Theoretical and experimental study of a new method for prediction of profile drag of airfoil sections

Theoretical and experimental studies are described which were conducted for the purpose of developing a new generalized method for the prediction of profile drag of single component airfoil sections with sharp trailing edges. This method aims at solution for the flow in the wake from the airfoil trailing edge to the large distance in the downstream direction; the profile drag of the given airfoil section can then easily be obtained from the momentum balance once the shape of velocity profile at a large distance from the airfoil trailing edge has been computed. Computer program subroutines have been developed for the computation of the profile drag and flow in the airfoil wake on CDC6600 computer. The required inputs to the computer program consist of free stream conditions and the characteristics of the boundary layers at the airfoil trailing edge or at the point of incipient separation in the neighborhood of airfoil trailing edge. The method described is quite generalized and hence can be extended to the solution of the profile drag for multi-component airfoil sections

Studies on the comparative biology of Aphanomyces invadans

Aphanomyces invadans Willoughby et al, 1995 (as A. invaderis) is the recently-named Oomycete fungus that has been shown to be involved in EUS (epizootic ulcerative syndrome), a highly damaging disease of wild and cultured, Asian freshwater and estuarine fishes. The present study shows that A. invadans is the only species, out of a number of isolates from EUS-affected areas in Thailand, that is capable of sustained growth in snakehead fish muscle tissue and reproducing EUS lesions, and is therefore pathognomic to the disease. A. invadans is characterised, and distinguished from the saprophytic isolates, by means of: growth at various temperatures; growth on different media; level of extracellular enzymes produced; susceptibility to various chemicals; aspects of zoospore and germling behaviour; ultrastructure; immunocytochemistry; protein and carbohydrate electrophoresis banding patterns; lectin and polyclonal antibody binding characteristics by means of Western blot analysis; biochemical fingerprinting using pyrolysis mass spectra (PyMS); and molecular studies involving random amplification of polymorphic DNA (RAPD). A. invadans is shown to be indistinguishable from pathogenic Aphanomyces isolates from two other fish diseases, namely Japanese mycotic granulomatosis (MG) and Australian red spot disease (RSD) using the techniques described above. RAPD analyses, in particular, showed that a wide ränge of EUS, MG and RSD isolates are not only conspecific, but probably constitute a single genetic clone. This strongly suggests that it is A. invadans, and not any other biological aetiology, that has spread across Asia causing ulcerative disease in fish. It is recommended that the name A. invadans is used to describe all EUS, MG and RSD pathogenic isolates. This work also shows that Aphanomyces isolates obtained from outbreaks of ulcerative mycosis (UM) of American menhaden, are distinct from A. invadans, and more similar to the saprophytic fungus Aphanomyces laevis. It is conjectured that the invasive UM pathogen has not been studied and that this may show greater similarity to A. invadans. In comparison to the other species tested, A. invadans is most similar to the crayfish plague fungus. Aphanomyces astaci, although A. invadans is shown to be unable to infect noble crayfish {Astacus astacus). Snakeheads {Channa striata) are shown to produce antibodies in response to infection by A. invadans, a finding which may have implications for the possible future development of vaccines. A. invadans is shown to be culturally and ultrastructurally less robust, and more susceptible to chemical treatment, than other saprolegniacean fungi tested, indicating that strategic water treatments, before fish are infected, should be a relatively effective means of control. It is argued that the culturally-fastidious nature of A. invadans could also indicate an inability to compete with natural saprophytes, that may act to restrict it to a pathogenic lifestyle. Possible adaptations of zoospores to pathogenicity include particular chemotactic behaviour; a capability for limited polyplanetism in the presence of a nutrient background, indirect germination, and a form of abbreviated life-cycle. An usually thin zoospore cyst wall, that appears to lack much of the encystment vesicle-derived material apparent on other saprolegniaceans, is believed to have some significance to the ecology of A. invadans, although what this may be is undetermined. Despite the obvious ability of A. invadans to degenerate muscle tissue in fish, cultures showed relatively low production of extracellular enzymes using agar diffusion techniques, indicating that protease activity may be induced. A. invadans zoospores and cysts' have distinctive lectin-binding characteristics, and of particular interest is their ability to cross-react with monoclonal antibodies raised against Phytophthora cinnamomi, a non-saprolegniacean Oomycete. Other features of A. invadans that may provide useful species-specific taxonomic markers include temperature-growth characters, a putative K body organelle with a distinctive substructure, specific electrophoretic bands, pyrolysis mass spectra (used here for the first time in Oomycete systematics), and RAPD fingerprints. Polyclonal antibodies (PAbs) proved very non-specific, but peroxidase

On some aspects of the noise propagation from supersonic aircraft

The noise problem associated with an aircraft flying at supersonic speeds is shown to depend primarily on the shock wave pattern formed by the aircraft. The noise intensity received by a ground observer from a supersonic aircraft flying at high as well as low altitudes, is shown to be high although it is of a transient nature. Continues

Rapidly Converging Activity Expansions For Representing The Thermodynamic Properties Of Fluid Systems: Gases, Non-Electrolyte Solutions, Weak And Strong Electrolyte Solutions

For dilute gases and non-electrolyte solutions in the McMillan–Mayer standard state, an activity expansion due to Mayer has great advantages over the normal concentration expansion (virial equation) for strongly associating species. For weakly interacting systems, both approaches are suitable. The activity expansion eliminates the need to differentiate between strong “chemical” interactions and weak “physical” interactions since the same equation is used in each situation. The equation has been modified to represent electrolyte solutions in the McMillan–Mayer standard state by requiring that it be consistent with the Debye–Hückel and higher order limiting laws for strong electrolytes and that it be equivalent to a chemical association model for weak electrolytes. The result is a compact equation which contains no arbitrary ion-size parameters and which does not require the classification of an electrolyte as strong or weak. For 2:2 electrolytes, the equation gives a very good fit to the anomalous low concentration region. For practical thermodynamic calculations, similar equations for molal activity coefficients are proposed; good fits of the data are obtained

Measurements of a single lateral jet injected into swirling crossflow

Experiments have been conducted to document the time-mean and turbulent flowfield of a deflected turbulent jet in a confined swirling crossflow. The jet-to-crossflow velocity ratio of 4 was investigated with swirler vane angles of 45 and 70 degrees. A six-orientation single hot-wire technique was used to measure the velocities and turbulence properties of the flow. In addition, a five-hole pitot probe technique was used to measure the time-mean velocities or verification purposes. The results are presented in the form of r-x plots to aid visualization of the fully three-dimensional flowfield. The swirl in the crossflow intensified the local velocity at the location of the injected jet, which effectively reduced the jet-to-crossflow velocity ratio. This caused the trajectory of the injected jet to follow the path of the local flow direction of the crossflow, and reduce its penetration into the crossflow. The time-mean velocity measurements using the hot-wire corresponded to pitot-probe data obtained in identical flow conditions. Turbulence stress data show the same trends as previous swirl flow data without lateral injection. The lateral jet was found to deflect the axis of the precessing vortex core

Tissue Doppler imaging following paediatric cardiac surgery : early patterns of change and relationship to outcome

In this study, tissue Doppler imaging (TDI) was used to assess changes in ventricular function following repair of congenital heart defects. The relationship between TDI indices, myocardial injury and clinical outcome was explored. Forty-five children were studied; 35 withcardiac lesions and 10 controls. TDI was performed preoperatively, on admission to paediatric intensive care unit (PICU) and day 1. Regional myocardial Doppler signals were acquired from the right ventricle (RV), left ventricle (LV) and septum. TDI indices included: peak systolicvelocities, isovolumetric velocities (IVV) and isovolumetric acceleration (IVA). Preoperatively, bi-ventricular TDI velocities in the study groupwere reduced compared with normal controls. Postoperatively, RV velocities were significantly reduced and this persisted to day-1 (PreOp vs. PICU and day-1: 7.7+2.2 vs. 3.4+1.0, P < 0.0001 and 3.55+1.29, P < 0.0001). LV velocities initially declined but recovered towards baseline by day-1 (PreOp vs. PICU: 5.31+1.50 vs. 3.51+1.23, P < 0.0001). Isovolumetric parameters in all regions were reduced throughout the postoperative period. Troponin-I release correlated with longer X-clamp times (r=0.82, P < 0.0001) and reduced RV velocities (r=0.42, P=0.028). Reduced pre- and postoperative LV velocities correlated with longer ventilation (PreOp: r=0.54, P=0.002; PostOp: r=0.42, P=0.026). This study identified reduced postoperative RV velocities correlated with myocardial injury while reduced LV TDI correlated with longer postoperative ventilation

Higher order Schrodinger and Hartree-Fock equations

The domain of validity of the higher-order Schrodinger equations is analyzed for harmonic-oscillator and Coulomb potentials as typical examples. Then the Cauchy theory for higher-order Hartree-Fock equations with bounded and Coulomb potentials is developed. Finally, the existence of associated ground states for the odd-order equations is proved. This renders these quantum equations relevant for physics.Comment: 19 pages, to appear in J. Math. Phy

Proteomic analysis of the EhV-86 virion

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

DNA cruciform arms nucleate through a correlated but non-synchronous cooperative mechanism

Inverted repeat (IR) sequences in DNA can form non-canonical cruciform structures to relieve torsional stress. We use Monte Carlo simulations of a recently developed coarse-grained model of DNA to demonstrate that the nucleation of a cruciform can proceed through a cooperative mechanism. Firstly, a twist-induced denaturation bubble must diffuse so that its midpoint is near the centre of symmetry of the IR sequence. Secondly, bubble fluctuations must be large enough to allow one of the arms to form a small number of hairpin bonds. Once the first arm is partially formed, the second arm can rapidly grow to a similar size. Because bubbles can twist back on themselves, they need considerably fewer bases to resolve torsional stress than the final cruciform state does. The initially stabilised cruciform therefore continues to grow, which typically proceeds synchronously, reminiscent of the S-type mechanism of cruciform formation. By using umbrella sampling techniques we calculate, for different temperatures and superhelical densities, the free energy as a function of the number of bonds in each cruciform along the correlated but non-synchronous nucleation pathways we observed in direct simulations.Comment: 12 pages main paper + 11 pages supplementary dat

Large Scale Structures a Gradient Lines: the case of the Trkal Flow

A specific asymptotic expansion at large Reynolds numbers (R)for the long wavelength perturbation of a non stationary anisotropic helical solution of the force less Navier-Stokes equations (Trkal solutions) is effectively constructed of the Beltrami type terms through multi scaling analysis. The asymptotic procedure is proved to be valid for one specific value of the scaling parameter,namely for the square root of the Reynolds number (R).As a result large scale structures arise as gradient lines of the energy determined by the initial conditions for two anisotropic Beltrami flows of the same helicity.The same intitial conditions determine the boundaries of the vortex-velocity tubes, containing both streamlines and vortex linesComment: 27 pages, 2 figure