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941.
Seung‐Yeop Kwak Soo Gyung Jung Young Seo Yoon Dae Woo Ihm 《Journal of Polymer Science.Polymer Physics》1999,37(13):1429-1440
In the present article, some new events on the surface morphology of the aromatic polyamide thin‐film‐composite (TFC) membranes were demonstrated in conjunction with their inherent chemical nature. In addition, the detailed, quantitative understanding of the microscopic surface features was shown to be essential in controlling the water permeability and eventually developing the high performance membranes. The surface roughness and the surface area were mainly affected by the existence or nonexistence of the crosslinking and/or the free amide groups not pertinent to the formation of the hydrogen bonding, which in turn contributed to the water permeability. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1429–1440, 1999 相似文献
942.
K. C. Nicolaou Phil S. Baran Rolf Jautelat Yun He Kin Chiu Fong Ha‐Soon Choi Won Hyung Yoon Yong‐Li Zhong 《Angewandte Chemie (International ed. in English)》1999,38(4):549-552
A seven‐step cascade reaction —in which selective mesylation, epoxide formation, epoxide lysis, cyclization, reiterative oxidation, and nitrogen–oxygen exchange occur sequentially—facilitates the construction of the maleic anhydride moiety of CP molecules 1 and 2 (>93% yield per step). Unstable intermediates of this reaction sequence were detected, providing evidence for the proposed mechanism and resulting in the discovery of a new chemical entity. 相似文献
943.
Swarna A. Gamage Julie A. Spicer Kit Y. Tsang Patrick D. O'Connor Jack U. Flanagan Woo‐Jeong Lee James M. J. Dickson Peter R. Shepherd William A. Denny Gordon W. Rewcastle 《化学:亚洲杂志》2019,14(8):1249-1261
Using a scaffold‐hopping approach, imidazo[1,2‐a]pyridine analogues of the ZSTK474 (benzimidazole) class of phosphatidylinositol 3‐kinase (PI3K) inhibitors have been synthesized for biological evaluation. Compounds were prepared using a heteroaryl Heck reaction procedure, involving the palladium‐catalysed coupling of 2‐(difluoromethyl)imidazo[1,2‐a]pyridines with chloro, iodo or trifluoromethanesulfonyloxy (trifloxy) substituted 1,3,5‐triazines or pyrimidines, with the iodo intermediates being preferred in terms of higher yields and milder reaction conditions. The new compounds maintain the PI3K isoform selectivity of their benzimidazole analogues, but in general show less potency. 相似文献
944.
Jin Koo Kim Sun Young Jeong Sae Hoon Lim Jang Hyeok Oh Seung‐Keun Park Jung Sang Cho Yun Chan Kang 《化学:亚洲杂志》2019,14(18):3127-3140
Increasing demand for sodium‐ion batteries (SIBs), one of the most feasible alternatives to lithium ion batteries (LIBs), has resulted because of their high energy density, low cost, and excellent cycling stability. Consequently, the design and fabrication of suitable electrode materials that govern the overall performance of SIBs are important. Aerosol‐assisted spray processes have gained recent prominence as feasible, scalable, and cost‐effective methods for preparing electrode materials. Herein, recent advances in aerosol‐assisted spray processes for the fabrication of nanostructured metal chalcogenides (e.g., metal sulfides, selenides, and tellurides) for SIBs, with a focus on improving the electrochemical performance of metal chalcogenides, are summarized. Finally, the improvements, limitations, and direction of future research into aerosol‐assisted spray processes for the fabrication of various electrode materials are presented. 相似文献
945.
Ji Yong Bae Dae‐Woong Jung Chan Bae Jeong Hong‐Seung Kim Jung Dae Kim Hyun‐Joo Ro Sangmi Jun Dong Uk Kim Jun Min Kim Gi‐Ra Yi Gaehang Lee Ki Soo Chang 《Particle & Particle Systems Characterization》2019,36(7)
The plasmonic photothermal (PPT) characteristics of gold nanostructures have been extensively investigated theoretically and experimentally due to their potential for use materials science and industry. The management of the size and shape of gold nanoparticles has been a key issue in the development of better solutions for PPT heat generation because their size and shape determine their resultant photothermal properties. However, the light absorption of gold nanostructures is mainly dependent on the wavelength and orientation of the incident light; hence, maintaining uniform size and shape is critical for achieving maximum photothermal energy. Morphologically homogeneous spherical gold nanoparticles, or super gold nanospheres prepared by slowly etching uniform octahedral gold nanoparticles, demonstrate better PPT heat generation compared with commercially available nonsmooth gold nanoparticles (GNSs). The PPT heating experiments show a maximum temperature difference of 5.7 °C between the super and ordinary GNSs with the same average maximum Feret's diameters, which result from the more efficient PPT heat power generation (20.6%) of the super GNSs. In an electromagnetic‐wave simulation, the super GNSs show lower polarization dependence and a 24.6% higher absorption cross‐section than ordinary GNSs. 相似文献
946.
Hui Hun Cho Su Ji Kim Ali Turab Jafry Byoungsang Lee Jun Hyuk Heo Seokyoung Yoon Sun Hwan Jeong Seong‐Il Kang Jung Heon Lee Jinkee Lee 《Particle & Particle Systems Characterization》2019,36(6)
Although nanoparticles (NPs) can be carefully engineered to have maximal stability and functionality desirable for use in diverse applications, they are generally not suitable for long‐term storage in solution. It is also difficult to store NPs in a dry state because dried NPs generally become aggregated and cannot easily be redispersed. Thus, a new strategy allowing long‐term storage of NPs with high stability, redispersibility, and functionality is highly demanded. By passivating the 13 nm gold nanoparticle (AuNP) surface with stabilizing agents and treating a paper substrate with both bovine serum albumin and sucrose after coating with a hydrophobic polyvinyl butyral layer, it is possible to fully redisperse (≈100%) dried AuNPs with colloidal stability comparable to that of as‐prepared AuNPs. Furthermore, AuNPs physically stabilized with polyvinylpyrrolidone can react with thiol‐containing compounds, such as 1,4‐dithiothreitol (DTT). Taking advantage of the oxidation reaction of hypochlorous acid with DTT, it is possible to demonstrate a paper‐based colorimetric sensor for detection of residual chlorine in water. Since this strategy is applicable to large‐sized AuNPs (30–90 nm), silver NPs, oleic acid‐capped magnetic NPs, and cetrimonium bromide‐passivated gold nanorods, it can be used for diverse NPs requiring long‐term storage for many applications. 相似文献
947.
Kyu Ho Van Jeong Park Sung Hwan Yoon Suk Ho Chung Min Suk Cha 《Proceedings of the Combustion Institute》2019,37(2):1997-2004
The oscillating lifted flame in a laminar nonpremixed nitrogen-diluted fuel jet is known to be a result of buoyancy, though the detailed physical mechanism of the initiation has not yet been properly addressed. We designed a systematic experiment to test the hypothesis that the oscillation is driven by competition between the positive buoyancy of flame and the negative buoyancy of a fuel stream heavier than the ambient air. The positive buoyancy was examined with various flame temperatures by changing fuel mole fraction, and the negative buoyancy was investigated with various fuel densities. The density of the coflow was also varied within a certain range by adding either helium or carbon dioxide to air, to study how it affected the positive and negative buoyancies at the same time. As a result, we found that the range of oscillation was well-correlated with the positive and the negative buoyancies; the former stabilized the oscillation while the latter triggered instability and became a source of the oscillation. Further measurements of the flow fields and OH radicals evidenced the important role of the negative buoyancy on the oscillation, detailing a periodic variation in the unburned flow velocity that affected the displacement of the flame. 相似文献
948.
Seo Woo Song Hyung Jong Bae Sudeok Kim Dong Yoon Oh Okju Kim Yunjin Jeong Sunghoon Kwon 《Particle & Particle Systems Characterization》2017,34(5)
Microparticle‐based drug delivery is a promising technology for small volume bioassay platforms. The general utilization of the drug‐loaded microparticles in the in vitro bioassay platforms requires the drug loading method, which should impregnate the general drug types (e.g., water insoluble) with high payload into the variously designed microparticles. Loading the drug into the prefabricated microparticles using solvent evaporation satisfies the requirement. However, similar to the “coffee‐ring effect,” drugs are loaded in a seriously nonuniform manner, caused by the capillary flow during the evaporation process. Here, it is presented that the freeze‐drying is an efficient way to load uniform and high amount of the drug into the prefabricated microparticles. It is demonstrated that freezing solvent can block the capillary flow during the solvent removal process, improving the loading uniformity. The delivered amount of drugs is linearly proportional to the initial loading amount of drugs. Also, this drug loading method is shown to be applied to the various drug types and the prefabricated microparticles with different properties. Considering many challenges to suppress the “coffee‐ring effect” that induces nonuniform impregnation/deposition, the proposed concept can be applied not only for microparticle‐based drug delivery but also for uniform coating applications (e.g., thin‐film coating, DNA/protein microarray). 相似文献
949.
A new modulation scheme that improves the bandwidth efficiency of an optical access link is proposed in this paper. It is implemented using non-orthogonal frequency shift keying (FSK) and quadrature amplitude modulation (QAM) simultaneously. We call the proposed technique non-orthogonal frequency quadrature amplitude modulation (NOFQAM). Especially, non-orthogonal FSK based on digital signal processing (DSP) is proposed for the first time. DSP-aided non-orthogonal FSK allows us to select RF carrier frequency irrespective of the channel bandwidth to allocate FSK symbols, unlike the existing orthogonal FSK. The non-orthogonality is implemented using a sequential correlation, where a received NOFQAM signal is correlated with only one RF carrier at a time by using DSP. After the sequential correlation is completed, both the FSK and the QAM symbols are recovered successfully and merged to generate the NOFQAM symbols. For experimental verification, a 20-km optical access link, which can transmit a 64-NOFQAM signal sampled at 10 Gsample/s, is implemented. We observed no increase in occupied channel bandwidth and a power penalty <0.5 dB compared to the 16-QAM scheme. A bit error rate lower than 10?11 was obtained for the frequency spacing considered herein, which corresponds to 3% of the used RF carrier (1.5 GHz) when there are 50 sampling points per 64-NOFQAM symbol. 相似文献
950.
Multiparameter kinetic analysis of alkaline hydrolysis of a series of aryl diphenylphosphinothioates: models for P=S neurotoxins
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Ik‐Hwan Um Jeong‐Yoon Han Young‐Hee Shin Julian M. Dust 《Journal of Physical Organic Chemistry》2017,30(7)
Alkaline hydrolysis of a series of X‐substituted‐phenyl diphenylphosphinothioates ( 2a‐i ) in 80 mol%/20 mol% DMSO at 25.0 ± 0.1°C has been studied kinetically and assessed through a multiparameter approach. Substrates 2a to 2i are approximately 12 to 22 times less reactive than their P=O analogues 1a to 1i (ie, the thio effect). The Brønsted‐type plot for the reactions of 2a to 2i is linear with βlg = ?0.43, consistent with a concerted mechanism. Hammett plots correlated with σo and σ? constants also support a concerted mechanism; the Yukawa‐Tsuno plot results in an excellent linear correlation with ρX = 1.26 and r = 0.30, indicating that expulsion of the leaving group occurs in the rate‐determining step (RDS). The ΔH? value increases from 10.5 to 11.7 and 13.9 kcal/mol as substituent X in the leaving group changes from 3,4‐(NO2)2 to 4‐NO2 and H, in turn, while TΔS? remains constant at ?6.0 kcal/mol. The strong dependence of ΔH? on the electronic nature of substituent X also indicates that the leaving group departs in the RDS. The reaction mechanism and origin of the thio effect are discussed by comparison of the current kinetic results with those reported for the reactions of 1a to 1i . The results suggest that for useful OP neurotoxins the mechanism of abiotic hydrolysis is concerted (with varying degrees of asynchronicity) when the substrate bears good leaving groups. 相似文献