Removal of atrazine from water using covalent sequestration

Monochlorotriazines including atrazine and its major metabolites, deethylatrazine and deisopropylatrazine, are susceptible to nucleophilic aromatic substitution. Competitive reactions to rank the relative reactivity of nucleophiles with atrazine reveal that constrained secondary amines are the most reactive. When the nucleophile is attached to a solid support, atrazine can be sequestered from solution. As proof of concept, polystyrene resins displaying constrained secondary amines are shown to sequester atrazine, deethylatrazine, and deisopropylatrazine from water. Sequestration can be followed spectrophotometrically or using a liquid chromatography mass spectrometry protocol. The kinetics of sequestration are similar to that of granulated charcoal. Evidence for covalent bond formation comes from control experiments with unreactive herbicides and degradation analysis of the solid support. Using both (1)H NMR spectroscopy and mass spectrometry, covalent adducts are identified in ratios close to what is calculated theoretically. This method for sequestration is effective at removing atrazine from pond water.     

Photosynthetic and transpirational responses of red spruce understory trees to light and temperature

Understory red spruce (Picea rubens Sarg.) trees, between 20 and 50 cm in height and 12 years or more in age, were collected from mid- and high-elevation stands in north-central Vermont and placed in a closed-cuvette system to measure photosynthetic and transpirational responses to photosynthetic photon flux density (PPFD) and temperature. Photosynthesis, dark respiration, transpiration and water-use efficiency of trees from both stands responded to changes in PPFD and temperature in similar ways. Trees from both stands exhibited maximum rates of net photosynthesis at temperatures between 15 and 20 degrees C, and exposure to higher temperatures resulted in reduced rates of photosynthesis and increased rates of respiration. Net photosynthetic rates generally increased with increasing light intensity but began to level off at 250 micro mol m(-2) s(-1). Water-use efficiency was maximal when temperature and PPFD were at 15 degrees C and above 400 micro mol m(-2) s(-1), respectively.     

金丝垂柳组织培养体系建立研究

对金丝垂柳组织培养技术进行了研究,结果表明:取外植体带有侧芽的茎条切段进行组织培养,以MS为基本培养基,附加不同浓度的6-BA和NAA进行分化诱导,可获得无根丛生苗,以附加不同浓度的NAA可获得生根植株。     

Seasonal patterns of carbohydrate reserves in red spruce seedlings

We studied seasonal dynamics of carbohydrate storage in red spruce (Picea rubens Sarg.) seedlings by measuring starch and sugar concentrations of old needles (>/= one year old), new needles (< one year old), stems, and roots in two stands in the Green Mountains of Vermont. Although the two stands differed in many site characteristics including percent slope, aspect, soil type, drainage, and 564 m in elevation, concentrations and seasonal patterns of carbohydrates were similar for the two stands. For all tissues, starch concentrations peaked in late spring, declined through summer, and reached a minimum in winter. Sugar concentrations were greater than starch concentrations in all months except May and June. Sugar concentrations peaked in winter, and old needles showed a significant increase in sugar concentration between February and March. This increase in sugar concentration occurred without any reduction in localized starch concentrations or reductions in sugar or starch concentrations in new needles, stems or roots. Because March measurements were made toward the end of a prolonged thaw, a time when increases in photosynthesis have been documented for red spruce, it is likely that the March increase in sugar concentrations resulted from photosynthesis during the thaw. Compared with stems and roots, needles generally contained the highest concentration of carbohydrates and exhibited the greatest seasonal change in carbohydrate concentration. Needles were also the largest reservoir of carbohydrates throughout the year, especially during winter. Because of the critical roles of needles in photosynthesis and storage of carbohydrates, we conclude that any factors that disrupt the accumulation or availability of carbohydrates in red spruce needles will greatly alter plant carbon relations.     

Secondary forest floristic composition, structure, and spatial pattern in subtropical China

Secondary evergreen broadleaved forests are precious remnants for biodiversity conservation and templates for sustainable management of natural forests in subtropical China. Floristic composition, size structure, and spatial pattern of dominant tree species have been investigated for a subtropical secondary evergreen broadleaved forest in the Huitong Yingzuijie National Forest Reserve, Hunan, China. The location of all trees greater than 4 cm in diameter at breast height (DBH) were mapped within a 0.96-ha plot in which species, DBH, and total tree height were recorded. Ripley’s K(t) function was used to analyze spatial patterns and associations. The secondary forest consisted of 74 tree species and 1,596 stems per hectare. A reverse-J shaped DBH classes distribution was observed for all stems and trees of later seral species whereas trees of earlier successional species were distributed irregularly. Significant aggregated spatial patterns were observed for all trees within the forest and for conspecific trees of each dominant species. This result, and a repulsive spatial pattern for interspecific trees of Choerospondias axillaries and Cyclobalanopsis glauca against other dominant tree species, support segregation hypothesis. Contributions of seed dispersal, topographic heterogeneity, and competition to spatial patterns of conspecific trees vary depending on tree species. Attractive spatial pattern among interspecific trees of Liquidambar fortunei, Liquidambar formosana, and Pinus massoniana reflects stochastic colonization of pioneer tree species and a facilitation relationship. Although deciduous species are long-lived and persist over long successional processes, they will eventually be replaced by late seral evergreen species within the secondary forest if no disturbance events occur.     

大肠杆菌感染可造成严重损失

大肠杆菌感染对世界养禽业造成了重大损失。大肠杆菌是商品家禽肠道中的正常栖居菌 ,并且还是环境中无处不在的 ,但其产毒菌株会引起局部或全身感染 ,结果造成鸡群死亡率增高 ,使商品产蛋鸡和种鸡的产蛋率下降 ;还可使肉鸡的生长率下降 ,胴体质量下降以及加工时废弃率增高     

Following the chain to elusive anglers

Obtaining reliable estimates of important parameters from recreational fisheries is problematic but critical for stock assessment and effective resource management. Sampling methodologies based on traditional design‐based sampling theory, is inadequate in obtaining representative catch and effort data, social or demographical characterization, or fisher behaviour from small hard‐to‐reach components within recreational fisheries (e.g. specialized sport fisheries) that may account for the majority of the catch for some species. A model‐based approach to sampling is necessary. Researchers in other disciplines including epidemiology and social sciences routinely survey rare or ‘hidden’ populations within the general community by penetration of social networks rather than by interception of individuals. We encourage fisheries researchers to rethink survey designs and consider the social elements of recreational fishing. Employing chain‐referral methods, such as respondent‐driven sampling (RDS), may be a statistically robust and cost‐effective option for sampling elusive sub‐elements within recreational fisheries. Chain‐referral sampling methodology is outlined and an example of a complemented ‘RDS‐recapture’ survey design is introduced as a cost‐effective application to estimating total catch in recreational fisheries.     

Management strategies for attenuating herbicide resistance: untoward consequences of their promotion

Herbicide resistance is of major concern to global agriculture and its management is therefore crucial to ensure agricultural productivity. Seven typically recommended management strategies are: (1) rotate herbicides, (2) use herbicide mixtures, (3) follow label directions, (4) include non-selective herbicides as rotational compounds, employ (5) economic thresholds and (6) cultural weed control practices, and (7) monitor changes in weed populations. The primary objective of these strategies is to reduce the selection pressure for resistance. There are many situations, however, where the above strategies are impractical/impossible to implement, ineffective, and/or counter-effective. Therefore, in this review we have outlined these conflicts and concluded that adopting the currently promoted herbicide resistance management strategies may not always be effective in delaying the onset of herbicide resistance.     

集思广益拓展禽病防控策略——第58届西方禽病会议内容精选

2009年5月22～25日,第58届西方禽病会议在美国加利福尼亚州萨卡拉门托市举行.该会议每年在美国定期举行,参会代表是来自全球的禽类健康专家.     

Regulation of mitochondrial biogenesis in skeletal muscle by CaMK

Endurance exercise training promotes mitochondrial biogenesis in skeletal muscle and enhances muscle oxidative capacity, but the signaling mechanisms involved are poorly understood. To investigate this adaptive process, we generated transgenic mice that selectively express in skeletal muscle a constitutively active form of calcium/calmodulin-dependent protein kinase IV (CaMKIV*). Skeletal muscles from these mice showed augmented mitochondrial DNA replication and mitochondrial biogenesis, up-regulation of mitochondrial enzymes involved in fatty acid metabolism and electron transport, and reduced susceptibility to fatigue during repetitive contractions. CaMK induced expression of peroxisome proliferator-activated receptor gamma coactivator 1 (PGC-1), a master regulator of mitochondrial biogenesis in vivo, and activated the PGC-1 gene promoter in cultured myocytes. Thus, a calcium-regulated signaling pathway controls mitochondrial biogenesis in mammalian cells.