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111.
M.A. Kale C.P. Joshi S.V. Moharil P.L. Muthal S.M. Dhopte 《Journal of luminescence》2008,128(7):1225-1228
LaCaAl3O7 phosphors activated by several ns2 impurities like Pb2+ and Bi3+, and rare-earth dopants were prepared by combustion synthesis. X-ray diffraction (XRD) results confirmed the formation of single-phase compounds. Variety of activators exhibited interesting photoluminescence in LaCaAl3O7 host. Combustion synthesis furnishes a quick method for preparing these phosphors. It is suggested that LaCaAl3O7-based materials can be developed as low-cost phosphors. 相似文献
112.
113.
CaSO4:Eu with particle size in submicron range was synthesized. Radiation induced Eu3+↔Eu2+ conversion as well as thermal conversion was studied. The samples showed thermal conversion above 400 °C. However, no radiation induced conversion in submicron range particles was observed. Particles heated above 400 °C coalesce and when heated at 925 °C bigger particles of 20 μm size were formed. Optical microscopy of these particles reveals red inclusion of about 5 μm inside CaSO4 particle. It is speculated that the red inclusion is CaS:Eu2+. 相似文献
114.
Fu N Allen AD Kobayashi S Sequeira PA Shang M Tidwell TT Mishima M 《Journal of the American Chemical Society》2007,129(19):6210-6215
Azacyclobutenone ylides 2 and 11 were generated in solution by laser flash photolysis of 2-diazoacetylpyridine (1) and 3-diazoacetylpyridazine (10), respectively, together with the corresponding ketenes. The ylides were identified by their characteristic IR and UV spectra: 2, nu (CH3CN) 1725 cm(-1), lambdamax 360 and 550 (br) nm; 11, nu (CH3CN) 1776 cm(-1), lambdamax 370 and 550 (br) nm. 2-Triisopropylsilyldiazoacetylpyridine 20 upon photolysis at 5 degrees C in CH3CN forms the ylide 21 as a rather persistent (T1/2 2 h at 25 degrees C) purple solution, nu (CH3CN) 1718 cm(-1), lambdamax 245, 378 and 546 (br) nm, but no ketene is observed. Quinolyl ylide 14 and pyridyl ylides 17 and 19 with Me and 2-pyridyl substituents, respectively, with characteristic IR and UV spectra were also generated. The 1H NMR spectrum of the pyridyl ring of 21 shows substantial upfield shifts relative to those of 20. Calculated nucleus-independent chemical shifts (NICS) for 2, 11, and 21 are comparable to those for benzocyclobutadiene (22) and benzocyclobutenone enolate (23), with substantial positive values for the 4-membered rings, while the NICS values for the 6-membered rings are significantly more positive than for benzene or pyridine. Significant bond alternation is also found in the calculated ylide structures, and these results suggest strong antiaromatic character for the 4-membered rings of 2, 11, 14, 17, 19, and 21, and greatly reduced aromatic character for the 6-membered rings. 相似文献
115.
Abdulwahab S. Almusallam Yaser M. Abdulraheem Mahmoud Shahat Pearl Korah 《Journal of Dispersion Science and Technology》2013,34(5):728-738
We report on the stability of titanium dioxide nanoparticles suspended in various aqueous solutions with and without the presence of a model organic contaminant—salicylic acid. The stability of the suspended nanoparticles was revealed by measuring the isoelectric point by means of zetapotential scans and measuring the growth kinetics of the hydrodynamic particle size by means of dynamic light scattering (DLS) under different pH conditions. Aggregated nanoparticle sizes were also examined using atomic force microscopy. It was found that salicylic acid had a dramatic impact on the aggregation behavior of TiO2 nanoparticles, suggesting that salicylic acid adsorbs to TiO2 nanoparticles surfaces. 相似文献
116.
Luo L Carson JD Molnar KS Tuske SJ Coales SJ Hamuro Y Sung CM Sudakin V Auger KR Dhanak D Jackson JR Huang PS Tummino PJ Copeland RA 《Journal of the American Chemical Society》2008,130(24):7584-7591
Human kinesin spindle protein (KSP)/hsEg5, a member of the kinesin-5 family, is essential for mitotic spindle assembly in dividing human cells and is required for cell cycle progression through mitosis. Inhibition of the ATPase activity of KSP leads to cell cycle arrest during mitosis and subsequent cell death. Ispinesib (SB-715992), a potent and selective inhibitor of KSP, is currently in phase II clinical trials for the treatment of multiple tumor types. Mutations that attenuate Ispinesib binding to KSP in vitro have been identified, highlighting the need for inhibitors that target different binding sites and inhibit KSP activity by novel mechanisms. We report here a small-molecule modulator, KSPA-1, that activates KSP-catalyzed ATP hydrolysis in the absence of microtubules yet inhibits microtubule-stimulated ATP hydrolysis by KSP. KSPA-1 inhibits cell proliferation and induces monopolar-spindle formation in tumor cells. Results from kinetic analyses, microtubule (MT) binding competition assays, and hydrogen/deuterium-exchange studies show that KSPA-1 does not compete directly for microtubule binding. Rather, this compound acts by driving a conformational change in the KSP motor domain and disrupts productive ATP turnover stimulated by MT. These findings provide a novel mechanism for targeting KSP and perhaps other mitotic kinesins. 相似文献
117.
Cheng PP Silvester D Wang G Kalyuzhny G Douglas A Murray RW 《The journal of physical chemistry. B》2006,110(10):4637-4644
How the efficiency of molecular quenching by Au nanoparticles depends on nanoparticle size is reported for (a) dynamic (collisional) quenching of four different fluorophores by three Au nanoparticles having similar protective layers but differing core diameters (1.1, 1.6, and 2.0 nm) and (b) static quenching in the electrostatic association between [Ru(bpy)3]2+ and five tiopronin-protected Au nanoparticles having core diameters from 1.3 to 3.9 nm. The quenching constants systematically increase with core size. In (a), the dynamic constants scale with the molar absorbance coefficients of the nanoparticles, showing the essentially of the absorbance/emission spectral overlap, and the associated nanoparticle core density of electronic states, in energy-transfer quenching. In (b), the fluorescence of the Au nanoparticle itself was enhanced by energy transfer from the [Ru(bpy)3]2+ fluorophore. 相似文献