Monte Carlo studies of skyrmion stabilization under geometric confinement and uniaxial strain

Geometric confinement (GC) of skyrmions in nanodomains plays a crucial role in skyrmion stabilization. This confinement effect decreases the magnetic field necessary for skyrmion formation and is closely related to the applied mechanical stresses. However, the mechanism of GC is unclear and remains controversial. Here, we numerically study the effect of GC on skyrmion stabilization and find that zero Dzyaloshinskii-Moriya interaction (DMI) coupling constants imposed on the boundary surfaces of small thin plates cause confinement effects, stabilizing skyrmions in the low-field region. Moreover, the confined skyrmions are further stabilized by tensile strains parallel to the plate, and the skyrmion phase extends to the low-temperature region. This stabilization occurs due to the bulk anisotropic DMI coupling constant caused by lattice deformations. Our simulation data are qualitatively consistent with reported experimental data on skyrmion stabilization induced by tensile strains applied to a thin plate of the chiral magnet ${\rm Cu_2OSeO_3}$.Comment: 33 pages, 16 figure

Extracting the Redox Orbitals in Li Battery Materials with High-Resolution X-Ray Compton Scattering Spectroscopy

We present an incisive spectroscopic technique for directly probing redox orbitals based on bulk electron momentum density measurements via high-resolution x-ray Compton scattering. Application of our method to spinel LixMn2O4, a lithium ion battery cathode material, is discussed. The orbital involved in the lithium insertion and extraction process is shown to mainly be the oxygen 2p orbital. Moreover, the manganese 3d states are shown to experience spatial delocalization involving 0.16 electrons per Mn site during the battery operation. Our analysis provides a clear understanding of the fundamental redox process involved in the working of a lithium ion battery.Comment: 24 pages, 3 figure

Smoking and Risk for Diabetes Incidence and Mortality in Korean Men and Women

This is an uncopyedited electronic version of an article accepted for publication in Diabetes Care. The American Diabetes Association, publisher of Diabetes Care, is not responsible for any errors or omissions in this version of the manuscript or any version derived from it by third parties. The definitive publisher-authenticated version will be available in a future issue of Diabetes Care in print and online a

Mechanisms controlling dissolved iron distribution in the North Pacific : a model study

Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): G03005, doi:10.1029/2010JG001541.Mechanisms controlling the dissolved iron distribution in the North Pacific are investigated using the Biogeochemical Elemental Cycling (BEC) model with a resolution of approximately 1° in latitude and longitude and 60 vertical levels. The model is able to reproduce the general distribution of iron as revealed in available field data: surface concentrations are generally below 0.2 nM; concentrations increase with depth; and values in the lower pycnocline are especially high in the northwestern Pacific and off the coast of California. Sensitivity experiments changing scavenging regimes and external iron sources indicate that lateral transport of sedimentary iron from continental margins into the open ocean causes the high concentrations in these regions. This offshore penetration only appears under a scavenging regime where iron has a relatively long residence time at high concentrations, namely, the order of years. Sedimentary iron is intensively supplied around continental margins, resulting in locally high concentrations; the residence time with respect to scavenging determines the horizontal scale of elevated iron concentrations. Budget analysis for iron reveals the processes by which sedimentary iron is transported to the open ocean. Horizontal mixing transports sedimentary iron from the boundary into alongshore currents, which then carry high iron concentrations into the open ocean in regions where the alongshore currents separate from the coast, most prominently in the northwestern Pacific and off of California.This work was supported by the U.S. National Science Foundation (EF‐0424599)

Transport reduction by current profile control in the reversed‐field pinch

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Delithiation/lithiation behavior of LiNi<inf>0.5</inf>Mn<inf>1.5</inf>O<inf>4</inf> studied by in situ and ex situ ^6,7Li NMR spectroscopy

Delithiation and lithiation behaviors of ordered spinel LiNi0.5Mn1.5O4 and disordered spinel LiNi0.4Mn1.6O4 were investigated by using in situ (in operando) 7Li NMR and ex situ 6Li MAS NMR spectroscopy. The in situ 7Li monitoring of the ordered spinel revealed a clear appearance and subsequent disappearance of a new signal from the well-defined phase Li0.5Ni0.5Mn1.5O4, suggesting the two-phase reaction processes among Li1.0Ni0.5Mn1.5O4, Li0.5Ni0.5Mn1.5O4, and Li0.0Ni0.5Mn1.5O4. Also, for the disordered spinel, Li0.5Ni0.4Mn1.6O4 was identified with a broad distribution in Li environment. High-resolution 6Li MAS NMR spectra were also acquired for the delithiated and lithiated samples to understand the detailed local structure around Li ions. We suggested that the nominal Li-free phase Li0.0Ni0.5Mn1.5O4 can accommodate a small amount of Li ions in its structure. The tetragonal phases Li2.0Ni0.5Mn1.5O4 and Li2.0Ni0.4Mn1.6O4, which occurred when the cell was discharged down to 2.0 V, were very different in the Li environment from each other. It is found that 6, 7Li NMR is highly sensitive not only to the Ni/Mn ordering in LiNi0.5Mn1.5O4 but also to the valence changes of Ni and Mn on charge-discharge process

Loss of the interferon-γ-inducible regulatory immunity-related GTPase (IRG), Irgm1, causes activation of effector IRG proteins on lysosomes, damaging lysosomal function and predicting the dramatic susceptibility of Irgm1-deficient mice to infection

The interferon-γ (IFN-γ)-inducible immunity-related GTPase (IRG), Irgm1, plays an essential role in restraining activation of the IRG pathogen resistance system. However, the loss of Irgm1 in mice also causes a dramatic but unexplained susceptibility phenotype upon infection with a variety of pathogens, including many not normally controlled by the IRG system. This phenotype is associated with lymphopenia, hemopoietic collapse, and death of the mouse.Deutscher Akademischer Austausch Dienst (DAAD); International Graduate School in Development Health and Disease (IGS-DHD); Deutsche For-schungsgemeinschaft (SFBs 635, 670, 680); Max-Planck-Gesellschaft (Max Planck Fellowship)

Confinement improvement with rf poloidal current drive in the reversed-field pinch

External control of the current profile in a reversed-field pinch (RFP), by means such as rf poloidal current drive, may have beneficial effects well beyond the direct reduction of Ohmic input power due to auxiliary heating. Reduction of magnetic turbulence associated with the dynamo, which drives poloidal current in a conventional RFP, may allow operation at lower density and higher electron temperature, for which rf current drive becomes efficient and the RFP operates in a more favorable regime on the n{tau} vs T diagram. Projected parameters for RFX at 2 MA axe studied as a concrete example. If rf current drive allows RFX to operate with {beta} = 10% (plasma energy/magnetic energy) at low density (3 {times} 10{sup 19} m{sup {minus}3}) with classical resistivity (i.e. without dynamo-enhanced power input), 40 ms energy confinement times and 3 keV temperatures will result, matching the performance of tokamaks of similar size