Comparison Of Stability Research Articles

Preliminary Studies on Changes in Static Plantar Pressure and Stabilometry in Patients with Ankylosing Spondylitis Undergoing an Exercise Program.

Background/Objectives: Studies have reported that patients suffering from ankylosing spondylitis (AS) have decreased postural stability in comparison to healthy subjects. Our study aims to compare static plantar pressure and stabilometry parameters in AS patients who performed an 8-week exercise program (spine motion and flexibility exercises; stretching of hamstring, erector spine, and shoulder muscles; control abdominal and diaphragm breathing exercises and chest expansion exercises), in three different testing conditions (eyes open, eyes closed, and head retroflexed). Methods: Plantar pressure (the loading of the first and fifth metatarsal heads (MT1, MT5) and calcaneus) and stabilometry (CoP path length, 90% confidence ellipse area, and maximum CoP speed) were recorded in 28 AS patients (age 56.64 ± 10.3 years; body mass index 29.4 ± 4.9 kg/m2) at the beginning of rehabilitation and after 8 weeks. At first evaluation, there were significant differences (p < 0.05) for the foot loading sites (MT1, MT5, and calcaneus), both for the right and left feet, when comparing eyes open with the other two testing situations. Results: After rehabilitation, significant differences were recorded between eyes-open and head-retroflexed conditions for MT1 (p = 0.03 for right; p = 0.004 for left) and calcaneus (p = 0.014 for right; p = 0.011 for left). A significantly higher CoP path length was registered in both initial and final assessments when tested with eyes closed. The maximum CoP speed had increased values at both evaluations when tested with head retroflexed. Conclusions: The CoP path length decreased after the physical exercise program, with a better postural stability after rehabilitation.

Development and characterisation of nutritionally enriched honey filling as novel alternative to commercial fat-based filling for bakery applications

This research aimed to develop a novel bakery filling ingredient using honey by incorporating watermelon rind (WMR) paste and xanthan gum (XG) as an alternative to conventional fat-based fillings. The study effectively optimised honey filling preparation using a Box-Behnken design, considering variables three key independent variables: WMR paste (10–30 % w/w of honey weight), XG (1–1.5 % w/w of honey weight), and vacuum drying time (5–10 h). The impact of these was systematically evaluated across baking stability, total phenolic content (TPC), firmness, and water activity of the honey filling. The optimal conditions for honey filling preparation were identified as 27.31 % WMR paste, 1.1 % XG, and a drying time of 8 h and 54 min. The incorporation of WMR paste led to notable improvements of TPC, total flavonoid content (TFC), antioxidant capacity; however, XG played a vital role in enhancing the baking stability and viscoelastic nature of honey filling samples. To comprehensively assess the physicochemical, rheological, and thermal characteristics, a comparison was drawn between raw honey, optimised honey filling (OHF), and a commercial chocolate filling (CCF) as a reference. The CCF exhibited slightly higher viscoelastic behaviour but lower structural stability in comparison to OHF. On the other hand, OHF demonstrated thermal properties like those of the CCF, with enhanced antioxidant activity, lower moisture content, and minimal fat content. Therefore, OHF introduces a bakery filling option as an alternative to CCF, with superior nutritional value and enhanced rheological stability.

Thermal Analysis of the Biodegradable Polymer PVA/PEO Blends

Poly(vinyl alcohol) (PVA) and poly(ethylene) oxide (PEO) are widely used water-soluble and biodegradable polymers that possesses high biocompatibility. In this work PVA/PEO blends were prepared via solution casting method, where the solvent was water. After drying, samples were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). Since DSC could not confirm the possible intermolecular interaction between PVA and PEO, infrared spectroscopy with Fourier transform (FT-IR) was utilized. Finally, the TG analysis revealed that degradation of PVA/PEO blends proceeds through tree stages, similar as neat PVA. Contrary, neat PEO thermally degrade through only one stage showing better thermal stability in comparison to PVA.

Systematic assessment of a multi–solid waste cementitious material: Feasibility and environmental impact

This study systematically assessed the feasibility of replacing ordinary Portland cement (OPC) with a multi–solid waste cementitious material (MSC) composed of ground granulated blast furnace slag (GGBS), steel slag (SS), red mud (RM), fly ash (FA), limestone powder (LP), and desulfurized gypsum (DG) in specific proportions of 28%, 25%, 21%, 11.5%, 9%, and 5.5%, respectively. The hydration characteristics were analyzed using hydration heat, XRD, TG–DTG, FTIR, and SEM–EDX tests. The heavy metal content and leaching concentration of the MSC were determined using inductively coupled plasma mass spectrometry (ICP–MS). The unconfined compressive strength (UCS), indirect tensile strength (ITS), and water stability of the MSC-stabilized clayey sand and stone chips were investigated. The results showed that synergistic hydration among multiple solid wastes generated abundant hydration products, including Ca(OH)2, C–(A)–S–H gels, and AFt crystals, which formed dense and compact microstructures. Furthermore, Pb and Cd in the raw material were effectively solidified by MSC hydration, with leaching concentrations as low as 0.181 and 0.002 mg/L, respectively. The contents and leaching concentrations of the other heavy metals were significantly lower than their limits. The pH of the MSC mortar leachate was stable at 11.56 with curing age, which complied with environmental safety standards. Moreover, MSC as a binder demonstrated higher UCS, ITS, and water stability in comparison to OPC. When MSC was added at a 6% dosage to stabilize clayey sand and stone chips, the UCS values measured after 7 days of curing were 2.82 MPa and 4.83 MPa, respectively. Finally, the MSC was successfully applied in practical projects, demonstrating its promising application prospects.

Protection of bovine serum albumin through encapsulation in hybrid vesicles

This study focuses on hybrid vesicles (HVs) formed through co-assembly of soy phosphatidylcholine (SPC) and a triblock copolymer (F127). After elucidating the superior stability of HVs over the assemblies of neat SPC and F127, these were encapsulated with bovine serum albumin (BSA), as model a thermolabile protein. Characterizations were performed using dynamic light scattering (DLS), electron microscopy, circular dichroism and high-sensitivity differential scanning calorimetry. The size of HVs increased slightly at higher proportion of F127 and upon encapsulation of BSA. In spite of this, vesicles remained spherical and displayed a smooth surface. They showed superior dilution stability in comparison to neat copolymer micelles and phospholipid vesicles. Their stability can be ascribed to hydrophobic association between the phospholipid and copolymer, and manifested into increase in phase transition temperature of the former. We found that HVs could protect BSA from denaturation and unfolding when challenged by high solution temperature, pH changes and salt incorporation.

Immobilization of Phospholipase D for Production of Phosphatidylserine via Enzyme-Inorganic Hybrid Nanoflower Strategy

Phosphatidylserine (PS) is a natural phospholipid with particular importance in the food, cosmetic, and pharmaceutical industries. Recently, the synthesis of PS mediated by phospholipase D (PLD) has drawn great attention. But the application of free PLD is limited by various drawbacks, including its instability under extreme conditions, difficulties in reuse and recovery, and high costs. In this work, saPLD-inorganic hybrid nanoflowers (saPLD@NFs) were synthesized with PLD from Streptomyces antibioticus (saPLD) as the organic component and Ca3(PO4)2 as the inorganic component. The saPLD@NFs demonstrated outstanding immobilization capability and achieved a 119% enzyme activity recovery rate. Furthermore, the saPLD@NFs exhibited better thermostability and pH stability in comparison to free saPLD. The PS yield of saPLD@NFs was about 57.4% in the first cycles and still reached 60.4% of its initial PS yield after four cycles. After 25 d storage at 4 °C, saPLD@NFs retained 66.5% of its original activity, but free saPLD only retained 38.3%, indicating that saPLD@NFs have excellent storage stability. Thus, this study established a new method of preparing PLD nanoflowers for effective PS synthesis, which might accelerate the practical utilization of this biocatalyst.

Enhanced stability of anthocyanins by cyclodextrin–metal organic frameworks: Encapsulation mechanism and application as protecting agent for grape preservation

Anthocyanins are promising naturally occurring food preservatives for enhancing the quality of food products due to their excellent antioxidant properties. However, their low stability hinders their food packaging application. Here, we propose a facile strategy to achieve the improved stability of anthocyanins encapsulated in γ-cyclodextrin metal-organic frameworks (CD-MOFs) with an in-depth exploration of their structure–property relationships. The adsorbed anthocyanins in CD-MOFs are stabilized by multiple cooperative non-covalent interactions including hydrogen bonding and van der Waals (vdW) interactions as demonstrated by density functional theory (DFT) calculations and spectroscopy analysis. Particularly, by ion-exchange of acetate ions into the pores of CD-MOFs, the resulting CD-MOFs (CD-MOF_OAc) shows a higher anthocyanins adsorption rate with a maximum loading capacity of 83.7 % at 1 min. Besides, CD-MOF_OAc possesses the more effective protecting effect on anthocyanins with at least two-fold enhancement of stability in comparison of free anthocyanins under heating and light irradiation. The anthocyanins encapsulated CD-MOFs films for fruit freshness was validated by the Kyoho experiment. This novel encapsulation system provides a new possibility for the potential use of CD-MOFs as the encapsulating material for anthocyanins in fruit preservation.

Indocyanine Green‐Glycogen Conjugates for Near‐Infrared‐Triggered Photothermal Cancer Therapy

AbstractPhotothermal reagents sensitive to near‐infrared (NIR) light are promising imaging agents and therapeutics for anticancer applications because of the deep tissue penetration of NIR light, allowing for spatiotemporal control over the therapeutic activity, with minimal damage to normal tissues. Herein, a new class of NIR‐sensitive biopolymer‐based nanoparticles is presented by covalently conjugating indocyanine green (ICG) onto the surface of naturally occurring glycogen nanoparticles. The resulting ICG‐glycogen conjugates exhibit a markedly enhanced aqueous stability in comparison to free ICG molecules. Furthermore, an efficient light‐to‐heat conversion is enabled by ICG‐glycogen conjugates, as evidenced by the elevated temperatures of their aqueous solutions upon exposure to NIR light. Critically, ICG‐glycogen conjugates are capable of cell internalization, and under NIR irradiation the effective eradication of breast cancer cells, demonstrating their potential in photothermal therapy for cancer.

Ensemble data assimilation for open channel water level forecasting under flow disturbances: A synthetic data study

Accurate water level forecasts are essential for effective river management. Data assimilation (DA), involving real-time model correction through observational data, serves as a pivotal approach to enhance the predictive precision of model-based state forecasting. Nevertheless, prevailing DA methodologies encounter constraints in swiftly and accurately forecasting water levels amidst substantial uncertainties stemming from flow disturbances. To surmount this challenge, an innovative joint ensemble Kalman filter (EnKF) framework that facilitates concurrent estimation of flow disturbances and water levels is proposed. By incorporating the flow disturbance state variable into the EnKF framework for water level assimilation, a joint EnKF framework that effectively estimates flow disturbances at known disturbance points through assimilation techniques is established. Additionally, for scenarios where the precise location of the flow disturbance point remains unknown, the introduction of a fictitious lateral outflow in proximity to the observation point allows estimation of the flow disturbance process of this fictitious outflow. Synthetic case study results demonstrate that the incorporation of flow disturbance assimilation yields superior water level estimations compared to scenarios disregarding flow disturbances, regardless of the concordance between estimated and actual disturbance flow values. Furthermore, even when the location of the disturbance point is known, utilization of a fictitious lateral outflow and and subsequent flow correction exhibits heightened robustness and stability in comparison to direct correction of the disturbance point's flow. Therefore, in practical applications, utilizing a fictitious lateral outflow and flow correction within the joint EnKF framework emerges as a more suitable approach, irrespective of the knowledge of disturbance location. The proposed method constitutes a substantial contribution to the field of water level forecasting in river systems under conditions of uncertain flow disturbances.

Suitability of ZnO Nanocomposite of Copolymer (PPy-PNVK-ZnO) (PPy = Polypyrrole; PNVK = Poly 9-vinyl carbazole) for the Detection of 6-Thioguanine: A DFT Analysis

Conducting polymers have extensively been exploited for the specific drug detection, through diverse drug responses. 6-Thioguanine (6-TG) is commonly used in the treatment of cancer and its level monitoring in the human body is essential to avoid the side effects due to its physiological metabolites. Computational synthesis of a novel sensor material, i.e. ZnO nanocomposite of copolymer (PPy-PNVK-ZnO) using polypyrrole (PPy-ZnO) and poly 9-vinyl carbazole (PNVK-ZnO) polymers, has been performed and investigated its sensing ability for 6-TG drug, using the density functional theory (DFT) based ab initio approach. Generalized gradient approximation (GGA), parameterized with Perdew, Burke and Ernzerhof (PBE) type parameterization furnishes novel resources on the studied molecular model. The molecular interactions have been analyzed in terms of the HOMO-LUMO gap, density of states (DOS), adsorption energy (Eads), recovery time (τ), Mulliken population, electron density plot and quantum molecular descriptors. The calculated negative adsorption energy confirms the stability of these polymers and observes the type of interaction with 6-TG, as physical adsorption, that also confirms the reusability of the prepared sensor and its low operational temperature. It has also been observed that ZnO nanocomposite of copolymer has favourable stability in comparison to its host counterparts, whereas the host PNVK has a better recovery time and PPy has a relatively better range of detection and highly reactive.

Encapsulation of different spice essential oils in quinoa protein isolate-gum Arabic coacervates for improved stability

A fully plant-based wall material, quinoa protein isolate-gum Arabic (QPI-GA) complex coacervate, was developed for stability improvement of different spice essential oils (EOs): Sichuan pepper EO (SPEO), ginger EO (GEO), and star anise EO (SAEO). The optimum pH and QPI-to-GA ratio to form QPI-GA coacervates were experimentally confirmed to be 3.6 and 4:1. IF, FTIR, and XRD analyses (shown in supplementary information) indicated that complex coacervation generated electrostatic interactions between QPI and GA molecules and caused a more ordered structure of QPI-GA coacervates. The QPI-GA coacervates exhibited high encapsulation efficiency for SPEO (82.53 ± 1.59 %), GEO (88.19 ± 2.37 %), and SAEO (84.68 ± 1.51 %). The encapsulated EOs showed substantially higher stability in comparison to free EOs, while some differences in each type of stability among encapsulated EOs were observed. Additionally, the QPI-GA coacervate wall materials made EOs stable in oral and gastric stages and sustainably release in intestinal stage, which contributed to the excellent absorption of EOs in simulated digestion.

CAS4DL: Christoffel adaptive sampling for function approximation via deep learning

The problem of approximating smooth, multivariate functions from sample points arises in many applications in scientific computing, e.g., in computational Uncertainty Quantification (UQ) for science and engineering. In these applications, the target function may represent a desired quantity of interest of a parameterized Partial Differential Equation (PDE). Due to the large cost of solving such problems, where each sample is computed by solving a PDE, sample efficiency is a key concern in these applications. Recently, there has been increasing focus on the use of Deep Neural Networks (DNN) and Deep Learning (DL) for learning such functions from data. In this work, we propose an adaptive sampling strategy, CAS4DL (Christoffel Adaptive Sampling for Deep Learning) to increase the sample efficiency of DL for multivariate function approximation. Our novel approach is based on interpreting the second to last layer of a DNN as a dictionary of functions defined by the nodes on that layer. With this viewpoint, we then define an adaptive sampling strategy motivated by adaptive sampling schemes recently proposed for linear approximation schemes, wherein samples are drawn randomly with respect to the Christoffel function of the subspace spanned by this dictionary. We present numerical experiments comparing CAS4DL with standard Monte Carlo (MC) sampling. Our results demonstrate that CAS4DL often yields substantial savings in the number of samples required to achieve a given accuracy, particularly in the case of smooth activation functions, and it shows a better stability in comparison to MC. These results therefore are a promising step towards fully adapting DL towards scientific computing applications.

Processability of Prussian White Cathode Active Materials for Sodium Ion Batteries-Towards a Green Electrode Preparation

Prussian whites, such as the here tested NaxMn0.8Fe1.2(CN)6 (PW), are promising candidates as Na-Ion cathode active materials for cost-effective and safe battery technologies. The use of abundant elements such as sodium, iron or manganese obtained in a sustainable way makes this technology extremely attractive, especially in grid storage applications where high energy densities are not of major concern.1,2 However, PWs still suffer from low electronic conductivity, limited capacity retention, and a high sensitivity towards moisture which results in structural changes and loss of cyclable Na.3,4 Different approaches can be utilized to mitigate these issues, such as surface coatings or strict handling of the materials under inert conditions, starting from the storage of PWs powders to slurry preparations and to the handling of electrodes.3,5 In this study, we investigated the changes in surface chemistry during ambient storage (here called wet storage) and during subsequent heating of stored material. ATR-IR and TGA-MS data of materials stored for different times ranging from 1 h to up to a week showed a sharp increase in moisture-content in the material. The increase plateaued after 24 h of storage. XRD analysis of stored material showed a clear trend of structural changes upon even small storage times (<1h). Furthermore, surface hydroxides and carbonates were found via ATR-IR and a reannealing at low temperatures (<200 °C) showed the reversible release of adsorbed and interstitial water, but surface hydroxides and carbonates were not easily removed and stayed on the surface.By conducting electrochemical testing in coin-cells we analyzed the difference in cycling performance of as-received and ambient stored materials, and materials washed in water. As seen in earlier studies we also saw a drastic change in the charge profile after storage, due to changes in crystal structure.4 Interestingly, we found that this detrimental effect is reversible if the electrodes are dried at elevated temperatures. The pH of water after washing PW materials was neutral indicating the absence of major ion exchange.6 This finding, combined with the effective drying of hydrated electrodes resulted in the formulation of a water-based slurry process.As seen in Figure 1, a cell built with electrodes made from a 1 week wet-stored CAM which were dried at 120 °C (blue lines) showed a drastic different charge profile, compared to a cell built with an as-received electrode (black lines, panel a). Interestingly a cell built with CAM stored for 1 week and heated to 150 °C (orange lines, panel b) and a cell built with a cathode from a H2O-based coating which was dried at 150 °C (green lines, panel b), looks almost identical to the NMP-cells. Therefore, we assume that most water can be removed easily, and a water-based slurry process is possible.Cycling tests of water-based and environmentally more sustainable hard-carbon/PW full-cells reveal a similar cycling stability in comparison to cells with electrodes made from a traditional NMP process.

Aqueous-Based Post-Treatment of Li- and Mn-Rich Ncm

To achieve lithium-ion batteries with high energy density at competitive prices for automotive and large-scale applications, cathode active materials (CAMs) based on Li- and Mn-rich NCMs (LMR-NCMs), like Li1.14(Ni0.26Co0.14Mn0.60)0.86O2, are promising candidates.[1] However, LMR-NCMs still suffer from high gassing, particularly during cell formation, and detrimental voltage and capacity fading over their cycle life.[2,3] Different approaches can be utilized to try to mitigate these issues, such as the use of electrolyte additives, novel material designs (compositional gradients, etc.), or post-treatments.[4–7] In this study, we investigated the effect of a water-based post-treatment of LMR-NCM. It consists of a washing process of the LMR-NCM that results in a partial delithiation of its near-suface region by a lithium/proton ion exchange, while at the same time avoiding transition metal dissolution. A recalcination of this protonated near-surface layer of the LMR-NCM particles results in the formation of a protective spinel-like surface layer. We observed that after this treatment, the gassing during formation is decreased by »10-fold. Furthermore, the cycling performance of graphite/LMR-NCM full-cells is also drastically increased.By conducting on-line electrochemical mass spectrometry (OEMS) measurements, we analyzed the gas evolution of as-received and post-treated LMR-NCMs during the first activation cycle. It is known from the literature that the activation of LMR-NCMs is accompanied by a strong O2 and CO2 evolution during the first charge.[2] As seen in Figure 1, CO2 is evolved simultaneously with O2 from Li/LMR-NCM half-cells, prepared with untreated, as-received LMR-NCM (as-received, black line). With post-treated LMR-NCM, both CO2 and O2-evolution during the activation cycle are reduced by »10-fold (post-treated, green line). Only a small amount of the first-charge capacity (<10%) is lost due to the post-treatment, as seen in Figure 1a, reflecting the slight extent of delithiation that is part of the post-treatment.As will be shown, cycling tests of graphite/LMR-NCM full-cells with a post-treated LMR-NCM reveal a greatly increased cycling stability in comparison to cells with an as-received material. Using TGA-MS, XPS and ICP-OES, we further elucidate the beneficial mechanism of the here developed water-based post-treatment.

Investigation of Brine pH Effect on the Rheological and Viscoelastic Properties of HPAM Polymer for an Optimized Enhanced Oil Recovery Design.

A novel approach to improve viscous and viscoelastic properties by exploiting the pH and salinity sensitivity of HPAM polymer is proposed in this paper. Polymer flooding is a well-developed and effective enhanced oil recovery technique. The design of the makeup brine is one of the most critical phases of a polymer flood project, since the brine composition, salinity, and pH directly influence the polymer viscosity and viscoelasticity. However, the viscoelastic properties of hydrolyzed polyacrylamide polymers have not been given much consideration during the design phase of polymer flood projects. Our experimental study focuses on the optimization of the makeup water design for polymer flooding by evaluating the optimum solution salinity and pH for better stability and improved viscoelastic behavior of the polymer. Initially, the brine salinity and ionic composition is adjusted and then hydrolyzed polyacrylamide (HPAM) polymer solutions of varying pH are prepared using the adjusted brine. Rheological experiments are conducted over a temperature range of 25–80 °C and at different aging times. Polymer thermal degradation as a function of pH is assessed by examining the solutions at 80 °C for 1 week. Amplitude sweep and frequency sweep tests are performed to determine the viscoelastic properties such as storage modulus, loss modulus, and relaxation time. A 15–40% increase in the polymer solution viscosity and a 20 times increase in relaxation time is observed in the pH range of 8–10 in comparison to the neutral solution. This can be attributed to the low-salinity ion-adjusted environment of the makeup brine and further hydrolysis and increased repulsion of polymer chains in an alkaline environment. These results indicate that the viscoelastic properties of a polymer are tunable and a basic pH is favorable for better synergy between the brine and the polymer. Alkaline low-salinity polymer solutions have exhibited 60% higher thermal stability in comparison to acidic solutions and thus can be successfully applied in high-temperature reservoirs. The results of this study show that polymer solutions with an optimum pH in the basic range exhibit a higher viscoelastic character and an increased resistance toward thermal degradation. Hence, the polymer solution salinity, ionic composition, and pH should be adjusted to obtain maximum oil recovery by the polymer flooding method. Finally, this study shows that more effective polymer solutions can be prepared by adjusting the pH and designing a low-salinity water/polymer recipe to get the additional benefit of polymer viscoelasticity. The optimized low-salinity alkaline conditions can reduce the residual oil saturation by stronger viscous and viscoelastic forces developed by more viscous polymers. The findings of this study can be employed to design an optimum polymer recipe by tuning the brine pH and salinity for maximum incremental oil recovery, particularly in high-temperature and high-salinity formations.

Beneficial Effects of Oxide-Based Additives on Li-and Mn-Rich Cathode Active Materials

To achieve high energy densities at costs needed for automotive applications, Li- and Mn-rich NCMs (LMR-NCMs; Li1+x(NiaCobMnc)1-xO2, with a+b+c=1 and x»0.1-0.2), are promising cathode active material (CAM) candidates.[1] However, these materials still suffer from high gassing, particularly during formation, and detrimental voltage and capacity fading over their cycle life.[2–5] Different approaches are employed to fix these issues, such as the use of additives, novel synthesis routes, or post-treatments.[6–9] In this study, we investigated the effect of an oxide-based solid-additive for an LMR-NCM CAM. We have observed that with the use of a model oxide, not only HF, but also residual water could be scavenged from the electrolyte. Furthermore, we show that this effect is not limited to surface coatings, but it is possible to use a model oxide in a functionalized separator or mixed into the electrode slurry for the same beneficial effect.By conducting On-line Electrochemical Mass Spectrometry (OEMS) measurements, we analyzed the gas evolution of the LMR-NCM CAM Li1.14(Ni0.26Co0.14Mn0.60)0.86O2 during the first activation cycle. It is known from literature that not only O2 and CO2 are evolved in this process, but also HF and H2O, which in turn can be observed as POF3 in the gas-phase.[10,11] As seen in Figure 1, POF3 is evolved simultaneously with CO2 for LMR-NCM half-cells with a non-functionalized polypropylene (PP) based separator (blue line). Surprisingly, no POF3 is evolved, if an oxide-modified separator is used (orange line). This is evidence for the HF-scavenging effect of these oxides. Further electrochemical tests have shown that full-cells with an oxide-modified separator have a greatly increased cycling stability in comparison to cells with a non-functionalized separator. Using TGA-MS, XPS, and Karl-Fischer titration, we further elucidate the beneficial mechanism of other oxide-based additives.

Morphology and properties of high molecular weight polyisobutylene and thermoplastic polyurethane elastomer

AbstractHigh molecular weight polyisobutylene (PIB) was modified by a mild and facile melt‐mixing process with thermoplastic polyurethane elastomer (TPU) in the presence of a compatibilizer, i.e., polypropylene‐g‐maleic anhydride (PP‐g‐MAH). Scanning electron microscopy (SEM) in combination with solvent etching revealed a significantly phase‐separated morphology due to different polarity of PIB and TPU. An evolution from dispersed phase to continuous phase for TPU was observed with the increase of TPU content, leading to an enhanced tensile strength of PIB/TPU blend in comparison to PIB. This phase‐separated morphology of PIB/TPU blend was confirmed by FTIR and thermal analysis. Rheological studies suggested that the PIB/TPU blend (30 wt% of TPU) exhibited a typical non‐Newtonian fluid behavior. More importantly, PIB/TPU blend was shown to possess enhanced thermal and oxidative/hydrolytic stability in comparison to TPU. SEM combined energy dispersive spectrometer (EDS) further elucidated that the surface chemical composition of PIB/TPU blend can be tailored through annealing, which further improved the biocompatibility as well as the oxidative/hydrolytic stability.

Synchronous frequency comparison beyond the Dick limit based on dual-excitation spectrum in an optical lattice clock

We present a synchronous frequency comparison method based on one cold-atom ensemble by using the dual-excitation spectrum technique, which can simultaneously detect the probabilities of two different clock transitions. We experimentally verify this synchronous frequency comparison method between |mF|=9/2 and |mF|=7/2 in a one-dimensional 87Sr optical lattice clock and the comparison instability is well below the Dick limit. We also extend the dual-excitation spectrum method to shorten the clock feedback cycle by a half in optical lattice clocks and experimentally demonstrate that the interleaved self-comparison instability is 1.4 times lower than that of the traditional operation method.

Effect of lanthanide (Ln=La, Nd, and Pr) doping on electrochemical performance of Ln2NiO4+δ−YSZ composite cathodes for solid oxide fuel cells

In this study, we prepared three different Ruddlesden−Popper (RP)-phase nickelate catalysts, i.e., La2NiO4+δ (LNO), Nd2NiO4+δ (NNO), and Pr2NiO4+δ (PNO) via solid-state route. These materials were used to fabricate composite cathodes through their combination with yttria stabilized zirconia (YSZ), which is the most widely used electrolyte material for solid oxide fuel cells. X-ray diffraction (XRD) analysis revealed that after the initial sintering all three RP-based materials had good chemical compatibility with YSZ without any reactive impurities. The electrochemical impedance spectroscopy study showed that, among the three samples, the PNO−YSZ cathode exhibited the best oxygen reduction reaction (ORR) activity, with an area specific resistance (ASR) of 0.64 Ω cm2 at 800 °C, which was 16% and 41% lower compared to that of NNO-YSZ (0.76 Ω cm2), and LNO-YSZ (1.09 Ω cm2), respectively. During the initial long-term operation for 60 h at 800 °C, the measured ASR degradation rate of LNO−YSZ was 3.56 %h−1, while NNO−YSZ and PNO−YSZ showed better stability in comparison (2.23 and 1.87 %h−1, respectively). The post XRD analysis revealed the presence of a pyrochlore secondary phases (Ln2Zr2O7) in all three samples, which was considered a major degradation mechanism of Ln2NiO4+δ-YSZ composite cathodes. However, the amount of the impurity phase exhibited the same tendency as the degradation rate of different cathodes (LNO > NNO > PNO), demonstrating that Pr doping at the A-site of the RP-phase effectively suppressed the formation of a the pyrochlore impurity phase against YSZ. Thus, our results suggest that the ORR activity and durability of Ln2NiO4+δ−YSZ composite cathodes strongly depends on the A-site lanthanides.

Artificial Solid Electrolyte Interphases for Lithium Metal Electrodes by Wet Processing: The Role of Metal Salt Concentration and Solvent Choice.

In this study, the artificial solid electrolyte interphase (SEI) formed on lithium metal when treated in ZnCl2 solutions is thoroughly investigated. The artificial SEI on lithium metal electrodes substantially decreases the interfacial resistance by ca. 80% and improves cycling stability in comparison to untreated lithium. The presence of a native SEI negatively affects the morphology and interfacial resistance of the artificial SEI. Increasing the ZnCl2 concentration in tetrahydrofuran (THF) (precursor solution) results in higher homogeneity of the surface morphology. Independent of the ZnCl2 concentrations, the artificial SEI is composed of Cx, CO, LiCl, Li2CO3, ZnCl2, and LixZny alloys. ZnCl2 (1 M) produces the most homogenous surface and additional surface species with carbonyl side groups. Nonetheless, the ZnCl2 concentration only has a small effect on the interfacial resistance or cycling stability. Using ethyl methyl carbonate (EMC) as the solvent significantly reduces the interfacial resistance to 7 Ω cm2, in comparison to 25 Ω cm2 for THF. The composition of the artificial SEIs varies depending on the solvent. Either way, the SEI consists of Cx LixC, LiCl, Li2CO3, ZnCl2, and LiZn alloys. The THF-based SEI additionally features ether and carbonyl groups, LiZnO, and Zn metal. For the artificial SEI formed with both solvents, the atomic percentage of the LiZn alloy increases close to the Li surface.