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Magnetic field

Jason W Sidabras, James E Richie, James S Hyde
In continuous-wave (CW) Electron Paramagnetic Resonance (EPR) a low-frequency time-harmonic magnetic field, called field modulation, is applied parallel to the static magnetic field and incident on the sample. Varying amplitude of the field modulation incident on the sample has consequences on spectral line-shape and line-height over the axis of the sample. Here we present a method of coupling magnetic field into the cavity using slots perpendicular to the sample axis where the slot depths are designed in such a way to produce an axially uniform magnetic field along the sample...
November 25, 2016: Journal of Magnetic Resonance
Alessandro Cresci, Rosario De Rosa, Nathan F Putman, Claudio Agnisola
Rheotaxis, the unconditioned orienting response to water currents, is a main component of fish behaviour. Rheotaxis is achieved using multiple sensory systems, including visual and tactile cues. Rheotactic orientation in open or low-visibility waters might also benefit from the stable frame of reference provided by the geomagnetic field, but this possibility has not been explored before. Zebrafish (Danio rerio) form shoals living in freshwater systems with low visibility, show a robust positive rheotaxis, and respond to geomagnetic fields...
November 30, 2016: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
Simone A Winkler, Franz Schmitt, Hermann Landes, Josh DeBever, Trevor Wade, Andrew Alejski, Brian K Rutt
Ultra High Field (UHF) MRI requires improved gradient and shim performance to fully realize the promised gains (SNR as well as spatial, spectral, diffusion resolution) that higher main magnetic fields offer. Both the more challenging UHF environment by itself, as well as the higher currents used in high performance coils, require a deeper understanding combined with sophisticated engineering modeling and construction, to optimize gradient and shim hardware for safe operation and for highest image quality. This review summarizes the basics of gradient and shim technologies, and outlines a number of UHF-related challenges and solutions...
November 30, 2016: NeuroImage
Alan J Stone, Nicholas P Blockley
Quantitative BOLD (qBOLD) is a non-invasive MR technique capable of producing quantitative measurements of the haemodynamic and metabolic properties of the brain. Here we propose a refinement of the qBOLD methodology, dubbed streamlined-qBOLD, in order to provide a clinically feasible method for mapping baseline brain oxygenation. In streamlined-qBOLD confounding signal contributions are minimised during data acquisition through the application of (i) a Fluid Attenuated Inversion Recovery (FLAIR) preparation to remove cerebral spinal fluid (CSF) signal contamination, (ii) a Gradient Echo Slice Excitation Profile Imaging (GESEPI) acquisition to reduce the effect of macroscopic magnetic field gradients and (iii) an Asymmetric Spin Echo (ASE) pulse sequence to directly measure the reversible transverse relaxation rate, R2'...
November 30, 2016: NeuroImage
Emmanuel C Obusez, Mark Lowe, Se-Hong Oh, Irene Wang, M S Jennifer Bullen, Paul Ruggieri, Virginia Hill, Daniel Lockwood, Todd Emch, Doksu Moon, Gareth Loy, Jonathan Lee, Matthew Kiczek, D O Manoj Massand, Volodymyr Statsevych, Todd Stultz, Stephen E Jones
PURPOSE: There have been an increasing number of studies involving ultra-high-field 7T of intracranial pathology, however, comprehensive clinical studies of neuropathology at 7T still remain limited. 7T has the advantage of a higher signal-to-noise ratio and a higher contrast-to-noise ratio, compared to current low field clinical MR scanners. We hypothesized 7T applied clinically, may improve detection and characterization of intracranial pathology. MATERIALS AND METHODS: We performed an IRB-approved 7T prospective study of patients with neurological disease who previously had lower field 3T and 1...
November 30, 2016: NeuroImage
Wennie Subramonian, Ta Yeong Wu, Siang-Piao Chai
In this work, heterogeneous photocatalysis was used to treat pulp and paper mill effluent (PPME). Magnetically retrievable Fe2O3-TiO2 was fabricated by employing a solvent-free mechanochemical process under ambient conditions. Findings elucidated the successful incorporation of Fe2O3 into the TiO2 lattice. Fe2O3-TiO2 was found to be an irregular and slightly agglomerated surface morphology. In comparison to commercial P25, Fe2O3-TiO2 exhibited higher ferromagnetism and better catalyst properties with improvements in surface area (58...
November 30, 2016: Journal of Environmental Management
Yuanwei Chen, Ying Wang, Xi Liu, Mai Lu, Jiangwei Cao, Tao Wang
Magnetic hyperthermia with the treating temperature range of 41-46 °C is an alternative therapy for cancer treatment. In this article, lanthanum strontium manganates (La1-x Sr x MnO3, 0.25 ≤ × ≤ 0.35) magnetic nanoparticles coated by hyaluronic acid (HA) which possesses the ability of targeting tumor cells were prepared by a simple hydrothermal method combined with a high-energy ball milling technique. The crystal structure, morphology, magnetic properties of the HA-coated magnetic nanoparticles (MNPs), and their heating ability under alternating magnetic field were investigated...
December 2016: Nanoscale Research Letters
Julia Faurie, Mathilde Baudet, Kondo Claude Assi, Dominique Auger, Guillaume Gilbert, Francois Tournoux, Damien Garcia
Recent studies have suggested that intracardiac vortex flow imaging could be of clinical interest to early diagnose the diastolic heart function. Doppler vortography has been intro-duced as a simple color Doppler method to detect and quantify intraventricular vortices. This method is able to locate a vortex core based on the recognition of an antisymmetric pattern in the Doppler velocity field. Because the heart is a fast-moving organ, high frame rates are needed to decipher the whole blood vortex dynamics during diastole...
November 29, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Scott L Fairhall, Jens Schwarzbach, Angelika Lingnau, Martijn Gerbrand Van Koningsbruggen, David Melcher
Brain representations of visual space are predominantly eye-centred (retinotopic) yet our experience of the world is largely world-centred (spatiotopic). A long-standing question is how the brain creates continuity between these reference frames across successive eye movements (saccades). Here we use functional magnetic resonance imaging (fMRI) to address whether spatially specific repetition suppression (RS) is evident during trans-saccadic perception. We presented two successive Gabor patches (S1 and S2) in either the upper or lower visual field, left or right of fixation...
November 29, 2016: NeuroImage
M Trassinelli, L Bernard Carlsson, S Cervera, M Eddrief, V H Etgens, E V Gafton, E Lacaze, E Lamour, A Lévy, S Macé, C Prigent, J-P Rozet, S Steydli, M Marangolo, D Vernhet
Investigations of the complex behavior of the magnetization of manganese arsenide thin films due to defects induced by irradiation of slow heavy ions are presented. In addition to the thermal hysteresis suppression already highlighted in Trassinelli et al (2014 Appl. Phys. Lett. 104 081906), we report here on new local magnetic features recorded by a magnetic force microscope at different temperatures close to the characteristic sample phase transition. Complementary measurements of the global magnetization in different conditions (applied magnetic field and temperatures) enable the film characterization to be completed...
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
John F Barry, Matthew J Turner, Jennifer M Schloss, David R Glenn, Yuyu Song, Mikhail D Lukin, Hongkun Park, Ronald L Walsworth
Magnetic fields from neuronal action potentials (APs) pass largely unperturbed through biological tissue, allowing magnetic measurements of AP dynamics to be performed extracellularly or even outside intact organisms. To date, however, magnetic techniques for sensing neuronal activity have either operated at the macroscale with coarse spatial and/or temporal resolution-e.g., magnetic resonance imaging methods and magnetoencephalography-or been restricted to biophysics studies of excised neurons probed with cryogenic or bulky detectors that do not provide single-neuron spatial resolution and are not scalable to functional networks or intact organisms...
November 22, 2016: Proceedings of the National Academy of Sciences of the United States of America
Edwin Barnes, J J Heremans, Djordje Minic
Weyl semimetals are predicted to realize the three-dimensional axial anomaly first discussed in particle physics. The anomaly leads to unusual transport phenomena such as the chiral magnetic effect in which an applied magnetic field induces a current parallel to the field. Here we investigate diagnostics of the axial anomaly based on the fundamental equations of axion electrodynamics. We find that materials with Weyl nodes of opposite chirality and finite energy separation immersed in a uniform magnetic field exhibit an anomaly-induced oscillatory magnetic field with a period set by the chemical potential difference of the nodes...
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
Hiroaki Ishizuka, Tomoya Hayata, Masahito Ueda, Naoto Nagaosa
The photovoltaic effect due to the adiabatic quantum phase in noncentrosymmetric Weyl semimetals is studied. We particularly focus on the case in which an external ac electric field is applied. By considering a generalized Weyl Hamiltonian with nonlinear terms, we show that the photocurrent is induced by circularly, rather than linearly, polarized light. This photovoltaic current can be understood as an emergent electromagnetic induction in momentum space; the Weyl node is a magnetic monopole in momentum space, the circular motion of which induces the electric field...
November 18, 2016: Physical Review Letters
Michael Schuler, Seth Whitsitt, Louis-Paul Henry, Subir Sachdev, Andreas M Läuchli
The low-energy spectra of many body systems on a torus, of finite size L, are well understood in magnetically ordered and gapped topological phases. However, the spectra at quantum critical points separating such phases are largely unexplored for (2+1)D systems. Using a combination of analytical and numerical techniques, we accurately calculate and analyze the low-energy torus spectrum at an Ising critical point which provides a universal fingerprint of the underlying quantum field theory, with the energy levels given by universal numbers times 1/L...
November 18, 2016: Physical Review Letters
R P M J W Notermans, R J Rengelink, W Vassen
We observe a dramatic difference in optical line shapes of a ^{4}He Bose-Einstein condensate and a ^{3}He degenerate Fermi gas by measuring the 1557-nm 2 ^{3}S-2 ^{1}S magnetic dipole transition (8 Hz natural linewidth) in an optical dipole trap. The 15 kHz FWHM condensate line shape is only broadened by mean field interactions, whereas the degenerate Fermi gas line shape is broadened to 75 kHz FWHM due to the effect of Pauli exclusion on the spatial and momentum distributions. The asymmetric optical line shapes are observed in excellent agreement with line shape models for the quantum degenerate gases...
November 18, 2016: Physical Review Letters
Kun Zhang, Chen Yuan, Fu-Sheng Guo, Yi-Quan Zhang, Yao-Yu Wang
In search of simple approaches to rationally enhance the energy barriers in polynuclear dysprosium single-molecule magnets, a new system containing two structurally closely related dinuclear dysprosium complexes, namely [Dy2(L)2(DBM)2(DMF)2] (1) and [Dy2(L)2(DBM)2(DMA)2]·2DMA (2) (HDBM = dibenzoylmethane, H2L = 2-hydroxy-N'-(2-hydroxy-3-methoxybenzylidene)benzohydrazide), is introduced and the structure-dependent magnetic properties are investigated. The two complexes display only slight variations in the coordination geometries of the Dy(iii) ion but display remarkably different magnetic behaviors...
December 2, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Kangkang Meng, Jun Miao, Xiaoguang Xu, Yong Wu, Jiaxing Xiao, Jianhua Zhao, Yong Jiang
We report modulated switching current density and spin-orbit torques (SOT) in MnGa/Ta films with inserting very thin Co2FeAl and Co layers. Ferromagnetic coupling has been found in MnGa/Co2FeAl/Ta, resulting in a decreased effective anisotropy field. On the contrary, in MnGa/Co/Ta, antiferromagnetic coupling plays a dominant role. The switching current density Jc in MnGa/Ta is 8.5 × 10(7) A/cm(2). After inserting 0.8-nm-thick Co2FeAl and Co, theJc becomes 5 × 10(7) A/cm(2) and 9 × 10(7) A/cm(2), respectively...
December 2, 2016: Scientific Reports
P Rauscher, B Betz, J Hauptmann, A Wetzig, E Beyer, C Grünzweig
The performance and degree of efficiency of transformers are directly determined by the bulk magnetic properties of grain oriented electrical steel laminations. The core losses can be improved by post manufacturing methods, so-called domain refinement techniques. All these methods induce mechanical or thermal stress that refines the domain structure. The most commonly used technique is laser scribing due to the no-contact nature and the ease of integration in existing production systems. Here we show how directional neutron dark-field imaging allows visualizing the impact of laser scribing on the bulk and supplementary domain structure...
December 2, 2016: Scientific Reports
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