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At least 775 records · Page 43Linked to original sources
PubMed2005

Intraocular lens factors that may affect anterior capsule contraction.

PURPOSE: To examine the various factors comprising intraocular lenses (IOLs) that may affect the degree of anterior capsule contraction after cataract surgery. DESIGN: Randomized controlled clinical trials. PARTICIPANTS: Three hundred thirty-one patients scheduled for bilateral cataract surgery were studied to compare the degree of anterior capsule contraction in fellow eyes that received different IOLs with regard to the following factors: (1) optic material-acrylic optic versus silicone optic; (2) optic design-round-edge optic versus sharp-edge optic; (3) haptic material-polymethyl methacrylate (PMMA) loop versus polyvinylidene fluoride loop; and (4) haptic material and design-single-piece acrylic haptic versus 3-piece PMMA haptic. The 2 IOLs implanted in the fellow eyes of each patient had almost the same material and design, except for the specific factor being compared. METHODS: All patients underwent phacoemulsification surgery with implantation of different IOLs in fellow eyes. MAIN OUTCOME MEASURES: The area of the anterior capsule opening was measured using the Scheimpflug videophotography system at 3 days or 1 week (baseline) and at 1, 3, and 6 months after surgery. The percent reduction in the anterior capsule opening area from baseline was determined at 1, 3, and 6 months after surgery. RESULTS: The mean percent reduction of the anterior capsule opening area was significantly greater in eyes with a silicone optic IOL than in eyes with an acrylic optic IOL. However, no significant difference was observed in the percent reduction between round-edge and sharp-edge optic IOLs, between PMMA and polyvinylidene fluoride loop IOLs, and between single-piece acrylic and 3-piece PMMA haptic IOLs. Strong associations were found in the percentage between round-edge and sharp-edge optic IOLs, between PMMA and polyvinylidene fluoride loop IOLs, and between single-piece acrylic and 3-piece PMMA haptic IOLs, whereas there was a relatively weak association between silicone and acrylic optic IOLs. CONCLUSIONS: Among the IOL factors examined, optic material affects most significantly the degree of anterior capsule contraction, whereas optic design and haptic material and design are not strongly related to anterior capsule contraction.

Acrylic Resins↗
PubMed2006

Theoretical study on the electrochemical behavior of norepinephrine at Nafion multi-walled carbon nanotubes modified pyrolytic graphite electrode.

DFT-B3LYP/6-31G (d, p) and HF/6-31G (d, p) calculations are performed for deoxidized norepinephrineat (NP(R)) and its oxidized form (NP(O)). The electrochemistry of norepinephrineat (NP) was studied by cyclic voltammetry (CV) at a pyrolytic graphite electrode modified by Nafion multi-walled carbon nanotubes (MWNTs) in phosphate buffers at pH 6.0, showing that the standard electrode potential of half reaction for NP(O), H+/NP(R) is 0.75l V. This experimental standard electrode potential of half reaction is consistent with that calculated using the energies of solvation and sum of electronic and thermal free energies of NP(R) and NP(O). The frontier orbital theory and Mülliken charges of molecular explain the electrochemical behavior of CV at modified electrode well. The singlet vertical excited states for NP(R) and NP(O) are also discussed.

Buffers↗
PubMed2005

A theoretical model describing the transfer characteristics of a membrane hydrophone and validation.

This paper presents a theoretical model describing the transfer characteristics of a bilaminar polyvinylidene fluoride membrane hydrophone. The model applied uses a matrix formulation for one-dimensional propagation in multi-layered media. Arbitrary interconnections of piezoelectric layers are possible. The electrical transfer characteristics of the hydrophone leg and cable are modelled as transmission lines using a two-port network approach. The model is validated against measured open-circuit sensitivities for a 25 microm film thickness 0.5 mm active element diameter bilaminar hydrophone (50 microm total film thickness). Good agreement between theory and experiment is demonstrated. A 9 microm film thickness 0.5 mm active element diameter bilaminar hydrophone (18 microm total film thickness) together with amplifier is also modelled. The voltage at the output stage of the amplifier is measured and, by knowledge of the transfer characteristics of the complete system, the pressure waveform at the hydrophone position is estimated and compared with the acoustic pressure waveform derived using a laser interferometer. Good agreement is obtained.

Acoustics↗
PubMed2006

Investigating perfluorohexane particles with high-frequency ultrasound.

Submicron particles filled with liquid perfluorocarbon are currently being studied as a potential ultrasound-targeted contrast agent. The objective of this study was to evaluate the scattering properties of these particles. Sets of perfluorohexane-filled particles of different average sizes (300 nm to 1000 nm) were produced with a constant total volume fraction. The attenuation coefficient was measured in the 15- to 50-MHz frequency range and was found to increase smoothly with frequency and to be independent of the amplitude and bandwidth of the transmitted pulse. The values range from 0.31 to 0.64 dB/mm at 30 MHz for mean particle size ranging from 970 to 310 nm, respectively. The backscattering spectra of the particle solutions were measured and showed no sign of nonlinear scattering. The backscattering coefficient increased with the power 3.9 +/- 0.3 of the frequency. These results confirm that liquid perfluorocarbon droplets behave as linear Rayleigh scatterers.

Contrast Media↗
PubMed2005

Comparison of electrocoagulation and chemical coagulation pretreatment for enhanced virus removal using microfiltration membranes.

This research studied virus removal by iron electrocoagulation (EC) followed by microfiltration (MF) in water treatment using the MS2 bacteriophage as a tracer virus. In the absence of EC, MF alone achieved less than a 0.5-log removal of MS2 virus, but, as the iron-coagulant dosage increased, the log virus removal increased dramatically. More than 4-log virus removal, as required by the Surface Water Treatment Rule, was achieved with 6-9 mg/L Fe(3+). The experimental data indicated that at lower iron dosages and pH (< approximately 8 mgFe/L and pH 6.3 and 7.3) negatively charged MS2 viruses first adsorbed onto the positively charged iron hydroxide floc particles before being removed by MF. At higher iron dosages and pH (> approximately 9 mgFe/L and pH 8.3), virus removal was attributed predominantly to enmeshment and subsequent removal by MF. Additionally, the experimental data showed no obvious influence of ionic strength in the natural water range of 10(-7)-10(-2)M on MS2 virus removal by EC-MF. Finally, EC pretreatment significantly outperformed chemical coagulation pretreatment for virus removal. The proposed mechanism for this improved performance by EC is that locally higher iron and virus concentrations and locally lower pH near the anode improved MS2 enmeshment by iron flocs as well as adsorption of MS2 viruses onto the iron floc particles.

Adsorption↗
PubMed2003

Sulfonation of polyvinylidene difluoride resin and its application in extraction of restriction enzymes from DNA digestion solutions.

Sulfonation of polyvinylidene difluoride (PVDF) resin was achieved by incubation of the resin with sulfuric acid at a moderately high temperature. The sulfonated PVDF (SPVDF) resin was studied for its ability to extract restriction enzymes from DNA digestion solutions. The SPVDF resin was effective in adsorbing restriction enzymes such as EcoRI and BamHI and the extraction procedure was easy and simple to perform. The adsorption depended upon the amount of the resin added. We found that 1 mg of the SPVDF resin could completely remove all restriction enzyme activity routinely used in DNA digestion within 2 min after its addition. Treatment of a digestion solution with the SPVDF resin did not change the reaction solution and the same digestion buffer could be used for another digestion of the same DNA with other enzymes. We also found that, in comparison with normal PVDF, the SPVDF resin adsorbed less DNA, resulting in less loss of DNA in the extraction step. The potential application of the SPVDF resin in other procedures of molecular cloning and enzyme purification is discussed.

Absorption↗
PubMed1992

Rapid filtration assays for protein kinase C activity and phorbol ester binding using multiwell plates with fitted filtration discs.

In the conventional approach protein kinase activity and phorbol ester binding associated with protein kinase C (PKC) are measured by initially incubating samples in either test tubes or multiwell plates, followed by filtration of the terminated reaction mixture using either a manifold filtration device or a cell harvester. Here we report a method in which both the incubations and filtrations necessary for the determination of either protein kinase activity or phorbol ester binding are carried out in the same multiwell plate with fitted filtration discs made of polyvinylidene difluoride (Durapore membrane). Due to the very low binding of protein to these filters, there is no interference caused by these filters during the incubation period of the assays. The drawback with these filters compared to commonly used cellulose acetate membrane filters is that they retain less of the phosphate acceptor substrate histone H1 (only 15%) if filtered and washed with standard 5% trichloroacetic acid. However, this can be overcome by increasing the trichloroacetic acid concentration to 25% during filtration. For phorbol ester binding determinations, the samples are incubated with [3H]phorbol 12,13-dibutyrate in the microwells, the ligand bound PKC is adsorbed onto DEAE-Sephadex beads, and the beads then are filtered and washed in the same microwells. Furthermore, this multiwell filtration approach can also be adopted to previously described cytosolic phorbol ester receptor assays, which have the broader conditions for optimal binding to receptors. Durapore membrane filters are found to work well for punching into scintillation vials and there is complete recovery of the radioactivity retained with the filters. In the protein kinase assay the background radioactivity is very low (< 200 cpm) and in the phorbol ester binding assay the nonspecific binding is less than 1%. Thus, these low background values result in at least a fourfold increase in sensitivity for these assays. Since the incubations and filtrations are carried out in the same well without any transfer of the sample, the coefficient of variation in multiple determinations is found to be low. Furthermore, this method is rapid and more convenient for analyzing a larger number of samples than conventional methods which use test tubes, and it is less expensive to set up compared to the automated methods that use a cell harvester.

Animals↗
PubMed1992

The direct hydrolysis of proteins containing tryptophan on polyvinylidene difluoride membranes by mercaptoethanesulfonic acid in the vapor phase.

A procedure for the amino acid analysis of polypeptides that contain tryptophan on polyvinylidene difluoride membranes is described. Lysozyme, carbonic anhydrase, phytochrome, and ovalbumin were tested. The protein, which was separated from others by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, was blotted from the gel onto a polyvinylidene difluoride membrane and directly hydrolyzed by 3 N mercaptoethanesulfonic acid vapor in a vacuum at 176 degrees C for 25 min. The hydrolysate was extracted with 0.1 N HCl and 30% methanol and used for amino acid analysis. The tested proteins were adequately hydrolyzed, and the recovery of tryptophan was very efficient.

Amino Acids↗