Mnemonic function in small vessel disease and associations with white matter tract microstructure.

Cerebral small vessel disease (SVD) is associated with deficits in working memory, with a relative sparing of long-term memory; function may be influenced by white matter microstructure. Working and long-term memory were examined in 106 patients with SVD and 35 healthy controls. Microstructure was measured in the uncinate fasciculi and cingula. Working memory was more impaired than long-term memory in SVD, but both abilities were reduced compared to controls. Regression analyses found that having SVD explained the variance in memory functions, with additional variance explained by the cingula (working memory) and uncinate (long-term memory). Performance can be explained in terms of integrity loss in specific white matter tract associated with mnemonic functions

Petrology of several late tertiary gabbroic plugs in the south Cariboo region, British Columbia

Four olivine gabbro plugs crop out on the basaltic plateau in the south Cariboo region of British Columbia. The plugs form elliptical knobs of unaltered gabbro which stand 100 to 200 feet above the plateau surface. They are 300 to 600 feet in greatest diameter, as seen in plan view. Two plugs, Mt. Begbie and Forestry Hill, are described in detail in this thesis. Alignment of tabular feldspar grains resulting from the upward flow of magma, has produced a foliation in both Mt. Begbie and Forestry Hill plugs. Foliation dips toward the centre at moderate to steep angles in both plugs. Small, scattered lenses of leucogabbro and picritic gabbro lie approximately in the plane of foliation. Marginal foliation is assumed to be roughly parallel to the walls of the plug. Foliation trends indicate that both plugs are funnel-shaped, increasing in diameter toward the surface. The essential minerals of the plugs are olivine, calcic-augite and plagioclase. They are strongly zoned indicating a disequilibrium environment of crystallization. From a consideration of mineralogical and chemical characteristics it is concluded that the original magma was an alkali basalt magma. Differentiation by fractional crystallization produced small volumes of marginal dolerite and pegmatitic gabbro in the outer portions of Mt. Begbie plug. The trend of differentiation leads to iron-enrichment in the marginal dolerite, and then to alkali-enrichment in the pegmatitic gabbro. The four plugs occupy former volcanic vents which, in late Tertiary time, fed lava to the surrounding plateau. The exposed portions of the plugs crystallized possibly within 50 to 150 feet of the surface. General geological relationship, petrological similarity, and the close comparison of fused whole-rock powders suggest a definite kinship of the plugs to the surrounding basaltic lava.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat

Late Pleistocene and Holocene glacial history of James Ross Island, Antarctic Peninsula

Studies of Quaternary glacial stratigraphy and morphology around the Antarctic Peninsula have shown that James Ross Island in the western Weddell Sea probably has the best occurrences of stratigraphic sections with dateable material in the region. The stratigraphy includes sections with indefinite radiocarbon age, and three separate aminozones can be recognized. Except for indications of an early deglaciation around c. 10,000 BP, the field evidence from northern James Ross Island suggests a glacial readvance around 7000 BP. It is concluded that the readvance reflects the combined effects of eustatic sea level rise and Holocene warming, leading to increased precipitation and a positive mass balance. The most recent large-scale deglaciation in the area took place around 6000–5000 BP. This confirms the evidence from lake sediments and moss banks in other parts of the Antarctic Peninsula region, which shows that, in most cases, the initiation of organic deposition took place after c. 6000 BP. The literature on the Holocene glacial and environmental history of the region is reviewed in light of the new field evidence