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981.
AsuhaTakuya Kobayashi Masao TakahashiHitoo Iwasa Hikaru Kobayashi 《Surface science》2003,547(3):275-283
Spectroscopic and electrical properties of ultrathin silicon dioxide (SiO2) layers formed with nitric acid have been investigated. The leakage current density of the as-grown SiO2 layers of 1.3 nm thickness is high. The leakage current density is greatly decreased by post-oxidation annealing (POA) treatment at 900 °C in nitrogen, and consequently it becomes lower than those for thermally grown SiO2 layers with the same thickness. X-ray photoelectron spectroscopy measurements show that high density suboxide species are present before POA and they are markedly decreased by POA. Fourier transformed infrared absorption measurements show that water and silanol group are present in the SiO2 layers before POA but they are removed almost completely by POA above 800 °C. The atomic density of the as-grown chemical SiO2 layers is 4% lower than that of bulk SiO2 layers, while it becomes 12% higher after POA. It is concluded that the high atomic density results from the desorption of water and OH species, and oxidation of the suboxide species, both resulting in the formation of SiO2. The valence band discontinuity energy at the Si/SiO2 interface increases from 4.1 to 4.6 eV by POA at 900 °C. The high atomic density enlarges the SiO2 band-gap energy, resulting in the increase in the band discontinuity energy. The decrease in the leakage current density by POA is attributed to (i) a reduction in the tunneling probability of charge carriers through SiO2 by the enlargement of the band discontinuity energy, (ii) elimination of trap states in SiO2, and (iii) elimination of interface states. 相似文献
982.
Masao Kaneko 《Journal of Chemical Sciences》1992,104(6):723-730
The amphiphilic porphinato zinc(II) complex (ZnP) containing four substituted amphiphilic alkyl chains was embedded in the
liposomes of l,2-dipalmitoyl-sn-glycero-3phosphocholine. The distance from the embedded ZnP to the outer phase was changed from 9 to 27 ? by changing the
substituted alkyl chain length. The electron transfer from the excited Zn complex to methylviologen (MV2+) or benzoquinone (BQ) added in the outer aqueous phase was studied. At first, quenching reactions were analyzed based on
dynamic and static reaction models of the excited state. For the MV2+ quencher, only the triplet excited state of the embedded ZnP reacted, and electron transfer occurred at a distance less than
12 ?. In BQ both the singlet and the triplet excited states reacted, and the reaction of the singlet state was a static one
indicating that BQ is incorporated into the liposomes. The distribution of the BQ molecule in the quenching sphere of ZnP
was presented based on calculations assuming a stepwise incorporation into the quenching sphere. 相似文献
983.
An analytical interpretation is made for the Monte Carlo results on the shape of an unrestricted random flight chain. Both the average shape and the time correlation function of the shape fluctuation are discussed. The Monte Carlo results are well reproduced by assuming that the shape of the chain is primarily determined by the first few normal modes. 相似文献
984.
The acid-catalyzed reaction of 1,1′-bis(α-hydroxy-α-phenylethyl)ferrocene gave several [4] ferrocenophanes including a peroxide derivative. Their structures have been confirmed by spectrometric methods and from a study of their reaction behavior. 相似文献
985.
986.
Le Prell CG Yagi M Kawamoto K Beyer LA Atkin G Raphael Y Dolan DF Bledsoe SC Moody DB 《The Journal of the Acoustical Society of America》2004,116(2):1044-1056
Brief cochlear excitotoxicity produces temporary neural swelling and transient deficits in auditory sensitivity; however, the consequences of long-lasting excitotoxic insult have not been tested. Chronic intra-cochlear infusion of the glutamate agonist AMPA (a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) resulted in functional deficits in the sound-evoked auditory brainstem response, as well as in behavioral measures of hearing. The electrophysiological deficits were similar to those observed following acute infusion of AMPA into the cochlea; however, the concentration-response curve was significantly shifted as a consequence of the slower infusion rate used with chronic cochlear administration. As observed following acute excitotoxic insult, complete functional recovery was evident within 7 days of discontinuing the AMPA infusion. Distortion product otoacoustic emissions were not affected by chronic AMPA infusion, suggesting that trauma to outer hair cells did not contribute to AMPA-induced deficits in acoustic sensitivity. Results from the current experiment address the permanence of deficits induced by chronic (14 day) excitotoxic insult as well as deficits in psychophysical detection of longer duration acoustic signals. 相似文献
987.
The stability constants (K) and the standard free energy (deltaG degrees ), enthalpy (deltaH degrees ), and entropy changes (deltaS degrees ) for the complexation of gamma-cyclodextrin with 34 enantiomeric and diastereomeric N-acetyl- and N-carbobenzyloxy-d/l-dipeptides with two aromatic moieties were determined in aqueous buffer solution at 298.15 K by titration microcalorimetry. Chiral recognition of the enantiomeric dipeptide pairs by gamma-cyclodextrin was found to be fairly poor, exhibiting only small percentage differences in K, while the diastereomeric dipeptides were discriminated to much greater extent with affinity differences of up to 6-7 times. The complex structures of several selected pairs were elucidated by NMR techniques. Combining the microcalorimetric and NMR data, the complexation and chiral recognition behavior of gamma-cyclodextrin is discussed in particular in terms of the length, bulkiness, and flexibility of the tether connecting the two aromatic moieties in a guest. 相似文献
988.
We report on the spectroscopy of the 5s(2) 1S0(F=9/2)-->5s5p 3P0(F=9/2) clock transition of 87Sr atoms (natural linewidth of 1 mHz) trapped in a one-dimensional optical lattice. Recoilless transitions with a linewidth of 0.7 kHz as well as the vibrational structure of the lattice potential were observed. By investigating the wavelength dependence of the carrier linewidth, we determined the magic wavelength, where the light shift in the clock transition vanishes, to be 813.5+/-0.9 nm. 相似文献
989.
An ultrastable optical clock based on neutral atoms trapped in an optical lattice is proposed. Complete control over the light shift is achieved by employing the 5s(2) 1S0-->5s5p 3P0 transition of 87Sr atoms as a "clock transition." Calculations of ac multipole polarizabilities and dipole hyperpolarizabilities for the clock transition indicate that the contribution of the higher-order light shifts can be reduced to less than 1 mHz, allowing for a projected accuracy of better than 10(-17). 相似文献
990.
Kazutaka Seo Mitsuru Hasegawa Masao Morita Hideto Yoshimura 《Physica C: Superconductivity and its Applications》1998,310(1-4):358-366
We have suggested that non-uniform currents occur due to certain design parameters, for example a combination of cabling pitches, in a previous study. In the present study, we evaluate the occurrences of non-uniform current distributions in terms of design parameters, i.e., the combination of cabling pitches, winding methods (solenoidal and pancake winding) and cross-sectional shape of the cable by numerical analyses. Finally, some basic design concepts to solve this problem are proposed. 相似文献