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951.
952.
R. Grange M. Haiml R. Paschotta G.J. Spühler L. Krainer M. Golling O. Ostinelli U. Keller 《Applied physics. B, Lasers and optics》2005,80(2):151-158
The reflectivity of a semiconductor saturable absorber mirror (SESAM) is generally expected to increase with increasing pulse energy. However, for higher pulse energies the reflectivity can decrease again; we call this a roll-over of the nonlinear reflectivity curve caused by inverse saturable absorption. We show for several SESAMs that the measured roll-over is consistent with two-photon absorption only for short (femtosecond) pulses, while a stronger (yet unidentified) kind of nonlinear absorption is dominant for longer (picosecond) pulses. These inverse saturable absorption effects have important technological consequences, e.g. for the Q-switching dynamics of passively mode-locked lasers. A simple equation using only measurable SESAM parameters and including inverse saturable absorption is derived for the Q-switched mode-locking threshold. We present various data and discuss the sometimes detrimental effects of this roll-over for femtosecond high repetition rate lasers, as well as the potentially very useful consequences for passively mode-locked multi-GHz lasers. We also discuss strategies to enhance or reduce this induced absorption by using different SESAM designs or semiconductor materials. PACS 42.60.Fc; 42.70.Nq; 78.20.Ci 相似文献
953.
Steven?D?Buckingham Luanda?Pym Andrew?K?Jones Laurence?Brown Mark?SP?Sansom David?B?Sattelle Philip?C?BigginEmail author 《BMC neuroscience》2005,6(1):2
Background
Nicotinic acetylcholine receptors (nAChRs) are pentameric proteins that are important drug targets for a variety of diseases including Alzheimer's, schizophrenia and various forms of epilepsy. One of the most intensively studied nAChR subunits in recent years has been α7. This subunit can form functional homomeric pentamers (α7)5, which can make interpretation of physiological and structural data much simpler. The growing amount of structural, pharmacological and physiological data for these receptors indicates the need for a dedicated and accurate database to provide a means to access this information in a coherent manner. 相似文献954.
To supplement existing data, solutions of are tabulated for primes with and . For , five new solutions 2^{32}$"> are presented. One of these, for , also satisfies the ``reverse' congruence . An effective procedure for searching for such ``double solutions' is described and applied to the range , . Previous to this, congruences are generally considered for any and fixed prime to see where the smallest prime solution occurs.
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We present a general approach for the measurement of the properties of optical pulses by exploiting features of the optical carrier domain. We demonstrate the principle of a novel balanced detection scheme that avoids the difficulties associated with homodyne detection in the baseband used in linear optical sampling methods so far. The residual timing instability of the repetition rate synchronization between mode-locked lasers is measured with the new detection technique. 相似文献
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A method for the determination of cyclosporin A in human whole blood and plasma is described which uses liquid chromatography with step gradient elution and a column switching technique. The chromatographic conditions chosen allow simple and rapid sample preparation, so that a result can be obtained within one hour. Blood and plasma are deproteinized with diluted methanol and an aliquot of the clear supernatant is directly injected. The detection limit for cyclosporin A is about 20 ng/ml starting from a 0.5 ml sample. The method is sensitive enough for monitoring the drug in the therapeutic range. 相似文献
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We study the general mathematical structure of unitary rational conformal field theories in two dimensions, starting from the Euclidean Green functions of the scaling fields. We show that, under certain assumptions, the scaling fields of such theories can be written as sums of products of chiral fields. The chiral fields satisfy an algebra whose structure constants are the matrix elements of Yang-Baxter- or braid-matrices whose properties we analyze. The upshot of our analysis is that two-dimensional conformal field theories of the type considered in this paper appear to be constructible from the representation theory of a pair of chiral algebras. 相似文献