滆湖轮虫群落结构与水质生态学评价

研究了浅水湖泊--滆湖的轮虫群落结构,并用轮虫污染指示种类、E/O值、QB/T值和生物多样性指数评价滆湖的水质和营养状况.在两周年的研究中,共发现轮虫69种,污染指示轮虫39种.优势种为萼花臂尾轮虫(Brachionua calyciflorus)、前节晶囊轮虫(Asplanchna priodonta)、针簇多肢轮虫(Polyarthra trigla)、长三肢轮虫(Filinia longiseta)和裂足臂尾轮虫(B.diversicornis).轮虫密度年平均值为1584 ind./L,生物量年平均值为5.982 1 mg/L.密度秋季最高,生物量夏季较高.轮虫物种多样性较低,多样性指数与其密度及生物量正相关.滆湖三个生态功能区轮虫的种类相似;湖区北部与中部的轮虫现存量差异不显著,与南部的差异显著,中部与南部间差异极显著.根据指示生物法、生物指数法和多样性指数法评价滆湖水质及营养类型,涌湖为富营养型.     

Impact of superheated steam roasting on changes in antioxidant and microstructure properties of raw and processed cocoa cotyledon

This research focused on the roasting of cocoa beans at 184 °C for 16 min duration in a superheated steam oven using two separate modes of heating: convection mode and superheated steam mode. After roasting, the antioxidant properties of the cooked cocoa were assessed as ferric reducing antioxidant power activity (FRAP), DPPH radical scavenging activity, total flavonoid content (TFC) and total phenol content (TPC). The micro structural properties of raw and processed cocoa beans were observed using scanning electron microscopy (SEM). As discovered in the scan, conventional roasting showed a nearly complete rapture of the cytoplasmic network system and the destruction of the organelles, whereas superheated steam mode showed satisfactory images. Studies indicated that superheated steam roasting preserved significantly (p < 0.05) greater antioxidant properties as opposed to conventional method of roasting.     

坡度对农田土壤动物群落结构及多样性的影响

为了研究坡度对土壤动物群落的影响,于2010年3月和9月分别对川中丘陵区坡度为5°、15°、25°的3种农田土壤动物进行了调查。共采集土壤动物11657只,隶属4门11纲21目,弹尾目、蜱螨目、颤蚓目和线虫为优势类群。土壤动物群落的类群数在3月随坡度增加无显著变化(P>0.05),9月则呈波动性上升(P<0.01)。群落密度在3月随坡度增加而显著下降(P<0.01),9月的变化趋势则相反(P<0.05)。群落多样性指数在3、9两月均随坡度增加呈显著波动性变化(P<0.05)。坡度对弹尾目、蜱螨目和线虫等主要类群的密度影响显著(P<0.05),并具季节差异。主成分分析(PCA)结果表明坡度对农田土壤动物的群落结构有明显影响,Sorenson和Morisita-Horn相似性系数进一步表明坡度在3月份主要影响土壤动物群落的类群组成,在9月主要影响优势类群的密度。研究结果表明坡度对土壤动物的群落结构、多样性及主要类群的密度有显著影响,并存在季节差异。     

Rates of decay for the survival probability of a mutant gene II The multitype case

This paper extends the results of [1] to the multitype case. For a multitype branching process that is slightly supercritical, approximations for the survival probability in terms of the maximal eigenvalue of the mean matrix and a generalized variance ² are developed. Our results improve upon those of Hoppe [5] and Eshel [3] that seek to validate a conjecture of Ewens [4].Research supported in part by NSF grant DMS 9007182     

Sowing different mixtures in dry acidic grassland produced priority effects of varying strength

Several longer-term assembly studies on ex-arable land have found that species that arrive first at a disturbed site can play a key role in the further development of the community and that this priority effect influences aboveground productivity, species diversity and stability of the grassland communities that develop. Restoration of nutrient poor, species rich grasslands is often limited by seed dispersal as well as the accessibility of suitable microsites for establishment. Sowing species (i.e. creating priority effects for further assembly) may help overcome such dispersal barriers, but the potential of using priority effects for restoration has not been tested in this type of dry grassland. We tested the hypothesis that sowing two different seed mixtures used for dry acidic grassland restoration onto a sandy substrate (which formed an equivalent to a primary succession) would create priority effects, and that these priority effects would be sustained over a number of years. We followed community assembly and measured aboveground productivity for four years after sowing. We found that priority effects caused by sowing of differently diverse mixtures did also occur in dry acidic grassland habitat, but that how persistent they were over time depended on the response variable considered. Priority effects on species number were not as strong as found in previous ex-arable land studies, whereas priority effects for aboveground productivity were still visible after 4 years. In addition, functional composition of the community still reflected the composition of the seed mixtures 4 years later. Our results suggest that priority effects can occur in nutrient-poor dry acidic grassland but in contrast to more nutrient-rich sites the breadth of responses affected may not be as wide.     

Spoil characteristics and vegetation development of an age series of mine spoils in a dry tropical environment

A series of coal mine spoils (5, 10, 12, 16 and 20-yr old) in a dry tropical environment was sampled to assess the changes with time in spoil characteristics, species composition and plant biomass. Coarse fragments (>2 mm) decreased with age of mine spoil while the proportion of 0.2–0.1 mm particles increased. Total soil N, mineral N, NaHCO₃-extractable Pi, and exchangeable K increased with age of mine spoil and these parameters were lower in mine spoils than native forest soil even after 20 years of succession. Exchangeable Na decreased with age of mine spoil and in 20-yr old spoil it was higher than native forest soil. Plant community composition changed with age. Only a few species participated in community formation. Species richness increased with age, while evenness and species diversity declined from 5-yr old to 16-yr old community with an increase in the 20-yr old community. A reverse trend occurred for concentration of dominance. Area-weighted shoot and root biomass of other species increased with the age of the mine spoil while that of Xanthium strumarium patches declined with age. Data collected on spoil features, microbial C, N and P, and shoot and root biomass when subjected to Discriminant Analysis indicated a continued profound effect of age. 10 and 12-yr old mine spoils were closer to each other, and 5 and 20-yr old spoils were farthest apart.     

稻田生物群落的能流参数

为了从能流动态来研究稻田生物群落,本文用田间调查和实验室测定等方法,取得了晚稻田生物群落的物种数量、生物量、热值、呼吸量、生产力、同化效率、摄食量等数据。据此,进一步估算了晚稻田生物群落的能量流动参数。根据其能量收支,用能量金字塔总结了晚稻田生物群落各类种群间的能量关系。     

Mini-scale bioprocessing systems for highly parallel animal cell cultures

Animal cells have been used extensively in therapeutic protein production. The growth of animal cells and the expression of therapeutic proteins are highly dependent on the culturing environments. A large number of experimental permutations need to be explored to identify the optimal culturing conditions. Miniaturized bioreactors are well suited for such tasks as they offer high-throughput parallel operation and reduce cost of reagents. They can also be automated and be coupled to downstream analytical units for online measurements of culture products. This review summarizes the current status of miniaturized bioreactors for animal cell cultivation based on the design categories: microtiter plates, flasks, stirred tank reactors, novel designs with active mixing, and microfluidic cell culture devices. We compare cell density and product titer, for batch or fed-batch modes for each system. Monitoring/controlling devices for engineering parameters such as pH, dissolved oxygen, and dissolved carbon dioxide, which could be applied to such systems, are summarized. Finally, mini-scale tools for process performance evaluation for animal cell cultures are discussed: total cell density, cell viability, product titer and quality, substrates, and metabolites profiles.     

Plant genetic determinants of arthropod community structure and diversity

To test the hypothesis that genes have extended phenotypes on the community, we quantified how genetic differences among cottonwoods affect the diversity, abundance, and composition of the dependent arthropod community. Over two years, five major patterns were observed in both field and common-garden studies that focused on two species of cottonwoods and their naturally occurring F1 and backcross hybrids (collectively referred to as four different cross types). We did not find overall significant differences in arthropod species richness or abundance among cottonwood cross types. We found significant differences in arthropod community composition among all cross types except backcross and narrowleaf cottonwoods. Thus, even though we found similar richness among cross types, the species that composed the community were significantly different. Using vector analysis, we found that the shift in arthropod community composition was correlated with percent Fremont alleles in the host plant, which suggests that the arthropod community responds to the underlying genetic differences among trees. We found 13 arthropod species representing different trophic levels that were significant indicators of the four different cross types. Even though arthropod communities changed in species composition from one year to the next, the overall patterns of community differences remained remarkably stable, suggesting that the genetic differences among cross types exert a strong organizing influence on the arthropod community. Together, these results support the extended phenotype concept. Few studies have observationally and experimentally shown that entire arthropod communities can be structured by genetic differences in their host plants. These findings contribute to the developing field of community genetics and suggest a strategy for conserving arthropod diversity by promoting genetic diversity in their host plants.     

废水自养生物脱氮技术研究进展

基于短程硝化和厌氧氨氧化的自养脱氮工艺是生物脱氮领域研究的热点,它的发现为低碳氮比废水的处理提供了新的思路。近些年来,人们陆续开发了SHARON、ANAMMOX、CANON、OLAND等自养生物脱氮工艺,进一步推动了高效、低耗脱氮技术的开发和研究。本文从工艺原理、特点等方面,对自养生物脱氮工艺的国内外研究状况进行了总结和对比,并提出了存在的问题及发展方向。