Mechanistic and kinetic insights of the formation of allene and propyne from the C3H3 reaction with water.

CONTEXT: Allene (H2C = C = CH2) and propyne (CH3-C≡CH) are important compounds in the combustion chemistry. They can be created from the reaction of proparyl radicals with water. In this study, therefore, a computational study into the C3H3 + H2O potential energy landscape has been carefully conducted. The computed results indicate that the reaction paths forming the products (allene: CH2CCH2 + •OH) and (propyne: HCCCH3 + •OH) prevail under the 300-2000 K temperature range, where the latter is much more predominant compared to the former. However, these two products are not easily formed under ambient conditions due to the high energy barriers. In the 300 - 2000 K temperature range, the branching ratio for the propyne + •OH product declines from 100 to 86%, whereas the allene + •OH product shows an increase, reaching 14% at 2000 K. The overall bimolecular rate constant of the title reaction can be presented by the modified Arrhenius expression of ktotal = 1.94 × 10-12 T0.14 exp[(-30.55 kcal.mol-1)/RT] cm3 molecule-1 s-1. The total rate constant at the ambient conditions in this work, 2.37 × 10-34 cm3 molecule-1 s-1, was found to be over five orders of magnitude lower than the total rate constant of the C3H3 + NH3 reaction, 7.98 × 10-29 cm3 molecule-1 s-1, calculated by Hue et al. (Int. J. Chem. Kinet. 2020, 4(2), 84-91). The results in this study contribute to elucidating the mechanism of allene and propylene formation from the C3H3 + H2O reaction, and they can be used for modeling C3H3-related systems under atmospheric and combustion conditions. METHODS: All the geometric structures of the C3H3 + H2O system were optimized by the B3LYP method in conjunction with the 6-311 + + G(3df,2p) basis set. Single-point energies of these species were calculated at the CCSD(T)/6-311 + + G(3df,2p) level of theory. The CCSD(T)/CBS level has also been used to compute single-point energies for the two major reaction channels (C3H3 + H2O → allene + •OH and C3H3 + H2O → propyne + •OH). Rate constants and branching ratios of the key reaction channels were calculated in the 300-2000 K temperature interval using the Chemrate software based on the transition state theory (TST) with Eckart tunneling corrections.

Recyclable and Biobased Vitrimers for Carbon Fibre-Reinforced Composites-A Review.

Economic and environmental concerns over the accumulation of end-of-life carbon fibre composite waste have led to increased attention to sustainable materials with low environmental impact. Over decades of research, vitrimers, a modern class of covalent adaptable networks, have bridged the gap between thermoplastics and thermosets. With the distinguishing feature of dynamic covalent bonds, vitrimers can be rearranged and reprocessed within their existing network structures in response to external stimuli such as heat or light. This poses a unique solution to repairing damaged composites, extending their service life, and reducing post-consumer waste. However, the synthesis of vitrimers often requires petrochemical consumption, which increases their carbon footprint. Using bio-based materials could be a promising solution to reduce the reliance on petrochemicals and their related pollution. This review compiles the contemporary requirements for bio-based vitrimers regarding their properties, scalability, and recycling features. This article also presents a comprehensive overview of the pathways to produce sustainable bio-based vitrimers and an overview of promising studies showing the potential uses of bio-derived vitrimers on carbon fibre composite productions.

Mechanistic and Kinetic Approach on the Propargyl Radical (C3H3) with the Criegee Intermediate (CH2OO).

The detailed reaction mechanism and kinetics of the C3H3 + CH2OO system have been thoroughly investigated. The CBS-QB3 method in conjunction with the ME/vRRKM theory has been applied to figure out the potential energy surface and rate constants for the C3H3 + CH2OO system. The C3H3 + CH2OO reaction leading to the CH2-[cyc-CCHCHOO] + H product dominates compared to the others. Rate constants of the reaction are dependent on temperatures (300-2000 K) and pressures (1-76,000 Torr), for which the rate constant of the channel C3H3 + CH2OO → CH2-[cyc-CCHCHOO] + H decreases at low pressures (1-76 Torr), but it increases with rising temperature if the pressure P ≥ 760 Torr. Rate constants of the three reaction channels C3H3 + CH2OO → CHCCH2CHO + OH, C3H3 + CH2OO → OCHCHCHCHO + H, and C3H3 + CH2OO → CHCHCHO + CH2O fluctuate with temperatures. The branching ratio of the C3H3 + CH2OO → CH2-[cyc-CCHCHOO] + H channel is the highest, accounting for 51-98.7% in the temperature range of 300-2000 K and 760 Torr pressure, while those of the channels forming the products PR10 (OCHCHCHCHO + H) and PR11 (CHCHCHO + CH2O) are the lowest, less than 0.1%, indicating that the contribution of these two reaction paths to the title reaction is insignificant. The proposed temperature- and pressure-dependent rate constants, together with the thermodynamic data of the species involved, can be confidently used for modeling CH2OO-related systems under atmospheric and combustion conditions.

Reactions of Methyl Radicals with Aniline Acting as Hydrogen Donors and as Methyl Radical Acceptors.

The present investigation theoretically reports the comprehensive kinetic mechanism of the reaction between aniline and the methyl radical over a wide range of temperatures (300-2000 K) and pressures (76-76,000 Torr). The potential energy surface of the C6H5NH2 + CH3 reaction has been established at the CCSD(T)//M06-2X/6-311++G(3df,2p) level of theory. The conventional transition-state theory (TST) was utilized to calculate rate constants for the elementary reaction channels, while the stochastic RRKM-based master equation framework was applied for the T- and P-dependent rate-coefficient calculation of multiwell reaction paths. Hindered internal rotation and Eckart tunneling treatments were included. The H-abstraction from the -NH2 group of aniline (to form P1 (C6H5NH + CH4)) has been found to compete with the CH3-addition on the C atom at the ortho site of aniline (to form IS2) with the atmospheric rate expressions (in cm3 molecule-1 s-1) as ka1 = 7.5 × 10-23 T3.04 exp[(-40.63 ± 0.29 kJ·mol-1)/RT] and kb2 = 2.29 × 10-3 T-3.19 exp[(-56.94 ± 1.17 kJ·mol-1)/RT] for T = 300-2000 K and P = 760 Torr. Even though rate constants of several reaction channels decrease with increasing pressures, the total rate constant ktotal = 7.71 × 10-17 T1.20 exp[(-40.96 ± 2.18 kJ·mol-1)/RT] of the title reaction still increases as the pressure increases in the range of 76-76,000 Torr. The calculated enthalpy changes for some species are in good agreement with the available experimental data within their uncertainties (the maximum deviation between theory and experiment is ∼11 kJ·mol-1). The T1 diagnostic and spin contamination analysis for all species involved have also been observed. This work provides sound quality rate coefficients for the title reaction, which will be valuable for the development of detailed combustion reaction mechanisms for hydrocarbon fuels.

Correction to Temperature and Pressure-Dependent Rate Constants for the Reaction of Propargyl Radical with Molecular Oxygen.

[This corrects the article DOI: 10.1021/acsomega.2c04316.].

Temperature and Pressure-Dependent Rate Constants for the Reaction of the Propargyl Radical with Molecular Oxygen.

Ab initio CCSD(T)/CBS(T,Q,5)//B3LYP/6-311++G(3df,2p) calculations have been conducted to map the C3H3O2 potential energy surface. The temperature- and pressure-dependent reaction rate constants have been calculated using the Rice-Ramsperger-Kassel-Marcus Master Equation model. The calculated results indicate that the prevailing reaction channels lead to CH3CO + CO and CH2CO + HCO products. The branching ratios of CH3CO + CO and CH2CO + HCO increase both from 18 to 29% with reducing temperatures in the range of 300-2000 K, whereas CCCHO + H2O (0-10%) and CHCCO + H2O (0-17%) are significant minor products. The desirable products OH and H2O have been found for the first time. The individual rate constant of the C3H3 + O2 → CH2CO + HCO channel, 4.8 × 10-14 exp[(-2.92 kcal·mol-1)/(RT)], is pressure independent; however, the total rate constant, 2.05 × 10-14 T0.33 exp[(-2.8 ± 0.03 kcal·mol-1)/(RT)], of the C3H3 + O2 reaction leading to the bimolecular products strongly depends on pressure. At P = 0.7-5.56 Torr, the calculated rate constants of the reaction agree closely with the laboratory values measured by Slagle and Gutman [Symp. (Int.) Combust.1988, 21, 875-883] with the uncertainty being less than 7.8%. At T < 500 K, the C3H3 + O2 reaction proceeds by simple addition, making an equilibrium of C3H3 + O2 ⇌ C3H3O2. The calculated equilibrium constants, 2.60 × 10-16-8.52 × 10-16 cm3·molecule-1, were found to be in good agreement with the experimental data, being 2.48 × 10-16-8.36 × 10-16 cm3·molecule-1. The title reaction is concluded to play a substantial role in the oxidation of the five-member radicals and the present results corroborate the assertion that molecular oxygen is an efficient oxidizer of the propargyl radical.

Cross-feeding between intestinal pathobionts promotes their overgrowth during undernutrition.

Child undernutrition is a global health issue associated with a high burden of infectious disease. Undernourished children display an overabundance of intestinal pathogens and pathobionts, and these bacteria induce enteric dysfunction in undernourished mice; however, the cause of their overgrowth remains poorly defined. Here, we show that disease-inducing human isolates of Enterobacteriaceae and Bacteroidales spp. are capable of multi-species symbiotic cross-feeding, resulting in synergistic growth of a mixed community in vitro. Growth synergy occurs uniquely under malnourished conditions limited in protein and iron: in this context, Bacteroidales spp. liberate diet- and mucin-derived sugars and Enterobacteriaceae spp. enhance the bioavailability of iron. Analysis of human microbiota datasets reveals that Bacteroidaceae and Enterobacteriaceae are strongly correlated in undernourished children, but not in adequately nourished children, consistent with a diet-dependent growth synergy in the human gut. Together these data suggest that dietary cross-feeding fuels the overgrowth of pathobionts in undernutrition.

Management of radiation-induced ulcers by singlestage reconstructive surgery: a prospective study.

Radiation-induced ulcers are a late-stage skin reaction after radiation therapy for cancer treatment. The present study examined the possibility of using a single-stage reconstructive procedure to manage radiation-related wounds. This prospective study recruited 30 participants who underwent radiation treatment for cancer or hemangioma. The patients ranged in age from 15 to 80 years. They were admitted to the Plastic, Reconstructive, and Regenerative Centre of Viet Nam National Burn Hospital from October 2013 to September 2017. For each patient, the surgeons discussed which reconstructive method would yield the best outcome. Patients' demographic data and information on the radiation-induced ulcer, the reconstructive method used, complications, and length of hospital stay were recorded. The mean age of all participants was 50 ± 36.3 years, and female patients were predominant (83.3%). Eighteen perforator flaps, five random-pattern flaps, three free flaps, three tissue expander flaps, and one full-thickness skin graft were employed, with no instances of recurrence or complications, except for total flap loss in two cases. The median length of stay was 43 days. These data suggest that immediate reconstruction may be a valuable option for managing radiation-induced ulcers.

Les radiodermites chroniques ulcéreuses sont une complication tardive des radiothérapies pour cancer. Cette étude prospective, réalisée dans le service de chirurgie plastique, reconstructive et régénérative de l'hôpital brûlologique national du Viêtnam d'octobre 2013 à septembre 2017, a examiné la possibilité de leur reconstruction en un seul temps chirurgical. Elle a concerné 30 patients irradiés pour cancer ou hémangiome, la meilleure méthode de reconstruction ayant à chaque fois été recherchée par le chirurgien. Les données démographiques, celles de la lésion, la méthode de reconstruction choisie, la durée de séjour et les complications ont été colligées. L'âge moyen était de 50 +/- 36,3 ans (15 ­ 80) et l'échantillon comprenait 83,3% de femmes. Nous avons réalisé 18 lambeaux perforants, 5 lambeaux au hasard, 3 lambeaux libres, 3 lambeaux après expansion et 1 greffe de peau totale. Deux lambeaux ont complétement nécrosé, il n'y a pas eu de récidive. La durée médiane de séjour était de 45 j. La reconstruction en 1 temps semble donc être possible dans le traitement des radiodermites chroniques.

Seasonal and geographical distribution of bacillary dysentery (shigellosis) and associated climate risk factors in Kon Tam Province in Vietnam from 1999 to 2013.

BACKGROUND: Bacillary dysentery (BD) is an acute bacterial infection of the intestine caused by Shigella spp., with clinical symptoms ranging from fever to bloody diarrhoea to abdominal cramps to tenesmus. In Vietnam, enteric bacterial pathogens are an important cause of diarrhoea and most cases in children under 5 years of age are due to Shigella strains. The serogroups S. flexneri and S. sonnei are considered to be the most common. The main objective of this study was to, for the first time, assess the seasonal patterns and geographic distribution of BD in Vietnam, and to determine the climate risk factors associated with the incidence of BD in Kon Tum Province, where the highest rate of bacillary dysentery was observed from 1999 to 2013. METHODS: The seasonal patterns and geographic distribution of BD was assessed in Vietnam using a seasonal-trend decomposition procedure based on loess. In addition, negative binomial regression models were used to determine the climate risk factors associated with the incidence of BD in Kon Tum Province, from 1999 to 2013. RESULTS: Overall, incidence rates of BD have slightly decreased over time (except for an extremely high incidence in 2012 in the north of Vietnam). The central regions (north/south central coast and central highlands) had relatively high incidence rates, whereas the northwest/east and Red River Delta regions had low incidence rates. Overall, seasonal plots showed a high peak in the mid-rainy reason and a second smaller peak in the early or late rainy season. The incidence rates significantly increased between May and October ("wet season") across the country. In Kon Tum Province, temperature, humidity, and precipitation were found to be positively associated with the incidence of BD. CONCLUSIONS: Our findings provide insights into the seasonal patterns and geographic distribution of BD in Vietnam and its associated climate risk factors in Kon Tum Province. This study may help clinicians and the general public to better understand the timings of outbreaks and therefore equip them with the knowledge to plan better interventions (such as improving water, sanitation, and hygiene conditions) during peak seasons. This can, in turn, prevent or reduce outbreaks and onwards transmission during an outbreak.

Comparison of the performance of serological kits for Helicobacter pylori infection with European and Asian study populations.

Most commercial kits for the detection of Helicobacter pylori were developed and validated with Western populations, and some have been found to perform less well with Asian populations. This study compared the performances of three serological kits with Swedish and Vietnamese peptic ulcer patients and asymptomatic individuals. The Pyloriset EIA-GIII and HM-CAP ELISA kits indicated that Asian populations had lower antibody titres to H. pylori than European populations. Despite the difference, the Pyloriset EIA-GIII kit performed well with Vietnamese peptic ulcer patients and population controls. The HM-CAP ELISA kit had a significantly lower performance with Asian populations that could not be improved by adjustments to the cut-off level. The Helicoblot 2.1 immunoblot kit performed equally well with Vietnamese and Swedish populations, although the response rate to the 35-kDa band was significantly lower with Vietnamese individuals.

Simple approaches towards the design of an attached-growth sponge bioreactor (AGSB) for wastewater treatment and reuse.

Wastewater treatment and reuse is being emphasized due to the shortage of water sources and the continuous deterioration of the aquatic environment. In this study, a novel sponge bioreactor was studied as a low cost, high efficiency alternative for an attached growth biological system. This was designed by combining of number of sponge trays. This emerging technology has many beneficial properties in wastewater treatment and reuse. The approaches towards the conditions for system design were: (i) selection of sponge types; (ii) selection of sponge shapes; and (iii) selection of designated slope of sponge tray. They were determined through a series of experiments using a laboratory-scale unit with synthetic wastewater. It was then tested with a pilot-scale unit at the predetermined optimum conditions. The results indicate that the highest biomass growth was found at the sponge type with a cell count of 70-90 cells/in(2) (6.45 cm(2)) The relationship between biomass growth and biological oxygen consumption was well established. The prism-shaped sponge (triangular polyurethane sponge of 70-90 cells/in(2) with designated slope of sponge tray at 10 degrees) led to the best performance in terms of both organic and nutrient removal efficiency.

Long-term follow-up of Helicobacter pylori eradication therapy in Vietnam: reinfection and clinical outcome.

AIM: To assess the long-term Helicobacter pylori reinfection rates, as well as the clinical outcome in peptic ulcer disease patients in Vietnam. METHOD: At a 1-year evaluation of H. pylori eradication treatment in 226 peptic ulcer patients, long-term H. pylori status was assessed with serology and/or culture, peptic ulcer status by gastroscopy, and DNA-fingerprinting performed with random amplified polymorphic DNA and restriction fragment polymorphism. RESULT: Follow-up was performed a mean 11 months after the post-treatment evaluation on day 30 after beginning of treatment. The overall reinfection rate was 23.5%, with 58.8% of the strains being identical to the pre-treatment isolates and 41.2% being different. Peptic ulcer was found in 22.9% of the reinfected patients and in 6.3% of the non-reinfected. At the long-term follow-up of successful eradication cases, 89.8% of the patients were free of peptic ulcer disease. The corresponding result was 58.7% in patients in whom H. pylori eradication failed. CONCLUSION: Following successful H. pylori eradication, reinfection with H. pylori in patients in Vietnam was found to be higher than in industrialized countries but the long-term recurrence of peptic ulcer disease was still low. Helicobacter pylori eradication treatment is therefore of value also in developing countries as the rate of peptic ulcer disease was low at the 1-year follow-up.

The importance of the level of metronidazole resistance for the success of Helicobacter pylori eradication.

AIMS: To evaluate the role of antibiotic susceptibility for the treatment outcome of proton pump inhibitor-dependent and independent Helicobacter pylori eradication regimens. METHODS: In a placebo-controlled clinical study of peptic ulcer patients with H. pylori infection, patients were randomized to receive lansoprazole, clarithromycin and tinidazole twice-daily, clarithromycin and tinidazole once-daily with lansoprazole or with placebo. Helicobacter pylori status was assessed by culture and antibiotic susceptibility by E-test minimal inhibitory concentration (MIC) in 205 clinical isolates. RESULTS: Primary resistance to clarithromycin and metronidazole was 1 and 76%, respectively. In metronidazole susceptible strains eradication rates were similar at > 90% for all treatment groups (P = 0.49). With low-level metronidazole resistance (4 microg/mL < MIC < 256 microg/mL), eradication rates were similar at >75% (P = 0.80). The major difference was found at high-level metronidazole resistance (MIC >or= 256 microg/mL) with 95%, 58% and 21% eradication in the lansoprazole, clarithromycin and tinidazole twice-daily, lansoprazole, clarithromycin and tinidazole once-daily and placebo, clarithromycin and tinidazole once-daily groups, respectively (P < 0.001). CONCLUSION: In the absence of antibiotic resistance, a once-daily therapy of only clarithromycin and tinidazole can achieve a high rate of H. pylori eradication. Such a combination could offer a simpler and cheaper treatment option for developing countries. The standard, twice-daily proton pump inhibitor-based triple therapy was shown to be efficient in H. pylori eradication even in the presence of high-level metronidazole resistance.

Helicobacter pylori eradication and peptic ulcer healing: the impact of deleting the proton pump inhibitor and using a once-daily treatment.

AIM: To compare cheaper and simpler once-daily regimens, with and without a proton pump inhibitor, with standard, twice-daily, triple therapy. METHODS: A randomized, placebo-controlled, treatment trial in Vietnam allocated 296 Helicobacter pylori-infected patients with peptic ulcer of >or= 5 mm to one of three regimens: (i) twice-daily: lansoprazole 30 mg, clarithromycin 250 mg and tinidazole 500 mg; (ii) once-daily: lansoprazole 60 mg, clarithromycin 500 mg and tinidazole 1000 mg; (iii) once-daily: placebo, clarithromycin 500 mg and tinidazole 1000 mg. H. pylori status was assessed by culture and immunoblot, ulcer healing by endoscopy and side-effects by structured questionnaires. RESULTS: Per protocol eradication (N = 256) was higher with standard therapy (87%) than with once-daily therapy (72%), and both were better than once-daily therapy without proton pump inhibitor (39%). Per protocol ulcer healing after standard therapy (83%) was not significantly better than that after once-daily therapy (73%), but better than that after therapy without proton pump inhibitor (65%). Side-effects were reported at similar rates in all groups. CONCLUSIONS: Proton pump inhibitor was needed for optimal eradication and ulcer healing. Twice-daily administration showed improved success rates when compared with once-daily therapies. Peptic ulcer healing was achieved even in patients treated with antibiotics only, confirming the central role of H. pylori in the pathophysiology of peptic ulcer disease.

Cross-resistance between triclosan and antibiotics in Pseudomonas aeruginosa is mediated by multidrug efflux pumps: exposure of a susceptible mutant strain to triclosan selects nfxB mutants overexpressing MexCD-OprJ.

Triclosan is an antiseptic frequently added to items as diverse as soaps, lotions, toothpaste, and many commonly used household fabrics and plastics. Although wild-type Pseudomonas aeruginosa expresses the triclosan target enoyl-acyl carrier protein reductase, it is triclosan resistant due to expression of the MexAB-OprM efflux system. Exposure of a susceptible Delta(mexAB-oprM) strain to triclosan selected multidrug-resistant bacteria at high frequencies. These bacteria hyperexpressed the MexCD-OprJ efflux system due to mutations in its regulatory gene, nfxB. The MICs of several drugs for these mutants were increased up to 500-fold, including the MIC of ciprofloxacin, which was increased 94-fold. Whereas the MexEF-OprN efflux system also participated in triclosan efflux, this antimicrobial was not a substrate for MexXY-OprM.

High-frequency flp recombinase-mediated inversions of the oriC-containing region of the Pseudomonas aeruginosa genome.

The genomes of the two clonally derived Pseudomonas aeruginosa prototypic strains PAO1 and DSM-1707 differ by the presence of a 2. 19-Mb inversion including oriC. Integration of two Flp recombinase target sites near the rrn operons containing the inversion endpoints in PAO1 led to Flp-catalyzed inversion of the intervening 1.59-Mb fragment, including oriC, at high frequencies (83%), favoring the chromosome configuration found in DSM-1707. The results indicate that the oriC-containing region of the P. aeruginosa chromosome can readily undergo and tolerate large inversions.

Involvement of GABA(A) receptors in myoclonus.

Alterations in multiple neurochemical systems have been reported in animal and human studies of posthypoxic myoclonus. It is impossible, however, to establish causative relationships between the observed changes and the myoclonic movements from these studies. Therefore, to establish causative links between neurochemical changes and myoclonus, ligands that target neurotransmitter systems that are altered in posthypoxic myoclonus were microinjected into the lateral ventricles of normal rats to identify the changes that can produce myoclonus. Of the ligands that were tested, only the GABA(A) antagonists produced myoclonus after intracerebroventricular administration, suggesting the importance of disinhibition of GABAergic systems in myoclonus. To further examine the role of GABA in myoclonus, GABAergic antagonists were microinjected into the nucleus reticularis of the thalamus (NRT), an area of the brain in which extensive pathologic changes are seen in posthypoxic animals. GABA(A), but not GABA(B), antagonists produced myoclonus after microinjection into the NRT. Earlier investigators have further reported the ability of GABA(A) antagonists to produce myoclonus after microinjection into the caudate. The data therefore suggest that disruption of activity at GABA(A) receptors at any one of a number of levels in the neural axis can produce myoclonus.