The thesis is to fabricate Al/APC-2 hybrid nanocomposite laminates and investigate their mechanical properties at elevated temperature. The prepregs of Carbon /PEEK were stacked into cross-ply [0/90]s and quasi-isotropic [0/45/90/-45] laminates spread uniformly with nanoparticles SiO2. The sheet surface was treated by chromic acid anodic method to achieve perfectly bonding with matrix PEEK. The prepregs were sandwiched with the Al alloy sheets. The modified diaphragm curing process was adopted to produce Al/APC-2 hybrid nanocomposite laminates. The hybrid nanocomposite laminates were a five-layer composite with two 0.55 mm thick Carbon/PEEK layers sandwiched by three 0.5 mm thick 2024-T3 Aluminum alloy sheets. The MTS 810 material testing machine was used to conduct the tension and fatigue tests. In addition, the MTS 651 environmental chamber was installed to control and keep the specific testing temperature, which was room temperature, 75¢XC, 100¢XC, 125¢XC and 150¢XC. The mechanical proper¬ties, such as ultimate tensile strength and longitudinal stiffness of hybrid cross-ply and quasi-isotropic nanocomposite laminates, were obtained from the static tensile test, and the stress-strain diagrams were plotted in the corresponding temperature. The constant stress amplitude tension-tension cyclic tests were carried out by using load-control mode at a sinusoidal loading with frequency of 5Hz and stress ratio R=0.1. The received fatigue data were plotted in normalized S-N curves at variously elevated temperature. In order to observe the failure mechanism of samples, the scanning electron microscope was used. From the summarized results, some conclusions were made. First, the slope changed at strain=0.1% in the stress-strain diagram, and led to a noticeable error between the experimental data and ones calculated according to Rule of Mixtures. Second, the Al/APC-2 cross-ply nanocomposite laminates were less resistant to fatigue than quasi-isotropic. Third, the ultimate tensile strength of both hybrid composite laminates was the lowest at 150¢XC. Fourth, the Al/APC-2 quasi-isotropic nanocomposite laminates were more resistant to the temperature effect. Finally, The mechanical proper¬ties were better for the surface treated by chromic acid anodic method than chemical etching.

Several research groups have applied elevated hydrostatic pressure to ONH astrocytes cultured on a rigid substrate as an in vitro model for glaucoma. These studies have shown significant biological effects and this hydrostatic pressure model is now becoming generally accepted in the ophthalmic community. However, since the applied pressures were modest the finding of significant biological effects due to pressure alone is surprising. We hypothesized that the application of hydrostatic pressure as described in these studies also altered gas tensions in the culture media. Our goal was to design equipment and carry out experiments to separate the biologic effects of pressure from those of hypoxia on cultured astrocytes. We designed equipment and carried out experiments to subject cultures of DITNC1 astrocytes to the four combinations of two levels of each parameter. We explored the morphology and migration rates of astrocytes, but observed no significant change in any of these properties.

Unbonded post-tensioned concrete slabs have been widely used in Canada and the United States since the 1960s, as they allow increased span-to-depth ratios and excellent control of deflections compared to non-prestressed reinforced concrete flexural members. The satisfactory fire performance of unbonded post-tensioned concrete slabs in North America was established by a series of standard fire tests performed in the United States during the 1960s. However, there is a paucity of data on the effect of elevated temperatures on cold-drawn prestressing steel, both in terms of post-fire residual mechanical properties and high-temperature stress relaxation, which can lead to significant prestress loss both during and after a fire. A detailed and comprehensive literature review is presented that provides background on the residual mechanical properties of prestressing steel, as well as on the creep-relaxation behaviour experienced at elevated temperatures under stress. The results of two test series are discussed; the first examining the effects of elevated temperatures on the residual mechanical properties of prestressing steel exposed to elevated temperatures. The second test series examines the irrecoverable and significant loss of prestress force that results from steel relaxation and other thermal effects experienced during heating. A preliminary analytical model is presented, capable of predicting the change in prestress force experienced by a stressed strand under transient heating. The model is then compared with experimental elevated temperature relaxation data. Finally, the analytical model developed and residual mechanical properties obtained through experimentation are used along with a pre-existing finite difference heat transfer model (developed for concrete slabs) to examine the effect of elevated temperature exposure on the residual flexural capacity of a typical unbonded post-tensioned example slab. Several parameters, such as heated length and concrete cover, are examined using the example structure. From this it was observed that, after one hour of exposure to a standard fire (ASTM E119), significant losses in effective prestress and moment capacity occurred even with the appropriate amount of concrete cover. This is a finding which is of the utmost practical importance to engineers engaged in the evaluation of fire damaged unbonded post-tensioned structures. / Thesis (Master, Civil Engineering) -- Queen's University, 2007-12-18 17:15:17.521 / Natural Sciences and Engineering Research Council of Canada, and the Department of Civil Engineering at Queen’s University

Roxithromycin is a semi-synthetic, macrolide antibiotic, derived from erythromycin A. It acts as a bacteriostatic drug at low concentrations and a bactericidal drug at high concentrations. It binds to the 50S subunit of the 70S ribosome, which causes the reversible inhibition of RNA-dependent bacterial protein synthesis. It is well known that active pharmaceutical ingredients (APIs) may exist in numerous solid states. Differences in the solid state significantly influence the physical and chemical properties of an API. The in vivo performance of a dosage form will also be influenced by the solid state properties of a given pharmaceutical active. The amorphous characteristics of APIs have a significant impact on their performance and thus offer the potential for exciting new pharmaceuticals. Whilst amorphous forms of poorly soluble APIs are more soluble than their crystalline counterparts, they tend to be physically unstable, which makes their formulation into solid dosage forms quite challenging. Roxithromycin has only 50% oral bioavailability due to its poor aqueous solubility and for this reason, its potential for optimal therapeutic effect are limited. Poor solubility is thus an important obstacle in formulation development. During this study, amorphous forms of roxithromycin were prepared via quench cooling, and desolvation of chloroform- and ethyl acetate solvates. These amorphous forms were characterised by means of several techniques, whilst their solubilities and stabilities were also investigated. The outcomes of the solubility studies illustrated the complexity of this API and its amorphous forms with regards to their interactions with water. Solubility studies confirmed the superior solubility of the roxithromycin glass (prepared through quench cooling) and amorphous forms (desolvation of solvates) over the roxithromycin monohydrate in water. The solubility in water improved in the order of roxithromycin monohydrate < roxithromycin glass < roxithromycin glass powder < amorphous chloroform desolvate. The roxithromycin monohydrate, as well as the amorphous forms of roxithromycin demonstrated stability over a one-month period of exposure 40°C and relative humidity (RH) of 75%. The roxithromycin glass powder tended to revert to the more stable crystalline monohydrate after week 3 of stability testing. The roxithromycin glass at lower temperatures of 25°C and 30°C (both at 75% RH) tended to transform into the more crystalline form at week 4 of the study. These transformations were, however, not as significant as during the 40°C / 75% RH study. The conclusion could therefore be made that this transformation into the crystalline form was more temperature – than moisture dependant. At a higher temperature (at identical humidity conditions), the transformation into the crystalline form was much faster. Stability studies on the two roxithromycin desolvates were also performed in order to determine whether these amorphous forms, would differ, with regards to their stability, from the glass prepared through heating and cooling. It was determined that the desolvates were more stable than the roxithromycin glass. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2012

Roxithromycin is a semi-synthetic, macrolide antibiotic, derived from erythromycin A. It acts as a bacteriostatic drug at low concentrations and a bactericidal drug at high concentrations. It binds to the 50S subunit of the 70S ribosome, which causes the reversible inhibition of RNA-dependent bacterial protein synthesis. It is well known that active pharmaceutical ingredients (APIs) may exist in numerous solid states. Differences in the solid state significantly influence the physical and chemical properties of an API. The in vivo performance of a dosage form will also be influenced by the solid state properties of a given pharmaceutical active. The amorphous characteristics of APIs have a significant impact on their performance and thus offer the potential for exciting new pharmaceuticals. Whilst amorphous forms of poorly soluble APIs are more soluble than their crystalline counterparts, they tend to be physically unstable, which makes their formulation into solid dosage forms quite challenging. Roxithromycin has only 50% oral bioavailability due to its poor aqueous solubility and for this reason, its potential for optimal therapeutic effect are limited. Poor solubility is thus an important obstacle in formulation development. During this study, amorphous forms of roxithromycin were prepared via quench cooling, and desolvation of chloroform- and ethyl acetate solvates. These amorphous forms were characterised by means of several techniques, whilst their solubilities and stabilities were also investigated. The outcomes of the solubility studies illustrated the complexity of this API and its amorphous forms with regards to their interactions with water. Solubility studies confirmed the superior solubility of the roxithromycin glass (prepared through quench cooling) and amorphous forms (desolvation of solvates) over the roxithromycin monohydrate in water. The solubility in water improved in the order of roxithromycin monohydrate < roxithromycin glass < roxithromycin glass powder < amorphous chloroform desolvate. The roxithromycin monohydrate, as well as the amorphous forms of roxithromycin demonstrated stability over a one-month period of exposure 40°C and relative humidity (RH) of 75%. The roxithromycin glass powder tended to revert to the more stable crystalline monohydrate after week 3 of stability testing. The roxithromycin glass at lower temperatures of 25°C and 30°C (both at 75% RH) tended to transform into the more crystalline form at week 4 of the study. These transformations were, however, not as significant as during the 40°C / 75% RH study. The conclusion could therefore be made that this transformation into the crystalline form was more temperature – than moisture dependant. At a higher temperature (at identical humidity conditions), the transformation into the crystalline form was much faster. Stability studies on the two roxithromycin desolvates were also performed in order to determine whether these amorphous forms, would differ, with regards to their stability, from the glass prepared through heating and cooling. It was determined that the desolvates were more stable than the roxithromycin glass. / Thesis (MSc (Pharmaceutics))--North-West University, Potchefstroom Campus, 2012

The concentration of atmospheric carbon dioxide (CO2) in the atmosphere has increased by 35% since pre-industrial levels. Projections for the next 100 years indicate an increase to levels between 490 and 1260 parts per million by volume (ppm) of CO2, equating to a 75 % to 350 % increase in concentration since the year 1750. Associated with this increase in [CO2] will be a 1.4 to 5.8?? C increase in lower atmospheric temperature. While past research has attempted to address the effects of such climatic changes on individual plant responses, predictions of plant responses at the ecosystem level are still highly uncertain. Difficulties lie in the enormous variation of plant responses to climate change variables among and within species, and between and within environmental conditions. Past research assumed that plants using either the C3 or C4 metabolic pathways would respond differently but predictably to climate-change variables based on their metabolic pathway. Recent evidence has suggested however, that the added interactions of external environmental variables and species-specific sensitivities to climate change make it difficult to predict plant and ecosystem responses to climate change. To investigate the mechanisms behind responses of Australian grasses to climate change, 2 pot experiments was conducted using growth cabinets to compare the effect of elevated CO2 and water-limitation on the invasive C4 grassland plant, Eragrostis curvula (E. curvula), native Australian C3 grassland plant, Austrodanthonia racemosa (A. racemosa), and wheat species, Triticum aestivum (T. aestivum). The experiment was run at ambient levels of CO2 maintained at 390 ppm compared to elevated levels of 740 ppm. Imposed restrictions to water supply consisted of gradually drying the soil down to 30 % available soil water (ASW) followed by re-wetting to 50 % ASW. Well-watered conditions for the experiment consisted of gradually drying the soil down to 50 % ASW, followed by rewetting to 95 % ASW. Plants were grown in mixtures and monocultures, consisting of 9 plants equally spaced in a grid design. The three significant findings of the thesis were that: 1) the metabolic pathway (C3 versus C4) was not always an accurate predictor of biomass accumulation under elevated CO2 in the plants studied. Previous research suggested that CO2-stimulation of photosynthesis in C3 plants would lead to greater increases in biomass under elevated CO2 compared to C4 plants, though both C3 and C4 plants could benefit from any reduction in stomatal conductance under dry conditions at elevated CO2. The results from the experiments in this thesis showed a strongly significant biomass response to elevated CO2 in both dry and wet conditions for C4 grass E. curvula. The C3 grass A. racemosa in dry conditions, did not. It was speculated that without the CO2-induced water conservation effect, the C3 grass experienced photosynthetic down-regulation and this precluded a positive biomass response under elevated CO2. 2) the magnitude and direction of biomass response to elevated CO2 was dependant on factors such as resource-availability and the phenotypic variability of the plants species. 3) critical analysis of results from this thesis, combined with past research on plant responses under elevated CO2 showed a tendency for researchers to repeatedly test plants from the Poaceae family, or close relatives of the Poaceae family. As a result, when past data were corrected for this lack of independence, there was no relationship between the evolution of the C3 and C4 metabolic pathway and biomass response to elevated CO2. Instead, other factors (such as growth rate, plant height, leaf number, etc) were presented as being more important in determining biomass response. These observations were supported by results found in this thesis.

Elevated water tanks are widely used to store water for drinking as well as for fire extinguishing purposes. After a severe earthquake, the need of water for drinking as well as fire control will increase dramatically. To ensure that water tanks remain functional after an earthquake, proper analysis method should be followed in order to calculate the response of a structure for earthquake. In this study, the lateral forces developed during earthquake are investigated from commercially available SAP2000 software and the results are compared with the 2006 edition of the ACI standard "Seismic Design of Liquid-Containing Concrete Structures and Commentary" (ACI 350.3-06). The elevated concrete tank is modeled for full, half-full and empty conditions. Linear modal time history analysis is performed using scaled ground motions. Three-directional ground motion records from five different earthquakes have been scaled to the design level and applied to the structure. Sloshing behavior of water inside the tank and the effect of vertical ground motion on the columns have been investigated. It is found that, vertical ground motions can increase the axial forces in columns by up to 20 %, and the ACI 350.3-06 design method is not always conservative. As seismic response depends on both the dynamic properties of the structure and the spectral characteristics of ground motions, more research is needed to understand and model the seismic response of elevated water tanks.

Cellular beams (CBs) have become increasingly popular in the UK and other countries over the recent years. However, the research into the behaviour of these beams has not advanced at the same rate. There is still no robust codified guidance available to design cellular beams and cellular composite beams at ambient and elevated temperatures. Meanwhile, numerical simulation approaches, such as Finite Element (FE) analysis, have enabled the researchers to advance their investigations into various behavioural aspects of these beams. In this research, the developed numerical models using the ABAQUS package were able to predict, to a high accuracy, the failure mode and failure load (temperature) of CBs and cellular composite beams at ambient and elevated temperatures.Within the investigations on cellular beams, it was found that predicting the correct failure mode by FE models can be extremely sensitive to the maximum load increment allowed in the software (for elastic-perfectly plastic stress-strain relationship for steel material) and also to the applied boundary conditions. In particular, slight changes in the boundary conditions applied to the top flange of the beam, can change the failure mode from web post buckling to Vierendeel mechanism. The buckling resistance of the web post of cellular composite beams was found to be sensitive to the amplitude of web imperfections at ambient temperature. However, the ultimate resistance of these beams was not affected by the amplitude of web imperfections at elevated temperature. This suggests that the 'Strut' model used in current design method to estimate the buckling resistance of the web post is not reasonable at elevated temperature and needs to be modified. The failure of cellular composite beams under a uniform distributed load (UDL) and at elevated temperatures, was governed by distorsional buckling before the development of web post buckling. Adding full-height web stiffeners to the beam in such cases improved their loading resistance at ambient temperature by up to 15% and prevented the occurrence of distorsional buckling at elevated temperature. Increasing the end-restraints decreased the deflections of CBs which are governed by catenary action at elevated temperature. However, this also critically promoted the occurrence of web post buckling which could be due to the P-∆ effects and instabilities resulting from the restrained expansion of the beam.Asymmetric beams showed a higher sensitivity and vulnerability to the magnitude of the load ratio than symmetric sections. This suggests a more prudent approach for the fire design of asymmetric beams as opposed to symmetric beams.

This thesis investigates, using finite element modelling and experimental investigation, the fracture of mesh reinforcement in composite floor slabs at elevated temperatures. The main objective of the research is the study of the bond strength between the welded mesh reinforcement and concrete at elevated temperatures, since this was found to be the principal behaviour that governs the fracture of the reinforcement in a composite floor slab.The experimental programme included steady state and transient pull-out tests carried out at temperatures varying from 20°C to 1000°C. However, unlike previous work, which concentrated on the bond of single bars, rectangular normal concrete prisms were constructed with one longitudinal bar, ensuring a bond length of 200 mm, and one transverse bar welded centrally. As a result, the influence of the weld of the mesh reinforcement in the bond strength between reinforcement and concrete was studied. The bond strength-slip-temperature relationship was obtained for various sized ribbed and plain bars. It was found that the 6, 7 and 8mm diameter ribbed mesh failed by fracture of the longitudinal bar at all temperatures, including ambient temperature. It was shown that the reduction of bond strength of ribbed mesh was similar to the reduction in strength of the bar, which together with the observed modes of failure, lead to the conclusion that ribbed mesh can be assumed to be fully bonded at all temperatures. The 10mm diameter ribbed mesh failed by splitting due to the cover-bar diameter ratio being small. In contrast, all the plain bars failed by fracture of the weld followed by pull-out of the bar. Therefore the correct bond stress-slip relationship should be modelled for smooth bars to accurately predict global structural behaviour.The investigation using finite element modelling utilizes the DIANA program. The incorporation by the author of the bond strength-slip-temperature relationship within the models permits a better prediction of fracture of the reinforcement in composite floor slabs. It has been shown that smooth bars are more beneficial since the bond is broken before fracture of the bar allowing strains to be distributed along the bar. In the case of ribbed bars the bond is such that localised strain will occur in the bar at crack locations leading quickly to fracture of the reinforcement.

The variation in the compressive strength of concrete block masonry was studied at elevated temperatures. Small specimens known as wallettes were used to obtain the compressive strength under steady state conditions. Eighteen wallettes were made of lightweight concrete blocks and 1:1:5 mortar proportion. The target temperatures were 20°C, 200°C, 400°C, 600°C, 700°C and 800°C. Initially load-deflection relationships were determined from the experimental wallettes and later they were converted into stress-strain relationships. Although the goal was to determine the compressive strength, other parameters were also studied such as modulus of elasticity, temperature-time relationships, modes of failure, material degradation, and change of colour.Lightweight concrete blocks were also tested to determine the compressive strength at equal temperatures applied for the wallettes. The blocks belonged to the same batch used for the wallettes. The tensile behaviour of mortar was determined at 20°C, 200°C and 400°C.Once the mechanical properties of the masonry wallettes, units and mortar were determined, they were used as input data to develop finite element models to simulate the same behaviour of the experimental wallettes. Finally, using the experimental and numerical results from the wallettes, they were used to predict the behaviour of 3m height walls.