914 research outputs found
Luther and Tamar
The George Frederick Harkins Lecture; discussion, pp 12-15; also presented as 1992 Lutheran Life Lecture. Reviewed Book: Steinmetz, David C. Luther and Tamar. Lutheran Theological Seminary Bulletin. Genesis 37-5
Luther and the Late Medieval Augustinians: Another Look
The question of the relationship of Martin Luther to the theological traditions of his own order, to which he was exposed in a lesser or greater degree, has remained one of the interesting, if unsolved problems of Luther research
Gender differentiation in higher education: educational specialization and labour market risks in Spain and Germany
The objective of this paper is to investigate the relationship between gender differentiation in tertiary education and labour market hazards. We analyze how differences between male and female tertiary graduates in the chosen degree level and field of study affect the likelihood to be unemployed or obtain a low status job. In order to learn about the role of institutional context, we compare Germany and Spain, two countries that differ with respect to horizontal (field of study) and vertical (degree level) segregation by gender as well as to the linkage between the education and labour market system. Using Labour Force Survey data from the year 2000, our results of logistic regression models as well as a non-linear decomposition technique generally confirm our expectation that the field of study explains a sizable portion of the gender gap in unemployment and low status jobs in both countries. Whereas the level of tertiary degree does not matter with respect to unemployment in either country, it explains part of the female disadvantage in holding a low status job in Spain. Moreover, our analyses show that women with a degree in a predominantly male field of study are not systematically disadvantaged compared to men. Finally, even though the role of the institutional context is hard to evaluate, it seems that, for the two selected countries, the horizontal and vertical gender segregation is more relevant in Spain than in Germany.' [author's abstract
Strong atom-field coupling for Bose-Einstein condensates in an optical cavity on a chip
An optical cavity enhances the interaction between atoms and light, and the
rate of coherent atom-photon coupling can be made larger than all decoherence
rates of the system. For single atoms, this strong coupling regime of cavity
quantum electrodynamics (cQED) has been the subject of spectacular experimental
advances, and great efforts have been made to control the coupling rate by
trapping and cooling the atom towards the motional ground state, which has been
achieved in one dimension so far. For N atoms, the three-dimensional ground
state of motion is routinely achieved in atomic Bose-Einstein condensates
(BECs), but although first experiments combining BECs and optical cavities have
been reported recently, coupling BECs to strong-coupling cavities has remained
an elusive goal. Here we report such an experiment, which is made possible by
combining a new type of fibre-based cavity with atom chip technology. This
allows single-atom cQED experiments with a simplified setup and realizes the
new situation of N atoms in a cavity each of which is identically and strongly
coupled to the cavity mode. Moreover, the BEC can be positioned
deterministically anywhere within the cavity and localized entirely within a
single antinode of the standing-wave cavity field. This gives rise to a
controlled, tunable coupling rate, as we confirm experimentally. We study the
heating rate caused by a cavity transmission measurement as a function of the
coupling rate and find no measurable heating for strongly coupled BECs. The
spectrum of the coupled atoms-cavity system, which we map out over a wide range
of atom numbers and cavity-atom detunings, shows vacuum Rabi splittings
exceeding 20 gigahertz, as well as an unpredicted additional splitting which we
attribute to the atomic hyperfine structure.Comment: 20 pages. Revised version following referees' comments. Detailed
notes adde
Fiber Fabry-Perot cavity with high finesse
We have realized a fiber-based Fabry-Perot cavity with CO2 laser-machined
mirrors. It combines very small size, high finesse F>=130000, small waist and
mode volume, and good mode matching between the fiber and cavity modes. This
combination of features is a major advance for cavity quantum electrodynamics
(CQED), as shown in recent CQED experiments with Bose-Einstein condensates
enabled by this cavity [Y. Colombe et al., Nature 450, 272 (2007)]. It should
also be suitable for a wide range of other applications, including coupling to
solid-state emitters, gas detection at the single-particle level, fiber-coupled
single-photon sources and high-resolution optical filters with large stopband.Comment: Submitted to New J. Phys
Toward a Broadband Astro-comb: Effects of Nonlinear Spectral Broadening in Optical Fibers
We propose and analyze a new approach to generate a broadband astro-comb by
spectral broadening of a narrowband astro-comb inside a highly nonlinear
optical fiber. Numerical modeling shows that cascaded four-wave-mixing
dramatically degrades the input comb's side-mode suppression and causes
side-mode amplitude asymmetry. These two detrimental effects can systematically
shift the center-of-gravity of astro-comb spectral lines as measured by an
astrophysical spectrograph with resolution \approx100,000; and thus lead to
wavelength calibration inaccuracy and instability. Our simulations indicate
that this performance penalty, as a result of nonlinear spectral broadening,
can be compensated by using a filtering cavity configured for double-pass. As
an explicit example, we present a design based on an Yb-fiber source comb (with
1 GHz repetition rate) that is filtered by double-passing through a low finesse
cavity (finesse = 208), and subsequent spectrally broadened in a 2-cm,
SF6-glass photonic crystal fiber. Spanning more than 300 nm with 16 GHz line
spacing, the resulting astro-comb is predicted to provide 1 cm/s (~10 kHz)
radial velocity calibration accuracy for an astrophysical spectrograph. Such
extreme performance will be necessary for the search for and characterization
of Earth-like extra-solar planets, and in direct measurements of the change of
the rate of cosmological expansion.Comment: 9 pages, 6 figure
Single-photon emission from Ni-related color centers in CVD diamond
Color centers in diamond are very promising candidates among the possible
realizations for practical single-photon sources because of their long-time
stable emission at room temperature. The popular nitrogen-vacancy center shows
single-photon emission, but within a large, phonon-broadened spectrum (~100nm),
which strongly limits its applicability for quantum communication. By contrast,
Ni-related centers exhibit narrow emission lines at room temperature. We
present investigations on single color centers consisting of Ni and Si created
by ion implantation into single crystalline IIa diamond. We use systematic
variations of ion doses between 10^8/cm^2 and 10^14/cm^2 and energies between
30keV and 1.8MeV. The Ni-related centers show emission in the near infrared
spectral range (~770nm to 787nm) with a small line-width (~3nm FWHM). A
measurement of the intensity correlation function proves single-photon
emission. Saturation measurements yield a rather high saturation count rate of
77.9 kcounts/s. Polarization dependent measurements indicate the presence of
two orthogonal dipoles.Comment: 8 pages, published in conference proceedings of SPIE Photonics Europe
201
Counterrotating Stars in Simulated Galaxy Disks
Counterrotating stars in disk galaxies are a puzzling dynamical feature whose
origin has been ascribed to either satellite accretion events or to disk
instabilities triggered by deviations from axisymmetry. We use a cosmological
simulation of the formation of a disk galaxy to show that counterrotating
stellar disk components may arise naturally in hierarchically-clustering
scenarios even in the absence of merging. The simulated disk galaxy consists of
two coplanar, overlapping stellar components with opposite spins: an inner
counterrotating bar-like structure made up mostly of old stars surrounded by an
extended, rotationally-supported disk of younger stars. The opposite-spin
components originate from material accreted from two distinct filamentary
structures which at turn around, when their net spin is acquired, intersect
delineating a "V"-like structure. Each filament torques the other in opposite
directions; the filament that first drains into the galaxy forms the inner
counterrotating bar, while material accreted from the other filament forms the
outer disk. Mergers do not play a substantial role and most stars in the galaxy
are formed in situ; only 9% of all stars are contributed by accretion events.
The formation scenario we describe here implies a significant age difference
between the co- and counterrotating components, which may be used to
discriminate between competing scenarios for the origin of counterrotating
stars in disk galaxies.Comment: 7 pages, 7 figures. Accepted for publication in MNRA
Redox-active ferrocene-modified Cowpea mosaic virus nanoparticles
A naturally occurring nanoparticle, the plant virus Cowpea mosaic virus, can be decorated with ferrocene derivatives, of various linker lengths with amine and carboxylategroups, on the external surface using a range of conjugation strategies. The multiple, organometallic, redox-active ferrocene moieties on the outer surface of the virus are electrochemically independent with reduction potentials that span a potential window of 0.16 V that are dependent on the site of modification and the nature of the ferrocene derivative. The number of ferrocenes coupled to each virus ranges from about 100 to 240 depending upon the conjugation site and the linker length and these redox active units can provide multielectron reservoirs
The Shared Preference Niche of Sympatric Asiatic Black Bears and Sun Bears in a Tropical Forest Mosaic
Ecologically similar species often coexist by partitioning use of habitats or resources. Such partitioning can occur through divergent or shared niches. We investigated overlap in habitat use and spatial co-occurrence by sympatric Asiatic black bears and sun bears in three habitats in Thailand, and thereby assessed which niche model best accounts for their coexistence.We used density of species-specific signs to assess habitat use. Signs of both bear species occurred in all three habitats, and on >60% of sampling transects. Both species fed mostly on fruit; insect feeding signs were uncommon, and were mostly from sun bears. Significant differences in habitat use occurred only in montane forest, the habitat in which fruit was most abundant; incidence of black bear sign there was six times higher than that of sun bears. Habitat use was similar between the two species in the other habitats, which comprised 85% of the area. Of 10 habitat attributes examined, fruiting tree density was the best predictor of occurrence for both species. Models that included interspecific competition (fresh foraging activity of the other species) were less supported than the top models without competition.Bear species co-occurrence at both coarse and fine spatial scales and use of the same resources (fruit trees) indicated common niche preferences. However, their habitat use differed in ways expected from their physical differences: larger black bears dominated in the most fruit-rich habitat, and smaller sun bears used less-preferred insects. These results indicate broadly overlapping fundamental niches combined with asymmetric competition—features consistent with the concept of shared preference niches. This model of the niche has received little attention in ecology, but appears to be relatively common in nature
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