美国各大城市的批发贸易空间变化

尽管对美国城市系统的研究已经很多,但关于批发贸易职能方面几乎未做过什么工作.从地理学观点确定出批发贸易这一概念的主要著作仅有万斯(Vance)著的《商家世界》.关于批发贸易的论述不是没有就是极为简单.本文集中研究40个批发贸易中心,对美国各大城市的批发贸易功能进行了检查.研究目的:(1)检验城市批发贸易优势随时间变化的程度;(2)用数值表示出个别SMSA①的排列次序转移的型式;(3)离析出促使这些城市的批发贸易作用变化的原动力;(4)提议建立一个可能被接受的美国城市系统批发贸易发生变化的模型.前两个目的可以通过检验排列次     

Ester Boserup's theory of agrarian change: a critical review

As discussions of the positive effect of population growth upon agricutural change have been less common than focus on the negative effects, Ester Boserup's book, "The Conditions of Agricultural Growth," and her subsequent work in which it is argued that population growth is the prime cause of agricultural change is of great importance. The objective of this essay is to review earlier attempts to relate the intensification of agriculture to population growth, to outline Boserup's theory, and to examine the criticisms which have been made of the theory. Boserup maintains that population growth is the cause rather than the result of agricultural change and that the principal change is the intensification of land use. The theory of agricultural development posed by Boserup is more subtle and complex than that of any of her predecessors. She sees population pressure as a major cause of change in land use, agricultural technology, land tenure systems, and settlement form. Boserup argues that population growth is independent of food supply and that population increase is a cause of changes in agriculture. The principal means of increasing agricultural output is intensification. Boserup's work has had a varied response from readers; other economists have been less than enthusiastic. It might seem as if the critics of Boserup's theory have left it in tatters. Her central argument, that intensification reduces labor productivity, remains unproven. There are few who would agree that an increase in the frequency of cropping is the only possible response to population pressure; the extensive margin can be extended, higher yielding crops adopted, and methods that increase yields introduced independently of increases in the frequency of cropping. Emigration or the control of numbers may relieve population pressure. Intensification can also take place without population pressure, under the stimulus of urban growth or the development of trade. It is difficult to accept that population pressure is the only cause or agrarian change or that the increased frequency of cropping is the only response to population pressure, yet the thesis is a fruitful interpretation of agrarian change. Assuming population growth as a change mechanism can lead to important new conclusions regarding the nature of agrarian change in western European history.     

有待开发的木质文物处理技术──细胞壁聚合物的化学改性

木质特性是木材的细胞壁聚合物的物理和化学性能综合作用的结果。在木材老化过程中,细胞壁聚合物的物理性能发生变化。细胞壁基质的降解和纤维素分子的解聚作用,导致强度不断下降、完整性逐渐损失。因此,当他水木质文物被干燥时,引起收缩、纹缝、破裂。对于木质文物修复的传统方法是用一种聚合物或多聚合物通过封护加固衰变木材使其恢复强度;或者当木质干燥时,用湿胀性化学试剂以避免收缩,维持其处于膨胀状态。从理论上讲,另一种方法将可能是从化学角度修复细胞基质和细胞聚合物,使其达到与原始状态相类似的状况。本文将集中介绍用简单的活性化学试剂、交联试剂或多聚物,使残留的细胞壁聚合物恢复原状的几种方法。     

石门坎与花苗

第三章跳出困境──石门坎的故事1903年的一天,一伙猎人遇上了詹姆斯·亚当即党居仁先生,他是中国内地会传教土,在贵州西部的安顺工作。从他们的装束上亚当先生知道他们属于苗族的一个部落,进而知晓他们一直在追猎野猪,又饥饿又疲乏,就拿出自己的饭食给他们吃。当在一起交谈的时候,亚当先生用明白、易懂的语句向他们讲述了邵稣基督的故事,以及耶稣如何在寻找并拯救迷途人们。’他也要来寻找我们吗？”苗族人问。“是的,”得到的是平静的回答,“耶稣会来寻找你们的。“通过较长时间的领会,他们终于有些明白了,竟然会有人热爱与关…     

Urbanization patterns: European versus less developed countries

This paper develops a model in which the interaction between transport costs, increasing returns to scale, and labor migration across sectors and regions creates a tendency for urban agglomeration. Demand from rural areas favors urban dispersion. European urbanization took place mainly in the 19th century, with higher costs of spatial interaction, weaker economies of scale, and a less-elastic supply of labor to the urban sector than in less developed countries (LDCs) today. These factors could help explain why primate cities dominate in LDCs, whereas a comparatively small share of urban population lives in Europe's largest cities.