排序方式: 共有132条查询结果,搜索用时 0 毫秒
21.
We consider the low-temperature specific heat spectra of long-range correlated quasiperiodic DNA molecules using a q-gaussian distribution, and compare them with those considering the Boltzmann-Gibbs distribution. The energy spectra are calculated using the one-dimensional Schrödinger equation in a tight-binding approximation with the on-site energy exhibiting long-range disorder and non-random hopping amplitudes. We focus our attention at the low temperature region, where the specific heat spectra presents a logarithmic-periodic oscillations as a function of the temperature T around a mean value given by a characteristic dimension of the energy spectrum. 相似文献
22.
The use of a Carr-Purcell-Meiboom-Gill (CPMG) echotrain to increase the 29Si NMR sensitivity in glasses was investigated. The echo intensity decay follows a stretched exponential behavior M(t) = M0 exp[−(t/t2)β] with values for the exponent β in the range of 0.41-0.65. The signal to noise in the spectra can be increased by a factor of up to 4 by taking the weighted sum of the spectra obtained from the individual echoes. However, differential T2 relaxation for the different Qn species is observed, with a shorter relaxation time for Q4 than Q3. Thus, summing of the echoes leads to distorted spectral intensities and quantitative information can no longer be obtained from the spectra. To circumvent the problem with differential T2 relaxation, an alternative approach is developed in which the spectral intensity for each chemical shift value is determined from the stretched exponential fit to its echo decay. With this approach, the sensitivity can be increased by a factor of up to 2.4, while quantitative information can still be obtained from the spectra. The increased sensitivity permitted the detection of five-coordinated silicon in a potassium silicate glass with natural 29Si abundance at ambient pressure. 相似文献
23.
Hybrid Deconvolution of Adaptive Optics Retinal Images from Wavefront Sensing 总被引:1,自引:0,他引:1 下载免费PDF全文
Adaptive optics can be used to compensate for the wave aberration of the human eyes to achieve high-resolution imaging in real time. However the correction & partial due to the limitation of hardware. We propose a kind of hybrid image post-processing method, which uses the blind deconvolution combined with the residual data in wavefront sensor to restore the partially adaptive optics corrected retinal image. This method is applied in the image restoration of the vivid human retinal images. The results show that it is effective to improve the retinal image quality. 相似文献
24.
B. Denker B. Galagan V. Osiko I. Shulman S. Sverchkov E. Dianov 《Applied physics. B, Lasers and optics》2009,95(4):801-805
A new Bi-doped Mg–Al–silicate glass is suggested and investigated. It can be fabricated by moderate-temperature routine technology.
The characteristic relaxation time of 300–800 μs in combination with the high quantum yield (up to 85%) and wide excitation
spectrum makes this glass a promising laser material. The obtained quadratic dependence of the visible absorption intensity
is an argument in favor of the hypothesis that the absorption and infrared luminescence in Bi-doped glasses are caused by
Bi2 dimers. 相似文献
25.
T.?S.?Biró G.?Purcsel K.?ürm?ssy 《The European Physical Journal A - Hadrons and Nuclei》2009,40(3):325-340
We review the idea of generating non-extensive stationary distributions based on aaabstract composition rules of the subsystem
energies, in particular the parton cascade method, using a Boltzmann equation with relativistic kinematics and modified two-body
energy composition rules. The thermodynamical behavior of such model systems is investigated. As an application hadronic spectra
with power law tails are analyzed in the framework of a quark coalescence model.
This paper is part of the Topical Issue Statistical Power Law Tails in High-Energy Phenomena. 相似文献
26.
We discuss a possible origin of Tsallis’ statistics from the correlation among constituents which reduces the phase space
of the system. We also show that a system of coupled linear harmonic oscillators can exhibit a Tsallis-type behavior.
This paper is part of the Topical Issue Statistical Power Law Tails in High-Energy Phenomena. 相似文献
27.
The optimization of erbium-doped Ta2O5 thin film waveguides deposited by magnetron sputtering onto thermally oxidized silicon wafer is described. Optical constants of the film were determined by ellipsometry. For the slab waveguides, background losses below 0.4 dB/cm at 633 nm have been obtained before post-annealing. The samples, when pumped at 980 nm yielded a broad photoluminescence spectrum (FWHM∼50 nm) centred at 1534 nm, corresponding to 4I13/2-4I15/2 transition of Er3+ ion. The samples were annealed up to 600 °C and both photoluminescence power and fluorescence lifetime increase with post-annealing temperature and a fluorescence lifetime of 2.4 ms was achieved, yielding promising results for compact waveguide amplifiers. 相似文献
28.
P. Sourková P. Nemec V. Nazabal V. Moizan R. Moncorgé 《Journal of luminescence》2009,129(10):1148-1153
Electronic transitions of Pr3+ ions in Ga-Ge-Sb-Se glasses corresponding to emissions in the infrared region were studied by means of absorption and emission spectroscopies and fluorescence lifetimes measurements. Transition probabilities, radiative lifetimes, branching ratios, and quantum efficiencies of most of the emission transitions including the infrared ones occurring around 1.3, 1.7, and 2.4 μm were estimated based on a standard Judd-Ofelt analysis. 相似文献
29.
The phase behavior of DOPE/DOTAP-DNA complexes in phase-separated oil(dodecane)/water mixtures was explored using Small Angle
X-Ray Scattering (SAXS) and Fluorescence Correlation Spectroscopy (FCS). Inverse micelles of DNA with cationic-lipid coating
were found in the oil phase. Varying the ratio between cationic and neutral lipids a transition from wormlike to spherical
structures is observed for both long ( ≈ 75000bp) and short (30-1246bp) DNA. In contrast to lipid/DNA complexes in the water
phase, there is no indication of condensed liquid-crystalline structures in the non-polar phase. In fact, FCS measurements
on short DNA oligomers complexed with cationic lipid in alkane give clear evidence for monomeric inverse micelles of DNA.
Dilution series revealed a critical lower concentration of lipids and DNA for observing lipid/DNA micelles. 相似文献
30.
Glasses in the MoO3-CuO-PbO system are obtained at high cooling rates (104-105 K/s) and characterized using X-ray diffraction (XRD), differential thermal analysis (DTA), infrared (IR) and X-ray photoelectron spectroscopy (XPS). Two glass formation regions are determined: one with compositions having a high MoO3 content (50-80 mol%) and the other in the PbO-rich compositions (65-80 mol%). In the region of MoO3-rich compositions the building units of the amorphous network are МоО6, МоО4 and CuO4 groups. For these high MoO3 contents and respectively low PbO concentrations, the lead oxide is supposed to act as a network modifier while at high content PbO is found to be the main glass network former. In latter case the structure of glasses is formed by chains of PbOn (n = 3, 4) polyhedra, between which there are isolated MoO4 and CuO4 complexes. IR and XPS data reveal the existence of Mo-O-Mo, Mo-O-Me(Me’) (where Me = Cu2+, Cu1+ and Me’ = Pb) and Me(Me’)-O-Me(Me’) bonds in the amorphous network. Surprising result is found for low PbO content (10 mol%) where the lead oxide acts as glass network modifier: the actual MoO3 content drops strongly which is accompanied with a significant increase of the actual CuO content with respect to their nominal MoO3-CuO composition. Such effect is not observed in PbO-rich composition (70 mol%) where PbO has a role of network former. 相似文献