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Best Improvement (best + improvement)
Selected AbstractsProperty enhancement of epoxy resins by using a combination of polyamide and montmorilloniteADVANCES IN POLYMER TECHNOLOGY, Issue 4 2007M. Bakar Abstract A bisphenol-A epoxy resin cured with triethylenetetramine was modified with the addition of a polyamide oligomer and a small amount of montmorillonite. Compositions with different amounts of modifiers were obtained and tested for their impact strength, flexural strength, and resistance to crack propagation. The latter was assessed by measuring the critical stress intensity factor in a three-point bending mode. Scanning electron microscopy was used to examine the sample fracture surfaces. It was found that the addition of 2% montmorillonite or 5% polyamide resulted in the best improvement of the impact strength and the critical stress intensity factor relative to the unmodified epoxy resin. However, the flexural strength and toughness measured under three-point bending mode was found to increase to a lesser extent. Hybrid compositions containing specific combinations of both modifier and nanofiller not only exhibited a higher impact strength and resistance to crack propagation but also displayed a synergistic effect in relation to the fracture energy. The results indicate that the improvement in mechanical properties of the epoxy resin was due to the formation of a heterogeneous morphology resulting from phase separation of the polymeric modifier. From the scanning electron microscopy and thermal analysis, it appears that the toughening may arise from chemical reactions that have taken place between the epoxy resin and the polymeric modifier, which was partially solubilized in the resin matrix. © 2008 Wiley Periodicals, Inc. Adv Polym Techn 26:223,231, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20103 [source] USE OF CLARIFYING AGENTS AND ULTRA FILTER TO DECREASE FUMARIC ACID, HMF AND INCREASE CLARITY OF APPLE JUICEJOURNAL OF FOOD QUALITY, Issue 3 2006YAHYA TULEK ABSTRACT In this study, the effects of eight different processing treatments of apple juice (AJ) production (Process 1: Ultra filtration [UF], Process 2: Activated charcoal [AC], Process 3: polyvinylpolypyrolidone [PVPP], Process 4: Gelatine [G] + Bentonite [B], Process 5: [G + B] + UF, Process 6: [G + B] + AC, Process 7: [G + B] + PVPP and Process 8: [G + B] + Kieselguhr [K]) on the fumaric acid (FA), hydroxymethylfurfural (HMF), color and clearness values of AJ were investigated. With the exception of Processes 1 and 5, AC, K, PVPP, G and B were used at various doses in other processes. FA, HMF, color and clearness values of control sample were determined as 3.24 mg/L, 3.84 mg/L, 48.5 (%T) and 94.1 (%T), respectively. The highest proportional decrement in FA and HMF values of the samples were observed with Process 6 at the level of 5. The fifth level of Process 6 resulted in 35.8% (3.24,2.08 mg/L) and 35.9% (3.84 to 2.46 mg/L) reductions in FA and HMF values, respectively. On the other hand, the best improvement in clearness of AJ was obtained with Process 6 at the fourth level and obtained as 98.9 (%T). [source] Evaluation of MR angiography at 7.0 Tesla MRI using birdcage radio frequency coils with end capsMAGNETIC RESONANCE IN MEDICINE, Issue 2 2008Chang-Ki Kang Abstract The purpose of this study was to evaluate the feasibility of MR angiography (MRA) at 7.0 Tesla (T) using optimized birdcage (BC) coils with simple end cap configurations. Shielded 16-rung high-pass BC coils were built with identical geometry and compared with different sizes and locations of end caps. To determine whether the end cap configuration was effective, the signal intensity profiles along the superior,inferior (S,I) direction were analyzed in phantom and in vivo human experiments. The effects were also investigated in two-dimensional (2D) and three-dimensional (3D) time-of-flight (TOF) MRA experiments. The signal intensity profiles showed that B1 homogeneity at the service end, that is, the end cap side, was improved as the diameter of the end caps increased and the end cap became closer to the coil end ring. The results of 2D and 3D TOF experiments showed the best improvement of vessel visibility at the BC coil with an 80% end cap, when compared with BC coils with other end cap sizes or without an end cap. In conclusion, the BC coil with an end cap was effective for improving S,I directional homogeneity and suitable for MRA applications, especially at ultrahigh field MRI, such as 7.0T. Magn Reson Med 60:330,338, 2008. © 2008 Wiley-Liss, Inc. [source] Transluzente oxidfaserverstärkte Glasmatrix-VerbundwerkstoffeMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 7 2003P. Fehling glass composites; fiber coating; atomic force microscopy; chemical vapour deposition Abstract Das Ziel der Untersuchungen ist die Entwicklung von transparenten Glasmatrix-Kompositen. Neben den mechanischen müssen dazu auch die optischen Eigenschaften der Komponenten aneinander angepaßt werden. Der Einfluß unterschiedlicher Faserbeschichtungen (Bornitrid-, Titandioxid-Einzelbeschichtung oder Bornitrid/Titandioxid-Doppelbeschichtung) auf die mechanischen und optischen Eigenschaften von Nextel 440-Faser verstärktem Glas wird untersucht. Mikromechanische Untersuchungen (push-in Tests) und 3-Punktbiegeversuche erbrachten die größte Verbesserung der Bruchzähigkeit für die Verbunde mit Bornitrid/Titandioxid-doppelbeschichteten Fasern. Die Verbunde mit Bornitrid bzw. Titandioxid Einzelschichten wurden durch Transmissionsmessungen im sichtbaren Spektralbereich charakterisiert. Translucent oxide fiber reinforced glasmatrix composites The aim of the work is the developement of transparent glass matrix composites. Therefore besides the mechanical properties also the optical properties of the components have to be adapted. In this study the influence of different fiber coatings (boron nitride, titanium oxide and a boron nitride/titanium oxide double coating) on the mechanical and optical properties of Nextel 440-fiber reinforced glass was investigated. Micromechanical investigations (push-in-tests) and 3-point-bending tests have shown the best improvement of the fracture toughness for the binary boron nitride/titanium oxide coating. For single coatings of boron nitride or titanium oxide the transparency was characterized by the transmission spectra. [source] Polystyrene,organoclay nanocomposites prepared by melt intercalation, in situ, and masterbatch methodsPOLYMER COMPOSITES, Issue 3 2006Ulku Yilmazer In this study, polystyrene (PS)/montmorillonite nanocomposites were prepared by melt intercalation, in situ polymerization, and masterbatch methods. In the masterbatch method, as the first step, a high clay content composite of PS,organoclay (masterbatch) was prepared by in situ polymerization, and then the prepared masterbatch was diluted to desired compositions with commercial PS in a twin-screw extruder. The structure and mechanical properties of the nanocomposites were examined. X-ray diffraction (XRD) analysis showed that the d -spacing of the in situ formed nanocomposites increased from 32.9 Å for the organoclay powder to 36.3 and 36.8 Å respectively in nanocomposites containing 0.73 and 1.6 wt% organoclay, indicating intercalation. However, the d -spacing of the other prepared materials remained nearly unchanged when compared with pure organoclay powder. Thus, at these low clay contents, in situ formed nanocomposites showed the best improvement in mechanical properties including tensile, impact strength, and Young's modulus. In situ polymerization method did not prove to be efficient at high clay loadings in terms of intercalation and mechanical properties. At high clay loadings, the effects of the three methods in promoting mechanical properties were not significantly different from each other. POLYM. COMPOS., 27:249,255, 2006. © 2006 Society of Plastics Engineers [source] Valorization of poly(butylene terephthalate) wastes by blending with virgin polypropylene: Effect of the composition and the compatibilizationPOLYMER ENGINEERING & SCIENCE, Issue 8 2008Najoua Barhoumi Blends of recycled poly(butylene terephthalate) (PBT) parts obtained from scrapped cars, and virgin polypropylene (PP), were prepared in a twin-screw extruder at different compositions. Selected compositions were also prepared with the presence of ethylene- co -glycidyl methacrylate copolymer (E-GMA) and ethylene/methyl acrylate/glycidyl methacrylate terpolymer (E-MA-GMA) compatibilizers. The effect of the composition and the type of compatibilizer, as well as the mixing conditions, on the morphology phase, thermal, viscoelastic behavior, and mechanical properties of the blends has been investigated. Blends PP/PBT of various composition exhibit a coarse morphology and a poor adherence between both phases, resulting in the decrease of ductility, whereas at weak deformation, PBT reinforced the tensile properties of PP. Addition of E-GMA and E-MA-GMA to the PP/PBT blend exhibited a significant change in morphology and improved ductility because of interfacial reactions between PBT end chains and epoxy groups of GMA that generate EG- g -PBT copolymer. Moreover, thermal and viscoelastic study indicated that the miscibility of PP and PBT has been improved further and the reactions were identified. The E-MA-GMA results in the best improvement of ductility. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Combining angiogenic gene and stem cell therapies for myocardial infarctionTHE JOURNAL OF GENE MEDICINE, Issue 9 2009Jennifer Pons Abstract Background Transplantation of stem cells from various sources into infarcted hearts has the potential to promote myocardial regeneration. However, the regenerative capacity is limited partly as a result of the low survival rate of the transplanted cells in the ischemic myocardium. In the present study, we tested the hypothesis that combining cell and angiogenic gene therapies would provide additive therapeutic effects via co-injection of bone marrow-derived mesenchymal stem cells (MSCs) with an adeno-associated viral vector (AAV), MLCVEGF, which expresses vascular endothelial growth factor (VEGF) in a cardiac-specific and hypoxia-inducible manner. Methods MSCs isolated from transgenic mice expressing green fluorescent protein and MLCVEGF packaged in AAV serotype 1 capsid were injected into mouse hearts at the border of ischemic area, immediately after occlusion of the left anterior descending coronary, individually or together. Engrafted cells were detected and quantified by real-time polymerase chain reaction and immunostaining. Angiogenesis and infarct size were analyzed on histological and immunohistochemical stained sections. Cardiac function was analyzed by echocardiography. Results We found that co-injection of AAV1-MLCVEGF with MSCs reduced cell loss. Although injection of MSCs and AAV1-MLCVEGF individually improved cardiac function and reduced infarct size, co-injection of MSC and AAV1-MLCVEGF resulted in the best improvement in cardiac function as well as the smallest infarct among all groups. Moreover, injection of AAV1-MLCVEGF induced neovasculatures. Nonetheless, injection of MSCs attracted endogenous stem cell homing and increased scar thickness. Conclusions Co-injection of MLCVEGF and MSCs in ischemic hearts can result in better cardiac function and MSC survival, compared to their individual injections, as a result of the additive effects of each therapy. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||