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At least 55 records · Page 3Linked to original sources
PubMed1988

Field evaluation of polycarbonate versus conventional safety glasses.

Of all the causes of eye injury, gunshot has recently been cited as resulting in the highest rate of blindness and the lowest rate of visual recovery. Many of these cases are hunting accidents in which safety glasses could have prevented or lessened ocular damage. To evaluate the effectiveness of various types of safety glasses, we fired a Remington automatic shotgun at mannequin heads fitted with one of four types of safety lenses. From a distance of 10 yards, only polycarbonate lenses provided even partial protection. At 30 yards, polycarbonate and heat-treated lenses provided the best protection, whereas chemically treated and CR39 lenses provided significantly less protection. We recommend that hunters using shotguns in areas of poor visibility wear widely available polycarbonate safety glasses as well as "hunter's orange" to minimize their risk of devastating ocular gunshot injury.

Accidents↗
PubMed1970

Comparative poliovirus permeability of silver, polycarbonate, and cellulose membrane filters.

Three types of filters, silver, polycarbonate, and cellulose, were evaluated for permeability toward poliovirus suspended in water, salt-containing, and proteinaceous solvents. The ability of virus to pass through cellulose filters depended on the suspending medium; virus did not pass through cellulose filters in either water or salt solution, whereas the use of protein solutions increased filterability. The virus permeability of both the silver and polycarbonate filters was independent of the suspending medium. Apparently, pore size alone determined their permeability toward poliovirus, and electrostatic forces between filters and the particles being filtered did not appear to play a significant role. Both the silver and polycarbonate filters appear to be promising tools for the separation of viruses from contaminating bacteria and fungi.

Carbonates↗
PubMed1981

Acid-fast microscopy on polycarbonate membrane filter sputum sediments.

Polycarbonate membrane filters were used to concentrate 916 sputum specimens for detecting acid-fast bacilli by microscopic examination. These results were compared with those of smears prepared from centrifugates and direct smears of the same specimens. Culture isolation, the control procedure, demonstrated the presence of acid-fast bacilli in 76 specimens. The number of positive specimens detected by microscopy was 82 on polycarbonate membrane filter concentrates, with an 80.2% sensitivity; 53 on centrifugate smears, with a 62.2% sensitivity; and 44 on direct smears, with a 55.8% sensitivity. Acid-fast microscopy results demonstrated that the sensitivity of the polycarbonate membrane filter sputum concentration method was superior to that of the recommended centrifuge concentration method and that the former method may be considered a rapid alternative when culture for acid-fast bacilli is impractical.

Filtration↗
PubMed1986

Patient reactions and granulocyte degranulation during hemodialysis with cuprophane and polycarbonate membranes. A double-blind study.

During dialysis with cuprophane or polycarbonate filters, a fall in neutrophil and eosinophil cell counts is observed. Total complement remains unchanged, but C3a increases indicating complement activation. Release of granular granulocyte proteins is observed indicating granulocyte activation. Patient reactions or biochemical findings indicate no significant difference when polycarbonate or cuprophane membranes are used, except perhaps less complement activation with polycarbonate. The biochemical observations may be due to complement activation or cell contact with the membrane.

Adult↗
PubMed1987

Plasma levels of main granulocyte components in patients dialyzed with polycarbonate and cuprophan membranes.

Plasma levels of granulocyte lactoferrin, granulocyte myeloperoxidase and granulocyte elastase in complex with alpha 1-proteinase inhibitor (E-alpha 1PI) were investigated in regular hemodialysis patients dialyzed with hollow-fiber dialyzers made from polycarbonate (FD 100) or cuprophan (GFS 120 H). Plasma levels of all these main granulocyte components increased significantly during hemodialysis. E-alpha 1PI levels were significantly higher in patients dialyzed with the polycarbonate compared with the cuprophan membrane, whereas the increases of myeloperoxidase and lactoferrin were not different for the two dialyzers. On the other hand, plasma C3a levels were higher in patients dialyzed with the cuprophan compared with the polycarbonate dialyzer. Therefore, granulocyte activation during hemodialysis does not necessarily need complement activation.

Blood Proteins↗
PubMed1990

Studies of chemotactic, chemotactic movement-inhibiting and random movement-inhibiting effects of interleukin-1 alpha and beta, tumour necrosis factors alpha and beta and interferon gamma on human neutrophils in assays using 'sparse-pore' polycarbonate (Nuclepore) membranes in the Boyden chamber.

Interleukin-1 alpha and beta (IL-1 alpha and beta), tumour necrosis factors alpha and beta (TNF alpha and beta) and interferon gamma (IFN gamma) were tested for their chemotactic effects, their effects on chemotactic movement towards N-formyl-methionyl-leucyl-phenylalanine (FMLP) and their effects on random locomotion of human peripheral blood neutrophils through polycarbonate membranes in Boyden-type chambers. Both IL-1 alpha and beta, but no other cytokine tested were chemotactic for neutrophils using 'sparse-pore' polycarbonate membrane. Both TNFs, but no other cytokine, inhibited neutrophil chemotactic movement towards FMLP using the same membrane. No cytokine influenced random migration of neutrophils through polycarbonate membrane of standard pore density. These results suggest that IL-1 may have a role as a chemotactic mediator of inflammation, but that TNFs may inhibit chemotactic migration of neutrophils into inflammatory lesions.

Biological Factors↗
PubMed2002

Competitive adsorption of blood proteins on gamma-irradiated-polycarbonate films.

Medical devices made of polycarbonates are generally sterilized by ionizing radiation. The effect of irradiation on the response of polycarbonate to various components of body fluids was studied in this work. Polycarbonate films prepared by solvent casting technique from various solvents were gamma-irradiated in the range of 0-200 kGy. Characterizations of the films were achieved by contact angle and water-uptake studies as well as atomic force microscope (AFM) images. It was found that gamma-irradiated films were more hydrophilic than unmodified films. AFM images showed that surface roughness increased with gamma irradiation. Protein adsorption experiments conducted with human plasma demonstrated that protein adsorptions drastically increased by increasing the applied irradiation dose. The unirradiated and gamma-irradiated films were contacted with human blood in in vitro systems. Loss of the blood cells and clotting times were followed. Loss of blood cells in the plasma contacting with gamma-irradiated films was negligible. Any significant change was also followed for clotting times with gamma-radiation dose.

Adsorption↗
PubMed2003

Surface treatment of polycarbonate films aimed at biomedical application.

Aiming to encapsulate pancreatic islets, a biocompatible polycarbonate membrane (Whatman) was treated with plasma argon in order to improve its surface properties. The argon plasma treatment decreased the hydrophobicity of the membrane by fixing polyvinylpyrrolidone (PVP) at the surface. The water angle contact decreased from 47 degrees to 20 degrees after this treatment, while the structure and pore diameter were preserved. The treatment also increased significantly the water permeability from 62 +/- 8 ml/min to 200 +/- 29 ml/min (P < 0.001). ToF-SIMS analyses revealed that the argon plasma treatment of the membrane allowed the installation of an uniform PVP layer at the surface. The concentration equilibrum in glucose was reached after 8 h diffusion for the treated membrane, while it was only 32.4 +/- 8.6% (P < 0.01) for the untreated membrane. The biocompatibility of the polycarbonate membrane was assessed after one month of implantation in rats and proved to be unaffected by the surface treatment. In conclusion, the present study provided sufficient information to establish a relationship between the physicochemical modifications of the PVP-plasma-treated polycarbonate membrane and the improvement in its permeability.

Animals↗
PubMed2003

[Improved method for determining bisphenol A in polycarbonate products without using dichloromethane].

An improved method for determination of bisphenol A (BPA), phenol (PH), p-tert-butylphenol (PTBP) and diphenylcarbonate (DPC) in polycarbonate products was developed without using the hazardous solvent dichloromethane. Polycarbonate samples were ground to powder or cut into small pieces, and 0.5 g was soaked in 5 mL of acetonitrile for 24 hours at 40 degrees C. The test solution was then filtered and subjected to HPLC analysis. The proposed method was evaluated by comparison of the results with those of the standard method for 14 polycarbonate products. Extraction ratios (average values obtained by the present method/average values obtained by the standard method) of BPA, PH, PTBP and DPC were 0.89-1.19, 0.89-1.14, 0.94-1.30 and 1.08-1.11, respectively. While 120 mL/sample of organic solvent is required in the standard method, only 5 mL/sample of acetonitrile was used in our new method.

Benzhydryl Compounds↗
PubMedDate not supplied

Comparison of polycarbonate and steel test surfaces for videokeratography.

BACKGROUND: Assessing video imaging systems for measuring corneal topography often requires test surfaces. Steel bearings have been employed, but manufacturers caution that high reflectance (> 90%) relative to the eye (< 10%) may compromise test findings. The differences between steel and polycarbonate test surfaces are quantified in this study. METHODS: Images of a steel and a polycarbonate sphere of known radius of curvature were obtained with the Tomey/Computed Anatomy Topographic Modeling System (TMS, Cambridge, Mass). Analysis was performed on the raw video data files and the resultant surface curvature estimates. RESULTS: The raw video images differed sufficiently to affect image processing. Polycarbonate yielded consistently better images. Many steel images (approximately 25%) contained data points that could not be processed; calculated surface contour was more variable for these. Differences were less obvious when these images were removed from the pool. CONCLUSIONS: Results support the manufacturer's caution against the use of steel surfaces for testing or calibration of the TMS instrument. Problems appear due to the fundamental differences in the intensity distributions of video images captured from high- and low-reflectance surfaces.

Calibration↗
PubMed2000

Content and release of bisphenol A from polycarbonate dental products.

Bisphenol A (BPA) is an endocrine disruptor, and is used as a raw material for bisphenol A diglycidyl methacrylate and polycarbonate, that are used in the dental materials. In this study, the total and released amounts of BPA from polycarbonate-based dental materials were measured with high-pressure liquid chromatography (HPLC). The specimens used were orthodontic brackets and denture base resins in the same condition as when obtained commercially were cut into 3 x 3 x 4 mm pieces and crushed into powder. The HPLC analysis was carried out after immersion of the specimens in water or ethanol for a determined time. The total amount of BPA in the specimens was analyzed after dissolution in chloroform. The amount of BPA released after immersion in water for 1 hr was 0.01-0.4 microgram/g for the block samples and 0.14-4.22 micrograms/g for the crushed samples, while that in ethanol for 1 hr was 0.12-9.42 micrograms/g for the block samples and 0.42-22.24 micrograms/g for the crushed samples. The control of BPA in the denture preform resin was 78.9 micrograms/g and this increased to 90.2 micrograms/g after heating to form dentures and then to 250 micrograms/g with mechanical crushing. The results of this study indicate that BPA is released from polycarbonates used in dentistry, and that the thermal conditions during the manufacturing of restorations may cause polymer decomposition resulting in the formation of BPA.

Acrylic Resins↗
PubMedDate not supplied

The retentive ability of various cementing agents for polycarbonate crowns.

The following conclusions may be made within the limitations of this investigation. - A composite resin processed directly against a roughened stainless steel dye, similar in shape to a primary anterior tooth, which has been shaped to receive a polycarbonate crown, shows the highest retentive force measured in pounds per square inch (psi). - A polmethacrylate resin, when used as a cement, also shows high values, probably due to its ability to unite chemically with polycarbonated acrylic and to its low film thickness. - Composite resins of low viscosity, low film thickness, and high compressive and tensile strengths proved also to provide good retentive values and would contribute insolubility to a greater degree than the unfilled resin. - Polycarboxylate, zinc phosphate, and reinforced zinc oxide-eugenol cements are not to be recommended as agents for cementing polycarbonate crowns. - It can be recommended on the basis of retention only, composite crowns should be fabricated directly onto the tooth preparations of carious primary anterior teeth.

Carbonates↗
PubMed1982

A polycarbonate filter technique for collection of sorted cells.

We describe the application of polycarbonate filters to the collection of cells sorted by flow cytometry. Cells are sorted directly onto polycarbonate filters and transferred to microscope slides which are then processed to dissolve the filter and remove pore outlines. The technique results in cell preparations which retain cellular morphology and have high cell recovery of 82-100%.

Animals↗
PubMed1988

Kinetics of chemo-attraction of polymorphonuclear leukocytes towards N-formyl peptide studied with a novel polycarbonate (Nucleopore) membrane in the Boyden chamber.

The motile responses of human polymorphonuclear leukocytes (PMN) to N-formyl-methionyl-leucyl-phenylalanine (FMLP) in the Boyden chamber using a new sparse-pore polycarbonate membrane (pores 3 micron in diameter and occupying 0.1% of surface area) were compared with those demonstrated by using a standard polycarbonate (Nuclepore) filtration membrane (pores 3 micron in diameter and occupying 5% of surface area). Motility of PMN in gradients of FMLP using the new membrane was not influenced by chemokinetic effects of the factor, and the 'background' migration of the cells was minimal. However, motility of PMN in gradients of FMLP using the standard membrane was found to be influenced by chemokinetic effects of the chemotactic factor, and the 'background' or 'control' migration (in the absence of chemotactic factor) of the cells was substantial. Greater directional migration of PMN according to steepness of the gradient of chemotactic factor was demonstrated with the use of the new membrane. The new membrane may be of considerable value in the further study of the chemotactic responses of PMN.

Chemotaxis, Leukocyte↗
PubMed2005

DNA separation with low-viscosity sieving matrix on microfabricated polycarbonate microfluidic chips.

Microfluidic devices have been fabricated on polycarbonate (PC) substrates by use of a hot embossing method using a silicon master template. By adding auxiliary lines around the functional channel on the silicon master, its lifetime was significantly prolonged and the bonding strength of the PC cover plate to the microfluidic chip was greatly improved. More than 300 polycarbonate microfluidic chips have been replicated with the same silicon mold. CE separation of Phi X-174/HaeIII DNA restriction fragments, with high resolution efficiency and good reproducibility, was achieved on these devices using the low-viscosity sieving matrix HPMC-50. Temperature was found to have a significant effect on separation efficiency.

Bacteriophage phi X 174↗
PubMed1979

Preparation of liposomes of defined size distribution by extrusion through polycarbonate membranes.

Liposomes of defined size and homogeneity have been prepared by sequential extrusion of the usual multilamellar vesicles through polycarbonate membranes. The process is easy, reproducible, produces no detectable degradation of the phospholipids, and can double the encapsulation efficiency of the liposome preparation. Multilamellar vesicles extruded by this technique are shown by both negative stain and freeze-fracture electron microscopy to have mean diameters approaching the pore diameter of the polycarbonate membrane through which they were extruded. When sequentially extruded down through a 0.2 micron membrane, the resulting vesicles exhibit a very homogeneous size distribution with a mean diameter of 0.27 micron while maintaining an acceptable level of encapsulation of the aqueous phase.

Carbonates↗
PubMed1996

Thermal properties and physical ageing behaviour of tyrosine-derived polycarbonates.

Tyrosine-derived polycarbonates are new carbonate-amide copolymers. These materials have been suggested for use in medical applications, but their thermal properties and their enthalpy relaxation kinetics (physical ageing behaviour) have so far not been evaluated in detail. Since structure-property correlations involving enthalpy relaxation are rarely investigated for biomedical polymers, a series of four tyrosine-derived polycarbonates was used as a model system to study the effect of pendant chain length on the thermal properties and the enthalpy relaxation kinetics. The chemical structure of the test polymers was identical except for the length of their respective pendant chains. This feature facilitated the identification of structure-property correlations. Quantitative differential scanning calorimetry was utilized to determine the thermal properties and to measure enthalpy relaxation kinetics. The glass transition temperature of this family of polymers decreased from 93 to 52 degrees C when the length of the pendant chain was increased from two to eight carbon atoms. Successive additions of methylene groups to the pendant chain made a fairly constant contribution to lowering the glass transition temperature. For pendant chains of four or more methylene groups, the rate of enthalpy relaxation was independent of the number of methylene groups in the pendant chain. The enthalpy relaxation data were fitted to the Cowie-Ferguson model and the relaxation times obtained were about 90 min. Dynamic mechanical analysis was employed to study the viscoelastic properties. The available observations indicate that the polymers become more flexible with increasing length of the pendant chain. The results suggest that the length of the pendant chain can be used effectively to control important material properties in this series of polymers.

Carbonates↗