The Design of Pumpjets for Hydrodynamic Propulsion

A procedure for use in the design of a wake adapted pumpjet mounted on the aft end of a body of revolution is presented. To this end, a pumpjet is designed for the Akron airship. The propulsor mass flow is selected to minimize kinetic energy losses through the duct and in the discharge jet. The shaft speed and disk size are selected to satisfy specified limits of cavitation performance and to provide acceptable blade loading. The streamtubes which pass through a propulsor mounted on a tapered afterbody follow essentially conical surfaces. A method is provided for defining these surfaces as a function of shroud geometry, rotor head distribution, and the energy distribution of the ingested mass flow. The three-dimensional effects to which the conical flow subjects the cylindrical blade design sections are described and a technique is presented which permits incorporation of these effects in the blade design procedure

Double-slot antennas on extended hemispherical dielectric lenses

An investigation of the coupling efficiencies to a gaussian-beam of a double-slot antenna on a hyperhemispherical lens is presented. It is shown that both lenses couple equally well to an appropriate gaussian beam (about 80 percent). The radiation patterns of both lenses with a double-slot antenna are computed using the ray-tracing method. The experimental radiation patterns are presented and show close agreement to the theoretically computed patterns

A Role for Msh6 But Not Msh3 in Somatic Hypermutation and Class Switch Recombination

Somatic hypermutation is initiated by activation-induced cytidine deaminase (AID), and occurs in several kilobases of DNA around rearranged immunoglobulin variable (V) genes and switch (S) sites before constant genes. AID deaminates cytosine to uracil, which can produce mutations of C:G nucleotide pairs, and the mismatch repair protein Msh2 participates in generating substitutions of downstream A:T pairs. Msh2 is always found as a heterodimer with either Msh3 or Msh6, so it is important to know which one is involved. Therefore, we sequenced V and S regions from Msh3- and Msh6-deficient mice and compared mutations to those from wild-type mice. Msh6-deficient mice had fewer substitutions of A and T bases in both regions and reduced heavy chain class switching, whereas Msh3-deficient mice had normal antibody responses. This establishes a role for the Msh2-Msh6 heterodimer in hypermutation and switch recombination. When the positions of mutation were mapped, several focused peaks were found in Msh6−/− clones, whereas mutations were dispersed in Msh3−/− and wild-type clones. The peaks occurred at either G or C in WGCW motifs (W = A or T), indicating that C was mutated on both DNA strands. This suggests that AID has limited entry points into V and S regions in vivo, and subsequent mutation requires Msh2-Msh6 and DNA polymerase

Carbon Monoxide in type II supernovae

Infrared spectra of two type II supernovae 6 months after explosion are presented. The spectra exhibit a strong similarity to the observations of SN 1987A and other type II SNe at comparable epochs. The continuum can be fitted with a cool black body and the hydrogen lines have emissivities that are approximately those of a Case B recombination spectrum. The data extend far enough into the thermal region to detect emission by the first overtone of carbon monoxide. The molecular emission is modeled and compared with that in the spectra of SN 1987A. It is found that the flux in the CO first overtone is comparable to that found in SN 1987A. We argue that Carbon Monoxide forms in the ejecta of all type II SNe during the first year after explosion.Comment: 6 pages, 6 figures, accepted for publications in A&

Bayesian Optimised Collection Strategies for Fatigue Testing : Constant Life Testing

This paper presents a statistical framework enabling optimal sampling and robust analysis of fatigue data. We create protocols using Bayesian maximum entropy sampling, which build on the staircase and step methods, removing the requirement of prior knowledge of the fatigue strength distribution for data collection. Results show improved sampling efficiency and parameter estimation over the conventional approaches. Statistical methods for distinguishing between distribution types highlight the role of the protocol in model distinction. Experimental validation of the above work is performed, showing the applicability of the methods in laboratory testing.Comment: 25 pages, 12 figures + 1 SI figur