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951.
Yuan Gao Jun Deng Chunwang Li Fengling Dang Zhuo Liao Zhijun Wu Liguang Li 《Biotechnology advances》2009,27(5):616
We studied the spray characteristics of inedible oil using experimental and simulation methods. Spray penetration, spray cone angle and spray tip speed were measured at different biodiesel ratios in a constant volume vessel with wide visualization and high back pressure, using a high-speed camera. The characteristics of biodiesel spray were simulated under the same conditions using Star-CD software. The experimental results showed that, as the ratio of biodiesel in the blends increased, spray penetration and spray speed increased, but the spray cone angle decreased. Throughout the spray injection period, the region at 0.05–0.475S (spray tip penetration) was a key area affecting spray cone angle. From 0.8 ms after injection, the spray penetration deviation ratios started to increase with increasing biodiesel blend ratios. Simulation results showed similar macroscopic spray characteristics to the experimental results for jatropha oil. The results also showed that the Sauter mean diameter of blend fuels was greater than that of diesel, and spray was more concentrated, due to the higher viscosity and surface tension of the biodiesel, compared with conventional diesel fuel. The macroscopic and microscopic spray properties of blended fuels containing 5%, 10% and 20% biodiesel were similar to diesel. 相似文献
952.
Summary A completely liquid-filled growth chamber for axenic cultures ofTetrahymena pyriformis is described; gas exchange is ensured across a synthetic membrane. The chamber may be incorporated into a continuous flow system with inoculation and removal of cell samples under sterile conditions. Initially, the generation time of the cells was slightly prolonged, about 10%, but after some cell doublings decreased to 5%. The capacity of the cells to form food vacuoles (endocytosis) was unaltered during growth in the chamber. The synthetic membrane was highly permeable to O2 and CO2; however, cells grown in the chamber contained small refractive granules. The culture chamber permits the culture volume to be varied and it may be used for other protozoa, bacteria, and even tissue culture cells. 相似文献
953.
黄淮海平原封丘试区水体理化性状的多元分析 总被引:4,自引:2,他引:2
在封丘试区内两个最具代表性水体(曹岗湖,潘店芦苇荡)水质调查的基础上,对主要水质指标及其集合进行方差分析和聚类分析,结果表明:封丘试区水体具有典型的北方水体特征,其水质的变化主要受季节影响,水体间无甚大差别。各水体pH值偏高(年平均值为8.0—9.0),属弱碱性;硬度较大(17.54—20.63德国度),均属硬水且有逐年上升趋势;离子总量较大(860—1448mg/L);碱度(4.57—5.20me/L)和主要营养物含量(总氮1.31—2.08mg/L,总磷0.100—0.135mg/L)较高,属富营养型水体。文中指出:该试区水体水质状况较好,渔业开发潜力较大,但磷是水体生物生产力的主要限制性营养物。 相似文献
954.
955.
Habitat preferences of four chironomid species associated with aquatic macrophytes were studied during the vegetation season from April to October at an irrigation reservoir located in Nagoya, Japan.The two smaller sized species,Corynoneura cuspis Tokunaga andPentapedilum tigrinum Hashimoto, were found to be abundant in two floating-leaved plants,Nymphoides indica O. Kuntze andTrapa japonica Flerov. Phytophages,C. cuspis larvae were observed freely moving on the surfaces of leaves and stems within both of these floating-leaved plant communities. Although found within both plant communities,P. tigrinum larvae, as facultative leaf miners, were more concentrated on the surfaces and within the leaves ofN. indica, which have a thin epidermis and thick mesophyll layer.The two larger sized species,Glyptotendipes viridis (Macquart) andPentapedilum sordens (van der Wulp), were found to be living principally within the stems ofN. indica and the petioles ofT. japonica. These parts of the plants, with thin epidermis and many lacunae in the parenchyma, are favorable for miners. 相似文献
956.
Density patterns ofLipiniella arenicola andChironomus muratensis were studied in Lake Wolderwijd (The Netherlands) using geostatistics, and compared with patterns of depth and silt contents of the sediment.L. arenicola was restricted to shallow (depth <1 m), sandy silt (silt content <5%), wind-exposed sediments.Ch. muratensis occurred all over the lake, but the highest densities were found in the sheltered silty North-West corner. Gut analyses of IV-instar larvae from the Ventjagers flats (Haringvliet, Lower Rhine-Meuse) showed thatL. arenicola fed by selectively grazing on benthic algae,Ch. muratensis by filtering and non-selective grazing, andCh. nudiventris by non-selective grazing. In the laboratory, behavioural responses to reduced oxygen concentrations were tested with the impedance conversion technique.L. arenicola was more sensitive to low oxygen concentrations (<3 mg l–1) than bothChironomus species. It is argued that the differences in resistance to hypoxia and feeding behaviour are in accordance with the differences in distribution patterns. The restriction ofL. arenicola to the pure sand habitats is not attributable to an especially high sensitivity to low dissolved oxygen concentrations alone. Several behavioural adaptations enableL. arenicola larvae to live in the shallow, wind-exposed pure-sand habitats: the ability to select food items, tube strength, and site selection of ovipositing females or planktonic larvae. 相似文献
957.
Questions
Management practices implemented on road verges are partly established to preserve biodiversity in agricultural landscapes. Their evaluation was primarily based on the analysis of the taxonomic structure and composition of communities. What is the relationship between management practices and the functional characteristics of road–field plants within elements?Location
West‐central France.Methods
We sampled the berm, the embankment and the field margin of 40 road–field boundaries located in west‐central France, an area where delayed mowing of some berms has been practised since 2009 for biodiversity reasons. We characterized management practices implemented on the different elements, i.e., the frequency and timing of mowing (early summer or late summer), the frequency of herbicide treatment in field margins and the N input rate. We retrieved from databases seven functional traits and types known to be influenced by management practices. To identify relationships between traits or types and environmental variables we first performed partial RLQ analyses to remove any potential confounding effect of the landscape context studied. We then computed fourth‐corner statistics to quantify relationships between traits or types, environmental variables and partial RLQ axes.Results
Late mowing of the berm promoted nitrophilous species within berms and competitive rather than ruderal species within arable field margins. The frequency of herbicide treatment in field margins promoted broad‐leaf species within this element and, to a lesser extent, within embankments. Finally, the functional characteristics of communities of the three elements were not influenced by the level of N input in field margins.Conclusions
In our environmental context, managing road verges affected the functional structure of plant assemblages both within them and within their adjacent arable field margins. We suggest a single early mowing of berms as a valuable practice for both conservation purposes and weed risk control in adjacent field margins. 相似文献958.
Conventional forensic DNA analysis involves a matching principle, which compares DNA profiles from evidential samples to those from reference samples of known origin. In casework, however, the accessibility to a reference sample is not guaranteed which limits the use of DNA as an investigative tool. This has led to the development of phenotype prediction, which uses SNP analysis to estimate the physical appearance of the sample donor. Physical traits, such as eye, hair and skin colour, have been associated with certain alleles within specific genes involved in the melanogenesis pathways. These genetic markers are also associated with ancestry and their trait prediction ability has mainly been assessed in European and North American populations. This has prompted research investigating the discriminatory power of these markers in other populations, especially those exhibiting admixture. South Africa is well known for its diversity, and the viability of these particular SNPs still needs to be assessed within this population. South African law currently restricts the use of DNA for molecular phenotyping, and there are also numerous ethical and social considerations, all of which are discussed. 相似文献
959.
Sajjad Ali Umar Zeb Wang Lei Haroon Khan Khurram Shehzad Hanif Khan Irfan Ullah 《农业工程》2018,38(5):329-333
Floristic inventory of village Sherpao, District Charsadda comprised of total 104 plant species belonging to 46 families and 95 genera. The leading families included Fabaceae, Asteraceae, Poaceae and contributed by 8 species one (7.69%).The most pre-dominant life form was therophytes having 35 species (33.65%). Most dominant habit of flora were herbs having 77 species (74%) followed by trees contributed by 18 species (17.30%) and shrubs having 9 species (8.65%). Leaf size spectra of the flora showed that the most dominant leaf size class were microphyll having 38 species (36.53%) followed by nanophyll contributed by 32 species (30.76%), mesophyll represented 22 species (21.15%) and leptophyll contributed by 12 species (11.53%). Based on habitat 77 species (74%) were xerophytic in nature followed by 14 species (13.46%) in wet condition and 13 species (12.5%) were present in both conditions. In 104 plant species 85 were non spiny and 19 were spiny. Plant growth and distribution are having strong correlation with environment. Therefore, it is important to understand the environmental aspects that affect plant growth and distribution. 相似文献
960.
不同国家甜菜种质资源遗传多样性研究 总被引:5,自引:0,他引:5
通过对来自12个国家的247份甜菜种质资源的16个描述型性状及10个数值型性状的遗传多样性进行分析,结果表明:16个描述型性状均表现出不同程度的遗传差异,多样性指数在0.4806~1.5230之间,平均值为0.8608,其中根肉色多样性指数最小,生长势的多样性指数最大;10个数值型性状的变异系数在1.29%~7.08%之间,平均为3.57%,α-氮含量最小,叶片数最大;不同国家甜菜种质资源的表型遗传差异大小为中国荷兰美国瑞典日本德国匈牙利波兰俄罗斯丹麦法国比利时。对247份材料表型进行聚类分析表明,在阈值为7.5时把材料分为5类,每个国家在5个分类中所占的比例均不同。鉴定筛选出的15份丰产资源和15份高糖资源,可在育种中做为品种产量改良及提高含糖率的亲本材料。 相似文献