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We report a synthetic material, [Co2(bipy)3(SO4)2(H2O)2](bipy) (CH3OH), (1, where bipy = 4,4'-bipyridyl) that contains discrete reactive and inert structural motifs that undergo a reversible substitution reaction involving the concerted and spatially controlled introduction of bipyridine and methanol molecules at the reactive sites. This reaction defines the pore geometry of the resulting open-framework structure and controls the manner in which this structure sorbs small molecules. The molecules involved in the reaction are positioned by an array of well-defined interactions during their path to binding to the metal centers. 相似文献
63.
Meehl GA Washington WM Collins WD Arblaster JM Hu A Buja LE Strand WG Teng H 《Science (New York, N.Y.)》2005,307(5716):1769-1772
Two global coupled climate models show that even if the concentrations of greenhouse gases in the atmosphere had been stabilized in the year 2000, we are already committed to further global warming of about another half degree and an additional 320% sea level rise caused by thermal expansion by the end of the 21st century. Projected weakening of the meridional overturning circulation in the North Atlantic Ocean does not lead to a net cooling in Europe. At any given point in time, even if concentrations are stabilized, there is a commitment to future climate changes that will be greater than those we have already observed. 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
66.
Preparations of erythrocyte glucose-6-phosphate dehydrogenase from normal individuals show similar degrees of inhibition by neutral salts. Preparations from Caucasian subjects with different hereditary deficiency syndromes differ from each other and from normal subjects, indicating a qualitative difference in these specific "deficient" enzymes. Sensitivity to neutral salts may be a means of detecting an amino acid substitution. 相似文献
67.
Tillage systems influence soil properties and may influence the availability of applied and mineralized soil N. This laboratory study (20°C) compared N cycling in two soils, a Wooster (fine, loamy Typic Fragiudalf) and a Hoytville (fine, illitic Mollic Epiaqualf) under continuous corn (Zea mays) production since at least 1963 with no-tillage (NT), minimum (CT) and plow tillage (PT) management. Fertilizer was added at the rate of 100 mg 15N kg–1–1 soil as 99.9% 15N as NH4Cl or Ca(NO3)2 and the soils were incubated in leaching columns for 1 week at 34 kPa before being leached periodically with 0.05 M CaCl2 for 26 weeks. As expected, the majority of the 15NO3– additions were removed from both soils with the first leaching. The majority of applied 15NH4+ additions were recovered as 15NO3– by week 5, with the NT soils demonstrating faster nitrification rates compared with soils under other tillage practices. For the remaining 22 weeks, only low levels of 15NO3– were leached from the soils regardless of tillage management. In the coarser textured Wooster soils (150 g clay kg–1), mineralization of native soil N in the fertilized soils was related to the total N content (r2 0.99) and amino acid N (r2 0.99), but N mineralization in the finer textured Hoytville (400 g clay kg–1) was constant across tillage treatments and not significantly related to soil total N or amino acid N content. The release of native soil N was enhanced by NH4+ or NO3– addition compared to the values released by the unfertilized control and exceeded possible pool substitution. The results question the use of incubation N mineralization tests conducted with unfertilized soils as a means for predicting soil N availability for crop N needs. 相似文献
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