Search NASA⌕ Search

SEARCH · Search NASA

Results for “ELECTROMAGNETIC FIELD”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Observation of the Electromagnetic Field Effect via Charge-Dependent Directed Flow in Heavy-Ion Collisions at the Relativistic Heavy Ion Collider

The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Noncentral collisions can produce strong magnetic fields on the order of 10 18 G , which offers a probe into the electrical conductivity of the QGP. In particular, quarks and antiquarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as v 1 ( y ) . Here, we present the charge-dependent measurements of d v 1 / d y near midrapidities for π ± , K ± , and p ( p ¯ ) in Au + Au and isobar ( Ru 44 96 + Ru 44 96 and Zr 40 96 + Zr 40 96 ) collisions at s NN = 200 GeV , and in Au + Au collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined dependence of the v 1 signal on collision system, particle species, and collision centrality can be qualitatively and semiquantitatively understood as several effects on constituent quarks. While the results in central events can be explained by the u and d quarks transported from initial-state nuclei, those in peripheral events reveal the impacts of the electromagnetic field on the QGP. Our data put valuable constraints on the electrical conductivity of the QGP in theoretical calculations. Published by the American Physical Society 2024

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Human electromagnetic field exposure in wearable communications systems: A review

While wearable technologies have taken essential parts of our daily lives, concerns on human health are often overseen. Mainly due to extreme proximity or direct physical contact to human skin, wearable communications devices are prone to cause higher levels of electromagnetic field (EMF) exposure at human skin surface than any other type of wireless technologies. Nevertheless, while focusing on theoretical aspects of human EMF exposure in wearable communications, prior work paid little to no attention on exact exposure levels generated by commercial wearable devices that are already widely used by public consumers. In this context, this paper provides an extensive review of SAR from various commercial wearable devices that are currently sold in the market, as well as the analytical framework and the current measurement methodologies for standard compliance tests. To extend the discussion to general wearable communications, this paper presents simulation results adopting representative antenna patterns, which leads to suggestion of separation distances to keep the current safety guidelines. In particular, considering the increasing interest in millimeter wave (mmW), this paper sheds light on EMF exposure evaluated at 60 GHz and compares to results from 2.4 GHz.

42 ENGINEERING↗
DOE OSTI2018

Quantum phases for point-like charged particles and for electrically neutral dipoles in an electromagnetic field

We point out that the known quantum phases for an electric/magnetic dipole moving in an electromagnetic (EM) field must be presented as the superposition of more fundamental quantum phases emerging for elementary charges. Using this idea, we find two new fundamental quantum phases for point-like charges, next to the known electric and magnetic Aharonov–Bohm (A–B) phases, named by us as the complementary electric and magnetic phases, correspondingly. We further demonstrate that these new phases can indeed be derived via the Schrödinger equation for a particle in an EM field, where however the operator of momentum is re-defined via the replacement of the canonical momentum of particle by the sum of its mechanical momentum and interactional field momentum for a system “charged particle and a macroscopic source of EM field”. The implications of the obtained results are discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Pulsed electromagnetic field induces Ca2+-dependent osteoblastogenesis in C3H10T1/2 mesenchymal cells through the Wnt-Ca2+/Wnt-β-catenin signaling pathway

Highlights: • C3H10T1/2 cell proliferation can be greatly promoted by PEMF exposure. • C3H10T1/2 cell differentiation into osteoblast can be induced upon the stimulation of PEMF. • Intracellular [Ca2+]i up-regulation was observed during the process of PEMF-induced C3H10T1/2 cell differentiation. • PEMF-induced C3H10T1/2 cell differentiation was Ca2+-dependent. • PEMF-induced [Ca2+]i elevation suggested a combination of Wnt/Ca2+ and Wnt/β-catenin signaling pathways. Pulsed electromagnetic fields (PEMFs) are effective in healing fractures and improving osteoporosis. However, their effect on mesenchymal cells remains largely unknown. In this study, the effects of PEMF on osteoblastogenesis and its underlying molecular signaling mechanisms were systematically investigated in C3H10T1/2 cells. C3H10T1/2 mesenchymal cells were exposed to 30-Hz PEMF bursts at various intensities for 3 consecutive days. The optimal PEMF exposure (30 Hz, 1 mT, 2 h/day) was applied in subsequent experiments. Our results suggest that intracellular [Ca{sup 2+}]i in C3H10T1/2 cells can be upregulated upon exposure to PEMF and that PEMF-induced C3H10T1/2 cell differentiation was Ca{sup 2+}-dependent. The pro-osteogenic effect of PEMF on Ca{sup 2+}-dependent osteoblast differentiation was then verified by alkaline phosphatase (ALP) and von Kossa staining. Furthermore, PEMF promoted the gene expression and protein synthesis of the Wnt/β-catenin pathway. Increased [Ca{sup 2+}]i in the nucleoplasm was followed by the mobilization and translocation of β-catenin into the nucleus in C3H10T1/2 cells. A model of Wnt/β-catenin signaling and the Wnt/Ca2+ signaling network is proposed. Taken together, these findings indicated for the first time that PEMF induces osteoblastogenesis through increased intracellular [Ca{sup 2+}]i and the Wnt-Ca2+/Wnt-β-catenin signaling pathway in C3H10T1/2 mesenchymal cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Asymptotic-preserving gyrokinetic implicit particle-orbit integrator for arbitrary electromagnetic fields

We extend the asymptotic preserving and energy conserving time integrator for charged-particle motion developed in Ricketson and Chacón (2020) to include finite Larmor-radius (FLR) effects in the presence of electric-field length-scales comparable to the particle gyro-radius (the gyro-kinetic limit). We introduce two modifications to the earlier scheme. The first is the explicit gyro-averaging of the electric field at the half time-step, along with an analogous modification to the current deposition, which we show preserves total energy conservation in implicit PIC schemes. The number of gyrophase samples is chosen adaptively, ensuring proper averaging for large timesteps and the recovery of full-orbit dynamics in the small time-step limit. The second modification is an alternating large and small time-step strategy that ensures the particle trajectory samples gyrophases evenly. We show that this strategy relaxes the time-step restrictions on the scheme, allowing even larger speed-ups than previously achievable. We demonstrate the new method with several single-particle motion tests in a variety of electromagnetic field configurations featuring gyro-scale variation in the electric field. Finally, the results demonstrate the advertised ability to capture FLR effects accurately even when significantly stepping over the gyration time-scale.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

On the Intensity of Radiation of an Electromagnetic Field by a Rotating Ferroelectric Sphere

It is shown that in the case when the spontaneous polarization vector P{sub 0} and the rotational frequency vector ω of a ferroelectric sphere do not coincide, electromagnetic waves will be radiated. The intensity of the radiation is calculated as a function of the coordinates and time, and the anisotropy of this radiation is proven. The distribution of the intensity of radiation is graphically illustrated in the form of a function of the central distance r.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Effects of near-field electromagnetic coupling in dimers of nanoparticles with a silver core and a J-aggregate dye shell

We report a theoretical study of the plasmon-exciton coupling effect on the absorption spectra of pairs of closely spaced double-layer hybrid nanoparticles consisting of a metallic core and a J-aggregate dye shell. The effect of frequency conversion of plasmonic lines due to the near-field interaction between plasmons and Frenkel excitons of the organic shell is demonstrated. The effect leads to the appearance of additional spectral lines in the long-wavelength part of the spectrum of the system of hybrid particles. The shapes and the relative intensities of the additional lines exactly reproduce the specific features of the original spectrum of plasmonic absorption bands in uncoated metallic nanoparticles. The discovered phenomenon can be used to design new types of high-sensitivity nanosensors, based on plasmon-exciton effects and principles of near-field optics. (nanophotonics)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Theoretical Modeling of Electromagnetic Field from Electron Bunches in Periodic Wire Medium

The interaction of relativistic electrons with periodic conducting structures results in radiation via a number of mechanisms. In case of crystals one obtains parametric X-ray radiation, its frequency is determined by the distance between crystallographic planes and the direction of electron beam. If instead of a crystal one considers a periodic structure of metallic wires with the spacing of the order of mm, it is plausible to expect the emission of radiation of a similar nature (“diffraction response”) at THz frequencies. Additionally, a “long-wave” radiation will occur in this case with wavelengths much larger then structure periods. In this contribution, we present different theoretical approaches for describing the electromagnetic radiation field from prolonged electron bunch propagated in the lattice of metallic wires. The validity of these analytical descriptions is checked by numerical simulations. We discuss the possible applications of aforementioned structure as sources of coherent THz radiation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Enhancement of local electromagnetic fields by periodic optical resonators

The periodically profiled metasurfaces of silicon and of the same surfaces coated with a thin layer of silver are experimentally investigated to improve the signal-to-noise ratio in the observation of Raman light scattering from molecular compounds. The noise in this case is the unavoidable background molecular luminescence. Our experimental and computer simulation data demonstrate an anomalous optical response due to the excitation of metal-dielectric surface resonances. An enhanced Raman scattering signal is observed from 5,5′-dithiobis(2-nitrobenzoic) acid (DTNB) organic molecules deposited on the metasurface. The proposed metasurface provides a significant enhancement of the RS signal in comparison with the luminescence signal and is an efficient substrate for realising giant Raman scattering of light. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Cancer epidemiology update, following the 2011 IARC evaluation of radiofrequency electromagnetic fields (Monograph 102)

Highlights: • Increased risk of brain, vestibular nerve and salivary gland tumors are associated with mobile phone use. • Nine studies (2011–2017) report increased risk of brain cancer from mobile phone use. • Four case-control studies (3 in 2013, 1 in 2014) report increased risk of vestibular nerve tumors. • Concern for other cancers: breast (male & female), testis, leukemia, and thyroid. • Based on the evidence reviewed it is our opinion that IARC's current categorization of RFR as a possible human carcinogen (Group 2B) should be upgraded to Carcinogenic to Humans (Group 1). Epidemiology studies (case-control, cohort, time trend and case studies) published since the International Agency for Research on Cancer (IARC) 2011 categorization of radiofrequency radiation (RFR) from mobile phones and other wireless devices as a possible human carcinogen (Group 2B) are reviewed and summarized. Glioma is an important human cancer found to be associated with RFR in 9 case-control studies conducted in Sweden and France, as well as in some other countries. Increasing glioma incidence trends have been reported in the UK and other countries. Non-malignant endpoints linked include acoustic neuroma (vestibular Schwannoma) and meningioma. Because they allow more detailed consideration of exposure, case-control studies can be superior to cohort studies or other methods in evaluating potential risks for brain cancer. When considered with recent animal experimental evidence, the recent epidemiological studies strengthen and support the conclusion that RFR should be categorized as carcinogenic to humans (IARC Group 1). Opportunistic epidemiological studies are proposed that can be carried out through cross-sectional analyses of high, medium, and low mobile phone users with respect to hearing, vision, memory, reaction time, and other indicators that can easily be assessed through standardized computer-based tests. As exposure data are not uniformly available, billing records should be used whenever available to corroborate reported exposures.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2024

Conservation law for electromagnetic fields in a space-time-varying medium and its implications

We discuss the propagation of electromagnetic waves in a space-time modulated medium, for which neither energy nor momentum remains conserved. We have found a new conservation law when modulation moves at a constant speed v in a traveling-wave fashion. We use this law to study how light is scattered inside such a medium. We consider both the subluminal (v < c) andsuperluminal (v > c) cases and find that they differ considerably in terms of what remains conserved. We show that the total number of photons is conserved in the subluminal case. In contrast, it is the difference between the forward and backward moving photons that remains conserved in the superluminal case. We also study the reciprocity issue for a space-time modulated medium and found that reciprocity holds in all situations. Here, we develop a quantum formulation of our scattering problem and show that the subluminal case is similar to the action of a beam splitter. In the superluminal case, photon pairs can be generated from vacuum in a fashion analogous to the two-mode frequency down-conversion process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Charge-dependent flow induced by electromagnetic fields in heavy ion collisions

The colliding heavy ions create extremely strong magnetic and electric fields that significantly affect the evolution of the produced quark-gluon plasma (QGP). The knowledge of these fields is essential for establishing the role of topological fluctuations in the QGP through the chiral magnetic effect and related anomaly-induced phenomena. In this talk, we describe our work on the evolution of the QGP in electric and magnetic fields in the framework of hydrodynamics supplemented, in a perturbative fashion, by the dynamical electromagnetism. The evolution of the QGP fluid is described within the iEBE-VISHNU framework. We find that the electromagnetically induced currents result in a charge-odd directed flow Δv 1 and a charge-odd Δv 3 flow both of which are odd in rapidity. Furthermore, while the predicted magnitude of these charge-odd flows agrees with the data from RHIC and LHC, the sign of the predicted asymmetry between the flows of positive and negative hadrons is opposite to the data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Toward accurate measurement of electromagnetic field by retrieving and refining the center position of non-uniform diffraction disks in Lorentz 4D-STEM

Recent advancement in scanning transmission electron microscopy (STEM) allows the use of 4D-STEM, a technique that captures an electron diffraction pattern at each scan point in STEM, to measure electrostatic and magnetic potential and field in materials. However, accurate measurement, separation of the magnetic and electric signals, and removal of artifacts remain challenging, especially in the presence of complex non-uniform diffraction contrast within the disks. In this work, based on dynamic simulations of 4D-STEM patterns built upon superstructures consisting of millions of atoms to account for different sample thickness and edge geometries, we show how the shape and intensity distribution of the central disk are affected by multiple scattering. We propose a robust refinement procedure through iteration of the spin-sensitive peak position of the disk-center in the circular Hough transform filtered images from experimental Lorentz 4D-STEM dataset after minimizing the possible artifacts, such as those due to the change of thickness, dynamic scattering, and scanning process. We verify that caution must be taken as in practice the rigid-disk-shift model used to reconstruct induction maps can easily break down due to disk-protrusion when there exists a nonconstant phase gradient or thickness within the width of the probe. Through quantitative analysis and comparing experiment with calculation the effect of the non-spin-related intensity distribution inside the disk as well as that causes the disk shift due to the intensity-protrusion can be removed, and high-quality magnetic field mapping is possible.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗