A First-Principles Study of Gas Molecule Adsorption on Carbon-, Nitrogen-, and Oxygen-Doped Two-Dimensional Borophene

A first-principles study was performed to investigate the adsorption properties of gas molecules (CO, CO2, NO, and NO2) on carbon- (C-), nitrogen- (N-), and oxygen-doped (O) borophene. The adsorption energies, adsorption configurations, Mulliken charge population, surface work functions, and density of states (DOS) of the most stable doped borophene/gas-molecule configurations were calculated, and the interaction mechanisms between the gas molecules and the doped borophene were further analyzed. The results indicated that most of the gas molecules exhibited strong chemisorption at the VB site (the center of valley bottom B–B bond) of the doped borophene (compared to pristine borophene). Electronic property analysis of the C-doped borophene/CO2 and the NO2 adsorption system revealed that there were numerous charge transfers from the C-doped borophene to the CO2 and NO2 molecules. This indicated that C-doped borophene was an electron donor, and the CO2 and NO2 molecules served as electron acceptors. In contrast to variations in the adsorption energies, electronic properties, and surface work functions of the different gas, C-, N-, and O-doped borophene adsorption systems, we concluded that the C-, N-, and O-doped borophene materials will improve the sensitivity of CO, CO2, and NO2 molecule; this improvement of adsorption properties indicated that C-, N-, and O-doped borophene materials are excellent candidates for surface work functions transistor to detect gas molecules.

Land suitability assessment of soils for rubber and cashew cultivation in the Coastal Area of Bodo City, Rivers State, Southern Nigeria

The research was carried out in Bodo city in Gokana Local Government of Rivers State, Southern Nigeria to evaluate the land suitability for rubber and cashew cultivation using the relevant land suitability guidelines for the cultivation of the two cash crops of interest. Mapping of the 100 ha of land in Bodo city was done using the rigid grid method of soil survey. The three mapping units (summit, middle slope and valley bottom) were identified and delineated. Three representative soil pedons of 2 m x 2 m x 2 m were dug and described by horizon from top to bottom (0 cm to 200 cm). Soil samples were collected from identifiable horizons and processed for laboratory analysis using standard routine laboratory methods most appropriate. The results showed that pedons 1 and 3 covering 86,000 ha of the entire study area were found to be moderately suitable for rubber cultivation with limitation in soil physical characteristics (texture) and fertility (low base saturation < 50 %). Pedon 2 covering 14,000 ha of the total land of the study area was marginally suitable due to limitation in soil fertility (low base saturation < 80 %). Pedon 1, 2, and 3 were also moderately suitable for cashew cultivation in the study area with limitation in soil physical characteristics (texture) and fertility (low organic carbon), while limitation in wetness (poor drainage) was peculiar to pedon 3 only. Thus, soils in the study area were moderately suitable for both rubber and cashew cultivation in the area.

Stress-strain numerical simulation for a microprofile subjected to orthogonal impact under constrained loading conditions

The present paper aims to describe shape changes in a microroughness model developed for the working surfaces of parts at degrees of deformation commensurate with the height of the original microprofile; to establish how the degree of microprofile upsetting affects its shape under constrained loading conditions; as well as to estimate the stress state of the microprofile by stress intensity. A numerical model describing the surface microprofile of parts was calculated using the ANSYS Workbench environment. Lead, tin, aluminum, and copper were used as microprofile materials. In addition, microprofile upsetting was computer simulated under constrained loading conditions. The valley bottom was found to rise at a 10–20% microprofile upsetting by 0.213–0.275 mm relative to the original profile height, depending on its material. The relative length of the smoothed microprofile section amounted to 0.786–0.925 mm of its original length. The base angle of the deformed microprofile reached 570 and 800 for copper and lead models, respectively. The depth of valleys ranged from 1.4 mm (23% of the original profile height) for lead models and from 1.8 mm (30% of the original profile height) for copper models. In the case of maximum microprofile upsetting, an increase in the yield strength of microrough material from 10 to 60 MPa contributed to a reduction in the base angle of the deformed microprofile, as well as relative length and the vertical rise of microprofile valleys at their highest point. No interlocking of lateral microprofile surfaces was observed. At a 50% upsetting, the stress state of the microprofile exceeded its ultimate strength by 4–8 times. The shape changes simulated for the microprofile from plastic metallic materials are described. The performed numerical simulation correlates well with the experimental results obtained for lead microprofile models. It is worth noting that the complete smoothing of the microprofile is likely to occur through the rise of valleys and the approaching of its lateral surfaces. The study results can be used for designing and manufacturing valve gate assemblies.

Global Polygons For Terrain Classification Divided Into Uniform Slopes And Basins

Global terrain classification data have been used for various issues that are known to be related to topography, such as estimation of soil types, estimation of Vs30, and creation of seismic hazard maps. However, due to the resolution of the DEMs used, the terrain classification data from previous studies could not discriminate small landforms, such as narrow valley bottom plains, and small-rises within the plains. We created a global polygon dataset of the shapefile format divided into uniform slopes from slope gradients and HAND (height above the nearest drainage) calculated using the 90m spatial resolution MERIT DEM, and combined this data with the unit catchments of MERIT-Basins. This dataset contains the calculated terrain measurements (slope gradient, HAND, surface texture, local convexity, Sinks) and polygon areas as attributes, as well as the ID number of the MERIT-Basins’ unit catchment. In addition, the results of k-means clustering using slope gradient, HAND, and surface texture, which can be joined with the dataset as a simple terrain classification, are also available. This dataset can be used as a proxy and is expected to contribute to the modeling and estimation of various points that are known to be related to topography.

Predicting Wetland Occurrence in the Arid to Semi—Arid 1 Interior of the Western Cape, South Africa, for Improved 2 Mapping and Management

As for drylands globally, there has been limited effort to map and characterize such wetlands in the Western Cape interior of South Africa. Thus, the study assessed how wetland occurrence and type in the arid to semi-arid interior of the Western Cape relate to key biophysical drivers, and, through predictive modelling, to contribute towards improved accuracy of the wetland map layer. Field-verified test areas were selected to represent the aridity gradient, rainfall seasonality, hydrogeomorphic (HGM) types and physiographic zones encompassed in the study area. The arid areas of the Karoo physiographic zones had: (1) a low (<1%) proportional area of wetland; (2) an almost complete absence of seepage slope wetlands; (3) ephemeral depressions, all non-vegetated; and (4) much of the wetland associated with valley bottoms confined within a channel. The less arid mountain zones had: (1) a much higher (>3%) proportional area of wetland; and (2) wetlands being predominantly hillslope seepages, but also including valley bottom wetlands. A spatial probability surface of wetland occurrence was generated based on the statistical relationship of verified wetland presence and absence data points with a range of catchment-scale predictor variables, including topographic metrics and hydrological/climatic variables. This layer was combined with raster images of most likely HGM type within the landscape to provide a final product of wetland occurrence, attributed by HGM type. Vulnerabilities of the wetlands were identified based on key attributes of the different wetland types, and recommendations were provided for refining the wetland map for the Western Cape.

New constraints on the exhumation history of the western Tauern Window (European Alps) from thermochronology, thermokinematic modeling, and topographic analysis

The Brenner normal fault bounds the Tauern Window to the west and accommodated a significant portion of the orogen-parallel extension in the Eastern Alps. Here, we use zircon (U–Th)/He, apatite fission track, and apatite (U–Th)/He dating, thermokinematic modeling, and a topographic analysis to constrain the exhumation history of the western Tauern Window in the footwall of the Brenner fault. ZHe ages from an E–W profile (parallel to the slip direction of the fault) decrease westwards from ~ 11 to ~ 8 Ma and suggest a fault-slip rate of 3.9 ± 0.9 km/Myr, whereas AFT and AHe ages show no spatial trends. ZHe and AFT ages from an elevation profile indicate apparent exhumation rates of 1.1 ± 0.7 and 1.0 ± 1.3 km/Myr, respectively, whereas the AHe ages are again spatially invariant. Most of the thermochronological ages are well predicted by a thermokinematic model with a normal fault that slips at a rate of 4.2 km/Myr between ~ 19 and ~ 9 Ma and produces 35 ± 10 km of extension. The modeling reveals that the spatially invariant AHe ages are caused by heat advection due to faulting and posttectonic thermal relaxation. The enigmatic increase of K–Ar phengite and biotite ages towards the Brenner fault is caused by heat conduction from the hot footwall to the cooler hanging wall. Topographic profiles across an N–S valley in the fault footwall indicate 1000 ± 300 m of erosion after faulting ceased, which agrees with the results of our thermokinematic model. Valley incision explains why the Brenner fault is located on the western valley shoulder and not at the valley bottom. We conclude that the ability of thermokinematic models to quantify heat transfer by rock advection and conduction is crucial for interpreting cooling ages from extensional fault systems.

Quaternary formations mapping in the region of Volta Grande do Rio Uruguai (Brazil)

Quaternary formations (detrital and weathered materials) are an important natural resource for different areas of scientific investigation, from understanding their relation to erosive processes and morphodynamic processes that create landforms or to understanding the history of the first human settlements (geoarcheology). Quaternary coverings can be formed in situ or be transported by external geologic agents. Regarding soils, Quaternary formations are related to landscape topography and are transformed according to the characteristics of this topography. Hence, classifying and mapping these soils is not always easy. The present article aims to map the Quaternary formations along a stretch of the Uruguay River basin known as Volta Grande (SC/RS-Brazil), by using topographic attributes derived from the SRTM GL1-Up Sampled digital elevation model, soil particle-size analysis, and a generated Multiresolution Index of Valley Bottom Flatness (MRVBF) index . The results of the analysis show that: (i) colluvium is the predominant Quaternary formation in the study area; (ii) there is a predominance of clay, corroborating previous studies of the region; (iii) the spatial distribution of the study area’s Quaternary formations reflect local slope dynamics based on morphology and topographic position; and, (iv) the existence of colluvium-alluvium on the Uruguay River’s banks indicates that slope attributes contributed to the pedogeomorphological dynamics of the study area and not only fluvial dynamics. Based on the results, the methodology applied in this study might be useful for pedogeomorphological studies, notably in the analysis and mapping of Quaternary formations, despite some of its limitations.

Carbon and Nitrogen Sourcing in High Elevation Landscapes of Mustang in Central Nepal

Mustang valley in the central Himalaya of Nepal is a unique landscape formed by massive soil mass during a glacial period, which is attributed to a mix of vegetations and long agricultural history. Soil nutrients and their sourcing is highly important to understand the vegetation assemblage and land productivity in this arid zone. Twenty soil samples (from 0 to 20 cm depth) were collected from three landscape positions in Mustang district: valley, ridge, and midslope. We explored nutrient sourcing using natural abundance carbon (δ13C) and nitrogen isotope (δ15N) employing isotope ratio mass spectrophotometry. The results showed that the total soil carbon (TC) and total nitrogen (TN) ranged from 0.3 to 10.5% and 0.3 to 0.7%, respectively. Similarly, the CN ratio ranged from 0.75 to 15.6, whereas soil pH ranged from 6.5 to 7.5. Valley soil showed higher values of TN, CN, and soil pH than the ridge and midslope soils. The valleys had more positive δ15N signatures than ridge and midslope, which indicates higher inorganic and organic N fertilizer inputs in the valley bottom than in the midslope and ridge. This suggests that a higher nutrient content in the valley bottom likely results from agro-inputs management and the transport of nutrients from the ridge and midslope. Soil pH and CN ratio were a non-limiting factor of nutrient availability in the study regions. These findings are crucial in understanding the nutrient dynamics and management in relation to vegetation and agricultural farming in this unique topography of the Trans-Himalayan zone of Mustang in central Nepal.