Faculty Publications (BioMed Central & Faculty of Science)
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Articles from BioMed Central by University of Victoria, Faculty of Science authors. Also other journal articles by UVic Faculty of Science authors.
Click on this link to see Work published with BioMed Central, Chemistry Central and SpringerOpen by researchers at University of Victoria.
Click on this link to see Work published with BioMed Central, Chemistry Central and SpringerOpen by researchers at University of Victoria.
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Item Emplacement of the Franklin large igneous province and initiation of the Sturtian Snowball Earth(Science Advances, 2022) Pu, Judy P.; Macdonald, Francis A.; Schmitz, Mark D.; Rainbird, Robert H.; Bleeker, Wouter; Peak, Barra A.; Flowers, Rebecca M.; Hoffman, Paul F.; Rioux, Matthew; Hamilton, Michael A.During the Cryogenian (720 to 635 Ma ago) Snowball Earth glaciations, ice extended to sea level near the equator. The cause of this catastrophic failure of Earth’s thermostat has been unclear, but previous geochronology has suggested a rough coincidence of glacial onset with one of the largest magmatic episodes in the geological record, the Franklin large igneous province. U-Pb geochronology on zircon and baddeleyite from sills associated with the paleo-equatorial Franklin large igneous province in Arctic Canada record rapid emplacement between 719.86 ± 0.21 and 718.61 ± 0.30 Ma ago, 0.9 to 1.6 Ma before the onset of widespread glaciation. Geologic observations and (U-Th)/He dates on Franklin sills are compatible with major post–Franklin exhumation, possibly due to development of mafic volcanic highlands on windward equatorial Laurentia and increased global weatherability. After a transient magmatic CO2 flux, long-term carbon sequestration associated with increased weatherability could have nudged Earth over the threshold for runaway ice-albedo feedback.Item Global chemical transport on hot Jupiters: Insights from the 2D VULCAN photochemical model(The Astrophysical Journal, 2024) Tsai, Shang-Min; Parmentier, Vivien; Mendonça, João M.; Tan, Xianyu; Deitrick, Russell; Hammond, Mark; Savel, Arjun; Zhang, Xi; Pierrehumbert, Raymond; Schwieterman, EdwardThe atmospheric dynamics of tidally locked hot Jupiters is characterized by strong equatorial winds. Understanding the interaction between global circulation and chemistry is crucial in atmospheric studies and interpreting observations. Two-dimensional (2D) photochemical transport models shed light on how the atmospheric composition depends on circulation. In this paper, we introduce the 2D photochemical (horizontal and vertical) transport model, VULCAN 2D, which improves on the pseudo-2D approaches by allowing for nonuniform zonal winds. We extensively validate our VULCAN 2D with analytical solutions and benchmark comparisons. Applications to HD 189733 b and HD 209458 b reveal a transition in mixing regimes: horizontal transport predominates below ∼0.1 mbar, while vertical mixing is more important at higher altitudes above 0.1 mbar. Motivated by the previously inferred carbon-rich atmosphere, we find that HD 209458 b with supersolar carbon-to-oxygen ratio (C/O) exhibits pronounced C2H4 absorption on the morning limb but not on the evening limb, due to horizontal transport from the nightside. We discuss when a pseudo-2D approach is a valid assumption and its inherent limitations. Finally, we demonstrate the effect of horizontal transport in transmission observations and its impact on the morning−evening limb asymmetry with synthetic spectra, highlighting the need to consider global transport when interpreting exoplanet atmospheres.Item Orbital stability and secular dynamics of the Proxima Centauri planetary system(The Astrophysical Journal, 2024) Livesey, Joseph; Barnes, Rory; Deitrick, RussellThe two innermost planets of the Proxima Centauri system are separated by just 0.02 au, inducing strong gravitational interactions between them. We assess this interaction by leveraging fast orbital stability indicators and find that orbital stability is very likely if the initial eccentricities of planets b and d are less than ∼0.2, but cannot confirm stability at larger values. We find that stability is not strongly affected by the true masses of the planets or by the distant planet c. However, mutual inclinations between 95° and 142° often result in unstable motion. We further explore the long-term evolution of the orbits in these stable regions of parameter space and find that circularization can take over 5 Gyr. This tidal evolution could support surface energy fluxes in excess of 1 W m−2 for over 1 Gyr, possibly affecting planet b's habitability.Item Thermal tides in neutrally stratified atmospheres: Revisiting the Earth’s Precambrian rotational equilibrium(Astronomy & Astrophysics, 2024) Farhat, Mohammad; Auclair-Desrotour, Pierre; Boué, Gwenaël; Deitrick, Russell; Laskar, JacquesRotational dynamics of the Earth, over geological timescales, have profoundly affected local and global climatic evolution, probably contributing to the evolution of life. To better retrieve the Earth’s rotational history, and motivated by the published hypothesis of a stabilized length of day during the Precambrian, we examined the effect of thermal tides on the evolution of planetary rotational motion. The hypothesized scenario is contingent upon encountering a resonance in atmospheric Lamb waves, whereby an amplified thermotidal torque cancels out the opposing torque generated by the oceans and solid interior, driving the Earth into rotational equilibrium. With this scenario in mind, we constructed an ab initio model of thermal tides on rocky planets describing a neutrally stratified atmosphere. The model takes into account dissipative processes with Newtonian cooling and diffusive processes in the planetary boundary layer. We retrieved, from this model, a closed-form solution for the frequency-dependent tidal torque, which captures the main spectral features previously computed using 3D general circulation models. In particular, under longwave heating, diffusive processes near the surface and the delayed thermal response of the ground prove to be responsible for attenuating, and possibly annihilating, the accelerating effect of the thermotidal torque at the resonance. When applied to the Earth, our model prediction suggests the occurrence of the Lamb resonance in the Phanerozoic, but with an amplitude that is insufficient for the rotational equilibrium. Interestingly, though our study was motivated by the Earth’s history, the generic tidal solution can be straightforwardly and efficiently applied in exoplanetary settings.Item Effects of ozone levels on climate through Earth history(Climate of the Past, 2023) Deitrick, Russell; Goldblatt, ColinMolecular oxygen in our atmosphere has increased from less than a part per million in the Archean Eon to a fraction of a percent in the Proterozoic and finally to modern levels during the Phanerozoic. The ozone layer formed with the early Proterozoic oxygenation. While oxygen itself has only minor radiative and climatic effects, the accompanying ozone has important consequences for Earth climate. Using the Community Earth System Model (CESM), a 3-D general circulation model (GCM), we test the effects of various levels of ozone on Earth's climate. When CO2 is held constant, the global-mean surface temperature decreases with decreasing ozone, with a maximum drop of ∼3.5 K at near total ozone removal. By supplementing our GCM results with 1-D radiative flux calculations, we are able to test which changes to the atmosphere are responsible for this temperature change. We find that the surface temperature change is caused mostly by the stratosphere being much colder when ozone is absent; this makes it drier, substantially weakening the greenhouse effect. We also examine the effect of the structure of the upper troposphere and lower stratosphere on the formation of clouds and on the global circulation. At low ozone, both high and low clouds become more abundant due to changes in the tropospheric stability. These generate opposing shortwave and longwave radiative forcings that are nearly equal. The Hadley circulation and tropospheric jet streams are strengthened, while the stratospheric polar jets are weakened, the latter being a direct consequence of the change in stratospheric temperatures. This work identifies the major climatic impacts of ozone, an important piece of the evolution of Earth's atmosphere.Item InSAR- and PCA-based inversion reveals the surface deformation and earthquake sequence in the Weiyuan-Rongxian shale gas field(Remote Sensing, 2024) Huo, Hongyu; Xu, Wenbin; Xie, Lei; Jiang, Kun; Jiang, YanIn recent years, the rapid expansion and development of the shale gas industry in the Sichuan Basin has coincided with a series of unexpected moderate-sized earthquakes. Given that the Sichuan Basin is situated within a stable interior block, the focal mechanism of the 2019 earthquake sequence (ML4.7, ML5.4, and ML5.2) in the Weiyuan-Rongxian area remains a subject of debate. In this study, we propose a joint InSAR- and PCA- based inversion method utilizing the distributed Mogi model to investigate the spatial-temporal characteristics of a gas reservoir and evaluate the induced Coulomb stress change. The surface deformation derived from Sentinel-1 data between 2015 and 2021 was consistent with the spatial distribution of production wells, and it correlated with the temporal changes in reservoir volume associated with the shale gas operating process. The Coulomb stress loading on the regional faults suggests that human activities associated with shale gas operation likely triggered the three moderate earthquakes. Furthermore, our results indicate Coulomb stress loadings of 10 kPa, 15 kPa, 5 kPa, 3 kPa, and 87 kPa on the Dongxingchang fault, Gaoqiao fault, Dayaokou fault, Niujingao fault, and Lijiachang fold, respectively. Consequently, fluid injection and extraction during shale gas development could be contributing to the elevated seismic activity in the Weiyuan-Rongxian area.Item Certain new applications of symmetric q-calculus for new subclasses of multivalent functions associated with the cardioid domain(Axioms, 2024) Srivastava, Hari M.; Breaz, Daniel; Khan, Shahid; Tchier, FairouzIn this work, we study some new applications of symmetric quantum calculus in the field of Geometric Function Theory. We use the cardioid domain and the symmetric quantum difference operator to generate new classes of multivalent q-starlike and q-convex functions. We examine a wide range of interesting properties for functions that can be classified into these newly defined classes, such as estimates for the bounds for the first two coefficients, Fekete–Szego-type functional and coefficient inequalities. All the results found in this research are sharp. A number of well-known corollaries are additionally taken into consideration to show how the findings of this research relate to those of earlier studies.Item Next generation seismic source detection by computer vision: Untangling the complexity of the 2016 Kaikōura earthquake sequence(Journal of Geophysical Research. Solid Earth, 2024) Tan, Fengzhou; Kao, Honn; Yi, Kwang Moo; Nissen, Edwin; Goerzen, Chet; Hutchinson, Jesse; Gao, Dawei; Farahbod, Amir M.Seismic source locations are fundamental to many fields of Earth and planetary sciences, such as seismology, volcanology and tectonics. However, seismic source detection and location are challenging when events cluster closely in space and time with signals tangling together at observing stations, such as they often do in major aftershock sequences. Though emerging algorithms and artificial intelligence (AI) models have made processing high volumes of seismic data easier, their performance is still limited, especially for complex aftershock sequences. In this study, we propose a novel approach that utilizes three-dimensional image segmentation—a computer vision technique—to detect and locate seismic sources, and develop this into a complete workflow, Source Untangler Guided by Artificial intelligence image Recognition (SUGAR). In our synthetic and real data tests, SUGAR can handle complex, energetic earthquake sequences in near real time better than skillful analysts and other AI and non-AI based algorithms. We apply SUGAR to the 2016 Kaikōura, New Zealand sequence and obtain five times more events than the analyst-based GeoNet catalog. The improved aftershock distribution illuminates a continuous fault system with extensive fracture zones beneath the segmented, discontinuous surface ruptures. Our method has broader applicability to non-earthquake sources and other time series image data sets.Item Explaining empirical dynamic modelling using verbal, graphical and mathematical approaches(Ecology and Evolution, 2024) Edwards, Andrew M.; Rogers, Luke; Holt, CarrieEmpirical dynamic modelling (EDM) is becoming an increasingly popular method for understanding the dynamics of ecosystems. It has been applied to laboratory, terrestrial, freshwater and marine systems, used to forecast natural populations and has addressed fundamental ecological questions. Despite its increasing use, we have not found full explanations of EDM in the ecological literature, limiting understanding and reproducibility. Here we expand upon existing work by providing a detailed introduction to EDM. We use three progressively more complex approaches. A short verbal explanation of EDM is then explicitly demonstrated by graphically working through a simple example. We then introduce a full mathematical description of the steps involved. Conceptually, EDM translates a time series of data into a path through a multi-dimensional space, whose axes are lagged values of the time series. A time step is chosen from which to make a prediction. The state of the system at that time step corresponds to a ‘focal point’ in the multi-dimensional space. The set (called the library) of candidate nearest neighbours to the focal point is constructed, to determine the nearest neighbours that are then used to make the prediction. Our mathematical explanation explicitly documents which points in the multi-dimensional space should not be considered as focal points. We suggest a new option for excluding points from the library that may be useful for short-term time series that are often found in ecology. We focus on the core simplex and S-map algorithms of EDM. Our new R package, pbsEDM, enhances understanding (by outputting intermediate calculations), reproduces our results and can be applied to new data. Our work improves the clarity of the inner workings of EDM, a prerequisite for EDM to reach its full potential in ecology and have wide uptake in the provision of advice to managers of natural resources.Item Authigenic carbonate burial within the Late Devonian Western Canada Sedimentary basin and its impact on the global carbon cycle(Geochemistry, Geophysics, Geosystems, 2024) Gazdewich, Sean; Hauck, Tyler; Husson, JonStable carbon isotope ratios (δ¹³C values) of marine carbonates are widely used to infer the relative burial rates of organic carbon, a source of oxygen to the ocean-atmosphere system. This inference, however, is based on the assumption that ocean-atmospheric carbon is buried either as organic carbon or as marine carbonate minerals. The burial of authigenic carbonate minerals formed within sediments after deposition, with low δ13C values (i.e., similar to organic carbon), has been proposed to explain high δ¹³C values in marine carbonates without the need for high burial fluxes of organic carbon. To test this hypothesis, we focus on the Late Devonian, a time period with both pervasive ocean anoxia and a severe reduction in shallow-water carbonate deposition—conditions hypothesized to promote authigenic carbonate formation. We present sedimentological and geochemical data from limestones and black shales of the Wabamun Group, Besa River and Exshaw formations of the Western Canada Sedimentary Basin. These data are compared to inorganic and organic weight percent measurements of North American shales acquired from the USGS National Geochemical Database (N = 4,437). Results show that basinal shale lack authigenic carbonate with low δ¹³C values and that the mean δ¹³C value of carbonate in these shales (−0.3‰) do not differ substantially from mean δ¹³C of carbonates in platform carbonates of a similar age (0.6‰). Furthermore, inorganic carbon content in Late Devonian shales (mean weight percent = 0.55%, N = 54) is lower than average Phanerozoic North American shale (mean of 1.95%, N = 4,055). Lastly, organic carbon-to-inorganic carbon ratios (OC:IC) of North American shales are well above 1 (mean = 3.72 for Late Devonian shales (N = 374), 2.25 for shales (N = 3,653) of all other ages). Therefore, even if the burial of fine-grained siliciclastic formations carrying authigenic carbonates were to increase, the concomitant increase in organic carbon burial would be even larger. Together, data from this study do not provide evidence that the burial of authigenic carbonate would have a significant effect on global carbon isotope mass balance.Item In vitro and in vivo synergetic radiotherapy with gold nanoparticles and docetaxel for pancreatic cancer(Pharmaceutics, 2024) Alhussan, Abdulaziz; Jackson, Nolan; Chow, Norman; Gete, Ermias; Wretham, Nicole; Dos Santos, Nancy; Beckham, Wayne; Duzenli, Cheryl; Chithrani, DevikaThis research underscores the potential of combining nanotechnology with conventional therapies in cancer treatment, particularly for challenging cases like pancreatic cancer. We aimed to enhance pancreatic cancer treatment by investigating the synergistic effects of gold nanoparticles (GNPs) and docetaxel (DTX) as potential radiosensitizers in radiotherapy (RT) both in vitro and in vivo, utilizing a MIA PaCa-2 monoculture spheroid model and NRG mice subcutaneously implanted with MIA PaCa-2 cells, respectively. Spheroids were treated with GNPs (7.5 μg/mL), DTX (100 nM), and 2 Gy of RT using a 6 MV linear accelerator. In parallel, mice received treatments of GNPs (2 mg/kg), DTX (6 mg/kg), and 5 Gy of RT (6 MV linear accelerator). In vitro results showed that though RT and DTX reduced spheroid size and increased DNA DSBs, the triple combination of DTX/RT/GNPs led to a significant 48% (p = 0.05) decrease in spheroid size and a 45% (p = 0.05) increase in DNA DSBs. In vivo results showed a 20% (p = 0.05) reduction in tumor growth 20 days post-treatment with (GNPs/RT/DTX) and an increase in mice median survival. The triple combination exhibited a synergistic effect, enhancing anticancer efficacy beyond individual treatments, and thus could be employed to improve radiotherapy and potentially reduce adverse effects.Item Environmental controls and phenology of sea ice algal growth in a future Arctic(Elementa: Science of the Anthropocene, 2024-05-15) Haddon, Antoine; Farnole, Patrick; Monahan, Adam H.; Sou, Tessa; Steiner, NadjaThe future of Arctic sea ice algae is examined using a regional ocean and sea ice biogeochemical model, with a simulation from 1980 to 2085, considering a future scenario with strong warming. To analyze the impacts of climate change, we computed key dates in the development of sympagic blooms, corresponding to the occurrence of specific growth conditions, and designed diagnostics of ice algal phenology to estimate the onset and peak of blooms. These diagnostics help understand how the timing of light and nutrient availability governs the growth of ice algae and how environmental controls will be altered by climate change across regions. With thinner ice, photosynthetically active radiation in bottom ice will reach levels sufficient for growth earlier, resulting in a better synchrony of high levels of light and nutrients. Increases in snow cover can potentially offset the effect of thinner ice, leading to shorter periods of favorable growth conditions in certain regions. The loss of sea ice cover before the late 21st century only impacts sympagic blooms at lower latitudes, as the timing of sea ice break-up shows little change relative to other key dates at higher latitudes. In response to climate change, the model simulates a modified spatial distribution of blooms, with the emergence of highly productive areas and the loss of blooms in other regions. However, the changes in the timing of growth conditions do not substantially alter the timing of blooms, and both onset and peak ice algae see little change. The simulated lack of sensitivity of bloom onset is attributed to the delay in sea ice freeze-up projected by the model, causing a reduction of overwintering ice algae. The resulting lower initial biomass at the beginning of spring then causes a delay in the development of blooms, offsetting earlier light from thinner ice.Item Exploring electrophilic hydrophosphination via metal phosphenium intermediates(Chemistry, 2024) Belli, Roman; Muir, Vanessa; Dyck, Nicholas; Pantazis, Dimitrios A.; Sousa, Tânia P. A.; Slusar, Carly R.; Parkin, Hayley; Rosenberg, LisaTwo Mo(0) phosphenium complexes containing ancillary secondary phosphine ligands have been investigated with respect to their ability to participate in electrophilic addition at unsaturated substrates and subsequent P−H hydride transfer to “quench” the resulting carbocations. These studies provide stoichiometric “proof of concept” for a proposed new metal-catalyzed electrophilic hydrophosphination mechanism. The more strongly Lewis acidic phosphenium complex, [Mo(CO)4(PR2H)(PR2)]+ (R=Ph, Tolp), cleanly hydrophosphinates 1,1-diphenylethylene, benzophenone, and ethylene, while other substrates react rapidly to give products resulting from competing electrophilic processes. A less Lewis acidic complex, [Mo(CO)3(PR2H)2(PR2)]+, generally reacts more slowly but participates in clean hydrophosphination of a wider range of unsaturated substrates, including styrene, indene, 1-hexene, and cyclohexanone, in addition to 1,1-diphenylethylene, benzophenone, and ethylene. Mechanistic studies are described, including stoichiometric control reactions and computational and kinetic analyses, which probe whether the observed P−H addition actually does occur by the proposed electrophilic mechanism, and whether hydridic P−H transfer in this system is intra- or intermolecular. Preliminary reactivity studies indicate challenges that must be addressed to exploit these promising results in catalysis.Item The vertebrate bone hypothesis: Understanding the impact of bone on vertebrate stoichiometry(Functional Ecology, 2024) May, Emily M.; El-Sabaawi , Rana1. Understanding how animals store and recycle nutrients is a major question in ecological stoichiometry, a field that applies mass-balance to ecological and physiological processes. However, ecological stoichiometry has thus far failed to accurately predict elemental demand and release in vertebrates. 2. Because they invest in bone, a tissue mineralized with calcium phosphate, vertebrates are phosphorus (P) rich, allowing them to uniquely impact P cycling. Nonetheless, bone's impact goes further than merely changing vertebrate body elemental content. 3. We propose a potential guiding hypothesis for vertebrate P stoichiometry called the ‘Vertebrate Bone Hypothesis (VBH)’. The VBH has three components: (1)Bone strongly impacts vertebrate whole-body %P and N:P. (2) Bone is a P storage tissue that acts in elemental homeostasis. (3)Bone does not have constant elemental content. 4. To characterize this hypothesis, we integrate bone physiology with stoichiometric principles, and we systematically review quantitative bone measurements to showcase cryptic diversity in vertebrate P content. 5. Finally, we apply the characteristics of the VBH to ontogeny and reproduction, both of which impact bone physiology and elemental demand, to demonstrate the context dependency of bone's stoichiometric impact.Item Climate variability leads to multiple oxygenation episodes across the Great Oxidation Event(Geophysical Research Letters, 2024) Ruiz, Daniel Garduno; Goldblatt, Colin; Ahm, Anne-Sofie C.The temporal relationship between global glaciations and the Great Oxidation Event (GOE) suggests that climate change played an important role in Earth's oxygenation. The potential role of temperature is captured by the stratigraphic proximity between glacial deposits and sediments containing mass-independent fractionation of sulfur isotopes (MIF-S). We use a time-dependent one-dimensional photochemical model to investigate whether temperature changes associated with global glaciations can drive oscillations in atmospheric O2 levels and MIF-S production across the GOE. We find that extreme climate change can cause atmospheric O2 to oscillate between pre (<10−6 times the present atmospheric level, PAL) and post-GOE (>10−5 PAL) levels. Post-glacial hot-moist greenhouse climates lead to post-GOE O2 levels because the abundant H2O vapor and oxidizing radicals drive the depletion of reduced species. This pattern is generally consistent with the MIF-S signal observed in the sedimentary record, suggesting a link between global glaciations and O2 oscillations across the GOE.Item Humpback whale (Megaptera novaeangliae) social calls in southern British Columbia(Marine Mammal Science, 2024) Molder, Zoe; Halliday, William; Reidy, Rhonda; Kraemer, Chloe; Juanes, FrancisHumpback whale (Megaptera novaeangliae) nonsong vocalizations, or social calls, are much more poorly understood than humpback song. We examined humpback whale social calls from a foraging ground in southern British Columbia (BC) and developed a catalog for humpback social calls in BC. We tagged four humpback whales on the eastern edge of Swiftsure Bank, BC, in early September 2020, with a passive acoustic and movement tag. We manually classified 32 call types in our data set based on comparisons with published classifications of humpback social calls. Many of the calls identified in our data set had similar characteristics to calls from other locations. We also used two statistical classification methods, a cluster analysis and a random forest. The cluster analysis grouped 20 of these call types into four categories, and the random forest classifier was able to accurately classify all 20 call types 87.6% of the time. This study fills a geographical gap of humpback whale social calls on foraging grounds and is a first step towards categorizing the social calls of humpback whales in BC.Item Seasonal variations in anthropogenic and natural particles induced by rising C02 levels(Atmosphere, 2024) Yang, Dongdong; Zhang, Hua; Li, JiangnanUsing an aerosol–climate coupled model, this paper has investigated the changes in distributions of anthropogenic and natural particles due to 4 × CO2-induced global warming, under the low emission scenario of Representative Concentration Pathway 4.5 (RCP4.5). Special attention is paid to the seasonal variations of aerosol size modes. With rising CO2 levels, surface warming, and changes in atmospheric circulations and hydrologic cycles are found during both summer (JJA) and winter (DJF). For anthropogenic particles, changes in fine anthropogenic particulate matter (PM2.5, particles with diameters smaller than 2.5 μm) decrease over high-latitude regions and increase over the tropics in both DJF and JJA. Global mean column concentrations of PM2.5 decrease by approximately 0.19 mg m−2, and concentrations of coarse anthropogenic particles (CPM, particles with diameters larger than 2.5 μm) increase by 0.005 mg m−2 in JJA. Changes in anthropogenic particles in DJF are similar to those in JJA, but the magnitudes of maximum regional changes are much smaller than those in JJA. The coarse anthropogenic particles (CPM, particles with diameters larger than 2.5 μm) increase over northern Africa and the Arabian Peninsula during JJA, whereas changes in anthropogenic CPM during DJF are minimal. During both JJA and DJF, changes in anthropogenic CPM are about two orders of magnitude smaller than those of anthropogenic PM2.5. Enhanced wet deposition by large-scale precipitation under rising CO2-induced surface warming is the critical factor affecting changes in anthropogenic particles. For natural particles, the distribution of change in the natural PM2.5 burden is similar to that of natural CPM, but much larger than natural CPM during each season. Both natural PM2.5 and CPM burdens increase over northern Africa and the Arabian Peninsula during JJA, but decrease over most of the continental regions during DJF. Changes in surface wind speed, divergence/convergence of surface wind, and precipitation are primary reasons for the variation of natural particles.Item EONS: A new biogeochemical model of Earth's oxygen, carbon, phosphorus, and nitrogen systems from the Archean to the present(Geochemistry, Geophysics, Geosystems, 2024) Horne, Julia; Goldblatt, ColinWe present Earth's Oxygenation and Natural Systematics (EONS): a new, fully coupled biogeochemical model of the atmosphere, ocean, and their interactions with the geosphere, which can reproduce major features of Earth's evolution following the origin of life to the present day. The model, consisting of 257 unique fluxes between 96 unique chemical reservoirs, includes an interactive biosphere, cycles of carbon, nitrogen, phosphorus, and oxygen, and climate. A nominal model run initialized in the Eoarchean resolves emergent surface oxygenation, nutrient limitations, and climate feedbacks. The modeled atmosphere oxygenates in stepwise fashion over the course of the Proterozoic; a nearly billion year lag after the evolution of photosynthesis at 3.5 Ga is followed by a great oxidation event at 2.4 Ga, which appears to be caused by the gradual buildup of organic matter on the continents imposing nutrient limitation on the biosphere by removing key nutrients from the ocean system. The simple climate system shows significant temperature shifts punctuate the oxygenation process, implying that major biological transitions possibly destabilized Earth's climate. This work demonstrates that forward modeling the entirety of Earth's history with relatively few imposed boundary forcings is feasible, that the Earth system is not at steady state, and that our understanding of coupled C-N-P-O cycling as it functions today can explain much of the Earth's evolution.Item Exposure of satellite tagged bowhead whales (Balaena mysticetus) to transiting vessels in the Eastern Canadian Arctic(Marine Mammal Science, 2024) Martin, Morgan; Halliday, William; Ferguson, Steven H; Young, Brent G.; Charish, Rachel; Dawson, Jackie; Fortune, Sarah M. E.; Juanes, Francis; Qaunaq, Levi; Insley, Stephen J.Climate change poses new challenges to Arctic marine mammals, with increasing vessel traffic and associated underwater noise pollution emerging as significant threats. The bowhead whale (Balaena mysticetus), an endemic Arctic cetacean, faces these new threats. The Eastern Canada-West Greenland (ECWG) bowhead whale population migrates through areas with the highest levels of vessel traffic in the Canadian Arctic. Here, we document the spatial and temporal overlap between 36 satellite-tagged ECWG bowhead whales and vessels equipped with Automatic Identification System (AIS) transponders during 2012–2017. We report 1,145 instances where vessels were within 125 km of a tagged whale, with 306 occurrences within distances ≤50 km. Overlap between vessels and tagged bowhead whales was quantified monthly within years to investigate individual whale encounter rates. Results indicate that ECWG bowhead whales encounter the majority (79%) of vessels annually during August–October, with the highest number of encounters (42%) observed in September. Encounter rates ranged from 0.25 to 0.51 vessels encountered per day per whale during August–October compared to <0.07 vessels per day in all other months in this study. To better inform conservation strategies, further research is required to assess bowhead whale behavioral responses relative to distance from vessels.Item Cadmium-doping slows trap emptying in ambient-air blade-coated formamidinium lead iodide perovskite solar cells(Advanced Energy Materials, 2024) Zhang, Dongyang; Khasnabis, Sutripto; Wang, Wanlong; Yeddu, Vishal; Moradi, Shahram; Awais, Muhammad; Nguyen, Hai-Dang; Reinecke, Sean B.; Haruta, Yuki; Godin, Robert; Tan, Furui; Saidaminov, MakhsudFormamidinium lead iodide (FAPbI3) in its α-phase is among the most desirable perovskite compositions for solar cells. However, because of its transition into the yellow δ-phase at room temperature, it is a challenge to process it in ambient air by scalable fabrication methods. Here the introduction of a trace amount of cadmium (in the form of CdI2) to FAPbI3 is reported and found that it enhances the stability of the perovskite's black α-phase polymorph, inhibits non-radiative recombination events, leads to pin-hole free compact surface morphology, and improves band energy alignment. The 0.6% Cd-doped FAPbI3 solar cells show a champion efficiency of 22.7% for 0.049 cm2 and 16.4% for cm2-scale pixels, which, to the best of the knowledge, are among the highest for air-ambient fully blade-coated pure FAPbI3 solar cells with an n-i-p architecture. Transient absorption microscopy measurements reveal that Cd doping reduces the number of trapped charges and increases their lifetimes, promoting charge accumulation and a higher photovoltage. The study sheds light on the potential of cadmium as a homovalent dopant for the stabilization and performance enhancement of FAPbI3 performance solar cells.