A review of low-cost scanners†

Abstract

This paper summarizes the characteristics of 19 scanners costing less than Dfl20000 (US$10000). It also describes the completeness of scanning performed by three of these low-cost scanners (from Agfa, Cannon and Houston Instruments) and the accuracy of one (SCAN-CAD of Houston Instruments). It was found that complete scanning occurs with resolutions of half the minimum map line width and that maximum errors of 0-5 mm were achieved.     

Young Workers in a Deindustrialising Economy: The Case of Christchurch, 1976–1996

Understanding the specificity of local labour markets is a more productive way of identifying employment dynamics in an era of de industrialisation than attending to universalist rhetorics on ‘the knowledge economy’. This article explores the employment destinations of young adults in the Christchurch labour market from the 1970s to recent times with a view to identifying how labour market opportunities facing them have changed, not only through the growth of part‐time work but also through the changing nature of access to full‐time work as sheltered ports of entry are replaced by requirements for tertiary education and training.     

Sedimentary environments associated with Glacial Lake Trimingham, Norfolk, UK

The site of Trimingham is situated where the Cromer Ridge, the largest topographic feature of northeast Norfolk, transects the coastline, providing an opportunity to study the ridge's internal structure and stratigraphy. It can be demonstrated that there were two glacial advances at this site, with an intervening phase of proglacial lake sedimentation that lasted for approximately 2000 years (Glacial Lake Trimingham). A detailed investigation of the sedimentology of the lake sediments enabled a facies reconstruction showing spatial and temporal changes within this lake. Ice-sheet retreat is indicated by an upward change from proximal to distal varve sequences, and a general shallowing of the lake followed by the deposition of marl-rich sediments and then aeolian and/or beach sands. A subsequent readvance of the ice-sheet is marked by further deposition of varved sediments and then by till deposition. This site provides an opportunity to study enviromental change over a known time period within the Anglian glaciation. It is suggested that this lake formed as the result of two ice-sheets coalescing and may be associated with the diachronously formed North Sea lake(s).     

Facies effects on the behaviour of Nd and Sr isotope systems in turbidite mudrocks during diagenesis

A detailed Sm/Nd, epsilon Nd and Rb/Sr profile through a 30-cm thick section of Silurian (Llandovery) interbedded turbiditic and hemipelagic mudrocks from the central Wales Basin shows well-marked chemical and isotopic trends. The variations reflect an interplay of depositional mode and diagenetic fractionation. Sm and Nd values are substantially higher and Sm/Nd ratios tend to be lower in the organic-rich hemipelagite layers due to diagenetic concentration in the hemipelagites. There is a corresponding depletion in the turbidite mudstones. Epsilon Nd values range from −0·8 to −7·1 and this is attributed to diagenetic modification of Sm/Nd ratios causing scatter in back-calculated epsilon values. Rubidium–strontium ratios in this succession fall within a narrow range, due to homogenization during diagenesis. By contrast, data from a hemipelagite-dominated (condensed) succession near the northern margin of the Welsh Basin show a lower range of epsilon Nd values and a higher scatter of Rb/Sr values, consistent with less fluid throughput during burial compaction and hence less diagenetic redistribution in these rocks. These patterns demonstrate the sensitivity of mudrock trace element and isotope compositions to both small-scale sedimentary structure and large-scale basin architecture.     

OVERCOMING THE APARTHEID LEGACY IN CAPE TOWN SCHOOLS*

ABSTRACT. Restructuring apartheid geographies of racial stratification and spatial segregation poses formidable challenges, not least in education. Increasing intraracial inequality also underscores the importance of widening access and opportunity. Although South African education is not constrained by the highly localized control found in the United States and the United Kingdom, school allocation policies and parental choices create geographies that intersect with those of race and residence. Spatial variations critically influence both the impacts of postapartheid policies and the patterns of school desegregation. In this article we explore the spatial impact of inequality, desegregation, and state policies in relation to fourteen secondary schools in Cape Town, distinguishing outcomes that reflect inherited inequalities and current policies from outcomes that reflect individual school strategies. Capital funding is insufficient to change inherited inequalities, and differential fees and fund‐raising capacities perpetuate inequalities in operational resources. Sharing resources, taxing fee income, and a measure of provincial control over feeder areas could reduce inequalities.     

A little goes a long way: discovery of a new mid-Holocene tephra in Sweden

This pilper reports the presence of a volcanic ash layer in western Sweden which is geochemically identiticd as the Kebister tephra. This tephrdpresenceof (dated c . 3600 ¹⁴C BP) was discovered at Kebister, Shetland and thc rcsults presented here indicate that the deposit may have a greater geographical distribution than previously thought. The geochemistry of the volcanic glass was analysed by using discrete grain electron probe microanalysis (EPMA). Thc SiO₂ content of the glass ranges from 66.19 to 71.96%, FeO content 2.73 to 6.07% and MgO content 0.15 to 0.57%_˜ The tephra can he distinguished from the more widespread Hekla 4 tephra ( c . 3800 ¹⁴C BP) on the basis of calcium and magnesium contents.