Consecutive Steps Research Articles

Cathode Electrochemical Behavior of Aluminum Electrolysis in NaF-NaCl Based Molten Salt

Selective and efficient electrochemical analytical methods for the depositing process of metal aluminum are significant and necessary. The electrochemical measurement methods are based on the means of cyclic voltammetry, square wave voltammetry and constant potential electrolysis. The above methods are used to analyze the depositing process of metal aluminum in NaF-NaCl-Al2O3 and NaF-NaCl-NaAlO2 molten salt. Cyclic voltammetry analysis showed that Al3+ ions were reduced to metal aluminum through two consecutive steps. From the analysis of square wave voltammetry curve, the main reaction on the electrode was the reduction of metal sodium in the NaF-NaCl system, and the electron transfer number of the reaction was 0.80. With the addition of NaAlO2 and Al2O3 in the electrolyte, the electron transfer numbers of the two reduction steps were about 3.0. The process of reduction of Al3+ ions to aluminum was further proved by the analysis of the electrolysis curve at constant potential. The diffusion rate of Al3+ions and the rate of Al3+ reduction reaction increased with the addition of NaAlO2 and Al2O3 and the change of the potential.

Silver Nanoparticle-Immobilized Cotton Fabric Serves as Flexible Surface-Enhanced Raman Scattering Substrate for Detection of Toxin

We designed composite materials containing silver nanoparticles (AgNPs) and cotton fabric (CF). The cellulose in cotton fabric contains -OH groups. These -OH groups were deprotonated by a pretreatment process, and Ag+ ions were allowed to bind. In the consecutive step, the Ag+ ions were reduced to fiber-bound AgNPs, generating AgNP@CF. Three different AgNP@CF composites were created, varying the concentration of the precursor AgNO3 solution. The composite materials were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), and FTIR spectroscopy. The AgNP@CF composites were assessed for the detection of toxins using the surface-enhanced Raman scattering (SERS) technique.

Adaptive Multi-Hypothesis Marginal Bayes Filter for Tracking Multiple Targets

Tracking multiple targets in the presence of unknown number of targets, missed detection, clutter, and noise is a challenging problem. To cope with this problem, a novel approach for generating the potential birth targets was developed, a mathematical model for multiple hypotheses was established, and an adaptive multi-hypothesis marginal Bayes filter is herein proposed in terms of the established mathematical model for multiple hypotheses and the novel birth approach. This filter delivers the existence probabilities of targets and their probability density functions. It uses multiple hypotheses to solve the data association problem to form the existence probabilities of targets and their probability density functions. To obviate the requirement for prior birth models, this filter uses the observations from two consecutive time steps to establish the birth models adaptively. Its tracking performance was tested by comparing it with other adaptive filters, showing that the proposed filter is robust, and it can obtain higher tracking accuracy than other filters.

Core–Shell catalyst particles for tandem catalysis: An experimental/numerical approach towards optimal design

Tandem catalysis is a promising approach to intensify chemical processes and increase their efficiency. On the other hand, the design of efficient, optimal and targeted tailored tandem catalysts is yet so challenging as the optimal catalyst loading is difficult to assess a priori. In this article, we present a concise route towards the design of optimal core–shell tandem catalyst particles on the example of coupled RWGS and FTS reactions for any specific spherical morphology. The route features five consecutive steps including: tandem system identification, catalyst synthesis, i.e. mono- and tandem-functional, catalyst characterization and initial performance test, kinetic modeling with parameter estimation if necessary, and optimal design of catalysts. The initial step features thermodynamic equilibrium calculations for RWGS and FTS showing a common operational window. Then, Pt and Co are selected as active metals and the formulation of the tandem catalyst is designed. For the second step, the synthesis route for the tandem catalyst Pt,CeO2@SiO2-Co, and the mono-functional catalysts, Pt@SiO2 and CeO2@SiO2-Co are presented. For the third step, all catalysts were tested for CO2 hydrogenation as an exemplary tandem process. A reduced transport model from literature was adjusted for RWGS and FTS reactions with kinetic expression from literature to enable numerical optimization. The kinetic parameters are estimated based on the performance tests of the mono-functional reference materials, i.e. Pt@SiO2 for RWGS and CeO2@SiO2-Co for FTS. The model is validated by cross comparison to the data from the tandem reaction setup. In the fifth step, the model was used for the numerical optimization of the catalyst loading on core and shell leading to the identification of the optimal design, resulting in a significant increase of C2+ Yield.

Online Conversion with Switching Costs: Robust and Learning-Augmented Algorithms

We introduce and study online conversion with switching costs, a family of online problems that capture emerging problems at the intersection of energy and sustainability. In this problem, an online player attempts to purchase (alternatively, sell) fractional shares of an asset during a fixed time horizon with length T. At each time step, a cost function (alternatively, price function) is revealed, and the player must irrevocably decide an amount of asset to convert. The player also incurs a switching cost whenever their decision changes in consecutive time steps, i.e., when they increase or decrease their purchasing amount. We introduce competitive (robust) threshold-based algorithms for both the minimization and maximization variants of this problem, and show they are optimal among deterministic online algorithms. We then propose learning-augmented algorithms that take advantage of untrusted black-box advice (such as predictions from a machine learning model) to achieve significantly better average-case performance without sacrificing worst-case competitive guarantees. Finally, we empirically evaluate our proposed algorithms using a carbon-aware EV charging case study, showing that our algorithms substantially improve on baseline methods for this problem.

The Online Pause and Resume Problem: Optimal Algorithms and An Application to Carbon-Aware Load Shifting

We introduce and study the online pause and resume problem. In this problem, a player attempts to find the k lowest (alternatively, highest) prices in a sequence of fixed length T, which is revealed sequentially. At each time step, the player is presented with a price and decides whether to accept or reject it. The player incurs a switching cost whenever their decision changes in consecutive time steps, i.e., whenever they pause or resume purchasing. This online problem is motivated by the goal of carbon-aware load shifting, where a workload may be paused during periods of high carbon intensity and resumed during periods of low carbon intensity and incurs a cost when saving or restoring its state. It has strong connections to existing problems studied in the literature on online optimization, though it introduces unique technical challenges that prevent the direct application of existing algorithms. Extending prior work on threshold-based algorithms, we introduce double-threshold algorithms for both variants of this problem. We further show that the competitive ratios achieved by these algorithms are the best achievable by any deterministic online algorithm. Finally, we empirically validate our proposed algorithm through case studies on the application of carbon-aware load shifting using real carbon trace data and existing baseline algorithms.

A serine carboxypeptidase-like acyltransferase catalyzes consecutive four-step reactions of hydrolyzable tannin biosynthesis in Camellia oleifera.

Hydrolyzable tannins (HTs), a class of polyphenolic compounds found in dicotyledonous plants, are widely used in food and pharmaceutical industries because of their beneficial effects on human health. Although the biosynthesis of simple HTs has been verified at the enzymatic level, relevant genes have not yet been identified. Here, based on the parent ion-fragment ion pairs in the feature fragment data obtained using UPLC-Q-TOF-/MS/MS, galloyl phenolic compounds in the leaves of Camellia sinensis and C. oleifera were analyzed qualitatively and quantitatively. Correlation analysis between the transcript abundance of serine carboxypeptidase-like acyltransferases (SCPL-ATs) and the peak area of galloyl products in Camellia species showed that SCPL3 expression was highly correlated with HT biosynthesis. Enzymatic verification of the recombinant protein showed that CoSCPL3 from C. oleifera catalyzed the four consecutive steps involved in the conversion of digalloylglucose to pentagalloylglucose. We also identified the residues affecting the enzymatic activity of CoSCPL3 and determined that SCPL-AT catalyzes the synthesis of galloyl glycosides. The findings of this study provide a target gene for germplasm innovation of important cash crops that are rich in HTs, such as C. oleifera, strawberry, and walnut.

Exploration of Vitamin B6-Based Redox-Active Pyridinium Salts Towards the Application in Aqueous Organic Flow Batteries.

Pyridoxal hydrochloride, a vitamin B6 vitamer, was synthetically converted to a series of diverse redox-active benzoyl pyridinium salts. Cyclic voltammetry studies demonstrated redox reversibility under basic conditions, and two of the most promising salts were subjected to laboratory-scale flow battery tests involving galvanostatic cycling at 10 mM in 0.1 M NaOH. In these tests, the battery was charged completely, corresponding to the transfer of two electrons to the electrolyte, but no discharge was observed. Both CV analysis and electrochemical simulations confirmed that the redox wave observed in the experimental voltammograms corresponds to a two-electron process. To explain the irreversibility in the battery tests, we conducted bulk electrolysis with the benzoyl pyridinium salts, affording the corresponding benzylic secondary alcohols. Computational studies suggest that the reduction proceeds in three consecutive steps: first electron transfer (ET), then proton-coupled electron transfer (PCET) and finally proton transfer (PT) to give the secondary alcohol. 1H NMR deuterium exchange studies indicated that the last PT step is not reversible in 0.1 M NaOH, rendering the entire redox process irreversible. The apparent reversibility observed in CV at the basic media likely arises from the slow rate of the PT step at the timescale of the measurement.

A wearable sensor and machine learning estimate step length in older adults and patients with neurological disorders

Step length is an important diagnostic and prognostic measure of health and disease. Wearable devices can estimate step length continuously (e.g., in clinic or real-world settings), however, the accuracy of current estimation methods is not yet optimal. We developed machine-learning models to estimate step length based on data derived from a single lower-back inertial measurement unit worn by 472 young and older adults with different neurological conditions, including Parkinson’s disease and healthy controls. Studying more than 80,000 steps, the best model showed high accuracy for a single step (root mean square error, RMSE = 6.08 cm, ICC(2,1) = 0.89) and higher accuracy when averaged over ten consecutive steps (RMSE = 4.79 cm, ICC(2,1) = 0.93), successfully reaching the predefined goal of an RMSE below 5 cm (often considered the minimal-clinically-important-difference). Combining machine-learning with a single, wearable sensor generates accurate step length measures, even in patients with neurologic disease. Additional research may be needed to further reduce the errors in certain conditions.

#2535 Development of a patient-centered outcome strategy for the CONVINCE trial

Abstract Background and Aims Patient-centered outcomes play an important role when assessing treatment effects. Patient-reported outcome (PRO) measures assessing symptoms and impacts are important tools to capture the patient perspective in clinical trials. However, careful consideration is needed when choosing PROs and PRO measures. Aspects such as the conceptual model, measurement model, validity, reliability, and responsiveness, as well as translation, interpretability of scores and burden for participants and investigators have to be considered when developing a patient-centered outcome strategy. The CONVINCE randomized controlled trial was funded by the European Union (HORIZON2020) to assess effects of high-dose hemodiafiltration (HDF) versus high-flux hemodialysis (HD). The primary outcome is all-cause mortality and one of the secondary outcomes is the experienced health status of the patients as measured by patient-reported outcomes. The aim of this study is to describe the approach for the development of a patient-centered outcome strategy using a domain-based approach that was implemented in the CONVINCE trial. Method The development of the patient-centered outcome strategy for the CONVINCE trial followed three consecutive steps: (1) targeted literature review to identify core outcome sets, as well as concepts and PRO measures in the field of dialysis; (2) semi-structured interviews and focus groups with dialysis patients (n = 13) and clinicians (n = 4) to determine health aspects, i.e. symptoms and impacts most relevant to patient population; (3) triangulation of results to determine the most relevant health domains to assess within the context of the CONVINCE trial and determination of PRO measures in due consideration of psychometric properties of respective instruments. Results We identified 97 PRO measures reported in previous dialysis studies, assessing more than 11 health domains and 41 disease-specific symptoms/problems relevant for dialysis patients. Core outcome sets, such as the SONG-HD and the ICHOM standard set for chronic kidney disease, indicated in total 19 outcomes that we classified as potential PROs. Interviews with patients and clinicians confirmed health domains and outcomes that were identified in the literature and provided further insights in terms of the level of importance of health domains. To balance the comprehensiveness of assessments and respondent burden, we decided to concentrate on 9 domains and 20 symptoms/problems according to the objectives of the trial. For the more proximal outcomes, i.e. recovery time and recovery time pattern, new items were developed by the CONVINCE consortium applying established state-of-the-art methods. For generic outcomes, e.g. fatigue, physical function, we decided to apply psychometrically advanced tools from the PROMIS® initiative, validated within a general population as well as various chronic health conditions. Conclusion Building upon core outcome sets by confirming health concepts most relevant for dialysis patients within the specific context of the CONVINCE trial, enabled us to develop a robust patient-centered outcome measurement strategy for the CONVINCE trial that assesses relevant health domains of dialyses patients in granular fashion using a domain-based approach. Further validation of the PRO measures should be considered, especially establishing meaningful change estimates to support interpretation of change in PRO measurement scores. Conference Abstract ERA EDTA; May 23-26, 2024; Stockholm, Sweden Kathrin I. Fischer, Peter J. Blankestijn, Krister Cromm, Michiel L. Bots, Claudia Barth, Bernard Canaud, Jörgen Hegbrant, Giovanni Strippoli, Andrew Davenport, Mark Woodward, Matthias Rose for the CONVINCE Scientific Committee and CONVINCE Investigators

Combustion Behavior of Cellulose Ester Fibrous Bundles from Used Cigarette Filters: Kinetic Analysis Study.

This study is focused on the detailed examination of the combustion properties and kinetic analysis of a cellulose acetate fibrous bundle (CAFB), separated from used cigarette filters. It was shown that the faster rate of CAFB heating allows a large amount of heat to be supplied to a combustion system in the initial stages, where the increase in heating rate has a positive response to ignition behavior. The best combustion stability of CAFB is achieved at the lowest heating rate. Through the use of different kinetic methods, it was shown that combustion takes place through two series of consecutive reaction steps and one independent single-step reaction. By optimizing the kinetic parameters within the proposed reaction models, it was found that the steps related to the generation of levoglucosenone (LGO) (by catalytic dehydration of levoglucosan (LG)) and acrolein (by breakdown of glycerol during CAFB burning-which was carried out through glycerol adsorption on a TiO2 surface in a the developed dehydration mechanism) represent rate-controlling steps, which are strongly controlled by applied heating rate. Isothermal predictions have shown that CAFB manifests very good long-term stability at 60 °C (which corresponds to storage in a sea shipping container), while at 200 °C, it shows a sudden loss in thermal stability, which is related to the physical properties of the sample.

Nickel-Catalyzed Cross-Coupling Reaction of Aryl Bromides/Nitriles with Imidazolium Salts Involving Inert C-N Bond Cleavage.

We herein present a nickel-catalyzed cross-coupling reaction of aryl halides and nitriles with imidazolium salts. A series of 2-arylated imidazoles could be obtained in moderate to good yields through inert C-N bond cleavage. The imidazolium salt in this reaction acts as both a coupling partner and N-heterocyclic carbene (NHC) ligand precursor. Mechanistic studies reveal that consecutive steps of migratory insertion of the NHC into the aryl C-Ni bond and β-C elimination might be involved in the proposed reaction mechanism.

ANALYSIS OF THE OUTCOMES OF IMPLEMENTING THE EXPERIMENTAL SYSTEM FOR FUTURE TRANSLATORS’ PROFESSIONAL TRAINING BASED ON LOCALIZATION

The ongoing evolution of the higher linguistic education system is primarily focused on addressing the demands of society and the government for competent translators. This necessitates corresponding modifications in the professional training, development, and personal growth of future translation personnel, with the ultimate goal of fostering their preparedness for localization. The paper aims to provide a comprehensive overview of the outcomes obtained from implementing an experimental system for teaching prospective translators in localization, as well as their subsequent analysis. Clear algorithmization is necessary for any experimental activity, including the professional training of prospective translators for localization. A linear pedagogical experiment was conducted to implement and experimentally verify the author’s pedagogical system. The experiment was designed in a series of consecutive steps. To test the hypothesis proposed in the study, it was deemed necessary to approve the structural and functional model of the experimental system. This approval was intended to establish a program of experimental work that aims to create the required pedagogical conditions in both academic and extracurricular classes. The ultimate goal is to enable students to develop themselves as individuals, both personally and professionally. The effectiveness of the presented results was demonstrated through the use of theoretical analysis of scientific literature on the research problem. This analysis facilitated the selection and comprehension of didactic material. Additionally, a critical and analytical examination of concepts, theories, and methods was conducted to identify potential solutions for the problem under investigation. Furthermore, mathematical statistics methods were employed to quantitatively calculate the obtained data. The author’s methodology of incorporating various experimental new designs into the professional training of future translators for localization is deemed effective, as evidenced by the generalized results of the preparedness of future translators for localization.

Process Intensification of the Continuous Synthesis of Bio-Derived Monomers for Sustainable Coatings Using a Taylor Vortex Flow Reactor.

We describe the optimization and scale-up of two consecutive reaction steps in the synthesis of bio-derived alkoxybutenolide monomers that have been reported as potential replacements for acrylate-based coatings (Sci. Adv.2020, 6, eabe0026). These monomers are synthesized by (i) oxidation of furfural with photogenerated singlet oxygen followed by (ii) thermal condensation of the desired 5-hydroxyfuranone intermediate product with an alcohol, a step which until now has involved a lengthy batch reaction. The two steps have been successfully telescoped into a single kilogram-scale process without any need to isolate the 5-hydroxyfuranone between the steps. Our process development involved FTIR reaction monitoring, FTIR data analysis via 2D visualization, and two different photoreactors: (i) a semicontinuous photoreactor based on a modified rotary evaporator, where FTIR and 2D correlation spectroscopy (2D-COS) revealed the loss of the methyl formate coproduct, and (ii) our fully continuous Taylor Vortex photoreactor, which enhanced the mass transfer and permitted the use of near-stoichiometric equivalents of O2. The use of in-line FTIR monitoring and modeling greatly accelerated process optimization in the Vortex reactor. This led to scale-up of the photo-oxidation in 85% yield with a projected productivity of 1.3 kg day-1 and a space-time yield of 0.06 mol day-1 mL-1. Higher productivities could be achieved while sacrificing yield (e.g., 4 kg day-1 at 40% yield). The use of superheated methanol at 200 °C in a pressurized thermal flow reactor accelerated the second step, the thermal condensation of 5-hydroxyfuranone, from a 20 h batch reflux reaction (0.5 L, 85 g) to a space time of <1 min in a reactor only 3 mL in volume operating with projected productivities of >700 g day-1. Proof of concept for telescoping the two steps was established with an overall two-step yield of 67%, producing a process with a projected productivity of 1.1 kg day-1 for the methoxybutenolide monomer without any purification of the 5-hydroxyfuranone intermediate.

Synthesis, crystal structure and anti-cancer activity of the complex chlorido-(η2-ethyl-ene)(quinolin-8-olato-κ2N,O)platinum(II) by experimental and theoretical methods.

The complex [Pt(C9H6NO)Cl(C2H4)], (I), was synthesized and structurally characterized by ESI mass spectrometry, IR, NMR spectroscopy, DFT calculations and X-ray diffraction. The results showed that the deprotonated 8-hy-droxy-quinoline (C9H6NO) coordinates with the PtII atom via the N and O atoms while the ethyl-ene coordinates in the η2 manner and in the trans position compared to the coordinating N atom. The crystal packing is characterized by C-H⋯O, C-H⋯π, Cl⋯π and Pt⋯π inter-actions. Complex (I) showed high selective activity against Lu-1 and Hep-G2 cell lines with IC50 values of 0.8 and 0.4 µM, respectively, 54 and 33-fold more active than cisplatin. In particular, complex (I) is about 10 times less toxic to normal cells (HEK-293) than cancer cells Lu-1 and Hep-G2. Furthermore, the reaction of complex (I) with guanine at the N7 position was proposed and investigated using the DFT method. The results indicated that replacement of the ethyl-ene ligand with guanine is thermodynamically more favorable than the Cl ligand and that the reaction occurs via two consecutive steps, namely the replacement of ethyl-ene with H2O and the water with the guanine mol-ecule.

A novel bifunctional electrochemical nanosensor for simultaneous detection of glucose and insulin based on NiO/Co3O4@CuAl LDH-MWCNT nanocomposite-modified carbon paste electrode

The appropriate development of electrocatalytic nanomaterials is a significant step for constructing high-quality non-enzymatic electrochemical sensors. In this work, we presented effective copper aluminum layered double hydroxide (CuAl LDH)-based nanoparticles with two consecutive optimization steps through nickel oxide/cobalt oxide (NiO/Co3O4) merging and subsequent assembly with multi-walled carbon nanotubes (MWCNT). The obtained nanostructures were characterized by using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction pattern (XRD), and field emission scanning electron microscope images (FE-SEM). The synthesized nanomaterials were used as a carbon paste electrode (CPE) material for simultaneous dual-signal evaluation of glucose and insulin. The response of the modified electrode was investigated by some electrochemical approaches, including cyclic voltammetry (CV), electrical impedance (EI), differential pulse voltammetry (DPV), and amperometric titration. The NiO/Co3O4 CuAl LDH@MWCNT electrode displayed multi-functional properties through two well-defined separated peaks toward glucose and insulin detection with a linear range of 0.01–26.5 mM and 0.02–70.0 nM, respectively. The detection limit values were obtained as 2.8 µM for glucose and 17.3 pM for insulin. The sensor showed good tolerance to common interfering agents, excellent sensitivity, and appropriate stability during 30 days of dry storage at room temperature. This sensor was also used for the quantification of glucose and insulin in human serum samples, obtaining the recovery rate of 101.0 %-103.7 % and 98.0 %-106.0 %, respectively, with all the RSD values below 3.0 %. This study represented an efficient simultaneous sensing platform for glucose and insulin detection, which warrants its operational application in clinical samples.

Green biocatalyst for decolorization of azo dyes from industrial wastewater: Coriolopsis trogii 2SMKN laccase immobilized on recycled brewer's spent grain.

This study presents an innovative approach for the reuse and recycling of waste material, brewer's spent grain (BSG) for creating a novel green biocatalyst. The same BSG was utilized in several consecutive steps: initially, it served as a substrate for the cultivation and production of laccase by a novel isolated fungal strain, Coriolopsis trogii 2SMKN, then, it was reused as a carrier for laccase immobilization, aiding in the process of azo dye decolorization and finally, reused as recycled BSG for the second successful laccase immobilization for six guaiacol oxidation, contributing to a zero-waste strategy. The novel fungal strain produced laccase with a maximum activity of 171.4 U/g after 6 days of solid-state fermentation using BSG as a substrate. The obtained laccase exhibited excellent performance in the decolorization of azo dyes, both as a free and immobilized, at high temperatures, without addition of harmful mediators, achieving maximum decolorization efficiencies of 99.0%, 71.2%, and 61.0% for Orange G (OG), Congo Red, and Eriochrome Black T (EBT), respectively. The immobilized laccase on BSG was successfully reused across five cycles of azo dye decolorization process. Notably, new green biocatalyst outperformed commercial laccase from Aspergillus spp. in the decolorization of OG and EBT. GC-MS and LC-MS revealed azo-dye degradation products and decomposition pathway. This analysis was complemented by antimicrobial and phytotoxicity tests, which confirmed the non-toxic nature of the degradation products, indicating the potential for safe environmental disposal.

Development of a novel sensitive single-tube nested PCR assay for the detection of African swine fever virus.

African swine fever (ASF) is a highly fatal and contagious viral disease caused by African swine fever virus (ASFV). It has caused significant economic losses to the swine industry and poses a serious threat to food security worldwide. Diagnostic tests with high sensitivity are essential for the effective management of ASF. Here, we describe a single-tube nested PCR (STN-PCR) assay for the detection of ASFV in which two consecutive amplification steps are carried out within a single tube. Two pairs of primers (outer and inner) were designed to target the p72 gene of ASFV. The primer concentrations, annealing temperatures, and number of amplification cycles were optimized to ensure the consecutive utilization of outer and inner primer pairs during amplification while minimizing the likelihood of amplicon contamination. In comparison with two conventional endpoint PCR assays (one of which is recommended by the World Organization for Animal Health), the newly developed STN-PCR assay demonstrated a 100-fold improvement in the limit of detection (LOD), detecting 100 copies of ASFV genomic DNA, whereas the endpoint PCR assays could detect no fewer than 10,000 copies. The clinical performance of the STN-PCR assay was validated using 95 tissue samples suspected of being positive for ASFV, and the assay showed 100% specificity. A Cohen's kappa value of 0.91 indicated perfect agreement between the assays. This new STN-PCR assay is a potentially valuable tool that will facilitate the control of ASF.

Multistep kinetics in self-induced sol–gel process of amorphous anhydride formation during thermal dehydration of potassium tetraborate tetrahydrate

AbstractThe physico-geometrical mechanism and kinetics of the multistep thermal dehydration of potassium tetraborate tetrahydrate was investigated as a model reaction to produce amorphous anhydrate via the self-induced sol–gel process. The thermal dehydration is composed of three consecutive dehydration steps: (1) a surface reaction in the solid-state accompanied by crack formation; (2) a rapid mass loss process accompanied by liquefaction to form the aggregate of the gel powders; and (3) the dehydration of gel powder aggregate to form a glassy anhydride. The changes in the contribution of the individual dehydration steps to the overall process according to the sample particle size and the heating rate (β) were identified as specific features of the multistep dehydration, which was characterized quantitatively using mathematical deconvolution analysis with log-normal four-parameter functions. The difficulty in determining the apparent activation energy (Ea) of the individual dehydration steps using isoconversional analysis due to the changes in the contribution depending on β values was addressed using modulated temperature thermogravimetry. Using the contributions and the apparent Ea of the individual dehydration steps as initial values, the kinetic description of the multistep thermal dehydration was refined through a kinetic deconvolution analysis using the cumulative kinetic equation. As a result, the individual dehydration steps were kinetically characterized as: (1) a surface reaction described by the first-order rate law with Ea,1 of approximately 68 kJ mol−1; (2) a reaction accompanied by liquefaction controlled by an autocatalytic rate behavior with Ea,2 of approximately 123 kJ mol−1; (3) a diffusion-controlled dehydration of gel powder with Ea,3 of approximately 82 kJ mol−1.

Unraveling Enyne Bonding via Dehydrogenation–Hydrogenation Processes in On‐Surface Synthesis with Terminal Alkynes

AbstractOn‐surface reactions of terminal alkynes in ultrahigh vacuum have attracted widespread attention due to their high technological promise. However, employing different precursors and substrate materials often intricate reaction schemes appear far from being well‐understood. Thus, recent investigations of alkyne coupling on noble metal surfaces suggest non‐dehydrogenative scenarios, contradicting earlier reports. Herein, the study employs noncontact atomic force microscopy (nc‐AFM) with high spatial resolution to conclusively characterize exemplary alkyne coupling products. Contrary to initial interpretations proposing dehydrogenative homocoupling on Ag(111), bond‐resolved AFM imaging reveals the expression of enyne motifs. Based on complementary, extensive density functional theory calculations, the pertaining reaction mechanisms are explored. It is proposed that enyne formation initiates with a direct carbon–carbon coupling between two alkyne groups, followed by surface‐assisted dehydrogenation‐hydrogenation processes. Thereby consecutive steps of atomic hydrogen cleavage, surface migration and recombination to a different carbon atom enable bridging via carbon–carbon double bonding. The new results shed light on subtle, but crucial surface‐mediated hydrogen transfer processes involved in the chemical bond formation, which are suggested to be of general relevance in on‐surface synthesis.