Conservation of 19th and early 20th century oil paintings : studies of pigment discolouration by scanning electron microscopy

University of Technology, Sydney. Faculty of Science.The discolouration of artistic oil paintings due to pigment interaction has been a concern for artists and painting conservators since the early 1800s. Since then there has been considerable speculation on the origin and mode of this discolouration. This project sought to determine what discolouring interactions between pigments exist in historic oil paintings and to understand the mechanisms involved. The discolouring pigment system was studied using x-ray diffraction, thermal analysis, x-ray microanalysis techniques and hydration experiments using an Environmental Scanning Electron Microscope. A discolouring chemical interaction between cadmium yellow (a cadmium sulfide pigment) and malachite (basic copper carbonate) was identified. The darkening reaction between copper containing pigments and the range of cadmium sulfide pigments was established to be the only discolouring that occurs between artistic pigments investigated in this work. This interaction occurs due to copper ions being mobile in the drying oils used for oil painting. The copper ions are taken up by the oil medium and transported throughout the oil layer to adjoining paint layers. Any cadmium sulfide present in the oil painting will undergo ion exchange at its surface with the copper ions in the medium to produce copper sulfide. The copper-cadmium ion exchange was found to continue until the cadmium sulfide is completely converted to copper sulfide. For the combination of cadmium yellow and malachite it was established that the discolouring copper sulfide was covellite, CuS

Seismic wavelet estimation: A frequency domain solution to a geophysical noisy input-output problem

Published versio

Oesophageal cancer: an overview of a deadly disease

Oesophageal cancer (OC) is one of the deadliest cancers in the world. Although it affects many people throughout East Africa, relatively little work has been done to fully understand this disease. This review addresses recent changes in the understanding of OC from a global perspective, with special attention given to OC in Kenya

Tension Empyema Thoracis

Tension empyema is a rare and life threatening complication of pleural space infection requiring emergent drainage to restore cardio-respiratory function. The authors report a case of a 27-yearold male patient with pulmonary tuberculosis, who presented with severe dyspnea, right sided chest pain, and persistent cough. He subsequently developed cardiovascular collapse requiring an emergent right chest tube which drained over 2 liters of pus under pressure. The cardiovascular system stabilized and he subsequently underwent decortication for trapped lung and had an uneventful postoperative stay. Tension empyema should be considered as a differential in young patients without a history of trauma, thoraco-abdominal procedures or thoracic surgery, who present with cough, fever and chest pain, with clinical findings of cardiovascular collapse.Keywords: Tension Empyema, Tuberculosis, Cardiac Arrest, Thoracostomy

Transverse frames for Petrov type I spacetimes: a general algebraic procedure

We develop an algebraic procedure to rotate a general Newman-Penrose tetrad in a Petrov type I spacetime into a frame with Weyl scalars $\Psi_{1}$ and $\Psi_{3}$ equal to zero, assuming that initially all the Weyl scalars are non vanishing. The new frame highlights the physical properties of the spacetime. In particular, in a Petrov Type I spacetime, setting $\Psi_{1}$ and $\Psi_{3}$ to zero makes apparent the superposition of a Coulomb-type effect $\Psi_{2}$ with transverse degrees of freedom $\Psi_{0}$ and $\Psi_{4}$.Comment: 10 pages, submitted to Classical Quantum Gravit

Inhibition of large conductance calcium-dependent potassium channel by Rho-kinase contributes to agonist-induced vasoconstriction

We tested the hypothesis that Rho-kinase inhibits the large-conductance, calcium and voltage dependent potassium (BKCa) channels thereby promoting vasoconstriction. Our results show that the Rho-kinase inhibitor, Y-27632, induced concentration-dependent relaxation in rat mesenteric artery. The selective BKCa channel inhibitors, iberiotoxin (0.1 mM) and tetraethylammonium (10 mM) increased the EC50 of Y-27632 more than 2-fold and decreased Y-27632-induced maximum relaxation (P<0.05). In the inside-out patch clamp configuration, constitutively active Rho-kinase (1mg/ml) attenuated BKCa channel activity induced by protein kinase G (PKG) (P<0.05). Y-27632 (10 mM) reversed the inhibitory effect of active Rhokinase (P<0.01). Furthermore, in the presence of Y-27632, addition of active Rho-kinase had no effect on PKG-stimulated BKCa channel activity. Taken together, our data suggest that Rho-kinase negatively regulates BKCa channels, thus providing a novel mechanism though which Rho-kinase increases smooth muscle contraction.Keywords: Rho, smooth muscle, hyperpolarization, vascular reactivity, mesenteric artery, patch clam

Distribution and Content of Dust in Overlapping Galaxy Systems

Partially overlapping galaxies are used to directly determine the effective absorption in spiral galaxy disks. The non-overlapping parts of the galaxies and symmetry considerations are used to reconstruct, via differential photometry, how much background galaxy light is lost in passing through the foreground disks.Comment: 4 PostScript pages; to appear in proceedings of "Dust-Morphology" Conference, Johannesburg, South Africa, 22-26 January 1996, ed. D. Block (Dordrecht: Kluwer); also available with 3 PostScript figures at http://www.astr.ua.edu/preprints/white

Do Epstein-Barr virus mutations and natural genome sequence variations contribute to disease?

Most of the world’s population is infected by the Epstein–Barr virus (EBV), but the incidence of the diseases associated with EBV infection differs greatly in different parts of the world. Many factors may determine those differences, but variation in the virus genome is likely to be a contributing factor for some of the diseases. Here, we describe the main forms of EBV genome sequence variation, and the mechanisms by which variations in the virus genome are likely to contribute to disease. EBV genome deletions or polymorphisms can also provide useful markers for monitoring disease. If some EBV strains prove to be more pathogenic than others, this suggests the possible value of immunising people against infection by those pathogenic strain

Role of Rigid Endoscopic Detorsion in the Management of Sigmoid Volvulus

Introduction: Sigmoid Volvulus (SV) is a common cause of bowel obstruction in Africa, affecting a relatively young and healthy population. There has been little research regarding the use of endoscopic detorsion in the management of SV from East Africa. The aim of this study was to determine the outcome of patients with SV managed by endoscopic detorsion at a single institution over a 9 year period.Methods: A retrospective review of all patients admitted with SV at Tenwek Hospital in Bomet, Kenya from January 2006 to October 2014 was done. Data were collected on demographics, clinical presentation, operative findings, management, and outcome.Results: There were 159 cases with a mean age of 41.1 years (range 15-87). Rigid endoscopic detorsion was attempted in 125 (79%) patients. The success, early recurrence, and mortality rate for rigid endoscopic detorsion was 79%, 6%, and 0% respectively. Eleven (13%, n=99) patients declined surgery after successful endoscopic detorsion, while 87 patients had semi-elective surgery, an average of 3.5 days post detorsion. Sixty patients had emergency surgery, with gangrenous bowel noted in 43 (72%) cases. Patients undergoing emergency surgery had a higher morbidity rate (27% vs. 5%, p=0.0002), and a higher mortality rate (12% vs. 0, p=0.002) compared to those having semi-elective surgery due to the presence of gangrenous bowel.Conclusion: Rigid endoscopic detorsion is appropriate in the initial management of any stable patient with clinical and radiological features suggestive of sigmoid volvulus without features of peritonitis.Keywords: Sigmoid Volvulus, Endoscopic Detorsion, Rigid Sigmoidoscopy, Outcomes

Confirmatory factor analysis of the Test of Performance Strategies (TOPS) among adolescent athletes

The aim of the present study was to examine the factorial validity of the Test of Performance Strategies (TOPS; Thomas et al., 1999) among adolescent athletes using confirmatory factor analysis. The TOPS was designed to assess eight psychological strategies used in competition (i.e. activation, automaticity, emotional control, goal-setting, imagery, negative thinking, relaxation and self-talk,) and eight used in practice (the same strategies except negative thinking is replaced by attentional control). National-level athletes (n = 584) completed the 64-item TOPS during training camps. Fit indices provided partial support for the overall measurement model for the competition items (robust comparative fit index = 0.92, Tucker-Lewis index = 0.88, root mean square error of approximation = 0.05) but minimal support for the training items (robust comparative fit index = 0.86, Tucker-Lewis index = 0.81, root mean square error of approximation = 0.06). For the competition items, the automaticity, goal-setting, relaxation and self-talk scales showed good fit, whereas the activation, emotional control, imagery and negative thinking scales did not. For the practice items, the attentional control, emotional control, goal-setting, imagery and self-talk scales showed good fit, whereas the activation, automaticity and relaxation scales did not. Overall, it appears that the factorial validity of the TOPS for use with adolescents is questionable at present and further development is required