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Electromagnetic Fields

Antoine Delmas, Lamia Belguerras, Nicolas Weber, Freddy Odille, Cédric Pasquier, Jacques Felblinger, Pierre-André Vuissoz
A Magnetic Resonance Imaging (MRI) scanner uses three different electromagnetic fields (EMF) to produce body images: a static permanent magnetic field (MF), several pulsed magnetic gradients, and a radiofrequency pulse. As a result, any occupation that includes an MRI exposes workers to a strong MF. The World Health Organization has now given the monitoring of occupational EMF exposure a high priority. One design for a low-cost, compact MF exposure monitor (« MR exposimeter ») uses a set of three orthogonally assembled Hall sensors...
January 19, 2018: Bioelectromagnetics
Martina Banchelli, Marella de Angelis, Cristiano D'Andrea, Roberto Pini, Paolo Matteini
An advanced optofluidic system for protein detection based on Raman signal amplification via dewetting and molecular gathering within temporary mesoscale assemblies is presented. The evaporation of a microliter volume of protein solution deposited in a circular microwell precisely follows an outward-receding geometry. Herein the combination of liquid withdrawal with intermolecular interactions induces the formation of self-assembled molecular domains at the solid-liquid interface. Through proper control of the evaporation rate, amplitude of the assemblies and time for spectral collection at the liquid edge are extensively raised, resulting in a local enhancement and refinement of the Raman response, respectively...
January 18, 2018: Scientific Reports
Fatemeh Adibzadeh, Margarethus M Paulides, Gerard C van Rhoon
BACKGROUND AND PURPOSE: To protect against any potential adverse effects to human health from localised exposure to radio frequency (100 kHz-3 GHz) electromagnetic fields (RF EMF), international health organisations have defined basic restrictions on specific absorption rate (SAR) in tissues. These exposure restrictions incorporate safety factors which are generally conservative so that exposures that exceed the basic restrictions are not necessarily harmful. The magnitude of safety margin for various exposure scenarios is unknown...
January 18, 2018: International Journal of Hyperthermia
Vadim R Munirov, Nathaniel J Fisch
The generation of the plasma current resulting from Bremsstrahlung absorption is considered. It is shown that the electric current is higher than the naive estimates assuming that electrons absorb only the photon momentum and using the Spitzer conductivity would suggest. The current enhancement is in part because electrons get the recoil momentum from the Coulomb field of ions during the absorption and in part because the electromagnetic power is absorbed asymmetrically within the electron velocity distribution space...
November 2017: Physical Review. E
J M García de la Cruz, J C Vassilicos, L Rossi
Experimental evidence of the scalar convergence towards a global strange eigenmode independent of the scalar initial condition in chaotic mixing is provided. This convergence, underpinning the independent nature of chaotic mixing in any passive scalar, is presented by scalar fields with different initial conditions casting statistically similar shapes when advected by periodic unsteady flows. As the scalar patterns converge towards a global strange eigenmode, the scalar filaments, locally aligned with the direction of maximum stretching, as described by the Lagrangian stretching theory, stack together in an inhomogeneous pattern at distances smaller than their asymptotic minimum widths...
November 2017: Physical Review. E
Takayoshi Sano, Yuki Tanaka, Natsumi Iwata, Masayasu Hata, Kunioki Mima, Masakatsu Murakami, Yasuhiko Sentoku
The interaction of dense plasmas with an intense laser under a strong external magnetic field has been investigated. When the cyclotron frequency for the ambient magnetic field is higher than the laser frequency, the laser's electromagnetic field is converted to the whistler mode that propagates along the field line. Because of the nature of the whistler wave, the laser light penetrates into dense plasmas with no cutoff density, and produces superthermal electrons through cyclotron resonance. It is found that the cyclotron resonance absorption occurs effectively under the broadened conditions, or a wider range of the external field, which is caused by the presence of relativistic electrons accelerated by the laser field...
October 2017: Physical Review. E
J Slim, F Rathmann, D Heberling
An implementation of the polynomial chaos expansion is introduced as a fast solver of the equations of beam and spin motion of charged particles in electromagnetic fields. We show that, based on the stochastic Galerkin method, our computational framework substantially reduces the required number of tracking calculations compared to the widely used Monte Carlo method.
December 2017: Physical Review. E
P Lunkenheimer, S Emmert, R Gulich, M Köhler, M Wolf, M Schwab, A Loidl
Why does a microwave oven work? How does biological tissue absorb electromagnetic radiation? Astonishingly, we do not have a definite answer to these simple questions because the microscopic processes governing the absorption of electromagnetic waves by water are largely unclarified. This absorption can be quantified by dielectric loss spectra, which reveal a huge peak at a frequency of the exciting electric field of about 20 GHz and a gradual tailing off toward higher frequencies. The microscopic interpretation of such spectra is highly controversial and various superpositions of relaxation and resonance processes ascribed to single-molecule or molecule-cluster motions have been proposed for their analysis...
December 2017: Physical Review. E
Yu O Averkov, Yu V Prokopenko, V M Yakovenko
The interaction between a tubular beam of charged particles and a dispersive metamaterial of cylindrical configuration has been investigated theoretically. This metamaterial may have negative permittivity and negative permeability simultaneously over a certain frequency range where it behaves like a left-handed metamaterial. The dispersion equation for the eigenmodes spectra of a metamaterial and the coupled modes spectra of the system have been derived and numerically analyzed. It has been found that the absolute beam instability of bulk-surface waves occurs because of peculiarities of the eigenmodes spectra of a left-handed metamaterial...
July 2017: Physical Review. E
Paula I Villar, Alejandro Soba
We present an alternative numerical approach to compute the number of particles created inside a cavity due to time-dependent boundary conditions. The physical model consists of a rectangular cavity, where a wall always remains still while the other wall of the cavity presents a smooth movement in one direction. The method relies on the setting of the boundary conditions (Dirichlet and Neumann) and the following resolution of the corresponding equations of modes. By a further comparison between the ground state before and after the movement of the cavity wall, we finally compute the number of particles created...
July 2017: Physical Review. E
Valentina Hartwig, Stefania Romeo, Olga Zeni
The purpose of this review is to make a contribution to build a comprehensive knowledge of the main aspects related to the occupational exposure to electromagnetic fields (EMFs) in magnetic resonance imaging (MRI) environments. Information has been obtained from original research papers published in international peer-reviewed journals in the English language and from documents published by governmental bodies and authorities. An overview of the occupational exposure scenarios to static magnetic fields, motion-induced, time-varying magnetic fields, and gradient and radiofrequency fields is provided, together with a summary of the relevant regulation for limiting exposure...
January 18, 2018: Medical & Biological Engineering & Computing
Peng Wei, Xiaole Han, Dong Xia, Taolin Liu, Hao Lang
Acoustic emission technology has been applied to many fields for many years. However, the conventional piezoelectric acoustic emission sensors cannot be used in extreme environments, such as those with heavy electromagnetic interference, high pressure, or strong corrosion. In this paper, a novel fiber-optic ring acoustic emission sensor is proposed. The sensor exhibits high sensitivity, anti-electromagnetic interference, and corrosion resistance. First, the principle of a novel fiber-optic ring sensor is introduced...
January 13, 2018: Sensors
P Maurer, J Prat-Camps, J I Cirac, T W Hänsch, O Romero-Isart
We theoretically show that a dipole externally driven by a pulse with a lower-bounded temporal width, and placed inside a cylindrical hollow waveguide, can generate a train of arbitrarily short and focused electromagnetic pulses. The waveguide encloses vacuum with perfect electric conducting walls. A dipole driven by a single short pulse, which is properly engineered to exploit the linear spectral filtering of the cylindrical hollow waveguide, excites longitudinal waveguide modes that are coherently refocused at some particular instances of time, thereby producing arbitrarily short and focused electromagnetic pulses...
July 28, 2017: Physical Review Letters
Wei Liu
We propose generalized magnetic mirrors that can be achieved by excitations of sole electric resonances. Conventional approaches to obtain magnetic mirrors rely heavily on exciting the fundamental magnetic dipoles, whereas here we reveal that, besides magnetic resonances, electric resonances of higher orders can be also employed to obtain highly efficient magnetic mirrors. Based on the electromagnetic duality, it is also shown that electric mirrors can be achieved by exciting magnetic resonances. We provide direct demonstrations of the generalized mirrors proposed in a simple system of a one-dimensional periodic array of all-dielectric wires, which may shed new light on many advanced fields of photonics related to resonant multipolar excitations and interferences...
September 22, 2017: Physical Review Letters
Umit Muhammet Kocyigit, Parham Taslimi, Fatih Gurses, Sinan Soylu, Sevgi Durna Dastan, İlhami Gulcin
The purpose of our study is to assist in understanding the effects of wireless electromagnetic waves on carbonic anhydrase (CA) and acetylcholinesterase (AChE) enzymes activities in the different tissues of the rats. For this purpose, two different groups each of which contains eight rats (n = 8) were formed as being control group and wireless electromagnetic wave-administered group. The rats were necropsied after 60 min from the injection of chemicals into the rats intraperitoneally. The different tissues of the rats were extracted...
January 17, 2018: Journal of Biochemical and Molecular Toxicology
Yasutaka Kitahama, Tamitake Itoh, Toshiaki Suzuki
To evaluate the shape of an Ag tip with regard to tip-enhanced Raman scattering (TERS) signal, the enhanced electromagnetic (EM) field and scattering spectrum, arising from surface plasmon resonance at the apex of the tip, were calculated using a finite-difference time domain (FDTD) method. In the calculated forward scattering spectra from the smooth Ag tip, the band appeared within the visible region, similar to the experimental results and calculation for a corrugated Ag cone. In the FDTD calculation of TERS, the Ag tip acting as a monopole antenna was adopted by insertion of a perfect electric conductor between the root of the tip and a top boundary surface of the calculation space...
January 5, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Johan F Triana, Daniel Pelaez Ruiz, Jose Luis Sanz-Vicario
The quantum photodynamics of a simple diatomic molecule with a permanent dipole immersed within an optical cavity containing a quantized radiation field is studied in detail. The chosen molecule under study, lithium fluoride (LiF), is characterized by the presence of an avoided crossing between the two lowest 11Σ potential energy curves (covalent-ionic diabatic crossing). Without field, after prompt excitation from the ground state 11Σ, the excited nuclear wave packet moves back and forth in the upper 21Σ state, but in the proximity of the avoided crossing, the non-adiabatic coupling transfers part of the nuclear wave packet to the lower 11Σ state, which eventually leads to dissociation...
January 16, 2018: Journal of Physical Chemistry. A
Vladimir P Drachev, Alexander V Kildishev, Joshua D Borneman, Kuo-Ping Chen, Vladimir M Shalaev, Konstantin Yamnitskiy, Robert A Norwood, Nasser Peyghambarian, Seth R Marder, Lazaro A Padilha, Scott Webster, Trenton R Ensley, David J Hagan, Eric W Van Stryland
Gold dipole nanoantennas embedded in an organic molecular film provide strong local electromagnetic fields to enhance both the nonlinear refractive index (n2) and two-photon absorption (2PA) of the molecules. An enhancement of 53× for 2PA and 140× for nonlinear refraction is observed for BDPAS (4,4'-bis(diphenylamino)stilbene) at 600 nm with only 3.7% of gold volume fraction. The complex value of the third-order susceptibility enhancement results in a sign change of n2 for the effective composite material relative to the pure BDPAS film...
January 15, 2018: Scientific Reports
Po-Chang Huang, Meng-Ting Cheng, How-Ran Guo
BACKGROUND: Electromagnetic hypersensitivity refers to health effects attributed to electromagnetic fields (EMF) exposure and has been formally named "idiopathic environmental intolerance attributed to electromagnetic fields" (IEI-EMF) by the World Health Organization. Because of the growing use of cell phones, IEI-EMF has become a global public health concern. A survey in 2007 in Taiwan showed that the prevalence rate of IEI-EMF was 13.3%, which is higher than rates in studies conducted previously...
January 15, 2018: Environmental Health: a Global Access Science Source
N Scott Litofsky, Douglas C Miller, Zhenzhou Chen, Agnes Simonyi, Diana Klakotskaia, Andrew Giritharan, Qi Feng, Diane McConnell, Jiankun Cui, Zezong Gu
OBJECTIVE: To determine early effects on outcome from traumatic brain injury (TBI) induced by controlled cortical impact (CCI) associated with anaemia in mice. HYPOTHESIS: Outcome from TBI with concomitant anaemia would be worse than TBI without anaemia. METHODS: CCI was induced with electromagnetic impaction in four groups of C57BL/6J mice: sham, sham+anaemia; TBI; and TBI+anaemia. Anaemia was created by withdrawal of 30% of calculated intravascular blood volume and saline replacement of equal volume...
January 15, 2018: Brain Injury: [BI]
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