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81.
Hernandez J Solla-Gullón J Herrero E Aldaz A Feliu JM 《The journal of physical chemistry. B》2005,109(26):12651-12654
The surface structure of gold nanorods has been determined by studying the behavior of electrochemical reactions sensitive to the structure and compared to that obtained by other structure characterization techniques. Lead underpotential deposition (UPD) reveals that the surface of the nanorods is composed by (111) and (110) domains, while (100) domains are practically absent from the surface. In the case of the oxygen reduction reaction, the formation of hydrogen peroxide as a final product of the reaction in the whole potential range also indicates that (100) domains are absent on the surface of the nanoparticles, corroborating the previous result. These results are compared with other surface structure information provided by other techniques. 相似文献
82.
83.
E.?DintwaEmail author M.?van?Zeebroeck E.?Tijskens H.?Ramon 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,39(1):77-85
The theory of elastic contact between two spherical bodies according to Hertz, Mindlin and others is used as a basis for an extension to include the contribution of the viscous effects to the total stress for viscoelastic spheres subjected to twisting moments. Expressions relating twisting moment to the radius of a stick region of the contact surface and the radius of the stick region to twist angle are derived. Two term power series truncations of the relations are then used to derive approximate expressions for torsional stiffness of the bodies. Validation of the model was by experiments utilising a rheometer device. Applications for the model in post-harvest agriculture include extraction of material surface properties for use in discrete element modelling of mechanical interactions of fruits and other spheroidal produce during machine handling.Received: 6 January 2004, Published online: 18 June 2004PACS:
46.35. + z Viscoelasticity, plasticity, viscoplasticity - 46.55. + d Tribology and mechanical contacts - 62.20.Dc Elasticity, elastic constants 相似文献
84.
85.
Absence of dc-conductivity in lambda-DNA 总被引:2,自引:0,他引:2
de Pablo PJ Moreno-Herrero F Colchero J Gómez Herrero J Herrero P Baró AM Ordejón P Soler JM Artacho E 《Physical review letters》2000,85(23):4992-4995
The electrical conductivity of biomaterials on a molecular scale is of fundamental interest in the life sciences. We perform first principles electronic structure calculations, which clearly indicate that lambda-DNA chains should present large resistance values. We also present two direct procedures to measure electrical currents through DNA molecules adsorbed on mica. The lower limit for the resistivity is 10(6) Omega . cm, in agreement with our calculations. We also show that low energy electron bombardment induces a rapid contamination and dramatically affects the measured conductivity, thus providing an explanation to recent reports of high DNA conductivity. 相似文献
86.
H. Herrero 《The European physical journal. Special topics》2007,146(1):235-247
Chebyshev collocation methods are high-order methods.
This means that high precision is obtained with low-order
expansions. Then `small' matrices appear in the numerical
implementation and reduced computing resources become necessary.
Thermoconvective fluid dynamics problems are large ones, involving
various partial differential equations for several fields in large
dimensions. The models present a number of difficulties, such as
the different orders of derivatives for the different fields, or
lack of information on the boundary conditions for pressure. This
paper presents a review of the specific characteristics of this
method when it is applied to thermoconvective problems: the
method, the types of problems, the different resulting models, the
strategies to overcome the difficulties of the different
derivative orders and the characteristics of the matrices, and the
convergence properties. A comparison of its efficiency with other
numerical methods like finite differences and finite elements is
included. 相似文献
87.
Andrew M. Herrero B.P. Gila Hung-Ta Wang T. Anderson B.S. Kang H. Shen Kurt V. Smith 《Applied Surface Science》2007,253(6):3298-3302
The use of cryogenic temperatures (∼77 K) during Au Schottky contact deposition onto n-GaAs produces an increase in barrier height from 0.73 eV for room temperature diodes to 0.82 eV. Not all Schottky metals show this enhancement—for example Pt and Ti do not show any significant change in barrier height whereas Au, Pd and Ni show increases between 7 and 18%. We used X-ray reflectivity to show that the main difference between Au deposited at 77 K and room temperature is a decreased metal roughness while the interfacial roughness between the Au and GaAs is basically the same. As the diodes are annealed to 300 °C both the difference in barrier height and interfacial roughness is lost. This is a simple method with potential for improving the performance of GaAs metal-semiconductor-field-effect-transistors (MESFETs). 相似文献
88.
This study presents a natural convection problem with a temperature-dependent viscosity fluid, driven by buoyancy and influenced
by horizontal temperature gradients. A numerical linear stability analysis of the stationary solutions is studied. The horizontal
temperature gradients tend to localize motion near the warmer zones and favour pattern formation in the direction perpendicular
to the gradient. In fact, the problem is almost 2D in the uniform heating case, but becomes totally 3D in the non-uniform
heating case. 相似文献
89.
90.
Every compact symmetric bilinear form B on a complex Hilbert space produces, via an antilinear representing operator, a real spectrum consisting of a sequence decreasing to zero. We show that the most natural analog of Courant's minimax principle for B detects only the evenly indexed eigenvalues in this spectrum. We explain this phenomenon, analyze the extremal objects, and apply this general framework to the Friedrichs operator of a planar domain and to Toeplitz operators and their compressions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献