Total Reaction Rate Research Articles

Competing Reaction Pathways in Gas-Phase Oxidation of C6H6 by Protonated H2O2.

Reactions between protonated hydrogen peroxide and benzene (and benzene-d6) have been studied in the gas phase using an FT-ICR mass spectrometer. Four competing paths for the bimolecular system were identified, namely, proton transfer, hydride abstraction, dissociative single-electron transfer, and an electrophilic addition of HO+ to give the Wheland intermediate [C6H6, OH]+ followed by a subsequent elimination of water. The three latter pathways correspond to three different ways to oxidize benzene. All reaction mechanisms have been modeled using quantum chemical methods, and the calculations are in agreement with the experimental observations. The total reaction rate proceeds at collision rate (slightly higher than the calculated Langevin capture rate), which exemplifies the high reactivity of H3O2+ toward arenes. These observations demonstrate a much richer chemical landscape than previously inferred from the corresponding condensed phase reaction, where only electrophilic substitution by solvated HO+ was described.

Selective methanol production via CO2 reduction on Cu2O revealed by micro-kinetic study combined with constant potential model

High efficiency electrocatalysis of greenhouse gas CO2 to liquid fuel methanol attracts great attentions that allows energy transformation from renewable electric energy to storable chemical energy. Catalytically converting CO2 to methanol using green hydrogen is a promising pathway to achieve carbon neutrality. In this work, the catalytic activity and product selectivity of the electrochemical CO2 reduction reaction on Cu2O were studied using a micro-kinetic model based on Marcus charge transfer theory. The constant potential model under the grand-canonical ensemble enables the accurate description of binding energies and ground-state charge transfer upon surface adsorption as a function of electrode potential. Firstly, the potential-dependent activation energies and rate constants of all possible elementary reactions involved in CO2 reduction are calculated. Then, the surface coverage and its derivative can be obtained in a steady-state approximation. Finally, the total reaction rate and partial reaction rate can be deduced, allowing for direct comparison with catalytic activity (current density) and product selectivity (Faradaic efficiency). It is found that CH3OH is the dominant product on the Cu2O(111) surface, while CO is the main product on the Cu2O(110) surface. Based on the derived total and partial reaction rates under the steady-state approximation, it is demonstrated that Cu2O(111) exhibits the highest electrocatalytic activity and methanol selectivity at U = −0.6 V vs. SHE. This research presents a methodology for predicting apparent electrocatalytic performance from microscopic reaction energy calculations, which can be applied to other important electrocatalytic reaction mechanisms and performance predictions.

Flame propagation, explosion hazard, and pollutant emission characterization of typical clean fuels leaks in plateau low-pressure region

To accelerate energy transformation and sustainable development, various countries are rushing to lay hydrogen doped natural gas pipelines. However, the installation of pipelines will pass through plateau low-pressure region, and the impact of low-pressure environments on the flame propagation, explosion hazards, and pollutant emission characteristics of hydrogen doped natural gas is not yet clear. To solve this problem, a combination of constant volume combustion experiment and numerical simulations is used. The characterization parameters of flame, explosion and pollutant concentration of natural gas/H2/air under low-pressure environment are obtained, and their chemical reaction kinetics are analyzed. When the pressure drops, the laminar burning velocity (LBV) of them increases, and the Lewis number (Le) gradually increases by more than 1. Thermal diffusion is stronger than mass diffusion, and the growth rate of flame thickness exceeds 26 %. The effect of hydrodynamic instability enhances, causing an increment in the average size of flame cells, the critical instability radius, and the Markstein length (Lu). At the equivalent ratio (φ) of 1, there is a change from negative to positive in the Lu, and flame stability continuously strengthens. The explosion overpressure is reduced by 78 % to 90 %, the explosion temperature by 16 % to 20 %. As the φ increases, the LBV exhibits an inverted U-shaped relationship, reaching its maximum value near “φ = 1″. The flame stability first weakens and then strengthens. The explosion hazard is strongest in the range of ”φ = 1–1.2″. With a decrease in pressure, the total reaction rate of fuel consumption is reduced by more than 50 %. The continuous reaction distance is extended by 12 %. Changes in pressure have a relatively weak impact on the content of CO and CO2. The increase in the φ results in an increase in CO content of over 7 %. The content of CO2 reaches its maximum value around “φ = 1″. It is an essential reference for the safe delivery of hydrogen energy and the reduction of environmental pollution.

Evaluation of leukocyte depletion of packed red blood cells for the prevention of clinically observed transfusion reactions at a medical center in Eastern Taiwan

ABSTRACT Objectives: The incidence of febrile nonhemolytic transfusion reactions (FNHTRs) is correlated with the level of cytokines released by donor leukocytes in blood bags during storage, which is the most common transfusion reaction. The study aimed to reveal whether the use of leukocyte-poor red blood cells (LPRBCs) can reduce the incidence of transfusion reactions to promote patient safety. Materials and Methods: From January 2014 to June 2022, 158,122 blood transfusion reports were collected from a medical center in Eastern Taiwan. Data were categorized into three groups according to usage prepromotion use of LPRBCs (January 2014–April 2016), promotion use of LPRBCs (May 2016 to February 2018), and full utilization of LPRBCs (March 2018 to June 2022). According to the American Association of Blood Bank Common Transfusion Reaction Reporting Form version 2.0 reporting system, FNHTRs were classified as moderate transfusion reactions. We used these data to analyze the association between LPRBC use and transfusion reaction rate. Results: At our hospital, the LPRBC usage rate from January 2014 to April 2016, May 2016 to February 2018, and March 2018 to June 2022 was 5.37%, 34.82%, and 56.45%, respectively. The total transfusion reaction rate from January 2014 to April 2016 was 1.66%, whereas the moderate reaction rate was 1.29%. The total transfusion and moderate reaction rates from May 2016 to February 2018 were 1.41% and 1.00%, whereas those from March 2018 to June 2022 were 0.95% and 0.63%, respectively. The total transfusion and moderate reaction rates from March 2018 to June 2022 decreased by 42.8% and 51.2%, respectively, compared with those from January 2014 to April 2016. We further compared the incidence of transfusion reactions caused by packed red blood cells (PRBC) and LPRBC products in different years. The results showed that between 2014 and 2022, the types of blood transfusion reaction caused using PRBC and LPRBC products are the mild transfusion reaction rate of 0.20%/0.20%, the moderate transfusion reaction rate of 1.61%/0.69%, the severe transfusion reaction rates 0.38%/0.16%, and the total transfusion reaction rates 2.19%/1.05%. Conclusion: Our study results indicate that both total transfusion and moderate reaction rates significantly decreased with increasing LPRBC usage rate. Based on our data analysis, LPRBC is more effective in reducing moderate and severe transfusion reactions than PRBC.

Curative Effect of Helicobacter Pylori Radical Treatment on Gastric Cancer Patients with Helicobacter Pylori Infection

To explore the role and value of radical treatment of Helicobacter pylori in patients with gastric cancer complicated with Helicobacter pylori infection. Methods: From January 2022 to January 2023, 152 patients with gastric cancer complicated with Helicobacter pylori infection who were treated in our hospital were included in this study by random number table method. According to whether each patient received radical treatment based on Helicobacter pylori infection while receiving chemotherapy treatment, they were divided into the control group of single chemotherapy treatment and the observation group of combined radical treatment of Helicobacter pylori. The difference of treatment indexes between the two groups was analyzed. Results: The effective rate of treatment in the observation group was 88.16%, the total adverse reaction rate was 39.47%, and the treatment satisfaction rate was 93.42%; The effective rate of treatment in the control group was 78.95%, the total adverse reaction rate was 68.42%, and the treatment satisfaction rate was 82.89%. The difference was statistically significant (P<0.05). Conclusion: For patients with gastric cancer complicated with Helicobacter pylori infection, while receiving chemotherapy for gastric cancer, radical treatment for Helicobacter pylori can significantly improve the effective rate of clinical symptom relief of disease treatment, reduce the incidence of adverse reactions during various treatments, and improve the overall satisfaction of patients and their families with treatment.

New Potential Energy Surface for the H + Cl2 Reaction and Quantum Dynamics Studies.

The reaction of H + Cl2 → HCl + Cl plays a crucial role in various fields. However, no previous study has investigated this reaction using accurate quantum mechanical methods. In this paper, we construct a global potential energy surface (PES) using the neural network method with more than 20,000 ab initio energies obtained by the MRCI-F12+Q method with the aug-cc-pV5Z basis and extrapolated to the complete basis set limit. The spin-orbit coupling of the Cl atom has been considered in the PES. With this new PES, product state-resolved quantum dynamics calculations for the H + Cl2 (v0 = 0, j0 = 0-2) → HCl + Cl reaction was carried out. Numerical results show that the initial rotational excitation of the Cl2 has negligible effects on the reactivity. Product state-resolved integral cross sections (ICS) and rate constants reveal that the HCl is most favorably produced in its v' = 2 vibrational state. The calculated product vibrational state-resolved and total reaction rate constants suggest that the new global PES is accurate enough, as compared with the available experimental measurements.

308nm excimer laser and tacrolimus ointment in the treatment of facial vitiligo: a systematic review and meta-analysis.

This study aimed to investigate the effects and safety of 308nm excimer laser (308nm EL) and tacrolimus ointment (TO) in the treatment of facial vitiligo (FV). We searched Cochrane Library, PUBMED, EMBASE, CNKI, and WANGFANG from inception to June 1, 2023. Outcomes included overall response rate (ORR), total adverse reaction rate (TARR), recurrence rate at 3-month (RR-3) and recurrence rate at 6-month (RR-6). The outcome data were presented as odds ratios (OR) with 95% confidence intervals (CI). The risk of bias was assessed by Cochrane risk-of-bias tool and data analysis was performed by RevMan 5.4 software. This study included a total of 19 trials involving 2085 patients. When comparing 308nm EL monotherapy with 308nm EL plus TO, significant differences in the ORR (OR = 4.29, 95% CI [2.97, 6.19], I2 = 0%, P < 0.001), RR-3 (OR = 0.18, 95% CI [0.05, 0.69], I2 = 0%, P = 0.01), and RR-6 (OR = 0.38, 95% CI [0.14, 1.03], I2 = 39%, P = 0.06) were found between the two managements. When comparing TO monotherapy with TO plus 308nm EL, its results showed significant differences in the ORR (OR = 4.21, 95% CI [2.90, 6.11], I2 = 0%, P < 0.001), TARR (OR = 0.42, 95% CI [0.22, 0.81], I2 = 4%, P = 0.009), and RR-3 (OR = 0.32, 95% CI [0.01, 8.03], P = 0.49) between the two modalities. The results of this study suggest that the combination of 308nm EL and TO is more effective than either treatment alone for the treatment of FV.

The Importance of Anharmonicity and Solvent Effects on the OH Radical Attack on Nucleobases.

Previous theoretical investigations of the reactions between an OH radical and a nucleobase have stated the most important pathways to be the C5-C6 addition for pyrimidines and the C8 addition for purines. Furthermore, the abstraction of a methyl hydrogen from thymine has also been proven an important pathway. The conclusions were based solely on gas-phase calculations and harmonic vibrational frequencies. In this paper, we supplement the calculations by applying solvent corrections through the polarizable continuum model (PCM) solvent model and applying anharmonicity in order to determine the importance of anharmonicity and solvent effects. Density functional theory (DFT) at the ωB97-D/6-311++G(2df,2pd) level with the Eckart tunneling correction is used. The total reaction rate constants are found to be 1.48 ×10-13 cm3 molecules-1s-1 for adenine, 1.02 ×10-11 cm3 molecules-1s-1 for guanine, 5.52 ×10-13 cm3 molecules-1s-1 for thymine, 1.47 ×10-13 cm3 molecules-1s-1 for cytosine and 7.59 ×10-14 cm3 molecules-1s-1 for uracil. These rates are found to be approximately two orders of magnitude larger than experimental values. We find that the tendencies observed for preferred pathways for reactions calculated in a solvent are comparable to the preferred pathways for reactions calculated in gas phase. We conclude that applying a solvent has a larger impact on more parameters compared to the inclusion of anharmonicity. For some reactions the inclusion of anharmonicity has no effect, whereas for others it does impact the energetics.

Study on the Efficacy of Shugan Jieyu Capsules Combined with Trazodone in Patients with PostStroke Depression and Insomnia

Objective: To analyze the effectiveness of applying ShuGan JieYu Capsules (SGJYC) combined with trazodone in patients with post-stroke depression (PSD) with insomnia. Methods: 60 cases of PSD with insomnia patients admitted to the hospital from May 2022 to May 2023 were selected and randomly divided into a reference group (trazodone) and a research group (SGJYC combined with trazodone) of 30 cases each. Statistics were analyzed using the Hamilton Depression Rating Scale (HAM-D), Pittsburgh Sleep Quality Index (PSQI), and Activities of Daily Living (ADL) scale before treatment and 4, 8, and 12 weeks after treatment. Results: Before treatment, The results of HAM-D, PSQI, and ADL scale studies in the two groups before treatment were not statistically significant (P &gt; 0.05); 4, 8, and 12 weeks after treatment, the results of HAM-D and PSQI studies in the research group were lower than that of the reference group, and the results of ADL scale studies were higher than that of the reference group. There was a significant difference between the groups (P &lt; 0.05). The total adverse reaction rate of the research group was lower than that of the reference group, and there was a significant difference between the groups (P &lt; 0.05). Conclusion: The combination of SGJYC and trazodone reduced depression in post-stroke patients, corrected insomnia, improved sleep quality, was safe, and had a low rate of adverse reactions.

A novel method for predicting the thermal stabilization temperature of organic Rankine cycle system working fluids based on transition state theory

The use of organic working fluids in organic Rankine cycle (ORC) systems may lead to thermal decomposition, which negatively impacts system performance and safety. In this work, a simplified theoretical method based on the transition state theory is proposed to predict the ideal maximum thermal stabilization temperature of organic working fluids. This method involves considering the initial decomposition reaction of the working fluids and calculating the total reaction rate of the initial decomposition. By setting an acceptable decomposition rate, the ideal maximum thermal stabilization temperature of the working fluid can be determined. Using this method, the total reaction rate constants of several typical hydrocarbon, hydrofluorocarbon and siloxane working fluids were obtained in the temperature range of 300∼700 K. The predicted maximum operational temperatures were in good agreement with most experimental results. The branch ratio analyses show that C–C bond cleavage contributed mainly to the decomposition of hydrocarbons, the removal of HF and C–C bond cleavage contributed mainly to that of HFCs, and the Si–C bond cleavage contributed mainly to that of siloxanes. Only considering these main reactions in the reaction rate calculation can greatly reduce calculation cost without significantly impacting the prediction accuracy.

Melt infiltration for the preparation of finely dispersed Ni-FeOx nanoparticles on SBA-15 for the hydrodeoxygenation of m-cresol

The polymer-assisted melting infiltration method was used to finely disperse Ni, Fe and bimetallic Ni-Fe precursors in ordered mesoporous SBA-15 support. This approach allowed to obtain small Ni nanoparticles, in the order of 2 nm in size, with finely dispersed iron oxide surrounding metallic Ni, without evidence of Ni-Fe alloy formation. The catalysts were used in the HDO reaction of m-cresol at 300 °C and atmospheric pressure. The conversion of m-cresol was found to be dependent on Ni content, with the total reaction rate decreasing when Ni is partially replaced by iron. Toluene was the main product obtained for both, mono Ni and bimetallic Ni-Fe catalysts, thus suggesting that nickel nanoparticles when in the form of small sized particles, are the active sites for deoxygenation, independent on the presence of oxophilic iron site in their proximity. Such findings will serve for the further design of effective catalysts for the upgrading of lignin-derived bio-oil.

Fondaparinux Results in Similar Pregnancy Outcomes with Lower Adverse Reaction Rates Compared to Low Molecular Weight Heparin in Chinese Recurrent Miscarriage Women.

Fondaparinux inhibits thrombin generation by inactivating factor Xa, which has the potential to treat recurrent miscarriage (RM). However, more clinical evidence is required to support its application in Chinese women with RM. This research aimed to compare the live birth rate, gestational weeks at delivery, birth weight, Apgar score of newborns, and adverse reaction rates between fondaparinux and low molecular weight heparin (LMWH) in Chinese women with RM. Totally, 132 women with RM treated with fondaparinux or LMWH were included in this retrospective study. According to the corresponding treatment, women with RM were divided into the fondaparinux cohort (N = 45) and LMWH cohort (N = 87). The live birth rate was 68.9% in the fondaparinux cohort and 56.3% in the LMWH cohort, which was not different between the two cohorts (P = 0.161). Multivariable logistics regression analysis suggested that only previous miscarriage times (≥ 4 times vs. < 4 times) were independently related to a lower possibility of live birth in women with RM (odds ratio = 0.431, P = 0.036). It was also observed that gestational weeks at delivery (38.1 ± 1.4 vs. 37.7 ± 1.7 weeks) (P = 0.258), birth weight (2,923.7 ± 355.0 vs. 2,807.8 ± 334.0 g) (P = 0.144), and Apgar score of newborns (9.8 ± 0.5 vs. 9.6 ± 0.8) (P = 0.175) were not different between the fondaparinux cohort and LMWH cohort. Inspiringly, the total adverse reaction rate was reduced in the fondaparinux cohort vs. the LMWH cohort (20.0% vs. 37.9%) (P = 0.036). Fondaparinux results in similar pregnancy outcomes with lower adverse reaction rates compared to LMWH in Chinese women with RM.

Influence of atmospheric oxidation capacity on atmospheric particulate matters concentration in Lanzhou

The atmospheric oxidation capacity (AOC) reflects the removal rate of atmospheric pollutants, and this index is typically characterized by the oxidant concentration or total reaction rate. The AOC plays a crucial role in the formation of atmospheric particulate matters and serves as an important indicator for studying changes in the concentration. In this study, we analyse the characteristics of atmospheric oxidants in Lanzhou based on data in the year of 2020 and 2021 retrieved from the Atmospheric Comprehensive Observation Station in Lanzhou. Empirical equations are applied to estimate the impact of atmospheric oxidative properties secondary generation concentrations of atmospheric particulate matters with different particle sizes. The results indicate that the annual average values of Ox were 146 μg/m3 in 2020 and 139 μg/m3 in 2021. The AOC was the highest in summer and lowest in winter. The correlation coefficient between O3 and Ox was significantly higher than that between NO2 and Ox, suggesting that O3 exerted a greater impact on the AOC in Lanzhou. A low AOC (MDA8 O3 ≤ 100 μg/m3) promoted the oxidation process of VOCs and other precursors, leading to the generation of secondary aerosols and subsequent formation of secondary particles. There were negative correlations between Ox and atmospheric particulate matters, secondary inorganic components, sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR), indicating that excessively high levels of Ox could inhibit the conversion rate of SO2 and NO2 into their respective forms to a certain extent.

Effect of Magnesium Sulfate Combined with Labetalol in the Treatment of Pregnancy-Induced Hypertension and Its Impact on Adverse Pregnancy Outcomes

Objective: To investigate the effect of magnesium sulfate combined with labetalol in treating hypertension in pregnancy (HIP) and its impact on adverse pregnancy outcomes. Methods: A total of 150 HIP patients treated at the Qujing Maternal and Child Healthcare Hospital from June 2020 to June 2023 were randomly assigned using the lottery method. They were divided into the control group (treated with magnesium sulfate alone, 75 cases), and the intervention group (magnesium sulfate + labetalol combined treatment, 75 cases). Blood pressure levels, total adverse reaction rates, total adverse pregnancy outcome rates, and total adverse fetal outcome rates were compared between the two groups. Results: Compared to the control group’s diastolic (87.94 ± 4.86 mmHg) and systolic (138.52 ± 9.23 mmHg) blood pressures, the intervention group showed lower levels of diastolic (78.95 ± 3.57 mmHg) and systolic (129.88 ± 7.47 mmHg) blood pressures (P &lt; 0.05). The intervention group exhibited a lower total adverse reaction rate (4.00%) compared to the control group (14.67%; P &lt; 0.05). Similarly, the total adverse pregnancy outcome rate in the intervention group (4.00%) was significantly lower than that in the control group (18.67%; P &lt; 0.05). Furthermore, the total adverse fetal outcome rate in the intervention group (6.67%) was lower than that in the control group (22.67%; P &lt; 0.05). Conclusion: The combination of magnesium sulfate and labetalol demonstrates significant efficacy in treating HIP. It effectively lowers blood pressure, improves pregnancy and fetal outcomes, is highly safe, and deserves promotion and application.

Clinical characteristics of hepatitis-associated aplastic anemia in children.

To understand the current situation of hepatitis-related aplastic anemia (HAAA) in children, we analyzed the patients with HAAA admitted to our hospital in the past 5 years to understand the disease characteristics and prognosis.The clinical data of patients with HAAA admitted to our hospital from February 2017 to May 2022 were retrospectively analyzed.A total of 81 patients with HAAA, 56 males and 25 females. The median onset age was 5.9 years. The median time from hepatitis to occurrence of hemocytopenia was 30 days, and the median follow-up time was 2.77 years. There were 23 cases (28.5%) of severe aplastic anemia (SAA), 50 cases of very severe aplastic anemia (VSAA), and 8 cases of non-severe aplastic anemia (NSAA). At the beginning of the disease, cytotoxic T lymphocyte (CTL) was higher than normal in 60% of patients, and the median CD4/CD8 ratio was 0.2. As of follow-up, 72 children survived, 4 were lost, and 5 died. Thirty-four cases were treated with immunosuppressive therapy (IST), with a median follow-up time of 0.97 years. The total reaction rate was 73.5% (25/34), the complete reaction rate was 67.6% (23/34), and the nonreaction rate was 26.5% (9/34). Multivariate analysis suggested that co-infection was an independent risk factor affecting the efficacy of IST at 6 months, with an OR value of 16.76, 95% CI (1.23, 227.95), P=0.034. No independent influencing factors were found at the end of follow-up.The proportion of CTL cells in peripheral blood of children with HAAA is relatively increased, and IST is effective in 73.5% of children. Co-infection may prolongs the time to response to IST.

Effect of pH on UV/H2O2-mediated removal of single, mixed and halogenated parabens from water

Adjusting pH values in aqueous environments can significantly improve the efficiency by which parabens and halo-parabens are removed. In this study, 20 neutral and deprotonated species were selected as models to investigate their pH-dependent removal mechanisms and kinetics by a UV/H2O2 process using density functional theory (DFT). Compared to neutral species, deprotonated species exhibit higher reactivity to HO• due to their high electron cloud density. H atom abstraction (HAA) reactions on the substitution groups are the most favorable pathways for neutral species, while radical adduct formation (RAF) reactions are the most favorable for deprotonated species. Single electron transfer (SET) reactions can be neglected for neutral species, while these reactions become a viable route for deprotonated molecules. The total reaction rate constants range from 1.63 × 109 to 3.74 × 1010 M− 1 s− 1 at pH 7.0, confirming the experimental results. Neutral and weakly alkaline conditions are favorable for the degradation of MeP and halo-parabens in the UV/H2O2 process. The order of removal efficiency at optimum pH is dihalo-parabens > mono-halo-parabens ≈ F, F-MeP > MeP. Furthermore, the transformation products must undergo oxidative degradation due to their high toxicity. Our findings provide new insights into the removal of parabens and their halogenated derivatives from wastewater.

Effect Evaluation of Madopar Combined with Pramipexole in the Treatment of Parkinson’s Patients

Objective: To analyze the clinical efficacy of Madopar combined with pramipexole in the treatment of Parkinson’s disease. Methods: This study was conducted from January 2021 to January 2023. This study involved 80 patients who were divided into two groups using a computerized randomization. The control group received pramipexole and the experimental group received both madopar and pramipexole. The treatment outcomes of these two groups were compared and analyzed. Results: The efficacy of the treatment received in the experimental group was 95.00%, which was higher than that of the control group (77.50%), whereas the total adverse reaction rate of the experimental group was 12.50%, which was lower than that of the control group, 35.00%; the difference was significant (P &lt; 0.05). There was no difference in the levels of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), C-reactive protein (CRP), miR-124, miR-137, and Unified Parkinson’s Disease Rating Scale (UPDRS) total score (UPDRS Ⅱ, UPDRS Ⅲ, and UPDRS Ⅳ scores) between the control group and the experimental group (P &gt; 0.05). After treatment, these indicators were significantly improved in the experimental group compared to the control group. Conclusion: Madopar combined with pramipexole in the treatment of Parkinson’s is both effective and safe. It delays the progression of the disease and has broad application prospects.

Theoretical Study on the Mechanisms, Kinetics, and Toxicity Evaluation of OH-Initiated Atmospheric Oxidation Reactions of Coniferyl Alcohol

In this paper, we investigated the mechanisms, kinetics, and toxicity evaluation of the OH-initiated reaction of coniferyl alcohol (4-(3-hydroxy-1-propenyl)-2-methoxyphenol) in the atmosphere using theoretical calculations. The initial reaction of coniferyl alcohol with OH radicals had two pathways, H-abstraction and OH-addition reactions. The total reaction rate constants were 2.32 × 10−9 cm3 molecule−1 s−1 (in gas-phase) and 9.44 × 109 s−1 M−1 (in liquid-phase) for the preliminary reactions of coniferyl alcohol with OH radicals at 298 K, respectively, and the half-lives of the total reaction (including all initial H-abstraction and OH-addition reactions) of coniferyl alcohol with OH radical in the atmosphere, urban and remote clouds were 8.3 × 10−2 h, 5.83 × 103 h and 9.27 × 102 h, respectively. The temperature had a strong and positive influence on the initial reaction rate constant. The branching ratios of H-abstraction and OH-addition reactions were 3.68% and 97.69%, respectively, making the OH-addition reactions become dominant reactions. The ecotoxicity evaluation revealed that the toxicity levels of coniferyl alcohol and its products were similar and non-toxic. However, all these products have developmental toxicity, with most of them having no mutagenicity. Therefore, further attention should be paid to the oxidation process and product toxicity evaluation of coniferyl alcohol in the atmosphere.

Lattice Boltzmann simulation of cathode catalyst layer degradation on transport reaction process within a proton exchange membrane fuel cell

The degradation of the catalyst layer significantly affects the gas transport and electrochemical processes in the porous electrodes, thus affecting the performance of proton exchange membrane fuel cells. To reveal the catalyst layer degradation impact, the microscopic porous structure of the cathode catalyst layer was reconstructed by a random algorithm in this work. Consequently, Lattice Boltzmann method was used to study the oxygen transport and electrochemical reaction processes at the limiting current density condition with considering the degradation of platinum, carbon particles, and ionomers under uniform and exponential degradation rates, respectively. The results reveal that the degradation of platinum reduces the reaction sites in the catalyst layer, thus deteriorating the electrochemical kinetics and lowering the total reaction rate. On the contrary, the degradation of carbon and ionomer shows two diametrically opposed effects. On the one hand, the oxygen transport is improved due to carbon and ionomer degradation, especially for ionomer degradation, thereby accelerating the total reaction rate. On the other hand, the degradation of carbon and ionomer triggers the detachment of platinum particles, leading to a decrease in reaction rate. In the early stages of the multi-component simultaneous degradation process, the total reaction rate is prohibited by oxygen transport limitation inside the catalyst layer; as the degradation degree increases, the oxygen transport through the ionomer films is enhanced and the electrochemical kinetics becomes the rate determining factor, especially for exponential degradation rate. This study provides a comprehensive assessment of the oxygen transport and electrochemical reaction within the catalyst layers with respect to different degrees of catalyst layer degradation, which can guide the design of high-performance anti-degradation catalyst layers for the next generation of fuel cells.

Understanding the reaction behavior of alanine under hydrothermal conditions through a network model

Here, we conduct the experiments to investigate the hydrothermal decomposition of alanine more systematically than previous reports and study the effects of various reaction conditions including reaction time, reaction temperature, and raw material concentration on reaction routes and products in detail. Then, a quantitative kinetic analysis is used to evaluate the experimental results, in which the reaction order is calculated, and the total reaction rate constant is unified. The calculation of the total reaction rate constants for the disappearance, decarboxylation, deamination, and dimerization of alanine in this study proves to be correct and successful by re-analyzing and comparing with previous reports. Furthermore, a network model is constructed to gain more insight into the reactions during the hydrothermal decomposition of alanine. The results show that the reaction behavior of alanine hydrolysis under various hydrothermal conditions can be understood by this network model and the calculated rate constants. The method presented here to study the mechanism and kinetics of hydrolysis is expected to be applicable to other amino acids.