| 51. |
|
|
| 52. |
- Sonnenburg, J. L., et al.
(författare)
-
Diet-microbiota interactions as moderators of human metabolism
- 2016
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 535:7610, s. 56-64
-
Tidskriftsartikel (refereegranskat)abstract
- It is widely accepted that obesity and associated metabolic diseases, including type 2 diabetes, are intimately linked to diet. However, the gut microbiota has also become a focus for research at the intersection of diet and metabolic health. Mechanisms that link the gut microbiota with obesity are coming to light through a powerful combination of translation-focused animal models and studies in humans. A body of knowledge is accumulating that points to the gut microbiota as a mediator of dietary impact on the host metabolic status. Efforts are focusing on the establishment of causal relationships in people and the prospect of therapeutic interventions such as personalized nutrition.
|
|
| 53. |
- Ståhl, Göran, et al.
(författare)
-
Plant functional traits have globally consistent effects on competition
- 2016
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 529, s. 204-U174
-
Tidskriftsartikel (refereegranskat)abstract
- Phenotypic traits and their associated trade-offs have been shown to have globally consistent effects on individual plant physiological functions(1-3), but how these effects scale up to influence competition, a key driver of community assembly in terrestrial vegetation, has remained unclear (4). Here we use growth data from more than 3 million trees in over 140,000 plots across the world to show how three key functional traits-wood density, specific leaf area and maximum height-consistently influence competitive interactions. Fast maximum growth of a species was correlated negatively with its wood density in all biomes, and positively with its specific leaf area in most biomes. Low wood density was also correlated with a low ability to tolerate competition and a low competitive effect on neighbours, while high specific leaf area was correlated with a low competitive effect. Thus, traits generate trade-offs between performance with competition versus performance without competition, a fundamental ingredient in the classical hypothesis that the coexistence of plant species is enabled via differentiation in their successional strategies(5). Competition within species was stronger than between species, but an increase in trait dissimilarity between species had little influence in weakening competition. No benefit of dissimilarity was detected for specific leaf area or wood density, and only a weak benefit for maximum height. Our trait-based approach to modelling competition makes generalization possible across the forest ecosystems of the world and their highly diverse species composition.
|
|
| 54. |
|
|
| 55. |
- Tobin, J. J., et al.
(författare)
-
A triple protostar system formed via fragmentation of a gravitationally unstable disk
- 2016
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 538:7626, s. 483-
-
Tidskriftsartikel (refereegranskat)abstract
- Binary and multiple star systems are a frequent outcome of the star formation process(1,2) and as a result almost half of all stars with masses similar to that of the Sun have at least one companion star(3). Theoretical studies indicate that there are two main pathways that can operate concurrently to form binary/multiple star systems: large-scale fragmentation of turbulent gas cores and filaments(4,5) or smaller-scale fragmentation of a massive protostellar disk due to gravitational instability(6,7). Observational evidence for turbulent fragmentation on scales of more than 1,000 astronomical units has recently emerged(8,9). Previous evidence for disk fragmentation was limited to inferences based on the separations of more-evolved pre-main sequence and protostellar multiple systems(10-13). The triple protostar system L1448 IRS3B is an ideal system with which to search for evidence of disk fragmentation as it is in an early phase of the star formation process, it is likely to be less than 150,000 years old(14) and all of the protostars in the system are separated by less than 200 astronomical units. Here we report observations of dust and molecular gas emission that reveal a disk with a spiral structure surrounding the three protostars. Two protostars near the centre of the disk are separated by 61 astronomical units and a tertiary protostar is coincident with a spiral arm in the outer disk at a separation of 183 astronomical units(13). The inferred mass of the central pair of protostellar objects is approximately one solar mass, while the disk surrounding the three protostars has a total mass of around 0.30 solar masses. The tertiary protostar itself has a minimum mass of about 0.085 solar masses. We demonstrate that the disk around L1448 IRS3B appears susceptible to disk fragmentation at radii between 150 and 320 astronomical units, overlapping with the location of the tertiary protostar. This is consistent with models for a protostellar disk that has recently undergone gravitational instability, spawning one or two companion stars.
|
|
| 56. |
- Tröstl, Jasmin, et al.
(författare)
-
The role of low-volatility organic compounds in initial particle growth in the atmosphere
- 2016
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 527-531
-
Tidskriftsartikel (refereegranskat)abstract
- About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday(1). Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres(2,3). In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles(4), thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth(5,6), leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer(7-10). Although recent studies(11-13) predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon(2), and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Kohler theory)(2,14), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown(15) that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10(-4.5) micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10(-4.5) to 10(-0.5) micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.
|
|
| 57. |
|
|
| 58. |
|
|
| 59. |
- Wang, Jian, et al.
(författare)
-
Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall
- 2016
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 539:7629, s. 416-419
-
Tidskriftsartikel (refereegranskat)abstract
- The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere(1). Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions(3-5), but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear(6-8). Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.
|
|
| 60. |
- Wiltgren, Filip
(författare)
-
SELF-LIMITED
- 2016
-
Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 535:7613, s. 586-586
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
|
|
