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101.
Simultaneous analysis of 210 prohibited substances in human urine by ultrafast liquid chromatography/tandem mass spectrometry in doping control
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102.
Rajangam Vinodh Mani Ganesh Mei Mei Peng Aziz Abidov Muthiahpillai Palanichamy Wang Seog Cha Hyun-Tae Jang 《高分子科学》2015,33(2):224-235
Microporous hypercross-linked conjugated quinonoid chromophores represent a novel class of amorphous polymers, synthesized by the reaction of anthracene with dimethoxy methane in the presence of FeCl3 catalyst. Their N2 adsorption isotherms confirm their microporous nature. Diffuse reflectance UV-Visible(DRS UV-Vis) spectroscopy confirms their matrix built with the conjugated quinonoids by their broad light absorption characteristics extending from 1000 nm to 200 nm with the absorbance maximum close to 400 nm. The catalyst cross-linked anthracene with ―CH2― bridges and subsequently dehydrogenating them to form quinonoids. Their Fourier transform infrared(FTIR) spectra showed their characteristic quinonoid vibrations between 1600 and 1700 cm-1. The synthesis of polymers was carried out at 30, 40, 50, 60, 70 and 80 ℃, but the quinonoid content of the polymer obtained at 80 ℃ was higher than that of the others. Their scanning electron microscopy(SEM) images showed microspheres of 1 to 5 μm size built with tiny particles. Their surfaces were not smooth. The polymer synthesized at 80 ℃ showed 5.1 wt% CO2 sorption at 25 ℃ and 0.1 MPa, but when it was recross-linked, the CO2 sorption increased to 8 wt%. Hence, hypercross-linked conjugated quinonoid chromophores of anthracene are good for sorption of CO2. 相似文献
103.
Sangya Chitranshi Dr. B. Adinarayana Mainak Das Dr. Won-Young Cha Prof. Dr. Dongho Kim Prof. Dr. A. Srinivasan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(56):12911-12915
Three distinct conformational structures of carbaoctaphyrins were prepared by incorporating bis-4,4'-biphenyl units in the macrocyclic core. The free-base form adopts a figure-eight conformation, whereas the protonation triggers a conformational change with a pyrrole ring inversion and acquires an open-framework structure. The insertion of bis-RhI metal ion in the macrocyclic core affords a singly twisted conformational structure. Furthermore, the local aromaticity in the bis-4,4'-biphenyl ring dominates the overall macrocyclic aromaticity in all three forms, and thus adopts nonaromatic characteristics. These results are supported by spectral as well as theoretical studies, and they are unambiguously confirmed by X-ray crystal analyses. 相似文献
104.
We consider systems that are subject to an external mixed Poisson shock process. Each shock can result in a failure of a system with a given probability and is survived with the complementary probability. Each shock additionally decreases the quality function that describes the performance of a system, thus forming the corresponding stochastic process. Expectations (unconditional and conditional on survival) and relevant variability characteristics for the stochastic quality function are derived. Some monotonicity properties of the conditional quality function are investigated and the future values of this function are derived. 相似文献
105.
Yubin Cha Yeonweon Choi Heekyoung Choi Hyesong Park Ju Hyun Kim 《Supramolecular chemistry》2018,30(3):227-233
A polymeric gel was prepared from a bis(3-cyanovinylcarbazole)-based derivative and a thymine-bearing calix[4]arene derivative via photo-cross-linking between 3-cyanovinylcarbazole and thymine groups by irradiation with 365 nm UV light, a novel and facile method to obtain a soft material. Values for storage and loss moduli of the bis(3-cyanovinylcarbazole)-based derivative and the thymine-bearing calix[4]arene derivative gradually increased during photoirradiation. This gel was transformed back to the solution state by decomposition of the polymer network to the monomers via irradiation with 312 nm UV light. 相似文献
106.
An ellipsometric method for measuring second-order cascaded phase shift is experimentally demonstrated in a KNbO(3) single crystal. We analyze the polarization state composed of the two orthogonal polarizations of the transmitted fundamental wave, one of which experiences intensity-dependent depletion and phase shift while the other does not. This method does not require a well-defined beam profile or interferometric stability. 相似文献
107.
Choi MG Ryu de H Jeon HL Cha S Cho J Joo HH Hong KS Lee C Ahn S Chang SK 《Organic letters》2008,10(17):3717-3720
The chemodosimetric behavior of dichlorofluorescein derivatives toward Hg(2+) ions was investigated. Simple chemodosimetric systems showed selective and efficient signaling behaviors toward micromolar concentrations of Hg(2+) ions over other common interfering metal ions in an aqueous environment. The signaling mechanism is selective mercuration of the 4',5'-position of the xanthene moiety, which results in efficient chromogenic and fluorogenic signaling of Hg(2+) ions in aqueous environment. 相似文献
108.
Park Y Cha M Shin W Lee H Ripmeester JA 《The journal of physical chemistry. B》2008,112(29):8443-8446
The tert-butyl alcohol (TBA) is the most hydrophobic of the simple alcohol and by itself does not form a clathrate hydrate with water. A genuine clathrate hydrate is synthesized by exposing a gaseous guest to solid TBA + H2O powders. Here, we examine three consecutive spectroscopic approaches of (1) the occurrence of a "free" OH stretching band (nu(OH)) signal of TBA molecules representing an absence of hydrogen bonding between the host water and guest TBA, (2) a tuning effect for creating fresh cages via the rearrangement of the host-water lattice, and finally (3) the existence of a critical guest concentration (CGC) that appears only when the TBA concentration is dilute. The present findings from this simple three-step approach can be extended to other alcoholic guest species with the specific modifications to provide the new insights into inclusion chemistry. 相似文献
109.
110.
Yusubov MS Funk TV Chi KW Cha EH Kim GH Kirschning A Zhdankin VV 《The Journal of organic chemistry》2008,73(1):295-297
Preparation, structural characterization, and reactivity of 3-[bis(trifluoroacetoxy)iodo]benzoic acid and 3-[hydroxy(tosyloxy)iodo]benzoic acid, new recyclable iodine(III) reagents derived from 3-iodosylbenzoic acid, are described. The reduced form of these reagents, 3-iodobenzoic acid, can be easily recovered from the reaction mixtures using ion-exchange resin or basic aqueous workup followed by acidification with HCl. 相似文献