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Abstract: Two-component systems capable of self-assembling into soft gel-phase materials are of considerable interest due to their tunability and versatility. This paper investigates two-component gels based on a combination of a L-lysine-based dendron and a rigid diamine spacer (1,4-diaminobenzene or 1,4-diaminocyclohexane). The networked gelator was investigated using thermal measurements, circular dichroism, NMR spectroscopy and small angle neutron scattering (SANS) giving insight into the macroscopic properties, nanostructure and molecular-scale organisation. Surprisingly, all of these techniques confirmed that irrespective of the molar ratio of the components employed, the “solid-like” gel network always consisted of a 1:1 mixture of dendron/diamine. Additionally, the gel network was able to tolerate a significant excess of diamine in the “liquid-like” phase before being disrupted. In the light of this observation, we investigated the ability of the gel network structure to evolve from mixtures of different aromatic diamines present in excess. We found that these two-component gels assembled in a component-selective manner, with the dendron preferentially recognising 1,4-diaminobenzene (>70?%), when similar competitor diamines (1,2- and 1,3-diaminobenzene) are present. Furthermore, NMR relaxation measurements demonstrated that the gel based on 1,4-diaminobenzene was better able to form a selective ternary complex with pyrene than the gel based on 1,4-diaminocyclohexane, indicative of controlled and selective ?–? interactions within a three-component assembly. As such, the results in this paper demonstrate how component selection processes in two-component gel systems can control hierarchical self-assembly.

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Abstract: This paper reports on the synthesis of zinc oxide (ZnO) nanostructures and examines the performance of nanocomposite thin-film transistors (TFTs) fabricated using ZnO dispersed in both n- and p-type polymer host matrices. The ZnO nanostructures considered here comprise nanowires and tetrapods and were synthesized using vapor phase deposition techniques involving the carbothermal reduction of solid-phase zinc-containing compounds. Measurement results of nanocomposite TFTs based on dispersion of ZnO nanorods in an n-type organic semiconductor ([6, 6]-phenyl-C-61-butyric acid methyl ester) show electron field-effect mobilities in the range 0.3-0.6 cm(2)V(-1)s(-1), representing an approximate enhancement by as much as a factor of 40 from the pristine state. The on/off current ratio of the nanocomposite TFTs approach 10(6) at saturation with off-currents on the order of 10 pA. The results presented here, although preliminary, show a highly promising enhancement for realization of high-performance solution-processable n-type organic TFTs.

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Abstract: We examine the formation of local moments in Heusler alloys of the composition Co2MnZ
where Z=Si or Al using the combined techniques of x-ray magnetic circular and linear dichroism. The existence of local moments in half-metallic Heusler alloys is reliant upon the band gap in the minority-spin states. By utilizing the element-specific nature of x-ray absorption techniques we are able to explore the degree of localization of moments on Co and Mn atoms. We observe a crucial difference in the localization of the Co moment when comparing Co2MnSi
CMS and Co2MnAl films that is consistent with the predicted larger minority-spin gap in the Co partial density of states for CMS. These results provide important evidence for the dominant role of the Co minority-spin states in realizing half-metallic ferromagnetism in this system

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Abstract: In magnetic metals the core-hole excitation by x rays leads to a sudden creation of an impurity that is screened in a spin-dependent way. A scattering experiment in the L3 region terminating with a 3s hole has already been shown to give information on the time scale of this screening process. Here we present a linear-rate model for the analysis of such experiments and apply this to Ni, Co, and Fe metals. This model yields quantitative results that could not be obtained before using an empirical model. The screening time constant in Ni (most likely ∼1.5 fs) is definitely longer than in Fe, which presumably is caused by narrow-band effects. The screening time is 0.43 fs in Co, while 0.18 fs is an upper limit in Fe metal. In agreement with the experiment, the model clarifies the variation in the dichroism due to the competition between the core-hole decay and the time it takes to accumulate the screening charge. Finally, the perspectives of this approach are briefly discussed including the importance of future experiments on diluted magnetic impurities.

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Abstract: The nucleobase–cation–symport-1 (NCS1) transporters are essential components of salvage pathways for nucleobases and related metabolites. Here, we report the 2.85-angstrom resolution structure of the NCS1 benzyl-hydantoin transporter, Mhp1, from Microbacterium liquefaciens. Mhp1 contains 12 transmembrane helices, 10 of which are arranged in two inverted repeats of five helices. The structures of the outward-facing open and substrate-bound occluded conformations were solved, showing how the outward-facing cavity closes upon binding of substrate. Comparisons with the leucine transporter LeuTAa and the galactose transporter vSGLT reveal that the outward- and inward-facing cavities are symmetrically arranged on opposite sides of the membrane. The reciprocal opening and closing of these cavities is synchronized by the inverted repeat helices 3 and 8, providing the structural basis of the alternating access model for membrane transport.