127 research outputs found
Interlayer Registry Determines the Sliding Potential of Layered Metal Dichalcogenides: The case of 2H-MoS2
We provide a simple and intuitive explanation for the interlayer sliding
energy landscape of metal dichalcogenides. Based on the recently introduced
registry index (RI) concept, we define a purely geometrical parameter which
quantifies the degree of interlayer commensurability in the layered phase of
molybdenum disulphide (2HMoS2). A direct relation between the sliding energy
landscape and the corresponding interlayer registry surface of 2H-MoS2 is
discovered thus marking the registry index as a computationally efficient means
for studying the tribology of complex nanoscale material interfaces in the
wearless friction regime.Comment: 13 pages, 7 figure
Nanomechanical Properties and Phase Transitions in a Double-Walled (5,5)@(10,10) Carbon Nanotube: ab initio Calculations
The structure and elastic properties of (5,5) and (10,10) nanotubes, as well
as barriers for relative rotation of the walls and their relative sliding along
the axis in a double-walled (5,5)@(10,10) carbon nanotube, are calculated using
the density functional method. The results of these calculations are the basis
for estimating the following physical quantities: shear strengths and diffusion
coefficients for relative sliding along the axis and rotation of the walls, as
well as frequencies of relative rotational and translational oscillations of
the walls. The commensurability-incommensurability phase transition is
analyzed. The length of the incommensurability defect is estimated on the basis
of ab initio calculations. It is proposed that (5,5)@(10,10) double-walled
carbon nanotube be used as a plain bearing. The possibility of experimental
verification of the results is discussed.Comment: 14 page
Hindered rolling and friction anisotropy in supported carbon nanotubes
Carbon nanotubes (CNTs) are well known for their exceptional thermal,
mechanical and electrical properties. For many CNT applications it is of the
foremost importance to know their frictional properties. However, very little
is known about the frictional forces between an individual nanotube and a
substrate or tip. Here, we present a combined theoretical and experimental
study of the frictional forces encountered by a nanosize tip sliding on top of
a supported multiwall CNT along a direction parallel or transverse to the CNT
axis. Surprisingly, we find a higher friction coefficient in the transverse
direction compared with the parallel direction. This behaviour is explained by
a simulation showing that transverse friction elicits a soft 'hindered rolling'
of the tube and a frictional dissipation that is absent, or partially absent
for chiral CNTs, when the tip slides parallel to the CNT axis. Our findings can
help in developing better strategies for large-scale CNT assembling and sorting
on a surface.Comment: 8 pages, 5 figure
The dispersion characteristics of the waves propagating in a spinning single-walled carbon nanotube
Elegant patterns of uncommon good taste: domestic silver by Thomas Fletcher and Sidney Gardiner
Quimby, Ian M. G.M.A.University of Delaware, Winterthur Program in Early American Cultur
Creation of an Adult Observation Unit
A growing segment of patients in hospitals are considered outpatients, classified as observation. These patients neither have the severity of illness nor the intensity of service to qualify as inpatients, yet are not well enough to be discharged. Hospitals have created observation units to address the clinical needs of this growing patient type to provide care in the right setting by managing emergency department throughput and utilizing the most efficient staffing resources. This article describes the change processes and improvements in quality, length of stay, and patient satisfaction, which occurred following the implementation of an adult observation unit
Love, in the gloaming. Words by L. E. Walker. Music by Rose Fenimore Gaynor.
5 p. 33 cm. Cover title. For medium voice and piano. In binders collection
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