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971.
Pamies R Zhu K Kjøniksen AL Knudsen KD Nyström B 《Journal of colloid and interface science》2008,326(1):76-88
Aqueous solutions of a thermoresponsive amphiphilic diblock copolymer, containing poly(N-isopropylacrylamide), in the presence of the anionic sodium dodecyl sulfate (SDS) surfactant can undergo a temperature-induced transition from loose intermicellar clusters to collapsed core–shell nanostructures. The polymer–surfactant mixtures have been characterized with the aid of turbidity, small-angle neutron scattering (SANS), intensity light scattering (ILS), dynamic light scattering (DLS), shear viscosity, and rheo-small angle light scattering (rheo-SALS). In the absence of SDS, compressed intermicellar structures are formed at intermediate temperatures, and at higher temperatures further aggregation is detected. The SANS results disclose a structure peak in the scattered intensity profile at the highest measured temperature. This peak is ascribed to the formation of ordered structures (crystallites). In the presence of a low amount of SDS, a strong collapse of the intermicellar clusters is observed at moderate temperatures, and only a slight renewed interpolymer association is found at higher temperatures because of repulsive electrostatic interactions. Finally, at moderate surfactant concentrations, temperature-induced loose intermicellar clusters are detected but no shrinking was registered in the considered temperature range. At a high level of SDS addition, large polymer–surfactant complexes appear at low temperatures, and these species are compressed at elevated temperatures. The rheo-SALS results show that the transition structures are rather fragile under the influence of shear flow. 相似文献
972.
具有均匀天空背景的高精度静态星模拟器设计 总被引:1,自引:0,他引:1
为解决现有星模拟器只关注星图模拟精度而忽略天空背景模拟的问题,设计了具有均匀天空背景的高精度静态星模拟器.重点阐述星模拟器的组成和工作原理,详细论述光学系统优化设计方法.根据模拟器光学系统透镜大、精度高的特点,采用筒套筒的镜筒设计形式;为了保证星图模拟精度,采用激光直写技术制作星点板,刻划精度优于±1μm.测试结果表明:设计的具有均匀天空背景的高精度静态星模拟器的星图模拟精度优于3″,天空背景均匀性优于95%,满足导航敏感器的高精度地面标定与功能测试需求. 相似文献
973.
利用同位旋相关的量子分子动力学模型模拟了 4He + 208 Pb的碰撞反应,发现中子质子产额比与 208 Pb的中子皮之间存在很好的线性关联,中子质子产额比可以作为中子皮厚度测量的一个探针。选取量子分子动力学模型中核物质状态方程的两套不同势参数进行模拟,通过对比发现,中子皮的厚度测量探针中子质子产额比对核物质状态方程中选择软势和硬势非常敏感,相同反应条件下,软势比硬势计算所得的中子质子产额比要低。无论选择何种状态方程参数,中子质子产额比与中子皮之间都存在线性关联。The reaction system of 4He + 208Pb has been simulated by Isospin-dependent Quantum Molecu-lar Dynamics (IQMD) mode and it was found that the neutron-to-proton yield ratio (Rnp) has a good linearrelationship with the neutron skin thickness of 208Pb. Therefore Rnp could be taken as a probe of neutron skin thickness of 208Pb. Using two sets of parameters for the nuclear equation of state (EOS) in IQMD model, it shows that Rnp is sensitive to nuclear equation of state. The calculation results of Rnp with the soft EOS is lower than the hard EOS. No matter which kind of EOS parameter has been chosen, however, Rnp holds a good linear correlation with the neutron skin thickness. 相似文献
974.
模糊投资组合是不确定性理论研究的重要领域.然而,由于人的理性局限性,投资者在决策的过程中,可能不是追求理性的效用最大化,而是追求心理满意度的最大化;在金融市场中,投资者不仅面临市场风险,也需要承担由自身因素产生的背景风险.因此,提出了一个考虑背景风险等因素的最大期望满意度模型,该模型的目标是最大化投资组合收益与最小收益证券的差值;最后,以上海证券交易所180指数的十支证券构成的的投资组合为例,分析了此模型在分散投资风险与增加满意度方面的有效性. 相似文献
975.
Studies of a Large Odd‐Numbered Odd‐Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8Mn
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Dr. Michael L. Baker Dr. Tom Lancaster Alessandro Chiesa Prof. Giuseppe Amoretti Dr. Peter J. Baker Claire Barker Prof. Stephen J. Blundell Prof. Stefano Carretta Prof. David Collison Prof. Hans U. Güdel Dr. Tatiana Guidi Prof. Eric J. L. McInnes Dr. Johannes S. Möller Dr. Hannu Mutka Dr. Jacques Ollivier Dr. Francis L. Pratt Prof. Paolo Santini Dr. Floriana Tuna Dr. Iñigo J. Vitorica‐Yrezabal Dr. Grigore A. Timco Prof. Richard E. P. Winpenny 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(5):1779-1788
The spin dynamics of Cr8Mn, a nine‐membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8Mn is a rare example of a large odd‐membered AF ring, and has an odd‐number of 3d‐electrons present. Odd‐membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated‐spin ground states. The chemical synthesis and structures of two Cr8Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground‐spin‐state crossing from S=1/2 to S=3/2 in Cr8Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin‐pair correlations and scalar‐spin chirality, shows a non‐collinear spin structure that fluctuates between non‐planar states of opposite chiralities. 相似文献
976.
Proton Transport in a Highly Conductive Porous Zirconium‐Based Metal–Organic Framework: Molecular Insight
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Dr. Daiane Damasceno Borges Dr. Sabine Devautour‐Vinot Dr. Hervé Jobic Dr. Jacques Ollivier Dr. Farid Nouar Dr. Rocio Semino Dr. Thomas Devic Dr. Christian Serre Prof. Francesco Paesani Prof. Guillaume Maurin 《Angewandte Chemie (International ed. in English)》2016,55(12):3919-3924
The water stable UiO‐66(Zr)‐(CO2H)2 MOF exhibits a superprotonic conductivity of 2.3×10?3 S cm?1 at 90 °C and 95 % relative humidity. Quasi‐elastic neutron scattering measurements combined with aMS‐EVB3 molecular dynamics simulations were able to probe individually the dynamics of both confined protons and water molecules and to further reveal that the proton transport is assisted by the formation of a hydrogen‐bonded water network that spans from the tetrahedral to the octahedral cages of this MOF. This is the first joint experimental/modeling study that unambiguously elucidates the proton‐conduction mechanism at the molecular level in a highly conductive MOF. 相似文献
977.
Dr. Hao Zhang Dr. Roxana Flacau Dr. Xin Du Dr. Pascal Manuel Dr. Junzhuang Cong Prof. Young Sun Prof. Junliang Sun Prof. Sihai Yang Prof. Guobao Li Fuhui Liao Prof. Jianhua Lin 《Chemphyschem》2016,17(8):1098-1103
TbMnO3 is an important multiferroic material with strong coupling between magnetic and ferroelectric orderings. Incommensurate magnetic ordering is suggested to be vital for this coupling in TbMnO3, which can be modified by doping at the site of Tb and/or Mn. Our study shows that a self‐doped solid solution Tb1?xMnyMnO3 (y≤x) can be formed with Mn doped into the site of Tb of TbMnO3. When y is small Tb1?xMnyMnO3 shows both ferroelectric and incommensurate magnetic orders at low temperature, which is similar to TbMnO3. However, if y is large enough, a commensurate antiferromagnetic ordering appears along with the incommensurate magnetic ordering to prevent the appearance of multiferroicity in Tb1?xMnyMnO3. That is to say, the magnetoeletric coupling can be broken by the co‐existence of a commensurate antiferromagnetic ordering. This finding may be useful to the study of TbMnO3. 相似文献
978.
Colloidal Properties of Aqueous Poly(vinyl acetate)–Borate Dispersions with Short‐Chain Glycol Ethers
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We report the influence of adding five short‐chain glycol ethers (SCGEs) on the structure, stability, and viscoelastic properties of aqueous dispersions of partially hydrolyzed poly(vinyl acetate) and borax. The properties of these gel‐like materials have been investigated as a function of the structure of the added SCGE both below and above the critical aggregation (or micellar) concentrations using 11B and 13C NMR, rheology, and small‐angle neutron scattering. The results indicate that the SCGE aggregation behavior is not affected by incorporation into the gel‐like network. However, changes in the viscoelasticity and structural properties of the dispersions were detected that can be correlated to the nature of the solvent system. Also, the ability of these materials to clean an unvarnished acrylic paint surface coated with synthetic soil has been evaluated using colorimetery, and the surface of the dispersion after cleaning was visualized with scanning electron microscopy. 相似文献
979.
Dr. Sarah E. Norman Adam H. Turner Dr. John D. Holbrey Dr. Tristan G. A. Youngs 《Chemphyschem》2016,17(23):3923-3931
The local solvation environment of uracil dissolved in the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate has been studied using neutron diffraction techniques. At solvent:solute (ionic liquid:uracil) ratios of 3:1 and 2:1, little perturbation of the ion–ion correlations compared to those of the neat ionic liquid are observed. We find that solvation of the uracil is driven predominantly by the acetate anion of the solvent. While short distance correlations exist between uracil and the imidazolium cation, the geometry of these contacts suggest that they cannot be considered as hydrogen bonds, in contrast to other studies by Araújo et al. (J. M. Araújo, A. B. Pereiro, J. N. Canongia‐Lopes, L. P. Rebelo, I. M. Marrucho, J. Phys. Chem. B 2013, 117, 4109–4120 ). Nevertheless, this combination of interactions of the solute with both the cation and anion components of the solvents helps explain the high solubility of the nucleobase in this media. In addition, favourable uracil–uracil contacts are observed, of similar magnitude to those between cation and uracil, and are also likely to aid dissolution. 相似文献
980.
Aronica C Jeanneau E El Moll H Luneau D Gillon B Goujon A Cousson A Carvajal MA Robert V 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(13):3666-3674
A new end-to-end azido double-bridged copper(II) complex [Cu(2)L(2)(N(3))2] (1) was synthesized and characterized (L=1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onato). Despite the rather long Cu-Cu distance (5.105(1) A), the magnetic interaction is ferromagnetic with J= +16 cm(-1) (H=-JS(1)S(2)), a value that has been confirmed by DFT and high-level correlated ab initio calculations. The spin distribution was studied by using the results from polarized neutron diffraction. This is the first such study on an end-to-end system. The experimental spin density was found to be localized mainly on the copper(II) ions, with a small degree of delocalization on the ligand (L) and terminal azido nitrogens. There was zero delocalization on the central nitrogen, in agreement with DFT calculations. Such a picture corresponds to an important contribution of the d(x2-y2) orbital and a small population of the d(z2) orbital, in agreement with our calculations. Based on a correlated wavefunction analysis, the ferromagnetic behavior results from a dominant double spin polarization contribution and vanishingly small ionic forms. 相似文献