Although the phylogenetic relationships between monocot orders are sufficiently understood, a timescale of their evolution is needed. Several studies on molecular clock dating are available, but ...their results have been biased by their calibration schemes. Recently, the fossilized birth-death model, a type of Bayesian dating method, was proposed, and it does not require prior calibration and allows the use all available fossils. Using this model, we conducted divergence-time estimations of monocots to explore their evolutionary timeline without calibration bias. This is the first application of this model to seed plants. The dataset contained the matK and rbcL chloroplast genes of 118 monocot genera covering all extant orders. We employed information from 247 monocot fossils, which exceeded previous dating analyses that used a maximum of 12 monocot fossils. The crown group of monocots was dated to approximately the Late Jurassic–Early Cretaceous periods, and most extant monocot orders were estimated to diverge throughout the Early Cretaceous. Our results overlapped with the divergence time of insect lineages, such as beetles and flies, suggesting an association with pollinators in early monocot evolution. In addition, we proposed three new orders based on divergence time: Orchidales separated from Asparagales and Tofieldiales and Arales separated from Aslimatales.
In this study, the evolution of dislocation densities during compressive deformation of nanoscale Cu/Nb single crystal multilayers with individual layer thickness of 20nm is investigated using ...Synchrotron X-ray micro-diffraction. The samples were subjected to successive compression straining up to a final cumulative strain of 35%. The nanolayer composite exhibited a maximum flow strength of ~1.6GPa at approximately 24% compressive strain. Synchrotron X-ray micro-diffraction experiments, using a monochromatic beam of 10keV energy were performed after each compression strain increment. We observed a significant increase in X-ray ring width peak broadening in both Cu and Nb layers up to strains of ~3.5% followed by saturation broadening at higher strains. This observation indicates that the interfaces of the Cu/Nb nanolayers are very effective in trapping and annihilating dislocation content during mechanical deformation.
Volcanoes Erupt Stressed Quartz Crystals Befus, K. S.; Manga, M.; Stan, C. ...
Geophysical research letters,
16 August 2019, Letnik:
46, Številka:
15
Journal Article
Recenzirano
Odprti dostop
Volcanic eruptions are energetic events driven by the imbalance of magmatic forces. The magnitudes of these forces remain poorly constrained because they operate in regions that are inaccessible, ...either underground or dangerous to approach. New techniques are needed to quantify the processes that drive eruptions and to probe magma storage conditions. Here we present X‐ray microdiffraction measurements of volcanic stress imparted as lattice distortions to the crystal cargo of magma from Yellowstone and Long Valley eruptions. Elevated residual stresses between 100 and 300 MPa are preserved in erupted quartz. Multiple volcanic forces could be culpable for the deformation so we analyzed crystals from pyroclastic falls, pyroclastic density currents, and effusive lavas. Stresses are preserved in all quartz but cannot be attributed to differences in eruption style. Instead, lattice deformation likely preserves an in situ measurement of the deviatoric stresses required for the brittle failure of viscous, crystal‐bearing glass during ascent.
Plain Language Summary
Because of inherent danger, volcano scientists have little direct understanding of the stresses active during volcanic eruptions. We propose that the crystal cargo carried by a volcanic eruption may preserve a record of those stresses. We used synchrotron X‐ray microdiffraction to measure crystal deformation in quartz from explosive and effusive eruptions from Yellowstone and Long Valley calderas. All the crystals were strained by stresses ranging from 100 to 300 MPa. These values are large but are not related to eruption style. The stresses may have been caused by crystal‐crystal impingements in the crystal‐rich magma chambers. More likely, we propose that the residual stresses record those required for brittle failure of the crystal‐bearing melt in the conduit during eruptive ascent.
Key Points
Explosive and effusive eruptions from volcanoes contain deformed quartz crystals with the same residual stresses
Residual stresses are proposed to originate from the stresses required to fragment magma
Residual stress may also originate from crystal‐crystal contacts in crystal‐rich magmatic mushes
Synchrotron x-ray microdiffraction (
μ
XRD
) allows characterization of a crystalline material in small, localized volumes. Phase composition, crystal orientation and strain can all be probed in ...few-second time scales. Crystalline changes over a large areas can be also probed in a reasonable amount of time with submicron spatial resolution. However, despite all the listed capabilities,
μ
XRD
is mostly used to study pure materials but its application in actual device characterization is rather limited. This article will explore the recent developments of the
μ
XRD
technique illustrated with its advanced applications in microelectronic devices and solar photovoltaic systems. Application of
μ
XRD
in microelectronics will be illustrated by studying stress and microstructure evolution in Cu TSV (through silicon via) during and after annealing. The approach allowing study of the microstructural evolution in the solder joint of crystalline Si solar cells due to thermal cycling will be also demonstrated.
Abstract
The morphologically diverse Commelinaceae consist of 41 genera with c. 650 species. Previous phylogenetic studies have revealed paraphyly of some taxa, but some of the infrafamilial taxa and ...most of the genera remain to be tested. To investigate phylogenetic relationships of the infrafamilial taxa and to test their monophyly, likelihood and Bayesian analyses with partial rbcL, matK and accD sequences were performed using 75 species from 33 genera of primarily eastern and south-eastern Asian Commelinaceae, with members of Haemodoraceae and Hanguanaceae as outgroups. The analyses resolved the early-diverging lineages of Commelineae and supported the monophyly of Dichorisandrinae and non-monophyly of Amischotolype, Belosynapsis, Murdannia, Pollia and Aneilema. Based on phylogenetics and morphology, we suggest that Palisotinae and Streptoliriinae should be raised to tribal rank, establishing subtribes Cochliostematinae, Commelininae and Murdanniinae, whereas Porandra, Belosynapsis, Anthericopsis are synonymized under Amischotolype, Cyanotis and Murdannia, respectively. Rhopalephora and two Australian Pollia spp. are moved to Aneilema. With all aforementioned taxonomic additions and changes, we propose a new classification for Commelinaceae, consisting of two subfamilies, six tribes, seven subtribes and 37 genera.
Defying the requirements of translational periodicity in 3D, rotation of the lattice orientation within an otherwise single crystal provides a new form of solid. Such rotating lattice single (RLS) ...crystals are found, but only as spherulitic grains too small for systematic characterization or practical application. Here we report a novel approach to fabricate RLS crystal lines and 2D layers of unlimited dimensions via a recently discovered solid-to-solid conversion process using a laser to heat a glass to its crystallization temperature but keeping it below the melting temperature. The proof-of-concept including key characteristics of RLS crystals is demonstrated using the example of Sb
S
crystals within the Sb-S-I model glass system for which the rotation rate depends on the direction of laser scanning relative to the orientation of initially formed seed. Lattice rotation in this new mode of crystal growth occurs upon crystallization through a well-organized dislocation/disclination structure introduced at the glass/crystal interface. Implications of RLS growth on biomineralization and spherulitic crystal growth are noted.
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