The internal barriers of rotation for the 209 polychlorinated biphenyls

The internal barrier of rotation (Erot) was calculated for all 209 polychlorinated biphenyls (PCBs) by using a semi-empirical method, viz. the Austin Model 1 (AMI) Hamiltonian. The difference in total energy between a forced planar state and an optimised twisted structure was defined as Erot. The Erot values were in the range of 8.33 to 483 kj/mol, and were significantly influenced by the number of chlorine atoms inortho position. An additional structural characteristic of the PCBs influencing Erot ofortho substituted congeners was substitution by chlorine atoms in vicinalmeta positions, which is assumed to prevent outward bending ofortho substituents. This so-called buttressing effect contributed with 4 to 31 kj/mol per added chlorine atom. In conclusion, the internal barrier of rotation, calculated for all 209 PCBs, provides an important structure dependent physico-chemical parameter for multivariate modelling of future quantitative structure-activity and structure-property relationships (QSARs/QSPRs).     

Phylogenetic analyses of sexual selection and sexual size dimorphism in pinnipeds

Pinnipedia contains some of the most spectacular examples of sexual size dimorphism, examples that are therefore frequently used to illustrate the theory of sexual selection. This paper addresses the question of whether a significant relationship between sexual selection and size dimorphism exists in a comparative context. Thus, harem size and body size data gathered from the literature were analysed with independent contrasts analyses. These investigations showed that sexual size dimorphism is not a consequence of an allometric relationship between male and female size. Instead, there is a clear relationship between harem size and sexual size dimorphism. Further analyses also revealed a significant relationship between harem size and male size whereas no such relationship existed for females. These results support the hypothesis that sexual size dimorphism in pinnipeds is the product of an exclusively male response to sexual selection.     

Risk-taking by female ducks: intra- and interspecific tests of nest defense theory

We tested several predictions of nest defense theory by observing variation in flushing distance and probability of nest abandonment within and between six species of waterfowl. In these species, only the females incubate eggs and attend offspring. First, we examined whether flushing distance by females varied in relation to clutch size, stage of incubation, and time of season, after controlling for the number of visits made to nests by observers. Revisits by observers appeared to affect flushing distance by females for reasons unrelated to the relative value of the current clutch. We found that as incubation progressed, females allowed observers to approach more closely before flushing from the nest. In some species, females with larger clutches allowed closer approaches to nests before flushing which was also consistent with nest defense theory. In contrast, time of season (Julian date) did not relate to flushing distance for any species. When species were compared, we found that species with moderate to high yearly mortality and high reproductive output per breeding attempt (e.g., northern shoveler and blue-winged teal) were less likely to abandon nesting attempts and exhibited riskier behavior (remained at nests when approached closely by observers) than species that had lower yearly mortality (e.g., mallard). Our results show that flushing distance and patterns of nest abandonment by female ducks conform to several predictions of nest defense theory.Correspondence to: M.R.L. Forbes     

The constitutively active Ah receptor (CA-AhR) mouse as a model for dioxin exposure - effects in reproductive organs

The dioxin/aryl hydrocarbon receptor (AhR) mediates most toxic effects of dioxins. In utero/lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) impairs fetal/neonatal development and the developing male reproductive tract are among the most sensitive tissues. TCDD causes antiestrogenic responses in rodent mammary gland and uterus and in human breast cancer cell lines in the presence of estrogen. Also, more recently an estrogen-like effect of TCDD/AhR has been suggested in the absence of estrogen. A transgenic mouse expressing a constitutively active AhR (CA-AhR) was developed as a model mimicking a situation of constant exposure to AhR agonists. Male and female reproductive tissues of CA-AhR mice were characterized for some of the effects commonly seen after dioxin exposure. Sexually mature CA-AhR female mice showed decreased uterus weight, while an uterotrophic assay in immature CA-AhR mice resulted in increased uterus weight. In immature mice, both TCDD-exposure and CA-AhR increased the expression of the estrogen receptor target gene Cathepsin D. When co-treated with 17β-estradiol no increase in Cathepsin D levels occurred in either TCDD-exposed or CA-AhR mice. In sexually mature male CA-AhR mice the weights of testis and ventral prostate were decreased and the epididymal sperm reserve was reduced. The results of the present study are in accordance with previous studies on dioxin-exposed rodents in that an activated AhR (here CA-AhR) leads to antiestrogenic effects in the presence of estrogen, but to estrogenic effects in the absence of estrogen. These results suggest the CA-AhR mouse model as a useful tool for studies of continuous low activity of the AhR from early development, resembling the human exposure situation.     

Infiltrating citizen-driven initiatives for sustainability

To examine how citizen-driven initiatives for sustainability strive to bring about change and spread their practices, efforts to link social movement, grassroots innovation and green-consumption movements theory are built upon. Göteborg’s citizen-driven waste-prevention initiatives, such as food waste recovery, creating common reuse spaces in housing blocks, exchanging used toys and repairing abandoned bicycles, are considered with data from observations, workshops, documents, social media communications and in-depth interviews. Citizen-driven initiatives succeeded in mobilizing material resources, displaying and reframing various rationales, and creating collaborative local networks to develop their waste-prevention practices. These practices infiltrated the municipal administration, matching incipient institutional mandates to minimize waste. By so doing, they bring within mainstream institutions radical rationales that can become activated in the future, contributing to diachronic change.     

Effects of aircraft noise and speech on prose memory: What role for working memory capacity?

Previous research indicates that aircraft noise and meaningful background speech are particularly detrimental to school adolescents' ability to remember what they read, but until now the effects from aircraft noise and speech have never been compared directly in an experiment. Furthermore, individual differences in susceptibility to these effects are not well understood. The present investigation addressed these two issues. Adolescents attending upper secondary school were recruited as participants and the data collection was made in their ordinary classrooms. The results from two experiments revealed that speech is more detrimental to prose memory than is aircraft noise, and individual differences in working memory capacity contributes more to individual differences in susceptibility to the effects of aircraft noise on prose memory than to the effects of speech. Some applied implications of those findings to noise abatement interventions are suggested.     

Occurrence and sorption properties of arsenicals in marine sediments

The content of total arsenic, the inorganic forms: arsenite (As(III)) and arsenate (As(V)), the methylated forms: monomethylarsonic acid and dimethylarsinic acid (DMA), trimethylarsenic oxide, tetramethylarsenonium ion and arsenobetaine was measured in 95 sediment samples and 11 pore water samples from the Baltic Sea near the island of Bornholm at depths of up to 100 m. As(III+V) and DMA were detected in the sediment and As(III+V) was detected in the sediment pore water. Average total As concentration of 10.6?±?7.4 mg/kg dry matter (DM) in the sediment corresponds to previously reported values in the Baltic Sea and other parts of the world. Existing data for on-site measurements of sorption coefficients (Kd) of arsenicals in marine and freshwater sediments show large variability from <1 to >1,000 L/kg. In this work, calculated sorption coefficients (Kd and Koc) for As(III+V) showed significant correlation with depth, dissolved oxygen (DO), salinity and sediment classification; for depths <70 m, salinity <11 %, DO >9 mg/L and sand/silt/clay sediments the Kd was 118?±?76 L/kg DM and for depths >70 m, salinity >11 %, DO?<?9 mg/L and muddy sediments the Kd was 513?±?233 L/kg DM. The authors recommend using the found Kd value for arsenic in marine sediments when conditions are similar to the Baltic Sea. At locations with significant anthropogenic point sources or where the local geology contains volcanic rock and sulphide mineral deposits, there may be significantly elevated arsenic concentrations, and it is recommended to determine on-site Kd values.     

西印度洋地区海草生态系统

海草是海洋被子植物,广泛分布在温带和热带的海岸带水域,是地球上水生生态系统中最具生产力的生物之一.     

东非和西印度洋沿海水产养殖的发展:食品安全和地方经济的前景和问题

本文回顾了东非和西印度洋的岛屿在海藻、软体动物、鱼类和甲壳类动物的沿海养殖经验和状况.在许多方面,这一地区的沿海水产养殖仍处于发展初期,迫切需要制定旨在提高收入,确保沿海居民对可担负的蛋白质的获得的发展战略.