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91.
James A. Phillips Anna R. Ley Patrick W. Treacy Benjamin M. Wahl Brittany C. Zehner Kelling J. Donald Samuel Gillespie 《International journal of quantum chemistry》2020,120(20):e26383
We have explored the structural and energetic properties of a series of RMX3-NH3 (M=Si, Ge; X=F, Cl; R=CH3, C6H5) complexes using density functional theory and low-temperature infrared spectroscopy. In the minimum-energy structures, the NH3 binds axially to the metal, opposite a halogen, while the organic group resides in an equatorial site. Remarkably, the primary mode of interaction in several of these systems seems to be hydrogen bonding (C-H--N) rather than a tetrel (N→M) interaction. This is particularly clear for the RMCl3-NH3 complexes, and analyses of the charge distributions of the acid fragment corroborate this assessment. We also identified a set of metastable geometries in which the ammonia binds opposite the organic substituent in an axial orientation. Acid fragment charge analyses also provide a clear rationale as to why these configurations are less stable than the minimum-energy structures. Matrix-isolation infrared spectra provide clear evidence for the occurrence of the minimum-energy form of CH3SiCl3–NH3, but analogous results for CH3GeCl3–NH3 are less conclusive. Computational scans of the M-N distance potentials for CH3SiCl3–NH3 and CH3GeCl3–NH3, both in the gas phase and bulk dielectric media, reveal a great deal of anharmonicity and a propensity for condensed-phase structural change. 相似文献
92.
Hualong Song Simon J. Allison Viktor Brabec Hannah E. Bridgewater Jana Kasparkova Hana Kostrhunova Vojtech Novohradsky Roger M. Phillips Jitka Pracharova Nicola J. Rogers Samantha L. Shepherd Peter Scott 《Angewandte Chemie (International ed. in English)》2020,59(34):14677-14685
Monosaccharides are added to the hydrophilic face of a self‐assembled asymmetric FeII metallohelix, using CuAAC chemistry. The sixteen resulting architectures are water‐stable and optically pure, and exhibit improved antiproliferative selectivity against colon cancer cells (HCT116 p53+/+) with respect to the non‐cancerous ARPE‐19 cell line. While the most selective compound is a glucose‐appended enantiomer, its cellular entry is not mainly glucose transporter‐mediated. Glucose conjugation nevertheless increases nuclear delivery ca 2.5‐fold, and a non‐destructive interaction with DNA is indicated. Addition of the glucose units affects the binding orientation of the metallohelix to naked DNA, but does not substantially alter the overall affinity. In a mouse model, the glucose conjugated compound was far better tolerated, and tumour growth delays for the parent compound (2.6 d) were improved to 4.3 d; performance as good as cisplatin but with the advantage of no weight loss in the subjects. 相似文献
93.
Morphology development during isothermal annealing of poly(ether-ester) multiblock copolymers with hard segments containing poly(tetramethylene isophthalate) is examined by differential scanning calorimetry (DSC) and small-angle x-ray scattering (SAXS). Reorganization in the solid-state occurs by melting and recrystallization. At temperatures close to the melting point, glass transition measurements after quenching from the annealing temperature suggest microphase mixing follows melting. The temperature of maximum recrystallization rate is elevated relative to that of isothermal crystallization. SAXS experiments suggest that a memory of the initial morphology is retained during annealing. Aspects of the DSC scans related to crystallization on cooling and rescanning also suggest that the morphology at the annealing temperature plays a governing role in the determination of the degree of order possible on cooling. The crystalline regions stable at the annealing temperature are envisioned to function in a dual role, acting as nucleation centers for recrystallization and as a form of “constraint” to ordering on cooling. © 1996 John Wiley & Sons, Inc. 相似文献
94.
Many mushroom species are consumed as food, while significant numbers are also utilised medicinally. Mushrooms are rich in nutrients and bioactive compounds. A growing body of in vitro, in vivo, and human research has revealed their therapeutic potentials, which include such properties as anti-pathogenic, antioxidant, anti-inflammatory, immunomodulatory, gut microbiota enhancement, and angiotensin-converting enzyme 2 specificity. The uses of medicinal mushrooms (MMs) as extracts in nutraceuticals and other functional food and health products are burgeoning. COVID-19 presents an opportunity to consider how, and if, specific MM compounds might be utilised therapeutically to mitigate associated risk factors, reduce disease severity, and support recovery. As vaccines become a mainstay, MMs may have the potential as an adjunct therapy to enhance immunity. In the context of COVID-19, this review explores current research about MMs to identify the key properties claimed to confer health benefits. Considered also are barriers or limitations that may impact general recommendations on MMs as therapy. It is contended that the extraction method used to isolate bioactive compounds must be a primary consideration for efficacious targeting of physiological endpoints. Mushrooms commonly available for culinary use and obtainable as a dietary supplement for medicinal purposes are included in this review. Specific properties related to these mushrooms have been considered due to their potential protective and mediating effects on human exposure to the SARS CoV-2 virus and the ensuing COVID-19 disease processes. 相似文献
95.
A molecular-dynamics model for crack propagation under steady-state conditions is used to study dynamic instabilities along a grain boundary in aluminum that occur when the crack speed approaches 1/3 of the material's Rayleigh wave speed. Instead of crack branching, as is characteristic for a crack propagating in a homogeneous environment, the instability of an intergranular crack results in a periodic series of dislocation bursts. These bursts limit the crack speed and produce velocity oscillations with a large increase in energy dissipation that increases the grain boundary toughness. 相似文献
96.
97.
98.
V. Barger A. D. Martin R. J. N. Phillips 《Zeitschrift fur Physik C Particles and Fields》1983,21(1):99-101
We point out properties of the “perpendicularev mass”, defined in terms of transverse momentap t byM T 2 (ev)=2|p eT | |p vT |?2p eT ·p vT , that make it particularly well suited toW mass and width determinations. We give an analytic expression for its distribution inW production and subsequentW→ev decay a \(\bar pp\) colliders, accurate to order 〈p WT 2 /M W 2 〉≈1%. A maximum likelihood fit of this formula to the five UA1 events givesM W=80.3 ?3 +6 GeV. 相似文献
99.
100.
N. Christopher Phillips 《Mathematische Nachrichten》1995,176(1):243-247
We prove the following two improvements of a result of Becker. (1) If A is a pro-C*-algebra, then every derivation on A is approximately inner. (2) If A is a separable σ-C*-algebra, and if every C* quotient of A has the property that every derivation on it is inner, then also every derivation on A is inner. We also give an example of a derivation on a separable σ-C*-algebra which is not inner but which induces an inner derivation on every C* quotient. 相似文献