Small-diameter Fibers Research Articles

Electrospun coaxial PPESK/PVDF fibrous membranes with thermal shutdown property used for lithium-ion batteries

A coaxial poly(phthalazinone ether sulfone ketone)/polyvinylidene fluoride fibrous membrane used for lithium-ion batteries was prepared by the electrospinning technique. The suitable processing parameters were chosen to obtain the core PPESK fibers with small diameter and shell PVDF fibers with large diameter simultaneously. The prepared coaxial PPESK/PVDF fibrous membranes exhibit superior thermal shutdown property and thermal dimensional stability. Meanwhile, the coaxial PPESK/PVDF membranes show larger porosity, better electrolyte wettability and higher ionic conductivity in comparison with the commercial PP/PE/PP separators. In addition, the coins cells using coaxial PPESK/PVDF membranes show excellent cycle performance, which demonstrates the membranes have the potential to be used as separators for high-performance lithium-ion batteries.

From Lab to Pilot Scale: Melt Electrospun Nanofibers of Polypropylene with Conductive Additives

In this paper, the feasibility of fabricating polypropylene (PP) nanofibers was investigated using conductive additives such as sodium stearate (NaSt), sodium oleate (NaOl) and Irgastat during melt electro spinning with a single nozzle lab and a 600- nozzle pilot scale device. Varying PP grades of high melt flow indices (MFI=450-1200 g/10 min) were used with different amounts of additives. The effects of the additives on the fiber diameters, thermal properties, electrical conductivity and polymer degradation were investigated. On a lab scale, fiber diameters of less than 500 nm were achieved with the compound of PP HL712FB, 4 wt% NaSt and 2 wt% Irgastat. The lab scale device was extended by a heatable spinning chamber, which affects fiber diameter reduction. The fabrication of nanofibers was in principle attributed to the increase in electrical conductivity with the introduction of the additives. On a pilot scale, the smallest fiber diameter of 6.64 μm could be achieved with PP HL508FB and 2 wt% NaSt. The comparison between the production of the fibers with a single nozzle and the pilot scale plant has revealed that a transfer of results is not possible without further ado. Due to the higher dwell time in the nozzle, a strong thermal degradation of the polymer could be detected with the high temperature size exclusion chromatography, whereby NaOl had the strongest influence on the thermal degradation. The high melt flow PP HL712FB and its compounds could not be processed with the pilot scale device due to its low viscosity, resulting in an insufficient pressure built up within the spinneret. Another reason for the non-spinnability of the material is the higher thermal and mechanical stress caused by the preceding melts preparation in an extrusion step. Further adjustments to the pilot plant are necessary to ensure a constant temperature distribution in the nozzle plate to achieve uniform fiber cross sections. The implementation of an uneven collector has successfully led to an even deposition of the fibers to obtain an isotropic non-woven fabric.

Sericin silk protein in peripheral nervous repair associated with the physical exercise of swimming in Wistar rats

ABSTRACTObjective: To verify the action of sericin associated to swim exercise with overload, on sciatic nerve repair in Wistar rats, after 22 days of nerve compression.Methods: Forty animals been composed of five groups: control, injury, injury-sericin, injury-swimming and injury-sericin-swimming. During the lesion procedure, sericin, in hydrolyzed form, applied directly to the injury in the injury-sericin and injury-sericin-swimming groups. Injury-swimming and injury-sericin-swimming groups underwent to 5 days per week for 3 weeks, with a 10% overload of the animal’s body weight, and a weekly progressive evolution of swimming time, lasting 15, 20 and 25 min/day. Pre and throughout the treatment period the animals performed evaluation of sciatic functional index and pressure pain threshold with digital von Frey filament. Euthanasia was performed on the 22nd postoperative day, and two fragments of the nerve were collected and prepared for descriptive and quantitative analysis.Results: The sciatic functional index assessment showed significant differences in the motor function of the control until the 14th day. Regarding the allodynia, there was revealed a significant improvement in injury-swimming performance relative to injury, injury-sericin and injury-sericin-swimming, and the number of viable and non-viable nerve fibers smaller than 4 μm in diameter was significantly higher in the injury-sericin-swimming.Conclusion: swimming showed a better evolution of the nociceptive threshold and allodynia. Sericin treatment had exacerbated pro-inflammatory characteristics. On the other hand, the association of sericine and swimming showed a possible regulatory effect by resting swimming exercise, with a significant increase of fibers of smaller diameter.

Clinicopathological correlations of sural nerve biopsies in TTR Val30Met familial amyloid polyneuropathy.

Familial amyloid polyneuropathy with the substitution of methionine for valine at position 30 in the TTR gene is the most common type of hereditary transthyretin amyloidosis. Although several authors have previously reported a size-dependent fibre loss, predominantly involving unmyelinated and small-diameter myelinated fibres, the mechanisms of nerve fibre loss have not been fully understood. In this study, we establish the morphometric pattern of peripheral neuropathy in patients with familial amyloid polyneuropathy and asymptomatic mutation carriers in the biopsies from our archive and correlated the pathological findings with clinical features. A total of 98 patients with familial amyloid polyneuropathy and 37 asymptomatic mutation carriers (TTR Val30Met mutation), aged between 17 and 84 years, who underwent sural nerve biopsy between 1981 and 2017 at Centro Hospitalar Universitário do Porto were studied. Thirty-one controls were included for comparison. The median age at nerve biopsy was 26.0 [interquartile range = 23.5–39.5] years for asymptomatic mutation carriers, 45.0 [35.0–60.0] years for patients with familial amyloid polyneuropathy and 44.0 [30.0–63.0] years for controls. The median duration between nerve biopsy and symptoms’ onset was 7.0 [3.3–11.8] years (range: 1–27 years) in the asymptomatic carriers. Most patients were in an earlier disease stage (93% with a polyneuropathy disability scale ≤2). Patients had loss of small and myelinated fibres compared with both asymptomatic carriers and controls (P < 0.001), whereas asymptomatic carriers showed loss of small myelinated fibres when compared with controls (P < 0.05). The loss of myelinated fibres increased with disease progression (P < 0.001), and patients in more advanced clinical stage showed more frequent amyloid deposition in the nerve (P = 0.001). There was a positive correlation between large myelinated fibre density and time to symptoms’ onset in the asymptomatic carriers that developed early-onset form of the disease (r = 0.52, P < 0.01). In addition, asymptomatic carriers with amyloid deposition already present in sural nerve biopsies developed symptoms earlier than those with no amyloid (P < 0.01). In conclusion, this study confirms that the loss of small fibre size is an initial event in familial amyloid polyneuropathy, already present in asymptomatic gene carriers, starting several years before the onset of symptoms. We show for the first time that large myelinated fibres’ loss and amyloid deposition are pathological features that correlate independently with short period to the onset of symptoms for asymptomatic carriers that developed early-onset form of the disease. These findings are therapeutically relevant, as it would allow for a better interpretation of the role of disease-modifying agents in transthyretin familial amyloid polyneuropathy.

Sandwich-structured fibrous membranes with low filtration resistance for effective PM2.5 capture via one-step needleless electrospinning

The airborne particulate matter has received much attention over the past 20 years because it has become the ninth largest preventable cause of disease in the global population. Therefore, there is a requirement for cost-effective air filters with excellent performance. Electrospun nanofiber membranes are emerging as one of the most versatile air filters for their small pore size distribution. However, it has proven to be extremely challenging to achieve a balance between low filtration resistance and high removal efficiency. Usually, small fiber diameter increases filtration efficiency but this is coupled with high-pressure drop irrespective of the particle size, so negatively influencing quality factor (QF). Herein, a low filtration resistance sandwich structured polyacrylonitrile (PAN) fibrous filters were fabricated through a controlled accumulation of bimodal sized fibers (172 ± 21 nm and 772 ± 118 nm) by alternate needleless electrospinning. The composite membrane possessed a heterogeneity structure and decreased package density, maintaining the same pore size with narrow distribution compared with the membrane consisting of single sized nanofibers. Consequently, the resulting sandwich structured filter after electrostatic removal demonstrates a lower filtration resistance (151.9 Pa) and competitive filtration efficiency (99.89%) to 260 nm mass median diameter sodium chloride (NaCl) aerosol particles compared with the nanofibers structured filter (207.76 Pa, 99.92%) under an airflow velocity of 32 L min−1. Moreover, the composite exhibited the highest QF, as well as excellent mechanical properties and good transmission. Furthermore, the productivity of sandwiched-structure membranes about 20 g h−1, which was several hundred times than traditional electrospinning, offered prospects for industrial production and commercial application. The present investigation may provide a feasible strategy for further improving and optimizing the comprehensive performance of electrospun filters.

The effect of specific surface area of macro fibers on energy absorption capacity of concrete

Energy absorption capacity is the salient property of concrete. Reinforcement of concrete with macro fibers is one of the techniques that has led to enhancement of this important feature of concrete. However, the effect of specific surface area of melt-spun polypropylene macro fibers has hardly been studied so far. In this work, the effect of this parameter on mechanical behavior of fiber reinforced concrete (FRC) was investigated. Diameter of macro fibers was varied by changing the melt feeding rate and fiber draw ratio. Changes in fibers diameter affect fibers specific surface area, which in turn influences the adhesion of fibers to the matrix in FRCs. In order to evaluate the FRCs behavior, bending tests were conducted and the area under load-displacement curves was studied. It was found that increase in specific surface area of fibers results in considerable increase in energy absorption capacity of the FRCs. Concrete reinforced with the larger diameter fibers exhibited 6× energy absorption capacity than the reference sample. This was found to be in line with the 14× energy absorption capacity of sample which was reinforced by smaller diameter fibers. This was attributed to the increase in total contact area between the finer fibers and the matrix as a direct consequence of the increase in number of fibers for a given fiber volume fraction.

The Effect of Electrospun Fiber Diameter on Astrocyte-Mediated Neurite Guidance and Protection.

The topography of electrospun fiber scaffolds modifies astrocytes toward in vivo-like morphologies and behaviors. However, little is known about how electrospun fiber diameter influences astrocyte behavior. In this work, aligned fibers with two distinct nanoscale fiber diameters (808 and 386 nm) were prepared, and the astrocyte response was measured over time. Astrocytes on the large diameter fibers showed significantly increased elongation as early as 2 h after seeding and remained significantly more elongated for up to 4 days compared to those on small diameter fibers. Astrocytes extending along larger diameter fibers were better equipped to support long neurite outgrowth from dorsal root ganglia neurons, and neurite outgrowth along these astrocytes was less branched than outgrowth along astrocytes cultured on small diameter fibers. The differences in astrocyte shape observed on the small or large diameter fibers did not translate into differences in GLT-1, GFAP, or GLAST protein expression. Thus, different fiber diameters were unable to influence astrocyte protein expression uniquely. Nevertheless, astrocytes cultured in either small or large fibers significantly increased their expression of GLT-1 compared to astrocytes cultured on nonfiber (film) controls. Fibrous-induced increases in astrocyte GLT-1 expression protected astrocyte/neuron cocultures from toxicity generated by high extracellular glutamate. Alternatively, astrocytes/neurons cultured on films were less able to protect these cells from culture conditions consisting of high glutamate levels. Biomaterials, such as the fibrous materials presented here, may help stimulate astrocytes to increase GLT-1 expression and uptake more glutamate, since astrocytes are less likely to uptake glutamate in neurodegenerative pathologies or following central nervous system injury.

Effect of Potassium Permanganate Modification on Plasticized Spinning Polyacrylonitrile Fibers with Different Diameters.

Plasticized spinning polyacrylonitrile (PAN) fibers with different diameters were chemically modified by potassium permanganate (KMnO4). The modification effects of different diameter fibers were studied for the first time. Differential scanning calorimetry (DSC) results show that, compared with the large diameter ones, small diameter modified fibers show lower cyclization starting temperature (Ti) and activation energy (E). Both kinds of fibers exhibit better modification effects compared with solution-spun fibers. For the small diameter fibers, chemical modification can occur at low treatment temperature, even at 70 °C. X-ray diffraction analysis (XRD) results show that modification not only occurs in the amorphous region of the fibers but also in the crystalline region.

Ramification of zinc oxide doped hydroxyapatite biocomposites for the mineralization of osteoblasts

Far-flung evolution in tissue engineering enabled the development of bioactive and biodegradable materials to generate biocomposite nanofibrous scaffolds for bone repair and replacement therapies. Polymeric bioactive nanofibers are to biomimic the native extracellular matrix (ECM), delivering tremendous regenerative potentials for drug delivery and tissue engineering applications. It's been known from few decades that Zinc oxide (ZnO) nanoparticles are enhancing bone growth and providing proliferation of osteoblasts when incorporated with hydroxyapatite (HAp). We attempted to investigate the interaction between the human foetal osteoblasts (hFOB) with ZnO doped HAp incorporated biocomposite poly(L-lactic acid)-co-poly(ε-caprolactone) and silk fibroin (PLACL/SF) nanofibrous scaffolds for osteoblasts mineralization in bone tissue regeneration. The present study, we doped ZnO with HAp (ZnO(HAp) using the sol-gel ethanol condensation technique. The properties of PLACL/SF/ZnO(HAp) biocomposite nanofibrous scaffolds enhanced with doped and blended ZnO/HAp were characterized using Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Contact angle and Tensile studies to determine the morphology, functionality, wettability and stability. The in vitro study results showed that the addition of ZnO and HAp enhances the secretion of bone mineral matrix (98%) with smaller fiber diameter (139.4 ± 27 nm) due to the presence of silk fibroin showing potential tensile properties (322.4%), and increased the proliferation of osteoblasts for bone tissue regeneration.

A novel fibrinogen gamma-chain mutation, p.Cys165Arg, causes disruption of the γ165Cys–Bβ227Cys disulfide bond and ultimately leads to hypofibrinogenemia

BackgroundCongenital hypofibrinogenemia is a type of hereditary disease characterized by impaired fibrinogen synthesis and/or secretion induced by mutations in the fibrinogen gene. ObjectivesWe investigated the phenotypes, genotypes, and pathogenesis of congenital hypofibrinogenemia in an affected family. Patients/methodsThe proband had a risk of bleeding; therefore, conventional coagulation screening was performed for the proband and her family members. Mutation sites in all exons and flanking sequences of FGA, FGB, and FGG were identified, with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) performed to indicate the expression of abnormal chains. The effect of the mutation sites on fibrinogen structure and function was predicted by molecular modeling, and purified plasma fibrinogen from the proband was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and scanning electron microscopy. Thromboelastography was applied to assess the risk of bleeding and clotting in the proband. ResultsFibrinogen levels in the proband were 1.21 g/L, 1.31 g/L, and 1.38 g/L according to Clauss assay, the prothrombin time method, and enzyme-linked immunosorbent assay, respectively. A novel heterozygous mutation (γCys165Arg), a heterozygous mutation (AαIle6Val), and two genetic polymorphisms (AαThr331Ala and BβArg478Lys) in fibrinogen were found in the proband, and MALDI-TOF MS indicated absence of the mutated chain in patient plasma. Additionally, the heterozygous mutation (γCys165Arg) displayed substitution of a nonpolar γ165Cys (low mass) with a positively charged Arg (high mass) along with a small fiber diameter and loose network structure. ConclusionsFibrinogen γCys165Arg mutations cause damage to the interchain disulfide bonds of fibrinogen and hinder fibrinogen secretion, possibly explaining the pathological mechanism associated with congenital hypofibrinogenemia.

CLINICAL EVALUATION OF EFFECTS OF LOW-LEVEL LASERS ON PAIN DURING CAVITY PREPARATION

Aim: To study the effects of low level laser on pain during cavity preparation.&#x0D; Background: Laser irradiation stabilizes the nerve membrane through an increase in adenosine triphosphate (ATP) production and enhanced redox system of the cell. Dental pulp is innervated by non- myelinated C fibres. Laser irradiation reduces the conduction of Ad and C fibres (small diameter fibres), both of which transmit nociceptive pain. The stabilization of the nerve membrane increases neural latency and decreases pain transmission. This study explores whether pre-irradiation with laser reduces pain perception during cavity preparation.&#x0D; Methodology: A clinical study was done on 50 patients reporting to Army Dental Centre(R&amp;R) having moderate and deep size carious lesions on first/second premolar’s bilaterally. The patients selected was apprehensive. On one side, low level lasers irradiation was done prior cavity preparation (Test). On the other contralateral tooth type cavity preparation was done without local anesthesia (Control). The patients pain threshold was noted for both control and test groups using Visual Analogue Scale (VAS). The data was computed and statiscally analyzed.&#x0D; Results: The patients exhibited reduce pain perception in tooth which had prior laser irradiation as compared to the control group.&#x0D; Conclusion: Laser analgesia with low level lasers can be used as routine protocol for reducing pain perception in apprehensive patients undergoing cavity preparation.

Electrospinning synthesis of Li-Fe-P/PAN based micro-nanofibers as precursors for LiFePO4 cathode material in Li-ion fiber battery applications

The increase popularity of wearable devices and smart textiles are being held back partly by better energy storage systems, which are based on electrochemical phenomena. Research in novel materials with optimal morphologies for better electrochemical performance is one the paths being followed. Micro/nano fibers are interesting morphologies as they present high surface areas, less agglomeration and flexibility, compared to micro/nano particles. In this article, precursor fibers for LiFePO4 cathode material, defined as lithium-iron-phosphorous/polyacrylonitrile (Li-Fe-P/PAN) precursor nanofibers, have been synthesized by the electrospinning method. The influence of electrospinning parameters such as voltage (V), flow rate (F) and distance between the collector and the tip of the syringe needle (D), on the morphology of the fibers have been studied mainly by scanning electron microscopy (SEM). Optimal morphological features such as less formation of beads, small fiber diameter, less polydispersity and high fiber alignment, were observed at V = 14 kV, F = 0.7 mL/h and D = 14 cm. The occurrence of nanofibers on the precursor Li-Fe-P/PAN material was observed through SEM, while the energy dispersive x-ray spectroscopy (EDS) confirms the presence of the fundamental elements in the precursor nanofibers.

Research on the electrospun foaming process to fabricate three‐dimensional tissue engineering scaffolds

ABSTRACTThree‐dimensional (3D) tissue engineering scaffolds were fabricated by an electrospun foaming process. A two‐dimensional (2D) membrane was fabricated first by the electrospinning technology, and then a sodium borohydride gas foaming process was used to expand the 2D membrane to a 3D tissue engineering scaffold. The effects of six process parameters on the foamed height of 3D scaffolds were systematically studied during fabrication using a L27(313) orthogonal design table. The mechanism of the gas foaming process was investigated by a porosity analysis and a scanning electron microscopy analysis of the scaffolds' surface and cross‐sectional morphology. Finally, wettability experiments and L929 fibroblast adhesion and proliferation experiments were carried out on the 3D scaffolds. The results showed that the concentration of polycaprolactone (PCL) has the most significant effect on height, and the optimal process parameters were 8 wt % PCL solution, 15 kV voltage, 4 mL h−1 flow rate, 20 cm distance, 60 min spinning time, and 5 g sodium borohydride. The 2D membrane with a smaller fiber diameter and higher porosity was more easily foamed. The fabricated 3D scaffold had good wettability, and cell absorbance (OD value) increased by 25.34% on day 7 over that of the 2D electrospun nanofibrous scaffold. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46898.

Collagen/poly(d,l-lactic-co-glycolic acid) composite fibrous scaffold prepared by independent nozzle control multi-electrospinning apparatus for dura repair

The objective of the present study was to evaluate non-woven collagen/poly(lactic-co-glycolic acid) fibrous scaffold (Col/PLGA FS) prepared by a co-electrospinning process using a novel multi syringe electrospinning system for dura repair. The morphological and mechanical properties of the fibrous scaffolds (FSs) were assessed by scanning electron microscopy (SEM) and a universal testing machine (UTM). The changes in chemical composition due to the incorporation of collagen into PLGA were determined by Fourier transform infrared spectroscopy-attenuated total reflection mode (FTIR-ATR). The biocompatibility of the FSs was also evaluated in vitro in cultures of mouse fibroblasts and in vivo by subcutaneous implantation studies in rats. SEM images of the samples showed that the fiber size distribution of Col/PLGA FS became narrow compared to that of PLGA FS due to the incorporation of collagen with small fiber diameter. The FTIR-ATR spectrum of Col/PLGA FS revealed the characteristic bands of collagen and PLGA, indicating the co-existence of two fibrous structures. The poor mechanical properties of collagen FS were improved by co-electrospinning with PLGA. In vitro L929 cell proliferation assay revealed that the cyto-compatibility of Col/PLGA FS was increased compared to that of PLGA FS. In addition, Col/PLGA FS showed increased hydrophilic properties sufficient to absorb the exudates at the interface with mild foreign body reactions. In animal studies using a traumatic brain injury (TBI) model, the incorporation of collagen induced increased macrophage chemotaxis, and the post-inflammatory reaction of these cells led to remarkable brain tissue regeneration.

Insulation System Using High-Temperature Fibrous Insulation Materials

ABSTRACTIn this study, we performed a preliminary research on an insulated sandwich structure using high-temperature fibrous insulation materials. Two types of fibrous materials, Saffil alumina and KCC cerakwool insulation materials, were selected. A sandwich specimen was invented to test the heat-shielding performance of the fibrous materials which were sandwiched by an Inconel plate and a titanium plate. The insulated sandwich structure was heated to 800°C for 2,000 seconds. The temperature profiles of the back side of the titanium plate were measured to compare the heat-shielding performance of the fibrous insulation materials. The microstructure of insulation materials, such as the fiber diameter, fiber orientation, and the parent materials of the fiber, was studied to understand how those characteristics influence the radiative properties of the fiber. The difference in microstructural parameters caused a difference in thermal resistance in the fibrous materials. The Saffil alumina insulation had a better performance than KCC cerakwool insulation because of its small fiber diameter and in-plane fiber orientation. The experimental results confirmed the heat transfer simulation results for fibrous materials done by other researchers. In addition, the reusability of high-temperature fibrous insulation, one of the important issues in real applications, was tested.

PA6 Nanofibre Production: A Comparison between Rotary Jet Spinning and Electrospinning

Polymer nanofibres are created from many different techniques, with varying rates of production. Rotary jet spinning is a relatively new technique for making nanofibres from both polymer solutions and melt. With electrospinning being by far the most widespread processing method for polymer nanofibres, we performed a direct comparison of polyamide 6 (PA6) nanofibre production between these two methods. It was found that electrospinning produced slightly smaller-diameter fibres, which scaled with a decrease in solution viscosity. In comparison, rotary jet spun fibres could be produced from a reduced range of polymer concentrations and exhibited therefore slightly larger diameters with greater variation. Crystallinity of the fibres was also compared between the two techniques and the bulk polymer, which showed a decrease in crystallinity compared to bulk PA6.

The Somatostatin Receptor-4 Agonist J-2156 Alleviates Mechanical Hypersensitivity in a Rat Model of Breast Cancer Induced Bone Pain.

In the majority of patients with breast cancer in the advanced stages, skeletal metastases are common, which may cause excruciating pain. Currently available drug treatments for relief of breast cancer-induced bone pain (BCIBP) include non-steroidal anti-inflammatory drugs and strong opioid analgesics along with inhibitors of osteoclast activity such as bisphosphonates and monoclonal antibodies such as denosumab. However, these medications often lack efficacy and/or they may produce serious dose-limiting side effects. In the present study, we show that J-2156, a somatostatin receptor type 4 (SST4 receptor) selective agonist, reverses pain-like behaviors in a rat model of BCIBP induced by unilateral intra-tibial injection of Walker 256 breast cancer cells. Following intraperitoneal administration, the ED50 of J-2156 for the relief of mechanical allodynia and mechanical hyperalgesia in the ipsilateral hindpaws was 3.7 and 8.0 mg/kg, respectively. Importantly, the vast majority of somatosensory neurons in the dorsal root ganglia including small diameter C-fibers and medium-large diameter fibers, that play a crucial role in cancer pain hypersensitivities, expressed the SST4 receptor. J-2156 mediated pain relief in BCIBP-rats was confirmed by observations of a reduction in the levels of phosphorylated extracellular signal-regulated kinase (pERK), a protein essential for central sensitization and persistent pain, in the spinal dorsal horn. Our results demonstrate the potential of the SST4 receptor as a pharmacological target for relief of BCIBP and we anticipate the present work to be a starting point for further mechanism-based studies.

Acute Muscle Fatigue In Men And Women Following Upper-limb Low-intensity Blood-flow Restricted Exercise

Low intensity blood flow restricted exercise (LIBFRE) elicits acute changes in torque output and muscle activation. The magnitude of these changes affect the chronic adaptions to this type of training. Despite its widespread use by men and women, it is not known whether the acute impact of LIBFRE follows a sexually dimorphic pattern. This is important because, when compared to men, women have muscle fibers of smaller diameter, higher density of type I muscle fibers, higher muscle capillarization and heightened muscle perfusion. All these factors likely influence blood flow, as well as acute muscle fatigue, during LIBFRE. PURPOSE: To explore whether muscle fatigue post-acute LIBFRE and high intensity resistance (HI) training follows a sexually dimorphic pattern. METHODS 62 healthy young persons (31 men: 21.7 ± 2.3; 31 women: 22.0 ± 2.0 yrs) were included in this study. One-repetition maximum (1RM) was determined in each participant before training. Participants completed 4 sets of unilateral biceps curl with (30+15+15+15 reps) and without BFR (10+10+10+10 reps). HI was performed at 75% 1RM and LIBFR at 20% 1RM with BFR (60% of arterial occlusion pressure). Maximum voluntary contraction (MVC) was measured at pre- and post-training time points. Muscle fatigue was quantified as the percent difference between pre- and post- training MVC. RESULTS: Both HI and LIBFR training protocols induced significant muscle fatigue in men and women from pre- to post-training (p<0.05). HI was more fatiguing than LIBFRE in both sexes (HI: ~ 35 vs. LIBFRE: ~ 25%, p<0.05). These results were sustained even after controlling for the differences in volume load between protocols. As importantly, the magnitude of torque decrement was similar between men and women after HI and LIBFR training (p>0.05). CONCLUSIONS: Performing upper-limb LIBFRE, using a multiple-set training protocol, is less fatiguing than HI resistance exercise in both men and women. Additionally, this effect is independent of differences in volume load between exercise protocols. Torque decrements in response to LIBFR and HI do not follow a sexually dimorphic pattern, providing evidence that there is no need to establish different guidelines for men and women when prescribing upper-limb LIBFR exercise. Supported by the Portuguese Science Foundation PTDC/ DTP-DES/5714/2014.

Using hydrodynamic focusing to predictably alter the diameter of synthetic silk fibers.

Spiders and silkworms provide a model of superior processing for multifunctional and highly versatile high-performance fibers. Mimicking the spider’s complex control system for chemical and mechanical gradients has remained an ongoing obstacle for synthetic silk production. In this study, the use of hydrodynamic fluid focusing within a 3D printed biomimetic spinning system to recapitulate the biological spinneret is explored and shown to produce predictable, small diameter fibers. Mirroring in silico fluid flow simulations using a hydrodynamic microfluidic spinning technique, we have developed a model correlating spinning rates, solution viscosity and fiber diameter outputs that will significantly advance the field of synthetic silk fiber production. The use of hydrodynamic focusing to produce controlled output fiber diameter simulates the natural silk spinning process and continues to build upon a 3D printed biomimetic spinning platform.

Differential expression of voltage-gated sodium channels in afferent neurons renders selective neural block by ionic direct current.

The assertion that large-diameter nerve fibers have low thresholds and small-diameter fibers have high thresholds in response to electrical stimulation has been held in a nearly axiomatic regard in the field of neuromodulation and neuroprosthetics. In contrast to the short pulses used to evoke action potentials, long-duration ionic direct current has been shown to block neural activity. We propose that the main determinant of the neural sensitivity to direct current block is not the size of the axon but the types of voltage-gated sodium channels prevalent in its neural membrane. On the basis of the variants of voltage-gated sodium channels expressed in different types of neurons in the peripheral nerves, we hypothesized that the small-diameter nociceptive fibers could be preferentially blocked. We show the results of a computational model and in vivo neurophysiology experiments that offer experimental validation of this novel phenomenon.