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11.
Electric field-controlled water permeation coupled to ion transport through a nanopore 总被引:1,自引:0,他引:1
We report molecular dynamics simulations of a generic hydrophobic nanopore connecting two reservoirs which are initially at different Na(+) concentrations, as in a biological cell. The nanopore is impermeable to water under equilibrium conditions, but the strong electric field caused by the ionic concentration gradient drives water molecules in. The density and structure of water in the pore are highly field dependent. In a typical simulation run, we observe a succession of cation passages through the pore, characterized by approximately bulk mobility. These ion passages reduce the electric field, until the pore empties of water and closes to further ion transport, thus providing a possible mechanism for biological ion channel gating. 相似文献
12.
Knippenberg S Deleuze MS Cleij TJ François JP Cederbaum LS Eland JH 《The journal of physical chemistry. A》2005,109(19):4267-4273
In continuation of a recent study of the electronic structure of norbornane [J. Chem. Phys., 2004, 121, 10525] by means of electron momentum spectroscopy (EMS), we present Green's Function calculations of the ionization spectrum of this compound at the ADC(3) level using basis sets of varying quality, along with accurate evaluations at the CCSD(T) level of the vertical (26.5 eV) and adiabatic (22.1 eV) double ionization thresholds under C(2v) symmetry. The obtained results are compared with newly recorded ultraviolet photoemission spectra (UPS), up to binding energies of 40 eV. The theoretical predictions are entirely consistent with experiment and indicate that, in a vertical depiction of ionization, shake-up states at binding energies larger than approximately 26.5 eV tend to decay via emission of a second electron in the continuum. A band of s-type symmetry that has been previously seen at approximately 25 eV in the electron impact ionization spectra of norbornane is entirely missing in the UPS measurements and theoretical ADC(3) spectra. With regard to these results and to the time scales characterizing electron-electron interactions in EMS (10(-17) s) as compared with that (10(-13) s) of photon-electron interactions in UPS, and considering the p-type symmetry of the electron momentum distributions for the nearest 1b(1) and 1b(2) orbitals, this additional band can certainly not be due to adiabatic double ionization processes starting from the ground electronic state of norbornane, or to exceptionally strong vibronic coupling interactions between cationic states derived from ionization of the latter orbitals. It is therefore tentatively ascribed to autoionization processes via electronically excited and possibly dissociating states. 相似文献
13.
Analytical HPLC methods for derivatized amylose chiral stationary phases were developed for the direct enantioseparation of substituted [1-(imidazo-1-yl)-1-phenylmethyl)] benzothiazolinone and benzoxazolinone derivatives with one stereogenic center. These analogues of fadrozole constitute new potent nonsteroidal inhibitors of aromatase (P450 arom.). The separations were made using normal phase methodology with mobile phase consisting of n-hexane-alcohol (ethanol, 1-propanol or 2-propanol) in various proportions, and a silica-based amylose tris-3,5-dimethylphenylcarbamate (Chiralpak AD), or tris-(S)-1-phenylethylcarbamate (Chiralpak AS). The effects of concentration of various aliphatic alcohols in the mobile phase were studied. Baseline separation (Rs > 1.5) was easily obtained in all cases, ethanol being often the more interesting modifier. The effects of structural features of the solutes along with the temperature of the column on the discrimination between the enantiomers were examined for different mobile phase compositions. 相似文献
14.
Iodice M Cusanno F Acha A Ambrozewicz P Aniol KA Baturin P Bertin PY Benaoum H Blomqvist KI Boeglin WU Breuer H Brindza P Bydzovský P Camsonne A Chang CC Chen JP Choi S Chudakov EA Cisbani E Colilli S Coman L Craver BJ De Cataldo G de Jager CW De Leo R Deur AP Ferdi C Feuerbach RJ Folts E Fratoni R Frullani S Garibaldi F Gayou O Giulani F Gomez J Gricia M Hansen JO Hayes D Higinbotham DW Holmstrom TK Hyde CE Ibrahim HF Jiang X Kaufman LJ Kino K Kross B Lagamba L LeRose JJ Lindgren RA 《Physical review letters》2007,99(5):052501
An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak. 相似文献
15.
We present phase diagrams for a polarized Fermi gas in an optical lattice as a function of temperature, polarization, and lattice filling factor. We consider the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO), Sarma or breached pair, and BCS phases, and the normal state and phase separation. We show that the FFLO phase appears in a considerable portion of the phase diagram. The diagrams have two critical points of different nature. We show how various phases leave clear signatures to momentum distributions of the atoms which can be observed after time of flight expansion. 相似文献
16.
Delevoye L Trébosc J Gan Z Montagne L Amoureux JP 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,186(1):94-99
A new decoupling composite pulse sequence is proposed to remove the broadening on spin S=1/2 magic-angle spinning (MAS) spectra arising from the scalar coupling with a quadrupolar nucleus I. It is illustrated on the (31)P spectrum of an aluminophosphate, AlPO(4)-14, which is broadened by the presence of (27)Al/(31)P scalar couplings. The multiple-pulse (MP) sequence has the advantage over the continuous wave (CW) irradiation to efficiently annul the scalar dephasing without reintroducing the dipolar interaction. The MP decoupling sequence is first described in a rotor-synchronised version (RS-MP) where one parameter only needs to be adjusted. It clearly avoids the dipolar recoupling in order to achieve a better resolution than using the CW sequence. In a second improved version, the MP sequence is experimentally studied in the vicinity of the perfect rotor-synchronised conditions. The linewidth at half maximum (FWHM) of 65 Hz using (27)Al CW decoupling decreases to 48 Hz with RS-MP decoupling and to 30 Hz with rotor-asynchronised MP (RA-MP) decoupling. The main phenomena are explained using both experimental results and numerical simulations. 相似文献
17.
J-P Bourgoin A Ruaudel-Teixier M Vandevyver M Roulliay A Barraud M Lequan R-M Lequan 《Macromolecular Symposia》1991,46(1):163-169
A strategy leading to the formation of conducting LB films without any doping treatment is investigated. The method consists of mixing, within the same layer, semi-amphiphilic and amphiphilic derivatives of the same electroactive nucleus (here Tetracyanoquinodimethane (TCNQ)). LB films obtained in this way with the sulphonium TCNQ salt as the semi-amphiphilic molecule and the octadecyl TCNQ as the amphiphilic one in the molecular ratio 1 to 2, are of high optical quality. Such films show a d.c. conductivity which is almost constant with variation in the number of layers, down to one bilayer. Preliminary results obtained by changing the nature of the counterion in the semi-amphiphilic molecule are in good agreement with those of the sulphonium TCNQ-octadecyl TCNQ0. 相似文献
18.
S. A. E. Boyer J-P. E. Grolier L. Pison C. Iwamoto H. Yoshida T. Iyoda 《Journal of Thermal Analysis and Calorimetry》2006,85(3):699-706
The
present work deals with the interactions between carbon dioxide, used as pressure
medium, either in the gas state (GCO2) or in the supercritical
state (SCCO2) and amphiphilic di-block copolymers PEOm-b-PMA(Az)n. The effect of
pressure on the isotropic transition of the PEOm-b-PMA(Az)n copolymer was investigated
using scanning transitiometry (ST). The experimental results were compared
with those measured when using ‘relatively inert’ mercury (Hg)
as pressure medium. Morphological observation of a PEOm-b-PMA(Az)n thin film submitted
to SCCO2 was performed by atomic force microscopy (AFM)
to investigate the nano-structure organization. These results indicate the
possibility of modifying the nano-structure in a specific way depending on
the CO2 physical state. 相似文献
19.
We propose a method to create a monopole structure in a multicomponent condensate by applying the basic methods used to create vortices and solitons experimentally in single-component condensates. We also show that by using a two-component structure for a monopole, we can avoid many problems related to the previously suggested three-component monopole. We discuss the observation and dynamics of such a monopole structure, and note that the dynamics of the two-component monopole differs from the dynamics of the three-component monopole. 相似文献
20.
Performance of laser-ultrasonic F-SAFT imaging 总被引:1,自引:0,他引:1
The resolution and signal-to-noise ratio of laser-ultrasonics to detect small and buried defects can be greatly enhanced by using the synthetic aperture focusing technique (SAFT). Originally developed in the time domain, SAFT can also be implemented in the frequency domain (F-SAFT) using the angular spectrum approach for a significant reduction in processing time. In this paper, an F-SAFT based data processing method especially adapted to laser-ultrasonic data is presented. This method allows for further significant improvements towards laser-ultrasonic imaging of small defects. It includes temporal deconvolution of the waveform data, control for an optimal aperture and frequency bandwidth as well as spatial interpolation of the subsurface images. All the above operations are well adapted to the frequency domain calculations and embedded in the F-SAFT data processing. Also, the aperture control and spatial interpolation allow a reduction of sampling requirements to further decrease both inspection and processing times. The above improvements are illustrated using laser-ultrasonic data taken from an aluminum sample with flat-bottom holes. 相似文献