Transesterification of soybean oil with methanol was investigated. Three stepwise and reversible reacttons are believed to occur. The effect of variations in mixing intensity (Reynolds number = 3,100 to 12,400) and temperature (30 to 70'CJ on the rate oireaction were studied while the molar ratio of alcohol to triglycerol (6:l) and the concentration of catalyst (0.20 wt% based on soybean oil) were held constant. The variations in mixing intensity appear to effect the reaction parallel to the variations in temperature. A reaction mechanism consisting of an initial mass transfer-controlled region followed by a kinetically controlled region is proposed. The experimental data for the latter region appear to be a good fit into a second-order kinetic mechanism. The reaction rate constants and the activation energies were determined for all the forward and reverse reactions. lAOCS 74,1457-1463 (1997).KEY WORDS: Biodiesel, kinetics, methyl esters, mixing, renewable fuels, soybean oil, transesterification. triglycerides.Over the last few years. fatty acid methyl esters have assumed importance as research has intensified on the utilization of vegetable oils and animal fats derivatives for liquid fuels, known as biodiesel. Fatty acid methyl esters are products of the transesterification of fats and oils with alcohols in the presence of an acid or an alkaline catalyst. Three consecutive and reversible reactions are believed to occur ( l ) . Mono-(MG) and diglycerides (DG) are the intermediates formed in these reactions.The variables affecting the transesterification process (also called alcoholysis) have been intensively investigated as widening industrial uses were found for esters (2-6). Molar ratio of alcohol to vegetable oil, type of catalyst, temperature, and presence of impurities such as free fatty acids and moisture are among the variables that have been studied.There are a number of kinetic studies in the literature on the transesterification of esters with alcohol. However, only a few of these studies deal with vegetable oils and fatty esters. The studies on the transesterification kinetics for nonfatty esters include: the determination of the reaction rate constants, the equilibrium constant, and the activation energy for the acid-catalyzed reaction of butanol with ethyl acetate (7) and ethanol with butyl acetate (8). .4 review by Sridharan and Mathai (9) on the transesterification reactions involving alco--To whom correspondence should be addressed. E-&. houreddini@unI.edu.holysis, acidolysis, vinyl interchange, and ester-ester inrerchange contains many of the reported studies.The transesterification kinetics for vegetable oils and fatty esters has been reported in a few studies. Dufek and coworkers (10) studied the acid-catalyzed esterification and transesterification of 9(1O)-carboxystearic acid and its mono-and dimethyl esters and reported unequal chemical reactivity for different carboxyl and carboxymethyl groups. Freedman and conorkers ( l ) investigated both acid-and alkaline-catalyzed transester...

Objective To determine the pooled global prevalence of olfactory and gustatory dysfunction in patients with the 2019 novel coronavirus (COVID-19). Data Sources Literature searches of PubMed, Embase, and Scopus were conducted on April 19, 2020, to include articles written in English that reported the prevalence of olfactory or gustatory dysfunction in COVID-19 patients. Review Methods Search strategies developed for each database contained keywords such as anosmia, dysgeusia, and COVID-19. Resulting articles were imported into a systematic review software and underwent screening. Data from articles that met inclusion criteria were extracted and analyzed. Meta-analysis using pooled prevalence estimates in a random-effects model were calculated. Results Ten studies were analyzed for olfactory dysfunction (n = 1627), demonstrating 52.73% (95% CI, 29.64%-75.23%) prevalence among patients with COVID-19. Nine studies were analyzed for gustatory dysfunction (n = 1390), demonstrating 43.93% (95% CI, 20.46%-68.95%) prevalence. Subgroup analyses were conducted for studies evaluating olfactory dysfunction using nonvalidated and validated instruments and demonstrated 36.64% (95% CI, 18.31%-57.24%) and 86.60% (95% CI, 72.95%-95.95%) prevalence, respectively. Conclusions Olfactory and gustatory dysfunction are common symptoms in patients with COVID-19 and may represent early symptoms in the clinical course of infection. Increased awareness of this fact may encourage earlier diagnosis and treatment, as well as heighten vigilance for viral transmission. To our knowledge, this is the first meta-analysis to report on the prevalence of these symptoms in COVID-19 patients.

Recognizing that previous experimental studies on constant-pressure, outwardly propagating, spherical flames with imaging capability were limited to pressures less than about 5 atm, and that pressures within internal combustion engines are substantially higher, a novel experimental apparatus was designed to extend the environmental pressure to 60 atm. Results substantiate previous observations of the propensity of cell formation over the flame surface due to hydrodynamic and diffusive-thermal instabilities and provide convincing evidence that wrinkled flame is the preferred mode of propagation in hydrogen/air mixtures in environments with pressures above only a few atmospheres. It is further shown that, by using helium as the diluent, and by reducing the oxygen concentration of the combustible, diffusional-thermal instability can be mostly suppressed and the hydrodynamic instability delayed. Stretch-free laminar flame speeds were subsequently determined for such smooth flames up to 20 atm and were compared with the calculated values, allowing for detailed chemistry and transport.

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Objective To determine whether radiologically defined sarcopenia at the C3 or L3 level as measured by computed tomography or magnetic resonance imaging is prognostic of overall survival (OS) in head and neck cancers (HNCs). Methods Literature searches of PubMed, Embase, and Scopus were conducted on July 12, 2019, to include articles written in the English language with no constraints on publication date. To be included in the analysis, articles had to report the prognostic impact of skeletal muscle mass measured radiologically at the C3 or L3 vertebral level in HNC patients; hazard ratios (HRs) for OS; 95% confidence intervals (CIs); be from a clinical trial, cohort, or case–control study; and have English full‐text availability. Articles were reviewed in consensus by two reviewers, with disagreements reviewed by a third reviewer. Preferred Reporting Items for Systematic Reviews and Meta‐Analyses and Meta‐analysis Of Observational Studies in Epidemiology Checklist guidelines were used for reporting. Study quality assessment was performed using Quality In Prognosis Studies tool. The random‐effects DerSimonian and Laird method was used for meta‐analysis. Results Ten articles, nine retrospective and one prospective, were included in this meta‐analysis (n = 2,181 patients). Significant differences were found in OS for HNC patients with sarcopenia (HR = 1.98; 95% CI: 1.64‐2.39; P < .00001). No heterogeneity was detected in either the overall or subgroup analyses. Conclusions Radiologically defined sarcopenia is a negative predictor of OS in patients with HNC. Early detection of sarcopenia in cancer patients may help guide nutritional and adjuvant support to improve treatment outcomes. Level of Evidence NA Laryngoscope, 131:333–341, 2021

In this Letter we present turbulent flame speeds and their scaling from experimental measurements on constant-pressure, unity Lewis number expanding turbulent flames, propagating in nearly homogeneous isotropic turbulence in a dual-chamber, fan-stirred vessel. It is found that the normalized turbulent flame speed as a function of the average radius scales as a turbulent Reynolds number to the one-half power, where the average radius is the length scale and the thermal diffusivity is the transport property, thus showing self-similar propagation. Utilizing this dependence it is found that the turbulent flame speeds from the present expanding flames and those from the Bunsen geometry in the literature can be unified by a turbulent Reynolds number based on flame length scales using recent theoretical results obtained by spectral closure of the transformed G equation.