Lymphocyte blast transformation responses and restriction fragment length analysis in the cheetah

An extensive genetic and physiological analysis of the cheetah by O'Brien et al. (1983; 1985; 1987) indicated that the cheetah showed monomorphism at the major histocompatability complex. This led O'Brien (1985) to propose that the cheetah suffered from an immunodeficiency and was highly susceptible to diseases. It was therefore decided to investigate cell-mediated and humoral immune responses and to apply the limited restriction fragment length analysis (using Pst 1 and Bam H1 enzymes) of the cheetah MHC I and MHC II genes. Antibody responses to antigens (feline viruses), as well as mitogen-induced lymphocyte blast transformation responses, were shown to be intact and comparable with that of the domestic cat, indicating a competent immune system in the cheetah. It was also suggested by the results that some polymorphism does exist in the MHC class II genes, but possibly not in the MHC class I genes.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.University of Pretoria.mn201

Prepyramid-to-pyramid transition of SiGe islands on Si(001)

The morphology of the first three-dimensional islands appearing during strained growth of SiGe alloys on Si(001) was investigated by scanning tunneling microscopy. High resolution images of individual islands and a statistical analysis of island shapes were used to reconstruct the evolution of the island shape as a function of size. As they grow, islands undergo a transition from completely unfacetted rough mounds (prepyramids) to partially {105} facetted islands and then they gradually evolve to {105} facetted pyramids. The results are in good agreement with the predictions of a recently proposed theoretical model

Exploring the origins of EEG motion artefacts during simultaneous fMRI acquisition: implications for motion artefact correction

Motion artefacts (MAs) are induced within EEG data collected simultaneously with fMRI when the subject’s head rotates relative to the magnetic field. The effects of these artefacts have generally been ameliorated by removing periods of data during which large artefact voltages appear in the EEG traces. However, even when combined with other standard post-processing methods, this strategy does not remove smaller MAs which can dominate the neuronal signals of interest. A number of methods are therefore being developed to characterise the MA by measuring reference signals and then using these in artefact correction. These methods generally assume that the head and EEG cap, plus any attached sensors, form a rigid body which can be characterised by a standard set of six motion parameters. Here we investigate the motion of the head/EEG cap system to provide a better understanding of MAs. We focus on the reference layer artefact subtraction (RLAS) approach, as this allows measurement of a separate reference signal for each electrode that is being used to measure brain activity. Through a series of experiments on phantoms and subjects, we find that movement of the EEG cap relative to the phantom and skin on the forehead is relatively small and that this non-rigid body movement does not appear to cause considerable discrepancy in artefacts between the scalp and reference signals. However, differences in the amplitude of these signals is observed which may be due to differences in geometry of the system from which the reference signals are measured compared with the brain signals. In addition, we find that there is non-rigid body movement of the skull and skin which produces an additional MA component for a head shake, which is not present for a head nod. This results in a large discrepancy in the amplitude and temporal profile of the MA measured on the scalp and reference layer, reducing the efficacy of MA correction based on the reference signals. Together our data suggest that the efficacy of the correction of MA using any reference-based system is likely to differ for different types of head movement with head shake being the hardest to correct. This provides new information to inform the development of hardware and post-processing methods for removing MAs from EEG data acquired simultaneously with fMRI data

Presence of antibodies to canine distemper virus, canine parvovirus and canine adenovirus type 1 in free-ranging jackals (Canis adustus and Canis mesomelas) in Zimbabwe

A survey of free-ranging jackals (Canis adustus and Canis mesomelas) in Zimbabwe was conducted to determine the prevalence of serum antibodies to canine distemper virus (CDV), canine parvovirus (CPV) and canine adenovirus type 1 (CAV-1). Sera from 16 Canis adustus and 22 Canis mesomelas were collected from 1990 to 1993 from various regions of Zimbabwe and assayed by means of immunofluorescent techniques. Seroprevalence in C. adustus and C. mesomelas respectively were 50% and 63,6% for CDV, 12,5% and 18,2% for CPV and 37,5 and 9,1 for CAV-1. These results demonstrate that jackals are infected with these viruses and may act as reservoirs of them, although their susceptibility to the viruses is not known.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat v.9 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Industry concentration and strategic trade policy in successive oligopoly

We study a policy game between exporting and importing countries in vertically linked industries. In a successive international Cournot oligopoly, we analyse incentives for using tax instruments strategically to shift rents vertically, between exporting and importing countries, and horizontally, between exporting countries. We show that the equilibrium outcome depends crucially on the relative degree of competitiveness in the upstream and downstream parts of the industry. With respect to national welfare, a more competitive upstream industry may benefit an exporting (upstream) country and harm an importing (downstream) country. On the other hand, a more competitive downstream industry may harm exporting countries.Financial support from the Norwegian Research Council, through the PETROPOL research programme, is gratefully acknowledged. The paper has been greatly improved by the suggestions of two anonymous referees. We also thank Hisashi Hokari and Frode Meland for valuable comments and suggestions

Come back Marshall, all is forgiven? : Complexity, evolution, mathematics and Marshallian exceptionalism

Marshall was the great synthesiser of neoclassical economics. Yet with his qualified assumption of self-interest, his emphasis on variation in economic evolution and his cautious attitude to the use of mathematics, Marshall differs fundamentally from other leading neoclassical contemporaries. Metaphors inspire more specific analogies and ontological assumptions, and Marshall used the guiding metaphor of Spencerian evolution. But unfortunately, the further development of a Marshallian evolutionary approach was undermined in part by theoretical problems within Spencer's theory. Yet some things can be salvaged from the Marshallian evolutionary vision. They may even be placed in a more viable Darwinian framework.Peer reviewedFinal Accepted Versio

The three-dimensional structure of Saturn's E ring

Saturn's diffuse E ring consists of many tiny (micron and sub-micron) grains of water ice distributed between the orbits of Mimas and Titan. Various gravitational and non-gravitational forces perturb these particles' orbits, causing the ring's local particle density to vary noticeably with distance from the planet, height above the ring-plane, hour angle and time. Using remote-sensing data obtained by the Cassini spacecraft in 2005 and 2006, we investigate the E-ring's three-dimensional structure during a time when the Sun illuminated the rings from the south at high elevation angles (> 15 degrees). These observations show that the ring's vertical thickness grows with distance from Enceladus' orbit and its peak brightness density shifts from south to north of Saturn's equator plane with increasing distance from the planet. These data also reveal a localized depletion in particle density near Saturn's equatorial plane around Enceladus' semi-major axis. Finally, variations are detected in the radial brightness profile and the vertical thickness of the ring as a function of longitude relative to the Sun. Possible physical mechanisms and processes that may be responsible for some of these structures include solar radiation pressure, variations in the ambient plasma, and electromagnetic perturbations associated with Saturn's shadow.Comment: 42 Pages, 13 Figures, modified to include minor proof correction

Accessing elite nurses for research: reflections on the theoretical and practical issues of telephone interviewing

Elite groups are interesting as they frequently are powerful (in terms of position, knowledge and influence) and enjoy considerable authority. It is important, therefore, to involve them in research concerned with understanding social contexts and processes. This is particularly pertinent in healthcare, where considerable strategic development and change are features of everyday practice that may be guided or perceived as being guided, by elites. This paper evolved from a study investigating the availability and role of nurses whose remit involved leading nursing research and development within acute NHS Trusts in two health regions in Southern England. The study design included telephone interviews with Directors of Nursing Services during which time the researchers engaged in a reflective analysis of their experiences of conducting research with an `elite' group. Important issues identified were the role of gatekeepers, engagement with elites and the use of the telephone interview method in this context. The paper examines these issues and makes a case for involving executive nurses in further research. The paper also offers strategies to help researchers design and implement telephone interview studies successfully to maximise access to the views and experiences of `hard to reach groups', such as elites, while minimising the associated disruption

Erosion-flooding interaction on a UK barrier

This paper presents a multi-temporal (centennial, decadal, event-based) analysis of Blakeney Spit, a mixed sand-gravel barrier located on the UK’s east coast. Since 2006, Blakeney Spit has experienced a less interventionist management approach that contrasts with the earlier regime of periodically bulldozing parts of the barrier to maintain a steeper cross-shore profile. Given recent endorsements of coastal management schemes that work with, rather than against, nature this case study provides a valuable opportunity to quantify the impact of management regime change on shoreline erosion rates, overwash processes and associated flood hazard

Flooding-erosion interactions: implications for coastal risk management

As routinely experienced coastal hazards, flooding and erosion are key considerations within coastal management plans and policy. Flooding and erosion hazards are often analysed separately, without due attention to their interaction. Low lying barrier islands exemplify coastal environments particularly affected by erosion-flooding interactions. Such environments often support substantial human populations, critical infrastructure, and diverse ecosystems. This study undertakes a high resolution, multidecadal shoreline change analysis at Blakeney Point, a mixed sand-gravel spit on the UK’s North Norfolk coast. The analysis spans two distinct management regimes: the ‘first era’ (1992-2005) where the eastern section of the barrier was periodically artificially reprofiled into a steep-sided trapezoid with a narrow crest; and the ‘second era’ (2006-2016) of no active intervention along the entire barrier. We find that over the past 130 years, Blakeney Point has retreated landward at a mean rate of 0.60 m a-1. Along the eastern section of Blakeney Point, we observe an increase in shoreline retreat rate between the two eras of 3 to 30 times depending on the choice of shoreline proxy (High Water Line, ridge line, or vegetation line). The lower shoreline retreat rates during the first era suggest that reprofiling fixed the shoreline position of the eastern barrier. Termination of the reprofiling regime, in combination with storm surge events in 2007 and 2013, resulted in accelerated retreat along the eastern section towards a more landward position. This has had implications for the western section of the spit which appears to have benefited from alongshore westward transport of sediment during the noninterventionist era, resulting in slowed landward retreat rates during this period. The importance of storm surge events should not be understated. During 2013-2014, overwashing along the eastern section of the barrier resulted in vegetation line retreat of up to 127 m. This retreat behaviour was not matched at lower elevations on the subaerial beach, suggesting lateral spreading of the barrier, a behaviour which has been shown elsewhere to involve increased landward retreat and barrier disintegration. Our findings suggest a change in the morphological character of the barrier under the non-interventionist management regime, with clear implications for erosion, flooding and their interactio