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排序方式: 共有133条查询结果,搜索用时 46 毫秒
81.
Highly Reactive Nonheme Iron(III) Iodosylarene Complexes in Alkane Hydroxylation and Sulfoxidation Reactions 下载免费PDF全文
Dr. Seungwoo Hong Dr. Bin Wang Dr. Mi Sook Seo Dr. Yong‐Min Lee Myoung Jin Kim Prof. Dr. Hyung Rok Kim Prof. Dr. Takashi Ogura Dr. Ricardo Garcia‐Serres Dr. Martin Clémancey Prof. Dr. Jean‐Marc Latour Prof. Dr. Wonwoo Nam 《Angewandte Chemie (International ed. in English)》2014,53(25):6388-6392
High‐spin iron(III) iodosylarene complexes bearing an N‐methylated cyclam ligand are synthesized and characterized using various spectroscopic methods. The nonheme high‐spin iron(III) iodosylarene intermediates are highly reactive oxidants capable of activating strong C? H bonds of alkanes; the reactivity of the iron(III) iodosylarene intermediates is much greater than that of the corresponding iron(IV) oxo complex. The electrophilic character of the iron(III) iodosylarene complexes is demonstrated in sulfoxidation reactions. 相似文献
82.
Rhodium(II)-catalyzed reactions of diazo compound and a variety of ethynyl compounds were carried out. These reactions provide a rapid route for preparing a variety of furo[2,3-b]pyran-6-one derivatives in one-pot via cascade reactions of metal carbenoid reaction/ketene formation/[2+2]cycloaddition/ring expansion. 相似文献
83.
Kyung Rok Kim Young Jun Yoon Seongjae Cho Jae Hwa Seo Jung-Hee Lee Jin-Hyuk Bae Eou-Sik Cho In Man Kang 《Current Applied Physics》2013,13(9):2051-2054
An In0.53Ga0.47As/InP heterojunction-channel tunneling field-effect transistor (TFET) with enhanced subthreshold swing (S) and on/off current ratio (Ion/Ioff) is studied. The proposed TFET achieves remarkable characteristics including S of 16.5 mV/dec, on-state current (Ion) of 421 μA/μm, Ion/Ioff of 1.2 × 1012 by design optimization in doping type of In0.53Ga0.47As channel at low gate (VGS) and drain voltages (VDS) of 0.5 V. Comparable performances are maintained at VDS below 0.5 V. Moreover, an extremely fast switching below 100 fs is accomplished by the device. It is confirmed that the proposed TFET has strong potentials for the ultra-low operating power and high-speed electron device. 相似文献
84.
Rok Tomi
David Heath Ester Heath Jernej Markelj Andreja Kandolf Borovak Helena Prosen 《Molecules (Basel, Switzerland)》2020,25(24)
In this study, a method was developed for the determination of five neonicotinoid pesticides (acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam) in propolis. Two sample preparation methods were tested: solid-phase extraction and the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. The identities of analytes were confirmed using liquid chromatography–tandem mass spectrometry (LC-MS/MS) in the selected reaction monitoring mode. Solid-phase extraction resulted in cleaner extracts; therefore, the SPE-LC-MS/MS method was validated according to the SANTE protocol in triplicate at two spiking levels (10 ng/g and 50 ng/g). The average recoveries of analytes ranged from 61% to 101%, except for clothianidin (10–20%). The LOD ranged from 0.2 ng/g to 4.4 ng/g, whereas the LOQ was in the range of 0.8 ng/g–14.7 ng/g. In order to compensate for the matrix effect, matrix-matched calibration was used. Good accuracy (relative error: 1.9–10.4%) and good linearity (R2 > 0.991) were obtained for all compounds. The optimised method was applied to 30 samples: 18 raw propolis and 12 ethanol tinctures. Acetamiprid, imidacloprid, and thiacloprid were detectable in seven samples but were still below the LOQ. This study is the first to report the determination of several neonicotinoid residues in propolis. 相似文献
85.
86.
An efficient and concise synthesis of the biologically interesting (+)‐machaeriol B ( 2 ) and its enantiomer 5 was accomplished from O‐phenylhydroxylamine ( 7 ) in four steps (Scheme 2). In addition, the first total synthesis of natural (+)‐machaeriol C ( 3 ) and its enantiomer 6 was achieved from the readily available ester 15 in eight steps (Scheme 4). The key strategies in the syntheses of 2 and 5 involved benzofuran formation through a [3,3]‐sigmatropic rearrangement and trans‐hexahydrodibenzopyran formation by a domino aldol‐type/hetero‐Diels–Alder reaction. In the case of 3 and 6 , the key steps were stilbene formation by a Horner–Wadsworth–Emmons reaction and trans‐hexahydrodibenzopyran formation by domino reactions. 相似文献
87.
It is conjectured that every fullerene graph is hamiltonian. Jendrol’ and Owens proved [J. Math. Chem. 18 (1995), pp. 83–90]
that every fullerene graph on n vertices has a cycle of length at least 4n/5. In this paper we, improve this bound to 5n/6 − 2/3. 相似文献
88.
Modulation of Melanogenesis and Antioxidant Status of Melanocytes in Response to Phototoxic Action of Doxycycline 下载免费PDF全文
Jakub Rok Ewa Buszman Artur Beberok Marcin Delijewski Michał Otręba Dorota Wrześniok 《Photochemistry and photobiology》2015,91(6):1429-1434
Doxycycline is a commonly used tetracycline antibiotic showing the broad spectrum of antibacterial action. However, the use of this antibiotic is often connected with the risk of phototoxic reactions that lead to various skin disorders. One of the factors influencing the photosensitivity reactions is the melanin content in melanocytes. In this study, the impact of doxycycline and UVA irradiation on cell viability, melanogenesis and antioxidant defense system in cultured normal human epidermal melanocytes (HEMn‐DP) was examined. The exposure of cells to doxycycline and UVA radiation resulted in concentration‐dependent loss in melanocytes viability and induced melanin biosynthesis. Significant changes were stated in cellular antioxidant enzymes activity: SOD, CAT and GPx, which indicates alterations of antioxidant defense system. The results obtained in vitro may explain the mechanisms of phototoxic reactions that occur in normal human epidermal melanocytes in vivo after exposure of skin to doxycycline and UVA radiation. 相似文献
89.
We study the effect of electron hopping in triple quantum dots modeled by the three-impurity Anderson model. We determine the range of hopping parameters where the system exhibits the two-channel Kondo effect and has non-Fermi-liquid properties in a wide temperature interval. As this interval is entered from above, the conductance through the side dots increases to a half of the conductance quantum, while the conductance through the system remains small. At lower temperatures the conductance through the system increases to the unitary limit as the system crosses over to the Fermi-liquid ground state. Measuring the differential conductance in a three-terminal configuration provides an experimental probe into the NFL behavior. 相似文献
90.
An efficient and concise total synthesis of naturally occurring pyranochalcones was achieved from readily available 2,4-dihydroxyacetophenone and 2,4-dihydroxy-6-methoxyacetophenone. The key steps in the synthetic strategy were ethylenediamine diacetate-catalyzed benzopyran formation and aldol reactions. 相似文献