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Hydrothermal (NN)-N-15-N-15 abundances constrain the origins of mantle nitrogen 期刊论文
NATURE, 2020, 580 (7803) : 367-+
作者:  Zhao, Steven;  Jang, Cholsoon;  Liu, Joyce;  Uehara, Kahealani;  Gilbert, Michael;  Izzo, Luke;  Zeng, Xianfeng;  Trefely, Sophie;  Fernandez, Sully;  Carrer, Alessandro;  Miller, Katelyn D.;  Schug, Zachary T.;  Snyder, Nathaniel W.;  Gade, Terence P.;  Titchenell, Paul M.;  Rabinowitz, Joshua D.;  Wellen, Kathryn E.
收藏  |  浏览/下载：14/0  |  提交时间：2020/05/13

Nitrogen is the main constituent of the Earth'  s atmosphere, but its provenance in the Earth'  s mantle remains uncertain. The relative contribution of primordial nitrogen inherited during the Earth'  s accretion versus that subducted from the Earth'  s surface is unclear(1-6). Here we show that the mantle may have retained remnants of such primordial nitrogen. We use the rare (NN)-N-15-N-15 isotopologue of N-2 as a new tracer of air contamination in volcanic gas effusions. By constraining air contamination in gases from Iceland, Eifel (Germany) and Yellowstone (USA), we derive estimates of mantle delta N-15 (the fractional difference in N-15/N-14 from air), N-2/Ar-36 and N-2/He-3. Our results show that negative delta N-15 values observed in gases, previously regarded as indicating a mantle origin for nitrogen(7-10), in fact represent dominantly air-derived N-2 that experienced N-15/N-14 fractionation in hydrothermal systems. Using two-component mixing models to correct for this effect, the (NN)-N-15-N-15 data allow extrapolations that characterize mantle endmember delta N-15, N-2/Ar-36 and N-2/He-3 values. We show that the Eifel region has slightly increased delta N-15 and N-2/Ar-36 values relative to estimates for the convective mantle provided by mid-ocean-ridge basalts(11), consistent with subducted nitrogen being added to the mantle source. In contrast, we find that whereas the Yellowstone plume has delta N-15 values substantially greater than that of the convective mantle, resembling surface components(12-15), its N-2/Ar-36 and N-2/He-3 ratios are indistinguishable from those of the convective mantle. This observation raises the possibility that the plume hosts a primordial component. We provide a test of the subduction hypothesis with a two-box model, describing the evolution of mantle and surface nitrogen through geological time. We show that the effect of subduction on the deep nitrogen cycle may be less important than has been suggested by previous investigations. We propose instead that high mid-ocean-ridge basalt and plume delta N-15 values may both be dominantly primordial features.


  
Wafer-scale single-crystal hexagonal boron nitride monolayers on Cu (111) 期刊论文
NATURE, 2020, 579 (7798) : 219-+
作者:  Luong, Duy X.;  Bets, Ksenia V.;  Algozeeb, Wala Ali;  Stanford, Michael G.;  Kittrell, Carter;  Chen, Weiyin;  Salvatierra, Rodrigo V.;  Ren, Muqing;  McHugh, Emily A.;  Advincula, Paul A.;  Wang, Zhe;  Bhatt, Mahesh;  Guo, Hua;  Mancevski, Vladimir;  Shahsavari, Rouzbeh
收藏  |  浏览/下载：80/0  |  提交时间：2020/07/03

Ultrathin two-dimensional (2D) semiconducting layered materials offer great potential for extending Moore'  s law of the number of transistors in an integrated circuit(1). One key challenge with 2D semiconductors is to avoid the formation of charge scattering and trap sites from adjacent dielectrics. An insulating van der Waals layer of hexagonal boron nitride (hBN) provides an excellent interface dielectric, efficiently reducing charge scattering(2,3). Recent studies have shown the growth of single-crystal hBN films on molten gold surfaces(4) or bulk copper foils(5). However, the use of molten gold is not favoured by industry, owing to its high cost, cross-contamination and potential issues of process control and scalability. Copper foils might be suitable for roll-to-roll processes, but are unlikely to be compatible with advanced microelectronic fabrication on wafers. Thus, a reliable way of growing single-crystal hBN films directly on wafers would contribute to the broad adoption of 2D layered materials in industry. Previous attempts to grow hBN monolayers on Cu (111) metals have failed to achieve mono-orientation, resulting in unwanted grain boundaries when the layers merge into films(6,7). Growing single-crystal hBN on such high-symmetry surface planes as Cu (111)(5,8) is widely believed to be impossible, even in theory. Nonetheless, here we report the successful epitaxial growth of single-crystal hBN monolayers on a Cu (111) thin film across a two-inch c-plane sapphire wafer. This surprising result is corroborated by our first-principles calculations, suggesting that the epitaxial growth is enhanced by lateral docking of hBN to Cu (111) steps, ensuring the mono-orientation of hBN monolayers. The obtained single-crystal hBN, incorporated as an interface layer between molybdenum disulfide and hafnium dioxide in a bottom-gate configuration, enhanced the electrical performance of transistors. This reliable approach to producing wafer-scale single-crystal hBN paves the way to future 2D electronics.


  
Exact Upscaling for Transport of Size-Distributed Colloids 期刊论文
WATER RESOURCES RESEARCH, 2019, 55 (2) : 1011-1039
作者:  Bedrikovetsky, P.;  Osipov, Y.;  Kuzmina, L.;  Malgaresi, G.
收藏  |  浏览/下载：4/0  |  提交时间：2019/11/26
upscaling  averaging  exact averaging of suspension-colloidal and reactive transport with distributed particle properties  reactive transport  exact solutions for 1-D reactive or colloidal flow for the upscaled system  aquifer contamination  
Decadal Delays in Groundwater Recovery from Nitrate Contamination Caused by Low O-2 Reduction Rates 期刊论文
WATER RESOURCES RESEARCH, 2018, 54 (12) : 9996-10012
作者:  Wild, Lisa M.;  Mayer, Bernhard;  Einsiedl, Florian
收藏  |  浏览/下载：10/0  |  提交时间：2019/04/09
mean transit time (MTT)  15N  O-2 reduction rate  denitrification  nitrate contamination  
Monitoring Stray Natural Gas in Groundwater With Dissolved Nitrogen. An Example From Parker County, Texas 期刊论文
WATER RESOURCES RESEARCH, 2018, 54 (9) : 6024-6041
作者:  Larson, Toti E.;  Nicot, Jean-Philippe;  Mickler, Patrick;  Castro, M. Clara;  Darvari, Roxana;  Wen, Tao;  Hall, Chris M.
收藏  |  浏览/下载：11/0  |  提交时间：2019/04/09
methane  groundwater  dissolved gas  hydraulic fracturing  natural gas  contamination  
The effect of site- and landscape-scale factors on lead contamination of leafy vegetables grown in urban gardens 期刊论文
LANDSCAPE AND URBAN PLANNING, 2018, 177: 38-46
作者:  Sung, Chan Yong;  Park, Cheon-Bo
收藏  |  浏览/下载：4/0  |  提交时间：2019/04/09
Urban gardener survey  Perceived food safety  Lead contamination sources  Gardens in industrial areas  Soil lead contamination  
Geophysics-Based Contaminant Mass Discharge Quantification Downgradient of a Landfill and a Former Pharmaceutical Factory 期刊论文
WATER RESOURCES RESEARCH, 2018, 54 (8) : 5436-5456
作者:  Balbarini, Nicola;  Ronde, Vinni;  Maurya, Pradip;  Fiandaca, Gianluca;  Moller, Ingelise;  Klint, Knud Erik;  Christiansen, Anders V.;  Binning, Philip J.;  Bjerg, Poul L.
收藏  |  浏览/下载：6/0  |  提交时间：2019/04/09
contaminant mass discharge  direct current resistivity  induced polarization  risk assessment  uncertainty  groundwater contamination  
Constructed soils for mitigating lead (Pb) exposure and promoting urban community gardening: The New York City Clean Soil Bank pilot study 期刊论文
LANDSCAPE AND URBAN PLANNING, 2018, 175: 184-194
作者:  Egendorf, Sara Perl;  Cheng, Zhongqi;  Deeb, Maha;  Flores, Victor;  Paltseva, Anna;  Walsh, Daniel;  Groffman, Peter;  Mielke, Howard W.
收藏  |  浏览/下载：4/0  |  提交时间：2019/04/09
Compost  Contamination  Glacial sediments  Manufactured soil  Technosol  Urban agriculture  
Automatic Correction of Contaminated Images for Assessment of Reservoir Surface Area Dynamics 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2018, 45 (12) : 6092-6099
作者:  Zhao, Gang;  Gao, Huilin
收藏  |  浏览/下载：4/0  |  提交时间：2019/04/09
Landsat  reservoir area  contamination  image enhancement  Google Earth Engine  
Impact of an historic underground gas well blowout on the current methane chemistry in a shallow groundwater system 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2018, 115 (2) : 296-301
作者:  Schout, Gilian;  Hartog, Niels;  Hassanizadeh, S. Majid;  Griffioen, Jasper
收藏  |  浏览/下载：7/0  |  提交时间：2019/11/27
groundwater contamination  well blowouts  methane  isotopic fingerprinting  anaerobic methane oxidation