Tetra­potassium cis-dioxido-trans-bis­(sulfato-κO)sulfato(κ2 O,O′)molybdate(VI)

The title compound, K4[MoVIO2(SO4)3], was precipitated from a melt of molybdenum(VI) oxide and potassium sulfate in potassium disulfate. The compound contains monomeric [MoVIO2(SO4)3]4− anions, with the MoVI atom, both oxide ligands, and the S atom and both ligating O atoms of the bidentate sulfate group lying on a crystallographic mirror plane. One of the potassium cations is nine-coordinate, while the other is eight-coordinate

catena-Poly[tetra­sodium [[cis-dioxido-trans-bis­(sulfato-κO)molybdate(VI)]-μ-sulfato-κ2 O:O′]]

Single crystals of the title compound, {Na4[MoVIO2(SO4)3]}n, were grown from a melt of MoO3 and Na2SO4 in Na2S2O7. In contrast to the structure of the isoformular K compound, K4[MoVIO2(SO4)3], with its monomeric anion, this sodium analogue contains a polymeric anion of the type {[MoVIO2(SO4)2-μ-(SO4)]4−}n. The MoVI cations, surrounded by two tightly bonded O atoms and four O atoms of one bridging and two terminal sulfato ligands, form zigzag chains parallel to [100]. All four Na+ cations are situated between the anionic chains and have distorted octa­hedral coordination spheres

Chiral logic computing with twisted antiferromagnetic magnon modes

Antiferromagnetic (AFM) materials offer an exciting platform for ultrafast information handling with low cross-talks and compatibility with existing technology. Particularly interesting for low-energy cost computing is the spin wave-based realization of logic gates, which has been demonstrated experimentally for ferromagnetic waveguides. Here, we predict chiral magnonic eigenmodes with a finite intrinsic, magnonic orbital angular momentum ℓ in AFM waveguides. ℓ is an unbounded integer determined by the spatial topology of the mode. We show how these chiral modes can serve for multiplex AFM magnonic computing by demonstrating the operation of several symmetry- and topology-protected logic gates. A Dzyaloshinskii–Moriya interaction may arise at the waveguide boundaries, allowing coupling to external electric fields and resulting in a Faraday effect. The uncovered aspects highlight the potential of AFM spintronics for swift data communication and handling with high fidelity and at a low-energy cost

Calibration of optical tweezers with positional detection in the back-focal-plane

We explain and demonstrate a new method of force- and position-calibration for optical tweezers with back-focal-plane photo detection. The method combines power spectral measurements of thermal motion and the response to a sinusoidal motion of a translation stage. It consequently does not use the drag coefficient of the trapped ob ject as an input. Thus, neither the viscosity, nor the size of the trapped ob ject, nor its distance to nearby surfaces need to be known. The method requires only a low level of instrumentation and can be applied in situ in all spatial dimensions. It is both accurate and precise: true values are returned, with small error-bars. We tested this experimentally, near and far from surfaces. Both position- and force-calibration were accurate to within 3%. To calibrate, we moved the sample with a piezo-electric translation stage, but the laser beam could be moved instead, e.g. by acousto-optic deflectors. Near surfaces, this precision requires an improved formula for the hydrodynamical interaction between an infinite plane and a micro-sphere in non-constant motion parallel to it. We give such a formula.Comment: Submitted to: Review of Scientific Instruments. 13 pages, 5 figures. Appendix added (hydrodynamically correct calibration

Stochastic dynamics and pattern formation of geometrically confined skyrmions

Ensembles of magnetic skyrmions in confined geometries are shown to exhibit thermally driven motion on two different time scales. The intrinsic fluctuating dynamics (t ∼ 1 ps) are governed by short-range symmetric and antisymmetric exchange interactions, whereas the long-time limit (t ≳ 10 ns) is determined by the coaction of skyrmion–skyrmion-repulsion and the system’s geometry. Micromagnetic simulations for realistic island shapes and sizes are performed and analyzed, indicating the special importance of skyrmion dynamics at finite temperatures. We demonstrate how the competition between skyrmion mobility and observation time directly affects the addressability of skyrmionic bits, which is a key challenge on the path of developing skyrmion-based room-temperature applications. The presented quasiparticle Monte Carlo approach offers a computationally efficient description of the diffusive motion of skyrmion ensembles in confined geometries, like racetrack memory setups

Continental-scale patterns of pathogen prevalence: a case study on the corncrake

Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient of prevalence from western to Eastern Europe negatively correlated with national agricultural yield, but positively correlated with corncrake census population sizes when only the most widespread lineage is considered. This likely reveals a possible impact of local agriculture intensity, which reduced host population densities in Western Europe and, potentially, insect vector abundance, thus reducing the transmission of pathogens. We conclude that in the corncrake system, where metapopulation dynamics resulted in variations in local census population sizes, but not in the genetic impoverishment of these populations, anthropogenic activity has led to a reduction in host populations and pathogen prevalence

On an Alternative Parametrization for the Theory of Complex Spectra

The purpose of this letter is threefold : (i) to derive, in the framework of a new parametrization, some compact formulas of energy averages for the electrostatic interaction within an (nl)N configuration, (ii) to describe a new generating function for obtaining the number of states with a given spin angular momentum in an (nl)N configuration, and (iii) to report some apparently new sum rules, actually a by-product of (i), for SU(2) > U(1) coupling coefficients.Comment: Published in Physics Letters A 147, 417-422 (1990