More Like this

1. Comparing in-situ and ex-situ stress measurements in polymineralic rocks

   Goddard, Rellie; Hansen, Lars N.; Wallis, David; Stipp, Michael; Holyoke, Caleb W.; Kohlstedt, David L.; Goldsby, David L.; Durham, William B.; Kumamoto, Kathryn M.; Thom, Christopher (December 2018, American Geophysical Union Fall Meeting)

   Constraints on the state of stress in the lithosphere are fundamental to understanding a breadth of geological phenomena. Paleo-stresses are generally estimated using microstructural elements for which there are experimentally calibrated relationships with applied stress, with an emphasis on recrystallised grain-size piezometers. However, it is often difficult to clearly distinguish newly recrystallised grains from the relict matrix. Furthermore, these grain-size piezometers are only applicable to rocks consisting of a single mineral. An alternative proxy for paleo-stress in polymineralic rocks is the average subgrain size. Unfortunately, estimates of subgrain size differ significantly among different measurement methods, and therefore, piezometers must be individually calibrated for the method used. Existing subgrain-size piezometers are based on calibrations using optical or transmission electron microscopy. We use electron backscatter diffraction (EBSD), a common method of subgrain-boundary characterisation, to calibrate subgrain-size piezometers for both olivine and quartz. To test the application of our olivine subgrain-size piezometer to polymineralic rocks, we deformed synthetic mixtures of olivine and orthopyroxene. Experiments were conducted using a Deformation-DIA apparatus at beamline 6BM-B Advanced Photon Source, Argonne National Laboratory. These experiments offer the unique possibility of simultaneously deforming the sample and measuring the average stresses within each phase using X-ray diffraction, before applying subgrain-size piezometry to the recovered samples. The results provide tests of (1) the manner in which stress is partitioned between phases, (2) whether the stresses measured in each phase by X-ray diffraction are comparable to those estimated by subgrain-size piezometry, and (3) whether stresses from subgrain piezometry can be used to estimate the macroscopic average applied stress. Stresses estimated from X-ray diffraction agree well with those made from subgrain-size piezometry in both monomineralic and polymineralic samples. In harzburgites, average stresses are similar in both phases and indicate that in this system, subgrain-size piezometric measurements from a single phase can be used to estimate the bulk stress. 

   more » « less
2. In situ and ex situ processes for synthesizing metal multilayers with electronically conductive interfaces

   https://doi.org/10.1063/5.0084573  

   Angeles, Frank; Shi, Xinping; Wilson, Richard B. (June 2022, Journal of Applied Physics)

   A number of technological applications and scientific experiments require processes for preparing metal multilayers with electronically and thermally conductive interfaces. We investigate how in situ vs ex situ synthesis processes affect the thermal conductance of metal/metal interfaces. We use time-domain thermoreflectance experiments to study thermal transport in Au/Fe, Al/Cu, and Cu/Pt bilayer samples. We quantify the effect of exposing the bottom metal layer to an ambient environment prior to deposition of the top metal layer. We observe that for Au/Fe, exposure of the Fe layer to air before depositing the top Au layer significantly impedes interfacial electronic currents. Exposing Cu to air prior to depositing an Al layer effectively eliminates interfacial electronic heat currents between the two metal layers. Exposure to air appears to have no effect on interfacial transport in the Cu/Pt system. Finally, we show that a short RF sputter etch of the bottom layer surface is sufficient to ensure a thermally and electronically conductive metal/metal interface in all materials we study. We analyze our results with a two-temperature model and bound the electronic interface conductance for the nine samples we study. Our findings have applications for thin-film synthesis and advance fundamental understanding of electronic thermal conductance at different types of interfaces between metals. 

   more » « less
3. Nitrification in a Subterranean Estuary: An Ex Situ and In Situ Method Comparison Determines Nitrate Is Available for Discharge

   https://doi.org/10.1029/2023JG007876  

   Wilson, Stephanie_J; Song, Bongkeun; Anderson, Iris_C; Tobias, Craig_R (June 2024, Journal of Geophysical Research: Biogeosciences)

   Abstract Subterranean estuaries (STEs) form in the subsurface where fresh groundwater and seawater meet and mix. Subterranean estuaries support a variety of biogeochemical processes including those transforming nitrogen (N). Groundwater is often enriched with dissolved inorganic nitrogen (DIN), and transformations in the STE determine the fate of that DIN, which may be discharged to coastal waters. Nitrification oxidizes ammonium (NH₄⁺) to nitrate, making DIN available for N removal via denitrification. We measured nitrification at an STE, in Virginia, USA using in situ and ex situ methods including conservative mixing models informed by in situ geochemical profiles, an in situ experiment with¹⁵NH₄⁺tracer injection, and ex situ sediment slurry incubations with¹⁵NH₄⁺tracer addition. All methods indicated nitrification in the STE, but the ex situ sediment slurries revealed higher rates than both the in situ tracr experiment and mixing model estimations. Nitrification rates ranged 55.0–183.16 μmol N m⁻² d⁻¹based on mixing models, 94.2–225 μmol N m⁻² d⁻¹in the in situ tracer experiment, and 36.6–109 μmol N m⁻² d⁻¹slurry incubations. The in situ tracer experiment revealed higher rates and spatial variation not captured by the other methods. The geochemical complexity of the STE makes it difficult to replicate in situ conditions with incubations and calculations based on chemical profiles integrate over longer timescales, therefore, in situ approaches may best quantify transformation rates. Our data suggest that STE nitrification produces NO₃⁻, altering the DIN pool discharged to overlying water via submarine groundwater discharge. 

   more » « less
4. Electrospray synthesis and in-situ sizing of nanoparticulate CsH2PO4

   https://doi.org/10.1080/02786826.2023.2279528  

   Varga, Áron; Downard, Andrew J.; Evoen, Vanessa; Giapis, Konstantinos P.; Flagan, Richard C.; Haile, Sossina M. (January 2024, Aerosol Science and Technology)
5. Portable and Composable Flow Graphs for In Situ Analytics

   https://doi.org/10.1109/LDAV53230.2021.00014  

   Shudler, Sergei; Petruzza, Steve; Pascucci, Valerio; Bremer, Peer-Timo (October 2021, IEEE Symposium on Large Data Analysis and Visualization (LDAV) 2021)