Polar bears (Ursus maritimus) are experiencing loss of sea ice habitats used to access their marine mammal prey. Simultaneously, ocean warming is changing ecosystems that support marine mammal ...populations. The interactive effects of sea ice and prey are not well understood yet may explain spatial–temporal variation in the response of polar bears to sea ice loss. Here, we examined the potential combined effects of sea ice, seal body condition, and atmospheric circulation patterns on the body condition, recruitment, diet, and feeding probability of 469 polar bears captured in the Chukchi Sea, 2008–2017. The body condition of ringed seals (Pusa hispida), the primary prey of females and subadults, was related to dietary proportions of ringed seal, feeding probability, and the body condition of females and cubs. In contrast, adult males consumed more bearded seals (Erignathus barbatus) and exhibited better condition when bearded seal body condition was higher. The litter size, number of yearlings per adult female, and the condition of dependent young were higher following winters characterized by low Arctic Oscillation conditions, consistent with a growing number of studies. Body condition, recruitment, and feeding probability were either not associated or negatively associated with sea ice conditions, suggesting that, unlike some subpopulations, Chukchi Sea bears are not currently limited by sea ice availability. However, spring sea ice cover declined 2% per year during our study reaching levels not previously observed in the satellite record and resulting in the loss of polar bear hunting and seal pupping habitat. Our study suggests that the status of ice seal populations is likely an important factor that can either compound or mitigate the response of polar bears to sea ice loss over the short term. In the long term, neither polar bears nor their prey are likely robust to limitless loss of their sea ice habitat.
Body condition, feeding, and recruitment of Chukchi Sea polar bears during 2008–2017 were influenced by sea ice conditions, ice seal body condition, and a climatic index. Spring feeding probability and body condition of females and dependent young were higher following years with higher ringed seal body condition. Adult males consumed more bearded seals and exhibited better condition when bearded seal body condition (blue) was higher. Recruitment was higher following winters with low winter Arctic Oscillations (green). Interactions among seal population status, sea ice conditions, and atmospheric circulation patterns likely influence spatial–temporal variation in the status of polar bear populations.
We study a coupled array of coherently driven photonic cavities, which maps onto a driven-dissipative XY spin-
model with ferromagnetic couplings in the limit of strong optical nonlinearities. Using ...a site-decoupled mean-field approximation, we identify steady-state phases with canted antiferromagnetic order, in addition to limit cycle phases, where oscillatory dynamics persist indefinitely. We also identify collective bistable phases, where the system supports two steady states among spatially uniform, antiferromagnetic, and limit cycle phases. We compare these mean-field results to exact quantum trajectory simulations for finite one-dimensional arrays. The exact results exhibit short-range antiferromagnetic order for parameters that have significant overlap with the mean-field phase diagram. In the mean-field bistable regime, the exact quantum dynamics exhibits real-time collective switching between macroscopically distinguishable states. We present a clear physical picture for this dynamics and establish a simple relationship between the switching times and properties of the quantum Liouvillian.
Climate change is expected to alter many species' habitat. A species' ability to adjust to these changes is partially determined by their ability to adjust habitat selection preferences to new ...environmental conditions. Sea ice loss has forced polar bears (Ursus maritimus) to spend longer periods annually over less productive waters, which may be a primary driver of population declines. A negative population response to greater time spent over less productive water implies, however, that prey are not also shifting their space use in response to sea ice loss. We show that polar bear habitat selection in the Chukchi Sea has not changed between periods before and after significant sea ice loss, leading to a 75% reduction of highly selected habitat in summer. Summer was the only period with loss of highly selected habitat, supporting the contention that summer will be a critical period for polar bears as sea ice loss continues. Our results indicate that bears are either unable to shift selection patterns to reflect new prey use patterns or that there has not been a shift towards polar basin waters becoming more productive for prey. Continued sea ice loss is likely to further reduce habitat with population-level consequences for polar bears.
Among polar bears (
), only parturient females den for extended periods, emerging from maternal dens in spring after having substantially depleted their energy reserves during a fast that can exceed ...8 months. Although den emergence coincides with a period of increasing prey availability, polar bears typically do not depart immediately to hunt, but instead remain at the den for up to a month. This delay suggests that there are likely adaptive advantages to remaining at the den between emergence and departure, but the influence of the timing and duration of this post-emergence period on cub survival has not been evaluated previously. We used temperature and location data from 70 denning bears collared within the Southern Beaufort Sea and Chukchi Sea subpopulations to estimate the phenology of the post-emergence period. We evaluated the influence of various spatial and temporal features on duration of the post-emergence period and evaluated the potential influence of post-emergence duration on litter survival early in the spring following denning. For dens that likely contained viable cubs at emergence (
= 56), mean den emergence occurred on 16 March (SE = 1.4 days) and mean departure on 24 March (SE = 1.6 days), with dates typically occurring later in the Chukchi Sea relative to Southern Beaufort Sea and on land relative to sea ice. Mean duration of the post-emergence period was 7.9 days (SE = 1.4) for bears that were observed with cubs later in the spring, which was over 4 times longer than duration of those observed without cubs (1.9 days). Litter survival in the spring following denning (
= 31 dens) increased from 0.5 to 0.9 when duration of the post-emergence period increased by ~4 days and other variables were held at mean values. Our limited sample size and inability to verify cub presence at emergence suggests that future research is merited to improve our understanding of this relationship. Nonetheless, our results highlight the importance of the post-emergence period in contributing to reproductive success and can assist managers in developing conservation and mitigation strategies in denning areas, which will be increasingly important as human activities expand in the Arctic.
We estimated density and abundance of the threatened southwest Alaska distinct population segment of northern sea otters (Enhydra lutris kenyoni) in two management units. We conducted aerial surveys ...in Bristol Bay and South Alaska Peninsula management units in 2016, and modeled sea otter density and abundance with Bayesian hierarchical distance sampling models and spatial environmental covariates (depth, distance to shore, depth × distance to shore). Spatial environmental covariates substantially impacted sea otter group density in both management units, but effects sizes differed between the two management units. Abundance (9,733 otters, 95% CrI 6,412–17,819) and density (0.82 otters/km2, 95% CrI 0.54–1.49) estimates for Bristol Bay indicated a moderate population size. In contrast, abundance (546 otters, 95% CrI 322–879) and density (0.06 otters/km2, 95% CrI 0.03–0.09) estimates indicated a relatively low population size in South Alaska Peninsula. Overall, our results highlight the importance of accounting for the detection process in monitoring at‐risk species to reduce the uncertainty associated with making conclusions about population declines.
Recent reductions in thickness and extent have increased drift rates of Arctic sea ice. Increased ice drift could significantly affect the movements and the energy balance of polar bears (Ursus ...maritimus) which forage, nearly exclusively, on this substrate. We used radio‐tracking and ice drift data to quantify the influence of increased drift on bear movements, and we modeled the consequences for energy demands of adult females in the Beaufort and Chukchi seas during two periods with different sea ice characteristics. Westward and northward drift of the sea ice used by polar bears in both regions increased between 1987–1998 and 1999–2013. To remain within their home ranges, polar bears responded to the higher westward ice drift with greater eastward movements, while their movements north in the spring and south in fall were frequently aided by ice motion. To compensate for more rapid westward ice drift in recent years, polar bears covered greater daily distances either by increasing their time spent active (7.6%–9.6%) or by increasing their travel speed (8.5%–8.9%). This increased their calculated annual energy expenditure by 1.8%–3.6% (depending on region and reproductive status), a cost that could be met by capturing an additional 1–3 seals/year. Polar bears selected similar habitats in both periods, indicating that faster drift did not alter habitat preferences. Compounding reduced foraging opportunities that result from habitat loss; changes in ice drift, and associated activity increases, likely exacerbate the physiological stress experienced by polar bears in a warming Arctic.
To compensate for greater westward and northward sea ice drift between 1987–1998 and 1999–2013, polar bears in the Beaufort and Chukchi seas increased their time active (8.1%–9.6%) or travel speeds (8.5%–8.9%). This increased their annual energy expenditures by 1.8%–3.6%, which could be met by capturing an additional 1–3 seals/year.
We examine whether tax-motivated income shifting by U.S. multinational corporations affects information asymmetry. Using a new firm-year measure of income shifting and a two-stage least squares ...approach, we find income shifting is positively associated with four measures of information asymmetry. Cross-sectional tests reveal that this effect is more pronounced for firms with large differences between foreign and domestic earnings growth. Using SFAS 131 to improve identification and establish evidence consistent with a causal relation between income shifting and information asymmetry, we demonstrate that the adverse impact of income shifting on information asymmetry is concentrated in firms that discontinue geographic earnings disclosures. Overall, our study provides evidence that significant consequences of information asymmetry are associated with tax-motivated income shifting.
The CADILLAC risk score was developed to identify patients at low risk for adverse cardiovascular events following ST elevation myocardial infarction (STEMI) treated with primary percutaneous ...coronary intervention (PPCI).
We performed a single center retrospective review of STEMI hospitalizations treated with PPCI from 2014 to 2018. Patients were stratified using the CADILLAC risk score into low risk, intermediate risk and high risk groups. Patients presenting with cardiac arrest or cardiogenic shock were excluded from the study. The primary outcome was adverse clinical events during initial hospitalization. Secondary outcomes were adverse clinical events at 30 days and 1 year following index hospitalization.
The study included 341 patients. Compared to patients with a low CADILLAC score, adverse clinical events were similar in the intermediate risk group during hospitalization (OR 1.23, CI 0.37-4.05, p 0.733) and at 30 days (OR 2.27, CI 0.93-5.56, p 0.0733) while adverse clinical events were significantly elevated in the high risk group during hospitalization (OR 4.75, CI 1.91-11.84, p 0.0008) and at 30 days (OR 8.73, CI 4.02-18.96, p < 0.0001). At 1 year follow-up, compared to the low risk CADILLAC group (9.4% adverse clinical event rate), cumulative adverse clinical events were significantly higher in the intermediate risk group (22.9% event rate, OR 2.86, CI 1.39-5.89, p 0.0044) and in the elevated risk group (58.6% event rate, OR 13.67, CI 6.81-27.43, p < 0.0001). The mortality rate was 0% for patients defined at low risk by CADILLAC score during hospitalization, as well up to 1 year follow up. On receiver operating curve analysis, discrimination of in-hospital adverse clinical events was fair using CADILLAC (C = 0.66, odds ratio 1.18; 95% CI 1.04-1.33; p = 0.0064) with somewhat better discrimination at 30-day follow-up (C = 0.719) and 1-year follow-up (C = 0.715).
Patients defined as low risk by the CADILLAC score following a STEMI were associated with lower mortality and adverse clinical event rates during hospitalization and up to 1 year following STEMI when compared to those with an intermediate or high CADILLAC score.
Large carnivores are imperiled globally, and characteristics making them vulnerable to extinction (e.g., low densities and expansive ranges) also make it difficult to estimate demographic parameters ...needed for management. Here we develop an integrated population model to analyze capture-recapture, radiotelemetry, and count data for the Chukchi Sea subpopulation of polar bears (Ursus maritimus), 2008-2016. Our model addressed several challenges in capture-recapture studies for polar bears by including a multievent structure reflecting location and life history states, while accommodating state uncertainty. Female breeding probability was 0.83 (95% credible interval CRI = 0.71-0.90), with litter sizes of 2.18 (95% CRI = 1.71-2.82) for age-zero and 1.61 (95% CRI = 1.46-1.80) for age-one cubs. Total adult survival was 0.90 (95% CRI = 0.86-0.92) for females and 0.89 (95% CRI = 0.83-0.93) for males. Spring on-ice densities west of Alaska were 0.0030 bears/km
(95% CRI = 0.0016-0.0060), similar to 1980s-era density estimates although methodological differences complicate comparison. Abundance of the Chukchi Sea subpopulation, derived by extrapolating density from the study area using a spatially-explicit habitat metric, was 2,937 bears (95% CRI = 1,552-5,944). Our findings are consistent with other lines of evidence suggesting the Chukchi Sea subpopulation has been productive in recent years, although it is uncertain how long this will continue given sea-ice loss due to climate change.
Chile is the world's leading copper producer (28.3%) and maintains approximately 23.0% of current global reserves. Chile is faced with a significant risk posed by its collection of the most ...unsustainable and antiquated smelter operations among major copper producers worldwide. Moreover, forecasts also indicate a trend toward higher proportions of copper sulphide ores that carry high impurities, especially arsenic. To achieve the planned production increases, improve competitiveness in the global market, and reduce reliance on international smelting capacities, Chile must make significant and justifiable investment into new and/or existing smelting operations through equipment modernization. The required investment for upgrades may be on the order of billions of dollars.
This review analyzes current roadblocks faced by the Chilean copper smelters and potential solutions according to environmental, economic and strategic factors. Recent advances in smelting technologies have focused on flash and bath smelting; despite a general trend toward flash furnace systems, recent bath furnace methods (e.g. China's SKS-BBS) are equally promising, particularly for varying and complex feeds. Strategic policies should focus on regionalized, non-integrated custom smelters, which can handle ores from a variety of sources while reducing overall operating costs. The government must play a fundamental role to incentivise the investments necessary to develop new smelter operations and upgrade existing infrastructure. With a large portion of copper concentrate exports coming from privately owned mines, synergistic efforts with industry partners will be crucial to increase overall smelting capacity and position Chile as a global leader in the smelting of copper concentrates.
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