Aluminum-zirconium alloys exhibit superior strength at elevated temperature in comparison to traditional aluminum casting alloys. These alloys are heat-treatable and their strength depends to a large extent on the quenching and aging steps of the heat treatment process. However, measurements show that the critical cooling rate necessary to retain 0.6 wt. pct. zirconium(the minimum amount necessary for significant strengthening) in a super-saturated solid solution with aluminum is 90ºC/s, which is un-attainable with traditional casting processes. On the other hand, the critical cooling rate necessary to retain 0.4 wt. pct vanadium and 0.1 wt. pct. zirconium in a super- saturated solidsolution with aluminum is only 40ºC/s; which suggests that substituting vanadium for zirconium significantly decreases the critical cooling rate of the alloy. This is an important finding as it means that, unlike the Al-0.6Zr alloy, the Al-0.4V-0.1Zr alloy may be processed into useful components by traditional high pressure die-casting. Moreover, measurements show that the hardness of the Al-0.4V-0.1Zr alloy increases upon aging at 400ºC and does not degrade even after holding the alloy at 300ºC for 100 hours. Also, measurements of the tensile yield strength of the Al-0.4V-0.1Zr alloy at 300ºC show that it is about 3 times higher than that of pure aluminum. This increase in hardness and strength is attributed to precipitation of Al3(Zr,V) particles. Examination of these particles with high resolution transmission electron microscopy (HRTEM) and conventional TEM show that vanadium co-precipitates with zirconium and aluminum and forms spherical particles that have the L12 crystal structure. It also shows that the crystallographic misfit between the precipitate particles and the aluminum matrix is almost eliminated by introducing vanadium into the Al3Zr precipitate and thatthe mean radius of the Al3(Zr,V) particles is in the range from 1nm to 7nm depending on the alloy composition and aging practice. Finally, it is found that adding small amounts of silicon to the Al-0.4V-0.1Zr alloy effectively accelerates formation of the Al3(Zr,V) precipitate.

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A very important aspect for the functioning of an organism is that cells adapt their behaviour to external stimuli. They continuously interact with their environment, and biochemical and physical cues can activate cellular signalling, which leads to changes in cell behaviour such as proliferation and shape. Understanding cells' interactions with their environment is also important for understanding diseases. For example mechanosensing, which is the sensing of the cell's mechanical environment, has been associated with cancer development. In order for a cell to be able to sense its mechanical environment, it needs to form attachments to the environment. In my thesis, I have worked on three different tasks: the development of a new measurement technique and the study of initial cell adhesion and of cell spreading. When a cell from suspension first comes into contact with a substrate, it forms initial attachment bonds with proteins on the substrate surface. These bonds are mediated through integrins, which are transmembrane heterodimers, binding to the cell's environment on one side and to the cell's cytoskeleton on the other side. I study this initial cell attachment by measuring the force needed to detach cells, called cell adhesion strength. For these experiments I built a detachment device, which allows the detachment of cells from a substrate by vibrating the substrate in liquid. The device combines cell incubation, detachment and imaging. I measured the dependence of initial integrin bond formation on external factors such as incubation temperature and substrate stiffness. Once initial integrin bonds are formed, many different proteins are recruited to the adhesion site in order to form stronger adhesions. Amongst these proteins are signalling proteins, which direct the behaviour of the cell as a whole. One of the first cellular reactions to a substrate after initial integrin binding is cell spreading. This can be seen by the cell changing its shape from spherical to dome-like on the substrate. Because cell spreading is a very early response of a cell to a substrate, the onset time of spreading can be used as a quantitative measure for the time it takes the cell to sense a substrate and signal shape change. In my work, I look at the distribution of the time of initial cell spreading in a population of cells. I measure this distribution under different growth conditions such as pH, change of incubation medium from DMEM to PBS, substrate stiffness and incubation temperature. In my detachment experiments, I observe that vibration accelerates cell spreading in those cells which remain on the substrate. This is a connection between the detachment experiments and the cell spreading experiments and it shows how cells react to external forces. By changing the medium temperature in the cell detachment and cell spreading experiments, I am able to analyse the kinetics of these two processes. I use a signalling network model to analyse the internal cellular signalling path that leads from a spherical to a spread cell.

OBJECTIVES: The aim of this study was to evaluate the bond strength of three different veneering porcelains fired over CP Titanium and a CAD/CAM ceramic cemented to CP Titanium. METHODS: Sixty-four bars of CP Titanium grade II (25±1x 3±0.5x 0.5±0.05 mm) were divided randomly into four groups: Group 1: Titankeramik (Vita Zahnfabrik), Group 2: Triceram (Dentaurum), Group 3: Initial Ti (GC), and Group 4: MKII blocks (Vita). Each veneer porcelain (groups 1-3) was applied with dimensions limited to 8x3x1mm and fired on CP Ti bars following the manufacturer’s instructions and ISO 9693 recommendations. Group 4, Vita Mark II blocks were sectioned into sixteen bars (8x3x1mm) and cemented with Multilink Implant cement (Ivoclar) on CP Ti bars. Fifteen specimens from each group were tested for bond strength by Schwickerath crack initiation test (ISO 9693) using an Instron machine; the mode of failure and bond interface was evaluated by SEM / EDS. RESULTSs: The data were analyzed statistically using ANOVA and Tukey ≤ 0.05. Group 4 is significantly higher than the other groups. Group 1 is significantly higher than group 3, but similar to group 2. SEM/EDS analysis reveals that the modes of failure for groups 1 - 4 are a mixture of adhesive, mixed, and cohesive failures. CONCLUSION: Cementing a milled ceramic to CP Ti produces bond strength significantly greater than conventional veneering porcelains. / 2018-09-28T00:00:00Z

Ho, Ching Man = 可柔韌的白鑄鐵 / 何靜雯. / Thesis submitted in: November 2007. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves ). / Text in English; abstracts in English and Chinese. / Ho, Ching Man = Ke rou ren de bai zhu tie / He Jingwen. / Chapter Chapter 1: --- Introduction --- p.1 / Chapter 1.1 --- Introduction of Composites --- p.1 / Chapter 1.1.1 --- Dispersion-Strengthened composites --- p.2 / Chapter 1.1.2 --- True Particulate Composites --- p.2 / Chapter 1.1.3 --- Fiber-Reinforced Composites --- p.2 / Chapter 1.1.4 --- Laminar Composites --- p.3 / Chapter 1.2 --- Mechanical Properties of Metal Matrix Composites --- p.4 / Chapter 1.2.1 --- Stress-Strain Test --- p.4 / Chapter 1.2.2 --- "Stiffness, Strength and Ductility" --- p.4 / Chapter 1.2.3 --- Hardness --- p.5 / Chapter 1.3 --- Fabrication of Metal Matrix Composites --- p.5 / Chapter 1.3.1 --- Liquid ´ؤ´ؤ State Processing --- p.6 / Chapter 1.3.1.1 --- Infiltration Processes --- p.6 / Chapter 1.3.1.2 --- Dispersion Processes --- p.7 / Chapter 1.3.1.3 --- Spray Processes --- p.7 / Chapter 1.3.1.4 --- In - Situ Processes --- p.8 / Chapter 1.3.2 --- Solid - State Processing --- p.8 / Chapter 1.3.2.1 --- Diffusion Bonding --- p.8 / Chapter 1.3.2.2 --- Deformation Processing --- p.9 / Chapter 1.3.2.3 --- Deposition Techniques --- p.9 / Chapter 1.4 --- Fabrication of Metal Matrix Composites by Spinodal Decomposition --- p.10 / Chapter 1.4.1 --- Phase Transformation --- p.10 / Chapter 1.4.2 --- Nucleation and Growth --- p.12 / Chapter 1.4.2.1 --- Kinetics of Nucleation and Growth --- p.12 / Chapter 1.4.2.2 --- Phase Separation by Nucleation and Growth --- p.14 / Chapter 1.4.3 --- Spinodal Decomposition --- p.14 / Chapter 1.4.3.1 --- Phase Separation by Spinodal Decomposition --- p.14 / Chapter 1.4.3.2 --- The Diffusion Equation for Spinodal Decomposition --- p.15 / Chapter 1.4.4 --- Methods to obtain large undercooling --- p.17 / Chapter 1.5 --- Aim of This Project --- p.18 / Chapter Chapter 2: --- Experimental --- p.26 / Chapter 2.1 --- Preparation of fused silica tube --- p.26 / Chapter 2.2 --- Preparation of Sample --- p.26 / Chapter 2.2.1 --- Weighing and Alloying --- p.26 / Chapter 2.2.2 --- Fluxing --- p.27 / Chapter 2.3 --- Slow Cooling --- p.28 / Chapter 2.4 --- Microstructure Analysis --- p.28 / Chapter 2.4.1 --- Optical Microscope (OM) Analysis --- p.28 / Chapter 2.4.2 --- Sample Preparation for Scanning Electron Microscope (SEM) Analysis --- p.29 / Chapter 2.4.3 --- Sample Preparation for Transmission Electron Microscope (TEM) Analysis --- p.29 / Chapter 2.4.3.1 --- Specimen Requirement --- p.29 / Chapter 2.4.3.2 --- "Cutting, Grinding and Polishing" --- p.30 / Chapter 2.4.3.3 --- Ion Milling --- p.31 / Chapter 2.5 --- Microstructure Characterization by TEM --- p.31 / Chapter 2.5.1 --- Indexing Diffraction Pattern --- p.31 / Chapter 2.5.2 --- Energy Dispersive X-Rav (EDX) Analysis --- p.32 / Chapter 2.6 --- Mechanical Properties --- p.33 / Chapter 2.6.1 --- Hardness Testing --- p.33 / Chapter 2.6.2 --- Compression Testing --- p.33 / Chapter 2.7 --- Characterizations of Non-spinodal Samples --- p.34 / Chapter Chapter 3: --- Study of the Relationship between Microstructures and Undercooling of Fe81C14Si5 --- p.41 / Chapter 3.1 --- Abstract --- p.41 / Chapter 3.2 --- Introduction --- p.42 / Chapter 3.3 --- Experiment --- p.42 / Chapter 3.4 --- Results --- p.44 / Chapter 3.5 --- Discussion --- p.46 / Chapter 3.6 --- Conclusion --- p.46 / Chapter Chapter 4: --- Ductile white cast iron --- p.56 / Chapter 4.1 --- Abstract --- p.56 / Chapter 4.2 --- Introduction --- p.57 / Chapter 4.3 --- Experimental --- p.58 / Chapter 4.4 --- Results --- p.60 / Chapter 4.5 --- Discussions --- p.66

Introduction: Rugby is a professional sport which places emphasises on strength, power, speed and endurance. Therefore the accurate assessment of rugby performance is very important for sports and exercise therapists to enable peak performance for the players. Lower limb strength is often tested by means of isokinetic testing, whilst functional power is tested by means of the vertical jump test. Sophisticated equipment used in the measurement of performance indicators, are often not available in smaller communities and rural areas. A good correlation between laboratory testing and functional testing could be of great value for determining performance in less fortunate communities. Aim of Study: To determine the relationship between isokinetic strength testing of the quadriceps and hamstring muscle groups and vertical jump performance in rugby players. Methods: Fifty one male, rugby players who were part of the Varsity Cup Tournament in (2011) participated in this study. Ethical approval was given by the Human Research Ethics Committee (HREC) of the University of Witwatersrand. Height and weight were measured. Isokinetic knee extensor and flexor strength was tested (Biodex system 4 dynamometer TM ) at 60˚/sec (5 repetitions), 180˚/sec (10 repetitions) and 300˚/sec (15 repetitions). A single leg vertical jump was done using the Vertec and the performance was assessed as maximal height jump in centimetres. Descriptive statistics (mean and standard deviation) are reported for all outcomes. The SPSS software (IBM. SPSS version 21) was used for analysis. A Pearson's Product Moment Correlation coefficient was calculated between the isokinetic parameters of quadriceps and hamstring muscles and the vertical jump height and power (watts). An independent t-test and a paired t-test were used to calculate the differences between the forward and backline players and the dominant (Dom) and non-dominant (ND) legs. Results: The mean age of the participants was 21.4 ± 1.2 years; they were 1.83 ± 7.4m tall and weighed 99.3 ± 13.8kg. There were 26 forward players (mean height of 1.88 ± 7.2m and mean weight of 109.9 ± 10.3kg) and 25 backline players (mean height of 1.80 ± 5.5m and mean weight of 88.3 ± 6.1kg). The forwards were significantly taller and heavier than the backline players (p = 0.0001). The forwards produced significant greater peak power in the vertical jump than the backline players in both the dominant and non-dominant legs (p=0.0001). The PT (Nm) decreased as the angular velocity increased from 60˚/sec to 300˚/sec. A significant negative correlation (r = - 0.313; p = 0.025) between peak torque (PT) concentric strength from the hamstrings at 60º/sec and the vertical jump height on the non-dominant side were found. Quadriceps PT to vertical power at the higher velocities showed significant correlations at 180º/sec (dominant: r = 0.294; p = 0.011) and 300º/sec (dominant: r = 0.352; p = 0.011; non-dominant: r = 0.293; p = 0.037). No significant correlations were found between peak torque and vertical jump height when corrected for body weight. When correlating PT and vertical jump power corrected for body weight significant negative correlations was found at 180º/sec (dominant: r = 0.319; p = 0.022; non-dominant: r = 0.305; p = 0.030) for the hamstrings. Conclusion: The findings from the presented study found no significant correlation between lower limb isokinetic knee muscle torque parameters and vertical jump performance in rugby union players. Future research should investigate the relationship between isokinetic testing and vertical jump height by including the parameters of a multi joint mechanism.

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Fifteen well-trained males, mid-thigh pull peak force (IPF 4403.61 ± 664.69N) and isometric peak force allometrically scaled (IPFa 226.04 ± 25.81) were assigned to two groups: repetition maximum training (RM) and relative intensity training (RI) for a twelve-week training intervention. The main effect of time showed a statistically significant difference in mean sprint performance and IPFa at the different time points (p < 0.001). There was a larger magnitude of within-subject effect with respect to sprint performance pre – post with the RI group (ES = 1.06, 7.19%) as compared to the RM group (ES = 0.567, 4.23%, p < 0.001), as well as a larger magnitude of within-subject effect with respect to IPFa pre – post with the RI group (ES = 0.426, 7.51%) as compared to the RM group (ES = 0.270, 13.29%). Furthermore, there was a non-statistically significant, moderate between-group difference in the change in IPFa from pre-post in favor of the RI group (ES=.75), and a large between-group difference in the change in sprint performance pre-post in favor of the RI group (ES=1.50). Results lead investigators to suggest the utilization of RI training tactics for the development of sprint performance when minimal sprint skill training is available.

The coupled effect of using geosynthetic reinforcement and randomly distributed fibers on the stability of slopes was evaluated using finite element modeling and limit equilibrium methods by analyzing a case study in Oslo, Norway. The main objective was to simulate the failure condition of the original slope and quantify the improved stability of a hypothetical reinforced slope constructed with geosynthetic layers and distributed discrete fibers. The stability of the slope was evaluated in both the short-term condition with its' undrained shear strength parameters, and the long-term drained condition. Results indicate that the combination of the techniques was found to have a possible increase of about 40% in the short-term condition and about 60% in the long-term condition of the factor safety associated with the slope. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Current scientific evidence suggests that when whole body vibration (WBV) is used as a warm-up prior to performing eccentric exercise, delayed-onset muscle soreness (DOMS) is mitigated and strength loss recovers faster. These benefits were observed primarily in nonresistance-trained individuals. The aim of this study was to determine if WBV could mitigate soreness and expedite strength recovery for resistance-trained individuals when used as a warm-up prior to eccentric exercise. Thirty resistance-trained males completed 300 maximal eccentric contractions of the quadriceps after warming up with (WBV) or without (CON) WBV. Both CON and WBV experienced significant isometric (27.8% and 30.5%, respectively) and dynamic (52.2% and 47.1%, respectively) strength loss immediately postexercise. Isometric strength was significantly depressed after 24 hours in the CON group (9.36% p < 0.01), but not in the WBV group (5.8% p = 0.1). Isometric strength was significantly depressed after 48 hours in the CON group (7.18% p < 0.05), but not in the WBV group (4.02% p = 0.25). Dynamic strength was significantly decreased in both the CON and WBV groups both at 24 hours (19.1% p < 0.001, and 16.1% p < 0.001, respectively), 48 hours (18.5% p < 0.01, and 14.5% p < 0.03), and 1 week postexercise (9.3% p = 0.03, and 3.5%, respectively). Pain as measured by visual analog scale (VAS) was significant in both CON and WBV groups at 24 and 48 hours postexercise, but the WBV experienced significantly less soreness than the CON group after 24 hours (28 mm vs. 46 mm p < 0.01 respectively), and 48 hours (38 mm vs. 50 mm p < 0.01). Pain as measured by pain pressure threshold (PPT) increased significantly in both groups after 24 and 48 hours, but there was no difference in severity of perceived soreness. The use of WBV as a warm-up may mitigate DOMS but does not appear to expedite the recovery of strength in the days following eccentric exercise in resistance-trained individuals.