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

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

Hong kong working class and union organization: A historical glimpse

This paper attempts to sketch a longitudinal profile on the evolution of a working class in Hong Kong context in light of the thesis of embourgeoisement. The increasing economic affluence in the 1980s and early 1990s appeared to have bred an optimism in society that the members of the working class were converging in life-style and consumption behaviour with the middle class in a process of embourgeoisement. However, the thesis of embourgeoisement comes under question again around the turn of the millennium in the advent of globalisation and the successive waves of recession that afflict Hong Kong. The vicissitudes of capitalistic competition, leading to business restructuring, corporate down-sizing and other austerity prescriptions of labour cost-saving, popularise the practices of flexi-hiring, atypical employment, outsourcing, labour shedding and retrenchment. The upshot of these austerity exercises has been the re-casualisation of the labour market and the emasculation of the employment and income security of a growing fringe of peripheral workers vulnerable to industrial deprivation and exploitation. As a consequence we now see a new industrial proletariat or urban sub-class emerging in post-industrial Hong Kong. Its “embrace” as a hybrid working class transcends a spectrum of blue-collar and service occupations. Because of the diversity in its composition, the prospects for a solidaristic working class to emerge are again remote. And the role of the trade unions in providing an effective leverage for uplifting and protecting their position is limited, as illustrated by the “impasse” now still looming over the proposed enactments to prescribe a minimum wage level and standard work hours

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

Mediating effect of pubertal stages on the family environment and neurodevelopment: An open-data replication and multiverse analysis of an ABCD Study®

Contains fulltext : 285495.pdf (Publisher’s version ) (Open Access)Increasing evidence demonstrates that environmental factors meaningfully impact the development of the brain (Hyde et al., 2020; McEwen and Akil, 2020). Recent work from the Adolescent Brain Cognitive Development (ABCD) Study® suggests that puberty may indirectly account for some association between the family environment and brain structure and function (Thijssen et al., 2020). However, a limited number of large studies have evaluated what, how, and why environmental factors impact neurodevelopment. When these topics are investigated, there is typically inconsistent operationalization of variables between studies which may be measuring different aspects of the environment and thus different associations in the analytic models. Multiverse analyses (Steegen et al., 2016) are an efficacious technique for investigating the effect of different operationalizations of the same construct on underlying interpretations. While one of the assets of Thijssen et al. (2020) was its large sample from the ABCD data, the authors used an early release that contained 38% of the full ABCD sample. Then, the analyses used several 'researcher degrees of freedom' (Gelman and Loken, 2014) to operationalize key independent, mediating and dependent variables, including but not limited to, the use of a latent factor of preadolescents' environment comprised of different subfactors, such as parental monitoring and child-reported family conflict. While latent factors can improve reliability of constructs, the nuances of each subfactor and measure that comprise the environment may be lost, making the latent factors difficult to interpret in the context of individual differences. This study extends the work of Thijssen et al. (2020) by evaluating the extent to which the analytic choices in their study affected their conclusions. In Aim 1, using the same variables and models, we replicate findings from the original study using the full sample in Release 3.0. Then, in Aim 2, using a multiverse analysis we extend findings by considering nine alternative operationalizations of family environment, three of puberty, and five of brain measures (total of 135 models) to evaluate the impact on conclusions from Aim 1. In these results, 90% of the directions of effects and 60% of the p-values (e.g. p > .05 and p < .05) across effects were comparable between the two studies. However, raters agreed that only 60% of the effects had replicated. Across the multiverse analyses, there was a degree of variability in beta estimates across the environmental variables, and lack of consensus between parent reported and child reported pubertal development for the indirect effects. This study demonstrates the challenge in defining which effects replicate, the nuance across environmental variables in the ABCD data, and the lack of consensus across parent and child reported puberty scales in youth.16 p

Hepatocyte growth factor enhances proteolysis and invasiveness of human nasopharyngeal cancer cells through activation of PI3K and JNK

AbstractThe hepatocyte growth factor (HGF) receptor, Met, is frequently overexpressed in nasopharyngeal cancer (NPC). Here, we showed for the first time that human NPC cells with high Met expression were more sensitive to the cell motility and invasion effect of HGF. The downregulation of Met by small interfering RNA decreased tumor cell invasion/migration. HGF significantly increased matrix metalloproteinase-9 production. This was inhibited by blocking phosphatidylinositide 3-kinase (PI3K) and c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase signaling pathways. We also demonstrated that PI3K induced activation of JNK, with Akt as a potential point of this cross-talk. These results provide new insights into the molecular mechanism responsible for NPC progression and metastasis

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

Comparison of Newtonian and Non-newtonian Fluid Models in Blood Flow Simulation in Patients With Intracranial Arterial Stenosis

BACKGROUND: Newtonian fluid model has been commonly applied in simulating cerebral blood flow in intracranial atherosclerotic stenosis (ICAS) cases using computational fluid dynamics (CFD) modeling, while blood is a shear-thinning non-Newtonian fluid. We aimed to investigate the differences of cerebral hemodynamic metrics quantified in CFD models built with Newtonian and non-Newtonian fluid assumptions, in patients with ICAS. METHODS: We built a virtual artery model with an eccentric 75% stenosis and performed static CFD simulation. We also constructed CFD models in three patients with ICAS of different severities in the luminal stenosis. We performed static simulations on these models with Newtonian and two non-Newtonian (Casson and Carreau-Yasuda) fluid models. We also performed transient simulations on another patient-specific model. We measured translesional pressure ratio (PR) and wall shear stress (WSS) values in all CFD models, to reflect the changes in pressure and WSS across a stenotic lesion. In all the simulations, we compared the PR and WSS values in CFD models derived with Newtonian, Casson, and Carreau-Yasuda fluid assumptions. RESULTS: In all the static and transient simulations, the Newtonian/non-Newtonian difference on PR value was negligible. As to WSS, in static models (virtual and patient-specific), the rheological difference was not obvious in areas with high WSS, but observable in low WSS areas. In the transient model, the rheological difference of WSS areas with low WSS was enhanced, especially during diastolic period. CONCLUSION: Newtonian fluid model could be applicable for PR calculation, but caution needs to be taken when using the Newtonian assumption in simulating WSS especially in severe ICAS cases

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

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