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471.
Thermally induced polytype transformations among the layered double hydroxides (LDHs) of Mg and Zn with Al 总被引:1,自引:0,他引:1
Thomas GS Radha AV Kamath PV Kannan S 《The journal of physical chemistry. B》2006,110(25):12365-12371
The hydrotalcite-like layered double hydroxide (LDH) of Mg with Al shows dramatic changes in the peaks arising from the (h0l)/(0kl) family of reflections in its powder X-ray diffraction pattern during thermal treatment. DIFFaX simulations show that these changes arise due to the transformation of the disordered 3R1 polytype into the 1H polytype on dehydration. The 1H polytype is an essential precursor to the decomposition reaction, which results in the formation of an oxide residue with the rock salt structure. In contrast, the LDH of Zn with Al does not undergo any such transformation, retaining the structure of the 3R1 polytype until decomposition into the oxide residue. Given the poor octahedral site preference of the Zn2+ ion, the 1H polytype is neither structurally stable nor is it topochemically necessary for the thermal decomposition of the Zn-Al LDH, the end product of the decomposition reaction being an oxide with the wurtzite structure. 相似文献
472.
Gordon-Salant S Yeni-Komshian GH Fitzgibbons PJ Schurman J 《The Journal of the Acoustical Society of America》2010,128(4):EL200-EL204
This study examined the effects of age and hearing loss on short-term adaptation to accented speech. Data from younger and older listeners in a prior investigation [Gordon-Salant et al. (2010). J. Acoust. Soc. Am. 128, 444-455] were re-analyzed to examine changes in recognition over four administrations of equivalent lists of English stimuli recorded by native speakers of Spanish and English. Results showed improvement in recognition scores over four list administrations for the accented stimuli but not for the native English stimuli. Group effects emerged but were not involved in any interactions, suggesting that short-term adaptation to accented speech is preserved with aging and with hearing loss. 相似文献
473.
A variety of generator-collector systems are reviewed, from the original rotating ring-disc electrodes developed in the 1950s, to very recent developments using new geometries and microelectrodes. An overview of both theoretical and experimental aspects are given, and the power of these double electrode systems in analytical electrochemistry is illustrated with a range of applications. 相似文献
474.
S. Archambault E. Behnke P. Bhattacharjee S. Bhattacharya X. Dai M. Das A. Davour F. Debris N. Dhungana J. Farine S. Gagnebin G. Giroux E. Grace C.M. Jackson A. Kamaha C. Krauss S. Kumaratunga M. Lafrenière M. Laurin I. Lawson L. Lessard I. Levine C. Levy R.P. MacDonald D. Marlisov J.-P. Martin P. Mitra A.J. Noble M.-C. Piro R. Podviyanuk S. Pospisil S. Saha O. Scallon S. Seth N. Starinski I. Stekl U. Wichoski T. Xie V. Zacek 《Physics letters. [Part B]》2012
475.
A one-pot synthesis of Au and Pt nanoparticles by the spontaneous reduction of chloroaurate and chloroplatinate ions using tetraaniline molecules has been elucidated. The importance of this work is that tetraaniline acts as a multifunctional molecule that accomplishes the complexation of aqueous chloroaurate and chloroplatinate ions by phase transferring them to organic medium and their subsequent reduction to yield Au and Pt nanoparticles in organic phase. The metal reduction is followed by polymerization of the amine to yield polyaniline, which subsequently caps the Au and Pt nanoparticles. Various analytical techniques have been used for probing the process of reduction of auric and platinic metal precursors like UV-vis, X-ray diffractogram (XRD) and transmission electron micrographic (TEM) analysis. Such prepared nanoparticles are utilized for the fabrication of novel modified electrodes towards the electrocatalytic oxidation of glucose. 相似文献
476.
Gordon-Salant S Yeni-Komshian GH Fitzgibbons PJ 《The Journal of the Acoustical Society of America》2010,128(5):3152-3160
This study investigated the effects of age and hearing loss on perception of accented speech presented in quiet and noise. The relative importance of alterations in phonetic segments vs. temporal patterns in a carrier phrase with accented speech also was examined. English sentences recorded by a native English speaker and a native Spanish speaker, together with hybrid sentences that varied the native language of the speaker of the carrier phrase and the final target word of the sentence were presented to younger and older listeners with normal hearing and older listeners with hearing loss in quiet and noise. Effects of age and hearing loss were observed in both listening environments, but varied with speaker accent. All groups exhibited lower recognition performance for the final target word spoken by the accented speaker compared to that spoken by the native speaker, indicating that alterations in segmental cues due to accent play a prominent role in intelligibility. Effects of the carrier phrase were minimal. The findings indicate that recognition of accented speech, especially in noise, is a particularly challenging communication task for older people. 相似文献
477.
Paula dos Passos Menezes Grace Anne Azevedo Dória Adriano Antunes de Souza Araújo Bruna Maria Hipólito Sousa Lucindo José Quintans-Júnior Rafaely Nascimento Lima Péricles Barreto Alves Flávio Machado Souza Carvalho Daniel Pereira Bezerra Francisco Jaime Bezerra Mendonça-Júnior Luciana Scotti Marcus Tullius Scotti Gabriel Francisco da Silva Thiago Mendonça de Aquino Adilson Rodrigues Sabino Eryvaldo Socrates Tabosa do Egito Mairim Russo Serafini 《Journal of inclusion phenomena and macrocyclic chemistry》2016,85(3-4):341-354
478.
S. R. Grace 《Mathematische Nachrichten》1989,141(1):117-127
In this paper, we present some new criteria for the oscillation of the differential equation with damping where p(t) and q(t) are allowed to change signs on [t0 ∞]. These criteria are obtained by using an integral averaging technique and can be applied in some special cases in which other classical oscillation results are not applicable. 相似文献
479.
The motion of large drops with Eötvos numbers as high as 1000 has been investigated in large tanks where wall effects are negligible. Shapes observed include ellipsoidal- and spherical-caps with and without skirts, crescents, biconcave disks, toroids and wobbling irregular forms. The ellipsoidal-cap drops are shown to obey an equation based upon an extension of the Davies and Taylor theory for bubbles in liquids, regardless of whether skirts are being formed and shed at the rear. 相似文献
480.