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It has long been debated whether elements heavier than zinc are formed continually, for example in core-collapse supernovae, or in rare events, such as neutron star mergers; here, studies of element abundances in a local ultrafaint dwarf galaxy provide evidence that these elements are formed during rare yet prolific stellar events. Nucleosynthesis in dwarf galaxy Reticulum II The recently discovered Milky Way satellite Reticulum II, an ultra-faint dwarf galaxy, provides an ideal model for the study of stellar nucleosynthesis, the creation of heavier elements from hydrogen, helium and other lighter elements and particles. It has long been debated whether elements heavier than zinc are formed continually, for example in core-collapse supernovae, or in rare events, such as neutron star mergers. Alexander Ji et al . used high-resolution spectroscopy to determine element abundances in nine young stars in Reticulum II, and find that seven of the nine show strong enhancements in heavy neutron-capture elements with abundances that follow the universal r-process pattern above barium. The enhancement is several orders of magnitude greater than that seen in other ultra-faint dwarf galaxies, implying that a single rare event produced the r-process material. Elements heavier than zinc are synthesized through the rapid (r) and slow (s) neutron-capture processes 1 , 2 . The main site of production of the r-process elements (such as europium) has been debated for nearly 60 years 2 . Initial studies of trends in chemical abundances in old Milky Way halo stars suggested that these elements are produced continually, in sites such as core-collapse supernovae 3 , 4 . But evidence from the local Universe favours the idea that r-process production occurs mainly during rare events, such as neutron star mergers 5 , 6 . The appearance of a plateau of europium abundance in some dwarf spheroidal galaxies has been suggested as evidence for rare r-process enrichment in the early Universe 7 , but only under the assumption that no gas accretes into those dwarf galaxies; gas accretion 8 favours continual r-process enrichment in these systems. Furthermore, the universal r-process pattern 1 , 9 has not been cleanly identified in dwarf spheroidals. The smaller, chemically simpler, and more ancient ultrafaint dwarf galaxies assembled shortly after the first stars formed, and are ideal systems with which to study nucleosynthesis events such as the r-process 10 , 11 . Reticulum II is one such galaxy 12 , 13 , 14 . The abundances of non-neutron-capture elements in this galaxy (and others like it) are similar to those in other old stars 15 . Here, we report that seven of the nine brightest stars in Reticulum II, observed with high-resolution spectroscopy, show strong enhancements in heavy neutron-capture elements, with abundances that follow the universal r-process pattern beyond barium. The enhancement seen in this ‘r-process galaxy’ is two to three orders of magnitude higher than that detected in any other ultrafaint dwarf galaxy 11 , 16 , 17 . This implies that a single, rare event produced the r-process material in Reticulum II. The r-process yield and event rate are incompatible with the source being ordinary core-collapse supernovae 18 , but consistent with other possible sources, such as neutron star mergers 19 .

\"The first major crossover of the Rebirth era starring the biggest heroes and villains in comics, this action-packed epic JUSTICE LEAGUE VS. SUICIDE SQUAD features an all-star creative team, including writers Joshua Williamson, Tim Seeley, Rob Williams and Si Spurrier, with superstar artists Jason Fabok, Tony S. Daniel, Jesus Merino, Fernando Pasarin, Robson Rocha, Howard Porter, Scot Eaton, Riley Rossmo, Christian Duce, Giuseppe Cafaro and more! The members of the Justice League are Earth's most powerful and famous superheroes ... but they aren't the only team in town. The Suicide Squad strikes from the shadows and does the jobs too dirty for superheroes to handle. Under the iron fist of Director Amanda Waller, these monsters and maniacs have operated in total secrecy ... until now. Batman is on their trail and the Squad's existence isn't something he or the Justice League can tolerate. It must be shut down. But while the heroes and antiheroes are distracted fighting each other, twisted mastermind Maxwell Lord assembles a nightmarish army of DC's deadliest villains to take out both teams!\"-- Provided by publisher.

Galactic building blocks The discovery last year of an extremely metal-poor star in the Sculptor dwarf galaxy cast doubt on a prevailing view — based on the apparent absence of the most metal-poor stars in present-day dwarf galaxies — that the long-known, classical dwarf satellite galaxies orbiting the Milky Way could not be building blocks of the Galaxy. New observations of this star, S1020549, indicate spectroscopic abundance patterns for 11 elements that are typical of metal-poor 'halo-type' stars. This suggests that the systems destroyed to form the Galactic halo billions of years ago were not fundamentally any different from the progenitors of present-day dwarf galaxies. Current models indicate that the Milky Way's stellar halo was assembled from many smaller systems, and recent studies claimed that the true Galactic building blocks must have been vastly different from the surviving dwarfs. But the overall abundance pattern of elements in S1020549, the most iron-poor star in the Sculptor dwarf galaxies, is now found to follow that seen in low-metallicity halo stars, indicating that the systems destroyed to form the halo billions of years ago were not fundamentally different from the progenitors of present-day dwarfs. Current cosmological models 1 , 2 indicate that the Milky Way’s stellar halo was assembled from many smaller systems. On the basis of the apparent absence of the most metal-poor stars in present-day dwarf galaxies, recent studies 3 claimed that the true Galactic building blocks must have been vastly different from the surviving dwarfs. The discovery of an extremely iron-poor star (S1020549) in the Sculptor dwarf galaxy based on a medium-resolution spectrum 4 cast some doubt on this conclusion. Verification of the iron-deficiency, however, and measurements of additional elements, such as the α-element Mg, are necessary to demonstrate that the same type of stars produced the metals found in dwarf galaxies and the Galactic halo. Only then can dwarf galaxy stars be conclusively linked to early stellar halo assembly. Here we report high-resolution spectroscopic abundances for 11 elements in S1020549, confirming its iron abundance of less than 1/4,000th that of the Sun, and showing that the overall abundance pattern follows that seen in low-metallicity halo stars, including the α-elements. Such chemical similarity indicates that the systems destroyed to form the halo billions of years ago were not fundamentally different from the progenitors of present-day dwarfs, and suggests that the early chemical enrichment of all galaxies may be nearly identical.

Milky way satellites: galaxies with a dark side Sophisticated optical astronomy projects such as the Sloan Digital Sky Survey are reaching a new threshold in detecting the least luminous galaxies in the Universe, and now at least twenty-three faint satellite galaxies are known in the region of the Milky Way. They range in luminosity from about a thousand to more than 100 million times that of the Sun. The velocities of the stars in these galaxies reveal that despite this variation in luminosity, each of the galaxies is similar in mass, at about 10 million times the mass of the Sun within their central 300 parsecs. The faintest of the Milky Way satellites are accordingly the most dark-matter-dominated galaxies known in the Universe. The Milky Way has at least twenty-three known satellite galaxies that shine with luminosities ranging from about a thousand to a billion times that of the Sun. Half of these galaxies were discovered 1 , 2 in the past few years in the Sloan Digital Sky Survey, and they are among the least luminous galaxies in the known Universe. A determination of the mass of these galaxies provides a test of galaxy formation at the smallest scales 3 , 4 and probes the nature of the dark matter that dominates the mass density of the Universe 5 . Here we use new measurements of the velocities of the stars in these galaxies 6 , 7 to show that they are consistent with them having a common mass of about 10 7 within their central 300 parsecs. This result demonstrates that the faintest of the Milky Way satellites are the most dark-matter-dominated galaxies known, and could be a hint of a new scale in galaxy formation or a characteristic scale for the clustering of dark matter.

The Large Magellanic Cloud (LMC) is the Milky Way’s most massive satellite galaxy, which only recently (~2 billion years ago) fell into our Galaxy. As stellar atmospheres preserve the composition of their natal cloud, the LMC’s recent infall makes its most ancient, metal-deficient (‘low-metallicity’) stars unique windows into early star formation and nucleosynthesis in a formerly distant region of the high-redshift universe. Here we present the elemental abundances of ten stars in the LMC with iron-to-hydrogen ratios ranging from ~1/300th to ~1/12,000th that of the Sun. Our most metal-deficient star is markedly more metal-deficient than any in the LMC with available detailed chemical abundance patterns and was probably enriched by a single extragalactic ‘first-star’ supernova. This star lacks appreciable carbon enhancement, as does our overall sample, unlike the lowest-metallicity stars in the Milky Way. This and other abundance differences affirm that the extragalactic early LMC experienced diverging enrichment processes compared to the early Milky Way. Early element production, driven by the earliest stars, thus, appears to proceed in an environment-dependent manner. Ten stars in the Large Magellanic Cloud exhibit very low elemental abundances, suggesting that they have experienced enrichment by the earliest generations of stars only. These stars provide a window into a distant region of the high-redshift universe.

The Milky Way is surrounded by dozens of ultrafaint (<10 5   L ☉ ) dwarf satellite galaxies 1 – 3 . They are the remnants of the earliest galaxies 4 , as confirmed by their ancient 5 and chemically primitive 6 , 7 stars. Simulations 8 – 10 suggest that these systems formed within extended dark matter halos and experienced early galaxy mergers and feedback. However, the signatures of these events would lie outside their core regions 11 , where spectroscopic studies are challenging 12 . Here we identify members of the Tucana II ultrafaint dwarf galaxy out to nine half-light radii, demonstrating the system to be markedly more spatially extended and chemically primitive than previously found. The distant stars in this galaxy are, on average, extremely metal poor (≲1/1000 of the solar iron abundance), affirming Tucana II as the most metal-poor known galaxy. We observationally establish an extended dark matter halo surrounding an ultrafaint dwarf galaxy out to 1 kpc, with a total mass of >10 7   M ☉ , consistent with a generalized Navarro–Frenk–White density profile. The extended nature of Tucana II suggests that it may have undergone strong bursty feedback or been the product of an early galactic merger 10 , 11 . We demonstrate that spatially extended stellar populations in ultrafaint dwarf galaxies 13 , 14 are observable, opening up the possibility for detailed studies of the stellar halos of relic galaxies. Stars in the Tucana II ultrafaint dwarf galaxy observed out to nine half-light radii reveal the presence of an extended dark matter halo with a total mass of >10 7 solar masses, consistent with a generalized Navarro–Frenk–White density profile and suggestive of past strong bursty feedback or an early galactic merger.

Superfluid 3 He is a paradigm for odd-parity Cooper pairing, ranging from neutron stars to uranium-based superconducting compounds. Recently it has been shown that 3 He, imbibed in anisotropic silica aerogel with either positive or negative strain, preferentially selects either the chiral A-phase or the time-reversal-symmetric B-phase. This control over basic order parameter symmetry provides a useful model for understanding imperfect unconventional superconductors. For both phases, the orbital quantization axis is fixed by the direction of strain. Unexpectedly, at a specific temperature T x , the orbital axis flops by 90 ∘ , but in reverse order for A and B-phases. Aided by diffusion limited cluster aggregation simulations of anisotropic aerogel and small angle X-ray measurements, we are able to classify these aerogels as either “planar\" and “nematic\" concluding that the orbital-flop is caused by competition between short and long range structures in these aerogels. When imbibed in an anisotropic silica aerogel, superfluid 3 He undergoes a temperature-driven “orbital flop\" transition, where the orbital quantization axis rotates by 90 degrees. Here, by simulating planar and nematic aerogel, M. D. Nguyen et al. show that the orbital flop transition is driven by the distinct large- and small-scale structures of the aerogel.

Obesity produces a chronic inflammatory state involving the NFκB pathway, resulting in persistent elevation of the noncanonical IκB kinases IKKε and TBK1. In this study, we report that these kinases attenuate β-adrenergic signaling in white adipose tissue. Treatment of 3T3-L1 adipocytes with specific inhibitors of these kinases restored β-adrenergic signaling and lipolysis attenuated by TNFα and Poly (I:C). Conversely, overexpression of the kinases reduced induction of Ucp1, lipolysis, cAMP levels, and phosphorylation of hormone sensitive lipase in response to isoproterenol or forskolin. Noncanonical IKKs reduce catecholamine sensitivity by phosphorylating and activating the major adipocyte phosphodiesterase PDE3B. In vivo inhibition of these kinases by treatment of obese mice with the drug amlexanox reversed obesity-induced catecholamine resistance, and restored PKA signaling in response to injection of a β-3 adrenergic agonist. These studies suggest that by reducing production of cAMP in adipocytes, IKKε and TBK1 may contribute to the repression of energy expenditure during obesity. Obesity is a complex metabolic disorder that is caused by increased food intake and decreased expenditure of energy. Obesity also increases the risk of developing type 2 diabetes, heart disease, stroke, arthritis, and certain cancers. There is considerable evidence to suggest that adipose tissue becomes less sensitive to catecholamines such as adrenaline in states of obesity, and that this reduced sensitivity in turn reduces energy expenditure. However, the details of this process are not fully understood. It is well established that obesity generates a state of chronic, low-grade inflammation in liver and adipose tissue, accompanied by the secretion of signaling proteins that prevent fat cells from responding to insulin, which leads to type 2 diabetes. Activation of the NFκB pathway is thought to have a central role in causing this inflammation. Now Mowers et al. have investigated whether inflammation caused by activation of the NFκB pathway also has a role in producing catecholamine resistance in fat cells. Obesity-dependent activation of the NFκB pathway increases the levels of a pair of enzymes, IKKε and TBK1. Mowers et al. found that elevated levels of these two enzymes reduced the ability of certain receptors (called β-adrenergic receptors) in the fat cells of obese mice to respond to catecholamines. High levels of the two enzymes also resulted in lower levels of a second messenger molecule called cAMP, which increases energy expenditure by elevating fat burning. However, treating the fat cells with drugs that interfere with the two enzymes restored sensitivity to catecholamine, allowing the fat cells to burn energy. Mowers et al. also treated obese mice with amlexanox, a drug that inhibits these enzymes, and found that this treatment made the mice sensitive to a synthetic catecholamine that triggered the release of energy from fat. Mowers et al. suggest, therefore, that IKKε and TBK1 respond to inflammation in the body by reducing catecholamine signaling, thus preventing energy expenditure. Drugs targeting these enzymes may be useful for treating conditions like obesity or type 2 diabetes.

The growing prominence of comparative political theory has inspired extensive and fruitful methodological reflection, raising important questions about the procedures that political theorists should apply when they select texts for study, interpret their passages, and assess their arguments. But, notably, comparative political theorists have mainly rejected the comparative methods used in the subfield of comparative politics, because they argue that applying the comparative method would compromise both the interpretive and the critical projects that comparative political theory should pursue. In this article, I describe a comparative approach for the study of political ideas that offers unique insight into how the intellectual and institutional contexts that political thinkers occupy influence their ideas. By systematically describing how political thinking varies across time and over space in relation to the contexts within which political thinkers live and work, the comparative method can serve as the foundation for both deconstructive critiques, which reveal the partial interests that political ideas presented as universally advantageous actually serve, and reconstructive critiques, which identify particular thinkers or traditions of political thought that, because of the contexts in which they developed, offer compelling critical perspectives on existing political institutions.