Circular Filaments Research Articles

ICTV Virus Taxonomy Profile: Spiraviridae.

The family Spiraviridae includes viruses that replicate in hyperthermophilic archaea from the genus Aeropyrum . The non-enveloped, hollow, cylindrical virions are formed from a coiling fibre that consists of two intertwining halves of a single circular nucleoprotein filament. A short appendage protrudes from each end of the cylindrical virion. The genome is circular, positive-sense, single-stranded DNA of 24 893 nucleotides. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) report on the family Spiraviridae, which is available at ictv.global/report/spiraviridae.

Computational Study of Zigzag Spacer Design with Elliptical Cross-Section Filaments

The large energy consumption of membrane desalination process has encouraged researchers to explore different spacer designs using Computational Fluid Dynamics (CFD) for maximizing permeate per unit of energy consumed. In previous studies of zigzag spacer designs, the filaments are modeled as circular cross sections in a two-dimensional geometry under the assumption that the flow is oriented normal to the filaments. In this work, we consider the 45° orientation of the flow towards the three-dimensional zigzag spacer unit, which projects the circular cross section of the filament as elliptical in a simplified two-dimensional domain. OpenFOAM was used to simulate the mass transfer enhancement in a reverse-osmosis desalination unit employing spiral wound membranes lined with zigzag spacer filaments. Properties that impact the concentration polarization and hence permeate flux were analyzed in the domain with elliptical filaments as well as a domain with circular filaments to draw suitable comparisons. The range of variation in characteristic parameters across the domain between the two different configurations is determined. It was concluded that ignoring the elliptical projection of circular filaments to the flow direction, can introduce significant margin of error in the estimation of mass transfer coefficient.

On the existence of leapfrogging pair of circular vortex filaments

AbstractWe propose and analyze a system of nonlinear partial differential equations describing the motion of a pair of vortex filaments. As a preliminary analysis, we first consider the case when the filaments are arranged as straight and parallel lines, and explicitly solve the system to show that the motion of the lines resemble that of point vortices moving in a plane. Then, we consider the motion of a pair of coaxial circular vortex filaments. We show that in this case, the system can be reduced to a two‐dimensional Hamiltonian system. Based on this formulation, we give a condition for the initial configuration and parameters of the filaments for leapfrogging to occur, and prove that the condition is in fact necessary and sufficient.

Twin CME Launched by a Blowout Jet Originated from the Eruption of a Quiet-Sun Mini-filament

We study a quiet-Sun blowout jet which is observed on 2014 May 16 by the instruments on board Solar Dynamics Observatory (SDO). We find the twin CME as jet-like and bubble-like CME simultaneously as observed by LASCO C2 on board Solar and Heliospheric Observatory (SoHO), Solar Terrestrial Relation Observatory (STEREO A and STEREO B/COR2). They are respectively associated with the eruption of the northern and southern sections of the filament. A circular filament is rooted at the internetwork region at the base of the blowout jet. The collective magnetic cancellation is observed by SDO/HMI line of sight (LOS) magnetograms at the northern end of the filament, which makes this filament unstable and further makes it to erupt in two different stages. In the first stage, northern section of the filament is ejected, and causes an evolution of the northern part of the blowout jet. This part of the blowout jet is further extended as a collimated plasma beam to form a jet-like CME. We also observe the plasma blobs at the northern edge of the blowout jet resulting from Kelvin-Helmholtz (K-H) instability in its twisted magneto-plasma spire. In the second stage, southern section of the filament erupts in form of deformed/twisted magnetic flux rope which forms the southern part of the blowout jet. This eruption is most likely caused by the eruption of the northern section of filament, which removes the confined magnetic field of the southern section of the filament. Alternative scenarios may be a magnetic implosion between these magnetic structures confined in a much larger magnetic domain. This eruption of southern section of the filament further results in the bubble-like CME in the outer corona.

Efficient calculation of the mutual inductance of arbitrarily oriented circular filaments via a generalisation of the Kalantarov-Zeitlin method

In this article, we present a new analytical formulation for calculation of the mutual inductance between two circular filaments arbitrarily oriented with respect to each other, as an alternative to Grover [1] and Babic [2] expressions reported in 1944 and 2010, respectively. The formula is derived via a generalisation of the Kalantarov-Zeitlin method, which showed that the calculation of mutual inductance between a circular primary filament and any other secondary filament having an arbitrary shape and any desired position with respect to the primary filament is reduced to a line integral. In particular, the obtained formula provides a solution for the singularity issue arising in the Grover and Babic formulas for the case when the planes of the primary and secondary circular filaments are mutually perpendicular. The efficiency and flexibility of the Kalantarov-Zeitlin method allow us to extend immediately the application of the obtained result to a case of the calculation of the mutual inductance between a primary circular filament and its projection on a tilted plane. Newly developed formulas have been successfully validated through a number of examples available in the literature, and by a direct comparison with the results of calculation performed by the FastHenry software.

A Fan Spine Jet: Nonradial Filament Eruption and the Plasmoid Formation

Abstract Using the data from SDO and NVST, we studied a circular filament eruption in association with the formation of jet under a nonaxisymmetric fan spine configuration. A nonradial motion of the filament toward a null point and the formation of a jet were presented in detail. This event contained a small circular filament, which was located above the polarity inversion line. The nonlinear force-free field extrapolation shows the presence of a nonaxisymmetric fan spine structure above the filament. Thus, the filament was confined by this magnetic field structure. Since the confining magnetic pressure decreases much faster toward the null point than anywhere else, the filament displayed a shift motion toward the null point that resulted in a collision, and a reconnection signature of bidirectional flows was observed. Due to the external magnetic reconnection, the topology of the filament field was reconfigured, accompanying by the scattered filament material spreading along nearby coronal loops, which resulted in a blowout jet. Particularly, some ejected plasma blobs were also observed in the vicinity of the interfaces between the filament and neighboring coronal loops. These blobs originating from the dissipation region may be plasmoids in association with tearing mode instability. We suggested that in pre-jet phase the nonaxisymmetric fan spine configuration can act on the erupting filament, laterally deflecting and channeling its motion toward the null point, which may facilitate the jet formation by magnetic reconnection.

Uniqueness of axisymmetric viscous flows originating from circular vortex filaments

The incompressible Navier-Stokes equations in R^3 are shown to admit a unique axisymmetric solution without swirl if the initial vorticity is a circular vortex filament with arbitrarily large circulation Reynolds number. The emphasis is on uniqueness, as existence has already been established in [10]. The main difficulty which has to be overcome is that the nonlinear regime for such flows is outside of applicability of standard perturbation theory, even for short times. The solutions we consider are archetypal examples of viscous vortex rings, and can be thought of as axisymmetric analogues of the self-similar Lamb-Oseen vortices in two-dimensional flows. Our method provides the leading term in a fixed-viscosity short-time asymptotic expansion of the solution, and may in principle be extended so as to give a rigorous justification, in the axisymmetric situation, of higher-order formal asymptotic expansions that can be found in the literature [7].

Topological Sieving of Rings According to Their Rigidity.

We present a novel mechanism for resolving the mechanical rigidity of nanoscopic circular polymers that flow in a complex environment. The emergence of a regime of negative differential mobility induced by topological interactions between the rings and the substrate is the key mechanism for selective sieving of circular polymers with distinct flexibilities. A simple model accurately describes the sieving process observed in molecular dynamics simulations and yields experimentally verifiable analytical predictions, which can be used as a reference guide for improving filtration procedures of circular filaments. The topological sieving mechanism we propose ought to be relevant also in probing the microscopic details of complex substrates.

Uniqueness of Axisymmetric Viscous Flows Originating from Positive Linear Combinations of Circular Vortex Filaments

Following the recent papers [9] and [10] by T. Gallay and V. \u{S}ver\'ak, in the line of work initiated by H. Feng and V. \u{S}ver\'ak in their paper [3], we prove the uniqueness of a solution of the axisymmetric Navier-Stokes equations without swirl when the initial data is a positive linear combination of Dirac masses.

Cover: Journal of Basic Microbiology. 2/2018

Journal of Basic MicrobiologyVolume 58, Issue 2 COVER PICTUREFree Access Cover: Journal of Basic Microbiology. 2/2018 First published: 02 February 2018 https://doi.org/10.1002/jobm.201870011AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract Cover illustration: Mixed filaments of G-1 and SF mutant of Arthrospira platensis (straight bundles) showing segregation of straight filament of SF mutant from the G-1 mutant (circular filaments). (Photo: P. K. Singh, Department of Botany, Banaras Hindu University, Varanasi, India) Volume58, Issue2February 2018 RelatedInformation

Impedance of a circular coil of arbitrary orientation in a conducting tube

We have developed a procedure to determined analytical expressions for the electromagnetic field and impedance of a circular induction coil having an arbitrary orientation in a conductive tube. Initially we express the field of a circular current filament in free space in terms of the global coordinate system referenced to tube axis. This is done by representing the filament field as a single layer potential and forming an integral over the layer using the source coordinates of a static Green’s kernel. A coordinate transform to local source coordinates referenced to the filament axis allows one to determine the coil source function from that of the filament via integration. The effects of induced current in the tube wall on the coil impedance can then be determined for an internal coil. By extension of the present results one can predict the arbitrary orientated coil impedance for an external coil and the impedance variations of a tilted coil due to flaws in tubes.

Eddy-Current Induction by a Coil Whose Axis is Perpendicular to that of a Tube

We have derived analytical expressions for the quasi-static time-harmonic electromagnetic field of a circular coil used to induce eddy currents in a tube or pipe, the axis of the coil being perpendicular to that of the conductor. The results are used to determine coil impedance variations with frequency and position due to induced current. The analysis is based on a derivation of the transverse electric field of a circular current filament in free space expressed as a single layer potential. Integration of the filament field yields the coil field and its impedance in the presence of a tube. We have used the theory and a numerical approximation in fitting the frequency dependence of experimental coil impedance and thereby determined accurate estimates of the electrical conductivity of an inconel tube and the coil lift-off. Finding these parameters is a preliminary step in evaluating coil interactions with flaws.

Stabilization of collapsing scroll waves in systems with random heterogeneities.

In three-dimensional reaction-diffusion systems, excitation waves may form and rotate around a one-dimensional phase singularity called the filament. If the filament forms a closed curve, it will shrink over time and eventually collapse. However, filaments may pin to non-reactive objects present in the medium, reducing their rate of collapse or even allowing them to persist indefinitely. We use numerical simulations to study how different arrangements of non-reactive spheres affect the dynamics of circular filaments. As the filament contracts, it gets closer to and eventually touches and pins to objects in its path. This causes two possible behaviors. The filament can detach from the spheres in its path, slowing down the rate of contraction, or it can remain pinned to a collection of spheres. In general, more or larger spheres increase the chance that the filament remains pinned, but there are exceptions. It is possible for a small number of small spheres to support the filament and possible for the filament to pass through a large number of large spheres. Our work yields insights into the pinning of scroll waves in excitable tissue such as cardiac muscle, where scar tissue acts in a way similar to the non-reactive domains.

Coil Block Designs With Good Homogeneity for MRI Magnets Based on SVD Eigenmode Strengths

This paper describes an improved method to determine coil block (CB) placements with good homogeneities for magnetic resonance imaging magnets. Each magnet has a main coil (MC) for strong magnetic fields in a volume of interest and a shield coil (SC) to make the magnetic fields weak outside the magnet. The CB placements are done in three steps and at every step, the SC magnetic moments are tuned. In step 1, approximate placements are done with axially distributed circular filament loop currents. According to the distribution, rough placements of CBs are done for the MC. In step 2, the CB cross-sectional shapes and positions are optimized to get good homogeneity with real numbers of winding turns. In step 3, the CB shapes are approximated with integer numbers of winding turns and conductor sizes, and the CB positions are tuned to get as good homogeneities as the step 1 result. In all steps, optimizations are done through truncated singular value decompositions. In steps 2 and 3, the placements are done with respect to eigenmode strengths, which are obtained in step 1. For a magnet with six MC-CBs, seven symmetric eigenmode strengths are tuned. The CB placements for magnets can be obtained with good homogeneities and integerized CB winding turns using the method.

Spatial confinement causes lifetime enhancement and expansion of vortex rings with positive filament tension

We study the impact of spatial confinement on the dynamics of three-dimensional (3D) excitation vortices with circular filaments. In a chemically active medium we observe a decreased contraction rate of such scroll rings and even expanding ones, despite their positive filament tension. All experimentally observed regimes of spatially confined scroll ring evolution are reproduced by full 3D numerical integration of the underlying reaction–diffusion equations. Additionally, we propose a kinematical model that takes into account the interaction of the scroll ring with a no-flux boundary. Its predictions agree quantitatively with data obtained from simulations of the reaction–diffusion model.

THE FORMATION AND ERUPTION OF A SMALL CIRCULAR FILAMENT DRIVEN BY ROTATING MAGNETIC STRUCTURES IN THE QUIET SUN

We present the first observation of the formation and eruption of a small circular filament driven by a rotating network magnetic field (RNF) in the quiet Sun. In the negative footpoint region of an inverse J-shaped dextral filament, the RNF was formed by the convergence to supergranular junctions of several magnetic flux patches of the same polarity, and it then rotated counterclockwise (CCW) for approximately 11 hr and showed up as a CCW rotating EUV cyclone, during which time the filament gradually evolved into a circular filament that surrounded the cyclone. When the calculated convergence and vortex flows appeared around the RNF during its formation and rotation phases, the injected magnetic helicity calculation also showed negative helicity accumulation during the RNF rotation that was consistent with the dextral chirality of the filament. Finally, the RNF rotation stopped and the cyclone disappeared, and, probably due to an emerging bipole and its forced cancellation with the RNF, the closure filament underwent an eruption along its axis in the (clockwise) direction opposite to the rotation directions of the RNF and cyclone. These observations suggest that the RNFs might play an important role in the formation of nearby small-scale circular filaments as they transport and inject magnetic energy and helicity, and the formation of the EUV cyclones may be a further manifestation of the helicity injected into the corona by the rotation of the RNFs in the photosphere. In addition, the new emerging bipole observed before the filament eruption might be responsible for destabilizing the system and triggering the magnetic reconnection which proves useful for the filament eruption.

Structure formation in gas-rich galactic discs with finite thickness: from discs to rings

Gravitational instabilities play an important role in structure formation of gas-rich high-redshift disc galaxies. In this paper, we revisit the axisymmetric perturbation theory and the resulting growth of structure by taking the realistic thickness of the disc into account. In the unstable regime, which corresponds for thick discs to a Toomre parameter below the critical value Q0, crit = 0.696, we find a fastest growing perturbation wavelength that is always a factor 1.93 times larger than in the classical razor-thin disc approximation. This result is independent of the adopted disc scaleheight and by this independent of temperature and surface density. In order to test the analytical theory, we compare it with a high-resolution hydrodynamical simulation of an isothermal gravitationally unstable gas disc with the typical vertical sech2 density profile and study its break up into rings that subsequently fragment into dense clumps. In the first phase, rings form, that organize themselves discretely, with distances corresponding to the local fastest growing perturbation wavelength. We find that the disc scaleheight has to be resolved initially with five or more grid cells in order to guarantee proper growth of the ring structures, which follow the analytical prediction. These rings later on contract to a thin and dense line, while at the same time accreting more gas from the inter-ring region. It is these dense, circular filaments, that subsequently fragment into a large number of clumps. Contrary to what is typically assumed, the clump sizes are therefore not directly determined by the fastest growing wavelength.

Effect of feed yarn parameters on air-jet textured yarn properties

In this study we report on the effect of feed yarn parameters viz., filament fineness, filament shape and total linear density on physical bulk, instability and strength of air-jet textured yarns. The yarns were textured under optimum process parameters. The inertial mass, surface area and directional bending effect of filaments affect the physical bulk, stability of loops and tensile strength of air-jet textured yarns. It is observed that an increase in linear density of filament results in a decrease in air-jet textured yarn physical bulk and loss in tenacity, while instability increases. Higher total yarn denier leads to higher physical bulk and instability and lower loss in tenacity. Trilobal polyester filament produces highest physical bulk and loss in tenacity; and lowest yarn instability, while rice shaped filament show lowest physical bulk. Circular filament show intermediate physical bulk and loss in tenacity and highest instability.

Crunching biofilament rings

We discuss a curious example for the collective mechanical behavior of coupled non-linear monomer units entrapped in a circular filament. Within a simple model we elucidate how multistability of monomer units and exponentially large degeneracy of the filament's ground state emerge as a collective feature of the closed filament. Surprisingly, increasing the monomer frustration, i.e., the bending prestrain within the circular filament, leads to a conformational softening of the system. The phenomenon, that we term polymorphic crunching, is discussed and applied to a possible scenario for membrane tube deformation by switchable dynamin or FtsZ filaments. We find an important role of cooperative inter-unit interaction for efficient ring-induced membrane fission.

Effects of Coil Misalignments on theMagnetic Field and Magnetic ForceComponents between Circular Filaments

Wireless transfer of electrical energy between air-cored circular coils can be achieved using contactless inductive power transfer (CIPT) system. Notwithstanding, the aim of designing CIPT systems is not always realized because of coil misalignments between the primary and the secondary coils. Based on this information, the author of this paper analyses the effects of lateral and angular misalignments on the magnetic field and the magnetic force between filamentarycircularcoilswhicharearbitrarilypositionedinspace.Thisinvestigation is achieved based on advanced and relevant models formulated in the literature. Detailed results obtained using SCILAB application software is given.