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The mathematical conditions for the best thermoelectric is well known but never realised in real materials. Here, the authors propose the Anderson transition in a narrow impurity band as a physical realisation of this seemingly unrealisable scenario.

Recent findings have sparked great interest in the putative magnetic receptor protein MagR. However, in vivo experiments have revealed no magnetic moment of MagR at room temperature. Nevertheless, the interaction of MagR and MagR fusion proteins with silica-coated magnetite beads have proven useful for protein purification. In this study, we recombinantly produced two different MagR proteins in Escherichia coli BL21(DE3) to (1) expand earlier protein purification studies, (2) test if MagR can magnetize whole E. coli cells once it is expressed to a high cytosolic, soluble titer, and (3) investigate the MagR-expressing E. coli cells’ magnetic properties at low temperatures. Our results show that MagR induces no measurable, permanent magnetic moment in cells at low temperatures, indicating no usability for cell magnetization. Furthermore, we show the limited usability for magnetic bead-based protein purification, thus closing the current knowledge gap between theoretical considerations and empirical data on the MagR protein.

A quantitative analysis of spin-echo NMR measurements of the local field distribution and the spin–spin relaxation time T _2 in the field-cooled superconducting state of the type-II superconductor La _3 Ni _2 B _2 N _3− _x shows evidence for two fluctuation modes of the weakly pinned vortex matter dominating T _2 at different temperatures: long wavelength diffusive modes in the vortex solid at low temperature, and plastic deformation of the viscous liquid close to the critical temperature T _c , with a broad crossover region in between where a more complex theory is required. We determine the melting temperature T _m = 11.5 K of the vortex matter as the temperature where the characteristic time of the plastic deformation slows down to the time scale set by the spin-echo experiment. This is preferred to the conventional estimates from a Lindemann criterion for the melting vortex solid since the quantitative description of T _2 near T _m by the viscous vortex liquid appears to be more consistent. It indicates that the plastic deformation mode might be important for T _2 in the mixed state of other type-II superconductors in the weak pinning regime near T _c as well.

Ferromagnetic spin fluctuations in itinerant-electron magnetic compounds RCo9Si4 (R = Y, La) were investigated by using magnetization and 59Co-NMR measurements. YCo9Si4 is an itinerant ferromagnet, while LaCo9Si4 is a nearly ferromagnetic metal. In YCo9Si4, the field dependence of the magnetization is well described by Takahashi’s spin-fluctuation theory for weak itinerant ferromagnets. In both YCo9Si4 and LaCo9Si4, the magnetic susceptibility, the Knight Shift and 1/T1T show a similar temperature dependence, which suggests that the ferromagnetic spin fluctuation is dominant in these compounds. The difference in the magnetic ground state of these compounds is possibly attributed to the fact that the energy scale of the ferromagnetic spin fluctuation in LaCo9Si4 is larger than that in YCo9Si4. [ABSTRACT FROM AUTHOR]