Study of the factors determining the mobility of ions in the polypyrrole films doped with aromatic sulfonate anions

The electrochemical redox behavior of the polypyrrole (PPy) films doped with benzenesulfonate (BS), p-toluenesulfonate (pTS) and naphtalene-1,5-disulfonate (NDS) was investigated by cyclic voltammetry, the chemical composition of the films was determined by XDS, the surface morphology was characterized by AFM, and the interactions between pyrrole oligomers and the anions were modeled with quantum chemical methods. It is the first detailed comparative study of the properties of these interesting systems with two complementing interactions (electrostatic and aromatic stacking). It was shown than these relatively similar aromatic sulfonate anions have rather different behavior in PPy films. The results showed that the redoxactivity of polypyrrole films doped with sulfonate ions increases in the sequence pTS < BS < NDS. The comparison of voltammograms measured in the presence of different anions with PPy films synthesized in the same solution show that the PPy/pTS films have the most densely packed and the PPy/NDS films the least densely packed structure of the three. The mobility of ions in these films is mainly determined by the packing of the films, which in turn partly depends on the interactions between the dopant-anion and polymer chains.     

Two-sample tests of the equality of two cumulative incidence functions

Typically, differences in the effect of treatment on competing risks are compared by a weighted log-rank test. This test compares the cause-specific hazard rates between the groups. Often the test does not agree with impressions gained from plots of the cumulative incidence functions. Here, we discuss two-sample tests of the equality of two cumulative incidence functions. The first test, based on a suggestion of Lin [1997. Non-parametric inference for cumulative incidence functions in competing risks studies. Statist. Med. 16, 901-910], compares the maximum difference between the two cumulative incidence functions. A Monte Carlo method is used to find p-values for the test. The second test, based on a suggestion of Pepe [1991. Inference for events with dependent risks in multiple endpoint studies. J. Amer. Statist. Assoc. 86, 770-778], compares the integrated difference between the functions. A new variance estimator is proposed for this statistic. A small simulation study is used to compare the various tests. The methods are illustrated on a bone marrow transplant study.     

Hydrogen‐Terminated Si Nanowires as Label‐Free Colorimetric Sensors in the Ultrasensitive and Highly Selective Detection of Fluoride Anions in Pure Water Phase

The detection of anions in pure water phase with colorimetric sensor is a long standing challenge. As one of the most important anions, F^– is associated with nerve gases and the refinement of uranium for nuclear weapons. However, limited by its anions nature, few of the reported colorimetric sensors can successfully applied to detect F^–1 in pure water phase. This work designs a colorimetric sensor for F^–1 pure water phase detection by taking the advantages of the strong specific binding between F and Si, as well as the color‐changing property of H‐terminated Si nanowires (SiNWs). The sensor demonstrates ultra‐sensitivity, high selectivity, and good stability. The results reveal particular interest for the development of new type aqueous phase anions sensors with SiNWs.     

Modelling of fracture toughness data in the ductile to brittle transition temperature region by statistical analysis

A fracture toughness database for a ferritic 22NiMoCr37 steel forging for 12.5, 25, 50 and 100 mm thick specimens tested at nine different temperatures has been analysed statistically. The method employed uses a statistical procedure based on competing risks to evaluate the fracture toughness and quantify the probability of cleavage fracture as a function of temperature, specimen thickness and ductile crack growth. This paper describes the application of the competing risks statistical methods to the fracture toughness database obtained from the joint European Project.     

Oxygen reduction on oxide/polypyrrole composite electrodes: effect of doping anions

Multilayered composite electrodes on glassy carbon, GC, having the structure GC/PPy/PPy(Ox)/PPy, with PPy the polypyrrole and Ox a mixed valence oxide of transition metals, exhibit high reactivity and stability towards the oxygen reduction reaction (orr), when the orr proceeds electrocatalytically on the oxide particles dispersed throughout the inner layer, PPy(Ox). However the nature and concentration of the doping anions, A, of PPy have a profound effect on the resulting orr currents, due to their effects on the conductivity and morphology of the PPy layers. The paper shows and discusses these effects in the case of the composite electrode with Ox = Cu_1.4Mn_1.6O₄ and A = Cl⁻, ClO₄⁻, NO₃⁻, PF₆⁻ and SO₄²⁻, in acid solution (pH 2.2). Optimal conditions were encountered with Cl⁻.     

Change-point diagnostics in competing risks models: Two posterior predictive <Emphasis Type="Italic">p</Emphasis>-value approaches

This paper presents a Bayesian diagnostic procedure for examining change-point assumption in the competing risks model framework. It considers the family of distributions arising from the cause-specific model as reported by Chiang (Introduction to stochastic processes in biostatistics. Wiley, New York, 1968) upon which change-points are added to accommodate possible distributional heterogeneity. Model departure, due to misspecification of change-points associated with either the overall survival distribution or cause-specific probabilities, is quantified in terms of a sequence of cumulative-sum statistics between each pair of adjacent change-points assumed. When assessing the asymptotic behavior of each sequence of cumulative-sum statistics using its posterior predictive p-values, see Rubin (Ann Stat 12:1151–1172, 1984) and partial posterior predictive p-values as reported by Bayarri and Berger (J Am Stat Assoc 95:1127–1142, 2000), we show that both types of p-values attain their greatest departure from 0.5 at the change-point that is missed in the assumed model, from which a diagnostic procedure is formalized. Statistical power of these two types of p-values is discussed.      

Reductive ethylation in ethereal solvents

Organic compounds, in particular anthracene and naphthalene, and two coals have been reductively ethylated in tetrahydrofuran (THF) and diglyme using alkali metals to form anions and ethyl iodide to produce ethylates. Product distributions were sensitive to experimental conditions. The rate of anion formation was controlled by their rate of desorption, probably as contact ion pairs, from the alkali metal surface. The enthalpy of formation of a solvated contact ion pair was ≈500 kJ mole^?1 mainly due to dipole-solvent interaction. 18-crown-6 ether was used to diagnose that, when treated with potassium in THF, anthracepe gave solvated contact ion pairs and probably di-anions whose reactions were characterized by the formation of ethyldihydroanthracene. Naphthalene under identical conditions gave loosely solvated mono-anions which reacted by electron transfer to give diethyldihydronaphthalene. With other alkali metals anthracene and naphthalene gave similar product distributions. The behaviour of other polynuclear aromatic hydrocarbons and of two coals was classified in the same way. It is suggested that when coals are readily solubilized by reductive alkylation mono-alkyldihydro products will predominate.     

K competing queues with geometric service requirements and linear costs: The μc-rule is always optimal

In this note, a discrete-time system of K competing queues with geometric service requirements and arbitrary arrival patterns is studied. When the cost per slot is linear in the queue sizes, it is shown that the μc-rule minimizes the expected discounted cost over the infinite horizon.     

Reductive bond cleavage of chloro-substituted 10-methyl- tribenzotriquinacenes: Transition between concerted and stepwise mechanisms

The electrochemical reduction of 1-chloro-, 1,4-dichloro- and 1,4,7-trichloro-10-methyl-tribenzotriquinacenes in ACN and DMF was found to occur by concerted electron transfer and bond breaking process, showing irreversible cyclic voltammetric peaks. However, the transition of the process to the stepwise mechanism upon increasing the driving force by raising the scan rate was established. Both CCl bonds are reduced successively in the dichloro compound, but only two bonds overall were reduced in the trichloro compound. The reduction mechanism is discussed. The homolytic dissociation energy of CCl bond in monochloro compound was estimated to be equal to 2.9 eV.     

Influence of case-carburizing and micro-defect on competing failure behaviors of Ni–Cr–W steel under gigacycle fatigue

Axial loading test was performed to investigate the influence of case-carburizing and micro-defect on competing failure behaviors of Ni–Cr–W Steel under gigacycle fatigue. The interior failures induced from inclusion and microstructural inhomogeneity become the predominant failure mode in the life regime beyond 10⁵ cycles. The case-carburizing has no effect on the fatigue strength with interior failure. Compared with the lower limit values of experimental S–N data, the predicted results by using GP distribution is relatively suitable. From the viewpoint of reliability, the modeling method of interior S–N curve with the maximum defect size at a given probability is satisfactory.