Browsing by Author "Wieser, Michael E."
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Item Open Access Bioavailable Strontium from Plants and Diagenesis of Dental Tissues at Olduvai Gorge, Tanzania(2018-07-11) Tucker, Laura Lillian; Mercader, Julio; Oetelaar, Gerald A.; Wieser, Michael E.Stable strontium isotope analysis is used to assess the migration and mobility of past populations of people and animals. This study aimed to determine the feasibility of conducting future studies using this method at Olduvai Gorge, Tanzania by determining the variability in biologically-available strontium (87Sr/86Sr) throughout the region from areas with metamorphic and volcanic bedrock, as well as recent unconsolidated lacustrine sediments. This was done by analysing modern plants collected from 33 different localities. As well, the degree to which archaeological animal teeth from Juma’s Korongo, a ~1-million-year-old site at Olduvai Gorge, have been affected by diagenetic alteration was assessed. To do this, the dentine and enamel of the teeth were analysed with and without pre-treatment with weak acetic acid: a protocol used for removing diagenetic strontium from dental specimens. There was no difference in 87Sr/86Sr values of volcanic (n=19) and metamorphic (n=9) sampling localities, but the lacustrine localities (n=5) had significantly higher values. 87Sr/86Sr values tended to decrease moving northeast towards the active volcano Oldoinyo Lengai, a major source of soil constituents for the area. Also, localities where trees were sampled had significantly higher 87Sr/86Sr values than those without them. Despite the homogeneous 87Sr/86Sr values described between metamorphic and volcanic localities, much higher values have been found in the northern extent of Serengeti National Park (Copeland et al., 2012), suggesting that animals who have immigrated into the area from long distances away can be identified as non-local. The animal teeth (n=7), which include zebras, crocodiles, and a hippopotamus, were all from local animals. There was a significant difference between enamel and dentine values after acid washing, suggesting that biogenic 87Sr/86Sr values are preserved in the enamel. These values were consistently higher than the modern bioavailable strontium values, possibly due to environmental differences between the past and present. The results of this study suggest that Olduvai Gorge is a suitable area for future studies using stable strontium isotope analysis, though more work is required to fully understand the inconsistencies between ancient and modern bioavailable strontium.Item Open Access Elucidating the chemistry of particulate and chlorinated nitrates in the troposphere through method development, and chamber and field studies(2020-09-22) Garner, Natasha Michelle; Osthoff, Hans D.; Gailer, Jürgen G.; Thurbide, Kevin B.; Wieser, Michael E.; Bertram, Timothy H.This thesis explores the chemistry of chlorinated and particulate nitrogen oxides in the troposphere which can impact the budgets of atmospheric oxidants and aerosol. Mixing ratios of nitryl chloride (ClNO2) were measured by chemical ionization mass spectrometry (CIMS) during the ORCA campaign in July 2015 on the west coast of Vancouver Island. Mean ClNO2 mixing ratios were small (< 10 pptv) with a maximum of 46 pptv, in part due to low precursor concentrations, i.e., of nitrogen dioxide (NO2) and ozone, and large nitrate radical sinks, e.g., titration by monoterpenes. Concentrations of ClNO2 were enhanced in air masses with elevated NO2 concentrations that had resided over the ocean, demonstrating the potential of ClNO2 to affect radical budgets in remote environments. The potential loss of ClNO2 by uptake on inorganic and secondary organic aerosol (SOA) was investigated in a newly constructed smog chamber. Uptake probabilities (γ) were determined by box modeling constrained to measured ClNO2 mixing ratios and SMPS derived aerosol surface area. An upper limit of γ< 4x10-4 was determined for (NH4)2SO4 and NH4HSO4 aerosol, but larger values were needed for monoterpene derived SOA, i.e., γ=(8+/-2)x10-4. Uptake of ClNO2 on SOA reduces its lifetime and impact on nitrogen oxide and chlorine budgets downwind of coastal areas where marine and continental air masses combine. A method to quantify NH4NO3 and NaNO3 aerosol by thermal dissociation cavity ring-down spectroscopy (TD-CRDS) was developed. At inlet temperatures of 540 °C and 620 °C, respectively, scatter plots of SMPS volume distribution data and TD-CRDS mixing ratios correlated (r2>0.9) with unity slopes in laboratory experiments. Sample ambient air measurements in Calgary, AB in August 2018 showed the presence of particulate organic nitrates at inlet temperatures < 350 °C (consistent with smog chamber experiments with limonene SOA) and of inorganic nitrate aerosol, demonstrating the potential of TD-CRDS for ambient particulate measurements.Item Open Access Geographic Origins, Status, and Identity at Paquimé, Northwest Chihuahua, Mexico(2018-04-27) Offenbecker, Adrianne M.; Katzenberg, Mary Anne; Wilson, Warren M.; McCafferty, Geoffrey G.; Wieser, Michael E.; Wright, Lori EllenThis thesis examines migration at Paquimé, an important prehistoric site in northwest Mexico that is widely recognized for its mix of Mesoamerican and Southwestern traits. The presence of foreign objects and ideology has stimulated debate over whether Medio Period (A.D. 1200-1450) culture change was due to the arrival of foreign elites in the Casas Grandes region or to local developments. A crucial step in addressing this debate is to determine if high status immigrants were indeed present at Paquimé, which is the goal of this study. This is accomplished by using radiogenic strontium and stable oxygen isotope analyses to determine the geographic origins of a large sample of individuals from Paquimé and the Viejo Period Convento site. Comparative samples from sites within and outside the Casas Grandes region were analyzed to identify potential geographic origins of non-local individuals. Mortuary analyses were then conducted to assess social status and identity. Finally, two bioarchaeological case studies from mortuary contexts with suspected human sacrifices are presented to examine the relationship between geographic origins and ritual violence, and to explore the impacts of migration on Medio Period social dynamics. The results indicate that ~87% of Paquimé individuals were born locally or came from within the Casas Grandes region, while 13% migrated from neighbouring regions, including the American Southwest and other parts of northwest or west Mexico. At Convento, ~92% were local to the Casas Grandes region. Although the Medio Period was characterized by migration from more distant locations when compared to the preceding Viejo Period, none of the immigrants from neighbouring regions received high status mortuary treatment. Instead, the most elaborate burials at Paquimé belong to locally-born individuals, whose status was likely linked to ritual authority. Furthermore, most of the sacrificial victims were non-locals. These results suggest that Medio Period culture change was driven primarily by internal stimuli, including population aggregation from within the Casas Grandes region and sociopolitical maneuvering by local elites. The results also indicate that social tensions and competition for status, power, and/or resources led to asymmetrical power dynamics between locals and immigrants, which sometimes played out in ritually-charged contexts.Item Open Access Ice Nucleation: Sulfate and Its Influence in Arctic and Rural and Urban NW Continental Precipitation(2019-08-20) Derksen, Mark; Norman, Ann-Lise; Else, Brent G. T.; Hobill, David W.; Wieser, Michael E.With the growth of urban centers and decline of natural ecosystems, the increasing presence of aerosol particles has the potential to have major impacts on climate. This study assessed the ice nucleation characteristics of anthropogenic and organic/biogenic sulfate sources in precipitation samples from the Arctic, Kananaskis (rural continental), and Calgary (Urban continental). Samples were analyzed using droplet freezing technique, isotopic analysis, and anion/cation measurements. Comparisons between deposition-based precipitation sampler and passive fog/rain sampler yielded no significant differences in ice nucleation characteristics. Arctic fog samples had distinct ice nucleating particle characteristics compared to rain and dry deposition samples. A 32% increase in the influence of biogenic matter was apparent in 2016 Arctic samples relative to 2014 samples. The influence of a continental biogenic and/or organic material was apparent in the ice nucleating characteristics of both rural and urban continental samples. Snow samples exhibited the greatest biogenic influence, followed by rain samples, and then dry deposition samples.Item Open Access Identifying Zinc Inputs to Heard and McDonald Islands Region using Zinc Concentrations and Isotopic Compositions(2020-08-24) Mohamed, Fwziah Ali Abdalali; Wieser, Michael E.; Yang, Lu; Hobill, David W.; Yau, Andrew W.; Mayer, BernhardZinc (Zn) availability in the ocean is thought to have the potential to impact the health and the biomass of phytoplankton communities in the ocean. The application of Zn isotopic composition is an effective approach to understand sources and environmental receptors of Zn in the ocean. An important challenge; however, is to measure the Zn isotopic composition reliably because of the limited range in Zn isotopic composition and the low amount of Zn found in the ocean. Zinc is a micronutrient that has received much attention due to its role in the biology of marine phytoplankton. Ocean surface water Zn concentrations are in the low nanomolar range, potentially limiting the growth of some phytoplankton species. Identifying and assessing Zn sources in the ocean can provide insights into the significance and the influence of Zn availability on phytoplankton growth. This thesis research project entails the development of a reliable method to explore the Zn sources in the vicinity of Heard and McDonald Islands, an Australian territory, in the Southern Ocean. The region of Heard and McDonald Islands, two of the most active volcanic islands in the world, is one of the regions in the Southern Ocean where large phytoplankton blooms are produced annually. This raises the possibility that the islands’ hydrothermal activity is releasing large amounts of trace elements including Zn to the water column thereby enhancing the biological productivity in the region. The development of the analytical method included a careful consideration of all factors that may affect Zn measurements, including Zn laboratory blanks introduced during the sample handling and preparation, isobaric interferences from the sample matrix, and the data reduction technique. Zinc concentrations and isotopic compositions were measured in seawater, suspended particles, sediments, and rock samples collected during the Heard Earth Ocean Biosphere Interactions (HEOBI) voyage in January and February of 2016 led by the Institute for Marine and Antarctic Studies (IMAS) at the University of Tasmania, Australia. Zinc concentrations and isotope amount ratio data indicated that; a possible Zn hydrothermal component may have been influencing the waters near McDonald Island and at a couple of stations in the waters surrounding Heard Island. A more definitive indication of possible Zn hydrothermal sources in the waters surrounding Heard and McDonald Islands could be possible if additional data including Zn excess and the concentration of mantle helium become available.Item Open Access Implementing Reflective Writing in Combination with Labatorials(2015-12-24) Sobhanzadeh, Mandana; Thompson, Robert Ian; Kalman, Calvin S; Miller-Young, Janice Elaine; Wieser, Michael E.Students are often not familiar with the language of science and as a result they have great difficulty understanding scientific texts. Students tend to memorize the materials that they see in the textbook without thinking about their meaning, because they believe that language and words hold the knowledge and they need to use the same words and terms in order to show their understanding. Such students who think that knowledge in science is a body of settled facts that comes from authority take a passive role in learning and become a receiver of knowledge, while those who try to make sense of the science language and construct their own understanding by questioning the knowledge presented to them are more likely to develop reasoning and critical thinking skills. The hermeneutical approach that is the basis of “Reflective Writing” encourages students to question what is presented to them and moves them from receiving knowledge to constructing their own understanding. Reflective writing was used in combination with a new style of introductory physics labs called 'Labatorials' at Mount Royal University (MRU) and the impact of these pedagogical tools on student learning, and in particular on how students learn, was investigated and analyzed in this study. Interviews with students who completed the reflective writing assignments in the introductory physics labatorials as well as an analysis of students’ reflective writing assignments helped us find key aspects that make the reflective writing activity useful to the students. Interviews were also used to find out if Labatorials are helpful to the students. The disciplined-focused epistemological beliefs questionnaire (DFEBQ) developed by Hofer (2000) was used in this project to find out whether the combinations of reflective writing and labatorials can change students’ epistemology. With these related projects, we establish three main results. First, we identified the main aspects that make reflective writing an effective learning activity in introductory physics courses. Second, we have also made progress in characterizing the positive and negative aspects of labatorials. Third, we have analyzed the possible changes that the combination of reflective writing and labatorials can have on students’ beliefs about knowledge and learning.Item Open Access Inversion Modelling of Copper Transport in Saccharomyces Cerevisiae(2020-05-12) Wilkins, Aaron Francis; Wieser, Michael E.; Karchewski, Brandon; Dettmer, Jan; Strous, MarcCopper is an essential nutrient but the uptake into cells is poorly understood. This dissertation summarizes the development of a mathematical system of equations to model the transport of copper in S. cerevisiae. Yeast is a model organism for studying the copper transport in human hepatic cells because the chaperone proteins and structures are well conserved between the species. An experiment is performed to investigate the transport between the growth media and the cells to model the process behind this important pathway. Transport mechanisms for this process are presented, mathematically modelled, and evaluated. Rate limited diffusion did not appear to be adequate in modelling the transport, but a term including a target copper concentration which cells actively maintain was introduced, and with a delayed activation, fit the data much more effectively. With this model, a framework is established for incorporating organelles to eventually model the intracellular copper transport and analyze the copper isotope distributions in the future. This work contributes to a larger initiative to incorporate copper isotope analysis as an innovative medical diagnostic tool in assessing human cellular pathology.Item Open Access Investigation of the effect gut microbiota have on the calcium isotopic composition in different calcium reservoirs of mice(2023-07) Walls, Dorothy Mae; Wieser, Michael E.; Gomes da Rocha, Claudia; Brown, Jo-Anne; Mayer, BernhardThe determination of the isotopic composition of calcium (Ca) in the body has gained increasing recognition as a powerful tool to monitor Ca metabolism, and bone metabolism in biological systems. Calcium is an essential mineral in the body and is critical for building and maintaining strong teeth and bones. Mishandling of this metal is associated with several diseases and disorders within the body. Therefore, understanding calcium metabolism is necessary to address the significance of this mineral, and the role it plays in the health of an individual. This thesis describes the development of an analytical technique to measure calcium isotope amount ratios in biological samples from as little as 670 ng, which is a two-fold decrease in the amount of Ca required compared to recent studies using MC TIMS. The technique was used to determine how the distribution of calcium isotopes changes in mice where calcium metabolism has been impacted by an altered composition of gut microbiota in the gastrointestinal tract of the mice. This technique developed in this thesis was applied to biological standard reference materials, and the δ(44/40Ca) isotope amount ratio of the reference materials NIST SRM 1400, NIST SRM 1486, and IAPSO were in good agreement and within uncertainty of literature data. Others were measured for Ca isotopic composition for the first time. The technique was then applied to the analysis of the calcium isotopic fractionation for three mouse groups with different gut bacterial compositions in four different tissue pools (diet, kidney, bone, and feces). Two cohorts of mice differentiated by age were investigated, where the first cohort was 91 days old, and the second was approximately 85 days old. There were no observed trends in the Ca isotopic compositions in the Ca reservoirs of the mice for given gut bacteria groups across the two cohorts. Therefore, we conclude that changes in gut microbiota do not produce a significant change in the redistribution of the isotopes of Ca in the different Ca pools in mice.Item Open Access Mobility at the Center of the Viking World(2020-04-23) Peschel, Emily M.; Katzenberg, Mary Anne; Dawson, Peter C.; Hallgrímsson, Benedikt; Wieser, Michael E.; Schillaci, Michael A.This dissertation examines migration at Gotland, an important island in Viking Age Scandinavia (750-1050 CE) that is widely recognized for its role in trade. Located off the southeast coast of Sweden in the Baltic Sea, Gotland connected western European and Eastern trade routes. Despite its economic importance, there has been little investigation into the political affiliation of this island. It is argued that Gotland was both independently ruled, and that it was a part of the Svear kingdom, a Swedish polity that ruled over the Baltic Sea. One step toward addressing the political identity of Gotland is to investigate mobility on the island. Although artifacts indicate trade occurred with much of the known world, the degree of migration to the island is not known. This project examines the degree of mobility of two skeletal populations from Gotland, Fröjel and Kopparsvik. Biological distance (biodistance) from cranial and dental nonmetric traits were used to assess gene flow between Gotlandic populations and among Scandinavian populations. Strontium isotope analysis was used to determine the geological origins of individuals from the Gotlandic populations. The dental biodistance results showed that Fröjel and Kopparsvik were biologically isolated from mainland Scandinavian populations. The cranial biodistance results, however, indicated a small biodistance between Kopparsvik and the Svear kingdom, while Fröjel remained isolated from biologcial interactions with the mainland populations. While dental nonmetric traits reflected the ancestral relationships among Scandinavian populations, cranial nonmetric traits indicated more recent changes to the population structure. These interpretations of migration on the island are corroborated by the increase in non-local individuals at the Kopparsvik cemetery throughout its use, as determined by strontium isotope analysis. While there were only local individuals interred at the cemetery during the earliest phase of use, there was an increase in nonlocal individuals throughout the latter half of the Viking Age. Gotland, therefore, saw increased Swedish presence throughout the Viking Age, which suggests an effort by the Svear kingdom to take advantage of trade on the island. Fröjel, however, remained isolated from gene flow and immigration, indicating that the Svear kingdom had limited authority on Gotland.Item Open Access Molecular Ions in Ion Upflows and their Effect on Hot Atomic Oxygen Production(2019-01-25) Foss, Victoria; Yau, Andrew W.; Cully, Christopher M.; Wieser, Michael E.We present results from the Imaging and Rapid Scanning Mass Spectrometer (IRM) on board the Enhanced Polar Outflow Probe (e-POP), on the occurrence morphology and frequency of molecular ions in the topside ionosphere. Molecular ions are observed at all e-POP altitudes at high latitudes, in much greater abundances than predicted by empirical models of the ionosphere, during both active and quiet times. Large count rate events occur in greater frequency in the pre-midnight sector (20-22 magnetic local time (MLT)). These large count rate events also show a correlation to the main and recovery phases of large geomagnetic storms. Molecular NO+ and O2+ ions can undergo dissociative recombination with electrons to produce non-thermal oxygen atoms, which disturb the local equilibrium and increase satellite drag in low Earth orbit (LEO). We simulate this production with the linearized Boltzmann equation using both the International Reference Ionosphere (IRI) and augmented models based on IRM observations. It is found that NO+ concentrations of 10% result in an apparent hot temperature of 0.19 eV, or 0.3 eV in the case of O2+. We discuss the significance of these results as well as their implications on magnetosphere-ionosphere-thermosphere (MIT) coupling.Item Open Access Optically Stimulated Luminescence Dosimetry in Permanent Breast Seed Implant Brachytherapy: a Monte Carlo Approach(2019-09-04) Nich, Steven; Kirkby, Charles; Smith, Wendy Lani; Husain, Siraj M.; Wieser, Michael E.Permanent breast seed implant (PBSI) brachytherapy, typically performed with low energy radioactive Pd-103 x-ray sources, is a convenient treatment option for many low risk breast cancer patients. Skin is a primary organ at risk (OAR) in PBSI and is susceptible to painful toxicities when exposed to large doses of radiation. The TG-43 formalism used to calculate clinical dose distributions relies on simple assumptions that often lead to inaccurate assessments of skin dose. In this thesis, sophisticated Monte Carlo dose calculations were performed using egs_brachy to determine conversion factors relating skin doses to doses accumulated in optically stimulated luminescence dosimeters (OSLDs). These were supplemented by a procedure to calibrate OSLDs to a Pd-103 source and experimentally derived OSLD calibration factors. These results enable in-vivo dosimetry of a PBSI patient's skin dose following treatment via OSLDs placed on the surface of the skin providing valuable measurements of the actual dose delivered.Item Open Access Optimising Ion Transport in a Thermal Ionisation Mass Spectrometer and Plasma Ion Source Using Monte Carlo Simulations(2019-09-20) Flowerdew, Jake Anthony Darri; Thompson, Robert Ian; Wieser, Michael E.; Jackel, Brian J.; Kwiatkowski, Anna A.; Friesen, Timothy P.The controlled collimation of ion beams is of paramount importance in particle accelerators, high energy beamlines, and detector systems, as it determines the functionality, sensitivity and resolution of the instruments. In this thesis the ion source of a thermal ionization mass spectrometer (TIMS), comprised of a heated filament followed by a series of ion optical lenses, was modelled and Monte Carlo simulations were performed using SIMION. The potentials of three of the electrostatic lenses were optimized, in order to maximize the illuminated area of the exit slit. The optimization method employed achieved up to a 44 % increase in experimental signal intensity when compared to the existing manufacturer-provided lens tuning algorithm. 3D plots were effective in visualizing whether this new voltage configuration leads to a solution which lies in a local or global optimum, showing that the previous tuning technique was rarely successful in achieving the global optimum. This modelling and optimization approach was then used to aid the commissioning of a plasma ion source at the TITAN experiment at TRIUMF. The Plasma Ion Source (PIS), comprised of a heated filament followed by an anode, Einzel lens and X-Y correction steerers, was modelled and Monte Carlo simulations were performed. Optimising the voltage configurations in these simulations has proved successful in the commissioning of the PIS at the TITAN experiment in thermal mode, where ions from the source have been characterised using the time-of-flight method. The PIS will be able to deliver important calibration beams to TITAN’s experiments and will also enable off-line, high precision isotope composition measurements with the Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF MS).Item Open Access Photonic aspects of networks: from long-distance quantum networks to the brain(2020-08-20) Kumar, Sourabh; Simon, Christoph; Barclay, Paul E.; Oblak, Daniel; Wieser, Michael E.; Sangouard, Nicolas D.Photons, the fundamental quanta of the electromagnetic field, travel at the fastest possible speed, and interact relatively weakly with the environment. These features make them ideal for several practical applications, particularly in the transport of both classical and quantum information. One could also wonder whether nature itself realized the usefulness of these unique entities and through evolution made living beings rely on them for some physiological functions. In my thesis, I cover an example for each of these roles a photon can take. As the first example, I describe our theoretical work pertaining to an important practical application where photons can carry quantum information and mediate entanglement between distant quantum computing nodes. We designed a novel quantum repeater architecture using superconducting processors and optical links, which we believe is the first concrete proposal towards this goal. We compared our repeater’s performance with a few other promising approaches and showed that ours could yield higher entanglement distribution rates with good fidelities in appropriate regimes. Such an architecture could be pertinent to envision a quantum internet in the future, something that would be analogous to, but much more secure and powerful in certain aspects than today’s classical internet. As the second example, I describe our theoretical work where we speculate on the potential role of photons observed in mammalian brains. Could we be using these photons as information carriers in addition to the well-known electrochemical signals? We show, based on detailed theoretical modelling, that myelinated axons could serve as good optical waveguides in the brain, which can answer this question in the affirmative. Ours is the first proposal identifying myelinated axons as potential optical waveguides. There is indirect experimental evidence to support this hypothesis, and we propose precise experiments to test the waveguide capabilities directly. Since these photons can also in principle carry quantum information, we further speculate on the existence of quantum networks in the brain. Our work could help develop a better understanding of some of the biggest unsolved problems in neuroscience, possibly including the generation of our subjective conscious experience.Item Open Access Study of the decay of Zr-96 by isotope geochemistry and Penning trap mass spectrometry(2018-04-30) Mayer, Adam John; Thompson, Robert Ian; Wieser, Michael E.; Dilling, Jens; Sharma, Kumar; Nair, Rajeev Sasidharan; Hobill, David W.Double-beta ( ßß) decay measurements are a class of nuclear studies with the objective of detecting a neutrinoless decay process. 96Zr is of particular interest as a ßß decay candidate as it has one of the shortest ßß-decay half-lives and largest Q-values. In addition, it is also unstable against the fourfold unique-forbidden single ß decay, decaying via 96Zr->96Nb which then immediately decays to 96Mo. These properties thus designate 96Zr as a unique system to test nuclear theory. Prior to the work outlined in this thesis, two published measurements of the 96Zr half-life yielded quite different results. A geochemical measurement of the decay in ancient zircon samples resulted in a value of T(1/2)=0.94(32)x10^19 a. Conversely, a direct count rate measurement found the ßß-decay half-life to be T( 1/2,ßß)=2.35(21)x10^19 a. The geochemical measurement of the 96Zr half-life does not discriminate between the two decay channels and thus, in conjunction with ßß-decay count-rate data, could provide a way to measure the single-beta decay rate. The aim of this project was to study this system through a series of experiments combining nuclear physics and geochemical techniques. First, the single and double-ß decay Q-values were measured using the JYFLTRAP mass spectrometer. This measurement significantly improved the Q-value uncertainties over previous measurements, refining the underlying nuclear theory to improve understanding of the single-ß decay path of 96Zr->96Nb. A study of the geochemical measurement was then performed. Zircon can remain a closed system over its lifetime and is especially suitable for this investigation due to its high Zr content and low Mo content. A novel method for the separation of molybdenum from zirconium was developed to enable the detection of the small amount of accumulated decay product as an excess compared to the natural Mo isotopic composition. The 96Mo isotopic anomaly in a 2.68 Ga zircon sample was determined to be 107(40) ppm, which translates to a 96Zr half-life of (1.8(+0.7/-0.4))x10^19 a. With the 2νßß partial decay half-life known to be 2.35(21)x10^19 a, a lower limit for the single ß decay half-life was set at T(1/2,ß)=3.5x10^19 a.Item Open Access Utility of a multi-tracer approach as a component of adaptive monitoring for municipal wastewater impacts(IWA Publishing, 2020-06-16) Tanna, Rajiv N.; Moncur, Michael C.; Birks, S. Jean; Gibson, John J.; Ptacek, Carol J.; Mayer, Bernhard; Wieser, Michael E.; Wrona, Fred J.; Munkittrick, Kelly R.Distinguishing municipal wastewater effluent (MWWE) from other industrial effluents or through an urbanized watershed can be challenging. In complex receiving environments, linking environmental responses to specific compounds or effluents is not always straight forward. In order to characterize the inherent complexity of tracing MWWE in aquatic systems influenced by multiple stressors, a proposed multi-tracer suite is intended to highlight areas of potential biological concern. Characterization and quantification of effluent exposure to aquatic biota in this manner is essential to shape policies intended to encourage wastewater infrastructure development (i.e. treatment plant upgrade) and broader environmental management. This paper describes the use of a comprehensive suite of tracers that includes isotopes in support of a core surveillance program, demonstrating its effectiveness both empirically and with respect to diagnostic value contributed to monitoring programs.Item Open Access Variability in resting-state brain networks(2020-02-03) Oliver i Alabau, Isaura; Davidsen, Jörn; Bray, Signe L.; Jackel, Brian J.; Wieser, Michael E.Recently, new studies have detected that group average brain networks display distinct organization compared with individual subject networks. In particular, each subject network presents a distinctive topology. How this variability affects the individual resting-state networks is a question we aim to solve. This is particularly important since specific resting-state networks, as the default mode network (DMN) and frontoparietal network (FPN), play an important role in early detection of neurophysiological diseases such as Alzheimer's, Parkinson, and attention-deficit hyperactivity disorder. In the analysis presented we will determine the robustness of the networks, first, and then quantify the variability in the connectivity structures. By using two distinct data sets, mapped with the same brain atlas, and three different similarity measures to infer resting-state networks, we show that the backbone of connectivity within the resting-state networks, DMN and FPN, does not vary significantly. While weaker connections do vary, they largely correspond to the links between the DMN and FPN. Overall, we find that the resting-state networks present a robust topology when a fixed atlas is used, and the recordings are sufficiently long.