Investigation into clay-based consolidants for conservation of 'yellow block sandstones' in Sydney's heritage buildings

University of Technology, Sydney. Faculty of Science.Many of the 19th century heritage buildings, located in Sydney, were built from locally quarried sandstone. After more than a century of natural weathering, a number of the sandstone buildings are showing signs of deterioration. In order to ascertain the appropriate preservation techniques of such buildings, an understanding of the mechanisms of degradation of these buildings stones must first be sought before consolidation treatment is carried out. The objectives of the thesis are to first characterise the degradation processes of selected heritage yellow block sandstone, followed by the synthesis and characterisation of potential polymer-clay nanocomposites as stone consolidating systems. In order to target particular degradation problems in heritage sandstones, a thorough understanding of the degradation mechanisms of the sandstone is essential before suitable materials are synthesised to prevent or slow down further damages to the stones. The novel approach of this thesis is to use a large range of analytical techniques for the characterisation of degraded yellow block sandstone samples. The methods of preparation of a series of novel polymer-clay nanocomposite consolidating systems can then be optimised according to the characteristics of each stone, and potential consolidant systems can be identified. Although various materials have been employed as stone consolidants in the past, the proposed use of polymer-clay nanocomposites as potential stone consolidants is a novel approach. A number of analytical methods including FTIR, NMR, XPS, XRD, SEM and thermal analysis were used to characterise the sandstone and to determine the degradation mechanisms of the sandstones in Sydney's heritage buildings. The yellow block sandstones were found to be composed of sand grains (60 - 68%) bound together by a kaolin-based cementing material (16 - 25%). As the silica sand is essentially inert, the study focused on the clay component of the stone. An increase in iron concentration on the stone surface contributed to the discolouration of the stone and provided a source of Fe³⁺ for the isomorphous substitution of Al³⁺ in the octahedral sites and possible Si⁴⁺ in the tetrahedral sites of the aluminosilicate layers in the cementing clay. The substitution resulted in the brittleness of the stone, but preserved the layered structure of the clay binder and retained the overall integrity of the sandstone. A change in pore size distribution was observed on weathering of the sandstone, with an increase in population of large pores providing greater access to atmospheric pollutants, soluble salts and rainwater to the sandstone core, making the already weathered stones more vulnerable to further degradation. Based on the model of degradation, the physical properties of Sydney sandstones and the aim to produce consolidants for easy application, hydrophilic polymer-clay nanocomposite systems were prepared. Montmorillonite was used as the clay component for its similar layer structure as the kaolinite presented in the cementing materials in the yellow block sandstone samples, while poly(vinyl alcohol), poly(acrylic acid) and poly(ethylene oxide) were used as the polymer component for their hydrophilic nature. AFM and XRD analysis were used to investigate the polymer-clay interactions in these composites. While the AFM analysis reveals the topography of the synthesised polymer-clay film without melting the samples, XRD analysis indicates the degree of separation of the montmorillonite clay platelets by the polymer chains through the detection of the shift of the XRD peaks. The intercalation and partial exfoliation of montmorillonite platelets in different hydrophilic polymer matrices was observed in both the solution and melt intercalation methods. PAAMMTa samples were found to be the best intercalated/exfoliated nanocomposites in the solution intercalation method. Although better separation of clay platelets was demonstrated in the XRD results using the melt intercalation method, it would not be considered a preferred method at present time due to the impractical nature of using solid products as stone consolidants. However, further research may provide solution for the dissolution of such materials in suitable solvents without affecting its consolidating ability. The hydrophilic nanocomposite materials investigated in this project show great potential as a new class of sandstone consolidants for the binding of porous weathered sandstones in Sydney's heritage buildings

Ferromagnetic transition metal implanted ZnO: a diluted magnetic semiconductor?

Recently theoretical works predict that some semiconductors (e.g. ZnO) doped with magnetic ions are diluted magnetic semiconductors (DMS). In DMS magnetic ions substitute cation sites of the host semiconductor and are coupled by free carriers resulting in ferromagnetism. One of the main obstacles in creating DMS materials is the formation of secondary phases because of the solid-solubility limit of magnetic ions in semiconductor host. In our study transition metal ions were implanted into ZnO single crystals with the peak concentrations of 0.5-10 at.%. We established a correlation between structural and magnetic properties. By synchrotron radiation X-ray diffraction (XRD) secondary phases (Fe, Ni, Co and ferrite nanocrystals) were observed and have been identified as the source for ferromagnetism. Due to their different crystallographic orientation with respect to the host crystal these nanocrystals in some cases are very difficult to be detected by a simple Bragg-Brentano scan. This results in the pitfall of using XRD to exclude secondary phase formation in DMS materials. For comparison, the solubility of Co diluted in ZnO films ranges between 10 and 40 at.% using different growth conditions pulsed laser deposition. Such diluted, Co-doped ZnO films show paramagnetic behaviour. However, only the magnetoresistance of Co-doped ZnO films reveals possible s-d exchange interaction as compared to Co-implanted ZnO single crystals.Comment: 27 pages, 8 figure

Analytical study on holographic superconductors in external magnetic field

We investigate the holographic superconductors immersed in an external magnetic field by using the analytical approach. We obtain the spatially dependent condensate solutions in the presence of the magnetism and find analytically that the upper critical magnetic field satisfies the relation given in the Ginzburg-Landau theory. We observe analytically the reminiscent of the Meissner effect where the magnetic field expels the condensate. Extending to the D-dimensional Gauss-Bonnet AdS black holes, we examine the influence given by the Gauss-Bonnet coupling on the condensation. Different from the positive coupling, we find that the negative Gauss-Bonnet coupling enhances the condensation when the external magnetism is not strong enough.Comment: revised version, to appear in JHE

Efficacy of a Solution Composed by Verbascoside, Polyvinylpyrrolidone (PVP) and Sodium Hyaluronate in the Treatment of Chemotherapy-induced Oral Mucositis in Children With Acute Lymphoblastic Leukemia

Summary: The aim of this study was to assess the efficacy of a solution composed by verbascoside, polyvinylpyrrolidone, and sodium hyaluronate (Mucosyte) in the treatment of chemotherapy- induced oral mucositi (OM). Patients between 5 and 18 years receiving chemotherapy for acute lymphoblastic leukemia and with OM grade 1 or 2 were randomized in group A (treated with Mucosyte, 3 mouthwashes/d per 8d) and group B (treated with placebo, ie, an inert water-based solution, 3 mouthwashes/d per 8 d). The OM scoring was performed at day 1 (diagnosis of OM- T0), after 3 days of treatment (T1), and at day 8 (T2). Pain was evaluated through the visual analog scale with the same timing of OM measurement. A total of 56 patients were included (28 patients per group). Group A experienced a statistically significant decline of OM at T2 (P=0.0038); a statistically significant difference in pain reduction between 2 groups both at T1 and at T2 (P < 0.005) was observed. The use of Mucosyte mouthwashes in children with chemotherapy-induced OM may be recommended as supportive therapy

Defining the roughness sublayer and its turbulent statistics

The roughness sublayer in a turbulent openchannel flow over a very rough wall is investigated experimentally both within the canopy and above using particle image velocimetry by gaining complete optical access with new methodologies without disturbing the flow. This enabled reliable estimates of the double-averaged mean and turbulence profiles to be obtained by minimizing and quantifying the usual errors introduced by limited temporal and spatial sampling. It is shown, for example, that poor spatial sampling can lead to erroneous vertical profiles in the roughness sublayer. Then, in order to better define and determine the roughness sublayer height, a methodology based on the measured spatial dispersion is proposed which takes into account temporal sampling errors. The results reveal values well below the usual more ad hoc estimates for all statistics. Finally, the doubleaveraged mean and turbulence statistics in the roughness sublayer are discussed

Combined antitumor effects of bee venom and cisplatin on human cervical and laryngeal carcinoma cells and their drug resistant sublines

In the present study, we investigated the possible combined anticancer ability of bee venom (BV) and cisplatin towards two pairs of tumour cell lines: parental cervical carcinoma HeLa cells and their cisplatin-resistant HeLa CK subline, as well as laryngeal carcinoma HEp-2 cells and their cisplatin-resistant CK2 subline. Additionally, we identified several peptides of BV in the BV sample used in the course of the study and determined the exact concentration of MEL. BV applied alone in concentrations of 30 to 60 μg ml-1 displayed dose-dependent cytotoxicity against all cell lines tested. Cisplatin-resistant cervical carcinoma cells were more sensitive to BV than their parental cell lines (IC50 values were 52.50 μg ml-1 for HeLa vs. 47.64 μg ml-1 for HeLa CK cells), whereas opposite results were obtained for cisplatin-resistant laryngeal carcinoma cells (IC50 values were 51.98 μg ml-1 for HEp-2 vs. &gt; 60.00 μg ml-1 for CK2 cells). Treatment with BV alone induced a necrotic type of cell death, as shown by characteristic morphological features, fast staining with ethidium-bromide and a lack of cleavage of apoptotic marker poly (ADP-ribose) polymerase (PARP) on Western blot. Combined treatment of BV and cisplatin induced an additive and/or weak synergistic effect towards tested cell lines, suggesting that BV could enhance the killing effect of selected cells when combined with cisplatin. Therefore, a greater anticancer effect could be triggered if BV was used in the course of chemotherapy. Our results suggest that combined treatment with BV could be useful from the point of minimizing the cisplatin concentration during chemotherapy, consequently reducing and/or postponing the development of cisplatin resistance

Indirect Ultraviolet Detection of Biologically Relevant Organic Acids by Capillary Electrophoresis

Indirect UV detection of fourteen short-chain organic acids (e.g., oxalic acid, citric acid, malonic acid, tartaric acid, methylmalonic acid, α-ketoglutaric acid, succinic acid, ethylmalonic acid, methylsuccinic acid, glutaric acid, apidic acid, methylglutaric acid, lactic acid and pyruvic acid) by capillary electrophoresis is described. The method used phthalate as the UV-absorbing additive in carbonate buffer and the non-absorbing analytes were detected indirectly at 230 nm. The influences of buffer pH, ionic strenght, concentration of phthalate and organic modifier on indirect signal response and migration behavior of the organic acids were investigated. Comparisons of reproducibility on migration time, limit of detection and separation efficiency among three types of capillary (e.g., polyacrylamide-coated, myristyltrimethylammonium bromide-coated and uncoated capillaries) were conducted. The method developed was applied to detect succinic acid, methylmalonic acid, citric acid, glutaric acid and lactic acid in human body fluids, and preliminary results were provided

Observation of associated near-side and away-side long-range correlations in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector

Two-particle correlations in relative azimuthal angle (Δϕ) and pseudorapidity (Δη) are measured in √sNN=5.02  TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1  μb-1 of data as a function of transverse momentum (pT) and the transverse energy (ΣETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) “near-side” (Δϕ∼0) correlation that grows rapidly with increasing ΣETPb. A long-range “away-side” (Δϕ∼π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δϕ) and ΣETPb dependence. The resultant Δϕ correlation is approximately symmetric about π/2, and is consistent with a dominant cos⁡2Δϕ modulation for all ΣETPb ranges and particle pT

Travailleurs et syndicats, hier et aujourd’hui

Cet article propose de dresser un portrait de l’évolution de la classe ouvrière à Hong Kong en posant l’hypothèse de son embourgeoisement puis de sa précarisation à partir du milieu des années 1990. La croissance économique dont a bénéficié la ville dans les années 1980 et au début des années 1990 a nourri l’optimisme de ses habitants qui vivaient alors, semble-t-il, une convergence des niveaux de vie et de consommation de la classe ouvrière et de la classe moyenne par un phénomène d’embourgeoisement. Cependant, au tournant du XXIe siècle, la thèse de l’embourgeoisement est remise en question par l’avènement de la mondialisation et les vagues de récession successives qui ont affecté Hong Kong. Les cycles économiques et la globalisation ont conduit à des restructurations, des licenciements et d’autres mesures d’austérité pour économiser sur la main-d’oeuvre. De nouveaux types de contrats de travail plus flexibles, le recours à la sous-traitance, sont également venus modifier la situation de la classe ouvrière. Les mesures d’austérité ont eu pour résultat une précarisation du marché du travail et la diminution des revenus d’un nombre croissant d’ouvriers. Ce phénomène a conduit à l’émergence d’un nouveau prolétariat industriel dans un Hong Kong postindustriel. Les membres de cette classe ouvrière, très éclectique, ne travaillent pas uniquement dans les services, comme cela est traditionnellement le cas. En raison de cette diversité, les chances de voir émerger une classe ouvrière solidaire sont minces et les syndicats semblent condamnés à ne jouer qu’un rôle limité dans la protection et l’amélioration du statut de la classe ouvrière. L’impasse dans laquelle se trouvent les négociations en cours pour établir un salaire minimum et des horaires de travail réglementés avec le Gouvernement de Hong Kong illustrent bien cette faiblesse. La première partie de cet article rappelle quelques fondements théoriques concernant les composantes de la classe ouvrière. La deuxième partie tente d’éclaircir le phénomène d’embourgeoisement vécu par la classe ouvrière depuis la Deuxième Guerre mondiale. Enfin, la troisième traite de la diversification et de la paupérisation croissantes que connaît la classe ouvrière hongkongaise depuis son entrée dans l’ère postindustrielle et qui coïncide plus ou moins avec la rétrocession du territoire hongkongais à la Chine en 1997