Coexistence of Chiari 2 malformation and moyamoya syndrome in a 17-year-old girl.

A 17-year-old female with Chiari 2 malformation developed cerebral infarction with angiographically typical bilateral moyamoya vessels manifesting as sudden onset of moderate left hemiparesis. Magnetic resonance imaging revealed multiple infarcts in the right frontal lobe, agenesis of the corpus callosum, upward herniation of the dorsal cerebellum, tectal beak of the midbrain, and downward herniation of the cerebellar vermis. Cerebral angiography demonstrated occlusion of the bilateral internal carotid arteries and basal moyamoya vessels. Single photon emission computed tomography showed significantly reduced regional cerebral blood flow in the right frontoparietal cortex. The cerebral vascular reactivity to acetazolamide was diminished in both cerebral hemispheres. She underwent superficial temporal artery-middle cerebral artery anastomosis combined with encephalo-myo-synangiosis on the right, and on the left 6 months later. Cerebral angiography performed 4 months after the second operation showed good patency of the bypasses and substantial collateral vessels in both cerebral hemispheres. This association may have happened by chance, and a common etiology is uncertain, but a currently undetermined genomic component might have contributed to the disease progression

Evaluation of sealed joint performance for the selection of sealants suitable for use in autoclaved lightweight concrete panels

The strength of autoclaved lightweight concrete (ALC) is evidently lower than that of normal concrete. Therefore, when movement occurs at a sealed joint between ALC panels, the sealant is required to deform and remain intact without damaging the ALC substrate. However, there is currently not sufficient information to permit evaluation of the expected performance of sealants applied to ALC substrates. In this study, static and dynamic tests were carried out in order to obtain an index that could be used to select the modulus of a sealant that can be expected to provide long-term performance when applied to an ALC substrate. To develop this index, an initial study was carried out in order to clarify actual joint movement between ALC panels of buildings; the expansion and contraction at the joint were measured, and shear joint movement was calculated based on the expected story-to-story drift of an external wall due to earthquake loads. Thereafter, in a subsequent stage of the study, five types of two-component polyurethane sealant products, of different elastic modulus, were subjected to tensile and shear tests from which the relationship between stress and the type of joint fracture was determined. The results from these tests revealed that when the stress is greater than 0.6 to 0.7 N/mm2, the ALC substrate is more easily fractured than the sealant. In a final stage of the study, the cyclic fatigue resistance of the same two-component sealants was evaluated using tensile and shear fatigue tests. Results from the fatigue tests indicated that the high modulus sealants lost adhesion from the ALC substrate at an early stage in the test. As well, the fatigue resistance of test specimens with joints having three-sided adhesion was lower than that of specimens having normally configured joints with adhesion on two sides of the sealant. Therefore, on the basis of results derived from all the studies, it was determined that a suitable sealant for use on ALC substrates is a sealant having a low modulus that is applied in the normal fashion as a two-sided joint. Copyright \ua9 2012 by ASTM International.Dr. Michael A. Lacasse: https://orcid.org/0000-0001-7640-3701Dr. Michael A. Lacasse: https://orcid.org/0000-0001-7640-3701Peer reviewed: YesNRC publication: Ye