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1.
Achard MF Bedel JP Marcerou JP Nguyen HT Rouillon JC 《The European physical journal. E, Soft matter》2003,10(2):129-134
Taking advantage of the great number of bent-core or “banana" compounds synthesized and studied in the laboratory, we describe
their behaviour under the application of an external electric field. If the field were a static one, we would work within
the frame of an equilibrium phase diagram in a (field E, temperature T) space where some phases would be simple dielectrics and others ferroelectric ones with a macroscopic polarization, either
spontaneous or induced by the field. In this paper, we deal with the basic responses of “banana” liquid crystals under the
application of a low frequency (1 to 100 Hz) AC field. Firstly square-wave voltages allow us to locate the phase boundary
between dielectric (at lower field) and ferroelectric phases (higher field) at a given temperature and field threshold. Then
we apply slowly varying AC voltages with shapes like triangle or “triple-plateau” to check out the stability of the induced
ferroelectric phase versus field removal. Three behaviours are encountered, the unstable one (short lifetime of the high-field ferroelectric phase)
where the macroscopic polarization is destroyed and then rebuilt in the opposite direction during each half period and usually
called “antiferroelectric”; the stable one (long lifetime) with a polarization that rotates at constant modulus which is labeled
as “ferroelectric” and a new one where the macroscopic polarization is proportional to the applied fied, we named this behaviour
as “superparaelectric”. Let us stress that these observations apply to the ferroelectric phases of the (E, T) phase diagram not to the zero field (0,T) phases observed in the usual phase characterization experiments except for an
eventual spontaneous ferroelectric phase.
Received 18 April 2002 and Received in final form 17 January 2003 Published online: 16 April 2003
RID="a"
ID="a"e-mail: marcerou@crpp.u-bordeaux.fr
RID="b"
ID="b"URL: http://www.crpp-bordeaux.cnrs.fr 相似文献
2.
A theoretical model based on the competition between short-pitch and long-pitch types of helical order is developed for thin
films of antiferroelectric smectic liquid crystals. In the case of the “bookshelf” structure of the film and non-polar surfaces,
subsurface perturbations of the ordering are found out analytically. Corresponding contributions to the free energies of the
different phases are analysed. The possibility of sufficient influence of the boundaries on phase sequences is predicted even
in the case of weak surface anchoring. A consistent explanation of the controversial experimental information is given; further
ways of experimental justification of the model assumptions are discussed.
Received 23 May 2002
RID="a"
ID="a"e-mail: mgorkoun@uos.de 相似文献
3.
P. Berthault H. Desvaux 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):65-73
NMR of laser-polarized xenon is used to probe the dissolution behaviour of the noble gas in different liquids. The dissolution
and self-relaxation rates are extracted via a macroscopic model, and comparison of the decay rate of the xenon magnetization in deuterated and non-deuterated solvent
pairs allows the determination of the pure dipole-dipole contribution to relaxation. A transient convective effect, tentatively
assigned to the xenon concentration gradient, is observed and characterized by diffusion encoding MRI experiments. The flow
of xenon penetrates inside the solvent near the walls of the NMR tube, the longitudinal images showing a “” shape, the transverse ones a “O” shape. This convection effect has implications for delivery conditions of laser-polarized
xenon in continuous flow experiments and magnetic resonance imaging.
Received 29 April 2002 / Received in final form 26 July 2002 Published online 22 October 2002
RID="a"
ID="a"e-mail: hdesvaux@cea.fr
RID="b"
ID="b"URA CNRS/CEA 331 相似文献
4.
J. Huikari M. Oinonen A. Algora J. Cederkäll S. Courtin P. Dessagne L. Fraile S. Franchoo H. Fynbo W.X. Huang A. Jokinen A. Knipper F. Marechal C. Miehé E. Nacher K. Peräjärvi E. Poirier L. Weissman J. Äystö 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):359-363
The β-decay of 75Sr to its mirror nucleus 75Rb was studied at the ISOLDE PSB facility at CERN by means of β-delayed γ and proton spectroscopy. The decay Q-value and β-delayed γ intensity were measured for the first time. These results, 10.60±0.22 MeV and 4.5+1.9
-0.7%, together with accurate measurements of the β-decay half-life and β-delayed proton branching ratio yielded the Gamow-Teller
strength 0.35±0.05 for the mirror transition. Implications of the results on studies of deformation effects and on the path
of the rapid proton capture process are discussed.
Received: 26 September 2002 / Accepted: 30 October 2002 / Published online: 18 February 2003
RID="a"
ID="a"e-mail: jussi.huikari@phys.jyu.lfi
Communicated by D. Schwalm 相似文献
5.
M.A. Caprio N.V. Zamfir E.A. McCutchan R.F. Casten Z. Berant H. Amro C.J. Barton C.W. Beausang D.S. Brenner J.R. Cooper R.L. Gill G. Gürdal A.A. Hecht C. Hutter R. Krücken D.A. Meyer J.R. Novak N. Pietralla P.H. Regan J.J. Ressler 《The European Physical Journal A - Hadrons and Nuclei》2003,16(2):177-180
Lifetime measurements for the 2+
1 levels of 162Er and 162Yb were obtained in β+/ɛ decay at the Yale Moving Tape Collector by fast electronic scintillation timing of β+γ coincidences.
Received: 2 September 2002 / Accepted: 1 October 2002 / Published online: 4 February 2003
RID="a"
ID="a"e-mail: mark.caprio@yale.edu
Communicated by J. ?yst? 相似文献
6.
M. Lach J. Styczeń W. Meczyński P. Bednarczyk A. Bracco J. Grebosz A. Maj J.C. Merdinger N. Schulz M.B. Smith K.M. Spohr J.P. Vivien M. Ziebliński 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):309-311
High-spin states of the 42Ca nucleus, populated in the 68 MeV 18O + 30Si reaction, have been studied in a γ-γ-recoil coincidence experiment. The level scheme of 42Ca has been extended up to 13.7 MeV. An elaborate decay pattern with various paths, together with high-quality DCO and polarization
information assigns spins and parities for almost all observed levels. The sequence of non-yrast positive-parity states is
discussed and compared with highly deformed bands in 36Ar and 40Ca.
Received: 26 November 2002 / Accepted: 11 December 2002 / Published online: 18 February 2003
RID="a"
ID="a"e-mail: Malgorzata.Lach@ifj.edu.pl
RID="b"
ID="b"Present address: TRIUMF, Vancouver, Canada.
RID="†"
ID="†"Deceased.
Communicated by D. Schwalm 相似文献
7.
S. Zschocke O.P. Pavlenko B. Kämpfer 《The European Physical Journal A - Hadrons and Nuclei》2002,15(4):529-537
QCD sum rules are evaluated at finite nucleon densities and temperatures to determine the change of mass parameters for the
lightest vector mesons ρ, ω and φ in a strongly interacting medium. For conditions relevant for the starting experiments at
HADES we find that the in-medium mass shifts of the ρ- and ω-mesons are governed, within the Borel QCD sum rule approach,
by the density and temperature dependence of the four-quark condensate. In particular, the variation of the strength of the
density dependence of the four-quark condensate reflects directly the decreasing mass of the ρ-meson and can lead to a change
of the sign of the ω-meson mass shift as a function of the density. In contrast, the in-medium mass of the φ-meson is directly
related to the chiral strange quark condensate which seems correspondingly accessible.
Received: 15 May 2002 / Accepted: 31 July 2002 / Published online: 10 December 2002
RID="a"
ID="a"e-mail: Kaempfer@fz.rossendorf.de
Communicated by A. Sch?fer 相似文献
8.
E. Roeckl 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):139-144
This review focusses on recent results obtained by using fusion-evaporation reactions for the production of N ≃ Z nuclei, the on-line mass separator of GSI for the preparation of the radioactive samples, and charged-particle and γ-ray
detectors for performing decay spectroscopy. The experimental results on prompt and β-delayed disintegration modes are discussed
in comparison with theoretical model predictions.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: e.roeckl@gsi.de 相似文献
9.
T. Faestermann R. Schneider A. Stolz K. Sümmerer E. Wefers J. Friese H. Geissel M. Hellström P. Kienle H.-J. Körner M. Mineva M. Münch G. Münzenberg C. Schlegel K. Schmidt P. Thirolf H. Weick K. Zeitelhack 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):185-188
Neutron deficient nuclei near 100Sn have been produced by fragmentation of a 1 .
AGeV 112Sn beam. The fragments were separated, identified and stopped in a highly segmented silicon strip detector stack. This detector
measured the total energy of emitted β+-particles. γ-radiation was measured with surrounding detectors. The half-lives for many nuclides have been determined for
the first time and give important information for the following topics: For the heaviest particle-stable odd-odd nuclei 90Rh, 94Ag and 98In we observed for the first time fast β-decays, compatible with superallowed Fermi transitions and confirmed such decays
for 78Y, 82Nb and 86Tc. We have also observed long-lived T = 0 states in some of these nuclei. We measured the half-lives of all rp-process waiting-point nuclei from 80Zr up to 92, 93Pd. In addition we find the proton drip line nucleus 77Y to decay dominantly via β-decay. To study the Gamov-Teller strength in the β-decay near the doubly magic 100Sn we measured the half-life, β- and γ-spectrum of 102Sn. We propose a level scheme for the daughter nuclide 102In and deduce the Gamov-Teller strength (B
GT = 4.0±0.6). This is one of the largest values known.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: thomas.faestermann@ph.tum.de 相似文献
10.
Y. Kojima M. Shibata A. Taniguchi T. Hanafusa E. Yoshida K. Shizuma Y. Kawase S. Yamada 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):331-336
The β--decay of 151Pr produced by the thermal neutron-induced fission of 235U has been studied using an on-line isotope separator. From an internal-conversion electron measurement with a Si(Li) detector,
K-conversion coefficients were obtained for 20 γ-transitions. Spins and parities of 6 excited levels in 151Nd were newly determined from the deduced multipolarities: even parities for the 543 and 627 keV levels, odd parities for
250 and 599 keV, (3/2, 5/2)+ for 685 keV, and (1/2, 3/2)+ for 880 keV. The level structure was compared with the rotation-vibration coupling Nilsson model.
Received: 28 June 2002 / Accepted: 31 October 2002 / Published online: 25 February 2003
RID="a"
ID="a"e-mail: ykojima@hiroshima-u.ac.jp
Communicated by J. ?yst? 相似文献
11.
K. Knorr L. Ehm M. Hytha B. Winkler W. Depmeier 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):297-303
The high-pressure behaviour of PbS was investigated by angular dispersive X-ray powder diffraction up to pressures of 6.8
GPa. Experiments were accompanied by first principles calculations at the density functional theory level. By combining both
methods reliable data for the elastic properties of rock-salt type α- and high-pressure β-PbS could be obtained. β-PbS could be determined to crystallise in the CrB-type (B33), with space group Cmcm. The reversible ferro-elastic α/β transition is of first order. It is accompanied by a large volume discontinuity of about 5% and a coexistence region of the
two phases. A gliding mechanism of {001} bilayers along one of the cubic 〈110〉 directions governs the phase transition which can be described in terms of group/subgroup relationships via a common subgroup, despite its reconstructive character. The quadrupling of the primitive unit cell indicates a wave vector
(0, 0,π/
a
) on the Δ-line of the Brillouin zone.
Received 11 October 2002 Published online 14 February 2003
RID="a"
ID="a"Also at: Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10, 16253 Praha 6, Czech Republic e-mail: knorr@min.uni-kiel.de
RID="b"
ID="b"Present address: University of Cambridge, Cavendish Laboratory (TCM), Madingley Road, Cambridge CB3 0HE, UK
RID="c"
ID="c"Present address: Johann-Wolfgang Goethe Universit?t, Mineralogisches Institut, Kristallographie, Senckenberganlage 30, D 60054 Frankfurt a.M.,
Germany 相似文献
12.
A nanosecond scale in situ probe reveals that a bulk linear polymer undergoes a sharp phase transition as a function of the degree of conversion, as
it nears the glass transition. The scaling behaviour is in the same universality class as percolation. The exponents γ and
β are found to be 1.7±0.1 and 0.41±0.01 in agreement with the best percolation results in three dimensions.
Received 29 August 2002
RID="a"
ID="a"e-mail: erzan@gursey.gov.tr e-mail: erzan@itu.edu.tr 相似文献
13.
I. Piqueras M.J.G. Borge Ph. Dessagne J. Giovinazzo A. Huck A. Jokinen A. Knipper C. Longour G. Marguier M. Ramdhane V. Rauch O. Tengblad G. Walter Ch. Miehé 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):313-329
The beta-decay of the N = Z, even-even nucleus 72Kr has been studied at the ISOLDE PSB facility at CERN. Measurements of βγ and βγγ coincidences have enriched the decay scheme
of the daughter nucleus 72Br with 27 new low spin levels. A more precise half-life of T
1/2 = 17.1(2) s has been determined. Strong feeding to the 72Br ground state is established yielding an unambiguous J
π = 1+ assignment for this state. Candidates for the 72Br g.s. wave function are discussed in the framework of a self-consistent deformed mean-field calculation with SG2 Skyrme
force and pairing correlations. A search for beta-delayed particle emission was made and an upper limit of 10-6 for this decay branch obtained. The cumulated experimental level density of 1+ states has been fitted with the constant temperature formula. The comparison indicates that most likely all 1+ levels up to 1.2 MeV have been observed in this investigation. The corresponding nearest-neighbour level spacing does not
follow a Poisson distribution. The Gamow-Teller strength distribution is compared, in terms of nuclear deformation, with different
calculations made in the framework of the quasiparticle random phase approximation.
Received: 7 February 2002 / Accepted: 31 October 2002 / Published online: 6 March 2003
RID="a"
ID="a"e-mail: borge@pinar2.csic.es
RID="b"
ID="b"Present address: Centre d' Etudes Nucléaires de Bordeaux-Gradignan, Le Haut Vigneau, F-33175 Gradignan Cedex, France.
RID="c"
ID="c"Present address: University Mentouri, 25000 Constantine, Algeria.
Communicated by J. ?yst? 相似文献
14.
B. Leblanc E. Lutton F. Axel 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):619-628
We present the first application of Genetic Algorithms to the analysis of data from an aperiodically ordered system, high
resolution X-Ray diffraction spectra from multilayer heterostructures arranged according to a deterministic or random scheme.
This method paves the way to the solution of the “inverse problem”, that is the retrieval of the generating disorder from
the investigation of the spectra of an unknown sample having non crystallographic, non quasi-crystallographic order.
Received 18 March 2002 / Received in final form 3 July 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: Evelyne.Lutton@inria.fr
RID="b"
ID="b"CNRS UMR 8502 相似文献
15.
16.
Zhi Ping Wang Xi Xia Liang 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(3):265-271
Rayleigh-Schr?dinger perturbation theory and an improved Wigner-Brillouin perturbation theory has been used to study the cyclotron
resonance of the polarons in ternary mixed crystals in the zero-temperature limit. The interaction between an electron and
two branches of longitudinal optical phonon modes is taken into account in the framework of the random-element-isodisplacement
model. The numerical results for several ternary mixed crystals show that the polaronic cyclotron energy and mass split successively
twice related to the higher and lower branches of longitudinal optical phonon modes of ternary mixed crystals. A non-linear
dependence of the polaronic cyclotron energy and mass on the composition x is found.
Received 19 March 2002 / Received in final form 21 March 2003 Published online 20 June 2003
RID="a"
ID="a"e-mail: xxliang@imu.edu.cn 相似文献
17.
D. Rudolph 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):161-165
During recent years the nuclear decay modes of discrete prompt proton and α-particle emission from (super)deformed high-spin
states have been discovered in nuclei in the vicinity of 56Ni. The latest news from experiments performed at EUROBALL and GAMMASPHERE regarding these decays are presented and discussed.
Published online: 31 October 2002
RID="a"
ID="a"e-mail: dirk.rudolph@kosufy.lu.se 相似文献
18.
19.
Nonlinear dielectric response of antiferroelectric liquid crystals has been studied in the smectic Cα* (SmCα*) phase. The linear dielectric spectrum shows a single relaxation of Debye type and its relaxation frequency is as high as
one hundred kHz. The profile of the third-order nonlinear dielectric spectrum varies in complex fashion with temperature.
In the vicinity of the SmA-SmCα* phase transition, experimentally obtained nonlinear spectra are well described by those calculated with phenomenological
theory of Landau type. The soft mode of the SmCα* phase shows critical slowing-down near the transition temperature. In the lower-temperature region of the SmCα* phase, the contribution from the soft mode of the SmCα* phase reduces and the other relaxation mode with Debye-type spectrum appears at several hundred Hz in the nonlinear spectrum.
The appearance of this low-frequency mode suggests that the cooperative fluctuation of directors over long range exists in
the SmCα* phase.
Received 19 April 2002 and Received in final form 23 July 2002
RID="a"
ID="a"e-mail: kimura@exp.t.u-tokyo.ac.jp 相似文献
20.
M. Sasaki V. Dupuis J.-P. Bouchaud E. Vincent 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(3):469-479
We study the deviations from perfect memory in negative temperature cycle spin glass experiments. It is known that the a.c.
susceptibility after the temperature is raised back to its initial value is superimposed to the reference isothermal curve
for large enough temperature jumps ΔT (perfect memory). For smaller ΔT, the deviation from this perfect memory has a striking non monotonous behavior: the `memory anomaly' is negative for small ΔT's, becomes positive for intermediate ΔT's, before vanishing for still larger ΔT's. We show that this interesting behavior can be reproduced by simple Random Energy trap models. We discuss an alternative
interpretation in terms of droplets and temperature chaos.
Received 23 May 2002 Published online 14 October 2002
RID="a"
ID="a"e-mail: sasaki@ipno.in2p3.fr 相似文献