Vibrational spectroscopy at electrolyte/electrode interfaces with graphene gratings.

Microscopic understanding of physical and electrochemical processes at electrolyte/electrode interfaces is critical for applications ranging from batteries, fuel cells to electrocatalysis. However, probing such buried interfacial processes is experimentally challenging. Infrared spectroscopy is sensitive to molecule vibrational signatures, yet to approach the interface three stringent requirements have to be met: interface specificity, sub-monolayer molecular detection sensitivity, and electrochemically stable and infrared transparent electrodes. Here we show that transparent graphene gratings electrode provide an attractive platform for vibrational spectroscopy at the electrolyte/electrode interfaces: infrared diffraction from graphene gratings offers enhanced detection sensitivity and interface specificity. We demonstrate the vibrational spectroscopy of methylene group of adsorbed sub-monolayer cetrimonium bromide molecules and reveal a reversible field-induced electrochemical deposition of cetrimonium bromide on the electrode controlled by the bias voltage. Such vibrational spectroscopy with graphene gratings is promising for real time and in situ monitoring of different chemical species at the electrolyte/electrode interfaces

Dynamical tunneling-assisted coupling of high-Q deformed microcavities using a free-space beam

We investigate the efficient free-space excitation of high-Q resonance modes in deformed microcavities via dynamical tunneling-assisted coupling. A quantum scattering theory is employed to study the free-space transmission properties, and it is found that the transmission includes the contribution from (1) the off-resonance background and (2) the on-resonance modulation, corresponding to the absence and presence of high-Q modes, respectively. The theory predicts asymmetric Fano-like resonances around high-Q modes in background transmission spectra, which are in good agreement with our recent experimental results. Dynamical tunneling across Kolmogorov-Arnold-Moser tori, which plays an essential role in the Fano-like resonance, is further studied. This efficient free-space coupling holds potential advantages to simplify experimental conditions and excite high-Q modes in higher-index-material microcavities

6-Chloro-N 4-methyl-N 4-phenyl­pyrimidine-4,5-diamine

In the title compound, C11H11ClN4, the dihedral angle between the aromatic rings is 66.47 (8)°. In the crystal, mol­ecules are linked by N—H⋯N hydrogen bonds, generating C(5) chains propagating in [010]. Slipped aromatic π–π stacking between centrosymmetrically related pairs of pyrim­idine rings also occurs [centroid–centroid separation = 3.7634 (12)Å and slippage = 1.715 Å]

6-Chloro-N-methyl-5-nitro-N-phenyl­pyrimidin-4-amine

In the title compound, C11H9ClN4O2, the dihedral angle between the aromatic rings is 79.67 (8)°. π–π stacking between centrosymmetrically related pairs of pyrimidine rings occurs along [100] [centroid–centroid separations = 3.4572 (8) and 3.5433 (7) Å]

(11-Methyl­pyrido[2,3-b][1,4]benzo­diazepin-6-yl)(phen­yl)methanone

In the title compound, C20H15N3O, the diazepine ring adopts a boat conformation. The dihedral angle between pyridine and benzene rings is 55.2 (1)°. The benzoyl phenyl ring forms dihedral angles of 49.4 (1) and 75.9 (1)°, respectively, with the pyridine and benzene rings. In the crystal, mol­ecules are linked into centrosymmetric dimers by pairs of C—H⋯N hydrogen bonds

Research on Chloride Penetration Resistance of Phosphoaluminate Cement Concrete

The chloride penetration resistance of phosphoaluminate cement (PAC) concrete was investigated in this study. The effects of mixture proportioning parameters, including cement content, water–cement ratio (w/c), and superplasticizer content on chloride ion penetration resistance of PAC concrete were investigated by the rapid chloride migration test (RCM). The result shows that the increase of cement content and the decrease of w/c can reduce the coefficient of chloride ion penetration of PAC concrete at a certain range. Moreover, the penetration of chloride ion can be declined effectively when polycarboxylate superplasticizer is employed. The PAC concrete exhibited better chloride penetration resistance compared with normal Portland cement (PC) concrete prepared with the same mixture proportioning parameters. This is due to the fact that the hydration mechanism and the hydration products of PAC concrete are different from that of PC concrete

NdO(NO3)

The title compound, neodymium(III) oxide nitrate, which is isostructural with LaO(NO3), arose from a solvothermal reaction. The Nd ion (site symmetry m) is ten-coordinated by eight O atoms of NO3 groups and two μ2-oxide ions. A three-dimensional structure is constructed by the inter­connection of NdO10 polyhedra. The oxide ion and the N atom and one of the nitrate O atoms possess site symmetry m

Quasi-Local Evolution of the Cosmic Gravitational Clustering in Halo Model

We show that the nonlinear evolution of the cosmic gravitational clustering is approximately spatial local in the $x$-$k$ (position-scale) phase space if the initial perturbations are Gaussian. That is, if viewing the mass field with modes in the phase space, the nonlinear evolution will cause strong coupling among modes with different scale $k$, but at the same spatial area $x$, while the modes at different area $x$ remain uncorrelated, or very weakly correlated. We first study the quasi-local clustering behavior with the halo model, and demonstrate that the quasi-local evolution in the phase space is essentially due to the self-similar and hierarchical features of the cosmic gravitational clustering. The scaling of mass density profile of halos insures that the coupling between $(x-k)$ modes at different physical positions is substantially suppressed. Using high resolution N-body simulation samples in the LCDM model, we justify the quasi-locality with the correlation function between the DWT (discrete wavelet transform) variables of the cosmic mass field. Although the mass field underwent a highly non-linear evolution, and the DWT variables display significantly non-Gaussian features, there are almost no correlations among the DWT variables at different spatial positions. Possible applications of the quasi-locality have been discussed.Comment: AAS Latex file, 33 pages, 7 figures included, accepted for publication in Ap