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991.
The intrinsic transport properties of zigzag graphene nanoribbons (ZGNRs) are investigated using first-principles calculations. It is found that although all ZGNRs have similar metallic band structure, they show distinctly different transport behaviors under bias voltages, depending on whether they are mirror symmetric with respect to the midplane between two edges. Asymmetric ZGNRs behave as conventional conductors with linear current-voltage dependence, while symmetric ZGNRs exhibit unexpected very small currents with the presence of a conductance gap around the Fermi level. This difference is revealed to arise from different coupling between the conducting subbands around the Fermi level, which is dependent on the symmetry of the systems. 相似文献
992.
Block M Bachelet C Bollen G Facina M Folden CM Guénaut C Kwiatkowski AA Morrissey DJ Pang GK Prinke A Ringle R Savory J Schury P Schwarz S 《Physical review letters》2008,100(13):132501
A new long-lived isomeric state in (65)Fe has been discovered with Penning trap mass spectrometry and high-precision mass measurements of the neutron-rich isotopes (63-65)Fe and (64-66)Co have been performed with the Low-Energy Beam and Ion Trap Facility at the NSCL. For the new isomer in (65)Fe an excitation energy of 402(5) keV has been determined from the measured mass difference between the isomeric and ground states. The mass uncertainties of all isotopes have been reduced by a factor of 10-100 compared to previous results. In the case of (64)Co the previous mass value was found to deviate by about 5 standard deviations from the new measurement. 相似文献
993.
Zhang W Liu G Zhao L Liu H Meng J Dong X Lu W Wen JS Xu ZJ Gu GD Sasagawa T Wang G Zhu Y Zhang H Zhou Y Wang X Zhao Z Chen C Xu Z Zhou XJ 《Physical review letters》2008,100(10):107002
Laser-based angle-resolved photoemission measurements with superhigh resolution have been carried out on an optimally doped Bi(2)Sr(2)CaCu(2)O(8) high temperature superconductor. New high energy features at approximately 115 meV and approximately 150 meV, in addition to the prominent approximately 70 meV one, are found to develop in the nodal electron self-energy in the superconducting state. These high energy features, which cannot be attributed to electron coupling with single phonon or magnetic resonance mode, point to the existence of a new form of electron coupling in high temperature superconductors. 相似文献
994.
Druart G Taboury J Guérineau N Haïdar R Sauer H Kattnig A Primot J 《Optics letters》2008,33(4):366-368
Diffractive axicons are optical components producing achromatic nondiffracting beams. They thus produce a focal line rather than a focal point for classical lenses. This gives the interesting property of a long focal depth. We show that this property can be used to design a simple imaging system with a linear variable zoom by using and translating a diffractive axicon as the only optical component. 相似文献
995.
Observation of multiple higher-order stopgaps from three-dimensional chalcogenide glass photonic crystals 总被引:1,自引:0,他引:1
Nicoletti E Zhou G Jia B Ventura MJ Bulla D Luther-Davies B Gu M 《Optics letters》2008,33(20):2311-2313
For the first time to our knowledge the observation of near-IR multiple higher-order stopgaps in three-dimensional photonic crystals (PhCs) fabricated using the direct-laser-writing method in thick chalcogenide glass films is reported. The fabrication and etching conditions necessary to realize well-defined structures are presented. The fabricated PhCs exhibit higher-order stopgaps, which are only evident in high-quality structures. The higher-order stopgaps observed permit these high-refractive-index and high-nonlinear PhCs to be used directly as functional photonic devices operating at telecommunication wavelengths without further miniaturizing structural dimensions. 相似文献
996.
In this paper, we present a theoretical investigation on the Faraday effect in paramagnetic neodymium gallium garnet (Nd3Ga5O12) by taking account of the SO and CF interactions, the superexchange interaction and the external magnetic field. It is demonstrated that under high magnetic field, the Faraday rotation (θ) is strongly nonlinear with the external magnetic field (He) while the coefficients of deeply dependent on the frequency of the incident light and temperature, and the Verdet constant V(θ/He) is also a function of He. Furthermore, theoretical calculations show that the reciprocity of the Faraday effect cannot be neglected under high magnetic field. The theoretical results are in good agreement with the experimental data. 相似文献
997.
The poly (N-isopropylacrylamide)-co-polystyrene (PNIPAM-co-PS) nanofibers have been fabricated by electrospinning, and the blends of PNIPAM-co-PS nanofibers with titanium dioxide (TiO(2)) nanoparticles have been characterized and utilized as the new nanocomposites to enhance the relevant detection sensitivity of biomolecular recognition of an anticancer drug daunorubicin. Our observations demonstrate that upon application of the nanoTiO(2)-PNIPAM-co-PS polymer nanocomposites, the drug molecules could be readily deposited on the surface of the relevant blends so that the remarkable enhancement effect of the new nanocomposites on the respective biorecognition of daunorubicin could be observed, suggesting the potential valuable application of the blending of the nanoTiO(2) and PNIPAM-co-PS polymer nanocomposites in high sensitive bioanalysis. 相似文献
998.
We report molecular dynamics simulation results of equilibrium and dynamical characteristics pertaining to the solvation of the dye coumarin 153 (C153) trapped within hydrophobic cavities of di- and trimethylated beta-cyclodextrins (CD) in aqueous solutions. We found that stable configurations of the encapsulated probe are characterized by a slanted docking, in which the plane of the C153 lies mostly parallel to one of the glucose units of the CD. "In and out" dynamical modes of the encapsulated probe present very small amplitudes. The rotational dynamics of the trapped coumarin can be cast in terms of a simple model that includes diffusive motions within a local restrictive environment coupled to the overall rotational motion of the CD. We have examined the early stages of the solvation response of the environment following a vertical excitation of the probe. Regardless of the degree of CD methylation, the water dynamical response seems to be completed within 2-3 ps and does not differ substantially from that observed for nonencapsulated probes. The CD response is characterized by a single, subpicosecond relaxation that involves intramolecular motions. We also explored dynamical modes that could account for the recently reported persistence of Stokes shifts in the nanosecond time domain. In all cases, the only sources of ultraslow dynamics that we detected were those associated with gauche-trans interconversions in primary hydroxyl chains of the CD, which do not seem to be directly connected to the electronic excitation of the probe. 相似文献
999.
Hardouin J Guénin E Malosse C Caron M Lecouvey M 《Rapid communications in mass spectrometry : RCM》2008,22(15):2287-2300
1-hydroxymethylene-1,1-bisphosphonic acids (HMBPs) are important drugs for the treatment of a variety of bone diseases. Since these compounds have no chromophore, their detection is challenging and mass spectrometry (MS) appears to be an appropriate sensitive tool. Our work deals with the analysis by electrospray ionization tandem mass spectrometry (ESI-MSn) of the well-known nitrogen-containing HMBP alendronate and of three analogues, considered as potential prodrugs. These four molecules share a common structure with different protecting groups on the phosphonic acid and on the amine functions. We describe the dissociation mechanisms of nitrogen-containing HMBPs in positive ion mode and we compare, in negative ion mode, our results with literature data. In both modes, the dissociations are essentially losses of ROH, and of phosphorus-containing species (HPO2, ROP(OH)2 and ROPO(OH)2), where R=H, C6H5, or CH3OC6H5. These fingerprints will be of great value for differentiating alendronate from its potential prodrugs in complex biological mixtures. 相似文献
1000.
Incoherent quasielastic neutron scattering study of molecular dynamics of 4-n-octyl-4'-cyanobiphenyl
Lefort R Morineau D Guégan R Ecolivet C Guendouz M Zanotti JM Frick B 《Physical chemistry chemical physics : PCCP》2008,10(20):2993-2999
We report incoherent quasielastic neutron scattering experiments on the thermotropic liquid crystal 4-n-octyl-4'-cyanobiphenyl. The combination of time-of-flight and backscattering data allows analysis of the intermediate scattering function over about three decades of relaxation times. Translational diffusion and uniaxial molecular rotations are clearly identified as the major relaxation processes in, respectively, the nanosecond and picosecond time scales. 相似文献