Atomically Local Electric Field Induced Interface Water Reorientation for Alkaline Hydrogen Evolution Reaction

The slow water dissociation process in alkaline electrolyte severely limits the kinetics of HER. The orientation of H₂O is well known to affect the dissociation process, but H₂O orientation is hard to control because of its random distribution. Herein, an atomically asymmetric local electric field was designed by IrRu dizygotic single-atom sites (IrRu DSACs) to tune the H₂O adsorption configuration and orientation, thus optimizing its dissociation process. The electric field intensity of IrRu DSACs is over 4.00×10¹⁰ N/C. The ab initio molecular dynamics simulations combined with in situ Raman spectroscopy analysis on the adsorption behavior of H₂O show that the M−H bond length (M=active site) is shortened at the interface due to the strong local electric field gradient and the optimized water orientation promotes the dissociation process of interfacial water. This work provides a new way to explore the role of single atomic sites in alkaline hydrogen evolution reaction.     

Probing the weak interactions between amino acids and carbon monoxide

The relatively weak interactions between some non-charged amino acids with CO were investigated theoretically by using density functional theory （DFT） method. The stretching frequency of CO correlates well with its bond length followed the Badger＇s rule, and the correlation between binding energy and Mulliken charge partition of CO was also investigated for the first time. 2007 Ying Wu Lin. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Sequential anisotropic Wiener filtering applied to 3D MRI data

We present three different sequential Wiener filters, namely, isotropic, orientation and anisotropic. The first one is similar to the classical Wiener filter in the sense that it uses an isotropic neighborhood to estimate its parameters. Here we present a sequential version of it. The orientation Wiener filter uses oriented neighborhoods to estimate the structure orientation present at each voxel, giving rise to a modified estimator of the parameters. Finally, the anisotropic Wiener filter combines both approaches adaptively so that the appropriate approach is locally selected. Several synthetic experiments are presented showing the performance of the filters with respect to their parameters. A mean square error analysis is performed using a publicly available magnetic resonance imaging (MRI) brain phantom and a comparison with other filtering approaches is carried out. In addition, results from filtering real MRI data are presented.     

On the combinatorics of an origami model

We consider the problem of how the assembly process of an origami model, made up of similar pieces, can be completed given that at each step there are several choices. A result is given in the language of graphs that provides a sufficient condition under which assembly of the model will never fail.     

Development of orientation during electrospinning of fibres of poly(ε-caprolactone)

We explore the influence of a rotating collector on the internal structure of poly(ε-caprolactone) fibres electrospun from a solution in dichloroethane. We find that above a threshold collector speed, the mean fibre diameter reduces as the speed increases and the fibres are further extended. Small-angle and wide-angle X-ray scattering techniques show a preferred orientation of the lamellar crystals normal to the fibre axis which increases with collector speed to a maximum and then reduces. We have separated out the processes of fibre alignment on the collector and the orientation of crystals within the fibres. There are several stages to this behaviour which correspond to the situations (a) where the collector speed is slower than the fibre spinning rate, (b) the fibre is mechanically extended by the rotating collector and (c) where the deformation leads to fibre fracture. The mechanical deformation leads to a development of preferred orientation with extension which is similar to the prediction of the pseudo-affine deformation model and suggests that the deformation takes place during the spinning process after the crystals have formed.     

Orientation of adsorbed molecules under the influence of electric fields

The dynamic orientation of vertically adsorbed polar molecules is investigated by switching on electric fields. The rotational properties of molecules are modulated by the electric field and the conical well. The orientation reveals multiple pronounced oscillations, depending on the specific field parameters. The range of oscillation is enhanced even in the presence of conical-well confinement. Furthermore, population concentration and inversion cyclically occur in the system, corresponding to distinctive molecular orientations. Specific field-free orientation is also obtained by turning off the field. The population can be concentrated or reversed for a long time. The thermal effect on the properties of orientation is analysed in detail.     

Orientation Imaging in Scanning Electron and Transmission Electron Microscopy for Characterization of the Shear Banding Phenomenon

The texture evolution during deformation of high purity fcc single crystals with initial (112) [11 ] orientation has been characterised in detail by transmission (TEM) and scanning (SEM–FEG) electron microscopes. The channel-die deformed samples up to reduction of about 1–1.5, first developing strongly anisotropic layers of elongated cells or twin-matrix plates and then compact clusters of SB. Substantial progress in understanding the mechanism of the SB formation was possible thanks to systematic local orientation measurements (orientation mapping) using SEM and TEM. These two techniques of local orientation measurements have been compared with respect to their applicability for the study of shear banding phenomenon and for characterization of the specific nanostructure of SB in metals with fcc lattice. It was shown that well-developed SB exhibit large orientation spreads up to 35–40° with respect to the adjacent areas outside the band. Most of these misorientations occur by rotations about the TD‖〈110〉 axis with significant further rotations about 〈112〉 poles. This ultimately leads to the formation of the texture components whose occurrence cannot be explained by models homogeneous deformation.     

Orientation-controlled synthesis and magnetism of single crystalline Co nanowires

Orientation control and the magnetic properties of single crystalline Co nanowires fabricated by electrodeposition have been systematically investigated. It is found that the orientation of Co nanowires can be effectively controlled by varying either the current density or the pore diameter of AAO templates. Lower current density or small diameter is favorable for forming the (1 0 0) texture, while higher current values or larger diameter leads to the emergence and enhancement of (1 1 0) texture of Co nanowires. The mechanism for the manipulated growth characterization is discussed in detail. The orientation of Co nanowires has a significant influence on the magnetic properties, resulting from the competition between the magneto-crystalline and shape anisotropy of Co nanowires. This work offers a simple method to manipulate the orientation and magnetic properties of nanowires for future applications.     

Torsion formulas for signed graphs

Following our recent exposition on the algebraic foundations of signed graphs, we introduce bond (circuit) basis matrices for the tension (flow) lattices of signed graphs, and compute the torsions of such matrices and Laplacians. We present closed formulas for the torsions of the incidence matrix, the Laplacian, bond basis matrices, and circuit basis matrices. These formulas show that the torsions of all such matrices are powers of 2, and so imply that the matroids of signed graphs are representable over any field of characteristic not 2. A notable feature of using torsion is that the Matrix-Tree formula for ordinary graphs and Zaslavsky’s formula for unbalanced signed graphs are unified into one Matrix-Basis formula in terms of the torsion of its Laplacian matrix, rather than in terms of its determinant, which vanishes for an ordinary graph unless one row is deleted from the incidence matrix.