Retinal synaptic function in the absence of the on pathway.

Complete Congenital Stationary Night Blindness (cCSNB) is a rare hereditary retinal disorder characterized by abnormal night vision. cCSNB is caused by postsynaptic defects in On bipolar cells (BCs) and is identified by the presence of an electroretinogram (ERG) with a normal a-wave, corresponding to photoreceptor function, and the absence of a b-wave, corresponding to a failure of On BC function. Through the study of genetic mutations in mouse that result in no b-wave ERG phenotypes, several proteins have been identified that play crucial roles in On BC signal transmission. I focused on four mouse models of cCSNB; Nyxnob (Nyctalopin mutant), mGluR6-/- (mGluR6 knockout), Gpr179nob5 (GPR179 mutant), and Lrit3-/- (LRIT3 knockout). These mutations effect proteins expressed by On BCs (rod and On Cone BCs). While all models of cCSNB share a no b-wave ERG phenotype I have discovered that several models differ. The differences between cCSNB animal models provide important clues into the functional roles of the proteins effected by the mutations. Specifically, Nyxnob retinal ganglion cells (RGCs), the output neurons of the retina, exhibit robust 3-5 Hz rhythmic spiking while mGluR6-/- RGCs rarely do. I explored potential mechanisms which underlie this phenomenon, not only by examining RGC activity, but also the properties of the upstream rod BCs which provide excitatory input to RGCs. I found that differences in the resting state of Nyxnob and mGluR6-/- rod BCs correlate with the differences in RGC rhythmic spiking activity. Also, I discovered that nyctalopin is required for normal potassium conductance in rod BCs. Additionally, I examined the role of two recently identified proteins expressed in On BCs, GPR179 (Peachey et al., 2012; Ray et al., 2014) and LRIT3 (Zeitz et al., 2013; Neuille et al., 2014). I discovered that GPR179 sets the sensitivity of the TRPM1 channel and is critical for a normal light-evoked response in rod BCs. I also discovered that LRIT3 is critical for the modulation and expression of TRPM1 channels in rod BC dendritic tips. My data not only add to the literature on animal models of cCSNB, but to the understanding of retinal circuitry in the normal retina

Toward Critical Social Media Pedagogy: The Intersection of Narrative, Social Media, and the Civic

This paper presents a theoretical meditation connecting the co-constructed, participatory narratives of social media with opportunities for increased participatory and critical civic engagement. We argue that teaching with and through social media uses practices to develop student agency, facilitate raised-consciousness, and encourage action-oriented problem solving by leveraging co-constructed processes and the social. We work toward a critical social media pedagogy by considering the possibilities of social media. These allow for storytelling across dimensions of time and space through co-constructed understandings of reality in order to bend the arc of narrative. Further, we contend that through social media storytelling, we see the development of preconditions for civic engagement engaging in identity formation, affinity building, and participation

On a mean field game formulation of fish stock exploitation

[Abstract unavailable

Prehistoric settlement and agriculture on the Eastern Moors of the Peak District.

The project is a study of soil erosion within the cairnfields on the Eastern Moors of Derbyshire. A range of Archaeological features and natural sedimentary sequences were excavated in the search for eroded sediments. The erosion evident at these features was dated by means of radiocarbon and optically stimulated luminescence dating. Contrary to previous assumptions as to the scale of erosion in later prehistory, which maintain that this was a severe problem, it is concluded that the evidence indicates a low degree of erosion for the Bronze Age. Erosion is concluded to have increased from the Iron Age with the establishment of extensive pasture land

Fluid Mud Formation in the Petitcodiac River, New Brunswick, Canada

Thesis advisor: Gail C. KinekeExperiments were conducted in the Petitcodiac River in New Brunswick, Canada during June and August 2006 to study high-concentrations of suspended sediment in a turbulent system. This study will evaluate the conditions necessary for fluid mud formation by investigating 1) the suppression of turbulence at gradient Richardson numbers greater than 0.25; 2) a threshold condition for the amount of sediment a flow can maintain in a turbulent suspension; and 3) the influence of flocculation on vertical suspended-sediment transport. Direct measurements of salinity, temperature, current velocity, and suspended-sediment concentration were collected during accelerating and decelerating flows and when fluid mud formed. In June, current velocities were typically above 1 m s-1 and suspended-sediment concentrations were generally less than 10 g l -1. In August, current velocities were typically less than 1.5 m s-1, suspended-sediment concentrations were greater than 10 g l -1, and a high-concentration bottom layer formed rapidly during decelerating flood currents. Gradient Richardson numbers for concentrations greater than 10 g l -1 were generally greater than 0.25, suggesting strong density gradients have the ability to suppress turbulence. Results from the Petitcodiac suggest a carrying capacity threshold might exist, but is based on a critical gradient Richardson number between 1.0 and 2.0 rather than the previously accepted value of 0.25. Differences in the evolution of disaggregated grain size distributions for settling suspensions suggest flocculation plays an important role for fluid mud formation by enhancing settling of fine sediments.Thesis (MS) — Boston College, 2009.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Geology and Geophysics

The utility of twins in developmental cognitive neuroscience research: How twins strengthen the ABCD research design

The ABCD twin study will elucidate the genetic and environmental contributions to a wide range of mental and physical health outcomes in children, including substance use, brain and behavioral development, and their interrelationship. Comparisons within and between monozygotic and dizygotic twin pairs, further powered by multiple assessments, provide information about genetic and environmental contributions to developmental associations, and enable stronger tests of causal hypotheses, than do comparisons involving unrelated children. Thus a sub-study of 800 pairs of same-sex twins was embedded within the overall Adolescent Brain and Cognitive Development (ABCD) design. The ABCD Twin Hub comprises four leading centers for twin research in Minnesota, Colorado, Virginia, and Missouri. Each site is enrolling 200 twin pairs, as well as singletons. The twins are recruited from registries of all twin births in each State during 2006–2008. Singletons at each site are recruited following the same school-based procedures as the rest of the ABCD study. This paper describes the background and rationale for the ABCD twin study, the ascertainment of twin pairs and implementation strategy at each site, and the details of the proposed analytic strategies to quantify genetic and environmental influences and test hypotheses critical to the aims of the ABCD study. Keywords: Twins, Heritability, Environment, Substance use, Brain structure, Brain functio

Tools, Processes, Participation: Social Media for Learning, Teaching, and Social Change

Despite attempted pedagogical shifts toward situated learning, social constructivism, and social practice theory, we find pedagogy for social media to remain primarily situated in behaviorist or cognitivist assumptions of learning. Moreover, in an attempt to craft our own participatory pedagogies of social media, we found ourselves returning to metaphors and language rooted in ontological assumptions of objectivism. That is to say, we continually referred to social media as a tool with affordances to be leveraged for learning. In this paper we examine three understandings of social media - as we see them - in literature, pedagogy, and practice. We categorize these understandings through the psychological perspectives of behaviorist, cognitivist, and sociocultural learning theories. In so doing, we imagine new ways of both using social media for teaching and learning as well as possible language to better reflect our own ontological and epistemological assumptions of social media

Quadratic BSDEs driven by a continuous martingale and application to utility maximization problem

In this paper, we study a class of quadratic Backward Stochastic Differential Equations (BSDEs) which arises naturally when studying the problem of utility maximization with portfolio constraints. We first establish existence and uniqueness results for such BSDEs and then, we give an application to the utility maximization problem. Three cases of utility functions will be discussed: the exponential, power and logarithmic ones