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991.
992.
Andrade L Micklander E Farhat I Bro R Engelsen SB 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,189(2):286-292
A new non-iterative curve resolution technique for resolving single decay profiles is proposed. The new technique, called DoubleSlicing, is based on the Decra (Direct Exponential Curve Resolution Algorithm) principle. While the original Decra was designed to resolve several decay curves simultaneously and thus fitting common pure exponentials, DoubleSlicing can resolve single decay profiles by a simple double data transformation followed by an analytical and unique three-way decomposition. The new approach is successfully demonstrated on experimental NMR CPMG relaxation data, measured on combinations of unmixed paramagnetic CuSO(4) solutions. Decay signals of the water component were acquired following an innovative experimental design that ensured no interaction between the components present in each sample under observation. DoubleSlicing proved to be accurate in estimating relaxation times differing in one order of magnitude (range: 19.6-159.4ms). Its performance was comparable to discrete exponential fitting with the advantage of being much faster - in terms of computation time, DoubleSlicing outperformed exponential fitting by a factor of four. 相似文献
993.
Marcerou JP Nguyen HT Bitri N Gharbi A Essid S Soltani T 《The European physical journal. E, Soft matter》2007,23(3):319-328
Usual ferroelectric compounds undergo a paraelectric-to-ferroelectric phase transition when the susceptibility of the electric polarization density changes its sign. The temperature is the only thermodynamic field that governs the phase transition. Chiral tilted smectics may also present an improper ferroelectricity when there is a tilt angle between the average long axis direction and the layer normal. The tilt angle is the order parameter of the phase transition which is governed by the temperature. Although the electric susceptibility remains positive, a polarization proportional to the tilt appears due to their linear coupling allowed by the chiral symmetry. Further complications come in when the chirality increases, as new phases are encountered with the same tilt inside the layers but a distribution of the azimuthal direction which is periodic with a unit cell of two (SmC(A)*, three (SmC(Fi1)*, four (SmC(Fi2)* or more (SmC(alpha)* layers. In most of these phases, the layer normal is a symmetry axis so there is no macroscopic polarization except for the SmC(Fi1)* in which the average long axis is tilted so the phase is ferrielectric. By studying a particular compound with only a SmC(Fi2)* and a SmC(alpha)* phase, we show that we recover the uniformly tilted ferroelectric SmC* when applying an electric field. We are thus led to build field-temperature phase diagrams for this class of compounds by combining different experimental techniques described here. 相似文献
994.
Braga WS Kimura NM Luders DD Sampaio AR Santoro PA Palangana AJ 《The European physical journal. E, Soft matter》2007,24(3):247-250
The phase diagram is an interesting field of research, particularly in lyotropic liquid crystals (LLC). In this way, one of the most important phase diagrams of this LLC system was reported by Yu and Saupe. Two uniaxial (calamitic--N(C) and discotic--N(D)) and one biaxial nematic (N(B)) phases were determined by these authors. Furthermore, in this phase diagram the classical isotropic phase (I was observed at high temperature as well as a reentrant isotropic phase (I(RE)) which takes place at lower temperature. Later, this phase diagram was also studied by several authors and in all cases the I(RE)-N(C)-I phase transitions were not observed. In this work, we present a study of this phase diagram through digital image processing and refractometry optical techniques. The occurrence of these phase transitions is investigated and characterized. In addition, the order parameter is obtained based on the Vuks hypothesis from a particular point, in the range of the N(C) phase, where the absolute value of the optical birefringence (Deltan is maximum. 相似文献
995.
This paper investigates finite-stretching corrections
to the classical Milner-Witten-Cates theory for semi-dilute
polymer brushes in a good solvent. The dominant correction to the
free energy originates from an entropic repulsion caused by the
impenetrability of the grafting surface, which produces a
depletion of segments extending a distance μ∝L-1
from the substrate, where L is the classical brush height. The
next most important correction is associated with the
translational entropy of the chain ends, which creates the
well-known tail where a small population of chains extend beyond
the classical brush height by a distance ξ∝L-1/3.
The validity of these corrections is confirmed by quantitative
comparison with numerical self-consistent field theory. 相似文献
996.
Laredo E Prutsky N Bello A Grimau M Castillo RV Müller AJ Dubois P 《The European physical journal. E, Soft matter》2007,23(3):295-303
Thermally stimulated depolarization currents, TSDC, wide-angle X-ray scattering, WAXS, differential scanning calorimetry,
DSC, and polarized light optical microscopy, PLOM, have been used to examine poly(L-lactide)-b -poly(
-caprolactone) diblock copolymers in a wide composition range. Both components are crystallizable and the miscibility in
the amorphous phase has been determined from the behavior of the primary relaxations which are the dielectric manifestation
of the glass transition, and also from the superstructural morphology revealed by PLOM and the compositional dependence of
the melting points as determined by DSC. Distinct segmental mobilities in the amorphous phase which can be well resolved by
TSDC are present; the
mode of the slower component shifts to lower temperatures as the PCL content increases while the glass transition of neat
PCL is present for all compositions. A relaxation times bimodal distribution is apparent for PCL-rich copolymers. The composition
dependence of the multiple glass transitions detected in these weakly segregated copolymers are predicted by the self-concentration
model for a miscible blend made of components with a large Tg contrast. 相似文献
997.
J.-H. Huang S.-Y. Zhu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):557-575
The normalized second-order
correlation of the emission fields from a driven four-level atomic
ensemble is investigated theoretically by using the state vector
method. The violation of Cauchy-Schwarz inequality, which indicates
the establishment of non-classical correlation between two emission
fields, has been found. The effects of various decays and time delay
on the correlation are discussed in detail, which are helpful in
finding the ways to obtain high non-classical correlation. This
technique for the generation of non-classical light is operable
based on the current experimental technology and will lead to some
potential applications in quantum information science. 相似文献
998.
L. Ye 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):413-416
We propose two schemes for generating a four-atom cluster state in a thermal
cavity. With the assistant of a strong classical field the
photon-number-dependent parts in the effective Hamiltonian are canceled.
Thus the schemes are insensitive to the thermal field. The schemes can also
be used to generate the cluster state for the trapped ions in thermal
motion. 相似文献
999.
J. B. Satinover D. Sornette 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(3):369-384
Human beings like to believe they are in control of their
destiny. This ubiquitous trait seems to increase motivation and persistence,
and is probably evolutionarily adaptive [J.D. Taylor, S.E. Brown, Psych. Bull. 103, 193 (1988); A. Bandura,
Self-efficacy: the exercise of control (WH Freeman, New
York, 1997)]. But how good really is our
ability to control? How successful is our track record in these areas? There
is little understanding of when and under what circumstances we may
over-estimate [E. Langer, J. Pers. Soc. Psych. 7, 185 (1975)] or even lose our ability to control and optimize outcomes,
especially when they are the result of aggregations of individual
optimization processes. Here, we demonstrate analytically using the theory
of Markov Chains and by numerical simulations in two classes of games, the
Time-Horizon Minority Game [M.L. Hart, P. Jefferies, N.F. Johnson, Phys. A 311, 275 (2002)] and the Parrondo Game
[J.M.R. Parrondo, G.P. Harmer, D. Abbott, Phys. Rev. Lett.
85, 5226 (2000); J.M.R. Parrondo, How to cheat a bad mathematician (ISI, Italy, 1996)], that agents
who optimize their strategy based on past information may actually perform
worse than non-optimizing agents. In other words, low-entropy (more
informative) strategies under-perform high-entropy (or random) strategies.
This provides a precise definition of the “illusion of control” in certain
set-ups a priori defined to emphasize the importance of optimization.
An erratum to this article is available at . 相似文献
1000.
Z. P. Niu Z. M. Zheng D. Y. Xing 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(3):281-287
Four-component Bogoliubov-de Gennes equations are applied to study
tunneling conductance spectra of ferromagnet/ferromagnet/d-wave
superconductor (F1/F2/d-wave S) tunnel junctions and to find
out signs of spin-triplet pairing correlations induced in the
proximity structure. The pairing correlations with equal spins
arises from the novel Andreev reflection (AR), which requires at
least three factors: the usual AR at the F2/S interface, spin
flip in the F2 layer, and superconducting coherence kept up in
the F2 layer. Effects of angle α between magnetizations of
the two F layers, polarizations of the F1 and F2 layers, the
thickness of the F2 layer, and the orientation of the d-wave S crystal on the tunneling conductance are investigated. A conversion
from a zero-bias conductance dip at α = 0 to a zero-bias
conductance peak at a certain value of α can be seen as a
sign of generated spin-triplet correlations. 相似文献