淮南六方堤多层土堤基塑流稳定性计算

本文研究了台阶状六方堤堤体荷重的弗里哀级数展开式和堤基应力计算系数的计算原理,通过堤基应力计算和塑流判别,对六方堤多层土堤基塑流稳定性进行了评价。     

花卉塑料大棚降温效果分析

本文对花卉塑料大棚夏季降温试验进行了分析,结果表明:采用直接阻挡太阳辐射的降温方法、棚膜外或棚膜内地面喷水的降温方法,其降温效果均好。这为成都地区花卉塑料大棚周年生产的科学管理提供了依据。     

The pollution of the marine environment by plastic debris: a review

The deleterious effects of plastic debris on the marine environment were reviewed by bringing together most of the literature published so far on the topic. A large number of marine species is known to be harmed and/or killed by plastic debris, which could jeopardize their survival, especially since many are already endangered by other forms of anthropogenic activities. Marine animals are mostly affected through entanglement in and ingestion of plastic litter. Other less known threats include the use of plastic debris by "invader" species and the absorption of polychlorinated biphenyls from ingested plastics. Less conspicuous forms, such as plastic pellets and "scrubbers" are also hazardous. To address the problem of plastic debris in the oceans is a difficult task, and a variety of approaches are urgently required. Some of the ways to mitigate the problem are discussed.     

华北地区壳内低速层与地壳流变的关系及其对强震孕育的影响

京津唐张地区普遍存在壳内低速层 ,鄂尔多斯块体内部没有发现低速层 ,壳内低速层的这种分布受新生代裂陷伸展的控制。华北地区中地壳下部和下地壳低速层是岩石塑性流变的结果 ,中地壳上部低速层是地壳裂陷伸展时形成的水平拆离带和韧性剪切带 ,岩石各向异性和流体作用可能是引起低速的原因。壳内软弱层 (低速和塑性流变层 )增强了块体层间的解耦作用 ,对地震孕育起着重要作用     

Occurrence, distribution and characteristics of beached plastic production pellets on the island of Malta (central Mediterranean)

The distribution, abundance and chemical characteristics of plastic production pellets on beaches of the island of Malta have been determined. Pellets were observed at all locations visited and were generally most abundant (>1000 m⁻² at the surface) on the backshores of beaches with a westerly aspect. Most pellets were disc-shaped or flattened cylinders and could be categorised as white, yellow, amber or brown. The polymeric matrix of all pellets analysed by infrared spectroscopy was polyethylene and the degree of yellowing or darkening was associated with an increase in the carbonyl index, hence extent of photo-oxidation or aging. Qualitatively, pellets are similar to those reported for other regions of the Mediterranean in surveys spanning three decades, suggesting that they are a general and persistent characteristic of the region.     

Plastic contamination in the decapod crustacean Nephrops norvegicus (Linnaeus, 1758)

The aim of this study was to determine the extent Nephrops consumes plastics in the Clyde Sea and if this intake occurs through their diet. Plastic contamination was found to be high in Nephrops, 83% of the animals sampled contained plastics (predominately filaments) in their stomachs. Tightly tangled balls of plastic strands were found in 62% of the animals studied but were least prevalent in animals which had recently moulted. No significant difference in plastic load was observed between males and females. Raman spectroscopy indicated that some of the microfilaments identified from gut contents could be sourced to fishing waste. Nephrops fed fish seeded with strands of polypropylene rope were found to ingest but not to excrete the strands. The fishery for Norway lobster, Nephrops norvegicus, is the most valuable in Scotland and the high prevalence of plastics in Nephrops may have implications for the health of the stock.     

Plastic marine debris on the Portuguese coastline: a matter of size?

Plastic debris is a worldwide threat to marine environments and Portugal is not immune to it. Though never quantified, items of all sizes can be found in the Portuguese coastline; therefore the objective of this work is the identification of main size classes in stranded plastic debris. Beaches sediment was sampled and in the laboratory plastic items were sorted in 11 classes from <1 to >10 mm, counted and weighted. Plastic size ranged from 50 μm to 20 cm and microplastics (<5 mm) were the majority (72%). Most plastic fits in the smaller size classes, due to expected high residence time in the sea enhancing degradation processes, which increase surface exposure and potentially persistent organic pollutants (POP) adsorption. These results point out the important contribution of microplastics to marine debris pollution, its risks, and the need to set a higher focus on this size class.     

Rethinking rewilding

The term ‘rewilding’ sounds as if it should have a straightforward meaning ‘to make wild again’. But in truth the term has a complex history and a host of meanings have been ascribed to it. Rewilding as a specific scientific term has its beginnings as a reference to the Wildlands Project, which was founded in 1991 and aimed to create North American core wilderness areas without human activity that would be connected by corridors. Words, however, do not stand still—they change over time and take on new meanings, while sometimes simultaneously retaining the older sense. Employing Foucault’s idea of historical genealogy, this article examines how the term rewilding was historically adopted and modified in ecological scientific discourse over the last two decades. This investigation probes what and, by extension, when and where, rewilding refers to as it has moved into various geographies across the globe. It then examines how the term has moved outside of science and been adopted by environmental activists as a plastic word. Taken as a whole, rewilding discourse seeks to erase human history and involvement with the land and flora and fauna. Such an attempted split between nature and culture may prove unproductive and even harmful. A more inclusive rewilding is a preferable strategy.     

Asteroidal processes recorded by polyphase deformation in a harzburgitic diogenite NWA 5480

Expectations regarding structural deformation of asteroidal meteorites have typically revolved around impact-induced shock metamorphism or the gravity-driven axial compression of cumulates at the base of magma chambers. Recent structural analyses, however, of several olivine-rich diogenites (harzburgites) reveal solid-state plastic deformation not attributable to either scenario and propose dynamic mantle movements in the parent body, assumed to be Vesta. In this study we examine the microstructures of pyroxene and olivine in the olivine-rich diogenite NWA 5480. Coarse-grained, poikilitic texture, exsolution lamellae and plastic deformation attest to polyphase deformation and a re-heating event, followed by relatively slow cooling. Observations suggest that impact events alone are insufficient to generate and sustain the thermal and deformation conditions required to achieve all of the observed features. The proposed dynamic mantle movements in the Vestan interior may offer a means of heat transport to the system to provide a thermal environment inducive to slow cooling as well as generate the incremental stress fields required for the polyphase plastic deformation observed in the olivine.