Existing reactors use uranium or plutonium—the stuff of bombs. Uranium reactors need the same fuel-enrichment technology that bomb-makers employ, and can thus give cover for clandestine weapons programmes. Plutonium is made from unenriched uranium in reactors whose purpose can easily be switched to bomb-making. Thorium, though, is hard to turn into a bomb; not impossible, but sufficiently uninviting a prospect that America axed thorium research in the 1970s. It is also three or four times as abundant as uranium. In a world where nuclear energy was a primary goal of research, rather than a military spin-off, it would certainly look worthy of investigation. And it is, indeed, being investigated.
Using a quasi-experimental opportunity offered by greatly restricted air pollution emissions during the Beijing Olympics compared to before and after the Olympics, the authors conducted the current study to compare ultrafine particles (UFPs) and fine particles (PM2.5) in their associations with biomarkers reflecting multiple pathophysiological pathways linking exposure and cardiorespiratory events.
The turkey eggs’ ability to ward off moisture is “not just protection against the school of hard knocks, it’s also protection against the microbial world,” says Maxwell Hincke, a biomaterials researcher at the University of Ottawa in Canada, who was not involved with the study. The calcium phosphate nanospheres found in this species' eggs seem uncommon — preliminary observations have not revealed similar structures in the eggs of other species. However, a 1982 study described similar nanospheres in the eggs of malleefowl (Leipoa ocellata), another Australian bird that nests in soil mounds. In the future, D’Alba plans to study how diverse nesting environments may have shaped the shell composition (see also: http://www.nature.com/news/nanoparticles-make-turkey-eggs-tough-to-crack-1.15039#/b1).
The authors have measured the single-crystal elasticity of the perovskite Pbnm-CaIrO3 and post-perovskite Cmcm-CaIrO3 using inelastic X-ray scattering. These materials are structural analogues to same phases of MgSiO3. Their results show that Cmcm-CaIrO3 is much more elastically anisotropic than Pbnm-CaIrO3, which offers an explanation for the enigmatic seismic wave velocity jump at the D′′ discontinuity.
David W. Mogk, Montana State University--professor of geology and contra/square dance caller Introduction Symmetry is one of the most difficult concepts for students to master in an introductory mineralogy course.
Characterised by long term cooling and abrupt ice sheet expansion on Antarctica ~14 Ma ago, the mid Miocene marked the beginning of the modern ice-house world, yet there is still little consensus on its causes, in part because carbon cycle dynamics are not well constrained. The authors used benthic foraminiferal B/Ca ratios to reconstruct relative changes in [CO32−] from the South Atlantic, East Pacific, and Southern Oceans. Our results suggest an increase of perhaps ~40 μmol/kg may have occurred between ~15 and 14 Ma in intermediate to deep waters in each basin.
Microimaging techniques, such as interference and infrared microscopy, can be used as a tool to directly monitor guest profiles within nanoporous materials. Observation of the variation in these profiles leads to unprecedented insight into transport phenomena, including intracrystalline diffusion and surface permeation.
Throughout Earth, rocks respond to changing physical and chemical conditions by converting one rock type to another. These conversions have conventionally been described in terms of solid-state mechanisms, in which new minerals nucleate and grow through exchange of elements by diffusion. The slow rates of solid-state diffusion suggested geological time scales for these processes. However, rocks in Earth's crust are not dry!
Sedimentary Mesozoic rocks from NW Greece (Epirus region), and particularly laminated phosphatized limestones, bedded chert-rich limestones and brecciated phosphatized limestones, were examined for their actinide content. Gamma-ray measurements using a HPGe detector showed that the above geological materials exhibit high radioactivity, mainly attributed to the 238U-series. The 238U content (up to 7700 Bq/Kg) was determined by the 1001 keV photopeak of 234mPa, the 238U daughter. Bulk geochemical analyses using ICP-OES/MS showed variable U concentrations with a notable value of 648 ppm in the case of dark organic-rich material hosted into the brecciated phosphatized limestones. Relatively high concentrations of Cd, probably related to apatite, were also revealed. On the other hand, the rock is geochemically depleted in LILE (e.g. Cs, Rb, K), as well as in As, Sb and Se in contrast to “average phosphorite”. Powder-XRD combined with optical microscopy, SEM-EDS and FTIR confirmed abundant apatite, besides calcite, as well as organic compounds (organic matter/O.M.) which should be associated to the high U content. According to Th/Sc vs. Zr/Sc discrimination diagrams the organic-rich part of the U-bearing phosphatised limestones exhibits a mafic trend, in contrast to the rest of the studied rocks lying close to typical pelagic sediments. However, Eu/Eu* vs. Ce/Ce* diagrams, in combination with SEM-EDS, indicated that the organic-rich part is a typical sedimentary material whereas the organic-poor (and also U-poor) part of the rock is secondary calcite related to surface waters. As far as we know, the studied rocks from NW Greece are classified among the richest U-bearing phosphatized limestones and/or sedimentary phosphorites in the world.
Using atomic and chemical force microscopy to probe the reactivity at the nanoscale of both types of nanoparticles, the authors were able to show that the primary reason for the low reactivity of b-GR is not the low surface/volume ratio but the passivation of the surface due to the presence of biological exopolymers (EPS).
In 1977, scientists discovered biological communities unexpectedly living around seafloor hydrothermal vents, far from sunlight and thriving on a chemical soup rich in hydrogen, carbon dioxide, and sulfur, spewing from the geysers. Inspired by these findings, scientists later proposed that hydrothermal vents provided an ideal environment with all the ingredients needed for microbial life to emerge on early Earth. A central figure in this hypothesis is a simple sulfur-containing carbon compound called “methanethiol” - a supposed geologic precursor of the Acetyl-CoA enzyme present in many organisms, including humans. Scientists suspected methanethiol could have been the “starter dough” from which all life emerged (see: http://www.whoi.edu/news-release/study-tests-theory-that-life-originated-at-deep-sea-vents).
Managed aquifer recharge (MAR) is a water reuse technique with the potential to meet growing water demands. In this bench-scale study, arsenic mobilization from arsenopyrite (FeAsS) was characterized for conditions relevant to MAR operations.
To investigate Ancestral Puebloan turquoise procurement strategies and trade networks, the authors analyzed 74 turquoise artifacts from Puebloan sites in the San Juan Basin and the Virgin Puebloan area in southern Utah and the Moapa Valley in Nevada by a technique we developed that identifies the geological source of turquoise artifacts using the isotope ratios of hydrogen and copper and a comparative database that contains the isotope fingerprints of 22 turquoise resource areas.
University of Nottingham-British Geological Survey Centre for Environmental Geochemistry (RT @MelJLeng: The new @UniofNottingham @BritGeoSurvey Centre for Environmental Geochemistry http://t.co/PinZD5QAw9)...
The analyses show the presence of U(IV) in soil as a non-crystalline species bound to amorphous Al-P-Fe-Si aggregates, and in porewater, as a distinct species associated with Fe and organic matter colloids.
The Center for Nanoscale Materials at Argonne National Laboratory is a joint partnership between the U.S. Department of Energy (DOE) and the State of Illinois, as part of DOE’S Nanoscale Science Research Center program.
To ensure survival, the exoskeletons of biological species are required to minimize the spatial extent of damage following attack or multi-hit events. Now, nanoindentation experiments on a transparent bivalve shell, which is made up of layered, diamond-shaped calcite crystals, show an increased energy dissipation density compared with single-crystal calcite, resulting in penetration resistance and deformation localization. The detailed mechanisms of this enhanced energy dissipation are revealed and include nanoscale deformation twinning around the penetration zone.
Ath Godelitsas's insight:
Researchers at MIT have analyzed shells to determine exactly why they are so resistant to penetration and damage, even though they are 99 percent calcite, a weak, brittle mineral. The shells’ unique properties emerge from a specialized nanostructure that allows optical clarity, as well as efficient energy dissipation and the ability to localize deformation, the researchers found. The results are published this week in the journal Nature Materials, in a paper co-authored by MIT graduate student Ling Li and professor Christine Ortiz (see also: https://newsoffice.mit.edu/2014/tough-nails-yet-clear-enough-read-through).
HAADF detector image of apatite (bright) cylinders in the matrix of carbonaceous matter
Ath Godelitsas's insight:
The authors have used microfabric, trace element and carbon isotope analyses to assess the environmental setting and redox conditions of the 2-billion-year-old P-rich deposits of the vent- or seep-influenced Zaonega Formation, northwest Russia. they identified phosphatized microorganism fossils that resemble modern methanotrophic archaea and sulphur-oxidizing bacteria, analogous to organisms found in modern seep settings and upwelling zones with a sharp redoxcline.
The evolution of oxygenic photosynthesis should have occurred some time before the oxidation of Earth/'s atmosphere 2.5 billion years ago. The molybdenum isotopic signature of shallow marine rocks that formed at least 2.95 billion years ago is consistent with deposition in waters that were receiving oxygen from photosynthesis at least half a billion years before the oxidation of the atmosphere.
The toughness of ceramic materials can be improved by introducing a polymeric or metallic ductile phase, yet most often this is at the expense of strength, stiffness and high-temperature stability. Now, a simple processing route based on widespread ceramic processing techniques is shown to produce bulk ceramics that mimic the structure of natural nacre and have a unique combination of high strength, toughness and stiffness, even at high temperatures.
Ath Godelitsas's insight:
Although natural materials that are both strong and tough rely on a combination of mechanisms operating at different length scales, the relevant structures have been extremely difficult to replicate. Here, the authors report a bioinspired approach based on widespread ceramic processing techniques for the fabrication of bulk ceramics without a ductile phase and with a unique combination of high strength (470 MPa), high toughness (22 MPa m1/2), and high stiffness (290 GPa). Because only mineral constituents are needed, these ceramics retain their mechanical properties at high temperatures (600 °C).
Three brittle swelling micas, Mica-n (n = 4, 3 and 2), were selected in order to analyze the influence of the layer charge in the formation of inner-sphere complexes (ISC). The contribution of the ISC has been analyzed thorough the evolution of the 060 reflection and the changes in the short-range order of the tetrahedral cations will be followed 29Si and 27Al MAS NMR. The results showed that ISC was favored in X-Mica-4 and that provoked a high distortion angle between the Si–Al tetrahedra.