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Tailoring magnetic energies to form dipole skyrmions and skyrmion lattices
Montoya, S. A.,Couture, S.,Chess, J. J.,Lee, J. C. T.,Kent, N.,Henze, D.,Sinha, S. K.,Im, M.-Y.,Kevan, S. D.,Fischer, P.,McMorran, B. J.,Lomakin, V.,Roy, S.,Fullerton, E. E. American Physical Society 2017 Physical Review B Vol.95 No.2
<P>The interesting physics and potential memory technologies resulting from topologically protected spin textures such as skyrmions have prompted efforts to discover new material systems that can host these kinds of magnetic structures. Here, we use the highly tunable magnetic properties of amorphous Fe/Gd multilayer films to explore the magnetic properties that lead to dipole-stabilized skyrmions and skyrmion lattices that form from the competition of dipolar field and exchange energy. Using both real space imaging and reciprocal space scattering techniques, we determined the range of material properties and magnetic fields where skyrmions form. Micromagnetic modeling closely matches our observation of small skyrmion features (similar to 50 to 70 nm) and suggests that these classes of skyrmions have a rich domain structure that is Bloch-like in the center of the film and more Neel-like towards each surface. Our results provide a pathway to engineer the formation and controllability of dipole skyrmion phases in a thin film geometry at different temperatures and magnetic fields.</P>
심재광,Kim Kwang-Sub,Couture Pierre,Denault André,곽영란,Yoo Kyung-Jong,Youn Young-Nam 대한마취통증의학회 2023 Korean Journal of Anesthesiology Vol.76 No.4
Off-pump coronary surgery requires mechanical cardiac displacement, which results in bi-ventricular systolic and diastolic dysfunction. Although transient, subsequent hemodynamic deterioration can be associated with poor prognosis and, in extreme cases, emergency conversion to on-pump surgery, which is associated with high morbidity and mortality. Thus, appropriate decision-making regarding whether the surgery can be proceeded based on objective hemodynamic targets is essential before coronary arteriotomy. For adequate hemodynamic management, avoiding myocardial oxygen supply-demand imbalance, which includes maintaining mean arterial pressure above 70 mmHg and preventing an increase in oxygen demand beyond the patient’s coronary reserve, must be prioritized. Maintaining mixed venous oxygen saturation above 60%, which reflects the lower limit of adequate global oxygen supply-demand balance, is also essential. Above all, severe mechanical cardiac displacement incurring compressive syndromes, which cannot be overcome by adjusting major determinants of cardiac output, should be avoided. An uncompromising form of cardiac constraint can be ruled out as long as the central venous pressure is not equal to or greater than the pulmonary artery diastolic (or occlusion) pressure, as this would reflect tamponade physiology. In addition, transesophageal echocardiography should be conducted to rule out mechanical cardiac displacement-induced ventricular interdependence, dyskinesia, severe mitral regurgitation, and left ventricular outflow tract obstruction with or without systolic motion of the anterior leaflet of the mitral valve, which cannot be tolerated during grafting. Finally, the ascending aorta should be carefully inspected for gas bubbles to prevent hemodynamic collapse caused by a massive gas embolism obstructing the right coronary ostium.
Resonant properties of dipole skyrmions in amorphous Fe/Gd multilayers
Montoya, S. A.,Couture, S.,Chess, J. J.,Lee, J. C. T.,Kent, N.,Im, M.-Y.,Kevan, S. D.,Fischer, P.,McMorran, B. J.,Roy, S.,Lomakin, V.,Fullerton, E. E. American Physical Society 2017 Physical Review B Vol.95 No.22
<P>The dynamic response of dipole skyrmions in Fe/Gd multilayer films is investigated by ferromagnetic resonance measurements and compared to micromagnetic simulations. We detail thickness-and temperature-dependent studies of the observed modes as well as the effects of magnetic field history on the resonant spectra. Correlation between the modes and the magnetic phase maps constructed from real-space imaging and scattering patterns allows us to conclude that the resonant modes arise from local topological features such as dipole skyrmions but do not depend on the collective response of a close-packed lattice of these chiral textures. Using micromagnetic modeling, we are able to quantitatively reproduce our experimental observations which suggests the existence of localized spin-wave modes that are dependent on the helicity of the dipole skyrmion. We identify four localized spin-wave excitations for the skyrmions that are excited under either in-plane or out-of-plane rf fields. Lastly we show that dipole skyrmions and nonchiral bubble domains exhibit qualitatively different localized spin-wave modes.</P>
J. L. Ullmann,A. J. Couture,A. L. Keksis,D. J. Vieira,,J. M. ODonnell,J. M. Wouters,M. Jandel,R. C. Haight,R. S. Rundberg,T. A. Bredeweg,T. Kawano,C. Y. Wu,J. A. Becker,A. Chyzh,B. Baramsai,G. E. Mitc 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
A careful new measurement of the ^(238)U(n,γ) cross section from 10 eV to 100 keV has been made using the DANCE detector at LANSCE. DANCE is a 4π calorimetric scintillator array consisting of 160 BaF^2 crystals. Measurements were made on a 48 mg/cm^2 depleted uranium target. The cross sections are in general in good agreement with previous measurements. The gamma-ray emission spectra, as a function of gamma multiplicity, were also measured and compared to model calculations.
김정은,Keagan Dunville,이준지,Ji Xin Cheng,Travis B. Conley,Cortni S. Couture,Wayne W Campbell 대한내분비학회 2017 Endocrinology and metabolism Vol.32 No.2
Background: Insulin resistance is associated with the higher content of intermuscular adipose tissue (IMAT) and the saturation of intramyocellular lipid (IMCL), but a paucity of data exist in humans. This study examined associations among IMAT content, IMCL saturation, and fasting glucose concentration in middle-aged and older adults with overweight or obesity. Methods: Seventy-five subjects (26 males, 49 females) were recruited and thigh muscle and IMAT were assessed using magnetic resonance imaging. Vastus lateralis tissue was acquired from a subset of nine subjects and IMCL content and saturation were assessed using nonlinear dual complex microscopy. Results: The characteristics of the 75 subjects were as follows: age 59±11 years, body mass index 30±5 kg/m2, fasting glucose concentration 5.2±0.5 mmol/L, fasting insulin concentration 12.2±7.3 μU/mL, fasting homeostatic model assessment of insulin resistance (HOMA-IR) 2.9±2.0 (mean±SD). IMAT to muscle tissue (MT) volume ratio was positively associated with the saturated fatty acid to unsaturated fatty acid ratio in IMCL. IMAT:MT was positively associated with fasting glucose concentration and HOMA-IR. IMCL saturation was positively associated with fasting glucose concentration while muscle cell area, IMCL area, and % IMCL in muscle cell were not associated with fasting glucose concentration. Conclusion: These results indicate that higher intermuscular fat content and IMCL saturation may impact fasting glucose concentration in middle-aged and older adults with overweight or obesity. The centralization of adipose tissue in the appendicular region of the body may promote insulin resistance.
Context dependency of Set1/COMPASS-mediated histone H3 Lys4 trimethylation
Thornton, Janet L.,Westfield, Gerwin H.,Takahashi, Yoh-hei,Cook, Malcolm,Gao, Xin,Woodfin, Ashley R.,Lee, Jung-Shin,Morgan, Marc A.,Jackson, Jessica,Smith, Edwin R.,Couture, Jean-Francois,Skiniotis, G Cold Spring Harbor Laboratory Press 2014 Genes & development Vol.28 No.2
<P>The stimulation of H3K4 trimethylation (H3K4me3) by H2B monoubiquitination (H2Bub) has been widely studied, and multiple mechanisms have been proposed for this form of histone cross-talk. Thornton et al. combine biochemical, structural, and in vivo approaches to provide a novel mechanism for the role of H2B ubiquitination machinery in the regulation of histone H3K4 methylation by COMPASS. This study demonstrates that the H2Bub machinery and Cps35/Swd2 function to focus the H3K4me3 activity of COMPASS at promoter-proximal regions in a context-dependent manner.</P>