Fiber Growth Research Articles

Calcium silicate nanowires-containing multicellular bioinks for 3D bioprinting of neural-bone constructs

The significant guiding roles of nerves in bone formation and remodeling have been largely overlooked during the past decades when it comes to designing bone regeneration scaffolds. The requirement of intrabony nerve regeneration cannot be fulfilled by current therapeutic options, resulting in delayed innervation. Constructing a bone organoid which takes intrabony nerves into account can be a feasible approach. Herein, in combination with the nanocomposite bioinks and multicellular 3D bioprinting technology, a biomimetic neural-bone construct was successfully developed for innervated bone regeneration. Neural cells and bone-related cells were orderly printed to imitate the simplified spatial distribution of bone and nerves. Besides, inorganic calcium silicate (CS) nanowires were synthesized and incorporated into the bioinks to serve as “bioactive factors” to regulate multicellular behaviors. CS nanowires containing-bioinks could obviously promote the long-term survival and spreading as well as osteogenic and neurogenic differentiation of encapsulated cells. Furthermore, the in vivo results demonstrated that the CS nanowires containing-bioinks for 3D bioprinting of neural-bone constructs could simultaneously accelerate the new bone formation and ingrowth of nerve fibers. Taken together, this study offers a new concept by using inorganic nanomaterials as the bioactive components of bioinks for complex tissue regeneration, which represents a potential strategy for the fabrication of bone organoid with enhanced restoration of innervation and innervated bone tissues.

Dietary cinnamaldehyde improves muscle protein content by promoting muscle fiber growth via PTP1B/IGF1/PI3K/AKTs-TOR/FOXO3a signaling pathway in grass carp (Ctenopharyngodon idella)

Flesh quality is evaluated according to nutritional value and sensory quality. Cinnamaldehyde (CIN) improves mammalian meat quality, but research relating this to aquaculture is scarce. In this study, five doses of CIN (0, 36, 72, 108, 144 mg/kg diet) were fed to grass carp (Ctenopharyngodon idella) for 60 days. The results show that CIN supplementation increased nutritional value by increasing crude protein content. CIN also improved the sensory quality by increasing the pH and collagen content, decreasing shear force, lactate, and cooking loss. These changes may be related to changes in muscle fiber growth by increasing myofiber diameter. The increased myofiber diameter induced by CIN is associated with TOR mRNA and protein levels, and down-regulated FOXO3a mRNA levels, which might be associated with PTP1B/IGF1/PI3K/AKTs-TOR/FOXO3a signaling. Based on muscle crude protein content, optimal CIN supplementation dosage was 88.01 mg/kg.

Submicron Topographically Patterned 3D Substrates Enhance Directional Axon Outgrowth of Dorsal Root Ganglia Cultured Ex Vivo.

A peripheral nerve injury results in disruption of the fiber that usually protects axons from the surrounding environment. Severed axons from the proximal nerve stump are capable of regenerating, but axons are exposed to a completely new environment. Regeneration recruits cells that produce and deposit key molecules, including growth factor proteins and fibrils in the extracellular matrix (ECM), thus changing the chemical and geometrical environment. The regenerating axons thus surf on a newly remodeled micro-landscape. Strategies to enhance and control axonal regeneration and growth after injury often involve mimicking the extrinsic cues that are found in the natural nerve environment. Indeed, nano- and micropatterned substrates have been generated as tools to guide axons along a defined path. The mechanical cues of the substrate are used as guides to orient growth or change the direction of growth in response to impediments or cell surface topography. However, exactly how axons respond to biophysical information and the dynamics of axonal movement are still poorly understood. Here we use anisotropic, groove-patterned substrate topography to direct and enhance sensory axonal growth of whole mouse dorsal root ganglia (DRG) transplanted ex vivo. Our results show significantly enhanced and directed growth of the DRG sensory fibers on the hemi-3D topographic substrates compared to a 0 nm pitch, flat control surface. By assessing the dynamics of axonal movement in time-lapse microscopy, we found that the enhancement was not due to increases in the speed of axonal growth, but to the efficiency of growth direction, ensuring axons minimize movement in undesired directions. Finally, the directionality of growth was reproduced on topographic patterns fabricated as fully 3D substrates, potentially opening new translational avenues of development incorporating these specific topographic feature sizes in implantable conduits in vivo.

A flax mutant with impaired intrusive growth of phloem and xylem fibres demonstrates constitutive gravitropic response

Intrusive growth is a type of growth in which a cell exceeds the growth rate of its neighbours and intrudes between them, reaching a much greater length. This process provides plant fibres with their exceptional length. Fibres are the most abundant cell type in the mechanical tissues of plants. At the same time, the plant fibres are of fundamental importance for the production of textiles, paper, biocomposites, etc. Here we describe a mutant of flax (reduced fibre 1, rdf) in which intrusive growth of fibres is impaired in both phloem and xylem. In addition to the intrinsic differences in fibre length, the mutant is characterized by a constitutive gravitropic response, mechanical aberrations at the macro- and nanolevels, disruption of the cambium and uneven transition of xylem cells to secondary cell wall formation. Gelatinous cell walls in both phloem and xylem of mutant plants have disturbed structure and reduced elasticity. The existence of this mutant-control pair offers both prospects for finding the molecular players involved in triggering intrusive growth, cell wall thickening and for understanding the principles of plant mechanical tissue functioning.

A glitch in the matrix: the pivotal role for extracellular matrix remodeling during muscle hypertrophy.

Multinuclear muscle fibers are the most voluminous cells in skeletal muscle and the primary drivers of growth in response to loading. Outside the muscle fiber, however, is a diversity of mononuclear cell types that reside in the extracellular matrix (ECM). These muscle-resident cells are exercise-responsive and produce the scaffolding for successful myofibrillar growth. Without proper remodeling and maintenance of this ECM scaffolding, the ability to mount an appropriate response to resistance training in adult muscles is severely hindered. Complex cellular choreography takes place in muscles following a loading stimulus. These interactions have been recently revealed by single-cell explorations into muscle adaptation with loading. The intricate ballet of ECM remodeling involves collagen production from fibrogenic cells and ECM modifying signals initiated by satellite cells, immune cells, and the muscle fibers themselves. The acellular collagen-rich ECM is also a mechanical signal-transducer and rich repository of growth factors that may directly influence muscle fiber hypertrophy once liberated. Collectively, high levels of collagen expression, deposition, and turnover characterize a well-trained muscle phenotype. The purpose of this review is to highlight the most recent evidence for how the ECM and its cellular components affect loading-induced muscle hypertrophy. We also address how the muscle fiber may directly take part in ECM remodeling, and whether ECM dynamics are rate limiting for muscle fiber growth.

Correlation between Chirality and Spherical Particle Formation Related to the Loss of Function of Thixotropic Additive Molecules

AbstractThe relationship between chirality and loss of function of thixotropic additive molecules with asymmetric carbon and helical fiber growth under high‐temperature exposure was investigated. Among the thixotropic additive molecules that impart gelation/fluidization ability during pressurization of the solvent, derivatives with high‐performance, helical fiber growth ability became mesoscopic spherical particles upon high‐temperature exposure. Conversely, derivatives that lost their fiber growth ability could not achieve solvent gelation. The growth pattern was such that the helical fibers were transformed into straight fibers. The right‐handed helical signal of the circular dichroism spectrum, which is indicative of chirality by structure formation, was inactivated upon high‐temperature exposure. Therefore, a low‐temperature process or heat treatment in an inert state under a N2 atmosphere is essential for maintaining chirality and helical fibrosis.

VMP1 Regulated by chi-miR-124a Effects Goat Myoblast Proliferation, Autophagy, and Apoptosis through the PI3K/ULK1/mTOR Signaling Pathway.

The production of goat meat is determined by the growth speed of muscle fibers, and the autophagy and apoptosis of myoblast cells is a crucial process in the growth of muscle fibers. The rapid growth of muscle fibers occurs from one month old to nine months old in goats; however, the mechanisms of myoblast cells’ autophagy and apoptosis in this process are still unknown. To identify candidate genes and signaling pathway mechanisms involved in myoblast apoptosis and autophagy, we compared the expression characteristics of longissimus dorsi tissues from Wu’an goats—a native goat breed of China—at 1 month old (mon1 group) and 9 months old (mon9 group). Herein, a total of 182 differentially expressed mRNAs (DEGs) in the mon1 vs. mon9 comparison, along with the KEGG enrichments, showed that the PI3K-Akt pathway associated with autophagy and apoptosis was significantly enriched. Among these DEGs, expression of vacuole membrane protein 1 (VMP1)—a key gene for the PI3K-Akt pathway—was significantly upregulated in the older goats relative to the 1-month-old goats. We demonstrated that VMP1 promotes the proliferation and autophagy of myoblasts, and inhibits their apoptosis. The integration analysis of miRNA–mRNA showed that miR-124a was a regulator of VMP1 in muscle tissue, and overexpression and inhibition of miR-124a suppressed the proliferation and autophagy of myoblasts. The PI3K/Akt/mTOR pathway was an important pathway for cell autophagy. Additionally, the activator of the PI3K/Akt/mTOR pathway, the expression of VMP1, and ULK1 were higher than the negative control, and the expression of mTOR was depressed. The expression of VMP1, ULK1, and mTOR was the opposite when the inhibitor was added to the myoblasts. These results show that the PI3K/Akt/mTOR pathway promoted the expression of VMP1 and ULK1. By using adenovirus-mediated apoptosis and proliferation assays, we found that that miR-124a inhibits myoblast proliferation and autophagy, and promotes their apoptosis by targeting VMP1. In conclusion, our results indicated that VMP1 was highly expressed in the LD muscle tissues of nine-month-old goats, and that it was regulated by miR-124a to inhibit myoblast cells’ apoptosis through the PI3K/Akt/mTOR pathway, and to promote proliferation and autophagy. These findings contribute to the understanding of the molecular mechanisms involved in myoblast proliferation, autophagy, and apoptosis.

Dilution-induced gel-sol-gel-sol transitions by competitive supramolecular pathways in water.

Fascinating properties are displayed by synthetic multicomponent supramolecular systems that comprise a manifold of competitive interactions, thereby mimicking natural processes. We present the integration of two reentrant phase transitions based on an unexpected dilution-induced assembly process using supramolecular polymers and surfactants. The co-assembly of the water-soluble benzene-1,3,5-tricarboxamide (BTA-EG4) and a surfactant at a specific ratio yielded small-sized aggregates. These interactions were modeled using the competition between self-sorting and co-assembly of both components. The small-sized aggregates were transformed into supramolecular polymer networks by a twofold dilution in water without changing their ratio. Kinetic experiments show the in situ growth of micrometer-long fibers in the dilution process. We were able to create systems that undergo fully reversible hydrogel-solution-hydrogel-solution transitions upon dilution by introducing another orthogonal interaction.

Temperature-dependent self-assembly of biofilaments during red blood cell sickling.

Molecular self-assembly plays a vital role in various biological functions. However, when aberrant molecules self-assemble to form large aggregates, it can give rise to various diseases. For example, sickle cell disease and Alzheimer's disease are caused by self-assembled hemoglobin fibers and amyloid plaques, respectively. Here, we study the assembly kinetics of such fibers using kinetic Monte Carlo simulation. We focus on the initial lag time of these highly stochastic processes, during which self-assembly is very slow. The lag time distributions turn out to be similar for two very different regimes of polymerization, namely, (a) when polymerization is slow and depolymerization is fast and (b) the opposite case, when polymerization is fast and depolymerization is slow. Using temperature-dependent on- and off-rates for hemoglobin fiber growth, reported in recent in vitro experiments, we show that the mean lag time can exhibit non-monotonic behavior with respect to the change in temperature.

Physiological and Neural Changes with Rehabilitation Training in a 53-Year Amputee: A Case Study

Many people who received amputation wear sEMG prostheses to assist in their daily lives. How these prostheses promote muscle growth and change neural activity remains elusive. We recruited a subject who had his left hand amputated for over 53 years to participate in a six-week rehabilitation training using an sEMG prosthesis. We tracked the muscle growth of his left forearm and changes in neural activity over six weeks. The subject showed an increase in fast muscle fiber in his left forearm during the training period. In an analysis of complex networks of neural activity, we observed that the -band network decreased in efficiency but increased in its capability to integrate information. This could be due to an expansion of the network to accommodate new movements enabled by rehabilitation training. Differently, we found that in the -band network, a band frequency related to motor functions, the efficiency of the network initially decreased but started to increase after approximately three weeks. The ability to integrate network information showed an opposite trend compared with its efficiency. rMT values, a measure that negatively correlates with cortical excitability, showed a sharp decrease in the first three weeks, suggesting an increase in cortical excitability. In the last three weeks, there was little to no change. These data indicate that rehabilitation training promoted fast muscle fiber growth and introduced neural activity changes in the subject during the first three weeks of training. Our study gave insights into how rehabilitation training with an sEMG prosthesis could lead to physiological and neural changes in amputees.

Role of stem cells-based in facial nerve reanimation: A meta-analysis of histological and neurophysiological outcomes.

BACKGROUNDTreatments involving stem cell (SC) usage represent novel and potentially interesting alternatives in facial nerve reanimation. Current literature includes the use of SC in animal model studies to promote graft survival by enhancing nerve fiber growth, spreading, myelinization, in addition to limiting fibrotic dege neration after surgery. However, the effectiveness of the clinical use of SC in facial nerve reanimation has not been clarified yet.AIMTo investigate the histological, neurophysiological, and functional outcomes in facial reanimation using SC, compared to autograft.METHODSOur study is a systematic review of the literature, consistently conducted according to the preferred reporting items for systematic reviews and meta-analyses statement guidelines. The review question was: In facial nerve reanimation on rats, has the use of stem cells revealed as effective when compared to autograft, in terms of histological, neurophysiological, and functional outcomes? Random-effect meta-analysis was conducted on histological and neurophysiological data from the included comparative studies.RESULTSAfter screening 148 manuscript, five papers were included in our study. 43 subjects were included in the SC group, while 40 in the autograft group. The meta-analysis showed no significative differences between the two groups in terms of myelin thickness [CI: -0.10 (-0.20, 0.00); I2 = 29%; P = 0.06], nerve fibers diameter [CI: 0.72 (-0.93, 3.36); I2 = 72%; P = 0.6], compound muscle action potential amplitude [CI: 1.59 (0.59, 3.77); I2 = 89%; P = 0.15] and latency [CI: 0.66 (-1.01, 2.32); I2 = 67%; P = 0.44]. The mean axonal diameter was higher in the autograft group [CI: 0.94 (0.60, 1.27); I2 = 0%; P ≤ 0.001].CONCLUSIONThe role of stem cells in facial reanimation is still relatively poorly studied, in animal models, and available results should not discourage their use in future studies on human subjects.

Current possibilities of pharmacological correction of neuroimmune joint damage in patients with knee osteoarthritis in long COVID conditions

Objective: to evaluate the efficacy and safety of the parenteral form of pharmaceutical chondroitin sulfate (CS) in neuroimmune joint damage in patients with early knee osteoarthritis (OA) in long COVID.Patients and methods. An open prospective controlled randomized study was conducted, its duration was 50 days of active controlled therapy. The study included 82 patients (age 57–63 years, men – 29, women – 53) with clinical symptoms of early knee OA and confirmed long COVID type 2 (persistence of symptoms 4–12 weeks after infection with SARS-CoV2). The diagnosis of OA was established in accordance with the updated classification criteria for early knee OA (2018).Patients were randomized into two groups: group 1 – the main group (n=42) and group 2 – control group (n=40). Patients in both groups received celecoxib at a dose of 200 mg with the possibility of reducing the dose to 100 mg or completely discontinuing the drug if necessary. Patients of the 1st group additionally received a parenteral form of CS (Chondroguard® solution for intramuscular and intraarticular administration, 100 mg/ml). At baseline (Day 1) and on the 50th day of the study, pain intensity was assessed in all patients using a visual analogue scale (VAS), the degree of functional impairment (FI) of the joints according to the Lequesne index, ultrasound of the knee joint was performed, CRP, D-dimer, fibrinogen, interleukin (IL) 1β, IL6 levels were studied. The presence of SARS-CoV2 was determined by polymerase chain reaction in scrapings from the mucous membrane of the nasal cavity and oropharynx, and a qualitative proteomic analysis was performed (1-2DE, MALDI-TOF/TOF-MS, PathCards database). The safety of therapy was assessed using the WHO and Naranjo scales.Results and discussion. It was established that CS therapy was well tolerated and was accompanied by a significant decrease in pain intensity according to VAS (U-test=5.71; p<0.0001), in FI according to the Lequesne scale (U-test=6.32; p<0.0001), in manifestations of synovitis and tendinitis in the group treated with CS and celecoxib, compared with the control group. During the treatment by CS a statistically significant (p<0.0001) decrease in the level of pro-inflammatory markers in the blood serum (CRP, IL6, IL1β), D-dimer and fibrinogen was noted. Proteomic analysis showed a decrease in the blood serum of patients of the 1st group of eotaxin 1, IL8, IL15, interferon γ inducible protein 10 levels, and an increase in the expression of nerve fiber growth factor β, an antagonist of the IL1 receptor.Conclusion. The use of pharmaceutical parenteral CS in combination with oral celecoxib in patients with early OA of the knee joint, the clinical signs of which manifested after infection with SARS-CoV2 and persisted in long COVID conditions, contributed to a decrease in the severity of pain and stiffness in the knee joint, as well as improved functional capabilities.

Tunable Coefficient of Thermal Expansion of Composite Materials for Thin-Film Coatings

In most engineering applications, the coefficients of thermal expansion (CTEs) of different materials in integrated structures are inconsistent, especially for the thin-film multilayered coatings. Therefore, mismatched thermal deformation is induced due to temperature variation, which leads to an extreme temperature gradient, stress concentration, and damage accumulation. Controlling the CTEs of materials can effectively eliminate the thermally induced stress within the layered structures and thus considerably improve the mechanical reliability and service life. In this paper, randomly distributed fibers are incorporated into the matrix material and thus utilized to tune the material CTE from the macroscopical viewpoint. To this end, finite element (FE) modeling is proposed for fiber-reinforced matrix composites. In order to overcome the challenges of creating numerical models at a mesoscale, the random distribution of fibers in three-dimensional space is realized by proposing a fiber growth algorithm with the control of the in-plane and out-of-plane angles of fibers. The homogenization method is adopted to facilitate the FE simulations by using the representative volume element (RVE) of composite materials. Periodic boundary conditions (PBC) are applied to realize the prediction of the equivalent CTE of macroscopic composite materials with randomly distributed fibers. In the established FE model, the random distribution of carbon fibers in the matrix makes it possible to tune the CTE of the composite material by considering the orientation of fibers in the matrix. The FE predictions show that the volume fraction of carbon fibers in the composite materials is found to be crucial to macroscopic CTE, but results in minor variations in Young’s modulus and shear modulus. With the developed ABAQUS plug-in program, the proposed tuning method for CTE is promising to be standardized for industrial practice.

Extraction of eco-friendly biocomposites from eulaliopsis binata: Mechanical, thermal and anti-bacterial studies

When compared to synthetic fibres, natural fibres are more environmentally friendly, biodegradable, and health-promoting. Novel technologies and methods for the growth of new plant fibres are being developed to replace both old conventional natural fibres and synthetic fibres. Eulaliopsis Binata, also known as Sabai Grass, is believed to have a high lignin concentration of upto 18.5 percent and a cellulose content of up to 55 percent. Natural cellulosic fibres were isolated from Eulaliopsis Binata and examined for their properties in this work. Compositional investigations, morphological studies, tensile properties, physical properties, thermal behaviour studies, and anti-bacterial research are all performed on the fibres obtained. The properties of Eulaliopsis Binata fibres were found to be nearly identical to those of conventional fibres, indicating that they could be employed in the production of coarse fibre fabrics, bio-based materials, and automotive interiors.

Improving Containerized Nursery Crop Sustainability: Effects of Conservation-driven Adaptations in Soilless Substrate and Water Use on Plant Growth and Soil-borne Disease Development

Containerized crop production faces increasing sustainability challenges with both soilless substrate and water use. To facilitate use of sustainable practices, we evaluated plant health impacts of two substrates, bark and wood fiber, which we contrasted with peat, a substrate that is slower to renew; this was overlaid with an analysis of the effects of water-saving–targeted irrigation reductions, compared with typical well-watered conditions. Health impacts were evaluated in two crops, considering both physiological and disease impacts for tomato with and without Phytophthora capsici, and chrysanthemum with and without Phytopythium helicoides. Substrate type was a strong determinant of plant health, wherein crops grown in a HydraFiber-peat mix (“fiber”) performed worse than those in bark and peat, with up to a 50% and 45% reduction in shoot biomass in tomato and chrysanthemum, respectively (P < 0.001). Tomato decline incidence from P. capsici was 3–6 times higher in fiber than other substrates, and fiber was the only substrate where the effect of P. capsici enhanced decline and rot development compared with noninoculated plants (P < 0.05). In bark, reduced irrigation consistently inhibited tomato and chrysanthemum growth and shoot water content (typically P < 0.001). In peat, whereas tomato growth was inhibited under reduced irrigation (P = 0.012–0.013), chrysanthemum growth was often unaffected. Growth in fiber was uniformly poor regardless of irrigation regime for both crops, and an irrigation treatment effect was not typically apparent. Reduced irrigation enhanced pathogen effects in fiber and peat for tomato and fiber and bark for chrysanthemum (P < 0.05). This is perhaps the first study to evaluate HydraFiber interactions with disease and reduced irrigation and suggests that this product consistently incurs costs to crop productivity. However, the peat-replacing bark substrate has strong potential to optimize plant growth physiologically and via disease suppression and can be used under reduced irrigation without compromising economic productivity of the system.

Effect of starvation and refeeding on reactive oxygen species, autophagy and oxidative stress in Chinese perch (Siniperca chuatsi) muscle growth.

In skeletal muscle, autophagy regulates the development and growth of muscle fibres and maintains the normal muscle metabolism. Under starvation and refeeding conditions, the effect of reactive oxygen species (ROS) levels on skeletal muscle autophagy is still unclear, although the excessive accumulation of ROS has been shown to increase autophagy in cells. The purpose of this study was to explore the effects of starvation and diet after starvation on the autophagy of adult Chinese perch muscle, and to determine the level of ROS in the muscle. We performed zero (Normal control), three and seven starvation treatments on adult Chinese perch, and returned to normal feeding for 3 days after starvation for 7 days. In the muscles of the adult Chinese perch muscle after 3 days of starvation, the autophagy marker protein LC3 and the number of autophagosomes remained basically the same as in the normal feeding situation. However, on starvation for 7 days, the mitochondrial autophagy was sensitive and the number of autophagosomes increased, but the antioxidant-related molecules (malondialdehyde, catalase, glutathione S-transferase, glutathione and anti-superoxide anion) decreased and the accumulation of ROS was obvious. In addition, the extended starvation time also increased the level of LC3 protein. However, by refeeding after starvation this nutritional stress resulted in a decrease in ROS levels and a partial restoration of antioxidant enzyme activity. Our data show that in the adult Chinese perch muscle, starvation could reduce the antioxidant activity through the accumulation of ROS, and that the number of autophagosomes continues to increase. Refeeding after starvation could effectively compensate for the level of ROS, and restore the mRNA abundance of antioxidant genes and the activity of antioxidant enzymes to reduce autophagy and improve feed efficiency. Further research should optimize starvation conditions to reduce autophagy in muscles and maintain normal muscle metabolism.

Does the Pathogenic Sequence of Skeletal Muscle Degeneration in Duchenne Muscular Dystrophy Begin and End with Unrestrained Satellite Cell Activation?

A recent study describing unique effects of myostatin inhibition on a severely dystrophic (mdx) muscle, and independent experiments showing that branched fibers are uniquely sensitive to activity-induced membrane rupture, have led to a new hypothesis of dystrophic pathogenesis. This hypothesis states that the absence of dystrophin directly results in some degree of unrestrained satellite cell activation that is not dependent upon prior fiber injury. The hypothesis further states that dystrophin promotes satellite cell quiescence, and that its absence directly results in a lack of control over the mechanism(s) by which muscle activity regulates satellite cell activation and fiber growth during passive stretch and concentric and eccentric exercise. The ultimate consequence of this lack of control is to produce branched, weak, and fragile fibers that accumulate at a rate dependent upon the history of activation for each dystrophic muscle. The purpose of this opinion paper is to summarize the results in support of this new hypothesis in an attempt to stimulate further research on the regulation of satellite cell activity in dystrophic muscle.

Low‐temperature Pr3Si2C2‐assisted liquid‐phase sintering of SiC with improved thermal conductivity

AbstractA novel Pr3Si2C2 additive was uniformly coated on SiC particles using a molten‐salt method to fabricate a high‐density SiC ceramics via liquid‐phase spark plasma sintering at a relatively low temperature (1400°C). According to the calculated Pr–Si–C‐phase diagram, the liquid phase was formed at ∼1217°C, which effectively improved the sintering rate of SiC by the solution–reprecipitation process. When the sintering temperature increased from 1400 to 1600°C, the thermal conductivity of SiC increased from 84 to 126 W/(m K), as a consequence of the grain growth. However, an increasing amount of the sintering additive increased the interfacial thermal resistance, resulting in a decrease of thermal conductivity of the materials. The highest thermal conductivity of 141 W/(m K) was obtained for the material having the largest SiC grains and an optimized amount of the additive at the grain boundaries and triple junctions. The proposed Pr3Si2C2‐assisted liquid‐phase sintering of SiC can be potentially used for the fabrication of SiC‐based ceramic composites, where a low sintering temperature would inhibit the grain growth of SiC fibers.

Kinetics and mechanisms for the densification and grain growth of the α-alumina fibers isothermally sintered at elevated temperatures

Understanding the densification and grain growth processes is essential for preparing dense alumina fibers with nanograins. In this study, the alumina fibers were prepared via isothermal sintering at 1200, 1300, 1400, and 1500 °C for 1–30 min. The phase, microstructure, and density of the sintered fibers were investigated using XRD, SEM, and Archimedes methods. It was found that the phase transformation during the isothermal sintering enhances the densification of Al2O3 fibers in the initial stage, while the pores generated during the phase transformation retard the densification in the later period. The kinetics and mechanisms for the densification and grain growth of the fibers were discussed based on the sintering and grain growth models. It was revealed that the densification process of the fibers sintered at 1500 °C is dominated by the lattice diffusion mechanism, while the samples sintered at 1200–1400 °C are dominated by the grain boundary diffusion mechanism. The grain growth of the Al2O3 fibers sintered at 1200–1300 °C is governed by surface-diffusion-controlled pore drag, and that sintered at 1400 °C is dominated by lattice-diffusion-controlled pore drag.

Potential Benefits of Combined Statin and Metformin Therapy on Resistance Training Response in Older Individuals.

Metformin and statins are currently the focus of large clinical trials testing their ability to counter age-associated declines in health, but recent reports suggest that both may negatively affect skeletal muscle response to exercise. However, it has also been suggested that metformin may act as a possible protectant of statin-related muscle symptoms. The potential impact of combined drug use on the hypertrophic response to resistance exercise in healthy older adults has not been described. We present secondary statin analyses of data from the MASTERS trial where metformin blunted the hypertrophy response in healthy participants (>65 years) following 14 weeks of progressive resistance training (PRT) when compared to identical placebo treatment (n = 94). Approximately one-third of MASTERS participants were taking prescribed statins. Combined metformin and statin resulted in rescue of the metformin-mediated impaired growth response to PRT but did not significantly affect strength. Improved muscle fiber growth may be associated with medication-induced increased abundance of CD11b+/CD206+ M2-like macrophages. Sarcopenia is a significant problem with aging and this study identifies a potential interaction between these commonly used drugs which may help prevent metformin-related blunting of the beneficial effects of PRT. Trial Registration: ClinicalTrials.gov, NCT02308228, Registered on 25 November 2014.