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The geographic distribution of streams and rivers drives a multitude of patterns and processes in hydrology, geomorphology, geography, and ecology. Therefore, a hydrographic network that accurately delineates both small streams and large rivers, along with their topographic and topological properties, with equal precision would be indispensable in the earth sciences. Currently, available global hydrographies do not feature small headwater streams in great detail. However, these headwaters are vital because they are estimated to contribute to more than 70 % of overall stream length. We aimed to fill this gap by using the MERIT Hydro digital elevation model at 3 arcsec (∼90 m at the Equator) to derive a globally seamless, standardised hydrographic network, the “Hydrography90m”, with corresponding stream topographic and topological information. A central feature of the network is the minimal upstream contributing area, i.e. flow accumulation, of 0.05 km2 (or 5 ha) to initiate a stream channel, which allowed us to extract headwater stream channels in great detail. By employing a suite of GRASS GIS hydrological modules, we calculated the range-wide upstream flow accumulation and flow direction to delineate a total of 1.6 million drainage basins and extracted globally a total of 726 million unique stream segments with their corresponding sub-catchments. In addition, we computed stream topographic variables comprising stream slope, gradient, length, and curvature attributes as well as stream topological variables to allow for network routing and various stream order classifications. We validated the spatial accuracy and flow accumulation of Hydrography90m against NHDPlus HR, an independent, national high-resolution hydrographic network dataset of the United States. Our validation shows that the newly developed Hydrography90m has the highest spatial precision and contains more headwater stream channels compared to three other global hydrographic datasets. This comprehensive approach provides a vital and long-overdue baseline for assessing actual streamflow in headwaters and opens new research avenues for high-resolution studies of surface water worldwide. Hydrography90m thus offers significant potential to facilitate the assessment of freshwater quantity and quality, inundation risk, biodiversity, conservation, and resource management objectives in a globally comprehensive and standardised manner. The Hydrography90m layers are available at https://doi.org/10.18728/igb-fred-762.1 (Amatulli et al., 2022a), and while they can be used directly in standard GIS applications, we recommend the seamless integration with hydrological modules in open-source QGIS and GRASS GIS software to further customise the data and derive optimal utility from it.

Abstract Earthquakes induced during hydraulic fracturing operations have occurred in a number of locales. However, in situ studies aimed to discern the triggering mechanism remain exclusively statistical in their nature. Here we calculate the fault slip tendencies of 11 hydraulic fracturing induced earthquakes in a historically aseismic area using a recently constructed quantitative model for the in‐situ stresses. It is shown that the ambient pore pressures of the nearby Duvernay unconventional reservoirs can provide enough ΔPf triggering fault movement. The local fluid pressures acting on the fault could readily be increased above the critical value if hydraulic connection exists between the fault and a propagating hydraulic fracture. The critical pressures necessary to induce slip are estimated using a probabilistic model that incorporates uncertainties of stress and fault's mechanical properties. These critical pressures are greater than the expected hydrostatic pressure but less the pore pressures of nearby unconventional reservoirs.

Metallic glasses deform along nanoscale shear bands, and while it is known that they affect the neighboring glass regions, exactly how is unclear. Here, the authors use magnetic force microscopy to atomically resolve the shear-band affected zone and show its effects extends much further than previously thought.

Using an ultrafast laser pulse as a substitution of continuous-wave laser to excite a magnetic film leads to high spin temperature and fast demagnetization, beneficial to the rapid and efficient photo-assisted magnetization (M) reversal. Here, ultrafast laser induced M reversal in perpendicular magnetic anisotropy L10 FePt films with different chemical ordering parameter (from S0.9) was investigated using magneto-optical Kerr effect (MOKE). It was found that the coercive field (Hc) without laser excitation increases from ∼0.8 to ∼4 kOe with increasing S, but Hc becomes smaller for enhanced laser fluence (F) and reaches an analogous small value of ∼0.2 kOe for F>12 mJ cm-2. Despite such a significant softening in films with high S, the laser induced M reversal rate is slightly less than 1 even for the applied field (H) much larger than 0.2 kOe. This reveals a small portion of spins are photo inactively pinned, as confirmed by magnetic force microscopy measurements. Such pinning sites may be reduced with improved chemical order and morphology. We also found an approximately inverse linear relation between the H and the corresponding threshold F to induce the M reversal in the film of high S, which can be described by an ultrafast thermal activated spin flip model.

Magnetic skyrmions might be used for building next-generation nanomagnetic and spintronic devices, as they have several perspective properties, such as topologically protected stability, nanoscale size, and ultra-low depinning current density. Here we study the influence of the edge effect on the current-induced generation of a magnetic skyrmion in a finite-length thin-film ferromagnetic nanotrack with interface-induced Dzyaloshinskii-Moriya interaction. It shows that a stable skyrmion or a bunch of skyrmions can be successfully generated as long as the distance between the current injection region and the nanotrack terminal is larger than a certain threshold. We investigate the failed skyrmion generation caused by the edge effect, which will lead to an error writing event. We also present the phase diagrams of the skyrmion generation obtained for different material and geometric parameters. Our results could be useful for designing skyrmion-based information storage devices.

A series of plate impact shock-reshock and shock-release experiments were conducted by using an one-stage light gas gun to determine the critical shear strength of the 2024 aluminum alloy under shock compression levels ranging from 0.66 to 3.05 GPa in the present study. In the experiments, a dual flyer plate assembly, i.e., the 2024 aluminum alloy flyer backed either by a brass plate or a PMMA plate, was utilized to produce reshock or release wave. The stress profiles of uniaxial plane strain wave propagation in the 2024 aluminum alloy sample under different pre-compressed states were measured by the embedded stress gauges. The stress-strain data at corresponding states were then calculated by a Lagrangian analysis method named as path line method. The critical shear strengths at different stress levels were finally obtained by self-consistent method. The results show that, at the low shock compression level (0.66 to 3.05 GPa), the critical shear strength of the 2024 aluminum alloy cannot be ignored and increases with the increasing longitudinal stress, which may be attributed to rate-dependence and/or pressure dependent yield behavior of the 2024 aluminum alloy.

This paper investigates the existence and uniqueness of mild solutions to the general nonlinear stochastic impulsive differential equations. By using Schaefer's fixed theorem and stochastic analysis technique, we propose sufficient conditions on existence and uniqueness of solution for stochastic differential equations with impulses. An example is also discussed to illustrate the effectiveness of the obtained results.