Diffusive Loss Research Articles

Evaluation of the turbulent hot jet flame characteristics for achieving high thermal efficiency of hybrid engine

Turbulent jet ignition with active pre-chamber (APC) could enhance the ultra-lean combustion stability thus improving the engine's thermal efficiency. Different APCs structures are analyzed in previous studies, but the lack of quantitative evaluation criteria makes it difficult to optimize the APC under various engine conditions. This paper aims to investigate the characteristic of APC hot jets and their effects on ignition capability and engine combustion performance from perspectives of jet velocity, temperature, turbulent kinetic energy (TKE), and turbulent intensity. The quantitatively evaluate method of hot jet activity based on the key intermediate species during the chemical reactions was proposed. Different APC jet flames and corresponding engine main chamber (MC) combustion performance were discussed by adjusting the APC nozzle diameter and number. The result showed that the jet velocity in a certain range of 450 to 700 m/s has a positive effect on igniting the ultra-lean mixture inside MC. The jet velocity mainly affects the ignition position of jet flame in MC, a higher jet velocity induces the ignition to occur near the cylinder wall and increases the thermal diffusion and heat losses, leading to the lower ignition ability. The jet temperature shows a relatively lower effect on igniting the ultra-lean mixture as the maximum jet flame temperature is over 2250 K. The jet TKE and velocity exhibit a strong correlation in engine performance. The jet turbulence intensity rather than jet TKE strongly influences igniting the ultra-lean mixture. The jet turbulence intensity in the range of 0.025 to 0.035 is beneficial to ignition ability and engine combustion performance. The 4-nozzle APC produces a relatively high jet activity. It’s confirmed that the jet activity higher than 0.055 is sufficient for igniting the ultra-lean mixture. The 4-nozzle APCs can achieve higher engine-indicated thermal efficiency (ITE) as compared to 6-nozzle APCs. The peak ITE of 51.6% is achieved by the 4-nozzle APC with an orifice diameter of 1.8 mm that meets all the good jet characteristics that can produce strong ignition capability.

Enhancement of NOx production in water by combining an air bubble plasma jet and an external magnetic field

Production of NOx (NO2− + NO3−) in water with an air bubble discharge plasma jet under the influence of an external axial steady magnetic field was investigated experimentally. The gas phase plasma parameters, rotational (Tr), vibrational (Tv) and electronic excitation (Tx) temperatures, and electron density (ne), as well as the liquid phase pH and the concentrations of nitrite (NO2−) and nitrate (NO3−), were measured as a function of treatment time and magnetic field strength. It was found that Tr, Tv, Tx, and ne slightly increased as a function of magnetic field strength in the gas phase plasma. The pH decreased both with treatment time and magnetic field strength. In the maximum field strength of 290 mT, the concentrations of NO2− and NO3− were ∼82% and ∼74%, respectively, greater than with B=0. With B=290 mT, the energy cost for producing NOx was ∼78% lower than with B=0. The energy cost may likely be reduced due to decreasing radial diffusion loss of charged species in the discharge with increasing magnetic field strength.

Improving Medical Imaging with Medical Variation Diffusion Model: An Analysis and Evaluation.

The Medical VDM is an approach for generating medical images that employs variational diffusion models (VDMs) to smooth images while preserving essential features, including edges. The primary goal of the Medical VDM is to enhance the accuracy and reliability of medical image generation. In this paper, we present a comprehensive description of the Medical VDM approach and its mathematical foundation, as well as experimental findings that showcase its efficacy in generating high-quality medical images that accurately reflect the underlying anatomy and physiology. Our results reveal that the Medical VDM surpasses current VDM methods in terms of generating faithful medical images, with a reconstruction loss of 0.869, a diffusion loss of 0.0008, and a latent loss of 5.740068×10-5. Furthermore, we delve into the potential applications of the Medical VDM in clinical settings, such as its utility in medical education and training and its potential to aid clinicians in diagnosis and treatment planning. Additionally, we address the ethical concerns surrounding the use of generated medical images and propose a set of guidelines for their ethical use. By amalgamating the power of VDMs with clinical expertise, our approach constitutes a significant advancement in the field of medical imaging, poised to enhance medical education, research, and clinical practice, ultimately leading to improved patient outcomes.

Commensal Cutibacterium acnes induce epidermal lipid synthesis important for skin barrier function.

Lipid synthesis is necessary for formation of epithelial barriers and homeostasis with external microbes. An analysis of the response of human keratinocytes to several different commensal bacteria on the skin revealed that Cutibacterium acnes induced a large increase in essential lipids including triglycerides, ceramides, cholesterol, and free fatty acids. A similar response occurred in mouse epidermis and in human skin affected with acne. Further analysis showed that this increase in lipids was mediated by short-chain fatty acids produced by Cutibacterium acnes and was dependent on increased expression of several lipid synthesis genes including glycerol-3-phosphate-acyltransferase-3. Inhibition or RNA silencing of peroxisome proliferator-activated receptor-α (PPARα), but not PPARβ and PPARγ, blocked this response. The increase in keratinocyte lipid content improved innate barrier functions including antimicrobial activity, paracellular diffusion, and transepidermal water loss. These results reveal that metabolites from a common commensal bacterium have a previously unappreciated influence on the composition of epidermal lipids.

Exploiting Microelectrode Geometry for Comprehensive Detection of Individual Exocytosis Events at Single Cells.

Carbon fiber microelectrodes are commonly used for real-time monitoring of individual exocytosis events at single cells. Since the nature of an electrochemical signal is fundamentally governed by mass transport to the electrode surface, microelectrode geometry can be exploited to achieve precise and accurate measurements. Researchers traditionally pair amperometric measurements of exocytosis with a ∼10-μm diameter, disk microelectrode in an "artificial synapse" configuration to directly monitor individual release events from single cells. Exocytosis is triggered, and released molecules diffuse to the "post-synaptic" electrode for oxidation. This results in a series of distinct current spikes corresponding to individual exocytosis events. However, it remains unclear how much of the material escapes detection. In this work, the performance of 10- and 34-μm diameter carbon fiber disk microelectrodes was directly compared in monitoring exocytosis at single chromaffin cells. The 34-μm diameter electrode was more sensitive to catecholamines and enkephalins than its traditional, 10-μm diameter counterpart, and it more effectively covered the entire cell. As such, the larger sensor detected more exocytosis events overall, as well as a larger quantal size, suggesting that the traditional tools underestimate the above measurements. Both sensors reliably measured l-DOPA-evoked changes in quantal size, and both exhibited diffusional loss upon adjustment of cell-electrode spacing. Finite element simulations using COMSOL support the improved collection efficiency observed using the larger sensor. Overall, this work demonstrates how electrode geometry can be exploited for improved detection of exocytosis events by addressing diffusional loss─an often-overlooked source of inaccuracy in single-cell measurements.

H2O degassing triggered by alkali depletion in bimodal magma injection processes – a new experimental approach

Abstract. The injection of mafic magma into a hydrous felsic magma chamber is a potential trigger mechanism for bimodal explosive volcanism. As H2O is the most abundant volatile component in magmas, the interaction and the degassing behavior of mildly peralkaline hydrous rhyolitic melt in contact with hydrous basaltic melt were investigated by decompression experiments. Preparatory hydration experiments and bimodal magma decompression experiments, as well as reference experiments, were carried out in an internally heated argon pressure vessel. Pre-hydrated rhyolite and basalt cylinders were perfectly contacted together in a precious-metal capsule, heated to 1348 K at 210 MPa, and thermally equilibrated for 10 min. The initial sample properties were determined by a bimodal reference experiment, quenched immediately after equilibration. To simulate the magma ascent, three bimodal samples and a decompression experiment with two contacted rhyolite cylinders for testing the experimental setup were decompressed with 0.17 or 1.7 MPa s−1 to the final pressure of 100 MPa and then quenched. All decompression experiments resulted in vesiculated samples. The H2O vesicles observed in the decompressed sample of the monomodal rhyolite–rhyolite reference experiment are homogeneously distributed throughout the sample. The former interface between the contacted glass cylinders is invisible after decompression and quench. This reference experiment proves that the two-cylinder design does not influence the degassing behavior of the hydrous melt, e.g., an increased formation of vesicles at possible nucleation sites at the contact plane of the cylinders. The undecompressed bimodal rhyolite–basalt sample shows crystal-free rhyolitic glass, whereas 3 µm sized idiomorphic magnetite crystals coexist with glass in the basaltic part of the sample. Within the 10 min run time, a ∼ 300 µm wide hybrid composition zone developed between the hydrous rhyolitic and basaltic endmembers, caused by diffusion-induced mixing processes. Decompression and quenching of the bimodal melts resulted in vesiculated glass samples. A ∼ 100 µm wide zone of alkali-depleted rhyolitic glass as part of the ∼ 300–560 µm wide hybrid zone is covered with an enhanced number of H2O vesicles compared to the pristine rhyolitic and basaltic glass volumes. We suggest that this enhanced vesiculated zone forms by a rapid diffusional loss of alkalis from the mildly peralkaline rhyolitic melt into the basaltic melt of the sample. The reduced alkali concentration significantly reduces the H2O solubility of the rhyolitic melt. This process enhances the H2O supersaturation necessary for vesicle formation during decompression. In summary, the new findings imply that convective magma ascent driven by the injection of hot basaltic magma into a hydrous peralkaline rhyolitic melt reservoir leads to enhanced H2O vesicle formation near the melt interface and thus to efficient degassing. This in turn can accelerate buoyancy-driven magma ascent and mingling and mixing processes that induce further degassing and potentially trigger explosive volcanic eruptions.

A Novel Method for Calculating Diffusion Coefficient of Shale Gas Reservoirs: A Case Study of Longmaxi Formation in Weiyuan Area, Sichuan Basin, China

The entire process of shale gas generation, migration, and accumulation involves the diffusion of shale gas, and it is impossible to disregard the harm that gas diffusion does to gas reservoirs. The research object for this paper is the Longmaxi Formation shale gas reservoir in the Weiyuan area of the Sichuan Basin. Based on Fick’s diffusion law, an innovative mathematical model of shale gas diffusion is established, and it is clarified that the diffusion amount mainly depends on the free gas content and the diffusion coefficient. Based on the theory of fluid dynamics, the calculation equation of formation paleo-pressure is innovatively deduced. The equation fully considers gas migration, temperature and pressure changes, and the pressure control effect of organic matter gas generation, and restores the evolution history of free gas content in the reservoir. The evolution process of temperature, pressure and stratigraphic physical properties in the study area is the first to calculate the diffusion evolution history and cumulative diffusion amount of shale gas reservoirs in the study area, the reliability of the calculation results is verified by geochemical parameters. Studies have revealed that the existing Longmaxi Formation shale in the Weiyuan area of Sichuan Basin varies from 14.10 to 16.50 × 104 m3/m2 per unit area, with an average diffusion loss of 0.30 × 1012 m3 gas in the positive part and 0.30 × 1012 m3 in the negative part. The total lost gas accounts for around 1.72 times the present recappable reserves and is estimated to be 0.43 × 1012 m3 in volume. It is clear that the migration and accumulation of natural gas are significantly influenced by the research of diffusion loss.

Diffusion of chromium of Cr-coated Zircaloy accident tolerant fuel cladding: Model development and experimental validation

A mechanistic model that calculates Cr diffusion for Cr-coated Zircaloy cladding based on Finite Difference Method (FDM) has been developed and validated. The developed model has been incorporated into TRANOX 2.0. The Cr-coated cladding was divided into multilayers (Zr, ZrCr2 and Cr), and chromium diffusion coefficients of each phase were obtained by experiments. The prediction of the model was validated with Cr distribution measured by EPMA through extensive high temperature annealing experiments conducted in the temperature range of 1000–1300 °C. The developed model can predict diffusional loss coating thickness of Cr-coated Accident Tolerant Fuel.

Helium isotope evidence for mixing of mantle-derived fluids and deeply penetrating surface waters in an obducted peridotite massif

We measured He and Ar in fresh peridotites from the Twin Sisters massif, Washington USA. 3He/4He ratios measured on >35 samples are highly variable (∼0.8 to ∼6 times the atmospheric ratio, RA). Step-heating of a subset of these samples in every case reveals a low 3He/4He component (∼1 RA) released at <1000 °C and a high 3He/4He component (>3 RA) above that temperature, but these components are not effectively isolated by crushing and powder fusion analysis. He-Ar systematics indicate an intimate association of two fluid-inclusion hosted components in the peridotites. The first is a ∼6 RA mantle component that is released at higher temperatures during step heating and is more abundant in dunite bands than surrounding harzburgites. The second component, released at low temperatures, has a 3He/4He ratio of 1.0 ± 0.5 RA, atmospheric 40Ar/36Ar, and 4He/40Ar far above atmospheric. It appears to be a mixture of mantle and radiogenic He sources introduced during obduction-related serpentinization, sometimes invisible, by surface-derived waters enriched with deeply-sourced helium.These data indicate that mantle noble gas signatures can be retained in lithospheric peridotites against both diffusive loss and radiogenic ingrowth over at least 108 year timescales, likely due to concentration and immobilization of He in fluid inclusions. However, the mantle signature can be greatly modified by pervasive and potentially cryptic fluid alteration during emplacement.

Sterically Stabilized Diblock Copolymer Nanoparticles Enable Efficient Preparation of Non-Aqueous Pickering Nanoemulsions.

We report the first example of a non-aqueous Pickering nanoemulsion, which comprises glycerol droplets dispersed in mineral oil. The droplet phase is stabilized by hydrophobic sterically stabilized poly(lauryl methacrylate)-poly(benzyl methacrylate) nanoparticles which are prepared directly in mineral oil using polymerization-induced self-assembly. First, a glycerol-in-mineral oil Pickering macroemulsion with a mean droplet diameter of 2.1 ± 0.9 μm is prepared via high-shear homogenization using excess nanoparticles as an emulsifier. Then, this precursor macroemulsion is subjected to high-pressure microfluidization (a single pass at an applied pressure of 20,000 psi) to produce glycerol droplets of approximately 200-250 nm diameter. Transmission electron microscopy studies indicate preservation of the distinctive superstructure produced by nanoparticle adsorption at the glycerol/mineral oil interface, thus confirming the Pickering nature of the nanoemulsion. Glycerol is sparingly soluble in mineral oil, thus such nanoemulsions are rather susceptible to destabilization via Ostwald ripening. Indeed, substantial droplet growth occurs within 24 h at 20 °C, as judged by dynamic light scattering. However, this problem can be suppressed by dissolving a non-volatile solute (sodium iodide) in glycerol prior to formation of the nanoemulsion. This reduces diffusional loss of glycerol molecules from the droplets, with analytical centrifugation studies indicating much better long-term stability for such Pickering nanoemulsions (up to 21 weeks). Finally, the addition of just 5% water to the glycerol phase prior to emulsification enables the refractive index of the droplet phase to be matched to that of the continuous phase, leading to relatively transparent nanoemulsions.

Origin and significance of ultra-slow calcite dissolution rates in deep sea sediments

Prediction of mineral-fluid reaction rates in geologic materials is subject to large uncertainties even though the rates are critical for many applications, from studies of past climate change to the engineering of carbon removal and storage. Deep sea carbonate sediments, which have been extensively cored and characterized at dozens of sites by ocean drilling programs, provide unique opportunities to examine how minerals and fluids react over multi-million-year timescales in natural conditions at low temperature. It has already been established that the calcite-fluid reaction in these systems is extremely slow, but the explanation for the ultra-slow rates, and the fact that non-zero rates persist for tens of millions of years, remains elusive. We extend the analysis of pore fluid Sr and Ca concentration data in the literature from ocean drilling archives to 21 drill sites in sediment sections where the fraction of carbonate is larger than 80% to systematically estimate the rates at which calcite dissolves and precipitates as a function of depth and sediment age. Pore fluid Sr/Ca used in this study, and Sr and Ca isotopes in other published analyses, provide estimates of the gross calcite dissolution rates, which are mostly balanced by secondary calcite precipitation. Pore fluid Ca concentration data provide key, previously underappreciated, information on the net calcite dissolution rates. Using these data we evaluate simple models for calcite reaction kinetics and pore fluid sediment evolution and conclude that (1) reaction rates are extremely slow because the reactive site density of the bulk sediment decreases continuously and systematically approximately as age−1, and (2) reaction persists to hundreds of meters burial depth and tens of millions of years because pore fluids never become closed due to diffusive communication with the oceans, and hence remain slightly undersaturated with respect to calcite. The systematic decrease in bulk reactive site density begins immediately upon deposition, greatly slowing the rate of dissolution and hence affecting models of calcite dissolution on the seafloor. The failure to reach equilibrium after millions of years and hundreds of meters of burial, is a consequence of extremely slow net reaction rates that cannot drive the pore fluids to equilibrium against the diffusive loss of Ca and DIC to the ocean. The existence of two or more calcite phases of different solubility is a likely source of a long-lived, but small, driving force for reaction, but its effect decreases with continued recrystallization and pore fluid evolution.

Study on ultrasonic nondestructive evaluation method for grain size of magnesium alloy components with complex profile

In order to solve the problems of difficult measurement, inaccurate results and serious interference of diffusion and attenuation in the nondestructive evaluation of grain size of magnesium alloy components with complex profile, the sound field models of plane, cylindrical and conical parts based on the multiple Gaussian sound beam method are studied, and the attenuation mechanism of ultrasonic propagation in the medium of complex components and the diffusion and attenuation components in curved test blocks are analyzed, An evaluation method of ultrasonic attenuation of grain size based on diffusion loss correction is proposed to eliminate the influence of complex components on the total amount of ultrasonic attenuation. The results show that the ultrasonic nondestructive evaluation method of grain size based on sound velocity diffusion correction can effectively reduce the system error and improve the accuracy of grain size evaluation of magnesium alloy components with complex profile.

In Situ Dispersion of Lignin in Polypropylene via Supercritical CO2 Extrusion Foaming: Effects of Lignin on Cell Nucleation and Foam Compression Properties.

Supercritical CO2 (scCO2) extrusion foamed high-melt-strength (HMS) polypropylene (PP) often suffers from low cell density, large cell sizes, and poor cell structure uniformity due to the poor nucleation rates of CO2 in the PP. To remedy this, various inorganic fillers have been used as heterogeneous nucleation agents. Although their efficient nucleation effects have been demonstrated, the preparation of these fillers causes some adverse effects on the environment/human health or involves relatively expensive processes or non-eco-friendly chemicals. In this work, biomass-based lignin is studied as a sustainable, lightweight, and cost-effective nucleating agent. It is found that scCO2 could assist in situ dispersion of lignin in the PP in the foaming process, leading to significantly increased cell density, smaller cells, and improved cell uniformity. The Expansion Ratio is also simultaneously improved due to reduced diffusive gas loss. The PP/lignin foams with low lignin loadings exhibit higher compression moduli and plateau strengths than the PP foams with the same densities owing to the improved cell uniformity and probably also the reinforcing effect of the small lignin particles in cell walls. Moreover, the energy absorption capability of the PP/lignin foam with 1 wt% lignin could match the PP foam with similar compression plateau strengths; even the density of the former is 28% lower than the latter. Therefore, this work provides a promising approach to a cleaner and more sustainable production of HMS PP foams.

Degradation of multi-layer CVD-coated cemented carbide in finish milling compacted graphite iron

Stricter regulations on emissions and higher demands on engine performance drive automotive industries to replace conventional gray cast iron with compacted graphite iron (CGI). CGI has a higher wear resistance, strength, elastic modulus, and almost double fatigue strength as to gray cast iron, yet the same positive properties make CGI more difficult to machine. This study focuses on finish milling CGI EN-GJV-450 with current industrial standard of tooling: cemented carbide with multi-layer CVD-coating of Ti(C,N)–Al2O3. At cutting speed of 150 m/min a total of 3126 cm3 of material after 190 passes was removed, while 1645 cm3 was removed after 100 passes in case of 250 m/min. Studying the wear evolution at different engagement times demonstrated an accelerated chemical wear of the Al2O3 top coating due to its reaction with MgO-containing inclusions that creates a softer reaction product of (Mg,Fe,Mn)Al2O4 spinel which is abraded and removed with the chip flow. Ti(C,N) coating layer experiences diffusional and mechanical (abrasion, debonding, micro-fracture) wear mechanisms. Exposure of cemented carbide substrate resulted in its rapid wear in the form of cratering and massive material loss on the flank where the latter eventually causes tool failure. The adherence of CGI to WC-Co facilitates diffusional loss of carbon and tungsten from WC grains. Carbon reacts with iron at the interface forming iron carbide, while residual tungsten alloys it thus forming (Fex,W1-x)3C. This phase can reduce the wear rate as it acts as a diffusion barrier, but its high brittleness enables its periodic removal by adhesive wear. Outward cobalt diffusion was also an active wear mechanism that facilitates further diffusion of carbon and tungsten but also weakens the WC-grain bonding, further facilitating adhesive wear by CGI flow. Deposition of oxide inclusions to exposed WC-Co work as an anti-stick for CGI adhesion and thus reduces the wear rate.

Cell aggregation is associated with enzyme secretion strategies in marine polysaccharide-degrading bacteria

Polysaccharide breakdown by bacteria requires the activity of enzymes that degrade polymers either intra- or extra-cellularly. The latter mechanism generates a localized pool of breakdown products that are accessible to the enzyme producers themselves as well as to other organisms. Marine bacterial taxa often show marked differences in the production and secretion of degradative enzymes that break down polysaccharides. These differences can have profound effects on the pool of diffusible breakdown products and hence on the ecological dynamics. However, the consequences of differences in enzymatic secretions on cellular growth dynamics and interactions are unclear. Here we study growth dynamics of single cells within populations of marine Vibrionaceae strains that grow on the abundant marine polymer alginate, using microfluidics coupled to quantitative single-cell analysis and mathematical modelling. We find that strains that have low extracellular secretions of alginate lyases aggregate more strongly than strains that secrete high levels of enzymes. One plausible reason for this observation is that low secretors require a higher cellular density to achieve maximal growth rates in comparison with high secretors. Our findings indicate that increased aggregation increases intercellular synergy amongst cells of low-secreting strains. By mathematically modelling the impact of the level of degradative enzyme secretion on the rate of diffusive oligomer loss, we find that enzymatic secretion capability modulates the propensity of cells within clonal populations to cooperate or compete with each other. Our experiments and models demonstrate that enzymatic secretion capabilities can be linked with the propensity of cell aggregation in marine bacteria that extracellularly catabolize polysaccharides.

Microsphere-based photoexcited efficient terahertz radiation at room temperature enhanced by Ag/PI/PMMA/ZnO circle hollow waveguide resonance

The discovery and development of efficient terahertz sources at room temperature could lead to comprehensive application foreground. Here, ZnO mesocrystal microspheres were prepared by hydrothermal method through self-assembly of nanosheets. High-frequency mechanical vibrations of charged nanostructures excited by a continuous 514.5 nm laser at room temperature can lead to radiative emission at 0.36 THz, conversion efficiency of which was only 0.015%. A sandwich-structured Ag/PI/PMMA/ZnO circle hollow terahertz waveguide was fabricated to obtain high-power terahertz radiation source. Nano Ag thin film effectively localized terahertz light in the waveguide and reduced diffusion losses because of high reflection. Then, Optical lenses were placed before and after the waveguide to form a resonant cavity, so that terahertz light was resonantly enhanced at certain length. Meanwhile, the thickness of the PI thin film was designed to enhance the interference of terahertz light. Besides, the incident angle of green laser had a great influence on its reflection path within the waveguide, which in turn affected the number of excitations of ZnO. The above comprehensive reasons have successfully improved the conversion efficiency by 5.5 and 8.3 times when the angle of incident laser was 0° and 30°, respectively. This work revealed a new strategy to design and fabricate terahertz sources with excellent properties simultaneously such as room temperature operation, stable performance, and high power output.

Charge transport and acoustic loss in lithium niobate-lithium tantalate solid solutions at temperatures up to 900 °C

Polar oxides, in particular solid solutions of lithium niobate and lithium tantalate (LNT, LiNb1-xTaxO3) are a variable model system to study fundamental materials properties due to miscibility of the edge compounds lithium niobate (LN, LiNbO3) and lithium tantalate (LT, LiTaO3) as well as tunable domain structures. Further new applications in the field of high-temperature actuators are aimed as LNT crystals potentially combine the advantages of the edge compounds with respect to high thermal stability and high piezoelectric coefficients. Beside LN and LT, LNT crystals of two compositions (LiNb0.88Ta0.12O3 and LiNb0.5Ta0.5O3) were grown by the Czochralski technique. Electrical conductivity, lithium diffusion and acoustic loss of LNT at high temperatures were investigated and correlated. Two techniques, namely impedance spectroscopy and resonant piezoelectric spectroscopy (RPS) are applied in this investigation. The electrical conductivity of investigated samples increases linearly in an Arrhenius presentation up to ∼605 °C. After a transition range of 605–620 °C, the conductivity increases linearly again for LT, but the slope is decreased by about 0.15 eV. This indicates that the conductivity below and above the Curie temperature is governed by a slightly different process. In contrast, LN shows a gradually increasing slope in the Arrhenius representation above the transition temperature range mentioned above. Here, a single activation energy cannot be assigned. The increase can be explained by the limited thermal stability of LN at elevated temperatures. Further, the acoustic loss in LNT thickness-shear mode resonators operated at about 2 and 10 MHz is determined by RPS and found to strongly increase above about 450 °C. In addition, the acoustic loss is modelled using independent materials data including electrical conductivity as determined here, and found to be in excellent agreement with the RPS data for the 10 MHz resonator. Based on the modelling, the loss above 450 °C is governed by conductivity-induced piezoelectric/carrier relaxation which can be attributed to lithium migration.

Absence of water content contrast between lithosphere and asthenosphere in subduction zone

The distribution of water between the rigid lithosphere and ductile asthenosphere is crucial for our understanding of the Earth's dynamics because it has been proposed that the origin of the lithosphere–asthenosphere boundary (LAB; i.e., the bottom of the tectonic plate) is related to a possible elevated water content in the asthenosphere. However, obtaining the depth profile of water content using mantle xenoliths is still challenging because of the rapid diffusive loss of hydrogen during magma ascent and eruption. In this study, we present diffusion profiles of water determined by FTIR mapping and SIMS line analysis for olivine and orthopyroxene of peridotite xenoliths from Ichinomegata maar in Northeast Japan. Extensive analysis of water contents in 17 xenolith samples revealed that these xenoliths exhibit a variety of zoning patterns, from which the timescale of diffusive loss was estimated. The xenoliths from Ichinomegata underwent only limited diffusive water loss (<1h duration), because of the low temperature of andesitic host magma and rapid quench in the maar deposit. Water contents of the mantle value are well-preserved in the homogeneous core parts of large olivine and pyroxene grains. The water contents of olivine suggest clear correlations with petrogenetic factors excepting those marking anomalous high values, implying hydrous metasomatism by a water-rich fluid. Combining the estimated water contents of the minerals and depth estimation of the xenolith samples, for the first time, we obtained the depth profile of water content of the mantle, including the LAB, down to ∼55 km. Our results show that olivine, orthopyroxene, and clinopyroxene in the lithospheric mantle (depth range in 28–38 km) contain 21 ± 2, 302 ± 64, and 616 ± 99 wt. ppm H2O, respectively, which are similar to those in the top of the asthenosphere (depth range in 39–52 km) that contain 20 ± 2, 258 ± 38, and 561 ± 80 wt. ppm H2O. In the region which has experienced local metasomatism, higher water contents are recorded (30 ± 4, 414 ± 48, and 741 ± 43 wt. ppm H2O). This study verifies that there is no water content contrast across the LAB in our studied area. Therefore, we support the ‘partial-melting model’ for the origin of the LAB rather than the ‘olivine-water model’ in the western Pacific Plate subduction zone.

Synergic effect of covalent and chemical sulfur fixation enhancing the immobilization-conversion of polysulfides in lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are promising as the next generation energy storage options. However, their wide applications have been technically challenged by the diffusion losses of polysulfides and polysulfide shuttle effect. In this work, the small organic molecules of 2,5-dichloropyrazine (2,5-DCP) were combined with Co-doped carbon (CoNC) flakes to achieve the synergic effect of the covalent and chemical sulfur fixation, so as that the immobilization-conversion of polysulfides in LSBs was greatly enhanced. More specifically, the nucleophilic substitution of the 2,5-DCP additive in the electrolyte with polysulfides formed the CS bonds. Through the further covalent N-Li bonds between the N atoms in 2,5-DCP and polysulfides, sulfur fixation was achieved in the form of solid organosulfur. Meanwhile, the CoNC flakes served as the sulfur cathode to chemically anchor the polysulfides. The interaction mechanism between CoNC/2,5-DCP and polysulfides was explored by the density functional theory (DFT) calculations and in-situ infrared spectroscopy. The results showed that the optimal “with 2,5-DCP” sample-assembled LSB exhibited an initial discharge specific capacity of 1244 mA h g−1 at 0.2C, and a capacity decay rate of 0.053% per cycle was displayed after 800 cycles at 1C. The good cycling stability with a high sulfur-loaded electrode sample suggested that the synergic effect of covalent/chemical sulfur fixation enabled the enhancement of polysulfides immobilization-conversion in LSBs.

Numerical study and optimization of GO/ZnO based perovskite solar cell using SCAPS

&lt;abstract&gt; &lt;p&gt;This paper focuses on the numerical study of hybrid organic-inorganic perovskite solar cells. It investigates the incorporation of a graphene oxide (GO) thin layer to enhance solar cell efficiency. The study demonstrates that the GO layer improves interaction with the absorber layer and enhances hole transportation, resulting in reduced recombination and diffusion losses at the absorber and hole transport layer (HTL) interface. The increased energy level of the Lower Unoccupied Molecular Orbital (LUMO) in GO acts as an excellent electron-blocking layer, thereby improving the V&lt;sub&gt;OC&lt;/sub&gt;. The objective is to explore different structures of perovskite solar cells to enhance their performance. The simulated solar cell comprises a GO/FASnI&lt;sub&gt;3&lt;/sub&gt;/TiO&lt;sub&gt;2&lt;/sub&gt;/ZnO/ITO sandwich structure, with FASnI&lt;sub&gt;3&lt;/sub&gt; and ZnO thicknesses adjusted to improve conversion efficiency. The impact of thickness on device performance, specifically the absorber and electron transport layers, is investigated. The fill factor (FF) changes as the absorber and electron transport layers (ETL) increase. The FF is an important parameter that determines PSC performance since it measures how effectively power is transferred from the cell to an external circuit. The optimized solar cell achieves a short-circuit current density (J&lt;sub&gt;SC&lt;/sub&gt;) of 27.27 mA/cm&lt;sup&gt;2&lt;/sup&gt;, an open-circuit voltage (V&lt;sub&gt;OC&lt;/sub&gt;) of 2.76 V, a fill factor (FF) of 27.05% and the highest power conversion efficiency (PCE) of 20.39% with 400 nm of FASnI&lt;sub&gt;3&lt;/sub&gt; and 300 nm of ZnO. These findings suggest promising directions for the development of more effective GO-based perovskite solar cells.&lt;/p&gt; &lt;/abstract&gt;