907 research outputs found
Stress distribution in the trochlear notch
n 16 cadaver humeroulnar joints, the distribution of subchondral mineralisation was assessed by CT osteoabsorptiometry and the position and size of the contact areas by polyether casting under loads of 10 N to 1280 N. Ulnas with separate olecranon and coronoid cartilaginous surfaces showed matching bicentric patterns of mineralisation. Under small loads there were separate contact areas on the olecranon and coronoid surfaces; these areas merged centrally as the load increased. They occupied as little as 9% of the total articular surface at 10 N and up to 73% at 1280 N. Ulnas with continuous cartilaginous surfaces also had density patterns with two maxima but those were less prominent, and in these specimens the separate contact areas merged at lower loads. The findings indicate a physiological incongruity of the articular surfaces which may serve to optimise the distribution of stress
Kontaktflächen des menschlichen Humeroulnargelenks in Abhängigkeit von der Anpreßkraft, ihr Zusammenhang mit subchondraler Mineralisierung und Gelenkflächenmorphologie der Incisurea trochlearis
Optical absorption of ion-beam sputtered amorphous silicon coatings
Low mechanical loss at low temperatures and a high index of refraction should make silicon
optimally suited for thermal noise reduction in highly reflective mirror coatings for gravitational wave
detectors. However, due to high optical absorption, amorphous silicon (aSi) is unsuitable for being used
as a direct high-index coating material to replace tantala. A possible solution is a multimaterial design,
which enables exploitation of the excellent mechanical properties of aSi in the lower coating layers. The
possible number of aSi layers increases with absorption reduction. In this work, the optimum heat
treatment temperature of aSi deposited via ion-beam sputtering was investigated and found to be 450 °C.
For this temperature, the absorption after deposition of a single layer of aSi at 1064 nm and 1550 nm
was reduced by more than 80%
Quantum-Dense Metrology
Quantum metrology utilizes entanglement for improving the sensitivity of
measurements. Up to now the focus has been on the measurement of just one out
of two non-commuting observables. Here we demonstrate a laser interferometer
that provides information about two non-commuting observables, with
uncertainties below that of the meter's quantum ground state. Our experiment is
a proof-of-principle of quantum dense metrology, and uses the additional
information to distinguish between the actual phase signal and a parasitic
signal due to scattered and frequency shifted photons. Our approach can be
readily applied to improve squeezed-light enhanced gravitational-wave detectors
at non-quantum noise limited detection frequencies in terms of a sub shot-noise
veto-channel.Comment: 5 pages, 3 figures; includes supplementary material
In-field entanglement distribution over a 96 km-long submarine optical fibre
Techniques for the distribution of quantum-secured cryptographic keys have
reached a level of maturity allowing them to be implemented in all kinds of
environments, away from any form of laboratory infrastructure. Here, we detail
the distribution of entanglement between Malta and Sicily over a 96 km-long
submarine telecommunications optical fibre cable. We used this standard
telecommunications fibre as a quantum channel to distribute
polarisation-entangled photons and were able to observe around 257 photon pairs
per second, with a polarisation visibility above 90%. Our experiment
demonstrates the feasibility of using deployed submarine telecommunications
optical fibres as long-distance quantum channels for polarisation-entangled
photons. This opens up a plethora of possibilities for future experiments and
technological applications using existing infrastructure.Comment: 6 pages, 4 figure
Demonstration of a quantum-enhanced fiber Sagnac interferometer
The injection of squeezed light can be used to improve the sensitivity of an interferometer beyond the limit imposed by the zero-point fluctuation of the electromagnetic field. Here, we report on the realization of such a quantum-enhanced interferometer with a fiber-based Sagnac topology. Continuous wave squeezed states at 1550 nm with a noise reduction of 6.4 dB below shot noise were produced by type I optical parametric amplification and subsequently injected into the dark port of the interferometer. A reduction of the interferometer shot noise by 4.5 dB was observed, and the enhancement of the signal-to-noise ratio for a phase modulation signal generated within the interferometer could be demonstrated. We achieved a 95% fiber transmission for the squeezed states, which suggests that corresponding fiber-based quantum metrology and communication systems are feasible
Design of a speed meter interferometer proof-of-principle experiment
The second generation of large scale interferometric gravitational wave
detectors will be limited by quantum noise over a wide frequency range in their
detection band. Further sensitivity improvements for future upgrades or new
detectors beyond the second generation motivate the development of measurement
schemes to mitigate the impact of quantum noise in these instruments. Two
strands of development are being pursued to reach this goal, focusing both on
modifications of the well-established Michelson detector configuration and
development of different detector topologies. In this paper, we present the
design of the world's first Sagnac speed meter interferometer which is
currently being constructed at the University of Glasgow. With this
proof-of-principle experiment we aim to demonstrate the theoretically predicted
lower quantum noise in a Sagnac interferometer compared to an equivalent
Michelson interferometer, to qualify Sagnac speed meters for further research
towards an implementation in a future generation large scale gravitational wave
detector, such as the planned Einstein Telescope observatory.Comment: Revised version: 16 pages, 6 figure
Cartilage degeneration in the human patellae and its relationship to the mineralisation of the underlying bone
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