Stray field signatures of N\'eel textured skyrmions in Ir/Fe/Co/Pt multilayer films

Skyrmions are nanoscale spin configurations with topological properties that hold great promise for spintronic devices. Here, we establish their N\'eel texture, helicity, and size in Ir/Fe/Co/Pt multilayer films by constructing a multipole expansion to model their stray field signatures and applying it to magnetic force microscopy (MFM) images. Furthermore, the demonstrated sensitivity to inhomogeneity in skyrmion properties, coupled with a unique capability to estimate the pinning force governing dynamics, portends broad applicability in the burgeoning field of topological spin textures.Comment: 6 pages, 4 figures, significantly revised and upgraded. For the updated supplementary material please contact one of the corresponding author

Theory of SIS tunnelling in cuprates

We show that the single-particle polaron Green's function describes SIS tunnelling in cuprates, including the absence of Ohm's law at high voltages, the dip/hump features in the first derivative of the current, a substantial incoherent spectral weight beyond quasiparticle peaks and unusual shape of the peaks. The theory allows us to determine the characteristic phonon frequencies, normal and superconducting gaps, impurity scattering rate, and the electron-phonon coupling from the tunnelling data.Comment: 10 pages, 2 figure

Resistance and Resistance Fluctuations in Random Resistor Networks Under Biased Percolation

We consider a two-dimensional random resistor network (RRN) in the presence of two competing biased percolations consisting of the breaking and recovering of elementary resistors. These two processes are driven by the joint effects of an electrical bias and of the heat exchange with a thermal bath. The electrical bias is set up by applying a constant voltage or, alternatively, a constant current. Monte Carlo simulations are performed to analyze the network evolution in the full range of bias values. Depending on the bias strength, electrical failure or steady state are achieved. Here we investigate the steady-state of the RRN focusing on the properties of the non-Ohmic regime. In constant voltage conditions, a scaling relation is found between $/_0$ and $V/V_0$, where $$ is the average network resistance, $_0$ the linear regime resistance and $V_0$ the threshold value for the onset of nonlinearity. A similar relation is found in constant current conditions. The relative variance of resistance fluctuations also exhibits a strong nonlinearity whose properties are investigated. The power spectral density of resistance fluctuations presents a Lorentzian spectrum and the amplitude of fluctuations shows a significant non-Gaussian behavior in the pre-breakdown region. These results compare well with electrical breakdown measurements in thin films of composites and of other conducting materials.Comment: 15 figures, 23 page

Employer’s management of employees affected by cancer

Return to work (RTW) following treatment can be problematic for cancer survivors. Although some people affected by cancer are able to continue working, a greater proportion of these survivors end up unemployed, retire early or change jobs than those without a diagnosis of cancer [1]. One of the reasons for not returning to work is the lack of understanding and support from employers and supervisors [2]. Currently, it is not clear what factors are likely to influence the employer’s management of employees recovering from cancer. This article reports the outcome from a review of the published literature on factors related to the current employer management of employed cancer survivors

Colossal topological Hall effect at the transition between isolated and lattice-phase interfacial skyrmions

The topological Hall effect is used extensively to study chiral spin textures in various materials. However, the factors controlling its magnitude in technologically-relevant thin films remain uncertain. Using variable-temperature magnetotransport and real-space magnetic imaging in a series of Ir/Fe/Co/Pt heterostructures, here we report that the chiral spin fluctuations at the phase boundary between isolated skyrmions and a disordered skyrmion lattice result in a power-law enhancement of the topological Hall resistivity by up to three orders of magnitude. Our work reveals the dominant role of skyrmion stability and configuration in determining the magnitude of the topological Hall effect

Optical conductivity of CuO_2 infinite-layer films

The infrared conductivity of CaCuO_2, SrCuO_{2-y}, and Sr_{0.85}Nd_{0.15}CuO_2 infinite-layer films is obtained from reflectivity measurements by taking into account the substrate contribution. SrCuO_{2-y} and Sr_{0.85}Nd_{0.15}CuO_2 exhibit extra-phonon modes and structured bands in the midinfrared, not found in stoichiometric CaCuO_2. These features mirror those observed in the perovskitic cuprates, thus showing that the polaronic properties of high-T_c superconductors are intrinsic to the CuO_2 planes.Comment: File latex, 5 p. incl. 4 fig. in epsf. Submitted to Solid State Com

The over-representation of binary DNA tracts in seven sequenced chromosomes

BACKGROUND: DNA tracts composed of only two bases are possible in six combinations: A+G (purines, R), C+T (pyrimidines, Y), G+T (Keto, K), A+C (Imino, M), A+T (Weak, W) and G+C (Strong, S). It is long known that all-pyrimidine tracts, complemented by all-purines tracts ("R.Y tracts"), are excessively present in analyzed DNA. We have previously shown that R.Y tracts are in vast excess in yeast promoters, and brought evidence for their role in gene regulation. Here we report the systematic mapping of all six binary combinations on the level of complete sequenced chromosomes, as well as in their different subregions. RESULTS: DNA tracts composed of the above binary base combinations have been mapped in seven sequenced chromosomes: Human chromosomes 21 and 22 (the major contigs); Drosophila melanogaster chr. 2R; Caenorhabditis elegans chr. I; Arabidopsis thaliana chr. II; Saccharomyces cerevisiae chr. IV and M. jannaschii. A huge over-representation, reaching million-folds, has been found for very long tracts of all binary motifs except S, in each of the seven organisms. Long R.Y tracts are the most excessive, except in D. melanogaster, where the K.M motif predominates. S (G, C rich) tracts are in excess mainly in CpG islands; the W motif predominates in bacteria. Many excessively long W tracts are nevertheless found also in the archeon and in the eukaryotes. The survey of complete chromosomes enables us, for the first time, to map systematically the intergenic regions. In human and other chromosomes we find the highest over-representation of the binary DNA tracts in the intergenic regions. These over-representations are only partly explainable by the presence of interspersed elements. CONCLUSIONS: The over-representation of long DNA tracts composed of five of the above motifs is the largest deviation from randomness so far established for DNA, and this in a wide range of eukaryotic and archeal chromosomes. A propensity for ready DNA unwinding is proposed as the functional role, explaining the evolutionary conservation of the huge excesses observed