Tectonics, volcanism, landscape structure and human evolution in the African Rift

Tectonic movements and volcanism in the African Rift have usually been considered of relevance to human evolution only at very large geographical and chronological scales, principally in relation to longterm topographic and climatic variation at the continental scale. At the more loca1 scale of catchment basins and individual sites, tectonic features are generally considered to be at worst disruptive and at best incidental features enhancing the preservation and exposure of early sites. We demonstrate that recent lava flows and fault scarps in a tectonically active region create a distinctive landscape structure with a complex and highly differentiated topography of enclosures, barriers and fertile basins. This landscape structure has an important potential impact on the co-evolution of prey-predator interactions and on interspecific relationships more generally. In particular, we suggest that it would have offered unique opportunities for the development of a hominid niche characterised by bipedalism, meat-eating and stone tool use. These landscape features are best appreciated by looking at areas which today have rapid rates of tectonic movement and frequent volcanic activity, as in eastern Afar and Djibouti. These provide a better analogy for the Plio-Pleistocene environments occupied by early hominids than the present-day landscapes where their fossil remains and artefacts have been discovered. The latter areas are now less active than was the case when the sites were formed. They have also been radically transfomed by ongoing geomorphological processes in the intervening millennia. Thus, previous attempts to reconstruct the local landscape setting adjacent to these early hominid sites necessarily rely on limited geological windows into the ancient land surface and thus tend to filter out small-scale topographic detail because it cannot be reliably identified. It is precisely this local detail that we consider to be of importance in understanding the environmental contribution to co-evolutionary developments

Lagrangian description of world-line deviations

We introduce a Lagrangian which can be varied to give both the equation of motion and world-line deviations of spinning particles simultaneously.Comment: to appear in IJT

Direct and alignment-insensitive measurement of cantilever curvature

We analytically derive and experimentally demonstrate a method for the simultaneous measurement of deflection for large arrays of cantilevers. The Fresnel diffraction patterns of a cantilever independently reveals tilt, curvature, cubic and higher order bending of the cantilever. It provides a calibrated absolute measurement of the polynomial coefficients describing the cantilever shape, without careful alignment and could be applied to several cantilevers simultaneously with no added complexity. We show that the method is easily implemented, works in both liquid mediums and in air, for a broad range of displacements and is especially suited to the requirements for multi-marker biosensors.Comment: 5 Pages, 4 figures, letter forma

General relativistic spinning fluids with a modified projection tensor

An energy-momentum tensor for general relativistic spinning fluids compatible with Tulczyjew-type supplementary condition is derived from the variation of a general Lagrangian with unspecified explicit form. This tensor is the sum of a term containing the Belinfante-Rosenfeld tensor and a modified perfect-fluid energy-momentum tensor in which the four-velocity is replaced by a unit four-vector in the direction of fluid momentum. The equations of motion are obtained and it is shown that they admit a Friedmann-Robertson-Walker space-time as a solution.Comment: Submitted to General Relativity and Gravitatio

Open and Closed Loop Stability of Hingeless Rotor Helicopter Air and Ground Resonance

The air and ground resonance instabilities of hingeless rotor helicopters are examined on a relatively broad parametric basis including the effects of blade tuning, virtual hinge locations, and blade hysteresis damping, as well as size and scale effects in the gross weight range from 5,000 to 48,000 pounds. A special case of a 72,000 pound helicopter air resonance instability is also included. The study shows that nominal to moderate and readily achieved levels of blade inertial hysteresis damping in conjunction with a variety of tuning and/or feedback conditions are highly effective in dealing with these instabilities. Tip weights and reductions in pre-coning angles are also shown to be effective means for improving the air resonance instability

Atherosusceptible Shear Stress Activates Endoplasmic Reticulum Stress to Promote Endothelial Inflammation.

Atherosclerosis impacts arteries where disturbed blood flow renders the endothelium susceptible to inflammation. Cytokine activation of endothelial cells (EC) upregulates VCAM-1 receptors that target monocyte recruitment to atherosusceptible regions. Endoplasmic reticulum (ER) stress elicits EC dysregulation in metabolic syndrome. We hypothesized that ER plays a central role in mechanosensing of atherosusceptible shear stress (SS) by signaling enhanced inflammation. Aortic EC were stimulated with low-dose TNFα (0.3 ng/ml) in a microfluidic channel that produced a linear SS gradient over a 20mm field ranging from 0-16 dynes/cm2. High-resolution imaging of immunofluorescence along the monolayer provided a continuous spatial metric of EC orientation, markers of ER stress, VCAM-1 and ICAM-1 expression, and monocyte recruitment. VCAM-1 peaked at 2 dynes/cm2 and decreased to below static TNFα-stimulated levels at atheroprotective-SS of 12 dynes/cm2, whereas ICAM-1 rose to a maximum in parallel with SS. ER expansion and activation of the unfolded protein response also peaked at 2 dynes/cm2, where IRF-1-regulated VCAM-1 expression and monocyte recruitment also rose to a maximum. Silencing of PECAM-1 or key ER stress genes abrogated SS regulation of VCAM-1 transcription and monocyte recruitment. We report a novel role for ER stress in mechanoregulation at arterial regions of atherosusceptible-SS inflamed by low-dose TNFα