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Electromagnetic field

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]
Shuo Li, Qiong Wu, Pinyi Ma, Yue Zhang, Daqian Song, Xinghua Wang, Ying Sun
A novel surface plasmon resonance (SPR) biosensor based on hollow gold nanospheres (HGNPs) and an improved sandwich assay was developed to detect rabbit IgG. The electromagnetic coupling between the HGNPs and Au film, and the notable plasmonic fields spread over the inner and outer surfaces of HGNPs, led to the considerable amplification of the SPR signal. Polydopamine-Ag@Fe3O4/reduced graphene oxide (PDA-Ag@Fe3O4/rGO) was introduced to bind detection antibody (Ab2) to form the improved sandwich structure. Ag nanoparticles were excited to produce SPR and their hot electrons were doped on graphene thin films, which amplified the response of biomolecules...
April 1, 2018: Talanta
Gökçen Kerimoğlu, Canan Güney, Şafak Ersöz, Ersan Odacı
The effects on human health of the electromagnetic field (EMF) emitted by mobile phones, used by approximately 7 billion people worldwide, have become an important subject for scientific research. Studies have suggested that the EMF emitted by mobile phones can cause oxidative stress in different tissues and age groups. Young people in adolescence, a time period when risky behaviors and dependences increase, use mobile phones more than adults. The EMF emitted by mobile phones, which are generally carried in the pocket or in bags when not in use, will very probably affect the sciatic nerve...
January 10, 2018: Journal of Chemical Neuroanatomy
Jianjia Yi, Sawyer D Campbell, Rui Feng, Shah Nawaz Burokur, Douglas H Werner
Complex electromagnetic structures can be designed by exploiting the concept of spatial coordinate transformations. In this paper, we define a coordinate transformation scheme that enables one to taper the electric field between two waveguides of different cross-sections. The electromagnetic field launched from the wide input waveguide is compressed in the proposed field tapering device and guided into the narrow output waveguide. In closed rectangular waveguide configurations, the taper can further play the role of a mode selector due to the output waveguide's cut-off frequency...
January 8, 2018: Optics Express
Tiecheng Wang, Shihao Zhang
Second harmonic generation from the two-layer structure where a transition-metal dichalcogenide monolayer is put on a one-dimensional grating has been studied. This grating supports bound states in the continuum which have no leakage lying within the continuum of radiation modes, we can enhance the second harmonic generation from the transition-metal dichalcogenide monolayer by more than four orders of magnitude based on the critical field enhancement near the bound states in the continuum. In order to complete this calculation, the scattering matrix theory has been extended to include the nonlinear effect and the scattering matrix of a two-dimensional material including nonlinear terms; furthermore, two methods to observe the bound states in the continuum are considered, where one is tuning the thickness of the grating and the other is changing the incident angle of the electromagnetic wave...
January 8, 2018: Optics Express
Rui Yang, Pei Yang, Yongchao Chen, Jiacheng Li, Zhenya Lei
We propose a sandwiched transparent epsilon-near-zero (ENZ) metamaterial screen to release the obliquely incident electromagnetic fields. More specifically, the transmission properties through ENZ metamaterials are investigated when incorporated with an interlayer of a meta-surface having periodic complementary spiral-resonator-matrixes. We show that both TE- and TM-polarized electromagnetic waves are capable of penetrating the ENZ metamaterials under a wide-angle range of illuminations, and the greatly enhanced transmissions are turning out to be frequency dispersionless for different polarized electromagnetic fields with different incident angles...
January 1, 2018: Optics Letters
Thomas Grosges, Dominique Barchiesi
We give a simple tool for the optimization of the dimensions of a metallic nanostrip illuminated at a given wavelength under normal incidence, to get a maximum of the electromagnetic field amplitude in the nanostrip. We propose an analytical formula that gives the widths and heights of the series of nanostrips that produce field enhancement. The validity of the analytical formula is checked by using the finite element method. This design of a nanostrip could be useful for sensors and thermally active components...
January 1, 2018: Optics Letters
Natalia A Loiko, Alexander A Miskevich, Valery A Loiko
We have derived an analytical solution for an incoherent component of light scattered by a normally illuminated monolayer of homogeneous spherical particles. It is based on the quasi-crystalline approximation of the theory of multiple scattering of waves as well as on the multipole expansion of electromagnetic fields and tensor Green's function in terms of vector spherical wave functions. We apply the solution to a description of scattering and absorption characteristics of partially ordered monolayers and monolayers with imperfect lattices...
January 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Gokhan Ariturk, Yusuf Ziya Ider
Magnetic resonance electrical properties tomography (MR-EPT), aiming at reconstructing the EP's at radio frequencies, uses the H<sup>+</sup> field (both magnitude and phase) distribution within the object. One of the MR-EPT algorithms, cr-MREPT, accurately reconstructs the internal tissue boundaries however it faces an artifact which occurs at the regions where the convective field, [ (∂H<sup>+</sup> / ∂x ) - i(∂H<sup>+</sup> / ∂y) i((∂H<sup>+</sup> / ∂x ) - i(∂H<sup>+</sup> / ∂y)) ] , has a low magnitude (at the noise level)...
January 12, 2018: Physics in Medicine and Biology
Daniel Wenz, Andre Kuehne, Till Huelnhagen, Armin M Nagel, Helmar Waiczies, Oliver Weinberger, Celal Oezerdem, Oliver Stachs, Soenke Langner, Erdmann Seeliger, Bert Flemming, Russell Hodge, Thoralf Niendorf
PURPOSE: The aim of this study was to achieve millimeter spatial resolution sodium in vivo MRI of the human eye at 7 T using a dedicated six-channel transceiver array. We present a detailed description of the radiofrequency coil design, along with electromagnetic field and specific absorption ratio simulations, data validation, and in vivo application. METHODS: Electromagnetic field and specific absorption ratio simulations were performed. Transmit field uniformity was optimized by using a multi-objective genetic algorithm...
January 12, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
F Kalafatakis, D Bekiaridis-Moschou, Eirini Gkioka, Magda Tsolaki
INTRODUCTION: Concerns about the possible adverse health effects of mobile phones (MP) have increased along with the expansion of their use. A number of research papers have tried to address this issue. Although many investigations concluded that MP use does have negative consequences, in terms of cognitive function of the human brain, the results so far have been divisive. A number of studies reported impairment of cognitive function after exposure to mobile phone electromagnetic field (MP EMF), while others observed no effect or improved performance...
September 2017: Hellenic Journal of Nuclear Medicine
Harry M C Choi, Alex K K Cheing, Gabriel Y F Ng, Gladys L Y Cheing
The present study investigated the effects of pulsed electromagnetic field (PEMF) on the tensile biomechanical properties of diabetic wounds at different phases of healing. Two intensities of PEMF were adopted for comparison. We randomly assigned 111 10-week-old male streptozotocin-induced diabetic Sprague-Dawley rats to two PEMF groups and a sham control group. Six-millimetre biopsy punched full thickness wounds were made on the lateral side of their hindlimbs. The PEMF groups received active PEMF delivered at 25 Hz with intensity of either 2 mT or 10 mT daily, while the sham group was handled in a similar way except they were not exposed to PEMF...
2018: PloS One
Jin-Kwan Park, Tae-Gyu Kang, Byung-Hyun Kim, Hee-Jo Lee, Hyang Hee Choi, Jong-Gwan Yook
A real-time humidity sensor based on a microwave resonator coupled with a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conducting polymer (CP) film is proposed in this paper. The resonator is patterned on a printed circuit board and is excited by electromagnetic field coupling. To enhance the sensitivity of the sensor, the CP film is located in the area with the strongest electric field in the resonator. To investigate the performance, the proposed sensor is placed alongside a reference sensor in a humidity chamber, and humidity is injected at room temperature...
January 11, 2018: Scientific Reports
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