Stable attachment of redox groups for modified electrodes via cyanuric chloride

Methylaminopropylviologen (MAV) was covalently attached to glassy carbon electrodes via cyuranic chloride. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of bound MAV on the electrode surfaces. Electrochemical experiments of these electrodes indicated that the bound MAV was stable and electrochemically active for extended periods of time in aqueous media. The surface coverage of MAV was in the range, of 2.0–3.0×10^?10 mol cm^?2.     

Mercury chloride film anode: Study of the characteristics of a mercury chloride film anode by chronopotentiometric methods

The Mercury Chloride Film Anode (MCFA) is proposed as a new working anode which compares favorably with platinum or other inert metal electrodes.Only organic compounds have been oxidized thus far at the MCFA. Since the oxidation of organic molecules is of considerable interest this is not a serious limitation. The use of this electrode is restricted to pH's less than 5. This, coupled with the interferences of high concentrations of certain anions like iodide, phosphate, and sulfate, represent the most serious restrictions to MCFA's analytical usage. A further interesting possibility of this electrode is its use as a working cathode or anode in solutions containing both reducible and oxidizable species.     

Oxalate/hydrogen peroxide chemiluminescence reaction. A 19F NMR probe of the reaction mechanism

The mechanism of the oxalate/hydrogen peroxide chemiluminescence reaction has been examined by magnetic resonance techniques. Investigation of the reactive intermediates involved in chemiluminescence was carried out with bis(2,6-difluorophenyl)oxalate (DFPO) using 19F NMR to probe its reactions with aqueous hydrogen peroxide. Formation and reactions of the intermediate hydroperoxy oxalate ester B along with the formation of the half ester product C and difluorophenol D were monitored by 19F NMR. When the reaction of DFPO and aqueous hydrogen peroxide was carried out in the presence of dansylphenylalanine, a typical fluorescent analyte, the intensity of the resonance due to the intermediate B was diminished in direct proportion to the concentration of the analyte. Comparison of the time/intensity profile of the chemiluminescence emission with that of the 19F NMR transient suggests that the hydroperoxy oxalate ester B is the likely 'reactive' intermediate, capable of participating in a chemically initiated electron exchange luminescence mechanism.     

Consequence analysis of blast wave from accidental gas explosions

Recently, consequence analyses of accidental gas explosions are often carried out to assess the risk of chemical plants, hazardous-materials sites and new energy systems. In these consequence analyses, it is indispensable to adequately predict the blast-wave (pressure-wave) intensity from gas deflagrations. Some prediction models already exist; however, most of them are based on the theory for explosives and adjusting parameters are needed for evaluating gas deflagrations. In this study, new prediction methods for gas deflagrations were developed. From theoretical analysis of blast-wave generation by a gas deflagration, an evaluation equation of the blast-wave intensity was derived. As the scale of gas deflagration becomes larger, flame front instability (especially hydrodynamic instability) would be more effective and the flame propagating velocity starts to be accelerated. Therefore, the equation was modified considering the effect of flame instability. The evaluations by this modified equation agreed well with the results of large scale experiments. By this analysis, it was found that not only total energy release but also combustion reaction rate has to be introduced into the prediction of gas deflagrations. Using this concept, a modified scale model to predict the blast-wave intensity was developed by improving the previous scale model introducing the term of combustion reaction rate as burning velocity. Furthermore, scale analysis was performed to develop the new scaling law. The universal relationship between scaled distance and overpressure has been realized by this new scaling law for gas deflagrations. In summary, these results provide new methods for accurate prediction of the blast-wave intensity from gas deflagrations.     

Copper(I) ion mediated self-organization of molecular rectangular boxes from 1,2-Bis(2-pyridylethynyl)benzene Ligands with bulky substituents

The reaction of chiral 1,2-bis(2-pyridylethynyl)benzene ligands with copper(I) ions in dichloromethane at room temperature gives rise to the formation of molecular rectangular boxes in high yields. The structures of these complexes were confirmed by X-ray crystallographic analysis. The compound CL1 crystallizes in the triclinic space group P1, with a = 13.707(4) A, b = 14.891(3) A, c = 12.030(1) A, alpha = 101.65(2) degrees, beta = 115.08(2) degrees, gamma = 97.66(1) degrees, V = 2110.8(2) A(3), Z = 1 (T = 288 K). The compound CL2 crystallizes in the triclinic space group P1, with a = 13.539(4) A, b = 14.755(2) A, c = 11.951(2) A, alpha = 101.70(1) degrees, beta = 115.11(1) degrees, gamma = 97.44(2) degrees, V = 2053.8(8) A(3), Z = 1 (T = 198 K). The formation of box-type structure is caused by steric hindrance between bulky substituents of the ligands.     

The burning rate’s effect on the flame length of weak fire whirls

This paper discusses why the visibly-determined flame length of a weak fire whirl increases as compared with the corresponding pool fire without spin. Here, a fire whirl is called weak when the pure aerodynamic effect of flow circulation has a negligible influence on the flame length. Split cylinders were used to apply a flow circulation to a 3-cm-diameter methane burner flame and a 3-cm-diameter ethanol pool fire. After applying the flow circulation, the flame length of the ethanol pool fire increased about three times, while little change was observed in the flame length of the methane burner flame. The difference is explained by the fact that the burning rate of the methane burner flame was fixed constant, whereas that of the ethanol pool fire increased due to the increased heat input to the fuel surface caused by a change in flame shape pushed toward the fuel surface. The experimental observations thus demonstrate that the burning-rate effect can significantly increase the flame length even under a weak circulation condition. Computational fluid dynamics (CFD) simulations were conducted to understand the detailed flow structure of a fire whirl. An analytical model was then developed based on the experimental observations and CFD calculations; the predicted relationship between the flame height and the burning rate agreed with experimental data.     

Temperature and carbon source effects on methane–air flame synthesis of CNTs

We have conducted experimental and numerical studies on flame synthesis of carbon nanotubes (CNTs) to investigate the effects of three key parameters – selective catalyst, temperature and available carbon sources – on CNT growth. Two different substrates were used to synthesize CNTs: Ni-alloy wire substrates to obtain curved and entangled CNTs and Si-substrates with porous anodic aluminum oxide (AAO) nanotemplates to grow well-aligned, self-assembled and size-controllable CNTs, each using two different types of laminar flames, co-flow and counter-flow methane–air diffusion flames. An appropriate temperature range in the synthesis region is essential for CNTs to grow on the substrates. Possible carbon sources for CNT growth were found to be the major species CO and those intermediate species C₂H₂, C₂H₄, C₂H₆, and methyl radical CH₃. The major species H₂, CO₂ and H₂O in the synthesis region are expected to activate the catalyst and help to promote catalyst reaction.     

An Investigation of Chaotic Diffusion in a Family of Hamiltonian Mappings Whose Angles Diverge in the Limit of Vanishingly Action

The chaotic diffusion for a family of Hamiltonian mappings whose angles diverge in the limit of vanishingly action is investigated by using the solution of the diffusion equation. The system is described by a two-dimensional mapping for the variables action, I, and angle, \(\theta \) and controlled by two control parameters: (i) \(\epsilon \), controlling the nonlinearity of the system, particularly a transition from integrable for \(\epsilon =0\) to non-integrable for \(\epsilon \ne 0\) and; (ii) \(\gamma \) denoting the power of the action in the equation defining the angle. For \(\epsilon \ne 0\) the phase space is mixed and chaos is present in the system leading to a finite diffusion in the action characterized by the solution of the diffusion equation. The analytical solution is then compared to the numerical simulations showing a remarkable agreement between the two procedures.