Modeling gas permeation through membranes by kinetic Monte Carlo: applications to H2, O2, and N2 in hydrated Nafion®

We present a simulation tool in order to predict gas permeation through heterogeneous, microphase separated structures. The method combines dissipative particle dynamics (DPD) with kinetic Monte Carlo (KMC). Morphologies obtained from DPD are mapped onto a high density grid on which gas diffusion takes place. Required input parameters for the KMC calculations are the gas solubility and gas diffusion constant within each of the pure phase components. Our method was tested and validated for permeation of H(2), O(2), and N(2) gasses through hydrated Nafion membranes at various temperatures and water contents. We predict that membranes that contain an equal volume fraction of water, those with the highest ion exchange capacity exhibit the largest N(2) and O(2) permeation rates. For membranes of the same ion exchange capacity the H(2), O(2), and N(2) and permeability increases approximately linearly with Bragg spacing. We also predict that O(2) gas permeation depends much more on bottleneck phenomena within the phase separated morphologies than H(2) gas permeation. Overall, the calculated H(2) and O(2) permeability is found to be slightly lower than experimental values. This is attributed to the robustness of DPD resulting in ～7% larger Bragg spacing as compared with experiment and∕or increased gas solubility within the polymer phase with water uptake.     

Chemical trend of Ln-M exchange couplings in heterometallic complexes with Ln = Gd, Tb, Dy, Ho, Er and M = Cu, V

The 4f-3d exchange couplings were definitively and precisely determined in the dinuclear complexes (Ln-M) involving double μ-oxo-bridges, by means of combined high-frequency electron paramagnetic resonance and pulsed-field magnetization techniques, revealing a monotonic decrease of ferromagnetic J(Ln-Cu) in the order of the atomic number, (64)Gd to (68)Er.     

Control of dynamics and molecular distribution in a self-spreading lipid bilayer using surface-modified metal nanoarchitectures

The molecular distribution and spreading dynamics of self-spreading lipid bilayers can be tuned by surface-modified metallic nanoarchitectures. Interactions between lipids and molecules in the surface modification alter the self-spreading behavior at the gate regions between adjacent nanoarchitectures, leading to molecular filtering/concentrating effects and modification of the dynamics. The hydrophilic surface can tune the spreading velocity without changing the molecular distribution in the spreading bilayer, whereas the hydrophobic surface provides a molecular concentrating function to the nanogates. This indicates that a combination of unmodified/hydrophobic/hydrophilic nanoarchitectures has a wide range of potential applications since it can be used to independently control the self-spreading dynamics and the molecular distribution.     

Derivation of the representations of BRS algebra in the Landau gauge by superspace formalism

The derivation of the representations of BRS algebra in the Landau gauge is simplified by the superspace formalism. It is shown that the operation of the metric matrix can be interpreted as a kind of inversion of the superspace.     

Behaviour of rhodamine B in aqueous LiCl solution

Absorption, pH and electric conductance of rhodamine BLiClH₂O solutions are examined. The obtained results show that aqueous rhodamine B has a tendency to dimerize by the addition of LiCl. Other features on the structural properties of rhodamine B in aqueous LiCl solutions are discussed briefly.     

Observation of pentads in deuterated polyacrylonitrile by NMR spectroscopy

The deuterium-decoupled methine proton spectra of polyacrylonitrile-β,β-d₂ were measured at 156°C in dimethylsulfoxide-d₆ solution. Splittings of triad peaks caused by pentad sequences were observed. The isotactic triad resonance was resolved into three peaks and the heterotactic resonance into two peaks, while the syndiotactic resonance was unresolved or resolved into three peaks. The splittings were assigned by comparing the probability of each pentad sequence with observed intensities. The pentad signal shifted to the higher magnetic field with increasing number of meso configurations as neighbors of the central triad. It was observed that the pentad of atactic polyacrylonitrile-β,β-d₂ obeyed Bernoullian statistics but that of isotactic polymer obtained by γ-ray irradiation of the canal complex seemingly obeyed first-order Markov statistics.     

Study on the single crystal growth of concentration gradient Ce:YAP rod and the dopant concentration dependence on the scintillation properties

Micro-pulling down (μ-PD) method allows to prepare single crystals quickly and relatively inexpensively. Since it is a melt growth and taking into account segregation phenomena, the μ-PD method allows also to obtain single crystals characterized by dopant concentration gradients. Especially, taking the advantage of the grown crystal high aspect ratio, it allows to prepare crystalline samples with variable and wide range concentrations of dopants. These samples can help in understanding the correlation between dopant concentration and luminescence properties.