2,845 research outputs found

    Expression levels of vascular endothelial growth factors A and C in patients with peptic ulcers and gastric cancer

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    Purpose: Vascular endothelial growth factor (VEGF) is one of the most important growth factors for metastatic tumors. To clarify the role of VEGF-A and C in patients with peptic ulcer disease (PUD) or gastric cancer (GC), we evaluated the expression levels of these two molecules. We also analyzed the effect of Helicobacter pylori infection on VEGF-A and C expression levels

    Development of a Self-assembly Technique for Drug-Delivering Hydroxyapatite Coatings for Ti-Based Implants

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    PhD 2010 QMTo facilitate the long term osteointegration of Ti implants of various forms, methods aiming to facilitate hydroxyapatite deposition and enhance its adhesion to the Ti surfaces have to be developed. This work investigates the novel route of Ti surface functionalization with self-assembled monolayers (SAMs) in order to facilitate hydroxyapatite deposition and strengthen its bonding with the Ti surface and further equip the surface with localized antibiotic delivery to combat post-implantation infections. The main findings demonstrate that the formation of SAMs on non-model Ti substrates is challenging, since it requires the simultaneous control of many factors to achieve a densely packed well-organized SAM on a large surface area. By pre-treating the substrate with techniques such as electropolishing, the initial surface contamination can be kept at minimum while the hydroxylated surface remains smooth for the formation of well-oriented SAMs. Hence, after electropolishing, the Ti surface could be functionalized with molecules carrying reactive or neutral groups to facilitate hydroxyapatite deposition and/or antibiotic immobilization. Such a surface functionalization is found to facilitate hydroxyapatite deposition. The hydroxyapatite formed on SAM-modified Ti surfaces is made of small crystals of 6 nm and a 12 μm thick hydroxyapatite film, which can grow in 1 month. The SAM modified surfaces are covered with hydroxyapatite spheres in less than 7 days, while no spheres are observed on the unmodified Ti surface under similar conditions. Enhanced hydroxyapatite deposition rates on SAM-modified surfaces are explained by a decrease of nucleation barrier for hydroxyapatite. Additionally, preliminary investigations demonstrate the possibility of further functionalizing the Ti surface to allow the immobilization of antibiotic (Ciprofloxacin here) simultaneously with hydroxyapatite growth. The release of Ciprofloxacin was found to occur after 1 day and continue up to 20 days. The combination of these two functionalities on the Ti surfaces could find applications in load-bearing implants

    Modeling and Propagation of Noisy Waveforms in Static Timing Analysis

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    A technique based on the sensitivity of the output to input waveform is presented for accurate propagation of delay information through a gate for the purpose of static timing analysis (STA) in the presence of noise. Conventional STA tools represent a waveform by its arrival time and slope. However, this is not an accurate way of modeling the waveform for the purpose of noise analysis. The key contribution of our work is the development of a method that allows efficient propagation of equivalent waveforms throughout the circuit. Experimental results demonstrate higher accuracy of the proposed sensitivity-based gate delay propagation technique, SGDP, compared to the best of existing approaches. SGDP is compatible with the current level of gate characterization in conventional ASIC cell libraries, and as a result, it can be easily incorporated into commercial STA tools to improve their accuracy.Comment: Submitted on behalf of EDAA (http://www.edaa.com/
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