Extreme climatic events have recently impacted marine ecosystems around the world, including foundation species such as corals and kelps. Here, we describe the rapid climate-driven catastrophic shift ...in 2014 from a previously robust kelp forest to unproductive large scale urchin barrens in northern California. Bull kelp canopy was reduced by >90% along more than 350 km of coastline. Twenty years of kelp ecosystem surveys reveal the timing and magnitude of events, including mass mortalities of sea stars (2013-), intense ocean warming (2014-2017), and sea urchin barrens (2015-). Multiple stressors led to the unprecedented and long-lasting decline of the kelp forest. Kelp deforestation triggered mass (80%) abalone mortality (2017) resulting in the closure in 2018 of the recreational abalone fishery worth an estimated $44 M and the collapse of the north coast commercial red sea urchin fishery (2015-) worth $3 M. Key questions remain such as the relative roles of ocean warming and sea star disease in the massive purple sea urchin population increase. Science and policy will need to partner to better understand drivers, build climate-resilient fisheries and kelp forest recovery strategies in order to restore essential kelp forest ecosystem services.
Several transiting super-Earths are expected to be discovered in the coming few years. While tools to model the interior structure of transiting planets exist, inferences about the composition are ...fraught with ambiguities. We present a framework to quantify how much we can robustly infer about super-Earth and Neptune-size exoplanet interiors from radius and mass measurements. We introduce quaternary diagrams to illustrate the range of possible interior compositions for planets with four layers (iron core, silicate mantles, water layers, and H/He envelopes). We apply our model to CoRoT-7b, GJ 436b, and HAT-P-11b. Interpretation of planets with H/He envelopes is limited by the model uncertainty in the interior temperature, while for CoRoT-7b observational uncertainties dominate. We further find that our planet interior model sharpens the observational constraints on CoRoT-7b's mass and radius, assuming the planet does not contain significant amounts of water or gas. We show that the strength of the limits that can be placed on a super-Earth's composition depends on the planet's density; for similar observational uncertainties, high-density super-Mercuries allow the tightest composition constraints. Finally, we describe how techniques from Bayesian statistics can be used to take into account in a formal way the combined contributions of both theoretical and observational uncertainties to ambiguities in a planet's interior composition. On the whole, with only a mass and radius measurement an exact interior composition cannot be inferred for an exoplanet because the problem is highly underconstrained. Detailed quantitative ranges of plausible compositions, however, can be found.
This paper is concerned with systemic risk in an interbank market, modelled as a directed graph of interbank obligations. This builds on the modelling paradigm of Eisenberg and Noe Eisenberg L, Noe ...TH (2001) Systemic risk in financial systems.
Management Sci.
47(2):236-249 by introducing costs of default if loans have to be called in by a failing bank. This immediately introduces novel and realistic effects. We find that, in general, many different clearing vectors can arise, among which there is a greatest clearing vector, arrived at by letting banks fail in succession until only solvent banks remain. Such a collapse should be prevented if at all possible. We then study situations in which consortia of banks may have the means and incentives to rescue failing banks. This again departs from the conclusions of the earlier work of Eisenberg and Noe, where in the absence of default losses there would be no incentive for solvent banks to rescue failing banks. We conclude with some remarks about how a rescue consortium might be constructed.
This paper was accepted by Wei Xiong, finance.
Woolly mammoths (Mammuthus primigenius) populated Siberia, Beringia, and North America during the Pleistocene and early Holocene. Recent breakthroughs in ancient DNA sequencing have allowed for ...complete genome sequencing for two specimens of woolly mammoths (Palkopoulou et al. 2015). One mammoth specimen is from a mainland population 45,000 years ago when mammoths were plentiful. The second, a 4300 yr old specimen, is derived from an isolated population on Wrangel island where mammoths subsisted with small effective population size more than 43-fold lower than previous populations. These extreme differences in effective population size offer a rare opportunity to test nearly neutral models of genome architecture evolution within a single species. Using these previously published mammoth sequences, we identify deletions, retrogenes, and non-functionalizing point mutations. In the Wrangel island mammoth, we identify a greater number of deletions, a larger proportion of deletions affecting gene sequences, a greater number of candidate retrogenes, and an increased number of premature stop codons. This accumulation of detrimental mutations is consistent with genomic meltdown in response to low effective population sizes in the dwindling mammoth population on Wrangel island. In addition, we observe high rates of loss of olfactory receptors and urinary proteins, either because these loci are non-essential or because they were favored by divergent selective pressures in island environments. Finally, at the locus of FOXQ1 we observe two independent loss-of-function mutations, which would confer a satin coat phenotype in this island woolly mammoth.
We demonstrate that silicon-vacancy (SiV) centers in diamond can be used to efficiently generate coherent optical photons with excellent spectral properties. We show that these features are due to ...the inversion symmetry associated with SiV centers. The generation of indistinguishable single photons from separated emitters at 5 K is demonstrated in a Hong-Ou-Mandel interference experiment. Prospects for realizing efficient quantum network nodes using SiV centers are discussed.
We present an analysis of the bulk composition of the MEarth transiting super-Earth exoplanet GJ 1214b using planet interior structure models. We consider three possible origins for the gas layer on ...GJ 1214b: direct accretion of gas from the protoplanetary nebula, sublimation of ices, and outgassing from rocky material. Armed only with measurements of the planet mass (M{sub p} = 6.55 {+-} 0.98 M{sub +}), radius (R{sub p} = 2.678 {+-} 0.13 R{sub +}), and stellar irradiation level, our main conclusion is that we cannot infer a unique composition. A diverse range of planet interiors fits the measured planet properties. Nonetheless, GJ 1214b's relatively low average density ({rho}{sub p} = 1870 {+-} 400 kg m{sup -3}) means that it almost certainly has a significant gas component. Our second major conclusion is that under most conditions we consider GJ 1214b would not have liquid water. Even if the outer envelope is predominantly sublimated water ice, the envelope will likely consist of a super-fluid layer sandwiched between vapor above and plasma (electrically conductive fluid) below at greater depths. In our models, a low intrinsic planet luminosity ({approx_lt}2TW) is needed for a water envelope on GJ 1214b to pass through the liquid phase.
We report on the noise spectrum experienced by few nanometer deep nitrogen-vacancy centers in diamond as a function of depth, surface coating, magnetic field and temperature. Analysis reveals a ...double-Lorentzian noise spectrum consistent with a surface electronic spin bath in the low frequency regime, along with a faster noise source attributed to surface-modified phononic coupling. These results shed new light on the mechanisms responsible for surface noise affecting shallow spins at semiconductor interfaces, and suggests possible directions for further studies. We demonstrate dynamical decoupling from the surface noise, paving the way to applications ranging from nanoscale NMR to quantum networks.
Rumination has been implicated as a risk factor for suicidal ideation and attempts, yet the literature to date has not been synthesized. We conducted a meta-analysis of the association between ...rumination and both suicidal ideation and attempts to consolidate the existing literature (k = 29). Results indicated that the relationships between global rumination (k = 13; Hedge's g = .74, p < .001, 95% CI .45, 1.04), brooding (k = 12; Hedge's g = .63, p < .001, 95% CI .35, .90), and reflection (k = 12; Hedge's g = .38, p = .002, 95% CI .10, .65) with suicidal ideation were significant. Associations between global rumination (k = 3; Hedge's g = .26, p < .001, 95% CI .08, .44) and brooding (k = 4; Hedge's g = .47, p = .004, 95% CI .02, .91) and suicide attempts were significant, but reflection (k = 4; Hedge's g = .09, p = .646, 95% CI −.54, .72) was unrelated. However, given the limited studies included in suicide attempt analyses-and the exclusive use of cross-sectional designs and heterogeneity with regard to samples and measures-these parameters should be taken with caution. Generally, age, gender, race/ethnicity, and year of publication were not moderators, and there was little evidence for publication bias across effects, with the exception of the effect of global rumination on suicidal ideation. Several future research directions are discussed.
Summary Major depression is one of the leading causes of premature death and disability. Although available drugs are effective, they also have substantial limitations. Recent advances in our ...understanding of the fundamental links between chronobiology and major mood disorders, as well as the development of new drugs that target the circadian system, have led to a renewed focus on this area. In this review, we summarise the associations between disrupted chronobiology and major depression and outline new antidepressant treatment strategies that target the circadian system. In particular, we highlight agomelatine, a melatonin-receptor agonist and selective serotonergic receptor subtype (ie, 5-HT2C ) antagonist that has chronobiotic, antidepressant, and anxiolytic effects. In the short-term, agomelatine has similar antidepressant efficacy to venlafaxine, fluoxetine, and sertraline and, in the longer term, fewer patients on agomelatine relapse (23·9%) than do those receiving placebo (50·0%). Patients with depression treated with agomelatine report improved sleep quality and reduced waking after sleep onset. As agomelatine does not raise serotonin levels, it has less potential for the common gastrointestinal, sexual, or metabolic side-effects that characterise many other antidepressant compounds.
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