2,361 research outputs found
Phase Control of Squeezed Vacuum States of Light in Gravitational Wave Detectors
Quantum noise will be the dominant noise source for the advanced laser
interferometric gravitational wave detectors currently under construction.
Squeezing-enhanced laser interferometers have been recently demonstrated as a
viable technique to reduce quantum noise. We propose two new methods of
generating an error signal for matching the longitudinal phase of squeezed
vacuum states of light to the phase of the laser interferometer output field.
Both provide a superior signal to the one used in previous demonstrations of
squeezing applied to a gravitational-wave detector. We demonstrate that the new
signals are less sensitive to misalignments and higher order modes, and result
in an improved stability of the squeezing level. The new signals also offer the
potential of reducing the overall rms phase noise and optical losses, each of
which would contribute to achieving a higher level of squeezing. The new error
signals are a pivotal development towards realizing the goal of 6 dB and more
of squeezing in advanced detectors and beyond
Evaluation of serum ARGS neoepitope as an osteoarthritis biomarker using a standardized model for exercise-induced cartilage extra cellular matrix turnover
Summary: Objective: To propose a standardized model for exercise-induced cartilage turnover and investigate residual levels and dynamics of biomarker serum ARGS (sARGS) in primary osteoarthritis (OA) patients and a supportive group of young healthy subjects. Method: The trial is a randomized, cross-over, exploratory study with interventions of exercise and inactivity. 20 subjects with knee OA, as well as 20 young healthy subjects (mean age 25.7 years (range; 19–30), 50% male), underwent cycling, running and resting interventions on separate days one week apart. Blood samples were taken at baseline, immediately, 1, 2, 3 and 24 h after activity start. sARGS was measured by sandwich ELISA. Results: Intraclass correlation between visits were 0.97 and 0.77 for the OA and healthy group, respectively. An acute drop in sARGS in response to high-intensity exercise was observed in both groups. Minute acute sARGS increase was observed in OA subjects in response to moderate intensity running and cycling, which normalized within 24 h. In healthy subjects an acute drop in sARGS was seen immediately after running, but not cycling, and no other changes were observed. A negative correlation between baseline Kellgren-Lawrence (KL) grade and baseline sARGS (r = −0.69, p = 0.002) in OA was found. A negative correlation between age and sARGS was found in healthy subjects (r = −0.67, p = <0.002). Conclusion: sARGS sensitivity to physical activity is considered low and sARGS is a reproducible and stable marker. Minute acute increases in sARGS were observed in the hours following moderate intensity exercise
ALMA observations of Elias 2–24: a protoplanetary disk with multiple gaps in the Ophiuchus molecular cloud
We present ALMA 1.3 mm continuum observations at 0. 2 (25 au) resolution of Elias 2–24, one of the largest and brightest protoplanetary disks in the Ophiuchus Molecular Cloud, and we report the presence of three partially resolved concentric gaps located at ∼20, 52, and 87 au from the star. We perform radiative transfer modeling of the disk to constrain its surface density and temperature radial profile and place the disk structure in the context of mechanisms capable of forming narrow gaps such as condensation fronts and dynamical clearing by actively forming planets. In particular, we estimate the disk temperature at the locations of the gaps to be 23, 15, and 12 K (at 20, 52, and 87 au, respectively), very close to the expected snowlines of CO (23–28 K) and N2 (12–15 K). Similarly, by assuming that the widths of the gaps correspond to 4–8× the Hill radii of forming planets (as suggested by numerical simulations), we estimate planet masses in the range of 0.2 1.5 – MJup, 1.0 8.0 – MJup, and 0.02 0.15 – MJup for the inner, middle, and outer gap, respectively. Given the surface density profile of the disk, the amount of “missing mass” at the location of each one of these gaps (between 4 and 20 MJup) is more than sufficient to account for the formation of such planets.Fil: Cieza, Lucas A.. Universidad Diego Portales; ChileFil: Casassus, Simon. Universidad de Chile; ChileFil: Pérez, Sebastian. Universidad de Chile; ChileFil: Hales, Antonio. Alma Observatory; ChileFil: Cárcamo, Miguel. Universidad de Chile; ChileFil: Ansdell, Megan. University of California at Berkeley; Estados UnidosFil: Avenhaus, Henning. Universitat Zurich; SuizaFil: Bayo, Amelia. Universidad de Valparaiso; ChileFil: Bertrang, Gesa H.-M.. Universidad Diego Portales; ChileFil: Cánovas, Hector. Agencia Espacial Europea; EspañaFil: Christiaens, Valentin. Universidad de Chile; ChileFil: Dent, William. Alma Observatory; ChileFil: Ferrero, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Olofsson, Johan. Universidad de Valparaiso; ChileFil: Orcajo, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Osses, Axel. Universidad de Chile; ChileFil: Peña Ramirez, Karla. Universidad de Antofagasta; ChileFil: Principe, David. Massachusetts Institute of Technology; Estados UnidosFil: Ruíz Rodríguez, Dary. Rochester Institute Of Technology; Estados UnidosFil: Schreiber, Matthias R.. Universidad de Valparaiso; ChileFil: Plas, Gerrit van der. Univ. Grenoble Alpes; SuizaFil: Williams, Jonathan P.. Institute For Astronomy, University Of Hawaii; Estados UnidosFil: Zurlo, Alice. Universidad Diego Portales; Chil
Are Debris Disks and Massive Planets Correlated?
Using data from the Spitzer Space Telescope Legacy Science Program
``Formation and Evolution of Planetary Systems'' (FEPS), we have searched for
debris disks around 9 FGK stars (2-10 Gyr), known from radial velocity (RV)
studies to have one or more massive planets. Only one of the sources, HD 38529,
has excess emission above the stellar photosphere; at 70 micron the
signal-to-noise ratio in the excess is 4.7 while at wavelengths < 30 micron
there is no evidence of excess. The remaining sources show no excesses at any
Spitzer wavelengths. Applying survival tests to the FEPS sample and the results
for the FGK survey published in Bryden et al. (2006), we do not find a
significant correlation between the frequency and properties of debris disks
and the presence of close-in planets. We discuss possible reasons for the lack
of a correlation.Comment: 24 pages, 3 figures. Accepted to Astrophysical Journa
An Estimate of Plasma Volume Changes Following Moderate-High Intensity Running and Cycling Exercise and Adrenaline Infusion
Introduction: Plasma volume (PV) changes in response to physical activity, possibly as a consequence of adrenergic activation. We estimated changes in PV in response to common exercise modalities; cycling and running as well as adrenaline infusion and control at rest.Methods: On separate days, forty circulatory healthy subjects [aged 60 years (range: 42–75)] with knee osteoarthritis underwent moderate-high intensity cycling, running, and intravenous adrenaline infusion to mimic the circulatory response to exercise. Blood samples were obtained from peripheral veins taken at several pre-defined time points before, during, and after the interventions. PV changes were estimated using venous hemoglobin and the derived hematocrit. The temporal associations between PV and selected biomarkers were explored.Results: Changes in PV were observed during all four interventions, and the response to cycling and running was similar. Compared to rest, PV decreased by -14.3% (95% CI: -10.0 to -18.7) after cycling, -13.9% (95% CI: -10.9 to -17.0) after running, and -7.8% (95% CI: -4.2 to -11.5) after adrenaline infusion.Conclusion: PV decreased in response to moderate-high intensity running and cycling. Adrenaline infusion mimicked the PV change observed during exercise, suggesting a separate influence of autonomic control on blood volume homeostasis. In perspective, a temporal association between PV and biomarker dynamics suggests that consideration of PV changes could be relevant when reporting plasma/serum constituents measured during exercise, but more research is needed to confirm this
The search for low-mass axion dark matter with ABRACADABRA-10cm
Two of the most pressing questions in physics are the microscopic nature of
the dark matter that comprises 84% of the mass in the universe and the absence
of a neutron electric dipole moment. These questions would be resolved by the
existence of a hypothetical particle known as the quantum chromodynamics (QCD)
axion. In this work, we probe the hypothesis that axions constitute dark
matter, using the ABRACADABRA-10cm experiment in a broadband configuration,
with world-leading sensitivity. We find no significant evidence for axions, and
we present 95% upper limits on the axion-photon coupling down to the
world-leading level GeV,
representing one of the most sensitive searches for axions in the 0.41 - 8.27
neV mass range. Our work paves a direct path for future experiments capable of
confirming or excluding the hypothesis that dark matter is a QCD axion in the
mass range motivated by String Theory and Grand Unified Theories.Comment: 17 pages, 12 figure
A Submillimeter View of Circumstellar Dust Disks in Ophiuchus
We present new multiwavelength submillimeter continuum measurements of the
circumstellar dust around 48 young stars in the Ophiuchus dark clouds.
Supplemented with previous 1.3 mm observations of an additional 99 objects from
the literature, the statistical distributions of disk masses and submillimeter
colors are calculated and compared to those in the Taurus-Auriga region. These
basic submillimeter properties of young stellar objects in both environments
are shown to be essentially identical. As with their Taurus counterparts, the
Oph circumstellar dust properties are shown to evolve along an empirical
evolution sequence based on the infrared spectral energy distribution. The
combined Oph and Taurus Class II samples (173 sources) are used to set
benchmark values for basic outer disk characteristics: M_disk ~ 0.005 solar
masses, M_disk/M_star ~ 1%, and ~ 2 (where between 350 microns and 1.3 mm). The precision of these numbers
are addressed in the context of substantial solid particle growth in the
earliest stages of the planet formation process. There is some circumstantial
evidence that disk masses inferred from submillimeter emission may be
under-estimated by up to an order of magnitude.Comment: accepted in ApJ; 38 pages, 11 figure
High contrast imaging at the LBT: the LEECH exoplanet imaging survey
In Spring 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began
its 130-night campaign from the Large Binocular Telescope (LBT) atop Mt
Graham, Arizona. This survey benefits from the many technological achievements
of the LBT, including two 8.4-meter mirrors on a single fixed mount, dual
adaptive secondary mirrors for high Strehl performance, and a cold beam
combiner to dramatically reduce the telescope's overall background emissivity.
LEECH neatly complements other high-contrast planet imaging efforts by
observing stars at L' (3.8 m), as opposed to the shorter wavelength
near-infrared bands (1-2.4 m) of other surveys. This portion of the
spectrum offers deep mass sensitivity, especially around nearby adolescent
(0.1-1 Gyr) stars. LEECH's contrast is competitive with other extreme
adaptive optics systems, while providing an alternative survey strategy.
Additionally, LEECH is characterizing known exoplanetary systems with
observations from 3-5m in preparation for JWST.Comment: 12 pages, 5 figures. Proceedings of the SPIE, 9148-2
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