2,932 research outputs found
On-Orbit Results and Lessons Learned from the ASTERIA Space Telescope Mission
The Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) was deployed from the International Space Station (ISS) on 20 November 2017, beginning a technology demonstration and opportunistic science mission to advance the state of the art in nanosatellite performance for astrophysical observations. The goal of ASTERIA is to achieve arcsecond-level line-of-sight pointing error and highly stable focal plane temperature control. These capabilities enable precision photometryâi.e. the careful measurement of stellar brightness over timeâwhich in turn allows investigation of astrophysical phenomena such as transiting exoplanets. By the end of the 90-day prime mission, ASTERIA had achieved line-of-sight pointing stability of approximately 0.5 arcseconds root mean square (RMS) over 20-minute observations, pointing repeatability of 1 milliarcsecond RMS from one observation to the next, and focal plane temperature stability better than ±0.01 K over 20-minute observations. This paper presents an overview of the ASTERIA flight and ground system, summarizes the pre-delivery test campaign, and discusses the on-orbit performance obtained by the pointing and thermal control subsystems. We also describe the process for planning opportunistic science observations and present lessons learned from development and operations. Having successfully operated for over 200 days as of this writing, ASTERIA is currently in an extended mission to observe nearby bright stars for transiting exoplanets
Demonstrating high-precision photometry with a CubeSat: ASTERIA observations of 55 Cancri e
ASTERIA (Arcsecond Space Telescope Enabling Research In Astrophysics) is a 6U
CubeSat space telescope (10 cm x 20 cm x 30 cm, 10 kg). ASTERIA's primary
mission objective was demonstrating two key technologies for reducing
systematic noise in photometric observations: high-precision pointing control
and high-stabilty thermal control. ASTERIA demonstrated 0.5 arcsecond RMS
pointing stability and 10 milliKelvin thermal control of its camera
payload during its primary mission, a significant improvement in pointing and
thermal performance compared to other spacecraft in ASTERIA's size and mass
class. ASTERIA launched in August 2017 and deployed from the International
Space Station (ISS) November 2017. During the prime mission (November 2017 --
February 2018) and the first extended mission that followed (March 2018 - May
2018), ASTERIA conducted opportunistic science observations which included
collection of photometric data on 55 Cancri, a nearby exoplanetary system with
a super-Earth transiting planet. The 55 Cancri data were reduced using a custom
pipeline to correct CMOS detector column-dependent gain variations. A Markov
Chain Monte Carlo (MCMC) approach was used to simultaneously detrend the
photometry using a simple baseline model and fit a transit model. ASTERIA made
a marginal detection of the known transiting exoplanet 55 Cancri e
(~\Rearth), measuring a transit depth of ppm. This is the
first detection of an exoplanet transit by a CubeSat. The successful detection
of super-Earth 55 Cancri e demonstrates that small, inexpensive spacecraft can
deliver high-precision photometric measurements.Comment: 23 pages, 9 figures. Accepted in A
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Endometrial Biopsy: Indications, Techniques and Recommendations. An Evidence-Based Guideline for Clinical Practice
This practice guideline provides updated evidence for the gynecologist who performs endometrial biopsy (EB) in gynecologic clinical practice. An international committee of gynecology experts developed the recommendations according to AGREE Reporting Guideline. An adequate tissue sampling is mandatory when performing an EB. Blind methods should not be first choice in patients with suspected endometrial malignancy. Hysteroscopy is the targeted-biopsy method with highest diagnostic accuracy and cost-effectiveness. Blind suction techniques are not reliable for the diagnosis of endometrial polyps. In low resources settings, and in absence of the capacity to perform office hysteroscopy, blind techniques could be used for EB. Hysteroscopic punch biopsy allows to collect only limited amount of endometrial tissue. grasp biopsy technique should be considered first choice in reproductive aged women, bipolar electrode chip biopsy should be preferred with hypotrophic or atrophic endometrium. EB is required for the final diagnosis of chronic endometritis. There is no consensus regarding which endometrial thickness cut-off should be used for recommending EB in asymptomatic postmenopausal women. EB should be offered to young women with abnormal uterine bleeding and risk factors for endometrial carcinoma. Endometrial pathology should be excluded with EB in nonobese women with unopposed
hyperestrogenism. Hysteroscopy with EB is useful in patients with abnormal bleeding even without sonographic evidence of pathology. EB has high sensitivity for detecting intrauterine pathologies. In postmenopausal women with uterine bleeding, EB is recommended. Women with sonographic endometrial thickness > 4mm using tamoxifen should undergo hysteroscopic EB
Procjena mikrostrukture alatnog Äelika za hladni rad nakon pretaljivanja pulsirajuÄim laserom
The aim of this study is the investigation of micro-structural behaviour of a Mat. No. 1.2379 (EN-X160CrMoV121; AISI D2) cold work tool steel after remelting with a precise pulsed Nd:YAG laser. The investigated steel is one of the most hard to weld tool steels, due to large amount of alloying elements. The analysis was done on single spots remelted with specific laser pulse shape and parameters, assuring crack-less solidification. Re-solidifi ed areas were investigated with microscopy, hardness measurements, X-ray spectroscopy and diffraction method. Laser treatment causes rapid solidification leading into a formation of a fine dendritic microstructures containing high amount of retained austenite causing a significant decrease of hardness.Namjena ove studije je ispitivanje ponaĆĄanja mikro strukture alatnoga Äelika za rad na hladno Mat. No.1.2379 (ENX160CrMoV121; AISI D2) po pretaljivanju s preciznim pulsiranim Nd:YAG laserom. Zbog velike koliÄine legirnih elemenata istraĆŸivani materijal spada u grupu vrlo teĆĄko zavarljivih alatnih Äelika. Analiza je provedena na pojedinim pretaljenim toÄkama koriĆĄtenjem specifi Änog oblika i parametara laserskog impulsa koji osiguravaju skruÄivanje bez pukotina. Pretaljena podruÄja su ispitivana mikroskopom, mjerenjem mikro tvrdoÄe, rendgenskom spektroskopijom i defrakcijskom metodom. Tretman laserom uzrokvao je brzo skruÄivanje koja dovodi do formiranja fi ne dendritiÄke strukture s velikim udjelom zaostalog austenita ĆĄto uzrokuje bitno smanjivanje tvrdoÄe
HD 219134 Revisited: Planet d Transit Upper Limit and Planet f Transit Nondetection with ASTERIA and TESS
HD 219134 is a K3V dwarf star with six reported radial-velocity discovered planets. The two innermost planets b and c show transits, raising the possibility of this system to be the nearest (6.53 pc), brightest (V = 5.57) example of a star with a compact multiple transiting planet system. Ground-based searches for transits of planets beyond b and c are not feasible because of the infrequent transits, long transit duration (~5 hr), shallow transit depths (<1%), and large transit time uncertainty (~half a day). We use the space-based telescopes the Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) and the Transiting Exoplanet Survey Satellite (TESS) to search for transits of planets f (P = 22.717 days and M sin i = 7.3 ± 0.04M_â) and d (P = 46.859 days and M sin i = 16.7 ± 0.64M_â). ASTERIA was a technology demonstration CubeSat with an opportunity for science in an extended program. ASTERIA observations of HD 219134 were designed to cover the 3Ï transit windows for planets f and d via repeated visits over many months. While TESS has much higher sensitivity and more continuous time coverage than ASTERIA, only the HD 219134 f transit window fell within the TESS survey's observations. Our TESS photometric results definitively rule out planetary transits for HD 219134 f. We do not detect the Neptune-mass HD 219134 d transits and our ASTERIA data are sensitive to planets as small as 3.6 R_â. We provide TESS updated transit times and periods for HD 219134 b and c, which are designated TOI 1469.01 and 1469.02 respectively
Systems genetics identifies a role for Cacna2d1 regulation in elevated intraocular pressure and glaucoma susceptibility
Glaucoma is a multi-factorial blinding disease in which genetic factors play an important role. Elevated intraocular pressure is a highly heritable risk factor for primary open angle glaucoma and currently the only target for glaucoma therapy. Our study helps to better understand underlying genetic and molecular mechanisms that regulate intraocular pressure, and identifies a new candidate gene, Cacna2d1, that modulates intraocular pressure and a promising therapeutic, pregabalin, which binds to CACNA2D1 protein and lowers intraocular pressure significantly. Because our study utilizes a genetically diverse population of mice with kno
Risk factors associated with adverse fetal outcomes in pregnancies affected by Coronavirus disease 2019 (COVID-19): a secondary analysis of the WAPM study on COVID-19.
Objectives To evaluate the strength of association between maternal and pregnancy characteristics and the risk of adverse perinatal outcomes in pregnancies with laboratory confirmed COVID-19. Methods Secondary analysis of a multinational, cohort study on all consecutive pregnant women with laboratory-confirmed COVID-19 from February 1, 2020 to April 30, 2020 from 73 centers from 22 different countries. A confirmed case of COVID-19 was defined as a positive result on real-time reverse-transcriptase-polymerase-chain-reaction (RT-PCR) assay of nasal and pharyngeal swab specimens. The primary outcome was a composite adverse fetal outcome, defined as the presence of either abortion (pregnancy loss before 22 weeks of gestations), stillbirth (intrauterine fetal death after 22 weeks of gestation), neonatal death (death of a live-born infant within the first 28 days of life), and perinatal death (either stillbirth or neonatal death). Logistic regression analysis was performed to evaluate parameters independently associated with the primary outcome. Logistic regression was reported as odds ratio (OR) with 95% confidence interval (CI). Results Mean gestational age at diagnosis was 30.6+/-9.5 weeks, with 8.0% of women being diagnosed in the first, 22.2% in the second and 69.8% in the third trimester of pregnancy. There were six miscarriage (2.3%), six intrauterine device (IUD) (2.3) and 5 (2.0%) neonatal deaths, with an overall rate of perinatal death of 4.2% (11/265), thus resulting into 17 cases experiencing and 226 not experiencing composite adverse fetal outcome. Neither stillbirths nor neonatal deaths had congenital anomalies found at antenatal or postnatal evaluation. Furthermore, none of the cases experiencing IUD had signs of impending demise at arterial or venous Doppler. Neonatal deaths were all considered as prematurity-related adverse events. Of the 250 live-born neonates, one (0.4%) was found positive at RT-PCR pharyngeal swabs performed after delivery. The mother was tested positive during the third trimester of pregnancy. The newborn was asymptomatic and had negative RT-PCR test after 14 days of life. At logistic regression analysis, gestational age at diagnosis (OR: 0.85, 95% CI 0.8-0.9 per week increase; pPeer reviewe
The Third Fermi Large Area Telescope Catalog of Gamma-ray Pulsars
We present 294 pulsars found in GeV data from the Large Area Telescope (LAT)
on the Fermi Gamma-ray Space Telescope. Another 33 millisecond pulsars (MSPs)
discovered in deep radio searches of LAT sources will likely reveal pulsations
once phase-connected rotation ephemerides are achieved. A further dozen optical
and/or X-ray binary systems co-located with LAT sources also likely harbor
gamma-ray MSPs. This catalog thus reports roughly 340 gamma-ray pulsars and
candidates, 10% of all known pulsars, compared to known before Fermi.
Half of the gamma-ray pulsars are young. Of these, the half that are undetected
in radio have a broader Galactic latitude distribution than the young
radio-loud pulsars. The others are MSPs, with 6 undetected in radio. Overall,
>235 are bright enough above 50 MeV to fit the pulse profile, the energy
spectrum, or both. For the common two-peaked profiles, the gamma-ray peak
closest to the magnetic pole crossing generally has a softer spectrum. The
spectral energy distributions tend to narrow as the spindown power
decreases to its observed minimum near erg s, approaching the
shape for synchrotron radiation from monoenergetic electrons. We calculate
gamma-ray luminosities when distances are available. Our all-sky gamma-ray
sensitivity map is useful for population syntheses. The electronic catalog
version provides gamma-ray pulsar ephemerides, properties and fit results to
guide and be compared with modeling results.Comment: 142 pages. Accepted by the Astrophysical Journal Supplemen
European Atlas of Natural Radiation
Natural ionizing radiation is considered as the largest contributor to the collective effective dose received by the world population. The human population is continuously exposed to ionizing radiation from several natural sources that can be classified into two broad categories: high-energy cosmic rays incident on the Earthâs atmosphere and releasing secondary radiation (cosmic contribution); and radioactive nuclides generated during the formation of the Earth and still present in the Earthâs crust (terrestrial contribution). Terrestrial radioactivity is mostly produced by the uranium and thorium radioactive families together with potassium. In most circumstances, radon, a noble gas produced in the radioactive decay of uranium, is the most important contributor to the total dose.
This Atlas aims to present the current state of knowledge of natural radioactivity, by giving general background information, and describing its various sources. This reference material is complemented by a collection of maps of Europe displaying the levels of natural radioactivity caused by different sources.
It is a compilation of contributions and reviews received from more than 80 experts in their field: they come from universities, research centres, national and European authorities and international organizations.
This Atlas provides reference material and makes harmonized datasets available to the scientific community and national competent authorities. In parallel, this Atlas may serve as a tool for the public to:
âą familiarize itself with natural radioactivity;
âą be informed about the levels of natural radioactivity caused by different sources;
âą have a more balanced view of the annual dose received by the world population, to which natural radioactivity is the largest contributor;
âą and make direct comparisons between doses from natural sources of ionizing radiation and those from man-made (artificial) ones, hence to better understand the latter.JRC.G.10-Knowledge for Nuclear Security and Safet
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