Chloroplastic responses of ponderosa pine (Pinus ponderosa) seedlings to ozone exposure

Integrity of chloroplast membranes is essential to photosynthesis. Loss of thylakoid membrane integrity has been proposed as a consequence of ozone (O(3)) exposure and therefore may be a mechanistic basis for decreased photosynthetic rates commonly associated with ozone exposure. To investigate this hypothesis, Pinus ponderosa seedlings were exposed to ambient air or ozone concentrations maintained at 0.15 or 0.30 microliter l(-1) for 10 h day(-1) for 51 days during their second growing season. Over the course of the study, foliage samples were periodically collected for thylakoid membrane, chlorophyll and protein analyses. Additionally, gas-exchange measurements were made in conjunction with foliage sampling to verify that observed chloroplastic responses were associated with ozone-induced changes in photosynthesis.Needles exposed to elevated ozone exhibited decreases in chlorophyll a and b content. The decreases were dependent on the duration and intensity of ozone exposure. When based on equal amounts of chlorophyll, ozone-exposed sample tissue exhibited an increase in total protein. When based on equal amounts of protein, ozone-exposed samples exhibited an increase in 37 kDa proteins, possibly consisting of breakdown products, and a possible decrease in 68 kDa proteins, Rubisco small subunit. There was also a change in the ratio of Photosystem I protein complexes CPI and CPII that may have contributed to decreased photosynthesis. Net photosynthetic rates were decreased in the high ozone treatment suggesting that observed structural and biochemical changes in the chloroplast were associated with alterations of the photosynthetic process.     

Dynamics of Tree and Shrub Vegetation in the Eastern Sayan Mountain Tundra

Russian Journal of Ecology - Climate change entails shifts in the ranges of woody plants along both latitudinal and altitudinal gradients in the boreal forest biome. In this study,...     

Cross-sectional mortality studies and air pollution risk assessment

The use of coefficients, derived from cross-sectional mortality studies, for air pollution risk assessment is quite controversial. In this study, the major limitations of cross-sectional studies are reviewed. The consistency of results from the major recent cross-sectional studies is examined, and the sensitivity of results to model specification is analyzed. Finally, the implications for risk assessment of our inquiries are discussed.     

陕西大暴雨时空分布特征及减灾对策

通过对陕西１９５７～１９９８年共４２年９７个测站的逐日降水量中大暴雨资料进行时间和空间尺度分析，总结归纳出陕西灾害性大暴雨的天气气候基本特征和规律性，并提出相应的减灾对策。     

Evaluation of the technoeconomic feasibility of electrochemical hydrogen peroxide production for decentralized water treatment

• Gas diffusion electrode (GDE) is a suitable setup for practical water treatment. • Electrochemical H₂O₂ production is an economically competitive technology. • High current efficiency of H₂O₂ production was obtained with GDE at 5–400 mA/cm². • GDE maintained high stability for H₂O₂ production for ~1000 h. • Electro-generation of H₂O₂ enhances ibuprofen removal in an E-peroxone process. This study evaluated the feasibility of electrochemical hydrogen peroxide (H₂O₂) production with gas diffusion electrode (GDE) for decentralized water treatment. Carbon black-polytetrafluoroethylene GDEs were prepared and tested in a continuous flow electrochemical cell for H₂O₂ production from oxygen reduction. Results showed that because of the effective oxygen transfer in GDEs, the electrode maintained high apparent current efficiencies (ACEs,>80%) for H₂O₂ production over a wide current density range of 5–400 mA/cm², and H₂O₂ production rates as high as ~202 mg/h/cm² could be obtained. Long-term stability test showed that the GDE maintained high ACEs (>85%) and low energy consumption (<10 kWh/kg H₂O₂) for H₂O₂ production for 42 d (~1000 h). However, the ACEs then decreased to ~70% in the following 4 days because water flooding of GDE pores considerably impeded oxygen transport at the late stage of the trial. Based on an electrode lifetime of 46 days, the overall cost for H₂O₂ production was estimated to be ~0.88 $/kg H₂O₂, including an electricity cost of 0.61 $/kg and an electrode capital cost of 0.27 $/kg. With a 9 cm² GDE and 40 mA/cm² current density, ~2–4 mg/L of H₂O₂ could be produced on site for the electro-peroxone treatment of a 1.2 m³/d groundwater flow, which considerably enhanced ibuprofen abatement compared with ozonation alone (~43%–59% vs. 7%). These findings suggest that electrochemical H₂O₂ production with GDEs holds great promise for the development of compact treatment technologies for decentralized water treatment at a household and community level.     

Modeling Diapause Termination of Rhipicephalus Appendiculatus using Statistical Tools to Detect Sudden Behavioral Changes and Time Dependencies

This paper presents statistical methodology to analyze longitudinal binary responses for which a sudden change in the response occurs in time. Probability plots, transition matrices, and change-point models and more advanced techniques such as generalized auto-regression models and hidden Markov chains are presented and applied on a study on the activity of Rhipicephalus appendiculatus, the major vector of Theileria parva, a fatal disease in cattle. This study presents individual measurements on female R. appendiculatus, which are terminating their diapause (resting status) and become active. Comprehending activity patterns is very important to better understand the ecology of R. appendiculatus. The model indicates that activity and non-activity act in an absorbing way meaning that once a tick becomes active it shows a tendency to remain active. The change-point model estimates that the sudden change in activity happens on December 10. The reaction of ticks on acceleration and changes in rainfall and temperature indicates that ticks can sense climatic changes. The study revealed the underlying not visually observable states during diapause development of the adult tick of R. appendiculatus. These states could be related to phases during the dynamic event of diapause development and post-diapause activity in R. appendiculatus.     

Prenatal diagnosis of NADH:ubiquinone oxidoreductase deficiency

NADH:ubiquinone oxidoreductase (complex I of the mitochondrial respiratory chain) deficiency is a severe disorder with an often early fatal outcome. Prenatal diagnosis for complex I defects currently relies mainly on biochemical assays of complex I in fetal tissues such as chorionic villi (CV), and is only in a minority of cases possible by means of mutational analysis of nuclear-encoded genes of complex I. We report on our experience to date with prenatal diagnosis in pregnancies at risk for complex I deficiency. We measured complex I activity in native CV and/or cultured CV in 23 pregnancies in 15 families. In accordance with the results of the investigations in CV, 15 children were born clinically unaffected. Two prenatally diagnosed unaffected fetuses and two prenatally diagnosed affected fetuses were lost prematurely with spontaneous or provoked abortions, respectively. Two affected children were born (prenatally found to be affected). In two pregnancies a discrepancy between native and cultured cells was found. We conclude that prenatal diagnosis for complex I deficiency can be reliably performed. Pitfalls were encountered in using cultured CV as a result of maternal cell contamination (MCC). Future research on pathogenic nuclear mutations underlying complex I deficiency will extend the possibilities for prenatal diagnosis at the molecular level. Copyright © 2001 John Wiley & Sons, Ltd.     

多级A/O工艺强化城市生活污水再生过程的污染物去除效果研究

北京市某城市污水厂在传统的A ²/O工艺基础上特别增设多级A/O(MAO)工艺强化脱氮除磷效果。以该污水厂各工艺单元出水为研究对象,通过对水质常规理化指标、紫外吸收光谱及其相关参数分析,并结合多元数据统计学手段,分析该工艺对城市污水中污染物的去除效果,特别是溶解性有机物(DOM)的去除。经MAO工艺强化后COD_Cr、DOC、TN、TP和N$H^{+}_{4}$-N的去除率分别为95.14%、89.70%、94.53%、97.26%和99.74%,达到GB 18918—2002《城镇污水处理厂污染物排放标准》一级A标准;增设MAO工艺后,提高了对DOM的去除率,DOM分子量和团聚化程度显著提高,化合物的稳定性增强。对污水再生过程处理单元水质化学指标与紫外光谱参数的相关性分析表明,芳香环上取代基类型以脂肪链为主时对脱氮除磷促进作用更加明显。