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541.
Paula Mayorga Burrezo Wangdong Zeng Michael Moos Marco Holzapfel Sofia Canola Fabrizia Negri Concepci Rovira Jaume Veciana Hoa Phan Jishan Wu Christoph Lambert Juan Casado 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(41):14609-14613
A complete experimental and theoretical study has been carried out for aromatic and quinoidal perylene‐based bridges substituted with bis(diarylamine) and bis(arylimine) groups respectively. The through‐bridge inter‐redox site electronic couplings (VAB) have been calculated for their respective mixed‐valence radical cation and radical anion species. The unusual similitudes of the resulting VAB values for the given structures reveal the intervention of molecular shapes with balanced semi‐quinoidal/semi‐aromatic structures in the charge delocalization. An identical molecular object equally responding to the injection of either positive or negative charges is rare in the field of organic π‐conjugated molecules. However, once probed herein for perylene‐based systems, it can be extrapolated to other π‐conjugated bridges. As a result, this work opens the door to the rational design of true ambipolar bulk and molecular conductors. 相似文献
542.
We report direct measurements of high-energy particles in a rare crossing of the diffusion region in Earth's magnetotail by the Wind spacecraft. The fluxes of energetic electrons up to approximately 300 keV peak near the center of the diffusion region and decrease monotonically away from this region. The diffusion region electron flux spectrum obeys a power law with an index of -3.8 above approximately 2 keV, and the electron angular distribution displays strong field-aligned bidirectional anisotropy at energies below approximately 2 keV, becoming isotropic above approximately 6 keV. These observations indicate significant electron acceleration inside the diffusion region. Ions show no such energization. 相似文献
543.
Phan Thien Thach 《Mathematical Programming》1992,53(1-3):339-359
In this paper we develop a decomposition method using a pricing mechanism which has been widely applied to linear and convex programs for a class of nonconvex optimization problems that are min concave cost flow problems under directed, uncapacitated networks with a hierarchical structure.This paper was completed during the author's stay supported by a Sophia lecturing-research Grant at Sophia University, Tokyo, Japan. 相似文献
544.
Electric and magnetic field observations on the Polar satellite at the subsolar magnetopause show that the magnetopause current is often striated. The largest of the resulting current channels are interpreted as electron diffusion regions because their widths are several electron skin depths and the electron flow U(e) within them does not satisfy E-->+U-->(e)xB-->=0. The data suggest that the magnetopause contains many such electron diffusion regions and that they are required because E-->xB-->/B(2) drifting electrons cannot carry the large filamentary currents imposed on the local plasma. The most probable interpretation of E-->+U-->(e)xB--> not equal 0 is that the pressure term on the right side of the generalized Ohm's law balances this inequality. 相似文献
545.
Kwak S Viet MT Lafleur M 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,162(1):198-205
31P NMR 1D profiling was successfully introduced to measure macroscale mutual-diffusion coefficients (D(m)) of phosphate ions in dextran gels. Series of 1D profiles describing the phosphate concentration along cylindrical dextran gels were acquired at different times. These profiles that included over 600 points could be fitted using equations derived from Fick's law, with D(m) as the single fitting parameter. Release and penetration profiles were recorded providing two alternative approaches for allowing the determination of D(m). The D(m) values were compared with microscale self-diffusion coefficients (D(s)) measured by pulsed field gradient spin echo (PFG-SE) technique. D(m) values, measured between 25 and 45 degrees C, were systematically lower than D(s). The experimental diffusion time and the associated diffusion length of D(s) (60 ms, 10 microm) are short compared to those of D(m) (up to 18 h, 50 mm). These scale differences are considered to be the origin of different D(s) and D(m) and provide information relative to the network in these gels. 相似文献
546.
Phan Dinh Diêu 《Mathematical Logic Quarterly》1971,17(1):421-425
547.
548.
A constitutive equation is derived from a Lodge—Yamamoto type of network theory for polymeric fluids. The network junctions are not assumed to move strictly as points of the continuum but allowed a certain “effective slip”. The rates of creation and destruction of junctions are assumed to depend on the instantaneous elastic energy of the network, or equivalently, the average extension of the network strand, in a simple manner. Agreement between model predictions and the I.U.P.A.C. data on L.D.P.E. is good. 相似文献
549.
Nishino MN Fujimoto M Phan TD Mukai T Saito Y Kuznetsova MM Rastätter L 《Physical review letters》2008,101(6):065003
Earth's magnetosphere is an obstacle to the supersonic solar wind and the bow shock is formed in the front side of it. In ordinary hydrodynamics, the flow decelerated at the shock is diverted around the obstacle symmetrically about the Earth-Sun line, which is indeed observed in the magnetosheath most of the time. Here we show a case under a very low-density solar wind in which duskward flow was observed in the dawnside magnetosheath. A Rankine-Hugoniot test shows that the magnetic effect is crucial for this "wrong flow" to appear. A full three-dimensional magnetohydrodynamics (MHD) simulation of the situation confirming this interpretation and earlier simulations is also performed. It is illustrated that in addition to the "wrong flow" feature, various peculiar characteristics appear in the global picture of the MHD flow interaction with the obstacle. 相似文献
550.
Howard Yi Fan Sim Jaslyn Ru Ting Chen Charlynn Sher Lin Koh Hiang Kwee Lee Xuemei Han Gia Chuong Phan‐Quang Jing Yi Pang Chee Leng Lay Srikanth Pedireddy In Yee Phang Edwin Kok Lee Yeow Xing Yi Ling 《Angewandte Chemie (International ed. in English)》2020,59(39):16997-17003
The electrochemical nitrogen reduction reaction (NRR) offers a sustainable solution towards ammonia production but suffers poor reaction performance owing to preferential catalyst–H formation and the consequential hydrogen evolution reaction (HER). Now, the Pt/Au electrocatalyst d‐band structure is electronically modified using zeolitic imidazole framework (ZIF) to achieve a Faradaic efficiency (FE) of >44 % with high ammonia yield rate of >161 μg mgcat?1 h?1 under ambient conditions. The strategy lowers electrocatalyst d‐band position to weaken H adsorption and concurrently creates electron‐deficient sites to kinetically drive NRR by promoting catalyst–N2 interaction. The ZIF coating on the electrocatalyst doubles as a hydrophobic layer to suppress HER, further improving FE by >44‐fold compared to without ZIF (ca. 1 %). The Pt/Au‐NZIF interaction is key to enable strong N2 adsorption over H atom. 相似文献