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Christian Federau, Soren Christensen, Zungho Zun, Sun-Won Park, Wendy Ni, Michael Moseley, Greg Zaharchuk
INTRODUCTION: The goal of this study was to assess the changes in arterial spin labeling (ASL) cerebral blood flow (CBF) and arterial transit time (ATT), and in apparent diffusion coefficient (ADC), before and after an acetazolamide challenge in moyamoya patients, as function of arterial stenosis severity. METHODS: Pre-operative patients diagnosed with moyamoya disease who could undergo MRI at 3.0T were recruited for this study. A multi-delay pseudo-continuous ASL and a diffusion-weighted sequence were acquired before and 15 min after acetazolamide injection...
December 2, 2016: Neuroradiology
A Ligia Focsan, Lowell D Kispert
In an organized assembly in Arabidopsis thaliana plant, proton loss from the radical cation of zeaxanthin (Zea(+)) was found to occur under intense illumination, a possible component in photoprotection. A stable neutral radical is formed because of the favorable proton loss at C4(4') position(s) of the terminal ends of Zea(+) that extends the unpaired spin density distribution (notation Zea(4) or Zea(4') by symmetry). Proton loss from the radical cation of β-carotene (β-car(+)) to available proton acceptors was also detected in a PSII sample upon irradiation...
November 19, 2016: Journal of Photochemistry and Photobiology. B, Biology
Mohamed M Fadlallah, Ahmed A Maarouf, Udo Schwingenschlögl, Ulrich Eckern
Graphene nanomeshes (GNMs), formed by creating a superlattice of pores in graphene, possess rich physical and chemical properties. Many of these properties are determined by the pore geometry. In this work, we use first principles calculations to study the magnetic and electronic properties of metal-doped nitrogen-passivated GNMs. We find that the magnetic behaviour is dependent on the pore shape (trigonal versus hexagonal) as dictated by the number of covalent bonds formed between the 3d metal and the passivating N atoms...
December 2, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
R Padam, Swati Pandya, S Ravi, S Ramakrishnan, A K Nigam, A K Grover, D Pal
We present the evolution of novel phenomena of magnetic compensation effect, exchange bias (EB) effect and the field induced anomalies in '[Formula: see text]' substituted multiferroic compound [Formula: see text]. A few percent of '[Formula: see text]' substitution for '[Formula: see text]' in [Formula: see text] results in the reversal of field cooled magnetization under low applied fields below compensation temperature T comp. Further, increase in the field leads to the spin reorientation transition (T SR)...
December 2, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Y Kubota, K Murata, J Miyawaki, K Ozawa, M C Onbasli, T Shirasawa, B Feng, Sh Yamamoto, R-Y Liu, S Yamamoto, S K Mahatha, P Sheverdyaeva, P Moras, C A Ross, S Suga, Y Harada, K L Wang, I Matsuda
An interface electron state at the junction between a three-dimensional topological insulator film, Bi2Se3, and a ferrimagnetic insulator film, Y3Fe5O12 (YIG), was investigated by measurements of angle-resolved photoelectron spectroscopy and x-ray absorption magnetic circular dichroism. The surface state of the Bi2Se3 film was directly observed and localized 3d spin states of the Fe(3+) in the YIG film were confirmed. The proximity effect is likely described in terms of the exchange interaction between the localized Fe 3d electrons in the YIG film and delocalized electrons of the surface and bulk states in the Bi2Se3 film...
December 2, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Ian Cook, Ting Wang, Mark Girvin, Thomas S Leyh
We are just beginning to understand the allosteric regulation of the human cytosolic sulfotransferase (SULTs) family-13 disease-relevant enzymes that regulate the activities of hundreds, if not thousands, of signaling small molecules. SULT1A1, the predominant isoform in adult liver, harbors two noninteracting allosteric sites, each of which binds a different molecular family: the catechins (naturally occurring flavonols) and nonsteroidal antiinflammatory drugs (NSAIDs). Here, we present the structure of an SULT allosteric binding site-the catechin-binding site of SULT1A1 bound to epigallocatechin gallate (EGCG)...
November 23, 2016: Proceedings of the National Academy of Sciences of the United States of America
Bin Ji, Hiroyuki Kaneko, Takafumi Minamimoto, Haruhisa Inoue, Hiroki Takeuchi, Katsushi Kumata, Ming-Rong Zhang, Ichio Aoki, Chie Seki, Maiko Ono, Masaki Tokunaga, Satoshi Tsukamoto, Koji Tanabe, Ryong-Moon Shin, Takeharu Minamihisamatsu, Seiji Kito, Barry J Richmond, Tetsuya Suhara, Makoto Higuchi
: Chemogenetic manipulation of neuronal activities has been enabled by a designer receptor (designer receptor exclusively activated by designer drugs, DREADD) that is activated exclusively by clozapine-N-oxide (CNO). Here, we applied CNO as a functional reporter probe to positron emission tomography (PET) of DREADD in living brains. Mutant human M4 DREADD (hM4Di) expressed in transgenic (Tg) mouse neurons was visualized by PET with microdose [(11)C]CNO. Deactivation of DREADD-expressing neurons in these mice by nonradioactive CNO at a pharmacological dose could also be captured by arterial spin labeling MRI (ASL-MRI)...
November 9, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Takuya Nomoto, Hiroaki Ikeda
A heavy-fermion superconductor UPt_{3} is a unique spin-triplet superconductor with multiple superconducting phases. Here, we provide the first report on a first-principles analysis of the microscopic superconducting gap structure. We find that the promising gap structure is an unprecedented E_{2u} state, which is completely different from the previous phenomenological E_{2u} models. Our obtained E_{2u} state has in-plane twofold vertical line nodes on small Fermi surfaces and point nodes with linear dispersion on a large Fermi surface...
November 18, 2016: Physical Review Letters
Joseph Barker, Gerrit E W Bauer
The magnetic insulator yttrium iron garnet can be grown with near perfection and is therefore and ideal conduit for spin currents. It is a complex material with 20 magnetic moments in the unit cell. In spite of being a ferrimagnet, YIG is almost always modeled as a simple ferromagnet with a single spin wave mode. We use the method of atomistic spin dynamics to study the temperature evolution of the full spin wave spectrum, in quantitative agreement with neutron scattering experiments. The antiferromagnetic or optical mode is found to suppress the spin Seebeck effect at room temperature and beyond due to thermally pumped spin currents with opposite polarization to the ferromagnetic mode...
November 18, 2016: Physical Review Letters
E Civardi, M Moroni, M Babij, Z Bukowski, P Carretta
^{75}As, ^{87}Rb, and ^{85}Rb nuclear quadrupole resonance (NQR) and ^{87}Rb nuclear magnetic resonance measurements in a RbFe_{2}As_{2} iron-based superconductor are presented. We observe a marked broadening of the ^{75}As NQR spectrum below T_{0}≃140  K which is associated with the onset of a charge order in the FeAs planes. Below T_{0} we observe a power-law decrease in the ^{75}As nuclear spin-lattice relaxation rate down to T^{*}≃20  K. Below T^{*} the nuclei start to probe different dynamics owing to the different local electronic configurations induced by the charge order...
November 18, 2016: Physical Review Letters
C Krumnow, L Veis, Ö Legeza, J Eisert
Tensor network states and specifically matrix-product states have proven to be a powerful tool for simulating ground states of strongly correlated spin models. Recently, they have also been applied to interacting fermionic problems, specifically in the context of quantum chemistry. A new freedom arising in such nonlocal fermionic systems is the choice of orbitals, it being far from clear what choice of fermionic orbitals to make. In this Letter, we propose a way to overcome this challenge. We suggest a method intertwining the optimization over matrix product states with suitable fermionic Gaussian mode transformations...
November 18, 2016: Physical Review Letters
Yaroslav V Kartashov, Vladimir V Konotop, Dmitry A Zezyulin, Lluis Torner
We address Bloch oscillations of a spin-orbit coupled atom in periodic potentials of two types: optical and Zeeman lattices. We show that in optical lattices the spin-orbit coupling allows controlling the direction of atomic motion and may lead to complete suppression of the oscillations at specific values of the coupling strength. In Zeeman lattices the energy bands are found to cross each other at the boundaries of the Brillouin zone, resulting in period doubling of the oscillations. In all cases, the oscillations are accompanied by rotation of the pseudospin, with a dynamics that is determined by the strength of the spin-orbit coupling...
November 18, 2016: Physical Review Letters
Siavash Golkar, Dung Xuan Nguyen, Matthew M Roberts, Dam Thanh Son
Fractional quantum Hall liquids exhibit a rich set of excitations, the lowest energy of which are the magnetorotons with dispersion minima at a finite momentum. We propose a theory of the magnetorotons on the quantum Hall plateaux near half filling, namely, at filling fractions ν=N/(2N+1) at large N. The theory involves an infinite number of bosonic fields arising from bosonizing the fluctuations of the shape of the composite Fermi surface. At zero momentum there are O(N) neutral excitations, each carrying a well-defined spin that runs integer values 2,3,…...
November 18, 2016: Physical Review Letters
H Jang, B Y Kang, B K Cho, M Hashimoto, D Lu, C A Burns, C-C Kao, J-S Lee
Half-filled electron systems, even with the maximized spin angular moment, have been given little attention because of their zero-orbital angular moment according to Hund's rule. Nevertheless, there are several measurements that show evidence of a nonzero orbital moment as well as spin-orbit coupling. Here we report for the first time the orbital order in a half-filled 4f-electron system GdB_{4}, using the resonant soft x-ray scattering at Gd M_{4,5}-edges. Furthermore, we discovered that the development of this orbital order is strongly coupled with the antiferromagnetic spin order...
November 18, 2016: Physical Review Letters
Xuepeng Qiu, William Legrand, Pan He, Yang Wu, Jiawei Yu, Rajagopalan Ramaswamy, Aurelien Manchon, Hyunsoo Yang
The magnitude of spin-orbit torque (SOT), exerted to a ferromagnet (FM) from an adjacent heavy metal (HM), strongly depends on the amount of spin current absorbed in the FM. We exploit the large spin absorption at the Ru interface to manipulate the SOTs in HM/FM/Ru multilayers. While the FM thickness is smaller than its spin dephasing length of 1.2 nm, the top Ru layer largely boosts the absorption of spin currents into the FM layer and substantially enhances the strength of SOT acting on the FM. Spin-pumping experiments induced by ferromagnetic resonance support our conclusions that the observed increase in the SOT efficiency can be attributed to an enhancement of the spin-current absorption...
November 18, 2016: Physical Review Letters
Ran Cheng, Satoshi Okamoto, Di Xiao
In a collinear antiferromagnet with easy-axis anisotropy, symmetry guarantees that the spin wave modes are doubly degenerate. The two modes carry opposite spin angular momentum and exhibit opposite chirality. Using a honeycomb antiferromagnet in the presence of the Dzyaloshinskii-Moriya interaction, we show that a longitudinal temperature gradient can drive the two modes to opposite transverse directions, realizing a spin Nernst effect of magnons with vanishing thermal Hall current. We find that magnons around the Γ point and the K point contribute oppositely to the transverse spin transport, and their competition leads to a sign change of the spin Nernst coefficient at finite temperature...
November 18, 2016: Physical Review Letters
Vladimir A Zyuzin, Alexey A Kovalev
We predict that a temperature gradient can induce a magnon-mediated spin Hall response in an antiferromagnet with nontrivial magnon Berry curvature. We develop a linear response theory which gives a general condition for a Hall current to be well defined, even when the thermal Hall response is forbidden by symmetry. We apply our theory to a honeycomb lattice antiferromagnet and discuss a role of magnon edge states in a finite geometry.
November 18, 2016: Physical Review Letters
Ryuji Takahashi, Naoto Nagaosa
We study theoretically the Berry curvature of the magnon induced by the hybridization with the acoustic phonons via the spin-orbit and dipolar interactions. We first discuss the magnon-phonon hybridization via the dipolar interaction, and show that the dispersions have gapless points in momentum space, some of which form a loop. Next, when both spin-orbit and dipolar interactions are considered, we show anisotropic texture of the Berry curvature and its divergence with and without gap closing. Realistic evaluation of the consequent anomalous velocity is given for yttrium iron garnet...
November 18, 2016: Physical Review Letters
Jian Kang, Rafael M Fernandes
The origin of the high-temperature superconducting state observed in FeSe thin films, whose phase diagram displays no sign of magnetic order, remains a hotly debated topic. Here we investigate whether fluctuations arising due to the proximity to a nematic phase, which is observed in the phase diagram of this material, can promote superconductivity. We find that nematic fluctuations alone promote a highly degenerate pairing state, in which both s-wave and d-wave symmetries are equally favored, and T_{c} is consequently suppressed...
November 18, 2016: Physical Review Letters
María Teresa Quirós, Colin Macdonald, Jesús Angulo, María Paz Muñoz
This detailed protocol describes the new Spin Saturation Transfer Difference Nuclear Magnetic Resonance protocol (SSTD NMR), recently developed in our group to study processes of mutual-site chemical exchange that are difficult to analyze by traditional methods. As the name suggests, this method combines the Spin Saturation Transfer method used for small molecules, with the Saturation Transfer Difference (STD) NMR method employed for the study of protein-ligand interactions, by measuring transient spin saturation transfer along increasing saturation times (build-up curves) in small organic and organometallic molecules undergoing chemical exchange...
November 12, 2016: Journal of Visualized Experiments: JoVE
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