Venus: mass, gravity field, atmosphere, and ionosphere as measured by the mariner 10 dual-frequency radio system     

Howard HT  Tyler GL  Fjeldbo G  Kliore AJ  Levy GS  Brunn DL  Dickinson R  Edelson RE  Martin WL  Postal RB  Seidel B  Sesplaukis TT  Shirley DL  Stelzried CT  Sweetnam DN  Zygielbaum AI  Esposito PB  Anderson JD  Shapiro II  Reasenberg RD 《Science (New York, N.Y.)》1974,183(4131):1297-1301

Analysis of the Doppler tracking data near encounter yields a value for the ratio of the mass of the sun to that of Venus of 408,523.9 +/- 1.2, which is in good agreement with prior determinations based on data from Mariner 2 and Mariner 5. Preliminary analysis indicates that the magnitudes of the fractional differences in the principal moments of inertia of Venus are no larger than 10(-4), given that the effects of gravity-field harmonics higher than the second are negligible. Additional analysis is needed to determine the influence of the higher order harmonics on this bound. Four distinct temperature inversions exist at altitudes of 56, 58, 61, and 63 kilometers. The X-band signal was much more rapidly attenuated than the S-band signal and disappeared completely at 52-kilometer altitude. The nightside ionosphere consists of two layers having a peak density of 10(4) electrons per cubic centimeter at altitudes of 140 and 120 kilometers. The dayside ionosphere has a peak density of 3 X 10(5) electrons per cubic centimeter at an altitude of 145 kilometers. The electron number density observed at higher altitudes was ten times less than that observed by Mariner 5, and no strong evidence for a well-defined plasmapause was found.  相似文献   

Variability in the yield of benzophenanthridine alkaloids in wildcrafted vs cultivated bloodroot (Sanguinaria canadensis L.)     

Graf TN  Levine KE  Andrews ME  Perlmutter JM  Nielsen SJ  Davis JM  Wani MC  Oberlies NH 《Journal of agricultural and food chemistry》2007,55(4):1205-1211

Populations of bloodroot [Sanguinaria canadensis L. (Papaveraceae)] are found throughout the eastern forests of North America, with particular abundance in the southern Appalachian Mountains. Increasingly, it is finding use in Europe as a nonantibiotic animal feed supplement to promote weight gain. As efforts to cultivate this herb are underway, there is a need to understand the effect of agronomic permutations on both the dry mass rhizome yield and the yield of benzophenanthridine alkaloids. Month-to-month variability of the concentration of the alkaloids sanguinarine and chelerythrine in both cultivated and wildcrafted bloodroot was examined. The alkaloid yield was consistently higher, but more variable, in wildcrafted plants. On average, cultivated rhizomes were both larger and more consistently sized than those that were wildcrafted. The concentration of a suite of trace elements was measured in soil that was collected concomitantly with each plant accession. Differences in element profiles were compared against alkaloid yields.  相似文献