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Phase equilibria and processing of infrared optical ceramics on the join CaLa2S4-La2S3
William B. White,Daniel L. Chess,Catherine A. Chess,Judith A. Marks 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.4
Processing techniques have been developed for the fabrication of optically transparent, theoretically dense CaLa2S4 – La2S3ceramics with a potential application as windows for the mid-infrared. Extreme care is needed to avoid oxygen. Best results were obtained by pre-sintering in an H2S/H2 atmosphere followed by hot-isostatic pressing. Microstructures, hardness measurements, and infrared absorption spectra serve to characterize the various processing procedures.
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>
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>
( Oladayo Folasire ),( Kylie A Mills ),( Donna J Sellers ),( Russ Chess Williams ) 대한소화기기능성질환·운동학회 2016 Journal of Neurogastroenterology and Motility (JNM Vol.22 No.1
Background/Aims The internal anal sphincter (IAS) plays an important role in maintaining continence and a number of neurotransmitters are known to regulate IAS tone. The aim of this study was to determine the relative importance of the neurotransmitters involved in the relaxant and contractile responses of the porcine IAS. Methods Responses of isolated strips of IAS to electrical field stimulation (EFS) were obtained in the absence and presence of inhibitors of neurotransmitter systems. Results Contractile responses of the sphincter to EFS were unaffected by the muscarinic receptor antagonist, atropine (1 mM), but were almost completely abolished by the adrenergic neuron blocker guanethidine (10 mM). Contractile responses were also reduced (by 45% at 5 Hz, P < 0.01) following desensitisation of purinergic receptors with α,β-methylene-ATP (10 mM). In the presence of guanethidine, atropine, and α,β-methylene-ATP, the remaining relaxatory responses to EFS were examined. These responses were not altered by the cyclooxygenase inhibitor, indomethacin (5 mM), the vasoactive intestinal polypeptide receptor antagonist, [D-p-Cl-Phe6,Leu17]- vasoactive intestinal peptide (PheLeu-VIP; 100 nM), or the purinoceptor antagonists, 8-phenyltheophyline (P1 receptors) or suramin (P2 receptors). However, relaxation responses were reduced by Nω-nitro-L-arginine (L-NNA; 100 mM), an inhibitor of nitric oxide synthesis (40-50% reduction), zinc protoprophyrin IX (10 mM), an inhibitor of carbon monoxide synthesis (20-40% reduction), and also propargylglycine (30 mM) and aminooxyacetic acid (30 mM), inhibitors of hydrogen sulphide synthesis (15-20% reduction). Conclusions Stimulation of IAS efferent nerves releases excitatory and inhibitory neurotransmitters: noradrenaline is the predominant contractile transmitter with a smaller component from ATP, whilst 3 gases mediate relaxation responses to EFS, with the combined contributions being nitric oxide > carbon monoxide > hydrogen sulfide. (J Neurogastroenterol Motil 2016;22:141-148)