Reel safety brake

A braking apparatus is described for a tape transport device having two stacked coaxial reels and feelers mounted in proximity to the reels for sensing the tape being wound on each reel. A device is mounted in proximity to adjacent central hubs of the reels to a simultaneously, frictionally engage both hubs and brake both reels. A mechanical actuator is coupled to both feelers and to the brake device. The brake means comprises a pair of rubber shoulders that extend in opposite directions relative to a common axis, and turns about the axis in response to either of the feelers

Overview: Exobiology in solar system exploration

In Aug. 1988, the NASA Ames Research Center held a three-day symposium in Sunnyvale, California, to discuss the subject of exobiology in the context of exploration of the solar system. Leading authorities in exobiology presented invited papers and assisted in setting future goals. The goals they set were as follows: (1) review relevant knowledge learned from planetary exploration programs; (2) detail some of the information that is yet to be obtained; (3) describe future missions and how exobiologists, as well as other scientists, can participate; and (4) recommend specific ways exobiology questions can be addressed on future exploration missions. These goals are in agreement with those of the Solar System Exploration Committee (SSEC) of the NASA Advisory Council. Formed in 1980 to respond to the planetary exploration strategies set forth by the Space Science Board of the National Academy of Sciences' Committee on Planetary and Lunar Exploration (COMPLEX), the SSEC's main function is to review the entire planetary program. The committee formulated a long-term plan (within a constrained budget) that would ensure a vital, exciting, and scientifically valuable effort through the turn of the century. The SSEC's goals include the following: determining the origin, evolution, and present state of the solar system; understanding Earth through comparative planetology studies; and revealing the relationship between the chemical and physical evolution of the solar system and the appearance of life. The SSEC's goals are consistent with the over-arching goal of NASA's Exobiology Program, which provides the critical framework and support for basic research. The research is divided into the following four elements: (1) cosmic evolution of the biogenic compounds; (2) prebiotic evolution; (3) origin and early evolution of life; and (4) evolution of advanced life

Modulated voltage metastable ionization detector

The output current from a metastable ionization detector (MID) is applied to a modulation voltage circuit. An adjustment is made to balance out the background current, and an output current, above background, is applied to an input of a strip chart recorder. For low level concentrations, i.e., low detected output current, the ionization potential will be at a maximum and the metastable ionization detector will operate at its most sensitive level. When the detected current from the metastable ionization detector increases above a predetermined threshold level, a voltage control circuit is activated which turns on a high voltage transistor which acts to reduce the ionization potential. The ionization potential applied to the metastable ionization detector is then varied so as to maintain the detected signal level constant. The variation in ionization potential is now related to the concentration of the constituent and a representative amplitude is applied to another input of said strip chart recorder

Soil moisture by extraction and gas chromatography

To determine moisture content of soils rapidly and conveniently extract moisture with methanol and determine water content of methanol extract by gas chromatography. Moisture content of sample is calculated from weight of water and methanol in aliquot and weight of methanol added to sample

Changing plant subsistence in Prehistoric Southwest Britain: archaeobotanical and anthracological evidence from the South Cadbury Environs Project

The thesis investigates changing agricultural practices and wood use across a landscape from the Neolithic to Romano-British period, through charred archaeobotanical remains: crops, weeds, wild herbaceous plants and wood charcoal, recovered during survey test-pitting and excavation as part of the multi-site, South Cadbury Environs Project (SCEP), South Somerset, England. Alongside abundant barley grain, the major wheat crop shifts from emmer to spelt in the Late Bronze Age, with the appearance of free threshing wheat towards the end of the Romano-British period. The quantity of crop remains increase in the Middle Iron Age contexts accompanied by new crop types including pulses. The crop composition is investigated through consideration of both the crops themselves and the physical and ecological characteristics of the accompanying weeds and wild taxa. The majority of crop-rich SCEP samples represent waste from the later stages of crop processing. Ecological assessment of the crop weeds from the fine sieving by-products of glume wheats points to differences between localities which are suggested to indicate a shift from Bronze Age spring sowing of glume wheat to autumn sowing in the Middle Iron Age, particularly at the limestone-scarp site of Sheepslait. The majority of the wood charcoal recovered from the SCEP samples seem to represent waste from fuel use. Across the landscape as a whole, the wood taxa utilised remained relatively stable throughout the periods, representing oak and ash lowland mixed deciduous woodland, woodland edge and hedgerow species. Ecological investigation of the wood taxa shows differences related to location. A marked temporal change in the taxa from the Sigwells area may indicate the sourcing of wood for particular tasks

Determination of wind from NIMBUS 6 satellite sounding data

Objective methods of computing upper level and surface wind fields from NIMBUS 6 satellite sounding data are developed. These methods are evaluated by comparing satellite derived and rawinsonde wind fields on gridded constant pressure charts in four geographical regions. Satellite-derived and hourly observed surface wind fields are compared. Results indicate that the best satellite-derived wind on constant pressure charts is a geostrophic wind derived from highly smoothed fields of geopotential height. Satellite-derived winds computed in this manner and rawinsonde winds show similar circulation patterns except in areas of small height gradients. Magnitudes of the standard deviation of the differences between satellite derived and rawinsonde wind speeds range from approximately 3 to 12 m/sec on constant pressure charts and peak at the jet stream level. Fields of satellite-derived surface wind computed with the logarithmic wind law agree well with fields of observed surface wind in most regions. Magnitudes of the standard deviation of the differences in surface wind speed range from approximately 2 to 4 m/sec, and satellite derived surface winds are able to depict flow across a cold front and around a low pressure center

Neutral Hydrogen Mapping of Virgo Cluster Blue Compact Dwarf Galaxies

A new installment of neutral hydrogen mappings of Blue Compact Dwarf galaxies, as defined by optical morphology, in and near the Virgo cluster is presented. The primary motivation was to search for outlying clouds of HI as potential interactive triggers of the enhanced star formation, and therefore the mapped galaxies were selected for large HI} mass, large optical diameter, and large velocity profile width. Approximately half the sample proved to have one or more small, low column density star-free companion clouds, either detached or appearing as an appendage in our maps, at resolution of order 4 kpc. Comparison is made to a sample of similarly mapped field BCD galaxies drawn from the literature; however, the Virgo cluster sample of mapped BCDs is still too small for conclusive comparisons to be made. We found, on the one hand, little or no evidence for ram pressure stripping nor, on the other, for extremely extended low column density HI envelopes. The HI rotation curves in most cases rise approximately linearly, and slowly, as far out as we can trace the gas.Comment: To appear in AJ, Dec. 200

A comparative analysis of rawinsonde and NIMBUS 6 and TIROS N satellite profile data

Comparisons are made between rawinsonde and satellite profiles in seven areas for a wide range of surface and weather conditions. Variables considered include temperature, dewpoint temperature, thickness, precipitable water, lapse rate of temperature, stability, geopotential height, mixing ratio, wind direction, wind speed, and kinematic parameters, including vorticity and the advection of vorticity and temperature. In addition, comparisons are made in the form of cross sections and synoptic fields for selected variables. Sounding data from the NIMBUS 6 and TIROS N satellites were used. Geostrophic wind computed from smoothed geopotential heights provided large scale flow patterns that agreed well with the rawinsonde wind fields. Surface wind patterns as well as magnitudes computed by use of the log law to extrapolate wind to a height of 10 m agreed with observations. Results of this study demonstrate rather conclusively that satellite profile data can be used to determine characteristics of large scale systems but that small scale features, such as frontal zones, cannot yet be resolved

Possible thermal metamorphism on the C, G, B, and F asteroids detected from their reflectance spectra in comparison with carbonaceous chondrites

Reflectance spectra (0.3-2.6μm) of the C, G, B, and F asteroids and carbonaceous chondrites are compared in detail. Mixing calculations of 13 carbonaceous chondrite powders including three unusual CI/CM meteorites are done to characterize reflectance spectra of the 23 C, G, B, and F asteroids. Similar calculations are done with Murchison (CM2) samples heated at 400-1000℃. Both of two sets of calculations show that the C, G, B, and F asteroids may contain a significant amount of thermally metamorphosed materials. Comparison of ultraviolet absorption strengths between 160 C, G, B, and F asteroids and 21 carbonaceous chondrite powders suggests that surface minerals of most of those asteroids are thermally metamorphosed at temperatures around 600-1000℃