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Synthetic hydrophilic polymers find promising applications in pharmacology, biotechnology and chemistry. The biocompatibility, biodegradability and pharmacological activity of these polymers depend much on their hydrophilic nature. This article summarizes the recent developments in the utilization of the different classes of these hydrophilic polymers as pharmacologically active agents, for enzyme modification and as catalysts and supports for chemical reactions. 相似文献
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Predatory carabids, staphylinids and spiders were monitored from 1981 to 1987 in a Dutch project concerning the development of arable farming systems. During this period epigeic predators in the conventional, integrated and organic systems were sampled using pitfall traps. The effects of crop type and farming system on species diversity, abundance and guild structure was analysed using trap data from wheat, pea, sugar beet, potato, onion and carrot fields. Predator abundance and species composition were found to be clearly affected by the farming system. However, in most cases the type of crop appeared to be of greater importance. Crops with a greater cover early in the season, like winter wheat and peas appeared to be more favourable than late and open crops like onions or carrots. Both system and crop effects were more apparent in carabids than in spiders or staphylinids. Only minor effects of farm management were found on species richness. Again, the crop itself seemed to be the main structuring factor. It is concluded that the presence and quality of predator populations is mainly determined by crop structure and crop-related factors. The role of favourable crops and field size in predator enhancement is discussed in relation to the agroecological infrastructure of the landscape. 相似文献
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Andreas Züttel 《Mitigation and Adaptation Strategies for Global Change》2007,12(3):343-365
Hydrogen storage and transportation or distribution is closely linked together. Hydrogen can be distributed continuously in
pipelines or batch wise by ships, trucks, railway or airplanes. All batch transportation requires a storage system but also
pipelines can be used as pressure storage system. Hydrogen exhibits the highest heating value per weight of all chemical fuels.
Furthermore, hydrogen is regenerative and environment friendly. There are two reasons why hydrogen is not the major fuel of
toady’s energy consumption: First of all, hydrogen is just an energy carrier. And, although it is the most abundant element
in the universe, it has to be produced, since on earth it only occurs in the form of water. This implies that we have to pay
for this energy, which results in a difficult economic task, because since the industrialization we are used to consuming
energy for free. The second difficulty with hydrogen as an energy carrier is the low critical temperature of 33 K, i.e. hydrogen
is a gas at room temperature. For mobile and in many cases also for stationary applications the volumetric and gravimetric
density of hydrogen in a storage system is crucial. Hydrogen can be stored by six different methods and phenomena: high pressure
gas cylinders (up to 800 bar), liquid hydrogen in cryogenic tanks (at 21 K), adsorbed hydrogen on materials with a large specific
surface area (at T < 100 K), absorbed on interstitial sites in a host metal (at ambient pressure and temperature), chemically bond in covalent
and ionic compounds (at ambient pressure), oxidation of reactive metals e.g. Li, Na, Mg, Al, Zn with water. These metals easily
react with water to the corresponding hydroxide and liberate the hydrogen from the water. Finally, the metal hydroxides can
be thermally reduced to the metals in a solar furnace. 相似文献
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为了探究胞外聚合物(EPS)对厌氧氨氧化颗粒污泥活性的影响,分别向厌氧氨氧化颗粒污泥中投加30mg/L的总胞外聚合物(IN-EPS),松散结合型胞外聚合物(LB-EPS)和紧密结合型胞外聚合物(TB-EPS).结果表明,3种EPS均可提高厌氧氨氧化颗粒污泥的活性.对于添加了IN-EPS,LB-EPS和TB-EPS的实验组,厌氧氨氧化颗粒污泥的氨氮去除速率分别增加了6.68%,10.5%和19.29%,厌氧氨氧化菌的生长速率分别增加了18.25%,21%,16.3%.三维荧光光谱法分析发现3种EPS的组成基本相同,以芳香族蛋白质和可溶性微生物产物为主.对EPS中的高丝氨酸内酯类(AHLs)信号分子进行检测,发现EPS中含有3种信号分子,分别是C4-HSL,C6-HSL和C10-HSL,外源投加这3种AHLs到厌氧氨氧化颗粒污泥中,结果发现C4-HSL和C6-HSL可以提高厌氧氨氧化颗粒污泥的活性和生长速率,这是EPS可以提高厌氧氨氧化菌活性的原因. 相似文献
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《Journal of Cleaner Production》2005,13(1):43-49
The most fundamental aspect in the ISO 14001 standard Environmental management systems—Specification with guidance for use is to find out ways by which an organisation influences environment to a significant degree. This paper examines environmental data from companies manufacturing products mainly from metals and/or polymers. The data were collected in a uniform way by use of special guidelines. Weighting or valuation methods often used in life cycle assessments were used to quantitatively compare and rank environmental aspects. The study results suggest that, in general, the largest environmental impact in the investigated manufacturing sub-sector can be associated with product use and/or disposal phases. This in turn shows a need for more attention on environmental work on the design for environment than what the ISO 14001 standard requires. It is further suggested that weighting or valuation methods can aid in determining the significance of environmental impacts and aspects in the context of ISO 14001. 相似文献
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Duplex kidneys occur in 0.8% of the general population, many of whom are asymptomatic. Children with duplex kidneys may be prone to urinary tract infections because of vesico-ureteric reflux or obstruction. Surgical management is usually required once symptoms occur. Increasing numbers of duplex kidneys are now prenatally diagnosed by ultrasound, resulting in the development of early postnatal strategies to try and reduce morbidity. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Numerous different bioreactor systems are applied for hydrogen production by dark fermentation. Thermophilic fermentations are gaining an increased interest due to the high hydrogen yields associated with them. In order to reach the best thermophilic fermentation system, 2 types of bioreactors, a trickling bed and a fluidized bed system, were constructed and operated under similar conditions. Both systems were designed to meet the requirements of thermophilic fermentations, such as reduction of hydrogen partial pressure, system immanence as its best as well as increasing cell densities. For comparing the 2 systems, the extreme thermophilic organism Caldicellulosiruptor owensensis OLT and a glucose-containing medium were employed. Parameters like hydraulic retention time, glucose concentration and stripping gas amount were varied. Each bioreactor system exhibited certain advantages; the trickling bed system enabled yields close to 3 mol-H2 (mol-glucose)?1 and productivities of 0.2 L L?1 h?1, but the application of stripping gas seemed to be obligatory. The fermentations in the fluidized bed system were characterized by slightly higher productivities (0.25 L L?1 h?1), but generally lower yields. However, operation of this system without stripping gas was possible. 相似文献
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《Journal of Cleaner Production》2007,15(3):280-287
This paper analyses the performance of ‘market-based’ and ‘feed-in tariff’ systems of renewable energy procurement, and comments on the impact of different procurement systems on investment in renewable energy. The ‘market-based’ British Renewables Obligation (RO) is not more cost-effective compared to the German feed in tariff. Although the nominal rates of payment per kWh of renewable energy are higher in Germany, this is more than offset by lower wind speeds in Germany producing a lower return on investment compared to the UK. A harmonised, EU-wide market-based system, would not improve cost-effectiveness, and may serve to reduce, rather than increase, local investment in renewable energy. On the other hand, nationally based green electricity certificate systems like the RO are not intrinsically biased against locally owned or co-operative ventures. Systems are needed which encourage a diversity of investment in renewable energy from local as well as institutional sources. 相似文献
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Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1,AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly basic anion exchanger resin D301 was compared. It was found that the aminated hypercrosslinked resins had the highest adsorption capacities among the tested polymers. The empirical Freundlich equation was successfully employed to describe the adsorption process. Specific surface area and micropore structure of the adsorbent, in company with tertiary amino groups on matrix affected the adsorption performance towards catechol. In addition, thermodynamic study was carried out to interpret the adsorption mechanism. Kinetic study testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate and increase the adsorption apparent activation energy. 相似文献
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《Environmental Science & Policy》2000,3(1):39-45
Integration of occupational health and safety matters into environmental management systems can bring many benefits to industrial companies. They can avoid duplicated measures and find optimal solutions, because the principles of prevention are similar in environmental protection and safety management. However, the methods currently used in environmental management and engineering such as life-cycle assessments, best available technology reports, and the models of industrial production can hinder this integration, because they take into account occupational risks only to a limited extent. People can also consider occupational safety risks more easily than environmental risks as a natural part of their work. This can lead to the situation where occupational risks are underestimated. 相似文献
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两种含氮高分子材料的热解烟气毒性评价 总被引:2,自引:0,他引:2
采用GA/T 506-2004中规定的产烟模型对2种含氮高分子材料进行热解,将实验动物动态暴露于热解烟气中并使用傅立叶变换红外分析仪(FTIR)对热解烟气进行成分分析,将成分分析的结果用模型进行计算.结果表明,在热解温度为600 ℃时,腈纶毛线的热解烟气毒性大大高于羊毛地毯的热解烟气毒性;在不考虑NO2的情况下N-气体值在0.5~1.3之间有受试动物死亡;烟气毒性的研究中数学计算方法不一定能完全替代动物实验;动物实验与成分分析、数学计算相结合在现阶段还是研究烟气毒性的较为有效的手段. 相似文献
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Tarisai Velempini Kriveshini Pillay Xavier Y.Mbian Omotayo A.Arotiba 《环境科学学报(英文版)》2019,31(5):280-296
Sulfur containing ion imprinted polymers(S-IIPs) were applied for the uptake of Hg(Ⅱ) from aqueous solution. Cysteamine which was used as the ligand for Hg(Ⅱ) complexation, was grafted along the epichlorohydrin crosslinked carboxylated carboxymethyl cellulose polymer chain through an amide reaction. The adsorption ability of S-IIPs towards Hg(Ⅱ)was investigated by kinetic and isotherm models, which, corresponding, showed that the adsorption process followed a pseudo-second-order, fitted well with the Langmuir isotherm with a maximum adsorption capacity of 80 mg/g. Moreover, thermodynamic studies indicated an endothermic and spontaneous reaction with the tendency of an enhanced randomness at the surface of the S-IIPs with temperature increases. S-IIPs indicated a high degree of selectivity towards Hg(Ⅱ) in the presence of Cu~(2+), Zn~(2+), Co~(2+), Pb~(2+)and Cd~(2+).Furthermore, the efficiency of S-IIPs was also evaluated against real samples showing86.78%, 91.88%, and 99.10% recovery for Hg(Ⅱ) wastewater, ground water and tap water,respectively. In this study, the adsorbent was successfully regenerated for five cycles, which allows for their reuse without significant loss of initial adsorption capability. 相似文献