The timing and location of dust formation in the remnant of SN 1987A

The discovery with the {\it Herschel Space Observatory} of bright far infrared and submm emission from the ejecta of the core collapse supernova SN\,1987A has been interpreted as indicating the presence of some 0.4--0.7\,M$_\odot$ of dust. We have constructed radiative transfer models of the ejecta to fit optical to far-infrared observations from the literature at epochs between 615 days and 24 years after the explosion, to determine when and where this unexpectedly large amount of dust formed. We find that the observations by day 1153 are consistent with the presence of 3$\times$10$^{-3}$M$_\odot$ of dust. Although this is a larger amount than has previously been considered possible at this epoch, it is still very small compared to the amount present in the remnant after 24 years, and significantly higher dust masses at the earlier epochs are firmly ruled out by the observations, indicating that the majority of the dust must have formed at very late times. By 8515-9200 days after the explosion, 0.6--0.8\,M$_\odot$ of dust is present, and dust grains with radii greater than 2\,$\mu$m are required to obtain a fit to the observed SED. This suggests that the dust mass increase at late times was caused by accretion onto and coagulation of the dust grains formed at earlier epochs. These findings provide further confirmation that core collapse supernovae can create large quantities of dust, and indicate that the reason for small dust masses being estimated in many cases is that the vast majority of the dust forms long after most supernovae have been detectable at mid-infrared wavelengths.Comment: 13 pages, 16 figures. Accepted for publication in MNRA

Reliability growth during a development testing program

Binomial and trinomial mathematical models for reliability growth studies - statistical analysis of system failure

Application of vascular aquatic plants for pollution removal, energy and food production in a biological system

Vascular aquatic plants such as water hyacinths (Eichhornia crassipes) (Mart.) Solms and alligator weeds (Alternanthera philoxeroides) (Mart.) Griesb., when utilized in a controlled biological system (including a regular program of harvesting to achieve maximum growth and pollution removal efficiency), may represent a remarkably efficient and inexpensive filtration and disposal system for toxic materials and sewage released into waters near urban and industrial areas. The harvested and processed plant materials are sources of energy, fertilizer, animal feed, and human food. Such a system has industrial, municipal, and agricultural applications

Contributions to comparative neuropathology

In 1959 the author of this thesis was awarded the degree of Doctor of Veterinary Medicine and Surgery of the University of Edinburgh for a thesis entitled "Observations on Swayback Disease of Lambs in South-East Scotland". That work comprised field and laboratory studies of naturally occurring swayback with emphasis upon the neuropathology of the disease. One of the conclusions reached was that contemporary ideas on the pathogenesis of the lesions in the central nervous system of affected lambs were unlikely to be correct and a more probable alternative hypothesis was advanced.Since that time concern with the pathogenesis of swayback has been sustained, and a more general interest has been developed in comparative neuropathology as a whole, especially in diseases of the very young animal, wherein developmental processes may interact with the more familiar pathological patterns of inflammation and degeneration. Growth of these interests has been facilitated by employment since I960 in the Department of Experimental Pathology of the Moredun Research Institute. The papers incorporated in this thesis represent a substantial proportion of the author's work of the past decade.The material falls naturally into five sections:- copper deficiency and swayback in sheep; copper deficiency and swayback in goats and swine; border disease of lambs; miscellaneous neuropathological conditions and developmental considerations. A continuous but sometimes tenuous thread of concern for the interactions of disease and development runs through the published work, culminating in an attempt to relate specific examples of such interactions to general concepts of teratology. This formed the basis of a lecture to the Royal Society of Medicine, an abstract of which is included amongst the publications.This thesis embodies the published results of a decade's experience in comparative neuropathology. The approach has been predominantly morpho¬ logical, and moat of the reports concern ruminants, though a variety of species both domestic and feral are included. Some studies of normal structure and development have also been carried out mainly to illuminate the background of pathological processes.At first an attempt has been made to describe, define, and analyse a given disease in terms of pathogenesis and aetiology, proceeding thereafter to research on particular aspects of the problem. Full development of this pattern has been achieved only in a few instances, notably swayback and Border disease. In swayback a general understanding of the process has been reached, and the remaining problems appear to centre around species and tissue differences in mitochondria and the effects of copper and other substances on the enzyme systems contained therein. 'With Border disease many broad avenues of research still require to be explored before a clear picture of the conuition can be obtained.No general conclusions are applicable to the work as a whole.The diseases which have been considered appear to have a nigh degree of host specificity and it is fortunate that the natural hosts can be used for experimental work. The problems and dangers of extrapolating experimental results and hypotheses from one species to another have been amply demonstrated, in the work on copper deficiency

The extinction and dust-to-gas structure of the planetary nebula NGC 7009 observed with MUSE

The large field and wavelength range of MUSE is well suited to mapping Galactic planetary nebulae (PN). The bright PN NGC 7009 was observed with MUSE on the VLT during the Science Verification of the instrument in seeing of 0.6". Emission line maps in hydrogen Balmer and Paschen lines were formed from analysis of the MUSE cubes. The measured electron temperature and density from the MUSE cube were employed to predict the theoretical hydrogen line ratios and map the extinction distribution across the nebula. After correction for the interstellar extinction to NGC 7009, the internal dust-to-gas ratio (A_V/N_H) has been mapped for the first time in a PN. The extinction map of NGC 7009 has considerable structure, broadly corresponding to the morphological features of the nebula. A large-scale feature in the extinction map, consisting of a crest and trough, occurs at the rim of the inner shell. The nature of this feature was investigated and instrumental and physical causes considered; no convincing mechanisms were identified to produce this feature, other than mass loss variations in the earlier asymptotic giant branch phase. The dust-to-gas ratio A_V/N_H increases from 0.7 times the interstellar value to >5 times from the centre towards the periphery of the ionized nebula. The integrated A_V/N_H is about 2 times the mean ISM value. It is demonstrated that extinction mapping with MUSE provides a powerful tool for studying the distribution of PN internal dust and the dust-to-gas ratio. (Abridged.)Comment: 10 pages, 7 figures. Accepted by A&

Upper estimate of martingale dimension for self-similar fractals

We study upper estimates of the martingale dimension $d_m$ of diffusion processes associated with strong local Dirichlet forms. By applying a general strategy to self-similar Dirichlet forms on self-similar fractals, we prove that $d_m=1$ for natural diffusions on post-critically finite self-similar sets and that $d_m$ is dominated by the spectral dimension for the Brownian motion on Sierpinski carpets.Comment: 49 pages, 7 figures; minor revision with adding a referenc