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采用生物栅技术处理上海市某一呈富营养化状态的河水。处理装置的9个廊道并联运行,连续进出水,平均每池处理水量为4.4 t/d。试验主要对比生物栅填料分别为球形填料、悬浮填料和组合填料时,对水体CODCr、SS、TN和TP等的去除效果,并分析了不同填料生物膜的微生物的数量变化。悬浮填料生物栅对CODCr、SS、TN、TP的去除率分别为33%~84%、42%~82%、6%~25%、15%~40%;组合填料生物栅分别为41%~79%、50%~93%、7%~28%、17%~44%;球形填料生物栅分别为34%~67%、34%~70%、5%~21%、10%~28%。结果表明组合填料生物栅和悬浮填料生物栅的污染去除效果优于球形填料。微生物测试结果表明,生物栅填料可以显著增加异养细菌特别是硝化细菌的数量,增强污染净化效果。 相似文献
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The nanometer scale topography of self‐assembling structural protein complexes in animals is believed to induce favorable cell responses. An important example of such nanostructured biological complexes is fibrillar collagen that possesses a cross‐striation structure with a periodicity of 69 nm and a peak‐to‐valley distance of 4–6 nm. Bovine collagen type I was assembled into fibrillar structures in vitro and sedimented onto solid supports. Their structural motif was transferred into a nickel replica by physical vapor deposition of a small‐grained metal layer followed by galvanic plating. The resulting inverted nickel structure was found to faithfully present most of the micrometer and nanometer scale topography of the biological original. This nickel replica was used as a die for the injection molding of a range of different thermoplastic polymers. Total injection molding cycle times were in the range of 30–45 seconds. One of the polymer materials investigated, polyethylene, displayed poor replication of the biological nanotopographical motif. However, the majority of the polymers showed very high replication fidelity as witnessed by their ability to replicate the cross‐striation features of less than 5 nm height difference. The latter group of materials includes poly(propylene), poly(methyl methacrylate), poly(L ‐lactic acid), polycaprolactone, and a copolymer of cyclic and linear olefins (COC). This work suggests that the current limiting factor for the injection molding of nanometer scale topography in thermoplastic polymers lies with the grain size of the initial metal coating of the mold rather than the polymers themselves.
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能源多元化对保障国家能源安全,紧跟世界能源发展趋势,及时转变能源发展战略的意义重大。分类讨论替代燃料,分析其发展态势和需要的支撑条件。 相似文献
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L. B. Brattsten 《Journal of chemical ecology》1988,14(10):1919-1939
Herbivorous insects have the capacity to develop behavioral, physiological, and biochemical resistance mechanisms in response to chemical selection pressures. Among natural insect-plant associations, there are several cases of target-site insensitivity to and enhanced metabolism of plant allelochemicals. There are also known instances of physiological defenses such as extra rapid excretion or storage of toxic compounds. Multiple defenses seem to be prevalent in natural insect-plant interactions that involve toxic compounds, possibly reflecting the long time these interactions have had to evolve compared to insect-synthetic insecticide interactions. Synthetic insecticides were introduced about 45 years ago. Until recently they have been used as single-active-component preparations. As such, they have been and are very effective in producing insect populations with enhanced detoxification ability and target-site insensitivity. Most insecticide-resistant insect populations have one major defense mechanism. This feature makes the synthetic insecticides very useful tools for studies of insect defenses against toxic chemicals. Information gained from studies with insecticides can shed light on the capabilities of insects to adapt to toxicants in their environment. In assessing the validity of work with synthetic insecticides for natural systems, the fundamental differences between these substances and allelochemicals, and in their presentation to the insects, must, however, be considered. The prevalence of multiple defenses and reliance on modified physiological processes in natural interactions may reflect different properties of the natural chemicals in being generally highly biodegradable and often less acutely toxic than synthetic insecticides. In many cases, the plant allelochemicals are presented to the insects as mixtures. It is, however, to be expected that pest insects will evolve effective multiple defenses against synthetic insecticides. About 20% of all resistant populations have already developed multiple defenses, in most cases combinations of enhanced metabolism and target-site insensitivity. This implies that current crop protection practices need to be modified to ensure the continued usefulness of synthetic insecticides. To achieve this, it is important to study intensively not only insect-insecticide interactions but also the interactions operating in natural insect-plant associations. 相似文献