1,924 research outputs found
Time-dependent gravity in southern California, May 1974 - Apr 1979
Gravity measurements were coordinated with the long baseline three dimensional geodetic measurements of the Astronomical Radio Interferometric Earth Surveying project which used radio interferometry with extra-galactic radio sources. Gravity data from 28 of the stations had a single reading standard deviation of 11 microgal which gives a relative single determination between stations a standard deviation of 16 microgal. The largest gravity variation observed, 80 microgal, correlated with nearby waterwell variations and with smoothed rainfall. Smoothed rainfall data appeared to be a good indicator of the qualitative response of gravity to changing groundwater levels at other suprasediment stations, but frequent measurement of gravity at a station was essential until the quantitative calibration of the station's response to groundwater variations was accomplished
SCORPIO-II: Spectral indices of weak Galactic radio sources
In the next few years the classification of radio sources observed by the
large surveys will be a challenging problem, and spectral index is a powerful
tool for addressing it. Here we present an algorithm to estimate the spectral
index of sources from multiwavelength radio images. We have applied our
algorithm to SCORPIO (Umana et al. 2015), a Galactic Plane survey centred
around 2.1 GHz carried out with ATCA, and found we can measure reliable
spectral indices only for sources stronger than 40 times the rms noise. Above a
threshold of 1 mJy, the source density in SCORPIO is 20 percent greater than in
a typical extra-galactic field, like ATLAS (Norris et al. 2006), because of the
presence of Galactic sources. Among this excess population, 16 sources per
square degree have a spectral index of about zero, suggesting optically thin
thermal emission such as Hii regions and planetary nebulae, while 12 per square
degree present a rising spectrum, suggesting optically thick thermal emission
such as stars and UCHii regions.Comment: 12 pages, 11 figures, accepted by MNRA
Long-term follow-up of pulmonary function in Fabry disease: A bi-center observational study.
Fabry disease (FD) is a lysosomal storage disorder leading to decreased α-galactosidase A enzyme activity and subsequent abnormal accumulation of glycosphingolipids in various organs. Although histological evidence of lung involvement has been demonstrated, the functional impact of these changes is less clear.
Adult patients with FD who had yearly pulmonary function tests (PFT) at two centers from 1999 thru 2015 were eligible for this observational study. Primary outcome measures were the change in forced expiratory volume in the first second (FEV1) and FEV1/FVC over time. As secondary outcome we investigated sex, smoking, enzyme replacement therapy (ERT), residual enzyme activity, and Mainz Severity Score Index as possible predictors.
95 patients (41% male, 38.2 ± 14.5 years) were included. The overall prevalence of bronchial obstruction (BO, (FEV1/FVC < 70%)) was 46%, with male sex, age and smoking as significant predictors. FEV1 decreased 29 ml per year (95% CI -36, -22 ml, p<0.0001). FEV1 decline was significantly higher in males (p = 0.009) and in patients on ERT (p = 0.004). Conclusion: Pulmonary involvement seems to be a relevant manifestation of Fabry disease, and routine PFTs should therefore be included in the multidisciplinary follow-up of these patients
Further Sunyaev-Zel'dovich observations of two Planck ERCSC clusters with the Arcminute Microkelvin Imager
We present follow-up observations of two galaxy clusters detected blindly via
the Sunyaev-Zel'dovich (SZ) effect and released in the Planck Early Release
Compact Source Catalogue. We use the Arcminute Microkelvin Imager, a dual-array
14-18 GHz radio interferometer. After radio source subtraction, we find a SZ
decrement of integrated flux density -1.08+/-0.10 mJy toward PLCKESZ
G121.11+57.01, and improve the position measurement of the cluster, finding the
centre to be RA 12 59 36.4, Dec +60 04 46.8, to an accuracy of 20 arcseconds.
The region of PLCKESZ G115.71+17.52 contains strong extended emission, so we
are unable to confirm the presence of this cluster via the SZ effect.Comment: 4 tables, 3 figures, revised after referee's comments and resubmitted
to MNRA
Preparation of distilled and purified continuous variable entangled states
The distribution of entangled states of light over long distances is a major
challenge in the field of quantum information. Optical losses, phase diffusion
and mixing with thermal states lead to decoherence and destroy the
non-classical states after some finite transmission-line length. Quantum
repeater protocols, which combine quantum memory, entanglement distillation and
entanglement swapping, were proposed to overcome this problem. Here we report
on the experimental demonstration of entanglement distillation in the
continuous-variable regime. Entangled states were first disturbed by random
phase fluctuations and then distilled and purified using interference on beam
splitters and homodyne detection. Measurements of covariance matrices clearly
indicate a regained strength of entanglement and purity of the distilled
states. In contrast to previous demonstrations of entanglement distillation in
the complementary discrete-variable regime, our scheme achieved the actual
preparation of the distilled states, which might therefore be used to improve
the quality of downstream applications such as quantum teleportation
Canonical Quantization of Spherically Symmetric Dust Collapse
Quantum gravity effects are likely to play a crucial role in determining the
outcome of gravitational collapse during its final stages. In this contribution
we will outline a canonical quantization of the LeMaitre-Tolman-Bondi models,
which describe the collapse of spherical, inhomogeneous, non-rotating dust.
Although there are many models of gravitational collapse, this particular class
of models stands out for its simplicity and the fact that both black holes and
naked singularity end states may be realized on the classical level, depending
on the initial conditions. We will obtain the appropriate Wheeler-DeWitt
equation and then solve it exactly, after regularization on a spatial lattice.
The solutions describe Hawking radiation and provide an elegant microcanonical
description of black hole entropy, but they raise other questions, most
importantly concerning the nature of gravity's fundamental degrees of freedom.Comment: 19 pages no figures. Contribution to a festschrift in honor of Joshua
N. Goldber
Perceptions of Crop Consultants and Crop Producers on Grazing Corn Residue in Nebraska
We conducted a survey to evaluate factors influencing consultant recommendations on grazing and producer grazing practices in Nebraska. Producers who did not graze cited soil compaction, inconvenience (lack of watering and fencing), and lack of access to livestock as major reasons for not grazing. Producers who allowed grazing and consultants who recommended grazing were more likely than those who did not favor grazing to perceive that grazing increased subsequent grain yields. Most consultants and producers reported making decisions on the basis of their personal observations. Findings from the survey can be used for enhanced Extension dissemination and research activities regarding grazing of residues
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