Aryne‐Induced Novel Tandem 1,2‐Addition/(3+2) Cycloaddition to Generate Imidazolidines and Pyrrolidines

A new “single‐flask” method was developed for the synthesis of imidazolidines and pyrrolidines with high stereoselectivity. First, a Schiff base was arylated with an aryne. Second, an intramolecular proton transfer took place from the methylene position to the anionic aryne ring. Third, the resultant ylide reacted with a second equivalent of the same Schiff base in situ or an electron‐deficient alkene through a (3+2) cycloaddition. These sequential tandem 1,2‐addition/(3+2) cycloaddition reactions led to the desired heterocycles in 63–88 % yields.     

ZnO‐Coated Carbon Nanotubes: Inter‐Diffusion of Carboxyl Groups and Enhanced Photocurrent Generation

ZnO is a defect‐governed oxide and emits light at both visible and UV regimes. This work employs atomic layer deposition to produce oxide particles on oxygenated carbon nanotubes, and the composites only show emission profiles at short wavelengths. The quenching of defect‐related emissions at long wavelengths is verified, owing to carboxyl diffusion into oxygen vacancies, and doping is supported by ZnCO₃ formation in oxide lattice. Fully coated tubes display an increased photocurrent and the quantum efficiency increases by 22 % relative to the bare nanotubes.     

Silver‐Assisted Chemical Etching on Silicon with Polyvinylpyrrolidone‐Mediated Formation of Silver Dendrites

Metal‐assisted chemical etching (MaCE) on silicon (Si)—mediated by polyvinylpyrrolidone (PVP)—is systematically investigated herein. It is found that the morphologies and crystallographic natures of the grown silver (Ag) dendrites can be significantly modulated, with the presence of PVP in the MaCE process leading to the formation of faceted Ag dendrites preferentially along the (111) crystallographic phase, rather than along the (200) phase. Further explorations of the PVP‐mediated effect on Si etching are also revealed. In contrast to the aligned Si nanowires formed by MaCE without PVP addition, only distributed nanopores with sizes of 200 to 400 nm appear on the Si surfaces in the presence of PVP. The origin of surface polishing on Si in the PVP‐mediated MaCE process can be attributed to the distinct transport pathway of holes supplied by the Ag⁺ ions, where the holes are injected directly into the primary Ag seeds, rather than through Ag dendrites, thus leading to the isotropic etching of the Si surface.     

Structural Studies and Anticancer Activity of a Novel Class of β‐Peptides

Functionalized oligomeric organic compounds with well‐defined β‐proline scaffold have been synthesized by a cycloadditive oligomerization approach in racemic and enantiopure forms. The structure of the novel β‐peptides was investigated by NMR spectroscopic and X‐ray methods determining the conformational shapes of the β‐proline oligomers in solution and solid states. The main structural elements subject to conformational switches are β‐peptide bonds between 5‐arylpyrrolidine‐2‐carboxylic acid units existing in Z/E configurations. The whole library of short β‐peptides and intermediate acrylamides has been tested on antiproliferative activity towards the hormone‐refractory prostate cancer cell line PC‐3 revealing several oligomeric compounds with low micromolar and submicromolar activities. Bromine‐substituted dimeric and trimeric acrylamides induced caspase‐dependent apoptosis of PC‐3 cells through cell‐cycle arrest and mitochondrial damage.     

The effect of disulfide bonds on protein folding,unfolding, and misfolding investigated by FT–Raman spectroscopy

Disulfide bond is relevant to many protein folding/unfolding functions and conformational diseases. To elucidate the effects of disulfide bonds on protein folding, unfolding, and misfolding, we performed Fourier transform–Raman measurements on serial chemical‐induced denaturations of bovine serum albumin (BSA). By directly monitoring Raman stretching at S–S (~507 cm⁻¹), S–H (~2566 cm⁻¹), amide I (1655 cm⁻¹ for α‐helix; 1667 cm⁻¹ for β‐sheet structure), and amide III (>1300 cm⁻¹ for α‐helix; 1246 cm⁻¹ for β‐sheet structure), the status of disulfide bonds and secondary structure of BSA at different states were elucidated. Both disulfide bonds and secondary structure (mostly in α‐helix) of BSA appeared relatively stable even when the protein was unfolded by urea solution. However, disulfide bonds were completely reduced and protein secondary structure changed from α‐helix to a relatively β‐sheet dominant when the protein was modified by the mixed solution of urea and dithiothreitol (urea/DTT). Adhering to these structural changes, the protein proceeded to different degrees of polymerization. BSA would aggregate into a high molecular mass (over 700 kDa) of protein ensemble when it was exposed to the mixed urea/DTT solution. An irreversible change in S–S/S–H conversion and secondary structure was responsible for protein misfolding. We demonstrate here that Fourier transform–Raman directly probe S–S/S–H conversion and secondary structural change of BSA at different states, and these results clearly indicate that disulfide bonds and secondary structure of BSA serve as concrete frameworks to stabilize protein structure. As the frameworks collapse, the protein undergoes an irreversible structural change and results in protein misfolding. Copyright © 2016 John Wiley & Sons, Ltd.     

Two‐dimensional reactive scattering with transmitted quantum trajectories

A simple and easy‐to‐implement method is presented for the study of time‐dependent reaction dynamics by propagating an ensemble of transmitted quantum trajectories. During the trajectory evolution, reflected trajectories are gradually removed and all the remaining trajectories represent the transmitted subensemble. The removal process of reflected trajectories avoids numerical instabilities arising from node formation in the reactant region, and allows stable long‐time propagation of transmitted trajectories. This method is applied to a two‐dimensional model chemical reaction. Excellent computational results are obtained for the time‐dependent reaction probabilities evaluated by the time integration of the probability flux. © 2014 Wiley Periodicals, Inc.     

Local Semicircle Law for Random Regular Graphs

We consider random d‐regular graphs on N vertices, with degree d at least (log N)⁴. We prove that the Green's function of the adjacency matrix and the Stieltjes transform of its empirical spectral measure are well approximated by Wigner's semicircle law, down to the optimal scale given by the typical eigenvalue spacing (up to a logarithmic correction). Aside from well‐known consequences for the local eigenvalue distribution, this result implies the complete (isotropic) delocalization of all eigenvectors and a probabilistic version of quantum unique ergodicity.© 2017 Wiley Periodicals, Inc.     

Nonlinear bending of rectangular orthotropic plate with two free edges and the other edges having nonuniform rotational flexibility

this paper presents a series solution to von Kármán nonlinear equations of a rectilinearly orthotropic rectangular plate under the combined action of lateral load and in-plane tension with the titled edge restraints. In the formulation the edge moments are replaced by an equivalent pressure near the edges. Using generalized double Fourier series for the deflection and stress function, governing equations are reduced to an infinite set of algebraic equations for coefficients in these series. Numerical results for deflections, bending moments and in-plane forces are graphically presented for various values of aspect ratio and material properties and for different edge conditions.     

Postbuckling of angle-ply and anisotropic plates

Summary An analysis based on the von Kármán-type large-deflection equations of plates is presented for the postbuckling behavior of homogeneous and symmetrically laminated anisotropic rectangular plates. Boundary conditions for both simply supported and clamped edges are considered. A solution is obtained by expressing the force function and transverse deflection as double series involving the appropriate beam eigen-functions. Numerical results are presented for graphite-epoxy angle-ply laminates and homogeneous anisotropic plates. In the cases of buckling of anisotropic plates and postbuckling of isotropic and orthotropic plates, the present solution is in good agreement with existing solutions.

---

Übersicht Es wird das Nachbeulverhalten von homogenen, symmetrisch geschichteten, anisotropen Rechteckplatten auf der Grundlage der von Kármán angegebenen Platten-Gleichungen für große Auslenkungen untersucht. Dabei werden sowohl einfach aufliegende, wie auch eingespannte Ränder als Randbedingungen berücksichtigt. Lösungen werden dadurch gewonnen, daß die Belastungsfunktion und die Querauslenkung als doppelte Reihen von geeigneten Balken-Eigenfunktionen angesetzt werden. Für Graphit-Epoxid-Schichtplatten und anisotrope homogene Platten werden numerische Ergebnisse mitgeteilt. Die erhaltenen Lösungen stimmen in den Fällen des Beulens von anisotropen Platten sowie des Nachbeulens von isotropen und orthotropen Platten gut mit bekannten Lösungen überein.

---

---

The results presented in this paper were obtained in the course of research sponsored by the National Research Council of Canada.     

IR,Raman, and Surface‐enhanced Raman Spectroscopic Study on Triruthenium Dipyridylamide Diruthenium Nickel Dipyridylamide Family: Metal‐metal Bonding and Structures

We report the infrared, Raman, and surface‐enhanced Raman scattering (SERS) spectra of triruthenium dipyridylamido complexes and of diruthenium mixed nickel metal‐string complexes. From the results of analysis on the vibrational modes, we assigned their vibrational frequencies and structures. The infrared band at 323–326 cm^?1 is assigned to the Ru₃ asymmetric stretching mode for [Ru₃(dpa)₄Cl₂]^0–2+. In these complexes we observed no Raman band corresponding to the Ru₃ symmetric stretching mode although this mode is expected to have substantial Raman intensity. There is no frequency shift in the Ru₃ asymmetric stretching modes for the complexes with varied oxidational states. No splitting in Raman spectra for the pyridyl breathing line indicates similar bonding environment for both pyridyls in dpa^– , thus a delocalized structure in the [Ru₃]^6–8+ unit is proposed. For Ru₃(dpa)₄(CN)₂ complex series, we assign the infrared band at 302 cm^?1 to the Ru₃ asymmetric stretching mode and the weak Raman line at 285 cm^?1 to the Ru₃ symmetric stretching. Coordination to the strong axial ligand CN^– weakens the Ru‐Ru bonding. For the diruthenium nickel complex [Ru₂Ni(dpa)₄Cl₂]^0–1+, the diruthenium stretching mode ν_Ru‐Ru is assigned to the intense band at 327 and 333 cm^?1 in the Raman spectra for the neutral and oxidized forms, respectively. This implies a strong Ru‐Ru metal‐metal bonding.