Mass-loading of bow shock pulsar wind nebulae

We investigate the dynamics of bow shock nebulae created by pulsars moving supersonically through a partially ionized interstellar medium. A fraction of interstellar neutral hydrogen atoms penetrating into the tail region of a pulsar wind will undergo photo-ionization due to the UV light emitted by the nebula, with the resulting mass loading dramatically changing the flow dynamics of the light leptonic pulsar wind. Using a quasi 1-D hydrodynamic model of relativistic flow we find that if a relatively small density of neutral hydrogen, as low as $10^{-4}$ cm$^{-3}$, penetrate inside the pulsar wind, this is sufficient to strongly affect the tail flow. Mass loading leads to the fast expansion of the pulsar wind tail, making the tail flow intrinsically non-stationary. The shapes predicted for the bow shock nebulae compare well with observations, both in H$\alpha$ and X-rays.Comment: 7 pages, 2 figures. Proceeding to the conference "High Energy Phenomena in Relativistic Outflow V", La Plata 2015, AAA Workshop Series 8, 201

The Effect of Diffusion on the Particle Spectra in Pulsar Wind Nebulae

A possible way to calculate particle spectra as a function of position in pulsar wind nebulae is to solve a Fokker-Planck transport equation. This paper presents numerical solutions to the transport equation with the processes of convection, diffusion, adiabatic losses, and synchrotron radiation included. In the first part of the paper the steady-state version of the transport equation is solved as a function of position and energy. This is done to distinguish the various effects of the aforementioned processes on the solutions to the transport equation. The second part of the paper deals with a time-dependent solution to the transport equation, specifically taking into account the effect of a moving outer boundary. The paper highlights the fact that diffusion can play a significant role in reducing the amount of synchrotron losses, leading to a modification in the expected particle spectra. These modified spectra can explain the change in the photon index of the synchrotron emission as a function of position. The solutions presented in this paper are not limited to pulsar wind nebulae, but can be applied to any similar central source system, e.g. globular clusters

Short Report: One-on-one consultation on protocol development and statistics analysis in health sciences postgraduate students

No Abstrac

Rekeningkunde vir die omgewing1

One of the main purposes of financial reporting is to provide a mechanism hy which management can report matters concerning custodianship of resources entrusted to them hy the stakeholders. One of these categories of stakeholders is the general public, which currently requires more information about the way the entity has discharged itself of its responsibility towards the ecology. However, the traditional financial accounting model is unable to account fo r ecologial assets and ecological capital. Several rather pragmatic suggestions have been made by researchers as to how to account fo r these aspects. One of these suggestions is quoted in this article, followed by a possible alternative by which ecological assets and ecological capital are introduced into the primary financial statements

Factors that Contributed to the Growth of the Kenya Assemblies of God Church: An Analysis of Multi-paradigms

Many churches in Africa lack recorded history for various reasons, such as scarcity of funds and/or scholars in the field of church history (cf. Kalu, 1993:166ff). This situation is more prevalent among the Pentecostal movements which, initially and for genuine reasons, were anti-intellectualist and emphasized ministry alone (Clark & Lederle et al, 1983:41; McNamee, 1974:27; and Hollenweger). Another possible explanation results from the fact that these churches are relatively young compared to their counterpart mainline churches. This lack of recorded history poses a hindrance to any efforts in evaluating the growth of such churches. There is an immediate need to understand the complex nature of the Pentecostal churches and how growth is motivated within their congregations. This is only possible if history is documented. Marwick (1989: 14) states that as memory is to the individual, so history is to the community or society. To fully appreciate history, it is necessary to have it recorded, not just for the present but also for future generations. A church may not be able to adequately evaluate its growth or understand itself without recorded history. This fact applies also to Assemblies of God Church (hereafter KAG) as one of the major Pentecostal movements in Kenya and other parts of the world (Anderson, 1992 & 1993; and Saayman, 1993). Recorded history is a treasure to any people, society or organisation (Brumback, 1977:iii). If history is not recorded within the life-span of pioneer members, it is likely that when the pioneers have departed, important information that makes the history complete, may die with them. The KAG church has over three decades worth of history and obviously, most of the pioneer members (both missionaries and nationals) are either gone or leaving the stage, one way or the other. As such, a reflection on its history is timely for the purpose of . evaluating both its growth and significance (cf. McIntire, 1984:40)

Kung’s Theory of Paradigm Shifts in Church History: An Evaluation

The theory of paradigms is a broad subject that has been discussed extensively from various perspectives including science, religion and history. Its strengths and weaknesses have been aptly considered. This research article seeks to investigate the extent of the theory\u27s applicability to church history. The question that we wish to address is: To what extent, is this theory of paradigms applicable in explaining the changes that have taken place through the history of Christianity

Workload of a South African University-based Health Research Ethics Committee in 2003 and 2007

Objective. To compare workloads of a university-based health research ethics committee (medical) for 2003 and 2007. Methods. Minutes and database records of all applications processed by the committee in 2003 and 2007 were examined. Results. General research applications increased from 439 to 553 in 2007 while clinical trial proposals declined from 102 to 86. Some 60 - 70% of applications required revision; 77 - 81% of general research applications and 86 - 97% of clinical trials were eventually approved. Conclusion. The workload puts an increasingly heavy burden on committee members and support staff. South African Journal of Bioethics & Law Vol. 1 (2) 2008: pp. 38-4