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991.
992.
993.
In‐Yup Jeon Loon‐Seng Tan Jong‐Beom Baek 《Journal of polymer science. Part A, Polymer chemistry》2008,46(11):3471-3481
Linear and hyperbranched poly(ether‐ketone)s (PEKs) containing flexible oxyethylene spacers grafted multiwalled carbon nanotube (PEK‐g‐MWNT) nanocomposites were prepared by direct Friedel‐Crafts acylation as the polymer forming and grafting reaction. To achieve the composites, in situ polycondensations of AB monomers 3‐(2‐phenoxyethoxy)benzoic acid (3‐PEBA) and 4‐(2‐phenoxyethoxy)benzoic acid (4‐PEBA), and AB2 monomer 3,5‐bis(2‐phenoxyethoxy)benzoic acid (3,5‐BPEBA) were carried out in the presence of multiwalled carbon nanotubes (MWNTs). The reaction conditions, polyphosphoric acid (PPA) with additional phosphorous phentoxide (P2O5) in the temperature range of 110–120 °C, were previously optimized. The conditions were used as the polymerization and grafting medium that were indeed benign not to damage MWNTs but strong enough to promote the covalent attachment of PEKs onto the surface of the electron‐deficient MWNTs. From scanning electron microscopy (SEM) and transmission electron microscopy studies, the polymers were uniformly grafted onto the MWNTs. The resultant nanocomposites are soluble in most strong acids such as trifluoroacetic acid, methanesulfonic acid, and sulfuric acid. Both isothermal and dynamic TGA studies in air showed that nanocomposites displayed improved thermo‐oxidative stability when compared with those of corresponding PEK homopolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3471–3481, 2008 相似文献
994.
We show that some Drinfeld modules of rank 2 on \Bbb Fq[T]{\Bbb F}_q[T] with complex multiplication have global minimal models. 相似文献
995.
The luminescent properties of alkaline earth orthosilicates M2SiO4 (M=Ba, Sr, Ca) doped with Eu2+ ions are investigated. Two emission bands are assigned to the f-d transitions of Eu2+ ions doped into two different cation sites in host lattices confirmed by electron paramagnetic resonance signal. Two emission bands show the different emission color variation with substituting M2+ cations with smaller cations. This behavior is discussed in terms of two competing factors of the crystal field strength and covalence. Also the decay times are in order of 600-1000 ns. These phosphors with maximum excitation of around 370 nm can be applied as a color-tunable phosphor for light-emitting diode based on ultraviolet chip/phosphor technology. 相似文献
996.
997.
Jae-Do Kim Jae-Kyoung Jung Byung-Cheol Jeon Chong-Du Cho 《Optics and Lasers in Engineering》2001,35(5)
A wide laser beam optical system for laser heat treatment processing has been designed with a pyramid polygon mirror, which is able to adjust the amplitude and frequency. It consists of a rotating pyramid polygon mirror made of copper and a cooling part that protects the surface of the mirror from damage by heat. The system provides a linear laser heat source with the wide scanning width. This can increase the efficiency of production and quality of products. The CO2 laser heat treatment has been processed on SNCM220 and SCM440 steels using the developed optical system. The width of specimens between 13 and 17 mm can be hardened for a single pass scanning. 相似文献
998.
A continuum theory to describe solvation in nondipolar quadrupolar solvents is developed by accounting for electronic polarizability. A general Hamiltonian for a solute–solvent system in an arbitrary nonequilibrium configuration is obtained in terms of two field variables—densities of the solvent quadrupole and induced dipole moments. Equilibrium solvation is studied by optimizing this Hamiltonian with account of cavity boundaries. As an application, electronic structures and free energies of small molecules in benzene are examined with ab initio methods. Solvation stabilization due to solvent quadrupole moments is found to be substantial; for the solutes considered here, it is comparable to and often in excess of that arising from solvent-induced dipole moments. 相似文献
999.
Suk Hun Lee Kunyoung Kim Yeong Uk Jeon Amit Kundu Prasanta Dey Jong Yeon Hwang Neeraj Kumar Mishra Hyung Sik Kim In Su Kim 《Tetrahedron letters》2019,60(34):150974
The synthesis of 3,3′-bis-7-indolylmethane derivatives is important for their further development as pharmaceutical compounds and other synthetic purposes. Herein, we describe the zinc- or acid-mediated cross-coupling reaction of 7-azaindoles with aldehydes, such as paraformaldehyde, alkyl aldehydes, aryl aldehydes, enal, and α-ketoaldehyde, providing the corresponding C3-linked bis-7-azaindole derivatives, which are a crucial class towards the development of novel bioactive compounds. High levels of site selectivity and functional group tolerance were observed. Synthesized 3,3′-bis-7-azaindole derivatives were evaluated against human breast adenocarcinoma cells (MCF-7) and human ovarian carcinoma cells (SKOV-3), respectively. Notably, compounds 3s and 4e displayed promising anticancer properties competitive with anticancer doxorubicin as a positive control. 相似文献
1000.
Subin Son Miae Won Ori Green Nir Hananya Amit Sharma Yukyoung Jeon Jong Hwan Kwak Jonathan L. Sessler Doron Shabat Jong Seung Kim 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(6):1753-1757
Activatable (turn‐on) probes that permit the rapid, sensitive, selective, and accurate identification of cancer‐associated biomarkers can help drive advances in cancer research. Herein, a NAD(P)H:quinone oxidoreductase‐1 (NQO1)‐specific chemiluminescent probe 1 is reported that allows the differentiation between cancer subtypes. Probe 1 incorporates an NQO1‐specific trimethyl‐locked quinone trigger moiety covalently tethered to a phenoxy‐dioxetane moiety through a para‐aminobenzyl alcohol linker. Bio‐reduction of the quinone to the corresponding hydroquinone results in a chemiluminescent signal. As inferred from a combination of in vitro cell culture analyses and in vivo mice studies, the probe is safe, cell permeable, and capable of producing a “turn‐on” luminescence response in an NQO1‐positive A549 lung cancer model. On this basis, probe 1 can be used to identify cancerous cells and tissues characterized by elevated NQO1 levels. 相似文献