Boron nitride nanotubes (BN-NTs) were synthesized by using excimer laser ablation at 1200 °C in different carrier gases. The main characteristic of the BN-NTs produced by this method is that nanotubes are of only one to three atomic layers thick, which could be attributed to the dominance of the axial growth rate over the radial growth rate. The diameter of the BN-NTs ranged from 1.5 to 8 nm. The tips of the BN-NTs are either a flat cap or of polygonal termination, in contrast to the conical ends of carbon nanotubes. The atomic ratio of boron to nitrogen as measured by means of parallel electron energy loss spectroscopy is 0.8, which is within the experimental error of the stoichiometry of hexagonal BN structure.

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Intramolecular H-migration reaction of hydroperoxyalkylperoxy radicals (OQOOH) is one of the most important reaction families in the low-temperature oxidation of hydrocarbon fuels. This reaction family is first divided into classes depending upon H atom transfer from -OOH bonded carbon or non-OOH bonded carbon, and then the two classes are further divided depending upon the ring size of the transition states and the types of the carbons from which the H atom is transferred. High pressure limit rate rules and pressure-dependent rate rules for each class are derived from the rate constants of a representative set of reactions within each class using electronic structure calculations performed at the CBS-QB3 level of theory. For the intramolecular H-migration reactions of OQOOH radicals for abstraction from an -OOH substituted carbon atom (-OOH bonded case), the result shows that it is acceptable to derive the rate rules by taking the average of the rate constants from a representative set of reactions with different sizes of the substitutes. For the abstraction from a non-OOH substituted carbon atom (non-OOH bonded case), rate rules for each class are also derived and it is shown that the difference between the rate constants calculated by CBS-QB3 method and rate constants estimated from the rate rules may be large; therefore, to get more reliable results for the low-temperature combustion modeling of alkanes, it is better to assign each reaction its CBS-QB3 calculated rate constants, instead of assigning the same values for the same reaction class according to rate rules. The intramolecular H-migration reactions of OQOOH radicals (a thermally equilibrated system) are pressure-dependent, and the pressure-dependent rate constants of these reactions are calculated by using the Rice-Ramsberger-Kassel-Marcus/master-equation theory at pressures varying from 0.01 to 100 atm. The impact of molecular size on the pressure-dependent rate constants of the intramolecular H-migration reactions of OQOOH radicals has been studied, and it is shown that the pressure dependence of the rate constants of intramolecular H-migration reactions of OQOOH radicals decreases with the molecular size at low temperatures and the impact of molecular size on the pressure-dependent rate constants decreases as temperature increases. It is shown that it is acceptable to derive the pressure-dependent rate rules by taking the average of the rate constants from a representative set of reactions with different sizes of the substitutes. The barrier heights follow the Evans-Polanyi relationship for each type of intramolecular hydrogen-migration reaction studied. All calculated rate constants are fitted by a nonlinear least-squares method to the form of a modified Arrhenius rate expression at pressures varying from 0.01 to 100 atm and at the high-pressure limit. Furthermore, thermodynamic parameters for all species involved in these reactions are calculated by the composite CBS-QB3 method and are given in NASA format.

The binuclear structure of Fe(2)(DTPB)(mu-O)(mu-Ac)Cl(BF(4))(2) (DTPB = 1,1,4,7,7-penta (2'-benzimidazol-2-ylmethyl)-triazaheptane, Ac = acetate) was characterized by UV-visible absorption and infrared spectra and NMR and ESR. The binding interaction of DNA with the diiron complex was examined spectroscopically. Supercoiled and linear DNA hydrolytic cleavage by the diiron complex is supported by the evidence from anaerobic reactions, free radical quenching, high performance liquid chromatography experiments, and enzymatic manipulation such as T4 ligase ligation, 5'-(32)P end-labeling, and footprinting analysis. The estimation of rate for the supercoiled DNA double strand cleavage shows one of the largest known rate enhancement factors, approximately 10(10) against DNA. Moreover, the DNA hydrolysis chemistry needs no coreactant such as hydrogen peroxide. The poor sequence-specific DNA cleavage indicated by the restriction analysis of the pBR322 DNA linearized by the diiron complex might be due to the diiron complex bound to DNA by a coordination of its two ferric ions to the DNA phosphate oxygens, as suggested by spectral characterizations. The hydrolysis chemistry for a variety of binuclear metal complexes including Fe(2)(DTPB)(mu-O)(mu-Ac)Cl(BF(4))(2) is compared. It is established that the dominant factors for the DNA hydrolysis activities of the binuclear metal complexes are the mu-oxo bridge, labile and anionic ligands, and open coordination site(s). Concerning the hydrolytic mechanisms, the diiron complex Fe(2)(DTPB)(mu-O)(mu-Ac)Cl(BF(4))(2) might share many points in common with the native purple acid phosphatases.