Preparation and Properties of Some Wood-Plastic Cornbinations Involving Some Tropical Commercial Woods

Radiation-induced wood-polymer composites have been prepared using some tropical commercial woods. These included Kapur (Dryobalanop sp.), Kempas (Koompassia sp.), Red Seraya (Shorea sp.), White Seraya (Parashorea sp.), and Jelutong (Dyera sp.). The wood specimens were modified by impregnation with monomers and followed by exposure to gamma radiation. Monomer systems used were methyl methacrylate, methyl methacrylate with 5% dioxane, acrylonitrile, 60:40 styrene-acrylonitrile comonomer, vinyl acetate, and vinylidene chloride. The resulting composite specimens exhibited significant increases in hardness and compressive strength, the extent of which appeared to depend on the amount and type of polymer present. Dimensional stability increased when the woods were impregnated with polymethyl methacrylate and improved further to about 35% on addition of a swelling agent, dioxane. Wood-polyvinylidene chloride composites gave high fire resistance as opposed to wood-polymethyl methacrylate which showed increased flammability. A 4-fold decrease in weight loss was observed in the fire-tube and crib tests conducted. The impregnated polymers were not totally resistant to termites. The polymers, not being nutrients, reduced the number of survivals after a 90-d test period. Polystyrene-acrylonitrile appeared toxic to the termites.     

Decoupling Combinatorial Complexity: a Two-Step Approach to Distributions of Runs

Methodology and Computing in Applied Probability - Runs statistics have found many applications in various fields and have attracted attentions of many researchers. Traditional methods used to...     

Poly(l‐glutamic acid)‐based micellar hydrogel with improved mechanical performance and proteins loading

Soft tissues, such as fat and skin, present high flexibility and are capable of withstanding large deformation in various functions. Hydrogels that can resemble the mechanical performance of soft tissue are unique and widely demanded. In this study, micellar hydrogels based on biocompatible poly(l ‐glutamic acid) (PLGA) were designed with the enhanced capacity to bear large deformation. Amphipathic triblock copolymer poly(ethylene glycol) acrylate‐co‐poly(ε‐caprolactone)‐co‐poly (ethylene glycol) acrylate (APEG‐PCL‐APEG) with two terminal double bonds was synthesized and self‐assembled into micelles. At the same time, graft copolymers, poly(l ‐glutamic acid)‐g‐hydroxyethyl methacrylate (PLGA‐g‐HEMA) with double bonds were synthesized. APEG‐PCL‐APEG micelles and PLGA‐g‐HEMA were mixed to construct micellar hydrogel via radical polymerization. The crystalline structure and hydrophobic aggregation of copolymers (APEG‐PCL‐APEG) were found to associate with PCL molecular weight. Due to the hydrophobic stress dissipation and crystalline structure of the micelles, the softness and toughness of hydrogels were promoted, exhibiting a 25% increase in ultimate strain. Moreover, the micellar hydrogels were able to load proteins with long‐term retention. In addition, under dynamic mechanical stimulation, the release of proteins could be accelerated. Besides, the micellar hydrogels also supported rabbit adipose‐derived stem cells (rASCs) growth, thus exhibiting the potential toward soft tissue engineering. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1115–1125     

Carbon nanotube arrays supported manganese oxide and its application in electrochemical capacitors

Manganese oxide (MnO_x) has been coated on carbon nanotubes (CNTs) and fabricated as the electrodes for electrochemical capacitors (ECs) by cathodic electrodeposition. In the process, randomly oriented CNT arrays are grown directly onto the Ti/Si substrates by chemical vapor deposition method. Potentiostatic method has been utilized for cathodic electrodeposition of MnO_x onto the surface of CNTs while immersed in KMnO₄ solution. The highly porosity and fibrous microstructure of the as-prepared MnO_x/CNT electrode is beneficial for the electrolyte access to the active material, whereas CNTs provide improved electronic conductivity. Electrochemical investigations show that the increase in the loading mass of MnO_x results in a significant reduction in the specific capacitances (SCs) of the MnO_x/CNT electrodes. The MnO_x/CNT electrode with MnO_x loading mass of 50 μg shows a high SC of 400 F g⁻¹ with good long cycle stability at a current density of 10 A g⁻¹, suggesting its potential application in ECs.     

The ortho‐Difluoroalkylation of Aryliodanes with Enol Silyl Ethers: Rearrangement Enabled by a Fluorine Effect

Presented herein is an intriguing effect of fluorine, and it allows difluoroenol silyl ethers to couple with aryliodanes in a redox‐neutral manner to afford ortho‐iodo difluoroalkylated arenes. The remaining iodide group provides a versatile platform for converting the products into various valuable difluoroalkylated arenes. The reaction shows excellent functional‐group compatibility and broad substrate scope. A DFT mechanistic study suggests that the fluorine effect facilitates a subtle nucleophilic attack of the oxygen atom of enol silyl ethers onto aryliodanes, therefore leading to a rearrangement.     

The effect of temporal separation of two Geiger mode avalanche photodiodes and variation of time bin widths on detection probabilities in LADAR system using two Geiger mode avalanche photodiodes

In this paper, the effect of temporal separation of two Geiger mode avalanche photodiodes and the variation of time bin widths on detection probabilities in LADAR system using two Geiger mode avalanche photodiodes (GmAPDs) was investigated. The system is implemented by using two GmAPDs with a beam splitter and applying comparative process to their ends. Then, the timing circuitry receives the electrical signals only if each GmAPD generates the electrical signals simultaneously. Although this system decreases the energy of a laser-return pulse scattered from the target, it is highly effective in reducing the false alarm probability because of the randomly distributed noise on the time domain. The temporal separation of two GmAPDs and the variation of the time bin widths result in the variation of detection probabilities. The experiments were performed to verify the effect of temporal separation of two GmAPDs and the variation of time bin widths on the detection probability in the LADAR system. As a result, the optimal temporal difference and the optimal time bin width were. Using these optimal values, a clear 3D image could be obtained by the simple acquisition of the raw time-of-flight data with high SNR.     

X‐ray structures,spectroscopic, electrochemical,thermal, antibacterial,and DFT studies of two nickel(II) and cobalt(III) complexes constructed from a new quinazoline‐type ligand

Two two‐dimensional supramolecular Nickel(II) and Cobalt(III) complexes, [Ni( L ² )₂]·2CH₃OH ( 1 ) and [2Co( L ² )₂] ( 2 ) ( HL ²  = 1‐(2‐{[(E)‐3‐bromo‐5‐chloro‐2‐hydroxybenzylidene]amino}phenyl)ethanone oxime), were synthesized via complexation of salts acetate with HL ¹ (2‐(3‐bromo‐5‐chloro‐2‐hydroxyphenyl)‐4‐methyl‐1,2‐dihydroquinazoline 3‐oxide, H is the deprotonatable hydrogen). During the reaction, the C–N bond in HL ¹ is converted into the C=N–OH group in HL ² . The spectroscopic data of both complexes were compared with the ligand HL ¹ . HL ¹ and both complexes were determined by single‐crystal X‐ray crystallography. The differently geometric features of the obtained complexes 1 and 2 are observed. In the crystal structure, 1 and 2 form an infinite 1‐D chain‐like and 2‐D supramolecular frameworks. EPR spectroscopy of 2 was investigated. Moreover, electrochemical properties and antimicrobial activities of both complexes were also studied. In addition, the calculated HOMO and LUMO energies show the character of HL ¹ , complexes 1 and 2 . The electronic transitions and spectral features of HL ¹ and both complexes were discussed by TD‐DFT calculations.     

Co(III)/Zn(II)-catalyzed dearomatization of indoles and coupling with carbenes from ene-yne ketones via intramolecular cyclopropanation

A straightforward and efficient protocol for dearomatizing indoles is described. The reaction, catalyzed by an inexpensive Co(III)/Zn(II) catalyst, starts from easily accessible N-pyrimidinyl indoles and ene-yne ketones. Mild reaction conditions, high diastereoselectivity, a broad substrate scope, effective functional group tolerance, and reasonable to remarkable yields were observed.     

Spin–Spin Coupling Between Two meta-Benzyne Moieties In a Quinolinium Tetraradical Cation Increases Their Reactivities

The reactivity of a carbon-centered σ,σ,σ,σ-type singlet-ground-state tetraradical containing two meta-benzyne moieties was examined in the gas phase. Surprisingly, the tetraradical showed higher reactivity than its individual meta-benzyne counterparts. The reactivity of meta-benzynes is controlled by their (calculated) distortion energy ΔE_2.3, singlet–triplet spitting ΔE_S–T, and electron affinity (EA_2.3) of the meta-benzyne moiety at the transition state geometry for hydrogen-atom abstraction reactions. The addition of a second meta-benzyne moiety to a meta-benzyne does not significantly change EA_2.3. However, ΔE_2.3 is substantially decreased for both meta-benzyne moieties in the tetraradical, and this explains their higher reactivities. The decrease in ΔE_2.3 for each meta-benzyne moiety in the tetraradical is rationalized by stabilizing spin–spin coupling between one radical site in each meta-benzyne moiety. Therefore, spin–spin coupling between the meta-benzyne moieties in this tetraradical increases its reactivity, whereas spin–spin coupling within each meta-benzyne moiety decreases its reactivity.