The effects of UV radiation A and B on diurnal variation in photosynthesis in three taxonomically and ecologically diverse microbial mats

Photosynthetic primary production, the basis of most global food chains, is inhibited by UV radiation. Evaluating UV inhibition is therefore important for assessing the role of natural levels of UV radiation in regulating ecosystem behavior as well as the potential impact of stratospheric ozone depletion on global ecosystems. As both photosynthesis and UV fluxes are subject to diurnal variations, we examined the diurnal variability of the effect of UV radiation on photosynthesis in three diverse algal mats. In one of the mats (Cyanidium caldarium) a small mean decrease in primary productivity over the whole day occurred when both UVA and UVB were screened out. In two of the mats (Lyngbya aestuarii and Zygogonium sp.) we found a mean increase in the total primary productivity over the day when UVB alone was screened and a further increase when UVA and UVB were both screened out. Variations in the effects of UV radiation were found at different times of the day. This diurnal variability may be because even under the same solar radiation flux, there are different factors that may control photosynthetic rate, including nutritional status and other physiological processes in the cell. The results show the importance of assessing the complete diurnal productivity. For some of the time points the increase in the mean was still within the standard deviations in primary productivity, illustrating the difficulty in dissecting UV effects from other natural variations.     

谈谈量子力学中的状态叠加原理

以对话的形式,介绍并评论了布洛欣采夫、狄拉克以及朗道和栗弗席茨关于状态叠加原理的不同表述.     

医药类专业物理课程教学存在的问题及对策

根据对国内69所普通高等院校医药类专业（本科）物理课程教学现状调查的结果,分析了在我国高等教育进入“大众化教育”的形势下,医药类专业物理课程教学中存在的4个急需解决的问题,指出了医药类专业物理课程教学改革的方向,并介绍了我们所做的一些工作。     

Raman spectroscopic analysis of cyanobacterial gypsum halotrophs and relevance for sulfate deposits on Mars

The Raman spectra of cyanobacterial species, Gloecapsa and Nostoc, in clear gypsum crystals from the Haughton Crater, Devon Island, Canadian High Arctic, site of a meteorite impact during the Miocene some 23 Mya, have been recorded using several visible and near-infrared excitation wavelengths. The best spectra were obtained using a green wavelength at 514.5 nm and a confocal microscope with an image footprint of about 2 micro in diameter and 2 micro theoretical depth. Raman biosignatures for beta-carotene and scytonemin were obtained for one type of colony and parietin and beta-carotene for another; chlorophyll was detected in both types of colony. The different combination of these radiation protectant biomolecules suggests that the two cyanobacterial colonies, namely Nostoc and Gloecapsa, are adopting different survival strategies in the system. Confocal spectroscopic probing of the gypsum crystals exhibited sufficient discrimination for the identification of the biomolecules through the gypsum crystal, in simulation of the detection of extant or extinct halotrophs. This supports the viability of Raman spectroscopic techniques for incorporation as part of the instrumentation suite of a robotic lander for planetary surface exploration for the detection of organisms inside sulfate crystals from previous hydrothermal activity on Mars.