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71.
72.
We report simultaneous generation of multiple conical second-harmonic waves in a two-dimensional nonlinear photonic structure when illuminated by two overlapping noncollinear fundamental beams. We show that this phenomenon is caused by the nonlinear ?erenkov radiation emitted due to the interaction of photons from each constituent fundamental beam as well as the virtual one propagating along the bisector of the two beams. In addition, by studying the asymmetric geometry of the interaction, we uniquely verify the effects of reciprocal vectors on the ?erenkov-type second-harmonic generation in nonlinear photonic structures. 相似文献
73.
We present wavelength- and temperature-dependent refractive index equations for 5% MgO-doped congruent PPLN and for 1% MgO-doped
stoichiometric PPLN crystals valid for a wide spectral and temperature range. The dispersion equations were derived from quasi-phase-matched
nonlinear interactions with these two crystal compositions in the near and mid-infrared. The results show a good agreement
with previously published frequency conversion experiments.
PACS 42.65.Ky; 42.65.Yj; 42.70.Mp 相似文献
74.
Yu‐Hao Li Shaoping Zheng Dr. Yves‐Marie Legrand Dr. Arnaud Gilles Dr. Arie Van der Lee Dr. Mihail Barboiu 《Angewandte Chemie (International ed. in English)》2018,57(33):10520-10524
Self‐assembled alkyl‐ureido‐benzo‐15‐crown‐5‐ethers are selective ionophores for K+ cations, which are preferred to Na+ cations. The transport mechanism is determined by the optimal coordination rather than classical dimensional compatibility between the crown ether hole and the cation diameter. Herein, we demonstrate that systematic changes of the structure lead to unexpected modifications in the cation‐transport activity and suffice to produce adaptive selection. We show that the main contribution to performance arises from optimal constraints on the conformational freedom, which are determined by the binding macrocycles, the nature of the hydrogen‐bonding groups, and the hydrophobic tails. Simple changes to the flexible 15‐crown‐5‐ether lead to selective carriers for Na+. Hydrophobic stabilization of the channels through mutual interactions between lipids and variable hydrophobic tails appears to be an important cause of increased activity. Oppositely, restricted translocation is achieved when constrained hydrogen‐bonded macrocyclic relays are less dynamic in a pore superstructure. 相似文献
75.
Voets IK de Vos WM Hofs B de Keizer A Conhen Stuart MA Steitz R Lott D 《The journal of physical chemistry. B》2008,112(23):6937-6945
The adsorption of mixed micelles of poly(4-(2-amino hydrochloride-ethylthio)-butylene)- block-poly(ethylene oxide), PAETB 49- b-PEO 212 and poly(4-(2-sodium carboxylate-ethylthio)-butylene)- block-poly(ethylene oxide), PCETB 47- b-PEO 212 on solid/liquid interfaces has been studied with light, X-ray, and neutron reflectometry. The structure of the adsorbed layer can be described with a two-layer model consisting of an inner layer formed by the coacervate of the polyelectrolyte blocks PAETB 49 and PCETB 47 ( approximately 1 nm) and an outer layer of PEO 212 blocks ( approximately 6 nm). The micelles unfold upon adsorption forming a rather homogeneous flat layer that exposes its polyethylene oxide chains into the solution, thus rendering the surface antifouling after modification with the micelles. 相似文献
76.
In this paper we prove finiteness principles for \({C^m{({\mathbb{R}^n},{\mathbb{R}^D)}}}\) and \({C^{m-1,1}(\mathbb{R}^n,\mathbb{R}^D)}\) selections. In particular, we provide a proof for a conjecture of Brudnyi-Shvartsman (1994) on Lipschitz selections for the case when the domain is \({X=\mathbb{R}^n}\). 相似文献
77.
78.
Wormlike aggregates from a supramolecular coordination polymer and a diblock copolymer 总被引:1,自引:0,他引:1
Yan Y Besseling NA de Keizer A Drechsler M Fokkink R Stuart MA 《The journal of physical chemistry. B》2007,111(40):11662-11669
The formation of wormlike micelles in mixed systems of a supramolecular coordination polymer Zn-L2EO4 and a diblock copolymer P2MVP41-b-PEO205 is investigated by light scattering and Cryo-TEM. By direct mixing at a stoichiometric charge ratio, the above mixtures proved to be capable of formation of spherical micelles with a radius of about 25 nm (Yan et al. Angew. Chem., Int. Ed.; 2007, 46, 1807-1809). Lately, we find wormlike micelles with a hydrodynamic radius >150 nm in a mixture with excess positive charge, that is, a negative charge fraction f- < 0.5. The transformation between wormlike and spherical micelles can be realized by variation of the mixing ratio through different protocols. Upon addition of negatively charged Zn-L2EO4 to a mixture with excess positively charged P2MVP41-b-PEO205, most of the wormlike micelles are transformed into spherical ones; upon addition of positively charged P2MVP41-b-PEO205 to a mixture of pure spherical micelles, wormlike micelles can be produced again. The effect of sample preparation protocol, sample history, and concentration on this transformation process is systematically reported in this article. A possible mechanism for the formation of wormlike micelles is proposed. 相似文献
79.
Measuring location, size, distribution, and loading of NiO crystallites in individual SBA-15 pores by electron tomography 总被引:1,自引:0,他引:1
Friedrich H Sietsma JR de Jongh PE Verkleij AJ de Jong KP 《Journal of the American Chemical Society》2007,129(33):10249-10254
By the combination of electron tomography with image segmentation, the properties of 299 NiO crystallites contained in 6 SBA-15 pores were studied. A statistical analysis of the particle size showed that crystallites between 2 and 6 nm were present with a distribution maximum at 3 and 4 nm, for the number-weighted and volume-weighted curves, respectively. Interparticle distances between nearest neighbors were 1-3 nm with very few isolated crystallites. In the examined pores, a local loading twice the applied average of 24 wt % NiO was found. This suggests that a very high local loading combined with a high dispersion is achievable. 相似文献
80.
Pol VG Langzam Y Zaban A 《Langmuir : the ACS journal of surfaces and colloids》2007,23(22):11211-11216
A simple microwave irradiation method for the large-scale synthesis of submicrometer-sized TiO2 rods at normal atmospheric pressure and the boiling temperature of the solvent is demonstrated. It is emphasized that only 1-3 min of microwave irradiation is adequate to react tetra-isopropyl orthotitanate with ethylene glycol to produce rods of titanium glycolate [TG] with diameters of approximately 0.4 microm and lengths up to 5 microm. The as-formed TG rods, followed by calcination under air for 2 h, fabricated anatase (500 degrees C) and rutile (900 degrees C) titania without changing their rod-shaped morphology. The crystallinity, structure, morphology, and thermal analysis are carried out by several techniques. A mechanism based on microwave superheating phenomena is presented with the support of previous reports and several control experiments. 相似文献