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1.
Electric field light scattering results on aqueous solutions of linear, flexible NaPSS at minimal ionic strength are reported.
Samples of molecular weights between 356 kg/mol and 2870 kg/mol were investigated. With increasing field strength the intensity
as a function of wavenumber develops a pronounced oscillating behaviour. Besides the well-known first peak a second maximum
is observed at the position at which a weak maximum for some samples already occurs at zero field. The overall intensity strongly
depends on the frequency of the electric field. The electro-optical effect shows a maximum at 300 kHz. Increasing the particle
concentration gives a large increase of the peak maximum, normalized to concentration. If plotted versus scattering angle the relative intensity increase is maximum for samples of medium molecular weight. The results strongly
indicate a stretching and alignment of the chains, thus leading to or enlarging the short range order of the chains.
Received 9 April 1999 and Received in final form 18 August 1999 相似文献
2.
J. Biegel C. Hundegger B. Nadig R. Weber 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):525-536
This paper resumes light scattering investigations of saltfree aqueous solutions of two component mixtures of charged spheres
by extending those measurements to systems in which one component is replaced by essentially stiff rodlike particles. In a
second step of investigations these were replaced by linear flexible particles. Fd-virus particles (length l=883 nm) or macromolecules of NaPSS of four different contour lengths have been used as representatives. Mostly the concentration
of latex spheres was fixed at 0.02 Vol%. The concentration of the other component was varied over a wide range. Concerning
the scattering intensity, the contribution of the latex spheres dominates, in particular in the systems containing NaPSS particles.
This simplifies the interpretation of data considerably. A rearrangement of the spheres is observed, depending on the shape
of the other sort of particles. These conclusions can be drawn from the shift of measured static structure factor with concentration c. A power law is found for the q-value of the maximum. The exponent depends on the properties of the second component. For the lower molecular weight (MW)
samples of NaPSS below a critical concentration, the exponent is smaller than 1/3, decreasing the more the smaller the MW
of the samples is. A tentative explanation in terms of charge number of NaPSS particles is given. The short time dynamics
has been explored too. From the data a “dynamically determined structure factor” can be derived, that can be compared with
the measured static structure factor. Good (fd) and fair (NaPSS) agreement is obtained respectively. Only at small wavenumbers
below the maximum of deviations occur which increase with concentration; they are consistent with hydrodynamic interaction.
Received 30 July 1998 and Received in final form 14 December 1998 相似文献
3.
J. Wuttke M. Seidl G. Hinze A. Tölle W. Petry G. Coddens 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(2):169-172
The dynamics of supercooled toluene, studied in a GHz-THz range by incoherent neutron and depolarized light scattering, is
found to be in full accord with mode coupling predictions. Around the susceptibility minimum, neutron spectra are wavenumber
independent and proportional to light scattering data; the fast -relaxation scaling law applies; amplitude and frequency diverge with power laws that extrapolate towards a crossover temperature
K.
Received: 20 June 1997 / Accepted: 3 November 1997 相似文献
4.
5.
F. Nad' P. Monceau J.M. Fabre 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):301-306
Conductivity and permittivity of the organic transfer salt (TMTTF)2Br have been measured at low frequencies (102-107 Hz) between room temperature down to 4 K. The real part of the permittivity, , is shown to grow below the temperature at which the conductivity is maximum due to charge localization of Mott-Hubbard type. reaches a maximum of 105-106 at 35 K-50 K depending on the samples. Decreasing temperature below , sharply decreases down to helium temperature through the antiferromagnetic phase transition at T N = 15 K. We explain the magnitude, the temperature and frequency dependence of as resulting from short range charge density wave states in the temperature range where charge localization occurs. This
interpretation is supported by recent X-ray scattering measurements.
Received: 10 October 1997 / Revised: 28 February 1998 / Accepted: 3 March 1998 相似文献
6.
M.B. Lacerda Santos M.A. Amato 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(3):393-400
Using a light-beating technique we have measured the damping time of thermal fluctuations of the nematic director for the
so called cylindrical or calamitic nematic (NC) phase of the lyotropic system K-laurate/decanol/. By varying the scattering angle in suitable geometries, we have been able to estimate the orientational diffusivities associated
to the three pure deformations of splay, twist and bend. A former measurement made in the disk-like ND phase of the same system yielded a large deviation between the splay and twist diffusivities. The effect was then attributed
to induced flows, or backflow, which could be responsible for the reduction of the splay viscosity. In fact, this is the analogous
effect, for disks, to the one recognized since long time ago arriving for rod-like molecules in a classical nematic, though
in this case it is associated with bend deformations. The analogy comes about thanks to the interchange of the role played
by disks and cylinders for, respectively, splay and bend fluctuations.The measurements reported here provide a new test on
the applicability of the backflow model to a nematic system composed of micelles, that is, aggregates made of amphiphilic
(surfactant) molecules, in its cylindrical-like variant, i.e. the NC phase. In addition, the comparative study made here with the previous results existing in the literature for the ND phase, allows us to conjecture on structural issues concerning lyotropic nematics.
Received: 29 April 1998 / Revised: 19 August 1998 / Accepted: 31 August 1998 相似文献
7.
V. Lesturgeon T. Nicolai D. Durand 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(1):71-82
Free radical co-polymerization of methyl methacrylate (MMA) and ethyl glycol dimethyl metacrylate (EGDMA) was investigated
in solution at different molar ratios R = [EGDMA]/[MMA] between 0 and 0.05. Initially mainly linear PMMA was formed with weight average molar mass 7.5 g/mol independent of R. At larger reaction extents branched polymers were formed and the systems gelled. The scattering intensity rose initially
with the reaction extent, but reached a plateau value at larger reaction extents. The plateau value increased strongly with
R. Dynamic light scattering showed the appearance of a slow relaxation not observed in linear PMMA solutions. The data can
be interpreted by assuming that the excess scattering originates from the branching points and relaxes through self diffusion
of the branched particles. The results agree with predictions of the percolation model for gelation and Rouse dynamics. Viscosity
measurements corroborate this interpretation. Measurements on a progressively diluted sample quenched close to the gel point
again showed quantitative agreement with the percolation model for gelation.
Received 11 May 1998 and Received in final form 22 October 1998 相似文献
8.
C. Caraby L. Adoui J.P. Grandin A. Cassimi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(1):53-56
We report the observation of resonances in the intensity correlation spectra of a 3D rubidium optical lattice, which we attribute
to light scattering from propagating atomic density fluctuations in the lattice. This process is the spontaneous analog of
the stimulated scattering mechanism recently described by Courtois et al.. We investigate the dependence of the new resonances on the lattice angle and show that they disappear for large angles,
thus resolving previous discrepancies on the subject.
Received: 30 January 1997 / Accepted: 9 October 1997 相似文献
9.
Summary We have performed extensive studies of a three-component microemulsion system composed of AOT-water-decane (AOT=sodium-bis-ethylhexyl-sulfosuccinate
is an ionic surfactant) using small-angle light scattering (SALS). The small-angle scattering intensities are measured in
the angular interval 0.001–0.1 radians, corresponding to a Bragg wave number range of 0.14 μm−1<Q<<1.4 μm−1. The measurements were made by changing temperature and volume fraction ϕ of the dispersed phase (water + AOT) in the range
0.05<ϕ<0.75. All samples have a fixed water-to-AOT molar ratio,w=[water]/[AOT]=40.8, in order to keep the same average droplet size in the stable one-phase region. With the SALS technique,
we have been able to observe all the phase boundaries of a very complex phase diagram with a percolation line and many structural
organizations within it. We observe at the percolation transition threshold, a scaling behavior of the intensity data. This
behavior is a consequence of a clustering among microemulsion droplets near the percolation threshold. In addition, we describe
in detail a structural transition from a droplet microemulsion to a bicontinuous one as suggested by a recent small-angle
neutron scattering experiment. The loci of this transition are located several degrees above the percolation temperatures
and are coincident with the maxima previously observed in shear viscosity. From the data analysis, we show that both the percolation
phenomenon and this novel structural transition are derived from a large-scale aggregation between microemulsion droplets. 相似文献
10.
11.
12.
A. Desaix O. Roubeau J. Jeftic J.G. Haasnoot K. Boukheddaden E. Codjovi J. Linarès M. Noguès F. Varret 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(2):183-193
We investigate the behaviour of photo-excitable, bistable systems, under permanent light irradiation, in presence of relaxation
towards the non-excited state. Cooperativity causes bistability of the steady state, leading to light-induced thermal and
optical hysteresis (LITH and LIOH). The light-induced instability is expected to induce demixtion, i.e. the coexistence of domains of the two stable steady states. Such effects are evidenced by magnetic and reflectivity measurements
on the spin-crossover solid solution: , with x= 0.3, 0.5, 0.85. Experimental data are in quantitative agreement with a simple macroscopic model which includes a non-linear
relaxation term in the master equation.
Received: 5 June 1997 / Accepted: 17 July 1998 相似文献
13.
A. Saint-Jalmes F. Gallet 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):489-494
Above a surface pressure threshold , we detect a buckled state in the low temperature solid phase of a phospholipid monolayer spread at the air-formamide interface.
Stable ripples are observed with a Brewster angle microscope, and light scattering provides measurements mNm-1, wavelength m and amplitude of a few nm for the deformation. A model, coupling the monolayer thickness and elongation, and consistent with the monolayer
texture, is also presented.
Received: 18 August 1997 / Revised: 9 December 1997 / Accepted: 29 January 1998 相似文献
14.
Calculation of dielectronic recombination cross sections and rate coefficients for heliumlike carbon
J.-G. Wang T.-Q. Chang Y.-Z. Qu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):231-235
A simplified relativistic configuration interaction method is used to calculate the dielectronic recombination cross sections
and rate coefficients for heliumlike carbon. In this method, the infinite resonant doubly excited states can be treated conveniently
in the frame of Quantum Defect Theory. Our calculated cross sections are in agreements with the experimental measurements
except for the 1s2lnl'(n=6,7) resonances. The total energy-integrated cross sections and rate coefficients over all dielectronic resonances are in
agreements with the experimental measurements within percent.
Received: 7 July 1997 / Revised: 7 October 1997 / Accepted: 8 December 1997 相似文献
15.
Sonic stop-bands for cubic arrays of rigid inclusions in air 总被引:2,自引:0,他引:2
M.S. Kushwaha B. Djafari-Rouhani L. Dobrzynski J.O. Vasseur 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):155-161
Extensive band structures have been computed for cubic arrays of rigid spheres and cubes in air. Complete stop bands are obtained
for the face-centered-cubic (fcc) structure; however, there is no gap for the body-centered-cubic (bcc) and simple-cubic (sc)
structures. These gaps start opening up for a filling fraction of (27%) for spherical (cubic) inclusions and tend to increase with the filling fraction, exhibiting a maximum at the close-packing.
We also propose a tandem structure that allows the achievement of an ultrawideband filter for environmental or industrial
noise in the desired frequency range. This work is motivated by the recent experimental measurement of sound attenuation on
the sculpture, by Eusebio Sempere, exhibited at the Juan March Foundation in Madrid (Nature 378, 241 (1995)) and complements the corresponding theoretical work (Appl. Phys. Lett. 70, 3218 (1997)).
Received: 24 October 1997 / Revised: 1 December 1997 and 26 January 1998 / Accepted: 6 March 1998 相似文献
16.
T. Striffler U. Stuhr H. Wipf H. Hahn S. Egelhaaf 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):245-251
By means of small-angle neutron scattering the microstructure of two nanocrystalline Pd samples (prepared by inert gas condensation)
has been studied at room temperature in a Q-range from [0pt] to [0pt] . An additional subsequent doping of the two samples with H as well as with D (concentrations < 4 at%) caused contrast variations
that provided more detailed structural information. The measured scattering intensity was modeled by a Porod contribution
from large heterogenities (e.g. pores) and a contribution from spherical grains with a log-normal distribution of their radii. To account for the presence
of grain boundaries, the grains were considered to be surrounded by a shell with a reduced Pd density and a thickness half
as large as the thickness of the grain boundaries. For the above model, the data of the H-doped, D-doped and undoped sample
were simultaneously fitted with one single set of adjustable parameters. The fits yielded for the two samples volume-weighted
mean grain radii of 10 nm and 13 nm. The values for the grain boundary thickness lie between 0.2 and 0.8 nm. Almost all of
the H- and D-atoms are, at low hydrogen concentrations, located in the grain boundaries.
Received 1 May 2000 相似文献
17.
V. Kumaran 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(4):519-527
The stability of wall modes in a flexible tube of radius R surrounded by a viscoelastic material in the region R < r < H R in the high Reynolds number limit is studied using asymptotic techniques. The fluid is a Newtonian fluid, while the wall
material is modeled as an incompressible visco-elastic solid. In the limit of high Reynolds number, the vorticity of the wall
modes is confined to a region of thickness in the fluid near the wall of the tube, where the small parameter , and the Reynolds number is , and are the fluid density and viscosity, and V is the maximum fluid velocity. The regime is considered in the asymptotic analysis, where G is the shear modulus of the wall material. In this limit, the ratio of the normal stress and normal displacement in the wall,
, is only a function of H and scaled wave number . There are multiple solutions for the growth rate which depend on the parameter .In the limit , which is equivalent to using a zero normal stress boundary condition for the fluid, all the roots have negative real parts,
indicating that the wall modes are stable. In the limit , which corresponds to the flow in a rigid tube, the stable roots of previous studies on the flow in a rigid tube are recovered.
In addition, there is one root in the limit which does not reduce to any of the rigid tube solutions determined previously. The decay rate of this solution decreases
proportional to in the limit , and the frequency increases proportional to .
Received: 5 November 1997 / Revised: 10 March 1998 / Accepted: 29 April 1998 相似文献
18.
N. Ghaouar M. Ben Henda A. Aschi A. Gharbi 《Journal of Macromolecular Science: Physics》2013,52(11):2150-2164
The self-assembly behaviour of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly (ethylene oxide) copolymers, (EO)13(PO)30(EO)13 (Pluronic L64), and (EO)70 (PO)30(EO)70 (Pluronic F68) in water and in p-xylene has been elucidated by using viscosity and dynamic light scattering measurements to investigate the effects of hydrophilic chains length on their conformational changes. The viscosity measurements were performed for a range of temperature varying from 27°C to 60°C and concentration from 4 to 60 mg/ml. The variation of the viscosity and the conformational changes in aqueous solution depends on the kinds of interactions and the balance between excluded volume effects and hydrophobic interactions. Some dynamic light scattering measurements were also performed at room temperature for the same range of concentration to provide more information on the micellar structures in aqueous and organic solution. 相似文献
19.
C. Dreyfus A. Aouadi R.M. Pick T. Berger A. Patkowski W. Steffen 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):401-419
We discuss the hydrodynamic equations which describe the shear dynamics of a liquid composed of anisotropic molecules, both
in its normal and its supercooled phases. We use these equations to analyze 90 depolarized light scattering experiments performed in the supercooled phase of a glass forming liquid, metatoluidine, and
show that the information extracted from this analysis is consistent with independent shear viscosity measurements performed
on that liquid in the same temperature range.
Received 28 April 1998 相似文献
20.
A. Kuhn S. Steuerwald K. Bergmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(1):57-70
Coherent population transfer between vibrational levels of the NO molecule induced by the interaction of two delayed laser
pulses, also referred to as stimulated Raman scattering involving adiabatic passage (STIRAP), is studied experimentally in
a molecular beam and in the bulk. The consequences of hyperfine splitting and Doppler broadening are discussed in detail.
Unlike in previous studies of this kind, transfer occurs simultaneously between more than one group of non degenerate levels.
In a molecular beam or in the bulk, the transfer efficiency of STIRAP exceeds that obtained by Stimulated Emission Pumping
(SEP) by a factor of 3.6 or 15, respectively. We estimate the absolute transfer efficiency T in the beam to be , while is found in the bulk. In both cases, this is of the maximum value expected from numerical studies. Possible reasons for this discrepancy are discussed. Finally we show
that the absorption of a pump pulse in a weakly absorbing medium is significantly enhanced by the presence of a copropagating
Stokes pulse when the Rabi frequency of the latter is smaller than the width of the Doppler profile . The relation of this observation to the phenomenon of Electromagnetically Induced Transparency (EIT), which is observed
for , is also discussed.
Received: 11 September 1997 / Revised: 28 October 1997 / Accepted: 29 October 1997 相似文献