Aquatic toxicity of di （2-eihylhexyl） phthalate to duckweeds

This study is concerned with the effects of di （2-ethylhexyl） phthalate （DEHP） on two kinds of duckweeds （Spirodela polyrhiza and Lemna minor）.The results indicate that DEHP has aquatic toxicity to Spirodela polyrhiza at 0.4 mg/L and to Lemna minor at over 0.1 mg/L by changing their physiologic-biochemical characteristics.The contents of duckweed chlorophyll and soluble protein decrease with increasing DEHP concentration after 7 d of exposure.DEHP shows the stimulating role in catalase （CAT） and superoxide dismutase （SOD） systems at relative low levels.At 0.01 mg/L and 0.005 mg/L,SOD activities of Spirodela polyrhiza and Lemna minor reach their peak values respectively,while CAT activity reaches its maximum value at 0.05 mg/L and 0.01 mg/L.When DEHP levels are too high,the protection enzyme system would be destroyed and plant growth is inhibited.The analysis of malondialdehyde （MDA） and Fourier transform infrared spectroscopy manifest that DEHP could affect the tested duckweeds by destroying its cell membranes,and Spirodela polyrhiza is more resistant to DEHP exposure than Lemna minor.     

A Mössbauer study of some coloured marbles (cipollino mandolato, rosso antico and fior di pesco): implications on the nature of their colour

⁵⁷Fe Mössbauer spectroscopy permits an explanation of the formation of the iron-bearing species present in three types of coloured marbles, known as cipollino mandolato, rosso antico and fior di pesco. Structural Fe²⁺ and Fe³⁺ located in silicates, together with the remains of weakly ferromagnetic hematite, arise from primary sediments. Fe²⁺ located in carbonates and anti-ferromagnetic hematite are formed by redox processes during marble formation. The relative contents of the iron species in the three types of marbles depend on the composition of the primary sediments and on local conditions during metamorphism. Knowledge of the type and amount of the iron species in marbles may help in the reconstruction of the redox processes, which took place during marble formation. The deviations of the Morin transition of the hematites play the role of genetic indicator because purity, crystallinity and the red hues of hematites in marbles can be related to the environment of formation.     

建筑的叙事性——卡罗.斯卡帕的古堡博物馆设计分析

通过阐述建筑叙事性的概念并对斯卡帕的古堡博物馆中诸方面的叙事性的分析,探讨在建筑设计中营造叙事性空间的可能性与方法,强调叙事性对于当代建筑的意义与重要性。