Temperature-driven micro-fracturing in granite: The interplay between microstructure, mineralogy and tensile strength.

High temperatures exert a significant influence on the mechanical and fluid flow properties of rocks and minerals. In crystalline rocks, differential thermal expansion of minerals is known to induce microfracture damage leading to changes in bulk volume and tensile strength. Here we report new data from thermally treated core samples of Devon Granite in order to constrain the interplay between tensile strength and thermally-induced damage with respect to the background mineralogy. A series of core samples was cyclically heated at temperatures ranging from 25 to 800 °C, with P-wave velocity and porosity measured after each cycle. Tensile strength decreased significantly from 9 MPa to less than 3 MPa as thermal treatment increased from 25 to 800 °C. The mechanical data were then compared to fracture density values obtained by optical maps of microfracture damage to assess the quantity and degree of linkage of intergranular and intragranular fractures using the FraqPaQ toolbox. The fracture density increased from 0.02 m m - 2 to 2.0 m m - 2 which is consistent with results obtained from direct physical parameters as calculated from elastic wave data. We conclude that the combined effects of thermal expansion and the α - ß phase transition within quartz crystals has a pronounced effect on tensile strength.

Atomic-scale age resolution of planetary events.

Resolving the timing of crustal processes and meteorite impact events is central to understanding the formation, evolution and habitability of planetary bodies. However, identifying multi-stage events from complex planetary materials is highly challenging at the length scales of current isotopic techniques. Here we show that accurate U-Pb isotopic analysis of nanoscale domains of baddeleyite can be achieved by atom probe tomography. Within individual crystals of highly shocked baddeleyite from the Sudbury impact structure, three discrete nanostructural domains have been isolated yielding average 206Pb/238U ages of 2,436±94 Ma (protolith crystallization) from homogenous-Fe domains, 1,852±45 Ma (impact) from clustered-Fe domains and 1,412±56 Ma (tectonic metamorphism) from planar and subgrain boundary structures. Baddeleyite is a common phase in terrestrial, Martian, Lunar and asteroidal materials, meaning this atomic-scale approach holds great potential in establishing a more accurate chronology of the formation and evolution of planetary crusts.

Neutralization of interferon-gamma in neonatal SOCS1-/- mice prevents fatty degeneration of the liver but not subsequent fatal inflammatory disease.

Mice lacking the suppressor of cytokine signalling-1 (SOCS1) die within weeks of birth with extensive fatty degeneration of the liver, consistent with acute hepatic toxicity to interferon-gamma (IFN-gamma), and inflammation of multiple organs. We show here that treatment for 1 week from birth with neutralizing antibody to IFN-gamma rescues SOCS1-/- mice from lethal liver disease but the mice subsequently succumb to chronic inflammatory lesions characterized by T-lymphocyte infiltration of skeletal muscle, pancreas, lung, liver and skin. Elevated blood levels of eosinophils, neutrophils and platelets were also observed and the thymic lymphocyte population was depleted of CD4+ CD8+ T cells and showed a reduced CD4 : CD8 ratio. All T-cell populations in thymus, spleen and lymph node exhibited an increased proportion of cells bearing the activation marker CD44. These data suggest an important role for SOCS1 in T-lymphocyte regulation.

Calcium losses resulting from an acute bout of moderate-intensity exercise.

The purpose of this study was to compare daily calcium (Ca) losses in sweat (S) and urine (U) on an exercise day (E) with losses on the preceding day (i.e., a rest day) during which no exercise (NE) was performed. Ten healthy male volunteers (23.9 +/- 3.2 years) performed a single bout of moderate exercise (running at 80% HRmax) for 45 min in a warm (32 degrees C, 58% relative humidity) environment on E. When E and NE were compared, neither Ca intake (1,232 +/- 714 and 1, 148 +/- 482 mg, respectively) nor urinary Ca excretion (206 +/- 128 and 189 +/- 130 mg, respectively) were different (p >.05). Sweat Ca losses during the exercise bout averaged 45 +/- 12 mg. The results indicate that, although a small amount of Ca is lost in sweat during 45 min of moderate-intensity exercise, measured (sweat and urine losses combined) Ca losses (251 +/- 128 and 189 +/- 130 mg) were not different (p >.05) between days (E and NE, respectively). These data suggest that moderate exercise for up to 45 min in a warm, humid environment does not markedly increase Ca intake requirements.

Effects of ingesting supplements designed to promote lean tissue accretion on body composition during resistance training.

This study examined the effects of ingesting nutritional supplements designed to promote lean tissue accretion on body composition alterations during resistance training. Twenty-eight resistance-trained males blindly supplemented their diets with maltodextrin (M), Gainers Fuel 1000 (GF), or Phosphagain (P). No significant differences were observed in absolute or relative total body water among groups. Energy intake and body weight significantly increased in all groups combined throughout the study with no group or interaction differences observed. Dual energy x-ray absorptiometry-determined body mass significantly increased in each group throughout the study with significantly greater gains observed in the GF and P groups. Lean tissue mass (excluding bone) gain was significantly greater in the P group, while fat mass and percent body fat were significantly increased in the GF group. Results indicate that total body weight significantly increased in each group and that P supplementation resulted in significantly greater gains in lean tissue mass during resistance training.