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排序方式: 共有78条查询结果,搜索用时 296 毫秒
41.
Wang L Xie H Qiao X Goffin A Hodgkinson T Yuan X Sun K Fuller GG 《Langmuir : the ACS journal of surfaces and colloids》2012,28(1):459-467
The interfacial viscoelastic behavior of natural silk fibroin at both the air/water and oil/water interfaces is reported. This natural multiblock copolymer is found to be strongly amphiphilic and forms stable films at these interfaces. The result is an interfacial layer that is rheologically complex with strong surface elastic moduli that are only slightly frequency-dependent. The kinetics of surface viscoelastic evolution are reported as functions of time for various concentrations of the spread films. Films deposited by Langmuir-Blodgett deposition were studied by scanning electron microscopy (SEM) to reveal a fibrous structure at the interface. The production of stable O/W emulsions by silk fibroin further confirms the generation of the elastic films at the oil/water interfaces. 相似文献
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The boundary-value problem of the reflection and transmission of light by a composite structure, wherein a surface-relief dielectric grating is coupled to a structurally chiral volume grating, has been formulated and solved with results showing the robust co-existence of phenomena characteristic of both types of grating: namely, Rayleigh–Wood anomalies and Bragg phenomena. A mechanism to strengthen the coupling between both grating types is included – namely, a quarter wave plate – whose birefringence converts normally incident linearly polarised light at the Bragg wavelength into transmitted circularly polarised light (and vice versa). It is possible to tailor the period of the sinusoidally corrugated surface-relief grating such that the scattering of obliquely incident light from above, by the surface grating, will lead to a specific non-specular order being scattered onto a path which is normally incident on the rest of the composite structure. Significantly, such orders exhibit the circular Bragg phenomenon in reflection and transmission only if both grating types are present, making this a “truly” coupled effect. 相似文献
44.
Diversity‐Oriented Synthesis of Drug‐Like Macrocyclic Scaffolds Using an Orthogonal Organo‐ and Metal Catalysis Strategy
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Dr. André Grossmann Sean Bartlett Matej Janecek Dr. James T. Hodgkinson Prof. David R. Spring 《Angewandte Chemie (International ed. in English)》2014,53(48):13093-13097
Small‐molecule modulators of biological targets play a crucial role in biology and medicine. In this context, diversity‐oriented synthesis (DOS) provides strategies toward generating small molecules with a broad range of unique scaffolds, and hence three‐dimensionality, to target a broad area of biological space. In this study, an organocatalysis‐derived DOS library of macrocycles was synthesized by exploiting the pluripotency of aldehydes. The orthogonal combination of multiple diversity‐generating organocatalytic steps with alkene metathesis enabled the synthesis of 51 distinct macrocyclic structures bearing 48 unique scaffolds in only two to four steps without the need for protecting groups. Furthermore, merging organocatalysis and alkene metathesis in a one‐pot protocol facilitated the synthesis of drug‐like macrocycles with natural‐product‐like levels of shape diversity in a single step. 相似文献
45.
Dr. Martin Dračínský Dr. Jan Vícha Kateřina Bártová Prof. Paul Hodgkinson 《Chemphyschem》2020,21(18):2075-2083
The factors contributing to the accuracy of quantum-chemical calculations for the prediction of proton NMR chemical shifts in molecular solids are systematically investigated. Proton chemical shifts of six solid amino acids with hydrogen atoms in various bonding environments (CH, CH2, CH3, OH, SH and NH3) were determined experimentally using ultra-fast magic-angle spinning and proton-detected 2D NMR experiments. The standard DFT method commonly used for the calculations of NMR parameters of solids is shown to provide chemical shifts that deviate from experiment by up to 1.5 ppm. The effects of the computational level (hybrid DFT functional, coupled-cluster calculation, inclusion of relativistic spin-orbit coupling) are thoroughly discussed. The effect of molecular dynamics and nuclear quantum effects are investigated using path-integral molecular dynamics (PIMD) simulations. It is demonstrated that the accuracy of the calculated proton chemical shifts is significantly better when these effects are included in the calculations. 相似文献
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Hodgkinson JT Galloway WR Saraf S Baxendale IR Ley SV Ladlow M Welch M Spring DR 《Organic & biomolecular chemistry》2011,9(1):57-61
Expedient syntheses of Pseudomonas quinolone signal (PQS) and related structural analogues using microwave and flow methods are reported. 相似文献
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NMR spectra of 78 cucurbitacin derivatives were analysed for evidence of conformational aberrations in the c-ring, and differences were found in the 9β-Me, 9β-H and 9α-H series. Evidence in support of postulated ring deformations was obtained from solvent-dependent and lanthanide shift spectra of selected model substances. 相似文献
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Robbins AJ Ng WT Jochym D Keal TW Clark SJ Tozer DJ Hodgkinson P 《Physical chemistry chemical physics : PCCP》2007,9(19):2389-2396
Advances in solid-state NMR methodology and computational chemistry are applied to the (19)F NMR of solid octafluoronaphthalene. It is demonstrated experimentally, and confirmed by density functional theory (DFT) calculations, that the spectral resolution in the magic-angle spinning spectrum is limited by the anisotropy of the bulk magnetic susceptibility (ABMS). This leads to the unusual observation that the resolution improves as the sample is diluted. DFT calculations provide assignments of each of the peaks in the (19)F spectrum, but the predictions are close to the limits of accuracy and correlation information from 2-D NMR is invaluable in confirming the assignments. The effects of non-Gaussian lineshapes on the use of 2-D NMR for mapping correlations of spectral frequencies (e.g. due to the ABMS) are also discussed. 相似文献