Master of Science

thesisThis study compared difficulties in emotion regulation among primary, secondary, and low callous-unemotional (CU) youth in a sample of 417 detained adolescents (306 boys, 111 girls). Mixture modeling on the basis of posttraumatic stress disorder (PTSD) symptoms identified two groups of youth high in CU traits consistent with primary and secondary CU. Youth were typologized on the basis of PTSD symptoms which represents a novel method that is consistent with the theory underlying secondary callousness. Compared to youth classified in the primary group, youth classified as secondary CU reported higher levels of PTSD symptoms, anxiety, trauma exposure, and difficulties with clarity of emotions and nonacceptance of emotions. Difficulties in emotion regulation reported by youth in the secondary versus primary groups may be related to processes involving emotional numbing in the aftermath of posttraumatic distress. The results of the current study have implications for the classification of primary and secondary CU as well as the clinical treatment of youth with these characteristics

Doctor of Philosophy

dissertationThis study investigated psychophysiological responding comparing youth with primary, acquired, and lower callous-unemotional (CU) traits in a sample of 361 detained adolescents (265 boys, 96 girls). Mixture modeling using posttraumatic stress symptoms (PTSS) to delineate groups resulted in two groups of youth high in CU traits that were consistent with primary and secondary, or acquired, CU variants. Compared to youth classified in the primary group, youth classified as acquired-CU self-reported higher levels of PTSS, trauma exposure, anxiety, and emotion dysregulation, consistent with previous studies. Psychophysiological responses, specifically electrodermal activity (EDA) and respiratory sinus arrhythmia (RSA), were measured during baseline, in response to a video task, and during recovery. Results of multilevel models indicated no differences between the primary- and acquired-CU youth in RSA, although the acquired CU group evidenced a less steep recovery slope in EDA. The results of the current study have implications for our understanding of the pathways underlying the development of CU traits as well as for informing interventions with youth with these characteristics. Future directions for research on the development of CU traits are discussed

Relation between Sexual and Gender Minority Status and Suicide Attempts Among Veterans Seeking Treatment for Military Sexual Trauma

There is limited study of suicidal behaviors among veterans identifying as sexual and gender minorities (SGMs), despite previous research indicating rates of suicide attempts are high within civilian SGM populations. Further, some research incorporating military service members suggests those identifying as SGMs are disproportionately exposed to military sexual trauma (MST), an additional risk factor for negative psychiatric sequelae. To address health care research disparities among minority veterans (i.e., women, those endorsing MST, SGMs), we examined presentations of veterans (N = 277) who attended initial consultation appointments for MST-related treatment and completed a semistructured clinical interview including demographic characteristics, history of suicide attempts (HSA), and a diagnostic evaluation. Twenty-eight (10.1%) veterans identified as SGMs. SGM/non-SGM groups were contrasted on suicidal and psychiatric morbidity outcomes. Overall, endorsement of HSA was high (30.7%). Despite similar clinical profiles, 53.6% of veterans who identified as SGM endorsed HSA in contrast with 28.1% of peers identifying as heterosexual and nontransgender, a significant effect of small-to-moderate size. Findings suggest assessment and clinical management of suicidality is of critical importance for clinicians providing services to veterans pursuing recovery from MST, generally, and may be especially so when delivering care to SGM. Further, results underscore the need for culturally competent delivery of trauma-focused interventions

Mapping the spatiotemporal dynamics of calcium signaling in cellular neural networks using optical flow

An optical flow gradient algorithm was applied to spontaneously forming net- works of neurons and glia in culture imaged by fluorescence optical microscopy in order to map functional calcium signaling with single pixel resolution. Optical flow estimates the direction and speed of motion of objects in an image between subsequent frames in a recorded digital sequence of images (i.e. a movie). Computed vector field outputs by the algorithm were able to track the spatiotemporal dynamics of calcium signaling pat- terns. We begin by briefly reviewing the mathematics of the optical flow algorithm, and then describe how to solve for the displacement vectors and how to measure their reliability. We then compare computed flow vectors with manually estimated vectors for the progression of a calcium signal recorded from representative astrocyte cultures. Finally, we applied the algorithm to preparations of primary astrocytes and hippocampal neurons and to the rMC-1 Muller glial cell line in order to illustrate the capability of the algorithm for capturing different types of spatiotemporal calcium activity. We discuss the imaging requirements, parameter selection and threshold selection for reliable measurements, and offer perspectives on uses of the vector data.Comment: 23 pages, 5 figures. Peer reviewed accepted version in press in Annals of Biomedical Engineerin

Magnetogenesis from Cosmic String Loops

Large-scale coherent magnetic fields are observed in galaxies and clusters, but their ultimate origin remains a mystery. We reconsider the prospects for primordial magnetogenesis by a cosmic string network. We show that the magnetic flux produced by long strings has been overestimated in the past, and give improved estimates. We also compute the fields created by the loop population, and find that it gives the dominant contribution to the total magnetic field strength on present-day galactic scales. We present numerical results obtained by evolving semi-analytic models of string networks (including both one-scale and velocity-dependent one-scale models) in a Lambda-CDM cosmology, including the forces and torques on loops from Hubble redshifting, dynamical friction, and gravitational wave emission. Our predictions include the magnetic field strength as a function of correlation length, as well as the volume covered by magnetic fields. We conclude that string networks could account for magnetic fields on galactic scales, but only if coupled with an efficient dynamo amplification mechanism.Comment: 10 figures; v3: small typos corrected to match published version. MagnetiCS, the code described in paper, is available at http://markcwyman.com/ and http://www.damtp.cam.ac.uk/user/dhw22/code/index.htm

A study exploring learners' informal learning space behaviors, attitudes, and preferences

What makes a successful informal learning space is a topic in need of further research. The body of discourse on informal space design is drawn from learning theory, placemaking and architecture, with a need for understanding of the synergy between the three. Findings from a longitudinal, quantitative and qualitative study at Sheffield Hallam University, explore learners' behaviours, attitudes and preferences towards informal learning spaces in higher education, within and outside of the context of the academic library. The learning spaces study contributes to the discourse on informal learning spaces design by producing a typology of nine learning space preference attributes which address aspects of learning theory, placemaking and architecture. The typology can be used to evaluate existing spaces and inform redevelopment of informal learning spaces in higher education institutions. Implementing the typology will be subject to localised conditions, but at Sheffield Hallam University the key conclusions have included developing a portfolio of discrete, interrelated learning environments, offering spaces with a clear identity and encouraging students to translate their learning preferences into space selection

Cellular Senescence: Defining a Path Forward.

Cellular senescence is a cell state implicated in various physiological processes and a wide spectrum of age-related diseases. Recently, interest in therapeutically targeting senescence to improve healthy aging and age-related disease, otherwise known as senotherapy, has been growing rapidly. Thus, the accurate detection of senescent cells, especially in vivo, is essential. Here, we present a consensus from the International Cell Senescence Association (ICSA), defining and discussing key cellular and molecular features of senescence and offering recommendations on how to use them as biomarkers. We also present a resource tool to facilitate the identification of genes linked with senescence, SeneQuest (available at http://Senequest.net). Lastly, we propose an algorithm to accurately assess and quantify senescence, both in cultured cells and in vivo

Towards an integrative understanding of soil biodiversity

Soil is one of the most biodiverse terrestrial habitats. Yet, we lack an integrative conceptual framework for understanding the patterns and mechanisms driving soil biodiversity. One of the underlying reasons for our poor understanding of soil biodiversity patterns relates to whether key biodiversity theories (historically developed for aboveground and aquatic organisms) are applicable to patterns of soil biodiversity. Here, we present a systematic literature review to investigate whether and how key biodiversity theories (species-energy relationship, theory of island biogeography, metacommunity theory, niche theory and neutral theory) can explain observed patterns of soil biodiversity. We then discuss two spatial compartments nested within soil at which biodiversity theories can be applied to acknowledge the scale-dependent nature of soil biodiversity.Peer reviewe