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51.
为探明14CO2在环境中的行为,采用同位素示踪技术研究了小麦对14CO2的吸收和积累动态.结果表明,通过叶片光合作用从空气中吸收的14CO2会向小麦其他部位组织输送并形成积累趋势.各部位组织的14C比活度在14CO2引入期间(0~28d)随时间呈线性增长,积累特征明显,增长速率为50.3~84.6 Bq/(g·d),大小顺序为根>茎>叶,尽管各组织14C比活度随时间的增长速率不同,但各组织中14C的比活度均有趋向于平衡的趋势.小麦对14CO2具有强烈的富集作用,富集系数最大值为23.1~25.8,平均为24.5±1.3.小麦对空气中14CO2的较高富集特性可用来作为监测大气14CO2污染的指示作物. 相似文献
52.
河南省安阳市内黄县三杨庄遗址是由于黄河下游洪水快速掩埋而保存的汉代文化遗址,是研究黄河流域历史气候变化与古河道变迁的理想载体。近年来,石英的光释光(OSL)测年技术广泛应用于水成沉积物的定年。本文选取三杨庄文化遗址区的一个深度为10.40 m 的剖面,使用细颗粒石英单片再生剂量(SAR)法OSL 技术测量了该剖面的8个样品的年龄,建立了剖面年代标尺,并与前人测得的加速器质谱(AMS)14C年龄进行了对比,结果显示:(1)三杨庄剖面年龄分布在约12.43 — 1.21 ka,沉积于整个全新世时期,剖面沉积速率波动幅度较大,在约3.91 — 3.15 ka(深度9.60 — 5.00 m)沉积速率很快,而3.91 ka 之前的早 — 中全新世时沉积速率较慢;(2)剖面深度8.60 — 5.00 m,14C年代相对OSL 年代出现严重高估,高估值随深度增加而增大,由约2 ka 变化到约7 ka,推断三杨庄剖面14C年代的高估可能是由于碳库效应的影响;(3)三杨庄剖面细颗粒石英OSL 测年结果指示细颗粒石英在河流-洪积相沉积物测定中的潜力。 相似文献
53.
Keeping the blood flowing—plasminogen activator genes and feeding behavior in vampire bats 总被引:1,自引:0,他引:1
Tellgren-Roth A Dittmar K Massey SE Kemi C Tellgren-Roth C Savolainen P Lyons LA Liberles DA 《Die Naturwissenschaften》2009,96(1):39-47
The blood feeding vampire bats emerged from New World leaf-nosed bats that fed on fruit and insects. Plasminogen activator,
a serine protease that regulates blood coagulation, is known to be expressed in the saliva of Desmodus rotundus (common vampire bat) and is thought to be a key enzyme for the emergence of blood feeding in vampire bats. To better understand
the evolution of this biological function, we studied the plasminogen activator (PA) genes from all vampire bat species in
light of their feeding transition to bird and subsequently mammalian blood. We include the rare species Diphylla ecaudata and Diaemus youngi, where plasminogen activator had not previously been studied and demonstrate that PA gene duplication observed in Desmodus is not essential to the vampire phenotype, but relates to the emergence of predominant mammalian blood feeding in this species.
Plasminogen activator has evolved through gene duplication, domain loss, and sequence evolution leading to change in fibrin-specificity
and susceptibility to plasminogen activator inhibitor-1. Before undertaking this study, only the four plasminogen activator
isoforms from Desmodus were known. The evolution of vampire bat plasminogen activators can now be linked phylogenetically to the transition in feeding
behavior among vampire bat species from bird to mammalian blood.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
54.
55.
Magdalini Soupioni Kyriaki Vlachou Alexandra Psarologou Argyro Bekatorou 《毒物与环境化学》2016,98(10):1191-1199
AbstractThe extent to which selected ethanol and lactic acid production bioprocesses contribute to whey waste abatement was examined. Alcoholic fermentation of whey was carried out by kefir cells immobilized on grape stalks, delignified cellulosic materials, or brewer's spent grains. Lactic acid fermentation was also performed by free kefir cells with or without addition of brewer's spent grains as promoting material. Since whey fermentation rate is affected by the lactose uptake rate, 14C-labeled lactose was used to study the fermentation ability of kefir. The highest reductions in biochemical oxygen demand and chemical oxygen demand of whey, about 68% and 52%, respectively, were achieved by lactic acid fermentation in 6 h at 37 °C and pH 5.5, in the presence of 120 g brewer's spent grains. Additionally, at the same conditions, the highest 14C-labeled lactose uptake rate by kefir and consequently the highest alcoholic fermentation rate were also recorded. However, greater reductions in biochemical oxygen demand and chemical oxygen demand of whey are required prior to final disposal. 相似文献
56.
Treatments of the cyanobacteria Nostoc muscorum and Nostoc calcicola with the insecticide endosulfan (5, 10, and 20?µg?mL?1) inhibited growth, photosynthetic pigments, photosynthetic, and nitrogenase activities. The sensitivity of N. muscorum to endosulfan was higher than that of N. calcicola. The toxic effect of endosulfan was more pronounced on phycocyanin; however, a considerable reduction in chlorophyll a and carotenoids was also noticed. 14C-fixation appeared to be more sensitive to the insecticide than photosynthetic oxygen evolution. Endosulfan caused strong inhibition of photosystem (PS) II activity whereas PS I was least affected. The inhibition of PS II activity was partially restored by electron donors (DPC, NH2OH, and MnCl2) at low dose of endosulfan. Nitrogenase activity was significantly suppressed in both species by the endosulfan at high dose (20?µg?mL?1). On the basis of our comparative analysis, N. calcicola was found to be endosulfan resistant and can be used in paddy fields for better productivity under pesticide stress. 相似文献
57.
Studies conducted on the distribution, fate and metabolism of DDT in a model ecosystem simulating a tropical marine environment of fish, Gobious nudiceps, Lethrinus harak, Gobious keinesis, Gobious nebulosis and white shrimp (Panaeus setiferus), show that DDT concentration in the water decreases rapidly within the first 24?h. Rapid accumulation of the pesticide in the biota also reaches a maximum level in 24?h before gradually declining. The bioaccumulation factors calculated for the fish species (G. keinesis) and white shrimp (P. Setiferus) were 270 and 351, respectively, after 24?h. There was a steady build up of DDT residues in the sediment during the first 24?h which continued to a maximum concentration of 6.66?ng/g in the seawater/fish/sediment ecosystem after 3 weeks and 5.27?ng/g in the seawater/shrimps/sediment ecosystem after 2.7 days. The depuration of the accumulated pesticide was slow with only 54% lost in G. nudiceps within 3 days of exposure in fresh sea water. By contrast, depuration was fast in the white shrimp, which lost 97% of the accumulated pesticide under the same conditions. DDT was found to be toxic to two of the fish species (G. nebulosis and L. harak) and to white shrimp, and the degree of toxicity was dependent on the particular species. The 24?h LC50 at room temperature for the fish species G. nebulosis and white shrimp was found to be 0.011 and 0.116?mg/kg, respectively. These levels are comparable to the ones recorded for the temperate organisms. Degradation of DDT to its primary metabolites, DDE and DDD, was found in all the compartments of the ecosystem with DDE being the major metabolite in the fish, shrimps and sediment, while in seawater, DDD dominated as the major metabolite. 相似文献
58.
C. Bastioli A. Cerutti I. Guanella G. C. Romano M. Tosin 《Journal of Polymers and the Environment》1995,3(2):81-95
The biodegradation behavior of insoluble crystalline polymers depends on both chemical structure and physical state. The physical state is strongly affected by the molding conditions; moreover the presence of natural hydrophylic substances such as starch can further influence the biodegradation process. This paper examines the biotic and abiotic degradation of thick injection-molded parts, made of pure poly--caprolactone (PCL) at different molecular weights, and of PCL in the presence of starch in the case of a commercial grade of Mater-Bi, produced by Novamont. The abiotic degradation was studied at 25 and 50°C, whereas the biotic degradation was followed in conditions of SCAS (semicontinuous activated sludges) at 25 and 50°C, soil burial, and controlled composting. The physical-chemical modifications provoked at the surface and in the bulk of the samples by the different types of degradation were determined by differential scanning calorimetry, viscometric and gravimetric analysis, scanning electron microscopy, and dynamic mechanical analysis. The mechanical modifications induced by the different environments were followed by tensile tests. It was demonstrated that the presence of starch significantly increases the apparent biodegradation rate of PCL, making even thick parts of ZI01U compatible with the composting process.Paper presented at the Bio/Environmentally Degradable Polymer Society—Third National Meeting, June 6–8, 1994, Boston, Massachusetts. 相似文献
59.
A de novo case of ‘pure’ trisomy 14q21 → qter is described which was detected at amniocentesis following an abnormal ultrasound scan of a 25–year-old woman. This is apparently the largest distal 14q duplication reported in a case surviving beyond the first trimester. The infant apipeared to have an association of clinical abnormalities previously observed in distal 14q trisomy and proximal 14q trisomy/mosaic trisomy 14. 相似文献
60.
摇蚊幼虫是淡水湖泊中分布广泛、数量极大的底栖动物。它们生活在底泥中,位移能力很小,个体又较大,被认为是水质监测和生态毒理学研究的理想生物。底栖动物能大量富集水中微量的有毒物质,这已有许多报道,而有关摇蚊幼虫富集底泥中的有毒物质的报道甚少,国内至今尚未见报道。摇蚊幼虫富集毒物与其它底栖动物比较,其生态学意义更大,因为摇蚊幼虫除了作为鱼饵通过水生食物链浓缩和转移毒物外,大量的幼虫终将羽化为成虫,一批批飞离水体,有毒物质有可能较快地被消除掉。 相似文献