Self-discharge in positively charged polypyrrole–cellulose composite electrodes

Self-discharge is one of the most critical issues to address to allow for industrialization of conducting polymer (CP) based electric energy storage devices. The present work investigates the underlying cause of self-discharge in positively charged polypyrrole (PPy), which is one of the most frequently studied CPs for such devices. The analyzed material is a composite of PPy and cellulose from Cladophora sp. algae forming a free standing paper-like material. From the time dependence of the potential decay as well as from independent spectroelectrochemical investigations the decay was attributed to a kinetically limiting Faradaic reaction, intrinsic to the polymer, forming a reactive intermediate that irreversibly reacts with its surroundings in a kinetically non-limiting following reaction. As such, nucleophilic addition of electrolyte nucleophiles is not found to be rate-determining. These results provide insight into the self-discharge phenomenon in p-doped CPs, and information regarding the potential range in which CPs can operate with insignificant self-discharge.     

Negative slope of resistivity–temperature curve and positive magnetoresistance in antiperovskite ZnCNi3−x Mn x (1.15≤x≤1.5)

In antiperovskite intermetallics ZnCNi_3?x Mn _x , the negative slope coefficient (NSC) dρ/dT of resistivity–temperature curves is observed when x=1.15,1.25,1.4,1.5. The sample with x=1.25 shows a semiconductor-like behavior in the whole temperature range of 15–290 K. By study of the magnetization, magnetoresistance, and low-temperature X-ray diffraction, it is found that Mn dopant significantly affects the physical properties of ZnCNi_3?x Mn _x by changing both the carrier density and the magnetism. The origin of the NSC dρ/dT can be ascribed to the change of hole-like carrier density, which is adjusted by Mn content. The existence of hole-like carriers can be understood rationally by the two-band model. The change of sign of magnetoresistance from positive to negative has been observed in ZnCNi_3?x Mn _x with the change of Mn content, which could be ascribed to the competition between the contribution from field-induced suppression of the thermally excited ferromagnetic spin fluctuations and the Lorentz contribution. When Mn content is low, the Lorentz contribution dominates the sign of magnetoresistance. On the other hand, when Mn content is high, the contribution from field-induced suppression of the thermally excited ferromagnetic spin fluctuations dominates the sign of magnetoresistance.     

Brin–Katok formula for the measure theoretic r-entropy

Entropy is undoubtedly among the most essential characteristics of dynamical systems. Calculations of various entropies are important but often difficult. This article is devoted to constructing the Brin–Katok formula for the measure theoretic r-entropy.     

Synthesis of worm-like superparamagnetic P(St-AA)@Fe3O4/SiO2 Janus composite particles

Novel Janus nanocomposite particles with superparamagnetic P(St-AA)@Fe₃O₄ seed microspheres as head and worm-like SiO₂ as body were successfully prepared. The effects of different variables such as the amount of cetyltrimethyl ammonium bromide (CTAB), tetraethyl orthosilicate (TEOS), and ammonia and the composition of inorganic precursors and surfactants on the morphologies of final particles were studied by transmission electron microscopy (TEM) and field-emission scanning electron microscopy (SEM). Due to the amphiphilic difference between the two parts as well as their special morphologies, the fabricated worm-like particles could be applied to stabilize oil/water mixtures even if owing relative hydrophilic properties that might provide a new category of functional solid surfactants in Pickering emulsions and the fabrication of hierarchical materials.     

Synthesis of TiO2 based on hydrothermal methods using elevated pressures and microwave conditions

Titanium dioxide (TiO₂), especially in its anatase form, is an effective photocatalyst under ultraviolet (UV) light. The particle size of TiO₂ is a critical factor to determine its photoactivity based on its quantum effectiveness under light irradiations. Thus, nanocrystalline TiO₂ has been widely accepted to significantly enhance this effect. The sol–gel method is generally used to synthesize the anatase form of nanocrystalline TiO₂. In this study, we expanded the synthesis method of TiO₂ to high pressures under direct heating (hydrothermal method) and indirect heating (microwave-assisted method). It was found that pH value is one of the major factors to control nano-sizes of TiO₂ particles, and the neutral condition in all methods is preferable for controlling the sizes of the prepared TiO₂ particles. The microwave-assisted method further improves quality of synthesized nano-size TiO₂ below 10 nm. These results have been confirmed by both the direct size measurement using TEM images and indirect determination using XRD peaks. The collected samples are further analyzed using UV–Vis spectroscopy to identify the particle size-dependent photoreactivity and to confirm the effectiveness of microwave-assisting under neutral conditions. DSC is also a powerful tool to identify the crystalline transition of TiO₂.     

Generation of single-crystalline domain in nano-scale silicon pillars by near-field short pulsed laser

We observe laser-induced grain morphology change in silicon nanopillars under a transmission electron microscopy (TEM) environment. We couple the TEM with a near-field scanning optical microscopy pulsed laser processing system. This novel combination enables immediate scrutiny on the grain morphologies that the pulsed laser irradiation produces. We find unusual transformation of the tip of the amorphous or polycrystalline silicon pillar into a single crystalline domain via melt-mediated crystallization. On the basis of the three-dimensional finite difference simulation result and the dark field TEM data, we propose that the creation of the distinct single crystalline tip originates from the dominant grain growth initiated at the apex of the non-planar liquid–solid interface. Our microscopic observation provides a fundamental basis for laser-induced conversion of amorphous nanostructures into coarse-grained crystals.     

Monte Carlo simulations of down-scattered neutron and knock-on deuteron spectra in deuterium-tritium capsule implosions

A Monte Carlo particle tracking (MCPT) code has been developed and coupled to hydrodynamic simulations to generate and track primary and scattered neutrons in addition to scattered charged particles by post-processing. This code uses one dimensional (1-D) deuterium-tritium implosion profiles, and the computed down-scattered neutron and knock-on deuteron spectra are analyzed for different areal densities. The mixing effects on the spectra of down-scattered neutron and knock-on deuteron are also investigated. The implementation of the numerical scheme is analyzed, and the particle splitting technique is adopted, which is proven to efficiently reduce computational effort.     

An inverse problem for Maxwell's equations in isotropic and non-stationary media

In this article, we consider Maxwell's equations in an isotropic, inhomogeneous and non-stationary medium. We discuss an inverse problem of determining the t-independent components of the coefficients ?, μ in the constitutive relations from a finite number of interior measurements. We prove a Lipschitz stability estimate for the inverse problem by applying the argument on the basis of Carleman estimate.     

The Electronic Absorption Spectra of Binuclear Complexes,[Cu(o-phen) (sal)No3 and [Cu2 (sacch)4(im)4] Crystal

The electronic absorption spectra of crystals of the title componds were recorded and the experimental results were explained quantitatively with the ligand field theory and the radial wave function of bound Cu(II) cation. With these spactra, the range of magnetic interactions between two Cu(II) ions of the title compounds are discussed.