32,124 research outputs found
InAs/InP single quantum wire formation and emission at 1.5 microns
Isolated InAs/InP self-assembled quantum wires have been grown using in situ
accumulated stress measurements to adjust the optimal InAs thickness. Atomic
force microscopy imaging shows highly asymmetric nanostructures with average
length exceeding more than ten times their width. High resolution optical
investigation of as-grown samples reveals strong photoluminescence from
individual quantum wires at 1.5 microns. Additional sharp features are related
to monolayer fluctuations of the two dimensional InAs layer present during the
early stages of the quantum wire self-assembling process.Comment: 4 pages and 3 figures submitted to Applied Physics Letter
On the Analysis of the Contact Conditions in Temporomandibular Joint Prostheses
Temporomandibular joint replacement (TMJR) is a complex surgical procedure in which the artificial joints available must assure the anatomical reconstruction and guarantee a good range of the natural temporomandibular joint (TMJ) movements. With this aim, different types of TMJ prostheses, including the stock prosthetic system and custom-made prostheses, are being currently implanted. Although temporomandibular joint replacements (TMJRs) are expected to accomplish their function during a number of years, they might actually fail and need to be replaced. This paper analyzes different design factors affecting the contact stress distributions within the TMJ prosthesis interface, which are consequently involved in their deterioration and final failure of the prosthetic device. With this purpose, a numerical model based on finite elements has been carried out in order to evaluate the stress states attained in different prosthesis configurations corresponding to general types of TMJ prostheses. On the other hand, the actual degradation of resected implants has been evaluated via optical microscopy. The linkage between the numerical simulations performed and experimental evidence allowed the authors to establish the different wear and damage mechanisms involved in the failure of stock TMJ prostheses. Indeed, the results obtained show that the contact stresses at the interface between the mandible and the glenoid fossa components play a key role in the failure process of the TMJR devices
Suspensions Thermal Noise in the LIGO Gravitational Wave Detector
We present a calculation of the maximum sensitivity achievable by the LIGO
Gravitational wave detector in construction, due to limiting thermal noise of
its suspensions. We present a method to calculate thermal noise that allows the
prediction of the suspension thermal noise in all its 6 degrees of freedom,
from the energy dissipation due to the elasticity of the suspension wires. We
show how this approach encompasses and explains previous ways to approximate
the thermal noise limit in gravitational waver detectors. We show how this
approach can be extended to more complicated suspensions to be used in future
LIGO detectors.Comment: 28 pages, 13 figure
Fermionic collective excitations in a lattice gas of Rydberg atoms
We investigate the many-body quantum states of a laser-driven gas of Rydberg
atoms confined to a large spacing ring lattice. If the laser driving is much
stronger than the van-der-Waals interaction among the Rydberg sates, these
many-body states are collective fermionic excitations. The first excited state
is a spin-wave that extends over the entire lattice. We demonstrate that our
system permits to study fermions in the presence of disorder although no
external atomic motion takes place. We analyze how this disorder influences the
excitation properties of the fermionic states. Our work shows a route towards
the creation of complex many-particle states with atoms in lattices
Creating collective many-body states with highly excited atoms
We study the collective excitation of a gas of highly excited atoms confined
to a large spacing ring lattice, where the ground and the excited states are
coupled resonantly via a laser field. Our attention is focused on the regime
where the interaction between the highly excited atoms is very weak in
comparison to the Rabi frequency of the laser. We demonstrate that in this case
the many-body excitations of the system can be expressed in terms of free
spinless fermions. The complex many-particle states arising in this regime are
characterized and their properties, e.g. their correlation functions, are
studied. In addition we investigate how one can actually experimentally access
some of these many-particle states by a temporal variation of the laser
parameters.Comment: 10 pages, 7 figure
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