A method to convert AVHRR Normalized Difference Vegetation Index time series to a standard viewing and illumination geometry

The bi-directional reflectance distribution function (BRDF) alters the seasonal and inter-annual variations exhibited in Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) data and this hampers the detection and, consequently, the interpretation of temporal variations in land-surface vegetation. The magnitude and sign of bi-directional effects in commonly used AVHRR data sets depend on land-surface properties, atmospheric composition and the type of atmospheric correction that is applied to the data. We develop an approach to estimate BRDF effects in AVHRR NDVI time series using the Moderate Resolution Imaging Spectrometer (MODIS) BRDF kernels and subsequently adjust NDVI time series to a standard illumination and viewing geometry. The approach is tested on NDVI time series that are simulated for representative AVHRR viewing and illumination geometry. These time series are simulated with a canopy radiative transfer model coupled to an atmospheric radiative transfer model for four different land cover types—tropical forest, boreal forest, temperate forest and grassland - and five different atmospheric conditions - turbid and clear top-of-atmosphere, turbid and clear top-of-atmosphere with a correction for ozone absorption and Rayleigh scattering applied (Pathfinder AVHRR Land data) and ground-observations (fully corrected for atmospheric effects). The simulations indicate that the timing of key phenological stages, such as start and end of growing season and time of maximum greenness, is affected by BRDF effects. Moreover, BRDF effects vary with latitude and season and increase over the time of operation of subsequent NOAA satellites because of orbital drift. Application of the MODIS kernels on simulated NVDI data results in a 50% to 85% reduction of BRDF effects. When applied to the global 18-year global Normalized Difference Vegetation Index (NDVI) Pathfinder data we find BRDF effects similar in magnitude to those in the simulations. Our analysis of the global data shows that BRDF effects are especially large in high latitudes; here we find that in at least 20% of the data BRDF errors are too large for accurate detection of seasonal and interannual variability. These large BRDF errors tend to compensate, however, when averaged over latitude.     

Prologue: Cultural Aspects of Learning Disabilities.

Discusses the concept of "learning disability," and introduces the articles in this issue of Canadian Psychologist. Topics covered include the relation between culture and learning, class associated learning abilities, learning in an alien culture (e.g., Canadian Indians), learning in an alien language (bilingualism), and learning in handicapped groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wavelength conversion from 1.3 to 1.55 mu m using split contact optical amplifiers

Wavelength conversion of data from an optical carrier at a wavelength of 1.31 mu m to an optical carrier within the 1.5- mu m telecommunications window was demonstrated using a split-contact semiconductor nonlinear Fabry-Perot optical amplifier. Conversion was achieved by modulating the amplifier gain seen by a 1.55- mu m continuous-wave signal by saturating an absorber section using a modulated 1.31- mu m signal. Data transfer was possible from 1.31 mu m up to wavelengths between 1.53 and 1.585 mu m for bit-rates of up to 400 Mb/s. The maximum output contrast ratio was 3:1 and the minimum power at 1.31 mu m required for switching was approximately 60 mu W. By optically pumping the amplifier to above the lasing threshold using the 1.31- mu m signal, conversion was obtained to a fixed multiwavelength output with a 10-dB contrast ratio.<>     

Dynamic modelling of service delivery

Planning to deliver excellent service by balancing demand and supply in the context of a set of business policies is not an easy task. How an organisation dynamically deploys its resources and people in response to external demand determines how quickly an organisation can deliver service to its customers. To model this you need to represent the flows of work through the organisation, the resources available and the relationships between intake of work, outputs, workstacks and time-to-deliver. You also need to understand how flexible the organisation is in dealing with uncertain and fluctuating intakes and the policies the organisation adopts in deploying this flexibility. We have constructed a model of the operations of a telecommunications company that incorporates all of these elements using the system dynamics approach. This paper describes how the model is constructed and gives examples of how it can be used to explain observed behaviours. It also explains how it has been used to guide decision making on resource requirements and the optimum mix between proactive and reactive approaches to service assurance.     

The PROBA/CHRIS mission: a low-cost smallsat for hyperspectral multiangle observations of the Earth surface and atmosphere

The European Space Agency's Project for On-Board Autonomy is intended to demonstrate a range of innovations in the design, construction, and operation of small satellites. It carries a number of scientific instruments, the most advanced of which is the Compact High-Resolution Imaging Spectrometer. A typical nadir image is 13 km /spl times/13 km in size and has 18 narrow spectral channels at 17-m spatial resolution. When operated at 34-m spatial resolution, the instrument can capture data in 62, almost contiguous, spectral channels. The platform is highly manoeuvrable: along-track pointing allows a given site to be imaged five times during a single overpass, while across-track pointing ensures that the revisit time for a site of interest is less than a week. This unique combination of spectral and angular sampling provides a rich source of data with which to study environmental processes in the atmosphere and at the Earth's surface.     

The ITER core imaging x-ray spectrometer: x-ray calorimeter performance

We describe the anticipated performance of an x-ray microcalorimeter instrument on ITER. As part of the core imaging x-ray spectrometer, the instrument will augment the imaging crystal spectrometers by providing a survey of the concentration of heavy ion plasma impurities in the core and possibly ion temperature values from the emission lines of different elemental ions located at various radial positions.     

Taking Care of Supply

A recurring theme for modern business is adaptability. The ability to exploit resources, skills and market position in new ways to increase returns on investment is paramount. Large companies in particular need to understand their internal and external supply chains to identify and evaluate new opportunities. BT has a history of developing and supplying all the services required by its end customers; but the world is changing rapidly, new types of player are emerging and BT now supplies its many services to many different types of customer — service providers, resellers and peers as well as end customers. There needs to be a way of understanding the implications of the different forms of customer/supplier relationship on the design and implementation of BT's systems.This paper presents a new set of patterns for businesses and their supply relationship. These patterns can be used to examine supply chains and the paper illustrates how these different supply relationships place different requirements on the operational support systems. Such patterns will be core to a flexible strategy within high performing, adaptable businesses.     

The 25 IEA energy efficiency policy recommendations to the G8 Gleneagles Plan of Action

The imperative to pursue energy efficiency improvements is clearly on the political agenda at all levels of governments. This paper explores the lessons from past attempts at galvanising international efforts to expand energy efficiency activities through the use of international-level recommendations. Drawing on these lessons, the paper outlines the IEA response to the call for policy advice on energy efficiency through the G8 Gleneagles Plan of Action. Specifically, the paper outlines a ‘necessary conditions’ framework that was used to develop a set of energy efficiency policy priorities and describes the subsequent recommendations presented to the G8 in Hokkaido–Toyako Summit in 2008. The recommendations cover 25 fields of action in seven priority areas: buildings, appliances, lighting, transport, industry, energy utilities and cross-sectoral issues. Together, the suite of recommendations sets out an ambitious road map for global energy efficiency improvement. If implemented globally without delay, they could save around 8.2 GtCO₂/yr or 96 EJ/yr by 2030. This is equivalent to roughly twice the current total EU energy-related CO₂ emissions.     

Order vs. Disorder: Cholesterol and Omega-3 Phospholipids Determine Biomembrane Organization

Lipid structural diversity strongly affects biomembrane chemico-physical and structural properties in addition to membrane-associated events. At high concentrations, cholesterol increases membrane order and rigidity, while polyunsaturated lipids are reported to increase disorder and flexibility. How these different tendencies balance in composite bilayers is still controversial. In this study, electron paramagnetic resonance spectroscopy, small angle neutron scattering, and neutron reflectivity were used to investigate the structural properties of cholesterol-containing lipid bilayers in the fluid state with increasing amounts of polyunsaturated omega-3 lipids. Either the hybrid 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine or the symmetric 1,2-docosahexaenoyl-sn-glycero-3-phosphocholine were added to the mixture of the naturally abundant 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine and cholesterol. Our results indicate that the hybrid and the symmetric omega-3 phospholipids affect the microscopic organization of lipid bilayers differently. Cholesterol does not segregate from polyunsaturated phospholipids and, through interactions with them, is able to suppress the formation of non-lamellar structures induced by the symmetric polyunsaturated lipid. However, this order/disorder balance leads to a bilayer whose structural organization cannot be ascribed to either a liquid ordered or to a canonical liquid disordered phase, in that it displays a very loose packing of the intermediate segments of lipid chains.