bluuebunny/crossref_metadata_2025 huggingface dataset:
Whose Prayer?
Authors: Salkever Stephen
Published: January 2007

Most modern readers of Aristotle's Politics assume that the regime “according to prayer” ( kat'euch ê n) in Book 7 is the culmination of the work as a whole, a utopia designed to guide political reform. I say no. This polis is not an ideal to be applied to practice, but one aspiration among several to be seriously examined and consulted by political people as they deliberate about what to do in particular situations. The prayer presented in chapters 4-12 is not meant to be understood as Aristotle's own, but as coming from one imagined voice among the several presented in the Nicomachean Ethics and Politics. Would Aristotle pray for this regime? No. It is instead the prayer of a “real man” (an anêr) fully committed to political life, someone who, unlike Aristotle, can imagine nothing more beautiful than a beautiful polis. Aristotle's subtlety here has important implications for understanding the philosophy/politics relationship.
Mechatronic systems: concepts and applications
Authors: Isermann R.
Published: January 2007

The synergetic integration of mechanical processes, microelectronics and information processing opens new possibilities to the design of processes as well as for its automatic control. The solution of tasks within mechatronic systems is performed on the process side and the digital-electronic side. As the interrelations during the design play an important role, simultaneous engineering has to take place from the very beginning. Mechatronic systems are developed for mechanical elements, machines, vehicles and precision mechanic devices. The integration of mechatronic systems can be performed by the components (hardware integration) and by information processing (software integration). The information processing consists of low-level and high-level feedback control, supervision and diagnosis and general process management. Special signal processing, model-based and adaptive methods are applied. With the aid of a knowledge base and inference mechanisms, mechatronic systems with increasing intelligence will be developed. The main goals are to increase systems performance, reliability and economy, and decrease production costs.
Time-frequency analysis of biomedical signals
Authors: Bianchi Anna M. , Mainardi Luca T. , Cerutti Sergio
Published: January 2007

In the last few years interest has been dedicated on the time-frequency analysis, especially in applications to biological signal processing. In fact, analysis in the frequency domain is a well standardized tool for the quantification of many clinical and physiological phenomena. The main limitation is constituted by the required stationarity of the signal in the analysis window, while a great number of biological situations are characterized instead by a dynamical evolution. In this paper the principal methods of time-frequency analysis are briefly described: the Cohen class of distributions, the wavelet transform and the recursive autoregressive estimation. Examples of application are shown on different clinical protocols: time-variant analysis of the heart rate variability signal during drug infusion, the evaluation of the dynamical power distribution in the electroencephalogram during surgery, the single sweep analysis of evoked potentials and the analysis of the magnetic resonance imaging spectroscopic signal. Advantages and disadvantages of the methods are highlighted, in particular we want to put into evidence how the different features of the presented procedures are able to enhance different characteristics of the signals.
Fibre-optic micro-spectrometers for biomedical sensing
Authors: Walsh J. E. , Kavanagh K. Y. , Fennell S. , Murphy J. , Harmey M.
Published: January 2007

The advent of fibre-optic micro-spectrometers in the past 10 years has introduced a broad range of novel biomedical sensing applications. These instruments offer increased flexibility, particularly at the front end, while still providing data comparable with the larger laboratory-based spectrometer systems. A number of key spectrometer specifications, of particular importance when examining biomedical samples, are discussed. These specification permutations also apply to the examination and quantification of a large range of physical, chemical, environmental and medical analytes and targets. Results for different system specifications, using an Ocean Optics S1000 micro-spectrometer, are presented using redox pigments in vitro as a sample analyte. The specifications discussed include spatial resolution, sample nature and volume, spectral range and resolution, signal-to-noise ratio and acquisition speed. The results presented show that a number of specification permutations can be combined to optimize system performance for particular analytes and targets.
Neural networks and pattern recognition techniques applied to optical fibre sensors
Authors: Lyons W. B. , Lewis E.
Published: January 2007

Some of the significant recent advances in the field of artificial neural networks (ANNs) applied to optical fibre sensors are reviewed. Particular attention is given to the use of ANNs in the enhancement of the performance of existing single point sensors, two- and three-dimensional measurements and developments in multipoint sensors and sensor arrays.
Plastic optical fibre sensors and devices
Authors: Bartlett Rebecca J. , Philip-Chandy Rekha , Eldridge Piers , Merchant David F. , Morgan Roger , Scully Patricia J.
Published: January 2007

This paper considers the impact of recent developments in polymer optical fibre (POF) and its application in optical fibre sensors and optical measurement. A discussion of techniques developed for POF-based sensors and devices, and their applications includes sensors to measure flow, biofilm growth, turbidity, toxicity, humidity, rotation and fluorescence. Techniques to photoinduce refractive index changes and physical gratings into POF, and chemically to remove the cladding and taper plastic optical fibres are described, along with the use of fluorescent dye-doped plastic optical fibres (FPOF) in sensors and devices.
Adaptive estimation for fuzzy TSK model-based predictive control
Authors: Mahfouf M. , Kandiah S. , Linkens D. A.
Published: January 2007

A long-range predictive control algorithm for nonlinear processes operating over a wide range is proposed and is based on the Takagi-Sugeno-Kang (TSK) piece-wise linear fuzzy modelling approach. The performance of the fuzzy modelling approach integrated with the proposed control algorithm to form an adaptive control scheme is examined using a series of experiments on a liquid level system and on a continuous stirred tank reactor (CSTR) system.
Design of a state feedback controller to achieve minimum eigenvalue differential sensitivity
Authors: Jin H. , McLean D.
Published: January 2007

This paper introduces a new design method using eigenstructure assignment. The differential sensitivity of the eigenvalues of the system is minimized. The method involves minimizing the least-squared error between the achievable and the desired eigenspace to achieve mode decoupling. A global measure of eigenvalue sensitivity for all desired eigenvalues that make the closed-loop system insensitive to perturbations or parameter variations is included in the method. The technique requires the use of a gradient-based algorithm. The method is illustrated by an example, which is intended to show a more flexible approach to eigenstructure assignment.
Design and application of PIP controllers: robust control of the IFAC93 benchmark
Authors: Taylor C. James , Chotai Arun , Young Peter C.
Published: January 2007

Proportional-integral-plus (PIP) controllers exploit the full power of optimal state variable feedback within a nonminimum state space (NMSS) setting. They are simple to implement and provide a logical extension of conventional proportional-integral/proportional-integral-derivative (PI/PID) controllers, with additional dynamic feedback and input compensators introduced automatically when the process is of greater than first order or has appreciable pure time delays. The present paper provides a tutorial introduction to the NMSS/PIP control design methodology and associated system identification procedure. The latter is based on the utilization of the simplified refined instrumental variable (SRIV) algorithm for the estimation of transfer function models. The practical utility of these techniques is illustrated by their application to the IFAC93 benchmark system, a seventh-order stochastic simulation whose parameters vary randomly within specified ranges. This benchmark provides a good simulation example for tutorial purposes, since it requires the control engineer to work through all the usual design steps, including identification of a low-order control model, control system design, and implementation using a standard programming language, in this case ‘C’. Finally, note that the statistical estimation tools described in the paper have been assembled as a tool-box within the Matlab™ software environment.
Validating BMS sensors for chiller condition monitoring
Authors: Wang Shengwei , Wang Jinbo , Burnett John
Published: January 2007

A method based on energy balance is developed for diagnosing and validating the health states of the building management system (BMS) sensors (faults and biases) for monitoring chiller condition. A normalized energy balance residual is defined and used as the indices for fault detection. A characteristic quantity is derived for diagnosing flow meter faults without needing to know the temperature sensor biases. A robust algorithm is developed for estimating the magnitude of the flow meter biases. The sensor fault validation method, verification of the method using dynamic simulation programs and application to an existing chilling plant are presented.
Applying MLP and RBF classifiers in embedded condition monitoring and fault diagnosis systems
Authors: Li Yuhua , Pont Michael J. , Jones N. Barrie , Twiddle John A.
Published: January 2007

In this paper, results are presented from a comprehensive series of studies aimed at assessing the suitability of multilayered perceptron (MLP) and radial basis function (RBF) networks for use in embedded, microcontroller-based, condition monitoring and fault diagnosis (CMFD) applications. Our assessment criteria include the performance of each classifier on a range of CMFD-related problems, such as situations where there may be multiple faults present simultaneously, or where ‘unknown’ faults may occur. In addition, the processor and memory requirements of each classifier are compared and discussed. On the basis of the results obtained in these studies, it is argued that each form of classifier has both strengths and weaknesses, and that neither is suitable for use in all CMFD applications. The paper concludes by demonstrating that, where memory and processor limits allow, the best performance may be obtained through use of a fusion classifier containing both MLP and RBF components.
The effects of air pollution on vegetation from a geographic perspective
Authors: Chang Eunmi , Terwilliger Valery J.
Published: January 2007

Researchers in many fields seek to understand the effects of anthropogenic changes in atmospheric chemistry on vegetation distributions. Particularly important needs for information from a pragmatic perspective include (1) relationships between short-and long-term metabolic consequences of pollutant uptake to vegetation distributions, and (2) indirect influences of air pollution on plant-community dynamics. Biogeography would be the appropriate discipline to make the most powerful contributions to these needs. This does not only mean gathering research output to show a broader picture. In addition, it means introducing new approaches from various fields in order to deepen understanding of spatial phenomena in the past and present, and to better predict patterns of the future. We review developments in both reductionist and holistic research approaches that have effectively enhanced knowledge of how atmospheric emissions affect vegetation. Limitations of these approaches are also discussed. We assume that the contributions of Geographic Information Systems and remote sensing to this line of inquiry are sufficiently appreciated by the bio- and physical geography community to be de-emphasized here. Instead, other approaches better known in more specialized disciplines that are leading to powerful insights from a more restricted sector of the biogeographical community are emphasized. A synthetic core role for physical and biogeography that more fully embraces developments in related disciplines is then proposed.
Geomorphology, ecology and river channel habitat: mesoscale approaches to basin-scale challenges
Authors: Newson M. D. , Newson C. L.
Published: January 2007

The physical component of river channel (instream) habitat is of acknowledged significance, particularly in headwater streams; furthermore, physical habitats have been heavily impacted by human needs for river services: principally flood defence (channel modification) and water resources (flow regulation). Despite the control exercised on physical habitats by fluvial geomorphology (channel shape, bed material size, bedforms and bars) and flow regime (including the varying hydraulics of flow around these forms), their interaction has hitherto lacked a distinctive spatial formulation and biological validation.

This article describes the challenges faced by a need (in both theoretical and practical areas) to understand the detail of physical habitat conditions in stream channels. A number of mesoscale approaches are emerging, both from ecology and geomorphology. We outline the field validation of a ‘habitat hydraulics’ approach to the interaction between river discharge and channel form. Qualitative ‘flow types’ are shown to be representative of discrete hydraulic conditions within mesoscale units of the channel bed described as ‘physical biotopes’. The approach is compared with parallel ecological research on ‘mesohabitats’ and ‘functional habitats’. The extent, pattern and discharge-variability of physical biotopes can be surveyed in the field and used as a spatial guide to biological sampling (in this case for benthic invertebrates). Biological patterns (at the scale sampled here) appear to respond first to the river continuum concept’s longitudinal zonation of the channel, but there is a marked secondary signal in statistical analyses from the pattern of biotopes.

Given the promise of the physical biotope approach, its logical extension in predictive mode is via the hierarchical concepts shared by freshwater ecologists and geomorphologists; however, there is little agreement on scale terminology, hierarchical principles and, above all, a truly geo-morphological channel classification, based on reaches, into which mesoscale habitat typologies could be fed. Assuming a relationship between biological diversity and that of physical biotopes it should be the aim of river managers, whether intervening in the channel form or its flow regime, to optimize certain parameters of the pattern of biotopes; these parameters should be a focus for future research. Both the rapid survey and proper description of these patterns will benefit from the application of remote-sensing technology, improved instruments for microscale hydraulic studies and a GIS approach based upon the spatial principles of landscape ecology.
Tropospheric layering of ozone in regions of urbanized complex and/or coastal terrain: a review
Authors: McKendry I. G. , Lundgren J.
Published: January 2007

Exchange of pollutants between the atmospheric boundary layer and free troposphere is an important (yet often neglected) process that tends to produce distinct layers of pollution in the lower troposphere. These layers represent a potential sink for pollutants from the boundary layer, have the potential to be mixed to ground and likely influence tropospheric chemistry and the global climate system. Factors influencing the vertical distribution of ozone in the troposphere are outlined as a prelude to a more specific discussion of elevated layers and myriad meteorological processes responsible for their development. Evidence from a range of geographical settings suggests that these phenomena are ubiquitous. A rich data set from the Lower Fraser Valley, British Columbia, is used to provide an inventory of layer structures and to highlight their diverse origins and histories. Approaches used to assess the impact of down-mixing of pollutants from elevated layers on ground-level concentrations of ozone are outlined and future research priorities recommended.
Variability and change in terrestrial snow cover: data acquisition and links to the atmosphere
Authors: Derksen C. , LeDrew E.
Published: January 2007

Terrestrial snow cover is of significance to global geophysical systems because of its influence on both climatological and hydrological processes. Snow cover acts as a layer which modifies energy exchange between the surface and atmosphere, and as the frozen storage term in the water balance, affecting runoff and streamflow. This review addresses two challenges with regard to snow cover: how to monitor this variable adequately over time, and how to couple trends and variability in snow cover to atmospheric circulation. Developments in remote-sensing technology have provided a range of satellite-derived data products which complement in situ snow measurement procedures. Variability in data spatial resolution and domain, temporal repeatability, time series length and the level of snow-cover information derived (for example, snow extent vs. snow water equivalent) means that data application plays a large role in the utilization of an appropriate dataset. Given the variability in snow-cover data properties, the state of knowledge regarding interactions between snow cover and the atmosphere is similarly mixed. No standardized trends in continental or hemispheric snow cover are evident and the direction of forcing between snow cover and the atmosphere is still ambiguous. Identified associations are typically regional in extent, and statistically moderate in strength, proving cause-and-effect relationships difficult to identify. Future research needs are outlined, with an emphasis on passive-microwave imagery. These data have the necessary characteristics (quantitative estimates of snow-water equivalent, all-weather imaging) to provide the input data to the process based studies necessary to isolate linkages between snow cover and the atmosphere.
Quantifying chaos in the atmosphere
Authors: Washington Richard
Published: January 2007

The atmosphere is known to be forced by a variety of energy sources, including radiation and heat fluxes emanating from the boundary layer associated with sea-surface temperature anomalies and land-surface features. The atmosphere is also subject to internal variability which is essentially unforced and is thought to be a basic characteristic of fluids. Whereas much work has been done in quantifying the links between external forcing of the atmosphere and its long-term response as well as the influence of boundary layer forcing in determining organized, large-scale modes of planetary-scale circulation, less is known about the importance of internal variability or chaos in determining the evolution of weather and climate. General circulation models (GCMs) now provide for this possibility. Multiple evolutions of the climate system may be computed in GCM simulations. Where these simulations are identical except for the conditions by which the model is initialized, the degree of departure in the evolution of climate from one model run to the next corresponds precisely to the degree of internal variability or chaos present in the model atmosphere. A methodology for quantifying this chaotic forcing is considered and is applied to century-long integrations of the UK Meteorological Office model HADAM2A.
The species-area relationship: new challenges for an old pattern
Authors: Lomolino Mark V.
Published: January 2007

The species-area relationship (i.e., the relationship between area and the number of species found in that area) is one of longest and most frequently studied patterns in nature. Yet there remain some important and interesting questions on the nature of this relationship, its causality, quantification and application for both ecologists and conservation biologists.

Traditionally, the species-area relationship describes the very general tendency for species number to increase with island area; a relationship whose slope declines (but remains positive) as area increases. The true relationship, however, may be much more complicated than this, and may in many cases approximate a sigmoidal relationship. On small islands, species number may vary independently of island area. Species richness then increases as we consider larger islands, but the curve eventually slows and asymptotes or levels off when richness equals that of the the source or mainland pool. The relationship may also include a secondary phase of increase in richness if island area becomes large enough to allow in situ speciation.

Causal explanations for this relationship may, therefore, need to be multifactorial and include a range of processes from disturbance and stochastic variation in habitat quality on the very small islands, to ecological interactions, immigration, extinction and, finally, evolution on the larger islands.
Riparian plant invasions: hydrogeomorphological control and ecological impacts
Authors: Tickner David P. , Angold Penelope G. , Gurnell Angela M. , Mountford J. Owen
Published: January 2007

Biological invasions are a threat to ecosystems across all biogeographical realms. Riparian habitats are considered to be particularly prone to invasion by alien plant species and, because riparian vegetation plays a key role in both aquatic and terrestrial ecosystems, research in this field has increased. Most studies have focused on the biology and autecology of invasive species and biogeographical aspects of their spread. However, given that hydrogeomorphological processes greatly influence the structure of riparian plant communities, and that these communities in turn affect hydrology and fluvial geomorphology, scant attention has been paid to the interactions between invasions and these physical processes. Similarly, relatively little research has been undertaken on competitive interactions between alien and native riparian plant species. Further research in these fields is necessary at a variety of spatial and temporal scales before the dynamics of riparian invasions, and their impacts, can be properly understood.
Forest mapping and monitoring with interferometric synthetic aperture radar (InSAR)
Authors: Balzter H.
Published: January 2007

A synthetic aperture radar (SAR) is an active sensor transmitting pulses of polarized electromagnetic waves and receiving the backscattered radiation. SAR sensors at different wavelengths and with different polarimetric capabilities are being used in remote sensing of the earth. The value of an analysis of backscattered energy alone is limited due to ambiguities in the possible ecological factor configurations causing the signal. From two SAR images taken from similar viewing positions with a short time-lag, interference between the two waves can be observed. By subtracting the two phases of the signals, it is feasible to eliminate the random contribution of the scatterers to the phase. The interferometric correlation and the interferometric phase contain additional information on the three-dimensional structure of the scattering elements in the imaged area. A brief review of SAR sensors is given, followed by an outline of the physical foundations of SAR interferometry and the practical data-processing steps involved. An overview of applications of InSAR to forest mapping and monitoring is given, covering tree-bole volume and biomass, forest types and land cover, fire scars, forest thermal state and forest canopy height.
Continuity and change in environmental systems: the case of shallow lake ecosystems
Authors: Lau S. S.S. , Lane S. N.
Published: January 2007

Traditional ideas concerning environmental management tend to be based upon simple relationships between cause and effect. Such approaches make the design of environmental management strategies fairly straightforward: once the cause of a problem has been identified, it is necessary only to address the cause and/or help the system to recover through some sort of attempt at restoration. In the case of shallow lake eutrophication, research in the 1960s and 1970s identified phosphorus as the key control on the trophic state of a lake and, hence, recommended reductions in the supply of phosphorus to lakes as the necessary remedial measure. However, subsequent research has illustrated that such measures were not always successful. This article reviews the science of shallow lake eutrophication to demonstrate the role of ecosystem-specific biological and chemical interactions in conditioning the response of lakes to remedial measures and, hence, shows how new ideas of complexity help us to understand the behaviour of lake ecosystems so that we can develop alternative environmental management strategies.
A review of the use of radio-echo sounding in glaciology
Authors: Plewes Louise A. , Hubbard Bryn
Published: January 2007

Radio-echo sounding (RES), or radar, is an established geophysical technique that has been, and continues to be, applied to investigate a variety of ice-mass properties. This review presents the physical theory and principles of radio-glaciology, and describes the various types of radar equipment commonly used, including modern, ground-penetrating radar (GPR) systems. The range of glaciological applications these systems have been used to investigate is summarized, along with promising avenues of current and future research.
Geomorphic process-disturbance corridors: a variation on a principle of landscape ecology
Authors: Butler David R.
Published: January 2007

The paradigm of landscape ecology describes a landscape as a mosaic of landscape elements including the matrix, patches and corridors. Corridors are described as linear disruptions to the matrix, produced by anthropogenic actions or by streams which produce riparian corridors. Snow avalanches and debris flows are other geomorphic processes that should be considered as geomorphic process corridors rather than as disturbance patches. They possess requisite linearity, and they accomplish the five functions of a corridor: habitat, conduit, filter, source and sink. The definition of corridor in landscape ecology should be modified to embrace the concept of geomorphic process corridors.
Aspects of the genesis, geomorphology and terminology of palsas: perennial cryogenic mounds
Authors: Gurney S. D.
Published: January 2007

Palsas are true perennial permafrost mounds. It is generally accepted that there are at least three mechanisms which might contribute to the initiation of their formation, although these are not necessarily mutually exclusive. These mechanisms can be termed: the ‘snow cover’ hypothesis; the ‘vegetation succession’ hypothesis; and the ‘buoyancy’ hypothesis. Furthermore, there are at least three types of palsas recognized, although the terminology relating to these different varieties is varied and disputed. It is clear that palsas are potentially extremely useful features for monitoring permafrost growth and decay in certain areas, and that a unified understanding of their growth and decay processes would aid this.
Riparian seed banks: structure, process and implications for riparian management
Authors: Goodson J. M. , Gurnell A. M. , Angold P. G. , Morrissey I. P.
Published: January 2007

After a brief description of the evolution of seed bank research, this review highlights the importance of the seed bank in understanding the character and dynamics of river margins. Through a discussion of published research on wetlands in general, the lack of research focused on riparian systems is highlighted. This is followed by an evaluation of current knowledge concerning the nature and dynamics of riparian seed banks and the factors that control the erosion, transport and deposition of riparian seeds. The paper concludes by (i) indicating the complexity of the interactions that control the riparian seed bank and that require understanding if the consequences of alterations in river flow regime and riparian management are to be fully understood and (ii) identifying some major research gaps relating to interactions between fluvial processes and riparian seed banks.
The 1755 Lisbon earthquake
Authors: Chester David K.
Published: January 2007

Affecting an area of ca. 800 000 km2and killing up to 100 000 people, the Lisbon earthquake of 1755 is probably the greatest seismic disaster to have struck western Europe. The shock waves of the earthquake placed a temporary brake on the emerging rationalism of the European Enlightenment and attempts to explain the disaster in terms of human sinfulness coloured many contemporary accounts. Notwithstanding these difficulties, through careful archival research it has proved possible to obtain relatively value-free accounts of most aspects of the earthquake and to use these not only to model the physical characteristics of and damage caused by the earthquake, but also to consider the implications for present day hazard assessment and urban planning. This paper reviews the progress that has been made in: identifying source and faulting mechanisms; the processes involved in the generation and impact of tsunamis; damage caused to different types of building and the use being made of historical earthquakes of different sizes - of which the 1755 event is the largest - in defining future hazard scenarios for Lisbon and other areas of Iberia.
The origin of sulphates: an example of sulphur isotopic applications
Authors: Eckardt Frank
Published: January 2007

This review is concerned with the technique of stable isotope analyses (δ34S‰) as a means of studying the sulphur cycle with particular emphasis on the formation of sulphate evaporites such as gypsum (CaSO4.2H2O). Gypsum is found in all settings that promote evaporation, including hot and cold desert environments. The technique of sulphur isotopic analysis lends itself to constraining the primary sources of sulphur as well as associated pathways of sulphur dispersal, which lead to the formation of sulphate. The review features gypsum in caves, salt pans and limestone walls with sulphur sources ranging from the marine environment to bedrock.
Applications of remote sensing, GIS and GPS in glaciology: a review
Authors: Gao Jay , Liu Yansui
Published: January 2007

Remote sensing has served as an efficient method of gathering data about glaciers since its emergence. The recent advent of Geographic Information Systems (GIS) and Global Positioning Systems (GPS) has created an effective means by which the acquired data are analysed for the effective monitoring and mapping of temporal dynamics of glaciers. A large number of researchers have taken advantage of remote sensing, GIS and GPS in their studies of glaciers. These applications are comprehensively reviewed in this paper. This review shows that glacial features identifiable from aerial photographs and satellite imagery include spatial extent, transient snowline, equilibrium line elevation, accumulation and ablation zones, and differentiation of ice/snow. Digital image processing (e.g., image enhancement, spectral ratioing and automatic classification) improves the ease and accuracy of mapping these parameters. The traditional visible light/infrared remote sensing of two-dimensional glacier distribution has been extended to three-dimensional volume estimation and dynamic monitoring using radar imagery and GPS. Longitudinal variations in glacial extent have been detected from multi-temporal images in GIS. However, the detected variations have neither been explored nor modelled from environmental and topographic variables. GPS has been utilized independent of remote sensing and GIS to determine glacier ice velocity and to obtain information about glacier surfaces. Therefore, the potential afforded by the integration of nonconventional remote sensing (e.g., SAR interferometry) with GIS and GPS still remains to be realized in glaciology. The emergence of new satellite images will make remote sensing of glaciology more predictive, more global and towards longer terms.
Patterns and processes of sediment sorting in gravel-bed rivers
Authors: Powell D. Mark
Published: January 2007

Sedimentological studies of coarse-grained alluvial rivers reveal patterns of bed material sorting at a variety of spatial scales ranging from downstream fining over the length of the long profile to the vertical segregation of a coarse surface layer at the scale of individual particles. This article reviews the mechanisms that sort bed material by size during sediment entrainment, transport and deposition and discusses some of the inter-relationships that exist between patterns and processes of sediment sorting at different spatial and temporal scales. At initiation of motion, sorting can arise from the preferential entrainment of the finer fractions from the heterogeneous bed sediments. Bedload grain-size distributions are modified during transport as different size fractions are routed along different transport pathways under the influence of nonuniform bed topography and associated flow patterns, and during deposition as the variable pocket geometry of the rough bed surface and turbulence intensity of the flow control the size of the particles that deposit. The review highlights the poor understanding of the many feedback linkages that exist between patterns and processes of sediment sorting at different scales and the need for a greater awareness of the spatial and temporal bounds of these linkages.
Combined analysis of digital terrain models and remotely sensed data in landscape investigations
Authors: Florinsky Igor V.
Published: January 2007

This article presents a review of the combined analysis of digital terrain models (DTMs) and remotely sensed data in landscape investigations. The utilization of remotely sensed data with DTMs has become an important trend in geomatics in the past two decades. Models of more than ten quantitative topographic variables are employed as ancillary data in the treatment of images. The article reviews the methods for DTM derivation and the basic problems of DTM operation that are important for handling DTMs with imagery, namely: 1) the choice of a DTM network type; 2) DTM resolution; 3) DTM accuracy; and 4) the precise superimposition of DTMs and images. The processing of remotely sensed data and DTMs in combination is used in the following procedures: 1) the image correction of the topographic effect; 2) the correction of geometric image distortion; 3) image classification; 4) statistical and comparative analyses of landscape data; and 5) three-dimensional landscape modelling. These procedures are applied to solve a wide range of problems in geobotany, geochemistry, soil science, geology, glaciology and other sciences. The joint use of imagery and DTMs can increase the total amount of information extracted from both types of data. The trend has been towards the incorporation of the combined analysis of remotely sensed data and DTMs into mixed environmental models. The following potential applications of the treatment of imagery in association with DTMs are identified: 1) the prediction of the migration and accumulation zones of water, mineral and organic substances moved by gravity along the land surface and in the soil; 2) the investigation of the relationships between topographically expressed geological structures and landscape properties; 3) the improvement of geological engineering in industrial planning (e.g., the construction of nuclear power stations, oil and gas pipelines and canals); and 4) the monitoring of existing industries. Digital models of plan, profile, mean and total accumulation curvatures, and nonlocal and combined topographic attributes should be included in data processing both to solve the problems indicated and to improve the outcome of some regular tasks (for example, the prediction of soil moisture distribution and fault recognition).
Power, knowledge and political ecology in the third world: a review
Authors: Bryant Raymond L.
Published: January 2007

Political ecology examines the political dynamics surrounding material and discursive struggles over the environment in the third world. The role of unequal power relations in constituting a politicized environment is a central theme. Particular attention is given to the ways in which conflict over access to environmental resources is linked to systems of political and economic control first elaborated during the colonial era. Studies emphasize the increased marginality and vulnerability of the poor as an outcome of such conflict. The impact of perceptions and discourses on the specification of environmental problems and interventions is also explored leading on to debates about the relative merits of indigenous and western scientific knowledge. Future research needs also to address issues linked to changing air and water quality, urban processes, organizational attributes and the human body.
The hydrogeomorphological e•ects of beaver dam-building activity
Authors: Gurnell Angela M.
Published: January 2007

A characteristic of beaver ecology is their ability to build dams and, thus, to modify the landscape to increase its suitability for their occupation. This ability gives beaver great significance as a geomorphic agent. In order to review the hydrogeomorphological effects of beaver dam-building activity, this article places a context on the likely distribution and magnitude of beaver activity by considering the spatial and temporal variability of distributions of beaver and the habitat characteristics which might favour the establishment of substantial beaver populations. A description is then given of the nature and potential dimensions of instream structures built by beaver and the environmental conditions under which dam building has been observed to occur. The hydrogeomorphological impact of dam building is then appraised both locally and at the landscape scale, illustrating the very significant process modification caused by beaver. While the European beaver, Castor fiber, is the main focus of this review, it necessarily draws extensively on the much larger literature concerning the North American beaver (Castor canadensis).
The scientific issues surrounding remote detection of submerged coral ecosystems
Authors: Holden Heather , LeDrew Ellsworth
Published: January 2007

According to the 1993 colloquium on the ‘Global status of coral reefs', our understanding of the global role of coral reefs is inadequate. To increase our understanding, an accurate large-scale mapping and monitoring programme is necessary. Historically, coastal zones have been mapped using traditional surveying tools such as topographic maps, nautical charts, existing aerial photographs and direct observations. Although less expensive than digital imagery, exclusive use of these traditional tools may not be practical for monitoring large or remote coral reef ecosystems accurately. Researchers are attempting to develop an adequate coral reef mapping system based on digital remote sensing, but are impeded by issues such as effects of the intervening water column and spectral distinction of bottom types. The two variables discussed, which will contribute to our understanding of the global role of coral reefs, are: 1) remote sensing of submerged coral reefs in general; and 2) remote sensing of coral bleaching in particular. A summary of radiative transfer theory is presented and case studies of attempts at mapping remotely the geographic extent and health of submerged ecosystems, as well as a discussion of the remote estimation of water depth and quality. Problems in the translation and delivery of information to the end user are presented, and possible solutions suggested.
Palaeofluvial geomorphology in southern Africa: a review
Authors: Dollar Evan S.J.
Published: January 2007

This article presents an overview of palaeofluvial geomorphology research in southern Africa. For the purposes of this article this includes South Africa, Zimbabwe, Namibia, Lesotho, Swaziland and Botswana. Although interest in fluvial systems has a long history in southern Africa, the scientific study of rivers was initiated by the discovery of the first alluvial diamond along the banks of the Orange River in 1867. Since then, significant progress has been made in unravelling the fluvial history of southern Africa from the early Archaean Ventersdorp Contact Reef River to modern channel process studies. The development of an understanding of palaeofluvial systems has occurred along two main lines. The first was alluvial diamond exploration work undertaken by the large mining houses. The second line was of a more ‘academic’ interest and included determining the impact of superimposition, tectonics, base level and climate changes. The review suggests that southern Africa fluvial systems have shown large-scale changes in drainage pattern, discharge and sediment yield and that these can be related to a complex set of causative factors including the geological template, the Jurassic rifting of Gondwana, tectonic episodes and climate change.
Fire in the cerrado (savannas) of Brazil: an ecological review
Authors: Mistry Jayalaxshmi
Published: January 2007

Fire is a major determinant of cerrado (savanna) vegetation in Brazil, and is used as a management tool during the dry season. This has consequently induced a long history of fire studies in the region. This article reviews past and present fire ecology studies in the cerrado, and emphasizes the need for a more applied approach to future work.
Optical remote-sensing techniques for the assessment of forest inventory and biophysical parameters
Authors: Wulder Mike
Published: January 2007

Forests are the most widely distributed ecosystem on the earth, affecting the lives of most humans daily, either as an economic good or an environmental regulator. As forests are a complex and widely distributed ecosystem, remote sensing provides a valuable means of monitoring them. Remote-sensing instruments allow for the collection of digital data through a range of scales in a synoptic and timely manner. Accordingly, a variety of image-processing techniques have been developed for the estimation of forest inventory and biophysical parameters from remotely sensed images. The use of remotely sensed images allows for the mapping of large areas efficiently and in a digital manner that allows for accuracy assessment and integration with geographic information systems. This article provides a summary of the image-processing methods which may be applied to remotely sensed data for the estimation of forest structural parameters while also acknowledging the various limitations that are presented. Current advancements in remote-sensor technology are increasing the information content of remotely sensed data and resulting in a need for new analysis techniques. These advances in sensor technology are occurring concurrently with changes in forest management practices, requiring detailed measurements intended to enable ecosystem-level management in a sustainable manner.

This review of remote-sensing image analysis techniques, with reference to forest structural parameters, illustrates the dependence between spatial resolution to the level of detail of the parameters which may be extracted from remotely sensed imagery. As a result, the scope of a particular investigation will influence the type of imagery required and the limits to the detail of the parameters that may be estimated. The complexity of parameters that may be extracted can be increased through combinations of image-processing techniques. For example, multitemporal analysis of image radiance values or multispectral image classification maps may be analysed to undertake the assessment of such forest characteristics as area of forest disturbances, forest succession and development, or sustainability of forest management practices. Further, the combination of spectral and spatial information extraction techniques shows promise for increasing the accuracy of estimates of forest inventory and biophysical parameters.
Progress in the study of desertification in China
Authors: Ding Dengshan , Bao Haosheng , Ma Yongli
Published: January 2007

The study of desertification in China began in 1977 with the UN Conference on Desertification. Since then, much progress has been made. This article reviews progress over the last five years in China. A brief description of desertification research in China is given, and developments and changes in the definition of desertification described. Finally, the causes and patterns of desertification are discussed.
Domestication and the origins of agriculture: an appraisal
Authors: Mannion A. M.
Published: January 2007

The first domestications of plants and animals, which occurred between 10 K years and 5 K years BP, and which underpinned the inception of agricultural systems, represent a major turning point in cultural and environmental history. Whilst much has been written on these topics, new archaeological discoveries and the development of new methods of data collection require that these issues should be reappraised. One example of a new archaeological discovery is that of evidence for rice cultivation prior to 10 K years BP in the middle Yangtze Basin of China. This region is now considered to be the likely centre of rice domestication and, because of the discovery of settlement structures, it may have been home to China’s oldest civilization. In addition, further age determination may establish this region of China as the earliest centre of agricultural innovation, instead of southwest Asia.

New methods of age estimation, notably by radiocarbon, have necessitated a reappraisal of the origins of agriculture in Mesoamerica, whilst biomolecular techniques are contributing to the identification of the wild relatives of domesticated plants and animals. Genetic analysis has also been applied to modern human populations in order to establish the relationships between different groups and thus to attempt to determine the movement of peoples in prehistory. Such relationships in Europe have been related to the spread of agriculture from its centre of origin in southwest Asia, although this is speculative rather than conclusive. Despite these advances, however, there is still no unequivocal evidence as to why agriculture was initiated.