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71.
R.D. Astumian 《Applied Physics A: Materials Science & Processing》2002,75(2):193-206
Non-equilibrium fluctuations, whether imposed externally or driven by an energy-releasing chemical reaction, can cause a protein
to cycle through several conformations. This cycling can drive a process thermodynamically uphill even though any one conformation
considered independently catalyzes the process in the downhill direction. This is because the different conformations have
different rate constants (energy barriers) between the states in the catalytic cycle. Even though each conformation individually
obeys detailed balance, the flashing between different energy profiles gives rise to a ratchet effect. Further, by exploiting
protein conformational dynamics, a single stochastic input can be converted into two phase-shifted internal parameters (e.g.
a kinetic barrier height and a binding well energy). This allows the output process to be driven nearly adiabatically, explaining
in part the very high efficiencies observed for some biological energy-transduction processes. The results apply equally to
driving a biochemical reaction away from equilibrium by an enzyme, to formation of an osmotic gradient across a membrane by
a molecular pump, or to motion and generation of force by a molecular motor.
Received: 8 February 2002 / Accepted: 4 March 2002 / Published online: 22 April 2002 相似文献
72.
T. Kanna M. Lakshmanan 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):249-254
Soliton interactions in systems modelled by coupled nonlinear Schr?dinger (CNLS) equations and encountered in phenomena such
as wave propagation in optical fibers and photorefractive media possess unusual features: shape changing intensity redistributions,
amplitude dependent phase shifts and relative separation distances. We demonstrate these properties in the case of integrable
2-CNLS equations. As a simple example, we consider the stationary two-soliton solution which is equivalent to the so-called
partially coherent soliton (PCS) solution discussed much in the recent literature.
Received 1st October 2001 / Received in final form 4 February 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: lakshman@bdu.ernet.in 相似文献
73.
G. Montagnoli S. Beghini F. Scarlassara A.M. Stefanini L. Corradi C.J. Lin G. Pollarolo Aage Winther 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):351-356
The two systems 40Ca + 90,96Zr have been studied by measuring nucleon transfer reactions at two energies near the Coulomb barrier, thus complementing
the available sub-barrier fusion cross-sections. Angular distributions for various transfer channels have been determined.
Significantly larger neutron transfer cross-sections are found for the target 96Zr that exhibits the larger enhancement in the sub-barrier fusion cross-sections. All data have been analyzed with a new model
for heavy-ion collisions that calculates simultaneously transfer cross-sections, fusion excitation functions and barrier distributions.
The model gives a good account of both transfer and fusion data.
Received: 2 May 2002 / Accepted: 4 June 2002 / Published online: 26 November 2002
RID="a"
ID="a"e-mail: montagnoli@pd.infn.it, Fax +39049 8277102, Tel. +39049 8277117.
RID="b"
ID="b"On leave from the China Institute for Atomic Energy, 102413 Beijing, China.
Communicated by C. Signorini 相似文献
74.
M. Di Toro V. Baran M. Colonna V. Greco S. Maccarone M. Cabibbo 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):155-161
In the reaction dynamics of intermediate-energy radioactive beams we can probe highly asymmetric nuclear matter in compressed
as well as dilute phases. In this report some predictions are presented, based on analytical results as well as on reaction
simulations. We suggest a series of experiments with RIB aimed to shed light on isospin properties of nuclear interactions
in the medium.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
75.
Fabrication, morphology and structural characterization of ordered single-crystal Ag nanowires 总被引:1,自引:0,他引:1
J. Zhang X. Wang X. Peng L. Zhang 《Applied Physics A: Materials Science & Processing》2002,75(4):485-488
Highly aligned Ag nanowires have been synthesized by dc electrodeposition within a hexagonal close-packed nanochannel anodic
aluminum oxide template. The pore diameter varies from 20 nm to 50 nm depending on the anodization voltage and temperature
for the two types of aqueous solutions, sulphuric and oxalic acids, respectively. The size and morphology of the Ag nanowire
arrays were measured by scanning electron microscopy and transmission electron microscopy. The images indicate that the highly
aligned Ag nanowires grow in the uniform nanochannels of the anodic alumina template and that the size of the nanowires depends
on the size of the nanochannels. X-ray diffraction, selected area electron diffraction pattern and high-resolution transmission
electron microscopy images show that the Ag nanowires are single-crystal. The temperature coefficient of resistivity (temperature
range from 4.2 K to 300 K) of the Ag nanowire arrays decreases with decreasing diameter of the nanowires.
Received: 5 November 2001 / Revised version: 12 March 2002 / Published online: 6 June 2002 相似文献
76.
J. Dabrowski J. Rożynek G.S. Anagnostatos 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):125-131
It is shown that among four models of the Nijmegen baryon-baryon interaction only model F --which leads to a repulsive potential
felt by the Σ hyperon inside the nucleus-- is consistent both with the analysis of Σ- atoms and of the (K
-,π) reactions. The Nijmegen models are used to determine the strong complex single-particle (s.p.) potential of Σ-, and to calculate the strong-interaction shifts and widths of the lowest observed levels of Σ- atoms. The results obtained with model F are in best agreement with the experimental data.
Received: 15 January 2002 / Accepted: 14 March 2002 相似文献
77.
R. Hoelzl K.-J. Range L. Fabry 《Applied Physics A: Materials Science & Processing》2002,75(4):525-534
Based on experimental findings we set up calculations of numerical modeling of gettering efficiencies for Cu in various silicon
wafers. Gettering efficiencies for Cu were measured by applying a reproducible spin-on contamination in the 1012 atoms/cm2 range, followed by a thermal treatment to redistribute the metallic impurity. Subsequently, the wafers were analyzed by a
novel wet chemical layer-by-layer etching technique in combination with inductively coupled plasma mass spectrometry. We investigated
p/p+ and n/n+ epitaxial wafers with different doping levels and different substrate-doping species. We have also investigated
gettering efficiencies of phosphorus-diffused p- and n-type wafers. Heavilyboron doped silicon exhibited a gettering efficiency
of ∼100%, while gettering by n+ silicon occurred for doping levels >3×1019 atoms/cm3 only. In another set of experiments we investigated the dependence of the gettering efficiency of p-type wafers with poly-silicon
back sides for different cooling rates and Cu spiking levels. A strong dependence on both parameters was found. Cu gettering
in p/p+ epitaxial wafers was modeled by calculating the increased solubility of Cu in p+ silicon compared to non-doped silicon
taking into account the Fermi-level effect, which stabilizes donors in p+ silicon, and the pairing reaction between Cu and
B. Calculated gettering efficiencies were in very good agreement with experimental results. Gettering in n+ silicon was similarly
modeled in terms of pairing reactions and the Fermi-level effect. But, for n-type silicon, many experimental uncertainties
existed; thus, we applied our expressions to solubility data of Hall and Racette to obtain the unknown parameters. The empirical
calculations were in good agreement even with results on n/n+ wafers. For phosphorus-diffused wafers we had to consider an
excess vacancy concentration of 1.2–5.5 times the equilibrium concentration to explain the experimental findings by the model.
Gettering by poly-silicon back sides was simulated by solving the time-dependent diffusion equation with boundary conditions
that take into account different surface reaction rates of silicon point defects. Using this advanced model, the experimentally
measured gettering efficiencies were reproduced within the uncertainty of the measurement.
Received: 3 September 2001 / Accepted: 4 September 2001 / Published online: 20 December 2001 相似文献
78.
J. Kurpeta G. Lhersonneau A. Płochocki J.C. Wang P. Dendooven A. Honkanen M. Huhta M. Oinonen H. Penttilä K. Peräjärvi J.R. Persson J. Äystö 《The European Physical Journal A - Hadrons and Nuclei》2002,13(4):449-460
The decay of neutron-rich isotope 113Ru obtained as on-line mass separated product of proton-induced fission has been investigated by γγ coincidence and spectrum
multiscaling measurements. Decay schemes for both low- and high-spin isomers of 113Ru have been constructed. The level scheme of 113Rh is considerably extended. Systematics of the lowest-lying rhodium levels is smooth. The picture of shape coexistence established
for neutron-rich Rh isotopes near-neutron midshell is confirmed with the observation of a K = 1/2 deformed band, with its 3/2+ state at 600 keV being the lowest-lying level and of probable 7/2+
and 5/2+
band members. A large fraction of β feeding is found to populate high-lying levels in 113Rh. The GT strength in 113Rum decay is significantly larger than for the decay of 113Rug and of lighter rhodium isotopes.
Received: 18 January 2001 / Accepted: 14 January 2002 相似文献
79.
A. Türler 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):271-274
In the past ten years, nuclear chemists have made considerable progress in developing fast on-line separation techniques,
which allowed to chemically characterize the first four transactinide elements Rf (rutherfordium, Z = 104), Db (dubnium, Z = 105), Sg (seaborgium, Z = 106), and recently also Bh (bohrium, Z = 107). In all cases the isolated nuclides were unambiguously identified by observing genetically linked decay chains. Nuclides
with production cross-sections of less than 100 pb and half-lives as short as a few seconds have been chemically isolated.
Thus, chemists have discovered or significantly contributed to the characterization of the nuclear-decay properties of a number
of transactinide nuclei. New techniques with greatly improved overall efficiencies should allow chemists to extend their studies
to even heavier elements such as Hs (hassium, Z = 108) and to the recently discovered superheavy elements with Z = 112 and 114, which can be produced only with picobarn cross-sections.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: andreas.tuerler@psi.ch 相似文献
80.
The compaction of granular packings or soils is a collective process which for higher densities becomes increasingly slower
reaching glassy behaviour. We present a study of this problem from various points of view, in particular we will represent
the evolving force network that percolates through the system by an inverse fiber rupture model.
Received 15 March 2002 and Received in final form 29 July 2002 相似文献