Comparative study of the effect of fuel deoxygenation and polar species removal on jet fuel surface deposition

The effect of near-complete deoxygenation and polar species removal on deposition propensity of a Jet A-1 fuel type, with marginal thermal oxidative stability was studied in a laboratory scale approach. The fuel deoxygenation was carried out via nitrogen purging and two types of bespoke zeolites were used separately in a packed bed reactor for partial polar separation. The treated fuel samples were assessed individually for deposition propensity, using “High Reynolds Thermal Stability(HiReTS)” test device. It was found that when the concentration of hydroperoxides in fuel is relatively high, polar removal is more effective way than the fuel deoxygenation in reducing carbona- ceous deposits. Furthermore, competitive adsorption of dissolved O 2 with polar species was studied for a model fuel doped with a few polar species, as well as for the Jet A-1 with marginal thermal stability, in the packed bed reactor with zeolite 3.7Å. The polar species added to the model fuel share the same functional groups as those in Jet A-1 with a strong im pact on fuel thermal degradation and surface deposition. These include hexanoic acids, heaxnol, hexanal, hexanone, phenyl amine (aniline), butylated hydroxytoluene(BHT), dibutyl disulfide and Fe naphthenate. A one-dimensional model for calculation of dissolved O 2 adsorption in the packed bed reactor was built using COMSOL Multiphysics. The modelling results were in good agreement with the induction period prior to the beginning of the O 2 adsorption, as well as the different stages of O 2 uptake during the competitive adsorption between dissolved O 2 and polar species in the Jet A-1 fuel. The calculation showed a discrep- ancy with the experimental results beyond the second phase of O 2 adsorption. More theories, assumptions and physical sub-models are required to build a more robust pre- dictive model. A new chemical reaction pathway based on the self-reaction of hydroperoxides was proposed as part of “Basic Autoxidation Scheme(BAS)” to justify the relatively high deposition propensity of the marginal fuel after near-complete deoxygenation. The vi- ability of this reaction pathway was supported by the quantum chemistry calculations

Effect of reactive sulfur removal by activated carbon on aviation fuel thermal stability

The effect of reactive sulfur removal from a Jet A-1 fuel with marginal thermal 3 stability on surface deposition propensity is reported. The sulfur removal was achieved 4 through adsorptive treatment the fuel with activated carbon.The treated fuel was as- 5 sessed for surface deposition propensity using a High Reynolds Thermal Stability(HiReTS)test 6 device. It was found that activated carbon has a strong adsorption capacity for removal 7 of reactive sulfur and Fe components from the fuel. This resulted in a substantial re- 8 duction of surface deposition propensity of the Jet A-1 fuel. 9 Density Functional Theory(DFT) was used to investigate the role of reactive sulfur and 10 Fe on thermal oxidative stability.Mechanistic pathways for intervention of these class 11 of species with hydroperoxides are proposed

Comparison between two doses of betamethasone administration with 12�hours vs. 24�hours intervals on prevention of respiratory distress syndrome: a randomised trial

The purpose of the present study was to compare the effect of a two-dose administration of betamethasone with 12�hours interval vs. 24�hours interval on neonatal respiratory distress syndrome (RDS). The study was performed as a randomised clinical trial on 201 pregnant women with a gestational age of 26�34�weeks. In one group 12�mg of betamethasone every 12�hours for two doses and in the other group 12�mg of betamethasone every 24�hours for two doses were prescribed intramuscularly. There were no significant differences between the two groups according to maternal age, parity, gravidity, BMI, neonatal sex, need to surfactant, NICU admission, NICU stay, neonatal death, neonatal sepsis and Apgar score at minutes 1 and 5, but the gestational age at the beginning of the study and delivery receiving complete course of betamethasone and neonatal weight were lower in 24�hours group. RDS, necrotising enterocolitis, intra-ventricular haemorrhage and chorioamnionitis were more in the 24�hours� group. Multiple regression analysis showed that RDS and IVH (p�=�.022, RR�=�0.07, CI95 0.006�0.96 and p�=�.013; RR�=�0.9, CI95 0.1�0.89, respectively) were more in the 24�hours group and neonatal death (p�=�.034, RR�=�4.7, CI95 1.07�16.2) and NEC (p�=�0.038, RR�=�2.5, CI95 1.7�3.7), were more in the 12�hours group. In conclusion, it seems that 12�hours interval betamethasone therapy may be considered as an alternative treatment in the case of preterm labour for acceleration of lung maturity; however, it is suggested that more studies should be performed on this issue and various morbidities.IMPACT STATEMENTWhat is already known on this subject: Administration of a single course of corticosteroids in all women with a gestational age of 24�34 weeks of pregnancy who are at risk for preterm labour and delivery has been recommended. The accepted regimen by National Institutes of Health (NIH) is an injection of betamethasone for two doses with 24�hours interval.What do the results of this study add: Twelve hours interval betamethasone therapy may be considered as an alternative treatment in the cases of preterm labour for acceleration of lung maturity.What are the implications of these findings for clinical practice and/or further research: Prescription of two doses (complete regimen) is more important than the interval between two doses for obtaining the maximum effect in a preterm birth. © 2018 Informa UK Limited, trading as Taylor & Francis Grou

Comparison between two doses of betamethasone administration with 12 hours vs. 24 hours intervals on prevention of respiratory distress syndrome: a randomised trial

The purpose of the present study was to compare the effect of a two-dose administration of betamethasone with 12 hours interval vs. 24 hours interval on neonatal respiratory distress syndrome (RDS). The study was performed as a randomised clinical trial on 201 pregnant women with a gestational age of 26�34 weeks. In one group 12 mg of betamethasone every 12 hours for two doses and in the other group 12 mg of betamethasone every 24 hours for two doses were prescribed intramuscularly. There were no significant differences between the two groups according to maternal age, parity, gravidity, BMI, neonatal sex, need to surfactant, NICU admission, NICU stay, neonatal death, neonatal sepsis and Apgar score at minutes 1 and 5, but the gestational age at the beginning of the study and delivery receiving complete course of betamethasone and neonatal weight were lower in 24 hours group. RDS, necrotising enterocolitis, intra-ventricular haemorrhage and chorioamnionitis were more in the 24 hours� group. Multiple regression analysis showed that RDS and IVH (p =.022, RR = 0.07, CI95 0.006�0.96 and p =.013; RR = 0.9, CI95 0.1�0.89, respectively) were more in the 24 hours group and neonatal death (p =.034, RR = 4.7, CI95 1.07�16.2) and NEC (p = 0.038, RR = 2.5, CI95 1.7�3.7), were more in the 12 hours group. In conclusion, it seems that 12 hours interval betamethasone therapy may be considered as an alternative treatment in the case of preterm labour for acceleration of lung maturity; however, it is suggested that more studies should be performed on this issue and various morbidities.IMPACT STATEMENTWhat is already known on this subject: Administration of a single course of corticosteroids in all women with a gestational age of 24�34 weeks of pregnancy who are at risk for preterm labour and delivery has been recommended. The accepted regimen by National Institutes of Health (NIH) is an injection of betamethasone for two doses with 24 hours interval. What do the results of this study add: Twelve hours interval betamethasone therapy may be considered as an alternative treatment in the cases of preterm labour for acceleration of lung maturity. What are the implications of these findings for clinical practice and/or further research: Prescription of two doses (complete regimen) is more important than the interval between two doses for obtaining the maximum effect in a preterm birth. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group

Comparison between maternal and neonatal outcome of PPROM in the cases of amniotic fluid index (AFI) of more and less than 5 cm

The study was performed on pregnant women with a gestational age of 26�32 weeks of pregnancy, who had been admitted to the hospital with a confirmed diagnosis of premature rupture of membranes. In all eligible women, ultrasounds were performed for the evaluation of amniotic fluid index. Then, the women were divided into two groups according to amniotic fluid index of �5 cm and <5 cm. These women were followed and monitored up to delivery. The women of the two groups did not have significant difference between them according to age, gestational age at the time of ruptured membrane, body mass index, gravidity, parity, gestational age at delivery and route of delivery. Maternal morbidities including chorioamnionitis, placental abruption, uterine atony after delivery and retention of placenta did not show significant difference between the two groups. There was no significant difference between the two groups� amniotic fluid index <5 cm and amniotic fluid index �5 cm, regarding neonatal morbidities, except for neonatal sepsis and neonatal death, which were higher in the amniotic fluid index <5 cm group 7(14.6%) versus 1(2.3%), p =.039, RR = 7.7 (95%CI 0.04�0.06) and 11(30.9%) versus 2(4.7%), p =.013, RR = 6.095 (95%CI = 1.26�29.31). In the subgroups of two categories of gestational ages of 260�296 and 300�346, neonatal morbidities were higher in the amniotic fluid index <5 cm group. The results suggest that amniotic fluid index <5 cm should be considered as a warning sign for predicting poor prognosis of pregnancy complicated by preterm premature rupture of membranes.Impact statementWhat is already known on this subject? In a retrospective study in 1993, the relationship between oligohydramnios (which was defined as the largest single packet of fluid less than 2 � 2 cm) at the time of hospital admission, and the outcome of mother, foetus and neonates in a gestational age of less than 35 weeks of pregnancy was evaluated. In the oligohydramnios group, chorioamnionitis and funistis were more common. Also, the mean gestational age at the time of delivery and neonatal weight was less than that of the normal amniotic fluid group. According to these results, it was concluded that a low amniotic fluid volume in the women with preterm premature rupture of membranes (PPROM) can be considered as a prognostic factor in the cases of conservative management of PPROM. In contrast, the other study, which was performed on a larger sample size (290 patients), could not show more cases of amnionitis in the cases of amniotic fluid index (AFI) of less than 5 cm; however, the latency period was shorter in comparison with AFI of more than 5 cm. What do the results of this study add? Chorioamnionitis, placental abruption and uterine atony after delivery, retention of placenta and route of delivery did not show a significant difference between the two groups. Respiratory distress syndrome (RDS), need of surfactant and intubation, intra ventricular haemorrhage (IVH) and duration of neonatal intensive care unit (NICU) admission did not show a significant difference between the two groups; however, the rate of neonatal sepsis and neonatal death were higher in the AFI <5 cm group. What are the implications of these findings for clinical practice and/or further research? The results suggest that AFI <5 cm should be considered as a warning sign for predicting poor prognosis of pregnancy complicated by PPROM. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group

Construction of a reduced chemical kinetic mechanism for autoxidation of n-paraffinic solvent – a model for aviation fuel

An optimised pseudo-detailed mechanism for autoxidation of liquid hydrocarbons, in the range of aviation fuel, is presented. The kinetic parameters of this mechanism were calculated using Density Functional Theory(DFT) with the B3LYP functional and cc-pVTZ basis set. A polar-free solvent composed of five normal alkanes in the range of Jet-A1 (C10 to C14) was used in a near-isothermal tube reactor to explore the kinetics of autoxidation, over a narrow range of temperature from 135 °C to 150 °C. The results of numerical integration of the optimised mechanism were in good agreement with the experimental data for the thermal autoxidation of the polar-free solvent. Furthermore, the mechanism was examined for prediction of cumulative amount of products of primary and secondary phase of autoxidation of polar-free solvent, over a period of 180 mins, obtained in a PetrOxy device. These species include hydroperoxides, alcohols, aldehydes and ketones