Plastic pollution and the open burning of plastic wastes

The open burning of plastic wastes is a practice that is highly prevalent across the globe, toxic to human and environmental health, and a critical—but often overlooked—aspect of plastic pollution. Most of the countries where such burning is widespread have laws and policies in place against it; open burning continues nevertheless. In this article, using data from ethnographic fieldwork in urban and rural sites in India, Indonesia, the Philippines, and Zambia, we examine local practices of open burning and investigate why regulations to tackle it have proven largely ineffective. Adopting a harm reduction approach, we then suggest preliminary measures to mitigate the health risks of open burning by targeting those plastics and packaging types that are most toxic when burned.     

亚洲中东部岩浆岩网络状分布与塑性流动网络

亚洲中东部的岩浆岩分布具有明显的网络状特征，共轭相交的岩浆岩带构成了晚古生代、中生代和新生代不同的岩浆岩网络系统。岩浆岩网络受岩石圈下层塑性流动网络的控制，是塑性流动带剪切变形、摩擦热效应及带内介质弱化、轻化，以至促成地幔上隆和岩浆上涌的结果。根据“塑性流动－岩浆岩”网络，推测了不同地质时期大陆构造变形的驱动边界、驱动力方向和古构造应力场，并探讨了网络构造的演变等问题     

The role of subgrain boundaries in partial melting

Evidence for partial melting along subgrain boundaries in quartz and plagioclase is documented for rocks from the Lost Creek Gneiss of the Llano Uplift, central Texas, the Wet Mountains of central Colorado, and the Albany-Fraser Orogen, southwestern Australia. Domains of quartz or plagioclase crystals along subgrain boundaries are preferentially involved in partial melting over unstrained domains of these minerals. Material along subgrain boundaries in quartz and plagioclase has the same morphology as melt pseudomorphs present along grain boundaries and is commonly laterally continuous with this former grain boundary melt, indicating the material along subgrain boundaries can also be categorized as a melt pseudomorph. Subgrain boundaries consist of arrays of dislocations within a crystal lattice, and unlike fractures would not act as conduits for melt migration. Instead, the presence of former melt along subgrain boundaries requires that partial melting occurred in these locations because it is kinetically more favorable for melting reactions to occur there. Preferential melting in high strain locations may be attributed to strain energy, which provides a minor energetic contribution to the reaction and leads to preferential melting in locations with weakened bonds, and/or the presence of small quantities of water associated with dislocations, which may enhance diffusion rates or locally lower the temperature needed for partial melting.     

Exploring the influence of loading geometry on the plastic flow properties of geological materials: Results from combined torsion + axial compression tests on calcite rocks

For technical reasons, virtually all plastic deformation experiments on geological materials have been performed in either pure shear or simple shear. These special case loading geometries are rather restrictive for those seeking insight into how microstructure evolves under the more general loading geometries that occur during natural deformation. Moreover, they are insufficient to establish how plastic flow properties might vary with the 3rd invariant of the deviatoric stress tensor (J₃) which describes the stress configuration, and so applications that use those flow properties (e.g. glaciological and geodynamical modelling) may be correspondingly compromised. We describe an inexpensive and relatively straightforward modification to the widely used Paterson rock deformation apparatus that allows torsion experiments to be performed under simultaneously applied axial loads. We illustrate the performance of this modification with the results of combined stress experiments performed on Carrara marble and Solnhofen limestone at 500°–600 °C and confining pressures of 300 MPa. The flow stresses are best described by the Drucker yield function which includes J₃-dependence. However, that J₃-dependence is small. Hence for these initially approximately isotropic calcite rocks, flow stresses are adequately described by the J₃-independent von Mises yield criterion that is widely used in deformation modelling. Loading geometry does, however, have a profound influence on the type and rate of development of crystallographic preferred orientation, and hence of mechanical anisotropy. The apparatus modification extends the range of loading geometries that can be used to investigate microstructural evolution, as well as providing greater scope for determining the shape of the yield surface in plastically anisotropic materials.     

Persistent organic pollutants carried by synthetic polymers in the ocean environment

Thermoplastic resin pellets are melted and formed into an enormous number of inexpensive consumer goods, many of which are discarded after a relatively short period of use, dropped haphazardly onto watersheds and then make their way to the ocean where some get ingested by marine life. In 2003 and 2004 pre-production thermoplastic resin pellets and post-consumer plastic fragments were collected and analyzed for contamination for persistent organic pollutants (POPs). Samples were taken from the North Pacific Gyre, and selected sites in California, Hawaii, and from Guadalupe Island, Mexico. The total concentration of PCBs ranged from 27 to 980 ng/g; DDTs from 22 to 7100 ng/g and PAHs from 39 to 1200 ng/g, and aliphatic hydrocarbons from 1.1 to 8600 microg/g. Analytical methods were developed to extract, concentrate and identify POPs that may have accumulated on plastic fragments and plastic pellets. The results of this study confirm that plastic debris is a trap for POPs.     

1990年10月天祝—景泰6.2级地震孕震过程剖析及其意义

本文依据天祝—景泰6.2级地震的地震构造、应力场条件及前兆分布,分析研究了该次地震的孕震过程。认为天祝一景泰6.2级地震的力源主要是NE向区域应力场的挤压,垂直差异运动对地震起了促震作用。孕震过程形成的震源应力场在空间上有四象限分布特征,时间上经历了孕育、形成、增强等阶段,相应地震源区则经历了弹性形变、塑性形变、塑性硬化及失稳错动的过程。     

Environmental impact of the MV CITA on the foreshore of Porth Hellick, Isles of Scilly

The grounding of the container feeder vessel MV CITA on Newfoundland Rocks, Isles of Scilly, had an effect on the surrounding biota and benthic environment. Included in the CITA's cargo were five 40 ft containers holding pallets of polyester film used in the production of audio and visual recording tapes. The wreckage presented a minor but potentially chronic source of pollution through the delayed release of polythene film, which was left on the seabed as it was considered insufficiently valuable to warrant salvage. The polythene disintegrated and was washed upon the foreshore of Porth Hellick in minute shreds. The adjacent foreshore and two control sites within the islands were analysed using a 5-strand line and vegetation survey with 10 random quadrats within each line to determine the environmental impact of the polythene.     

碎石桩复合地基承力性状有限元分析

本文通过对碎石桩复合地基的简化，采用有限元方法分析了复合地基的附加应力与桩身应力的分布特征；讨论了桩土应力此与桩土模量比，以及荷载及置换率的相互关系；揭了桩体变形和复合地基塑性区扩展的基本规律。即从不同角度探讨了复合地基的承力性状。     

榴辉岩相变质岩中石榴石的塑性微裂隙

在变质岩中石榴石广泛发育微裂隙，这些微裂隙一直认为是在脆性变形过程中产生的。本文应用透射电子显微镜（ＴＥＭ）研究证明，在榴辉岩相变质岩中，石榴石的微裂隙是塑性变形的产物。同时较为深入的探讨了这些塑性微裂隙的形成机制     

玻璃钢夹砂管在顶管工程中的应用

近年来,玻璃钢夹砂管在（管工程中的到越来越广泛的应用,以广州市某污水工程顶管施工为例,介绍了玻璃钢夹砂管在流砂地层的应用,以及在顶管施工中所要注意的事项和应对措施,以供工程技术人员和同类工程参考。