430 research outputs found
Chromatin from sperm of Bivalvia molluscs Specific features of nucleosomal organization
AbstractIn chromatin from the sperm of two Bivalvia molluscs a highly basic low molecular mass sperm-specific protein (S-protein) has been found in addition to the full complement of histones. It is shown that sperm chromatin preserves nucleosomal organization, some parameters of which are specific: (i) DNase I cuts DNA within the sperm nuclei with dinucleosomal periodicity; (ii) linker DNA of the nucleosome is significantly elongated. The S-protein is shown to be located on the linker DNA
Steady-state spin densities and currents
This article reviews steady-state spin densities and spin currents in
materials with strong spin-orbit interactions. These phenomena are intimately
related to spin precession due to spin-orbit coupling which has no equivalent
in the steady state of charge distributions. The focus will be initially on
effects originating from the band structure. In this case spin densities arise
in an electric field because a component of each spin is conserved during
precession. Spin currents arise because a component of each spin is continually
precessing. These two phenomena are due to independent contributions to the
steady-state density matrix, and scattering between the conserved and
precessing spin distributions has important consequences for spin dynamics and
spin-related effects in general. In the latter part of the article extrinsic
effects such as skew scattering and side jump will be discussed, and it will be
shown that these effects are also modified considerably by spin precession.
Theoretical and experimental progress in all areas will be reviewed
Experience of machine vision application in optical NDT systems
Two automated optical inspection systems – for defects detection of in the ligature under UV irradiation and for non-destructive testing of pipeline inner surface – were described. The features of constructions and algorithms of the developed software with using the computer vision techniques were presented. Engineered systems were introduced successfully into commercial operation.Описаны две автоматизированные системы оптического контроля – для обнаружения дефектов в лигатуре под ультрафиолетовым облучением и для внутритрубной дефектоскопии поверхности. Представлены особенности конструкций и алгоритмы функционирования разработанного программного обеспечения с использованием методов технического зрения. Сконструированные системы успешно сданы в промышленную эксплуатацию
A non-linear optimal estimation inverse method for radio occultation measurements of temperature, humidity and surface pressure
An optimal estimation inverse method is presented which can be used to
retrieve simultaneously vertical profiles of temperature and specific humidity,
in addition to surface pressure, from satellite-to-satellite radio occultation
observations of the Earth's atmosphere. The method is a non-linear, maximum
{\it a posteriori} technique which can accommodate most aspects of the real
radio occultation problem and is found to be stable and to converge rapidly in
most cases. The optimal estimation inverse method has two distinct advantages
over the analytic inverse method in that it accounts for some of the effects of
horizontal gradients and is able to retrieve optimally temperature and humidity
simultaneously from the observations. It is also able to account for
observation noise and other sources of error. Combined, these advantages ensure
a realistic retrieval of atmospheric quantities.
A complete error analysis emerges naturally from the optimal estimation
theory, allowing a full characterisation of the solution. Using this analysis a
quality control scheme is implemented which allows anomalous retrieval
conditions to be recognised and removed, thus preventing gross retrieval
errors.
The inverse method presented in this paper has been implemented for bending
angle measurements derived from GPS/MET radio occultation observations of the
Earth. Preliminary results from simulated data suggest that these observations
have the potential to improve NWP model analyses significantly throughout their
vertical range.Comment: 18 (jgr journal) pages, 7 figure
Magneto-gyrotropic effects in semiconductor quantum wells (review)
Magneto-gyrotropic photogalvanic effects in quantum wells are reviewed. We
discuss experimental data, results of phenomenological analysis and microscopic
models of these effects. The current flow is driven by spin-dependent
scattering in low-dimensional structures gyrotropic media resulted in asymmetry
of photoexcitation and relaxation processes. Several applications of the
effects are also considered.Comment: 28 pages, 13 figure
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