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At least 397 records · Page 22Linked to original sources
PubMed1989

[Transverse dimensional stability of whole jaw models of different materials].

Whole jaw models of 6 different materials were examined for their transverse dimensional stability. Under standardized conditions impressions were made of a mandibular phantom with 4 stylized crown stumps using the double mix-spray technique with additively cross-linking silicon. Of these, test models were prepared and measured using the original model as reference. The high-strength dental stones Die Keen and Fuji Rock showed the highest dimensional stability. On account of their shrinkage during polymerization, the epoxy resins Blue Star E and Metapox as well as Blue Star P, a polyurethane, were found to have smaller transverse stump interspaces. Data for electroplated silver models were between those for dental stones and plastic materials.

Calcium Sulfate↗
PubMed1989

[Compressive strength of metal-ceramic occlusal veneers].

Ceramometallic specimens, circular in section, of varying thickness and manufactured by means of different procedures, have been tested to destruction of the ceramic layer under a once-through continuously increasing force at defined points. Identical specimens were used to determine the number of load cycles under increasing continuous stress of 430 N until the ceramic layer failed. The fatigue strength increased with the thickness of the metallic layer and was further increased by a high inherent strength of the ceramic layer. In restorations with only a thin metallic layer (foil crowns) and/or low strength values of the metal (electroplated ceramic crowns) an overall thickness of the layers of more than 1.5 mm is recommended in the occlusal area to avoid premature failure.

Bite Force↗
PubMedDate not supplied

Behaviour of urinary nickel in low-level occupational exposure.

The study tested the feasibility of using urinary nickel (Ni-U) as a biological indicator to assess exposure to soluble nickel compounds in electroplating departments at concentrations well below the current TLV-TWA. Two groups of workers were studied: Group A, consisting of 13 subjects and Group B consisting of 10 subjects, with an average weekly nickel exposure of nickel in air (Ni-A) greater than or equal to 10 micrograms/m3 (Group A) and less than 10 micrograms/m3 (Group B). Air samples and urine specimens were taken on 4 consecutive days from Monday to Thursday. The mean Ni-U levels in both groups were significantly higher than in the reference group. The Ni-U levels in end-of-shift spot samples showed a tendency to increase over the week; this trend was more marked in Group A. Closer correlations between Ni-A and Ni-U were found using the postshift Ni-U values of Thursday: the test was well correlated both with the Ni-A levels of the same day and with the mean levels of the previous days. The results suggest that Ni-U is a sufficiently sensitive indicator for use in monitoring low-level occupational exposure, especially if Ni-A concentrations are above 10 micrograms/m3.

Adolescent↗
PubMed1986

[Evaluation of the biological effect of polishing powders].

Polishing powders are applied as abrasives at the treatment of various metal surfaces prior to their electroplating. The polishing powder is composed of: technical paraffin, dibutyl phthalate, technical borax, ammonium sulfate, aloxite or corundum and, as a carrier, sawdust of decidous or coniferous trees. Evaluated were: exposure to the polishing powder dust of workers operating polishing machines, as well as fibrogenic properties of the powder in an experiment on animals polishing machines, and irritating and allergic effects upon human skin (determination of irritation halftime, rubbing, damping and epidermal tests). The results demonstrated that the mean geometric concentrations of the dust ranged from 3.1 to 6.4 mg/m3 of air, whereas the dust respirable fraction constituted approx. 20% of the total dust concentration. The content of free crystalline silica in the dust did not surpans 2%. In the experiment on animals the dust exhibited cytolytic effects and induced reactive lesions in form of granulomas. The content of hydroxyproline in rats' lungs when affected by the polishing powder approximated the values obtained with quartz of weak fibrogenic properties. Basing on dermatological studies, the irritating effects of the polishing powder were defined as medium, whereas the allergic effects as weak.

Animals↗
PubMed1988

[The modification of different element levels in human blood by occupational cadmium exposure].

The influence of occupational cadmium exposure on the electrolyte (Ca, Mg) and trace element (Fe, Cu, Zn, Mn) concentrations in blood, erythrocytes and serum was investigated. The study was performed at 62 cadmium exposed persons and 38 men not occupationally exposed. The cadmium blood levels of the workers from eight factories (cadmium electroplating, cadmium stearate processing and hard soldering) ranged from 1.0 to 23.7 micrograms Cd/l blood (median 4.2 micrograms/l), of the normal persons from 0.3 to 4.1 micrograms Cd/l blood (median 1.6 micrograms/l). Around 90% of the cadmium was found in the erythrocytes. The cadmium levels in serum were much lower and increased negligibly with elevated blood cadmium concentrations. An influence of cadmium on the concentrations of calcium, iron, copper and manganese in the blood compartments could not be found. In the compartments plasma and erythrocytes higher magnesium levels were detected in comparison to the normal group; a correlation to the cadmium levels did not exist. The medians for the zinc levels in blood, erythrocytes and serum in the exposed groups were significantly higher than the normal zinc levels and correlated with the blood cadmium levels. For blood samples with cadmium concentrations exceeding 10 micrograms/l the ratio of zinc to cadmium was reduced against zinc in spite of elevated zinc and increasing cadmium levels. A negative significant correlation was calculated for the relationships of cadmium and zinc in blood and erythrocytes. A significant change of the element concentrations in the sense of a transfer from one compartment to another was not detected.

Adult↗
PubMedDate not supplied

The chemical nature of the microelectronics industry.

Many of the processes used in semiconductor fabrication involve chemical reactions. These reactions range from fundamental procedures such as electroplating and cleaning to plasma reactions and ion implantation. This article analyzes the various steps of the semiconductor fabrication process in light of their chemical nature.

Chemical Phenomena↗
PubMed1986

Electrical therapy for cardiovascular emergencies.

This presentation summarizes advances in electrical therapy of cardiovascular emergencies. The urgency of delivering definitive therapy is emphasized, and the roles of automatic internal and external defibrillators, practical external pacing, and mechanical techniques for cardioversion and defibrillation are evaluated. Standard position of the electroplates is recommended except in patients who have permanently implanted pacemakers. In these patients, the defibrillation electrodes should be at least 5 inches from the pacemaker generator. The energy requirement for defibrillation of ventricular fibrillation is reviewed, with the conclusion that the initial defibrillatory shock should be 200 J. The determinants of the transthoracic impedance are important, especially if low-energy shocks are to be used, since a high transthoracic impedance results in a poor success rate for defibrillation with low-energy shocks. When high-energy (360 J) shocks are to be used, transthoracic impedance appears to be of less importance.

Arrhythmias, Cardiac↗
PubMed1982

Contact dermatitis from cyanide plating solutions.

Two cases of contact dermatitis from electroplating solutions were attributed to irritation from cyanide salts. Both demonstrated similar clinical features. In neither could concomitant contact allergy to other constituents of the plating solutions be demonstrated. In one case, irritation could not be attributed to the alkalinity of the plating solution. Contact dermatitis from cyanide plating solutions may be associated with systemic symptoms, since cyanide is rapidly absorbed through the skin. Poor handling and hygiene techniques in the workplace should be corrected immediately.

Adolescent↗
PubMed1982

[Histopathological aspects of chromium ulcers].

The authors describe two cases of "cromeholes". Both patients were working in electroplating. The pathology of these lesions demonstrate that it refers to caustic ulcers with necrosis of the epidermis and superficial dermis, with tendency to hyperplasia of neighbouring epidermis and important infiltration of the vessels and specially of the sweat glands.

Adult↗
PubMed1983

[Evaluation of exposure and of the biological effects in galvanic chromium plating by different technologies].

In the hard electroplating process, chromium exposure is heavier than in the bright process. The average urinary chromium was 9,7 +/- 7,2 micrograms/g cr. in the 31 bright plating subjects; comparing only the chromium bath workers of the two process, the difference was statistically significant (13,0 +/- 7,5 micrograms/g cr. against 7,6 +/- 4,4 micrograms/g cr. t = 2,4; p less than 0,0025). In a control group composed of 22 sanitary workers, the average urinary chromium was 1,9 +/- 1,4 micrograms/g cr. We found chromium rhinopathy in 40% of the hard process subjects and in 20% of the bright process subjects. Sputum cytologic examination was not correlated with the chromium level exposure. In the exposed workers we found 37% insufficient specimens and 53% metaplasia plus dysplasia; in the 42 control subjects we found 64% insufficient specimens, 33% metaplasia and no dysplasia.

Chromium↗
PubMed1983

[Perforation of the nasal septum of occupational origin].

Perforations of nasal septum as typical effects of exposure to certain hazards are a particular health problem among the diseases of upper respiratory tract mucous membranes (entry 10 on the list of occupational diseases). To obtain more data on etiopathogenetic factors and correlations between the clinical picture and exposure duration, the documentation of the patients in whom perforation was diagnosed during 1972-1979 was analysed epidemiologically. The examinations covered 185 workers of various industrial branches-salina, chemical plants, leather plants, tanneries, electroplating plants-who developed nasal septum perforation due to local effects of working environment irritants. In the test group the nasal septum was defected mostly in those exposed to chromium compounds (46.5%) and in salina workers (44.3%). In the remaining 9.2% of subjects the septum perforation resulted from exposure to arsenic, nickel, silicone compounds, cadmium, fluorine, soda and ammonia. The clinical course of the disease was presented as classified by industrial branch, occupational exposure, age and length of employment. In addition, procedures of diagnostics, certification and prevention were considered.

Abscess↗
PubMedDate not supplied

[Combined use of disaggregants and galvanic current in cerebrocardio-vascular pathology].

The efficiency of combined use of the disaggregant aspirin and electroplate current on the precordial area was studied in 230 patients with coronary heart disease concurrent with cerebral disorders. The procedure was shown to have a positive action on the time course of clinical symptoms, the status of central hemodynamics, physical fitness, and psychoemotional status of the patients.

Adult↗
PubMed1993

Copper accumulation by a strain of Pseudomonas putida.

A study on the copper accumulation by resting cells of copper-resistant bacteria, isolated from activated sludge and electroplating effluent, was conducted. The best selected strain, identified as Pseudomonas putida II-11, retained copper ions, Cu(II), as high as 6.5% of its dry weight. Bacterial cells grown in the sulphate-limiting medium had the highest copper removal capacity [RC, mg of Cu(II)/g of dry cells], while the presence of glucose or sodium azide did not affect Cu(II) RC of the bacterial cells. A possible mechanism of Cu(II) accumulation by this bacterium is suggested.

Adsorption↗
PubMed1998

A rapid epidemiological assessment of dental erosion to assist in settling an industrial dispute.

A rapid epidemiological assessment (REA) of industrial dental erosion was undertaken with the aim of formulating a range of treatment strategies which could be used to settle an industrial dispute. This dispute concerned compensation for a group of adult male metalworkers who had complained of dental sensitivity and that their teeth had been "eaten by acid" at their workplace, an electroplating factory in Springs near Johannesburg, South Africa. The REA methods employed included a clinical examination, a structured socio-demographic questionnaire and colour photographs of each subject. Sixty per cent of the subjects reported pain and/or sensitivity to eating and/or drinking, 76 per cent showed varying degrees of loss of tooth structure, and 25 per cent reported teeth had been lost as a result of the industrial erosion. The project involved negotiating with mine management and trade union representatives, each with conflicting interests, and with people's oral health and large sums of money at stake. In this context, the aim of the research was to design an instrument to resolve conflict and to promote oral health at an industrial site, while retaining scientific objectivity and rigour. As a result of the REA, the workers who were examined are in the process of being compensated, while the National Union of Mineworkers and mine management are engaged in reaching a settlement. Preventive measures have been initiated at the factory. The area has been declared a "respiratory zone", which makes the wearing of respiratory masks obligatory.

Acids↗
PubMed1997

Preparation of multilayered materials in cross-section for in situ TEM tensile deformation studies.

The success of in situ transmission electron microscopy experimentation is often dictated by proper specimen preparation and sample design procedures. We have developed a novel technique permitting the production of tensile specimens of multilayered films in cross-section for in situ deformation studies. Of primary, importance in the development of this technique is the production of an electron transparent micro-gauge section. This micro-gauge section predetermines the position at which plastic deformation, crack nucleation and growth, and failure are observed. In short, we report in detail, a unique combination of specimen preparation procedural steps and the design of a multilayer foil sample. The ability of these procedures to facilitate the success of in situ TEM tensile studies of layered materials in cross-section is demonstrated using a Cu-Zr multilayer foil.

Copper↗
PubMed1990

One hundred years of chromium and cancer: a review of epidemiological evidence and selected case reports.

The present review is motivated by the fact that 100 years have passed since the first cancer case in a chromium worker was reported in Scotland. Old and recent case reports and epidemiological studies among chromate workers are reviewed to elucidate the importance of valency states and water solubility of chromium compounds for carcinogenic potency. It is concluded that all chromium[VI] compounds should be considered carcinogenic among exposed populations, and that no evidence has been presented indicating that human exposure to chromium[III] is associated with increased cancer risk. Strong evidence has been presented that zinc chromate is a potent carcinogen and suggests that calcium chromate may be a potent carcinogen. Evidence also suggests that water-soluble chromates in general may be more potent carcinogens than those with low solubility. Primary and secondary prevention of chromate-related cancer and the success in preventive measures are briefly discussed, and recommendations for future research are made.

Chromates↗
PubMed2006

Surface modification of metallic cardiovascular stents by strongly adhering aliphatic polyester coatings.

This article reports on a novel two-step strategy for the coating of cardiovascular stents by strongly adhering biocompatible and biodegradable aliphatic polyesters. First, a precoating of poly(ethylacrylate) (PEA) was electrografted onto the metallic substrate by cathodic reduction of the parent monomer in dimethylformamide (DMF). The electrodeposition of PEA, in a good solvent of it, was confirmed by both Infra-red and Raman spectroscopies. The pendant ester groups of PEA were then chemically reduced into aluminum alkoxides, able to initiate the ring-opening polymerization (ROP) of either D,L-lactide (LA) or epsilon-caprolactone (CL). Growth of biodegradable PLA or PCL coatings from the adhering precoating was confirmed by both Infra-red and Raman spectroscopies, and directly observed by scanning electron microscopy (SEM). This type of coating can act as an anchoring layer for the subsequent casting of drug-loaded polyester films allowing the controlled release of antiproliferative agents for the treatment of in-stent restenosis.

Biocompatible Materials↗
PubMed2006

Electrolytic deposition of calcium phosphate/chitosan coating on titanium alloy: growth kinetics and influence of current density, acetic acid, and chitosan.

Electrolytically deposited calcium phosphate/chitosan coating demonstrated good bone marrow stromal cell attachment. The aim of this study was to understand the coating's growth kinetics as well as the effects of current density, acetic acid, and chitosan on the coating's formation. The scanning electron micrographs found that calcium phosphate crystals homogeneously distributed into chitosan aggregates as early as 30 min. X-ray diffraction patterns and Fourier transform infrared spectra demonstrated that the coating experienced a compositional conversion from octacalcium phosphate to carbonate apatite during the deposition process. Electric current influenced the deposition. Higher current density accelerated the process and induced faster and more chitosan deposition. Both acetic acid and chitosan were found to inhibit calcium phosphate deposition. Chitosan was thought to induce stronger effects than acetic acid did. Furthermore, the inhibitive effect related to their concentration in the electrolyte. When chitosan concentration increased to a certain degree, this inhibitive effect not only affected calcium phosphate deposition, but also affected its own deposition. The chitosan content within the hybrid coating was small, which could be verified through Raman spectrum. At the same time, no clear evidence of chemical reactions could be found between these two components. We considered that both components were just naturally wrapped to form as a whole.

Alloys↗