Filament Shape Research Articles

Bonded straight and helical flagellar filaments form ultra-low-density glasses

We study how the three-dimensional shape of rigid filaments determines the microscopic dynamics and macroscopic rheology of entangled semidilute Brownian suspensions. To control the filament shape we use bacterial flagella, which are microns-long helical or straight filaments assembled from flagellin monomers. We compare the dynamics of straight rods, helical filaments, and shape-diblock copolymers composed of seamlessly joined straight and helical segments. Caged by their neighbors, straight rods preferentially diffuse along their long axis, but exhibit significantly suppressed rotational diffusion. Entangled helical filaments escape their confining tube by corkscrewing through the dense obstacles created by other filaments. By comparison, the adjoining segments of the rod-helix shape-diblocks suppress both the translation and the corkscrewing dynamics. Consequently, the shape-diblock filaments become permanently jammed at exceedingly low densities. We also measure the rheological properties of semidilute suspensions and relate their mechanical properties to the microscopic dynamics of constituent filaments. In particular, rheology shows that an entangled suspension of shape rod-helix copolymers forms a low-density glass whose elastic modulus can be estimated by accounting for how shear deformations reduce the entropic degrees of freedom of constrained filaments. Our results demonstrate that the three-dimensional shape of rigid filaments can be used to design rheological properties of semidilute fibrous suspensions.

Dual Material Fused Filament Fabrication via Core–Shell Die Design

In this work a fused filament fabrication (FFF) die design, capable of extruding two thermoplastics simultaneously in a core–shell configuration, is demonstrated as a means to produce composite structures in a single step. Despite the enormous advancements in 3D printing, fabrication of FFF objects with a composite structure remains a challenge due to the difficulty in finding dies to extrude such structures. We used polyethylene terephthalate glycol (PETG) and high-density polyethylene (HDPE) filaments to perform core–shell 3D printing. HDPE is one of the most commonly produced plastics but rarely used in FFF due to the severe warpage caused by volume changes upon its crystallization. Rheological and thermal analyses suggest the use of HDPE as a shell material due to its extremely short reptation time and sharp melting peak that facilitate superior surface contact and interlayer weld strength at the interface between neighboring FFF tracks. PETG is a commonly used 3D printing filament with excellent printability and sufficient zero shear viscosity to help maintain the extruded filament shape against shrinkage induced by the HDPE shell. Impact and tensile properties of core–shell objects revealed tremendous improvements in the impact resistance and toughness especially at 30 vol % HDPE shell with 1280% and 150% enhancement in impact resistance when compared to individual components: PETG and HDPE, respectively. Scanning electron microscopy was used to analyze the fracture morphology of the tested specimens to obtain an understanding of the fracture mechanism leading to the increased impact resistance. Using this die design can help open avenues of fabricating high impact resistance materials suitable for high performance applications and using HDPE in 3D printed objects with its superior solvent resistance.

Small Leaves, Big Diversity: Citizen Science and Taxonomic Revision Triples Species Number in the Carnivorous Drosera microphylla Complex (D. Section Ergaleium, Droseraceae).

The carnivorous Drosera microphylla complex from southwest Western Australia comprises a group of rare, narrowly endemic species that are potentially threatened by habitat destruction and illegal collection, thus highlighting a need for accurate taxonomic classification to facilitate conservation efforts. Following extensive fieldwork over two decades, detailed studies of both Australian and European herbaria and consideration of both crucial contributions by citizen scientists and social media observations, nine species of the D. microphylla complex are here described and illustrated, including four new species: D. atrata, D. hortiorum, D. koikyennuruff, and D. reflexa. The identities of the previously described infraspecific taxa D. calycina var. minor and D. microphylla var. macropetala are clarified. Both are here lectotypified, reinstated, and elevated to species rank. A replacement name, D. rubricalyx, is provided for the former taxon. Key morphological characters distinguishing the species of this complex include the presence or absence of axillary leaves, lamina shape, petal colour, filament shape, and style length. A detailed identification key, comparison figures, and a distribution map are provided. Six of the nine species are recommended for inclusion on the Priority Flora List under the Conservation Codes for Western Australian Flora and Fauna.

ESTIMATION OF HYDRODYNAMIC ENTRY LENGTH IN MEMBRANE FLOW CHANNELS WITH PERIODIC OBSTRUCTIONS USING CFD

This paper includes analysis of the flow development region in spacer-filled membrane channels using Computational Fluid Dynamics (CFD) technique. Various spacer geometric parameters such as filament spacing, thickness, spacer placement and filament shape, and Reynolds number are investigated to determine their effect on flow pattern, shear stress, and entrance length. The CFD simulations show that when the flow is steady, the fully developed and repeating velocity profiles are achieved within 6-7 filaments. The entrance length in case of steady flow, in many spacers, is therefore found almost the same as in the empty channel. In unsteady flow, the transient effects are noticed after sufficient number of filaments. The entrance lengths in different spacers, hence, are found significant. The filament shape also has a strong influence on flow structure and shear stress. In spacer with square-shaped filament and spacing 2, the flow is steady up to Reynolds number of 500 whereas in triangular filament the critical Reynolds number is 100-300, indicating it to be more suitable for producing time-dependent fluid flow and enhancing heat and mass transfer in membrane channels.

Multi-parameter-encoded 4D printing of liquid crystal elastomers for programmable shape morphing behaviors

Shear-induced mesogen alignments are commonly used to program the morphing behaviors of liquid crystal elastomers (LCEs) in the material extrusion process of 4D printing. The 4D printing parameters are intimately relevant to the alignment degrees and actuation strains of printed LCEs filaments. Nevertheless, there is still a lack of systematic research on the interaction of 4D printing parameters on shape morphing behavior of LCEs so far. Here, the multi-parameter-encoded 4D printing is proposed for systematically uncovering the process-structure-property relationships and programming the shape morphing behaviors of LCEs. The impact of multiple parameters (print speed, extrusion pressure, printing height, and UV light intensity) on the filament shape and actuation strains are analyzed using experiments and simulations, respectively. The role of UV light intensity on the TNI has been revealed and adopted for programming the threshold temperature, immediate state and actuation strain of printed LCEs. To demonstrate the feasibility of the multi-parameter-encoded 4D printing method, various parameters codes are integrated into the samples with the same geometric features and successfully enable distinct localized shape morphing behaviors. The multi-parameter-encoded 4D printing method allows on-demand modulation of local deformation features of LCEs structures solely through parametric design, thus providing additional design freedom and versatile tools for building soft robotics, artificial muscles, flexible electronics, etc.

Petrocosmea panzhouensis (Gesneriaceae), a new species from Guizhou, China

The two species with lobed leaves, viz., Petrocosmea henryi and P. weiyigangii are very distinctive from other species of Petrocosmea. Here, the third species with lobed leaves, named Petrocosmea panzhouensis, from western Guizhou, China, is described. The new species is most similar to P. henryi on shape of leaf blade margin and straight filaments, but it is distinguished from the latter by shape of bracts, and shape and length of anthers. The new taxon is assessed as “Data Deficient” (DD), according to the IUCN standards.

Numerical study of satellite droplet formation in dripping faucet

• Dynamic relation between the liquid/gas interface, pressure and velocity profile has been investigated. • Physics of capillary wave generation in liquid filament has been analyzed. • Satellite drop generation depends on the acceleration and distribution of the axial velocity at the cone-filament junction. • Satellite drop is less likely to be formed at high inlet velocity and low surface tension coefficient. Dynamics of primary and satellite drop formation has wide engineering applications. Drop formation from a vertical capillary tube in air goes through various stages that include necking, bifurcation, recoil, wave generation and secondary necking and bifurcation. In this study, the problem has been studied numerically where the free surface of the pendant drop is tracked by a coupled level set and volume-of-fluid method with the surface tension force determined by the continuum surface force model. The evolution of the complete droplet separation process has been simulated. The numerical results have been compared with published experimental data. The mechanism for the recoiling of the liquid filament after droplet detachment and the subsequent formation of a satellite droplet has been studied and dynamic correlation among liquid/gas interface topology, velocity and pressure field has been investigated. Bell shaped distribution of axial velocity profile and fast acceleration at the cone-filament junction has been found to lead to satellite drop generation. Parametric studies on the effects of inlet velocity, surface tension coefficient and viscosity have been performed. Satellite droplet is less likely to be formed at high inlet velocity and low surface tension coefficient. Viscosity, on the other hand, has been found to play an important role on the shape of liquid filament and satellite droplet. These findings can help better understanding of drop-on-demand liquid dispensing, inkjet printing, spray combustion and many more engineering applications.

Identification and Characterization of Genes Related to Ampicillin Antibiotic Resistance in Zymomonas mobilis

Antibiotics can inhibit or kill microorganisms, while microorganisms have evolved antibiotic resistance strategies to survive antibiotics. Zymomonas mobilis is an ideal industrial microbial chassis and can tolerate multiple antibiotics. However, the mechanisms of antibiotic resistance and genes associated with antibiotic resistance have not been fully analyzed and characterized. In this study, we investigated genes associated with antibiotic resistance using bioinformatic approaches and examined genes associated with ampicillin resistance using CRISPR/Cas12a-based genome-editing technology. Six ampicillin-resistant genes (ZMO0103, ZMO0893, ZMO1094, ZMO1650, ZMO1866, and ZMO1967) were identified, and five mutant strains ZM4∆0103, ZM4∆0893, ZM4∆1094, ZM4∆1650, and ZM4∆1866 were constructed. Additionally, a four-gene mutant ZM4∆ARs was constructed by knocking out ZMO0103, ZMO0893, ZMO1094, and ZMO1650 continuously. Cell growth, morphology, and transformation efficiency of mutant strains were examined. Our results show that the cell growth of ZM4∆0103 and ZM4∆ARs was significantly inhibited with 150 μg/mL ampicillin, and cells changed to a long filament shape from a short rod shape. Moreover, the transformation efficiencies of ZM4∆0103 and ZM4∆ARs were decreased. Our results indicate that ZMO0103 is the key to ampicillin resistance in Z. mobilis, and other ampicillin-resistant genes may have a synergetic effect with it. In summary, this study identified and characterized genes related to ampicillin resistance in Z. mobilis and laid a foundation for further study of other antibiotic resistance mechanisms.

Investigation of waves in the strengthened net

The movements of a reinforced net are considered. Mesh systems are used in various areas of modern technology, aviation, fishing, and construction. In recent years, much attention has been drawn to the complete equations that describe the motion of a deformable thread. In accordance with the studied task, the reinforcement of the net is carried out by adding terms in the equations of motion. In the planar case, the static behavior of the structure is investigated, and equations of motion are derived that allow the study of motion. The problem of wave propagation in deformable filament systems, taking into account a significant deviation of the filament shape from the original rectilinear one, is mathematically very difficult, since the equations of motion are a system of nonlinear differential equations in partial derivatives. To solve the problem, the method of characteristics is used. As well the method of characteristics solves the problem of the propagation of unloading waves (in the case of a load, shock waves arise). Depending on the velocity distribution at the boundary, the distribution of the strain constant on the characteristics is determined. The results are constructed by numerical integration of the integrals of the characteristics found by the method. The solution using the characteristic equations shows the occurrence of traveling waves.

Chaos and irreversibility of a flexible filament in periodically driven Stokes flow.

The flow of Newtonian fluid at low Reynolds number is, in general, regular and time-reversible due to absence of nonlinear effects. For example, if the fluid is sheared by its boundary motion that is subsequently reversed, then all the fluid elements return to their initial positions. Consequently, mixing in microchannels happens solely due to molecular diffusion and is very slow. Here, we show, numerically, that the introduction of a single, freely floating, flexible filament in a time-periodic linear shear flow can break reversibility and give rise to chaos due to elastic nonlinearities, if the bending rigidity of the filament is within a carefully chosen range. Within this range, not only the shape of the filament is spatiotemporally chaotic, but also the flow is an efficient mixer. Overall, we find five dynamical phases: the shape of a stiff filament is time-invariant-either straight or buckled; it undergoes a period-two bifurcation as the filament is made softer; becomes spatiotemporally chaotic for even softer filaments but, surprisingly, the chaos is suppressed if bending rigidity is decreased further.

On Stretching, Bending, Shearing, and Twisting of Actin Filaments I: Variational Models.

Mechanochemical simulations of actomyosin networks are traditionally based on one-dimensional models of actin filaments having zero width. Here, and in the follow up paper (arXiv, DOI 10.48550/arXiv.2203.01284), approaches are presented for more efficient modeling that incorporates stretching, shearing, and twisting of actin filaments. Our modeling of a semiflexible filament with a small but finite width is based on the Cosserat theory of elastic rods, which allows for six degrees of freedom at every point on the filament's backbone. In the variational models presented in this paper, a small and discrete set of parameters is used to describe a smooth filament shape having all degrees of freedom allowed in the Cosserat theory. Two main approaches are introduced: one where polynomial spline functions describe the filament's configuration, and one in which geodesic curves in the space of the configurational degrees of freedom are used. We find that in the latter representation the strain energy function can be calculated without resorting to a small-angle expansion, so it can describe arbitrarily large filament deformations without systematic error. These approaches are validated by a dynamical model of a Cosserat filament, which can be further extended by using multiresolution methods to allow more detailed monomer-based resolution in certain parts of the actin filament, as introduced in the follow up paper. The presented framework is illustrated by showing how torsional compliance in a finite-width filament can induce broken chiral symmetry in the structure of a cross-linked bundle.

Polyurethane shape memory filament yarns: Melt spinning, carbon-based reinforcement, and characterization

The aim of this work was to develop and characterize polyurethane-based shape memory polymer filament yarns of a suitable diameter and thermo-mechanical performance for use in tailored multi-sectorial applications. Different polymer compositions – pure shape memory polyurethane and shape memory polyurethane composites with 0.3 and 0.5 wt.% of multi-walled carbon nanotubes or carbon black as additives – were studied. Filaments were obtained using a melt spinning process that allowed the production of the permanent and temporary shape of the shape memory polyurethane filament. Two drawing speeds (20 and 32 m/min) were studied. Characterization techniques such as the tensile test, differential scanning calorimetry, and dynamic mechanical analysis were used to investigate the shape-memory effect of the filaments. Pure and additive shape memory polyurethane filament yarns of a controlled diameter were produced. The results indicated that the pure shape memory polyurethane on the temporary shape had the highest tensile strength (234 MPa). Filaments with carbon black revealed a significant strain (335%) in the permanent shape with respect to the other filaments. The melt spinning process influenced the soft segment glass transition temperature (Tgs) significantly, with a decrease in the temporary shape (first heating) as compared to the permanent shape (second and third heating). However, only the 0.5% multi-walled carbon nanotubes additive clearly influenced the filament, increasing the Tgs by 10°C. The additives also influenced the shape-memory effect, obtaining an increased fixity ratio (up to 97%) with the multi-walled carbon nanotubes additive and an increased recovery ratio (up to 86%) with the carbon black additive.

Suppression of Filament Defects in Embedded 3D Printing

Embedded 3D printing enables the manufacture of soft, intricate structures. In the technique, a nozzle is embedded into a viscoelastic support bath and extrudes filaments or droplets. While embedded 3D printing expands the printable materials space to low-viscosity fluids, it also presents new challenges. Filament cross-sections can be tall and narrow, have sharp edges, and have rough surfaces. Filaments can also rupture or contract due to capillarity, harming print fidelity. Through digital image analysis of in situ videos of the printing process and images of filaments just after printing, we probe the effects of ink and support rheology, print speeds, and interfacial tension on defects in individual filaments. Using model materials, we determine that if both the ink and support are water-based, the local viscosity ratio near the nozzle controls the filament shape. If the ink is slightly more viscous than the support, a round, smooth filament is produced. If the ink is oil-based and the support is water-based, the capillary number, or the product of the ink speed and support viscosity divided by the interfacial tension, controls the filament shape. To suppress contraction and rupture, the capillary number should be high, even though this leads to trade-offs in roughness and roundness. Still, inks at nonzero interfacial tension can be advantageous, since they lead to much rounder and smoother filaments than inks at zero interfacial tension with equivalent viscosity ratios.

Dynamics of a rigid-flexible coupling system in a uniform flow

Dynamics of two-dimensional flow past a rigid flat plate with a trailing closed flexible filament acting as a deformable afterbody are investigated numerically by an immersed boundary-lattice Boltzmann method for the fluid flow and a finite element method for the filament motion. The effects of Reynolds number ( $Re$ ) and length ratio ( $Lr$ ) on the flow patterns and dynamics of the rigid-flexible coupling system are studied. Based on our numerical results, five typical state modes have been identified in $Lr\unicode{x2013}Re$ plane in terms of the filament shape and corresponding dynamics, i.e. static deformation, micro-vibration, multi-frequency flapping, periodic flapping and chaotic flapping modes, respectively. Benefiting from the passive flow control by using the flexible filament as a deformable afterbody, the coupled system may enjoy a significant drag reduction (up to $22\,\%$ ) compared with bare plate scenarios ( $Lr=1$ ). Maximum drag reduction achieved at $L_{c,{min}} \in [1.8, 2]$ is often accompanied by the onset of the system state transition. The flow characteristic and its relation to the change in hydrodynamic drag are further explored in order to reveal the underlying mechanisms of the counterintuitive dynamical behaviour of the coupled system. The scaling laws for the form drag and the friction drag, which arise from the pressure and viscous effects, respectively, are proposed to estimate the overall drag acting on the system. The results obtained in the present study may shed some light on understanding the dynamical behaviour of rigid-flexible coupling systems.

Effect of Base Oil and Thickener on Texture and Flow of Lubricating Greases: Insights from Bulk Rheometry, Optical Microrheology and Electron Microscopy

The structure and flow behavior of lubricating greases depend on the base oil and the type and concentration of the dissolved thickener. In this study, the linear viscoelastic properties of greases were characterized by combining oscillatory shear and squeeze flow covering a broad frequency range (0.1–105 rad s−1). Multiple-particle tracking (MPT) microrheology and scanning electron microscopy (SEM) provided further insight into local viscoelastic properties and sample structure on a submicron-length scale. The type and viscosity of the base oil did not affect the absolute value of the complex viscosity and the filament shape formed by a given thickener. High-frequency shear modulus data, however, indicated that the thickener lithium 12-hydroxystearate formed stiffer networks/filaments in poly-α-olefins than in mineral oils. As expected, the viscosity increased with increased thickener concentrations, but microscopy and high-frequency rheometry revealed that the thickness, length, and stiffness of the individual filaments did not change. In mineral oil, the 12-hydroxystearate thickeners yielded higher viscosity than the corresponding stearates with the same metal ion. The filamentous lithium thickeners created stronger networks than the roundish aggregates formed by magnesium and zinc stearate. Network mesh sizes varying between approximately 100 nm and 300 nm were consistently determined from SEM image analysis and MPT experiments. The MPT experiments further disclosed the existence of gel-like precursors of approximately 130 µm at thickener concentrations far below the critical value at which a sample-spanning network resulting in a characteristic grease texture is formed.

나도 풍란을 이용한 속간 교잡종의 수정 및 배형성과 종자 발달에 대한 연구

On 5-7 days after artificial pollination using NadoPungRan(Phalenopsis japonica), native orchid in Korea, pollen were germinated in sticky stigma and pollen tube elongation in style were observed. on 14 days after pollination. In this period, ovule primodia appeared to round pronunciation shape. But filament shape and Megaspore Mother Cell were appeared on 34 days after pollination. Ovule which is ready fertilization, was matured in 40-50 days after pollination. In these time, pollen tube elongation were continued and entirely surrounded ovule sac. On 54-64 days after pollination, pollen tube penetrated to ovule sac and fertilization were completed. After fertilization, zygote was divided to two cell in longitudinal division and upper small cell was developed into proembryo and bottom large cell divided two cell which make suspensor cell. On 110 days after pollination, matured embryo and suspensor which have 16 filament leg, were observed and seed were matured on about 140 days after pollination. To breed intergeneric hybrids between NadoPungRan and Moth orchid, pods were collected in week after pollination and seed germination using artificial medium were tried. Young ovules before 56 days after pollination were not germinated. Ovules on 69 days after pollination were good for germination and to get hybrids.

나도 풍란을 이용한 속간 교잡종의 수정 및 배형성과 종자 발달에 대한 연구

On 5-7 days after artificial pollination using NadoPungRan(Phalenopsis japonica), native orchid in Korea, pollen were germinated in sticky stigma and pollen tube elongation in style were observed. on 14 days after pollination. In this period, ovule primodia appeared to round pronunciation shape. But filament shape and Megaspore Mother Cell were appeared on 34 days after pollination. Ovule which is ready fertilization, was matured in 40-50 days after pollination. In these time, pollen tube elongation were continued and entirely surrounded ovule sac. On 54-64 days after pollination, pollen tube penetrated to ovule sac and fertilization were completed. After fertilization, zygote was divided to two cell in longitudinal division and upper small cell was developed into proembryo and bottom large cell divided two cell which make suspensor cell. On 110 days after pollination, matured embryo and suspensor which have 16 filament leg, were observed and seed were matured on about 140 days after pollination. To breed intergeneric hybrids between NadoPungRan and Moth orchid, pods were collected in week after pollination and seed germination using artificial medium were tried. Young ovules before 56 days after pollination were not germinated. Ovules on 69 days after pollination were good for germination and to get hybrids.

나도 풍란을 이용한 속간 교잡종의 수정 및 배형성과 종자 발달에 대한 연구

On 5-7 days after artificial pollination using NadoPungRan(Phalenopsis japonica), native orchid in Korea, pollen were germinated in sticky stigma and pollen tube elongation in style were observed. on 14 days after pollination. In this period, ovule primodia appeared to round pronunciation shape. But filament shape and Megaspore Mother Cell were appeared on 34 days after pollination. Ovule which is ready fertilization, was matured in 40-50 days after pollination. In these time, pollen tube elongation were continued and entirely surrounded ovule sac. On 54-64 days after pollination, pollen tube penetrated to ovule sac and fertilization were completed. After fertilization, zygote was divided to two cell in longitudinal division and upper small cell was developed into proembryo and bottom large cell divided two cell which make suspensor cell. On 110 days after pollination, matured embryo and suspensor which have 16 filament leg, were observed and seed were matured on about 140 days after pollination. To breed intergeneric hybrids between NadoPungRan and Moth orchid, pods were collected in week after pollination and seed germination using artificial medium were tried. Young ovules before 56 days after pollination were not germinated. Ovules on 69 days after pollination were good for germination and to get hybrids.

Preliminary Study and First Evidence of Presence of Microplastics in Green Mussel, Perna viridis from Phuket

Plastics can reach the coastal environment and could impact the marine environment. Mussels are marine organisms which are prone to be exposed to microplastics pollution. Therefore, in this preliminary study, the commercially important green mussel (Perna viridis) collected at the Koh Phee Canal in Phuket, Phuket Province, southern peninsular Thailand, was investigated. The collected mussels from aquaculture farm fell into three age groups, namely 1 year-1 month, 1 year-7 months, and 1 year-9 months. Results from the investigation showed 200 items of microplastics present in Perna viridis with 76 items (38%) in flushed water and 124 items (62%) in the soft tissue. The average counts of microplastics in soft tissue and flushed water were 4.13 items per individual and 2.53 items per individual, respectively. Blue color (98 items, 49%) and filament shape (185 items, 92.5%) were the most common color and shape of microplastics in the mussel tissues and the flushed water. The dominant polymers as microplastics were identified as polyester and polyethylene terephthalate, which are common polymer types used in protective packaging and containers. The statistical post hoc tests showed no significant differences by age group in the microplastics accumulation in the Perna viridis (p<0.05). Further studies are required to understand the accumulation rates and residence times of microplastics across the food webs for better understanding on their impacts on human health. The results from this study provide a baseline level of microplastics contamination in green mussel aquaculture located at Phuket, and urgent measures are needed to prevent contamination of food for human consumption and related health problems.

Main modes of microfilament particles deformation in rough channels

The fate and transport of microfilaments in complex structured porous systems are largely affected by the geometry of the irregular pore space in these media. Local features of fluid flow, including local flow instabilities, vorticities, stagnant zones, and reverse flows, which result from the spatially varying pore throat size and altering shear stresses along the channel due to the presence of rough walls, can cause various modes of deformation of filaments and them being carried in reverse direction of the general fluid flow. Furthermore, the buildup of microfilaments along the channel can clog the pore space and rearrange the flow in the channel. In this study, we focus on investigating the role of channel wall roughness on the motion and deformation of five deformable filaments flowing in a channel filled with fluid. A bead-spring model is used for the filament model. At low Reynolds numbers, roughness simply increases the length of the path line along which the filament is being transported. Moreover, at higher Reynolds numbers, the filament closer to the walls can get stuck in the dead flow zones within the rough geometry peaks. The filaments closer to the centerline of the channel undergo less deformation compared to those located closer to the walls. A larger Reynolds number or a more rough geometry of the walls can result in a more wiggly form of the filament. Intermediate roughness and a medium Reynolds number result in more of a hairpin-like filament shape.