350 research outputs found
Experimental Results for a Flapped Natural-laminar-flow Airfoil with High Lift/drag Ratio
Experimental results have been obtained for a flapped natural-laminar-flow airfoil, NLF(1)-0414F, in the Langley Low-Turbulence Pressure Tunnel. The tests were conducted over a Mach number range from 0.05 to 0.40 and a chord Reynolds number range from about 3.0 x 10(6) to 22.0 x 10(6). The airfoil was designed for 0.70 chord laminar flow on both surfaces at a lift coefficient of 0.40, a Reynolds number of 10.0 x 10(6), and a Mach number of 0.40. A 0.125 chord simple flap was incorporated in the design to increase the low-drag, lift-coefficient range. Results were also obtained for a 0.20 chord split-flap deflected 60 deg
Color van der Waals forces between heavy quarkonia in effective QCD
The perturbative renormalization group for light-front QCD Hamiltonian
produces a logarithmically rising interquark potential already in second order,
when all gluons are neglected. There is a question if this approach produces
also color van der Waals forces between heavy quarkonia and of what kind. This
article shows that such forces do exist and estimates their strength, with the
result that they are on the border of exclusion in naive approach, while more
advanced calculation is possible in QCD.Comment: 7 pages, elsart, bibliography in .bbl file, to be submitted to
Physics Letters
Short read Illumina data for the de novo assembly of a non-model snail species transcriptome (Radix balthica, Basommatophora, Pulmonata), and a comparison of assembler performance
Peer reviewe
Mechanisms of the Vertical Secular Heating of a Stellar Disk
We investigate the nonlinear growth stages of bending instability in stellar
disks with exponential radial density profiles.We found that the unstable modes
are global (the wavelengths are larger than the disk scale lengths) and that
the instability saturation level is much higher than that following from a
linear criterion. The instability saturation time scales are of the order of
one billion years or more. For this reason, the bending instability can play an
important role in the secular heating of a stellar disk in the direction.
In an extensive series of numerical -body simulations with a high spatial
resolution, we were able to scan in detail the space of key parameters (the
initial disk thickness , the Toomre parameter , and the ratio of dark
halo mass to disk mass ). We revealed three distinct
mechanisms of disk heating in the direction: bending instability of the
entire disk, bending instability of the bar, and heating on vertical
inhomogeneities in the distribution of stellar matter.Comment: 22 pages including 8 figures. To be published in Astronomy Letters
(v.29, 2003
Phylogeography of a Land Snail Suggests Trans-Mediterranean Neolithic Transport
Background: Fragmented distribution ranges of species with little active dispersal capacity raise the question about their place of origin and the processes and timing of either range fragmentation or dispersal. The peculiar distribution of the land snail Tudorella sulcata s. str. in Southern France, Sardinia and Algeria is such a challenging case. Methodology: Statistical phylogeographic analyses with mitochondrial COI and nuclear hsp70 haplotypes were used to answer the questions of the species' origin, sequence and timing of dispersal. The origin of the species was on Sardinia. Starting from there, a first expansion to Algeria and then to France took place. Abiotic and zoochorous dispersal could be excluded by considering the species' life style, leaving only anthropogenic translocation as parsimonious explanation. The geographic expansion could be dated to approximately 8,000 years before present with a 95% confidence interval of 10,000 to 3,000 years before present. Conclusions: This period coincides with the Neolithic expansion in the Western Mediterranean, suggesting a role of these settlers as vectors. Our findings thus propose that non-domesticated animals and plants may give hints on the direction and timing of early human expansion routes
Functional Complexity of the Axonal Growth Cone: A Proteomic Analysis
The growth cone, the tip of the emerging neurite, plays a crucial role in establishing the wiring of the developing nervous system. We performed an extensive proteomic analysis of axonal growth cones isolated from the brains of fetal Sprague-Dawley rats. Approximately 2000 proteins were identified at ≥99% confidence level. Using informatics, including functional annotation cluster and KEGG pathway analysis, we found great diversity of proteins involved in axonal pathfinding, cytoskeletal remodeling, vesicular traffic and carbohydrate metabolism, as expected. We also found a large and complex array of proteins involved in translation, protein folding, posttranslational processing, and proteasome/ubiquitination-dependent degradation. Immunofluorescence studies performed on hippocampal neurons in culture confirmed the presence in the axonal growth cone of proteins representative of these processes. These analyses also provide evidence for rough endoplasmic reticulum and reveal a reticular structure equipped with Golgi-like functions in the axonal growth cone. Furthermore, Western blot revealed the growth cone enrichment, relative to fetal brain homogenate, of some of the proteins involved in protein synthesis, folding and catabolism. Our study provides a resource for further research and amplifies the relatively recently developed concept that the axonal growth cone is equipped with proteins capable of performing a highly diverse range of functions
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A simple digital-optical system to improve accuracy of hot-wire measurements
A high precision traverse mechanism with micro-resolution was designed to capture accurately the velocity profile of the very thin turbulent attachment line on a swept body. To ensure that the traverse mechanism could position the hot wire reliably, a simple digital optical system was designed to check the performance of the traverse by measuring the displacement of the hot wire: a vertical displacement of 2.4µm was achievable and this could be further reduced to 0.6µm using micro-stepping. Due to the simplicity of the set-up it was equally useful for probe wall positioning and the velocity profiles captured clearly demonstrated that the optical set-up helped in resolving the near wall flow more accurately, regardless of the thinness of the boundary layer. The captured data compare well with the results from similar investigations, with arguably higher precision achieved
Spatial Stability of Incompressible Attachment-Line Flow
Linear stability analysis of incompressible attachment-line flow is presented within the spatial framework. The system of perturbation equations is solved using spectral collocation. This system has been solved in the past using the temporal approach and the current results are shown to be in excellent agreement with neutral temporal calculations. Results amenable to direct comparison with experiments are then presented for the case of zero suction. The global solution method utilized for solving the eigenproblem yields, aside from the well-understood primary mode, the full spectrum of least-damped waves. Of those, a new mode, well separated from the continuous spectrum is singled out and discussed. Further, relaxation of the condition of decaying perturbations in the far-field results in the appearance of sinusoidal modes akin to those found in the classical Orr-Sommerfeld problem. Finally, the continuous spectrum is demonstrated to be amenable to asymptotic analysis. Expressions are derived for the location, in parameter space, of the continuous spectrum, as well as for the limiting cases of practical interest. In the large Reynolds number limit the continuous spectrum is demonstrated to be identical to that of the Orr-Sommerfeld equation
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