Granitic plutonism is the principal agent of crustal differentiation, but linking granite emplacement to crust formation requires knowledge of the magmatic evolution, which is notoriously difficult ...to reconstruct from bulk rock compositions. We unlocked the plutonic archive through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia. This granite type forms by the reworking of sedimentary materials by mantle-like magmas instead of by remelting ancient metamorphosed igneous rocks as widely believed. I-type magmatism thus drives the coupled growth and differentiation of continental crust.
We present a revised and complete optical afterglow light curve of the binary neutron star merger GW170817, enabled by deep Hubble Space Telescope (HST) F606W observations at 584 days post-merger, ...which provide a robust optical template. The light curve spans 110-362 days, and is fully consistent with emission from a relativistic structured jet viewed off-axis, as previously indicated by radio and X-ray data. Combined with contemporaneous radio and X-ray observations, we find no spectral evolution, with a weighted average spectral index of 〈 β 〉 = − 0.583 0.013 , demonstrating that no synchrotron break frequencies evolve between the radio and X-ray bands over these timescales. We find that an extrapolation of the post-peak temporal slope of GW170817 to the luminosities of cosmological short gamma-ray bursts matches their observed jet break times, suggesting that their explosion properties are similar, and that the primary difference in GW170817 is viewing angle. Additionally, we place a deep limit on the luminosity and mass of an underlying globular cluster (GC) of L 6.7 × 103 L , or M 1.3 × 104 M , at least 4 standard deviations below the peak of the GC mass function of the host galaxy, NGC 4993. This limit provides a direct and strong constraint that GW170817 did not form and merge in a GC. As highlighted here, HST (and soon the James Webb Space Telescope) enables critical observations of the optical emission from neutron star merger jets and outflows.
MCScan is an algorithm able to scan multiple genomes or subgenomes in order to identify putative homologous chromosomal regions, and align these regions using genes as anchors. The MCScanX toolkit ...implements an adjusted MCScan algorithm for detection of synteny and collinearity that extends the original software by incorporating 14 utility programs for visualization of results and additional downstream analyses. Applications of MCScanX to several sequenced plant genomes and gene families are shown as examples. MCScanX can be used to effectively analyze chromosome structural changes, and reveal the history of gene family expansions that might contribute to the adaptation of lineages and taxa. An integrated view of various modes of gene duplication can supplement the traditional gene tree analysis in specific families. The source code and documentation of MCScanX are freely available at http://chibba.pgml.uga.edu/mcscan2/.
Collisionless shock nonstationarity arising from microscale physics influences shock structure and particle acceleration mechanisms. Nonstationarity has been difficult to quantify due to the small ...spatial and temporal scales. We use the closely spaced (subgyroscale), high-time-resolution measurements from one rapid crossing of Earth's quasiperpendicular bow shock by the Magnetospheric Multiscale (MMS) spacecraft to compare competing nonstationarity processes. Using MMS's high-cadence kinetic plasma measurements, we show that the shock exhibits nonstationarity in the form of ripples.
Are we adapting to climate change? Berrang-Ford, Lea; Ford, James D.; Paterson, Jaclyn
Global environmental change,
02/2011, Letnik:
21, Številka:
1
Journal Article
Recenzirano
▶Reporting on adaptation actions is limited but increasing. ▶ Adaptations are most likely to be stimulated by climatic variability and are often mainstreamed and proactive. ▶ Long-term, proactive ...adaptation planning is more likely to be undertaken by government. ▶ The global distribution of adaptation reports is inequitable. ▶ Adaptation profiles differ between high and low income countries.
Human systems will have to adapt to climate change. Understanding of the magnitude of the adaptation challenge at a global scale, however, is incomplete, constrained by a limited understanding of if and how adaptation is taking place. Here we develop and apply a methodology to track and characterize adaptation action; we apply these methods to the peer-reviewed, English-language literature. Our results challenge a number of common assumptions about adaptation while supporting others: (1) Considerable research on adaptation has been conducted yet the majority of studies report on vulnerability assessments and natural systems (or
intentions to act), not adaptation actions. (2) Climate change is rarely the sole or primary motivator for adaptation action. (3) Extreme events are important adaptation stimuli across regions. (4) Proactive adaptation is the most commonly reported adaptive response, particularly in developed nations. (5) Adaptation action is more frequently reported in developed nations, with middle income countries underrepresented and low-income regions dominated by reports from a small number of countries. (6) There is limited reporting on adaptations being developed to take advantage of climate change or focusing on women, elderly, or children.
During a magnetopause crossing the Magnetospheric Multiscale spacecraft encountered an electron diffusion region (EDR) of asymmetric reconnection. The EDR is characterized by agyrotropic beam and ...crescent electron distributions perpendicular to the magnetic field. Intense upper-hybrid (UH) waves are found at the boundary between the EDR and magnetosheath inflow region. The UH waves are generated by the agyrotropic electron beams. The UH waves are sufficiently large to contribute to electron diffusion and scattering, and are a potential source of radio emission near the EDR. These results provide observational evidence of wave-particle interactions at an EDR, and suggest that waves play an important role in determining the electron dynamics.
The role and properties of lower hybrid waves in the ion diffusion region and magnetospheric inflow region of asymmetric reconnection are investigated using the Magnetospheric Multiscale (MMS) ...mission. Two distinct groups of lower hybrid waves are observed in the ion diffusion region and magnetospheric inflow region, which have distinct properties and propagate in opposite directions along the magnetopause. One group develops near the ion edge in the magnetospheric inflow, where magnetosheath ions enter the magnetosphere through the finite gyroradius effect and are driven by the ion‐ion cross‐field instability due to the interaction between the magnetosheath ions and cold magnetospheric ions. This leads to heating of the cold magnetospheric ions. The second group develops at the sharpest density gradient, where the Hall electric field is observed and is driven by the lower hybrid drift instability. These drift waves produce cross‐field particle diffusion, enabling magnetosheath electrons to enter the magnetospheric inflow region thereby broadening the density gradient in the ion diffusion region.
Key Points
Two groups of lower hybrid waves are observed in the ion diffusion and magnetospheric inflow regions
In the magnetospheric inflow region lower hybrid waves develop when cold magnetospheric ions are present and can heat cold ions
In the diffusion region lower hybrid waves develop at the density gradient and can cause cross‐field particle diffusion
Diabetic nephropathy involves a renal inflammatory response induced by the diabetic milieu. Macrophages accumulate in diabetic kidneys in association with the local upregulation of monocyte ...chemoattractant protein-1 (MCP-1); however, the contribution of macrophages to renal injury and the importance of MCP-1 to their accrual are unclear. Therefore, we examined the progression of streptozotocin (STZ)-induced diabetic nephropathy in mice deficient in MCP-1 in order to explore the role of MCP-1-mediated macrophage accumulation in the development of diabetic kidney damage. Renal pathology was examined at 2, 8, 12 and 18 weeks after STZ treatment in MCP-1 intact (+/+) and deficient (-/-) mice with equivalent blood glucose and hemoglobin A1c levels. In MCP-1(+/+) mice, the development of diabetic nephropathy was associated with increased kidney MCP-1 production, which occurred mostly in tubules, consistent with our in vitro finding that elements of the diabetic milieu (high glucose and advanced glycation end products) directly stimulate tubular MCP-1 secretion. Diabetes of 18 weeks resulted in albuminuria and elevated plasma creatinine in MCP-1(+/+) mice, but these aspects of renal injury were largely suppressed in MCP-1(-/-) mice. Protection from nephropathy in diabetic MCP-1(-/-) mice was associated with marked reductions in glomerular and interstitial macrophage accumulation, histological damage and renal fibrosis. Diabetic MCP-1(-/-) mice also had a smaller proportion of kidney macrophages expressing markers of activation (inducible nitric oxide synthase or sialoadhesin) compared to diabetic MCP-1(+/+) mice. In conclusion, our study demonstrates that MCP-1-mediated macrophage accumulation and activation plays a critical role in the development of STZ-induced mouse diabetic nephropathy.
The spontaneous formation of a chiral phase via molecular recognition in a system consisting of achiral components is reported. Specifically, the liquid crystalline behaviour of two molecular ...complexes assembled by hydrogen bonding between a stilbazole-based template and alkoxybenzoic acids has been characterised. The complexes exhibit the heliconical twist-bend nematic phase (NTB) over a broad temperature range despite the hydrogen-bond acceptor not being liquid crystalline and the donor exhibiting the conventional achiral nematic phase.
Using observations of Earth's bow shock by the Magnetospheric Multiscale mission, we show for the first time that active magnetic reconnection is occurring at current sheets embedded within the ...quasi‐parallel shock's transition layer. We observe an electron jet and heating but no ion response, suggesting we have observed an electron‐only mode. The lack of ion response is consistent with simulations showing reconnection onset on sub‐ion time scales. We also discuss the impact of electron heating in shocks via reconnection.
Plain Language Summary
For the first time, we document an observation of magnetic reconnection occurring at Earth's bow shock. The observations have been made by NASA's Magnetospheric Multiscale mission while the bow shock is under a “quasi‐parallel” geometry, which typically results in a highly disordered structure. Models of shock waves in space plasmas do not currently account for reconnection. This therefore introduces a new avenue of research into how shocks can repartition energy when slowing the solar wind from supersonic to subsonic flow. The observations also introduce a new regime for magnetic reconnection, for which we observe only an electron response at an ion scale reconnecting structure. This work will also attract interest from the broader astrophysics community, as reconnection at shocks may influence cosmic ray generation.
Key Points
Reconnecting current sheets have been observed at a quasi‐parallel bow shock
The ion‐scale current sheet exhibits only an electron jet and heating, with no ion response
Consistent with kinetic simulations, reconnection relaxes complexity in the shock transition region
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