Widespread permafrost degradation in Canada's western Arctic has led to formation of shoreline retrogressive thaw slumps (SRTS), a process influential in modifying water and biogeochemical balances ...of tundra lakes. To investigate hydrological effects of SRTS, water sampling campaigns were conducted in 2004, 2005, and 2008 for paired lakes (undisturbed vs SRTS) in the upland region adjacent to the Mackenzie Delta, Northwest Territories, Canada. An isotope mass balance model to estimate evaporation/inflow, precipitation/inflow, water yield, and runoff ratio was developed incorporating seasonal evaporative drawdown effects and a mixing model to simulate gradients in marine-continental atmospheric moisture. Site-specific water balance results revealed systematically higher evaporation/inflow and precipitation/inflow for lakes with active SRTS compared to undisturbed lakes, and typically higher ratios of these indicators associated with stabilized versus active SRTS. Water yields were higher for active SRTS sites compared to undisturbed and stabilized SRTS sites, suggesting that slumping is an initial but not a sustained source of water delivery to lakes. Catchments with wildfire history were found to have lower water yields, attributed to reduced permafrost influence on runoff generation. Conceptually, we define a permafrost thaw trajectory whereby undisturbed sites, active SRTS, stabilized SRTS, and ancient SRTS represent progressive stages of permafrost thaw. We postulate that release of additional runoff is mainly due to permafrost thaw in active SRTS, which also promotes lake expansion, talik formation, and subsurface connectivity. Eventual stabilization of slumps and reduced runoff is expected once permafrost thaw sources are exhausted, at which time lakes may become more reliant on replenishment by direct precipitation. The effect of snow catch in slumps appears to be subordinate to permafrost thaw sources based on eventual decline in runoff once thaw slumps stabilize. Improved, site-specific hydrologic understanding is expected to assist with ongoing research into carbon cycling and biogeochemical feedbacks in the region.
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•Isotope balance used to interpret new 18O and 2H data from 60 thermokarst lakes•Corrections applied for seasonal volume changes and continental-marine air mixing•Evaporation/inflow, precipitation/inflow, water yield and runoff ratios estimated•Water balance trends found to be driven by climate gradients and thaw trajectory•Systematic runoff responses also found for shoreline thaw slumping and wildfire
Abstract For thirty years there has been a debate about whether low calorie sweeteners (LCS) provide a benefit for body weight management. Early studies showed that when consumed alone in a beverage ...appetite and food intake were increased. Some, observational longitudinal cohort studies reported an association between LCS usage and increasing BMI, suggesting that LCS may actually promote weight gain. In the ensuing decades numerous additional observational and experimental trials have been conducted with the experimental trials nearly uniformly showing a benefit for LCS, either in weight loss or weight gain prevention. The observational trials have been more inconsistent with two recent meta-analyses indicating either a small positive association between LCS usage and BMI (weighted group mean correlation, p = 0.03) or an inverse association with body weight change (-1.35 kg, p = .004). Numerous potential mechanisms have been explored, mostly in animal models, in an attempt to explain this association but none have yet been proven in humans. It is also possible that the association between LCS and BMI increase in the observational studies may be due to reverse causality or residual confounding. Randomized controlled trials are consistent in showing a benefit of LCS which suggests that simple behavioral engagement by individuals attempting to control their weight is a sufficiently strong signal to overcome any potential mechanism that might act to promote energy intake and weight gain. Based on existing evidence, LCS can be a useful tool for people actively engaged in managing their body weight for weight loss and maintenance.
Particle Markov chain Monte Carlo methods. Discussion ANDRIEU, Christophe; DOUCET, Arnaud; PAPASPILIOPOULOS, Omiros ...
Journal of the Royal Statistical Society. Series B, Statistical methodology,
2010, Volume:
72
Journal Article
Hydrogenases are metalloenzymes that are key to energy metabolism in a variety of microbial communities. Divided into three classes based on their metal content, the Fe-, FeFe-, and NiFe-hydrogenases ...are evolutionarily unrelated but share similar nonprotein ligand assemblies at their active site metal centers that are not observed elsewhere in biology. These nonprotein ligands are critical in tuning enzyme reactivity, and their synthesis and incorporation into the active site clusters require a number of specific maturation enzymes. The wealth of structural information on different classes and different states of hydrogenase enzymes, biosynthetic intermediates, and maturation enzymes has contributed significantly to understanding the biochemistry of hydrogen metabolism. This review highlights the unique structural features of hydrogenases and emphasizes the recent biochemical and structural work that has created a clearer picture of the FeFe-hydrogenase maturation pathway.
Evolutionary History of the Hymenoptera Peters, Ralph S.; Krogmann, Lars; Mayer, Christoph ...
Current biology,
04/2017, Volume:
27, Issue:
7
Journal Article
Peer reviewed
Open access
Hymenoptera (sawflies, wasps, ants, and bees) are one of four mega-diverse insect orders, comprising more than 153,000 described and possibly up to one million undescribed extant species 1, 2. As ...parasitoids, predators, and pollinators, Hymenoptera play a fundamental role in virtually all terrestrial ecosystems and are of substantial economic importance 1, 3. To understand the diversification and key evolutionary transitions of Hymenoptera, most notably from phytophagy to parasitoidism and predation (and vice versa) and from solitary to eusocial life, we inferred the phylogeny and divergence times of all major lineages of Hymenoptera by analyzing 3,256 protein-coding genes in 173 insect species. Our analyses suggest that extant Hymenoptera started to diversify around 281 million years ago (mya). The primarily ectophytophagous sawflies are found to be monophyletic. The species-rich lineages of parasitoid wasps constitute a monophyletic group as well. The little-known, species-poor Trigonaloidea are identified as the sister group of the stinging wasps (Aculeata). Finally, we located the evolutionary root of bees within the apoid wasp family “Crabronidae.” Our results reveal that the extant sawfly diversity is largely the result of a previously unrecognized major radiation of phytophagous Hymenoptera that did not lead to wood-dwelling and parasitoidism. They also confirm that all primarily parasitoid wasps are descendants of a single endophytic parasitoid ancestor that lived around 247 mya. Our findings provide the basis for a natural classification of Hymenoptera and allow for future comparative analyses of Hymenoptera, including their genomes, morphology, venoms, and parasitoid and eusocial life styles.
•The most comprehensive dataset ever compiled for inferring the phylogeny of Hymenoptera•A major radiation of primarily ectophytic sawflies (Eusymphyta) is hypothesized•A major radiation of parasitoid wasps (Parasitoida) is identified•The phylogenetic origins of wasp-waisted wasps, stinging wasps, and bees are resolved
Peters et al. infer a time-calibrated and statistically solid phylogenetic tree of the mega-diverse insect order Hymenoptera (sawflies, wasps, ants, and bees) from the analysis of phylogenomic data. This sheds new light on the early history of this intriguing group, as well as on the origins and radiation of parasitoids, stinging wasps, and bees.
Sergey Brin, a cofounder of Google, once compared the perfect search engine to "the mind of God." As the modern face of promiscuous knowledge, however, Google's divine omniscience traffics in news, ...maps, weather, and porn indifferently. This book, begun by the late Kenneth Cmiel and completed by his close friend John Durham Peters, provides a genealogy of the information age from its early origins up to the reign of Google. It examines how we think about fact, image, and knowledge, centering on the different ways that claims of truth are complicated when they pass to a larger public. To explore these ideas, Cmiel and Peters focus on three main periods—the late nineteenth century, 1925 to 1945, and 1975 to 2000, with constant reference to the present. Cmiel's original text examines the growing gulf between politics and aesthetics in postmodern architecture, the distancing of images from everyday life in magical realist cinema, the waning support for national betterment through taxation, and the inability of a single presentational strategy to contain the social whole. Peters brings Cmiel's study into the present moment, providing the backstory to current controversies about the slipperiness of facts in a digital age. A hybrid work from two innovative thinkers, Promiscuous Knowledge enlightens our understanding of the internet and the profuse visual culture of our time.
Severe asthma is a high-burden disease. Real-world data on mepolizumab in patients with severe eosinophilic asthma is needed to assess whether the data from randomised controlled trials are ...applicable in a broader population.The Australian Mepolizumab Registry (AMR) was established with an aim to assess the use, effectiveness and safety of mepolizumab for severe eosinophilic asthma in Australia.Patients (n=309) with severe eosinophilic asthma (median age 60 years, 58% female) commenced mepolizumab. They had poor symptom control (median Asthma Control Questionnaire (ACQ)-5 score of 3.4), frequent exacerbations (median three courses of oral corticosteroids (OCS) in the previous 12 months), and 47% required daily OCS. Median baseline peripheral blood eosinophil level was 590 cells·µL
Comorbidities were common: allergic rhinitis 63%, gastro-oesophageal reflux disease 52%, obesity 46%, nasal polyps 34%.Mepolizumab treatment reduced exacerbations requiring OCS compared with the previous year (annualised rate ratio 0.34 (95% CI 0.29-0.41); p<0.001) and hospitalisations (rate ratio 0.46 (95% CI 0.33-0.63); p<0.001). Treatment improved symptom control (median ACQ-5 reduced by 2.0 at 6 months), quality of life and lung function. Higher blood eosinophil levels (p=0.003) and later age of asthma onset (p=0.028) predicted a better ACQ-5 response to mepolizumab, whilst being male (p=0.031) or having body mass index ≥30 (p=0.043) predicted a lesser response. Super-responders (upper 25% of ACQ-5 responders, n=61, 24%) had a higher T2 disease burden and fewer comorbidities at baseline.Mepolizumab therapy effectively reduces the significant and long-standing disease burden faced by patients with severe eosinophilic asthma in a real-world setting.
Animals exhibit a diversity of movement tactics 1. Tracking resources that change across space and time is predicted to be a fundamental driver of animal movement 2. For example, some migratory ...ungulates (i.e., hooved mammals) closely track the progression of highly nutritious plant green-up, a phenomenon called “green-wave surfing” 3–5. Yet general principles describing how the dynamic nature of resources determine movement tactics are lacking 6. We tested an emerging theory that predicts surfing and the existence of migratory behavior will be favored in environments where green-up is fleeting and moves sequentially across large landscapes (i.e., wave-like green-up) 7. Landscapes exhibiting wave-like patterns of green-up facilitated surfing and explained the existence of migratory behavior across 61 populations of four ungulate species on two continents (n = 1,696 individuals). At the species level, foraging benefits were equivalent between tactics, suggesting that each movement tactic is fine-tuned to local patterns of plant phenology. For decades, ecologists have sought to understand how animals move to select habitat, commonly defining habitat as a set of static patches 8, 9. Our findings indicate that animal movement tactics emerge as a function of the flux of resources across space and time, underscoring the need to redefine habitat to include its dynamic attributes. As global habitats continue to be modified by anthropogenic disturbance and climate change 10, our synthesis provides a generalizable framework to understand how animal movement will be influenced by altered patterns of resource phenology.
•Ungulates moved to track forage in landscapes with wave-like spring green-up•Patterns of green-up explained where migratory behavior occurred in many ecosystems•At the species level, migrants and residents received equivalent foraging benefits•Movement tactics represent behavioral adaptations to specific landscapes
Using GPS-tracking from 61 populations of four ungulate species, Aikens et al. provide evidence that the dynamic nature of forage resources generates the diversity of movement tactics used by animals. Specifically, patterns of spring green-up shaped how closely animals tracked resources and where migration occurred across temperate ecosystems.
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