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Results for “Quartz”

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At least 667 records · Page 37Linked to original sources
PubMed1990

Smoking habits and lifetime occupational exposure to gases or dusts, including asbestos and quartz, in a Norwegian community.

Past or present occupational airborne exposure was recorded with a self-administered questionnaire sent to a random sample (N = 4992) of the 15- to 70-year-old population of Hordaland County, Norway. Completed questionnaires were returned by 90% of the sample. The respondents comprised 39% smokers, 20% ex-smokers, and 41% nonsmokers. Altogether 46% of the men and 12% of the women had a history of occupational gas or dust exposure. Occupational asbestos exposure was reported by 10% of the men and 0.4% of the women, and quartz exposure had been experienced by 8% of the men and 0.4% of the women. Smokers with a history of asbestos exposure represented 5% of the male population. Thirty percent of the smokers reported having been advised to stop smoking by a physician. The asbestos-exposed smokers had not received such advice more often than the smokers not exposed to asbestos. The findings indicate that airborne occupational exposure is widespread in the Norwegian County of Hordaland.

Adolescent↗
PubMedDate not supplied

[Competitive adsorption of human fibrinogen on an amorphic quartz surface].

The kinetics of adsorption of fibrinogen on the surface of amorphous quartz from binary solutions containing human serum albumin and gamma-globulin was studied by the method of fluorescence of total internal reflection. A model of energetically nonhomogeneous interactions in the surface/protein system was used to explain the mechanism of competitive adsorption of proteins.

Adsorption↗
PubMedDate not supplied

Use of a synthetic low-fusing quartz glass-ceramic material for the fabrication of metal-ceramic restorations.

The development of natural aesthetics has been facilitated by various innovative ceramic materials and techniques. Although metal-ceramic restorations have traditionally been the standard for durable and predictable restorations, the use of metal core materials may result in dense, opaque restorations. The incorporation of low-fusing porcelain materials has enabled the provision of translucent restorations that enable sufficient light transmission and strength. This article presents two comparative case reports that demonstrate the clinical application of a synthetic low-fusing quartz glass-ceramic material for the fabrication of aesthetic and functional metal-ceramic restorations.

Adult↗
PubMedDate not supplied

[Study with a quartz resonator of a new natural informational channel associated with quantum properties of the physical space (vacuum)].

The results on long-time measurements of differential frequency of two quartz generators are presented. One generator is placed into magnetic system creating a vector potential field, and the other (calibration generator) is situated out of this system. It was found that oscillations of frequency difference occur with periods to 20 h and 22.5 h were revealed. Tangents to the Earth parallel at the moments of observation of value minima form three distinct subsets of directions. The traditional physical concepts do not explain these results. These results are in a good agreement with hypothesis about the anisotropic interaction of objects in nature (due to the new fundamental vector constant, cosmological vector potential Ag) and hence a new informational channel. The possibility is discussed that external factors affect biological objects via the new information channel.

Earth, Planet↗
PubMed2002

Water monitoring system for oil contamination using polymer-coated quartz crystal microbalance chemical sensor.

A water monitoring system with a new chemical sensor for oil contamination was developed. The sensor had an organic polymer film on a quartz crystal microbalance (QCM). The organic film was a hydrocarbon polymer and had high affinities for the organic compounds of petroleum products such as gasoline, kerosene, diesel oil and fuel oil. The monitoring system as composed of a sampling part, a purging part, a humidity control part and a sensor part. The oil in contaminated river water could be detected whose threshold odour number (TON) was less than three. The detecting time was less than 5 min depending on the oil kindness. This system was tested using artificially contaminated river water with the oils, to be found that the sensitivity was kept steady for longer than 6 months with 400 detections of diesel oil and heavy oil. Moreover, the oil kind could be discriminated with only one sensor device by analyzing the desorption response curves obtained by flowing a clean air on the sensor instead of the purging air.

Environmental Monitoring↗
PubMed2002

Detecting odorous materials in water using quartz crystal microbalance sensors.

Water drawn from rivers into purification plants must be checked for the presence of odorous materials because oil or organic-solvent contamination of the water may occur. If the detection of odorous materials in water is untimely or fails, the consequences can be serious. Therefore, the water must be checked continuously. We have developed a water-monitoring system that uses a highly sensitive electronic nose consisting of quartz crystal microbalance sensors to detect odorous materials in water. The nose is sensitive enough to detect petroleum hydrocarbons without water vapor at a low-ppb level. However, the nose is very sensitive to humidity and temperature. We have thus developed a method for accurately maintaining the humidity and temperature in the sensor cell. Experimental results show that the developed system can quickly detect contaminated water that was mixed with gasoline, kerosene, or benzene (concentration: several hundred ppb level), and we should be able to classify the pollutant by using pattern recognition of the dynamic sensor response.

Fresh Water↗
PubMedDate not supplied

Light dynamic properties of a synthetic, low-fusing, quartz glass-ceramic material.

Significant material advancements have resulted in the increased application of porcelain materials as an ideal restorative substitute for tooth enamel and dentin. This discussion introduces a synthetic, low-fusing, quartz glass-ceramic system for the fabrication of fixed dental prostheses. This article evaluates and compares the properties of this ceramic system with regard to its applicability for use in contemporary dental practices. The theoretical aspects are supplemented by clinical case studies that highlight examples of the authentic results achievable using the low-fusing restorative material.

Adult↗
PubMed2002

[The simultaneous determination of iron(III) and aluminium(III) in quartz sand by first derivative spectrophotometry].

It is found that in a buffer solution of HAc-NaAc (pH-6.0), iron (III) and aluminium (III) react with ethylene glycol diethy diaminoteracetic acid (EGTA), pyrogallol red (PR) and cetylpyridinium bromide (CPB) to form quarternary complex. Micro iron (III) and aluminium (III) can be simultaneous determined by the first derivative spectrophotometry of the quarternary complex. The RSD for the determinations of iron and aluminium are 4.5% and 1.1% respectively, and the recoveries are 93%-98% and 95%-102% respectively. This method has been applied to the determination of micro iron and aluminum in quartz sand with satisfactory results.

Aluminum↗
PubMedDate not supplied

[Quartz sand as an adsorbent for purification of extracellular glucose oxidase from Penicillium funiculosum 46.1].

The procedure of purification of extracellular glucose oxidase (GO, EC 1.1.3.4) from culture-liquid filtrate (CLF) of the fungus Penicillum funiculosum 46.1 using alluvial quartz sand as an adsorbent has been developed. The modification of sand by changing the charge and polarity did not lead to a significant increase in its adsorption capacity towards GO. The effectiveness of sand and aluminum oxide, used as sorbents for isolation of GO from CLF, was compared. Glucose oxidase, isolated from CLF by adsorption on sand, exhibited a greater catalytic activity compared to the enzyme specimens obtained by column chromatography on CLF. Sand adsorbed GO from P. funiculosum 46.1 more effectively than aluminum oxide. It is concluded that sand may be used for fractionation of partly purified GO.

Adsorption↗
PubMed1992

[Dermatologic risks of quartz-halogen lamps].

Halogene sources are used increasingly in general illumination. Their quartz envelop is technically necessary, but presents the disadvantage of to letting the emitted UVA, UVB and UVC go through. Originally used as in indirect lighting, they have been introduced as desk-top lamps, without filter. We have proceeded to the verification of their output with a spectrophotometer calibrated by actinometry and we have calculated their relative erythemal efficacy according to the Parrish's action spectrum for human erythema. We found that, at 10 cm from the human skin, the irradiance was able to induce a minimal erythema in about 10 minutes on clear back skin. At working distance (50 cm), a barely perceptible erythema could be observed on the back of the hands after 8 consecutive hours working. We also found that sunburn cells were present in the skin sensitized with a potent phototoxic agent (8-methoxypsoralen) applied 15 minutes before a 4-6 minutes irradiation with the halogen source (at 20 cm), thus, indicating a potential risk for local phototoxicity and photoallergy. The cumulative doses per year, for 4 hours exposure per day, five days a week, reaches 125 minimal erythemal doses, equivalent to the average yearly exposure of individuals for work and leisure. If one assumes that this regimen is maintained for 30 years, the risk for induction of skin cancers on the dorsal aspect of the hands and the forearms, may be increased by a 3.4 factor, according to the widely accepted previsional models.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythema↗
PubMed2006

Bridging the gap between macroscopic and spectroscopic studies of metal ion sorption at the oxide/water interface: Sr(II), Co(II), and Pb(II) sorption to quartz.

Metal sorption mechanisms were investigated for strontium, cobalt, and lead using sodium chloride, sodium nitrate, and sodium perchlorate as background electrolytes and quartz as the adsorbent. Spectroscopic analyses of concentrated sorption samples were evaluated for their ability to provide insight into the controlling sorption process for more dilute systems. For strontium, outer-sphere complexes identified using X-ray absorption spectroscopy (XAS) of concentrated samples were consistent with macroscopic sorption data collected in more dilute systems. XAS results indicated that cobalt formed a new solid phase upon sorption to silica. Macroscopic studies of cobalt sorption supported the spectroscopic data for total cobalt concentrations of 10(-5) M, regardless of the background electrolyte composition or concentration. At a lower total cobalt concentration (10(-7) M), adsorption appeared to be the prevailing mechanism of cobalt removal. Spectroscopic results suggested that lead adsorbed as an inner-sphere complex on silica. The decrease of lead removal with increasing chloride concentration was attributed to competition with aqueous lead-chloride complexes, based on thermodynamic calculations.

Adsorption↗
PubMed1975

[The effect of asbestos cement, UICC asbestos samples and quartz on the peritoneum of the mouse].

Aqueous suspensions of asbestos cement powder injected experimentally into the peritoneal cavity of mice act as a fibrogenic agent, as do chrysotile asbestos or chrysotile asbestos-containing soil samples. The fibrotic nodules caused by the dust resemble morphologically silicosis granulomas. In addition, asbestos cement has a characteristically strong cytotoxic effect during the first 2 weeks of the experiment. It is suggested that this is due to the chrysotile asbestos and/or the calcite component of the powder. Amosite and crocidolite, on the other hand, induce a diffuse peritoneal fibrosis with the appearance of numerous foreign body giant cells and asbestos bodies. Dust particles displaced to the regional lymph nodes are frequent in the animals treated with quartz, asbestos cement and asbestos-containing soil samples. A spindle cell type sarcoma arising from the visceral peritoneum is observed in animals injected with crocidolite or asbestos cement. In addition, dusts containing chrysotile asbestos induce considerable amyloidosis of the liver and spleen.

Amyloidosis↗
PubMed1991

[Ab-interno sclerostomy with the excimer laser via a quartz fiber in albino rabbits].

After attempting to induce experimental glaucoma in 20 albino rabbits by topical administration of 0.1% dexamethasone, ab-interno sclerostomy with an excimer laser at 308 nm via a quartz fiber was performed in one eye of each animal. Preoperatively, the sclera was stained with a UV-absorbing drug (sulfisomidine) in 10 rabbits; to shield the lens from scattered radiation, another UV absorber (fluorescein) was injected additionally into the anterior chamber. The other 10 rabbits were operated on without pretreatment. A full-thickness sclerostomy was performed in all animals. Most of the eyes upon operated showed minimal inflammation in the first few postoperative days. The intraocular pressure in the operated eyes was reduced compared to the fellow eye for about 3 months. Histology showed a 50-microns broad, smooth, thermally damaged zone at the edges of the sclerostomy. Clinical and histological investigation showed no evidence of UV-induced damage on the lens or retina in either group. Application of the UV absorber led to a significant decrease in the number of pulses required to perforate the sclera, but had no influence on the clinical history.

Animals↗
PubMedDate not supplied

[Adsorption of human serum albumin on the original and albuminized surface of quartz].

The method of TIRF is used for obtaining kinetic curves of HSA adsorption on coated and uncoated silica surfaces. Using the model of energetic heterogeneous surface an analysis of positive effect of passivation as a result of transformation of energetic heterogeneity of quartz surfaces from rectangular to exponential is performed.

Humans↗
PubMed1975

Investigations into the determination of the cytotoxicity of quartz dust by physical methods.

The methods of thermally stimulated luminescence (t.s.l), thermally stimulated exoelectron emission (t.s.e.e.), electron spin resonance (e.s.r), and infrared spectroscopy (i.r.) have been used to investigate whether the specific cytotoxic activities of SiO2 dust of various origins can be attributed to physical parameters. After interaction of toxic dusts with water an increase in the intensity of the t.s.l. peaks below room temperature has been detected whereas no effect could be observed in the case of inert materials. Dusts of weak cytotoxicity have been characterized by infrared absorption bands at 3610 cm-1 and 3685 cm-1. The results of the present studies emphasize the significance of silanol groups and adsorption properties in relation to the fibrogenic activity of quartz dusts.

Dust↗
PubMed1990

[Early detection of scleroderma in quartz dust exposed workers and workers with silicosis by determining serum beta-galactosidase activity].

Progressive systemic sclerosis (PSS) is a rare disease belonging to the collagen diseases. PSS is frequently observed in workers with an intensive exposure to crystalline silica and with silicosis in the GDR. The recognition as an occupational disease is regulated by law. The elevated beta-galactosidase activity in the serum of patients with silicosis and beginning PSS can be used for detecting of early stages of PSS. References are given to medical care of patients with silicosis and exposure to quartz.

Adolescent↗