Towards Precision Measurements of the Optical Depth to Reionization Using 21 cm Data and Machine Learning

Billings, Tashalee S ProQuest Dissertations & Theses University of Penn 2022 해외박사(DDOD)

The Epoch of Reionization (EoR) was a phase transition from a neutral state to an ionized state where the first generation of luminous objects were able to heat and ionize the surrounding predominantly neutral hydrogen gas. Detection of brightness temperature fluctuations from the redshifted hyperfine 21 cm line of neutral hydrogen would provide a direct three-dimensional probe of astrophysics and cosmology during this period. Another important property of reionization is the redshift of its midpoint, when half the hydrogen in the intergalactic medium (IGM) was ionized. This quantity is often estimated by using the cosmic microwave background (CMB) optical depth, tau . Since the optical depth is obtained by integrating along the line of sight, it provides just one number to characterize reionization. As a result, this can be converted into a constraint for the midpoint under the assumption of a parametric form for the ionization history. This is also a probe of the EoR.Upcoming measurements of the high-redshift 21cm signal from the EoR are a promising probe of the astrophysics of the first galaxies and of cosmological parameters. In particular, the optical depth tau to the last scattering surface of the CMB should be tightly constrained by direct measurements of the neutral hydrogen state at high redshift. A robust measurement of $\au$ from 21cm data would help eliminate it as a nuisance parameter from CMB estimates of cosmological parameters. Previous proposals for extracting tau from future 21cm datasets have typically used the 21cm power spectra generated by semi-numerical models to reconstruct the reionization history. I present in this thesis a different approach which uses convolution neural networks (CNNs) trained on mock images of the 21cm EoR signal to extract tau. I constructed a CNN that improves upon on previously proposed architectures, and perform an automated hyperparameter optimization. I showed that well-trained CNNs are able to accurately predict tau, even when removing Fourier modes that are expected to be corrupted by bright foreground contamination of the 21cm signal.I then began answering a slightly different question that involved raining three different Bayesian models using mock images of ionized fields of hydrogen to extract the ionization fraction of hydrogen by only looks at one redshift to infer the ionization fraction of each simulated image. I showed that for a simple fully Bayesian network it is possible to successfully produces predicted values that are closely aligned with the true values and the model was tuned to find the ``best'' generalized model architecture for this particular problem.

Effects of tone level and signal-to-noise ratio on neural encoding

Billings, Curtis J University of Washington 2008 해외박사(DDOD)

The central auditory system (CAS) changes as a function of auditory deprivation and stimulation, reorganizing throughout the lifespan according to the auditory input that is available to the individual. Hearing aid amplification can be used as a model for studying the effects of auditory stimulation on the CAS. In theory, when sound is amplified by a hearing aid, neural response patterns should be larger in amplitude and shorter in latency when compared with unaided neural responses. However, two previous experiments indicate that this is not the case; when 20 dB of gain was provided by a hearing aid, there were no significant differences between unaided and aided neural responses patterns (Billings et al., 2007 Tremblay et al., 2006). Presumably, an interaction is occurring between the way sound is processed by the hearing aid and encoded by the CAS. One possibility is that the hearing aid introduces additional noise into the system, hence, maintaining similar signal-to-noise ratios (SNRs) across unaided and aided conditions. The purpose of this study was to determine the effect of tone level and SNR on the latency and amplitude of the evoked response. In agreement with animal and human signal-in-noise experiments, we hypothesized that SNR, rather than absolute signal level, would be the key factor determining human cortical auditory evoked potential (CAEP) characteristics. We recorded CAEPs from 15 normal-hearing young adults in response to signal-in-noise stimuli. A 1000 Hz tone was presented at two tone levels while continuous background noise levels were varied in 6 equivalent SNR steps. These 12 conditions were used to determine the effects of signal level and SNR level on CAEP components P1, N1, P2, and N2. As hypothesized, amplitude increased and latency decreased with increasing SNR. In addition, there was no main effect of tone level, indicating that the morphology of the P1-N1-P2 complex is driven primarily by SNR rather than absolute tone level. These results extend our understanding of how the CAS encodes signals-in-noise, and potentially help explain previous results found in aided CAEP conditions. The importance of SNR in determining the magnitude and timing of the evoked response highlights the importance of taking background noise and its audibility into account when recording aided CAEPs.

"Israel served the Lord": The book of Joshua as paradoxical portrait of faithful Israel

Billings, Rachel Margaret Harvard University 2010 해외박사(DDOD)

Two major frameworks have dominated scholarly reading of the book of Joshua within the past century: the literary "discovery" of the Deuteronomistic History and the archaeological discovery of evidence that enabled analysis of the historical data underlying the story of Israel's occupation of Canaan. This dissertation will address the fragmentation often brought about by the latter development and offer a more wholistic reading of the book with a focus on its meaning and purpose as a literary work, building upon several other recent attempts at such a reading in the process. In response to the scholarly observation that the book of Joshua is fraught with tensions that are not easily understood or resolved, I propose as a starting point the surprising "verdict" in Josh 24:31 that "Israel served the Lord during all the days of Joshua." When it is taken seriously as a literary clue that points to a theological interpretation of the totality of Israel's actions in the book of Joshua, it broadens and deepens the reader's understanding of Israel's service to the Lord, allowing it to encompass Israel's repentance and YHWH's mercy, not only Israel's obvious acts of obedience. Through this hermeneutical and literary lens, I consider two pairs of stories and a major set of themes in the book of Joshua: the stories of Rahab and Achan, the stories of the Gibeonites and the Transjordanian altar, and the themes of Israel's complete or incomplete taking of the land of Canaan. I argue that the way in which the book of Joshua presents these stories reminds Israel of the dynamic nature of its identity as YHWH's people---an identity that demands a continued response of obedience parallel to YHWH's ever-unfolding work on Israel's behalf. The book of Joshua portrays Israel's obedience as not merely an unattainable ideal or a thing of the past, but a living reality that unfolds when YHWH's people acknowledge His claim upon them and strive to serve Him. In this way, the book of Joshua tells the story of Israel's early days in the land in a way that makes it available as a resource for Israel's life before YHWH throughout the ages.

Former Florida State Probation Officers Who Have Supervised Adult Sex Offenders regarding How Empathy Is Displayed by the Sex Offenders

Billings, M. Dawn Ashford University ProQuest Dissertations & Theses 2020 해외박사(DDOD)

Connecting assessment to information technology competence

Billings, Linda L University of Minnesota 2000 해외박사(DDOD)

Research has shown that computer-based assessment holds unlimited promise for the future of competency-based assessment in a variety of educational and work settings. Along with the growth of technology based assessment there has been an increasing need for assessment of information technology competence. This research explored the use of computer-based assessment to measure information technology competencies. The purpose of the study was to analyze the content validity of National Education Training Group (NETg) computer-based assessment software, relative to the Minnesota Information Technology Competency List (MITCL). This was accomplished by developing a NETg assessment, the Minnesota Information Technology Competence Assessment Instrument (MITCAI), that was aligned with the objectives of the MITCL. The utility of NETg was evaluated during a pilot study of an abridged NETg assessment that was administered by Minnesota State Colleges and Universities. The relationship between a pilot test of Skills Assessment Manager (SAM), another assessment software, and the NETg assessment was also analyzed. Participants' self-assessment of their information technology competence, and their grades in a beginning MS Office course, were compared to the assessments to investigate concurrent validity. Predictive factors that were evaluated include demographics and computer related experience. The assessment instruments did not prove to be valid and reliable for purposes of measuring the entire MITCL. A sub-group of the study sample who participated in the SAM pilot test expressed a preference for the SAM assessment.

A heuristic method for scheduling and dispatching of factory production using multiclass fluid networks

Billings, Ronald Lester The University of Texas at Austin 2003 해외박사(DDOD)

This dissertation describes a two-phase heuristic method for scheduling and dispatching production in a factory. In the first phase, the production flow is modeled as a multiclass fluid network. This fluid queueing model is a relaxation of the deterministic factory scheduling problem (in addition to being a limit of the stochastic queueing model) so it functions as an approximation of a discrete flexible job-shop with WIP and ongoing inputs. However, buffer levels are allowed to have non-integer values, equipment processing can be simultaneously shared between different products, and a single lot can begin processing at a downstream step before it completely finishes at the previous step. By solving a finite series of quadratic (or linear) programs, an optimal (or nearly optimal) control policy is found for this fluid relaxation problem (with a weighted holding cost objective). In the second phase, production in the discrete factory queueing network is scheduled ahead of time or dispatched in real time by minimizing the deviation of the production from the optimal fluid control policy. Starting assignments are set with a mixed-integer program, and special techniques are used for comprehending batching and for avoiding sequence-dependent set-ups.

12-year follow-up study of child custody mediation: A focus on child and family functioning

Billings, Lisa Laumann University of Virginia 2001 해외박사(DDOD)

Long-term follow-up data were obtained on a sample of low-income families who had been randomly assigned to mediate or litigate their child custody disputes. Results indicated that mediation can lead to important changes in the family functioning of divorced families even 12 years after initial dispute resolution. In comparison to families that litigated, nonresidential parents who mediated maintained more contact with their children and were involved more in their children's day-to-day upbringing. Increased contact with nonresidential parents did not lead to increased interparental conflict: No differences were found between the mediation and litigation groups in level of interparental conflict. Unexpectedly, children whose parents mediated were significantly more likely to make multiple informal changes in their residential arrangements. No differences between the mediation and litigation groups were found across any of the indices of children's well-being—that is, either in terms of their global psychological functioning or according to more subtle measures of their inner experience. When the children who made multiple changes in residence were excluded from the group comparions, however, evidence emerged that mediation children reported fewer internalizing problems and tended to report fewer externalizing symptoms. Close nonresidential parent-child relationships, reduced conflict and feeling less caught in the middle of parental conflict, an authoritative parenting style, and a lack of multiple changes in residential arrangements all predicted children's positive adjustment. Finally, nonresidential parent involvement was only linked to children's well-being in families with low levels of ongoing interparental conflict.

Preparing to teach English language learners: An analysis of teachers' online interactions

Billings, Elsa S Stanford University 2004 해외박사(DDOD)

Emerging technologies such as the Internet, online video, and synchronous/asynchronous communication tools show promise in addressing problematic issues in teacher education and professional development (Eastmond, 1998), including addressing the gap between theory and practice, supporting critical analysis of pedagogy, and situating learning in practice as it depicts the complex nature of teaching (Ball, 2002; Center for Education, 2001; Grant, 1996). However, the degree to which courses that utilize these technologies are founded on solid pedagogical theory and research is unclear. This is particularly the case with online courses which are cropping up across the United States. This study explored the effectiveness of an online course created by researchers and educators at Stanford University. The course was one in a series of online courses around effective practices in teaching English language learners (ELLs) that led to California's Cross-Cultural, Language and Academic Development (CLAD) certification. California's CLAD program has existed in various forms since the early 1980's, yet research on it is very limited (Walqui, 1998; Whitenack, 1995). The course utilized a multimedia, online platform with video cases of effective practice in classrooms with ELLs as the main form of instruction. Study participants were 21 in-service teachers. Transcripts of online discussions served as the data source. This study utilized qualitative content analyses of online discussions, descriptive statistics, and a Reflection Rubric specifically developed for this study. Findings showed mixed, yet promising evidence of conceptual change, reflection, and community development. Each of these areas was present in this online CLAD course, with issues that surfaced around each mirroring those found in face-to-face courses. Findings revealed instances of new knowledge and conceptual changes in understanding, as well as deficits and reliance on prior conceptions based mainly on personal experiences. Participants' willingness to reflect on practice varied, as did the depth of their reflection in the times that they did reflect. Many participants avoided reflection altogether, especially on their own practice. Implications stemming from this study include contributions for the advancement of online courses, diversity training, and the development of a theoretical framework with which to both design and study online courses.

Sex. Aliens. Harvard? Rhetorical boundary-work in the media: (A case study of the role of journalists in the social construction of scientific authority)

Billings, Linda Indiana University 2005 해외박사(DDOD)

With science and the media playing prominent roles in contemporary life, it is important to understand the cultural authority of science and the role of the media in maintaining this authority. This paper will report on a case study of journalists' participation in the social construction of scientific authority. The case involves print media coverage of controversial scientific research conducted by a tenured professor of psychiatry at Harvard Medical School, a Pulitzer Prize winner, and a well-known authority in his field. When this elite scientist embarked upon the study of people who believe they have been abducted by aliens he drew fire for stepping outside the boundaries of "real" science, despite his stellar credentials and long history of accomplishment. Much of this fire took place on the field of the mass media. The boundaries of science and scientific authority were tested in this case, and journalists played a role in the boundary-work. Employing the sensitizing concept of boundary-work to guide analysis of media content, this case study explores how journalists constructed scientific authority in their coverage of Mack's abduction research, and to what ends, and how scientific and journalistic norms operate in media coverage of science. Rhetoric is a primary tool for constructing social reality, and the rhetoric of science is a key source---for the purposes of this study, arguably the sole source---of the cultural authority of science. Burke's dramatistic criticism is thus employed as a primary analytic tool in this study, to excavate the landscape of symbolic communication. The aim of this study is to illuminate ambiguity, complexity, motives and meanings in this case. It is intended to be thought provoking, instructive, and productive, to enrich the ongoing examination of the cultural roles of science and journalism.

Thyroid Hormone Signaling during Chick Retinal Development

Billings, Nathan Andrew Harvard University 2011 해외박사(DDOD)

Thyroid Hormone (TH) is a small iodinated molecule that effects gene expression in virtually every type of vertebrate tissue. Appropriate levels of TH are critical for the proper development and maturation of several tissues, including the brain, cochlea, and retina. The objectives of this dissertation were to examine the competence and autonomy of retinal cells to respond to TH signaling during early development. To address these open questions we used a well characterized central nervous system (CNS) tissue, the retina. TH signaling components are expressed during retinal development in dynamic spatial and temporal patterns. First, to probe the competence of retinal cells to mount a transcriptional response to TH, reporters that included thyroid response elements (TREs) were introduced into developing retinal tissue. Some TREs were positively activated by TR+TH in the developing outer nuclear layer (ONL), where photoreceptors reside, as well as in the outer neuroblastic layer (ONBL) where cycling progenitor cells are located. Other TREs were actively repressed by TR+TH in cells of the ONBL. A central-nasal domain was revealed reflective of a global repression in NR signaling which corresponded temporally with the genesis of photoreceptors and spatially with the developing rod-free zone (RFZ). The transcriptional response to these TREs provided a starting point to examine the cell autonomy of the deiodinase enzymes, which provide tissue-specific activation of TH, during development. Dio2 (TH-activating) RNA is restricted to the ONL whereas Dio3 RNA is expressed in progenitor cells. However, it was unknown as to whether Dio2+ cells functioned non-autonomously by activating TH for neighboring cells (as is modeled in the brain), or cell autonomously in only post-mitotic immature photoreceptors. Using a systematic approach of single and double short hairpin RNA (shRNA) knock-down, combined with hormone modulation, we demonstrated a cell autonomous requirement for Dio2 and T3 signaling and that Dio2 is expressed at low, but biologically relevant levels, in a subset of cells outside the ONL. Additionally, these data suggest an under-appreciated requirement for TH signaling in retinal progenitor cells during development. Our experiments help to define the complex roles of the deiodinases and TH signaling during chick retinal development.