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published_or_final_version / Speech and Hearing Sciences / Master / Master of Science in Audiology

Infants prefer familiar adults (e.g. parents) to unfamiliar adults (e.g. strangers), but they also vary in which strangers they prefer. By 6-months, infants look longer at attractive than unattractive faces (e.g., Langlois et al., 1987); and by 12-months, infants show approach behaviors toward attractive strangers and withdrawal behaviors toward unattractive strangers (Langlois, Roggman, & Rieser-Danner, 1990). These preferences may be due to a mechanism referred to as cognitive averaging (e.g., Rubenstein, Kalakanis, & Langlois, 1999). Infants cognitively average face exemplars to form a face prototype. Infants likely perceive attractive faces as familiar because these faces are similar to the face prototype; and they likely perceive unattractive faces as especially novel because these face are dissimilar from the face prototype. Even young infants may be more motivated to approach attractive than unattractive faces but do not fully express this motivation due to limitations in locomotion and communication. I applied EEG asymmetry to study neural correlates of approach and withdrawal motivation in response to attractive and unattractive faces with 6- and 10-month-olds. More specifically, I measured EEG alpha power at mid-frontal regions while 39 infants viewed a series of attractive and unattractive faces. Left EEG asymmetry relates to approach motivation whereas right EEG asymmetry relates to withdrawal motivation. I predicted infants would show greater left EEG asymmetry (i.e., approach motivation) when viewing attractive faces than when viewing unattractive faces, and that 6-montholds would show even greater left asymmetry than 10-month-olds due to developmental differences in stranger wariness. Results supported the main hypothesis but not hypotheses regarding age. Infant EEG asymmetry was greater in response to attractive faces than unattractive faces suggesting that infants are more motivated to approach attractive people than unattractive people as early as 6-months. These results link visual preferences evident at 6-months to overt behaviors evident by 12-months providing additional information regarding rudiments of attractiveness stereotypes. Furthermore, this investigation supports the use of EEG asymmetry methodology to measure infant approach/withdrawal motivation, providing infant researchers one more tool to better understand how infants evaluate novel individuals in their social environment as they decide whom to approach and whom to avoid. / text

This experiment examined the effects of extinction on rate of responding and several topographical and temporal measures in adult humans. Three college students were trained to type the sequence 1•5•3 on a numeric keypad on a computer. The subjects were exposed to different fixed-ratio schedules of reinforcement (FR1, FR 5, and FR10 respectively) and extinction. Subjects displayed typical schedule performances during the maintenance phase of the experiment. During extinction the performances were disrupted, they showed a "break and run" pattern and a general decrease in responding. Also, new topographical and temporal patterns emerged. These data are consistent with those reported for non-human species and special human populations.

MSc (Med), Faculty of Health Sciences, University of the Witwatersrand, 2009 / Background: RTS,S candidate malaria vaccine has been shown to be highly immunogenic in children and infants, but the protective immune mechanisms still remain to be clearly elucidated. It is believed that RTS,S elicits a strong neutralizing humoral immune response directed against surface-exposed sporozoite proteins and cell mediated immune (CMI) responses characterized by predominantly CD4+ Th1 cells. The objective of this study was to investigate humoral and cell-mediated immune responses to the RTS,S/AS02D malaria vaccine and its association with protection against infection and disease by P. falciparum. Methodology and Principal Findings: This secondary data analysis from data of a phase I/IIb randomized, double-blind, controlled trial, included 154 healthy infants living in rural Mozambique, previously immunized with RTS,S/AS02D candidate malaria vaccine or the control Engerix-B™ vaccine. Antibodies against circumsporozoite protein (CSP) and hepatitis-B surface antigen (HBsAg) were measured with a standard ELISA. Fresh blood intracellular staining assay was performed to evaluate the expression of IL-2 and IFN-γ by CD4+ and CD8+ cells in response to in vitro stimulation of specific peptides. Data was evaluated for association with the risk of malaria detected by both active and passive case detection of infection over a period of 6 months post dose 3. Anti-HBs antibody geometric mean titers declined from 10,082 mIU/mL one month post Dose 3 to 2,751 mIU/mL at 12 months post Dose 3 in the RTS,S/AS02D group; anti-HBs v geometric mean titers were 392.4 mIU/mL and 263.9 mIU/mL, respectively in the Engerix- BTM group. Anti-CSP antibody geometric mean titers declined from 199.9 EU/mL one month post Dose 3 to 7.3 EU/mL at 12 months post Dose 3 in the RTS,S/AS02D group. Median stimulation indices of HBs-specific IL-2 and IFN-γ producing CD8+ T cells was higher in the RTS,S/AS02D group than in control group (Wilcoxon rank sum p-values for IFN-γ = 0.015, for IL-2 = 0.030) at 10.5 weeks post immunization. Median stimulation indices of anti-CSP specific IFN-γ producing CD8+ T cells at the same time point was 1.13 (IQR: 0.79 - 1.67; p=0.029). For specific IL-2-producing CD4+ T cells, the median SI was 1.14 (IQR: 0.74 – 1.60, p=0.043) at 10.5 weeks post dose three. The reduction in hazards of malaria infection were 18.3 % (95% CI: -267.9 – 81.8, p=0.793) and -12.0 % (95% CI: -295 – 68.2, p=0.86) for specific IL-2 CD4+ stimulation indices; For specific CD8+ IFN-γ stimulation indices the hazards were -103.6% (95% CI: -690.9 – 47.6; p=0.305) and 48.8% (95% CI: -97.0 – 86.7; p=0.33) at four and 10.5 weeks post immunization respectively. Conclusion: The RTS,S/AS02D vaccine was immunogenic and has elicited detectable levels of CSP specific cell mediated responses. No evidence of association was found between the antibodies anti-CSP and specific cell mediated responses and the risk of malaria.

Caramel is a mixture of sugars, milk proteins, fat and water cooked at high temperatures to initiate Maillard reactions. We study caramels as ‘active emulsion-filled protein gels’, in which fat droplets are chemically-bonded to a background gel matrix of cross-linked proteins in a concentrated aqueous sugar solution. A ‘caramel region’ in composition space is delimited by the varying the four ingredients; sugar, milk protein, fat and water. The boundaries of the composition space define various modes of ‘failure’. Boundaries are determined for transitions to toffee and emulsification failure leaking out of the caramel, and protocol dependent failures, scum formation during the cooking step and subsequent boil over or the formation of a ‘creme Chantilly. Oscillatory rheology within the caramel region reveals that we can superpose the mechanical spectra of all caramels into a single pair of G'(ω),G''(ω) master curves using time-composition superposition (tCS) over 12 decades of frequency, so that all caramels are instances of an underlying ‘universal material’. The master curve is an example of a very lightly cross-linked amorphous polymer, a weak rubber. Utilising the cross-over point of G'(ω) and G''(ω) as a common point to compare caramel master curves the viscous and elastic dependency of caramel is determined and linked to the caramels ingredients. Viscosity is dependent on the aqueous sugar content and the elastic dependency on protein content. This insight constrains the molecular mechanisms for structure formation, and implies that measuring a couple of parameters suffices to predict the rheology of caramels over 12 orders of magnitude in frequency.

Incidents affecting the livestock industry are unavoidable in today's society. These incidents can happen at livestock shows across the country putting thousands of exhibitors, visitors, employees and livestock in danger. The purpose of this study was to determine local officials' perceptions and awareness of incident planning and response pertaining to selected livestock shows. Little research has been completed in this area; therefore, this foundational study was needed. The objectives of this study were to determine local officials' awareness of livestock shows and incident response plans for those livestock shows. In addition, the researcher wanted to describe the roles of local officials in incident planning and response at livestock shows. Level of communication and perceptions of challenges at livestock shows and among local officials were also evaluated. Lastly, the researcher wanted to describe local officials' recommendations for effective incident planning and response related to livestock shows. Five participants remarked on the value of this study and agreed to participate. These participants included livestock show officials involved in incident planning and response or local emergency management officials. Each participant was interviewed, and then data were transcribed and categorized to consensus. Nine themes arose including: background information, challenges, communication, example incidents, executing incident response, incident response planning, incident response training, miscellaneous and need for planning. It was concluded that all participants were aware of the selected livestock shows. However, levels of awareness varied by participant due to work-related experiences with the livestock show. The two livestock show participants were aware of specific incident response plans for the livestock show, while the three local emergency management officials were aware of city emergency management plans. Each participant remarked upon their roles in planning and executing incident response. In addition, communication was thought to be one of the key factors to successful incident planning and response. Challenges ranging from lack of communication to training for incident response were stated. Lastly, participants remarked on recommendations for others planning for incident response at livestock shows. These recommendations included communication, preplanning, building relationship with key stakeholders, training, and a need for more planning and research in this area. It is recommended that this study be replicated with scaled objectives for measuring awareness of livestock shows and incident response plans. Also, replicate this study to determine level of training in incident response and safe handling of livestock. It is recommended to describe communication between livestock shows and local emergency management officials. Lastly, it is recommended to replicate this study with regional livestock shows and state fairs.

HarpinPss, a proteinaceous elicitor from Pseudomonas syringae pv. syringae, is a glycine-rich, cysteine-lacking, heat-stable protein. It can elicit the hypersensitive response (HR) when delivered to the surface of plant cells. HRAP (hypersensitive response assisting protein) is an amphipathic protein purified from sweet pepper and could intensify harpinPss¡Vmediated HR in sweet pepper. In the previous research, harpinPss was present as monomer, dimer, trimer, tetramer, and ocatamer forms in neutral pH buffer. Only monomer and dimer forms of harpinPss induced hypersensitive response in nonhost plants. HRAP could cause multimeric forms of harpinPss dissociation into monomer forms. The interaction between HRAP and harpinPss is an important issue. HRAP contained three positively charged regions, a typical signal peptide and a cAMP-dependent phosphorylation site. In this study, these regions of HRAP would be truncated and identified whether these truncated HRAP fragments could promote harpinPss dissociation. Different combinations of truncated HRAP and harpinPss were used to identify the protein-interaction regions between two proteins. HarpinPss triggers HR via interaction with cAMP phosphorated region of HRAP and MAPK pathway transduction. When cAMP region of HRAP was truncated, harpinPss still triggers HR via polymerization and anchor on lipid bilayers to form an ion-conducting pore.

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The frequency following potential (FFP) is an auditory evoked response which crudely replicates the waveform of the stimulus. The origins of this far-field potential have been localized to the cochlea and specific auditory nuclei. The initiation site of the FFP along the cochlear partition has been thought to be dependent upon stimulus sound pressure level. Low stimulus levels elicit FFP from the apical turn of the cochlea, while moderate and high stimulus levels may elicit FFP from a large segment of the partition, including the basal turn. Simultaneous masking studies have contributed to the knowledge of this potential, but results from these studies may be confounded by interference from bioelectric potentials generated by distortion products from the masking noise. This investigation used non-simultaneous masking tones set at the subject's pulsation threshold level (PTL). This psychophysical method provides a representation of the frequency-resolving properties of the auditory periphery in a repeated gap masking paradigm. Patterns of the relative masking effect of each masking tone were plotted and compared for several probe levels and in the presence or absence of a continuous, high-pass masking noise. Tuning patterns derived in high-pass making noise effectively represented apical turn FFP. Those patterns without masking noise represented whole-cochlea FFP. The results of this study demonstrarted tuning patterns that reflected diminished FFP amplitudes in the primary 500 Hz region as well as in an extended secondary range of 800 to 2000 Hz, depending on the stimulus-masking parameters. Tuning patterns in high-pass masking noise were consistently flatter in the primary and secondary regions than for the tuning patterns without masking noise. The secondary regions of the tuning patterns extended above 2000 Hz for the patterns obtained without high-pass masking. Tuning patterns were consistently broader for the high stimulus level than for the moderate stimulus level. The multiple cochlear initiation sites for the FFP preclude its use as an audiological tool for the assessment of low-frequency hearing. However, the potential is suggested as a method to assess whole-cochlear response for the difficult-to-test patients with suspected profound hearing loss.