Magnetic particles and strings in iron langasite

AbstractMagnetic topological defects can store and carry information. Replacement of extended defects, such as domain walls and Skyrmion tubes, by compact magnetic particles that can propagate in all three spatial directions may open an extra dimension in the design of magnetic memory and data processing devices. We show that such objects can be found in iron langasite, which exhibits a hierarchy of non-collinear antiferromagnetic spin structures at very different length scales. We derive an effective model describing long-distance magnetic modulations in this chiral magnet and find unusual two- and three-dimensional topological defects. The order parameter space of our model is similar to that of superfluid 3He-A, and the particle-like magnetic defect is closely related to the Shankar monopole and hedgehog soliton in the Skyrme model of baryons. Mobile magnetic particles stabilized in non-collinear antiferromagnets can play an important role in antiferromagnetic spintronics.

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Interconversion of multiferroic domains and domain walls

Nature Communications ◽

10.1038/s41467-021-22808-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

E. Hassanpour ◽

M. C. Weber ◽

Y. Zemp ◽

L. Kuerten ◽

A. Bortis ◽

...

Keyword(s):

Domain Wall ◽

Physical Properties ◽

Domain Walls ◽

Three Dimensional ◽

Topological Defects ◽

Long Range Order ◽

Two Dimensional ◽

Domain Structures ◽

Topological Singularities ◽

Ordered State

AbstractSystems with long-range order like ferromagnetism or ferroelectricity exhibit uniform, yet differently oriented three-dimensional regions called domains that are separated by two-dimensional topological defects termed domain walls. A change of the ordered state across a domain wall can lead to local non-bulk physical properties such as enhanced conductance or the promotion of unusual phases. Although highly desirable, controlled transfer of these properties between the bulk and the spatially confined walls is usually not possible. Here, we demonstrate this crossover by confining multiferroic Dy0.7Tb0.3FeO3 domains into multiferroic domain walls at an identified location within a non-multiferroic environment. This process is fully reversible; an applied magnetic or electric field controls the transformation. Aside from expanding the concept of multiferroic order, such interconversion can be key to addressing antiferromagnetic domain structures and topological singularities.

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Topological defect-mediated skyrmion annihilation in three dimensions

Communications Physics ◽

10.1038/s42005-021-00675-4 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Max T. Birch ◽

David Cortés-Ortuño ◽

Nguyen D. Khanh ◽

Shinichiro Seki ◽

Aleš Štefančič ◽

...

Keyword(s):

Topological Defect ◽

Three Dimensional ◽

Topological Defects ◽

Two Dimensions ◽

Three Dimensions ◽

Elastic Band ◽

Spin Structures ◽

Transition Mechanism ◽

Field Dependent ◽

Magnetic Skyrmions

AbstractThe creation and annihilation of magnetic skyrmions are mediated by three-dimensional topological defects known as Bloch points. Investigation of such dynamical processes is important both for understanding the emergence of exotic topological spin textures, and for future engineering of skyrmions in technological applications. However, while the annihilation of skyrmions has been extensively investigated in two dimensions, in three dimensions the phase transitions are considerably more complex. We report field-dependent experimental measurements of metastable skyrmion lifetimes in an archetypal chiral magnet, revealing two distinct regimes. Comparison to supporting three-dimensional geodesic nudged elastic band simulations indicates that these correspond to skyrmion annihilation into either the helical and conical states, each exhibiting a different transition mechanism. The results highlight that the lowest energy magnetic configuration of the system plays a crucial role when considering the emergence and stability of topological spin structures via defect-mediated dynamics.

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Using Externally Bonded CFRP to Repair a PCCP with Broken Wires under Combined Loads

International Journal of Polymer Science ◽

10.1155/2019/8053808 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11

Author(s):

Kejie Zhai ◽

Hongyuan Fang ◽

Bing Fu ◽

Fuming Wang ◽

Benyue Hu

Keyword(s):

Prestressed Concrete ◽

Three Dimensional ◽

Soil Pressure ◽

Long Distance ◽

Stress Strain ◽

Wire Breakage ◽

Water Pipelines ◽

Externally Bonded ◽

Prestressed Concrete Cylinder Pipe ◽

Three Dimensional Finite Element

Prestressed concrete cylinder pipe (PCCP) is widely used for long-distance water pipelines throughout the world. However, prestressing wire breakage is the most common form of PCCP damage. For some pipelines that cannot be shut down, a new technique for in-service PCCP repair by externally bonding the pipe with layers of carbon fiber reinforced polymer (CFRP) was proposed. A set of three-dimensional finite element models of the repaired PCCP have been proposed and implemented in the ABAQUS software, which took into account the soil pressure, the weight of the PCCP, the weight of the water, and the hydrostatic pressure. The stress–strain features of the PCCP repaired with CFRP of various thicknesses were analyzed. The stress–strain features of different wire breakage rates for the repaired PCCP were also analyzed. The results showed that the strains and stresses decreased at the springline if the PCCP was repaired with CFRP, which improved the operation of the PCCP. It has been found that the wire breakage rates had a significant effect on the strains and stresses of each PCCP component, but CFRP failed to reach its potential tensile strength when other materials were broken.

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Research of Pipeline Weld Detection Based on Magnetic Memory Technology

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.940.222 ◽

2014 ◽

Vol 940 ◽

pp. 222-225

Author(s):

Fei Fei Long ◽

Jian Zeng Wang ◽

Li Li ◽

Jun Ru Zhao

Keyword(s):

Strain State ◽

Evaluation Method ◽

Magnetic Memory ◽

Metal Magnetic Memory ◽

Safe Operation ◽

Long Distance ◽

Peak Period ◽

Detection Evaluation ◽

Metal Magnetic Memory Method ◽

Testing Work

Ensuring the safe operation of pipeline and monitoring it to prevent sudden accidents are an important task of current nondestructive testing work because of our country is in the peak period of long-distance pipeline construction. Welding cracks are common and most dangerous flaw in the root of the failure of the welded joints . Metal magnetic memory method is the only viable detection , evaluation method currently used for diagnosing the stress-strain state of serving welding crack in the early stages. So this article designs weld cracks of the general pipeline, establish a method to detect pipeline weld crack by metal magnetic memory method.

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Topological Defects and Goldstone Excitations in Domain Walls between Ferromagnetic Quantum Hall Liquids

Physical Review Letters ◽

10.1103/physrevlett.82.402 ◽

1999 ◽

Vol 82 (2) ◽

pp. 402-405 ◽

Cited By ~ 40

Author(s):

Vladimir I. Fal'ko ◽

S. V. Iordanskii

Keyword(s):

Domain Walls ◽

Quantum Hall ◽

Topological Defects ◽

Quantum Hall Liquids

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The Calculation of Train Slipstreams on Platform of Underground High-Speed Rail Station

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.842.445 ◽

2013 ◽

Vol 842 ◽

pp. 445-448

Author(s):

Wei Chao Yang ◽

Chuan He ◽

Li Min Peng

Keyword(s):

High Speed ◽

Three Dimensional ◽

Horizontal Distribution ◽

Wake Flow ◽

Railway Tunnel ◽

Long Distance ◽

Near Wake ◽

High Speed Rail ◽

Numerical Work ◽

Rail Station

This paper describes the results of numerical work to determine the flow structures of the slipstream and wake of a high speed train on platforms of underground rail station using three-dimensional compressible Euler equation. The simulations were carried out on a model of a simplified three-coach train and typical cross-section of Chinese high-speed railway tunnel. A number of issues were observed: change process of slipstreams, longitudinal and horizontal distribution characteristics of train wind. Localized velocity peaks were obtained near the nose of the train and in the near wake region. Maximum and minimum velocity values were also noticed near to the nose rear tip. These structures extended for a long distance behind the train in the far wake flow. The slipstream in platform shows the typical three-dimensional characteristics and the velocity is about 4 m/s at 6 m away from the edge of platform.

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Systematic functional characterization of antisense eRNA of protocadherin α composite enhancer

Genes & Development ◽

10.1101/gad.348621.121 ◽

2021 ◽

Vol 35 (19-20) ◽

pp. 1383-1394

Author(s):

Yuxiao Zhou ◽

Siyuan Xu ◽

Mo Zhang ◽

Qiang Wu

Keyword(s):

Gene Expression ◽

Molecular Mechanisms ◽

Single Cells ◽

Functional Characterization ◽

Three Dimensional ◽

Elongation Factor ◽

Locked Nucleic Acid ◽

Loop Formation ◽

Long Distance ◽

Enhancer Region

Enhancers generate bidirectional noncoding enhancer RNAs (eRNAs) that may regulate gene expression. At present, the eRNA function remains enigmatic. Here, we report a 5′ capped antisense eRNA PEARL (Pcdh eRNA associated with R-loop formation) that is transcribed from the protocadherin (Pcdh) α HS5-1 enhancer region. Through loss- and gain-of-function experiments with CRISPR/Cas9 DNA fragment editing, CRISPRi, and CRISPRa, as well as locked nucleic acid strategies, in conjunction with ChIRP, MeDIP, DRIP, QHR-4C, and HiChIP experiments, we found that PEARL regulates Pcdhα gene expression by forming local RNA–DNA duplexes (R-loops) in situ within the HS5-1 enhancer region to promote long-distance chromatin interactions between distal enhancers and target promoters. In particular, increased levels of eRNA PEARL via perturbing transcription elongation factor SPT6 lead to strengthened local three-dimensional chromatin organization within the Pcdh superTAD. These findings have important implications regarding molecular mechanisms by which the HS5-1 enhancer regulates stochastic Pcdhα promoter choice in single cells in the brain.

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Магнитостатическая энергия доменных стенок в одноосных пленках конечных размеров

Физика твердого тела ◽

10.21883/ftt.2019.10.48247.278 ◽

2019 ◽

Vol 61 (10) ◽

pp. 1767

Author(s):

П.М. Ветошко ◽

Ф.П. Ветошко ◽

В.Г. Шавров ◽

В.И. Щеглов

Keyword(s):

Domain Walls ◽

Magnetic Sensors ◽

Magnetization Distribution ◽

Magnetic Memory ◽

Spintronic Devices ◽

Domain Structures ◽

Magnetic Elements ◽

Uniform Magnetization ◽

Equilibrium Configurations ◽

Equivalent Currents

AbstractThe solution to the problem of calculating the magnetostatic interaction energy of domain walls in uniaxial magnetics with a uniform magnetization distribution inside the domains is given. In carrying out the calculations, the principle of equivalent currents is used, assuming a uniform distribution of magnetization and its representation by equivalent currents flowing along the domain walls and along the surface. Analytical expressions for the mutual induction of two rectangular conductors with an arbitrary aspect ratio have been obtained. Results may be helpful in determining equilibrium configurations of domain structures in magnetic elements of spintronic devices, magnetic sensors and magnetic memory.

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Distinct contracted conformations of the Tcra/Tcrd locus during Tcra and Tcrd recombination

Journal of Experimental Medicine ◽

10.1084/jem.20100772 ◽

2010 ◽

Vol 207 (9) ◽

pp. 1835-1841 ◽

Cited By ~ 36

Author(s):

Han-Yu Shih ◽

Michael S. Krangel

Keyword(s):

In Situ Hybridization ◽

Fluorescence In Situ Hybridization ◽

Three Dimensional ◽

Double Negative ◽

Thymocyte Development ◽

Double Positive ◽

Long Distance ◽

Large Pool ◽

Antigen Receptor Loci

Studies have suggested that antigen receptor loci adopt contracted conformations to promote long-distance interactions between gene segments during V(D)J recombination. The Tcra/Tcrd locus is unique because it undergoes highly divergent Tcrd and Tcra recombination programs in CD4−CD8− double negative (DN) and CD4+CD8+ double positive (DP) thymocytes, respectively. Using three-dimensional fluorescence in situ hybridization, we asked whether these divergent recombination programs are supported by distinct conformational states of the Tcra/Tcrd locus. We found that the 3′ portion of the locus is contracted in DN and DP thymocytes but not in B cells. Remarkably, the 5′ portion of the locus is contracted in DN thymocytes but is decontracted in DP thymocytes. We propose that the fully contracted conformation in DN thymocytes allows Tcrd rearrangements involving Vδ gene segments distributed over 1 Mb, whereas the unique 3′-contracted, 5′-decontracted conformation in DP thymocytes biases initial Tcra rearrangements to the most 3′ of the available Vα gene segments. This would maintain a large pool of distal 5′ Vα gene segments for subsequent rounds of recombination. Thus, distinct contracted conformations of the Tcra/Tcrd locus may facilitate a transition from a Tcrd to a Tcra mode of recombination during thymocyte development.

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