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81.
J. Ibez A. Rapaport C. Boney R. Oliva R. Cusc A. Bensaoula L. Artús 《Journal of Raman spectroscopy : JRS》2012,43(2):237-240
We use Raman scattering to investigate the folded longitudinal acoustic (LA) phonons in a series of InxGa1−xN/GaN superlattices (SLs) grown by molecular beam epitaxy with different compositions (15% < x < 38%) and SL periods (from 8 to 20 nm). A novel, ultralow wavenumber filtering module, which provides access to ultralow wavenumber Raman modes on single‐grating spectrometers, has been used to perform the Raman measurements. Zone‐folding effects are observed, and the wavenumber behavior of the folded LA modes is well reproduced with a linear dispersion for the folded LA modes as predicted by elastic continuum theory. We employ the wavenumber of the doublets to evaluate the period of the SLs. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
82.
Shengzhi Zhao Alexandra Rapaport Jun Dong Bin Chen Peizhen Deng Michael Bass 《Optics & Laser Technology》2006,38(8):645-648
The fluorescence emission spectra of Cr:Nd:YAG crystal are measured and the effective stimulated emission cross-section of the crystal is obtained from −80 to +80 °C. A linear temperature dependence between −80 and +80 °C is reported for the 1.064-μm peak stimulated emission cross-section of Cr:Nd:YAG crystal. 相似文献
83.
In pursuit-evasion games, when a barrier occurs, splitting the state space into capture and evasion areas, in order to characterize this manifold, the study of the minimum time function requires discontinuous generalized solutions of the Isaacs equation. Thanks to the minimal oriented distance from the target, we obtain a characterization by approximation with continuous functions. The barrier is characterized by the largest upper semicontinuous viscosity subsolution of a variational inequality. This result extends the Isaacs semipermeability property. 相似文献
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Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co2+Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed. 相似文献
88.
The three dimensional pseudo-spin model of KD2PO4 (DKDP) has been investigated by using the Monte Carlo method. The model is found to exhibit simultaneous longitudinal ferroelectric and transverse antiferro-electric behaviour, and the results are shown to be in good quantitative agreement with experiment. 相似文献
89.
Amphiphilic β-sheet peptides decorated by acidic amino acids may spontaneously assemble into ordered monolayers at interfaces as well as form hydrogels at near physiological pH values. Here we monitored interactions between the peptide Pro-Asp-(Phe-Asp)(5)-Pro and the mildly amphiphilic chemotherapeutic drug doxorubicin (Dox). The peptide in the form of monolayers at the air water interface was found to enhance Dox adsorption, pointing to favorable interactions between the amphiphilic peptide and Dox. In solutions the fluorescence emission of Dox which was fitted to the Stern-Volmer quenching models suggested the formation of Dox associated forms >25 μM and larger forms at >100 μM. In presence of the peptide these larger associated forms appeared already at Dox concentrations >50 μM, indicating enhanced interactions between Dox and the peptide in the β-sheet conformation. Peptide hydrogels loaded with the drug showed sustained release profiles over several days. Smaller fractions of the drug were released with increase in either peptide or initially loaded drug concentrations. The released Dox was found to retain its cytotoxic activity in vitro. This study provides insights on the interactions between the amphiphilic and acidic peptide and Dox that are useful for the bottom up development of Dox-loaded peptide hydrogels for local drug delivery applications. 相似文献
90.
It was shown in Kifer (Israel J Math, 2013) that for any subshift of finite type considered with a Gibbs invariant measure the numbers of multiple recurrencies to shrinking cylindrical neighborhoods of almost all points are asymptotically Poisson distributed. Here we not only extend this result to all \(\psi \) -mixing shifts with countable alphabet but actually show that for all points the distributions of these numbers are asymptotically close either to Poisson or to compound Poisson distributions. It turns out that for all nonperiodic points a limiting distribution is always Poisson while at the same time for periodic points there may be no limiting distribution at all unless the shift invariant measure is Bernoulli in which case the limiting distribution always exists. Thus we describe, essentially completely, limiting distributions of multiple recurrence numbers in this setup. As a corollary we obtain also that the first occurence time of the multiple recurrence event is asymptotically exponentially distributed. Most of the results are new also for the widely studied single recurrencies case (see, for instance, Haydn and Vaienti Discret Contin Dyn Syst A 10:589–616, 2004; Probab Theory Relat Fields 144:517–542, 2009; Abadi and Saussol Stoch Process Appl 121:314–323, 2011; Abadi and Vergne Nonlinearity 21:2871–2885, 2008), as well. 相似文献