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排序方式: 共有400条查询结果,搜索用时 125 毫秒
1.
2.
Yuen Cheong Tse Dr. Robert Hein Edward J. Mitchell Zongyao Zhang Prof. Paul D. Beer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(58):14550-14559
Anion receptors employing two distinct sensory mechanisms are rare. Herein, we report the first examples of halogen-bonding porphyrin BODIPY [2]rotaxanes capable of both fluorescent and redox electrochemical sensing of anions. 1H NMR, UV/visible and electrochemical studies revealed rotaxane axle triazole group coordination to the zinc(II) metalloporphyrin-containing macrocycle component, serves to preorganise the rotaxane binding cavity and dramatically enhances anion binding affinities. Mechanically bonded, integrated-axle BODIPY and macrocycle strapped metalloporphyrin motifs enable the anion recognition event to be sensed by the significant quenching of the BODIPY fluorophore and cathodic perturbations of the metalloporphyrin P/P+. redox couple. 相似文献
3.
Utilization of Active Ni to Fabricate Pt–Ni Nanoframe/NiAl Layered Double Hydroxide Multifunctional Catalyst through In Situ Precipitation 下载免费PDF全文
Dr. Liangfeng Luo Haiyuan Lu Prof. Gang Zhou Prof. Weixin Huang Prof. Xun Hong Prof. Yuen Wu Prof. Yadong Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(38):13181-13185
Integration of different active sites into metallic catalysts, which may impart new properties and functionalities, is desirable yet challenging. Herein, a novel dealloying strategy is demonstrated to decorate nickel–aluminum layered double hydroxide (NiAl–LDH) onto a Pt–Ni alloy surface. The incorporation of chemical etching of Pt–Ni alloy and in situ precipitation of LDH are studied by joint experimental and theoretical efforts. The initial Ni‐rich Pt–Ni octahedra transform by interior erosion into Pt3Ni nanoframes with enlarged surface areas. Furthermore, owing to the basic active sites of the decorated LDH together with the metallic sites of Pt3Ni, the resulting Pt–Ni nanoframe/NiAl–LDH composites exhibit excellent catalytic activity and selectivity in the dehydrogenation of benzylamine and hydrogenation of furfural. 相似文献
4.
5.
Summary Heat transfer to fibers formed in dry spinning has been subjected to fundamental analysis. Solutions of the equation of energy have been derived and tested with experimental data. Results were deemed satisfactory in view of the accuracy of the experimental data. The present work is believed to yield a good representation of the heat transfer in the dry spinning process.Nomenclature
h
heat transfer coefficient, cal/cm2 °C sec
-
k
thermal conductivity, cal/cm °C sec
-
r
radial distance, cm
-
t
time, sec
-
Z
axial distance, cm
-
A
surface area, cm2
-
A
n
or n-th root of
-
A
0
energy required for solvent evaporation, cal/sec cm3
-
C
p
specific heat cal/gm °C
-
J
0
Bessel function of first kind, order zero
-
J
1
Bessel function of first kind, order one
-
J
2
Bessel function of first kind, order two
-
N
k/(R
2
C
p
V)
-
Q
volumetric flow rate cm3/sec
-
R
outside radius, cm
-
T
point temperature, °C
-
T
S
surface temperature °C
-
T
0
initial fiber temperature °C
-
T
ambient air temperature, °C
-
average fiber temperature, °C
-
1
average fiber temperature of preceding segment, °C
-
V
average fiber velocity relative to air strean, cm/sec
-
V
r
radial velocity component, cm/sec
-
V
z
axial velocity components, cm/sec
-
V
direction velocity component cm/sec
-
W
weight of solvent evaporated in a given fiber segment, gms
-
n
a solution of the equation J
0(X)=0
-
heat of vaporization of solvent, cal/gm
-
dimension
-
r/R
-
density, gms/cc 相似文献
6.
Elnaz Miandoabchi Farzaneh Daneshzand Reza Zanjirani Farahani Wai Yuen Szeto 《The Journal of the Operational Research Society》2015,66(6):894-913
This paper aims to model and investigate the discrete urban road network design problem, using a multi-objective time-dependent decision-making approach. Given a base network made up with two-way links, candidate link expansion projects, and candidate link construction projects, the problem determines the optimal combination of one-way and two-way links, the optimal selection of capacity expansion projects, and the optimal lane allocations on two-way links over a dual time scale. The problem considers both the total travel time and the total CO emissions as the two objective function measures. The problem is modelled using a time-dependent approach that considers a planning horizon of multiple years and both morning and evening peaks. Under this approach, the model allows determining the sequence of link construction, the expansion projects over a predetermined planning horizon, the configuration of street orientations, and the lane allocations for morning and evening peaks in each year of the planning horizon. This model is formulated as a mixed-integer programming problem with mathematical equilibrium constraints. In this regard, two multi-objective metaheuristics, including a modified non-dominated sorting genetic algorithm (NSGA-II) and a multi-objective B-cell algorithm, are proposed to solve the above-mentioned problem. Computational results for various test networks are also presented in this paper. 相似文献
7.
Dr. Song Song Vincent Fung Kin Yuen Dr. Lu Di Dr. Qiming Sun Prof. Dr. Kang Zhou Prof. Dr. Ning Yan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20018-20022
Production of renewable, high-value N-containing chemicals from lignocellulose will expand product diversity and increase the economic competitiveness of the biorefinery. Herein, we report a single-step conversion of furfural to pyrrole in 75 % yield as a key N-containing building block, achieved via tandem decarbonylation–amination reactions over tailor-designed Pd@S-1 and H-beta zeolite catalytic system. Pyrrole was further transformed into dl -proline in two steps following carboxylation with CO2 and hydrogenation over Rh/C catalyst. After treating with Escherichia coli, valuable d -proline was obtained in theoretically maximum yield (50 %) bearing 99 % ee. The report here establishes a route bridging commercial commodity feedstock from biomass with high-value organonitrogen chemicals through pyrrole as a hub molecule. 相似文献
8.
Dr. On Ying Yuen Dr. Chau Ming So 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23644-23650
This study describes the first palladium-catalyzed, site-selective α- and γ-arylation of α,β-unsaturated ketones with (hetero)aryl halides. A wide range of hetero(aryl)halides coupled with α,β-unsaturated ketones, and transformation into the arylated products proceeded with excellent to good yields. The site selectivity of the reaction is switchable by simply changing the phosphine ligand to access either α-arylated or γ-arylated products in good to excellent yields by using a low catalyst loading, and the method demonstrates good functional-group compatibility. 相似文献
9.
Pui Sum Yuen 《Optik》2014
Using unit cell of smaller edge lengths to calculate the initial phases can reduce the size of the initial image. 相似文献
10.
Yanping Guan Bilian Li Wei Wei Siyi Wang Vivian‐min Yuen Yao Liu Zheng Ao Shan Zhou Hang Tian Min Huang Xingrong Song Guoping Zhong 《Biomedical chromatography : BMC》2019,33(12)
Dexmedetomidine is an important sedative agent administered as premedication to achieve procedural sedation in children. To describe the correlation between the genetic state and the concentration of dexmedetomidine, it is necessary to develop a specific, time‐saving and economical method for detection of dexmedetomidine in plasma samples. In this work, an ultra‐high‐performance liquid chromatography (UHPLC)–tandem mass spectrometry method has been established and validated for detection of dexmedetomidine in plasma from pediatric population. After a simple liquid–liquid extraction with an organic solution, the analytes were separated on an ACQUITY BEH C18 column (2.1 mm × 50 mm, 1.7 μm particle size) by gradient elution with the mobile phase of acetonitrile and 1‰ aqueous formic acid (flow rate 0.3 mL min?1). Mass spectrometry measurements were performed under the positive selected reaction monitoring and the mass transitions monitored were m/z 201.3 → 95.1, 204.2 → 98.0 for dexmedetomidine and deuterated medetomidine (internal standard), respectively. Validation of the method based on China Food and Drug Administration guidelines showed acceptable selectivity. The UHPLC method employed a stable isotope‐labeled internal standard, showed good specificity and was successfully used to detect dexmedetomidine in plasma samples from 260 pediatric patients. A subsequent application of this method to a pharmacogenetic study was also described. Importantly, this is the first study to report the correlation between CYP2A6 rs835309 activity and concentration of dexmedetomidine. 相似文献