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941.
We introduce a new high accuracy second-order finite-difference time-domain (FDTD) algorithm based on non-standard finite differences, and use it to investigate light propagation in subwavelength structures such as photonic crystals. 相似文献
942.
Anthony T. Giduthuri Ezekiel O. Adekanmbi Soumya K. Srivastava James G. Moberly 《Electrophoresis》2021,42(5):656-666
Rare earth elements (REEs) are widely used across different industries due to their exceptional magnetic and electrical properties. In this work, Cupriavidus necator is characterized using dielectrophoretic ultra-high-frequency measurements, typically in MHz range to quantify the properties of cytoplasm in C. necator for its metal uptake/bioaccumulation capacity. Cupriavidus necator, a Gram-negative bacteria strain is exposed to REEs like europium, samarium, and neodymium in this study. Dielectrophoretic crossover frequency experiments were performed on the native C. necator species pre- and post-exposure to the REEs at MHz frequency range. The net conductivity of native C. necator, Cupriavidus europium, Cupriavidus samarium, and Cupriavidus neodymium are 15.95 ± 0.029 μS/cm, 16.15 ± 0.028 μS/cm, 16.05 ± 0.029 μS/cm, 15.61 ± 0.005 μS/cm respectively. The estimated properties of the membrane published by our group are used to develop a microfluidic sorter by modeling and simulation to separate REE absorbed C. necator from the unabsorbed native C. necator species using COMSOL Multiphysics commercial software package v5.5. 相似文献
943.
Dr. Michael Andresini Dr. Arianna Tota Prof. Leonardo Degennaro Dr. James A. Bull Prof. Renzo Luisi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(69):17293-17321
Recent years have seen a marked increase in the occurrence of sulfoximines in the chemical sciences, often presented as valuable motifs for medicinal chemistry. This has been prompted by both pioneering works taking sulfoximine containing compounds into clinical trials and the concurrent development of powerful synthetic methods. This review covers recent developments in the synthesis of sulfoximines concentrating on developments since 2015. This includes extensive developments in both S−N and S−C bond formations. Flow chemistry processes for sulfoximine synthesis are also covered. Finally, subsequent transformations of sulfoximines, particularly in N-functionalization are reviewed, including N−S, N−P, N−C bond forming processes and cyclization reactions. 相似文献
944.
945.
Silicon nitride/silicon oxide interlayers for solar cell passivating contacts based on PECVD amorphous silicon
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This Letter demonstrates improved passivating contacts for silicon solar cells consisting of doped silicon films together with tunnelling dielectric layers. An improvement is demonstrated by replacing the commonly used silicon oxide interfacial layer with a silicon nitride/silicon oxide double interfacial layer. The paper describes the optimization of such contacts, including doping of a PECVD intrinsic a‐Si:H film by means of a thermal POCl3 diffusion process and an exploration of the effect of the refractive index of the SiNx. The n+ silicon passivating contact with SiNx /SiOx double layer achieves a better result than a single SiNx or SiOx layer, giving a recombination current parameter of ~7 fA/cm2 and a contact resistivity of ~0.005 Ω cm2, respectively. These self‐passivating electron‐selective contacts open the way to high efficiency silicon solar cells. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
946.
Dewakar Sangaraju Peter W. Villalta Susith Wickramaratne James Swenberg Natalia Tretyakova 《Journal of the American Society for Mass Spectrometry》2014,25(7):1124-1135
Human exposure to 1,3-butadiene (BD) present in automobile exhaust, cigarette smoke, and forest fires is of great concern because of its potent carcinogenicity. The adverse health effects of BD are mediated by its epoxide metabolites such as 3,4-epoxy-1-butene (EB), which covalently modify genomic DNA to form promutagenic nucleobase adducts. Because of their direct role in cancer, BD-DNA adducts can be used as mechanism-based biomarkers of BD exposure. In the present work, a mass spectrometry-based methodology was developed for accurate, sensitive, and precise quantification of EB-induced N-7-(1-hydroxy-3-buten-2-yl) guanine (EB-GII) DNA adducts in vivo. In our approach, EB-GII adducts are selectively released from DNA backbone by neutral thermal hydrolysis, followed by ultrafiltration, offline HPLC purification, and isotope dilution nanoLC/ESI+-HRMS3 analysis on an Orbitrap Velos mass spectrometer. Following method validation, EB-GII lesions were quantified in human fibrosarcoma (HT1080) cells treated with micromolar concentrations of EB and in liver tissues of rats exposed to sub-ppm concentrations of BD (0.5–1.5 ppm). EB-GII concentrations increased linearly from 1.15?±?0.23 to 10.11?±?0.45 adducts per 106 nucleotides in HT1080 cells treated with 0.5–10 μM DEB. EB-GII concentrations in DNA of laboratory rats exposed to 0.5, 1.0, and 1.5 ppm BD were 0.17?±?0.05, 0.33?±?0.08, and 0.50?±?0.04 adducts per 106 nucleotides, respectively. We also used the new method to determine the in vivo half-life of EB-GII adducts in rat liver DNA (2.20?±?0.12 d) and to detect EB-GII in human blood DNA. To our knowledge, this is the first application of nanoLC/ESI+-HRMS3 Orbitrap methodology to quantitative analysis of DNA adducts in vivo. Figure a
? 相似文献
947.
Kirsty McKay Tara L. Salter Andrew Bowfield James L. Walsh Ian S. Gilmore James W. Bradley 《Journal of the American Society for Mass Spectrometry》2014,25(9):1528-1537
Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources. Figure
? 相似文献
948.
Large Hexagonal Bi‐ and Trilayer Graphene Single Crystals with Varied Interlayer Rotations
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Zheng Yan Yuanyue Liu Long Ju Zhiwei Peng Dr. Jian Lin Dr. Gunuk Wang Dr. Haiqing Zhou Changsheng Xiang E. L. G. Samuel Carter Kittrell Dr. Vasilii I. Artyukhov Prof. Feng Wang Prof. Boris I. Yakobson Prof. James M. Tour 《Angewandte Chemie (International ed. in English)》2014,53(6):1565-1569
Bi‐ and trilayer graphene have attracted intensive interest due to their rich electronic and optical properties, which are dependent on interlayer rotations. However, the synthesis of high‐quality large‐size bi‐ and trilayer graphene single crystals still remains a challenge. Here, the synthesis of 100 μm pyramid‐like hexagonal bi‐ and trilayer graphene single‐crystal domains on Cu foils using chemical vapor deposition is reported. The as‐produced graphene domains show almost exclusively either 0° or 30° interlayer rotations. Raman spectroscopy, transmission electron microscopy, and Fourier‐transformed infrared spectroscopy were used to demonstrate that bilayer graphene domains with 0° interlayer stacking angles were Bernal stacked. Based on first‐principle calculations, it is proposed that rotations originate from the graphene nucleation at the Cu step, which explains the origin of the interlayer rotations and agrees well with the experimental observations. 相似文献
949.
Dramatic Influence of an Anionic Donor on the Oxygen‐Atom Transfer Reactivity of a MnV–Oxo Complex
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Heather M. Neu Dr. Matthew G. Quesne Tzuhsiung Yang Dr. Katharine A. Prokop‐Prigge Prof. Kyle M. Lancaster James Donohoe Prof. Serena DeBeer Dr. Sam P. de Visser Prof. David P. Goldberg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(45):14584-14588
Addition of an anionic donor to an MnV(O) porphyrinoid complex causes a dramatic increase in 2‐electron oxygen‐atom‐transfer (OAT) chemistry. The 6‐coordinate [MnV(O)(TBP8Cz)(CN)]? was generated from addition of Bu4N+CN? to the 5‐coordinate MnV(O) precursor. The cyanide‐ligated complex was characterized for the first time by Mn K‐edge X‐ray absorption spectroscopy (XAS) and gives Mn?O=1.53 Å, Mn?CN=2.21 Å. In combination with computational studies these distances were shown to correlate with a singlet ground state. Reaction of the CN? complex with thioethers results in OAT to give the corresponding sulfoxide and a 2e?‐reduced MnIII(CN)? complex. Kinetic measurements reveal a dramatic rate enhancement for OAT of approximately 24 000‐fold versus the same reaction for the parent 5‐coordinate complex. An Eyring analysis gives ΔH≠=14 kcal mol?1, ΔS≠=?10 cal mol?1 K?1. Computational studies fully support the structures, spin states, and relative reactivity of the 5‐ and 6‐coordinate MnV(O) complexes. 相似文献
950.
Halotriazolium Axle Functionalised [2]Rotaxanes for Anion Recognition: Investigating the Effects of Halogen‐Bond Donor and Preorganisation
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James M. Mercurio Richard C. Knighton Dr. James Cookson Prof. Paul D. Beer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11740-11749
The anion‐templated synthesis of three novel halogen‐bonding 5‐halo‐1,2,3‐triazolium axle containing [2]rotaxanes is described, and the effects of altering the nature of the halogen‐bond donor atom together with the degree of inter‐component preorganisation on the anion‐recognition properties of the interlocked host investigated. The ability of the bromotriazolium motif to direct the halide‐anion‐templated assembly of interpenetrated [2]pseudorotaxanes was studied initially; bromide was found to be the most effective template. As a consequence, bromide anion templation was used to synthesise the first bromotriazolium axle containing [2]rotaxane, the anion‐binding properties of which, determined by 1H NMR spectroscopic titration experiments, revealed enhanced bromide and iodide recognition relative to a hydrogen‐bonding protic triazolium rotaxane analogue. Two halogen‐bonding [2]rotaxanes with bromo‐ and iodotriazolium motifs integrated into shortened axles designed to increase inter‐component preorganisation were also synthesised. Anion 1H NMR spectroscopic titration experiments demonstrated that these rotaxanes were able to bind halide anions even more strongly, with the iodotriazolium axle integrated rotaxane capable of recognising halides in aqueous solvent media. Importantly, these observations suggest that a halogen‐bonding interlocked host binding domain, in combination with increased inter‐component preorganisation, are requisite design features for a potent anion receptor. 相似文献