Reduction of acoustic disturbances in the test section of supersonic wind tunnels by laminarizing their nozzle and test section wall boundary layers by means of suction

The feasibility of quiet, suction laminarized, high Reynolds number (Re) supersonic wind tunnel nozzles was studied. According to nozzle wall boundary layer development and stability studies, relatively weak area suction can prevent amplified nozzle wall TS (Tollmien-Schlichting) boundary layer oscillations. Stronger suction is needed in and shortly upstream of the supersonic concave curvature nozzle area to avoid transition due to amplified TG (Taylor-Goertler) vortices. To control TG instability, moderately rapid and slow expansion nozzles require smaller total suction rates than rapid expansion nozzles, at the cost of larger nozzle length Re and increased TS disturbances. Test section mean flow irregularities can be minimized with suction through longitudinal or highly swept slots (swept behind local Mach cone) as well as finely perforated surfaces. Longitudinal slot suction is optimized when the suction-induced crossflow velocity increases linearly with surface distance from the slot attachment line toward the slot (through suitable slot geometry). Suction in supersonic blowdown tunnels may be operated by one or several individual vacuum spheres

Program of Research in Laminar Flow Control in the JIAFS at NASA Langley Research Center

At high Reynolds numbers, the performance of a low drag suction LFC airplane is essentially controlled by the induced drag and the turbulent friction drag of the nonlaminarized area. The question then arises as to how the airplane cruise lift to drag ratio (L/D) sub cruise) cruise increases with increasing extent of laminar flow 0 sub lam./0 sub total (0 = airplane wetted area). In particular, the question arises as to the airplane performance in the optimum case with all laminar flow over the airplane wetted area. Design approaches of all laminar flow LFC airplanes which optimize the airplane range . R = eta sub ov times (L/D) times H times lambda n(W sub 0/W sub E) are considered

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 $z$ direction. In an extensive series of numerical $N$-body simulations with a high spatial resolution, we were able to scan in detail the space of key parameters (the initial disk thickness $z_0$, the Toomre parameter $Q$, and the ratio of dark halo mass to disk mass $M_{\rm h} / M_{\rm d}$). We revealed three distinct mechanisms of disk heating in the $z$ 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

Economics of renewable energy expansion and security of supply: A dynamic simulation of the German electricity market

We explore the impact of renewable energy under free market conditions on the security of energy supply using data for the German electricity market. We design a fundamental electricity market model, where renewable energy capacity is not driven by expansion goals, but is dynamically modeled as an economically-driven investment option. Furthermore, we analyze the economics of five policy scenarios designed to secure both electricity supply and renewable energy expansion. Our analysis demonstrates that renewable energy expansion leads to conventional power plant shut-downs (due to economic losses) and, as a result, to energy shortages. We find that the application of a fixed feed-in tariff mechanism for renewable energy (i.e. a fixed payment for the provided energy) is an appropriate instrument to simultaneously achieve renewable energy expansion and uninterrupted energy supply. However, when internalizing the external costs of electricity generation, the scenario of a free market for renewable energy together with subsidies for conventional power plants becomes the most cost efficient option

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