Several different materials, including one which was porous, were studied to assess their properties as pacemaker electrode tips. Leads were implanted in sheep for periods up to one year. Electrical measurements were made during the implant period and histopathological examination performed after sacrifice. Although titanium vapor-deposited carbon, and silver did not lower the chronic stimulation threshold below that of platinum, their electrical characteristics were within generally acceptable limits. Zinc evoked a severe tissue reaction and a high threshold. Porous titanium alloy electrodes demonstrated reduced dislodgement, more frequent attachment and a lower sensing impedance than other electrodes. 相似文献
Poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) dispersions are synthesized via conventional oxidative polymerization under various synthetic (reaction times and formulations) and doping conditions (in situ and postpolymerization) with the introduction of dialysis as an additional purification step. Conductivities of films produced from these synthesized dispersions are one to three orders of magnitude higher than the equivalent commercial PEDOT/PSS reference film. In situ doped PEDOT/PSS dispersions give films that are more conductive than those doped postpolymerization. Optimum conductivity of 5.2 ± 0.7 S cm?1 is obtained from PEDOT/PSS dispersions (1:2.5 EDOT:PSS mass ratio) synthesized for 12 h with doping efficiency of 73%. Under these synthetic conditions, the film most likely has the optimal microstructure, i.e., optimal PEDOT chain length and ideal distribution and balance of PEDOT/PSS segments and free PSS chains, favoring charge transport and processability. Capillary electrophoresis is presented here as a novel method for measuring free and doped PSS in PEDOT/PSS dispersions.
Silver is increasingly being used in garments to exploit its antibacterial properties. Information on the presence of silver nanoparticles (AgNPs) in garments and their in vivo penetration across healthy and impaired skin from use is limited. We investigated the presence of AgNPs in a silver containing garment and in the stratum corneum (SC) of healthy subjects (CTRLs) and individuals with atopic dermatitis (AD). Seven CTRLs and seven AD patients wore a silver sleeve (13% Ag w/w) 8?h/day for five days on a forearm and a placebo sleeve on the other forearm. After five days, the layers of the SC were collected by adhesive tapes. The silver particles in the garment and SC were characterized by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) and atomic force microscopy (AFM). AFM and SEM revealed the presence of sub-micrometre particles having a broad range of sizes (30–500?nm) on the surface of the garment that were identified as silver. On the SC tapes collected from different depths, aggregates with a wide range of sizes (150?nm–2?μm) and morphologies were found. Most aggregates contained primarily silver, although some also contained chlorine and sulfur. There was no clear difference in the number or size of the aggregates observed in SC between healthy and AD subjects.After use, AgNPs and their aggregates were present in the SC at different depths of both healthy subjects and AD patients. Their micrometre size suggests that aggregation likely occurred in the SC. 相似文献
The purpose of this study was to evaluate the effect of mechanical retention by etching and chemical bonding by silanizing porcelain surfaces on their shear bond strength to etched enamel. The individual contributions of the two processes were compared with the bond strength obtained by the combined treatment. The effect of applying fit-checker paste to etched porcelain surface was also examined before and after re-etching. The 5 groups were compared between Mirage shade A2 (N=25) and Mirage shade 65 (N=25) porcelains. Following surface treatment of porcelain and resin bonding to etched enamel, the specimens were thermocycled 600 times between 5° and 55°C and debonded in shear mode. Results indicated that, overall, Mirage shade 65 porcelain was twice as strong as Mirage shade A2. However, the 5 treatment groups for each shade showed remarkable similarity, with the highest bond achieved by both etching and silanizing the porcelain. The bond strength from etching or silanizing alone was not significant. Use of a fit-checker paste lowered the bond strength, possibly by chemical contamination. There was no evidence of physical obliteration of the microporosities on the etched surface with the use of a silane coupling agent or the fit-checker if removed completely. It was concluded that optimum bond strength of porcelain to etched enamel is obtained by both etching and silanizing the surface. Caution should be exercised when using a silicone-based fit-checker paste. Further study is recommended. 相似文献
A simple, accurate, precise and sensitive potentiometric assay for the determination of acetycholine (Ach) in pure and biological samples is described. The method is based on the construction of an Ach sensor using carbon paste containing 1–10% (w/w) 2,3,6-trimethyl o-β-cyclodextrin doped as an ionophore with tricresyl phosphate (TCP) (a plasticizer) and potassium tetrakis-p-chlorophenyl borate (TKB). The increase in the potentiometric response of the carbon paste electrode CPE toward Ach is characterized by a slope of 57.4 ± 0.5 mV/decade in the range of 103–10?5 M Ach solution. The detection limit and correlation factors are calculated. The optimization of various experimental conditions is described. A successful application of the new CPE to determine Ach in the homogenates of cotton leaf worm “Spodoptera littoralis” is presented. 相似文献