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DOE OSTI2024

Decoupling of the onset of anharmonicity between a protein and its surface water around 200 K

The protein dynamical transition at ~200 K, where the biomolecule transforms from a harmonic, non-functional form to an anharmonic, functional state, has been thought to be slaved to the thermal activation of dynamics in its surface hydration water. Here, by selectively probing the dynamics of protein and hydration water using elastic neutron scattering and isotopic labeling, we found that the onset of anharmonicity in the two components around 200 K is decoupled. The one in protein is an intrinsic transition, whose characteristic temperature is independent of the instrumental resolution time, but varies with the biomolecular structure and the amount of hydration, while the one of water is merely a resolution effect.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1972

Lunar mass spectrometer test program

The procedures are described along with results obtained in a test program conducted to demonstrate the performance of a candidate lunar mass spectrometer. The instrument was designed to sample and measure gases believed to exist in the lunar atmosphere at the surface. The subject instrument consists of a cold cathode ion source, a small quadrupole mass analyzer and an off axis electron multiplier ion counting detector. The major program emphasis was placed on demonstrating instrument resolution, sensitivity and S/N ratio over the mass range 0-150 amu and over a partial pressure range from 10 to the minus 9th power to 10 to the minus 13th power torr. Ultrahigh vacuum tests were conducted and the minimum detectable partial pressure for neon, argon, krypton and xenon was successfully determined for the spectrometer using isotopes of these gases. With the exception of neon, the minimum detectable partial pressure is approximately 4 x 10 to the minus 14th power torr for the above gases.

Torney, F. L.↗

NASA NTRS1972

Dissipation mechanisms in a pair of solar-wind discontinuities.

A pair of sharp closely spaced discontinuities in the solar wind was recorded by the high time resolution instruments aboard Ogo 5 on Mar. 14, 1968. There is plasma turbulence within the double structure, and there appear to be small-amplitude hydromagnetic waves radiating from the discontinuities. The generation of the plasma turbulence is discussed in terms of magnetic drift waves. Although it seems probable that the surfaces are tangential discontinuities, arguments are also advanced that the double structure may represent the Petschek mechanism in which rapid field-line merging occurs between standing waves.

Unti, T. W. J.↗

NASA NTRS1974

Ultraviolet stellar spectrophotometry from a balloon platform

A 40 centimeter diameter aperture, balloon-borne telescope and ultraviolet spectrometer is described and selected scientific results are briefly reviewed. The general configuration of the 0.4 angstrom resolution instrument is shown and the utilization of servo-controlled secondary mirror, image dissector detector, and special mirror coatings are discussed. An outlook for astronomical research in the mid-ultraviolet from balloon-borne telescopes is presented together with future development plans for JSC's balloon-borne payload.

Kondo, Y.↗

NASA NTRS1976

A study of meteor spectroscopy and physics from earth-orbit: A preliminary survey into ultraviolet meteor spectra

Preliminary data required to extrapolate available meteor physics information (obtained in the photographic, visual and near ultraviolet spectral regions) into the middle and far ultraviolet are presented. Wavelength tables, telluric attenuation factors, meteor rates, and telluric airglow data are summarized in the context of near-earth observation vehicle parameters using moderate to low spectral resolution instrumentation. Considerable attenuation is given to the problem of meteor excitation temperatures since these are required to predict the strength of UV features. Relative line intensities are computed for an assumed chondritic composition. Features of greatest predicted intensities, the major problems in meteor physics, detectability of UV meteor events, complications of spacecraft motion, and UV instrumentation options are summarized.

Meisel, D. D.↗

NASA NTRS1978

Rice University observations of the galactic center

The most sensitive of the four balloon fight observations of the galactic center made by Rice University was conducted in 1974 from Rio Cuarto, Argentina at a float altitude of 4 mbar. The count rate spectrum of the observed background and the energy spectrum of the galactic center region are discussed. The detector used consists of a 6 inch Nal(T 1ambda) central detector collimated to approximately 15 deg FWHM by a Nal(T lamdba) anticoincidence shield. The shield in at least two interaction mean free paths thick at all gamma ray energies. The instrumental resolution is approximately 11% FWHM at 662 keV. Pulses from the central detector are analyzed by two 256 channel PHA's covering the energy range approximately 20 keV to approximately 12 MeV. The detector is equatorially mounted and pointed by command from the ground. Observations are made by measuring source and background alternately for 10 minute periods. Background is measured by rotating the detector 180 deg about the azimuthal axis.

Meegan, C. A.↗

NASA NTRS1977

The use of Landsat for monitoring water parameters in the coastal zone

Landsats 1 and 2 have been successful in detecting and quantifying suspended sediment and several other important parameters in the coastal zone, including chlorophyll, particles, alpha (light transmission), tidal conditions, acid and sewage dumps, and in some instances oil spills. When chlorophyll a is present in detectable quantities, however, it is shown to interfere with the measurement of sediment. The Landsat banding problem impairs the instrument resolution and places a requirement on the sampling program to collect surface data from a sufficiently large area. A sampling method which satisfies this condition is demonstrated.

Bowker, D. E.↗

NASA NTRS1977

Theoretical brightness temperature profiles of atmospheric pure H2 rotational quadrupole lines - Jupiter and Uranus

With the advent of high-resolution instruments and their use high above most of the telluric water vapor, the hydrogen pure rotational quadrupole lines at 28, 17, and 12 microns from the atmospheres of the outer planets may be observed. Best values for the line strengths, pressure-broadening coefficients, diffusion constants, and pressure shifts for these rotational transitions are calculated. The collisionally narrowed Galatry profile is used to calculate brightness temperature line profiles for these H2 transitions for the outer planets, Jupiter and Uranus. The effects of the H2 rotational-translational continuum and of the NH3 v2 band are also included.

Goorvitch, D.↗

NASA NTRS1978

The ISEE 1 and 2 Medium Energy Particles Experiment

The Medium Energy Particles Experiment (MEPE) on board ISEE 1 and 2 consists of the WIM instrument on ISEE 1 and the KED instrument on ISEE 2. Both instruments employ solid-state detectors and magnetic analysis to measure the angular, energy, and intensity distributions of protons (ions) above 24 keV and electrons above 20 keV. The WIM instrument also includes a composition measurement employing Delta E-by-E and time-of-flight techniques. Three-parameter analysis is performed above 250 keV/nucleon, and single parameter analysis is performed above 125 keV/nucleon for helium through oxygen. Three-dimensional angular distributions are obtained through the use of a scan platform in the WIM instrument and multiple detector heads in the KED instrument. A variety of operational modes are used to optimize data collection from both instruments. Resolutions up to 128 channels in energy, 192 samples over the unit sphere in angle, and 0.095 sec in time are available.

Williams, D. J.↗

NASA NTRS1979

Intensities and N2 collision-broadening coefficients measured for selected H2O absorption lines between 715 and 732 nm

Intensities and N2 collision-broadening coefficients are measured for 62 water vapor absorption lines between 715 and 732 nm potentially applicable to laser remote sensing of atmospheric water vapor. Absolute line strengths and widths were determined from spectra corrected for instrument resolution, air-path absorption and Lorentz and Doppler broadening for pure water vapor and water vapor-nitrogen mixtures in a multipass absorption cell with a base path length of 25 m (White cell). Line strengths are observed to range from 4 x 10 to the -25th to 4 x 10 to the -23rd kayser/molecule per sq cm, and collision broadening coefficients are found to be approximately equal to 0.1 kayser/atm.

Wilkerson, T. D.↗

NASA NTRS1979

An investigation of a mathematical model for atmospheric absorption spectra

A computer program that calculates absorption spectra for slant paths through the atmosphere is described. The program uses an efficient convolution technique (Romberg integration) to simulate instrument resolution effects. A brief information analysis is performed on a set of calculated spectra to illustrate how such techniques may be used to explore the quality of the information in a spectrum.

Niple, E. R.↗

NASA NTRS1981

IUE detection of bursts of H Ly-alpha emission from Saturn

A new investigation is reported of the potential sources of Ly-alpha emission in a series of observations of the Saturnian system carried out between January and July 1980 using the short wavelength spectrograph of the IUE Observatory. It is noted that north-south maps of the Ly-alpha emission across the planet disk show pronounced spatial asymmetries in emission brightness. These asymmetries vary to a marked extent on a time scale of days and are interpreted as bursts of Ly-alpha emission of as much as 1 kR brightness averaged over a 6 x 10 arcsec area, above a constant planetary emission level of 700-800 R. In fact, the Ly-alpha emission peaks manifest themselves as essentially point source features in these data; it is pointed out that if the emitting region is smaller than the 6 x 10 arcsec instrumental resolution, the surface brightness must be proportionally higher.

Clarke, J. T.↗

NASA NTRS1983

Infrared molecular emissions from comets

The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued.

Weaver, H. A.↗

NASA NTRS1982

Measurements of the properties of solar wind plasma relevant to studies of its coronal sources

Interplanetary measurements of the speeds, densities, abundances, and charge states of solar wind ions are diagnostic of conditions in the source region of the solar wind. The absolute values of the mass, momentum, and energy fluxes in the solar wind are not known to an accuracy of 20%. The principal limitations on the absolute accuracies of observations of solar wind protons and alpha particles arise from uncertain instrument calibrations, from the methods used to reduce the data, and from sampling biases. Sampling biases are very important in studies of alpha particles. Instrumental resolution and measurement ambiguities are additional major problems for the observation of ions heavier than helium. Progress in overcoming some of these measurement inadequacies is reviewed.

Neugebauer, M.↗

NASA NTRS1983

Absolute band strengths of halocarbons F-11 and F-12 in the 8- to 16-micron region

The infrared strengths of three vibrational band systems of halocarbon F-11 and four vibrational band systems of halocarbon F-12 in the 'atmospheric window' between 8 and 16 microns were measured at 296 + or - 1 K using a Fourier transform infrared spectrometer. These results were obtained at a maximum instrumental resolution of 0.06/cm. The measurements of the total infrared band strengths for F-11 and F-12 would indicate approximately 17% and 5% greater absorbance, respectively, than those strengths used in recent greenhouse warming calculations by Ramanathan (1975), Wang et al. (1976), and Lacis et al. (1981), and consequently, a corresponding increase in the possible atmospheric warming effect by these halocarbons.

Kagann, R. H.↗

NASA NTRS1983

Interstellar absorption lines in the spectrum of 3C 273

Absorption lines near the rest wavelengths of the Si IV doublet (wavelengths 1393.76, 1402.77) with equivalent widths 533 and 235 mA are reported in the spectrum of QSO 3C 273. The profiles show the nature of hot gas along a high-latitude (b = 64 deg) line of sight through our entire halo. The lines have full width at half-maxima of 100 km/s, compared to an instrumental resolution of 35 km/s, are centered at zero velocity, and show no evidence for components with equivalent widths greater than 50 mA at an absolute value of v greater than 75 km/s. The absence of high peculiar velocities is consistent with published spectra of halo gas over shorter pathlengths. The implications of this result are discussed, with particular reference to the possible connection between galactic halos and QSO absorption lines, for which C IV and Si IV usually have a broader velocity range.

York, D. G.↗

NASA NTRS1984

Infrared molecular emissions from comets

Weaver, H. A.↗

NASA NTRS1984

Detection of far-infrared forbidden O I and forbidden O III emission from the galaxy M82

Observations in M82 of the lowest-lying transitions of neutral and doubly ionized oxygen, forbidden O I 63.2 microns and forbidden O III 88.4 microns, which have wavelengths at which the extinction toward M82 is negligible, are reported. For O III, the +220 km/s velocity of the line center with respect to the local standard of rest, the 300 km/s intrinsic line width, and the asymmetry of the profile are consistent with the systemic velocity and rotational broadening seen in other ionic lines in the nucleus of M82. The fraction of oxygen that is present in doubly ionized form, indicates that the ionization state is similar to that found in H II regions in the disk of the Milky Way Galaxy. The central velocity of the O I line is +130 km/s, and no broadening in excess of instrumental resolution is seen. This result appears to rule out association of this emission with the periphery of the central H II region.

Watson, D. M.↗