生活在土地上的人们:20世纪全球人口和耕地的变化

本研究评述了20世纪全球耕地分布发生的主要变化.在20世纪,耕地基数大幅度减小,人均耕地从1900年的0.75hm2/人下降到1990年的0.35 hm2/人.     

Simple screening models of NAPL dissolution in the subsurface

Three simple screening models of nonaqueous phase liquid (NAPL) dissolution in the subsurface are proposed based on the NAPL mass conservation and the assumption of proportionality between the residual NAPL source zone concentration and the remaining residual NAPL mass. The purpose of the proposed models is to predict the solute concentration in the zone of the residual NAPL as a result of dissolution. The predicted source zone concentration decrease is used to simulate and account for the decrease of dissolution rate with time. The proposed simple NAPL dissolution models enable the pseudo-equilibrium formulation to be used and therefore the numerical simulations for field application problems can be simplified compared to the non-equilibrium counterpart. With proper choice of empirical parameters, the proposed simple screening models can work as well as more complex dissolution rate correlation models, such as that of Imhoff et al. [Water Resour. Res. 30 (1994) 307-320]. It is found that the proposed models are very good for quantifying non-equilibrium dissolution, which is characterized by tailing of breakthrough curves. The models are especially useful for situations of small residual NAPL saturation, which are typical for many field applications.     

Colloid transport in a geochemically heterogeneous porous medium: aquifer tank experiment and modeling

To examine colloid transport in geochemically heterogeneous porous media at a scale comparable to field experiments, we monitored the migration of silica-coated zirconia colloids in a two-dimensional layered porous media containing sand coated to three different extents by ferric oxyhydroxides. Transport of the colloids was measured over 1.65 m and 95 days. Colloid transport was modeled by an advection-dispersion-deposition equation incorporating geochemical heterogeneity and colloid deposition dynamics (blocking). Geochemical heterogeneity was represented as favorable (ferric oxyhydroxide-coated) and unfavorable (uncoated sand) deposition surface areas. Blocking was modeled as random sequential adsorption (RSA). Release of deposited colloids was negligible. The time to colloid breakthrough after the onset of blocking increased with increasing ferric oxyhydroxide-coated surface area. As the ferric oxyhydroxide surface area increased, the concentration of colloids in the breakthrough decreased. Model-fits to the experimental data were made by inverse solutions to determine the fraction of surface area favorable for deposition and the deposition rate coefficients for the favorable (ferric oxyhydroxide-coated) and unfavorable sites. The favorable deposition rate coefficient was also calculated by colloid filtration theory. The model described the time to colloid breakthrough and the blocking effect reasonably well and estimated the favorable surface area fraction very well for the two layers with more than 1% ferric oxyhydroxide coating. If mica edges in the uncoated sand were considered as favorable surface area in addition to the ferric oxyhydroxide coatings, the model predicted the favorable surface area fraction accurately for the layer with less than 1% ferric oxyhydroxide coating.     

Learning during competitive positioning in the nest: do nestlings use ideal free ‘foraging’ tactics?

Begging behaviour of nestling birds may involve more than a simple, honest source of information for parents to use in provisioning. Many aspects of begging behaviour relate instead to sibling competition for food items within the nest, and we might expect evidence of adaptive learning and behavioural adjustment in response to experience of the competitive environment. In this study, we consider begging in different locations within the nest as analogous to foraging in different patches, varying in food availability. Using hand-feeding trials, we created zones of differing profitability within an artificial nest by adjusting either the prey size or number of items delivered, and allowed only indirect competition between pairs of southern grey shrike (Lanius meridionalis) nestlings. Nestlings demonstrated the ability to detect differences in zone profitability and position themselves accordingly. By the end of both the prey size and delivery rate trials nestlings had increased the amount of time spent in the high quality zone. Such movement in response to differences in load quality, as well as frequency, demonstrates the ability of nestlings to learn about their environment and to facultatively adjust their begging in order to maximise energetic rewards.     

Catalytic decomposition performance for O3 and NO2 in humid indoor air on a MnOx/Al2O3 catalyst modified by a cost-effective chemical grafting method

Processes based on non-thermal plasma (NTP) for indoor air treatment inevitably lead to the formation of toxic by-products such as ozone (O₃) and nitrogen oxides (NO_x). Adding a step of heterogeneous catalysis in series with NTP could allow for the decomposition of the by-products. Therefore, different catalysts were developed based on transition metal oxides, such as NiO_x, CoO_x and MnO_x with different weight percentage 1, 5 and 10 wt.%, deposited on a γ-Al₂O₃ support. The O₃ removal efficiency (ORE) and the NO_x removal efficiency (NRE) were very encouraging in dry air: about 65% and 80%, respectively, by using 2 g 5 wt.% MnO_x/Al₂O₃ catalyst under the experimental conditions. However, strongly negative effects of relative humidity (RH) on the catalytic decomposition performance were observed. To overcome this limitation, the catalyst surface was modified to make it hydrophobic using a cost-effective chemical grafting method. This treatment consisted in impregnating the 5 wt.% MnO_x/Al₂O₃ catalyst with different trichloro(alkyl)silanes (TCAS). The effects of different linker lengths and amounts of TCAS for the hydrophobicity and the decomposition performance of surface-modified catalysts under humid conditions were investigated. Our results show that the surface-modified catalyst with the shortest linker and 0.25 mmol/g_cat of modifying agent represents the best catalytic decomposition performance for O₃. Its ORE is 41% at 60% RH, which is twice that of the non-modified catalyst.     

Manipulation of sex differences in parental care

Summary In a species with biparental care two parents cooperate to provide the appropriate amount of care for the young. Recent theoretical treatments consider the evolutionarily stable investment strategy. Under most conditions, the parental investment of the two partners should be negatively correlated, with the shortfall of one partner being partially compensated for by the other. Previous experimental manipulations of biparental care have involved removal of one partner, yet the response of a widowed bird may differ from that of a mated bird whose partner is doing less than its fair share of parental care. We present the first data involving subtle manipulations of sex differences in parental care where both partners continue to care for the young. This study involves pairs in a nestbox colony of european starlings (Sturnus vulgaris L.) with all brood sizes manipulated to five chicks. Pairs were randomly assigned to three groups: (i) male parental care reduced; (ii) female parental care reduce; and (iii) control pairs. Parental care was manipulated by attaching small weights to the base of a bird's tail feathers. Regardless of sex, nest visitation rate was reduced in the weighted birds with an incomplete compensatory increase by their unweighted partner. Additional parental duties were also considered, including shifts in prey type delivered to the nest, in both weighted birds and their partners. The shift in diet and the overall lower total visitation rate in experimental nests contributed to slower chick growth and lower chick weights than in control nests. The data accord with models suggesting that equality of invesment in biparental species is evolutionarily stable, but reveal new dimensions of parental response that need to be taken into account in theoretical treatments.     

Choice and utilization of oviposition sites by female Calopteryx maculata (Odonata: Calopterygidae)

Summary Females of the damselfly Calopteryx maculata (de Beauvois) initially choose the larger of a pair of adjacent oviposition sites, about 70% of the time (Table 1), or whichever of two equal sized sites had other ovipositing females on it (about 88% of the time-Table 2). These criteria for initial choice between a pair of sites also interact. Incoming females generally (57 to 74% of the time-Table 3) joined others on the small site rather than ovipositing alone at the adjacent, bigger site. When pairs of large and small sites were replicated across eight locations, there were nonsignificant trends towards greater utilization (eggs laid) of the larger of a pair of oviposition sites within locations (Table 4). The lack of agreement between initial choice and utilization shows that other factors besides size are important in the choice and use of oviposition sites. These include disturbance by males, the presence of other females and choice criteria that can only be assessed during oviposition. When all sites at the eight locations were equal in size, there was considerable day to day and location to location variation in eggs laid (Fig. 1). Viewed over periods of several days, some sites are obviously less attractive than others in terms of cumulative numbers of eggs laid at them. When the amount of vegetation was varied among locations, those with the bigger oviposition sites were used more often, somtimes significantly so, but there were also significant reversals (small sites used more often) (Table 5, Fig. 1). Thus, there is no simple effect of size on the utilization of oviposition sites by Calopteryx maculata females, despite a clear tendency for females to make initial choices based on this criterion. The considerable among and within location variation in number of eggs laid may reflect additional choice criteria or the interaction of size, the presence of other females, disturbance, and location.     

三重底线的平衡:Pick‘n Pay人的可持续的商业面貌

21世纪的可持续发展必须合并有对雇员和消费者进行培训和教育的措施.了解情况、负责任和有见识的消费者选择有助于通过三赢获得整个市场的可持续性:提高消费者的生活质量、降低环境与社会影响,以及增加具有可持续性思想的公司的市场分额.Pick'n Pay集团把可持续性经济增长看成是有道德的商业从业人员的首要责任在追逐经济增长和环境保护这一对目标时,该公司认识到社会-经济增长和环境保护的关系不能割裂,而人们生活质量的提高不能以环境破坏为代价.涉及雇员和社区组织双方的保护计划,是Pick'n Pay的内在的法人社会责任计划.在公司(和社会)内从事HIV/AIDS的相关工作,是Pick'n Pav法人社会责任计划的主要目标之一.