Rheological and petrological implications for a stagnant lid regime on Venus

AbstractVenus is physically similar to Earth but with no oceans and a hot dense atmosphere. Its near-random distribution of impact craters led to the inferences of episodic global resurfacing and a stagnant lid regime, and imply that it is not currently able to lose proportionately as much heat as Earth. This paper shows that a CO2-induced asthenosphere and decoupling of the mantle lid from the crust, caused by the elevated surface temperature, enables lid rejuvenation. Global hypsography implies a rate of 4·0±0·5km²a−1 and an implied heat loss rate of 32·8±3·6TW, ~90% of a scaled Earth-like rate of heat loss of 36TW. Estimates of the rate of lid rejuvenation by plume activity – 0·07 to 0·09km²a−1– imply that ten times the number of observed plumes are required to equal this rate of heat loss. However, lid rejuvenation by convection allows Venus to maintain a stable tectonic regime, with subcrustal horizontal extension (half-spreading) rates of between 25 and 50mma−1 determined from fits to topographic profiles across the principal rift systems. While the surface is largely detached from these processes, the association of rifting and other processes does imply that Venus is geologically active at the present day

Priming as a means of preventing skill failure under pressure

Copyright @ 2010 Human KineticsThe present study examined the effectiveness of a priming paradigm in alleviating skill failure under stress. The priming intervention took the form of a scrambled sentence task. Experiment 1: Thirty-four skilled field-hockey players performed a dribbling task in low-and high-pressure situations under single task, skill-focused, and priming conditions. Results revealed a significant increase in performance time from low to high pressure. In addition, performance in the priming condition was significantly better than in the control and skill-focused conditions. Experiment 2: Thirty skilled field-hockey players completed the same dribbling task as in Experiment 1; however, in addition to the control and skill-focused conditions, participants were allocated to either a positive, neutral, or negative priming condition. Results revealed significant improvements in performance time from the skill focus to the control to the priming condition for the positive and neutral groups. For the negative group, times were significantly slower in the priming condition. Results are discussed in terms of utilizing priming in a sporting context

Integrin activation takes shape.

Integrins are cell surface adhesion receptors that are essential for the development and function of multicellular animals. Here we summarize recent findings on the regulation of integrin affinity for ligand (activation), one mechanism by which cells modulate integrin function. The focus is on the structural basis of integrin activation, the role of the cytoplasmic domain in integrin affinity regulation, and potential mechanisms by which activation signals are propagated from integrin cytoplasmic domains to the extracellular ligand-binding domain

Capsule independent uptake of the fungal pathogen Cryptococcus neoformans into brain microvascular endothelial cells.

Cryptococcosis is a life-threatening fungal disease with a high rate of mortality among HIV/AIDS patients across the world. The ability to penetrate the blood-brain barrier (BBB) is central to the pathogenesis of cryptococcosis, but the way in which this occurs remains unclear. Here we use both mouse and human brain derived endothelial cells (bEnd3 and hCMEC/D3) to accurately quantify fungal uptake and survival within brain endothelial cells. Our data indicate that the adherence and internalisation of cryptococci by brain microvascular endothelial cells is an infrequent event involving small numbers of cryptococcal yeast cells. Interestingly, this process requires neither active signalling from the fungus nor the presence of the fungal capsule. Thus entry into brain microvascular endothelial cells is most likely a passive event that occurs following ‘trapping’ within capillary beds of the BBB

Dynamic holographic interferometry using a Bi12SiO20 photorefractive crystal and monomode optical fibres

Dynamic holographic interferometry using polarization preserving opticai fibres as light guides and incorporating a photorefractive Bi12SiO20 (BSO) crystal as the recording medium is described. An experimental investigation of the recording of time average holograms through the diffusion process (employing anisotropic self-diffraction) and the drift process (application of d.c. and a.c. electric fields across the crystal) is also described. The holographic interferometer was optimised to produce holograms with a high diffraction efficiency and a high signal-to-noise ratio. Results are presented on optimising parameters such as the writing beam angle and writing beam intensity ratio. The advantages that can be gained by deploying this holographic interferometer in an industrial environment, where the laser light is guided to the location of the object by means of monomode fibres and images are stored within a photorefractive crystal is described. The holographic interferometer is capable of producing time average and double exposure interferograms of vibrating and deformed objects which can be displayed in real time