ABSTRACT
Crystals of pyroxene are common in meteorites but few compositions have been recognized in astronomical environments due to the limited chemistries included in laboratory studies. We present ...quantitative room-temperature spectra of 17 Mg-, Fe-, and Ca-bearing ortho- and clinopyroxenes, and a Ca-pyroxenoid in order to discern trends indicative of crystal structure and a wide range of composition. Data are produced using a diamond anvil cell: our band strengths are up to six times higher than those measured in KBr or polyethylene dispersions, which include variations in path length (from grain size) and surface reflections that are not addressed in data processing. Pyroxenes have varied spectra: only two bands, at 10.22 and 15.34 μm in enstatite (En99), are common to all. Peak wavelengths generally increase as Mg is replaced by Ca or Fe. However, two bands in MgFe-pyroxenes shift to shorter wavelengths as the Fe component increases from 0 to 60 per cent. A high-intensity band shifts from 11.6 to 11.2 μm and remains at 11.2 μm as Fe increases to 100 per cent; it resembles an astronomical feature normally identified with olivine or forsterite. The distinctive pyroxene bands between 13 and 16 μm show promise for their identification in Mid-Infrared-Instrumentspectra obtained with the James Webb Space Telescope. The many pyroxene bands between 40 and 80 μm could be diagnositic of silicate mineralogy if data were obtained with the proposed Space Infrared Telescope for Cosmology and Astrophysics. Our data indicate that comparison between room-temperature laboratory bands for enstatite and cold ∼10 − K astronomical dust features at wavelengths $\gtrsim 28~\mu$m can result in the identification of (Mg,Fe)- pyroxenes that contain 7–15 per cent less Fe– than their true values because some temperature shifts mimic some compositional shifts. Therefore some astronomical silicates may contain more Fe, and less Mg, than previously thought.
ABSTRACT
We present new room-temperature 1100–1800-cm−1 spectra of melilite silicates and 600–2000-cm−1 spectra of three randomly orientated fine-grained carbonates to determine the possible ...carrier(s) of a 6.9-μm absorption feature observed in a variety of dense astronomical environments, including young stellar objects and molecular clouds. We focus on the low-mass post-asymptotic giant branch star Sakurai’s Object, which has been forming substantial quantities of carbonaceous dust since an eruptive event in the 1990s. Large melilite grains cannot be responsible for the 6.9-μm absorption feature because the similarly shaped feature in the laboratory spectrum was produced by very low (0.1 per cent by mass) carbonate contamination, which was not detected at other wavelengths. Due to the high band strength of the 6.9-μm feature in carbonates, we conclude that carbonates carry the astronomical 6.9-μm feature. Replacement of melilite with carbonates in models of Sakurai’s Object improves fits to the 6–7-μm Spitzer spectra without significantly altering other conclusions of Bowey’s previous models except that there is no link between the feature and the abundance of melilite in meteorites. With magnesite (MgCO3), the abundance of 25-μm-sized SiC grains is increased by 10–50 per cent and better constrained. The mass of carbonate dust is similar to the mass of polycyclic aromatic hydrocarbon dust. Existing experiments suggest that carbonates are stable below 700 K; however, it is difficult to ascertain the applicability of these experiments to astronomical environments, and more studies are required.
STUDY DESIGN.Analysis of explanted MAGnetic Expansion Control (MAGEC) growing rods.
OBJECTIVE.To analyze explanted MAGEC rods used in management of early onset scoliosis and identify the mode of ...failure in such cases.
SUMMARY OF BACKGROUND DATA.Magnetically controlled growing rods are increasingly used as the option of choice for early onset scoliosis. However, being more complex than conventional growing rods they are perhaps more likely to succumb to multifarious failure modes. In addition, metallosis has been reported around failed MAGEC rods.
METHODS.Explanted MAGEC rods from seven UK spinal centers were obtained for independent analysis. Thirty-four MAGEC rods, from 18 children, explanted for reasons including failure of rod lengthening and maximum rod distraction reached, were cut open to allow internal components to be evaluated and assessed.
RESULTS.Externally, all MAGEC rods showed localized marks, which were termed “growth marks” as they indicated growth of the rod in vivo, on the extending bar component. After cutting open, titanium wear debris was found inside all 34 (100%) MAGEC rods. Ninety-one percent (31/34) of MAGEC rods showed measurable wear of the extending bar, towards the magnet end. Substantial damage to the radial bearing was seen inside 74% (25/34) of MAGEC rods while O-ring seal failure was seen in 53% (18/34) of cases. In 44% (15/34) of MAGEC rods the drive pin was fractured but this was felt to be an effect of rod failure, not a cause.
CONCLUSION.The combination of high volumes of titanium wear debris alongside O-ring seal damage likely accounts for the metallosis reported clinically around some MAGEC rods. Based on this explant data, a failure mechanism in MAGEC rods due to the natural off axis loading in the spine was proposed. This is the largest data set reporting a complete analysis of explanted MAGEC rods to date.Level of Evidence4
Absorption coefficients associated with atomic motions of species expected in astronomical environments are determined from infrared measurements of various hydrosilicates, hydrated magnesium oxide, ...and the Al-bearing chain silicate, sapphirine. Band types measured include O—H stretching modes near 3 μm, Si—O stretching motions near 10 μm, Si—O—Si bends near 14 μm, O—Si—O bends near 20 μm, and translations of cations such as Mg and Ca near 50-200 μm. We obtain data from films of varying thickness and use a ratioing method. First, bandstrengths of O—H fundamentals were determined from spectra obtained from films of controlled thicknesses, generally 6 μm. The O—H absorbance strength was then used to accurately determine thickness for a thinner film of each mineral (found to be <1 μm), thus providing bandstrengths of all other absorptions. Thin films were prepared such that the fundamental lattice modes showed intrinsic behaviour (i.e. band shapes were unchanged upon further thinning) and O—H modes are well resolved above the spectral noise. Bandstrengths were found to depend weakly on structure and should be applicable to other silicate minerals, allowing estimation of elemental concentrations independent of knowing the speciation of dust in astronomical environments. Comparison with observational data of NGC 6302 suggests that lizardite and saponite could be present in addition to refractory minerals.
Infrared spectral properties of silicate grains in interplanetary dust particles (IDPs) were compared with those of astronomical silicates. The ∼10-micrometer silicon-oxygen stretch bands of IDPs ...containing enstatite (MgSiO$_3$), forsterite (Mg$_2$SiO$_4$), and glass with embedded metal and sulfides (GEMS) exhibit fine structure and bandwidths similar to those of solar system comets and some pre-main sequence Herbig Ae/Be stars. Some GEMS exhibit a broad, featureless silicon-oxygen stretch band similar to those observed in interstellar molecular clouds and young stellar objects. These GEMS provide a spectral match to astronomical "amorphous" silicates, one of the fundamental building blocks from which the solar system is presumed to have formed.
This paper describes a James Clerk Maxwell Telescope (JCMT) legacy survey that has been awarded roughly 500 hr of observing time to be carried out from 2007 to 2009. In this survey, we will map with ...SCUBA‐2 (Submillimetre Common‐User Bolometer Array 2) almost all of the well‐known low‐mass and intermediate‐mass star‐forming regions within 0.5 kpc that are accessible from the JCMT. Most of these locations are associated with the Gould Belt. From these observations, we will produce a flux‐limited snapshot of star formation near the Sun, providing a legacy of images, as well as point‐source and extended‐source catalogs, over almost 700 deg2of sky. The resulting images will yield the first catalog of prestellar and protostellar sources selected by submillimeter continuum emission, and should increase the number of known sources by more than an order of magnitude. We will also obtain with the array receiver HARP (Heterodyne Array Receiver Program) CO maps, in three CO isotopologues, of a large typical sample of prestellar and protostellar sources. We will then map the brightest hundred sources with the SCUBA‐2 polarimeter (POL‐2), producing the first statistically significant set of polarization maps in the submillimeter. The images and source catalogs will be a powerful reference set for astronomers, providing a detailed legacy archive for future telescopes, includingALMA,Herschel, andJWST.
Two groups of 5-year-old children whose fathers' occupations differed markedly in education and skill levels were seen in preschool, where they were given tests of performance IQ, receptive ...vocabulary and grammar, verbal working memory, phonological sensitivity, letter knowledge, and novice reading ability. At the end of first grade, academic achievement was assessed. Marked group differences were observed on most measures. Most differences remained after performance IQ effects were controlled. When general verbal ability effects were controlled, differences in phonological sensitivity and word-level reading and arithmetic achievement remained. When phonological sensitivity effects were also controlled, differences remained only in arithmetic performance. The same general pattern of results was observed in converging hierarchical multiple regression analyses. Overall, the results are consistent with the view that socioeconomic status differences in word-level reading achievement are mediated partly through preexisting differences in phonological sensitivity.
Purpose
Determine the incidence of metallosis around MAGEC rods.
Methods
A multicentre explant database was searched to identify cases with complete intraoperative findings at rod removal. Surgeons ...removing rods detailed the presence or absence of tissue metallosis associated with rods. More recently surgeons measured the ‘length’ of tissue metallosis. Prior to rod disassembly, the majority underwent testing with an external remote controller (ERC). The impact of clinical and explant variables on metallosis was assessed.
Results
Sixty-six cases were identified. Mean age at insertion was 8.1 ± 2.3 years with mean duration of implantation 37.6 ± 15.1 months.
Tissue metallosis was noted at revision surgery in 52/66 cases (79%). Metallosis was noted more commonly when rods were removed during fusion surgery than rod removal/exchange (97% vs. 58% (
p
= < 0.01)). The mass at insertion was greater in cases with metallosis (25.9 ± 7.8 kg vs. 21.1 ± 6.2 kg,
p
= 0.04).
Length of tissue metallosis was reported for 45 rods, median 9 cm (range 1–25). Metallosis was noted in 43/59 (73%) rods that produced no force and 22/30 (73%) rods that produced some force on ERC activation (
p
= 0.96). Wear debris was found within the actuator in all rods, and all but 3 rods had damaged O-rings.
Conclusion
MAGEC rods are associated with tissue metallosis in the majority of cases. It is seen with functional rods as well as failed rods and appears related to wear debris within the actuator and high rates of O-ring failure. Until the implications of metal debris in children are known, we urge caution with the use of this implant.
STUDY DESIGN.Laboratory analysis of explanted MAGnetic Expansion Control (MAGEC) growing rods.
OBJECTIVE.The aim of this study was to measure the force produced by explanted MAGEC rods compared with ...new rods and assess the influence of clinical variables.
SUMMARY OF BACKGROUND DATA.MAGEC rods are increasingly used in early-onset scoliosis. Some data are available describing the structure of explanted MAGEC rods, but to date, no study has assessed their function.
METHODS.Explanted MAGEC rods were received from seven UK and one Danish center. The force produced by explanted rods on activation with the external remote controller was measured using a dedicated jig. Forces were compared with two unused rods as well as the manufacturerʼs defined standard (42 Ibf). Clinical variables were collected from contributing centers where possible and correlated with the force measurements.
RESULTS.Forty-five MAGEC rods from 25 cases were received for analysis. The mean age at insertion was 8.6 years and rods were in vivo for a mean of 2.7 years in predominantly dual rod constructs. Two unused MAGEC rods produced a mean force of 45.3 (0.25) and 50.2 (1.4) Ibf, above the manufacturerʼs stated standard. Of the 45 explanted rods, 10 (22%) produced force greater or equal to manufacturerʼs standard, mean 46.7 (2.7) Ibf. Six rods (13%) produced some force but less than the manufacturerʼs standard, mean 34.8 (3.6) Ibf. Twenty-nine rods (64%) produced no force. The duration the rods were in vivo was significantly negatively correlated with the force produced on testing (r = −0.63, P < 0.005). Of the 12 rods implanted longer than 38 months, none produced any force.
CONCLUSION.This is the first study of the force, and hence likely function, of explanted MAGEC rods. The majority of explanted rods produced no force, while others produced reduced force. These findings raise questions regarding the longevity of the implant and further clinical outcome studies are recommended.Level of Evidence4
Dust emission from the Type II supernova SN 2002hh in NGC 6946 has been detected at mid-infrared wavelengths by the Spitzer Space Telescope from 590 to 758 days after outburst and confirmed by higher ...angular resolution Gemini North mid-IR observations. The day 600 5.8-24 km emission can be fit by a 290 K blackbody having a luminosity of 1.6 x 10 super(7) L sub( ). The minimum emitting radius of 1.1 x 10 super(17) cm is too large for the emitting dust to have been formed in the supernova ejecta. Using radiative transfer models and realistic dust grain parameters, fits to the observed flux distribution could be obtained with an optically thick dust shell having a mass of 0.10-0.15 M sub( ), corresponding to a total dust+gas mass in excess of 10 M sub( ), suggesting a massive M supergiant or luminous blue variable precursor to this self-obscured object.
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