Stacking Patterns Research Articles

Palaeoenvironmental setting and depositional model of upper Messinian microbialites of the Salento Peninsula (Southern Italy): A central Mediterranean Terminal Carbonate Complex

The Terminal Carbonate Complex (TCC) is an upper Messinian shallow-water succession characterized by abundant oolites deposits and microbial-derived carbonates mainly known from the Western Mediterranean. The importance of the TCC derives from the close relation of its deposition with the Messinian salinity crisis and from the presence of large and diversified microbialite assemblages, which represent a rare occurrence in the Cenozoic marine sedimentary record. In this paper we provide the first detailed description of a carbonate system closely comparable to the TCC located in the central Mediterranean. This succession crops out at the southern end of the Salento Platform (South-eastern Italy) and has been investigated by means of stratigraphic, sedimentary, palaeontological and Sr isotopes analyses. Special attention has been given to the microbialite facies, with a detailed textural characterization focused on the reconstruction of their depositional and palaeoenvironmental settings. The Salento Platform TCC mainly consists of oolites deposits, Porites colonization and a diversified microbialite assemblage including six different facies, which developed mostly under shallow-water, normal marine salinity and warm climatic conditions. The overall stacking pattern is given by the superposition of three main sequences, each one including lowstand, transgressive and highstand system tracts. The Salento Platform TCC is dated to the late Messinian; our microfacies and geochemical data suggest that it could have developed during the first stage of the MSC; these carbonates are in fact followed by a sharp unconformity sealed by thick breccia deposits, possibly related to the onset of the Messinian erosional surface and to the subsequent stages of the Messinian salinity crisis. • We report the presence of the Terminal Carbonate Complex in the central Mediterranean. • The Salento Platform Terminal Carbonate Complex has been dated to the late Messinian. • A depositional system made of three superimposed sequences has been recognized. • Six microbial-derived facies have been identified, their palaeoenvironment described. • The Salento TCC has been ascribed to the first stage of the Messinian salinity crisis.

Paleosols in distal alluvial sequences and their formation mechanisms: Insights from a high-resolution record in a foreland basin during early Miocene (SE France)

The stratigraphic distribution of paleosols provides a framework to investigate the controls on distal alluvial fan architecture. This study focused on paleosol-bound alluvial cycles (PACs) from the southern Digne-Valensole foreland Basin (SE France, early Miocene). We investigated the duration of the paleosol formation and identified the controlling mechanisms on their temporal and spatial distribution. Paleosols formed primarily from fine-grained sediments (65% shale, 16% lime mud). We identified three pedotypes: Calcisols from reddening throughout the weathering profile, Bw horizon overlying Bk horizon; vertic Calcisols with similar features including slickensides; and gleyic Calcisols showing saturated conditions superimposed on well-drained Calcisol features. Duration of Calcisol formation, estimated from the time span of aggrading PACs, was compatible with those from Quaternary Calcisols: median 11 to 29 kyr for maturity Stage II, > 90% of the dataset); range 20–58 kyr for maturity Stage III-IV. The shortest PACs time spans (< 10 kyr) indicate episodic sedimentation in the distal floodplain. Spatially or temporally variable sediment input in the intermediate floodplain prevented the development of paleosols at short time scales, resulting in longer PACs time spans (40 to 70 kyr) in the range of astronomical-related climate cycles. Autogenic processes also controlled the PACs stacking pattern as illustrated by stacked meter scale PACs formed during periods of relative sea-lowering indicative of a regular down-dip slope limiting river entrenchment; or during a period of high base-level in areas of low sediment supply suggesting complete diversion of the flow laterally from the previous course. The age-constrained PACs enabled to document on high-resolution time scales (a few to 100 s of kyr) the interactions between two components of the alluvial architecture, the episodic aggradation and the pedogenic processes that are difficult to determine in fossil alluvial successions. • Paleosol-bound alluvial cycles studied at 10 4 to 10 5 timescales over 3.5 Myr. • Durations of Aquitanian Calcisol formation were comparable to Quaternary ones. • Episodic floodplain aggradation is documented for timescale shorter than 10 kyr. • The potential of paleosol maturity in evaluating climate fluctuations is discussed. • Autogenic controls were identified from stacking pattern of Calcisols.

Review on the Comparative Sedimentology of Late Jurassic Transgressive Deposits of Tendaguru Hill - Mandawa Basin (Tanzania) and Wagad Hill - Kachchh Basin (India)

This review study has focused on existing sedimentological information of Late Jurassic transgressive deposits of Tendaguru Formation (110 m thick), Mandawa basin, Tanzania exposed around Tendaguru hill and Kanthkot Formation (150 m thick), Kachchh basin, India exposed near Wagad hill. Based on comparison between the two coeval deposits shows variable transgressive characteristics. Studies have revealed that during transgression there existed a storm-dominated sedimentary facies in Kanthkot Formation and tidally influenced facies type in Tendaguru Formation. Both represent similar cyclic sedimentation patterns and high-energy transgressive deposits into different depositional regimes. Lithofacies review reveals that Kachchh basin (Wagad region) was an open marine and relatively deeper and steeper shelf environment in late Jurassic time. However, Mandawa basin (Tendaguru region) was a restricted marginal marine with an estuarine setting. Faunal affinities in both formations indicate a shallow marine environment of deposition with variable depth.The close similarity of transgressive episodes and upward stacking pattern of facies successions in both basins indicates overall shallowing of the sea that correlates with the global trend of relative sea-level fall during late Jurassic time.

Reservoir Architecture in Tide-Dominated Estuary: A Case Study of McMurray Formation Oil Sand Reservoir in the Athabasca Block, Canada

This paper presents a detailed description of the sedimentary characteristics and architecture model of the tidal-dominated estuary reservoir in the Lower Cretaceous McMurray formation. Based on a thorough study of the core data, 13 lithofacies were recognized. The lithofacies associations were divided into nine types of architecture elements, that is channel, salt marsh, fluvial point bar, tidal point bar, mud flat, mixed flat, sand flat, tidal bar and offshore. Through the combination of high resolution seismic data and well data, the architecture model was established. The boundary surfaces of each architecture elements are depicted and the logging characteristics is concluded. The cross-section is constructed to reveal the superimposition model of different architectural elements with the seismic profiles. The plane and vertical distribution of architectural elements are revealed and the sedimentary model is constructed. In the longitudinal section of estuary, the architecture elements is fluvial deposits (channel, fluvial point bar, and salt marsh), tidal flat (mud flat, mixed flat, and sand flat), tidal bar, tidal flat and offshore from land to sea. In the cross section, tidal bar, sand flat, mixed flat, mud flat, tidal point bar and salt marsh are distributed successively from the center to the sides. Tidal bars and sand flats are the best reservoirs in terms of physical properties. We focus on the analysis of their architecture and summarize their stacking patterns. We propose tidal bars as compounds are lateral accretion. Tidal bar has high-angle continued lateral accretion, with a dip angle of 6–12°. Sand flat also has lateral-migrated characteristics, but their dip angle is 2–6° which is smaller than tidal bars. As a result, the dimension and stack of a single tidal bar and sand flat are quantified. The tidal bar was lateral stacking or vertical stacking with lateral-migrated or forward-migrated sand flat and existed vertical and lateral erosion-filling phenomenon. Tidal bars have width of 100–550 m and length of 800–2,400 m, and sand flats are 300–2,500 m long. Tidal bars and sand flats made up the best reservoirs. The study provides some insights for future research of estuarine sedimentary patterns and reservoir architecture.

Chronology constraints on the complex sedimentary stratigraphy of the paleo-Yangtze incised valley in China

Numerous studies have documented the sedimentary sequences of the Yangtze Delta in response to relative sea-level changes since the Last Glacial Maximum (LGM). However, the pre-LGM sedimentary history of the paleo-Yangtze Delta remains unknown, especially for the formation timing of the basal fluvial sedimentary succession in the paleo-Yangtze incised valley. Here, based on luminescence dating techniques, the sedimentary stratigraphy of three sediment cores (YD016, YD014 and YD006) were constrained and the sedimentary successions were analyzed. Combining with previously published sedimentary sequences, we infer spatiotemporal variation of the stratigraphic architectures over the Yangtze Delta through the time spanning from the late Pleistocene to the Holocene (∼50–0 ka). Our reconstruction for the paleogeography and environmental evolution of the paleo-Yangtze incised valley showed that the basal fluvial channel belts in the paleovalley associated with coeval laterally extensive paleosol-bearing stratigraphy at the interfluves occurred in the transition between marine isotope stage (MIS) 3 and MIS 2; the overlying sedimentary successions are characterized by the post-glacial floodplain deposits formed between 19 and 12 ka, and estuary to shallow marine deposits during early Holocene (11–8 ka); and then the upper most is the Yangtze Delta depositional systems dated to mid-to-late Holocene (since ∼8 ka). Correlations of the chronostratigraphy of sediment cores over the cross-sections in this region suggest that a superimposed compound fluvial channel complex has probably characterized the paleo-Yangtze incised valley systems since MIS 3. Apart from the post-LGM infilling of the LGM incised valley, the basal MIS 3 fluvial deposits might represent the earlier infilling over another incised valley, which might be formed during MIS 4 although our cores have not reached yet. Such hierarchical incised valley systems in the paleo-Yangtze Delta were likely related to the late Quaternary sea-level changes. In addition, the relict inherited topography since the last glacial period could have played an important role in the stacking patterns of the paleo-Yangtze incised valleys.

Effects of conjugated structure on electronic and transport properties in organic–inorganic hybrid superlattices Cd2Se2(C2H4N2)1/2

By inducing π-conjugated organic molecule C2H4N2 in group II–VI based CdSe network structure materials, the band structures and carrier transport of organic–inorganic hybrid superlattices Cd2Se2(C2H4N2)1/2 were investigated via first-principles calculations based on the density functional theory. With different stacking patterns, it is found that the carrier mobility can be modulated by 5–6 orders of magnitude. The physical mechanism of the high carrier mobility in the hybrid structures has been revealed, which means dipole organic layers realize electron delocalization via electrostatic potential difference and build-in electric field. Our calculations shown that the dipole organic layers originate from asymmetric π-conjugated organic molecules and the charges movement between molecules, while symmetric organic molecules tend to electrostatic balance. And although the electronic transport properties were highly restrained by the flat bands of organic layers around Fermi energy in most structures, we found that the collective electrostatic effect can lead to very high electron mobility in AA1 and AA2 stacking systems, which might be attributed to the superposition of molecule electrostatic potential along with electrons transfer between molecules. Furthermore, it is also found that the anisotropy of electron mobility can be modulated via the difference directions of dipole layers.

Geophysical Well Log Appraisal of Okpella Field within Offshore Niger Delta Basin of Nigeria

The Production data of Okpella Field, located within the Offshore Niger Delta Basin, Nigeria, revealed that the Okpella Field attained peak annual hydrocarbon production of 430175 MBO (Million Barrel of Oil) in 2008, and the production has presently dropped to 7839 MBO per annum. Therefore, an appraisal study was conducted to identify opportunities for reversing the low production. The sought opportunities were bypassed reservoirs with pay zones. This study uses geophysical Well log data, Biostratigraphic data, and Production data to appraise Okpella Field. The hydrocarbon production data were analyzed for the produced reservoirs to establish the positive effects of the Bypassed hydrocarbon reservoirs zone within Okpella Field Offshore Niger Delta Basin. Before this study, the operating company had previously identified six reservoirs. They were named major reservoirs Sand A to F, of which major reservoirs B, C, and E are gas-bearing, major reservoir D bears gas and oil, and major reservoir F bears condensates. Three additional reservoirs with pay zones were identified within this study, and they were named Bypassed A to C. Bypassed A is gas bearing, Bypassed B is oil and gas and Bypassed C is oil-bearing. The petrophysical analysis of the wells within Okpella Field determined the various reservoir properties such as the gross thickness, net thickness, net to gross ratio, the volume of shale, porosity, and hydrocarbon saturation of the major reservoir and bypassed reservoir zones. Some of the reservoirs are amalgamated upward coarsening sand bodies of distal fan lobes within the Low-stand systems tract. Others are leveed channel proximal. The Biostratigraphy data were integrated with the stacking pattern of the Gamma-ray log motif, revealing the sequence boundaries and inferring the possible depositional environment. The reservoirs within the Okpella Field were deposited within the Low-Stand System Tract (LST), reflecting a high energy environment, possibly the shoreface depositional environment.

Discrimination of tectonic influence from volcano‐sedimentary successions: An example from the Janggi Basin, south‐eastern part of the Korean Peninsula

AbstractIn extensional and transtensional basins, the dual action of basin‐forming tectonism and explosive volcanic activity results in deposition of complex volcano‐sedimentary successions. Since both aspects contemporaneously affect sediment‐dispersal systems, it is difficult to distinguish one from the other by analyzing volcano‐sedimentary successions. To discriminate tectonic influence, basin fills of the Miocene, pull‐apart Janggi Basin were investigated. Here, the contemporaneous influence of tectonic subsidence and explosive volcanism formed &lt;966 m thick, conformable volcano‐sedimentary successions composed of laterally extensive, pumice‐bearing, unwelded pyroclastic deposits and nonmarine sedimentary rocks formed under humid climatic conditions. Based on Laser Ablation – Multiple Collector – Inductively Coupled Plasma Mass Spectrometry zircon U–Pb age data, these successions were deposited from 21.1 ± 0.2 to 20.1 ± 0.1 Ma. After deposition of basinwide, tens of metres thick, and unwelded pyroclastic deposits, the directly overlying facies successions (FS‐1 and FS‐2) show contrasting depositional features to the classical model of volcaniclastic sedimentation. Facies succession‐1 is represented by fluvial conglomerates composed mostly of (sub)rounded pebble and cobble sourced from basement. The supply of basement‐derived clasts through fluvial systems resulted from development of physiographic relief during or soon after the eruption by syndepositional tectonic subsidence. Facies succession‐2 occurs directly on pyroclastic deposits that cover FS‐1 and show coarsening‐upward trends, and is composed of basal lacustrine mudstones and overlying resedimented volcaniclastic sandstones showing a progradational geometry, interpreted as a result of progressive filling of the lake by remobilized volcaniclastic sediments. Occurrence of basal lacustrine laminated mudstones indicates that syndepositional creation of the accommodation by tectonic subsidence exceeded forceful input of pyroclastic and remobilized volcaniclastic sediments, resulting in a delayed sedimentary response to explosive volcanic eruptions. This study shows that, despite voluminous production of volcaniclastic sediments, tectonic activity controlled sediment type and stacking patterns. Therefore, these depositional features allow to discriminate tectonic effects from complex volcano‐sedimentary successions, enabling to reconstruct basin evolution.

Terrace Morpho-Sedimentary Sequences on the Sibari Plain (Calabria, Southern Italy): Implication for Sea Level and Tectonic Controls

The Sibari Plain (northeastern Calabria) shows a well-developed stair of late Quaternary marine/coastal terraces resulting from the interaction between sea level fluctuations and tectonic uplift. This paper (i) provides a stratigraphic description of terraced deposits between the Raganello and Coscile rivers, (ii) assesses the relative controls of eustacy and uplift on the staircase formation, and (iii) unravels the Quaternary morphosedimentary evolution of the study area. A geomorphological approach was coupled with stratigraphic field surveys. Photo interpretation, topographic map analyses, and field surveys allowed us to map ten orders of terraces forming telescopically incised valley-fills. Based on the uppermost position of foreshore deposits on inner margins and an average uplift rate of ~1 mm/y, inferred from the Marine Isotope Stage (MIS) 5.5, terraces were correlated with highstands. Sedimentological and stratigraphic analyses allowed us to recognize four assemblages of genetically associated sedimentary facies related to superimposed and juxtaposed coastal and alluvial systems, showing a seaward-stepping architecture. Based on stratal geometry and facies association, we argue that alluvial/fluvial sediments and coastal depositional systems formed contemporaneously along the same terrace. Terrace arrangement resulted from repeated cycles of valley incision (sea level fall) and aggradational to progradational stacking pattern (sea level rise and highstands) in a framework of sustained uplift.

Structural control and tectono-sedimentary evolution of the Gulf of Cadiz, SW Iberia since the late Miocene: Implications for contourite depositional system

The Gulf of Cadiz Contourite Depositional System (GCCS) developed due to the interaction of the Mediterranean Outflow Water (MOW) with the middle continental slope of the SW Iberian continental margin. The GCCS evolved in a complex tectonic setting within the foreland of the Betic Orogeny and near the Nubia-Eurasia plate boundary. This study used tectonostratigraphic analysis of an extensive 2D multichannel seismic reflection dataset to investigate how inherited basin configuration and tectonic activity controlled sedimentary stacking pattern and evolution of the GCCS. Three regional tectonostratigraphic units (U1-U3) were recognised in the margin. The younger seismic unit U3 corresponds to the Miocene-Quaternary foreland basin system where the contourite system is generated. Seismic analysis also detected the dextral strike-slip Gil Eanes Fault Zone (described herein for the first time), the Cadiz Fault, the Albufeira-Guadalquivir-Doñana Basement High and several diapiric structures. Integrated analysis of seismic profiles showing these tectonic structures with thickness and earthquake distribution maps suggest four tectono-sedimentary domains. The distinct characteristics shown by contourite features in the different domains, depends at broad-scale on the tectonic-control of the accommodation space (i.e., subsidence or uplift) and at local-scale on the presence of structural highs and fault-related depressions. Both influence bottom-current circulation and thus the evolution of the contourite deposits through the late Miocene and Quaternary. Three main stages have been recognised in the Gulf of Cadiz evolution: 1) the region was the western continuation of the Betic Corridor until the final re-opening of the Strait of Gibraltar (8–5.3 Ma). In this stage there is a predominance of turbidites or hemipelagic deposits, dependant on tectonic activity; 2) with the final re-opening of the Mediterranean-Atlantic connection there is the onset of the Pliocene- Quaternary contourite depositional system (5.3–2.0 Ma). Short-term changes in sedimentation during this stage, from contourite to turbidite deposits, indicate periods of increased tectonic activity; and 3) after the onset of the transpressive tectonic regime in the area (from 2.0 Ma), sedimentation became more homogeneous suggesting stable conditions (decrease of tectonic activity) with dominant contourite deposition. This work highlights the remarkable influence of structural features and tectonic events in controlling the seafloor relief and in turn in influenced the local oceanic circulation processes that controlling the morphology and sedimentary evolution of contourite systems.

Tailoring Photoinduced Nonequilibrium Magnetizations in In2Se3 Bilayers

AbstractMagnetization generation and accumulation in intrinsically nonmagnetic materials is one of the key routes to various exotic applications, especially realizing fast information storage and memory devices. Among the various approaches for magnetization injection, light irradiation is advantageous for its noncontacting and non‐invasive nature, and has been receiving great attention during the past few decades. In the current work, a quadratic response theory and first‐principles calculations are applied to reveal photoinduced magnetization in recently discovered 2D In2Se3 bilayers. The ferroelectric In2Se3 bilayers can be (meta‐) stabilized in versatile stacking patterns, exhibiting largely tunable electronic band structure, and optical feature. Hence, it is suggested that under circularly polarized light illumination, the system can show different photoinduced magnetization responses with large contrast in different stacking patterns. The magnetizations are composed by both spin and orbital angular momentum contributions, which can reach as large as 1μB under a laser with intermediate intensity (≈109 W cm–2). This magnitude can be easily observed and furthermore manipulated in the state‐of‐the‐art experimental techniques. The proposal suggests a candidate material platform to explore the interplay among spintronics, orbitronics, nonlinear optics, and ferroelectrics in a single platform.

Enhancement of the flexural and impact properties laminated biocomposite by new natural fibres for artificial lower limb socket

ABSTRACT For several purposes, involving sickness, injuries, and genetic abnormalities, artificial limbs may be necessitated. Artificial limbs must be altered and modified regularly since the human physique vagaries with time owing to gaining or changing body mass. The utilisation of natural fibres as a potential substitute for fabricating a below-knee prosthesis socket will be highlighted in this study. To construct a below-knee socket, a vacuum bagging process was utilised. Woven flax, sisal, cotton, carbon, and glass fibre have formed in the laminates. The effect of various fibre stacking patterns on certain physical and mechanical properties was investigated. Multiple mechanical tests, including flexural, maximum shear stress, and impact tests, were performed as part of the experimental portion of this work. The findings of this study revealed that ingesting various kinds of reinforcing materials had a significant impact on the characteristics of fabricated composites, with the virtues of (flexural strength, flexural modulus, max. Shear stress, impact strength, and fracture toughness) improving as the volume fraction of materials increased. This review focuses on the assets of flax, sisal, and cotton fibre hybrid strengthened PMMA composites (hybridised in a variety of volume proportions and lamination layups) that have yet to be tested as a superior alternative for the creation of prosthetic sockets.

Use of the FMVSS-214 static bending test to evaluate an automobile side door impact beam made of glass fiber-reinforced plastic

A side door impact beam absorbs energy and plays an important role in preventing intrusion of another vehicle into the occupant area. Impact beams are being actively researched to reduce vehicle weight while still meeting the strength requirements of environmental regulations and to improve fuel efficiency and enhance safety. No study has subjected a lightweight glass fiber-reinforced plastic (GFRP) impact beam to the Body in White (BIW) Federal Motor Vehicle Safety Standard (FMVSS)-214 quasi-static test. We compared three beams that differed in shape and stacking pattern. We performed three-point bending analyses, bending tests (including after bracket tightening), and static bending tests of door assemblies. The best GFRP beam (B) and a steel model were compared in terms of BIW static bending performance. The front-door GFRP beam exhibited an average reaction force 135% of that mandated by the FMVSS-214S test specification, an intermediate average reaction force 158% of that required, and a final force 154% of that required. In terms of bending performance, the initial average reaction force was 9.5% higher than that of the steel impact beam, and the rear door force was 6.6% lower. The reaction force of the GFRP beam decreased rapidly as breakage occurred after bending through 110.0–120.0 mm; however, the average reaction force was similar to that of the steel beam. Thus, the GFRP impact beam met the legal requirements but weighed 30% less than the steel beam.

Architecture, controlling factors and evolution history of unidirectionally upstream-migrating turbidite channels: A case study from southern Qiongdongnan Basin, northern South China Sea

In the last decade, the discovery of unidirectionally upstream-migrating turbidite channels (UUMTCs) has aroused the interest of deepwater geologists due to giant gas fields explored in UUMTCs. However, their architecture, controlling factors and evolution history are unclear enough. Here, 3D seismic data from the Beijiao sag of the southern Qiongdongnan basin (QDNB) are used to document previously undescribed characteristics of seven UUMTCs in the lower middle Miocene. The results show that (1) UUMTCs are 5–10 km in length and 0.5 km in width and gradually terminate downslope, whose scales are far smaller than normal (relatively large-scale) UDMTCs elsewhere; (2) Stacking patterns of UUMTCs are characterized by unidirectional migration of multiple channel-levee complexes, whose seismic reflections record unilateral transition from high to low amplitudes from channel axis to off-axis positions; (3) Dip gradients (angles) of trajectories of UUMTCs are variable in the alongslope and downslope cross sections; (4) Polygonal faults are absent in the channel axes of UUMTCs and occur in the channel off-axis positions; (5) Channels (C1∼7) perpendicular to the slope are characterized by unidirectional migrations in the relatively steep slope, in contrast coeval channels (C8, 9) approximately parallel to the slope are featured by vertical aggradation in the gentle slope.Unlike terrigenous siliceous lithology of large-scale UUMTCs elsewhere, it is inferred that the lithology of herein (small-scale) UUMTCs is transitional from coarse-grained (carbonate sandstones) debris in the channel axis to fine-grained debris in the channel off-axis positions. Their controlling factors are summarized: carbonate sediment supply, relative sea level fluctuation, alongslope contour currents and local slope configuration. The orientation between turbidity flows and contour currents, controlled by local slope configuration, plays a vital role in the stacking pattern of channels, which are characterized by unidirectional migration of channels perpendicular to the strike of slope and are featured by vertical aggradation of channels parallel to the slope. Dip gradients are for the first time proposed as an optimal parameter for appraising the intensity change of contour currents crossing channels during their interaction, in agreement with the previous flume-tank experiments. Our study could provide some clarity on the formation and evolution of UUMTCs.

Molecular Dynamics Study of Melting Behavior of Planar Stacked Ti–Al Core–Shell Nanoparticles

Selective laser sintering (SLS) is one of the most commonly used methods in additive manufacturing, due to its high prototyping speed and applicability to various materials. In the present work, molecular dynamics (MD) simulations were performed to study the thermodynamic behaviors of the planar stacked nanoparticles (NPs) model and explore the potential capability of the SLS process with nano-sized metal powders in the zero-gravity space environment. A multi-particle model of titanium–aluminum (Ti–Al) core–shell NP with a particle radius of 50 Å was constructed to investigate the characteristics of the melted pattern during sintering. Two patterns with different spatial densities were considered to study the influence of particle stacking on the melting process. Various core volume fractions and heating rates were examined to investigate their effects on the quality of the final sintered product. The stacked-NPs models with core volume fractions (CVFs) of 3%, 12%, and 30% were linearly heated up to 1100 K from room temperature (298 K) with heating rates of 0.04, 0.2, 0.5, and 1.0 K ps−1. The initial fusion temperature and final sintering temperature for each stacking pattern were obtained via the validation from the radial distribution function, mean squared displacement, and the radius of the gyration analysis. The 30% CVF yields the largest neck size before the melting point, while beyond the melting point, a larger core helps delay the formation of the fully-melted products. It is observed that using the close-packed stacked-NPs model under a slow heating rate (long melting duration) would help form a stable, completely sintered product with a relatively low final sintering temperature.

Multiscale hierarchical structures from a nanocluster mesophase.

Spontaneous hierarchical self-organization of nanometre-scale subunits into higher-level complex structures is ubiquitous in nature. The creation of synthetic nanomaterials that mimic the self-organization of complex superstructures commonly seen in biomolecules has proved challenging due to the lack of biomolecule-like building blocks that feature versatile, programmable interactions to render structural complexity. In this study, highly aligned structures are obtained from an organic-inorganic mesophase composed of monodisperse Cd37S18 magic-size cluster building blocks. Impressively, structural alignment spans over six orders of magnitude in length scale: nanoscale magic-size clusters arrange into a hexagonal geometry organized inside micrometre-sized filaments; self-assembly of these filaments leads to fibres that then organize into uniform arrays of centimetre-scale bands with well-defined surface periodicity. Enhanced patterning can be achieved by controlling processing conditions, resulting in bullseye and 'zigzag' stacking patterns with periodicity in two directions. Overall, we demonstrate that colloidal nanomaterials can exhibit a high level of self-organization behaviour at macroscopic-length scales.

Impact of arrangement, length and chemical potential on the robustness of graphene induced photonic bandgap in photonic crystals

The study of photonic crystals, artificial materials whose dielectric properties can be tailored according to the stacking pattern of their constituents, remains an attractive research area. Very recently, the propagation of light waves in periodic and quasiperiodic graphene embedded dielectric multilayers has also been considered. The presence of graphene between consecutive layers induces the emergence of the so-called graphene induced photonic bandgap. In this article, we employ a transfer-matrix treatment to study the effects of (i) random arrangement of the layers, (ii) length of the multilayer and (iii) chemical potential of graphene on the robustness of the graphene induced photonic bandgap (GIPBG) in one dimensional graphene-embedded photonic crystals. The photonic crystals considered here are composed of two dielectric materials, namely, silicon dioxide (layer A=SiO2) and titanium dioxide (layer B=TiO2). Our numerical results quantitatively show that the random arrangement and length of the multilayers cause minor changes in the bandgap edge of the low frequency GIPBG, i.e., the low frequency GIPBG is robust regarding composition and length of the structures. On the other hand, the chemical potential strongly affects the robustness of the low frequency GIPBG. In fact, the low frequency GIPBG is strongly dependent on the properties of graphene, reinforcing that it is possible to adjust its width and bandgap edge by tuning the chemical potential via a gate voltage.

Quantitative reconstruction of Holocene ground displacements in the offshore part of the Campi Flegrei caldera (southern Italy): Perspectives from seismo-stratigraphic and archaeological data

Analysis of high-resolution seismic profiles integrated with archaeological data along the coast has allowed quantifying the last ∼10 ka BP displacements in the offshore part of the Campi Flegrei resurgent caldera, one of the world's highest-risk volcanic areas. Previous onland studies revealed that, following the Neapolitan Yellow Tuff (NYT) eruption at 15 ka, post-caldera evolution was associated with rapid ground uplift and subsidence cycles. In this paper, we use the stacking pattern of Prograding Wedges (PWs) and Aggrading Fills (AF) to reconstruct relative sea-level changes and estimate the amount of vertical deformation in the Pozzuoli Bay, the submerged part of the caldera. We document five generations of prograding wedges (PW1 to PW5), associated with as many periods of relative ground stability between uplift and subsidence. Instead, deposition of aggrading fills above prograding wedges underpins the subsidence that typically follows volcanic unrest and uplift. The older wedges PW1 and PW2 are larger and likely indicate whole-caldera uplift events. In particular, the development of PW2 starting from ∼5.2 ka is related to the rapid growth of a resurgent dome in the central part of the caldera. After ∼3.7 ka, subsidence prevailed in the caldera leading to deposition of an aggrading fill (AF2). However, subsidence was interrupted by short-term uplift episodes in historical times at (100 BCE-100 CE, 600–700 CE, 1430–1538 CE) that led to the growth of comparatively minor-sized wedges PW1 to PW3, respectively. Displacement of coastal infrastructures of the Roman age (∼2 ka BP) is consistent with the vertical motion retrieved by the seismostratigraphic analysis, and further indicates the existence of two deformation signals. A short-wavelength signal confined to the Pozzuoli Bay reflects the contribution of an intra-caldera source. This signal is superposed to a long-wavelength regional subsidence increasing between Naples and Procida Island from 1.5 to 2 mm/a, respectively. The east-to-west enhancing subsidence likely reflects the transition between the uplifting Apennines and the foundered Tyrrhenian back-arc basin.

Study of Two-Dimensional Janus WXY (X≠Y= S, Se, and Te) Trilayer Homostructures for Photovoltaic Applications Using DFT Screening of Different Stacking Patterns.

Based on the first-principles density functional theory, Janus WXY (X ≠ Y = S, Se, and Te) trilayer homostructures for different stacking patterns are studied in this work to analyze their appropriateness in fabricating photovoltaic (PV) devices. A total of fifteen trilayer homostructures are proposed, corresponding to the suitable five stacking patterns, such as AAA, AA′A, ABA, AB′A, and A′BA′ for each Janus WXY (X ≠ Y = S, Se, and Te) material. Structural and energetic parameters for all the fifteen structures are evaluated and compared to find energetically stable structures, and dynamic stability is confirmed by phonon dispersion curves. All these configurations being homostructure, lattice mismatch is found to be very low (∼0.05%), unlike heterostructure, making them feasible for optoelectronics and PV applications. WSSe AAA, WSSe AA′A, and WSeTe AA′A are dynamically stable along with negative binding energy and show type-II band alignment, enabling effective spatial carrier separation of photogenerated carriers. The optical properties of dynamically stable WSSe AAA and WSSe AA′A structures are also calculated, and the absorption coefficients at the visible light region are found to be ∼3.5 × 105 cm–1, which is comparable to the perovskite material absorption coefficient. Moreover, we have compared the optical characteristics of dynamically stable WSSe AAA and WSSe AA′A structures with their monolayer structures to realize the significance of stacking trilayer structures. Electrical properties such as mobility and conductivity for dynamically stable WSSe AAA and WSSe AA′A structures are evaluated to suggest them as a probable efficient material in PV technology.

Observational data-based sequence stratigraphy of a clastic wedge within an active foreland basin, Spirit River Formation, west-central Alberta, Canada

The Spirit River Formation forms a third-order clastic wedge that consists of strongly progradational to aggradational parasequence sets following a maximum transgression. This observed parasequence stacking pattern is opposite from the traditional sequence stratigraphic models following a maximum marine transgression. The previously recognized gas-charged but low permeability reservoir sandstone bodies of the progradational succession were disregarded as it has required the recent technological advancement of horizontal wells with multistage hydraulic fracturing to exploit them. The unusual parasequence stacking pattern of the progradational succession was unraveled by detailed logging of 10's of cored intervals and 1,000's of wells with log suites for facies analysis and sequence stratigraphy. Evaluation of the local basin controls on parasequence set stacking patterns shows a high sediment influx relative to the available and rate of creation of new accommodation space relationship controlled the initial strongly progradational stacking pattern of the lower part of the Spirit River Formation. A high sediment influx was maintained, but a significant increase in accommodation from increased tectonic activity and associated subsidence resulted in the overlying strongly aggradational parasequence set stacking pattern of the upper part of the Spirit River Formation. Understanding the local basin controls on sedimentation and accommodation that helps predict parasequence set stacking patterns leads to better unconventional exploration and exploitation opportunities worldwide of clastic wedges.