Small-diameter Fibers Research Articles

An Ideal Structure for Li-Ion Battery Separators

Among all types of Li-ion battery (LIB) separators, fibrous mats have the advantage of low cost, low mass, and high porosity. Fibrous Poly(Vinylidene difluoride) (PVDF) shows promising results because of its stability and affinity for electrolytes commonly employed in Li-ion cells. Despite numerous studies published on LIB separators, none reports structure-property relationships for the identification of an ideal structure. We investigated the properties of a melt-blowable PVDF and produced meltblown PVDF mats in scale-up equipment with the objective of elucidating its performance as a LIB separator. We also present a new class of LIB separators, PVDF-based highly-branched, colloidal polymer particulates called soft dendritic colloids that are produced by shear-driven polymer precipitation within a highly turbulent nonsolvent flow, followed by filtration. We show that the morphology of the resulting PVDF particulates can be modulated from fibrous soft dendritic colloids (SDC) to thin and highly porous sheet-like particles.Through a scale-up system, we obtained high-quality meltblown PVDF with high homogeneity, low number of defects, an average fiber diameter of 1.4 μm, and pore size as low as 0.9 μm. Small fiber diameter provides high-surface area and high-electrolyte uptake. We show interactions of the meltblown PVDF with the electrolyte lead to a morphology change in the fibers. The highest ionic conductivity was ~ 9.6 mS/cm, and the first-cycle capacity was 140 mAh/g (Li/LiCoO2). After melt-pressing, the thickness and pore size decrease, but the mats electrolyte absorbency and conductivity decrease commensurately. PVDF SDC separators show high porosity (up to 80%) and high particle surface area, which results in high conductivity (1.2 mS/cm), high-electrolyte uptake (325%), and high-cell capacity (112 mAh/g in Li/LiCoO2 cell) with <10% loss after 50 cycles. Both processes yield separators with low thermal shrinkage (<5% at 90 ºC) and high tensile strength (<0.5% offset at 1000 psi), with the highest-performing separator possessing low average fiber diameter with a wide diameter distribution.Both meltblowing and shear-driven precipitation are facile and versatile processes for high-volume fabrication of LIB separators with one single polymer without necessarily requiring post-processing and with characteristics similar to commercially available battery separators. Our findings show that battery separators should be fabricated with a low pore size (<2 µm) but also with a wide pore distribution. When the strength and openness of the micropores are coupled with a dense net of nanopores, an ideal Li-ion battery separator is obtained.

Brain imaging signature of neuropathic pain phenotypes in small-fiber neuropathy: altered thalamic connectome and its associations with skin nerve degeneration.

Small-fiber neuropathy (SFN) has been traditionally considered as a pure disorder of the peripheral nervous system, characterized by neuropathic pain and degeneration of small-diameter nerve fibers in the skin. Previous functional magnetic resonance imaging studies revealed abnormal activations of pain networks, but the structural basis underlying such maladaptive functional alterations remains elusive. We applied diffusion tensor imaging to explore the influences of SFN on brain microstructures. Forty-one patients with pathology-proven SFN with reduced skin innervation were recruited. White matter connectivity with the thalamus as the seed was assessed using probabilistic tractography of diffusion tensor imaging. Patients with SFN had reduced thalamic connectivity with the insular cortex and the sensorimotor areas, including the postcentral and precentral gyri. Furthermore, the degree of skin nerve degeneration, measured by intraepidermal nerve fiber density, was associated with the reduction of connectivity between the thalamus and pain-related areas according to different neuropathic pain phenotypes, specifically, the frontal, cingulate, motor, and limbic areas for burning, electrical shocks, tingling, mechanical allodynia, and numbness. Despite altered white matter connectivity, there was no change in white matter integrity assessed with fractional anisotropy. Our findings indicate that alterations in structural connectivity may serve as a biomarker of maladaptive brain plasticity that contributes to neuropathic pain after peripheral nerve degeneration.

Process‐structure‐property relationship of meltblown poly (styrene–ethylene/butylene–styrene) nonwovens

AbstractWith the advance of the thermoplastic plastic elastomer (TPE) technology, there are growing interest and needs for using these materials in the meltblowing process where benefits of small fiber diameters of meltblowns can be combined with rubber‐like elastic properties of elastomers. Performances and utilities of wide ranges of meltblown products such as facemask, medical barrier, wound‐care, diaper can be drastically improved with additions of TPE. In this study, a new elastomeric meltblown fabric was successfully made with the styrene–ethylene/butylene–styrene (SEBS) block copolymer, and the relationship among structure, tensile properties, and meltblowing process parameters are studied. We found that median fiber diameter increases with the polymer mass throughout and decreases with air pressure, and fabric solidity has significantly influenced by die collector distance (DCD). The pore sizes of the fabrics are directly influenced by fiber diameters at the given DCD, but higher DCD increases the pore size due to their open structures. All SEBS nonwovens exhibit high strain at break, larger than 400%. Processing parameters significantly affect tensile properties, and this can be attributed to the fabric structure changes. The reduction of fiber diameter tends to increase the tensile strength of the fabric as it created more fiber‐to‐fiber bond points.

Melt Electrospinning of Nanofibers from Medical-Grade Poly(ε-Caprolactone) with a Modified Nozzle.

Melt electrospun fibers, in general, have larger diameters than normally achieved with solution electrospinning. This study uses a modified nozzle to direct-write melt electrospun medical-grade poly(ε-caprolactone) onto a collector resulting in fibers with the smallest average diameter being 275±86nmunder certain processing conditions. Within a flat-tipped nozzle is a small acupuncture needle positioned so that reduces the flow rate to ≈0.1µL h-1 and has the sharp tip protruding beyond the nozzle, into the Taylor cone. The investigations indicate that 1-mm needle protrusion coupled with a heating temperature of 120°C produce the most consistent, small diameter nanofibers. Using different protrusion distances for the acupuncture needle results in an unstable jet that deposited poor quality fibers that, in turn, affects the next adjacent path. The material quality is notably affected by the direct-writing speed, which became unstable above 10mm min-1 . Coupled with a dual head printer, first melt electrospinning, then melt electrowriting could be performed in a single, automated process for the first time. Overall, the approach used here resulted in some of the smallest melt electrospun fibers reported to date and the smallest diameter fibers from a medical-grade degradable polymer using a melt processing technology.

Glyoxalation of Kraft lignin and optimization of electrospinning process parameters for producing polyacrylonitrile/KL nanomats for potential applications as carbon material

In this work, Kraft lignin (KL), glyoxalated KL and its blends with polyacrylonitrile (PAN/KL) were electrospun by solution electrospinning in order to investigate the morphology of the mats to be used in carbon material applications. The process parameters to obtain PAN/KL nanofibers with higher amount of KL and without defects were optimized. Three types of KL were used in this work: non-purified (KL), purified (KLp) and glyoxalated (KLg). The effects of the glyoxalation reaction time and the ratio of glyoxal-to-KL were, also, investigated in order to improve the molar mass of the KL. The results show that the molar mass of each glyoxalated KL increases compared to that of the standard KL. The molar mass remained unchanged with increasing the reaction time and ratio of glyoxal-to-KL. All obtained nanofiber mats were characterized by scanning electron microscopy (SEM) and their morphology showed to be dependent on the ratio of the PAN/KL used. Increasing the KL content decreases the diameter of the nanofibers. The maximum KL content in the PAN/KL blend, required to produce nanofibers without defects and with small fiber diameter, was 50 wt.%, making this material promising for a carbon material precursor. For the case of KLg, nanomats with beads were obtained with 70 and 80 wt.% KLg in the blend. Thermal properties of the nanomats showed a direct relationship to the content of KL used and its molar mass. In addition, these results point to a new approach for the application of KL and PAN/KL nanofibers.

Survivability of integrated fiber Bragg grating sensors in ballistic protection fabrics for high velocity impact testing

Abstract This research demonstrates that fiber Bragg grating (FBG) strain sensors can survive and provide useful strain information when integrated into a woven fabric subjected to ballistic impact testing. In this work, FBGs were integrated into a single-layer, Kevlar® fabric, sensing mat, placed between a 30-layer Kevlar® fabric shoot pack and clay backing material, and then impacted with an 8.23 g, 12.69 mm diameter, steel ball bearing at velocities up to 285 m/s. Three different optical fiber types, with differing fiber coatings and fiber diameters, were tested. The FBG strain response was determined from the full-spectrum FBG response which was interrogated at 100 kHz throughout the impact event. The difference in FBG strain response for the different coatings and fiber diameters were compared. Additionally, the degradation of the coatings after repeated impacts were visually characterized, showing that smaller diameter fibers behaved better with a more elastic coating.

Chronic pain: a long-term sequela of epidermal necrolysis (Stevens-Johnson syndrome/toxic epidermal necrolysis) - prevalence, clinical characteristics and risk factors.

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are associated with various sequelae. Chronic pain, one of these sequelae, has never been systematically evaluated. To assess the persistence of pain in a single-centre cohort of 113 consecutive patients with SJS/TEN. From this cohort, 81 patients were interviewed more than 1year after the initial episode and included in the study. Data were collected according to standardized questionnaires. From the 81 interviewed patients, 52 patients (64%) were painless and 29 patients (36%) were painful. Chronic pain syndrome was associated with a more severe initial acute phase of the disease (larger extent of detachment, higher SCORTEN, increased rate of admission in ICU and complications, and longer hospital stay). Pain was mainly located at the level of eyes (55%), mouth and lower limbs (38-41%), with a moderate daily intensity on average (4.7/10). The 'affective' descriptors prevailed over the 'sensory' descriptors, with the exception of burning and itching sensations. Finally, regarding provoked pain, mechanical allodynia (to brushing and pressure) was more marked than thermal allodynia. The persistence of chronic pain after SJS/TEN is a common phenomenon. Sensory descriptors are consistent with sensitization of both small-diameter nerve fibres (burning and itching sensations) and large-diameter nerve fibres (mechanical allodynia), but the affective-emotional components of pain largely predominate. Complex mechanisms lead to persistent pain as long-term sequela of SJS/TEN, among which mechanisms, psychological factors related to post-traumatic stress disorder probably play a key role.

Biodegradable CA/CPB electrospun nanofibers for efficient retention of airborne nanoparticles

The increase of the industrialization process brought the growth of pollutant emissions into the atmosphere. At the same time, the demand for advances in aerosol filtration is evolving towards more sustainable technologies. Electrospinning is gaining notoriety, once it enables to produce polymeric nanofibers with different additives and also the obtaining of small pore sizes and fiber diameters; desirable features for air filtration materials. Therefore, this work aims to evaluate the filtration performance of cellulose acetate (CA) nanofibers and cationic surfactant cetylpyridinium bromide (CPB) produced by electrospinning technique for retention of aerosol nanoparticles. The pressure drop and collection efficiency measurements of sodium chloride (NaCl) aerosol particles (diameters from 7 to 300 nm) were performed using Scanning Mobility Particle Sizer (SMPS). The average diameter of the electrospun nanofibers used was 239 nm, ranging from 113 to 398 nm. Experimental results indicated that the nanofibers showed good permeability (10−11 m2) and high-efficiency filtration for aerosol nanoparticles (about 100 %), which can include black carbon (BC) and the new coronavirus. The pressure drop was 1.8 kPa at 1.6 cm s-1, which is similar to reported for some high-efficiency nanofiber filters. In addition, it also retains BC particles present in air, which was about 90 % for 375 nm and about 60 % for the 880 nm wavelength. Finally, this research provided information for future designs of indoor air filters and filter media for facial masks with renewable, non-toxic biodegradable, and potential antibacterial characteristics.

Laser-induced nanofibrous titania film electrode: A new approach for energy storage materials

Abstract The research described here proposes a novel use of titanium oxide nanofibrous film as advanced electrode material for high performance supercapacitors. High frequency picosecond laser pulses were employed to generate a film of oxidized Ti on Ti substrate. Physico-chemical characterizations and morphological studies revealed the formation of fibrous TiO2 micro/nano-structures. The electrochemical measurements of the generated nanostructures showed their improved electrochemical properties and proved the feasibility of using laser pulses for fabrication of advanced electrodes with high specific capacitance. Also, our results showed by double laser processing, the average diameter of the generated TiO2 fibers decreased from 300 nm to the range of 60–70 nm. Combination of having higher porosity (smaller fiber diameters) and more oxidized Ti results in better supercapacitance behaviours. These studies demonstrated the usefulness of laser generated nanofibrous film as a novel electrode material for high performance supercapacitors. It can lead to promising methods for fabrication of advanced electrodes with high energy and power density with excellent cyclic stability.

Fiber Threshold Accommodation as a Mechanism of Burst and High-Frequency Spinal Cord Stimulation

Burst and high-frequency spinal cord stimulation (SCS), in contrast to low-frequency stimulation (LFS, < 200 Hz), reduce neuropathic pain without the side effect of paresthesia, yet it is unknown whether these methods' mechanisms of action (MoA) overlap. We used empirically based computational models of fiber threshold accommodation to examine the three MoA. Waveforms used in SCS are composed of cathodic, anodic, and rest phases. Empirical studies of human peripheral sensory nerve fibers show different accommodation effects occurring in each phase. Notably, larger diameter fibers accommodate more than smaller fibers. We augmented our computational axon model to replicate fiber threshold accommodation behavior for diameters from 5 to 15 μm in each phase. We used the model to predict threshold change in variations of burst, high frequency, and LFS. The accommodation model showed that 1) inversion of larger and smaller diameter fiber thresholds produce a therapeutic window in which smaller fibers fire while larger ones do not and 2) the anodic pulses increase accommodation and perpetuate threshold inversion from burst to burst and between cathodic pulses in burst, high frequency, and variations, resulting in an amplitude "window" in which larger fibers are inactivated while smaller fibers fire. No threshold inversion was found for traditional LFS. The model, based on empirical data, predicts that, at clinical amplitudes, burst and high-frequency SCS do not activate large-diameter fibers that produce paresthesia while driving medium-diameter fibers, likely different from LFS, which produce analgesia via different populations of dorsal horn neural circuits.

Manuka Honey Reduces NETosis on an Electrospun Template Within a Therapeutic Window.

Manuka honey, a topical wound treatment used to eradicate bacteria, resolve inflammation, and promote wound healing, is a focus in the tissue engineering community as a tissue template additive. However, its effect on neutrophil extracellular trap formation (NETosis) on a tissue engineering template has yet to be examined. As NETosis has been implicated in chronic inflammation and fibrosis, the reduction in this response within the wound environment is of interest. In this study, Manuka honey was incorporated into electrospun templates with large (1.7–2.2 µm) and small (0.25–0.5 µm) diameter fibers at concentrations of 0.1%, 1%, and 10%. Template pore sizes and honey release profiles were quantified, and the effect on the NETosis response of seeded human neutrophils was examined through fluorescence imaging and myeloperoxidase (MPO) analysis. The incorporation of 0.1% and 1% Manuka honey decreased NETosis on the template surface at both 3 and 6 h, while 10% honey exacerbated the NETosis response. Additionally, 0.1% and 1% Manuka honey reduced the MMP-9 release of the neutrophils at both timepoints. These data indicate a therapeutic window for Manuka honey incorporation into tissue engineering templates for the reduction in NETosis. Future in vivo experimentation should be conducted to translate these results to a physiological wound environment.

Polymer of intrinsic microporosity (PIM) based fibrous mat: combining particle filtration and rapid catalytic hydrolysis of chemical warfare agent simulants into a highly sorptive, breathable, and mechanically robust fiber matrix

Highly selective and lightweight protective suits featuring excellent breathability, mechanical robustness, and catalytic degradation performance toward chemical warfare agents (CWAs) are highly desirable for first responders and the military. However, current multilayered state-of-the-art chemical/biological (CB) protective textiles containing activated carbon and separate aerosol-protective layers exhibit several drawbacks including high thermal burden and secondary contamination. Herein, we present for the first time, a highly sorptive, breathable, and mechanically strong aerosol-protective layered fabric with prominent catalytic degradation capability of CWA simulant, through novel material selection and engineering design. The electrospun polymer of intrinsic microporosity (PIM-1) fiber web with hierarchical porosity is used as a matrix material, preventing toxic gas penetration while providing pathways for air and water vapor molecules. Polyacrylonitrile (PAN) nanofibers assembled with PIM-1 fibers via a layer-by-layer electrospun-deposition approach are shown to achieve significantly enhanced mechanical integrity and filtration efficiency, due to the high polar chemical structure and small fiber diameter of PAN. The subsequent incorporation of UiO-66-NH2 particles, a Zr-based metal-organic framework (MOF), further enhances the sorption capacity while maintaining excellent filtration efficiency, mechanical strength, and breathability, and also endows the fiber web with remarkable catalytic degradation towards CWA simulants. The resulting PIM/PAN/MOF composite fiber mat demonstrates unprecedented integrated properties with water vapor transmission rate of 1,013 g/m2·24 h, surface area of 574 m2/g, increased tensile strength (more than 70 times compared to neat PIM-1 fiber web), and PM2.5 and PM10 filtration efficiency of 99.88% and 99.94%, respectively, comparable to commercial polypropylene (PP) non-woven textile. This facile and effective fabrication of such a multifunctional composite fiber mat is valuable for the design of protective garments in health care, personal protective gear, and law enforcement and military uniforms.

Air-side pressure drop of polymeric hollow fibre heat exchangers

Polymeric hollow fibre heat exchangers are an alternative to common metal heat exchangers in low-temperature applications. Their advantages are low cost, low weight, and corrosion resistance. The heat transfer surface consists of hundreds or even thousands of fibres of small diameter. There are several studies on thermal performance of the polymeric hollow fibre heat exchangers, but the pressure drop is also a crucial part of the design. The arrangement, known as the bank of tubes, is common for the heat exchangers and there are relations used to estimate the pressure drop of flow passing the bank of tubes. Those are based on extensive experimental research with steel tubes. The tubes of polymeric hollow fibre are flexible. The pressure drop predicted by the known relations are underestimated.

Electrospun Composite Nanofibrous Materials Based on (Poly)-Phenol-Polysaccharide Formulations for Potential Wound Treatment.

In this paper, we focus on the preparation of electrospun composite nanofibrous materials based on (poly)-phenol-polysaccharide formulation. The prepared composite nanofibres are ideally suited as a controlled drug delivery system, especially for local treatment of different wounds, owing to their high surface and volume porosity and small fibre diameter. To evaluate the formulations, catechin and resveratrol were used as antioxidants. Both substances were embedded into chitosan particles, and further subjected to electrospinning. Formulations were characterized by determination of the particle size, encapsulation efficiency, as well as antioxidant and antimicrobial properties. The electrospinning process was optimised through fine-tuning of the electrospinning solution and the electrospinning parameters. Scanning electron microscopy was used to evaluate the (nano)fibrous structure, while the successful incorporation of bio substances was assessed by X-ray Photoelectron Spectroscopy and Fourier transform infrared spectroscopy. The bioactive properties of the formed nanofibre -mats were evaluated by measuring the antioxidative efficiency and antimicrobial properties, followed by in vitro substance release tests. The prepared materials are bioactive, have antimicrobial and antioxidative properties and at the same time allow the release of the incorporated substances, which assures a promising use in medical applications, especially in wound care.

Effect of Processing Parameters on the Diameter and Morphology of Electrospun Iron-Modified Montmorillonite (Fe-MMT)/Polycaprolactone Nanofibers

Iron-modified montmorillonite-filled polycaprolactone nanofiber mats were produced via electrospinning with varying applied voltage, flow rate, needle-tip-to-collector distance, and needle diameter. Scanning electron microscopy (SEM) was used to observe fiber morphology and characteristics. The effects of varying process parameters on various fiber characteristics were evaluated using a two-level fractional factorial experimental design. The effect of voltage on fiber diameter differed with varying flow rate. At 32 ml/hr, the average fiber diameter decreased from 518.38 nm ± 289.37 nm to 466.43 nm ± 312.36 nm when the voltage is increased. At 42 ml/hr the effect of voltage on fiber diameter was reversed. The average fiber diameter was also found to decrease from 516.03 nm ± 283.48 nm to 467.96 nm ± 318.07 nm with decreasing tip-to-collector distance at 32 mL/hr flow rate. The variation of the effect of the factors on fiber diameter was mainly due to a significant loss of material observed at 12 kV and 15 cm tip-to-collector distance. Bead formation was observed for all runs with more beads being formed at 12 kV applied voltage and 15 cm tip-to-collector distance. Spherical beads were observed at 12 kV and 15 cm tip-to-collector distance while spindle-like beads were present in nanofiber membranes spun at high voltage and at the combination of low voltage and low tip-to-collector distance. The parameter setting combination of 19 kV, 32 ml/hr flow rate, 10 cm tip-to-collector distance, and 0.514 mm needle diameter yielded the lowest fiber diameter with the least amount of beading and small bead size. Small fiber diameters and less beading provide larger surface area and more exposure of the Fe-MMT particles for more efficient adsorption.

Ultrafine, self-crimp, and electret nano-wool for low-resistance and high-efficiency protective filter media against PM0.3

Frequent outbreaks of emerging infectious diseases (EIDs) make personal protective filter media in high demand. Electrospun nanofibrous materials are proved to be very effective in resisting virus-containing fine particles owing to their small fiber diameters; however, hindered by the intrinsic close-packing character of fine fibers, electrospun filters suffer from a relatively high air resistance, thereby poor breathing comfort. Here, we report a biomimetic and one-step strategy to create ultrafine and curly wool-like nanofibers, named nano-wool, which exhibit fluffy assembly architecture and powerful electret effect. By achieving the online self-crimp and in-situ charging of nanofibers, the curly electret nano-wool shows a small diameter of ~0.6 μm (two orders of magnitude lower than natural wool: ~20 μm) and an ultrahigh porosity of 98.7% simultaneously, together with an ultrahigh surface potential of 13260 V (one order of magnitude higher than previous filters). The structural advantages and powerful electret effect enable nano-wool to show excellent filtration efficacy (>99.995% for PM0.3) and low air resistance (55 Pa). Additionally, nano-wool can be easily scaled up, not only holding great industrial prospect in personal protective respirators, but also paving the way for developing next-generation wool in a cost-efficient and multifunctional form.

Development of light-transmitting concrete – A review

This paper provides an overview on the development of Light-transmitting Concrete (LTC). Concrete is improved in terms of transparency by installing optical fibres into the concrete. The application of LTC in building enables light transmission, which reduces light energy consumptions and carbon footprint, providing a more sustainable living environment. This paper also discusses the current development and application of LTC. Some of the previous research regarding the microstructure and mechanical properties of LTC in terms of compressive strength and light transmittance properties are also discussed. LTC has greater light transmittance with higher fibre volumetric fraction, smaller fibre diameter and spacing. However, the relationship between the factors and the light transmitting properties of LTC is yet to be investigated. Besides the fibre parameters, other environmental factors should also be considered to investigate the applicability and durability of LTC. There is still lack of investigation on the physical and mechanical properties of LTC especially in the applications for structural performance. Further research is required to investigate the fibre–matrix interfacial bond strength of LTC and measures should be taken to improve the mechanical strength of LTC. Besides buildings, there is also a research potential on the application of LTC on civil and infrastructure in terms of traffic safety.

Effects of faba bean on growth performance and fillet texture of Yellow River carp, Cyprinus carpio haematopterus

A three-month feeding trial was conducted to investigate the effects of faba bean (Vicia faba L.) on growth performance, intramuscular collagen content, muscle cellularity and fillet texture of Yellow River carp, Cyprinus carpio haematopterus. Carps with an initial weight 500 ± 20 g were randomly divided into two treatments: commercial feed group (CFG) and faba bean group (FBG). Compared to CFG, the results indicated that carps fed with faba bean had poor growth performance, higher intramuscular collagen content, smaller fiber diameter and wider intermyofibrillar space. However, the fiber density was not influenced (P > 0.05). The faba bean components showed lower crude protein and amino acid imbalance, especially, the deficiency in the sulfuric amino acid. The raw-fillet and cooked-fillet texture of FBG were both significantly greater than that of CFG (P < 0.05). Muscle fiber diameter and cooked-fillet texture showed significant negative correlation (P < 0.05), significant positive correlation between intramuscular collagen content and cooked-fillet texture (P < 0.05), and no significant correlation between muscle fiber density and fillet texture (P> 0.05). In summary, faba bean could improve the fillet quality for Yellow River carp. These findings would contribute to define the optimal nutritional conditions of pond culture to improve the flesh quality of Cyprinus carpio haematopterus.

Effect of fiber diameter on thermal properties of short-glass-fiber-reinforced PTFE-based composites

Polytetrafluoroethylene (PTFE) matrix has been reinforced by short glass fiber (SGF) with various diameters (8, 4 and 2 μm) in this experiment, and the effects of fiber diameter on the thermal properties of PTFE-based composites, including thermal resistance index (THRI), thermal conductivity (λ), melting temperature (Tm), coefficient of thermal expansion (CTEz) and high-temperature compression-creep, are investigated. The results show that the thermal properties could be improved with the amount of SGF. However, this could be due to the fact that the packings have been compelled by different compression forces caused by composite shrinkage during preparation, the interface between packing with large diameter and PTFE matrix is significantly different from that of the small one, resulting in the crystallinity (Xc), and THRI of PTFE-based composites decreases with the decreasing fiber diameter. Moreover, the small-diameter fiber is easier to debond from PTFE matrix due to the inferior physical stability of interface, the λ decreases with the decrease of the fiber diameter, while CTEz and creep strain value increases. From XRD analysis, the results of crystallite size revealed that the lamella thickness of composite decreases, which means that the Tm of the PTFE-based composites has also decreased with the decreasing fiber diameter.

Early accentuated muscle hypertrophy is strongly associated with myonuclear accretion

The current study explored whether the marked hypertrophic response noted with a short-term unilateral concurrent exercise paradigm was associated with more prominent changes in myonuclei accretion, ribosome biogenesis, and capillarization compared with resistance exercise alone (RE). Ten men (age 25 ± 4 yr) performed aerobic and resistance exercise (AE + RE) for one leg while the other leg did RE. Muscle biopsies were obtained before and after 5 wk of training and subjected to fiber-type specific immunohistochemical analysis, and quantification of total RNA content and mRNA/rRNA transcript abundance. Type II fiber cross-sectional area (CSA) increased with both AE + RE (22%) and RE (16%), while type I fiber CSA increased mainly with AE + RE (16%). The change score tended to differ between legs for type I CSA (P = 0.099), and the increase in smallest fiber diameter was greater in AE + RE than RE (P = 0.029). The number of nuclei per fiber increased after AE + RE in both fiber types, and this increase was greater (P = 0.027) than after RE. A strong correlation was observed between changes in number of nuclei per fiber and fiber CSA in both fiber types, for both AE + RE and RE (r > 0.8, P < 0.004). RNA content increased after AE + RE (24%, P = 0.019), but the change-scores did not differ across legs. The capillary variables generally increased in both fiber types, with no difference across legs. In conclusion, the accentuated hypertrophic response to AE + RE was associated with more pronounced myonuclear accretion, which was strongly correlated with the degree of fiber hypertrophy. This suggests that myonuclear accretion could play a role in facilitating muscle hypertrophy also during very short training periods.