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At least 271 records · Page 15Linked to original sources
PubMed1984

The effect of a proline-rich polypeptide (PRP) on the humoral immune response. II. PRP induces differentiation of helper cells from glass-nonadherent thymocytes (NAT) and suppressor cells from glass-adherent thymocytes (GAT).

Normal mice given thymocyte subpopulations preincubated with a proline-rich polypeptide (PRP) and immunized with SRBC show enhanced or suppressed humoral immune response measured by the number of plaque-forming cells (PFC). PRP induces differentiation of cells exhibiting helper or suppressive function from NAT and GAT respectively. Moreover, it was demonstrated that PRP-induced helper cells lost their activity after treatment with anti-Lyt 1,1 and the PRP-induced suppressor cells after treatment with anti-Lyt 2,1 monoclonal antibodies.

Animals↗
PubMed2001

Preliminary report: prescription of prism-glasses by the Measurement and Correction Method of H.-J. Haase or by conventional orthoptic examination: a multicenter, randomized, double-blind, cross-over study.

In a multicenter, randomized, double-blind, cross-over study in the Netherlands, the effectiveness of (prism-)glasses prescribed by the Measurement and Correction Method of H.-J. Haase (MKH) was compared to that of glasses prescribed by conventional orthoptic examination. Nine pairs of MKH-optometrists and orthoptists recruited patients who primarily presented with asthenopia, and each prescribed the patient (prism-)glasses. A questionnaire for asthenopia was developed that rated headache and tired eyes as 0-7 days per week and none-light-medium-severe, respectively. Light sensitivity, problems with focusing, near-work problems and burning eyes were each rated as: never-occasionally-often-always. A patient was eligible if he scored 'medium', 'often' or '5 days a week' twice; or 'medium' (etc.) once and 'light' (etc.) twice. Controls, in contrast to the patients, typically answered 'none' or 'never' to half of the complaints, but 37% of them would have passed the admission criteria. Among other criteria were: 18 to 40 years of age, horizontal angle < 4 degrees, vertical < 1.7 degrees, acuity > or = 0.8, stereopsis threshold disparity < 120". Seventy-two patients fulfilled all criteria and returned sufficient questionnaires. They wore the first glasses for six weeks, were without glasses for two weeks, and then wore the second glasses for six weeks. At the start, halfway and at the end of each 6-week period, questionnaires were filled out; 97% were returned. Only 19 of the orthoptists' glasses contained prisms (14 horizontal, 5 vertical; horizontal average of all glasses 0.49 PD, vertical 0.05 PD). Five of the orthoptists' glasses were plano. All MKH glasses contained prisms, 53 of 72 both horizontal and vertical, 18 only horizontal and one only vertical (horizontal average of all glasses 2.83 PD, vertical 0.79 PD). The starting levels of complaints were high and both glasses improved complaints dramatically. The starting levels were lower, but not significantly, in the second 6-week period and improvement was less outspoken. Because of these differences, the two periods had to be evaluated separately. The primary outcome of the study was defined as the difference between the effect of the MKH glasses and that of the orthoptists' glasses in the first and second 6-week periods. For problems with focusing, in the first 6-week period, and for tired eyes, in the second 6-week period, the difference exceeded the difference that had been defined as clinically significant (one day per week less headache or half the distance light-medium or half the distance occasionally-often), but it did not reach statistical significance. The statistical power was approximately 0.7 for demonstrating this clinically significant difference. Statistical significance was not reached in multivariate repeated measure ANOVA either. Forty-four patients preferred to keep the MKH glasses, 25 the orthoptists' glasses, including one plano. It is striking that 25% of the patients did not prefer the glasses that, according to the questionnaire, improved their complaints the most. A year after the study, the questionnaire was sent again to all patients: The levels of complaints after a year were similar to those at the end of the second 6-week period, whether they had preferred the MKH or the orthoptists' glasses, and were similar to the levels in controls. The most conspicuous finding was that both glasses improved the complaints dramatically. Apart from the prisms, other reasons could be: spherical and cylindrical correction, improved wearing comfort of the frame, placebo effect, Hawthorne effect and regression to the mean.

Adolescent↗
PubMed2001

Mechanical properties of glass-only porcelains prepared by the use of two feldspathic frits with different thermal properties.

Low- and non-leucite-containing commercial porcelains with low firing temperatures have become popular. However, improving the strength of glass porcelains is difficult. The purpose of this study was to determine if dispersed glass particles could be used as a reinforcing agent for an all-glass porcelain. We produced 3 feldspathic glasses (high-fusing, medium-fusing, low-fusing) by melting powders consisting of potassium-feldspar and 0, 5, or 20 mass% Na2O, respectively. For high-fusing, medium-fusing, and low-fusing feldspathic glasses, the deformation temperatures were 945 degrees C, 647 degrees C, and 518 degrees C, and the thermal expansion coefficient values were 8.6 x 10(-6)/degrees C, 10.3 x 10(-6)/degrees C, and 13.4 x 10(-6)/degrees C between 25 degrees C and the glass-transition temperature, respectively. The high-fusing-glass (or medium-fusing-glass) powders were mixed with low-fusing-glass powders before being fired into test specimens. The mean flexural strength and fracture toughness (K1C) of 3 single-glass porcelains ranged from 57 to 63 MPa and from 0.68 to 0.73 MPa m(1/2), respectively, presenting no significant differences in one-way ANOVA. However, the flexural strength of 50% high-fusing-glass + 50% low-fusing-glass porcelain was 114 MPa (p < 0.05) and K1C was 1.2 MPa m(1/2) (p < 0.05). Microcracks were observed with a back-scattered scanning electron microscope and were associated with the high- (or medium-) fusing glass particles, suggesting residual stress in the low-fusing-glass matrix due to a coefficient of thermal expansion mismatch between the dispersed glass particles and the matrix glass. The dispersing glass particles appeared to act as a reinforcing agent for strengthening a glassy porcelain.

Aluminum Silicates↗
PubMedDate not supplied

Dosimetric and spectroradiometric investigations of glass filtered solar UV.

The aims of this paper were to investigate how glass-filtered UV irradiances vary with glass thickness, lamination of the glass and the effect of solar zenith angle (SZA), and to measure the glass-filtered UV exposures to different receiving planes with a newly developed UVA dosimeter. Spectroradiometric and dosimetric techniques were employed in the experimental approach. The percentage of the glass-filtered solar UV compared to the unfiltered UV ranged from 59% to 70% and was influenced to a small extent by the glass thickness and the SZA. The laminated glass transmitted 11 to 12% and the windscreen glass transmitted 2.5-2.6%. The influence of the SZA was less for the thicker glass than it was for the thinner glass. The change in transmission was less than 14% for the SZA between 48 degrees and 71 degrees. There was negligible influence due to the SZA on the glass-transmitted UV of the laminated and windscreen glass. The influence of the glass thickness in the range of 2-6 mm on the percentage transmission was less than 16%. The influences of the glass thickness and the SZA on the glass-transmitted UV have been incorporated in the use of a UVA dosimeter for the glass-transmitted UV exposures. The UVA dosimeter was employed in the field to measure the glass-filtered UV exposures to different receiving planes. The UVA dosimeter reported has the potential for personal solar UVA exposure measurements.

Dose-Response Relationship, Radiation↗
PubMed1998

Glass fiber contamination of cigarette filters: an additional health risk to the smoker?

We report here the results of studies documenting the contamination of a cigarette-appearing smoking article labeled Eclipse with glass fibers, fragments, and particles. Eclipse, a product of the R. J. Reynolds Tobacco Company (RJR), was commercialized in June of 1996. Eclipse is unlike conventional cigarettes in that, like its predecessor Premier, it is designed to heat and not burn tobacco. The purpose of Eclipse was to simplify the chemical composition and reduce the biological activity of the mainstream and sidestream smoke and to achieve a significant reduction of environmental tobacco smoke. In Eclipse, tobacco pyrolysis is reduced by a carbon fuel rod that serves as a heat source for generating an aerosol having nicotine and tobacco flavor. The carbon rod, at the tip of the cigarette, is insulated and bound with two wrapping mats of glass fibers. Recently, Eclipse has been modified to address consumer complaints of burdensome draw and off-taste. The redesigned Eclipse, which we have termed the NEW Eclipse, has an unconventional filter-appearing mouthpiece that consists of a cellulose acetate cylindrical bundle with a central hollow tunnel. In our analysis of Eclipse, glass fibers (length:width aspect ratio, > or = 3:1) were: (a) observed protruding from the tip; (b) identified on the white cigarette wrapping paper; (c) viewed on the surface of the cork-appearing tipping paper; (d) found in the pack residue; (e) discovered lying freely on the cut surface of the filter by both light and electron microscopy; (f) harvested from the filter with adhesive tape; and (g) displaced when Eclipse was smoked mechanically. In a study of Eclipse that had not been removed from carefully opened packs, we observed that > or = 95% of the filters were contaminated with glass fibers (Eclipse: Regular, n = 114/120, 95%; Milds, n = 118/120, 98%; Menthol, n = 120/120, 100%). Likewise, 99% of NEW Eclipse had glass fibers on the redesigned filter (Regular, n = 119/120). In contrast, glass fibers were never observed on the filters of conventional United States filter cigarettes that had been used as controls (n = 0/120, 0%). In a study of Eclipse (n = 60), the number of glass fibers contaminating the filter surface ranged from 5 to 55. Glass fibers as well as fiber fracture items [aspect ratio, < 3:1 (e.g., particles, fragments, bits, chips, flakes, specks, and dust)] were discovered in the pack residue. The average number of glass fibers in the residue of a pack of Eclipse was 7,548 (SE +/- 3443; range, 1,164 to 26,725 glass fibers/pack; n = 7 packs). The thin and fragile glass fibers of the insulation mats had most likely been broken and fragmented in the high-speed multiple-step Eclipse manufacturing operation. Invariably, puffing on Eclipse discharged glass fibers and glass particles from the filter into the smoker's mouth. Subsequently, the bioresistant glass fibers and microscopic glass dust are inhaled and/or ingested. Contamination of Eclipse filters with glass fibers and glass dust poses a potential and unnecessary health hazard to uninformed consumers. Eclipse is a paradigm of the health danger that may be imposed by technically complex tobacco articles and nicotine delivery devices promoted by an unregulated industry to smokers worldwide, many of whom are addicted to nicotine and who seek a less hazardous cigarette.

Drug Contamination↗
PubMed1996

Protein adsorption to a bioactive glass with special reference to precorrosion.

The protein adsorption properties of the bioactive glass S53P4 were studied using albumin, IgG, and fibrinogen solutions (1 mg/mL) as well as diluted plasma, serum, and 1:1:1 mixtures of albumin, IgG, and fibrinogen. The bioactive glass granules (315-500 microns) were used in the experiments without pretreatments or as precorroded with an Si-rich or a Ca,P-rich layer. The protein adsorption properties of S53P4 were compared to a commercial bioactive glass (Bioglass), an inert glass, an experimental glass ceramic, titanium (Ti), and hydroxyapatite (HA). The untreated S53P4 bound in Trisbuffered saline mainly albumin from diluted plasma and serum and the 1:1:1 (1 mg of each) mixture of albumin, IgG, and fibrinogen. No binding of fibrinogen was observed. The omission of NaCl from the buffer used in the experiments increased the number of proteins bound by the S53P4. Most of the albumin bound by the glass could be detached with 0.5-1M NaCl speaking for electrostatic protein bonding. The protein adsorption properties of Bioglass resembled those of S53P4. The Ca,P-rich layer glass, the inert glass, the glass ceramic, HA, and Ti all bound several plasma and serum proteins, including fibrinogen. The Si-rich layer glass showed protein binding properties resembling the untreated glass more than the Ca,P-rich layer glass. The protein adsorption test used in the present study revealed differences in the protein adsorption properties of the studied materials, which may reflect differences in their surface potentials. It also functioned in registration of corrosion-induced changes in the surface properties of the S53P4. As judged by the protein adsorption properties, the untreated S53P4 could have a higher biocompatibility than the two precorroded glasses. Precorrosion, especially the formation of the Ca,P-rich layer, increased the number of proteins bound by the S53P4. Thus, a precorroded glass as compared to the untreated glass could be a better carrier of specific proteins that may be used to improve the biocompatibility of the bioactive glass.

Biocompatible Materials↗
PubMed2004

Calcium phosphates and glass composite coatings on zirconia for enhanced biocompatibility.

Calcium phosphates (CaP) and phosphate-based glass (P-glass, xCaO-(0.55-x) Na(2)O-0.45P(2)O(5) composition) composite coatings were obtained on a strong ZrO(2) to improve biocompatibility, the mechanical strength and biological activity. Hydroxyapatite (HA) and P-glass mixed powder slurries were coated on the ZrO(2) substrate, and subsequently heat-treated to obtain CaP- and P-glass composite coatings. The effects of glass composition (x=0.3, 0.4, 0.5 mol), mixing ratio of glass to HA (30%, 40%, 50% wt/wt), and heat treatment temperature (800 degrees C, 900 degrees C, 1000 degrees C) on the coating properties were investigated. After heat treatment, additional calcium phosphates, i.e., dicalcium phosphate (DCP) and tricalcium phosphate (TCP), were crystallized, resulting in the formation of triphasic calcium phosphates (HA-TCP-DCP) surrounded by a glass phase. The relative amounts of the crystalline phases varied with coating variables. The higher heat treatment temperature and glass amount, and the lower CaO content in the glass composition rendered the composite coatings to retain the higher amounts of TCP and DCP while the initial HA decreased. These appearance of additional crystalline phases and reduction of HA amount were attributed to the combined effects, i.e., the melting-crystallization of P-glass and the reaction between glass liquid phase and HA powder during thermal treatment. As a result of the glass phase in the composite coatings, their microstructures became much denser when compared to the pure HA coating. In particular, a completely dense structure was obtained at coating conditions with large amount of glass addition (50 wt%) at the glass composition of lower CaO content (0.3 mol CaO), and the following heat treatment above 800 degrees C for 2h. As a result, the adhesion strengths of the composite coating layers were significantly improved when compared to the pure HA coating. The highest strength of the composite coating was approximately 40 MPa, an improvement of approximately 80% with respect to the pure HA coating. The composite coatings showed much higher dissolution rates than the pure HA coating due to the newly formed crystallines (TCP and DCP) and the remaining glass phase. The osteoblast-like cells grew and spread actively on the composite coating samples. The proliferation numbers and alkaline phosphate (ALP) activities of the cells on the composite coatings were improved by approximately 30-40% when compared to Thermanox control and ZrO(2) substrate, and were comparable to the pure HA coating. These findings suggested that the CaP and P-glass composites are potentially useful for hard tissue coating system, due to their morphological and mechanical integrity, enhanced bioactivity, and favorable responses to the osteoblast-like cells.

Adhesiveness↗
PubMed2006

Spectral cullet classification in the mid-infrared field for ceramic glass contaminants detection.

The presence of glass-like contaminants inside waste glass products, usually resulting from both industrial and differentiated urban waste collection, has greatly increased in recent years, due to the introduction to the market of a large amount of goods manufactured from ceramic glass. The presence of contaminants in the glass recycling streams reduces product quality and increases production costs. The detection of ceramic glass detection is an unresolved problem, as such material looks like normal glass and can only be detected by trained personnel. In this study an innovative approach to ceramic glass recognition, based on the spectral signature in the mid-infrared (MIR) field, was proposed and investigated. The study specifically addressed the spectral characterization of glass and ceramic glass fragments collected in a real recycling plant from two different production lines: coloured container glass and white container glass. To define suitable inspection strategies to separate the useful (glass) from the polluting (ceramic glass) materials at the recycling plants, fragments presenting different colour, thickness, size, shape and manufacturing were selected. Both dirty and clean cullet was considered. The analyses, carried out in the MIR spectral field (2280-4480 nm), show that ceramic glass and glass fragments can be recognized according to their different spectral signature. In particular, by selecting a specific wavelength ratio the two classes of materials can be rapidly recognized, suggesting the possibility of developing an integrated hardware and software sorting system for 'on-line' ceramic glass separation.

Ceramics↗
PubMedDate not supplied

Effect of terminal sterilization by irradiation on amber Type I and Type III glass containers containing veterinary oxytetracycline suspension.

The purpose of this study is to determine the effect of terminal sterilization by gamma irradiation on 500-mL amber Type I and Type III glass containers (bottles) containing oxytetracycline (OTC) (25% W/V) suspension formulated using 20% (W/V) phospholipids syrup. The formulation was developed for veterinary parenteral administration. The results of terminal sterilization were used to assess the acceptability for this suspension product. OTC is light-sensitive and needs to be stored in amber glass containers. Amber Type I and Type III glass containers were considered for this formulation during development. Type I is a highly resistant, borosilicate glass (oxidized glass). Type III, which is soda-lime glass (reduced glass, see Materials and Methods), may also be used for parenteral products. The amber Type I and Type III glass containers, containing the suspension, were irradiated at 20-40 kGy for 150 min. In order to determine the sterility of the suspension, ampoules of the biological indicator, Bacillus pumilus, were placed in a number of bottles of the suspension. The bottles with the biological indicators were then positioned among the rest of the production bottles as per a radiation dose-mapping study conducted at the sterilization facility. Potency determination and stability evaluations for OTC were performed using high pressure liquid chromatography (HPLC). The results indicate that the gamma irradiation dose of 20-40 kGy for 150 min was able to inactivate 10(6) Bacillus pumilus spores in ampoules. After gamma sterilization, OTC concentration, pH, particle size, endotoxins, and sterility were evaluated. The assay results were comparable for the suspension in amber Type I and Type III glass containers. Sterility and pyrogenicity were measured by the USP Membrane Filtration Method and USP Bacterial Endotoxins Test, respectively. The suspension in the amber Type III glass container was also chemically (HPLC) and physically (suspension mean particle size, viscosity, density, and syringeability) stable for at least 12 months at room temperature. However, amber Type I glass darkened following irradiation, leading to a substantial reduction in glass transparency. The appearance of amber Type III glass was acceptable. Thus, the "reduced" glass, such as soda-lime, was found to be much less susceptible to darkening than the highly oxidized borosilicate amber. Due to the potential aesthetic concerns with Type I glass, the amber Type III glass container was selected for this suspension formulation.

Chromatography, High Pressure Liquid↗
PubMed2001

Effect of thermal treatment on bioactive glass microstructure, corrosion behavior, zeta potential, and protein adsorption.

Bioactive glass ceramic is characterized by high mechanical strength and a slow rate of bone bonding. To understand the factors contributing to a decrease in the rate of bone bonding to bioactive glass ceramic, we evaluated the effect of different percentages of bioactive glass crystallization on corrosion behavior, zeta potential, and serum protein adsorption. X-ray diffraction analysis showed that heat treatment of bioactive glass in the temperature range 550 degrees -700 degrees C resulted in the precipitation of Na(2)Ca(2)Si(3)O(9) crystals in the glass matrix. The percentage of crystallization increased in the order: 5%, 8%, 45%, and 83% after thermal treatment at 550 degrees, 600 degrees, 650 degrees, and 700 degrees C/1 h, respectively. Scanning electron microscopic analyses of bioactive glass treated at 550 degrees C showed major glass in glass-phase separation. Moreover, energy-dispersive X-ray analyses indicated that during crystallization P is concentrated in the glassy phase. Induced-coupled plasma analyses showed that after 24 h immersion in simulated body fluid, the concentration of the released P ion increased as the crystallization percentage of bioactive glass increased. zeta potential of bioactive glass samples containing 5% crystallization had a statistically significant higher negative value than control untreated bioactive glass (p <.02). Control untreated bioactive glass adsorbed a statistically significant higher amount of serum protein than bioactive glass samples containing 5% crystallization (p <.02). Results of our study suggest that inhibition of protein adsorption might be responsible for the slow rate of bone bonding to bioactive glass ceramic. It is also possible that conformation changes inhibit the activity of the protein adsorbed onto thermally treated bioactive glass.

Adsorption↗
PubMed2003

Effect of increasing silver content in phosphate-based glasses on biofilms of Streptococcus sanguis.

Silver is a powerful antibacterial ion that may be useful for dealing with localized infections, such as periodontitis. However, the use of silver in this role could be significantly improved by the development of an effective means of delivery. Phosphate-based glasses may provide a means of delivering the ions in a controlled manner. In our study, we have examined the effect of increasing silver content in phosphate-based glasses on biofilms of Streptococcus sanguis. Glasses of nominally the same dissolution rate were doped with silver at 1, 5,10, and 15 mol % and the number of colony-forming units (CFUs) determined after 6 and 24 h in a constant depth film fermenter (CDFF). The 1 mol % silver showed little change between 6 and 24 h. However, only 0.5 log CFUs were present on the glass containing 5 mol % at 6 h, and this reduced to virtually zero at 24 h. Few viable bacteria were found on the 10 mol % glass at both 6 and 24 h. The 15 mol % glass was investigated in this experiment, but no viable counts were detected. In a second set of experiments, glasses with 10 and 15 mol % silver were tested in the CDFF for up to 192 h. For the 10 mol % silver glass, there was approximately 0.8 log CFUs on this glass, which dropped to almost zero at 50 h. This was approximately 1.5-2.0 log reduction in CFUs compared to controls, and this difference was maintained for the first 50 h. After 50 h, there was a slow increase in the CFUs on all samples. However, CFUs on the 10 mol % silver glass were still suppressed up to 192 h compared to the controls. However, both controls also exhibited a decrease in viable counts at 50 h; this may have been due to carryover of silver into the control sample holders. However, this was minimized by the specimen layout in the CDFF and by having gaps between specimen sets. For the 15 mol % silver glass, counts for both this glass and the controls decreased to virtually zero between 24 and 48 h, but the numbers slowly increased up to 170 h, but the number of CFUs was suppressed compared to the 10 mol % glass at the same time point. The decrease seen is clearly the effect of the silver ions; however, the slow increase in CFUs may be accounted for by the biofilms forming thick layers on top of the glass discs inhibiting the release of ions from the glass by forming a "sacrificial layer" through which further ions have to diffuse.

Anti-Bacterial Agents↗