Open University

About: Open University is a education organization based out in Milton Keynes, United Kingdom. It is known for research contribution in the topics: Context (language use) & Population. The organization has 11702 authors who have published 35020 publications receiving 1110835 citations. The organization is also known as: Open University, The & Open University.

The manga integral field unit fiber feed system for the sloan 2.5 m telescope

Abstract: We describe the design, manufacture, and performance of bare-fiber integral field units (IFUs) for the SDSS-IV survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) on the the Sloan 2.5 m telescope at Apache Point Observatory. MaNGA is a luminosity-selected integral-field spectroscopic survey of 104 local galaxies covering 360–1030 nm at R ~ 2200. The IFUs have hexagonal dense packing of fibers with packing regularity of 3 μm (rms), and throughput of 96 ± 0.5% from 350 nm to 1 μm in the lab. Their sizes range from 19 to 127 fibers (3–7 hexagonal layers) using Polymicro FBP 120:132:150 μm core:clad:buffer fibers to reach a fill fraction of 56%. High throughput (and low focal-ratio degradation (FRD)) is achieved by maintaining the fiber cladding and buffer intact, ensuring excellent surface polish, and applying a multi-layer anti-reflection (AR) coating of the input and output surfaces. In operations on-sky, the IFUs show only an additional 2.3% FRD-related variability in throughput despite repeated mechanical stressing during plate plugging (however other losses are present). The IFUs achieve on-sky throughput 5% above the single-fiber feeds used in SDSS-III/BOSS, attributable to equivalent performance compared to single fibers and additional gains from the AR coating. The manufacturing process is geared toward mass-production of high-multiplex systems. The low-stress process involves a precision ferrule with a hexagonal inner shape designed to lead inserted fibers to settle in a dense hexagonal pattern. The ferrule ID is tapered at progressively shallower angles toward its tip and the final 2 mm are straight and only a few microns larger than necessary to hold the desired number of fibers. Our IFU manufacturing process scales easily to accommodate other fiber sizes and can produce IFUs with substantially larger fiber counts. To assure quality, automated testing in a simple and inexpensive system enables complete characterization of throughput and fiber metrology. Future applications include larger IFUs, higher fill factors with stripped buffer, de-cladding, and lenslet coupling.

The Binary Frequency Among Carbon-enhanced, s-Process-rich, Metal-poor Stars

Abstract: Original article can be found at: --http://www.journals.uchicago.edu/--Copyright The American Astronomical Society

Isotopic constraints on the structural relationships between the Lesser Himalayan Series and the High Himalayan Crystalline Series, Garhwal Himalaya

Abstract: Nd and Sr isotope systematics may provide important constraints on the location of major thrust systems that separate lithologically similar sedimentary sequences. The potential of the technique is illustrated by this isotopic study of the Main Central thrust system of the Himalaya. Nd isotope data from the Garhwal Himalaya indicate that metasedimentary rocks from the Vaikrita Group (Nd = –14 to –19) correlate closely with those from the High Himalayan Crystalline Series, which constitutes the hanging-wall lithologies of the Main Central thrust. In contrast, metasedimentary rocks from the Munsiari Group (Nd = –23 to –28) show marked similarities to the Lesser Himalayan Series in the footwall of the Main Central thrust. Sr isotopes support the correlations in that the Vaikrita Group shows partial reequilibration at 500 Ma, whereas the Munsiari Group has not undergone Sr isotope homogenization since 1800 Ma. Thus, the Vaikrita thrust that juxtaposes these two formations is recognized as the Main Central thrust in Garhwal Himalaya. The thrust coincides, approximately, with the location of the kyanite isograd, confirming that inverted metamorphism is characteristic of both hanging wall and footwall of the Main Central thrust. Along the Tons thrust (known locally as the Srinagar thrust) 50 km south of the Main Central thrust, low-grade quartzarenites with Nd-Sr isotope and trace element characteristics typical of Lesser Himalayan formations have been emplaced on phyllites and siltstones with geochemical characteristics of the High Himalayan Crystalline Series. The field relationships most probably result from out-of-sequence thrusting in which Lesser Himalayan Series rocks to the north were emplaced over low-grade equivalents of the High Himalayan Crystalline Series preserved in the external part of the orogen. This study establishes the value of isotope data for lithostratigraphic correlations within orogenic belts.