Pull-in Instability Study of Carbon Nanotube Tweezers Under the Influence of Van der Waals Forces

The pull-in instability of two nanotubes under van der Waals force is studied. The cantilever beam with large deformation model is used. The influence of nanotube parameters such as the interior radius, the gap distance between the two nanotubes, etc, on the pull-in instability is studied. The critical nanotube length is determined for each specific set of nanotube parameters. The Galerkin method is applied to discretize the governing equations, and it shows good convergence.

Morphological Stability of Epitaxial Thin Elastic Films by Van Der Waals Force

The morphological stability of epitaxial thin elastic films on a substrate by van der Waals force is discussed. It is found that only van der Waals force with negative Hamaker constant (A < 0) tends to stabilize the film, and the lower bound for the Hamaker constant is also obtained for the stability of thin film. The critical value of the undulation wavelength is found to be a function of both film thickness and external stress. The charateristic time-scale for surface mass diffusion scales to the fourth power to the wavelength of the perturbation.

Combined effect of surface tension, gravity and van der Waals force induced by a non-contact probe tip on the shape of liquid surface

Aiming at understanding how a liquid film on a substrate affects the atomic force microscopic image in experiments, we present an analytical representation of the shape of liquid surface under van der Waals interaction induced by a non-contact probe tip. The analytical expression shows good consistence with the corresponding numerical results. According to the expression, we find that the vertical scale of the liquid dome is mainly governed by a combination of van der Waals force, surface tension and probe tip radius, and is weekly related to gravity. However, its horizontal extension is determined by the capillary length.

Influence of van der Waals and Casimir Forces on Electrostatic Torsional Actuators

The influence of van der Waals (vdW) and Casimir forces on the stability of the electrostatic torsional nanoelectromechanical systems (NEMS) actuators is analyzed in the paper. With the consideration of vdW and Casimir effects, the dependence of the critical tilting angle and pull-in voltage on the sizes of structure is investigated. And the influence of vdW torque is compared with that of Casimir torque. The modified coefficients of vdW and Casimir torques on the pull-in voltage are, respectively, calculated. When the gap is sufficiently small, pull-in can still take place with arbitrary small angle perturbation because of the action of vdW and Casimir torques even if there is not electrostatic torque. And the critical pull-in gaps for two cases are, respectively, derived.

Dynamic Stability of Electrostatic Torsional Actuators with van Der Waals Effect

electrostatic torsional nano-electro-mechanical systems (NEMS) actuators is analyzed in the paper. The dependence of the critical tilting angle and voltage is investigated on the sizes of structure with the consideration of vdW effects. The pull-in phenomenon without the electrostatic torque is studied, and a critical pull-in gap is derived. A dimensionless equation of motion is presented, and the qualitative analysis of it shows that the equilibrium points of the corresponding autonomous system include center points, stable focus points, and unstable saddle points. The Hopf bifurcation points and fork bifurcation points also exist in the system. The phase portraits connecting these equilibrium points exhibit periodic orbits, heteroclinic orbits, as well as homoclinic orbits.

Variational Approach to the Thomas-Fermi Equation

By the semi-inverse method, a variational principle is obtained for the Thomas-Fermi equation, then the Ritz method is applied to solve an analytical solution, which is a much simpler and more efficient method.

Mitochondrial cytochrome b gene sequence diversity in the Korean hare, Lepus coreanus Thomas (Mammalia, Lagomorpha)

Partial sequences of the mitochondrial cytochrome b gene of the Korean hare (Lepus coreanus) were analyzed to determine the degree of genetic diversity. Nine haPlotyes were observed, and the maximum Tamura-Nei nucleotide distance among them was 2.8%, indicating that genetic diversity of L. coreanus is moderate. In order to clarify the Korean hare's taxonomic status and relationship with the Manchurian hare (L. mandshuricus) and the Chinese hare (L. sinensis), these nine haplotypes of the Korean hare were compared with 13 haplotypes from five other species of eastern Asian Lepus including L. mandshwicus and L. sinensis. The Korean hare was distinct in its cytochrome b gene, and it is confirmed that L. coreanus is a valid species, as noted by Jones and Johnson (1965, Univ. Kansas Publ. (Mus. Nat. Hist.) 16:357). Further analyses of mtDNA cytochrome b gene with additional specimens of L. coreanus from North Korea and other species of Lepus from eastern Asia are needed to clarify the taxonomic status of the divergent mtDNA clades of L. mandshuricus and L. sinensis.

Reply to van Oven: Suggestions and caveats for naming mtDNA haplogroup

The authors thank all subjects for their participation and Mr. Wen-Zhi Wang for helpful assistance with the data analysis. This study was supported in part by grants (30725044) from the National Natural Science Foundation of China.

亚洲南部球果蝠Sphaerias blanfordi(Thomas,1891)的亚种分化

球果蝠Sphaerias blanfordi(Thomas,1891)是亚洲南部喜马拉雅-印度支那地区的特有种,甚为罕见而少有报道.曾被认为是单型种,几乎无雄性特征的描述.蔡桂全和张遁治(1980)根据采自西藏东南部墨脱的2只雄性标本订了一亚种一墨脱亚种Sphaerias blanfordi motuoensis,其主要特征是颈下侧有一对灰黄色的圆形毛斑.中国科学院昆明动物研究所先后在云南西北部高黎贡山地区采获25号标本(9♂♂,16♀♀),发现球果蝠两性在外形上有明显的性别差异,雄性的颈下侧有一对圆形、灰黄色的刷状毛斑,但雌性均无;对比墨脱标本,认为墨脱亚种的鉴别特征不可靠,亚种不能成立.Lunde(2003)曾报道采自越南北部Mt.Tay Con Linh Ⅱ地区的43号标本,其前臂长和上犬齿外宽明显与印度、缅甸和云南西北部高黎贡山地区的标本不同,可能是真正的地理亚种.

Geographic variation of the Anderson's Niviventer (Niviventer andersoni) (Thomas, 1911) (Rodentia: Muridae) of two new subspecies in China verified with cranial morphometric variables and pelage characteristics

A total of 66 specimens of Niviventer andersoni with intact skulls was investigated on pelage characteristics and cranial morphometric variables. The data were subjected to principal component analyses as well as to discriminant analyses, and measurement

System size dependence of associated yields in hadron-triggered jets STAR Collaboration

We present results on the system size dependence of high transverse momentum di-hadron correlations at root s(NN) = 200 GeV as measured by STAR at RHIC. Measurements in d + Au, Cu + Cu and Au + Au collisions reveal similar jet-like near-side correlation yields (correlations at small angular separation Delta phi similar to 0, Delta eta similar to 0) for all systems and centralities. Previous measurements have shown Chat the away-side (Delta phi similar to pi) yield is suppressed in heavy-ion collisions. We present measurements of the away-side Suppression as a function of transverse momentum and centrality in Cu + Cu and Au + Au collisions. The suppression is found to be similar in Cu + Cu and An + An collisions at a similar number of participants. The results are compared to theoretical calculations based on the patron quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will further constrain dynamic energy loss models and provide information about the dynamic density profile in heavy-ion collisions. (C) 2009 Elsevier B.V. All rights reserved.

Measurement of the Bottom Quark Contribution to Nonphotonic Electron Production in p plus p Collisions at root s=200 GeV

The contribution of B meson decays to nonphotonic electrons, which are mainly produced by the semileptonic decays of heavy-flavor mesons, in p + p collisions at root s = 200 GeV has been measured using azimuthal correlations between nonphotonic electrons and hadrons. The extracted B decay contribution is approximately 50% at a transverse momentum of p(T) >= 5 GeV/c. These measurements constrain the nuclear modification factor for electrons from B and D meson decays. The result indicates that B meson production in heavy ion collisions is also suppressed at high p(T).

Higher Moments of Net Proton Multiplicity Distributions at RHIC

200 GeV corresponding to baryon chemical potentials (mu(B)) between 200 and 20 MeV. Our measurements of the products kappa sigma(2) and S sigma, which can be related to theoretical calculations sensitive to baryon number susceptibilities and long-range correlations, are constant as functions of collision centrality. We compare these products with results from lattice QCD and various models without a critical point and study the root s(NN) dependence of kappa sigma(2). From the measurements at the three beam energies, we find no evidence for a critical point in the QCD phase diagram for mu(B) below 200 MeV.

Three-Particle Coincidence of the Long Range Pseudorapidity Correlation in High Energy Nucleus-Nucleus Collisions

We report the first three-particle coincidence measurement in pseudorapidity (Delta eta) between a high transverse momentum (p(perpendicular to)) trigger particle and two lower p(perpendicular to) associated particles within azimuth |Delta phi| < 0.7 in root s(NN) = 200 GeV d + Au and Au + Au collisions. Charge ordering properties are exploited to separate the jetlike component and the ridge (long range Delta eta correlation). The results indicate that the correlation of ridge particles are uniform not only with respect to the trigger particle but also between themselves event by event in our measured Delta eta. In addition, the production of the ridge appears to be uncorrelated to the presence of the narrow jetlike component.