Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A.

The nearby Supernova 1987A was accompanied by a burst of neutrino emission, which indicates that a compact object (a neutron star or black hole) was formed in the explosion. There has been no direct observation of this compact object. In this work, we observe the supernova remnant with JWST spectroscopy, finding narrow infrared emission lines of argon and sulfur. The line emission is spatially unresolved and blueshifted in velocity relative to the supernova rest frame. We interpret the lines as gas illuminated by a source of ionizing photons located close to the center of the expanding ejecta. Photoionization models show that the line ratios are consistent with ionization by a cooling neutron star or a pulsar wind nebula. The velocity shift could be evidence for a neutron star natal kick.

The reliability of digital images when used to assess burn wounds.

Sixty burn wounds were assessed in person. The same observer later assessed them using digital images of different sizes. The file sizes tested were 2.25, 5.5 and 9 MByte per image. There was good agreement between the diagnoses of burn depth made using the digital images and those made in person, with kappa scores of 0.53-0.60. There were no major differences between the three file sizes. The assessments made of the partial-thickness burns showed a lower rate of agreement between the in-person and the digital image assessments and for these burns the 2.25 MByte images were apparently as good or better than the larger images. There was little difference between the three file sizes in terms of observer confidence, usefulness of the location shot, or perceived image quality. There was no significant advantage in using larger file sizes to assess burn wounds.

Radio-frequency probe for bubble size and velocity measurements.

A radio frequency (rf) probe that can provide local void fraction and interface velocity measurements in a gas-liquid two-phase flow was developed. The probe response to bubble passage was investigated with single-bubble controlled experiments. For a fixed geometry, the probe response was dependent on the dielectric constant of the medium surrounding the probe tip (air or water) and on the frequency of the carrier signal supplied to the probe. Bubble lengths (< 1 cm) and average bubble approach velocities (< 160 cm/s) were independently measured by two light sources and detectors placed at a known distance from each other and sensing the passage of each bubble. By choosing a sensitive probe tip length of 2.75-3 mm, the rf probe output provided enough information to determine the bubble length and velocity. The results obtained by the two independent methods show reasonable agreement (+/-10%).

Optical probe for local void fraction and interface velocity measurements.

In view of the importance of obtaining unsteady local void fraction and interface velocities in liquid-vapor two-phase flows, an optical probe with a controlled tip geometry was developed and is described. In order to minimize the disturbances caused to the flow field by the presence of the probe, its dimensions have been miniaturized. The electronic and hydrodynamic responses of the probe were investigated experimentally. The probe was found to be sensitive to both the interface velocities and the phase present at the probe tip. A possible explanation for the behavior of the probe is presented. Within the velocity range checked and with proper calibration, the optical probe described can be used to determine both local void fractions and interface velocities.

Reflectance measurements on cavity radiators.

A knowledge of the emissivity of a cavity radiator may be deduced from reflectance measurements, but these may be difficult to make if the cavity has a small aperture and low reflectance. The use of a He-Ne laser as a source facilitates such measurements. Results are presented for one ceramic and three metallic cavities that have been used in photometric and spectroradoimetric standards work. An integrating sphere method appears more satisfactory than a goniophotometric approach.