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1.
Gueroui Z Freyssingeas E Place C Berge B 《The European physical journal. E, Soft matter》2003,11(1):105-108
We observed fluctuations of elongated DNA molecules by fluorescence microscopy. The molecules are fixed at both ends and undulate.
Mode analysis of the thermally excited undulations of the labeled DNA molecules gives access to the spectral density of the
amplitude fluctuations. From these measurements we estimate the tension acting on the DNA molecules. We found the forces to
be within the entropic elasticity range of a typical DNA molecule (measured on the single-molecule level).
Received: 11 November 2002 / Accepted: 12 May 2002 / Published online: 4 June 2003
RID="a"
ID="a"Present address: Center for Studies in Physics and Biology, Rockefeller University, 1230 York Avenue, New York, NY 10021, USA. e-mail: zoherg@rockefeller.edu 相似文献
2.
Twist stiffness and an asymmetric bending stiffness of a polymer or a polymer bundle is captured by the elastic ribbon model.
We investigate the effects a ring geometry induces to a thermally fluctuating ribbon, finding bend-bend coupling in addition
to twist-bend coupling. Furthermore, due to the geometric constraint the polymer's effective bending stiffness increases.
A new parameter for experimental investigations of polymer bundles is proposed: the mean square diameter of a ribbonlike ring,
which is determined analytically in the semiflexible limit. Monte Carlo simulations are performed which affirm the model's
prediction up to high flexibility. 相似文献
3.
Finken R Lamura A Seifert U Gompper G 《The European physical journal. E, Soft matter》2008,27(3):309-321
The stochastic motion of a two-dimensional vesicle in linear shear flow is studied at finite temperature. In the limit of
small deformations from a circle, Langevin-type equations of motion are derived, which are highly nonlinear due to the constraint
of constant perimeter length. These equations are solved in the low-temperature limit and using a mean-field approach, in
which the length constraint is satisfied only on average. The constraint imposes non-trivial correlations between the lowest
deformation modes at low temperature. We also simulate a vesicle in a hydrodynamic solvent by using the multi-particle collision
dynamics technique, both in the quasi-circular regime and for larger deformations, and compare the stationary deformation
correlation functions and the time autocorrelation functions with theoretical predictions. Good agreement between theory and
simulations is obtained. 相似文献
4.
Zyn VI 《The European physical journal. E, Soft matter》2008,25(1):51-59
A mathematical model of the volumetric part of plasma polymerization influenced by gravity is presented. Plasma-activated
adhesion of monomer molecules to a surface of a germinal particle is assumed as a basic mechanism of particulate growth. The
continuity equation for the flow of matter through the discharge has been formulated and solved in two extreme asymptotic
approximations --for small and major duration of the process. Several non-equilibrium distribution functions of the polymer
were obtained, for instance, an amount of the particles as a function of their size or time of fall. Within the adopted model
this function demonstrates a sharp downward increase inside a discharge. In addition it contains such parameters as the free
fall acceleration or reaction rate coefficients, variations of which enable control of the discharge and properties of the
disperse medium. 相似文献
5.
Realization of Ultraviolet Electroluminescence from ZnO Homojunction Fabricated on Silicon Substrate with p-Type ZnO:N Layer Formed by Radical N2O Doping 下载免费PDF全文
ZnO homojunction light-emitting diodes are fabricated on Si(100) substrates by plasma assisted metal organic chemical vapour deposition. A p-type layer of nitrogen-doped ZnO film is formed using radical N2O as the acceptor precursor. The n-type ZnO layer is composed of un-doped ZnO film. The device exhibits desirable rectifying behaviour with a turn-on voltage of 3.3 V and a reverse breakdown voltage higher than 6 V. Distinct electrolumineseence emissions centred at 395nm and 490nm are detected from this device at forward current higher than 20mA at room temperature. 相似文献
6.
7.
近红外高光谱图像结合CARS算法对鸭梨SSC含量定量测定 总被引:3,自引:0,他引:3
高光谱数据量大、 维数高且原始光谱噪声明显、 散射严重等特征导致光谱建模时关键波长变量提取困难。 基于此,提出采用竞争性自适应重加权算法(CARS)对近红外高光谱数据进行关键变量选择。 鸭梨作为研究对象。 采用决定系数r2、 预测均方根误差RMSEP和验证集标准偏差和预测集标准偏差的比值RPD值进行模型性能评估。 基于选择的关键变量建立PLS模型(CARS-PLS)与全光谱变量建立的PLS模型进行比较发现CARS-PLS模型仅仅使用原始变量中15.6%的信息获得了比全变量PLS模型更好的鸭梨SSC含量预测结果,r2pre,RMSEP和RPD分别为0.908 2,0.312 0和3.300 5。 进一步与基于蒙特卡罗无信息变量MC-UVE和遗传算法(GA)获得的特征变量建立的PLS模型比较发现,CARS不仅可以去除原始光谱数据中的无信息变量,同时也能够对共线性的变量进行压缩去除,该方法能够有效地用于高光谱数据变量的选择。 结果表明,近红外高光谱技术结合CARS-PLS模型能够用于鸭梨可溶性固形物SSC含量的定量预测。 从而为基于近红外高光谱技术预测水果内部品质的研究提供了参考。 相似文献
8.
A.-H. Sato 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):137-140
Power spectrum densities for the number of tick quotes per minute
(market activity) on three currency markets (USD/JPY, EUR/USD, and
JPY/EUR) for periods from January 1999 to December 2000 are
analyzed. We find some peaks on the power spectrum densities at a few
minutes. We develop the double-threshold agent model and confirm
that stochastic resonance occurs for the market activity of this model.
We propose a hypothesis that the periodicities found on the power spectrum
densities can be observed due to stochastic resonance. 相似文献
9.
Estimation of Charge Exchange Recombination Emission Based on Diagnostic Neutral Beam on the Experimental Advanced Superconducting Tokamak 下载免费PDF全文
Diagnostic neutral beam (DNB) attenuation and charge exchange recombination emission are estimated on EAST tokamak. Approximately 40% of the beam with the energy of 50 keV can reach the plasma centre (r = 0) for the typical parameters of the Experimental Advanced Superconducting Tokamak (EAST) plasma. Emissivities of CVI (n = 8 → 7, 529.0nm) and OVⅢ (n = 10 →9, 607.Ohm) visible charge exchange recombination emissions based on the DNB are estimated. The emissivities of the visible bremsstrahlung emission near this wavelength are also calculated for comparison. The results show that the charge exchange recombination emission is about two orders of magnitude greater than the bremsstrahlung emission. It is theoretically indicated that the ratio of signal of charge exchange recombination spectroscopy to the noise from background bremsstrahlung emission, S/N, is large enough in the EAST tokamak with the typical designed parameters. The present results are helpful for experiment design of charge-exchange recombination spectroscopy based on the DNB in the EAST tokamak. 相似文献
10.
Fluorescence spectral changes of Rhodamine 6G in ethanol and glycerol solutions and deposited as a film on a silica surface have been studied using a wide range of pumping field fluence at 532 nm at room temperature. Blue shift of the fluorescence spectra and fluorescence quenching of the dye molecule in solution are observed at high excitation fluence values. Such effects are not reported for the film sample. The effects are interpreted as the result of population redistribution in the solute-solvent molecular system induced by the high fluence field and the fluence dependence of the radiationless decay mechanism. 相似文献