1,842 research outputs found
Proper Motions in Compact Symmetric Objects
We discuss recent measurements of proper motions of the hotspots of Compact
Symmetric Objects. Source expansion has been detected in ten CSOs so far and
all these objects are very young (<3000 years). In a few sources ages have also
been estimated from energy supply and spectral ageing arguments and these
estimates are comparable. This argues that these sources are close to
equipartition and that standard spectral ageing models apply. Proper motions
studies are now constraining hotspot accelerations, side-to-side motions and
differences in hotspot advance speeds between the two hotspots within sources.
Although most CSOs are young sources their evolution is unclear. There is
increasing evidence that in some objects the CSO structure represents a new
phase of activity within a recurrent source.Comment: 10 pages, 3 figures, Accepted by Publications of the Astronomical
Society of Australia (Vol. 20), as part of the proceedings of the 3rd GPS/CSS
workshop, eds. T. Tzioumis, W. de Vries, I. Snellen, A. Koekemoe
Low-Temperature Specific Heat of an Extreme-Type-II Superconductor at High Magnetic Fields
We present a detailed study of the quasiparticle contribution to the
low-temperature specific heat of an extreme type-II superconductor at high
magnetic fields. Within a T-matrix approximation for the self-energies in the
mixed state of a homogeneous superconductor, the electronic specific heat is a
linear function of temperature with a linear- coefficient
being a nonlinear function of magnetic field . In the range of magnetic
fields H\agt (0.15-0.2)H_{c2} where our theory is applicable, the calculated
closely resembles the experimental data for the borocarbide
superconductor YNiBC.Comment: 7 pages, 2 figures, to appear in Physical Review
New structural and magnetic aspects of the nanotube system Na2V3O7
We present new experimental results of low temperature x-ray synchrotron
diffraction, neutron scattering and very low temperature (mK-range) bulk
measurements on the nanotube system {\tube}. The crystal structure determined
from our data is similar to the previously proposed model (P. Millet {\it et
al.} J. Solid State Chem. , 676 (1999)), but also deviates from it in
significant details. The structure comprises nanotubes along the c-axis formed
by stacking units of two V-rings buckled in the -plane. The space group is
P and the composition is nonstoichiometric, Na(2-x)V3O7, x=0.17. The
thermal evolution of the lattice parameters reveals anisotropic lattice
compression on cooling. Neutron scattering experiments monitor a very weak
magnetic signal at energies from -20 to 9 meV. New magnetic susceptibility,
specific heat measurements and decay of remanent magnetization in the 30 mK -
300 mK range reveal that the previously observed transition at ~76 mK is
spin-glass like with no long-range order. Presented experimental observations
do not support models of isolated clusters, but are compatible with a model of
odd-legged S=1/2 spin tubes possibly segmented into fragments with different
lengths
Making Decisions to Identify Forage Shrub Species for Versatile Grazing Systems
Grazing systems in many parts of the world face large challenges, including a declining natural resource base (e.g. soil fertility), marked fluctuations in feed production across seasons and years, climate change (including the contribution of greenhouse gases from livestock), and market demands for sustainable and ethical production systems. The ‘Enrich’ project was established in Australia (Revell et al. 2008; Bennell et al. 2010) within this broad context of emerging challenges to explore the potential of using Australian native perennial shrub species as part of the feedbase for sheep and cattle in southern Australia. The underlying rationale was to: add perennial shrub species into the existing annual-based pasture feedbase so that the forage system could tolerate extended dry periods but provide green edible plant material during periods where a ‘feed gap’ would otherwise exist; be productive on marginal soils where other productive options are limited (Masters et al. 2010); and have a positive effect on gut function and health (Vercoe et al. 2007); i.e. a versatile grazing system. This paper outlines the research approach that was taken, and reports on a ‘decision tree’ to prioritise species from an initial large list, based on a wide range of plant characteristics and how they can be used in a grazing system
Ursinus College Alumni Journal, February 1952
President\u27s page • Mr. Charles Lachman elected Vice-President • The Price of Freedom: Founders Day address • 693 students register at Ursinus for 1951-52 • Dr. George Pfahler honored • Christmas at Ursinus • All-Ursinus cast stars in TV program • Scholarships at Ursinus • Ursinus College featured in the Sunday Bulletin • Paul Wagner teaching on University of the Air • Dr. A. Lewis, Jr. named chief product engineer • A good time had by all on Old Timers\u27 Day • Alfred Gemmell appointed curator • Ursinus Women\u27s Club luncheon December 1st • G. B. Whistler Donahue in Port Lyautey • Air Force offers direct appointments • Alumni Memorial Scholarship Fund • Reginald H. Helfferich to survey relief needs on world tour • Reminiscence about early Ursinus professors • Sports review: Mr. Bailey elected conference president; Spangler to coach Ursinus basketball; Men\u27s basketball outlook; Wrestling prospects; 1951 football review; Soccer 1951; Women\u27s hockey team takes 7 placements on all-college teams • News about ourselves • Necrologyhttps://digitalcommons.ursinus.edu/alumnijournal/1043/thumbnail.jp
Mapping far-IR emission from the central kiloparsec of NGC 1097
Using photometry of NGC 1097 from the Herschel PACS (Photodetector Array
Camera and Spectrometer) instrument, we study the resolved properties of
thermal dust continuum emission from a circumnuclear starburst ring with a
radius ~ 900 pc. These observations are the first to resolve the structure of a
circumnuclear ring at wavelengths that probe the peak (i.e. lambda ~ 100
micron) of the dust spectral energy distribution. The ring dominates the
far-infrared (far-IR) emission from the galaxy - the high angular resolution of
PACS allows us to isolate the ring's contribution and we find it is responsible
for 75, 60 and 55% of the total flux of NGC 1097 at 70, 100 and 160 micron,
respectively. We compare the far-IR structure of the ring to what is seen at
other wavelengths and identify a sequence of far-IR bright knots that
correspond to those seen in radio and mid-IR images. The mid- and far-IR band
ratios in the ring vary by less than +/- 20% azimuthally, indicating modest
variation in the radiation field heating the dust on ~ 600 pc scales. We
explore various explanations for the azimuthal uniformity in the far-IR colors
of the ring including a lack of well-defined age gradients in the young stellar
cluster population, a dominant contribution to the far-IR emission from dust
heated by older (> 10 Myr) stars and/or a quick smoothing of local enhancements
in dust temperature due to the short orbital period of the ring. Finally, we
improve previous limits on the far-IR flux from the inner ~ 600 pc of NGC 1097
by an order of magnitude, providing a better estimate of the total bolometric
emission arising from the active galactic nucleus and its associated central
starburst.Comment: Accepted for publication in the A&A Herschel Special Editio
Molecular gas in the central regions of the latest-type spiral galaxies
Using the IRAM 30m telescope, we have surveyed an unbiased sample of 47
nearby spiral galaxies of very late (Scd-Sm) Hubble-type for emission in the
CO(1-0) and CO(2-1) lines. The sensitivity of our data (a few mK) allows
detection of about 60% of our sample in at least one of the CO lines. The
median detected H2 mass is 1.4\times 10^7 \msun within the central few kpc,
assuming a standard conversion factor. We use the measured line intensities to
complement existing studies of the molecular gas content of spiral galaxies as
a function of Hubble-type and to significantly improve the statistical
significance of such studies at the late end of the spiral sequence. We find
that the latest-type spirals closely follow the correlation between molecular
gas content and galaxy luminosity established for earlier Hubble types. The
molecular gas in late-type galaxies seems to be less centrally concentrated
than in earlier types. We use Hubble Space Telescope optical images to
correlate the molecular gas mass to the properties of the central galaxy disk
and the compact star cluster that occupies the nucleus of most late-type
spirals. There is no clear correlation between the luminosity of the nuclear
star cluster and the molecular gas mass, although the CO detection rate is
highest for the brightest clusters. It appears that the central surface
brightness of the stellar disk is an important parameter for the amount of
molecular gas at the galaxy center. Whether stellar bars play a critical role
for the gas dynamics remains unclear, in part because of uncertainties in the
morphological classifications of our sample.Comment: 27 pages, 15 figures, accepted by A&
Origin of strange metallic phase in cuprate superconductors
The origin of strange metallic phase is shown to exist due to these two
conditions---(i) the electrons are strongly interacting such that there are no
band and Mott-Hubbard gaps, and (ii) the electronic energy levels are crossed
in such a way that there is an electronic energy gap between two energy levels
associated to two different wave functions. The theory is also exploited to
explain (i) the upward- and downward-shifts in the -linear resistivity
curves, and (ii) the spectral weight transfer observed in the soft X-ray
absorption spectroscopic measurements of the La-Sr-Cu-O Mott insulator.Comment: To be published in J. Supercond. Nov. Mag
The Milky Way Bulge: Observed properties and a comparison to external galaxies
The Milky Way bulge offers a unique opportunity to investigate in detail the
role that different processes such as dynamical instabilities, hierarchical
merging, and dissipational collapse may have played in the history of the
Galaxy formation and evolution based on its resolved stellar population
properties. Large observation programmes and surveys of the bulge are providing
for the first time a look into the global view of the Milky Way bulge that can
be compared with the bulges of other galaxies, and be used as a template for
detailed comparison with models. The Milky Way has been shown to have a
box/peanut (B/P) bulge and recent evidence seems to suggest the presence of an
additional spheroidal component. In this review we summarise the global
chemical abundances, kinematics and structural properties that allow us to
disentangle these multiple components and provide constraints to understand
their origin. The investigation of both detailed and global properties of the
bulge now provide us with the opportunity to characterise the bulge as observed
in models, and to place the mixed component bulge scenario in the general
context of external galaxies. When writing this review, we considered the
perspectives of researchers working with the Milky Way and researchers working
with external galaxies. It is an attempt to approach both communities for a
fruitful exchange of ideas.Comment: Review article to appear in "Galactic Bulges", Editors: Laurikainen
E., Peletier R., Gadotti D., Springer Publishing. 36 pages, 10 figure
Quantum Gas Mixtures and Dual-Species Atom Interferometry in Space
The capability to reach ultracold atomic temperatures in compact instruments
has recently been extended into space. Ultracold temperatures amplify quantum
effects, while free-fall allows further cooling and longer interactions time
with gravity - the final force without a quantum description. On Earth, these
devices have produced macroscopic quantum phenomena such as Bose-Einstein
condensation (BECs), superfluidity, and strongly interacting quantum gases.
Quantum sensors interfering the superposition of two ultracold atomic isotopes
have tested the Universality of Free Fall (UFF), a core tenet of Einstein's
classical gravitational theory, at the level. In space, cooling the
elements needed to explore the rich physics of strong interactions and
preparing the multiple species required for quantum tests of the UFF has
remained elusive. Here, utilizing upgraded capabilities of the multi-user Cold
Atom Lab (CAL) instrument within the International Space Station (ISS), we
report the first simultaneous production of a dual species Bose-Einstein
condensate in space (formed from Rb and K), observation of
interspecies interactions, as well as the production of K ultracold
gases. We have further achieved the first space-borne demonstration of
simultaneous atom interferometry with two atomic species (Rb and
K). These results are an important step towards quantum tests of UFF in
space, and will allow scientists to investigate aspects of few-body physics,
quantum chemistry, and fundamental physics in novel regimes without the
perturbing asymmetry of gravity
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