Growing-Season Temperature Change across Four Decades in an Arctic Tundra Pond

We examined temperature dynamics across a 42-year period in a low-centered tundra polygon pond on the Arctic Coastal Plain of northern Alaska to assess potential changes in thermal dynamics for ponds of this type. Using water temperature data from a pond near Barrow (now Utqiaġvik), Alaska, studied intensively during 1971 – 73 and again in 2007 – 12, we built an empirical model coupling historical air temperatures to measured pond temperatures for four summers. We then used the model to predict summer pond temperatures over a 42-year span, including 1974 – 2008, for which direct aquatic temperature records do not exist. Average pond temperatures during the growing season (1 May through 31 October) increased by 0.5˚C decade-1 or 2.2˚C over the 42-year period. Our simulations predicted the average date of spring thaw for the pond as 2 June (± 3 d), which did not change over the 42-year time period. However, average pond temperature during the first 30 days of the growing season increased from 1971 to 2012, suggesting that recently, ponds are warmer in early spring. The average date of pond sediment freeze over the 42 years shifted later by 15 days, from 28 September in 1971 to 13 October in 2012. These changes correspond to a growing season that has increased in length by 14 days, from 118 days in 1971 to 132 days in 2012. Contemporary temperature measurements in other shallow tundra ponds in northern Alaska show a high degree of temporal coherence (r = 0.93 – 0.99), which warrants the general conclusion that tundra ponds on Alaska’s Arctic Coastal Plain have undergone a significant change in thermal dynamics over the past four decades. Our results provide a means to incorporate these pond types into larger-scale simulations of Arctic climate change.Nous avons examiné la dynamique des températures sur une période de 42 ans dans un étang de polygone de toundra concave sur la plaine côtière arctique du nord de l’Alaska dans le but d’évaluer les changements potentiels sur le plan de la dynamique thermique des étangs de ce type. À l’aide des données de la température de l’eau provenant d’un étang situé près de Barrow (maintenant Utqiaġvik), en Alaska, étang ayant fait l’objet d’études intensives de 1971 à 1973 et de 2007 à 2012, nous avons construit un modèle empirique en couplant les températures de l’air historiques aux températures de quatre étés observées à l’étang. Ensuite, nous nous sommes servis de ce modèle pour prévoir les températures estivales de l’étang sur une période de 42 ans, incluant la période allant de 1974 à 2008, pour lesquelles il n’existe pas de données de températures aquatiques directes. Pendant la saison de croissance (du 1er mai au 31 octobre), les températures moyennes de l’étang ont augmenté de 0,5 ˚C par décennie-1 ou de 2,2 ˚C sur la période de 42 ans. Nos simulations ont permis de prévoir une date moyenne pour le dégel du printemps (± 3 j), ce qui n’a pas changé pendant la période de 42 ans. Cependant, la température moyenne de l’étang au cours des 30 premiers jours de la saison de croissance a augmenté entre 1971 et 2012, ce qui laisse entendre que depuis récemment, les étangs sont plus chauds au début du printemps. Sur la période de 42 ans, la date moyenne de gel des sédiments de l’étang a été retardée de 15 jours, passant ainsi du 28 septembre en 1971 au 13 octobre en 2012. Ces changements correspondent à une saison de croissance dont la durée a rallongé de 14 jours, passant de 118 jours en 1971 à 132 jours en 2012. Les mesures de températures contemporaines d’autres étangs de toundra peu profonds du nord de l’Alaska affichent un haut degré de cohérence temporelle (r = 0,93 – 0,99), ce qui permet de tirer la conclusion générale que les étangs de toundra de la plaine côtière arctique de l’Alaska ont connu un important changement sur le plan de la dynamique thermique au cours des quatre dernières décennies. Nos résultats permettent d’incorporer ces types d’étangs à des simulations à plus grande échelle du changement climatique de l’Arctique

Hierarchical Bayesian Detection Algorithm for Early-Universe Relics in the Cosmic Microwave Background

A number of theoretically well-motivated additions to the standard cosmological model predict weak signatures in the form of spatially localized sources embedded in the cosmic microwave background (CMB) fluctuations. We present a hierarchical Bayesian statistical formalism and a complete data analysis pipeline for testing such scenarios. We derive an accurate approximation to the full posterior probability distribution over the parameters defining any theory that predicts sources embedded in the CMB, and perform an extensive set of tests in order to establish its validity. The approximation is implemented using a modular algorithm, designed to avoid a posteriori selection effects, which combines a candidate-detection stage with a full Bayesian model-selection and parameter-estimation analysis. We apply this pipeline to theories that predict cosmic textures and bubble collisions, extending previous analyses by using: (1) adaptive-resolution techniques, allowing us to probe features of arbitrary size, and (2) optimal filters, which provide the best possible sensitivity for detecting candidate signatures. We conclude that the WMAP 7-year data do not favor the addition of either cosmic textures or bubble collisions to the standard cosmological model, and place robust constraints on the predicted number of such sources. The expected numbers of bubble collisions and cosmic textures on the CMB sky within our detection thresholds are constrained to be fewer than 4.0 and 5.2 at 95% confidence, respectively.Comment: 34 pages, 18 figures. v3: corrected very minor typos to match published versio

Agonist-Induced Endocytosis of Muscarinic Cholinergic Receptors: Relationship to Stimulated Phosphoinositide Turnover

The ability of muscarinic cholinergic receptors to activate phosphoinositide turnover following agonist-induced internalization has been investigated. Incubation of SH-SY5Y neuroblastoma cells with oxotremorine-M resulted in a time-dependent endocytosis of both muscarinic receptors and Α subunits of G q and G 11 , but not of isoforms of phosphoinositide-specific phospholipase C, into a subfraction of smooth endoplasmic reticulum (V 1 ). Agonist-induced increases in diacylglycerol mass and in 32 P-phosphatidate labeling, much of which was of the tetraenoic species, were also observed in the V 1 fraction, but these increases persisted when the agonist-induced translocation of receptors into the V 1 fraction was blocked. All enzymes of the phosphoinositide cycle were detectable in the V 1 fraction. However, with the exception of phosphatidylinositol 4-kinase, none was enriched when compared with cell lysates. Both 32 P-labeling studies and enzyme assays point to a very limited capacity of this fraction to synthesize phosphatidylinositol 4,5-bisphosphate, whereas the synthesis of phosphatidylinositol 4-phosphate is robust. These results indicate that endocytosed receptors do not appear to retain their ability to activate phosphoinositide turnover. The availability of the substrate for phospholipase C, phosphatidylinositol 4,5-bisphosphate, may be one factor that limits the activity of muscarinic receptors in this subcellular compartment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65644/1/j.1471-4159.1997.68041473.x.pd

Cytoskeletal and Phosphoinositide Requirements for Muscarinic Receptor Signaling to Focal Adhesion Kinase and Paxillin

The mechanism whereby agonist occupancy of muscarinic cholinergic receptors elicits an increased tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin has been examined. Addition of oxotremorine-M to SH-SY5Y neuroblastoma cells resulted in rapid increases in the phosphorylation of FAK ( t 1/2 = 2 min) and paxillin that were independent of integrin-extracellular matrix interactions, cell attachment, and the production of phosphoinositide-derived second messengers. In contrast, the increased tyrosine phosphorylations of FAK and paxillin were inhibited by inclusion of either cytochalasin D or mevastatin, agents that disrupt the cytoskeleton. Furthermore, phosphorylation of FAK and paxillin could be prevented by addition of either wortmannin or LY-294002, under conditions in which the synthesis of phosphatidylinositol 4-phosphate was markedly attenuated. These results indicate that muscarinic receptor-mediated increases in the tyrosine phosphorylation of FAK and paxillin in SH-SY5Y neuroblastoma cells depend on both the maintenance of an actin cytoskeleton and the ability of these cells to synthesize phosphoinositides.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66183/1/j.1471-4159.1998.70030940.x.pd

Pebble and Rock Band: Heuristic Resolution of Repeats and Scaffolding in the Velvet Short-Read de Novo Assembler

BACKGROUND: Despite the short length of their reads, micro-read sequencing technologies have shown their usefulness for de novo sequencing. However, especially in eukaryotic genomes, complex repeat patterns are an obstacle to large assemblies. PRINCIPAL FINDINGS: We present a novel heuristic algorithm, Pebble, which uses paired-end read information to resolve repeats and scaffold contigs to produce large-scale assemblies. In simulations, we can achieve weighted median scaffold lengths (N50) of above 1 Mbp in Bacteria and above 100 kbp in more complex organisms. Using real datasets we obtained a 96 kbp N50 in Pseudomonas syringae and a unique 147 kbp scaffold of a ferret BAC clone. We also present an efficient algorithm called Rock Band for the resolution of repeats in the case of mixed length assemblies, where different sequencing platforms are combined to obtain a cost-effective assembly. CONCLUSIONS: These algorithms extend the utility of short read only assemblies into large complex genomes. They have been implemented and made available within the open-source Velvet short-read de novo assembler

Collective aggressiveness limits colony persistence in high‐ but not low‐elevation sites at Amazonian social spiders

Identifying the traits that foster group survival in contrasting environments is important for understanding local adaptation in social systems. Here, we evaluate the relationship between the aggressiveness of social spider colonies and their persistence along an elevation gradient using the Amazonian spider, Anelosimus eximius. We found that colonies of A. eximius exhibit repeatable differences in their collective aggressiveness (latency to attack prey stimuli) and that colony aggressiveness is linked with persistence in a site‐specific manner. Less aggressive colonies are better able to persist at high‐elevation sites, which lack colony‐sustaining large‐bodied prey, whereas colony aggression was not related to chance of persistence at low‐elevation sites. This suggests that low aggressiveness promotes colony survival in high‐elevation, prey‐poor habitats, perhaps via increased tolerance to resource limitation. These data reveal that the collective phenotypes that relate to colony persistence vary by site, and thus, the path of social evolution in these environments is likely to be affected.Colony‐level selection on collective aggressiveness varies with elevation in social spiders. Aggressive societies are disfavoured at high elevation sites, but their odds of persistence increase in lowland rain forests.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152489/1/jeb13532_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152489/2/jeb13532.pd