Amplification of Reynolds number dependent processes by wave distortion

A system using a hot-wire transducer as an analog of a liquid droplet of propellant was employed to investigate the ingredients of the acoustic instability of liquid-propellant rocket engines. It was assumed that the combustion process was vaporization-limited and that the combustion chamber was acoustically similar to a closed-closed right-circular cylinder. Before studying the hot-wire closed-loop system (the analog system), a microphone closed-loop system, which used the response of a microphone as the source of a linear feedback exciting signal, was investigated to establish the characteristics of self-sustenance of acoustic fields. Self-sustained acoustic fields were found to occur only at resonant frequencies of the chamber. In the hot-wire closed-loop system, the response of hot-wire anemometer was used as the source of the feedback exciting signal. The self-sustained acoustic fields which developed in the system were always found to be harmonically distorted and to have as their fundamental frquency a resonant frequency for which there also existed a second resonant frequency which was approximately twice the fundamental frequency

Sound wave shear wave interaction with oblique shock fronts Final report, 1 Sep. 1967 - 31 Aug. 1968

Downstream flow field produced by interaction of plane sound waves or plane shear waves with oblique shock fron

Bose-Einstein condensation in a circular waveguide

We have produced Bose-Einstein condensates in a ring-shaped magnetic waveguide. The few-millimeter diameter non-zero bias ring is formed from a time-averaged quadrupole ring. Condensates which propagate around the ring make several revolutions within the time it takes for them to expand to fill the ring. The ring shape is ideally suited for studies of vorticity in a multiply-connected geometry and is promising as a rotation sensor.Comment: 4 pages, 4 figure

Obtaining wildlife values information for management: the wildlife attitudes and values scale (WAVS).

22 page

Department of Homeland Security Science and Technology Directorate: Developing Technology to Protect America

In response to a congressional mandate and in consultation with Department of Homeland Security's (DHS) Science and Technology Directorate (S&T), the National Academy conducted a review of S&T's effectiveness and efficiency in addressing homeland security needs. This review included a particular focus that identified any unnecessary duplication of effort, and opportunity costs arising from an emphasis on homeland security-related research. Under the direction of the National Academy Panel, the study team reviewed a wide variety of documents related to S&T and homeland security-related research in general. The team also conducted interviews with more than 200 individuals, including S&T officials and staff, officials from other DHS component agencies, other federal agencies engaged in homeland security-related research, and experts from outside government in science policy, homeland security-related research and other scientific fields.Key FindingsThe results of this effort indicated that S&T faces a significant challenge in marshaling the resources of multiple federal agencies to work together to develop a homeland security-related strategic plan for all agencies. Yet the importance of this role should not be underestimated. The very process of working across agencies to develop and align the federal homeland security research enterprise around a forward-focused plan is critical to ensuring that future efforts support a common vision and goals, and that the metrics by which to measure national progress, and make changes as needed, are in place

A Preliminary Report on the Frequency of Scrapie Susceptibility Alleles in Hampshire Sheep

Blood samples were collected from a total of 201 animals in five purebred Hampshire sheep flocks. DNA was isolated from the samples, and the protein-coding region of the prion protein gene was amplified using the polymerase chain reaction. The allelic frequencies of the prion protein codons 171 and 136 were determined. Results revealed that the codon 171 alleles Q, R, and H were present at frequencies of 72%, 27% and 1%, respectively. A subset of samples (n=48) was randomly selected for codon 136 genotyping. The codon 136 V allele, an allele not frequently observed in Suffolk sheep, was present in animals from three of five flocks at a frequency ranging from 7 to 33% of the animals tested within each flock. These data comprise the first report on the prevalence of scrapie susceptibility alleles in Hampshire sheep