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| 2. |
- Andersson, Claes, 1973, et al.
(författare)
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Group size and cultural complexity
- 2014
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 511:7507, s. E1-
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Tidskriftsartikel (refereegranskat)abstract
- A decade ago, Henrich1 proposed group size as a driver of cultural complexity. Derex et al now present experimental results they say support this ‘group size hypothesis’ by seemingly showing that larger groups perform better than smaller groups under imitation-based cultural evolution. Our reanalysis of their experimental data, however, shows that larger groups actually perform worse than smaller groups. Thus, contrary to their claim, their data are consistent with empirical evidence discounting the group size hypothesis for non-food producing societies.
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| 3. |
- Bjerkeli, Per, 1977, et al.
(författare)
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Resolved images of a protostellar outflow driven by an extended disk wind.
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 540:7633, s. 406-409
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Tidskriftsartikel (refereegranskat)abstract
- Young stars are associated with prominent outflows of molecular gas. The ejection of gas is believed to remove angular momentum from the protostellar system, permitting young stars to grow by the accretion of material from the protostellar disk. The underlying mechanism for outflow ejection is not yet understood, but is believed to be closely linked to the protostellar disk. Various models have been proposed to explain the outflows, differing mainly in the region where acceleration of material takes place: close to the protostar itself ('X-wind', or stellar wind), in a larger region throughout the protostellar disk (disk wind), or at the interface between the two. Outflow launching regions have so far been probed only by indirect extrapolation because of observational limits. Here we report resolved images of carbon monoxide towards the outflow associated with the TMC1A protostellar system. These data show that gas is ejected from a region extending up to a radial distance of 25 astronomical units from the central protostar, and that angular momentum is removed from an extended region of the disk. This demonstrates that the outflowing gas is launched by an extended disk wind from a Keplerian disk.
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| 4. |
- Buitink, S., et al.
(författare)
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A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 531:7592, s. 70-73
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Tidskriftsartikel (refereegranskat)abstract
- Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017–1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal1 comes from accelerators capable of producing cosmic rays of these energies2. Cosmic rays initiate air showers—cascades of secondary particles in the atmosphere—and their masses can be inferred from measurements of the atmospheric depth of the shower maximum3 (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground4. Current measurements5 have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays6, 7, 8 is a rapidly developing technique9 for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front6, 12. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017–1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017–1017.5 electronvolt range.
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| 5. |
- Burstein, R., et al.
(författare)
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Mapping 123 million neonatal, infant and child deaths between 2000 and 2017
- 2019
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 574:7778, s. 353-358
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Tidskriftsartikel (refereegranskat)abstract
- Since 2000, many countries have achieved considerable success in improving child survival, but localized progress remains unclear. To inform efforts towards United Nations Sustainable Development Goal 3.2—to end preventable child deaths by 2030—we need consistently estimated data at the subnational level regarding child mortality rates and trends. Here we quantified, for the period 2000–2017, the subnational variation in mortality rates and number of deaths of neonates, infants and children under 5 years of age within 99 low- and middle-income countries using a geostatistical survival model. We estimated that 32% of children under 5 in these countries lived in districts that had attained rates of 25 or fewer child deaths per 1,000 live births by 2017, and that 58% of child deaths between 2000 and 2017 in these countries could have been averted in the absence of geographical inequality. This study enables the identification of high-mortality clusters, patterns of progress and geographical inequalities to inform appropriate investments and implementations that will help to improve the health of all populations. © 2019, The Author(s).
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| 6. |
- Chomiuk, L., et al.
(författare)
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Binary orbits as the driver of gamma-ray emission and mass ejection in classical novae
- 2014
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 514:7522, s. 339-
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Tidskriftsartikel (refereegranskat)abstract
- Classical novae are the most common astrophysical thermonuclear explosions, occurring on the surfaces of white dwarf stars accreting gas from companions in binary star systems(1). Novae typically expel about 10(-4) solar masses of material at velocities exceeding 1,000 kilometres per second. However, the mechanism of mass ejection in novae is poorly understood, and could be dominated by the impulsive flash of thermonuclear energy(2), prolonged optically thick winds(3) or binary interaction with the nova envelope(4). Classical novae are now routinely detected at gigaelectronvolt gamma-ray wavelengths(5), suggesting that relativistic particles are accelerated by strong shocks in the ejecta. Here we report high-resolution radio imaging of the gamma-ray-emitting nova V959 Mon. We find that its ejecta were shaped by the motion of the binary system: some gas was expelled rapidly along the poles as a wind from the white dwarf, while denser material drifted out along the equatorial plane, propelled by orbital motion(6,7). At the interface between the equatorial and polar regions, we observe synchrotron emission indicative of shocks and relativistic particle acceleration, thereby pinpointing the location of gamma-ray production. Binary shaping of the nova ejecta and associated internal shocks are expected to be widespread among novae(8), explaining why many novae are gamma-ray emitters(5).
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| 7. |
- de Vries, B. L., et al.
(författare)
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Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 490:7418, s. 74-76
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Tidskriftsartikel (refereegranskat)abstract
- Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets(1). Collisions between such bodies produce small dust particles(2), the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg2-2xFe2xSiO4) has been done for the protoplanetary disk HD 100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids(5,6) (x approximate to 0.29). In the cold outskirts of the beta Pictoris system, an analogue to the young Solar System, olivine crystals were detected(7) but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets(8,9). Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of beta Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01 +/- 0.001) and show that they make up 3.6 +/- 1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System(8-10), even though beta Pictoris is more massive and more luminous and has a different planetary system architecture.
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| 8. |
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| 9. |
- Heywood, I., et al.
(författare)
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Inflation of 430-parsec bipolar radio bubbles in the Galactic Centre by an energetic event
- 2019
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 573:7773, s. 235-237
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Tidskriftsartikel (refereegranskat)abstract
- The Galactic Centre contains a supermassive black hole with a mass of four million Suns1 within an environment that differs markedly from that of the Galactic disk. Although the black hole is essentially quiescent in the broader context of active galactic nuclei, X-ray observations have provided evidence for energetic outbursts from its surroundings2. Also, although the levels of star formation in the Galactic Centre have been approximately constant over the past few hundred million years, there is evidence of increased short-duration bursts3, strongly influenced by the interaction of the black hole with the enhanced gas density present within the ring-like central molecular zone4 at Galactic longitude |l| < 0.7 degrees and latitude |b| < 0.2 degrees. The inner 200-parsec region is characterized by large amounts of warm molecular gas5, a high cosmic-ray ionization rate6, unusual gas chemistry, enhanced synchrotron emission7,8, and a multitude of radio-emitting magnetized filaments9, the origin of which has not been established. Here we report radio imaging that reveals a bipolar bubble structure, with an overall span of 1 degree by 3 degrees (140 parsecs × 430 parsecs), extending above and below the Galactic plane and apparently associated with the Galactic Centre. The structure is edge-brightened and bounded, with symmetry implying creation by an energetic event in the Galactic Centre. We estimate the age of the bubbles to be a few million years, with a total energy of 7 × 1052 ergs. We postulate that the progenitor event was a major contributor to the increased cosmic-ray density in the Galactic Centre, and is in turn the principal source of the relativistic particles required to power the synchrotron emission of the radio filaments within and in the vicinity of the bubble cavities.
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| 10. |
- Karlsson, Fredrik, 1984, et al.
(författare)
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Gut metagenome in European women with normal, impaired and diabetic glucose control
- 2013
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 498:7452, s. 99-103
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Tidskriftsartikel (refereegranskat)abstract
- Type 2 diabetes (T2D) is a result of complex gene-environment interactions, and several risk factors have been identified, including age, family history, diet, sedentary lifestyle and obesity. Statistical models that combine known risk factors for T2D can partly identify individuals at high risk of developing the disease. However, these studies have so far indicated that human genetics contributes little to the models, whereas socio-demographic and environmental factors have greater influence(1). Recent evidence suggests the importance of the gut microbiota as an environmental factor, and an altered gut microbiota has been linked to metabolic diseases including obesity(2,3), diabetes(4) and cardiovascular disease(5). Here we use shotgun sequencing to characterize the faecal metagenome of 145 European women with normal, impaired or diabetic glucose control. We observe compositional and functional alterations in the metagenomes of women with T2D, and develop a mathematical model based on metagenomic profiles that identified T2D with high accuracy. We applied this model to women with impaired glucose tolerance, and show that it can identify women who have a diabetes-like metabolism. Furthermore, glucose control and medication were unlikely to have major confounding effects. We also applied our model to a recently described Chinese cohort(4) and show that the discriminant metagenomicmarkers for T2D differ between the European and Chinese cohorts. Therefore, metagenomic predictive tools for T2D should be specific for the age and geographical location of the populations studied.
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