Effect of Stretching on β-Phase Content of Isotactic Polypropylene Melt Containing β-Nucleating Agent

Pure isotactic polypropylene (iPP) and that containing 0.2 wt% of a β-nucleating agent (β-NA) were extruded through a slit die. Simultaneously, the extruded melt was stretched at the die exit with different stretching rates (SR). The change of β-phase content with different SR was investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The results indicate that, for pure iPP, the content of β-phase first increases with increasing SR till it reaches a maximum and then it gradually decreases. However, for the case of β-nucleated iPP, it decreases monotonously with increasing SR. The spatial confinement is considered as the best explanation for the suppression of β-phase in the nucleated iPP melt upon stretching.     

Chemoselective Borane‐Catalyzed Hydroarylation of 1,3‐Dienes with Phenols

A B(C₆F₅)₃‐catalyzed hydroarylation of a series of 1,3‐dienes with various phenols has been established through a combination of theoretical and experimental investigations, affording structurally diverse ortho‐allyl phenols. DFT calculations show that the reaction proceeds through a borane‐promoted protonation/Friedel–Crafts pathway involving a π‐complex of a carbocation–anion contact ion pair. This protocol features simple and mild reaction conditions, broad functional‐group tolerance, and low catalyst loading. The obtained ortho‐allyl phenols could be further converted into flavan derivatives using B(C₆F₅)₃ with good cis diastereoselectivity. Furthermore, this transformation was applied in the late‐stage modification of pharmaceutical compounds.     

Platinum/Nickel Bicarbonate Heterostructures towards Accelerated Hydrogen Evolution under Alkaline Conditions

Heterostructured nanomaterials, generally have physicochemical properties that differ from those of the individual components, and thus have potential in a wide range of applications. New platinum (Pt)/nickel bicarbonate (Ni(HCO₃)₂) heterostructures are designed for an efficient alkaline hydrogen evolution reaction (HER). Notably, the specific and mass activity of Pt in Pt/Ni(HCO₃)₂ are substantially improved compared to the bare Pt nanoparticles (NPs). The Ni(HCO₃)₂ provides abundant water adsorption/dissociation sites and modulate the electronic structure of Pt, which determine the elementary reaction kinetics of alkaline HER. The Ni(HCO₃)₂ nanoplates offer a platform for the uniform dispersion of Pt NPs, ensuring the maximum exposure of active sites. The results demonstrate that, Ni(HCO₃)₂ is an effective catalyst promoter for alkaline HER.     

Stereoconvergent,Redox‐Neutral Access to Tetrahydroquinoxalines through Relay Epoxide Opening/Amination of Alcohols

We present an economical catalytic procedure to convert readily available 1,2‐diaminobenzenes and terminal epoxides into valuable 1,2,3,4‐tetrahydroquinoxalines in a highly enantioselective fashion. This procedure operates through relay zinc and iridium catalysis, and achieves redox‐neutral and stereoconvergent production of valuable chiral heterocycles from racemic starting materials with water as the only side product. The use of commercially available reagents and catalysts and a convenient procedure also make this catalytic method attractive for practical application.     

Passively mode-locked Nd:LuVO(4) laser with a GaAs wafer

We report on the passive mode locking of a diode-pumped Nd:LuVO(4) laser with a GaAs wafer as output coupler. Using the interference modulation effect of the GaAs wafer, high-power continuous-wave mode locking with a pulse width of about 7.1 ps and an average output power of 3.11 W was achieved. Our result shows that Nd:LuVO(4) could be an excellent gain medium for diode-pumped high-power mode-locked lasers.     

Effects of temperature on performances and hydration process of sulphoaluminate cement-based dual liquid grouting material and its mechanisms

Journal of Thermal Analysis and Calorimetry - In order to find out the rules of the effect of temperature on performances and hydration process of sulphoaluminate cement-based dual liquid grouting...     

Control of a multigroup COVID-19 model with immunity: treatment and test elimination

Nonlinear Dynamics - This paper introduces a multigroup COVID-19 model with immunity, in which the total population of each group is partitioned into five compartments, that is, susceptible,...     

Investigation into stress recovery behavior of shape memory polyurethane fiber

In this work, the stress recovery behavior of shape memory polyurethane (SMPU) fiber was investigated. The as‐spun SMPU fibers were subjected to various programing‐recovery conditions. It was observed that recovering at 100 °C generated higher recovery stress than recovering at 150 °C. It was also found that, while hot‐drawn programed fiber has higher recovery stress than cold‐drawn programed fiber if recovered at 100 °C, cold‐drawn programed fiber has higher stabilized recovery stress than hot‐drawn programed counterpart when recovered at 150 °C. A morphological model was proposed based on the results from differential scanning calorimetry, Fourier transform infrared spectrometry, and X‐ray diffraction to understand the physics behind the different stress recovery behaviors. It is found that SMPU experiences different phase transitions and phase separations under different programing and stress recovery conditions. It is concluded that the two sequential phase separations taking place at 100 and 150 °C are primarily responsible for the differences in the stress recovery behavior. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1429–1440     

The Derivative Nonlinear Schrödinger Equation with Zero/Nonzero Boundary Conditions: Inverse Scattering Transforms and N-Double-Pole Solutions

In this paper, we report a rigorous theory of the inverse scattering transforms (ISTs) for the derivative nonlinear Schrödinger (DNLS) equation with both zero boundary conditions (ZBCs) and nonzero boundary conditions (NZBCs) at infinity and double zeros of analytical scattering coefficients. The scattering theories for both ZBCs and NZBCs are addressed. The direct scattering problem establishes the analyticity, symmetries, and asymptotic behaviors of the Jost solutions and scattering matrix, and properties of discrete spectra. The inverse scattering problems are formulated and solved with the aid of the matrix Riemann–Hilbert problems, and the reconstruction formulae, trace formulae and theta conditions are also posed. In particular, the IST with NZBCs at infinity is proposed by a suitable uniformization variable, which allows the scattering problem to be solved on a standard complex plane instead of a two-sheeted Riemann surface. The reflectionless potentials with double poles for the ZBCs and NZBCs are both carried out explicitly by means of determinants. Some representative semi-rational bright–bright soliton, dark–bright soliton, and breather–breather solutions are examined in detail. These results and idea can also be extended to other types of DNLS equations such as the Chen–Lee–Liu-type DNLS equation, Gerdjikov–Ivanov-type DNLS equation, and Kundu-type DNLS equation and will be useful to further explore and apply the related nonlinear wave phenomena.