Matrix factorization method for the Hamiltonian structure of integrable systems

We demonstrate that the process of matrix factorization provides a systematic mathematical method to investigate the Hamiltonian structure of non-linear evolution equations characterized by hereditary operators with Nijenhuis property.     

Highly dispersed Mn2O3−Co3O4 nanostructures on carbon matrix as heterogeneous Fenton-like catalyst

This work reports the synthesis of various carbon (Vulcan XC-72 R) supported metal oxide nanostructures, such as Mn₂O₃, Co₃O₄ and Mn₂O₃−Co₃O₄ as heterogeneous Fenton-like catalysts for the degradation of organic dye pollutants, namely Rhodamine B (RB) and Congo Red (CR) in wastewater. The activity results showed that the bimetallic Mn₂O₃−Co₃O₄/C catalyst exhibits much higher activity than the monometallic Mn₂O₃/C and Co₃O₄/C catalysts for the degradation of both RB and CR pollutants, due to the synergistic properties induced by the Mn−Co and/or Mn (Co)−support interactions. The degradation efficiency of RB and CR was considerably increased with an increase of reaction temperature from 25 to 45°C. Importantly, the bimetallic Mn₂O₃−Co₃O₄/C catalyst could maintain its catalytic activity up to five successive cycles, revealing its catalytic durability for wastewater purification. The structure–activity correlations demonstrated a probable mechanism for the degradation of organic dye pollutants in wastewater, involving •OH radical as well as Mn²⁺/Mn³⁺ or Co²⁺/Co³⁺ redox couple of the Mn₂O₃−Co₃O₄/C catalyst.     

Quantal Information Entropies for Atoms

The polynomials occurring in the wave functionsof hydrogenic excited states are found to presentdifficulties for a straightforward analytical approachto the study of associated information entropies. A method is suggested to deal with them. It isthen applied to calculate the information entropy forthe Jacobi polynomial. A model calculation is presentedto examine the effect of screening on the entropy sum. It is seen that the sum does not depend onthe choice of screening.     

Kinetics of the reactions of OH with alkanes

The rate coefficients for the reactions of OH with ethane (k₁), propane (k₂), n-butane (k₃), iso-butane (k₄), and n-pentane (k₅) have been measured over the temperature range 212–380 K using the pulsed photolysis-laser induced fluorescence (PP-LIF) technique. The 298 K values are (2.43±0.20) × 10^?13, (1.11 ± 0.08) × 10^?12, (2.46 ± 0.15) × 10^?12, (2.06 ± 0.14) × 10^?12, and (4.10 ± 0.26) × 10^?12 cm³ molecule^?1 s^?1 for k₁, k₂, k₃, k₄, and k₅, respectively. The temperature dependence of k₁ and k₂ can be expressed in the Arrhenius form: k₁ = (1.03 ± 0.07) × 10^?11 exp[?(1110 ± 40)/T] and k₂ = (1.01 ± 0.08) × 10^?11 exp[?(660 ± 50)/T]. The Arrhenius plots for k₃ – k₅ were clearly curved and they were fit to three parameter expressions: k₃ = (2.04 ± 0.05) × 10^?17 T² exp[(85 ± 10)/T] k₄ = (9.32 ± 0.26) × 10^?18 T² exp[(275 ± 20)/T]; and k₅ = (3.13 ± 0.25) × 10^?17 T² exp[(115 ± 30)/T]. The units of all rate constants are cm³ molecule^?1 s^?1 and the quoted uncertainties are at the 95% confidence level and include estimated systematic errors. The present measurements are in excellent agreement with previous studies and the best values for atmospheric calculations are recommended. © 1994 John Wiley & Sons, Inc.     

Observation of autoionization resonances in uranium by step-wise laser photoionization

A large number of autoionization resonances have been observed in uranium in the energy range 50,590–51,560cm^–1 by two-step three-photon ionization technique, using two copper vapor laser pumped dye lasers. A Rydberg series converging to the ionization limit of UII at 1749cm^–1 (⁶ L _13/2) has been identified. Some of these resonances are very narrow with a fwhm of 0.1cm^–1. Possible origins of these are discussed.     

Synthetic ion channels with rigid-rod pi-stack architecture that open in response to charge-transfer complex formation

We describe the design, synthesis, and evaluation of synthetic ion channels with a new rigid-rod pi-stack architecture that open in response to guest binding by aromatic electron donor-acceptor interactions. Highly cooperative and highly selective ligand gating is shown to yield anion selective, small ion channels that have the characteristic plum color of the charge-transfer complexes formed between the dialkoxynaphthalene ligands and the stacked naphthalenediimide acceptors of the channel.     

Synthesis of terminal disaccharide unit of Klebsiella pneumoniae ssp. R20

Synthesis of the terminal disaccharide unit of a novel α-(1→2) linked heptoglycan of K. pneumoniae ssp. strain R20 from methyl α-d-mannopyranoside has been presented. Central to the strategy is the application of Sharpless asymmetric dihydroxylation to introduce a new center at C-6 position of mannopyranoside. The coupling of two heptoglycans (12 and 13) was accomplished by a Lewis acid catalyst.     

Kinetic studies of the reactions of O2(b 1sigma(g)+) with several atmospheric molecules

Thermal rate coefficients for the removal (reaction + quenching) of O2(1sigma(g)+) by collision with several atmospheric molecules were determined to be as follows: O3, k3(210-370 K) = (3.63 +/- 0.86) x 10(-11) exp((-115 +/- 66)/T); H2O, k4(250-370 K) = (4.52 +/- 2.14) x 10(-12) exp((89 +/- 210)/T); N2, k5(210-370 K) = (2.03 +/- 0.30) x 10(-15) exp((37 +/- 40)/T); CO2, k6(298 K) = (3.39 +/- 0.36) x 10(-13); CH4, k7(298 K) = (1.08 +/- 0.11) x 10(-13); CO, k8(298 K) = (3.74 +/- 0.87) x 10(-15); all units in cm3 molecule(-1) s(-1). O2(1sigma(g)+) was produced by directly exciting ground-state O2(3sigma(g)-) with a 762 nm pulsed dye laser. The reaction of O2(1sigma(g)+) with O3 was used to produce O(3P), and temporal profiles of O(3P) were measured using VUV atomic resonance fluorescence in the presence of the reactant to determine the rate coefficients for removal of O2(1sigma(g)+). Our results are compared with previous values, where available, and the overall trend in the O2(1sigma(g)+) removal rate coefficients and the atmospheric implications of these rate coefficients are discussed. Additionally, an upper limit for the branching ratio of O2(1sigma(g)+) + CO to give O(3P) + CO2 was determined to be < or = 0.2% and this reaction channel is shown to be of negligible importance in the atmosphere.     

Study of the kinetics of the reactions of NO3 with HO2 and OH

The Absolute rate constants for the gas-phase reactions of NO₃ with HO₂ and OH have been determined using the discharge flow laser magnetic resonance method (DF-LMR). Since OH was found to be produced in the reaction of HO₂ with NO₃, C₂F₃Cl was used to scavenge it. The overall rate constant, k₁, for the reaction, HO₂ + NO₃ → products, was measured to be k₁=(3.0 ± 0.7)×10^?12 cm³ molecule^?1 s^?1 at (297 ± 2) K and P=(1.4 – 1.9) torr. This result is in reasonable agreement with the previous studies. Direct detection of HO₂ and OH radicals and the use of three sources of NO₃ enabled us to confirm the existence of the channel producing OH:HO₂+NO₃→OH+NO₂+O₂ (1a); the other possible channel is HO₂+NO₃→HNO₃+O₂ (1b). From our measurements and the computer simulations, the branching ratio, k_1a/(k_1a + k_1b), was estimated to be (1.0). The rate coefficient for the reaction of OH with NO₃ was determined to be (2.1 ± 1.0) × 10^?11 cm³ molecule^?1 s^?1. © 1993 John Wiley & Sons, Inc.