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991.
Cerium oxide is commonly added to silicate glasses as an optical property modifier. In particular, UV absorption, decoloration via redox coupling, and resistance to radiation-induced darkening are influenced by the addition of this rare-earth oxide. However, the limited solubility and visible color of rare-earth oxides in silicate glasses prevent any further beneficial enhancement of properties which might result from increasing the CeO2 content. In contrast, rare-earth oxides are extremely soluble in phosphate glasses; for example, a binary cerium phosphate glass can incorporate up to 40 mol% CeO2. Moreover, since the UV absorption edge of the phosphate network is blue-shifted compared to the silicate network, the effect of the Ce3+ absorption band tail on yellow coloration can be minimized.In this study, glasses in the cerium aluminosilicophosphate system were synthesized and a variety of physical and optical properties were measured including: density, refractive index, glass transition temperature, hardness, fracture toughness, and the location of the UV absorption edge. At ~9 mol% CeO2, these cerium aluminosilicophosphate glasses exhibit similar coloration to commercially available silicate glasses which contain ~0.4 mol% CeO2. Semi-quantitative photoemission analysis of the Ce oxidation states showed insignificant differences in the Ce3+/Ce4+ ratio between the phosphate and silicate glass systems. 相似文献
992.
Pietro Galinetto Maria Cristina Mozzati Marco Simone Grandi Marcella Bini Doretta Capsoni Stefania Ferrari Vincenzo Massarotti 《Journal of Raman spectroscopy : JRS》2010,41(10):1276-1282
Thermal stability and phase homogeneity of the triphylite LiFePO4 compound were investigated by means of Raman spectroscopy. A detailed check of phase homogeneity of undoped samples obtained from different preparation routes—hydrothermal, sol–gel, and solid state synthesis—and Mn‐doped compounds from solid‐state synthesis was performed by means of a mapping of the Raman spectra. The triphylite compositional and structural properties were carefully investigated also with the help of structural refinements and magnetic techniques, which also allowed us to reveal and identify the impurity phases formed together with the olivine LiFePO4. The effect of laser irradiation on the triphylite thermal stability was thoroughly investigated and related to the synthesis route, to the doping, and to the sample homogeneity. The thermal stability of iron oxides, present both as synthesis products and as consequence of the irradiation itself, was also analyzed following the magnetite→maghemite→hematite phase transformation. All the experimental observations concur in indicating that the effectiveness of the laser heating on these compounds mainly depends on grain size and the degree of order of the olivine structure, the highest thermal stability being displayed in the case of the nonhomogenous undoped samples obtained from solid‐state preparation, which show a highly ordered triphylite phase. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
993.
Francesca Caramia Caterina Mainero Francesca Gragnani Emanuele Tinelli Marco Fiorelli Vanessa Ceschin Patrizia Pantano Elisabetta Bucci Veronica Barra Luigi Bozzao Giovanni Antonini 《Magnetic resonance imaging》2010
Myotonic dystrophy type 1 (DM1) is a multisystemic disease involving multiple organ systems including central nervous system (CNS) and muscles. Few studies have focused on the central motor system in DM1, pointing to a subclinical abnormality in the CNS. The aim of our study was to investigate patterns of cerebral activation in DM1 during a motor task using functional MRI (fMRI). Fifteen DM1 patients, aged 20 to 59 years, and 15 controls of comparable age were scanned during a self-paced sequential finger-to-thumb opposition task of their dominant right hand. Functional MRI images were analyzed using SPM99. Patients underwent clinical and genetic assessment; all subjects underwent a conventional MR study. Myotonic dystrophy type 1 patients showed greater activation than controls in bilateral sensorimotor areas and inferior parietal lobules, basal ganglia and thalami, in the ipsilateral premotor area, insula and supplementary motor area (corrected P<.05). Analysis of the interaction between disease and age showed that correlation with age was significantly greater in patients than in controls in bilateral sensorimotor areas and in contralateral parietal areas. Other clinical and MR characteristics did not correlate with fMRI. Functional changes in DM1 may represent compensatory mechanisms such as reorganization and redistribution of functional networks to compensate for ultrastructural and neurochemical changes occurring as part of the accelerated aging process. 相似文献
994.
Ultrasonic methods are well known as powerful and reliable tool for defect detection. In the previous decades focus and interest
have been directed to non-contact sensors and methods, showing many advantages over contact techniques where inspection depends
on contact conditions (pressure, coupling medium, contact area). The non-contact hybrid ultrasonic method described here is
of interest for many applications, requiring periodic inspection in service or after manufacturing. Despite the potential
impact of laser-generated ultrasound in many areas of industry, robust tools for studying the phenomenon are lacking and thus
limit the design and optimization of non-destructive testing and evaluation techniques. Here a specific numerical method is
presented to efficiently and accurately solve ultrasound wave propagation problems with frequencies in the MHz range traveling
in relatively large bodies and through air. This work improves a previous numerical model where propagation of the acoustic
waves through air had not been considered, allowing us to simulate the presence of a non-contact transducer in reception in
order to simulate numerically the complete experimental setup. It is very important to limit the amount of air to be considered
in the FE analyses; otherwise the computational cost would often exceed the resources available. A way to solve the problem
is to implement non-reflecting boundary conditions. A non-reflecting boundary condition allows all outgoing waves to exit
the domain at the boundary where they have been imposed without reflection; thus, it is possible to model only the portion
of air between the non-contact transducer and the solid under testing. Several numerical and experimental analyses were conducted
on a 136 lb AREMA rail; here we study in detail two fully non-contact testing configurations for the rail head and web. The
information that can be acquired is very valuable for choosing the right setup and configuration when performing non-contact
hybrid ultrasonic inspection. 相似文献
995.
996.
F. Amorini V. Sipala G. Cardella L. Auditore C. Boiano B. Carbone A. Di Pietro G. Fallica P. Figuera P. Finocchiaro L. Grassi E. La Guidara P. Guazzoni I. Lombardo D. Loria A. Pappalardo A. Piazza S. Pirrone N. Randazzo F. Rizzo L. Zetta 《Nuclear Physics B - Proceedings Supplements》2009,173(1):194-197
997.
Gianfranco Carotenuto Cornelia L. Hison Filomena Capezzuto Mariano Palomba Pietro Perlo Pellegrino Conte 《Journal of nanoparticle research》2009,11(7):1729-1738
An effective method of preparation of bismuth nanopowders by thermal decomposition of bismuth dodecyl-mercaptide Bi(SC12H25)3 and preliminary results on their thermoelectric properties are reported. The thermolysis process leads to Bi nanoparticles
due to the efficient capping agent effect of the dodecyl-disulfide by-product, which strongly bonds the surface of the Bi
clusters, preventing their aggregation and significantly reducing their growth rate. The structure and morphology of the thermolysis
products were investigated by differential scanning calorimetry, thermogravimetry, X-ray diffractometry, 1H nuclear magnetic resonance spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. It has been shown
that the prepared Bi nanopowder consists of spherical shape nanoparticles, with the average diameter depending on the thermolysis
temperature. The first results on the thermoelectric characterization of the prepared Bi nanopowders reveal a peculiar behavior
characterized by a semimetal–semiconductor transition, and a significant increase in the Seebeck coefficient when compared
to bulk Bi in the case of the lowest grain size (170 nm). 相似文献
998.
The power of energy‐resolved tandem mass spectrometry experiments for resolution of isomers: the case of drug plasma stability investigation of multidrug resistance inhibitors 下载免费PDF全文
999.
1000.