitted in automobile exhaust gas. II The mutagenicity of diesel exhaust particle extracts.

The mutagenic activities of diesel exhaust particles were examined by means of the Ames test. Two types of diesel vehicles (passenger car and truck) were operated on a chassis dynamometer at constant speeds (idling, 20, 40, 60 and 80 km/h) and variable speeds (the ten-mode pattern, the M-15 mode and typical traffic patterns in Tokyo). The exhaust particles were collected on quartz glass fiber filters, which were then extracted with benzene-ethanol mixture (4 : 1, v/v). Each extract was tested by the Ames Salmonella assay. The exhaust particle extracts of both vehicles showed high mutagenic activities on TA 98 and TA 100 strains with and without metabolic activation. The mutagenic activity per km at constant speed driving increased with increase of the speed. Furthermore, acceleration and deceleration caused increases of mutagenic activities per km. The mutagenic activities of the exhausts of both vehicles were positively correlated with particle emission but not with the main gaseous emissions (nitrogen oxides, hydrocarbons, carbon monoxide and carbon dioxide).

Investigation of the mechanical strength of fiber-optic waveguides used in optical communications systems

The results are given of investigations of the mechanical strength of fiber-optic waveguides, prepared by the method of chemical deposition from the gaseous phase, and of waveguides having a quartz-glass core and an optically reflecting cladding of silicone polymer. A description is given of a horizontal breaking test machine specially designed for this purpose. The Weibull statistics were used for analyzing the strength of long waveguides. A maximum breaking strength of 4.4 GPa was attained for quartz-glass fibers having a polymer cladding, applied during the drawing process, with a 50% probability of breakage occurring in meter-long lengths.

Low-loss fiber-optical directional couplers

A method was developed for the fabrication of directional couplers for multimode quartz glass fiber waveguides. These couplers were made by electric-arc welding without preliminary etching away of the cladding. Couplers with branching into two or three channels were characterized by average additional losses of 1.4 and 2.5 dB, respectively. The return-channel isolation of 50–60 dB was evidence of a high directionality of these couplers. The mode composition of the radiation was also determined.

Material dispersion in quartz glass fiber waveguides

The dispersion of the refractive index n (λ) of the core (GeO2+SiO2) and cladding (SiO2) of a two-layer fiber blank was determined in the wavelength range 0.8–2.6 μ similar determinations were made for KV, KSG, and KV70 (anhydrous) quartz glasses. The spectral distribution of the material dispersion (λ /c)(d 2n /dλ 2) and numerical aperture of the waveguide layer were determined. Zero material dispersion of various samples of pure SiO2 was observed in the range 1.26–1.30 μ and similar results were obtained for the fibers at 1.3 to 1.32 μ. The near-field method was used to determine the spectral distribution of the aperture of a glass fiber waveguide drawn from the prepared blank and it was found that the material dispersion in the finished waveguide was the same as in the blank (within the limits of the experimental error). In the 1.6 μ range, where the total losses in the waveguide were less than 1 dB/km, the material dispersion amounted to 24 psec (nmkm)−1.

Methods of obtaining quartz glass fiber

Methods of obtaining quartz glass fiber

Malleable cast iron—Its history in the United States

There are few published studies analyzing the effects of different ferrule lengths of endodontically treated teeth in relationship to newly developed fiber-reinforced and zirconia dowel systems.This in vitro study compared the effect of 3 different ferrule lengths on the fracture resistance and fracture patterns of crowned endodontically treated teeth restored with 4 different esthetic dowel systems.The crowns of 123 human maxillary canines were removed at the cementoenamel junction and the roots were endodontically treated. Three master tooth models were prepared to ferrule lengths of 1.0 mm, 1.5 mm, and 2.0 mm to produce 3 master analogs. Each root was embedded in autopolymerizing resin with a 0.2-mm layer of silicone impression material to simulate the periodontal ligament. Forty analogs of each master tooth, with ferrule lengths of 1.0 mm, 1.5 mm, and 2.0 mm were produced with copy-milling (Celay system). Each group was further subdivided into 4 groups of 10 specimens each and restored with 4 different esthetic dowel systems (quartz fiber, glass fiber, glass fiber plus zirconia, and zirconia). All dowels were luted with adhesive resin cement (RelyX ARC), restored with composite cores (Valux Plus), and Ni-Cr alloy (Wiron 99) complete crowns. All specimens were loaded at 130 degrees to the long axes in a universal testing machine at a crosshead speed of 1 mm/min until fracture. Fracture patterns were classified as failures above or below the incisal third of the roots. The data were analyzed with 2-way ANOVA and Tukey HSD tests (α=.05). A Fisher exact test was conducted for evaluation of the mode of failure (α=.05).Mean failure loads (kg) for quartz fiber, glass fiber, glass fiber plus zirconia, and zirconia groups, respectively, with the 3 ferrule lengths were: 1.0-mm ferrule specimens: 98.09 ± 2.90, 85.36 ± 2.82, 80.24 ± 1.88, 70.11 ± 2.48; 1.5-mm ferrule specimens: 101.0 ± 2.88, 87.58 ± 2.83, 89.8 ± 2.09, 82.71 ± 2.14; 2.0-mm ferrule specimens: 119.5±1.78, 99.84±1.23, 98.6 ± 1.64, 95.42 ± 1.02. Teeth prepared with 2.0-mm ferrules demonstrated significantly higher fracture thresholds (P<.001). There were no significant differences in fracture patterns.Increasing the ferrule length of the endodontically treated teeth from 1 mm to 1.5 mm in specimens restored with quartz-fiber and glass-fiber dowels did not produce significant increases in the failure loads (P=.084, P=.119, respectively). No significant difference was detected between glass-fiber and glass-fiber plus zirconia dowels with 1.5-mm and 2.0-mm ferrules (P=.218, P=.244, respectively). However, fracture thresholds were higher for all 4 dowel systems when the specimens were prepared with a 2.0-mm ferrule length (P<.001).