Fast Radio Bursts: Constraints on the Dispersing Medium

Fast radio bursts appear to exhibit large dispersion measures, typically exceeding any expected galactic interstellar contribution, especially along the moderate to high-galactic-latitude directions in which such events have been most often observed. The dispersions have been therefore interpreted as extragalactic, leading to the inference that the sources of the bursts are at Gpc distances. This then implies that the bursts are extremely energetic events, originating from quite small volumes (due to the millisecond burst durations). To circumvent the energetic difficulties, Loeb, Shvartzvald, & Maoz (2014) propose that the bursts are produced by flares near the surfaces of M stars or contact binaries within a local volume of the galaxy. Most of the dispersion would then occur in the overlying stellar coronae. With the dispersion concentrated in a relatively high density region, the quadratic dispersion approximation breaks down as the plasma frequency is comparable to (although less than) the propagation frequency. The observed dispersion curves are closely quadratic, however, consistent with a low density medium, ruling out this model. Because any model invoking local galactic sources would require a concentrated high density dispersing medium, it appears highly likely that the dispersions occur in the intergalactic medium. This medium, probably containing most of the baryon content of the universe, is expected to be highly structured on large scales. Hot gas within clusters and especially groups of galaxies may contribute significantly to the observed dispersion. Optical and X-ray observations, including redshifts and combined with cosmological dispersion measures, can probe the distribution of the IGM and determine how much of it lies outside the X-ray luminous concentrations seen in clusters and groups

Radiowave scattering and ultra-long-baseline interferometry

Interstellar scattering can irretrievably blur the images of compact radio sources when examined with extremely high resolution. Because of this effect, diffraction limited observations of extragalactic sources with an Earth-Moon baseline will only be possible at frequencies above about 7 GHz, in which case the resolution will be approx. = to or less than 20 microarcsec. Preliminary observations to determine the potential usefulness of such resolving power are discussed. The simplest of these would consist of a search for interstellar scintillations in compact sources at 10 GHz, which would provide an effective resolution about equal to that of an Earth-Moon baseline at this frequency. Also important in this context is the development of very long baseline interferometry in near-Earth orbit, as any ultra high resolution observations, if appropriate, would require intermediate baselines for mapping

Memory systems for signal generating photoelectric image detectors

Digital systems are discussed which have the capacity to handle the large amounts of information contained in a typical image. It was used with a high gain pulse counting television camera tube, with a silicon target image detector and an analog to digital converter between the detector and the memory

Micro-Perspectives on 19th-century Russian Living Standards

Russia, livings standards, economic history

Special Pyrheliometer Shroud Development

To insure that the insolation values accurately represent the input power to a power conversion unit the field of view (FOV) of the concentrator aperture and the insolation radiometer must be the same. The calculations, implementation, and results of this approach are covered. Three instruments were used to measure the insolation: an Eppley Normal Incidence Radiometer (NIP) and two versions of the kendall cavity radiometer. The shrouds used to limit the FOV of the radiometers were designed to simulate the FOV of the PDC-1 concentrater with the cold water cavity calorimeter. This technique of matching the FOV of an insolation radiometer to the FOV of a specific concentrater and receiver aperture appears to be both practical and effective. The efficiency of a power conversion unit will be too low if the insolation is measured with a radiometer which has a FOV which is larger than the FOV of the concentrator

Micro-Perspectives on Living Standards in Nineteenth-Century Russia

In recent years economic historians have turned new attention to questions about standards of living in pre-revolutionary Russia. However, most of the studies to date have focused on a narrow range of measures for predominantly urban areas. We expand on the existing literature with a micro-level analysis, which employs a broader set of measures of wellbeing for a small rural region in central Russia. Our findings suggest that living standards were improving over the nineteenth century, even in such seemingly less dynamic rural areas. Income and consumption patterns, human capital development, and the distribution of resources in the countryside were more variegated than a ‘subsistence’ approach has typically allowed. The micro-level context presented here suggests that state and local institutions should be emphasized in future analyses of rural living standards in pre-Soviet Russia.Russia, livings standards, economic history

Parabolic Dish Concentrator (PDC-1)

The design, construction, and installation of the Parabolic Dish Concentrator, Type 1 (PDC-1) has been one of the most significant JPL concentrator projects because of the knowledge gained about this type of concentrator and the development of design, testing, and analysis procedures which are applicable to all solar concentrator projects. The need for these procedures was more clearly understood during the testing period which started with the prototype panel evaluation and ended with the performance characterization of the completed concentrator. For each phase of the test program, practical test procedures were required and these procedures defined the mathematical analysis which was essential for successful concentrator development. The concentrator performance appears to be limited only by the distortions resulting from thermal gradients through the reflecting panels. Simple optical testing can be extremely effective, but comprehensive mechanical and optical analysis is essential for cost effective solar concentrator development