644 research outputs found
New ultrarapid-scanning interferometer for FT-IR spectroscopy with microsecond time-resolution
A novel Fourier-transform infrared (FT-IR) rapid-scan spectrometer has been
developed (patent pending EP14194520.4) which yields 1000 times higher time
resolution as compared to conventional rapid-scanning spectrometers. The
central element to achieve faster scanning rates is based on a sonotrode whose
front face represents the movable mirror of the interferometer. A prototype
spectrometer with a time resolution of 13 μs was realized, capable of fully
automated long-term measurements with a flow cell for liquid samples, here a
photosynthetic membrane protein in solution. The performance of this novel
spectrometer is demonstrated by recording the photoreaction of
bacteriorhodopsin initiated by a short laser pulse that is synchronized to the
data recording. The resulting data are critically compared to those obtained
by step-scan spectroscopy and demonstrate the relevance of performing
experiments on proteins in solution. The spectrometer allows for future
investigations of fast, non-repetitive processes, whose investigation is
challenging to step-scan FT-IR spectroscopy
On reflection of Alfven waves in the solar wind
We have revisited the problem of propagation of toroidal and linear Alfven waves formulated by Heinemann and Olbert (1980) to compare WKB and non-WKB waves and their effects on the solar wind. They considered two solar wind models and showed that reflection is important for Alfven waves with periods of the order of one day and longer, and that non-WKB Alfven waves are no more effective in accelerating the solar wind than WKB waves. There are several recently published papers which seem to indicate that Alfven waves with periods of the order of several minutes should be treated as non-WKB waves and that these non-WKB waves exert a stronger acceleration force than WKB waves. The purpose of this paper is to study the origin of these discrepancies by performing parametric studies of the behavior of the waves under a variety of different conditions. In addition, we want to investigate two problems that have not been addressed by Heinemann and Olbert, namely, calculate the efficiency of Alfven wave reflection by using the reflection coefficient and identify the region of strongest wave reflection in different wind models. To achieve these goals, we investigated the influence of temperature, electron density distribution, wind velocity and magnetic field strength on the waves. The obtained results clearly demonstrate that Alfven wave reflection is strongly model dependent and that the strongest reflection can be expected in models with the base temperatures higher than 10(exp 6) K and with the base densities lower than 7 x 10(exp 7) cm(exp -3). In these models as well as in the models with lower temperatures and higher densities, Alfven waves with periods as short as several minutes have negligible reflection so that they can be treated as WKB waves; however, for Alfven waves with periods of the order of one hour or longer reflection is significant, requiring a non-WKB treatment. We also show that non-WKB, linear Alfven waves are always less effective in accelerating the plasma than WKB Alfven waves. Finally, it is evident from our results that the region of strongest wave reflection is usually located at the base of the models, and hence that interpretation of wave reflection based solely on the reflection coefficient can be misleading
Internal effective field sources for spin torque nano pillar oscillators
In this paper we numerically conduct micromagnetic modelling with an expended
micromagnetic model that includes the spin torque term and an impedance model
to investigate methods to replace external field sources with internal ones and
to investigate its tuneability on nanopillar geometries. We present results for
three methods: interlayer coupling, large perpendicular anisotropy and
magnetostatic coupling. The internal field sources are evaluated as function of
frequency shift with current, its dependency on temperature and are tested
against analytical predictions.Comment: 27 pages, 11 figures, submitted to Journal of Applied Physic
Detailed clay mineralogy of the TriassicJurassic boundary section at Kendlbachgraben (Northern Calcareous Alps, Austria)
The Triassic-Jurassic boundary (TJB) is marked by one of the five largest
Phanerozoic mass extinctions. To constrain existing models for TJB events, we obtained a
stratigraphically highly resolved dataset from a marine section at Kendlbachgraben, Austria.
The topmost Triassic Ko¨ssen Formation contains low to medium-charged smectite and vermiculite
as alteration products of mafic-ultramafic minerals. The clay minerals in the boundary mudstone are
kaolinite 5 illite + muscovite >> smectite > chlorite. Predominant kaolinite suggests humid climate
and abundant terrigenous input. In the lowermost Jurassic, the clay mineral pattern changes to illite +
muscovite >> kaolinite >> smectite, which reflects change to less humid and more moderate climate.
The topmost Ko¨ssen Formation also contains clay spherules. Their composition, shape and size
indicate that they are alteration products of airborne volcanic glass droplets solidified in the air,
settled in the sea and altered rapidly with negligible transport in terrestrial or marine environments.
Our data are consistent with sudden climatic change at the TJB, as a result of large-scale volcanic
activity of the Central Atlantic Magmatic Province which produced distal airfall volcanic ash
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