4,910 research outputs found
Legalism in an Evangelical Church
The essay that follows developed from a remark that the author made at one of the larger intersynodical conferences. The remark was to the effect that there is much legalism rampant in our circles, that the result is stagnation and retrogression in all areas of church life, and that for this reason sincere and general repentance is necessary before we may anticipate a turn for the better. The expression legalism in our circles was not generally understood. It was intended to describe one aspect of all our activity in thought, speech, and endeavor, based on a comprehensive observation of life and in particular on a study of history
Magnetic behavior of EuCu2As2: Delicate balance between antiferromagnetic and ferromagnetic order
The Eu-based compound, EuCu2As2, crystallizing in the ThCr2Si2-type
tetragonal structure, has been synthesized and its magnetic behavior has been
investigated by magnetization (M), heat-capacity (C) and electrical resistivity
(rho) measurements as a function of temperature (T) and magnetic field (H) as
well as by 151Eu Moessbauer measurements. The results reveal that Eu is
divalent ordering antiferromagnetically below 15 K in the absence of magnetic
field, apparently with the formation of magnetic Brillouin-zone boundary gaps.
A fascinating observation is made in a narrow temperature range before
antiferromagnetism sets in: That is, there is a remarkable upturn just below 20
K in the plot of magnetic susceptibility versus T even at low fields, as though
the compound actually tends to order ferromagnetically. There are corresponding
anomalies in the magnetocaloric effect data as well. In addition, a small
application of magnetic field (around 1 kOe at 1.8 K) in the antiferromagnetic
state causes spin-reorientation effect. These results suggest that there is a
close balance between antiferromagnetism and ferromagnetism in this compoundComment: Phys. Rev. B, in pres
A comparison of the optical properties of radio-loud and radio-quiet quasars
We have made radio observations of 87 optically selected quasars at 5 GHz
with the VLA in order to measure the radio power for these objects and hence
determine how the fraction of radio-loud quasars varies with redshift and
optical luminosity. The sample has been selected from the recently completed
Edinburgh Quasar Survey and covers a redshift range of 0.3 < z < 1.5 and an
optical absolute magnitude range of -26.5 < M_{B} < -23.5 (h, q_{0} = 1/2). We
have also matched up other existing surveys with the FIRST and NVSS radio
catalogues and combined these data so that the optical luminosity-redshift
plane is now far better sampled than previously. We have fitted a model to the
probability of a quasar being radio-loud as a function of absolute magnitude
and redshift and from this model infer the radio-loud and radio-quiet optical
luminosity functions. The radio-loud optical luminosity function is featureless
and flatter than the radio-quiet one. It evolves at a marginally slower rate if
quasars evolve by density evolution, but the difference in the rate of
evolutions of the two different classes is much less than was previously
thought. We show, using Monte-Carlo simulations, that the observed difference
in the shape of the optical luminosity functions can be partly accounted for by
Doppler boosting of the optical continuum of the radio-loud quasars and explain
how this can be tested in the future.Comment: 33 pages, 9 postscript figures, uses the AAS aaspp4 LaTeX style file,
to appear in the 1 February 1999 issue of The Astrophysical Journa
Integrated Structure and Semantics for Reo Connectors and Petri Nets
In this paper, we present an integrated structural and behavioral model of
Reo connectors and Petri nets, allowing a direct comparison of the two
concurrency models. For this purpose, we introduce a notion of connectors which
consist of a number of interconnected, user-defined primitives with fixed
behavior. While the structure of connectors resembles hypergraphs, their
semantics is given in terms of so-called port automata. We define both models
in a categorical setting where composition operations can be elegantly defined
and integrated. Specifically, we formalize structural gluings of connectors as
pushouts, and joins of port automata as pullbacks. We then define a semantical
functor from the connector to the port automata category which preserves this
composition. We further show how to encode Reo connectors and Petri nets into
this model and indicate applications to dynamic reconfigurations modeled using
double pushout graph transformation
Efficient single-cycle pulse compression of an ytterbium fiber laser at 10 MHz repetition rate
Over the past years, ultrafast lasers with average powers in the 100 W range
have become a mature technology, with a multitude of applications in science
and technology. Nonlinear temporal compression of these lasers to few- or even
single-cycle duration is often essential, yet still hard to achieve, in
particular at high repetition rates. Here we report a two-stage system for
compressing pulses from a 1030 nm ytterbium fiber laser to single-cycle
durations with 5 J output pulse energy at 9.6 MHz repetition rate. In
the first stage, the laser pulses are compressed from 340 to 25 fs by spectral
broadening in a krypton-filled single-ring photonic crystal fiber (SR-PCF),
subsequent phase compensation being achieved with chirped mirrors. In the
second stage, the pulses are further compressed to single-cycle duration by
soliton-effect self-compression in a neon-filled SR-PCF. We estimate a pulse
duration of ~3.4 fs at the fiber output by numerically back-propagating the
measured pulses. Finally, we directly measured a pulse duration of 3.8 fs (1.25
optical cycles) after compensating (using chirped mirrors) the dispersion
introduced by the optical elements after the fiber, more than 50% of the total
pulse energy being in the main peak. The system can produce compressed pulses
with peak powers >0.6 GW and a total transmission exceeding 70%
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