Slow Rate Research Articles

Federated learning using model projection for multi-center disease diagnosis with non-IID data

Multi-center disease diagnosis aims to build a global model for all involved medical centers. Due to privacy concerns, it is infeasible to collect data from multiple centers for training (i.e., centralized learning). Federated Learning (FL) is a decentralized framework that enables multiple clients (e.g., medical centers) to collaboratively train a global model while retaining patient data locally for privacy. However, in practice, the data across medical centers are not independently and identically distributed (Non-IID), causing two challenging issues: (1) catastrophic forgetting at clients, i.e., the local model at clients will forget the knowledge received from the global model after local training, causing reduced performance; and (2) invalid aggregation at the server, i.e., the global model at the server may not be favorable to some clients after model aggregation, resulting in a slow convergence rate. To mitigate these issues, an innovative Federated learning using Model Projection (FedMoP) is proposed, which guarantees: (1) the loss of local model on global data does not increase after local training without accessing the global data so that the performance will not be degenerated; and (2) the loss of global model on local data does not increase after aggregation without accessing local data so that convergence rate can be improved. Extensive experimental results show that our FedMoP outperforms state-of-the-art FL methods in terms of accuracy, convergence rate and communication cost. In particular, our FedMoP also achieves comparable or even higher accuracy than centralized learning. Thus, our FedMoP can ensure privacy protection while outperforming centralized learning in accuracy and communication cost.

Slow precipitate coarsening kinetics in extremely fine nanograined Ni-Cr alloys

Grain boundaries significantly influence the nucleation and growth of precipitates in supersaturated solid solutions. However, due to the inherent instability of grain boundaries in nanograined metals, the precipitation process usually occurs concurrently with grain growth during thermal annealing, making it difficult to reveal the grain size effect on the precipitate coarsening behavior. In this study, nanograined Ni-48Cr (at.%) supersaturated alloys with grain sizes ranging from about 85 nm to 10 nm were fabricated by plastic deformation, in which the relaxed grain boundaries led to the extremely fine nanograined structure having good thermal stability. During the high-temperature annealing process, nanoscale Cr particles were precipitated from the nanograined matrix, forming a nanograined dual-phase structure. The growth kinetics of the Cr precipitates in the extremely fine nanograined structures are different from the larger grain size samples, showing a trend that the smaller the as-deformed grain size, the slower the precipitate coarsening rate. Detailed microstructural characterization and kinetic analysis indicate that the extremely fine nanograined structure may change the rate-limiting process for precipitate coarsening from lattice diffusion to grain boundary diffusion as grain size is refined to about a few tens nanometers, which leads to a slow coarsening rate. The nanograined dual-phase Ni-Cr alloy of the annealed 10 nm sample shows the highest strength among these samples as well as excellent thermal stability, which provides guidance for the design of high-performance alloys.

Drivers of organic carbon distribution and accumulation in the northern Barents Sea

Sedimentary properties and accumulation rates on the continental shelf and in the deep sea reflect temporal oceanographic, biological and chemical processes occurring in the water column and the sediment surface. We used the radionuclides 210Pb, 226Ra, and 137Cs activities to estimate sedimentation rates during the last century at nine stations in the northern Barents Sea region. Elemental (C, N) and stable isotopic composition (δ13C, δ15N) were also analysed from the nine stations sampled in August 2018, and, for five other stations sampled in August and December 2019, and in March and May 2021. Sediment accumulation rates varied between 130 and 1 410 g m−2 y−1. The < 63 μm normalized total organic carbon (TOC63) and the total nitrogen from the sediment surface varied between 0.90–2.56 % and 0.13–0.33 %, respectively. Ice-free shelf stations had higher TOC63 and possibly fresher organic matter (high δ13C, low δ15N) than ice-covered more northern stations. The opposite trend was observed for total inorganic carbon. We found that these trends in biogeochemical parameters were spatially structured by the winter sea ice concentration and biological production differences, and exhibited a south-north separation of the Polar Front region. The low and stable organic carbon accumulation rate (1.7–13.4 g Corg/m−2(−|-) y−1; ARtoc) is a function of slow sedimentation rates, and high degradation and residence time in the water column and at the sediment–water interface. Overall, the ARtoc has been stable for the past 100 years, with a slight increase from the early 1970s to the present at the shelf and slope stations. Our results highlight that spatial scales of variability of the studied sedimentary parameters are linked to spatial patterns of important environmental variables (e.g., chlorophyll-a, sea ice concentration) in the region. In contrast, no seasonal differences were observed in the sediment parameters of revisited stations, and the dated sediment geochemical profiles did not exhibit substantial longer-term variation. This means that climate-induced changes in variables that modify the sedimentary geochemistry of the environment may affect benthic community activity and structure before leaving a record in ARtoc.

Hydrogen embrittlement of the nickel alloy UNS N07718 for two different heat-treating schedules

The role of the nickel alloy 718 microstructure has been widely discussed and it is well established the δ phase detrimental effect on the material’s ductility and toughness when exposed to hydrogen. However, other microstructural features that might influence the embrittlement process are more elusive, which requires more in-depth studies. Having selected heat-treating schedules to mitigate δ phase precipitation, this work aims to assess the hydrogen embrittlement of two alloy 718 variants with nominal yield strengths of 120 and 150 ksi. Fundamentally, the idea is to understand the extent of the hydrogen damage caused by an increase in mechanical strength beyond the limit of 140 ksi specified in the API 6ACRA. Slow strain rate (SSR) and fracture toughness (FT) testing were applied to evaluate the mechanical behavior under cathodic polarization. The microstructure of both variants is comprised of recrystallized austenite grains and a very low content of grain boundary δ phase. Nanosized disk-shaped γ″ particles are also present for both variants, although the 150 ksi material shows a higher volume fraction and a finer distribution of this phase. Despite having the same overall fracture features, nanostructure differences between the variants and the consequent impact on hydrogen apparent solubility and slip planarity produced lower values of plastic elongation and initiation fracture toughness for the stronger material.

Study on the influence of water supply and drainage pipeline damage on urban silt ground collapse

Underground drainage pipelines play crucial roles in urban construction and development. Over time, these pipelines may incur damage and leakage due to aging and changes in surrounding loads. Ruptures and leaks in pipelines can lead to water seepage through cracks, resulting in erosion of surrounding soil layers and the formation of underground cavities. The loss of support in the soil above these cavities can lead to structural instability and eventual ground collapse. Such collapses can disrupt urban transportation systems, leading to significant social and economic consequences. This study specifically investigates ground collapse phenomena resulting from damage to drainage pipelines in silty soil within the Yellow River flood area in Zhengzhou City. By considering the influence of seepage velocity at the damaged pipeline section, the study differentiates between seepage erosion and scour erosion, conducting theoretical analyses and calculations for each scenario. The results show that ① when the surrounding area of the pipeline is damaged and the slow seepage rate causes a change in the critical groundwater level ΔH ≥ (Lσt )/((1 – n)γw), the soil around the pipeline will be damaged by seep erosion; ② when the water flow velocity at the damaged area of the pipeline is reached V 0 = 2λ(γs – γw )a 2 B 2/(9μ(B 2 – b 2)), the water flow impacts the soil and causes erosion damage. The critical pressure within the pipeline can be derived from the stress state where the pipeline is damaged P1=ρ2[2λ(γs−γw)a2B2/(9μ(B2−b2))] ; ③ the underground cavity formed by water flow erosion is assumed to be an “soil arch.” The stress analysis on it obtains the critical span of the “soil arch” when the “soil arch” is damaged 2b = [2c(H + h) + Kaγ(H + h)2 tan φ – P]/(H + h/3). This study provides a theoretical basis and technical support for the management of silty ground collapse in the Yellow River flood area.

Mass transfer and kinetic measurement and modeling for CO2 absorption into aqueous EAE and water-lean EAE/NMP solvents

Chemical absorption using amine solvent is currently available technology for CO2 capture from post-combustion flue gas. It is hindered by high operating cost and high capital cost due to high regeneration energy and slow CO2 absorption rate of amine solvent. Water-lean solvent of 2-(ethylamino) ethanol (EAE)/1-methyl-2-pyrrolidinone (NMP)/water could be a potential solution as it achieved significantly low regeneration energy of 2.3 GJ/tCO2 tested in a pilot plant. However, kinetics of CO2 reaction with EAE and mass transfer rate of CO2 absorption into EAE/NMP solvent are not fully understood. In this work, kinetics of CO2 absorption into unloaded aqueous EAE in 1–5 mol/L at 300–313 K and mass transfer of CO2 absorption into CO2-loaded EAE/NMP water-lean solvent in 5 mol/L with equilibrium CO2 partial pressure (PCO2*) range of 0.3–7 kPa at 312 K were studied in a wetted wall column. Kinetic data of aqueous EAE is interpreted by zwitterion mechanism, and the reaction is of first order with respect to EAE concentration in 1–5 mol/L at 300–313 K. CO2 absorption rate (kg’) of EAE/NMP water-lean solvent is 1.3–2.1 times greater than aqueous EAE due to the greater CO2 physical solubility. At lean and rich loading conditions, 5 M EAE in 3NMP/1water and 9NMP/1water show 2–7 times faster kg’ than 30 % MEA, and 1.4–2.5 times faster kg’ than 30 % PZ. It is found that EAE activity coefficient may increase in the presence of NMP in the solvent, and the estimated EAE activity coefficient in 1NMP/1water, 3NMP/1water, and 9NMP/1water are 2.13, 3.50, and 4.72, respectively. CO2 capacity of EAE/NMP solvent is 2–3.7 times greater than 30 % MEA and 1.2–2 times greater than 30 % PZ.

Injectable and high-strength PLGA/CPC loaded ALN/MgO bone cement for bone regeneration by facilitating osteogenesis and inhibiting osteoclastogenesis in osteoporotic bone defects

Osteoporosis (OP) can result in slower bone regeneration than the normal condition due to the imbalance between osteogenesis and osteoclastogenesis, making osteoporotic bone defects healing a significant clinical challenge. Calcium phosphate cement (CPC) is a promising bone substitute material due to its good osteoinductive activity, however, the drawbacks such as fragility, slow degradation rate and incapability to control bone loss restrict its application in osteoporotic bone defects treatment. Currently, we developed the PLGA electrospun nanofiber sheets to carry alendronate (ALN) and magnesium oxide nanoparticle (nMgO) into CPC, therefore, to obtain a high-strength bone cement (C/AM-PL/C). The C/AM-PL/C bone cement had high mechanical strength, anti-washout ability, good injection performance and drug sustained release capacity. More importantly, the C/AM-PL/C cement promoted the osteogenic differentiation of bone marrow mesenchymal stem cells and neovascularization via the release of Mg2+ (from nMgO) and Ca2+ (during the degradation of CPC), and inhibited osteoclastogenesis via the release of ALN in vitro. Moreover, the injection of C/AM-PL/C cement significantly improved bone healing in an OP model with femur condyle defect in vivo. Altogether, the injectable C/AM-PL/C cement could facilitate osteoporotic bone regeneration, demonstrating its capacity as a promising candidate for treatment of OP-related bone defects.

Tumor Protein D52 Regulates Paligenosis in Exocrine Pancreatic Acinar Cells

Background: Paligenosis is a conserved cellular plasticity program in which fully differentiated cells reenter the cell cycle in order to regenerate lost tissue during injury. This process is utilized by cells that have a slow turnover rate and lack dedicated stem cells, as is the case with exocrine pancreatic acinar cells. Acinar cells, which synthesize and secrete digestive enzymes necessary for macronutrient digestion, undergo paligenosis in response to damage induced by the inflammatory disease pancreatitis. During paligenosis, acinar cells first downscale their secretory apparatus by upregulating autophagy, and then take on a mucinous-ductal-progenitor-like identity in a process called acinar to ductal metaplasia (ADM) prior to proliferation. This phenomenon can be recapitulated in rodent models in vivo utilizing repeated episodes of cerulein-induced pancreatitis or in 18-hour suspension culture during which primary isolated acinar cells dedifferentiate to a progenitor-like state. We have previously reported that markers of the endolysosomal secretory pathway in acinar cells are rapidly lost during models of experimental pancreatitis and suspension culture. Tumor Protein D52, which regulates endolysosomal traffcking and secretion in acinar cells, undergoes lysosomal degradation at the onset of experimental pancreatitis; furthermore, restoring D52 expression by adenovirus in isolated acinar cells maintains secretion during experimental pancreatitis as well as maintains acinar differentiation in suspension culture. Hypothesis: Degradation of D52, and loss of the endolysosomal secretory pathway, are pivotal events during the initial stages of paligenosis. Methods: To study the role of D52 and the regulation of paligenosis, we generated tamoxifen-inducible, acinar specific D52 knockout mice (D52KOac), and markers of paligenosis (ADM, proliferation) were assessed by immunoblot, qPCR, and immunostaining. Mice were given tamoxifen at 2-3 months of age to ensure normal pancreatic development, and tissues were harvested 21 days after tamoxifen. Results: Compared to controls, D52KOac exhibited 2.5-fold upregulation of the ductal markers Sox9 and CK19, 50% reduction of Ptf1α, and a 5-fold increase in β-catenin; these markers signify the presence of ADM and cells with progenitor-like characteristics. Cell cycle regulation and proliferation were also observed in D52KOac by a nearly 3-fold increase in cyclin D and increased Ki67+ nuclei. Conclusions: These data support that loss of D52 in pancreatic acinar cells induces spontaneous paligenosis in the absence of cellular injury and inflammation. These findings point to a previously unrecognized role for D52 in the regulation of acinar cell differentiation and plasticity. Given that paligenosis is a key pathway involved in the development of pancreatic neoplasms and adenocarcinoma, studying D52-regulated paligenosis will reveal additional insights into this critical protective mechanism. American Pancreatic Association Foundation Young Investigator Award. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Efficient mini-batch stochastic gradient descent with Centroidal Voronoi Tessellation for PDE-constrained optimization under uncertainty

The study of optimal control problems under uncertainty plays an important role in scientific numerical simulations. This class of optimization problems is frequently utilized in engineering, biology and finance. Although stochastic gradient descent is a well-known stochastic optimization technique for solving the approximate optimal control problem, it often exhibits a slow convergence rate due to the inherent variance in gradient approximation. To address this issue, we propose a more efficient stochastic optimization algorithm based on Centroidal Voronoi Tessellation sampling. This strategy reduces the error in gradient estimation compared to the conventional mini-batch stochastic gradient descent method. Our approach involves dividing the whole snapshot set into several Voronoi cells with low variance and extracting samples with good uniformity from each region to construct an unbiased estimation of the full gradient. Our method can economically and stably approximate numerical optimal control functions even with a fixed step size. Numerical results demonstrate that the proposed method is a reliable algorithm with great potential for applications in the field of optimization.

Randomized Double-Blind Placebo-Controlled Trial of the Effects of Oral Trehalose in Spinocerebellar Ataxia Type 3: An Interim Analysis

IntroductionSpinocerebellar ataxia type 3 (SCA3) is a neurodegenerative disease characterized by increasingly worsening ataxia and non-ataxia features, negatively impacting patients’ quality of life. This study was designed to test formally evaluate whether oral trehalose was effective in SCA3 patients. MethodsIn this double-blind, randomized controlled trial, SCA3 patients received either 100g oral trehalose or 30g maltose to improve ataxia severity over six months. We also measured other clinical (non-ataxia), patient-reported (quality of life, motivations), and safety endpoints. An unscheduled interim analysis was conducted using two-way ANOVAs to analyze the interaction between time (baseline, 3-months, 6-months) and intervention (Trehalose vs. Placebo). ResultsFifteen participants (Trehalose = 7 vs. Placebo = 8) completed the study at the time of interim analysis. There was no interaction effect on the ataxia severity, and available data suggested an estimated sample size of 132 (66 per arm) SCA3 patients required to demonstrate changes in a 6-month trial. There were significant interaction effects for executive function (ƞ2 = 0.28–0.43). Safety data indicated that 100g oral trehalose was well-tolerated. ConclusionWe performed an unplanned interim analysis due to a slow recruitment rate. The new estimated sample size was deemed unfeasible, leading to premature termination of the clinical trial. In this small, current sample of SCA3 patients, 100g oral trehalose did not differentially impact on ataxia severitycompared to placebo. Interestingly, our findings may suggest an improvement in executive function. Future efforts will require a large multi-country, multi-center study to investigate the potential effect of trehalose.

Determination of hydrogen compatibility for Cu-Al-Ni-Fe-Mn cast alloys prepared by varying Al and Ni contents

Hydrogen compatibility of Cu-Al-Ni-Fe-Mn cast alloys was investigated via slow strain rate tensile tests in high-pressure hydrogen gas. Four types of alloys were prepared by varying the Al and/or Ni contents. Larger Al and Ni contents resulted in more elongated microstructures with smaller grains and more precipitates, respectively. The tensile strength of the alloys increased with larger Al and/or Ni contents, whereas the ductility decreased only by adding a larger amount of Al. The maximum tensile strength was produced by adding larger amounts of both Al and Ni, which was fairly higher than those of stable austenitic stainless steels. Despite the difference in the microstructures and tensile strengths of the alloys, the hydrogen contents and hydrogen diffusivities showed no substantial difference. Additionally, their reduction in area measured after the tensile tests was not degraded by the high-pressure hydrogen gas, revealing an excellent resistance to hydrogen embrittlement.

Biomimetic phase change capsules with conch shell structures for improving thermal energy storage efficiency

Latent heat storage system utilizing a packed-bed setup with encapsulated phase change materials (EPCMs) can address the issues of mismatched energy supply and demand, in addition to preventing the leakage concerns associated with unencapsulated PCMs, which has a broad application prospect. Drawing on the principles of biomimicry, this work proposes bionic-conch and bionic-mitochondrial encapsulation models for PCMs and analyzes the heat transfer performance with different structures. Significantly, the thermal energy storage efficiency of the bionic-conch structure surpassed that of the bionic-mitochondrial and straight-fin structures by 43.11 % and 14.62 %, respectively. The enhanced thermal energy storage efficiency of the bionic-conch is attributed to the spiral fins within, which considerably amplify the heat exchange surface area. Furthermore, in order to obtain the bionic-conch capsule structure with optimal thermal properties, the present work investigates the influence of fins on the melting characteristics of PCMs. The results show that increasing fins empower the thermal energy storage efficiency by 402.89 % and thermal response rate by 616.93 %, respectively. However, there is an issue of slow melting process in the annular region and incorporating an array of a slightly off-center heat-conducting ring (SOHR) is considered to enhance localized heat transfer. The suggest that it can alleviate the problem of slow heat transfer rate in the local annular region and increase the average internal temperature. Furthermore, in order to compensate for the loss of thermal energy capacity of the fin structure, this work also investigated the effect of different wall thicknesses on the thermal performance of the phase change capsule. Interestingly, decreasing the wall thickness significantly increases the heat capacity. In concrete terms, the thermal energy capacity of 0.5 mm wall thickness is increased by 22.87 % compared to 2 mm. This study may provide new enlightenment for the optimization of green energy.

Effect of milk protein-galactomannans interaction on meltdown behavior in the aerated frozen model system

The microstructure of ice cream and frozen desserts is known to influence their meltdown behavior. In this study, we hypothesized that the interaction of milk protein and galactomannans, specifically the phase separation often observed between hydrocolloids and protein, along with the interaction of hydrocolloids in the serum phase, affected meltdown behavior in non-fat aerated frozen foam. Ice creams were made with protein contents from 4 to 8%, with the addition of guar gum or locust bean gum. The effect of κ-carrageenan in protein and galactomannans was also studied. Melting characteristics were compared to the rheological and structural characteristics of the ice cream as well as to the phase separation in the mix and drip-through solution. The freezing-melting process inhibited microscopic and macroscopic phase separation in most locust bean gum samples, primarily due to the cryo-gel maintaining structural integrity and altering hydrocolloid-proteins interactions. The cryo-gel structure also led to slow melting rates and stable melted foams in the 4% milk protein system even in the absence of milk fat globules and clusters. Increasing milk protein from 4% to 8% in locust bean gum samples resulted in faster melting and a transition to complete dripping, indicating the disruption of the cryo-gel structure by increased proteins. In contrast, all guar gum samples fully dripped through the mesh with a fast melting rate. A negative trend was found between phase separation and melting rate in the guar gum samples containing κ-carrageenan, indicating that the diminishing interaction between the two immiscible phases accelerated liquid drainage.

Discovery and characterization of two novel polyethylene terephthalate hydrolases: One from a bacterium identified in human feces and one from the Streptomyces genus

Polyethylene terephthalate (PET) is widely used for various industrial applications. However, owing to its extremely slow breakdown rate, PET accumulates as plastic trash, which negatively affects the environment and human health. Here, we report two novel PET hydrolases: PpPETase from Pseudomonas paralcaligenes MRCP1333, identified in human feces, and ScPETase from Streptomyces calvus DSM 41452. These two enzymes can decompose various PET materials, including semicrystalline PET powders (Cry-PET) and low-crystallinity PET films (gf-PET). By structure-guided engineering, two variants, PpPETaseY239R/F244G/Y250G and ScPETaseA212C/T249C/N195H/N243K were obtained that decompose Cry-PET 3.1- and 1.9-fold faster than their wild-type enzymes, respectively. The co-expression of ScPETase and mono-(2-hydroxyethyl) terephthalate hydrolase from Ideonella sakaiensis (IsMHETase) resulted in 1.4-fold more degradation than the single enzyme system. This engineered strain degraded Cry-PET and gf-PET by more than 40% and 6%, respectively, after 30 d. The concentrations of terephthalic acid (TPA) in the Cry-PET and gf-PET degradation products were 37.7% and 25.6%, respectively. The discovery of these two novel PET hydrolases provides opportunities to create more powerful biocatalysts for PET biodegradation.

Synthesis and characterization of a dithiodiglycolic acid-incorporated poly(glycerol sebacate) exhibiting lipase resistance and antibacterial properties

Poly(glycerol sebacate) (PGS), a crosslinked network synthesized by polycondensation of glycerol and sebacic acid, has found successful utilization in various tissue engineering applications because of its biocompatibility, ease of synthesis, surface-erosion biodegradability, rubber-like elasticity, and adjustable mechanical properties. However, its fast in vivo degradation and lack of intrinsic antibacterial activity may be a concern for specific applications. The functional groups of glycerol and sebacic acid can react with those of other monomers, offering unlimited possibilities for generating new crosslinked networks tailored for particular purposes. Herein, we synthesized a series of poly(glycerol sebacate dithiodiglycolate) (PGSDTG) by incorporation of dithiodiglycolic acid (DTG) in the synthesis of PGS. PGSDTG exhibited the reduced stiffness, sensitive to glutathione (GSH), resistance to lipase degradation, and inhibition of the adhesion and growth of bacteria. The PGSDTG containing 45.6 wt% of DTG exhibited the lowest degradation rate with more than 80 % of PGSDTG weight remained at day 28 and the lowest bacterial inactivation rates of 99.2 ± 0.5 % and 82.5 ± 11.0 % against S. aureus and E. coli. This study suggested that PGSDTG may serve as a suitable antibacterial scaffold material for repairing or regenerating tissues characterized by a slow healing rate.

Effect of steel-refractory reactions on inclusion modification in lanthanum-, cerium-, and yttrium-added steels

The reactions of rare earth elements (REEs) with refractory materials significantly affect their effective concentrations and inclusion modifications in molten steel. This study investigated the influence of steel-refractory reactions on the modification of inclusions in lanthanum-, cerium-, and yttrium-added steels utilizing three types of commonly used crucibles as smelting vessels. Steel-refractory reactions were found to strongly affect inclusions with different outcomes for smelting in MgO, Al2O3, and MgO·Al2O3 crucibles. The RE-crucible reactions affected the evolution and size of inclusions in molten steel by influencing the content of [Mg] and [Al]. The RE-MgO crucible reactions increased [Mg] content, leading to more MgO inclusions and a smaller average size. The RE-Al2O3 crucible reactions increased [Al] content, resulting in more REAlO3 inclusions and a bigger average size. The reactions of La, Ce, and Y with MgO·Al2O3 crucibles had varying effects on the evolution of inclusions. La and Ce selectively eroded the crucible, mostly reacting with the Al2O3 component and generating REAlO3 inclusions. In contrast, the slow reaction rate of Y with the crucible and the formation of the dense Y2O3 layer at the steel/crucible interface made it react almost simultaneously with both MgO and Al2O3 components, and the modification of inclusions was dominated by [Mg] rather than [Al]. The above conclusions provided more information on how the reactions between rare earth elements and refractory materials affected inclusions in rare earth steels during smelting. They also enriched the theory of inclusion control in steel and offered new controlling strategies.

Unveiling the hydroesterification of 1,3-butadiene with carbonyl cobalt ionic liquids: Facilitation of cationic protonic hydrogen for active species formation

The 1,3-butadiene hydroesterification products, such as methyl pentenoate and dimethyl adipate, play a significant role in the production of nylon, plasticizers, and pharmaceutical intermediates. However, due to its unique π-π conjugated system, slow reaction rate, and difficulties in controlling regioselectivity, butadiene presents itself as an incredibly challenging substrate. The development of efficient and low-cost catalysts has gained substantial attention in both theoretical studies and industrial applications due to the high cost or extremely high pressure requirements. In this study, carbonyl cobalt ionic liquids were innovatively employed as catalysts to facilitate the synthesis of monoesters from hydroesterification of butadiene under mild conditions. A series of carbonyl cobalt ionic liquids with different cations were prepared and characterized for their structural properties using IR, ESI, IC, and DFT calculations. The yield of methyl pentenoate was comparable to that of Co2CO8 at 400 bar, and the catalysts exhibited high selectivity to methyl 3-pentenoates (>95 %), establishing a stable, efficient, and low-cost catalytic system. The experiments revealed that the type of the cation in ionic liquids remarkably influence their catalytic performance. Electrostatic potential calculations further confirmed that this performance is tightly related to the dissociation and migration behaviors of protons, leading to the proposal of a screening method for ionic liquids. In this paper, we further calculated the qualitative reaction kinetics and proposed a reaction mechanism in conjunction with previous studies. The reaction is hypothesized to begin with the formation of the active species HCo(CO)4 by proton exchange of [HX]+[Co(CO)4]−, in line with our experimental findings and theoretical calculations. This study presents an innovative approach to overcome the challenges associated with butadiene hydroesterification and paves the way for the development of more efficient and cost-effective catalytic systems.

Effects of rosemary extract addition on starch bioavailability and antioxidant properties of extruded pet foods

This study aimed to investigate the effects of rosemary extract (RE) addition on the starch digestion and antioxidant properties of extruded pet foods. Pet foods were extruded using rice, round pea (RP), and wrinkled pea (WP) flours as the sole starch sources with RE incorporated at levels of 0 (control), 1.0, 10.0, and 30.0g/kg (RE0, RE1, RE10, and RE30, respectively). High-amylose WP pet food exhibited lower damaged/gelatinized starch content compared with rice and RP pet foods. The total phenolic contents and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability of the pet foods notably increased after the addition of RE, showing a clear upward trend as the incorporation level was elevated. RE10 (except for rice) and RE30 significantly decreased the starch digestibility of pet foods according to in vitro testing, with the greatest reduction observed for the high-amylose WP sample. Although RE1 did not significantly impact the overall in vitro and in vivo starch digestibility, the treatment consistently postponed the peak times of postprandial blood glucose responses to all the three extruded diets in beagles. The results indicated that RE effectively enhanced the antioxidant properties of extruded pet foods and slowed starch digestion rates.

Influence of hydrogen volume/specimen surface area ratio on hydrogen embrittlement sensitivity of X52 pipeline steel

In the transition towards green energy, long distance transportation of gaseous hydrogen by pipeline is considered to be an economically attractive solution. For safe transportation of hydrogen, it is important to conduct relevant mechanical tests in representative hydrogen environments and working conditions of pipelines to demonstrate acceptable hydrogen embrittlement resistance of the steel. One important issue is the testing condition for the ratio of gaseous hydrogen volume over specimen surface area required in mechanical testing since this has not been specified in any testing standards and codes or investigated. This study investigated this issue by performing slow strain rate tensile (SSRT) testing of an X52 pipeline steel in gaseous hydrogen with different ratios of hydrogen volume/specimen surface area, Rv/s, ml/mm2. It was found that, with increasing Rv/s ratio, the area reduction of the steel decreased and hydrogen embrittlement sensitivity increased in the range of the Rv/s ratios investigated. The saturating Rv/s ratio appeared to be ∼2.0 beyond which the effect of Rv/s ratio on hydrogen embrittlement sensitivity was relatively small. The macroscopic and microscopic observations on both the fracture and side surfaces of the SSRT tested specimens also found that the tendency to cleavage fracture increased with increasing Rv/s ratio. The results of the ab initio molecular dynamics (AIMD) simulations performed also predicted a dependence of hydrogen embrittlement on hydrogen volume when Rv/s ratio is relatively small.

Anticipating the lifespan: Predicting the durability of an anode-supported solid oxide fuel cell short stack over 50,000 h

In the present study, the operational lifetime of a solid oxide fuel (SOFC) short stack is predicted by investigating the performance degradation of both the short stack and its cells throughout 1000 ​h at 800 ​°C. The short stack and integral cell voltages are continuously measured during the long-term test, with electrochemical impedance spectroscopy (EIS) conducted every 200 ​h. The short stack voltage decreased rapidly for the initial 200–300 ​h and afterwards, it decreased at a slow rate due to the increase in the Ohmic and polarization resistances in the same manner. Scanning electron microscopy results show that there is no delamination or cracking among constituent layers of the short-stack cells. The single degradation effects of the Ni coarsening in the anode, cation migration and surface segregation in cathode and oxide scale growth in metallic interconnect mesh are successfully integrated into a comprehensive lifetime prediction model. The experimentally measured voltage degradation data of the short stack fits well with the developed mathematical model and allows the successful prediction of the lifetime up to 50,000 ​h.