331 research outputs found
The responses of central octavolateralis cells to moving sources
Müller HM, Fleck A, Bleckmann H. The responses of central octavolateralis cells to moving sources. Journal of Comparative Physiology A. 1996;179:455-471
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Diving-flight aerodynamics of a peregrine falcon (Falco peregrinus)
This study investigates the aerodynamics of the falcon Falco peregrinus while diving. During a dive peregrines can reach velocities of more than 320 km h⁻¹. Unfortunately, in freely roaming falcons, these high velocities prohibit a precise determination of flight parameters such as velocity and acceleration as well as body shape and wing contour. Therefore, individual F. peregrinus were trained to dive in front of a vertical dam with a height of 60 m. The presence of a well-defined background allowed us to reconstruct the flight path and the body shape of the falcon during certain flight phases. Flight trajectories were obtained with a stereo high-speed camera system. In addition, body images of the falcon were taken from two perspectives with a high-resolution digital camera. The dam allowed us to match the high-resolution images obtained from the digital camera with the corresponding images taken with the high-speed cameras. Using these data we built a life-size model of F. peregrinus and used it to measure the drag and lift forces in a wind-tunnel. We compared these forces acting on the model with the data obtained from the 3-D flight path trajectory of the diving F. peregrinus. Visualizations of the flow in the wind-tunnel uncovered details of the flow structure around the falcon's body, which suggests local regions with separation of flow. High-resolution pictures of the diving peregrine indicate that feathers pop-up in the equivalent regions, where flow separation in the model falcon occurred
Atomic force microscopy of Bacillus spore surface morphology
Bacillus spore surface morphology was imaged with atomic force microscopy (AFM) to determine if characteristic surface features could be used to distinguish between four closely related species; Bacillus anthracis Sterne strain, Bacillus thuringiensis var. kurstaki, Bacillus cereus strain 569, and Bacillus globigii var. niger. AFM surface height images showed an irregular topography across the curved upper surface of the spores. Phase images showed a superficial grain structure with different levels of phase contrast and significant differences in average surface morphologies among the four species. Although spores of the same species showed similarities, there was significant variability within each species. Overall, AFM revealed that spore surface morphology is rich with information, which can be used to distinguish a sample of about 20 spores from a similar number of spores of closely related species. Statistical analysis of spore morphology from a combination of amplitude and phase images for a small sample allows differentiation between, B. anthracis and its close relatives
Jet Propellant 8 versus Alternative Jet Fuels
The Air Force is the largest user of jet fuel in the Department of Defense DOD, consuming 2.4 billion gallons per year. In light of environmental impacts associated with using nonrenewable fuel sources and national security concerns regarding dependency on foreign oil, it is no surprise that the United States is paying more attention to alternative fuels. Both DOD and Air Force energy strategies address the need to develop and produce such fuels. The DOD has made a commitment to energy security, establishing an energy initiative that strives to modernize infrastructure, increase utility and energy conservation, enhance demand reduction, and improve energy flexibility, thereby saving taxpayer dollars and reducing emissions that contribute to air pollution and global climate change. This initiative has the following four goals 1. Maintain or enhance operational effectiveness while reducing total force energy demands 2. Increase energy strategic resilience by developing alternative assured fuels and energy 3. Enhance operational and business effectiveness by institutionalizing energy considerations and solutions in DoD planning business processes 4. Establish and monitor Department-wide energy metrics
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The peregrine falcon's rapid dive: on the adaptedness of the arm skeleton and shoulder girdle
During a dive, peregrine falcons (Falco peregrinus) can reach a velocity of up to 320 km h− 1. Our computational fluid dynamics simulations show that the forces that pull on the wings of a diving peregrine can reach up to three times the falcon’s body mass at a stoop velocity of 80 m s− 1 (288 km h− 1). Since the bones of the wings and the shoulder girdle of a diving peregrine falcon experience large mechanical forces, we investigated these bones. For comparison, we also investigated the corresponding bones in European kestrels (Falco tinnunculus), sparrow hawks (Accipiter nisus) and pigeons (Columba livia domestica). The normalized bone mass of the entire arm skeleton and the shoulder girdle (coracoid, scapula, furcula) was significantly higher in F. peregrinus than in the other three species investigated. The midshaft cross section of the humerus of F. peregrinus had the highest second moment of area. The mineral densities of the humerus, radius, ulna, and sternum were highest in F. peregrinus, indicating again a larger overall stability of these bones. Furthermore, the bones of the arm and shoulder girdle were strongest in peregrine falcons
The BCL9-2 proto-oncogene governs estrogen receptor alpha expression in breast tumorigenesis
The majority of human breast cancers express estrogen receptor {Alpha} (ER), which is important for therapy with anti-estrogens. Here we describe the role of BCL9-2, a proto-oncogene previously characterized as co-activator of Wnt/{beta}-catenin signaling, for mammary tumorigenesis in mice and human. ER positive human breast cancers showed overexpression of BCL9-2 and tamoxifen treated patients with high BCL9-2 demonstrated a better survival. BCL9-2 was upregulated during puberty and pregnancy in normal mammary epithelia, but downregulated in the involuted gland. BCL9-2 overexpression in vivo delayed the mammary involution and induced alveolar hyperplasia. Moreover, aged BCL9-2 transgenic mice developed ductal-like mammary tumors with high nuclear ER expression. We found, that primary cell cultures of BCL9-2 breast tumors responded to tamoxifen treatment. Moreover, BCL9-2 regulated the expression of ER and the proliferation of human breast cancer cells independently of {beta}-catenin. Finally, we describe a novel mechanism, how BCL9-2 regulates ER transcription by interaction with Sp1 through the proximal ESR1 gene promoter. In summary, BCL9-2 induces ER positive breast cancers in vivo, regulates ER expression by a novel {beta}-catenin independent mechanism in breast cancer cells, and might predict the therapy response to tamoxifen treatment
Unintended Consequences: Potential Downsides of the Air Force\u27s Conversion to Biofuels
The desire to reduce US dependence on foreign energy, ongoing environmental concerns, and the rising cost of petroleum have sparked significant development of greener alternative and renewable energy sources such as alcohol-based biofuels. To address these issues, the Department of Defense DOD has moved to diminish its reliance on petroleum for fueling aircraft and ground equipment. The US Air Force, in alignment with DOD objectives, has initiated several goals for reducing its use of energy: (1) decrease the use of petroleum-based fuel by 2 percent annually for the vehicle fleet, (2) increase the use of alternative fuel in motor vehicles annually by 10 percent, (3) certify all aircraft and weapon systems for a 5050 alternative fuel blend by 2011, and (4) have Air Force aircraft flying on 50 percent alternative fuel blends by 2016.1 This aggressive timetable moves the world s single largest petroleum consumer, the DOD, squarely into the alternative energies market. As the world s most prodigious fuel consumer, the DOD would likely drive segments of the aviation and motor fuels markets around the world to meet the demand for newly formulated alternative fuels and to convert existing fuel delivery systems to support the new market. Although conversion to alternative fuels can clearly lower the production of carbon dioxide, the risks that potential fuel spills pose to soil and groundwater are only now becoming clear
Hydrodynamic object recognition using pressure sensing
Hydrodynamic sensing is instrumental to fish and some amphibians. It also represents, for underwater vehicles, an alternative way of sensing the fluid environment when visual and acoustic sensing are limited. To assess the effectiveness of hydrodynamic sensing and gain insight into its capabilities and limitations, we investigated the forward and inverse problem of detection and identification, using the hydrodynamic pressure in the neighbourhood, of a stationary obstacle described using a general shape representation. Based on conformal mapping and a general normalization procedure, our obstacle representation accounts for all specific features of progressive perceptual hydrodynamic imaging reported experimentally. Size, location and shape are encoded separately. The shape representation rests upon an asymptotic series which embodies the progressive character of hydrodynamic imaging through pressure sensing. A dynamic filtering method is used to invert noisy nonlinear pressure signals for the shape parameters. The results highlight the dependence of the sensitivity of hydrodynamic sensing not only on the relative distance to the disturbance but also its bearing
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Interaction of barn owl leading edge serrations with freestream turbulence
The silent flight of barn owls is associated with wing and feather specialisations. Three special features are known: a serrated leading edge that is formed by free-standing barb tips which appears as a comb-like structure, a soft dorsal surface, and a fringed trailing edge. We used a model of the leading edge comb with 3D-curved serrations that was designed based on 3D micro-scans of rows of barbs from selected barn-owl feathers. The interaction of the flow with the serrations was measured with Particle-Image-Velocimetry in a flow channel at uniform steady inflow and was compared to the situation of inflow with freestream turbulence, generated from the turbulent wake of a cylinder placed upstream. In steady uniform flow, the serrations caused regular velocity streaks and a flow turning effect. When vortices of different size impacted the serrations, the serrations reduced the flow fluctuations downstream in each case, exemplified by a decreased root-mean-square value of the fluctuations in the wake of the serrations. This attenuation effect was stronger for the spanwise velocity component, leading to an overall flow homogenization. Our findings suggest that the serrations of the barn owl provide a passive flow control leading to reduced leading-edge noise when flying in turbulent environments
The mTOR kinase inhibitor Everolimus decreases S6 kinase phosphorylation but fails to reduce mutant huntingtin levels in brain and is not neuroprotective in the R6/2 mouse model of Huntington's disease
<p>Abstract</p> <p>Background</p> <p>Huntington's disease (HD) is a progressive neurodegenerative disorder caused by a CAG repeat expansion within the huntingtin gene. Mutant huntingtin protein misfolds and accumulates within neurons where it mediates its toxic effects. Promoting mutant huntingtin clearance by activating macroautophagy is one approach for treating Huntington's disease (HD). In this study, we evaluated the mTOR kinase inhibitor and macroautophagy promoting drug everolimus in the R6/2 mouse model of HD.</p> <p>Results</p> <p>Everolimus decreased phosphorylation of the mTOR target protein S6 kinase indicating brain penetration. However, everolimus did not activate brain macroautophagy as measured by LC3B Western blot analysis. Everolimus protected against early declines in motor performance; however, we found no evidence for neuroprotection as determined by brain pathology. In muscle but not brain, everolimus significantly decreased soluble mutant huntingtin levels.</p> <p>Conclusions</p> <p>Our data suggests that beneficial behavioral effects of everolimus in R6/2 mice result primarily from effects on muscle. Even though everolimus significantly modulated its target brain S6 kinase, this did not decrease mutant huntingtin levels or provide neuroprotection.</p
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