610 research outputs found
Recommended from our members
From Supply Chains to Total Product Systems
The evolution of supply chain management and practice has had an integral and expanding role in contemporary global economic and socio-political change over the past 25 years or so. Thi srole is moving closer to centre stage with the emergence of business models equating to 'total product systems'. The impacts of advanced supply chain practice include driving fundamental changes in approach to product design, the concept of 'product', production methods, distribution, marketing, aftermarket support and end-of-life (EOL) reprocessing. Viewed in their full context, methods in supply chain management (SCM) have major influences on societal functioning and on economic development at global, national and local levels. Even the supply chains for simple products can involve several different industries and link many companies, large and small. Those for complex products may span several technological domains and economic sectors, linking hundreds or sometimes thousands of companies
Transport in heterogeneous porous media
We present a new algorithm for modelling single phase transport of a tracer in porous
media which demonstrates that structure on all scales affects macroscopic transport behaviour.
We marry the robustness of the continuous time random walk (CTRW) framework
with the simplicity of a Monte Carlo approach to reservoir simulation. We simulate
transport as a series of particles transitioning between nodes with probability (t).dt that
a particle will first arrive at a nearest neighbor in a time t to t + dt. To this end we first
determine the mixing rules and transition probability ADE(t) for transport governed by
the advection-dispersion equation (ADE) (Rhodes and Blunt, 2006).
We validate our algorithm by simulating advective transport in bond percolation
clusters at the critical point. We compute the histogram of flow speeds using the velocities
from the bonds on the backbone and find the multifractal spectrum for two-dimensional
lattices with linear dimension L _ 2000 and in three dimensions for L _ 250. We
demonstrate that in the limit of large systems all the negative moments of the velocity
distribution become ill-defined. However, to model transport, the velocity histogram
should be weighted by the flux to obtain a well-defined mean travel time. Finally, we use
CTRWtheory to demonstrate that anomalous transport is observed whose characteristics
can be related to the multifractal properties of the system.
We next demonstrate a pore-to-reservoir simulation methodology which is consistent
across all scales of interest. At the micron scale, we fit a truncated power law (t) for
the distribution of particle transition times from pore to pore simulations. To do this
we use our transport algorithm on a geologically representative network model of Berea
sandstone and compare the results to the explicit modelling of advection and molecular
diffusion by Bijeljic and Blunt (2006). We find that the results are similar. We then
demonstrate the effect of increasing pore scale heterogeneity on the power law exponent
(_) by stretching the distribution of throat radii in our network model. We show that by
increasing the spread of velocities within the network we decrease _ making the transport
more anomalous - in keeping with the consensus currently in the literature. This (t) is
then used to calculate transport on the mm to cm scale.
We can then move up to the metre/grid block scale by using the transit time distribution
from the mm-cm simulation to model transport in an explicit, geologically
representative model of heterogeneity found within a grid block of the reservoir. From
these numerical experiments we determine the (t) appropriate for transport on grid
block scale systems characterized by Peclet (Pe) number and the type of heterogeneity
within the system. This allows us to account for small scale uncertainty by interpreting
(t) probabilistically and running simulations for different possible realizations of the
reservoir heterogeneity.
At the field scale, we represent the reservoir as an unstructured network of nodes
connected by links. For each node-to-node transition, we use our upscaled (t) from a
simulation of transport at the smaller scale. We account for small-scale uncertainty by
parameterising (t) in terms of sub-scale heterogeneity and Peclet number.
We demonstrate the methodology by finding a (t) for each scale of interest taking
into consideration the relevant physics at that scale and using the appropriate function
in a million-cell reservoir model. We show that the macroscopic behaviour can be very
different from that predicted by assuming that the ADE operates at the small scale.
Small-scale structure dramatically retards the advance of the plume with the particles
becoming trapped in the slow moving pores/regions increasing breakthrough times by an
order of magnitude compared to those predicted by the ADE
Ethics and International Relations, 2nd ed.
In today’s world, citizens, statesmen, and men and women in uniform are faced almost daily with real questions about terrorism, torture, humanitarian intervention, and foreign assistance. They must return again and again to the problem of determining when the use of military force might be an appro- priate response to the horrors of the day. For these individuals Gordon Gra- ham’s Ethics and International Relations is an invaluable work. It is stimulating, challenging, insightful, and, perhaps most unusually, helpful. Not by any stretch of the imagination is this a “how-to” book, with explicit guidance or facile answers. Rather, it represents an understanding of the contending logics that lead to competing conclu- sions about right or wrong action, or nonaction, on the global stage
Rebuilding after emergency: Revamping agricultural research in Sierra Leone after civil war
"The civil war in Sierra Leone, caused by a mix of political, social, and economic factors, had a huge impact on the overall economy in general and on the performance of the agricultural sector in particular. The agricultural research system of Sierra Leone was severely affected by the civil war. Research infrastructure was destroyed, laboratories were damaged and abandoned, and well-trained researchers and scientists fled from the country. With the cessation of hostilities in 2002, the government of Sierra Leone concentrated its efforts on the resettlement of displaced persons and on social and economic reconstruction. The efforts of the government include the rehabilitation and reorganization of the former National Agricultural Research Coordinating Council (NARCC), which was coordinating agricultural research in Sierra Leone. The Sierra Leone Agricultural Research Institute (SLARI) Act was passed by the parliament of Sierra Leone in 2007 to replace NARCC. As a new organization, SLARI needed to make strategic decisions to guide its operations in order to make it effective in responding to the demands of stakeholders within the food and agriculture system. To provide a focus for SLARI and link its agenda to national development priorities, a strategic plan and operational plan were developed. The methodology used to design the SLARI strategic plan applied an organizational innovation model through which the plan was nested within the strategic plan of the Forum for Agricultural Research in Africa (FARA) and Conseil Ouest et Center Africain pour la Recherche et le Développement Agricoles (CORAF) / West and Central African Council for Agricultural Research and Development (WECARD), and the operational plan was hinged on Comprehensive African Agricultural Development Program (CAADP) and Framework for African Agricultural Productivity (FAAP) principles. This would ensure synergy with regional and subregional strategies. The strategic plan would promote increased coordination, interaction, interlinkages, partnerships, and networks among the various agents associated with agricultural research for development systems in Sierra Leone. It would also help achieve SLARI's vision of increasing food security and wealth among Sierra Leone's rural population. For SLARI to make a meaningful contribution to agricultural development in Sierra Leone, the operational plan must be implemented in such a way that the results envisaged in the strategic plan can be achieved. This requires funds and commitment from all stakeholders, especially the government of Sierra Leone." from authors' abstractwar, Agriculture, Development, Research, Strategic plan, Operational plan, Science and technology, Agricultural research,
Tamm-Horsfall glycoprotein binds IgG with high affinity
Tamm-Horsfall glycoprotein binds IgG with high affinity. Tamm-Horsfall protein (THP), a monomelic glycoprotein (Mr 80 to 100 kDa), is produced by the mammalian kidney's thick ascending limb of Henle cells and excreted into the urine. The function of THP is uncertain. Here we report that a high molecular weight contaminant in sheep THP (sTHP) preparations was identified as sheep IgG by its positive reaction with donkey anti-sheep IgG antibody and with protein G. To answer the question of whether sTHP and sheep IgG co-purified because of a physical interaction between the two proteins, an enzyme-linked immunosorbent assay (ELISA) using immobilized sTHP and soluble sheep IgG was performed. Analysis of the ELISA data identified the presence of two sets of binding sites: a high affinity site (Kd 10-12 to 10-13 M) and a lower affinity site (Kd 10-10 to 10-11 M). The ELISA detected a similar high affinity interaction between human THP (hTHP) and human IgG. The binding of sheep IgG to immobilized sTHP was inhibited by soluble sTHP. These observations suggest an additional factor to be considered in studies addressing THP's potential immuno-regulatory function
Biophysical and Economic Factors of Climate Change Impact Chain in the Agriculture Sector of ECOWAS
The chapter assesses key biophysical and economic factors of climate change impact chain in the agriculture sector of the Economic Community of West African States (ECOWAS), mainly within the decade following the launching of the Comprehensive Africa Agricultural Development Programme (CAADP) and Maputo Accord. This is done through a review of literature and analysis of data mainly from international databases. We find that land resources for agricultural production are substantial, but land degradation and land productivity are serious problems, particularly in the context of climate change. Although the region has experienced unprecedented growth, financing agricultural development is still an issue. Developing quality infrastructure and stimulating agricultural trade may provide a win-win strategy to build resilience to climate change and strengthen economic development. The economics of adaptation to climate change in the agricultural sector of ECOWAS has mainly focused on the magnitude of costs and returns on country-wide and technology-specific measures. There is a need, however, to integrate biophysical and economic factors of climate change impact chain in sound analytical frameworks to provide “multi-metric” considerations of non-monetary and nonmarket measures, risks, inequities, and behavioral biases in addressing climate change
Neuronal Network Oscillations in the Control of Human Movement
The overarching aim of this thesis was to use neuroimaging and neuromodulation techniques to further understand the relationship between cortical oscillatory activity and the control of human movement. Modulations in motor cortical beta and alpha
activity have been consistently implicated in the preparation, execution, and termination of movement. Here, I describe the outcome of four studies designed to further elucidate these motor-related changes in oscillatory activity.
In Chapter 3, I report the findings of a study that used an established behavioural paradigm to vary the degree of uncertainty during the preparation of movement. I demonstrate that preparatory alpha and beta desynchronisation reflect a process of
disengagement from the existing network to enable the creation of functional assemblies required for movement. Importantly, I also demonstrate a novel neural signature of transient alpha synchrony, that occurs after preparatory desynchronisation, that
underlies the recruitment of functional assemblies required for directional control.
The study described in Chapter 4 was designed to further investigate the functional role of preparatory alpha and beta desynchronisation by entraining oscillatory activity in the primary motor cortex (M1) using frequency-specific transcranial alternating current stimulation. No significant effects of stimulation were found on participant response times. However, no clear conclusion could be drawn due to limitations of the stimulation parameters that were used.
In Chapter 5, I explored the inverse relationship between M1 beta power and cortical excitability using single-pulse transcranial magnetic stimulation to elicit motor-evoked potentials (MEPs). The amplitude of MEPs collected during a period of beta
desynchronisation was significantly greater than during a resting baseline. Conversely, the amplitude of MEPs collected during the post-movement beta rebound that follows the termination of a movement was significantly reduced compared to baseline. This
finding confirms the inverse relationship between M1 beta power and cortical excitability.
The study in Chapter 6 explored the effect of experimental context on M1 beta power. When the participant was cued to expect an upcoming motor task, resting beta power was significantly increased, then when the likelihood of an upcoming motor requirement
decreased, there was a significant concurrent decrease in resting beta power. This reflects increased coherence and functional connectivity within M1 and other motor areas, to ‘recalibrate’ the motor system in preparation for a synchronous input signal to
more readily recruit the required functional assembly
Holographic enhanced remote sensing system
The Holographic Enhanced Remote Sensing System (HERSS) consists of three primary subsystems: (1) an Image Acquisition System (IAS); (2) a Digital Image Processing System (DIPS); and (3) a Holographic Generation System (HGS) which multiply exposes a thermoplastic recording medium with sequential 2-D depth slices that are displayed on a Spatial Light Modulator (SLM). Full-parallax holograms were successfully generated by superimposing SLM images onto the thermoplastic and photopolymer. An improved HGS configuration utilizes the phase conjugate recording configuration, the 3-SLM-stacking technique, and the photopolymer. The holographic volume size is currently limited to the physical size of the SLM. A larger-format SLM is necessary to meet the desired 6 inch holographic volume. A photopolymer with an increased photospeed is required to ultimately meet a display update rate of less than 30 seconds. It is projected that the latter two technology developments will occur in the near future. While the IAS and DIPS subsystems were unable to meet NASA goals, an alternative technology is now available to perform the IAS/DIPS functions. Specifically, a laser range scanner can be utilized to build the HGS numerical database of the objects at the remote work site
- …