Island Formation Research Articles

Enhancing Luminescence Efficiency by Controlled Island Formation of CsPbBr3 Perovskite

AbstractCsPbBr3 is an inorganic perovskite material that is promising for light‐emitting applications. Such applications are known to benefit from an island‐type active layer structure, which enhances the device's light emission efficiency. Here, the impact of the environment on the island formation in thermally deposited bilayers of CsPbBr3/LiBr is investigated. It is demonstrated that the island formation occurs only in humid environments, leading to an enhancement of the photoluminescence quantum yield by a factor of 350. Time‐resolved grazing‐incidence wide‐angle X‐ray scattering experiments document the island growth process and reveal that the LiBr has already changed the perovskite crystal orientation prior to the island formation.

Analysis of the Spatio-temporal variations of thermal patterns of Shiraz city by satellite images and GIS processing

In recent years, climate change has caused an increase in the air temperature and consequently the temperature of the earth's surface. The temperature of the earth's surface has had various effects on urban life and has caused the formation of thermal islands in cities. Thermal islands are one of the important criteria in regional planning. The city of Shiraz is considered to be a large population center in the southwest of Iran on the one hand and one of the important tourism centers of Iran on the other hand, so the purpose of this research is to monitor the spatial form of thermal islands in this city. The satellite images of Shiraz city were first collected and extracted in the hot periods of the year from 1985-to 2020 using the data of Landsat’s 4 and 5 (TM), 7 (ETM+), and 8 (OLI/TIRS). After required preprocessing, the Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), Normalized Difference Built-up Index (NDBI), and the urban heat dispersion index were determined by the Urban Thermal Field Variance Index (UTFVI). The regions with UHI, the variation of the temperature in the city, and the relationship between the LST and surface vegetation were evaluated based on the results of image processing to determine the UHIs of Shiraz. The temporal variations of the temperature pattern of Shiraz city indicated that about 12.76 km2 was added to the area of the fourth temperature class from 1985 to 2020. Results of NDVI evaluation in the studied period showed a decline in the vegetation from 22.28 km2 in 1985 to 17.54 km2 in 2020 due to alteration of the land use which can explain the formation and increase of the UHIs in the mentioned regions. At the beginning of the investigated period (1985), the temperature of the earth's surface was 17°Celsius and reached 21°Celsius at the end of the period (2020). The monitoring of the spatial form of the surface temperature of the earth shows that heat islands are moving from the outskirts of the city towards the city center. UTFVI also revealed that the awful regions (very hot temperatures) are mainly concentrated in the west and north-west to the south west of Shiraz (including some parts of districts 9 and 10), south east of district 7, and north of district 1.

Monitoring the Growth and Development of River Islands of the Tigris River between Zabin

The river islands are among the most prominent geomorphic features in the course of the Tigris River within the river section under study, as the area has been covered for 36 years from 1984 to 2019 and the study area is strictly limited between the mouth of the upper zab and the lower zab. The most important natural factors that contributed and still contribute to the present day to facilitate the construction process of the river islands were illustrated by clarifying the effect of geological factors and the slope of the stream and the effect of curves, in addition to clarifying the role of water discharges as well as clarifying the role of the riverine load important and essential in the direct impact on the growth of islands In addition to the human factor, by identifying the most effective human investments in the formation or creation of conditions appropriate for the formation of river islands represented by gravel and sand quarries. In order to monitor the geomorphic development taking place in the river islands in the river course between the two zabines during the first two periods of time, they were chosen before the establishment of the Mosul Dam in 1984 from the sensor type (TM) and the second visual for the year 2019 of the type sensor (Landsat8) to highlight the growth and development of the river islands by comparing the islands Existing in the visuals for the different periods, and then to give a clear picture of the nature of the operations that it witnessed and the resulting development in the numbers, sizes and shapes of the river islands during the study years.

River Islands of Khazir River A Geomorphological Study Along the Area from Nedoush Valley to the Upper Zap

The study tackled the phenomenon of river islands in the Al-Kazir river, along the Nedoush valley to the Upper Zab river, which is part of the administrative borders of Mosul and Erbil governorates in northern Iraq. It addresses the main natural and human factors that facilitate the formation of the river islands, including the impact of geological factors and climate, the slope of the stream, and meanders, in addition to delineating the direct fundamental role of the river load on the islands’ formation. It also shows the impact of human factors such as agriculture, grazing, and most importantly, quarries. Then shows the difference in the islands’ numbers and sizes along the study area.

The Urban Expansion Impact on Climate Change for the City of Baghdad

The urbanization and climate change phenomena are global problems whose negative effects have been exacerbated in cities, and they are a reason for the formation of global warming and urban heat islands. The research came to shed light on the urban expansion of Baghdad for four decades which extended between (1981-2021) using the ArcMap Gis10.7 technique, then evaluating the impact of this expansion on the city’s climate. The climate data were taken from Baghdad station by remote sensing technique for the same period. To clarify and analyse the relationship between the expansion and climatic data, Microsoft Excel was used. The results indicated a strong relationship between them, as urbanization rates increased, especially during the fourth cycle, to (85%), affecting all climatic elements, causing a rise in temperatures to 24362C as well as specific and relative humidity rates. While atmospheric pressure rates decreased to 100.64 kPa and that affected the wind speed, in addition to a clear fluctuation in rainfall and solar radiation rates.

A METHODOLOGICAL APPROACH TO THE DEVELOPMENT AND MAPPING OF THEURBAN LAND COVER OF THE CITY OF SOFIA

The present study presents for the first time the development of a methodology for the creation of an urban land cover of the city of Sofia, which will serve the needs of the study of the local climate zones of the Bulgarian capital. For the development of the nomenclature of the land cover, data from an orthophoto image, the Urban Atlas and cadastre of the city of Sofia were used, using a number of geospatial techniques. The end result is a classification of various objects from the urban landscape of the Bulgarian capital, divided into 11 classes and 22 sub-classes, which form the main mesoclimatic factors in the city. The results show a large percentage of low-rise buildings built of bricks with dark rooftops, which implies higher temperatures in the city and the formation of urban heat islands of different sizes and a big percentage of industrial sites (38.3%) which also affects the quality of the atmospheric air in the city of Sofia.

Study of the spectrum effect on the threshold of resonant magnetic perturbation penetration on J-TEXT

The spectrum effect on the penetration of resonant magnetic perturbation (RMP) is studied with upgraded in-vessel RMP coils on J-TEXT. The poloidal spectrum of the RMP field, especially the amplitudes of 2/1 and 3/1 components, can be varied by the phase difference between the upper and lower coil rows, Δϕ = ϕ top−ϕ bottom, where ϕ top and ϕ bottom are the toroidal phases of the n = 1 field of each coil row. The type of RMP penetration is found to be related to Δϕ, including the RMP penetration of either 2/1 or 3/1 RMP and the successive penetrations of 3/1 RMP followed by the 2/1 RMP. For cases with penetration of only one RMP component, the penetration thresholds measured by the corresponding resonant component are close for various Δϕ. However, the 2/1 RMP penetration threshold is significantly reduced if the 3/1 locked island is formed in advance. The changes in the rotation profile due to 3/1 locked island formation could partially contribute to the reduction of the 2/1 thresholds.

Effects of an epitaxial graphene layer for the growth of nickel silicides on a Ni(111) substrate

In this paper, we report on an in-depth study on the growth of nickel silicides, either on a clean Ni(111) substrate or in the presence of a previously-grown epitaxial single graphene (Gr) layer, by means of Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and scanning tunneling microscopy (STM). We demonstrate that two different nickel silicides, namely Ni3Si and Ni2Si, progressively form as the annealing temperature is increased from 450 °C to 600 °C. The presence of the Gr layer does not change the nature of the two silicide phases but rather affects the morphology of the silicide overlayer. Indeed, in the presence of Gr, the deposited silicon atoms intercalate by passing through the Gr defects or domain boundaries and accumulate on specific sample areas, resulting in the formation of multilayer silicide islands. In the absence of Gr, the deposited silicon atoms react uniformly with the nickel substrate, resulting in the formation of homogeneous large scale silicide layers.

The dynamics of single-to-multi layer transition in bacterial swarms

Wet self-propelled rods at high densities can exhibit a state of mesoscale turbulence: a disordered lattice of vortices with chaotic dynamics and a characteristic length scale. Such a state is commonly studied by a two-dimensional continuum model. However, less is known about the dynamic behaviour of self-propelled rods in three- or quasi-two- dimensions, which can be found in biological systems, for example, during the formation of bacterial aggregates and biofilms. In this study, we characterised the formation of multi-layered islands in a monolayer of swarming cells using the rod-shaped bacteria B. subtilis as a model system. We focused on how bacteria form multiple layers and how the presence of stress affects the multiple layer formation. Following our previous study where we reported that the initiation of the multilayer formation can be accounted by the framework of motility-induced phase separation (MIPS), this study analysed how this phase separation is impacted by the presence of stress, specifically under the exposure to a gradient of antibiotic. The analyses show that in the presence of an antibiotic gradient, the multi-layer formation happens by a nucleation and growth of well-defined multilayered clusters instead of by the uncontrolled emergence of the multilayer, resembling the traditional thermodynamic processes of binodal and spinodal decomposition respectively. Finally, the multilayer gives place to waves of bacteria that can travel towards high concentrations of antibiotics and that resemble travelling waves predicted by simulations of mixtures of passive and active particles.

New records of hexanchiform sharks (Elasmobranchii: Neoselachii) from the Late Cretaceous of Antarctica with comments on previous reports and described taxa

ABSTRACT Sharks are virtually absent from coastal Antarctica since the Late Eocene glaciations, but this group exhibited a notable austral diversity during the Cretaceous and Paleogene. Several species have already been described from the Aptian-Eocene successions of the Larsen Basin exposed in the James Ross Island area (northern Antarctic Peninsula) and the predominantly deep-water Hexanchiformes have a record that, although still rare, has been continually increased. Four species of this group are currently known from that basin: Notidanodon pectinatus, Xampylodon dentatus, Rolfodon thompsoni, and Rolfodon tatere. Such records are especially concentrated in the Gamma Member of the Snow Hill Island Formation (or Herbert Sound Member of Santa Marta Formation), on James Ross Island. Here we described four teeth assigned to X. dentatus and one identified as R. tatere from upper Campanian sections of James Ross Island, highlighting the nomenclatural changes that led to the definition of Xampylodon and Rolfodon. Some specimens of X. dentatus presented here are considerably more complete or represent teeth of different positions than most previous records. The material assigned to R. tatere represents the oldest record of this species in the world, extending its time range by more than 10 million years.

Macrotermes natalensis termite colonies in seasonally flooded savannas

In seasonally inundated landscapes of southern central Africa very large termite mounds of Macrotermes natalensis offer a refuge for flood-intolerant trees during the flood season. In the matrix landscape surrounding these islands the seasonally waterlogged and then anaerobic soil conditions and the browsing by megaherbivores during the dry season allow for grass and herbaceous vegetation only. During the rainy season each termitarium forms an isolated island which due to its relative dryness allows survival of the trees and the associated fauna. During the dry season the termites try to establish new colonies with new mounds. However, the successful formation of new termitaria islands seems to be a rare event. In this case study from Dundumwezi in the Kafue National Park, Zambia, we provide a description of the termitaria islands and their vegetation. Furthermore, we analyse spatial patterns of termite mound islands in the surroundings of Kafue National Park und Bangweulu Plains / Kasanka National Park based on remote sensing imagery. Our results confirm that competition among colonies of large termitaria in homogeneous habitats causes very regular spatial patterns.

Land in Water: The Study of Land Reclamation and Artificial Islands Formation in the UAE Coastal Zone: A Remote Sensing and GIS Perspective

The United Arab Emirate’s rapid population growth is coupled with an increase in the consumption of natural resources such as fresh air, sunlight, land, and water. In the past two decades, the demand for land has augmented both away from the coast and significantly near the coast. Within coastal zones, artificial reclamation of land in the sea is the most desirable way to meet the demand for land necessary for the development of the most modern urban areas. Seaward reclamation (land in the water) necessitates the construction of artificially reclaimed areas that are extended into the sea using innovative modern construction techniques. The majority of these building requirements are necessitated by a number of key factors and have diverse outcomes. Even though this type of urban expansion is not new, the scale and motivations of land reclamation have been drastically altered due to geological and human-induced factors. The purpose of this paper is to assess the increase in seaward land expansion, particularly in the seven UAE coastal emirates. Using satellite data, particularly from 1990 to 2021, the total increase in land due to newly developed reclaimed areas in all UAE coastal emirates is calculated. Satellite images from the Landsat series are used to analyze the tremendous growth since the early 2000s. In addition, the study of shoreline maps of 1990, 2000, 2010, and 2021 for the seven emirates revealed that the 22 km long Ajman and UAQ front coast experienced a notable shoreline retreat with a net erosion area of 300 m2 and an annual rate of 30 my−1 over the past 21 years (2000–2021). Depending on the type of construction design used to describe the process, a methodical sorting is also recommended. The impacts of the Dubai offshore reclaimed islands on the adjacent coastlines in Ajman and Umm Al Quwain (UAQ), as well as the potential impact of earthquake tremors along the Zagros fold belt region, are the subjects of this study. In this study, all seven coastal emirates are considered, and the largest reclamation projects are located in Dubai, Abu Dhabi, Ras-Al Khaimah (RAK), and Fujairah, with Dubai leading the way; it has expanded its coastal areas by more than 68 km2 at present, and another 35 km2 will be reclaimed soon to finish Palm Deira.

Fertile Island Effect by Three Typical Woody Plants on Wetlands of Ebinur Lake, northwestern China

Desertification poses a permanent threat to the security of arid ecosystems. Perennial arid vegetation plays a crucial role in maintaining the structure and function of arid ecosystems and slowing the process of desertification by forming “fertile islands” under the tree canopy. However, the process of formation and development of these fertile islands remains uncertain. Here, we explored how three typical woody plants (i.e., Populus euphratica, Haloxylon ammodendron, and Nitraria tangutorum) in the Ebinur Lake Basin of northwestern China differed in their soil nitrogen and phosphorus. 1) Significant differences of organic carbon and total and available nitrogen/phosphorus were observed in the soil among the three typical woody plant-dominated ecosystems. Populus euphratica had significant differences of N and P contents between the canopy and bare soils, except for ammonium nitrogen. 2) Our RDA analysis revealed that the major factors that influenced the soil nutrient differences among the three vegetations were plant crown width, soil water content, salinity, and pH. 3) The organic carbon content of bare soil was significantly correlated with N and P in all the three vegetations. This study contributes to our understanding of the factors that influence the fertile island effect in arid ecosystems, which may contribute to soil conservation in arid areas.

Contact Enhancement in Nanoparticle Assemblies through Electrophoretic Deposition.

A strong interparticle connection needs to be realized to harvest unique nanoscale features of colloidal nanoparticles (NPs) in film structures. Constructing a strong contact and adhesion of NPs on a substrate is an essential process for improved NP film properties, and therefore, its key factors should be determined by understanding the NP deposition mechanism. Herein, we investigated the critical factors leading to the robust and strong adherence of the film structure and revealed that the NP deposition mechanism involved the role of surfactant ligands during electrophoretic deposition (EPD). The high amount of surfactant ligand treatment results in a high deposition rate of NPs in the early stage; however, the ligand treatment does not influence the deposition rate in the later stage. Furthermore, the deposition mechanism is found to involve three steps during EPD: island formation, lateral growth, and layer-by-layer deposition. Rapid NP deposition kinetics controlled by ligand treatments demonstrate the strong contact and adhesion of NP film structures; they are characterized by the fast charge transfer, low resistivity, and rigid NP layers of the Cu2-x S NP-based devices. Finally, the controlled role of surfactant ligands in EPD enables design of high-performance nanostructured NP film devices with contact enhancement.

Tripolar guide magnetic fields due to island coalescence in solar wind current sheets: Simulation and theory

Reconnecting current sheets (CSs) in the solar wind near 1 AU have been previously identified that exhibit a modified Hall magnetic field perturbation of the nominal guide field characterized by a “tripolar” structure with depressions on both sides of a central maximum [Eriksson et al., Astrophys. J. 805, 43 (2015)]. Such CSs were inferred to contain multiple interacting islands based on measurements from all four Cluster satellites. A new set of 2D particle-in-cell simulations have been performed providing the foundation for a theoretical model for the origin of the tripolar guide-field perturbation. The simulations are initialized with a thin CS unstable to the formation of many small islands that undergo pairwise coalescence and growth. The guide field depressions develop as the result of a balance between the electrostatic (curl-free or irrotational) and electromagnetic (divergence-free or solenoidal) components of the parallel electric field. Field-line and flow-line tracing provide additional support for the model by demonstrating how a level of charge separation sufficient to support a large electrostatic potential can be maintained following island coalescence. A parameter study reveals that the plasma beta is the primary quantity controlling the evolution of the tripolar field. Dependence on the initial guide-field strength is also investigated.

Evaluation of a Green Roof for Heat Mitigation in a Building Located in a City with a Hot and Humid Climate

The expansion of the urban population has contributed to the formation of urban agglomerates; whose spatial morphology favors the formation of heat islands. The installation of Green Roofs (GR) is a strategy that can be applied to mitigate the effects of this phenomenon, especially in regions lacking vegetation cover. The objective of this paper is to evaluate, through Computational Fluid Dynamics (CFD), the potential to reduce the internal temperature of a building located in the city of Rio de Janeiro, Brazil. The temperatures of the inner surface of the roof were measured in two buildings, one with GR and one without GR. This information was used as input data into Solidworks software to simulate the heat distribution inside the building. Results indicated that the temperature was reduced by about 2°C in the building with GR, proving the technology's effectiveness, notably in the hottest months of the year.

Investigation of the temperature stability of germanium-rich SiGe layers on Si(111) substrates

In this work, we investigated fully relaxed SiGe and pure Ge layers on Si(111) substrates, regarding their temperature stability. The layers were annealed at various temperatures up to 650 °C directly after growth. The Ge content of the Si1−xGex layers was varied between 0.6 and 1. We investigated effects due to surface segregation of Ge in the SiGe layers. During heat treatment, different surface reconstructions were observed. The SiGe layers remained smooth with a root-mean square surface roughness below 0.5 nm up to temperatures of 500 °C and a 7 × 7 surface reconstruction was seen. Annealing at higher temperatures corresponding to a 7 × 7–“1 × 1” phase transition, the surface roughness increased to more than 2 nm and island formation was observed. We measured the in-plane lattice constant of the surface as a function of temperature and confirmed a strong effect of Ge segregation on the surface strain. The Ge accumulation at the surface was confirmed by angle-resolved X-ray photoelectron spectroscopy. The high adatom density of the “1 × 1” reconstruction in combination with compressive strain led to island nucleation when cooling down. Pure Ge layers remained smooth even after annealing up to 650 °C.

History of Colonization of Jeju Island (Republic of Korea) by the Water Fleas (Crustacea: Cladocera) Is Reflected by the Seasonal Changes in Their Fauna and Species Associations

The aim of this paper is to study the species composition, structure and seasonal dynamics of the cladoceran fauna and species associations in inland water bodies of Jeju Island (Republic of Korea). Only 47 taxa were found in 199 samples. Such faunal paucity could be explained by the existence of only a few types of aquatic environments on Jeju Island as compared to continental China and the Far East of Russia, with their great diversity of water types. We have demonstrated a high significance of the tropical species on Jeju. Our data confirm seasonal faunistic changes in the continental waters of Jeju Island. The rate of tropical taxa is highest in September, after the monsoon season, while the Far Eastern endemic taxa are more common in winter. At the same time, the contribution of Boreal taxa to the fauna of the island is low even in winter. Species associations have been revealed based on binominal distribution; they change significantly from summer to winter. However, a contribution of Boreal taxa to the species associations also is minimal (even in winter), whereas tropical taxa contribute to them greatly (including in winter). We can propose a rough scheme of faunal formation exploring the whole set of obtained information. Initially, at the earlier stages of the island formation, its fauna was consisted of some pre-Pleistocene taxa. Then, during the Pleistocene time, Jeju Island was secondarily interconnected with more southern territories, and tropical species have colonized it. Recent Boreal cladoceran invaders arrived at the island water bodies later when they were already inhabited by formed associations, and for this reason only few of them were able to settle down there. Such a scheme is a hypothesis which needs to be checked by the future phylogeographic studies.

Predicting the impacts of urban development on seasonal urban thermal environment in Guwahati city, northeast India

The formation and intensification of the urban heat island (UHI) phenomenon over an urban area largely depend on its land surface properties, which alters the urban thermal environment. So, assessing and predicting the effect of land use land cover (LULC) change on thermal environment of urban area is crucial. In this context, the present study aims to analyze the LULC change and its effect on land surface temperature (LST) and the UHI phenomenon over Guwahati city, northeast India, from 1995 to 2020 using Landsat data. A significant increase in built-up land of about 147.5% is seen during 1995–2020, while vegetation and cropland show decreasing trend of about 47% and 27%, respectively. Moreover, the future simulation of LULC using the Artificial Neural Network (ANN) based Cellular Automata (CA) model suggests a continuous increase in urban built-up land to about 10.18% during 2020–2030. The future prediction result of seasonal LST using XGB (Extreme Gradient Boosting) regression suggests that around 86.73% in 2025 and 94.53% in 2030 will have to face higher LST of 15 °C-<20 °C in the summer season and 82.58% in 2025 and 97.16% in 2030 of 25 °C-<30 °C zone in the winter season. The distribution of urban thermal field variance index (UTFVI) maps suggest the occurrence of the strongest UTFVI zones over the built-up land while none UTFVI over the surrounding rural region, suggesting a positive UHI phenomenon. Over the predicted years, a notable increase in the strongest UTFVI zone in the built-up region is seen, more significantly in summer than in winter.

Assessment of hydro-morpho dynamics of the Nile River confluence scour

ABSTRACT Confluences of rivers are important component of river systems. Confluence scour is significant geomorphologically because it is a node in a channel network that controls sediment distribution, thus controlling the formation of channel migration. Nile River confluences take various shapes, such as downstream islands. Due to the construction of Aswan High Dam, major changes in hydrological characteristics downstream of the dam have affected river morphology, including the formation of islands. The purpose of this study is to investigate the hydrodynamic and morphological parameters for the Nile River confluences to provide an appropriate formula to predict confluence scour depth. For the current study, six confluence areas were selected. A numerical model was used to calculate the hydraulic characteristics of the Nile River. Geometric, morphological, and hydrodynamic analyses of selected confluences were performed in different years. Five confluence scour equations were applied to compute scour depths for the selected confluences. The scour depths for the specified confluences were calculated using five confluence scour equations. Field observations were compared to the calculated scour depths. The selected confluence scour equations didn’t have a satisfying performance for estimating the confluence scour depth in the Nile River. A new dimensionless confluence scour equation has been established.