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161.
Micromagnetic simulations have been used to explore the interaction between ferrimagnetic domain walls (DWs) and ferroelastic twin walls (TWs) below the Verwey transition in magnetite (Fe3O4). Simulations were performed using a thin-foil geometry in order to replicate the domain patterns observed experimentally using transmission electron microscopy. The magnetic microstructure is shown to be highly sensitive to the physical dimensions and crystallographic orientation of the foil, the spatial distribution and crystallographic classification of the TWs and the temperature/field history of the sample. A method to calculate the phase shift of a beam of electrons passing through the micromagnetic simulations is applied. The resulting phase maps provide a robust interpretation of experimental images obtained using Fresnel-mode Lorentz microscopy and off-axis electron holography. The interaction between ferrimagnetic and ferroelastic DWs during field cycling provides an explanation for the low-temperature ‘field-memory effect’ in magnetite. 相似文献
162.
Mark A. Olson Adam B. Braunschweig Dr. Lei Fang Taichi Ikeda Dr. Rafal Klajn Ali Trabolsi Dr. Paul J. Wesson Diego Benítez Dr. Chad A. Mirkin Prof. Bartosz A. Grzybowski Prof. J. Fraser Stoddart Prof. 《Angewandte Chemie (International ed. in English)》2009,48(10):1792-1797
Side‐chain poly[2]catenanes at the click of a switch! A bistable side‐chain poly[2]catenane has been synthesized and found to form hierarchical self‐assembled hollow superstructures of nanoscale dimensions in solution. Molecular electromechanical switching (see picture) of the material is demonstrated, and the ground‐state equilibrium thermodynamics and switching kinetics are examined as the initial steps towards processible molecular‐based electronic devices and nanoelectromechanical systems.
163.
Robert Pazik Dr. Renata Tekoriute Sebastian Håkansson Dr. Rafal Wiglusz Dr. Wieslaw Strek Prof. Gulaim A. Seisenbaeva Dr. Yurii K. Gun'ko Prof. Vadim G. Kessler Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(28):6820-6826
Investigation of the solvent and alkoxide precursor effect on the nonhydrolytic sol–gel synthesis of oxide nanoparticles by means of an ether elimination (Bradley) reaction indicates that the best crystallinity of the resulting oxide particles is achieved on application of aprotic ketone solvents, such as acetophenone, and of smallest possible alkoxide groups. The size of the produced primary particles is always about 5 nm caused by intrinsic mechanisms of their formation. The produced particles, possessing the composition of natural highly insoluble minerals, are biocompatible. Optical characteristics of the perovskite complex oxide nanoparticles can easily be controlled through doping with rare earth cations; for example, by Eu3+. They can be targeted through surface modification by anchoring the directing biomolecules through a phosphate or phosphonate moiety. Testing of the distribution of Eu‐doped BaTiO3 particles, modified with ethylphosphonic acid, demonstrates their facile uptake by the plants with active fluid transport, resulting finally in their enhanced concentration within the cell membranes. 相似文献
164.
Summary Given any local maringaleM inR
d
orl
2, there exists a local martingaleN inR
2, such that |M|=|N|, [M]=[N], and «M»=«N». It follows in particular that any inequality for martingales inR
2 which involves only the processes |M|, [M] and «M» remains true in arbitrary dimension. WhenM is continuous, the processes |M|2 and |M| satisfy certain SDE's which are independent of dimension and yield information about the growth rate ofM. This leads in particular to tail estimates of the same order as in one dimension. The paper concludes with some new maximal inequalities in continuous time.Research supported by NSF grant DMS-9002732 and by AFOSR Contract F49620 85C 0144 相似文献
165.
166.
Anna?Baranik Anna?Gagor Ignasi?Queralt Eva?Marguí Rafal?Sitko Beata?ZawiszaEmail authorView authors OrcID profile 《Mikrochimica acta》2018,185(5):264
A nanocomposite prepared from graphene nanosheets and cerium nanoparticles (G/CeO2) was applied to the extraction of Se(IV), As(V), As(III), Cu(II) and Pb(II). The structure of G/CeO2 was investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The optimal pH values for extraction are 4.0 for As(V), 3.0 for Se(IV), and 6.0 for both Cu(II) and Pb(II). The maximum adsorption capacity of G/CeO2 (expressed as mg·g?1) were calculated by the Langmuir model and are found to be 8.4 for As(V), 14.1 for Se(IV), 50.0 for Cu(II) and 75.6 for Pb(II). The sorbent was applied to dispersive solid phase microextraction prior to direct quantitation by energy-dispersive X-ray fluorescence spectrometry without the need for prior elution. The limits of detection (in ng·mL?1 units) are 0.10 for As(V), 0.11 for Se(IV), 0.19 for Cu(II) and 0.21 for Pb(II). The precisions (RSDs) are <4.5%. The accuracy of the method (1 - 4%) was verified by analysis of the certified reference material (CRM 1640a - natural water). The method was successfully applied in ultratrace element determination and to the speciation of selenium in environmental waters. 相似文献
167.
Rafal Zuzak Dr. Ruth Dorel Dr. Marek Kolmer Prof. Marek Szymonski Dr. Szymon Godlewski Prof. Antonio M. Echavarren 《Angewandte Chemie (International ed. in English)》2018,57(33):10500-10505
A unified approach to the synthesis of the series of higher acenes up to previously unreported undecacene has been developed through the on‐surface dehydrogenation of partially saturated precursors. These molecules could be converted into the parent acenes by both atomic manipulation with the tip of a scanning tunneling and atomic force microscope (STM/AFM) as well as by on‐surface annealing. The structure of the generated acenes has been visualized by high‐resolution non‐contact AFM imaging and the evolution of the transport gap with the increase of the number of fused benzene rings has been determined on the basis of scanning tunneling spectroscopy (STS) measurements. 相似文献
168.
Alison C Twitchett Rafal E Dunin-Borkowski Robert J Hallifax Ronald F Broom Paul A Midgley 《Microscopy and microanalysis》2005,11(1):66-78
Off-axis electron holography is used to measure electrostatic potential profiles across a silicon p-n junction, which has been prepared for examination in the transmission electron microscope (TEM) in two different specimen geometries using focused ion beam (FIB) milling. Results are obtained both from a conventional unbiased FIB-milled sample and using a novel sample geometry that allows a reverse bias to be applied to an FIB-milled sample in situ in the TEM. Computer simulations are fitted to the results to assess the effect of TEM specimen preparation on the charge density and the electrostatic potential in the thin sample. 相似文献
169.
Characterization of magnetic nanoparticles using energy-selected transmission electron microscopy. 总被引:2,自引:0,他引:2
María J Sayagués Teresa C Rojas Asunción Fernández Rafal E Dunin-Borkowski Ron C Doole John L Hutchison 《Microscopy and microanalysis》2002,8(5):403-411
Fe, Co, and Ni magnetic nanoparticles have been characterized using energy-selected imaging in a high-resolution transmission electron microscope. The samples comprised Fe/FeO x and Co/CoO x nanoparticles synthesized by inert gas evaporation and a Ni/C nano-composite prepared by a sonochemical method. All of the particles examined were found to be between 5 and 30 nm in size, with the Fe and Co crystals coated in 5-10 nm of metal oxide layer and the Ni metallic crystallites embedded in an amorphous carbon spherical matrix. 相似文献
170.