A comparative political economy of regional migration and labour mobility in West and Southern Africa

Based on a collaboration with the late Lionel Cliffe, this article suggests agendas and methods for analysing regional patterns of migration and labour mobility in Southern and West Africa. It locates local communities in regional patterns and global processes using two key organising concepts: first, the regionalisation of Africa, as outlined in Samir Amin's work. We consider continuities and discontinuities with the paradigms of ‘Africa of the labour reserves’ and ‘Africa of the colonial trade economy’ to understand contemporary realities. Second, this article explores the mechanisms and characteristics of cheap labour on different scales of analysis. This includes a discussion of the theories that explored the relations of reproduction of labour, and the reproduction of the labour system as a whole. In doing so, it rethinks the modes of production discourse to highlight the continuing importance of situations where capitalism exists alongside non-capitalist relations of production and reproduction

Civil Procedure by Contract: A Convoluted Confluence of Private Contract and Public Procedure in Need of Congressional Control

There is great appeal to the notion that parties to a contract may provide in their agreement for how certain aspects of any dispute that may subsequently arise will be resolved. The appeal is so great, in fact, that both parties and courts have embraced the use and enforcement of pre-litigation agreements ( PLAs ). These agreements take a variety of forms. Parties may agree to the forum in which their dispute will be resolved. They may designate the law that will be applied to the resolution of the dispute. Parties may designate what evidence may or may not be presented as proof of their respective positions and what burden of proof should govern the weighing of the evidence presented. Parties may designate who will resolve their dispute, in terms of judge or jury. And they even may designate that the dispute will not be heard by a judicial tribunal at all, but rather will be re- solved outside the courts by means of some form of alternative dispute resolution ( ADR )

Radiotherapy response evaluation using FDG PET-CT - established and emerging applications.

Radiation therapy is a common component of curative cancer treatment. However, there is a significant incidence of treatment failure. In these cases salvage surgical options are sometimes appropriate. Accurate assessment of response and early recognition of treatment success or failure is therefore critical to guide treatment decisions and impacts on survival and the morbidity of treatment. Traditionally, treatment response has depended upon anatomical measurement of disease. However, this may not correlate well with the presence of disease, especially after radiotherapy. Combined positron emission tomography and computed tomography (PET-CT) imaging employs radioactive tracers to identify molecular characteristics of tissue. PET imaging exploits the fact that malignancies have characteristic molecular profiles which differ compared to surrounding tissues. The complementary anatomical and functional information facilitates accurate non-invasive assessment of surrogate biomarkers of disease activity. This article reviews the rationale for PET-CT response assessment in radiation oncology, describing current uses of 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG) PET-CT in treatment response following radiotherapy in head and neck, oesophageal, rectal and brain tumours. Emerging applications of FDG PET-CT in cervical and lung carcinomas and hepato-pancreatico-biliary (HPB) tumours particularly pancreatic carcinoma and liver metastases (post selective internal radiotherapy treatment (SIRT)) are reviewed. Finally, the limitations of FDG PET-CT are considered, highlighting areas for future development

Equilibrium states and chaos in an oscillating double-well potential

We investigate numerically parametrically driven coupled nonlinear Schrödinger equations modeling the dynamics of coupled wave fields in a periodically oscillating double-well potential. The equations describe, among other things, two coupled periodically curved optical waveguides with Kerr nonlinearity or Bose-Einstein condensates in a double-well potential that is shaken horizontally and periodically in time. In particular, we study the persistence of equilibrium states of the undriven system due to the presence of the parametric drive. Using numerical continuations of periodic orbits and calculating the corresponding Floquet multipliers, we find that the drive can (de)stabilize a continuation of an equilibrium state indicated by the change in the (in)stability of the orbit, showing that parametric drives can provide a powerful control to nonlinear (optical- or matter-wave-) field tunneling. We also discuss the appearance of chaotic regions reported in previous studies that is due to destabilization of a periodic orbit. Analytical approximations based on an averaging method are presented. Using perturbation theory, the influence of the drive on the symmetry-breaking bifurcation point is analyzed. © 2014 American Physical Society

Numerical and Experimental Investigation of Circulation in Short Cylinders

In preparation for an experimental study of magnetorotational instability (MRI) in liquid metal, we explore Couette flows having height comparable to the gap between cylinders, centrifugally stable rotation, and high Reynolds number. Experiments in water are compared with numerical simulations. Simulations show that endcaps corotating with the outer cylinder drive a strong poloidal circulation that redistributes angular momentum. Predicted azimuthal flow profiles agree well with experimental measurements. Spin-down times scale with Reynolds number as expected for laminar Ekman circulation; extrapolation from two-dimensional simulations at $Re\le 3200$ agrees remarkably well with experiment at $Re\sim 10^6$. This suggests that turbulence does not dominate the effective viscosity. Further detailed numerical studies reveal a strong radially inward flow near both endcaps. After turning vertically along the inner cylinder, these flows converge at the midplane and depart the boundary in a radial jet. To minimize this circulation in the MRI experiment, endcaps consisting of multiple, differentially rotating rings are proposed. Simulations predict that an adequate approximation to the ideal Couette profile can be obtained with a few rings

Virtual discussions to support climate risk decision making on farms

Climate variability represents a significant risk to farming enterprises. Effective extension of climate information may improve climate risk decision making and adaptive management responses to climate variability on farms. This paper briefly reviews current agricultural extension approaches and reports stakeholder responses to new web-based virtual world ‘discussion-support’ tools developed for the Australian sugar cane farming industry. These tools incorporate current climate science and sugar industry better management practices, while leveraging the social-learning aspects of farming, to provide a stimulus for discussion and climate risk decision making. Responses suggest that such virtual world tools may provide effective support for climate risk decision making on Australian sugar cane farms. Increasing capacity to deliver such tools online also suggests potential to engage large numbers of farmers globally

Mass Transfer by Stellar Wind

I review the process of mass transfer in a binary system through a stellar wind, with an emphasis on systems containing a red giant. I show how wind accretion in a binary system is different from the usually assumed Bondi-Hoyle approximation, first as far as the flow's structure is concerned, but most importantly, also for the mass accretion and specific angular momentum loss. This has important implications on the evolution of the orbital parameters. I also discuss the impact of wind accretion, on the chemical pollution and change in spin of the accreting star. The last section deals with observations and covers systems that most likely went through wind mass transfer: barium and related stars, symbiotic stars and central stars of planetary nebulae (CSPN). The most recent observations of cool CSPN progenitors of barium stars, as well as of carbon-rich post-common envelope systems, are providing unique constraints on the mass transfer processes.Comment: Chapter 7, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G. Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe

Outflows from the high-mass protostars NGC 7538 IRS1/2 observed with bispectrum speckle interferometry -- Signatures of flow precession

NGC 7538 IRS1 is a high-mass (approx. 30 M_sun) protostar with a CO outflow, an associated UCHII region, and a linear methanol maser structure, which might trace a Keplerian-rotating circumstellar disk. The directions of the various associated axes are misaligned with each other. We investigate the near-infrared morphology of the source to clarify the relations among the various axes. K'-band bispectrum speckle interferometry was performed at two 6-meter-class telescopes -- the BTA 6m telescope and the 6.5m MMT. Complementary IRAC images from the Spitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales. High-dynamic range images show fan-shaped outflow structure in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the context of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is approx. 280 years and its half-opening angle is 40 degrees. A possible triggering mechanism is non-coplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar NGC 7538 IRS2 as a close binary with separation of 195 mas. We find indications for shock interaction between the outflow activities in IRS1 and IRS2. Indications of outflow precession have been discovered to date in a number of massive protostars, all with large precession angles 20--45 degrees. This might explain the difference between the outflow widths in low- and high-mass stars and add support to a common collimation mechanism.Comment: 20 pages; 8 figures; Accepted by A&A on April 10, 2006; Image quality reduced due to astro-ph file size limitations; Please download a version with high-quality images from http://www.mpifr-bonn.mpg.de/staff/tpreibis/ngc7538.pd

Gaussian Process Modelling for Uncertainty Quantification in Convectively-Enhanced Dissolution Processes in Porous Media

Numerical groundwater flow and dissolution models of physico-chemical processes in deep aquifers are usually subject to uncertainty in one or more of the model input parameters. This uncertainty is propagated through the equations and needs to be quantified and characterised in order to rely on the model outputs. In this paper we present a Gaussian process emulation method as a tool for performing uncertainty quantification in mathematical models for convection and dissolution processes in porous media. One of the advantages of this method is its ability to significantly reduce the computational cost of an uncertainty analysis, while yielding accurate results, compared to classical Monte Carlo methods. We apply the methodology to a model of convectively-enhanced dissolution processes occurring during carbon capture and storage. In this model, the Gaussian process methodology fails due to the presence of multiple branches of solutions emanating from a bifurcation point, i.e., two equilibrium states exist rather than one. To overcome this issue we use a classifier as a precursor to the Gaussian process emulation, after which we are able to successfully perform a full uncertainty analysis in the vicinity of the bifurcation point

ODRL Policy Modelling and Compliance Checking

This paper addresses the problem of constructing a policy pipeline that enables compliance checking of business processes against regulatory obligations. Towards this end, we propose an Open Digital Rights Language (ODRL) profile that can be used to capture the semantics of both business policies in the form of sets of required permissions and regulatory requirements in the form of deontic concepts, and present their translation into Answer Set Programming (via the Institutional Action Language (InstAL)) for compliance checking purposes. The result of the compliance checking is either a positive compliance result or an explanation pertaining to the aspects of the policy that are causing the noncompliance. The pipeline is illustrated using two (key) fragments of the General Data Protect Regulation, namely Articles 6 (Lawfulness of processing) and Articles 46 (Transfers subject to appropriate safeguards) and industrially-relevant use cases that involve the specification of sets of permissions that are needed to execute business processes. The core contributions of this paper are the ODRL profile, which is capable of modelling regulatory obligations and business policies, the exercise of modelling elements of GDPR in this semantic formalism, and the operationalisation of the model to demonstrate its capability to support personal data processing compliance checking, and a basis for explaining why the request is deemed compliant or not