A single-crystal structure determination of Nd8Sr2Si6O26 apatite, a prototype intermediate-temperature electrolyte for solid oxide fuel cells grown by the floating-zone method, was completed using ...the combination of Laue neutron diffraction and Raman spectroscopy. While neutron diffraction was in good agreement with P63/m symmetry, the possibility of P63 could not be convincingly excluded. This ambiguity was removed by the collection of orientation-dependent Raman spectra that could only be consistent with P63/m. The composition of Nd8Sr2Si6O26 was independently verified by powder X-ray diffraction in combination with electron probe microanalysis, with the latter confirming a homogeneous distribution of Sr and the absence of chemical zonation commonly observed in apatites. This comprehensive crystallochemical description of Nd8Sr2Si6O26 provides a baseline to quantify the efficacy of cation vacancies, oxygen superstoichiometry, and symmetry modification for promoting oxygen-ion mobility.
Strasser DC, Falconer JA, Herrin JS, Bowen SE, Stevens AB, Uomoto J. Team functioning and patient outcomes in stroke rehabilitation.
To evaluate the relationship between rehabilitation team ...functioning and stroke patient outcomes.
Prospective observational study.
Veterans Administration (VA) inpatient and subacute rehabilitation units.
Forty-six VA rehabilitation teams, including 530 rehabilitation team members from 6 disciplines (medicine, nursing, social work, physical therapy, occupational therapy, speech language pathology) and 1688 stroke patients treated by the teams.
Not applicable.
Ten scales assessing team member perceptions of team functioning (communication, perceived effectiveness, physician involvement, physician support, teamness, utility of quality information, innovation, interprofessional relationships, order and organization, task orientation) and 3 primary patient outcome variables—functional improvement, discharge home, and length of rehabilitation stay (LOS).
Three of the 10 measures of team functioning were significantly associated with patient functional improvement (P<.05): task orientation, order and organization, and utility of quality information. One measure of team functioning—effectiveness—was significantly associated with LOS (P<.05). None of the team variables predicted discharge destination. Aspects of team functioning that were important to outcomes differed depending on the outcome of interests. Efforts directed toward improving team activities and relationships, including collaborative planning and problem solving and the use of feedback information, may enhance rehabilitation treatment effectiveness.
Characteristics of team functioning predict selected rehabilitation outcomes.
Abstract
The EXO-200 experiment searched for neutrinoless double-beta decay of
136
Xe with a single-phase liquid xenon detector. It used an active mass of 110 kg of 80.6%-enriched liquid xenon in an ...ultra-low background time projection chamber with ionization and scintillation detection and readout. This paper describes the design and performance of the various support systems necessary for detector operation, including cryogenics, xenon handling, and controls. Novel features of the system were driven by the need to protect the thin-walled detector chamber containing the liquid xenon, to achieve high chemical purity of the Xe, and to maintain thermal uniformity across the detector.
Stomatopods are shallow-water crustaceans that employ powerful dactyl appendages to hunt their prey. Deployed at high velocities, these hammer-like clubs or spear-like devices are able to inflict ...substantial impact forces. Here we demonstrate that dactyl impact surfaces consist of a finely-tuned mineral gradient, with fluorapatite substituting amorphous apatite towards the outer surface. Raman spectroscopy measurements show that calcium sulphate, previously not reported in mechanically active biotools, is co-localized with fluorapatite. Ab initio computations suggest that fluorapatite/calcium sulphate interfaces provide binding stability and promote the disordered-to-ordered transition of fluorapatite. Nanomechanical measurements show that fluorapatite crystalline orientation correlates with an anisotropic stiffness response and indicate significant differences in the fracture tolerance between the two types of appendages. Our findings shed new light on the crystallochemical and microstructural strategies allowing these intriguing biotools to optimize impact forces, providing physicochemical information that could be translated towards the synthesis of impact-resistant functional materials and coatings.
Ureilite meteorites contain iron silicide minerals including suessite (Fe,Ni)3Si, hapkeite (Fe2Si) and xifengite (Fe5Si3). Despite occurring mostly in brecciated varieties presumed to be derived from ...the regolith of the ureilite parent asteroid, suessite has also been confirmed in one lithology of a dimict ureilite (NWA 1241). In contrast, Si-bearing Fe-metals occur in both brecciated and unbrecciated ureilites, implying that they were formed throughout the ureilite parent asteroid. We examined major, minor and trace element data of Fe-metals in seven brecciated ureilites (DaG 319, DaG 999, DaG 1000, DaG 1023, DaG 1047, EET 83309, and EET 87720) in addition to the dimict ureilite NWA 1241.
In this study we show that the silicides and Si-bearing metals in ureilites have similar siderophile trace element patterns; therefore, the precursors to the silicides were indigenous to the ureilite parent body. Si-free kamacite grains in brecciated ureilites show flatter, more chondritic siderophile element patterns. They may also be derived from the interior of the ureilite parent body, but some may be of exogenous origin (impactor debris), as are rare taenite grains.
On Earth, iron silicides are often formed under high-temperature and strongly reducing conditions (e.g. blast furnaces, lightning strikes). On the Moon, hapkeite (Fe2Si) and other silicides have been found in the regolith where they were formed by impact-induced space weathering. In the Stardust aerogel, iron silicides derived from comet Wild2 were also formed by an impact-related reduction process. Silicides in ureilite regolith breccias may have formed by similar processes but ureilites additionally contain abundant elemental carbon which probably acted as a reducing agent, thus larger and more abundant silicide grains were formed than in the lunar regolith or cometary material. The origin of suessite in NWA 1241 may be analogous to that of reduced lithologies in the terrestrial mantle, although a regolith origin may also be possible since this sample is shown here to be a dimict breccia.
– This article explores what the recovery of 2008 TC3 in the form of the Almahata Sitta meteorites may tell us about the source region of ureilites in the main asteroid belt. An investigation is made ...into what is known about asteroids with roughly the same spectroscopic signature as 2008 TC3. A population of low‐inclination near‐Earth asteroids is identified with spectra similar to 2008 TC3. Five asteroid families in the Main Belt, as well as a population of ungrouped asteroids scattered in the inner and central belts, are identified as possible source regions for this near‐Earth population and 2008 TC3. Three of the families are ruled out on dynamical and spectroscopic grounds. New near‐infrared spectra of 142 Polana and 1726 Hoffmeister, lead objects in the two other families, also show a poor match to Almahata Sitta. Thus, there are no Main Belt spectral analogs to Almahata Sitta currently known. Space weathering effects on ureilitic materials have not been investigated, so that it is unclear how the spectrum of the Main Belt progenitor may look different from the spectra of 2008 TC3 and the Almahata Sitta meteorites. Dynamical arguments are discussed, as well as ureilite petrogenesis and parent body evolution models, but these considerations do not conclusively point to a source region either, other than that 2008 TC3 probably originated in the inner asteroid belt.
Characterization of large area APDs for the EXO-200 detector Neilson, R.; LePort, F.; Pocar, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2009, Letnik:
608, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Enriched Xenon Observatory (EXO)-200 uses 468 large area avalanche photodiodes (LAAPDs) for detection of scintillation light in an ultra-low-background liquid xenon (LXe) detector. We describe ...initial measurements of dark noise, gain and response to xenon scintillation light of LAAPDs at temperatures from room temperature to 169
K—the temperature of liquid xenon. We also describe the individual characterization of more than 800 LAAPDs for selective installation in the EXO-200 detector.
A cheap and direct solution towards engineering better catalysts through identification of novel materials is required for a sustainable energy system. Perovskite oxides have emerged as potential ...candidates to replace the less economically attractive Pt and IrO2 water splitting catalysts. In this work, excellent electrical conductivity (980 S cm−1) was found for the double perovskite of composition GdBa0.6Sr0.4Co2O6−δ which is consistent with a better oxygen evolution reaction activity with the onset polarisation of 1.51 V with respect to a reversible hydrogen electrode (RHE). GdBa1−xSrxCo2O6−δ with increasing Sr content was found to crystallise in the higher symmetry tetragonal P4/mmm space group in comparison with the undoped GdBaCo2O6−δ which is orthorhombic (Pmmm), and yields higher oxygen uptake, accompanied by higher Co oxidation states. This outstanding electrochemical performance is explained by the wider carrier bandwidth, which is a function of Co–O–Co buckling angles and Co–O bond lengths. Furthermore the higher oxygen evolution activity was observed despite the formation of non-lattice oxides (mainly hydroxide species) and enrichment of alkaline earth ions on the surface.
A nonlinear power distribution network model for characterizing the immunity of integrated circuits (ICs) to electrical fast transients (EFTs) is proposed and validated. The model includes ...electrostatic discharge (ESD) protection diodes and passive impedances between power domains. Model parameters are based on external measurements using a vector network analyzer and curve tracer. Impedance is measured between pins while the IC is biased and operating, and is used to determine individual elements of the network model. Inclusion of active power-clamp circuitry is also explored. The model is able to successfully predict pin currents and voltages during EFTs on the power pin when the IC is operating or turned off and when the ESD power clamp is either activated or not activated. This model might be used to evaluate the immunity of the IC in a variety of systems and to better understand why failures occur within the IC and how to fix them.
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