A toxic dipeptide from the defense glands of the colorado beetle     

Daloze D  Braekman JC  Pasteels JM 《Science (New York, N.Y.)》1986,233(4760):221-223

The Colorado beetle is protected against predators by the secretions of defensive glands located on the pronotum and the elytra. The single major compound of the secretion was identified as gamma-L-glutamyl-L-2-amino-3(Z),5-hexadienoic acid by spectroscopic and chemical methods. This compound, which contains a nonprotein beta,gamma- unsaturated amino acid, is toxic to ants (Myrmica rubra) at a concentration 10(-2) molar, which is less than its estimated concentration in the secretion (1.8 x 10(-1) molar).  相似文献   

Will growth hormone swell milk surplus?     

Sun M 《Science (New York, N.Y.)》1986,233(4760):150-151

A debate is raging over whether commercial introduction of bovine growth hormone will exacerbate the financial problems of small dairy farmers.  相似文献   

Gold     

Abelson PH 《Science (New York, N.Y.)》1986,233(4760):141

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Ballistic missile defense: cost of space-based laser     

Hoffert MI  Miller G 《Science (New York, N.Y.)》1986,234(4780):1057-1060

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Age of the earliest african anthropoids     

Fleagle JG  Bown TM  Obradovich JD  Simons EL 《Science (New York, N.Y.)》1986,234(4781):1247-1249

The earliest fossil record of African anthropoid primates (monkeys and apes) comes from the Jebel Qatrani Formation in the Fayum depression of Egypt. Reevaluation of both geologic and faunal evidence indicates that this formation was deposited in the early part of the Oligocene Epoch, more than 31 million years ago, earlier than previous estimates. The great antiquity of the fossil higher primates from Egypt accords well with their primitive morphology compared with later Old World higher primates. Thus, the anthropoid primates and hystricomorph rodents from Fayum are also considerably older than the earliest higher primates and rodents from South America.  相似文献   

Optical experiments and weak interactions     

Bouchiat MA  Pottier L 《Science (New York, N.Y.)》1986,234(4781):1203-1210

Recent optical experiments have demonstrated cases in which mirror symmetry in stable atoms is broken during absorption of light. These results, which are in contradiction with quantum electrodynamics, support the theory of unification of the electromagnetic and weak forces. The interpretation of these experimental results is based on exchanges of weak neutral Z(0) bosons between the electrons and the nucleus of the atom. The information obtained from low-energy experiments is different from, but complementary to, the results of high-energy experiments. Sensitive measurements in a simple, reliably computable atom are in quantitative agreement with the standard electroweak theory and put stringent constraints on alternative models. Attaining sufficient accuracy in the experiments and the computations for the electroweak radiative corrections to manifest themselves is now the challenge for experimenters and theorists.  相似文献   

The Universe in Depth: Very long time exposures provide some intriguing hints about the evolution of galaxies, the curvature of the universe, and why the night sky is dark     

Waldrop MM 《Science (New York, N.Y.)》1986,234(4781):1202

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Global manufacturing competition     

Abelson PH 《Science (New York, N.Y.)》1986,232(4755):1181

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Changing climate: geothermal evidence from permafrost in the alaskan arctic   总被引：2，自引：0，他引：2  

Lachenbruch AH  Marshall BV 《Science (New York, N.Y.)》1986,234(4777):689-696

Temperature profiles measured in permafrost in northernmost Alaska usually have anomalous curvature in the upper 100 meters or so. When analyzed by heat-conduction theory, the profiles indicate a variable but widespread secular warming of the permafrost surface, generally in the range of 2 to 4 Celsius degrees during the last few decades to a century. Although details of the climatic change cannot be resolved with existing data, there is little doubt of its general magnitude and timing; alternative explanations are limited by the fact that heat transfer in cold permafrost is exclusively by conduction. Since models of greenhouse warming predict climatic change will be greatest in the Arctic and might already be in progress, it is prudent to attempt to understand the rapidly changing thermal regime in this region.  相似文献   

Atmospheric carbon dioxide and summer soil wetness     

Maccracken MC  Schlesinger ME  Riches MR 《Science (New York, N.Y.)》1986,234(4777):659-660

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