Static pentane extraction as a potential alternative to Soxhlet extraction for polypropylene olive oil overall migration limit measurements

Static pentane extraction of olive oil from polypropylene was evaluated as a safer, higher throughput alternative to pentane Soxhlet extraction for the recovery of olive oil from polypropylene for overall migration limit determinations. Static, ambient temperature, pentane extraction achieved quantitative recovery of olive oil from polypropylene plaques prepared by using the OM‐5 overall migration limit protocol. In addition to validation data for static extractions, a modified esterification procedure is presented as a means to accommodate the larger sample sets that are enabled with static extraction.     

PEDOT:PSS nano-gels for highly electrically conductive silver/epoxy composite adhesives

In this work, we report a methanol-facilitated approach to directly use aqueous Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate) (PEDOT:PSS) in the silver/epoxy composites for preparation of highly electrically conductive adhesives (ECAs) and an investigation of the interaction between PEDOT:PSS nano-gels and silver microflakes. PEDOT:PSS nano-gel (18?<?d?<?30 nm) aqueous dispersion is immiscible with epoxy resin and difficult to incorporate into the conventional silver-filled ECAs. To overcome this challenge, we used methanol to facilitate the dispersion of PEDOT:PSS and silver microflake in epoxy resin. The synergetic interactions between PEDOT:PSS and silver and the effect of methanol were investigated using dynamic light scattering (DLS), atomic force microscopy, Kelvin probe force microscopy, and scanning electron microscope. When PEDOT:PSS was exposed to methanol, its morphology changed from coil to coil/linear structure; the contact potential difference between silver microflake and PEDOT:PSS increased from 9.47 to 22.56 mV, showing an increased conductivity between PEDOT:PSS and silver microflake. It was found that the introduction of a small amount of PEDOT:PSS (0.1 wt%) to the conventional ECA with 60 wt% silver microflake remarkably improved the electrical conductivity from 104 to 386 S/cm. A significantly high conductivity of 2526 S/cm was achieved by further increasing the PEDOT:PSS concentration to 1 wt%. The impact of PEDOT:PSS on the adhesive bonding strength towards copper substrate was also examined; the bonding strength slightly decreased when <?1 wt% PEDOT:PSS was used, but abruptly dropped when PEDOT:PSS content was further increased beyond 1 wt%. The incorporation of the optimal 1 wt% PEDOT:PSS into conventional ECAs with 60% silver microflake greatly increased the electrical conductivities by 25 times with limited impact on the shear strength. The results provide insights to the synergetic interplay of conductive polymer and metallic fillers, and might have profound technical implications on the development of advanced conductive composites.     

Thermal characteristics of unsaturated dicarboxylic acid durable press finishing systems

Thermoanalytical (TA) studies including differential scanning calorimetric (DSC) and thermogravimetric (TG) analyses were carried out to measure characteristics of dried mixtures based on two unsaturated polycarboxylic acids. Model 9% treatment (pad) solutions of maleic (M) and/or itaconic (I) acid, with and without potassium peroxydisulfate (K) as the free-radical initiator, were prepared with sodium hypophosphite (H) as the catalyst and vacuum oven-dried. DSC thermograms varied with each component; even the presence of a small amount of component K was evident. TG residue production and maximum rates of weight loss were the most useful thermal parameters. Residue/rate factors, used previously as predictors, were calculated. Previous studies indicated that high residues and low rates were indicators of combinations of reactants that resulted in good durable press treatments for fabrics. Residue/rate factors were used to rank the six mixtures that reflect actual fabric treatment combinations: MH, IH, MIH, and those same three with the initiator present. Rankings indicated that the presence of the initiator significantly increased the residue/rate factor for IHK and for MIHK. The presence of the initiator appears more beneficial to itaconic acid than to maleic acid. The rankings by the TA predictor agreed with textile properties measuring appearance and strength. © 1994 John Wiley & Sons, Inc.     

Effect of water on the strength of filled polychloroprene vulcanizates

Three commercial rubber compounds used in marine applications were immersed in water or in 3.5% NaCl solution for up to 250 days. Tear strengths, measured with the “trousers” test piece, decreased in the order dry > salt water exposed > fresh water exposed, and changes of up to 50% were seen. Tensile strengths also decreased, but not always in the same proportion, suggesting a possible change in structure of the voids which initiate fracture. Results are discussed in terms of osmotic swelling and extraction of rubber components.     

Effect of disinfectant solutions on gutta-percha and resilon cones

The aim of this study was to evaluate the effects of the 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and MTAD solutions on the surface of gutta‐percha and Resilon cones by using atomic force microscopy (AFM). Accessory cones were washed and dried. The cones were randomly divided into six groups: gutta‐percha immersed in NaOCl, CHX, and MTAD, and Resilon immersed in NaOCl, CHX, and MTAD. AFM images of the same area were made in different periods of time. JPK? Image Processing Software was used to evaluate the images. The parameters used to evaluate the changes were RMS and line profiles. No statistically significant change was observed in the RMS values. The line profiles detected changes only for gutta‐percha surfaces after immersion in NaOCl and MTAD solutions. In conclusion, 5.25% NaOCl and MTAD are associated with local changes in surface roughness of gutta‐percha cones. No change was observed when 2% CHX was used. The use of all tested solutions did not produce any changes on Resilon surface. Microsc. Res. Tech. 75:791–795, 2012. © 2012 Wiley Periodicals, Inc.     

Doxorubicin eluting beads—2: methods for evaluating drug elution and in-vitro:in-vivo correlation

DC Bead™ is a sulfonate-modified, PVA-based microspherical embolisation agent approved for the treatment of hypervascular tumours and arterio-venous malformations. The beads have previously been shown to actively sequester oppositely charged drugs, such as doxorubicin hydrochloride (dox) by an ion-exchange mechanism. In order to characterise the release kinetics and predict the in vivo behaviour of drug eluting beads (DEB), two elution methods were utilised. The first, an application of the USP dissolution method Type II - Apparatus, enables study of the complete elution of loaded DC Bead in less than 4 h, allowing relatively rapid comparison to be made between different products and formulations. Release data obtained using this method were fitted to first order kinetics (R ² > 0.998) and the elution constants shown to increase with the total surface area of the beads exposed to the elution medium. Diffusion coefficients were calculated adopting the Fickian diffusion model, which predicted slow elution rates under physiological conditions. The second method involved the use of a T-Apparatus where the drug experiences an element of diffusion through a static environment. This method was developed to resemble the in vivo situation in embolisation procedures more closely. Slow release of dox from DC Bead with half-lives over 1,500 h were predicted for all size ranges using a slow release model. A strong linear relationship was found between the release data from T-Apparatus and pharmacokinetic data obtained from patients treated with DC Bead loaded with dox in transarterial chemoembolisation (TACE) procedures. These data indicated a Level A in vitro–in vivo correlation (IVIVC) for the first 24 h post embolisation. Both systems developed were automated and good reproducibility was obtained for all samples, demonstrating the usefulness of these elution techniques for product development and comparative testing.     

Estimation of the strength of adhesion between a thermoresponsive polymer coating and nitinol wire

As polymer coatings become more widely used in the biomedical device industry, both to improve biocompatibility and as coatings for localised drug delivery, quantitative methods to measure the adhesive strength between coatings and substrates become a very important consideration. The aim of this study was to take a method for estimating the interfacial fracture toughness of a film to a flat substrate and apply it to Nitinol wires used in the production of medical devices. An investigation into the affect of surface roughness on the fracture toughness was also conducted. For the present study, a thermoresponsive based Poly (N-isopropylacrylamide) polymer was coated onto nitinol wire substrates and the adhesion strength between the polymer and wire was measured using a nanoindentation technique. Different surface treated nitinol wires, with different surface topography and roughness were used, and the affect of these surface properties on adhesion strength was investigated. Results showed that it was possible to apply the delamination technique to wire samples and obtain fracture toughness values. Results also showed that the surface roughness is an important parameter that can affect the adhesion between a coating and the substrate. It was found that, as the average surface roughness increased so also did the adhesive strength between the coating and wire sample.     

Electrocatalytic hydrogen gas generation by cobalt molybdenum disulfide (CoMoS2) synthesized using alkyl-containing thiomolybdate precursors

Cobalt molybdenum disulfide, (CoMoS₂) catalysts are evaluated as active electrocatalysts for the production of hydrogen gas in acidic aqueous media. These highly-active hydrogen evolution reaction (HER) catalysts are obtained from pretreatment of ammonium tetrathiomolybdate (ATM) with different amines precursors, and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and their surface areas are determined by Brunauer–Emmett–Teller (BET) surface area analyses. Electrochemical studies indicate that these CoMoS₂ materials exhibit enhanced catalytic performance for hydrogen gas production with overpotentials ranging from 0.127 to 0.144 V, which are significant less than CoMoS₂ synthesized directly from ATM under the same synthetic techniques (0.173 V). These CoMoS₂ catalysts are also stable in the presence of strong acidic media after a considerably long period of time (10 h) for maintaining their efficiencies for hydrogen gas evolution.     

Pt/C containing different platinum loadings for use as electrocatalysts in alkaline PBI-based direct glycerol fuel cells

This study shows the influence of the Pt percentage in Pt catalysts (Pt/C) on their application in Direct Glycerol Fuel Cells (DGFC). Catalysts with 20, 30, 40 and 60% Pt were prepared by formic acid reduction. X-Ray Diffraction (XRD) confirmed the formation of Pt fcc nanocrystals (with average sizes between 3 and 4 nm). Thermogravimetric analysis (TGA) corroborated the Pt loadings and the Transmission Electron Microscopy (TEM) images show a homogeneous distribution of the Pt nanoparticles, with larger particles at higher Pt percentages. Electrochemical measurements reveal that higher Pt percentages promote the activity of the glycerol electroxidation reaction, resulting in lower onset potentials, higher current densities and reduced poisoning of the Pt surface. Single cell tests confirm these results, with greater maximum power density at higher Pt percentages, although the glycerol crossover effect starts to become significant in the 60% Pt/C catalyst, owing to the reduced thickness of this catalytic layer. A final product selectivity analysis indicates that tartronate is the preferential glycerol electroxidation product, along with glycerate and oxalate in lower proportions, with minor amounts of glycolate and mesoxalate. In general, a thicker catalytic layer is associated with the formation of more oxidized products.     

A highly conserved intraspecies homolog of the Saccharomyces cerevisiae elongation factor-3 encoded by the HEF3 gene

A paralog (intraspecies homolog) of the Saccharomyces cerevisiae YEF3 gene, encoding elongation factor-3, has been sequenced in the course of the yeast genome project, and identified by database searching; this gene has been designated HEF3. Bioinformatic and Northern blot analysis indicate that the HEF3 gene is not expressed during vegetative growth. Deletion of the HEF3 gene reveals no growth defects, nor any defects in mating or sporulation. A high copy 2μ clone of HEF3 was constructed, and was shown to be unable to complement a null allele of yef3. Finally, an in vitro assay for ribosome-stimulated ATPase activity was performed with isogenic HEF3 and Δhef3 strains; no difference in biochemical activity could be detected in these strains. From these results, we conclude that the HEF3 gene does not encode a functional homolog of YEF3. © 1998 John Wiley & Sons, Ltd.