4,948 research outputs found
Detection of Anomalous Microwave Emission in the Pleiades Reflection Nebula with WMAP and the COSMOSOMAS Experiment
We present evidence for anomalous microwave emission (AME) in the Pleiades
reflection nebula, using data from the seven-year release of the Wilkinson
Microwave Anisotropy Probe (WMAP) and from the COSMOSOMAS experiment. The flux
integrated in a 1-degree radius around R.A.=56.24^{\circ}, Dec.=23.78^{\circ}
(J2000) is 2.15 +/- 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data
show no significant emission, but allow to set upper limits of 0.94 and 1.58 Jy
(99.7% C.L.) respectively at 10.9 and 14.7 GHz, which are crucial to pin down
the AME spectrum at these frequencies, and to discard any other emission
mechanisms which could have an important contribution to the signal detected at
22.8 GHz. We estimate the expected level of free-free emission from an
extinction-corrected H-alpha template, while the thermal dust emission is
characterized from infrared DIRBE data and extrapolated to microwave
frequencies. When we deduct the contribution from these two components at 22.8
GHz the residual flux, associated with AME, is 2.12 +/- 0.12 Jy (17.7-sigma).
The spectral energy distribution from 10 to 60 GHz can be accurately fitted
with a model of electric dipole emission from small spinning dust grains
distributed in two separated phases of molecular and atomic gas, respectively.
The dust emissivity, calculated by correlating the 22.8 GHz data with
100-micron data, is found to be 4.36+/-0.17 muK/MJy/sr, a value that is rather
low compared with typical values in dust clouds. The physical properties of the
Pleiades nebula indicate that this is indeed a much less opaque object than
others were AME has usually been detected. This fact, together with the broad
knowledge of the stellar content of this region, provides an excellent testbed
for AME characterization in physical conditions different from those generally
explored up to now.Comment: Accepted for publication in ApJ. 12 pages, 8 figure
COSMOSOMAS Observations of the CMB and Galactic Foregrounds at 11 GHz: Evidence for anomalous microwave emission at high Galactic Latitude
We present observations with the new 11 GHz radiometer of the COSMOSOMAS
experiment at the Teide Observatory (Tenerife). The sky region between 0 deg <=
RA <= 360 deg and 26 deg <= DEC 49 deg (ca. 6500 square degrees) was observed
with an angular resolution of 0.9 deg. Two orthogonal independent channels in
the receiving system measured total power signals from linear polarizations
with a 2 GHz bandwidth. Maps with an average sensitivity of 50 microK per beam
have been obtained for each channel. At high Galactic latitude (|b|>30deg) the
11 GHz data are found to contain the expected cosmic microwave background as
well as extragalactic radiosources, galactic synchrotron and free-free
emission, and a dust-correlated component which is very likely of galactic
origin. At the angular scales allowed by the window function of the experiment,
the dust-correlated component presents an amplitude \Delta T aprox. 9-13 microK
while the CMB signal is of order 27 microK. The spectral behaviour of the
dust-correlated signal is examined in the light of previous COSMOSOMAS data at
13-17 GHz and WMAP data at 22-94 GHz in the same sky region. We detect a
flattening in the spectral index of this signal below 20 GHz which rules out
synchrotron radiation as being responsible for the emission. This anomalous
dust emission can be described by a combination of free-free emission and
spinning dust models with a flux density peaking around 20 GHz.Comment: 17 pages, 10 tables, 20 figures. Details on the COSMOSOMAS experiment
can be found at http://www.iac.es/project/cmb/cosmosomas
Regional variation in digital cushion pressure in the forefeet of horses and elephants
In this study, we seek to understand how the digital cushion morphologies evident in horse and elephant feet influence internal and external foot pressures. Our novel use of invasive blood pressure monitoring equipment, combined with a pressure pad and force plate, enabled measurements of (ex vivo) digital cushion pressure under increasing axial loads in seven horse and six elephant forefeet. Linear mixed effects models (LMER) revealed that internal digital cushion pressures increase under load and differ depending on region; elephant feet experienced higher magnitudes of medial digital cushion pressure, whereas horse feet experienced higher magnitudes of centralised digital cushion pressure. Direct comparison of digital cushion pressure magnitudes in both species, at equivalent loads relative to body weight, revealed that medial and lateral pressures increased more rapidly with load in elephant limbs. Within the same approximate region, internal pressures exceeded external, palmar pressures (on the sole of the foot), supporting previous Finite Element (FE) predictions. High pressures and large variations in pressure may relate to the development of foot pathology, which is a major concern in horses and elephants in a captive/domestic environment
Hafnium carbide formation in oxygen deficient hafnium oxide thin films
On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO)
contaminated with adsorbates of carbon oxides, the formation of hafnium carbide
(HfC) at the surface during vacuum annealing at temperatures as low as 600
{\deg}C is reported. Using X-ray photoelectron spectroscopy the evolution of
the HfC surface layer related to a transformation from insulating into
metallic state is monitored in situ. In contrast, for fully stoichiometric
HfO thin films prepared and measured under identical conditions, the
formation of HfC was not detectable suggesting that the enhanced adsorption
of carbon oxides on oxygen deficient films provides a carbon source for the
carbide formation. This shows that a high concentration of oxygen vacancies in
carbon contaminated hafnia lowers considerably the formation energy of hafnium
carbide. Thus, the presence of a sufficient amount of residual carbon in
resistive random access memory devices might lead to a similar carbide
formation within the conducting filaments due to Joule heating
Monte Carlo simulations of fluid vesicles with in plane orientational ordering
We present a method for simulating fluid vesicles with in-plane orientational
ordering. The method involves computation of local curvature tensor and
parallel transport of the orientational field on a randomly triangulated
surface. It is shown that the model reproduces the known equilibrium
conformation of fluid membranes and work well for a large range of bending
rigidities. Introduction of nematic ordering leads to stiffening of the
membrane. Nematic ordering can also result in anisotropic rigidity on the
surface leading to formation of membrane tubes.Comment: 11 Pages, 12 Figures, To appear in Phys. Rev.
High spatial resolution and high contrast optical speckle imaging with FASTCAM at the ORM
In this paper, we present an original observational approach, which combines,
for the first time, traditional speckle imaging with image post-processing to
obtain in the optical domain diffraction-limited images with high contrast
(1e-5) within 0.5 to 2 arcseconds around a bright star. The post-processing
step is based on wavelet filtering an has analogy with edge enhancement and
high-pass filtering. Our I-band on-sky results with the 2.5-m Nordic Telescope
(NOT) and the lucky imaging instrument FASTCAM show that we are able to detect
L-type brown dwarf companions around a solar-type star with a contrast DI~12 at
2" and with no use of any coronographic capability, which greatly simplifies
the instrumental and hardware approach. This object has been detected from the
ground in J and H bands so far only with AO-assisted 8-10 m class telescopes
(Gemini, Keck), although more recently detected with small-class telescopes in
the K band. Discussing the advantage and disadvantage of the optical regime for
the detection of faint intrinsic fluxes close to bright stars, we develop some
perspectives for other fields, including the study of dense cores in globular
clusters. To the best of our knowledge this is the first time that high
contrast considerations are included in optical speckle imaging approach.Comment: Proceedings of SPIE conference - Ground-based and Airborne
Instrumentation for Astronomy III (Conference 7735), San Diego 201
Spatially varying relevance of hydrometeorological hazards for vegetation productivity extremes
Cooperative Hydration of Pyruvic Acid in Ice
About 3.5 ± 0.3 water molecules are still involved in the exothermic hydration of 2-oxopropanoic acid (PA) into its monohydrate (2,2-dihydroxypropanoic acid, PAH) in ice at 230 K. This is borne out by thermodynamic analysis of the fact that Q_H(T) = [PAH]/[PA] becomes temperature independent below ∼250 K (in chemically and thermally equilibrated frozen 0.1 ≤ [PA]/M ≤ 4.6 solutions in D_2O), which requires that the enthalpy of PA hydration (ΔHH ∼ −22 kJ mol^(-1)) be balanced by a multiple of the enthalpy of ice melting (ΔH_M = 6.3 kJ mol^(-1)). Considering that:  (1) thermograms of frozen PA solutions display a single endotherm, at the onset of ice melting, (2) the sum of the integral intensities of the ^1δ_(PAH) and ^1δ_(PA) methyl proton NMR resonances is nearly constant while, (3) line widths increase exponentially with decreasing temperature before diverging below ∼230 K, we infer that PA in ice remains cooperatively hydrated within interstitial microfluids until they vitrify
GaBoDS: The Garching-Bonn Deep Survey - III. Lyman-Break Galaxies in the Chandra Deep Field South
We present first results of our search for high-redshift galaxies in deep CCD
mosaic images. As a pilot study for a larger survey, very deep images of the
Chandra Deep Field South (CDFS), taken withWFI@MPG/ESO2.2m, are used to select
large samples of 1070 U-band and 565 B-band dropouts with the Lyman-break
method. The data of these Lyman-break galaxies are made public as an electronic
table. These objects are good candidates for galaxies at z~3 and z~4 which is
supported by their photometric redshifts. The distributions of apparent
magnitudes and the clustering properties of the two populations are analysed,
and they show good agreement to earlier studies. We see no evolution in the
comoving clustering scale length from z~3 to z~4. The techniques presented here
will be applied to a much larger sample of U-dropouts from the whole survey in
near future.Comment: 11 pages, 11 figures, replaced with version accepted by A&A. Minor
changes and tabular appendix with LBG catalogues. Version with full
resolution figures available at
http://www.astro.uni-bonn.de/~hendrik/2544.pd
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