18,212 research outputs found
Instrumentation for Impedance Measurements in the ELF/VLF Band for Geophysical Investigations
No full textElectromagnetic investigations of the upper layers of the earth are of particular interest to earth scientists and mining geophysics companies. This thesis outlines a novel hand-held electronic instrument that performs shallow earth surface impedance measurements to depths of 100 m or less. The device named “TranSIM” (Transient Surface Impedance Meter) operates in the ELF/VLF frequency band and utilises both remote single frequency military transmitter signals and naturally occurring sferics to perform broad band surface impedance measurements.
The device incorporates high precision GPS which provides survey point co-ordinates and accurate date-time stamping, enabling data synchronisation and cooperative surveying across multiple devices. A wireless communications link to a host computer was implemented, enabling high speed data transfer with the host computer for data logging and post-processing.
A Windows@ based software application was developed to provide software control of on-board electronics and for advanced data processing and data logging. The application incorporates satellite map imagery with live up-dates of GPS tracking data. Pseudo real-time data analysis is presented through a rich graphical user interface.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)Griffith School of EngineeringScience, Environment, Engineering and TechnologyFull Tex
TCCON data from Wollongong (AU), Release GGG2014.R0
No full textThe Total Carbon Column Observing Network (TCCON) is a network of ground-based Fourier Transform Spectrometers that record direct solar absorption spectra of the atmosphere in the near-infrared. From these spectra, accurate and precise column-averaged abundances of atmospheric constituents including CO2, CH4, N2O, HF, CO, H2O, and HDO, are retrieved. This data set contains observations from the TCCON station at Wollongong, Australia.Contact person: David Griffith [email protected]
Low-Profile Floating Antennas for Coastal Communications
No full textThe size, orientation and features of an antenna are critically important in sea surface
radio communications. The performance of the communication link is dependent on
antenna height, radiation pattern and antenna-seawater interaction. This research focusses
on the design and development of a short-range radio communication system with lowprofile,
low cost antennas that ensure reliable data transmission in a shallow seawater
environment.
Given the high conductivity and relative permittivity of seawater, the system used the
seawater as a conducting ground plane of infinite extent. This thesis reports the system
challenges resulting from a non-planar sea surface and an imperfect ground conductivity.
Given the high propagation loss through seawater at Ultra High Frequencies (UHF), the
approach undertaken was a hybrid architecture consisting of a subsurface transmitter
close to the ocean bottom (depth < 5 m) with a transmission line to the surface antenna,
or a tethered but floating transmitter with an integrated antenna. Different techniques
aimed at establishing communication links between the antenna and shore, another
antenna and an Unmanned Air Vehicle (UAV) hovering above it, are reported. In all
cases, the antenna moves laterally and rotates in all three axes with the wind and ocean
currents, and vertically with waves and tides.
In the first technique, a communications link from a subsurface transmitter to a floating
monopole antenna through an insulated wire surrounded by seawater was designed,
constructed and tested. The attenuation is dependent on the wire and insulation thickness
and this influences the characteristic impedance of the transmission line. A quarter wave
monopole antenna was formed by placing the wire through a spherical polystyrene float
with a length of approximately one quarter wavelength. The attenuation through the insulated wire was approximately 38 dB/m. The vertically polarized radiation is
omnidirectional in the plane of the water surface. Using a 10 dBm transmitter and a
1.5 m long subsurface transmission line, the maximum horizontal communications
distance was less than 5 m between floating transceivers and up to 35 m to a slightly
elevated shore receiver when the receiver sensitivity was -116 dBm. The packet loss for
a 30m separation between transceivers was 1.73%. When the insulated wire was replaced
by a flexible coaxial cable, the transmission line attenuation and the propagation range
across the surface to a slightly elevated receiver, extended to more than 140 m in light
wind conditions.
The second technique was to use a floating transmitter with an integrated antenna. The
antenna with the transceiver was located in a sealed 9 cm diameter Polyvinyl Chloride
(PVC) pipe with a flexible rope tethered to the ocean floor. Two antenna designs were
constructed and tested: a monopole and a modified spiral (hemispherical). The latter was
assessed using a small conductive ground plane together with the sea surface. This
antenna was optimized using Computer Simulation Technology (CST) and fabricated
using 3D printing and vacuum forming. While the hemispherical antenna radiation beam
is principally vertical, the horizontal propagation distance was measured as greater than
135 m for the receiver sensitivity of -116 dBm.
The final part of the research was the design and construction of a real-world prototype
(floating buoy). Vacuum forming and 3D printing techniques were used to construct a
waterproof enclosure to contain both the hemispherical antenna and the electronic
circuitry. These techniques give a low-cost solution and the buoy can be modified to
integrate ocean sensing elements. The buoy can be opened, and batteries can easily be
replaced to increase the longevity of the transmitter. Due to the transparent structure of
the buoy, the transceiver circuit could be partly powered with solar energy.
The longest transmission distance across the ocean surface was greater than 140 m using
a low-profile hemispherical antenna integrated into the plastic enclosure containing the
electronics given a transmitter power of +10 dBm and a receiver sensitivity of -116 dBm.
The unit had a diameter of 20 cm and a height of less than 15 cm.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Eng & Built EnvScience, Environment, Engineering and TechnologyFull Tex
Advantages and limitations of using Caco-2 cells for in vitro M cell model
No full textGriffith Health, School of Medical ScienceFull Tex
TCCON data from Darwin (AU), Release GGG2014.R0
No full textThe Total Carbon Column Observing Network (TCCON) is a network of ground-based Fourier Transform Spectrometers that record direct solar absorption spectra of the atmosphere in the near-infrared. From these spectra, accurate and precise column-averaged abundances of atmospheric constituents including CO2, CH4, N2O, HF, CO, H2O, and HDO, are retrieved. This data set contains observations from the TCCON station at Darwin, Australia.Contact person: David Griffith [email protected]
Infinitude: Investigating the Aesthetics of Complex Patterns through Printmaking
No full textThis doctoral project presents an aesthetic inquiry into works on paper and installation that are distinguished by a contemplative development of non-mimetic patterns. Relief etchings and linocuts dominate the research, spanning a range of media, including drawings, monoprints, kinetic sculpture, and video. This research is based upon an improvisational methodology that is diversified in response to the interactivity between ideation and material engagement. Change and constancy, motion and stasis, and form and formlessness are co-dependent, conceptual binaries establishing the foundation of this dialectical inquiry.
Seeking to reconcile a transformative flux with constancy, geometry is examined as a means of understanding the relational dynamic between mind and matter and as a reference for a speculative, cosmological inquiry. Through my studio research, I have developed a pictorial language from essential motifs, and the exegesis argues that through its metaphoric agency, the particularity of art indicates an immanent materiality. This is consolidated by my research on how physics informs our understanding of materiality, with etchings made in response to the philosophy of physicist David Bohm.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)Queensland College of ArtArts, Education and LawFull Tex
Exploring the Spoken Language Development of School-Aged Children on the Autism Spectrum with Minimal Verbal Language
No full textChildren on the autism spectrum demonstrate wide variation in their expressive communication skills, with a significant proportion having minimal verbal language. Research has tried to identify factors that might influence or predict language acquisition, with limited success. Further research is needed to understand, and ultimately address, the communication needs of this group of children to better support their communication development. Therefore, the primary aim of this study was to investigate spoken language development in children on the autism spectrum with minimal verbal language by addressing three research questions:
1. What are the social communication profiles of school age children on the autism spectrum with minimal verbal language?
2. What proportion of school age children on the autism spectrum with minimal verbal language develop spoken language over a 4-year period?
3. Do children on the autism spectrum who do and do not go on to develop spoken language differ based on their (a) social-communication skills or (b) personal, family, and environmental factors?
The study used data from children with minimal verbal language participating in the Longitudinal study of Australian Students with Autism, a cross-sequential study investigating the educational experiences and outcomes of students on the autism spectrum. Data at four time points were drawn from a set of measures of child and family demographics, autism characteristics, social-communication skills, and adaptive behaviour. A mixed methods approach was used to address the research questions, including qualitative content analysis methods and descriptive and inferential statistics.
Results of this study indicate that just over half of the participants developed some level of spoken language ability over the 4-year period. When comparing groups of developers and nondevelopers of language, no significant differences were found for the social-communication skills evaluated on The Pragmatics Profile of Everyday Communication Skills in Children (PP); however, a medium effect size was found for interaction with adults. While no significant differences were found between groups on the identified factors, medium effect sizes were also reported for autism characteristics, parent education, and parent diagnoses.
Findings provide valuable information regarding the language abilities of children with minimal verbal language, including subgroups within this population, and how they present with complex profiles of social-communication skills as well as personal, family, and environmental factors. These skills and factors require investigation in larger groups of children to determine their potential significance in the language development of children on the autism spectrum with minimal verbal language. Findings offer preliminary evidence for a new method for quantifying qualitative insights into children’s social-communication skills using the PP. Collectively, these findings will assist professionals working with this group of children by providing a better understanding of the unique profiles of children on the autism spectrum who enter formal schooling with minimal verbal language, that can be used to tailor and implement individualised supports aimed at facilitating and promoting positive communication outcomes.Thesis (Masters)School Educ & Professional StArts, Education and LawFull Tex
Totally Tuned In: Peak Performance in Professional Screen Acting
No full textThe aim of the current research program was to empirically investigate the experience of peak performance in the context of professional screen acting. Five studies were conducted employing an exploratory sequential mixed methods research approach. Three qualitative studies explored the subjective peak screen acting performance experience. Semi-structured interviews were conducted with five professional screen actors. The first two studies employed an interpretative phenomenological analysis. The first study revealed that peak screen acting performances were a present, connected, and heightened state of living as the character (i.e., the peak performance state). Peak screen acting performances were achieved through performance preparation. Actors reported developing self-efficacy and acceptance due to feeling prepared. The second study revealed that professional interpersonal relationships either facilitated or inhibited screen acting performances. Further, intrinsic motivation facilitated, whilst performance pressure inhibited peak performances. The third study employed a deductive frequency analysis to explore whether flow was related to peak screen acting performances. Flow was partially associated with peak screen acting performances. Experiential dimensions of flow were most strongly associated with peak performances. The combined results of the first three qualitative studies indicated that a three-level hierarchy of needs may best represent the process that assists actors reach peak performance in screen acting.
The final two studies used quantitative methodology to extend upon the first three studies. Participants were professional actors with various levels of professional experience. Participants completed a self-report online survey measuring general performance, the peak performance state, performance preparation, support, trust, respect, self-efficacy, psychological safety, acceptance, intrinsic motivation, pressure,worry, and flow. The fourth study (N = 167) tested whether the three-level hierarchy of needs accounted for the variance in peak screen acting performance. Hierarchical multiple regressions revealed that the three-level hierarchy of needs significantly accounted for the peak performance state whilst only two levels of the hierarchy significantly accounted for general performance. Overall, performance preparation and intrinsic motivation were the strongest significant unique positive predictors of peak screen acting performance. The fifth study (N = 152) assessed whether flow accounted for the variance in peak screen acting performances. Standard multiple regressions revealed that flow significantly accounted for general performance and the peak performance state. The challenge-skills balance, concentration on the task at hand, action-awareness merging, and the autotelic experience positively and uniquely predicted general performance and/or the peak performance state.
In summary, the current research generated new knowledge that has theoretical and practical implications for performance in screen acting. One major contribution is the hierarchy of needs which outlines a structured approach for attaining peak performance in screen acting. The hierarchy of needs highlights the importance of actors cultivating not only preparation and performance skills, but also positive psychological qualities and professional interpersonal skills. Thus, peak performance in screen acting is suggested to involve an interaction of skill-based, psychological, and interpersonal factors. Using clinical and positive psychology principles, actors may increase their performance potential by developing performance self-efficacy, acceptance, and performance pressure management strategies. Moreover, actors are recommended to make intrinsically motivated career and performance choices. Building professional interpersonal skills and relationships through training and networking may further support actors reach peak performances.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Applied PsychologyGriffith HealthFull Tex
Investigating M cell signal transduction pathways using multi-labelling of M cells with putative markers and bacterial transport
No full textGriffith Health, School of Medical ScienceFull Tex
Methodological differences in Pavlovian fear learning, extinction and return of fear
No full textExamining methodological differences in fear conditioning and extinction studies is a growing area of research, inspired by the recent ‘replication crisis’ in psychological research. Determining whether methodological differences of fear conditioning and extinction paradigms contribute to inconsistent findings is important in terms of the translational value of this paradigm as an experimental analogue of exposure-based cognitive behavioural therapy. The aim of this thesis was to improve the experimental methodology of fear conditioning and extinction studies, by addressing three key questions: 1) Are there parameters of fear conditioning and extinction tasks that differentiate successful from unsuccessful extinction in studies with children and youth; 2) Do different types and combinations of within-phase subjective measures affect within-phase physiological and between-phase measures of fear conditioning and extinction; and 3) Does behavioural memory reconsolidation in the form of cue reactivation with versus without instructions differentially impact extinction and return of fear?
Question one was addressed by conducting a systematic review of 35 fear conditioning and extinction studies conducted with children and adolescents (Chapter 2, Ryan et al., 2019). This review revealed that successful extinction was observed in studies that used fear irrelevant shapes (CS) and tones (US) (recommended for all youth) or fear relevant faces (CS) and screams (US) (recommended only for adolescents) as well as those studies that used 8 – 12 CS trials per acquisition and extinction phase. The most commonly used and effective dependent measures were skin conductance responses (SCRs) and subjective ratings of CS valence, fearfulness and arousal. Fear potentiated startle (FPS) was also effective, however less commonly used with children. It was suggested that standard measures be adopted for subjective ratings
scales to assist in comparisons across studies. It was recommended that both physiological measures of SCRs and/or FPS be assessed, as well as within-phase subjective measures of US expectancy ratings and CS evaluations and between-phase measures of CS valence, CS arousal and subjective anxiety. Also, additional measures of contingency awareness and US intensity and pleasantness after the conditioning phase was recommended. The review identified unresolved issues and directions for future research to further clarify the most effective designs and measures.
The first experimental study (Chapter 3, Ryan et al., 2021) aimed to address one of the issues identified in Ryan et al. (2019) relating to whether different combinations of within-phase subjective measures of US expectancy and CS evaluations would influence skin conductance responses and between-phase subjective ratings of CS valence, CS arousal and subjective anxiety. The fear conditioning and extinction study involved 88 participants aged between 17- 25 years recruited from first year university psychology students. The Control condition (N =22) included the assessment of SCRs and between-phase ratings. Relative to the Control condition, the US Expectancy condition (N= 21) additionally included within-phase US expectancy ratings throughout each phase, the CS Evaluation condition (N = 21) additionally included within-phase CS evaluations, and the All Measures condition (N = 23) additionally included both within-phase US expectancy and CS evaluations. Within-phase subjective measures influenced learning by changes in arousal measured by SCRs, however they did not influence between-phase ratings. Rating the within-phase US expectancy alone resulted in successful conditioning, extinction and extinction retention of differential SCRs. Providing the within-phase CS evaluation alone resulted in successful conditioning but no extinction of differential SCRs although extinction did occur at the end of the test phase. For the control condition (no within-phase measures), there was also no extinction of SCRs that remained until the end of the test phase. Rating both within-
phase measures resulted in successful conditioning and extinction of differential SCRs; however, the arousal was elevated compared to other conditions. The All measures condition also had a return of differential SCRs during the test phase. It was concluded that researchers need to consider the aims and objectives of their study because different types and combinations of within-phase subjective ratings may influence the outcomes.
The second experimental study (Chapter 4, Ryan et al., under review) investigated a notable methodological difference in behavioural memory reconsolidation studies, in which some studies but not others include instructions before the cue reactivation manipulation. The goal was to determine whether instructions influence extinction and the return of differential fear responses. Participants were recruited from first year university psychology students (N = 109) with an age range of 17 - 40 years. Four conditions tested the role of instructions on cue reactivation by presenting the cue with (CS+ Instruct) and without instructions (CS+ Only) relative to two conditions that controlled for the role of instructions alone (Instruct Only) and no cue or instructions (Control). Participants completed acquisition, extinction and test phases within a single session, using fear relevant dog pictures and an aversive auditory unconditional stimulus (US). Measures included skin conductance responses (SCRs), within-phase US expectancy, between-phase CS evaluations and subjective anxiety. No condition differences were found - all conditions demonstrated extinction retention of SCRs in the test phase. There were also no condition differences in US expectancy ratings within-phase and CS evaluations between-phase. Subjective anxiety ratings also showed no differences between conditions, although fear reduced after extinction for all conditions. The findings found no support for instructions before cue reactivation and no support for behavioural memory reconsolidation.
Three general conclusions were drawn from the results of the systematic review and the two experimental studies: 1) Parameters of fear conditioning and extinction tasks can differentiate successful from unsuccessful extinction; 2) Different types and combinations of within-phase subjective measures affect physiological measures of fear conditioning and extinction studies; and 3) Cue reactivation with or without instructions during behavioural memory consolidation does not impact extinction and the return of fear. Future research implications and recommendations are discussed. The findings from the current PhD program of research have methodological implications for future fear conditioning and extinction studies and add to the literature focused on improving scientific rigour and the replication crisis in psychological research.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Applied PsychologyGriffith HealthFull Tex
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