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1.
We present small angle neutron scattering measurements on binary aqueous solutions of some short-chain amphiphiles (diols,
triols, glycols and diglycols) at room temperature. The spectra were analysed in terms of the Teubner-Strey phenomenological
formula which allows to obtain a measure for the amphiphilicity strength of each system (amphiphilicity factor f
a). In some systems, however, other models, valid for micellar solutions, give also a good representation of the spectra. As
a result, we find that, independently of the type of hydrophilic group side (oxydrilic or oxirane), these systems cover the
entire accessible amphiphilicity scale ( -1 < f
a < 1). Some disordered systems ( f
a > 1) presumably are able to form micelle-like aggregates.
Received 12 June 2002 Published online: 16 April 2003
RID="a"
ID="a"e-mail: giovanni.darrigo@uniroma1.it 相似文献
2.
R.F. Alvarez‐Estrada 《Annalen der Physik》2006,15(6):379-415
We consider a nonequilibrium statistical system formed by many classical non‐relativistic particles of opposite electric charges (plasma) and by the classical dynamical electromagnetic (EM) field. The charges interact with one another directly through instantaneous Coulomb potentials and with the dynamical degrees of freedom of the transverse EM field. The system may also be subject to external influences of: i) either static, but spatially inhomogeneous, electric and magnetic fields (case 1)), or ii) weak distributions of electric charges and currents (case 2)). The particles and the dynamical EM field are described, for any time t > 0, by the classical phase‐space probability distribution functional (CPSPDF) f and, at the initial time (t = 0), by the initial CPSPDF fin. The CPSPDF f and fin, multiplied by suitable Hermite polynomials (for particles and field) and integrated over all canonical momenta, yield new moments. The Liouville equation and fin imply a new nonequilibrium linear infinite hierarchy for the moments. In case 1), fin describes local equilibrium but global nonequilibrium, and we propose a long‐time approximation in the hierarchy, which introduces irreversibility and relaxation towards global thermal equilibrium. In case 2), the statistical system, having been at global thermal equilibrium, without external influences, for t ≤ 0, is subject to weak external charge‐current distributions: then, new hierarchies for moments and their long‐time behaviours are discussed in outline. As examples, approximate mean‐field (Vlasov) approximations are treated for both cases 1) and 2). 相似文献
3.
Eckhard Koch 《等离子体物理论文集》1969,9(4):307-323
The behaviour of a weakly ionized plasma in external, arbitrarily time-dependent, electromagnetic fields is treated within the framework of kinetic theory. The Boltzmann kinetic equation is solved using the Lorentz ansatz, taking into account elastic collisions between electrons and neutral particles and assuming that the collision frequency is independent of the electron velocity. The drift velocity of electrons enters into the isotropic part f0 and into the direction-dependent part f1 of the electron distribution function. A method is given for the calculation of the drift velocity, which is calculated explicitly for the important but difficult case of a sinusoidal electric field in the presence of a magnetic switching field. f0 and f1 are calculated; f0 is investigated generally. f0 consists of an expansion in generalized Laguerre polynomials. The influence of the electromagnetic fields on the distribution function and its time variation is discussed and the relaxation behaviour is shown. The following two special cases are calculated explicitly: a linear rising electric field and a sinusoidal electric field, both in the presence of a constant magnetic field. 相似文献
4.
Kinetic properties of a granular gas of viscoelastic particles in a homogeneous cooling state are studied analytically and numerically. We employ the most recent expression for the velocity-dependent restitution coefficient for colliding viscoelastic particles, which allows us to describe systems with large inelasticity. In contrast to previous studies, the third coefficient a3 of the Sonine polynomials expansion of the velocity distribution function is taken into account. We observe a complicated evolution of this coefficient. Moreover, we find that a3 is always of the same order of magnitude as the leading second Sonine coefficient a2; this contradicts the existing hypothesis that the subsequent Sonine coefficients a2,a3…, are of an ascending order of a small parameter, characterizing particles inelasticity. We analyze evolution of the high-energy tail of the velocity distribution function. In particular, we study the time dependence of the tail amplitude and of the threshold velocity, which demarcates the main part of the velocity distribution and the high-energy part. We also study evolution of the self-diffusion coefficient D and explore the impact of the third Sonine coefficient on the self-diffusion. Our analytical predictions for the third Sonine coefficient, threshold velocity and the self-diffusion coefficient are in a good agreement with the numerical finding. 相似文献
5.
A model reaction system is considered consisting of a heat bath of argon atoms (c) and small concentrations of SF6-molecules (m) and electrons (e) (number densities: ne ? nm ? nc). Within the model the time behaviour of the electron velocity distribution function is studied under the influence of elastic electron-argon collisions and electron SF6 attachment collisions. On the basis of the distribution function time-dependent macroscopic quantities (kinetic electron temperature. nonequilibrium rate constant of the attachment reaction) are calculated. 相似文献
6.
Xue-xiang Xu 《International Journal of Theoretical Physics》2012,51(7):2056-2065
We theoretically study the squeezing effect in a 3-wave mixing process, generated by the operator S3 o exp[m(a1a2-a1fa2f)+n(a1a3-a1fa3f)]S_{3}\equiv \exp[\mu(a_{1}a_{2}-a_{1}^{\dagger}a_{2}^{\dagger})+\nu(a_{1}a_{3}-a_{1}^{\dagger}a_{3}^{\dagger})]. The corresponding 3-mode squeezed vacuum state in Fock space and its uncertainty relation are presented. It turns out that S 3 may exhibit enhanced squeezing. By virtue of integration within an ordered product (IWOP) of operators, we also give the S 3’s normally ordered expansion. Finally, we calculate the Wigner function of 3-mode squeezed vacuum state by using the Weyl ordering invariance under similar transformations. 相似文献
7.
傅里叶变换是现代光学发展的重要理论工具。自1991年Caola首次定义傅里叶自函数以来1,它在光学领域的应用研究日趋活跃。本文首先对傅里叶自函数定义进行扩展,再讨论其维格纳分布函数及其矩,研究它们在光学中的应用。最后推导出傅里叶自函数应用于光学变换器成象时的变换矩阵。 相似文献
8.
Ultracold nonequilibrium plasma created by a dye laser has been studied by the molecular dynamics method. Electrons and protons in this model of nonequilibrium plasma interacted according to the Coulomb law. In the case of electron-proton interaction and a distance between particles r < a 0 (Bohr radius), the interaction energy is constant, e 2/a 0 (e is the charge of electron). An initial proton kinetic energy is set randomly so that the average kinetic energy is 0.01–1 K. Initial full electron energy is also set randomly, but at the same time it is positive; i.e., all the electrons according to our task are located in the continuous spectrum. Average kinetic electron energy per one particle varies from 1 to 50 K. The motion equations in periodical boundary condition for this system have been solved by molecular dynamics method. We have calculated the distribution function in the region near the ionization threshold. The distribution function is being described using electron state density in the nearest neighbor approximation with activity correction. 相似文献
9.
The ion transverse velocity distribution functions and the fraction η of ions heated above a certain energy W
1 are calculated as applied to the ion cyclotron resonance heating method of isotope separation. It is assumed that the longitudinal
ion velocity distribution in a plasma source is nonequilibrium. Under high heating temperatures, the averaged ion transverse
velocity distribution becomes essentially nonequilibrium and exhibits two maxima. The ion heating efficiency η is calculated
for W
1=40 eV and various values of the parameter p=λ/L, where λ is the wavelength of the electric field of an antenna and L is the heating zone extension. The relative contributions of the time-of-flight and Doppler broadenings are evaluated. 相似文献
10.
11.
Analysis of the control and subordination is carried out for the system of nonlinear stochastic equations describing fluctuations
with the 1/f spectrum and with the interaction of nonequilibrium phase transitions. It is shown that the control equation of the system
has a distribution function that decreases upon an increase in the argument in the same way as the Gaussian distribution function.
Therefore, this function can be used for determining the Gibbs-Shannon informational entropy. The local maximum of this entropy
is determined, which corresponds to tuning of the stochastic equations to criticality and indicates the stability of fluctuations
with the 1/f spectrum. The values of parameter q appearing in the definition of these entropies are determined from the condition that the coordinates of the Gibbs-Shannon
entropy maximum coincide with the coordinates of the Tsallis entropy maximum and the Renyi entropy maximum for distribution
functions with a power dependence. 相似文献
12.
The high-velocity distribution of a two-dimensional dilute gas of Maxwell molecules under uniform shear flow is studied. First
we analyze the shear-rate dependence of the eigenvalues governing the time evolution of the velocity moments derived from
the Boltzmann equation. As in the three-dimensional case discussed by us previously, all the moments of degreek⩾4 diverge for shear rates larger than a critical valuea
c
(k)
, which behaves for largek asa
c
(k)
∼k
−1. This divergence is consistent with an algebraic tail of the formf(V) ∼V
−4-σ(a), where σ is a decreasing function of the shear rate. This expectation is confirmed by a Monte Carlo simulation of the Boltzmann
equation far from equilibrium. 相似文献
13.
Sorin Bastea Raffaele Esposito Joel L. Lebowitz Rossana Marra 《Journal of statistical physics》2006,124(2-4):445-483
We derive hydrodynamic equations describing the evolution of a binary fluid segregated into two regions, each rich in one species,which are separated (on the macroscopic scale) by a sharp interface. Our starting point is a Vlasov-Boltzmann (VB) equation describing the evolution of the one particle position and velocity distributions, fi (x, v, t), i = 1, 2. The solution of the VB equation is developed in a Hilbert expansion appropriate for this system. This yields incompressible Navier-Stokes equations for the velocity field u and a jump boundary condition for the pressure across the interface. The interface, in turn, moves with a velocity given by the normal component of u. 相似文献
14.
Ronald Leven 《等离子体物理论文集》1969,9(1):29-44
Beam-plasma-interaction is theoretically investigated on the basis of the non-linear Vlasov equation. The case of amplifying longitudinal waves is described by a non-linear approximation including “quasilinear” and mode-coupling terms. By evaluating the electric field vector E(x, t) and the distribution functions fa(x, v, t) for the beam and plasma electrons in Fourier series and approximating the non-oscillating parts of the fa by the first terms in an expansion using Hermite polynomials in velocity space a system of ordinary differential equations for the complex wave number k, the mean and thermal velocities and the quasimoments bas is obtained, which can be solved numerically, if terms with E for which m + n > 3 are neglected. The numerical results will be given in a further part of the paper. 相似文献
15.
Ronald Leven 《等离子体物理论文集》1970,10(1):27-50
The spatial variations of the electric field E and the electron distribution function fa for the case of beam plasma amplification are computed on the basis of a nonlinear approximation developed in the earlier parts of the present paper [1–3]. The essential results are: With increasing distance x from the point, where the beam enters the plasma, the amplitude Ã1 of the first harmonic increases, reaches a maximum value at some point xm and than decreases monotonically without reaching a further maximum. In the region around xm we find a large increase of the higher harmonics, i.e. increasing nonlinearity, and also an increasing phase velocity, which soon approches the beam velocity. The non-oscillating part of the distribution function of the beam electrons deformes, but not so much as the quasilinear theory predicts, so that amplitude settling must be interpreted as a nonlinear but not as a quasilinear effect. The results show a good agreement with some typical experiments on beam plasma interaction. 相似文献
16.
Ac susceptibility at low temperatures of Pr0.75Na0.25Mn1-xFexO3 (0 ≤ x ≤ 0.30) is investigated. The peak value of the real component of ac susceptibility χ' at the freezing temperature Tf is suppressed with the increasing frequency. The peak value of χ' shows a linear relation between Tf and the logarithm of the frequency ω. The normalized slope P = ΔTf/TfΔlgω, which is much lower than canonical insulating spin glass systems in which 0.06 ≤ P ≤ 0.08. The peak value of the imaginary component of the ac susceptibility χ' at Tf for the x = 0, 0.02, 0.30 samples increases with increasing frequency, suggesting a cluster glass ground state with a coexistence of charge-ordered phase and correlated ferromagnetic clusters in spin glass matrix. The peak value of χ' at Tf for the x = 0.10 sample decreases with increasing frequency, suggesting a phase separation ground state. The peak value of χ' at Tf for the x = 0.05 sample decreases with increasing frequency for ω ≤ 52 Hz and increases subsequently till 701 Hz, and then decreases with further increasing frequency for ω ≥ 1501 Hz. This complex behaviour is ascribed to the competition between the effects of large and little ferromagnetic clusters in the sample. The ground state of x = 0.05 sample is a transition state from cluster glass to phase separation. 相似文献
17.
The specific features of the dielectric spectra of statistical mixtures in the form of heterogeneous systems with spherical
particles chaotically arranged in the space have been investigated. The distribution function of relaxation times f(τ) has been restored. It has been established that the relaxation times are continuously distributed within a wide interval
[τ1, τ2]. Different methods for broadening the relaxation time distribution interval and approximating the relaxation time distribution
function f(τ) have been analyzed. It has been demonstrated that f(τ) is a nonmonotonic function with two maxima at the boundaries and a minimum in the vicinity of the midpoint of the interval
[τ1, τ2]. These features of the relaxation time distribution function are responsible for the large difference between the average
relaxation frequencies of the permittivity and the dielectric loss (electrical conductivity). 相似文献
18.
We investigate the radiative decays of the φ-meson to the scalar mesons a0(980) and f0(980). We demonstrate that, contrary to earlier claims, these decays should be of the same order of magnitude for a molecular state and for a compact state and, therefore, the available experimental information is consistent with both a molecular as well as a compact structure of the scalars. Thus, the radiative decays of the φ-meson into scalars establish a sizable K¯ component of the scalar mesons, but do not allow to discriminate between molecules and compact states. 相似文献
19.
Recently, much research has indicated that more and more cancers pose a threat to human life. Cancers are caused by oncogenes. Many human oncogenes have been found and most of them are located on chromosomes. The discovery of the oncogene plays a significant role in the treatment of cancer. The p53 tumor suppressor gene has received much attention because it frequently mutates or deletes in tumor cells of most people. Thus, the study of oncogenes is significant. In order to establish the Galois field (GF(7)), the indefinite gene is introduced as D and oncogene is introduced as O, and P. Taking the polynomial coefficients a0, a1, a2 ∈ GF(7) and the bijective function f:GF(7) → {D,A,C,O,G,T,P}, where f(0) = D, f(1) = A, f(2) = C, f(3) = O, f(4) = G, f(5) = T, and f(6) = P, the bijective φ may be written as φ(a0 + a1x + a2x2). Based on the algebraic structure, we can not only analyse the DNA sequence of oncogenes, but also predict possible new cancers. 相似文献