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Electromagnetic Fields

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https://www.readbyqxmd.com/read/28215003/improved-electromagnetic-tracking-for-catheter-path-reconstruction-with-application-in-high-dose-rate-brachytherapy
#1
Elodie Lugez, Hossein Sadjadi, Chandra P Joshi, Selim G Akl, Gabor Fichtinger
PURPOSE: Electromagnetic (EM) catheter tracking has recently been introduced in order to enable prompt and uncomplicated reconstruction of catheter paths in various clinical interventions. However, EM tracking is prone to measurement errors which can compromise the outcome of the procedure. Minimizing catheter tracking errors is therefore paramount to improve the path reconstruction accuracy. METHODS: An extended Kalman filter (EKF) was employed to combine the nonlinear kinematic model of an EM sensor inside the catheter, with both its position and orientation measurements...
February 18, 2017: International Journal of Computer Assisted Radiology and Surgery
https://www.readbyqxmd.com/read/28213224/ordered-titanium-templates-functionalized-by-gold-films-for-biosensing-applications-towards-non-enzymatic-glucose-detection
#2
Katarzyna Grochowska, Mariusz Szkoda, Jakub Karczewski, Gerard Śliwiński, Katarzyna Siuzdak
Recently, metal nanostructures evoke much interest due to application potential in highly sensitive detectors in biochemistry and medical diagnostics. In this work we report on preparation and characteristics of thin (1-100nm) Au films deposited onto highly ordered structured titanium templates for SERS (Surface Enhanced Raman Spectroscopy) and electrochemical sensing. The Ti templates are formed by selective removal of TiO2 nanotubes out of as-anodized titanium substrate. The surface of the obtained material reproduce precisely the bottom layer of the nanotubes and consists of a uniformly distributed dimples with diameter of ~100nm...
May 1, 2017: Talanta
https://www.readbyqxmd.com/read/28211479/decoupling-absorption-and-emission-processes-in-super-resolution-localization-of-emitters-in-a-plasmonic-hotspot
#3
David L Mack, Emiliano Cortés, Vincenzo Giannini, Peter Török, Tyler Roschuk, Stefan A Maier
The absorption process of an emitter close to a plasmonic antenna is enhanced due to strong local electromagnetic (EM) fields. The emission, if resonant with the plasmonic system, re-radiates to the far-field by coupling with the antenna via plasmonic states, whose presence increases the local density of states. Far-field collection of the emission of single molecules close to plasmonic antennas, therefore, provides mixed information of both the local EM field strength and the local density of states. Moreover, super-resolution localizations from these emission-coupled events do not report the real position of the molecules...
February 17, 2017: Nature Communications
https://www.readbyqxmd.com/read/28208709/human-exposure-to-electromagnetic-fields-from-parallel-wireless-power-transfer-systems
#4
Feng Wen, Xueliang Huang
The scenario of multiple wireless power transfer (WPT) systems working closely, synchronously or asynchronously with phase difference often occurs in power supply for household appliances and electric vehicles in parking lots. Magnetic field leakage from the WPT systems is also varied due to unpredictable asynchronous working conditions. In this study, the magnetic field leakage from parallel WPT systems working with phase difference is predicted, and the induced electric field and specific absorption rate (SAR) in a human body standing in the vicinity are also evaluated...
February 8, 2017: International Journal of Environmental Research and Public Health
https://www.readbyqxmd.com/read/28208417/terahertz-generation-from-laser-driven-ultrafast-current-propagation-along-a-wire-target
#5
H B Zhuo, S J Zhang, X H Li, H Y Zhou, X Z Li, D B Zou, M Y Yu, H C Wu, Z M Sheng, C T Zhou
Generation of intense coherent THz radiation by obliquely incidenting an intense laser pulse on a wire target is studied using particle-in-cell simulation. The laser-accelerated fast electrons are confined and guided along the surface of the wire, which then acts like a current-carrying line antenna and under appropriate conditions can emit electromagnetic radiation in the THz regime. For a driving laser intensity ∼3×10^{18}W/cm^{2} and pulse duration ∼10 fs, a transient current above 10 KA is produced on the wire surface...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28203122/evaluation-of-the-effect-of-radiofrequency-radiation-emitted-from-wi-fi-router-and-mobile-phone-simulator-on-the-antibacterial-susceptibility-of-pathogenic-bacteria-listeria-monocytogenes-and-escherichia-coli
#6
M Taheri, S M J Mortazavi, M Moradi, S Mansouri, G R Hatam, F Nouri
Mobile phones and Wi-Fi radiofrequency radiation are among the main sources of the exposure of the general population to radiofrequency electromagnetic fields (RF-EMF). Previous studies have shown that exposure of microorganisms to RF-EMFs can be associated with a wide spectrum of changes ranged from the modified bacterial growth to the alterations of the pattern of antibiotic resistance. Our laboratory at the nonionizing department of the Ionizing and Non-ionizing Radiation Protection Research Center has performed experiments on the health effects of exposure to animal models and humans to different sources of electromagnetic fields such as cellular phones, mobile base stations, mobile phone jammers, laptop computers, radars, dentistry cavitrons, magnetic resonance imaging, and Helmholtz coils...
January 2017: Dose-response: a Publication of International Hormesis Society
https://www.readbyqxmd.com/read/28201884/equation-of-motion-for-the-solvent-polarization-apparent-charges-in-the-polarizable-continuum-model-application-to-time-dependent-ci
#7
Silvio Pipolo, Stefano Corni, Roberto Cammi
The dynamics of the electrons for a molecule in solution is coupled to the dynamics of its polarizable environment, i.e., the solvent. To theoretically investigate such electronic dynamics, we have recently developed equations of motion (EOM) for the apparent solvent polarization charges that generate the reaction field in the Polarizable Continuum Model (PCM) for solvation and we have coupled them to a real-time time-dependent density functional theory (RT TDDFT) description of the solute [S. Corni et al., J...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28197174/extremely-low-frequency-electromagnetic-fields-stimulation-modulates-autoimmunity-and-immune-responses-a-possible-immuno-modulatory-therapeutic-effect-in-neurodegenerative-diseases
#8
REVIEW
Fabio Guerriero, Giovanni Ricevuti
Increasing evidence shows that extremely low frequency electromagnetic fields (ELF-EMFs) stimulation is able to exert a certain action on autoimmunity and immune cells. In the past, the efficacy of pulsed ELF-EMFs in alleviating the symptoms and the progression of multiple sclerosis has been supported through their action on neurotransmission and on the autoimmune mechanisms responsible for demyelination. Regarding the immune system, ELF-EMF exposure contributes to a general activation of macrophages, resulting in changes of autoimmunity and several immunological reactions, such as increased reactive oxygen species-formation, enhanced phagocytic activity and increased production of chemokines...
December 2016: Neural Regeneration Research
https://www.readbyqxmd.com/read/28194649/numerical-modeling-of-percutaneous-auricular-vagus-nerve-stimulation-a-realistic-3d-model-to-evaluate-sensitivity-of-neural-activation-to-electrode-position
#9
Amine M Samoudi, Stefan Kampusch, Emmeric Tanghe, Jozsef C Széles, Luc Martens, Eugenijus Kaniusas, Wout Joseph
OBJECTIVE: Percutaneous stimulation of the auricular branch of the vagus nerve (pVNS) by miniaturized needle electrodes in the auricle gained importance as a treatment for acute and chronic pain. The objective is to establish a realistic numerical model of pVNS and investigate the effects of stimulation waveform, electrodes' depth, and electrodes' position on nerve excitation threshold and the percentage of stimulated nerves. METHODS: Simulations were performed with Sim4Life...
February 13, 2017: Medical & Biological Engineering & Computing
https://www.readbyqxmd.com/read/28192786/static-non-reciprocity-in-mechanical-metamaterials
#10
Corentin Coulais, Dimitrios Sounas, Andrea Alù
Reciprocity is a general, fundamental principle governing various physical systems, which ensures that the transfer function-the transmission of a physical quantity, say light intensity-between any two points in space is identical, regardless of geometrical or material asymmetries. Breaking this transmission symmetry offers enhanced control over signal transport, isolation and source protection. So far, devices that break reciprocity (and therefore show non-reciprocity) have been mostly considered in dynamic systems involving electromagnetic, acoustic and mechanical wave propagation associated with fields varying in space and time...
February 13, 2017: Nature
https://www.readbyqxmd.com/read/28191921/design-of-hybrid-nanostructural-arrays-to-manipulate-sers-active-substrates-by-nanosphere-lithography
#11
Xiaoyu Zhao, Jiahong Wen, Mengning Zhang, Dunhui Wang, Yaxin Wang, Lei Chen, Yongjun Zhang, Jinghai Yang, Youwei Du
An easy-handling and low-cost method is utilized to controllably fabricate nanopattern arrays as the surface-enhanced Raman scattering (SERS) active substrates with high density of SERS-active areas (hot spots). A hybrid silver array of nanocaps and nanotriangles are prepared by combining magnetron sputtering and plasma etching. By adjusting the etching time of polystyrene (PS) colloid spheres array in silver nanobowls, the morphology of the arrays can be easily manipulated to control the formation and distribution of hot spots...
February 17, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28191445/tunable-random-lasing-behavior-in-plasmonic-nanostructures
#12
Ashish Yadav, Liubiao Zhong, Jun Sun, Lin Jiang, Gary J Cheng, Lifeng Chi
Random lasing is desired in plasmonics nanostructures through surface plasmon amplification. In this study, tunable random lasing behavior was observed in dye molecules attached with Au nanorods (NRs), Au nanoparticles (NPs) and Au@Ag nanorods (NRs) respectively. Our experimental investigations showed that all nanostructures i.e., Au@AgNRs, AuNRs & AuNPs have intensive tunable spectral effects. The random lasing has been observed at excitation wavelength 532 nm and varying pump powers. The best random lasing properties were noticed in Au@AgNRs structure, which exhibits broad absorption spectrum, sufficiently overlapping with that of dye Rhodamine B (RhB)...
2017: Nano Converg
https://www.readbyqxmd.com/read/28191324/effect-of-logarithmic-and-linear-frequency-scales-on-parametric-modelling-of-tissue-dielectric-data
#13
Saqib Salahuddin, Emily Porter, Paul M Meaney, Martin O'Halloran
The dielectric properties of biological tissues have been studied widely over the past half-century. These properties are used in a vast array of applications, from determining the safety of wireless telecommunication devices to the design and optimisation of medical devices. The frequency-dependent dielectric properties are represented in closed-form parametric models, such as the Cole-Cole model, for use in numerical simulations which examine the interaction of electromagnetic (EM) fields with the human body...
February 2017: Biomedical Physics & Engineering Express
https://www.readbyqxmd.com/read/28190610/optimised-analytical-models-of-the-dielectric-properties-of-biological-tissue
#14
Saqib Salahuddin, Emily Porter, Finn Krewer, Martin O' Halloran
The interaction of electromagnetic fields with the human body is quantified by the dielectric properties of biological tissues. These properties are incorporated into complex numerical simulations using parametric models such as Debye and Cole-Cole, for the computational investigation of electromagnetic wave propagation within the body. These parameters can be acquired through a variety of optimisation algorithms to achieve an accurate fit to measured data sets. A number of different optimisation techniques have been proposed, but these are often limited by the requirement for initial value estimations or by the large overall error (often up to several percentage points)...
February 9, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28187249/parallel-transmission-rf-pulse-design-with-strict-temperature-constraints
#15
Cem M Deniz, Giuseppe Carluccio, Christopher Collins
RF safety in parallel transmission (pTx) is generally ensured by imposing specific absorption rate (SAR) limits during pTx RF pulse design. There is increasing interest in using temperature to ensure safety in MRI. In this work, we present a local temperature correlation matrix formalism and apply it to impose strict constraints on maximum absolute temperature in pTx RF pulse design for head and hip regions. Electromagnetic field simulations were performed on the head and hip of virtual body models. Temperature correlation matrices were calculated for four different exposure durations ranging between 6 and 24 min using simulated fields and body-specific constants...
February 10, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28186652/on-the-contribution-of-curl-free-current-patterns-to-the-ultimate-intrinsic-signal-to-noise-ratio-at-ultra-high-field-strength
#16
Andreas Pfrommer, Anke Henning
The ultimate intrinsic signal-to-noise ratio (SNR) is a coil independent performance measure to compare different receive coil designs. To evaluate this benchmark in a sample, a complete electromagnetic basis set is required. The basis set can be obtained by curl-free and divergence-free surface current distributions, which excite linearly independent solutions to Maxwell's equations. In this work, we quantitatively investigate the contribution of curl-free current patterns to the ultimate intrinsic SNR in a spherical head-sized model at 9...
February 10, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28186145/dissipation-and-resonance-frequency-shift-of-a-resonator-magnetically-coupled-to-a-semiclassical-spin
#17
J M de Voogd, J J T Wagenaar, T H Oosterkamp
We calculate the change of the properties of a resonator, when coupled to a semiclassical spin by means of the magnetic field. Starting with the Lagrangian of the complete system, we provide an analytical expression for the linear response function for the motion in the case of a mechanical resonator and the current for the case of an electromagnetic resonator, thereby considering the influence of the resonator on the spin and vice versa. This analysis shows that the resonance frequency and effective dissipation factor can change significantly due to the relaxation times of the spin...
February 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28177156/from-maxwell-s-equations-to-the-theory-of-current-source-density-analysis
#18
Sergey L Gratiy, Geir Halnes, Daniel Denman, Michael J Hawrylycz, Christof Koch, Gaute T Einevoll, Costas A Anastassiou
Despite the widespread use of current-source density (CSD) analysis of extracellular potential recordings in the brain, the physical mechanisms responsible for the generation of the signal are still debated. While the extracellular potential is thought to be exclusively generated by the transmembrane currents, recent studies suggest that extracellular diffusive, advective and displacement currents-traditionally neglected-may also contribute considerably towards extracellular potential recordings. Here, we first justify the application of the electro-quasistatic approximation of Maxwell's equations to describe the electromagnetic field of physiological origin...
February 8, 2017: European Journal of Neuroscience
https://www.readbyqxmd.com/read/28176875/millitesla-magnetic-field-effects-on-the-photocycle-of-an-animal-cryptochrome
#19
Dean M W Sheppard, Jing Li, Kevin B Henbest, Simon R T Neil, Kiminori Maeda, Jonathan Storey, Erik Schleicher, Till Biskup, Ryan Rodriguez, Stefan Weber, P J Hore, Christiane R Timmel, Stuart R Mackenzie
Drosophila have been used as model organisms to explore both the biophysical mechanisms of animal magnetoreception and the possibility that weak, low-frequency anthropogenic electromagnetic fields may have biological consequences. In both cases, the presumed receptor is cryptochrome, a protein thought to be responsible for magnetic compass sensing in migratory birds and a variety of magnetic behavioural responses in insects. Here, we demonstrate that photo-induced electron transfer reactions in Drosophila melanogaster cryptochrome are indeed influenced by magnetic fields of a few millitesla...
February 8, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28176870/dynamical-beam-manipulation-based-on-2-bit-digitally-controlled-coding-metasurface
#20
Cheng Huang, Bo Sun, Wenbo Pan, Jianhua Cui, Xiaoyu Wu, Xiangang Luo
Recently, a concept of digital metamaterials has been proposed to manipulate field distribution through proper spatial mixtures of digital metamaterial bits. Here, we present a design of 2-bit digitally-controlled coding metasurface that can effectively modulate the scattered electromagnetic wave and realize different far-field beams. Each meta-atom of this metasurface integrates two pin diodes, and by tuning their operating states, the metasurface has four phase responses of 0, π/2, π, and 3π/2, corresponding to four basic digital elements "00", "01", "10", and "11", respectively...
February 8, 2017: Scientific Reports
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