排序方式: 共有49条查询结果,搜索用时 218 毫秒
1.
Dongshuang Wu Kohei Kusada Tomokazu Yamamoto Takaaki Toriyama Syo Matsumura Ibrahima Gueye Okkyun Seo Jaemyung Kim Satoshi Hiroi Osami Sakata Shogo Kawaguchi Yoshiki Kubota Hiroshi Kitagawa 《Chemical science》2020,11(47):12731
We report the synthesis of high-entropy-alloy (HEA) nanoparticles (NPs) consisting of five platinum group metals (Ru, Rh, Pd, Ir and Pt) through a facile one-pot polyol process. We investigated the electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy, which is the first direct observation of the electronic structure of HEA NPs. Significantly, the HEA NPs possessed a broad valence band spectrum without any obvious peaks. This implies that the HEA NPs have random atomic configurations leading to a variety of local electronic structures. We examined the hydrogen evolution reaction (HER) and observed a remarkably high HER activity on HEA NPs. At an overpotential of 25 mV, the turnover frequencies of HEA NPs were 9.5 and 7.8 times higher than those of a commercial Pt catalyst in 0.05 M H2SO4 and 1.0 M KOH electrolytes, respectively. Moreover, the HEA NPs showed almost no loss during a cycling test and were much more stable than the commercial Pt catalyst. Our findings on HEA NPs may provide a new paradigm for the design of catalysts.RuRhPdIrPt high-entropy-alloy nanoparticles with a broad and featureless valence band spectrum show high hydrogen evolution reaction activity. 相似文献
2.
Fuks Olga Ibrahima Fayadhoi Tomin Pavel Tchelepi Hamdi A. 《Transport in Porous Media》2019,126(1):115-137
Transport in Porous Media - In the context of stochastic two-phase flow in porous media, one is often interested in estimating the statistics of fluid saturations in the reservoir. In this work, we... 相似文献
3.
Regis F. Babindamana Cheikh Thiecoumba Gueye 《Journal of Mathematical Modelling and Algorithms》2011,10(3):277-291
We present a new approach of the decoding algorithm for Gabidulin Codes. In the same way as efficient erasure decoding for
Generalized Reed Solomon codes by using the structure of the inverse of the VanderMonde matrices, we show that, the erasure(t
erasures mean that t components of a code vector are erased) decoding Gabidulin code can be seen as a computation of three
matrice and an affine permutation, instead of computing an inverse from the generator or parity check matrix. This significantly
reduces the decoding complexity compared to others algorithms. For t erasures with t ≤ r, where r = n − k, the erasure algorithm decoding for Gab
n, k
(g) Gabidulin code compute the t symbols by simple multiplication of three matrices. That requires rt + r(k − 1) Galois field multiplications, t(r − 1) + (t + r)k field additions, r
2 + r(k + 1) field negations and t(k + 1) field inversions. 相似文献
4.
In order to solve a quadratic 0/1 problem, some techniques, consisting in deriving a linear integer formulation, are used.
Those techniques, called “linearization”, usually involve a huge number of additional variables. As a consequence, the exact
resolution of the linear model is, in general, very difficult.
Our aim, in this paper, is to propose “economical” linear models. Starting from an existing linearization (typically the so-called
“classical linearization”), we find a new linearization with fewer variables. The resulting model is called “Miniaturized”
linearization. Based on this approach, we propose a new linearization scheme for which numerical tests have been performed. 相似文献
5.
6.
Crosslinked hyaluronan gels are used in various applications where their stability is a prerequisite. The sensitivity of such gels to hyaluronidase can be determined as an index of stability by several approaches: chromatography, electrophoresis, and viscometry. We describe here a test based on the colorimetric determination of the N-acetyl-d-glucosamine released by hyaluronidase in standardized conditions. The sensitivities to bovine testicular hyaluronidase of 11 different gels used to fill skin wrinkles (Restylane; Perlane; Juvéderm 18, 24, 24HV, 30, and 30HV; Surgiderm 18, 24XP, 30, and 30XP) were compared.The method was reproducible, easy to perform, not time-consuming and allowed us to demonstrate that the sensitivity to testicular hyaluronidase was dependent on the degree of crosslinking of the gels and also on their monophasic/biphasic nature. Under our conditions, Surgiderm 30, 24XP and 30XP were the most resistant gels.We propose to retain the hyaluronidase test to predict the in situ stability of a crosslinked gel used to fill skin wrinkles. 相似文献
7.
Graziano Guella Giuseppe Chiasera Ibrahima N'Diaye Francesco Pietra 《Helvetica chimica acta》1994,77(5):1203-1221
Kinetic and equilibrium studies show that typical xenicanes such as dictyolactone ( 1 ) and 4-hydroxydictyolactone ( 3 ) undergo slow conformation medium-ring flipping between the predominant trans-( 1a or 3a ; Me(20) trans to H–C(3)) and the minor cis-conformers ( 1b or 3b ; Me(20) cis to H–C(3); see Scheme 1). The formation of the latter is inhibited in heterocyclic-ring-opened congeners such as 18-acetoxy-4-hydroxydictyo-19-al ( 7 ). Molecular-mechanics calculations suggest that typical-xenicane cis-conformers are disfavoured by mainly C(4)–C(5) torsional strain. This is confirmed by the observation of two sizably populated cis-and trans-conformers for the unnatural 4-oxoxenicanes 10–12 . Unusually facile thermal (E)→(Z) isomerization of xenicanes 1,3,10–12 , and 7 is also observed (→ 13–17 and 9 , resp.; Scheme 3), reflecting great strain relief in the transition state. Conflicting results in the literature now fit into this scheme which provides a basis for unravelling recognition phenomena with these biologically active systems. 相似文献
8.
Ibra Gueye Dioum Jacques Vedel Bernard Tremillon 《Journal of Electroanalytical Chemistry》1982,137(2):219-226
Molten potassium tetrachlorogallate and potassium tetraiodogallate were studied in terms of halogenoacidity, based on X? ion-exchange. Titration of KX solution with GaX3 were achieved and characterized by the shift of cathodic voltammetric curves. Autodissociation constants Ki,X/mol2 kg?1 were determined: ?log Ki,Cl=4.25±0.05 and ?log Ki,I=2.6±0.05, as well as the solubility values of KX: 0.41±0.02 and 0.80±0.02 mol kg?1 for KCl and KI respectively. 相似文献
9.
Ibrahima Tounkara 《Comptes Rendus Mathematique》2018,356(4):360-364
A slice of finite groups is a pair consisting of a finite group G and a subgroup S of G. In this paper, we show that some properties of finite groups extend to slices of finite groups. In particular, by analogy with B-groups, we introduce the notion of -slice, and show that any slice of finite groups admits a largest quotient -slice. 相似文献
10.
Fuks Olga Ibrahima Fayadhoi Tomin Pavel A. Tchelepi Hamdi 《Transport in Porous Media》2020,132(1):113-133
Transport in Porous Media - The paper presents a novel approach for uncertainty propagation in multicomponent two-phase displacements. This approach originates from and extends the frozen... 相似文献