An interferometric technique for B/A measurement

An isentropic phase method is described for measuringin vitro the acoustic nonlinearity parameterB/A of several aqueous buffers, protein solutions, lipid oils, and emulsions. The technique relies upon the use of an acoustic interferometer to measure the small changes in sound speed that accompany a rapid hydrostaticpressure change of between one and two atmospheres. Average accuracies of 0.85% are attainable with this method

Aggregation Behavior of a Willow Flea Beetle, \u3ci\u3eAltica Subplicata\u3c/i\u3e (Coleoptera: Chrysomelidae)

This study examined the aggregation behavior of a specialist insect herbivore, Altica subplicata (Coleoptera: Chrysomelidae), on its host plant, Salix cordata. Mark-recapture experiments were conducted in patches of S. cordata growing along the shores of Lake Huron. Beetles aggregated on individual host plants, but did not aggregate in larger areas containing many host plants. Plants colonized by marked beetles had significantly higher abundances of unmarked beetles than did plants that were not colonized by marked beetles. Experimental manipulations of the number of beetles present on plants showed that colonization rates by marked beetles were higher on plants with conspecifics than on plants which had all beetles removed the previous day. The sex of beetles, however, did not influence colonization behavior; both male and female beetles colonized plants regardless of the sex of beetles already present on plants. These results are discussed with respect to possible explanations for aggregation, and the role of aggregation and movement in influencing insect distributions

Measurement of pressure and assessment of cavitation for a 22.5-kHz intra-arterial angioplasty device

This study was performed to understand better the mechanisms of action of an (22.5 kHz) ultrasonic wire catheter device used to remove atheromatous plaque in diseased blood vessels (ultrasonic angioplasty). During a clinical procedure, the wire acts as an acoustic waveguide to transfer acoustic energy from a generator outside the body to the ball tip of the wire, which is inserted in the blood vessel. The acoustic field radiated by the vibrating ball tip (1.5- to 3.0-mm diameter), was mapped in a relatively large (600 L) water tank and compared to the field from a well-characterized simple source. A dipolelike radiation pattern due to the translating ball tip was observed. At low power settings, standing wave effects in a smaller cylindrical volume (200-mm diameter, 350-mm height), which was used to simulate anthropometric dimensions, increase relative to the larger tank measurements. The standing wave ratio is dependent upon the pc characteristics of the medium and the dimensions of the volume, rather than on the absorption at this frequency. At high power-settings of the device, cavitation at the tip of the wire was measured using a 20-MHz passive cavitation detection scheme

Facilities for meteorological research at NASA Goddard/Wallops Flight Facility

The technical characteristics of the Atmospheric Sciences Research Facility, the improvements being made to the instrumentation there which will enhance its usefulness in atmospheric research, and several of the on-going research programs are described. Among the area of atmospheric research discussed are clouds and precipitation, lightning, ozone, wind, and storms. Meteorological instruments including Doppler radar, spectrophotometers, and ozone sensors are mentioned. Atmospheric research relevant to aircraft design and COMSTAR communication satellites is briefly discussed

Dipolar coordinates

Derivation of dipolar coordinates and basic vector formulas in dipolar coordinate system - application to magnetohydrodynamic problem

Evolution of a Primordial Black Hole Population

We reconsider in this work the effects of an energy absorption term in the evolution of primordial black holes (hereafter PBHs) in the several epochs of the Universe. A critical mass is introduced as a boundary between the accreting and evaporating regimes of the PBHs. We show that the growth of PBHs is negligible in the Radiation-dominated Era due to scarcity of energy density supply from the expanding background, in agreement with a previous analysis by Carr and Hawking, but that nevertheless the absorption term is large enough for black holes above the critical mass to preclude their evaporation until the universe has cooled sufficiently. The effects of PBH motion are also discussed: the Doppler effect may give rise to energy accretion in black-holes with large peculiar motions relative to background. We discuss how cosmological constraints are modified by the introduction of the critical mass since that PBHs above it do not disturb the CMBR. We show that there is a large range of admissible masses for PBHs above the critical mass but well below the cosmological horizon. Finally we outline a minimal kinetic formalism, solved in some limiting cases, to deal with more complicated cases of PBH populationsComment: RevTex file, 8 pp., 3 .ps figures available upon request from [email protected]

Black Hole Relics and Inflation: Limits on Blue Perturbation Spectra

Blue primordial power spectra have spectral index $n>1$ and arise naturally in the recently proposed hybrid inflationary scenario. An observational upper limit on {\em n} is derived by normalizing the spectrum at the quadrupole scale and considering the possible overproduction of Planck mass relics formed in the final stage of primordial black hole evaporation. In the inflationary Universe with the maximum reheating temperature compatible with the observed quadrupole anisotropy, the upper limit is $n=1.4$, but it is slightly weaker for lower reheat temperatures. This limit applies over 57 decades of mass and is therefore insensitive to cosmic variance and any gravitational wave contribution to the quadrupole anisotropy. It is also independent of the dark matter content of the Universe and therefore the bias parameter. In some circumstances, there may be an extended dust-like phase between the end of inflation and reheating. In this case, primordial black holes form more abundantly and the upper limit is $n=1.3$.Comment: 26 pages, LaTex, 9 figures available upon request, FERMILAB Pub-94/109-

Study of growth parameters for refractory carbide single crystals Quarterly status report no. 6, 1 Jun. - 1 Sep. 1965

Growth parameters for refractory tantalum carbide single crystal

An aerodynamic comparison of blown and mechanical high lift airfoils

Short takeoff and landing (STOL) performance utilizing a circulation control airfoil was successfully demonstrated on the A-6 CCW (circulation control wing). Controlled flight at speeds as slow as 67 knots was demonstrated. Takeoff ground run and liftoff speed reductions in excess of 40 and 20 percent respectively were achieved. Landing ground roll and approach speeds were similarly reduced. The technology demonstrated was intended to be useable on modern high performance aircraft. STOL performance would be achieved through the combination of a 2-D vectored nozzle and a circulation control type of high lift system. The primary objective of this demonstration was to attain A-6 CCW magnitude reductions in takeoff and landing flight speed and ground distance requirements using practical bleed flow rates from a modern turbofan engine for the blown flap system. Also, cruise performance could not be reduced by the wing high lift system. The A-6 was again selected as the optimum demonstration vehicle. The procedure and findings of the study to select the optimum high lift wing design are documented. Some findings of a supercritical airfoil and a comparison of 2-D and 3-D results are also described