Penguins past and present: Trace elements, stable isotopes, and population dynamics in Antarctic and sub-Antarctic penguins and seals

Antarctica and the sub-Antarctic are remote regions where the impacts from climate change and anthropogenic activities are increasingly apparent. Previous studies show that the Antarctic is warming and has been affected by anthropogenic contaminants. Marine predators such as penguins and seals are commonly used in these regions as sentinels of ecosystem health as predator tissues can be used as non-invasive proxies of diet, population trends, and contaminant exposure. This thesis includes two separate studies which investigate the influence of climate change and human activity on Antarctic and sub-Antarctic ecosystems. First, Adelie penguin (Pygoscelis adeliae) eggshell samples were collected from four distinct regions of the Antarctic peninsula and analyzed for 12 heavy metals. Results were compared by geographic location, human activity, and trophic level differences to delineate drivers of variation. The main significant factors were geographic location and foraging; the influence of human presence was not an apparent driver, except for Zn. The toxic heavy metals As and Al were present in all samples suggesting ecosystem wide contamination, but Cd and Pb were widely undetectable. These results provide a baseline for future study of heavy metal exposure in Antarctic penguins using eggshell. Second, sediment cores were collected from two distinct sites on South Georgia Island, a sub-Antarctic island home to two key marine predators, the King Penguin (Aptenodytes patagonicus) and Antarctic fur seal (Arctocephalus gazella). Populations dynamics of these species have been affected by human exploitation and warming climate over the past two centuries, but records are sporadic. The sediment cores were determined to represent a 150-170 year time series. Dated sections were analyzed for total carbon (TN%), total nitrogen (TN%), δ13C, δ15N, and enumeration of biological remains (seal hairs and penguin feathers). These proxies of penguin and seal abundance were correlated with known changes in King Penguin populations since the early 1900s. These results provide details regarding the timing of penguin and seal recovery from exploitation concurrent with recent glacial retreat. This study validates the use of sediment cores as proxies for historical penguin and seal abundance on sub-Antarctic islands, allowing better management of these populations as the region continues to experience environmental change

Measuring Replicative Life Span in the Budding Yeast

Aging is a degenerative process characterized by a progressive deterioration of cellular components and organelles resulting in mortality. The budding yeast Saccharomyces cerevisiae has been used extensively to study the biology of aging, and several determinants of yeast longevity have been shown to be conserved in multicellular eukaryotes, including worms, flies, and mice 1. Due to the lack of easily quantified age-associated phenotypes, aging in yeast has been assayed almost exclusively by measuring the life span of cells in different contexts, with two different life span paradigms in common usage 2. Chronological life span refers to the length of time that a mother cell can survive in a non-dividing, quiescence-like state, and is proposed to serve as a model for aging of post-mitotic cells in multicellular eukaryotes. Replicative life span, in contrast, refers the number of daughter cells produced by a mother cell prior to senescence, and is thought to provide a model of aging in mitotically active cells. Here we present a generalized protocol for measuring the replicative life span of budding yeast mother cells. The goal of the replicative life span assay is to determine how many times each mother cell buds. The mother and daughter cells can be easily differentiated by an experienced researcher using a standard light microscope (total magnification 160X), such as the Zeiss Axioscope 40 or another comparable model. Physical separation of daughter cells from mother cells is achieved using a manual micromanipulator equipped with a fiber-optic needle. Typical laboratory yeast strains produce 20-30 daughter cells per mother and one life span experiment requires 2-3 weeks

Non Mean-Field Quantum Critical Points from Holography

We construct a class of quantum critical points with non-mean-field critical exponents via holography. Our approach is phenomenological. Beginning with the D3/D5 system at nonzero density and magnetic field which has a chiral phase transition, we simulate the addition of a third control parameter. We then identify a line of quantum critical points in the phase diagram of this theory, provided that the simulated control parameter has dimension less than two. This line smoothly interpolates between a second-order transition with mean-field exponents at zero magnetic field to a holographic Berezinskii-Kosterlitz-Thouless transition at larger magnetic fields. The critical exponents of these transitions only depend upon the parameters of an emergent infrared theory. Moreover, the non-mean-field scaling is destroyed at any nonzero temperature. We discuss how generic these transitions are.Comment: 15 pages, 7 figures, v2: Added reference

Quantum Chi-Squared and Goodness of Fit Testing

The density matrix in quantum mechanics parameterizes the statistical properties of the system under observation, just like a classical probability distribution does for classical systems. The expectation value of observables cannot be measured directly, it can only be approximated by applying classical statistical methods to the frequencies by which certain measurement outcomes (clicks) are obtained. In this paper, we make a detailed study of the statistical fluctuations obtained during an experiment in which a hypothesis is tested, i.e. the hypothesis that a certain setup produces a given quantum state. Although the classical and quantum problem are very much related to each other, the quantum problem is much richer due to the additional optimization over the measurement basis. Just as in the case of classical hypothesis testing, the confidence in quantum hypothesis testing scales exponentially in the number of copies. In this paper, we will argue 1) that the physically relevant data of quantum experiments is only contained in the frequencies of the measurement outcomes, and that the statistical fluctuations of the experiment are essential, so that the correct formulation of the conclusions of a quantum experiment should be given in terms of hypothesis tests, 2) that the (classical) $\chi^2$ test for distinguishing two quantum states gives rise to the quantum $\chi^2$ divergence when optimized over the measurement basis, 3) present a max-min characterization for the optimal measurement basis for quantum goodness of fit testing, find the quantum measurement which leads both to the maximal Pitman and Bahadur efficiency, and determine the associated divergence rates.Comment: 22 Pages, with a new section on parameter estimatio

Meta-Tracker: Fast and Robust Online Adaptation for Visual Object Trackers

This paper improves state-of-the-art visual object trackers that use online adaptation. Our core contribution is an offline meta-learning-based method to adjust the initial deep networks used in online adaptation-based tracking. The meta learning is driven by the goal of deep networks that can quickly be adapted to robustly model a particular target in future frames. Ideally the resulting models focus on features that are useful for future frames, and avoid overfitting to background clutter, small parts of the target, or noise. By enforcing a small number of update iterations during meta-learning, the resulting networks train significantly faster. We demonstrate this approach on top of the high performance tracking approaches: tracking-by-detection based MDNet and the correlation based CREST. Experimental results on standard benchmarks, OTB2015 and VOT2016, show that our meta-learned versions of both trackers improve speed, accuracy, and robustness.Comment: Code: https://github.com/silverbottlep/meta_tracker

Increasing Campus Sense of Belonging through LLC Participation: To Gems Camp We Go

Gemstone seeks to develop students’ research and collaboration skills, foster leadership opportunities, and provide a sense of belonging on a large campus utilizing the Best Practices Model (BPM) and a variety of high impact practices (HIPs), like a Gemstone-specific orientation program called Gems Camp. While studies have demonstrated that LLCs increase students’ sense of belonging, the goal of this study is to explicitly test via propensity score matching if (a) enrollment in the Gemstone Honors Program increases sense of belonging compared to university students not in Gemstone and (b) attendance at Gems Camp increases sense of belonging in Gemstone students. Gemstone students (N=221) had an increased sense of belonging compared to matched university students (N=221). Moreover, Gemstone students who attended Gems Camp (N=92) had an increased sense of belonging compared to matched Gemstone students who did not attend Gems Camp (N=92). In conclusion, the Gemstone Honors Program is an example of an LLC with scaffolded high impact practices, such as intentional first year programming, undergraduate research, and collaborative projects, that promotes an increase in students’ sense of belonging, providing a model for other LLCs to consider in their programming efforts

The [OIII]λ5007\lambda5007 equivalent width distribution at z ∼2\sim2: The redshift evolution of the extreme emission line galaxies

We determine the [OIII]$\lambda5007$ equivalent width (EW) distribution of $1.700<\rm{z}<2.274$ rest-frame UV-selected (M$_{\rm{UV}}<-19$) star-forming galaxies in the GOODS North and South fields. We make use of deep HDUV broadband photometry catalogues for selection and 3D-HST WFC3/IR grism spectra for measurement of line properties. The [OIII]$\lambda5007$ EW distribution allows us to measure the abundance of extreme emission line galaxies (EELGs) within this population. We model a log-normal distribution to the [OIII]$\lambda5007$ rest-frame equivalent widths of galaxies in our sample, with location parameter $\mu=4.24\pm0.07$ and variance parameter $\sigma= 1.33\pm0.06$. This EW distribution has a mean [OIII]$\lambda5007$ EW of 168$\pm1\r{A}$. The fractions of $\rm{z}\sim2$ rest-UV-selected galaxies with [OIII]$\lambda5007$ EWs greater than $500, 750$ and $1000\r{A}$ are measured to be $6.8^{+1.0}_{-0.9}\%$, $3.6^{+0.7}_{-0.6}\%$, and $2.2^{+0.5}_{-0.4}\%$ respectively. The EELG fractions do not vary strongly with UV luminosity in the range ($-21.6<M_{\rm{UV}}<-19.0$) considered in this paper, consistent with findings at higher redshifts. We compare our results to $\rm{z}\sim5$ and $\rm{z}\sim7$ studies where candidate EELGs have been discovered through Spitzer/IRAC colours, and we identify rapid evolution with redshift in the fraction of star-forming galaxies observed in an extreme emission line phase (a rise by a factor $\sim10$ between $\rm{z}\sim2$ and $\rm{z}\sim7$). This evolution is consistent with an increased incidence of strong bursts in the galaxy population of the reionisation era. While this population makes a sub-dominant contribution of the ionising emissivity at $\rm{z}\simeq2$, EELGs are likely to dominate the ionising output in the reionisation era.Comment: Submitted to MNRAS. 13 pages, 6 figure

The Meaning Students Make as Participants in Short-Term Immersion Programs

The purpose of this article is to present the results of a multi-site case study designed to investigate students’ experiences as participants in four week-long immersion programs (New York City, Peru, the Czech Republic, Chicago). Results highlight the significance of the context of the trips and specific characteristics of the trip (e.g., getting out of the bubble, boundary crossing, and personalizing), which served as the springboard for learning and meaning making. In particular, meaning making focused on developing new understandings of social issues, privilege, and stereotypes, reframing experiences upon participants’ return, and shifting sense of purpose and career planning

Learning Rotation Adaptive Correlation Filters in Robust Visual Object Tracking

Visual object tracking is one of the major challenges in the field of computer vision. Correlation Filter (CF) trackers are one of the most widely used categories in tracking. Though numerous tracking algorithms based on CFs are available today, most of them fail to efficiently detect the object in an unconstrained environment with dynamically changing object appearance. In order to tackle such challenges, the existing strategies often rely on a particular set of algorithms. Here, we propose a robust framework that offers the provision to incorporate illumination and rotation invariance in the standard Discriminative Correlation Filter (DCF) formulation. We also supervise the detection stage of DCF trackers by eliminating false positives in the convolution response map. Further, we demonstrate the impact of displacement consistency on CF trackers. The generality and efficiency of the proposed framework is illustrated by integrating our contributions into two state-of-the-art CF trackers: SRDCF and ECO. As per the comprehensive experiments on the VOT2016 dataset, our top trackers show substantial improvement of 14.7% and 6.41% in robustness, 11.4% and 1.71% in Average Expected Overlap (AEO) over the baseline SRDCF and ECO, respectively.Comment: Published in ACCV 201

Investigating the blood-host plasticity and dispersal of Anopheles coluzzii using a novel field-based methodology

Background: The biting behaviour and dispersal of insect vectors in the field underlies the transmission of many diseases. Here, a novel collection methodology coupled with the molecular analysis of blood-meal sources and digestion rates is introduced with the aim of aiding the understanding of two critical and relatively understudied mosquito behaviours: plasticity in blood-host choice and vector dispersal. Results: A collection strategy utilising a transect of mosquito traps placed at 50 m intervals allowed the collection of blood-fed Anopheles coluzzii from a malaria-endemic village of southern Ghana where human host availability ranged from zero (a cattle pen), increasing until humans were the dominant host choice (the middle of the village). Blood-meal analysis using PCR showed statistically significant variation in blood-meal origins for mosquitoes collected across the 250 m transect: with decreasing trend in Bovine Blood Index (OR = 0.60 95% CI: 0.49-0.73, P < 0.01) and correspondingly, an increasing trend in Human Blood Index (OR = 1.50 95% CI: 1.05-2.16, P = 0.028) as the transect approached the village. Using qPCR, the host DNA remaining in the blood meal was quantified for field-caught mosquitoes and calibrated according to timed blood digestion in colony mosquitoes. Time since blood meal was consumed and the corresponding distance the vector was caught from its blood-host allowed the estimation of An. coluzzii dispersal rates. Within 7 hours of feeding, mosquitoes typically remained within 50 m of their blood-host but at 60 hours they had dispersed up to 250 m. Conclusions: Using this methodology the remarkably small spatial scale at which An. coluzzii blood-host choice can change was demonstrated. In addition, conducting qPCR on host blood from field-caught mosquitoes and calibrating with timed experiments with colonised mosquitoes presents a novel methodology for investigating the dispersal behaviour of vectors. Future adaptations to this novel method to make it broadly applicable to other types of setting are also discussed.Universiteit Stellenbosch, National Institute for Health Research, National Health and Medical Research Counci