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971.
《Journal of Polymer Science.Polymer Physics》2018,56(5):383-390
Twisted and coiled polymer (TCP) is a promising linear artificial muscle fabricated from nylon or other polymeric fibers, whose geometric structure is similar to a coil spring. TCP muscle is actuated reversibly with negative coefficients of thermal expansion. Twisting, coiling, and annealing are the main fabricating procedures. Annealing is the key process to form TCP muscles with stable performance. To modify and enhance actuation performance, it is necessary to explore and reveal influences of annealing process on thermal actuation (contraction strain, nominal modulus, and geometrical characteristic). Therefore, a new TCP fabrication and test platform is first established, which can quantize key geometrical and force parameters by multiple precise sensors. Then, four types of TCP muscles using nylon 6 fibers with varied diameters are fabricated and annealed under different conditions. As one of the important factors in annealing process, the nominal tensile stress is adjusted and controlled. Meanwhile, the contraction strain and nominal modulus are tested compared with the general annealing method. Finally, the experiment results show that contraction strain can be enhanced about two times (nominal modulus decreases accordingly) by increasing annealing stress, and the actuation performance can be remodeled reversibly by adjusting annealing stress and annealing repetitively. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 383–390 相似文献
972.
Andrzej Malysa Joanna Wezgowiec Sylwia Orzeszek Wojciech Florjanski Marek Zietek Mieszko Wieckiewicz 《Molecules (Basel, Switzerland)》2021,26(5)
For long-term successful use of ceramic materials in dental procedures, it is necessary to ensure reliable bonding of restorations to dental substrates. This can be achieved by the application of a proper luting cement and through additional surface conditioning. The present systematic review summarizes the most up-to-date evidence on the use of different surface modification methods to enhance the bond strength of dental ceramics to the hard tissues of the teeth. The authors of the review searched the Web of Science, Scopus, and MEDLINE databases to identify relevant articles published between 1 January 2010 and 1 January 2020. A total of 4892 records were identified, and after screening, the full text of 159 articles was evaluated, which finally resulted in the inclusion of 19 studies. The available reports were found to be heterogeneous in terms of materials and methodology, and therefore, only within-studies comparison was performed instead of comparison between studies. A statistically significant difference in the bond strength between the samples treated with different methods of surface conditioning, or between conditioned and nonconditioned samples, was revealed by most of the studies. Predominantly, the studies showed that a combination of mechanical and chemical methods was the most effective way of enhancing bond strength. Artificial aging and luting cement were also identified as the factors significantly influencing bond strength. 相似文献
973.
Dr. Carsten Lüdtke Dr. Sebastian Sobottka Dr. Julian Heinrich Dr. Phil Liebing Dr. Stefanie Wedepohl Prof. Dr. Biprajit Sarkar Prof. Dr. Nora Kulak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3273-3277
[Cu( phen )2]2+ ( phen =1,10-phenanthroline) is the first and still one of the most efficient artificial nucleases. In general, when the phen ligand is modified, the nucleolytic activity of its CuII complex is significantly reduced. This is most likely due to higher steric bulk of such ligands and thus lower affinity to DNA. CuII complexes with phen ligands having fluorinated substituents (F, CF3, SF5, SCF3) surprisingly showed excellent DNA cleavage activity—in contrast to the unsubstituted [Cu( phen )2]2+—in the absence of the otherwise required classical, bioabundant external reducing agents like thiols or ascorbate. This nucleolytic activity correlates well with the half-wave potentials E1/2 of the complexes. Cancer cell studies show cytotoxic effects of all complexes with fluorinated ligands in the low μm range, whereas they were less toxic towards healthy cells (fibroblasts). 相似文献
974.
《Journal of separation science》2017,40(9):2062-2070
The extraction of linarin from Flos chrysanthemi indici by ethanol was investigated. Two modeling techniques, response surface methodology and artificial neural network, were adopted to optimize the process parameters, such as, ethanol concentration, extraction period, extraction frequency, and solvent to material ratio. We showed that both methods provided good predictions, but artificial neural network provided a better and more accurate result. The optimum process parameters include, ethanol concentration of 74%, extraction period of 2 h, extraction three times, solvent to material ratio of 12 mL/g. The experiment yield of linarin was 90.5% that deviated less than 1.6% from that obtained by predicted result. 相似文献
975.
Visible‐Light‐Driven CO2 Reduction with Carbon Nitride: Enhancing the Activity of Ruthenium Catalysts
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Ryo Kuriki Dr. Keita Sekizawa Prof. Dr. Osamu Ishitani Prof. Dr. Kazuhiko Maeda 《Angewandte Chemie (International ed. in English)》2015,54(8):2406-2409
A heterogeneous photocatalyst system that consists of a ruthenium complex and carbon nitride (C3N4), which act as the catalytic and light‐harvesting units, respectively, was developed for the reduction of CO2 into formic acid. Promoting the injection of electrons from C3N4 into the ruthenium unit as well as strengthening the electronic interactions between the two units enhanced its activity. The use of a suitable solvent further improved the performance, resulting in a turnover number of greater than 1000 and an apparent quantum yield of 5.7 % at 400 nm. These are the best values that have been reported for heterogeneous photocatalysts for CO2 reduction under visible‐light irradiation to date. 相似文献
976.
977.
Based on the joint tree model introduced by Liu, the genera of further types of graphs not necessary to have certain symmetry can be obtained. In this paper, we obtain the genus of a new type of graph with weak symmetry. As a corollary, the genus of complete tripartite graph K n,n,l (l≥n≥2) is also derived. The method used here is more direct than those methods, such as current graph, used to calculate the genus of a graph and can be realized in polynomial time. 相似文献
978.
979.
Yan Xiang Jiangju Si Qi Zhang Yang Liu Hong Guo 《Journal of polymer science. Part A, Polymer chemistry》2009,47(3):925-934
A novel series of artificial glycoprotein, peptide‐chitosan copolymers with secondary structural side chain have been synthesized by ring‐opening polymerization of L ‐tryptophan N‐carboxyanhydride under homogeneous conditions. Their chemical structures and polymerization degree (DP) were characterized by IR, 13C NMR, and XRD spectra. Distinctly secondary protein structure has been found in the poly‐L ‐tryptophan side chains of copolymers and with the lengthening of side chain (i.e., the increase of DP at the same time), its conformations could transfer from β‐sheet to α‐helix. The content of α‐helix reaches about 41% when DP of polytryptophan is 22. The solubility of graft copolymers in polar solvent strongly depends on the length of poly‐L ‐tryptophan side chains. Unique fluorescence emission at 360 nm has been observed in the glycopolymers and the intensity shows the positive‐correlation with the increasing of DP of polytryptophan. Importantly, the fluorescence effect can be quenched easily by the coordination with copper ions which provides the possibility on the biosensor design. In comparison with chitosan, glycopolymers also present impressively enhanced compressive strength and elastic modules when it is blended with epoxy E 44 to form epoxy‐copolymer hybrid resin. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 925–934, 2009 相似文献
980.
The Locally Conservative Galerkin (LCG) Method — a Discontinuous Methodology Applied to a Continuous Framework
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Rhodri L. T. Bevan Raoul vanLoon & Perumal Nithiarasu 《advances in applied mathematics and mechanics.》2009,1(3):319-340
This paper presents a comprehensive overview of the element-wise
locally conservative Galerkin (LCG) method. The LCG method was
developed to find a method that had the advantages of the
discontinuous Galerkin methods, without the large computational and
memory requirements. The initial application of the method is
discussed, to the simple scalar transient convection-diffusion
equation, along with its extension to the Navier-Stokes equations
utilising the Characteristic Based Split (CBS) scheme. The
element-by-element solution approach removes the standard finite
element assembly necessity, with an face flux providing continuity
between these elemental subdomains. This face flux provides explicit
local conservation and can be determined via a simple small
post-processing calculation. The LCG method obtains a unique
solution from the elemental contributions through the use of simple
averaging. It is shown within this paper that the LCG method
provides equivalent solutions to the continuous (global) Galerkin
method for both steady state and transient solutions. Several
numerical examples are provided to demonstrate the abilities of the
LCG method. 相似文献