Bilateral paramedian thalamic infarction: Neuropsychological and perfusional followup study.

Conducted a 2-yr follow-up of a woman (aged 35 yrs) who had a bilateral paramedian thalamic infarction and suffered from a sudden impairment of consciousness followed by a global deficit of cognitive functions. Two years after clinical onset, verbal and visuospatial memory, verbal fluency, constructional praxia, and categorization were mainly affected. In the acute phase, a single-photon emission-computed tomography study showed a severe and diffuse cerebral blood flow (CBF) impairment, more marked on the right side. Radioisotope uptake in frontal and temporal cortices was still reduced 2 yrs later. The CBF depression in these regions suggests that the decline of cognitive functions could be due to an interruption of thalamocortical projections. A degenerative process rather than a "diaschisis" could be responsible for the long-lasting deficit of cognitive functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Mechanism of Corrosion-Induced Roughening of Glass Surfaces

Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and solution analysis by inductively coupled plasma mass spectrometry (ICP-MS) were used to investigate the molecular scale processes responsible for the roughening of glass surfaces due to aqueous corrosion. The study of atomically smooth fiber and melt surfaces allowed direct investigation of the atomic and molecular scale effects of dissolution on surface roughness. The combined use of these analytical techniques clearly showed that the change in RMS roughness with aqueous corrosion could be directly related to the concentration of silica released to solution from the glass; cation leaching alone did not generate detectable roughening. It is well known that nano-/microscale surface roughness can influence strength, optical response, adsorptivity, and other surface properties of glass. It is shown here that the roughening of silicate glass surfaces can be expected based on the amount of silica released from the glass and does not show a dependence on the extent of modifier ion leaching. It is also suggested that the glass composition dependence of this roughening may be a measure of the nanoscale heterogeneity of the glass network structure.     

Mechanochemical Wear of Soda Lime Silica Glass in Humid Environments

The mechanochemical wear of multicomponent glasses was studied under controlled humidity conditions using a reciprocating ball‐on‐flat tribometer. For dry conditions, the surfaces were extensively damaged by scratching for all of the glasses, while for humid conditions the wear behavior varied with the glass composition suggesting a chemical effect on scratch behaviors of glass surfaces. The wear of soda lime silica (also called sodium calcium silicate) glass was suppressed with increasing humidity, while the borosilicate and barium boroaluminosilicate glasses showed an increase in wear volume with increasing humidity. The unique humidity dependence of the observed mechanochemical wear of soda lime silica glass supports the hypothesis that hydronium ion formation in the sodium‐leached sites of the soda lime glass enhances its wear resistance.     

Sol-gel prepared Ni-alumina composite materials

The sol-gel method has been utilized for the preparation of dense, homogeneous ceramic-metal composites with up to 50% Ni in Al₂O₂. Examination by SEM and TEM shows that the materials consist of micrometre-size Al₂O₃ with metallic Ni in isolated regions from 50 m down to nanometre size. The density ranges from 97% (10% Ni) to 74% (50% Ni) of the theoretical number. The hardness decreases from 18 GPa for pure alumina to 10 GPa for alumina containing 50% Ni. The fracture toughness increases significantly from K _1c=3–4 MPa m^1/2 to K _1c=8.5 MPa m^1/2. The elastic and shear moduli decrease from E=400 GPa and G=160 GPa for pure alumina to E=320 GPa and G=135 GPa when containing 50% Ni. The electrical resistivity is 10⁶m with 10 to 40% Ni but decreases drastically at 50% Ni content.     

Glass Surface Layer Density by Neutron Depth Profiling

Several lithium-disilicate ( Li₂O∙2SiO₂ ) glass samples were synthesized, polished and subjected to static leach tests for varying periods of time in an HCl solution (pH 4) at 90°C. The presence of an alteration layer on the leached specimens was independently confirmed using infrared spectroscopy. These samples were then analyzed with neutron depth profiling (NDP), and for all exposure times between 1 and 20 h, a leached layer was detected by NDP. The residual concentration of ⁶Li in the alteration layer was observed to be approximately 10% of the bulk glass value. The 7.5 h and 17.5 h samples were cross-sectioned using focused ion beam milling, and the thickness of the alteration layer on the samples was measured directly using scanning electron microscopy to be 9.8 and 22.9 μm, respectively. The areal density of the gel layers — determined by deconvolution of the NDP spectra — was coupled with the SEM measurement to give densities of 1.46 ± 0.08 g/cm³ for the 7.5 h specimen and 1.46 ± 0.05 g/cm³ for the 17.5 h specimen. This preliminary work shows that NDP can be used to determine the average density of gel layers formed owing to leaching of alkali-silicate glass.