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Objectives: To determine whether patients presenting with a first transient ischaemic attack (TIA) subsequently show increased rates of brain atrophy compared with age matched controls; and to assess potential risk [...]

The solution for the stress state present in the vicinity of transverse matrix cracks within a composite laminate is typically obtained by assuming a regular crack spacing geometry for the problem and applying a shear-lag analysis. In order to explore the validity of this underlying assumption, the probability density function for the location of the next transverse matrix crack within a crack bounded region is examined. The regular crack spacing assumption is shown to be reasonable from an engineering point of view. Continuing with this assumption, a generalized shear-lag model for multilayer, off-axis laminates subjected to full in-plane loads is developed. This model is used to quantitatively evaluate the effective elastic properties of the damaged material. The results are applicable to materials such as ceramic matrix or polymer matrix unidirectional fiber systems where damage in the form of transverse matrix cracks arises.

Two recently drilled Caribbean sites contain expanded sedimentary records of the late Paleocene thermal maximum, a dramatic global warming event that occurred at ca. 55 Ma. The records document significant environmental changes, including deep-water oxygen deficiency and a mass extinction of deep-sea fauna, intertwined with evidence for a major episode of explosive volcanism. We postulate that this volcanism initiated a reordering of ocean circulation that resulted in rapid global warming and dramatic changes in the Earth's environment.

The Flin Flon Belt is a complex ('Amisk collage') of distinct tectono-stratigraphic assemblages that was brought together at a relatively early stage in the tectonic evolution of the Paleoproterozoic Trans-Hudson orogen. Four main tectono-stratigraphic assemblage types are recognized: isotopically juvenile oceanic arc (1.90-1.88 Ga), ocean floor (ca. 1.90 Ga), oceanic plateau/ocean island, and isotopically evolved arc (1.921.90 Ga). Oceanic arc assemblages include tholeiitic, calc-alkaline, and lesser shoshonitic volcanic and volcaniclastic rocks, as well as turbidites and arc-rift volcanic rocks. The tectono-stratigraphic assemblages were juxtaposed in an accretionary complex (Amisk collage) at ca. 1.88-1.87 Ga, probably as a result of arc-arc collision/collisions. Accretionary collage structures are largely obliterated by subsequent deformation and metamorphic events, but can be inferred where cut by calc-alkaline plutons related to a 1.866-1.838 Ga arc. Coeval sub-aerial volcanism is recorded in ca. 1.87-1.85 Ga calc-alkaline to shoshonitic volcaniclastic sequences. Unroofing of the accretionary collage, development of a paleosol, and deposition of continental (alluvial-fluvial) sedimentary rocks occurred ca. 1.851-.84 Ga, coeval with the waning stages of post-accretion arc magmatism. Stabilization of the Flin Flon Belt by 1.85-1.84 Ga as part of a Philippines- or Japan-like micro-continent is attributed to both tectonic and magmatic thickening of the lithosphere.

At a macroscopic level, a composite lamina may be considered as a homogeneous orthotropic solid whose directional strengths are random variables. Incorporation of these random variable strengths into failure models, either interactive or noninteractive, allows for the evaluation of the lamina reliability under a given stress state. Using a noninteractive criterion for demonstration purposes, laminate reliabilities are calculated assuming previously established load sharing rules for the redistribution of load as the failure of laminae occurs. The matrix cracking predicted by ACK theory is modeled to allow a loss of stiffness in the fiber direction. The subsequent failure in the fiber direction is controlled by a modified bundle theory. Results using this modified bundle model are compared with previous models, which did not permit separate consideration of matrix cracking, as well as to results obtained from experimental data.