10,609 research outputs found
Multi-epoch infrared photometry of the star forming region G173.58+2.45
We present a multi-epoch infrared photometric study of the intermediate-mass
star forming region G173.58+2.45. Photometric observations are obtained using
the near-infrared filters and narrow-band filters centered at the
wavelengths of H (1-0) S(1) (2.122 m) and [FeII] (1.644 m) lines.
The H image shows molecular emission from shocked gas, implying the
presence of multiple star formation and associated outflow activity. We see
evidence for several collimated outflows. The most extended jet is at least
0.25 pc in length and has a collimation factor of 10, which may be
associated with a binary system within the central cluster, resolved for the
first time here. This outflow is found to be episodic; probably occurring or
getting enhanced during the periastron passage of the binary. We also find that
the variable star in the vicinity of the outflow source, which was known as a
FU Ori type star, is probably not a FU Ori object. However, it does drive a
spectacular outflow and the variability is likely to be related to accretion,
when large clouds of gas and dust spiral in towards the central source. Many
other convincing accretion-outflow systems and YSO candidates are discovered in
the field.Comment: 15 pages, 9 figures, accepted for publication in MNRA
Microwave microstrip resonator measurements of Y1Ba2Cu3O(7-x) and Bi2Sr2Ca1Cu2O(8-y) thin films
Radio frequency (RF) surface resistance measurement experiments on high T(sub c) thin films were performed. The method uses a microstrip resonator comprising a top gold conductor strip, an alumina dielectric layer, and a separate superconductivity ground plane. The surface resistance of the superconducting ground plane can be determined, with reference to a gold calibration standard, from the measured quality factor of the half-wave resonator. Initial results near 7 GHz over the temperature range from 25 to 300 K are presented for YBa2Cu3O(7-x) and Bi2Sr2CaCu2O(8-y) thin film samples deposited by an electron beam flash evaporation process. The RF surface resistance at 25 K for both materials in these samples was found to be near 25 milliohms
Breaking down the link between luminous and dark matter in massive galaxies
We present a study on the clustering of a stellar mass selected sample of
galaxies with stellar masses M*>10^10Msol at redshifts 0.4<z<2.0, taken from
the Palomar Observatory Wide-field Infrared Survey. We examine the clustering
properties of these stellar mass selected samples as a function of redshift and
stellar mass, and find that galaxies with high stellar masses have a
progressively higher clustering strength than galaxies with lower stellar
masses. We also find that galaxies within a fixed stellar mass range have a
higher clustering strength at higher redshifts. We further estimate the average
total masses of the dark matter haloes hosting these stellar-mass selected
galaxies. For all galaxies in our sample the stellar-mass-to-total-mass ratio
is always lower than the universal baryonic mass fraction and the
stellar-mass-to-total-mass ratio is strongly correlated with the halo masses
for central galaxies, such that more massive haloes contain a lower fraction of
their mass in the form of stars. The remaining baryonic mass is included
partially in stars within satellite galaxies in these haloes, and as diffuse
hot and warm gas. We also find that, at a fixed stellar mass, the
stellar-to-total-mass ratio increases at lower redshifts. This suggests that
galaxies at a fixed stellar mass form later in lower mass dark matter haloes,
and earlier in massive haloes. We interpret this as a `halo downsizing' effect.Comment: Proceedings of the IAU Symposium No. 277, 2010 "Tracing the Ancestry
of Galaxies on the Land of our Ancestors"; Eds. Carignan, Freeman and Combe
Construction and evaluation of classifiers for forensic document analysis
In this study we illustrate a statistical approach to questioned document
examination. Specifically, we consider the construction of three classifiers
that predict the writer of a sample document based on categorical data. To
evaluate these classifiers, we use a data set with a large number of writers
and a small number of writing samples per writer. Since the resulting
classifiers were found to have near perfect accuracy using leave-one-out
cross-validation, we propose a novel Bayesian-based cross-validation method for
evaluating the classifiers.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS379 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Characterization of Legacy Sediment variations in accretion and carbon dynamics following dam removal in a recently restored tidal freshwater wetland
Damming disrupts the natural flow of sediment to adjoining water bodies resulting in the accumulation of Legacy Sediments (LS). While the impact of LS inputs has been well investigated in lotic Mid-Atlantic piedmont stream restorations, (i.e. milldam removal 1,2,3,4,5,), there have been few studies investigating LS following dam removal in low-gradient coastal plain streams. The objectives of this study were to quantify spatial and temporal variations of LS characteristics in a low-gradient tidal stream restoration within the lower James River watershed. Secondary objectives were to assess the current temporal and spatial variability in sediment deposition within the recently restored Kimages Creek wetlands and adjacent, unaltered wetlands of Harris Creek to investigate current sedimentation processes in a restoration setting
α<sub>1L</sub>-adrenoceptors mediate contraction of human erectile tissue
α1-adrenoceptor antagonists can impact upon sexual function and have potential in the treatment of erectile dysfunction. Human erectile tissue contains predominantly α1A-adrenoceptors, and here we examined whether contractions of this tissue are mediated by the functional phenotype, the α1L-adrenoceptor. Functional experiments using subtype selective agonists and antagonists, along with radioligand ([3H]tamsulosin) binding assays, were used to determine the α1-adrenoceptor population. A61603, a α1A-adrenoceptor agonist, was a full agonist with a potency 21-fold greater than that of noradrenaline. The α1A- and α1D-adrenoceptor antagonist tamsulosin antagonized noradrenaline responses with high affinity (pKD = 9.7 ± 0.3), whilst BMY7378 (100 nM) (α1D-adrenoceptor antagonist) failed to antagonize responses. In contrast, relatively low affinity estimates were obtained for both prazosin (pKD = 8.2 ± 0.1) and RS17053 (pKD = 6.9 ± 0.2), antagonists which discriminate between the α1A- and α1L-adrenoceptors. [3H]Tamsulosin bound with high affinity to the receptors of human erectile tissue (pKD = 10.3 ± 0.1) with a receptor density of 28.1 ± 1.4 fmol mg−1 protein. Prazosin displacement of [3H]tamsulosin binding revealed a single homogenous population of binding sites with a relatively low affinity for prazosin (pKi = 8.9). Taken together these data confirm that the receptor mediating contraction in human erectile tissue has the pharmacological properties of the α1L-adrenoceptor. Keywords: Erectile tissue, α1-adrenoceptor subtypes, α1L-adrenoceptor, Tamsulosin, Prazosi
Influence of classical resonances on chaotic tunnelling
Dynamical tunnelling between symmetry-related stable modes is studied in the
periodically driven pendulum. We present strong evidence that the tunnelling
process is governed by nonlinear resonances that manifest within the regular
phase-space islands on which the stable modes are localized. By means of a
quantitative numerical study of the corresponding Floquet problem, we identify
the trace of such resonances not only in the level splittings between
near-degenerate quantum states, where they lead to prominent plateau
structures, but also in overlap matrix elements of the Floquet eigenstates,
which reveal characteristic sequences of avoided crossings in the Floquet
spectrum. The semiclassical theory of resonance-assisted tunnelling yields good
overall agreement with the quantum-tunnelling rates, and indicates that partial
barriers within the chaos might play a prominent role
Factors Driving Sow Breeding Operations to Become Large
This study examines the influences of economic and non-economic variables on the size of U.S. sow breeding operations using a probit model. Data from a national survey of U.S. hog operations identifying two different size categories were used in this study. Findings indicate that factors such as operations located in Delta States, climate controlled facilities, specialized operation, breeding practices, and risk attitudes toward investments influence decisions to establish breeding operations with 500 or more sows. Producers located in Iowa were more likely to choose breeding operations with 499 or less sows.Farm Management,
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