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Glass Microspheres (glass + microsphere)
Selected AbstractsMechanical load induced by glass microspheres releases angiogenic factors from neonatal rat ventricular myocytes cultures and causes arrhythmiasJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 5b 2008D. Y. Barac Abstract In the present study, we tested the hypothesis that similar to other mechanical loads, notably cyclic stretch (simulating pre-load), glass microspheres simulating afterload will stimulate the secretion of angiogenic factors. Hence, we employed glass microspheres (average diameter 15.7 ,m, average mass 5.2 ng) as a new method for imposing mechanical load on neonatal rat ventricular myocytes (NRVM) in culture. The collagen-coated microspheres were spread over the cultures at an estimated density of 3000 microspheres/mm2, they adhered strongly to the myocytes, and acted as small weights carried by the cells during their contraction. NRVM were exposed to either glass microspheres or to cyclic stretch, and several key angiogenic factors were measured by RT-PCR. The major findings were: (1) In contrast to other mechanical loads, such as cyclic stretch, microspheres (at 24 hrs) did not cause hypertrophy. (2) Further, in contrast to cyclic stretch, glass microspheres did not affect Cx43 expression, or the conduction velocity measured by means of the Micro-Electrode-Array system. (3) At 24 hrs, glass microspheres caused arrhythmias, probably resulting from early afterdepolarizations. (4) Glass microspheres caused the release of angiogenic factors as indicated by an increase in mRNA levels of vascular endothelial growth factor (80%), angiopoietin-2 (60%), transforming growth factor-, (40%) and basic fibroblast growth factor (15%); these effects were comparable to those of cyclic stretch. (5) As compared with control cultures, conditioned media from cultures exposed to microspheres increased endothelial cell migration by 15% (P<0.05) and endothelial cell tube formation by 120% (P<0.05), both common assays for angiogenesis. In conclusion, based on these findings we propose that loading cardiomyocytes with glass microspheres may serve as a new in vitro model for investigating the role of mechanical forces in angiogenesis and arrhythmias. [source] Curing behavior and mechanical properties of hollow glass microsphere/bisphenol a dicyanate ester compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Jinhe Wang Abstract Hollow glass microsphere (HGS)/bisphenol A dicyanate ester (BADCy) composites have been prepared by mechanical mixing, followed by a stepped curing process. The effect of HGS on the curing behavior of BADCy was studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The mechanical properties of the composites were examined by mechanical tests, and the improvements of the mechanical properties were investigated by scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). The results show that HGS is catalytic for the polycyclomerization of the BADCy, which is advantageous to reduce the maximal processing temperature. The impact strength, flexural strength, flexural modulus and storage modulus of BADCy are improved. The improvements of the mechanical properties without sacrificing thermal properties, the ability of lowing processing temperature and the low cost make HGS good filler for cyanate ester resin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Short-Range Structure of Yttrium Alumino-Silicate Glass for Cancer Radiotherapy: Car,Parrinello Molecular Dynamics Simulations,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Jamieson K. Christie We present Car,Parrinello molecular dynamics (CPMD) simulations of yttrium alumino-silicate (YAS) glass. Alumino-silicate glass microspheres are used as vectors of yttrium radioisotopes in cancer radiotherapy; understanding in detail how yttrium is bound within the glass network is important to control the unwanted release of radioactive yttrium in the bloodstream. Our simulations, focused on a specific composition relevant to practical applications, show that silicon and aluminum form a disordered glass network, where Si is mainly four-coordinated, whereas, Al is mainly four- and five-coordinated. Yttrium cations have a network-modifying role, disrupting the alumino-silicate network by breaking Si(Al)O bonds and coordinating the resulting non-bridging oxygens (NBO). The local environment of yttrium in the glass turns out to be rather flexible: between five and eight oxygen atoms, with a marked predominance of NBO, are found coordinated to a central Y cation, leading to a corresponding broad and multimodal distribution of OYO angles. [source] Mechanical load induced by glass microspheres releases angiogenic factors from neonatal rat ventricular myocytes cultures and causes arrhythmiasJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 5b 2008D. Y. Barac Abstract In the present study, we tested the hypothesis that similar to other mechanical loads, notably cyclic stretch (simulating pre-load), glass microspheres simulating afterload will stimulate the secretion of angiogenic factors. Hence, we employed glass microspheres (average diameter 15.7 ,m, average mass 5.2 ng) as a new method for imposing mechanical load on neonatal rat ventricular myocytes (NRVM) in culture. The collagen-coated microspheres were spread over the cultures at an estimated density of 3000 microspheres/mm2, they adhered strongly to the myocytes, and acted as small weights carried by the cells during their contraction. NRVM were exposed to either glass microspheres or to cyclic stretch, and several key angiogenic factors were measured by RT-PCR. The major findings were: (1) In contrast to other mechanical loads, such as cyclic stretch, microspheres (at 24 hrs) did not cause hypertrophy. (2) Further, in contrast to cyclic stretch, glass microspheres did not affect Cx43 expression, or the conduction velocity measured by means of the Micro-Electrode-Array system. (3) At 24 hrs, glass microspheres caused arrhythmias, probably resulting from early afterdepolarizations. (4) Glass microspheres caused the release of angiogenic factors as indicated by an increase in mRNA levels of vascular endothelial growth factor (80%), angiopoietin-2 (60%), transforming growth factor-, (40%) and basic fibroblast growth factor (15%); these effects were comparable to those of cyclic stretch. (5) As compared with control cultures, conditioned media from cultures exposed to microspheres increased endothelial cell migration by 15% (P<0.05) and endothelial cell tube formation by 120% (P<0.05), both common assays for angiogenesis. In conclusion, based on these findings we propose that loading cardiomyocytes with glass microspheres may serve as a new in vitro model for investigating the role of mechanical forces in angiogenesis and arrhythmias. [source] Processing of Lightweight, High-Strength Porcelains Using an Alumina Cement to Replace Feldspars and ClaysJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2000Weon-Pil Tai New lightweight, high-strength porcelain bodies, using only nonplastic raw materials such as glass microspheres, quartz, and alumina cement, were fabricated and the effect of quartz particle size was investigated. Decreases in the green strength, relative to an increasing content of glass microspheres, were attributed to the decrease in the density and the relative decrease in the volume of alumina cement. The phases in the fired body were glass, ,-quartz, cristobalite, anorthite, and a small amount of ,-alumina. The large quartz particles (10,32 ,m in size) could not be densified to closed porosity, because of underfiring, whereas smaller quartz particles (4,10 ,m in size) permitted densification to closed porosity at 1300°C. The high flexural strength when using medium-sized quartz particles (6,20 ,m, content of 30 wt%) was attributed to a stronger prestress and higher density that was due to better vitrification. [source] Whispering gallery modes in silicon nanocrystal coated microcavitiesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009P. Bianucci Abstract We present photoluminescence studies of silicon-nanocrystal (Si-NC) coated microcavities. The particular geometries studied are hollow fibers where there is a Si-NC coating in the inner surface and regular optical fibers and glass microspheres where the coating is on the outside surface. The coatings were prepared using an inexpensive and straightforward solution-based process that yields a high-quality film. The measured photoluminescence spectra from the resonators show high Q -factor (between 1200 and 2800) resonant modes that correspond with the whispering gallery modes expected from the confinement geometries. The presence of these modes is also an indication that the emission of the Si-NCs is coupled to the cavity. The combination of Si-NCs and optical microcavities with strong confinement has promising potential for applications like sensing, optical communications and may be a possible route toward a Si-NC laser. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||