Lithium storage mechanisms and effect of partial cobalt substitution in manganese carbonate electrodes

A promising group of inorganic salts recently emerged for the negative electrode of advanced lithium-ion batteries. Manganese carbonate combines low weight and significant lithium storage properties. Electron paramagnetic resonance (EPR) and magnetic measurements are used to study the environment of manganese ions during cycling in lithium test cells. To observe reversible lithium storage into manganese carbonate, preparation by a reverse micelles method is used. The resulting nanostructuration favors a capacitive lithium storage mechanism in manganese carbonate with good rate performance. Partial substitution of cobalt by manganese improves cycling efficiency at high rates.     

On the Stability of Stationary Wave Maps}

Equivariant wave maps from into have smooth, stationary solutions which are critical points of the energy subject to constant charge. These solutions are globally stable under equivariant perturbations. Consequently, there exists a large set of initial data, with no degree or energy restrictions, for which the Cauchy problem is globally well-posed. Received:     

Conductance of metallic single-wall nanotubes with single magnetic impurities

Using a model of conducting cylinder with a few number of impurities on its surface, we investigate the effects of magnetic impurity scattering on the conductance of metallic single-wall carbon nanotubes. The nonlinear part of conductance, which is due to the interaction of conduction electrons with impurities, is obtained. The signature of Kondo anomaly is found in the nonlinear conductance and it is shown that its amplitude strongly depends on the position of impurities and diameter of nanotube.     

Solvent and substitution effects on the structure and properties of a half-sandwich complex of vanadium with a terminal borylene ligand: Theoretical study

The structures and properties of a terminal borylene vanadium complexes CpV(CO)₃(BNH₂) were explored using theoretical methods. The density of states (DOS) was beneficially used to analyze the main features of electronic structure. The influence of solvent on the structural parameters, frontier orbital energies and wavelength absorption maxima (λ_max) of this structure was studied. These calculations were performed in different solvents, i.e. cyclohexane, dichloromethane, tetrahydrofuran, chlorobenzene, and chloroform, utilizing the self-consistent reaction field (SCRF) theory. Also, substituent effect in CpV(CO)₃(BNR₂) complexes on the structure and properties was investigated.     

An optimized preparation of bismaleimide–diamine co‐polymer matrices

The main aim of this study was to develop an improved method for the preparation of a bismaleimide–diamine (BMI/DDM) polymer matrix, achieving shorter curing time, longer processing time (pot life), and good thermal mechanical properties. A matrix of BMI/DDM thermoset was prepared at optimal conditions and formulation, containing BMI and DDM in a 2:1 mol ratio with 0.1 wt% of dicumyl peroxide (DCP) as the curing accelerator. An optimal temperature of 150°C was selected for both melt‐mixing and curing processes. The mechanism of matrix preparation was also investigated using differential scanning calorimetry and quantitative Fourier transformed infrared analysis. DCP at the optimal concentration was found to accelerate cross‐linking reactions between BMI and DDM without inhibiting the chain‐extension reaction of BMI. The specified formulation exhibited longer gel time (208 s/g) and shorter post‐curing time (2 h) compared to other formulations. In addition, thermomechanical behavior and thermal stability were analyzed by dynamic mechanical analysis and thermomechanical analysis, and thermogravimetric analysis, respectively. The storage modulus (E′), glass transition temperature (T_g), and decomposition temperature (T_d) of the BMI/DDM thermosets increased with the BMI content of the formulations, while the coefficient of thermal expansion and damping behavior (tan δ) decreased in a similar manner, primarily because of an increase in the degree of cross‐linking. Copyright © 2014 John Wiley & Sons, Ltd.     

Weighted sub-Bergman Hilbert spaces in the unit disk

We study sub-Bergman Hilbert spaces in the weighted Bergman space A _α ². We generalize the results already obtained by Kehe Zhu for the standard Bergman space A ².     

Modules Whose t-Closed Submodules Have a Summand as a Complement

We define and investigate T ₁₁-type modules as a generalization of t-extending modules, and modules satisfying C ₁₁ condition. A module M is said to be T ₁₁-type if every t-closed submodule of M has a complement which is a direct summand. Direct sums of T ₁₁-type modules inherit the property. Some equivalent conditions for a module M to be T ₁₁-type are given. We characterize a module M for which every direct summand satisfies T ₁₁ condition. If R _R is T ₁₁-type, then R/Z ₂(R _R ) is a C ₂ ring if and only if it is a von Neumann regular ring. Applying this result, we characterize a right t-extending (resp., finitely Σ-t-extending, or Σ-t-extending) ring R for which R/Z ₂(R _R ) is von Neumann regular.     

Semi-quantitative trace analysis of nuclear fast red by surface enhanced resonance Raman scattering

The dye nuclear fast red has been detected and determined semi-quantitatively by means of surface enhanced resonance Raman scattering (SERRS) and surface enhanced Raman scattering (SERS), using laser exciting wavelengths of 514.5 and 632.8 nm, respectively, by employing a citrate-reduced silver colloid. A good linear correlation is observed for the dependence of the intensities of the SERRS bands at 989 cm⁻¹ (R=0.9897) and 1278 cm⁻¹ (R=0.9872) on dye concentration over the range 10⁻⁹ to 10⁻⁷ M, when using an exciting wavelength of 514.5 nm. At dye concentrations above 10⁻⁷ M, the concentration dependence of the SERRS signals is non-linear. This is almost certainly due to the coverage of the colloidal silver particles being in excess of a full monolayer of the dye. A linear correlation is also observed for the dependence of the intensities of the SERS bands at 989 cm⁻¹ (R=0.9739) and 1278 cm⁻¹ (R=0.9838) on the dye concentration over the range 10⁻⁸ to 10⁻⁶ M when using an exciting wavelength of 632.8 nm. Strong fluorescence prevented collection of resonance Raman scattering (RRS) spectra from powdered samples or aqueous solutions of the dye using an exciting wavelength of 514.5 nm, but weak bands were observed in the spectra obtained from both powdered and aqueous samples of the dye using an exciting wavelength of 632.8 nm. A study of the pH dependence of SERRS/SERS and UV–VIS absorption spectra revealed the presence of different ionisation states of the dye. The limits of detection for nuclear fast red by SERRS (514.5 nm), SERS (632.8 nm) and visible spectroscopy (535 nm) are 9, 89 and 1000 ng ml⁻¹, respectively.     

Water desalination across functionalized silicon carbide nanosheet membranes: insights from molecular simulations

Desalination of seawater can be an effective way to access drinking water. In this study, the performance of functionalized silicon carbide nanosheet (SiCNS) membranes for water desalination was investigated using molecular dynamics (MD) simulations. For this purpose, four types of membranes with various functionalized pores were considered to investigate their capabilities in water desalination. The chemical functions of fluorine (–F) (system S1), hydrogen (–H) (systems S2 and S3), and hydrogen (–H) and hydroxyl (–OH) (system S4) were bonded to the pore edge of the SiCNS membranes. Also, the effect of the number of pores in the membrane on the water permeability was studied between systems S2 and S3. The SiCNS membrane was placed at the center of the simulation box and the external pressure was applied to the system in the range of 10–100 MPa. The water permeability, salt rejection, potential of mean force of ions, water density, water density map, and radial distribution function (RDF) of water molecules were calculated in this work. The results demonstrated that the water permeability increases by adding hydrophilic chemical functions such as –F and –OH on the pore edge.