61 research outputs found
Quantum-limited optical time transfer for future geosynchronous links
The combination of optical time transfer and optical clocks opens up the
possibility of large-scale free-space networks that connect both ground-based
optical clocks and future space-based optical clocks. Such networks promise
better tests of general relativity, dark matter searches, and gravitational
wave detection. The ability to connect optical clocks to a distant satellite
could enable space-based very long baseline interferometry (VLBI), advanced
satellite navigation, clock-based geodesy, and thousand-fold improvements in
intercontinental time dissemination. Thus far, only optical clocks have pushed
towards quantum-limited performance. In contrast, optical time transfer has not
operated at the analogous quantum limit set by the number of received photons.
Here, we demonstrate time transfer with near quantum-limited acquisition and
timing at 10,000 times lower received power than previous approaches. Over 300
km between mountaintops in Hawaii with launched powers as low as 40 W,
distant timescales are synchronized to 320 attoseconds. This nearly
quantum-limited operation is critical for long-distance free-space links where
photons are few and amplification costly -- at 4.0 mW transmit power, this
approach can support 102 dB link loss, more than sufficient for future time
transfer to geosynchronous orbits
Synchronization of Distant Optical Clocks at the Femtosecond Level
The use of optical clocks/oscillators in future ultra-precise navigation,
gravitational sensing, coherent arrays, and relativity experiments will require
time comparison and synchronization over terrestrial or satellite free-space
links. Here we demonstrate full unambiguous synchronization of two optical
timescales across a free-space link. The time deviation between synchronized
timescales is below 1 fs over durations from 0.1 s to 6500 s, despite
atmospheric turbulence and kilometer-scale path length variations. Over several
days, the time wander is 40 fs peak-to-peak. Our approach relies on the two-way
reciprocity of a single-spatial-mode optical link, valid to below 225
attoseconds across a turbulent 4-km path. This femtosecond level of
time-frequency transfer should enable optical networks using state-of-the-art
optical clocks/oscillators.Comment: 19 pages, 9 figure
Structure and Colors of Diffuse Emission in the Spitzer Galactic First Look Survey
We investigate the density structure of the interstellar medium using new
high-resolution maps of the 8 micron, 24 micron, and 70 micron surface
brightness towards a molecular cloud in the Gum Nebula, made as part of the
Spitzer Space Telescope Galactic First Look Survey. The maps are correlated
with 100 micron images measured with IRAS. At 24 and 70 micron, the spatial
power spectrum of surface brightness follows a power law with spectral index
-3.5. At 24 micron, the power law behavior is remarkably consistent from the
0.2 degree size of our maps down to the 5 arcsecond spatial resolution. Thus,
the structure of the 24 micron emission is self-similar even at milliparsec
scales. The combined power spectrum produced from Spitzer 24 micron and IRAS 25
micron images is consistent with a change in the power law exponent from -2.6
to -3.5. The decrease may be due to the transition from a two-dimensional to
three-dimensional structure. Under this hypothesis, we estimate the thickness
of the emitting medium to be 0.3 pc.Comment: 13 Pages, 3 Figures, to be published in Astrophysical Journal
Supplement Series (Spitzer Special Issue), volume 154. Uses aastex v5.
Golimumab in refractory uveitis related to spondyloarthritis. Multicenter study of 15 patients
Objective: To assess the efficacy of golimumab (GLM) in refractory uveitis associated to spondyloarthritis (SpA). Methods: Multicenter study of SpA-related uveitis refractory to at least one immunosuppressive drug. The main outcome variables were degree of anterior and posterior chamber inflammation, visual acuity, and macular thickness. Results: Fifteen patients (13 men/2 women; 18 affected eyes; mean age 39±6 years) were evaluated. The underlying SpA subtypes were ankylosing spondylitis (n=8), psoriatic arthritis (n=6) and non-radiographic axial SpA (n=1). The ocular involvement patterns were recurrent anterior uveitis in 8 patients and chronic anterior uveitis in 7. Before GLM they have received methotrexate (n=13), sulfasalazine (n=6), pulses of methylprednisolone (n=4), azathioprine (n=3), leflunomide (n=2) and cyclosporine (n=1). Ten of them had also been treated with TNF-? blockers; etanercept (n=7), adalimumab (n=7), infliximab (n=6), and certolizumab (n=1). GLM was given at the standard dose (50 mg/sc/monthly) as monotherapy (n=7) or in combination with conventional immunosuppressive drugs (n=8), mainly methotrexate. Most patients had rapid and progressive improvement of intraocular inflammation parameters. The median number of cells in the anterior chamber at 2 years (0 [0-0]) was significantly reduced compared to baseline findings (1 [0-3]); p=0.04). The mean best corrected visual acuity value also improved (0.84±0.3 at 2 years versus 0.62±0.3 at baseline; p=0.03). Only minor side effects were observed after a mean follow-up of 23±7 months. Conclusions: Our results indicate that GLM may be a useful therapeutic option in refractory SpA-related uveitis
The lung cancer exercise training study: a randomized trial of aerobic training, resistance training, or both in postsurgical lung cancer patients: rationale and design
<p>Abstract</p> <p>Background</p> <p>The Lung Cancer Exercise Training Study (LUNGEVITY) is a randomized trial to investigate the efficacy of different types of exercise training on cardiorespiratory fitness (VO<sub>2peak</sub>), patient-reported outcomes, and the organ components that govern VO<sub>2peak </sub>in post-operative non-small cell lung cancer (NSCLC) patients.</p> <p>Methods/Design</p> <p>Using a single-center, randomized design, 160 subjects (40 patients/study arm) with histologically confirmed stage I-IIIA NSCLC following curative-intent complete surgical resection at Duke University Medical Center (DUMC) will be potentially eligible for this trial. Following baseline assessments, eligible participants will be randomly assigned to one of four conditions: (1) aerobic training alone, (2) resistance training alone, (3) the combination of aerobic and resistance training, or (4) attention-control (progressive stretching). The ultimate goal for all exercise training groups will be 3 supervised exercise sessions per week an intensity above 70% of the individually determined VO<sub>2peak </sub>for aerobic training and an intensity between 60 and 80% of one-repetition maximum for resistance training, for 30-45 minutes/session. Progressive stretching will be matched to the exercise groups in terms of program length (i.e., 16 weeks), social interaction (participants will receive one-on-one instruction), and duration (30-45 mins/session). The primary study endpoint is VO<sub>2peak</sub>. Secondary endpoints include: patient-reported outcomes (PROs) (e.g., quality of life, fatigue, depression, etc.) and organ components of the oxygen cascade (i.e., pulmonary function, cardiac function, skeletal muscle function). All endpoints will be assessed at baseline and postintervention (16 weeks). Substudies will include genetic studies regarding individual responses to an exercise stimulus, theoretical determinants of exercise adherence, examination of the psychological mediators of the exercise - PRO relationship, and exercise-induced changes in gene expression.</p> <p>Discussion</p> <p>VO<sub>2peak </sub>is becoming increasingly recognized as an outcome of major importance in NSCLC. LUNGEVITY will identify the optimal form of exercise training for NSCLC survivors as well as provide insight into the physiological mechanisms underlying this effect. Overall, this study will contribute to the establishment of clinical exercise therapy rehabilitation guidelines for patients across the entire NSCLC continuum.</p> <p>Trial Registration</p> <p>NCT00018255</p
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Planck intermediate results XIII : Constraints on peculiar velocities
Peer reviewe
The Science Performance of JWST as Characterized in Commissioning
This paper characterizes the actual science performance of the James Webb
Space Telescope (JWST), as determined from the six month commissioning period.
We summarize the performance of the spacecraft, telescope, science instruments,
and ground system, with an emphasis on differences from pre-launch
expectations. Commissioning has made clear that JWST is fully capable of
achieving the discoveries for which it was built. Moreover, almost across the
board, the science performance of JWST is better than expected; in most cases,
JWST will go deeper faster than expected. The telescope and instrument suite
have demonstrated the sensitivity, stability, image quality, and spectral range
that are necessary to transform our understanding of the cosmos through
observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures;
https://iopscience.iop.org/article/10.1088/1538-3873/acb29
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
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