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Abstract A calorimetric method for measurement of the copolymerization rate over a wide range of conversions has been derived. The well-known methyl methacrylate-styrene system was used as the example to prove the efficiency of the approach proposed. 相似文献
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This study examined intensity range as a function of elicitation task (reading and automatic speech sequences), musical training, and the interaction between task and musical training in 31 college students. The results indicated significant differences in loudness range by experiental task. Intensity range for the descending automatic sequence was significantly greater than that for the ascending and reading tasks. While the overall effect of musical training was nonsignificant, there was a significant interaction between task and training, with musicians having a significantly greater mean range on the ascending task. A comparison between ascending and descending tasks indicated a significant mean difference between lower limits and no significant mean difference between upper limits. The range for the reading probe was located approximately in the middle of the total available intensity range. 相似文献
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This study investigated the effects of prolonged loud reading on trained and untrained subjects. Subjects were eight young women singers, and eight young women with limited musical experience. Each subject underwent videostroboscopic examination prior to and following 1 h of prolonged loud reading. The pretest and posttest videotaped samples were randomized and presented to three experienced judges, who evaluated various aspects of laryngeal appearance and vibratory characteristics. Analyses of group data revealed that untrained subjects showed a small but significant increase in amplitude of vocal fold excursion following the experimental task. No significant differences were noted in the trained singer group. When individual variation was analyzed, it was found that most subjects did not show many changes from pretest to posttest. It was concluded that a l-h loud-reading task was not sufficient to induce notable laryngeal alterations 相似文献
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Transition Metal Peroxofluoro Complexes. III. Preparation, Crystal Structure, and Vibrational Spectra of K6Ta3(O2)3OF13 · H2O Containing a m?-Oxo-diperoxo-octafluoroditantalate(V) Anion K6Ta3(O2)3OF13 · H2O has been prepared from solution and his crystal structure was determined by X-ray single crystal investigation: Space group Pnma, lattice constants a = 1 653.6 pm, b = 883.5 pm, c = 1 365.8 pm, Z = 4, R = 0.033. The compound yields [Ta(O2)F5]2? groups as well as m?-oxo-bridged [Ta2O(O2)2F8]4? anions with very diffrent O? O distances within the peroxo groups (139 pm vs. 164 and 175 pm) correlating well with the i.r. and Raman spectra. The different bonding in connection with an oxo-bridge is discussed. 相似文献
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Transition Metal Peroxofluoro Complexes. IX. Crystal Structure of Ba3[Ti(O2)F5]2 · 2 H2O The pale yellow hydrat Ba3[Ti(O2)F5]2 · 2 H2O crystallizes tetragonal (space group P42/mbc, a = 1 248.5(3), c = 812.2(2) pm; Z = 4; R = 0.026 for 404 independent reflections). It contains isolated [Ti(O2)F5]3? anions. Thermal decomposition leads directly to α-Ba3Ti2O2F10, which is isotypic to α-Ba3Al2F12. 相似文献
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On the Existence of the Compound K2TiOF4: Pyrohydrolytic Degradation of K2TiF6 and Thermochemical Behaviour of K2Ti(O2)F4 · H2O In an attempt to prepare K2TiOF4 we used the following three ways; solid-state reaction of K2TiF6, TiO2, and KF, pyrohydrolysis of K2TiF6 at 450 and 550°C, and thermal decomposition of K2Ti(O2)F4 · H2O. In each case the reaction products were mixtures of several compounds, always containing the kryolith-phase K2+xTiOxF6?x and TiO2. At 130°C K2Ti(O2)F4 · H2O forms K2Ti(O2)F4 by loss of H2O, and at 230°C the peroxogroup decomposes, yielding K2TiOF4 as main product. K2TiOF4 crystallizes tetragonally with the following lattice parameters: a = 769.7(1) and c = 1153.9(2)pm. The i.r. spectrum shows an absorption band at 810 cm?1, pointing to infinite chains of ? Ti? O? Ti? O? . 相似文献
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Khalil H Mahajan D Rafailovich M Gelfer M Pandya K 《Langmuir : the ACS journal of surfaces and colloids》2004,20(16):6896-6903
Concurrent sonolysis of iron pentacarbonyl and poly(ethylene glycol)-400 (PEG-400) in hexadecane solvent proceeds via zero-order kinetics and results in Fe nanoparticles encapsulated in PEG-400 (Fe-PEG). The transmission electron microscopy images show Fe-PEG consisting of <3 nm Fe particles that are evenly dispersed in the PEG matrix. M?ssbauer and X-ray absorption fine structure/X-ray absorption near-edge structure data reveal an ordered PEG assembly that helps protect the zerovalent Fe core. The Fe nanoparticles in Fe-PEG are superparamagnetic with a magnetization value of 45 emu/g-Fe at 10 KOe. The rheology of the synthesized material shows an unusual increase in viscosity with temperature that is likely due to lower critical saturation temperature phase segregation over 40 degrees C. The low-temperature mobility of the PEG-400 moiety in Fe-PEG would allow facile ligation of the Fe0 core with biologically and chemically active groups. 相似文献