2313 matches in the database.
These are records: 1 - 30.
[1] [2] [3] [4] [5] … [78]
1.
LAAKE, REBECCA A.
DEPICTION OF SEXUALITY IN MUSIC VIDEOS.
Degree: MEd, Education : Health Promotion and Education, 2005, University of Cincinnati
► The purpose of this study was to examine the sexual messages depicted…
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▼ The purpose of this study was to examine the sexual messages depicted in music videos based on gender and music television network. A sizeable percentage of adolescents currently engage in sexual behavior. The depiction of sexuality in the media may affect adolescents’ perception of and involvement in sexual behaviors. The findings of this study may be particularly useful to professionals interested in developing effective interventions aimed at preventing such involvement. A 4-page coding sheet was developed to assess sexuality in music videos. The coding sheet consisted of three primary subscales: 1) attire; 2) dance/behavior; 3) location of sexual activity. The units of analysis were music videos aired on MTV, MTV2, BET, and GAC during August 2004. One-hour segments of music videos were taped daily for two weeks. Depictions of attire, dance/behavior, and sexual activity were tallied. Subscale items were summed by gender, resulting in total sex subscale scores. Results indicated a sizeable percentage of music videos contained sexual themes and sexual depictions. A series of analyses of variance were conducted and found significant differences (p < .05) based on an array of demographic variables. More specifically, female attire was more sexually provocative than male attire. In addition, female behavior was more sexually provocative than male behavior. Significant differences were also found based on music television network. A series of analyses of variance were conducted that found significantly more sexually explicit attire and sexually explicit behavior of characters on BET than characters on MTV, MTV2, or GAC. Furthermore, BET had an average sex score of 758.88 depictions per video of sexual attire and sexual behavior, followed by MTV with an average sex score of 206.75 depictions per video.
Advisors/Committee Members: King, Dr. Keith A.
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2.
Labde, Rohan Khushal.
Preparation and Characterization of Polyethylene Terephthalate/Montmorillonite Nanocomposites by In-situ Polymerization Method.
Degree: MS, Chemical Engineering, 2010, University of Toledo
► Polymer nanocomposites are prepared by dispersing small quantities (0.5-10% by weight) of…
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▼ Polymer nanocomposites are prepared by dispersing small quantities (0.5-10% by weight) of nano-sized particles which have high aspect ratios (100-1500) and high surface area (in excess of 750-800 m2/g) into the polymer matrices. Polymer nanocomposites offer improvements over conventional composites in mechanical, thermal and barrier properties without substantially increasing the density or affecting the light transmission properties of the base polymer. The objective of this project is to develop a new process for preparation of polyethylene terephthalate (PET)/montmorillonite (MMT/Na+MMT) nanocomposite and to characterize it. During the study, we tried to disperse natural clay (Na+MMT) in PET polymer monomers by different methods. Natural MMT clay has been chosen to prepare PET nanocomposites because previous studies with organoclays have shown that organically modified clays get thermally degraded at PET preparation and processing temperatures (~280 °C) and because of degradation, PET nanocomposites do not show expected improvement in properties. PET nanocomposites were prepared by dispersing pristine MMT (Na+MMT) clays into ethylene glycol (esterification-ES clay addition) and bishydroxy ethylene terephthalate (polycondensation-PC clay addition). Thermal, mechanical and barrier properties of these nanocomposites have been studied in comparison to those of neat PET. Differential scanning calorimetry (DSC) results were used to study thermal properties and it was observed that regardless of weight percentage of Na+MMT clay in PET matrices, there were no significant changes in glass transition temperatures (Tg) or melting temperatures (Tm) of the nanocomposites compared to neat PET. It was observed, however, that crystallization rate had increased at higher clay loading because of agglomeration of clay in the PET polymer matrices. For 0.5 wt% ES clay addition PET nanocomposite, tensile strength and tensile modulus observed to be increased by 85% and 92% respectively compared to that of neat PET. As clay percentage increased further, decrease in mechanical properties was noticed because of agglomeration of clay. Compared with neat PET, 0.5 wt% ES clay addition nanocomposite showed 30-40% increase in oxygen barrier properties. Different theoretical models were used to calculate values of tensile modulus and oxygen permeation for given clay content in the PET matrix and compared with experimental values of PET/ Na+MMT nanocomposites. It is concluded that the ES clay addition method resulted into better dispersion of Na+MMT clay into the PET matrices than the PC clay addition method. It is very easy and efficient method to prepare PET/Na+MMT nanocomposites and results into the nanocomposites having better properties than that of neat PET without organic modification of natural MMT.
Advisors/Committee Members: Jabarin, Saleh.
Subjects: Chemical engineering
Keywords: PET; Polyethylene Terephthalate; Nanocomposite; clay; MMT; Montmorillonite; In situ polymerization
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3.
LaBeaud, Angelle Desiree.
New Understanding of the Epidemiology of Rift Valley Fever Virus in Kenya.
Degree: MS, Clinical Research, 2009, Case Western Reserve University
► Rift Valley fever virus (RVFV) is an emerging high priority pathogen that…
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▼ Rift Valley fever virus (RVFV) is an emerging high priority pathogen that threatens livestock and human health. In order to define the range of human transmission during interepidemic and epidemic periods in Kenya, archived sera (N = 1263) were tested for anti-RVFV IgG by ELISA and plaque reduction neutralization testing. RVFV seroprevalence was 10.8% overall and varied significantly by location, gender and age. Because most RVF outbreaks occur in remote locations following floods, environmental risk factors and human sequelae are not fully known. During an interepidemic period in 2006 a randomized household survey (N=248) was performed to examine age- and location-specific RVFV seroprevalence rates, and their association with health status and animal/non-animal exposures. Overall RVFV seroprevalence was 13% and interepidemic RVFV transmission was documented. Seropositivity increased with older age, rural village, male sex, and abortus disposal. The extent of epidemic and interepidemic RVFV transmission is greater than previously documented.
Advisors/Committee Members: Dawson, Neal V.
Subjects: Epidemiology; Health; Public health; Virology
Keywords: Rift Valley fever virus; Kenya; viral hemorrhagic fevers; bioterrorism; arboviruses; Bunyaviridae; risk factors; epidemiology
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4.
Labelle, Maurice Marc Jr.
Traces of Empire: Decolonization and the United States in Lebanon, 1941-1967.
Degree: PhD, History, 2012, University of Akron
► This dissertation explores how the United States became an “imperial” power in…
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▼ This dissertation explores how the United States became an “imperial” power in Lebanese imaginations after its political decolonization. As Lebanon obtained its full constitutional independence in 1946, a shift occurred in how Lebanese peoples perceived and encountered U.S. global power. Despite the United States’ anti-imperial rhetoric and support for Lebanese self-determination, many Lebanese increasingly grew disenchanted with real and imagined U.S. interferences in national and regional affairs, as well as Washington’s apparent blatant disregard for Arab human rights. In particular, U.S. public declarations in favor of Zionism and support toward the creation of Israel—a perceived product and surrogate of Western imperialism—in May 1948 led many to question U.S. motives in the Middle East, interrogate the United States’ so-called anti-imperial tradition, and equate Lebanon’s post-independence present with its colonized past. Despite being self-governing, Lebanese society imagined itself in a constant state of decolonization as traces of empire remained and jeopardized Lebanon’s sovereignty. The U.S. military intervention in the Lebanese civil war of 1958 contributed to ongoing constructions that considered Washington to be openly disregarding Lebanese public opinion and stepping into the shoes of fading imperial powers in the Middle East: Britain and France. The U.S. sale of Hawk anti-aircraft missiles to Israel in 1962 and, finally, the popular belief that the United States colluded with Israel during the third Arab-Israeli war of 1967 formalized the process in which U.S. “empire” became a reality in Lebanese mindscapes. By the war’s end, many Lebanese peoples viewed the United States as being far from exceptional as it had fully embraced an “imperial” policy and culture like others before it and stood at odds with decolonization.
Advisors/Committee Members: Hixson, Walter.
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5.
LaBerge, Kelsen.
Exploratory Research on a Method for Detecting Shaft Radial Cracks: Severity, Location, and Feasibility.
Degree: PhD, EMC - Mechanical Engineering, 2008, Case Western Reserve University
► Crack failure is among the most dreaded failures experienced in rotating machinery.…
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▼ Crack failure is among the most dreaded failures experienced in rotating machinery. It is therefore important to be able to detect a crack before failure occurs and cost effective to know the location and severity of a crack making it possible to predict the behavior and life of the machinery. This dissertation outlines a method of crack detection using the elastic wave created by the snapping shut of a radial crack to determine these characteristics. To determine the feasibility of such a method, preliminary research is performed by examining the behavior of a crack in 4-point-bending. A theoretical solution for the elastic wave behavior is determined by modeling the behavior as the collinear impact between two shafts. A theoretical impact velocity is found using finite element modeling to examine crack geometry. A pendulum experiment is performed in order to examine the validity of the assumed theoretical acceleration at the shaft end. The experimental acceleration response is smaller than the theory because the volume of air caught between the shaft face and the wall has to be expelled. This is explained by Reynolds lubrication equation which proves this hypothesis. An experiment to test the 4-point-bending theory is presented. More work is needed to determine the feasibility of such a crack detection method, such as running a 4-point-bending experiment as the design for which is presented.
Advisors/Committee Members: Adams, Maurice.
Subjects: Engineering; Mechanical engineering
Keywords: crack; rotor; rotating machinery; elastic waves; crack detection
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6.
LaBlanc, Kelly J.
USING GLACIAL DISPERSAL PATTERNS TO UNDERSTAND THE SPATIAL DISTRIBUTION OF SUBGLACIAL QUARRYINGDr.
Degree: PhD, Arts and Sciences : Geology, 2007, University of Cincinnati
► Quarrying of bedrock beneath a glacier produces coarse-grained sediment, helps maintain bed…
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▼ Quarrying of bedrock beneath a glacier produces coarse-grained sediment, helps maintain bed roughness, and creates rock tools for abrasion. Despite the importance of the process in the formation of glacial landforms and sediments, much remains unknown about its basic mechanics, controlling mechanisms, and rates. Characterizing the variation of quarrying along glacial flowlines is vital in understanding the quarrying process. If the pebble dispersal patterns preserved in glacial sediments do not conform to those predicted by a given model for quarrying, then the ice dynamics and process mechanics that control quarrying are unlikely to be consistent with that model. Three linear functions describing the spatial distribution of quarrying intensity along a glacial flowline were tested using pebble dispersal patterns preserved in the glaciated valleys in the Sawatch Range of Colorado and in the Appalachian Ice Complex of the South Mountain Batholith region of Nova Scotia. The functions represent simple forms of three unique distributions: 1) a case where quarrying is increasing in intensity down a glacial flowline, 2) a case where quarrying is decreasing in intensity down a glacial flowline, and 3) a constant case where quarrying intensity is uniform along the flowline. Iterative computer models combine the quarrying intensity distributions with information on the bedrock distribution and flow history of the study areas to predict pebble dispersal patterns. The modeled dispersal patterns were compared to observed patterns statistically to identify the best fit. The case where quarrying intensity is distally increasing was found to best predict observed pebble dispersal patterns. Modeling indicated that dispersal patterns were probably created during the advance phase with only minor modification during the retreat phase. Dispersal patterns in the South Mountain Batholith area are mostly the result of the last phase of glaciation with little inheritance from previous phases. The agreement between the two study areas suggests that the controls on quarrying or that quarrying mechanisms are independent of the size of the ice mass. The increasing intensity of quarrying in the marginal area is likely due to increased frequency and magnitude of water pressure changes in subglacial cavities.
Advisors/Committee Members: Lowell, Dr. Thomas V.
Subjects: Geology
Keywords: subglacial erosion, quarrying, glacial dispersal, Sawatch Range, Nova Scotia
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7.
Labovitz, Katie E.
A Content Analysis of the Gender of Academy Award Nominees and Winners for Films Released between 1927 and 2010.
Degree: MS, Journalism (Communication), 2011, Ohio University
► Using a coding instrument designed specifically for this study, the researcher analyzed…
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▼ Using a coding instrument designed specifically for this study, the researcher analyzed the gender of Academy Award nominees and winners in all categories in which potential for direct competition between women and men existed. This study examined if there was gender discrepancy in terms of whose work was recognized in the film industry by the Academy of Motion Pictures Arts and Sciences. Data from 83 Academy Awards ceremonies honoring the films released from 1927 to 2010 yielded 1,471 cases that, when analyzed, supported the statement that more men than women have been nominated for, and winners of, Academy Awards in every category other than Costume Design. Examining the results by year of nominations, wins, and categories showed trends in the numbers of women and men nominees and winners. Even though men nominees and winners still dominate every ceremony, there is a pattern of more women being nominated for and winning Academy Awards. Recent decades have also shown an increase in the number of categories that included female Academy Award nominees.
Advisors/Committee Members: Bernt, Joseph.
Subjects: Communication; Film Studies; Gender; Journalism; Motion Pictures
Keywords: Academy Awards; Gender; Academy Award Nominations; Academy Award Wins; Women in Film; Film Industry
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8.
Labronici, Marcos.
Effect of silicone interlayer on carbon fiber reinforced PMR-15 composite: Processing and characterization.
Degree: PhD, Macromolecular Science, 1994, Case Western Reserve University
► The objective of this work is to study the effect of silicone…
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▼ The objective of this work is to study the effect of silicone as an interlayer material in carbon fiber reinforced PMR-15 polyimide composites. Viscous and elastomeric silicones are applied as interlayers to these composites in order to develop a tougher and microcrack resistant composite, while preserving the excellent thermo-oxidative resistance of the PMR-15 polyimide matrix. Carbon fiber is continuously coated with high molecular weight polydimethylsiloxane and polymethylvinylsiloxane (780,000) in hexane. Uncured polydimethylsiloxane (PDMS gum) is the viscous interlayer studied and polydimethylsiloxane (PDMS elastomer) and polymethylvinylsiloxane (PVMS elastomer) cured with peroxides are the two forms of silicone elastomers studied. The effect of the amount and the type of these forms of silicones on the mechanical and dynamic mechanical properties of unidirectional composites are studied. It is shown that the silicone interlayer enhances impact strength, toughness, and microcrack resistance. The enhancement depends on the interlayer thickness, coating process, and laminate fabrication process chosen as well as the type of the silicone. Flexural and interlaminar shear strength is found to drop with the presence of the interlayer. It is demonstrated that the mechanical proper ties of the composites with silicone interlayers is not affected by thermal aging at 300°C for 100 h. The dynamic mechanical properties of the composites are determined and compared with uncoated carbon fiber reinforced PMR-15 polyimide composites. The presence of the interlayers are observed by the appearance of a new relaxation peak in dynamic mechanical spectra. The temperature of this peak is found to be a good indication of the degree of the cure of the silicone elastomer. Apparent activation energy of the α transition of the matrix in the modified composites varies with the amount and type of silicone interlayer in concert with the impact strength. The variation of the activation energy is explained in terms of structural changes within the matrix that arise from interfacial effects due to the presence of the soft interlayer. The main structural change within the matrix is believed to be a decrease in the free volume caused by the relieving of internal stress
Advisors/Committee Members: Ishida, Hatsuo.
Subjects: Plastics Technology
Keywords: Silicone interlayer; Carbon fiber reinforced PMR-15 composite
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9.
Lab, Scott.
Structural Evaluation of LIC-310-0396 Box Beams with Advanced Strand Deterioration.
Degree: MS, Engineering : Civil Engineering, 2010, University of Cincinnati
► Four adjacent prestressed concrete box beams were removed from a decommissioned bridge…
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▼ Four adjacent prestressed concrete box beams were removed from a decommissioned bridge and tested to destruction. The beams were 36 inches wide by 17 inches deep and had a span length of 37 feet 6 inches. Each beam contained fourteen, 1/2 inch diameter, stress relieved prestressed strands. All of the prestressed strands were arranged in one layer, which was located below the stirrups. One beam was in good condition, with the only visible deterioration being longitudinal cracking. One beam had three corroded prestressed strands visible and a large spalled segment which, when removed, exposed two additional prestressed strands. The remaining two beams were badly deteriorated, with spalled concrete exposing seven corroded prestressed strands. The provisions of the AASHTO LRFD Bridge Design Specifications, the AASHTO Standard Specifications, and the PCI Design Handbook were used to evaluate the loss of prestressing force. The measured prestressing force loss was closest to the AASHTO LRFD Bridge Design Specifications, but all three methods provided conservative estimates of prestressing force loss. The bridge had been designed using the AASHTO Standard Specifications. The provisions of the Standard Specifications were conservative in determining the ultimate loading for the undeteriorated beam. The provisions of the Standard Specifications were also conservative in determining the ultimate load for the deteriorated beam if the deteriorated strands were assumed ineffective. The deteriorated concrete box beams were all ductile and had final deflections exceeding L/50. The original bridge was rated using the test results. When following the provisions of the AASHTO Standard Specifications, the designed service loading for the bridge would have exceeded the ultimate loading of one deteriorated middle span beam. A failure of this beam would not have caused a progressive failure of the middle span under service loadings. Following the Load Factor Rating method for the middle span beams, the loadings exceeded the strength of the members. Therefore, load restrictions would have been required for the bridge had it not been decommissioned.
Advisors/Committee Members: Miller, Richard.
Subjects: Civil engineering
Keywords: destructive testing; deteriorated; prestressed; box beam; bridge
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10.
Labuda Schrop, Susan M.
The Relationship between Patient Socioeconomic Status and Patient Satisfaction: Does Patient-Physician Communication Matter?.
Degree: PhD, College of Arts and Sciences / Department of Sociology, 2011, Kent State University
► The therapeutic efficacy of the patient-physician interaction plays a central role in…
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▼ The therapeutic efficacy of the patient-physician interaction plays a central role in medicine. Many factors impact the patient-physician interaction, and ultimately affect health outcomes. Health follows a social gradient. Being poor matters to health and health care access in the U.S. with socioeconomic status being a strong, consistent predictor of morbidity and mortality. Health disparities include differences in health status; access to, utilization, and quality of care; and health care delivery. Unequal treatment of patients on the basis of their personal or group characteristics warrants attention, unequal treatment not justified by the patient’s underlying health condition or treatment preference. This dissertation examined the relationship between patient socioeconomic status and patient satisfaction, and determined if patient-physician communication mediated this relationship. Three hypotheses were tested though secondary analyses of data from the Direct Observation of Primary Care study, a landmark multi-method study representing the most comprehensive glimpse into the content and context of family medicine outpatient visits to date. The data supported hypothesis 1. Patients’ insurance status related significantly to physician-patient communication. Patients insured by Medicaid had visits that were significantly more physician-centered. In addition, male patients, patients with better physical health, and patients whose visits were more complex had visits that were more patient-centered. Conversely, as patients’ mental health improved, the visits became more physician-centered. Results were mixed for hypothesis 2. Satisfaction with the care-delivery site was unrelated to communication but was significantly related to patient age and overall health with older and healthier patients rating the site significantly higher. Communication related significantly to satisfaction with the physician and overall satisfaction. Satisfaction with the physician and overall satisfaction increased significantly as the visit became more patient-centered. In addition, older patients, those with better overall health and shorter visits rated satisfaction with the physician and overall satisfaction significantly higher. The data did not support hypothesis 3. There was no relationship between socioeconomic status and patient satisfaction. The next steps need to be creating and validating easy-to-administer patient satisfaction measures and the determining the optimal balance between patient-centered and physician-centered communication measured by validated instruments.
Advisors/Committee Members: Gallagher, Timothy.
Subjects: Sociology
Keywords: patient-physician communication; medical communication; patient satisfaction; patient-centered communication; physician-centered communication
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12.
Lachat, Veronique M.
Understanding Oil Resistance of Nitrile Rubber: CN Group Interactions at Interfaces.
Degree: PhD, Polymer Science, 2008, University of Akron
► Nitrile rubber (NBR) is copolymer of acrylonitrile and butadiene. It is resistant…
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▼ Nitrile rubber (NBR) is copolymer of acrylonitrile and butadiene. It is resistant to swelling by hydrocarbon oils. Swelling and thermal degradation decrease as acrylonitrile content increases. Infrared-visible Sum Frequency Spectroscopy (SFS) is used in the present study to probe the molecular origin of oil resistance. SFS is a surface specific spectroscopic technique and was used to probe an NBR/liquid interface. Oil resistance of the NBR is reflected in changes in the SFS spectra of NBR at the interface. As reference materials, two additional polymers polyacrylonitrile (PAN) and polybutadiene (PBD) were included and analyzed prior to analyzing the nitrile rubber. SFS analysis of the film revealed a shift of the CN stretching mode at the sapphire/PAN interface compared to that of PAN bulk when the PAN film was annealed above its glass transition temperature. This demonstrates how environment affects nitrile dipole-dipole interaction. The influence of liquid environment on the PAN surface was directly assessed by comparing the SFS spectra of the PAN/air to that of PAN/heptane and PAN/water interfaces. This showed a minor effect of the solvent on the nitrile CN stretching mode of PAN. The second section was devoted to the analysis of PBD. A positive shift of the methylene stretching mode of PBD is detected in the SFS spectrum. This indicates that the polar sapphire surface influences the specific vibrational mode of PBD. Finally, NBR rubbers with 40% or 20% acrylonitrile content (ACN) were characterized. In the SFS spectra of NBR (40% and 20 ?N)/air surfaces, a new vibrational band was observed at 2050 cm-1, in addition to the CN stretching mode of nitrile rubber at 2233 cm-1. This band was not detected in bulk NBR (40% and 20% ACN). Additives in bulk NBR were determined using High Performance Liquid Chromatography (HPLC). Results suggested the presence of amines molecules. However, purified NBR also showed the 2050 cm-1 band. There are a limited number of assignments that can be present in this range. This includes nitrile groups interacting with salts. Probable assignments are proposed after considering the chemical compounds present in NBR emulsion polymerization. The final part of this dissertation is concerned with the interaction between an NBR film and two solvents: heptane and toluene. No change at the sapphire/NBR interface upon heptane exposure indicates the stability of the NBR film in contact with heptane. This is in accord with the oil resistance of NBR to hydrocarbon solvents. Solubilization of the NBR rubber thin film after toluene exposure is revealed by changes in the SFS spectrum at the sapphire/NBR interface. This shows that SFS is capable of accurately detecting molecular changes at polymer/liquid interfaces. SFS results are consistent with the resistance of NBR to aliphatic solvent and instablity in aromatic solvents. Quantitative interpretation of the oil resistance will require an assignment of the 2050 cm-1 absorption band.
Advisors/Committee Members: Dhinojwala, Ali.
Subjects: Polymers
Keywords: nitrile rubber; solvent resistance; Sum Frequency Spectroscopy
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13.
LACHEY, JENNIFER LYNN.
THE ROLE OF THE CENTRAL GLUCAGON-LIKE PEPTIDE-1 IN MEDIATING VISCERAL ILLNESS.
Degree: PhD, Medicine : Interdisciplinary (Medical Science Scholars, Neuroscience), 2002, University of Cincinnati
► Central administration of glucagon-like peptide-1 (GLP-1) produces responses similar to those produced…
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▼ Central administration of glucagon-like peptide-1 (GLP-1) produces responses similar to those produced by a toxic LiCl dose, the prototypical visceral illness-inducing agent. These responses include anorexia, conditioned taste aversion (CTA) learning and distinct Fos activation. Importantly, in the rat, LiCl administration Fos activates a significant number of preproglucagon-producing cells. Additionally, in the rat, pretreatment with a GLP-1 receptor (GLP-1R) antagonist attenuates these illness responses. Together, these data led to the hypothesis that the central GLP-1 system mediates visceral illness. To further describe GLP-1 action in visceral illness, we determined LiCl ability to elicit anorexia, CTA learning and Fos activation in mice lacking GLP-1 signaling (GLP-1R -/-) expecting these responses would be absent or attenuated. Consistent with this prediction, GLP-1R -/- mice exhibit reduced Fos activation in brain regions downstream of GLP-1R signaling compared to +/+ controls. In contrast to our prediction, GLP-1R -/- mice are anorectic and form a CTA in response to LiCl. These data support the idea that there is a species difference between mouse and rat for the visceral illness system or that unknown interactions for GLP-1 and/or its antagonists exist. Our finding that central GLP-1 administration is able to support CTA learning in mouse as it does in rat does not support species differences as the primary explanation for the discrepant pharmacological and genetic data. Furthermore, GLP-1 is not able to support a CTA in GLP-1 -/- mice. This result supports the contention that these effects are mediated by the sole identified GLP-1 receptor. Taken together, these results raise the possibility that developmental compensation occurs in GLP-1 -/- mice such that alternate systems mediate the effects of LiCl to produce visceral illness responses.
Advisors/Committee Members: Seeley, Dr. Randy J.
Subjects: Biology, Neuroscience
Keywords: visceral illness; glucagon-like peptide-1; nucleus of the solitary tract; emesis; lithium chloride
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14.
Lachhman, Shem Benjamin.
Roller-Cast Poly-Dimethylsiloxane as a Non-Hermetic Encapsulant for MEMS Packaging.
Degree: MS, EECS - Electrical Engineering, 2012, Case Western Reserve University
► This thesis describes the development of a roller-casting process for multi-layered poly-dimethylsiloxane…
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▼ This thesis describes the development of a roller-casting process for multi-layered poly-dimethylsiloxane films to be used as an encapsulant for implantable MEMS. Accelerated lifetime studies were conducted at 40°C and 85°C in saline solution on sixteen samples each containing eight interdigitated electrode arrays and encapsulated with Dow Corning MDX4-4210 Biomedical Grade Elastomer. A custom environmental testing system designed for long-term, unmonitored testing was built to acquire resistance measurements. Select samples received surface treatments prior to PDMS deposition to enhance adhesion and were evaluated by pull-off tests before and after soak testing. Test results show lifetimes up to 40 days for samples tested at 85°C. Samples in 40°C saline solution are still under test with no device failures after 68 days. The estimated maximum lifetime of packages made using the roller casting method based on previously published data is 5.5 years at physiological temperature (37°C) and 22.2 years at 25°C.
Advisors/Committee Members: Zorman, Christian.
Subjects: Electrical Engineering
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15.
Lach, Michelle R.
Technology in the arts.
Degree: MFA, Art, 1998, Ohio State University
► Computers offer both the artist and the viewer a new vehicle through…
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▼ Computers offer both the artist and the viewer a new vehicle through which to speak, listen and interact. Suddenly, it seems the world looks very different when seen through digital eyes. Many artists believe that conceptual ideas matter more, but the impact of digital media on art is unwavering. It is now possible to shape and share sounds, pictures, movies, sculptures, and more with a single tool.The exhibition titled Hybrids is a multi-media, interactive installation consisting of three separate yet totally integrated works. Hybrids are crossbreeds, mongrels, and monsters, balanced on the precipice between species and kind. They emerge nameless in the boundaries. These hybrids are part of a subterranean garden somewhere between Eden and Armageddon where there is no chance of salvation, only messy amalgams of flesh and machine, woman and wire. These pieces merge organic form with hardware.The Hybrids exhibition embodies three components: Beckoning, Seedpod: Parthenogenesis and (Re)genesis: Lilith 0 & Lilith 1. Beckoning is created through the metamorphosed layers of tissue-wire and wax, sinews and skin that later compose her self-generating sister components. The Nagini, a cyborg-goddess, part woman and part snake, emerges in a loop, forever mediated by, yet interrupting, the machinery that gave birth to her. Embedded in this monstrous fusion, she is simultaneously an invitation and a warning. Seedpod: Parthenogenesis is a gigantic, chimerical ovum turned ever-inward. Multi-eyed with lenses vaguely reminiscent of the insect world, the internal surfaces reflected are simultaneously deep and superficial. The cyclical patterns of light emanating from the origin evoke conception. However, peering in to examine any future progeny one sees only the guts of the machine. (Re) genesis: Lilith 0 & Lilith 1 takes form through the filtered (anti)history of women. The shrouded heads of the sister-clones push through thicket, through bronze and aluminum. They are bound electronically, accruing enough current to generate cellular divisions in the pools above them. The pools are filters, distorting and warping the images as the sister-clones mock and distort reproduction, offering in their pools a proliferation of promiscuous microorganisms. The integration of these components exemplifies the coexistence of contradictory qualities.Digital reality continues the ancient human struggle between two mutually exclusive elements: the reality of the degeneration of human flesh, and the apparition of escape from the body and its secretions to the technological body. Yet, how close are we to human fertility downloaded into artificial life forms? Humanity and technology reflect the same. They are found at the same time and place, which is both necessary and impossible. They move together, but they cover each other over and are never separated from one another creating a haven for the inevitable crossbreed of human and non-human.
Advisors/Committee Members: Dallas-Swann, Susan.
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16.
Lacki, Brian Cameron.
Cosmic Rays in Star-Forming Galaxies.
Degree: PhD, Astronomy, 2011, Ohio State University
► Cosmic rays (CRs) are high energy particles that are found wherever in…
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▼ Cosmic rays (CRs) are high energy particles that are found wherever in the Universe star formation is occurring. I investigate several problems in the propagation of CRs in star-forming galaxies. By applying analytic models and numerically solving the “leaky box” differential equation, I calculate the population of primary and secondary CR protons, electrons and positrons in model star-forming galaxies and their nonthermal emission. Observations show that the synchrotron radio emission of star-forming galaxies grows linearly with the infrared emission from dust-obscured young stars; this is the FIR-radio correlation (FRC). To explain the correlation, I constructed one-zone models of galaxies over the dynamic range of the FRC. I found that the FRC is caused by conspiracies of several factors, including CR escape from galaxies, ultraviolet (UV) dust opacity, non-synchrotron cooling, and secondary electrons and positrons generated by CR protons. The conspiracies have great implications for the evolution of the FRC at high redshift, preserving it and allowing variations in the FIR-radio ratio for submillimeter galaxies. Recent gamma-ray observations of M82 and NGC 253 indicate that CR protons lose much of their energy to collisions in these galaxies’ dense gas, where they generate unstable pions that decay into gamma rays and secondary particles. The ratio of gamma-ray to radio luminosity indicates that secondary electrons mostly do not cool by synchrotron emission, supporting a conspiracy origin of the FRC. I also compare the intensities of the diffuse cosmic gamma-ray background to the X-ray and radio backgrounds. From this comparison, I find that Inverse Compton is a minority of the X-ray background, and that the radio background is probably not from starbursts. Finally, I modeled the nonthermal X-ray emission from starburst galaxies, both synchrotron from TeV electrons and Inverse Compton from GeV electrons. The synchrotron emission is enhanced by gamma-gamma pair production in the intense infrared radiation of starbursts. Synchrotron and Inverse Compton emission make up 1 - 10% of the observed diffuse hard X-ray emission observed in starburst galaxies.
Advisors/Committee Members: Thompson, Todd.
Subjects: Astronomy; Astrophysics
Keywords: cosmic rays; galaxies; radio emission from galaxies; gamma rays from galaxies; cosmic radio background; cosmic gamma-ray background
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17.
Lackner, Laura L.
Investigating the Mechanism of Escherichia coli Min Protein Dynamics.
Degree: PhD, Molecular Biology and Microbiology, 2006, Case Western Reserve University
► In Escherichia coli the pole-to-pole oscillation of the MinC division inhibitor is…
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▼ In Escherichia coli the pole-to-pole oscillation of the MinC division inhibitor is required for proper placement of the division machinery. The membrane association/dissociation cycle of MinC is driven by the MinD ATPase and the MinE topological specificity factor, which themselves undergo a coupled oscillatory localization cycle. During this cycle, MinD and a portion of MinE assemble on the membrane along one cell half in a pattern resembling a test tube (the MinD/E tube), while another portion of MinE assembles at the rim of this tube forming a ring-like structure (E-ring). To understand the biochemical mechanisms behind Min protein dynamics, we investigated the interactions of purified Min proteins with ATP and phospholipid vesicles. We found that the ATP-bound form of MinD binds phospholipid vesicles in a cooperative fashion and recruits both MinC and MinE to the vesicles. In addition, we found that MinE stimulates the dissociation of MinC, MinD, and itself from the vesicles. Thus, ATP and MinE play critical roles in regulating the association and dissociation, respectively, of the Min proteins and the membrane. MinE has two known functional domains: the N-terminal anti-MinCD domain (DMinE) and the C-terminal topological specificity and dimerization domain (TSMinE). We investigated the contributions of each domain of MinE in the regulation of Min protein-membrane dissociation. We found that DMinE is necessary and sufficient to stimulate dissociation of the Min proteins from the membrane. However, TSMinE is required to establish Min protein oscillation in a majority of cells. In addition, TSMinE is also required for E-ring formation. These results suggest that TSMinE and perhaps E-ring formation play a critical role in Min protein oscillation by helping to initiate and/or sustain Min protein dynamics. Characterization of the MinD mutant MinDK16R revealed an additional role for MinE. While MinE does not induce MinDK16R oscillation, MinE does promote the accumulation of MinDK16R into static membrane-associated spiral-like structures. We propose that these structures may represent a stage in the dynamic Min protein oscillation cycle, therefore, suggesting that MinE has at least two roles in Min protein dynamics, regulating Min protein-membrane dissociation and regulating Min protein spiral formation.
Advisors/Committee Members: de Boer, Piet.
Keywords: Min system; MinD; MinE; cell division; E.coli cell division
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18.
Lackney, Lisa M.
From Nostalgia to Cruelty: Changing Stories of Love, Violence, and Masculinity in Postwar Japanese Samurai Films.
Degree: MA, History, 2010, University of Akron
► Samurai films not only educated Americans about how to think of Japan,…
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▼ Samurai films not only educated Americans about how to think of Japan, but also provided an opportunity for postwar Japanese to collectively process the effects of Japan's postwar subjugation and rapid but often inequitable economic development. A close examination of samurai films indicates two predominant forms between 1953 and 1970. Far from being a static genre that embraced choreographed fight scenes and larger-than-life heroes, postwar samurai films reflected the changing values of their time: samurai films of the mid-1950s called for a return to prewar values while 1960s films used cynicism and violence to critique the failures of society. Values espoused by nostalgic films popular in the decade or so after the end of the Second World War form a sharp contrast to the repudiation of those values in films of the following decade and highlight the principal tensions—both generational and demographic—that would accompany Japan’s re-emergence as an independent nation and industrial powerhouse by the 1970s.
Advisors/Committee Members: Zhao, Gang.
Subjects: Fine Arts; Gender; History
Keywords: Japan; samurai; film; cinema; popular culture; masculinity; romance; violence; Kurosawa; postwar
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19.
Lacombe, Véronique Anne.
Muscle Glycogen Metabolism in Horses: Interactions Between Substrate Availability, Exercise Performance and Carbohydrate Administration.
Degree: PhD, Veterinary Clinical Sciences, 2003, Ohio State University
► Horses undertake recreational activities that decrease muscle glycogen stores. Similar to humans,…
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▼ Horses undertake recreational activities that decrease muscle glycogen stores. Similar to humans, muscle glycogen availability may influence exercise performance. In the first study, a model of glycogen depletion was developed and used to investigate the effect of muscle glycogen availability on the athletic capacity of horses. We demonstrated that exercise-induced muscle glycogen depletion was associated with a 60% decrease in anaerobic capacity during subsequent exercise, without effect on aerobic capacity. To rule out any confounding effects of other exercise-induced changes, a second study investigated the effects of muscle glycogen depletion and subsequent replenishment on athletic capacity. In a blinded crossover study, seven fit horses received either an intravenous glucose or saline infusion after exercise. Run time to fatigue, accumulated oxygen deficit and blood lactate concentration during a subsequent high-speed exercise test were greater for the horses with normal muscle glycogen concentration than for the horses with persistent muscle glycogen depletion. It was concluded that muscle glycogen availability influences anaerobic capacity and ability to perform high-intensity exercise in horses. Given the critical role of adequate glycogen stores in enabling optimal performance, the factors and mechanisms affecting muscle glycogen replenishment in horses were studied. We first demonstrated that intravenous glucose infusion (6g/kg) hastened muscle glycogen resynthesis compared to saline infusion. The effect of 3 isoenergetic diets of varying glycemic indices on the rates of muscle glycogen synthesis after exercise was evaluated in a crossover study. Seven horses received either a high soluble carbohydrate diet (grain, HCO), or a low soluble carbohydrate diet (hay, LCO), or a mixed diet (M) every 8 hours for 72 hours after exercise. We demonstrated that muscle glycogen resynthesis is slower in horses than in humans. Feeding high-glycemic index (HCO) meals hastened muscle glycogen replenishment compared to LCO and MCO diets by increasing blood glucose and insulin availability to skeletal muscle. Finally, insulin-sensitive glucose transporters (GLUT-4) were characterized in equine muscles by Western blotting. We demonstrated that exercise increased GLUT-4 protein content by 27%. Replenishment of muscle glycogen stores after carbohydrate administration, either by glucose infusion or diet, attenuated the increase in GLUT-4 protein content of skeletal muscle.
Advisors/Committee Members: Hinchcliff, Kenneth W.
Subjects: Biology, Veterinary Science
Keywords: Anaerobic capacity; muscle glycogen resynthesis; glycemic index; GLUT-4 glucose transporter; lactate
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20.
Lacunza, Mariana A.
“Digital Aesthetics and Notions of Identity in Contemporary Bolivian Filmmaking” “Estéticas digitales y nociones de identidad en el cine boliviano contemporáneo”.
Degree: PhD, Spanish and Portuguese, 2011, Ohio State University
► Digital Aesthetic and Notions of Identity in Contemporary Bolivian Filmmaking examines two…
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▼ Digital Aesthetic and Notions of Identity in Contemporary Bolivian Filmmaking examines two related issues: on one hand, the emergence of new aesthetic currents made possible by the specific properties of digital formats; on the other, the emergence of new forms of distribution and exhibition. By comparing two different groups of digital films (those made by a new generation of young globally-recognized directors that stand for an auteur cinema in Bolivia, and those made by marginal communities in collaboration with the collective group TAFA that works outside the limits of the official film industry), I explore how digital technologies have been the driving force behind the flowering of the Bolivian film industry (traditionally seen as a minor industry even across Latin America) and the means by which Bolivian filmmakers engage with local, national and international issues and dynamics in innovative ways. My study also examines larger theoretical questions about how digital technologies are helping to reformulate national identity within the context of the Evo Morales administration and enhance the performance of cultural citizenship. My work has also important implications for debates within the discipline of film studies– particularly in terms of the democratizing potential of digital technologies. In surveying the transformative effect of digital technologies on Bolivian filmmaking and community-based politics, my dissertation questions the hypothesis of some critics that the so-called “digital revolution” would remain circumscribed to a tiny sphere of more wealthy individuals and nations.
Advisors/Committee Members: Podalsky, Laura.
Subjects: Latin American Studies
Keywords: bolivian film; Latin American digital aesthetics; Latin American digital film; young auteur cinema; TAFA; Manifiesto 3b´s; indigenous community films, afro bolivian films; cultural citizenship; national identity; alternative subjectivities
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21.
Ladd, Adam J.
Bernini's Cornaro Chapel: Visualizing Mysticism in the Age of Reformation.
Degree: MA, College of the Arts / School of Art, 2012, Kent State University
► This thesis examines the interaction between the viewer, the depicted Cornaro men,…
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▼ This thesis examines the interaction between the viewer, the depicted Cornaro men, and the scene of Teresa’s transverberation. The result is a fresh interpretation of Bernini’s Cornaro Chapel. Rarely has the theatricality of Bernini’s Cornaro Chapel gone unmentioned in literature. Scholarship thus far, however, has not gone beyond the formal, visual qualities of the chapel that suggest a theater space. I suggest that these qualities were more than just aesthetic choices—they were intended as an important aspect of the overall message being communicated to the viewer. The theme presented to the viewer of this chapel was one that carried with it a recent history of controversy and debate. The post-Tridentine Roman Church walked a fine line between acceptance and condemnation of mystical theology, as it had the potential to either confirm God’s divine interaction with the Roman Church, or to inspire protest and dissent against the rigid orthodoxy inherent in the Catholic faith. To guide the viewer toward an appropriate response to the subject matter, this thesis suggests that Bernini intentionally designed the chapel space as a play-within-a-play, a popular Baroque device that Bernini explored just years before the Cornaro commission in his play The Impresario. This creative device serves to focus the attention of the audience on the interaction that takes place between audience and performance, as the real audience sees a performed audience reacting to the play-within-a-play. In the Cornaro Chapel, the viewer witnesses a performance of Teresa’s mystical experiences to an audience of the Cornaro men, seven of whom were Cardinals of the Church. As such, we witness the creation of a canonized saint within the confines of the Church’s sanctioned system of doctrinal validation. We are reminded that such validation does not come from us, but from the upper echelons of Church hierarchy. Both the viewer’s experience and understanding of this miracle is controlled by Bernini’s structuring of the chapel space.
Advisors/Committee Members: Medicus, Gustav.
Subjects: Aesthetics; Art Criticism; Art History; Fine Arts; Gender Studies; History; Performing Arts; Religious History; Theater History; Theology
Keywords: Bernini; Counter-Reformation; Teresa of Avila; Teresa de Jesus; Baroque; Baroque sculpture; play-within-a-play; theatrum mundi; Federico Cornaro
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23.
Ladd, James E.
"Plugged-in blue".
Degree: MFA, Art, 1997, Ohio State University
► This M.F.A. thesis visually examines aspects of the role that television has…
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▼ This M.F.A. thesis visually examines aspects of the role that television has come to play in our homes. I take an aesthetic look at how we have adapted to its presence by using the TV set as the central object of a personal history shrine.The two photographic genres that are employed in this work are the formal portrait and the fabricated image. Color portraits, which comprise the majority of the images in this body of work, consist of individuals posed beside their most watched television set as if it has become the newest member of the family. These portraits highlight significant details of their home TV viewing environment.Larger, fabricated images depict my personal vision of private moments in front of the television. By utilizing models, props and an array of lighting techniques, I create a photographic performance in the attempt to understand the pervasive experience of television as it is revealed in the private moments of our lives.
Advisors/Committee Members: Harned, Richard.
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25.
LADEINDE, OYEBOLA O.
Genetic and Environmental Factors Influencing Wheezing in African Americans.
Degree: MS, Medicine : Epidemiology (Environmental Health), 2008, University of Cincinnati
► Objectives To determine whether genetic variants in the interleukin 4 (IL-4) and…
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▼ Objectives To determine whether genetic variants in the interleukin 4 (IL-4) and interleukin 13 (IL-13) genes influence recurrent wheezing in African American children and if these effects are modified by exposure to diesel exhaust particles (DEP), environmental tobacco smoke (ETS) and sensitization to allergens.Study Design A birth cohort of 643 children was evaluated annually by a questionnaire, physical examination, skin prick testing and buccal swabbing to obtain DNA samples. The relationship of ETS and DEP exposure, sensitization and genotype with the outcome of recurrent wheezing was analyzed. Results The prevalence of sensitization was 44.4% and recurrent wheezing was 16.4% at the third year visit. The odds of recurrent wheezing in African American children was significantly increased when they were sensitized to the aeroallergens; meadow fescue, red cedar, ragweed, penicillium, cockroach and cat. Conclusions In African American children with a family history of sensitization, exposure to red cedar, ragweed, penicillium, cockroach and cat increases the odds of recurrent wheezing.
Advisors/Committee Members: Haynes, Erin.
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26.
LADHA, PARAG.
POLYMERIC MEMBRANE SUPPORTED BILAYER LIPID MEMBRANES RECONSTITUTED WITH BIOLOGICAL TRANSPORT PROTEINS.
Degree: MS, Engineering : Materials Science, 2006, University of Cincinnati
► The purpose of this research was to develop stable bilayer lipid membranes…
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▼ The purpose of this research was to develop stable bilayer lipid membranes (BLM’s) on flexible synthetic supports and reconstitute them with biological transport proteins. Porous polymeric substrates such as nylon, polyester, and polycarbonate membranes as well as an ionomeric membrane (Nafion®) were evaluated as scaffolds for stabilization of lipid bilayers. BLM’s formed on these substrates were made functional by reconstitution of ion channels and proteins in them. The activity of the gramicidin ion channel reconstituted in the BLM was followed by measuring ionic resistance across the BLM which was found to decrease in the presence of a permeable cation medium. On a charged substrate like Nafion, the POPE lipid used in this work, with a positively charged head group could form stable BLM’s on Nafion due to electrostatic interaction with the negatively charged sulfonic acid groups on the surface of Nafion membrane. Proton pump reconstitution in these artificial BLM’s showed that the protein was active on reconstitution and responded to a dose of ATP by transporting H+ ions across the BLM. This activity was measured by following pH in the outer chamber as ATP was supplied in the inner chamber. These studies have shown that phospholipid bilayers can be formed on a wide variety of polymeric membranes. These bilayer incorporated with membrane proteins maintain the functional properties of the native membrane proteins. These simple methods can provide biological synthetic composites mimicking biological function.
Advisors/Committee Members: Boerio, Dr. James.
Subjects: Engineering, Materials Science
Keywords: phospholipids, BLM, gramicidin D, porous membranes, proton pumps
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27.
Ladianou, Aikaterini.
Logos Gynaikos: Feminine Voice in Archaic Greek Poetry.
Degree: PhD, Greek and Latin, 2009, Ohio State University
► This dissertation argues that feminine voice can be found in Archaic Greek…
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▼ This dissertation argues that feminine voice can be found in Archaic Greek poetry. Attempting to answer this question, I tried to build a case for a feminine voice that is historically contextualized, since it is constructed within the context of archaic Greece. For this thesis, such a voice is not as a natural, physical voice but a constructed gendered voice. In the beginning, Sappho’s construction of feminine voice is considered as dialogic. Sappho re-reads, re-writes Homeric epic as a feminine epic: polyphonic, against dichotomies and hierarchies. In the case of Sappho, feminine voice is constructed as the voice of the persona loquens, be that Sappho or the female performer. In Homer, a similar feminine voice is constructed as the voice of Helen, a poetic female figure. Thus, Homer constructs a double, unfixed, polyphonic feminine voice that functions as an alternative poetic discourse within the Iliad. Finally, in Alcman the female voice of the chorus proves to be essentially masculine. Thus, emphasizing hierarchical models, or male models of desire, the chorus is reinforcing patriarchal structures. Building on French feminist theory and late Bakhtinian discussions, this thesis attempts to map down polyphony, multiplicity, fluidity and mutability as the main characteristics of a feminine voice. By demonstrating how both male and female authors are able to construct a feminine voice with the aforementioned characteristics essentialist arguments are avoided. Hence, both Sappho and Homer produce a feminine voice, a multiple, dialogic, unfixed voice. The use of such a feminine voice is an ideological choice with sociopolitical implications. My objective was to explore a feminine voice that is neither essentialist nor victimized: if Sappho’s feminine voice is not anchored on her gender, it is a position in language rather than a biologically defined position, then, an écriture feminine can be composed by male writers as well. Moreover, if Sappho is able to speak at the same time within and against the specific androcentric society, then, indeed, the subaltern woman, and her voice, does exist.
Advisors/Committee Members: Batstone, William.
Subjects: Classical studies
Keywords: archaic poetry; greek; Sappho; Homer; Alcman; gender; feminine voice; french feminist theory
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28.
Laditka, Robyn Mackenzie.
The Influence of Argumentativeness, Verbal Aggressiveness, and Affective Orientation on Roommate Communication Satisfaction and Roommate Affinity.
Degree: MA, Communication, 2006, University of Akron
► The purpose of this study was to determine if there was a…
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▼ The purpose of this study was to determine if there was a relationship between three specific communication traits and roommate communication satisfaction. The three traits this study examined included: verbal aggressiveness, argumentativeness, and affective orientation. Two Hundred four participants were asked to complete a questionnaire measuring argumentativeness, verbal aggressiveness, affective orientation and roommate communication satisfaction. The findings indicated there was no significant relationship between roommate communication satisfaction and argumentativeness, nor was there was significant relationship between roommate communication satisfaction and affective orientation. However, the results did show a significant negative relationship between roommate communication satisfaction and verbal aggressiveness. Implications of these findings, and suggestions for future research are discussed.
Advisors/Committee Members: Rancer, Andrew.
Keywords: Argumentativeness; Verbal Aggressiveness; Affective Orientation; Roommate Communication Satisfaction; Roommate Satisfaction; Roommate Affinity; Affinity
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29.
Lad, Manish.
Characterization of Atmospheric Noise and Precipitation Static in the Long Range Navigation (Loran-C) Band for Aircraft.
Degree: MS, Electrical Engineering (Engineering), 2004, Ohio University
► This Thesis investigates the effects of noise caused by lightning discharges and…
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▼ This Thesis investigates the effects of noise caused by lightning discharges and Precipitation Static (P-Static) in the Loran-C band, as observed by an airborne receiver. To characterize the noise, an airborne data collection system was used to store the radio frequency samples from both a loop (H-field) antenna and a wire (E-field) antenna. Flight test data were collected and analyzed under nominal, P-Static, and nearby thunderstorm conditions. Based on the research described in this thesis it was found that: 1) E-field and H-field antennas are affected similarly by lightning-induced noise; 2) In the presence of thunderstorms, the noise increase for both antennas was less than 2.3 dB; and 3) An H-field antenna effectively mitigates aircraft P-Static noise in the Loran-C band.
Advisors/Committee Members: van Graas, Frank.
Keywords: Loran-C
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30.
Lado, Beatrice H.
Characteristics of Listeria monocytogenes Important for Pulsed Electric Field Process Optimization.
Degree: PhD, Food Science and Nutrition, 2003, Ohio State University
► Processing-resistant Listeria monocytogenes strains appear sporadically in ready-to-eat food, and constitute a…
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▼ Processing-resistant Listeria monocytogenes strains appear sporadically in ready-to-eat food, and constitute a considerable challenge to food processors. Pulsed electric field (PEF) is an alternative to thermal processing and it inactivates pathogens in liquid food. The high-intensity electric pulses kill rapidly microbial contaminants. Since L. monocytogenes is among the most PEF-resistant non-sporing foodborne pathogens, this study focused on identifying characteristics of Listeria that may be useful for PEF process optimization. Resistance to PEF treatment, at 25 kV/cm, varied among L. monocytogenes strains suspended in 0.1% NaCl (pH 7.0) or 50% acid whey (pH 4.2). Listeria monocytogenes OSY-8578 was identified as a potential target strain for process optimization, based on its high PEF-resistance. Resistance to PEF could not be associated with genotypic differences, as determined by pulsed field gel electrophoresis or arbitrarily primed-polymerase chain reaction method. However, the target strain, OSY-8578, had a unique genotype, which is potentially useful for its identification. Sublethal PEF process (15 kV/cm for 29 micros) did not induce general stress response, a physiological state with over-expression of major molecular chaperones. On the contrary, expression of the chaperones, GroEL, GroES and DnaJ decreased within 5 to 20 min after PEF treatment. The decrease in expression was more marked for Scott A (PEF-sensitive) than OSY-8578 (PEF-resistant). Interestingly, the chaperone expression profile, after PEF treatment, paralleled an increased sensitivity of the pathogen to mild heat. This sensitization was not observed when mild heating was applied prior to PEF. Lactobacillus plantarum ATCC 8014, but not L. innocua ATCC 33090, was identified as potential surrogate of the target L. monocytogenes , OSY-8578, when these bacteria were suspended in a neutral simple medium (e.g., 0.1% NaCl solution) and treated at 25 kV/cm for 144 micros. Inactivation of Listeria by PEF was greater in acid or acidified whey (pH 4.2) than in sweet whey (pH 6.8) or in 0.1% NaCl (pH 7.0). In acid or acidified cheese whey, Lb. plantarum was more resistant to PEF than was L. monocytogenes OSY-8578; the former bacterium, therefore, may serve as a surrogate of the latter in such media.
Advisors/Committee Members: Yousef, Ahmed E.
Keywords: Listeria, pulsed electric field, target, chaperone, GroEL, GroES, DnaJ, surrogate, sensitization
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