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91.
We used polymorphic microsatellite markers to study patterns of queen and worker reproduction in annual nests of the wasp Vespula germanica in its introduced range in Australia. We found that queens were typically polyandrous (at least 85.4% mated multiply), with the minimum number of male mates ranging from 1 to 7. Calculations based on nestmate worker relatedness (r=0.46) yielded an estimate of effective queen mating frequency of 2.35. Queens were unrelated to their mates (r=-0.01), indicating that mating occurred at random within Australian V. germanica populations. In addition, the distribution of the minimum number of male mates of queens followed a Poisson distribution. This result suggested that the probability of a queen remating was not affected by previous copulations. We also discovered that mates of polyandrous queens contributed unequally to progeny production leading to significant male reproductive skew within nests. Analyses of nestmate male genotypes revealed that queens usually produced most or all males. However, workers were responsible for the production of many males in a few nests, and, in contrast to theoretical expectations, two of these nests were apparently queenright.  相似文献   
92.
Detailed surveys of intertidal sediments have been performed along the north and south shores of the Inner Clyde estuary, UK. Surface sediment data reveal significant spatial variation in Cr content and an association with major sediment characteristics and location within the estuary. Depth variation for Cr and other heavy metals cannot be explained by variation in major geochemical controls such as grain size and organic matter and highlights the impact of historical contamination on sediment quality. These elevated levels at depth may still have environmental impact through redox-reactivity, in association with iron and manganese. Sequential extraction of sediments and pore water analysis of Cr(VI) and Cr(III) provide detailed information on release potential from the sediments. The implication of Cr mobility for biota in the estuary has been assessed by the analysis of a common marine bivalve, Mytilus edulis (Blue Mussel) and a burrowing polychaete, Nereis diversicolor (rag worm) from a number of survey sites. Bioconcentration factors for Mytilus indicate that the weakly held portion of sediment Cr is available for uptake and in the case of Nereis, bioaccumulation appears to be inhibited by sediment organic matter.  相似文献   
93.
Halogenated and nonhalogenated hydrocarbon contaminants are currently found in natural waterways, groundwater, and soils as a result of spills and careless disposal practices. The development of proper treatment methodologies for the waste streams producing this environmental damage is now a subject of growing concern. A significant number of these waste stream compounds are chemically stable and are thus resistant to environmental degradation. Numerous researchers have investigated the use of ionizing radiation to decompose chlorinated hydrocarbons in diverse matrices and have proposed various free-radical-induced reaction mechanisms. This article is divided into two sections. First, we present data on experimentally measured, radiolytically induced decomposition of hazardous wastes and toxic substances using accelerator-generated bremsstrahlung sources and gamma radiation from cobalt-60. Data are presented on the radiolytically induced reduction in concentration of volatile organic compounds (VOCs) dissolved in water and in air, polychlorinated biphenyls (PCBs) dissolved in oil, high explosives dissolved in groundwater, and chemical weapon surrogates. The results of these studies suggest the potential use of ionizing radiation as a method of hazardous waste treatment. The second section of this article describes the technical aspects of a field-scale radiolytic decomposition site cleanup demonstration using an electron accelerator. A portable, commercially available electron accelerator was set up at the Lawrence Livermore National Laboratory's (LLNL's) Site 300, a Superfund site, where vacuum extraction wells were removing trichloroethylene (TCE) vapor from a ground spill into the unsaturated soil zone. The accelerator was retrofitted into the existing vacuum extraction system such that the extracted TCE-containing vapor passed through the accelerator beam for treatment. The concentration of TCE in the vapor was reduced by an amount dependent on the accelerator beam power. Production of reaction products in the vapor was measured as a function of absorbed dose.  相似文献   
94.

We consider the street experiences of a group of urban children living in a large East Midlands town in the UK. Our attention focuses upon an issue that has seldom been examined, neighbourhood bullying. We highlight how some children, through their propinquity within neighbourhood spaces, clash and collide to such an extent that their experiences of a locality become severely blighted. For these unfortunate young people local environments are tyrannical spaces, defined in terms of 'no-go areas', danger and threat. These are not remarkable geographies, however, and we suggest that like many school environments, where bullying has increasingly been recognised and disclosed, within many localities there is a 'hidden' geography of fear waiting to be uncovered. The paper is organised into five parts: first, we briefly examine the concept of bullying, particularly in relation to young people in schools; secondly, we extend these ideas into a neighbourhood context drawing upon recent ideas of 'self', 'other' and microgeographies; thirdly, we outline the research project from which this article emerges; fourthly, we look at some empirical evidence from an urban case study that draws attention to the form and consequences of neighbourhood bullying; lastly, we discuss the relevance of these findings to future policy and practice, particularly in relation to the management of neighbourhood spaces. We propose that systematically applied local strategies to tackle bullying within neighbourhoods are needed, particularly those which engage young people and adults together through a whole community approach.  相似文献   
95.
Twin-screw extrusion was used to prepare the composites consisting of PLA and three types of sugarcane bagasse residues (up to 30 wt%) derived from different steps of a biorefinery process. Each residue had different composition, particle size and surface reactivity due to chemical and biological (enzyme, microbes) treatments that the biomass was subjected to. The effects of different residue characteristics on properties, crystallization behaviors and morphologies of PLA composites were investigated. Besides, a small amount (2 wt%) of coupling agent, Desmodur® VKS 20 (DVKS), was used to improve the interfacial bonding between PLA and bagasse residues. The results indicated that in the presence of 2 % DVKS, PLA composite with pretreated residue exhibited the maximum strength properties (98.94 % tensile strength and 93.91 % flexural strength of neat PLA), while PLA composite with fermentation residue exhibited the minimum strength properties (88.98 % tensile strength and 81.91 % flexural strength of neat PLA).  相似文献   
96.
97.
Although often overlooked, pets and other animals intersect with organizations in interesting, important ways. We seek to define how various animals intersect with organizations, highlight opportunities for theory development, and illustrate important areas for future research. We also explore how pandemics such as COVID-19 might affect the animals we highlight.  相似文献   
98.
尽管继续有科学不确定性,但表明当前捕捞实践不可持续的证据与日俱增.在国家层次和国际层次上,人们越来越认真地对待关于过度捕捞及其对穷国食品保障的潜在威胁的告诫.近年来已经看到了一波改善渔业管理的协议.然而,无论在当地社区和传统可能处于危急之中的富国,还是在鱼类对于食品供应也具有根本重要性而且捕捞是沿海地区少数几种生活来源之一的穷国,对减少世界捕捞船队的规模都有强大阻力.  相似文献   
99.
This paper reports an experimental investigation of converting waste medium density fibreboard (MDF) sawdust into chars and activated carbon using chemical activation and thermal carbonisation processes. The MDF sawdust generated during the production of architectural mouldings was characterised and found to have unique properties in terms of fine particle size and high particle density. It also has a high content of urea formaldehyde resin used as a binder in the manufacturing of MDF board. Direct thermal carbonisation and chemical activation of the sawdust by metal impregnation and acid (phosphoric acid) treatment prior to pyrolysis treatment were carried out. The surface morphology of the raw dust, its chars and activated carbon were examined using scanning electron microscopy (SEM). Adsorptive properties and total pore volume of the materials were also analysed using the BET nitrogen adsorption method. Liquid adsorption of a reactive dye (Levafix Brilliant red E-4BA) by the derived sawdust carbon was investigated in batch isothermal adsorption process and the results compared to adsorption on to a commercial activated carbon (Filtrasorb F400). The MDF sawdust carbon exhibited in general a very low adsorption capacity towards the reactive dye, and physical characterisation of the carbon revealed that the conventional chemical activation and thermal carbonisation process were ineffective in developing a microporous structure in the dust particles. The small size of the powdery dust, the high particle density, and the presence of the urea formaldehyde resin all contributed to the difficulty of developing a proper porous structure during the thermal and chemical activation process. Finally, activation of the dust material in a consolidated form (cylindrical pellet) only achieved very limited improvement in the dye adsorption capacity. This original study, reporting some unexpected outcomes, may serve as a stepping-stone for future investigations of recycle and reuse of the waste MDF sawdust which is becoming an increasing environmental and cost liability.  相似文献   
100.
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