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71.
Oh Kuen Kwon Jun Ha Lee Jungchul Park Ki-Sub Kim Jeong Won Kang 《Current Applied Physics》2013,13(2):360-365
A tunable graphene-nanoribbon (GNR)-resonator was investigated via classical molecular dynamics simulations. Resonance frequencies increased with increasing externally applied gate-force and axial-strain, and could be tuned above several hundred GHz. Tunable resonance frequencies achieved from the gate force were higher than those achieved from the axial-strain. The operating frequencies of GNR-resonators without axial-strain or with small axial-strains were most widely tuned by the gate, and almost linearly increased with increasing mean deflection. As the axial strain increased, the tunable ranges of the GNR-resonators were exponentially decreased, although the operating frequencies increased. GNR-resonators without axial-strain could be applied to wide-range-tuners, whereas GNR-resonators with high axial-strain could be applied to high-frequency-fine-tuners. 相似文献
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Relationships between structure,ionization profile and sensitivity of exogenous anabolic steroids under electrospray ionization and analysis in human urine using liquid chromatography–tandem mass spectrometry 下载免费PDF全文
Eunju Cha Sohee Kim Hee Won Kim Kang Mi Lee Ho Jun Kim Oh‐Seung Kwon Jaeick Lee 《Biomedical chromatography : BMC》2016,30(4):555-565
The relationships between the ionization profile, sensitivity, and structures of 64 exogenous anabolic steroids (groups I–IV) was investigated under electrospray ionization (ESI) conditions. The target analytes were ionized as [M + H]+ or [M + H–nH2O]+ in the positive mode, and these ions were used as precursor ions for selected reaction monitoring analysis. The collision energy and Q3 ions were optimized based on the sensitivity and selectivity. The limits of detection (LODs) were 0.05–20 ng/mL for the 64 steroids. The LODs for 38 compounds, 14 compounds and 12 compounds were in the range of 0.05–1, 2–5 and 10–20 ng/mL, respectively. Steroids including the conjugated keto‐functional group at C3 showed good proton affinity and stability, and generated the [M + H]+ ion as the most abundant precursor ion. In addition, the LODs of steroids using the [M + H]+ ion as the precursor ion were mostly distributed at low concentrations. In contrast, steroids containing conjugated/unconjugated hydroxyl functional groups at C3 generated [M + H ? H2O]+ or [M + H ? 2H2O]+ ions, and these steroids showed relatively high LODs owing to poor stability and multiple ion formation. An LC‐MS/MS method based on the present ionization profile was developed and validated for the determination of 78 steroids (groups I–V) in human urine. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Indothiazinone is a natural 3-acylindole alkaloid, isolated from a culture of myxobacterial strain. It was found to possess antibacterial activity against yeast and filamentous fungi. Indothiazinone is also structurally related with a mammalian endogenous aryl hydrocarbon receptor ligand, (2-(1′H-indole-3′-carbonyl)thiazol-4-carboxylic acid methyl ester (ITE). In this article, the synthesis of indothiazinone has been disclosed for the first time. Key feature includes direct and selective 3-acylation of indole in the presence of Lewis acid. In addition, an efficient preparation of N-substituted indothiazinone derivatives has been demonstrated. 相似文献
76.
Tae Hee Kim Hyun Mo Lee Hee Soo Park Sung Dong Kim Su Jin Kwon Atsushi Tahara Hideo Nagashima Bun Yeoul Lee 《应用有机金属化学》2019,33(4)
The original Sasol catalytic system for ethylene tetramerization is composed of a Cr source, a PNP ligand, and MAO (methylaluminoxane). The use of expensive MAO in excess has been a critical concern in commercial operation. Many efforts have been made to replace MAO with non‐coordinating anions (e.g., [B(C6F5)4]?); however, most of such attempts were unsuccessful. Herein, an extremely active catalytic system that avoids the use of MAO is presented. The successive addition of two equivalent [H(OEt2)2]+[B(C6F5)4]? and one equivalent CrCl3(THF)3 to (acac)AlEt2 and subsequent treatment with a PNP ligand [CH3(CH2)16]2C(H)N(PPh2)2 ( 1 ) yielded a complex presumably formulated as [ 1 ‐CrAl (acac)Cl3(THF)]2+[B(C6F5)4]?2, which exhibited high activity when combined with iBu3Al (1120 kg/g‐Cr/h; ~4 times that of the original Sasol system composed of Cr (acac)3, iPrN(PPh2)2, and MAO). Via the introduction of bulky trialkylsilyl substituents such as –SiMe3, –Si(nBu)3, or –SiMe2(CH2)7CH3 at the para‐position of phenyl groups in 1 (i.e., by using [CH3(CH2)16]2C(H)N[P(C6H4‐p‐SiR3)2]2 instead of 1 ), the activities were dramatically improved, i.e., tripled (2960–3340 kg/g‐Cr/h; more than 10 times that of the original Sasol system). The generation of significantly less PE (<0.2 wt%) even at a high temperature is another advantage achieved by the introduction of bulky trialkylsilyl substituents. NMR studies and DFT calculations suggest that increase of the steric bulkiness on the alkyl‐N and P‐aryl moieties restrict the free rotation around (alkyl)N–P (aryl) bonds, which may cause the generation of more robust active species in higher proportion, leading to extremely high activity along with the generation of a smaller amount of PE. 相似文献
77.
Myungjin Jo Shinrye Lee Yu-Mi Jeon Seyeon Kim Younghwi Kwon Hyung-Jun Kim 《Experimental & molecular medicine》2020,52(10):1652
TAR DNA-binding protein 43 (TDP-43) is a highly conserved nuclear RNA/DNA-binding protein involved in the regulation of RNA processing. The accumulation of TDP-43 aggregates in the central nervous system is a common feature of many neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), Alzheimer’s disease (AD), and limbic predominant age-related TDP-43 encephalopathy (LATE). Accumulating evidence suggests that prion-like spreading of aberrant protein aggregates composed of tau, amyloid-β, and α-synuclein is involved in the progression of neurodegenerative diseases such as AD and PD. Similar to those of prion-like proteins, pathological aggregates of TDP-43 can be transferred from cell-to-cell in a seed-dependent and self-templating manner. Here, we review clinical and experimental studies supporting the prion-like spreading of misfolded TDP-43 and discuss the molecular mechanisms underlying the propagation of these pathological aggregated proteins. The idea that misfolded TDP-43 spreads in a prion-like manner between cells may guide novel therapeutic strategies for TDP-43-associated neurodegenerative diseases.Subject terms: Neurodegenerative diseases, Neurodegeneration 相似文献
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A low-dynamic tone-compression technique is developed for realistic image rendering that can make three-dimensional (3D) images similar to realistic scenes by overcoming brightness dimming in the 3D display mode. The 3D surround provides varying conditions for image quality, illuminant adaptation, contrast, gamma, color, sharpness, and so on. In general, gain/offset adjustment, gamma compensation, and histogram equalization have performed well in contrast compression; however, as a result of signal saturation and clipping effects, image details are removed and information is lost on bright and dark areas. Thus, an enhanced image mapping technique is proposed based on space-varying image compression. The performance of contrast compression is enhanced with complex adaptation in a 3D viewing surround combining global and local adaptation. Evaluating local image rendering in view of tone and color expression, noise reduction, and edge compensation confirms that the proposed 3D image-mapping model can compensate for the loss of image quality in the 3D mode. 相似文献
80.
We analyse the use of options for online advertisement publishers. By providing a discount or rewards to advertisers, publishers can utilise their uncertain service capacity, page-views, more efficiently. We use Generalised Nash Bargaining to study the feasibility of the option contract and solve for an optimal value for the option price. We compare the revenues and benefits from advertisements under the option contract, with those without the options using numerical studies. We also study the impact of pricing and other components in the game on the optimal option price, the publisher's revenues, and the advertiser's benefits from the advertisements. 相似文献