Conformation‐Specific Circular Dichroism Spectroscopy of Cold,Isolated Chiral Molecules

The CD spectroscopy of a chiral compound in solution yields an average CD value derived from all of the conformations of a chiral molecule. By contrast, CD spectroscopy of cold chiral molecules in the gas phase distinguishes specific conformers of a chiral molecule, but the weak CD effect has limited the practical application of this technique. Reported herein is the first resonant two‐photon ionization CD spectra of ephedrines in a supersonic jet using circularly polarized laser pulses, which were generated by synchronizing the oscillation of the photoelastic modulator with the laser firing. The spectra exhibited well‐resolved CD bands which were specific for the conformations and vibrational modes of each enantiomer. The CD signs and magnitudes of the jet‐cooled chiral molecules were very sensitive to their conformations and thus offered crucial information for determining the three‐dimensional structures of chiral species, as conducted in combination with quantum chemical calculations.     

Stretchable and transparent hydrogels as soft conductors for dielectric elastomer actuators

A soft ionic conductor can serve as an artificial nerve in an artificial muscle. A polyacrylamide hydrogel is synthesized containing a hygroscopic salt, lithium chloride. Two layers of the hydrogel are used as ionic conductors to sandwich a dielectric elastomer and fabricate a highly stretchable and transparent actuator. When the two layers of the hydrogels are subject to a voltage, the actuator reduces its thickness and expands. An areal strain of 134% is demonstrated. The voltage‐strain curves are calculated by using a model that accounts for the elastic constraint of the hydrogel and the inhomogeneous deformation of the actuator. For actuators fabricated with the hydrogel of various thicknesses and with the dielectric elastomer of various prestretches, excellent agreements are found between experimental data and theoretical predictions. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1055–1060     

Iterative second-order derivative-based deinterlacing algorithm

In this paper, we introduce an iterative second-order derivative-based intra-field deinterlacing algorithm (ISDD). The proposed ISDD is composed of two steps: (1) preprocessing by a fast second-order derivative-based deinterlacing algorithm (FSDD), (2) iteratively refining the interpolated pixel by minimizing a mass second-order function. The function includes three components: the derivative difference, directional derivative, and isophote smoothing. The derivative difference is used to detect any intensity discontinuity in an image; the directional derivative is a supplement to the derivative difference to avoid oversmoothing; and isophote smoothing can reduce artifacts. The proposed ISDD can preserve image features and reduce the artifacts caused by conventional deinterlacing methods. Compared with existing deinterlacing algorithms, the proposed algorithm improves the peak signal-to-noise ratio while maintaining high efficiency.     

A study of atypical grain growth properties for SnO2 thin films

SnO₂ thin films were grown on Si substrate using the chemical vapor deposition(CVD) method. The surface of the thin film was examined using a transmission electron microscope (TEM) and a scanning electron microscope (SEM). Atypical shaped grains and atypical columnar structures were observed on the SnO₂ thin films that were exposed to air after first deposition and during re-deposition in anaerobic conditions in the CVD. The electrical properties of SnO₂ thin films feature a lower range of resistance in single mode, but after the atypical particles appear, the electrical resistance decreased.     

Supported copper triflate as an efficient catalytic system for the synthesis of highly functionalized 2-naphthol Mannich bases under solvent free condition

Various heterogeneous catalysts (Lewis acid) have been prepared and screened for the synthesis of Betti bases in an attempt to reduce the environmental hazards associated with the conventional homogeneous Lewis acid system. And we found especially Cu(OTf)₂·SiO₂ catalyzes the three-component coupling of aldehyde, 2-naphthol, and alicyclic amine to generate Betti base with high efficiency under neat conditions without additional co-catalyst or additive in air. The reaction is not sensitive to water and occurs smoothly in water as well.