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A previously derived two-step mechanism describing high-temperature autoignition in alkanes is augmented by addition of a CO2-production step to account for subsequent heat release, producing a three-step reduced mechanism that can facilitate computational investigations at MILD conditions. Comparisons of ignition-times and well-stirred-reactor S-shaped temperature/residence-time curves for propane mixtures suggest that this greatly simplified chemical-kinetic scheme may produce predictions of sufficient accuracy for many applications. A distinctive aspect of the proposed simplified description is that, unlike other available reduced mechanisms, it is free from empiricism, in that it is systematically derived from detailed chemistry by incorporating steady-state approximations for chemical intermediates. [ABSTRACT FROM AUTHOR]

Importance: Ataxia with oculomotor apraxia type 1 (AOA1) is an autosomal recessive cerebellar ataxia due to mutations in the aprataxin gene (APTX) that is characterized by early-onset cerebellar ataxia, oculomotor apraxia, axonal motor neuropathy, and eventual decrease of albumin serum levels., Objectives: To improve the clinical, biomarker, and molecular delineation of AOA1 and provide genotype-phenotype correlations., Design, Setting, and Participants: This retrospective analysis included the clinical, biological (especially regarding biomarkers of the disease), electrophysiologic, imaging, and molecular data of all patients consecutively diagnosed with AOA1 in a single genetics laboratory from January 1, 2002, through December 31, 2014. Data were analyzed from January 1, 2015, through January 31, 2016., Main Outcomes and Measures: The clinical, biological, and molecular spectrum of AOA1 and genotype-phenotype correlations., Results: The diagnosis of AOA1 was confirmed in 80 patients (46 men [58%] and 34 women [42%]; mean [SD] age at onset, 7.7 [7.4] years) from 51 families, including 57 new (with 8 new mutations) and 23 previously described patients. Elevated levels of α-fetoprotein (AFP) were found in 33 patients (41%); hypoalbuminemia, in 50 (63%). Median AFP level was higher in patients with AOA1 (6.0 ng/mL; range, 1.1-17.0 ng/mL) than in patients without ataxia (3.4 ng/mL; range, 0.8-17.2 ng/mL; P < .01). Decreased albumin levels (ρ = -0.532) and elevated AFP levels (ρ = 0.637) were correlated with disease duration. The p.Trp279* mutation, initially reported as restricted to the Portuguese founder haplotype, was discovered in 53 patients with AOA1 (66%) with broad white racial origins. Oculomotor apraxia was found in 49 patients (61%); polyneuropathy, in 74 (93%); and cerebellar atrophy, in 78 (98%). Oculomotor apraxia correlated with the severity of ataxia and mutation type, being more frequent with deletion or truncating mutations (83%) than with presence of at least 1 missense variant (17%; P < .01). Mean (SD) age at onset was higher for patients with at least 1 missense mutation (17.7 [11.4] vs 5.2 [2.6] years; P < .001)., Conclusions and Relevance: The AFP level, slightly elevated in a substantial fraction of patients, may constitute a new biomarker for AOA1. Oculomotor apraxia may be an optional finding in AOA1 and correlates with more severe disease. The p.Trp279* mutation is the most frequent APTX mutation in the white population. APTX missense mutations may be associated with a milder phenotype.

Multiple level esophageal pH studies were performed in 23 neurologically damaged infants and children for evaluation of gastroesophageal reflux (GER) and feeding difficulties. The patients were placed in one of three anatomic groups based on the extent of their neurologic injury. Seven children had an acute cerebral injury due to closed head trauma or infections. Six patients with perinatal asphyxia or progressive encephalopathy had a global CNS insult. Eight children with CNS malformations or intraventricular hemorrhage had subacute cerebral damage. Two patients with generalized seizure disorders could not be anatomically classified. In all groups, abnormalities detected at the distal esophagus were also noted at more proximal levels. The middle esophageal probe demonstrated a significant difference (P less than .02) for the longest reflux episode between patients with subacute cerebral injury and those with a global insult. The difference (P less than .02) for the longest reflux episode detected by the distal pH sensor in globally damaged children compared with those with acute cerebral injury also persisted at the middle and proximal esophageal levels. Comparing these same groups, a difference (P less than .02) in acid clearance time and percentage of time pH less than 4 was noted only at the proximal esophageal level. Only the middle and proximal pH probes detected differences (P less than .02) for acid clearance time between patients with both types of cerebral damage and those with a global injury. In infants and children with CNS damage and suspected GER, monitoring the proximal and middle esophageal pH provides important information not detected by the distal esophageal sensor.(ABSTRACT TRUNCATED AT 250 WORDS)