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901.
A. Aparicio G. Bertelli C. Chiosi J. M. Garcia-Pelayo 《Astrophysics and Space Science》1990,169(1-2):37-39
We present preliminary results of CCD BV photometry of the old open cluster King 2. The values obtained for the main parameters are:E(B-V)=0.31, (m-M)0=13.78, metal content approximately solar, and age 6×109 yr. From the comparison with synthetic colour-mgnitude diagrams generated by models with overshoot we try to answer the question whether or not convective elements generated in the core can penetrate into the surrounding stable zone (separated by a discontinuity of molecular weight).Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
902.
Chondrules were extracted from a disaggregated sample of the Allegan meteorite. Individual chondrules were examined with apparatus incorporating two orthogonal binocular microscopes, and their three major axes measured. Maximum chondrule diameters ranged from 0.15 to 2.75 mm with a peak in distribution between 0.35 and 0.75 mm. The chondrule size distribution was found not to conform to Rosin's law. The chondrules were found to depart from sphericity by only small amounts. The authors still believe that the melting of nebula dust-ball agglomerates by some high-energy event was the most probable mechanism for the formation of chondrules. 相似文献
903.
904.
G. Thuillier G. Schmidtke C. Erhardt B. Nikutowski A. I. Shapiro C. Bolduc J. Lean N. Krivova P. Charbonneau G. Cessateur M. Haberreiter S. Melo V. Delouille B. Mampaey K. L. Yeo W. Schmutz 《Solar physics》2014,289(12):4433-4452
Onboard the International Space Station (ISS), two instruments are observing the solar spectral irradiance (SSI) at wavelengths from 16 to 2900 nm. Although the ISS platform orientation generally precludes pointing at the Sun more than 10?–?14 days per month, in November/December 2012 a continuous period of measurements was obtained by implementing an ISS ‘bridging’ maneuver. This enabled observations to be made of the solar spectral irradiance (SSI) during a complete solar rotation. We present these measurements, which quantify the impact of active regions on SSI, and compare them with data simultaneously gathered from other platforms, and with models of spectral irradiance variability. Our analysis demonstrates that the instruments onboard the ISS have the capability to measure SSI variations consistent with other instruments in space. A comparison among all available SSI measurements during November–December 2012 in absolute units with reconstructions using solar proxies and observed solar activity features is presented and discussed in terms of accuracy. 相似文献
905.
906.
Joseph A. Burns 《Icarus》1981,45(2):263-274
An extended photometric time series in the J and K bands of Neptune has a complex appearance which appears to require the simultaneous presence of three periodicities plus related harmonics in the (J-K) color. The most apparent of the fundamental periods is N1 = 17.73 hr. The two others are at N2 = 18.56 and N3 = 18.29 hr and may be the result of amplitude modulation of a previously reported period of 18.42 hr. We interpret the presence of multiple periodicity as indicating that distinct systems of zonal winds exist on the planet. We argue that these wind systems are probably confined to moderate or high latitudes on the basis of recent omages of the planet taken in a spectral region of strong CH4 absorption, and, by analogy to the zonal wind systems that exist in Jupiter's atmosphere, deduce a period of rotation for the body of the planet of 18.2 ± 0.4 hr. Zonal wind contrasts of up to 109 m sec?1 are implied in the atmosphere of Neptune by these observations. 相似文献
907.
The loss rate of fast electrons (with an energy much higher than the energy of the plasma electron thermal motion), when they
leave a magnetic cavern during a disturbance of the magnetic field azimuthal symmetry, is studied. The cases of point and
volume sources of fast particles have been considered. The plasma density in the cavern is supposed to be low, so that collisions
of fast electrons with plasma particles can be neglected. The effect of the electric field on particle motion is neglected
because it is assumed that the electric charge particles outgoing from the cavern is compensated by the counter current of
plasma conductivity electrons. The dependence of the loss value on the harmonic number and the amplitude of the cavern boundary
radius disturbance has been obtained. 相似文献
908.
909.
Geochronology of anthropogenic pollutants in riparian wetland sediments of the Lippe River (Germany) 总被引:2,自引:0,他引:2
S. Heim J. Schwarzbauer A. Kronimus R. Littke C. Woda A. Mangini 《Organic Geochemistry》2004,35(11-12):1409
Anthropogenic pollutants were determined in a dated sediment core, collected from a riparian wetland of the Lippe River (Ruhr district, Germany). The historical trend in heavy metals, polycyclic aromatic hydrocarbons, organochlorines, polychlorinated biphenyls and linear alkylbenzenes as well as more recent contaminants such as industrial additives, organotins, synthetic musks, methyltriclosan and some other compounds were determined for the time period between 1930 and 1986. Emission sources, information on technical production and usage, as well as on the individual pollution pathways, with appropriate environmental stability, were considered in the interpretation of the sediment contamination over the past 50 years.Contaminants were analysed and interpreted according to two different criteria: (a) the origin of the main contaminants as related to mining and industrial activities as well as municipal sewage and agricultural effluents and (b) the pollution history. Due to a significant appearance of formerly missing contaminants in sediments deposited since 1970, we suggest classifying contaminants as either common (predating 1970) or modern (postdating 1970).In summary, the study provided a comprehensive reconstruction of the pollution history of the Lippe River system. 相似文献
910.
An analysis is made of the oil pollution of the Ob river waters using a long-term (1993–2013) hydrochemical monitoring of oil fields in Khanty-Mansi Autonomous Okrug. Contents of oil hydrocarbons (OHC) were determined in 4277 samples from the main Ob channel, and in 7076 samples from its anabranches by using infrared spectrometry. An increase in MAC (0.05 mg/dm3) was observed in 28% of the samples from the main channel, and in 32% from the anabranches. The total percentage of samples with an extremely high (> 50 MAC) and high (30–50 MAC) pollution level made up 0.3% of the samples for the anabranches, and 0.1% for the main channel. Maximum pollution was revealed in the eastern part of Okrug, from its eastern boundary to the mouth of the Trom’egan river which is associated with a considerable number of accidents on the pipelines within the Nizhnevartovskii district. The upper and lower quantiles in the most polluted anabranches, Pasl and Bagras, are 0.03–01.7 and 0.032–0.16 mg/dm3, respectively, whereas in the main Ob channel they vary from 0.022 to 0.065 mg/dm3 (0.4–1.2 MAC). The methods of geoinformatics and mathematical statistics were used to assess a dependence of OHC on the number of pollution sources (well clusters, and the area of oil spills) in zones at different distances from the river channels. By calculating the Spearman correlation coefficients, it was shown that OHC contents are dependent mainly on the number of wells, and on the area of oil spills located at less than 2 km from the channels. 相似文献