Directed C−H Activation and Tandem Cross-Coupling Reactions Using Palladium Nanocatalysts with Controlled Oxidation

Controlled oxidation of palladium nanoparticles provided high-valent Pd^IV oxo-clusters which efficiently promote directed C−H halogenation reactions. In addition, palladium nanoparticles can undergo changes in oxidation states to provide both high-valent Pd^IV and low-valent Pd⁰ species within one system, and thus a tandem reaction of C−H halogenation and cross-coupling (C−N, C−C, and C−S bond formation) was successfully established.     

In‐Depth TEM Investigation on Structural Inhomogeneity within a Primary LixNi0.835Co0.15Al0.015O2 Particle: Origin of Capacity Decay during High‐Rate Discharge

The structural stability of cathode materials during electrochemical reactions, in particular, under high‐rate discharge, is pertinent to the design and development of new electrode materials. This study investigates the structural inhomogeneity that develops within a single LiNi_0.835Co_0.15Al_0.015O₂ (NCA83) particle during a fast discharging process under different cutoff voltages. Some of the NCA83 particles discharged from a high cutoff voltage (4.8 V) developed surface areas in which the layered structure was recovered, although the interiors retained the degraded spinel structure. These micro‐ and nano‐scale structural inversions from high cutoff voltage seem highly correlated with structural evolutions in the initial charged state, and may ultimately degrade the cycling stability. This study advances understanding of the structural inhomogeneity within primary particles during various electrochemical processes and may facilitate the development of new Ni‐rich cathode materials.     

Differentiation Between Hepatocellular Carcinoma and Colorectal Cancer Liver Metastases on High-Resolution Magic Angle Spinning Spectroscopy: Preliminary Study

To explore the potential of high-resolution magic angle spinning (HRMAS) ¹H nuclear magnetic resonance (NMR) spectroscopy for differentiation and metabolite characterization of hepatocellular carcinoma (HCC) and colorectal liver metastases (CRLM), we prospectively included 21 pathologically confirmed malignant hepatic tumors (8 HCC and 13 CRLM) and 26 non-tumorous hepatic parenchyma from 26 patients who underwent hepatic tumor resection. Using intact tissue samples obtained during surgery, HRMAS ¹H NMR spectroscopy was performed at 11.7 T. All observable metabolite signals were acquired using a water-presaturated standard one-dimensional Carr–Purcell–Meiboom–Gill sequence. Metabolomic profiles contributing to the differentiation of HCC and CRLM and of each tumor and non-tumorous hepatic parenchyma were represented by orthogonal partial least squares discriminant analysis (OPLS-DA) and loading plots. Metabolite intensity normalized by total spectral intensities in both tumors was compared using student’s t tests. OPLS-DA and loading plots demonstrated good separation between tumors and non-tumorous hepatic parenchyma. The metabolomic characteristics of HCC showed separation from those of CRLMs according to OPLS-DA. Compared with CRLM, HCC showed significantly elevated levels of glucose (P < 0.01) and sn-Glycero-3-phosphocholine (P < 0.01), and decreased levels of hypoxanthine (P = 0.04). HCC and CRLM could be differentiated by the metabolic profile using HRMAS ¹H NMR spectroscopy.     

Characteristics of light emission from surface plasmons based on rectangular silver gratings

We investigated the characteristics of transmitted light from propagating surface plasmons based on rectangular silver gratings. The results calculated by rigorous coupled-wave analysis presented that silver diffraction gratings can produce significant transmittance and conversion efficiency, comparable to the case of dielectric gratings. Especially, silver gratings optimized at a wide range of grating thickness and period may lead to an improved diffraction efficiency larger than 64%. Moreover, the effect of silver oxide layer on the transmittance was examined and a bimetallic structure with a thin gold coating was introduced to prevent an oxidation of silver substrates. As a practical sensor application, silver grating-based surface plasmon resonance (SPR) configuration showed an enhanced sensitivity associated with an increase of surface reaction area and strong excitations of local plasmon fields, outperforming a conventional thin-film-based SPR structure.     

InGaAsP/InP DH Ridge Waveguide Phase Modulator with High Modulation Efficiency

The P-p-n-N InGaAsP/InP ridge waveguide phase modulator has been fabricated and investigated at a wavelength of 1550nm. The phase modulation efficiency measured by the Fabry-Perot resonance method is as high as 34°/V.mm for TE mode. The QEO effect becomes dominant from -4V to -8V.     

Evidence for viscoelastic effects in surface capillary waves of molten polymer films

The surface dynamics of supported ultrathin polystyrene films with thickness comparable to the radius of gyration were investigated by surface sensitive x-ray photon correlation spectroscopy. We show for the first time that the conventional model of capillary waves on a viscous liquid has to be modified to include the effects of a shear modulus in order to explain both static and dynamic scattering data from ultrathin molten polymer films.     

Conformational preferences and cis-trans isomerization of azaproline residue

The conformational study of N-acetyl-N'-methylamide of azaproline (Ac-azPro-NHMe, the azPro dipeptide) is carried out using ab initio HF and density functional methods with the self-consistent reaction field method to explore the effects of the replacement of the backbone CHalpha group by the nitrogen atom on the conformational preferences and prolyl cis-trans isomerization in the gas phase and in solution (chloroform and water). The incorporation of the Nalpha atom into the prolyl ring results in the different puckering, backbone population, and barriers to prolyl cis-trans isomerization from those of Ac-Pro-NHMe (the Pro dipeptide). In particular, the azPro dipeptide has a dominant backbone conformation D (beta2) with the cis peptide bond preceding the azPro residue in both the gas phase and solution. This may be ascribed to the favorable electrostatic interaction or intramolecular hydrogen bond between the prolyl nitrogen and the amide hydrogen following the azPro residue and to the absence of the unfavorable interactions between electron lone pairs of the acetyl carbonyl oxygen and the prolyl Nalpha. This calculated higher population of the cis peptide bond is consistent with the results from X-ray and NMR experiments. As the solvent polarity increases, the conformations B and B* with the trans peptide bond become more populated and the cis population decreases more, which is opposite to the results for the Pro dipeptide. The conformation B lies between conformations D and A (alpha) and conformation B* is a mirror image of the conformation B on the phi-psi map. The barriers to prolyl cis-trans isomerization for the azPro dipeptide increase with the increase of solvent polarity, and the cis-trans isomerization proceeds through only the clockwise rotation with omega' approximately +120 degrees about the prolyl peptide bond for the azPro dipeptide in the gas phase and in solution, as seen for the Pro dipeptide. The pertinent distance d(N...H-NNHMe) and the pyramidality of imide nitrogen can describe the role of this hydrogen bond in stabilizing the transition state structure and the lower rotational barriers for the azPro dipeptide than those for the Pro dipeptide in the gas phase and in solution.