考虑河道输水损失的大型泵站系统运行优化

大型泵站前池水位变化频繁且变化幅度较大时,机组经常偏离高效区运行,造成能源浪费。泵站系统中除了主机组、辅助设备和输变电设施消耗能量外,河道的输水水量损失和水力损失也综合成泵站所抽提水体的水能损失,进而影响泵站的运行性能。根据水源水位变化,在调水目的地水位一定的情况下,考虑河道输水水力损失与水量损失,首先分别确定调水目的地需要流量与泵站抽水扬程、抽水流量之间的关系,避免了优化计算过程中水位的重复迭代,极大减小了计算量与计算时间。以长江三江营最大潮差、平均潮差、最小潮差3个典型日为例,在南水北调东线淮安站站下水位及需要流量一定的情况下,以系统日运行费用最少为优化目标,建立优化模型,并采用模拟退火-粒子群算法(SA-PSO,simulated annealing-particle swarm optimization)求解,计算结果表明,与水泵设计角度运行方案相比,泵站系统实施变角优化运行,其运行费用可分别节约0.62%~2.26%、0.33%~3.26%和0.22%~0.83%。     

重庆北碚区土壤水热耦合模型研究

以南方的土壤和气候条件为背景,在裸露土壤的非恒温模型一维非饱和水流运动方程后增加根系吸水函数项得到作物地的土壤一维非饱和水流运动方程,与土壤中非稳态热流方程构成作物地的土壤水热耦合运移模型,联合初始边界条件,采用隐式差分法进行数值求解.结果表明：该水热运移耦合模型模拟值与实测值基本吻合,其拟合精度随土层深度增加而提高.     

气体射流冲击对流换热系数试验研究

在气体射流冲击试验装置上，冲击温度105～135℃，气流速度6.7～14.4m／s，相对湿度0～30%的范围内，进行了对流换热系数的研究，得到如下结论：物料表面温度T接近饱和温度T_s时，对流换热系数值出现转折，拐点前对流换热系数h为拐点后的3～12倍。在表面温度Ts时，可获得较大的对流换热系数，对流换热系数h随温度、气流速度和湿度的增大而增大，最大可达1403w／(m²·K)。在表面温度T>T_s时，对流换热系数值明显变小，且与0%相对湿度的对流换热系数值接近一致；在气流速度为恒定时，温度和湿度对对流换热系数影响不明显；在温度为恒定时，对流换热系数随气流速度的增加而增大，湿度变化对其影响不明显，对流换热系数h在120～136w／(m²·K)范围内。     

Estimating N transfers between N<Subscript>2</Subscript>-fixing actinorhizal species and the non-N<Subscript>2</Subscript>-fixing<Emphasis Type="Italic"> Prunus avium</Emphasis> under partially controlled conditions

Two methods of N transfer between plants—by litter decomposition and root-to-root exchange—were examined in mixed plantations of N-fixing and non-fixing trees. Nitrogen transfers from decaying litters were measured by placing ¹⁵N-labelled litters from four actinorhizal tree species around shoots of containerized Prunus avium. Nitrogen transfers by root-to-root exchanges were measured after foliar NO₃-¹⁵N fertilization of Alnus subcordata and Elaeagnus angustifolia growing in containers in association with P. avium. During the first 2 years of litter decomposition, from 5–20% of the N, depending on the litter identity, was released and taken up by P. avium. N availability in the different litters was strongly correlated with the amount of water-soluble N, which was highest in leaves of E. angustifolia. In the association between fixing and non-fixing plants, 7.5% of the A. subcordata N and 25% of E. angustifolia N was transferred to P. avium by root exchange. These results showed that the magnitude of N transfers by root exchange depended on the associated N₂-fixing species. Among the species investigated, E. angustifolia displayed the highest capacity for exudating N from roots as well as for releasing N from litters. These qualities make this tree a promising species for enhancing wood yields in mixed stands.     

Multiple Metal Resistant Transferable Phenotypes in Bacteria as Indicators of Soil Contamination with Heavy Metals (6 pp)

Background, Aim and Scope   Environmental contamination by heavy metals affects microbial communities. The number of single and multiple heavy metal resistant bacteria may be an indictor of the level of contamination. This paper details the isolation and characterisation of metal resistant microorganisms isolated from rhizosphere/soil samples obtained from an abandoned zinc, lead and copper mine and a local unaffected site. This data was compared to the level of heavy metal in the soils to establish the effect of metals on the microbial community and to determine the relationship between pollutant levels and resistant strains. This paper outlines the diversity of transferable resistance determinants between both sites and details the levels of heavy metal resistant bacteria and those expressing transferable multiple heavy metal tolerance.Methods   The sample sites were located in Co. Galway, Ireland. The first sample site (site A) was a former lead, zinc and copper mine, which was closed in 1961 due to exhaustion of ore. The second site (site B) was located two and a half kilometres from the mining site and was not affected by the mining operations. Composite soil samples were characterised for general soil matrix composition, organic content, pH and general chemical parameters. The soil was also enumerated for the total viable heterotrophic counts and tested on Pseudomonas selective agar (PSA) for total Pseudomonas counts and Sucrose Asparagine (SA), which is semi-selective for fluorescent Pseudomonas.Results and Discussion   Samples from both site A and site B were analysed by atomic absorption spectrophotometry for the presence of heavy metals. In the case of copper, which has a Dutch list recommended minimum permissible level of 190 &#181;g/Kg dry weight, the levels detected at site A were 1270 &#181;g/Kg dry weight while site B was detected at 36 &#181;g/Kg. The arsenic levels detected at site A were eight times the permissible level (416 &#181;g/Kg) while only half the permissible level was found at site B (13 &#181;g/Kg). Zinc concentrations were also high at site A (4460 &#181;g/Kg) while at site B (553 &#181;g/Kg) they were well below the Dutchlist guidelines (720 &#181;g/Kg). A large number of heavy metal tolerant strains were isolated from both sites. 270 isolates (site A (170) and site B (100)) were screened against 8 metals to examine the extent of multiple resistance. 82% of the strains from site A were found to be resistant to 5 metals. A total of 18% showed resistance to all 8 metals and of those examined only 4% were resistant to only one metal. In contrast isolates from site B showed no multiple resistance to more than 5 metals, while 62% showed resistance to individual metals only. Site A had a higher level of multiple heavy metal resistance strains. Stains isolated from site A had 23 (14%) isolates resistant to zinc, copper, nickel, arsenic and cobalt and site B had no bacteria resistant to all five of these selected metals. The transferability of heavy metal resistance was investigated in the case of 60 multiple heavy metal resistant isolates taken from site A and 50 multiple resistance isolates from site B. Transfer was only detected in isolates from site A, 13% showed transfer and expression of copper, zinc and arsenic resistance determinants. In most cases the transconjugants only expressed resistance to copper, zinc and arsenic, which were the metals, used for selection. This co-transfer of all three determinants suggests a genetic link between these resistance determinants.Conclusion   Heavy metal resistant bacteria are present in both sites, however, the number and presence of multiple transferable resistance phenotypes are confined to the isolates from the heavy metal contaminated site. The presence of high levels of heavy metals selects these multiple resistance phenotypes. Within these communities there seems to be little diversity between the microorganisms, which provides a hugely preferable environment for gene transfer of such metal resistant determinants.Recommendation and Perspective   The experiments have shown a microbes ability to mobilize heavy metal determinants and a relationship between heavy metal resistance and metal contamination has been identified These multiple heavy metal resistant bacteria could eventually be used for detection and qualification of the level of heavy metal-polluted soil/water environments.     

Calculation of Capacity of Vertically Loaded RC Joint of Local Transf er from Square Column to Straight Wall

On the basis of experimental results on four specimens of vertically loaded RC joints of local transfer from square column to straight wall, interaction between the transfer beam and the straight wall above it is analyzed. In the test, the effect of height of armpit on the transfer beam upon the behavior of the joint is specially studied. As a result, determination of the design shear force and shear capacity of the transfer beam and calculation of capacity of the straight wall are suggested, taking into account the effect of shear span ratio of the beam.     

Transfer of disease resistance within the genus Brassica through asymmetric somatic hybridization

Summary Asymmetric somatic hybrid plants between Brassica napus L. (oilseed rape genome AACC) and a transgenic line of Brassica nigra L. Koch (black mustard genome BB) were tested for their resistance against rapeseed pathogens Phoma lingam (black leg disease) and Plasmodiophora brassicae (club root disease). The transgenic B. nigra line used (hygromycin-resistant, donor) is highly resistant to both fungi, whereas B. napus (recipient) is highly susceptible. The asymmetric somatic hybrids were produced using the donor-recipient fusion method (with X-irradiation of donor protoplasts) reported by Zelcer et al. (1978) for the production of cybrids. Using hygromycin-B for selection, a total of 332 hybrid calli were obtained. Regenerants, resistant or susceptible to both diseases, were selected. Many hybrids expressed resistance to only one pathogen. Dot blot experiments showed that the asymmetric hybrid plants contained varying amounts of the donor genomic DNA. Furthermore, a correlation was detected between the radiation dose and the degree of donor DNA elimination.     

Studies of the mechanism of transgene integration into plant protoplasts: improvement of the transformation rate

Summary The production of transgenic plants by means of direct gene transfer to protoplasts is now a widely-used technique. The biological mechanisms underlying the transformation are still poorly understood, but many investigations have attempted to shed light on some components of this process. Varying the experimental conditions has in some cases led to better transformation rates, but further improvements of the protocols are possible. Such improvements will require a better understanding of how the alien DNA enters the cells, becomes integrated into the chromosomes and is treated as a part of the plant genome. Irradiation with sublethal doses of X-rays or UV-light has been shown to increase the transformation frequency, while certain drugs have been shown to act in a similar manner. The effects of these and other factors are discussed.Abbreviations Aph aphidicolin - ATF absolute transformation frequency - BLM bleomycin - CaMV cauliflower mosaic virus - CAT chloramphenicol acetyl transferase - CHO Chinese hamster ovary cells - EF enhancement factor - Nos nopaline synthase - NPTII neomycin phosphotransferase II - Ocs octopine synthase - PEG polyethyleneglycol - RTF relative transformation frequency     

Genetic transformation of Brassica

Tissue culture regeneration of plants from Brassica species can be achieved from various explant types. Their performance, however, varies with the genotype and age of the explant and is sensitive to medium supplements and Agrobacterium cocultivation. Most Brassica transformations were carried out using Agrobacterium and it was established that nopaline and agropine strains of A. tumefaciens and A. rhizogenes, respectively, are the most efficient. Application of virulence gene induction is ambiguous. Binary vectors are mostly applied in spite of indications that cointegrate vectors are more efficient. Cotransformation is successful with two different bacteria or with one bacterium carrying both plasmids, however, it has proved problematic to integrate the two transgenes into separate loci. Transformations with wild type rol genes develop hairy roots, from which transgenic plants can be regenerated. Vectorless transformation is feasible with microprojectile bombardment of microspore derived embryos being the most promising. Antibiotic markers providing resistance to kanamycin, hygromycin, and spectinomycin are applicable as selectable markers, while chloramphenicol is not suitable. Among herbicides, phosphinotricin gives good results while chlorsulfuron is unsuitable for in vitro selection. Major therapeutic antibiotics being successfully applied are carbenicillin, cefotaxime, amoxycillin, and ticarcillin. Standard methods for evaluating transgenic plants also have been applied to Brassica species. Some breeding objectives obtained through genetic transformation are presented.