Hydrogen Storage in Partially Exfoliated Magnesium Diboride Multilayers.

Metal boride nanostructures have shown significant promise for hydrogen storage applications. However, the synthesis of nanoscale metal boride particles is challenging because of their high surface energy, strong inter- and intraplanar bonding, and difficult-to-control surface termination. Here, it is demonstrated that mechanochemical exfoliation of magnesium diboride in zirconia produces 3-4 nm ultrathin MgB2 nanosheets (multilayers) in high yield. High-pressure hydrogenation of these multilayers at 70 MPa and 330 °C followed by dehydrogenation at 390 °C reveals a hydrogen capacity of 5.1 wt%, which is ≈50 times larger than the capacity of bulk MgB2 under the same conditions. This enhancement is attributed to the creation of defective sites by ball-milling and incomplete Mg surface coverage in MgB2 multilayers, which disrupts the stable boron-boron ring structure. The density functional theory calculations indicate that the balance of Mg on the MgB2 nanosheet surface changes as the material hydrogenates, as it is energetically favorable to trade a small number of Mg vacancies in Mg(BH4 )2 for greater Mg coverage on the MgB2 surface. The exfoliation and creation of ultrathin layers is a promising new direction for 2D metal boride/borohydride research with the potential to achieve high-capacity reversible hydrogen storage at more moderate pressures and temperatures.

Characterization of volumetric growth of intracranial meningiomas in Maori and Pasifika populations in New Zealand.

BACKGROUND: Maori and Pasifika populations in New Zealand have a higher incidence and prevalence of intracranial meningioma (IM). We sought to evaluate the volumetric growth rate of meningiomas under surveillance in these populations. METHODS: From July 2002 to October 2020, 336 patients with a total of 408 IM underwent conservative management with serial radiological surveillance at Auckland City Hospital and met the criteria for the study. Inclusion criteria included: age >16 at diagnosis, ≥2 appropriate scans one or more years apart. Exclusion criteria included previous cranial irradiation, a diagnosis of Neurofibromatosis and prior treatment of meningioma. Demographic and clinical data were obtained from the electronic medical records. Imaging data were recorded from the first and last scans. We utilized open-source image processing software (3D Slicer) for semi-automated segmentation and volume calculation. Consistent with previous literature, we calculated the relative growth rate (RGR, %/year) and annual volume change (AVC, cm3 /year) over time. RESULTS: Four hundred and eight meningiomas were volumetrically characterized for a mean duration of 6.2 years. The Maori and Pasifika populations (n = 134/393) demonstrated a higher RGR (31.41 versus 14.33%/year) (P = 0.026) and AVC (2.05 versus 0.95 cm3 ) (P = 0.025) compared to the control population. They also presented at a younger age and had a higher rate of tumour multiplicity. Males represented only 17.6% of the cohort but exhibited a higher growth rate (AVC = 2.52 cm3 /year) than females (AVC = 0.99 cm3 /year) (P = 0034). CONCLUSIONS: Maori and Pasifika populations in New Zealand have a higher incidence and volumetric growth rate of IM compared to a control population. This warrants further clinical, histopathological and genomic analysis.

Routine multidisciplinary cerebrovascular meetings do not reduce aneurysm clipping case load: a cohort study.

BACKGROUND: Structured multidisciplinary care is an increasingly popular tool in the management of many complex disease processes; however, there is little published data regarding the effects of such a process on management of intracranial aneurysms and neurosurgical case loads. There is some resistance in the neurosurgical community to routine involvement of interventional neuroradiologists in the care of patients with intracranial aneurysms due to concerns regarding maintenance of neurosurgical case loads and training capabilities. At our tertiary Australian hospital, we have implemented a weekly multidisciplinary cerebrovascular meeting (MDCVM) facilitating routine discussion of these cases between neurosurgeons and interventional neuroradiologists. METHODS: This study identified management modalities for ruptured and unruptured cerebral aneurysms diagnosed at our centre for a 2-year period before and after the implementation of MDCVM culminating in a 4-year retrospective cohort study. The pre- and post-MDCVM cohorts were well matched for demographics with 162 and 224 patients, respectively. RESULTS: There is no significant difference in percentage or absolute numbers of endovascular or surgical cases in the pre-MDCVM (103; 73.0% versus 38; 27.0%, respectively) or post-MDCVM cohorts (105; 79.5% versus 27; 20.5%, respectively), reflecting a maintained surgical case load after the implementation of MDCVM (P = 0.21). There were no significant differences in any confounding variables including age, sex, aneurysm size/location, Fisher or World Federation of Neurosurgical Societies (WFNS) grade. CONCLUSIONS: Implementation of MDCVM did not impact on active management case loads with consistent numbers and percentages for both endovascular and microsurgical management.