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61.
62.
Scanning probe microscopy characterization of gold-chemisorbed poplar plastocyanin mutants 总被引:1,自引:0,他引:1
L. Andolfi B. Bonanni G. W. Canters M. Ph. Verbeet S. Cannistraro 《Surface science》2003,530(3):181-194
Two poplar plastocyanin mutants adsorbed onto gold electrodes have been characterized at single molecule level by scanning probe microscopy. Immobilization of the two redox metalloprotein mutants on Au(1 1 1) surface was achieved by either a disulphide bridge (PCSS) or a single thiol (PCSH), both the anchoring groups having been introduced by site-directed mutagenesis. Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) analysis gives evidence of a stable and robust binding of both mutants to gold. The lateral dimensions, as estimated by STM, and the height above the gold substrate, as evaluated by AFM, of the two mutants well agree with crystallographic sizes. A narrower height distribution is observed for PCSS compared to PCSH, corresponding to a more homogeneous orientation of the former mutant adsorbed onto gold. Major differences between the mutants are observed by electrochemical STM. In particular, the image contrast of adsorbed PCSS is affected by tuning the external electrochemical potential to the redox levels of the mutant, consistent with some involvement of copper active site in the tunneling process. On the contrary, no contrast variation is observed in electrochemical STM of adsorbed PCSH. Moreover, scanning tunneling spectroscopy experiments reveal asymmetric I–V characteristics for single PCSS proteins, reminiscent of a rectifying-like behaviour, whereas an almost symmetric I–V relation is observed for PCSH. 相似文献
63.
Collective properties of a relativistic electron beam injected into a high intensity optical lattice
I. A. Andriyash Ph. Balcou V. T. Tikhonchuk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(3):533-540
Behaviour of a relativistic electron bunch, injected and trapped in a high intensity
optical lattice resulting from the interference of two laser beams is studied. The optical
lattice modifies the phase space distribution of the electron bunch due to the trapping
and compression of the electrons by a ponderomotive force. High-frequency longitudinal
beam eigenmodes of the trapped electron bunch are described in the framework of fluid and
kinetic models. Such beam oscillations are expected to play a pivotal role in a stimulated
Raman scattering of laser beams on the electrons. 相似文献
64.
D. Rodríguez G. Ban D. Durand F. Duval X. Fléchard E. Liénard F. Mauger A. Méry O. Naviliat-Cuncic J. -C. Thomas Ph. Velten 《The European Physical Journal A - Hadrons and Nuclei》2009,42(3):397-400
The LPCTrap setup at GANIL is fully operational since 2006. The first breakthrough was the detection of 100000 coincidences between the $ \beta$ particles and the recoil ions from the decay of 6He+ produced by the SPIRAL source. After preparation, the decaying nuclei are confined in a transparent Paul trap which is surrounded by a $ \beta$ -telescope made of a double-sided silicon strip detector followed by a scintillator, and by a micro-channel plate position-sensitive detector to record in coincidence the $ \beta$ particles and the recoil ions. Simulations of this system are needed in order to study possible systematic effects and extract with high accuracy the $ \beta$ - $ \nu$ angular-correlation coefficient. A code based on Geant4 is well suited for this purpose. In this contribution the results from the simulations compared with those from the experiment will be presented and discussed. 相似文献
65.
Yu. V. Gulyaev S. A. Nikitov L. V. Zhivotovskii A. A. Klimov Ph. Tailhades L. Presmanes C. Bonningue C. S. Tsai S. L. Vysotskii Yu. A. Filimonov 《JETP Letters》2003,77(10):567-570
A new type of photonic crystals is proposed. The new crystals have a forbidden gap in the microwave spectrum of magnetostatic spin waves, and, by analogy with photonic crystals, they are called magnon crystals. Specimens of such crystals were fabricated on the basis of yttrium iron garnet films. The surfaces of ferromagnetic films containing two-dimensional etched hole structures were studied by atomic force and magnetic force mag-netometry. The propagation of spin waves through the magnon crystals was investigated. 相似文献
66.
H. Bailliet R. Boucheron J.-P. Dalmont Ph. Herzog S. Moreau J.-C. Valière 《Applied Acoustics》2012,73(3):191-197
An experiment has been set up to study multimodal acoustic propagation inside a cylindrical duct in presence of a turbulent mean flow. This paper describes the preliminary work which has been found necessary for assembling the experiment together with first measurement results. In order to set up this experimental facility, a high level acoustic source was developed to generate higher propagating modes in the presence of mean flow. A microphonic antenna was designed for detecting the propagating modes. LDV measurements were performed and synchronous detection was used to extract both the mean flow and the acoustic components of the particle velocity. Results of aeraulic measurements are presented. Then, results of acoustic velocity measurements are compared to results obtained from the microphonic antenna. 相似文献
67.
First-order phase transitions in finite systems can be defined through the bimodality of the distribution of the order parameter. This definition is equivalent to the one based on the inverted curvature of the thermodynamic potential. Moreover we show that it is in a one-to-one correspondence with the Yang–Lee theorem in the thermodynamic limit. Bimodality is a necessary and sufficient condition for zeroes of the partition sum in the control intensive variable complex plane to be distributed on a line perpendicular to the real axis with a uniform density, scaling like the number of particles. 相似文献
68.
Dinu LC Muller HG Kazamias S Mullot G Augé F Balcou P Paul PM Kovacev M Breger P Agostini P 《Physical review letters》2003,91(6):063901
The absolute timing of the high-harmonic attosecond pulse train with respect to the generating IR pump cycle has been measured for the first time. The attosecond pulses occur 190+/-20 as after each pump field maxima (twice per optical cycle), in agreement with the "short" quantum path of the quasiclassical model of harmonic generation. 相似文献
69.
The order–disorder phase transition on the α-Ga(0 1 0) structure was studied by spot-profile analysis low energy electron diffraction (SPA-LEED). A low temperature diffraction pattern reveals a small splitting of the overlayer spots which corresponds to a real-space distance of 81 Å, equivalent to 18 unit cells. The splitting is interpreted as caused by a regular ordering of anti-phase domains of the low-temperature phase. Due to the low symmetry of the surface, the domain boundaries are aligned only in one direction, giving rise to a regular, one-dimensional grid. The temperature dependence of the intensity and width of the reconstruction-induced diffraction spots is also investigated. It suggests that the phase transition takes place at a critical temperature Tc=232 K and that anti-phase boundary proliferation plays a role. 相似文献
70.
S. Soriano C. Dufour K. Dumesnil Ph. Mangin 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):469-478
Below its ordering temperature (T
N
= 90 K), bulk bcc Eu has a helical magnetic state with propagation vectors along the three equivalent 〈100〉 directions. In
contrast, epitaxial (110)Eu films exhibit a unique magnetic ordering: the domain with a magnetic helix propagating along the
in-plane [001] direction vanishes on cooling, at the expense of other domains with helices propagating along [100] and [010].
This paper is devoted to the study of the stability of the magnetic domains in an external magnetic field using neutron scattering
experiments and macroscopic magnetization measurements. The helix propagating along the [001] direction can be restored by
the application of an external field along this direction. On the contrary, when a magnetic field is applied along an intermediate
direction, specifically [10], the domain with a helix propagating along [001] is suppressed. Both effects depend on the film thickness. They are explained
if one considers that, because of the low magnetic anisotropy of Eu, a helix with a propagation vector parallel to (or close
to) the applied magnetic field is energetically more favourable than cycloidal structures with unchanged propagation vectors.
Finally, the amplitudes of the propagation vectors and their directions (that are modified in films compared to bulk) do not
vary under magnetic field. 相似文献