Stages Of Cycling Research Articles

Validity and reproducibility of the CALERA Research Sensor to estimate core temperature at different intensities of a cycling exercise in the heat

Recent heatwaves have highlighted the importance of accurate and continuous core temperature (TCORE) monitoring in sports settings. For example, accentuated rises in TCORE caused by physical exercises under environmental heat stress increase the risk of heat illnesses. Thus, using valid and reproducible devices is essential to ensure safe sports practice. In this study, we assessed the validity and reproducibility of the Calera Research Sensor (CRS) in estimating the TCORE of male and female participants during cycling exercise in a hot environment. Seven male (age: 36.2 ± 10.1 years) and eight female cyclists (age: 30.1 ± 5.0 years) underwent two identical cycling trials in a dry-bulb temperature of 32 °C and relative humidity of 60%. The protocol consisted of an initial 10-min rest followed by a 60-min exercise comprising 10 min at 20%, 25 min at 55%, and 25 min at 75% of maximal aerobic power, and an additional 25 min of post-exercise recovery. TCORE was recorded simultaneously every minute using a gastrointestinal capsule (TGi) and the CRS (TSENSOR). Bland–Altman analysis was performed to calculate bias, upper (LCS) and lower (LCI) concordance limits, and the 95% confidence interval (95%CI). The maximum acceptable difference between the two devices was predetermined at ±0.4 °C. A mixed linear model was used to assess the paired differences between the two measurement systems, considering the participants, trials, and environmental conditions as random effects and the cycling stages as fixed effects. An intra-class correlation coefficient (ICC) of 0.98 was recorded when analyzing data from the entire experiment. A non-significant bias value of 0.01 °C, LCS of 0.38 °C, LCI of −0.35 °C, and CI95% of ±0.36 °C were found. When analyzing data according to the participants’ sex, CRS reproducibility was high in both sexes: ICC values of 0.98 and 0.99 were reported for males and females, respectively. CI95% was 0.35 °C in experiments with males and 0.37 °C with females, thereby falling within the acceptable margin of difference. Therefore, CRS was considered valid (compared to TGi) and reproducible in estimating TCORE in both sexes at various intensities of cycling exercise in the heat.

Using a fiber Bragg grating technique to investigate temperature cycling strain of pressed TATB‐based polymer‐bonded explosives

AbstractPressed 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB)‐based polymer‐bonded explosive (PBX) exhibits significant anisotropic and irreversible expansion characteristics during temperature cycling, resulting in both safety and service issues. The anisotropic and irreversible expansion properties of PBX have shown to be closely related to the microstructures, including explosive crystals, binders, micro voids, el. Fiber Bragg grating (FBG) technology has advantages of high reliability, accuracy, and sensitivity, which is more conducive to real‐time capture of the changes in strain throughout the temperature cycling. In this study, temperature cycling strain monitoring experiments of PBX pressed under different thermal–mechanical coupling loading conditions were studied using FBG technology. The effect of the pressing parameters on the anisotropic and irreversible expansion characteristics of the PBX's during temperature cycling was measured and analyzed, taking into account potential microstructural factors such as crystal orientation, binders, and porosity. The results indicated that the strain on the side and top of PBX cylinders were distributed with increasing strain in the direction of higher density. The strain stratification was significant during the high‐temperature stage of temperature cycling and was not obvious during the low‐temperature stage. The degree of strain stratification decreased with an increase in temperature cycling cycles and increased with higher pressing temperatures. The anisotropic expansion of PBX cylinders increased with an increase in temperature during cycling and decreased with a reduction in temperature. The axial expansion degree of PBX cylinders pressed under different compression conditions in the later cycles of temperature cycling is consistent with the different crystal orientations intensity inside them.

Iron nutritional efficiency, cycling and export in oil palm cultivated at different ages

Iron (Fe) plays a fundamental role in the nutrition of plants, yet its role in oil palm remains understudied. This study aims to unlock the role of Fe by analyzing its cycling and export different stages of oil palm tree growth. The experiment was conducted in Thailand, Pará State (Brazil), in a dystrophic Yellow Ferralsol, in a split-block, with four replications and seven treatments (plant age; 2, 3, 4, 5, 6, 7, and 8). The concentration, accumulation, recycling, immobilization, and export of Fe were evaluated, in addition to Fe use efficiency, in all plant organs. Analysis of variance (p < 0.05) was carried out on the results and regression model adjustments. The concentration and accumulation of Fe in the stem was greatest at the eighth year of the plants, and the fruit had higher Fe export values in the eighth year of the oil palm as well. As plants aged, the Fe concentration, accumulation, export, and use efficiency increased. Oil palm accumulates and immobilizes more Fe in its organs than it exports, a fact that contributes to the cycling and nutrition of the Fe in the plant. This research paves the way for future studies to explore how Fe can be optimized in oil palm trees to unlock their full potential.

Understanding mechanical stresses upon solid-state battery electrode cycling using discrete element method

Solid-state batteries (SSBs) often fall behind conventional lithium-ion batteries (LIBs) in performance. Electrochemical cycling protocols, in particular under isostatic compression, present ample opportunities for improvement to mitigate issues like contact loss and aging among numerous other challenges. This study introduces a novel Discrete Element Method (DEM) workflow to assess the effectiveness of uniaxial and isostatic compression as proceeding electrode preparation on the conductivity and structural integrity of SSBs. Isostatic compression achieves conductivity levels comparable to uniaxial compression with significantly reduced pressure requirements. In contrast, uniaxial compression at elevated loads, while resulting in higher conductivity, subjects the particles to significant stress, increasing the risk of cracking and deformation of the SSB materials. This study shows the impact of mechanical stress during different stages of electrochemical cycling on the microstructure's integrity to provide valuable insights into electrochemistry-mechanics couplings, which can be challenging to evaluate experimentally.

In Situ Characterizations of the Dynamics of Cathode Electrolyte Interfaces at Different Current Densities.

LiNi0.8Mn0.1Co0.1O2 with high nickel content plays a critical role in enabling lithium metal batteries (LMBs) to achieve high specific energy density, making them a prominent choice for electric vehicles (EVs). However, ensuring the long-term cycling stability of the cathode electrolyte interfaces (CEIs), particularly at fast-charge conditions, remains an unsolved challenge. The decay mechanism associated with CEIs and electrolytes in LMB at high current densities is still not fully understood. To address this issue, in situ Fourier transform infrared (FTIR) is employed to observe the dynamic process of formation/disappearance/regeneration of CEIs during charge and discharge cycles. These dynamic processes further exacerbate the instability of CEIs as current density increases, leading to rupture and dissolution of CEIs and subsequent deterioration in battery performance because of continuous electrolyte reactions. Additionally, the dynamic changes occurring within individual components of CEIs at different cycling stages and various current densities are also discussed. The results demonstrate that excellent capacity retention at small current density is attributed to enrichment of inorganic compounds (Li2CO3, LiF, etc.) and rendering better stability and smaller expansion of CEIs. The key to achieving excellent electrochemical performance at high current densities lies on protecting CEIs, mainly inorganic components.

Imaging the dynamics of murine uterine contractions in early pregnancy†.

Uterine muscle contractility is essential for reproductive processes including sperm and embryo transport, and during the uterine cycle to remove menstrual effluent. Even still, uterine contractions have primarily been studied in the context of preterm labor. This is partly due to a lack of methods for studying the uterine muscle contractility in the intact organ. Here, we describe an imaging-based method to evaluate mouse uterine contractility of both the longitudinal and circular muscles in the cycling stages and in early pregnancy. By transforming the image-based data into three-dimensional spatiotemporal contractility maps, we calculate waveform characteristics of muscle contractions, including amplitude, frequency, wavelength, and velocity. We report that the native organ is highly contractile during the progesterone-dominant diestrus stage of the cycle when compared to the estrogen-dominant proestrus and estrus stages. We also observed that during the first phase of uterine embryo movement when clustered embryos move toward the middle of the uterine horn, contractions are dynamic and non-uniform between different segments of the uterine horn. In the second phase of embryo movement, contractions are more uniform and rhythmic throughout the uterine horn. Finally, in Lpar3-/- uteri, which display faster embryo movement, we observe global and regional increases in contractility. Our method provides a means to understand the wave characteristics of uterine smooth muscle in response to modulators and in genetic mutants. Better understanding uterine contractility in the early pregnancy stages is critical for the advancement of artificial reproductive technologies and a possibility of modulating embryo movement during clinical embryo transfers.

A New Method for In-Situ Characterization of Solid-State Batteries Based on Optical Coherence Tomography.

With the in-depth study of solid-state batteries (SSBs), various in situ and ex situ characterization technologies have been widely used to study them. The performance and reliability of SSBs are limited by the formation and evolution of lithium dendrites at the interfaces between solid electrodes and solid electrolytes. We propose a new method based on optical coherence tomography (OCT) for in situ characterization of the internal state of solid-state batteries. OCT is a low-loss, high-resolution, non-invasive imaging technique that can provide real-time monitoring of cross-sectional images of internal structures of SSBs. The morphology, growth, and evolution of lithium dendrites at different stages of cycling under various conditions can be visualized and quantified by OCT. Furthermore, we validate and correlate the OCT results with scanning electron microscopy (SEM) and XPS, proving the accuracy and effectiveness of the OCT characterization method. We reveal the interfacial phenomena and challenges in SSBs and demonstrate the feasibility and advantages of OCT as a powerful tool for in situ and operando imaging of battery interfaces. This study provides new insights into the mechanisms and factors that affect SSB performance, safety, and lifetime, and suggests possible solutions for improvement and application in the field of applied energy.

Effect of Ultramarathon Trail Running at Sea Level and Altitude on Alveolar-Capillary Function and Lung Diffusion.

Endurance exercise at altitude can increase cardiac output and pulmonary vascular pressure to levels that may exceed the stress tolerability of the alveolar-capillary unit. This study examined the effect of ultramarathon trail racing at different altitudes (ranging from <1000 m to between 1500 and 2700 m) on alveolar-capillary recruitment and lung diffusion. Cardiac and lung function were examined before and after an ultramarathon in 67 runners (age: 41 ± 9 yr, body mass index: 23 ± 2 kg·m -2 , 10 females), and following 12-24 h of recovery in a subset ( n = 27). Cardiac biomarkers (cTnI and BNP) were assessed from whole blood, whereas lung fluid accumulation (comet tails), stroke volume (SV), and cardiac output ( Q ) were quantified via echocardiography. Lung diffusing capacity for carbon monoxide (DLco) and its components, alveolar membrane conductance (Dm) and capillary blood volume (Vc), were determined via a single-breath method at rest and during three stages of submaximal semirecumbent cycling (20, 30, and 40 W). Average race time was 25 ± 12 h. From pre- to post-race, there was an increase in cardiac biomarkers (cTnI: 0.04 ± 0.02 vs 0.13 ± 0.03 ng·mL -1 , BNP: 20 ± 2 vs 112 ± 21 pg·mL -1 ; P < 0.01) and lung comet tails (2 ± 1 vs 7 ± 6, P < 0.01), a decrease in resting and exercise SV (76 ± 2 vs 69 ± 2 mL, 40 W: 93 ± 2 vs 88 ± 2 mL; P < 0.01), and an elevation in Q at rest (4.1 ± 0.1 vs 4.6 ± 0.2 L·min -1 , P < 0.01; 40 W: 7.3 ± 0.2 vs 7.4 ± 0.3 L·min -1 , P = 0.899). Resting DLco and Vc decreased after the race ( P < 0.01), whereas Dm was unchanged ( P = 0.465); however, during the three stages of exercise, DLco, Vc, and Dm were all reduced from pre- to post-race (40 W: 36.3 ± 0.9 vs 33.0 ± 0.8 mL·min -1 ·mm Hg -1 , 83 ± 3 vs 73 ± 2 mL, 186 ± 6 vs 170 ± 7 mL·min -1 ·mm Hg -1 , respectively; P < 0.01). When corrected for alveolar volume and Q , DLco decreased from pre- to post-race ( P < 0.01), and changes in DLco were similar for all ultramarathon events ( P > 0.05). Competing in an ultramarathon leads to a transient increase in cardiac injury biomarkers, mild lung-fluid accumulation, and impairments in lung diffusion. Reductions in DLco are predominantly caused by a reduced Vc and possible pulmonary capillary de-recruitment at rest. However, impairments in alveolar-capillary recruitment and Dm both contribute to a fall in exertional DLco following an ultramarathon. Perturbations in lung diffusion were evident across a range of event distances and varying environmental exposures.

Suppressing the damage of deposited Mn(II) ions to graphite anode in lithium‐ion batteries by electrolyte additive agent and positive material coating

AbstractSEM and EDS techniques are carried out to demonstrate the variation of morphology and chemical compound on the surface of graphite anode, which suggest a well‐accepted concept that the manganese ions have serious influence on the reversible capacity fade of graphite anode in lithium ion batteries. Based the main chemical compounds of the inorganic layer on the graphite surface, the evolution steps of graphite structure damaged by Mn ions are derived. Although the amount of deposited manganese ions is small, these play an important role in the catalytic decomposition of the electrolyte. Moreover, Raman analysis shows that the structure of the graphite anode becomes irregular at initial SEI formation cycles and tends to be stable at subsequent cycles. This structure variation is probably generated from the manganese ion deposition and the solid electrolyte interphase (SEI) film formation. According to the capacity tests, the cycling performance of NCM811/graphite lithium‐ion batteries could be improved 50% by FEC additive and B2O3 surface coating. FEC additive maybe benefit graphite forming a stable SEI film in the early stages of cycling to suppress the damage of Mn2+ ions, then improving the cycling performance.

Atomistic-Scale Simulations Toward the Understanding of the Conversion–Alloying Mechanism in Li-Ion Battery Anodes

The increasing demands for energy storage call for improved capacity and cycling stability of modern Li-ion batteries (LIBs). However, the application of the state-of-the-art LIB anode material – graphite is limited as graphite underperforms as a high-rate/high-storage-capacity anode. Alternatively, materials capable of alloying with Li-ions have attracted attention as a promising pathway to solve high-rate and high-capacity challenges. Furthermore, when alloying reaction in a material is coupled with irreversible conversion reaction, the materials operating under such mechanism exhibit a high Li-ion storage capacity and long-term stability during electrochemical cycling. However, despite the optimistic performance of these materials, a number of parameters need to be optimized and fundamentally understood.Among the unknowns for the conversion/alloying materials are the atomistic details of the reaction mechanism - understanding the atomistic structure during transformations is a pre-requisite for the future rational optimization of the materials. Furthermore, amorphization, which is prevalent in these materials, severely limits the conventional characterization methods essentially impeding further development and understanding the degradation mechanisms. Hence, to investigate the atomistic structure changes, we proposed a computational methodology for these conversion-alloying materials and their reaction mechanism by taking amorphous substoichiometric silicon nitride as a showcase system [1]. The molecular dynamics (MD) simulations utilized the ReaxFF parameter set which was specifically developed for the investigation. Subsequently, the experimental pair distribution functions (PDF) were used to verify the modeling results.While the reactive molecular dynamics was coupled with the PDF simulation to complement the experimental measurements, the effective and practical approach guided us to the atomistic structure evolution understanding for LIBs in a conversion–alloying process, revealing the bond coordinations around the Si atoms in the active material. Consequently, the analysis opened an in-depth understanding of the cycling stability of substoichiometric a-SiNx anode materials by revealing the atomistic features relevant to the changes this material undergoes during lithiation and delithiation processes in a LIB. Furthermore, the proposed approach allows modeling of the changes at the atomistic scale for the amorphous materials and predicting the experimental PDF at different cycling stages, verifying the modeling outcome. The topic also addresses the applications of the approach for other anode materials.

Layer-Resolved Mechanical Degradation of a Ni-Rich Positive Electrode

The effects of electrochemical aging on the mechanical properties of electrodes in lithium-ion batteries are challenging to measure and are largely unknown. Mechanochemical degradation processes occur at different scales within an electrode and understanding the correlation between the degradation of mechanical properties, electrochemical aging, and morphological changes is crucial for mitigating battery performance degradation. This paper explores the evolution of mechanical and electrochemical properties at the layer level in a Ni-rich positive electrode during the initial stages of electrochemical cycling. The investigation involves complementary cross-section analyses aimed at unraveling the connection between observed changes on both macroscopic and microscopic scales. The macroscopic constitutive properties were assessed using a U-shaped bending test method that had been previously developed. The compressive modulus exhibited substantial dependency on both the porous structure and binder properties. It experienced a notable reduction with electrolyte wetting but demonstrated an increase with cycling and aging. During the initial stages of aging, electrochemical impedance spectra revealed increased local resistance near the particle–electrolyte interface. This is likely attributable to factors such as secondary particle grain separation and the redistribution of carbon black. The swelling of particles, compression of the binder phase, and enhanced particle contact were identified as probable factors adding to the elevation of the elastic modulus within the porous layer as a result of cycling.

Transformation-mediated in-situ β recrystallization in laser powder-bed fusion additively manufactured Ti-6Al-4V

Achieving equiaxed grain structure is highly sought after in metal processing for most critical structural applications but it is seldom realized in Ti-6Al-4V additively manufactured (AM) by laser powder-bed fusion (LPBF) due to its unique thermal environment in favor of columnar grain growth. To convert columnar grains into equiaxed, post heat treatment in the β phase field is often adopted to initiate recrystallization of prior-β grains. This study demonstrates the achievement of equiaxed prior-β grain structure in situ in LPBF Ti-6Al-4V via epitaxial recrystallization mediated by α → β phase transformation taking place in the rapid heating stage of LPBF thermal cycling. In this rapid reverse phase transformation process, new β nuclei of distinct variants to their parent prior-β grain nucleate directly on α matrix in accordance with Burgers orientation relationship and grow towards the surrounding α matrix while α is transforming to β within a specific prior-β grain. This hypothesis is strongly supported by the experimental evidence that a significant fraction of β/β grain boundaries are featured with misorientations near 60° in both as-built Ti-6Al-4V and those subjected to post rapid heat treatment. This essentially excludes conventional recrystallization as the mechanism responsible for the evolution of equiaxed prior-β grain structure in the as-built state. The new finding unveils the critical role of LPBF thermal cycling and associated phase transformation in microstructure evolution and paves the way for the development of high-quality AM Ti-6Al-4V with reduced performance anisotropy.

Influence of Formation Temperature on Cycling Stability of Sodium-Ion Cells: A Case Study of Na3V2(PO4)2F3|HC Cells

Sodium-ion batteries are cheaper and attractive alternatives to lithium-ion batteries, particularly for low-energy and high-power applications. In this regard, a targeted cell design is essential to achieve optimal cycling performances and reduced cell impedance. While optimized electrode and electrolyte formulations are important, the formation protocol -initial cycles that establish the electrode-electrolyte interphase- significantly impacts cell impedance and interphase stability. In this study, we investigate the influence of formation temperature on the nature of interphases formed in Na3V2(PO4)2F3 (NVPF)|hard carbon (HC) cells. Our findings reveal that the interphase’s nature and chemical composition evolve with the formation temperature. Moreover, cell temperature affects interphase dissolution and reformation, suggesting the potential benefits of employing mixed high and low temperatures during formation cycles to achieve desired interphase properties. A formation protocol coupling cycling stages at different temperatures (55 °C–25 °C–0 °C) exhibits an edge over with respect to low impedance, slightly higher reversible capacity and long cycling stability compared to the cells formed solely at 55 °C. The results presented underscore the necessity of exploring formation protocols including not only high temperatures but also colder temperatures, like 0 °C and below. This approach is pivotal for advancing the understanding of interphase dynamics and optimizing sodium-ion battery performance.

Fracture behavior of yellow sandstone under freeze–thaw cycles with varied saturation states: An investigation of mode I fracture

In cold regions, the behavior of fissured rock in rock engineering is significantly affected by freeze–thaw (F–T) cycles. To investigate the impact of freeze–thaw cycles on rock fracture behavior, freeze–thaw cycle treatment, and fracture tests were conducted on Cracked Straight Through Brazilian Disc (CSTBD) specimens. The freeze–thaw treatment notably degraded the physical and mechanical properties of the rock, marked by a downward trend in fracture load, toughness, and energy. A considerable volume of data suggests that the impact of freeze–thaw (F–T) on yellow sandstone was predominantly during the initial stages of cycling, with this trend stabilizing as the number of cycles increased. Microscopic analysis via Scanning Electron Microscopy (SEM) uncovered the patterns of freeze–thaw damage in yellow sandstone. Dry rocks exhibited crack propagation, while water-saturated rocks displayed pore and crack expansion. The Digital Image Correlation (DIC) method illuminated the evolution of the high strain zone during the fracturing process. The mode I fracture process revealed a gradual expansion of the high strain zone originating from the crack tip, intensifying with increased load. As freeze–thaw cycles progressed, damage accumulation was gradual, and the path of mode I crack propagation grew increasingly intricate from a macroscopic perspective. Additionally, the quantification of fractal dimensions, achieved through the analysis of binarized SEM images, corroborates these observations at a microscopic level.

Modeling Battery Formation: Boosted SEI Growth, Multi-Species Reactions, and Irreversible Expansion

This work proposes a semi-empirical model for the SEI growth process during the early stages of lithium-ion battery formation cycling and aging. By combining a full-cell model which tracks half-cell equilibrium potentials, a zero-dimensional model of SEI growth kinetics, and a semi-empirical description of cell thickness expansion, the resulting model replicated experimental trends measured on a 2.5 Ah pouch cell, including the calculated first-cycle efficiency, measured cell thickness changes, and electrolyte reduction peaks during the first charge dQ/dV signal. This work also introduces an SEI growth boosting formalism that enables a unified description of SEI growth during both cycling and aging. This feature can enable future applications for modeling path-dependent aging over a cell’s life. The model further provides a homogenized representation of multiple SEI reactions enabling the study of both solvent and additive consumption during formation. This work bridges the gap between electrochemical descriptions of SEI growth and applications toward improving industrial battery manufacturing process control where battery formation is an essential but time-consuming final step. We envision that the formation model can be used to predict the impact of formation protocols and electrolyte systems on SEI passivation and resulting battery lifetime.

Lithium Morphology Evolution through Crosslinked Poly(ethylene oxide) Solid Polymer Electrolyte

Solid-state, lithium metal batteries are promising candidates for developing the safe, energy-dense devices needed to transition to an electrified economy. However, lithium is highly reactive, making it thermodynamically unstable when in contact with many electrolyte materials. Achieving uniform Li plating and stripping during cycling is the key for enabling high energy Li metal batteries. The lithium stripping and plating mechanism is complicated as it can be affected by the cathode, electrolyte and lithium anode, and the resulting solid electrolyte interphase (SEI). In particular, the mechanism is not well understood in solid polymer electrolytes.In this work, we investigate lithium morphology evolution through a solid polymer electrolyte at different stages of battery cycling. Crosslinked poly(ethylene oxide) (xPEO) solid polymer electrolyte is used as a model electrolyte and full cells using single crystal LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode, dry xPEO electrolyte and lithium from two commercial sources are assembled. Our results show that different lithium sources lead to different Coulombic efficiencies and capacity fade rate of the full cells assembled. The lithium morphology evolution at different stages of cycling is examined using scanning electron microscopy and the lithium plating/stripping mechanism are compared between these two commercial lithium anodes. Furthermore, the lithium morphology is compared to a gel polymer composite electrolyte with the same host polymer (xPEO). The dry solid polymer produces a smoother morphology than the gel polymer composite electrolyte without pit formation. A better understanding of the roles of each of these components (pristine Li surface chemistry, microstructure, dry vs gel polymer electrolyte) is essential to control for uniform lithium stripping and plating.

Understanding the lithiation intermediates of a silicon-based alloying anode by using operando diffraction and Raman spectroscopic techniques

In the present study, the effect of lithiation on a chalcopyrite phase, cadmium silicon phosphide (CdSiP2) anode is studied. This silicon-based phosphide anode helps in overcoming certain challenges encountered towards the application of elemental silicon anode for lithium-ion battery. Despite of having a fairly high band gap, this material represents outstanding cycling stability for lithium storage. Half-cell configuration results in a capacity of 970 mAh g−1 towards the end of 500 cycles at an applicable rate of 300 mA g−1, whereas a capacity of 645 mAh g−1 is obtained at a rate of 5000 mA g−1 for about 1800 cycles. The rate capability studies suggest highly reversible storage processes when switching from extremely high current rates such as 30 A g−1. Full-cell studies indicate highly stable charge-discharge voltage profiles with an appreciable capacity of around 400 mAh g−1 towards the end of 1400 cycles. Further, in-situ X-ray diffraction (XRD) analysis indicates conversion processes and confirms the formation of phases such as Li3P, LiCdP, Li5SiP3, Li13Si4, Li22Si5 and CdLi at various stages of charge-discharge cycling.

Surface roughness and microhardness of enamel white spot lesions treated with different treatment methods

ObjectiveTo analyse the surface roughness and microhardness of artificial enamel white spot lesions before and after WSL formation, after treatment (Opalsutre™ microabrasion, Sylc® bioactive glass, and ICON® resin infiltration), and after pH cycling with the help of the profilometer surface roughness tester and the digital Vickers microhardness tester. Materials and methodsSeventy-five extracted molars were used to acquire one hundred specimens. 50 specimens were randomly assigned to five groups (n = 10) for the surface roughness study: 1) Sound group, 2) WSL group, 3) micro abrasion (MA; Opalustre, Ultradent, South Jordan, UT, USA), 4) bioactive glass 45S5 Sylc powder (Sylc; Denfotex Research Ltd, Inverkeithing, UK), and 5) ICON resin infiltration (ICON; DMG, Hamburg, Germany). An additional 25 specimens were used to obtain 50 enamel slabs for the surface microhardness study, which were also assigned to the same groups. All groups underwent a final stage of pH cycling. Surface roughness and surface microhardness measurements were performed at different stages for all groups. ResultsRegarding surface roughness, ICON significantly reduced the surface roughness compared to Opalustre and Sylc, with no significant difference between Opalustre and Sylc. In terms of surface microhardness, ICON showed the highest improvement, followed by Sylc and then Opalustre. Both surface roughness and microhardness were significantly affected by demineralization, partially improved after treatment, and then regressed significantly after pH cycling. ConclusionICON resin infiltrant can be considered as a superior treatment option for improving surface roughness and microhardness, while Opalustre demonstrated relatively the poorest performance compared to the other treatment options. It is noteworthy that the pH cycling procedure had an adverse impact irrespective of the treatment option used.

Changes in the Strength and Leaching Characteristics of Steel Slag-Oil Shale Residue-Based Filling Paste in a Complex Erosive Environment

Our research group prepared a new filling paste consisting of steel slag–oil shale residue and no admixtures. It was used as the research object to explore the combined effect of chloride and dry–wet cycling-driven erosion on the long-term stability of a cemented filling paste made of total solid wastes. Macroscopic experiments and microscopic analyses methods were employed. The influence of solutions with different mass fractions of chloride salts and different cycling periods on the uniaxial compressive strength and toxicity of the steel slag–oil shale residue-based filling paste was studied, and the deterioration mechanisms of the steel slag–oil shale residue-based filling paste under combined erosion from chloride and dry–wet cycling were investigated. The test results showed that in the same cycling conditions, the strength of the steel slag-oil shale residue-based filling paste increased first with the increase in the mass fraction of the chloride solution and then decreased with the increase in the mass fraction of the chloride solution after reaching the peak value; the leached concentrations of heavy metal ions decreased with increasing chloride salt mass fraction. With an increase in the number of dry–wet cycles, the compressive strength of the specimens in the chloride salt solution with a mass fraction of 0 (pure water) first increases and then tends to be stable. The strength of samples in 5% and 10% chloride salt solutions increased first and then decreased with an increase in the number of dry–wet cycles. The leached concentrations of heavy metal ions from the samples in all three solutions first decreased and then stabilized. The prehydration products of the steel slag–oil shale residue-based filling paste were C-S-H gels, AFt and Friedel’s salt, and these increased with increasing chloride salt mass fraction and the number of dry–wet cycles. However, the hydration reactions of the samples in the 0% chloride solution nearly stopped in the later stages of cycling, and the samples in 5% and 10% chloride salt solutions developed local cracks due to the accumulation of hydration products. The results showed that the number of dry–wet cycles and the chloride salt mass fraction affected the strength and leaching characteristics of the steel slag–oil shale residue-based filling paste by changing the type and amount of erosion products. The test results provide a scientific basis for the promotion and application of backfilling pastes made from total solid wastes.

Long cycle performance of NC@VN/MnO cathode for AZIBs based on Mn/V relay type collaboration

Aqueous zinc ion batteries (AZIBs) have received great attention because of their non-toxicity, high safety, low cost, high abundance, and high specific power. However, their specific capacity is still low compared with lithium ion battery, and current academic research interesting has been focused on developing new cathode materials with high specific capacity. In this study, a Mn/V hybrid polymer framework is designed by a simple self-polymerization scheme. During subsequent calcination, ultrafine VN quantum dots and MnO nanoparticles are generated in situ and stably encapsulated inside N-doped carbon (NC) shells to obtain a novel hybrid cathode NC@VN/MnO for AZIBs. According to the density functional theory (DFT) calculation, the hybrids of MnO and VN can generate both interfacial effects and built-in electric fields that significantly accelerate ion and electron transport by tuning the intrinsic electronic structure, thus enhancing electrochemical performance. A synergistic strategy of composition and structural design allows the rechargeable AZIBs to achieve low-cost and excellent long-cycle performance based on a relay type collaboration at different cycling stages. Consequently, the NC@VN/MnO cathode has output a capacity of 108.3 mA h g−1 after 12,000 cycles at 10 A g−1. These results clearly and fully demonstrate the advantages of the hybrid cathode NC@VN/MnO.