Low temperature oxidation of n-hexane in a flow reactor

The risk of igniting a flammable mixture in fuel tank vapor space is a major concern in aviation safety. In order to analyze the hazards and develop mitigation strategies, it is necessary to characterize the explosive properties of kerosene vapor–air mixtures over wide ranges of initial conditions. n-Hexane has been extensively used in our laboratory as a single component surrogate of kerosene. In the present study, hexane oxidation by oxygen was studied in a flow reactor at equivalence ratios of 0.7, 1 and 1.5 for mixtures diluted at 90% with nitrogen. Residence time was set at 2 s and the pressure at 100 kPa. The evolution of the gas phase composition at the reactor exit was studied over the range 450–1000 K. Laser-based diagnostics and gas chromatography analysis were used to characterize the exit mixture composition. The chemical species measurements revealed three distinct regimes of oxidation, namely (i) the cool flame region from 600 to 650 K, (ii) the NTC region between 675 and 775 K, and (iii) the high temperature oxidation regime from 800 K. The modeling study demonstrated the capability of reproducing most of the trends observed experimentally

Chemical modification of L-glutamine to alpha-amino glutarimide on autoclaving facilitates Agrobacterium infection of host and non-host plants: A new use of a known compound

<p>Abstract</p> <p>Background</p> <p>Accidental autoclaving of L-glutamine was found to facilitate the <it>Agrobacterium </it>infection of a non host plant like tea in an earlier study. In the present communication, we elucidate the structural changes in L-glutamine due to autoclaving and also confirm the role of heat transformed L-glutamine in <it>Agrobacterium </it>mediated genetic transformation of host/non host plants.</p> <p>Results</p> <p>When autoclaved at 121°C and 15 psi for 20 or 40 min, L-glutamine was structurally modified into 5-oxo proline and 3-amino glutarimide (α-amino glutarimide), respectively. Of the two autoclaved products, only α-amino glutarimide facilitated <it>Agrobacterium </it>infection of a number of resistant to susceptible plants. However, the compound did not have any <it>vir </it>gene inducing property.</p> <p>Conclusions</p> <p>We report a one pot autoclave process for the synthesis of 5-oxo proline and α-amino glutarimide from L-glutamine. Xenobiotic detoxifying property of α-amino glutarimide is also proposed.</p

Nasopharyngeal pneumococcal carriage in South Asian infants:Results of observational cohort studies in vaccinated and unvaccinated populations

BACKGROUND: Nasopharyngeal pneumococcal carriage (NPC) is a prerequisite for invasive pneumococcal disease and reduced carriage of vaccine serotypes is a marker for the protection offered by the pneumococcal conjugate vaccine (PCV). The present study reports NPC during the first year of life in a vaccinated (with PCV10) cohort in Bangladesh and an unvaccinated cohort in India. METHODS: A total of 450 and 459 infants were recruited from India and Bangladesh respectively within 0-7 days after birth. Nasopharyngeal swabs were collected at baseline, 18 and 36 weeks after birth. The swabs were processed for pneumococcal culture and identification of serotypes by the Quellung test and polymerase chain reaction (PCR). An identical protocol was applied at both sites. RESULTS: Prevalence of NPC was 48% in the Indian and 54.8% in the Bangladeshi cohort at 18 weeks. It increased to 53% and 64.8% respectively at 36 weeks. The average prevalence of vaccine serotypes was higher in the Indian cohort (17.8% vs 9.8% for PCV-10 and 26.1% vs17.6% for PCV-13) with 6A, 6B, 19F, 23F, and 19A as the common serotypes. On the other hand, the prevalence of non-vaccine serotypes was higher (43.6% vs 27.1% for non-PCV13) in the Bangladeshi cohort with 34, 15B, 17F, and 35B as the common serotypes. Overcrowding was associated with increased risk of pneumococcal carriage. The present PCV-13 vaccine would cover 28%-30% and 47%-48% serotypes in the Bangladeshi and Indian cohorts respectively. CONCLUSIONS: South Asian infants get colonised with pneumococci early in infancy; predominantly vaccine serotypes in PCV naïve population (India) and non-vaccine serotypes in the vaccinated population (Bangladesh). These local findings are important to inform the public health policy and the development of higher valent pneumococcal vaccines

Deep learning model for diagnosing polycystic ovary syndrome using a comprehensive dataset from Kerala hospitals

Polycystic ovary syndrome (PCOS) requires early and precise diagnosis to manage and prevent long-term health consequences effectively. In this research, a large dataset of healthcare data gathered from various hospitals in Kerala, India, was evaluated using multiple machine learning (ML) and deep learning (DL) models to identify a highly reliable and accurate prediction of PCOS. The six algorithms used for comparison with the proposed DL model are support vector classification, random forest, logistic regression, k-nearest neighbors, and gaussian naive Bayes; they were selected due to their strengths in handling features in large datasets. The highly parameterized neural networks were tuned using efficient approaches like Optuna and genetic algorithms. The results indicated that the model implemented using our proposed combination of DL model and Optuna, outperformed the traditional models, achieving 93.55% reliability. This suggests the potential for using deep learning for decision-making in diagnosing PCOS. This method demonstrates the importance of integrating various data types with powerful analytic tools in medical diagnostics to support customized therapy

Experimental Study of the Oxidation of N -Tetradecane in a Jet-Stirred Reactor (JSR) and Detailed Chemical Kinetic Modeling

International audienc

Oxidation of commercial and surrogate bio-Diesel fuels (B30) in a jet-stirred reactor at elevated pressure: Experimental and modeling kinetic study

International audienceThe oxidation of a commercial B30 (30% FAME by vol.) bio-Diesel fuel and a B30 bio-Diesel surrogate fuel (49% n-decane, CAS 124-18-5; 21% 1-methylnaphthalene, CAS 90-12-0; 30% methyl octanoate, CAS 111-11-5, in mole) was performed using a pressurized fused-silica jet-stirred reactor under the same initial experimental conditions (560–1030 K, 6 and 10 atm, equivalence ratios of 0.25–1.5, 10,300 ppm of carbon). The results of this series of experiments consisted of concentration profiles of reactants, stable intermediates and products measured as a function of temperature by low-pressure probe sampling followed by Fourier transform infrared absorption spectrometry and gas chromatography analyses. The results obtained with the commercial and surrogate B30 mixtures were compared with each other, showing that the mixture n-decane/1-methylnaphthalene/methyl octanoate 49/21/30% in mole is an excellent simple B30 Diesel fuel surrogate. A detailed chemical kinetic reaction mechanism consisting of 7748 reactions involving 1964 species was proposed based on previous chemical kinetic reaction mechanisms for the oxidation of n-decane, methyl octanoate, and 1-methylnaphthalene under similar conditions. The kinetic modeling showed reasonable agreement between the present data and computations over the entire range of conditions considered in this study

Experimental and modeling study of the oxidation of n- and iso-butanal

Veloo PS, Dagaut P, Togbé C, et al. Experimental and modeling study of the oxidation of n- and iso-butanal. Combustion And Flame. 2013;160(9):1609-1626.Understanding the kinetics of large molecular weight aldehydes is essential in the context of both conventional and alternative fuels. For example, they are key intermediates formed during the low-temperature oxidation of hydrocarbons as well as during the high-temperature oxidation of oxygenated fuels such as alcohols. In this study, an experimental and kinetic modeling investigation of n-butanal (n-butyraldehyde) and iso-butanal (iso-butyraldehyde or 2-methylpropanal) oxidation kinetics was performed. Experiments were performed in a jet stirred reactor and in counterflow flames over a wide range of equivalence ratios, temperatures, and pressures. The jet stirred reactor was utilized to observe the evolution of stable intermediates and products for the oxidation of n- and iso-butanal at elevated pressures and low to intermediate temperatures. The counterflow configuration was utilized for the determination of laminar flame speeds. A detailed chemical kinetic interpretative model was developed and validated consisting of 244 species and 1198 reactions derived from a previous study of the oxidation of propanal (propionaldehyde). Extensive reaction pathway and sensitivity analysis was performed to provide detailed insight into the mechanisms governing low-, intermediate-, and high-temperature reactivity. The simulation results using the present model are in good agreement with the experimental laminar flame speeds and well within a factor of two of the speciation data obtained in the jet stirred reactor. (c) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved