Dissimilar Metal Solution from Solid Alloys as Observed for Steels and Nickel‐Based Alloys in the Presence of Lead‐Based Liquid Alloys or Liquid Tin

The solution of elements from metallic alloys is analyzed, notably the initial stage characterized by solution in proportion to the alloy composition and subsequent selective leaching of alloying elements. For the latter stage of the process, characteristic features of the originating depletion zone are derived for different formation mechanisms. The results are compared with observations for steels and nickel-based alloys after exposure to lead-based liquid alloys or liquid tin, and, where possible, the prevailing mechanism is identified. Furthermore, the influence of dissolved oxygen and formation of intermetallic compounds are addressed.

A Hybrid Landslide Susceptibility Model Obtained from Different Models (Raster or Vector, Expert or Semi-Expert) with the Correct Parameter

This study aims to determine how to choose the correct parameter for a specific study area in landslide susceptibility and how it gives results in vector or raster-based models. In the literature, factor parameters of landslide preparing and triggering conditions are used deliberately or randomly in raster or vector-based models. In this study, the landslide inventory was analyzed together with geological, topographic-morphological, environmental, and triggering parameters, and the parameters specific to the study area and its scale were decided. In order to obtain high efficiency from the models, the parameter data were taken from the landslide depletion zone. Raster-based models and vector-based models were created according to qualitative and quantitative approaches. Model outputs resulted in close Roc Curve results ranging from 0.79 to 0.92. The study area was divided into slope units and then the model output data were transferred to these units. In order to make the result easier to use, the units obtained according to the result of each model were combined, thus a single map output was obtained from 5 different raster and vector-based models. Overall, this study presents 1) the importance of the use of landslide inventory and how to use the inventory. 2) Parameters should be selected according to field analysis and field-scale rather than randomly. 3) By combining raster and vector-based on landslide susceptibility studies, make it easier to use as a base map in hazard and risk studies with a single output.

A comparative geological, tectonic and geomorphological assessment of the Charlotte, Regent and Madina landslides, Western area, Sierra Leone

This work focused on three landslide events that have attracted significant public concern due to the associated calamities they recorded in 1945, 2017 and 2019, i.e. the Charlotte, Regent and Madina landslides, respectively. Their geology, tectonics (structural discontinuities) and geomorphology, i.e. their GTG characteristics were studied to establish links between them and the landslide events.Field surveys were conducted, particularly on the Charlotte landslide, where the identification of geological structures was impeded to an extent by its obliteration by vegetation and sediment accumulations on relatively planar sections of the landslide area. Remote sensing and GIS techniques (earth imagery and drone images) enhanced the mapping and determination of landslides’ geometric and geomorphic parameters. Laboratory analyses of rock and soil samples provided the landslides’ petrological characterisation and were used to determine the particle-size distribution in the slide-prone soil.The study indicated a change in the gabbroic rock composition, variable geomorphological characteristics, and nature/pattern and density of the discontinuities. These factors, to a large extent, determined the nature and magnitude of the rainfall-triggered landslides. Charlotte lithology slightly differed from the other two landslides and recorded higher Silica (Si) and Aluminum (Al) and lower iron (Fe) from X-Ray Fluorescence (XRF) than rocks of Regent and Madina landslides. The study also revealed only a tenuous correlation between rock composition and weathering depth. The slope angles at the landslides’ prominent scarps (depletion zone) are steep (> 45 degrees) with altitudes of approximately 270 m, 200 m and 470 m above sea level for Charlotte, Regent and Madina, respectively. Unlike the Charlotte landslide, both Regent and Madina landslides are active, but geometrically, their area, length and run-out distances have relatively high variance with a coefficient of variance equals to 1. Information derived from this work can help understand the spatial variation in landslide characteristics and develop a susceptibility map.

Ultra-Fast, Pad-Scale Modeling of Hydraulic Fracturing and Depletion for Optimizing Development Plans in the Eagle Ford Play

As the number of wells drilled in regions with existing producing wells increases, understanding the detrimental impact of these by the depleted zone around parent wells becomes more urgent and important. This understanding should include being able to predict the extent and heterogeneity of the depleted region near the pre-existing wells, the resulting altered stress field, and the effect of this on newly created fractures from adjacent child wells. In this paper we present a workflow that addresses the above concern in the Eagle Ford shale play, using numerical simulations of fracturing and reservoir flow, to define the effect of the depletion zone on child wells and match their field production data. We utilize an ultra-fast hydraulic fracture and depletion model to conduct several hundred numerical simulations, with varying values of permeability and surface area, seeking for cases that match the field production data. Multiple solutions exist that match the field data equally well, and we used additional field production data of parent-child well-interaction, to select the most plausible model. Results show that the depletion zone is strongly non-uniform and that large reservoir regions remain undepleted. We observe two important effects of the depleted zone on fractures from child wells drilled adjacent to the parents. Some fractures propagate towards low pressure zones and do not contribute to production. Others are repelled by the higher stress region that develops around the depletion zone, propagate into undepleted rock, and have production rates commensurate to that from other child wells drilled away from depleted region. The observations are validated by the field data. Results are being used to optimize well placement and well spacing for subsequent field operations, with the objective to increase the effectiveness of the child wells.

Effects of Ti-bearing inclusions on intragranular ferrite nucleation

The effect of Ti-bearing inclusion characteristics, such as size and marginal composition, on intragranular ferrite (IGF) nucleation has been explored in single sample through SEM and EDS. It can be seen that Ti-bearing inclusions can induce IGF nucleation, and this nucleation ability was scaled by the number of its induced lathes. Statistical analysis suggested that this ability may be correlated with inclusion size, and independent of Ti2O3 content in inclusion. The former can be attributed to the classical theory of heterogeneous nucleation. The latter can be explained by the relationship between the diffusion quantity of Mn and its solubility in Ti2O3 based on the theory of an Mn-depletion zone. Moreover, a probabilistic feature was observed in the nucleation phenomenon which may be due to a small difference in formation energy between the ferrite side plate and the IGF. These results may be helpful to clarify the nature of oxide metallurgy of a Ti-bearing inclusion.

An expanding bacterial colony forms a depletion zone with growing droplets

Bacterial droplets formed in a depletion zone following its spread over a large agar plate.

The impact of geometrical confinement in a slab on the behavior of tracer particles near active glucose oxidase micropump

Patches of surface-immobilized and catalytically active enzyme, immersed into a solution with the corresponding substrate, induce flow in the solution. Such systems are currently investigated as a promising direction in the development of self-powered micropumps that could operate autonomously within microfluidic devices. Here, we investigate the influence of confinement, within a slab of height H, on the response exhibited by silica tracer particles sedimented near a chemically active glucose oxidase patch which is immersed into a glucose solution of very low ionic strength. Irrespective of the value H, within the range explored in this study, a region depleted of tracers forms around the patch. When H is not much larger than the radius of the patch, the rate of growth of the depletion zone depends on H; somewhat surprisingly, this dependence is influenced by the glucose concentration. The results are discussed within the context of a simple model for a chemically active patch.

An expanding bacterial colony forms a depletion zone with growing droplets

Many species of bacteria have developed means to spread on solid surfaces. This study focuses on the expansion of Pseudomonas aeruginosa on an agar gel surface. We report the occurrence and spread of a depletion zone, where the layer of bacteria on the agar becoming thinner. The depletion zone occurs within an expanded colony under conditions of minimal water evaporation. It is colocalized with a higher concentration of rhamnolipids, the biosurfactants that are produced by the bacteria and accumulate in the older region of the colony. With continued growth in bacterial population, dense droplets occur and coalesce in the depletion zone, displaying remarkable fluid dynamic behavior. Whereas expansion of a central depletion zone requires activities of live bacteria, new zones can be seeded by adding rhamnolipids. These depletion zones due to the added surfactants expand quickly, even on plates covered by bacteria that have been killed by ultraviolet light. We propose a model to account for the observed properties, taking into consideration bacterial growth and secretion, osmotic swelling, fluid volume expansion, cell-cell interaction, and interfacial fluid dynamics involving Marangoni flow.SignificanceBacterial growth and pattern formation have strong bearing on their biological functions, such as their spread and accumulation, biofilm growth & its effects on infection and antibiotic resistance. The bacterial species of this study, Pseudomonas aeruginosa, is a human pathogen responsible for frequent infections in wounds, airways, and urinary tract, particularly when involving the use of catheters. The findings of this study and the mechanisms we propose offer new insights on the important behaviors of bacterial collective motility, pattern dynamics, and biofilm growth.