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971.
Chang-ting Wang Jinfan Chen Jiayuan Xu Fangfang Wei Chi Yung Yam Keith Man-Chung Wong Patrick H.-L. Sit Wey Yang Teoh 《Materials Today Chemistry》2021
The CO2 reduction reaction is an imperative piece of technology that closes the carbon cycle in many critical energy conversion and chemical manufacturing processes. Here, we report two new iridium (III) terpyridine-based photocatalysts capable of selective reduction of CO2 to CO under visible light (λ ≥ 420 nm). The first photocatalyst, [Ir–COOH], was functionalized with the carboxyl group on the phenylpyridine, whereas the second, [Ir-PhCOOH], was attached to a phenyl spacer on the terpyridine. The [Ir-PhCOOH] was characterized by a higher extinction coefficient than [Ir–COOH], thus allowing more absorption of photons. Although both photocatalysts require two-electron activation, the [Ir-PhCOOH] is more readily activated as a result of the more negatively charged Ir center. These photocatalysts show exclusive selectivities in the production of CO. The turnover frequencies for [Ir–COOH] and [Ir-PhCOOH] were 19 and 10 h?1, respectively, under visible light irradiation. The e-e-H-H pathway was identified as the most favorable, consisting of the rate-limiting step in the conversion of 1COOH to 1CO, and where the barrier is significantly lower for [Ir-PhCOOH] than for [Ir–COOH]. 相似文献
972.
Ling Chen Shing‐Chung Wong Tianxi Liu Xuehong Lu Chaobin He 《Journal of Polymer Science.Polymer Physics》2004,42(14):2759-2768
Fracture properties and deformation mechanisms of nanoclay‐reinforced maleic anhydride‐modified polypropylene (MAPP) were investigated. Elastic–plastic fracture mechanics was employed to characterize the toughness in light of substantial postyield deformation for the reinforced MAPP. Upon introduction of 2.5 wt % clay loading in maleated MAPP, it was observed that tensile strength, modulus, and fracture initiation toughness concomitantly increased substantially. Continued increase in clay loading thereafter only led to stiffening and strengthening effects to the detriment of fracture toughness. A plot of the J‐integral initiation fracture toughness versus the plastic zone size demonstrated that toughening arose from plastic deformation in the reinforced matrix. Careful examination of deformed tensile specimens using small angle X‐ray scattering (SAXS) showed 2.5 wt % clay gave rise to the highest equatorial scattering, which indicates the presence of microvoids in the matrix. The SAXS results were consistent with that shown in subcritically loaded crack‐tip deformation zone using transmission electron microscopy. Thus, both macroscale three‐point bend fracture data and SAXS results led us to consistent findings and conclusions. Further increase in clay loading above 2.5 wt % reduced the scattering the matrix plasticity and thus the fracture toughness. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2759–2768, 2004 相似文献
973.
974.
S.M.H. Wong 《The European Physical Journal C - Particles and Fields》2000,14(4):643-671
In the last years, the need for the color octet state in inclusive P-wave charmonium decay has been firmly established. However,
the implications of this in the corresponding exclusive reactions have not been fully recognized. We argue for the necessity
of the color octet in P- and higher-wave quarkonium decay. Using a set of phenomenologically constructed baryon wave functions,
we consider the decay into an octet and decuplet baryon–antibaryon pair. By doing so, we subject the wave functions to a test of applicability.
We show that the color singlet component alone is insufficient to account for the experimental measurements, and only by including
the color octet contribution can the partial theoretical decay widths be brought into the range of the data. By the present
and earlier applications of the set of wave functions, these show themselves to be reasonable model wave functions at around
the scale –20 GeV.
Received: 1 March 1999 / Published online: 18 May 2000 相似文献
975.
True random number generators are in general more secure than pseudo random number generators. In this paper, we propose a novel true random number generator which generates a 256-bit random number by computer mouse movement. It is cheap, convenient and universal for personal computers. To eliminate the effect of similar movement patterns generated by the same user, three chaos-based approaches, namely, discretized 2D chaotic map permutation, spatiotemporal chaos and “MASK” algorithm, are adopted to post-process the captured mouse movements. Random bits generated by three users are tested using NIST statistical tests. Both the spatiotemporal chaos approach and the “MASK” algorithm pass the tests successfully. However, the latter has a better performance in terms of efficiency and effectiveness and so is more practical for common personal computer applications. 相似文献
976.
Tests currently used for condoms are surrogates for the challenges they face in use. The tests involve looking for holes and slow stretching to break. This article describes a test that adds cyclic strain to a level well below breakage, and examines the differences among brands and types of condom. It is shown that there are very significant differences in resistance to cyclic straining. Such a test could be developed into a standard test for condom acceptability. 相似文献
977.
By optimizing chromatographic conditions of an ion chromatographic system, we identified and measured the major inorganic and organic anions (chloride, nitrate, malate, sulfate, phosphate and citrate) in the xylem saps of two contrasting tolerant oilseed rape (Brassica juncea L.) varieties (the high Cd-accumulating genotype Xikou Huazi and the low Cd-accumulating genotype Liangting Huazi). Cadmium concentrations in xylem saps were determined by graphite furnace atomic absorption spectrometry. By analyzing the relationship between anion and cadmium concentrations, we considered that the relatively low phosphate concentrations in Xikou Huazi xylem saps might relate to the relatively high xylem transport of Cd for this genotype, and malate in oilseed rape xylem saps seemed to participate in the long-distance Cd translocation process. Our work might not only be very useful for understanding the mechanisms of Cd hyperaccumulation for Xikou Huazi, but also very beneficial for future application of Xikou Huazi in phytoremediation. 相似文献
978.
Amido analogs of geldanamycin, an ansamycin anticancer agent, were designed, synthesized, and assayed with SKBR3 cells, in which stability of HER2 receptor tyrosine kinase is dependent on the chaperone Hsp90. An amide was employed as a trisubstituted alkene isostere at the C8,9 position, which provided for a simplified, convergent synthesis through two major fragments, an aniline-amine left-hand portion and a dicarboxylic acid right-hand piece. 相似文献
979.
AR and bilinear time series models are expressed as time series chain graphical models, based on which, it is shown that the
coefficients of AR and bilinear models are the conditional correlation coefficients conditioned on the other components of
the time series. Then a graphically based procedure is proposed to test the significance of the coefficients of AR and bilinear
time series. Simulations show that our procedure performs well both in sizes and powers.
This work was supported by the Hong Kong Polytechnic University Research Council, the National Natural Science Foundation
of China (Grant No. 10671044) and the Science and Technology Bureau of Guangzhou Municipal Government of China (Grant No.
LSBH-017) 相似文献
980.