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https://www.readbyqxmd.com/read/28345901/recyclable-single-component-rare-earth-metal-catalysts-for-cycloaddition-of-co2-and-epoxides-at-atmospheric-pressure
#1
Zhiwen Zhao, Jie Qin, Chen Zhang, Yaorong Wang, Dan Yuan, Yingming Yao
Ionic rare-earth metal complexes 1-4 bearing an imidazolium cation were synthesized, which, as single-component catalysts, showed good activity in catalyzing cyclic carbonate synthesis from epoxides and CO2. In the presence of 0.2 mol % catalyst, monosubstituted epoxides bearing different functional groups were converted into cyclic carbonates in 60-97% yields under atmospheric pressure. In addition, bulky/internal epoxides with low reactivity yielded cyclic carbonates in 40-95% yields. More importantly, the readily available samarium complex 2 was reused for six successive cycles without any significant loss in its catalytic activity...
March 27, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28345669/a-coupled-human-earth-model-perspective-on-long-term-trends-in-the-global-marine-fishery
#2
E D Galbraith, D A Carozza, D Bianchi
The global wild marine fish harvest increased fourfold between 1950 and a peak value near the end of the 20th century, reflecting interactions between anthropogenic and ecological forces. Here, we examine these interactions in a bio-energetically constrained, spatially and temporally resolved model of global fisheries. We conduct historical hindcasts with the model, which suggest that technological progress can explain most of the 20th century increase of fish harvest. In contrast, projections extending this rate of technological progress into the future under open access suggest a long-term decrease in harvest due to over-fishing...
March 27, 2017: Nature Communications
https://www.readbyqxmd.com/read/28345208/increased-synthetic-control-gaining-access-to-predicted-mg2-si5-n8-and-%C3%AE-ca2-si5-n8
#3
Philipp Bielec, Wolfgang Schnick
Nitridosilicates represent an intriguing class of materials and are typically made up of highly condensed tetrahedral network structures. Alkaline-earth nitridosilicates emerged as unique host materials for Eu(2+) doped luminophores which found broad application in phosphor-converted (pc)-LEDs. In contrast to common strategies of preparing nitridosilicates by bottom-up syntheses, we have now succeeded to post-synthetically design nitridosilicates by ion exchange in metal halide melts. We describe the syntheses of hitherto unknown but predicted alkaline-earth nitridosilicates, Mg2 Si5 N8 and β-Ca2 Si5 N8 ...
March 27, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28345058/nonrainfall-water-origins-and-formation-mechanisms
#4
Kudzai Farai Kaseke, Lixin Wang, Mary K Seely
Dryland ecosystems cover 40% of the total land surface on Earth and are defined broadly as zones where precipitation is considerably less than the potential evapotranspiration. Nonrainfall waters (for example, fog and dew) are the least-studied and least-characterized components of the hydrological cycle, although they supply critical amounts of water for dryland ecosystems. The sources of nonrainfall waters are largely unknown for most systems. In addition, most field and modeling studies tend to consider all nonrainfall inputs as a single category because of technical constraints, which hinders prediction of dryland responses to future warming conditions...
March 2017: Science Advances
https://www.readbyqxmd.com/read/28345049/biomimetic-mineral-self-organization-from-silica-rich-spring-waters
#5
Juan Manuel García-Ruiz, Elias Nakouzi, Electra Kotopoulou, Leonardo Tamborrino, Oliver Steinbock
Purely inorganic reactions of silica, metal carbonates, and metal hydroxides can produce self-organized complex structures that mimic the texture of biominerals, the morphology of primitive organisms, and that catalyze prebiotic reactions. To date, these fascinating structures have only been synthesized using model solutions. We report that mineral self-assembly can be also obtained from natural alkaline silica-rich water deriving from serpentinization. Specifically, we demonstrate three main types of mineral self-assembly: (i) nanocrystalline biomorphs of barium carbonate and silica, (ii) mesocrystals and crystal aggregates of calcium carbonate with complex biomimetic textures, and (iii) osmosis-driven metal silicate hydrate membranes that form compartmentalized, hollow structures...
March 2017: Science Advances
https://www.readbyqxmd.com/read/28345044/continental-igneous-rock-composition-a-major-control-of-past-global-chemical-weathering
#6
Clément P Bataille, Amy Willis, Xiao Yang, Xiao-Ming Liu
The composition of igneous rocks in the continental crust has changed throughout Earth's history. However, the impact of these compositional variations on chemical weathering, and by extension on seawater and atmosphere evolution, is largely unknown. We use the strontium isotope ratio in seawater [((87)Sr/(86)Sr)seawater] as a proxy for chemical weathering, and we test the sensitivity of ((87)Sr/(86)Sr)seawater variations to the strontium isotopic composition ((87)Sr/(86)Sr) in igneous rocks generated through time...
March 2017: Science Advances
https://www.readbyqxmd.com/read/28345041/one-pot-synthesis-of-amino-acid-precursors-with-insoluble-organic-matter-in-planetesimals-with-aqueous-activity
#7
Yoko Kebukawa, Queenie H S Chan, Shogo Tachibana, Kensei Kobayashi, Michael E Zolensky
The exogenous delivery of organic molecules could have played an important role in the emergence of life on the early Earth. Carbonaceous chondrites are known to contain indigenous amino acids as well as various organic compounds and complex macromolecular materials, such as the so-called insoluble organic matter (IOM), but the origins of the organic matter are still subject to debate. We report that the water-soluble amino acid precursors are synthesized from formaldehyde, glycolaldehyde, and ammonia with the presence of liquid water, simultaneously with macromolecular organic solids similar to the chondritic IOM...
March 2017: Science Advances
https://www.readbyqxmd.com/read/28345037/pure-climb-creep-mechanism-drives-flow-in-earth-s-lower-mantle
#8
Francesca Boioli, Philippe Carrez, Patrick Cordier, Benoit Devincre, Karine Gouriet, Pierre Hirel, Antoine Kraych, Sebastian Ritterbex
At high pressure prevailing in the lower mantle, lattice friction opposed to dislocation glide becomes very high, as reported in recent experimental and theoretical studies. We examine the consequences of this high resistance to plastic shear exhibited by ringwoodite and bridgmanite on creep mechanisms under mantle conditions. To evaluate the consequences of this effect, we model dislocation creep by dislocation dynamics. The calculation yields to an original dominant creep behavior for lower mantle silicates where strain is produced by dislocation climb, which is very different from what can be activated under high stresses under laboratory conditions...
March 2017: Science Advances
https://www.readbyqxmd.com/read/28345033/improved-estimates-of-ocean-heat-content-from-1960-to-2015
#9
Lijing Cheng, Kevin E Trenberth, John Fasullo, Tim Boyer, John Abraham, Jiang Zhu
Earth's energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the data-rich Argo era are colocated with locations of earlier ocean observations, to quantify this error...
March 2017: Science Advances
https://www.readbyqxmd.com/read/28344378/the-long-and-the-short-of-it-a-global-analysis-of-hawkmoth-pollination-niches-and-interaction-networks
#10
Steven D Johnson, Marcela Moré, Felipe W Amorim, William A Haber, Gordon W Frankie, Dara A Stanley, Andrea A Coccuci, Robert A Raguso
1. Proboscis length has been proposed as a key dimension of plant pollination niches, but this niche space has not previously been explored at regional and global scales for any pollination system. Hawkmoths are ideal organisms for exploring pollinator niches as they are important pollinators in most of the biodiverse regions of the earth and vary greatly in proboscis length, with some species having the longest proboscides of all insects. 2. Using datasets for nine biogeographical regions spanning the Old and New World, we ask whether it is possible to identify distinct hawkmoth pollination niches based on the frequency distribution of proboscis length, and whether these niches are reflected in the depths of flowers that are pollinated by hawkmoths...
January 2017: Functional Ecology
https://www.readbyqxmd.com/read/28344052/keeping-fat-on-time-circadian-control-of-adipose-tissue
#11
REVIEW
Stine Ninel Hansen, Julia Peics, Zachary Gerhart-Hines
Circadian clocks harmonize processes ranging from intracellular biochemistry to whole-body physiology in accordance with the Earth's 24 hour rotation. These intrinsic oscillators are based on an interlocked transcriptional-translational feedback loop comprised from a set of core clock factors. In addition to maintaining rhythmicity in nearly every cell of the body, these clock factors also mediate tissue specific metabolic functions. In this review, we will explore how the molecular clock shapes the unique features of different adipose depots...
March 23, 2017: Experimental Cell Research
https://www.readbyqxmd.com/read/28342661/climate-change-and-human-infectious-diseases-a-synthesis-of-research-findings-from-global-and-spatio-temporal-perspectives
#12
Lu Liang, Peng Gong
The life cycles and transmission of most infectious agents are inextricably linked with climate. In spite of a growing level of interest and progress in determining climate change effects on infectious disease, the debate on the potential health outcomes remains polarizing, which is partly attributable to the varying effects of climate change, different types of pathogen-host systems, and spatio-temporal scales. We summarize the published evidence and show that over the past few decades, the reported negative or uncertain responses of infectious diseases to climate change has been growing...
March 22, 2017: Environment International
https://www.readbyqxmd.com/read/28342327/influence-of-terrestrial-radionuclides-on-environmental-gamma-exposure-in-a-uranium-deposit-in-para%C3%A3-ba-brazil
#13
José Araújo Dos Santos Júnior, Romilton Dos Santos Amaral, Rômulo Simões Cezar Menezes, Juan Reinaldo Estevez Álvarez, Josineide Marques do Nascimento Santos, Zahily Herrero Fernández, Jairo Dias Bezerra, Alberto Antônio da Silva, Kennedy Francys Rodrigues Damascena, José de Almeida Maciel Neto
One of the main natural uranium deposits in Brazil is located in the municipality of Espinharas, in the State of Paraíba. This area may present high levels of natural radioactivity due to the presence of these radionuclides. Since this is a populated area, there is need for a radioecological dosimetry assessment to investigate the possible risks to the population. Based on this problem, the objective of this study was to estimate the environmental effective dose outdoors in inhabited areas influenced by the uranium deposit, using the specific activities of equivalent uranium, equivalent thorium and (40)K and conversion factors...
March 22, 2017: Ecotoxicology and Environmental Safety
https://www.readbyqxmd.com/read/28342154/aluminum-fractionation-in-acidic-soils-and-river-sediments-in-the-upper-mero-basin-galicia-nw-spain
#14
L Palleiro, C Patinha, M L Rodríguez-Blanco, M M Taboada-Castro, M T Taboada-Castro
This study aims to determine aluminum fractions in the fine earth of acidic soils under different land uses (forest, pasture and cultivation) and in the river bed sediments of the headwater of the Mero River in order to identify and quantify Al-bearing phases to assess Al mobility and potential bioavailability (environmental availability) in the monitoring area. Sequential extraction is used to evaluate the Al partitioning into six fractions operationally defined: soluble/exchangeable/specifically adsorbed, bound to manganese oxides, associated with amorphous compounds, aluminum bound to oxidizable organic matter, associated with crystalline iron oxides, and residual fraction (aluminum within the crystal lattices of minerals)...
March 24, 2017: Environmental Geochemistry and Health
https://www.readbyqxmd.com/read/28341676/anaerobic-methane-oxidation-driven-by-microbial-reduction-of-natural-organic-matter-in-a-tropical-wetland
#15
Edgardo I Valenzuela, Alejandra Prieto-Davó, Nguyen E López-Lozano, Alberto Hernández-Eligio, Leticia Vega-Alvarado, Katy Juárez, Ana Sarahí García-González, Mercedes G López, Francisco J Cervantes
Wetlands constitute the main natural source of methane on Earth due to their high content of natural organic matter (NOM), but key drivers such as electron acceptors supporting methanotrophic activities in these habitats are poorly understood. We performed anoxic incubations using freshly collected sediment along with water samples harvested from a tropical wetland, amended with (13)C-methane (0.67 atm) to test the capacity of its microbial community to perform anaerobic methane oxidation (AOM) linked to the reduction of the humic fraction of its NOM...
March 24, 2017: Applied and Environmental Microbiology
https://www.readbyqxmd.com/read/28341594/itraq-based-proteomics-analysis-of-hippocampus-in-spatial-memory-deficiency-rats-induced-by-simulated-microgravity
#16
Tingmei Wang, Hailong Chen, Ke Lv, Guohua Ji, Yongliang Zhang, Yanli Wang, Yinghui Li, Lina Qu
It has been demonstrated that simulated microgravity (SM) may lead to cognitive dysfunction. However, the underlying mechanism remains unclear. In present study, tail-suspension (30°) rat was employed to explore the effects of 28 days of SM on hippocampus-dependent learning and memory capability and the underlying mechanisms. We found that 28-day tail-suspension rats displayed decline of learning and memory ability in Morris water maze (MWM) test. Using iTRAQ-based proteomics analysis, a total of 4774 proteins were quantified in hippocampus...
March 21, 2017: Journal of Proteomics
https://www.readbyqxmd.com/read/28340775/quantification-of-226-ra-at-environmental-relevant-levels-in-natural-waters-by-icp-ms-optimization-validation-and-limitations-of-an-extraction-and-preconcentration-approach
#17
François Lagacé, Delphine Foucher, Céline Surette, Olivier Clarisse
Radium (Ra) at environmental relevant levels in natural waters was determined by ICP-MS after an off-line pre-concentration procedure. The latter consisted of Ra selective elution from potential interfering elements (i.e. other alkaline earth cations: Ba(2+), Sr(2+), Ca(2+), Mg(2+)) on a series of two different ion exchange resins (AG50W-X8 and Sr-resin). The overall analytical method was optimized according to the instrumental performance, the volume of water sample loaded on resins, and the sample salinity...
May 15, 2017: Talanta
https://www.readbyqxmd.com/read/28340528/znfe2o4-nanotapers-slag-assistant-growth-and-enhanced-photoelectrochemical-efficiency
#18
Xuefeng She, Zhuo Zhang
In this study, ZnFe2O4 (ZFO) nanotapers are fabricated on the ZnO nanorods (NRs) by recycling rare-earth oxide (REO) slag as the iron source, which thereby exhibits dramatically enhanced photoelectrochemical (PEC) efficiency. Our studies demonstrate that the electron-hole separation and charge migration can be facilitated by the cascade band alignment of ZFO and ZnO and the branched nanotaper structures. Not only the iron source, the slag particles can also act as the passivation layers, leading to improved electron lifetime and significant PEC enhancement...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28339274/exact-model-of-vacancy-mediated-solute-transport-in-magnesium
#19
Ravi Agarwal, Dallas R Trinkle
Most substitutional solutes in solids diffuse via vacancies. However, widely used analytic models for diffusivity make uncontrolled approximations in the relations between atomic jump rates that reduce accuracy. Symmetry analysis of the hexagonal close packed crystal identifies more distinct vacancy transitions than prior models, and a Green function approach computes diffusivity exactly for solutes in magnesium. We find large differences for the solute drag of Al, Zn, and rare earth solutes, and improved diffusion activation energies-highlighting the need for exact analytic transport models...
March 10, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28339263/electronic-stopping-of-slow-protons-in-transition-and-rare-earth-metals-breakdown-of-the-free-electron-gas-concept
#20
D Roth, B Bruckner, M V Moro, S Gruber, D Goebl, J I Juaristi, M Alducin, R Steinberger, J Duchoslav, D Primetzhofer, P Bauer
The electronic stopping cross sections (SCS) of Ta and Gd for slow protons have been investigated experimentally. The data are compared to the results for Pt and Au to learn how electronic stopping in transition and rare earth metals correlates with features of the electronic band structures. The extraordinarily high SCS observed for protons in Ta and Gd cannot be understood in terms of a free electron gas model, but are related to the high densities of both occupied and unoccupied electronic states in these metals...
March 10, 2017: Physical Review Letters
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