895 resultados para Anticorrosion coating


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OBJECTIVES This study sought to study the efficacy and safety of newer-generation drug-eluting stents (DES) compared with bare-metal stents (BMS) in an appropriately powered population of patients with ST-segment elevation myocardial infarction (STEMI). BACKGROUND Among patients with STEMI, early generation DES improved efficacy but not safety compared with BMS. Newer-generation DES, everolimus-eluting stents, and biolimus A9-eluting stents, have been shown to improve clinical outcomes compared with early generation DES. METHODS Individual patient data for 2,665 STEMI patients enrolled in 2 large-scale randomized clinical trials comparing newer-generation DES with BMS were pooled: 1,326 patients received a newer-generation DES (everolimus-eluting stent or biolimus A9-eluting stent), whereas the remaining 1,329 patients received a BMS. Random-effects models were used to assess differences between the 2 groups for the device-oriented composite endpoint of cardiac death, target-vessel reinfarction, and target-lesion revascularization and the patient-oriented composite endpoint of all-cause death, any infarction, and any revascularization at 1 year. RESULTS Newer-generation DES substantially reduce the risk of the device-oriented composite endpoint compared with BMS at 1 year (relative risk [RR]: 0.58; 95% confidence interval [CI]: 0.43 to 0.79; p = 0.0004). Similarly, the risk of the patient-oriented composite endpoint was lower with newer-generation DES than BMS (RR: 0.78; 95% CI: 0.63 to 0.96; p = 0.02). Differences in favor of newer-generation DES were driven by both a lower risk of repeat revascularization of the target lesion (RR: 0.33; 95% CI: 0.20 to 0.52; p < 0.0001) and a lower risk of target-vessel infarction (RR: 0.36; 95% CI: 0.14 to 0.92; p = 0.03). Newer-generation DES also reduced the risk of definite stent thrombosis (RR: 0.35; 95% CI: 0.16 to 0.75; p = 0.006) compared with BMS. CONCLUSIONS Among patients with STEMI, newer-generation DES improve safety and efficacy compared with BMS throughout 1 year. It remains to be determined whether the differences in favor of newer-generation DES are sustained during long-term follow-up.

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Superparamagnetic iron oxide nanoparticles for biomedical applications are usually coated with organic molecules to form a steric barrier against agglomeration. The stability of these coatings is well established in the synthesis medium but is more difficult to assess in physiological environment. To obtain a first theoretical estimate of their stability in such an environment, we perform density functional theory calculations of the adsorption of water, polyvinyl alcohol (PVA) and polyethylene glycol (PEG) coating molecules, as well as the monomer and dimer of glycine as a prototype short peptide, on the (110) surface of magnetite (Fe3O4) in vacuo. Our results show that PVA binds significantly stronger to the surface than both PEG and glycine, while the difference between the latter two is quite small. Depending on the coverage, the wateradsorption strength is intermediate between PVA and glycine. Due to its strongly interacting OH side groups, PVA is likely to remain bound to the surface in the presence of short peptides. This stability will have to be further assessed by molecular dynamics in the solvated state for which the present work forms the basis.

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Purpose: The purpose of this study was to evaluate the bone formation capability of polyetheretherketone (PEEK) and carbon fiber-reinforced PEEK (CFR-PEEK) implants coated with different titanium and hydroxyapatite plasma-sprayed layers after 2 and 12 weeks. Methods: In six sheep 108 implants were placed in the pelvis. Altogether six different surface modifications were tested. After 2 and 12 weeks, n = 3 implants per group were examined histologically and n = 6 implants per group were tested by a pull-out test. Results: Biomechanically (p = 0.001) as well as histologically (p > 0.05) surface coating of PEEK/CFR-PEEK led to an increase of osseointegration from 2 to 12 weeks. After 12 weeks, coated implants demonstrated significant (p < 0.001) higher pull-out values in comparison to uncoated implants. Overall, the double coating (titanium bond layer and hydroxyapatite top layer) showed the most favorable results after 2 and 12 weeks. Conclusions: Plasma-sprayed titanium and hydroxyapatite coatings on PEEK or CFR-PEEK demonstrated a significant improvement of osseointegration.

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A set of optimized deposition conditions for the inner wall coating of fused silica tubes with amorphous selenium was elaborated. The method is based on the vapor transport deposition of pure elemental selenium on a cooled substrate held at liquid nitrogen temperatures. Morphological and structural examination of the deposited layer was performed by optical microscopy and X-ray diffraction studies. Neutron activated selenium was used to monitor the deposition pattern and its stability under high gas flows. Monte Carlo simulations allowed the estimation of the different Se species composing the amorphous phase, at the given experimental deposition conditions. The versatility of the coating method presented in this work allows for the coating of tubes of different lengths and diameters, opening the way for several applications of amorphous selenium films in various fields.

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Ferromanganese coatings have been found on glacial erratics in Lydonia Canyon, off the United States northeastern coast. The coatings, which are about 17 µm thick, consist of an outer manganese-rich layer which covers the top of the erratic, a middle transitional layer, and an internal iron-rich layer that encircles the entire surface of the erratic. Chemical analyses of the coatings, when compared with similar data on abyssal marine ferromanganese deposits, reveal comparable Mn/Fe ratios, higher P and Ti concentrations, and an order of magnitude less of Co, Ni, Cu, and most other metals. A comparison of the Lydonia Canyon coatings with desert varnishes reveals obvious chemical, mineralogical, and morphological differences.

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The influence of nanosecond laser pulses applied by laser shock peening without absorbent coating (LSPwC) with a Q-switched Nd:YAG laser operating at a wavelength of λ = 1064 nm on 6082-T651 Al alloy has been investigated. The first portion of the present study assesses laser shock peening effect at two pulse densities on three-dimensional (3D) surface topography characteristics. In the second part of the study, the peening effect on surface texture orientation and micro-structure modification, i.e. the effect of surface craters due to plasma and shock waves, were investigated in both longitudinal (L) and transverse (T) directions of the laser-beam movement. In the final portion of the study, the changes of mechanical properties were evaluated with a residual stress profile and Vickers micro-hardness through depth variation in the near surface layer, whereas factorial design with a response surface methodology (RSM) was applied. The surface topographic and micro-structural effect of laser shock peening were characterised with optical microscopy, InfiniteFocus® microscopy and scanning electron microscopy (SEM). Residual stress evaluation based on a hole-drilling integral method confirmed higher compression at the near surface layer (33 μm) in the transverse direction (σmin) of laser-beam movement, i.e. − 407 ± 81 MPa and − 346 ± 124 MPa, after 900 and 2500 pulses/cm2, respectively. Moreover, RSM analysis of micro-hardness through depth distribution confirmed an increase at both pulse densities, whereas LSPwC-generated shock waves showed the impact effect of up to 800 μm below the surface. Furthermore, ANOVA results confirmed the insignificant influence of LSPwC treatment direction on micro-hardness distribution indicating essentially homogeneous conditions, in both L and T directions.

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We present the possibility of a low work-function material, calcium aluminate electride, being used for a coating on a bare electrodynamic tether system. Analyses suggest that the coating would eliminate the need for an active cathodic device like a hollow cathode and, consequently, eliminate the need for an expellant to the hollow cathode, thus resulting in an electrodynamic tether system that requires no consumables. Applications include on-orbit power generation and deorbiting debris from low Earth orbit in a simple and trouble-free manner.

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During fertilization in marine invertebrates, fusion between sperm and egg cell membranes occurs at the tip of the sperm acrosomal process. In abalone sperm the acrosomal process is coated with an 18-kDa protein. In situ, this protein has no effect on the egg vitelline envelope, but in vitro it is a potent fusagen of liposomes. Thus, the 18-kDa protein may mediate membrane fusion between the gametes, a step in gamete recognition known to restrict heterospecific fertilization in other species. The cDNA and deduced amino acid sequences of the 18-kDa protein were determined for five species of California abalone. The deduced amino acid sequences exhibit extraordinary divergence; the percent identity varies from 27% to 87%. Analysis of nucleotide substitution shows extremely high frequencies of amino acid-altering substitution compared to silent substitution, demonstrating that positive Darwinian selection promotes the divergence of this protein. However, amino acid replacement is conservative with respect to size and polarity of residue. The data support the developing idea that in free-spawning marine invertebrates, the proteins mediating fertilization may be subjected to intense, and as yet unknown, selective forces. The extraordinary divergence of fertilization proteins may be related to the establishment of barriers to heterospecific fertilization.

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A chemical sensor based on a coated long-period grating has been prepared and characterized. Designer coatings based on polydimethylsiloxane were prepared by the incorporation of diphenylsiloxane and titanium cross-linker in order to provide enhanced sensitivity for a variety of key environmental pollutants and optimal refractive index of the coating. Upon microextraction of the analyte into the polymer matrix, an increase in the refractive index of the coating resulted in a change in the attenuation spectrum of the long-period grating. The grating was interrogated using ring-down detection as a means to amplify the optical loss and to gain stability against misalignment and power fluctuations. Chemical differentiation of cyclohexane and xylene was achieved and a detection limit of 300 ppm of xylene vapour was realized.