Terrace Structure Research Articles

STRUCTURE AND DEVELOPMENT OF THE MIDDLE PLEISTOCENE TERRACE OF THE STYR RIVER IN THE AREA OF THE KHRINNYKY RESERVOIR

The article presents new results of the study of the structure of the Middle Pleistocene terrace of the Styr River, probably the oldest among the river terraces preserved in the Styr valley. The main objects of the study were natural outcrops of alluvial and cover deposits, confined to the steep banks of the Khrinnytky Reservoir in the vicinity of the villages of Boremel and Naberezhne. The study was focused on the lower part of the section of terrace sediments, which lies under the Dubno (Vytachiv) soil horizon, which is correlated with the 3rd marine isotope stage (MIS 3). The elevation of the terrace surface above the palaeo-Styr water level is about 20–25 m (16–21 m above the average water level in the reservoir), and the thickness of the loess-palaesoil cover varies from 4–5 m, where the terrace height is minimal, to over 15 m , where the terrace surface is the highest. The main stratigraphic horizons of the Upper Pleistocene are reliably recognized in the section, including two soil horizons of the regional stratigraphic scheme - the widespread Dubno and locally preserved Horohiv (MIS 5). The latter is associated with the base of the loess-palaeosol sequence. The Horohiv pedocomplex is mostly lack in the loess-palaeosol sequences of the coastal cliffs, and if present, it is poorly preserved (truncated), exposed at different altitudes (6–12 m above the reservoir). The poor preservation of the Horohiv pedocomplex is a consequence of intense aeolian (blowing) processes that occurred prior to the formation of the terrace loess cover. The abnormally high altitudinal position of the Horohiv pedocomplex is associated with the accumulation of aeolian sands at the final stage of terrace formation (end of the MIS 6). The presence of paleocryogenic features (syngenetic frost veins and cryoturbations) in the upper part of the alluvium, which can be formed both in permafrost and deep seasonal freezing, indicates its accumulation in periglacial and/or subperiglacial conditions. Key words: river terrace; alluvium; Pleistocene; eolian processes; Volyn’ Upland; Styr River valley.

Structure, Age, and Formation Stages of the First River Terraces in the Selenga Drainage Basin

Structure, Age, and Formation Stages of the First River Terraces in the Selenga Drainage Basin

Coseismic and Tectonic Time-Scale Deformations of an Island Arc Based on Studies of East Coast of Kamchatka Peninsula (Far East, Russia)

Geologic structure of the late Holocene accumulative marine terrace on the coast of Kamchatka Bay (Kamchatka Peninsula) has been studied. The ages and relative hypsometric position of beach ridges composing the terrace allowed us to identify two types of vertical movements of the coast: periodic fast (coseismic) and slow time-scale uplift or subsidence. Large-amplitude vertical coseismic movements (up to 1‒2 meters) occur on average once in about 1200‒1300 years, and slow movements occur at an average rate from a fraction of a millimeter to about 2 mm per year. Coseismic motions represent relaxation of elastic deformations accumulated during the interseismic interval of the seismic cycle, neither exceed them nor accumulate. Slow motions set the general trend of vertical deformations of the coast. It is assumed that the subsiding central parts of the eastern bays of Kamchatka Peninsula (Avachinsky, Kronotsky and Kamchatsky) and depressions between the eastern peninsulas (Kronotsky, Shipunsky) and the main massif of Kamchatka form an arc-parallel extension zone, which is nearest to the deep-water trench, and that extension is caused by the migration of the subducted part of the Pacific plate toward the Pacific Ocean. Under the eastern Shipunsky and Kronotsky peninsulas, the arc-normal extension of the earth’s crust of the Kamchatka segment of the Kuril-Kamchatka island arc is replaced by a zone of transverse compression.

Characterization of graphene films formed using radical plasma species

Previously the authors of this paper have reported the synthesis of highly tethered, planarized graphene films on 6H-SiC(0001) using a two-step CF4-based plasma assisted synthesis (PAS) process. In the first step, silicon was selectively etched from the SiC surface to form a carbon-rich overlayer, and in the second step, a rapid thermal anneal was used to form the graphene film from this carbon-rich layer. The etch process was performed in an inductively coupled plasma-reactive ion etching system and utilized both physical etching due to ions and chemical etching due to radicals. This paper reports the plasma assisted synthesis of few-layer graphene films using only the radical species produced in a CF4-based plasma. That is, only chemical etching was involved in the selective etching process. This was achieved by placing a physical mask over the substrate to block the ion flux and allowing the microplasma formed from the ambient radical species to etch the SiC surface. This process followed by the rapid thermal anneal is referred to as microplasma assisted synthesis (MPAS) of graphene. The resulting graphene films were characterized using x-ray photoelectron spectroscopy, Raman spectroscopy and atomic force microscopy. These analyses reveal that the MPAS films are less tethered than those produced by the PAS process, and they reflect the step and terrace structure of the initial SiC substrate. Consequently, the few layer graphene films formed using MPAS show marked progress toward the quasi-freestanding graphene films formed by high temperature sublimation. Overall, these results suggest that a radical based etching process may provide a chemical route to the synthesis of quasi-freestanding graphene on SiC. Additionally, these results provide insight into the roles of radicals and ions in the etching process.

The Organic Ligand Etching Method for Constructing In Situ Terraced Protective Layer Toward Stable Aqueous Zn Anode.

The stability of aqueous Zn-ion batteries (AZIBs) is highly dependent on the reversibility of stripping/plating Zn anode. In this work, an organic ligand etching method is proposed to develop a series of in situ multifunctional protective layers on Zn anode. Particularly, the 0.02m [Fe(CN) 6]3- etching solutions can spontaneously etch the Zn anode, creating an in situ protective layer with unique terraced structure, which blocks the direct contact between the electrode and electrolyte and increases the area for Zn2+ ions deposition. Interestingly, all elements in the organic ligands (i.e., C, N, Zn, and Fe) exhibit strong zincophilic, significantly promoting zinc deposition kinetics and enhancing 3D nucleation behavior to inhibit zinc dendrite growth. As a result, the etched Zn anode can provide as high a Coulombic efficiency of 99.6% over 1000 cycles and sustain over 400 h long-term stability at a high current density of 10mA cm-2 . As general validation, the small amount of metal cations additives (e.g., Ni2+ , Mn2+ , and Cu2+ ) can accelerate the synthesis of artificial interface layers with 3D structures and also regulate zinc deposition behavior. This work provides a new idea from the perspective of etching solution selection for surface modification of Zn metal anode.

Width-dependent band gap of arm-chair graphene nanoribbons formed on vicinal SiC substrates by MBE

Formation and electronic states of graphene nanoribbons with arm-chair edges (AGNR) are studied on the SiC(0001) vicinal surfaces toward the [] direction. The surface step and terrace structures of both 4H and 6H-SiC substrates are used as the growth templates of one-dimensional arrays of AGNRs, which are prepared using the carbon molecular beam epitaxy followed by hydrogen intercalation. A band gap is observed above the π-band maximum by angle-resolved photoelectron spectroscopy (ARPES) for the both samples. The average widths of the AGNRs are 6 and 10 nm, and the estimated average band gaps are 0.40 and 0.28 eV for the 4H- and 6H- substrates, respectively. A simple and phenomenological inverse relation between the energy gap and AGNR width works in the analyses of the ARPES data.

Terrace mode of the Keck telescope primary mirror.

It has been well-established that for the extremely large segmented-mirror telescopes (ELTs) currently under construction, segment clocking (in-plane rotation) will result in piston errors between neighboring segments. By contrast, the Keck telescopes utilize a fundamentally different edge sensor geometry, which should in principle render them insensitive to this effect. However, we show that as the result of a systematic internal misalignment of the Keck edge sensors, they in fact suffer from clocking-dependent effects that are remarkably similar to those anticipated for segmented-mirror ELTs. The Keck telescopes thus provide a convenient testbed for studying segment clocking and its associated effects. Analysis of Keck phasing data shows that the segment clocking effects are not random, but systematic and lead to a global segment misalignment mode of striking symmetry in which the primary mirror assumes a terraced structure. This terrace mode has been known for some time at Keck but has only recently been understood to be a direct consequence of segment clocking. A quantitative measurement of terrace mode can be used to diagnose and calibrate segment clocking effects at Keck and for future ELTs.

Drainage of paddy terraces impacts structures and soil properties in the globally important agricultural heritage of Hani Paddy Terraces, China

Marginalization and abandonment of paddy terraces are widespread, but their effects on the sustainability of subsequent agricultural production are still unknown. Hani Paddy Terraces, included in Globally Important Agriculture Heritage Systems, are threatened by paddy fields drainage. Here, changes in terrace structure, the productivity of topsoil (0–20 cm), and soil water holding capacity at 0–70 cm depth were determined in a case study of Hani Paddy Terraces in Amengkong River Basin in Yuanyang County in Southwestern China, which had been converted into dryland terraces for 2–14 years. Our results showed that: (1) The degree of terrace structures degradation exhibited a U-shaped curve with increasing time since draining, with those drained for 5–9 years having the best structure; (2) Soil productivity index decreased first and then increased with time after conversion; (3) Maximum water holding capacity at 0–70 cm soil depth dramatically decreased after conversion and such trend became increasingly obvious with increasing time since conversion. Our study revealed that drainage of paddy terraces along with associated changes in crop and field management led to an increase in soil productivity, but degradation of terrace structures and a decrease in water holding capacity will inhibit restoration to paddy terraces. These findings enhance the understanding of the biophysical changes due to marginalization in paddy terraces.

Evidentiranje suhozidne terasirane krajine v Vipavski dolini

Terraced landscapes are important to the cultural and environmental characteristics of many regions worldwide. Accurate and comprehensive documentation of these landscapes is challenging, especially when inventorying dry-stone walled terraced landscapes and abandoned agricultural terraces. Even inventory methods based on LIDAR and fieldwork do not capture all of the mapped information. To address this challenge, the study proposed the inclusion of additional data sources into the inventory process, specifically aerial photographs from drones and photographs taken with advanced GPS devices. The combination of already-tested methods and other data sources enabled a more comprehensive and accurate inventory process. The improved methodology was tested in three cadastral municipalities of the Vipava Valley (Črniče, Gojače and Vrtovin), where the terraces have predominantly dry-stone risers with different heights. A large percentage of the terraced landscape in the selected cadastral municipalities is abandoned, so the terraced structures are overgrown by vegetation and forest; in Gojače, almost half of the terraced landscape is like this. In some places, the terraced landscape has become almost completely unrecognizable. With an improved inventory methodology, both active and abandoned agricultural terraces can be mapped.

Комплексные археологические и геофизические исследования в портовой части Херсонеса Таврического

The best results of researching archaeological sites in the coastal zone come from integrated interdisciplinary approach involving modern geophysical methods. The analysis of the archaeological material obtained during excavations of the “diamond-shaped tower” in the water area near the port quarters of Chersonese suggests that the structure was constructed in the ninth and tenth centuries AD. The results of research on this site show that from the ninth and tenth to the period from the late eleventh to the first half of the thirteenth centuries the sea level in Karantinnaia Bay rose by ca 1 meter. The data obtained by continuous seismoacoustic profiling were used to identify continuous changes of the coastline in result of transgression and accumulation of the bottom sediments in the section of the water area near the port district of Chersonese. The analysis of the built-up seismogeological sections and isobath map enabled the research group to identify 3 terraces and associated morphological elements indicating the location of ancient coastlines in different historical periods. A spatial relationship has been established between the archaeological objects found at the sea bottom and the position of the underwater terraces. A reconstruction of the ninth- and tenth-century coastline has been suggested according to the archaeological data. The location of the “diamond-shaped tower” and the construction remains discovered in 2019 on the same terrace suggests that the structures existed approximately at the same time. Electrical prospecting research using bottom electrotomography explored the sediment structure of marine terraces to a depth of 10 m. The research results have determined bottom anomalies corresponding to various stages of development of the coast of Karantinnaia Bay. An extended linear anomaly, located 40–50 m from the modern coast and hidden by a layer of bottom soil up to 3 m thick, most likely corresponds to the early period of the ancient city. The sea in this area is ca 2–3 m deep.

Mite community assemblage in Italian traditional and in high-density olive groves

Notwithstanding a still widespread and considerable weight of traditional olive groves throughout Italy, there is large interest in investing in new plantations, different both for cultivars and agronomic approaches, and to renew at least partially the olive-oil heritage. Furthermore, Italy is one of the main importing countries in the world of oil and table olives. To match the internal demand and boost olive-oil production, the National Olive Plan suggests adopting modern high-density plantations like other EU Countries (e.g., Spain). Traditional groves are partly replaced by high-density olive crops, which are more profitable due to substantially lower operating costs. Furthermore, the introduction of new olive crops may induce changes in agricultural landscape/agroecosystem (e.g., plain areas vs terraced structures), and may lead to undesirable effects on the environment and pest control. The surveys on the presence and abundance of the main animal groups in traditional and high-density olive crops can be informative, mainly referring to the different ecological/functional roles they can assume (phytophagous, predatory, and vectoring role of pathogens). Mite communities are susceptible to different types of plantation density and eventual environmental effects. Concerning olives, not so many contributions approached screening on the acarofauna, and previous screenings were mainly focused on soil. The characterization of the acarofauna resident on epigeic part of olive groves may be indicative about the status of the agroecosystem and effect of plantation densities.

Competitive growth between the top and bottom layers of few-layer graphene at the domain boundary merging stage

Compared with monolayer graphene, few-layer graphene (FLG) also has a broader application prospect in the fields of composite materials, conductive coatings, metal corrosion prevention and electronic devices requiring tunable electronic structures. Herein, FLG is grown on Cu foil by chemical vapor deposition (CVD) and the merging of graphene domain boundary (GDB) network is directly observed by optical microscope (OM). Raman spectra and energy dispersive spectroscopy (EDS) results show that the defect degree of graphene at GDBs is lower than that at domain interior. Raman mapping results indicate that the structure of FLG grown at 980 °C is inhomogeneous and there exist a terraced structure at the GDBs. The atomic force microscopy (AFM) results show that the FLG grown at 980 °C has about ∼7 layers at the GDBs and ∼13 layers at domain interior, respectively. In addition, the Raman spectra results also disclose an unusual phenomenon that graphene at GDBs grown at 980 °C has lower ID/IG ratios than that grown at 1000 °C. A competitive growth mechanism of the top and bottom layers of FLG is proposed to shed light on the synergistic effect of catalysis of Cu and temperature on the late growth stage of FLG.

CVD controlled preparation and growth mechanism of 2H-WS2 nanosheets

In this work, tungsten disulfide (WS2) nanosheets with good morphology are prepared by improved chemical vapor deposition (CVD) using a mixture of transition metal oxides and chalcogenide as precursors. By optimizing the growth conditions, the high-quality WS2 nanosheets with different morphologies, including large triangular, hexagonal, small triangular, terraced and spiral structures are obtained as the growth temperature of 850 °C, Ar gas flow rate of 50 sccm and holding time for 15 min. The detailed structural analyses by XRD, XPS, TEM and Raman measurements suggest that that the deposited WS2 nanosheets exhibit the 2H phase structure with high crystallization quality and uniform distribution of W and S elements. The formation of large triangular, hexagonal, and small triangular structures is related to the growth rate of different crystal planes of S atoms or W atoms. In addition, the formation of terraced and spiral stacking structures originates from the difference of supersaturation of precursors, which can be explained by the layer-by-layer stacking (LBL) growth and the spiral-dislocation-driven (SDD) mechanisms, respectively.

Self-template mechanism of “selective silicon dissolution” for the construction of functional rice husk biochar

The global greenhouse effect is serious, and many countries have reached a consensus on carbon neutrality. The high-value utilization of agricultural waste is of great significance for carbon emission reduction, while the use of agricultural waste to prepare biochar products is containing lots of application prospects. Rice husk is with high content of carbon and reticulated silica skeleton structure, which could be the “self-template” for construction of functional rice husk biochar. In this paper, high-performance rice husk-derived biochar is prepared from rice husk with KOH or K2CO3 as the “selective silicon dissolution” agent and activator, namely “one-step silicon-dissolving” and “selective two-step silicon-dissolving” methods, respectively. The results show that K2CO3 as a silicon dissolution only works at high temperatures, while at 900 °C biochar could be with a specific surface area of 1764.66 m2/g and without orderly terraced pore structure. Rice husk-derived biochar obtains a surface area of 3011.06 m2/g and a layered pore structure from “KOH selective two-step silicon-dissolving”, which is more favorable to the maintenance of microporous and ultra-microporous structures. It provides a theoretical basis and new idea for the construction of functional rice husk-derived biochar.

Imprint effect on energy storage performance of Aurivillius Bi3TaTiO9 thin films

We report the imprint effect on the energy storage performance of Bi-layered perovskite (Aurivillius) Bi3TaTiO9 (BTTO) thin films. BTTO thin films were fabricated on single-crystal Nb-doped SrTiO3 substrates using pulsed laser deposition, where the BTTO thin films showed epitaxial c-axis orientation crystal growth with square-shaped grains of terrace structures. The BTTO thin films exhibited ferroelectric hysteresis loops with a remnant polarization of several μC/cm2. An imprint phenomenon in the ferroelectric hysteresis loops occurred by applying the heat treatment of the BTTO thin film. By varying the annealing time (for 5 and 10 min at 550 °C in a vacuum of 10−5 Torr), we elucidated the imprint effect on the energy storage performance. We suggest that oxygen deficiencies induced by the heat treatment cause an imprint effect in the ferroelectric hysteresis loops. As a result, the imprint effect contributed to an increase in the stored energy density and a decrease in the energy loss density in the energy storage performance of the BTTO thin films. Our results demonstrate that the imprint effect can be a critical factor in achieving improved energy efficiency for energy storage performance, which provides new insights into the potential applications of energy storage devices with Bi-layered perovskite BTTO thin films.

Macrosteps formation on 4H-SiC surfaces via Si melting within a sandwich configuration

With a view to designing a homogeneous and controlled step-bunched morphology on large monocrystalline 4H-SiC(0001) surfaces, a sandwich configuration was investigated. A piece of silicon was melted between two 4H-SiC 4° off wafers, allowing a better spreading of the liquid than with a Si drop approach. Using as low liquid Si thickness as 30 µm, homogeneously highly step-bunched surfaces were obtained, though with irregular step shapes. This was found to be the result of time dependent dissolution of the SiC-bottom wafer under the natural vertical thermal gradient of the setup. The most parallel step and terrace structures were generated using 400 µm thick liquid Si though this led to long range inhomogeneities associated with complex mass transport. The proposed mechanism includes the combined effects of H2 etching at the edges acting as C pump and electromagnetic convection rolls for long range transport of these dissolved C atoms.

Effects of different management measures on soil conservation and the influence of environmental conditions: a case study involving UAV remote sensing on the Loess Plateau

AbstractTo curb further deterioration due to soil erosion, the Chinese government has successively implemented a series of ecological improvement projects across the Loess Plateau (LP). This study used unmanned aerial vehicle remote sensing combined with the revised universal soil loss equation to quantitatively evaluate the soil conservation rate (SR) under 10 management measures and further incorporated the topographic slope into the analysis to describe the impacts of terrain changes. The results showed that the average SR of plots under artificial management measures was 61.24 ± 0.004% (P < 0.01), whereas that under non‐artificial measures was 47.90 ± 0.007% (P < 0.01), which showed that human activities on the LP beneficially improved the SR. In addition, benefiting from the Grain to Green Project, cultivated fields, and economic forests exist only in areas with gentle slopes, and both these areas experience almost no threat of soil loss. A terraced structure exerts an obvious effect on extremely steep slopes (>40°), and a greater slope is associated with a more evident effect. However, the risk of structural failure also increases. In addition, due to restricted water conditions, the effects of existing soil and water conservation measures that use tree planting as the main method have the characteristics of horizontal and vertical zonation differentiation. Valley bottom and semi‐humid areas are more profitable, and other areas are more suitable for planting drought‐tolerant shrubs. In addition to guiding the deployment of future soil and water conservation measures, this study can provide a theoretical basis for adjusting the existing low‐efficiency measures.

The Formation of Terraces on Asteroid (101955) Bennu

AbstractThe surface of the rubble‐pile asteroid (101955) Bennu has been characterized in detail by the OSIRIS‐REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission. By examining global and local digital terrain models, we observed that Bennu possesses terraces, that is, a series of roughly latitude‐parallel, step‐like slope breaks. These partially circumscribe the poles and extend east‐west over several longitudinal quadrants at mid‐ to high (≥30°) latitudes. The terraces are subtle in amplitude, with heights ranging from 1 to 5 m. They often exhibit back‐wasting that results in V‐shaped scarps that open downslope in some locations. When boulders >5–10 m are absent at or near a terrace, the steeper portion (the drop) of the terrace lacks rocks, whereas the flatter portion (the bench) of the terrace has accumulations of rocks at its crest. When boulders >5–10 m are present, their steep downslope faces often make up the drop from the terrace crest, and they retain debris upslope, thereby enhancing the terrace structure. A geotechnical stability analysis indicates that Bennu's surface is likely unstable and that surface cohesion is <0.6 Pa. Bennu's terraces strongly resemble scarps generated in laboratory and numerical simulations of a cohesionless granular bed as the slope of the bed increases quasi‐statically. We conclude that terraces are probably actively forming on Bennu as its surface slowly fails owing to creep induced by spin acceleration.

The effects of Eu3+ doping on the epitaxial growth and photovoltaic properties of BiFeO3 thin films

1 Eu 3+ doping induces a phase transition from tetragonal to rhombohedral for BiFeO 3 film; 2 A decrease in coercivity and a sharp change in band gap upon Eu 3+ doping have been observed; 3 Eu 3+ can be used to tailor the photovoltaic effect of ITO/Eu x Bi 1- x FeO 3 / Ca 0.96 Ce 0.04 MnO 3 ; Nowadays, photovoltaic effect has been widely studied in various ferroelectric materials due to its applications as optoelectronic devices. In this work, with BiFeO 3 (BFO) films as the photovoltaic materials, we report the effects of Eu 3+ doping content on the phase structure, ferroelectric and optical properties of BFO films grown on Ca 0.96 Ce 0.04 MnO 3 /YAlO 3 (001) substrate. We found that a small doping level of 0.05 could induce a phase change of BFO from tetragonal to rhombohedral, due to the shrinking of the lattice upon Eu 3+ doping and the breaking of surface terrace structure induced by Ca 0.96 Ce 0.04 MnO 3 layer. This results in a sharp band gap reduction from 3.30 eV to 2.60 eV, and a decrease in the coercivity of ferroelectric polarization switching. Based on these findings, we investigate the photovoltaic effects of ITO/Eu x Bi 1- x FeO 3 /Ca 0.96 Ce 0.04 MnO 3 vertical capacitors. It is found that the short-circuit current density ( J sc ) decreases with increasing Eu 3+ doping, whereas the open-circuit voltage ( V oc ) first increases to a level of 0.1 V and then decreases with further Eu 3+ doping. This could be explained by the combined effect of Schottky-junction and depolarization field on the photovoltaic process. Our research suggests that a moderate Eu 3+ doping is helpful for enhancing the photovoltaic effect of BFO thin film devices. .

Phase-engineering terraced structure of edge-rich α-Mo2C for efficient hydrogen evolution reaction

Molybdenum carbide (Mo2C) nanomaterials have become potential candidates for hydrogen evolution reaction (HER) electrocatalysts. However, the electrocatalytic performance of powdery Mo2C is restricted because of the insufficient active sites and structural integrity of the organic binders. In this study, α-Mo2C nanosheets with a terraced structure and numerous edges were directly synthesized on a Cu/Mo substrate as a self-supported electrode and used as an electrocatalyst for HER without binder and transfer processes. The terraced α-Mo2C nanosheets exposed numerous active sites with mixed polymorphs (1T and 1H phases) and Bernal (AB) stacking. They showed long-term stability and satisfactory HER activity, with overpotentials of 226, 324, and 294 mV vs. RHE (at a current density of 10 mA·cm−2) and Tafel slopes of 74, 104, and 63 mV/dec in 1.0 M KOH, 1.0 M PBS, and 0.5 M H2SO4, respectively. Density functional theory calculations revealed that the 1T-1H interface and Bernal stacking at the terraced α-Mo2C enhance the electrocatalytic performance compared to 2D α-Mo2C.