Surface Decomposition Research Articles

An assessment of the Arabic RH5 Neolithic fishing community’s mortuary practices by examining human rib cross-sections for bioerosion patterns

The purpose of this research is to offer a micro-anatomical skeletal means for understanding the funeral practices of the Neolithic fishing community of Ra’s al Hamra 5, which is located on the Arabian Peninsula. The archaeological site is located on the Oman gulf of the Arabian Sea coast near the suburb of Qurum; located near the Omani capital Muscat. Archaeological evidence dates the graveyard between 3800 BCE. and 3300 BCE. The burials focused on in this research come from Area 43, a part of the site that held partially burnt and commingled human remains. The study was conducted on 24 histological samples taken from ribs. The traces of bioerosion found on the non-burnt and burnt samples are analyzed. The percentage of bioerosion for each samplehas been documented (area of involvement; Ct.BAD/Ct.Ar.). Less than 5% of the rib cross-sections lack diagenetic alteration. Of the remaining samples, 52.2% show less than 49% diagenetic alteration of the cortical cross-sectional area, while 47.8% of the samples show greater than 50% or more of diagenetic change to the bone matrix. The variability in bioerosion indicates that different lengths of surface decomposition time were involved during funeral practices.This suggests that there may have been a degree of cultural variation employed as these Neolithic people buried their dead. Our results suggest that some of the remains were buried shortly after death. Other remains were exposed to open-air decomposition prior to both burning and burial.

Local heat generated by a focused He+ ion beam

A focused He+ beam with a beam diameter less than 1 nm is heating up the targeted surface for a He+ dose larger than 1 × 1020 ions cm−2. The temperature can reach 1000 °C locally, resulting in surface decomposition or chemical reactions. This temperature was measured by fabricating gold nanodisks down to 20 nm in diameter and 10 nm in thickness on mica and sapphire surfaces. The melting and vaporization of these nanodisks were used to determine this temperature according to the known gold nanocluster melting temperature variations as a function of their volume. This local heat production is very negative for precise He+ nanolithography resist processes but advantageous without a resist when used to directly nano-sculpture a nanomaterial when a very thermally conductive support like sapphire is selected.

Effects of Thermal Annealing on Optical Properties of Be-Implanted GaN Thin Films by Spectroscopic Ellipsometry

Wide bandgap III-V compounds are the key materials for the fabrication of short-wavelength optical devices and have important applications in optical displays, optical storage devices and optical communication systems. Herein, the variable-angle spectroscopic ellipsometry (SE) measurements are performed to investigate the thickness and optical properties of beryllium-implanted gallium nitride thin films that have been deposited on (0001) sapphire substrates by using low-pressure metalorganic chemical vapor deposition (LPMOCVD). The film layer details are described by using Parametric Semiconductor oscillators and Gaussian oscillators in the wavelength range of 200–1600 nm. The thickness, refractive indices and extinction coefficients of the Be-implanted films are determined at room temperature. Analysis of the absorption coefficient shows that the optical absorption edge of Be-implanted films changes from 3.328 eV to 3.083 eV in the temperature range of 300–850 K. With the variable temperature, Eg is demonstrated to follow the formula of Varshni. A dual-beam ultraviolet–visible spectrophotometer (UV–VIS) is used to study the crystal quality of samples, indicating that the quality of rapid thermal annealing (RTA) sample is better than that unannealed sample. By transport of ions in matter (TRIM) simulation and SE fitting the depths of Be implanted gallium nitride (GaN) films are estimated and in good agreement. The surface and cross-section morphologies are characterized by atomic force microscopy (AFM) and scanning electron microscope (SEM), respectively. The surface morphologies and thickness measurements of the samples show that RTA can improve crystal quality, while increasing the thickness of the surface roughness layer due to partial surface decomposition in the process of thermal annealing.

Direct growth of graphene on GaN via plasma-enhanced chemical vapor deposition under N2 atmosphere

One of the bottlenecks in the implementation of graphene as a transparent electrode in modern opto-electronic devices is the need for complicated and damaging transfer processes of high-quality graphene sheets onto the desired target substrates. Here, we study the direct, plasma-enhanced chemical vapor deposition (PECVD) growth of graphene on GaN-based light-emitting diodes (LEDs). By replacing the commonly used hydrogen (H2) process gas with nitrogen (N2), we were able to suppress GaN surface decomposition while simultaneously enabling graphene deposition at <800 °C in a single-step growth process. Optimizing the methane (CH4) flow and varying the growth time between 0.5 h and 8 h, the electro-optical properties of the graphene layers could be tuned to sheet resistances as low as ∼1 kΩ/□ with a maximum transparency loss of ∼12%. The resulting high-quality graphene electrodes show an enhanced current spreading effect and an increase of the emission area by a factor of ∼8 in operating LEDs.

Noble-metal-free Ni3C as co-catalyst on LaNiO3 with enhanced photocatalytic activity

In this study, Ni3C nanoparticles (NPs) were loaded on LaNiO3 NPs as a co-catalyst during the photocatalytic H2 evolution. The evolution rate of the LaNiO3-3 wt%Ni3C composite (4093.9 μmol g−1 h−1) is about 5 times and 2 times as that of pristine LaNiO3 NPs (819.2 μmol g−1 h−1), and 1 wt% Pt loaded LaNiO3 NPs (1927 μmol g−1 h−1). The effects of co-catalyze with Ni3C on light absorption, electron-hole spatial separation, and surface H2-evolution kinetics are investigated. Loading with Ni3C can enhance the spatial separation of electron-hole pairs, and improve the H2-evolution kinetics. Further investigation shows that surface decomposition of LaNiO3 NPs can only be observed when the Ni3C content is over 3 wt%, caused by the reductive carbon source needed in the loading process. This work indicates that transition metal carbide can be a promising co-catalyst candidate for oxides in photocatalytic applications without concerning corrosion from the reductive carbonaceous precursors in the loading process.

Kinetic effects of polymorphs and surface areas on adsorption and photocatalytic decomposition of acetaldehyde on titania

Adsorption and photocatalytic decomposition behaviors of gas-phase acetaldehyde (CH3CHO), together with carbon dioxide (CO2) formation have been measured for pure titania (TiO2) powders with three types of polymorphs (anatase, brookite, and rutile) under UV-light illumination, and assessed by a kinetic model that takes into account the immediate decomposition of CH3CHO attached on the surface, and the gradual decomposition of CH3CHO adsorbed on the surface. Experimental data are well reproduced by the present model, highlighting how adsorption-related pathways markedly contribute to overall CH3CHO removal kinetics even for pure titanias. Although the initial removal rate depends on the surface area, which affects the adsorption capacity, it is suggested that specific surface area-based adsorbability and decomposition reactivity are enhanced by heightened crystallinity. Our kinetic analysis demonstrates that anatase exhibits the highest photocatalytic activity as a result of superior adsorbability, as well as superior decomposition reactivity, compared to other polymorphs.

Elucidating Aluminum-Ion Intercalation and Its Effects on the Local Crystalline Framework Using Solid-State NMR Spectroscopy

Rechargeable multivalent-ion batteries are safe and low-cost alternatives to traditional lithium-ion batteries. However, higher Coulombic charge density of the multivalent ions results into sluggish diffusion of their respective cations within crystalline transition metal compounds. The Chevrel phases Mo6X8, where X is a chalcogen atom (e.g., S or Se) are among the few materials known to reversibly and electrochemically intercalate both divalent (e.g. Mg2+, Zn 2+, etc.) and trivalent (Al3+) ions. Thus, understanding the ion intercalation and charge transfer mechanisms within these unique compounds may provide insights into the molecular-level design of new intercalation electrodes for rechargeable multivalent ion batteries. Here, we use multi-nuclear solid-state magic-angle-spinning (MAS) NMR spectroscopy to reveal the ion intercalation and charge transfer mechanisms of zinc and aluminum intercalation in Chevrel electrodes Mo6S8 and Mo6Se8. Ex situ single pulse solid-state 27Al MAS NMR measurements were performed on the thio-chevrel electrodes at different states-of-charge to observe changes in the environments and to quantify the local populations of aluminum ions within the host crystal structure, revealing both intercalated ions and additional aluminum species associated with surface layers and/or decomposition products. Al-Mo6Se8 batteries were made for the first time and their electrochemical properties were compared to the thio-chevrel Mo6S8. Ex situ 77Se and 95Mo measurements on the seleno-chevrel Mo6Se8 at charged and discharged states revealed that the electrons are transferred to the anionic chalcogen framework the electron charge transfer mechanism and its effects on the local crystalline framework environments upon aluminum ion intercalation. These results were then generalized for zinc intercalation into chevrel phase electrodes.Overall, the solid-state NMR measurements combined with the electrochemical measurements yield molecular-level insights into the coupled aluminum ion intercalation and electron charge transfer processes that occur in a model crystalline transition metal electrode. Unique reversible anionic redox reactions were observed for multivalent ion intercalation into chevrel, which is very different that typically observed for lithium-ion intercalation into transition metal oxides, where the electrons are stored into the d-orbitals of the transition metal. The results suggest materials design principles aimed at designing multivalent-ion intercalation electrodes with improved electrochemical properties. Figure 1

Separate in Latent Space: Unsupervised Single Image Layer Separation

Many real world vision tasks, such as reflection removal from a transparent surface and intrinsic image decomposition, can be modeled as single image layer separation. However, this problem is highly ill-posed, requiring accurately aligned and hard to collect triplet data to train the CNN models. To address this problem, this paper proposes an unsupervised method that requires no ground truth data triplet in training. At the core of the method are two assumptions about data distributions in the latent spaces of different layers, based on which a novel unsupervised layer separation pipeline can be derived. Then the method can be constructed based on the GANs framework with self-supervision and cycle consistency constraints, etc. Experimental results demonstrate its successfulness in outperforming existing unsupervised methods in both synthetic and real world tasks. The method also shows its ability to solve a more challenging multi-layer separation task.

Determination of active sites during gasification of biomass char with CO2 using temperature-programmed desorption. Part 2: Influence of ash components

The present work is the second part of a study conducted with the aim to determine the amount of active sites present on the surface of a biomass char participating in the gasification reaction with CO2 using the temperature programmed desorption (TPD) technique. In part 1, the methodology and experimental results during TPD of partially gasified samples of beech wood char (WC1600) using CO2 as gasification agent are presented. This work focusses on the influence of the main inorganic ash components of WC1600 on the CO2 and CO signals obtained during TPD of partially gasified char samples. Furthermore, an activated carbon with ash content lower than 1 wt-% is impregnated with Ca and K and partially gasified followed by a TPD analysis. CO2 and CO signals obtained during TPD result from decomposition of oxygenated surface complexes and decomposition reactions of ash components. During gasification, three different kinds of sites are present on the surface of the char: stable, reactive and catalytically active sites. The latter are a measure of the catalytic influence of inorganic matter during char gasification. From the analysis of the TPD spectra, it can be concluded that gasification of WC1600 is dominated by the catalytic influence exerted by Ca and K. Formation of oxygenated surface complexes on WC1600 is limited, possibly due to the high temperature at which the sample was pyrolyzed (1600 °C). However, a direct correlation between specific conversion rate and the amount of reactive and catalytically active sites is developed from the experimental results, corrected by the contribution of ash decomposition.

Thermal stability of CH3NH3PbIxCl3-x versus [HC(NH2)2]0.83Cs0.17PbI2.7Br0.3 perovskite films by X-ray photoelectron spectroscopy

The thermal stability of CH3NH3PbIxCl3-x and [HC(NH2)2]0.83Cs0.17PbI2.7Br0.3 perovskite films was studied in-situ by X-ray photoelectron spectroscopy. It was found that below 85 °C both of them are relatively stable. After annealing above 85 °C, we observe a clear perovskite surface decomposition, i.e., a release of organic cations and creation of “metallic lead”. The mixed cation lead mixed halide perovskite, however, decomposes at a much lower rate. For both perovskite films, the metallic to the total lead ratio changes with the same rate for the same annealing temperatures. The release of A-site cations from the ABX3 crystal structure of perovskite and/or creation of “metallic lead” causes also a small shift of the valence band maximum towards the Fermi level. The release of [HC(NH2)2]± or Cs± is not as significant as the release of CH3NH3±; therefore, it may explain why [HC(NH2)2]0.83Cs0.17PbI2.7Br0.3 solar cells are thermally more stable. Therefore, as the stability of CH3NH3PbIxCl3-x is same as the stability of [HC(NH2)2]0.83Cs0.17PbI2.7Br0.3 below 85 °C, there must be more severe degradation pathways that are currently underappreciated on the solar cell level.

Surface defect formation in polyimide film via ion migration from glass substrate

Migration of ions such as sodium from a glass surface to organic materials in contact is critical for the use of glass as a supporting material for film casting. In this study, we report the surface defect formation of annealed poly(pyromellitic dianhydride-co-4,4′-oxydianiline) (PMDA-ODA) film after detaching the film from soda-lime glass via ion migration. The defect was porous and sodium was observed as one of the major impurities in the defect. We propose that the defect forms as a result of the ion migration from glass and thermal decomposition of PMDA-ODA. The ions released from glass at a sufficiently high temperature form hydroxide compounds during the floating of the film on the water and readily attacks the imide ring at the glass-film interface. The ionic bonds are broken by thermal annealing and diffuse throughout the film, finally defects form by both segregation of ions to the film surface and PMDA-ODA decomposition.

Stabilization of Lithium Cobalt Phosphate Cathodes via Artificial Interphases

Olivine LiCoPO4 (LCP) exhibits a rare combination of high theoretical capacity (167 mAh g−1), excellent thermal stability, and high redox potential (4.8 V vs vs Li/Li+), making it a promising candidate for high voltage lithium batteries. Despite these attractive properties, practical implementation of this electrode chemistry has been limited by stability issues at the cathode-electrolyte interface, including parasitic electrolyte reactions, surface decomposition of the electrode material, and Co dissolution. Carbon coating and substitutions of Co by Fe and other cations improve the performance, however the cycling stability needs further improvement. In an effort to address these issues, we deposited thin, conformal metal oxide surface coatings on substituted LCP powder and investigated the effects of these coatings on the performance of carbon-coated substituted LCP/MCMB graphite full cells with a standard carbonate electrolyte. Remarkably, some of these coatings clearly improved operation of carbon-coated substituted LCP cells as compared to the as-prepared cathode powder. Observed improvements in capacity retention relate to stabilization of the cathode-electrolyte interface and suppression of electrolyte oxidation, as measured by online electrochemical mass spectroscopy (OEMS) of evolved gases within the cell. Together, these results suggest artificial interphases are a viable pathway toward stabilizing LCP and achieving commercial viability.

Effects of 1,9-dibromnonane on the structural, photophysical properties and stability of cesium lead bromide perovskite nanocrystals

The CsPbBr3@Cs4PbBr6 nanocrystals (NCs) could be synthesized by multiple Cs-oleate injections as adding the 1,9-dibromnonane in the reaction solution. The 1,9-dibromnonane could provide Br− ions and the rich Br− ions effectively restrain the generation of CsBr. The Cs4PbBr6 wrapped around the CsPbBr3 NCs and the size of crystalline grain was increased with increasing the Cs-oleate as excess oleylamine. The quantum yield for 14S4DN reached to 99.3 % due to the decrease of defects and the surface passivation of Cs4PbBr6. There are more oleylammonium bromide on the surface of CsPbBr3 NCs as synthesized with 1,9-dibromnonane. The ligand shell and the surface passivation of Cs4PbBr6 restrained the decomposition of surface, consequently improved the stability of moisture and light for CsPbBr3 NCs. When the CsPbBr3@Cs4PbBr6 NCs were immersed in water under UV light (365 nm) for 2 h, the PL intensity could retain 90.4 %, while the 11S1 (traditional CsPbBr3 NCs) was only 10.9 %. It indicated the stability of moisture and light for CsPbBr3 NCs were greatly improved, because Cs4PbBr6 NCs effectively passivated the surface of CsPbBr3 NCs and restrained the generation of traps states.

Joint weighted least squares for normal decomposition of 3D measurement surface

3D optical and laser measurement devices can obtain the digital representation of physical objects by boundary surface meshes. Such a representation, however, has no semantic information to describe the object’s basic shape and its geometric details individually. Meanwhile, existing mesh filters, which process surface normals as signals defined on the Gauss sphere, mainly deal with noise corrupted by measurement and computational errors. While useful in that they preserve geometric structures, they are not intended for filtering out geometric details whose scales are much larger than that of noise. We assume that a 3D surface contains three geometric properties, i.e. geometric detail, structural pattern, and smooth-varying shape, and consider normals as surface signals defined over both the input mesh and the underlying surface of this mesh. We propose a joint weighted least squares (JWLS) to solve the challenging problem of how to filter out the detailed appearance (geometric details) and preserve intrinsic geometric properties (structural patterns) of any measurement surface simultaneously. Specifically, we first suppress high-contrast detail normals, and then detect salient feature normals to produce a feature-guided normal field, and finally jointly fit the original shape. We have shown that a variety of geometric processing tasks benefit from our JWLS, e.g. detail-preserving bas-relief modeling, detail-free mesh smoothing, and detail-enhancing Laplacian coating.

Insights into adsorption performances and direct decomposition mechanisms of NO on [FeO]1+-ZSM-5: A density functional theory study

The density functional theory (DFT) has been employed to systematically investigate the successive adsorption performances of two NO molecules onto [FeO]1+-ZSM-5 surface and subsequent direct decomposition mechanisms by using cluster model in this paper. The adsorption results indicate that there are four stable adsorption configurations of the first NO molecule on [FeO]1+-ZSM-5, all of which are exothermic and strong chemisorption. Beginning with different adsorption configurations of first NO molecule on [FeO]1+-ZSM-5 followed by the adsorption of the second NO molecule, all four direct decomposition mechanisms are studied in which N2O molecule acts as the key reaction intermediate, N2 and O2 act as the target products. Based on thermodynamic analysis, η2-NO path that starts with adsorption of the first NO as O-down and follows the Eley-Rideal mechanism is proposed, in which ONNO species and N2O are the key catalytic intermediates. The full catalytic reaction is exothermic by 43.76 kcal/mol. The rate-determining step is the formation of N2(ads), i.e. N2O(ads) → N2(ads) + O(ads) and its barrier energy is 39.09 kcal/mol.

The Veiled Statuary: A Lesson from Sculpture to Vision Psychology

Visual artists can be considered the precursors of students of the visual system. Paintings and graphic arts have been attentively examined by vision scientists, while sculpture has been considered less. Here we intend to fill this gap by illustrating how artists faced what seems an impossible challenge: to carve a stone so that it looks like a transparent veil. The success of the artists in reproducing the veil can be assessed by exploring the hundreds of Internet pages dedicated to ‘veiled statuary’. We chose some of the most admired statues and tried to ‘glean’ the sculptor’s technique. Two of these artworks are the work of Greek artists, the other statues were carved by baroque and modern sculptors. We did not find a single technique but, rather, a diversity of solutions, as is to be expected in an exploration in which opposites must be reconciled: an observer has to catch the presence of something elastic, thin, and transparent in a surface made of a rigid and opaque material. We checked the ability of the sculptor to render such properties by submitting samples of veiled statues to some observers who were asked to judge the strength of the veiling effect, and to categorize the perceived materials and features, such as transparency and thinness. The results confirm the artists’ knowledge of visual cues that are able to convey a complex set of information and meanings: material categorization, materials properties, perceptual decomposition of surfaces, completion of perceptual fragments into unitary percepts.

Bottom-up synthesis of graphene via hydrothermal cathodic reduction

To date, considerable effort had been devoted to developing a bottom-up synthesis method of graphene, but the methods have been mostly limited to chemical vapor deposition and SiC surface decomposition. Herein, we demonstrated the bottom-up synthesis of graphene via hydrothermal cathodic reduction. In the developed process, the hydrothermal conditions were tuned to enhance the electrochemical reaction and prevent the formation of undesirable amorphous carbon. The nature of the deposited carbonaceous material depends strongly on the temperature, and changes from amorphous carbon into graphitic carbon and graphene with increasing temperature. This should be because of the enhanced oxidative etching effect of amorphous carbon under hydrothermal condition. Finally, the hydrothermal electrochemical reaction enabled graphene growth on a cathode surface at 300 °C.

γ-radiation effects on metal oxide particles and their wetted surfaces

ABSTRACTTypical metal oxide corrosion products of structural materials have been irradiated with γ-rays in ultra-pure water to investigate the effect of radiation on the surface oxide and the nature of adsorbed water. Analysis techniques including thermal gravimetric analysis, differential thermal analysis, diffuse reflectance infrared Fourier transform spectroscopy, and X-ray photoelectron spectroscopy before and after γ-irradiation were employed to investigate surface structural effects and adsorbed water behaviour. The production of H2 in the oxide nanoparticle mixtures was investigated by gas chromatography to probe the mechanism of radiolysis in the water/oxide mixtures and the relationship with surface water. The nature of water at the surface of the oxides was affected by γ-radiation and the relationship was dependent on the particle composition. The rate of H2 production was shown to be oxide dependent, and higher rates of H2 formation were attributed to the decomposition of surface adsorbed water. Changes to the surface chemistry and H2 production rates were found to be highly dependent on the surface chemistry of the metal oxide nanoparticle and no bulk structural changes were observed.

Heterogeneous seawater phosphorus concentrations during the Sturtian glaciation: Evidence from P/Fe ratios of Fulu Formation ironstone in South China

Phosphorus (P) is one of the key bio-limiting elements in the modern ocean, and controls marine primary productivity over the geological time scales. It is proposed that the Ediacaran atmosphere oxygenation and animal evolution might have been triggered by high seawater P concentration in Cryogenian oceans. Seawater P concentration can be reconstructed by the ratio of phosphorus to iron [expressed as (P/Fe)100] in ironstones. Here we measured the P/Fe ratios of the banded iron formation (BIF) from the Cryogenian Fulu Formation in South China. The (P/Fe)100 ratios of the Fulu BIF vary between 0.08 and 1.81 (mean = 0.45, n = 22), considerably lower than the values of coeval BIF deposited in other continents (mean = 1.24, n = 74). Variation of P/Fe ratio of ironstones may suggest a large seawater P concentration gradient during the Sturtian glaciation, which is comparable to, or even higher than, that in the modern ocean (~1.2 μM in North Atlantic and ~2.6 μM in North Pacific). Though being explained in different ways, the heterogeneous seawater P concentration requires active organic matter production in the surface ocean and/or decomposition in the ocean interior as well as possible onset of thermohaline circulation during the Sturtian glaciation. Finally, our study suggests that precipitation of BIF in the completely ice-covered ocean was unlikely.

Counting Feynman-like graphs: Quasimodularity and Siegel–Veech weight

We prove the quasimodularity of generating functions for counting torus covers, with and without Siegel–Veech weight. Our proof is based on analyzing decompositions of flat surfaces into horizontal cylinders. The quasimodularity arises from representing the generating series as a contour integral of quasi-elliptic functions. This provides an alternative proof of the quasimodularity results of Bloch–Okounkov, Eskin–Okounkov and Chen–Möller–Zagier, and generalizes the results of Böhm–Bringmann–Buchholz–Markwig for simple ramification covers.