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Results for “Polystyrenes”

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At least 685 records · Page 38Linked to original sources

PubMed1976

Density-gradient sedimentation in silica sols. Anomalous shifts in the banding densities of polystyrene "latex" beads.

When polystyrene "latex" beads are centrifuged to equilibrium in gradients of Nalcoag 1030, Nalcoag 1034A and Ludox 130M, which are commercial formulations of colloidal silica, the beads at densities that may be markedly lower or higher than the bulk density. Addition to the gradient of small amounts of certain polymers restores the banding densities towards the expected value. These findings closely mimic previously observed "density shifts" of biological particles. A possible model for this anomalous behavior is discussed.

Centrifugation, Density Gradient↗

PubMed2004

Hypernatraemia induced by sodium polystyrene sulphonate (Kayexalate) in two extremely low birth weight newborns.

Hyperkalaemia is a life-threatening electrolyte disorder that can occur in the first week of life in almost 50% of preterm infants with a birth weight less than 1000 g [extremely low birth weight (ELBW)]. Serum potassium values higher than 7 mmol x l-1 are associated with cardiac arrhythmias and an increased incidence of intraventricular haemorrhage and periventricular leucomalacia. Therapeutic options to treat this dangerous imbalance comprise calcium gluconate, insulin plus glucose, albuterol/salbutamol inhalation. Administration of cation-exchange resin such as sodium polystyrene sulphonate (Kayexalate) is effective in lowering plasma potassium, although complications following oral or rectal administration are reported in newborns. We describe two ELBW infants affected by hyperkalaemia, treated with Kayexalate, who developed serious hypernatraemia, that has never been reported before in preterm infants.

Cation Exchange Resins↗

PubMed2002

Removal of endotoxin in blood by polymyxin B immobilized polystyrene-derivative fiber.

Polymyxin B, a cationic cyclic decapeptide antibiotic, is well known to bind endotoxin and to neutralize its toxicity. Based on this principle, polymyxin B was immobilized on the chloroacetamidomethylated polystyrene fiber that is reinforced by polypropylene. The adsorbing capacity of the obtained fibers (polymyxin B immobilized fiber [PMX-F]) was evaluated on endotoxin and other serum components in serum and on heparin in phosphate-buffered saline. Fluorescein isothiocyanate-labeled or tetramethylrhodamine isothiocyanate-labeled lipopolysaccharide (LPS) was used as endotoxin. The measurement of the fluorescence intensity showed that PMX-F adsorbed these LPSs depending on their concentration and on amount. The adsorption of endotoxin was confirmed by desorption of LPS from PMX-F as well. PMX-F adsorbed serum amyloid protein A besides LPS, but neither C-reactive protein nor low-density lipoprotein. The adsorbing property of heparin was low.

Absorption↗

PubMedDate not supplied

Serologic procedures performed in hydrophilized polystyrene cuvettes and borate glass tubes: a comparative study.

Serologic procedures were performed in parallel using hydrophilized polystyrene cuvettes and conventional glass test tubes. Consistent and comparable results were obtained with both containers. No significant differences in antibody titer, specificity, neutralization, or elution were observed. The effect of a proteolytic enzyme on red blood cell antigen was not altered by the hydrophilized plastic tubes. There was no difference in the stability of immune sera stored in glass or plastic at 4 degrees C and--30 degrees C. However, hemolysis of stored red blood cells was significantly slower in the hydrophilized plastic cuvettes.

Agglutinins↗

PubMed1991

Sudden death in infants sleeping on polystyrene-filled cushions.

BACKGROUND: Infants are at risk for both the sudden infant death syndrome (SIDS) and accidental suffocation. On postmortem examination, however, it is difficult to distinguish one from the other without information from the scene of death. Healthy infants are assumed to be able to turn their heads and, if not otherwise restrained, to obtain fresh air. We assessed this assumption in an investigation of infant deaths that occurred during sleep on cushions filled with polystyrene beads. METHODS: We obtained data on 25 deaths from the U.S. Consumer Product Safety Commission. We also used mechanical and animal models to study physiologic aspects of ventilation relevant to these results, by simulating the effects on an infant of breathing into a cushion. We measured the effects of softness, malleability (molding of the cushion about an infant's head), airflow resistance, and rebreathing of expired gases. RESULTS: All 25 study infants were prone when found dead, and at least 88 percent were face down with nose and mouth obstructed by the cushion. SIDS was the diagnosis in 19 of the 23 infants who underwent autopsy. Our findings show, however, that the cushion would have limited movement of the infant's head to obtain fresh air, and the amount of rebreathing we estimated to have occurred in the infants was lethal in a rabbit model. CONCLUSIONS: Accidental suffocation by rebreathing was the most likely cause of death in most of the 25 infants studied. Consequently, there is a need to reassess the cause of death in the 28 to 52 percent of the victims of SIDS who are found with their faces straight down. Safety regulations setting standards for softness, malleability, and the potential for rebreathing are needed for infant bedding.

Air Movements↗

PubMed2004

Comparison in fractal dimension between those obtained from structure factor and viscoelasticity of gel networks of 1,3:2,4-bis-O-(p-methylbenzylidene)-D-sorbitol in polystyrene melt at gel point.

We investigated time evolution of shear moduli in the physical gelation process of 1,3:2,4-bis-O-(p-methylbenzylidene)-D-sorbitol in polystyrene melt. At the gel point, storage and loss shear moduli, G' and G", were described by the power law of frequency omega, G' approximately G" approximately omegan, with the critical exponent n being nearly equal to 2/3, in agreement with the value predicted by the percolation theory. We also investigated the structure factor over two decades in length scale at gel point by using ultra-small-angle X-ray scattering, and small-angle X-ray scattering. We found the power-law behavior in low-q region, indicating that the gel network forms the self-similar structure with mass-fractal dimension. Comparison between the exponent of mass-fractal dimension from structure factor and that from viscoelasticity indicates that hydrodynamic interactions are completely screened out and the excluded volume effects are dominant in the gel. The gel strength was found to increase with the decrease in the lower limit length scale of fractality.

Benzylidene Compounds↗

PubMed2005

Small-angle neutron scattering of dilute polystyrene chains at the protein limit of a colloid-polymer mixture.

The present work investigates the structure of large polystyrene (PS) chains in solutions of small poly(ethyl methacrylate) (PEMA) microgel particles in toluene. Toluene is a good solvent for the PS chains. The PEMA colloids have an outer radius of R=11 nm which is much smaller in size than the radius of gyration Rg=58 nm of the PS chains. The system is considered to represent the protein limit of polymer-colloid mixtures. Structural investigation is performed by small-angle neutron scattering (SANS) using an appropriate contrast matching. This could be achieved by dissolving fully deuterated PS chains (D8-PS) in solutions of hydrogenated PEMA colloids in hydrogenated toluene (H-toluene). It is first demonstrated that PEMA colloids are satisfactorily contrast matched for SANS in H-toluene if the PEMA concentration does not exceed 200 g/l. Based on these findings, D8-PS is investigated by SANS in pure H-toluene and three different PEMA concentrations in H-toluene. The results indicate a drastic shrinking of D8-PS chain dimensions with increasing PEMA content. Comparison with model curves of star-branched Gaussian chains and Gaussian rings suggest a striking similarity of the respective density-density correlation of those models with the shrunken D8-PS chains. Along with this, a shrinking as large as 0.5 was estimated when the PEMA content reached 200 g/l.

Bacteriophage T4↗

PubMed2005

Integral equation theory for atactic polystyrene melt with a coarse-grained model.

In this work, an integral equation approach to investigate the atactic polystyrene (aPS) melt based on polymer reference interaction site model (PRISM) theory is proposed. The intramolecular structure factors, required as input to PRISM theory, are obtained from the semiflexible chain model. With a novel coarse-graining procedure and the explicit-atom molecular-dynamics (MD) simulations for aPS, the parameters needed for the coarse-grained model are obtained by using an automatic simplex optimization. These parameters can be used to describe the structure and thermodynamic properties of the complex aPS melt and good agreement is obtained between the theory and MD simulations. The proposed integral equation approach provides a basis for describing the structure and properties of PS nanocomposites where the application of molecular simulation is difficult.

Algorithms↗

PubMed1978

Labeling of monodisperse polystyrene microspheres with tightly bound 51Cr.

Monodisperse radioactive polystyrene latex microspheres have been prepared by attachment of chromium-51 to latex spheres. Labeling was by emulsion polymerization of chromium acetylacetonate dissolved in styrene monomer using commercially available microspheres. This was accomplished with two successive polymerization steps: radiation excitation and radical polymerization initiated with potassium persulfate. After attachment of the label the particle suspension was purified by repeated centrifugation wash cycles to remove labile radioactivity. Results indicate a radioactive binding yield of greater than 80% to the particles. The stability of the label was tested in in vivo and in vitro leaching studies. In these tests, the activity leaching rate was estimated to be less than 0.2% per day.

Chromium Radioisotopes↗

PubMed1998

Use of dried smooth lipopolysaccharide antigen coated polystyrene plates for diagnosis of bovine brucellosis by enzyme immunoassay.

Polystyrene plates (96 well) were sensitized with Brucella abortus smooth lipopolysaccharide (SLPS) antigen and then air dried at room temperature (RT) for about 1 hour to dry. Dryness was judged complete when a buffer meniscus was absent from the bottom of the well. The plates were resealed kept on the bench at RT for the duration of the study. Testing was done over 13 months by competitive and indirect ELISAs (C- and IELISA) for bovine antibody to B. abortus using panels of sera from B. abortus S19 vaccinated, unexposed and infected cattle. Testing revealed that consistent results were obtained over the test period suggesting that air drying may be a suitable alterative for storage of plates sensitized with some antigens, in particular, smooth lipopolysaccharide.

Animals↗

PubMedDate not supplied

Blocking of non-specific sorption in ELISA on formylated polystyrene beads.

The effect of pH of the blocking solution on the non-specific sorption of peroxidase conjugates to the 0.63-cm formylated polystyrene beads was studied. Anti-G-HRP and BSA-HRP sorption was shown to dramatically depend on pH of blocking protein solutions and was minimum at pH=pI. Sorption of G-HRP weakly depended on pH of the blocking buffer. The blocking efficiency of proteins on unmodified beads, as well as of Tween-20 on formylated beads appeared to be pH independent. The optimized blocking step resulted in a multiple decrease in the non-specific sorption of conjugates on formylated beads.

Adsorption↗

PubMedDate not supplied

Studies on the in vitro release characteristics of ibuprofen-loaded polystyrene microparticles.

Ibuprofen-loaded polystyrene microparticles were prepared by the emulsion-solvent evaporation process from an aqueous system. The effects of different parameters on the drug content and on the release of the drug from the microparticles were investigated. The drug content, in all the formulations, was less than the theoretical drug loading. The lower drug content was due to drug partitioning to the external aqueous phase during formulation. Statistical analysis revealed that the variation in the concentrations of the emulsion stabilizer and the organic disperse phase volume did not significantly alter the release of the drug. Although an increase in drug loading increased drug release from the microparticles, a biphasic linear relationship was observed between the time required for 50% drug release and the drug loading. The effect of size of the microparticles on drug release was more important for the low drug-loaded microparticles than that for the high drug-loaded microparticles. Such release behaviour from the microparticles was explained on the basis of the morphological structure of the microparticles.

Calorimetry, Differential Scanning↗

PubMedDate not supplied

Effect of production variables on the physical characteristics of ibuprofen-loaded polystyrene microparticles.

Ibuprofen-loaded polystyrene microparticles were prepared by the emulsion-solvent evaporation method from an aqueous system containing methylcellulose as the emulsion stabilizer. The effect of production variables on the formation and the physical characteristics of the microparticles were studied. While an increase in stirring speed, concentration of emulsion stabilizer up to a critical value and disperse phase volume decreased the mean diameter of the particles, increase in drug loading and concentrations of emulsion stabilizer beyond the critical value tended to increase in size. The microparticles, except those prepared at higher stirring speeds, and with higher disperse phase volumes and drug-loads, were found to be spherical.

Drug Carriers↗

PubMed2002

Platelet adhesion onto a polystyrene surface under static conditions: role of specific platelet receptors and effect of divalent cations.

An experimental model was used to elucidate the basic mechanisms involved in the interaction of platelets with an artificial surface. The role of divalent cations and the involvement of specific platelet membrane receptors were evaluated. Isolated platelets were allowed to interact with a polystyrene surface for 20 min in the presence of divalent cations (Ca2+, Mg2+ or Zn2+), a chelating agent (ethylenediaminetetraacetic, EDTA), and specific antibodies to the main platelet receptors, glycoproteins (GP) Ib and IIb-IIIa. The degree of platelet interaction was evaluated using light and electron microscopy. Morphometric analysis was performed to follow up the progression of platelet shape changes after surface activation. Neither Ca2+ nor Mg2+ influenced the number of adherent platelets or the degree of spreading on the polymer. Only Zn2+ induced a statistically significant increase in the rate of platelet adhesion (P<0.01) with higher proportion of fully spread platelets (P<0.01). Chelation of internal pools of divalent cations did not modify the rates of platelet adhesion but prevented platelet spreading. Presence of monoclonal antibodies to GPIb and GP IIb-IIIa did not result in significant differences in the studied parameters. These results suggest that platelet adhesion onto artificial surfaces, in the absence of flow and plasma proteins, is more dependent on cellular motility, where Zn2+ could play an important role, and less dependent on major receptorial mechanisms.

Antibodies, Monoclonal↗

PubMed1982

Monitoring of workers exposure to low levels of airborne monomers in a polystyrene production plant.

Exposure of workers to sub-ppm levels of airborne monomers, namely ethyl acrylate, methyl methacrylate, n-butyl acrylate, styrene, alpha-methylstyrene, and 2-ethylhexyl acrylate, in a polystyrene production plant was measured in the same sample on a single gas chromatographic column. The best separation and sensitivity were obtained with a 3 m X 3.175 mm stainless steel column packed with 10% FFAP on Chromosorb and a temperature programmed from 70 degrees C to 110 degrees C. A total of 106 air samples were collected on 150 mg charcoal tubes from the breathing zone of workers, from areas near reactors, and from places where monomers were unloaded from trucks and tank cars. Samples were analyzed in a manner similar to the method recommended by NIOSH. The mean TWA concentrations in a worker's breathing zone were 89, 66, 49, 120, 41 and 1 ppb for ethyl acrylate, methyl methacrylate, n-butyl acrylate, styrene, alpha-methylstyrene, and 2-ethylhexyl acrylate, respectively. The highest TWA breathing zone concentration was 14.8 ppm for styrene, which occurred during unloading and sampling of the monomer for a quality check. The mean TWA concentration of monomers in the air of the workplace were 1.1 ppm, 169, 36, 54, 10, and 30 ppb for the same 6 compounds mentioned above. The highest area TWA concentration was 57 ppm for ethyl acrylate, which occurred outdoors at the truck and tank car unloading site. It was concluded that use of two separate local exhaust ventilating systems in this polymerization process were effective in maintaining negative pressure within the reactors under all circumstances of use. These engineering controls and care in handling monomers have resulted in a relatively safe working environment.

Acrylates↗

PubMed1991

Internal wall losses of pharmaceutical dusts during closed-face, 37-mm polystyrene cassette sampling.

A current practice for the determination of personal exposures to dusts involves the aspiration of known quantities of air through membrane filters held in 37-mm plastic cassettes. Samples are collected with the cassettes in the closed-face configuration. A major negative bias error has been identified with this sampling procedure for low-level pharmaceutical dusts. For the pharmaceuticals studied, on average, 62% of the active dust collected in each sample was found on the inside surface of the cassette top. Only 22% of the total active ingredient of the dust was found on the filters. The remaining 16% was found on the inside of the cassette bottoms; electrostatic attraction appears to be the reason that pharmaceutical dusts adhere to the inside surface of the cassette. Adherence to the inside surfaces of the polystyrene cassette occurs without regard to the type of material used to seal the two-piece cassette together. The use of shrink wrap versus plastic tape versus using no sealing material had no effect on where or how much of the active ingredient was found on the inside cassette surfaces. Because very little active ingredient was identified in backup cassettes, it is hypothesized that the active ingredient found on the inside of the bottom portion of the cassettes (past the filter and support pad) got there by falling off the filter during filter removal from the cassette prior to analysis. To eliminate both of these errors, an internal cassette extraction procedure was developed that (1) negates the error caused by static charging and (2) eliminates the need for opening the cassettes prior to analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants, Occupational↗

PubMed2002

Preparation and sensitization of polystyrene latex beads by some antigens and antibodies. Factors affecting sensitivity and specificity of latex agglutination tests.

Polystyrene latex beads were polymerized at two different pH (7.3 and 9.5) and their ability to create latex agglutination systems were studied. Sensitization of these latexes by DNA, antibodies to C-reactive protein, myoglobin, and human IgG. was conducted. Sensitivity and specificity of these systems were compared. Practical recommendations are given for preparation of such systems.

Animals↗

PubMedDate not supplied

Total stepwise solid-phase peptide-oligonucleotide conjugate synthesis on macroporous polystyrene.

An efficient total stepwise solid-phase synthesis of oligonucleotide-peptide conjugates on a macroporous polystyrene is described. Extending our homoserine linker approach, we prepared a range of fluorescein-labelled conjugates containing one of two different peptides together with oligonucleotides containing 2'-deoxynucleoside or 2'-O-methylribonucleoside phosphodiesters, or gapmers containing 2'-deoxyphosphorothioate sequences flanked by 2'-O-methyl wings.

Amino Acid Sequence↗