SCUBA-2 is a 10 000-bolometer submillimetre camera on the James Clerk Maxwell Telescope. The instrument commissioning was completed in 2011 September, and full science operations began in 2011 ...October. To harness the full potential of this powerful new astronomical tool, the instrument calibration must be accurate and well understood. To this end, the algorithms for calculating the line-of-sight opacity have been improved, and the derived atmospheric extinction relationships at both wavebands of the SCUBA-2 instrument are presented. The results from over 500 primary and secondary calibrator observations have allowed accurate determination of the flux conversion factors (FCF) for the 850 and 450 μm arrays. Descriptions of the instrument beam shape and photometry methods are presented. The calibration factors are well determined, with relative calibration accuracy better than 5 per cent at 850 μm and 10 per cent at 450 μm, reflecting the success of the derived opacity relations as well as the stability of the performance of the instrument over several months. The sample size of the calibration observations and accurate FCFs have allowed the determination of the 850 and 450 μm fluxes of several well-known submillimetre sources, and these results are compared with previous measurements from SCUBA.
Three biosorbents, crab carapace, the macroalgae Fucus vesiculosus and peat were compared with two commercial materials, an activated-carbon and an ion-exchange resin for the removal of copper from ...aqueous media. Kinetic models of Lagergren first-order, pseudo-second order and intraparticular diffusion were used to model the data. The process for all materials is best represented by the pseudo-second order rate model. Langmuir and Freundlich isotherms were used to describe the sorption equilibrium data. Maximum uptake values were 79.4, 114.9 and 71.4mgg−1 for crab carapace, F. vesiculosus and ion-exchange resin, respectively. Langmuir and Freundlich isotherm models could not be fitted to the experimental data for peat and activated-carbon. Ion-exchange was calculated to contribute ∼75%, 77% and 44% to the total biosorption by crab carapace, F. vesiculosus and peat, respectively. The removal efficiencies of crab carapace and F. vesiculosus were >95% and comparable with those achieved using ion-exchange resin. Results from this study suggest that both crab carapace and F. vesiculosus are efficient and effective biosorbent materials for the removal of copper from aqueous solutions and given that they are also low-cost, may be considered viable alternatives to activated-carbon and ion-exchange resin.
We present new observations with the Infrared Spectrograph on board the Spitzer Space Telescope of the solid-CO sub(2) absorption feature near 15 km in the spectra of eight field stars behind the ...Taurus complex of dark clouds. Solid CO sub(2) is detected in six lines of sight. New results are combined with previous data to investigate the correlation of CO sub(2) column density with those of other major ice constituents (H sub(2)O and CO) and with extinction. CO sub(2) is shown to display a "threshold extinction" effect, i.e., a minimum extinction (A sub(0) = 4.3 c 1.0 mag) required for detection, behavior similar to that previously reported for H sub(2)O and CO. We find a particularly tight correlation through the origin between N(CO sub(2)) and N(H sub(2)O), confirming that these species form in tandem and coexist in the same (polar) ice layer on the grains. The observed composition of the mantles is broadly consistent with the predictions of photochemical models with diffusive surface chemistry proposed by Ruffle & Herbst. Comparison of our results for Taurus with published data for Serpens indicates significant differences in ice composition consistent with enhanced CO sub(2) production in the latter cloud. Our results also place constraints on the distribution of elemental oxygen between ices and other potential reservoirs. Assuming a constant N(H) to extinction ratio, we show that 665% of the solar O abundance is accounted for by summing the contributions of ices (626%), refractory dust (630%) and gas-phase CO (69%). If the Sun is an appropriate standard for the interstellar medium, the "missing" oxygen may reside in atomic O I gas and/or (undetected) O sub(2) within the ices.
We conducted a deep search for deuterated water (HDO) in the Oort Cloud comet C/2014 Q2 (Lovejoy), through infrared (IR) spectroscopy with NIRSPEC at the Keck Observatory. In this Letter, we present ...our detections of HDO and water (H2O) in comet Lovejoy on 2015 February 4 (post-perihelion) after 1 hr integration on source. The IR observations allowed simultaneous detection of H2O and HDO, yielding production rates of 5.9 0.13 × 1029 and 3.6 1.0 × 1026 molecules s−1, respectively. The simultaneous detection permitted accurate determination of the isotopic ratio (D/H) in water of 3.02 0.87 × 10−4, i.e., larger than the value for water in terrestrial oceans (or Vienna Standard Mean Ocean Water, VSMOW) by a factor of 1.94 0.56. This D/H ratio in water exceeds the value obtained independently at millimeter wavelengths (0.89 0.25 VSMOW; pre-perihelion). We discuss these parameters in the context of origins and emphasize the need for contemporaneous measurements of HDO and H2O.
► We sampled in Comet C/2007 W1 (Boattini) 11 molecular abundances, and retrieved three cosmogonic indicators. ► The abundance ratios of almost all trace volatiles are among the highest ever observed ...in a comet. ► The comet revealed a complex outgassing, with the polar species presenting very asymmetric spatial profiles. ► We interpret the emission profiles in terms of release from two distinct moieties of ice.
We measured the chemical composition of Comet C/2007 W1 (Boattini) using the long-slit echelle grating spectrograph at Keck-2 (NIRSPEC) on 2008 July 9 and 10. We sampled 11 volatile species (H
2O, OH
∗, C
2H
6, CH
3OH, H
2CO, CH
4, HCN, C
2H
2, NH
3, NH
2, and CO), and retrieved three important cosmogonic indicators: the ortho-para ratios of H
2O and CH
4, and an upper-limit for the D/H ratio in water. The abundance ratios of almost all trace volatiles (relative to water) are among the highest ever observed in a comet. The comet also revealed a complex outgassing pattern, with some volatiles (the polar species H
2O and CH
3OH) presenting very asymmetric spatial profiles (extended in the anti-sunward hemisphere), while others (e.g., C
2H
6 and HCN) showed particularly symmetric profiles. We present emission profiles measured along the Sun–comet line for all observed volatiles, and discuss different production scenarios needed to explain them. We interpret the emission profiles in terms of release from two distinct moieties of ice, the first being clumps of mixed ice and dust released from the nucleus into the sunward hemisphere. The second moiety considered is very small grains of nearly pure polar ice (water and methanol, without dark material or apolar volatiles). Such grains would sublimate only very slowly, and could be swept into the anti-sunward hemisphere by radiation pressure and solar-actuated non-gravitational jet forces, thus providing an extended source in the anti-sunward hemisphere.
(ProQuest: Formulae and/or non-USASCII text omitted)We report production rates for H sub(2) O and eight trace molecules (CO, C sub(2) H sub(6), CH sub(4), CH sub(3) OH, NH sub(3), H sub(2) CO, HCN, C ...sub(2) H sub(2)) in the dynamically new, Sun-grazing Comet C/2012 S1 (ISON), using high-resolution spectroscopy at Keck II and the NASA IRTF on 10 pre-perihelion dates encompassing heliocentric distances R sub(h)= 1.21-0.34 AU. Measured water production rates spanned two orders of magnitude, consistent with a long-term heliocentric power law Q... .Abundance ratios for CO, C sub(2) H sub(6), and CH sub(4) with respect to H sub(2) O remained constant with R sub(h) and below their corresponding mean values measured among a dominant sample of Oort Cloud comets. CH sub(3) OH was also depleted for R sub(h)> 0.5 AU, but was closer to its mean value for R sub(h)< or = 0.5 AU. The remaining four molecules exhibited higher abundance ratios within 0.5 AU: for R sub(h)> 0.8 AU, NH sub(3) and C sub(2) H sub(2) were consistent with their mean values while H sub(2) CO and HCN were depleted. For R sub(h)< 0.5 AU, all four were enriched, with NH sub(3), H sub(2) CO, and HCN increasing most. Spatial profiles of gas emission in ISON consistently peaked sunward of the dust continuum, which was asymmetric antisunward and remained singly peaked for all observations. NH sub(3) within 0.5 AU showed a broad spatial distribution, possibly indicating its release in the coma provided that optical depth effects were unimportant. The column abundance ratio NH sub(2)/H sub(2) O at 0.83 AU was close to the "typical" NH/OH from optical wavelengths, but was higher within 0.5 AU. Establishing its production rate and testing its parentage (e.g., NH sub(3)) require modeling of coma outflow.
This paper presents the hardened properties of a high-performance fibre-reinforced fine-aggregate concrete extruded through a 9mm diameter nozzle to build layer-by-layer structural components in a ...printing process. The printing process is a digitally controlled additive method capable of manufacturing architectural and structural components without formwork, unlike conventional concrete construction methods. The effects of the layering process on density, compressive strength, flexural strength, tensile bond strength and drying shrinkage are presented together with the implication for mix proportions. A control concrete (mould-cast specimens) had a density of approximately 2250kg/m3, high strength (107MPa in compression, 11MPa in flexure) and 3MPa in direct tension, together with a relatively low drying shrinkage of 175μm (cured in water) and 855μm (cured in a chamber at 20°C and 60% relative humidity) at 184days. In contrast well printed concrete had a density of 2350kg/m3, compressive strength of 75–102MPa, flexural strength of 6–17MPa depending on testing direction, and tensile bond strength between layers varying from 2.3 to 0.7MPa, reducing as the printing time gap between layers increased. The well printed concrete had significantly fewer voids greater than 0.2mm diameter (1.0%) when compared with the mould-cast control (3.8%), whilst samples of poorly printed material had more voids (4.8%) mainly formed in the interstices between filaments. The additive extrusion process was thus shown to retain the intrinsic high performance of the material.
This paper presents the experimental results concerning the mix design and fresh properties of a high-performance fibre-reinforced fine-aggregate concrete for printing concrete. This concrete has ...been designed to be extruded through a nozzle to build layer-by-layer structural components. The printing process is a novel digitally controlled additive manufacturing method which can build architectural and structural components without formwork, unlike conventional concrete construction methods. The most critical fresh properties are shown to be extrudability and buildability, which have mutual relationships with workability and open time. These properties are significantly influenced by the mix proportions and the presence of superplasticiser, retarder, accelerator and polypropylene fibres. An optimum mix is identified and validated by the full-scale manufacture of a bench component.
We report production rates, rotational temperatures, and related parameters for gases in C/2013 R1 (Lovejoy) using the Near InfraRed SPECtrometer at the Keck Observatory, on six UT dates spanning ...heliocentric distances (R sub(h)) that decreased from 1.35 AU to 1.16 AU (pre-perihelion). We quantified nine gaseous species (H sub(2)O, OH*, CO, CH sub(4), HCN, C sub(2)H sub(6), CH sub(3)OH, NH sub(3), and NH sub(2)) and obtained upper limits for two others (C sub(2)H sub(2) and H sub(2)CO). Compared with organics-normal comets, our results reveal highly enriched CO, (at most) slightly enriched CH sub(3)OH, C sub(2)H sub(6), and HCN, and CH sub(4) consistent with "normal", yet depleted, NH sub(3), C sub(2)H sub(2), and H sub(2)CO. Rotational temperatures increased from ~50 K to ~70 K with decreasing R sub(h), following a power law in R sub(h) of -2.0 + or - 0.2, while the water production rate increased from 1.0 to 3.9 x 10 super(28) molecules s super(-1), following a power law in R sub(h) of -4.7 + or - 0.9. The ortho-para ratio for H sub(2)O was 3.01 + or - 0.49, corresponding to spin temperatures (T sub(spin)) > or =, slanted 29 K (at the 1sigma level). The observed spatial profiles for these emissions showed complex structures, possibly tied to nucleus rotation, although the cadence of our observations limits any definitive conclusions. The retrieved CO abundance in Lovejoy is more than twice the median value for comets in our IR survey, suggesting this comet is enriched in CO. We discuss the enriched value for CO in comet C/2013 R1 in terms of the variability of CO among Oort Cloud comets.
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