Filament Surface Research Articles

Microwave-assisted fracture toughness improvement in additively manufactured polylactic acid–copper composite

The composition variation in composites' structure can be customized to expand their applications for antennae, capacitors, and heat transfer devices. In this study, a fused deposition modeling technique was utilized to customize composition variation in a polylactic acid–copper composite structure. The significant differences in constituents' thermal properties can induce defects and residual stresses, limiting composites' fracture toughness. This property can be improved by post-manufacturing processes such as microwave-assisted heat treatment of composites containing constituents with different dielectric properties. In this work, samples involving a composite part sandwiched between two symmetrical polymer sections were additively manufactured. The composite layers were deposited after selective impregnation of a polylactic acid filament surface with micro-size copper particles. Four sets of manufactured samples were exposed to a 2.45 GHz microwave with 3 kW power for 30, 60, 75, and 90 s. The tensile fracture test results showed that 75 s of exposure improved the interlayer fracture toughness of composites significantly by 37%, the highest among all treatment conditions. Based on microscopy and thermal analysis, it was discussed that decreasing the size of microvoids in the layers, the percentage of polymer crystallinity, and residual stress would benefit fracture toughness of exposed composites.

Neuronal death in pneumococcal meningitis is triggered by pneumolysin and RrgA interactions with β-actin.

Neuronal damage is a major consequence of bacterial meningitis, but little is known about mechanisms of bacterial interaction with neurons leading to neuronal cell death. Streptococcus pneumoniae (pneumococcus) is a leading cause of bacterial meningitis and many survivors develop neurological sequelae after the acute infection has resolved, possibly due to neuronal damage. Here, we studied mechanisms for pneumococcal interactions with neurons. Using human primary neurons, pull-down experiments and mass spectrometry, we show that pneumococci interact with the cytoskeleton protein β-actin through the pilus-1 adhesin RrgA and the cytotoxin pneumolysin (Ply), thereby promoting adhesion and invasion of neurons, and neuronal death. Using our bacteremia-derived meningitis mouse model, we observe that RrgA- and Ply-expressing pneumococci co-localize with neuronal β-actin. Using purified proteins, we show that Ply, through its cholesterol-binding domain 4, interacts with the neuronal plasma membrane, thereby increasing the exposure on the outer surface of β-actin filaments, leading to more β-actin binding sites available for RrgA binding, and thus enhanced pneumococcal interactions with neurons. Pneumococcal infection promotes neuronal death possibly due to increased intracellular Ca2+ levels depending on presence of Ply, as well as on actin cytoskeleton disassembly. STED super-resolution microscopy showed disruption of β-actin filaments in neurons infected with pneumococci expressing RrgA and Ply. Finally, neuronal death caused by pneumococcal infection could be inhibited using antibodies against β-actin. The generated data potentially helps explaining mechanisms for why pneumococci frequently cause neurological sequelae.

Super-hydrophobic F-TiO2@PP membranes with nano-scale “coral”-like synapses for waste oil recovery

Super-hydrophobic F-TiO2@PP membranes were developed from polypropylene (PP) non-woven fabric by in situ cross-linking polymerization of trifluorofluorooctyl methacrylate (FOMA) and sol–gel-derived titanium dioxide with vinyltriethoxysilane (VTES). Due to the formation of super-hydrophobic “coral”-like synapses on the filamentous surfaces of PP non-woven fabric, F-TiO2@PP membranes showed extremely high water contact angles up to 157° and capability of rapidly absorbing oil drops. The F-TiO2@PP membranes were also able to expel water from water-in-oil emulsions with robustly high oil permeate fluxes (up to 11,000 L m−2h−1 under gravity), water removing efficiency (up to 99.7%), re-usability and long-term stability even at the presence of surfactant and salts. Such superior performance could lead to potential applications in rapid collection and efficient purification of recovered oily organic components from waste liquids or accidental oil discharges in marine or continental situations.

Regularised non-uniform segments and efficient no-slip elastohydrodynamics

Abstract

Four novel Myxobolus species (Cnidaria: Myxozoa) infecting Anatolian khramulya Capoeta tinca (Cyprinidae) in northern Turkey.

We identified Myxobolus anatolicus Pekmezci, Yardimci, Yilmaz & Polat, 2014 and 4 novel Myxobolus species from the Anatolian khramulya Capoeta tinca (Cyprinidae) in northern Turkey based on morphology, histology, and phylogenetic analysis. M. karaeri sp. nov. plasmodia were observed in the skin doublets between fin rays, the surfaces of the operculum, the gill arch membrane, and in the skin of the fin base. M. samsunensis sp. nov. plasmodia were observed in epithelial tissue inside and on the surface and midline of the gill filaments. M. cakmaki sp. nov. presented as a typical vascular species, which develops in large plasmodia at the end of the gill filaments. The chondrophilic M. ekingeni sp. nov. was detected by histology inside the cartilaginous gill arch and the cartilaginous gill rays of the filaments. Phylogenetic analysis of small subunit ribosomal DNA sequences revealed that M. karaeri sp. nov. and M. samsunensis sp. nov. were clustered with Myxobolus species that infect gills, scales, and fins of cyprinids. M. cakmaki sp. nov. grouped with Myxobolus species that exclusively infect the gills of cyprinids. No molecular data were available for M. ekingeni sp. nov.

Static Fatigue of SiC/SiC Minicomposites at High Temperatures Up to 1200 °C in Air: Multiscale Approach

The present paper investigates the static fatigue behavior of Hi-Nicalon fiber-reinforced SiC–SiC minicomposites at high temperatures in the 900–1200 °C range, and under tensile stresses above the proportional limit. The stress–rupture time relation was analyzed with respect to subcritical crack growth in filaments and fiber tow fracture. Slow crack growth from flaws located at the surface of filaments is driven by the oxidation of free carbon at the grain boundaries. Lifetime of the reinforcing tows depends on the statistical distribution of filament strength and on structural factors, which are enhanced by temperature increase. The rupture time data were plotted in terms of initial stresses on reinforcing filaments. The effect of temperature and load on the stress–rupture time relation for minicomposites was investigated using results of fractography and predictions of minicomposite lifetime using a model of subcritical growth for critical filaments. The critical filament is the one whose failure by slow crack-growth triggers unstable fracture of the minicomposite. This is identified by the strength–probability relation provided by the cumulative distribution function for filament strength at room temperature. The results were compared to the fatigue behavior of dry tows. The influence of various factors related to oxidation, including multiple failures, load sharing, and variability, was analyzed.

Cellular and Genomic Properties of Haloferax gibbonsii LR2-5, the Host of Euryarchaeal Virus HFTV1.

Hypersaline environments are the source of many viruses infecting different species of halophilic euryarchaea. Information on infection mechanisms of archaeal viruses is scarce, due to the lack of genetically accessible virus–host models. Recently, a new archaeal siphovirus, Haloferax tailed virus 1 (HFTV1), was isolated together with its host belonging to the genus Haloferax, but it is not infectious on the widely used model euryarcheon Haloferax volcanii. To gain more insight into the biology of HFTV1 host strain LR2-5, we studied characteristics that might play a role in its virus susceptibility: growth-dependent motility, surface layer, filamentous surface structures, and cell shape. Its genome sequence showed that LR2-5 is a new strain of Haloferax gibbonsii. LR2-5 lacks obvious viral defense systems, such as CRISPR-Cas, and the composition of its cell surface is different from Hfx. volcanii, which might explain the different viral host range. This work provides first deep insights into the relationship between the host of halovirus HFTV1 and other members of the genus Haloferax. Given the close relationship to the genetically accessible Hfx. volcanii, LR2-5 has high potential as a new model for virus–host studies in euryarchaea.

Ice-Templated Cellulose Nanofiber Filaments as a Reinforcement Material in Epoxy Composites.

Finding renewable alternatives to the commonly used reinforcement materials in composites is attracting a significant amount of research interest. Nanocellulose is a promising candidate owing to its wide availability and favorable properties such as high Young’s modulus. This study addressed the major problems inherent to cellulose nanocomposites, namely, controlling the fiber structure and obtaining a sufficient interfacial adhesion between nanocellulose and a non-hydrophilic matrix. Unidirectionally aligned cellulose nanofiber filament mats were obtained via ice-templating, and chemical vapor deposition was used to cover the filament surfaces with an aminosilane before impregnating the mats with a bio-epoxy resin. The process resulted in cellulose nanocomposites with an oriented structure and a strong fiber–matrix interface. Diffuse reflectance infrared Fourier transform and X-ray photoelectron spectroscopy studies revealed the presence of silane on the filaments. The improved interface, resulting from the surface treatment, was observable in electron microscopy images and was further confirmed by the significant increase in the tan delta peak temperature. The storage modulus of the matrix could be improved up to 2.5-fold with 18 wt% filament content and was significantly higher in the filament direction. Wide-angle X-ray scattering was used to study the orientation of cellulose nanofibers in the filament mats and the composites, and the corresponding orientation indices were 0.6 and 0.53, respectively, indicating a significant level of alignment.

Structural Changes in the Myosin Motors Induced by Stretch and Phosphorylation of the Myosin Regulatory Light Chain in Rat Cardiac Trabeculae

The contractility of cardiac muscle is potentiated by phosphorylation of the myosin regulatory light chain (RLC) and by length-dependent activation, but the molecular pathways mediating these effects remain unclear. Here we studied the role of structural changes in the thick filament in the activation of cardiac muscle by stretch and RLC phosphorylation. We used fluorescence polarization from bifunctional sulphorhodamine probes on the N- and C-lobes of the myosin RLC to monitor changes in the orientation of the myosin motors induced by increasing the sarcomere length in the range 2.0-2.3 µm in relaxed and partially calcium-activated demembranated cardiac trabeculae, at different levels of RLC phosphorylation. We show that under relaxing or diastolic conditions at near physiological temperature and lattice spacing the RLC lobe orientations are consistent with about one third of the myosin motors being folded onto the filament surface in the interacting-heads motif seen in isolated filaments. This folded conformation is disrupted by cooling relaxed trabecula, but not by RLC phosphorylation or stretch at diastolic [Ca2+]. These results indicate that in near-physiological conditions the myosin filament is not switched on by RLC phosphorylation or by the titin-based passive tension at longer sarcomere lengths in diastole, as suggested previously. However, stretching cardiac trabecula at near-systolic [Ca2+] triggers a stress-dependent activation of the thick filament and a delayed increase in active force. Physiological levels of RLC phosphorylation potentiate both the stress-dependent release of myosin motors from the folded state and the stretch-activated force. We conclude that the increase in heart contractility induced by RLC phosphorylation and stretch can be explained by an inter-filament signaling pathway involving both thin filament sensitization and thick filament mechano-sensing (Supported by Wellcome Trust, BHF, UK).

Clusters of a Few Bound Cofilins Sever Actin Filaments

Cofilin is an essential actin filament severing protein that accelerates the assembly dynamics and turnover of actin networks by increasing the number of filament ends where subunits add and dissociate. It binds filament subunits stoichiometrically and cooperatively, forming clusters of contiguously-bound cofilin at sub-saturating occupancies. Filaments partially occupied with cofilin sever at boundaries between bare and cofilin-decorated segments. Imaging studies concluded that bound clusters must reach a critical size (Cc) of 13–100 cofilins to sever filaments. In contrast, structural and modeling studies suggest that a few or even a single cofilin can sever filaments, possibly with different severing rate constants. How clusters grow through the cooperative incorporation of additional cofilin molecules, specifically if they elongate asymmetrically or uniformly from both ends and if they are modulated by filament shape and external force, also lacks consensus. Here, using hydrodynamic flow to visualize individual actin filaments with TIRF microscopy, we found that neither flow-induced filament bending, tension, nor surface attachment conditions substantially affected the kinetics of cofilin binding to actin filaments. Clusters of bound cofilin preferentially extended toward filament pointed ends and displayed severing competency at small sizes (Cc < 3), with no detectable severing dependence on cluster size. These data support models in which small clusters of cofilin introduce local, but asymmetric, structural changes in actin filaments that promote filament severing with a rate constant that depends weakly on the size of the cluster.

Stretchable strain sensors with dentate groove structure for enhanced sensing recoverability

Stretchable strain sensors based on conductive polymer composites commonly utilize elastic polymers as the matrix. However, elastic polymers always show strong mechanical hysteresis effect leading to shoulder peak phenomenon and thereby poor recoverability of strain sensors. Herein, we design a stretchable rough filament strain sensor with dentate groove structure to eliminate the shoulder peak phenomenon and improve recoverability. The filament strain sensor is fabricated by the extrusion of poly(styrene-b-ethylene-b-butylene-b-styrene) (SEBS) filament constructing dentate groove structure and the subsequent ultrasonic treatment decorating carbon nanotubes (CNTs) on the surface of the SEBS filament. It is interesting to find that the strain sensing range of rough SEBS/CNTs filaments with dentate groove structure is wider than that of smooth filaments. More importantly, the rough filament strain sensors exhibit significantly enhanced recoverability without shoulder peak during the releasing process while the rough dentate groove structure has minor effects on the mechanical properties of SEBS filaments. The great improvement is ascribed to the uniform distribution of deformation because of the dentate groove structure, which induces reduction of the mechanical hysteresis effect and thereby decreases residual strain. Moreover, the rough filament strain sensors have a favorable integration of good stability, fast response time of 300 ms (0.5% strain is applied with a high strain rate of 500 mm/min) and excellent durability (1976 cycles at the strain of 50%). The rough filament strain sensors can accurately and stably monitor both large and subtle human motions (such as body motion, expression and phonation), showing broad application prospects in wearable devices.

Viral Hijack of Filamentous Surface Structures in Archaea and Bacteria.

The bacterial and archaeal cell surface is decorated with filamentous surface structures that are used for different functions, such as motility, DNA exchange and biofilm formation. Viruses hijack these structures and use them to ride to the cell surface for successful entry. In this review, we describe currently known mechanisms for viral attachment, translocation, and entry via filamentous surface structures. We describe the different mechanisms used to exploit various surface structures bacterial and archaeal viruses. This overview highlights the importance of filamentous structures at the cell surface for entry of prokaryotic viruses.

Synergistic effect of plasticizer and nucleating agent on crystallization behavior of polylactide during fused filament fabrication

Polylactide (PLA) materials manufactured by fused filament fabrication (FFF) technique are usually in amorphous form and thereby exhibit poor mechanical properties and thermal resistance. Overcoming this issue requires a good knowledge of the crystallization behavior of PLA materials during the FFF process. In this work, a plasticizer (polyethylene glycol, PEG) and a nucleating agent (tetramethylene-dicarboxylic dibenzoyl-hydrazide, TMC-306), were added in PLA matrix, separately and synergistically, to tailor crystallization behavior of FFF-printed PLA parts. At a bed temperature of 60 °C, PEG played a stronger effect on crystallization behavior than the nucleating agent TMC and even the combination of TMC and PEG. This resulted in an increase of the crystallinity from 8% for both neat PLA and PLA/TMC samples to 18% for the samples containing PEG. With the increase of the bed temperature to 90 °C, TMC and PEG separately or synergistically had prominent effects on enhancing the crystallization ability of PLA during the FFF process, leading to the highly crystalline PLA parts with the crystallinities in the range of 30–40%. By means of wide angle X-ray diffraction and scanning electron microscopy measurements, shear-induced crystal structures were indentified at the filament surface as well as the weld interface. Nevertheless, the shear-induced effect had negligible influence on the final crystallinity of PLA parts. Instead, PLA parts with a high crystallinity can be attained, only when the material characteristics and the printing conditions are in favor of cold crystallization of PLA. The unique crystallization behavior of FFF-printed PLA materials offers guidelines for the fabrication of products with controlled crystallinity and hierarchical structures for specific applications.

Generation and Demolishment Mechanisms of Vapor Bubble Around Hot Tungsten Filament in Superfluid Helium-4

The electric transport I–V characteristics of a tungsten filament immersed in superfluid helium are experimentally studied. The forward sweep I–V characteristics show an abrupt jump from the linear ohmic regime (C state) to the high-resistance non-ohmic regime (H state). In the H state, the filament is covered with a He gas bubble. In the C state, there is no gas bubble, that is, liquid He directly touches the filament surface. The transitions between these two states exhibit a well-developed hysteresis and bistability. The transition from the H state to the C state occurs at the equilibrium gas–liquid phase transition point, as reported by Date et al. (J Phys Soc Jpn 35(4):1190, 1973), whereas the C-to-H-state transition occurs in the superheat region.

The influence of environmental calcium on the branchial morphology in a catadromous fish.

Eels are exposed to Ca2+ changes during migration between seawater and freshwater. The gill is the main organ of active calcium transport and has a large surface area to be particularly sensitive to environmental changes in the aquatic environment. In this research, we focused on the morphological changes of gill tissues when eels are faced with the environmental calcium challenges. Based on the results of hematoxylin and eosin (HE) staining and immunohistochemistry, compared with the control group (normal Ca2+ environment), the filament and lamella lengths and lamellar frequency (LF) appeared higher in high calcium environment and lower in deficient calcium environment, while the lamella width and filamental lamellar surface area (SAFL) decreased in high calcium environment and increased in deficient calcium environment. And there was no difference in the number filaments in first right gill arch in the three Ca2+ water environment. Transmission electron microscopy was employed to examine the ultrastructural changes in gills in different Ca2+ water environment. The nucleus and endoplasmic reticulum had a tendency to expand in calcium-deficient water, but had a tendency to shrink in high-calcium water comparing with the control group. This study provides the support that branchial surface areas are regulated in different Ca2+ waters through a list of calcium transporters including CACNB2.

Анализ влияния плазменной активации на энергию поверхности волокон сверхвысокомолекулярного полиэтилена, на прочность волокон и армированных волокнами композитов

Completely saturated chemical bonds in ultrahigh-molecular-weight polyethylene (UHMWPE) fibers — are a reason for their low surface energy (FSE), i.e. inert properties. Elongated crystal structure of UHMWPE molecules ensures high anisotropic tensile strength of the fibers. An inertness is a problem for utilization these fibers in high-strength composites production. Surface energy (SE) difference of the fibers and a binder in fiber/matrix system hinders chemical interaction at interphase boundary and worsens fiber wettability. Increase in their FSE is a topical task for this problem decision. Necessary condition of FSE increase is the integrity of molecule structure, lying under modified surface. Low temperature, nonequilibrium plasma (LTP) treatment in a medium of argon and argon/propane mixture, used in this work for plasma activation of fibers’ surface, permits to abide by this condition. However, plasma ion bombardment during a process of activation can modify interior crystal structure and, as a result, decrease their strength. The rovings SK75 (Holland) and D800 (China) were used for study of the properties of UHMWPE fibers after plasma treatment. Activation effect on FSE, strength, and fibers’ wetting by water and epoxy binder before and after ageing was studied. Capillary wetting of the fibers by distilled water used for FSE evaluation. The data of filaments surface structure and their diameter change at maximal load, obtained by optical microscope study, were used for the analysis of FSE and epoxy matrix effect on the strength of fiber/matrix systems. Essential distinction of SK75 and D800 fibers properties is ascertained. Negative effect of fibers’ and matrix’s stiffness, as well as increased FSE of stiff fibers on the strength of fiber/matrix system is revealed.

Direct Filament Dryer With Moisture And Dust Absorbent For 3D Printing Plastic Filaments

Industrial Revolution 4.0 requires every line of life to apply technology, especially in the field of prototyping. 3D PrintingFDM (Fused Deposition Modeling) technology is used for the needs of rapid prototyping. The plastic filament material is the main requirement in printing FDM or FFF (Fused Filament Fabrication). However, there are poor print quality problems in this storage process because all types of plastic filaments used in this 3D printing technology are affected by moisture and dust. The moisture of the plastic filament can be seen if there is a hiss in the printing process and the surface of the printing result becomes rough. At the same time, the dust on the filament will clog the hot end nozzle. Current 3D printing technology is used to reduce this problem by storing filaments in the filament box dryer. However, this storage has several drawbacks. It is less efficient and practical because the filament box can only hold one of the plastic filament rolls. From this problem, we tried to create "Direct Filament Dryer with Moisture and Dust Absorbent for 3D Printing Plastic Filaments". The principle of this tool is to put the filament into the heating chamber. This room contains silica gel as a damper for moisture and a sponge to clean the dust on the filament's surface. The heating room temperature is controlled by a thermostat, which will keep the temperature between 40-50 °C. This research uses R&amp;D techniques with the 4D method, namely, Define, Design, Develop, and Disseminate. Meanwhile, to test the results of this research by comparing the printing results between plastic filaments that are allowed to become damp and dusty with technology. Therefore, it was concluded that using made the filament surface smooth without any rough parts.

3D-printed electrode as a new platform for electrochemical immunosensors for virus detection

Simple, low-cost, and sensitive new platforms for electrochemical immunosensors for virus detection have been attracted attention due to the recent pandemic caused by a new type of coronavirus (SARS-CoV-2). In the present work, we report for the first time the construction of an immunosensor using a commercial 3D conductive filament of carbon black and polylactic acid (PLA) to detect Hantavirus Araucaria nucleoprotein (Np) as a proof-of-concept. The recognition biomolecule was anchored directly at the filament surface by using N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride and N-Hydroxysuccinimide (EDC/NHS). Conductive and non-conductive composites of PLA were characterized using thermal gravimetric analysis (TGA), revealing around 30% w/w of carbon in the filament. Morphological features of composites were obtained from SEM and TEM measurements. FTIR measurement revealed that crosslinking agents were covalently bonded at the filament surface. Electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for the evaluation of each step involved in the construction of the proposed immunosensor. The results showed the potentiality of the device for the quantitative detection of Hantavirus Araucaria nucleoprotein (Np) from 30 μg mL−1 to 240 μg mL−1 with a limit of detection of 22 μg mL−1. Also, the proposed immunosensor was applied with success for virus detection in 100x diluted human serum samples. Therefore, the PLA conductive filament with carbon black is a simple and excellent platform for immunosensing, which offers naturally carboxylic groups able to anchor covalently biomolecules.

Development of 7-Segment Numeral Display Using Electrochromic Yarns for Advanced Functional Textiles

Development of electrochromic yarns opens up a high-tech option for the development of next-generation fashion textiles. Previous work has introduced electrochromic yarns comprising a metal wire core wrapped with organometallic compounds and conjugated polymers, but has reported unsatisfying colour-changing contrast and weavability. Here we report a tungsten trioxide (WO3)-electroplated high-contrast electrochromic filament suitable for weaving, and a 7-segment display embroidered with such filaments. The electroplating conditions have been optimised through elemental analysis via X-ray photoelectron spectroscopy (XPS), with the aid of coating morphology observation via scanning electron microscopy (SEM). We have learnt that sufficient WO3 for an evident change of colour can be deposited on the filament surface at -0.5V (vs. AgCl) in 30s. This low voltage and short coating duration have shown possibility for up scaled production of the electrochromic filament. Connecting the 7-segment display with ESP8266 Wi-Fi micro-controller unit, through remote signal input on ‘Blynk’ (an open-access mobile platform), we have demonstrated a double-digit ‘chance of rainfall’. Our study offers guidance on the design of textile-based information displays.

CO2 conversion in a coaxial dielectric barrier discharge plasma reactor in the presence of mixed ZrO2-CeO2

Dielectric barrier discharge (DBD) plasma in packed bed reactors are widely used in the environment and energy (such as CO2 conversion). Packing material is a key factor in the reaction of splitting CO2 into CO and O2 by dielectric barrier discharge plasma. To get higher CO2 conversion, grinding balls made of a mixture of ZrO2 and CeO2 in a certain proportion was employed as packing material in this work. The effects of discharge power, feed flow rate, packing length, circulating water temperature and particle size on discharge characteristics and CO2 conversion were investigated to have a better understanding of the performance of the packing material. The reactor discharge behavior was observed by determining the product gas composition and plasma power consumption to determine CO2 conversion and energy efficiency. The packing of the catalyst in the reactor makes the discharge mode from the initial filament discharge to the combination of filament discharge and surface discharge. Compared with oxides composed of a single substance, the two oxides of the composite catalyst can interact, possibly achieving a synergistic effect. Typical results showed that this mixed material had a better property than the reported materials like BaTiO3, Al2O3, ZrO2 and so on which consist of a single substance. The maximum CO2 conversion reached 64.38 % and the maximum energy efficiency reached 8.76 %, which is currently the highest in the known literature. The higher circulating water temperature and larger particle size lead to the decrease of CO2 conversion and energy efficiency. The best performance of the mixture catalyst may be attributed to the oxygen vacancies, which stabilizes the atomic oxygen produced in the reaction and thus facilitates the conversion of CO2.