Laminar Flame Speed, Ignition Delay Time, and CO Laser Absorption Measurements of a Gasoline-like Blend of Pentene Isomers.

The combustion properties of a gasoline-like blend of pentene isomers were determined using multiple types of experimental measurements. The representative mixture (Mix A) is composed of 5.7% 1-pentene (1-C5H10), 39.4% 2-pentene (2-C5H10), 12.5% 2-methyl-1-butene (2M1B), and 42.4% 2-methyl-2-butene (2M2B) (% mol). Laminar flame speeds were measured at equivalence ratios of 0.7-1.5 in a constant-volume combustion chamber, and ignition delay times (including both OH* and CH* diagnostics) as well as CO time-history profiles were performed in shock tubes, in highly diluted mixtures (0.995 He/Ar), at a stoichiometric condition for temperatures ranging from 1350 to 1750 K, and at near-atmospheric pressure. Two additional unbalanced mixtures removing either 2M2B (Mix B) or 2-C5H10 (Mix C) were studied in a shock tube to collect CO time histories, representing the most stringent validation constraints, as these two pentenes constitute the biggest proportions in Mix A and exhibit opposite behaviors in terms of reactivity due to their chemical structure differences. Numerical predictions using a recent validated chemical kinetics mechanism encompassing all pentene isomers from Grégoire et al. ( Fuel2022, 323, 124223) are presented. The use of a complex blend of four pentene isomers in the present paper provided a capstone test of the current mechanism's ability to model pentene-isomer combustion chemistry, with very good results that reflect positively on the current state of the art in pentene isomer kinetics modeling.

Experimental and Chemical Kinetics Study of the Effects of Halon 1211 (CF2BrCl) on the Laminar Flame Speed and Ignition of Light Hydrocarbons.

In this study, the effect of Halon 1211 (CF2BrCl) on the ignition delay time and laminar flame speed of CH4, C2H4, and C3H8 were investigated experimentally for the first time. The results showed that the effects of Halon 1211 on the ignition delay time are strongly dependent on the hydrocarbon: the ignition delay time of CH4 is significantly decreased by Halon 1211 addition, while a significant increase in the ignition delay time was observed with C2H4 for the lowest temperatures investigated. Ignition delay times for C3H8 were slightly increased, mostly on the low-temperature side and for the fuel-rich case. A significant reduction in the laminar flame speed was observed for all of the fuels. A tentative chemical kinetics model was assembled from existing models and completed with reactions that have been determined in the literature or estimated when necessary. The experimental results were reproduced satisfactorily by the model, and a chemical analysis showed that most of the effects of Halon 1211 on the ignition delay times of C2H4 and C3H8 are due to the consumption of H radical through the reaction HBr + H ⇄ Br + H2. In the case of methane, the CF2 radical promotes the formation of H via CF2 + CH3 ⇄ CH2:CF2 + H, which then promotes the branching reaction H + O2 ⇄ OH + O. The laminar flame speed results can be explained using catalytic cycles involving Br atoms that are similar to those reported in the literature for CF3Br. This study exhibits the need for a better estimation of the chlorine atom chemistry during the combustion of hydrocarbons in the presence of fire suppressants.

Increasing the clozapine: norclozapine ratio with co-administration of fluvoxamine to enhance efficacy and minimize side effects of clozapine therapy.

Although clozapine is the only antipsychotic agent to have demonstrated superior efficacy in treatment-refractory schizophrenia, one- to two-thirds of patients do not respond adequately despite acceptable dosages and plasma levels. Moreover, a significant number of patients stop the therapy for various reasons, including its side effects, many of which are thought to be related to its active metabolite, norclozapine. However, combining clozapine with the SSRI antidepressant fluvoxamine decreases norclozapine formation by inhibiting the CYP450 1A2 isoenzyme. Lowering norclozapine levels in this way while maintaining therapeutic clozapine levels increases the clozapine: norclozapine ratio; the potential benefits include both a reduction of such side effects as sedation, weight gain, metabolic disturbances, and neutropenia, and an increase in efficacy. The optimal ratio of clozapine to norclozapine has not yet been defined, but a ratio of two or more implies that saturation of clozapine metabolism has been reached. We hypothesize that co-administration of clozapine and fluvoxamine at dosages that will produce therapeutic plasma levels of clozapine and a clozapine: norclozapine ratio of two or more will increase efficacy and tolerability of clozapine therapy in treatment-resistant schizophrenic patients.

Age-dependent discrepancies between computerized and paper cognitive testing in patients with schizophrenia.

Computer-based cognitive testing is gaining in popularity because of desirable features such as ease of use, standardized administration and online data acquisition. Information technology and computer familiarity are clearly influenced by age in the general population, but the impact of this situation on cognitive testing of patients with schizophrenia has received little attention. In the present paper, participants underwent cognitive testing with computer and paper versions of the same tests. Patients underperformed controls by 1.36 DS (paper tests) and 2.27 DS (computer tests) after controlling for education. Results were highly correlated but patients with schizophrenia were disproportionately impaired on computer tests compared with their paper counterparts. Moreover, for subtests implying active keyboard input from the participant, the difference between paper and computer scores correlated with age in patients, a pattern that was not found in controls. These results have methodological implications because of the implied risk of measuring (lack of) computer proficiency in addition to bona fide cognitive deficits. They confirm, moreover, that patients with schizophrenia are victims of the "digital divide", which adds to the potential benefits of approaches like computer assisted cognitive remediation in this population.

Intramolecular orbital alignments in serine protease/protein inhibitor complexes.

By an analysis of PDB crystal structures, the mean conformations of protein strands bound in serine protease active sites are shown to contain extensively aligned atomic orbitals. The active-serine-bearing segment of each enzyme (subtilisin BPN' and beta-trypsin) also contains such alignments. The participating orbitals are almost identical in each system. All of the alignments converge on the targeted linkage. They suggest that a kind of through-strand polarizability is being optimized by evolution, presumably due to corresponding benefits in proteolysis rate. Such polarizability would help to explain the high values of kcat seen for long oligopeptide substrates. The idea predicts long substrates to be relatively reactive even under non-enzymatic conditions, which in fact they are.