共查询到20条相似文献,搜索用时 31 毫秒
1.
V.P. Zhdanov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(3):485-489
To illustrate complex spatio-temporal effects which are possible in cellular reactions with a small number of particles, we
present Monte Carlo simulations of the formation of oscillatory spark-like patterns in a model completely stochastic Ca+2 oscillator. Our analysis shows that in order to observe such patterns the minimum average number of Ca+2 ions in the cytosol may be as low as about 50.
Received 21 April 2002 / Received in final form 19 June 2002 Published online 14 October 2002
RID="a"
ID="a"e-mail: zhdanov@catalysis.nsk.su 相似文献
2.
K. Broderix M. Weigt A. Zippelius 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(3):441-455
We consider the gelation of particles which are permanently connected by random crosslinks, drawn from an ensemble of finite-dimensional
continuum percolation. To average over the randomness, we apply the replica trick, and interpret the replicated and crosslink-averaged
model as an effective molecular fluid. A Mayer-cluster expansion for moments of the local static density fluctuations is set
up. The simplest non-trivial contribution to this series leads back to mean-field theory. The central quantity of mean-field
theory is the distribution of localization lengths, which we compute for all connectivities. The highly crosslinked gel is
characterized by a one-to-one correspondence of connectivity and localization length. Taking into account higher contributions
in the Mayer-cluster expansion, systematic corrections to mean-field can be included. The sol-gel transition shifts to a higher
number of crosslinks per particle, as more compact structures are favored. The critical behavior of the model remains unchanged
as long as finite truncations of the cluster expansion are considered. To complete the picture, we also discuss various geometrical
properties of the crosslink network, e.g. connectivity correlations, and relate the studied crosslink ensemble to a wider class of ensembles, including the Deam-Edwards
distribution.
Received on 24 April 2002 Published online 14 October 2002
RID="a"
ID="a"deceased
RID="b"
ID="b"e-mail: weigt@theorie.physik.uni-goettingen.de 相似文献
3.
Z. Gulácsi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(3):295-301
We report for the first time exact ground-states deduced for the D
= 2 dimensional generic periodic Anderson model at finite U, the Hamiltonian of the model not containing direct hopping terms for f-electrons (
t
f
= 0). The deduced itinerant phase presents non-Fermi liquid properties in the normal phase, emerges for real hybridization matrix
elements, and not requires anisotropic unit cell. In order to deduce these results, the plaquette operator procedure has been
generalised to a block operator technique which uses blocks higher than an unit cell and contains f-operator contributions acting only on a single central site of the block.
Received 1st July 2002 / Received in final form 16 September 2002 Published online 19 December 2002
RID="a"
ID="a"e-mail: gulacsi@heavy-ion.atomki.hu 相似文献
4.
Transition to Fulde-Ferrel-Larkin-Ovchinnikov phases near the tricritical point: an analytical study
R. Combescot C. Mora 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(4):397-406
We explore analytically the nature of the transition to the Fulde-Ferrel-Larkin-Ovchinnikov superfluid phases in the vicinity
of the tricritical point, where these phases begin to appear. We make use of an expansion of the free energy up to an overall
sixth order, both in order parameter amplitude and in wavevector. We first explore the minimization of this free energy within
a subspace, made of arbitrary superpositions of plane waves with wavevectors of different orientations but same modulus. We
show that the standard second order FFLO phase transition is unstable and that a first order transition occurs at higher temperature.
Within this subspace we prove that it is favorable to have a real order parameter and that, among these states, those with
the smallest number of plane waves are preferred. This leads to an order parameter with a cos(
.
) dependence, in agreement with preceding work. Finally we show that the order parameter at the transition is only very slightly
modified by higher harmonics contributions when the constraint of working within the above subspace is released.
Received 20 February 2002 / Received in final form 4 June 2002 Published online 13 August 2002 相似文献
5.
H. Fehske A.P. Kampf M. Sekania G. Wellein 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):11-16
In order to clarify the physics of the crossover from a Peierls band insulator to a correlated Mott-Hubbard insulator, we
analyze ground-state and spectral properties of the one-dimensional half-filled Holstein-Hubbard model using quasi-exact numerical
techniques. In the adiabatic limit the transition is connected to the band to Mott insulator transition of the ionic Hubbard
model. Depending on the strengths of the electron-phonon coupling and the Hubbard interaction the transition is either first
order or evolves continuously across a narrow intermediate phase with finite spin, charge, and optical excitation gaps.
Received 7 July 2002 / Received in final form 21 October 2002 Published online 27 January 2003
RID="a"
ID="a"e-mail: holger.fehske@physik.uni-greifswald.de 相似文献
6.
Kellerbauer A. Blaum K. Bollen G. Herfurth F. Kluge H.-J. Kuckein M. Sauvan E. Scheidenberger C. Schweikhard L. 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):53-64
For a detailed study of the accuracy of the Penning trap mass spectrometer ISOLTRAP all expected sources of uncertainty were
investigated with respect to their contributions to the uncertainty of the final result. In the course of these investigations,
cross-reference measurements with singly charged carbon clusters 12C+
n were carried out. The carbon cluster ions were produced by use of laser-induced desorption, fragmentation, and ionization
of C60 fullerenes and injected into and stored in the Penning trap system. The comparison of the cyclotron frequencies of different
carbon clusters has provided detailed insight into the residual systematic uncertainty of ISOLTRAP and yielded a value of
8×10-9. This also represents the current limit of mass accuracy of the apparatus. Since the unified atomic mass unit is defined
as 1/12 of the mass of the 12C atom, it will be possible to carry out absolute mass measurements with ISOLTRAP in the future.
Received 7 June 2002 Published online 6 November 2002
RID="a"
ID="a"e-mail: a.kellerbauer@cern.ch
RID="b"
ID="b"Current address: Centre de Physique des Particules de Marseille, 13288 Marseille Cedex 9, France. 相似文献
7.
8.
E. Müller-Hartmann A. Reischl 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):173-183
The derivation of effective spin models describing the low energy magnetic properties of undoped CuO2-planes is reinvestigated. Our study aims at a quantitative determination of the parameters of effective spin models from those of a multi-band model and is supposed to be relevant
to the analysis of recent improved experimental data on the spin wave spectrum of La2CuO4. Starting from a conventional three-band model we determine the exchange couplings for the nearest and next-nearest neighbor
Heisenberg exchange as well as for 4- and 6-spin exchange terms via a direct perturbation expansion up to 12th (14th for the 4-spin term) order with respect to the copper-oxygen hopping tpd. Our results demonstrate that this perturbation expansion does not converge for hopping parameters of the relevant size.
Well behaved extrapolations of the couplings are derived, however, in terms of Padé approximants. In order to check the significance
of these results from the direct perturbation expansion we employ the Zhang-Rice reformulation of the three band model in
terms of hybridizing oxygen Wannier orbitals centered at copper ion sites. In the Wannier notation the perturbation expansion
is reorganized by an exact treatment of the strong site-diagonal hybridization. The perturbation expansion with respect to
the weak intersite hybridizations is calculated up to 4th order for the Heisenberg coupling and up to 6th order for the 4-spin
coupling. It shows excellent convergence and the results are in agreement with the Padé approximants of the direct expansion.
The relevance of the 4-spin coupling as the leading correction to the nearest neighbor Heisenberg model is emphasized.
Received 8 June 2001 / Received in final form 28 May 2002 Published online 19 July 2002 相似文献
9.
N.A. Taylanov G.R. Berdiyorov 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):343-348
The problem of the thermal and magnetic destruction of the critical state in composite superconductors is investigated. The
initial distributions of temperature and electromagnetic field are assumed to be essentially inhomogeneous. The limit of the
thermomagnetic instability in quasi-stationary approximation is determined. The obtained integral criterion, unlike the analogous
criterion for a homogeneous temperature profile, is shown to take into account the influence of any part of the superconductor
on the threshold for critical-state instability.
Received 11 October 2001 / Received in final form 30 November 2002 Published online 14 February 2003
RID="a"
ID="a"e-mail: taylanov@iaph.tkt.uz 相似文献
10.
Bo-Wen Xiao Xin Qian Bo-Qiang Ma 《The European Physical Journal A - Hadrons and Nuclei》2002,15(4):523-527
The electromagnetic form factor of the kaon meson is calculated in the light-cone formalism of the relativistic constituent
quark model. The calculated K+ form factor is consistent with almost all of the available experimental data at low-energy scale, while other properties
of the kaon could also be interrelated in this representation with reasonable parameters. Predictions of the form factors
for the charged and neutral kaons at a higher-energy scale are also given, and we find the non-zero K0 form factor at Q
2≠ 0 due to the mass difference between the strange and down quarks inside K0.
Received: 21 June 2002 / Accepted: 29 July 2002 / Published online: 3 December 2002
RID="a"
ID="a"e-mail: mabq@phy.pku.edu.cn
Communicated by A. Sch?fer 相似文献
11.
Y. Pavlyukh W. Hübner 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):239-246
We present a method for the numerical investigation of the electron dynamics in small metallic clusters in intense laser fields.
We obtain information about collective excitations and relaxation processes in the Na
9
+
and Pt3 clusters analyzing the power spectrum of the dipole moment within a mean-field approach. The power spectrum is computed for
various laser pulse parameters as well as for the limit of an infinitely short laser pulse. Due to the basis set expansion
of the wave function our method is capable to follow the dynamics not only of the whole electron cloud, but of any particular
molecular orbital.
Received 28 March 2002 / Received in final form 31 May 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: pavlyukh@mpi-halle.de 相似文献
12.
We study the force-induced unfolding of random disordered RNA or single-stranded DNA polymers. The system undergoes a second-order
phase transition from a collapsed globular phase at low forces to an extensive necklace phase with a macroscopic end-to-end
distance at high forces. At low temperatures, the sequence inhomogeneities modify the critical behaviour. We provide numerical
evidence for the universality of the critical exponents which, by extrapolation of the scaling laws to zero force, contain
useful information on the ground-state (f = 0) properties. This provides a good method for quantitative studies of scaling exponents characterizing the collapsed globule.
In order to get rid of the blurring effect of thermal fluctuations, we restrict ourselves to the ground state at fixed external
force. We analyze the statistics of rearrangements, in particular below the critical force, and point out its implications
for force-extension experiments on single molecules.
Received 18 June 2002 and Received in final form 23 September 2002
RID="a"
ID="a"e-mail: muller@ipno.in2p3.fr 相似文献
13.
M. Sawicka J.M. Daugas H. Grawe S. Cwiok D.L. Balabanski R. Béraud C. Bingham C. Borcea M. La Commara G. de France G. Georgiev M. Górska R. Grzywacz M. Hass M. Hellström Z. Janas M. Lewitowicz H. Mach I. Matea G. Neyens C. O' Leary F. de Oliveira Santos R.D. Page M. Pfützner Zs. Podolyák K. Rykaczewski M. Stanoiu J. Żylicz 《The European Physical Journal A - Hadrons and Nuclei》2003,16(1):51-54
Decay-spectroscopy study of the 67mFe isomer has been performed at GANIL. This isomer is found to have an energy of 387 keV and a half-life of 75(21) μs. An
intermediate excited state is introduced at 367 keV. The results are interpreted in terms of various nuclear models, and a
deformed shape is inferred for 67Fe.
Received: 12 August 2002 / Accepted: 12 September 2002 / Published online: 17 January 2003
RID="a"
ID="a"e-mail: sawicka@ganil.fr and sawicka@zsjlin.igf.fuw. edu.pl
Communicated by W. Henning 相似文献
14.
B. Pilawa I. Keilhauer G. Fischer S. Knorr J. Rahmer A. Grupp 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):321-330
The magnetic properties of the cyclic compound [Fe6(bicine)6] LiClO4
. 2MeOH are reported. The cluster Fe6(bicine)6 forms an antiferromagnetically coupled ring structure of Fe III ions. The magnetic susceptibility is measured between 2 and 300 K and yields the exchange coupling of J/k
B = - 27.5±0.5 K. The field dependence of the magnetic moment is studied at 3 and 6 K in magnetic fields up to 5 T. The zero-field
splitting of the first excited spin states with S = 2 and 3 are determined by ESR at 94 GHz. The intra-molecular interactions of the Fe III ions are analyzed and the on-site anisotropy of the Fe III due to the ligand-configuration is determined to d /k
B = - 0.633±0.008K.
Received 28 October 2002 / Received in final form 22 February 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: bernd@piobelix.physik.uni-karlsruhe.de 相似文献
15.
D.C. Cabra G.L. Rossini 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):529-532
We study the breaking of parity symmetry in the 2+1 Gross-Neveu model at finite temperature with chemical potential μ, in
the presence of an external magnetic field. We find that the requirement of gauge invariance, which is considered mandatory
in the presence of gauge fields, breaks parity at any finite temperature and provides for dynamical mass generation, preventing
symmetry restoration for any non-vanishing μ. The dynamical mass becomes negligibly small as temperature is raised.
Received 4 April 2002 / Received in final form 12 July 2002 Published online 15 October 2002
RID="a"
ID="a"e-mail: cabra@venus.fisica.unlp.edu.ar 相似文献
16.
Z. Iqbal Y. Zhang H. Grebel S. Vijayalakshmi A. Lahamer G. Benedek M. Bernasconi J. Cariboni I. Spagnolatti R. Sharma F.J. Owens M.E. Kozlov K.V. Rao M. Muhammed 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(4):509-515
Evidence is presented for the formation of a solid phase based on the smallest fullerene, C20, in thin diamond-like carbon films deposited by ultraviolet laser ablation from diamond onto nickel substrates at room temperature
in the presence of 10-4 torr of cyclohexane or benzene. Laser desorption mass spectrometry from the films shows the presence of C20, C21 and C22 species, while micro-Raman spectroscopy and electron diffraction from selected particles together with first principle density-functional
calculations, indicate a cubic solid with dodecahedral C20 cages as building blocks. Unlike solid C60 and fully protonated C20, which are bound by van der Waals forces, the proposed structure is stabilized by linking of the C20 dodecahedra with bridging carbon atoms at interstitial tetrahedral sites to form a face-centered-cubic lattice with 22 carbon
atoms per unit cell.
Received 10 October 2002 / Received in final form 24 December 2002 Published online 6 March 2003
RID="a"
ID="a"e-mail: zafar.iqbal@njit.edu 相似文献
17.
A. Borah S. Ghosh S. Nandy 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):221-225
The novel inelastic collision properties of two-soliton interaction for an n-component coupled higher order nonlinear Schr?dinger equation are studied. Some interesting features of three soliton interactions,
related to the integrability of the n-component coupled higher order nonlinear Schr?dinger equation are also discussed.
Received 17 April 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: abhijit@iitg.ernet.in
RID="b"
ID="b"e-mail: sasanka@iitg.ernet.in
RID="c"
ID="c"e-mail: sudipta@iitg.ernet.in 相似文献
18.
A. Lucchesini S. Gozzini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(2):209-215
By using a diode laser spectrometer based on a commercial heterostructure diode laser operating in free-running mode, line shape parameters of some ammonia ro-vibrational overtones at 790 nm have been measured at room temperature. These
weak absorption lines have been detected by using the wavelength modulation spectroscopy technique with second-harmonic detection.
The broadening and shifting coefficients have been obtained for ten absorption lines by fitting the collected second-harmonic
absorption features and varying the pressure of different buffer gases.
Received 13 February 2002 / Received in final form 18 September 2002 Published online 17 December 2002
RID="a"
ID="a"e-mail: alex@ifam.pi.cnr.it 相似文献
19.
Th. Desaive M. Hennenberg G. Lebon 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):641-647
In this work, we study the problem of onset of thermal convection in a rotating saturated porous medium heated from below.
The effect of rotation is restricted to the Coriolis force, neglecting thus the centrifugal effects, the porous medium is
described by Brinkman's model. The linear eigenvalue problem is solved by means of a modified Galerkin method. The behavior
of the critical temperature gradient is discussed in terms of various parameters of the system for both stationary and overstable
convections. Finally a weakly nonlinear analysis is provided to derive amplitude equations and to study the onset of Küppers-Lortz
instability.
Received 24 June 2002 / Received in final form 11 September 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: tdesaive@ulg.ac.be 相似文献
20.
J.V. Jovanović S.B. Vrhovac Z.Lj. Petrović 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(3):335-342
Transport properties of ion swarms in presence of Resonant Charge Transfer (RCT) collisions are studied using Momentum Transfer
Theory (MTT). It was shown that, not surprisingly, RCT collisions may be represented as a special case of elastic scattering.
Using the developed MTT we tested a previously available anisotropic set of cross-sections for Ar+Ar
+ collisions by making the comparisons with the available data for the transverse diffusion coefficient. We also developed
an anisotropic set of Ne+Ne
+ integral cross-sections based on the available data for mobility, longitudinal and transverse diffusion. Anisotropic sets
of cross-sections are needed for Monte Carlo simulations of ion transport and plasma models.
Received 16 June 2002 / Received in final form 2nd August 2002 Published online 24 September 2002
RID="a"
ID="a"e-mail: vrhovac@phy.bg.ac.yu
RID="b"
ID="b"e-mail: zoran@phy.bg.ac.yu 相似文献