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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Solar and galactic cosmic ray exposure of Surveyor 3 as determined from cosmogenic radionuclide measurements

The proton-produced Na-22 content of samples of Surveyor 3 TV camera, surface sampler scoop, and other components was determined by nondestructive gamma ray spectrometry. The contributions of the nine most prominent solar flares to Na-22 production were calculated to be 18 dpm/kg. The observed activity in the Surveyor 3 samples was 62 + or - dpm/kg. This indicates a galactic proton contribution of about 44 dpm/kg, which adjusted for spallation of Al gives a value of 42 dpm/kg. This is compared to measurements of 88 dpm/kg in the Lost City meteorite which had an orbit extending to 2.35 AU, with a 4 pi bombardment as compared to the 2 pi bombardment of the samples on the lunar surface. The agreement between Na-22 production in Surveyor 3 and the Lost City meteorite offers evidence that the galactic cosmic ray flux is almost the same at 1 Au and at 2.35 AU.

Rancitelli, L. A.↗
NASA NTRS1972

Cosmogenic radionuclides in the Allende and Murchison carbonaceous chondrites.

Measurements were made of Na-22, Al-26, Mn-54, and Co-60 produced by cosmic rays in five samples of the Allende C3 meteorite and in one specimen of Murchison (C2); Sc-46, V-48, Cr-51, and Co-57 were also measured in several of these samples. Comparison of observed Allende Co-60 activities with calculated neutron-capture production rates yields a depth scale for Allende that appears unambiguous to about 30-cm depth. Using this scale, the production of Al-26 is constant to a depth in excess of 30 cm, Na-22 activity increases 30% from near the surface of Allende to 20- to 30-cm depth, and Mn-54 production increases 50% over the same depth range.

Cressy, P. J., Jr.↗
NASA NTRS1972

Cosmogeneic radionuclides in the Havero meteorite.

An 87-gram sample of the Havero ureilite has been analyzed by nondestructive gamma-ray spectrometry. The results of the measurements, in dpm/kg at time of fall, are: Na-22, 71 plus or minus 3; Al-26, 43 plus or minus 3; Sc-46, 3.4 plus or minus 2.1; Mn-54, 35 plus or minus 6; Co-60, less than or equal to 0.7, 2 sigma limit. Havero has 77 plus or minus 14% of the Al-26 activity calculated for its chemical composition. When averaged with previously reported analyses of Goalpara and Novo Urei, ureilites as a class have 74 plus or minus 7% of their expected Al-26 activity. The depletion in Al-26 could be the coincidental result of identical 'shielding' effects in three meteorites of apparently very different preatmospheric sizes. Alternatively, ureilites may have been exposed to a lower cosmic-ray flux than that experienced by most chondrites, probably the result of characteristically different orbits.

Cressy, P. J., Jr.↗
NASA NTRS1975

Assessment of left ventricular ejection fraction by radionuclide angiography. Comparison to echocardiography and serial measurements in patients with myocardial infarction

Measurements of the left ventricular ejection fraction were compared in patients with previous myocardial infarctions. Left ventricular ejection fraction was measured by the radioisotopic method serially in patients early after an acute myocardial infarction and during the convalescence period. Ultrasound recordings were obtained utilizing a commercially available ultrasonoscope and a 1/9 cm transducer focused at 10 cm with a repetition rate of 1000 impulses per second. All recordings were made on a visicorder oscillography.

Schelbert, H. R.↗
NASA NTRS1976

Cross sections for He and Ne isotopes in natural Mg, Al, and Si, He isotopes in CaF2, Ar isotopes in natural Ca, and radionuclides in natural Al, Si, Ti, Cr, and stainless steel induced by 12- to 45-MeV protons

Stacks of thin Mg, Al, Si, Ca, CaF2, Ti, and stainless steel foils were bombarded in twelve irradiations by a variable energy cyclotron. Cross sections are reported for He and Ne in natural Mg, Al, and Si, and for He in CaF2, and for Ar in natural Ca, as determined from mass spectrometer analysis of the inert gases. In addition, cross sections of Na-22 in natural Al and Si, of V-48 in natural Ti, and of Cr-51, Mn-52, and Co-57 in stainless steel are reported. From these were deduced Cr-51 and Mn-52 cross sections in natural Cr.

Walton, J. R.↗
NASA NTRS1977

Lunar regolith dynamics based on analysis of the cosmogenic radionuclides Na-22, Al-26, and Mn-53

Depth profiles of Na-22 and Al-26 in the upper portions of five lunar cores are analyzed. From the analyses, it is concluded that the natural gardening processes on the lunar surface result in mixing of the regolith to a depth of 2-3 cm over a time period which is short compared with the half-life of Al-26 (0.73 m.y.). It is also concluded that the rotary drill processes which were used to obtain the deep drill samples generally resulted in loss and/or mixing of the upper portions of the cores. In contrast, the near-surface regions of the drive tube cores appear to have a well-preserved stratigraphy. Analysis of Mn-53 in samples of six lunar rocks helps substantiate the accuracy of age date estimates by other means, and provides definite information that the total lunar surface exposure of two of these rocks has occurred during a single surface event which continued to their collection.

Fruchter, J. S.↗
NASA NTRS1983

Radionuclide Counting Technique Measures Wind Velocity

Proposed technique for measuring wind velocity based on inverse-squarelaw variation of radioactive counting rates. In proposal, radioative source is deposited on bottom of light, hollow sphere and suspended by flexible wire over radiation counter, Anemometer based on this concept is self-contained, portable, yet not too fragile. Used for extended periods of time, even at remote, inhospitable and inaccessible sites.

Singh, J. J.↗
NASA NTRS1981

A radionuclide counting technique for measuring wind velocity

A technique for measuring wind velocities of meteorological interest is described. It is based on inverse-square-law variation of the counting rates as the radioactive source-to-counter distance is changed by wind drag on the source ball. Results of a feasibility study using a weak bismuth 207 radiation source and three Geiger-Muller radiation counters are reported. The use of the technique is not restricted to Martian or Mars-like environments. A description of the apparatus, typical results, and frequency response characteristics are included. A discussion of a double-pendulum arrangement is presented. Measurements reported herein indicate that the proposed technique may be suitable for measuring wind speeds up to 100 m/sec, which are either steady or whose rates of fluctuation are less than 1 kHz.

Singh, J. J.↗
NASA NTRS1982

Studies of lunar regolith dynamics using measurements of cosmogenic radionuclides in lunar rocks, soils and cores

The present investigation is concerned with two types of measurements. The first deals with the use of Al-26 to define regolith gardening processes which have occurred in the upper portion of the lunar cores that were collected both by the deep drilling and drive tube operations. The second portion of the study involves the use of Mn-53 and Al-26 concentrations to determine the surface exposure histories of individual rocks over the past ten million years. It is found that during the past two million years, 15011 has had a history of simple gardening with an accumulation rate of 2 cm/m.y. The Apollo 15 Station 2 boulder appears to have been in place for about five million years. The 'shadowed' soil (75237) shows a shielding effect of about 40%. The Apollo 16 Station 9 boulder appears to have been in place for about four million years and thus is apparently not related to the South Ray Crater event.

Fruchter, J. S.↗