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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Concerning the meteoritic origin of the Puchezh-Katunki crater

Criticism of the works of Vardaniants (1961) and Goretskii (1962) regarding the origin of the Puchezh-Katunki crater, and development of a new hypothesis regarding this disturbance. Although Vardaniants defines the Puchezh-Katunki disturbance as a structure of explosive nature and assumes that the explosion originated as a consequence of accumulation of gases in the crystalline basement of the Russian platform, he lacks evidence to qualify this explosion as coming from a depth. Goretskii's tectonic-injection hypothesis attributes the formation of the disturbance to penetration of an intrusion of basic and ultrabasic rocks into the Paleozoic rocks of the platform. It is shown that, even if the intrusion were spread somewhere at depth, it could not account for the extent of the deformation in the disturbance. It is suggested that this disturbance is of meteoritic origin, since the structure and morphology of the region are similar to the sloping conical surface produced by an explosive meteor crater. The energy, mass, and size of the asteroid which could cause such a disturbance are estimated, and it is shown that the probability of the occurrence of an impact of this size is finite over geological time.

Firsov, L.↗
NASA NTRS1973

On the formation of the lunar mascons

A new mascon hypothesis is proposed which accounts for: (1) the existence of lunar mascons for more than 3 b.y., (2) the evidence for extensive volcanic activity from 3.7 to 3.2 b.y. ago, (3) the existence of negative gravity anomaly rings, (4) insufficient mare material in Mare Orientale, and (5) the lack of mascons associated with craters smaller than 200 km diameter. Moreover, it provides a simple mechanism for mass transfer into the basins. The hypothesis is based on the perturbations introduced into a spherically symmetric thermal evolution model of the moon by a giant impact.

Arkani-Hamed, J.↗
NASA NTRS1974

Seismic scattering and shallow structure of the moon in Oceanus Procellarum

Scattering in a high-Q medium has been the best hypothesis to date for explaining the observation of a long, reverberating train of waves in lunar seismographs. To test this hypothesis qualitatively, two experiments were devised which simulated this scattering and reproduced actual lunar seismographs. Pulses were propagated across a plate with grooves cut half-way through, and then were propagated along the edge of a plate with holes drilled within a skin depth of the edge. The seismographs of near impacts and moonquakes recorded by the Apollo 12 station in two frequency bands were studied. The impacts were those of S4B Saturn boosters and LM ascent stages. Interpretation of these data suggests the existence of a scattering layer 25 km thick with a Q of 5000. The density of the scatterers decreases with depth, suggesting that they are associated with cratering, or that they consist of cracks which anneal with depth.

Dainty, A. M.↗
NASA NTRS1974

The Hubble relation for nonstandard candles and the origin of the redshift of quasars

It is shown that the magnitude-log (redshift) relation for brightest quasars can have a slope different from the value expected for standard candles. The value of this slope depends on the luminosity function and its evolution. Therefore the difference of this slope from the expected value cannot be used as evidence against the cosmological origin of the redshift of the quasars. It is shown that the observed variation of the luminosity of the brightest objects with redshift is consistent with the cosmological hypothesis and that it agrees with (and perhaps could be used to complement) the luminosity function obtained from V/Vm analysis. It is also shown that the nonzero slope of the magnitude-log (redshift) relation rules out the local quasar hypothesis, where it is assumed that the sources are nearby (less than 500 Mpc), that the bulk of their redshift is intrinsic, and that there is no dependence on distance of the intrinsic properties of the sources.

Petrosian, V.↗
NASA NTRS1974

Nonstationary atmospheric boundary layer turbulence simulation

Report on a new and general technique for simulating atmospheric turbulence-like random processes which are statistically homogeneous along the horizontal and nonhomogeneous along the vertical. This technique is general in the sense that it can be used for a broad class of similar problems. Like the other presently available schemes, the techniques presented are based on the Dryden hypothesis and Taylor's frozen eddy hypothesis; however, they go a step further by utilizing certain self-similarity properties of the Dryden spectral density function which permits the development of height invariant filters. These filters are in turn used to generate vertically homogeneous (statistically) random processes from which turbulence at any specified level in the boundary layer can be simulated, thus facilitating the simulation of a nonstationary turbulence process along the flight path of an aircraft during take-off or landing.

Fichtl, G. H.↗
NASA NTRS1974

Starspots on flare stars

Sizes of starspots on flare stars can be derived from the author's convection-cell hypothesis. The sizes are in fair agreement with those observed on YY Gem, CC Eri, and BY Dra by Bopp and Evans (1973). The hypothesis predicts that periodic brightness variations due to starspots are restricted to stars brighter than a critical absolute visual magnitude. A convective model of a starspot on YY Gem has been computed, assuming that the missing flux is in the form of Alfven waves. It is found that the surface field must exceed 10,000 G, and is probably less than about 30,000 G. With a surface field of 20,000 G, the effective temperature of the spot is in the range from 1590 to 1890 K, depending on the field gradient. These figures are to be compared with an effective temperature of 2000 K estimated from observations by Bopp and Evans. Efficient dynamo action is shown to be a possible mechanism for generating such large surface fields. There is a possibility that tidal effects may influence starspot formation.

Mullan, D. J.↗
NASA NTRS1974

Arousal and hallucinatory activity under two isolation conditions

Experimental exploration of the hypothesis that soundproof-room and water-immersion isolation environments differ with respect to the variety of physiological responses and reported hallucinations they elicit. The results obtained support the hypothesis in regard to physiological responses only.

Levin, J.↗
NASA NTRS1975

Hot vibrating white dwarf models of pulsating X-ray sources

The hypothesis that pulsating X-ray sources could be vibrating white dwarfs is investigated. The masses are calculated for several white-dwarf models having various modes of vibration which have the observed eigenfrequencies of the Centaurus X-3 and the Hercules X-1 sources. If the hypothesis is correct, Cen X-3 is vibrating radially in the fundamental mode or not higher than the first two overtones, and its mass is in the range 0.7-1.2 solar masses. The Her X-1 source would be vibrating in a quadrupole P mode, and would have a mass in the range 1.1-1.25 solar masses.

Cameron, A. G. W.↗
NASA NTRS1975

Dynamics of lunar origin and orbital evolution

The considerable differences in bulk composition of the moon and the earth have led most investigators to favor the capture hypothesis of lunar origin. However, upon closer examination all forms of the hypothesis still seem much less plausible dynamically than formation by accretion, i.e., acquisition of the moon in many small pieces rather than as predominantly one body. Models of accretion do suggest that the proto-lunar matter had a significantly different history from the proto-earth matter. A better understanding of collisions is needed to infer the compositional consequences of this history. Recent work on the acceleration of the moon's orbit exacerbates the time scale problem of orbital evolution. However, it now is much clearer that the locus of tidal dissipation is in the oceans and hence that the solution to the time scale problem lies in differing oceanic configurations in the past.

Kaula, W. M.↗
NASA NTRS1976

Relative effectiveness of several simulated jet engine noise spectral treatments in reducing annoyance in a TV-viewing situation

An experiment was conducted in order to determine the relative effectiveness of several hypothetical jet engine noise treatments and to test hypothesis that speech interference, at least in part, mediates annoyance in a TV-viewing situation. Twenty-four subjects watched television in a simulated living room. Recorded jet flyover noises were presented in such a way as to create the illusion that aircraft were actually flying overhead. There were 27 stimuli (nine spectra at three overall levels) presented at an average rate of approximately one flight every 2 minutes. Subjects judged the annoyance value of individual stimuli using either a category rating method or magnitude estimation method in each of two 1-hour sessions. The spectral treatments most effective in reducing annoyance were at 1.6 Khz and 800 Hz, in that order. The degree of annoyance reduction resulting from all treatments was affected by the overall sound level of the stimuli, with the greatest reduction at the intermediate overall sound level, about 88 to 89 db(A), peak value. The results are interpreted as supporting the hypothesis that speech interference, at least in part, mediates annoyance with aircraft noise in a TV-viewing situation.

Gunn, W. J.↗
NASA NTRS1975

Empirical evidence concerning absorption lines and radiation pressure in quasi-stellar objects

Empirical spectroscopic evidence is examined for the hypothesis that radiation pressure having large gradients with wavelength plays a crucial role in maintaining patterns of redshift differences in quasars. Seventy-four absorption-line redshift systems in 32 quasars and two Seyfert galaxies are analyzed and discussed in terms of the radiation-pressure line-locking hypothesis. Redshift line ratios greater than unity are computed for each quasar and plotted as histograms. Ratios which may indicate line and edge locking are identified, including those of the C IV and Mg II doublets and those of the N III/C III, He II/O III, C II/He I, Ly-beta/H I, and H I/He I ionization edges.

Burbidge, E. M.↗
NASA NTRS1976

Shear strength of metal-sapphire contacts

The shear strength of polycrystalline Ag, Cu, Ni, and Fe contacts on clean (0001) sapphire has been studied in ultrahigh vacuum. Both clean metal surfaces and surfaces exposed to O2, Cl2, and C2H4 were used. The results indicate that there are two sources of strength of Al2O3-metal contacts: an intrinsic one that depends on the particular clean metal in contact with Al2O3 and an additional one due to intermediate films. The shear strength of the clean metal contacts correlated directly with the free energy of oxide formation for the lowest metal oxide, in accord with the hypothesis that a chemical bond is formed between metal cations and oxygen anions in the sapphire surface. Contacts formed by metals exposed to chlorine exhibited uniformly low shear strength indicative of van der Waals bonding between chlorinated metal surfaces and sapphire. Contacts formed by metals exposed to oxygen exhibited enhanced shear strength, in accord with the hypothesis that an intermediate oxide layer increases interfacial strength.

Pepper, S. V.↗
NASA NTRS1975

Mechanisms of radio-protection by catecholamines in the hamster /Mesocricetus auratus/

Experiments were conducted on normal and splenectomized male and female hamsters between 2 and 3 months old subjected to a whole-body exposure of 1000 or 2000 rads in a Co-60 source with a view toward evaluating their radio-protection by norepinephrine, isoproterenol, and phenylephrine. Vasoconstriction hypoxia mechanism of radio-protection is examined along with the hypothesis that isoproterenol protects by hypercalcemia-induced cell proliferation. Radiation experiment results are found to be consistent with the hypothesis that stimulation of alpha receptors results in radio-protection through a tissue hypoxia mechanism. Beta agonists seem to protect by a hypotensive-hypoxia mechanism. The catecholamines protect against the hematopoietic syndrome, but show no evidence of protection against the gastrointestinal syndrome.

Prewitt, R. L.↗
NASA NTRS1977

Concepts and methods for describing critical phenomena in fluids

The predictions of theoretical models for a critical-point phase transistion in fluids, namely the classical equation with third-degree critical isotherm, that with fifth-degree critical isotherm, and the lattice gas, are reviewed. The renormalization group theory of critical phenomena and the hypothesis of universality of critical behavior supported by this theory are discussed as well as the nature of gravity effects and how they affect cricital-region experimentation in fluids. The behavior of the thermodynamic properties and the correlation function is formulated in terms of scaling laws. The predictions of these scaling laws and of the hypothesis of universality of critical behavior are compared with experimental data for one-component fluids and it is indicated how the methods can be extended to describe critical phenomena in fluid mixtures.

Sengers, J. V.↗
NASA NTRS1977

Vertical and horizontal fluxes of ozone at the tropopause from the first year of GASP data

Ozone measurements taken from commercial airlines (GASP data) are used to estimate the vertical and horizontal fluxes of ozone near the tropopause. The annual average flux of O3 into the troposphere at 30 to 50 deg N is nearly the same as indirect estimates based on surface O3 data, thus supporting the hypothesis that the amount of ozone in the troposphere is essentially controlled by injection from the stratosphere. The present GASP estimates of the total flux of O3 into the troposphere verify the model results of Cunnold et al. (1975), although the distribution of flux between mean motions and diffusion is different and suggests that models with coarse horizontal resolution must continue to parameterize much vertical transport by diffusion coefficients. A significant variation in the east-west spatial autocorrelation function of O3 near the tropopause is found to be about 1900 km. Monthly estimates of the horizontal transient eddy flux of ozone are generally smaller than seasonal or yearly results based on ozonesonde data. This is perhaps because the present estimates are made over monthly periods to reduce the influence of correlation between the annual variations in ozone and meridional wind. The available data support the hypothesis that transient eddy fluxes of O3 have large longitudinal variations.

Nastrom, G. D.↗
NASA NTRS1973

Ionospheric scintillation studies

The diffracted field of a monochromatic plane wave was characterized by two complex correlation functions. For a Gaussian complex field, these quantities suffice to completely define the statistics of the field. Thus, one can in principle calculate the statistics of any measurable quantity in terms of the model parameters. The best data fits were achieved for intensity statistics derived under the Gaussian statistics hypothesis. The signal structure that achieved the best fit was nearly invariant with scintillation level and irregularity source (ionosphere or solar wind). It was characterized by the fact that more than 80% of the scattered signal power is in phase quadrature with the undeviated or coherent signal component. Thus, the Gaussian-statistics hypothesis is both convenient and accurate for channel modeling work.

Rino, C. L.↗
NASA NTRS1977

Search for correlation between asteroid families and classes

A correlation between membership in a dynamically defined asteroid family and membership in a given asteroid spectral class is sought. Examination of 10 families each with five or more classified members indicates a correlation for the 4 families whose existence is best established, and no correlation for the remaining 6 families. This conclusion supports the break-up hypothesis for the origin of some families, while not contradicting that hypothesis for any family.

Hansen, O.↗
NASA NTRS1977

Comments on the origins of the diffuse interstellar bands

Most work in recent years on the unidentified diffuse interstellar bands has been concentrated on the hypothesis that they are produced by some process in solid grains. We review that hypothesis and the arguments which support it, and find that diffuse band formation by certain classes of molecules should not yet be ruled out. Since several relevant observations have been made in the last four years, the observational data on the bands are reviewed. It would appear that these data are as consistent with molecular origins for the bands as with grain origins. Types of molecular transitions which give rise to 'diffuse' bands are described. These transitions can occur in relatively simple molecules composed of cosmically abundant elements and can produce broad, unresolvable profiles without destroying the molecule. New observations are suggested which could produce decisive evidence with which to determine whether the diffuse bands originate in grains, molecules, or both.

Smith, W. H.↗