32,857 research outputs found
Magnesium and magnesium alloys as degradable metallic biomaterials
Drawbacks associated with permanent metallic implants lead to the search for degradable metallic biomaterials. Magnesium has been considered as it is essential to bodies and has a high biodegradation potential. For magnesium and its alloys to be used as biodegradable implant materials, their degradation rates should be consistent with the rate of healing of the affected tissue, and the release of the degradation products should be within the body's acceptable absorption levels. Conventional magnesium degrades rapidly, which is undesirable. In this study, biodegradation behaviours of high purity magnesium and commercial purity magnesium alloy AZ31 in both static and dynamic Hank's solution have been systematically investigated. The results show that magnesium purification and selective alloying are effective approaches to reduce the degradation rate of magnesium. In the static condition, the corrosion products accumulate on the materials surface as a protective layer, which results in a lower degradation rate than the dynamic condition. Anodised coating can significantly further reduce the degradation rate of magnesium. This study indicates that magnesium can be used as degradable implant materials as long as the degradation is controlled at a low rate. Magnesium purification, selective alloying and anodised coating are three effective approaches to reduce the rate of degradation
The calibratrion of dopplergrams and magnetograms at BBSO
The calibration procedure for the Big Bear Solar Observatory (BBSO) videomagnetograph in which the radial velocity of the sidereal rotation of the Sun is used as a calibrator is described. One of the key points of the procedure is to eliminate the effects of the Earth's motion relative to the Sun and the temperature instability of the birefringent filter by tuning the bandpass of the birefringent filter. The other is to make the light level of the direct image of the videomagnetograph the same both in Doppler and in Zeeman modes in order to reduce the errors introduced by imperfect linearity of the transfer curve of the camera tube. Some practical problems of calibration are discussed for further improvement
Transmission statistics and focusing in single disordered samples
We show in microwave experiments and random matrix calculations that in
samples with a large number of channels the statistics of transmission for
different incident channels relative to the average transmission is determined
by a single parameter, the participation number of the eigenvalues of the
transmission matrix, M. Its inverse, M-1, is equal to the variance of relative
total transmission of the sample, while the contrast in maximal focusing is
equal to M. The distribution of relative total transmission changes from
Gaussian to negative exponential over the range in which M-1 changes from 0 to
1. This provides a framework for transmission and imaging in single samples.Comment: 9 pages, 4 figure
Quantum computation in decoherence-free subspace with superconducting devices
We propose a scheme to implement quantum computation in decoherence-free
subspace with superconducting devices inside a cavity by unconventional
geometric manipulation. Universal single-qubit gates in encoded qubit can be
achieved with cavity assisted interaction. A measurement-based two-qubit
Controlled-Not gate is produced with parity measurements assisted by an
auxiliary superconducting device and followed by prescribed single-qubit gates.
The measurement of currents on two parallel devices can realize a projective
measurement, which is equivalent to the parity measurement on the involved
devices.Comment: v2: thoroughly rewritten version with title and motivation changed;
v3: published version with detail dirivation
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