scholarly journals Translatory and rotatory motion of exchange-bias capped Janus particles controlled by dynamic magnetic field landscapes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rico Huhnstock ◽  
Meike Reginka ◽  
Andreea Tomita ◽  
Maximilian Merkel ◽  
Kristina Dingel ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Exchange Bias ◽  
Pulse Sequence ◽  
Pulse Sequences ◽  
Janus Particles ◽  
Particle Rotation ◽  
Layer System ◽  
Applied Pulse ◽  
Magnetization State ◽  
Analyte Detection

AbstractMagnetic Janus particles (MJPs), fabricated by covering a non-magnetic spherical particle with a hemispherical magnetic in-plane exchange-bias layer system cap, display an onion magnetization state for comparably large diameters of a few microns. In this work, the motion characteristics of these MJPs will be investigated when they are steered by a magnetic field landscape over prototypical parallel-stripe domains, dynamically varied by superposed external magnetic field pulse sequences, in an aqueous medium. We demonstrate, that due to the engineered magnetization state in the hemispherical cap, a comparably fast, directed particle transport and particle rotation can be induced. Additionally, by modifying the frequency of the applied pulse sequence and the strengths of the individual field components, we observe a possible separation between a combined or an individual occurrence of these two types of motion. Our findings bear importance for lab-on-a-chip systems, where particle immobilization on a surface via analyte bridges shall be used for low concentration analyte detection and a particle rotation over a defined position of a substrate may dramatically increase the immobilization (and therefore analyte detection) probability.

scholarly journals Mechanisms of coherent re-arrangement for long-lived spin order

2021 ◽  
Vol 2 (2) ◽  
pp. 741-749
Author(s):  
Florin Teleanu ◽  
Paul R. Vasos
Keyword(s):  
Magnetic Field ◽  
Magnetic Resonance ◽  
Pulse Sequence ◽  
Pulse Sequences ◽  
Building Blocks ◽  
Main Magnetic Field ◽  
Nuclear Spins ◽  
Spin Order ◽  
Magnetic Symmetry ◽  
Year 2000

Abstract. Long-lived spin order-based approaches for magnetic resonance rely on the transition between two magnetic environments of different symmetries, one governed by the magnetic field of the spectrometer and the other where this strong magnetic field is inconsequential. Research on the excitation of magnetic-symmetry transitions in nuclear spins is a scientific field that debuted in Southampton in the year 2000. We advanced in this field carrying the baggage of pre-established directions in NMR spectroscopy. We propose to reveal herein the part of discoveries that may have been obscured by our choice to only look at them through the experience of such pre-established directions at the time. The methodological developments that are emphasised herein are the mechanisms of translation between the symmetric and non-symmetric environments with respect to the main magnetic field B0. More specifically, we look again thoroughly at zero-quantum rotations in the starting blocks of long-lived state populations, magnetisation transfers between hyperpolarised heteronuclei, and protons. These pulse sequences seed subsequent magnetic mechanisms that contribute to further applications. For instance, we show how some of the introduced coherence rotations were combined with classical pulse blocks to obtain two-dimensional correlations between protons and heteronuclei. We hope the pulse sequence building blocks discussed herein will open further perspectives for magnetic resonance experiments with long-lived spin order.

scholarly journals Mechanisms of coherent re-arrangement for long-lived spin order

2021 ◽  
Author(s):  
Florin Teleanu ◽  
Paul R. Vasos
Keyword(s):  
Magnetic Field ◽  
Magnetic Resonance ◽  
Pulse Sequence ◽  
Pulse Sequences ◽  
Building Blocks ◽  
Main Magnetic Field ◽  
Nuclear Spins ◽  
Spin Order ◽  
Selective Inversion ◽  
Potential Applications

Abstract. Long-lived spin order-based approaches for magnetic resonance rely on the transition between two magnetic environments of different symmetry, one governed by the magnetic field of the spectrometer and the other where this strong magnetic field is inconsequential. Research on the excitation of magnetic-symmetry transitions in nuclear spins is a scientific field that debuted in Southampton in the years 2000. We advanced in this field carrying the baggage of pre-established directions in NMR spectroscopy. We propose to reveal in this text the part of discoveries that may have been obscured by our choice to only look at them through the experience of such pre-established directions, at the time. Focussing on potential applications, we may have insufficiently emphasised in the manuscripts the methodological developments that necessitated most scientific effort. Such methods developments foster most of the progress in NMR. Thus, we present the contributed mechanisms of translation between the symmetric and non-symmetric environments with respect to the main magnetic field B0, free of any utilitarian perspective. The concept of zero-quantum rotations in the starting blocks of long-lived state populations, magnetisation transfers between hyperpolarised heteronuclei and protons, and selective inversion for long-lived coherences are discussed, as well as hybrid 2D methods based on both insensitive nuclei excitation (“INEPT”) and long-lived spin order. We can see at this point that these magnetic wheels will take a longer time than we initially thought to set in motion new applications in studies of slow diffusion, angiography, or large-protein structure. However, these pulse sequences seed subsequent magnetic mechanisms that are sure to contribute to applications. For instance, some of the introduced coherence rotations were combined with classical pulse blocks to obtain 2D correlations between protons and heteronuclei. We hope the pulse sequence building blocks discussed herein open further perspectives for magnetic resonance experiments with long-lived spin order.

scholarly journals Sensitivity of PS/CoPd Janus particles to an external magnetic field

RSC Advances ◽  
2021 ◽  
Vol 11 (28) ◽  
pp. 17051-17057
Author(s):  
Anna Eichler-Volf ◽  
Yara Alsaadawi ◽  
Fernando Vazquez Luna ◽  
Qaiser Ali Khan ◽  
Simon Stierle ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
Janus Particles ◽  
Weak Magnetic Fields

PS/CoPd Janus particles respond very sensitively to application of low external magnetic fields. Owing to the magnetic properties, the PS/CoPd particles may be used, for example, to sense the presence of weak magnetic fields as micro-magnetometers.

Giant exchange bias induced via tuning interfacial spins in polycrystalline Fe3O4/CoO bilayers

2021 ◽  
Author(s):  
Fanghua Tian ◽  
Yebei Li ◽  
Qizhong Zhao ◽  
Kaiyan Cao ◽  
Dingchen Wang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Exchange Bias

A giant exchange bias of 9600 Oe was achieved under a magnetic field HFC = 20 kOe in Fe3O4/CoO films.

Magnetic field dependence of threshold electric field for magnetoelectric switching of exchange-bias polarity

2017 ◽  
Vol 122 (7) ◽  
pp. 073905 ◽  
Author(s):  
Thi Van Anh Nguyen ◽  
Yu Shiratsuchi ◽  
Atsushi Kobane ◽  
Saori Yoshida ◽  
Ryoichi Nakatani
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Field Dependence ◽  
Exchange Bias ◽  
Magnetic Field Dependence

Exchange Bias Induced in Polycrystalline Co/FeMn-Structures by Magnetic Field Cooling

2012 ◽  
Vol 190 ◽  
pp. 81-84
Author(s):  
N.G. Chechenin ◽  
I.O. Dzhun ◽  
S.A. Dushenko ◽  
E.A. Konstantinova
Keyword(s):  
Magnetic Field ◽  
Exchange Bias ◽  
Resonance Field ◽  
Bias Effect ◽  
Exchange Bias Effect ◽  
Annealing Temperatures ◽  
Layer Deposition ◽  
High Annealing ◽  
Thin Interlayer ◽  
Anneal Temperature

Using the method of angular dependence of ferromagnetic resonance field the magnetic properties of Si/SiO2/Cu/Co/FeMn/Cu and Si/SiO2/Cu/Co/Cu/FeMn/Cu structures were investigated. The layer deposition was carried out by magnetron sputtering in absence of an external magnetic field. It was established that thermal annealing with further cooling down in presence of a magnetic field can generate an exchange bias at anneal temperature significantly below the bulk antiferromagnetic Néel temperature. It was also shown that a thin interlayer between ferromagnetic and antiferromagnetic layers reduces the exchange bias effect at low anneal temperatures, however, makes this effect more stable at high annealing temperatures.

Fast ρ-NQR Imaging with Slice Selection

1996 ◽  
Vol 51 (5-6) ◽  
pp. 353-356 ◽  
Author(s):  
H. Robert ◽  
D. J. Pusiol
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Gradient ◽  
Pulse Sequence ◽  
Magnetic Field Gradient ◽  
Rotating Frame ◽  
Spectroscopy Technique ◽  
Zero Crossing ◽  
Spatially Resolved ◽  
Spectroscopic Information

Abstract A combination of a new pulse sequence allowing fast data acquisition in the rotating frame version of NQR (ρ-NQRI) together with a method for slice selection, is reported. The procedure allows us to record the magnetization evolution during its motion in the rotating frame. At the same time a zero-crossing external magnetic field gradient is applied in order to select a determined slice of the object to be imaged. The experiments reported are the first steps toward a fast tridimensional ρ-NQRI; even more, as the spectroscopic information is preserved during the spatial encoding procedure, it could be considered as a 3D spatially resolved NQR spectroscopy technique.

scholarly journals Optimization of pulse sequences in ultrafast magnetic resonance imaging for the diagnosis of acute abdominal pain caused by gastrointestinal disease

2020 ◽  
Vol 9 (8) ◽  
pp. 205846012094924 ◽  
Author(s):  
Akitoshi Inoue ◽  
Akira Furukawa ◽  
Norihisa Nitta ◽  
Kai Takaki ◽  
Shinichi Ohta ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Abdominal Pain ◽  
Magnetic Resonance ◽  
Diagnostic Accuracy ◽  
Acute Abdominal Pain ◽  
Pulse Sequence ◽  
Pulse Sequences ◽  
Resonance Imaging ◽  
True Fisp ◽  
Significant Difference

Background Magnetic resonance imaging (MRI) is widely used to diagnose acute abdominal pain; however, it remains unclear which pulse sequence has priority in acute abdominal pain. Purpose To investigate the diagnostic accuracy of MRI and to assess the conspicuity of each pulse sequence for the diagnosis of acute abdominal pain due to gastrointestinal diseases Material and Methods We retrospectively enrolled 60 patients with acute abdominal pain who underwent MRI for axial and coronal T2-weighted (T2W) imaging, fat-suppressed (FS)-T2W imaging, and true-fast imaging with steady-state precession (True-FISP) and axial T1-weighted (T1W) imaging and investigated the diagnosis with endoscopy, surgery, histopathology, computed tomography, and clinical follow-up as standard references. Two radiologists determined the diagnosis with MRI and rated scores of the respective sequences in assessing intraluminal, intramural, and extramural abnormality using a 5-point scale after one month. Diagnostic accuracy was calculated and scores were compared by Wilcoxon-signed rank test with Bonferroni correction. Results Diagnostic accuracy was 90.0% and 93.3% for readers 1 and 2, respectively. Regarding intraluminal abnormality, T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in both readers. FS-T2W imaging was superior to True-FISP in reader 2 ( P < 0.0083). For intramural findings, there was no significant difference in reader 1, whereas T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in reader 2 ( P < 0.0083). For extramural findings, FS-T2W imaging was superior to T2W, T1W, and True-FISP imaging in both readers ( P < 0.0083). Conclusion T2W and FS-T2W imaging are pivotal pulse sequences and should be obtained before T1W and True-FISP imaging.

P1813Impact of cardiac MRI imaging on detection rates of myocarditis

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
A Morgenstern ◽  
B Mikolich ◽  
D Morgenstern ◽  
J R Mikolich
Keyword(s):  
Chest Pain ◽  
Cardiac Imaging ◽  
Cardiac Mri ◽  
Detection Rate ◽  
Pulse Sequence ◽  
T2 Mapping ◽  
Pulse Sequences ◽  
Gadolinium Enhancement ◽  
Detection Rates ◽  
The Impact

Abstract Background The Lake Louise Criteria for the diagnosis of myocarditis by cardiac MRI (CMR) was published in 2009 (JACC April 2009; 53(17): 1475–1487) utilizing T2 STIR, “early” gadolinium enhancement (EGE) and late gadolinium enhancement (LGE). In 2012, our CMR unit adopted a chest pain protocol to enhance detection of inflammatory heart disease, using all 3 pulse sequences. In 2017, T1 relaxing mapping and T2 relaxation mapping were added to the chest pain protocol. Purpose This study was designed to assess the impact of pulse sequence changes in the CMR chest pain protocol on the detection rate of myocarditis. Methods An institutional cardiac imaging database was queried for all patients with chest pain who underwent a CMR study from 2009 thru 2018. The number of newly diagnosed cases of myocarditis per year was computed, based on the prevailing CMR diagnostic criteria at that time. The detection rate of new myocarditis cases per year, was calculated by dividing the number of new cases by the total of CMR studies performed for evaluation of chest pain, during each calendar year. Results Of the 4,946 patients in the cardiac imaging database, 2,126 patients underwent CMR imaging for complaints of chest pain. Detection rates of myocarditis by year are shown in Figure 1. Prior to inclusion of T1 STIR pulse sequences, CMR detection of myocarditis was nearly nil. Use of T2 STIR imaging allowed for an increased rate of myocarditis detection. However, addition of T1 mapping and T2 mapping in 2017 resulted in another increase in myocarditis detection rates from baseline. Figure 1. Detection rate of myocarditis. Conclusions Detection rates of myocarditis using CMR were improved by using T2 STIR pulse sequences, per the initial Lake Louise Criteria. Further enhancement of myocarditis detection rates is achieved by addition of T1 and T2 mapping. These CMR impact data provide additional support for the adoption of the recently modified Lake Louise Criteria (JACC Dec 2018; 72(24): 3158–3176).

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