University of Alaska System
  • Fairbanks, United States
Recent publications
Purpose Prior cancer research is limited by inconsistencies in defining rurality. The purpose of this study was to describe the prevalence of cancer risk factors and cancer screening behaviors across various county-based rural classification codes, including measures reflecting a continuum, to inform our understanding of cancer disparities according to the extent of rurality. Methods Using an ecological cross-sectional design, we examined differences in cancer risk factors and cancer screening behaviors from the Behavioral Risk Factor Surveillance System and National Health Interview Survey (2008–2013) across rural counties and between rural and urban counties using four rural–urban classification codes for counties and county-equivalents in 2013: U.S. Office of Management and Budget, National Center for Health Statistics, USDA Economic Research Service’s rural–urban continuum codes, and Urban Influence Codes. Results Although a rural-to-urban gradient was not consistently evident across all classification codes, the prevalence of smoking, obesity, physical inactivity, and binge alcohol use increased (all ptrend < 0.03), while colorectal, cervical and breast cancer screening decreased (all ptrend < 0.001) with increasing rurality. Differences in the prevalence of risk factors and screening behaviors across rural areas were greater than differences between rural and urban counties for obesity (2.4% vs. 1.5%), physical activity (2.9% vs. 2.5%), binge alcohol use (3.4% vs. 0.4%), cervical cancer screening (6.8% vs. 4.0%), and colorectal cancer screening (4.4% vs. 3.8%). Conclusions Rural cancer disparities persist across multiple rural–urban classification codes, with marked variation in cancer risk factors and screening evident within rural regions. Focusing only on a rural–urban dichotomy may not sufficiently capture subpopulations of rural residents at greater risk for cancer and cancer-related mortality.
Hot flow anomalies (HFAs) and foreshock bubbles (FBs) are frequently observed in Earth's foreshock, which can significantly disturb the bow shock and therefore the magnetosphere‐ionosphere system and can accelerate particles. Previous statistical studies have identified the solar wind conditions (high solar wind speed and high Mach number, etc.) that favor their generation. However, backstreaming foreshock ions are expected to most directly control how HFAs and FBs form, whereas the solar wind may partake in the formation process indirectly by determining foreshock ion properties. Using Magnetospheric Multiscale mission and Time History of Events and Macroscale Interactions during Substorms mission, we perform a statistical study of foreshock ion properties around 275 HFAs and FBs. We show that foreshock ions with a high foreshock‐to‐solar wind density ratio (>∼3%), high kinetic energy (>∼600 eV), large ratio of kinetic energy to thermal energy (>∼0.1), and large ratio of perpendicular temperature to parallel temperature (>∼1.4) favor HFA and FB formation. We also examine how these properties are related to solar wind conditions: high solar wind speed and oblique bow shock (angle between the interplanetary magnetic field and the bow shock normal θBn∼45° ${\theta }_{\text{Bn}}\sim 45{}^{\circ}$) favor high kinetic energy of foreshock ions; foreshock ions have large ratio of kinetic energy to thermal energy at large θBn ${\theta }_{\text{Bn}}$ (>30°); small θBn ${\theta }_{\text{Bn}}$ (<30°), high Mach number, and closeness to the bow shock favor a high foreshock‐to‐solar wind density ratio. Our results provide further understanding of HFA and FB formation.
Simple scaling analysis of terms in the Navier‐Stokes momentum equation for Earth's atmosphere suggests that winds at heights above 120 km should be smooth and laminar, with little spatial variation over horizontal scale lengths smaller than several hundred kilometers. However, there is increasing evidence that this traditional understanding may fail to account for several important processes, including both waves and small‐scale ion‐neutral momentum coupling. Here, we examine the thermospheric neutral wind field over Alaska in unprecedented detail using observations from an array of four ground‐based all‐sky imaging Fabry‐Perot interferometers, processed using a new geophysical inverse algorithm, to derive high‐resolution maps of all three wind components, with a temporal cadence of 30 seconds. The reconstructed high‐resolution neutral winds showed synoptic‐scale agreement with prior observations and previously validated techniques, with all results exhibiting behavior in agreement with basic physics. However, stacked time‐series plots of vector wind components reveal significantly more spatial and temporal structure than previously reported. In particular, the observed responses included complex wave‐like behavior and highly geographically variable vertical winds. Local flow features were observed at spatial scales as small as 100 km at times, with temporal scales as short as a few tens of minutes. Instances of close spatial and temporal correlations were observed between the wind fields reconstructed from green‐line spectra and ionospheric flows observed independently by SuperDARN.
The grey wolf (Canis lupus) was the first species to give rise to a domestic population, and they remained widespread throughout the last Ice Age when many other large mammal species went extinct. Little is known, however, about the history and possible extinction of past wolf populations or when and where the wolf progenitors of the present-day dog lineage (Canis familiaris) lived1–8. Here we analysed 72 ancient wolf genomes spanning the last 100,000 years from Europe, Siberia and North America. We found that wolf populations were highly connected throughout the Late Pleistocene, with levels of differentiation an order of magnitude lower than they are today. This population connectivity allowed us to detect natural selection across the time series, including rapid fixation of mutations in the gene IFT88 40,000–30,000 years ago. We show that dogs are overall more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, suggesting a domestication process in the east. However, we also found that dogs in the Near East and Africa derive up to half of their ancestry from a distinct population related to modern southwest Eurasian wolves, reflecting either an independent domestication process or admixture from local wolves. None of the analysed ancient wolf genomes is a direct match for either of these dog ancestries, meaning that the exact progenitor populations remain to be located.
An elastic map $\mathbf {T}$ T describes the strain-stress relation at a particular point $\mathbf {p}$ p in some material. A symmetry of $\mathbf {T}$ T is a rotation of the material, about $\mathbf {p}$ p , that does not change $\mathbf {T}$ T . We describe two ways of inferring the group $\mathcal {S} _{ \mathbf {T} }$ S T of symmetries of any elastic map $\mathbf {T}$ T ; one way is qualitative and visual, the other is quantitative. In the first method, we associate to each $\mathbf {T}$ T its “monoclinic distance function” "Equation missing" on the unit sphere. The function "Equation missing" is invariant under all of the symmetries of $\mathbf {T}$ T , so the group $\mathcal {S} _{ \mathbf {T} }$ S T is seen, approximately, in a contour plot of "Equation missing" . The second method is harder to summarize, but it complements the first by providing an algorithm to compute the symmetry group $\mathcal {S} _{ \mathbf {T} }$ S T . In addition to $\mathcal {S} _{ \mathbf {T} }$ S T , the algorithm gives a quantitative description of the overall approximate symmetry of $\mathbf {T}$ T . Mathematica codes are provided for implementing both the visual and the quantitative approaches.
Polar bears (Ursus maritimus) and brown bears (Ursus arctos) are sister species possessing distinct physiological and behavioural adaptations that evolved over the last 500,000 years. However, comparative and population genomics analyses have revealed that several extant and extinct brown bear populations have relatively recent polar bear ancestry, probably as the result of geographically localized instances of gene flow from polar bears into brown bears. Here, we generate and analyse an approximate 20X paleogenome from an approximately 100,000-year-old polar bear that reveals a massive prehistoric admixture event, which is evident in the genomes of all living brown bears. This ancient admixture event was not visible from genomic data derived from living polar bears. Like more recent events, this massive admixture event mainly involved unidirectional gene flow from polar bears into brown bears and occurred as climate changes caused overlap in the ranges of the two species. These findings highlight the complex reticulate paths that evolution can take within a regime of radically shifting climate. A paleogenome from an approximately 100,000-year-old polar bear shows massive prehistoric, and largely unidirectional, gene flow from polar bears into brown bears at a time of climate change-induced overlap in the ranges of the two species. This admixture event cannot be detected using genomic data from living polar bears.
Changes to Pacific walruses (Odobenus rosmarus divergens) habitat and foraging behavior may affect exposure to both toxic and essential trace elements in walrus tissue. This study measured the trace element concentrations of silver (Ag), arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), total (THg) and methyl mercury (MeHg), selenium (Se), lead (Pb), and zinc (Zn) in walrus skeletal muscle sampled during 2009–2015. Females had significantly higher concentrations of THg (p = 0.021), MeHg (p = 0.037), Cd (p = 0.021), Cu (p = 0.003), and Se (p = 0.001) compared to males. Females with no calf had significantly higher concentrations of Cd compared to females with a calf (p = 0.001) and pregnant females and females with a calf had significantly lower Se concentrations compared to females with a yearling or no calf (p < 0.05). Bering Sea males had significantly higher Ni concentrations (p = 0.001) and significantly lower Se (p = 0.006) and Zn concentrations (p = 0.001) compared to other locations. THg, MeHg, and As tissue concentrations decreased with age (p < 0.01), suggesting these toxic elements are not accumulating in this tissue while Cd increased with age (p < 0.05). The narrower range in ele- ment concentrations among pregnant and nursing females may indicate less variation in prey species, and coupled with the reproductive needs for essential elements, suggests they may be more vulnerable to changes in prey availability compared to other walruses.
Lack of tree fecundity data across climatic gradients precludes the analysis of how seed supply contributes to global variation in forest regeneration and biotic interactions responsible for biodiversity. A global synthesis of raw seedproduction data shows a 250‐fold increase in seed abundance from cold‐dry to warm‐wet climates, driven primarily by a 100‐fold increase in seed production for a given tree size. The modest (threefold) increase in forest productivity across the same climate gradient cannot explain the magnitudes of these trends. The increase in seeds per tree can arise from adaptive evolution driven by intense species interactions or from the direct effects of a warm, moist climate on tree fecundity. Either way, the massive differences in seed supply ramify through food webs potentially explaining a disproportionate role for species interactions in the wet tropics. A global synthesis of raw seedproduction data shows a 250‐fold increase in seed abundance from cold‐dry to warm‐wet climates, driven by a 100‐fold increase in seed production for a given tree size. The increase in seeds per tree can arise from adaptive evolution driven by intense species interactions or from the direct effects of a warm, moist climate on tree fecundity.
Ground‐based very low frequency (VLF) transmitters located around the world generate signals that leak through the bottom side of the ionosphere in the form of whistler mode waves. Wave and particle measurements on satellites have observed that these man‐made VLF waves can be strong enough to scatter trapped energetic electrons into low pitch angle orbits, causing loss by absorption in the lower atmosphere. This precipitation loss process is greatly enhanced by intentional amplification of the whistler waves using a newly discovered process called rocket exhaust driven amplification (REDA). Satellite measurements of REDA have shown between 30 and 50 dB intensification of VLF waves in space using a 60 s burn of the 150 g/s thruster on the Cygnus satellite that services the International Space Station. This controlled amplification process is adequate to deplete the energetic particle population on the affected field lines in a few minutes rather than the multi‐day period it would take naturally. Numerical simulations of the pitch angle diffusion for radiation belt particles use the UCLA quasi‐linear Fokker Planck model to assess the impact of REDA on radiation belt remediation of newly injected energetic electrons. The simulated precipitation fluxes of energetic electrons are applied to models of D‐region electron density and bremsstrahlung X‐rays for predictions of the modified environment that can be observed with satellite and ground‐based sensors.
Plain Language Summary In Earth's Van Allen radiation belts, energetic particles are magnetically trapped to form a hazardous environment for spacecraft and astronauts. These particles can stay trapped for years before they are scattered toward the atmosphere by resonant interactions with plasma waves. Among these waves, the electromagnetic ion cyclotron (EMIC) waves are particularly important in the removal of energetic ions and relativistic electrons. The EMIC wave excitation is often associated with strong ion anisotropy, which gradually develops as particles injected from the magnetotail drift around the Earth at different speeds depending on their energy and pitch angle. Here, we propose a new scenario of localized EMIC wave excitation, in which the injected perpendicular‐moving and bouncing ions are abruptly separated by their associated diamagnetic dips, to develop strong ion anisotropy inside the dip structure and generate EMIC waves. This scenario is validated via case and statistical observations, together with numerical simulations that reproduce most of the observational signatures, which reveals the importance of the magnetic dips as traveling hotspots of EMIC wave activities. These insights indicate the localized and dynamical removal of energetic particles and provide key revision to the prevailing radiation belt models.
Plain Language Summary Very‐Low‐Frequency (VLF) transmitter waves have been well known to drive important electron precipitation in the near‐Earth space. However, the capability of VLF transmitters to accelerate electrons has mostly been overlooked and assumed to be negligible. By performing two‐dimensional Fokker–Planck diffusion simulations, we quantify the role of VLF transmitters and other naturally occurring plasma waves in electron acceleration in the inner belt and slot region. We found that VLF transmitter waves can simultaneously accelerate higher energy electrons and drive electron loss at lower energies. However, the net acceleration is typically suppressed by stronger pitch angle diffusion due to lightning‐generated whistlers and plasmaspheric hiss. Recent studies have reported the achievable rocket exhaust driven amplification (REDA) of VLF transmitter waves by 20–30 dB. We adopt various amplification factors to determine the preferred wave amplitude of VLF transmitters for acceleration. The critical amplification factor is 5, when the acceleration is enough to overcome the combined scattering causing net acceleration. The acceleration occurs within 1 min with amplification factor of 50 dB, which can be achieved in the future REDA experiment. Our study provides the first estimation of the capability and efficiency of VLF transmitter waves to accelerate electrons and provides a feasible test to theoretical predictions.
The temperature-size rule predicts that climate warming will lead to faster growth rates for juvenile fishes but lower adult body size. Testing this prediction is central to understanding the effects of climate change on population dynamics. We use fisheries-independent data (1999-2019) to test predictions of age-specific climate effects on body size in eastern Bering Sea walleye pollock (Gadus chalcogrammus). This stock supports one of the largest food fisheries in the world but is experiencing exceptionally rapid warming. Our results support the predictions that weight-at-age increases with temperature for young age classes (ages 1, 3-4) but decreases with temperature for old age classes (ages 7-15). Simultaneous demonstrations of larger juveniles and smaller adults with warming have thus far been rare, but pollock provide a striking example in a fish of exceptional ecological and commercial importance. The age-specific response to temperature was large enough (0.5 – 1 SD change in log weight-at-age) to have important implications for pollock management, which must estimate current and future weight-at-age to calculate allowable catch, and for the Bering Sea pollock fishery.
The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential.
Diel vertical migration (DVM) is common in zooplankton populations worldwide. Every day, zooplankton leave the productive surface ocean and migrate to deepwater to avoid visual predators and return to the surface at night to feed. This behavior may also help retain migrating zooplankton in biological hotspots. Compared to fast and variable surface currents, deep ocean currents are sluggish, and can be more consistent. The time spent in the subsurface layer is driven by day length and the depth of the surface mixed layer. A subsurface, recirculating eddy has recently been described in Palmer Deep Canyon (PDC), a submarine canyon in a biological hotspot located adjacent to the West Antarctic Peninsula. Circulation model simulations have shown that residence times of neutrally buoyant particles increase with depth within this feature. We hypothesize that DVM into the subsurface eddy increases local retention of migrating zooplankton in this feature and that shallow mixed layers and longer days increase residence times. We demonstrate that simulated vertically migrating zooplankton can have residence times on the order of 30 days over the canyon, which is five times greater than residence times of near‐surface, nonmigrating zooplankton within PDC and other adjacent coastal regions. The potential interaction of zooplankton with this subsurface feature may be important to the establishment of the biological hotspot around PDC by retaining food resources in the region. Acoustic field observations confirm the presence of vertical migrators in this region, suggesting that zooplankton retention due to the subsurface eddy is feasible.
Disentangling the evolutionary relationships of rapidly radiating clades is often challenging because of low genetic differentiation and potentially high levels of gene flow among diverging taxa. The genus Sporophila consists of small Neotropical birds that show, in general, relatively low genetic divergence, but particularly high speciation rates and pronounced variation in secondary sexual traits (e.g., plumage color), which can be important in generating premating reproductive isolation. In cases like these, the use of genome-wide sequence data can increase the resolution to uncover a clade’s evolutionary history. Here, we used a phylogenomic approach to study the evolutionary history and genetic structure of the Variable Seedeater superspecies complex, which includes S. corvina, S. intermedia, and S. americana. Using ∼25,000 genome-wide single nucleotide polymorphisms (SNPs), we confirmed that the Variable Seedeater superspecies complex is monophyletic. However, a phylogenetic reconstruction based on a mitochondrial marker (ND2) resulted in a discordant tree topology, particularly in the position of Wing-barred Seedeater S. americana, which might be due to a mitochondrial capture event. Our results suggest historical gene flow among lineages, particularly between species with conflicting topologies. Among the four phenotypically variable S. corvina subspecies, our structure analyses identified three main distinct genetic groups (K = 3), and that the entirely black subspecies, S. c. corvina, is derived from within a pied-colored clade. Further, we inferred widespread gene flow across the whole species’ distribution, including between subspecies. However, gene flow was about 100 times lower at the geographic boundaries of the entirely black and the pied subspecies, suggesting an important role for plumage divergence in limiting gene flow. Overall, our findings suggest that the early diversification of the Sporophila genus occurred rapidly despite historical gene flow between lineages and that divergence in plumage color possibly influences the extent of gene flow among taxa.
The application of a distributed energy balance model over nine years at an hourly time step to a 20 × 20 m grid cell over Glacier Zongo (Bolivia, 16°S) enabled assessment of the climate factors that control the interseasonal and interannual variability of its surface mass balance. The model was validated by comparing the measured and simulated discharge at the outlet, albedo at the Automatic Weather Station, surface state and annual mass balance both glacier‐wide and as a function of altitude. Analysis of the mean monthly energy fluxes highlighted the importance of the meteorological conditions over October and November on the variability of the annual surface mass balance. Two sensitivity analyses are presented, one of the distribution of precipitation over time which maintains a physical coherence between the different meteorological variables and one of the impact of prolonged periods of intense cloud radiative forcing on the surface mass balance. The distribution of precipitation events over time and their associated amounts are the main drivers of the interannual variability of the surface mass balance via an albedo feedback effect. Additionally, prolonged periods of negative cloud radiative forcing, specifically over the month of November, notably reduce the melt rate.
The hepatitis B virus (HBV) is highly infectious, with over 292 million chronically infected people worldwide and up to 2.4 million in the United States. Following infection, clinically silent liver damage can ensue, but symptoms or signs of advanced disease, including cirrhosis and hepatocellular carcinoma, can take decades to emerge. HBV has the heaviest public health burden of all hepatitis viruses and has now surpassed other major communicable diseases (eg, HIV, diarrheal disease, malaria, tuberculosis) as a leading cause of death globally. Preventing transmission is essential, and efforts are in place to reinforce screening, vaccination, and routine follow-up. Three safe and effective vaccines are available in the United States and other countries for HBV prevention, and the benefits of vaccination in preventing infection and its sequelae have been substantiated. For the first time in over 25 years, a new Food and Drug Administration-approved vaccine is available that offers a high degree of immunogenicity after 2, rather than 3, injections. Persistent challenges include the underutilization of vaccination, choice of vaccine, incomplete vaccinations, varying needs in different populations, management of nonresponders or those with undocumented or incompletely documented vaccination courses, and questions about whether and when booster injections may be needed. A panel of US academic hepatologists with expertise and experience in preventing and managing HBV infection have collaborated to write this practical clinical paper intended to guide clinicians in vaccinating for HBV and address questions that regularly arise in the clinic.
Species occurrence records are vital data streams in marine conservation with a wide range of important applications. From 2001–2020, the Monterey Bay Aquarium led an international research collaboration to understand the life cycle, ecology, and behavior of white sharks ( Carcharodon carcharias ) in the southern California Current. The collaboration was devoted to tagging juveniles with animal-borne sensors, also known as biologging. Here we report the full data records from 59 pop-up archival (PAT) and 20 smart position and temperature transmitting (SPOT) tags that variously recorded pressure, temperature, and light-level data, and computed depth and geolocations for 63 individuals. Whether transmitted or from recovered devices, raw data files from successful deployments ( n = 70) were auto-ingested from the manufacturer into the United States (US) Animal Telemetry Network’s (ATN) Data Assembly Center (DAC). There they have attributed a full suite of metadata, visualized within their public-facing data portal, compiled for permanent archive under the DataONE Research Workspace member node, and are accessible for download from the ATN data portal.
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416 members
Sven O E Ebbesson
  • Professor emeritus
Shiva Hullavarad
  • Records and Information Management
M. Zhang
  • Agriculture and Horticulture
Sherry L Tamone
  • Natural Sciences
Vladimir E Romanovsky
  • Geophysical Institute
Fairbanks, United States