Overwintering Habitat of American Dipper, Cinclus mexicanus, Observed in an Arctic Groundwater Spring Feeding on Dolly Varden, Salvelinus malma

Perennial groundwater springs along the Alaska and Yukon North Slope provide overwintering habitat for various organisms, including birds and fishes. We observed an American Dipper, Cinclus mexicanus, in the open water of a perennial spring situated in Fish Creek, Yukon, in Ivvavik National Park on 8 March 2018. The observation at Fish Creek was among the most northern documented sightings of an American Dipper during the winter in North America. Moreover, the observation was approximately 650 km farther north than where American Dippers have been documented overwintering in Yukon, making this the most northern Canadian observation documented for this species in any season. Additionally, the American Dipper was photographed feeding on a juvenile Dolly Varden, Salvelinus malma. Although American Dippers are known to feed on small fish, our observation was a novel documentation of a trophic interaction between both species during winter. The open-water habitat in Fish Creek, which is important for both species and has not been previously described, was short (~730 m long), shallow (mean = 20 cm deep), narrow (mean = 2.8 m wide), and cold (mean water temperature = 0.34ºC). While there is little information regarding the ecological interactions of American Dipper overwintering in the Arctic, we note that all observations in the North Slope area during winter occurred in river systems also used by Dolly Varden, which indicates that juvenile Dolly Varden could be an important source of food for American Dipper in winter.Les sources d’eau souterraine pérennes le long du versant nord de l’Alaska et du Yukon procurent un habitat d’hivernage à divers organismes, y compris les oiseaux et les poissons. Le 8 mars 2018, nous avons observé un cincle d’Amérique (Cinclus mexicanus) dans l’eau libre d’une source pérenne située au ruisseau Fish, dans le parc national Ivvavik, au Yukon. L’observation faite au ruisseau Fish figurait parmi les observations hivernales les plus nordiques du cincle d’Amérique à avoir été répertoriées en Amérique du Nord. Cette observation a été faite à environ 650 km plus au nord que l’endroit où l’habitat d’hivernage des cincles d’Amérique a été documenté au Yukon, ce qui représente l’observation la plus nordique au Canada à avoir été consignée pour cette espèce à n’importe quelle saison. Par surcroît, le cincle d’Amérique a été photographié en train de se nourrir d’un omble malma juvénile (Salvelinus malma). Bien que l’on sache que les cincles d’Amérique se nourrissent de petits poissons, l’observation que nous avons documentée constituait un nouveau cas d’interaction trophique entre les deux espèces pendant l’hiver. L’habitat en eau libre du ruisseau Fish, qui est important pour les deux espèces et n’a pas encore été décrit, était court (environ 730 m de long), peu profond (moyenne de 20 cm de profondeur), étroit (moyenne de 2,8 m de largeur) et froid (moyenne de la température de l’eau = 0,34 ºC). Bien qu’il existe peu d’information sur les interactions écologiques du cincle d’Amérique hivernant dans l’Arctique, notons qu’en hiver, toutes les observations faites dans la région du versant nord ont eu lieu dans des réseaux hydrographiques où vit également l’omble malma, ce qui laisse croire que l’omble malma juvénile pourrait représenter une source de nourriture importante pour le cincle d’Amérique en hiver

Scattering theory for the Schr\"odinger-Debye System

We study the Schr\"odinger-Debye system over $\mathbb{R}^d$ iu_t+\frac 12\Delta u=uv,\quad \mu v_t+v=\lambda |u|^2 and establish the global existence and scattering of small solutions for initial data in several function spaces in dimensions $d=2,3,4$. Moreover, in dimension $d=1$, we prove a Hayashi-Naumkin modified scattering result.Comment: 22 page

In the loop: a social network approach to the willingness to communicate in the L2 (L2 WTC)

Despite the conceptual importance of investigating the social context(s) in which second-language (L2) learning and use take place, the decade-old “social turn” within the field of second-language acquisition (SLA) has yet to produce a “parsimonious system of valid and generalizable parameters to describe contextual characteristics” (Dörnyei, 2009a, p. 238). Accordingly, investigating social network structure has recently been suggested as a general approach to examining the link between person and environment (Beckner, et al., 2009). In the current thesis, I offer a network approach in which second-language (L2) learning and use is regarded both as purposeful and as constrained by one’s social relationships. Subsequently, in a first-of-its-kind study within SLA, I apply social network analysis – a diverse array of formally-defined measures of social position and other socio-structural features – to conceptualize and empirically test the relationship between social structure and the willingness to communicate in the L2 (L2 WTC), defined as the “readiness to enter into discourse at a particular time with a specific person or persons, using a L2” (MacIntyre, et al., 1998, p. 547). In a study of Chinese-speaking international students at a British university, trait-like L2 WTC is found to predict cross-cultural adjustment, suggesting the role of actively engaging with one’s new cultural surroundings in establishing an adaptive person-environment fit. Subsequently, in the first study to apply modern, graph-theoretic notions of social position to a network of L2 learners, a significant relationship is found between various notions of structural position among a network of international English-for-Academic-Purposes students, and dispositional L2 WTC. Overall, the results support L2 WTC as both purposeful and constrained, learned from one’s past interactions, yet pushing the individual to take advantage of opportunities to communicate in the L2. Implications, limitations, and future directions of a social network approach to L2 learning and use are also discussed

Power laws, Discontinuities and Regional City Size Distributions

Urban systems are manifestations of human adaptation to the natural environment. City size distributions are the expression of hierarchical processes acting upon urban systems. In this paper, we test the entire city size distributions for the southeastern and southwestern United States (1990), as well as the size classes in these regions for power law behavior. We interpret the differences in the size of the regional city size distributions as the manifestation of variable growth dynamics dependent upon city size. Size classics in the city size distributions are snapshots of stable states within urban systems in flux

Is a Recent Surge in Global Warming Detectable?

The global mean surface temperature is widely studied to monitor climate change. A current debate centers around whether there has been a recent (post-1970s) surge/acceleration in the warming rate. This paper addresses whether an acceleration in the warming rate is detectable from a statistical perspective. We use changepoint models, which are statistical techniques specifically designed for identifying structural changes in time series. Four global mean surface temperature records over 1850-2023 are scrutinized within. Our results show limited evidence for a warming surge; in most surface temperature time series, no change in the warming rate beyond the 1970s is detected. As such, we estimate minimum changes in the warming trend for a surge to be detectable in the near future

Inuit observations of a tunicata bloom unusual for the amundsen gulf, western Canadian arctic

© 2020, Canadian Science Publishing. All rights reserved. Inuit are at the forefront of ecosystem change in the Arctic, yet their observations and interpretations are rarely reported in the literature. Climate change impacts are rapidly unfolding in the Arctic and there is a need for monitoring and reporting unique observations. In this short communication, we draw upon observations and experiential knowledge from western Canadian Inuit (Inuvialuit) harvesters combined with a scientific assessment to describe and interpret an unusual account of gelatinous organisms at high densities during summer 2019 in eastern Amundsen Gulf, near Ulukhaktok, Northwest Territories. The gelatinous organisms were identified as primarily appendicularian larvaceans (Oikopleura spp., pelagic tunicates) and their gelatinous “houses”. The organisms were observed within 3–5 km of the marine coast, from ∼1–2 m below the surface and to depths of ∼30 m with an underwater camera. Pelagic tunicates have rarely been documented in the eastern Amundsen Gulf and, to our knowledge, this was the first time these organisms had been noted by the people of Ulukhaktok. The pelagic tunicates clogged subsistence fishing nets and Inuvialuit harvesters were concerned about negative impacts to marine mammals and fishes, which they depend on for food security. These interpretations highlight major knowledge gaps for appendicularians in the Arctic

In the loop: a social network approach to the willingness to communicate in the L2 (L2 WTC)

Despite the conceptual importance of investigating the social context(s) in which second-language (L2) learning and use take place, the decade-old “social turn” within the field of second-language acquisition (SLA) has yet to produce a “parsimonious system of valid and generalizable parameters to describe contextual characteristics” (Dörnyei, 2009a, p. 238). Accordingly, investigating social network structure has recently been suggested as a general approach to examining the link between person and environment (Beckner, et al., 2009). In the current thesis, I offer a network approach in which second-language (L2) learning and use is regarded both as purposeful and as constrained by one’s social relationships. Subsequently, in a first-of-its-kind study within SLA, I apply social network analysis – a diverse array of formally-defined measures of social position and other socio-structural features – to conceptualize and empirically test the relationship between social structure and the willingness to communicate in the L2 (L2 WTC), defined as the “readiness to enter into discourse at a particular time with a specific person or persons, using a L2” (MacIntyre, et al., 1998, p. 547). In a study of Chinese-speaking international students at a British university, trait-like L2 WTC is found to predict cross-cultural adjustment, suggesting the role of actively engaging with one’s new cultural surroundings in establishing an adaptive person-environment fit. Subsequently, in the first study to apply modern, graph-theoretic notions of social position to a network of L2 learners, a significant relationship is found between various notions of structural position among a network of international English-for-Academic-Purposes students, and dispositional L2 WTC. Overall, the results support L2 WTC as both purposeful and constrained, learned from one’s past interactions, yet pushing the individual to take advantage of opportunities to communicate in the L2. Implications, limitations, and future directions of a social network approach to L2 learning and use are also discussed

Group testing models with unknown link function

Group testing through the use of pooling has proven to be an efficient method of reducing the time and cost associated with screening for a binary characteristic of interest such as infection status. A topic of key interest in this area involves the development of regression models that relate the individual level covariates to the binary pool testing responses. The research in this area has primarily focused on parametric regression models. In this poster, we will introduce a new estimation method which can handle multi-dimensional covariates while assuming the link is unknown. The asymptotic properties of our estimators are also presented. We investigate the performance of our method through simulation and by applying it to a hepatitis data set obtained from the National Health and Nutrition Examination Survey

Improving long-term disaster recovery research in Australia through boosting dataset comparability

Emergencies and disasters are increasing in frequency and complexity in Australia and around the world.1 It is well established that the effects of these events take a long time to recover from. There is strong and growing evidence to show that different segments of society are exposed to disasters in different ways, with people and communities affected in interconnected and compounding ways