UVolution, a photochemistry experiment in low earth orbit: Investigation of the photostability of carbonates exposed to martian-like UV radiation conditions

The detection and identification of carbonates on Mars are of prime importance to establish the evolution of its atmosphere, correlated to the history of the liquid water, or even to determine the existence of a possible ancient biological activity. Till date, no large deposits of carbonates have been found. In fact, their detection is specific to local areas and in very low amounts. The absence of such deposits is commonly attributed to the harsh environmental conditions at the surface of Mars. Additionally, the presence of UV radiation has been proposed to explain their photodecomposition and hence their absence. However, contradictory results from laboratory experiments mimicking Mars’ surface UV radiation did not resolve the behaviour of carbonates in such an environment, which is why we exposed, in low Earth orbit and in laboratory experiments, both abiotic and biotic calcium carbonates to UV radiation of wavelength above 200 nm, the same spectral distribution as the one reaching the surface of Mars. For low Earth orbit (LEO) exposure, this was done for the UVolution experiment on board the BIOPAN ESA module, which was set outside a Russian Foton automated capsule, and exposed to space conditions for 12 days in September 2007. The targeted carbonates are biominerals and abiotic samples. Our laboratory results mainly show that the exposed carbonates appear to be stable to UV radiation if directly exposed to it. The LEO experiment results tend to the same conclusion, but the integrated exposition time to Solar UV during the experiment is not sufficient to be conclusive. However, the stability of the biominerals derived from the laboratory experiment could strengthen the interest to explore deeper their potential as life records at Mars. Hence, they should be considered as primary targets for in situ analyses during future missions.     

Statistical study of EUV and X-ray transient brightenings

Using the visual inspection and base difference method and data from the X-ray Telescope(XRT)onboard Hinode and TRACE with improved spatial and temporal resolution,we selected 48 X-ray transient brightenings(XTBs)and 237 EUV transient brightenings(ETBs)to study the connection between these two types of transient brightenings(TBs).These ETBs and XTBs have smaller areas(8.42 Mm2 and 36.3 Mm2,respectively,on average)and shorter durations(9.0 rain and 6.9 min,respectively,on average)than previous studies.These XTBs show three types of morphological structure: point-like,single-loop and multiple-loop.We find only 20% of the ETBs have corresponding XTBs while the other 80% have no X-ray signatures at all.This is presumably due to the small amount of released energy,which is not enough to heat the plasma to coronal temperatures which produce X-ray emission rather than being due to the limitation of spatial resolution and temperature sensitivity of the X-ray instrument.These small ETBs may significantly contribute to the coronal heating.     

用原子吸收仪进行钛的紫外分光光度测定

在原子吸收仪上添置了一个自制的简易比色皿托架，成功地利用原子吸收仪进行TiO2与二安替比林甲烷显色的分光光度测定。     

On the use of UV spectrophotometry to assess dissolved organic carbon origin variations in the Upper Rhône River

To detect temporal changes and the origin of the refractory dissolved organic matter in the Upper Rhône River, UV light absorbance (A) at 285 nm and quantitative dissolved organic carbon (DOC) measurements were carried out. Data from 63 visits to the main channel over a period of two years and from visits to different waterbodies in the alluvial plain before and after a flood are presented. There was a good correlation between A (0.019–0.160) and the DOC content (1.40–9.81 mg/L) for the waterbodies, but not for the river axis with lower A (0.013–0.044) and DOC content (1.13–2.20 mg/L). Due to this good correlation, the DOC content could be quantified for the waterbodies by absorbance measurements only. For the river water this indirect determination of the DOC content was not possible. However, the A/DOC ratio showed changes in the composition of DOC of river water and provided indications about the origin of the dissolved organic matter in the Upper Rhône River.     

非常规气象要素在紫外线预报中的应用

利用吉林省业务运行的WRF模式,计算了与紫外线指数相关的气温、湿度、云量、风速等常规气象要素和地表向下的短波辐射通量、地面热通量、反照率等非常规气象要素,利用长春市紫外线观测资料,分析了紫外线辐射与常规和非常规气象要素的相关性。基于长春市紫外线观测实况,以常规气象要素、非常规气象要素、混合气象要素为因子,利用相同的统计建模方法,分别建立紫外线预报模型。结果表明:大气短波辐射等非常规气象要素与紫外线指数的相关性,明显高于气温、云量、比湿、风速等常规气象要素;应用非常规气象要素和混合气象要素的紫外线预报方程,显著优于常规气象要素;基于混合气象要素的紫外线预报方程,与基于非常规气象要素的预报方程比较,预报性能差异不大。此外,应用常规气象要素建立的分季节紫外线预报方程,其预报效果明显优于全年预报方程。应用非常规气象要素建立的分季节紫外线预报方程,与全年预报方程相比,预报效果差异不大。     

广州地区太阳分光辐射的某些变化特征

利用广州地区1985—1990年的太阳分光辐射的连续观测资料（观测角度为23°11′），研究了广州地区紫外辐射、可见光辐射（光合有效辐射）、近红外辐射的某些特征。结果指出，每年7—10月份各分光辐射及总辐射总量较大。月总辐射中可见光辐射占总辐射的百分比年平均为47.3%，相应的紫外辐射和近红外辐射分别占7.1%和45.6%。文中还分析了晴天条件下分光辐射的变化和1990年紫外辐射变化的某些特征，并分析和讨论了分光辐射与云量、日照时间等因子的相关。     

Solar-Blind Diamond Detectors for Lyra, the Solar VUV Radiometer on Board Proba II

Fabrication, packaging and experimental results on the calibration of metal-semiconductor-metal (MSM) photodetectors made on diamond are reported. LYRA (Lyman- RAdiometer onboard PROBA-2) will use diamond detectors for the first time in space for a solar physics instrument. A set of measurement campaigns was designed to obtain the XUV-to-VIS responsivity of the devices and other characterizations. The measurements of responsivity in EUV and VUV spectral ranges (40–240 nm) have been carried out by the Physkalisch-Technische Bundesanstalt (PTB) in Germany at the electron storage ring BESSY II. The longer wavelength range from 210 to 1127 nm was measured with monochromatic light by using a Xe-lamp at IMO-IMOMEC. The diamond detectors exhibit a photoresponse which lie in the 35–65 mA/W range at 200 nm (corresponding to an external quantum efficiency of 20–40%) and indicate a visible rejection ratio (200–500 nm) higher than four orders of magnitude.     

昆明下半年紫外辐射变化及与云的关系分析

依据2003年8月1日到2003年12月31日同步观测得到的地面紫外辐射资料,分析了紫外辐射的变化特征。结果显示,在实际天气条件下,紫外辐射变化没有我们所认为的那种有特别明显的规律。云对到达地面的紫外辐射可能有着十分复杂和重要的作用。     

The NO2 Absorption Spectrum. IV: The 200–400 nm Region at 220 K

Previous experiments in the 400–500 nm region (Coquart et al., 1995) have been extended to the 200–400 nm region to determine the absorption cross-sections of NO₂ at 220 K. The NO₂ and N₂O₄ cross-sections are obtained simultaneously from a calculation applied to the data resulting from measurements at low pressures. A comparison between the NO₂ cross-sections at 220 K and at ambient temperature shows that the low temperature cross-sections are generally lower, except in the region of the absorption peaks. Comparisons are also made with previous data at temperature close to 220 K.