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https://www.readbyqxmd.com/read/29120423/astronomy-the-star-that-would-not-die
#1
Stan Woosley
No abstract text is available yet for this article.
November 8, 2017: Nature
https://www.readbyqxmd.com/read/29097526/backlash-after-shutdown-of-swiss-astronomy-institute
#2
Gretchen Vogel
No abstract text is available yet for this article.
November 3, 2017: Science
https://www.readbyqxmd.com/read/29094696/a-gravitational-wave-standard-siren-measurement-of-the-hubble-constant
#3
(no author information available yet)
On 17 August 2017, the Advanced LIGO and Virgo detectors observed the gravitational-wave event GW170817-a strong signal from the merger of a binary neutron-star system. Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source. This sky region was subsequently observed by optical astronomy facilities, resulting in the identification of an optical transient signal within about ten arcseconds of the galaxy NGC 4993...
November 2, 2017: Nature
https://www.readbyqxmd.com/read/29092210/spectrographs-for-astrophotonics
#4
N Blind, E Le Coarer, P Kern, S Gousset
The next generation of extremely large telescopes (ELT), with diameters up to 39 meters, is planned to begin operation in the next decade and promises new challenges in the development of instruments since the instrument size increases in proportion to the telescope diameter D, and the cost as D(2) or faster. The growing field of astrophotonics (the use of photonic technologies in astronomy) could solve this problem by allowing mass production of fully integrated and robust instruments combining various optical functions, with the potential to reduce the size, complexity and cost of instruments...
October 30, 2017: Optics Express
https://www.readbyqxmd.com/read/29092197/imaging-through-a-thin-scattering-layer-and-jointly-retrieving-the-point-spread-function-using-phase-diversity
#5
Tengfei Wu, Jonathan Dong, Xiaopeng Shao, Sylvain Gigan
Recently introduced angular-memory-effect based techniques enable non-invasive imaging of objects hidden behind thin scattering layers. However, both the speckle-correlation and the bispectrum analysis are based on the statistical average of large amounts of speckle grains, which determines that they can hardly access the important information of the point-spread-function (PSF) of a highly scattering imaging system. Here, inspired by notions used in astronomy, we present a phase-diversity speckle imaging scheme, based on recording a sequence of intensity speckle patterns at various imaging planes, and experimentally demonstrate that in addition to being able to retrieve the image of hidden objects, we can also simultaneously estimate the pupil function and the PSF of a highly scattering imaging system without any guide-star nor reference...
October 30, 2017: Optics Express
https://www.readbyqxmd.com/read/29092164/uv-superconducting-nanowire-single-photon-detectors-with-high-efficiency-low-noise-and-4-k-operating-temperature
#6
E E Wollman, V B Verma, A D Beyer, R M Briggs, B Korzh, J P Allmaras, F Marsili, A E Lita, R P Mirin, S W Nam, M D Shaw
For photon-counting applications at ultraviolet wavelengths, there are currently no detectors that combine high efficiency (> 50%), sub-nanosecond timing resolution, and sub-Hz dark count rates. Superconducting nanowire single-photon detectors (SNSPDs) have seen success over the past decade for photon-counting applications in the near-infrared, but little work has been done to optimize SNSPDs for wavelengths below 400 nm. Here, we describe the design, fabrication, and characterization of UV SNSPDs operating at wavelengths between 250 and 370 nm...
October 30, 2017: Optics Express
https://www.readbyqxmd.com/read/29081556/country-over-citation-ratios
#7
Victoria Bakare, Grant Lewison
There is a clear tendency for authors of scientific papers to over-cite the papers by their fellow countrymen (and countrywomen) relative to the percentage presence of their papers in world output in the same field. We investigated the Over-Citation Ratio (OCR) as a function of this percentage, and the effects of different scientific fields and publication years. For cancer research, we also compared clinical with basic research. We found that the OCR for a given percentage presence has been decreasing over the period 1980-2010, probably because of better communications...
2017: Scientometrics
https://www.readbyqxmd.com/read/29048062/ductile-mode-grinding-of-reaction-bonded-silicon-carbide-mirrors
#8
Zhichao Dong, Haobo Cheng
The demand for reaction-bonded silicon carbide (RB-SiC) mirrors has escalated recently with the rapid development of space optical remote sensors used in astronomy or Earth observation. However, RB-SiC is difficult to machine due to its high hardness. This study intends to perform ductile mode grinding to RB-SiC, which produces superior surface integrity and fewer subsurface damages, thus minimizing the workload of subsequent lapping and polishing. For this purpose, a modified theoretical model for grain depth of cut of grinding wheels is presented, which correlates various processing parameters and the material characteristics (i...
September 10, 2017: Applied Optics
https://www.readbyqxmd.com/read/29047838/convolution-and-fourier-transform-based-reconstructors-for-pyramid-wavefront-sensor
#9
Iuliia Shatokhina, Ronny Ramlau
In this paper, we present two novel algorithms for wavefront reconstruction from pyramid-type wavefront sensor data. An overview of the current state-of-the-art in the application of pyramid-type wavefront sensors shows that the novel algorithms can be applied in various scientific fields such as astronomy, ophthalmology, and microscopy. Assuming a computationally very challenging setting corresponding to the extreme adaptive optics (XAO) on the European Extremely Large Telescope, we present the results of the performed end-to-end simulations and compare the achieved AO correction quality (in terms of the long-exposure Strehl ratio) to other methods, such as matrix-vector multiplication and preprocessed cumulative reconstructor with domain decomposition...
August 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/29047583/using-confidence-intervals-to-evaluate-the-focus-alignment-of-spectrograph-detector-arrays
#10
Travis W Sawyer, Kyle S Hawkins, Michael Damento
High-resolution spectrographs extract detailed spectral information of a sample and are frequently used in astronomy, laser-induced breakdown spectroscopy, and Raman spectroscopy. These instruments employ dispersive elements such as prisms and diffraction gratings to spatially separate different wavelengths of light, which are then detected by a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) detector array. Precise alignment along the optical axis (focus position) of the detector array is critical to maximize the instrumental resolution; however, traditional approaches of scanning the detector through focus lack a quantitative measure of precision, limiting the repeatability and relying on one's experience...
June 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/29041252/large-format-platinum-silicide-microwave-kinetic-inductance-detectors-for-optical-to-near-ir-astronomy
#11
P Szypryt, S R Meeker, G Coiffard, N Fruitwala, B Bumble, G Ulbricht, A B Walter, M Daal, C Bockstiegel, G Collura, N Zobrist, I Lipartito, B A Mazin
We have fabricated and characterized 10,000 and 20,440 pixel Microwave Kinetic Inductance Detector (MKID) arrays for the Dark-speckle Near-IR Energy-resolved Superconducting Spectrophotometer (DARKNESS) and the MKID Exoplanet Camera (MEC). These instruments are designed to sit behind adaptive optics systems with the goal of directly imaging exoplanets in a 800-1400 nm band. Previous large optical and near-IR MKID arrays were fabricated using substoichiometric titanium nitride (TiN) on a silicon substrate. These arrays, however, suffered from severe non-uniformities in the TiN critical temperature, causing resonances to shift away from their designed values and lowering usable detector yield...
October 16, 2017: Optics Express
https://www.readbyqxmd.com/read/29041228/orbital-angular-momentum-mode-groups-multiplexing-transmission-over-2-6-km-conventional-multi-mode-fiber
#12
Long Zhu, Andong Wang, Shi Chen, Jun Liu, Qi Mo, Cheng Du, Jian Wang
Twisted light carrying orbital angular momentum (OAM) is a special kind of structured light that has a helical phase front, a phase singularity, and a doughnut intensity profile. Beyond widespread developments in manipulation, microscopy, metrology, astronomy, nonlinear and quantum optics, OAM-carrying twisted light has seen emerging application of optical communications in free space and specially designed fibers. Instead of specialty fibers, here we show the direct use of a conventional graded-index multi-mode fiber (MMF) for OAM communications...
October 16, 2017: Optics Express
https://www.readbyqxmd.com/read/29041073/improved-wavefront-correction-for-coherent-image-restoration
#13
Claudius Zelenka, Reinhard Koch
Coherent imaging has a wide range of applications in, for example, microscopy, astronomy, and radar imaging. Particularly interesting is the field of microscopy, where the optical quality of the lens is the main limiting factor. In this article, novel algorithms for the restoration of blurred images in a system with known optical aberrations are presented. Physically motivated by the scalar diffraction theory, the new algorithms are based on Haugazeau POCS and FISTA, and are faster and more robust than methods presented earlier...
August 7, 2017: Optics Express
https://www.readbyqxmd.com/read/29040418/translational-medicine-in-the-age-of-big-data
#14
Nicholas P Tatonetti
The ability to collect, store and analyze massive amounts of molecular and clinical data is fundamentally transforming the scientific method and its application in translational medicine. Collecting observations has always been a prerequisite for discovery, and great leaps in scientific understanding are accompanied by an expansion of this ability. Particle physics, astronomy and climate science, for example, have all greatly benefited from the development of new technologies enabling the collection of larger and more diverse data...
October 12, 2017: Briefings in Bioinformatics
https://www.readbyqxmd.com/read/29022595/astronomy-ring-detected-around-a-dwarf-planet
#15
Amanda A Sickafoose
No abstract text is available yet for this article.
October 11, 2017: Nature
https://www.readbyqxmd.com/read/28989177/-cii-emission-from-l1630-in-the-orion-b-molecular-cloud
#16
C H M Pabst, J R Goicoechea, D Teyssier, O Berné, B B Ochsendorf, M G Wolfire, R D Higgins, D Riquelme, C Risacher, J Pety, F Le Petit, E Roueff, E Bron, A G G M Tielens
CONTEXT: L1630 in the Orion B molecular cloud, which includes the iconic Horsehead Nebula, illuminated by the star system σ Ori, is an example of a photodissociation region (PDR). In PDRs, stellar radiation impinges on the surface of dense material, often a molecular cloud, thereby inducing a complex network of chemical reactions and physical processes. AIMS: Observations toward L1630 allow us to study the interplay between stellar radiation and a molecular cloud under relatively benign conditions, that is, intermediate densities and an intermediate UV radiation field...
October 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28886623/near-ir-photoluminescence-of-c60
#17
Dmitry V Strelnikov, Bastian Kern, Manfred M Kappes
We have observed that C60(+) ions isolated in cryogenic matrices show distinct near-IR photoluminescence upon excitation in the near-IR range. By contrast, UV photoexcitation does not lead to measurable luminescence. Near-IR C60(+) photoluminescence is a one-photon process. The emission is mainly concentrated in one band and corresponds to (2)A1u ← (2)E1g relaxation. We present experimental data for the Stokes shift, power, and temperature dependencies as well as the quantum efficiency of the photoluminescence...
September 25, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28858308/astronomy-cosmic-exhumation
#18
Steven N Shore
No abstract text is available yet for this article.
August 30, 2017: Nature
https://www.readbyqxmd.com/read/28826381/the-hermetic-frontispiece-contextualising-john-dee-s-hieroglyphic-monad
#19
Peter J Forshaw
This essay examines the elaborate title pages of some of alchemist, astrologer, and bibliophile John Dee's publications with a focus on the two best known works that feature his famous Hieroglyphic Monad, the Propaedeumata Aphoristica (1558) and Monas Hieroglyphica (1564). The aim is to cast light on its context, identify sources for some textual influences in the works, unpack the visual symbolism in the two "monadic" title pages in relation to the two complementary sciences of "superior" and "inferior" astronomy, speculate on some of the more enigmatic details, and conclude with a brief discussion of a possible astrological significance to the dates of composition of the Monas Hieroglyphica...
August 21, 2017: Ambix
https://www.readbyqxmd.com/read/28816252/astronomy-a-turbulent-stellar-atmosphere-in-full-view
#20
Gail H Schaefer
No abstract text is available yet for this article.
August 16, 2017: Nature
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