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The properties of the negative parity states of55Fe and57Fe are investigated in the framework of the intermediate coupling model. In the model, a neutron or a quasineutron is coupled to anharmonic vibrations of the core. Anharmonicities of the vibrations are estimated through the observed properties of the core. Energy levels, spectroscopic factors and electromagnetic properties have been calculated. The results of the present calculations are also compared with available experimental results and other theoretical results. The model reasonably accounts for many of the properties of the low-lying states. 相似文献
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The effect of the radiative cooling of electrons on the gravitational collapse of cold dust grains with fluctuating electric
charge is investigated. We find that the radiative cooling as well as the charge fluctuations, both, enhance the growth rate
of the Jeans instability. However, the Jeans length, which is zero for cold grains and nonradiative plasma, becomes finite
in the presence of radiative cooling of electrons and is further enhanced due to charge fluctuations of grains resulting in
an increased threshold of the spatial scale for the Jeans instability. 相似文献
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The LSD (Logic for Structure Determination) program gener-ates organic molecular structures from 1D and 2D NMR data without resorting to chemical shift databases. Its use in the res-olution of natural product structure determination problems has been already reported in the literature. This paper describes how data and structures are internally represented and pro-cessed by LSD to build solution structures. 相似文献
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James D. Grayson Matthew P. Baumgartner Cleide Dos Santos Souza Samuel J. Dawes Imane Ghafir El Idrissi Jennifer C. Louth Sasha Stimpson Emma Mead Charlotte Dunbar Joanna Wolak Gary Sharman David Evans Anastasia Zhuravleva Margarita Segovia Roldan Nicola Antonio Colabufo Ke Ning Claire Garwood James A. Thomas Benjamin M. Partridge Antonio de la Vega de Leon Valerie J. Gillet Amlia P. Rauter Beining Chen 《Chemical science》2021,12(10):3768
Amyloid β oligomers (Aβo) are the main toxic species in Alzheimer''s disease, which have been targeted for single drug treatment with very little success. In this work we report a new approach for identifying functional Aβo binding compounds. A tailored library of 971 fluorine containing compounds was selected by a computational method, developed to generate molecular diversity. These compounds were screened for Aβo binding by a combined 19F and STD NMR technique. Six hits were evaluated in three parallel biochemical and functional assays. Two compounds disrupted Aβo binding to its receptor PrPC in HEK293 cells. They reduced the pFyn levels triggered by Aβo treatment in neuroprogenitor cells derived from human induced pluripotent stem cells (hiPSC). Inhibitory effects on pTau production in cortical neurons derived from hiPSC were also observed. These drug-like compounds connect three of the pillars in Alzheimer''s disease pathology, i.e. prion, Aβ and Tau, affecting three different pathways through specific binding to Aβo and are, indeed, promising candidates for further development.A new approach combining virtual screening, 19F and STD NMR, and biochemical assays using hiPSC and targetting multiple pathways involving Aβ, PrPC and Tau provides a more effective strategy for Alzheimer''s disease drug discovery than Aβ only approach. 相似文献
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Ultrasonic propagation in slurries 总被引:1,自引:0,他引:1
Experimental measurements have been made of the ultrasonic velocity and attenuation in some simple suspensions of, mainly, silicon carbide in water and in ethylene glycol. These are compared with theoretical predictions based on a novel hydrodynamic model. Predicted ultrasonic velocities are in excellent agreement with the measured values. Predicted and measured ultrasonic attenuations do not agree as well. However, the suspensions give rise to excess attenuations rising to a few hundred nepers per metre and special experimental techniques were needed to measure ultrasonic properties. To predict attenuations to within, say, 20% for mixtures such as these is a major achievement. 相似文献
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R. Helburn M. Bartoli K. Pohaku J. Maxka D. Compton B. Creedon C. Stimpson 《Journal of Physical Organic Chemistry》2007,20(5):321-331
Hydrophobic forms of the N,N‐dialkyl‐4‐nitroaniline (DNAP) (p‐O2NC6H4NR2) ( 1a–f ) and alkyl‐4‐nitrophenyl ether (p‐O2NC6H4OR) ( 2a–c ) solvatochromic π* indicators have been characterized and compared with respect to: (a) solvatochromic bandshape, (b) sensitivity expressed as ?s , ( / d π * ), and (c) trends in ? s with increasing length of alkyl chain(s) on the probe molecule. ? Octyl 4‐nitrophenyl ether (p‐O2NC6H4OC8H17) ( 2b ) and ? decyl 4‐nitrophenyl ether (p‐O2N C6H4 OC10H21) ( 2c ) were synthesized and their solvatochromic UV/Vis absorption bands were found to maintain a Gausso‐Lorentzian bandshape for the indicators in non‐polar and alkyl substituted aromatic solvents, for example, hexane(s) and mesitylene. Corresponding absorption bands for 1a–f display increasing deviation from a Gausso‐Lorentzian shape in the same solvents as the alkyl chains on the indicator are increased in length all the way to C10 and C12, for example, N,N‐didecyl‐4‐nitroaniline (p‐O2NC6H4N (C10H21)2) and N,N‐didodecyl‐4‐nitroaniline (p‐O2NC6H4N (C12H25)2) ( 1d–f ). A plot of ? s versus Cn follows a 1st order decay for the DNAP indicators but is linear for the alkyl 4‐nitrophenyl ethers. A discussion of how the long alkyl chains on the two types of indicators affect the orientation and overlap of n and π * orbitals, and resulting solvatochromic bands is presented. For DNAP, overextending the alkyl chains to obtain greater hydrophobic character may cause the alkane component to dominate solute‐solvation processes at the expense of the probe's fundamental solvatochromic character. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献