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排序方式: 共有108条查询结果,搜索用时 31 毫秒
71.
Synthesis of juniperonic acid [(all-Z)-5,11,14,17-eicosatetraenoic acid], has been achieved in eight steps and in 19% overall yield starting from eicosapentaenoic acid. 相似文献
72.
The first synthesis of (all-Z)-1-[(2-phenylethyl)amino]-octadeca-6,9,12,15-tetraen-3-one has been achieved in nine steps and in 13% overall yield using eicosapentaenoic acid as the starting material. 相似文献
73.
Schröder-Turk GE Varslot T de Campo L Kapfer SC Mickel W 《Langmuir : the ACS journal of surfaces and colloids》2011,27(17):10475-10483
We report that a specific realization of Schwarz's triply periodic hexagonal minimal surface is isotropic with respect to the Doi-Ohta interface tensor and simultaneously has minimal packing and stretching frustration similar to those of the commonly found cubic bicontinuous mesophases. This hexagonal surface, of symmetry P6(3)/mmc with a lattice ratio of c/a = 0.832, is therefore a likely candidate geometry for self-assembled lipid/surfactant or copolymer mesophases. Furthermore, both the peak position ratios in its powder diffraction pattern and the elastic moduli closely resemble those of the cubic bicontinuous phases. We therefore argue that a genuine possibility of experimental misidentification exists. 相似文献
74.
Trond R. Henninen Marta Bon Feng Wang Daniele Passerone Rolf Erni 《Angewandte Chemie (International ed. in English)》2020,59(2):839-845
Little is known about metallic clusters consisting merely of a dozen of atoms or even less, despite of their importance in catalysis and crystal nucleation. Scanning transmission electron microscopy (STEM) provides direct atomic structure information but has inherently suffered from limited time resolution. We employ fast dynamic STEM combined with a spatio‐temporal image denoising algorithm to explore the structure and stability of Pt clusters on carbon, which represents a highly relevant catalysis system. At room temperature, dynamic amorphous 2D structures are found, while above ≈300 °C, the clusters transform into a crystalline state. Our experimental and theoretical data reveal an unexpected strong trend of the crystalline clusters to exhibit the face‐centered cubic, bulk structure of Pt with cuboidal geometries being most prominent. 相似文献
75.
Trond A. Abrahamsen Olav Nygaard Märt Põldvere 《Journal of Mathematical Analysis and Applications》2006,314(1):67-74
Thin and thick sets in normed spaces were defined and studied by M.I. Kadets and V.P. Fonf in 1983. In this paper, we give a new characterization of thick sets in terms of weak integrability of Banach space valued measurable functions. We also characterize thick sets in terms of boundedness of vector measures, and explain how this concept is related to the theory of barrelled spaces. 相似文献
76.
A dynamic model of money stock/flow relations for a generic economic agent is developed, and employed to model and discuss the long-range (decades) impact of returns on any form of saved or invested money on a macroeconomy. It is shown that, subject to realistic assumptions about behavior of economic agents, a macro-economic system with positive returns must eventually reach a depression-like economic state. The observed disproportionate growth of financial sectors in recent years is explained by the proposed model. Simulation runs are presented. An indicator for economic fragility is proposed. 相似文献
77.
Direct search methods have been an area of active research in recent years. On many real-world problems involving computationally
expensive and often noisy functions, they are one of the few applicable alternatives. However, although these methods are
usually easy to implement, robust and provably convergent in many cases, they suffer from a slow rate of convergence.
Usually these methods do not take the local topography of the objective function into account. We present a new algorithm
for unconstrained optimisation which is a modification to a basic generating set search method. The new algorithm tries to
adapt its search directions to the local topography by accumulating curvature information about the objective function as
the search progresses.
The curvature information is accumulated over a region thus smoothing out noise and minor discontinuities. We present some
theory regarding its properties, as well as numerical results. Preliminary numerical testing shows that the new algorithm
outperforms the basic method most of the time, sometimes by significant relative margins, on noisy as well as smooth problems.
This work was supported by the Norwegian Research Council (NFR). 相似文献
78.
Dr. Trine P. Petersen Sahar Mirsharghi Dr. Pia C. Rummel Dr. Stefanie Thiele Prof. Dr. Mette M. Rosenkilde Dr. Andreas Ritzén Prof. Dr. Trond Ulven 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(28):9343-9350
A three‐step continuous‐flow synthesis system and its application to the assembly of a new series of chemokine receptor ligands directly from commercial building blocks is reported. No scavenger columns or solvent switches are necessary to recover the desired test compounds, which were obtained in overall yields of 49–94 %. The system is modular and flexible, and the individual steps of the sequence can be interchanged with similar outcome, extending the scope of the chemistry. Biological evaluation confirmed activity on the chemokine CCR8 receptor and provided initial structure–activity‐relationship (SAR) information for this new ligand series, with the most potent member displaying full agonist activity with single‐digit nanomolar potency. To the best of our knowledge, this represents the first published example of efficient use of multistep flow synthesis combined with biological testing and SAR studies in medicinal chemistry. 相似文献
79.
Nataliya A. Mishchuk Trond Heldal Tormod Volden Janko Auerswald Helmut Knapp 《Electrophoresis》2009,30(20):3499-3506
A microfluidic pump based on electroosmosis of the second kind was designed and fabricated. Experimental results using DC and AC voltages showed a close to second‐order relationship between flow and voltage, in good agreement with theory. The experimental flow rates were considerably lower than the predicted maximum for the micropumps, which can be attributed to the hydrodynamic resistance of the channel network. This also indicates that higher flow velocities are obtainable for modified pump designs. 相似文献
80.
Crassous J Chardonnet C Saue T Schwerdtfeger P 《Organic & biomolecular chemistry》2005,3(12):2218-2224
Parity violation (PV) at the molecular level is known to be responsible for a tiny energy difference between the two enantiomers of a chiral molecule. This parity violation energy difference (PVED) has not yet been detected by experiment. In the last few years, the search for PV effects in molecules has made important steps ahead for several reasons. On one hand, very accurate infra-red spectroscopy measurements were performed by metrologists on bromochlorofluoromethane (CHFClBr) with a 10 Hz accuracy, which so far is the most precise. On the other hand, relativistic calculations were used for the evaluation of DeltaE(PV) allowing for a screening of favorable molecules for future measurements. The synthesis of such chiral molecules with high parity violation effects is currently being investigated. In memory of Professor Jean-Bernard Robert. 相似文献