Kodiak Brown Bears Surf the Salmon Red Wave: Direct Evidence from GPS Collared Individuals

One of the goals of Ecosystems Base Fisheries Management (EBFM) is recognizing and mitigating indirect effects of fisheries on trophic interactions. Most research on indirect effects has considered how the abundance of managed fishes influences trophic interactions with other species. However, recent work has shown that attributes besides abundance, such as life history variation, can strongly mediate species interactions.  For example, phenological variation within prey species may enhance foraging opportunities for mobile predators by increasing the duration over which predators can target vulnerable life stages of prey.  Here, we present direct evidence of individual brown bears (Ursus arctos middendorffi) exploiting variation in sockeye salmon spawning phenology by tracking salmon runs across a 2,800 km2 region of Kodiak Island.  Data from 40 GPS collared brown bears show bears visited multiple spawning sites in synchrony with the order of spawning phenology.  The average time spent feeding on salmon was 67 days, while the average duration of spawning for one population was only 40 days.  The number of sites used was correlated with the number of days a bear exploited salmon, suggesting phenological variation in the study area influenced bear access to salmon, a resource which strongly influences bear fitness.  These results suggest fisheries managers attempting to maximize harvest while minimizing impacts on brown bears should strive to protect the population diversity that underlies the phenological variation used by wildlife consumers.  These results underscore the need to understand how fisheries affect life history diversity in addition to abundance in order to minimize negative effects of fisheries management on non-target species, a goal of EBFM

Correlating metal redox potentials to Co(III)K(I) catalyst performances in carbon dioxide and propene oxide ring opening copolymerization

Carbon dioxide copolymerization is a front-runner CO2 utilization strategy but its viability depends on improving the catalysis. So far, catalyst structure-performance correlations have not been straightforward, limiting the ability to predict how to improve both catalytic activity and selectivity. Here, a simple measure of a catalyst ground-state parameter, metal reduction potential, directly correlates with both polymerization activity and selectivity. It is applied to compare performances of 6 new heterodinuclear Co(III)K(I) catalysts for propene oxide (PO)/CO2 ring opening copolymerization (ROCOP) producing poly(propene carbonate) (PPC). The best catalyst shows an excellent turnover frequency of 389 h−1 and high PPC selectivity of >99 % (50 °C, 20 bar, 0.025 mol% catalyst). As demonstration of its utility, neither DFT calculations nor ligand Hammett parameter analyses are viable predictors. It is proposed that the cobalt redox potential informs upon the active site electron density with a more electron rich cobalt centre showing better performances. The method may be widely applicable and is recommended to guide future catalyst discovery for other (co)polymerizations and carbon dioxide utilizations

Insights into the mechanism of carbon dioxide and propylene oxide ring-opening copolymerization using a Co(III)/K(I) heterodinuclear catalyst

A combined computational and experimental investigation into the catalytic cycle of carbon dioxide and propylene oxide ring-opening copolymerization is presented using a Co(III)K(I) heterodinuclear complex (Deacy, A. C. Co(III)/Alkali-Metal(I) Heterodinuclear Catalysts for the Ring-Opening Copolymerization of CO2 and Propylene Oxide. J. Am. Chem. Soc. 2020, 142(45), 19150−19160). The complex is a rare example of a dinuclear catalyst, which is active for the copolymerization of CO2 and propylene oxide, a large-scale commercial product. Understanding the mechanisms for both product and byproduct formation is essential for rational catalyst improvements, but there are very few other mechanistic studies using these monomers. The investigation suggests that cobalt serves both to activate propylene oxide and to stabilize the catalytic intermediates, while potassium provides a transient carbonate nucleophile that ring-opens the activated propylene oxide. Density functional theory (DFT) calculations indicate that reverse roles for the metals have inaccessibly high energy barriers and are unlikely to occur under experimental conditions. The rate-determining step is calculated as the ring opening of the propylene oxide (ΔGcalc† = +22.2 kcal mol–1); consistent with experimental measurements (ΔGexp† = +22.1 kcal mol–1, 50 °C). The calculated barrier to the selectivity limiting step, i.e., backbiting from the alkoxide intermediate to form propylene carbonate (ΔGcalc† = +21.4 kcal mol–1), is competitive with the barrier to epoxide ring opening (ΔGcalc† = +22.2 kcal mol–1) implicating an equilibrium between alkoxide and carbonate intermediates. This idea is tested experimentally and is controlled by carbon dioxide pressure or temperature to moderate selectivity. The catalytic mechanism, supported by theoretical and experimental investigations, should help to guide future catalyst design and optimization

Advances in heterometallic ring-opening (co)polymerisation catalysis

Truly sustainable plastics require renewable feedstocks coupled with efficient production and end-of-life degradation/recycling processes. Some of the most useful degradable materials are aliphatic polyesters, polycarbonates and polyamides, which are often prepared via ring-opening (co)polymerisation (RO(CO)P) using an organometallic catalyst. While there has been extensive research into ligand development, heterometallic cooperativity offers an equally promising yet underexplored strategy to improve catalyst performance, as heterometallic catalysts often exhibit significant activity and selectivity enhancements compared to their homometallic counterparts. This review describes advances in heterometallic RO(CO)P catalyst design, highlighting the overarching structure-activity trends and reactivity patterns to inform future catalyst design

Young Adults’ Conceptions of the Sacred in Finland Today

Peer reviewe

Integration and Rebirth through Confrontation: Fight Club and American Beauty as Contemporary Religious Parables

In this article, I discuss the religious significance of two recent American films which raise pertinent questions about the nature and quality of human existence, its anxieties and aspirations, at the turn of the millennium. Both David Fincher's Fight Club and Sam Mendes' American Beauty wrestle with the efficacy of confrontation as a means of attaining redemption from the disconnectedness and estrangement that characterises the lives of the protagonists in each of these pictures. The import that the trajectories of these characters have for the film audience will also be examined, insofar as these films are accredited by some viewers with helping to facilitate a remedy to the malaise and disaffection in their lives that these protagonists exemplify

Modeling the interaction between salmon management and consumption by coastal brown bears

Abstract Harvest management policy for species with strong trophic connections can reverberate through food webs and cause unintended consequences, such as altering the abundance of a harvested species' predators or prey. Pacific salmon (Oncorhynchus spp.), a key food for many predators and an economically valuable harvested species, is generally managed for maximum sustained harvests without explicit consideration for the freshwater and terrestrial food webs that they support. The density of brown bear (Ursus arctos) populations in Alaska, USA, is correlated with the amount of salmon they can access and consume, so it seems likely their populations are inadvertently affected by salmon management. We simulated the effect of salmon management policy on brown bears by customizing a general bear–salmon model using empirical data from three watersheds in southwest Kodiak, Alaska. Our goal was to quantify the effect of current salmon management policy (i.e., escapement goals and early/late run allocations) on salmon consumption by brown bears. Bears in the individually‐based model evaluated the value of each foraging site based on salmon abundance, salmon vulnerability, and competition with other bears and made movement decisions (among salmon spawning sites) accordingly. A validation of the model based on empirical brown bear foraging data revealed that simulated bears selected the same salmon spawning locations but visited more sites and fished for more days compared to real bears. In simulations across variables (salmon abundance, phenological variation, bear competition, and bear density), consumption of salmon by bears was remarkably resilient to changes in salmon abundance within the range of current high and low escapement goals, as long as all run‐timing variation and salmon sub‐populations were preserved. Mean salmon consumption increased by ~20% as escapement approximately doubled from the regional lower escapement goal of 625,000 to the upper goal of 1,270,000, but rapidly declined if salmon abundance decreased below the minimum escapement goal. In this system, salmon management policy, designed to achieve maximum sustained yield, also provides adequate salmon for the current bear population. This model creates a potentially useful tool for assessing the knock‐on effects of future changes to salmon management policy

Insights into the mechanism of carbon dioxide and propylene oxide ring-opening copolymerization using a Co(III)/K(I) heterodinuclear catalyst

A combined computational and experimental investigation into the catalytic cycle of carbon dioxide and propylene oxide ring-opening copolymerization is presented using a Co(III)K(I) heterodinuclear complex (Deacy, A. C.&nbsp;Co(III)/Alkali-Metal(I) Heterodinuclear Catalysts for the Ring-Opening Copolymerization of CO2&nbsp;and Propylene Oxide.&nbsp;J. Am. Chem. Soc.&nbsp;2020,&nbsp;142(45), 19150&minus;19160). The complex is a rare example of a dinuclear catalyst, which is active for the copolymerization of CO2&nbsp;and propylene oxide, a large-scale commercial product. Understanding the mechanisms for both product and byproduct formation is essential for rational catalyst improvements, but there are very few other mechanistic studies using these monomers. The investigation suggests that cobalt serves both to activate propylene oxide and to stabilize the catalytic intermediates, while potassium provides a transient carbonate nucleophile that ring-opens the activated propylene oxide. Density functional theory (DFT) calculations indicate that reverse roles for the metals have inaccessibly high energy barriers and are unlikely to occur under experimental conditions. The rate-determining step is calculated as the ring opening of the propylene oxide (&Delta;Gcalc&dagger;&nbsp;= +22.2 kcal mol&ndash;1); consistent with experimental measurements (&Delta;Gexp&dagger;&nbsp;= +22.1 kcal mol&ndash;1, 50 &deg;C). The calculated barrier to the selectivity limiting step, i.e., backbiting from the alkoxide intermediate to form propylene carbonate (&Delta;Gcalc&dagger;&nbsp;= +21.4 kcal mol&ndash;1), is competitive with the barrier to epoxide ring opening (&Delta;Gcalc&dagger;&nbsp;= +22.2 kcal mol&ndash;1) implicating an equilibrium between alkoxide and carbonate intermediates. This idea is tested experimentally and is controlled by carbon dioxide pressure or temperature to moderate selectivity. The catalytic mechanism, supported by theoretical and experimental investigations, should help to guide future catalyst design and optimization.</p