Formation Of Different Layers Research Articles

Photoluminescence in halogeno copper(Ⅰ) methyl thiolate polymers via in situ DMSO decomposition reaction

Five halogeno-copper thiolate coordination polymers, Cu12Cl6(SCH3)6(DMSO) 1, Cu3X(SCH3)2 (2, 4), and Cu2X(SCH3) (X = Br, I) (3, 5) were solvothermally prepared by employing DMSO, which is used as a thiolate source via in situ decomposition. The X-ray crystallographic data revealed one type of 3D network structure composed of Atlas spheres. Additionally, two types of 2D layered bromo/iodo isostructural complexes were found, and the differences between these two types are attributed to the different connection modes of their Cu3X2(SCH3)2 chains. Sharing the halogen atoms in Cu3X2(SCH3)2 chain or bridging the chains via additional copper atoms could lead to the formation of different layers with a Cu:X:SCH3 ratio of 3:1:2 or 2:1:1, respectively. The absorption and emission spectral data described the influence of the ratio and species of halogen elements in copper thiolate complexes. From the spectroscopic studies, long-lived phosphorescence was detected, the characteristic lifetime of which depends on the crystal internal structures as well as the constituent halogen atoms.

Mechanistic origins of concrete pumping: a comprehensive outlook and way forward

The construction of high-rise buildings and tunnels necessitates pumping concrete over long distances. Concrete pumping is a complex physico-chemical process that results in the formation of different layers with distinct characteristics inside the pipe. A thin cement paste/mortar layer formed at the concrete–pipe interface, called the lubrication layer (LL), is vital for facilitating concrete pumping. Engineering the pumping process involves understanding the origin and controlling the onset, magnitude and velocity of the LL. However, the formation, evolution and characteristics of the LL are still largely unexplored. This paper presents a comprehensive review of the mechanistic origins of the LL, its influencing parameters and measured data on LL thickness using various techniques to date. An attempt is made to find an overall link between different theories (shear-induced particle migration, wall depletion theory etc.) in terms of concrete rheology. The paper also provides a fundamental understanding of the different mechanisms involved in LL formation, with the help of different theories put forth by researchers in the field of particle rheology. Based on the insights derived from the discussions, recommendations are made for future research directions in concrete pumping.

Physical features’ characterization of the water-in-mineral oil macro emulsion stabilized by a nonionic surfactant

Water-in-oil (w/o) emulsions are widely used in the food and pharmaceutical industries, among others. Moreover, the most common type of emulsion produced and handled in the oil industry processes is the w/o emulsion. This study investigates the features of a water-in-mineral oil macro-emulsion formulated with mineral oil as the continuous phase and Span 83 as the nonionic surfactant. Emulsions are prepared at room temperature according to the hydrophilic–lipophilic difference (HLD) theory and were tested for the mean droplet size and droplet size distribution, viscosity, and kinetic stability. An empirical correlation was introduced that estimates the viscosity of the water-in-mineral oil macro-emulsions and captures the non-Newtonian behavior at larger water fractions. The effect of electrolyte and internal phase concentration was specifically assessed on the emulsion flocculation and the stability of the system. Stability tests show a threshold electrolyte concentration exists after which droplets coalesce upon collision and flocculation. Salting out is most likely the responsible mechanism of phase separation in the emulsions with higher electrolyte concentrations. The results imply that sedimentation is accountable for the formation of different layers in emulsion with time. The sedimentation rate was intensified for emulsion with smaller water content (64% variation in 3 days between 10% emulsion and 40% emulsion) and concentrated emulsions were found to be more stable. Also, the size of the droplets was influenced by the NaCl concentration, surfactant concentration, and phase ratio.

Palladium nanoparticles dispersed on functionalized macadamia nutshell biomass for formic acid-mediated removal of chromium(VI) from aqueous solution

Driven by the need for sustainably sourced catalysts and the use of reaction systems that generate environmentally benign by-products, the present study aimed to deposit stable, dispersed palladium (Pd) nanoparticles on the modified surfaces of granular macadamia nutshell (MNS) biomass for catalytic reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)). Through wet impregnation with Pd(II) ions and subsequent hydrazine-mediated reduction to Pd(0), Pd nanoparticles were embedded in a scaffold of polyethyleneimine grafted on bleached MNS previously coated with a chemically bound layer of polyglycidyl methacrylate. Imagery from scanning electron microscopy showed the formation of different layers of the polymeric coating and dispersed palladium resulting from surface modification and palladium nanoparticle synthesis, respectively. X-ray diffraction analysis confirmed the formation of Pd on the modified MNS surface and suggested an estimated crystallite size of 5.0 nm. The supported nanoparticles exhibited catalytic activity in formic acid-mediated Cr(VI) reduction and showed promising stability with consecutive reuse. These findings set the stage for advanced studies into performance optimization.

Sequential formation of different layers of dystrophic neurites in Alzheimer's brains.

Alzheimer’s disease (AD) is characterized by the presence of neuritic plaques in which dystrophic neurites (DNs) are typical constituents. We recently showed that DNs labeled by antibodies to the tubular endoplasmic reticulum (ER) protein reticulon-3 (RTN3) are enriched with clustered tubular ER. However, multi-vesicle bodies are also found in DNs, suggesting that different populations of DNs exist in brains of AD patients. To understand how different DNs evolve to surround core amyloid plaques, we monitored the growth of DNs in AD mouse brains (5xFAD and APP/PS1ΔE9 mice) by multiple approaches, including 2-dimensional and 3-dimesnional (3D) electron microscopy (EM). We discovered that a pre-autophagosome protein ATG9A was enriched in DNs when a plaque was just beginning to develop. ATG9A-positive DNs were often closer to the core amyloid plaque, while RTN3-immunoreactive DNs were mostly located in the outer layers of ATG9A-positive DNs. Proteins such as RAB7 and LC3 appeared in DNs at later stages during plaque growth, likely accumulated as a part of large autophagy vesicles, and were distributed relatively furthest from the core amyloid plaque. Reconstructing the 3D structure of different morphologies of DNs revealed that DNs in AD mouse brains were constituted in three layers that are distinct by enriching different types of vesicles, as validated by immune-EM methods. Collectively, our results provide the first evidence that DNs evolve from dysfunctions of pre-autophagosomes, tubular ER, mature autophagosomes, and the ubiquitin proteasome system during plaque growth.

Drying effects and dry matter losses during seasonal storage of spruce wood chips under practical conditions

The storage of wood chips is important for the biomass supply chain as it compensates for temporal differences in production and consumption. Typical storage-related problems are dry matter and energy losses due to microbial activity.In extensive field trials, we investigated the storage of spruce wood chips from forest residues (FRC) and from energy roundwood (ERC) with and without rain protection under Central European conditions. Additionally, we examined the storage of unchipped piles.The results indicate that the investigated factors, i. e. storage duration, season, assortment and rain protection, have a statistically significant influence on moisture content and dry matter loss of wood chips. During five months of storage, the highest decline in moisture content was 22.6 %-points, the highest dry matter loss 11.1 %. In winter, energy losses reached up to 11.3 %. In summer, energy contents did not change or even increased slightly (max. 4.7 %). Pile temperature and dry matter losses were significantly positively correlated in FRC. Formation of different layers within the piles could be detected. Storage performance was better in unchipped than in chipped energy roundwood. Storage of unchipped forest residues was not beneficial concerning energy content, but fuel quality increased due to reduced ash and fine particle content.Clear best practice recommendations could be drawn regarding wood chip storage under Central European conditions. During winter, FRC should be stored with rain protection or as short as possible while during a dry and warm summer, wood chips can be stored with only few restrictions.

Chemical vapor deposition growth of large single-crystal bernal-stacked bilayer graphene from ethanol

Using ethanol as a precursor, single-crystal bilayer graphene domains with dimensions up to hundreds of micrometer, one of the largest reported so far, were synthesized on Cu foils by chemical vapor deposition (CVD). Raman spectroscopy analysis revealed that the bilayers are homogeneously AB-stacked, with very low D-band intensity. Selected area electron diffraction analysis also confirmed the bernal stacking order and the large area crystallinity. Surprisingly, decreasing ethanol pressure in CVD shows an unambiguous tread from self-limited single layer to a multi-layer graphene, and there exists a narrow window of ethanol pressure which is preferred for the formation of large domain bilayer graphene. This suggests the dual effect of ethanol in graphene growth and demonstrates that the formation of different layers of graphene can be controlled by carefully tuning single parameter: ethanol pressure.

Capacitance Improvement of Semiconductor Electrode By LbL Modification

In the last decades, supercapacitors have been considered as one of the most promising energy storage devices due to their large power density and their long cycle life. Carbon and binder-free technologies have been recently proposed based on the consolidation of semiconductor nanostructures to use as device electrodes [1, 2] due to its wider mechanical and thermal stability. Among oxide films, NiO has been intensively investigated in supercapacitors based on their high theoretical specific capacity values (2584 F/g), high chemical stability, ready availability and lower cost. Electrodes requirements of a supercapacitor, and consequently their delivered capacitance, are largely dependent on the microstructure characteristics. In particular, it strongly depends on the increase of the active surface area avoiding electronic conductivity fall. In fact, a well-connected mesoporous structure, with a high and narrow pore size distribution exhibits greatly improved electrochemical performance. The processing of those ceramic films through inexpensive and ecofriendly powder technologies is challenging. Among different approaches, the use of the colloidal techniques allows nanostructures tailoring, strengthening the control over the specific final properties. In this work, colloidal routes have been explored to improve the electrochemical response of a pseudocapacitor electrode based on a NiO nanostructure consolidated at low temperature (325°C) [3]. At this time, we have considered the surface modification of Ni(OH)2 nanoplatelets synthesized by ultrasound through the addition of polyelectrolytes to the suspension. The formation of different layers with polycationic and polyanionic electrolytes was studied. Polyethylenimine (PEI) and Polyacrylic Acid (PAA) were used as polyelectrolytes to form a Layer by Layer system. As a result the modified Ni(OH)2 nanoplatelets were stabilized in suspension and shaped by Electrophoretic Deposition (EPD) on Ni substrates, for later sinterization of films which were electrochemically tested. [1] D.-H. Ha, M.A. Islam and R.D. Robinson, Binder-free and carbon-free nanoparticle batteries: A method for nanoparticle electrodes without polymeric binders or carbon black, Nano Lett .12, 2012, 5122–5130. [2] S.Cabanas-Polo, Z. González, A.J. Sanchez-Herencia, B.Ferrari, A.Caballero, L.Hernan and J.Morales. Cyclability of binder-free β-Ni(OH)2 anodes shapes by EPD for Li-ion batteries, J. Eu. Cer. Soc., 35, 2015, 573-584 [3] Z. González, B.Ferrari, A.J. Sanchez-Herencia, , A.Caballero and J.Morales. A One-Step and Binder-Free Method to CoatStructures with NiO nanoplatelets. Influence of the Particle Packing in Supercapacitor Electrodes. J. Electrochem. Soc.

Oxidation and crystallization behavior of calcium europium silicon nitride thin films during rapid thermal processing

Luminescent thin films were fabricated on silicon wafers using reactive magnetron sputtering of Ca, Si and Eu in Ar/N2 atmosphere. In order to activate the luminescence, the as-deposited nitride films were heated to 1100°C by a rapid thermal processing treatment. X-ray diffraction measurements reveal the crystal phases that form during thermal treatment. By recording scanning electron microscopy images of the surface and the cross-section of the film at different radial locations, the formation of different layers with a thickness depending on the radial position is revealed. Energy dispersive x-ray spectroscopy analysis of these cross-sections reveals the formation of an oxide top layer and a nitride bottom layer. The thickness of the top layer increases as a function of radial position on the substrate and the thickness of the bottom layer decreases accordingly. The observation of different 4f65d1→4f7 Eu2+ luminescence emission bands at different radial positions correspond to divalent Eu doped Ca3Si2O4N2, Ca2SiO4 and CaSiO3, which is in agreement with the phases identified by X-ray diffraction analysis. A mechanism for the observed oxidation process of the nitride films is proposed that consists of a stepwise oxidation from the as-deposited amorphous nitride state to crystalline Ca3Si2O4N2, to Ca2SiO4 and finally CaSiO3. The oxidation rate and final state of oxidation show a strong temperature–time dependency during anneal treatment.

Effects of Altered Catecholamine Metabolism on Pigmentation and Physical Properties of Sclerotized Regions in the Silkworm Melanism Mutant

Catecholamine metabolism plays an important role in the determination of insect body color and cuticle sclerotization. To date, limited research has focused on these processes in silkworm. In the current study, we analyzed the interactions between catecholamines and melanin genes and their effects on the pigmentation patterns and physical properties of sclerotized regions in silkworm, using the melanic mutant melanism (mln) silkworm strain as a model. Injection of β-alanine into mln mutant silkworm induced a change in catecholamine metabolism and turned its body color yellow. Further investigation of the catecholamine content and expression levels of the corresponding melanin genes from different developmental stages of Dazao-mln (mutant) and Dazao (wild-type) silkworm revealed that at the larval and adult stages, the expression patterns of melanin genes precipitated dopamine accumulation corresponding to functional loss of Bm-iAANAT, a repressive effect of excess NBAD on ebony, and upregulation of tan in the Dazao-mln strain. During the early pupal stage, dopamine did not accumulate in Dazao-mln, since upregulation of ebony and black genes led to conversion of high amounts of dopamine into NBAD, resulting in deep yellow cuticles. Scanning electron microscope analysis of a cross-section of adult dorsal plates from both wild-type and mutant silkworm disclosed the formation of different layers in Dazao-mln owing to lack of NADA, compared to even and dense layers in Dazao. Analysis of the mechanical properties of the anterior wings revealed higher storage modulus and lower loss tangent in Dazao-mln, which was closely associated with the altered catecholamine metabolism in the mutant strain. Based on these findings, we conclude that catecholamine metabolism is crucial for the color pattern and physical properties of cuticles in silkworm. Our results should provide a significant contribution to Lepidoptera cuticle tanning research.

Application of the voltammetry of microparticles for dating archaeological lead using polarization curves and electrochemical impedance spectroscopy

The application of the voltammetry of microparticles methodology to date archaeological lead artifacts, based on the time-dependent formation of different layers of lead oxides, whose relative amount can be estimated from polarization curves and electrochemical impedance spectroscopy (EIS), is presented. This approach is complemented by additional data using square wave voltammetry data. Calibration of the method was performed with the help of a series of well-documented, lead pieces from the funds of different Spanish museums, covering since the 7th century BC to nowadays.

Interaction of Solid Metals with Melts Containing Nonmetallic Impurities

We present a systematic survey of the mechanisms of interaction of solid metals (Me) with melts (L) taking into account the activity of nonmetallic impurities (I) and suggest a general scheme of interaction of components in Me–L–I systems. The physicochemical aspects of formation of different layers on the Me–L phase boundary are analyzed. Special attention is given to the conditions of formation of protective layers with various functional properties. It is shown that this problem can be solved theoretically within the framework of the problem of reaction-controlled diffusion by taking into account the behavior of the concentrations of the components on the phase boundaries.

Histochemistry of the cuticle of the crab Menippe rumphii (Fabricius) (Crustacea: Brachyura) in relation to moulting

Histological and histochemical methods have been employed to study the formation and growth of the exoskeleton in relation to the moulting cycle of the crab Menippe rumphii (Fabricius). In the premoult condition the epidermal cells secrete a two-layered cuticle. Later these layers are widened by the secretions coming from the reserve cells, tegumental glands, and the Leydig cells. The fully formed cuticle of the intermoult crab is divisible into four layers, epicuticle, exocuticle, mesocuticle, and endocuticle. Histochemical observations on different cells have revealed that the tegumental glands secrete both neutral and acid mucopolysaccharides. The reserve cells are positive to PAS, BPB, Sudan Black B and Alizarin Red S techniques indicating the presence of carbohydrates, proteins, lipids, and mineral calcium. The Leydig cells are loaded with enzymes, including alkaline phosphatase, acid phosphatase, lipase, and phenoloxidase. Other histochemical tests have been employed to investigate the formation of different layers of the cuticle.