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Study DesignRadiologic imaging measurement study.PurposeTo assess the accuracy of detecting lateral mass and facet joint injuries of the subaxial cervical spine on plain radiographs using computed tomography (CT) scan images as a reference standard; and the integrity of morphological landmarks of the lateral mass and facet joints of the subaxial cervical spine.Overview of LiteratureInjuries of lateral mass and facet joints potentially lead to an unstable subaxial cervical spine and concomitant neurological sequelae. However, no study has evaluated the accuracy of detecting specific facet joint injuries.MethodsEight spinal surgeons scored four sets of the same, randomly re-ordered, 30 cases with and without facet joint injuries of the subaxial cervical spine. Two surveys included conventional plain radiographs series (test) and another two surveys included CT scan images (reference). Facet joint injury characteristics were assessed for accuracy and reliability. Raw agreement, Fleiss kappa, Cohen's kappa and intraclass correlation coefficient statistics were used for reliability analysis. Majority rules were used for accuracy analysis.ResultsOf the 21 facet joint injuries discerned on CT scan images, 10 were detected in both plain radiograph surveys (sensitivity, 0.48; 95% confidence interval [CI], 0.26-0.70). There were no false positive facet joint injuries in either of the first two X-ray surveys (specificity, 1.0; 95% CI, 0.63-1.0). Five of the 11 cases with missed injuries had an injury below the lowest visible articulating level on radiographs. CT scan images resulted in superior inter- and intra-rater agreement values for assessing morphologic injury characteristics of facet joint injuries.ConclusionsPlain radiographs are not accurate, nor reliable for the assessment of facet joint injuries of the subaxial cervical spine. CT scans offer reliable diagnostic information required for the detection and treatment planning of facet joint injuries.

In this paper, we present boron isotope analyses of variably degassed rhyolitic glasses from Long Valley, California. The following results indicate that pre-eruptive boron isotopic signatures were preserved in degassed glasses: (1) averaged secondary ionization mass spectrometry (SIMS) measurements of [H.sub.2]O-rich (~3 wt%) melt inclusions from late erupted Bishop Tuff pumice are indistinguishable from positive thermal ionization mass spectrometry (PTIMS) analysis of vesiculated groundmass glass ([[delta].sup.11]B = +5.0 [+ or -] 0.9% and + 5.4 [+ or -] 0.5 [per thousand], respectively); (2) SIMS spot-analyses on [H.sub.2]O-poor obsidian (~0.15 wt% [H.sub.2]O) from younger Glass Mountain Dome YA (average [[delta].sup.11]B = + 5.2 [+ or -] 1.0 [per thousand]) overlap with compositionally similar late Bishop Tuff melt inclusions; and (3) four variably degassed obsidian samples from the 0.6 ka Mono Craters ([H.sub.2]O between 0.74 and 0.10 wt%) are homogeneous with regard to boron (average [[delta].sup.11]B = + 3.2 [+ or -] 0.8 [per thousand], MSWD=0.4). Insignificant variations in [[delta].sup.B] between early and late Bishop Tuff melt inclusion glasses agree with published experimental data that predict minor [sup.11]B depletion in hydrous melts undergoing gas-saturated fractional crystallization. Melt inclusions from two crystal-rich post-caldera lavas (Deer Mountain and South Deadman Dome) are comparatively boron-rich (max. 90 ppm B) and have lower [[delta].sup.11]B values (average [[delta].sup.11]B = + 2.2 [+ or -] 0.8 [per thousand] and -0.4 [+ or -] 1.0 [per thousand]) that are in strong contrast to the boron isotopic composition of post-caldera crystal-poor rhyolites (27 ppm B; [[delta].sup.11]B = + 5.7 [+ or -] 0.8 [per thousand]). These variations in [[delta].sup.11]B are too large to be caused by pre-eruptive degassing. Instead, we favor assimilation of [[delta].sup.11]B depleted low-temperature hydrothermally altered intrusive rocks subsequent to fresh rhyolite recharge.

Magnesium-rich silicate chondrules and calcium-, aluminum-rich refractory inclusions (CAIs) are fundamental components of primitive chondritic meteorites. It has been suggested that concentration of these early-formed particles by nebular sorting processes may lead to accretion of planetesimals, the planetary bodies that represent the building blocks of the terrestrial planets. In this case, the size distributions of the particles may constrain the accretion process. Here we present new particle size distribution data for Northwest Africa 5717, a primitive ordinary chondrite (ungrouped 3.05) and the well-known carbonaceous chondrite Allende (CV3). Instead of the relatively narrow size distributions obtained in previous studies ( Ebel et al., 2016; Friedrich et al., 2015; Paque and Cuzzi, 1997 , and references therein), we observed broad size distributions for all particle types in both meteorites. Detailed microscopic image analysis of Allende shows differences in the size distributions of chondrule subtypes, but collectively these subpopulations comprise a composite “chondrule” size distribution that is similar to the broad size distribution found for CAIs. Also, we find accretionary ‘dust’ rims on only a subset (∼15–20%) of the chondrules contained in Allende, which indicates that subpopulations of chondrules experienced distinct histories prior to planetary accretion. For the rimmed subset, we find positive correlation between rim thickness and chondrule size. The remarkable similarity between the size distributions of various subgroups of particles, both with and without fine grained rims, implies a common size sorting process. Chondrite classification schemes, astrophysical disk models that predict a narrow chondrule size population and/or a common localized formation event, and conventional particle analysis methods must all be critically reevaluated. We support the idea that distinct “lithologies” in NWA 5717 are nebular aggregates of chondrules. If ≥cm-sized aggregates of chondrules can form it will have implications for planet formation and suggests the sticking stage is where the preferential size physics is operating. [ABSTRACT FROM AUTHOR]

Measured and modeled Ca and Ti isotopic fractionation effects in a diverse suite of refractory inclusions are used to understand processes of condensation in the solar protoplanetary disk where they and their precursor materials formed. This coordinated approach reveals largely decoupled isotopic signatures and implies that few, if any, of the studied inclusions can be considered primary condensates. All studied inclusions are enriched in light Ca isotopes (∼−0.2 to − 2.8 ‰ / amu ), but only two show correspondingly light Ti isotopes. Studied inclusions exhibit both heavy and light Ti isotope enrichments (∼0.3 to − 0.4 ‰ / amu ). These refractory element isotopic signatures, therefore, suggest admixture and reprocessing of earlier formed materials with distinct condensation histories. Along with coordinated measurements of 50 Ti isotopic anomalies, which span a range from ∼0 to ∼40 epsilon-unit excesses, the comparison of measured and modeled fractionation of Ca and Ti isotopes provides a powerful approach to understanding primitive nebular processes and environments in the protoplanetary disk. Remarkable evidence for Ca isotopic zoning within a typical Type B1 inclusion exemplifies the potential record of the earliest solar nebula that is likely lost and/or overprinted in the isotopic compositions of more volatile elements (e.g., Mg, Si, and O) by later modification processes. [ABSTRACT FROM AUTHOR]

Highlights • All measured particle size distributions are significantly broader than previously reported. • In Allende ∼85% of particles are unrimmed and in direct contact with meteorite host matrix. • When present, rim thicknesses appear correlated to underlying particle size. • All particle size distributions measured are very similar in shape after scaling to a common mean size. • Size-selective aerodynamics allow particle sticking to proceed to larger aggregation sizes. [ABSTRACT FROM AUTHOR]