M.Tech. / Essential oils are volatile oils, generally odorous, which occur in certain plants or specified parts of plants, and are recovered by accepted procedures, such that the nature and composition of the product is, as nearly as practicable, unchanged by such procedures (ISO, 1968). The principal uses are as: flavouring agent, medicinal and aromatherapy application. Today, the essential oils are sought-after for innumerable applications starting from markers for plant identifications to bases for semi-synthesis of highly complex molecules. The extraction of highly delicate essential oils from plants remains a crucial step in all these applications. By using steam to mediate the extraction, it is possible to maintain mild conditions and effect superior extraction. In the current work, an integrated procedure for steam extraction followed by volatiles sampling and analysis from the leaves of the Eucalyptus tree was explored. There are two problems to overcome in the extraction from solid plant materials: that of releasing the essential oils from solid matrix and letting it diffuse out successfully in a manner that can be scaled-up to industrial volumes. Towards this end, the effect of different parameters, such as temperature, pressure and extraction time on the extraction yield was investigated and the experimental results show that all of these temperatures (90 °C, 97°C, and 99°C), were significant parameters affecting yield. Increase in yield was observed as pressure was increased and the use of high pressure (150 kPa) in steam extraction units permits much more rapid and complete distillation of essential oils over atmospheric pressure. The yield was calculated from the relation between the essential oil mass extracted and the raw material mass used in the extraction. The volatiles, Eucalyptus oil in vapour form released from the leaves were condensed and analyzed using Gas chromatography, and eight major components were found to be contained in this species. A mathematical model based on diffusion of essential oil from the leaves was developed. Using a numerical method, the best diffusion coefficient was established for different operating conditions by comparing the model concentration of oil remaining in the leaves with the experimental amount of oil recovered; hence minimizing the sum of squared errors. It was found that one cannot simply assume that the oil leached and recovered was the same as that originally present in the leaves. The initial mass of oil was determined by fitting the diffusion model to the data. An Arrhenius model was used to account for the effect of temperature. The resulting expression for the diffusion coefficient as a function of temperature can now be used to model the large scale extraction of the essential oils from Eucalyptus leaves.

In 2008, there were more than 5,200 workplace fatalities in the United States (BLS, 2010b). During the same time period, U.S. employees missed almost 1.1 million days from work (BLS, 2010c). Accidents are unexpected outcomes that result not only from individuals' behaviors, but from contextual factors (Krause, 1997; Reason, 1990). Therefore, unsafe behaviors have to be interpreted according to a combination of what is occurring in the environment and what the individual is doing in that environment. The present study sought to create a more comprehensive model of safety by means of macroergonomics. Macroergonomics utilizes sociotechnical systems theory to posit that a work system is composed of a personnel subsystem (i.e., ways individuals perform tasks), a technological subsystem (i.e., tasks to be performed), and external factors (Hendrick, 2002a). Perceived control over work hours, an aspect of the technological subsystem, was examined as an antecedent of work-family conflict. Supervisor instrumental support, an aspect of the personnel subsystem, was examined as a moderator of the relationships between perceived control over work hours and work-family conflict. Supervisors have an imperative role in employees' perception of control over their work hours (Kelly & Moen, 2007). Supervisor instrumental support was also hypothesized to moderate the relationships between work-family conflict and safety performance. Supervisors who support their employees in their work-family matters exceed mandatory requirements set forth to protect workers' safety and health (Mearns, Hope, Ford, & Tetrick, 2010). A majority of the 360 participants in the present study were grocery store employees who worked in the front end of the store as cashiers. Job tenure in this particular grocery store chain was an average of 7 years (SD = 5.96) and the average number of hours worked per week was 31 (SD = 8.55). The employees were an average age of 38 years old (SD = 15.25). Two hundred and sixty-two (73%) of the participants were female, 330 (92%) were White, 196 (55%) employees were married or living as married, 146 (41%) employees identified themselves as parents with children living at home, and 58 (16%) employees provided elder care. The data were analyzed using a moderated mediation model. An employee's perceived control over his/her work hours was negatively associated with work-to-family and family-to-work conflict. Work-to-family conflict was not significantly associated with either safety compliance or participation. In contrast, family-to-work conflict was significantly associated with both safety compliance and participation. These findings replicate Cullen and Hammer's (2007) findings that family-to-work conflict, but not work-to-family conflict, is negatively associated with safety compliance and participation. The replication of these significant findings gives support to macroergonomics' assertion that external forces (i.e., family) can affect the safety of employees. All of the meditating and moderating relationships proposed in this dissertation were not significant. I conducted post hoc analyses to determine other possible significant paths in the model examined. The FSSB dimension of supervisor instrumental support was found to positively affect both safety compliance and participation. Supervisor instrumental support was also found to directly affect work-to-family conflict. Overall FSSB and its subdimensions demonstrated similar patterns in the hypothesized relationships and in additional relationships examined. Numerous implications can be recognized from this dissertation. First, interdisciplinary approaches to safety research are emerging and important in the pursuit of safer work environments. Macroergonomics and I/O psychology have commonalities that lend themselves to a good partnership where researchers can learn from each other and collaborate to advance the study of safety. Second, organizations need to focus on the stressors their employees experience as part of their safety programs, and numerous studies, including this dissertation, have found that family-to-work conflict impacts safety compliance and participation. Future safety research may incorporate macroergonomics, which emphasizes that focusing on one adverse aspect of the system may not be enough to create valuable change if there are other adverse factors still creating demands elsewhere in the system. This will allow for a more comprehensive model that ensures certain aspects of the system are not neglected, which can reduce effectiveness of constructs used to create positive changes.

If a group of engineering deans were asked whether students at their institutions were successful and why, what information might they immediately or subconsciously use to measure or gauge the engineering students’ success? If only academic performance outcomes like GPA, individual course grades, or graduation rate race to their minds, then their rationale aligns with the majority of researchers. My research seeks to shift the mindset that frames engineering student success mainly within the boundaries of academic performance measures. By measuring students’ perceived autonomy, competence, social integration and relatedness within their programs, and aspirations after graduation, one can more accurately judge whether engineering students are achieving holistic student success. By utilizing surveys and exit interviews for freshmen Summer Bridge Program (SBP) participants, interviewing continuing and past SBP participants, and surveying engineering seniors, this research gathered more in-depth information on students’ experiences. In turn, one can better understand how the structures of engineering summer and undergraduate programs either contribute to or detract from student success and motivation. Results from SBP freshmen indicated that community building, structured studying, real-world experiences, residential life, and mentorship were perceived as valuable components by the students. Also, a perceived difficulty gap, based on students’ prior engineering experience(s), was uncovered. For continuing SBP students, there was an emphasis on Black community, leadership, and discourse when moving from SBP to larger departments. Lastly, within the seniors, we found that students tend to choose engineering careers regardless of their undergraduate experiences. This information can be used in practice for enhancing programmatic planning and design as well as potentially developing novel program components that contribute to students becoming more self-determined, motivated engineers. It is my hope that one day in the near future, engineering education faculty, administrators, and leaders will cultivate and measure success based on a more comprehensive assessment of lived experiences and better recognize how their decisions regarding programmatic structures impact students’ success and motivation.

Indiana University-Purdue University Indianapolis (IUPUI) / Mechanical force environment is a major factor that influences cellular homeostasis and remodeling. The prevailing wisdom in this field demonstrated that a threshold of mechanical forces or deformation was required to affect cell signaling. However, by using a fluorescence resonance energy transfer (FRET)-based approach, we found that C28/I2 chondrocytes exhibited an increase in RhoA activities in response to high shear stress (10 or 20 dyn/cm2), while they showed a decrease in their RhoA activities to intermediate shear stress at 5 dyn/cm2. No changes were observed under low shear stress (2 dyn/ cm2). The observed two-level switch of RhoA activities was closely linked to the shear stress-induced alterations in actin cytoskeleton and traction forces. In the presence of constitutively active RhoA (RhoA-V14), intermediate shear stress suppressed RhoA activities, while high shear stress failed to activate them. Collectively, these results herein suggest that intensities of shear stress are critical in differential activation and inhibition of RhoA activities in chondrocytes.

This research investigated the behavior of nonseismically detailed reinforced concrete exterior beam-column joints subjected to bidirectional lateral cyclic loading using nonlinear finite element analysis (NLFEA). Beam-column joints constitute a critical component in the load path of reinforced concrete buildings due to their fundamental role in integrating the overall structural system. Earthquake reconnaissance reports reveal that failure of joints has contributed to partial or complete collapse of reinforced concrete buildings designed without consideration for large lateral loads, resulting in significant economic impact and loss of life. Such infrastructure exists throughout seismically active regions worldwide, and the large-scale risk associated with such deficiencies is not fully known. Computational strategies provide a useful complement to the existing experimental literature on joint behavior and are needed to more fully characterize the failure processes in seismically deficient beam-column joints subjected to realistic failure conditions. Prior to this study, vulnerable reinforced concrete corner beam-column joints including the slab had not been analyzed using nonlinear finite element analysis and compared with experimental results. The first part of this research focused on identification and validation of a constitutive modeling strategy capable of simulating the behaviors known to dominate failure of beam-column joints under cyclic lateral load using NLFEA. This prototype model was formulated by combining a rotating smeared crack concrete constitutive model with a reinforcing bar plasticity model and nonlinear bond-slip formulation. This model was systematically validated against experimental data, and parametric studies were conducted to determine the sensitivity of the response to various material properties. The prototype model was then used to simulate the cyclic response of four seismically deficient beam-column joints which had been previously evaluated experimentally. The simulated joints included: a one-way exterior joint, a two-way beam-column exterior corner joint, and a series of two-way beam-column-slab exterior corner joints with varying degrees of seismic vulnerability. The two-way corner joint specimens were evaluated under simultaneous cyclic bidirectional lateral and cyclic column axial loading. For each specimen, the ability of the prototype model to capture the strength, stiffness degradation, energy dissipation, joint shear strength, and progressive failure mechanisms (e.g. cracking) was demonstrated.

Nobel laureate Dr. Carl Wieman, renowned for his leadership in science education, is the latest addition to UBC's Faculty of Science. UBC's Dr. David Dolphin is the winner of the 2006 Gerhard Herzberg Canada Gold Medal for Science and Engineering.

Indiana University-Purdue University Indianapolis (IUPUI) / Multiresolution image fusion is an emerging area of research for use in military and commercial applications. While many methods for image fusion have been developed, improvements can still be made. In many cases, image fusion methods are tailored to specific applications and are limited as a result. In order to make improvements to general image fusion, novel methods have been developed based on the wavelet transform and empirical variance. One particular novelty is the use of directional filtering in conjunction with wavelet transforms. Instead of treating the vertical, horizontal, and diagonal sub-bands of a wavelet transform the same, each sub-band is handled independently by applying custom filter windows. Results of the new methods exhibit better performance across a wide range of images highlighting different situations.

Indiana University-Purdue University Indianapolis (IUPUI) / Hydrogels prepared from photopolymerization have been widely used in many biomedical applications. Ultraviolet (200-400 nm) or visible (400-800 nm) light can interact with light-sensitive compounds called photoinitiators to form radical species that trigger photopolylmerization. Since UV light has potential to cause cell damage, visible light-mediated photopolymerization has attracted much attention. The conventional method to fabricate hydrogels under visible light exposure requires usage of co-initiator triethanolamine (TEA) at high concentration (∼200 mM), which reduces cell viability. Therefore, the first objective of this thesis was to develop a new method to form poly(ethylene glycol)-diacrylate (PEGDA) hydrogel without using TEA. Specifically, thiol-containing molecules (e.g. dithiothreitol or cysteine-containing peptides) were used to replace TEA as both co-initiator and crosslinker. Co-monomer 1-vinyl-2-pyrrolidinone (NVP) was used to accelerate gelation kinetics. The gelation rate could be tuned by changing the concentration of eosinY or NVP. Variation of thiol concentration affected degradation rate of hydrogels. Many bioactive motifs have been immobilized into hydrogels to enhance cell attachment and adhesion in previous studies. In this thesis, pendant peptide RGDS was incorporated via two methods with high incorporation efficiency. The stiffness of hydrogels decreased when incorporating RGDS. The second objective of this thesis was to fabricate hydrogels using poly(ethylene glycol)-tetra-acrylate (PEG4A) macromer instead of PEGDA via the same step-and-chain-growth mixed mode mechanism. Formation of hydrogels using PEGDA in this thesis required high concentration of macromer (∼10 wt.%). Since PEG4A had two more functional acrylate groups than PEGDA, hydrogels could be fabricated using lower concentration of PEG4A (∼4 wt.%). The effects of NVP concentration and thiol content on hydrogel properties were similar to those on PEGDA hydrogels. In addition, the functionality and chemistry of thiol could also affect hydrogel properties.

Indiana University-Purdue University Indianapolis (IUPUI) / As liver disease becomes more prevalent, the development of an in vitro culture system to study disease progression and its repair mechanisms is essential. Typically, 2D cultures are used to investigate liver cell (e.g., hepatocyte) function in vitro; however, hepatocytes lose function rapidly when they were isolated from the liver. This has promoted researchers to develop 3D scaffolds to recreate the natural microenvironment of hepatic cells. For example, gelatin-based hydrogels have been increasingly used to promote cell fate processes in 3D. Most gelatin-based systems require the use of physical gelation or non-specific chemical crosslinking. Both of these methods yield gelatin hydrogels with highly interdependent material properties (e.g., bioactivity and matrix stiffness). The purpose of this thesis research was to prepare modularly crosslinked gelatin-based hydrogels for studying the influence of independent matrix properties on hepatic cell fate in 3D. The first objective was to establish tunable gelatin-based thiol-norbornene hydrogels and to demonstrate that the mechanical and biological properties of gelatin hydrogels can be independently adjusted. Furthermore, norbornene and heparin dual-functionalized gelatin (i.e., GelNB-Hep) was prepared and used to sequester and slowly release hepatocyte growth factor (HGF). The second objective was to investigate the viability and functions of hepatocytes encapsulated in gelatin-based hydrogels. Hepatocellular carcinoma cells, Huh7, were used as a model cell type to demonstrate the cytocompatibility of the system. The properties of GelNB hydrogels were modularly tuned to systematically evaluate the effects of matrix properties on cell viability and functions, including CYP3A4 activity and urea secretion. The last objective was to examine the effect of heparin immobilization on hepatocyte viability and functions. The conjugation of heparin onto GelNB led to suppressed Huh7 cell metabolic activity and improved hepatocellular functions. This hybrid hydrogel system should provide a promising 3D cell culture platform for studying cell fate processes.

Indiana University-Purdue University Indianapolis (IUPUI) / Lithium-ion battery is one kind of rechargeable battery, and also renewable, sustainable and portable. With the merits of high density, slow loss of charge when spare and no memory effect, lithium-ion battery is widely used in portable electronics and hybrid vehicles. Apart from its advantages, safety is a major concern for Lithium-ion batteries due to devastating incidents with laptop and cell phone batteries. Overcharge and over-discharge are two of the most common electrical abuses a lithium-ion battery suffers. In this thesis, a fuzzy-rule-based system is proposed to detect the over-charge and over-discharge failure in early time. The preliminary results for the failure signatures of overcharged and over-discharged lithium-ion are listed based on the experimental results under both room temperature and high temperature. A fuzzy-rule-based model utilizing these failure signatures is developed and validated. For over-charge case, the abnormal increase of the surface temperature and decrease of the voltage are captured. While for over discharge case, unusual temperature increase during overcharge phases and abnormal current decrease during overcharge phases are obtained. The inference engine for fuzzy-rule-based system is designed based on these failure signatures. An early warning signal will be given by this algorithm before the failure occurs. This failure detection and early warning system is verified to be effective through experimental validation. In the validation test, the proposed methods are successfully implemented in a real-time system for failure detection and early warning. The result of validation is compatible with the design expectation. Finally an accurate failure detection and early warning system is built and tested successfully.