1,509 research outputs found
Which Osteotomy for Osteonecrosis of the Femoral Head and Which Patient for the Osteotomy?
Transtrochanteric curved varus osteotomy (TCVO) and transtrochanteric rotational osteotomy (TRO) are joint-preserving procedures for osteonecrosis of the femoral head. The purpose of this review is to provide up-to-date guidelines for the osteotomies. One retrospective comparison revealed that TCVO has shorter operation time, less bleeding, lower incidence of osteophyte formation, and lower rate of secondary collapse. To obtain successful results of the osteotomy, the patient should be younger than 40 years and should have a body mass index of less than 24 kg/m2. The osteotomy should be performed in early stages of femoral head osteonecrosis before marked collapse of the femoral head. The patient should have a medium-size lesion and an enough viable bone to restore the intact articular surface and subchondral bone in the weight-bearing area
Orientational Melting in Carbon Nanotube Ropes
Using Monte Carlo simulations, we investigate the possibility of an
orientational melting transition within a "rope" of (10,10) carbon nanotubes.
When twisting nanotubes bundle up during the synthesis, orientational
dislocations or twistons arise from the competition between the anisotropic
inter-tube interactions, which tend to align neighboring tubes, and the torsion
rigidity that tends to keep individual tubes straight. We map the energetics of
a rope containing twistons onto a lattice gas model and find that the onset of
a free "diffusion" of twistons, corresponding to orientational melting, occurs
at T_OM > 160 K.Comment: 4 page LaTeX file with 3 figures (10 PostScript files
Effect of Potential Energy Distribution on the Melting of Clusters
We find that the potential energy distribution of atoms in clusters can consistently explain many important phenomena related to the phase changes of clusters, such as the nonmonotonic variation of melting temperature with size, the dependence of melting, boiling, and sublimation temperatures on the interatomic potentials, the existence of a surface-melted phase, and the absence of a premelting peak in heat capacity curves. We also find a new type of premelting mechanism in double icosahedral Pd19 clusters, where one of the two internal atoms escapes to the surface at the premelting temperature.Peer reviewe
The survival of holes as thru-holes in thru-hole epitaxy: How can holes in 2D layers not sealed off during multiple stacking of those layers?
Thru-hole epitaxy was recently reported to be able to grow readily detachable
domains crystallographically aligned with the underlying substrate over 2D mask
material transferred onto a substrate. While the experimental demonstration of
thru-hole epitaxy of GaN over multiple stacks of -BN was evident, the
detailed mechanism of how small holes in each stack of -BN survived as
thru-holes during multiple stacking of -BN was not intuitively clear. Here,
we show through Monte Carlo simulations that in what conditions holes in each
stack of 2D mask layers can survive as thru-holes during multiple stacking. If
more holes are laterally connected, the survival rate of thru-holes increases
resulting in the epitaxial connectedness. This computational work verifies and
supports that thru-hole epitaxy is attributed to the epitaxial connectedness
established by thru-holes survived even through multiple stacks.Comment: 14 pages, 6 figure
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