The pressure dependence of the thermal decomposition of N2O

The pressure dependence of the thermal decomposition of nitrous oxide was investigated behind shock waves at temperatures between 1570 K and 3100 K and pressures from 0.3 atm to 450 atm. Nitrous oxide concentration profiles were measured using IR emission from the 4.5-μm ν₁ band of N₂O. The pressure dependence of the measured rate constant was described using simple Lindemann fits, resulting in the following low- and high-pressure limiting rate coefficients: These values were used to extrapolate current measurements of the rate coefficient to lower temperatures, where the agreement with past work is excellent. Therefore the limiting rate coefficients given above should be suitable for kinetic modeling over a temperature range of 800–2000 K and pressures up to 450 atm. © 1996 John Wiley & Sons, Inc.     

Ignition delay time measurements and modeling for gasoline at very high pressures

Ignition delay times (IDT) for high-octane-number gasolines and gasoline surrogates were measured at very high pressures behind reflected shock waves. Fuels tested include gasoline, gasoline with oxygenates, and two surrogate fuels, one dominated by iso-octane and one by toluene. RON/MON for the fuels varied from 101/94 to 106.5/91.5. Measurements were conducted in synthetic air at pressures from 30 to 250 atm, for temperatures from 700 to 1100 K, and equivalence ratios near 0.85. Results were compared with a recent gasoline mechanism of Mehl et al. (2017). IDT measurements of the iso-octane-dominated surrogate were very well reproduced by the model over the entire pressure and temperature range. IDT measurements for the toluene-dominated surrogate were also reproduced by the model to a lesser extent. By contrast, IDT measurements for the neat gasoline and gasoline with oxygenates, show excellent agreement with the trends of the Mehl et al. model only below 900 K. Above 900 K, the model returned IDT values for the two gasolines that were approximately 1.6× the measured values. Finally, we observed that IDT measurements for the toluene-dominated surrogate fuel and the two gasolines, near 70 atm and below 900 K, appeared to be shortened, possibly by non-homogeneous ignition or non-ideal gas processes. This dataset provides a critically needed set of IDT targets to test and refine boosted gasoline models at high pressures.     

Analysis of thrombin‐antithrombin complex formation using microchip electrophoresis and mass spectrometry

Preterm birth (PTB) related health problems take over one million lives each year, and currently, no clinical analysis is available to determine if a fetus is at risk for PTB. Here, we describe the preparation of a key PTB risk biomarker, thrombin‐antithrombin (TAT), and characterize it using dot blots, MS, and microchip electrophoresis (µCE). The pH for fluorescently labeling TAT was also optimized using spectrofluorometry and spectrophotometry. The LOD of TAT was measured in µCE. Lastly, TAT was combined with six other PTB risk biomarkers and separated in µCE. The ability to make and characterize TAT is an important step toward the development of an integrated microfluidic diagnostic for PTB risk.     

Facile Formation of β‐thioGlcNAc Linkages to Thiol‐Containing Sugars,Peptides, and Proteins using a Mutant GH20 Hexosaminidase

Thioglycosides are hydrolase‐resistant mimics of O‐linked glycosides that can serve as valuable probes for studying the role of glycosides in biological processes. The development of an efficient, enzyme‐mediated synthesis of thioglycosides, including S‐GlcNAcylated proteins, is reported, using a thioglycoligase derived from a GH20 hexosaminidase from Streptomyces plicatus in which the catalytic acid/base glutamate has been mutated to an alanine (SpHex E314A). This robust, easily‐prepared, engineered enzyme uses GlcNAc and GalNAc donors and couples them to a remarkably diverse set of thiol acceptors. Thioglycoligation using 3‐, 4‐, and 6‐thiosugar acceptors from a variety of sugar families produces S‐linked disaccharides in nearly quantitative yields. The set of possible thiol acceptors also includes cysteine‐containing peptides and proteins, rendering this mutant enzyme a promising catalyst for the production of thio analogues of biologically important GlcNAcylated peptides and proteins.     

A shock tube study of the pyrolysis of NO2

NO₂ concentration profiles in shock-heated NO₂/Ar mixtures were measured in the temperature range of 1350–2100 K and pressures up to 380 atm using Ar⁺ laser absorption at 472.7 nm, IR emission at 6.25±0.25 μm, and visible emission at 300–600 nm. In the course of this study, the absorption coefficient of NO₂ at 472.7 nm was measured at temperatures from 300 K to 2100 K and pressures up to 75 atm. Rate coefficients for the reactions NO₂+M→NO+O+M (1), NO₂+NO₂→2NO+O₂ (2a), and NO₂+NO₂→NO₃+NO (2b) were derived by comparing the measured and calculated NO₂ profiles. For reaction (1), the following low- and high-pressure limiting rate coefficients were inferred which describe the measured fall-off curves in Lindemann form within 15% [FORMULA] The inferred rate coefficient at the low- pressure limit, k_1o, is in good agreement with previous work at higher temperatures, but the energy of activation is lower by 20 kJ/mol than reported previously. The pressure dependence of k₁ observed in the earlier work of Troe [1] was confirmed. The rate coefficient inferred for the high pressure limit, k_1∞, is higher by a factor of two than Troe's value, but in agreement with data obtained by measuring specific energy-dependent rate coefficients. For the reactions (2a) and (2b), least-squares fits of the present data lead to the following Arrhenius expressions: [FORMULA] For reaction (2), the new data agree with previously recommended values of k_2a and k_2b, although the present study suggests a slightly higher preexponential factor for k_2a. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 483–493, 1997.     

The Palo Verde reactor neutrino experiment a test for long baseline neutrino oscillations

Our collaboration has installed a long baseline neutrino oscillation experiment at the Palo Verde Nuclear Generating Station in Arizona. 12 tons of Gd loaded liquid scintillator, in a segmented detector, are used to search for oscillations at 740 m distance to three reactors. The anti-neutrino capture on the proton serves as detection reaction. The experiment is expected to reach a sensitivity of Δm² > 1.3 · 10⁻³ eV² and sin²2Θ > 0.1. Our range of sensitivity is tuned to test the ν_μ ↔ ν_e solution of the atmospheric neutrino anomaly.