128 research outputs found
Development of a prototype plastic space erectable satellite
Prototype erectable communications satellite of spherical design using plastic memory effec
Development of a prototype plastic space erectable satellite Quarterly report, Dec. 1965 - Feb. 1966
Plastic space erectable satellit
Development of a prototype plastic space erectable satellite Quarterly report, Jun. - Aug. 1966
Copper plated high-density polyethylene film evaluation for space erectable satellite desig
Development of a prototype plastic space erectable satellite Quarterly report, Mar. - May 1966
Mechanical and tensile properties of polyethylene films for prototype plastic space erectable structure
Geant4 Silver Anniversary: 25 years enabling scientific production
This paper summarizes Geant4 contribution to scientific research over the
past 25 years through a scientometric analysis of the results with which it has
been associated. The scientometric data collected from scholarly literature and
databases are evaluated with methods pertaining to econometrics and ecology to
quantify relevant traits, diversity and disparity in their scientific and
geographic distributions, and to identify statistically significant trends. The
analysis reviews the contribution of Geant4 to the field - experimental
particle physics - that originally motivated its development and highlights its
role in other research domains including nuclear physics and engineering,
astrophysics and space science, biomedical physics, archaeology and the
cultural heritage.Comment: Presented at the 16th Topical Seminar on Innovative Particle and
Radiation Detectors (IPRD23), Siena, Ital
The clumpy structure of Eridani's debris disc revisited by ALMA
Eridani is the closest star to our Sun known to host a debris
disc. Prior observations in the (sub-)millimetre regime have potentially
detected clumpy structure in the disc and attributed this to interactions with
an (as yet) undetected planet. However, the prior observations were unable to
distinguish between structure in the disc and background confusion. Here we
present the first ALMA image of the entire disc, which has a resolution of
1.6"1.2". We clearly detect the star, the main belt and two point
sources. The resolution and sensitivity of this data allow us to clearly
distinguish background galaxies (that show up as point sources) from the disc
emission. We show that the two point sources are consistent with background
galaxies. After taking account of these, we find that resolved residuals are
still present in the main belt, including two clumps with a
significance -- one to the east of the star and the other to the northwest. We
perform -body simulations to demonstrate that a migrating planet can form
structures similar to those observed by trapping planetesimals in resonances.
We find that the observed features can be reproduced by a migrating planet
trapping planetesimals in the 2:1 mean motion resonance and the symmetry of the
most prominent clumps means that the planet should have a position angle of
either or . Observations over multiple epochs
are necessary to test whether the observed features rotate around the star.Comment: 16 pages, 10 figures, accepted for publication in MNRA
MAPlex: A massively parallel sequencing ancestry analysis multiplex for Asia-Pacific populations
© 2019 The Authors Current forensic ancestry-informative panels are limited in their ability to differentiate populations in the Asia-Pacific region. MAPlex (Multiplex for the Asia-Pacific), a massively parallel sequencing (MPS) assay, was developed to improve differentiation of East Asian, South Asian and Near Oceanian populations found in the extensive cross-continental Asian region that shows complex patterns of admixture at its margins. This study reports the development of MAPlex; the selection of SNPs in combination with microhaplotype markers; assay design considerations for reducing the lengths of microhaplotypes while preserving their ancestry-informativeness; adoption of new population-informative multiple-allele SNPs; compilation of South Asian-informative SNPs suitable for forensic AIMs panels; and the compilation of extensive reference and test population genotypes from online whole-genome-sequence data for MAPlex markers. STRUCTURE genetic clustering software was used to gauge the ability of MAPlex to differentiate a broad set of populations from South and East Asia, the West Pacific regions of Near Oceania, as well as the other globally distributed population groups. Preliminary assessment of MAPlex indicates enhanced South Asian differentiation with increased divergence between West Eurasian, South Asian and East Asian populations, compared to previous forensic SNP panels of comparable scale. In addition, MAPlex shows efficient differentiation of Middle Eastern individuals from Europeans. MAPlex is the first forensic AIM assay to combine binary and multiple-allele SNPs with microhaplotypes, adding the potential to detect and analyze mixed source forensic DNA
The NIKA2 large-field-of-view millimetre continuum camera for the 30 m IRAM telescope
Context. Millimetre-wave continuum astronomy is today an indispensable tool for both general astrophysics studies (e.g. star formation, nearby galaxies) and cosmology (e.g. cosmic microwave background and high-redshift galaxies). General purpose, large-field-of-view instruments are needed to map the sky at intermediate angular scales not accessible by the high-resolution interferometers (e.g. ALMA in Chile, NOEMA in the French Alps) and by the coarse angular resolution space-borne or ground-based surveys (e.g. Planck, ACT, SPT). These instruments have to be installed at the focal plane of the largest single-dish telescopes, which are placed at high altitude on selected dry observing sites. In this context, we have constructed and deployed a three-thousand-pixel dual-band (150âGHz andâ260 GHz, respectively 2âmm and 1.15âmm wavelengths) camera to image an instantaneous circular field-of-view of 6.5âarcmin in diameter, and configurable to map the linear polarisation at 260âGHz.
Aims. First, we are providing a detailed description of this instrument, named NIKA2 (New IRAM KID Arrays 2), in particular focussing on the cryogenics, optics, focal plane arrays based on Kinetic Inductance Detectors, and the readout electronics. The focal planes and part of the optics are cooled down to the nominal 150âmK operating temperature by means of an adhoc dilution refrigerator. Secondly, we are presenting the performance measured on the sky during the commissioning runs that took place between October 2015 and April 2017 at the 30-m IRAM telescope at Pico Veleta, near Granada (Spain).
Methods. We have targeted a number of astronomical sources. Starting from beam-maps on primary and secondary calibrators we have then gone to extended sources and faint objects. Both internal (electronic) and on-the-sky calibrations are applied. The general methods are described in the present paper.
Results. NIKA2 has been successfully deployed and commissioned, performing in-line with expectations. In particular, NIKA2 exhibits full width at half maximum angular resolutions of around 11 and 17.5 arcsec at respectively 260 and 150âGHz. The noise equivalent flux densities are, at these two respective frequencies, 33±2 and 8±1 mJy s1/2. A first successful science verification run was achieved in April 2017. The instrument is currently offered to the astronomy community and will remain available for at least the following ten years
Early science with the Large Millimetre Telescope: Deep LMT/AzTEC millimetre observations of Ï” Eridani and its surroundings
Ï” Eridani is a nearby, young Sun-like star that hosts a ring of cool debris analogous to the Solar system's Edgeworth-Kuiper belt. Early observations at (sub-)mm wavelengths gave tentative evidence of the presence of inhomogeneities in the ring, which have been ascribed to the effect of a putative low eccentricity planet, orbiting close to the ring. The existence of these structures has been recently challenged by high-resolution interferometric millimetre observations. Here, we present the deepest single-dish image of Ï” Eridani at millimetre wavelengths, obtained with the Large Millimetre Telescope Alfonso Serrano (LMT). The main goal of these LMT observations is to confirm (or refute) the presence of non-axisymmetric structure in the disc. The dusty ring is detected for the first time along its full projected elliptical shape. The radial extent of the ring is not spatially resolved and shows no evidence, to within the uncertainties, of dust density enhancements. Additional features of the 1.1 mm map are: (i) the presence of significant flux in the gap between the ring and the star, probably providing the first exo-solar evidence of Poynting-Robertson drag, (ii) an unambiguous detection of emission at the stellar positionwith a flux significantly above that expected from Ï” Eridani's photosphere, and (iii) the identification of numerous unresolved sources which could correspond to background dusty star-forming galaxies.This work would have not been possible without the long-term financial support from the Mexican Science and Technology Funding Agency, CONACyT (Consejo Nacional de Ciencia y TecnologĂa) during the construction and operational phase of the Large Millimetre Telescope Alfonso Serrano, as well as support from the US National Science Foundation via the University Radio Observatory program, the Instituto Nacional de AstrofĂsica, Optica y ElectrĂłnica (INAOE) and the University of Massachusetts, Amherst (UMass). MC, EB, FCSM, MO and RLV work was supported by CONACyT research grants SEP-2009-134985 and SEP-2011-169554. GMK is supported by the Royal Society as a Royal Society University Research Fellow. CE is partly supported by Spanish grant AYA2014-55840-P. JPM is supported by a UNSW Vice Chancellor's Postdoctoral Fellowship. SL acknowledges support from CONACyT through grant 238631
Effect of sitagliptin on cardiovascular outcomes in type 2 diabetes
BACKGROUND: Data are lacking on the long-term effect on cardiovascular events of adding sitagliptin, a dipeptidyl peptidase 4 inhibitor, to usual care in patients with type 2 diabetes and cardiovascular disease. METHODS: In this randomized, double-blind study, we assigned 14,671 patients to add either sitagliptin or placebo to their existing therapy. Open-label use of antihyperglycemic therapy was encouraged as required, aimed at reaching individually appropriate glycemic targets in all patients. To determine whether sitagliptin was noninferior to placebo, we used a relative risk of 1.3 as the marginal upper boundary. The primary cardiovascular outcome was a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for unstable angina. RESULTS: During a median follow-up of 3.0 years, there was a small difference in glycated hemoglobin levels (least-squares mean difference for sitagliptin vs. placebo, -0.29 percentage points; 95% confidence interval [CI], -0.32 to -0.27). Overall, the primary outcome occurred in 839 patients in the sitagliptin group (11.4%; 4.06 per 100 person-years) and 851 patients in the placebo group (11.6%; 4.17 per 100 person-years). Sitagliptin was noninferior to placebo for the primary composite cardiovascular outcome (hazard ratio, 0.98; 95% CI, 0.88 to 1.09; P<0.001). Rates of hospitalization for heart failure did not differ between the two groups (hazard ratio, 1.00; 95% CI, 0.83 to 1.20; P = 0.98). There were no significant between-group differences in rates of acute pancreatitis (P = 0.07) or pancreatic cancer (P = 0.32). CONCLUSIONS: Among patients with type 2 diabetes and established cardiovascular disease, adding sitagliptin to usual care did not appear to increase the risk of major adverse cardiovascular events, hospitalization for heart failure, or other adverse events
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