Climate variability 50,000 years ago in mid-latitude Chile as reconstructed from tree rings

High-resolution proxies of past climate are essential for a better understanding of the climate system. Tree rings are routinely used to reconstruct Holocene climate variations at high temporal resolution, but only rarely have they offered insight into climate variability during earlier periods. Fitzroya cupressoides-a South American conifer which attains ages up to 3,600 years-has been shown to record summer temperatures in northern Patagonia during the past few millennia. Here we report a floating 1,229-year chronology developed from subfossil stumps of F. cupressoides in southern Chile that dates back to approximately 50,000 14C years before present. We use this chronology to calculate the spectral characteristics of climate variability in this time, which was probably an interstadial (relatively warm) period. Growth oscillations at periods of 150-250, 87-94, 45.5, 24.1, 17.8, 9.3 and 2.7-5.3 years are identified in the annual subfossil record. A comparison with the power spectra of chronologies derived from living F. cupressoides trees shows strong similarities with the 50,000-year-old chronology, indicating that similar growth forcing factors operated in this glacial interstadial phase as in the current interglacial conditions.     

铑催化剂上CO的吸附态及其加氢反应

用红外光谱法测定表明：各种硅胶负载仲进型铑催化剂上，线ＣＯ／桥ＣＯ红外吸收强度比值与金属助剂（Ｍ）的关系变化顺序为（５０：１）（Ｒｈ－Ｍｎ）〉（２２：１）（Ｒｈ－Ｌｉ）〉（９．１：１）（Ｒｈ－Ｍｎ－Ｆｅ－Ｌｉ）〉（３．５：１）（Ｒｈ－Ｆｅ）〉２．８：１）（Ｒｈ）。在各种Ｒｈ－Ｍ／ＳｉＯ２催化剂上，线、桥ＣＯ吸附态的加氢原位ＦＴＩＲ跟踪实验表明：随着加氢的进行，线ＣＯ／桥ＣＯ吸收强度比值均逐渐减少…