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Magnetic field

Amélie Juhin, Philippe Sainctavit, Katharina Ollefs, Marcin Sikora, Adriano Filipponi, Pieter Glatzel, Fabrice Wilhelm, Andrei Rogalev
X-ray magnetic circular dichroism is measured at the Fe K pre-edge in yttrium iron garnet using two different procedures that allow reducing the intrinsic broadening due to the 1s corehole lifetime. First, deconvolution of XMCD data measured in total fluorescence yield (TFY) with an extremely high signal-to-noise ratio enables a factor of 2.4 to be gained in the XMCD intensity. Ligand field multiplet calculations performed with different values of intrinsic broadening show that deconvolving such high quality XMCD data is similar to reducing the lifetime broadening from a 1s corehole to a 2p corehole...
October 26, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
C Gunnar Werncke, Mohammed-Amine Bouammali, Julie Baumard, Nicolas Suaud, Cyril Martins, Nathalie Guihéry, Laure Vendier, Jianxia Zheng, Jean-Baptiste Sortais, Christophe Darcel, Sylviane Sabo-Etienne, Jean-Pascal Sutter, Sébastien Bontemps, Céline Pichon
A family of four-coordinate Fe(II) complexes formed with N,N'-chelating amido-pyridine ligands was synthesized, and their magnetic properties were investigated. These distorted tetrahedral complexes exhibit significant magnetic anisotropy with zero-field splitting parameter D ranging between -17 and -12 cm(-1). Ab initio calculations enabled identification of the structural factors that control the nature of the magnetic anisotropy and the rationalization of the variation of D in these complexes. It is shown that a reduced N-Fe-N angle involving the chelating nitrogen atoms of the ligands is at the origin of the negative D value and that the torsion between the two N-Fe-N planes imposed by steric hindrances further increases the |D| value...
October 26, 2016: Inorganic Chemistry
Anissa Abi-Dargham, Guillermo Horga
The field of medicine is moving toward the use of biomarkers for the optimization of individualized care. This is a particular challenge for the field of psychiatry, in which diagnosis is based on a descriptive collection of behaviors without the availability of any objective test to stratify patients. Neuroimaging techniques such as molecular imaging with positron-emission tomography (PET) or structural and functional magnetic resonance imaging (MRI) provide an opportunity to bring psychiatry from an era of subjective descriptive classification into objective and tangible brain-based measures...
October 26, 2016: Nature Medicine
Seiichi Yamamoto, Tadashi Watabe, Hayato Ikeda, Yasukazu Kanai, Kazuhiro Ichikawa, Motonao Nakao, Katsuhiko Kato, Jun Hatazawa
PURPOSE: Positron emission tomography (PET) has high sensitivity for imaging radioactive tracer distributions in subjects. However, it is not possible to image free radical distribution in a subject by PET. Since free radicals are quite reactive, they are related to many diseases, including but not limited to cancer, inflammation, strokes, and heart disease. The Overhauser enhanced magnetic resonance imaging (OMRI) is so far the only method that images free radical distribution in vivo...
October 2016: Medical Physics
Dan Nguyen, David Thomas, Minsong Cao, Daniel O'Connor, James Lamb, Ke Sheng
PURPOSE: Magnetic resonance imaging (MRI)-guided Co-60 provides daily and intrafractional MRI soft tissue imaging for improved target and critical organ tracking. To increase delivery efficiency, the system uses three Co-60 sources at 120° apart, allowing up to 600 cGy combined dose rate at isocenter. Despite the potential tripling in output, creating a delivery plan that uses all three sources is considerably unintuitive. Here, the authors computerize the triplet orientation optimization using column generation, an approach that was demonstrated effective in integrated beam orientation and fluence optimization for noncoplanar therapies...
October 2016: Medical Physics
Oliver J Gurney-Champion, Thijs Bruins Slot, Eelco Lens, Astrid van der Horst, Remy Klaassen, Hanneke W M van Laarhoven, Geertjan van Tienhoven, Jeanin E van Hooft, Aart J Nederveen, Arjan Bel
PURPOSE: Biliary stents may cause susceptibility artifacts, gradient-induced artifacts, and radio frequency (RF) induced artifacts on magnetic resonance images, which can hinder accurate target volume delineation in radiotherapy. In this study, the authors investigated and quantified the magnitude of these artifacts for stents of different materials. METHODS: Eight biliary stents made of nitinol, platinum-cored nitinol, stainless steel, or polyethylene from seven vendors, with different lengths (57-98 mm) and diameters (3...
October 2016: Medical Physics
Yachao Zhang
A reliable prediction of magnetic properties of surface-supported molecules containing 3d/4f spin carriers has challenged the electronic structure theory for decades. Here we tackle this problem with Hubbard-U corrected van der Waals density functional (vdW-DF), incorporating strong correlation effects of the localized electrons and dispersion interactions involved in the molecule-surface binding. By fitting the spin state energetics of a series of Fe(ii) compounds with varying ligand field strength, we find that the optimal U value for vdW-DF is much smaller than that for the local density approximation (LDA) while quite similar to that for the generalized gradient approximation (GGA)...
September 28, 2016: Journal of Chemical Physics
Antoine Carof, Mathieu Salanne, Thibault Charpentier, Benjamin Rotenberg
Using molecular simulations, we analyze the microscopic processes driving the Nuclear Magnetic Resonance (NMR) relaxation of quadrupolar cations in water. The fluctuations of the Electric Field Gradient (EFG) experienced by alkaline and magnesium cations, which determine the NMR relaxation time, are mainly due to the dynamics of water molecules in their solvation shell. The dynamics of the ion plays a less important role, with the exception of the short-time dynamics in the lighter Li(+) case, for which rattling in the solvent cage results in oscillations of the EFG autocorrelation function (ACF)...
September 28, 2016: Journal of Chemical Physics
Hamish G Hiscock, Daniel R Kattnig, David E Manolopoulos, P J Hore
We present a new method for calculating the product yield of a radical pair recombination reaction in the presence of a weak time-dependent magnetic field. This method successfully circumvents the computational difficulties presented by a direct solution of the Liouville-von Neumann equation for a long-lived radical pair containing many hyperfine-coupled nuclear spins. Using a modified formulation of Floquet theory, treating the time-dependent magnetic field as a perturbation, and exploiting the slow radical pair recombination, we show that one can obtain a good approximation to the product yield by considering only nearly degenerate sub-spaces of the Floquet space...
September 28, 2016: Journal of Chemical Physics
Yong-Ming Liu, Rui-Qing Chen, Zi-Qing Wu, Jing Zhu, Jian-Yu Shi, Hui-Meng Lu, Peng Shang, Da-Chuan Yin
The contact angle is an important parameter that is essential for studying interfacial phenomena. The contact angle can be measured using commercially available instruments. However, these well-developed instruments may not function or may be unsuitable for use in some special environments. A simulated microgravity generated by a large gradient magnetic field is such an environment in which the current measurement instruments cannot be installed. To measure the contact angle in this environment, new tools must be designed and manufactured to be compatible with the size and physical environment...
September 2016: Review of Scientific Instruments
Swarupananda Pradhan
The three axis vector magnetic field measurement based on the interaction of a single elliptically polarized light beam with an atomic system is described. The magnetic field direction dependent atomic responses are extracted by the polarimetric detection in combination with laser frequency modulation and magnetic field modulation techniques. The magnetometer geometry offers additional critical requirements like compact size and large dynamic range for space application. Further, the three axis magnetic field is measured using only the reflected signal (one polarization component) from the polarimeter and thus can be easily expanded to make spatial array of detectors and/or high sensitivity field gradient measurement as required for biomedical application...
September 2016: Review of Scientific Instruments
Liangping Wang, Xinjun Zhang, Tieping Sun, Wentin Mao
A kind of fast shutter for protecting the diagnosis devices in Z pinch experiments is introduced in this paper. The shutter is composed of a pulling rod, a magnetic core, and a solenoid. Different from the traditional coils which were used at the voltage of 220 V, the solenoid we used must endure the high voltage of 5-10 kV and the deformation which maybe caused by the 5-10 T intense magnetic field. A creative configuration for the solenoid is developed including the winding guide, insulating sleeve, and stainless-steel sleeve...
September 2016: Review of Scientific Instruments
John R Kirtley, Lisa Paulius, Aaron J Rosenberg, Johanna C Palmstrom, Connor M Holland, Eric M Spanton, Daniel Schiessl, Colin L Jermain, Jonathan Gibbons, Y-K-K Fung, Martin E Huber, Daniel C Ralph, Mark B Ketchen, Gerald W Gibson, Kathryn A Moler
Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ0/Hz(1/2). This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes the spacing between the sample surface and the SQUID pickup loop...
September 2016: Review of Scientific Instruments
S Schmuck, J Fessey, J E Boom, L Meneses, P Abreu, E Belonohy, I Lupelli
At the tokamak Joint European Torus (JET), the electron cyclotron emission spectra in O-mode and X-mode polarisations are diagnosed simultaneous in absolute terms for several harmonics with two Martin-Puplett interferometers. From the second harmonic range in X-mode polarisation, the electron temperature profile can be deduced for the outboard side (low magnetic field strength) of JET but only for some parts of the inboard side (high magnetic field strength). This spatial restriction can be bypassed, if a cutoff is not present inside the plasma for O-mode waves in the first harmonic range...
September 2016: Review of Scientific Instruments
Naoki Ichijo, Kazuyuki Takeda, Kazuhiko Yamada, K Takegoshi
We propose a simple data-analysis scheme to determine the coupling constant and the asymmetry parameter of nuclear quadrupolar interactions in field-swept nuclear magnetic resonance (NMR) for static powder samples. This approach correlates the quadrupolar parameters to the positions of the singularities, which can readily be found out as sharp peaks in the field-swept pattern. Moreover, the parameters can be determined without quantitative acquisition and elaborate calculation of the overall profile of the pattern...
October 7, 2016: Journal of Chemical Physics
Zhendong Fu, Yinguo Xiao, Artem Feoktystov, Vitaliy Pipich, Marie-Sousai Appavou, Yixi Su, Erxi Feng, Wentao Jin, Thomas Brückel
The magnetic-field-induced assembly of magnetic nanoparticles (NPs) provides a unique and flexible strategy in the design and fabrication of functional nanostructures and devices. We have investigated the field-induced self-assembly of core-shell iron oxide NPs dispersed in toluene by means of small-angle neutron scattering (SANS). The form factor of the core-shell NPs was characterized and analyzed using SANS with polarized neutrons. Large-scale aggregates of iron oxide NPs formed above 0.02 T as indicated by very-small-angle neutron scattering measurements...
October 26, 2016: Nanoscale
D Sztenkiel, M Foltyn, G P Mazur, R Adhikari, K Kosiel, K Gas, M Zgirski, R Kruszka, R Jakiela, Tian Li, A Piotrowska, A Bonanni, M Sawicki, T Dietl
The significant inversion symmetry breaking specific to wurtzite semiconductors, and the associated spontaneous electrical polarization, lead to outstanding features such as high density of carriers at the GaN/(Al,Ga)N interface-exploited in high-power/high-frequency electronics-and piezoelectric capabilities serving for nanodrives, sensors and energy harvesting devices. Here we show that the multifunctionality of nitride semiconductors encompasses also a magnetoelectric effect allowing to control the magnetization by an electric field...
October 26, 2016: Nature Communications
Dongge Deng, Xinjun Wu, Su Zuo
A new stress measuring sensor is proposed to evaluate the axial stress in steel wires. Without using excitation and induction coils, the sensor mainly consists of a static magnetization unit made of permanent magnets and a magnetic field measurement unit containing Hall element arrays. Firstly, the principle is illustrated in detail. Under the excitation of the magnetization unit, a spatially varying magnetized region in the steel wire is utilized as the measurement region. Radial and axial magnetic flux densities at different lift-offs in this region are measured by the measurement unit to calculate the differential permeability curve and magnetization curve...
October 6, 2016: Sensors
S Waanders, M Visscher, R R Wildeboer, T O B Oderkerk, H J G Krooshoop, B Ten Haken
Sentinel lymph node biopsy has become a staple tool in the diagnosis of breast cancer. By replacing the morbidity-plagued axillary node clearance with removing only those nodes most likely to contain metastases, it has greatly improved the quality of life of many breast cancer patients. However, due to the use of ionizing radiation emitted by the technetium-based tracer material, the current sentinel lymph node biopsy has serious drawbacks. Most urgently, the reliance on radioisotopes limits the application of this procedure to small parts of the developed world, and it imposes restrictions on patient planning and hospital logistics...
November 21, 2016: Physics in Medicine and Biology
Gandhali Bapat, Chaitali Labade, Amol Chaudhari, Smita Zinjarde
Silica nanoparticles (SiNPs) find applications in the fields of drug delivery, catalysis, immobilization and sensing. Their synthesis can be mediated in a facile manner and they display broad range compatibility and stability. Their existence in the form of spheres, wires and sheets renders them suitable for varied purposes. This review summarizes the use of silica nanostructures in developing techniques for extraction, detection and degradation of pesticides. Silica nanostructures on account of their sorbent properties, porous nature and increased surface area allow effective extraction of pesticides...
June 10, 2016: Advances in Colloid and Interface Science
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