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Distribution of glycerol ethers in Turpan soils:implications for use of GDGT-based proxies in hot and dry regions

Frontiers of Earth Science 2018年第4期12卷 862-876页

作者： Jingjie ZANG Yanyan LEI Huan YANG State Key Laboratory of Biogeology and Environmental Geology School of Earth SciencesChina University of GeoseiencesWuhan 430074China Department of Geology and Environmental Science University of PittsburghPittsburghPA 15260USA

Proxies based on glycerol dialkyl glycerol tetraethers (GDGTs), a suite of membrane lipids occurring ubiquitously in soils, have generated increasing interest in quantitative paleo-environmental reconstruction. Hot and dry climates are likely to have occurred in the geological past; however, the limitations and applicability of these proxies to hot and dry environments are still unknown. In this study, we analyzed the GDGT distribution in the Turpan (TRP) basin of China, where the highest soil temperature can be approximately 70A degrees C, and the mean annual precipitation (MAP) is 15.3 mm. We compared GDGT-based proxies among TRP soils, Nanyang (NY) soils, and Kunming (KM) soils; these three sites exhibit similar mean annual air temperature (MAAT) albeit contrasting temperature seasonality and MAP. Archaeal isoprenoidal GDGTs (isoGDGTs) dominate over bacterial branched GDGTs (brGDGTs) in most TRP soils; this is a characteristic GDGT distribution pattern for soils from dry regions globally. Another feature is the anomalously high GDGT-0/crenarchaeol ratio, which is generally attributed to the contribution of anaerobic methanogenic archaea by previous studies; however, these anaerobic archaea are unlikely to be highly abundant in the dry TRP soils, indicating that certain uncultured halophilic Euryarchaeota are likely to produce a significant amount of GDGT-0 that finally results in a high GDGT-0/Cren ratio. The changes in the salinity of the TRP soils appear to be an important factor affecting the MBT'(5ME) and the relative abundance of 6- vs. 5-methyl pentamethylated brGDGTs (IRIIa'). This is likely to introduce certain scatters in the correlations between MBT'(5ME) and MAAT and that between IRIIa' and pH determined at the global scale. A comparison of the MBT'(5ME)-inferred temperature between TRP, NY, and KM soils does not indicate a significant bias toward summer temperature, indicating that brGDGT paleothermometers in soils could reflect the MAAT.

关键词： GDGTs Turpan soils semi-arid and arid areas salinity MBT5ME' Soil Salinity Likely Membrane Lipids Glyceryl Ethers high temperature Soil temperature dry conditions drought Proxy

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Correlation Analyses between Ultraviolet Radiation, Global Solar Radiation, and Metrological Variables and the COVID-19 Cases in Arid Climate

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Advances in Infectious Diseases 2022年第2期12卷 163-174页

作者： Maghrabi Abdullrahman National Centre for Applied Physics King Abdulaziz City for Science and Technology Riyadh Saudi Arabia

The transmission of infectious diseases is influenced by several meteorological factors. In this study, the influence of several such factors in the transmission of COVID-19 (from 26 March 2020 to 29 July 2021) in the arid weather of Riyadh, Saudi Arabia was investigated using the Spearman and Kendall rank tests. The factors considered were the average, maximum, and minimum values of air temperatures, air pressure, wind speed, relative humidity, absolute humidity, dew point temperatures, and the average values of the global solar radiation and ultraviolet radiation at bands A and B. The data on meteorological factors were obtained from the King Abdulaziz City for Science and Technology (KACST) weather station, whereas the data on the daily COVID-19 cases were obtained from the official webpage of the Saudi Arabian Ministry of Health (MOH). The results revealed that air temperature (average, minimum, and maximum) average and maximum wind speed, maximum dew point temperature, global solar radiation, and ultraviolet radiation at A and B bands are positively associated with the daily number of COVID-19 cases reported in Riyadh. However, relative humidity, atmospheric pressure (averages, minimum, and maximum) is anti-correlated with the number of daily COVID-19 cases, while absolute humidity exerts no influence. These results are in total agreement with some of the previously established studies and are either contradicted partly or totally with others conducted at several locations around the world. The results could help not only epidemiologists understand the behavior of COVID-19 against meteorological variables but also national and international organizations and healthcare policymakers devise control strategies to combat the virus.

关键词： COVID-19 dry conditions Meteorology Ultraviolet Radiation Correlation

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ARTIFICIAL AGING TESTS WITH DEFECTIVE COMPOSITE INSULATORS 19th

ARTIFICIAL AGING TESTS WITH DEFECTIVE COMPOSITE INSULATORS

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The ⅪⅩ International Conference on Gas Discharges and Their Applications

作者： B.LUTZ F.LIANG J.ZHANG Z.GUAN L.WANG Laboratory of Advanced Technology of Electrical Engineering and Energy Graduate School at ShenzhenTsinghua University

ISBN: (纸本)9771003651221

＜正＞In this study,artificial aging tests with composite insulators containing different defects at the sheath-core interface were *** including copper strips,wood strips and weak adhesion between sheath and core were *** samples were stressed by a stepwise increasing AC test voltage while the leakage current and the surface temperature were *** effect of the defect type,defect length and of absorbed water on the aging process was investigated in dry environment. In case that the leakage current exceeded 0.2 mA, samples containing wetted or conductive defects exhibited a significant increase of surface *** highest temperature developed at the defects’ edges near to the ground electrode where puncturing of the silicone rubber sheath finally *** puncturing mechanism is critical for the long-term performance of composite insulators since further aging mechanisms may be triggered afterwards.

关键词： composite insulators surface temperature leakage currents Grounding electrodes dry conditions Hygroscopic Water insulators Composites aging mechanism Sheaths Accelerated aging

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