The interaction between groundwater and surface water along the Tambo and Nicholson rivers, southeast Australia, was investigated using super(222)Rn, Cl, differential flow gauging, head gradients, ...electrical conductivity (EC) and temperature profiles. Head gradients, temperature profiles, Cl concentrations and super(222)Rn activities all indicate higher groundwater fluxes to the Tambo River in areas of increased topographic variation where the potential to form large groundwater-surface water gradients is greater. Groundwater discharge to the Tambo River calculated by Cl mass balance was significantly lower (1.48 x 10 super(4) to 1.41 x 10 super(3) m super(3) day super(-1)) than discharge estimated by super(222)Rn mass balance (5.35 x 10 super(5) to 9.56 x 10 super(3) m super(3) day super(-1)) and differential flow gauging (5.41 x 10 super(5) to 6.30 x 10 super(3) m super(3) day super(-1)) due to bank return waters. While groundwater sampling from the bank of the Tambo River was intended to account for changes in groundwater chemistry associated with bank infiltration, variations in bank infiltration between sample sites remain unaccounted for, limiting the use of Cl as an effective tracer. Groundwater discharge to both the Tambo and Nicholson rivers was the highest under high-flow conditions in the days to weeks following significant rainfall, indicating that the rivers are well connected to a groundwater system that is responsive to rainfall. Groundwater constituted the lowest proportion of river discharge during times of increased rainfall that followed dry periods, while groundwater constituted the highest proportion of river discharge under baseflow conditions (21.4% of the Tambo in April 2010 and 18.9% of the Nicholson in September 2010).
Soil moisture and temperature are some of the most important controls for a wide variety of geochemical and ecological processes in the vadose zone (VZ). Soil moisture is highly variable both ...spatially and temporally. The development of methods to measure it on various scales has been the subject of much activity. Recently, geoscientists have been increasingly interested in measuring temperature as a proxy for hydrologic properties and parameters, including soil moisture. Here, we discuss the motivation, primary concepts, equipment, and fundamental thermal and hydraulic models related to heat and water transport in variably saturated porous media. A large variety of methods for heat tracing, including both passive and active-heating methodologies, are detailed. Heat tracing methods offer the capacity to measure soil moisture on a scale from ~1cm up to several km using temperature, a parameter whose measurement in VZ studies is often required anyway due to its effect on many subsurface processes. Furthermore, heat-tracing methods are not affected by high salinity pore water that can limit electromagnetic soil moisture methods. We also review coupled thermo-hydro VZ modelling software and VZ thermal regime studies and identify several knowledge gaps. With the intention to serve as an introduction to VZ heat-tracing, this review consolidates recent advances and outlines potential themes for future research.
•Heat-tracing opens new possibilities for vadose zone studies.•Temperature measurements can be used in several ways to estimate soil moisture content.•A comprehensive review of passive and active-heating method developments is presented.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The growth of electrodeposited lithium microstructures on metallic lithium electrodes has prevented their use in rechargeable lithium batteries due to early performance degradation and safety ...implications. Understanding the evolution of lithium microstructures during battery operation is crucial for the development of an effective and safe rechargeable lithium-metal battery. This study employs both synchrotron and laboratory X-ray computed tomography to investigate the morphological evolution of the surface of metallic lithium electrodes during a single cell discharge and over numerous cycles, respectively. The formation of surface pits and the growth of mossy lithium deposits through the separator layer are characterised in three-dimensions. This has provided insight into the microstructural evolution of lithium-metal electrodes during rechargeable battery operation, and further understanding of the importance of separator architecture in mitigating lithium dendrite growth.
The growth of dendritic and mossy deposits through the separator of lithium batteries can result in battery short circuiting and failure.
In situ
X-ray CT provides insight into evolution of lithium-metal electrodes during battery operation.
Defects in strongly correlated materials such as V
2
O
3
play influential roles on their electrical properties. Understanding the defects' structure is of paramount importance. In this project, we ...investigate defect structures in V
2
O
3
grown
via
a flux method. We use AFM to see surface features in several large flake-like particles that exhibit characteristics of spiral growth. We also use Bragg coherent diffractive imaging (BCDI) to probe in 3 dimensions a smaller particle without flake-like morphology and note an absence of the pure screw dislocation characteristic of spiral growth. We identified and measured several defects by comparing the observed local displacement of the crystal, measured
via
BCDI to well-known models of the displacement around defects in the crystal. We identified two
partial dislocations in the crystal. We discuss how defects of different types influence the morphology of V
2
O
3
crystals grown
via
a flux method.
Here, Fohtung and colleagues capture nanoscale three-dimensional defects in vanadium(
iii
) oxide nanocrystals using X-ray Bragg coherent diffractive imaging.
Stars form by accreting material from their surrounding disks. There is a consensus that matter flowing through the disk is channelled onto the stellar surface by the stellar magnetic field. This is ...thought to be strong enough to truncate the disk close to the corotation radius, at which the disk rotates at the same rate as the star. Spectro-interferometric studies in young stellar objects show that hydrogen emission (a well known tracer of accretion activity) mostly comes from a region a few milliarcseconds across, usually located within the dust sublimation radius.sup.1-3. The origin of the hydrogen emission could be the stellar magnetosphere, a rotating wind or a disk. In the case of intermediate-mass Herbig AeBe stars, the fact that Brackett gamma (Brgamma) emission is spatially resolved rules out the possibility that most of the emission comes from the magnetosphere.sup.4-6 because the weak magnetic fields (some tenths of a gauss) detected in these sources.sup.7,8 result in very compact magnetospheres. In the case of T Tauri sources, their larger magnetospheres should make them easier to resolve. The small angular size of the magnetosphere (a few tenths of a milliarcsecond), however, along with the presence of winds.sup.9,10 make the interpretation of the observations challenging. Here we report optical long-baseline interferometric observations that spatially resolve the inner disk of the T Tauri star TW Hydrae. We find that the near-infrared hydrogen emission comes from a region approximately 3.5 stellar radii across. This region is within the continuum dusty disk emitting region (7 stellar radii across) and also within the corotation radius, which is twice as big. This indicates that the hydrogen emission originates in the accretion columns (funnel flows of matter accreting onto the star), as expected in magnetospheric accretion models, rather than in a wind emitted at much larger distance (more than one astronomical unit).
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FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Thermal dispersion, caused by fluid velocity and temperature fluctuations in the pore space and the effects of hydrodynamic mixing on the temperature field, controls convective heat transport in ...saturated porous media. While the thermal dispersion coefficient, a governing parameter in the thermal equilibrium model (TEM), has been investigated for natural systems, the dependence of the thermal dispersion coefficient on particle size remains undetermined. Previous research found that the relationship between the thermal dispersion coefficient and flow velocity follows a power law and that there may be a temperature difference between the solid and fluid phase (thermal non-equilibrium). However, experiments are limited to discrete particle sizes and comparison of the dispersion-velocity relationship is impeded by different experimental approaches. We conducted a series of separate heat and solute transport experiments in a column filled with uniform porous media consisting of different sized glass spheres for a range of flow velocities. The thermal and solute dispersion coefficients obtained from experimental measurements were correlated with flow velocities through the thermal or solute Péclet number. Our results demonstrate that, while solute dispersion is independent of particle size, the dependence of the TEM based thermal dispersion coefficient on flow rates is influenced by the particle size. This is caused by the fact that, unlike solute transport, heat exchanges between fluid and particles and that this induces thermal non-equilibrium between both phases. The results have significant implications for quantifying forced convective heat transport in natural porous media because thermal non-equilibrium between the phases is not considered. The porous media particle size must be considered when selecting appropriate values for the thermal dispersion coefficient.
•We evaluate how the thermal dispersion coefficient in a thermal equilibrium model will depend on the particle.•Solute experiments confirm that the solid-to-fluid heat transfer efficiency decreases as the particle size increases.•Thermal dispersion coefficient must reflect the particle size when the thermal equilibrium heat transport model is used.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Using microcalorimetry, we follow changes in the association free energy of β-cyclodextrin (CD) with the hydrophobic part of adamantane carboxylate (AD) due to added salt or polar (net-neutral) ...solutes that are excluded from the molecular interacting surfaces. Changes in binding constants with solution osmotic pressure (water activity) translate into changes in the preferential hydration upon complex formation. We find that these changes correspond to a release of 15−25 solute-excluding waters upon CD/AD association. Reflecting the preferential interaction of solute with reactants versus products, we find that changes in hydration depend on the type of solute used. All solutes used here result in a large change in the enthalpy of the CD−AD binding reaction. In one class of solutes, the corresponding entropy change is much smaller, while in the other class, the entropy change almost fully compensates the solute-specific enthalpy. For many of the solutes, the number of waters released correlates well with their effect on air−water surface tensions. We corroborate these results using vapor pressure osmometry to probe individually the hydration of reactants and products of association, and we discuss the possible interactions and forces between cosolute and hydrophobic surfaces responsible for different kinds of solute exclusion.
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IJS, KILJ, NUK, PNG, UL, UM
Understanding and manipulation of the forces assembling DNA/RNA helices have broad implications for biology, medicine, and physics. One subject of significance is the attractive force between dsDNA ...mediated by polycations of valence ≥3. Despite extensive studies, the physical origin of the "like-charge attraction" remains unsettled among competing theories. Here we show that triple-strand DNA (tsDNA), a more highly charged helix than dsDNA, is precipitated by alkaline-earth divalent cations that are unable to condense dsDNA. We further show that our observation is general by examining several cations (Mg²⁺, Ba²⁺, and Ca²⁺) and two distinct tsDNA constructs. Cation-condensed tsDNA forms ordered hexagonal arrays that redissolve upon adding monovalent salts. Forces between tsDNA helices, measured by osmotic stress, follow the form of hydration forces observed with condensed dsDNA. Probing a well-defined system of point-like cations and tsDNAs with more evenly spaced helical charges, the counterintutive observation that the more highly charged tsDNA (vs. dsDNA) is condensed by cations of lower valence provides new insights into theories of polyelectrolytes and the biological and pathological roles of tsDNA. Cations and tsDNAs also hold promise as a model system for future studies of DNA—DNA interactions and electrostatic interactions in general.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Hard X‐ray microscopy is a prominent tool suitable for nanoscale‐resolution non‐destructive imaging of various materials used in different areas of science and technology. With an ongoing effort to ...push the 2D/3D imaging resolution down to 10 nm in the hard X‐ray regime, both the fabrication of nano‐focusing optics and the stability of the microscope using those optics become extremely challenging. In this work a microscopy system designed and constructed to accommodate multilayer Laue lenses as nanofocusing optics is presented. The developed apparatus has been thoroughly characterized in terms of resolution and stability followed by imaging experiments at a synchrotron facility. Drift rates of ∼2 nm h−1 accompanied by 13 nm × 33 nm imaging resolution at 11.8 keV are reported.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
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