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- electromagnetic pulse
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- V.N. Karazin Kharkiv National University
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- Centro de laseres pulsados and University of Salamanca
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Carboxymethylcellulose-based magnetic Au or Ag nanosystems: Eminent candidates in catalysis, sensing applications based on SERS, and electrochemistry
摘要： An increasing demand for metal gold- and/or silver-based nanomaterials in optics, catalysis, and electrochemical sensing research calls for the development of a new, clean, and environmentally friendly methodology for the production of metal-containing composites. Herein, we report a novel method for fabrication of dispersed carboxymethylcellulose stabilized iron oxide nanoparticles capable to adsorb silver and gold ions onto the surface. Simultaneously, Ag or Au ions are trapped on the magnetic carrier surface and reduced into metal nanoparticles without the action of another reducing agent. The magnetic silver nanocomposite with dumbbell-like structures and magnetic gold nanocomposite with strawberry-like structures, both of different composition (5, 10, and 20 wt.% metal contents), were prepared and characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray powder diffraction, and atomic absorption spectroscopy. Subsequently, the prepared magnetic silver and gold nanocomposites (cMNPs-Ag and cMNPs-Au, respectively) were studied as sufficient candidates in catalysis, sensing applications based on SERS, and electrochemistry. The catalytic properties were demonstrated with the reduction of 4-nitrophenol to 4-aminophenol as a model reaction, where very high rate constants of nanocomposites ranging between 0.25 and 4.12 min?1 were determined. The TOF values were calculated to be from 20.87 to 95.34 min?1. Glassy carbon electrodes modified with cMNPs-Au or cMNPs-Ag nanocomposites were used for successful determination of H2O2 by means of cyclic voltammetry. Obtained results revealed the well-defined reduction peak around ?0.45 V indicating small overpotential necessary for H2O2 detection and detection limits were found to be 2.82 × 10?7 mol L?1 (cMNPs-Ag) and 3.04 × 10?7 mol L?1 (cMNPs-Au). Utilization of nanocomposites as active SERS substrates was demonstrated on the analysis of Rhodamine 6G. The determined enhancement factors were 2 × 107 (cMNPs-Au, 20 wt.% Au content) and 3.2 × 107 (cMNP-Ag, 20 wt.% Ag content).
关键词： Catalyst,Electrochemical nonenzymatic sensor,Carboxymethylcellulose,SERS substrate,Magnetic-gold and magnetic-silver nanocomposites
更新于2025-09-04 15:30:14
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Influence of magnetic filter and magnetic cage in negative ion production in helicon oxygen plasma
摘要： Negative ion rich oxygen plasma at low pressure is produced in a Helicon Plasma Source setup, which is primarily designed to perform electronegative gas plasma experiments including the studies of ion-ion plasma. The negative ion fraction and hence the negative ion density are obtained by using a two probe technique in which the electron current is obtained by using an RF compensated cylindrical Langmuir probe and positive ion saturation current is obtained by using an RF compensated planar probe. By measuring the negative ion fraction, both with and without a magnetic filter, the importance of the magnetic filter field in the production of negative ions in oxygen plasma is investigated. The maximum value of negative ion fraction a (n?/ne) is calculated to be approximately around 9 when the value of temperature ratio c (Te/T?) is taken as 10. The observed negative ion fraction and other plasma parameters are explained by considering the set of reactions that are involved in the production and loss of negative ions.
关键词： magnetic cage,magnetic filter,helicon plasma,oxygen plasma,negative ion
更新于2025-09-04 15:30:14
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Magnetic, half-metallicity and electronic studies of Cd1-xZnxCr2Se4 chromium selenospinels
摘要： We have studied the magnetism of crystalline Cd1-xZnxCr2Se4 spinels with (0.35 ≤ x ≤ 0.55) under magnetic field up to 15 T. The total magnetic moment, Curie temperature, lattice parameter and exchange integrals were found to decrease with Zn substitution. Ab-initio calculations carried out using full potential augmented plane wave (FP-LAPW) method were performed to study the magnetic, and electronic structure using generalized gradient approximation (GGA) and the modified Becke-Johnson (mBJ) to correct the gap’s energy. The obtained results were in good agreement with the experimental ones. It is shown that there is a competition between ferromagnetic (FM) and antiferromagnetic (AFM) interactions: the super-exchange mechanism slightly increases the AFM contribution and keeps the FM the dominant mechanism in this range of substitution. From the density of states, we demonstrate that the system keeps the half-metallic state for the composition range 0.125 ≤ x ≤ 0.55 with 100% spin polarization. Our results highlight that it is possible to obtain a half-metallic semiconductor with tunable magnetic state which is promising for applications in spintronics.
关键词： magnetic competition,half-metallic,DOS,magnetization,mBJ,magnetic moment,Spinels
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Nara, Japan (2018.10.9-2018.10.12)] 2018 IEEE 7th Global Conference on Consumer Electronics (GCCE) - Magnetic Levitation Wireless Charging Platform with Adjustable Magnetic Levitation Height and Resonant Frequency for a Better Charging Efficiency
摘要： This paper mainly focuses on the combination of magnetic levitation height adjustment and wireless charging. The magnetic levitation height adjustment is provided by adding both an electromagnetic levitation coil and a ready-made magnetic levitation platform. This design changes the magnetic field strength of the electromagnetic levitation coil with a Pulse-Width-Modulation (PWM) signal in order to adjust the magnetic levitation height. The wireless charging uses a wireless charging coil with an adjustable resonant frequency and coordinates with the height of the magnetic levitation to find a better wireless charging efficiency.
关键词： Magnetic Levitation Wireless Charging Platform,Magnetic Levitation Height,Electromagnetic Levitation Coil
更新于2025-09-04 15:30:14
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Diagnostic of stellar magnetic fields with cumulative circular polarisation profiles
摘要： Information about stellar magnetic ?eld topologies is obtained primarily from high-resolution circular polarisation (Stokes V) obser- vations. Because of their generally complex morphologies, the stellar Stokes V pro?les are usually interpreted with elaborate inversion techniques such as Zeeman Doppler imaging (ZDI). Here we further develop a new method for interpreting circular polarisation sig- natures in spectral lines using cumulative Stokes V pro?les (anti-derivative of Stokes V). This method is complimentary to ZDI and can be applied to validate the inversion results or when the available observational data are insu?cient for an inversion. Based on the rigorous treatment of polarised line formation in the weak-?eld regime, we show that, for rapidly rotating stars, the cumulative Stokes V pro?les contain information about the spatially resolved longitudinal magnetic ?eld density. Rotational modulation of these pro?les can be employed for a simple, qualitative characterisation of the stellar magnetic ?eld topologies. We apply this diagnostic method to the archival observations of the weak-line T Tauri star V410 Tau and Bp He-strong star HD 37776. We show that the magnetic ?eld in V410 Tau is dominated by an azimuthal component, in agreement with the ZDI map that we recover from the same data set. For HD 37776 the cumulative Stokes V pro?le variation indicates the presence of multiple regions of positive and negative ?eld polarity. This behaviour agrees with the ZDI results, but contradicts the popular hypothesis that the magnetic ?eld of this star is dominated by an axisymmetric quadrupolar component.
关键词： stars: individual: HD 37776,stars: magnetic ?eld,stars: individual: V410 Tau,magnetic ?elds,stars: activity
更新于2025-09-04 15:30:14
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[IEEE 2018 48th European Microwave Conference (EuMC) - Madrid, Spain (2018.9.23-2018.9.27)] 2018 48th European Microwave Conference (EuMC) - A Mechanically Tunable Artificial Magnetic Conductor Using 3-D Printing Technology
摘要： In this paper, a novel rotationally tunable artificial magnetic conductor (AMC) for antenna enhancements is proposed. The designed AMC unit cell consists of two rotational elements which are designed by using 3-D printing technology. The operating frequency range of the multiband AMC shifts as the rotational elements move in different angles. Simulations are carried out in CST Microwave Studio (MWS) in order to demonstrate the phase reflection change by using the proposed mechanical structure. Results show that the proposed AMC provides a stable narrow-band-pass operation bandwidth of 0.2 GHz at low-frequency range and a wide band-pass operation bandwidth of 1.4 GHz at higher frequency ranges. The results also show a stable frequency shift response as rotation angles of incidence go up to 90?. The proposed AMC structure can also provide a band-stop frequency response.
关键词： radio propagation,3-D printing,Artificial Magnetic Conductor (AMC),mechanical system
更新于2025-09-04 15:30:14
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Multifunctional Magnetic Bead-Based Dynamic Light Scattering Aptasensor with Rapid and Feasible Determination of Disease-Related Biomarkers
摘要： A simple and feasible sensing strategy based on target-induced aggregation of aptasensor-conjugated multifunctional magnetic beads was designed for sensitive detection of low-abundant proteins (carcinoembryonic antigen, CEA, used as an example), coupling with dynamic light scatting technique.
关键词： Aptasensor,Cancer markers,Magnetic beads,Dynamic light scattering
更新于2025-09-04 15:30:14
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Pattern Recognition and Signal Analysis in Medical Imaging || Computer-Aided Diagnosis for Diagnostically Challenging Breast Lesions in DCE-MRI
摘要： Breast cancer is the most common cancer among women, but has an encouraging cure rate if diagnosed at an early stage. Thus, early detection of breast cancer continues to be the key for effective treatment. Magnetic resonance (MR) imaging is an emerging and promising new modality for detection and further evaluation of clinically, mammographically, and sonographically occult cancers [134,402]. Acquisition of temporal sequences of between three and six MR images depicting the kinetics of contrast agent molecules in the breast tissue allows for detecting and assessing suspicious tissue disorders with high sensitivity, even in the mammographically dense breasts of young women. Yet, the multitemporal nature of the three-dimensional image data poses new challenges to radiologists as the key-information, reflected by subtle temporal changes of the signal intensity, is only perceivable if all images of the temporal sequence are considered simultaneously.
关键词： Computer-aided diagnosis,Dynamic contrast-enhanced MR,Magnetic resonance imaging,Non-mass-enhancing lesions,Breast cancer
更新于2025-09-04 15:30:14
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A NEW PHOTOBIOMODULATION TECHNIQUE PRODUCES A NEUROPROTECTIVE EFFECT ON AMYLOID Aβ25-35 PEPTIDE INDUCED TOXICITY IN MICE BY SYNERGISTIC MECHANISMS WHEN APPLIED BOTH ON THE HEAD AND ABDOMEN
摘要： In this work the effect of the weak combined MFs was studied in vivo in heritable animal model of AD: well characterized mice transgenic for mutant APPswe and mutant presenilin 1 (PS1dE9) that cause early onset familial Alzheimer’s disease (AD). Transgenic mice (Tg) and control C3H mice were exposed to the same MF at age of 8 months. Mice were also exposed by MF in two groups at the same time (Tg+MF and C3H+MF). A setup for generating a MF consisted of two pairs of coaxial Helmhollz coils oriented along the geomagnetic ?eld vector. A direct current was supplied to one of the pairs of coils to generate a constant component of MF with induction of 42 mcT. An alternating current signal produced by a programmable sinusoidal current generator was fed to other pair of coils to create a variable component of MF with induction of amplitude of 80 nT. The current signal was the sum of two signals with frequencies of 4.38 and 4.88 Hz. Estimation of amyloid plaque loads was performed by counting amyloid plaques, staining with thio?avine S, of the next brain areas: in the CA1 and CA3 ?elds of the hippocampus and temporal cortex of Tg mice. The effect of MFs on Ab deposits was revealed in Tg mice. That Tg+MF group showed the decreased density of plaques with small and middle sizes in the cortex and with large and middle size in the CA3, the ?eld of the hippocampus. In CA1 ?eld the tendency of the increase of small plaques was observed followed by a decrease of density of plaques with middle sizes. Thus, the data suggest that MFs can be applied for preventive purposes in a group of risk of AD.
关键词： animal model,weak combined magnetic fields,Alzheimer’s disease,amyloid-b
更新于2025-09-04 15:30:14
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Spin–Lattice Relaxation and Diffusion Processes in Aqueous Solutions of Gadolinium-Based Upconverting Nanoparticles at Different Magnetic Fields
摘要： We investigated the influence of gadolinium (Gd)-based upconverting nanoparticles (UCNPs) on water spin–lattice relaxation (T1) and diffusion at different magnetic field strengths (0.4 T and 9.4 T). Our findings show that smaller NPs (12 nm compared to 19 nm) were more favourable for proton relaxivity. We also demonstrate that using simplified Solomon–Bloembergen–Morgan (SBM) model we can associate two measured diffusion coefficients with processes occurring near the surface of UCNPs and in bulk water. Using the relationship between relaxation and diffusion, we can estimate not only the total impact of NPs on relaxation of water molecules, but also the impact on relaxation of local water molecules, directly connected to paramagnetic Gd3+ ions in NPs. Different magnetic field strengths did not alter the spin–lattice relaxivity of NPs. This suggests that Gd-based UCNPs could be developed into high-performance multimodal magnetic resonance imaging contrast agents working over a broad range of imaging field strengths used in clinical routine.
关键词： Magnetic fields,MRI contrast agents,Gadolinium-based upconverting nanoparticles,Diffusion processes,Spin–lattice relaxation
更新于2025-09-04 15:30:14