Observations on the open fields: the present position of studies in British field systems

Debate over the orgins and development of field systems in the British Isles continues within the framework provided by a collection of studies published in 1973. Some of the criticisms made by reviewers of that collective volume are answered here but this discussion paper focuses principally on two sets of arguments which have given a different emphasis to the debate on field systems during the past six years. This paper considers first McCloskey's view of open fields as products of behaviour towards risk and then Dodgshon's re-interpretation of the evolution of field systems in relation to changes in law.     

Early Trimpi events from lightning-induced electric fields in the ionosphere: An alternative explanation

Two classes of ‘Trimpi’ modulation of VLF signals in the Earth-ionosphere waveguide have been identified in the literature. The more common type occurs l s or more after causative lightning strokes, the second in less than 100 ms. We explore the possibility that these early Trimpi events result from lighting-generated, electric field impulses lowering the mirror altitudes of trapped electrons. To overcome the mirror force on energetic electrons, upward-directed electric fields with strengths of a few tens of mV/m are required. This is well within the range of electric fields observed on sounding rockets above thunderstorms.     

Equatorial penetration of magnetic disturbance effects in the thermosphere and ionosphere

The neutral dynamic and electrodynamic coupling between high and low latitudes, and the mutual interactions between these two processes, are investigated. For 22 March 1979, when a sudden increase in magnetic activity occurred, we have analyzed the following experimental data: (a) neutral densities and cross-track neutral winds as a function of latitude (0°–80°) near 200 km from a satellite-borne accelerometer; (b) hourly mean H-component magnetic data from the Huancayo Observatory (0.72°S, 4.78°E; dipole geomagnetic coordinates) magnetometer; and (c) hourly mean foF2 measurements from the ionosonde at Huancayo. Comparisons are also made with a self-consistent thermosphere-ionosphere general circulation model and with observationally-based empirical models of winds and density.In concert with the increase in magnetic activity to K_p levels of 5–7, a nighttime (2230 LT) westward intensification of the neutral wind approaching 400 ± 100 ms⁻¹ occurred near the magnetic equator on 22 March 1979, accompanied by a 35% increase in neutral mass density. About 2 h after each of two substorm commencements associated with periods of southward IMF, ∼100γ and ∼200γ reductions in the daytime Huancayo H-component (corrected for ring current effects) are interpreted in terms of ∼0.5 and ∼1.0 mVm⁻¹ westward perturbation electric fields, respectively. An intervening 2-hour period of northward IMF preceded a positive equatorial magnetic perturbation of about 200γ. Time scales for field variations are a few hours, suggesting that processes other than Alfven shielding are involved. Variations in f₀F2 (∼ ± 1.0 MHz) over Huancayo are consistent with the inferred electric fields and magnetic variations. Similar equatorial perturbations are found through examination of other magnetic disturbances during 1979.     

Early Islamic pigments at Nishapur,north-eastern Iran: studies on the painted fragments preserved at The Metropolitan Museum of Art

Pigments appearing on ninth–twelfth-century AD-carved stucco, wall painting, and terracotta friezes excavated at Nishapur in north-eastern Iran were investigated by optical reflectance spectroscopy, micro X-ray fluorescence spectrometry (μ-XRF), X-ray diffractometry (XRD), micro-Raman spectroscopy (μ-Raman), and scanning electron microscopy (SEM). Many of the pigments identified including vermilion, red lead, hematite, limonite, carbon black, atacamite, calcite, and gypsum have been identified in previous studies of pigments used in later Islamic periods. However, a series of unusual pigments such as wulfenite, pyromorphite, phoenicochroite, and jarosite were also found in the present study. The association of kaolinite and alunite with limonite and other Fe-bearing yellow pigments points to a local provenance for these pigments. In addition, the presence of orpiment in the vermilion may be indicative that the vermilion was artificially manufactured. These findings suggest that pigment use and manufacturing during the ninth to eleventh centuries in Nishapur was still in a trial-and-error stage and the palette known from the twelfth century onwards had not yet been systematized.     

Small-scale fluctuations of magnetic and electric components of the ELF and VLF wave fields in the sub-auroral topside ionosphere : stochastic characteristics of the wave field

When the Interkosmos-14 and Interkosmos-19 satellites crossed the region of spatially varying electron concentration in the topside ionosphere adjacent to the high-latitude boundary of the main ionospheric trough, it was discovered that there were simultaneous fluctuations of plasma density, temperature and the amplitudes (H_x and E_y) of the ELF and VLF radio/plasma emissions. The probability characteristics of the naturally perpendicular H_x and E_y fluctuations are analysed. The correlation coefficient R(_H, E_y) turned out to be less than 0.6 at frequencies of F ⩽ 4.65 kHz, while at higher frequencies R increases, up to 0.9 at 15 kHz. The following interpretations are proposed:

1. 1.1. While measuring noise emissions, as a rule a mixture of numerous elementary waves is recorded.
2. 2.2. At frequencies exceeding the local lower hybrid resonance frequency (in our case f_LHR ≈ 5 kHz), a mixture of electromagnetic waves experiencing the influence of the inhomogeneous electron concentration N_e is registered.
3. 3.3. At frequencies which are lower than the local value f_LHR the mixture mainly consists of ELF waves. The wave field has a complicated structure, and the dynamical coherence between electric and magnetic field components is not as simple as at VLF frequencies (f ≈ 15 kHz).
4. 4.4. It is shown that the wave components for a mixture of electromagnetic and electrostatic waves (for instance a mixture of VLF and lower hybrid frequency waves) have a lower correlation coefficient because the electrostatic waves are unrelated to the electromagnetic waves.
5. 5.5. The correlation analysis offers an opportunity to detect the presence of waves of various types in the wave mixture.

     

Reduction of the effects of non-stationarity in studies of amplitude statistics of radio wave backscatter

By studying the statistics of fluctuations in amplitude of radio signals backscattered from the atmosphere and lower ionosphere, it is possible to obtain information about the scatterers. This procedure has been applied previously, but often relatively long data series have been used (e.g. 10–30 min) in order to produce reliable amplitude distributions. Unfortunately, the nature of the scatterers can often change considerably over such a time interval and this can distort the amplitude distributions. An alternative approach, applied in this work, is to use much shorter data sets, derive a parameter representative of each data set (e.g. the Rice parameter) and then examine the statistics of this derived parameter over a longer period. Computer modelling was used to examine the statistics of such a parameter and some surprising results emerged, even for relatively long data series. Several examples of the application of this new method will be presented.     

明早期瓷器铭文的观察

文章依据目前所知明代早期瓷器铭文资料,就这些瓷器书铭格式的渊源、性质及所反映的瓷器生产方式和生产关系作了科学的分析和探讨。     

早期游牧文化起源问题探析

以整个欧亚草原为视角,对比资料相对丰富且具有代表性的内蒙古东南部、萨彦-阿尔泰地区和黑海北岸三个地区畜牧向游牧转变期的材料,对早期游牧起源问题提出自己的一些看法。研究表明,公元前8世纪以前这三个地区都存在自身特色明显、畜牧业发达的遗存,但其中只有萨彦-阿尔泰地区可能已经转变成游牧经济,而内蒙古东南部和黑海地区在同时期可能还没有进入真正的游牧社会。欧亚草原地区各地早期游牧的起源不是同步的,也不是一条直线发展的,最早的游牧很有可能出现在远离发达农业文明且畜牧业发达的草原地带,而与发达农业文明毗邻且与之关系密切的地区游牧则产生的晚一些。     

中国早期文明研究中的几个问题

本文提出了有关中国早期文明研究的几个问题:第一,对中国古代文明中相关文化的崩溃和消失现象应该予以重视和研究;第二,在古代文明研究中要注意“中国”概念的形成和使用问题, 对一些基本概念要进行分析,对“中国”观念认同的形成及其所包涵文化的融合和变迁进行了研究; 第三,利用“集体记忆”理论,对炎黄传说形成过程及其本质作了初步分析,结合疑古派成果,认为将炎黄传说作为史前古史框架使用应慎重考虑。     

Dental evidence of biological affinity and environmental conditions in prehistoric Trentino (Italy) samples from the Neolithic to the Early Bronze Age

The use of teeth in anthropological analyses has always provided valuable information on the subsistence patterns of human communities, as well as the biological relationships among them. The present study analyses the permanent dentition of several diachronically continuing samples from the Trentino alpine region of Italy from the Neolithic to the Early Bronze Age. The study of both metric and non‐metric dental traits show a strong level of homogeneity from the earlier to the later samples, indicating little external biological influence from surrounding areas. However, the evidence of oral pathology and linear enamel hypoplasia highlights a trend of increase in defects, particularly between the Neolithic and the Copper Age. This has been ascribed to a shift towards more intense agricultural activities and pastoralism, that led to a change in diet and to an increased sedentism. Copyright © 1999 John Wiley & Sons, Ltd.     

早期南社画家行状考

南社中的画家于字鼓吹革命的同时,并以绘画寄情明志、砥砺品节。本梳理有关史料,稽考黄宾虹、蔡哲夫、诸贞壮等投身民主革命中的行状,及对其艺术发展的关联与影响。以此钩沉近一个世纪前画家活动的时空背景,从中揭示形成其艺术成就的早期动因。     

“早期夏文化学术研讨会”纪要

2008年7月18～20日,由北京大学震旦古代文明研究中心、河南省文物考古研究所和郑州市文物考古研究院共同主办的"早期夏文化学术研讨会"在河南郑州召开.会议回顾了学术界几十年来探索早期夏文化的历程,总结了早期夏文化研究所获得的阶段性成果,讨论了学术界目前关心的早期夏文化研究中的热点问题,指明了早期夏文化研究的方向.这次会议在夏文化研究历史中将具有里程碑式的意义.     

试析早期铜器在文明进程中的地位

关于中国早期铜器的研究,是一个重大的学术课题。近年来,已引起学术界众多专家学者的极大关注。在人类历史发展长河中,早期铜器的出现不仅促使生产力发展水平发生质的飞跃,而且表明社会生产力与生产关系将要发生巨大的变革。铜器作为人类社会进入文明时代的重要标志,在中国古代社会文明起源中发挥了重要的作用。鉴于此,本文主要利用田野考古发掘资料,就早期铜器在文明进程中的地位问题进行初步探讨。     

Estimation of soil erosion on cultivated fields on the hilly Meghalaya Plateau,North-East India

The estimation of soil erosion rates in complex subtropical agricultural systems of hilly environment is difficult and most of the traditional methods have serious limitations. The ¹³⁷Cs technique allows to obtain relatively quickly retrospective medium term soil erosion results. The objective of this study was using ¹³⁷Cs approach to quantify soil loss under agricultural system which develops under growing human pressure on the hilly terrain of the Meghalaya Plateau. The measured values of caesium inventory for all sampling points are between 2% and 63% of the reference value of caesium inventory. The estimated annual soil loss for sampling points located on the slope are between 29 and 79 Mg·ha⁻¹·yr⁻¹ in the case of an improved mass balance model. It means that soil erosion in this manually tilled agricultural area cannot be neglected.