Rubidium-strontium age and elemental and isotopic abundances of some trace elements in lunar samples     

Murthy VR  Schmitt RA  Rey P 《Science (New York, N.Y.)》1970,167(3918):476-479

Data on six lunar crystalline rocks give an apparent Rb-Sr isochron age of 4.42 +/- 0.24 x 10(9) years (95 percent confidence limits) and initial (87)Sr/(86)Sr ratio similar to that in a basaltic achondrite. Relationships between K, Rb, Sr, and Ba and depletion of Eu in these samples point to plagioclase separation from the melts that produced these rocks. The abundance of (157)Gd in the three lunar samples is similar to terrestrial abundance within < 0.2 percent, thus setting a limit of < 6 x 10(15) neutrons per square centimeter for the integrated thermal neutron flux difference between lunar and terrestrial materials.  相似文献   

A Lunar Occultation of the Dust-Scattering Halo Around GX 5-1 Observed with ROSAT     

Predehl P  Schmitt JH  Snowden SL  Trümper J 《Science (New York, N.Y.)》1992,257(5072):935-937

The x-ray source GX 5-1 in the galactic bulge has been observed with the position-sensitive proportional counter onboard the R?ntgen satellite (ROSAT) during and after a lunar occultation. Extended emission around the source was unambiguously discovered while the central source was behind the lunar rim. This emission is interpreted as a dust-scattering halo around GX 5-1 that has a fractional intensity of 28 percent, implying a grain column density between GX 5-1 and Earth of approximately 3 x 10(10) per square centimeter. The halo derived from imaging during the ROSAT all-sky survey is identical to that obtained from the lunar occultation, thus demonstrating that the ROSAT x-ray mirror scattering has not changed as compared with the mirror properties as measured in preflight calibrations.  相似文献   

THE FIRST FREE-LIVING FRESHWATER JELLYFISH FROM SOUTH AMERICA     

Porter CE  Schmitt WL 《Science (New York, N.Y.)》1942,96(2501):515-516

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Spatial Variability of Turbulent Mixing in the Abyssal Ocean   总被引：3，自引：0，他引：3  

KL Polzin  JM Toole  JR Ledwell  RW Schmitt 《Science (New York, N.Y.)》1997,276(5309):93-96

Ocean microstructure data show that turbulent mixing in the deep Brazil Basin of the South Atlantic Ocean is weak at all depths above smooth abyssal plains and the South American Continental Rise. The diapycnal diffusivity there was estimated to be less than or approximately equal to 0.1 x 10(-4) meters squared per second. In contrast, mixing rates are large throughout the water column above the rough Mid-Atlantic Ridge, and the diffusivity deduced for the bottom-most 150 meters exceeds 5 x 10(-4) meters squared per second. Such patterns in vertical mixing imply that abyssal circulations have complex spatial structures that are linked to the underlying bathymetry.  相似文献   

Medieval sciences     

Schmitt CB 《Science (New York, N.Y.)》1979,204(4392):493

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Discovery of microwave emission from four nearby solar-type g stars     

Güdel M  Schmitt JH  Benz AO 《Science (New York, N.Y.)》1994,265(5174):933-935

Radio waves from the sun were detected 50 years ago, but the microwave detection of other single solar-type stars has remained a challenge. Here, the discovery of four solar-type radio stars is reported. These "solar twin" G stars are radio sources up to 3000 times stronger than the quiet sun. The microwaves most likely originate from a large number of relativistic electrons, possibly produced along with coronal heating, a process that is not understood. Two of the stars are younger than the sun and rotate more rapidly; the dynamo process in the stellar interior is therefore presumably more vigorous, resulting in enhanced coronal activity. One of the detections, however, is an old, metal-deficient G dwarf.  相似文献   

A VACUUM TUBE METHOD OF TEMPERATURE CONTROL     

Schmitt FO  Schmitt OH 《Science (New York, N.Y.)》1931,73(1889):289-290

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AN UNRECORDED CAUSE OF "RED WATER"     

Schmitt WL 《Science (New York, N.Y.)》1943,98(2532):39-40

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A Spatially Resolved X-ray Image of a Star Like the Sun     

Schmitt JH  Kürster M 《Science (New York, N.Y.)》1993,262(5131):215-218

Observations made with the x-ray satellite ROSAT (Roentgen Satellite) have produced the first spatially resolved x-ray image of a corona around a star like our sun. The star is the secondary in the eclipsing binary system alpha Coronae Borealis (CrB), which consists of one star of spectral type A0V and one of type G5V. The x-ray light curve of alpha CrB shows a total x-ray eclipse during secondary optical minimum, with the G star behind the A star. The totality of the eclipse demonstrates that the A-type component in alpha CrB is x-ray dark and that the x-ray flux arises exclusively from the later-type companion. The x-ray eclipse ingress and egress are highly asymmetric compared with the optical eclipse, indicating a highly asymmetric x-ray intensity distribution on the surface of the G star. From a detailed modeling of the ingress and egress of the x-ray light curve, an eclipse map of the G star was constructed by a method based on an optimization by simulated annealing.  相似文献   

Surface ices and the atmospheric composition of pluto     

Owen TC  Roush TL  Cruikshank DP  Elliot JL  Young LA  de Bergh C  Schmitt B  Geballe TR  Brown RH  Bartholomew MJ 《Science (New York, N.Y.)》1993,261(5122):745-748

Observations of the 1.4- to 2.4-micrometer spectrum of Pluto reveal absorptions of carbon monoxide and nitrogen ices and confirm the presence of solid methane. Frozen nitrogen is more abundant than the other two ices by a factor of about 50; gaseous nitrogen must therefore be the major atmospheric constituent. The absence of carbon dioxide absorptions is one of several differences between the spectra of Pluto and Triton in this region. Both worlds carry information about the composition of the solar nebula and the processes by which icy planetesimals formed.  相似文献