Filament Width Research Articles

Non-ideal magnetohydrodynamics of self-gravitating filaments

Context. Filaments have been studied in detail through observations and simulations. A range of numerical works have separately investigated how chemistry and diffusion effects, as well as magnetic fields and their structure impact the gas dynamics of the filament. However, non-ideal effects have hardly been explored thus far. Aims. We investigate how non-ideal magnetohydrodynamic (MHD) effects, combined with a simplified chemical model affect the evolution and accretion of a star-forming filament. Methods. We modeled an accreting self-gravitating turbulent filament using LEMONGRAB, a one-dimensional (1D) non-ideal MHD code that includes chemistry. We explore the influence of non-ideal MHD, the orientation and strength of the magnetic field, and the cosmic ray ionization rate, on the evolution of the filament, with particular focus on the width and accretion rate. Results. We find that the filament width and the accretion rate are determined by the magnetic field properties, including the initial strength, the coupling with the gas controlled by the cosmic ray ionization rate, and the orientation of the magnetic field with respect to the accretion flow direction. Increasing the cosmic-ray ionization rate leads to a behavior closer to that of ideal MHD, reducing the magnetic pressure support and, hence, damping the accretion efficiency with a consequent broadening of the filament width. For the same reason, we obtained a narrower width and a larger accretion rate when we reduced the initial magnetic field strength. Overall, while these factors affect the final results by approximately a factor of 2, removing the non-ideal MHD effects results in a much greater variation (up to a factor of 7). Conclusions. The inclusion of non-ideal MHD effects and the cosmic-ray ionization is crucial for the study of self-gravitating filaments and in determining critical observable quantities, such as the filament width and accretion rate.

Design and characterization of protein-based, pH-responsive hydrogels with potential biomedical applications.

Hydrogels are composed of polymer networks capable of absorbing large amounts of aqueous solutions while maintaining their three-dimensional structures. The extensive variety of polymerizing compounds and chemical strategies for polymer crosslinking lead to a vast range of applications. Thus, hydrogels are used in bioseparation and bioremediation and for multiple biomedical purposes such as drug delivery, tissue scaffolding and wound dressing. Protein-based hydrogels are specifically suited for biomedical applications because they are biocompatible and biodegradable, likely resulting in none or low toxicity. Proteins with polymerization capabilities are typically good candidates for protein-base hydrogelation. Here, we leverage the polymerization behavior of proteins involved in the inflammatory response to form non-covalent, pH-responsive hydrogels. We describe the basic pH-, concentration-, and time-dependent hydrogenation process, as well as hydrogel characterization using transmission and scanning electron microscopy. With the latter techniques, we have analyzed the macrostructure organization of the protein polymer networks, reporting on filament width and pore size. Moreover, we show that the rheology properties of the hydrogels depend on their molecular composition. Our studies set the foundation to explore other molecular components to tune hydrogel viscoelastic properties and add functionality.

PHANGS–JWST First Results: The Dust Filament Network of NGC 628 and Its Relation to Star Formation Activity

PHANGS–JWST mid-infrared (MIR) imaging of nearby spiral galaxies has revealed ubiquitous filaments of dust emission in intricate detail. We present a pilot study to systematically map the dust filament network (DFN) at multiple scales between 25 and 400 pc in NGC 628. MIRI images at 7.7, 10, 11.3, and 21 μm of NGC 628 are used to generate maps of the filaments in emission, while PHANGS–HST B-band imaging yields maps of dust attenuation features. We quantify the correspondence between filaments traced by MIR thermal continuum/polycyclic aromatic hydrocarbon (PAH) emission and filaments detected via extinction/scattering of visible light; the fraction of MIR flux contained in the DFN; and the fraction of H ii regions, young star clusters, and associations within the DFN. We examine the dependence of these quantities on the physical scale at which the DFN is extracted. With our highest-resolution DFN maps (25 pc filament width), we find that filaments in emission and attenuation are cospatial in 40% of sight lines, often exhibiting detailed morphological agreement; that ∼30% of the MIR flux is associated with the DFN; and that 75%–80% of the star formation in H ii regions and 60% of the mass in star clusters younger than 5 Myr are contained within the DFN. However, the DFN at this scale is anticorrelated with looser associations of stars younger than 5 Myr identified using PHANGS–HST near-UV imaging. We discuss the impact of these findings on studies of star formation and the interstellar medium, and the broad range of new investigations enabled by multiscale maps of the DFN.

Near thermal-electric field controlled electrohydrodynamic 3D printing of high aspect ratio microstructures

Electrohydrodynamic (EHD) printing is an effective method for high-resolution two-dimensional patterning because of its high material compatibility. The latest research on three-dimensional (3D) structure fabrication has been reported for metal nanoparticles, small molecular materials, and phase change materials by process regulation. One of the main challenges in conventional EHD 3D printing of polymers is the low accuracy of filament deposition and stacking at the microscale. It is difficult to achieve a high aspect ratio (AR) for printed structures. This study develops an external field-assisted EHD printing process for polymer materials, where the filament formation can be improved by the near thermal field and the stacking accuracy of filaments is further promoted by applying an alternating voltage between layers. The feasibility of this method is demonstrated by printing polystyrene, a typical polymer material, on the silicon substrate with. The regulatory effect of the process parameters on the filament width is explored. The influence of the external thermal field on filament formation and deposition is discussed, and a promotion mechanism is revealed of alternating voltage for accurate deposition. Based on these combinative effects, micro-scale 3D structures with a high AR are successfully printed on the insulating substrate with three kinds of polymers.

Adaptive Estimation and Detection of Filament Width Deviation during 3D Robotic Printing of Construction Materials

3D Concrete Printing (3DCP) is an emerging topic in both industry and research, it helps to save construction time while increasing the complexity of building objects, this advantage allows to print urban furniture of simple shapes from recyclable materials, as well as complex shapes with variable and greater curvature. The 3DCP process is performed by a complex system composed of different parts including robot, pump and materials. The quality of printing can be affected by changes of material behavior and imperfect combination of printing system parameters. Conventional printing tasks require human operator to make decision for the intervention on the printing system when the printing quality deteriorates, which does not meet the requirement for a closed-loop control of the printing quality. In this work, we propose an integrated approach based on Fault Detection and Isolation method for real-time monitoring of printing quality and automatic detection and isolation of a geometric fault that occurs to the printed object during a robotized 3D concrete printing process.

A Quarter Century of Guitar Nebula/Filament Evolution

We have collected a new deep Chandra X-Ray Observatory exposure of PSR B2224+65 and the “Guitar Nebula,” mapping the complex X-ray structure. This is accompanied by a new Hubble Space Telescope (HST) Hα image of the head of the Guitar. Comparing the HST and Chandra structures in four epochs over 25 yr, we constrain the evolution of the TeV particles that light up the filament. Cross-field diffusion appears to be enhanced, likely by the injected particles, behind the filament’s sharp leading edge, explaining the filament width and its evolving surface brightness profile.

The typical width of Herschel filaments

Context. Dense molecular filaments are widely believed to be representative of the initial conditions of star formation in interstellar clouds. Characterizing their physical properties, such as their transverse size, is therefore of paramount importance. Herschel studies suggest that nearby (d < 500 pc) molecular filaments have a typical half-power width of ∼0.1 pc, but this finding has been questioned recently on the ground that the measured widths tend to increase with distance to the filaments. Aims. Here we revisit the dependence of measured filament widths on distance or, equivalently, spatial resolution in an effort to determine whether nearby molecular filaments have a characteristic half-power width or whether this is an artifact of the finite resolution of the Herschel data. Methods. We perform a convergence test on the well-documented B211/213 filament in Taurus by degrading the resolution of the Herschel data several times and reestimating the filament width from the resulting column density profiles. We also compare the widths measured for the Taurus filament and other filaments from the Herschel Gould Belt Survey to those found for synthetic filaments with various types of simple, idealized column density profiles (Gaussian, power law, and Plummer-like). Results. We find that the measured filament widths do increase slightly as the spatial resolution worsens and/or the distance to the filaments increases. However, this trend is entirely consistent with what is expected from simple beam convolution for filaments with density profiles that are Plummer-like and have intrinsic half-power diameters of ∼0.08–0.1 pc and logarithmic slopes 1.5 < p < 2.5 at large radii, as directly observed in many cases, including for the Taurus filament. Due to the presence of background noise fluctuations, deconvolution of the measured widths from the telescope beam is difficult and quickly becomes inaccurate. Conclusions. We conclude that the typical half-power filament width of ∼0.1 pc measured with Herschel in nearby clouds most likely reflects the presence of a true common scale in the filamentary structure of the cold interstellar medium, at least in the solar neighborhood. We suggest that this common scale may correspond to the magnetized turbulent correlation length in molecular clouds.

Study on filament width of type-I ELM in EAST using VUV imaging system and simulation

The poloidal width of the filaments induced by the type-I edge localized mode has power dependence in EAST. The poloidal widths of the filaments observed by the high-speed vacuum ultraviolet (VUV) imaging system are proportional to the heating power and the ELM size. To understand this power dependence, the BOUT++ nonlinear simulations have been performed with the reconstructed equilibriums from the experimental measurements in this paper. The synthetic filament structures from BOUT++ nonlinear simulation match the experimental observations by the VUV imaging system. The BOUT++ nonlinear simulations also reproduce the power dependence of the filament widths and the ELM size. The filament width and the ELM size are inversely proportional to the toroidal mode number. The low-n mode has a broader radial and poloidal structure, which causes the larger filament width and ELM size. In the high input power case, the mode spectrum shifts to low-n, a result of increasing peeling drive. Besides, we found the β p in a higher input power case leads to a broader pedestal, expanding the radial mode structure of the peeling-ballooning mode.

Improving 3D food printing performance using computer vision and feedforward nozzle motion control

3D food printing is an emerging technology to customize food designs and produce personalized foods. Food printing materials are diverse in rheological properties, which makes reliable extrusion-based 3D printing with constant printing parameters a challenge. Food printing often suffers from improper extrusion because of the varying elasticity of the food materials. In this study, a computer vision (CV)-based method is developed to measure the instant extrusion rate and width under constant extrusion pressure/force. The measured extrusion rate and extruded filament width were used to conduct a feedforward control of nozzle motion for a pneumatic 3D food printer. As a result, the CV-based control method improves extrusion line accuracy to 97.6–100% and prevents under-extrusion of white chocolate spread, cookie dough, and processed cheese. The method can also be used to customize filament width with less than 8% of deviation from the target. With a simple measurement setup and a user-friendly software interface, this CV-based method is deployable to most food printing applications to reduce trial-and-error experiments when printing a new food material.

Magnetization Loss Measurements of Spiral Copper-Plated Multifilament Coated Conductors With Various Filament and Conductor Widths

We can achieve both small magnetization loss and the robustness against local defect or local normal transition by winding copper-plated multifilament coated conductor spirally. The particular focus of this study is the impact of narrowing conductor (tape) width as well as filament width on magnetization losses. We measured the magnetization losses of various spiral copper-plated multifilament coated conductors, separated them into hysteresis losses and coupling losses, and examined the impact of narrowing filament width and conductor width. We demonstrated that the magnetization loss of the spiral 2 mm-wide coated conductor with 0.2 mm-wide filaments and 10 μm-thick copper was one-twentieth of that of a flat standard 4 mm-wide coated conductor in transverse ac magnetic fields of 65.44 Hz.

Measurements of Coupling Time Constants and Geometry Factors of Coupling Losses in Spiral Copper-Plated Multifilament Coated Conductors

Spiral geometry is effective to reduce coupling time constants of copper-plated multifilament coated conductors. We wound copper-plated multifilament coated conductors with various specifications spirally on round cores, and measured their magnetization losses in a wide range of frequency to determine their coupling time constants as well as the geometry factors of coupling losses. The core diameter was decreased down to 2.5 mm in order to show the feasibility of such conductors with reasonably high overall current density. The influence of various conductor parameters such as copper thickness, conductor width, and number of striations (filament width) as well as core diameter on coupling time constants and geometry factors were studied. By using the obtained coupling time constants and geometry factors, we calculated coupling losses of various conductors, whereas we calculated their hysteresis losses by using Brandt and Indenbom's formulae. These calculated hysteresis losses and coupling losses were compared with measured magnetization losses for various conductors.

Rolling characteristics of multi-filamentary Bi-2223/AgAu tapes and roller diameter′s effect on transport properties

37-filamentary Bi-2223/ AgAu tapes were fabricated by powder in tube technique. The round wire (φ1.51 mm) were rolled to 0.30 mm tapes by 150 mm, 250 mm and 300 mm roller through flat rolling, respectively. A fundamental understanding of filaments deformation and roll diameter′s effect on critical current properties were systematically investigated. By analyzing the stress distribution on cross section during rolling, it can be understood that the deformation of the filaments at different positions during the rolling of multi-filamentary Bi-2223/AgAu tape is inhomogeneous. According to the deformation extent of filaments, the cross section of the tape can be divided into three areas, namely easy deformation zone, difficult deformation zone and free deformation zone. The average filament width in the free deformation zone is only 65.1 % of the filament width in the easy deformation zone. It can be noticed that the Jc values increase monotonously with increasing roller diameter. Due to more sufficiently deformed filament and flat interfaces, Jc reached the maximum value of 15.7 kA/cm2 on the 300 mm roller sample.

In vitro Tau Aggregation Inducer Molecules Influence the Effects of MAPT Mutations on Aggregation Dynamics.

Alzheimer’s disease (AD) and Alzheimer’s disease-related dementias (ADRDs) affect 6 million Americans, and they are projected to have an estimated health care cost of $355 billion for 2021. A histopathological hallmark of AD and many ADRDs is the aberrant intracellular accumulation of the microtubule-associated protein tau. These neurodegenerative disorders that contain tau aggregates are collectively known as tauopathies, and recent structural studies have shown that different tauopathies are characterized by different “strains” of tau filaments. In addition, mutations in the gene that encodes for tau protein expression have been associated with a group of tauopathies known as frontotemporal dementias with parkinsonism linked to chromosome 17 (FTDP-17 or familial frontotemporal dementia). In vitro studies often use small molecules to induce tau aggregation as tau is extremely soluble and does not spontaneously aggregate under typical laboratory conditions, and the use of authentic filaments to conduct in vitro studies is not feasible. This study highlights how different inducer molecules can have fundamental disparities to how disease-related mutations affect the aggregation dynamics of tau. Using three different classes of tau aggregation inducer molecules, we characterized disease-relevant mutations in tau’s PGGG motifs at positions P301S, P332S, and P364S. When comparing these mutations to wild-type tau, we found that depending on the type of inducer molecule used, we saw fundamental differences in total aggregation, aggregation kinetics, immunoreactivity, and filament numbers, length, and width. These data are consistent with the possibility that different tau aggregation inducer molecules make different structural polymorphs, although this possibility would need to be confirmed by high-resolution techniques such as cryo-electron microscopy. The data also show that disease-associated missense mutations in tau impact tau aggregation differently depending on the mechanism of aggregation induction.

Additive manufacturing of complexly shaped SiC with high density via extrusion-based technique – Effects of slurry thixotropic behavior and 3D printing parameters

Additive manufacturing of dense SiC parts was achieved via an extrusion-based process followed by electrical-field assisted pressure-less sintering. The aim of this research was to study the effect of the rheological behavior of SiC slurry on the printing process and quality, as well as the influence of 3D printing parameters on the dimensions of the extruded filament, which are directly related to the printing precision and quality. Different solid contents and dispersant- Darvan 821A concentrations were studied to optimize the viscosity, thixotropy and sedimentation rate of the slurry. The optimal slurry was composed of 77.5 wt% SiC, Y2O3 and Al2O3 powders, 0.25 wt% dispersant and 0.01 wt% defoamer. The printing parameters studied included extrusion pressure, nozzle size, layer height and printing speed; the one that had the most prominent effect on filament width and height was indicated as layer height. The nozzle inner diameter of 1.04 mm, speed of 350 mm/min, layer height of 0.7 mm and extrusion air pressure of 0.31 MPa were the optimal printing parameters. Furthermore, the relationship between the printing parameters and the filament dimensions was successfully predicted by using machine learning and grey system theory. Finally, the relative density of the printed SiC parts sintered at 1900 oC reached 94.7±1.5%.

Printing and electromagnetic characteristics of 3D printing frequency selective surface using graphene

• Graphene modifies silver ink from shear thinning effect to fluid model behavior. • Cross model ink presents better printing precision than Carreau-Yasuda ink. • High static viscosity contributes to high printing precision in direct ink writing. • Connected graphene sheets contribute to highly electromagnetic performance matching. The study of Frequency Selective Surface (FSS) by Direct ink writing (DIW) has attracted much attention due to the convenience and effectiveness of 3D printing technology. However, the limited printing precision of DIW has heavily restricted its applications as the electromagnetic performance is highly sensitive to it, especially the precision at the microscale. Herein, the ultra-high printing precision of FSS was achieved through DIW by the uniformly dispersed graphene sheets to deeply modify the rheological behavior and the steric hindrance effect. Thus, the highly precision of the printed filament width as thin as 67 μm with a space of only 42 μm were achieved, which is difficult for conventional DIW, and no structural distortion is found after 3D printing, no matter it was 2D printed on a flat surface or the sharply skewed hook face, or even 3D printed to architectural structures. According to the highly improved precision, the electromagnetic performance matching between the designed model and the printed physical FSS device was perfectly achieved, reducing the center frequency error less than 0.3 GHz, and the transmission coefficient error less than 0.046. Our work promises an effective and easy preparation of high-quality FSS from the aid of graphene.

Extrusion 3D bioprinting of functional self-supporting neural constructs using a photoclickable gelatin bioink

Many in vitro models of neural physiology utilize neuronal networks established on two-dimensional substrates. Despite the simplicity of these 2D neuronal networks, substrate stiffness may influence cell morphology, network interactions and how neurons communicate and function. With this perspective, three-dimensional (3D) gel encapsulation is a powerful to recapitulating aspects of in vivo features, yet such an approach is often limited in terms of the level of resolution and feature size relevant for modelling aspects of brain architecture. Here, we report 3D bioplotting of rat primary cortical neural cells using a hydrogel system comprising gelatin norbornene (GelNB) and poly (ethylene glycol) dithiol (PEGdiSH). This bioink benefits from a rapid photo-click chemistry, yielding eight-layer crosshatch neural scaffolds and a filament width of 350 µm. The printability of this system depends on hydrogel concentration, printing temperature, extrusion pressure and speed. These parameters were studied via quantitative comparison between rheology and filament dimensions to determine the optimal printing conditions. Under optimal conditions, cell viability of bioprinted primary cortical neurons at day 1 (68 ± 2%) and at day 7 (68 ± 1%) were comparable to the 2D control group (72 ± 7%). The present study relates material rheology and filament dimensions to generate compliant free-standing neural constructs through bioplotting of low-concentration GelNB-PEGdiSH, which may provide a step forward to study 3D neuronal function and network formation.

Geosmin-producing Scytonema foetidum sp. nov. (Scytonemataceae, Cyanobacteria): morphology and molecular phylogeny

A novel Scytonema species, Scytonema foetidum sp. nov. is described by combining morphological and genetic evidences. Two clonal strains of the new species were isolated from a wet soil sample taken from the Khek River in the lower northern part of Thailand. This species is morphologically similar to S. hofmanii, but can be differentiated by a small filament width, conically rounded apical cell, and sheath present throughout the whole trichome. The 16S ribosomal RNA (rRNA), rbcLX, and nifH phylogenetic trees indicated that S. foetidum clearly formed a unique cluster within the Scytonema sensu stricto clade and shared low 16S rRNA sequence similarity (<98.4%) with the phylogenetically related taxa, supporting separation at species level. The 16S-23S rRNA internal transcribed spacer (ITS) sequences of S. foetidum also possessed unique secondary structures in D1-D1', Box B, and V3 helices, differentiating this species from other known Scytonema species. Furthermore, S. foetidum could produce the odoriferous compound, geosmin.

A Heating-Assisted Direct Ink Writing Method for Preparation of PDMS Cellular Structure with High Manufacturing Fidelity.

In response to the fact that most of the current research on silicone 3D printing suffers from structure collapse and dimensional mismatch, this paper proposes a heating-assisted direct writing printing method for commercial silicone rubber materials for preparing silicone foam with enhanced fidelity. In the experimental processes, the effects of substrate temperature, printing pressure, and printing speed on the filament width were investigated using a controlled variable method. The results showed the following: (1) the diameter of silicone rubber filaments was positively correlated with the printing pressure and substrate temperature, but negatively correlated with the printing speed; (2) the filament collapse of the large filament spaced foams was significantly improved by the addition of the thermal field, which, in turn, improved the mechanical properties and manufacturing stability of the silicon foams. The heating-assisted direct writing process in this paper can facilitate the development of the field of microelectronics and the direct printing of biomaterials.

An experimental assessment of filament-extrusion models used in slicer software for 3D food-printing applications

Various filament-extrusion models have been assessed for their accuracy in predicting the width of filament deposited during extrusion-based 3D printing of food materials. Slicer software uses such models in algorithms to determine appropriate nozzle toolpaths and material extrusion flow rates for printing 3D structures. Prediction and experiment were compared for various printer operating conditions encompassing slow-to moderate-speed and coarse-to fine-resolution 3D food printing. The model that assumes filaments of oblong cross-section predicts filament width well. Fractionated animal fat and 20% rice-starch gel generally form smooth, continuous and stable filaments over a broad range of printer operating conditions, making them ideal materials for 3D food printing. Practical issues in 3D food printing were highlighted, including the non-uniformity of filament width that results from even the slightest build-platform slope or nozzle skew, and the relevance of the extrusion multiplier in slicer software for fine-tuning 3D printing to account for differences in rheology between food materials. • Slicers use filament models to compute toolpaths and extrusion rates in 3D-printing. • Various filament models were assessed in the context of 3D food printing. • Model that assumes filaments of oblong cross-section predicts filament width well. • Even slight build-platform slope or nozzle skew affect filament-width uniformity.

HV-LDMOS Device Engineering Insights for Moving Current Filament to Enhance ESD Robustness

In this article, a novel design approach for improving electrostatic discharge (ESD) robustness of high-voltage laterally double-diffused MOS (LDMOS) devices is presented using detailed 3-D TCAD simulations. The proposed method considers engineering both static filament and dynamic/moving current filaments in LDMOS design. Physical insights and engineering approaches for moving filaments at higher stress current levels are presented. Dynamic filament motion and its relation to n-p-n turn-on engineering with an optimum p-well profile and substrate biasing are revealed. A unique window failure in LDMOS near snapback is discussed for the first time. A detailed analysis is presented on filament width engineering by using optimum drain diffusion length (DL) and its influence on static filament-induced window failures. This approach resulted in ten-time improvement in ESD robustness for self-protecting concepts. Finally, different fundamental questions related to the origin of filament motion are explored (using 3-D TCAD) with the help of engineered LDMOS Designs.