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21.
Two new complexes, [Cu(mamba)2] and [Mn(mamba)2] (mamba−, N-(2-methylpyridine)-2-aminomethyl benzoate) were synthesized and characterized by X-ray crystallography. Whereas the [Cu(mamba)2] complex crystallizes in a monoclinic P21/c space group, the [Mn(mamba)2] complex crystallizes in a triclinic space group. The nature of the metal ion greatly influences the lattices and the molecular structures of the compounds. In the crystal lattice of the copper complex are four cocrystallized methanol solvent, which are all involved in building six strong H-bonds with the complex. However, the lattice for the manganese complex contain only one cocrystallized methanol, along with one NaClO4, that is also involved in making one H-bond with the [Mn(mamba)2] unit. Nevertheless, the sodium ion is coordinated to the ClO4−, the methanol and two [Mn(mamba)2] to form a stable extended chain metal complex. Electrochemical studies indicated that both complexes undergo quasi reversible one electron reduction in acetonitrile. 相似文献
22.
H2O2应激条件下的活性酵母细胞衍生物的研究 总被引:4,自引:0,他引:4
对过氧化氢(H2O2)应激条件下产生的活性酵母衍生物(Live Yeast Cell Derivative,LYCD)进行了研究,结果表明:LYCD对细胞具有明显的促呼吸作用,其作用大小与制备LYCD过程中所加入的H2O2的刺激强度有关。另外,对LYCD中两种重要的抗氧剂-还原型谷胶甘肽(GSH)和超氧化物歧化酶(SOD)的测定分析结果显示:在H2O2的作用下,应激反应发生15min时,LY-CD中SOD的比活力最强,发生30min时,GSH的含量最高,不同的应激产物有各自产生的最佳时间。 相似文献
23.
Ferrous Iron Stimulates Phenol Oxidase Activity and Organic Matter Decomposition in Waterlogged Wetlands 总被引:1,自引:0,他引:1
Peter?M.?Van?BodegomEmail author Rob?Broekman Jerry?Van?Dijk Chris?Bakker Rien?Aerts 《Biogeochemistry》2005,76(1):69-83
Soil organic matter decomposition is limited at waterlogged conditions by the low activity of extracellular enzymes like phenol
oxidases. In this paper, we show that ferrous iron (Fe2+), which is abundant in waterlogged soils, significantly stimulates phenol oxidase activity both in pure enzyme assays and
in waterlogged soil slurries from nutrient-poor dune slacks. However, the effects in soil slurries were less strong than in
enzyme assays. Both the addition of Fe2+ and the initial presence of Fe2+ stimulated phenol oxidase activity at the microaerophilic conditions tested. This stimulation is attributed to the catalysis
of additional OH radical production, promoting the oxidation of phenolics. Subsequently, the presence of Fe2+ strongly increased total decomposition rates of soil organic matter, measured as CO2 production and Cotton strip Tensile Strength Loss. There is circumstantial evidence that this stimulation by Fe2+ could be important for decomposition in wetlands at field conditions, but its relevance compared to the effects of other
compounds still needs to be elucidated. These results emphasise the crucial role of water quality in determining extracellular
enzyme activity and decomposition in waterlogged wetlands. 相似文献
24.
25.
VOLKER H. W. RUDOLF 《Ecological Entomology》2011,36(6):744-750
1. A predator's ability to suppress its prey depends on the level of interference among predators. While interference typically decreases with increasing habitat complexity, it often increases with increasing size differences among individuals. However, little is known about how variation in intrinsic factors such as population size structure alters predator–prey interactions and how this intrinsic variation interacts with extrinsic variation. 2. By experimentally varying the level of vegetation cover and the size structure of the predatory damselfly Ischnura posita Hagen, we examined the individual and interactive effects of variation in habitat complexity and predator size structure on prey mortality. 3. Copepod prey survival linearly increased as the I. posita size ratio decreased and differed by up to 31% among different predator size structures. Size classes had an additive effect on prey survival, most likely because intraspecific aggression appeared size‐independent and size classes differed in microhabitat preference: large I. posita spent 14% more time foraging on the floor than small larvae and spent more time in the vegetation with increasing habitat complexity. Despite this difference in microhabitat use among size classes, habitat structure did not influence predation rates or interference among size classes. 4. In general, results suggest that seasonal and spatial variation in the size structure of populations could drive some of the discrepancies in predator‐mediated prey suppression observed in nature, and this variation could exceed the effects of variation in habitat structure. 相似文献
26.
High-temperature biotrickling filtration of hydrogen sulphide 总被引:1,自引:0,他引:1
Biofiltration of malodorous reduced sulphur compounds such as hydrogen sulphide has been confined to emissions that are at
temperatures below 40°C despite the fact that there are many industrial emissions (e.g. in the pulp and paper industry) at
temperatures well above 40°C. This paper describes our study on the successful treatment of hydrogen sulphide gas at temperatures
of 40, 50, 60 and 70°C using a microbial community obtained from a hot spring. Three biotrickling filter (BTF) systems were
set up in parallel for a continuous run of 9 months to operate at three different temperatures, one of which was always at
40°C as a mesophilic control and the other two were for exploring high-temperature operation up to 70°C. The continuous experiment
and a series of batch experiments in glass bottles (250 ml) showed that addition of glucose and monosodium glutamate enhanced
thermophilic biofiltration of hydrogen sulphide gas and a removal rate of 40 g m−3 h−1 was achieved at 70°C. We suggest that the glucose is acting as a carbon source for the existing microbial community in the
BTFs, whereas glutamate is acting as a compatible solute. The use of such organic compounds to enhance biodegradation of hydrogen
sulphide, particularly at high temperatures, has not been demonstrated to our knowledge and, hence, has opened up a range
of possibilities for applying biofiltration to hot gas effluent. 相似文献
27.
本研究主要探讨黄龙自然保护区森林生态系统年净初级生产力水平和栖息地复杂程度对小型兽类物种多样性的影响。将调查区按海拔高度分为4 个调查点,每点的年净初级生产力水平各不相同,分别为: 24.9 MJ / (m2·a) ; 21.5 MJ / (m2·a) ; 17.5 MJ / (m2·a) 和14.1 MJ / (m2·a) 。在选择调查点时,同时考虑栖息地复杂程度,在生产力水平较高的调查点选择栖息地复杂程度较低的地点,而在生产力较低的调查点选择栖息地复杂程度较高的地点调查,以便分析森林生态系统年净初级生产力水平与栖息地复杂程度对小型兽类物种多样性的影响。采用鼠铗捕获小型兽类。结果表明,小型兽类物种多样性与森林生态系统年净初级生产力水平有密切关系,随着海拔升高,森林生态系统年净初级生产力的降低,所捕获的小型兽类生物量随之降低,其物种多样性也随之下降。小型兽类物种多样性也与栖息地复杂程度有关,森林生态系统年净初级生产力水平在一定范围内,大于17.5 MJ / (m2·a) ,栖息地复杂度的增加可以降低年净初级生产力水平对小型兽类物种多样性的影响。然而,森林生态系统年净初级生产力水平降低到一定程度时,小于14.1 MJ / (m2·a) ,生产力水平则为影响小型兽类物种多样性的主要因子。此外,小型兽类的生物量与森林生态系统年净初级生产力和栖息地复杂程度也有类似的关系。 相似文献
28.
阔叶红松(Pinus koraiensis)林是东北东部山区的地带性森林植被, 阐明其生产力的影响因素, 对于理解温带森林生产力维持机制具有重要意义。该研究依托小兴安岭典型阔叶红松林9 hm2动态监测样地, 基于2005和2015年的30 m × 30 m样方内所有胸径>6.5 cm的木本植物的调查数据, 计算各样方的树冠结构复杂性、物种多样性和林分胸高断面积, 结合各样方的地形和土壤理化性质数据, 拟合结构方程模型, 定量分析影响典型阔叶红松林生产力的直接和间接因素。研究结果显示: 树冠结构复杂性和物种多样性与生产力显著正相关, 且树冠结构复杂性对生产力的影响显著高于物种多样性; 树冠结构复杂性对生产力的作用分为树冠垂直分层和树冠可塑性, 其中树冠垂直分层是树冠结构复杂性影响阔叶红松林生产力的主要因素, 而树冠可塑性无显著影响; 林分胸高断面积与生产力显著正相关, 其解释权重仅次于树冠结构复杂性, 树冠结构复杂性与物种多样性均通过影响林分胸高断面积对阔叶红松林生产力产生间接影响; 考虑不同树冠结构复杂性时, 坡度和土壤全磷含量代表的环境因素在调节生产力上发挥的作用存在差异, 移除树冠垂直分层的作用后两者与生产力呈显著的负相关关系。综上可知, 在典型阔叶红松林中, 树冠结构复杂性比物种多样性更有效地解释了生产力的变化, 同时不可忽视其他生物和非生物因素对生产力的作用。 相似文献
29.
Modulation of beta-oxidation and proton conductance pathway of brown adipose tissue in hypo- and hyperinsulinemic states 总被引:3,自引:0,他引:3
J Seydoux E R Trimble F Bouillaud F Assimacopoulos-Jeannet S Bas D Ricquier J P Giacobino L Girardier 《FEBS letters》1984,166(1):141-145
The metabolic capacity of interscapular brown adipose tissue of hypoinsulinemic (diabetic) rats is decreased and a reduced beta-oxidative capacity contributes to this metabolic alteration. It was thus of interest to compare, in diabetic and in chronically (8 days) insulin-infused rats, the beta-oxidative capacity and indices of the thermogenic state (GDP-binding and 32 000 Mr protein) in this tissue. Mitochondrial GDP-binding and 32 000 Mr protein were both decreased in diabetic rats compared to appropriate controls and markedly increased as was also the beta-oxidative capacity in hyperinsulinemic rats. 相似文献
30.
1. Ship‐induced waves can affect the physical characteristics of lake and river shorelines, and laboratory studies have shown effects on littoral invertebrates. Here, we explored whether these effects could be observed under field conditions along a natural lake shore affected by wave sequences (trains) produced by boats. 2. Individuals of five invertebrate species (Bithynia tentaculata, Calopteryx splendens, Dikerogammarus villosus, Gammarus roeselii, Laccophilus hyalinus) were exposed to waves with increasing shear stress in five habitats differing in structural complexity. 3. Detachment of invertebrates increased with increasing shear stress and was best modelled using sigmoid response curves. Habitat structural complexity mitigated the effects of shear stress, and detachment rate was influenced more by habitat type than by species. A threshold (90% of the individual invertebrates unaffected) stress level of 0.64 N m?2 was found for a structurally complex reed habitat, compared to 0.37 N m?2 for a simple sand habitat. 4. Shear stress associated with wave trains created by recreational boating at a distance of 35 m from the shore and at a speed of 11 km h?1 resulted in 45% detachment of littoral invertebrates. Decreasing the boat‐to‐shore distance to 20 m increased wave shear stress by 30% and invertebrate detachments up to 75%. 5. Disturbance of littoral habitats and invertebrate assemblages are widespread in inland waters used for recreational and/or commercial navigation. Our findings show that the integrity of littoral zones of navigable surface waters could be much improved by implementing management measures such as physically protecting complex habitats with dense reed belts and tree roots, and reducing boat speeds and increasing their minimum shoreline distance. 相似文献