Wheat Pasture Poisoning.

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Sr-Nd isotope geochemistry of the early Precambrian sub-alkaline mafic igneous rocks from the southern Bastar craton, Central India

Sr–Nd isotope data are reported for the early Precambrian sub-alkaline mafic igneous rocks of the southern Bastar craton, central India. These mafic rocks are mostly dykes but there are a few volcanic exposures. Field relationships together with the petrological and geochemical characteristics of these mafic dykes divide them into two groups; Meso-Neoarchaean sub-alkaline mafic dykes (BD1) and Paleoproterozoic (1.88 Ga) sub-alkaline mafic dykes (BD2). The mafic volcanics are Neoarchaean in age and have very close geochemical relationships with the BD1 type. The two groups have distinctly different concentrations of high-field strength (HFSE) and rare earth elements (REE). The BD2 dykes have higher concentrations of HFSE and REE than the BD1 dykes and associated volcanics and both groups have very distinctive petrogenetic histories. These rocks display a limited range of initial 143Nd/144Nd but a wide range of apparent initial 87Sr/86Sr. Initial 143Nd/144Nd values in the BD1 dykes and associated volcanics vary between 0.509149 and 0.509466 and in the BD2 dykes the variation is between 0.510303 and 0.510511. All samples have positive εNd values the BD1 dykes and associated volcanics have εNd values between +0.3 and +6.5 and the BD2 dykes between +1.9 to +6.0. Trace element and Nd isotope data do not suggest severe crustal contamination during the emplacement of the studied rocks. The positive εNd values suggest their derivation from a depleted mantle source. Overlapping positive εNd values suggest that a similar mantle source tapped by variable melt fractions at different times was responsible for the genesis of BD1 (and associated volcanics) and BD2 mafic dykes. The Rb–Sr system is susceptible to alteration and resetting during post-magmatic alteration and metamorphism. Many of the samples studied have anomalous apparent initial 87Sr/86Sr suggesting post-magmatic changes of the Rb–Sr system which severely restricts the use of Rb–Sr for petrogenetic interpretation

Experimental validation of the radiographic union score for tibial fractures (RUST) using micro-computed tomography scanning and biomechanical testing in an in-vivo rat model

Copyright © 2018 BY THE JOURNAL of BONE AND JOINT SURGERY, INCORPORATED. Background: The Radiographic Union Score for Tibial fractures (RUST) and the modified version of the system, mRUST, are popular standards for assessing fracture-healing progress with use of radiographs. To our knowledge, this is the first study to experimentally validate the ability of RUST and mRUST to accurately assess bone-healing progression with use of both micro-computed tomography (micro-CT) scanning and biomechanical testing. Methods: Adult male rats (n = 29) underwent osteotomy with a midshafit fracture gap repaired with use of a poly-etheretherketone plate. Anteroposterior and lateral radiographs were made of the repaired femora prior to rat death at end points of 5, 6, 7, 8, 9, and 17 weeks, and 2 fellowship-trained orthopaedic trauma surgeons independently assigned RUST and mRUST scores to repaired femora. The repaired and intact contralateral femora were then dissected. Bones underwent dissection, micro-CT scanning, and biomechanical torsion testing at the end points. Results: RUST scores ranged from 5 to 12 and mRUST scores ranged from 5 to 16. Intraclass correlation coefficients (ICCs) were 0.89 (95% confidence interval [CI]: 0.78 to 0.94) for RUST and 0.86 (95% CI: 0.74 to 0.93) for mRUST, which fall within the almost perfect agreement category for ICCs. Spearman rank correlation coefficients (RS) showed correlation of RUST (RS range, 0.456 to 0.818) and mRUST (RS range, 0.519 to 0.862) with micro-CT measurements of mineralized callus volume (BV), total callus volume (TV), and BV/TV ratio, but less so with bone mineral density (BMD). Additionally, RUST (RS range, 0.524 to 0.863) and mRUST (RS range, 0.434 to 0.850) were correlated with some biomechanical properties. A RUST score of 10 or an mRUST score of 15 may be considered the threshold above which a plated bone is healed because, at these scores, 120% or 140% of failure torque, respectively, was achieved by the repaired femora as compared with the intact contralateral femora. Conclusions: RUST and mRUST both show strong statistical correlations with micro-CT and biomechanical parameters. Clinical Relevance: RUST and mRUST scoring systems provide clinicians with validated, reliable, and available tools to assess the progress of fracture-healing

Biomechanical properties and thermal characteristics of frozen versus thawed whole bone

© IMechE 2020. Biomechanics research often requires cadaveric whole bones to be stored in a freezer and then thawed prior to use; however, the literature shows a variety of practices for thawing. Consequently, this is the first study to report the mechanical properties of fully frozen versus fully thawed whole bone as ‘proof of principle’. Two groups of 10 porcine ribs each were statistically equivalent at baseline in length, cross-sectional area, and bone mineral density. The two groups were stored in a freezer for at least 24 h, thawed in air at 23 °C for 4 h while temperature readings were taken to establish the time needed for thawing, and once again returned to the freezer for at least 24 h. Mechanical tests to failure using three-point bending were then done on the ‘frozen’ group immediately after removal from the freezer and the ‘thawed’ group when steady-state ambient air temperature was reached. Temperature readings over the entire thawing period were described by the line-of-best-fit formula T = (28.34t − 6.69)/(t + 0.38), where T = temperature in degree Celsius and t = time in hours, such that frozen specimens at t = 0 h had a temperature of −17 °C and thawed specimens at t = 1.75 h reached a steady-state temperature of 20 °C–23 °C. Mechanical tests showed that frozen versus thawed specimens had an average of 32% higher stiffness k, 34% higher ultimate force Fu, 28% lower ultimate displacement δu, 40% lower ultimate work Wu, 43% higher elastic modulus E, 37% higher ultimate normal stress σu, and 33% higher ultimate shear stress τu. Whole ribs failed at midspan primarily by transverse cracking (16 of 20 cases), oblique cracking (three of 20 cases), or surface denting (one of 20 cases), each having unique shapes for force versus displacement graphs differentiated mainly by ultimate force location