Comparative studies of scatterers observed by MF radars in tbe southern hemisphere mesosphere

Using data from three radar sites (low, mid and high latitude) we study the aspect sensitivity of mesospheric scatterers probed by MF radars operating at or near a frequency of 2 MHz. The aspect sensitivity (θ_s) is calculated by the spatial correlation technique. Calculations of θ_s arc further extended to estimate the lcngth-to-depth ratio of the scatterers which indicate that the scattcrers arc quasi-specular. We find that high and mid latitude sites exhibit clear seasonal behaviour, with maxima occurring in the local summer while the low latitude site shows no significant seasonal behaviour.     

Absolute reflectivities and aspect sensitivities of VHF radio wave scatterers measured with the SOUSY radar

By accurately calibrating the SOUSY radar in West Germany it has been made possible to measure absolute values of effective reflection coefficients and turbulence structure constants. Some typical values of these parameters as a function of altitude are presented. Such profiles are presented for both a vertically directed beam, and also for two beams directed 7° off-vertical. Comparisons of powers on the vertical and off-vertical beams show that scatter became more aspect sensitive at the tropopause and in the lower stratosphere, but, unexpectedly, scatter was observed to become considerably more isotropic in the higher regions of the stratosphere (above 15–18 km) on this occasion. An enhancement of signal from the tropopause occurred not only on the vertical beam, but also on the off-vertical beams.Comparisons of signal strengths scattered from the mesosphere and measured with the vertical and off-vertical beams showed that for the present observations mesospheric scatter was close to isotropic. The backscatter cross-sections at VHF have been compared with other measurements at medium and high frequencies at other locations, and these comparisons help set some limits on the scales of turbulent and specular scatterers in the mesosphere.     

Meteor observations by the Arecibo 430 MHz incoherent scatter radar—I. Results from time-integrated observations

The paper discusses an incoherent scatter radar (ISR) power profile interference detection and meteor filtering technique and presents the meteor interference statistics derived from the Arecibo 430 MHz ISR. The statistics obtained from the Arecibo ISR are comparable with the meteor statistics obtained by other radar and optical techniques. Using the hourly rate of meteor flux, the average visual magnitude of the meteors i s estimated to be as faint as + 14, probably, the faintest ever reported. For low echo meteors, the mean ablation height exhibits a logarithmic relationship with the returned power below 105 km. However, once the echo power exceeds a certain threshold, the mean height remains constant at 107 km for all meteors irrespective of their returned power. The unique aspect of the meteor trails reported here is that they are observed in the radial direction of the radar beam. The lack of aspect sensitivity and the high meteor rate detected by the Arecibo 430 MHz system seem to suggest that the scattering mechanism in the UHF range of frequencies may be different from the mechanism operating at VHF. Some future prospects of exploiting; meteor trails to study the neutral wind and other aspects of the meteor region are also proposed.     

The influence of geomagnetic activity on the upper mesosphere lower thermosphere in the auroral zone. II. Horizontal winds

A spaced antenna partial reflection radar located at Mawson, Antarctica (67°S, 63°E, invariant latitude 70°S), has been used to measure the horizontal wind field in the height range 70–110 km. Three years of data (1985–1987) from the radar have been analysed in order to investigate correlations between geomagnetic activity (determined from the local K-index) and the horizontal wind. Results are analysed using a randomization technique and show that larger winds are measured during geomagnetically active periods in both the raw (or unfiltered) wind values and in the medium-frequency (2–6 h period) and high-frequency (1–3 h period) components. The raw winds tend to be shifted towards the geographic NW to NE quadrant in the early morning hours during high K-times. The observed correlation is seen down to 86 km and shows a seasonal dependence. The mean r.m.s. velocity of the radar scatterers and the angular spread of the return echoes are also found to be correlated with geomagnetic activity. The medium- and high-frequency components of the wind are polarized in the magnetic zonal direction during all seasons of the year.     

Processing ochre in the Middle Stone Age: Testing the inference of prehistoric behaviours from actualistically derived experimental data

The increase in the presence of ‘ochre’ in African Middle Stone Age contexts has been employed, together with changes in human biology and behaviour, to support the hypothesis that ‘modern’ cognitive abilities arose in Africa. The consistent exploitation of ochre is interpreted as evidence for colour symbolism, a proxy for the origin of language and a defining aspect of ‘modern’ human behaviour. That humans attached considerable symbolic value to red ochres in particular is illustrated by ethnographic examples. Research has shown that wear patterns indicative of abrasive processing methods prevail, but many archaeological specimens also exhibit wear traces not derived from grinding or scraping alone. Building on former research, I present here the results of an experimental study devised to infer the methods employed to extract powder from ochre during the African Middle Stone Age. The prospect of ascertaining at least some of the likely uses to which ochre may have been put, is also explored. I conclude that functional data derived from actualistic experiments can be used to enhance our understanding of some aspects of prehistoric behaviour.     

丝织品老化程度检测方法探讨

古代丝织品老化程度的检测有助于了解丝织品的有保存状况及保护方法的选择与改进,为研究适用于检测古代丝织品老化程度的方法,在对丝织品的物理,化学老化特征及性能研究的基础上,对可能用作检测丝织品老化程度的方法进行了系统的对比分析。用抗拉强度分析,色差分析,粘度测定,氨基酸分析,红外光谱分析,热分析,扫描电镜观察,X射线射分析等对经光老化,热老化和水解老化等人工老化的白色丝织品进行分析,结果表明,粘度分析是一种较为灵敏,且经济实用的检测方法,氮基酸分析是一种有效的确定丝织品保存状的手段,显微红外和热分析所用的样品量很少,如果能找出较为灵敏的定量指标,会有实用价值,扫描电镜观察,X－射线衍射分析对老化程度的检测有一定的难度,色差分析难以定量表征丝织品的强度变化。     

Bison breeding characteristics and interpretation of archaeological seasonality revisited

Bison breeding behaviour has been used for the last three decades as the basis for developing methods for assigning season‐of‐occupation estimates to archaeological sites on the North American Plains. These methods are based upon the supposition that the North American bison breeding season is extremely short and that genetically controlled ontological characteristics such as foetal growth and tooth eruption sequences can therefore be used to infer site seasonality in a reasonably straightforward and precise manner. This paper reviews bison population studies conducted during the past 30 years to reassess present understandings of the length of North American bison breeding seasons. It is concluded that the bison breeding season regularly extends over a period of three to four months, and that initiation of ontological development will therefore also vary over the same period of time. Bison development characteristics cannot provide a reliable or precise means of assigning seasonality to archaeological sites on the North American Plains. It is suggested that methods using physical characteristics such as dental cementum incrementation which are directly affected by seasonal changes could be more productive. Copyright © 2006 John Wiley & Sons, Ltd.     

Fluid flow in shear zones: insights from the geometry and evolution of ore bodies at Renco gold mine,Zimbabwe

The geometry of mineral deposits can give insights into fluid flow in shear zones. Lode gold ore bodies at Renco Mine, in the Limpopo Belt, Zimbabwe, occur as siliceous breccias and mylonites within amphibolite facies shear zones that dip either gently or steeply. The two sets of ore bodies formed synchronously from hydrothermal fluids. The ore bodies are oblate, but have well‐defined long axes. Larger ore bodies are more oblate. High‐grade gold ore shoots have long axes that plunge down dip; this direction is perpendicular to the long axes of the low‐grade ore bodies. The centres of the high‐grade ore bodies align within the low‐grade ore bodies along strike in both gently and steeply dipping groups. The range of sizes and shapes of the ore bodies are interpreted as a growth sequence. Geometrical models are proposed for the gently and steeply dipping ore bodies, in which individual ore bodies grow with long axes plunging down dip, and merge to form larger, more oblate ore bodies. The models show that when three or more ore bodies coalesce, the long axis of the merged ore body is perpendicular to the component ore bodies, and that ore bodies in the deposit may have a range of shapes due to both growth of individual ore bodies, and their coalescence. The long axes of the high‐grade ore bodies are parallel to the shear directions of both the gently and steeply dipping dip slip shear zones, which were the directions of greatest permeability and fluid flow. The larger, lower grade bodies, which may have formed by coalescence, are elongate perpendicular to these directions.     

In Praise of Interdisciplinary Archaeology

Abstract

The study of instabilities has long been a central aspect of physical theories and experimental investigation. Chaotic behaviour is a more recently recognized general feature of physical systems, expecially hard-driven dynamical systems. This review describes physical models illustrating these phenomena and seeks to indicate their application to understanding a variety of problems outside physics. Thus, the occurrence of instabilities is advanced as the reason why different sciences have developed independently, and why their results cannot be regarded as deducible from the fundamental laws of physics. In particular, sociology and political science are seen as attempting to deal with extreme cases of chaotic behaviour resulting from widespread instability. Finally, a simple physical model of stop-go oscillations is described, and interpreted as a warning against over-optimistic expectations that modern attempts at participatory democracy are compatible with a stable society.     

Palaeolithic Human Subsistence in Mount Carmel (Israel). A Taphonomic Assessment of Middle and Early Upper Palaeolithic Faunal Remains from Tabun,Skhul and el‐Wad

Detailed archaeozoological studies of Middle and Early Upper Palaeolithic (250–40 kya) faunal assemblages from Tabun, Skhul and el‐Wad caves, located in Mount Carmel (Israel), are presented here, expanding on the previous palaeontological analyses carried out by Garrod and Bate in the 1930´s and by Garrard five decades later. Despite the well‐known excavation bias of the older excavations, this study makes greater use of modern taphonomic techniques and statistical procedures, providing new palaeoeconomic insights into the subsistence behaviour of modern humans, Neanderthals and their predecessors in the Levant. The results show that anatomically modern humans (AMH) were more efficient at hunting and foraging in terms of human mobility as well as an incipient prey specialisation. In addition, different uses of the Tabun cave through time have been identified. Tabun B, initially considered as a palaeontological accumulation, was also occasionally accessed by Neanderthals in order to exploit naturally trapped ungulates, and there were sporadic and logistic occupations in Tabun D, one of the oldest Middle Palaeolithic assemblages in the area. Contrastingly, Tabun C showed a comparatively more residential use, which coincided with the new mobility capabilities of AMH. Whereas the intensity of human occupation at el‐Wad varied through time, levels G and F showed very brief occupations in comparison with levels D and E, which showed abundant evidence of human activity. Copyright © 2011 John Wiley & Sons, Ltd.     

Class,ethnicity, and voting behaviour in Australia∗

This paper assesses the importance of a range of social structural influences on Australian electoral behaviour, with specific reference to ethnicity and occupational class. The analysis is conducted on two levels. Firstly, aggregate level data is employed, using the 1976 census matched by federal electorate to the 1977 election results. Techniques from factorial ecology are used to construct conceptually unambiguous measures of constituency characteristics, and these are related to voting behaviour using multivariate techniques. Secondly, individual level survey data collected in 1979 are used to confirm the importance of the socioeconomic cleavage and urban‐rural divisions. They also indicate that ethnicity has an appreciable influence on electoral behaviour among those born in Mediterranean countries. Northern Europeans (mainly British) prove to be no different in their electoral behaviour than native‐born Australians, while the results for Eastern Europeans are inconclusive.     

An exploration of regional climate change scenarios for Scotland

Based on a high resolution regional climate model (RCM) experiment, a climate change scenario for Scotland for the end of this century is constructed with the aim of exploring the added value of utilising a regional rather than a global model (GCM) for climate change scenario construction. Spatial variations in regional seasonal average temperature and precipitation change are analysed and the local response of ‘extreme’ weather events to climate warming is assessed using daily model output. The analyses suggest that in comparison with the GCM, the RCM does not provide fundamentally different patterns of seasonal climate change and daily weather response over Scotland, although it does capture more subtle spatial variations in these changes. The RCM also simulates more realistic daily weather events than the GCM, although the relative changes in the frequencies of daily extremes are not greatly different. However, with the limited length of the single model simulation analysed here, it is not easy to establish how robust and significant are the sub‐national patterns of climate response across Scotland. To improve the quality and comprehensiveness of regional climate change scenario information, a number of research issues remain to be addressed.     

Experimental estimates of electron density variations at the reflection height of VLF signals

To study the behaviour of the electron concentration at the reflection level of very low frequency (VLF) waves, two years of phase and amplitude records of the 12.9 kHz signals emitted from Omega-Argentina (43.20°S; 294.60°E) and received at Tucumán (26.90°S; 294.70°E) have been used. The experimental results are compared with values derived from the International Reference Ionosphere model (IRI-79). The experimental data show a seasonal variation not predicted by the model. Differences are explained in terms of changes of night-time atomic oxygen concentration, which control the electron density profile at the base of the night-time D-region, not taken into account in the IRI model. Values of atomic oxygen necessary to explain VLF data are comparable with published data.     

A deconvolution technique for measuring D-region radio wave backscatter

A new deconvolution technique similar to that used by Jones and Thiele (1991) was used to determine the positions and Doppler shifts of D-region scatteres at Bribie Island (152°E, 27°S). The new technique performs analysis in the frequency domain. It is introduced and measurements of the aspect sensitivity and angular spread of D-region backscatter at 1.98 MHz are shown. These results are similar to those obtained by others.     

Population Synthesis: Comparing the Major Techniques Using a Small, Complete Population of Firms

Recently, disaggregate modeling efforts that rely on microdata have received wide attention by scholars and practitioners. Synthetic population techniques have been devised and are used as a viable alternative to the collection of microdata that normally are inaccessible because of confidentiality concerns or incomplete because of high acquisition costs. The two most widely discussed synthetic techniques are the synthetic reconstruction method (IPFSR), which makes use of iterative proportional fitting (IPF) techniques, and the combinatorial optimization (CO) method. Both methods are described in this article and then evaluated in terms of their ability to recreate a known population of firms, using limited data extracted from the parent population of the firms. Testing a synthetic population against a known population is seldom done, because obtaining an entire population usually is too difficult. The case presented here uses a small, complete population of firms for the City of Hamilton, Ontario, for the year 1990; firm attributes compiled are number of employees, 3-digit standard industrial classification, and geographic location. Results are summarized for experiments based upon various combinations of sample size and tabulation detail designed to maximize the accuracy of resulting synthetic populations while holding input data costs to a minimum. The output from both methods indicates that increases in sample size and tabulation detail result in higher quality synthetic populations, although the quality of the generated population is more sensitive to increases in tabular detail. Finally, most tests conducted with the created synthetic populations suggest that the CO method is superior to the IPFSR method.     

Climate change, uncertainty and prehistoric hunter–gatherer mobility

The onset of Little Ice Age conditions in California’s Sierra Nevada mountains resulted in increased temporal and spatial variability, and hence uncertainty regarding the distribution and production of resources targeted by its inhabitants, the Western Mono. The Mono responded with a risk-averse strategy composed of lowland winter population aggregation supported by logistical forays and seasonal residential dispersals to the high country, both ways of averaging variance in environmental productivity. These patterns were reconstructed using surface archaeology, GIS, and two straightforward spatial statistics, nearest-neighbor and variance-to-mean ratios, that combined provide a robust, objective picture of population aggregation and dispersal and the scale of these phenomena in different environments and seasons. These diverse strategies conform to expectations regarding the best ways for hunter–gatherers to cope with uncertainty, particularly in mountain environments. Despite this, the residentially mobile aspect of the pattern is rare in mountains and probably the result of historical connections between the Mono and Great Basin groups employing similar behaviors. Ultimately, this research suggests that climate change and environmental variability condition risk-averse, satisficing economic behaviors focused more on security than optimization, implying that pronounced environmental variability runs counter to economic intensification and its association with the evolution of more complex societies.     

A Gender Gap in Australia? Commonwealth Elections 1910-96

This article describes and tests a process which generates the 'pro-coalition gender gap' in electoral behaviour which has been observed in recent research. More detailed analysis, however, indicates that this gap is more apparent than real: for almost three-quarters of the electorate (those who are not members of trade unions) the electoral behaviour of men and women is virtually identical. Further, sex segregation in the workforce appears at least as much as women's participation in the workforce to underlie the 'pro-coalition' gap. These results imply that this (at least partially artifactual) gap is likely to persist into the foreseeable future.     

The Zone Definition Problem in Location-Allocation Modeling

Location-allocation modeling is a frequently used set of techniques for solving a variety of locational problems, some of which can be politically sensitive. The typical application of a location-allocation model involves locating facilities by selecting a set of sites from a larger set of candidate sites, with the selection procedure being a function of “optimality” in terms of the allocation of demand to the selected sites. In this paper we examine the sensitivity of one particular type of location-allocation model, the p-median procedure, to the definition of spatial units for which demand is measured. We show that a p-median solution is optimal only for a particular definition of spatial units and that variations in the definition of spatial units can cause large deviations in optimal facility locations. The broad implication of these findings is that the outcome of any location-allocation procedure using aggregate data should not be relied upon for planning purposes. This has important implications for a large variety of applications.     

SYSTEM IDENTIFICATION OF LANDFILL SEISMIC RESPONSE

Assessment of landfill seismic response necessitates the availability of reliable dynamic material properties. During the past decade, geophysical surveys and computational studies have been conducted to investigate the seismic response of the Operating Industries, Inc. (OII) landfill in Southern California. In this paper, a survey and summary of available research results is presented. In addition, a set of Oil input-output seismic records during six earthquakes is thoroughly analysed. Spectral analyses are conducted to shed light on the landfill dynamic response characteristics. A simple shear beam model is found to be useful in modelling the landfill resonant behaviour. System identification techniques are employed to estimate the landfill stiffness and damping properties. These properties are defined by minimising the difference between computed and recorded acceleration response spectra at the landfill top. The identified stiffness properties are found to be near the lower bound of those documented through geophysical measure-ments. Identified damping of about 5% (at resonance) is within the range of earlier investigations. Comparisons of the computed and recorded accelerations show: (I) effectiveness of a linear viscous shear beam model in simulating the landfill dynamic behaviour, for the recorded small to moderate levels of dynamic excitation (up to 0.26 g peak lateral acceleration), and (ii) potential of the employed system identification procedure for analysis of input-output seismic motions.     

ION BEAM ANALYSIS OF COPPER AND COPPER ALLOY COINS

In recent years ion beam techniques have become more and more important since in most cases the analysis of copper and copper alloy coins has to be non-destructive. It is therefore of interest to study the relative advantages of several nuclear methods for a certain type of metal. The results are presented here of a comparison between three non-destructive ion beam techniques: particle induced X-ray emission, proton activation analysis and fast neutron activation analysis.