Grain‐scale permeabilities of faceted polycrystalline aggregates

Porous synthetic quartzites and amphibolites, each with faceted pore walls, were synthesized and evaluated to examine the permeability of pore networks similar to those of the lower crust and mantle. Quartzite with a fluid in equilibrium with an Mg–clinopyroxene contained connected networks of pores with a dihedral angle of 30° bounded by walls that were 10–50% faceted. The relationship of their permeability (k) to porosity (φ) is approximated by the previously determined relationship for relatively nonfaceted synthetic quartzite Amphibolite with an HF fluid contained fluorotremolite and a connected network of pores bounded by walls exhibiting 78–90% faceting. These materials showed much lower k for a given φ, with an apparent permeability threshold at φ_c = 0.04. A curve fit to these data yields The results suggest that moderate faceting has little effect on the transmission of fluids through rocks, but extensive faceting significantly alters permeability. This difference is most likely produced through isolation of the fluid to the grain corners at low φ with extensive faceting. Rocks with pores that tend toward faceting may impede the flow of fluids and melt.     

李鸿章与晚清漕粮海运

晚清漕粮海运与李鸿章的关系密不可分.他通过恢复海运扩大漕粮海运的参与省份,调整海运规章、抚恤海运群体,扶植轮船招商局、促进漕粮运输工具近代化等方式,对漕粮海运的变革产生了全方位影响,成为推动中国社会走向近代的重要人物.     

Common good and private justice: letters of marque and the utilitas publica in fourteenth-century Marseilles

Political debate, even in medieval Europe, has often centred upon the relationship between individual liberties and the greater good. Fourteenth-century town councils had to think about protecting private property while ensuring the greater public good. The council registers of late medieval Marseilles offer the opportunity for insight into this public–private dichotomy through an examination of the council's decisions to suspend temporarily the execution of letters of marque. In fourteenth-century Marseilles, letters of marque helped citizens gain restitution from foreign debtors through a judicial authorisation to seize foreign assets. The suspensions, justified in the language of the utilitas publica, were declared for two reasons: to protect the integrity of the town's market by ensuring an ample supply of labourers and victuals, and to protect the town's honourable reputation when dignitaries visited. Study of these suspensions illustrates an overarching philosophy in urban government – that the public good must be safeguarded against private advantage.     

Integrating Geomorphological Assessments and Oral Histories in Catchment Management: Implications for the Mulgrave River,Northeastern Australia

The dramatic decline in the integrity of Australian river systems in recent decades has seen the development of landcare and catchment management groups across the continent as the main facilitators of river rehabilitation works. There is growing concern for the need to develop adaptive management frameworks that assist informed decision making through the integration of social and geomorphological knowledge into catchment planning. In the Mulgrave River Catchment of northeastern Queensland, difficult management decisions have to be made with limited access to knowledge of natural processes and baseline geomorphological data. To date management decisions have been based almost exclusively on oral histories that state that point bars are accreting and the river is becoming shallower due to bank erosion. As a result bank stabilisation and removal of sand from within the channel have been recommended in the absence of any geomorphological assessments. This study compares oral histories of river bank erosion in the Mulgrave River with geomorphic evidence to highlight the need for integrated landscape scenario planning. The results of grain size analysis of bank and bed material from 27 locations, involving 47 samples, suggest that bank erosion cannot be delivering sediments to point bars. Furthermore, qualitative analysis of historic parish maps and aerial photographs shows that there has only been moderate bank erosion at three locations along the Mulgrave River since European settlement. The study demonstrates the important role that geomorphological investigations have for catchment management and the need for management frameworks that integrate geomorphological processes and landholder priorities for sustainable river management.