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Pediatric patients supported by ventricular assist devices form a growing and challenging population. They are high-risk, and heterogeneous (in terms of age, neurodevelopment stage, and underlying anatomy) and relatively low-volume. Standardization of care across the various ages and stages is difficult. Multidisciplinary teams managing these patients must have a good understanding of growth and development to provide optimal care and creative options for growth, development, and adherence in order to achieve improved outcomes for pediatric ventricular assist device patients.

Introduction Sodium pentobarbital (Nembutal) is a barbiturate used in research as an anesthetic in many animal models. The injectable form of this drug has lately become difficult to procure and prohibitively expensive. Due to this lack of availability, researchers have begun to compound injectable sodium pentobarbital from so-called “nonpharmaceutical” pentobarbital. Some oversight agencies have objected to this practice, claiming a lack of quality control and degradation of the drug. We sought with this study to establish both: 1) a protocol for the preparation of injectable sodium pentobarbital, and 2) standard operating procedures to monitor the quality of the preparation and degradation of the drug over time. Methods Our preparation consists of a mixture of sodium pentobarbital in alkaline aqueous solution, propylene glycol, and ethanol. Pentobarbital content in this preparation was assayed by high-pressure liquid chromatography (HPLC). We also assayed pentobarbital content over time in preparations of various ages up to 6 years old. Results We determined that the drug degraded at a maximum of 0.5% per year in our preparation (alkaline water/propylene glycol/ethanol) when stored in the dark at room temperature. A yellow discoloration developed after about 2 years, which we have arbitrarily determined disqualifies the preparation from use as an anesthetic. Attempts to spectroscopically assay this discoloration were not successful. Chemicals Pentobarbital sodium (CID: 14075609)

Menisci are two crescent shaped fibrocartilaginous structures that provide fundamental load distribution and support within the knee joint. Their unique shape transmits axial stresses (i.e. "body force") into hoop or radial stresses. The menisci are primarily an inhomogeneous aggregate of glycosaminoglycans (GAGs) supporting bulk compression and type I collagen fibrils sustaining tension. It has been shown that the superficial meniscal layers are functionally homogeneous throughout the three distinct regions (anterior, central and posterior) using a 300 μm diameter spherical indenter tip, but the deep zone of the meniscus has yet to be mechanically characterized at this scale. Furthermore, the distribution and content of GAG throughout the human meniscal cross-section have not been examined. This study investigated the mechanical properties, via indentation, of the human deep zone meniscus among three regions of the lateral and medial menisci. The distribution of GAGs through the cross-section was also documented. Results for the deep zone of the meniscus showed the medial posterior region to have a significantly greater instantaneous elastic modulus than the central region. No significant differences in the equilibrium modulus were seen when comparing regions or the hemijoint. Histological results revealed that GAGs are not present until at least ~600 μm from the meniscal surface. Understanding the role and distribution of GAG within the human meniscus in conjunction with the material properties of the meniscus will aid in the design of tissue engineered meniscal replacements.

Fatigue crack growth in open holes in aluminium alloys 2024-T351 and 2650 was investigated. Tests were carried out using plates containing plain holes and cold expanded holes in aluminium. The tests explored the influence of the applied stress, the ratio of the minimum to the maximum applied stress, R, and crack closure. Longer fatigue lives of specimens with cold expanded holes were obtained provided that the applied load ratio was less than 0.7, and the maximum applied stress was less than 0.5 of the yield strength. The decrease in fatigue crack growth in cold-expanded specimens was related to higher crack opening stresses which is a consequence of the presence of compressive residual stresses arising from cold expansion. Fatigue crack growth rates were described as a function of an effective stress intensity factor, which was determined using measured crack opening stress. Measured crack opening stress was also compared with opening stress determined from fatigue crack growth rates.