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排序方式: 共有1275条查询结果,搜索用时 15 毫秒
61.
Van T. Tran Zi‐Qi Li Omar Apolinar Joseph Derosa Matthew V. Joannou Steven R. Wisniewski Martin D. Eastgate Keary M. Engle 《Angewandte Chemie (International ed. in English)》2020,59(19):7409-7413
We report that Ni(COD)(DQ) (COD=1,5‐cyclooctadiene, DQ=duroquinone), an air‐stable 18‐electron complex originally described by Schrauzer in 1962, is a competent precatalyst for a variety of nickel‐catalyzed synthetic methods from the literature. Due to its apparent stability, use of Ni(COD)(DQ) as a precatalyst allows reactions to be conveniently performed without use of an inert‐atmosphere glovebox, as demonstrated across several case studies. 相似文献
62.
Dr. Thomas M. Osborn Popp Ariel Z. Plantz Prof. Omar M. Yaghi Prof. Jeffrey A. Reimer 《Chemphyschem》2020,21(1):32-35
Understanding the factors that affect self-diffusion in isoreticular and multivariate (MTV) MOFs is key to their application in drug delivery, separations, and heterogeneous catalysis. Here, we measure the apparent self-diffusion of solvents saturated within the pores of large single crystals of MOF-5, IRMOF-3 (amino-functionalized MOF-5), and 17 MTV-MOF-5/IRMOF-3 materials at various mole fractions. We find that the apparent self-diffusion coefficient of N,N-dimethylformamide (DMF) may be tuned linearly between the diffusion coefficients of MOF-5 and IRMOF-3 as a function of the linker mole fraction. We compare a series of solvents at saturation in MOF-5 and IRMOF-3 to elucidate the mechanism by which the linker amino groups tune molecular diffusion. The ratio of the self-diffusion coefficients for solvents in MOF-5 to those in IRMOF-3 is similar across all solvents tested, regardless of solvent polarity. We conclude that average pore aperture, not solvent-linker chemical interactions, is the primary factor responsible for the different diffusion dynamics upon introduction of an amino group to the linker. 相似文献
63.
The heat capacity at constant pressure of CuGe2P3 is measured in the temperature range from 180 to 550 K. Standard enthalpies and entropies relative to 298.15 K are calculated from the heat capacity data. The Debye temperature in the high-temperature limit is estimated to be about 710 K. 相似文献
64.
Muna E. Raypah Ahmad Fairuz Omar Jelena Muncan Musfirah Zulkurnain Abdul Rahman Abdul Najib 《Molecules (Basel, Switzerland)》2022,27(7)
Honey is a natural product that is considered globally one of the most widely important foods. Various studies on authenticity detection of honey have been fulfilled using visible and near-infrared (Vis-NIR) spectroscopy techniques. However, there are limited studies on stingless bee honey (SBH) despite the increase of market demand for this food product. The objective of this work was to present the potential of Vis-NIR absorbance spectroscopy for profiling, classifying, and quantifying the adulterated SBH. The SBH sample was mixed with various percentages (10–90%) of adulterants, including distilled water, apple cider vinegar, and high fructose syrup. The results showed that the region at 400–1100 nm that is related to the color and water properties of the samples was effective to discriminate and quantify the adulterated SBH. By applying the principal component analysis (PCA) on adulterants and honey samples, the PCA score plot revealed the classification of the adulterants and adulterated SBHs. A partial least squares regression (PLSR) model was developed to quantify the contamination level in the SBH samples. The general PLSR model with the highest coefficient of determination and lowest root means square error of cross-validation ( and ) was acquired. The aquaphotomics analysis of adulteration in SBH with the three adulterants utilizing the short-wavelength NIR region (800–1100 nm) was presented. The structural changes of SBH due to adulteration were described in terms of the changes in the water molecular matrix, and the aquagrams were used to visualize the results. It was revealed that the integration of NIR spectroscopy with aquaphotomics could be used to detect the water molecular structures in the adulterated SBH. 相似文献
65.
Mostafa El Khomsi Hamada Imtara Mohammed Kara Anouar Hmamou Amine Assouguem Brahim Bourkhiss Mahmoud Tarayrah Mashail N. AlZain Nurah M. Alzamel Omar Noman Driss Hmouni 《Molecules (Basel, Switzerland)》2022,27(2)
Anchusa italica Retz has been used for a long time in phytotherapy. The aim of the present study was to determine the antioxidant and antibacterial activities of extracts from the leaves and roots of Anchusa italica Retz. We first determined the content of phenolic compounds and flavonoids using Folin–Ciocalteu reagents and aluminum chloride (AlCl3). The antioxidant activity was determined using three methods: reducing power (FRAP), 2.2-diphenyl-1-picrylhydrazyl (DPPH), total antioxidant capacity (TAC). The antimicrobial activity was investigated against four strains of Escherichia coli, two strains of Klebsiella pneumoniae and coagulase-negative Staphylococcus, and one fungal strain of Candida albicans. The results showed that the root extract was rich in polyphenols (43.29 mg GAE/g extract), while the leave extract was rich in flavonoids (28.88 mg QE/g extract). The FRAP assay showed a strong iron reduction capacity for the root extract (IC50 of 0.11 µg/mL) in comparison to ascorbic acid (IC50 of 0.121 µg/mL). The DPPH test determined an IC50 of 0.11 µg/mL for the root extract and an IC50 of 0.14 µg/mL for the leaf extract. These values are low compared to those for ascorbic acid (IC50 of 0.16 µg/mL) and BHT (IC50 0.20 µg/mL). The TAC values of the leaf and root extracts were 0.51 and 0.98 mg AAE/g extract, respectively. In vitro, the extract showed inhibitory activity against all strains studied, with diameters of zones of inhibition in the range of 11.00–16.00 mm for the root extract and 11.67–14.33 mm for the leaf extract. The minimum inhibitory concentration was recorded for the leaf extract against E. coli (ATB:57), corresponding to 5 mg/mL. Overall, this research indicates that the extracts of Anchusa italica Retz roots and leaves exert significant antioxidant and antibacterial activities, probably because of the high content of flavonoids and polyphenols. 相似文献
66.
Henri Balard Alain Saada Jacques Hartmann Omar Aouadj And Eugne Papirer 《Macromolecular Symposia》1996,108(1):63-80
The surface properties of the fillers are determining for obtaining high performance filled polymers. Yet, their determination is most difficult. This paper proposes to use inverse gas chromatography, either at infinite dilution or finite concentration conditions, to estimate surface energy and nanomorphological characteristics, but also surface heterogeneity of different clays, talcs of various origins and ground muscovites. 相似文献
67.
Zhihua Xie Dimitrios Pavlidis Pablo Salinas Christopher C. Pain Omar K. Matar 《国际流体数值方法杂志》2020,92(7):765-784
A novel control volume finite element method with adaptive anisotropic unstructured meshes is presented for three-dimensional three-phase flows with interfacial tension. The numerical framework consists of a mixed control volume and finite element formulation with a new P1DG-P2 elements (linear discontinuous velocity between elements and quadratic continuous pressure between elements). A “volume of fluid” type method is used for the interface capturing, which is based on compressive control volume advection and second-order finite element methods. A force-balanced continuum surface force model is employed for the interfacial tension on unstructured meshes. The interfacial tension coefficient decomposition method is also used to deal with interfacial tension pairings between different phases. Numerical examples of benchmark tests and the dynamics of three-dimensional three-phase rising bubble, and droplet impact are presented. The results are compared with the analytical solutions and previously published experimental data, demonstrating the capability of the present method. 相似文献
68.
Information entropy metrics have been applied to a wide range of problems that were abstracted as complex networks. This growing body of research is scattered in multiple disciplines, which makes it difficult to identify available metrics and understand the context in which they are applicable. In this work, a narrative literature review of information entropy metrics for complex networks is conducted following the PRISMA guidelines. Existing entropy metrics are classified according to three different criteria: whether the metric provides a property of the graph or a graph component (such as the nodes), the chosen probability distribution, and the types of complex networks to which the metrics are applicable. Consequently, this work identifies the areas in need for further development aiming to guide future research efforts. 相似文献
69.
Michele Arcangelo Quinto Juan Manuel Monti Mario Enrique Alcocer Avila Philippe F. Weck Omar Ariel Fojón Roberto Daniel Rivarola Christophe Champion 《X射线光谱测定》2020,49(1):95-98
The present work focuses on studying the contribution of the Auger electron emission in proton-induced interactions in biological matter. The Monte Carlo track-structure code, TILDA-V, was then used for modeling the protons beams of 10 keV to 100 MeV in biological matter, namely, water vapor and hydrated DNA. The main ionizing processes are described by means of an extensive set of ab initio differential and total cross sections computed within a quantum-mechanical CDW-EIS approximation. 相似文献
70.
Dongyi Liu Ahmed M. El‐Zohry Maria Taddei Clemens Matt Laura Bussotti Zhijia Wang Jianzhang Zhao Omar F. Mohammed Mariangela Di Donato Stefan Weber 《Angewandte Chemie (International ed. in English)》2020,59(28):11591-11599
We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long‐lived triplet charge‐transfer (3CT) state, based on the electron spin control using spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT‐ISC takes 8 ns to produce the 3NI* state. Then the slow secondary CS (125 ns) gives the long‐lived 3CT state (0.94 μs in deaerated n‐hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as 1NI*→1CT→3NI*→3CT. With time‐resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron‐spin polarization pattern was observed for the naphthalimide‐localized triplet state. Our spiro compact dyad structure and the electron spin‐control approach is different to previous methods for which invoking transition‐metal coordination or chromophores with intrinsic ISC ability is mandatory. 相似文献