Compared with non-degradable materials, biodegradable biomaterials play an increasingly important role in the repairing of severe bone defects, and have attracted extensive attention from ...researchers. In the treatment of bone defects, scaffolds made of biodegradable materials can provide a crawling bridge for new bone tissue in the gap and a platform for cells and growth factors to play a physiological role, which will eventually be degraded and absorbed in the body and be replaced by the new bone tissue. Traditional biodegradable materials include polymers, ceramics and metals, which have been used in bone defect repairing for many years. Although these materials have more or fewer shortcomings, they are still the cornerstone of our development of a new generation of degradable materials. With the rapid development of modern science and technology, in the twenty-first century, more and more kinds of new biodegradable materials emerge in endlessly, such as new intelligent micro-nano materials and cell-based products. At the same time, there are many new fabrication technologies of improving biodegradable materials, such as modular fabrication, 3D and 4D printing, interface reinforcement and nanotechnology. This review will introduce various kinds of biodegradable materials commonly used in bone defect repairing, especially the newly emerging materials and their fabrication technology in recent years, and look forward to the future research direction, hoping to provide researchers in the field with some inspiration and reference.
A two‐step strategy for the transition‐metal‐free C−H functionalization of arenes using unsymmetrical iodonium salts as versatile synthetic linchpins is presented. The key to the success of this ...strategy is the identification of the 3,5‐dimethyl‐4‐isoxazolyl (DMIX) group as a superior dummy ligand, which enables not only site‐selective C−H functionalization to afford unsymmetrical iodonium salts, but also highly selective aryl transfer during the subsequent metal‐free coupling reaction. Both electron‐rich and moderately electron‐deficient arenes can be converted into the iodonium salts through C−H functionalization, allowing for diverse structural elaboration by metal‐free C−N, C−C, C−S, and C−O coupling.
A two‐step C−H functionalization applicable to both electron‐rich and electron‐deficient arenes is described. The method does not require a transition‐metal catalyst and allows rapid structural diversification through the incorporation of various functionalities into complex molecules.
Previous studies on the mechanisms of peripheral nerve injury (PNI) have mainly focused on the pathophysiological changes within a single injury site. However, recent studies have indicated that ...within the central nervous system, PNI can lead to changes in both injury sites and target organs at the cellular and molecular levels. Therefore, the basic mechanisms of PNI have not been comprehensively understood. Although electrical stimulation was found to promote axonal regeneration and functional rehabilitation after PNI, as well as to alleviate neuropathic pain, the specific mechanisms of successful PNI treatment are unclear. We summarize and discuss the basic mechanisms of PNI and of treatment via electrical stimulation. After PNI, activity in the central nervous system (spinal cord) is altered, which can limit regeneration of the damaged nerve. For example, cell apoptosis and synaptic stripping in the anterior horn of the spinal cord can reduce the speed of nerve regeneration. The pathological changes in the posterior horn of the spinal cord can modulate sensory abnormalities after PNI. This can be observed in cases of ectopic discharge of the dorsal root ganglion leading to increased pain signal transmission. The injured site of the peripheral nerve is also an important factor affecting post-PNI repair. After PNI, the proximal end of the injured site sends out axial buds to innervate both the skin and muscle at the injury site. A slow speed of axon regeneration leads to low nerve regeneration. Therefore, it can take a long time for the proximal nerve to reinnervate the skin and muscle at the injured site. From the perspective of target organs, long-term denervation can cause atrophy of the corresponding skeletal muscle, which leads to abnormal sensory perception and hyperalgesia, and finally, the loss of target organ function. The mechanisms underlying the use of electrical stimulation to treat PNI include the inhibition of synaptic stripping, addressing the excessive excitability of the dorsal root ganglion, alleviating neuropathic pain, improving neurological function, and accelerating nerve regeneration. Electrical stimulation of target organs can reduce the atrophy of denervated skeletal muscle and promote the recovery of sensory function. Findings from the included studies confirm that after PNI, a series of physiological and pathological changes occur in the spinal cord, injury site, and target organs, leading to dysfunction. Electrical stimulation may address the pathophysiological changes mentioned above, thus promoting nerve regeneration and ameliorating dysfunction.
The intercalation compounds with various electrochemically active or inactive elements in the layered structure have been the subject of increasing interest due to their high capacities, good ...reversibility, simple structures, and ease of synthesis. However, their reversible intercalation/deintercalation redox chemistries in previous compounds involve a single cationic redox reaction or a cumulative cationic and anionic redox reaction. Here we report an anionic redox chemistry and structural stabilization of layered sodium chromium sulfide. It was discovered that the sulfur in sodium chromium sulfide is electrochemically active, undergoing oxidation/reduction rather than chromium. Significantly, sodium ions can successfully move out and into without changing its lattice parameter c, which is explained in terms of the occurrence of chromium/sodium vacancy antisite during desodiation and sodiation processes. Our present work not only enriches the electrochemistry of layered intercalation compounds, but also extends the scope of investigation on high-capacity electrodes.The rational design of intercalation electrodes is largely confined to the optimization of redox chemistry of transition metals and oxygen. Here, the authors report the single anionic redox process in NaCrS
where it is sulfur rather than chromium that works as the electrochemical active species.
•We tested the interfacial tensile and shear strengths between the old and new mortars of recycled aggregate concrete.•We investigated the changes of the microstructure of the interfacial zones by ...SEM scanning technique.•We quantified the strength improvement achieved by use of nano-SiO2 and nano-carbon tubes.•We established the interaction diagram of the interfacial shear and tensile strengths based on the test results.
This paper evaluates the effect of Nano-SiO2 and multi-walled carbon nanotubes addition on the interfacial tensile and shear strengths of recycled aggregate concrete. Tension and shear tests were conducted for the interfacial strengths between the new and old mortars. Scanning electron microscopy was also conducted to identify the change of the microstructure of the nanomaterial modified interfacial transition zones. The results indicated that addition of the Nano-SiO2 and the carbon nanotubes can generally improve the interfacial tensile and shear strengths at dosages not exceeding 1.0 and 0.2 wt%, and the maximum tensile and shear strength improvements, 51% and 53%, respectively, were both obtained by use of the carbon nanotubes. Scanning electron microscopy results confirmed that the strength improvement came from the nucleation and filling effect and pozzolanic activity of the Nano-SiO2 and the nucleation, filling and bridging effect of the carbon nanotubes. An interaction diagram between the interfacial tensile and shear strengths were established following the Mohr-Coulomb strength theory. The internal friction angle of the modified recycled aggregate concrete was found to be in close range with the reference specimens (±8%), possibly due to the similar influencing mechanism of the nanomaterials on the shear and tensile strength of the interfaces.
Release of ATP from astrocytes is required for Ca2+ wave propagation among astrocytes and for feedback modulation of synaptic functions. However, the mechanism of ATP release and the source of ATP in ...astrocytes are still not known. Here we show that incubation of astrocytes with FM dyes leads to selective labelling of lysosomes. Time-lapse confocal imaging of FM dye-labelled fluorescent puncta, together with extracellular quenching and total-internal-reflection fluorescence microscopy (TIRFM), demonstrated directly that extracellular ATP or glutamate induced partial exocytosis of lysosomes, whereas an ischaemic insult with potassium cyanide induced both partial and full exocytosis of these organelles. We found that lysosomes contain abundant ATP, which could be released in a stimulus-dependent manner. Selective lysis of lysosomes abolished both ATP release and Ca2+ wave propagation among astrocytes, implicating physiological and pathological functions of regulated lysosome exocytosis in these cells.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Artificial ground freezing (AGF) has been widely used as a temporary soil stabilization and waterproofing technique in geotechnical practices (e.g., tunnel construction). Many sources of uncertainty ...exist during AGF. Firstly, groundwater seepage flow can adversely affect the freezing efficacy. Secondly, freeze pipe inclination inevitably occurs during installation, which is likely to yield an unfrozen path and elevate construction risk. Thirdly, as a key soil parameter, the spatial variability in thermal conductivity can also affect the freezing process. In this work, a unit cell model of freeze pipes is established by a coupled thermo-hydraulic finite element method to examine the effects of these sources of uncertainty. The pipe inclination is considered in the unit cell model by prescribing various values of freeze pipe spacing. The thermal conductivity of soil solid is simulated as a three-dimensional lognormal random field to account for the spatial variability of soil. Results are tabulated to evaluate the additional freezing time required in the AGF system due to the existence of these uncertainties. The findings are capable of determining a reasonable range of freeze pipe spacings and the corresponding critical seepage velocity, and can offer practitioners a rule of thumb for estimating freeze pipe spacing.
Accidental oil leaks and spills can often result in severe soil and groundwater pollution. In situ chemical oxidation (ISCO) is a powerful and efficient remediation technology. In this review, the ...applications and recent advances of three commonly applied in-situ oxidants (hydrogen peroxide, persulfate, and permanganate), and the gap in remediation efficiency between lab-scale and field-scale applications is critically assessed. Feasible improvements for these measures, especially solutions for the ‘rebound effect’, are discussed. The removal efficiencies reported in 108 research articles related to petroleum-contaminated soil and groundwater were analyzed. The average remediation efficiency of groundwater (82.7%) by the three oxidants was higher than that of soil (65.8%). A number of factors, including non-aqueous phase liquids, adsorption effect, the aging process of contaminants, low-permeability zones, and vapor migration resulted in a decrease in the remediation efficiency and caused the residual contaminants to rebound from 19.1% of the original content to 57.7%. However, the average remediation efficiency of ISCO can be increased from 40.9% to 75.5% when combined with other techniques. In the future, improving the utilization efficiency of reactive species and enhancing the contact efficiency between oxidants and petroleum contaminants will be worthy of attention. Multi-technical combinations, such as the ISCO coupled with phase-transfer, viscosity control, controlled release or natural attenuation, can be effective methods to solve the rebound problem.
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•In-situ chemical oxidation is an effective method for petroleum polluted sites.•The rebound of petroleum concentration prevents to reach the remediation goal.•The non-aqueous contaminants and matrix back diffusion are worthy of attention.•Other technologies can improve treatment efficiency of in-situ chemical oxidation.
Tooth loss is suggested to be associated with an increased risk of dementia in many studies. But the relationship between tooth loss and dementia is not yet fully understood. This systematic review ...and meta-analysis aimed to determine the relative effect of tooth loss on dementia risk.
An electronic search of PubMed, Scopus, Embase, and Web of Knowledge was conducted in March 2018 to identify relevant observational studies with the English language restriction. Studies were included if they assessed the relationship between tooth loss and risk of dementia. Study quality was detected by the modified Downs and Black scale. Odds risks (ORs) were pooled using a random-effects model in the crude model.
The literature search initially yielded 1574 articles, and 21 observational studies published between 1994 and 2017 were finally included for the analyses. The crude results with random-effects model showed that patients with multiple tooth loss had higher incidence of dementia (OR 2.62, 95% CI 1.90-3.61, P < 0.001, I
= 90.40%). The association remained noted when only adjusted results were pooled from 18 studies (OR 1.55, 95% CI 1.41-1.70, P = 0.13, I
= 28.00%). Meta-regression analysis showed that study design explained about 16.52% of heterogeneity in the crude model. The overall quality rating scores of studies ranged from 11 to 16.
Findings from this review evidenced that tooth loss is positively associated with an increased risk of dementia in adults. Future well-designed longitudinal researches examining the direct and indirect relationship between tooth loss and dementia risk are encouraged.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Recovery from injury to the peripheral nervous system is different from that of the central nervous system in that it can lead to gene reprogramming that can induce the expression of a series of ...regeneration-associated genes. This eventually leads to axonal regeneration of injured neurons. Although some regeneration-related genes have been identified, the regulatory network underlying axon regeneration remains largely unknown. To explore the regulator of axon regeneration, we performed RNA sequencing of lumbar L4 and L5 dorsal root ganglion (DRG) neurons at different time points (0, 3, 6, 12 hours, 1, 3 and 7 days) after rat sciatic nerve crush. The isolation of neurons was carried out by laser capture microscopy combined with NeuN immunofluorescence staining. We found 1228 differentially expressed genes in the injured sciatic nerve tissue. The hub genes within these differentially expressed genes include Atf3, Jun, Myc, Ngf, Fgf2, Ezh2, Gfap and Il6. We verified that the expression of the enhancer of zeste homologue 2 gene (Ezh2) was up-regulated in DRG neurons after injury, and this up-regulation differed between large- and small-sized dorsal root ganglion neurons. To investigate whether the up-regulation of Ezh2 impacts axonal regeneration, we silenced Ezh2 with siRNA in cultured DRG neurons and found that the growth of the newborn axons was repressed. In our investigation into the regulatory network of Ezh2 by interpretive phenomenal analysis, we found some regulators of Ezh2 (including Erk, Il6 and Hif1a) and targets (including Atf3, Cdkn1a and Smad1). Our findings suggest that Ezh2, as a nerve regeneration-related gene, participates in the repair of the injured DRG neurons, and knocking down the Ezh2 in vitro inhibits the axonal growth of DRG neurons. All the experimental procedures approved by the Administration Committee of Experimental Animals of Jiangsu Province of China (approval No. S20191201-201) on March 21, 2019.
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