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Hunter LR 《Science (New York, N.Y.)》1991,252(5002):73-79
Sensitive experiments have been developed that search for electric dipole moments of atoms, molecules, and the neutron. These experiments play an important role in deciding which of the myriad theoretical models correctly describes violations of the principle of time-reversal invariance. 相似文献
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Hunter JS 《Science (New York, N.Y.)》1980,210(4472):869-874
Mandated measurement methods are required by regulatory agencies and other government groups. These methods exist for measuring almost all physical, chemical, and biological phenomena. The methods have been culled from the literature, from the organizations that write voluntary standards, and some have been developed by the agencies. Few provide adequate estimates of precision, and fewer still provide any evaluation of interlaboratory bias. The societal costs of these poor measurements are large. Much needs to be done to meet the physical and statistical requirements for establishing and maintaining dependable measurements. Excepting those directly supported by the National Bureau of Standards, most of the nation's measurement systems are uncontrolled. 相似文献
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Davis ST Benson BG Bramson HN Chapman DE Dickerson SH Dold KM Eberwein DJ Edelstein M Frye SV Gampe RT Grifffen RJ Harris PA Hassell AM Holmes WD Hunter RN Knick VB Lackey K Lovejoy B Luzzio MJ Murray D Parker P Rocque WJ Shewchuk-Chapman L Veal JM Walker DH Kuyper LF 《Science (New York, N.Y.)》2002,298(5602):2327
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The toxicity of A1 that has been mobilized in soil, streams, and lakes through acid deposition primarily has been attributed to mononuclear A1 species. Polynuclear A1 species are more toxic than mononuclear species, but they have not been considered to be significant in the environment. Aluminum-27 nuclear magnetic resonance (NMR) spectra of forested spodosol soil horizon samples show the presence of polynuclear A1O(4)A1(12)(OH)(24)(H(2)O)(12)(7+). The AlO(4)A1(12)(OH)(24)(H(2)O)(12)(7+) species accounted for 30 percent of the aqueous A1 observable by NMR, and this could make a significant contribution to the toxicity of the A1 in these soils. 相似文献