Catalysis of 3‐Carboxy‐1,2‐benzisoxazole Decarboxylation by Hydrophobic Antibody Binding Pockets

Monoclonal antibodies were generated against a 3‐phenyl‐1,2‐benzisoxazole derivative and shown to catalyze the solvent‐sensitive decarboxylation of 3‐carboxy‐1,2‐benzisoxazoles. In addition to rate accelerations up to 2300‐fold over background, the antibodies exhibit distinctive selectivities for substrates bearing 5‐ or 6‐NO₂ substituents, with preferential decarboxylation of the less reactive substrate in one case. These effects are the likely consequence of substrate destabilization, achieved by forcing the carboxylate group into a relatively apolar binding pocket and stabilization of the charge‐delocalized transition state through dispersive interactions. Comparison with a more active antibody decarboxylase previously raised against 2‐acetamido‐naphthalene‐1,5‐disulfonate suggests, however, that a judicious mix of polar and apolar interactions may ultimately be more effective for achieving high decarboxylase activity.     

Quadruple Decker [3.3][3.3][3.3]Orthocyclophane Acetal—An Orthocyclophane Ladder

Through clever bridging of orthocyclophanes (in this case by acetalization), molecules such as 1 can be formed with four benzene rings in a stacked face-to-face arrangement. UV/Vis spectroscopic and electrochemical properties of 1 are governed by π–π through-space interactions within the molecule.     

Differences between PREMIER combustion in a natural gas spark-ignition engine and knocking with pressure oscillations

PREMIER (PREmixed Mixture Ignition in the End-gas Region) combustion occurs with auto-ignition in the end-gas region when the main combustion flame propagation is nearly finished. Auto-ignition is triggered by the increases in pressure and temperature induced by the main combustion flame. Similarly to engine knocking, heat is released in two stages when engines undergo this type of combustion. This pattern of heat release does not occur during normal combustion. However, engine knocking induces pressure oscillations that cause fatal damage to engines, whereas PREMIER combustion does not. The purpose of this study was to elucidate PREMIER combustion in natural gas spark-ignition engines, and differentiate the causes of knocking and PREMIER combustion. We applied combustion visualization and in-cylinder pressure analysis using a compression–expansion machine (CEM) to investigate the auto-ignition characteristics in the end-gas region of a natural gas spark-ignition engine. We occasionally observed knocking accompanied by pressure oscillations under the spark timings and initial gas conditions used to generate PREMIER combustion. No pressure oscillations were observed during normal and PREMIER combustion. Auto-ignition in the end-gas region was found to induce a secondary increase in pressure before the combustion flame reached the cylinder wall, during both knocking and PREMIER combustion. The auto-ignited flame area spread faster during knocking than during PREMIER combustion. This caused a sudden pressure difference and imbalance between the flame propagation region and the end-gas region, followed by a pressure oscillation.     

Low temperature deposited Zr-B film applicable to extremely thin barrier for copper interconnect

We have prepared thin Zr-B films at low temperatures as a new material applicable to an extremely thin barrier against Cu diffusion in Si-ULSI metallization. The obtained Zr-B films mainly consist of the ZrB₂ phase with a nanocrystalline texture on SiO₂ and a fiber texture on Cu. The resistivity of the Zr-B films depends on the substrate of SiO₂ or Cu. The constituent ratio of B/Zr is almost 2, though the contaminants of oxygen, nitrogen, and carbon are incorporated in the film. The nanocrystalline structure of the Zr-B film on SiO₂ is stable due to annealing at temperatures up to 500 °C for 30 min. We applied the 3-nm thick Zr-B film to a diffusion barrier between Cu and SiO₂, and the stable barrier properties were confirmed. We can demonstrate that the thin Zr-B film is a promising candidate for thin film application to a metallization material in Si-ULSIs.     

Inhomogeneous spin state in the organic conductor κ-(BEDT-TTF)4Hg2.78Cl8

The static and dynamical local spin susceptibility of the nonstoichiometric organic conductor, κ-(BEDT-TTF)₄Hg_2.78Cl₈, is studied by ¹³C NMR spectroscopy from room temperature down to 1.7 K. We observe a gradual growth of inhomogeneity in the spin state as a spectral broadening down to the lowest temperature, which is sustained even under 0.4 GPa but suppressed under 0.8 GPa. The emergence of the inhomogeneity is discussed in the light of the doped triangular-lattice Mott insulator.     

Numerical analysis on auto-ignition of a high pressure hydrogen jet spouting from a tube

In this study, a direct numerical simulation based on compressible flow dynamics has been applied to the autoignition and extinction of a high-pressure hydrogen jet spouting from a tube. The diameter of the tube is 4.8 mm. The length of the tube is 71 mm. At the inlet, pressure is set at 3.6, 5.3 and 21.1 MPa, and temperature is set at 300 K for all cases. To explore the autoignition of hydrogen jet, two-dimensional axisymmetric Navier–Stokes equations with a detailed chemical kinetics and rigorous transport properties have been employed. The hydrogen jet through the tube is choked. The numerical results show that the high-pressure hydrogen jet produces a semi-spherical shock wave in the ambient air at the early time of jetting. The shock wave heats up the air to a high temperature and causes the autoignition of the hydrogen and air mixture in the tube as well as at the tube exit.     

Enhanced gas-sensing behaviour of Ru-doped SnO2 surface: A periodic density functional approach

A theoretical study on Ru-doped rutile SnO₂(1 1 0) surface has been carried out by means of periodic density functional theory (DFT) at generalized gradient approximation (GGA-RPBE) level with a periodic supercell approach. Electronic structure analysis was performed based on the band structure and partial density of states. The results provide evidence that the electronic structures of SnO₂(1 1 0) surface are modified by the surface Ru dopant, in which Ru 4d orbital are located at the edge of the band gap region. It is demonstrated that molecular oxygen adsorption characteristics on stoichiometric SnO₂(1 1 0) surface are changed from endothermic to exothermic due to the existence of surface Ru dopant. The dissociative adsorption of molecular oxygen on the Ru_5c/SnO₂(1 1 0) surface is exothermic, which indicates that Ru could act as an active site to increase the oxygen atom species on SnO₂(1 1 0) surface. Our present study reveals that the Ru dopant on surface is playing both electronic and chemical role in promoting the SnO₂ gas-sensing property.     

Contributions from the indirect ionic interactions to the elastic constants in the rock-salt structure crystals

Under the harmonic approximation, the contributions from the indirect ionic interactions to the elastic constants are calculated for the alkali halide and silver halide crystals with the rock-salt structure. The coupling constants of the indirect ionic interactions are calculated by the self-consistent field treatment of the local density approximation and the spherical solid model. The calculated values of the coupling constants are large for the silver ion. The indirect ionic interaction significantly affects the elastic constants. It quantitatively explains the deviation from the Cauchy relation in alkali halide crystals. Moreover, it provides a clear account for the large values of the deviation from the Cauchy relation in AgCl and AgBr.