121 research outputs found
Single frequency CW and Q-switched operation of a diode-pumped Nd:YAG 1.3µm ring laser
The use of an acousto-optic modulator in a ring laser to enforce unidirectional and hence single-frequency operation has been extended to the 1.3µm lines in Nd:YAG. We have also been able to obtain stable simultaneous operation on a single frequency in each of the 1.319µm and 1.338µm transitions either CW or Q-switched. The mechanism behind this behaviour is described and implications for other laser systems are discussed. When operated single frequency, up to 155 mW of CW output is produced, and 30 pJ, 40 nsec Q-switched pulses have been obtained
Stable high repetition rate single frequency Q-switched Nd:YAG ring laser
Reliable single-frequency operation of a diode-pumped, Q-switched, Nd:YAG ring laser at high repetition frequencies up to 25kHz has been achieved by active stabilisation of the prelase power. Average powers of 250mW have been obtained for a 1.2 watt diode pump
Current Distribution in the Three-Dimensional Random Resistor Network at the Percolation Threshold
We study the multifractal properties of the current distribution of the
three-dimensional random resistor network at the percolation threshold. For
lattices ranging in size from to we measure the second, fourth and
sixth moments of the current distribution, finding {\it e.g.\/} that
where is the conductivity exponent and is the
correlation length exponent.Comment: 10 pages, latex, 8 figures in separate uuencoded fil
Polynomial Modular Frobenius Manifolds
The moduli space of Frobenius manifolds carries a natural involutive
symmetry, and a distinguished class - so-called modular Frobenius manifolds -
lie at the fixed points of this symmetry. In this paper a classification of
semi-simple modular Frobenius manifolds which are polynomial in all but one of
the variables is begun, and completed for three and four dimensional manifolds.
The resulting examples may also be obtained from higher dimensional manifolds
by a process of folding. The relationship of these results with orbifold
quantum cohomology is also discussed
Light propagation in statistically homogeneous and isotropic universes with general matter content
We derive the relationship of the redshift and the angular diameter distance
to the average expansion rate for universes which are statistically homogeneous
and isotropic and where the distribution evolves slowly, but which have
otherwise arbitrary geometry and matter content. The relevant average expansion
rate is selected by the observable redshift and the assumed symmetry properties
of the spacetime. We show why light deflection and shear remain small. We write
down the evolution equations for the average expansion rate and discuss the
validity of the dust approximation.Comment: 42 pages, no figures. v2: Corrected one detail about the angular
diameter distance and two typos. No change in result
Light propagation in statistically homogeneous and isotropic dust universes
We derive the redshift and the angular diameter distance in rotationless dust
universes which are statistically homogeneous and isotropic, but have otherwise
arbitrary geometry. The calculation from first principles shows that the
Dyer-Roeder approximation does not correctly describe the effect of clumping.
Instead, the redshift and the distance are determined by the average expansion
rate, the matter density today and the null geodesic shear. In particular, the
position of the CMB peaks is consistent with significant spatial curvature
provided the expansion history is sufficiently close to the spatially flat
LambdaCDM model.Comment: 33 pages. v2: Published version. Corrected typo
Interaction of rheumatoid factor and Entamoeba histolytica
The amoebae's cytotoxicity test and the amoebae's lysis test were used to show possible interactions between rheumatoid factor (RF) and Entamoeba histolytica. Amoebae's cytotoxic activity (ACA) was inhibited by affinity chromatography purified antiamoebae rabbit IgG (RIgG). Enhanced inhibition could be demonstrated with RIgG plus RF. But the same marked inhibition of ACA could be seen when replacing RF by heat inactivated normal human serum as a control. About 50% amoebae's lysis occurred when amoebae were brought together with native normal human serum (NNHS) as a source of complement. Amoebae's lysis increased to 60% when incubated with NHS plus human antiamoebae antibodies. No further augmentation could be obtained by the addition of RF. Using RIgG instead of human antibodies the lysis rate did not increase. Incubation of amoebae, NNHS, RIgG and RF even reduced amoebae's lysis. RF neither has an effect on ACA nor on complement mediated AL in vitro
Basic Methods for Computing Special Functions
This paper gives an overview of methods for the numerical evaluation of special functions, that is, the functions that arise in many problems from mathematical physics, engineering, probability theory, and other applied sciences. We consider in detail a selection of basic methods which are
frequently used in the numerical evaluation of special functions: converging and asymptotic series, including Chebyshev expansions, linear recurrence relations, and numerical quadrature. Several other methods are available and some of these will be discussed in less detail. We give examples of recent software for special functions where these methods are used. We mention a list of new publications on computational aspects of special functions available on our website
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