Experimental study of aqueous fluid infiltration into quartzite: implications for the kinetics of fluid redistribution and grain growth driven by interfacial energy reduction

To investigate the kinetics of interfacial energy‐driven fluid infiltration, experiments were carried out in a quartzite–water system at 621–925°C and 0.8 GPa. Infiltration couples were made by juxtaposing presynthesized dry quartzite cylinders and fluid reservoirs. The infiltration process was confirmed by the presence of pores at the quartzite grain edges. As predicted from theoretical considerations and previous experiments, wetting fluids such as pure water and NaCl aqueous solution infiltrated into quartzite, whereas nonwetting CO₂‐rich fluids did not. Newly precipitated quartz layers at the surfaces of the infiltrated sample proved that infiltration took place by a dissolution–precipitation mechanism. The enhancement of grain growth by fluid infiltration was observed over the entire range of experimental temperatures. The fluid fraction, gauged by the porosity of the run products, increases at the infiltration front and then decreases towards the fluid reservoir to form a high‐porosity zone with a maximum porosity of 2.3–2.9%. As infiltration proceeds, the high‐porosity zone advances like a travelling wave. This porosity wave is probably caused by a grain curvature gradient resulting from preferential grain growth in the infiltrated part of the quartzite, perhaps combined with other factors. The infiltration kinetics were modelled with a steady‐state diffusion model over the high‐porosity zone. The solubility difference between dissolving and precipitating grains was deduced to be 2 × 10^?2?3 × 10^?1 wt %. The experimentally obtained infiltration rate of aqueous fluid in the steady‐state diffusion regime (2 ± 0.5 × 10^?8 m sec^?1 at 823°C) is much faster than the estimated metamorphic fluid flux rates, so that interfacial energy‐driven fluid redistribution in quartz‐rich layers could significantly contribute to the fluid flux in high‐grade metamorphism, at least over a short distance. Cathodoluminescence observations of the run products revealed that the grain growth of quartzite in the presence of fluid proceeds extensively, which would promote the chemical equilibration between fluid and rock more effectively than would volume diffusion in quartz crystals.     

1955～1956年上海首次城市人口紧缩与粮食供应

1955~1956年,上海市经历了新中国成立以来首次大规模的城市人口疏散。为了应对日益严峻的城市人口压力,上海市动员了大批外来农民回原籍生产,并组织城市失业人口前往江西等地参加垦荒建设,期间共有50余万城市人口被疏散。从人口形势与粮食供给关系来看,城市粮食供应困难是导致这次城市人口疏散的重要原因。这一事件影响到此后的国家政策走向。     

民国时期江汉平原的粮食市场

粮食贸易在民国时期江汉平原的农村经济中占有重要地位,粮商及粮商组织、粮食加工和运输、粮食价格、粮食集散和粮食存储等几个方面反映了民国时期江汉平原的粮食市场的基本情况。粮食贸易将大量的基层市场、少量中间市场和几个中心市场联系在一起,粮食价格的趋同性表明这个地区当时存在着完整的粮食贸易体系,但相关市场特征又表明这个市场是不完善的。     

The escape from famine in the Northern Netherlands: a reconsideration using the 1690s harvest failures and a broader Northwest European perspective

A long historiography has concluded that the Northern Netherlands was famine free by the seventeenth century. However, this view has been established on limited grain price data and an unclear chronology, lacking a broader comparative perspective, and relying heavily on the explanation that Amsterdam was the centre point of the international grain trade. Using newly compiled burials data for the Northern and Southern Netherlands and Northern France, and integrating these with rye prices, we confirm empirically that price spikes had reduced mortality effects in the Northern Netherlands compared to the Southern Netherlands and Northern France, though the escape was greater in the cities than the countryside. The only time in the period 1551–1699 that a strong and generalized association between price spikes and mortality occurred across wide areas of the Northern Netherlands was in the famine of 1556/7. However, the international grain trade cannot explain everything. Markets in the Northern Netherlands were no more effective at smoothing out food crises than in the Southern Netherlands or Northern France. We offer alternative explanations: the reduced role of famine-related diseases spread by warfare, and the interaction (especially in the cities) between wages and poor relief.     

邮轮旅游供应链的旅行社激励机制研究:组织游客奖励还是营销推广扶持?

考虑到旅行社在我国邮轮旅游销售供应链中的重要性,邮轮港口所在地政府为推进邮轮旅游产业发展,普遍对旅行社实施两种激励政策——组织游客奖励与营销推广扶持。但两类激励政策对当地政府、邮轮公司及旅行社的效益影响尚不明确。本文首先建立“政府-邮轮公司-旅行社”三阶段主从博弈模型,以研究两种激励政策对两企业运营决策的作用机理,并给出政府在最大化市场需求目标下的最优激励政策。其次,借助数值仿真实验分析了不同情形下基于最优激励政策时市场需求和企业利润的变化。结果表明:站在政府角度,激励政策有两种选择——仅采取营销推广激励或者两种激励方式并存,而且最优激励设计受到补贴预算、旅行社营销推广能力及其岸上游收益的影响。站在旅行社角度,作为激励政策的直接受益方,其定价与营销努力决策会受到两类激励方式的不同影响;而对于营销推广能力较强的旅行社,可以依赖于政府奖励适当提高船票价格,以改善当前国内邮轮市场的低价竞争。站在邮轮公司角度,即使自身没有直接得到激励资金,其仍能间接获得激励政策所带来的红利。研究结论可为政府的邮轮旅游激励政策的设计提供理论参考,并为邮轮公司与旅行社在面对政府财政干预时提供决策建议。     

Agnes of Burgundy: an eleventh-century woman as monastic patron

As an eleventh-century monastic patron, Agnes of Burgundy was generous, thoughtful, and involved; she galvanized others into endowing monasteries and won the respect of the houses she supported. The association with grateful abbeys helped her and her husband, Geoffrey Martel, to establish the legitimacy of their rule. In this symbiosis, Agnes used the system for all it was worth, even eventually retiring as an old lady into one of her foundations, while religious life in west-central France flourished, aided by her support. Yet, although enormously wealthy and powerful, she did not act with full autonomy. Her life was shaped by the biological determinants of menarche and menopause; by involvement in familial strategies to advance her spouse's and children's careers; by limitations on her use of feudal power; and by gender roles that patterned behavior. She, and every other woman like her, functioned within a web of gender, class, and family constraints and expectations.     

Restructuring Beijing's Social Space: Observations on the Olympic Games in 2008

Two American geographers comment on the preceding analysis of restructuring of Beijing's social space (Feng et al., 2007) by presenting observations on the city's Olympic Games, forthcoming in the summer of 2008. The authors focus on some of the more salient geographical impacts stemming from construction, relocation, and related measures undertaken by the authorities to accommodate the event. Included in the paper are sections on environmental concerns (particularly air pollution), infrastructure (water supply, automobile traffic, and mass transit), and relocation and displacement of residents (particularly of migrants and other disadvantaged segments of the population). Journal of Economic Literature, Classification Numbers: I31, O15, O18, P20. 2 figures, 2 tables, 44 references.     

Exchange Rate Policy and the Central and East European Financial Crisis

A prominent specialist on economic developments in the former Soviet Union and Central and Eastern European (CEE) countries examines the ways in which the global financial crisis of 2008-2010 has impacted the economies of the 10 new eastern member states of the European Union (CEE-10). The author assesses the multiple preconditions of the crisis (e.g., excessive current account deficits, large foreign debt, inadequate currency reserves, immense credit expansion, rising inflation and real estate prices) as well as the rapid financial adjustments that had to be undertaken to overcome it (e.g., current account rebalancing, reducing budget deficits, pension and fiscal reform). He devotes considerable attention to the key issue of how the differences in exchange rate policies in these countries affected their abilities to respond to the crisis and outlines measures that should be implemented to enhance the crisis management capability of non-eurozone states relying on currency boards or floating exchange rates.