Medical Support to Demining in Sudan

With an area of more than one million square miles (2,589,988 square kilometers), Sudan is the largest country on the African continent and has been at the center of decades of conflict since it gained its independence in 1959. The Comprehensive Peace Agreement signed in January 2005 brought to end a vicious civil war and marked the beginning of an era of relative peace. This article outlines the health challenges involved in mine action in Sudan and highlights the actions taken by the United Nations Mine Action Office in Sudan to address issues of medical support to humanitarian-demining operations in a particularly difficult environment

An evaluation of small-area statistical methods for detecting excess risk: with applications in breast and colon cancer mortality in Scotland 1986-1995

The need to report data at small-area level is constantly increasingly. In a society which is both health-conscious and environmentally aware, statistics at small-area level have a high degree of political significance. This type of data is required to plan and implement regional policies and apportion health care in accordance to the differing needs of the population. Recent advances in computer power has brought many advances to this area of study. For all the advances in technology and methodology, the problem of small numbers consistently appears. Is there an excess risk or is it down to chance? This is a question which is paramount in small-area statistics and will be addressed in this thesis. An overview of the thesis is provided below: Chapter 1 introduces the concept of small-area statistics and some of the social and political issues connected with this topic. There is a discussion of the analysis of small-area health data and the principal ideas that need to be considered in a statistical, political and social sense in this area of work. The aims of ISD Scotland are introduced and how they can be linked to this field of study. Chapter 2 describes an overview of the methods used in small-area statistics. The chapter begins by firstly considering the Standardised Incidence Ratio (SIR) which is the technique mainly used in the basic analysis done by ISD Scotland. Other techniques are then considered, however not all of these techniques are directly comparable to each other. The strengths and weaknesses of these techniques in previous research are discussed to give an idea of how the techniques perform in different scenarios. Chapter 3 is a simulation study of three of the techniques discussed in Chapter 2, these being the SIR, Circular Spatial Scan and Flexibly-Shaped Spatial Scan. The reason for this simulation study is to evaluate these techniques on simulated data arising from real scenarios. The strengths and weaknesses of these techniques are then highlighted which will prove helpful when analysing the data in Chapter 4. Chapter 4 provides an analysis of the mortality of breast and colon cancer in Scotland in the ten-year time period from 1986 to 1995. Using data provided by ISD Scotland, the analysis is carried out to identity any potential mortality clusters in both diseases. Chapter 5 provides a conclusion to this research by providing a summary of findings of the thesis and gives recommendations based upon these findings. A discussion is also given for potential further study in this field that could provide some value to ISD Scotland as they look to other ways of analysing their small-area data

Kelvin-Helmholtz instability in a current-vortex sheet at a 3D magnetic null

We report here, for the first time, an observed instability of a Kelvin-Helmholtz nature occurring in a fully three-dimensional (3D) current-vortex sheet at the fan plane of a 3D magnetic null point. The current-vortex layer forms self-consistently in response to foot point driving around the spine lines of the null. The layer first becomes unstable at an intermediate distance from the null point, with the instability being characterized by a rippling of the fan surface and a filamentation of the current density and vorticity in the shear layer. Owing to the 3D geometry of the shear layer, a branching of the current filaments and vortices is observed. The instability results in a mixing of plasma between the two topologically distinct regions of magnetic flux on either side of the fan separatrix surface, as flux is reconnected across this surface. We make a preliminary investigation of the scaling of the system with the dissipation parameters. Our results indicate that the fan plane separatrix surface is an ideal candidate for the formation of current-vortex sheets in complex magnetic fields and, therefore, the enhanced heating and connectivity change associated with the instabilities of such layers

Quantifying three dimensional reconnection in fragmented current layers

There is growing evidence that when magnetic reconnection occurs in high Lundquist number plasmas such as in the Solar Corona or the Earth's Magnetosphere it does so within a fragmented, rather than a smooth current layer. Within the extent of these fragmented current regions, the associated magnetic flux transfer and energy release occur simultaneously in many different places. This investigation focusses on how best to quantify the rate at which reconnection occurs in such layers. An analytical theory is developed which describes the manner in which new connections form within fragmented current layers in the absence of magnetic nulls. It is shown that the collective rate at which new connections form can be characterized by two measures; a total rate which measures the true rate at which new connections are formed and a net rate which measures the net change of connection associated with the largest value of the integral of E || E|| through all of the non-ideal regions. Two simple analytical models are presented which demonstrate how each should be applied and what they quantify

A spatial covariance (123)I-5IA-85380 SPECT study of α4β2 nicotinic receptors in Alzheimer's disease

Alzheimer's disease (AD) is characterized by widespread degeneration of cholinergic neurons, particularly in the basal forebrain. However, the pattern of these deficits and relationship with known brain networks is unknown. In this study, we sought to clarify this and used 123I-5-iodo-3-[2(S)-2-azetidinylmethoxy] pyridine (1235IA-85380) single photon emission computed tomography to investigate spatial covariance of α4β2 nicotinic acetylcholine receptors in AD and healthy controls. Thirteen AD and 16 controls underwent 1235IA-85380 and regional cerebral blood flow (99mTc-exametazime) single photon emission computed tomography scanning. We applied voxel principal component (PC) analysis, generating series of principal component images representing common intercorrelated voxels across subjects. Linear regression generated specific α4β2 and regional cerebral blood flow covariance patterns that differentiated AD from controls. The α4β2 pattern showed relative decreased uptake in numerous brain regions implicating several networks including default mode, salience, and Papez hubs. Thus, as well as basal forebrain and brainstem cholinergic system dysfunction, cholinergic deficits mediated through nicotinic acetylcholine receptors could be evident within key networks in AD. These findings may be important for the pathophysiology of AD and its associated cognitive and behavioral phenotypes

Comparison of magnetic energy and helicity in coronal jet simulations

Context. While non-potential (free) magnetic energy is a necessary element of any active phenomenon in the solar corona, its role as a marker of the trigger of the eruptive process remains elusive. Meanwhile, recent analyses of numerical simulations of solar active events have shown that quantities based on relative magnetic helicity could highlight the eruptive nature of solar magnetic systems. Aims. Based on the unique decomposition of the magnetic field into potential and non-potential components, magnetic energy and helicity can also both be uniquely decomposed into two quantities. Using two 3D magnetohydrodynamics parametric simulations of a configuration that can produce coronal jets, we compare the dynamics of the magnetic energies and of the relative magnetic helicities. Methods. Both simulations share the same initial setup and line-tied bottom-boundary driving profile. However, they differ by the duration of the forcing. In one simulation, the system is driven sufficiently so that a point of no return is passed and the system induces the generation of a helical jet. The generation of the jet is, however, markedly delayed after the end of the driving phase; a relatively long phase of lower-intensity reconnection takes place before the jet is eventually induced. In the other reference simulation, the system is driven during a shorter time, and no jet is produced. Results. As expected, we observe that the jet-producing simulation contains a higher value of non-potential energy and non-potential helicity compared to the non-eruptive system. Focussing on the phase between the end of the driving-phase and the jet generation, we note that magnetic energies remain relatively constant, while magnetic helicities have a noticeable evolution. During this post-driving phase, the ratio of the non-potential to total magnetic energy very slightly decreases while the helicity eruptivity index, which is the ratio of the non-potential helicity to the total relative magnetic helicity, significantly increases. The jet is generated when the system is at the highest value of this helicity eruptivity index. This proxy critically decreases during the jet-generation phase. The free energy also decreases but does not present any peak when the jet is being generated. Conclusions. Our study further strengthens the importance of helicities, and in particular of the helicity eruptivity index, to understand the trigger mechanism of solar eruptive events