小球藻(Chlorella vulgaris)与高岭土在实验条件下的凝聚沉降行为研究

用比浊法研究了小球藻与高岭土在实验条件下的凝聚沉降行为。结果表明，小球藻与高岭土的凝聚沉降是受颗粒表面理化作用力控制的过程。环境条件通过改变颗粒间的理化作用，在不同程度上促进或抑制颗粒凝聚沉降，根据颗粒凝聚沉降的特点，可将粘土用于水污染治理。     

Climate as a group level phenomenon: Theoretical assumptions and methodological considerations

Climate is a group‐level phenomenon that should be measured and studied at the group level. The group level has theoretical and methodological advantages over the individual level. In this paper, I theoretically review the assumptions in measuring climate at the individual and group levels and demonstrate that the group‐level assumptions are more adequate for climate research because of their influences in exposure to events, interpretation of events, and preservation of perceptions. Methodologically, I discuss advantages in group‐level climate measurement accuracy that are based on multiple evaluators of climate and I suggest group aggregation is an organizational form of “wisdom of the crowds.” Finally, I point to three topics that remain to be investigated to understand climate at the group level better. The first is use of variability measures to compensate for information that is lost in aggregation. The second is challenging the assumption that formal organizational structure defines the group boundaries. I suggest that other levels of analysis apply to group‐level climate measurement and demonstrate the use of informal, more natural groups as an additional level. Third, I point to recently developed statistical procedures that can aid the study of climate perception emergence over time.     

Historical spatial reconstruction of a spawning‐aggregation fishery

Aggregations of individual animals that form for breeding purposes are a critical ecological process for many species, yet these aggregations are inherently vulnerable to exploitation. Studies of the decline of exploited populations that form breeding aggregations tend to focus on catch rate and thus often overlook reductions in geographic range. We tested the hypothesis that catch rate and site occupancy of exploited fish‐spawning aggregations (FSAs) decline in synchrony over time. We used the Spanish mackerel (Scomberomorus commerson) spawning‐aggregation fishery in the Great Barrier Reef as a case study. Data were compiled from historical newspaper archives, fisher knowledge, and contemporary fishery logbooks to reconstruct catch rates and exploitation trends from the inception of the fishery. Our fine‐scale analysis of catch and effort data spanned 103 years (1911–2013) and revealed a spatial expansion of fishing effort. Effort shifted offshore at a rate of 9.4 nm/decade, and 2.9 newly targeted FSAs were reported/decade. Spatial expansion of effort masked the sequential exploitation, commercial extinction, and loss of 70% of exploited FSAs. After standardizing for improvements in technological innovations, average catch rates declined by 90.5% from 1934 to 2011 (from 119.4 to 11.41 fish/vessel/trip). Mean catch rate of Spanish mackerel and occupancy of exploited mackerel FSAs were not significantly related. Our study revealed a special kind of shifting spatial baseline in which a contraction in exploited FSAs occurred undetected. Knowledge of temporally and spatially explicit information on FSAs can be relevant for the conservation and management of FSA species.     

Phenylacetonitrile is a male specific repellent in gregarious desert locusts, Schistocerca gregaria

Summary. The behavioural response of desert locust individuals to adult male volatiles had been investigated in a dynamic Y-T-olfactometer. Synthetic blends of a postulated adult male-produced aggregation pheromone with or without phenylacetonitrile were not attractive to fifth-instar nymphs, young or mature adults of both sexes. Instead phenylacetonitrile had a repellent effect, which was strongest in sexually mature males. The repellent effect of phenylacetonitrile was not modified by the other components of the adult male pheromone bouquet. Even at low concentrations tested the source of the pheromone was avoided. These results are in agreement with recent studies showing that this male specific pheromone is employed by mature gregarious males in sexual behaviour and acts as a courtship inhibiting pheromone. Low concentrations of phenylacetonitrile or the postulated adult male aggregation pheromone blend without phenylacetonitrile may signal the presence of swarm fellows and eventually initiate visually guided congregation behaviour in gregarious locusts. Whether this effect does significantly contribute to swarm cohesion needs further studies.     

Effect of colour on male orientation to female pheromone in the black chafer Holotrichia loochooana loochooana

Summary. Under field conditions significantly more black chafer, Holotrichia loochooana loochooana (Sawada) (Coleoptera: Scarabaeidae) males landed on black and gray sources than white ones containing 10 mg of female pheromone, anthranilic acid. When a broader spectrum of colours was tested the frequency of male landing was intensively proportional to as the lightness of the colour of the lures. These findings demonstrated that mate location by H. l. loochooana males is dependent on both olfactory and visual stimuli of the source. In contrast, female aggregation was not affected by colour.     

多纤维捕集过程中细颗粒湍流团聚模拟研究

基于随机多层纤维过滤介质算法建立了平板式三维拟态化结构.利用计算流体力学-颗粒群平衡模型（CFD-PBM）对多纤维捕集过程中细颗粒湍流团聚进行数值模拟研究,并采用分区法求解颗粒群平衡方程（PBE）.通过控制变量法分析表明：多纤维捕集过程中存在着明显的颗粒团聚行为.粉尘颗粒的团聚程度随停留时间增加而增强,当t ≥ l/v（速度方向模型尺寸长度/入口风速）,团聚逐渐趋于稳定;当v_max·t ≤ l,入口风速越大,颗粒团聚程度和团聚速率越大,最终的团聚程度取决于入口风速和停留时间;颗粒粒径越大,粉尘颗粒的团聚程度和团聚速率越小.出口颗粒平均粒径与初始粒径相比增长倍数越小.粉尘颗粒体积分数越大,颗粒团聚程度以及团聚速率越大.当v=0.1m/s,d_p=1.0μm,VF >0.003636,Bin-7~Bin-0区间数量浓度对数分布呈线性比例关系.     

纳米银与微塑料在模拟垃圾填埋柱中的共迁移特征

以模拟垃圾填埋柱和人工配制渗滤液,探讨了纳米银（AgNPs）和微塑料（MPs）在垃圾填埋场中的迁移行为.结果发现,无论是单体系还是二元体系,随着填埋时间增长,AgNPs和MPs颗粒在渗滤液中稳定性增强,在填埋场中迁移能力增大,可能导致填埋中晚期有更多的污染颗粒随渗滤液流出填埋场.当AgNPs和MPs共存时,相对于单体系促进了AgNPs的迁移而轻微地抑制了MPs的迁移.结合DLVO理论和胶体过滤理论分析,一方面是由于流动性更高的MPs可作为AgNPs的载体,同时与AgNPs竞争固相介质上的吸附位点,从而促进AgNPs的迁移.另一方面,共存的AgNPs降低了MPs颗粒的表面负电荷使其稳定性减弱,并通过预沉积在固相介质上提供额外的MPs沉积位点,从而抑制MPs的迁移.     

Semi-automatic reduction and upscaling of large models: A farm management example

Research questions at the regional, national and global scales frequently require the upscaling of existing models. At large scales, simple model aggregation may have a prohibitive computational cost and lead to over-detailed problem representation. Methods that guide model simplification and revision have the potential to support the choice of the appropriate level of detail or heterogeneity within upscaled models. Efficient upscaling will retain only the heterogeneity that contributes to accurate aggregated results. This approach to model revision is challenging, because automatic generation of alternative models is difficult and the set of possible revised models is very large. In the case where simplification alone is considered, there are at least n²−1 possible simplified models where n is the number of model variables. Even with the availability of High Performance Computing, it is not possible to evaluate every possible simplified model if the number of model variables is greater than roughly 35. To address these issues, we propose a method that extends an existing procedure for simplifying and aggregating mechanistic models based on replacing model variables with constants. The method generates simplified models by selectively aggregating existing model variables, retaining existing model structure while reducing the size of the set of possible models and ordering them into a search tree. The tree is then searched selectively. We illustrate the method using a catchment scale optimization model with c. 50,000 variables (Farm-adapt) in the context of adaptation to climatic change. The method was successful in identifying redundant model variables and an adequate model 10% smaller than the original model. We discuss how the procedure can be extended to other large models and compare the method to those proposed by others. We conclude by urging model developers to regard their models as a starting point and to consider the need for alternative models during model development.     

Aggregation and dissolution of silver nanoparticles in a laboratory-based freshwater microcosm under simulated environmental conditions

Silver nanoparticles (NP) are used in several applications, including their use as antimicrobial agents in textiles, personal care, and other domestic products. As such, there is a high potential for the release of silver nanoparticles (AgNP) in the aquatic environment. In aquatic ecosystems, nanomaterials are affected by abiotic factors, such as temperature, that alter their chemistry and influence their fate in the environment. Preliminary studies indicate that NP tend to form aggregates which are potentially more recalcitrant than unaggregated NP. These and other fate processes are largely dependent on both the characteristics of the NP and that of the environment. In this study, lab experiments were conducted to investigate the physicochemical properties and temperature solubility of AgNP (<100 nm) that may potentially influence the fate and behavior of AgNP in the aqueous environment. Results indicated that, under these tested conditions, AgNP may be transformed in size and thereby affect fate, bioavailability, and toxicity. In this study, a novel method was used to determine whether AgNP would form agglomerates, or behave as isolated particles, or dissolve when in aqueous media and under different environmental conditions. The new aspects evaluated in this study demonstrated that AgNP are transformed in both size and state under variable environmental conditions.     

The role of built environment on pedestrian crash frequency

This study investigates (i) the link of land use and road design on pedestrian safety and (ii) the effect of the level of spatial aggregation on the frequency of pedestrian accidents. For this purpose, pedestrian accident frequency models were developed for New York City based on an extensive dataset collected from different sources over a period of 5 years. The assembled dataset provides a rich source of variables (land-use, demographics, transit supply, road network and travel characteristics) and two different crash frequency outcomes: total and fatal-only collision counts. Among other things, it was observed that the census tract analysis (disaggregate data) provides more insightful and consistent results than the analysis at the zip code level. The results indicate that tracts with greater fraction of industrial, commercial, and open land use types have greater likelihood for crashes while tracts with a greater fraction of residential land use have significantly lower likelihood of pedestrian crashes. Moreover, census tracts that have a greater number of schools and transit stops - which are determinants of pedestrian activity - are more likely to have greater crashes. Results also show that the likelihood of pedestrian-vehicle collision increases with the number of lanes and road width. This suggests that retrofitting or narrowing the roads could possibly reduce the risk of pedestrian crashes.