Periodicity in tree rings from the corn belt     

Meko DM  Stockton CW  Blasing TJ 《Science (New York, N.Y.)》1985,229(4711):381-384

Previous tree-ring studies indicated that the total area affected by drought in the western United States has rhythmically expanded and contracted over the past 300 years, with a period near the 18.6-year lunar nodal and 22-year double-sunspot cycles. Recently collected tree-ring data from the U.S. Corn Belt for the years 1680 to 1980 were examined for evidence of either of these cycles on a regional scale. Spectral analysis indicated no periodicity in the eastern part of the Corn Belt, but a significant 18.33-year period in the western part. The period length changed from 17.60 to 20.95 years between the first 150 years and the last 151. High-resolution frequency analysis showed that the structure of the 18.33-year spectral peak was complex, with contributions from several frequencies near both the lunar nodal and double-sunspot periods. A t-test of difference of means in reconstructed annual precipitation weakly corroborated a previous finding of an association between drought area and the phase of the double-sunspot cycle. Both the high-resolution frequency analysis and the t-test results indicate that the periodic component of drought near 20 years is too weak and irregular to be of use in drought forecasting for the Corn Belt.  相似文献   

Diploid-Triploid Mosaicism: An Unusual Phenomenon in Side-Necked Turtles (Platemys platycephala)     

Bickham JW  Tucker PK  Legler JM 《Science (New York, N.Y.)》1985,227(4694):1591-1593

Diploid and diploid-triploid mosaic individuals of Platemys platycephala were found in natural populations. In mosaic specimens, the blood, spleen, liver, and testis contained both diploid and triploid cells. The ratio of triploid to diploid cells was more variable among individuals than among somatic tissues within an individual. Only diploid cells underwent meiosis in males; haploid gametes were produced. There appears to be geographic variation for mosaicism in that only diploids were found in Bolivia, whereas diploids and diploid-triploid mosaics occured in Surinam.  相似文献   

In reply: retirement age for chinese scientists     

Sun M 《Science (New York, N.Y.)》1985,230(4727):738

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Something strange from cygnus x-3     

Waldrop MM 《Science (New York, N.Y.)》1985,228(4705):1298

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TV Scientists: More Good Than Bad     

Sun M 《Science (New York, N.Y.)》1985,228(4705):1294

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Key problems in science and technology in Thailand     

Yuthavong Y  Sripaipan C  Kirtikara K  Glankwamdee A  Trakulku K 《Science (New York, N.Y.)》1985,227(4690):1007-1011

Science and technology can make substantial contributions to socio-economic development in Thailand. In order to promote such contributions, problem areas and specific problems of high priority need to be defined, and possible solutions outlined. Important criteria for selecting priority areas and key problems include relevance to development, the availability of human resources and the possibility of their development, the cutting-edge advantage to be gained by development, the possibility of international collaboration, and the possibility of integration with culture and environment. These criteria suggest in Thailand a focus on the development of bioscience and biotechnology, materials science, electronics, and information science.  相似文献   

Some other books of interest: golden past, golden future     

L K 《Science (New York, N.Y.)》1985,230(4725):536-537

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NRC Stands by Its Rule on University Reactors     

Crawford M 《Science (New York, N.Y.)》1985,229(4708):36

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Stable carbon isotope ratios of rock varnish organic matter: a new paleoenvironmental indicator     

Dorn RI  Deniro MJ 《Science (New York, N.Y.)》1985,227(4693):1472-1474

Stable carbon isotope ratios of organic matter in rock varnishes of Holocene age from western North America and the Middle East show a strong association with the environment. This isotopic variability reflects the abundance of plants with different photosynthetic pathways in adjacent vegetation. Analyses of different layers of varnish on late Pleistocene desert landforms indicate that the carbon isotopic composition of varnish organic matter is a paleoenvironmental indicator.  相似文献   

Margin to craton expansion of late ordovician benthic marine invertebrates     

Bretsky PW  Klofak SM 《Science (New York, N.Y.)》1985,227(4693):1469-1471

A biostratigraphic survey of 57 Late Ordovician marine shelly invertebrates from the Climacograptus manitoulinensis zone of eastern Canada supports suggestions that throughout the Early Phanerozoic benthic marine speciations occurred preferentially in marginal marine environments. The species subsequently spread onto the craton. There is no obvious positive correlation between the times of first appearance of new associations or novel communities along the continental margin and the first appearance on the craton of the species making up these communities. Taxonomic similarities between marine communities that occupied both marginal and cratonic regimes may reflect a more static local ecology than the evolutionary dynamics of a piecemeal species-by-species reassembly.  相似文献