Coil Segments Research Articles

A comprehensive numerical approach to coil placement in cerebral aneurysms: mathematical modeling and in silico occlusion classification.

Endovascular coil embolization is one of the primary treatment techniques for cerebral aneurysms. Although it is a well-established and minimally invasive method, it bears the risk of suboptimal coil placement which can lead to incomplete occlusion of the aneurysm possibly causing recurrence. One of the key features of coils is that they have an imprinted natural shape supporting the fixation within the aneurysm. For the spatial discretization, our mathematical coil model is based on the discrete elastic rod model which results in a dimension-reduced 1D system of differential equations. We include bending and twisting responses to account for the coils natural curvature and allow for the placement of several coils having different material parameters. Collisions between coil segments and the aneurysm wall are handled by an efficient contact algorithm that relies on an octree based collision detection. In time, we use a standard symplectic semi-implicit Euler time stepping method. Our model can be easily incorporated into blood flow simulations of embolized aneurysms. In order to differentiate optimal from suboptimal placements, we employ a suitable in silico Raymond-Roy-type occlusion classification and measure the local packing density in the aneurysm at its neck, wall region and core. We investigate the impact of uncertainties in the coil parameters and embolization procedure. To this end, we vary the position and the angle of insertion of the micro-catheter, and approximate the local packing density distributions by evaluating sample statistics.

Correction to Emergent Dispersion and Sorting Behaviors of Carbon Nanotubes When Combining Short Conjugated Oligomers with Nonconjugated Coil Segments

Correction to Emergent Dispersion and Sorting Behaviors of Carbon Nanotubes When Combining Short Conjugated Oligomers with Nonconjugated Coil Segments

Emergent Dispersion and Sorting Behaviors of Carbon Nanotubes When Combining Short Conjugated Oligomers with Nonconjugated Coil Segments

Emergent Dispersion and Sorting Behaviors of Carbon Nanotubes When Combining Short Conjugated Oligomers with Nonconjugated Coil Segments

Donor-Acceptor Assembly of Amphiphilic Molecules Based on 9,10-Distyrylanthracene Derivatives with Terminal Naphthalene Groups.

Amphiphilic rod-coil compounds have excellent photophysical properties and can be assembled into supramolecular nanostructures of different sizes in water or polar solvents. Herein, we synthesized the amphiphilic compounds 2N-DSA, 4N-DSA, and 6N-DSA with 9,10-distyrylanthracene (DSA) as the core and a naphthalene unit as the terminal group that connected DSA through a tetraethylene glycol chain. These compounds have excellent aggregation-induced emission (AIE) properties in aqueous solution and are assembled into worm-like fragments or different sizes of spherical assemblies, defending the volume ratio of the rod to coil segments. Notably, the donor-acceptor interaction between DSA and electron- deficient compounds 2,4,6-trinitrophenol (TNP), 2,4,5,7-tetranitrofluorenone (TNF), and tetraethylene glycol dinitrobenzoate (TGDNB) forms a charge transfer complex, which can be used as a nanoreactor to improve the yield of the Suzuki coupling reaction about 8-10 times. The experimental results reveal that the synergy effect of the donor-acceptor, intermolecular π-π stacking, and hydrophobic-hydrophilic interactions significantly influences the morphology of aggregates and the efficiency of the nanoreactor.

(Third Place Poster Award) Synthesis and Characterization of Block Copolymer Dispersants for Semiconducting Single-Walled Carbon Nanotubes

To leverage the full potential of the outstanding electronic properties of semiconducting single-walled carbon nanotubes (s-CNTs), it is essential to disperse and sort high purity s-CNTs from a heterogeneous mixture. Due to the inherent insolubility of CNTs, various organic dispersing agents that non-covalently interact with CNTs have been successfully used. These dispersants include small molecule surfactants and aromatic compounds, conjugated polymers, DNA, and polyelectrolytes. Of the macromolecular dispersants, polymers with conjugated backbones are widely studied because they can wrap around or strongly adsorb on CNTs to create very stable dispersions in organic solvents. Most of these conjugated polymers are based on polythiophenes or polyfluorenes, which depending on the structure and composition can sort specific chiralities of s-CNTs with over 99.99% semiconducting purity.In this work, we explore conjugated polymer-based block copolymers for sorting and dispersing s-CNTs. Non-conjugated block copolymer-based dispersants have been reported by us and others with varying degrees of success in aqueous and organic solvents. Here we present our recent studies on the synthesis of ABA triblock copolymer-based CNT dispersants where B is the conjugated block and A is the non-conjugated block. The synthesis of the ABA triblock can be achieved by separately synthesizing the rod segments and the coil segments, each with reactive chain end functionalities, and then coupling the rod segments with the coil segments via reaction of the chain ends using, for example, a click reaction. Alternatively, the rod segment or the coil segment can be synthesized first and used as a macroinitiator for the polymerization of the other segment. Each of these two methods offers some advantages and disadvantages. A series of these ABA triblocks with fixed B block length and varying A block lengths were synthesized and evaluated for their ability to sort and disperse ArcD and HiPCO CNTs. A second series of ABA triblocks with fixed A block lengths but increasing B block lengths were also synthesized. We will present the challenges associated with the synthesis and purification of these block copolymer dispersants. As the middle-conjugated B block wraps around the CNTs, we anticipate the two peripheral A blocks to interact with the organic solvent toluene to further solubilize the CNTs. Our studies show that the presence of the A blocks significantly increases the sorting efficiency while preserving the chirality selectiveness of the B block. As the length of the B block increases, the sorting yields can be significantly improved as well. We further discuss the role of the dispersity of the B block if any on the dispersion of s-CNTs.

Lipid oxidation induced protein scission in an oleogel as a model food

Lipid oxidation induced protein scission was investigated in oleogel using beta-lactoglobulin (whey protein isolate) as gelator. Extracted cleaved peptides were measured using high resolution mass spectrometry (FT-ICR-MS), which was provided by an automatically generated annotation list approach to identify relevant masses and sum formula using the isotopic pattern. The identified oxidized peptides were then further evaluated using partial least squares regression to relevant lipid hydroperoxide formation data, which provide the significance and importance of the peptides toward lipid induced scission. Thereby, the most important peptides are located at the surface of the protein in random coil segments and especially at the ends of the protein sequence. The most important amino acids were cysteine and aliphatic amino acids, which undergo scission mostly by the α-amidation pathway. The findings compare well with studies investigating depletion of amino acids initiated by lipid oxidation in systems containing bovine albumin or gamma-globulin.

The interaction between LC8 and LCA5 reveals a novel oligomerization function of LC8 in the ciliary-centrosome system

Dynein light chain LC8 is a small dimeric hub protein that recognizes its partners through short linear motifs and is commonly assumed to drive their dimerization. It has more than 100 known binding partners involved in a wide range of cellular processes. Recent large-scale interaction studies suggested that LC8 could also play a role in the ciliary/centrosome system. However, the cellular function of LC8 in this system remains elusive. In this work, we characterized the interaction of LC8 with the centrosomal protein lebercilin (LCA5), which is associated with a specific form of ciliopathy. We showed that LCA5 binds LC8 through two linear motifs. In contrast to the commonly accepted model, LCA5 forms dimers through extensive coiled coil formation in a LC8-independent manner. However, LC8 enhances the oligomerization ability of LCA5 that requires a finely balanced interplay of coiled coil segments and both binding motifs. Based on our results, we propose that LC8 acts as an oligomerization engine that is responsible for the higher order oligomer formation of LCA5. As LCA5 shares several common features with other centrosomal proteins, the presented LC8 driven oligomerization could be widespread among centrosomal proteins, highlighting an important novel cellular function of LC8.

Finite element analysis of the temperature distribution within a Conduction-Cooled, MgB2-based MRI superconducting coil segment

Superconducting magnets used for Magnetic Resonance Imaging (MRI) scanners need to keep temperature gradients minimized in order to retain thermal and operating current margin. We have used 3D finite element analysis (FEA) simulation in COMSOL Multiphysics software that includes both conductive heat transfer and radiative heating to calculate the temperature distribution both along the winding direction and across the cross-section of an MRI segment coil at its equilibrium operating temperature. We have also modelled the evolution of the thermal properties during cool-down from ambient temperature. The heat capacity and thermal conductivity of the magnet winding were computed for use within this simulation. The heat capacity as a function of temperature was calculated using a rule of mixtures. This procedure was also used for the thermal conductivity along the direction of the wire. However, the thermal conductivity within the composite cross section (x- and y-directions) was computed using a 2D FEA model. Based on this, a time-dependent, 3D coil model was built to calculate the coil temperature throughout the winding during cool-down in our test cryostat system. The model included a heat leak component to the coil current contacts via conduction through the current leads as well as a radiative component from the surfaces of the cryostat. A key result was that a maximum coil ΔTmax = 5.1 K (=maximum temperature within the winding -minimum temperature in the winding) was seen and a coil Ic margin of 12.75 A was predicted at steady state, with our first current lead design. A second set of more optimized current leads significantly lowered the ΔTmax within the coil at the steady state. The coil Ic margin has been analyzed for different current lead designs.

Low-Energy-Consumption and Electret-Free Photosynaptic Transistor Utilizing Poly(3-hexylthiophene)-Based Conjugated Block Copolymers.

Neuromorphic computation possesses the advantages of self‐learning, highly parallel computation, and low energy consumption, and is of great promise to overcome the bottleneck of von Neumann computation. In this work, a series of poly(3‐hexylthiophene) (P3HT)‐based block copolymers (BCPs) with different coil segments, including polystyrene, poly(2‐vinylpyridine) (P2VP), poly(2‐vinylnaphthalene), and poly(butyl acrylate), are utilized in photosynaptic transistor to emulate paired‐pulse facilitation, spike time/rate‐dependent plasticity, short/long‐term neuroplasticity, and learning−forgetting−relearning processes. P3HT serves as a carrier transport channel and a photogate, while the insulating coils with electrophilic groups are for charge trapping and preservation. Three main factors are unveiled to govern the properties of these P3HT‐based BCPs: i) rigidity of the insulating coil, ii) energy levels between the constituent polymers, and iii) electrophilicity of the insulating coil. Accordingly, P3HT‐b‐P2VP‐based photosynaptic transistor with a sought‐after BCP combination demonstrates long‐term memory behavior with current contrast up to 105, short‐term memory behavior with high paired‐pulse facilitation ratio of 1.38, and an ultralow energy consumption of 0.56 fJ at an operating voltage of −0.0003 V. As far as it is known, this is the first work to utilize conjugated BCPs in an electret‐free photosynaptic transistor showing great potential to the artificial intelligence technology.

A hybrid spiral-bobbin eddy current testing probe for detection of crack of arbitrary orientation in steam generator tubes

ABSTRACT This paper presents a new hybrid spiral-bobbin probe (S-bobbin probe) of transmitting-receiving (TR) mode for efficient eddy current testing (ECT) of steam generator tubes in nuclear power plants. The new probe of novel configuration can solve the major drawback of the conventional bobbin type ECT probe, i.e., insensitive to circumferential cracks. The excitation coil of the new probe consists of 2 coil segments of spiral geometry and 2 coil segments of half circle geometry which are sequentially connected to form a full coil loop. To acquire defect signal of low lift-off noise, the TR probe mode is adopted and the shape of the pick-up coil is selected the same as that of the excitation coil. As the S-bobbin probe can induce eddy currents in two different directions, it can detect cracks in SG tubes of arbitrary orientations. In order to demonstrate the validity and efficiency of the new S-bobbin probe, simulations and experiments were carried out with a prototype S-bobbin probe and tube specimens with circumferential or axial artificial cracks. The simulation and experimental results agree well, and both of them reveal that a crack in any direction can be properly detected and evaluated by using the new probe.

Low-resistance joint development for segment-fabrication of high-temperature superconducting fusion magnets

Two designs have been proposed for segment-fabrication of the high-temperature superconducting (HTS) helical coils in the FFHR-d1 helical fusion reactor, joint-winding of the HTS coils wound by connecting conductor segments, and the ‘remountable’ HTS magnet (here ‘remountable’ means being able to mount and demount repeatedly) assembled from coil segments with demountable joints. A bridge-type mechanical lap joint and mechanical edge joint are planned to be applied to those two designs, respectively. This paper presents the progress in electrical and mechanical performances of the mechanical joints of HTS conductors and methods to evaluate their quality for segment-fabrication of HTS helical coils. R&D of joint performance has progressed during this decade and it shows acceptable performance for the HTS helical coils. The contact-probing current transfer length method and x-ray computer tomography scanning are promising for quality assessment of the joints and HTS tapes.

Liquid-Crystal Ordering and Microphase Separation in the Lamellar Phase of Rod-Coil-Rod Triblock Copolymers. Molecular Theory and Computer Simulations.

A molecular model of the orientationally ordered lamellar phase exhibited by asymmetric rod-coil-rod triblock copolymers has been developed using the density-functional approach and generalizing the molecular-statistical theory of rod-coil diblock copolymers. An approximate expression for the free energy of the lamellar phase has been obtained in terms of the direct correlation functions of the system, the Flory-Huggins parameter and the Maier-Saupe orientational interaction potential between rods. A detailed derivation of several rod-rod and rod-coil density-density correlation functions required to evaluate the free energy is presented. The orientational and translational order parameters of rod and coil segments depending on the temperature and triblock asymmetry have been calculated numerically by direct minimization of the free energy. Different structure and ordering of the lamellar phase at high and low values of the triblock asymmetry is revealed and analyzed in detail. Asymmetric rod-coil-rod triblock copolymers have been simulated using the method of dissipative particle dynamics in the broad range of the Flory-Huggins parameter and for several values of the triblock asymmetry. It has been found that the lamellar phase appears to be the most stable one at strong segregation. The density distribution of the coil segments and the segments of the two different rods have been determined for different values of the segregation strength. The simulations confirm the existence of a weakly ordered lamellar phase predicted by the density-functional theory, in which the short rods separate from the long ones and are characterized by weak positional ordering.

Different Mechanisms of Translational Symmetry Breaking in Liquid-Crystal Coil–Rod–Coil Triblock Copolymers

A molecular-statistical theory of coil-rod–coil triblock copolymers with orientationally ordered rod-like fragments has been developed using the density functional approach. An explicit expression for the free energy has been obtained in terms of the direct correlation functions of the reference disordered phase, the Flory–Huggins parameter and the potential of anisotropic interaction between rigid rods. The theory has been used to derive several phase diagrams and to calculate numerically orientational and translational order parameter profiles for different polymer architecture as a function of the Flory–Huggins parameter, which specifies the short-range repulsion and as functions of temperature. In triblock copolymers, the nematic–lamellar transition is accompanied by the translational symmetry breaking, which can be caused by two different microscopic mechanisms. The first mechanism resembles a low dimensional crystallization and is typical for conventional smectic liquid crystals. The second mechanism is related to the repulsion between rod and coil segments and is typical for block copolymers. Both mechanisms are analyzed in detail as well as the effects of temperature, coil fraction and the triblock asymmetry on the transition into the lamellar phase.

Tuning the Double Gyroid Phase Window in Block Copolymers via Polymer Chain Conformation Near the Interface

Block copolymer network morphologies have been proven interesting for applications ranging from mechanical to transport and optical properties. The shape of the polymer chain and its ability to stretch across an interface can be used as handles to target these network morphologies. Here, we show that the double gyroid phase window is broadened when there is a flexible segment near the interface and narrowed when a more constrained segment is placed there by using a series of poly(styrene-b-peptoid) block copolymers in which the polypeptoid block chain conformation can be tuned to adopt either a helical or a coil conformation (NRpe6 vs Npe6). The double gyroid phase is accessed in both block copolymer series, while the phase boundaries are shifted toward larger polypeptoid volume fractions in the helix-forming PS–(NRpe6Nmey) series, due to the more compact helix segment (i.e., the helix segment has the same chain volume as its random coil counterpart but occupies less space). The space-filling difference between the helix and coil segment is further confirmed by the smaller domain spacing of PS–(NRpe6Nme39) compared to PS–(Npe6Nme36) (13.9 nm vs 14.3 nm) despite the former having a longer polypeptoid block. Furthermore, a broadened double gyroid phase window is accessed in the PS–(Npe6Nmey) series that has a flexible coil segment near the interface. These results demonstrate the possibility of tuning the double gyroid phase in linear block copolymers by chain conformation near the interface alone, highlighting chain conformation as a versatile handle in block copolymer design.

The Reduction of Force Component Produced by Short Sides by Analyzing the Corner of Coil in Planar Motor with Halbach Magnet Array

The planar motor with moving-magnet is purely levitated by the stator coils. The forces produced by coils are calculated with the analytical model of magnet array and coil surface model for applying to the real time control. Take the coil and the Halbach magnet array which is at 45 degree with the long side of coil for analysis. The force component produced by short sides can be eliminated for conveniently controlling when the length of coil takes certain dimension. In practice, the force component produced by short sides is small but not zero. There are two reasons, one is the higher harmonics and the other is the corner segments of coil. The force integral expressions of coil corner segments are given by the Lorenz force law. Then the forces numerically calculated with harmonic model and coil full model are verified by comparing with the magnetic surface charge model and finite element model. In order to reduce the force component produced by short sides, the different corners of coil are analyzed. Comparing the forces of different corners of coil, the force component produced by short sides can be significantly reduced with slightly change of the other force components.

Investigations into the role of non-bond interaction on gelation mechanism of silk fibroin hydrogel.

Silk fibroin hydrogel not only has biocompatibility, but also has environmental response ability. It plays an important role in the development of material. The gelation mechanism of silk fibroin hydrogel is very important to textile and medicine fields. The molecular dynamics simulation was used to discuss the structure and non-bond interaction of silk fibroin hydrogel. The results show that the non-bond interactions between silk fibroin molecules and water molecules have certain influence on the formation of silk fibroin hydrogel. According to the hydrogen bond analysis, the hydrogen bonds are mainly formed between random coil peptide fragments at the two ends of silk fibroin molecules and residues 252-254 are the key residues. The electrostatic and polar solvation interactions between silk fibroin molecules plays a major role in cross-linking of the coil segments of two silk fibroin molecules.

Secondary Structures of Polypeptide-Based Diblock Copolymers Influence the Microphase Separation of Templates for the Fabrication of Microporous Carbons

In this study, we synthesized two forms of the polypeptide-based rod–coil diblock copolymer poly(ethylene oxide-b-γ-benzyl-l-glutamate) (PEO-b-PBLG), comprising hydrophilic PEO as the coil segment ...

Air-Cycle Energy-Saving IH Rice Cooker Based on Phase Change Heat Storage

This device combines phase change heat storage with air circulation, and proposes a new three-dimensional honeycomb grid structure on the phase change material carrier structure. The reasonable use of steam residual heat and the use of a segmented electromagnetic coil structure reduce the heat loss and power consumption of IH rice cooker. Utilizing the hot steam generated in the heating stage of the rice cooker, the low-temperature waste heat is recycled in the low-temperature phase-change thermal storage module designed by the device. At the same time, the electromagnetic coil is segmented. Besides, the fuzzy control is used to determine the actual amount of rice to be cooked to determine the number of coil segments used in the heating stage to reduce power consumption.

Optimizing selective stimulation of peripheral nerves with arrays of coils or surface electrodes using a linear peripheral nerve stimulation metric

Objective. We present a PNS oracle, which solves these computation time and linearity problems and is, therefore, well-suited for fast optimization of voltage distributions in contact electrode arrays and current drive patterns in non-contact magnetic coil arrays. Approach. The PNS oracle metric for a nerve fiber is computed from an electric field map using only linear operations (projection, differentiation, convolution, scaling). Due to its linearity, this PNS metric can be precomputed for a set of coil or electrode segments, allowing rapid PNS prediction and comparison of any possible coil or electrode stimulation configuration constructed from this set. The PNS oracle is closely related to the classical activating function and modified driving functions but is adjusted to better correlate with full neurodynamic modeling of myelinated mammalian nerves. Main results. We validated the PNS oracle in three MRI gradient coils and two body models and found good correlation between the PNS oracle and the full neurodynamic modeling approach (R2 > 0.995). Finally, we demonstrated its potential utility by optimizing the driving currents and voltages of arrays of 108 magnetic coils or 108 contact electrodes to selectively stimulate target nerves in the lower leg. Significance. Peripheral nerve stimulation (PNS) by electromagnetic fields can be accurately simulated using coupled electromagnetic and neurodynamic modeling. Such simulations are slow and non-linear in the electric field, which makes it difficult to iteratively optimize coil and electrode configurations or drive patterns aiming to avoid PNS or to initiate it for therapeutic purposes.

Efficient Wireless Power Transfer With Capacitively Segmented RF Coils

Wireless power transfer systems have been widely applied in the field of portable and implantable devices, featuring contact-free and reliable energy supply. Novel implant systems, such as brain-computer interfaces, impose the challenges of strong miniaturization and operation under loosely coupled conditions. Therefore, maximizing power transfer efficiency while decreasing the size of transmitter and receiver structures becomes a central research question. This paper presents a unified design strategy of modeling, analyzing and optimizing planar spiral coils with integrated capacitive elements, so-called capacitively segmented coils, for operation in wireless power transfer interfaces. It mathematically analyzes and experimentally verifies that the combination of capacitive coil segmentation, increased operational frequencies and geometrical coil optimization can be used to establish wireless power transfer links with comparatively high efficiency, small size and limited detuning effects in lossy dielectric environments. The paper embraces the formulation and verification of a broadband analytical link model based on partial element equivalent circuits, which is subsequently used to determine dominant coupling and loss mechanisms and to optimize the coils' geometries for high efficiency. Moreover, an extended analysis shows how the capacitive coil segmentation can effectively suppress dielectric losses and non-uniform current distributions by canceling the inductive contribution of every coil segment at the frequency of operation. Utilizing these methods, an exemplary 40.68MHz wireless power link with a 30mm primary and a 10mm secondary coil is designed and evaluated: With a maximum efficiency of up to 31% in biological tissue at 20mm separation distance, it features efficiency levels which are up to ten times higher and a specific absorption rate which is up to five times lower compared to non-segmented systems. When operated at 150MHz in air, efficiency levels are up to 1.5 times higher than in state-of-the-art systems of the same size.