The Thresher : lucky imaging without the waste

JAH acknowledges funding from the Science and Technology Facilities Council of the United Kingdom.In traditional lucky imaging (TLI), many consecutive images of the same scene are taken with a high frame-rate camera, and all but the sharpest images are discarded before constructing the final shift-and-add image. Here, we present an alternative image analysis pipeline – The Thresher – for these kinds of data, based on online multi-frame blind deconvolution. It makes use of all available data to obtain the best estimate of the astronomical scene in the context of reasonable computational limits; it does not require prior estimates of the point-spread functions in the images, or knowledge of point sources in the scene that could provide such estimates. Most importantly, the scene it aims to return is the optimum of a justified scalar objective based on the likelihood function. Because it uses the full set of images in the stack, The Thresher outperforms TLI in signal-to-noise ratio; as it accounts for the individual-frame PSFs, it does this without loss of angular resolution. We demonstrate the effectiveness of our algorithm on both simulated data and real Electron-Multiplying CCD images obtained at the Danish 1.54-m telescope (hosted by ESO, La Silla). We also explore the current limitations of the algorithm, and find that for the choice of image model presented here, non-linearities in flux are introduced into the returned scene. Ongoing development of the software can be viewed at https://github.com/jah1994/TheThresher.Publisher PDFPeer reviewe

Phosphonate cycling supports methane and ethylene supersaturation in the phosphate-depleted western North Atlantic Ocean

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sosa, O. A., Burrell, T. J., Wilson, S. T., Foreman, R. K., Karl, D. M., & Repeta, D. J. Phosphonate cycling supports methane and ethylene supersaturation in the phosphate-depleted western North Atlantic Ocean. Limnology and Oceanography, (2020), doi:10.1002/lno.11463.In oligotrophic ocean regions, dissolved organic phosphorus (DOP) plays a prominent role as a source of phosphorus (P) to microorganisms. An important bioavailable component of DOP is phosphonates, organophosphorus compounds with a carbon‐phosphorus (C‐P) bond, which are ubiquitous in high molecular weight dissolved organic matter (HMWDOM). In addition to being a source of P, the degradation of phosphonates by the bacterial C‐P lyase enzymatic pathway causes the release of trace hydrocarbon gases relevant to climate and atmospheric chemistry. In this study, we investigated the roles of phosphate and phosphonate cycling in the production of methane (CH4) and ethylene (C2H4) in the western North Atlantic Ocean, a region that features a transition in phosphate concentrations from coastal to open ocean waters. We observed an inverse relationship between phosphate and the saturation state of CH4 and C2H4 in the water column, and between phosphate and the relative abundance of the C‐P lyase marker gene phnJ . In phosphate‐depleted waters, methylphosphonate and 2‐hydroxyethylphosphonate, the C‐P lyase substrates that yield CH4 and C2H4, respectively, were readily degraded in proportions consistent with their abundance and bioavailability in HMWDOM and with the concentrations of CH4 and C2H4 in the water column. We conclude that phosphonate degradation through the C‐P lyase pathway is an important source and a common production pathway of CH4 and C2H4 in the phosphate‐depleted surface waters of the western North Atlantic Ocean and that phosphate concentration can be an important control on the saturation state of these gases in the upper ocean.We thank the captain and crew of the R/V Neil Armstrong and chief scientist Benjamin Van Mooy for supporting and leading research at sea. Chiara Santinelli and Eric Grabowski provided analyses of dissolved organic carbon. This research was funded by NSF Chemical Oceanography award OCE‐1634080 to D.J.R. Additional support was provided by the Gordon and Betty Moore Foundation grant 3794 to D.M.K. and grant 6000 to D.J.R., and the Simons Collaboration on Ocean Processes and Ecology (SCOPE) program grant 329108 to D.M.K., E.F.D., and D.J.R

Assessing the diagnostic accuracy of the identification of hyperkinetic disorders following the introduction of government guidelines in England

<p>Abstract</p> <p>Background</p> <p>Previous studies have suggested that both underdiagnosis and overdiagnosis routinely occur in ADHD and hyperkinesis (hyperkinetic disorders). England has introduced governmental guidelines for these disorders' detection and treatment, but there has been no study on clinical diagnostic accuracy under such a regime.</p> <p>Methods</p> <p>All open cases in three Child and Adolescent Mental Health Services (CAMHS) in the South East of England were assessed for accuracy in the detection of hyperkinetic disorders, using a two-stage process employing the Strengths and Difficulties Questionnaire (SDQ) for screening, with the cut-off between "unlikely" and "possible" as the threshold for identification, and the Development And Well-Being Assessment (DAWBA) as a valid and reliable standard.</p> <p>Results</p> <p>502 cases were collected. Their mean age 11 years (std dev 3 y); 59% were clinically diagnosed as having a hyperkinetic disorder including ADHD. Clinicians had missed two diagnoses of hyperkinesis and six of ADHD. The only 'false positive' case was one that had become asymptomatic on appropriate treatment.</p> <p>Conclusion</p> <p>The identification of children with hyperkinetic disorders by three ordinary English CAMHS teams appears now to be generally consistent with that of a validated, standardised assessment. It seems likely that this reflects the impact of Governmental guidelines, which could therefore be an appropriate tool to ensure consistent accurate diagnosis internationally.</p

Lattice Resistance and Peierls Stress in Finite-size Atomistic Dislocation Simulations

Atomistic computations of the Peierls stress in fcc metals are relatively scarce. By way of contrast, there are many more atomistic computations for bcc metals, as well as mixed discrete-continuum computations of the Peierls-Nabarro type for fcc metals. One of the reasons for this is the low Peierls stresses in fcc metals. Because atomistic computations of the Peierls stress take place in finite simulation cells, image forces caused by boundaries must either be relaxed or corrected for if system size independent results are to be obtained. One of the approaches that has been developed for treating such boundary forces is by computing them directly and subsequently subtracting their effects, as developed by V. B. Shenoy and R. Phillips [Phil. Mag. A, 76 (1997) 367]. That work was primarily analytic, and limited to screw dislocations and special symmetric geometries. We extend that work to edge and mixed dislocations, and to arbitrary two-dimensional geometries, through a numerical finite element computation. We also describe a method for estimating the boundary forces directly on the basis of atomistic calculations. We apply these methods to the numerical measurement of the Peierls stress and lattice resistance curves for a model aluminum (fcc) system using an embedded-atom potential.Comment: LaTeX 47 pages including 20 figure

Bayesian Methods for Exoplanet Science

Exoplanet research is carried out at the limits of the capabilities of current telescopes and instruments. The studied signals are weak, and often embedded in complex systematics from instrumental, telluric, and astrophysical sources. Combining repeated observations of periodic events, simultaneous observations with multiple telescopes, different observation techniques, and existing information from theory and prior research can help to disentangle the systematics from the planetary signals, and offers synergistic advantages over analysing observations separately. Bayesian inference provides a self-consistent statistical framework that addresses both the necessity for complex systematics models, and the need to combine prior information and heterogeneous observations. This chapter offers a brief introduction to Bayesian inference in the context of exoplanet research, with focus on time series analysis, and finishes with an overview of a set of freely available programming libraries.Comment: Invited revie

Experimental Implementation of Optical Clockwork without Carrier-Envelope Phase Control

We demonstrate an optical clockwork without camer-envelope phase control using sum-frequency generation between a CW optical parametric oscillator at 3.39 μm and a modelocked Tisapphire laser with dominant spectral peaks at 834 and 670 nm

Optical Clockwork without Carrier-Envelope Phase Control

We demonstrate optical clockwork without carrier-envelope phase control using sum-frequency generation between a cw optical parametric oscillator at 3.39 μm and a mode-locked Ti:sapphire laser with dominant spectral peaks at 834 nm and 670 nm

Phase-Coherent Synthesis of Optical Frequencies and Waveforms

Precision phase control of an ultrawide-bandwidth optical-frequency comb has produced remarkable and unexpected progress in both areas of optical-frequency metrology and ultrafast optics. A frequency comb (with 100 MHz spacing) spanning an entire optical octave (\u3e300 THz) has been produced, corresponding to millions of marks on a frequency “ruler” that are stable at the Hz level. The precision comb has been used to establish a simple optical clock based on an optical transition of iodine molecules, providing an rf clock signal with a frequency stability comparable to that of an optical standard, and which is superior to almost all conventional rf sources. To realize a high-power cw optical frequency synthesizer, a separate, widely tunable single-frequency cw laser has been employed to randomly access the stabilized optical comb and lock to any desired comb component. Carrier-envelope phase stabilization of few-cycle optical pulses has recently been realized. This advance in femtosecond technology is important for both extreme non-linear optics and optical-frequency metrology. With two independent femtosecond lasers, we have not only synchronized their relative pulse timing at the femtosecond level, but have also phase-locked their carrier frequencies, thus establishing phase coherence between the two lasers. By coherently stitching the optical bandwidth together, a “synthesized” pulse has been generated with its 2nd-order autocorrelation signal displaying a shorter width than those of the two “parent” lasers

Clinical, radiologic, pathologic, and molecular characteristics of long-term survivors of diffuse intrinsic pontine glioma (DIPG): a collaborative report from the International and European Society for Pediatric Oncology DIPG registries

Purpose Diffuse intrinsic pontine glioma (DIPG) is a brainstem malignancy with a median survival of &lt; 1 year. The International and European Society for Pediatric Oncology DIPG Registries collaborated to compare clinical, radiologic, and histomolecular characteristics between short-term survivors (STSs) and long-term survivors (LTSs). Materials and Methods Data abstracted from registry databases included patients from North America, Australia, Germany, Austria, Switzerland, the Netherlands, Italy, France, the United Kingdom, and Croatia. Results Among 1,130 pediatric and young adults with radiographically confirmed DIPG, 122 (11%) were excluded. Of the 1,008 remaining patients, 101 (10%) were LTSs (survival ≥ 2 years). Median survival time was 11 months (interquartile range, 7.5 to 16 months), and 1-, 2-, 3-, 4-, and 5-year survival rates were 42.3% (95% CI, 38.1% to 44.1%), 9.6% (95% CI, 7.8% to 11.3%), 4.3% (95% CI, 3.2% to 5.8%), 3.2% (95% CI, 2.4% to 4.6%), and 2.2% (95% CI, 1.4% to 3.4%), respectively. LTSs, compared with STSs, more commonly presented at age &lt; 3 or &gt; 10 years (11% v 3% and 33% v 23%, respectively; P &lt; .001) and with longer symptom duration ( P &lt; .001). STSs, compared with LTSs, more commonly presented with cranial nerve palsy (83% v 73%, respectively; P = .008), ring enhancement (38% v 23%, respectively; P = .007), necrosis (42% v 26%, respectively; P = .009), and extrapontine extension (92% v 86%, respectively; P = .04). LTSs more commonly received systemic therapy at diagnosis (88% v 75% for STSs; P = .005). Biopsies and autopsies were performed in 299 patients (30%) and 77 patients (10%), respectively; 181 tumors (48%) were molecularly characterized. LTSs were more likely to harbor a HIST1H3B mutation (odds ratio, 1.28; 95% CI, 1.1 to 1.5; P = .002). Conclusion We report clinical, radiologic, and molecular factors that correlate with survival in children and young adults with DIPG, which are important for risk stratification in future clinical trials