A method for studying the biomechanical load response of the (in vitro) lumbar spine under dynamic flexion-shear loads

A method was developed to study the biomechanical response of the lumbar motion segment (Functional Spinal Unit, FSU) under a dynamic (transient) load in flexion. In order to inflict flexion-distraction types of injuries (lap seat-belt injuries) different load pulses were transferred to the specimen by means of a padded pendulum. The load response of the specimen was measured with a force and moment transducer. The flexion angulation and displacements were determined by means of high-speed photography. Two series of tests were made with ten specimens in each and with two different load pulses: one moderate load pulse (peak acceleration 5 g, rise time 30 ms, duration 150 ms) and one severe load pulse (peak acceleration 12 g, rise time 15 ms, duration 250 ms). The results showed that the moderate load pulse caused residual permanent deformations at a mean bending moment of 140 Nm and a mean shear force of 430 N at a mean flexion angulation of 14 degrees. The severe load pulse caused evident signs of failure of the segments at a mean bending moment of 185 Nm and a mean shear force of 600 N at a mean flexion angulation of 19 degrees. Significant correlations were found between the load response and the size of the specimen, as well as between the load response and the bone mineral content (BMC) in the two adjacent vertebrae. Comparisons with lumbar spine response to static flexion-shear loading indicated that the specimens could withstand higher bending moments before injury occurred during dynamic loading, but the deformations at injury tended to be smaller for dynamic loading.     

Airborne scatterometers: investigating ocean backscatter under low and high-wind conditions

Attempting to understand and predict weather on a local and global basis has challenged both the scientific and engineering communities. One key parameter in understanding the weather is the ocean surface wind vector because of its role in the energy exchange at the air-sea surface. scatterometers, radars that measure the reflectivity of a target offer a tool with which to remotely monitor these winds from tower-, aircraft-, and satellite-based platforms. This paper introduces three current airborne scatterometer systems, and presents data collected by these instruments under low-, moderate-, and high-wind conditions. The paper focuses on airborne scatterometers because of their ability to resolve submesoscale variations in wind fields. Discrepancies between existing theory and the observations are noted and the concerns in measuring low-wind speeds discussed. Finally, the application of using this technology for estimating the surface-wind vector during a hurricane is demonstrated     

Initial Stages in the Metal-dusting Process on Alloy 800

The initial stages of the metal-dusting process on Alloy 800 at 620 °C were investigated by light optical microscopy, RAMAN spectroscopy, atomic-force microscopy, Auger electron spectroscopy, transmission-electron microscopy and electron back-scatter diffraction. As it turned out the incubation period for metal-dusting is characterized by simultaneous formation of a heterogeneously growing oxide scale and deposition of carbon. The material surface shows different tarnish colors depending on the substrate-grain orientation with different susceptibility to the beginning of metal-dusting attack. “Low-index” grains were not attacked within the times investigated while the other grain orientations showed pitting. Carbon is evidently incorporated into the oxide scale from the very beginning of exposure with different intensities depending on the underlying substrate-grain orientation leading to differences in the tarnish colors. As a consequence carbides are formed even underneath “dense” oxide layers. Evidently metal-dusting attack starts at positions of the oxide scale where “higher carbon concentrations” are present.     

Noninvasive assessment of the direct action of oral nifedipine and nicardipine on left ventricular contractile state in patients with systemic hypertension: importance of reflex sympathetic responses

BACKGROUND: Alveolar macrophages from patients with sarcoidosis were analyzed for their ability to secrete tumor necrosis factor-alpha (TNF-alpha), interleukin-1-beta (IL-1-beta), and interleukin-6 (IL-6). RESULTS: Constitutive release of all three monokines in these patients was concomitantly increased in the active state of disease in comparison with inactive sarcoidosis or healthy control subjects. Alveolar macrophages from patients with inactive sarcoidosis compared with cells from healthy subjects showed increased spontaneous secretion of TNF-alpha and IL-6 only, whereas the constitutive release of IL-1-beta was similar as in healthy volunteers. In vitro stimulation of alveolar macrophages from healthy control subjects with lipopolysaccharide or pokeweed mitogen led to a time- and dose-dependent enhanced secretion of TNF-alpha, IL-1-beta, and IL-6. In a similar manner, with corresponding cells from patients with sarcoidosis the secretion of all three cytokines could be further increased by stimulation with lipopolysaccharide or pokeweed mitogen. CONCLUSIONS: The data presented indicate that an increased release of TNF-alpha, IL-1-beta, and IL-6 correlates to disease activity and may play a critical part in the pathogenesis of sarcoidosis.     

Radiosity with Well Distributed Ray Sets

In this paper we present a new radiosity algorithm, based on the notion of a well distributed ray set (WDRS). A WDRS is a set of rays, connecting mutually visible points and patches, that forms an approximate representation of the radiosity operator and the radiosity distribution. We propose an algorithm that constructs an optimal WDRS for a given accuracy and mesh. The construction is based on discrete importance sampling as in previously proposed stochastic radiosity algorithms, and on quasi Monte Carlo sampling. Quasi Monte Carlo sampling leads to faster convergence rates and the fact that the sampling is deterministic makes it possible to represent the well distributed ray set very efficiently in computer memory. Like previously proposed stochastic radiosity algorithms, the new algorithm is well suited for computing the radiance distribution in very complex diffuse scenes, when it is not feasible to explicitly compute and store form factors as in classical radiosity algorithms. Experiments show that the new algorithm is often more efficient than previously proposed Monte Carlo radiosity algorithms by half an order of magnitude and more.