1,721,019 research outputs found
The structuring effect of the alkyl domains on the polar network of ionic liquid mixtures: a molecular dynamics study
Full text linkBy using molecular dynamics simulations, we investigate the structural and dynamic properties of mixtures of 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, [C(1)C(1)im][Tf2N] and 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [C(12)C(1)im][Tf2N] (also C-1 and C-12 in short). Such mixtures feature an imidazolium bistriflimide salt with a very short alkyl chain, not giving rise to any nano-segregation as a pure component, with another one with a longer alkyl chain that exhibits a substantial nano-segregation as a pure liquid. As the mole fraction of the long-chain component C-12 is increased, the so-called pre-peak of the structure factor S(q), occurring in the region 1-3 nm(-1), shows a shift to higher values of the wavevector q, mirroring a decrease of the corresponding correlation length. Moreover, the intensity of the pre-peak strongly increases with the C-12 concentration. These results are in very good agreement with experimental X-ray scattering data in the literature. On the other hand, the diffusion of the ions is found to exhibit a simple behaviour consistent with the increased viscosity of the mixture, and these results are also in good agreement with NMR experimental data from the literature. The simulation results are rationalized as caused by a structuring effect, similar to the hydrophobic effect, of the alkyl domains of the C-12 component dissolved in the "solvent" represented by the C-1 cation, the Tf2N- anion and the C-12 cation head. In short, the exclusion of the alkyl chains from the polar network, a process mostly governed by electrostatic interactions, favours the formation of hydrophobic domains, which in turn exert a structuring effect on the ions of the polar domains, favouring a stronger ionic interaction. This is finally reflected in a shorter correlation length and a higher intensity of the pre-peak of the structure factor S(q) as the C-12 mole fraction is increased. At variance with the microscopic structure, the diffusion of all three types of ions is not strongly influenced by the nano-segregation and is essentially dependent on the viscosity of the mixture
Near-field hydrodynamic interactions determine travelling wave directions of collectively beating cilia
No full textCilia can beat collectively in the form of a metachronal wave, and we investigate how near-field hydrodynamic interactions between cilia can influence the collective response of the beating cilia. Based on the theoretical framework developed in the work of Meng et al . (Meng et al . 2021 Proc. Natl Acad. Sci. USA 118 , e2102828118), we find that the first harmonic mode in the driving force acting on each individual cilium can determine the direction of the metachronal wave after considering the finite size of the beating trajectories, which is confirmed by our agent-based numerical simulations. The stable wave patterns, e.g. the travelling direction, can be controlled by the driving forces acting on the cilia, based on which one can change the flow field generated by the cilia. This work can not only help to understand the role of the hydrodynamic interactions in the collective behaviours of cilia, but can also guide future designs of artificial cilia beating in the desired dynamic mode.National Natural Science Foundation of China http://dx.doi.org/10.13039/501100001809Wenzhou InstituteBeijing National Laboratory for Condensed MatterAlexander von Humboldt Foundation 100005156Max Planck Societ
LiquidLiquid Phase Separation of Viologen Bistriflimide/Benzene Mixtures: Role of the Dual Ionic and Organic Nature of Ionic Liquids
No full textLiquid-liquid phase separation occurs at room temperature when mixing an excess of benzene with solid viologen bistriflimide salts with various alkyl side-chain lengths. A liquid phase composed of (almost) pure benzene is above the other sponge-like liquid phase with salt absorbed in benzene. Nuclear magnetic resonance experiments indicate that the mole ratio of benzene/salt in the sponge-like phase remains unchanged upon varying the amounts of (nonexcessive) salt or benzene. Moreover, the benzene/viologen salt mole ratio in the sponge-like phase increases linearly with respect to the side-chain length of the cation. Similarly, when an excess of viologen salt is added in benzene, a sponge-like liquid phase composed of salt absorbed by benzene is observed in equilibrium with some solid viologen salt neither dissolved nor absorbed by the solvent. The mole ratio of the sponge-like liquid phase again increases linearly with side-chain length, while it remains independent of the relative amount of benzene and viologen salt as long as the latter is in excess. Finally, when appropriate amounts of benzene and viologen salt are mixed, a single sponge-like liquid phase is observed at an intermediate composition between the lower and upper limits. Molecular dynamics simulations reveal that because of their dual ionic and organic nature, when absorbed in benzene, the studied salts form nanoscale segregated liquid structures, akin ionic liquids, with a continuous polar network composed of anions and cationic charged groups, along with nonpolar domains composed of alkyl cationic side chains. Benzene molecules are preferentially absorbed inside the nonpolar region, which effectively expands the nonpolar region to be sponge-like and consequently liquidizes the viologen salt. The linearity of the benzene/salt ratio in the upper and lower phase boundaries comes from the fact that the effective volume of the nonpolar region for accommodating benzene molecules grows linearly with cationic alkyl side-chain length. The occurrence of the above phenomena is attributed to the nonpolar feature of benzene molecules, and there is no evidence of pi-pi or ion-pi interaction between the ions and benzene molecules. Moreover, the diffusion of benzene in the sponge-like phase is found to be close to that in n-alkanes, supporting the idea of nanoscale segregation of polar and nonpolar regions in the sponge-like phase. The revealed mechanism is anticipated to be general for understanding liquid-liquid phase separation observed in mixtures of organic salts (ionic liquids) having relatively long alkyl chains with small organic molecules
Molecular dynamics simulations of microscopic structural transition and macroscopic mechanical properties of magnetic gels
No full textMagnetic gels with embedded micro-/nano-sized magnetic particles in cross-linked polymer networks can be actuated by external magnetic fields, with changes in their internal microscopic structures and macroscopic mechanical properties. We investigate the responses of such magnetic gels to an external magnetic field, by means of coarse-grained molecular dynamics simulations. We find that the dynamics of magnetic particles are determined by the interplay of magnetic dipole–dipole interactions, polymer elasticity, and thermal fluctuations. The corresponding microscopic structures formed by the magnetic particles, such as elongated chains, can be controlled by the external magnetic field. Furthermore, the magnetic gels can exhibit reinforced macroscopic mechanical properties, where the elastic modulus increases algebraically with the magnetic moments of the particles in the form of ∝(m−mc)2 when magnetic chains are formed. This simulation work can not only serve as a tool for studying the microscopic and the macroscopic responses of the magnetic gels, but also facilitate future fabrications and practical controls of magnetic composites with desired physical properties.National Natural Science Foundation of China 10.13039/501100001809Max Planck SocietyWenzhou Institute of Biomaterials and Engineering 10.13039/501100013910Beijing National Laboratory for Condensed Matter PhysicsChina Postdoctoral Science Foundation 10.13039/501100002858European Research Council 10.13039/50110000078
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Supplemental Material - Aberrant phenotypes of circulating γδ-T cells may be involved in the onset of systemic lupus erythematosus
No full textSupplemental Material for Aberrant phenotypes of circulating γδ-T cells may be involved in the onset of systemic lupus erythematosus by Shiwen Yuan, Cuicui Wang, Yanting Zeng, Jiawei Li, Weinian Li, Zhixiang He, Jinghua Ye, Fangfei Li, Yi Chen, Xiaojun Lin, Yan Xu, Na Yu and Xiaoyan Cai in Lupus</p
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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