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排序方式: 共有534条查询结果,搜索用时 15 毫秒
411.
Dick Yan Tam Ziwen Dai Miu Shan Chan Ling Sum Liu Man Ching Cheung Dr. Frederic Bolze Dr. Chung Tin Dr. Pik Kwan Lo 《Angewandte Chemie (International ed. in English)》2016,55(1):164-168
We demonstrate the use of two different wavelength ranges of excitation light as inputs to remotely trigger the responses of the self‐assembled DNA devices (D‐OR). As an important feature of this device, the dependence of the readout fluorescent signals on the two external inputs, UV excitation for 1 min and/or near infrared irradiation (NIR) at 800 nm fs laser pulses, can mimic function of signal communication in OR logic gates. Their operations could be reset easily to its initial state. Furthermore, these DNA devices exhibit efficient cellular uptake, low cytotoxicity, and high bio‐stability in different cell lines. They are considered as the first example of a photo‐responsive DNA logic gate system, as well as a biocompatible, multi‐wavelength excited system in response to UV and NIR. This is an important step to explore the concept of photo‐responsive DNA‐based systems as versatile tools in DNA computing, display devices, optical communication, and biology. 相似文献
412.
In this paper, an exact Branch and Bound Algorithm has been developed to solve a difficult global optimization problem concerning the design of space thrusters. This optimization problem is hard to solve mainly because the objective function to be minimized is implicit and must be computed by using a Finite Element method code. In a previous paper, we implement a method based on local search algorithms and we then proved that this problem is non convex yielding a strong dependency between the obtained local solution and the starting points. In this paper, by taking into account a monotonicity hypothesis that we validated numerically, we provide properties making it possible the computation of bounds. This yields the development of a topology optimization Branch and Bound code. Some numerical examples show the efficiency of this new approach. 相似文献
413.
Laurence Nicod Frederic Chitry Eric Gaubert Marc Lemaire Henri Barnier 《Journal of inclusion phenomena and macrocyclic chemistry》1999,34(2):143-154
Combined nanofiltration-complexation is applied to the separation of caesium and strontium from a solution containing a large concentration of sodium. Caesium and strontium complexation was studied using various water soluble resorcinarene-type ligands. Combined with nanofiltration these ligands improved the separation of caesium and strontium from sodium by the FILMTEC NF 70 membrane. 相似文献
414.
Cabooter D Billen J Terryn H Lynen F Sandra P Desmet G 《Journal of chromatography. A》2008,1204(1):1-10
To contribute to the current debate about the "ideal" particle size range (sub-2mum vs. supra-2mum), the present study compares the kinetic performance of some commercially available sub-2mum and 3.5mum particles used under quasi-adiabatic conditions via the kinetic plot method. Under the adopted assumption that viscous heating effects can be neglected (which is uncertain in a pressure range above 400bar), the obtained kinetic plots show that, provided each particle size is used in a column with properly optimized length, the gain in separation speed that sub-2mum particle columns might have over maximally performing 2.5mum particle columns is very small. Sub-2mum particle columns can only yield a gain in separation speed in the range of high-speed/low-resolution-separations (total time based on k=10 below 5 or 10min). And even in this range, the actual gain that can be expected is only marginally small (only a few %). The present study hence suggests that the development and the use of particles in the 2-3mum range should deserve more attention than it did in the past few years. However, to be competitive, this 2-3mum material should be packed in relatively long columns, with a packing quality matching that of the current best performing 3.5mum particle columns. The supra-2mum particles should also be able to withstand the same pressures as the sub-2mum particle material one is comparing it to. 相似文献
415.
Younes Makoudi Mohamed El Garah Frank Palmino Eric Duverger Madjid Arab Frederic Cherioux 《Surface science》2008,602(16):2719-2723
The couple sulfonato/Si(1 1 1)-7 × 7 leads to remarkable 2D chiral molecular assembly with a stability improved at room temperature. The voltage-dependency of the STM images has been experimentally investigated and the correlation between STM images and PDOS has been studied. The proposed empirical model of the adsorption of molecules on Si(1 1 1)-7 × 7 has been justified by the experimental and theoretical data. 相似文献
416.
Pakula M Padilla F Laugier P Kaczmarek M 《The Journal of the Acoustical Society of America》2008,123(4):2415-2423
This paper is devoted to the experimental determination of distinctive macroscopic structural (porosity, tortuosity, and permeability) and mechanical (Biot-Willis elastic constants) properties of human trabecular bones. Then, the obtained data may serve as input parameters for modeling wave propagation in cancellous bones using Biot's theory. The goal of the study was to obtain experimentally those characteristics for statistically representative group of human bones (35 specimens) obtained from a single skeletal site (proximal femur). The structural parameters were determined using techniques devoted to the characterization of porous materials: electrical spectroscopy, water permeametry, and microcomputer tomography. The macroscopic mechanical properties, Biot-Willis elastic constants, were derived based on the theoretical consideration of Biot's theory, micromechanical statistical models, and experimental results of ultrasonic studies for unsaturated cancellous bones. Our results concerning structural parameters are consistent with the data presented by the other authors, while macroscopic mechanical properties measured within our studies are situated between the other published data. The discrepancies are mainly attributed to different mechanical properties of the skeleton frame, due to strong structural anisotropy varying from site to site. The results enlighten the difficulty to use Biot's theory for modeling wave propagation in cancellous bone, implying necessity of individual evaluation of input parameters. 相似文献
417.
Pawel?UznanskiEmail author Joanna?Zakrzewska Frederic?Favier Slawomir?Kazmierski Ewa?Bryszewska 《Journal of nanoparticle research》2017,19(3):121
A comparative study of amine and silver carboxylate adducts [R1COOAg-2(R2NH2)] (R1 = 1, 7, 11; R2 = 8, 12) as a key intermediate in NPs synthesis is carried out via differential scanning calorimetry, solid-state FT-infrared spectroscopy, 13C CP MAS NMR, powder X-ray diffraction and X-ray photoelectron spectroscopy, and various solution NMR spectroscopies (1H and 13C NMR, pulsed field gradient spin-echo NMR, and ROESY). It is proposed that carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination as opposed to bridging bidentate coordination of pure silver carboxylates resulting from the formation of dimeric units. All complexes are packed as lamellar bilayer structures. Silver carboxylate/amine complexes show one first-order melting transition. The evidence presented in this study shows that phase behavior of monovalent metal carboxylates are controlled, mainly, by head group bonding. In solution, insoluble silver salt is stabilized by amine molecules which exist in dynamic equilibrium. Using (bis)amine-silver carboxylate complex as precursor, silver nanoparticles were fabricated. During high-temperature thermolysis, the (bis)amine-carboxylate adduct decomposes to produce silver nanoparticles of small size. NPs are stabilized by strongly interacting carboxylate and trace amounts of amine derived from the silver precursor interacting with carboxylic acid. A corresponding aliphatic amide obtained from silver precursor at high-temperature reaction conditions is not taking part in the stabilization. Combining NMR techniques with FTIR, it was possible to follow an original stabilization mechanism. 相似文献
418.
A sufficient condition for the convergence of degenerated weighted U-statistics of order k is proved. From this, the previous results by O'Neil and Redner(10) for k = 2 and Major,(7) which appeared to be very different, are related. 相似文献
419.
L. Saviot E. Duval J.F. Jal A.J. Dianoux 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):661-666
Relaxations in amorphous bis-phenol A polycarbonate are studied by neutron scattering, as a function of temperature below
the glass transition. Two different processes are observed. One is very fast, with a characteristic time (∼ 0.3 ps), that
is independent of temperature and momentum transfer. Conversely the other is slower, with a time which is dependent on temperature
and momentum transfer. The very fast localized anharmonic motion is interpreted by the overdamping of low-frequency vibrational
modes, by nearby dynamic holes. The slower relaxation is thermally activated and momentum transfer dependent. It corresponds
to molecular group motions and possibly to the short-time regime of the segmental relaxation.
Received 29 February 2000 and Received in final form 13 June 2000 相似文献
420.
Samundeeswari Mariappan Balasekaran Adelheid Hagenbach Dieter Lentz Frederic Poineau 《无机化学与普通化学杂志》2019,645(16):1052-1056
The {N(C2H5)4}2[UF6] · 2H2O ( 1 ), {N(C2H5)4}2[HfF6] · 2H2O ( 2 ), and {N(C2H5)4}2[CeF6] · 6H2O ( 3 ) salts were prepared in high yield (ca. 80 %) from the reaction of MF4 with tetraethylammonium fluoride in propylene carbonate and for the first time their solid‐state structures characterized by single‐crystal X‐ray diffraction. The compounds 1 , 2 and 3 crystallize in the space groups Pcca, P21/n1 and Pca21, respectively. In 1 , 2 , and 3 the MF62– anions are almost octahedral with average M–F distances of 2.16, 1.999, and 2.148 Å. 相似文献