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21.
Dr. Adam Mames Dariusz Gołowicz Dr. Mariusz Pietrzak Dr. Krzysztof Kazimierczuk Prof. Sławomir Szymański Dr. Tomasz Ratajczyk 《Chemphyschem》2020,21(6):540-545
Triptycene derivatives are widely utilized in different fields of chemistry and materials sciences. Their physicochemical properties, often of pivotal importance for the rational design of triptycene-based functional materials, are influenced by noncovalent interactions between substituents mounted on the triptycene skeleton. Herein, a unique interaction between electron-rich substituents in the peri position and the silyl group located on the bridgehead sp3-carbon is discussed on the example of 1,4-dichloro-9-(p-methoxyphenyl)-silyltriptycene (TRPCl) which exists in solution in the form of two rotamers differing by dispositions, syn or anti, of the Si−CPh (the CPh atom is from the p-methoxyphenyl group) bond against the peri-Cl atom. For the first time, substantial differences between the Si−CPh bonds in these two dispositions are identified, based on indirect experimental and direct theoretical evidence. For these two orientations, the experimental 1J(Si,CPh) values differ by as much as 10 percent. The differences are explained in terms of effective electron density transfer from the peri-Cl atom to the antibonding σ* orbitals of the Si−X bonds (X=H, CPh) oriented anti to that atom. The electronic effects are revealed by an NBO analysis. Connections of these observations with the notion of blue-shifting hydrogen bonds are discussed. 相似文献
22.
Hyejin Hyeon Ho Bong Hyun Boram Go Sung Chun Kim Yong-Hwan Jung Young-Min Ham 《Molecules (Basel, Switzerland)》2022,27(1)
Magnolia flower buds are a source of herbal medicines with various active compounds. In this study, differences in the distribution and abundance of major essential oils, phenolic acids, and primary metabolites between white flower buds of Magnolia heptapeta and violet flower buds of Magnolia denudata var. purpurascens were characterised. A multivariate analysis revealed clear separation between the white and violet flower buds with respect to primary and secondary metabolites closely related to metabolic systems. White flower buds contained large amounts of monoterpene hydrocarbons (MH), phenolic acids, aromatic amino acids, and monosaccharides, related to the production of isoprenes, as MH precursors, and the activity of MH synthase. However, concentrations of β-myrcene, a major MH compound, were higher in violet flower buds than in white flower buds, possibly due to higher threonine levels and low acidic conditions induced by comparatively low levels of some organic acids. Moreover, levels of stress-related metabolites, such as oxygenated monoterpenes, proline, and glutamic acid, were higher in violet flower buds than in white flower buds. Our results support the feasibility of metabolic profiling for the identification of phytochemical differences and improve our understanding of the correlated biological pathways for primary and secondary metabolites. 相似文献
23.
Choong‐Hee Lee Sung‐Hyung Lee Kwang‐Chun Go Sung‐Min Oh Jae Sheung Shin Jae‐Hyun Kim 《ETRI Journal》2015,37(5):856-866
A heterogeneous network (HetNet) is a network topology composed by deploying multiple HetNets under the coverage of macro cells (MCs). It can improve network throughput, extend cell coverage, and offload network traffic; for example, the network traffic of a 5G mobile communications network. A HetNet involves a mix of radio technologies and various cell types working together seamlessly. In a HetNet, coordination between MCs and small cells (SCs) has a positive impact on the performance of the networks contained within, and consequently on the overall user experience. Therefore, to improve user‐perceived service quality, HetNets require high‐efficiency network protocols and enhanced radio technologies. In this paper, we introduce a 5G HetNet comprised of MCs and both fixed and mobile SCs (mSCs). The featured mSCs can be mounted on a car, bus, or train and have different characteristics to fixed SCs (fSCs). In this paper, we address the technical challenges related to mSCs. In addition, we analyze the network performance under two HetNet scenarios — MCs and fSCs, and MCs and mSCs. 相似文献
24.
K Nilson J Åhlund MN Shariati J Schiessling P Palmgren B Brena E Göthelid F Hennies Y Huismans F Evangelista P Rudolf M Göthelid N Mårtensson C Puglia 《The Journal of chemical physics》2012,137(4):044708
X-ray spectroscopy studies of potassium intercalated metal-free phthalocyanine multilayers adsorbed on Al(110) have been undertaken. Photoelectron spectroscopy measurements show the presence of several charge states of the molecules upon K intercalation, due to a charge transfer from the alkali. In addition, the comparison of valence band photoemission spectra with the density functional theory calculations of the density of states of the H(2)Pc(-) anion indicates a filling of the formerly lowest unoccupied molecular orbital by charge transfer from the alkali. This is further confirmed by x-ray absorption spectroscopy (XAS) studies, which show a decreased density of unoccupied states. XAS measurements in different experimental geometries reveal that the molecules in the pristine film are standing upright on the surface or are only slightly tilted away from the surface normal but upon K intercalation, the molecular orientation is changed in that the tilt angle of the molecules increases. 相似文献
25.
Optical Review - A novel color removal method for digital color images is proposed. In this method, differences of colors in an input color image are reflected effectively, and the perceived... 相似文献
26.
R. Kruszka M. Ekielski K. Gołaszewska K. Korwin-Mikke Z. Sidor M. Wzorek D. Pierścińska R. Sarzała T. Czyszanowski A. Piotrowska 《Opto-Electronics Review》2011,19(1):51-55
The results of modelling of the influence of photonic crystal on the performance of VCSEL-type semiconductor laser structure
are shown and indicate that the use of those structures would significantly improve the working parameters of the devices.
The method of fabrication of photonic crystals in the Bragg mirrors of GaAs/AlGaAs-based VCSELs is presented. 相似文献
27.
28.
J. Dubowik I. Gościańska Y. Kudryavtsev 《The European physical journal. Special topics》2008,158(1):113-118
We report on FMR experiments performed for the first time on thin Ni-Mn-Ga films clamped to the mica substrates and then fully
released from them. The aim is to evaluate the role of magnetoelastic coupling in stressed Ni-Mn-Ga Heusler alloy films that
undergo martensitic transformation. The experimental results show that the difference in the effective magnetization 4π(Meff tubes-Meff films) is negligible in the austenite phase and it increases to about 1–1.5 kG at temperatures well below the martensitic transformation.
The data suggests that magnetoelastic coupling in the martensite phase of Ni-Mn-Ga thin films is typical of normal thin magnetic
films with magnetostriction of about 50 ppm. 相似文献
29.
Low-field microwave absorption has been measured as a function of magnetic field in a series of thin film structures exhibiting or not exhibiting the giant magnetoresistance effect (GMR). Although a close correlation has been found between the microwave absorption and GMR, an additional absorption due to magnetization reversal is shown to have substantial effect on the overall microwave response. 相似文献
30.