Preparation of nanofibre yarns from electrospun nonwoven strips

From ancient to modern time, humans have been trying to use finer fibres to make fibrous products for various purposes and believing that finer fibres have better aesthetic qualities. So far, the commercial fibres have been reduced to microns in diameter, but it seems difficult to further reduce the fibre fineness to submicrons using conventional fibre-making techniques.Electrospinning is a promising technique to produce continuous fibres with diameters on nanometre scales. This technique involves stretching a polymer fluid under a strong electric field into fine filaments, which are deposited randomly on the electrode collector forming a nonwoven nanofibre mat in most cases. Despite considerable efforts in exploring the applications of electrospun nanofibres in non-fibrous fields [1], very limited work has been conducted on using this material to process mechanically robust nanofibre yarns [2,3]

Electrospinning of Continuous Nanofiber Bundles and Twisted Nanofiber Yarns

Spinning is a prehistoric technology in which endless filaments, shorter fibers or twisted fibers are put together to produce yarns that serve as key element to assemble multifarious structural designs for diverse functions. Electrospinning has been regarded as the most effective and versatile technology to produce nanofibers with controlled fiber morphology, dimension and functional components from various polymeric materials (Dersch et al., 2007, Frenot and Chronakis, 2003, Schreuder-Gibson et al., 2002). However, most electrospun fibers are produced in the form of randomly-oriented nonwoven fiber mats (Doshi and Reneker, 1995, Madhavamoorthi, 2005). The relatively low mechanical strength and difficulty in tailoring the fibrous structure have restricted their applications. With the rapid development in nanoscience and nanotechnology, yarns composed of nanofibers may uncover new opportunities for development of well-defined three dimensional nano fibrous architectures. This chapter focuses on recent research and advancement in electrospinning of nanofiber bundles and nanofiber yarns. The preparation, morphology, mechanical properties and potential applications of these fibrous materials are discussed in details

Monitoring Local Changes in Granite Rock Under Biaxial Test: A Spatiotemporal Imaging Application With Diffuse Waves

International audienceDiffuse acoustic or seismic waves are highly sensitive to detect changes of mechanical properties in heterogeneous geological materials. In particular, thanks to acousto-elasticity, we can quantify stress changes by tracking acoustic or seismic relative velocity changes in the material at test.In this paper, we report on a small-scale laboratory application of an innovative time-lapse tomography technique named Locadiff to image spatio-temporal mechanical changes on a granite sample under biaxial loading, using diffuse waves at ultrasonic frequencies ( 300 kHz to 900 kHz). We demonstrate the ability of the method to image reversible stress evolution and deformation process, together with the development of reversible and irreversible localized micro-damage in the specimen at an early stage. Using full-field infrared thermography, we visualize stress induced temperature changes and validate stress images obtained from diffuse ultrasound. We demonstrate that the inversion with a good resolution can be achieved with only a limited number of receivers distributed around a single source, all located at the free surface of the specimen. This small-scale experiment is a proof of concept for frictional earthquake-like failure (e.g. stick slip) research at laboratory scale as well as large scale seismic applications, potentially including active fault monitoring

Strip twisted electrospun nanofiber yarns: Structural effects on tensile properties

Nanofiber yarns with controlled twist levels were prepared by twisting a narrow fibrous strip cut directly from electrospun nanofiber mats. The effects of fiber morphology, diameter and orientation, as well as the yarn twist level on the yarn tensile properties were examined. For the yarns made from randomly oriented fine uniform nanofibers (e.g., diameter 359 nm) and beaded nanofibers, the tensile strength increased with increasing the yarn twist level. Higher fiber diameter (e.g., 634 nm) led to the tensile strength having an initial increase and then decrease trend. The modulus increased with the twist level for all the yarns studied. However, the elongation at break increased initially with the twist level and subsequently decreased. The orientation of aligned fibers within the fiber strip greatly influenced the yarn tensile properties. When the fibers were oriented along the fiber length direction, both tensile strength and modulus were the largest

Formiranje produkata Maillardove reakcije u odležanom octu od sirka i zaštitni učinak melanoidina iz octa na jetru štakora oštećenu tetraklormetanom

Research background. The processing method generally affects the toxicity and biological activity of aged sorghum vinegar. This study investigates the changes in the intermediate Maillard reaction products of sorghum vinegar during ageing and the in vivo hepatoprotective effects of pure melanoidin obtained from it. Experimental approach. High-performance liquid chromatography (HPLC) and fluorescence spectrophotometry were utilized to quantify intermediate Maillard reaction products. The CCl4-induced liver damage in rats was used to evaluate the protective role of pure melanoidin in rat liver. Results and conclusions. Compared with the initial concentration, the 18-month ageing process caused a 1.2- to 3.3-fold increase in the concentrations of intermediate Maillard reaction products, i.e. 5-hydroxymethylfurfural (HMF), 5-methylfurfural (MF), methyglyoxal (MGO), glyoxal (GO) and advanced glycation end products (AGEs). The concentrations of HMF in the aged sorghum vinegar were 6.1-fold higher than the 450 μM limit standard for honey, implying the need for shortening the ageing of the vinegar in practice for safety concerns. Pure melanoidin (Mr>3.5 kDa) demonstrated significant protective effects against CCl4-induced rat liver damage, as evidenced by normalized serum biochemical parameters (transaminases and total bilirubin), suppressing hepatic lipid peroxidation and reactive oxygen species, as well as increasing glutathione amount and restoring antioxidant enzyme activities. Histopathological analysis revealed that melanoidin in vinegar reduced cell infiltration and vacuolar hepatocyte necrosis in rat liver. The findings demonstrated that a shortened ageing process should be considered in practice to ensure the safety of aged sorghum vinegar. Vinegar melanoidin is a potential alternative for the prevention of hepatic oxidative damage. Novelty and scientific contribution. This study demonstrates that the manufacturing process had a profound influence on the generation of vinegar intermediate Maillard reaction products. In particular, it revealed the in vivo hepatoprotective effect of pure melanoidin from aged sorghum vinegar, and provides insight into the in vivo biological activity of melanoidin.Pozadina istraživanja. Postupak pripreme često utječe na toksičnost i biološku aktivnost odležanog octa od sirka. U ovom su radu ispitane promjene u međuproduktima Maillardove reakcije u octu od sirka tijekom starenja, te in vivo hepatoprotektivni učinak čistog melanoidina izdvojenog iz dobivenog octa. Eksperimentalni pristup. Međuprodukti Maillardove reakcije određeni su visokodjelotvornom tekućinskom kromatografijom i fluorescencijskom spektrofotometrijom. Hepatoprotektivno djelovanje čistog melanoidina ispitano je na jetri šakora oštećenoj tetraklormetanom. Rezultati i zaključci. U usporedbi s početnom koncentracijom, koncentracija međuprodukata Maillardove reakcije u octu odležanom tijekom 18 mjeseci, i to 5-hidroksimetilfurfurala (HMF), 5-metilfurfurala (MF), metilglioksala (MGO), glioksala (GO) i konačnih produkata glikacije (engl. AGEs), porasla je za 1,2 do 3,3 puta. Koncentracija HMF-a u odležanom octu od sirka bila je 6,1 puta veća od dozvoljene granice od 450 μM u medu kao standardu, što znači da je u praksi potrebno skratiti vrijeme odležavanja octa radi postizanja sigurnosti njegove uporabe za potrošače. Čisti melanoidin (Mr>3,5 kDa) je učinkovito štitio jetru štakora od oštećenja izazvanih tetraklormetanom, što su potvrdili normalizirani biokemijski parametri seruma (aktivnost transaminaze i koncentracija ukupnih bilirubina), smanjena lipidna peroksidacija u jetri i manja količina reaktivnih spojeva kisika, te veća količina glutationa uz obnovljenu aktivnost enzima. Histopatološka analiza je pokazala da je melanoidin u octu smanjio staničnu infiltraciju i nekrozu hepatocita u jetri štakora. Rezultati pokazuju da bi u praksi trebalo razmotriti skraćeno vrijeme odležavanja octa od sirka, da bi on bio siguran za primjenu. Melanoidin iz octa može se koristiti umjesto lijekova za zaštitu jetre od oksidacijskog oštećenja. Novina i znanstveni doprinos. U radu je prikazano da postupak proizvodnje bitno utječe na stvaranje međuprodukata Maillardove reakcije u octu. Poglavito je prikazan in vivo hepatoprotektivni učinak čistog melanoidina iz odležanog octa od sirka, te je dan uvid u in vivo biološku aktivnost melanoidina

Revealing historical observations and future projections of precipitation over Northwest China based on dynamic downscaled CMIP6 simulations

The warming climate driven by global change has great potential in altering regional and global hydrologic cycles, thus leading to considerable changes in spatial variability and temporal pattern of precipitation. Northwest China (NW) has witnessed a significant wetting trend over the past decades, while the persistence of this wetting trend and potential changes in precipitation under future climate impacts remains elusive. In this study, long-term meteorological observations were used to probe historical variations of precipitation from 1951 to 2020, and the WRF model was employed as a regional climate model to examine future precipitation patterns over NW. Two 9-year downscaled WRF simulations were conducted comprising of historical (WRF-HIST; 2012–2020) and future climate change scenarios (WRF-SSP585; 2047–2055) using bias-corrected global climate model outputs from Coupled Model Intercomparison Project Phase 6 (CMIP6). Compared with ground observations, the WRF model exhibited strong capability in capturing the spatial pattern and temporal variations of precipitation across the NW. Intense precipitation was mainly found in stations located at northern NW and southeastern NW. Summertime precipitation substantially contributed to annual precipitation over the study region. Future precipitation projections suggest significant decreases of precipitation across the southern and eastern NW, with a stronger reduction magnitude in summer. Further, extreme precipitation events were projected to decrease in spring and summer, suggesting that the NW may become drier and the wetting trend may shift to another pattern in the 2050s under the SSP585 climate scenario. Overall, this study reveals historical and future potential changes in precipitation over NW through a high-resolution, dynamically downscaled dataset from WRF modeling, which in turn will help inform regional mitigation and adaption on potential impacts of future climate change on NW

Ultra-Strong Long-Chain Polyamide Elastomers With Programmable Supramolecular Interactions and Oriented Crystalline Microstructures

Polyamides are one of the most important polymers. Long-chain aliphatic polyamides could bridge the gap between traditional polyamides and polyethylenes. Here we report an approach to preparing sustainable ultra-strong elastomers from biomass-derived long-chain polyamides by thiol-ene addition copolymerization with diamide diene monomers. The pendant polar hydroxyl and non-polar butyrate groups between amides allow controlled programming of supramolecular hydrogen bonding and facile tuning of crystallization of polymer chains. The presence of thioether groups on the main chain can further induce metal–ligand coordination (cuprous-thioether). Unidirectional step-cycle tensile deformation has been applied to these polyamides and significantly enhances tensile strength to over 210 MPa while maintaining elasticity. Uniaxial deformation leads to a rearrangement and alignment of crystalline microstructures, which is responsible for the mechanical enhancement. These chromophore-free polyamides are observed with strong luminescence ascribed to the effect of aggregation-induced emission (AIE), originating from the formation of amide clusters with restricted molecular motions

A Microarray Study of Middle Cerebral Occlusion Rat Brain with Acupuncture Intervention

Microarray analysis was used to investigate the changes of gene expression of ischemic stroke and acupuncture intervention in middle cerebral artery occlusion (MCAo) rat brain. Results showed that acupuncture intervention had a remarkable improvement in neural deficit score, cerebral blood flow, and cerebral infarction volume of MCAo rats. Microarray analysis showed that a total of 627 different expression genes were regulated in ischemic stroke. 417 genes were upregulated and 210 genes were downregulated. A total of 361 different expression genes were regulated after acupuncture intervention. Three genes were upregulated and 358 genes were downregulated. The expression of novel genes after acupuncture intervention, including Tph1 and Olr883, was further analyzed by Real-Time Quantitative Polymerase Chain Reaction (RT-PCR). Upregulation of Tph1 and downregulation of Olr883 indicated that the therapeutic effect of acupuncture for ischemic stroke may be closely related to the suppression of poststroke depression and regulation of olfactory transduction. In conclusion, the present study may enrich our understanding of the multiple pathological process of ischemic brain injury and indicate possible mechanisms of acupuncture on ischemic stroke

Human UC-MSC-derived exosomes facilitate ovarian renovation in rats with chemotherapy-induced premature ovarian insufficiency

Premature ovarian insufficiency (POI) induced by chemotherapy is an intractable disorder with a considerable incidence that commonly results in insufficient fertility and concomitant complications in female patients. Due to limitations in the current progress in POI diagnosis and treatment, there is an urgent need to develop novel remedies to improve ovarian function and protect fertility. The ameliorative effect of human umbilical cord mesenchymal stem cells (hUCMSCs) and exosomes derived from them in POI treatment could be a new hope for patients. Herein, we identified exosomes from hUCMSCs (hUCMSC-Exos). Then, systematic infusion of hUCMSC-Exos was accomplished via tail intravenous injection to investigate the feasibility of the treatment of rats with chemotherapy-induced POI by intraperitoneal injection of cyclophosphamide (CTX) and busulfan (BUS). Ovarian functions in the indicated group were evaluated, including oestrous cycle, serum sex hormone levels, follicle counts, ovarian pathological changes, proliferation and apoptosis of granulosa cells (GCs), and reproductive ability testing. Furthermore, the potential influence of hUCMSC-Exos on ovarian tissues was illuminated by conducting RNA-seq and multifaceted bioinformatics analyses. POI rats with hUCMSC-Exos transplantation exhibited a decrease in follicle-stimulating hormone (FSH) and apoptosis of GCs but an increase in oestradiol (E2), anti-Müllerian hormone (AMH), and the number of ovarian follicles and foetuses in the uterus. And the immunomodulation- and cellular vitality-associated gene sets in rats had also undergone moderate changes. Our data indicated the feasibility of hUCMSC-Exos in improving ovarian function and protecting fertility in chemotherapy-induced POI rats. HUCMSC-Exos can improve the local microenvironment of ovarian tissue in POI rats by participating in immune regulation, cellular viability, inflammation regulation, fibrosis and metabolism, and other related signal pathways