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1.
N.-K. Lee T.A. Vilgis 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(4):451-465
We study the elastic properties of single A/B random copolymer chains, with a specific sequence and use them as theoretical
model for so called HP proteins. HP proteins carry hydrophilic (P) and hydrophobic (H) monomers. We predict a rich structure
in the force-extension relations which can be attributed to the information in the sequence. The variational method is used
to probe local minima on the path of stretching and releasing for the chain molecules. At a given force, we find multiple
configurations which are separated by energy barriers. A collapsed globular configuration consists of several domains which
unravel cooperatively. Upon stretching, the unfolding path shows a stepwise pattern corresponding to the unfolding of each
domain. While releasing, several cores can be created simultaneously in the middle of the chain, resulting in a different
path of collapse. The long-range interactions and stiffness of the chain simplify the potential landscape given by the disorder
in sequence.
Received 5 March 2002 / Received in final form 16 May 2002 Published online 13 August 2002 相似文献
2.
V. Bernard N. Kaiser Ulf -G. Meißner A. Schmidt 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(4):317-325
We consider the spin-averaged nucleon forward Compton scattering amplitude in heavy baryon chiral perturbation theory including all terms to order
. The chiral prediction for the spin-averaged forward Compton scattering amplitude is in good agreement with the data for photon energies110 MeV. We also evaluate the nucleon electric and magnetic Compton polarizabilities to this order and discuss the uncertainties of the various counter terms entering the chiral expansion of these quantities. 相似文献
3.
E.?Tomasi-GustafssonEmail author F.?Lacroix C.?Duterte G.?I.?Gakh 《The European Physical Journal A - Hadrons and Nuclei》2005,24(3):419-430
We perform a global analysis of the experimental data of the electromagnetic nucleon form factors, in space-like and time-like regions. We give the expressions of the observables in annihilation processes, such as p + ¯↦ℓ+ + ℓ-, ℓ = e or μ, in terms of form factors. We discuss some of the phenomenological models proposed in the literature for the space-like region, and consider their analytical continuation to the time-like region. After determining the parameters through a fit on the available data, we give predictions for the observables which will be experimentally accessible with large statistics, polarized annihilation reactions 相似文献
4.
M. Samsel-Czekała G. Kontrym-Sznajd G. Döring W. Schülke J. Kwiatkowska F. Maniawski S. Kaprzyk A. Bansil 《Applied Physics A: Materials Science & Processing》2003,77(1):87-92
A reconstruction technique based on the solution of the Radon transform in terms of Jacobi polynomials is used to obtain the
3D electron momentum density, ϱ(p), from nine high-resolution Compton profiles (CPs) for a Cu0.9Al0.1 disordered alloy single crystal. The method was also applied to theoretical CPs computed within the Korringa–Kohn–Rostoker
coherent potential approximation (KKR-CPA) first-principles scheme for the same nine orientations of the crystal. The experimental
ϱ(p) is in satisfactory agreement with the theoretical ϱ(p), shows most details of the Fermi surface (FS) and exhibits electron correlation effects. We comment on the map of the FS
obtained by folding the reconstructed ϱ(p) into the first Brillouin zone, which yields the occupation number density, ϱ(k). A test of the validity of data via a consistency condition (within our reconstruction algorithm) as well as the propagation
of experimental noise in the reconstruction of both ϱ(p) and ϱ(k) are investigated.
Received: 24 October 2001 / Accepted: 20 January 2002 / Published online: 3 June 2002
RID="*"
ID="*"Corresponding author. Fax: +48-71/344-10-29, E-mail: samsel@int.pan.wroc.pl 相似文献
5.
H. B. Zhu H. X. Ge L. Y. Dong S. Q. Dai 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(1):103-108
Based on the Nagel-Schreckenberg (NaSch)
model of traffic flow, a modified cellular automaton (CA) traffic
model with the density-dependent randomization (abbreviated as the
DDR model) is proposed to simulate traffic flow. The fundamental
diagram obtained by simulation shows the ability of this modified
NaSch model to capture the essential features of traffic flow,
e.g., synchronized flow, metastable state, hysteresis and phase
separation at higher densities. Comparisons are made between this
DDR model and the NaSch model, also between this DDR model and the
VDR model. And the underlying mechanism is analyzed. All these
results indicate that the presented model is reasonable and more
realistic. 相似文献
6.
I. K. Bensafa P. Achenbach M. Ases Antelo C. Ayerbe D. Baumann R. Böhm D. Bosnar E. Burtin X. Defaÿ N. D'Hose M. Ding M. O. Distler L. Doria H. Fonvieille J. M. Friedrich J. Friedrich J. García Llongo P. Janssens G. Jover Mañas M. Kohl G. Laveissière M. Lloyd M. Makek J. Marroncle H. Merkel P. Merle U. Müller L. Nungesser B. Pasquini R. Pérez Benito J. Pochodzalla M. Potokar G. Rosner S. Sánchez Majos M. Seimetz S. Širca T. Spitzenberg G. Tamas R. Van de Vyver L. Van Hoorebeke Th. Walcher M. Weis 《The European Physical Journal A - Hadrons and Nuclei》2007,32(1):69-75
The beam-helicity asymmetry has been measured simultaneously for the reactions
p→epγ and
p→epπ
0 in the Δ(1232)-resonance region at Q
2 = 0.35(GeV/c)2. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The
results are compared with calculations based on dispersion relations for virtual Compton scattering and with the MAID model
for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining
discrepancies may be ascribed to an imperfect parametrization of some γ
(*)
N→πN multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels (γ and π
0) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization. 相似文献
7.
8.
By using the Al'tshuler-Aronov-Spivak (AAS) model, we give the amplitude changing with Rashba spin-orbit interaction (SOI) and Dresselhaus SOI strength. In the first idea 1D square loop (SL), Rashba SOI acts on two sides while Dresselhaus SOI acts on the other two sides. In the second SL, we consume Rashba SOI and Dresselhaus SOI act on four sides simultaneously. This model can be replaced by another one that Rashba SOI and Dresselhaus SOI act on every side independently, and each side is twice long. We theoretically illustrate the influence of the Dresselhaus SOI on node position and number. To explain the “half oscillation” phenomenon found in experiment, we apply Dresselhaus SOI to the ideal 1D SL. The conclusion is that the Dresselhaus SOI has a strong effect on the emergence of “half oscillation”. 相似文献
9.
Atsushi Goto Tadashi Shimizu Kenjiro Hashi Shinobu Ohki 《Applied Physics A: Materials Science & Processing》2008,93(2):533-536
We present a scheme of surface-sensitive nuclear magnetic resonance in optically pumped semiconductors, where an NMR signal from a part of the surface of a bulk compound semiconductor is detected
apart from the bulk signal. It utilizes optically oriented nuclei with a long spin-lattice relaxation time as a polarization
reservoir for the second (target) nuclei to be detected. It provides a basis for the nuclear spin polarizer [IEEE Trans. Appl. Supercond. 14:1635, 2004], which is a polarization reservoir at the surface of the optically pumped semiconductor that polarizes nuclear spins in
a target material in contact through the nanostructured interfaces. 相似文献
10.
T. Ouchterlony I.V. Zozoulenko C.-K. Wang K.-F. Berggren C. Gould A.S. Sachrajda 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):361-370
We study the conductance of a square quantum dot, modeling the potential with a self-consistent Thomas-Fermi approximation.
The resulting potential is characterized by level statistics indicative of mixed chaotic and regular electron dynamics within
the dot in spite of the regular geometry of the gates defining the dot. We calculate numerically, for the case of a quantum
dot with soft confinement, the weak localization (WL) correction. We demonstrate that this confining potential may generate
either Lorentzian or linear lineshapes depending on the number of modes in the leads. Finally, we present experimental WL
data for a lithographically square dot and compare the results with numerical calculations. We analyze the experimental results
and numerical simulations in terms of semiclassical and random matrix theory (RMT) predictions and discuss their limitations
as far as real experimental structures are concerned. Our results indicate that direct application of the above predictions
to distinguish between chaotic and regular dynamics in a particular cavity can not always lead to reliable conclusions as
the shape and magnitude of the WL correction can be strongly sensitive to the geometry-specific, non-universal features of
the system.
Received 13 May 1998 相似文献