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Electromagnetic field

Abraham I Harte
Electromagnetic fields which solve the vacuum Maxwell equations in one spacetime are well known to also be solutions in all spacetimes with conformally related metrics. This provides a sense in which electromagnetism alone cannot be used to measure certain aspects of geometry. We show that there is actually much more which cannot be so measured; relatively little of a spacetime's geometry is in fact imprinted in any particular electromagnetic field. This is demonstrated by finding a much larger class of metric transformations-involving five free functions-which preserve Maxwell solutions both in vacuum, without local currents, and also for the force-free electrodynamics associated with a tenuous plasma...
April 7, 2017: Physical Review Letters
Natalia Cichoń, Michał Bijak, Elżbieta Miller, Joanna Saluk
As a result of ischaemia/reperfusion, massive generation of reactive oxygen species occurs, followed by decreased activity of antioxidant enzymes. Extremely low frequency electromagnetic fields (ELF-EMF) can modulate oxidative stress, but there are no clinical antioxidant studies in brain stroke patients. The aim of our study was to investigate the effect of ELF-EMF on clinical and antioxidant status in post-stroke patients. Fifty-seven patients were divided into two groups: ELF-EMF and non-ELF-EMF. Both groups underwent the same 4-week rehabilitation program...
April 21, 2017: Bioelectromagnetics
Xiaolin Kang, Qifeng Ruan, Han Zhang, Feng Bao, Jun Guo, Minghua Tang, Si Cheng, Jianfang Wang
Concave nanocrystals usually exhibit a large electromagnetic-field enhancement and superior catalytic performance due to their sharp corners, negative curvature and high-index facets. Conventional gold bipyramids (AuBPs) possess intriguing plasmonic properties which are attractive for various applications while the surface curvature of the reported bipyramids has not been fine-tuned to concave or convex structures to date. Additionally, the longitudinal surface plasmon resonance (LSPR) wavelengths of conventional AuBPs are mostly located in the range of 650-1350 nm and the sizes of these nanoparticles are usually not beyond 350 nm, which are not facilitated to some nano-focusing and nanophotonic applications...
April 21, 2017: Nanoscale
Andreas Andrikopoulos, Adam Adamopoulos, Ioannis Seimenis, Constantinos Miltiadis Koutsojannis
Microwave diathermy (MWD) is a therapeutic system that is in use for some decades now in all physiotherapy settings, according to national facility establishment regulations. Diathermy devices probably lack validity, as working time passes, introducing the need of control/reset of the device by qualified personnel, in order to maintain its effectiveness in sessions and accurately deliver the energy output the physiotherapist asks for. However, while in the field of physical therapy MWD has been a vital part for practicing the profession of physiotherapist, there is not a clear evidence of health burden due to incorrect usability...
April 21, 2017: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
T S Robinson, F Consoli, S Giltrap, S J Eardley, G S Hicks, E J Ditter, O Ettlinger, N H Stuart, M Notley, R De Angelis, Z Najmudin, R A Smith
We report on the development and deployment of an optical diagnostic for single-shot measurement of the electric-field components of electromagnetic pulses from high-intensity laser-matter interactions in a high-noise environment. The electro-optic Pockels effect in KDP crystals was used to measure transient electric fields using a geometry easily modifiable for magnetic field detection via Faraday rotation. Using dielectric sensors and an optical fibre-based readout ensures minimal field perturbations compared to conductive probes and greatly limits unwanted electrical pickup between probe and recording system...
April 20, 2017: Scientific Reports
Vincenzo Amendola, Roberto Pilot, Marco Frasconi, Onofrio M Maragò, Maria Antonia Iatì
In the last two decades, plasmon resonance in gold nanoparticles (Au NPs) has been the subject of intense research efforts. Plasmon physics is intriguing and its precise modelling proved to be challenging. In fact, plasmons are highly responsive to a multitude of factors, either intrinsic to the Au NPs or from the environment, and recently the need emerged for the correction of standard electromagnetic approaches with quantum effects. Applications related to plasmon absorption and scattering in Au NPs are impressively numerous, ranging from sensing to photothermal effects to cell imaging...
May 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Wei Ma, Liguang Xu, André F de Moura, Xiaoling Wu, Hua Kuang, Chuanlai Xu, Nicholas A Kotov
The field of chiral inorganic nanostructures is rapidly expanding. It started from the observation of strong circular dichroism during the synthesis of simple nanoparticles (NPs) and their assemblies mediated by biomolecules and expanded to sophisticated synthetic protocols involving nanostructures from metals, semiconductors, ceramics, and nanocarbons. Besides the well-established chirality transfer from bioorganic molecules, other methods to impart handedness to nanoscale matter specific to inorganic materials were discovered, including three-dimentional lithography, multiphoton chirality transfer, polarization effects in nanoscale assemblies, and others...
April 20, 2017: Chemical Reviews
Jun Zhang, Alexander Sumich, Grace Y Wang
Due to its attributes, characteristics, and technological resources, the mobile phone (MP) has become one of the most commonly used communication devices. Historically, ample evidence has ruled out the substantial short-term impact of radiofrequency electromagnetic field (RF-EMF) emitted by MP on human cognitive performance. However, more recent evidence suggests potential harmful effects associated with MP EMF exposure. The aim of this review is to readdress the question of whether the effect of MP EMF exposure on brain function should be reopened...
April 20, 2017: Bioelectromagnetics
Taktom Sadeghi, Amirmasoud Ahmadi, Maryam Javadian, Sayyed Asghar Gholamian, Mouloud Agajani Delavar, Sedigheh Esmailzadeh, Bahare Ahmadi, Mozhgan Sadat Hassanpour Hadighi
AIM: The issue of preterm birth due to exposure to magnetic fields from power lines is unclear. Exposure to electromagnetic field in uterus has been hypothesized as possible preterm birth. The aim of the present study was to determine whether living closer to high voltage power lines increased the risk of preterm labor. METHODS: In a nested case-control study, 135 cases of singleton live spontaneous preterm birth in Rohani hospital, Babol, Iran, during the period between 2013 and 2014 were studied...
April 18, 2017: Romanian Journal of Internal Medicine, Revue Roumaine de Médecine Interne
Elena Lucano, Micaela Liberti, Tom Lloyd, Francesca Apollonio, Steve Wedan, Wolfgang Kainz, Leonardo M Angelone
PURPOSE: This study aims to investigate how the positions of the feeding sources of the transmit radiofrequency (RF) coil, field orientation direction with respect to the patient, and patient dimensions affect the global and local electromagnetic exposure in human body models. METHODS: Three RF coil models were implemented, namely a specific two-source (S2) feed and two multisource feed configurations: generic 32-source (G32) and hybrid 16-source (H16). Thirty-two feeding conditions were studied for the S2, whereas two were studied for the G32 and H16...
April 18, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Yicheng Chen, Zhaoxia Zheng, Mingyang Gong, Fengqi Yu
Power consumption and communication distance have become crucial challenges for SIM card RFID (radio frequency identification) applications. The combination of long distance 2.45 GHz radio frequency (RF) technology and low power 2 kHz near distance communication is a workable scheme. In this paper, an ultra-low frequency 2 kHz near field communication (NFC) method suitable for SIM cards is proposed and verified in silicon. The low frequency transmission model based on electromagnetic induction is discussed...
April 14, 2017: Sensors
Monireh Arjmand, Abdolreza Ardeshirylajimi, Hossein Maghsoudi, Esmaeel Azadian
Nowadays, tissue engineering by using stem cells in combination with scaffolds and bioactive molecules has made significant contributions to the regeneration of damaged bone tissues. Since the usage of bioactive molecules including, growth factors to induce differentiation is safety limited in clinical applications, and it has also been previously observed that extremely low frequency pulsed electromagnetic fields (PEMF) can be effective in the enhancement of proliferation rate and osteogenic differentiation of stem cells, the aim of this study was investigating the osteoinductive potential of PEMF in combination with Poly(caprolactone) (PCL) nanofibrous scaffold...
April 17, 2017: Journal of Cellular Physiology
Sergey N Galyamin, Andrey V Tyukhtin, Anton A Peshkov
This study analyzes the radiation produced by a point charge intersecting the interface between a vacuum and a chiral isotropic medium. We deduce analytical expressions for the Fourier components of an electromagnetic field in both vacuum and medium for arbitrary charge velocity. The main focus is on investigating the far field in a vacuum. The distinguishing feature of the interface with a chiral isotropic medium is that the field in the vacuum area contains both copolarization (coinciding with the polarization of the self-field of a charge) and cross-polarization (orthogonal to the polarization of the self-field)...
March 2017: Physical Review. E
Carlos G Avendaño, Arturo Reyes
We theoretically study the dispersion relation for axially propagating electromagnetic waves throughout a one-dimensional helical structure whose pitch and dielectric and magnetic properties are spatial random functions with specific statistical characteristics. In the system of coordinates rotating with the helix, by using a matrix formalism, we write the set of differential equations that governs the expected value of the electromagnetic field amplitudes and we obtain the corresponding dispersion relation...
March 2017: Physical Review. E
Tayaba Miah, Deepak Kamat
There has been an exponential increase in the use of electronic devices over the past few decades. This has led to increased exposure to electromagnetic fields (EMF). Electric fields result from differences in voltage, whereas magnetic fields result from the flow of electric current. Higher-frequency waves of EMF have more energy than lower-frequency waves, and thus generally tend to be more harmful. An EMF activates cellular stress response and also causes breaks in DNA strands. There are many methodological barriers to effectively measuring the associations of EMF and childhood cancers...
April 1, 2017: Pediatric Annals
Hao Yang, Haobo Cheng, Hengyu Wu, Tan Wang
To meet the special demands in small-scale discontinuous optical surface fabrication, the integrated magnetorheological jet polishing (IMJP) tool with multiple motion degrees is introduced in this paper. Four jetting models are implemented and investigated by means of the IMJP tool for practical manufacture. To ensure steady jetting in a long distance, ideal distribution characteristics of the magnetic field in the structure is proposed, based on electromagnetic theory. The magnetic field distribution is simulated subsequently using the finite element analysis method, and three key parameters in the IMJP tool structure are optimized through the simulations...
April 10, 2017: Applied Optics
Leilei Wang, Fanyu Kong, Zhilin Xia, Yunxia Jin, Haopeng Huang, Linxin Li, Junming Chen, Yun Cui, Jianda Shao
In this study, two kinds of Au-coated gratings (ACGs) with a period of 1740 lines/mm were fabricated and evaluated. For these ACG samples, magnetron sputtering and e-beam evaporation were used as the gold deposition process, and the samples had a bandwidth of at least 170 nm, with the -1st-order diffraction efficiency exceeding 90% around the center wavelength of 800 nm. The one-on-one damage threshold of ACGs fabricated by magnetron sputtering and e-beam evaporation measured at a pulse width of 60 fs was 0...
April 10, 2017: Applied Optics
José A Rodrigo
Plasmonic nanoparticles are able to control light at nanometre-scale by coupling electromagnetic fields to the oscillations of free electrons in metals. Deposition of such nanoparticles onto substrates with tailored patterns is essential, for example, in fabricating plasmonic structures for enhanced sensing. This work presents an innovative micro-patterning technique, based on optoelectic printing, for fast and straightforward fabrication of curve-shaped circuits of plasmonic nanoparticles deposited onto a transparent electrode often used in optoelectronics, liquid crystal displays, touch screens, etc...
April 13, 2017: Scientific Reports
Swapnil Bhuktare, Arnab Bose, Hanuman Singh, Ashwin A Tulapurkar
A gyrator is a non-reciprocal two port device with 180° phase shift in the transmissions between two ports. Though electromagnetic realizations of gyrators have been well studied, devices based on other forms of interaction are relatively unexplored. Here we demonstrate a device in which signal is transmitted via magneto-elastic coupling, can function as a gyrator. The device is built on a piezoelectric substrate: one port of this device has interdigital transducers (IDTs) and the other port has a periodic array of nickel/gold lines...
April 12, 2017: Scientific Reports
Wee Chong Tan, Yongqing Cai, Rui Jie Ng, Li Huang, Xuewei Feng, Gang Zhang, Yong-Wei Zhang, Christian A Nijhuis, Xinke Liu, Kah-Wee Ang
Black phosphorus carbide (b-PC) is a new family of layered semiconducting material that has recently been predicted to have the lightest electrons and holes among all known 2D semiconductors, yielding a p-type mobility (≈10(5) cm(2) V(-1) s(-1) ) at room temperature that is approximately five times larger than the maximum value in black phosphorus. Here, a high-performance composite few-layer b-PC field-effect transistor fabricated via a novel carbon doping technique which achieved a high hole mobility of 1995 cm(2) V(-1) s(-1) at room temperature is reported...
April 12, 2017: Advanced Materials
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