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Assessments of and Applications for High Spatio-Temporal Resolution X-Ray Detectors for Use in Medical Imaging
No full textPh.D.Endovascular image guided interventions (EIGI) are a minimally invasive alternative for the treating stroke and other vascular diseases that minimize patient discomfort and have reduced mortality and morbidity. The image quality delivered to physicians, both in spatial and temporal resolution, can influence diagnostic and treatment decisions directly related to patient outcomes. Current state-of-the-art detector systems provide sub-optimal spatial resolution for visualization of fine image detail and temporal resolution has been limited to tens of frames per second at best. The medical physics research group at the University at Buffalo's Canon Stroke and Vascular Research Center has worked to improve both these aspects of imaging detectors, including an array of region-of-interest, small field-of-view, high-resolution detectors, and a new high-speed high-resolution direct-detector capable of providing high-quality images and detailed blood flow patterns. The high-resolution properties of a region-of-interest "Hi-Def" detector was assessed with a family of detector metrics designated Relative Object Detectability (ROD) metrics. The ROD metrics are a task-based group of metrics that compare the relative imaging capabilities of different detector systems. The ROD metric is the product of a detector DQE and a simulated object function, integrated over all spatial frequencies, and divided by the respective integral of another detector. This metric gives an idealized comparison of the performance of two imaging systems in detecting specific objects. Another metric from the ROD family is the Generalized Relative Object Detectability (G-ROD) metric. This metric is calculated in a manner similar to the ROD metric but uses the Generalized DQE (G-DQE) which takes into account elements of the detector system such as focal spot size, scatter, etc. The final metric calculated was the Generalized Measured Relative Object Detectability (GM-ROD). The GM-ROD is measured using images of real objects, which gives the most accurate comparison of detector systems relative performance. The GM-ROD is calculated from the ratio of the square of the Fourier transform of the object's image, divided by the generalized NNPS (GNNPS), integrated over all spatial frequencies, and divided by the respective integral of another detector. The bulk of this dissertation is principally concerned with the effects of high-speed motion and the application of high-speed detectors to new challenges. The first question examined is the effect of motion blur due to rapid gantry-motion, particularly during the acquisition of Cone-Beam CT (CBCT). The magnitude of the blur in individual projections is examined in relation to different factors such as gantry speed, object position, and x-ray pulse duration. This study was followed up by examining the contributions of individual projections to reconstructions. To do this, a detailed phantom was simulated and individual projections were intentionally blurred. From these blurred projections, the initial phantom was reconstructed using filtered backprojection, the reconstructed image was compared to the initial phantom, and the magnitude of blur was measured.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*
Ballistic Y-Branch Switches: Current Progress and Future Plans
No full textM.S.There has been a drive to make electronic devices smaller, faster, and more efficient over the past several decades. In order to accomplish this, many researchers have been looking for novel technologies and devices to replace MOSFETs. One such type of device is the Y-branch switch (YBS). By applying an electric field across the source waveguide, the wavefunction of the electrons can be shifted to steer them down the desired "branch" of the intersection. Such YBSs can be easily be used to form traditional logic gates. It would therefore be unnecessary to develop and transition to a completely new digital logic system, but the novel behavior of these devices does offer an easier path to potentially better logic systems. While YBSs have been fabricated in the past, they have all suffered from either poor gate efficiency or significant leakage current. We believe that high-κ dielectric gates will solve this and have been working on fabricating such gates on a YBS, and we have thus far successfully fabricated functional three-terminal ballistic junctions. I have also created the basic framework for simulations of such devices using Silvaco Atlas, and have proposed several options to achieve the desired independent high-κ dielectric gates.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*
The Study of Vacuum-Driven Microfluidic Networks and Their Pumping Methods
No full textPh.D.The object of this thesis is to study the vacuum-driven microfluidic networks and their pumping methods for sample preparation and potential application in point-of-care testing. The components used in the vacuum-driven microfluidics are studied to understand how to design microfluidic networks using vacuum-driven pumping. Vacuum-driven microfluidic platform delivers the sample using the vacuum-driven micropumping, which requires no external pumps and no real-time control while sample flowing, so called passive pumping. The sample is delivered along the channel due to the generated pressure difference across the liquid column. One approach in vacuum-driven micropumping is to utilize the gas solubility of poly-dimethylsiloxane (PDMS). PDMS is one of the most widely used materials in microfluidic devices, and it has gas solubility high enough to utilize as a micropumping. The gas concentration inside the PDMS is subject to the ambient gas condition. For instance, the degassed PDMS can reabsorb the gas molecules from the ambient if the PDMS is returned to the atmospheric pressure under the room temperature with an ample area. In microfluidic devices, the PDMS reabsorbs the gas molecules from the ambient microchannel, making the pressure inside the dead-end channel being lower pressure than atmospheric pressure. Another approach is to utilize the gas-permeability of PDMS. Thin membrane of PDMS can transmit the gas molecules across it when a pressure difference exists across this membrane. Combine the components such as valves, mixing functions, sample preparation can be achieved in vacuum-driven microfluidic platform. First, a compact vacuum-driven micropumping usable for conventional microfluidic platforms was introduced. A small PDMS slab with a thin membrane was designed for utilizing gas permeability of PDMS. The pump can be used by simply bonding to the outlet of microfluidic channels. A constant flow with a rate ranging from 0.8 〖[nls〗^(-1)] to 7.5 〖[nls〗^(-1)] was achieved by adjusting the PDMS wall thickness and the diffusion. In addition, a gas pressure inside the microchannel was discussed using ideal gas law. Second, microvalve designs were studied to achieve sequential sample injection with temporary stop valve and retention valves. Inherent problems of inlet pressure difference effect on backflow phenomenon in passive pumpings were discussed. Utilizing backflow for potential immunoassay applications was introduced. Third, a combination of vacuum-driven micropumping with other micropumping methods, centrifugal pumping was studied. Two applications were studied. First, recirculation of sample inside the chamber concept was studied. Switching two types of actuation methods were discussed. The goal is to achieve a high success rate of detection for potential ELISA (enzyme-linked immunosorbent assay) application, which is left as a future work. In addition, a serial dilution scheme was proposed. Quantitative real time PCR was performed to evaluate ten-fold serial dilution series. The operation time of the proposed device can be ~ 45 min. while this can be shortened by several approaches such as surface coatings. The linearity of the proposed device can achieve R^2>0.99, which is comparable to the manual preparation. Lastly, studies were summarized, and future works to achieve point-of-care testing application were discussed. The vacuum-driven microfluidic platform can be useful in many applications such as sample preparation, disease screening test.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*
Effectiveness of Dental Class II Malocclusion Correction with Invisalign as Compared to Fixed Appliances in Non Growing Individuals
No full textM.S.Purpose: To evaluate the pretreatment and posttreatment dentoskeletal effects of non growing individuals with dental Class II malocclusion treated with either clear aligners or fixed appliances, both using Class II elastics. Materials and Methods: A retrospective cohort study was completed. Digital lateral cephalograms of 65 adult healthy patients treated non-extraction using Class II elastics with Invisalign (37, mean age: 33.9 years, SD: 12.14) and fixed appliances (28, mean age: 18.9 years, SD: 1.9) were compared cephalometrically using Dolphin 3D software. Eighteen cephalometric variables were evaluated that included 12 angular and 6 linear measurements. Mann Whitney U test was used to assess dentoskeletal changes between two groups and Wilcoxon Signed Rank test was used to assess changes within groups. Results: There were statistical significant differences found for SNA, ANB, Y axis, SN-GoGn, FMA, LI-NB (mm), U6-PP (mm), L6-MP (mm) and LI-MP (mm) with p-value <0.05.There was extrusion seen with incisors and molars in both the groups except for intrusion of lower incisors (1.3 mm) in clear aligner group. Mandibular counterclockwise rotation (Yaxis :-0.6,p=0.041, SnGoGn: -0.5,p=0.024 was seen with clear aligners and clockwise rotation with fixed appliances (Y axis: 0.85,p=0.041,SnGoGn: 0.9,p=0.024). Conclusion: This study concluded that there were statistically significant dentoskeletal changes seen in Class II patients treated with clear aligners and fixed appliances. There was improved vertical control of anterior and posterior teeth, and torque control of lower incisors, with CAT relative to fixed appliances. The upper and lower incisors proclined in fixed appliance group whereas the upper incisors retroclined in clear aligner group.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*
Seismic Interaction of High-Voltage Substation Equipment Interconnected by Flexible-Bus Conductors
No full textPh.D.Substations are key parts of the electrical power grid, and consist of different types of equipment such as transformers, circuit breakers, surge arresters, disconnect switches and post insulators. In addition to electrical design considerations, these equipment must be qualified for seismic safety in accordance with IEEE standards. Currently, such qualification does not explicitly account for interaction between interconnected equipment through flexible-bus conductors. Instead, the standards recommend providing significant slack between interconnected equipment, so that the effect of interconnection is minimized. Such slack is often impractical for utility companies, due to electrical clearance requirements, and stability considerations under wind and ice loading. Furthermore, the standards presume that sudden tautness may develop in conductors due to diverging relative displacements of the equipment. To account for this effect and possible nonlinear dynamic response of conductors, the standards specify additional terminal forces or equipment base moments to be considered in seismic qualification. Such additional forces/moments would render much of current qualification invalid. Therefore, there is interest among utilities in quantifying the actual effects of interaction to possibly adapt the standards with less conservative measures. Such quantification is the focus of this research. Experiments were carried out with interconnected equipment and various flexible conductor types commonly used by utilities. Forces and moments at the conductor terminals as well as equipment base moments were measured. A new computational method was developed to model conductor dynamics. Based on experiments and computational modeling, nonlinear dynamics is found to be due to parametric resonances between in-plane and out-of-plane modes. However, violent conductor dynamics due to such nonlinear coupling does not occur in interconnected equipment subjected to transient ground motion. Nonlinear coupling mildly affects the response of interconnected equipment, causing slight aberrations in terminal forces, but does not significantly influence equipment base moments. Besides the mild occurrences of nonlinearity, the response of the interconnected system is essentially linear, and modal analysis is applicable. The mode involving diverging relative displacements has smaller participation in the interconnected system response; the mode with the equipment displacing together largely determines the overall response, particularly base moments. These findings are envisioned to form a basis to rationally adapt IEEE standards for seismic qualification of equipment better accounting for interconnection through flexible conductors.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*
The Construction of the National and Gendered Identities of Armenian Women in the Samtskhe-Javakheti Region, Georgia
No full textM.A.This study investigates the construction of national and gendered identities of Armenian women living in the Samtskhe-Javakheti region in Georgia, a region with a highly complex socio-political history. Based on conducted interviews with Armenian women living in this region, and analyses of existing documents, and policies related to national identity and women's rights that were issued by the Georgian government, the study shows that transitioning to democracy, Georgia incorporated several policies protecting rights of Armenian minorities, nonetheless, minorities are weakly integrated into the wider Georgian society. Especially Armenian women, who constitute one of the largest national minorities in Georgia and consider Georgia to be their home country, have been excluded from the political and social life of the country. Conducted in-depth interviews describe the daily challenges of Armenian women, wanting to embrace Georgian national identity and gender roles while simultaneously practicing their religion, culture, and language to preserve their ethnic identity. This study suggests that the Georgian government should pay closer attention to the needs of Armenian communities and needs of Armenian women in Georgia if it wants to build a stronger democracy and embrace the rights of minorities, as well as to create strong relationships between ethnic Georgians and ethnic Armenians. Conclusions in the study are made based on participants' personal experiences, thoughts, believes, perceptions.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*
Comparison of Extraction and Non-Extraction Treatment Outcomes in Patients with Anterior Open Bites and Hyperdivergent Mandibular Plane Angles
No full textM.S.Objectives: A hyperdivergent skeletal pattern is commonly involved in the etiology of open bites. Surgical treatment provides the most effective means of correcting the skeletal pattern and when refused by patients, alternative methods are considered including extraction of teeth. Extraction of posterior teeth has been described to decrease the hypothesized occlusal wedge facilitating a counter-clockwise, closing rotation of the mandible. This retrospective study was performed to evaluate the cephalometric skeletal vertical and dental changes with the extraction of premolars in hyperdivergent open bite cases and to compare the effects relative to non-extraction treatment in growing and non-growing patients treated at UB Orthodontics clinic. Methods: 58 patients treated at the UB Orthodontics clinic were included, having a pre-treatment high mandibular plane angle and dental anterior open bite or tendency for it. Lateral cephalograms were measured at pre-treatment (T1) and post-treatment (T2) to record the vertical facial height, mandibular plane angle, dental protrusion and vertical position of incisors and molars. The Mann-Whitney nonparametric test was used to analyze the difference between groups. Results: Statistical analyses revealed no significant difference in changes of the mandibular plane angle and vertical facial height between extraction group and non-extraction group. Significant differences were observed between groups regarding incisor retrusion, retroclination and extrusion as well as extrusion of mandibular molars. Conclusion: There was no significant difference in mandibular plane angle and vertical facial height between groups. Findings of this study do not provide evidence toward the rationale of removing premolars to decrease the occlusal wedge in order to reduce the mandibular plane angle in growing and non-growing patients with open bite.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*
The Effects of Physician's Physical Attractiveness on Patient Deception when Discussing Sexual Health
No full textM.A.Physicians depend on open and honest conversation with their patients in order to properly assess and provide appropriate healthcare; however, emerging research reveals many patients regularly lie to their physicians. Among the most consequential issues about which patients lie involves sexual health and behavior. As part of a larger study on patient deception, 290 participants were asked if they had ever lied to a physician about sexual health and, if they had, if that physician was their primary physician. Participants also completed a range of socio-demographics and were asked to rate their physician's looks on a scale of 1-10. More than half (58%) of participants reported to have lied to physicians about sexual health. Multiple logistic regression revealed links between deception and their primary physician's physical attractiveness, indicating a significant negative relationship between physician attractiveness and self-reported patient deception. Further, female participants were more likely to lie about their sexual health than male participants, and younger participants were more likely to lie about their sexual health than older patients. Implications for patient deception regarding sexual health are explored.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*
Quality Assurance of Inkjet 3D Printing for Bioprinting Application
No full textM.S.Inkjet 3D printing has emerged greatly in bioprinting and a lot of research is still needed for improving quality and accuracy for printing. In this research, quality of jetting is studied with identifying pinching behavior for droplet formation. The DOD, i.e., drop on demand method-based inkjet printer with a piezoelectric actuator and hydraulic pressure control system and jet driver is used for experimentation. Strobing technology is used with a high resolution of camera for collecting image recordings. The experiment is conducted by generating the random values table for operating conditions for each pressure set from -2.00 to pressure -6.00. The jetting behavior and quality of jetting is observed and characterized with nature and description for jetting, including satellite formation, alignment, ligament formation, stability and unstable nature for jetting. The effect of operating parameters such as pressure, voltage, excitation waveform, dwell time, echo time, fall time, rise time on jetting and droplet formation are discussed with a case study with DI water. Further experiments are conducted and image recordings are observed for expected pinching behavior. Experiment results show that classification for pinching behavior, quality of jetting and optimal operating conditions are recognized with image recordings.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*
Development and Manufacturing of a Ductile Cooling Phase Change Material
No full textM.S.In this study, the use of a thermally passivated hydrogel composite material for personal cooling purposes offering high flexibility and conformability has been demonstrated. Thermal and mechanical evaluation of the hydrogel composite revealed high degrees of tailorability in its composition and material arrangement to tend to specific requirements. The composite exhibits a superior cold retention capability ranging from 1.35 hours to 12.41 hours based on the tested samples. Mechanical testing of the samples indicates a measure of their flexibility and toughness offering a Young's Modulus in the range of 0.14 MPa to 1.54 MPa and fracture energy in the range of 10.40 kJ m-2 to 112.65 kJ m-2 based on the tested samples. This research studies the various factors that influence the thermal and mechanical properties of the hydrogel composite and their impact on the same. It establishes the scope and potential use of hydrogel as a Phase Change Material (PCM) based personalized cooling solution with tailorable mechanical properties.**To request an accessible version of the file(s) associated with this item, contact [email protected]. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.*