Imaging of conductivity distributions using audio-frequency electromagnetic data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Ki Ha; Morrison, H.F.

1990-10-01

The objective of this study has been to develop mathematical methods for mapping conductivity distributions between boreholes using low frequency electromagnetic (em) data. In relation to this objective this paper presents two recent developments in high-resolution crosshole em imaging techniques. These are (1) audio-frequency diffusion tomography, and (2) a transform method in which low frequency data is first transformed into a wave-like field. The idea in the second approach is that we can then treat the transformed field using conventional techniques designed for wave field analysis.

Iterative Nonlinear Tikhonov Algorithm with Constraints for Electromagnetic Tomography

NASA Technical Reports Server (NTRS)

Xu, Feng; Deshpande, Manohar

2012-01-01

Low frequency electromagnetic tomography such as the capacitance tomography (ECT) has been proposed for monitoring and mass-gauging of gas-liquid two-phase system under microgravity condition in NASA's future long-term space missions. Due to the ill-posed inverse problem of ECT, images reconstructed using conventional linear algorithms often suffer from limitations such as low resolution and blurred edges. Hence, new efficient high resolution nonlinear imaging algorithms are needed for accurate two-phase imaging. The proposed Iterative Nonlinear Tikhonov Regularized Algorithm with Constraints (INTAC) is based on an efficient finite element method (FEM) forward model of quasi-static electromagnetic problem. It iteratively minimizes the discrepancy between FEM simulated and actual measured capacitances by adjusting the reconstructed image using the Tikhonov regularized method. More importantly, it enforces the known permittivity of two phases to the unknown pixels which exceed the reasonable range of permittivity in each iteration. This strategy does not only stabilize the converging process, but also produces sharper images. Simulations show that resolution improvement of over 2 times can be achieved by INTAC with respect to conventional approaches. Strategies to further improve spatial imaging resolution are suggested, as well as techniques to accelerate nonlinear forward model and thus increase the temporal resolution.

Advanced Fast 3-D Electromagnetic Solver for Microwave Tomography Imaging.

PubMed

Simonov, Nikolai; Kim, Bo-Ra; Lee, Kwang-Jae; Jeon, Soon-Ik; Son, Seong-Ho

2017-10-01

This paper describes a fast-forward electromagnetic solver (FFS) for the image reconstruction algorithm of our microwave tomography system. Our apparatus is a preclinical prototype of a biomedical imaging system, designed for the purpose of early breast cancer detection. It operates in the 3-6-GHz frequency band using a circular array of probe antennas immersed in a matching liquid; it produces image reconstructions of the permittivity and conductivity profiles of the breast under examination. Our reconstruction algorithm solves the electromagnetic (EM) inverse problem and takes into account the real EM properties of the probe antenna array as well as the influence of the patient's body and that of the upper metal screen sheet. This FFS algorithm is much faster than conventional EM simulation solvers. In comparison, in the same PC, the CST solver takes ~45 min, while the FFS takes ~1 s of effective simulation time for the same EM model of a numerical breast phantom.

Low-Resolution Electromagnetic Tomography (LORETA) of changed Brain Function Provoked by Pro-Dopamine Regulator (KB220z) in one Adult ADHD case.

PubMed

Steinberg, Bruce; Blum, Kenneth; McLaughlin, Thomas; Lubar, Joel; Febo, Marcelo; Braverman, Eric R; Badgaiyan, Rajendra D

Attention Deficit-Hyperactivity Disorder (ADHD) often continues into adulthood. Recent neuroimaging studies found lowered baseline dopamine tone in the brains of affected individuals that may place them at risk for Substance Use Disorder (SUD). This is an observational case study of the potential for novel management of Adult ADHD with a non-addictive glutaminergic-dopaminergic optimization complex KB200z. Low-resolution electromagnetic tomography (LORETA) was used to evaluate the effects of KB220z on a 72-year-old male with ADHD, at baseline and one hour following administration. The resultant z-scores, averaged across Eyes Closed, Eyes Open and Working Memory conditions, increased for each frequency band, in the anterior, dorsal and posterior cingulate regions, as well as the right dorsolateral prefrontal cortex during Working Memory, with KB220z. These scores are consistent with other human and animal neuroimaging studies that demonstrated increased connectivity volumes in reward circuitry and may offer a new approach to ADHD treatment. However, larger randomized trials to confirm these results are required.

Low-Resolution Electromagnetic Tomography (LORETA) of changed Brain Function Provoked by Pro-Dopamine Regulator (KB220z) in one Adult ADHD case

PubMed Central

Steinberg, Bruce; Blum, Kenneth; McLaughlin, Thomas; Lubar, Joel; Febo, Marcelo; Braverman, Eric R.; Badgaiyan, Rajendra D

2016-01-01

Attention Deficit-Hyperactivity Disorder (ADHD) often continues into adulthood. Recent neuroimaging studies found lowered baseline dopamine tone in the brains of affected individuals that may place them at risk for Substance Use Disorder (SUD). This is an observational case study of the potential for novel management of Adult ADHD with a non-addictive glutaminergic-dopaminergic optimization complex KB200z. Low-resolution electromagnetic tomography (LORETA) was used to evaluate the effects of KB220z on a 72-year-old male with ADHD, at baseline and one hour following administration. The resultant z-scores, averaged across Eyes Closed, Eyes Open and Working Memory conditions, increased for each frequency band, in the anterior, dorsal and posterior cingulate regions, as well as the right dorsolateral prefrontal cortex during Working Memory, with KB220z. These scores are consistent with other human and animal neuroimaging studies that demonstrated increased connectivity volumes in reward circuitry and may offer a new approach to ADHD treatment. However, larger randomized trials to confirm these results are required. PMID:27610420

[EEG source localization using LORETA (low resolution electromagnetic tomography)].

PubMed

Puskás, Szilvia

2011-03-30

Eledctroencephalography (EEG) has excellent temporal resolution, but the spatial resolution is poor. Different source localization methods exist to solve the so-called inverse problem, thus increasing the accuracy of spatial localization. This paper provides an overview of the history of source localization and the main categories of techniques are discussed. LORETA (low resolution electromagnetic tomography) is introduced in details: technical informations are discussed and localization properties of LORETA method are compared to other inverse solutions. Validation of the method with different imaging techniques is also discussed. This paper reviews several publications using LORETA both in healthy persons and persons with different neurological and psychiatric diseases. Finally future possible applications are discussed.

Detection of foreign body using fast thermoacoustic tomography with a multielement linear transducer array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nie Liming; Xing Da; Yang Diwu

2007-04-23

Current imaging modalities face challenges in clinical applications due to limitations in resolution or contrast. Microwave-induced thermoacoustic imaging may provide a complementary modality for medical imaging, particularly for detecting foreign objects due to their different absorption of electromagnetic radiation at specific frequencies. A thermoacoustic tomography system with a multielement linear transducer array was developed and used to detect foreign objects in tissue. Radiography and thermoacoustic images of objects with different electromagnetic properties, including glass, sand, and iron, were compared. The authors' results demonstrate that thermoacoustic imaging has the potential to become a fast method for surgical localization of occult foreignmore » objects.« less

Geophysical identification of subsurface cavities and fractures near a Superfund site south of Rockford, Illinois

NASA Astrophysics Data System (ADS)

Adams, Ryan Frye

The ACME Superfund site is one of many Superfund sites in Northern Illinois. This 20 acre (8.1 ha) site was contaminated by various volatile organic compounds (VOC's) and heavy metals during the 1960-1980s. To more fully understand the potential extent of the karst system and its interaction with contaminants, both surface and borehole geophysics including seismic refraction tomography, frequency domain electromagnetics, electrical resistivity, ground penetrating radar, as well as natural gamma and electromagnetic well logs, were undertaken over an approximately 3,000 square meter grid in a field immediately south of the ACME site. Seismic refraction tomography provided information on lithology and fluctuations in the bedrock surface in the depth range 6 to 8 m. Refraction, combined with electromagnetic conductivity, also allowed mapping of potential soil pipes and/or filled sinkholes in the overlying soils. These could channel surface waters into the karst conduit system. Frequency domain electromagnetics proved to be the most successful tool for the identifying possible karst conduits below the bedrock surface. Zones of reduced conductivity suggest a series of interconnected solutionally enlarged fractures in an orthogonal pattern at a depth of approximately 8 m immediately south of the ACME site.

Electromagnetic navigated positioning of the maxilla after Le Fort I osteotomy in preclinical orthognathic surgery cases.

PubMed

Berger, Moritz; Nova, Igor; Kallus, Sebastian; Ristow, Oliver; Eisenmann, Urs; Freudlsperger, Christian; Seeberger, Robin; Hoffmann, Jürgen; Dickhaus, Hartmut

2017-03-01

Inaccuracies in orthognathic surgery can be caused during face-bow registration, model surgery on plaster models, and intermaxillary splint manufacturing. Electromagnetic (EM) navigation is a promising method for splintless digitized maxillary positioning. After performing Le Fort I osteotomy on 10 plastic skulls, the target position of the maxilla was guided by an EM navigation system. Specially implemented software illustrated the target position by real-time multistage colored three-dimensional imaging. Accuracy was determined by using pre- and postoperative cone beam computed tomography. The high accuracy of the EM system was underlined by the fact that it had a navigated maxilla position discrepancy of only 0.4 mm, which was verified by postoperative cone beam computed tomography. This preclinical study demonstrates a precise digitized approach for splintless maxillary repositioning after Le Fort I osteotomy. The accuracy and intuitive illustration of the introduced EM navigation system is promising for potential daily use in orthognathic surgery. Copyright © 2016 Elsevier Inc. All rights reserved.

Quantum tomography for measuring experimentally the matrix elements of an arbitrary quantum operation.

PubMed

D'Ariano, G M; Lo Presti, P

2001-05-07

Quantum operations describe any state change allowed in quantum mechanics, including the evolution of an open system or the state change due to a measurement. We present a general method based on quantum tomography for measuring experimentally the matrix elements of an arbitrary quantum operation. As input the method needs only a single entangled state. The feasibility of the technique for the electromagnetic field is shown, and the experimental setup is illustrated based on homodyne tomography of a twin beam.

Quantitative EEG and low resolution electromagnetic tomography (LORETA) imaging of patients with persistent auditory hallucinations.

PubMed

Lee, Seung-Hwan; Wynn, Jonathan K; Green, Michael F; Kim, Hyun; Lee, Kang-Joon; Nam, Min; Park, Joong-Kyu; Chung, Young-Cho

2006-04-01

Electrophysiological studies have demonstrated gamma and beta frequency oscillations in response to auditory stimuli. The purpose of this study was to test whether auditory hallucinations (AH) in schizophrenia patients reflect abnormalities in gamma and beta frequency oscillations and to investigate source generators of these abnormalities. This theory was tested using quantitative electroencephalography (qEEG) and low-resolution electromagnetic tomography (LORETA) source imaging. Twenty-five schizophrenia patients with treatment refractory AH, lasting for at least 2 years, and 23 schizophrenia patients with non-AH (N-AH) in the past 2 years were recruited for the study. Spectral analysis of the qEEG and source imaging of frequency bands of artifact-free 30 s epochs were examined during rest. AH patients showed significantly increased beta 1 and beta 2 frequency amplitude compared with N-AH patients. Gamma and beta (2 and 3) frequencies were significantly correlated in AH but not in N-AH patients. Source imaging revealed significantly increased beta (1 and 2) activity in the left inferior parietal lobule and the left medial frontal gyrus in AH versus N-AH patients. These results imply that AH is reflecting increased beta frequency oscillations with neural generators localized in speech-related areas.

Approach to intraoperative electromagnetic navigation in orthognathic surgery: A phantom skull based trial.

PubMed

Berger, Moritz; Kallus, Sebastian; Nova, Igor; Ristow, Oliver; Eisenmann, Urs; Dickhaus, Hartmut; Kuhle, Reinald; Hoffmann, Jürgen; Seeberger, Robin

2015-11-01

Intraoperative guidance using electromagnetic navigation is an upcoming method in maxillofacial surgery. However, due to their unwieldy structures, especially the line-of-sight problem, optical navigation devices are not used for daily orthognathic surgery. Therefore, orthognathic surgery was simulated on study phantom skulls, evaluating the accuracy and handling of a new electromagnetic tracking system. Le-Fort I osteotomies were performed on 10 plastic skulls. Orthognathic surgical planning was done in the conventional way using plaster models. Accuracy of the gold standard, splint-based model surgery versus an electromagnetic tracking system was evaluated by measuring the actual maxillary deviation using bimaxillary splints and preoperative and postoperative cone beam computer tomography imaging. The distance of five anatomical marker points were compared pre- and postoperatively. The electromagnetic tracking system was significantly more accurate in all measured parameters compared with the gold standard using bimaxillary splints (p < 0.01). The data shows a discrepancy between the model surgical plans and the actual correction of the upper jaw of 0.8 mm. Using the electromagnetic tracking, we could reduce the discrepancy of the maxillary transposition between the planned and actual orthognathic surgery to 0.3 mm on average. The data of this preliminary study shows a high level of accuracy in surgical orthognathic performance using electromagnetic navigation, and may offer greater precision than the conventional plaster model surgery with bimaxillary splints. This preliminary work shows great potential for the establishment of an intraoperative electromagnetic navigation system for maxillofacial surgery. Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Tomography reconstruction methods for damage diagnosis of wood structure in construction field

NASA Astrophysics Data System (ADS)

Qiu, Qiwen; Lau, Denvid

2018-03-01

The structural integrity of wood building element plays a critical role in the public safety, which requires effective methods for diagnosis of internal damage inside the wood body. Conventionally, the non-destructive testing (NDT) methods such as X-ray computed tomography, thermography, radar imaging reconstruction method, ultrasonic tomography, nuclear magnetic imaging techniques, and sonic tomography have been used to obtain the information about the internal structure of wood. In this paper, the applications, advantages and disadvantages of these traditional tomography methods are reviewed. Additionally, the present article gives an overview of recently developed tomography approach that relies on the use of mechanical and electromagnetic waves for assessing the structural integrity of wood buildings. This developed tomography reconstruction method is believed to provide a more accurate, reliable, and comprehensive assessment of wood structural integrity

Electromagnetic-Optical Coherence Tomography Guidance of Transbronchial Solitary Pulmonary Nodule Biopsy

DTIC Science & Technology

2015-07-01

death accounting for more deaths than breast , prostate and colon combined. Early diagnosis is critical to patient survival, however the vast majority...of lung malignancies are detected only once symptoms arise and the cancer has spread, at which time patients have little chance of cure...and electromagnetic (EM) navigation for spatial guidance to targeted lung nodules, and OCT for microscopic volumetric imaging. The OCT optic fiber

Obsessive-compulsive dimension localized using low-resolution brain electromagnetic tomography (LORETA).

PubMed

Sherlin, Leslie; Congedo, Marco

2005-10-21

Electroencephalographic mapping techniques have been used to show differences between normal subjects and those diagnosed with various mental disorders. To date, there is no other research using the techniques of low-resolution brain electromagnetic tomography (LORETA) with the obsessive-compulsive disorder (OCD) population. The current investigation compares current source density measures of persons with OCD symptoms to an age-matched control group. The main finding is excess current source density in the Beta frequencies in the cingulate gyrus. This Beta activity is primarily located in the middle cingulate gyrus as well as adjacent frontal parieto-occipital regions. Lower frequency Beta is prominent more anteriorly in the cingulate gyrus whereas higher frequency Beta is seen more posteriorly. These preliminary findings indicate the utility of LORETA as a clinical and diagnostic tool.

Three-dimensional analysis of the surface registration accuracy of electromagnetic navigation systems in live endoscopic sinus surgery.

PubMed

Chang, C M; Fang, K M; Huang, T W; Wang, C T; Cheng, P W

2013-12-01

Studies on the performance of surface registration with electromagnetic tracking systems are lacking in both live surgery and the laboratory setting. This study presents the efficiency in time of the system preparation as well as the navigational accuracy of surface registration using electromagnetic tracking systems. Forty patients with bilateral chronic paranasal pansinusitis underwent endoscopic sinus surgery after undergoing sinus computed tomography scans. The surgeries were performed under electromagnetic navigation guidance after the surface registration had been carried out on all of the patients. The intraoperative measurements indicate the time taken for equipment set-up, surface registration and surgical procedure, as well as the degree of navigation error along 3 axes. The time taken for equipment set-up, surface registration and the surgical procedure was 179 +- 23 seconds, 39 +- 4.8 seconds and 114 +- 36 minutes, respectively. A comparison of the navigation error along the 3 axes showed that the deviation in the medial-lateral direction was significantly less than that in the anterior-posterior and cranial-caudal directions. The procedures of equipment set-up and surface registration in electromagnetic navigation tracking are efficient, convenient and easy to manipulate. The system accuracy is within the acceptable ranges, especially on the medial-lateral axis.

Terahertz wide aperture reflection tomography.

PubMed

Pearce, Jeremy; Choi, Hyeokho; Mittleman, Daniel M; White, Jeff; Zimdars, David

2005-07-01

We describe a powerful imaging modality for terahertz (THz) radiation, THz wide aperture reflection tomography (WART). Edge maps of an object's cross section are reconstructed from a series of time-domain reflection measurements at different viewing angles. Each measurement corresponds to a parallel line projection of the object's cross section. The filtered backprojection algorithm is applied to recover the image from the projection data. To our knowledge, this is the first demonstration of a reflection computed tomography technique using electromagnetic waves. We demonstrate the capabilities of THz WART by imaging the cross sections of two test objects.

Cortical hypoactivation during resting EEG in schizophrenics but not in depressives and schizotypal subjects as revealed by low resolution electromagnetic tomography (LORETA).

PubMed

Mientus, Susanne; Gallinat, Jürgen; Wuebben, Yvonne; Pascual-Marqui, Roberto D; Mulert, Christoph; Frick, Kurt; Dorn, Hans; Herrmann, Werner M; Winterer, Georg

2002-11-30

This study was performed in order to address the question whether the newly introduced technique of low-resolution electromagnetic tomography (LORETA) is able to detect hypofrontality in schizophrenic patients. We investigated resting EEGs of 19 unmedicated schizophrenics and 20 normal subjects. For comparison, we also investigated 19 subjects with schizotypal personality and 30 unmedicated depressive patients. A significant increase of delta activity was found in schizophrenic patients over the whole cortex, most strongly in the anterior cingulate gyrus and temporal lobe (fusiform gyrus). Both schizotypal subjects and depressive subjects showed significantly less delta, theta and beta activity in the anterior cingulum, a decrease of alpha1 activity in the right temporal lobe and a decrease of alpha2 activity in the left temporal lobe. The results suggest general cortical hypoactivation, most pronounced in the anterior cingulate and temporal lobe in schizophrenics, whereas there is evidence for a complex, frequency-dependent spatial pattern of hyperactivation in schizotypal subjects and depressive patients. The results are discussed within a neurophysiological and methodological framework.

Cerebrospinal Fluid Biomarkers of Alzheimer's Disease Correlate With Electroencephalography Parameters Assessed by Exact Low-Resolution Electromagnetic Tomography (eLORETA).

PubMed

Hata, Masahiro; Tanaka, Toshihisa; Kazui, Hiroaki; Ishii, Ryouhei; Canuet, Leonides; Pascual-Marqui, Roberto D; Aoki, Yasunori; Ikeda, Shunichiro; Sato, Shunsuke; Suzuki, Yukiko; Kanemoto, Hideki; Yoshiyama, Kenji; Iwase, Masao

2017-09-01

Recently, cerebrospinal fluid (CSF) biomarkers related to Alzheimer's disease (AD) have garnered a lot of clinical attention. To explore neurophysiological traits of AD and parameters for its clinical diagnosis, we examined the association between CSF biomarkers and electroencephalography (EEG) parameters in 14 probable AD patients. Using exact low-resolution electromagnetic tomography (eLORETA), artifact-free 40-sesond EEG data were estimated with current source density (CSD) and lagged phase synchronization (LPS) as the EEG parameters. Correlations between CSF biomarkers and the EEG parameters were assessed. Patients with AD showed significant negative correlation between CSF beta-amyloid (Aβ)-42 concentration and the logarithms of CSD over the right temporal area in the theta band. Total tau concentration was negatively correlated with the LPS between the left frontal eye field and the right auditory area in the alpha-2 band in patients with AD. Our study results suggest that AD biomarkers, in particular CSF Aβ42 and total tau concentrations are associated with the EEG parameters CSD and LPS, respectively. Our results could yield more insights into the complicated pathology of AD.

Conflict monitoring and adjustment in the task-switching paradigm under different memory load conditions: an ERP/sLORETA analysis.

PubMed

Deng, Yuqin; Wang, Yan; Ding, Xiaoqian; Tang, Yi-Yuan

2015-02-11

The aim of the present study was to examine electrophysiological and behavioral changes caused by different memory loads in a task-switching paradigm. A total of 31 healthy individuals were subjected to a task, in which the stimulus-response reversal paradigm was combined with the task-switching paradigm. The event-related potentials were recorded and the N2 component, an index of conflict processing, was measured. In addition, the neural sources of N2 were further analyzed by standardized low-resolution brain electromagnetic tomography. The event-related potential results showed that high memory load triggered a higher N2 mean amplitude. Moreover, the standardized low-resolution brain electromagnetic tomography data showed that high memory load caused an increase in current densities at the anterior cingulate cortex and the prefrontal cortex in the task-switching paradigm. In summary, our findings provide electrophysiological evidence to interpret possible influences of memory loads on conflict monitoring and modulation during the task switching. These results imply that the working memory load overrules the influence of task-switching performance on the intensification of cognitive control.

Real-time FDG PET Guidance during Biopsies and Radiofrequency Ablation Using Multimodality Fusion with Electromagnetic Navigation

PubMed Central

Kadoury, Samuel; Abi-Jaoudeh, Nadine; Levy, Elliot B.; Maass-Moreno, Roberto; Krücker, Jochen; Dalal, Sandeep; Xu, Sheng; Glossop, Neil; Wood, Bradford J.

2011-01-01

Purpose: To assess the feasibility of combined electromagnetic device tracking and computed tomography (CT)/ultrasonography (US)/fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) fusion for real-time feedback during percutaneous and intraoperative biopsies and hepatic radiofrequency (RF) ablation. Materials and Methods: In this HIPAA-compliant, institutional review board–approved prospective study with written informed consent, 25 patients (17 men, eight women) underwent 33 percutaneous and three intraoperative biopsies of 36 FDG-avid targets between November 2007 and August 2010. One patient underwent biopsy and RF ablation of an FDG-avid hepatic focus. Targets demonstrated heterogeneous FDG uptake or were not well seen or were totally inapparent at conventional imaging. Preprocedural FDG PET scans were rigidly registered through a semiautomatic method to intraprocedural CT scans. Coaxial biopsy needle introducer tips and RF ablation electrode guider needle tips containing electromagnetic sensor coils were spatially tracked through an electromagnetic field generator. Real-time US scans were registered through a fiducial-based method, allowing US scans to be fused with intraprocedural CT and preacquired FDG PET scans. A visual display of US/CT image fusion with overlaid coregistered FDG PET targets was used for guidance; navigation software enabled real-time biopsy needle and needle electrode navigation and feedback. Results: Successful fusion of real-time US to coregistered CT and FDG PET scans was achieved in all patients. Thirty-one of 36 biopsies were diagnostic (malignancy in 18 cases, benign processes in 13 cases). RF ablation resulted in resolution of targeted FDG avidity, with no local treatment failure during short follow-up (56 days). Conclusion: Combined electromagnetic device tracking and image fusion with real-time feedback may facilitate biopsies and ablations of focal FDG PET abnormalities that would be challenging with conventional image guidance. © RSNA, 2011 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101985/-/DC1 PMID:21734159

Distributed RF Tomography for Tunnel Detection: Suitable Inversion Schemes

DTIC Science & Technology

2009-01-01

methods, ranging from seismic to electromagnetic waves, or from gravity to optics, from impedance tomography to magnetotellurics, no technique...unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Borehole GPR, which may...one manner to different targets (when targets are well-resolved). In particular, the wavefront generated by the array , when excited by one of these

Can electromagnetic-navigated maxillary positioning replace occlusional splints in orthognathic surgery? A clinical pilot study.

PubMed

Berger, Moritz; Nova, Igor; Kallus, Sebastian; Ristow, Oliver; Freudlsperger, Christian; Eisenmann, Urs; Dickhaus, Hartmut; Engel, Michael; Hoffmann, Jürgen; Seeberger, Robin

2017-10-01

Because of the inaccuracy of intermaxillary splints in orthognathic surgery, intraoperative guidance via a real time navigation system might represent a suitable method for enhancing the precision of maxillary positioning. Therefore, in this clinical trial, maxillary repositioning after Le Fort I osteotomy was guided splintless by an electromagnetic navigation system. Conservatively planned maxillary reposition in each of 5 patients was transferred to a novel software module of the electromagnetic navigation system. Intraoperatively, after Le Fort I osteotomy, the software guided the maxilla to the targeted position. Accuracy was evaluated by pre- and postoperative cone beam computer tomography imaging (the vectorial distance of the incisal marker points was measured in three dimensions) and compared with that of a splint transposed control group. The repositioning of the maxilla guided by the electromagnetic navigation system was intuitive and simple to accomplish. The achieved maxillary position with a deviation of 0.7 mm on average to the planned position was equally accurate compared with that of the splint transposed control group of 0.5 mm (p > 0.05). The data of this clinical study display good accuracy for splintless electromagnetic-navigated maxillary positioning. Nevertheless, this method does not surpass the splint-encoded gold standard with regard to accuracy. Future investigations will be necessary to show the full potential of electromagnetic navigation in orthognathic surgery. Copyright © 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Electromagnetic holographic sensitivity field of two-phase flow in horizontal wells

NASA Astrophysics Data System (ADS)

Zhang, Kuo; Wu, Xi-Ling; Yan, Jing-Fu; Cai, Jia-Tie

2017-03-01

Electromagnetic holographic data are characterized by two modes, suggesting that image reconstruction requires a dual-mode sensitivity field as well. We analyze an electromagnetic holographic field based on tomography theory and Radon inverse transform to derive the expression of the electromagnetic holographic sensitivity field (EMHSF). Then, we apply the EMHSF calculated by using finite-element methods to flow simulations and holographic imaging. The results suggest that the EMHSF based on the partial derivative of radius of the complex electric potential φ is closely linked to the Radon inverse transform and encompasses the sensitivities of the amplitude and phase data. The flow images obtained with inversion using EMHSF better agree with the actual flow patterns. The EMHSF overcomes the limitations of traditional single-mode sensitivity fields.

Current status of the real-time processing of complex radar signatures

NASA Astrophysics Data System (ADS)

Clay, E.

The real-time processing technique developed by ONERA to characterize radar signatures at the Brahms station is described. This technique is used for the real-time analysis of the RCS of airframes and rotating parts, the one-dimensional tomography of aircraft, and the RCS of electromagnetic decoys. Using this technique, it is also possible to optimize the experimental parameters, i.e., the analysis band, the microwave-network gain, and the electromagnetic window of the analysis.

Double-blind, placebo-controlled, multiple-ascending-dose study on the pharmacodynamics of ABIO-08/01, a new CNS drug with potential anxiolytic activity. 2. EEG-tomography findings based on LORETA (low-resolution brain electromagnetic tomography).

PubMed

Saletu, Bernd; Anderer, Peter; Wolzt, Michael; Nosiska, Dorothea; Assandri, Alessandro; Noseda, Emanuele; Nannipieri, Fabrizio; Saletu-Zyhlarz, Gerda M

2009-01-01

Effects of ABIO-08/01, a new potentially anxiolytic isoxazoline, on regional electrical brain generators were investigated by 3-dimensional EEG tomography. In a double- blind, placebo-controlled, multiple-ascending-dose study, 16 healthy males (30.2 +/- 5.7 years) received 3 oral drug doses (10, 20, 40 mg) and placebo for 7 days (8-day wash-out) in a randomized non-balanced design for phase-1 studies. A 3-min vigilance-controlled (V) EEG, a 4-min resting (R) EEG with eyes closed, a 1-min eyes-open (EO) EEG and psychometric tests were performed 0, 1 and 6 h after taking the drug on days 1 and 5. Low-resolution brain electromagnetic tomography (LORETA) was computed from the spectrally analyzed EEG data, and differences between drug and placebo were displayed as statistical parametric maps. Data were registered to the Talairach-Tournoux Human Brain Atlas available as a digitized MRI. An overall omnibus significance test followed by a voxel-by-voxel t test demonstrated significant regional EEG changes after ABIO-08/01 versus placebo, dependent on recording condition, dose and time. While in the EO-EEG specifically the lowest dose of ABIO-08/01 induced pronounced sedative effects (delta/theta and beta increase) 1 h after acute and slightly less so after superimposed administration, in the 6th hour a decrease in alpha and beta activity signaled less sedative and more relaxant action. In the V-EEG these changes were less pronounced, in the R-EEG partly opposite. Hemisphere-specific changes were observed, suggesting increases in LORETA power over the left temporal, parietal, superior frontal regions and decreases over the right prefrontal, temporal pole and occipital regions. These LORETA changes are discussed in the light of neuroimaging findings on anxiety and anxiolytics. 2009 S. Karger AG, Basel.

Effect of the 5-HT(1A) partial agonist buspirone on regional brain electrical activity in man: a functional neuroimaging study using low-resolution electromagnetic tomography (LORETA).

PubMed

Anderer, P; Saletu, B; Pascual-Marqui, R D

2000-12-04

In a double-blind, placebo-controlled study, the effects of 20 mg buspirone - a 5-HT(1A) partial agonist - on regional electrical generators within the human brain were investigated utilizing three-dimensional EEG tomography. Nineteen-channel vigilance-controlled EEG recordings were carried out in 20 healthy subjects before and 1, 2, 4, 6 and 8 h after drug intake. Low-resolution electromagnetic tomography (LORETA; Key Institute for Brain-Mind Research, software: http://www.keyinst.unizh.ch) was computed from spectrally analyzed EEG data, and differences between drug- and placebo-induced changes were displayed as statistical parametric maps. Data were registered to the Talairach-Tournoux human brain atlas available as a digitized MRI (McConnell Brain Imaging Centre: http://www.bic.mni.mcgill.ca). At the pharmacodynamic peak (1st hour), buspirone increased theta and decreased fast alpha and beta sources. Areas of theta increase were mainly the left temporo-occipito-parietal and left prefrontal cortices, which is consistent with PET studies on buspirone-induced decreases in regional cerebral blood flow and fenfluramine-induced serotonin activation demonstrated by changes in regional cerebral glucose metabolism. In later hours (8th hour) with lower buspirone plasma levels, delta, theta, slow alpha and fast beta decreased, predominantly in the prefrontal and anterior limbic lobe. Whereas the results of the 1st hour speak for a slight CNS sedation (more in the sense of relaxation), those obtained in the 8th hour indicate activation. Thus, LORETA may provide useful and direct information on drug-induced changes in central nervous system function in man.

Nonlinear inversion of borehole-radar tomography data to reconstruct velocity and attenuation distribution in earth materials

USGS Publications Warehouse

Zhou, C.; Liu, L.; Lane, J.W.

2001-01-01

A nonlinear tomographic inversion method that uses first-arrival travel-time and amplitude-spectra information from cross-hole radar measurements was developed to simultaneously reconstruct electromagnetic velocity and attenuation distribution in earth materials. Inversion methods were developed to analyze single cross-hole tomography surveys and differential tomography surveys. Assuming the earth behaves as a linear system, the inversion methods do not require estimation of source radiation pattern, receiver coupling, or geometrical spreading. The data analysis and tomographic inversion algorithm were applied to synthetic test data and to cross-hole radar field data provided by the US Geological Survey (USGS). The cross-hole radar field data were acquired at the USGS fractured-rock field research site at Mirror Lake near Thornton, New Hampshire, before and after injection of a saline tracer, to monitor the transport of electrically conductive fluids in the image plane. Results from the synthetic data test demonstrate the algorithm computational efficiency and indicate that the method robustly can reconstruct electromagnetic (EM) wave velocity and attenuation distribution in earth materials. The field test results outline zones of velocity and attenuation anomalies consistent with the finding of previous investigators; however, the tomograms appear to be quite smooth. Further work is needed to effectively find the optimal smoothness criterion in applying the Tikhonov regularization in the nonlinear inversion algorithms for cross-hole radar tomography. ?? 2001 Elsevier Science B.V. All rights reserved.

Development of Self-Potential Tomography for Early Warning System of rainfall induced Landslides: Electro-kinetic Effects and Sandbox Experiments

NASA Astrophysics Data System (ADS)

Hattori, K.; Yamazaki, T.; Terajima, T.; Huang, Q.

2017-12-01

Electro-kinetic effects is one of the possible mechanism for ULF electromagnetic phenomena preceeding landlisdes and large earthquakes. To understand general tendencies of electromagnetic changes related to electro-kinetic effects, we struggle with the integrated research to clarify the coupling among hydrological, geotechnical, and electromagnetic changes. Our final goal is to understand the ULF elecromagnetic phenomena in order to develop a simple technology for earthquake monitoring/forecasting. So, in this paper, we first show the observed waveforms possibly related to the Boso slow slip events in 2003 and 2007 and indoor landslide experiments with artificial rainfall. Then, numerical computations on the self-potential variation by the simulated groundwater flow, and compare the results with those observed by laboratory experiments. In the result, the simulated self-potential variation is consistent with observed one. FInally, we developed self-potential tomography to estimate the ground water condition. And we also characterize the pressure from the self-potential data, and compare the result with observed pressure head that is measured by pore-pressure gauge and found that the inverted pressure head is consistent with observed one. In addition, we apply the self-potential data observed by the flume test. The estimated pressure head from observed self-potential data shows the consistency with observed pressure head. And estimated pressure head also show the characteristic distribution before the landslide occurred. These facts are highly suggestive in effectiveness of the self-potential tomography to monitor groundwater changes associated with landslide. The details will be given in our presentation.

Fourier phase in Fourier-domain optical coherence tomography.

PubMed

Uttam, Shikhar; Liu, Yang

2015-12-01

Phase of an electromagnetic wave propagating through a sample-of-interest is well understood in the context of quantitative phase imaging in transmission-mode microscopy. In the past decade, Fourier-domain optical coherence tomography has been used to extend quantitative phase imaging to the reflection-mode. Unlike transmission-mode electromagnetic phase, however, the origin and characteristics of reflection-mode Fourier phase are poorly understood, especially in samples with a slowly varying refractive index. In this paper, the general theory of Fourier phase from first principles is presented, and it is shown that Fourier phase is a joint estimate of subresolution offset and mean spatial frequency of the coherence-gated sample refractive index. It is also shown that both spectral-domain phase microscopy and depth-resolved spatial-domain low-coherence quantitative phase microscopy are special cases of this general theory. Analytical expressions are provided for both, and simulations are presented to explain and support the theoretical results. These results are further used to show how Fourier phase allows the estimation of an axial mean spatial frequency profile of the sample, along with depth-resolved characterization of localized optical density change and sample heterogeneity. Finally, a Fourier phase-based explanation of Doppler optical coherence tomography is also provided.

Center-of-Mass Tomography and Wigner Function for Multimode Photon States

NASA Astrophysics Data System (ADS)

Dudinets, Ivan V.; Man'ko, Vladimir I.

2018-06-01

Tomographic probability representation of multimode electromagnetic field states in the scheme of center-of-mass tomography is reviewed. Both connection of the field state Wigner function and observable Weyl symbols with the center-of-mass tomograms as well as connection of the Grönewold kernel with the center-of-mass tomographic kernel determining the noncommutative product of the tomograms are obtained. The dual center-of-mass tomogram of the photon states are constructed and the dual tomographic kernel is obtained. The models of other generalized center-of-mass tomographies are discussed. Example of two-mode even and odd Schrödinger cat states is presented in details.

Integration of GIS, Electromagnetic and Electrical Methods in the Delimitation of Groundwater Polluted by Effluent Discharge (Salamanca, Spain): A Case Study.

PubMed

Montes, Rubén Vidal; Martínez-Graña, Antonio Miguel; Martínez Catalán, José Ramón; Arribas, Puy Ayarza; Sánchez San Román, Francisco Javier; Zazo, Caridad

2017-11-10

The present work envisages the possible geometry of a contaminated plume of groundwater near hospital facilities by combining GIS (Geographic Information System) and geophysical methods. The rock underlying the soil and thin sedimentary cover of the study area is moderately fractured quartzite, which makes aquifers vulnerable to pollution. The GIS methodology is used to calculate the area that would be affected by the effluent source of residual water, based on algorithms that consider ground surface mapping (slopes, orientations, accumulated costs and cost per distance). Geophysical methods (electromagnetic induction and electric resistivity tomography) use changes in the electrical conductivity or resistivity of the subsurface to determine the geometry of the discharge and the degree of contamination. The model presented would allow a preliminary investigation regarding potential corrective measures.

Integration of GIS, Electromagnetic and Electrical Methods in the Delimitation of Groundwater Polluted by Effluent Discharge (Salamanca, Spain): A Case Study

PubMed Central

Montes, Rubén Vidal; Sánchez San Román, Francisco Javier; Zazo, Caridad

2017-01-01

The present work envisages the possible geometry of a contaminated plume of groundwater near hospital facilities by combining GIS (Geographic Information System) and geophysical methods. The rock underlying the soil and thin sedimentary cover of the study area is moderately fractured quartzite, which makes aquifers vulnerable to pollution. The GIS methodology is used to calculate the area that would be affected by the effluent source of residual water, based on algorithms that consider ground surface mapping (slopes, orientations, accumulated costs and cost per distance). Geophysical methods (electromagnetic induction and electric resistivity tomography) use changes in the electrical conductivity or resistivity of the subsurface to determine the geometry of the discharge and the degree of contamination. The model presented would allow a preliminary investigation regarding potential corrective measures. PMID:29125556

A Quantum Field Approach for Advancing Optical Coherence Tomography Part I: First Order Correlations, Single Photon Interference, and Quantum Noise.

PubMed

Brezinski, M E

2018-01-01

Optical coherence tomography has become an important imaging technology in cardiology and ophthalmology, with other applications under investigations. Major advances in optical coherence tomography (OCT) imaging are likely to occur through a quantum field approach to the technology. In this paper, which is the first part in a series on the topic, the quantum basis of OCT first order correlations is expressed in terms of full field quantization. Specifically first order correlations are treated as the linear sum of single photon interferences along indistinguishable paths. Photons and the electromagnetic (EM) field are described in terms of quantum harmonic oscillators. While the author feels the study of quantum second order correlations will lead to greater paradigm shifts in the field, addressed in part II, advances from the study of quantum first order correlations are given. In particular, ranging errors are discussed (with remedies) from vacuum fluctuations through the detector port, photon counting errors, and position probability amplitude uncertainty. In addition, the principles of quantum field theory and first order correlations are needed for studying second order correlations in part II.

Electromagnetic Tracking Navigation to Guide Radiofrequency Ablation (RFA) of a Lung Tumor

PubMed Central

Amalou, Hayet; Wood, Bradford J.

2013-01-01

Radiofrequency ablation (RFA) may be an option for patients with lung tumors who have unresectable disease and are not suitable for available palliative modalities. RFA electrode positioning may take several attempts, necessitating multiple imaging acquisitions or continuous use of CT (Computed Tomography). Electromagnetic tracking utilizes miniature sensors integrated with RFA equipment to guide tools in real-time, while referencing to pre-procedure imaging. This technology was demonstrated successfully during a lung tumor ablation, and was more accurate at targeting the tumor, compared to traditional freehand needle insertion. It is possible, although speculative and anecdotal, that more accuracy could prevent unnecessary repositioning punctures and decrease radiation exposure. Electromagnetic tracking has theoretical potential to benefit minimally invasive interventions. PMID:23207535

EEG low-resolution brain electromagnetic tomography (LORETA) in Huntington's disease.

PubMed

Painold, Annamaria; Anderer, Peter; Holl, Anna K; Letmaier, Martin; Saletu-Zyhlarz, Gerda M; Saletu, Bernd; Bonelli, Raphael M

2011-05-01

Previous studies have shown abnormal electroencephalography (EEG) in Huntington's disease (HD). The aim of the present investigation was to compare quantitatively analyzed EEGs of HD patients and controls by means of low-resolution brain electromagnetic tomography (LORETA). Further aims were to delineate the sensitivity and utility of EEG LORETA in the progression of HD, and to correlate parameters of cognitive and motor impairment with neurophysiological variables. In 55 HD patients and 55 controls a 3-min vigilance-controlled EEG (V-EEG) was recorded during midmorning hours. Power spectra and intracortical tomography were computed by LORETA in seven frequency bands and compared between groups. Spearman rank correlations were based on V-EEG and psychometric data. Statistical overall analysis by means of the omnibus significance test demonstrated significant (p < 0.01) differences between HD patients and controls. LORETA theta, alpha and beta power were decreased from early to late stages of the disease. Only advanced disease stages showed a significant increase in delta power, mainly in the right orbitofrontal cortex. Correlation analyses revealed that a decrease of alpha and theta power correlated significantly with increasing cognitive and motor decline. LORETA proved to be a sensitive instrument for detecting progressive electrophysiological changes in HD. Reduced alpha power seems to be a trait marker of HD, whereas increased prefrontal delta power seems to reflect worsening of the disease. Motor function and cognitive function deteriorate together with a decrease in alpha and theta power. This data set, so far the largest in HD research, helps to elucidate remaining uncertainties about electrophysiological abnormalities in HD.

Low-resolution electromagnetic brain tomography (LORETA) of monozygotic twins discordant for chronic fatigue syndrome.

PubMed

Sherlin, Leslie; Budzynski, Thomas; Kogan Budzynski, Helen; Congedo, Marco; Fischer, Mary E; Buchwald, Dedra

2007-02-15

Previous work using quantified EEG has suggested that brain activity in individuals with chronic fatigue syndrome (CFS) and normal persons differs. Our objective was to investigate if specific frequency band-pass regions and spatial locations are associated with CFS using low-resolution electromagnetic brain tomography (LORETA). We conducted a co-twin control study of 17 pairs of monozygotic twins where 1 twin met criteria for CFS and the co-twin was healthy. Twins underwent an extensive battery of tests including a structured psychiatric interview and a quantified EEG. Eyes closed EEG frequency-domain analysis was computed and the entire brain volume was compared of the CFS and healthy twins using a multiple comparison procedure. Compared with their healthy co-twins, twins with CFS differed in current source density. The CFS twins had higher delta in the left uncus and parahippocampal gyrus and higher theta in the cingulate gyrus and right superior frontal gyrus. These findings suggest that neurophysiological activity in specific areas of the brain may differentiate individuals with CFS from those in good health. The study corroborates that slowing of the deeper structures of the limbic system is associated with affect. It also supports the neurobiological model that the right forebrain is associated with sympathetic activity and the left forebrain with the effective management of energy. These preliminary findings await replication.

Fourier phase in Fourier-domain optical coherence tomography

PubMed Central

Uttam, Shikhar; Liu, Yang

2015-01-01

Phase of an electromagnetic wave propagating through a sample-of-interest is well understood in the context of quantitative phase imaging in transmission-mode microscopy. In the past decade, Fourier-domain optical coherence tomography has been used to extend quantitative phase imaging to the reflection-mode. Unlike transmission-mode electromagnetic phase, however, the origin and characteristics of reflection-mode Fourier phase are poorly understood, especially in samples with a slowly varying refractive index. In this paper, the general theory of Fourier phase from first principles is presented, and it is shown that Fourier phase is a joint estimate of subresolution offset and mean spatial frequency of the coherence-gated sample refractive index. It is also shown that both spectral-domain phase microscopy and depth-resolved spatial-domain low-coherence quantitative phase microscopy are special cases of this general theory. Analytical expressions are provided for both, and simulations are presented to explain and support the theoretical results. These results are further used to show how Fourier phase allows the estimation of an axial mean spatial frequency profile of the sample, along with depth-resolved characterization of localized optical density change and sample heterogeneity. Finally, a Fourier phase-based explanation of Doppler optical coherence tomography is also provided. PMID:26831383

Electromagnetic navigation diagnostic bronchoscopy for small peripheral lung lesions.

PubMed

Makris, D; Scherpereel, A; Leroy, S; Bouchindhomme, B; Faivre, J-B; Remy, J; Ramon, P; Marquette, C-H

2007-06-01

The present study prospectively evaluated the diagnostic yield and safety of electromagnetic navigation-guided bronchoscopy biopsy, for small peripheral lung lesions in patients where standard techniques were nondiagnostic. The study was conducted in a tertiary medical centre on 40 consecutive patients considered unsuitable for straightforward surgery or computed tomography (CT)-guided transthoracic needle aspiration biopsy, due to comorbidities. The lung lesion diameter was mean+/-sem 23.5+/-1.5 mm and the depth from the visceral-costal pleura was 14.9+/-2 mm. Navigation was facilitated by an electromagnetic tracking system which could detect a position sensor incorporated into a flexible catheter advanced through a bronchoscope. Information obtained during bronchoscopy was superimposed on previously acquired CT data. Divergence between CT data and data obtained during bronchoscopy was calculated by the system's software as a measure of navigational accuracy. All but one of the target lesions was reached and the overall diagnostic yield was 62.5% (25-40). Diagnostic yield was significantly affected by CT-to-body divergence; yield was 77.2% when estimated divergence was

Long-Term Effects of Concussion on Electrophysiological Indices of Attention in Varsity College Athletes: An Event-Related Potential and Standardized Low-Resolution Brain Electromagnetic Tomography Approach.

PubMed

Ledwidge, Patrick S; Molfese, Dennis L

2016-12-01

This study investigated the effects of a past concussion on electrophysiological indices of attention in college athletes. Forty-four varsity football athletes (22 with at least one past concussion) participated in three neuropsychological tests and a two-tone auditory oddball task while undergoing high-density event-related potential (ERP) recording. Athletes previously diagnosed with a concussion experienced their most recent injury approximately 4 years before testing. Previously concussed and control athletes performed equivalently on three neuropsychological tests. Behavioral accuracy and reaction times on the oddball task were also equivalent across groups. However, athletes with a concussion history exhibited significantly larger N2 and P3b amplitudes and longer P3b latencies. Source localization using standardized low-resolution brain electromagnetic tomography indicated that athletes with a history of concussion generated larger electrical current density in the left inferior parietal gyrus compared to control athletes. These findings support the hypothesis that individuals with a past concussion recruit compensatory neural resources in order to meet executive functioning demands. High-density ERP measures combined with source localization provide an important method to detect long-term neural consequences of concussion in the absence of impaired neuropsychological performance.

Long-Term Effects of Concussion on Electrophysiological Indices of Attention in Varsity College Athletes: An Event-Related Potential and Standardized Low-Resolution Brain Electromagnetic Tomography Approach

PubMed Central

Molfese, Dennis L.

2016-01-01

Abstract This study investigated the effects of a past concussion on electrophysiological indices of attention in college athletes. Forty-four varsity football athletes (22 with at least one past concussion) participated in three neuropsychological tests and a two-tone auditory oddball task while undergoing high-density event-related potential (ERP) recording. Athletes previously diagnosed with a concussion experienced their most recent injury approximately 4 years before testing. Previously concussed and control athletes performed equivalently on three neuropsychological tests. Behavioral accuracy and reaction times on the oddball task were also equivalent across groups. However, athletes with a concussion history exhibited significantly larger N2 and P3b amplitudes and longer P3b latencies. Source localization using standardized low-resolution brain electromagnetic tomography indicated that athletes with a history of concussion generated larger electrical current density in the left inferior parietal gyrus compared to control athletes. These findings support the hypothesis that individuals with a past concussion recruit compensatory neural resources in order to meet executive functioning demands. High-density ERP measures combined with source localization provide an important method to detect long-term neural consequences of concussion in the absence of impaired neuropsychological performance. PMID:27025905

Diagnostic Imaging and Newer Modalities for Thoracic Diseases: PET/Computed Tomographic Imaging and Endobronchial Ultrasound for Staging and Its Implication for Lung Cancer.

PubMed

Counts, Sarah J; Kim, Anthony W

2017-08-01

Modalities to detect and characterize lung cancer are generally divided into those that are invasive [endobronchial ultrasound (EBUS), esophageal ultrasound (EUS), and electromagnetic navigational bronchoscopy (ENMB)] versus noninvasive [chest radiography (CXR), computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI)]. This chapter describes these modalities, the literature supporting their use, and delineates what tests to use to best evaluate the patient with lung cancer. Copyright © 2017 Elsevier Inc. All rights reserved.

Near-Field Resonance Microwave Tomography and Holography

NASA Astrophysics Data System (ADS)

Gaikovich, K. P.; Smirnov, A. I.; Yanin, D. V.

2018-02-01

We develop the methods of electromagnetic computer near-field microwave tomography of distributed subsurface inhomogeneities of complex dielectric permittivity and of holography (shape retrieval) of internally homogeneous subsurface objects. The methods are based on the solution of the near-field inverse scattering problem from measurements of the resonance-parameter variations of microwave probes above the medium surface. The capabilities of the proposed diagnostic technique are demonstrated in the numerical simulation for sensors with a cylindrical capacitor as a probe element, the edge capacitance of which is sensitive to subsurface inhomogeneities.

Electromagnetic Navigation Diagnostic Bronchoscopy

PubMed Central

Gildea, Thomas R.; Mazzone, Peter J.; Karnak, Demet; Meziane, Moulay; Mehta, Atul C.

2006-01-01

Rationale: Electromagnetic navigation bronchoscopy using superDimension/Bronchus System is a novel method to increase diagnostic yield of peripheral and mediastinal lung lesions. Objectives: A prospective, open label, single-center, pilot study was conducted to determine the ability of electromagnetic navigation bronchoscopy to sample peripheral lung lesions and mediastinal lymph nodes with standard bronchoscopic instruments and demonstrate safety. Methods: Electromagnetic navigation bronchoscopy was performed using the superDimension/Bronchus system consisting of electromagnetic board, position sensor encapsulated in the tip of a steerable probe, extended working channel, and real-time reconstruction of previously acquired multiplanar computed tomography images. The final distance of the steerable probe to lesion, expected error based on the actual and virtual markers, and procedure yield was gathered. Measurements: 60 subjects were enrolled between December 2004 and September 2005. Mean navigation times were 7 ± 6 min and 2 ± 2 min for peripheral lesions and lymph nodes, respectively. The steerable probe tip was navigated to the target lung area in all cases. The mean peripheral lesions and lymph nodes size was 22.8 ± 12.6 mm and 28.1 ± 12.8 mm. Yield was determined by results obtained during the bronchoscopy per patient. Results: The yield/procedure was 74% and 100% for peripheral lesions and lymph nodes, respectively. A diagnosis was obtained in 80.3% of bronchoscopic procedures. A definitive diagnosis of lung malignancy was made in 74.4% of subjects. Pneumothorax occurred in two subjects. Conclusion: Electromagnetic navigation bronchoscopy is a safe method for sampling peripheral and mediastinal lesions with high diagnostic yield independent of lesion size and location. PMID:16873767

Imaging biological tissues with electrical conductivity contrast below 1 S m−1 by means of magnetoacoustic tomography with magnetic induction

PubMed Central

Hu, Gang; Li, Xu; He, Bin

2010-01-01

Magnetoacoustic tomography with magnetic induction (MAT-MI) is a recently introduced imaging modality for noninvasive electrical impedance imaging, with ultrasound imaging resolution and a contrast reflecting the electrical conductivity properties of tissues. However, previous MAT-MI systems can only image samples that are much more conductive than real human or animal tissues. To image real biological tissue samples, a large-current-carrying coil that can give stronger magnetic stimulations and stronger MAT-MI acoustic signals is employed in this study. The conductivity values of all the tissue samples employed in this study are also directly measured using a well calibrated four-electrode system. The experimental results demonstrated the feasibility to image biological tissues with electrical conductivity contrast below 1.0 S∕m using the MAT-MI technique with safe level of electromagnetic energy applied to tissue samples. PMID:20938494

Imaging biological tissues with electrical conductivity contrast below 1 S m-1 by means of magnetoacoustic tomography with magnetic induction

NASA Astrophysics Data System (ADS)

Hu, Gang; Li, Xu; He, Bin

2010-09-01

Magnetoacoustic tomography with magnetic induction (MAT-MI) is a recently introduced imaging modality for noninvasive electrical impedance imaging, with ultrasound imaging resolution and a contrast reflecting the electrical conductivity properties of tissues. However, previous MAT-MI systems can only image samples that are much more conductive than real human or animal tissues. To image real biological tissue samples, a large-current-carrying coil that can give stronger magnetic stimulations and stronger MAT-MI acoustic signals is employed in this study. The conductivity values of all the tissue samples employed in this study are also directly measured using a well calibrated four-electrode system. The experimental results demonstrated the feasibility to image biological tissues with electrical conductivity contrast below 1.0 S/m using the MAT-MI technique with safe level of electromagnetic energy applied to tissue samples.

A Quantum Field Approach for Advancing Optical Coherence Tomography Part I: First Order Correlations, Single Photon Interference, and Quantum Noise

PubMed Central

Brezinski, ME

2018-01-01

Optical coherence tomography has become an important imaging technology in cardiology and ophthalmology, with other applications under investigations. Major advances in optical coherence tomography (OCT) imaging are likely to occur through a quantum field approach to the technology. In this paper, which is the first part in a series on the topic, the quantum basis of OCT first order correlations is expressed in terms of full field quantization. Specifically first order correlations are treated as the linear sum of single photon interferences along indistinguishable paths. Photons and the electromagnetic (EM) field are described in terms of quantum harmonic oscillators. While the author feels the study of quantum second order correlations will lead to greater paradigm shifts in the field, addressed in part II, advances from the study of quantum first order correlations are given. In particular, ranging errors are discussed (with remedies) from vacuum fluctuations through the detector port, photon counting errors, and position probability amplitude uncertainty. In addition, the principles of quantum field theory and first order correlations are needed for studying second order correlations in part II. PMID:29863177

Transbronchial needle aspiration with a new electromagnetically-tracked TBNA needle

NASA Astrophysics Data System (ADS)

Choi, Jae; Popa, Teo; Gruionu, Lucian

2009-02-01

Transbronchial needle aspiration (TBNA) is a common method used to collect tissue for diagnosis of different chest diseases and for staging lung cancer, but the procedure has technical limitations. These limitations are mostly related to the difficulty of accurately placing the biopsy needles into the target mass. Currently, pulmonologists plan TBNA by examining a number of Computed Tomography (CT) scan slices before the operation. Then, they manipulate the bronchoscope down the respiratory track and blindly direct the biopsy. Thus, the biopsy success rate is low. The diagnostic yield of TBNA is approximately 70 percent. To enhance the accuracy of TBNA, we developed a TBNA needle with a tip position that can be electromagnetically tracked. The needle was used to estimate the bronchoscope's tip position and enable the creation of corresponding virtual bronchoscopic images from a preoperative CT scan. The TBNA needle was made with a flexible catheter embedding Wang Transbronchial Histology Needle and a sensor tracked by electromagnetic field generator. We used Aurora system for electromagnetic tracking. We also constructed an image-guided research prototype system incorporating the needle and providing a user-friendly interface to assist the pulmonologist in targeting lesions. To test the feasibility of the accuracy of the newly developed electromagnetically-tracked needle, a phantom study was conducted in the interventional suite at Georgetown University Hospital. Five TBNA simulations with a custom-made phantom with a bronchial tree were performed. The experimental results show that our device has potential to enhance the accuracy of TBNA.

Modafinil improves information processing speed and increases energetic resources for orientation of attention in narcoleptics: double-blind, placebo-controlled ERP studies with low-resolution brain electromagnetic tomography (LORETA).

PubMed

Saletu, Michael; Anderer, Peter; Saletu-Zyhlarz, Gerda Maria; Mandl, Magdalena; Saletu, Bernd; Zeitlhofer, Josef

2009-09-01

Recent neuroimaging studies in narcolepsy discovered significant gray matter loss in the right prefrontal and frontomesial cortex, a critical region for executive processing. In the present study, event-related potential (ERP) low-resolution brain electromagnetic tomography (LORETA) was used to investigate cognition before and after modafinil as compared with placebo. In a double-blind, placebo-controlled cross-over design, 15 patients were treated with a 3-week fixed titration scheme of modafinil and placebo. The Epworth Sleepiness Scale (ESS), Maintenance of Wakefulness Test (MWT) and auditory ERPs (odd-ball paradigm) were obtained before and after the 3 weeks of therapy. Latencies, amplitudes and LORETA sources were determined for standard (N1 and P2) and target (N2 and P300) ERP components. The ESS score improved significantly from 15.4 (+/- 4.0) under placebo to 10.2 (+/- 4.1) under 400mg modafinil (p=0.004). In the MWT, latency to sleep increased nonsignificantly after modafinil treatment (11.9+/-6.9 versus 13.3+/-7.1 min). In the ERP, N2 and P300 latencies were shortened significantly. While ERP amplitudes showed only minor changes, LORETA revealed increased source strengths: for N1 in the left auditory cortex and for P300 in the medial and right dorsolateral prefrontal cortex. LORETA revealed that modafinil improved information processing speed and increased energetic resources in prefrontal cortical regions, which is in agreement with other neuroimaging studies.

Electromagnetic induction imaging with a radio-frequency atomic magnetometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deans, Cameron; Marmugi, Luca, E-mail: l.marmugi@ucl.ac.uk; Hussain, Sarah

2016-03-07

We report on a compact, tunable, and scalable to large arrays imaging device, based on a radio-frequency optically pumped atomic magnetometer operating in magnetic induction tomography modality. Imaging of conductive objects is performed at room temperature, in an unshielded environment and without background subtraction. Conductivity maps of target objects exhibit not only excellent performance in terms of shape reconstruction but also demonstrate detection of sub-millimetric cracks and penetration of conductive barriers. The results presented here demonstrate the potential of a future generation of imaging instruments, which combine magnetic induction tomography and the unmatched performance of atomic magnetometers.

Invisibility Cloak Printed on a Photonic Chip

PubMed Central

Feng, Zhen; Wu, Bing-Hong; Zhao, Yu-Xi; Gao, Jun; Qiao, Lu-Feng; Yang, Ai-Lin; Lin, Xiao-Feng; Jin, Xian-Min

2016-01-01

Invisibility cloak capable of hiding an object can be achieved by properly manipulating electromagnetic field. Such a remarkable ability has been shown in transformation and ray optics. Alternatively, it may be realistic to create a spatial cloak by means of confining electromagnetic field in three-dimensional arrayed waveguides and introducing appropriate collective curvature surrounding an object. We realize the artificial structure in borosilicate by femtosecond laser direct writing, where we prototype up to 5,000 waveguides to conceal millimeter-scale volume. We characterize the performance of the cloak by normalized cross correlation, tomography analysis and continuous three-dimensional viewing angle scan. Our results show invisibility cloak can be achieved in waveguide optics. Furthermore, directly printed invisibility cloak on a photonic chip may enable controllable study and novel applications in classical and quantum integrated photonics, such as invisualising a coupling or swapping operation with on-chip circuits of their own. PMID:27329510

Invisibility Cloak Printed on a Photonic Chip

NASA Astrophysics Data System (ADS)

Feng, Zhen; Wu, Bing-Hong; Zhao, Yu-Xi; Gao, Jun; Qiao, Lu-Feng; Yang, Ai-Lin; Lin, Xiao-Feng; Jin, Xian-Min

2016-06-01

Invisibility cloak capable of hiding an object can be achieved by properly manipulating electromagnetic field. Such a remarkable ability has been shown in transformation and ray optics. Alternatively, it may be realistic to create a spatial cloak by means of confining electromagnetic field in three-dimensional arrayed waveguides and introducing appropriate collective curvature surrounding an object. We realize the artificial structure in borosilicate by femtosecond laser direct writing, where we prototype up to 5,000 waveguides to conceal millimeter-scale volume. We characterize the performance of the cloak by normalized cross correlation, tomography analysis and continuous three-dimensional viewing angle scan. Our results show invisibility cloak can be achieved in waveguide optics. Furthermore, directly printed invisibility cloak on a photonic chip may enable controllable study and novel applications in classical and quantum integrated photonics, such as invisualising a coupling or swapping operation with on-chip circuits of their own.

Brain Oscillatory Activity during Spatial Navigation: Theta and Gamma Activity Link Medial Temporal and Parietal Regions

ERIC Educational Resources Information Center

White, David J.; Congedo, Marco; Ciorciari, Joseph; Silberstein, Richard B.

2012-01-01

Brain oscillatory correlates of spatial navigation were investigated using blind source separation (BSS) and standardized low resolution electromagnetic tomography (sLORETA) analyses of 62-channel EEG recordings. Twenty-five participants were instructed to navigate to distinct landmark buildings in a previously learned virtual reality town…

EEG mapping and low-resolution brain electromagnetic tomography (LORETA) in diagnosis and therapy of psychiatric disorders: evidence for a key-lock principle.

PubMed

Saletu, Bernd; Anderer, Peter; Saletu-Zyhlarz, Gerda M; Pascual-Marqui, Roberto D

2005-04-01

Different psychiatric disorders, such as schizophrenia with predominantly positive and negative symptomatology, major depression, generalized anxiety disorder, agoraphobia, obsessive-compulsive disorder, multi-infarct dementia, senile dementia of the Alzheimer type and alcohol dependence, show EEG maps that differ statistically both from each other and from normal controls. Representative drugs of the main psychopharmacological classes, such as sedative and non-sedative neuroleptics and antidepressants, tranquilizers, hypnotics, psychostimulants and cognition-enhancing drugs, induce significant and typical changes to normal human brain function, which in many variables are opposite to the above-mentioned differences between psychiatric patients and normal controls. Thus, by considering these differences between psychotropic drugs and placebo in normal subjects, as well as between mental disorder patients and normal controls, it may be possible to choose the optimum drug for a specific patient according to a key-lock principle, since the drug should normalize the deviant brain function. This is supported by 3-dimensional low-resolution brain electromagnetic tomography (LORETA), which identifies regions within the brain that are affected by psychiatric disorders and psychopharmacological substances.

Volumetric full-range magnetomotive optical coherence tomography

PubMed Central

Ahmad, Adeel; Kim, Jongsik; Shemonski, Nathan D.; Marjanovic, Marina; Boppart, Stephen A.

2014-01-01

Abstract. Magnetomotive optical coherence tomography (MM-OCT) can be utilized to spatially localize the presence of magnetic particles within tissues or organs. These magnetic particle-containing regions are detected by using the capability of OCT to measure small-scale displacements induced by the activation of an external electromagnet coil typically driven by a harmonic excitation signal. The constraints imposed by the scanning schemes employed and tissue viscoelastic properties limit the speed at which conventional MM-OCT data can be acquired. Realizing that electromagnet coils can be designed to exert MM force on relatively large tissue volumes (comparable or larger than typical OCT imaging fields of view), we show that an order-of-magnitude improvement in three-dimensional (3-D) MM-OCT imaging speed can be achieved by rapid acquisition of a volumetric scan during the activation of the coil. Furthermore, we show volumetric (3-D) MM-OCT imaging over a large imaging depth range by combining this volumetric scan scheme with full-range OCT. Results with tissue equivalent phantoms and a biological tissue are shown to demonstrate this technique. PMID:25472770

Source localization of small sharp spikes: low resolution electromagnetic tomography (LORETA) reveals two distinct cortical sources.

PubMed

Zumsteg, Dominik; Andrade, Danielle M; Wennberg, Richard A

2006-06-01

We have investigated the cortical sources and electroencephalographic (EEG) characteristics of small sharp spikes (SSS) by using statistical non-parametric mapping (SNPM) of low resolution electromagnetic tomography (LORETA). We analyzed 7 SSS patterns (501 individual SSS) in 6 patients who underwent sleep EEG studies with 29 or 23 scalp electrodes. The scalp signals were averaged time-locked to the SSS peak activity and subjected to SNPM of LORETA values. All 7 SSS patterns (mean 72 individual SSS, range 11-200) revealed a very similar and highly characteristic transhemispheric oblique scalp voltage distribution comprising a first negative field maximum over ipsilateral lateral temporal areas, followed by a second negative field maximum over the contralateral subtemporal region approximately 30 ms later. SNPM-LORETA consistently localized the first component into the ipsilateral posterior insular region, and the second component into ipsilateral posterior mesial temporo-occipital structures. SSS comprise an amalgam of two sequential, distinct cortical components, showing a very uniform and peculiar EEG pattern and cortical source solutions. As such, they must be clearly distinguished from interictal epileptiform discharges in patients with epilepsy. The awareness of these peculiar EEG characteristics may increase our ability to differentiate SSS from interictal epileptiform activity. The finding of a posterior insular source might serve as an inspiration for new physiological considerations regarding these enigmatic waveforms.

Quantitative EEG and Low-Resolution Electromagnetic Tomography (LORETA) Imaging of Patients Undergoing Methadone Treatment for Opiate Addiction.

PubMed

Wang, Grace Y; Kydd, Robert R; Russell, Bruce R

2016-07-01

Methadone maintenance treatment (MMT) has been used as a treatment for opiate dependence since the mid-1960s. Evidence suggests that methadone binds to mu opiate receptors as do other opiates and induces changes in neurophysiological function. However, little is known, about how neural activity within the higher frequency gamma band (>30 Hz) while at rest changes in those stabilized on MMT despite its association with the excitation-inhibition balance within pyramidal-interneuron networks. Our study investigated differences in resting gamma power (37-41 Hz) between patients undergoing MMT for opiate dependence, illicit opiate users, and healthy controls subjects. Electroencephalographic data were recorded from 26 sites according to the international 10-20 system. Compared with the healthy controls subjects, people either undergoing MMT (mean difference [MD] = 0.32, 95% CI = 0.09-0.55, P < .01) or currently using illicit opiates (MD = 0.31, 95% CI = 0.06-0.56, P = .01) exhibited significant increased gamma power. The sLORETA (standardized low-resolution electromagnetic tomography) between-group comparison revealed dysfunctional neuronal activity in the occipital, parietal, and frontal lobes in the patients undergoing MMT. A more severe profile of dysfunction was observed in those using illicit opiates. Our findings suggest that long-term exposure to opioids is associated with disrupted resting state network, which may be reduced after MMT. © EEG and Clinical Neuroscience Society (ECNS) 2015.

Electrocortical Reactivity During Self-referential Processing in Female Youth With Borderline Personality Disorder.

PubMed

Auerbach, Randy P; Tarlow, Naomi; Bondy, Erin; Stewart, Jeremy G; Aguirre, Blaise; Kaplan, Cynthia; Yang, Wenhui; Pizzagalli, Diego A

2016-07-01

Borderline personality disorder (BPD) is debilitating, and theoretical models have postulated that cognitive-affective biases contribute to the onset and maintenance of BPD symptoms. Despite advances, our understanding of BPD pathophysiology in youth is limited. The present study used event-related potentials (ERPs) to identify cognitive-affective processes that underlie negative self-referential processing in BPD youth. Healthy females ( n = 33) and females with BPD ( n = 26) 13 to 22 years of age completed a self-referential encoding task while 128-channel electroencephalography data were recorded to examine early (i.e., P1 and P2) and late (late positive potential [LPP]) ERP components. Whole-brain standardized low-resolution electromagnetic tomography explored intracortical sources underlying significant scalp ERP effects. Compared to healthy females, participants with BPD endorsed, recalled, and recognized fewer positive and more negative words. Moreover, unlike the healthy group, females with BPD had faster reaction times to endorse negative versus positive words. In the scalp ERP analyses, the BPD group had greater P2 and late LPP positivity to negative as opposed to positive words. For P2 and late LPP, whole-brain standardized low-resolution electromagnetic tomography analyses suggested that females with BPD overrecruit frontolimbic circuitry in response to negative stimuli. Collectively, these findings show that females with BPD process negative self-relevant information differently than healthy females. Clinical implications and future directions are discussed.

Electrocortical Reactivity During Self-referential Processing in Female Youth With Borderline Personality Disorder

PubMed Central

Auerbach, Randy P.; Tarlow, Naomi; Bondy, Erin; Stewart, Jeremy G.; Aguirre, Blaise; Kaplan, Cynthia; Yang, Wenhui; Pizzagalli, Diego A.

2016-01-01

BACKGROUND Borderline personality disorder (BPD) is debilitating, and theoretical models have postulated that cognitive-affective biases contribute to the onset and maintenance of BPD symptoms. Despite advances, our understanding of BPD pathophysiology in youth is limited. The present study used event-related potentials (ERPs) to identify cognitive-affective processes that underlie negative self-referential processing in BPD youth. METHODS Healthy females (n = 33) and females with BPD (n = 26) 13 to 22 years of age completed a self-referential encoding task while 128-channel electroencephalography data were recorded to examine early (i.e., P1 and P2) and late (late positive potential [LPP]) ERP components. Whole-brain standardized low-resolution electromagnetic tomography explored intracortical sources underlying significant scalp ERP effects. RESULTS Compared to healthy females, participants with BPD endorsed, recalled, and recognized fewer positive and more negative words. Moreover, unlike the healthy group, females with BPD had faster reaction times to endorse negative versus positive words. In the scalp ERP analyses, the BPD group had greater P2 and late LPP positivity to negative as opposed to positive words. For P2 and late LPP, whole-brain standardized low-resolution electromagnetic tomography analyses suggested that females with BPD overrecruit frontolimbic circuitry in response to negative stimuli. CONCLUSIONS Collectively, these findings show that females with BPD process negative self-relevant information differently than healthy females. Clinical implications and future directions are discussed. PMID:28626812

Transperineal ultrasound-guided implantation of electromagnetic transponders in the prostatic fossa for localization and tracking during external beam radiation therapy.

PubMed

Garsa, Adam A; Verma, Vivek; Michalski, Jeff M; Gay, Hiram A

2014-01-01

To describe a transperineal ultrasound-guided technique for implantation of electromagnetic transponders into the prostatic fossa. Patients were placed in the dorsal lithotomy position, and local anesthetic was administered. On ultrasound, the bladder, urethra, vesicourethral anastomosis, rectum, and the prostatic fossa were carefully identified. Three transponders were implanted into the prostatic fossa under ultrasound guidance in a triangular configuration and implantation was verified by fluoroscopy. Patients underwent computed tomography (CT) simulation approximately 1 week later. All patients in this study were subsequently treated with intensity modulated radiation therapy (IMRT) to the prostatic fossa. From 2008 to 2012, 180 patients received transperineal implantation of electromagnetic transponders into the prostatic fossa and subsequently received IMRT. There were no cases of severe hematuria or rectal bleeding requiring intervention. There were no grade 3 or 4 toxicities. Three patients (1.7%) had a transponder missing on the subsequent CT simulation. Thirteen patients (7.3%) had transponder migration with a geometric residual that exceeded 2 mm for 3 consecutive days (5.6%) or rotation that exceeded 10 degrees for 5 consecutive days (1.7%). These patients underwent a resimulation CT scan to identify the new transponder coordinates. A transperineal technique for implantation of electromagnetic transponders into the prostatic fossa is safe and well tolerated, with no severe toxicity after implantation. There is a low rate of transponder loss or migration.

Functional brain MRI in patients complaining of electrohypersensitivity after long term exposure to electromagnetic fields.

PubMed

Heuser, Gunnar; Heuser, Sylvia A

2017-09-26

Ten adult patients with electromagnetic hypersensitivity underwent functional magnetic resonance imaging (fMRI) brain scans. All scans were abnormal with abnormalities which were consistent and similar. It is proposed that fMRI brain scans be used as a diagnostic aid for determining whether or not a patient has electromagnetic hypersensitivity. Over the years we have seen an increasing number of patients who had developed multi system complaints after long term repeated exposure to electromagnetic fields (EMFs). These complaints included headaches, intermittent cognitive and memory problems, intermittent disorientation, and also sensitivity to EMF exposure. Regular laboratory tests were within normal limits in these patients. The patients refused to be exposed to radioactivity. This of course ruled out positron emission tomography (PET) and single-photon emission computed tomography (SPECT) brain scanning. This is why we ordered fMRI brain scans on these patients. We hoped that we could document objective abnormalities in these patients who had often been labeled as psychiatric cases. Ten patients first underwent a regular magnetic resonance imaging (MRI) brain scan, using a 3 Tesla Siemens Verio MRI open system. A functional MRI study was then performed in the resting state using the following sequences: A three-dimensional, T1-weighted, gradient-echo (MPRAGE) Resting state network. The echo-planar imaging (EPI) sequences for this resting state blood oxygenation level dependent (BOLD) scan were then post processed on a 3D workstation and the independent component analysis was performed separating out the various networks. Arterial spin labeling. Tractography and fractional anisotropy. All ten patients had abnormal functional MRI brain scans. The abnormality was often described as hyper connectivity of the anterior component of the default mode in the medial orbitofrontal area. Other abnormalities were usually found. Regular MRI studies of the brain were mostly unremarkable in these patients. We propose that functional MRI studies should become a diagnostic aid when evaluating a patient who claims electrohypersensitivity (EHS) and has otherwise normal studies. Interestingly, the differential diagnosis for the abnormalities seen on the fMRI includes head injury. It turns out that many of our patients indeed had a history of head injury which was then followed sometime later by the development of EHS. Many of our patients also had a history of exposure to potentially neurotoxic chemicals, especially mold. Head injury and neurotoxic chemical exposure may make a patient more vulnerable to develop EHS.

New Prospecting Standarts and Its Comparison with International Regulations in Sinkhole and Cave Investigations

NASA Astrophysics Data System (ADS)

Karabulut, S.; Cengiz Cinku, M.; Tezel, O.

2016-12-01

The aim of this study is to investigate the prospecting standarts in sinkhole and cave characterization comparing it with the present standarts given by the American Society for Testing and Materials (ASTM) and the British Standart (BSI). Cave and sinkholes which are important geological occurences could cause hazard and collapse of the ground where residental areas could be under risk. The depth of sinkholes could reach up to hundreds of meters and their width to tens of meters. Most caves which are under conserve and characterized as a natural protected area, a non-destructive investigation is required which is only undertaken by geophysical applications. Two different type of standarts are given in the literature to investigate this kind of geological occurences. The first is the ASTM (1999) standart which offers to use Gravity/Microgravity, Ground Penetrating Radar (GPR) and Electromagnetic, while the BSI standart (1999) depends on the initial application of GPR, Electromagnetic, Electrical Resistivity and Crosshole Seismic. In Turkey however, there are limited studies in cave/sinkhole detection and no standartization in prospecting is presented. For this purpose, we applied a geophysical study in the Yarımburgaz cave, Istanbul/Turkey. In the scope of this study, Microgravity, Electric Tomography, Tomography of Seismic Refraction and Surface Wave Analysis, GPR and Microtremor methods are applied on four different profiles. It has been shown that the outputs of the methods differ as a result of the climatic conditions, properties of the geological environment and the depth/size/shape of the sinkhole/cave. Besides this, the area of application which is either inside the city center, steep valley or on the sea/streamside show also discrepancy in the order of preference of the geophysical application methods when considering the anomalies on different mediums. The results obtained from GPR are deep in relation with the thickness of the clayey unit, the water content of the medium and the thickness of the cave/sinkhole. Microgravity, GPR and Microtremor measurements were applied successfull and easily in the inner-city, while Electric Tomography, Seismic Refraction and MASW Methods showed reliable results which are obtained rapidly.

Computed tomography image using sub-terahertz waves generated from a high-T{sub c} superconducting intrinsic Josephson junction oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashiwagi, T., E-mail: kashiwagi@ims.tsukuba.ac.jp; Minami, H.; Kadowaki, K.

2014-02-24

A computed tomography (CT) imaging system using monochromatic sub-terahertz coherent electromagnetic waves generated from a device constructed from the intrinsic Josephson junctions in a single crystalline mesa structure of the high-T{sub c} superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} was developed and tested on three samples: Standing metallic rods supported by styrofoam, a dried plant (heart pea) containing seeds, and a plastic doll inside an egg shell. The images obtained strongly suggest that this CT imaging system may be useful for a variety of practical applications.

Effect of Mobile Phone-Induced Electromagnetic Field on Brain Hemodynamics and Human Stem Cell Functioning: Possible Mechanistic Link to Cancer Risk and Early Diagnostic Value of Electronphotonic Imaging.

PubMed

Bhargav, Hemant; Srinivasan, T M; Varambally, S; Gangadhar, B N; Koka, Prasad

2015-01-01

The mobile phones (MP) are low power radio devices which work on electromagnetic fields (EMFs), in the frequency range of 900-1800 MHz. Exposure to MPEMFs may affect brain physiology and lead to various health hazards including brain tumors. Earlier studies with positron emission tomography (PET) have found alterations in cerebral blood flow (CBF) after acute exposure to MPEMFs. It is widely accepted that DNA double-strand breaks (DSBs) and their misrepair in stem cells are critical events in the multistage origination of various leukemia and tumors, including brain tumors such as gliomas. Both significant misbalance in DSB repair and severe stress response have been triggered by MPEMFs and EMFs from cell towers. It has been shown that stem cells are most sensitive to microwave exposure and react to more frequencies than do differentiated cells. This may be important for cancer risk assessment and indicates that stem cells are the most relevant cellular model for validating safe mobile communication signals. Recently developed technology for recording the human bio-electromagnetic (BEM) field using Electron photonic Imaging (EPI) or Gas Discharge Visualisation (GDV) technique provides useful information about the human BEM. Studies have recorded acute effects of Mobile Phone Electromagnetic Fields (MPEMFs) using EPI and found quantifiable effects on human BEM field. Present manuscript reviews evidences of altered brain physiology and stem cell functioning due to mobile phone/cell tower radiations, its association with increased cancer risk and explores early diagnostic value of EPI imaging in detecting EMF induced changes on human BEM.

Development of computational small animal models and their applications in preclinical imaging and therapy research.

PubMed

Xie, Tianwu; Zaidi, Habib

2016-01-01

The development of multimodality preclinical imaging techniques and the rapid growth of realistic computer simulation tools have promoted the construction and application of computational laboratory animal models in preclinical research. Since the early 1990s, over 120 realistic computational animal models have been reported in the literature and used as surrogates to characterize the anatomy of actual animals for the simulation of preclinical studies involving the use of bioluminescence tomography, fluorescence molecular tomography, positron emission tomography, single-photon emission computed tomography, microcomputed tomography, magnetic resonance imaging, and optical imaging. Other applications include electromagnetic field simulation, ionizing and nonionizing radiation dosimetry, and the development and evaluation of new methodologies for multimodality image coregistration, segmentation, and reconstruction of small animal images. This paper provides a comprehensive review of the history and fundamental technologies used for the development of computational small animal models with a particular focus on their application in preclinical imaging as well as nonionizing and ionizing radiation dosimetry calculations. An overview of the overall process involved in the design of these models, including the fundamental elements used for the construction of different types of computational models, the identification of original anatomical data, the simulation tools used for solving various computational problems, and the applications of computational animal models in preclinical research. The authors also analyze the characteristics of categories of computational models (stylized, voxel-based, and boundary representation) and discuss the technical challenges faced at the present time as well as research needs in the future.

A multimodal image guiding system for Navigated Ultrasound Bronchoscopy (EBUS): A human feasibility study

PubMed Central

Hofstad, Erlend Fagertun; Amundsen, Tore; Langø, Thomas; Bakeng, Janne Beate Lervik; Leira, Håkon Olav

2017-01-01

Background Endobronchial ultrasound transbronchial needle aspiration (EBUS-TBNA) is the endoscopic method of choice for confirming lung cancer metastasis to mediastinal lymph nodes. Precision is crucial for correct staging and clinical decision-making. Navigation and multimodal imaging can potentially improve EBUS-TBNA efficiency. Aims To demonstrate the feasibility of a multimodal image guiding system using electromagnetic navigation for ultrasound bronchoschopy in humans. Methods Four patients referred for lung cancer diagnosis and staging with EBUS-TBNA were enrolled in the study. Target lymph nodes were predefined from the preoperative computed tomography (CT) images. A prototype convex probe ultrasound bronchoscope with an attached sensor for position tracking was used for EBUS-TBNA. Electromagnetic tracking of the ultrasound bronchoscope and ultrasound images allowed fusion of preoperative CT and intraoperative ultrasound in the navigation software. Navigated EBUS-TBNA was used to guide target lymph node localization and sampling. Navigation system accuracy was calculated, measured by the deviation between lymph node position in ultrasound and CT in three planes. Procedure time, diagnostic yield and adverse events were recorded. Results Preoperative CT and real-time ultrasound images were successfully fused and displayed in the navigation software during the procedures. Overall navigation accuracy (11 measurements) was 10.0 ± 3.8 mm, maximum 17.6 mm, minimum 4.5 mm. An adequate sample was obtained in 6/6 (100%) of targeted lymph nodes. No adverse events were registered. Conclusions Electromagnetic navigated EBUS-TBNA was feasible, safe and easy in this human pilot study. The clinical usefulness was clearly demonstrated. Fusion of real-time ultrasound, preoperative CT and electromagnetic navigational bronchoscopy provided a controlled guiding to level of target, intraoperative overview and procedure documentation. PMID:28182758

Low-resolution electromagnetic tomography (LORETA) in children with cochlear implants: a preliminary report.

PubMed

Henkin, Yael; Kishon-Rabin, Liat; Tatin-Schneider, Simona; Urbach, Doron; Hildesheimer, Minka; Kileny, Paul R

2004-12-01

The current preliminary report describes the utilization of low-resolution electromagnetic tomography (LORETA) in a small group of highly performing children using the Nucleus 22 cochlear implant (CI) and in normal-hearing (NH) adults. LORETA current density estimations were performed on an averaged target P3 component that was elicited by non-speech and speech oddball discrimination tasks. The results indicated that, when stimulated with tones, patients with right implants and NH adults (regardless of stimulated ear) showed enhanced activation in the right temporal lobe, whereas patients with left implants showed enhanced activation in the left temporal lobe. When stimulated with speech, patients with right implants showed bilateral activation of the temporal and frontal lobes, whereas patients with left implants showed only left temporal lobe activation. NH adults (regardless of stimulated ear) showed enhanced bilateral activation of the temporal and parietal lobes. The differences in activation patterns between patients with CI and NH subjects may be attributed to the long-term exposure to degraded input conditions which may have resulted in reorganization in terms of functional specialization. The difference between patients with right versus left implants, however, is intriguing and requires further investigation.

Utilizing 2D Electrical Resistivity Tomography and Very Low Frequency Electromagnetics to Investigate the Hydrogeology of Natural Cold Springs Near Virginia City, Southwest Montana

NASA Astrophysics Data System (ADS)

Khalil, Mohamed A.; Bobst, Andrew; Mosolf, Jesse

2018-04-01

Virginia City, Montana, is located in the northern Rocky Mountains of the United States. Two natural springs supply the city's water; however, the source of that water is poorly understood. The springs are located on the east side of the city, on the edge of an area affected by landslides. 2D electric resistivity tomography (ERT) and very low frequency electromagnetics (VLF-EM) were used to explore the springs and landslides. Two intersecting 2D resistivity profiles were measured at each spring, and two VLF profiles were measured in a landslide zone. The inverted 2D resistivity profiles at the springs reveal high resistivity basalt flows juxtaposed with low resistivity volcanic ash. The VLF profiles within the landslide show a series of fracture zones in the basalt, which are interpreted to be a series of landslide scarps. Results show a strong correlation between the inferred scarps and local topography. This study provides valuable geological information to help understand the source of water to the springs. The contact between the fractured basalt and the ash provides a sharp contrast in permeability, which causes water to flow along the contact and discharge at outcrop. The fracture zones along the scarps in the landslide deposits provide conduits of high secondary permeability to transmit water to the springs. The fracture zones near the scarps may also provide targets for municipal supply wells.

Valproate selectively reduces EEG activity in anterior parts of the cortex in patients with idiopathic generalized epilepsy. A low resolution electromagnetic tomography (LORETA) study.

PubMed

Béla, Clemens; Mónika, Bessenyei; Márton, Tóth; István, Kondákor

2007-07-01

To localize the cortical area where the anticonvulsive drug valproate (VPA) exerts its effect in patients with idiopathic generalized epilepsy (IGE). In a prior study we investigated 15 IGE patients in the untreated condition and compared their low resolution electromagnetic tomography (LORETA) results to a normal control group. The investigation of these patients was continued in the present study. All the 15 patients were treated with VPA and were followed by the authors. EEG was recorded after 3 months of VPA treatment in the seizure-free patients. A total of 2min of 19-channels, common reference-recorded, waking-relaxed background activity (without paroxysmal and other, non-stationary elements) was analyzed. "Activity" (current density, amper/meters squared) was given in four frequency bands (delta, theta, alpha, beta). Band-related group differences between the present LORETA results (treated condition) and the prior LORETA results (untreated condition) were computed for all the 2394 voxels by t-tests for interdependent datasets. The statistically significant (p<0.01, uncorrected) differences of activity were projected to real cortical anatomy using the Talairach Brain Atlas. Statistically significant differences between the untreated and treated condition emerged in the delta and theta bands. VPA decreased delta and theta activity in the entire frontal cortex, insula, anterior temporal cortex and hippocampus, and in the anterior part of the parietal cortex. VPA decreased activity in parts of the cortex that display ictogenic properties and contribute to seizure generation in IGE. Furthermore, the anatomical distribution of the drug effect exactly corresponded to the VPA-related accumulation of neuroprotective proteins reported in experimental papers.

A bronchoscopic navigation system using bronchoscope center calibration for accurate registration of electromagnetic tracker and CT volume without markers.

PubMed

Luo, Xiongbiao

2014-06-01

Various bronchoscopic navigation systems are developed for diagnosis, staging, and treatment of lung and bronchus cancers. To construct electromagnetically navigated bronchoscopy systems, registration of preoperative images and an electromagnetic tracker must be performed. This paper proposes a new marker-free registration method, which uses the centerlines of the bronchial tree and the center of a bronchoscope tip where an electromagnetic sensor is attached, to align preoperative images and electromagnetic tracker systems. The chest computed tomography (CT) volume (preoperative images) was segmented to extract the bronchial centerlines. An electromagnetic sensor was fixed at the bronchoscope tip surface. A model was designed and printed using a 3D printer to calibrate the relationship between the fixed sensor and the bronchoscope tip center. For each sensor measurement that includes sensor position and orientation information, its corresponding bronchoscope tip center position was calculated. By minimizing the distance between each bronchoscope tip center position and the bronchial centerlines, the spatial alignment of the electromagnetic tracker system and the CT volume was determined. After obtaining the spatial alignment, an electromagnetic navigation bronchoscopy system was established to real-timely track or locate a bronchoscope inside the bronchial tree during bronchoscopic examinations. The electromagnetic navigation bronchoscopy system was validated on a dynamic bronchial phantom that can simulate respiratory motion with a breath rate range of 0-10 min(-1). The fiducial and target registration errors of this navigation system were evaluated. The average fiducial registration error was reduced from 8.7 to 6.6 mm. The average target registration error, which indicates all tracked or navigated bronchoscope position accuracy, was much reduced from 6.8 to 4.5 mm compared to previous registration methods. An electromagnetically navigated bronchoscopy system was constructed with accurate registration of an electromagnetic tracker and the CT volume on the basis of an improved marker-free registration approach that uses the bronchial centerlines and bronchoscope tip center information. The fiducial and target registration errors of our electromagnetic navigation system were about 6.6 and 4.5 mm in dynamic bronchial phantom validation.

A bronchoscopic navigation system using bronchoscope center calibration for accurate registration of electromagnetic tracker and CT volume without markers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Xiongbiao, E-mail: xiongbiao.luo@gmail.com

2014-06-15

Purpose: Various bronchoscopic navigation systems are developed for diagnosis, staging, and treatment of lung and bronchus cancers. To construct electromagnetically navigated bronchoscopy systems, registration of preoperative images and an electromagnetic tracker must be performed. This paper proposes a new marker-free registration method, which uses the centerlines of the bronchial tree and the center of a bronchoscope tip where an electromagnetic sensor is attached, to align preoperative images and electromagnetic tracker systems. Methods: The chest computed tomography (CT) volume (preoperative images) was segmented to extract the bronchial centerlines. An electromagnetic sensor was fixed at the bronchoscope tip surface. A model wasmore » designed and printed using a 3D printer to calibrate the relationship between the fixed sensor and the bronchoscope tip center. For each sensor measurement that includes sensor position and orientation information, its corresponding bronchoscope tip center position was calculated. By minimizing the distance between each bronchoscope tip center position and the bronchial centerlines, the spatial alignment of the electromagnetic tracker system and the CT volume was determined. After obtaining the spatial alignment, an electromagnetic navigation bronchoscopy system was established to real-timely track or locate a bronchoscope inside the bronchial tree during bronchoscopic examinations. Results: The electromagnetic navigation bronchoscopy system was validated on a dynamic bronchial phantom that can simulate respiratory motion with a breath rate range of 0–10 min{sup −1}. The fiducial and target registration errors of this navigation system were evaluated. The average fiducial registration error was reduced from 8.7 to 6.6 mm. The average target registration error, which indicates all tracked or navigated bronchoscope position accuracy, was much reduced from 6.8 to 4.5 mm compared to previous registration methods. Conclusions: An electromagnetically navigated bronchoscopy system was constructed with accurate registration of an electromagnetic tracker and the CT volume on the basis of an improved marker-free registration approach that uses the bronchial centerlines and bronchoscope tip center information. The fiducial and target registration errors of our electromagnetic navigation system were about 6.6 and 4.5 mm in dynamic bronchial phantom validation.« less

Ionospheric tomography using Faraday rotation of Automatic Dependent Surveillance Broadcast (UHF) signals Ionospheric Measurement From ADS-B Signals

NASA Astrophysics Data System (ADS)

Cushley, Alex Clay

The proposed launch of a CubeSat carrying the first space-borne ADS-B receiver by RMCC will create a unique opportunity to study the modification of radio waves following propagation through the ionosphere as the signals propagate from the transmitting aircraft to the passive satellite receiver(s). Experimental work is described which successfully demonstrated that ADS-B data can be used to reconstruct two-dimensional electron density maps of the ionosphere using techniques from computerized tomography. Ray-tracing techniques are used to determine the characteristics of individual waves, including the wave path and the state of polarization at the satellite receiver. The modelled Faraday rotation is determined and converted to TEC along the ray-paths. The resulting TEC is used as input for CIT using ART. This study concentrated on meso-scale structures 100--1000 km in horizontal extent. The primary scientific interest of this thesis was to show the feasibility of a new method to image the ionosphere and obtain a better understanding of magneto-ionic wave propagation. Keywords: Automatic Dependent Surveillance-Broadcast (ADS-B), Faraday rotation, electromagnetic (EM) waves, radio frequency (RF) propagation, ionosphere (auroral, irregularities, instruments and techniques), electron density profile, total electron content (TEC), computer ionospheric tomography (CIT), algebraic reconstruction technique (ART).

Neural systems and time course of proactive interference in working memory.

PubMed

Du, Yingchun; Zhang, John X; Xiao, Zhuangwei; Wu, Renhua

2007-01-01

The storage of information in working memory suffers as a function of proactive interference. Many works using neuroimaging technique have been done to reveal the brain mechanism of interference resolution. However, less is yet known about the time course of this process. Event-related potential method(ERP) and standardized Low Resolution Brain Electromagnetic Tomography method (sLORETA) were used in this study to discover the time course of interference resolution in working memory. The anterior P2 was thought to reflect interference resolution and if so, this process occurred earlier in working memory than in long-term memory.

A High-Resolution Endoscope of Small Diameter Using Electromagnetically Vibration of Single Fiber

NASA Astrophysics Data System (ADS)

Matsunaga, Tadao; Hino, Ryunosuke; Makishi, Wataru; Esashi, Masayoshi; Haga, Yoichi

For high resolution visual inspection in the narrow space of the human body, small diameter endoscope has been developed which utilize electromagnetically vibration of single fiber. Thin endoscopes are effective for inspection in the narrow space of the human body, for example, in the blood vessel, lactiferous duct for detection infiltration of breast cancer, and periodontal gap between gingiva and tooth. This endoscope consists of single optical fiber and photofabricated driving coils. A collimator lens and a cylindrical permanent magnet are fixed on the optical fiber, and the tilted driving coils have been patterned on a 1.08 mm outer diameter thin tube. The fiber is positioned at the center of the tube which is patterned the coils. When an electrical alternating current at the resonance frequency is supplied to the coils, the permanent magnet which is fixed to the fiber is vibrated electromagnetically and scanned one or two dimensionally. This paper reports small diameter endoscope by using electromagnetically vibration of single fiber. Optical coherence tomography imaging has also been carried out with the fabricated endoscope and cross-section image of sub-surface skin of thumb was observed.

The electromagnetic response of human skin in the millimetre and submillimetre wave range.

PubMed

Feldman, Yuri; Puzenko, Alexander; Ben Ishai, Paul; Caduff, Andreas; Davidovich, Issak; Sakran, Fadi; Agranat, Aharon J

2009-06-07

Recent studies of the minute morphology of the skin by optical coherence tomography revealed that the sweat ducts in human skin are helically shaped tubes, filled with a conductive aqueous solution. This, together with the fact that the dielectric permittivity of the dermis is higher than that of the epidermis, brings forward the supposition that as electromagnetic entities, the sweat ducts could be regarded as low Q helical antennas. The implications of this statement were further investigated by electromagnetic simulation and experiment of the in vivo reflectivity of the skin of subjects under varying physiological conditions (Feldman et al 2008 Phys. Rev. Lett. 100 128102). The simulation and experimental results are in a good agreement and both demonstrate that sweat ducts in the skin could indeed behave as low Q antennas. Thus, the skin spectral response in the sub-Terahertz region is governed by the level of activity of the perspiration system and shows the minimum of reflectivity at some frequencies in the frequency band of 75-110 GHz. It is also correlated to physiological stress as manifested by the pulse rate and the systolic blood pressure. As such, it has the potential to become the underlying principle for remote sensing of the physiological parameters and the mental state of the examined subject.

Bilinear Time-frequency Analysis for Lamb Wave Signal Detected by Electromagnetic Acoustic Transducer

NASA Astrophysics Data System (ADS)

Sun, Wenxiu; Liu, Guoqiang; Xia, Hui; Xia, Zhengwu

2018-03-01

Accurate acquisition of the detection signal travel time plays a very important role in cross-hole tomography. The experimental platform of aluminum plate under the perpendicular magnetic field is established and the bilinear time-frequency analysis methods, Wigner-Ville Distribution (WVD) and the pseudo-Wigner-Ville distribution (PWVD), are applied to analyse the Lamb wave signals detected by electromagnetic acoustic transducer (EMAT). By extracting the same frequency component of the time-frequency spectrum as the excitation frequency, the travel time information can be obtained. In comparison with traditional linear time-frequency analysis method such as short-time Fourier transform (STFT), the bilinear time-frequency analysis method PWVD is more appropriate in extracting travel time and recognizing patterns of Lamb wave.

Nondestructive evaluation of the preservation state of stone columns in the Hospital Real of Granada

NASA Astrophysics Data System (ADS)

Moreno de Jong van Coevorden, C.; Cobos Sánchez, C.; Rubio Bretones, A.; Fernández Pantoja, M.; García, Salvador G.; Gómez Martín, R.

2012-12-01

This paper describes the results of the employment of two nondestructive evaluation methods for the diagnostic of the preservation state of stone elements. The first method is based on ultrasonic (US) pulses while the second method uses short electromagnetic pulses. Specifically, these methods were applied to some columns, some of them previously restored. These columns are part of the architectonic heritage of the University of Granada, in particular they are located at the patio de la capilla del Hospital Real of Granada. The objective of this work was the application of systems based on US pulses (in transmission mode) and the ground-penetrating radar systems (electromagnetic tomography) in the diagnosis and detection of possible faults in the interior of columns.

Photonic Breast Tomography and Tumor Aggressiveness Assessment

DTIC Science & Technology

2011-07-01

incorporates, in optical domain, the vector subspace classification method, Multiple Signal Classification ( MUSIC ). MUSIC was developed by Devaney...and co-workers for finding the location of scattering targets whose size is smaller than the wavelength of acoustic waves or electromagnetic waves...general area of array processing for acoustic and radar time-reversal imaging [12]. The eigenvalue equation of TR matrix is solved, and the signal and

Physics Flash August 2016

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kippen, Karen Elizabeth

Physics Flash is the newsletter for the Physics Division at Los Alamos National Laboratory. This newsletter is for August 2016. The following topics are covered: "Accomplishments in the Trident Laser Facility", "David Meyerhofer elected as chair-elect APS Nominating Committee", "HAWC searches for gamma rays from dark matter", "Proton Radiography Facility commissions electromagnetic magnifier", and "Cosmic ray muon computed tomography of spent nuclear fuel in dry storage casks."

Development of computational small animal models and their applications in preclinical imaging and therapy research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Tianwu; Zaidi, Habib, E-mail: habib.zaidi@hcuge.ch; Geneva Neuroscience Center, Geneva University, Geneva CH-1205

The development of multimodality preclinical imaging techniques and the rapid growth of realistic computer simulation tools have promoted the construction and application of computational laboratory animal models in preclinical research. Since the early 1990s, over 120 realistic computational animal models have been reported in the literature and used as surrogates to characterize the anatomy of actual animals for the simulation of preclinical studies involving the use of bioluminescence tomography, fluorescence molecular tomography, positron emission tomography, single-photon emission computed tomography, microcomputed tomography, magnetic resonance imaging, and optical imaging. Other applications include electromagnetic field simulation, ionizing and nonionizing radiation dosimetry, and themore » development and evaluation of new methodologies for multimodality image coregistration, segmentation, and reconstruction of small animal images. This paper provides a comprehensive review of the history and fundamental technologies used for the development of computational small animal models with a particular focus on their application in preclinical imaging as well as nonionizing and ionizing radiation dosimetry calculations. An overview of the overall process involved in the design of these models, including the fundamental elements used for the construction of different types of computational models, the identification of original anatomical data, the simulation tools used for solving various computational problems, and the applications of computational animal models in preclinical research. The authors also analyze the characteristics of categories of computational models (stylized, voxel-based, and boundary representation) and discuss the technical challenges faced at the present time as well as research needs in the future.« less

Imaging the cortical effect of lamotrigine in patients with idiopathic generalized epilepsy: a low-resolution electromagnetic tomography (LORETA) study.

PubMed

Clemens, Béla; Piros, Pálma; Bessenyei, Mónika; Tóth, Márton; Hollódy, Katalin; Kondákor, István

2008-10-01

Anatomical localization of the cortical effect of lamotrigine (LTG) in patients with idiopathic generalized epilepsy (IGE). 19 patients with untreated IGE were investigated. EEG was recorded in the untreated condition and 3 months later when LTG treatment abolished the seizures. 19-channel EEG was recorded, and a total of 2min artifact-free, waking EEG was processed to low-resolution electromagnetic tomography (LORETA) analysis. Activity (that is, current source density, A/m(2)) was computed in four frequency bands (delta, theta, alpha, and beta), for 2394 voxels that represented the cortical gray matter and the hippocampi. Group differences between the untreated and treated conditions were computed for the four bands and all voxels by multiple t-tests for interdependent datasets. The results were presented in terms of anatomical distribution and statistical significance. p<0.01 (uncorrected) changes (decrease of activity) emerged in the theta and the alpha bands. Theta activity decreased in a large cluster of voxels including parts of the temporal, parietal, occipital cortex bilaterally, and in the transverse temporal gyri, insula, hippocampus, and uncus on the right side. Alpha activity decreased in a relatively smaller cortical area involving the right temporo-parietal junction and surrounding parts of the cortex, and part of the insula on the right side. LTG decreased theta activity in several cortical areas where abnormally increased theta activity had been found in a prior study in another cohort of untreated IGE patients [Clemens, B., Bessenyei, M., Piros, P., Tóth, M., Seress, L., Kondákor, I., 2007b. Characteristic distribution of interictal brain electrical activity in idiopathic generalized epilepsy. Epilepsia 48, 941-949]. These LTG-related changes might be related to the decrease of seizure propensity in IGE.

Effects of the South American psychoactive beverage ayahuasca on regional brain electrical activity in humans: a functional neuroimaging study using low-resolution electromagnetic tomography.

PubMed

Riba, Jordi; Anderer, Peter; Jané, Francesc; Saletu, Bernd; Barbanoj, Manel J

2004-01-01

Ayahuasca, a South American psychotropic plant tea obtained from Banisteriopsis caapi and Psychotria viridis, combines monoamine oxidase-inhibiting beta-carboline alkaloids with N,N-dimethyltryptamine (DMT), a psychedelic agent showing 5-HT(2A) agonist activity. In a clinical research setting, ayahuasca has demonstrated a combined stimulatory and psychedelic effect profile, as measured by subjective effect self-assessment instruments and dose-dependent changes in spontaneous brain electrical activity, which parallel the time course of subjective effects. In the present study, the spatial distribution of ayahuasca-induced changes in brain electrical activity was investigated by means of low-resolution electromagnetic tomography (LORETA). Electroencephalography recordings were obtained from 18 volunteers after the administration of a dose of encapsulated freeze-dried ayahuasca containing 0.85 mg DMT/kg body weight and placebo. The intracerebral power density distribution was computed with LORETA from spectrally analyzed data, and subjective effects were measured by means of the Hallucinogen Rating Scale (HRS). Statistically significant differences compared to placebo were observed for LORETA power 60 and 90 min after dosing, together with increases in all six scales of the HRS. Ayahuasca decreased power density in the alpha-2, delta, theta and beta-1 frequency bands. Power decreases in the delta, alpha-2 and beta-1 bands were found predominantly over the temporo-parieto-occipital junction, whereas theta power was reduced in the temporomedial cortex and in frontomedial regions. The present results suggest the involvement of unimodal and heteromodal association cortex and limbic structures in the psychological effects elicited by ayahuasca. Copyright 2004 S. Karger AG, Basel

Comparative analysis of background EEG activity in childhood absence epilepsy during valproate treatment: a standardized, low-resolution, brain electromagnetic tomography (sLORETA) study.

PubMed

Shin, Jung-Hyun; Eom, Tae-Hoon; Kim, Young-Hoon; Chung, Seung-Yun; Lee, In-Goo; Kim, Jung-Min

2017-07-01

Valproate (VPA) is an antiepileptic drug (AED) used for initial monotherapy in treating childhood absence epilepsy (CAE). EEG might be an alternative approach to explore the effects of AEDs on the central nervous system. We performed a comparative analysis of background EEG activity during VPA treatment by using standardized, low-resolution, brain electromagnetic tomography (sLORETA) to explore the effect of VPA in patients with CAE. In 17 children with CAE, non-parametric statistical analyses using sLORETA were performed to compare the current density distribution of four frequency bands (delta, theta, alpha, and beta) between the untreated and treated condition. Maximum differences in current density were found in the left inferior frontal gyrus for the delta frequency band (log-F-ratio = -1.390, P > 0.05), the left medial frontal gyrus for the theta frequency band (log-F-ratio = -0.940, P > 0.05), the left inferior frontal gyrus for the alpha frequency band (log-F-ratio = -0.590, P > 0.05), and the left anterior cingulate for the beta frequency band (log-F-ratio = -1.318, P > 0.05). However, none of these differences were significant (threshold log-F-ratio = ±1.888, P < 0.01; threshold log-F-ratio = ±1.722, P < 0.05). Because EEG background is accepted as normal in CAE, VPA would not be expected to significantly change abnormal thalamocortical oscillations on a normal EEG background. Therefore, our results agree with currently accepted concepts but are not consistent with findings in some previous studies.

[Localization of attention related cortical structures by evoked potentials].

PubMed

Szelenberger, W

2000-01-01

Attention is an ambiguous concept, difficult to direct implementation in neurophysiological studies. The paper presents application of the Continuous Attention Test (CAT) items as stimuli in event related potential (ERP) studies on attention. Stimuli with high demand of attention result in enlarged N1 component in occipital derivations. Spatial analysis revealed increased positivity in frontal derivations. Three-dimensional image of cortical current density by means of Low Resolution Electromagnetic Tomography (LORETA) revealed sources of N1 component in occipital, parietal and postero-temporal derivations with the maximal current value at 17 Brodmann area. After target stimuli increase of current density in frontal derivations was observed, with the maximal value in the left 9 Brodmann area.

Final Report (2010-2015) for the Topical Collaboration on Quantitative Jet and Electromagnetic Tomography (JET) of Extreme Phases of Matter in Heavy-ion Collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyulassy, Miklos; Romatschke, Paul; Bass, Steffen

2015-08-31

During the 5-year funding period (2010-2015), the JET Collaboration carried out a comprehensive research program with coordinated efforts involving all PI members and external associated members according to the plan and milestones outlined in the approved JET proposal. We identified important issues in the study of parton energy loss and made significant progress toward NLO calculations; advanced event-by-event hydrodynamic simulations of bulk matter evolution; developed Monte Carlo tools that combine different parton energy loss approaches, hydrodynamic models and parton recombination model for jet hadronization; and carried out the first comprehensive phenomenological study to extract the jet transport parameter.

Current use of imaging and electromagnetic source localization procedures in epilepsy surgery centers across Europe.

PubMed

Mouthaan, Brian E; Rados, Matea; Barsi, Péter; Boon, Paul; Carmichael, David W; Carrette, Evelien; Craiu, Dana; Cross, J Helen; Diehl, Beate; Dimova, Petia; Fabo, Daniel; Francione, Stefano; Gaskin, Vladislav; Gil-Nagel, Antonio; Grigoreva, Elena; Guekht, Alla; Hirsch, Edouard; Hecimovic, Hrvoje; Helmstaedter, Christoph; Jung, Julien; Kalviainen, Reetta; Kelemen, Anna; Kimiskidis, Vasilios; Kobulashvili, Teia; Krsek, Pavel; Kuchukhidze, Giorgi; Larsson, Pål G; Leitinger, Markus; Lossius, Morten I; Luzin, Roman; Malmgren, Kristina; Mameniskiene, Ruta; Marusic, Petr; Metin, Baris; Özkara, Cigdem; Pecina, Hrvoje; Quesada, Carlos M; Rugg-Gunn, Fergus; Rydenhag, Bertil; Ryvlin, Philippe; Scholly, Julia; Seeck, Margitta; Staack, Anke M; Steinhoff, Bernhard J; Stepanov, Valentin; Tarta-Arsene, Oana; Trinka, Eugen; Uzan, Mustafa; Vogt, Viola L; Vos, Sjoerd B; Vulliémoz, Serge; Huiskamp, Geertjan; Leijten, Frans S S; Van Eijsden, Pieter; Braun, Kees P J

2016-05-01

In 2014 the European Union-funded E-PILEPSY project was launched to improve awareness of, and accessibility to, epilepsy surgery across Europe. We aimed to investigate the current use of neuroimaging, electromagnetic source localization, and imaging postprocessing procedures in participating centers. A survey on the clinical use of imaging, electromagnetic source localization, and postprocessing methods in epilepsy surgery candidates was distributed among the 25 centers of the consortium. A descriptive analysis was performed, and results were compared to existing guidelines and recommendations. Response rate was 96%. Standard epilepsy magnetic resonance imaging (MRI) protocols are acquired at 3 Tesla by 15 centers and at 1.5 Tesla by 9 centers. Three centers perform 3T MRI only if indicated. Twenty-six different MRI sequences were reported. Six centers follow all guideline-recommended MRI sequences with the proposed slice orientation and slice thickness or voxel size. Additional sequences are used by 22 centers. MRI postprocessing methods are used in 16 centers. Interictal positron emission tomography (PET) is available in 22 centers; all using 18F-fluorodeoxyglucose (FDG). Seventeen centers perform PET postprocessing. Single-photon emission computed tomography (SPECT) is used by 19 centers, of which 15 perform postprocessing. Four centers perform neither PET nor SPECT in children. Seven centers apply magnetoencephalography (MEG) source localization, and nine apply electroencephalography (EEG) source localization. Fourteen combinations of inverse methods and volume conduction models are used. We report a large variation in the presurgical diagnostic workup among epilepsy surgery centers across Europe. This diversity underscores the need for high-quality systematic reviews, evidence-based recommendations, and harmonization of available diagnostic presurgical methods. Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.

Using Optical Coherence Tomography to Reveal the Hidden History of The Landsdowne Virgin of the Yarnwinder by Leonardo da Vinci and Studio.

PubMed

Targowski, Piotr; Iwanicka, Magdalena; Sylwestrzak, Marcin; Frosinini, Cecilia; Striova, Jana; Fontana, Raffaella

2018-06-18

Optical coherence tomography (OCT) was used for non-invasive examination of a well-known, yet complex, painting from the studio of Leonardo da Vinci in combination with routine imaging in various bands of electromagnetic radiation. In contrast with these techniques, OCT provides depth-resolved information. Three post-processing modalities were explored: cross-sectional views, maps of scattering from given depths, and their 3D models. Some hidden alterations of the painting owing to past restorations were traced: retouching and overpainting with their positioning within varnish layers as well as indications of a former transfer to canvas. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Review of progress in quantitative NDE. [Nondestructive Evaluation (NDE)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1991-01-01

This booklet is composed of abstracts from papers submitted at a meeting on quantitative NDE. A multitude of topics are discussed including analysis of composite materials, NMR uses, x-ray instruments and techniques, manufacturing uses, neural networks, eddy currents, stress measurements, magnetic materials, adhesive bonds, signal processing, NDE of mechanical structures, tomography,defect sizing, NDE of plastics and ceramics, new techniques, optical and electromagnetic techniques, and nonlinear techniques. (GHH)

Early caries imaging and monitoring with near-infrared light.

PubMed

Fried, Daniel; Featherstone, John D B; Darling, Cynthia L; Jones, Robert S; Ngaotheppitak, Patara; Bühler, Christopher M

2005-10-01

Enamel is highly transparent in the near infrared (NIR); therefore, this region of the electromagnetic spectrum is suited ideally for the development of new optical diagnostic tools for the detection and imaging of early dental caries. This article discusses the NIR optical properties of sound and demineralized dental enamel and the potential use of polarization sensitive optical coherence tomography and NIR transillumination for the imaging of dental caries.

Source localization of intermittent rhythmic delta activity in a patient with acute confusional migraine: cross-spectral analysis using standardized low-resolution brain electromagnetic tomography (sLORETA).

PubMed

Kim, Dae-Eun; Shin, Jung-Hyun; Kim, Young-Hoon; Eom, Tae-Hoon; Kim, Sung-Hun; Kim, Jung-Min

2016-01-01

Acute confusional migraine (ACM) shows typical electroencephalography (EEG) patterns of diffuse delta slowing and frontal intermittent rhythmic delta activity (FIRDA). The pathophysiology of ACM is still unclear but these patterns suggest neuronal dysfunction in specific brain areas. We performed source localization analysis of IRDA (in the frequency band of 1-3.5 Hz) to better understand the ACM mechanism. Typical IRDA EEG patterns were recorded in a patient with ACM during the acute stage. A second EEG was obtained after recovery from ACM. To identify source localization of IRDA, statistical non-parametric mapping using standardized low-resolution brain electromagnetic tomography was performed for the delta frequency band comparisons between ACM attack and non-attack periods. A difference in the current density maximum was found in the dorsal anterior cingulated cortex (ACC). The significant differences were widely distributed over the frontal, parietal, temporal and limbic lobe, paracentral lobule and insula and were predominant in the left hemisphere. Dorsal ACC dysfunction was demonstrated for the first time in a patient with ACM in this source localization analysis of IRDA. The ACC plays an important role in the frontal attentional control system and acute confusion. This dysfunction of the dorsal ACC might represent an important ACM pathophysiology.

WKB analysis of relativistic Stern–Gerlach measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmer, Matthew C., E-mail: m.palmer@physics.usyd.edu.au; Takahashi, Maki, E-mail: m.takahashi@physics.usyd.edu.au; Westman, Hans F., E-mail: hwestman74@gmail.com

2013-09-15

Spin is an important quantum degree of freedom in relativistic quantum information theory. This paper provides a first-principles derivation of the observable corresponding to a Stern–Gerlach measurement with relativistic particle velocity. The specific mathematical form of the Stern–Gerlach operator is established using the transformation properties of the electromagnetic field. To confirm that this is indeed the correct operator we provide a detailed analysis of the Stern–Gerlach measurement process. We do this by applying a WKB approximation to the minimally coupled Dirac equation describing an interaction between a massive fermion and an electromagnetic field. Making use of the superposition principle wemore » show that the +1 and −1 spin eigenstates of the proposed spin operator are split into separate packets due to the inhomogeneity of the Stern–Gerlach magnetic field. The operator we obtain is dependent on the momentum between particle and Stern–Gerlach apparatus, and is mathematically distinct from two other commonly used operators. The consequences for quantum tomography are considered. -- Highlights: •Derivation of the spin observable for a relativistic Stern–Gerlach measurement. •Relativistic model of spin measurement using WKB approximation of Dirac equation. •The derived spin operator is distinct from two other commonly used operators. •Consequences for quantum tomography are considered.« less

Forward Field Computation with OpenMEEG

PubMed Central

Gramfort, Alexandre; Papadopoulo, Théodore; Olivi, Emmanuel; Clerc, Maureen

2011-01-01

To recover the sources giving rise to electro- and magnetoencephalography in individual measurements, realistic physiological modeling is required, and accurate numerical solutions must be computed. We present OpenMEEG, which solves the electromagnetic forward problem in the quasistatic regime, for head models with piecewise constant conductivity. The core of OpenMEEG consists of the symmetric Boundary Element Method, which is based on an extended Green Representation theorem. OpenMEEG is able to provide lead fields for four different electromagnetic forward problems: Electroencephalography (EEG), Magnetoencephalography (MEG), Electrical Impedance Tomography (EIT), and intracranial electric potentials (IPs). OpenMEEG is open source and multiplatform. It can be used from Python and Matlab in conjunction with toolboxes that solve the inverse problem; its integration within FieldTrip is operational since release 2.0. PMID:21437231

Image Fusion During Vascular and Nonvascular Image-Guided Procedures☆

PubMed Central

Abi-Jaoudeh, Nadine; Kobeiter, Hicham; Xu, Sheng; Wood, Bradford J.

2013-01-01

Image fusion may be useful in any procedure where previous imaging such as positron emission tomography, magnetic resonance imaging, or contrast-enhanced computed tomography (CT) defines information that is referenced to the procedural imaging, to the needle or catheter, or to an ultrasound transducer. Fusion of prior and intraoperative imaging provides real-time feedback on tumor location or margin, metabolic activity, device location, or vessel location. Multimodality image fusion in interventional radiology was initially introduced for biopsies and ablations, especially for lesions only seen on arterial phase CT, magnetic resonance imaging, or positron emission tomography/CT but has more recently been applied to other vascular and nonvascular procedures. Two different types of platforms are commonly used for image fusion and navigation: (1) electromagnetic tracking and (2) cone-beam CT. Both technologies would be reviewed as well as their strengths and weaknesses, indications, when to use one vs the other, tips and guidance to streamline use, and early evidence defining clinical benefits of these rapidly evolving, commercially available and emerging techniques. PMID:23993079

Magnetic Resonance Based Electrical Properties Tomography: A Review

PubMed Central

Zhang, Xiaotong; Liu, Jiaen

2014-01-01

Frequency-dependent electrical properties (EPs; conductivity and permittivity) of biological tissues provide important diagnostic information (e.g. tumor characterization), and also play an important role in quantifying radiofrequency (RF) coil induced Specific Absorption Rate (SAR) which is a major safety concern in high- and ultrahigh-field Magnetic Resonance Imaging (MRI) applications. Cross-sectional imaging of EPs has been pursued for decades. Recently introduced Electrical Properties Tomography (EPT) approaches utilize the measurable RF magnetic field induced by the RF coil in an MRI system to quantitatively reconstruct the EP distribution in vivo and non-invasively with a spatial resolution of a few millimeters or less. This paper reviews the Electrical Properties Tomography approach from its basic theory in electromagnetism to the state of the art research outcomes. Emphasizing on the imaging reconstruction methods rather than experimentation techniques, we review the developed imaging algorithms, validation results in physical phantoms and biological tissues, as well as their applications in in vivo tumor detection and subject-specific SAR prediction. Challenges for future research are also discussed. PMID:24803104

Computer assisted positioning of the proximal segment after sagittal split osteotomy of the mandible: Preclinical investigation of a novel electromagnetic navigation system.

PubMed

Nova, Igor; Kallus, Sebastian; Berger, Moritz; Ristow, Oliver; Eisenmann, Urs; Freudlsperger, Christian; Hoffmann, Jürgen; Dickhaus, Hartmut

2017-05-01

Modifications of the temporomandibular joint position after mandible osteotomy are reluctantly accepted in orthognathic surgery. To tackle this problem, we developed a new navigation system using miniaturized electromagnetic sensors. Our imageless navigation approach is therefore optimized to avoid complications of previously proposed optical approaches such as the interference with established surgical procedures and the line of sight problem. High oblique sagittal split osteotomies were performed on 6 plastic skull mandibles in a laboratory under conditions comparable to the operating theatre. The subsequent condyle reposition was guided by an intuitive user interface and performed by electromagnetic navigation. To prove the suitability and accuracy of this novel approach for condyle navigation, the positions of 3 titanium marker screws placed on each of the proximal segments were compared using pre- and postoperative Cone Beam Computed Tomography (CBCT) imaging. Guided by the electromagnetic navigation system, positioning of the condyles was highly accurate in all dimensions. Translational discrepancies up to 0,65 mm and rotations up to 0,38° in mean could be measured postoperatively. There were no statistically significant differences between navigation results and CBCT measurements. The intuitive user interface provides a simple way to precisely restore the initial position and orientation of the proximal mandibular segments. Our electromagnetic navigation system therefore yields a promising approach for orthognathic surgery applications. Copyright © 2017 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Three-dimensional Fréchet sensitivity kernels for electromagnetic wave propagation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strickland, C. E.; Johnson, T. C.; Odom, R. I.

2015-08-28

Electromagnetic imaging methods are useful tools for monitoring subsurface changes in pore-fluid content and the associated changes in electrical permittivity and conductivity. The most common method for georadar tomography uses a high frequency ray-theoretic approximation that is valid when material variations are sufficiently small relative to the wavelength of the propagating wave. Georadar methods, however, often utilize electromagnetic waves that propagate within heterogeneous media at frequencies where ray theory may not be applicable. In this paper we describe the 3-D Fréchet sensitivity kernels for EM wave propagation. Various data functional types are formulated that consider all three components of themore » electric wavefield and incorporate near-, intermediate-, and far-field contributions. We show that EM waves exhibit substantial variations for different relative source-receiver component orientations. The 3-D sensitivities also illustrate out-of-plane effects that are not captured in 2-D sensitivity kernels and can influence results obtained using 2-D inversion methods to image structures that are in reality 3-D.« less

Current techniques for the real-time processing of complex radar signatures

NASA Astrophysics Data System (ADS)

Clay, E.

A real-time processing technique has been developed for the microwave receiver of the Brahms radar station. The method allows such target signatures as the radar cross section (RCS) of the airframes and rotating parts, the one-dimensional tomography of aircraft, and the RCS of electromagnetic decoys to be characterized. The method allows optimization of experimental parameters including the analysis frequency band, the receiver gain, and the wavelength range of EM analysis.

Atomic vapor quantum memory for a photonic polarization qubit.

PubMed

Cho, Young-Wook; Kim, Yoon-Ho

2010-12-06

We report an experimental realization of an atomic vapor quantum memory for the photonic polarization qubit. The performance of the quantum memory for the polarization qubit, realized with electromagnetically-induced transparency in two spatially separated ensembles of warm Rubidium atoms in a single vapor cell, has been characterized with quantum process tomography. The process fidelity better than 0.91 for up to 16 μs of storage time has been achieved.

Electromagnetic navigated condylar positioning after high oblique sagittal split osteotomy of the mandible: a guided method to attain pristine temporomandibular joint conditions.

PubMed

Berger, Moritz; Nova, Igor; Kallus, Sebastian; Ristow, Oliver; Eisenmann, Urs; Dickhaus, Hartmut; Engel, Michael; Freudlsperger, Christian; Hoffmann, Jürgen; Seeberger, Robin

2018-05-01

Reproduction of the exact preoperative proximal-mandible position after osteotomy in orthognathic surgery is difficult to achieve. This clinical pilot study evaluated an electromagnetic (EM) navigation system for condylar positioning after high-oblique sagittal split osteotomy (HSSO). After HSSO as part of 2-jaw surgery, the position of 10 condyles was intraoperatively guided by an EM navigation system. As controls, 10 proximal segments were positioned by standard manual replacement. Accuracy was measured by pre- and postoperative cone beam computed tomography imaging. Overall, EM condyle repositioning was equally accurate compared with manual repositioning (P > .05). Subdivided into 3 axes, significant differences could be identified (P < .05). Nevertheless, no significantly and clinically relevant dislocations of the proximal segment of either the EM or the manual repositioning method could be shown (P > .05). This pilot study introduces a guided method for proximal segment positioning after HSSO by applying the intraoperative EM system. The data demonstrate the high accuracy of EM navigation, although manual replacement of the condyles could not be surpassed. However, EM navigation can avoid clinically hidden, severe malpositioning of the condyles. Copyright © 2017 Elsevier Inc. All rights reserved.

Motionless phase stepping in X-ray phase contrast imaging with a compact source

PubMed Central

Miao, Houxun; Chen, Lei; Bennett, Eric E.; Adamo, Nick M.; Gomella, Andrew A.; DeLuca, Alexa M.; Patel, Ajay; Morgan, Nicole Y.; Wen, Han

2013-01-01

X-ray phase contrast imaging offers a way to visualize the internal structures of an object without the need to deposit significant radiation, and thereby alleviate the main concern in X-ray diagnostic imaging procedures today. Grating-based differential phase contrast imaging techniques are compatible with compact X-ray sources, which is a key requirement for the majority of clinical X-ray modalities. However, these methods are substantially limited by the need for mechanical phase stepping. We describe an electromagnetic phase-stepping method that eliminates mechanical motion, thus removing the constraints in speed, accuracy, and flexibility. The method is broadly applicable to both projection and tomography imaging modes. The transition from mechanical to electromagnetic scanning should greatly facilitate the translation of X-ray phase contrast techniques into mainstream applications. PMID:24218599

Neurophysiology of the cortical pain network: revisiting the role of S1 in subjective pain perception via standardized low-resolution brain electromagnetic tomography (sLORETA).

PubMed

Nir, Rony-Reuven; Lev, Rina; Moont, Ruth; Granovsky, Yelena; Sprecher, Elliot; Yarnitsky, David

2008-11-01

Multiple studies have supported the usefulness of standardized low-resolution brain electromagnetic tomography (sLORETA) in localizing generators of scalp-recorded potentials. The current study implemented sLORETA on pain event-related potentials, primarily aiming at validating this technique for pain research by identifying well-known pain-related regions. Subsequently, we pointed at investigating the still-debated and ambiguous topic of pain intensity coding at these regions, focusing on their relative impact on subjective pain perception. sLORETA revealed significant activations of the bilateral primary somatosensory (SI) and anterior cingulate cortices and of the contralateral operculoinsular and dorsolateral prefrontal (DLPFC) cortices (P < .05 for each). Activity of these regions, excluding DLPFC, correlated with subjective numerical pain scores (P < .05 for each). However, a multivariate regression analysis (R = .80; P = .024) distinguished the contralateral SI as the only region whose activation magnitude significantly predicted the subjective perception of noxious stimuli (P = .020), further substantiated by a reduced regression model (R = .75, P = .008). Based on (1) correspondence of the pain-activated regions identified by sLORETA with the acknowledged imaging-based pain-network and (2) the contralateral SI proving to be the most contributing region in pain intensity coding, we found sLORETA to be an appropriate tool for relevant pain research and further substantiated the role of SI in pain perception. Because the literature of pain intensity coding offers inconsistent findings, the current article used a novel tool for revisiting this controversial issue. Results suggest that it is the activation magnitude of SI, which solely establishes the significant correlation with subjective pain ratings, in accordance with the classical clinical thinking, relating SI lesions to diminished perception of pain. Although this study cannot support a causal relation between SI activation magnitude and pain perception, such relation might be insinuated.

Effect of low-frequency rTMS on electromagnetic tomography (LORETA) and regional brain metabolism (PET) in schizophrenia patients with auditory hallucinations.

PubMed

Horacek, Jiri; Brunovsky, Martin; Novak, Tomas; Skrdlantova, Lucie; Klirova, Monika; Bubenikova-Valesova, Vera; Krajca, Vladimir; Tislerova, Barbora; Kopecek, Milan; Spaniel, Filip; Mohr, Pavel; Höschl, Cyril

2007-01-01

Auditory hallucinations are characteristic symptoms of schizophrenia with high clinical importance. It was repeatedly reported that low frequency (

Low-resolution brain electromagnetic tomography (LORETA) identifies brain regions linked to psychometric performance under modafinil in narcolepsy.

PubMed

Saletu, Michael; Anderer, Peter; Semlitsch, Heribert V; Saletu-Zyhlarz, Gerda Maria; Mandl, Magdalena; Zeitlhofer, Josef; Saletu, Bernd

2007-01-15

Low-resolution brain electromagnetic tomography (LORETA) showed a functional deterioration of the fronto-temporo-parietal network of the right hemispheric vigilance system in narcolepsy and a therapeutic effect of modafinil. The aim of this study was to determine the effects of modafinil on cognitive and thymopsychic variables in patients with narcolepsy and investigate whether neurophysiological vigilance changes correlate with cognitive and subjective vigilance alterations at the behavioral level. In a double-blind, placebo-controlled crossover design, EEG-LORETA and psychometric data were obtained during midmorning hours in 15 narcoleptics before and after 3 weeks of placebo or 400 mg modafinil. Cognitive investigations included the Pauli Test and complex reaction time. Thymopsychic/psychophysiological evaluation comprised drive, mood, affectivity, wakefulness, depression, anxiety, the Symptom Checklist 90 and critical flicker frequency. The Multiple Sleep Latency Test (MSLT) and the Epworth Sleepiness Scale (ESS) were performed too. Cognitive performance (Pauli Test) was significantly better after modafinil than after placebo. Concerning reaction time and thymopsychic variables, no significant differences were observed. Correlation analyses revealed that a decrease in prefrontal delta, theta and alpha-1 power correlated with an improvement in cognitive performance. Moreover, drowsiness was positively correlated with theta power in parietal and medial prefrontal regions and beta-1 and beta-2 power in occipital regions. A less significant correlation was observed between midmorning EEG LORETA and the MSLT; between EEG LORETA and the ESS, the correlation was even weaker. In conclusion, modafinil did not influence thymopsychic variables in narcolepsy, but it significantly improved cognitive performance, which may be related to medial prefrontal activity processes identified by LORETA.

Low resolution brain electromagnetic tomography in a realistic geometry head model: a simulation study

NASA Astrophysics Data System (ADS)

Ding, Lei; Lai, Yuan; He, Bin

2005-01-01

It is of importance to localize neural sources from scalp recorded EEG. Low resolution brain electromagnetic tomography (LORETA) has received considerable attention for localizing brain electrical sources. However, most such efforts have used spherical head models in representing the head volume conductor. Investigation of the performance of LORETA in a realistic geometry head model, as compared with the spherical model, will provide useful information guiding interpretation of data obtained by using the spherical head model. The performance of LORETA was evaluated by means of computer simulations. The boundary element method was used to solve the forward problem. A three-shell realistic geometry (RG) head model was constructed from MRI scans of a human subject. Dipole source configurations of a single dipole located at different regions of the brain with varying depth were used to assess the performance of LORETA in different regions of the brain. A three-sphere head model was also used to approximate the RG head model, and similar simulations performed, and results compared with the RG-LORETA with reference to the locations of the simulated sources. Multi-source localizations were discussed and examples given in the RG head model. Localization errors employing the spherical LORETA, with reference to the source locations within the realistic geometry head, were about 20-30 mm, for four brain regions evaluated: frontal, parietal, temporal and occipital regions. Localization errors employing the RG head model were about 10 mm over the same four brain regions. The present simulation results suggest that the use of the RG head model reduces the localization error of LORETA, and that the RG head model based LORETA is desirable if high localization accuracy is needed.

Hyperventilation in Patients With Focal Epilepsy: Electromagnetic Tomography, Functional Connectivity and Graph Theory - A Possible Tool in Epilepsy Diagnosis?

PubMed

Mazzucchi, Edoardo; Vollono, Catello; Losurdo, Anna; Testani, Elisa; Gnoni, Valentina; Di Blasi, Chiara; Giannantoni, Nadia M; Lapenta, Leonardo; Brunetti, Valerio; Della Marca, Giacomo

2017-01-01

Hyperventilation (HV) is a commonly used electroencephalogram activation method. We analyzed EEG recordings in 22 normal subjects and 22 patients with focal epilepsy of unknown cause. We selected segments before (PRE), during (HYPER), and 5 minutes after (POST) HV. To analyze the neural generators of EEG signal, we used standard low-resolution electromagnetic tomography (sLORETA software). We then computed EEG lagged coherence, an index of functional connectivity, between 19 regions of interest. A weighted graph was built for each band in every subject, and characteristic path length (L) and clustering coefficient (C) have been computed. Statistical comparisons were performed by means of analysis of variance (Group X Condition X Band) for mean lagged coherence, L and C. Hyperventilation significantly increases EEG neural generators (P < 0.001); the effect is particularly evident in cingulate cortex. Functional connectivity was increased by HV in delta, theta, alpha, and beta bands in the Epileptic group (P < 0.01) and only in theta band in Control group. Intergroup analysis of mean lagged coherence, C and L, showed significant differences for Group (P < 0.001), Condition (P < 0.001), and Band (P < 0.001). Analysis of variance for L also showed significant interactions: Group X Condition (P = 0.003) and Group X Band (P < 0.001). In our relatively small group of epileptic patients, HV is associated with activation of cingulate cortex; moreover, it modifies brain connectivity. The significant differences in mean lagged coherence, path length, and clustering coefficient permit to hypothesize that this activation method leads to different brain connectivity patterns in patients with epilepsy when compared with normal subjects. If confirmed by other studies involving larger populations, this analysis could become a diagnostic tool in epilepsy.

Quantum memory for squeezed light.

PubMed

Appel, Jürgen; Figueroa, Eden; Korystov, Dmitry; Lobino, M; Lvovsky, A I

2008-03-07

We produce a 600-ns pulse of 1.86-dB squeezed vacuum at 795 nm in an optical parametric amplifier and store it in a rubidium vapor cell for 1 mus using electromagnetically induced transparency. The recovered pulse, analyzed using time-domain homodyne tomography, exhibits up to 0.21+/-0.04 dB of squeezing. We identify the factors leading to the degradation of squeezing and investigate the phase evolution of the atomic coherence during the storage interval.

Quantitative EEG and neurofeedback in children and adolescents: anxiety disorders, depressive disorders, comorbid addiction and attention-deficit/hyperactivity disorder, and brain injury.

PubMed

Simkin, Deborah R; Thatcher, Robert W; Lubar, Joel

2014-07-01

This article explores the science surrounding neurofeedback. Both surface neurofeedback (using 2-4 electrodes) and newer interventions, such as real-time z-score neurofeedback (electroencephalogram [EEG] biofeedback) and low-resolution electromagnetic tomography neurofeedback, are reviewed. The limited literature on neurofeedback research in children and adolescents is discussed regarding treatment of anxiety, mood, addiction (with comorbid attention-deficit/hyperactivity disorder), and traumatic brain injury. Future potential applications, the use of quantitative EEG for determining which patients will be responsive to medications, the role of randomized controlled studies in neurofeedback research, and sensible clinical guidelines are considered. Copyright © 2014 Elsevier Inc. All rights reserved.

Project MANTIS: A MANTle Induction Simulator for coupling geodynamic and electromagnetic modeling

NASA Astrophysics Data System (ADS)

Weiss, C. J.

2009-12-01

A key component to testing geodynamic hypotheses resulting from the 3D mantle convection simulations is the ability to easily translate the predicted physiochemical state to the model space relevant for an independent geophysical observation, such as earth's seismic, geodetic or electromagnetic response. In this contribution a new parallel code for simulating low-frequency, global-scale electromagnetic induction phenomena is introduced that has the same Earth discretization as the popular CitcomS mantle convection code. Hence, projection of the CitcomS model into the model space of electrical conductivity is greatly simplified, and focuses solely on the node-to-node, physics-based relationship between these Earth parameters without the need for "upscaling", "downscaling", averaging or harmonizing with some other model basis such as spherical harmonics. Preliminary performance tests of the MANTIS code on shared and distributed memory parallel compute platforms shows favorable scaling (>70% efficiency) for up to 500 processors. As with CitcomS, an OpenDX visualization widget (VISMAN) is also provided for 3D rendering and interactive interrogation of model results. Details of the MANTIS code will be briefly discussed here, focusing on compatibility with CitcomS modeling, as will be preliminary results in which the electromagnetic response of a CitcomS model is evaluated. VISMAN rendering of electrical tomography-derived electrical conductivity model overlain by an a 1x1 deg crustal conductivity map. Grey scale represents the log_10 magnitude of conductivity [S/m]. Arrows are horiztonal components of a hypothetical magnetospheric source field used to electromagnetically excite the conductivity model.

Motion tracking to enable pre-surgical margin mapping in basal cell carcinoma using optical imaging modalities: initial feasibility study using optical coherence tomography

NASA Astrophysics Data System (ADS)

Duffy, M.; Richardson, T. J.; Craythorne, E.; Mallipeddi, R.; Coleman, A. J.

2014-02-01

A system has been developed to assess the feasibility of using motion tracking to enable pre-surgical margin mapping of basal cell carcinoma (BCC) in the clinic using optical coherence tomography (OCT). This system consists of a commercial OCT imaging system (the VivoSight 1500, MDL Ltd., Orpington, UK), which has been adapted to incorporate a webcam and a single-sensor electromagnetic positional tracking module (the Flock of Birds, Ascension Technology Corp, Vermont, USA). A supporting software interface has also been developed which allows positional data to be captured and projected onto a 2D dermoscopic image in real-time. Initial results using a stationary test phantom are encouraging, with maximum errors in the projected map in the order of 1-2mm. Initial clinical results were poor due to motion artefact, despite attempts to stabilise the patient. However, the authors present several suggested modifications that are expected to reduce the effects of motion artefact and improve the overall accuracy and clinical usability of the system.

Imaging cerebral haemorrhage with magnetic induction tomography: numerical modelling.

PubMed

Zolgharni, M; Ledger, P D; Armitage, D W; Holder, D S; Griffiths, H

2009-06-01

Magnetic induction tomography (MIT) is a new electromagnetic imaging modality which has the potential to image changes in the electrical conductivity of the brain due to different pathologies. In this study the feasibility of detecting haemorrhagic cerebral stroke with a 16-channel MIT system operating at 10 MHz was investigated. The finite-element method combined with a realistic, multi-layer, head model comprising 12 different tissues, was used for the simulations in the commercial FE package, Comsol Multiphysics. The eddy-current problem was solved and the MIT signals computed for strokes of different volumes occurring at different locations in the brain. The results revealed that a large, peripheral stroke (volume 49 cm(3)) produced phase changes that would be detectable with our currently achievable instrumentation phase noise level (17 m degrees ) in 70 (27%) of the 256 exciter/sensor channel combinations. However, reconstructed images showed that a lower noise level than this, of 1 m degrees , was necessary to obtain good visualization of the strokes. The simulated MIT measurements were compared with those from an independent transmission-line-matrix model in order to give confidence in the results.

Radar attenuation tomography using the centroid frequency downshift method

USGS Publications Warehouse

Liu, L.; Lane, J.W.; Quan, Y.

1998-01-01

A method for tomographically estimating electromagnetic (EM) wave attenuation based on analysis of centroid frequency downshift (CFDS) of impulse radar signals is described and applied to cross-hole radar data. The method is based on a constant-Q model, which assumes a linear frequency dependence of attenuation for EM wave propagation above the transition frequency. The method uses the CFDS to construct the projection function. In comparison with other methods for estimating attenuation, the CFDS method is relatively insensitive to the effects of geometric spreading, instrument response, and antenna coupling and radiation pattern, but requires the data to be broadband so that the frequency shift and variance can be easily measured. The method is well-suited for difference tomography experiments using electrically conductive tracers. The CFDS method was tested using cross-hole radar data collected at the U.S. Geological Survey Fractured Rock Research Site at Mirror Lake, New Hampshire (NH) during a saline-tracer injection experiment. The attenuation-difference tomogram created with the CFDS method outlines the spatial distribution of saline tracer within the tomography plane. ?? 1998 Elsevier Science B.V. All rights reserved.

Integration of Geophysical Methods By A Generalised Probability Tomography Approach

NASA Astrophysics Data System (ADS)

Mauriello, P.; Patella, D.

In modern science, the propensity interpretative approach stands on the assumption that any physical system consists of two kinds of reality: actual and potential. Also geophysical data systems have potentialities that extend far beyond the few actual models normally attributed to them. Indeed, any geophysical data set is in itself quite inherently ambiguous. Classical deterministic inversion, including tomography, usu- ally forces a measured data set to collapse into a few rather subjective models based on some available a priori information. Classical interpretation is thus an intrinsically limited approach requiring a very deep logical extension. We think that a way to high- light a system full potentiality is to introduce probability as the leading paradigm in dealing with field data systems. Probability tomography has been recently introduced as a completely new approach to data interpretation. Probability tomography has been originally formulated for the self-potential method. It has been then extended to geo- electric, natural source electromagnetic induction, gravity and magnetic methods. Fol- lowing the same rationale, in this paper we generalize the probability tomography the- ory to a generic geophysical anomaly vector field, including the treatment for scalar fields as a particular case. This generalization makes then possible to address for the first time the problem of the integration of different methods by a conjoint probabil- ity tomography imaging procedure. The aim is to infer the existence of an unknown buried object through the analysis of an ad hoc occurrence probability function, blend- ing the physical messages brought forth by a set of singularly observed anomalies.

A brief perspective on computational electromagnetics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nachman, A.

1996-06-01

There is a growing interest in many quarters in acquiring the ability to predict all manner of electromagnetic (EM) effects. These effects include radar scattering attributes of objects (airplanes, missles, tanks, ships, etc.); the mutal interference of a multitude of antennas on board a single aircraft or ship; the performance of integrated circuits (IC); the propagation of waves (radio and radar) over long distances with the help of hindrance of complicated tomography and ionospheric/atmospheric ducting; and the propagation of pulses through dispersive media (soil, treetops, or concrete) to detect pollutants or hidden targets, or to assess the health of runways.more » All of the above require extensive computation and, despite the fact that Maxwell`s equations are linear in all these cases, codes do not exist which will do the job in a timely and error-controlled manner. This report briefly discusses how this can be rectified. 16 refs.« less

Development of the EM tomography system by the vertical electromagnetic profiling (VEMP) method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miura, Y.; Osato, K.; Takasugi, S.

1995-12-31

As a part of the {open_quotes}Deep-Seated Geothermal Resources Survey{close_quotes} project being undertaken by the NEDO, the Vertical ElectroMagnetic Profiling (VEMP) method is being developed to accurately obtain deep resistivity structure. The VEMP method acquires multi-frequency three-component magnetic field data in an open hole well using controlled sources (loop sources or grounded-wire sources) emitted at the surface. Numerical simulation using EM3D demonstrated that phase data of the VEMP method is very sensitive to resistivity structure and the phase data will also indicate presence of deep anomalies. Forward modelling was also used to determine required transmitter moments for various grounded-wire and loopmore » sources for a field test using the WD-1 well in the Kakkonda geothermal area. Field logging of the well was carried out in May 1994 and the processed field data matches well the simulated data.« less

Comparison of Low Resolution Electromagnetic Tomography Imaging Between Subjects With Mild and Severe Obstructive Sleep Apnea Syndrome: A Preliminary Study

PubMed Central

Lee, Hyun-Kwon; Shin, Hyun-Sil; Hong, Seok-Chan

2008-01-01

Objective The purpose of this study was to identify the regions of the brain associated with recurrent nocturnal chronic hypoxic episodes in patients with untreated obstructive sleep apnea syndrome (OSAS) using low-resolution electromagnetic tomography (LORETA) and quantitative electroencephalography (QEEG). Methods Nocturnal polysomnograph (NPSG) and subsequent morning electroencephalograph (EEG) were measured in 20 subjects with OSAS. Mild (n=10 ages 39.5±12.1 years) and severe (n=10 ages 41.7±13.6 years) right-handed male OSAS subjects were selected by interview and questionnaires including the NPSG, Beck Depression Inventory, Beck Anxiety Inventory, Epworth Sleepiness Scale, and Pittsburgh Sleep Quality Index. The LORETA and QEEG were compared between the severe and mild OSAS groups by frequency bands (delta 1-3 Hz, theta 4-7 Hz, alpha 8-12 Hz, beta1 13-18 Hz, beta2 19-21 Hz, beta3 22-30 Hz, and total 1-30 Hz) made by spectral analysis during resting with the eyes closed. Results The LORETA analysis showed decreased alpha activity at the right posterior cingulate gyrus (Brodmann area 23) in cases with severe OSAS compared to mild OSAS (p<0.05). For the QEEG, the absolute power of the alpha activity (8-12 Hz) was decreased in P3 (p=0.047), PZ (p=0.039) and O2 (p=0.04) in cases with severe OSAS compared to mild OSAS cases. The LORETA and QEEG analyses had similar results with regard to band, activation and location. Conclusion The decreased activity of the alpha frequency in the right posterior cingulate gyrus, in patients with severe OSAS compared to those with mild OSAS, suggests that chronic repeated short-term hypoxia during sleep, in OSAS, could provoke cortical brain dysfunction associated with cognitive dysfunction such as memory and attention. PMID:20046408

Working Memory and Neurofeedback.

PubMed

YuLeung To, Eric; Abbott, Kathy; Foster, Dale S; Helmer, D'Arcy

2016-01-01

Impairments in working memory are typically associated with impairments in other cognitive faculties such as attentional processes and short-term memory. This paper briefly introduces neurofeedback as a treatment modality in general, and, more specifically, we review several of the current modalities successfully used in neurofeedback (NF) for the treatment of working memory deficits. Two case studies are presented to illustrate how neurofeedback is applied in treatment. The development of Low Resolution Electromagnetic Tomography (LORETA) and its application in neurofeedback now makes it possible to specifically target deep cortical/subcortical brain structures. Developments in neuroscience concerning neural networks, combined with highly specific yet practical NF technologies, makes neurofeedback of particular interest to neuropsychological practice, including the emergence of specific methodologies for treating very difficult working memory (WM) problems.

Needle placement for piriformis injection using 3-D imaging.

PubMed

Clendenen, Steven R; Candler, Shawn A; Osborne, Michael D; Palmer, Scott C; Duench, Stephanie; Glynn, Laura; Ghazi, Salim M

2013-01-01

Piriformis syndrome is a pain syndrome originating in the buttock and is attributed to 6% - 8% of patients referred for the treatment of back and leg pain. The treatment for piriformis syndrome using fluoroscopy, computed tomography (CT), electromyography (EMG), and ultrasound (US) has become standard practice. The treatment of Piriformis Syndrome has evolved to include fluoroscopy and EMG with CT guidance. We present a case study of 5 successful piriformis injections using 3-D computer-assisted electromagnet needle tracking coupled with ultrasound. A 6-degree of freedom electromagnetic position tracker was attached to the ultrasound probe that allowed the system to detect the position and orientation of the probe in the magnetic field. The tracked ultrasound probe was used to find the posterior superior iliac spine. Subsequently, 3 points were captured to register the ultrasound image with the CT or magnetic resonance image scan. Moreover, after the registration was obtained, the navigation system visualized the tracked needle relative to the CT scan in real-time using 2 orthogonal multi-planar reconstructions centered at the tracked needle tip. Conversely, a recent study revealed that fluoroscopically guided injections had 30% accuracy compared to ultrasound guided injections, which tripled the accuracy percentage. This novel technique exhibited an accurate needle guidance injection precision of 98% while advancing to the piriformis muscle and avoiding the sciatic nerve. The mean (± SD) procedure time was 19.08 (± 4.9) minutes. This technique allows for electromagnetic instrument tip tracking with real-time 3-D guidance to the selected target. As with any new technique, a learning curve is expected; however, this technique could offer an alternative, minimizing radiation exposure.

Prostate tumor alignment and continuous, real-time adaptive radiation therapy using electromagnetic fiducials: clinical and cost-utility analyses.

PubMed

Quigley, Martin M; Mate, Timothy P; Sylvester, John E

2009-01-01

To evaluate the accuracy, utility, and cost effectiveness of a new electromagnetic patient positioning and continuous, real-time monitoring system, which uses permanently implanted resonant transponders in the target (Calypso 4D Localization System and Beacon transponders, Seattle, WA) to continuously monitor tumor location and movement during external beam radiation therapy of the prostate. This clinical trial studied 43 patients at 5 sites. All patients were implanted with 3 transponders each. In 41 patients, the system was used for initial alignment at each therapy session. Thirty-five patients had continuous monitoring during their radiation treatment. Over 1,000 alignment comparisons were made to a commercially available kV X-ray positioning system (BrainLAB ExacTrac, Munich, Germany). Using decision analysis and Markov processes, the outcomes of patients were simulated over a 5-year period and measured in terms of costs from a payer's perspective and quality-adjusted life years (QALYs). All patients had satisfactory transponder implantations for monitoring purposes. In over 75% of the treatment sessions, the correction to conventional positioning (laser and tattoos) directed by an electromagnetic patient positioning and monitoring system was greater than 5 mm. Ninety-seven percent (34/35) of the patients who underwent continuous monitoring had target motion that exceeded preset limits at some point during the course of their radiation therapy. Exceeding preset thresholds resulted in user intervention at least once during the therapy in 80% of the patients (28/35). Compared with localization using ultrasound, electronic portal imaging devices (EPID), or computed tomography (CT), localization with the electromagnetic patient positioning and monitoring system yielded superior gains in QALYs at comparable costs. Most patients positioned with conventional tattoos and lasers for prostate radiation therapy were found by use of the electromagnetic patient positioning and monitoring system to have alignment errors exceeding 5 mm. Almost all patients undergoing external beam radiation of the prostate have been shown to have target organ movement exceeding 3 mm during radiation therapy delivery. The ability of the electromagnetic technology to monitor tumor target location during the same time as radiation therapy is being delivered allows clinicians to provide real time adaptive radiation therapy for prostate cancer. This permits clinicians to intervene when the prostate moves outside the radiation isocenter, which should decrease adverse events and improve patient outcomes. Additionally, a cost-utility analysis has demonstrated that the electromagnetic patient positioning and monitoring system offers patient outcome benefits at a cost that falls well within the payer's customary willingness to pay (WTP) threshold of $50,000 per QALY.

Thermoacoustic Contrast of Prostate Cancer due to Heating by Very High Frequency Irradiation

PubMed Central

Hull, D; Thomas, M; Griep, SK; Jacobsohn, K; See, WA

2015-01-01

Applying the thermoacoustic (TA) effect to diagnostic imaging was first proposed in the 1980s. The object under test is irradiated by high-power pulses of electromagnetic energy, which heat tissue and cause thermal expansion. Outgoing TA pressure pulses are detected by ultrasound transducers and reconstructed to provide images of the object. The TA contrast mechanism is strongly dependent upon the frequency of the irradiating electromagnetic pulse. When very high frequency (VHF) electromagnetic irradiation is utilized, TA signal production is driven by ionic content. Prostatic fluids contain high levels of ionic metabolites, including citrate, zinc, calcium, and magnesium. Healthy prostate glands produce more ionic metabolites than diseased glands. VHF pulses are therefore expected to generate stronger TA signal in healthy prostate glands than in diseased glands. A benchtop system for performing ex vivo thermoacoustic computed tomography with VHF energy is described and images are presented. The system utilizes irradiation pulses of 700 ns duration exceeding 20 kW power. Reconstructions frequently visualize anatomic landmarks such as the urethra and verumontanum. TA reconstructions from three freshly excised human prostate glands with little, moderate, and severe cancerous involvement are compared with histology. TA signal strength is negatively correlated with percent cancerous involvement in this small sample size. For the 45 regions of interest analyzed, a reconstruction value of 0.4 mV provides 100% sensitivity but only 29% specificity. This sample size is far too small to draw sweeping conclusions, but the results warrant a larger volume study including comparison of TA images to the gold standard, histology. PMID:25554968

Thermoacoustic contrast of prostate cancer due to heating by very high frequency irradiation.

PubMed

Patch, S K; Hull, D; Thomas, M; Griep, S K; Jacobsohn, K; See, W A

2015-01-21

Applying the thermoacoustic (TA) effect to diagnostic imaging was first proposed in the 1980s. The object under test is irradiated by high-power pulses of electromagnetic energy, which heat tissue and cause thermal expansion. Outgoing TA pressure pulses are detected by ultrasound transducers and reconstructed to provide images of the object. The TA contrast mechanism is strongly dependent upon the frequency of the irradiating electromagnetic pulse. When very high frequency (VHF) electromagnetic irradiation is utilized, TA signal production is driven by ionic content. Prostatic fluids contain high levels of ionic metabolites, including citrate, zinc, calcium, and magnesium. Healthy prostate glands produce more ionic metabolites than diseased glands. VHF pulses are therefore expected to generate stronger TA signal in healthy prostate glands than in diseased glands. A benchtop system for performing ex vivo TA computed tomography with VHF energy is described and images are presented. The system utilizes irradiation pulses of 700 ns duration exceeding 20 kW power. Reconstructions frequently visualize anatomic landmarks such as the urethra and verumontanum. TA reconstructions from three freshly excised human prostate glands with little, moderate, and severe cancerous involvement are compared with histology. TA signal strength is negatively correlated with percent cancerous involvement in this small sample size. For the 45 regions of interest analyzed, a reconstruction value of 0.4 mV provides 100% sensitivity but only 29% specificity. This sample size is far too small to draw sweeping conclusions, but the results warrant a larger volume study including comparison of TA images to the gold standard, histology.

Development of Early Warning System for Landslide Using Electromagnetic, Hydrological, Geotechnical, and Geological Approaches

NASA Astrophysics Data System (ADS)

Huang, Q.; Hattori, K.; Chae, B.

2011-12-01

The Joint Research Collaboration Program (JRCP) for Chinese-Korean-Japanese (CKJ) Research Collaboration is a new cooperative scheme for joint funding from Chinese Department of International Cooperation of the Ministry of Science and Technology (DOIC), Korea Foundation for International Cooperation of Science and Technology (KICOS) and Japan Science and Technology Agency (JST). In this paper, we will introduce the funded CKJ project entitled "Development of early warning system for landslide using electromagnetic, hydrological, geotechnical, and geological approaches". The final goal of the project is to develop a simple methodology for landslide monitoring/forecasting (early warning system) using self potential method in the frame work of joint research among China, Korea, and Japan. The project is developing a new scientific and technical methodology for prevention of natural soil disasters. The outline of the project is as follows: (1) basic understanding on the relationship between resistivity distribution and moisture in soil and their visualization of their dynamical changes in space and time using tomography technique, (2) laboratory experiments of rainfall induced landslides and sandbox for practical use of the basic understanding, (3) in-situ experiments for evaluation. Annual workshops/symposia, seminars will be organized for strengthening the scientific collaborations and exchanges. In consideration of the above issues, integration of geological, hydrological, geotechnical characteristics with electromagnetic one are adopted as the key approach in this project. This study is partially supported by the Joint Research Collaboration Program, DOIC, MOST, China (2010DFA21570) and the National Natural Science Foundation of China (40974038, 41025014).

EDITORIAL: Introduction to the special issue on electromagnetic inverse problems: emerging methods and novel applications Introduction to the special issue on electromagnetic inverse problems: emerging methods and novel applications

NASA Astrophysics Data System (ADS)

Dorn, O.; Lesselier, D.

2010-07-01

Inverse problems in electromagnetics have a long history and have stimulated exciting research over many decades. New applications and solution methods are still emerging, providing a rich source of challenging topics for further investigation. The purpose of this special issue is to combine descriptions of several such developments that are expected to have the potential to fundamentally fuel new research, and to provide an overview of novel methods and applications for electromagnetic inverse problems. There have been several special sections published in Inverse Problems over the last decade addressing fully, or partly, electromagnetic inverse problems. Examples are: Electromagnetic imaging and inversion of the Earth's subsurface (Guest Editors: D Lesselier and T Habashy) October 2000 Testing inversion algorithms against experimental data (Guest Editors: K Belkebir and M Saillard) December 2001 Electromagnetic and ultrasonic nondestructive evaluation (Guest Editors: D Lesselier and J Bowler) December 2002 Electromagnetic characterization of buried obstacles (Guest Editors: D Lesselier and W C Chew) December 2004 Testing inversion algorithms against experimental data: inhomogeneous targets (Guest Editors: K Belkebir and M Saillard) December 2005 Testing inversion algorithms against experimental data: 3D targets (Guest Editors: A Litman and L Crocco) February 2009 In a certain sense, the current issue can be understood as a continuation of this series of special sections on electromagnetic inverse problems. On the other hand, its focus is intended to be more general than previous ones. Instead of trying to cover a well-defined, somewhat specialized research topic as completely as possible, this issue aims to show the broad range of techniques and applications that are relevant to electromagnetic imaging nowadays, which may serve as a source of inspiration and encouragement for all those entering this active and rapidly developing research area. Also, the construction of this special issue is likely to have been different from preceding ones. In addition to the invitations sent to specific research groups involved in electromagnetic inverse problems, the Guest Editors also solicited recommendations, from a large number of experts, of potential authors who were thereupon encouraged to contribute. Moreover, an open call for contributions was published on the homepage of Inverse Problems in order to attract as wide a scope of contributions as possible. This special issue's attempt at generality might also define its limitations: by no means could this collection of papers be exhaustive or complete, and as Guest Editors we are well aware that many exciting topics and potential contributions will be missing. This, however, also determines its very special flavor: besides addressing electromagnetic inverse problems in a broad sense, there were only a few restrictions on the contributions considered for this section. One requirement was plausible evidence of either novelty or the emergent nature of the technique or application described, judged mainly by the referees, and in some cases by the Guest Editors. The technical quality of the contributions always remained a stringent condition of acceptance, final adjudication (possibly questionable either way, not always positive) being made in most cases once a thorough revision process had been carried out. Therefore, we hope that the final result presented here constitutes an interesting collection of novel ideas and applications, properly refereed and edited, which will find its own readership and which can stimulate significant new research in the topics represented. Overall, as Guest Editors, we feel quite fortunate to have obtained such a strong response to the call for this issue and to have a really wide-ranging collection of high-quality contributions which, indeed, can be read from the first to the last page with sustained enthusiasm. A large number of applications and techniques is represented, overall via 16 contributions with 45 authors in total. This shows, in our opinion, that electromagnetic imaging and inversion remain amongst the most challenging and active research areas in applied inverse problems today. Below, we give a brief overview of the contributions included in this issue, ordered alphabetically by the surname of the leading author. 1. The complexity of handling potential randomness of the source in an inverse scattering problem is not minor, and the literature is far from being replete in this configuration. The contribution by G Bao, S N Chow, P Li and H Zhou, `Numerical solution of an inverse medium scattering problem with a stochastic source', exemplifies how to hybridize Wiener chaos expansion with a recursive linearization method in order to solve the stochastic problem as a set of decoupled deterministic ones. 2. In cases where the forward problem is expensive to evaluate, database methods might become a reliable method of choice, while enabling one to deliver more information on the inversion itself. The contribution by S Bilicz, M Lambert and Sz Gyimóthy, `Kriging-based generation of optimal databases as forward and inverse surrogate models', describes such a technique which uses kriging for constructing an efficient database with the goal of achieving an equidistant distribution of points in the measurement space. 3. Anisotropy remains a considerable challenge in electromagnetic imaging, which is tackled in the contribution by F Cakoni, D Colton, P Monk and J Sun, `The inverse electromagnetic scattering problem for anisotropic media', via the fact that transmission eigenvalues can be retrieved from a far-field scattering pattern, yielding, in particular, lower and upper bounds of the index of refraction of the unknown (dielectric anisotropic) scatterer. 4. So-called subspace optimization methods (SOM) have attracted a lot of interest recently in many fields. The contribution by X Chen, `Subspace-based optimization method for inverse scattering problems with an inhomogeneous background medium', illustrates how to address a realistic situation in which the medium containing the unknown obstacles is not homogeneous, via blending a properly developed SOM with a finite-element approach to the required Green's functions. 5. H Egger, M Hanke, C Schneider, J Schöberl and S Zaglmayr, in their contribution `Adjoint-based sampling methods for electromagnetic scattering', show how to efficiently develop sampling methods without explicit knowledge of the dyadic Green's function once an adjoint problem has been solved at much lower computational cost. This is demonstrated by examples in demanding propagative and diffusive situations. 6. Passive sensor arrays can be employed to image reflectors from ambient noise via proper migration of cross-correlation matrices into their embedding medium. This is investigated, and resolution, in particular, is considered in detail, as a function of the characteristics of the sensor array and those of the noise, in the contribution by J Garnier and G Papanicolaou, `Resolution analysis for imaging with noise'. 7. A direct reconstruction technique based on the conformal mapping theorem is proposed and investigated in depth in the contribution by H Haddar and R Kress, `Conformal mapping and impedance tomography'. This paper expands on previous work, with inclusions in homogeneous media, convergence results, and numerical illustrations. 8. The contribution by T Hohage and S Langer, `Acceleration techniques for regularized Newton methods applied to electromagnetic inverse medium scattering problems', focuses on a spectral preconditioner intended to accelerate regularized Newton methods as employed for the retrieval of a local inhomogeneity in a three-dimensional vector electromagnetic case, while also illustrating the implementation of a Lepskiĭ-type stopping rule outsmarting a traditional discrepancy principle. 9. Geophysical applications are a rich source of practically relevant inverse problems. The contribution by M Li, A Abubakar and T Habashy, `Application of a two-and-a-half dimensional model-based algorithm to crosswell electromagnetic data inversion', deals with a model-based inversion technique for electromagnetic imaging which addresses novel challenges such as multi-physics inversion, and incorporation of prior knowledge, such as in hydrocarbon recovery. 10. Non-stationary inverse problems, considered as a special class of Bayesian inverse problems, are framed via an orthogonal decomposition representation in the contribution by A Lipponen, A Seppänen and J P Kaipio, `Reduced order estimation of nonstationary flows with electrical impedance tomography'. The goal is to simultaneously estimate, from electrical impedance tomography data, certain characteristics of the Navier--Stokes fluid flow model together with time-varying concentration distribution. 11. Non-iterative imaging methods of thin, penetrable cracks, based on asymptotic expansion of the scattering amplitude and analysis of the multi-static response matrix, are discussed in the contribution by W-K Park, `On the imaging of thin dielectric inclusions buried within a half-space', completing, for a shallow burial case at multiple frequencies, the direct imaging of small obstacles (here, along their transverse dimension), MUSIC and non-MUSIC type indicator functions being used for that purpose. 12. The contribution by R Potthast, `A study on orthogonality sampling' envisages quick localization and shaping of obstacles from (portions of) far-field scattering patterns collected at one or more time-harmonic frequencies, via the simple calculation (and summation) of scalar products between those patterns and a test function. This is numerically exemplified for Neumann/Dirichlet boundary conditions and homogeneous/heterogeneous embedding media. 13. The contribution by J D Shea, P Kosmas, B D Van Veen and S C Hagness, `Contrast-enhanced microwave imaging of breast tumors: a computational study using 3D realistic numerical phantoms', aims at microwave medical imaging, namely the early detection of breast cancer. The use of contrast enhancing agents is discussed in detail and a number of reconstructions in three-dimensional geometry of realistic numerical breast phantoms are presented. 14. The contribution by D A Subbarayappa and V Isakov, `Increasing stability of the continuation for the Maxwell system', discusses enhanced log-type stability results for continuation of solutions of the time-harmonic Maxwell system, adding a fresh chapter to the interesting story of the study of the Cauchy problem for PDE. 15. In their contribution, `Recent developments of a monotonicity imaging method for magnetic induction tomography in the small skin-depth regime', A Tamburrino, S Ventre and G Rubinacci extend the recently developed monotonicity method toward the application of magnetic induction tomography in order to map surface-breaking defects affecting a damaged metal component. 16. The contribution by F Viani, P Rocca, M Benedetti, G Oliveri and A Massa, `Electromagnetic passive localization and tracking of moving targets in a WSN-infrastructured environment', contributes to what could still be seen as a niche problem, yet both useful in terms of applications, e.g., security, and challenging in terms of methodologies and experiments, in particular, in view of the complexity of environments in which this endeavor is to take place and the variability of the wireless sensor networks employed. To conclude, we would like to thank the able and tireless work of Kate Watt and Zoë Crossman, as past and present Publishers of the Journal, on what was definitely a long and exciting journey (sometimes a little discouraging when reports were not arriving, or authors were late, or Guest Editors overwhelmed) that started from a thorough discussion at the `Manchester workshop on electromagnetic inverse problems' held mid-June 2009, between Kate Watt and the Guest Editors. We gratefully acknowledge the fact that W W Symes gave us his full backing to carry out this special issue and that A K Louis completed it successfully. Last, but not least, the staff of Inverse Problems should be thanked, since they work together to make it a premier journal.

Deep Europe today: Geophysical synthesis of the upper mantle structure and lithospheric processes over 3.5 Ga

USGS Publications Warehouse

Artemieva, I.M.; Thybo, H.; Kaban, M.K.; ,

2006-01-01

We present a summary of geophysical models of the subcrustal lithosphere of Europe. This includes the results from seismic (reflection and refraction profiles, P- and S-wave tomography, mantle anisotropy), gravity, thermal, electromagnetic, elastic and petrological studies of the lithospheric mantle. We discuss major tectonic processes as reflected in the lithospheric structure of Europe, from Precambrian terrane accretion and subduction to Phanerozoic rifting, volcanism, subduction and continent-continent collision. The differences in the lithospheric structure of Precambrian and Phanerozoic Europe, as illustrated by a comparative analysis of different geophysical data, are shown to have both a compositional and a thermal origin. We propose an integrated model of physical properties of the European subcrustal lithosphere, with emphasis on the depth intervals around 150 and 250 km. At these depths, seismic velocity models, constrained by body-and surface-wave continent-scale tomography, are compared with mantle temperatures and mantle gravity anomalies. This comparison provides a framework for discussion of the physical or chemical origin of the major lithospheric anomalies and their relation to large-scale tectonic processes, which have formed the present lithosphere of Europe. ?? The Geological Society of London 2006.

A review of anisotropic conductivity models of brain white matter based on diffusion tensor imaging.

PubMed

Wu, Zhanxiong; Liu, Yang; Hong, Ming; Yu, Xiaohui

2018-06-01

The conductivity of brain tissues is not only essential for electromagnetic source estimation (ESI), but also a key reflector of the brain functional changes. Different from the other brain tissues, the conductivity of whiter matter (WM) is highly anisotropic and a tensor is needed to describe it. The traditional electrical property imaging methods, such as electrical impedance tomography (EIT) and magnetic resonance electrical impedance tomography (MREIT), usually fail to image the anisotropic conductivity tensor of WM with high spatial resolution. The diffusion tensor imaging (DTI) is a newly developed technique that can fulfill this purpose. This paper reviews the existing anisotropic conductivity models of WM based on the DTI and discusses their advantages and disadvantages, as well as identifies opportunities for future research on this subject. It is crucial to obtain the linear conversion coefficient between the eigenvalues of anisotropic conductivity tensor and diffusion tensor, since they share the same eigenvectors. We conclude that the electrochemical model is suitable for ESI analysis because the conversion coefficient can be directly obtained from the concentration of ions in extracellular liquid and that the volume fraction model is appropriate to study the influence of WM structural changes on electrical conductivity. Graphical abstract ᅟ.

Memory for light as a quantum process.

PubMed

Lobino, M; Kupchak, C; Figueroa, E; Lvovsky, A I

2009-05-22

We report complete characterization of an optical memory based on electromagnetically induced transparency. We recover the superoperator associated with the memory, under two different working conditions, by means of a quantum process tomography technique that involves storage of coherent states and their characterization upon retrieval. In this way, we can predict the quantum state retrieved from the memory for any input, for example, the squeezed vacuum or the Fock state. We employ the acquired superoperator to verify the nonclassicality benchmark for the storage of a Gaussian distributed set of coherent states.

New trend in electron holography

NASA Astrophysics Data System (ADS)

Tanigaki, Toshiaki; Harada, Ken; Murakami, Yasukazu; Niitsu, Kodai; Akashi, Tetsuya; Takahashi, Yoshio; Sugawara, Akira; Shindo, Daisuke

2016-06-01

Electron holography using a coherent electron wave is a promising technique for high-resolution visualization of electromagnetic fields in and around objects. The capability of electron holography has been enhanced by the development of new technologies and has thus become an even more powerful tool for exploring scientific frontiers. This review introduces these technologies including split-illumination electron holography and vector-field electron tomography. Split-illumination electron holography, which uses separated coherent waves, overcomes the limits imposed by the lateral coherence requirement for electron waves in electron holography. Areas that are difficult to observe using conventional electron holography are now observable. Exemplified applications include observing a singular magnetic domain wall in electrical steel sheets, local magnetizations at anti-phase boundaries, and electrostatic potentials in metal-oxide-semiconductor field-effect transistors. Vector-field electron tomography can be used to visualize magnetic vectors in three dimensions. Two components of the vectors are reconstructed using dual-axis tomography, and the remaining one is calculated using div B   =  0. A high-voltage electron microscope can be used to achieve precise magnetic reconstruction. For example, magnetic vortices have been visualized using a 1 MV holography electron microscope.

Regularized solution of a nonlinear problem in electromagnetic sounding

NASA Astrophysics Data System (ADS)

Piero Deidda, Gian; Fenu, Caterina; Rodriguez, Giuseppe

2014-12-01

Non destructive investigation of soil properties is crucial when trying to identify inhomogeneities in the ground or the presence of conductive substances. This kind of survey can be addressed with the aid of electromagnetic induction measurements taken with a ground conductivity meter. In this paper, starting from electromagnetic data collected by this device, we reconstruct the electrical conductivity of the soil with respect to depth, with the aid of a regularized damped Gauss-Newton method. We propose an inversion method based on the low-rank approximation of the Jacobian of the function to be inverted, for which we develop exact analytical formulae. The algorithm chooses a relaxation parameter in order to ensure the positivity of the solution and implements various methods for the automatic estimation of the regularization parameter. This leads to a fast and reliable algorithm, which is tested on numerical experiments both on synthetic data sets and on field data. The results show that the algorithm produces reasonable solutions in the case of synthetic data sets, even in the presence of a noise level consistent with real applications, and yields results that are compatible with those obtained by electrical resistivity tomography in the case of field data. Research supported in part by Regione Sardegna grant CRP2_686.

The adaptive pattern of the auditory N1 peak revealed by standardized low-resolution brain electromagnetic tomography

PubMed Central

Zhang, Fawen; Deshpande, Aniruddha; Benson, Chelsea; Smith, Mathew; Eliassen, James; Fu, Qian-Jie

2011-01-01

The N1 peak in the late auditory evoked potential (LAEP) decreases in amplitude following stimulus repetition, displaying an adaptive pattern. The present study explored the functional neural substrates that may underlie the N1 adaptive pattern using standardized Low Resolution Electromagnetic Tomography (sLORETA). Fourteen young normal hearing (NH) listeners participated in the study. Tone bursts (80 dB SPL) were binaurally presented via insert earphones in trains of ten; the inter-stimulus interval was 0.7 s and the inter-train interval was 15 s. Current source density analysis was performed for the N1 evoked by the 1st, 2nd and 10th stimuli (S1, S2 and S10) at three different timeframes that corresponded to the latency ranges of the N1 waveform subcomponents (70–100, 100–130 and 130–160 ms). The data showed that S1 activated broad regions in different cortical lobes and the activation was much smaller for S2 and S10. Response differences in the LAEP waveform and sLORETA were observed between S1 and S2, but not between the S2 and S10. The sLORETA comparison map between S1 and S2 response showed the activation was located in the parietal lobe for the 70–100 ms timeframe, the frontal and limbic lobes for the 100–130 ms timeframe, and the frontal lobe for the 130–160 ms timeframe. These sLORETA comparison results suggest a parieto-frontal network that might help to sensitize the brain to novel stimuli by filtering out repetitive and irrelevant stimuli. This study demonstrates that sLORETA may be useful for identifying generators of scalp-recorded event related potentials and for examining the physiological features of these generators. This technique could be especially useful for cortical source localization in individuals who cannot be examined with functional magnetic resonance imaging or magnetoencephalography (e.g., cochlear implant users). PMID:21658681

The adaptive pattern of the auditory N1 peak revealed by standardized low-resolution brain electromagnetic tomography.

PubMed

Zhang, Fawen; Deshpande, Aniruddha; Benson, Chelsea; Smith, Mathew; Eliassen, James; Fu, Qian-Jie

2011-07-11

The N1 peak in the late auditory evoked potential (LAEP) decreases in amplitude following stimulus repetition, displaying an adaptive pattern. The present study explored the functional neural substrates that may underlie the N1 adaptive pattern using standardized Low Resolution Electromagnetic Tomography (sLORETA). Fourteen young normal hearing (NH) listeners participated in the study. Tone bursts (80 dB SPL) were binaurally presented via insert earphones in trains of 10; the inter-stimulus interval was 0.7s and the inter-train interval was 15s. Current source density analysis was performed for the N1 evoked by the 1st, 2nd and 10th stimuli (S(1), S(2) and S(10)) at 3 different timeframes that corresponded to the latency ranges of the N1 waveform subcomponents (70-100, 100-130 and 130-160 ms). The data showed that S(1) activated broad regions in different cortical lobes and the activation was much smaller for S(2) and S(10). Response differences in the LAEP waveform and sLORETA were observed between S(1) and S(2), but not between the S(2) and S(10). The sLORETA comparison map between S(1) and S(2) responses showed that the activation was located in the parietal lobe for the 70-100 ms timeframe, the frontal and limbic lobes for the 100-130 ms timeframe, and the frontal lobe for the 130-160 ms timeframe. These sLORETA comparison results suggest a parieto-frontal network that might help to sensitize the brain to novel stimuli by filtering out repetitive and irrelevant stimuli. This study demonstrates that sLORETA may be useful for identifying generators of scalp-recorded event related potentials and for examining the physiological features of these generators. This technique could be especially useful for cortical source localization in individuals who cannot be examined with functional magnetic resonance imaging or magnetoencephalography (e.g., cochlear implant users). Copyright © 2011 Elsevier B.V. All rights reserved.

Protracted parahippocampal activity associated with Sean Harribance

PubMed Central

Persinger, Michael A; Saroka, Kevin S

2012-01-01

Aims: Previous research published by Venkatasubramanian et al. (2008) in this journal showed markedly enhanced functional magnetic resonance imaging (fMRI) activity within the right parahippocampal region of a gifted person while he experienced accurate telepathic impression. The present research is designed to discern if Sean Harribance, a reliable psychic who reported independently verified accurate histories of others during his intuitive state, would also show similar enhancement as measured by standardized low resolution electromagnetic tomography (sLORETA). Materials and Methods and Results: The raw data from the unique electroencephalographic pattern displayed by Sean Harribance (the Harribance configuration) during his intuitive state revealed a peak increase of power within the upper beta range (20-30 Hz) within the right parahippocampal region only. Conclusions: The congruence of the region of activation during “telepathy” by Sean Harribance and Gerard Senehi, especially when the specific electromagnetic and cellular characteristics are considered, suggests the parahippocampal region may be a focus for exploration of the mechanisms by which these phenomena might occur. PMID:22869999

Changes in the central nervous system during long-duration space flight: implications for neuro-imaging

NASA Astrophysics Data System (ADS)

Newberg, A. B.; Alavi, A.

The purpose of this paper is to review the potential functional and morphological effects of long duration space flight on the human central nervous system (CNS) and how current neuroimaging techniques may be utilized to study these effects. It must be determined if there will be any detrimental changes to the CNS from long term exposure to the space environment if human beings are to plan interplanetary missions or establish permanent space habitats. Research to date has focused primarily on the short term changes in the CNS as the result of space flight. The space environment has many factors such as weightlessness, electromagnetic fields, and radiation, that may impact upon the function and structure of the CNS. CNS changes known to occur during and after long term space flight include neurovestibular disturbances, cephalic fluid shifts, alterations in sensory perception, changes in proprioception, psychological disturbances, and cognitive changes. Animal studies have shown altered plasticity of the neural cytoarchitecture, decreased neuronal metabolism in the hypothalamus, and changes in neurotransmitter concentrations. Recent progress in the ability to study brain morphology, cerebral metabolism, and neurochemistry in vivo in the human brain would provide ample opportunity to investigate many of the changes that occur in the CNS as a result of space flight. These methods include positron emission tomography (PET), single photon emission computed tomography (SPECT), and magnetic resonance imaging (MRI).

An AST-ELM Method for Eliminating the Influence of Charging Phenomenon on ECT.

PubMed

Wang, Xiaoxin; Hu, Hongli; Jia, Huiqin; Tang, Kaihao

2017-12-09

Electrical capacitance tomography (ECT) is a promising imaging technology of permittivity distributions in multiphase flow. To reduce the effect of charging phenomenon on ECT measurement, an improved extreme learning machine method combined with adaptive soft-thresholding (AST-ELM) is presented and studied for image reconstruction. This method can provide a nonlinear mapping model between the capacitance values and medium distributions by using machine learning but not an electromagnetic-sensitive mechanism. Both simulation and experimental tests are carried out to validate the performance of the presented method, and reconstructed images are evaluated by relative error and correlation coefficient. The results have illustrated that the image reconstruction accuracy by the proposed AST-ELM method has greatly improved than that by the conventional methods under the condition with charging object.

An AST-ELM Method for Eliminating the Influence of Charging Phenomenon on ECT

PubMed Central

Wang, Xiaoxin; Hu, Hongli; Jia, Huiqin; Tang, Kaihao

2017-01-01

Electrical capacitance tomography (ECT) is a promising imaging technology of permittivity distributions in multiphase flow. To reduce the effect of charging phenomenon on ECT measurement, an improved extreme learning machine method combined with adaptive soft-thresholding (AST-ELM) is presented and studied for image reconstruction. This method can provide a nonlinear mapping model between the capacitance values and medium distributions by using machine learning but not an electromagnetic-sensitive mechanism. Both simulation and experimental tests are carried out to validate the performance of the presented method, and reconstructed images are evaluated by relative error and correlation coefficient. The results have illustrated that the image reconstruction accuracy by the proposed AST-ELM method has greatly improved than that by the conventional methods under the condition with charging object. PMID:29232850

GEANT4 Tuning For pCT Development

NASA Astrophysics Data System (ADS)

Yevseyeva, Olga; de Assis, Joaquim T.; Evseev, Ivan; Schelin, Hugo R.; Paschuk, Sergei A.; Milhoretto, Edney; Setti, João A. P.; Díaz, Katherin S.; Hormaza, Joel M.; Lopes, Ricardo T.

2011-08-01

Proton beams in medical applications deal with relatively thick targets like the human head or trunk. Thus, the fidelity of proton computed tomography (pCT) simulations as a tool for proton therapy planning depends in the general case on the accuracy of results obtained for the proton interaction with thick absorbers. GEANT4 simulations of proton energy spectra after passing thick absorbers do not agree well with existing experimental data, as showed previously. Moreover, the spectra simulated for the Bethe-Bloch domain showed an unexpected sensitivity to the choice of low-energy electromagnetic models during the code execution. These observations were done with the GEANT4 version 8.2 during our simulations for pCT. This work describes in more details the simulations of the proton passage through aluminum absorbers with varied thickness. The simulations were done by modifying only the geometry in the Hadrontherapy Example, and for all available choices of the Electromagnetic Physics Models. As the most probable reasons for these effects is some specific feature in the code, or some specific implicit parameters in the GEANT4 manual, we continued our study with version 9.2 of the code. Some improvements in comparison with our previous results were obtained. The simulations were performed considering further applications for pCT development.

Topography of activation deficits in schizophrenia during P300 task related to cognition and structural connectivity.

PubMed

Molina, Vicente; Bachiller, Alejandro; de Luis, Rodrigo; Lubeiro, Alba; Poza, Jesús; Hornero, Roberto; Alonso, Joan Francesc; Mañanas, Miguel Angel; Marqués, Patricia; Romero, Sergio

2018-02-02

The study of cerebral underpinnings of schizophrenia may benefit from the high temporal resolution of electromagnetic techniques, but its spatial resolution is low. However, source imaging approaches such as low-resolution brain electromagnetic tomography (LORETA) allow for an acceptable compromise between spatial and temporal resolutions. We combined LORETA with 32 channels and 3-Tesla diffusion magnetic resonance (Dmr) to study cerebral dysfunction in 38 schizophrenia patients (17 first episodes, FE), compared to 53 healthy controls. The EEG was acquired with subjects performing an odd-ball task. Analyses included an adaptive window of interest to take into account the interindividual variability of P300 latency. We compared source activation patters to distractor (P3a) and target (P3b) tones within- and between-groups. Patients showed a reduced activation in anterior cingulate and lateral and medial prefrontal cortices, as well as inferior/orbital frontal regions. This was also found in the FE patients alone. The activation was directly related to IQ in the patients and controls and to working memory performance in controls. Symptoms were unrelated to source activation. Fractional anisotropy in the tracts connecting lateral prefrontal and anterior cingulate regions predicted source activation in these regions in the patients. These results replicate the source activation deficit found in a previous study with smaller sample size and a lower number of sensors and suggest an association between structural connectivity deficits and functional alterations.

Quantitative EEG abnormalities in persons with "pure" epileptic predisposition without epilepsy: a low resolution electromagnetic tomography (LORETA) study.

PubMed

Puskás, S; Bessenyei, M; Fekete, I; Hollódy, K; Clemens, B

2010-09-01

Epileptic predisposition means genetically determined, increased seizure susceptibility. Neurophysiological evaluation of this condition is still lacking. In order to investigate "pure epileptic predisposition" (without epilepsy) in this pilot study the authors prospectively recruited ten persons who displayed generalized tonic-clonic seizures precipitated by 24 or more hours of sleep deprivation but were healthy in any other respects. 21-channel EEGs were recorded in the morning, in the waking state, after a night of sufficient sleep in the interictal period. For each person, a total of 120s artifact-free EEG was processed to low resolution electromagnetic tomography (LORETA) analysis. LORETA activity (Ampers/meters squared) was computed for 2394 voxels, 19 active electrodes and 1Hz very narrow bands from 1 to 25Hz. The data were compressed into four frequency bands (delta: 0.5-4.0Hz, theta: 4.5-8.0Hz, alpha: 8.5-12.0Hz, beta: 12.5-25.0Hz) and projected onto the MRI figures of a digitized standard brain atlas. The band-related LORETA results were compared to those of ten, age- and sex-matched healthy persons using independent t-tests. p<0.01 differences were accepted as statistically significant. Statistically significant decrease of alpha activity was found in widespread, medial and lateral parts of the cortex above the level of the basal ganglia. Maximum alpha decrease and statistically significant beta decrease were found in the left precuneus. Statistically not significant differences were delta increase in the medial-basal frontal area and theta increase in the same area and in the basal temporal area. The significance of alpha decrease in the patient group remains enigmatic. beta decrease presumably reflects non-specific dysfunction of the cortex. Prefrontal delta and theta increase might have biological meaning despite the lack of statistical significance: these findings are topographically similar to those reported in idiopathic generalized epilepsy in previous investigations. Quantitative EEG characteristics of the genetically determined epilepsy predisposition were given in terms of frequency bands and anatomical distribution. Copyright 2010 Elsevier B.V. All rights reserved.

Integration of microwave tomography with magnetic resonance for improved breast imaging

PubMed Central

Meaney, Paul M.; Golnabi, Amir H.; Epstein, Neil R.; Geimer, Shireen D.; Fanning, Margaret W.; Weaver, John B.; Paulsen, Keith D.

2013-01-01

Purpose: Breast magnetic resonance imaging is highly sensitive but not very specific for the detection of breast cancer. Opportunities exist to supplement the image acquisition with a more specific modality provided the technical challenges of meeting space limitations inside the bore, restricted breast access, and electromagnetic compatibility requirements can be overcome. Magnetic resonance (MR) and microwave tomography (MT) are complementary and synergistic because the high resolution of MR is used to encode spatial priors on breast geometry and internal parenchymal features that have distinct electrical properties (i.e., fat vs fibroglandular tissue) for microwave tomography. Methods: The authors have overcome integration challenges associated with combining MT with MR to produce a new coregistered, multimodality breast imaging platform—magnetic resonance microwave tomography, including: substantial illumination tank size reduction specific to the confined MR bore diameter, minimization of metal content and composition, reduction of metal artifacts in the MR images, and suppression of unwanted MT multipath signals. Results: MR SNR exceeding 40 dB can be obtained. Proper filtering of MR signals reduces MT data degradation allowing MT SNR of 20 dB to be obtained, which is sufficient for image reconstruction. When MR spatial priors are incorporated into the recovery of MT property estimates, the errors between the recovered versus actual dielectric properties approach 5%. Conclusions: The phantom and human subject exams presented here are the first demonstration of combining MT with MR to improve the accuracy of the reconstructed MT images. PMID:24089930

Robust electromagnetically guided endoscopic procedure using enhanced particle swarm optimization for multimodal information fusion.

PubMed

Luo, Xiongbiao; Wan, Ying; He, Xiangjian

2015-04-01

Electromagnetically guided endoscopic procedure, which aims at accurately and robustly localizing the endoscope, involves multimodal sensory information during interventions. However, it still remains challenging in how to integrate these information for precise and stable endoscopic guidance. To tackle such a challenge, this paper proposes a new framework on the basis of an enhanced particle swarm optimization method to effectively fuse these information for accurate and continuous endoscope localization. The authors use the particle swarm optimization method, which is one of stochastic evolutionary computation algorithms, to effectively fuse the multimodal information including preoperative information (i.e., computed tomography images) as a frame of reference, endoscopic camera videos, and positional sensor measurements (i.e., electromagnetic sensor outputs). Since the evolutionary computation method usually limits its possible premature convergence and evolutionary factors, the authors introduce the current (endoscopic camera and electromagnetic sensor's) observation to boost the particle swarm optimization and also adaptively update evolutionary parameters in accordance with spatial constraints and the current observation, resulting in advantageous performance in the enhanced algorithm. The experimental results demonstrate that the authors' proposed method provides a more accurate and robust endoscopic guidance framework than state-of-the-art methods. The average guidance accuracy of the authors' framework was about 3.0 mm and 5.6° while the previous methods show at least 3.9 mm and 7.0°. The average position and orientation smoothness of their method was 1.0 mm and 1.6°, which is significantly better than the other methods at least with (2.0 mm and 2.6°). Additionally, the average visual quality of the endoscopic guidance was improved to 0.29. A robust electromagnetically guided endoscopy framework was proposed on the basis of an enhanced particle swarm optimization method with using the current observation information and adaptive evolutionary factors. The authors proposed framework greatly reduced the guidance errors from (4.3, 7.8) to (3.0 mm, 5.6°), compared to state-of-the-art methods.

Review of progress in quantitative NDE

NASA Astrophysics Data System (ADS)

s of 386 papers and plenary presentations are included. The plenary sessions are related to the national technology initiative. The other sessions covered the following NDE topics: corrosion, electromagnetic arrays, elastic wave scattering and backscattering/noise, civil structures, material properties, holography, shearography, UT wave propagation, eddy currents, coatings, signal processing, radiography, computed tomography, EM imaging, adhesive bonds, NMR, laser ultrasonics, composites, thermal techniques, magnetic measurements, nonlinear acoustics, interface modeling and characterization, UT transducers, new techniques, joined materials, probes and systems, fatigue cracks and fracture, imaging and sizing, NDE in engineering and process control, acoustics of cracks, and sensors. An author index is included.

Identifying target regions for vigilance improvement under hormone replacement therapy in postmenopausal syndrome patients by means of electroencephalographic tomography (LORETA).

PubMed

Saletu, B; Anderer, P; Saletu-Zyhlarz, G M; Gruber, D; Metka, M; Huber, J

2005-04-01

Daytime fatigue, which at the neurophysiological level is due to vigilance decrements, is a frequent complaint in postmenopausal women. In a three-arm, 2-month, parallel group-design study, vigilance-promoting effects of a novel continuous combination (=Climodien 2/3) of estradiol valerate (EV; 2 mg) and dienogest (DNG; 3 mg) were compared with the effects of both EV alone and placebo in 55 insomniac, postmenopausal syndrome patients. Low-resolution brain electromagnetic tomography (LORETA) was undertaken to identify the cerebral target regions of hormone replacement therapy. An omnibus significance test revealed Climodien to increase activity in 882 of 2,394 voxels in the alpha-2 band, followed by 733, 706, and 664 voxels in the beta-2, beta-1, and beta-3 bands, and 509 voxels in the delta band, whereas 2 mg EV alone did not produce a significant suprathreshold activity. Current density increased predominantly in the right hemisphere, which had already been described in the literature as the center of the vigilance system. In the fast alpha range, which plays a major role in the context of vigilance, increased activity was found in the right prefrontal, temporal, and superior parietal cortices, i.e., those brain areas of the right-sided fronto-parietal neuronal network that are responsible for sustained attention. A further activity increase was seen in the anterior cingulate gyrus associated with attentional control and conflict monitoring. The right temporal lobe showed increased current density in all frequency bands. Electroencephalographic tomography (LORETA) identified the right-hemispheric vigilance system as the target region of Climodien.

Sura heating facility transmissions to the CASSIOPE/e-POP satellite

NASA Astrophysics Data System (ADS)

James, H. G.; Frolov, V. L.; Andreeva, E. S.; Padokhin, A. M.; Siefring, C. L.

2017-02-01

Throughout a nighttime pass of the CASSIOPE satellite at an altitude of about 1300 km above the Sura heating facility, transmission of O-mode radiation from Sura to the enhanced Polar Outflow Probe (e-POP) Radio Receiver Instrument on CASSIOPE was maintained. Also, during this pass, continuous VHF/UHF transmission from the e-POP Coherent Electromagnetic Radio Tomography radio beacon to three coordinated ground receivers in the Sura vicinity was achieved. Tomography of the VHF/UHF received wave data based on total electron content permitted the two-dimensional distribution of ionospheric ambient electron plasma frequency fpe to be determined in the latitude-altitude space between Sura and CASSIOPE. The foF2 values about 0.1 MHz above the Sura pump frequency of 4.3 MHz were measured by the tomography. We examine the question of whether the observations can be explained on the basis of classic propagation in a smooth ionosphere. Tracing of rays from Sura toward CASSIOPE orbital locations finds most rays reflected away from the topside by the patchy ionospheric structure in bottomside fpe. It is concluded that O-mode ducting in underdense field-aligned irregularities is responsible for maintaining the transionospheric transmission across the 2 min pass. O- to Z-mode "radio-window" conversion in the F region bottomside is not required to explain these data.

Alteration of Electro-Cortical Activity in Microgravity

NASA Astrophysics Data System (ADS)

Schneider, Stefan; Brummer, Vera; Carnahan, Heather; Askew, Christopher D.; Guardiera, Simon; Struder, Heiko K.

2008-06-01

There is growing interest in the effects of weightlessness on central nervous system (CNS) activity. Due to technical and logistical limitations it presently seems impossible to apply imaging techniques as fMRI or PET in weightless environments e.g. on ISS or during parabolic flights. Within this study we evaluated changes in brain cortical activity using low resolution brain electromagnetic tomography (LORETA) during parabolic flights. Results showed a distinct inhibition of right frontal area activity >12Hz during phases of microgravity compared to normal gravity. We conclude that the inhibition of high frequency frontal activity during microgravity may serve as a marker of emotional anxiety and/or indisposition associated with weightlessness. This puts a new light on the debate as to whether cognitive and sensorimotor impairments are attributable to primary physiological effects or secondary psychological effects of a weightless environment.

A LORETA study of mental time travel: similar and distinct electrophysiological correlates of re-experiencing past events and pre-experiencing future events.

PubMed

Lavallee, Christina F; Persinger, Michael A

2010-12-01

Previous studies exploring mental time travel paradigms with functional neuroimaging techniques have uncovered both common and distinct neural correlates of re-experiencing past events or pre-experiencing future events. A gap in the mental time travel literature exists, as paradigms have not explored the affective component of re-experiencing past episodic events; this study explored this sparsely researched area. The present study employed standardized low resolution electromagnetic tomography (sLORETA) to identify electrophysiological correlates of re-experience affect-laden and non-affective past events, as well as pre-experiencing a future anticipated event. Our results confirm previous research and are also novel in that we illustrate common and distinct electrophysiological correlates of re-experiencing affective episodic events. Furthermore, research from this experiment yields results outlining a pattern of activation in the frontal and temporal regions is correlated with the time frame of past or future events subjects imagined. Copyright © 2010 Elsevier Inc. All rights reserved.

Integrated geophysical investigations in a fault zone located on southwestern part of İzmir city, Western Anatolia, Turkey

NASA Astrophysics Data System (ADS)

Drahor, Mahmut G.; Berge, Meriç A.

2017-01-01

Integrated geophysical investigations consisting of joint application of various geophysical techniques have become a major tool of active tectonic investigations. The choice of integrated techniques depends on geological features, tectonic and fault characteristics of the study area, required resolution and penetration depth of used techniques and also financial supports. Therefore, fault geometry and offsets, sediment thickness and properties, features of folded strata and tectonic characteristics of near-surface sections of the subsurface could be thoroughly determined using integrated geophysical approaches. Although Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Seismic Refraction Tomography (SRT) methods are commonly used in active tectonic investigations, other geophysical techniques will also contribute in obtaining of different properties in the complex geological environments of tectonically active sites. In this study, six different geophysical methods used to define faulting locations and characterizations around the study area. These are GPR, ERT, SRT, Very Low Frequency electromagnetic (VLF), magnetics and self-potential (SP). Overall integrated geophysical approaches used in this study gave us commonly important results about the near surface geological properties and faulting characteristics in the investigation area. After integrated interpretations of geophysical surveys, we determined an optimal trench location for paleoseismological studies. The main geological properties associated with faulting process obtained after trenching studies. In addition, geophysical results pointed out some indications concerning the active faulting mechanism in the area investigated. Consequently, the trenching studies indicate that the integrated approach of geophysical techniques applied on the fault problem reveals very useful and interpretative results in description of various properties of faulting zone in the investigation site.

TDR measurements looking for complex dielectric permittivity and complex magnetic permeability in lossy materials

NASA Astrophysics Data System (ADS)

Persico, Raffaele

2017-04-01

TDR probes can be exploited for the measure of the electromagnetic characteristics of the soil, or of any penetrable material. They are commonly exploited as instruments for the measure of the propagation velocity of the electromagnetic waves in the probed medium [1], in its turn useful for the proper focusing of GPR data [2-5]. However, a more refined hardware and processing can allow to extrapolate from these probes also the discrimination between dielectric and magnetic characteristics of the material under test, which can be relevant for a better interpretation of the buried scenario or in order to infer physical-chemical characteristics of the material at hand. This requires a TDR probe that can work in frequency domain, and in particular that allows to retrieve the reflection coefficient at the air soil interface. It has been already shown [6] that in lossless cases this can be promising. In the present contribution, it will be shown at the EGU conference that it is possible to look for both the relative complex permittivity and the relative magnetic permeability of the probed material, on condition that the datum has an acceptable SNR and that some diversity of information is guaranteed, either by multifrequency data or by a TDR that can prolong its arms in the soil. References [1] F. Soldovieri, G. Prisco, R. Persico, Application of Microwave Tomography in Hydrogeophysics: some examples, Vadose Zone Journal, vol. 7, n. 1 pp. 160-170, Feb. 2008. [2] I. Catapano, L. Crocco, R. Persico, M. Pieraccini, F. Soldovieri, "Linear and Nonlinear Microwave Tomography Approaches for Subsurface Prospecting: Validation on Real Data", IEEE Trans. on Antennas and Wireless Propagation Letters, vol. 5, pp. 49-53, 2006. [3] G. Leucci, N. Masini, R. Persico, F. Soldovieri." GPR and sonic tomography for structural restoration : the case of the Cathedral of Tricarico", Journal of Geophysics and Engineering, vol. 8, pp. S76-S92, Aug. 2011. [4] S. Piscitelli, E. Rizzo, F. Cristallo, V. Lapenna, L. Crocco, R. Persico, F. Soldovieri, GPR and Microwave Tomography for Detecting shallow Cavities in the Historical Area of Sassi of Matera (Southern Italy), Near Surface Geophysics, vol. 5, pp. 275-285, 2007. [5] R. Persico, Introduction to Ground Penetrating Radar: Inverse Scattering and data processing. Wiley, 2014, ISBN 9781118305003. [6] R. Persico, Preliminary experiments about the measure of the magnetic properties of a material by means of TDR probes, Proc. EGU Meeting, Vienna, April 17-22, 2016

Effects of the Effect of Ultra High Frequency Mobile Phone Radiation on Human Health.

PubMed

Moradi, Mosa; Naghdi, Nasrollah; Hemmati, Hamidreza; Asadi-Samani, Majid; Bahmani, Mahmoud

2016-05-01

Public and occupational exposure to electromagnetic fields due to the growing trend of electronic devices may cause adverse effects on human health. This paper describes the risk of mutation and sexual trauma and infertility in masculine sexual cell by mobile phone radiations. In this study, we measured the emitted dose from a radiofrequency device, such as switching high voltage at different frequencies using a scintillation detector. The switching high voltage power supply (HVPS) was built for the Single Photon Emission Computed Tomography (SPECT) system. For radiation dosimetry, we used an ALNOR scintillator that can measure gamma radiation. The simulation was performed by MATLAB software, and data from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) were used to verify the simulation. We investigated the risks that result from the waves, according to a report by International Commission on Non Ionizing Radiation Protection (ICNIRP), to every organ of the body is defined by the beam and electromagnetic radiation from this electronic device on people. The results showed that the maximum personal dose over a 15-min period working at the mentioned HVPS did not exceed 0.31 μSV/h (with an aluminum shield). So, according to other sources of radiation, continuous working time of the system should not be more than 10 hours. Finally, a characteristic curve for secure working with modules at different frequencies was reported. The RF input signal to the body for maximum penetration depth (δ) and electromagnetic energy absorption rate (SAR) of biological tissue were obtained for each tissue. The results of this study and International Commission of Non Ionization Radiation Protection (ICNIRP) reports showed the people who spend more than 50 minutes a day using a cell phone could have early dementia or other thermal damage due to the burning of glucose in the brain.

Effect of Ultra High Frequency Mobile Phone Radiation on Human Health

PubMed Central

Moradi, Mosa; Naghdi, Nasrollah; Hemmati, Hamidreza; Asadi-Samani, Majid; Bahmani, Mahmoud

2016-01-01

Introduction Public and occupational exposure to electromagnetic fields due to the growing trend of electronic devices may cause adverse effects on human health. This paper describes the risk of mutation and sexual trauma and infertility in masculine sexual cell by mobile phone radiations. Methods In this study, we measured the emitted dose from a radiofrequency device, such as switching high voltage at different frequencies using a scintillation detector. The switching high voltage power supply (HVPS) was built for the Single Photon Emission Computed Tomography (SPECT) system. For radiation dosimetry, we used an ALNOR scintillator that can measure gamma radiation. The simulation was performed by MATLAB software, and data from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) were used to verify the simulation. Results We investigated the risks that result from the waves, according to a report by International Commission on Non Ionizing Radiation Protection (ICNIRP), to every organ of the body is defined by the beam and electromagnetic radiation from this electronic device on people. The results showed that the maximum personal dose over a 15-min period working at the mentioned HVPS did not exceed 0.31 μSV/h (with an aluminum shield). So, according to other sources of radiation, continuous working time of the system should not be more than 10 hours. Finally, a characteristic curve for secure working with modules at different frequencies was reported. The RF input signal to the body for maximum penetration depth (δ) and electromagnetic energy absorption rate (SAR) of biological tissue were obtained for each tissue. Conclusion The results of this study and International Commission of Non Ionization Radiation Protection (ICNIRP) reports showed the people who spend more than 50 minutes a day using a cell phone could have early dementia or other thermal damage due to the burning of glucose in the brain. PMID:27382458

Brine delineation and monitoring with electrical resistivity tomography and electromagnetic borehole logging at the Fort Knox well field near West Point, Kentucky

USGS Publications Warehouse

Henderson, Rory; Unthank, Michael D.; Zettwoch, Douglas D.; Lane, John W.

2010-01-01

The potable water system at Fort Knox is threatened by brine contamination from improperly abandoned natural gas exploration wells. The Fort Knox well field is located near the town of West Point, Kentucky, in the flood plain of the Ohio River. At the site, unconsolidated sediments approximately 30 – 40 m thick, overlie shale and porous limestone. Brine is believed to flow vertically from the underlying formations to the unconsolidated aquifer through damaged or leaky well casings under a high hydraulic gradient from the artificially pressurized porous limestone, which is utilized for natural gas storage by a regional energy company. Upon reaching the unconsolidated aquifer, brinecontaminated groundwater enters water supply production wells under the pumping‐induced gradient. As part of the Fort Knox remediation strategy to reduce the impact of brine contamination, electrical resistivity tomography (ERT) and borehole electromagnetic (EM) logs are being collected annually to detect gross changes in subsurface conductivity. The 2009 ERT data show areas of high conductivity on the western (contaminated) side of the site with conductivities more than an order of magnitude higher than on the eastern (uncontaminated) side of the site. The areas of high conductivity are interpreted as brine contamination, consistent with known regions of brine contamination. Conductivities from the EM logs are consistent with the results from the ERT inversions. The EM logs show little change between 2008 and 2009, except for some small changes in the brine distribution in well PZ1. Yearly ERT surveys will be continued to detect new areas of brine contamination and monitor the remediation effort.

Design and evaluation of a computed tomography (CT)-compatible needle insertion device using an electromagnetic tracking system and CT images.

PubMed

Shahriari, Navid; Hekman, Edsko; Oudkerk, Matthijs; Misra, Sarthak

2015-11-01

Percutaneous needle insertion procedures are commonly used for diagnostic and therapeutic purposes. Although current technology allows accurate localization of lesions, they cannot yet be precisely targeted. Lung cancer is the most common cause of cancer-related death, and early detection reduces the mortality rate. Therefore, suspicious lesions are tested for diagnosis by performing needle biopsy. In this paper, we have presented a novel computed tomography (CT)-compatible needle insertion device (NID). The NID is used to steer a flexible needle (φ0.55 mm) with a bevel at the tip in biological tissue. CT images and an electromagnetic (EM) tracking system are used in two separate scenarios to track the needle tip in three-dimensional space during the procedure. Our system uses a control algorithm to steer the needle through a combination of insertion and minimal number of rotations. Noise analysis of CT images has demonstrated the compatibility of the device. The results for three experimental cases (case 1: open-loop control, case 2: closed-loop control using EM tracking system and case 3: closed-loop control using CT images) are presented. Each experimental case is performed five times, and average targeting errors are 2.86 ± 1.14, 1.11 ± 0.14 and 1.94 ± 0.63 mm for case 1, case 2 and case 3, respectively. The achieved results show that our device is CT-compatible and it is able to steer a bevel-tipped needle toward a target. We are able to use intermittent CT images and EM tracking data to control the needle path in a closed-loop manner. These results are promising and suggest that it is possible to accurately target the lesions in real clinical procedures in the future.

Computed tomography (CT)-compatible remote center of motion needle steering robot: Fusing CT images and electromagnetic sensor data.

PubMed

Shahriari, Navid; Heerink, Wout; van Katwijk, Tim; Hekman, Edsko; Oudkerk, Matthijs; Misra, Sarthak

2017-07-01

Lung cancer is the most common cause of cancer-related death, and early detection can reduce the mortality rate. Patients with lung nodules greater than 10 mm usually undergo a computed tomography (CT)-guided biopsy. However, aligning the needle with the target is difficult and the needle tends to deflect from a straight path. In this work, we present a CT-compatible robotic system, which can both position the needle at the puncture point and also insert and rotate the needle. The robot has a remote-center-of-motion arm which is achieved through a parallel mechanism. A new needle steering scheme is also developed where CT images are fused with electromagnetic (EM) sensor data using an unscented Kalman filter. The data fusion allows us to steer the needle using the real-time EM tracker data. The robot design and the steering scheme are validated using three experimental cases. Experimental Case I and II evaluate the accuracy and CT-compatibility of the robot arm, respectively. In experimental Case III, the needle is steered towards 5 real targets embedded in an anthropomorphic gelatin phantom of the thorax. The mean targeting error for the 5 experiments is 1.78 ± 0.70 mm. The proposed robotic system is shown to be CT-compatible with low targeting error. Small nodule size and large needle diameter are two risk factors that can lead to complications in lung biopsy. Our results suggest that nodules larger than 5 mm in diameter can be targeted using our method which may result in lower complication rate. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Three-Dimensional Electroencephalographic Changes on Low-Resolution Brain Electromagnetic Tomography (LORETA) During the Sleep Onset Period.

PubMed

Park, Doo-Heum; Ha, Jee Hyun; Ryu, Seung-Ho; Yu, Jaehak; Shin, Chul-Jin

2015-10-01

Electroencephalographic (EEG) patterns during sleep are markedly different from those measured during the waking state, but the process of falling asleep is not fully understood in terms of biochemical and neurophysiological aspects. We sought to investigate EEG changes that occur during the transitional period from wakefulness to sleep in a 3-dimensional manner to gain a better understanding of the physiological meaning of sleep for the brain. We examined EEG 3-dimensionally using LORETA (low-resolution electromagnetic tomography), to localize the brain region associated with changes that occur during the sleep onset period (SOP). Thirty-channel EEG was recorded in 61 healthy subjects. EEG power spectra and intracortical standardized LORETA were compared between 4 types of 30-second states, including the wakeful stage, transition stage, early sleep stage 1, and late sleep stage 1. Sleep onset began with increased delta and theta power and decreased alpha-1 power in the occipital lobe, and increased theta power in the parietal lobe. Thereafter, global reductions of alpha-1 and alpha-2 powers and greater increases of theta power in the occipito-parietal lobe occurred. As sleep became deeper in sleep stage 1, beta-2 and beta-3, powers decreased mainly in the frontal lobe and some regions of the parieto-temporo-limbic area. These findings suggest that sleep onset includes at least 3 steps in a sequential manner, which include an increase in theta waves in the posterior region of the brain, a global decrease in alpha waves, and a decrease in beta waves in the fronto-central area. © EEG and Clinical Neuroscience Society (ECNS) 2014.

On the use of particle filters for electromagnetic tracking in high dose rate brachytherapy.

PubMed

Götz, Th I; Lahmer, G; Brandt, T; Kallis, K; Strnad, V; Bert, Ch; Hensel, B; Tomé, A M; Lang, E W

2017-09-12

Modern radiotherapy of female breast cancers often employs high dose rate brachytherapy, where a radioactive source is moved inside catheters, implanted in the female breast, according to a prescribed treatment plan. Source localization relative to the patient's anatomy is determined with solenoid sensors whose spatial positions are measured with an electromagnetic tracking system. Precise sensor dwell position determination is of utmost importance to assure irradiation of the cancerous tissue according to the treatment plan. We present a hybrid data analysis system which combines multi-dimensional scaling with particle filters to precisely determine sensor dwell positions in the catheters during subsequent radiation treatment sessions. Both techniques are complemented with empirical mode decomposition for the removal of superimposed breathing artifacts. We show that the hybrid model robustly and reliably determines the spatial positions of all catheters used during the treatment and precisely determines any deviations of actual sensor dwell positions from the treatment plan. The hybrid system only relies on sensor positions measured with an EMT system and relates them to the spatial positions of the implanted catheters as initially determined with a computed x-ray tomography.

Shielding of Sensitive Electronic Devices in Magnetic Nanoparticle Hyperthermia Using Arrays of Coils

NASA Astrophysics Data System (ADS)

Spirou, S. V.; Tsialios, P.; Loudos, G.

2015-09-01

In Magnetic Nanoparticle Hyperthermia (MNH) an externally applied electromagnetic field transfers energy to the magnetic nanoparticles in the body, which in turn convert this energy into heat, thus locally heating the tissue they are located in. This external electromagnetic field is sufficiently strong so as to cause interference and affect sensitive electronic equipment. Standard shielding of magnetic fields involves Faraday cages or coating with high-permeability shielding alloys; however, these techniques cannot be used with optically sensitive devices, such as those employed in Optical Coherence Tomography or radionuclide imaging. In this work we present a method to achieve magnetic shielding using an array of coils. The magnetic field generated by a single coil was calculated using the COMSOL physics simulation toolkit. Software was written in C/C++ to import the single-coil data, and then calculate the positions, number of turns and currents in the shielding coils in order to minimize the magnetic field strength at the desired location. Simulations and calculations have shown that just two shielding coils can reduce the magnetic field by 2-3 orders of magnitude.

The performance of the spatiotemporal Kalman filter and LORETA in seizure onset localization.

PubMed

Hamid, Laith; Sarabi, Masoud; Japaridze, Natia; Wiegand, Gert; Heute, Ulrich; Stephani, Ulrich; Galka, Andreas; Siniatchkin, Michael

2015-08-01

The assumption of spatial-smoothness is often used to solve the bioelectric inverse problem during electroencephalographic (EEG) source imaging, e.g., in low resolution electromagnetic tomography (LORETA). Since the EEG data show a temporal structure, the combination of the temporal-smoothness and the spatial-smoothness constraints may improve the solution of the EEG inverse problem. This study investigates the performance of the spatiotemporal Kalman filter (STKF) method, which is based on spatial and temporal smoothness, in the localization of a focal seizure's onset and compares its results to those of LORETA. The main finding of the study was that the STKF with an autoregressive model of order two significantly outperformed LORETA in the accuracy and consistency of the localization, provided that the source space consists of a whole-brain volumetric grid. In the future, these promising results will be confirmed using data from more patients and performing statistical analyses on the results. Furthermore, the effects of the temporal smoothness constraint will be studied using different types of focal seizures.

Vadose Zone Transport Field Study: Status Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gee, Glendon W.; Ward, Anderson L.

2001-11-30

Studies were initiated at the Hanford Site to evaluate the process controlling the transport of fluids in the vadose zone and to develop a reliable database upon which vadose-zone transport models can be calibrated. These models are needed to evaluate contaminant migration through the vadose zone to underlying groundwaters at Hanford. A study site that had previously been extensively characterized using geophysical monitoring techniques was selected in the 200 E Area. Techniques used previously included neutron probe for water content, spectral gamma logging for radionuclide tracers, and gamma scattering for wet bulk density. Building on the characterization efforts of themore » past 20 years, the site was instrumented to facilitate the comparison of nine vadose-zone characterization methods: advanced tensiometers, neutron probe, electrical resistance tomography (ERT), high-resolution resistivity (HRR), electromagnetic induction imaging (EMI), cross-borehole radar (XBR), and cross-borehole seismic (XBS). Soil coring was used to obtain soil samples for analyzing ionic and isotopic tracers.« less

Intelligence and EEG current density using low-resolution electromagnetic tomography (LORETA).

PubMed

Thatcher, R W; North, D; Biver, C

2007-02-01

The purpose of this study was to compare EEG current source densities in high IQ subjects vs. low IQ subjects. Resting eyes closed EEG was recorded from 19 scalp locations with a linked ears reference from 442 subjects ages 5 to 52 years. The Wechsler Intelligence Test was administered and subjects were divided into low IQ (< or =90), middle IQ (>90 to <120) and high IQ (> or =120) groups. Low-resolution electromagnetic tomographic current densities (LORETA) from 2,394 cortical gray matter voxels were computed from 1-30 Hz based on each subject's EEG. Differences in current densities using t tests, multivariate analyses of covariance, and regression analyses were used to evaluate the relationships between IQ and current density in Brodmann area groupings of cortical gray matter voxels. Frontal, temporal, parietal, and occipital regions of interest (ROIs) consistently exhibited a direct relationship between LORETA current density and IQ. Maximal t test differences were present at 4 Hz, 9 Hz, 13 Hz, 18 Hz, and 30 Hz with different anatomical regions showing different maxima. Linear regression fits from low to high IQ groups were statistically significant (P < 0.0001). Intelligence is directly related to a general level of arousal and to the synchrony of neural populations driven by thalamo-cortical resonances. A traveling frame model of sequential microstates is hypothesized to explain the results.

A Simultaneous and Continuous Excitation Method for High-Speed Electrical Impedance Tomography with Reduced Transients and Noise Sensitivity

PubMed Central

Mylvaganam, Saba

2018-01-01

This paper presents a concept for soft field tomographic scan of all the projections of electromagnetic waves emanating from an array of electrodes. Instead of the sequential excitation of all pairs of electrodes in the list of all projections, the new method present here consists of a single and continuous excitation. This excitation signal is the linear combination of the excitation signals in the projection set at different AC frequencies. The response to a given projection is discriminated by selecting the corresponding AC frequency component in the signal spectra of the digitally demodulated signals. The main advantage of this method is the suppression of transients after each projection, which is particularly problematic in electrical impedance tomography due to contact impedance phenomena and skin effect. The second benefit over the sequential scan method is the increased number of samples for each measurement for reduced noise sensitivity with digital demodulation. The third benefit is the increased temporal resolution in high-speed applications. The main drawback is the increased number of signal sources required (one per electrode). This paper focuses on electrical impedance tomography, based on earlier work by the authors. An experimental proof-of-concept using a simple 4-electrodes electrical impedance tomographic system is presented using simulations and laboratory data. The method presented here may be extended to other modalities (ultrasonic, microwave, optical, etc.). PMID:29597327

Robust electromagnetically guided endoscopic procedure using enhanced particle swarm optimization for multimodal information fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Xiongbiao, E-mail: xluo@robarts.ca, E-mail: Ying.Wan@student.uts.edu.au; Wan, Ying, E-mail: xluo@robarts.ca, E-mail: Ying.Wan@student.uts.edu.au; He, Xiangjian

Purpose: Electromagnetically guided endoscopic procedure, which aims at accurately and robustly localizing the endoscope, involves multimodal sensory information during interventions. However, it still remains challenging in how to integrate these information for precise and stable endoscopic guidance. To tackle such a challenge, this paper proposes a new framework on the basis of an enhanced particle swarm optimization method to effectively fuse these information for accurate and continuous endoscope localization. Methods: The authors use the particle swarm optimization method, which is one of stochastic evolutionary computation algorithms, to effectively fuse the multimodal information including preoperative information (i.e., computed tomography images) asmore » a frame of reference, endoscopic camera videos, and positional sensor measurements (i.e., electromagnetic sensor outputs). Since the evolutionary computation method usually limits its possible premature convergence and evolutionary factors, the authors introduce the current (endoscopic camera and electromagnetic sensor’s) observation to boost the particle swarm optimization and also adaptively update evolutionary parameters in accordance with spatial constraints and the current observation, resulting in advantageous performance in the enhanced algorithm. Results: The experimental results demonstrate that the authors’ proposed method provides a more accurate and robust endoscopic guidance framework than state-of-the-art methods. The average guidance accuracy of the authors’ framework was about 3.0 mm and 5.6° while the previous methods show at least 3.9 mm and 7.0°. The average position and orientation smoothness of their method was 1.0 mm and 1.6°, which is significantly better than the other methods at least with (2.0 mm and 2.6°). Additionally, the average visual quality of the endoscopic guidance was improved to 0.29. Conclusions: A robust electromagnetically guided endoscopy framework was proposed on the basis of an enhanced particle swarm optimization method with using the current observation information and adaptive evolutionary factors. The authors proposed framework greatly reduced the guidance errors from (4.3, 7.8) to (3.0 mm, 5.6°), compared to state-of-the-art methods.« less

Quantitative EEG and Current Source Density Analysis of Combined Antiepileptic Drugs and Dopaminergic Agents in Genetic Epilepsy: Two Case Studies.

PubMed

Emory, Hamlin; Wells, Christopher; Mizrahi, Neptune

2015-07-01

Two adolescent females with absence epilepsy were classified, one as attention deficit and the other as bipolar disorder. Physical and cognitive exams identified hypotension, bradycardia, and cognitive dysfunction. Their initial electroencephalograms (EEGs) were considered slightly slow, but within normal limits. Quantitative EEG (QEEG) data included relative theta excess and low alpha mean frequencies. A combined treatment of antiepileptic drugs with a catecholamine agonist/reuptake inhibitor was sequentially used. Both patients' physical and cognitive functions improved and they have remained seizure free. The clinical outcomes were correlated with statistically significant changes in QEEG measures toward normal Z-scores in both anterior and posterior regions. In addition, low resolution electromagnetic tomography (LORETA) Z-scored source correlation analyses of the initial and treated QEEG data showed normalized patterns, supporting a neuroanatomic resolution. This study presents preliminary evidence for a neurophysiologic approach to patients with absence epilepsy and comorbid disorders and may provide a method for further research. © EEG and Clinical Neuroscience Society (ECNS) 2014.

Face-elicited ERPs and affective attitude: brain electric microstate and tomography analyses.

PubMed

Pizzagalli, D; Lehmann, D; Koenig, T; Regard, M; Pascual-Marqui, R D

2000-03-01

Although behavioral studies have demonstrated that normative affective traits modulate the processing of facial and emotionally charged stimuli, direct electrophysiological evidence for this modulation is still lacking. Event-related potential (ERP) data associated with personal, traitlike approach- or withdrawal-related attitude (assessed post-recording and 14 months later) were investigated in 18 subjects during task-free (i.e. unrequested, spontaneous) emotional evaluation of faces. Temporal and spatial aspects of 27 channel ERP were analyzed with microstate analysis and low resolution electromagnetic tomography (LORETA), a new method to compute 3 dimensional cortical current density implemented in the Talairach brain atlas. Microstate analysis showed group differences 132-196 and 196-272 ms poststimulus, with right-shifted electric gravity centers for subjects with negative affective attitude. During these (over subjects reliably identifiable) personality-modulated, face-elicited microstates, LORETA revealed activation of bilateral occipito-temporal regions, reportedly associated with facial configuration extraction processes. Negative compared to positive affective attitude showed higher activity right temporal; positive compared to negative attitude showed higher activity left temporo-parieto-occipital. These temporal and spatial aspects suggest that the subject groups differed in brain activity at early, automatic, stimulus-related face processing steps when structural face encoding (configuration extraction) occurs. In sum, the brain functional microstates associated with affect-related personality features modulate brain mechanisms during face processing already at early information processing stages.

Event-related-potential low-resolution brain electromagnetic tomography (ERP-LORETA) suggests decreased energetic resources for cognitive processing in narcolepsy.

PubMed

Saletu, Michael; Anderer, Peter; Saletu-Zyhlarz, Gerda Maria; Mandl, Magdalena; Zeitlhofer, Josef; Saletu, Bernd

2008-08-01

Event-related potentials (ERPs) are sensitive measures of both perceptual and cognitive processes. The aim of the present study was to identify brain regions involved in the processes of cognitive dysfunction in narcolepsy by means of ERP tomography. In 17 drug-free patients with narcolepsy and 17 controls, ERPs were recorded (auditory odd-ball paradigm). Latencies, amplitudes and LORETA sources were determined for standard (N1 and P2) and target (N2 and P300) ERP components. Psychometry included measures of mental performance, affect and critical flicker fusion frequency (CFF). In the ERPs patients demonstrated delayed cognitive N2 and P300 components and reduced amplitudes in midline regions, while N1 and P2 components did not differ from controls. LORETA suggested reduced P300 sources bilaterally in the precuneus, the anterior and posterior cingulate gyri, the ventrolateral prefrontal cortex and the parahippocampal gyrus. In psychometry, patients demonstrated deteriorated mood, increased trait anxiety, decreased CFF and a trend toward reduced general verbal memory and psychomotor activity. Narcoleptic patients showed prolonged information processing, as indexed by N2 and P300 latencies and decreased energetic resources for cognitive processing. Electrophysiological aberrations in brain areas related to the 'executive attention network' and the 'limbic system' may contribute to a deterioration in mental performance and mood at the behavioral level.

Structural and energetic processes related to P300: LORETA findings in depression and effects of antidepressant drugs.

PubMed

Anderer, P; Saletu, B; Semlitsch, H V; Pascual-Marqui, R D

2002-01-01

Noninvasive electrophysiological neuroimaging applied to cognitive components of event-related potentials (ERPs) may differentiate between structural and energetic processes related to information processing. The structural level, revealed by the location of the local maxima of the current source density distribution, describes the time-dependent network of activated brain areas. The magnitude of the source strength, a measure of the energetic component, describes the allocation of processing resources. ERPs were recorded in an odd-ball paradigm and low-resolution brain electromagnetic tomography (LORETA) was applied for standard and target ERP components. In a group of 60 menopausal depressed patients of 45-60 years of age, reduced P300 source strength was observed bilaterally, temporally and medially prefrontally reaching to rostal parts of the anterior cingulate, compared with 29 age-matched controls. In a double-blind, placebo-controlled study, 2 mg of the antidepressant citalopram induced a significant increase of P300 source strength in the (left) prefrontal cortex and precuneus compared with placebo, reaching to the posterior cingulate. Similar increases were observed after 800 mg S-adenosyl-L-methionine (SAMe) administered intravenously in ten young healthy subjects aged 22-33, and they were even more pronounced in ten elderly healthy subjects aged 56-71. Thus, ERP-tomography identified changes in energetic sources in brain areas predominantly involved in depression and in antidepressant action.

The electrophysiological "delayed effect" of focal interictal epileptiform discharges. A low resolution electromagnetic tomography (LORETA) study.

PubMed

Clemens, Béla; Piros, Pálma; Bessenyei, Mónika; Varga, Edit; Puskás, Szilvia; Fekete, István

2009-08-01

Collating the findings regarding the role of focal interictal epileptiform discharges (IEDs) on CNS functions raises the possibility that IEDs might have negative impact that outlasts the duration of the spike-and-wave complexes. The aim of this study was the electrophysiological demonstration of the "delayed effect" of the IEDs. 19-channel, linked-ears referenced, digital waking EEG records of 11 children (aged 6-14 years, eight with idiopathic, three with cryptogenic focal epilepsy, showing a single spike focus) were retrospectively selected from our database. A minimum of 20 (preferably, 30), 2-s epochs containing a single focal spike-and-wave complex were selected (Spike epochs). Thereafter, Postspike-1 (Ps1), Postspike-2 (Ps2) and Postspike-3 (Ps3) epochs were selected, representing the first and second seconds (Ps1), the third and fourth seconds (Ps2) and the fifth and sixth seconds (Ps3) after the Spike epoch, respectively. Interspike epochs (Is) were selected at a distance at least 10s after the Spike epoch. Individual analysis: the frequency of interest (FOI=the individual frequency of the wave component of the IEDs), and the region of interest (ROI=the site of the IEDs) were identified by reading the raw EEG waveform and the instant power spectrum. Very narrow band LORETA (low resolution electromagnetic tomography) analysis at the FOI and ROI was carried out. Age-adjusted, Z-transformed LORETA "activity" (=current source density, amperes/meters squared) was compared in the Spike, Ps1, Ps2, Ps3 and Is epochs. the greatest (uppermost pathological) Z-scores and the greatest spatial extension of the LORETA-abnormality were always found in the Spike epochs, followed by the gradual decrease of activity in terms of severity and spatial extension in the Ps1, Ps2, Ps3 epochs. The lowest (baseline) level and extension of the abnormality was found in the Is epochs. Group analysis: average values of activity across the patients were computed for the temporal decrease of the abnormality. a clear tendency for the decrease of abnormality was demonstrated. the "delayed effect" of the IEDs was demonstrated electrophysiologically and quantified. The method may be utilized in the individual assessment of the effect of IEDs on cortical activity, the degree and temporo-spatial extension of the abnormality.

Three-dimensional localization of abnormal EEG activity in migraine: a low resolution electromagnetic tomography (LORETA) study of migraine patients in the pain-free interval.

PubMed

Clemens, Béla; Bánk, József; Piros, Pálma; Bessenyei, Mónika; Veto, Sára; Tóth, Márton; Kondákor, István

2008-09-01

Investigating the brain of migraine patients in the pain-free interval may shed light on the basic cerebral abnormality of migraine, in other words, the liability of the brain to generate migraine attacks from time to time. Twenty unmedicated "migraine without aura" patients and a matched group of healthy controls were investigated in this explorative study. 19-channel EEG was recorded against the linked ears reference and was on-line digitized. 60 x 2-s epochs of eyes-closed, waking-relaxed activity were subjected to spectral analysis and a source localization method, low resolution electromagnetic tomography (LORETA). Absolute power was computed for 19 electrodes and four frequency bands (delta: 1.5-3.5 Hz, theta: 4.0-7.5 Hz, alpha: 8.0-12.5 Hz, beta: 13.0-25.0 Hz). LORETA "activity" (=current source density, ampers/meters squared) was computed for 2394 voxels and the above specified frequency bands. Group comparison was carried out for the specified quantitative EEG variables. Activity in the two groups was compared on a voxel-by-voxel basis for each frequency band. Statistically significant (uncorrected P < 0.01) group differences were projected to cortical anatomy. Spectral findings: there was a tendency for more alpha power in the migraine that in the control group in all but two (F4, C3) derivations. However, statistically significant (P < 0.01, Bonferroni-corrected) spectral difference was only found in the right occipital region. The main LORETA-finding was that voxels with P < 0.01 differences were crowded in anatomically contiguous cortical areas. Increased alpha activity was found in a cortical area including part of the precuneus, and the posterior part of the middle temporal gyrus in the right hemisphere. Decreased alpha activity was found bilaterally in medial parts of the frontal cortex including the anterior cingulate and the superior and medial frontal gyri. Neither spectral analysis, nor LORETA revealed statistically significant differences in the delta, theta, and beta bands. LORETA revealed the anatomical distribution of the cortical sources (generators) of the EEG abnormalities in migraine. The findings characterize the state of the cerebral cortex in the pain-free interval and might be suitable for planning forthcoming investigations.

Shallow subsurface imaging of the Piano di Pezza active normal fault (central Italy) by high-resolution refraction and electrical resistivity tomography coupled with time domain electromagnetic data

NASA Astrophysics Data System (ADS)

Villani, Fabio; Tulliani, Valerio; Fierro, Elisa; Sapia, Vincenzo; Civico, Riccardo

2015-04-01

The Piano di Pezza fault is the north-westernmost segment of the >20 km long Ovindoli-Pezza active normal fault-system (central Italy). Although existing paleoseismic data document high vertical Holocene slip rates (~1 mm/yr) and a remarkable seismogenic potential of this fault, its subsurface setting and Pleistocene cumulative displacement are still poorly known. We investigated for the first time by means of high-resolution seismic and electrical resistivity tomography coupled with time domain electromagnetic (TDEM) measurements the shallow subsurface of a key section of the Piano di Pezza fault. Our surveys cross a ~5 m-high fault scarp that was generated by repeated surface-rupturing earthquakes displacing some Late Holocene alluvial fans. We provide 2-D Vp and resistivity images which clearly show significant details of the fault structure and the geometry of the shallow basin infill material down to 50 m depth. We can estimate the dip (~50°) and the Holocene vertical displacement of the master fault (~10 m). We also recognize in the hangingwall some low-velocity/low-resistivity regions that we relate to packages of colluvial wedges derived from scarp degradation, which may represent the record of several paleo-earthquakes older than the Late Holocene events previously recognized by paleoseismic trenching. Conversely, due to the limited investigation depth of seismic and electrical tomography, the estimation of the cumulative amount of Pleistocene throw is hampered. Therefore, to increase the depth of investigation, we performed 7 TDEM measurements along the electrical profile using a 50 m loop size both in central and offset configuration. The recovered 1-D resistivity models show a good match with 2-D resistivity images in the near surface. Moreover, TDEM inversion results indicate that in the hangingwall, ~200 m away from the surface fault trace, the carbonate pre-Quaternary basement may be found at ~90-100 m depth. The combined approach of electrical and seismic data coupled with TDEM measurements provides a robust constraint to the Piano di Pezza fault cumulative offset. Our data are useful for better reconstructing the deep structural setting of the Piano di Pezza basin and assessing the role played by extensional tectonics in its Quaternary evolution.

Simulation of photoacoustic tomography (PAT) system in COMSOL and comparison of two popular reconstruction techniques

NASA Astrophysics Data System (ADS)

Sowmiya, C.; Thittai, Arun K.

2017-03-01

Photoacoustic imaging is a molecular cum functional imaging modality based on differential optical absorption of the incident laser pulse by the endogeneous tissue chromophores. Several numerical simulations and finite element models have been developed in the past to describe and study Photoacoustic (PA) signal generation principles and study the effect of variation in PA parameters. Most of these simulation work concentrate on analyzing extracted 1D PA signals and each of them mostly describe only few of the building blocks of a Photoacoustic Tomography (PAT) imaging system. Papers describing simulation of the entire PAT system in one simulation platform, along with reconstruction is seemingly rare. This study attempts to describe how a commercially available Finite Element software (COMSOL(R)), can serve as a single platform for simulating PAT that couples the electromagnetic, thermodynamic and acoustic pressure physics involved in PA phenomena. Further, an array of detector elements placed at the boundary in the FE model can provide acoustic pressure data that can be exported to Matlab(R) to perform tomographic image reconstruction. The performance of two most commonly used image reconstruction techniques; namely, Filtered Backprojection (FBP) and Synthetic Aperture (SA) beamforming are compared. Results obtained showed that the lateral resolution obtained using FBP vs. SA largely depends on the aperture parameters. FBP reconstruction was able to provide a slightly better lateral resolution for smaller aperture while SA worked better for larger aperture. This interesting effect is currently being investigated further. Computationally FBP was faster, but it had artifacts along the spherical shell on which the data is projected.

EEG topography and tomography (LORETA) in the classification and evaluation of the pharmacodynamics of psychotropic drugs.

PubMed

Saletu, Bernd; Anderer, Peter; Saletu-Zyhlarz, Gerda M

2006-04-01

By multi-lead computer-assisted quantitative analyses of human scalp-recorded electroencephalogram (QEEG) in combination with certain statistical procedures (quantitative pharmaco-EEG) and mapping techniques (pharmaco-EEG mapping or topography), it is possible to classify psychotropic substances and objectively evaluate their bioavailability at the target organ, the human brain. Specifically, one may determine at an early stage of drug development whether a drug is effective on the central nervous system (CNS) compared with placebo, what its clinical efficacy will be like, at which dosage it acts, when it acts and the equipotent dosages of different galenic formulations. Pharmaco-EEG maps of neuroleptics, antidepressants, tranquilizers, hypnotics, psychostimulants and nootropics/cognition-enhancing drugs will be described. Methodological problems, as well as the relationships between acute and chronic drug effects, alterations in normal subjects and patients, CNS effects and therapeutic efficacy will be discussed. Imaging of drug effects on the regional brain electrical activity of healthy subjects by means of EEG tomography such as low-resolution electromagnetic tomography (LORETA) has been used for identifying brain areas predominantly involved in psychopharmacological action. This will be shown for the representative drugs of the four main psychopharmacological classes, such as 3 mg haloperidol for neuroleptics, 20 mg citalopram for antidepressants, 2 mg lorazepam for tranquilizers and 20 mg methylphenidate for psychostimulants. LORETA demonstrates that these psychopharmacological classes affect brain structures differently. By considering these differences between psychotropic drugs and placebo in normal subjects, as well as between mental disorder patients and normal controls, it may be possible to choose the optimum drug for a specific patient according to a key-lock principle, since the drug should normalize the deviant brain function. Thus, pharmaco-EEG topography and tomography are valuable methods in human neuropsychopharmacology, clinical psychiatry and neurology.

MEG-EEG Information Fusion and Electromagnetic Source Imaging: From Theory to Clinical Application in Epilepsy.

PubMed

Chowdhury, Rasheda Arman; Zerouali, Younes; Hedrich, Tanguy; Heers, Marcel; Kobayashi, Eliane; Lina, Jean-Marc; Grova, Christophe

2015-11-01

The purpose of this study is to develop and quantitatively assess whether fusion of EEG and MEG (MEEG) data within the maximum entropy on the mean (MEM) framework increases the spatial accuracy of source localization, by yielding better recovery of the spatial extent and propagation pathway of the underlying generators of inter-ictal epileptic discharges (IEDs). The key element in this study is the integration of the complementary information from EEG and MEG data within the MEM framework. MEEG was compared with EEG and MEG when localizing single transient IEDs. The fusion approach was evaluated using realistic simulation models involving one or two spatially extended sources mimicking propagation patterns of IEDs. We also assessed the impact of the number of EEG electrodes required for an efficient EEG-MEG fusion. MEM was compared with minimum norm estimate, dynamic statistical parametric mapping, and standardized low-resolution electromagnetic tomography. The fusion approach was finally assessed on real epileptic data recorded from two patients showing IEDs simultaneously in EEG and MEG. Overall the localization of MEEG data using MEM provided better recovery of the source spatial extent, more sensitivity to the source depth and more accurate detection of the onset and propagation of IEDs than EEG or MEG alone. MEM was more accurate than the other methods. MEEG proved more robust than EEG and MEG for single IED localization in low signal-to-noise ratio conditions. We also showed that only few EEG electrodes are required to bring additional relevant information to MEG during MEM fusion.

Some Student Conceptions of Electromagnetic Induction

ERIC Educational Resources Information Center

Thong, Wai Meng; Gunstone, Richard

2008-01-01

Introductory electromagnetism is a central part of undergraduate physics. Although there has been some research into student conceptions of electromagnetism, studies have been sparse and separated. This study sought to explore second year physics students' conceptions of electromagnetism, to investigate to what extent the results from the present…

The Utility of EEG in Attention Deficit Hyperactivity Disorder: A Replication Study.

PubMed

Swatzyna, Ronald J; Tarnow, Jay D; Roark, Alexandra; Mardick, Jacob

2017-07-01

The routine use of stimulants in pediatrics has increased dramatically over the past 3 decades and the long-term consequences have yet to be fully studied. Since 1978 there have been 7 articles identifying electroencephalogram (EEG) abnormalities, particularly epileptiform discharges in children with attention deficit hyperactivity disorder (ADHD). Many have studied the prevalence of these discharges in this population with varying results. An article published in 2011 suggests that EEG technology should be considered prior to prescribing stimulants to children diagnosed with ADHD due to a high prevalence of epileptiform discharges. The 2011 study found a higher prevalence (26%) of epileptiform discharges when using 23-hour and sleep-deprived EEGs in comparison with other methods of activation (hyperventilation or photostimulation) and conventional EEG. We sought to replicate the 2011 results using conventional EEG with the added qEEG technologies of automatic spike detection and low-resolution electromagnetic tomography analysis (LORETA) brain mapping. Our results showed 32% prevalence of epileptiform discharges, which suggests that an EEG should be considered prior to prescribing stimulant medications.

Computational Electromagnetic Studies for Low-Frequency Compensation of the Reflector Impulse-radiating Antenna

DTIC Science & Technology

2015-03-26

COMPUTATIONAL ELECTROMAGNETIC STUDIES FOR LOW-FREQUENCY COMPENSATION OF THE REFLECTOR IMPULSE-RADIATING ANTENNA THESIS Casey E. Fillmore, Capt, USAF... ELECTROMAGNETIC STUDIES FOR LOW-FREQUENCY COMPENSATION OF THE REFLECTOR IMPULSE-RADIATING ANTENNA THESIS Presented to the Faculty Department of Electrical and...2015 DISTRIBUTION STATEMENT A APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. AFIT-ENG-MS-15-M-011 COMPUTATIONAL ELECTROMAGNETIC STUDIES FOR LOW

Electromagnetic Scattering Analysis of Large Size Asteroids/Comets for Reflection/Transmission Tomography (RTT)

NASA Technical Reports Server (NTRS)

Deshpande, Manohar

2011-01-01

A precise knowledge of the interior structure of asteroids, comets, and Near Earth Objects (NEO) is important to assess the consequences of their impacts with the Earth and develop efficient mitigation strategies. Knowledge of their interior structure also provides opportunities for extraction of raw materials for future space activities. Low frequency radio sounding is often proposed for investigating interior structures of asteroids and NEOs. For designing and optimizing radio sounding instrument it is advantageous to have an accurate and efficient numerical simulation model of radio reflection and transmission through large size bodies of asteroid shapes. In this presentation we will present electromagnetic (EM) scattering analysis of electrically large size asteroids using (1) a weak form formulation and (2) also a more accurate hybrid finite element method/method of moments (FEM/MOM) to help estimate their internal structures. Assuming the internal structure with known electrical properties of a sample asteroid, we first develop its forward EM scattering model. From the knowledge of EM scattering as a function of frequency and look angle we will then present the inverse scattering procedure to extract its interior structure image. Validity of the inverse scattering procedure will be presented through few simulation examples.

On the use of particle filters for electromagnetic tracking in high dose rate brachytherapy

NASA Astrophysics Data System (ADS)

Götz, Th I.; Lahmer, G.; Brandt, T.; Kallis, K.; Strnad, V.; Bert, Ch; Hensel, B.; Tomé, A. M.; Lang, E. W.

2017-10-01

Modern radiotherapy of female breast cancers often employs high dose rate brachytherapy, where a radioactive source is moved inside catheters, implanted in the female breast, according to a prescribed treatment plan. Source localization relative to the patient’s anatomy is determined with solenoid sensors whose spatial positions are measured with an electromagnetic tracking system. Precise sensor dwell position determination is of utmost importance to assure irradiation of the cancerous tissue according to the treatment plan. We present a hybrid data analysis system which combines multi-dimensional scaling with particle filters to precisely determine sensor dwell positions in the catheters during subsequent radiation treatment sessions. Both techniques are complemented with empirical mode decomposition for the removal of superimposed breathing artifacts. We show that the hybrid model robustly and reliably determines the spatial positions of all catheters used during the treatment and precisely determines any deviations of actual sensor dwell positions from the treatment plan. The hybrid system only relies on sensor positions measured with an EMT system and relates them to the spatial positions of the implanted catheters as initially determined with a computed x-ray tomography.

The unexplored avenues of human skin: electromagnetic properties in the sub-THz band

NASA Astrophysics Data System (ADS)

Feldman, Y.; Safrai, E.; Ben Ishai, P.; Puzenko, A.; Agranat, A. J.; Caduff, A.

2012-03-01

Recent studies of the minute morphology of the skin by optical coherence tomography showed that the sweat ducts in human skin become helically shaped tubes in the Epidermis and are filled with an aqueous solution. When considered as entities embedded in a dielectric media, they resemble helical antennas. The spectral response obtained by our computer simulations coincides with the analytical prediction of antenna theory and support this hypothesis, if a fast enough current mechanism exists in the duct. In particular the strongest spectral response of the simulation was noted around the predicted frequencies (240 GHz and 380 GHz) for the respective normal and axial modes of the helical structure. Furthermore, circular dichroism of the reflected electromagnetic field is a characteristic property of such helical antennas and it was shown that it is indeed a characteristic of the simulation model. Fast proton hopping is posited as the current mechanism. Consequently experimental evidence is presented that the spectral response of the skin in the sub-Terahertz region is governed by the level of activity of the perspiration system. This in turn is moderated by the Sympathetic Nerve Response and is demonstrated by the correlation to physiological stress as manifested by the pulse rate and the systolic blood pressure. These physical relaxations are tonic in nature (lasting more than a minute). Could the phasic characteristic of emotional excitation also be evident in the reflection coefficient? By applying techniques borrowed from psychiatric science we hope to answer this point in our paper.

Electromagnetic organ tracking allows for real-time compensation of tissue shift in image-guided laparoscopic rectal surgery: results of a phantom study.

PubMed

Wagner, M; Gondan, M; Zöllner, C; Wünscher, J J; Nickel, F; Albala, L; Groch, A; Suwelack, S; Speidel, S; Maier-Hein, L; Müller-Stich, B P; Kenngott, H G

2016-02-01

Laparoscopic resection is a minimally invasive treatment option for rectal cancer but requires highly experienced surgeons. Computer-aided technologies could help to improve safety and efficiency by visualizing risk structures during the procedure. The prerequisite for such an image guidance system is reliable intraoperative information on iatrogenic tissue shift. This could be achieved by intraoperative imaging, which is rarely available. Thus, the aim of the present study was to develop and validate a method for real-time deformation compensation using preoperative imaging and intraoperative electromagnetic tracking (EMT) of the rectum. Three models were compared and evaluated for the compensation of tissue deformation. For model A, no compensation was performed. Model B moved the corresponding points rigidly to the motion of the EMT sensor. Model C used five nested linear regressions with increasing level of complexity to compute the deformation (C1-C5). For evaluation, 14 targets and an EMT organ sensor were fit into a silicone-molded rectum of the OpenHELP phantom. Following a computed tomography, the image guidance was initiated and the rectum was deformed in the same way as during surgery in a total of 14 experimental runs. The target registration error (TRE) was measured for all targets in different positions of the rectum. The mean TRE without correction (model A) was 32.8 ± 20.8 mm, with only 19.6% of the measurements below 10 mm (80.4% above 10 mm). With correction, the mean TRE could be reduced using the rigid correction (model B) to 6.8 ± 4.8 mm with 78.7% of the measurements being <10 mm. Using the most complex linear regression correction (model C5), the error could be reduced to 2.9 ± 1.4 mm with 99.8% being below 10 mm. In laparoscopic rectal surgery, the combination of electromagnetic organ tracking and preoperative imaging is a promising approach to compensating for intraoperative tissue shift in real-time.

Classification and evaluation of the pharmacodynamics of psychotropic drugs by single-lead pharmaco-EEG, EEG mapping and tomography (LORETA).

PubMed

Saletu, B; Anderer, P; Saletu-Zyhlarz, G M; Arnold, O; Pascual-Marqui, R D

2002-01-01

Utilizing computer-assisted quantitative analyses of human scalp-recorded electroencephalogram (EEG) in combination with certain statistical procedures (quantitative pharmaco-EEG) and mapping techniques (pharmaco-EEG mapping), it is possible to classify psychotropic substances and objectively evaluate their bioavailability at the target organ: the human brain. Specifically, one may determine at an early stage of drug development whether a drug is effective on the central nervous system (CNS) compared with placebo, what its clinical efficacy will be like, at which dosage it acts, when it acts and the equipotent dosages of different galenic formulations. Pharmaco-EEG profiles and maps of neuroleptics, antidepressants, tranquilizers, hypnotics, psychostimulants and nootropics/cognition-enhancing drugs will be described in this paper. Methodological problems, as well as the relationships between acute and chronic drug effects, alterations in normal subjects and patients, CNS effects, therapeutic efficacy and pharmacokinetic and pharmacodynamic data will be discussed. In recent times, imaging of drug effects on the regional brain electrical activity of healthy subjects by means of EEG tomography such as low-resolution electromagnetic tomography (LORETA) has been used for identifying brain areas predominantly involved in psychopharmacological action. This will be demonstrated for the representative drugs of the four main psychopharmacological classes, such as 3 mg haloperidol for neuroleptics, 20 mg citalopram for antidepressants, 2 mg lorazepam for tranquilizers and 20 mg methylphenidate for psychostimulants. LORETA demonstrates that these psychopharmacological classes affect brain structures differently.

Microwave Tomographic approach for masonry investigation: some real results

NASA Astrophysics Data System (ADS)

Bavusi, M.; di Napoli, R.; Soldovieri, F.

2010-04-01

Ground Penetrating Radar (GPR) is an electromagnetic technique very appreciated by the community of the archaeologist and cultural heritage end-users community thanks to its appealing features in terms of non invasivity and rapidity of measurement and diagnostics. However, GPR data requires a high operator expertise in the data processing and interpretation. In the archaeological investigation, this drawback can be mitigated by the availability of a priori information about the archaeological scenario. On the other hand, in the case of the historical heritage, when the knowledge of constructive modalities and material of the structure may be completely missed, it is necessary to undertake other strategies of processing and interpretation. One of these can be provided by the use of novel inversion algorithms such as the Microwave Tomography (MT) which allows to reduce the subjectivity and the time consuming during the data processing. In this paper the MT was applied on raw data collected at two historical buildings of Chania (Crete, Greece). The first edifice is the Venizelo's House affected by visible fractures in its walls made up of cemented irregular stones. The second one is the headquarters of Prefecture of Chania showing some fractures along the floors. For these raw data, microwave tomography provided well detailed images which allowed to infer the fracture geometry and their extension in the host medium. This suggests microwave tomography can be a reliable complete processing tool requiring only the definition of the background scenario in terms of the dielectric permittivity and the conductivity of the host medium.

How Do Pre-Service Teachers Picture Various Electromagnetic Phenomenon? A Qualitative Study of Pre-Service Teachers' Conceptual Understanding of Fundamental Electromagnetic Interaction

ERIC Educational Resources Information Center

Beer, Christopher P.

2010-01-01

This study analyzes the nature of pre-service teachers' conceptual models of various electromagnetic phenomena, specifically electrical current, electrical resistance, and light/matter interactions. This is achieved through the students answering the three questions on electromagnetism using a free response approach including both verbal and…

Seismic velocity anisotropy and heterogeneity beneath the Mantle Electromagnetic and Tomography Experiment (MELT) region of the East Pacific Rise from analysis of P and S body waves

USGS Publications Warehouse

Hammond, W.C.; Toomey, D.R.

2003-01-01

We use teleseismic P and S delay times and shear wave splitting measurements to constrain isotropic and anisotropic heterogeneity in the mantle beneath the southern East Pacific Rise (SEPR). The data comprise 462 P and S delay times and 18 shear wave splitting observations recorded during the Mantle Electromagnetic and Tomography (MELT) Experiment. We estimate the mantle melt content (F) and temperature (T) variation from the isotropic velocity variation. Our results indicate that the maximum variation in F beneath our array is between zero and ???1.2%, and maximum variation in T is between zero and ???100 K. We favor an explanation having partial contributions from both T and F. We approximate the seismic anisotropy of the upper mantle with hexagonal symmetry, consistent with the assumption of two dimensionality of mantle flow. Our new tomographic technique uses a nonlinear inversion of P and slow S polarization delay times to simultaneously solve for coupled VP and VS heterogeneity throughout the model and for the magnitude of anisotropy within discrete domains. The domain dimensions and the dip of the anisotropy are fixed for each inversion but are varied in a grid search, obtaining the misfit of the models to the body wave delay data and to split times of vertically propagating S waves. The data misfit and the isotropic heterogeneity are sensitive to domain dimensions and dip of anisotropy. In a region centered beneath the SEPR the best average dip of the hexagonal symmetry axis is horizontal or dipping shallowly (<30??) west. Given the resolution of our data, a subaxial region characterized by vertically aligned symmetry axes may exist but is limited to be <80 km deep. We infer that the mantle flow beneath the SEPR is consistent with shallow asthenospheric return flow from the direction of the South Pacific superswell.

Electromagnetic topology: Characterization of internal electromagnetic coupling

NASA Technical Reports Server (NTRS)

Parmantier, J. P.; Aparicio, J. P.; Faure, F.

1991-01-01

The main principles are presented of a method dealing with the resolution of electromagnetic internal problems: Electromagnetic Topology. A very interesting way is to generalize the multiconductor transmission line network theory to the basic equation of the Electromagnetic Topology: the BLT equation. This generalization is illustrated by the treatment of an aperture as a four port junction. Analytical and experimental derivations of the scattering parameters are presented. These concepts are used to study the electromagnetic coupling in a scale model of an aircraft, and can be seen as a convenient means to test internal electromagnetic interference.

[Experimental research on the electromagnetic radiation immunity of a kind of portable monitor].

PubMed

Yuan, Jun; Xiao, Dongping; Jian, Xin

2010-11-01

The paper is focused on a kind of portable monitor that is widely used in military hospitals. In order to study the electromagnetic radiation immunity of the monitor, the experiments of electromagnetic radiation caused by radio frequency continuous wave in reverberation chamber and by ultra wide band (UWB) electromagnetic pulse have been done. The study results show that UWB electromagnetic pulse interferes observably the operating state of the monitor. It should be paid high attention to take protective measures. The monitor tested has some electromagnetic immunity ability for radio frequency continuous wave radiation. The frequent abnormal phenomena are baseline drift and waveform distortion. The electromagnetic sensitivity of the monitor is related to the frequency of interference source. The monitor tested is most sensitive to the frequency of 390 MHz.

[Electromagnetic pollution (electrosmog)--potential hazards of our electromagnetic future].

PubMed

Nowak, D; Radon, K

2004-02-26

The term electromagnetic environment encompasses the totality of all electric, magnetic and electromagnetic fields generated by natural and technical sources. A differentiation is made between low- and high-frequency electromagnetic fields. Typical sources of the former are domestic electricity Exposure to the latter is, for example, associated with the sue of mobile telephones. Studies on the health-related effects of electromagnetic fields are available in particular for the low-frequency range, based on an appropriate estimation of exposure. A number of these studies reveal an association between exposure to this type of electromagnetic fields and the occurrence of infantile leukemia in the highest exposure category. For high-frequency electromagnetic fields the number of epidemiological studies is limited. An increased risk of an accident occurring through the use of a cellular phone while driving has consistently been shown. Against the background of our limited knowledge about possible adverse effects of exposure to mobile phone transmitters, and the inability of the public to influence such exposure, transparency in the communication of the risks involved is of great importance.

Novel electro-optical coupling technique for magnetic resonance-compatible positron emission tomography detectors.

PubMed

Olcott, Peter D; Peng, Hao; Levin, Craig S

2009-01-01

A new magnetic resonance imaging (MRI)-compatible positron emission tomography (PET) detector design is being developed that uses electro-optical coupling to bring the amplitude and arrival time information of high-speed PET detector scintillation pulses out of an MRI system. The electro-optical coupling technology consists of a magnetically insensitive photodetector output signal connected to a nonmagnetic vertical cavity surface emitting laser (VCSEL) diode that is coupled to a multimode optical fiber. This scheme essentially acts as an optical wire with no influence on the MRI system. To test the feasibility of this approach, a lutetium-yttrium oxyorthosilicate crystal coupled to a single pixel of a solid-state photomultiplier array was placed in coincidence with a lutetium oxyorthosilicate crystal coupled to a fast photomultiplier tube with both the new nonmagnetic VCSEL coupling and the standard coaxial cable signal transmission scheme. No significant change was observed in 511 keV photopeak energy resolution and coincidence time resolution. This electro-optical coupling technology enables an MRI-compatible PET block detector to have a reduced electromagnetic footprint compared with the signal transmission schemes deployed in the current MRI/PET designs.

Novel experimental technique for 3D investigation of high-speed cavitating diesel fuel flows by X-ray micro computed tomography

NASA Astrophysics Data System (ADS)

Lorenzi, M.; Mitroglou, N.; Santini, M.; Gavaises, M.

2017-03-01

An experimental technique for the estimation of the temporal-averaged vapour volume fraction within high-speed cavitating flow orifices is presented. The scientific instrument is designed to employ X-ray micro computed tomography (microCT) as a quantitative 3D measuring technique applied to custom designed, large-scale, orifice-type flow channels made from Polyether-ether-ketone (PEEK). The attenuation of the ionising electromagnetic radiation by the fluid under examination depends on its local density; the transmitted radiation through the cavitation volume is compared to the incident radiation, and combination of radiographies from sufficient number of angles leads to the reconstruction of attenuation coefficients versus the spatial position. This results to a 3D volume fraction distribution measurement of the developing multiphase flow. The experimental results obtained are compared against the high speed shadowgraph visualisation images obtained in an optically transparent nozzle with identical injection geometry; comparison between the temporal mean image and the microCT reconstruction shows excellent agreement. At the same time, the real 3D internal channel geometry (possibly eroded) has been measured and compared to the nominal manufacturing CAD drawing of the test nozzle.

Military applications and examples of near-surface seismic surface wave methods (Invited)

NASA Astrophysics Data System (ADS)

sloan, S.; Stevens, R.

2013-12-01

Although not always widely known or publicized, the military uses a variety of geophysical methods for a wide range of applications--some that are already common practice in the industry while others are truly novel. Some of those applications include unexploded ordnance detection, general site characterization, anomaly detection, countering improvised explosive devices (IEDs), and security monitoring, to name a few. Techniques used may include, but are not limited to, ground penetrating radar, seismic, electrical, gravity, and electromagnetic methods. Seismic methods employed include surface wave analysis, refraction tomography, and high-resolution reflection methods. Although the military employs geophysical methods, that does not necessarily mean that those methods enable or support combat operations--often times they are being used for humanitarian applications within the military's area of operations to support local populations. The work presented here will focus on the applied use of seismic surface wave methods, including multichannel analysis of surface waves (MASW) and backscattered surface waves, often in conjunction with other methods such as refraction tomography or body-wave diffraction analysis. Multiple field examples will be shown, including explosives testing, tunnel detection, pre-construction site characterization, and cavity detection.

Novel experimental technique for 3D investigation of high-speed cavitating diesel fuel flows by X-ray micro computed tomography.

PubMed

Lorenzi, M; Mitroglou, N; Santini, M; Gavaises, M

2017-03-01

An experimental technique for the estimation of the temporal-averaged vapour volume fraction within high-speed cavitating flow orifices is presented. The scientific instrument is designed to employ X-ray micro computed tomography (microCT) as a quantitative 3D measuring technique applied to custom designed, large-scale, orifice-type flow channels made from Polyether-ether-ketone (PEEK). The attenuation of the ionising electromagnetic radiation by the fluid under examination depends on its local density; the transmitted radiation through the cavitation volume is compared to the incident radiation, and combination of radiographies from sufficient number of angles leads to the reconstruction of attenuation coefficients versus the spatial position. This results to a 3D volume fraction distribution measurement of the developing multiphase flow. The experimental results obtained are compared against the high speed shadowgraph visualisation images obtained in an optically transparent nozzle with identical injection geometry; comparison between the temporal mean image and the microCT reconstruction shows excellent agreement. At the same time, the real 3D internal channel geometry (possibly eroded) has been measured and compared to the nominal manufacturing CAD drawing of the test nozzle.

A letter of intent for an experiment to study strong electromagnetic fields at RHIC via multiple electromagnetic processes

NASA Technical Reports Server (NTRS)

Fatyga, M.; Norbury, John W.

1992-01-01

An experimental program at the Relativistic Heavy Ion Collider (RHIC) which is designed to study nonperturbative aspects of electrodynamics is outlined. Additional possibilities for new studies of electrodynamics via multiple electromagnetic processes are also described.

Geoelectrical Tomographies for the study of some landslide areas in the Lucanian Apennine Chain (Southern Italy)

NASA Astrophysics Data System (ADS)

Perrone, A.; Lapenna, V.; Piscitelli, S.; Rizzo, E.; Sdao, F.

2003-04-01

In the frame of the two projects supported by the Italian Ministry of Research: "Design of geophysical monitoring network in areas of the Basilicata Region characterized by a high hydrogeological hazard" and "Geomorphological study and landslides control in some areas of the Basilicata region characterized by historical-cultural heritage", we developed a research activity focussed on a 2D electromagnetic monitoring and modelling of landslide bodies. Basilicata region (Southern Italy), being dissected by numerous and often significant rivers and characterized by the outcrop of terrains with bad mechanical properties, is one of the more exposed regions of the southern Apennine chain to hydrogeologic hazard and shows a complete panorama of mass movements. In order to study some landslide areas located in the Basilicata region, such as Varco Izzo, Latronico, Campomaggiore and Maratea, we carried out 2D electrical resistivity imaging (ERI), 2D-3D self-potential tomographies and maps, combining advanced technologies for data acquisition and new methods for data inversion (Loke and Barker, 1996; McCann and Forster, 1990; Patella, 1997). The geophysical results allowed us: to outline the discontinuity between landslide material and bedrock, to identify the possible reactivation surfaces, to obtain useful information about the thickness of the mobilised material and the main patterns of the underground fluid flow. Geophysical results were compared with the data coming from geological and hydrogeological surveys and from the analysis of aerial photo and boreholes. The good correlation between the main anomalous geoelectrical zones, the main structural lineaments and hydrogeological characteristics of the investigated areas, allowed us to consider the used geoelectrical methods as a possible powerful tool to investigate landslide areas characterised by very complex geology.

Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sajib, Saurav Z. K.; Jeong, Woo Chul; Oh, Tong In

Anisotropy of biological tissues is a low-frequency phenomenon that is associated with the function and structure of cell membranes. Imaging of anisotropic conductivity has potential for the analysis of interactions between electromagnetic fields and biological systems, such as the prediction of current pathways in electrical stimulation therapy. To improve application to the clinical environment, precise approaches are required to understand the exact responses inside the human body subjected to the stimulated currents. In this study, we experimentally evaluate the anisotropic conductivity tensor distribution of canine brain tissues, using a recently developed diffusion tensor-magnetic resonance electrical impedance tomography method. At lowmore » frequency, electrical conductivity of the biological tissues can be expressed as a product of the mobility and concentration of ions in the extracellular space. From diffusion tensor images of the brain, we can obtain directional information on diffusive movements of water molecules, which correspond to the mobility of ions. The position dependent scale factor, which provides information on ion concentration, was successfully calculated from the magnetic flux density, to obtain the equivalent conductivity tensor. By combining the information from both techniques, we can finally reconstruct the anisotropic conductivity tensor images of brain tissues. The reconstructed conductivity images better demonstrate the enhanced signal intensity in strongly anisotropic brain regions, compared with those resulting from previous methods using a global scale factor.« less

Gravimetric water distribution assessment from geoelectrical methods (ERT and EMI) in municipal solid waste landfill.

PubMed

Dumont, Gaël; Pilawski, Tamara; Dzaomuho-Lenieregue, Phidias; Hiligsmann, Serge; Delvigne, Frank; Thonart, Philippe; Robert, Tanguy; Nguyen, Frédéric; Hermans, Thomas

2016-09-01

The gravimetric water content of the waste material is a key parameter in waste biodegradation. Previous studies suggest a correlation between changes in water content and modification of electrical resistivity. This study, based on field work in Mont-Saint-Guibert landfill (Belgium), aimed, on one hand, at characterizing the relationship between gravimetric water content and electrical resistivity and on the other hand, at assessing geoelectrical methods as tools to characterize the gravimetric water distribution in a landfill. Using excavated waste samples obtained after drilling, we investigated the influences of the temperature, the liquid phase conductivity, the compaction and the water content on the electrical resistivity. Our results demonstrate that Archie's law and Campbell's law accurately describe these relationships in municipal solid waste (MSW). Next, we conducted a geophysical survey in situ using two techniques: borehole electromagnetics (EM) and electrical resistivity tomography (ERT). First, in order to validate the use of EM, EM values obtained in situ were compared to electrical resistivity of excavated waste samples from corresponding depths. The petrophysical laws were used to account for the change of environmental parameters (temperature and compaction). A rather good correlation was obtained between direct measurement on waste samples and borehole electromagnetic data. Second, ERT and EM were used to acquire a spatial distribution of the electrical resistivity. Then, using the petrophysical laws, this information was used to estimate the water content distribution. In summary, our results demonstrate that geoelectrical methods represent a pertinent approach to characterize spatial distribution of water content in municipal landfills when properly interpreted using ground truth data. These methods might therefore prove to be valuable tools in waste biodegradation optimization projects. Copyright © 2016 Elsevier Ltd. All rights reserved.

A three-dimensional thermal and electromagnetic model of whole limb heating with a MAPA.

PubMed

Charny, C K; Levin, R L

1991-10-01

Previous studies by the authors have shown that if properly implemented, the Pennes assumptions can be applied to quantify bioheat transfer during extremity heating. Given its relative numerical simplicity and its ability to predict temperatures in thermoregulated tissue, the Pennes model of bioheat transfer was utilized in a three-dimensional thermal model of limb heating. While the arterial blood temperature was assumed to be radially uniform within a cross section of the limb, axial gradients in the arterial and venous blood temperatures were computed with this three-dimensional model. A realistically shaped, three-dimensional finite element model of a tumor-bearing human lower leg was constructed and was "attached" mathematically to the whole body thermal model of man described in previous studies by the authors. The central as well as local thermoregulatory feedback control mechanisms which determine blood perfusion to the various tissues and rate of evaporation by sweating were input into the limb model. In addition, the temperature of the arterial blood which feeds into the most proximal section of the lower leg was computed by the whole body thermal model. The variations in the shape of the tissues which comprise the limb were obtained from computerized tomography scans. Axial variations in the energy deposition patterns along the length of the limb exposed to a miniannular phased array (MAPA) applicator were also input into this model of limb heating. Results indicate that proper positioning of the limb relative to the MAPA is a significant factor in determining the effectiveness of the treatment. A patient-specific hyperthermia protocol can be designed using this coupled electromagnetic and thermal model.

3D reconstruction of the magnetic vector potential using model based iterative reconstruction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhat, K. C.; Aditya Mohan, K.; Phatak, Charudatta

Lorentz transmission electron microscopy (TEM) observations of magnetic nanoparticles contain information on the magnetic and electrostatic potentials. Vector field electron tomography (VFET) can be used to reconstruct electromagnetic potentials of the nanoparticles from their corresponding LTEM images. The VFET approach is based on the conventional filtered back projection approach to tomographic reconstructions and the availability of an incomplete set of measurements due to experimental limitations means that the reconstructed vector fields exhibit significant artifacts. In this paper, we outline a model-based iterative reconstruction (MBIR) algorithm to reconstruct the magnetic vector potential of magnetic nanoparticles. We combine a forward model formore » image formation in TEM experiments with a prior model to formulate the tomographic problem as a maximum a-posteriori probability estimation problem (MAP). The MAP cost function is minimized iteratively to determine the vector potential. Here, a comparative reconstruction study of simulated as well as experimental data sets show that the MBIR approach yields quantifiably better reconstructions than the VFET approach.« less

Parametric source of two-photon states with a tunable degree of entanglement and mixing: Experimental preparation of Werner states and maximally entangled mixed states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cinelli, C.; Di Nepi, G.; De Martini, F.

2004-08-01

A parametric source of polarization-entangled photon pairs with striking spatial characteristics is reported. The distribution of the output electromagnetic k modes excited by spontaneous parametric down-conversion and coupled to the output detectors can be very broad. Using these states realized over a full entanglement ring output distribution, the nonlocal properties of the generated entanglement have been tested by standard Bell measurements and by Ou-Mandel interferometry. A 'mode-patchwork' technique based on the quantum superposition principle is adopted to synthesize in a straightforward and reliable way any kind of mixed state, of large conceptual and technological interest in modern quantum information. Tunablemore » Werner states and maximally entangled mixed states have indeed been created by this technique and investigated by quantum tomography. A study of the entropic and nonlocal properties of these states has been undertaken experimentally and theoretically, by a unifying variational approach.« less

3D reconstruction of the magnetic vector potential using model based iterative reconstruction.

PubMed

Prabhat, K C; Aditya Mohan, K; Phatak, Charudatta; Bouman, Charles; De Graef, Marc

2017-11-01

Lorentz transmission electron microscopy (TEM) observations of magnetic nanoparticles contain information on the magnetic and electrostatic potentials. Vector field electron tomography (VFET) can be used to reconstruct electromagnetic potentials of the nanoparticles from their corresponding LTEM images. The VFET approach is based on the conventional filtered back projection approach to tomographic reconstructions and the availability of an incomplete set of measurements due to experimental limitations means that the reconstructed vector fields exhibit significant artifacts. In this paper, we outline a model-based iterative reconstruction (MBIR) algorithm to reconstruct the magnetic vector potential of magnetic nanoparticles. We combine a forward model for image formation in TEM experiments with a prior model to formulate the tomographic problem as a maximum a-posteriori probability estimation problem (MAP). The MAP cost function is minimized iteratively to determine the vector potential. A comparative reconstruction study of simulated as well as experimental data sets show that the MBIR approach yields quantifiably better reconstructions than the VFET approach. Copyright © 2017 Elsevier B.V. All rights reserved.

3D reconstruction of the magnetic vector potential using model based iterative reconstruction

DOE PAGES

Prabhat, K. C.; Aditya Mohan, K.; Phatak, Charudatta; ...

2017-07-03

Lorentz transmission electron microscopy (TEM) observations of magnetic nanoparticles contain information on the magnetic and electrostatic potentials. Vector field electron tomography (VFET) can be used to reconstruct electromagnetic potentials of the nanoparticles from their corresponding LTEM images. The VFET approach is based on the conventional filtered back projection approach to tomographic reconstructions and the availability of an incomplete set of measurements due to experimental limitations means that the reconstructed vector fields exhibit significant artifacts. In this paper, we outline a model-based iterative reconstruction (MBIR) algorithm to reconstruct the magnetic vector potential of magnetic nanoparticles. We combine a forward model formore » image formation in TEM experiments with a prior model to formulate the tomographic problem as a maximum a-posteriori probability estimation problem (MAP). The MAP cost function is minimized iteratively to determine the vector potential. Here, a comparative reconstruction study of simulated as well as experimental data sets show that the MBIR approach yields quantifiably better reconstructions than the VFET approach.« less

Study on textile comfort properties of polypropylene blended stainless steel woven fabric for the application of electromagnetic shielding effectiveness

NASA Astrophysics Data System (ADS)

Palanisamy, S.; Tunakova, V.; Karthik, D.; Ali, A.; Militky, J.

2017-10-01

In this study, the different proportion of conductive component blended with polypropylene yarn were taken for making conductive textile samples for analysis of electromagnetic shielding effectiveness, fabric bending moment and air permeability. The ASTM D4935 coaxial transmission line method was used to study the electromagnetic shielding. Electromagnetic shielding effectiveness of textile structures containing different percentage of metal content ranges from 1 to 50 dB at high frequency range. Breathability of structures, more precisely air permeability was considered as one of important parameters for designing of electromagnetic radiation protective fabrics for certain applications. The bending moment of samples is decreases with increasing metal component percent.

Parametric vs. non-parametric statistics of low resolution electromagnetic tomography (LORETA).

PubMed

Thatcher, R W; North, D; Biver, C

2005-01-01

This study compared the relative statistical sensitivity of non-parametric and parametric statistics of 3-dimensional current sources as estimated by the EEG inverse solution Low Resolution Electromagnetic Tomography (LORETA). One would expect approximately 5% false positives (classification of a normal as abnormal) at the P < .025 level of probability (two tailed test) and approximately 1% false positives at the P < .005 level. EEG digital samples (2 second intervals sampled 128 Hz, 1 to 2 minutes eyes closed) from 43 normal adult subjects were imported into the Key Institute's LORETA program. We then used the Key Institute's cross-spectrum and the Key Institute's LORETA output files (*.lor) as the 2,394 gray matter pixel representation of 3-dimensional currents at different frequencies. The mean and standard deviation *.lor files were computed for each of the 2,394 gray matter pixels for each of the 43 subjects. Tests of Gaussianity and different transforms were computed in order to best approximate a normal distribution for each frequency and gray matter pixel. The relative sensitivity of parametric vs. non-parametric statistics were compared using a "leave-one-out" cross validation method in which individual normal subjects were withdrawn and then statistically classified as being either normal or abnormal based on the remaining subjects. Log10 transforms approximated Gaussian distribution in the range of 95% to 99% accuracy. Parametric Z score tests at P < .05 cross-validation demonstrated an average misclassification rate of approximately 4.25%, and range over the 2,394 gray matter pixels was 27.66% to 0.11%. At P < .01 parametric Z score cross-validation false positives were 0.26% and ranged from 6.65% to 0% false positives. The non-parametric Key Institute's t-max statistic at P < .05 had an average misclassification error rate of 7.64% and ranged from 43.37% to 0.04% false positives. The nonparametric t-max at P < .01 had an average misclassification rate of 6.67% and ranged from 41.34% to 0% false positives of the 2,394 gray matter pixels for any cross-validated normal subject. In conclusion, adequate approximation to Gaussian distribution and high cross-validation can be achieved by the Key Institute's LORETA programs by using a log10 transform and parametric statistics, and parametric normative comparisons had lower false positive rates than the non-parametric tests.

Magnetoacoustic Tomography with Magnetic Induction for Electrical Conductivity based Tissue imaging

NASA Astrophysics Data System (ADS)

Mariappan, Leo

Electrical conductivity imaging of biological tissue has attracted considerable interest in recent years owing to research indicating that electrical properties, especially electrical conductivity and permittivity, are indicators of underlying physiological and pathological conditions in biological tissue. Also, the knowledge of electrical conductivity of biological tissue is of interest to researchers conducting electromagnetic source imaging and in design of devices that apply electromagnetic energy to the body such as MRI. So, the need for a non-invasive, high resolution impedance imaging method is highly desired. To address this need we have studied the magnetoacoustic tomography with magnetic induction (MAT-MI) method. In MAT-MI, the object is placed in a static and a dynamic magnetic field giving rise to ultrasound waves. The dynamic field induces eddy currents in the object, and the static field leads to generation of acoustic vibrations from Lorentz force on the induced currents. The acoustic vibrations are at the same frequency as the dynamic magnetic field, which is chosen to match the ultrasound frequency range. These ultrasound signals can be measured by ultrasound probes and are used to reconstruct MAT-MI acoustic source images using possible ultrasound imaging approaches .The reconstructed high spatial resolution image is indicative of the object's electrical conductivity contrast. We have investigated ultrasound imaging methods to reliably reconstruct the MAT-MI image under the practical conditions of limited bandwidth and transducer geometry. The corresponding imaging algorithm, computer simulation and experiments are developed to test the feasibility of these different methods. Also, in experiments, we have developed a system with the strong static field of an MRI magnet and a strong pulsed magnetic field to evaluate MAT-MI in biological tissue imaging. It can be seen from these simulations and experiments that conductivity boundary images with millimeter resolution can be reliably reconstructed with MAT-MI. Further, to estimate the conductivity distribution throughout the object, we reconstruct a vector source image corresponding to the induced eddy currents. As the current source is uniformly present throughout the object, we are able to reliably estimate the internal conductivity distribution for a more complete imaging. From the computer simulations and experiments it can be seen that MAT-MI method has the potential to be a clinically applicable, high resolution, non-invasive method for electrical conductivity imaging.

From episodic to habitual prospective memory: ERP-evidence for a linear transition

PubMed Central

Meier, Beat; Matter, Sibylle; Baumann, Brigitta; Walter, Stefan; Koenig, Thomas

2014-01-01

Performing a prospective memory task repeatedly changes the nature of the task from episodic to habitual. The goal of the present study was to investigate the neural basis of this transition. In two experiments, we contrasted event-related potentials (ERPs) evoked by correct responses to prospective memory targets in the first, more episodic part of the experiment with those of the second, more habitual part of the experiment. Specifically, we tested whether the early, middle, or late ERP-components, which are thought to reflect cue detection, retrieval of the intention, and post-retrieval processes, respectively, would be changed by routinely performing the prospective memory task. The results showed a differential ERP effect in the middle time window (450–650 ms post-stimulus). Source localization using low resolution brain electromagnetic tomography analysis suggests that the transition was accompanied by an increase of activation in the posterior parietal and occipital cortex. These findings indicate that habitual prospective memory involves retrieval processes guided more strongly by parietal brain structures. In brief, the study demonstrates that episodic and habitual prospective memory tasks recruit different brain areas. PMID:25071519

Brain-heart coupling at the P300 latency is linked to anterior cingulate cortex and insula--a cardio-electroencephalographic covariance tracing study.

PubMed

Panitz, Christian; Wacker, Jan; Stemmler, Gerhard; Mueller, Erik M

2013-09-01

Prior work on the coupling of cortical and cardiac responses to feedback demonstrated that feedback-evoked single-trial EEG magnitudes 300 ms post-stimulus predict the degree of subsequent cardiac acceleration. The main goal of the current study was to explore the neural sources of this phenomenon using (a) independent component analysis in conjunction with dipole fitting and (b) low resolution electromagnetic tomography (LORETA) in N=14 participants who performed a gambling task with feedback presented after each trial. It was shown that independent components localized near anterior cingulate cortex produced robust within-subjects correlations with feedback-evoked heart-period, suggesting that anterior cingulate cortex activity 300ms after feedback presentation predicts the strength of subsequent cardiac acceleration. Moreover, interindividual differences in evoked left insular cortex LORETA-estimated activity at around 300ms moderated within-subjects EEG-heart period correlations. These results suggest that key regions of central autonomic control are involved in cortico-cardiac coupling evoked by feedback stimuli. Copyright © 2013 Elsevier B.V. All rights reserved.

Study on coupled shock absorber system using four electromagnetic dampers

NASA Astrophysics Data System (ADS)

Fukumori, Y.; Hayashi, R.; Okano, H.; Suda, Y.; Nakano, K.

2016-09-01

Recently, the electromagnetic damper, which is composed of an electric motor, a ball screw, and a nut, was proposed. The electromagnetic damper has high responsiveness, controllability, and energy saving performance. It has been reported that it improved ride comfort and drivability. In addition, the authors have proposed a coupling method of two electromagnetic dampers. The method enables the characteristics of bouncing and rolling or pitching motion of a vehicle to be tuned independently. In this study, the authors increase the number of coupling of electromagnetic dampers from two to four, and propose a method to couple four electromagnetic dampers. The proposed method enables the characteristics of bouncing, rolling and pitching motion of a vehicle to be tuned independently. Basic experiments using proposed circuit and motors and numerical simulations of an automobile equipped with the proposed coupling electromagnetic damper are carried out. The results indicate the proposed method is effective.

Binary black holes' effects on electromagnetic fields.

PubMed

Palenzuela, Carlos; Anderson, Matthew; Lehner, Luis; Liebling, Steven L; Neilsen, David

2009-08-21

In addition to producing gravitational waves, the dynamics of a binary black hole system could induce emission of electromagnetic radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We here study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as a possible enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves.

Effect of ray and speed perturbations on ionospheric tomography by over-the-horizon radar: A new method, useful for SuperDarn radar

NASA Astrophysics Data System (ADS)

Eisenbeis, J.; Roy, C.; Bland, E. C.; Occhipinti, G.

2017-12-01

Most recent methods in ionospheric tomography are based on the inversion of the total electron content measured by ground-based GPS receivers. As a consequence of the high frequency of the GPS signal and the absence of horizontal raypaths, the electron density structure is mainly reconstructed in the F2 region (300 km), where the ionosphere reaches the maximum of ionization, and is not sensitive to the lower ionospheric structure. We propose here a new tomographic method of the lower ionosphere (Roy et al., 2014), based on the full inversion of over-the-horizon (OTH) radar data and applicable to SuperDarn data. The major advantage of our methodology is taking into account, numerically and jointly, the effect that the electron density perturbations induce not only in the speed of electromagnetic waves but also on the raypath geometry. This last point is extremely critical for OTH/SuperDarn data inversions as the emitted signal propagates through the ionosphere between a fixed starting point (the radar) and an unknown end point on the Earth surface where the signal is backscattered. We detail our ionospheric tomography method with the aid of benchmark tests in order to highlight the sensitivity of the radar related to the explored observational parameters: frequencies, elevations, azimuths. Having proved the necessity to take into account both effects simultaneously, we apply our method to real backscattered data from Super Darn and OTH radar. The preliminary solution obtained with the Hokkaido East SuperDARN with only two frequencies (10MHz and 11MHz), showed here, is stable and push us to deeply explore a more complete dataset that we will present at the AGU 2017. This is, in our knowledge, the first time that an ionospheric tomography has been estimated with SuperDarn backscattered data. Reference: Roy, C., G. Occhipinti, L. Boschi, J.-P. Moliné, and M. Wieczorek (2014), Effect of ray and speed perturbations on ionospheric tomography by over-the-horizon radar: A new method, J. Geophys. Res. Space Physics, 119, doi:10.1002/2014JA020137.

Navigation with Electromagnetic Tracking for Interventional Radiology Procedures

PubMed Central

Wood, Bradford J.; Zhang, Hui; Durrani, Amir; Glossop, Neil; Ranjan, Sohan; Lindisch, David; Levy, Eliott; Banovac, Filip; Borgert, Joern; Krueger, Sascha; Kruecker, Jochen; Viswanathan, Anand; Cleary, Kevin

2008-01-01

PURPOSE To assess the feasibility of the use of preprocedural imaging for guide wire, catheter, and needle navigation with electromagnetic tracking in phantom and animal models. MATERIALS AND METHODS An image-guided intervention software system was developed based on open-source software components. Catheters, needles, and guide wires were constructed with small position and orientation sensors in the tips. A tetrahedral-shaped weak electromagnetic field generator was placed in proximity to an abdominal vascular phantom or three pigs on the angiography table. Preprocedural computed tomographic (CT) images of the phantom or pig were loaded into custom-developed tracking, registration, navigation, and rendering software. Devices were manipulated within the phantom or pig with guidance from the previously acquired CT scan and simultaneous real-time angiography. Navigation within positron emission tomography (PET) and magnetic resonance (MR) volumetric datasets was also performed. External and endovascular fiducials were used for registration in the phantom, and registration error and tracking error were estimated. RESULTS The CT scan position of the devices within phantoms and pigs was accurately determined during angiography and biopsy procedures, with manageable error for some applications. Preprocedural CT depicted the anatomy in the region of the devices with real-time position updating and minimal registration error and tracking error (<5 mm). PET can also be used with this system to guide percutaneous biopsies to the most metabolically active region of a tumor. CONCLUSIONS Previously acquired CT, MR, or PET data can be accurately codisplayed during procedures with reconstructed imaging based on the position and orientation of catheters, guide wires, or needles. Multimodality interventions are feasible by allowing the real-time updated display of previously acquired functional or morphologic imaging during angiography, biopsy, and ablation. PMID:15802449

Descriptive Study of Electromagnetic Wave Distribution for Various Seating Positions: Using Digital Textbooks

ERIC Educational Resources Information Center

Seomun, GyeongAe; Kim, YoungHwan; Lee, Jung-Ah; Jeong, KwangHoon; Park, Seon-A; Kim, Miran; Noh, Wonjung

2014-01-01

To better understand environmental electromagnetic wave exposure during the use of digital textbooks by elementary school students, we measured numeric values of the electromagnetic fields produced by tablet personal computers (TPCs). Specifically, we examined the distribution of the electromagnetic waves for various students' seating positions in…

Study on the electromagnetic radiation characteristics of discharging excimer laser system

NASA Astrophysics Data System (ADS)

Zhao, Duliang; Liang, Xu; Fang, Xiaodong; Wang, Qingsheng

2016-10-01

Excimer laser in condition of high voltage, large current and fast discharge will produce strong electromagnetic pulse radiation and electromagnetic interference on the around electrical equipment. The research on characteristics and distribution of excimer laser electromagnetic radiation could provide important basis for electromagnetic shielding and suppressing electromagnetic interference, and further improving the electromagnetic compatibility of system. Firstly, electromagnetic radiation source is analyzed according to the working principle of excimer laser. The key test points of the electromagnetic radiation, hydrogen thyratron, main discharge circuit and laser outlet, are determined by the mechanical structure and the theory of electromagnetic radiation. Secondly, characteristics of electromagnetic field were tested using a near field probe on the key positions of the vertical direction at 20, 50, and 80 cm, respectively. The main radiation frequencies and the radiation field characteristics in the near field are obtained. The experimental results show that the main radiation frequencies distribute in 47, 65, and 130 MHz for electric field and the main radiation frequencies distribute in 34, 100, and 165 MHz for magnetic field. The intensity of electromagnetic field decreases rapidly with the increase of test distance. The higher the frequency increases, the faster the amplitude attenuate. Finally, several electromagnetic interference suppression measurement methods are proposed from the perspective of electromagnetic compatibility according to the test results.

Cognitive inhibition of number/length interference in a Piaget-like task: evidence by combining ERP and MEG.

PubMed

Joliot, Marc; Leroux, Gaëlle; Dubal, Stéphanie; Tzourio-Mazoyer, Nathalie; Houdé, Olivier; Mazoyer, Bernard; Petit, Laurent

2009-08-01

We combined event-related potential (ERP) and magnetoencephalography (MEG) acquisition and analysis to investigate the electrophysiological markers of the inhibitory processes involved in the number/length interference in a Piaget-like numerical task. Eleven healthy subjects performed four gradually interfering conditions with the heuristic "length equals number" to be inhibited. Low resolution tomography reconstruction was performed on the combined grand averaged electromagnetic data at the early (N1, P1) and late (P2, N2, P3(early) and P3(late)) latencies. Every condition was analyzed at both scalp and regional brain levels. The inhibitory processes were visible on the late components of the electromagnetic brain activity. A right P2-related frontal orbital activation reflected the change of strategy in the inhibitory processes. N2-related SMA/cingulate activation revealed the first occurrence of the stimuli processing to be inhibited. Both P3 components revealed the working memory processes operating in a medial temporal complex and the mental imagery processes subtended by the precuneus. Simultaneous ERP and MEG signal acquisition and analysis allowed to describe the spatiotemporal patterns of neural networks involved in the inhibition of the "length equals number" interference. Combining ERP and MEG ensured a sensitivity which could be reached previously only through invasive intracortical recordings.

A novel platform for electromagnetic navigated ultrasound bronchoscopy (EBUS).

PubMed

Sorger, Hanne; Hofstad, Erlend Fagertun; Amundsen, Tore; Langø, Thomas; Leira, Håkon Olav

2016-08-01

Endobronchial ultrasound transbronchial needle aspiration (EBUS-TBNA) of mediastinal lymph nodes is essential for lung cancer staging and distinction between curative and palliative treatment. Precise sampling is crucial. Navigation and multimodal imaging may improve the efficiency of EBUS-TBNA. We demonstrate a novel EBUS-TBNA navigation system in a dedicated airway phantom. Using a convex probe EBUS bronchoscope (CP-EBUS) with an integrated sensor for electromagnetic (EM) position tracking, we performed navigated CP-EBUS in a phantom. Preoperative computed tomography (CT) and real-time ultrasound (US) images were integrated into a navigation platform for EM navigated bronchoscopy. The coordinates of targets in CT and US volumes were registered in the navigation system, and the position deviation was calculated. The system visualized all tumor models and displayed their fused CT and US images in correct positions in the navigation system. Navigating the EBUS bronchoscope was fast and easy. Mean error observed between US and CT positions for 11 target lesions (37 measurements) was [Formula: see text] mm, maximum error was 5.9 mm. The feasibility of our novel navigated CP-EBUS system was successfully demonstrated. An EBUS navigation system is needed to meet future requirements of precise mediastinal lymph node mapping, and provides new opportunities for procedure documentation in EBUS-TBNA.

The use of FDEM in hydrogeophysics: A review

NASA Astrophysics Data System (ADS)

Boaga, Jacopo

2017-04-01

Hydrogeophysics is a rapidly evolving discipline emerging from geophysical methods. Geophysical methods are nowadays able to illustrate not only the fabric and the structure of the underground, but also the subsurface processes that occur within it, as fluids dynamic and biogeochemical reactions. This is a growing wide inter-disciplinary field, specifically dedicated to revealing soil properties and monitoring processes of change due to soil/bio/atmosphere interactions. The discipline involves environmental, hydrological, agricultural research and counts application for several engineering purposes. The most frequently used techniques in the hydrogeophysical framework are the electric and electromagnetic methods because they are highly sensitive to soil physical properties such as texture, salinity, mineralogy, porosity and water content. Non-invasive techniques are applied in a number of problems related to characterization of subsurface hydrology and groundwater dynamic processes. Ground based methods, as electrical tomography, proved to obtain considerable resolution but they are difficult to extend to wider exploration purposes due to their logistical limitation. Methods that don't need electrical contact with soil can be, on the contrary, easily applied to broad areas. Among these methods, a rapidly growing role is played by frequency domain electro-magnetic (FDEM) survey. This is due thanks to the improvement of multi-frequency and multi-coils instrumentation, simple time-lapse repeatability, cheap and accurate topographical referencing, and the emerging development of inversion codes. From raw terrain apparent conductivity meter, FDEM survey is becoming a key tool for 3D soil characterization and dynamics observation in near surface hydrological studies. Dozens of papers are here summarized and presented, in order to describe the promising potential of the technique.

Two-dimensional probabilistic inversion of plane-wave electromagnetic data: methodology, model constraints and joint inversion with electrical resistivity data

NASA Astrophysics Data System (ADS)

Rosas-Carbajal, Marina; Linde, Niklas; Kalscheuer, Thomas; Vrugt, Jasper A.

2014-03-01

Probabilistic inversion methods based on Markov chain Monte Carlo (MCMC) simulation are well suited to quantify parameter and model uncertainty of nonlinear inverse problems. Yet, application of such methods to CPU-intensive forward models can be a daunting task, particularly if the parameter space is high dimensional. Here, we present a 2-D pixel-based MCMC inversion of plane-wave electromagnetic (EM) data. Using synthetic data, we investigate how model parameter uncertainty depends on model structure constraints using different norms of the likelihood function and the model constraints, and study the added benefits of joint inversion of EM and electrical resistivity tomography (ERT) data. Our results demonstrate that model structure constraints are necessary to stabilize the MCMC inversion results of a highly discretized model. These constraints decrease model parameter uncertainty and facilitate model interpretation. A drawback is that these constraints may lead to posterior distributions that do not fully include the true underlying model, because some of its features exhibit a low sensitivity to the EM data, and hence are difficult to resolve. This problem can be partly mitigated if the plane-wave EM data is augmented with ERT observations. The hierarchical Bayesian inverse formulation introduced and used herein is able to successfully recover the probabilistic properties of the measurement data errors and a model regularization weight. Application of the proposed inversion methodology to field data from an aquifer demonstrates that the posterior mean model realization is very similar to that derived from a deterministic inversion with similar model constraints.

[Proposal for magnetic/electromagnetic fields protection norms on national level].

PubMed

Dordević, Drago; Raković, Dejan

2008-01-01

The modern life is not possible without application of magnetic/electromagnetic fields, which can be both helpful and harmful for human body. The non-ionizing radiation, especially magnetic/electromagnetic fields of all frequencies (0-300 GHz), can have many harmful effects on the human health that is confirmed by numerous epidemiological studies, studies with volunteers, animal studies, and in vitro studies. Proposal for magnetic/electromagnetic fields protection norms on national level based on the WHO Program for Environment, International Commission on Non-Ionizing Radiation Protection (ICNIRP)], and WHO International EMF Project. Protection from harmful effects of the magnetic/electromagnetic fields is still a great problem in many countries of modern society--huge costs, impaired quality of life, and more important, damage to the human health. Numerous data and publications of harmful effects of the magnetic/electromagnetic fields represents one's country basic necessary documentation for making decisions and law documents for protection norms on national level concerning the health maintenance according to the ICNIRP normatives.

A sLORETA study for gaze-independent BCI speller.

PubMed

Xingwei An; Jinwen Wei; Shuang Liu; Dong Ming

2017-07-01

EEG-based BCI (brain-computer-interface) speller, especially gaze-independent BCI speller, has become a hot topic in recent years. It provides direct spelling device by non-muscular method for people with severe motor impairments and with limited gaze movement. Brain needs to conduct both stimuli-driven and stimuli-related attention in fast presented BCI paradigms for such BCI speller applications. Few researchers studied the mechanism of brain response to such fast presented BCI applications. In this study, we compared the distribution of brain activation in visual, auditory, and audio-visual combined stimuli paradigms using sLORETA (standardized low-resolution brain electromagnetic tomography). Between groups comparisons showed the importance of visual and auditory stimuli in audio-visual combined paradigm. They both contribute to the activation of brain regions, with visual stimuli being the predominate stimuli. Visual stimuli related brain region was mainly located at parietal and occipital lobe, whereas response in frontal-temporal lobes might be caused by auditory stimuli. These regions played an important role in audio-visual bimodal paradigms. These new findings are important for future study of ERP speller as well as the mechanism of fast presented stimuli.

Study on magnetic force of electromagnetic levitation circular knitting machine

NASA Astrophysics Data System (ADS)

Wu, X. G.; Zhang, C.; Xu, X. S.; Zhang, J. G.; Yan, N.; Zhang, G. Z.

2018-06-01

The structure of the driving coil and the electromagnetic force of the test prototype of electromagnetic-levitation (EL) circular knitting machine are studied. In this paper, the driving coil’s structure and working principle of the EL circular knitting machine are firstly introduced, then the mathematical modelling analysis of the driving electromagnetic force is carried out, and through the Ansoft Maxwell finite element simulation software the coil’s magnetic induction intensity and the needle’s electromagnetic force is simulated, finally an experimental platform is built to measure the coil’s magnetic induction intensity and the needle’s electromagnetic force. The results show that the theoretical analysis, the simulation analysis and the results of the test are very close, which proves the correctness of the proposed model.

Prediction of Treatment Outcome in Patients with Obsessive-Compulsive Disorder with Low-Resolution Brain Electromagnetic Tomography: A Prospective EEG Study.

PubMed

Krause, Daniela; Folkerts, Malte; Karch, Susanne; Keeser, Daniel; Chrobok, Agnieszka I; Zaudig, Michael; Hegerl, Ulrich; Juckel, Georg; Pogarell, Oliver

2015-01-01

The issue of predicting treatment response and identifying, in advance, which patient will profit from treating obsessive-compulsive disorder (OCD) seems to be an elusive goal. This prospective study investigated brain electric activity [using Low-Resolution Brain Electromagnetic Tomography (LORETA)] for the purpose of predicting response to treatment. Forty-one unmedicated patients with a DSM-IV diagnosis of OCD were included. A resting 32-channel EEG was obtained from each participant before and after 10 weeks of standardized treatment with sertraline and behavioral therapy. LORETA was used to localize the sources of brain electrical activity. At week 10, patients were divided into responders and non-responders (according to a reduction of symptom severity >50% on the Y-BOCS). LORETA analysis revealed that at baseline responders showed compared to non-responders a significantly lower brain electric activity within the beta 1 (t = 2.86, p < 0.05), 2 (t = 2.81, p < 0.05), and 3 (t = 2.76, p < 0.05) frequency bands and ROI analysis confirmed a reduced activity in alpha 2 (t = 2.06, p < 0.05) in the anterior cingulate cortex (ACC). When baseline LORETA data were compared to follow-up data, the analysis showed in the responder group a significantly lower brain electrical resting activity in the beta 1 (t = 3.17. p < 0.05) and beta 3 (t = 3.11. p < 0.05) frequency bands and equally for the ROI analysis of the orbitofrontal cortex (OFC) in the alpha 2 (t = 2.15. p < 0.05) frequency band. In the group of non-responders the opposite results were found. In addition, a positive correlation between frequency alpha 2 (rho = 0.40, p = 0.010), beta 3 (rho = 0.42, p = 0.006), delta (rho = 0.33, p = 0.038), theta (rho = 0.34, p = 0.031), alpha 1 (rho = 0.38, p = 0.015), and beta1 (rho = 0.34, p = 0.028) of the OFC and the bands delta (rho = 0.33, p = 0.035), alpha 1 (rho = 0.36, p = 0.019), alpha 2 (rho = 0.34, p = 0.031), and beta 3 (rho = 0.38, p = 0.015) of the ACC with a reduction of the Y-BOCS scores was identified. Our results suggest that measuring brain activity with LORETA could be an efficient and applicable technique to prospectively identify treatment responders in OCD.

Prediction of Treatment Outcome in Patients with Obsessive-Compulsive Disorder with Low-Resolution Brain Electromagnetic Tomography: A Prospective EEG Study

PubMed Central

Krause, Daniela; Folkerts, Malte; Karch, Susanne; Keeser, Daniel; Chrobok, Agnieszka I.; Zaudig, Michael; Hegerl, Ulrich; Juckel, Georg; Pogarell, Oliver

2016-01-01

The issue of predicting treatment response and identifying, in advance, which patient will profit from treating obsessive-compulsive disorder (OCD) seems to be an elusive goal. This prospective study investigated brain electric activity [using Low-Resolution Brain Electromagnetic Tomography (LORETA)] for the purpose of predicting response to treatment. Forty-one unmedicated patients with a DSM-IV diagnosis of OCD were included. A resting 32-channel EEG was obtained from each participant before and after 10 weeks of standardized treatment with sertraline and behavioral therapy. LORETA was used to localize the sources of brain electrical activity. At week 10, patients were divided into responders and non-responders (according to a reduction of symptom severity >50% on the Y-BOCS). LORETA analysis revealed that at baseline responders showed compared to non-responders a significantly lower brain electric activity within the beta 1 (t = 2.86, p < 0.05), 2 (t = 2.81, p < 0.05), and 3 (t = 2.76, p < 0.05) frequency bands and ROI analysis confirmed a reduced activity in alpha 2 (t = 2.06, p < 0.05) in the anterior cingulate cortex (ACC). When baseline LORETA data were compared to follow-up data, the analysis showed in the responder group a significantly lower brain electrical resting activity in the beta 1 (t = 3.17. p < 0.05) and beta 3 (t = 3.11. p < 0.05) frequency bands and equally for the ROI analysis of the orbitofrontal cortex (OFC) in the alpha 2 (t = 2.15. p < 0.05) frequency band. In the group of non-responders the opposite results were found. In addition, a positive correlation between frequency alpha 2 (rho = 0.40, p = 0.010), beta 3 (rho = 0.42, p = 0.006), delta (rho = 0.33, p = 0.038), theta (rho = 0.34, p = 0.031), alpha 1 (rho = 0.38, p = 0.015), and beta1 (rho = 0.34, p = 0.028) of the OFC and the bands delta (rho = 0.33, p = 0.035), alpha 1 (rho = 0.36, p = 0.019), alpha 2 (rho = 0.34, p = 0.031), and beta 3 (rho = 0.38, p = 0.015) of the ACC with a reduction of the Y-BOCS scores was identified. Our results suggest that measuring brain activity with LORETA could be an efficient and applicable technique to prospectively identify treatment responders in OCD. PMID:26834658

Some Student Conceptions of Electromagnetic Induction

NASA Astrophysics Data System (ADS)

Thong, Wai Meng; Gunstone, Richard

2008-01-01

Introductory electromagnetism is a central part of undergraduate physics. Although there has been some research into student conceptions of electromagnetism, studies have been sparse and separated. This study sought to explore second year physics students’ conceptions of electromagnetism, to investigate to what extent the results from the present study are similar to these results from other studies, and to uncover any new forms of alternative conceptions. Data for this study came from 15 in-depth interviews. Three previously unreported alternative conceptions were identified in the study: 1) induced current varies proportionately with current in solenoid; 2) there must be contact between magnetic flux and the external coil in order for any emf to be induced in the coil; 3) coulombic or electrostatic potential difference is present in an induced electric field. These alternative conceptions were manifested in these students’ explanations of electromagnetic phenomena presented to them during the interviews.

Effects of chronic exposure to electromagnetic waves on the auditory system.

PubMed

Özgür, Abdulkadir; Tümkaya, Levent; Terzi, Suat; Kalkan, Yıldıray; Erdivanlı, Özlem Çelebi; Dursun, Engin

2015-08-01

The results support that chronic electromagnetic field exposure may cause damage by leading to neuronal degeneration of the auditory system. Numerous researches have been done about the risks of exposure to the electromagnetic fields that occur during the use of these devices, especially the effects on hearing. The aim of this study is to evaluate the effects of the electromagnetic waves emitted by the mobile phones through the electrophysiological and histological methods. Twelve adult Wistar albino rats were included in the study. The rats were divided into two groups of six rats. The study group was exposed to the electromagnetic waves over a period of 30 days. The control group was not given any exposure to the electromagnetic fields. After the completion of the electromagnetic wave application, the auditory brainstem responses of both groups were recorded under anesthesia. The degeneration of cochlear nuclei was graded by two different histologists, both of whom were blinded to group information. The histopathologic and immunohistochemical analysis showed neuronal degeneration signs, such as increased vacuolization in the cochlear nucleus, pyknotic cell appearance, and edema in the group exposed to the electromagnetic fields compared to the control group. The average latency of wave in the ABR was similar in both groups (p > 0.05).

Electromagnetic Properties Analysis on Hybrid-driven System of Electromagnetic Motor

NASA Astrophysics Data System (ADS)

Zhao, Jingbo; Han, Bingyuan; Bei, Shaoyi

2018-01-01

The hybrid-driven system made of permanent-and electromagnets applied in the electromagnetic motor was analyzed, equivalent magnetic circuit was used to establish the mathematical models of hybrid-driven system, based on the models of hybrid-driven system, the air gap flux, air-gap magnetic flux density, electromagnetic force was proposed. Taking the air-gap magnetic flux density and electromagnetic force as main research object, the hybrid-driven system was researched. Electromagnetic properties of hybrid-driven system with different working current modes is studied preliminary. The results shown that analysis based on hybrid-driven system can improve the air-gap magnetic flux density and electromagnetic force more effectively and can also guarantee the output stability, the effectiveness and feasibility of the hybrid-driven system are verified, which proved theoretical basis for the design of hybrid-driven system.

Comparison of Commercial Electromagnetic Interface Test Techniques to NASA Electromagnetic Interference Test Techniques

NASA Astrophysics Data System (ADS)

Smith, V.

2000-11-01

This report documents the development of analytical techniques required for interpreting and comparing space systems electromagnetic interference test data with commercial electromagnetic interference test data using NASA Specification SSP 30237A "Space Systems Electromagnetic Emission and Susceptibility Requirements for Electromagnetic Compatibility." The PSpice computer simulation results and the laboratory measurements for the test setups under study compare well. The study results, however, indicate that the transfer function required to translate test results of one setup to another is highly dependent on cables and their actual layout in the test setup. Since cables are equipment specific and are not specified in the test standards, developing a transfer function that would cover all cable types (random, twisted, or coaxial), sizes (gauge number and length), and layouts (distance from the ground plane) is not practical.

Comparison of Commercial Electromagnetic Interface Test Techniques to NASA Electromagnetic Interference Test Techniques

NASA Technical Reports Server (NTRS)

Smith, V.; Minor, J. L. (Technical Monitor)

2000-01-01

This report documents the development of analytical techniques required for interpreting and comparing space systems electromagnetic interference test data with commercial electromagnetic interference test data using NASA Specification SSP 30237A "Space Systems Electromagnetic Emission and Susceptibility Requirements for Electromagnetic Compatibility." The PSpice computer simulation results and the laboratory measurements for the test setups under study compare well. The study results, however, indicate that the transfer function required to translate test results of one setup to another is highly dependent on cables and their actual layout in the test setup. Since cables are equipment specific and are not specified in the test standards, developing a transfer function that would cover all cable types (random, twisted, or coaxial), sizes (gauge number and length), and layouts (distance from the ground plane) is not practical.

Numerical implementation of magneto-acousto-electrical tomography (MAET) using a linear phased array transducer

NASA Astrophysics Data System (ADS)

Soner Gözü, Mehmet; Zengin, Reyhan; Güneri Gençer, Nevzat

2018-02-01

In this study, the performance and implementation of magneto-acousto-electrical tomography (MAET) is investigated using a linear phased array (LPA) transducer. The goal of MAET is to image the conductivity distribution in biological bodies. It uses the interaction between ultrasound and a static magnetic field to generate velocity current density distribution inside the body. The resultant voltage due to velocity current density is sensed by surface electrodes attached on the body. In this study, the theory of MAET is reviewed. A 16-element LPA transducer with 1 MHz excitation frequency is used to provide beam directivity and steerability of acoustic waves. Different two-dimensional numerical models of breast and tumour are formed to analyze the multiphysics problem coupled with acoustics and electromagnetic fields. In these models, velocity current density distributions are obtained for pulse type ultrasound excitations. The static magnetic field is assumed as 1 T. To sense the resultant voltage caused by the velocity current density, it is assumed that two electrodes are attached on the surface of the body. The performance of MAET is shown through sensitivity matrix analysis. The sensitivity matrix is obtained for two transducer positions with 13 steering angles between -30\\circ to 30\\circ with 5\\circ angular intervals. For the reconstruction of the images, truncated singular value decomposition method is used with different signal-to-noise ratio (SNR) values (20 dB, 40 dB, 60 dB and 80 dB). The resultant images show that the perturbation (5 mm  ×  5 mm) placed 35 mm depth can be detected even if the SNR is 20 dB.

Jet and electromagnetic tomography (JET) of extreme phases of matter in heavy-ion collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinz, Ulrich

2015-08-31

The Ohio State University (OSU) group contributed to the deliverables of the JET Collaboration three major products: 1. The code package iEBE-VISHNU for modeling the dynamical evolution of the soft medium created in relativistic heavy-ion collisions, from its creation all the way to final freeze-out using a hybrid approach that interfaces a free-streaming partonic pre-equilbrium stage with a (2+1)-dimensional viscous relativistic fluid dynamical stage for the quark-gluon plasma (QGP) phase and the microscopic hadron cascade UrQMD for the hadronic rescattering and freeze-out stage. Except for UrQMD, all dynamical evolution components and interfaces were developed at OSU and tested and implementedmore » in collaboration with the Duke University group. 2. An electromagnetic radiation module for the calculation of thermal photon emission from the QGP and hadron resonance gas stages of a heavy-ion collision, with emission rates that have been corrected for viscous effects in the expanding medium consistent with the bulk evolution. The electromagnetic radiation module was developed under OSU leadership in collaboration with the McGill group and has been integrated in the iEBE-VISHNU code package. 3. An interface between the Monte Carlo jet shower evolution and hadronization codes developed by the Wayne State University (WSU), McGill and Texas A&M groups and the iEBE-VISHNU bulk evolution code, for performing jet quenching and jet shape modification studies in a realistically modeled evolving medium that was tuned to measured soft hadron data. Building on work performed at OSU for the theoretical framework used to describe the interaction of jets with the medium, initial work on the jet shower Monte Carlo was started at OSU and moved to WSU when OSU Visiting Assistant Professor Abhijit Majumder accepted a tenure track faculty position at WSU in September 2011. The jet-hydro interface was developed at OSU and WSU and tested and implemented in collaboration with the McGill, Texas A&M, and LBNL groups.« less

Evaluation of the preimplantation worksheet in determining Calypso eligibility for men prescribed postprostatectomy radiotherapy with electromagnetic transponder guidance.

PubMed

Hamilton, Daniel George; Jones, Kingsley; So, Kevin

2017-01-01

This study aimed to assess the design and performance of the preimplant suitability worksheet in determining Calypso eligibility for prostate cancer patients prescribed postprostatectomy radiotherapy with electromagnetic transponder guidance. The medical records and radiotherapy planning datasets of 75 patients prospectively recruited between June 2015 and September 2016 to a Phase 2 trial evaluating electromagnetic transponder-guided postprostatectomy radiotherapy were retrospectively examined. Correlation and differences between computed tomography (CT)-defined greater trochanter and prostatic fossa landmarks were evaluated. Receiver operating characteristic curves were also generated to assess the expected and observed accuracy of the worksheet in determining Calypso eligibility. Strong correlation was demonstrated between anterior surface to planning CT-defined greater trochanter and prostate bed center distances (r = 0.95, p <0.001), with a mean difference between measurements of 1.1 cm (95% confidence interval [CI]: 0.9 to 1.3). A similar correlation coefficient was found for surface to greater trochanter location and posterior beacon location (r = 0.92, p <0.001) but with a reduced mean difference of 0.4 cm (95% CI: 0.1 to 0.6). Performance of the worksheet as assessed by planning CT data demonstrated excellent accuracy as a test to determine eligibility (area under the curve: 0.97; 95% CI: 0.92 to 1.00); however, this was not replicated using the same data captured clinically (area under the curve 0.83; 95% CI: 0.68 to 0.98). Although the greater trochanter is a good surrogate for the prostate bed center, it is better associated with the posterior beacon location. As a result, the worksheet will underestimate the truly eligible population if performed accurately and according to manufacturer guidelines. Theoretically, the worksheet could be improved if a cut off of 20 cm is used and the greater trochanter is accurately identified; however, the latter appears to be difficult to achieve in practice. Copyright © 2017 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

Imaging water velocity and volume fraction distributions in water continuous multiphase flows using inductive flow tomography and electrical resistance tomography

NASA Astrophysics Data System (ADS)

Meng, Yiqing; Lucas, Gary P.

2017-05-01

This paper presents the design and implementation of an inductive flow tomography (IFT) system, employing a multi-electrode electromagnetic flow meter (EMFM) and novel reconstruction techniques, for measuring the local water velocity distribution in water continuous single and multiphase flows. A series of experiments were carried out in vertical-upward and upward-inclined single phase water flows and ‘water continuous’ gas-water and oil-gas-water flows in which the velocity profiles ranged from axisymmetric (single phase and vertical-upward multiphase flows) to highly asymmetric (upward-inclined multiphase flows). Using potential difference measurements obtained from the electrode array of the EMFM, local axial velocity distributions of the continuous water phase were reconstructed using two different IFT reconstruction algorithms denoted RT#1, which assumes that the overall water velocity profile comprises the sum of a series of polynomial velocity components, and RT#2, which is similar to RT#1 but which assumes that the zero’th order velocity component may be replaced by an axisymmetric ‘power law’ velocity distribution. During each experiment, measurement of the local water volume fraction distribution was also made using the well-established technique of electrical resistance tomography (ERT). By integrating the product of the local axial water velocity and the local water volume fraction in the cross section an estimate of the water volumetric flow rate was made which was compared with a reference measurement of the water volumetric flow rate. In vertical upward flows RT#2 was found to give rise to water velocity profiles which are consistent with the previous literature although the profiles obtained in the multiphase flows had relatively higher central velocity peaks than was observed for the single phase profiles. This observation was almost certainly a result of the transfer of axial momentum from the less dense dispersed phases to the water, which occurred preferentially at the pipe centre. For upward inclined multiphase flows RT#1 was found to give rise to water velocity profiles which are more consistent with results in the previous literature than was the case for RT#2—which leads to the tentative conclusion that the upward inclined multiphase flows investigated in the present study did not contain significant axisymmetric velocity components.

An ECT/ERT dual-modality sensor for oil-water two-phase flow measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Pitao; Wang, Huaxiang; Sun, Benyuan

2014-04-11

This paper presents a new sensor for ECT/ERT dual-modality system which can simultaneously obtain the permittivity and conductivity of the materials in the pipeline. Quasi-static electromagnetic fields are produced by the inner electrodes array sensor of electrical capacitance tomography (ECT) system. The results of simulation show that the data of permittivity and conductivity can be simultaneously obtained from the same measurement electrode and the fusion of two kinds of data may improve the quality of the reconstructed images. For uniform oil-water mixtures, the performance of designed dual-modality sensor for measuring the various oil fractions has been tested on representative datamore » and the results of experiments show that the designed sensor broadens the measurement range compared to single modality.« less

Holography of Wi-fi Radiation.

PubMed

Holl, Philipp M; Reinhard, Friedemann

2017-05-05

Wireless data transmission systems such as wi-fi or Bluetooth emit coherent light-electromagnetic waves with a precisely known amplitude and phase. Propagating in space, this radiation forms a hologram-a two-dimensional wave front encoding a three-dimensional view of all objects traversed by the light beam. Here we demonstrate a scheme to record this hologram in a phase-coherent fashion across a meter-sized imaging region. We recover three-dimensional views of objects and emitters by feeding the resulting data into digital reconstruction algorithms. Employing a digital implementation of dark-field propagation to suppress multipath reflection, we significantly enhance the quality of the resulting images. We numerically simulate the hologram of a 10-m-sized building, finding that both localization of emitters and 3D tomography of absorptive objects could be feasible by this technique.

Holography of Wi-fi Radiation

NASA Astrophysics Data System (ADS)

Holl, Philipp M.; Reinhard, Friedemann

2017-05-01

Wireless data transmission systems such as wi-fi or Bluetooth emit coherent light—electromagnetic waves with a precisely known amplitude and phase. Propagating in space, this radiation forms a hologram—a two-dimensional wave front encoding a three-dimensional view of all objects traversed by the light beam. Here we demonstrate a scheme to record this hologram in a phase-coherent fashion across a meter-sized imaging region. We recover three-dimensional views of objects and emitters by feeding the resulting data into digital reconstruction algorithms. Employing a digital implementation of dark-field propagation to suppress multipath reflection, we significantly enhance the quality of the resulting images. We numerically simulate the hologram of a 10-m-sized building, finding that both localization of emitters and 3D tomography of absorptive objects could be feasible by this technique.

Electrical brain activity and response to olanzapine in schizophrenia: a study with LORETA images of P300.

PubMed

Sumiyoshi, Tomiki; Higuchi, Yuko; Kawasaki, Yasuhiro; Matsui, Mie; Kato, Kanade; Yuuki, Hiromi; Arai, Hirofumi; Kurachi, Masayoshi

2006-09-30

The aim of this study was to evaluate the change in the distribution for the P300 generator, as demonstrated by Low Resolution Electromagnetic Tomography (LORETA) images, in patients with schizophrenia during treatment with olanzapine. Data were obtained from five right-handed patients treated with olanzapine for 6 months. Five right-handed normal volunteers also participated in the study. LORETA images of P300 in response to the odd-ball auditory discrimination task revealed a left dominant lateralized high current source density in the temporal lobes in all control subjects. Although this pattern of brain activation was not evident in patients at baseline, 6-month treatment with olanzapine recovered the left dominant pattern of the electrical density in the temporal regions, such as the Heschl gyrus, and improved performance on a test of verbal learning and memory. Scores of the Brief Psychiatric Rating Scale and the Global Assessment of Functioning Scale also improved during treatment. These results provide the first suggestion that enhancement of verbal memory and the functional status by treatment with some antipsychotic drugs may be associated with modulations of the anatomical configuration of electrical brain activity in patients with schizophrenia.

Hydrogeophysical investigation of Logan, MT using electrical techniques and diving wave refraction tomography

NASA Astrophysics Data System (ADS)

Stipe, T. D.

2014-12-01

Logan, Montana USA is located on the Gallatin river, one of the three rivers forming the headwaters of the Missouri river. Hydrogeological studies by the Montana Bureau of Mines and Geology have assumed that the location at Logan is a pinch-point for the local Gallatin watershed. Shallow groundwater is expected to discharge into the Gallatin river because depth to bedrock near the river is shallow (~5 meters). Groundwater monitoring wells indicate dry Tertiary sediments overlying bedrock, suggesting surface and groundwater systems are disconnected. We deployed shallow seismic refraction, electrical resistivity, spontaneous potential, and electromagnetic surveys to investigate the groundwater system in the study area. Geophysical measurements were preferentially obtained near the Gallatin river and close to shallow monitoring wells. Hand samples of Mississippian aged rocks of the Madison group were collected from local outcrops to help correlate geophysical results with properties of the carbonate rich bedrock. Preliminary interpretations of geophysical data confirm the shallow bedrock and dry sediments encountered in nearby wells. These results suggest that the pinch-point is located upstream or groundwater follows a network of preferential flow paths through limestone bedrock within the study area.

Architecting the Safety Assessment of Large-scale Systems Integration

DTIC Science & Technology

2009-12-01

Electromagnetic Radiation to Ordnance ( HERO )  Hazards of Electromagnetic Radiation to Fuel (HERF) The main reason that this particular safety study... radiation , high voltage electric shocks and explosives safety. 1. Radiation Hazards (RADHAZ) RADHAZ describes the hazards of electromagnetic radiation ...OP3565/NAVAIR 16-1-529 [19 and 20], these hazards are segregated as follows:  Hazards of Electromagnetic

Combining energy and Laplacian regularization to accurately retrieve the depth of brain activity of diffuse optical tomographic data

NASA Astrophysics Data System (ADS)

Chiarelli, Antonio M.; Maclin, Edward L.; Low, Kathy A.; Mathewson, Kyle E.; Fabiani, Monica; Gratton, Gabriele

2016-03-01

Diffuse optical tomography (DOT) provides data about brain function using surface recordings. Despite recent advancements, an unbiased method for estimating the depth of absorption changes and for providing an accurate three-dimensional (3-D) reconstruction remains elusive. DOT involves solving an ill-posed inverse problem, requiring additional criteria for finding unique solutions. The most commonly used criterion is energy minimization (energy constraint). However, as measurements are taken from only one side of the medium (the scalp) and sensitivity is greater at shallow depths, the energy constraint leads to solutions that tend to be small and superficial. To correct for this bias, we combine the energy constraint with another criterion, minimization of spatial derivatives (Laplacian constraint, also used in low resolution electromagnetic tomography, LORETA). Used in isolation, the Laplacian constraint leads to solutions that tend to be large and deep. Using simulated, phantom, and actual brain activation data, we show that combining these two criteria results in accurate (error <2 mm) absorption depth estimates, while maintaining a two-point spatial resolution of <24 mm up to a depth of 30 mm. This indicates that accurate 3-D reconstruction of brain activity up to 30 mm from the scalp can be obtained with DOT.

Morphology of human sweat ducts observed by optical coherence tomography and their frequency of resonance in the terahertz frequency region

NASA Astrophysics Data System (ADS)

Tripathi, Saroj R.; Miyata, Eisuke; Ishai, Paul Ben; Kawase, Kodo

2015-03-01

It is crucial to understand the various biological effects induced by terahertz (THz) electromagnetic waves with the rapid development of electronic and photonic devices operating in the THz frequency region. The presence of sweat glands plays an important role in THz wave interactions with human skin. We investigated the morphological features of sweat ducts using optical coherence tomography (OCT) to further understand such phenomena. We observed remarkable features of the ducts, such as their clear helical structure. The intersubject and intrasubject variations in the diameter of sweat ducts were considerably smaller than the variations in other structural parameters, such as length and number of turns. Based on the sweat duct dimensions and THz dielectric properties of skin measured using terahertz time-domain spectroscopy (THz-TDS), we calculated the resonating frequency of the sweat duct under the assumption of it functioning as a helical antenna. Here, we show that the resonance frequency in the axial mode of operation lies in the THz wave region with a centre frequency of 0.44 +/- 0.07 THz. We expect that these findings will further our understanding of the various health consequences of the interaction of THz waves with human beings.

A gradiometric version of contactless inductive flow tomography: theory and first applications

PubMed Central

Wondrak, Thomas; Stefani, Frank

2016-01-01

The contactless inductive flow tomography (CIFT) is a measurement technique that allows reconstructing the flow of electrically conducting fluids by measuring the flow-induced perturbations of one or various applied magnetic fields and solving the underlying inverse problem. One of the most promising application fields of CIFT is the continuous casting of steel, for which the online monitoring of the flow in the mould would be highly desirable. In previous experiments at a small-scale model of continuous casting, CIFT has been applied to various industrially relevant problems, including the sudden changes of flow structures in case of argon injection and the influence of a magnetic stirrer at the submerged entry nozzle. The application of CIFT in the presence of electromagnetic brakes, which are widely used to stabilize the flow in the mould, has turned out to be more challenging due to the extreme dynamic range between the strong applied brake field and the weak flow-induced perturbations of the measuring field. In this paper, we present a gradiometric version of CIFT, relying on gradiometric field measurements, that is capable to overcome those problems and which seems, therefore, a promising candidate for applying CIFT in the steel casting industry. This article is part of the themed issue ‘Supersensing through industrial process tomography’. PMID:27185963

In vivo microwave-based thermoacoustic tomography of rats (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lin, Li; Zhou, Yong; Wang, Lihong V.

2016-03-01

Microwave-based thermoacoustic tomography (TAT), based on the measurement of ultrasonic waves induced by microwave pulses, can reveal tissue dielectric properties that may be closely related to the physiological and pathological status of the tissues. Using microwaves as the excitation source improved imaging depth because of their deep penetration into biological tissues. We demonstrate, for the first time, in vivo microwave-based thermoacoustic imaging in rats. The transducer is rotated around the rat in a full circle, providing a full two-dimensional view. Instead of a flat ultrasonic transducer, we used a virtual line detector based on a cylindrically focused transducer. A 3 GHz microwave source with 0.6 µs pulse width and an electromagnetically shielded transducer with 2.25 MHz central frequency provided clear cross-sectional images of the rat's body. The high imaging contrast, based on the tissue's rate of absorption, and the ultrasonically defined spatial resolution combine to reveal the spine, kidney, muscle, and other deeply seated anatomical features in the rat's abdominal cavity. This non-invasive and non-ionizing imaging modality achieved an imaging depth beyond 6 cm in the rat's tissue. Cancer diagnosis based on information about tissue properties from microwave band TAT can potentially be more accurate than has previously been achievable.

Multi-scale Computational Electromagnetics for Phenomenology and Saliency Characterization in Remote Sensing

DTIC Science & Technology

2016-07-15

AFRL-AFOSR-JP-TR-2016-0068 Multi-scale Computational Electromagnetics for Phenomenology and Saliency Characterization in Remote Sensing Hean-Teik...SUBTITLE Multi-scale Computational Electromagnetics for Phenomenology and Saliency Characterization in Remote Sensing 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER... electromagnetics to the application in microwave remote sensing as well as extension of modelling capability with computational flexibility to study

Multi-scale Computational Electromagnetics for Phenomenology and Saliency Characterization in Remote Sensing

DTIC Science & Technology

2016-07-15

AFRL-AFOSR-JP-TR-2016-0068 Multi-scale Computational Electromagnetics for Phenomenology and Saliency Characterization in Remote Sensing Hean-Teik...SUBTITLE Multi-scale Computational Electromagnetics for Phenomenology and Saliency Characterization in Remote Sensing 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER...electromagnetics to the application in microwave remote sensing as well as extension of modelling capability with computational flexibility to study

Simulation study of localization of electromagnetic waves in two-dimensional random dipolar systems.

PubMed

Wang, Ken Kang-Hsin; Ye, Zhen

2003-12-01

We study the propagation and scattering of electromagnetic waves by random arrays of dipolar cylinders in a uniform medium. A set of self-consistent equations, incorporating all orders of multiple scattering of the electromagnetic waves, is derived from first principles and then solved numerically for electromagnetic fields. For certain ranges of frequencies, spatially localized electromagnetic waves appear in such a simple but realistic disordered system. Dependence of localization on the frequency, radiation damping, and filling factor is shown. The spatial behavior of the total, coherent, and diffusive waves is explored in detail, and found to comply with a physical intuitive picture. A phase diagram characterizing localization is presented, in agreement with previous investigations on other systems.

[Dosimetric aspects in studying the biological action of nonionizing electromagnetic radiation].

PubMed

Karpov, V N; Galkin, A A; Davydov, B I

1984-01-01

In order to clarify mechanisms of biological reactions, it is very important to study the absorption and spatial distribution of the absorbed electromagnetic energy. The procedures and methods of calculating the electromagnetic energy absorption of biological specimens exposed to nonionizing electromagnetic irradiation in a wide frequency range (0-300 GHz) are described. Also presented are formulas and plots to be used in calculating the specific absorption of the dose rate by biological specimens, with the inclusion of resonance absorption, polarization of the incident electromagnetic wave, presence of reflecting surfaces and grounding. The extrapolation of the average energy absorption from one animal species to another and to man is discussed, assuming that spatial and energy distributions are equivalent. The notion of the irradiation quality coefficient is introduced. The magnitudes of the coefficients are given as related to the irradiation frequency and polarization type. A mathematical relation is offered to determine the safety of a complex spectrum of electromagnetic irradiation. The relation takes into consideration different dimensionality of the parameters of the electromagnetic field in the low- and high-frequency ranges.

Electromagnetic navigation versus fluoroscopy in aortic endovascular procedures: a phantom study.

PubMed

Tystad Lund, Kjetil; Tangen, Geir Arne; Manstad-Hulaas, Frode

2017-01-01

To explore the possible benefits of electromagnetic (EM) navigation versus conventional fluoroscopy during abdominal aortic endovascular procedures. The study was performed on a phantom representing the abdominal aorta. Intraoperative cone beam computed tomography (CBCT) of the phantom was acquired and merged with a preoperative multidetector CT (MDCT). The CBCT was performed with a reference plate fixed to the phantom that, after merging the CBCT with the MDCT, facilitated registration of the MDCT volume with the EM space. An EM field generator was stationed near the phantom. Navigation software was used to display EM-tracked instruments within the 3D image volume. Fluoroscopy was performed using a C-arm system. Five operators performed a series of renal artery cannulations using modified instruments, alternatingly using fluoroscopy or EM navigation as the sole guidance method. Cannulation durations and associated radiation dosages were noted along with the number of cannulations complicated by loss of guidewire insertion. A total of 120 cannulations were performed. The median cannulation durations were 41.5 and 34.5 s for the fluoroscopy- and EM-guided cannulations, respectively. No significant difference in cannulation duration was found between the two modalities (p = 0.736). Only EM navigation showed a significant reduction in cannulation duration in the latter half of its cannulation series compared with the first half (p = 0.004). The median dose area product for fluoroscopy was 0.0836 [Formula: see text]. EM-guided cannulations required a one-time CBCT dosage of 3.0278 [Formula: see text]. Three EM-guided and zero fluoroscopy-guided cannulations experienced loss of guidewire insertion. Our findings indicate that EM navigation is not inferior to fluoroscopy in terms of the ability to guide endovascular interventions. Its utilization may be of particular interest in complex interventions where adequate visualization or minimal use of contrast agents is critical. In vivo studies featuring an optimized implementation of EM navigation should be conducted.

Assessment of Electromagnetic Fields at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Ficklen, Carter B.

1995-01-01

This report presents the results of an assessment of ElectroMagnetic Fields (EMF) completed at NASA Langley Research Center as part of the Langley Aerospace Research Summer Scholars Program. This project was performed to determine levels of electromagnetic fields, determine the significance of the levels present, and determine a plan to reduce electromagnetic field exposure, if necessary. This report also describes the properties of electromagnetic fields and their interaction with humans. The results of three major occupational epidemiological studies is presented to determine risks posed to humans by EMF exposure. The data for this report came from peer-reviewed journal articles and government publications pertaining to the health effects of electromagnetic fields.

Electromagnetic perception and individual features of human beings.

PubMed

Lebedeva, N N; Kotrovskaya, T I

2001-01-01

An investigation was made of the individual reactions of human subjects exposed to electromagnetic fields. We performed the study on 86 volunteers separated into two groups. The first group was exposed to the electromagnetic field of infralow frequencies, whereas the second group was exposed to the electromagnetic field of extremely high frequencies. We found that the electromagnetic perception of human beings correlated with their individual features, such as EEG parameters, the critical frequency of flash merging, and the electric current sensitivity. Human subjects who had a high-quality perception of electromagnetic waves showed an optimal balance of cerebral processes, an excellent functional state of the central nervous system, and a good decision criterion.

Artworks characterization at THz frequencies: preliminary results via the Fiber-Coupled Terahertz Time Domain System

NASA Astrophysics Data System (ADS)

Catapano, Ilaria; Soldovieri, Francesco

2015-04-01

In the research field of art and archaeology, scientific observation and analysis are hugely demanded to gather as more information as possible on the materials and techniques used to create artworks as well as in previous restoration actions. In this frame, diagnostic tools exploiting electromagnetic waves deserve massive interest tanks to their ability to provide non-invasive and possibly contactless characterization of the investigated objects. Among the electromagnetic diagnostic technologies, those working at frequencies belonging to the 0.1-10 THz range are currently deserving an increased attention since THz waves are capable of penetrating into optically opaque materials (up to the preparation layers), without direct contact and by involving sufficiently low energy to be considered as perfectly non-invasive in practice [1,2]. Moreover, being THz non-ionizing radiations, a moderate exposure to them implies minor long term risks to the molecular stability of the historical artifact and humans. Finally, recent developments of THz technology have allowed the commercialization of compact, flexible and portable systems. One of them is the Fiber-Coupled Terahertz Time Domain System (FICO) developed by Z-Omega, acquired by the Institute of Electromagnetic Sensing of the Environment (IREA) in 2013. This system works in the range from 60GHz to 3THz with a waveform acquisition speed up to 500Hz, it is equipped with fiber optic coupled transmitting and receiving probes and, few months ago, has been potentiated by means of an automatic positioning system enabling to scan a 150mm x 150mm area. In the frame of the IREA research activities regarding cultural heritage, the FICO system is currently adopted to perform both spectroscopy and imaging, which are the two kind of analysis wherein THz technology can be profitably explored [3]. In particular, THz spectroscopy is used to distinguish different artists materials by exploiting their peculiar fingerprint in the absorption spectra, while imaging includes THz tomography and it is considered to obtain non-invasive cross-section images of the artwork under test. Preliminary experiments regarding laboratory designed objects and not precious artworks have been carried out at the IREA laboratory mainly to trace measurements protocols and deeply investigate the diagnostic capabilities of the FICO system. The obtained results will be illustrated and discussed at the conference. REFERENCES [1] K. Fukunaga and I. Hosako, Innovative non-invasive analysis techniques for cultural heritage using terahertz technology, C.R. Physique 11, 519-526, 2010. [2] M. Perenzoni and D. J. Paul, Physics and Applications of Terahertz Radiation, Springer Series in Optical Sciences 173, 2014. [3] J.P. Guillet, B. Recur, L. Frederique, B. Bousquet, L. Canioni, I. Manek-Hönninger, P. Desbarats, P.Mounaix, Review of Terahertz Tomography Techniques, J. Infrared MilliTerahz Waves 35, 382-411, 2014.

An electric and electromagnetic geophysical approach for subsurface investigation of anthropogenic mounds in an urban environment

NASA Astrophysics Data System (ADS)

Pazzi, Veronica; Tapete, Deodato; Cappuccini, Luca; Fanti, Riccardo

2016-11-01

Scientific interest in mounds as geomorphological features that currently represent topographic anomalies in flat urban landscapes mainly lies on the understanding of their origin, either purely natural or anthropogenic. In this second circumstance, another question is whether traces of lost buildings are preserved within the mound subsurface and can be mapped as remnants testifying past settlement. When these landforms have been modified in centuries for civilian use, structural stability is a further element of concern. To address these issues we applied a geophysical approach based on a very low frequency electromagnetic (VLF-EM) technique and two-dimensional electrical resistivity tomography (2D-ERT) and integrated it with well-established surface survey methods within a diagnostic workflow of structural assessment. We demonstrate the practical benefits of this method in the English Cemetery of Florence, Italy, whose mixed nature and history of morphological changes are suggested by archival records. The combination of the two selected geophysical techniques allowed us to overcome the physical obstacles caused by tomb density and to prevent interference from the urban vehicular traffic on the geophysical signals. Eighty-two VLF-EM profiles and five 2D-ERTs were collected to maximise the spatial coverage of the subsurface prospection, while surface indicators of instability (e.g., tomb tilt, location, and direction of ground fractures and wall cracks) were mapped by standard metric survey. High resistive anomalies (> 300 and 400 Ωm) observed in VLF-EM tomographies are attributed to remnants of the ancient perimeter wall that are still buried along the southern side of the mound. While no apparent correlation is found between the causes of tomb and ground movements, the crack pattern map supplements the overall structural assessment. The main outcome is that the northern portion of the retaining wall is classed with the highest hazard rate. The impact of this cost-effective approach is to inform the design of maintenance and restoration measures based on improved geognostic knowledge. The geophysical and surface evidence informs decisions on where interventions are to be prioritised and whether costly invasive investigations are needed.

Effects of Pulsed Electromagnetic Fields on Return to Sports After Arthroscopic Debridement and Microfracture of Osteochondral Talar Defects: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial.

PubMed

Reilingh, Mikel L; van Bergen, Christiaan J A; Gerards, Rogier M; van Eekeren, Inge C; de Haan, Rob J; Sierevelt, Inger N; Kerkhoffs, Gino M M J; Krips, Rover; Meuffels, Duncan E; van Dijk, C N; Blankevoort, Leendert

2016-05-01

Osteochondral defects (OCDs) of the talus usually affect athletic patients. The primary surgical treatment consists of arthroscopic debridement and microfracture. Various possibilities have been suggested to improve the recovery process after debridement and microfracture. A potential solution to obtain this goal is the application of pulsed electromagnetic fields (PEMFs), which stimulate the repair process of bone and cartilage. The use of PEMFs after arthroscopic debridement and microfracture of an OCD of the talus leads to earlier resumption of sports and an increased number of patients that resume sports. Randomized controlled trial; Level of evidence, 1. A total of 68 patients were randomized to receive either PEMFs (n = 36) or placebo (n = 32) after arthroscopic treatment of an OCD of the talus. The primary outcomes (ie, the number of patients who resumed sports and time to resumption of sports) were analyzed with Kaplan-Meier curves as well as Mann-Whitney U, chi-square, and log-rank tests. Secondary functional outcomes were assessed with questionnaires (American Orthopaedic Foot and Ankle Society ankle-hindfoot score, Foot and Ankle Outcome Score, EuroQol, and numeric rating scales for pain and satisfaction) at multiple time points up to 1-year follow-up. To assess bone repair, computed tomography scans were obtained at 2 weeks and 1 year postoperatively. Almost all outcome measures improved significantly in both groups. The percentage of sport resumption (PEMF, 79%; placebo, 80%; P = .95) and median time to sport resumption (PEMF, 17 weeks; placebo, 16 weeks; P = .69) did not differ significantly between the treatment groups. Likewise, there were no significant between-group differences with regard to the secondary functional outcomes and the computed tomography results. PEMF does not lead to a higher percentage of patients who resume sports or to earlier resumption of sports after arthroscopic debridement and microfracture of talar OCDs. Furthermore, no differences were found in bone repair between groups. Netherlands Trial Register NTR1636. © 2016 The Author(s).

Association between electromagnetic field exposure and abortion in pregnant women living in Tehran

PubMed Central

Abad, Masoumeh; Malekafzali, Hossein; Simbar, Masoumeh; Seyed Mosaavi, Hassan; Merghati Khoei, Effat

2016-01-01

Background: Health-related quality of life is affected by electromagnetic field exposure in each person everyday life. However, this is extremely controversial issue. Objective: Investigation of the associations between electromagnetic field exposure and miscarriage among women of Tehran. Materials and Methods: In this longitudinal study, 462 pregnant women with gestational age <12 wks from seven main regions of Tehran city in Iran with similar social and cultural status were participated. Women were interviewed face-to face to collect data. Reproductive information was collected using medical file recorded in those hospitals the subjects had delivery. The measuring device measured electromagnetic waves, Narda safety test solutions with valid calibration date at the entrance door of their houses. Results: A significant likelihood of miscarriage in women who exposed to significant level of electromagnetic wave. However, this association was not confirmed by Wald test. Conclusion: This study may not provide strong or consistent evidence that electromagnetic field exposure is associated or cause miscarriage. This issue may be due to small sample size in this study. PMID:27326421

On the asymptotic character of electromagnetic waves in a Friedmann Robertson Walker universe

NASA Astrophysics Data System (ADS)

Haghighipour, Nader

2005-02-01

Asymptotic properties of electromagnetic waves are studied within the context of Friedmann Robertson Walker (FRW) cosmology. Electromagnetic fields are considered as small perturbations on the background spacetime and Maxwell’s equations are solved for all three cases of flat, closed and open FRW universes. The asymptotic character of these solutions is investigated and their relevance to the problem of cosmological tails of electromagnetic waves is discussed.

Near surface geophysical techniques on subsoil contamination: laboratory experiments

NASA Astrophysics Data System (ADS)

Capozzoli, Luigi; Giampaolo, Valeria; Rizzo, Enzo

2016-04-01

Hydrocarbons contamination of soil and groundwater has become a serious environmental problem, because of the increasing number of accidental spills caused by human activities. The starting point of any studies is the reconstruction of the conceptual site model. To make valid predictions about the flow pathways following by hydrocarbons compound is necessary to make a correct reconstruction of their characteristics and the environment in which they move. Near-surface geophysical methods, based on the study of electrical and electromagnetic properties, are proved to be very useful in mapping spatial distribution of the organic contaminants in the subsurface. It is well known, in fact, that electrical properties of the porous media are significantly influenced by hydrocarbons because, when contaminants enter the rock matrix, surface reaction occur between the contaminant and the soil grain surface. The main aim of this work is to investigate the capability of near-surface geophysical methods in mapping and monitoring spatial distribution of contaminants in a controlled setting. A laboratory experiment has been performed at the Hydrogeosite Laboratory of CNR-IMAA (Marsico Nuovo, PZ) where a box-sand has been contaminated by diesel. The used contaminant is a LNAPL, added to the sand through a drilled pipe. Contaminant behaviour and its migration paths have been monitored for one year by Electrical Resistivity measurements. In details, a Cross Borehole Electrical Resistivity Tomography techniques were used to characterize the contamination dynamics after a controlled hydrocarbon spillage occurring in the vadose zone. The approach with cross-borehole resistivity imaging provide a great advantage compared to more conventional surface electrical resistivity tomography, due to the high resolution at high depth (obviously depending on the depth of the well instrumented for the acquisition). This method has been shown to provide good information on the distribution of electrical properties of the subsoil at high depths and, in some cases, a detailed assessment of dynamic processes in the subsurface environment (Binley et al., 2002). Our study confirms the link between hydrocarbons contamination and geoelectrical signal and the capability of cross-hole electrical resistivity tomographies to realize a non-invasive characterization of LNAPL contamination of the media. Although, the electrical behaviour is much more complex and the relation with the contaminants depends also by time of investigation.

Developing Pre-Service Teachers' Subject Matter Knowledge of Electromagnetism by Integrating Concept Maps and Collaborative Learning

ERIC Educational Resources Information Center

Govender, Nadaraj

2015-01-01

This case study explored the development of two pre-service teachers' subject matter knowledge (SMK) of electromagnetism while integrating the use of concept maps (CM) and collaborative learning (CL) strategies. The study aimed at capturing how these pre-service teachers' SMK in electromagnetism was enhanced after having been taught SMK in a…

Improving high school physical science students' understanding of the electromagnetic spectrum: A modified diagram approach

NASA Astrophysics Data System (ADS)

Quebedeaux, James Edward

The focus of this study was to identify major conceptual difficulties that selected public high school physical science students encounter in understanding a standard electromagnetic spectrum diagram. A research-driven, modified version of that standard diagram was used in this study to determine the value added to student understanding of electromagnetic waves. A content analysis was performed on electromagnetic spectrum diagrams found in US textbooks from the 1950s through the present. A class of public high school physical science students participated in a study consisting of four activities conducted during a three-week unit. Students were given a pre- and post-achievement test and a pre- and post-survey on the regions of the electromagnetic spectrum. At the conclusion of each activity, selected students were interviewed and each co-constructed a concept map with the researcher. The Electromagnetic Spectrum Literacy Rubric (ESLR) was designed and used to assess students' conceptual understanding periodically as they proceeded through the unit study. A mixed methods analysis was performed, employing both qualitative and quantitative data. A paired t-test determined that there was a statistically significant difference (p = 0.014) between the pre- and post-achievement test scores for the class of students participating in the unit study. Effect sizes also determined that students have difficulties with mathematical calculations and wave properties. These topics present conceptual challenges which must be overcome to understand and use an electromagnetic spectrum diagram effectively.

Prototype Engineered Barrier System Field Test (PEBSFT); Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramirez, A.L.; Buscheck, T.; Carlson, R.

1991-08-01

This final report represents a summary of data and interpretations obtained from the Prototype Engineered Barrier System Field Test (PEBSFT) performed in G-Tunnel within the Nevada Test Site. The PEBSFT was conducted to evaluate the applicability of measurement techniques, numerical models, and procedures developed for future field tests that will be conducted in the Exploratory Studies Facilities (ESF) at Yucca Mountain. The primary objective of the test was to provide a basis for determining whether tests planned for the ESF have the potential to be successful. Chapter 1 on high frequency electromagnetic tomography discusses the rock mass electromagnetic permittivity andmore » attenuation rate changes that were measured to characterize the water distribution in the near field of a simulated waste container. The data are used to obtain quantitative estimates of how the moisture content in the rock mass changes during heating and to infer properties of the spatial variability of water distribution, leading to conclusions about the role of fractures in the system. Chapter 2 discusses the changes in rock moisture content detected by the neutron logging probe. Chapter 3 permeability tests discusses the characterization of the in-situ permeability of the fractured tuff around the borehole. The air permeability testing apparatus, the testing procedures, and the data analysis are presented. Chapter 4 describes the moisture collection system installed in the heater borehole to trap and measure the moisture volumes. Chapter 5 describes relative humidity measurements made with the thermocouple psychrometer and capacitance sensors. Chapter 6 discusses gas pressure measurements in the G-Tunnel, addressing the calibration and installation of piezoresistive-gaged transducers. Chapter 7 describes the calibration and installation of thermocouples for temperature measurements. Chapter 8 discusses the results of the PEBSFT.« less

Electromagnetic navigation technology for more precise electrode placement in the foramen ovale: a technical report.

PubMed

Van Buyten, Jean-Pierre; Smet, Iris; Van de Kelft, Erik

2009-07-01

Introduction. Interventional pain management techniques require precise positioning of needles or electrodes, therefore fluoroscopic control is mandatory. This imaging technique does however not visualize soft tissues such as blood vessels. Moreover, patient and physician are exposed to a considerable dose of radiation. Computed tomography (CT)-scans give a better view of soft tissues, but there use requires presence of a radiologist and has proven to be laborious and time consuming. Objectives. This study is to develop a technique using electromagnetic (EM) navigation as a guidance technique for interventional pain management, using CT and/or magnetic resonance (MRI) images uploaded on the navigation station. Methods. One of the best documented interventional procedures for the management of trigeminal neuralgia is percutaneous radiofrequency treatment of the Gasserian ganglion. EM navigation software for intracranial applications already exists. We developed a technique using a stylet with two magnetic coils suitable for EM navigation. The procedure is followed in real time on a computer screen where the patient's multislice CT-scan images and three-dimensional reconstruction of his face are uploaded. Virtual landmarks on the screen are matched with those on the patient's face, calculating the precision of the needle placement. Discussion. The experience with EM navigation acquired with the radiofrequency technique can be transferred to other interventional pain management techniques, for instance, for the placement of a neuromodulation electrode close to the Gasserian ganglion. Currently, research is ongoing to extend the software of the navigation station for spinal application, and to adapt neurostimulation hardware to the EM navigation technology. This technology will allow neuromodulation techniques to be performed without x-ray exposure for the patient and the physician, and this with the precision of CT/MR imaging guidance. © 2009 International Neuromodulation Society.

A study of the electromagnetic shielding mechanisms in the GHz frequency range of graphene based composite layers

NASA Astrophysics Data System (ADS)

Drakakis, E.; Kymakis, E.; Tzagkarakis, G.; Louloudakis, D.; Katharakis, M.; Kenanakis, G.; Suchea, M.; Tudose, V.; Koudoumas, E.

2017-03-01

We report on the mechanisms of the electromagnetic interference shielding effect of graphene based paint like composite layers. In particular, we studied the absorption and reflection of electromagnetic radiation in the 4-20 GHz frequency of various dispersions employing different amounts of graphene nanoplatelets, polyaniline, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), special attention given on the relative contribution of each process in the shielding effect. Moreover, the influence of the composition, the thickness and the conductivity of the composite layers on the electromagnetic shielding was also examined.

Detailed measurements of shower properties in a high granularity digital electromagnetic calorimeter

NASA Astrophysics Data System (ADS)

van der Kolk, N.

2018-03-01

The MAPS (Monolithic Active Pixel Sensors) prototype of the proposed ALICE Forward Calorimeter (FoCal) is the highest granularity electromagnetic calorimeter, with 39 million pixels with a size of 30 × 30 μm2. Particle showers can be studied with unprecedented detail with this prototype. Electromagnetic showers at energies between 2 GeV and 244 GeV have been studied and compared with GEANT4 simulations. Simulation models can be tested in more detail than ever before and the differences observed between FoCal data and GEANT4 simulations illustrate that improvements in electromagnetic models are still possible.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butler, W; Merrick, G; Kurko, B

Purpose: To quantify the effect of metal hip prosthesis on the ability to track and localize electromagnetic transponders. Methods: Three Calypso transponders were implanted into two prostate phantoms. The geometric center of the transponders were identified on computed tomography and set as the isocenter. With the phantom stationary on the treatment table and the tracking array 14-cm above the isocenter, data was acquired by the Calypso system at 10 Hz to establish the uncertainty in measurements. Transponder positional data was acquired with unilateral hip prostheses of different metallic compositions and then with bilateral hips placed at variable separation from themore » phantom. Results: Regardless of hip prosthesis composition, the average vector displacement in the presence of a unilateral prosthesis was < 0.5 mm. The greatest contribution to overall vector displacement occurred in the lateral dimension. With bilateral hip prosthesis, the average vector displacement was 0.3 mm. The displacement in the lateral dimension was markedly reduced compared with a unilateral hip, suggesting that there was a countervailing effect with bilateral hip prosthesis. The greatest average vector displacement was 0.6 mm and occurred when bilateral hip prostheses were placed within 4 cm of the detector array. Conclusion: Unilateral and bilateral hip prostheses did not have any meaningful effect on the ability to accurately track electromagnetic transponders implanted in a prostate phantom. At clinically realistic distances between the hip and detection array, the average tracking error is negligible.« less

Exposure to electromagnetic fields aboard high-speed electric multiple unit trains.

PubMed

Niu, D; Zhu, F; Qiu, R; Niu, Q

2016-01-01

High-speed electric multiple unit (EMU) trains generate high-frequency electric fields, low-frequency magnetic fields, and high-frequency wideband electromagnetic emissions when running. Potential human health concerns arise because the electromagnetic disturbances are transmitted mainly into the car body from windows, and from there to passengers and train staff. The transmission amount and amplitude distribution characteristics that dominate electromagnetic field emission need to be studied, and the exposure level of electromagnetic field emission to humans should be measured. We conducted a series of tests of the on board electromagnetic field distribution on several high-speed railway lines. While results showed that exposure was within permitted levels, the possibility of long-term health effects should be investigated.

High temperature electromagnetic characterization of thermal protection system tile materials

NASA Technical Reports Server (NTRS)

Heil, Garrett G.

1993-01-01

This study investigated the impact of elevated temperatures on the electromagnetic performance of the LI-2200 thermal protection system. A 15-kilowatt CO2 laser was used to heat an LI-2200 specimen to 3000 F while electromagnetic measurements were performed over the frequency range of l9 to 21 GHz. The electromagnetic measurement system consisted of two Dual-Lens Spot-Focusing (DLSF) antennas, a sample support structure, and an HP-8510B vector network analyzer. Calibration of the electromagnetic system was accomplished with a Transmission-Reflection-Line (TRL) procedure and was verified with measurements on a two-layer specimen of known properties. The results of testing indicated that the LI-2200 system's electromagnetic performance is slightly temperature dependent at temperatures up to 3000 F.

Electromagnetic Concepts in Mathematical Representation of Physics.

ERIC Educational Resources Information Center

Albe, Virginie; Venturini, Patrice; Lascours, Jean

2001-01-01

Addresses the use of mathematics when studying the physics of electromagnetism. Focuses on common electromagnetic concepts and their associated mathematical representation and arithmetical tools. Concludes that most students do not understand the significant aspects of physical situations and have difficulty using relationships and models specific…

Electromagnetic Radiation Disturbed the Photosynthesis of Microcystis aeruginosa at the Proteomics Level.

PubMed

Tang, Chao; Yang, Chuanjun; Yu, Hui; Tian, Shen; Huang, Xiaomei; Wang, Weiyi; Cai, Peng

2018-01-11

Photosynthesis of Microcystis aeruginosa under Electromagnetic Radiation (1.8 GHz, 40 V/m) was studied by using the proteomics. A total of 30 differentially expressed proteins, including 15 up-regulated and 15 down-regulated proteins, were obtained in this study. The differentially expressed proteins were significantly enriched in the photosynthesis pathway, in which the protein expression levels of photosystems II cytochrome b559 α subunit, cytochrome C550, PsbY, and F-type ATP synthase (a, b) decreased. Our results indicated that electromagnetic radiation altered the photosynthesis-related protein expression levels, and aimed at the function of photosynthetic pigments, photosystems II potential activity, photosynthetic electron transport process, and photosynthetic phosphorylation process of M. aeruginosa. Based on the above evidence, that photoreaction system may be deduced as a target of electromagnetic radiation on the photosynthesis in cyanobacteria; the photoreaction system of cyanobacteria is a hypothetical "shared target effector" that responds to light and electromagnetic radiation; moreover, electromagnetic radiation does not act on the functional proteins themselves but their expression processes.

Time-dependent entropy evolution in microscopic and macroscopic electromagnetic relaxation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker-Jarvis, James

This paper is a study of entropy and its evolution in the time and frequency domains upon application of electromagnetic fields to materials. An understanding of entropy and its evolution in electromagnetic interactions bridges the boundaries between electromagnetism and thermodynamics. The approach used here is a Liouville-based statistical-mechanical theory. I show that the microscopic entropy is reversible and the macroscopic entropy satisfies an H theorem. The spectral entropy development can be very useful for studying the frequency response of materials. Using a projection-operator based nonequilibrium entropy, different equations are derived for the entropy and entropy production and are applied tomore » the polarization, magnetization, and macroscopic fields. I begin by proving an exact H theorem for the entropy, progress to application of time-dependent entropy in electromagnetics, and then apply the theory to relevant applications in electromagnetics. The paper concludes with a discussion of the relationship of the frequency-domain form of the entropy to the permittivity, permeability, and impedance.« less

The dissipation of electromagnetic waves in plasmas

NASA Astrophysics Data System (ADS)

Basov, N. G.

The present anthology includes articles concerning the experimental study of the interaction of high power electromagnetic waves with collisionless plasmas and with electrons. Among the topics covered are the nonlinear dissipation of electromagnetic waves in inhomogeneous collisionless plasmas, the collisionless absorption of electromagnetic waves in plasmas and 'slow' nonlinear phenomena, the nonlinear effects of electron plasma waves propagating in an inhomogeneous plasma layer, and secondary-emission microwave discharges having large electron transit angles.

Strategies for improving the resolution of electrical and electromagnetic geophysical measurements for three-dimensional inverse modeling of CO2 movement

NASA Astrophysics Data System (ADS)

Commer, M.; Kowalsky, M. B.; Dafflon, B.; Wu, Y.; Hubbard, S. S.

2013-12-01

Geologic carbon sequestration is being evaluated as a means to mitigate the effects of greenhouse gas emissions. Efforts are underway to identify adequate reservoirs and to evaluate the behavior of injected CO2 over time; time-lapse geophysical methods are considered effective tools for these purposes. Pilot studies have shown that the invasion of CO2 into a background pore fluid can alter the electrical resistivity, with increases from CO2 in the super-critical or gaseous phase, and decreases from CO2 dissolved in groundwater (especially when calcite dissolution is occurring). Because of their sensitivity to resistivity changes, electrical and electromagnetic (EM) methods have been used in such studies for indirectly assessing CO2 saturation changes. While the electrical resistance tomography (ERT) method is a well-established technique for both crosswell and surface applications, its usefulness is limited by the relatively low-resolution information it provides. Controlled-source EM methods, including both frequency-domain and time-domain (transient EM) methods, can offer improved resolution. We report on three studies that aim to maximize the information content of electrical and electromagnetic measurements in inverse modeling applications that target the monitoring of resistivity changes due to CO2 migration and/or leakage. The first study considers a three-dimensional crosswell data set collected at an analogue site used for investigating CO2 distribution and geochemical reactivity within a shallow formation. We invert both resistance and phase data using a gradient-weighting method for descent-based inversion algorithms. This method essentially steers the search direction in the model space using low-cost non-linear conjugate gradient methods towards the more computationally expensive Gauss-Newton direction. The second study involves ERT data that were collected at the SECARB Cranfield site near Natchez, Mississippi, at depths exceeding 3000 m. We employ a ratio data inversion scheme, where the time-lapse input data are given by the measured ERT data normalized by their baseline values. We investigate whether three-dimensional time-lapse inversions yield improved results compared to two-dimensional results that were previously reported. Finally, we present a synthetic study that investigates a novel time-domain controlled-source EM method that has the potential for exploiting the resolution properties of vertically oriented source antennas while avoiding their logistical difficulties. A vertical source is replaced by an array of multiple horizontal dipoles arranged in a circle such that all dipoles have a common endpoint in the center. Overall, this study presents significant advances in developing adequate geophysical techniques to monitor CO2 migration and/or potential leaks in geological reservoirs.

[Influence of electromagnetic radiation on toxicity of Vipera lebetina obtusa venom].

PubMed

Abiev, G A; Babaev, E I; Topchieva, Sh A; Chumburidze, T B; Nemsitsveridze, N G

2009-11-01

The aim of the article was to study the effect of electromagnetic radiation on toxicity of Vipera lebetina obtusa venom. It was found that mice intoxicated with snake venom, with moderate to high exposure to electromagnetic radiation and mice intoxicated with venom, which had not been exposed to the radiation showed the same symptoms of intoxication and death. At the same time, the longevity of mice intoxicated with venom exposed to electromagnetic radiation was higher. The longevity of mice in control group was 25+/-5 min. The longevity of mice intoxicated with exposed to electromagnetic radiation snake venom was from 29 to 60 min. The research showed that the longevity of mice intoxicated with snake venom rose with the level of electromagnetic radiation intensity the snake was exposed to. Accordingly, snake venom, with exposure to high intensity electromagnetic radiation is less toxic.

Abnormalities of P300 cortical current density in unmedicated depressed patients revealed by LORETA analysis of event-related potentials.

PubMed

Kawasaki, Toshihiko; Tanaka, Shin; Wang, Jijun; Hokama, Hiroto; Hiramatsu, Kenichi

2004-02-01

The purpose of the present study was to investigate the neural substrates underlying event-related potential (ERP) abnormalities, with respect to the generators of the ERP components in depressed patients. Using an oddball paradigm, ERP from auditory stimuli were recorded from 22 unmedicated patients with current depressive episodes and compared with those from 22 age- and gender-matched normal controls. Cortical current densities of the N100 and P300 components were analyzed using low-resolution electromagnetic tomography (LORETA). Group differences in cortical current density were mapped on a 3-D cortex model. The results revealed that N100 cortical current densities did not differ between the two groups, while P300 cortical current densities were significantly lower in depressed patients over the bilateral temporal lobes, the left frontal region, and the right temporal-parietal area. Furthermore, the cortical area in which the group difference in P300 current density had been identified was remarkably larger over the right than the left hemisphere, thus supporting the hypothesis of right hemisphere dysfunction in depression.

Characteristic changes in brain electrical activity due to chronic hypoxia in patients with obstructive sleep apnea syndrome (OSAS): a combined EEG study using LORETA and omega complexity.

PubMed

Toth, Marton; Faludi, Bela; Wackermann, Jiri; Czopf, Jozsef; Kondakor, Istvan

2009-11-01

EEG background activity of patients with obstructive sleep apnea syndrome (OSAS, N = 25) was compared to that of normal controls (N = 14) to reflect alterations of brain electrical activity caused by chronic intermittent hypoxia in OSAS. Global and regional (left vs. right, anterior vs. posterior) measures of spatial complexity (Omega) were used to characterize the degree of spatial synchrony of EEG. Low resolution electromagnetic tomography (LORETA) was used to localize generators of EEG activity in separate frequency bands. Comparing patients to controls, lower Omega complexity was found globally and in the right hemisphere. Using LORETA, an increased medium frequency activity was seen bilaterally in the precuneus, paracentral and posterior cingulate cortex. These findings indicate that alterations caused by chronic hypoxia in brain electrical activity in regions associated with influencing emotional regulation, long-term memory and the default mode network. Global synchronization (lower Omega complexity) may indicate a significantly reduced number of relatively independent, parallel neural processes due to chronic global hypoxic state in apneic patients as well as over the right hemisphere.

Abnormal Error Monitoring in Math-Anxious Individuals: Evidence from Error-Related Brain Potentials

PubMed Central

Suárez-Pellicioni, Macarena; Núñez-Peña, María Isabel; Colomé, Àngels

2013-01-01

This study used event-related brain potentials to investigate whether math anxiety is related to abnormal error monitoring processing. Seventeen high math-anxious (HMA) and seventeen low math-anxious (LMA) individuals were presented with a numerical and a classical Stroop task. Groups did not differ in terms of trait or state anxiety. We found enhanced error-related negativity (ERN) in the HMA group when subjects committed an error on the numerical Stroop task, but not on the classical Stroop task. Groups did not differ in terms of the correct-related negativity component (CRN), the error positivity component (Pe), classical behavioral measures or post-error measures. The amplitude of the ERN was negatively related to participants’ math anxiety scores, showing a more negative amplitude as the score increased. Moreover, using standardized low resolution electromagnetic tomography (sLORETA) we found greater activation of the insula in errors on a numerical task as compared to errors in a non-numerical task only for the HMA group. The results were interpreted according to the motivational significance theory of the ERN. PMID:24236212

A navigation system for flexible endoscopes using abdominal 3D ultrasound

NASA Astrophysics Data System (ADS)

Hoffmann, R.; Kaar, M.; Bathia, Amon; Bathia, Amar; Lampret, A.; Birkfellner, W.; Hummel, J.; Figl, M.

2014-09-01

A navigation system for flexible endoscopes equipped with ultrasound (US) scan heads is presented. In contrast to similar systems, abdominal 3D-US is used for image fusion of the pre-interventional computed tomography (CT) to the endoscopic US. A 3D-US scan, tracked with an optical tracking system (OTS), is taken pre-operatively together with the CT scan. The CT is calibrated using the OTS, providing the transformation from CT to 3D-US. Immediately before intervention a 3D-US tracked with an electromagnetic tracking system (EMTS) is acquired and registered intra-modal to the preoperative 3D-US. The endoscopic US is calibrated using the EMTS and registered to the pre-operative CT by an intra-modal 3D-US/3D-US registration. Phantom studies showed a registration error for the US to CT registration of 5.1 mm ± 2.8 mm. 3D-US/3D-US registration of patient data gave an error of 4.1 mm compared to 2.8 mm with the phantom. From this we estimate an error on patient experiments of 5.6 mm.

Electrical conductivity structure of the mantle derived from inversion of geomagnetic observatory data: implications for lateral variations in temperature, composition and water content.

NASA Astrophysics Data System (ADS)

Munch, Federico; Grayver, Alexander; Khan, Amir; Kuvshinov, Alexey

2017-04-01

As most of Earth's interior remains geochemically unsampled, geophysical techniques based on seismology, geodesy, gravimetry, and electromagnetic studies play prominent roles because of their ability to sense structure at depth. Although seismic tomography maps show a variety of structures, separating thermal and compositional contributions from seismic velocities alone still remains a challenging task. Alternatively, as electrical conductivity is sensitive to temperature, chemical composition, oxygen fugacity, water content, and the presence of melt, it can serve for determining chemistry, mineralogy, and physical structure of the deep mantle. In this work we estimate and invert local C-responses (period range 3-100 days) for a number of worldwide geomagnetic observatories to map lateral variations of electrical conductivity in Earth's mantle (400-1600 km depth). The obtained conductivity profiles are interpreted in terms of basalt fraction in a basalt-harzburgite mixture, temperature structure, and water content variations. Interpretation is based on a self-consistent thermodynamic calculation of mineral phase equilibria, electrical conductivity databases, and probabilistic inverse methods.

Post flooding damage assessment of earth dams and historical reservoirs using non-invasive geophysical techniques

NASA Astrophysics Data System (ADS)

Sentenac, Philippe; Benes, Vojtech; Budinsky, Vladimir; Keenan, Helen; Baron, Ron

2017-11-01

This paper describes the use of four geophysical techniques to map the structural integrity of historical earth reservoir embankments which are susceptible to natural decay with time. The four techniques that were used to assess the post flood damage were 1. A fast scanning technique using a dipole electromagnetic profile apparatus (GEM2), 2. Electrical Resistivity Tomography (ERT) in order to obtain a high resolution image of the shape of the damaged/seepage zone, 3. Self-Potential surveys were carried out to relate the detected seepage evolution and change of the water displacement inside the embankment, 4. The washed zone in the areas with piping was characterised with microgravimetry. The four geophysical techniques used were evaluated against the case studies of two reservoirs in South Bohemia, Czech Republic. A risk approach based on the Geophysical results was undertaken for the reservoir embankments. The four techniques together enabled a comprehensive non-invasive assessment whereby remedial action could be recommended where required. Conclusions were also drawn on the efficiency of the techniques to be applied for embankments with wood structures.

Neural responses to negative feedback are related to negative emotionality in healthy adults

PubMed Central

Santesso, Diane L.; Bogdan, Ryan; Birk, Jeffrey L.; Goetz, Elena L.; Holmes, Avram J.

2012-01-01

Prior neuroimaging and electrophysiological evidence suggests that potentiated responses in the anterior cingulate cortex (ACC), particularly the rostral ACC, may contribute to abnormal responses to negative feedback in individuals with elevated negative affect and depressive symptoms. The feedback-related negativity (FRN) represents an electrophysiological index of ACC-related activation in response to performance feedback. The purpose of the present study was to examine the FRN and underlying ACC activation using low resolution electromagnetic tomography source estimation techniques in relation to negative emotionality (a composite index including negative affect and subclinical depressive symptoms). To this end, 29 healthy adults performed a monetary incentive delay task while 128-channel event-related potentials were recorded. We found that enhanced FRNs and increased rostral ACC activation in response to negative—but not positive—feedback was related to greater negative emotionality. These results indicate that individual differences in negative emotionality—a putative risk factor for emotional disorders—modulate ACC-related processes critically implicated in assessing the motivational impact and/or salience of environmental feedback. PMID:21917847

Assessment of multiple geophysical techniques for the characterization of municipal waste deposit sites

NASA Astrophysics Data System (ADS)

Gaël, Dumont; Tanguy, Robert; Nicolas, Marck; Frédéric, Nguyen

2017-10-01

In this study, we tested the ability of geophysical methods to characterize a large technical landfill installed in a former sand quarry. The geophysical surveys specifically aimed at delimitating the deposit site horizontal extension, at estimating its thickness and at characterizing the waste material composition (the moisture content in the present case). The site delimitation was conducted with electromagnetic (in-phase and out-of-phase) and magnetic (vertical gradient and total field) methods that clearly showed the transition between the waste deposit and the host formation. Regarding waste deposit thickness evaluation, electrical resistivity tomography appeared inefficient on this particularly thick deposit site. Thus, we propose a combination of horizontal to vertical noise spectral ratio (HVNSR) and multichannel analysis of the surface waves (MASW), which successfully determined the approximate waste deposit thickness in our test landfill. However, ERT appeared to be an appropriate tool to characterize the moisture content of the waste, which is of prior information for the organic waste biodegradation process. The global multi-scale and multi-method geophysical survey offers precious information for site rehabilitation studies, water content mitigation processes for enhanced biodegradation or landfill mining operation planning.

Observing Resonant Entanglement Dynamics in Circuit QED

NASA Astrophysics Data System (ADS)

Mlynek, J. A.; Abdumalikov, A. A.; Fink, J. M.; Steffen, L.; Lang, C.; van Loo, A. F.; Wallraff, A.

2012-02-01

We study the resonant interaction of up to three two-level systems and a single mode of an electromagnetic field in a circuit QED setup. Our investigation is focused on how a single excitation is dynamically shared in this fourpartite system. The underlying theory of the experiment is governed by the Tavis-Cummings-model, which on resonance predicts dynamics known as vacuum Rabi oscillations. The resonant situation has already been studied spectroscopically with three qubits [1] and time resolved measurements have been carried out in a tripartite system [2]. Here we are able to observe the coherent oscillations and their √N- enhancement by tracking the populations of all three qubits and the resonator. Full quantum state tomography is used to verify that the dynamics generates the maximally entangled 3-qubit W-state when the cavity state factorizes. The √N-speed-up offers the possibility to create W-states within a few ns with a fidelity of 75%. We compare the resonant collective method to an approach, which achieves entanglement by sequentially tuning qubits into resonance with the cavity.[4pt] [1] J. M. Fink, Physical Review Letters 103, 083601 (2009)[0pt] [2] F. Altomare, Nature Physics 6, 777--781 (2010)

University Students' Understanding of Electromagnetic Induction

ERIC Educational Resources Information Center

Guisasola, Jenaro; Almudi, Jose M.; Zuza, Kristina

2013-01-01

This study examined engineering and physical science students' understanding of the electromagnetic induction (EMI) phenomena. It is assumed that significant knowledge of the EMI theory is a basic prerequisite when students have to think about electromagnetic phenomena. To analyse students' conceptions, we have taken into account the fact that…

Risk perception and public concerns of electromagnetic waves from cellular phones in Korea.

PubMed

Kim, Kyunghee; Kim, Hae-Joon; Song, Dae Jong; Cho, Yong Min; Choi, Jae Wook

2014-05-01

In this study, the difference between the risk perception of electromagnetic waves from cellular phones and the risk perception of other factors such as environment and food was analyzed. The cause of the difference in the psychological and social factors that affect the group with high risk perception of electromagnetic waves was also analyzed. A questionnaire survey on the risk perception of electromagnetic waves from cellular phones was carried out on 1001 subjects (men and women) over the age of 20. In the group with high risk perception of electromagnetic waves from cellular phones, women had higher risk perception than men. Logistic regression analysis, where the group with high risk perception of electromagnetic waves and the group with low risk perception were used as dependent variables, indicated that the risk perception of electromagnetic waves in women was 1.815 times statistically significantly higher than the risk perception of men (95% CI: 1.340-2.457). Also, high risk perception of electromagnetic waves from cellular phones was observed when the subjects considered that they had more personal knowledge (OR: 1.416, 95% CI: 1.216-1.648), that the seriousness of the risk to future generations was high (OR: 1.410, 95% CI: 1.234-1.611), and their outrage for the occurrence of accidents related to electromagnetic waves was high (OR: 1.460, 95% CI: 1.264-1.686). The results of this study need to be sufficiently considered and reflected in designing the risk communication strategies and communication methods for the preventive measures and advice on electromagnetic waves from cellular phones. © 2014 Wiley Periodicals, Inc.

Acute neuroprotective effects of extremely low-frequency electromagnetic fields after traumatic brain injury in rats.

PubMed

Yang, Yang; Li, Ling; Wang, Yan-Gang; Fei, Zhou; Zhong, Jun; Wei, Li-Zhou; Long, Qian-Fa; Liu, Wei-Ping

2012-05-10

Traumatic brain injury commonly has a result of a short window of opportunity between the period of initial brain injury and secondary brain injury, which provides protective strategies and can reduce damages of brain due to secondary brain injury. Previous studies have reported neuroprotective effects of extremely low-frequency electromagnetic fields. However, the effects of extremely low-frequency electromagnetic fields on neural damage after traumatic brain injury have not been reported yet. The present study aims to investigate effects of extremely low-frequency electromagnetic fields on neuroprotection after traumatic brain injury. Male Sprague-Dawley rats were used for the model of lateral fluid percussion injury, which were placed in non-electromagnetic fields and 15 Hz (Hertz) electromagnetic fields with intensities of 1 G (Gauss), 3 G and 5 G. At various time points (ranging from 0.5 to 30 h) after lateral fluid percussion injury, rats were treated with kainic acid (administered by intraperitoneal injection) to induce apoptosis in hippocampal cells. The results were as follows: (1) the expression of hypoxia-inducible factor-1α was dramatically decreased during the neuroprotective time window. (2) The kainic acid-induced apoptosis in the hippocampus was significantly decreased in rats exposed to electromagnetic fields. (3) Electromagnetic fields exposure shortened the escape time in water maze test. (4) Electromagnetic fields exposure accelerated the recovery of the blood-brain barrier after brain injury. These findings revealed that extremely low-frequency electromagnetic fields significantly prolong the window of opportunity for brain protection and enhance the intensity of neuroprotection after traumatic brain injury. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Emerging nondestructive inspection methods for aging aircraft

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beattie, A; Dahlke, L; Gieske, J

This report identifies and describes emerging nondestructive inspection (NDI) methods that can potentially be used to inspect commercial transport and commuter aircraft for structural damage. The nine categories of emerging NDI techniques are: acoustic emission, x-ray computed tomography, backscatter radiation, reverse geometry x-ray, advanced electromagnetics, including magnetooptic imaging and advanced eddy current techniques, coherent optics, advanced ultrasonics, advanced visual, and infrared thermography. The physical principles, generalized performance characteristics, and typical applications associated with each method are described. In addition, aircraft inspection applications are discussed along with the associated technical considerations. Finally, the status of each technique is presented, with amore » discussion on when it may be available for use in actual aircraft maintenance programs. It should be noted that this is a companion document to DOT/FAA/CT-91/5, Current Nondestructive Inspection Methods for Aging Aircraft.« less

Navigation bronchoscopy for diagnosis and small nodule location

PubMed Central

Muñoz-Largacha, Juan A.; Litle, Virginia R.

2017-01-01

Lung cancer continues to be the most common cause of cancer death. Screening programs for high risk patients with the use of low-dose computed tomography (CT) has led to the identification of small lung lesions that were difficult to identify using previous imaging modalities. Electromagnetic navigational bronchoscopy (ENB) is a novel technique that has shown to be of great utility during the evaluation of small, peripheral lesions, that would otherwise be challenging to evaluate with conventional bronchoscopy. The diagnostic yield of navigational bronchoscopy however is highly variable, with reports ranging from 59% to 94%. This variability suggests that well-defined selection criteria and standardized protocols for the use of ENB are lacking. Despite this variability, we believe that this technique is a useful tool evaluating small peripheral lung lesions when patients are properly selected. PMID:28446971

Effect of radio frequency waves of electromagnetic field on the tubulin.

PubMed

Taghi, Mousavi; Gholamhosein, Riazi; Saeed, Rezayi-Zarchi

2013-09-01

Microtubules (MTs) are macromolecular structures consisting of tubulin heterodimers and present in almost every eukaryotic cell. MTs fulfill all conditions for generation of electromagnetic field and are electrically polar due to the electrical polarity of a tubulin heterodimer. The calculated static electric dipole moment of about 1000 Debye makes them capable of being aligned parallel to the applied electromagnetic field direction. In the present study, the tubulin heterodimers were extracted and purified from the rat brains. MTs were obtained by polymerization in vitro. Samples of microtubules were adsorbed in the absence and in the presence of electromagnetic fields with radio frequency of 900 Hz. Our results demonstrate the effect of electromagnetic field with 900 Hz frequency to change the structure of MTs. In this paper, a related patent was used that will help to better understand the studied subject.

77 FR 64935 - Reliability Standards for Geomagnetic Disturbances

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-24

... Ridge Study'') on the effects of electromagnetic pulses on the Bulk-Power System. Available at http... . \\6\\ Oak Ridge National Laboratory, Electromagnetic Pulse: Effects on the U.S. Power Grid: Meta-R-319... issued reports assessing the threat to the United States from Electromagnetic Pulse (EMP) attack in 2004...

Geochemical mapping in polluted floodplains using handheld XRF, geophysical imaging, and geostatistics

NASA Astrophysics Data System (ADS)

Hošek, Michal; Matys Grygar, Tomáš; Popelka, Jan; Kiss, Timea; Elznicová, Jitka; Faměra, Martin

2017-04-01

In the recent years researchers have enjoyed noticeable improvements of portable analytical and geophysical methods, which allow studying floodplain architecture and deciphering pollutant distribution more easily than ever before. Our area of interest was floodplain of the Ploučnice River, particularly a pollution hotspot in Boreček, severely impacted by U mining between the 1970s and late 1980s, in particular a "radioactive flood" in 1981. In the area, we used hand drill coring and in situ (field) analysis of so acquired sediments by handheld X-ray fluorescence spectrometer (XRF), which gave us information about depth profiles of pollutants (Ba, U, Zn) and the Al/Si and Zr/Rb ratios, i.e., proxies for sediment lithology. We found that spatial distribution of pollutants (control by depth and position in the floodplain) is apparently complex and discontinuous. In some places, contamination is buried by a couple decimetres of less polluted sediments, while in other places the peak pollution is near surface, apparently without a straightforward connection with the surface topography and the distance to the river channel. We thus examined the floodplain architecture, the internal structure of the floodplain using two geophysical methods. First of them, dipole electromagnetic profiling (DEMP, also denoted EMP, MP, or Slingram) quickly acquires average electric resistivity in top strata in selected areas, which was actually top 3 m with our particular instrument. Second, electric resistivity tomography (ERT) produces much more detailed information on resistivity with depth resolution of ca 0.5 m to the depth of ca 5 m in selected lines. ERT thus allows identifying boundaries of electric resistivity domains (sediment bodies) and DEMP their spatial distribution. Based on the obtained data, we divided the floodplain to five segments with specific topography, pollution characteristics, and electric resistivity. We suppose that those segments are lithogenetic floodplain units. Those findings must, however, be checked by sediment examination and analysis in selected points. We processed the crucial characteristics obtained by geochemical mapping, namely depth of maximum pollution, amount of contamination, and lithology (Al/Si and Zr/Rb ratios), using geostatistics. Moreover, some parts of floodplain were dated by optically stimulated luminescence (OSL) which revealed, that recycling of top decimetres of floodplain fine fill (silts) in Boreček site has proceeded relatively recently (in decades and centuries) as compared to deeper lying coarser (sandy) strata (millennia). The results of geochemical mapping show complexity of pollution hotspots and need of their integrated interpretation. Key words: Dipole electromagneting profilling, electric resistivity tomography, floodplain contamination, geochemical mapping

Electromagnetic radiation accompanying gravitational waves from black hole binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolgov, A.; Postnov, K., E-mail: dolgov@fe.infn.it, E-mail: kpostnov@gmail.com

The transition of powerful gravitational waves, created by the coalescence of massive black hole binaries, into electromagnetic radiation in external magnetic fields is considered. In contrast to the previous calculations of the similar effect we study the realistic case of the gravitational radiation frequency below the plasma frequency of the surrounding medium. The gravitational waves propagating in the plasma constantly create electromagnetic radiation dragging it with them, despite the low frequency. The plasma heating by the unattenuated electromagnetic wave may be significant in hot rarefied plasma with strong magnetic field and can lead to a noticeable burst of electromagnetic radiationmore » with higher frequency. The graviton-to-photon conversion effect in plasma is discussed in the context of possible electromagnetic counterparts of GW150914 and GW170104.« less

Direct chill casting of aluminium alloys under electromagnetic interaction by permanent magnet assembly

NASA Astrophysics Data System (ADS)

Bojarevičs, Andris; Kaldre, Imants; Milgrāvis, Mikus; Beinerts, Toms

2018-05-01

Direct chill casting is one of the methods used in industry to obtain good microstructure and properties of aluminium alloys. Nevertheless, for some alloys grain structure is not optimal. In this study, we offer the use of electromagnetic interaction to modify melt convection near the solidification interface. Solidification under various electromagnetic interactions has been widely studied, but usually at low solidification velocity and high thermal gradient. This type of interaction may succeed fragmentation of dendrite arms and transport of solidification nuclei thus leading to improved material structure and properties. Realization of experimental small-scale crystallizer and electromagnetic system has been described in this article.

Design considerations of electromagnetic force in a direct drive permanent magnet brushless motor

NASA Astrophysics Data System (ADS)

Chen, H. S.; Tsai, M. C.

2008-04-01

In this paper, a numerical study of electromagnetic force associated with the width of stator teeth, width of rotor back iron, and slot opening for a ten-pole nine-slot direct drive permanent magnet brushless motor is presented. The study calculates the amplitude of the electromagnetic force on the rotating rotor by using the finite-element method. The results show that the amplitude of electromagnetic force, which may cause the noise and vibration of motors, changes with the variation of these above mentioned three factors. The relationship between the considerations of output torque and the minimization of noise and vibration is also established in this paper.

[Study on effects of bioelectric parameters of rats in electromagnetic radiation of HV transmission line].

PubMed

Zhang, Anying; Pang, Xiaofeng; Yuan, Ping

2007-02-01

With the development of economy and coming of information era, the chance of exposure to electromagnetic fields with various frequencies has been increased for every human. The effects of electromagnetic radiattion on human being's health are versatile. To study the effects of bioelctronic parameters of rats in the electromagnetic radiations of HV transmission line, EEG, ECG and CMAP were measured in rats exposed to simulating high-voltage transmission line electromagnetic radiation for over one year. Brain tissues were studied by Fourier transform infrared spectroscopy. The results showed that no significant difference between exposed group and control group in EEG; however the FT-infrared spectra of brain tissues were different; the ECG of the exposed animals was considerably altered. Significant slowing of heart rate was observed in those rates exposed to EMFs; the latent period of CMAP in exposed group were not different compared with those of control group however there was a significant difference in wave amplitude of CMAP between the exposed group and control group. All results indicated that there must be some effects on bioelectric parameters of rats exposed to electromagnetic radiation of high-voltage transmission line for a long time.

Electromagnetic shielding effectiveness of 3D printed polymer composites

NASA Astrophysics Data System (ADS)

Viskadourakis, Z.; Vasilopoulos, K. C.; Economou, E. N.; Soukoulis, C. M.; Kenanakis, G.

2017-12-01

We report on preliminary results regarding the electromagnetic shielding effectiveness of various 3D printed polymeric composite structures. All studied samples were fabricated using 3D printing technology, following the fused deposition modeling approach, using commercially available filaments as starting materials. The electromagnetic shielding performance of the fabricated 3D samples was investigated in the so called C-band of the electromagnetic spectrum (3.5-7.0 GHz), which is typically used for long-distance radio telecommunications. We provide evidence that 3D printing technology can be effectively utilized to prepare operational shields, making them promising candidates for electromagnetic shielding applications for electronic devices.

Hypothesis on how to measure electromagnetic hypersensitivity.

PubMed

Tuengler, Andreas; von Klitzing, Lebrecht

2013-09-01

Electromagnetic hypersensitivity (EHS) is an ill-defined term to describe the fact that people who experience health symptoms in the vicinity of electromagnetic fields (EMFs) regard them as causal for their complaints. Up to now most scientists assume a psychological cause for the suffering of electromagnetic hypersensitive individuals. This paper addresses reasons why most provocation studies could not find any association between EMF exposure and EHS and presents a hypothesis on diagnosis and differentiation of this condition. Simultaneous recordings of heart rate variability, microcirculation and electric skin potentials are used for classification of EHS. Thus, it could be possible to distinguish "genuine" electromagnetic hypersensitive individuals from those who suffer from other conditions.

How do pre-service teachers picture various electromagnetic phenomenon? A qualitative study of pre-service teachers' conceptual understanding of fundamental electromagnetic interaction

NASA Astrophysics Data System (ADS)

Beer, Christopher P.

This study analyzes the nature of pre-service teachers' conceptual models of various electromagnetic phenomena, specifically electrical current, electrical resistance, and light/matter interactions. This is achieved through the students answering the three questions on electromagnetism using a free response approach including both verbal and pictorial representation. The student responses are then analyzed qualitatively and quantitatively utilizing a multi-tiered approach. These analyses include epistemological representation, misconceptions, correct conceptions, and the impact of high school physics exposure on student conceptions. This study is unique in three primary respects; the free response questionnaire approach, a subject group that consists of pre-service teachers, and a primarily female demographic.

Accretion disk dynamics in X-ray binaries

NASA Astrophysics Data System (ADS)

Peris, Charith Srian

Accreting X-ray binaries consist of a normal star which orbits a compact object with the former transferring matter onto the later via an accretion disk. These accretion disks emit radiation across the entire electromagnetic spectrum. This thesis exploits two regions of the spectrum, exploring the (1) inner disk regions of an accreting black hole binary, GRS1915+105, using X-ray spectral analysis and (2) the outer accretion disks of a set of neutron star and black hole binaries using Doppler Tomography applied on optical observations. X-ray spectral analysis of black hole binary GRS1915+105: GRS1915+105 stands out as an exceptional black hole primarily due to the wild variability exhibited by about half of its X-ray observations. This study focused on the steady X-ray observations of the source, which were found to exhibit significant curvature in the harder coronal component within the RXTE/PCA band-pass. The roughly constant inner-disk radius seen in a majority of the steady-soft observations is strongly reminiscent of canonical soft state black-hole binaries. Remarkably, the steady-hard observations show the presence of growing truncation in the inner-disk. A majority of the steady observations of GRS1915+105 map to the states observed in canonical black hole binaries which suggests that within the complexity of this source is a simpler underlying basis of states. Optical tomography of X-ray binary systems: Doppler tomography was applied to the strong line features present in the optical spectra of X-ray binaries in order to determine the geometric structure of the systems' emitting regions. The point where the accretion stream hits the disk, also referred to as the "hotspot'', is clearly identified in the neutron star system V691 CrA and the black hole system Nova Muscae 1991. Evidence for stream-disk overflows exist in both systems, consistent with relatively high accretion rates. In contrast, V926 Sco does not show evidence for the presence of a hotspot which is consistent with its lower accretion state. The donor stars in V691 CrA and Nova Muscae 1991 were also detected.

Electromagnetic bone segment tracking to control femoral derotation osteotomy-A saw bone study.

PubMed

Geisbüsch, Andreas; Auer, Christoph; Dickhaus, Hartmut; Niklasch, Mirjam; Dreher, Thomas

2017-05-01

Correction of rotational gait abnormalities is common practice in pediatric orthopaedics such as in children with cerebral palsy. Femoral derotation osteotomy is established as a standard treatment, however, different authors reported substantial variability in outcomes following surgery with patients showing over- or under-correction. Only 60% of the applied correction is observed postoperatively, which strongly suggests intraoperative measurement error or loss of correction during surgery. This study was conducted to verify the impact of error sources in the derotation procedure and assess the utility of a newly developed, instrumented measurement system based on electromagnetic tracking aiming to improve the accuracy of rotational correction. A supracondylar derotation osteotomy was performed in 21 artificial femur sawbones and the amount of derotation was quantified during the procedure by the tracking system and by nine raters using a conventional goniometer. Accuracy of both measurement devices was determined by repeated computer tomography scans. Average derotation measured by the tracking system differed by 0.1° ± 1.6° from the defined reference measurement . In contrast, a high inter-rater variability was found in goniometric measurements (range: 10.8° ± 6.9°, mean interquartile distance: 6.6°). During fixation of the osteosynthesis, the tracking system reliably detected unintentional manipulation of the correction angle with a mean absolute change of 4.0° ± 3.2°. Our findings show that conventional control of femoral derotation is subject to relevant observer bias whereas instrumental tracking yields accuracy better than ±2°. The tracking system is a step towards more reliable and safe implementation of femoral correction, promising substantial improvements of patient safety in the future. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1106-1112, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Rat testicular impairment induced by electromagnetic radiation from a conventional cellular telephone and the protective effects of the antioxidants vitamins C and E

PubMed Central

Al-Damegh, Mona Abdullah

2012-01-01

OBJECTIVE: The aim of this study was to investigate the possible effects of electromagnetic radiation from conventional cellular phone use on the oxidant and antioxidant status in rat blood and testicular tissue and determine the possible protective role of vitamins C and E in preventing the detrimental effects of electromagnetic radiation on the testes. MATERIALS AND METHODS: The treatment groups were exposed to an electromagnetic field, electromagnetic field plus vitamin C (40 mg/kg/day) or electromagnetic field plus vitamin E (2.7 mg/kg/day). All groups were exposed to the same electromagnetic frequency for 15, 30, and 60 min daily for two weeks. RESULTS: There was a significant increase in the diameter of the seminiferous tubules with a disorganized seminiferous tubule sperm cycle interruption in the electromagnetism-exposed group. The serum and testicular tissue conjugated diene, lipid hydroperoxide, and catalase activities increased 3-fold, whereas the total serum and testicular tissue glutathione and glutathione peroxidase levels decreased 3-5 fold in the electromagnetism-exposed animals. CONCLUSION: Our results indicate that the adverse effect of the generated electromagnetic frequency had a negative impact on testicular architecture and enzymatic activity. This finding also indicated the possible role of vitamins C and E in mitigating the oxidative stress imposed on the testes and restoring normality to the testes. PMID:22892924

Rat testicular impairment induced by electromagnetic radiation from a conventional cellular telephone and the protective effects of the antioxidants vitamins C and E.

PubMed

Al-Damegh, Mona Abdullah

2012-07-01

The aim of this study was to investigate the possible effects of electromagnetic radiation from conventional cellular phone use on the oxidant and antioxidant status in rat blood and testicular tissue and determine the possible protective role of vitamins C and E in preventing the detrimental effects of electromagnetic radiation on the testes. The treatment groups were exposed to an electromagnetic field, electromagnetic field plus vitamin C (40 mg/kg/day) or electromagnetic field plus vitamin E (2.7 mg/kg/day). All groups were exposed to the same electromagnetic frequency for 15, 30, and 60 min daily for two weeks. There was a significant increase in the diameter of the seminiferous tubules with a disorganized seminiferous tubule sperm cycle interruption in the electromagnetism-exposed group. The serum and testicular tissue conjugated diene, lipid hydroperoxide, and catalase activities increased 3-fold, whereas the total serum and testicular tissue glutathione and glutathione peroxidase levels decreased 3-5 fold in the electromagnetism-exposed animals. Our results indicate that the adverse effect of the generated electromagnetic frequency had a negative impact on testicular architecture and enzymatic activity. This finding also indicated the possible role of vitamins C and E in mitigating the oxidative stress imposed on the testes and restoring normality to the testes.

The role of FDG-PET in detecting rejection after liver transplantation.

PubMed

Watson, Ashley M; Bhutiani, Neal; Philips, Prejesh; Davis, Eric G; Eng, Mary; Cannon, Robert M; Jones, Christopher M

2018-05-15

The activation and increased metabolic activity of T cells in acute cellular rejection could allow fluoro-2-deoxyglucose positron emission tomography to be utilized for detection of acute cellular rejection. The objective of this study was to evaluate the effectiveness of fluoro-2-deoxyglucose positron emission tomography in detecting acute cellular rejection in the clinical setting. Fluoro-2-deoxyglucose positron emission tomography studies were performed on 88 orthotopic liver transplant patients at 7 and 17 days postoperatively (first positron emission tomography and second positron emission tomography, respectively). Additional studies were performed if patients had suspicion of rejection and at resolution of rejection (third positron emission tomography and fourth positron emission tomography, respectively). A circular region of interest was placed over the liver for semiquantitative evaluation of fluoro-2-deoxyglucose positron emission tomography images by means of standard uptake values. Eighteen of 88 patients in our study (20.5%) had histologically proven acute cellular rejection during a 16 ± 11 day follow-up. There was no significant difference between the standard uptake values of first positron emission tomography among non-rejecters versus rejecters (2.05 ±0.46 non-rejecters versus 1.82 ± 0.40 rejecters, P = .127). Within the rejection cohort, the standard uptake values from the third positron emission tomography (rejection) were higher compared to the first positron emission tomography (baseline) (2.41 ± 0.48 third positron emission tomography versus 1.82 ± 0.41 first positron emission tomography, P < .001). Increased signal on fluoro-2-deoxyglucose positron emission tomography over baseline is associated with acute cellular rejection in liver transplant recipients. Additional prospective validation studies are essential to define the role of fluoro-2-deoxyglucose positron emission tomography scan as an early marker for acute cellular rejection. Copyright © 2018 Elsevier Inc. All rights reserved.

Students' Performance Awareness, Motivational Orientations and Learning Strategies in a Problem-Based Electromagnetism Course

ERIC Educational Resources Information Center

Saglam, Murat

2010-01-01

This study aims to explore problem-based learning (PBL) in conjunction with students' confidence in the basic ideas of electromagnetism and their motivational orientations and learning strategies. The 78 first-year geology and geophysics students followed a three-week PBL instruction in electromagnetism. The students' confidence was assessed…

Analysis of Arguments Constructed by First-Year Engineering Students Addressing Electromagnetic Induction Problems

ERIC Educational Resources Information Center

Almudi, Jose Manuel; Ceberio, Mikel

2015-01-01

This study explored the quality of arguments used by first-year engineering university students enrolled in a traditional physics course dealing with electromagnetic induction and related problem solving where they had to assess whether the electromagnetic induction phenomenon would occur. Their conclusions were analyzed for the relevance of the…

Engaging Students in Applied Electromagnetics at the University of San Diego

ERIC Educational Resources Information Center

Lumori, M. L. D.; Kim, E. M.

2010-01-01

Two possible topical approaches that have been applied to teaching an upper-division undergraduate electrical engineering applied electromagnetics course are presented. Each approach was applied to one of two offerings of the course, taught in different semesters. In either case, the course includes the study of electromagnetic theory and…

When to Perform Antenna Measurements in a Near-Field Range or a Short Tapered Chamber

DTIC Science & Technology

2017-03-01

study was undertaken to quantify and compare electromagnetic device (i.e., antenna) measurements using the US Army Research Laboratory’s (ARL’s) near...results for future antennas under test in the most cost-effective manner (man-hours, custom mount, etc.) 15. SUBJECT TERMS electromagnetic , chamber...study was undertaken to quantify and compare electromagnetic (EM) device (i.e., antenna) measurements using the US Army Research Laboratory’s (ARL

Research on radiation characteristic of plasma antenna through FDTD method.

PubMed

Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

2014-01-01

The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic.

The role of electromagnetic stimulation in the management of established non-union of long bone fractures: what is the evidence?

PubMed

Griffin, X L; Warner, F; Costa, M

2008-04-01

Non-union following long bone fractures is a cause of significant morbidity to the patient. The management of this condition has proved difficult for the orthopaedic surgeon. Much research has been carried out on the use of electromagnetic stimulation in the healing of non-union. The objective of this review is to determine what evidence exists to support electromagnetic stimulation in the management of established non-union of long bone fractures. A systematic search was carried out of the peer-reviewed English language literature to identify all studies investigating electromagnetic stimulation in the treatment of non-union of fractures of long bones. Three of the articles reviewed were randomised clinical trials. Forty-six other studies were also included in the review. There is a consensus that electromagnetic stimulation is an effective adjunct to conventional therapy when used in the management of non-union of long bone fractures.

Understanding and manipulating the RF fields at high field MRI

PubMed Central

Ibrahim, Tamer S.; Hue, YiK-Kiong; Tang, Lin

2015-01-01

This paper presents a complete overview of the electromagnetics (radiofrequency aspect) of MRI at low and high fields. Using analytical formulations, numerical modeling (computational electromagnetics), and ultrahigh field imaging experiments, the physics that impacts the electromagnetic quantities associated with MRI, namely (1) the transmit field, (2) receive field, and (3) total electromagnetic power absorption, is analyzed. The physical interpretation of the above-mentioned quantities is investigated by electromagnetic theory, to understand ‘What happens, in terms of electromagnetics, when operating at different static field strengths?’ Using experimental studies and numerical simulations, this paper also examines the physical and technological feasibilities by which all or any of these specified electromagnetic quantities can be manipulated through techniques such as B1 shimming (phased array excitation) and signal combination using a receive array in order to advance MRI at high field strengths. Pertinent to this subject and with highly coupled coils operating at 7 T, this paper also presents the first phantom work on B1 shimming without B1 measurements. PMID:19621335

Extremely low frequency 7 Hz 100 microT electromagnetic radiation promotes differentiation in the human epithelial cell line HaCaT.

PubMed

Lisi, Antonella; Foletti, Alberto; Ledda, Mario; Rosola, Emanuela; Giuliani, Livio; D'Emilia, Enrico; Grimaldi, Settimio

2006-01-01

Electromagnetic therapy is a treatment method in which an electromagnetic or magnetic stimulus is used to achieve physiological changes in the body. The specific aim of the present work concerns the effectiveness of low frequency electromagnetic fields to modify the biochemical properties of human keratinocytes (HaCaT). Cells exposed to a 7 Hz 100 microT electromagnetic field for one hour (twice daily), indicated modification in shape and morphology. These modifications were also associated with different actin distribution as revealed by phalloidin fluorescence analysis. Indirect immunofluorescence with fluorescent antibodies against involucrin and beta-Catenin, both differentiation and adhesion markers, revealed an increase in involucrin and beta-Catenin expression, supporting the conclusion that exposure to electromagnetic field carries keratinocytes to an upper differentiation level. This study confirms our previous observation and supports the hypothesis that 7 Hz electromagnetic field, may modify cell biochemistry interfering in the differentiation and cellular adhesion of normal keratinocytes.

Gravitational scattering of electromagnetic radiation

NASA Technical Reports Server (NTRS)

Brooker, J. T.; Janis, A. I.

1980-01-01

The scattering of electromagnetic radiation by linearized gravitational fields is studied to second order in a perturbation expansion. The incoming electromagnetic radiation can be of arbitrary multipole structure, and the gravitational fields are also taken to be advanced fields of arbitrary multipole structure. All electromagnetic multipole radiation is found to be scattered by gravitational monopole and time-varying dipole fields. No case has been found, however, in which any electromagnetic multipole radiation is scattered by gravitational fields of quadrupole or higher-order multipole structure. This lack of scattering is established for infinite classes of special cases, and is conjectured to hold in general. The results of the scattering analysis are applied to the case of electromagnetic radiation scattered by a moving mass. It is shown how the mass and velocity may be determined by a knowledge of the incident and scattered radiation.

Measuring the electromagnetic chirality of 2D arrays under normal illumination.

PubMed

Garcia-Santiago, X; Burger, S; Rockstuhl, C; Fernandez-Corbaton, I

2017-10-15

We present an electromagnetic chirality measure for 2D arrays of subwavelength periodicities under normal illumination. The calculation of the measure uses only the complex reflection and transmission coefficients from the array. The measure allows the ordering of arrays according to their electromagnetic chirality, which further allows a quantitative comparison of different design strategies. The measure is upper bounded, and the extreme properties of objects with high values of electromagnetic chirality make them useful in both near- and far-field applications. We analyze the consequences that different possible symmetries of the array have on its electromagnetic chirality. We use the measure to study four different arrays. The results indicate the suitability of helices for building arrays of high electromagnetic chirality, and the low effectiveness of a substrate for breaking the transverse mirror symmetry.

Investigation on the electromagnetic centring technique in compressor with labyrinth seal structure

NASA Astrophysics Data System (ADS)

Zhang, W.; Feng, C.; Cheng, J.; Feng, Q.; Wu, W.

2017-08-01

At present, the piston of compressors with labyrinth seal structure generally runs eccentrically, which causes uneven radial clearance, serious leakages and lower volumetric efficiency. This has become an urgent problem in the development of labyrinth compressors. In this study, electromagnetic levitation technology was introduced to achieve concentric centering between the piston and cylinder, and the conventional cantilever structure for the piston centering was replaced by a simple support structure using the through-piston rod. Furthermore, the simulation model of the electromagnetic centering system was established and the experimental prototype was built. The mathematical simulation model was verified by comparing simulated and tested results. Then, the centering effect of the system was assessed and the variation of the leakage in the compressor was studied by models using dynamic mesh technology. The results showed that the radial clearance between piston and cylinder can be maintained in the range of -0.3 mm to 0.3 mm through the electromagnetic centering control. In addition, the inner leakage of the compressor was quite appreciable without the electromagnetic control. However, it was reduced by 1.8 times with the introduction of the electromagnetic control. Thus, it can be concluded that the precise centering between the piston and the cylinder can be achieved by the introduction of the electromagnetic centering technique.

Effects of exposure to 2100MHz GSM-like radiofrequency electromagnetic field on auditory system of rats.

PubMed

Çeliker, Metin; Özgür, Abdulkadir; Tümkaya, Levent; Terzi, Suat; Yılmaz, Mustafa; Kalkan, Yıldıray; Erdoğan, Ender

The use of mobile phones has become widespread in recent years. Although beneficial from the communication viewpoint, the electromagnetic fields generated by mobile phones may cause unwanted biological changes in the human body. In this study, we aimed to evaluate the effects of 2100MHz Global System for Mobile communication (GSM-like) electromagnetic field, generated by an electromagnetic fields generator, on the auditory system of rats by using electrophysiological, histopathologic and immunohistochemical methods. Fourteen adult Wistar albino rats were included in the study. The rats were divided randomly into two groups of seven rats each. The study group was exposed continuously for 30days to a 2100MHz electromagnetic fields with a signal level (power) of 5.4dBm (3.47mW) to simulate the talk mode on a mobile phone. The control group was not exposed to the aforementioned electromagnetic fields. After 30days, the Auditory Brainstem Responses of both groups were recorded and the rats were sacrificed. The cochlear nuclei were evaluated by histopathologic and immunohistochemical methods. The Auditory Brainstem Responses records of the two groups did not differ significantly. The histopathologic analysis showed increased degeneration signs in the study group (p=0.007). In addition, immunohistochemical analysis revealed increased apoptotic index in the study group compared to that in the control group (p=0.002). The results support that long-term exposure to a GSM-like 2100MHz electromagnetic fields causes an increase in neuronal degeneration and apoptosis in the auditory system. Copyright © 2016 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Experimental measurement and theoretical modeling of microwave scattering and the structure of the sea surface influencing radar observations from space

NASA Technical Reports Server (NTRS)

Arnold, David; Kong, J. A.

1992-01-01

The electromagnetic bias is an error present in radar altimetry of the ocean due to the non-uniform reflection from wave troughs and crests. A study of the electromagnetic bias became necessary to permit error reduction in mean sea level measurements of satellite radar altimeters. Satellite radar altimeters have been used to find the upper and lower bounds for the electromagnetic bias. This report will present a theory using physical optics scattering and an empirical model of the short wave modulation to predict the electromagnetic bias. The predicted electromagnetic bias will be compared to measurements at C and Ku bands.

Structural monitoring via microwave tomography-enhanced GPR: the Montagnole test site

NASA Astrophysics Data System (ADS)

Catapano, Ilaria; Di Napoli, Rosario; Soldovieri, Francesco; Bavusi, Massimo; Loperte, Antonio; Dumoulin, Jean

2012-08-01

Structural integrity assessment and monitoring of infrastructures are key factors to prevent and manage crisis events (natural disasters, terrorist attacks and so on) and ensure urban safety. This necessity motivates huge interest towards design, optimization and integration of non-invasive remote and in situ diagnostic techniques. In this framework, ground penetrating radar (GPR) is a well-assessed instrumentation, which allows one to attain information on the inner status of man-made structures while avoiding invasive tests. However, despite its potential, a more widespread use of GPR is actually affected by the difficulties in providing highly informative and easily interpretable images as an outcome of the overall diagnostics procedure. This drawback can be mitigated thanks to the use of microwave tomography (MT) as a data processing tool able to enhance the achievable reconstruction capabilities, and several proofs of its effectiveness have been already shown. In this paper, the potential of the MT approach is investigated in the framework of structural monitoring by an experiment carried out in the Montagnole test site in the French Alps, where the progressive damage of a one-scale concrete beam has been monitored thanks to the integration of several electromagnetic sensing techniques. In this framework, the capability of the MT-enhanced GPR strategy is examined with respect to the possibility of providing information about the damage of the rebar grid of the beam.

Comparison of GATE/GEANT4 with EGSnrc and MCNP for electron dose calculations at energies between 15 keV and 20 MeV.

PubMed

Maigne, L; Perrot, Y; Schaart, D R; Donnarieix, D; Breton, V

2011-02-07

The GATE Monte Carlo simulation platform based on the GEANT4 toolkit has come into widespread use for simulating positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging devices. Here, we explore its use for calculating electron dose distributions in water. Mono-energetic electron dose point kernels and pencil beam kernels in water are calculated for different energies between 15 keV and 20 MeV by means of GATE 6.0, which makes use of the GEANT4 version 9.2 Standard Electromagnetic Physics Package. The results are compared to the well-validated codes EGSnrc and MCNP4C. It is shown that recent improvements made to the GEANT4/GATE software result in significantly better agreement with the other codes. We furthermore illustrate several issues of general interest to GATE and GEANT4 users who wish to perform accurate simulations involving electrons. Provided that the electron step size is sufficiently restricted, GATE 6.0 and EGSnrc dose point kernels are shown to agree to within less than 3% of the maximum dose between 50 keV and 4 MeV, while pencil beam kernels are found to agree to within less than 4% of the maximum dose between 15 keV and 20 MeV.

Computer-assisted surgery: virtual- and augmented-reality displays for navigation during urological interventions.

PubMed

van Oosterom, Matthias N; van der Poel, Henk G; Navab, Nassir; van de Velde, Cornelis J H; van Leeuwen, Fijs W B

2018-03-01

To provide an overview of the developments made for virtual- and augmented-reality navigation procedures in urological interventions/surgery. Navigation efforts have demonstrated potential in the field of urology by supporting guidance for various disorders. The navigation approaches differ between the individual indications, but seem interchangeable to a certain extent. An increasing number of pre- and intra-operative imaging modalities has been used to create detailed surgical roadmaps, namely: (cone-beam) computed tomography, MRI, ultrasound, and single-photon emission computed tomography. Registration of these surgical roadmaps with the real-life surgical view has occurred in different forms (e.g. electromagnetic, mechanical, vision, or near-infrared optical-based), whereby the combination of approaches was suggested to provide superior outcome. Soft-tissue deformations demand the use of confirmatory interventional (imaging) modalities. This has resulted in the introduction of new intraoperative modalities such as drop-in US, transurethral US, (drop-in) gamma probes and fluorescence cameras. These noninvasive modalities provide an alternative to invasive technologies that expose the patients to X-ray doses. Whereas some reports have indicated navigation setups provide equal or better results than conventional approaches, most trials have been performed in relatively small patient groups and clear follow-up data are missing. The reported computer-assisted surgery research concepts provide a glimpse in to the future application of navigation technologies in the field of urology.

In vivo electric conductivity of cervical cancer patients based on B₁⁺ maps at 3T MRI.

PubMed

Balidemaj, E; de Boer, P; van Lier, A L H M W; Remis, R F; Stalpers, L J A; Westerveld, G H; Nederveen, A J; van den Berg, C A T; Crezee, J

2016-02-21

The in vivo electric conductivity (σ) values of tissue are essential for accurate electromagnetic simulations and specific absorption rate (SAR) assessment for applications such as thermal dose computations in hyperthermia. Currently used σ-values are mostly based on ex vivo measurements. In this study the conductivity of human muscle, bladder content and cervical tumors is acquired non-invasively in vivo using MRI. The conductivity of 20 cervical cancer patients was measured with the MR-based electric properties tomography method on a standard 3T MRI system. The average in vivo σ-value of muscle is 14% higher than currently used in human simulation models. The σ-value of bladder content is an order of magnitude higher than the value for bladder wall tissue that is used for the complete bladder in many models. Our findings are confirmed by various in vivo animal studies from the literature. In cervical tumors, the observed average conductivity was 13% higher than the literature value reported for cervical tissue. Considerable deviations were found for the electrical conductivity observed in this study and the commonly used values for SAR assessment, emphasizing the importance of acquiring in vivo conductivity for more accurate SAR assessment in various applications.

Pulsed magnetic field excitation sensitivity of match-type electric blasting caps

NASA Astrophysics Data System (ADS)

Parson, Jonathan; Dickens, James; Walter, John; Neuber, Andreas A.

2010-10-01

This paper presents a study on energy deposition and electromagnetic compatibility of match-type electroexplosive devices (EEDs), which recently have found more usage in pulsed power environments with high electromagnetic interference (EMI) background. The sensitivity of these devices makes them dangerous to intended and unintended radiation produced by devices commonly used in pulsed power environments. Match-type EEDs have been found to be susceptible to such low levels of energy (7-8 mJ) that safe operation of these EEDs is vital when in use near devices that produce high levels of pulsed EMI. The scope of this paper is to provide an investigation that incorporates results of similar studies to provide detonation characteristics of these EEDs. The three topics included in this study are sensitivity testing, modeling of the thermodynamic heat propagation, and electromagnetic compatibility from pulsed electromagnetic radiation. The thermodynamic joule heating of the primary explosive has been modeled by a solution to the 1D heat equation. A simple pulsed generator, Marx generator with an inductive load, was used for the electromagnetic compatibility assessment of the coupled field between the pulse generator and shorted EED. The results of the electromagnetic compatibility assessment relate the resistive, inductive, and capacitive components of the pulse generator to the area of the shorted EED.

[Morphological structure of rat epiphysis exposed to electromagnetic radiation from communication devices].

PubMed

Yashchenko, S G; Rybalko, S Yu

Pineal gland is one of the most important components of homeostasis - the supporting system of the body. It participates in the launch of stress responses, restriction of their development, prevention of adverse effects on the body. There was proved an impact of electromagnetic radiation on the epiphysis. However, morphological changes in the epiphysis under exposure to electromagnetic radiation of modern communication devices are studied not sufficiently. For the time present the population is daily exposed to electromagnetic radiation, including local irradiation on the brain. These date determined the task of this research - the study of the structure of rat pineal gland under the exposure to electromagnetic radiation from personal computers and mobile phones. These date determined the task of this research - the study of the structure of rat pineal gland under the exposure to electromagnetic radiation from personal computers and mobile phones. Performed transmission electron microscopy revealed signs of degeneration of dark and light pinealocytes. These signs were manifested in the development of a complex of general and specific morphological changes. There was revealed the appearance of signs of aging and depletion transmission electron microscopy both in light and dark pinealocytes. These signs were manifested in the accumulation of lipofuscin granules and electron-dense "brain sand", the disappearance of nucleoli, cytoplasm vacuolization and mitochondrial cristae enlightenment.

Pulsed magnetic field excitation sensitivity of match-type electric blasting caps.

PubMed

Parson, Jonathan; Dickens, James; Walter, John; Neuber, Andreas A

2010-10-01

This paper presents a study on energy deposition and electromagnetic compatibility of match-type electroexplosive devices (EEDs), which recently have found more usage in pulsed power environments with high electromagnetic interference (EMI) background. The sensitivity of these devices makes them dangerous to intended and unintended radiation produced by devices commonly used in pulsed power environments. Match-type EEDs have been found to be susceptible to such low levels of energy (7-8 mJ) that safe operation of these EEDs is vital when in use near devices that produce high levels of pulsed EMI. The scope of this paper is to provide an investigation that incorporates results of similar studies to provide detonation characteristics of these EEDs. The three topics included in this study are sensitivity testing, modeling of the thermodynamic heat propagation, and electromagnetic compatibility from pulsed electromagnetic radiation. The thermodynamic joule heating of the primary explosive has been modeled by a solution to the 1D heat equation. A simple pulsed generator, Marx generator with an inductive load, was used for the electromagnetic compatibility assessment of the coupled field between the pulse generator and shorted EED. The results of the electromagnetic compatibility assessment relate the resistive, inductive, and capacitive components of the pulse generator to the area of the shorted EED.

The Effect of Guided Note Taking during Lectures on Thai University Students' Understanding of Electromagnetism

ERIC Educational Resources Information Center

Narjaikaew, Pattawan; Emarat, Narumon; Cowie, Bronwen

2009-01-01

This paper reports on the implementation of a guided note taking strategy to promote Thai students' understanding of electromagnetism during a lecture course. The aim of the study was to enhance student learning of electromagnetism concepts. The developed guided notes contain quotations, diagrams, pictures, problems, and blank spaces to encourage…

Research Studies on Electromagnetically Induced Transparency

DTIC Science & Technology

2010-01-20

allowing the same simple equations to be used to simulate nonlinear and quantum optics with the N-photon states generated in this regime. One...induced transparency, photon interactions with atoms, nonclassical states of the electromagnetic field, including entangled photon states , quantum ...them. This is important because optical nonlinearities when produced using electromagnetically induced transparency continue to increase in the

Modeling Electromagnetic Scattering From Complex Inhomogeneous Objects

NASA Technical Reports Server (NTRS)

Deshpande, Manohar; Reddy, C. J.

2011-01-01

This software innovation is designed to develop a mathematical formulation to estimate the electromagnetic scattering characteristics of complex, inhomogeneous objects using the finite-element-method (FEM) and method-of-moments (MoM) concepts, as well as to develop a FORTRAN code called FEMOM3DS (Finite Element Method and Method of Moments for 3-Dimensional Scattering), which will implement the steps that are described in the mathematical formulation. Very complex objects can be easily modeled, and the operator of the code is not required to know the details of electromagnetic theory to study electromagnetic scattering.

Electromagnetically induced transparency (EIT)-like transmission in side-coupled complementary split-ring resonators.

PubMed

Guo, Yinghui; Yan, Lianshan; Pan, Wei; Luo, Bin; Wen, Kunhua; Guo, Zhen; Luo, Xiangang

2012-10-22

We investigate a plasmonic waveguide system based on side-coupled complementary split-ring resonators (CSRR), which exhibits electromagnetically induced transparency (EIT)-like transmission. LC resonance model is utilized to explain the electromagnetic responses of CSRR, which is verified by simulation results of finite difference time domain method. The electromagnetic responses of CSRR can be flexible handled by changing the asymmetry degree of the structure and the width of the metallic baffles. Cascaded CSRRs also have been studied to obtain EIT-like transmission at visible and near-infrared region, simultaneously.

Highly Stretchable and Transparent Electromagnetic Interference Shielding Film Based on Silver Nanowire Percolation Network for Wearable Electronics Applications.

PubMed

Jung, Jinwook; Lee, Habeom; Ha, Inho; Cho, Hyunmin; Kim, Kyun Kyu; Kwon, Jinhyeong; Won, Phillip; Hong, Sukjoon; Ko, Seung Hwan

2017-12-27

Future electronics are expected to develop into wearable forms, and an adequate stretchability is required for the forthcoming wearable electronics considering various motions occurring in human body. Along with stretchability, transparency can increase both the functionality and esthetic features in future wearable electronics. In this study, we demonstrate, for the first time, a highly stretchable and transparent electromagnetic interference shielding layer for wearable electronic applications with silver nanowire percolation network on elastic poly(dimethylsiloxane) substrate. The proposed stretchable and transparent electromagnetic interference shielding layer shows a high electromagnetic wave shielding effectiveness even under a high tensile strain condition. It is expected for the silver nanowire percolation network-based electromagnetic interference shielding layer to be beyond the conventional electromagnetic interference shielding materials and to broaden its application range to various fields that require optical transparency or nonplanar surface environment, such as biological system, human skin, and wearable electronics.

Descriptive study of electromagnetic wave distribution for various seating positions: using digital textbooks.

PubMed

Seomun, GyeongAe; Kim, YoungHwan; Lee, Jung-Ah; Jeong, KwangHoon; Park, Seon-A; Kim, Miran; Noh, Wonjung

2014-04-01

To better understand environmental electromagnetic wave exposure during the use of digital textbooks by elementary school students, we measured numeric values of the electromagnetic fields produced by tablet personal computers (TPCs). Specifically, we examined the distribution of the electromagnetic waves for various students' seating positions in an elementary school that uses digital textbooks. Electric and magnetic fields from TPCs were measured using the HI-3603 Visual Display Terminal/ Very Low Frequency (VDT/VLF) radiation measurement system. Electromagnetic field values from TPCs measured at a student's seat and at a teacher's computer were deemed not harmful to health. However, electromagnetic field values varied based on the distance between students, other electronic devices such as a desktop computers, and student posture while using a TPC. Based on these results, it is necessary to guide students to observe proper posture and to arrange seats at an appropriate distance in the classroom.

Functional imaging with low-resolution brain electromagnetic tomography (LORETA): a review.

PubMed

Pascual-Marqui, R D; Esslen, M; Kochi, K; Lehmann, D

2002-01-01

This paper reviews several recent publications that have successfully used the functional brain imaging method known as LORETA. Emphasis is placed on the electrophysiological and neuroanatomical basis of the method, on the localization properties of the method, and on the validation of the method in real experimental human data. Papers that criticize LORETA are briefly discussed. LORETA publications in the 1994-1997 period based localization inference on images of raw electric neuronal activity. In 1998, a series of papers appeared that based localization inference on the statistical parametric mapping methodology applied to high-time resolution LORETA images. Starting in 1999, quantitative neuroanatomy was added to the methodology, based on the digitized Talairach atlas provided by the Brain Imaging Centre, Montreal Neurological Institute. The combination of these methodological developments has placed LORETA at a level that compares favorably to the more classical functional imaging methods, such as PET and fMRI.

Microwave ablation devices for interventional oncology.

PubMed

Ward, Robert C; Healey, Terrance T; Dupuy, Damian E

2013-03-01

Microwave ablation is one of the several options in the ablation armamentarium for the treatment of malignancy, offering several potential benefits when compared with other ablation, radiation, surgical and medical treatment modalities. The basic microwave system consists of the generator, power distribution system and antennas. Often under image (computed tomography or ultrasound) guidance, a needle-like antenna is inserted percutaneously into the tumor, where local microwave electromagnetic radiation is emitted from the probe's active tip, producing frictional tissue heating, capable of causing cell death by coagulation necrosis. Half of the microwave ablation systems use a 915 MHz generator and the other half use a 2450 MHz generator. To date, there are no completed clinical trials comparing microwave devices head-to-head. Prospective comparisons of microwave technology with other treatment alternatives, as well as head-to-head comparison with each microwave device, is needed if this promising field will garner more widespread support and use in the oncology community.

Augmented reality environment for temporomandibular joint motion analysis.

PubMed

Wagner, A; Ploder, O; Zuniga, J; Undt, G; Ewers, R

1996-01-01

The principles of interventional video tomography were applied for the real-time visualization of temporomandibular joint movements in an augmented reality environment. Anatomic structures were extracted in three dimensions from planar cephalometric radiographic images. The live-image fusion of these graphic anatomic structures with real-time position data of the mandible and the articular fossa was performed with a see-through, head-mounted display and an electromagnetic tracking system. The dynamic fusion of radiographic images of the temporomandibular joint to anatomic temporomandibular joint structures in motion created a new modality for temporomandibular joint motion analysis. The advantages of the method are its ability to accurately examine the motion of the temporomandibular joint in three dimensions without restraining the subject and its ability to simultaneously determine the relationship of the bony temporomandibular joint and supporting structures (ie, occlusion, muscle function, etc) during movement before and after treatment.

A homodyne detector integrated onto a photonic chip for measuring quantum states and generating random numbers

NASA Astrophysics Data System (ADS)

Raffaelli, Francesco; Ferranti, Giacomo; Mahler, Dylan H.; Sibson, Philip; Kennard, Jake E.; Santamato, Alberto; Sinclair, Gary; Bonneau, Damien; Thompson, Mark G.; Matthews, Jonathan C. F.

2018-04-01

Optical homodyne detection has found use as a characterisation tool in a range of quantum technologies. So far implementations have been limited to bulk optics. Here we present the optical integration of a homodyne detector onto a silicon photonics chip. The resulting device operates at high speed, up 150 MHz, it is compact and it operates with low noise, quantified with 11 dB clearance between shot noise and electronic noise. We perform on-chip quantum tomography of coherent states with the detector and show that it meets the requirements for characterising more general quantum states of light. We also show that the detector is able to produce quantum random numbers at a rate of 1.2 Gbps, by measuring the vacuum state of the electromagnetic field and applying off-line post processing. The produced random numbers pass all the statistical tests provided by the NIST test suite.

Background Noise Analysis in a Few-Photon-Level Qubit Memory

NASA Astrophysics Data System (ADS)

Mittiga, Thomas; Kupchak, Connor; Jordaan, Bertus; Namazi, Mehdi; Nolleke, Christian; Figeroa, Eden

2014-05-01

We have developed an Electromagnetically Induced Transparency based polarization qubit memory. The device is composed of a dual-rail probe field polarization setup colinear with an intense control field to store and retrieve any arbitrary polarization state by addressing a Λ-type energy level scheme in a 87Rb vapor cell. To achieve a signal-to-background ratio at the few photon level sufficient for polarization tomography of the retrieved state, the intense control field is filtered out through an etalon filtrating system. We have developed an analytical model predicting the influence of the signal-to-background ratio on the fidelities and compared it to experimental data. Experimentally measured global fidelities have been found to follow closely the theoretical prediction as signal-to-background decreases. These results suggest the plausibility of employing room temperature memories to store photonic qubits at the single photon level and for future applications in long distance quantum communication schemes.

Room Temperature Memory for Few Photon Polarization Qubits

NASA Astrophysics Data System (ADS)

Kupchak, Connor; Mittiga, Thomas; Jordan, Bertus; Nazami, Mehdi; Nolleke, Christian; Figueroa, Eden

2014-05-01

We have developed a room temperature quantum memory device based on Electromagnetically Induced Transparency capable of reliably storing and retrieving polarization qubits on the few photon level. Our system is realized in a vapor of 87Rb atoms utilizing a Λ-type energy level scheme. We create a dual-rail storage scheme mediated by an intense control field to allow storage and retrieval of any arbitrary polarization state. Upon retrieval, we employ a filtering system to sufficiently remove the strong pump field, and subject retrieved light states to polarization tomography. To date, our system has produced signal-to-noise ratios near unity with a memory fidelity of >80 % using coherent state qubits containing four photons on average. Our results thus demonstrate the feasibility of room temperature systems for the storage of single-photon-level photonic qubits. Such room temperature systems will be attractive for future long distance quantum communication schemes.

Study on the adjustment capability of the excitation system located inside superconducting machine electromagnetic shield

NASA Astrophysics Data System (ADS)

Xia, D.; Xia, Z.

2017-12-01

The ability for the excitation system to adjust quickly plays a very important role in maintaining the normal operation of superconducting machines and power systems. However, the eddy currents in the electromagnetic shield of superconducting machines hinder the exciting magnetic field change and weaken the adjustment capability of the excitation system. To analyze this problem, a finite element calculation model for the transient electromagnetic field with moving parts is established. The effects of three different electromagnetic shields on the exciting magnetic field are analyzed using finite element method. The results show that the electromagnetic shield hinders the field changes significantly, the better its conductivity, the greater the effect on the superconducting machine excitation.

[Changes in physico-chemical parameters of homeopathic remedies ferrum metallicum CH6 and ferrum metallicum CH30 after exposure to high frequency electromagnetic radiation of low intensity].

PubMed

Mendez, N M

2005-01-01

It is considered the microwaves electromagnetic radiation do not affect the materials, alive or not, when used in low power. In high power, the interaction effects would be the material warming (thermal effect). However, in the last years, the studies about electromagnetic radiation with low power (non thermal effect) in the human being have been increasing. It was found out the electromagnetic radiation, even with low power, can affect the living organisms and biosubstratum. In the present work the influence of electromagnetic radiation (2.45 GHz 500 W/cm2), on physical and chemical parameters of the homeopathic pharmaceutics products in shown.

Susceptibility study of audio recording devices to electromagnetic stimulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halligan, Matthew S.; Grant, Steven L.; Beetner, Daryl G.

2014-02-01

Little research has been performed to study how intentional electromagnetic signals may couple into recording devices. An electromagnetic susceptibility study was performed on an analog tape recorder, a digital video camera, a wired computer microphone, and a wireless microphone system to electromagnetic interference. Devices were subjected to electromagnetic stimulations in the frequency range of 1-990 MHz and field strengths up to 4.9 V/m. Carrier and message frequencies of the stimulation signals were swept, and the impacts of device orientation and antenna polarization were explored. Message signals coupled into all devices only when amplitude modulated signals were used as stimulation signals.more » Test conditions that produced maximum sensitivity were highly specific to each device. Only narrow carrier frequency ranges could be used for most devices to couple messages into recordings. A basic detection technique using cross-correlation demonstrated the need for messages to be as long as possible to maximize message detection and minimize detection error. Analysis suggests that detectable signals could be coupled to these recording devices under realistic ambient conditions.« less

Evaluation of effect of high frequency electromagnetic field on growth and antibiotic sensitivity of bacteria.

PubMed

Salmen, Saleh H; Alharbi, Sulaiman A; Faden, Asmaa A; Wainwright, M

2018-01-01

This study was aimed to evaluate the impact of high frequency electromagnetic fields (HF-EMF at 900 and 1800 MHz) on DNA, growth rate and antibiotic susceptibility of S. aureus , S. epidermidis , and P. aeruginosa . In this study, bacteria were exposed to 900 and 1800 MHz for 2 h and then inoculated to new medium when their growth rate and antibiotic susceptibility were evaluated. Results for the study of bacterial DNA unsuccessful to appearance any difference exposed and non-exposed S. aureus and S. epidermidis . Exposure of S. epidermidis and S. aureus to electromagnetic fields mostly produced no statistically significant decrease in bacterial growth, except for S. aureus when exposure to 900 MHz at 12 h. Exposure of P. aeruginosa to electromagnetic fields at 900 MHz however, lead to a significant reduction in growth rate, while 1800 MHz had insignificant effect. With the exception of S. aureus , treated with amoxicillin (30 µg) and exposed to electromagnetic fields, radiation treatment had no significant effect on bacterial sensitivity to antibiotics.

Study of plasma environments for the integrated Space Station electromagnetic analysis system

NASA Technical Reports Server (NTRS)

Singh, Nagendra

1992-01-01

The final report includes an analysis of various plasma effects on the electromagnetic environment of the Space Station Freedom. Effects of arcing are presented. Concerns of control of arcing by a plasma contactor are highlighted. Generation of waves by contaminant ions are studied and amplitude levels of the waves are estimated. Generation of electromagnetic waves by currents in the structure of the space station, driven by motional EMF, is analyzed and the radiation level is estimated.

Determining Detection and Classification Potential of Munitions using Advanced EMI Sensors in the Underwater Environment

DTIC Science & Technology

2016-11-01

focuses on characterizing Electromagnetic Induction (EMI) responses in the underwater setting through numerical and experimental studies with the...marine EMI sensing. 15. SUBJECT TERMS Munitions Response, Electromagnetic Induction, Unexploded Ordnance, Classification 16. SECURITY CLASSIFICATION...using Advanced EMI Sensors in the Underwater Environment.” The project focuses on characterizing Electromagnetic Induction (EMI) responses in the

Applied Computational Electromagnetics Society Journal. Volume 7, Number 1, Summer 1992

DTIC Science & Technology

1992-01-01

previously-solved computational problem in electrical engineering, physics, or related fields of study. The technical activities promoted by this...in solution technique or in data input/output; identification of new applica- tions for electromagnetics modeling codes and techniques; integration of...papers will represent the computational electromagnetics aspects of research in electrical engineering, physics, or related disciplines. However, papers

Pulsed electromagnetic field with or without exercise therapy in the treatment of benign prostatic hyperplasia

PubMed Central

Elgohary, Hany M; Tantawy, Sayed A

2017-01-01

[Purpose] To investigate the effect of pulsed electromagnetic field with or without exercise therapy in the treatment of benign prostatic hyperplasia. [Subjects and Methods] Sixty male patients aged 55–65 years with benign prostatic hyperplasia were invited to participate in this study. Patients were randomly assigned to Group A (n=20; patients who received pulsed electromagnetic field in addition to pelvic floor and aerobic exercises), Group B (n=20; patients who received pulsed electromagnetic field), and Group C (n=20; patients who received placebo electromagnetic field). The assessments included post-void residual urine, urine flow rate, prostate specific antigen, white blood cells count, and International Prostate Symptom Score were weighed, before and after a 4-week intervention. [Results] There were significant differences in Group A and B in all parameters. Group C showed non-significant differences in all measured variables except for International Prostate Symptom Score. Among groups, all parameters showed highly significant differences in favor of Group A. There were non-significant differences between Group A and B and significant difference between Groups A and C and between Groups B and C. [Conclusion] The present study demonstrated that electromagnetic field had a significant impact on the treatment of benign prostatic hyperplasia. Accordingly, electromagnetic field can be utilized alone or in combination with other physiotherapy modalities. Moreover, clinicians should have the capacity to perceive the advantages accomplished using extra treatment alternatives. Electromagnetic field is a safe, noninvasive method and can be used for the treatment of benign prostatic hyperplasia. PMID:28878453

Research on Radiation Characteristic of Plasma Antenna through FDTD Method

PubMed Central

Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

2014-01-01

The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic. PMID:25114961

Helicopter electromagnetic and magnetic geophysical survey data, Hunton anticline, south-central Oklahoma

USGS Publications Warehouse

Smith, Bruce D.; Smith, David V.; Deszcz-Pan, Maryla; Blome, Charles D.; Hill, Patricia

2011-01-01

This report is a digital data release for multiple geophysical surveys conducted in the Hunton anticline area of south-central Oklahoma. The helicopter electromagnetic and magnetic surveys were flown on March 16–17, 2007, in four areas of the Hunton anticline in south-central Oklahoma. The objective of this project is to improve the understanding of the geohydrologic framework of the Arbuckle-Simpson aquifer. The electromagnetic sensor for the helicopter electromagnetic survey consisted of six different transmitter-receiver orientations that measured the earth's electrical response at six distinct frequencies from approximately 500 Hertz to approximately 115,000 Hertz. The electromagnetic measurements were converted to electrical resistivity values, which were gridded and plotted on georeferenced maps. The map from each frequency represents a different depth of investigation for each area. The range of subsurface investigation is comparable to the depth of shallow groundwater. The four areas selected for the helicopter electromagnetic study, blocks A–D, have different geologic and hydrologic settings. Geophysical and hydrologic information from U.S. Geological Survey studies are being used by modelers and resource managers to develop groundwater resource plans for the Arbuckle-Simpson aquifer.

Microfabricated sensors for the measurement of electromagnetic fields in biological tissues

NASA Astrophysics Data System (ADS)

Monberg, James; Henning, Albert K.

1995-09-01

Public awareness of the risks of exposure to electromagnetic radiation has grown over the past ten yeras. The effects of power lines on human and animal health have drawn particular attention. Some longitudinal studies of cancer rates near power lines show a significant correlation, while others show a null result. The studies have suffered from inadequate sensors for the measurement of electromagnetic radiation in vivo. In this work, we describe the design, construction, and testing of electrically passive, microfabricated single-pole antennas and coils. These sensors will be used in vivo to study the effects of electromagnetic radiation on animals. Our testing to date has been limited to in vitro studies of the magnetic field probes. Magnetic field pickup coils were fabricated with up to 100 turns, over a length of up to 1000 micrometers . Measurements were carried out with the sensors in air, and in water of various saline concentrations. Magnetic fields were applied using a Helmholtz coil. Both dc and ac fields were applied. The results indicate that small-area measurements of electromagnetic fields in vitro can be made successfully, provided adequate shielding and amplification are used.

Self-reported symptoms associated with exposure to electromagnetic fields: a questionnaire study.

PubMed

Küçer, Nermin; Pamukçu, Tuğba

2014-01-01

Abstract In the last years, it has been discussed frequently whether there are any harmful effects of electromagnetic fields on human health. Electromagnetic fields are generated by several natural and man-made sources. Part of the electromagnetic spectrum called Radiofrequency is used in communication systems such as mobile (cellular) phone and computer. The aim of our study was to explore different self-reported symptoms that may be associated with exposure to electromagnetic fields. This survey study was conducted, using a questionnaire, on 350 people aged +9 years in Turkey. The chi-square test was used for data analysis. Self-reported symptoms were headache, vertigo/dizziness, fatigue, forgetfulness, sleep disturbance-insomnia, tension-anxiety, joint and bone pain, lacrimation of the eyes, hearing loss and tinnitus. As a result of the survey, the study has shown that users of mobile phone and computer more often complained of headache, joint and bone pain, hearing loss, vertigo/dizziness, tension-anxiety symptoms according to time of daily usage (p < 0.05). In users of mobile phone and computer, women significantly (p < 0.05) complained more often of headache, vertigo/dizziness, fatigue, forgetfulness and tension-anxiety than men.

Simulation of π 0-γ separation study for proposed CMS forward electromagnetic calorimeter

DOE PAGES

Roy, Ashim; Jain, Shilpi; Banerjee, Sunanda; ...

2016-11-11

The Forward Electromagnetic Calorimeter of the CMS detector is going to be upgraded in the high luminosity running as the energy of the present Electromagnetic Calorimeter (PbWO4) will degrade in the high luminosity (luminosity 10 34 cm -2 s -1) running due to extensive radiation (hadron flux 10 13 neutrons cm, -2). Shashlik Electromagnetic Calorimeter which consists of alternate layers of 1.5 mm LYSO(Ce) crystal plates and 2.5 mm Tungsten absorbers, was a proposal for high luminosity running. One of the performance points for any electromagnetic calorimeter is the ability to separate π 0 s from true photons, since finalmore » states with photons are a clean and one of the most important final states in proton-proton collisions at the LHC. As a result, the objective of this project is to study the possibility of π 0 and γ separation in the Shashlik detector using Multivariate Analysis (MVA) technique.« less

Simulation of π 0-γ separation study for proposed CMS forward electromagnetic calorimeter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roy, Ashim; Jain, Shilpi; Banerjee, Sunanda

The Forward Electromagnetic Calorimeter of the CMS detector is going to be upgraded in the high luminosity running as the energy of the present Electromagnetic Calorimeter (PbWO4) will degrade in the high luminosity (luminosity 10 34 cm -2 s -1) running due to extensive radiation (hadron flux 10 13 neutrons cm, -2). Shashlik Electromagnetic Calorimeter which consists of alternate layers of 1.5 mm LYSO(Ce) crystal plates and 2.5 mm Tungsten absorbers, was a proposal for high luminosity running. One of the performance points for any electromagnetic calorimeter is the ability to separate π 0 s from true photons, since finalmore » states with photons are a clean and one of the most important final states in proton-proton collisions at the LHC. As a result, the objective of this project is to study the possibility of π 0 and γ separation in the Shashlik detector using Multivariate Analysis (MVA) technique.« less

A new device for improving dental implants anchorage: a histological and micro-computed tomography study in the rabbit.

PubMed

Barak, Shlomo; Neuman, Moshe; Iezzi, Giovanna; Piattelli, Adriano; Perrotti, Vittoria; Gabet, Yankel

2016-08-01

In the present study, a new healing cap that could generate a pulsed electromagnetic field (PEMF) around titanium implants to stimulate peri-implant osteogenesis was tested in the rabbit model. A total of 22 implants were inserted in the proximal tibial metaphysis of 22 rabbits. A healing cap containing the active device was inserted in half of the implants (11 test implants); an "empty" healing cap was inserted in the other ones (11 control implants). The animals were euthanized after 2 and 4 weeks, and the samples were processed for micro-computed tomography and histology. The peri-implant volume was divided into coronal (where the PEMF was the strongest) and apical regions. Most of the effects of the tested device were confined to the coronal region. Two weeks post-implantation, test implants showed a significant 56% higher trabecular bone fraction (BV/TV), associated with enhanced trabecular number (Tb.N, +37%) and connectivity density (Conn.D, +73%) as compared to the control group; at 4 weeks, the PEMF induced a 69% increase in BV/TV and 34% increase of Tb.N. There was no difference in the trabecular thickness (Tb.Th) at either time point. Furthermore, we observed a 48% higher bone-to-implant contact (BIC) in the test implants vs. controls after 2 weeks; this increase tended to remain stable until the fourth week. Mature trabecular and woven bone were observed in direct contact with the implant surface with no gaps or connective tissue at the bone-implant interface. These results indicate that the PEMF device stimulated early bone formation around dental implants resulting in higher peri-implant BIC and bone mass already after 2 weeks which suggests an acceleration of the osseointegration process by more than three times. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The therapeutic effect of a pulsed electromagnetic field on the reproductive patterns of male Wistar rats exposed to a 2.45-GHz microwave field

PubMed Central

Kumar, Sanjay; Kesari, Kavindra Kumar; Behari, Jitendra

2011-01-01

INTRODUCTION: Environmental exposure to man-made electromagnetic fields has been steadily increasing with the growing demand for electronic items that are operational at various frequencies. Testicular function is particularly susceptible to radiation emitted by electromagnetic fields. OBJECTIVES: This study aimed to examine the therapeutic effects of a pulsed electromagnetic field (100 Hz) on the reproductive systems of male Wistar rats (70 days old). METHODS: The experiments were divided into five groups: microwave sham, microwave exposure (2.45 GHz), pulsed electromagnetic field sham, pulsed electromagnetic field (100 Hz) exposure, and microwave/pulsed electromagnetic field exposure. The animals were exposed for 2 hours/day for 60 days. After exposure, the animals were sacrificed, their sperm was used for creatine and caspase assays, and their serum was used for melatonin and testosterone assays. RESULTS: The results showed significant increases in caspase and creatine kinase and significant decreases in testosterone and melatonin in the exposed groups. This finding emphasizes that reactive oxygen species (a potential inducer of cancer) are the primary cause of DNA damage. However, pulsed electromagnetic field exposure relieves the effect of microwave exposure by inducing Faraday currents. CONCLUSIONS: Electromagnetic fields are recognized as hazards that affect testicular function by generating reactive oxygen species and reduce the bioavailability of androgen to maturing spermatozoa. Thus, microwave exposure adversely affects male fertility, whereas pulsed electromagnetic field therapy is a non-invasive, simple technique that can be used as a scavenger agent to combat oxidative stress. PMID:21876981

Determination of grain-size characteristics from electromagnetic seabed mapping data: A NW Iberian shelf study

NASA Astrophysics Data System (ADS)

Baasch, Benjamin; Müller, Hendrik; von Dobeneck, Tilo; Oberle, Ferdinand K. J.

2017-05-01

The electric conductivity and magnetic susceptibility of sediments are fundamental parameters in environmental geophysics. Both can be derived from marine electromagnetic profiling, a novel, fast and non-invasive seafloor mapping technique. Here we present statistical evidence that electric conductivity and magnetic susceptibility can help to determine physical grain-size characteristics (size, sorting and mud content) of marine surficial sediments. Electromagnetic data acquired with the bottom-towed electromagnetic profiler MARUM NERIDIS III were analysed and compared with grain size data from 33 samples across the NW Iberian continental shelf. A negative correlation between mean grain size and conductivity (R=-0.79) as well as mean grain size and susceptibility (R=-0.78) was found. Simple and multiple linear regression analyses were carried out to predict mean grain size, mud content and the standard deviation of the grain-size distribution from conductivity and susceptibility. The comparison of both methods showed that multiple linear regression models predict the grain-size distribution characteristics better than the simple models. This exemplary study demonstrates that electromagnetic benthic profiling is capable to estimate mean grain size, sorting and mud content of marine surficial sediments at a very high significance level. Transfer functions can be calibrated using grains-size data from a few reference samples and extrapolated along shelf-wide survey lines. This study suggests that electromagnetic benthic profiling should play a larger role for coastal zone management, seafloor contamination and sediment provenance studies in worldwide continental shelf systems.

Hydraulic continuity and biological effects of low strength very low frequency electromagnetic waves: Case of microbial biofilm growth in water treatment.

PubMed

Gérard, Merlin; Noamen, Omri; Evelyne, Gonze; Eric, Valette; Gilles, Cauffet; Marc, Henry

2015-10-15

This study aims to elucidate the interactions between water, subjected to electromagnetic waves of very low frequency (VLF) (kHz) with low strength electromagnetic fields (3.5 mT inside the coils), and the development of microbial biofilms in this exposed water. Experimental results demonstrate that in water exposed to VLF electromagnetic waves, the biomass of biofilm is limited if hydraulic continuity is achieved between the electromagnetic generator and the biofilm media. The measured amount of the biofilm's biomass is approximately a factor two lower for exposed biofilm than the non-exposed biofilm. Measurements of electromagnetic fields in the air and simulations exhibit very low intensities of fields (<10 nT and 2 V/m) in the biofilm-exposed region at a distance of 1 m from the electromagnetic generator. Exposure to electric and magnetic fields of the quoted intensities cannot explain thermal and ionizing effects on the biofilm. A variable electrical potential with a magnitude close to 20 mV was detected in the tank in hydraulic continuity with the electromagnetic generator. The application of quantum field theory may help to explain the observed effects in this case. Copyright © 2015 Elsevier Ltd. All rights reserved.

[The IARC carcinogenicity evaluation of radio-frequency electromagnetic field: with special reference to epidemiology of mobile phone use and brain tumor risk].

PubMed

Yamaguchi, Naohito

2013-01-01

The International Agency for Research on Cancer of World Health Organization announced in May 2011 the results of evaluation of carcinogenicity of radio-frequency electromagnetic field. In the overall evaluation, the radio-frequency electromagnetic field was classified as "possibly carcinogenic to humans", on the basis of the fact that the evidence provided by epidemiological studies and animal bioassays was limited. Regarding epidemiology, the results of the Interphone Study, an international collaborative case-control study, were of special importance, together with the results of a prospective cohort study in Denmark, case-control studies in several countries, and a case-case study in Japan. The evidence obtained was considered limited, because the increased risk observed in some studies was possibly spurious, caused by selection bias or recall bias as well as residual effects of confounding factors. Further research studies, such as large-scale multinational epidemiological studies, are crucially needed to establish a sound evidence base from which a more conclusive judgment can be made for the carcinogenicity of the radio-frequency electromagnetic field.

Comments on "Radiofrequency electromagnetic fields and some cancers of unknown etiology: An ecological study".

PubMed

Mortazavi, S A R; Mortazavi, Ghazal; Mortazavi, S M J

2017-12-31

This correspondence refers to the Science of the Total Environment article by Gonzalez-Rubio et al. entitled "Radiofrequency electromagnetic fields and some cancers of unknown etiology: An ecological study". Authors of this paper have presented the findings of their preliminary epidemiological study which combined epidemiology, statistics and geographical information systems (GIS). Gonzalez-Rubio et al. have analyzed the possible link between exposure to Radiofrequency Electromagnetic Fields (RF-EMF) in the city of Albacete, Spain and the incidence of cancers such as lymphomas, and brain tumors. The shortcomings of this study are discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Vegetation Use for Resolving Electromagnetic Compatibility and Ecology Issues

NASA Astrophysics Data System (ADS)

Zvezdina, M. Yu; Shokova, Yu A.; Cherckesova, L. V.; Golovko, T. M.; Cherskaya, A. A.

2017-05-01

The wide spread of Information and Communication Technologies and the development of Internet-enabled mobile applications have aggravated electromagnetic compatibility and ecology problems. Inability to excite electromagnetic field of a desired structure and strength with traditional approaches actualizes additional actions, including providing diffraction on propagation path, to resolve these issues. Diffraction on a stand-alone obstacle along the propagation path and the one on set of obstacles near receive antenna location can be considered as the additional actions in ultrashort band. The accomplished studies have shown that one the most effective means to lower electromagnetic field strength is to shield the receive antenna with vegetation from jamming radio equipment. Moreover, vegetation resolves electromagnetic ecology issues, for the energy flux density can be lowered by about two orders of magnitude.

Magnetic Imaging: a New Tool for UK National Nuclear Security

NASA Astrophysics Data System (ADS)

Darrer, Brendan J.; Watson, Joe C.; Bartlett, Paul; Renzoni, Ferruccio

2015-01-01

Combating illicit trafficking of Special Nuclear Material may require the ability to image through electromagnetic shields. This is the case when the trafficking involves cargo containers. Thus, suitable detection techniques are required to penetrate a ferromagnetic enclosure. The present study considers techniques that employ an electromagnetic based principle of detection. It is generally assumed that a ferromagnetic metallic enclosure will effectively act as a Faraday cage to electromagnetic radiation and therefore screen any form of interrogating electromagnetic radiation from penetrating, thus denying the detection of any eventual hidden material. In contrast, we demonstrate that it is actually possible to capture magnetic images of a conductive object through a set of metallic ferromagnetic enclosures. This validates electromagnetic interrogation techniques as a potential detection tool for National Nuclear Security applications.

Magnetic Imaging: a New Tool for UK National Nuclear Security

PubMed Central

Darrer, Brendan J.; Watson, Joe C.; Bartlett, Paul; Renzoni, Ferruccio

2015-01-01

Combating illicit trafficking of Special Nuclear Material may require the ability to image through electromagnetic shields. This is the case when the trafficking involves cargo containers. Thus, suitable detection techniques are required to penetrate a ferromagnetic enclosure. The present study considers techniques that employ an electromagnetic based principle of detection. It is generally assumed that a ferromagnetic metallic enclosure will effectively act as a Faraday cage to electromagnetic radiation and therefore screen any form of interrogating electromagnetic radiation from penetrating, thus denying the detection of any eventual hidden material. In contrast, we demonstrate that it is actually possible to capture magnetic images of a conductive object through a set of metallic ferromagnetic enclosures. This validates electromagnetic interrogation techniques as a potential detection tool for National Nuclear Security applications. PMID:25608957

Electromagnetic thrusters for spacecraft prime propulsion

NASA Technical Reports Server (NTRS)

Rudolph, L. K.; King, D. Q.

1984-01-01

The benefits of electromagnetic propulsion systems for the next generation of US spacecraft are discussed. Attention is given to magnetoplasmadynamic (MPD) and arc jet thrusters, which form a subset of a larger group of electromagnetic propulsion systems including pulsed plasma thrusters, Hall accelerators, and electromagnetic launchers. Mission/system study results acquired over the last twenty years suggest that for future prime propulsion applications high-power self-field MPD thrusters and low-power arc jets have the greatest potential of all electromagnetic thruster systems. Some of the benefits they are expected to provide include major reductions in required launch mass compared to chemical propulsion systems (particularly in geostationary orbit transfer) and lower life-cycle costs (almost 50 percent less). Detailed schematic drawings are provided which describe some possible configurations for the various systems.

Magnetic imaging: a new tool for UK national nuclear security.

PubMed

Darrer, Brendan J; Watson, Joe C; Bartlett, Paul; Renzoni, Ferruccio

2015-01-22

Combating illicit trafficking of Special Nuclear Material may require the ability to image through electromagnetic shields. This is the case when the trafficking involves cargo containers. Thus, suitable detection techniques are required to penetrate a ferromagnetic enclosure. The present study considers techniques that employ an electromagnetic based principle of detection. It is generally assumed that a ferromagnetic metallic enclosure will effectively act as a Faraday cage to electromagnetic radiation and therefore screen any form of interrogating electromagnetic radiation from penetrating, thus denying the detection of any eventual hidden material. In contrast, we demonstrate that it is actually possible to capture magnetic images of a conductive object through a set of metallic ferromagnetic enclosures. This validates electromagnetic interrogation techniques as a potential detection tool for National Nuclear Security applications.

Conversion of electromagnetic energy in Z-pinch process of single planar wire arrays at 1.5 MA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liangping, Wang; Mo, Li; Juanjuan, Han

The electromagnetic energy conversion in the Z-pinch process of single planar wire arrays was studied on Qiangguang generator (1.5 MA, 100 ns). Electrical diagnostics were established to monitor the voltage of the cathode-anode gap and the load current for calculating the electromagnetic energy. Lumped-element circuit model of wire arrays was employed to analyze the electromagnetic energy conversion. Inductance as well as resistance of a wire array during the Z-pinch process was also investigated. Experimental data indicate that the electromagnetic energy is mainly converted to magnetic energy and kinetic energy and ohmic heating energy can be neglected before the final stagnation. Themore » kinetic energy can be responsible for the x-ray radiation before the peak power. After the stagnation, the electromagnetic energy coupled by the load continues increasing and the resistance of the load achieves its maximum of 0.6–1.0 Ω in about 10–20 ns.« less

Positioning and Microvibration Control by Electromagnets of an Air Spring Vibration Isolation System

NASA Technical Reports Server (NTRS)

Watanabe, Katsuhide; Cui, Weimin; Haga, Takahide; Kanemitsu, Yoichi; Yano, Kenichi

1996-01-01

Active positioning and microvibration control has been attempted by electromagnets equipped in a bellows-type, air-spring vibration isolation system. Performance tests have been carried out to study the effects. The main components of the system's isolation table were four electromagnetic actuators and controllers. The vibration isolation table was also equipped with six acceleration sensors for detecting microvibration of the table. The electromagnetic actuators were equipped with bellows-type air springs for passive support of the weight of the item placed on the table, with electromagnets for active positioning, as well as for microvibration control, and relative displacement sensors. The controller constituted a relative feedback system for positioning control and an absolute feedback system for vibration isolation control. In the performance test, a 1,490 kg load (net weight of 1,820 kg) was placed on the vibration isolation table, and both the positioning and microvibration control were carried out electromagnetically. Test results revealed that the vibration transmission was reduced by 95%.

Propagation of three-dimensional bipolar ultrashort electromagnetic pulses in an inhomogeneous array of carbon nanotubes

NASA Astrophysics Data System (ADS)

Fedorov, Eduard G.; Zhukov, Alexander V.; Bouffanais, Roland; Timashkov, Alexander P.; Malomed, Boris A.; Leblond, Hervé; Mihalache, Dumitru; Rosanov, Nikolay N.; Belonenko, Mikhail B.

2018-04-01

We study the propagation of three-dimensional (3D) bipolar ultrashort electromagnetic pulses in an inhomogeneous array of semiconductor carbon nanotubes. The heterogeneity is represented by a planar region with an increased concentration of conduction electrons. The evolution of the electromagnetic field and electron concentration in the sample are governed by the Maxwell's equations and continuity equation. In particular, nonuniformity of the electromagnetic field along the axis of the nanotubes is taken into account. We demonstrate that depending on values of the parameters of the electromagnetic pulse approaching the region with the higher electron concentration, the pulse is either reflected from the region or passes it. Specifically, our simulations demonstrate that after interacting with the higher-concentration area, the pulse can propagate steadily, without significant spreading. The possibility of such ultrashort electromagnetic pulses propagating in arrays of carbon nanotubes over distances significantly exceeding characteristic dimensions of the pulses makes it possible to consider them as 3D solitons.

Examination of electromagnetic powers with the example of a uc(Faraday) disc dynamo

NASA Astrophysics Data System (ADS)

Reich, Felix A.; Müller, Wolfgang H.

2018-03-01

This paper studies the mathematical form of electromagnetic powers and their influence on the balance of energy by using the example of a uc(Faraday) disc. First, two forms of energy (and balances thereof) are discussed. These employ different forms of powers, which can be distinguished w.r.t. their physical origins and their interpretations in context with the notions of supply and production. The stationary uc(Faraday) disc experiment is modeled following the description by Kovetz (Electromagnetic theory, Oxford University Press, Oxford, 2000). Concepts for formulating the electromagnetic field equations for the rotating disc are discussed, and the corresponding approximate analytical solutions are presented. Based on the obtained electromagnetic fields, the powers of the disc are analyzed for a stationary process. The conversion of mechanical power to heating and electromagnetic powering of an external resistor is explained. The paper concludes with the computation of the time evolution of the angular velocity for a magnetically induced breaking process of the disc.

Semiannual Status Report. [excitation of electromagnetic waves in the whistler frequency range

NASA Technical Reports Server (NTRS)

1994-01-01

During the last six months, we have continued our study of the excitation of electromagnetic waves in the whistler frequency range and the role that these waves will play in the acceleration of electrons and ions in the auroral region. A paper entitled 'Electron Beam Excitation of Upstream Waves in the Whistler Mode Frequency Range' was listed in the Journal of Geophysical Research. In this paper, we have shown that an anisotropic electron beam (or gyrating electron beam) is capable of generating both left-hand and right-hand polarized electromagnetic waves in the whistler frequency range. Since right-hand polarized electromagnetic waves can interact with background electrons and left-hand polarized waves can interact with background ions through cyclotron resonance, it is possible that these beam generated left-hand and right-hand polarized electromagnetic waves can accelerate either ions or electrons (or both), depending on the physical parameters under consideration. We are currently carrying out a comprehensive study of the electromagnetic whistler and lower hybrid like waves observed in the auroral zone using both wave and particle data. Our first task is to identify these wave modes and compare it with particle observations. Using both the DE-1 particle and wave measurements, we can positively identify those electromagnetics lower hybrid like waves as fast magnetosonic waves and the upper cutoff of these waves is the local lower hybrid frequency. From the upper cutoff of the frequency spectrum, one can infer the particle density and the result is in very good agreement with the particle data. Since these electromagnetic lower hybrid like waves can have frequencies extended down to the local ion cyclotron frequency, it practically confirms that they are not whistler waves.

Electromagnetic Showers at High Energy

ERIC Educational Resources Information Center

Loos, J. S.; Dawson, S. L.

1978-01-01

Some of the properties of electromagnetic showers observed in an experimental study are illustrated. Experimental data and results from quantum electrodynamics are discussed. Data and theory are compared using computer simulation. (BB)

Rostral Anterior Cingulate Cortex Theta Current Density and Response to Antidepressants and Placebo in Major Depression

PubMed Central

Korb, Alexander S.; Hunter, Aimee M.; Cook, Ian A.; Leuchter, Andrew F.

2009-01-01

Objective To assess whether pretreatment theta current density in the rostral anterior cingulate (rACC) and medial orbitofrontal cortex (mOFC) differentiates responders from non-responders to antidepressant medication or placebo in a double-blinded study. Methods Pretreatment EEGs were collected from 72 subjects with Major Depressive Disorder (MDD) who participated in one of three placebo-controlled trials. Subjects were randomized to receive treatment with fluoxetine, venlafaxine, or placebo. Low-resolution brain electromagnetic tomography (LORETA) was used to assess theta current density in the rACC and mOFC. Results Medication responders showed elevated rACC and mOFC theta current density compared to medication non-responders (rACC: p=0.042; mOFC: p=0.039). There was no significant difference in either brain region between placebo responders and placebo non-responders. Conclusions Theta current density in the rACC and mOFC may be useful as a biomarker for prediction of response to antidepressant medication. Significance This is the first double-blinded treatment study to examine pretreatment rACC and mOFC theta current density in relation to antidepressant response and placebo response. Results support the potential clinical utility of this approach for predicting clinical outcome to antidepressant treatments in MDD. PMID:19539524

Determining Electrical Properties Based on B1 Fields Measured in an MR Scanner Using a Multi-channel Transmit/Receive Coil: a General Approach

PubMed Central

Liu, Jiaen; Zhang, Xiaotong; Van de Moortele, Pierre-Francois; Schmitter, Sebastian

2013-01-01

Electrical Property Tomography (EPT) is a recently developed noninvasive technology to image the electrical conductivity and permittivity of biological tissues at Larmor frequency in Magnetic Resonance (MR) scanners. The absolute phase of the complex radio-frequency (RF) magnetic field (B1) is necessary for electrical property calculation. However, due to the lack of practical methods to directly measure the absolute B1 phases, current EPT techniques have been achieved with B1 phase estimation based on certain assumptions on object anatomy, coil structure and/or electromagnetic wave behavior associated with the main magnetic field, limiting EPT from a larger variety of applications. In this study, using a multi-channel transmit/receive coil, the framework of a new general approach for EPT has been introduced, which is independent on the assumptions utilized in previous studies. Using a human head model with realistic geometry, a series of computer simulations at 7T were conducted to evaluate the proposed method under different noise levels. Results showed that the proposed method can be used to reconstruct the conductivity and permittivity images with noticeable accuracy and stability. The feasibility of this approach was further evaluated in a phantom experiment at 7T. PMID:23743673

Source analysis of alpha rhythm reactivity using LORETA imaging with 64-channel EEG and individual MRI.

PubMed

Cuspineda, E R; Machado, C; Virues, T; Martínez-Montes, E; Ojeda, A; Valdés, P A; Bosch, J; Valdes, L

2009-07-01

Conventional EEG and quantitative EEG visual stimuli (close-open eyes) reactivity analysis have shown their usefulness in clinical practice; however studies at the level of EEG generators are limited. The focus of the study was visual reactivity of cortical resources in healthy subjects and in a stroke patient. The 64 channel EEG and T1 magnetic resonance imaging (MRI) studies were obtained from 32 healthy subjects and a middle cerebral artery stroke patient. Low Resolution Electromagnetic Tomography (LORETA) was used to estimate EEG sources for both close eyes (CE) vs. open eyes (OE) conditions using individual MRI. The t-test was performed between source spectra of the two conditions. Thresholds for statistically significant t values were estimated by the local false discovery rate (lfdr) method. The Z transform was used to quantify the differences in cortical reactivity between the patient and healthy subjects. Closed-open eyes alpha reactivity sources were found mainly in posterior regions (occipito-parietal zones), extended in some cases to anterior and thalamic regions. Significant cortical reactivity sources were found in frequencies different from alpha (lower t-values). Significant changes at EEG reactivity sources were evident in the damaged brain hemisphere. Reactivity changes were also found in the "healthy" hemisphere when compared with the normal population. In conclusion, our study of brain sources of EEG alpha reactivity provides information that is not evident in the usual topographic analysis.

Dynamic change in mitral regurgitant orifice area: comparison of color Doppler echocardiographic and electromagnetic flowmeter-based methods in a chronic animal model.

PubMed

Shiota, T; Jones, M; Teien, D E; Yamada, I; Passafini, A; Ge, S; Sahn, D J

1995-08-01

The aim of the present study was to investigate dynamic changes in the mitral regurgitant orifice using electromagnetic flow probes and flowmeters and the color Doppler flow convergence method. Methods for determining mitral regurgitant orifice areas have been described using flow convergence imaging with a hemispheric isovelocity surface assumption. However, the shape of flow convergence isovelocity surfaces depends on many factors that change during regurgitation. In seven sheep with surgically created mitral regurgitation, 18 hemodynamic states were studied. The aliasing distances of flow convergence were measured at 10 sequential points using two ranges of aliasing velocities (0.20 to 0.32 and 0.56 to 0.72 m/s), and instantaneous flow rates were calculated using the hemispheric assumption. Instantaneous regurgitant areas were determined from the regurgitant flow rates obtained from both electromagnetic flowmeters and flow convergence divided by the corresponding continuous wave velocities. The regurgitant orifice sizes obtained using the electromagnetic flow method usually increased to maximal size in early to midsystole and then decreased in late systole. Patterns of dynamic changes in orifice area obtained by flow convergence were not the same as those delineated by the electromagnetic flow method. Time-averaged regurgitant orifice areas obtained by flow convergence using lower aliasing velocities overestimated the areas obtained by the electromagnetic flow method ([mean +/- SD] 0.27 +/- 0.14 vs. 0.12 +/- 0.06 cm2, p < 0.001), whereas flow convergence, using higher aliasing velocities, estimated the reference areas more reliably (0.15 +/- 0.06 cm2). The electromagnetic flow method studies uniformly demonstrated dynamic change in mitral regurgitant orifice area and suggested limitations of the flow convergence method.

LORETA current source density for duration mismatch negativity and neuropsychological assessment in early schizophrenia.

PubMed

Miyanishi, Tomohiro; Sumiyoshi, Tomiki; Higuchi, Yuko; Seo, Tomonori; Suzuki, Michio

2013-01-01

Patients with schizophrenia elicit cognitive decline from the early phase of the illness. Mismatch negativity (MMN) has been shown to be associated with cognitive function. We investigated the current source density of duration mismatch negativity (dMMN), by using low-resolution brain electromagnetic tomography (LORETA), and neuropsychological performance in subjects with early schizophrenia. Data were obtained from 20 patients meeting DSM-IV criteria for schizophrenia or schizophreniform disorder, and 20 healthy control (HC) subjects. An auditory odd-ball paradigm was used to measure dMMN. Neuropsychological performance was evaluated by the brief assessment of cognition in schizophrenia Japanese version (BACS-J). Patients showed smaller dMMN amplitudes than those in the HC subjects. LORETA current density for dMMN was significantly lower in patients compared to HC subjects, especially in the temporal lobes. dMMN current density in the frontal lobe was positively correlated with working memory performance in patients. This is the first study to identify brain regions showing smaller dMMN current density in early schizophrenia. Further, poor working memory was associated with decreased dMMN current density in patients. These results are likely to help understand the neural basis for cognitive impairment of schizophrenia.

Quantitative EEG and LORETA: valuable tools in discerning FTD from AD?

PubMed

Caso, Francesca; Cursi, Marco; Magnani, Giuseppe; Fanelli, Giovanna; Falautano, Monica; Comi, Giancarlo; Leocani, Letizia; Minicucci, Fabio

2012-10-01

Drawing a clinical distinction between frontotemporal dementia (FTD) and Alzheimer's disease (AD) is tricky, particularly at the early stages of disease. This study evaluates the possibility in differentiating 39 FTD, 39 AD, and 39 controls (CTR) by means of power spectral analysis and standardized low resolution brain electromagnetic tomography (sLORETA) within delta, theta, alpha 1 and 2, beta 1, 2, and 3 frequency bands. Both analyses revealed in AD patients, relative to CTR, higher expression of diffuse delta/theta and lower central/posterior fast frequency (from alpha1 to beta2) bands. FTD patients showed diffuse increased theta power compared with CTR and lower delta relative to AD patients. Compared with FTD, AD patients showed diffuse higher theta power at spectral analysis and, at sLORETA, decreased alpha2 and beta1 values in central/temporal regions. Spectral analysis and sLORETA provided complementary information that might help characterizing different patterns of electroencephalogram (EEG) oscillatory activity in AD and FTD. Nevertheless, this differentiation was possible only at the group level because single patients could not be discerned with sufficient accuracy. Copyright © 2012 Elsevier Inc. All rights reserved.

Comparative analysis of the electroencephalogram in patients with Alzheimer's disease, diffuse axonal injury patients and healthy controls using LORETA analysis.

PubMed

Ianof, Jéssica Natuline; Fraga, Francisco José; Ferreira, Leonardo Alves; Ramos, Renato Teodoro; Demario, José Luiz Carlos; Baratho, Regina; Basile, Luís Fernando Hindi; Nitrini, Ricardo; Anghinah, Renato

2017-01-01

Alzheimer's disease (AD) is a dementia that affects a large contingent of the elderly population characterized by the presence of neurofibrillary tangles and senile plaques. Traumatic brain injury (TBI) is a non-degenerative injury caused by an external mechanical force. One of the main causes of TBI is diffuse axonal injury (DAI), promoted by acceleration-deceleration mechanisms. To understand the electroencephalographic differences in functional mechanisms between AD and DAI groups. The study included 20 subjects with AD, 19 with DAI and 17 healthy adults submitted to high resolution EEG with 128 channels. Cortical sources of EEG rhythms were estimated by exact low-resolution electromagnetic tomography (eLORETA) analysis. The eLORETA analysis showed that, in comparison to the control (CTL) group, the AD group had increased theta activity in the parietal and frontal lobes and decreased alpha 2 activity in the parietal, frontal, limbic and occipital lobes. In comparison to the CTL group, the DAI group had increased theta activity in the limbic, occipital sublobar and temporal areas. The results suggest that individuals with AD and DAI have impairment of electrical activity in areas important for memory and learning.

In vivo mapping of current density distribution in brain tissues during deep brain stimulation (DBS)

NASA Astrophysics Data System (ADS)

Sajib, Saurav Z. K.; Oh, Tong In; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2017-01-01

New methods for in vivo mapping of brain responses during deep brain stimulation (DBS) are indispensable to secure clinical applications. Assessment of current density distribution, induced by internally injected currents, may provide an alternative method for understanding the therapeutic effects of electrical stimulation. The current flow and pathway are affected by internal conductivity, and can be imaged using magnetic resonance-based conductivity imaging methods. Magnetic resonance electrical impedance tomography (MREIT) is an imaging method that can enable highly resolved mapping of electromagnetic tissue properties such as current density and conductivity of living tissues. In the current study, we experimentally imaged current density distribution of in vivo canine brains by applying MREIT to electrical stimulation. The current density maps of three canine brains were calculated from the measured magnetic flux density data. The absolute current density values of brain tissues, including gray matter, white matter, and cerebrospinal fluid were compared to assess the active regions during DBS. The resulting current density in different tissue types may provide useful information about current pathways and volume activation for adjusting surgical planning and understanding the therapeutic effects of DBS.

Monitoring dynamic reactions of red blood cells to UHF electromagnetic waves radiation using a novel micro-imaging technology.

PubMed

Ruan, Ping; Yong, Junguang; Shen, Hongtao; Zheng, Xianrong

2012-12-01

Multiple state-of-the-art techniques, such as multi-dimensional micro-imaging, fast multi-channel micro-spetrophotometry, and dynamic micro-imaging analysis, were used to dynamically investigate various effects of cell under the 900 MHz electromagnetic radiation. Cell changes in shape, size, and parameters of Hb absorption spectrum under different power density electromagnetic waves radiation were presented in this article. Experimental results indicated that the isolated human red blood cells (RBCs) do not have obviously real-time responses to the ultra-low density (15 μW/cm(2), 31 μW/cm(2)) electromagnetic wave radiation when the radiation time is not more than 30 min; however, the cells do have significant reactions in shape, size, and the like, to the electromagnetic waves radiation with power densities of 1 mW/cm(2) and 5 mW/cm(2). The data also reveal the possible influences and statistical relationships among living human cell functions, radiation amount, and exposure time with high-frequency electromagnetic waves. The results of this study may be significant on protection of human being and other living organisms against possible radiation affections of the high-frequency electromagnetic waves.

A Comparison of Antenna Measurements in a Near-Field Range and a Newly Renovated Short-Tapered Chamber

DTIC Science & Technology

2016-09-01

SUPPLEMENTARY NOTES 14. ABSTRACT This study was undertaken to quantify and compare electromagnetic device (i.e., antenna) measurements using the US Army...15. SUBJECT TERMS electromagnetic , chamber, near-field range, anechoic chamber, antenna measurement 16. SECURITY CLASSIFICATION OF: 17...undertaken to quantify and compare electromagnetic (EM) device (i.e., antenna) measurements using the US Army Research Laboratory’s (ARL’s) near-field

First Studies for the Development of Computational Tools for the Design of Liquid Metal Electromagnetic Pumps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maidana, Carlos O.; Nieminen, Juha E.

Liquid alloy systems have a high degree of thermal conductivity, far superior to ordinary nonmetallic liquids and inherent high densities and electrical conductivities. This results in the use of these materials for specific heat conducting and dissipation applications for the nuclear and space sectors. Uniquely, they can be used to conduct heat and electricity between nonmetallic and metallic surfaces. The motion of liquid metals in strong magnetic fields generally induces electric currents, which, while interacting with the magnetic field, produce electromagnetic forces. Electromagnetic pumps exploit the fact that liquid metals are conducting fluids capable of carrying currents, which is amore » source of electromagnetic fields useful for pumping and diagnostics. The coupling between the electromagnetics and thermo-fluid mechanical phenomena and the determination of its geometry and electrical configuration, gives rise to complex engineering magnetohydrodynamics problems. The development of tools to model, characterize, design, and build liquid metal thermomagnetic systems for space, nuclear, and industrial applications are of primordial importance and represent a cross-cutting technology that can provide unique design and development capabilities as well as a better understanding of the physics behind the magneto-hydrodynamics of liquid metals. Here, first studies for the development of computational tools for the design of liquid metal electromagnetic pumps are discussed.« less

First Studies for the Development of Computational Tools for the Design of Liquid Metal Electromagnetic Pumps

DOE PAGES

Maidana, Carlos O.; Nieminen, Juha E.

2017-02-01

Liquid alloy systems have a high degree of thermal conductivity, far superior to ordinary nonmetallic liquids and inherent high densities and electrical conductivities. This results in the use of these materials for specific heat conducting and dissipation applications for the nuclear and space sectors. Uniquely, they can be used to conduct heat and electricity between nonmetallic and metallic surfaces. The motion of liquid metals in strong magnetic fields generally induces electric currents, which, while interacting with the magnetic field, produce electromagnetic forces. Electromagnetic pumps exploit the fact that liquid metals are conducting fluids capable of carrying currents, which is amore » source of electromagnetic fields useful for pumping and diagnostics. The coupling between the electromagnetics and thermo-fluid mechanical phenomena and the determination of its geometry and electrical configuration, gives rise to complex engineering magnetohydrodynamics problems. The development of tools to model, characterize, design, and build liquid metal thermomagnetic systems for space, nuclear, and industrial applications are of primordial importance and represent a cross-cutting technology that can provide unique design and development capabilities as well as a better understanding of the physics behind the magneto-hydrodynamics of liquid metals. Here, first studies for the development of computational tools for the design of liquid metal electromagnetic pumps are discussed.« less

Study of a condition for the mode conversion from purely perpendicular electrostatic waves to electromagnetic waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalaee, Mohammad Javad, E-mail: mjkalaee@ut.ac.ir; Katoh, Yuto, E-mail: yuto@stpp.gp.tohoku.ac.jp

One of the mechanisms for generating electromagnetic plasma waves (Z-mode and LO-mode) is mode conversion from electrostatic waves into electromagnetic waves in inhomogeneous plasma. Herein, we study a condition required for mode conversion of electrostatic waves propagating purely perpendicular to the ambient magnetic field, by numerically solving the full dispersion relation. An approximate model is derived describing the coupling between electrostatic waves (hot plasma Bernstein mode) and Z-mode waves at the upper hybrid frequency. The model is used to study conditions required for mode conversion from electrostatic waves (electrostatic electron cyclotron harmonic waves, including Bernstein mode) into electromagnetic plasma wavesmore » (LO-mode). It is shown that for mode conversion to occur in inhomogeneous plasma, the angle between the boundary surface and the magnetic field vector should be within a specific range. The range of the angle depends on the norm of the k vector of waves at the site of mode conversion in the inhomogeneous region. The present study reveals that inhomogeneity alone is not a sufficient condition for mode conversion from electrostatic waves to electromagnetic plasma waves and that the angle between the magnetic field and the density gradient plays an important role in the conversion process.« less

Food collection and response to pheromones in an ant species exposed to electromagnetic radiation.

PubMed

Cammaerts, Marie-Claire; Rachidi, Zoheir; Bellens, François; De Doncker, Philippe

2013-09-01

We used the ant species Myrmica sabuleti as a model to study the impact of electromagnetic waves on social insects' response to their pheromones and their food collection. We quantified M. sabuleti workers' response to their trail, area marking and alarm pheromone under normal conditions. Then, we quantified the same responses while under the influence of electromagnetic waves. Under such an influence, ants followed trails for only short distances, no longer arrived at marked areas and no longer orientated themselves to a source of alarm pheromone. Also when exposed to electromagnetic waves, ants became unable to return to their nest and recruit congeners; therefore, the number of ants collecting food increases only slightly and slowly. After 180 h of exposure, their colonies deteriorated. Electromagnetic radiation obviously affects social insects' behavior and physiology.

Electromagnetic inhibition of high frequency thermal bonding machine

NASA Astrophysics Data System (ADS)

He, Hong; Zhang, Qing-qing; Li, Hang; Zhang, Da-jian; Hou, Ming-feng; Zhu, Xian-wei

2011-12-01

The traditional high frequency thermal bonding machine had serious radiation problems at dominant frequency, two times frequency and three times frequency. Combining with its working principle, the problems of electromagnetic compatibility were studied, three following measures were adopted: 1.At the head part of the high frequency thermal bonding machine, resonant circuit attenuator was designed. The notch groove and reaction field can make the radiation being undermined or absorbed; 2.The electromagnetic radiation shielding was made for the high frequency copper power feeder; 3.Redesigned the high-frequency oscillator circuit to reduce the output of harmonic oscillator. The test results showed that these measures can make the output according with the national standard of electromagnetic compatibility (GB4824-2004-2A), the problems of electromagnetic radiation leakage can be solved, and good social, environmental and economic benefits would be brought.

Electromagnetic immunity of infusion pumps to GSM mobile phones: a systematic review.

PubMed

Calcagnini, Giovanni; Censi, Federica; Triventi, Michele; Mattei, Eugenio; Bartolini, Pietro

2007-01-01

Electromagnetic interference with life-sustaining medical care devices has been reported by various groups. Previous studies have demonstrated that volumetric and syringe pumps are susceptible to false alarm buzzing and blocking, when exposed to various electromagnetic sources. The risk of electromagnetic interference depends on several factors such as the phone-emitted power, distance and carrier frequency, phone model and antenna type. The main recommendations and the relevant harmonized standard are also reported and discussed. >From the data available in literature emerges that, for distances lower than 1 m there is a non negligible risk of electromagnetic interferences, although significant differences exists in the reported minimum distances. Interference effects clinically relevant for the patients are rare. No permanent damage to the pumps has been ever reported, although in several cases intervention of personnel is required to resume normal operation.

An inhomogeneous thermal block model of man for the electromagnetic environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, I.; Gandhi, O.P.

An inhomogeneous four layer block thermal model of a human body, composed of 476 electromagnetic-sensitive cubical cells has been developed to study the effects of electromagnetic radiation. Varying tissue properties defined by thermal conductivity, specific heat, blood flow rate and metabolic heat production are accounted for by equations. Peripheral cell temperature is weight-averaged for total cell volume and is thereby higher than actual skin temperature. During electromagnetic field exposure, additional factors considered are increased blood flow rate caused by vasodilation and sweat-induced heat loss. Hot spots have been located in the model and numerical results are presented. Subjected to planemore » wave iradiation, the model's sweating and insensible perspiration cease and all temperatures converge. Testing during electromagnetic hyperthemia shows all temperature body parts to increase approximately at the same rate.« less

Particle simulation of electromagnetic emissions from electrostatic instability driven by an electron ring beam on the density gradient

NASA Astrophysics Data System (ADS)

Horký, Miroslav; Omura, Yoshiharu; Santolík, Ondřej

2018-04-01

This paper presents the wave mode conversion between electrostatic and electromagnetic waves on the plasma density gradient. We use 2-D electromagnetic code KEMPO2 implemented with the generation of density gradient to simulate such a conversion process. In the dense region, we use ring beam instability to generate electron Bernstein waves and we study the temporal evolution of wave spectra, velocity distributions, Poynting flux, and electric and magnetic energies to observe the wave mode conversion. Such a conversion process can be a source of electromagnetic emissions which are routinely measured by spacecraft on the plasmapause density gradient.

Dynamic viscoelasticity measurement under alternative torque using electromagnetically spinning method with quadruple electromagnets.

PubMed

Matsuura, Yusuke; Hirano, Taichi; Sakai, Keiji

2017-07-01

In this study, we developed a novel type of rheological measurement system. Here, a spherical probe is driven to rotate periodically by applying torques using quadruple electromagnets in a noncontact manner. Moreover, this system is an enhancement of our electromagnetically spinning (EMS) viscometer, which is widely used for measuring rheological flow curves in various industrial fields. The quadruple EMS method provides the frequency spectrum of viscoelasticity, in addition to shear viscosity, in a steady flow by switching the operation modes of the driving torque. We show the results obtained for Newtonian fluids and viscoelastic materials and demonstrate the validity of the system.

Emergent spin electromagnetism induced by magnetization textures in the presence of spin-orbit interaction (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatara, Gen, E-mail: gen.tatara@riken.jp; Nakabayashi, Noriyuki; Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 Japan

2014-05-07

Emergent electromagnetic field which couples to electron's spin in ferromagnetic metals is theoretically studied. Rashba spin-orbit interaction induces spin electromagnetic field which is in the linear order in gradient of magnetization texture. The Rashba-induced effective electric and magnetic fields satisfy in the absence of spin relaxation the Maxwell's equations as in the charge-based electromagnetism. When spin relaxation is taken into account besides spin dynamics, a monopole current emerges generating spin motive force via the Faraday's induction law. The monopole is expected to play an important role in spin-charge conversion and in the integration of spintronics into electronics.

Relating Engineering Technology Students' Experiences in Electromagnetics with Performance in Communications Coursework: A Mixed-Methods Study

ERIC Educational Resources Information Center

Richards, Grant P.

2009-01-01

This study presents the results of a multi-year mixed-methods study of students' performance (n = 94) and experiences (n = 28) with electromagnetics in an elective Electrical and Computer Engineering Technology RF communications course. Data sources used in this study include academic transcripts, course exams, interviews, a learning styles…

The impact of electromagnetic radiation of different parameters on platelet oxygen metabolism - in vitro studies.

PubMed

Lewicka, Małgorzata; Henrykowska, Gabriela A; Pacholski, Krzysztof; Szczęsny, Artur; Dziedziczak-Buczyńska, Maria; Buczyński, Andrzej

2015-01-01

Electromagnetic radiation emitted by a variety of devices, e.g. cell phones, computers and microwaves, interacts with the human body in many ways. Research studies carried out in the last few decades have not yet resolved the issue of the effect of this factor on the human body and many questions are left without an unequivocal answer. Various biological and health-related effects have not been fully recognized. Thus further studies in this area are justified. A comparison of changes within catalase enzymatic activity and malondialdehyde concentration arising under the influence of the electromagnetic radiation emitted by car electronics, equipment used in physiotherapy and LCD monitors. The suspension of human blood platelets at a concentration of 1 × 109/0.001 dm 3, obtained from whole blood by manual apheresis, was the study material. Blood platelets were exposed to an electromagnetic field for 30 min in a laboratory stand designed for the reconstruction of the electromagnetic radiation generated by car electronics, physiotherapy equipment and LCD monitors. The changes in catalase activity and malondialdehyde concentration were investigated after the exposure and compared to the control values (unexposed material). An increase in catalase activity and malondialdehyde concentration was observed after 30 min exposure of platelets to EMF regardless of the radiation source. The most significant changes determining the degree of oxidative stress were observed after exposure to the EMF generated by car electronics. The low frequency electromagnetic fields generated by car electronics, physiotherapy equipment and LCD monitors may be a cause of oxidative stress in the human body and may lead to free radical diseases.

INTRODUCTION Introduction to the conference proceeding of the Workshop on Electromagnetic Inverse ProblemsThe University of Manchester, UK, 15-18 June, 2009

NASA Astrophysics Data System (ADS)

Dorn, Oliver; Lionheart, Bill

2010-11-01

This proceeding combines selected contributions from participants of the Workshop on Electromagnetic Inverse Problems which was hosted by the University of Manchester in June 2009. The workshop was organized by the two guest editors of this conference proceeding and ran in parallel to the 10th International Conference on Electrical Impedance Tomography, which was guided by Bill Lionheart, Richard Bayford, and Eung Je Woo. Both events shared plenary talks and several selected sessions. One reason for combining these two events was the goal of bringing together scientists from various related disciplines who normally might not attend the same conferences, and to enhance discussions between these different groups. So, for example, one day of the workshop was dedicated to the broader area of geophysical inverse problems (including inverse problems in petroleum engineering), where participants from the EIT community and from the medical imaging community were also encouraged to participate, with great success. Other sessions concentrated on microwave medical imaging, on inverse scattering, or on eddy current imaging, with active feedback also from geophysically oriented scientists. Furthermore, several talks addressed such diverse topics as optical tomography, photoacoustic tomography, time reversal, or electrosensing fish. As a result of the workshop, speakers were invited to contribute extended papers to this conference proceeding. All submissions were thoroughly reviewed and, after a thoughtful revision by the authors, combined in this proceeding. The resulting set of six papers presenting the work of in total 22 authors from 5 different countries provides a very interesting overview of several of the themes which were represented at the workshop. These can be divided into two important categories, namely (i) modelling and (ii) data inversion. The first three papers of this selection, as outlined below, focus more on modelling aspects, being an essential component of any successful inversion, whereas the other three papers discuss novel inversion techniques for specific applications. In the first contribution, with the title A Novel Simplified Mathematical Model for Antennas used in Medical Imaging Applications, the authors M J Fernando, M Elsdon, K Busawon and D Smith discuss a new technique for modelling the current across a monopole antenna from which the radiation fields of the antenna can be calculated very efficiently in specific medical imaging applications. This new technique is then tested on two examples, a quarter wavelength and a three quarter wavelength monopole antenna. The next contribution, with the title An investigation into the use of a mixture model for simulating the electrical properties of soil with varying effective saturation levels for sub-soil imaging using ECT by R R Hayes, P A Newill, F J W Podd, T A York, B D Grieve and O Dorn, considers the development of a new visualization tool for monitoring soil moisture content surrounding certain seed breeder plants. An electrical capacitance tomography technique is employed for verifying how efficiently each plant utilises the water and nutrients available in the surrounding soil. The goal of this study is to help in developing and identifying new drought tolerant food crops. In the third contribution Combination of Maximin and Kriging Prediction Methods for Eddy-Current Testing Database Generation by S Bilicz, M Lambert, E Vazquez and S Gyimóthy, a novel database generation technique is proposed for its use in solving inverse eddy-current testing problems. For avoiding expensive repeated forward simulations during the creation of this database, a kriging interpolation technique is employed for filling uniformly the data output space with sample points. Mathematically this is achieved by using a maximin formalism. The paper 2.5D inversion of CSEM data in a vertically anisotropic earth by C Ramananjaona and L MacGregor considers controlled-source electromagnetic techniques for imaging the earth in a marine environment. It focuses in particular on taking into account anisotropy effects in the inversion. Results of this technique are demonstrated from simulated and from real field data. Furthermore, in the contribution Multiple level-sets for elliptic Cauchy problems in three-dimensional domains by A Leitão and M Marques Alves the authors consider a TV-H1regularization technique for multiple level-set inversion of elliptic Cauchy problems. Generalized minimizers are defined and convergence and stability results are provided for this method, in addition to several numerical experiments. Finally, in the paper Development of in-vivo fluorescence imaging with the matrix-free method, the authors A Zacharopoulos, A Garofalakis, J Ripoll and S Arridge address a recently developed non-contact fluorescence molecular tomography technique where the use of non-contact acquisition systems poses new challenges on computational efficiency during data processing. The matrix-free method is designed to reduce computational cost and memory requirements during the inversion. Reconstructions from a simulated mouse phantom are provided for demonstrating the performance of the proposed technique in realistic scenarios. We hope that this selection of strong and thought-provoking papers will help stimulating further cross-disciplinary research in the spirit of the workshop. We thank all authors for providing us with this excellent set of high-quality contributions. We also thank EPSRC for having provided funding for the workshop under grant EP/G065047/1. Oliver Dorn, Bill Lionheart School of Mathematics, University of Manchester, Alan Turing Building, Oxford Rd Manchester, M13 9PL, UK E-mail: oliver.dorn@manchester.ac.uk, bill.lionheart@manchester.ac.uk Guest Editors

Idiopathic environmental intolerance attributed to electromagnetic fields: a content analysis of British newspaper reports.

PubMed

Eldridge-Thomas, Buffy; Rubin, G James

2013-01-01

Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) is a controversial condition in which people describe symptoms following exposure to electromagnetic fields from everyday electrical devices. However, double-blind experiments have found no convincing evidence that electromagnetic fields cause these symptoms. In this study, we assessed whether recent newspaper reporting in the UK reflected this scientific evidence. We searched a database of newspaper articles to identify all those that contained IEI-EMF related keywords and selected a random sample of 60 for content analysis. For our primary outcomes, we assessed how many articles mainly or wholly presented an electromagnetic cause for IEI-EMF and how many discussed unproven treatments for the condition such as strategies intended to reduce exposure to electromagnetic fields or the use of complementary and alternative therapies. We also assessed whether the type of information source used by a newspaper article (e.g. scientist, person with IEI-EMF, politician) or the type of newspaper (broadsheet, tabloid, local or regional) was associated with either outcome. Of the 60 articles, 43 (71.7%) presented a mainly electromagnetic cause, compared to 13 (21.7%) which presented mainly non-electromagnetic causes and 4 (6.7%) which did not discuss a cause. 29 (48.3%) did not mention any potential treatment, while 24 (40.0%) mentioned eletromagnetic field related strategies and 12 (20.0%) mentioned complementary or alternative therapies. Articles which quoted someone with IEI-EMF were significantly more likely to report an electromagnetic cause and to present unproven treatments. Those which used a scientist as a source were more likely to present a non-electromagnetic cause for the condition. The widespread poor reporting we identified is disappointing and has the potential for to encourage more people to misattribute their symptoms to electromagnetic fields. Scientists should remain engaged with the media to counteract this effect.

Health Effects of Electromagnetic Fields: A Review of Literature.

ERIC Educational Resources Information Center

White, George L.; And Others

1995-01-01

Current evidence suggests that the effects of electromagnetic fields (EMF) disturb cell homeostasis at very low intensities by influencing discrete intracellular magnetic fields. The article reviews current research about the health effects of EMF, examining historical implications, childhood studies, adult studies, and popular press reports, and…

NUMERICAL STUDY OF ELECTROMAGNETIC WAVES GENERATED BY A PROTOTYPE DIELECTRIC LOGGING TOOL

EPA Science Inventory

To understand the electromagnetic waves generated by a prototype dielectric logging tool, a
numerical study was conducted using both the finite-difference, time-domain method and a frequency- wavenumber method. When the propagation velocity in the borehole was greater than th...

Parametric study of electromagnetic waves propagating in absorbing curved S ducts

NASA Technical Reports Server (NTRS)

Baumeister, Kenneth J.

1989-01-01

A finite-element Galerkin formulation has been developed to study attenuation of transverse magnetic (TM) waves propagating in two-dimensional S-curved ducts with absorbing walls. In the frequency range where the duct diameter and electromagnetic wave length are nearly equal, the effect of duct length, curvature (duct offset), and absorber wall thickness was examined. For a given offset in the curved duct, the length of the S-duct was found to significantly affect both the absorptive and reflective characteristics of the duct. For a straight and a curved duct with perfect electric conductor terminations, power attenuation contours were examined to determine electromagnetic wall properties associated with maximum input signal absorption. Offset of the S-duct was found to significantly affect the value of the wall permittivity associated with the optimal attenuation of the incident electromagnetic wave.

Novel methodology to characterize electromagnetic exposure of the brain

NASA Astrophysics Data System (ADS)

Crespo-Valero, Pedro; Christopoulou, Maria; Zefferer, Marcel; Christ, Andreas; Achermann, Peter; Nikita, Konstantina S.; Kuster, Niels

2011-01-01

Due to the greatly non-uniform field distribution induced in brain tissues by radio frequency electromagnetic sources, the exposure of anatomical and functional regions of the brain may be a key issue in interpreting laboratory findings and epidemiological studies concerning endpoints related to the central nervous system. This paper introduces the Talairach atlas in characterization of the electromagnetic exposure of the brain. A hierarchical labeling scheme is mapped onto high-resolution human models. This procedure is fully automatic and allows identification of over a thousand different sites all over the brain. The electromagnetic absorption can then be extracted and interpreted in every region or combination of regions in the brain, depending on the characterization goals. The application examples show how this methodology enhances the dosimetry assessment of the brain based on results obtained by either finite difference time domain simulations or measurements delivered by test compliance dosimetry systems. Applications include, among others, the detailed dosimetric analysis of the exposure of the brain during cell phone use, improved design of exposure setups for human studies or medical diagnostic and therapeutic devices using electromagnetic fields or ultrasound.

Complementary Electromagnetic Non-Destructive Evaluation

NASA Astrophysics Data System (ADS)

Tian, Gui Yun; Wilson, John; Morozov, Maxim

2011-06-01

The use of non-destructive evaluation (NDE) for defect detection and failure prediction in structures and specimens is widespread in energy industries, aimed at ageing power plants and pipelines, material degradation, fatigue and radiation damage, etc. At present there are no suitable electromagnetic NDE methods for the measurement and characterization of material degradation, in irradiated samples in particular, which is very important and timely for the nuclear power industry in the UK. This paper reports recent developments in the field of electromagnetic (EM) NDE at Newcastle University, including pulsed eddy current (PEC), pulsed magnetic flux leakage (PMFL), magnetic Barkhausen emission (MBE) and magneto-acoustic emission (MAE). As different EM methods have different strengths, an integrative EM framework is introduced. Case studies through the second round robin tests organized by the Universal Network for Magnetic Non-Destructive Evaluation (UNMNDE), representing eighteen leading research groups worldwide in the area of electromagnetic NDE, are reported. Twelve samples with different ageing times and rolling reduction ratios were tested using different magnetic methods among the UNMNDE members. Based on the studies, the complementary characteristics of electromagnetic techniques for NDE are discussed.

A Challenging Issue in the Etiology of Speech Problems: The Effect of Maternal Exposure to Electromagnetic Fields on Speech Problems in the Offspring

PubMed Central

Zarei, S.; Mortazavi, S. M. J.; Mehdizadeh, A. R.; Jalalipour, M.; Borzou, S.; Taeb, S.; Haghani, M.; Mortazavi, S. A. R.; Shojaei-fard, M. B.; Nematollahi, S.; Alighanbari, N.; Jarideh, S.

2015-01-01

Background Nowadays, mothers are continuously exposed to different sources of electromagnetic fields before and even during pregnancy.  It has recently been shown that exposure to mobile phone radiation during pregnancy may lead to adverse effects on the brain development in offspring and cause hyperactivity. Researchers have shown that behavioral problems in laboratory animals which have a similar appearance to ADHD are caused by intrauterine exposure to mobile phones. Objective The purpose of this study was to investigate whether the maternal exposure to different sources of electromagnetic fields affect on the rate and severity of speech problems in their offspring. Methods In this study, mothers of 35 healthy 3-5 year old children (control group) and 77 children and diagnosed with speech problems who had been referred to a speech treatment center in Shiraz, Iran were interviewed. These mothers were asked whether they had exposure to different sources of electromagnetic fields such as mobile phones, mobile base stations, Wi-Fi, cordless phones, laptops and power lines. Results We found a significant association between either the call time (P=0.002) or history of mobile phone use (months used) and speech problems in the offspring (P=0.003). However, other exposures had no effect on the occurrence of speech problems. To the best of our knowledge, this is the first study to investigate a possible association between maternal exposure to electromagnetic field and speech problems in the offspring. Although a major limitation in our study is the relatively small sample size, this study indicates that the maternal exposure to common sources of electromagnetic fields such as mobile phones can affect the occurrence of speech problems in the offspring. PMID:26396971

A Challenging Issue in the Etiology of Speech Problems: The Effect of Maternal Exposure to Electromagnetic Fields on Speech Problems in the Offspring.

PubMed

Zarei, S; Mortazavi, S M J; Mehdizadeh, A R; Jalalipour, M; Borzou, S; Taeb, S; Haghani, M; Mortazavi, S A R; Shojaei-Fard, M B; Nematollahi, S; Alighanbari, N; Jarideh, S

2015-09-01

Nowadays, mothers are continuously exposed to different sources of electromagnetic fields before and even during pregnancy.  It has recently been shown that exposure to mobile phone radiation during pregnancy may lead to adverse effects on the brain development in offspring and cause hyperactivity. Researchers have shown that behavioral problems in laboratory animals which have a similar appearance to ADHD are caused by intrauterine exposure to mobile phones. The purpose of this study was to investigate whether the maternal exposure to different sources of electromagnetic fields affect on the rate and severity of speech problems in their offspring. In this study, mothers of 35 healthy 3-5 year old children (control group) and 77 children and diagnosed with speech problems who had been referred to a speech treatment center in Shiraz, Iran were interviewed. These mothers were asked whether they had exposure to different sources of electromagnetic fields such as mobile phones, mobile base stations, Wi-Fi, cordless phones, laptops and power lines. We found a significant association between either the call time (P=0.002) or history of mobile phone use (months used) and speech problems in the offspring (P=0.003). However, other exposures had no effect on the occurrence of speech problems. To the best of our knowledge, this is the first study to investigate a possible association between maternal exposure to electromagnetic field and speech problems in the offspring. Although a major limitation in our study is the relatively small sample size, this study indicates that the maternal exposure to common sources of electromagnetic fields such as mobile phones can affect the occurrence of speech problems in the offspring.

Effects of a pulsed electromagnetic therapy on multiple sclerosis fatigue and quality of life: a double-blind, placebo controlled trial.

PubMed

Lappin, Martha S; Lawrie, Fraser Wilson; Richards, Todd L; Kramer, Eric D

2003-01-01

There is a growing literature on the biological and clinical effects of pulsed electromagnetic fields. Some studies suggest that electromagnetic therapies may be useful in the treatment of chronic illnesses. This study is a follow-up to a placebo controlled pilot study in which multiple sclerosis (MS) patients exposed to weak, extremely low frequency pulsed electromagnetic fields showed significant improvements on a composite symptom measure. To evaluate the effects of a pulsed electromagnetic therapy on MS related fatigue, spasticity, bladder control, and overall quality of life. A multi-site, double-blind, placebo controlled, crossover trial. Each subject received 4 weeks of the active and placebo treatments separated by a 2-week washout period. The University of Washington Medical Center in Seattle Wash, the Neurology Center of Fairfax in Fairfax, Va, and the headquarters of the Multiple Sclerosis Association of America in Cherry Hill, NJ. 117 patients with clinically definite MS. Daily exposure to a small, portable pulsing electromagnetic field generator. The MS Quality of Life Inventory (MSQLI) was used to assess changes in fatigue, bladder control, spasticity, and a quality of life composite. Paired t-tests were used to assess treatment differences in the 117 subjects (81% of the initial sample) who completed both treatment sessions. Improvements in fatigue and overall quality of life were significantly greater on the active device. There were no treatment effects for bladder control and a disability composite, and mixed results for spasticity. Evidence from this randomized, double-bind, placebo controlled trial is consistent with results from smaller studies suggesting that exposure to pulsing, weak electromagnetic fields can alleviate symptoms of MS. The clinical effects were small, however, and need to be replicated. Additional research is also needed to examine the possibility that ambulatory patients and patients taking interferons for their MS may be most responsive to this kind of treatment.

[The electroporation effects of high power pulse microwave and electromagnetic pulse irradiation on the membranes of cardiomyocyte cells and the mechanism therein involved].

PubMed

Deng, Hua; Wang, Dewen; Peng, Ruiyun; Wang, Shuiming; Chen, Jiankui; Zhang, Sa; Dong, Bo; Wang, Xiaomin

2005-08-01

Though there is ongoing public concern on potential hazards and risk of electromagnetic radiation, the bioeffects mechanism of electromagnetic fields remains obscure. Heart is one of the organs susceptive to electromagnetic fields (EMF). This study was designed to assess the influence of high power pulse microwave and electromagnetic pulse irradiation on cardiomyocytes, to explore the critical mechanism of electromagnetic fields, and to explain the regular course of injury caused by exposure to pulse EMF. Cultured cardiomyocytes were irradiated by high power pulse microwave and electromagnetic pulse first, then a series of apparatus including atom force microscope, laser scanning confocal microscope and flow cytometer were used to examine the changes of cell membrane conformation, structure and function. After irradiation, the cardiomyocytes pulsated slower or stop, the cells conformation was abnormal, the cells viability declined, and the percentage of apoptosis and necrosis increased significantly (P< 0.01). The cell membrane had pores unequal in size, and lost its penetration character. The concentration of Na+, K+, Ca2+, Cl-, Mg2+, Ca2+ and P3+ in cell culture medium increased significantly (P< 0.01). and the concentration of Ca2+ in cells ([Ca2+]i) decreased significantly (P<0.01). The results indicated that cardiomyocytes are susceptible to non-ionizing radiation. Pulse electromagnetic field can induce cardiomyocytes electroporation, and can do great damage to cells conformation, structure and function. Electroporation is one of the most critical mechanisms to explain the athermal effects of electromagnetic radiation.

Study on electromagnetic radiation and mechanical characteristics of coal during an SHPB test

NASA Astrophysics Data System (ADS)

Chengwu, Li; Qifei, Wang; Pingyang, Lyu

2016-06-01

Dynamic loads provided by a Split Hopkinson pressure bar are applied in the impact failure experiment on coal with an impact velocity of 4.174-17.652 m s-1. The mechanical property characteristics of coal and an electromagnetic radiation signal can be detected and measured during the experiment. The variation of coal stress, strain, incident energy, dissipated energy and other mechanical parameters are analyzed by the unidimensional stress wave theory. It suggests that with an increase of the impact velocity, the mechanical parameters and electromagnetic radiation increased significantly and the dissipated energy of the coal sample has a high discrete growing trend during the failure process of coal impact. Combined with the received energy of the electromagnetic radiation signal, the relationship between these mechanical parameters and electromagnetic radiation during the failure process of coal burst could be analyzed by the grey correlation model. The results show that the descending order of the gray correlation degree between the mechanical characteristics and electromagnetic radiation energy are impact velocity, maximum stress, the average stress, incident energy, the average strain, maximum strain, the average strain rate and dissipation energy. Due to the correlation degree, the impact velocity and incident energy are relatively large, and the main factor affecting the electromagnetic radiation energy of coal is the energy magnitude. While the relationship between extreme stress and the radiation energy change trend is closed, the stress state of coal has a greater impact on electromagnetic radiation than the strain and destruction which can deepen the research of the coal-rock dynamic disaster electromagnetic monitoring technique.

Purely electromagnetic spacetimes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, B. V.

The Rainich's program of describing metrics induced by pure electromagnetic fields is implemented in a simpler way by using the Ernst formalism and increasing the symmetry of spacetime. Stationary metrics possessing one, two or three Killing vectors are studied and classified. Three branches of solutions exist. Electromagnetically induced mass terms appear in two of them, including a class of solutions in harmonic functions. The static subcase is discussed too. Relations to other well-known electrovacuum metrics are elucidated.

[Organization of monitoring of electromagnetic radiation in the urban environment].

PubMed

Savel'ev, S I; Dvoeglazova, S V; Koz'min, V A; Kochkin, D E; Begishev, M R

2008-01-01

The authors describe new current approaches to monitoring the environment, including the sources of electromagnetic radiation and noise. Electronic maps of the area under study are shown to be made, by constructing the isolines or distributing the actual levels of controlled factors. These current approaches to electromagnetic and acoustic monitoring make it possible to automate a process of measurements, to analyze the established situation, and to simplify the risk controlling methodology.

Fast-Turnoff Transient Electromagnetic (TEM) Field Study at the Mars Analog Site of Rio Tinto, Spain

NASA Astrophysics Data System (ADS)

Jernsletten, J. A.

2005-03-01

This report describes a Fast-Turnoff Transient Electromagnetic (TEM) study at the Peña de Hierro ("Berg of Iron") field area of the Mars Analog Research and Technology Experiment (MARTE), near the towns Rio Tinto and Nerva, Andalucia region, Spain.

Students' Development of Representational Competence through the Sense of Touch

ERIC Educational Resources Information Center

Magana, Alejandra J.; Balachandran, Sadhana

2017-01-01

Electromagnetism is an umbrella encapsulating several different concepts like electric current, electric fields and forces, and magnetic fields and forces, among other topics. However, a number of studies in the past have highlighted the poor conceptual understanding of electromagnetism concepts by students even after instruction. This study aims…

Effect of electromagnetic field emitted by cellular phones on fetal heart rate patterns.

PubMed

Celik, Onder; Hascalik, Seyma

2004-01-15

The study was planned to determine the effects of electromagnetic fields produced by cellular phones on baseline fetal heart rate, acceleration and deceleration. Forty pregnant women undergoing non-stress test were admitted to the study. Non-stress test was obtained while the subjects were holding the CP on stand by mode and on dialing mode, each for 5 min. Similar recordings were taken while there were no phones around for 10 min. Electromagnetic fields produced by cellular phones do not cause any demonstrable affect in fetal heart rate, acceleration and deceleration.

A theoretical study of hot plasma spheroids in the presence of low-frequency electromagnetic waves

NASA Astrophysics Data System (ADS)

Ahmadizadeh, Y.; Jazi, B.; Barjesteh, S.

2016-07-01

While taking into account thermal motion of electrons, scattering of electromagnetic waves with low frequency from hot plasma spheroids is investigated. In this theoretical research, ions are heavy to respond to electromagnetic fluctuations. The solution of scalar wave equation in spheroidal coordinates for electric potential inside the plasma spheroids are obtained. The variations of resonance frequencies vs. Debye length are studied and consistency between the obtained results in this paper and the results for the well-known plasma objects such as plasma column and spherical plasma have been proved.

Fast, automatic, and accurate catheter reconstruction in HDR brachytherapy using an electromagnetic 3D tracking system.

PubMed

Poulin, Eric; Racine, Emmanuel; Binnekamp, Dirk; Beaulieu, Luc

2015-03-01

In high dose rate brachytherapy (HDR-B), current catheter reconstruction protocols are relatively slow and error prone. The purpose of this technical note is to evaluate the accuracy and the robustness of an electromagnetic (EM) tracking system for automated and real-time catheter reconstruction. For this preclinical study, a total of ten catheters were inserted in gelatin phantoms with different trajectories. Catheters were reconstructed using a 18G biopsy needle, used as an EM stylet and equipped with a miniaturized sensor, and the second generation Aurora(®) Planar Field Generator from Northern Digital Inc. The Aurora EM system provides position and orientation value with precisions of 0.7 mm and 0.2°, respectively. Phantoms were also scanned using a μCT (GE Healthcare) and Philips Big Bore clinical computed tomography (CT) system with a spatial resolution of 89 μm and 2 mm, respectively. Reconstructions using the EM stylet were compared to μCT and CT. To assess the robustness of the EM reconstruction, five catheters were reconstructed twice and compared. Reconstruction time for one catheter was 10 s, leading to a total reconstruction time inferior to 3 min for a typical 17-catheter implant. When compared to the μCT, the mean EM tip identification error was 0.69 ± 0.29 mm while the CT error was 1.08 ± 0.67 mm. The mean 3D distance error was found to be 0.66 ± 0.33 mm and 1.08 ± 0.72 mm for the EM and CT, respectively. EM 3D catheter trajectories were found to be more accurate. A maximum difference of less than 0.6 mm was found between successive EM reconstructions. The EM reconstruction was found to be more accurate and precise than the conventional methods used for catheter reconstruction in HDR-B. This approach can be applied to any type of catheters and applicators.

Borehole temperature variability at Hoher Sonnblick, Austria

NASA Astrophysics Data System (ADS)

Heinrich, Georg; Schöner, Wolfgang; Prinz, Rainer; Pfeiler, Stefan; Reisenhofer, Stefan; Riedl, Claudia

2016-04-01

The overarching aim of the project 'Atmosphere - permafrost relationship in the Austrian Alps - atmospheric extreme events and their relevance for the mean state of the active layer (ATMOperm)' is to improve the understanding of the impacts of atmospheric extreme events on the thermal state of the active layer using a combined measurement and modeling approach as the basis for a long-term monitoring strategy. For this purpose, the Sonnblick Observatory at the summit of Hoher Sonnblick (3106 m.a.s.l) is particularly well-suited due to its comprehensive long-term atmospheric and permafrost monitoring network (i.a. three 20 m deep boreholes since 2007). In ATMOperm, a robust and accurate permanent monitoring of active layer thickness at Hoher Sonnblick will be set up using innovative monitoring approaches by automated electrical resistivity tomography (ERT). The ERT monitoring is further supplemented by additional geophysical measurements such as ground penetrating radar, refraction seismic, electromagnetic induction and transient electromagnetics in order to optimally complement the gained ERT information. On the other hand, atmospheric energy fluxes over permafrost ground and their impact on the thermal state of permafrost and active layer thickness with a particular focus on atmospheric extreme events will be investigated based on physically-based permafrost modeling. For model evaluation, the borehole temperature records will play a key role and, therefore, an in-depth quality control of the borehole temperatures is an important prerequisite. In this study we will show preliminary results regarding the borehole temperature variability at Hoher Sonnblick with focus on the active layer. The borehole temperatures will be related to specific atmospheric conditions using the rich data set of atmospheric measurements of the site in order to detect potential errors in the borehole temperature measurements. Furthermore, we will evaluate the potential of filling gaps in the time series by cross checking all available information of the three boreholes. Furthermore, the already available ERT profiles will serve as additional information source improving the quality of the measured borehole temperatures.

Effects of cell phone radiofrequency signal exposure on brain glucose metabolism.

PubMed

Volkow, Nora D; Tomasi, Dardo; Wang, Gene-Jack; Vaska, Paul; Fowler, Joanna S; Telang, Frank; Alexoff, Dave; Logan, Jean; Wong, Christopher

2011-02-23

The dramatic increase in use of cellular telephones has generated concern about possible negative effects of radiofrequency signals delivered to the brain. However, whether acute cell phone exposure affects the human brain is unclear. To evaluate if acute cell phone exposure affects brain glucose metabolism, a marker of brain activity. Randomized crossover study conducted between January 1 and December 31, 2009, at a single US laboratory among 47 healthy participants recruited from the community. Cell phones were placed on the left and right ears and positron emission tomography with ((18)F)fluorodeoxyglucose injection was used to measure brain glucose metabolism twice, once with the right cell phone activated (sound muted) for 50 minutes ("on" condition) and once with both cell phones deactivated ("off" condition). Statistical parametric mapping was used to compare metabolism between on and off conditions using paired t tests, and Pearson linear correlations were used to verify the association of metabolism and estimated amplitude of radiofrequency-modulated electromagnetic waves emitted by the cell phone. Clusters with at least 1000 voxels (volume >8 cm(3)) and P < .05 (corrected for multiple comparisons) were considered significant. Brain glucose metabolism computed as absolute metabolism (μmol/100 g per minute) and as normalized metabolism (region/whole brain). Whole-brain metabolism did not differ between on and off conditions. In contrast, metabolism in the region closest to the antenna (orbitofrontal cortex and temporal pole) was significantly higher for on than off conditions (35.7 vs 33.3 μmol/100 g per minute; mean difference, 2.4 [95% confidence interval, 0.67-4.2]; P = .004). The increases were significantly correlated with the estimated electromagnetic field amplitudes both for absolute metabolism (R = 0.95, P < .001) and normalized metabolism (R = 0.89; P < .001). In healthy participants and compared with no exposure, 50-minute cell phone exposure was associated with increased brain glucose metabolism in the region closest to the antenna. This finding is of unknown clinical significance.

Integrated use of surface geophysical methods for site characterization — A case study in North Kingstown, Rhode Island

USGS Publications Warehouse

Johnson, Carole D.; Lane, John W.; Brandon, William C.; Williams, Christine A.P.; White, Eric A.

2010-01-01

A suite of complementary, non‐invasive surface geophysical methods was used to assess their utility for site characterization in a pilot investigation at a former defense site in North Kingstown, Rhode Island. The methods included frequency‐domain electromagnetics (FDEM), ground‐penetrating radar (GPR), electrical resistivity tomography (ERT), and multi‐channel analysis of surface‐wave (MASW) seismic. The results of each method were compared to each other and to drive‐point data from the site. FDEM was used as a reconnaissance method to assess buried utilities and anthropogenic structures; to identify near‐surface changes in water chemistry related to conductive leachate from road‐salt storage; and to investigate a resistive signature possibly caused by groundwater discharge. Shallow anomalies observed in the GPR and ERT data were caused by near‐surface infrastructure and were consistent with anomalies observed in the FDEM data. Several parabolic reflectors were observed in the upper part of the GPR profiles, and a fairly continuous reflector that was interpreted as bedrock could be traced across the lower part of the profiles. MASW seismic data showed a sharp break in shear wave velocity at depth, which was interpreted as the overburden/bedrock interface. The MASW profile indicates the presence of a trough in the bedrock surface in the same location where the ERT data indicate lateral variations in resistivity. Depths to bedrock interpreted from the ERT, MASW, and GPR profiles were similar and consistent with the depths of refusal identified in the direct‐push wells. The interpretations of data collected using the individual methods yielded non‐unique solutions with considerable uncertainty. Integrated interpretation of the electrical, electromagnetic, and seismic geophysical profiles produced a more consistent and unique estimation of depth to bedrock that is consistent with ground‐truth data at the site. This test case shows that using complementary techniques that measure different properties can be more effective for site characterization than a single‐method investigation.

Contribution of geophysical methods in the study of the floodplain structure (the Litavka River, the Czech Republic)

NASA Astrophysics Data System (ADS)

Kotková, Kristýna; Matys Grygar, Tomáš; Tůmová, Štěpánka; Elznicová, Jitka

2017-04-01

Mining and processing of polymetallic ores near the city of Příbram (the Czech Republic) have strongly impacted the fluvial system of the Litavka River. Beside of polymetallic mining during several hundred years with a peak between 1850 and 1950, the Litavka River was also influenced by uranium ore mining between 1948 and 1989. Severe contamination of the Litavka River system is known, but the alluvial architecture and specific distribution of contamination has not yet been satisfactorily described. However, such pieces of information are necessary for the predictions of the future behaviour of contaminants in the river system. We used geophysical methods for visualisation of subsurface layers of sediments and we have proved them very useful for the survey of the floodplain structure. It is especially advantageous when the surface topography of the floodplain does not reveal its internal structure, e.g. due to floodplain levelling by aggradation. Specifically, dipole electromagnetic profiling, also denoted electromagnetic induction sensing (DEMP) was used for quick detection of major heterogeneities in the floodplain structure. In addition, electrical resistivity tomography (ERT) was used for the exploration of lines across the heterogeneities shown by DEMP. This approach allows to choose the appropriate plan for the subsequent sampling in the floodplain to include all its structural (lithogenetic) units. Such rational strategy allows for reducing total amount of sampled sites without the risk of losing important information and production of false images. Both used geophysical tools and manual drill coring and the elemental analysis by handheld X-ray fluorescence spectrometry produced clear images of floodplain architecture and pollutant distribution. The internal structure of the Litavka River floodplain shows that lateral deposition and reworking of sediments played the main roles in the floodplain building. In the next centuries the lateral channel movement will rework contamination which is maximal in the current channel belt.

Fast, automatic, and accurate catheter reconstruction in HDR brachytherapy using an electromagnetic 3D tracking system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poulin, Eric; Racine, Emmanuel; Beaulieu, Luc, E-mail: Luc.Beaulieu@phy.ulaval.ca

2015-03-15

Purpose: In high dose rate brachytherapy (HDR-B), current catheter reconstruction protocols are relatively slow and error prone. The purpose of this technical note is to evaluate the accuracy and the robustness of an electromagnetic (EM) tracking system for automated and real-time catheter reconstruction. Methods: For this preclinical study, a total of ten catheters were inserted in gelatin phantoms with different trajectories. Catheters were reconstructed using a 18G biopsy needle, used as an EM stylet and equipped with a miniaturized sensor, and the second generation Aurora{sup ®} Planar Field Generator from Northern Digital Inc. The Aurora EM system provides position andmore » orientation value with precisions of 0.7 mm and 0.2°, respectively. Phantoms were also scanned using a μCT (GE Healthcare) and Philips Big Bore clinical computed tomography (CT) system with a spatial resolution of 89 μm and 2 mm, respectively. Reconstructions using the EM stylet were compared to μCT and CT. To assess the robustness of the EM reconstruction, five catheters were reconstructed twice and compared. Results: Reconstruction time for one catheter was 10 s, leading to a total reconstruction time inferior to 3 min for a typical 17-catheter implant. When compared to the μCT, the mean EM tip identification error was 0.69 ± 0.29 mm while the CT error was 1.08 ± 0.67 mm. The mean 3D distance error was found to be 0.66 ± 0.33 mm and 1.08 ± 0.72 mm for the EM and CT, respectively. EM 3D catheter trajectories were found to be more accurate. A maximum difference of less than 0.6 mm was found between successive EM reconstructions. Conclusions: The EM reconstruction was found to be more accurate and precise than the conventional methods used for catheter reconstruction in HDR-B. This approach can be applied to any type of catheters and applicators.« less

New shielding configurations for a simultaneous PET/MRI scanner at 7T

PubMed Central

Peng, Bo J.; Wu, Yibao; Cherry, Simon R.; Walton, Jeffrey H.

2014-01-01

Understanding sources of electromagnetic interference are important in designing any electronic system. This is especially true when combining positron emission tomography (PET) and magnetic resonance imaging (MRI) in a multimodality system as coupling between the subsystems can degrade the performance of either modality. For this reason, eliminating radio frequency (RF) interference and gradient-induced eddy currents have been major challenges in building simultaneous hybrid PET/MRI systems. MRI requires negligible RF interference at the Larmor resonance frequency, while RF interference at almost any frequency may corrupt PET data. Moreover, any scheme that minimizes these interactions would, ideally, not compromise the performance of either subsystem. This paper lays out a plan to resolve these problems. A carbon fiber composite material is found to be a good RF shield at the Larmor frequency (300 MHz in this work) while introducing negligible gradient eddy currents. This carbon fiber composite also provides excellent structural support for the PET detector components. Low frequency electromagnetic radiation (81 kHz here) from the switching power supplies of the gradient amplifiers was also found to interfere with the PET detector. Placing the PET detector module between two carbon fiber tubes and grounding the inner carbon fiber tube to the PET detector module ground reduced this interference. Further reductions were achieved by adding thin copper (Cu) foil on the outer carbon fiber case and electrically grounding the PET detector module so that all 3 components had a common ground, i.e. with the PET detector in an electrostatic cage. Finally, gradient switching typical in MRI sequences can result in count losses in the particular PET detector design studied. Moreover, the magnitude of this effect depends on the location of the detector within the magnet bore and which MRI gradient is being switched. These findings have a bearing on future designs of PET/MRI systems. PMID:24380812

Excitation of Surface Electromagnetic Waves on Railroad Rail

DOT National Transportation Integrated Search

1978-03-31

UMTA's Office of Rail Technology research programs aim to improve urban rail transportation systems safety. This rail-transit research study attempts to develop an onboard, separate and independent obstacle-detection system--Surface Electromagnetic W...

Practicing Reiki does not appear to routinely produce high-intensity electromagnetic fields from the heart or hands of Reiki practitioners.

PubMed

Baldwin, Ann Linda; Rand, William Lee; Schwartz, Gary E

2013-06-01

The study objective was to determine whether Reiki practice increases the electromagnetic field strength from the heart and hands of Reiki practitioners. This study repeated experiments performed 20 years ago that detected exceptionally high-strength electromagnetic fields (100 nT) from the hands of several energy healers. The equipment used was far more sensitive than in the original studies. Using a Magnes 2500 WH SQUID, the electromagnetic field from the hands and heart of each of 3 Reiki masters was measured when they were (1) not practicing Reiki, (2) sending Reiki to a distant person, and (3) sending Reiki to a person in the room. Similar measurements were made on 4 Reiki-naïve volunteers before and after they received a Reiki training/attunement enabling them to self-administer Reiki. The study setting was the Scripps Institute, San Diego, CA. Magnetic field intensity of hands and heart recorded over 5-minute sessions with corresponding frequency spectra. For all subjects, under all conditions, sensors closest to the heart and the hands produced spikes of 2 pT corresponding to the heartbeat. Recordings from 2 Masters and 1 volunteer showed a low-intensity sine wave oscillation of 0.25-0.3 Hz (intensity 0.1-0.5 pT) whether or not they were practicing Reiki. This oscillation probably reflected respiratory sinus arrhythmia, judged by comparison with recent previous studies. These signals were not detected in the original studies. In the current study, no electromagnetic field intensities greater than 3 pT were observed in any of the recordings. Practicing Reiki does not appear to routinely produce high-intensity electromagnetic fields from the heart or hands. Alternatively, it is possible that energy healing is stimulated by tuning into an external environmental radiation, such as the Schumann resonance, which was blocked in the present study by the strong magnetic shielding surrounding the SQUID.

An Improved High-Sensitivity Airborne Transient Electromagnetic Sensor for Deep Penetration

PubMed Central

Chen, Shudong; Guo, Shuxu; Wang, Haofeng; He, Miao; Liu, Xiaoyan; Qiu, Yu; Zhang, Shuang; Yuan, Zhiwen; Zhang, Haiyang; Fang, Dong; Zhu, Jun

2017-01-01

The investigation depth of transient electromagnetic sensors can be effectively increased by reducing the system noise, which is mainly composed of sensor internal noise, electromagnetic interference (EMI), and environmental noise, etc. A high-sensitivity airborne transient electromagnetic (AEM) sensor with low sensor internal noise and good shielding effectiveness is of great importance for deep penetration. In this article, the design and optimization of such an AEM sensor is described in detail. To reduce sensor internal noise, a noise model with both a damping resistor and a preamplifier is established and analyzed. The results indicate that a sensor with a large diameter, low resonant frequency, and low sampling rate will have lower sensor internal noise. To improve the electromagnetic compatibility of the sensor, an electromagnetic shielding model for a central-tapped coil is established and discussed in detail. Previous studies have shown that unclosed shields with multiple layers and center grounding can effectively suppress EMI and eddy currents. According to these studies, an improved differential AEM sensor is constructed with a diameter, resultant effective area, resonant frequency, and normalized equivalent input noise of 1.1 m, 114 m2, 35.6 kHz, and 13.3 nV/m2, respectively. The accuracy of the noise model and the shielding effectiveness of the sensor have been verified experimentally. The results show a good agreement between calculated and measured results for the sensor internal noise. Additionally, over 20 dB shielding effectiveness is achieved in a complex electromagnetic environment. All of these results show a great improvement in sensor internal noise and shielding effectiveness. PMID:28106718

The accuracy of an electromagnetic navigation system in lateral skull base approaches.

PubMed

Komune, Noritaka; Matsushima, Ken; Matsuo, Satoshi; Safavi-Abbasi, Sam; Matsumoto, Nozomu; Rhoton, Albert L

2017-02-01

Image-guided optical tracking systems are being used with increased frequency in lateral skull base surgery. Recently, electromagnetic tracking systems have become available for use in this region. However, the clinical accuracy of the electromagnetic tracking system has not been examined in lateral skull base surgery. This study evaluates the accuracy of electromagnetic navigation in lateral skull base surgery. Cadaveric and radiographic study. Twenty cadaveric temporal bones were dissected in a surgical setting under a commercially available, electromagnetic surgical navigation system. The target registration error (TRE) was measured at 28 surgical landmarks during and after performing the standard translabyrinthine and middle cranial fossa surgical approaches to the internal acoustic canal. In addition, three demonstrative procedures that necessitate navigation with high accuracy were performed; that is, canalostomy of the superior semicircular canal from the middle cranial fossa, 1 cochleostomy from the middle cranial fossa, 2 and infralabyrinthine approach to the petrous apex. 3 RESULTS: Eleven of 17 (65%) of the targets in the translabyrinthine approach and five of 11 (45%) of the targets in the middle fossa approach could be identified in the navigation system with TRE of less than 0.5 mm. Three accuracy-dependent procedures were completed without anatomical injury of important anatomical structures. The electromagnetic navigation system had sufficient accuracy to be used in the surgical setting. It was possible to perform complex procedures in the lateral skull base under the guidance of the electromagnetically tracked navigation system. N/A. Laryngoscope, 2016 127:450-459, 2017. © 2016 The American Laryngological, Rhinological and Otological Society, Inc.

[Effect of decimeter polarized electromagnetic radiation on germinating capacity of seeds].

PubMed

Polevik, N D

2013-01-01

The effect of a polarization structure of electromagnetic radiation on the germinating capacity of seeds of such weeds as Green foxtail (Setaria viridis) and Green amaranth (Amaranthus retroflexus) has been studied. Seeds have been exposed to impulse electromagnetic radiation in a frequency of 896 MHz with linear, elliptical right-handed and elliptical left-handed polarizations at different power flux density levels. It is determined that the effect of the right-handed polarized electromagnetic radiation increases and the influence of the left-handed polarized one reduces the germinating capacity of seeds compared to the effect of the linearly polarized electromagnetic radiation. It is shown that the seeds have an amplitude polarization selectivity as evinced by the major effect of the right-handed polarized radiation on seeds. An electrodynamic model as the right-handed elliptically polarized antenna with the given quantity of the ellipticity of polarization is suggested to use in description of this selectivity.

[Saccharomyces cerevisiae as a model organism for studying the carcinogenicity of non-ionizing electromagnetic fields and radiation].

PubMed

Voĭchuk, S I

2014-01-01

Medical and biological aspects of the effects of non-ionizing electromagnetic (EM) fields and radiation on human health are the important issues that have arisen as a result of anthropogenic impact on the biosphere. Safe use of man-made sources of non-ionizing electromagnetic fields and radiation in a broad range of frequencies--static, radio-frequency and microwave--is a subject of discussions and speculations. The main problem is the lack of understanding of the mechanism(s) of reception of EMFs by living organisms. In this review we have analyzed the existing literature data regarding the effects of the electromagnetic radiation on the model eukaryotic organism--yeast Saccharomyces cerevisiae. An attempt was made to estimate the probability of induction of carcinogenesis in humans under the influence of magnetic fields and electromagnetic radiation of extremely low frequency, radio frequency and microwave ranges.

Research of glass fibre used in the electromagnetic wave shielding and absorption composite material

NASA Astrophysics Data System (ADS)

Xu, M.; Jia, F.; Bao, H. Q.; Cui, K.; Zhang, F.

2016-07-01

Electromagnetic shielding and absorption composite material plays an important role in the defence and economic field. Comparing with other filler, Glass fibre and its processed product—metal-coated glass fibre can greatly reduce the material's weight and costs, while it still remains the high strength and the electromagnetic shielding effectiveness. In this paper, the electromagnetic absorption mechanism and the reflection mechanism have been investigated as a whole, and the shielding effectiveness of the double-layer glass fibre composite material is mainly focused. The relationship between the shielding effectiveness and the filled glass fibre as well as its metal-coated product's parameters has also been studied. From the subsequent coaxial flange and anechoic chamber analysis, it can be confirmed that the peak electromagnetic shielding effectiveness of this double-layer material can reach -78dB while the bandwidth is from 2GHz to 18GHz.

Illusion optics: Optically transforming the nature and the location of electromagnetic emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Jianjia; Tichit, Paul-Henri; Burokur, Shah Nawaz, E-mail: shah-nawaz.burokur@u-psud.fr

Complex electromagnetic structures can be designed by using the powerful concept of transformation electromagnetics. In this study, we define a spatial coordinate transformation that shows the possibility of designing a device capable of producing an illusion on an antenna radiation pattern. Indeed, by compressing the space containing a radiating element, we show that it is able to change the radiation pattern and to make the radiation location appear outside the latter space. Both continuous and discretized models with calculated electromagnetic parameter values are presented. A reduction of the electromagnetic material parameters is also proposed for a possible physical fabrication ofmore » the device with achievable values of permittivity and permeability that can be obtained from existing well-known metamaterials. Following that, the design of the proposed antenna using a layered metamaterial is presented. Full wave numerical simulations using Finite Element Method are performed to demonstrate the performances of such a device.« less

The effects of annealing temperature on the permittivity and electromagnetic attenuation performance of reduced graphene oxide

NASA Astrophysics Data System (ADS)

Wu, Fan; Zeng, Qiao; Xia, Yilu; Sun, Mengxiao; Xie, Aming

2018-05-01

Reduced graphene oxide (RGO) has been prepared through the thermal reduction method with different annealing temperatures to explore the effects of temperature on the permittivity and electromagnetic attenuation performance. The real and imaginary parts of permittivity increase along with the decrease in the oxygen functional group and the increase in the filler loading ratio. A composite only loaded with 1 wt. % of RGO can possess an effective electromagnetic absorption bandwidth of 7.60 GHz, when graphene oxide was reduced under 300 °C for 2 h. With the annealing temperature increased to 700 °C and the well reduced RGO loaded 7 wt. % in the composite, the electromagnetic interference shielding efficiency can get higher than 35 dB from 2 to 18 GHz. This study shows that controlling the oxygen functional groups on the RGO surface can also obtain an ideal electromagnetic attenuation performance without any other decorated nanomaterials.

THz electromagnetic radiation driven by intense relativistic electron beam based on ion focus regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Qing; Xu, Jin; Zhang, Wenchao

The simulation study finds that the relativistic electron beam propagating through the plasma background can produce electromagnetic (EM) radiation. With the propagation of the electron beam, the oscillations of the beam electrons in transverse and longitudinal directions have been observed simultaneously, which provides the basis for the electromagnetic radiation. The simulation results clearly show that the electromagnetic radiation frequency can reach up to terahertz (THz) wave band which may result from the filter-like property of plasma background, and the electromagnetic radiation frequency closely depends on the plasma density. To understand the above simulation results physically, the dispersion relation of themore » beam-plasma system has been derived using the field-matching method, and the dispersion curves show that the slow wave modes can couple with the electron beam effectively in THz wave band, which is an important theoretical evidence of the EM radiation.« less

Modulation of a compressional electromagnetic wave in a magnetized electron-positron quantum plasma.

PubMed

Amin, M R

2015-09-01

Amplitude modulation of a compressional electromagnetic wave in a strongly magnetized electron-positron pair plasma is considered in the quantum magnetohydrodynamic regime. The important ingredients of this study are the inclusion of the external strong magnetic field, Fermi quantum degeneracy pressure, particle exchange potential, quantum diffraction effects via the Bohm potential, and dissipative effect due to collision of the charged carriers. A modified-nonlinear Schödinger equation is developed for the compressional magnetic field of the electromagnetic wave by employing the standard reductive perturbation technique. The linear and nonlinear dispersions of the electromagnetic wave are discussed in detail. For some parameter ranges, relevant to dense astrophysical objects such as the outer layers of white dwarfs, neutron stars, and magnetars, etc., it is found that the compressional electromagnetic wave is modulationally unstable and propagates as a dissipated electromagnetic wave. It is also found that the quantum effects due to the particle exchange potential and the Bohm potential are negligibly small in comparison to the effects of the Fermi quantum degeneracy pressure. The numerical results on the growth rate of the modulation instability is also presented.

Comparison of velocity-log data collected using impeller and electromagnetic flowmeters

USGS Publications Warehouse

Newhouse, M.W.; Izbicki, J.A.; Smith, G.A.

2005-01-01

Previous studies have used flowmeters in environments that are within the expectations of their published ranges. Electromagnetic flowmeters have a published range from 0.1 to 79.0 m/min, and impeller flowmeters have a published range from 1.2 to 61.0 m/min. Velocity-log data collected in five long-screened production wells in the Pleasant Valley area of southern California showed that (1) electromagnetic flowmeter results were comparable within ??2% to results obtained using an impeller flowmeter for comparable depths; (2) the measured velocities from the electromagnetic flowmeter were up to 36% greater than the published maximum range; and (3) both data sets, collected without the use of centralizers or flow diverters, produced comparable and interpretable results. Although either method is acceptable for measuring wellbore velocities and the distribution of flow, the electromagnetic flowmeter enables collection of data over a now greater range of flows. In addition, changes in fluid temperature and fluid resistivity, collected as part of the electromagnetic flowmeter log, are useful in the identification of flow and hydrogeologic interpretation.

Comparison of velocity-log data collected using impeller and electromagnetic flowmeters.

PubMed

Newhouse, M W; Izbicki, J A; Smith, G A

2005-01-01

Previous studies have used flowmeters in environments that are within the expectations of their published ranges. Electromagnetic flowmeters have a published range from 0.1 to 79.0 m/min, and impeller flowmeters have a published range from 1.2 to 61.0 m/min. Velocity-log data collected in five long-screened production wells in the Pleasant Valley area of southern California showed that (1) electromagnetic flowmeter results were comparable within +/-2% to results obtained using an impeller flowmeter for comparable depths; (2) the measured velocities from the electromagnetic flowmeter were up to 36% greater than the published maximum range; and (3) both data sets, collected without the use of centralizers or flow diverters, produced comparable and interpretable results. Although either method is acceptable for measuring wellbore velocities and the distribution of flow, the electromagnetic flowmeter enables collection of data over a now greater range of flows. In addition, changes in fluid temperature and fluid resistivity, collected as part of the electromagnetic flowmeter log, are useful in the identification of flow and hydrogeologic interpretation.

Electromagnetic and light scattering by nonspherical particles XV: Celebrating 150 years of Maxwell's electromagnetics

NASA Astrophysics Data System (ADS)

Macke, Andreas; Mishchenko, Michael I.

2016-07-01

The 15th Electromagnetic and Light Scattering Conference (ELS-XV) was held in Leipzig, Germany from 21 to 26 of June 2015 (Fig. 1). This conference built on the great success of the previous meetings held in Amsterdam (1995) [1], Helsinki (1997) [2], New York City (1998) [3], Vigo (1999), Halifax (2000) [4], Gainesville (2002) [5], Bremen (2003) [6], Salobreña (2005) [7], St. Petersburg (2006) [8], Bodrum (2007) [9], Hatfield (2008) [10], Helsinki (2010) [11], Taormina (2011) [12], and Lille [13] as well as the workshops held in Bremen (1996, 1998) and Moscow (1997). As usual, the main objective of this conference was to bring together scientists, engineers, and PhD students studying various aspects of electromagnetic scattering and to provide a relaxed atmosphere for in-depth discussion of theory, measurements, and applications. Furthermore, ELS-XV supported the United Nations "Year of Light" and celebrated the 150th anniversary of Maxwell's electromagnetics. Maxwell's paper on "A Dynamical Theory of the Electromagnetic Field" [14] was published in 1865 and has widely been acknowledged as one of the supreme achievements in the history of science.

Individual differences in cardiac vagal tone are associated with differential neural responses to facial expressions at different spatial frequencies: an ERP and sLORETA study.

PubMed

Park, Gewnhi; Moon, Eunok; Kim, Do-Won; Lee, Seung-Hwan

2012-12-01

A previous study has shown that greater cardiac vagal tone, reflecting effective self-regulatory capacity, was correlated with superior visual discrimination of fearful faces at high spatial frequency Park et al. (Biological Psychology 90:171-178, 2012b). The present study investigated whether individual differences in cardiac vagal tone (indexed by heart rate variability) were associated with different event-related brain potentials (ERPs) in response to fearful and neutral faces. Thirty-six healthy participants discriminated the emotion of fearful and neutral faces at broad, high, and low spatial frequencies, while ERPs were recorded. Participants with low resting heart rate variability-characterized by poor functioning of regulatory systems-exhibited significantly greater N200 activity in response to fearful faces at low spatial frequency and greater LPP responses to neutral faces at high spatial frequency. Source analyses-estimated by standardized low-resolution brain electromagnetic tomography (sLORETA)-tended to show that participants with low resting heart rate variability exhibited increased source activity in visual areas, such as the cuneus and the middle occipital gyrus, as compared with participants with high resting heart rate variability. The hyperactive neural activity associated with low cardiac vagal tone may account for hypervigilant response patterns and emotional dysregulation, which heightens the risk of developing physical and emotional problems.

Electrical source localization by LORETA in patients with epilepsy: Confirmation by postoperative MRI

PubMed Central

Akdeniz, Gülsüm

2016-01-01

Background: Few studies have been conducted that have compared electrical source localization (ESL) results obtained by analyzing ictal patterns in scalp electroencephalogram (EEG) with the brain areas that are found to be responsible for seizures using other brain imaging techniques. Additionally, adequate studies have not been performed to confirm the accuracy of ESL methods. Materials and Methods: In this study, ESL was conducted using LORETA (Low Resolution Brain Electromagnetic Tomography) in 9 patients with lesions apparent on magnetic resonance imaging (MRI) and in 6 patients who did not exhibit lesions on their MRIs. EEGs of patients who underwent surgery for epilepsy and had follow-ups for at least 1 year after operations were analyzed for ictal spike, rhythmic, paroxysmal fast, and obscured EEG activities. Epileptogenic zones identified in postoperative MRIs were then compared with localizations obtained by LORETA model we employed. Results: We found that brain areas determined via ESL were in concordance with resected brain areas for 13 of the 15 patients evaluated, and those 13 patients were post-operatively determined as being seizure-free. Conclusion: ESL, which is a noninvasive technique, may contribute to the correct delineation of epileptogenic zones in patients who will eventually undergo surgery to treat epilepsy, (regardless of neuroimaging status). Moreover, ESL may aid in deciding on the number and localization of intracranial electrodes to be used in patients who are candidates for invasive recording. PMID:27011626

Brain signatures of monetary loss and gain: outcome-related potentials in a single outcome gambling task

PubMed Central

Kamarajan, Chella; Porjesz, Bernice; Rangaswamy, Madhavi; Tang, Yongqiang; Chorlian, David B.; Padmanabhapillai, Ajayan; Saunders, Ramotse; Pandey, Ashwini K.; Roopesh, Bangalore N.; Manz, Niklas; Stimus, Arthur T.; Begleiter, Henri

2009-01-01

This study evaluates the event-related potential (ERP) components in a single outcome gambling task that involved monetary losses and gains. The participants were 50 healthy young volunteers (25 males and 25 females). The gambling task involved valence (loss and gain) and amount (50¢ and 10¢) as outcomes. The outcome-related negativity (ORN/N2) and outcome-related positivity (ORP/P3) were analyzed and compared across conditions and gender. Monetary gain (compared to loss) and higher amount (50¢ compared to 10¢) produced higher amplitudes and shorter latencies in both ORN and ORP components. Difference wave plots showed that earlier processing (200-400 ms) is dominated by the valence (loss/gain) while later processing (after 400 ms) is marked by the amount (50¢/10¢). Functional mapping using Low Resolution Electromagnetic Tomography (LORETA) indicated that the ORN separated the loss against gain in both genders, while the ORP activity distinguished the 50¢ against 10¢ in males. This study further strengthens the view that separate brain processes/circuitry may mediate loss and gain. Although there were no gender differences in behavioral and impulsivity scores, ORN and ORP measures for different task conditions had significant correlations with behavioral scores. This gambling paradigm may potentially offer valuable indicators to study outcome processing and impulsivity in normals as well as in clinical populations. PMID:18775749

Electrical source localization by LORETA in patients with epilepsy: Confirmation by postoperative MRI.

PubMed

Akdeniz, Gülsüm

2016-01-01

Few studies have been conducted that have compared electrical source localization (ESL) results obtained by analyzing ictal patterns in scalp electroencephalogram (EEG) with the brain areas that are found to be responsible for seizures using other brain imaging techniques. Additionally, adequate studies have not been performed to confirm the accuracy of ESL methods. In this study, ESL was conducted using LORETA (Low Resolution Brain Electromagnetic Tomography) in 9 patients with lesions apparent on magnetic resonance imaging (MRI) and in 6 patients who did not exhibit lesions on their MRIs. EEGs of patients who underwent surgery for epilepsy and had follow-ups for at least 1 year after operations were analyzed for ictal spike, rhythmic, paroxysmal fast, and obscured EEG activities. Epileptogenic zones identified in postoperative MRIs were then compared with localizations obtained by LORETA model we employed. We found that brain areas determined via ESL were in concordance with resected brain areas for 13 of the 15 patients evaluated, and those 13 patients were post-operatively determined as being seizure-free. ESL, which is a noninvasive technique, may contribute to the correct delineation of epileptogenic zones in patients who will eventually undergo surgery to treat epilepsy, (regardless of neuroimaging status). Moreover, ESL may aid in deciding on the number and localization of intracranial electrodes to be used in patients who are candidates for invasive recording.

Abnormal EEG Power Spectra in Acute Transient Global Amnesia: A Quantitative EEG Study.

PubMed

Imperatori, Claudio; Farina, Benedetto; Todini, Federico; Di Blasi, Chiara; Mazzucchi, Edoardo; Brunetti, Valerio; Della Marca, Giacomo

2018-06-01

Transient global amnesia (TGA) is a clinical syndrome characterized by retrograde and anterograde amnesia without other neurological deficits. Although electroencephalography (EEG) methods are commonly used in both clinical and research setting with TGA patients, few studies have investigated neurophysiological pattern in TGA using quantitative EEG (qEEG). The main aim of the present study was to extend these previous findings by exploring EEG power spectra differences between patients with acute TGA and healthy controls using the exact low-resolution brain electromagnetic tomography software (eLORETA). EEG was recorded during 5 minutes of resting state. Sixteen patients (mean age: 66.81 ± 7.94 years) during acute TGA and 16 healthy subjects were enrolled. All patients showed hippocampal or parahippocampal signal abnormalities in diffusion-weighted magnetic resonance imaging performed from 2 to 5 days after the onset of TGA. Compared with healthy controls, TGA patients showed a decrease of theta power localized in the temporal lobe (Brodmann areas, BAs 21-22-38) and frontal lobe (BAs 8-9-44-45). A decrease of EEG beta power in the bilateral precuneus (BA 7) and in the bilateral postcentral gyrus (BAs 3-4-5) was also observed in TGA individuals. Taken together, our results could reflect the neurophysiological substrate of the severe impairment of both episodic memory and autobiographical memory which affect TGA patients during the acute phase.

Relativistic laser-plasma interactions in the quantum regime.

PubMed

Eliasson, Bengt; Shukla, P K

2011-04-01

We consider nonlinear interactions between a relativistically strong laser beam and a plasma in the quantum regime. The collective behavior of electrons is modeled by a Klein-Gordon equation, which is nonlinearly coupled with the electromagnetic wave through the Maxwell and Poisson equations. This allows us to study nonlinear interactions between arbitrarily large-amplitude electromagnetic waves and a quantum plasma. We have used our system of nonlinear equations to study theoretically the parametric instabilities involving stimulated Raman scattering and modulational instabilities. A model for quasi-steady-state propagating electromagnetic wave packets is also derived, and which shows possibility of localized solitary structures in a quantum plasma. Numerical simulations demonstrate collapse and acceleration of electrons in the nonlinear stage of the modulational instability, as well as possibility of the wake-field acceleration of electrons to relativistic speeds by short laser pulses at nanometer length scales. Our study is relevant for understanding the localization of intense electromagnetic pulses in a quantum plasma with extremely high electron densities and relatively low temperature.

Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

NASA Astrophysics Data System (ADS)

Cadena, M. S. Reyes; Chapul, L. Sánchez; Pérez, Javiér; García, M. N. Jiménez; López, M. A. Jiménez; Espíndola, M. E. Sánchez; Perez, R. Paniagua; Hernández, N. A.; Paniagua, G.; Uribe, F.; Nava, J. J. Godina; Segura, M. A. Rodríguez

2008-08-01

We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-β) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animals subjected to ELF together with the transfer factor.

Acquisition, Processing, and Analysis of Continuous Multi-Offset GPR Data for Problems in Hydrogeophysics: Is it Worth the Cost? (Invited)

NASA Astrophysics Data System (ADS)

Bradford, J. H.

2009-12-01

Commercial development of multi-channel ground-penetrating radar (GPR) systems has made acquisition of continuous multi-offset (CMO) data more cost effective than ever. However, additional operator training, equipment costs, field and analysis time, and computation requirements necessarily remain substantially higher than conventional fixed offset GPR surveys. The choice to conduct a CMO survey is a target driven optimization problem where in many cases the added value outweighs the additional cost. Drawing examples from surface water, groundwater, snow, and glacier hydrology, I demonstrate a range of information that can be derived from CMO data with particular emphasis on estimating material properties of relevance to hydrological problems. Careful data acquisition is key to accurate property measurements. CMO geometries can be constructed with a single-channel system although with a significant loss of time and personnel efficiency relative to modern multi-channel systems. Using procedures such as common-midpoint stacking and pre-stack velocity filtering, it is possible to substantially improve the signal-to-noise ratio in GPR reflection images. However, the primary advantage of CMO data is dense sampling of a wide aperture of travelpaths through the subsurface. These data provide the basis for applying tomographic imaging techniques. Reflection velocity tomography in the pre-stack migration domain provides a robust approach to constructing accurate and detailed electromagnetic velocity models. These models in turn are used in conjunction with petrophysical models to estimate hydrologic properties such as porosity. Additionally, we can utilize the velocity models in conjunction with analysis of the frequency dependent attenuation to evaluate real and complex dielectric permittivity. The real and complex components of dielectric permittivity may have differing sensitivity to different components of the hydrologic system. Understanding this behavior may lead to improved understanding of relevant lithologic properties such as bulk clay content or fluid chemical composition during biodegradation of hydrocarbon contaminants. In addition to velocity tomography, CMO data enable reflection attenuation difference tomography. While time-lapse attenuation difference tomography using crosswell GPR transmission data is a well established technique for imaging conductive tracers in groundwater systems, it is not common for reflection data. Numerical examples based on a realistic aquifer model show that surface data can provide resolution of conductive tracer zones that is comparable to cross well data, thereby minimizing the need for invasive and expensive boreholes.

Information system building of the urban electromagnetic environment

NASA Astrophysics Data System (ADS)

Wang, Jiechen; Rui, Yikang; Shen, Dingtao; Yu, Qing

2007-06-01

The pollution of urban electromagnetic radiation has become more serious, however, there is still lack of a perfect and interactive User System to manage, analyze and issue the information. In this study, taking the electromagnetic environment of Nanjing as an example, an information system based on WebGIS with the techniques of ArcIMS and JSP has been developed, in order to provide the services and technique supports for information query of public and decision making of relevant departments.

Metronidazole as a protector of cells from electromagnetic radiation of extremely high frequencies

NASA Astrophysics Data System (ADS)

Kuznetsov, Pavel E.; Malinina, Ulia A.; Popyhova, Era B.; Rogacheva, Svetlana M.; Somov, Alexander U.

2006-08-01

It is well known that weak electromagnetic fields of extremely high frequencies cause significant modification of the functional status of biological objects of different levels of organization. The aim of the work was to study the combinatory effect of metronidazole - the drug form of 1-(2'hydroxiethil)-2-methil-5-nitroimidazole - and electromagnetic radiation of extremely high frequencies (52...75 GHz) on the hemolytic stability of erythrocytes and hemotaxis activity of Infusoria Paramecium caudatum.

Nonlinear interferometric vibrational imaging

NASA Technical Reports Server (NTRS)

Boppart, Stephen A. (Inventor); Marks, Daniel L. (Inventor)

2009-01-01

A method of examining a sample, which includes: exposing a reference to a first set of electromagnetic radiation, to form a second set of electromagnetic radiation scattered from the reference; exposing a sample to a third set of electromagnetic radiation to form a fourth set of electromagnetic radiation scattered from the sample; and interfering the second set of electromagnetic radiation and the fourth set of electromagnetic radiation. The first set and the third set of electromagnetic radiation are generated from a source; at least a portion of the second set of electromagnetic radiation is of a frequency different from that of the first set of electromagnetic radiation; and at least a portion of the fourth set of electromagnetic radiation is of a frequency different from that of the third set of electromagnetic radiation.

Electromagnetized gold nanoparticles mediate direct lineage reprogramming into induced dopamine neurons in vivo for Parkinson's disease therapy

NASA Astrophysics Data System (ADS)

Yoo, Junsang; Lee, Euiyeon; Kim, Hee Young; Youn, Dong-Ho; Jung, Junghyun; Kim, Hongwon; Chang, Yujung; Lee, Wonwoong; Shin, Jaein; Baek, Soonbong; Jang, Wonhee; Jun, Won; Kim, Soochan; Hong, Jongki; Park, Hi-Joon; Lengner, Christopher J.; Moh, Sang Hyun; Kwon, Youngeun; Kim, Jongpil

2017-10-01

Electromagnetic fields (EMF) are physical energy fields generated by electrically charged objects, and specific ranges of EMF can influence numerous biological processes, which include the control of cell fate and plasticity. In this study, we show that electromagnetized gold nanoparticles (AuNPs) in the presence of specific EMF conditions facilitate an efficient direct lineage reprogramming to induced dopamine neurons in vitro and in vivo. Remarkably, electromagnetic stimulation leads to a specific activation of the histone acetyltransferase Brd2, which results in histone H3K27 acetylation and a robust activation of neuron-specific genes. In vivo dopaminergic neuron reprogramming by EMF stimulation of AuNPs efficiently and non-invasively alleviated symptoms in mouse Parkinson's disease models. This study provides a proof of principle for EMF-based in vivo lineage conversion as a potentially viable and safe therapeutic strategy for the treatment of neurodegenerative disorders.

[Measurement and study report as a part of the control system for human safety and health protection against electromagnetic fields and electromagnetic radiation (0 Hz-300 GHz)].

PubMed

Aniołczyk, Halina

2007-01-01

The National Control System for safety and health protection against electromagnetic fields (EMF) and electromagnetic radiation (EMR) (0 Hz-300 GHz) is constantly analyzed in view of Directive 2004/40/EC. Reports on the effects of investments (at the designing stage or at the stage of looking for their localization) on the environment and measurement and study reports on the objects already existing or being put into operation are important elements of this system. These documents should meet both national and European Union's legislation requirements. The overriding goal of the control system is safety and health protection of humans against electromagnetic fields in the environment and in occupational settings. The author pays a particular attention to provisions made in directives issued by relevant ministers and to Polish standards, which should be documented in measurement and study reports published by the accredited laboratories and relating to the problems of human safety and health protection. Similar requirements are valid for the Reports. Therefore, along with measurement outcomes, the reports should include data on the EMF exposure classification at work-posts and the assessment of occupational risk resulting from EMF exposure or at least thorough data facilitating such a classification.

Pulsed electromagnetic fields after arthroscopic treatment for osteochondral defects of the talus: double-blind randomized controlled multicenter trial

PubMed Central

van Bergen, Christiaan JA; Blankevoort, Leendert; de Haan, Rob J; Sierevelt, Inger N; Meuffels, Duncan E; d'Hooghe, Pieter RN; Krips, Rover; van Damme, Geert; van Dijk, C Niek

2009-01-01

Background Osteochondral talar defects usually affect athletic patients. The primary surgical treatment consists of arthroscopic debridement and microfracturing. Although this is mostly successful, early sport resumption is difficult to achieve, and it can take up to one year to obtain clinical improvement. Pulsed electromagnetic fields (PEMFs) may be effective for talar defects after arthroscopic treatment by promoting tissue healing, suppressing inflammation, and relieving pain. We hypothesize that PEMF-treatment compared to sham-treatment after arthroscopy will lead to earlier resumption of sports, and aim at 25% increase in patients that resume sports. Methods/Design A prospective, double-blind, randomized, placebo-controlled trial (RCT) will be conducted in five centers throughout the Netherlands and Belgium. 68 patients will be randomized to either active PEMF-treatment or sham-treatment for 60 days, four hours daily. They will be followed-up for one year. The combined primary outcome measures are (a) the percentage of patients that resume and maintain sports, and (b) the time to resumption of sports, defined by the Ankle Activity Score. Secondary outcome measures include resumption of work, subjective and objective scoring systems (American Orthopaedic Foot and Ankle Society – Ankle-Hindfoot Scale, Foot Ankle Outcome Score, Numeric Rating Scales of pain and satisfaction, EuroQol-5D), and computed tomography. Time to resumption of sports will be analyzed using Kaplan-Meier curves and log-rank tests. Discussion This trial will provide level-1 evidence on the effectiveness of PEMFs in the management of osteochondral ankle lesions after arthroscopy. Trial registration Netherlands Trial Register (NTR1636) PMID:19591674

Discrimination between pre-seismic electromagnetic anomalies and solar activity effects

NASA Astrophysics Data System (ADS)

Koulouras, G.; Balasis, G.; Kiourktsidis, I.; Nannos, E.; Kontakos, K.; Stonham, J.; Ruzhin, Y.; Eftaxias, K.; Cavouras, D.; Nomicos, C.

2009-04-01

Laboratory studies suggest that electromagnetic emissions in a wide frequency spectrum ranging from kilohertz (kHz) to very high megahertz (MHz) frequencies are produced by the opening of microcracks, with the MHz radiation appearing earlier than the kHz radiation. Earthquakes are large-scale fracture phenomena in the Earth's heterogeneous crust. Thus, the radiated kHz-MHz electromagnetic emissions are detectable not only in the laboratory but also at a geological scale. Clear MHz-to-kHz electromagnetic anomalies have been systematically detected over periods ranging from a few days to a few hours prior to recent destructive earthquakes in Greece. We should bear in mind that whether electromagnetic precursors to earthquakes exist is an important question not only for earthquake prediction but mainly for understanding the physical processes of earthquake generation. An open question in this field of research is the classification of a detected electromagnetic anomaly as a pre-seismic signal associated with earthquake occurrence. Indeed, electromagnetic fluctuations in the frequency range of MHz are known to be related to a few sources, including atmospheric noise (due to lightning), man-made composite noise, solar-terrestrial noise (resulting from the Sun-solar wind-magnetosphere-ionosphere-Earth's surface chain) or cosmic noise, and finally, the lithospheric effect, namely pre-seismic activity. We focus on this point in this paper. We suggest that if a combination of detected kHz and MHz electromagnetic anomalies satisfies the set of criteria presented herein, these anomalies could be considered as candidate precursory phenomena of an impending earthquake.

Discrimination between preseismic electromagnetic anomalies and solar activity effects

NASA Astrophysics Data System (ADS)

Koulouras, Gr; Balasis, G.; Kontakos, K.; Ruzhin, Y.; Avgoustis, G.; Kavouras, D.; Nomicos, C.

2009-04-01

Laboratory studies suggest that electromagnetic emissions in a wide frequency spectrum ranging from kHz to very high MHz frequencies are produced by the opening of microcracks, with the MHz radiation appearing earlier than the kHz radiation. Earthquakes are large-scale fracture phenomena in the Earth's heterogeneous crust. Thus, the radiated kHz-MHz electromagnetic emissions are detectable not only at laboratory but also at geological scale. Clear MHz-to-kHz electromagnetic anomalies have been systematically detected over periods ranging from a few days to a few hours prior to recent destructive earthquakes in Greece. We bear in mind that whether electromagnetic precursors to earthquakes exist is an important question not only for earthquake prediction but mainly for understanding the physical processes of earthquake generation. An open question in this field of research is the classification of a detected electromagnetic anomaly as a pre-seismic signal associated to earthquake occurrence. Indeed, electromagnetic fluctuations in the frequency range of MHz are known to related to a few sources, i.e., they might be atmospheric noise (due to lightning), man-made composite noise, solar-terrestrial noise (resulting from the Sun-solar wind-magnetosphere-ionosphere-Earth's surface chain) or cosmic noise, and finally, lithospheric effect, namely pre-seismic activity. We focus on this point. We suggest that if a combination of detected kHz and MHz electromagnetic anomalies satisfies the herein presented set of criteria these anomalies could be considered as candidate precursory phenomena of an impending earthquake.

Risk assessment of electromagnetic fields exposure with metallic orthopedic implants: a cadaveric study.

PubMed

Crouzier, D; Selek, L; Martz, B-A; Dabouis, V; Arnaud, R; Debouzy, J-C

2012-02-01

Metallic materials are well known to strongly interact with electromagnetic fields. While biological effects of such field have been extensively studied, only few works dealt with the interactions of electromagnetic waves with passive metallic device implanted in biological system. Hence only several numerical and phantom simulation studies were focusing on this aspect, whereas no in situ anatomic experiment has been previously performed. In this study the effect of electromagnetic waves on eight different orthopaedic medical devices (six plates from 55 to 318mm length, a total knee and a total hip prosthesis) were explored on six human cadavers. To mimic a random environmental exposure resulting from the most common frequencies band used in domestic environment and medical applications (TV and radio broadcasting, cell phone communication, MRI, diathermy treatment), a multifrequency generator emitting in VHF, UHF, GSM and GCS frequency bands was used. The different medical devices were exposed to an electromagnetic field at 50W/m(2) and 100W/m(2). After 6min exposure, the temperature was measured on three points close to each medical device, and the induced currents were estimated. No significant temperature increase (<0.2°C) was finally detected; beside, a slight induced tension (up to 1.1V) was recorded but would appear too low to induce any biological side effect. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

A review of seismoelectric data processing techniques

NASA Astrophysics Data System (ADS)

Warden, S. D.; Garambois, S.; Jouniaux, L.; Sailhac, P.

2011-12-01

Seismoelectric tomography is expected to combine the sensitivity of electromagnetic methods to hydrological properties such as water-content and permeability, to the high resolution of conventional seismic surveys. This innovative exploration technique seems very promising as it could characterize the fluids contained in reservoir rocks and detect thin layers invisible to other methods. However, it still needs to be improved before it can be successfully applied to real case problems. One of the main issues that need to be addressed is the development of wave separation techniques enabling to recover the signal of interest. Seismic waves passing through a fluid-saturated porous layered medium convert into at least two types of electromagnetic waves: the coseismic field (type I), accompanying seismic body and surface waves, and the independently propagating interface response (type II). The latter occurs when compressional waves encounter a contrast between electrical, chemical or mechanical properties in the subsurface, thus acting as a secondary source that can be generally approximated by a sum of electrical dipoles oscillating at the first Fresnel zone. Although properties of the medium in the vicinity of the receivers can be extracted from the coseismic waves, only the interface response provides subsurface information at depth, which makes it critical to separate both types of energy. This is a delicate problem, as the interface response may be several orders of magnitude weaker than the coseismic field. However, as reviewed by Haines et al. (2007), several properties of the interface response can be used to identify it: its dipolar amplitude pattern, its opposite polarity on opposite sides of the shot point and the electromagnetic velocity at which it travels, several orders of magnitude greater than seismic velocities. This latter attribute can be exploited to implement filtering techniques in frequency-wavenumber (f-k) and radon (tau-p) domain, which we have done on synthetic seismoelectric data created using SKB, a modeling program written by Stéphane Garambois, from LGIT (Laboratoire de Géophysique Interne et Tectonophysique, Grenoble, France). We will assess the efficiency of these methods, discuss how they affect signal amplitudes and how they can be improved by sparsity-promoting approaches.

Effects of Gender and Collaborative Learning Approach on Students' Conceptual Understanding of Electromagnetic Induction

ERIC Educational Resources Information Center

Adolphus, Telima; Omeodu, Doris

2016-01-01

The study investigates the effect of gender and collaborative learning approach on students' conceptual understanding of electromagnetic induction in Secondary Schools in Nigeria. Three research questions and 2 hypotheses were formulated to guide the research. The research design adopted for this study is the quasi-experimental design. In…

Non-Thermal Electromagnetic Radiation Damage to Lens Epithelium

PubMed Central

Bormusov, Elvira; P.Andley, Usha; Sharon, Naomi; Schächter, Levi; Lahav, Assaf; Dovrat, Ahuva

2008-01-01

High frequency microwave electromagnetic radiation from mobile phones and other modern devices has the potential to damage eye tissues, but its effect on the lens epithelium is unknown at present. The objective of this study was to investigate the non-thermal effects of high frequency microwave electromagnetic radiation (1.1GHz, 2.22 mW) on the eye lens epithelium in situ. Bovine lenses were incubated in organ culture at 35°C for 10-15 days. A novel computer-controlled microwave source was used to investigate the effects of microwave radiation on the lenses. 58 lenses were used in this study. The lenses were divided into four groups: (1) Control lenses incubated in organ culture for 10 to15 days. (2) Electromagnetic radiation exposure group treated with 1.1 GHz, 2.22 mW microwave radiation for 90 cycles of 50 minutes irradiation followed by 10 minutes pause and cultured up to 10 days. (3) Electromagnetic radiation exposure group treated as group 2 with 192 cycles of radiation and cultured for 15 days. (4) Lenses exposed to 39.5ºC for 2 hours 3 times with 24 hours interval after each treatment beginning on the second day of the culture and cultured for 11 days. During the culture period, lens optical quality was followed daily by a computer-operated scanning laser beam. At the end of the culture period, control and treated lenses were analyzed morphologically and by assessment of the lens epithelial ATPase activity. Exposure to 1.1 GHz, 2.22 mW microwaves caused a reversible decrease in lens optical quality accompanied by irreversible morphological and biochemical damage to the lens epithelial cell layer. The effect of the electromagnetic radiation on the lens epithelium was remarkably different from those of conductive heat. The results of this investigation showed that electromagnetic fields from microwave radiation have a negative impact on the eye lens. The lens damage by electromagnetic fields was distinctly different from that caused by conductive heat. PMID:19517034

Toward the Kelvin’s Formula Paradox

DTIC Science & Technology

2016-09-01

at rest no matter what its constitutive equation will be. 15. SUBJECT TERMS thermodynamics , electromagnetism, ponderomotive forces, Kelvin’s...a novel, mostly thermodynamic , analysis of the electromagnetic forces, acting in polarizable materials. When fulfilling those V&V studies of

Electromagnetism Adapted for Life Science Students

ERIC Educational Resources Information Center

Gurr, F. M.; And Others

1974-01-01

Describes the study of electronics as a terminal course in electromagnetism. A lecture-laboratory approach is used with a strong emphasis on practical experience. Outlines the major topics of the lecture program and describes the activities used in the laboratory. (GS)

B Removal by Zr Addition in Electromagnetic Solidification Refinement of Si with Si-Al Melt

NASA Astrophysics Data System (ADS)

Lei, Yun; Ma, Wenhui; Sun, Luen; Dai, Yongnian; Morita, Kazuki

2016-02-01

This study investigated a new process of enhancing B removal by adding small amounts of Zr in the electromagnetic solidification refinement of Si with Si-Al melt. B in Si was removed by as much as 97.2 pct by adding less than 1057 ppma Zr, and the added Zr was removed by as much as 99.7 pct. In addition, Zr is more effective in enhancing B removal than Ti in the same electromagnetic solidification refining process.

Reducing electromagnetic irradiation and fields alleviates experienced health hazards of VDU work.

PubMed

Hagström, M; Auranen, J; Johansson, O; Ekman, R

2012-04-01

Word Heath Organisation (WHO) outlined in 2005 recommendations, how to treat people suffering from the functional impairment electrohypersensitivity in its document "Electromagnetic fields and public health". Unfortunately the reduction of electromagnetic fields was not considered as a treatment option. The aim of the current study was to shield the computer user from the emitted electromagnetic irradiation and fields and to correlate that to the subjective symptoms reported by electrohypersensitive volunteers. The irradiation of the shielding cabinets was recorded. They housed either separate computer screens or whole laptops. When the volunteers had used the shielding cabinet for 1-7 years, they were able work with their computers whole working day, Those who had used the shielding cabined for 2-3 months were partially symptom free. The person who had used the cabinet only for 1 week reported some alleviation of her nausea. it seems that reducing the electromagnetic irradiation of the computer can lessen the symptoms of electrohypersensitivity and permit working without problems. Further studies are needed to clarify how the symptoms of different organ systems recover and make computer users to work also professionally. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Joint Electromagnetic Spectrum Management Operations

DTIC Science & Technology

2012-03-20

electromagnetic radiation to ordnance ( HERO ), hazards of electromagnetic radiation to fuels (HERF), and natural phenomena effects of lightning and...fuels HERO hazards of electromagnetic radiation to ordnance HERP hazards of electromagnetic radiation to personnel HF high frequency HN host... electromagnetic pulse (EMP); hazards of EM radiation to personnel, ordnance ,

Electromagnetic Spectrum Test and Evaluation Process

DTIC Science & Technology

2010-01-01

HERO , hazards of electromagnetic radiation to ordnance ; HERP, hazards of electromagnetic radiation to personnel; HERF, hazards of electromagnetic ... electromagnetic pulse (EMP); electronic protection; electrostatic dis- charge (ESD); hazards of electromagnetic radi- ation to personnel (HERP), ordnance ...including ordnance containing electrically initiated devices, to be mutually compatible in their intended

Numerical Study of Plasmonic Efficiency of Gold Nanostripes for Molecule Detection

PubMed Central

2015-01-01

In plasmonics, the accurate computation of the electromagnetic field enhancement is necessary in determining the amplitude and the spatial extension of the field around nanostructures. Here, the problem of the interaction between an electromagnetic excitation and gold nanostripes is solved. An optimization scheme, including an adaptive remeshing process with error estimator, is used to solve the problem through a finite element method. The variations of the electromagnetic field amplitude and the plasmonic active zones around nanostructures for molecule detection are studied in this paper taking into account the physical and geometrical parameters of the nanostripes. The evolution between the sizes and number of nanostripes is shown. PMID:25734184

Phase control of squeezed state in double electromagnetically induced transparency system with a loop-transition structure

NASA Astrophysics Data System (ADS)

Li, Yuan; Zhou, Yusheng; Wang, Yong; Ling, Qiang; Chen, Bing; Dou, Yan; Zhang, Wei; Gao, Weiqing; Guo, Zhiqiang; Zhang, Junxiang

2018-03-01

We theoretically study the squeezed probe light passing through a double electromagnetically induced transparency (DEIT) system, in which a microwave field and two coupling lights drive a loop transition. It is shown that the output squeezing can be maintained in both two transparency windows of DEIT, and it can also be manipulated by the relative phase of the three driving fields. The influence of the intensity of applied fields and the optical depth of atoms on the squeezing is also investigated. This study offers possibilities to manipulate the squeezing propagation in atomic media by the phase of electromagnetic fields.

Electromagnetic hypersensitivity: The opinion of an observer neurologist

NASA Astrophysics Data System (ADS)

Marc-Vergnes, Jean-Pierre

2010-11-01

Electromagnetic hypersensitivity (EHS) is a recent, uncertain and somehow confusing concept. It is now widely agreed that people claiming to be EHS really experience symptoms. However, no evidence for a causal link between the symptoms and electromagnetic fields (EMF) has been reported. Thus, we have to wonder whether EHS constitutes truly a relevant entity. Most of the previous studies suffer from methodological flaws. Owing to the quantification of symptoms, the interdisciplinary assessment of patients, and the use of personal exposimeters, the recent studies are of better quality. A set of convergent associated signs suggests that individual neuropsychic factors take a prominent, but maybe not unique, part in this condition.

[Patient exposure to electromagnetic fields in magnetic resonance scanners: a review].

PubMed

Guibelalde del Castillo, E

2013-12-01

The use of non-ionizing electromagnetic fields in the low frequency end of the electromagnetic spectrum and static fields, radiofrequencies (RF), and microwaves is fundamental both in modern communication systems and in diagnostic medical imaging techniques like magnetic resonance imaging (MRI). The proliferation of these applications in recent decades has led to intense activity in developing regulations to guarantee their safety and to the establishment of guidelines and legal recommendations for the public, workers, and patients. In April 2012 it was foreseen that the European Parliament and Council would approve and publish a directive on the minimum health and safety requirements regarding the exposure of workers to the risks arising from electromagnetic fields, which would modify Directive 2004/40/EC. New studies related to the exposure to electromagnetic radiation and its impact on health published in recent years have led to a new postponement, and it is now foreseen that the directive will come into effect in October 2013. One of the most noteworthy aspects of the new version of the directive is the exclusion of the limits of occupational exposure to electromagnetic fields in the clinical use of MRI. In exchange for this exception, physicians and experts in protection against non-ionizing radiation are asked to make additional efforts to train workers exposed to non-ionizing radiation and to establish mechanisms to guarantee the correct application of non-ionizing electromagnetic fields in patients, along similar lines to the principles of justification and optimization established for ionizing radiation. On the basis of the most recently published studies, this article reviews some safety-related aspects to take into account when examining patients with MRI with high magnetic fields. Copyright © 2013 SERAM. Published by Elsevier Espana. All rights reserved.

Contribution of electromagnetic and tomographic technique to the study of the impact of salinity in soils of the experimental station of Al Ain Atti (Errachidia, Morocco)

NASA Astrophysics Data System (ADS)

Benamara, A.; El Harnafi, M.; Ammar, A.

2017-03-01

Soil salinity is widespread particularly in arid areas. Much work has been done to remedy this natural contamination and make them more favorable to receive experimental soil of vegetation adapted to grow in these contrasting environments of scarce water resources. Over the 80 years, Morocco has experienced excessive dryness whose effects have been severely felt in the region of Errachidia. The depletion of the Quaternary alluvial aquifer has required the exploitation of deep reservoirs. In order to optimize the use of salt water in arid, the Institute of Agricultural Research tested soil experimenting three plant species; the Triplex, Acacia and Cypress. This experiment was not only economic objectives; increasing agricultural yields and production, but also reduce the impact of desertification in this region. So these are environmental reasons which have led researchers to realize this experiment whose purpose is to examine the ability of these plants to grow and adapt to irrigation by saline water from the deep aquifer in place. The experimental site is located on the left bank of the national road to Erfoud (Errachidia). In its entirety, the redesigned covering about 10 hectares. The studies that have been conducted mainly concerned pedogenetic analyzes and observations the development height of the plantation tested, regardless of the experimental ground heterogeneity. This is why we undertook a geophysical survey which aims to provide information on the quality of the tested soils and accumulation of salinity at different depths of the experimental ground. To achieve our goal, we used the technique of electrical and electromagnetic investigation in order to identify the main lines of a possible spatial heterogeneity. Recall that the work of OKAY (2010) on an experiment coring by examining the evolution of the newly formed fracturing have proved that the result of resistivity measurement is correlated with that of the chargeability. The electrical resistivity is closely related to the concentration of mineral particles. Characterization studies at the La Ronde tailings mine (Agnico-Eagle Ltd, in Abitibi), showed quite encouraging results (Campos, 2004; Anterrieu, 2006). Since it is a salt-bearing areas (highly conductive) and given that the induced polarization is very sensitive to the ground conductivity; by measurement of residual potential, so we took measures chargeability tomography, the result is compared to the resistivity measured at different soils (control and irrigated), which will better clarify the impact of salinity on the quality of the disturbed soil. Indeed, the chargeability response it possible to characterize the different irrigated soils and its variation is attributed not only to the effect of saline irrigation but also the existence of an heterogeneity of the original ground. Prospecting in electrical tomography has displayed vertically and horizontally anomalies existing within the experimental site of the station of Ain Al Atti, it showed that: - accumulation of salinity becomes wider going from the control ground to that of Acacias. - surveyed the ground at least appear more homogeneous in surface, but their conductivity varies in depth. - salinity origin and the concretion formed on the surface greatly influenced chargeability and resistivity measured on the different experimental soils.

Effects of Millimeter-Wave Electromagnetic Radiation on the Experimental Model of Migraine.

PubMed

Sivachenko, I B; Medvedev, D S; Molodtsova, I D; Panteleev, S S; Sokolov, A Yu; Lyubashina, O A

2016-02-01

Effects of millimeter-wave electromagnetic radiation (40 GHz frequency, 0.01 mW power) on the spontaneous fi ring of convergent neurons of the spinal trigeminal nucleus and their responses to electrical stimulation of the dura mater were studied in neurophysiological experiments on rats. Irradiation of the area of cutaneous receptive fields of spinal trigeminal nucleus reversibly inhibited both spontaneous discharges and activity induced by electrical stimulation of the dura mater. The second and third exposures to electromagnetic radiation with an interval of 10 min were ineffective. These results suggest that suppression of neuronal excitability in the spinal trigeminal ganglion can be a mechanism of the anti-migraine effects of electromagnetic radiation observed in clinical practice.

Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cadena, M. S. Reyes; Chapul, L. Sanchez; Perez, Javier

2008-08-11

We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-{beta}) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animalsmore » subjected to ELF together with the transfer factor.« less

Designed electromagnetic pulsed therapy: clinical applications.

PubMed

Gordon, Glen A

2007-09-01

First reduced to science by Maxwell in 1865, electromagnetic technology as therapy received little interest from basic scientists or clinicians until the 1980s. It now promises applications that include mitigation of inflammation (electrochemistry) and stimulation of classes of genes following onset of illness and injury (electrogenomics). The use of electromagnetism to stop inflammation and restore tissue seems a logical phenomenology, that is, stop the inflammation, then upregulate classes of restorative gene loci to initiate healing. Studies in the fields of MRI and NMR have aided the understanding of cell response to low energy EMF inputs via electromagnetically responsive elements. Understanding protein iterations, that is, how they process information to direct energy, we can maximize technology to aid restorative intervention, a promising step forward over current paradigms of therapy.

Electromagnetic Launch Vehicle Fairing and Acoustic Blanket Model of Received Power Using FEKO

NASA Technical Reports Server (NTRS)

Trout, Dawn H.; Stanley, James E.; Wahid, Parveen F.

2011-01-01

Evaluating the impact of radio frequency transmission in vehicle fairings is important to electromagnetically sensitive spacecraft. This study employs the multilevel fast multipole method (MLFMM) from a commercial electromagnetic tool, FEKO, to model the fairing electromagnetic environment in the presence of an internal transmitter with improved accuracy over industry applied techniques. This fairing model includes material properties representative of acoustic blanketing commonly used in vehicles. Equivalent surface material models within FEKO were successfully applied to simulate the test case. Finally, a simplified model is presented using Nicholson Ross Weir derived blanket material properties. These properties are implemented with the coated metal option to reduce the model to one layer within the accuracy of the original three layer simulation.

Application of electromagnetic-acoustic transducers for nondestructive testing in steel bridge structures.

DOT National Transportation Integrated Search

1996-01-01

This report presents the results of a study to (1) assess the applicability of electromagnetic-acoustic transducers for nondestructive evaluation of stresses in bridge structures and (2) evaluate the new ultrasonic instruments as an effective techniq...

Validating electromagnetic walking stick rail surface crack measuring systems : final report.

DOT National Transportation Integrated Search

2016-06-01

A series of field studies were undertaken to evaluate electromagnetic walking stick systems and their ability to measure the depth : of damage from surface breaking cracks. In total, four railroads, and four suppliers participated in the project. The...

Electromagnetic disturbance of electric drive system signal is extracted based on PLS

NASA Astrophysics Data System (ADS)

Wang, Yun; Wang, Chuanqi; Yang, Weidong; Zhang, Xu; Jiang, Li; Hou, Shuai; Chen, Xichen

2018-05-01

At present ISO11452 and GB/T33014 specified by electromagnetic immunity are narrowband electromagnetic radiation, but our exposure to electromagnetic radiation at ordinary times is not only a narrowband electromagnetic radiation, and some broadband electromagnetic radiation, and even some of the more complex electromagnetic environment. In terms of Electric vehicles, electric drive system is a kind of complex electromagnetic disturbance source, is not only a narrow-band signal, there are a lot of broadband signal, this paper puts forward PLS data processing method is adopted to analyze the electric drive system of electromagnetic disturbance, this kind of method to extract the data can be provide reliable data support for future standards.

Joint Services Electronics Program

NASA Astrophysics Data System (ADS)

Tinkham, Michael

1989-07-01

Topics addressed include: Electronic Theory of Semiconductor Alloys and Superlattices; Pressure Dependence of Photo Luminescence Excitation in GaAs/Al(x)Ga(1-x)As Multi-Quantum Wells; X Ray Surface Characterization; High Temperature Superconductivity; Quantum and Charging Phenomena in Mesoscopic Josephson Junctions; Nonlinear Dynamics of Electronic Neural Networks; Structural and Electronic Studies of Semiconductor Interfaces and Surfaces; Interaction of Ultrashort Laser Pulses with Semiconductor Surfaces; Multiphoton Vibrational Excitation of Molecules; Analytical and Numerical Determination of the Fields of Antennas near an Interface Between Two Half-Spaces with Significantly Different Wave Numbers; Theoretical Study of Lateral-Wave Propagation in Horizontally-Layered Media; Lateral Electromagnetic Waves from a Horizontal Antenna for Remote Sensing in the Ocean; Lateral Electromagnetic Pulses Generated by Horizontal and Vertical Dipoles on the Boundary Between Two Dielectrics; Theoretical Study of Isolated and Coupled Strip Antennas; Theoretical Study of Electromagnetic Pulses with a Slow Rate of Decay; Experimental Study of Electromagnetic Pulses with a Slow Rate of Decay; Properties of Closed Loops of Pseudodipoles; Asymptotic Solution for the Charge and Current Near the Open End of a Linear Tubular Antenna; Closed Loops of Parallel Coplanar Dipoles - Electrically Short Elements; Harmonic Generation in High-Temperature Superconductors and Resonant Closed Loops of Dipoles.

Broadband electromagnetic analysis of compacted kaolin

NASA Astrophysics Data System (ADS)

Bore, Thierry; Wagner, Norman; Cai, Caifang; Scheuermann, Alexander

2017-01-01

The mechanical compaction of soil influences not only the mechanical strength and compressibility but also the hydraulic behavior in terms of hydraulic conductivity and soil suction. At the same time, electric and dielectric parameters are increasingly used to characterize soil and to relate them with mechanic and hydraulic parameters. In the presented study electromagnetic soil properties and suction were measured under defined conditions of standardized compaction tests. The impact of external mechanical stress conditions of nearly pure kaolinite was analyzed on soil suction and broadband electromagnetic soil properties. An experimental procedure was developed and validated to simultaneously determine mechanical, hydraulic and broadband (1 MHz-3 GHz) electromagnetic properties of the porous material. The frequency dependent electromagnetic properties were modeled with a classical mixture equation (advanced Lichtenecker and Rother model, ALRM) and a hydraulic-mechanical-electromagnetic coupling approach was introduced considering water saturation, soil structure (bulk density, porosity), soil suction (pore size distribution, water sorption) as well as electrical conductivity of the aqueous pore solution. Moreover, the relaxation behavior was analyzed with a generalized fractional relaxation model concerning a high-frequency water process and two interface processes extended with an apparent direct current conductivity contribution. The different modeling approaches provide a satisfactory agreement with experimental data for the real part. These results show the potential of broadband electromagnetic approaches for quantitative estimation of the hydraulic state of the soil during densification.

A Comparative Study of the Precision of Carstens and Northern Digital Instruments Electromagnetic Articulographs

ERIC Educational Resources Information Center

Savariaux, Christophe; Badin, Pierre; Samson, Adeline; Gerber, Silvain

2017-01-01

Purpose: This study compares the precision of the electromagnetic articulographs used in speech research: Northern Digital Instruments' Wave and Carstens' AG200, AG500, and AG501 systems. Method: The fluctuation of distances between 3 pairs of sensors attached to a manually rotated device that can position them inside the measurement volumes was…

The Relationship between Pre-Service Teachers' Awareness Levels of Electromagnetic Pollution and Other Environmental Problems

ERIC Educational Resources Information Center

Koklukaya, Ayse Nesibe; Guven Yildirim, Ezgi; Selvi, Mahmut

2017-01-01

Purpose: The purpose of this study is to find out the relationship between the awareness level of preservice science teachers' conscious use of technological devices, which cause electromagnetic pollution, and their awareness level of related environmental problems. Research Methods: In this study, a mixed design method was used. A relational…

Debye screening and a Thomas - Fermi model of a dyonic atom in a two potential theory of electromagnetism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolf, C.

1993-02-01

We study the screening of a central Abelian dyon by a surrounding dyon cloud in a two potential theory of electromagnetism. A generalized formula for the Debye screening length is obtained and a Thomas - Fermi Model for a charged cloud surrounding a central Dyonic Core is studied. 20 refs.

Preparation and characterization of TiO2 coated Fe nanofibers for electromagnetic wave absorber.

PubMed

Jang, Dae-Hwan; Song, Hanbok; Lee, Young-In; Lee, Kun-Jae; Kim, Ki Hyeon; Oh, Sung-Tag; Lee, Sang-Kwan; Choa, Yong-Ho

2011-01-01

Recently, electromagnetic interference (EMI) and electromagnetic compatibility (EMC) have become serious problems due to the growth of electronic device and next generation telecommunication. It is necessary to develop new electromagnetic wave absorbing material to overcome the limitation of electromagnetic wave shielding materials. The EMI attenuation is normally related to magnetic loss and dielectric loss. Therefore, magnetic material coating dielectric materials are required in this reason. In this study, TiO2 coated Fe nanofibers were prepared to improve their properties for electromagnetic wave absorption. Poly(vinylpyrrolidone) (PVP) and Iron (III) nitrate nonahydrate (Fe(NO3)3 x 9H2O) were used as starting materials for the synthesis of Fe oxide nanofibers. Fe oxide nanofibers were prepared by electrospinning in an electric field and heat treatment. TiO2 layer was coated on the surface of Fe oxide nanofibers using sol-gel process. After the reduction of TiO2 coated Fe oxide nanofibers, Fe nanofibers with a TiO2 coating layer of about 10 nm were successfully obtained. The morphology and structure of fibers were characterized by SEM, TEM, and XRD. In addition, the absorption properties of TiO2 coated Fe nanofibers were measured by network analyzer.

Human Health and Exposure to Electromagnetic Radiation

DTIC Science & Technology

1992-07-01

electromagnetic field exposures and cancer. Studies of electrical and electronic workers are suggestive of such a link, but are subject to the confounding factor ...associations between cancer and electrical installations 108 51 Factors associated with increased risk of childhood cancer in the Denver studies 109 52...It is important in epidemiological studies to make Arenuous efforts to adjust for possible confounding factors , many - in particular the early

A non-linear induced polarization effect on transient electromagnetic soundings

NASA Astrophysics Data System (ADS)

Hallbauer-Zadorozhnaya, Valeriya Yu.; Santarato, Giovanni; Abu Zeid, Nasser; Bignardi, Samuel

2016-10-01

In a TEM survey conducted for characterizing the subsurface for geothermal purposes, a strong induced polarization effect was recorded in all collected data. Surprisingly, anomalous decay curves were obtained in part of the sites, whose shape depended on the repetition frequency of the exciting square waveform, i.e. on current pulse length. The Cole-Cole model, besides being not directly related to physical parameters of rocks, was found inappropriate to model the observed distortion, due to induced polarization, because this model is linear, i.e. it cannot fit any dependence on current pulse. This phenomenon was investigated and explained as due to the presence of membrane polarization linked to constrictivity of (fresh) water-saturated pores. An algorithm for mathematical modeling of TEM data was then developed to fit this behavior. The case history is then discussed: 1D inversion, which accommodates non-linear effects, produced models that agree quite satisfactorily with resistivity and chargeability models obtained by an electrical resistivity tomography carried out for comparison.

Identifying Treatment Response of Sertraline in a Teenager with Selective Mutism using Electrophysiological Neuroimaging

PubMed Central

Eugene, Andy R.; Masiak, Jolanta

2016-01-01

Background Selective Mutism is described as the inability to verbally express oneself in anxiety provoking social situations and may result in awkward social interactions in school-aged children. In this case-report we present the baseline electrophysiological neuroimaging results and after treatment with Sertraline for 6-weeks. Methods A 20-channel EEG event-related potential recording was acquired during an internal voice task at baseline prior to the initiation of 50mg of Sertraline and then repeated 6-weeks after treatment with Sertraline. EEG signals were processed for movement, eye-blink, and muscle artifacts and ERP signal averaging was completed. ERPs were analyzed using Standard Low Resolution Brain Electromagnetic Tomography (sLORETA). Results At baseline, Sertraline increased the neuronal activation in the middle temporal gyrus and the anterior cingulate gyrus from baseline in the patient following 6-weeks of treatment. Conclusion Our findings suggest that electrophysiological neuroimaging may provide a creative approach for personalizing medicine by providing insight to the pharmacodynamics of antidepressants. PMID:27468379

Identifying Treatment Response of Sertraline in a Teenager with Selective Mutism using Electrophysiological Neuroimaging.

PubMed

Eugene, Andy R; Masiak, Jolanta

2016-06-01

Selective Mutism is described as the inability to verbally express oneself in anxiety provoking social situations and may result in awkward social interactions in school-aged children. In this case-report we present the baseline electrophysiological neuroimaging results and after treatment with Sertraline for 6-weeks. A 20-channel EEG event-related potential recording was acquired during an internal voice task at baseline prior to the initiation of 50mg of Sertraline and then repeated 6-weeks after treatment with Sertraline. EEG signals were processed for movement, eye-blink, and muscle artifacts and ERP signal averaging was completed. ERPs were analyzed using Standard Low Resolution Brain Electromagnetic Tomography (sLORETA). At baseline, Sertraline increased the neuronal activation in the middle temporal gyrus and the anterior cingulate gyrus from baseline in the patient following 6-weeks of treatment. Our findings suggest that electrophysiological neuroimaging may provide a creative approach for personalizing medicine by providing insight to the pharmacodynamics of antidepressants.

Quantum state and mode profile tomography by the overlap

NASA Astrophysics Data System (ADS)

Tiedau, J.; Shchesnovich, V. S.; Mogilevtsev, D.; Ansari, V.; Harder, G.; Bartley, T. J.; Korolkova, N.; Silberhorn, Ch

2018-03-01

Any measurement scheme involving interference of quantum states of the electromagnetic field necessarily mixes information about the spatiotemporal structure of these fields and quantum states in the recorded data. We show that in this case, a trade-off is possible between extracting information about the quantum states and the structure of the underlying fields, with the modal overlap being either a goal or a convenient tool of the reconstruction. We show that varying quantum states in a controlled way allows one to infer temporal profiles of modes. Vice versa, for the known quantum state of the probe and controlled variable overlap, one can infer the quantum state of the signal. We demonstrate this trade-off by performing an experiment using the simplest on-off detection in an unbalanced weak homodyning scheme. For the single-mode case, we demonstrate experimentally inference of the overlap and a few-photon signal state. Moreover, we show theoretically that the same single-detector scheme is sufficient even for arbitrary multi-mode fields.

First observations of large-scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite

NASA Astrophysics Data System (ADS)

Thampi, Smitha V.; Yamamoto, Mamoru; Tsunoda, Roland T.; Otsuka, Yuichi; Tsugawa, Takuya; Uemoto, Jyunpei; Ishii, Mamoru

2009-09-01

First observations of large-scale wave structure (LSWS) and the subsequent development of equatorial spread F (ESF), using total electron content (TEC) derived from the ground based reception of beacon signals from the CERTO (Coherent Electromagnetic Radio Tomography) radio beacon on board C/NOFS (Communications/Navigation Outage Forecasting System) satellite, are presented. Selected examples of TEC variations, using measurements made during January 2009 from Bac Lieu, Vietnam (9.2°N, 105.6°E geographic, 1.7°N magnetic dip latitude) are presented to illustrate two key findings: (1) LSWS appears to play a more important role in the development of ESF than the post-sunset rise (PSSR) of the F-layer, and (2) LSWS can appear well before E region sunset. Other findings, that LSWS does not have significant zonal drift in the initial stages of growth, and can have zonal wavelengths of several hundred kilometers, corroborate earlier reports.

Advances in PET/MR instrumentation and image reconstruction.

PubMed

Cabello, Jorge; Ziegler, Sibylle I

2018-01-01

The combination of positron emission tomography (PET) and MRI has attracted the attention of researchers in the past approximately 20 years in small-animal imaging and more recently in clinical research. The combination of PET/MRI allows researchers to explore clinical and research questions in a wide number of fields, some of which are briefly mentioned here. An important number of groups have developed different concepts to tackle the problems that PET instrumentation poses to the exposition of electromagnetic fields. We have described most of these research developments in preclinical and clinical experiments, including the few commercial scanners available. From the software perspective, an important number of algorithms have been developed to address the attenuation correction issue and to exploit the possibility that MRI provides for motion correction and quantitative image reconstruction, especially parametric modelling of radiopharmaceutical kinetics. In this work, we give an overview of some exemplar applications of simultaneous PET/MRI, together with technological hardware and software developments.

Effectiveness of low-cost electromagnetic shielding using nail-together galvanized steel: Test results. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, P.F.; Kennedy, E.L.; McCormack, R.G.

1992-09-01

The sensitivity of modern electronic equipment has increased the need for costly electromagnetic shielding. To reduce this cost, the U.S. Army Construction Engineering Research Laboratories (USACERL) has developed a new concept for shielding design that uses 28-gauge galvanized steel and standard galvanized nails. In this study, an electromagnetically shielded structure using the concept was designed, built, and evaluated for shielding effectiveness. The galvanized material was mounted to the standard USACERL test aperture and nailed to the wooden module frame, and the shielding effectiveness of the new construction design was measured using radio frequency antennas and receivers. Evaluations showed that themore » nail-together structure proved adequate for many shielding applications. However, while the galvanized steel met most shielding application requirements, this process added multiple seams to the structure, which decreased shielding in many instances by as much as 40 dB. Electromagnetic shielding, Electromagnetic pulse C3I Facilities.« less

An electromagnetic modulator based on electrically controllable metamaterial analogue to electromagnetically induced transparency.

PubMed

Fan, Yuancheng; Qiao, Tong; Zhang, Fuli; Fu, Quanhong; Dong, Jiajia; Kong, Botao; Li, Hongqiang

2017-01-16

Electromagnetically induced transparency (EIT) is a promising technology for the enhancement of light-matter interactions, and recent demonstrations of the EIT analogue realized in artificial micro-structured medium have remarkably reduced the extreme requirement for experimental observation of EIT spectrum. In this paper, we propose to electrically control the EIT-like spectrum in a metamaterial as an electromagnetic modulator. A diode acting as a tunable resistor is loaded in the gap of paired wires to inductively tune the magnetic resonance, which induces remarkable modulation on the EIT-like spectrum through the metamaterial sample. The experimental measurements confirmed that the prediction of electromagnetic modulation in three narrow bands on the EIT-like spectrum, and a modulation contrast of up to 31 dB was achieved on the transmission through the metamaterial. Our results may facilitate the study on active/dynamical technology in translational metamaterials, which connect extraordinary manipulations on the flow of light in metamaterials, e.g., the exotic EIT, and practical applications in industry.

Primary experimental study on safety of deep brain stimulation in RF electromagnetic field.

PubMed

Jun, Xu; Luming, Li; Hongwei, Hao

2009-01-01

With the rapid growth of clinical application of Deep Brain Stimulation, its safety and functional concern in the electromagnetic field, another pollution becoming much more serious, has become more and more significant. Meanwhile, the measuring standards on Electromagnetic Compatibility (EMC) for DBS are still incomplete. Particularly, the knowledge of the electromagnetic field induced signals on the implanted lead is ignorant while some informal reports some side effects. This paper briefly surmised the status of EMC standards on implantable medical devices. Based on the EMC experiments of DBS device we developed, two experiments for measuring the induced voltage of the deep brain stimulator in RF electromagnetic field were reported. The measured data showed that the induced voltage in some frequency was prominent, for example over 2V. As a primary research, we think these results would be significant to cause researcher to pay more attention to the EMC safety problem and biological effects of the induced voltage in deep brain stimulation and other implantable devices.

Calculation of electromagnetic force in electromagnetic forming process of metal sheet

NASA Astrophysics Data System (ADS)

Xu, Da; Liu, Xuesong; Fang, Kun; Fang, Hongyuan

2010-06-01

Electromagnetic forming (EMF) is a forming process that relies on the inductive electromagnetic force to deform metallic workpiece at high speed. Calculation of the electromagnetic force is essential to understand the EMF process. However, accurate calculation requires complex numerical solution, in which the coupling between the electromagnetic process and the deformation of workpiece needs be considered. In this paper, an appropriate formula has been developed to calculate the electromagnetic force in metal work-piece in the sheet EMF process. The effects of the geometric size of coil, the material properties, and the parameters of discharge circuit on electromagnetic force are taken into consideration. Through the formula, the electromagnetic force at different time and in different positions of the workpiece can be predicted. The calculated electromagnetic force and magnetic field are in good agreement with the numerical and experimental results. The accurate prediction of the electromagnetic force provides an insight into the physical process of the EMF and a powerful tool to design optimum EMF systems.

Electromagnetic Effects Harmonization Working Group (EEHWG) - Lightning Task Group : report on aircraft lightning strike data

DOT National Transportation Integrated Search

2002-07-01

In 1995, in response to the lightning community's desire to revise the zoning criteria on aircraft, the Electromagnetic Effects Harmonization Working Group (EEHWG) decided that lightning attachments to aircraft causing damage should be studied and co...

Podolsky electromagnetism at finite temperature: Implications on the Stefan-Boltzmann law

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonin, C. A.; Bufalo, R.; Pimentel, B. M.

2010-01-15

In this work we study Podolsky electromagnetism in thermodynamic equilibrium. We show that a Podolsky mass-dependent modification to the Stefan-Boltzmann law is induced and we use experimental data to limit the possible values for this free parameter.

A study of occurrence rates of Electromagnetic Interference (EMI) to aircraft with a focus on HIRF (external) High Intensity Radiated Fields

NASA Technical Reports Server (NTRS)

Shooman, Martin L.

1994-01-01

This report presents the methodology and results of a subjective study done by Polytechnic University to investigate Electromagnetic Interference (EMI) events on aircraft. The results cover various types of EMI from on-board aircraft systems, passenger carry-on devices, and externally generated disturbances. The focus of the study, however, was on externally generated EMI, termed High Intensity Radiated Fields (HIRF), from radars, radio and television transmitters, and other man-made emitters of electromagnetic energy. The study methodology used an anonymous questionnaire distributed to experts to gather the data. This method is known as the Delphi or Consensus Estimation technique. The questionnaire was sent to an expert population of 230 and there were 57 respondents. Details of the questionnaire, a few anecdotes, and the statistical results of the study are presented.

Considerations for human exposure standards for fast-rise-time high-peak-power electromagnetic pulses.

PubMed

Merritt, J H; Kiel, J L; Hurt, W D

1995-06-01

Development of new emitter systems capable of producing high-peak-power electromagnetic pulses with very fast rise times and narrow pulse widths is continuing. Such directed energy weapons systems will be used in the future to defeat electronically vulnerable targets. Human exposures to these pulses can be expected during testing and operations. Development of these technologies for radar and communications purposes has the potential for wider environmental exposure, as well. Current IEEE C95.1-1991 human exposure guidelines do not specifically address these types of pulses, though limits are stated for pulsed emissions. The process for developing standards includes an evaluation of the relevant bioeffects data base. A recommendation has been made that human exposure to ultrashort electromagnetic pulses that engender electromagnetic transients, called precursor waves, should be avoided. Studies that purport to show the potential for tissue damage induced by such pulses were described. The studies cited in support of the recommendation were not relevant to the issues of tissue damage by propagated pulses. A number of investigations are cited in this review that directly address the biological effects of electromagnetic pulses. These studies have not shown evidence of tissue damage as a result of exposure to high-peak-power pulsed microwaves. It is our opinion that the current guidelines are sufficiently protective for human exposure to these pulses.

Next generation distal locking for intramedullary nails using an electromagnetic X-ray-radiation-free real-time navigation system.

PubMed

Hoffmann, Michael; Schröder, Malte; Lehmann, Wolfgang; Kammal, Michael; Rueger, Johannes Maria; Herrman Ruecker, Andreas

2012-07-01

Distal locking marks one challenging step during intramedullary nailing that can lead to an increased irradiation and prolonged operation times. The aim of this study was to evaluate the reliability and efficacy of an X-ray-radiation-free real-time navigation system for distal locking procedures. A prospective randomized cadaver study with 50 standard free-hand fluoroscopic-guided and 50 electromagnetic-guided distal locking procedures was performed. All procedures were timed using a stopwatch. Intraoperative fluoroscopy exposure time and absorbed radiation dose (mGy) readings were documented. All tibial nails were locked with two mediolateral and one anteroposterior screw. Successful distal locking was accomplished once correct placement of all three screws was confirmed. Successful distal locking was achieved in 98 cases. No complications were encountered using the electromagnetic navigation system. Eight complications arose during free-hand fluoroscopic distal locking. Undetected secondary drill slippage on the ipsilateral cortex accounted for most problems followed by undetected intradrilling misdirection causing a fissural fracture of the contralateral cortex while screw insertion in one case. Compared with the free-hand fluoroscopic technique, electromagnetically navigated distal locking provides a median time benefit of 244 seconds without using ionizing radiation. Compared with the standard free-hand fluoroscopic technique, the electromagnetic guidance system used in this study showed high reliability and was associated with less complications, took significantly less time, and used no radiation exposure for distal locking procedures. Therapeutic study, level II.

High-Altitude Electromagnetic Pulse (HEMP) Testing

DTIC Science & Technology

2015-07-09

Electromagnetic Pulse Horizontal Electromagnetic Pulse Advanced Fast Electromagnetic Pulse Nuclear Weapons Effect Testing and Environments 16. SECURITY... Weapons of Mass Destruction Agency (USANCA). In order to effectively determine criteria compliance, the TO/PE must thoroughly understand the...ELECTROMAGNETIC ENVIRONMENT AND EFFECTS. A.1 The electromagnetic environment produced by a nuclear weapon consists of the ionization of the atmosphere and

Electromagnetic Compatibility Design of the Computer Circuits

NASA Astrophysics Data System (ADS)

Zitai, Hong

2018-02-01

Computers and the Internet have gradually penetrated into every aspect of people’s daily work. But with the improvement of electronic equipment as well as electrical system, the electromagnetic environment becomes much more complex. Electromagnetic interference has become an important factor to hinder the normal operation of electronic equipment. In order to analyse the computer circuit compatible with the electromagnetic compatibility, this paper starts from the computer electromagnetic and the conception of electromagnetic compatibility. And then, through the analysis of the main circuit and system of computer electromagnetic compatibility problems, we can design the computer circuits in term of electromagnetic compatibility. Finally, the basic contents and methods of EMC test are expounded in order to ensure the electromagnetic compatibility of equipment.

Electromagnetic Radiofrequency Radiation Emitted from GSM Mobile Phones Decreases the Accuracy of Home Blood Glucose Monitors

PubMed Central

Mortazavi, SMJ; Gholampour, M; Haghani, M; Mortazavi, G; Mortazavi, AR

2014-01-01

Mobile phones are two-way radios that emit electromagnetic radiation in microwave range. As the number of mobile phone users has reached 6 billion, the bioeffects of exposure to mobile phone radiation and mobile phone electromagnetic interference with electronic equipment have received more attention, globally. As self-monitoring of blood glucose can be a beneficial part of diabetes control, home blood glucose testing kits are very popular. The main goal of this study was to investigate if radiofrequency radiation emitted from a common GSM mobile phone can alter the accuracy of home blood glucose monitors. Forty five female nondiabetic students aged 17-20 years old participated in this study. For Control-EMF group (30 students), blood glucose concentration for each individual was measured in presence and absence of radiofrequency radiation emitted by a common GSM mobile phone (HTC touch, Diamond 2) while the phone was ringing. For Control- Repeat group (15 students), two repeated measurements were performed for each participant in the absence of electromagnetic fields. The magnitude of the changes between glucose levels in two repeated measurements (|ΔC|) in Control-Repeat group was 1.07 ± 0.88 mg/dl while this magnitude for Control-EMF group was 7.53 ± 4.76 mg/dl (P < 0.001, two-tailed test). To the best of our knowledge, this is the first study to assess the electromagnetic interference in home blood glucose monitors. It can be concluded that electromagnetic interference from mobile phones has an adverse effect on the accuracy of home blood glucose monitors. We suggest that mobile phones should be used at least 50 cm away from home blood glucose monitors. PMID:25505778

Electromagnetic Radiofrequency Radiation Emitted from GSM Mobile Phones Decreases the Accuracy of Home Blood Glucose Monitors.

PubMed

Mortazavi, Smj; Gholampour, M; Haghani, M; Mortazavi, G; Mortazavi, Ar

2014-09-01

Mobile phones are two-way radios that emit electromagnetic radiation in microwave range. As the number of mobile phone users has reached 6 billion, the bioeffects of exposure to mobile phone radiation and mobile phone electromagnetic interference with electronic equipment have received more attention, globally. As self-monitoring of blood glucose can be a beneficial part of diabetes control, home blood glucose testing kits are very popular. The main goal of this study was to investigate if radiofrequency radiation emitted from a common GSM mobile phone can alter the accuracy of home blood glucose monitors. Forty five female nondiabetic students aged 17-20 years old participated in this study. For Control-EMF group (30 students), blood glucose concentration for each individual was measured in presence and absence of radiofrequency radiation emitted by a common GSM mobile phone (HTC touch, Diamond 2) while the phone was ringing. For Control- Repeat group (15 students), two repeated measurements were performed for each participant in the absence of electromagnetic fields. The magnitude of the changes between glucose levels in two repeated measurements (|ΔC|) in Control-Repeat group was 1.07 ± 0.88 mg/dl while this magnitude for Control-EMF group was 7.53 ± 4.76 mg/dl (P < 0.001, two-tailed test). To the best of our knowledge, this is the first study to assess the electromagnetic interference in home blood glucose monitors. It can be concluded that electromagnetic interference from mobile phones has an adverse effect on the accuracy of home blood glucose monitors. We suggest that mobile phones should be used at least 50 cm away from home blood glucose monitors.

Assessment of the Therapeutic Effectiveness of Deep Electromagnetic Stimulation in Patients with Chronic Low Back Pain.

PubMed

Przedborska, Agnieszka; Misztal, Małgorzata; Raczkowski, Jan W

2015-10-01

The study presents the results of the application of deep electromagnetic stimulation (DEMS) therapy in the treatment of low back pain. The study aimed to evaluate and compare pain severity before and after deep electromagnetic stimulation sessions and to assess persistence of the analgesic effect and identify factors which influenced it significantly. The study enrolled a series of 105 consecutive patients with chronic low back pain who underwent a series of 10 sessions of deep electromagnetic stimulation. The effectiveness of the therapy was assessed according to VAS and Laitinen scores. Risk factors significantly affecting the stability of analgesic effect after DEMS therapy were identified using the Cox regression model. Statistically significant pain relief was observed after deep electromagnetic therapy. Both the Laitinen and VAS scales demonstrated the reduction in pain intensity by half (Me (IQR): 6 (5-9) before the therapy vs. 3 (24) afterwards, p<0.0001 for Laitinen scale and 7 (6-8) before vs. 3 (2-5) after the therapy, p<0.0001 for VAS). During 12-month follow up, pain recurred in 84 (80%) patients. Pain recurrence within a year after the therapy was stimulated in a statistically significant manner by pain duration (HR=1.032, 95% CI: 0.988-1.078; p=0.032) and the co-occurrence of degenerative joint disease (HR=5.521, 95%CI: 2.905-10.493; p=0.001). 1. Deep electromagnetic stimulation is an effective treatment in patients with chronic low back pain. 2. The degree of effectiveness of this modality in the longer term depends on the cause and duration of pain.