Sequentially releasing self-healing hydrogel fabricated with TGFβ3-microspheres and bFGF to facilitate rat alveolar bone defect repair

Resorption and loss of alveolar bone leads to oral dysfunction and loss of natural or implant teeth. Biomimetic delivery of growth factors based on stem cell recruitment and osteogenic differentiation, as the key steps in natural alveolar bone regenerative process, has been an area of intense research in recent years. A mesoporous self-healing hydrogel(DFH) with basic fibroblast growth factor(bFGF) entrapment and transforming growth factor β3(TGFβ3)-loaded chitosan microspheres(CMs) was developed. The formulation was optimized by multiple tests of self-healing, in-bottle inversion, SEM, rheological, swelling rate and in vitro degradation. In vitro tubule formation assays, cell migration assays, and osteogenic differentiation assays confirmed the ability of DFH to promote blood vessels, recruit stem cells, and promote osteogenic differentiation. The optimum DFH formula is 0.05 ml 4ArmPEG-DF(20%) added to 1 ml CsGlu(2%) containing bFGF(80 ng) and TGFβ3-microspheres(5 mg). The results of in vitro release studied by Elisa kit, indicated an 95% release of b FGF in7 d and long-term sustained release of TGFβ3. For alveolar defects rat models, the expression levels of CD29 and CD45, the bone volume fraction, trabecular number, and trabecular thickness of new bone monitored by Micro-CT in DFH treatment groups were significantly higher than others(*P < 0.05, vs Model). HE and Masson staining show the same results.In conclusion, DFH is a design of bionic alveolar remodelling microenvironment, that is in early time microvessels formed by b FGF provide nutritious to recruited endogenous stem cells, then TGFβ3 slowly released speed up the process of new bones formation to common facilitate rat alveolar defect repair. The DFH with higher regenerative efficiency dovetails nicely with great demand due to the requirement of complicated biological processes.

Climate warming over 1961–2019 and impacts on permafrost zonation in Northeast China

In boreal forest ecosystems, permafrost and forest types are mutually interdependent;permafrost degradation impacts forest ecosystem structure and functions. The Xing’an permafrost in Northeast China is on the southern margin of the Eastern Asia latitudinal permafrost body. Under a warming climate, permafrost undergoes rapid and extensive degradation. In this study, the frost-number (Fn) model based on air temperatures and ground surface temperatures was used to predict the distribution of the Xing’an permafrost, and, temporal and spatial changes in air and ground-surface temperatures from 1961 to 2019 are analyzed. The results show that Northeast China has experienced a rapid and substantial climate warming over the past 60 years. The rises in mean annual air and mean annual ground-surface temperatures were higher in permafrost zones than those in the seasonal frost zone. The frost numbers of air and ground-surface temperatures were calculated for determining the southern limit of latitudinal permafrost and for permafrost zonation. The southern limits of discontinuous permafrost, sporadic permafrost, and latitudinal permafrost moved northward significantly. According to the air-temperature frost-number criteria for permafrost zoning, compared with that in the 1960s, the extent of Xing’an permafrost in Northeast China had decreased by 40.6% by the 2010s. With an average rate of increase in mean annual air temperatures at 0.03 ℃ a^(−1), the extent of permafrost in Northeast China will decrease to 26.42 × 10^(4) by 2020, 14.69 × 10^(4) by 2040 and to 11.24 × 10^(4) km^(2) by 2050. According to the ground-surface temperature frost-number criteria, the southern limit of latitudinal permafrost was at the 0.463. From the 1960s to the 2010s, the extent of latitudinal permafrost declined significantly. Due to the nature of the ecosystem-protected Xing’an-Baikal permafrost, management and protection (e.g., more prudent and effective forest fire management and proper logging of forests) of the Xing’an permafrost eco-environment should be strengthened.

Instability of cylinder wake under open-loop active control

Instability of a wake controlled by a streamwise Lorentz force is investigated through a Floquet stability analysis. The streamwise Lorentz force, which is a two-dimensional control input created by an electromagnetic actuator located on the cylinder surface,adjusts the base flow to affect the three-dimensional wake instability and achieve wake stabilization and transition delay. The instability mode at a Reynolds number Re = 300 can be transformed from B to A with N = 1.0, where N is an interaction number representing the strength of the Lorentz force relative to the inertial force in the fluid. The wake flow is Floquet stable when N increases to 1.3. The spanwise perturbation wavelengths are 3.926 D and 0.822 D in the modes A and B, respectively, where D is the cylinder diameter. In addition, the oscillating amplitudes of drag and lift are reduced with the increase in the interaction number. Particle tracing is used to explore the essential physical mechanism for mode transformation. The path lines show that suppression of flow separation hinders the fluid deformation and rotation, leading to the decrease in elliptic and hyperbolic instability regions, which is the material cause of mode transformation.All of the results indicate that wake stabilization and transition delay can be achieved under open-loop active control via the streamwise Lorentz force.

Improving the protective effects of a FGF for peripheral nerve injury repair using sulfated chitooligosaccharides

Injury to the peripheral nerves can result in temporary or life-long neuronal dysfunction and subsequent economic or social disability. Acidic fibroblast growth factor(a FGF) promotes the growth and survival of neurons and is a possible treatment for peripheral nerve injury. Yet,the actual therapeutic utility of a FGF is limited by its short half-life and instability in vivo. In the present study,we prepared sulfated chitooligosaccharides(SCOS),which have heparinlike properties,to improve the bioactivity of a FGF. We investigated the protective effects of SCOS with or without a FGF on RSC96 cells exposed to Na2 S2 O4 hypoxia/reoxygenation injury. Cell viability was measured by MTT assay and cytotoxicity induced by Na2 S2 O4 was assessed by lactate dehydrogenase(LDH) release into the culture medium. Pretreatment with a FGF and SCOS dramatically decreased LDH release after injury compared to pretreatment with a FGF or SCOS alone. We subsequently prepared an a FGF/SCOS thermo-sensitive hydrogel with poloxamer and examined its effects in vivo. Paw withdrawal thresholds and thermal withdrawal latencies were measured in rats with sciatic nerve injury. Local injection of the a FGF/SCOS hydrogels(a FGF: 40,80 μg/kg) increased the efficiency of sciatic nerve repair compared to a FGF(80 μg/kg) hydrogel alone. Especially a FGF/SCOS thermo-sensitive hydrogel decreased paw withdrawal thresholds from 117.75 ± 8.38(g,4 d) to 65.74 ± 3.39(g,10 d),but a FGF alone group were 140.58 ± 27.54(g,4 d) to 89.12 ± 5.60(g,10 d)(a FGF dose was 80 μg/kg,P < 0.05,n = 8). The thermal withdrawal latencies decreased from 11.61 ± 2.26(s,4 d) to 2.37 ±0.67(s,10 d). However,a FGF alone group were from 17.69 ± 1.47(s,4 d) to4.65 ± 1.73(s,10 d)(P < 0.05,n = 8). Furthermore,the a FGF/SCOS hydrogels also exhibited good biocompatibility in mice. In summary,SCOS improved the protective effects of a FGF in RSC96 cells injured with Na2S2O4 and increased the efficiency of nerve repair and recovery of function in rats with sciatic nerve injury. These findings pave an avenue for the development of novel prophylactic and therapeutic strategies for peripheral nerve injury.

Effects of daily nitrogen and phosphorus input on planktonic community metabolism in a semi-enclosed bay by mesocosm experiment

Planktonic metabolism plays an important role in affecting the energy transportation and carbon cycle of the marine ecosystem.However,its regulation mechanism remains unclear under the continuously exogenous nutrient inputs in nearshore waters.In this study,a mesocosm experiment was conducted in a semi-enclosed bay,the Daya Bay,to explore the responses of plankton metabolic balance and community structure to a concentration gradient of daily nitrogen and phosphorus inputs.The results showed that nutrient enrichments promoted phytoplankton biomass,total primary production,and community respiration,and the promoting effect enhanced alongwith the increase of nutrient concentration.However,the net community production fluctuated more violently between autotrophic and heterotrophic with the increase of nutrient inputs and tended to be more heterotrophic from the 5 th day to the 10 th day of the experiment.In addition,the daily flux of nitrogen and phosphorus,2μmol/(L·d)and 0.066μmol/(L·d),respectively,could be regarded as a potential threshold for ecosystem stability and health,since most of the ecological characteristics related to plankton structure and function have undergone significant changes when the nutrient level is higher than that.In the nearshore enclosed or semi-enclosed waters,nutrient from continuous terrigenous input is likely to be concentrated and exceed this level,indicating the ecological risks due to the metabolic unbalance and the deterioration of plankton community structure.

Amplification mechanism of perturbation energy in controlled backward-facing step flow

A body force resembling the streamwise Lorentz force which decays exponentially in the wall-normalwise direction is applied in the primary and secondary separation bubbles to modify the base flow and thereby adjust the amplification rate of the perturbation energy.The amplification mechanisms are investigated numerically via analyzing the characteristics of the terms in the Reynolds-Orr equation which describes the growth rate of the perturbation energy.The results demonstrate that the main convective term always promotes the increase in the growth rate while the viscous terms usually play the reverse role.The contours of the product of the wall-normalwise and streamwise perturbation velocities distribute on both sides of the isoline,which represents the zero wall-normalwise gradient of the streamwise velocity in the base flow,due to the Kelvin-Helmholtz(KH)instability.For the case without control,the isoline downstream the reattachment point of the primary separation bubble is closer to the lower wall,and thus the viscous term near the lower wall might suppress the amplification rate.For the case in which the body force only acts on the secondary separation bubble,the secondary separation bubble is removed,and the magnitude of the negative wall-normalwise gradient of the base flow streamwise velocity decreases along the streamwise direction,and thus the growth rate of the perturbation energy is smaller than that for the case without control.For the case where the body force acts on both the separation bubbles,the secondary separation bubble is removed,the isoline stays in the central part of the channel,and thereby the viscous term has less effects on the amplification rate of which the peak value could be the maximum one for some control number.

Active control of noise amplification in the flow over a square leading-edge flat plate utilizing DBD plasma actuator

Perturbation is generally considered as the flow noise,and its energy can gain transient growth in the separation bubble.The amplified perturbations may cause unstable Kelvin–Helmohltz vortices which induce the three-dimensional transition.Active control of noise amplification via dielectric barrier discharge plasma actuator in the flow over a square leading-edge flat plate is numerically studied.The actuator is installed near the plate leading-edge where the separation bubble is formed.The maximum energy amplification of perturbations is positively correlated with the separation bubble scale which decreases with the increasing control parameters.As the magnitude of noise amplification is reduced,the laminar-turbulent transition is successfully suppressed.

Creating a bionic scaffold via light-curing liquid crystal ink to reveal the role of osteoid-like microenvironment in osteogenesis

Osteoid plays a crucial role in directing cell behavior and osteogenesis through its unique characteristics,including viscoelasticity and liquid crystal(LC)state.Thus,integrating osteoid-like features into 3D printing scaffolds proves to be a promising approach for personalized bone repair.Despite extensive research on viscoelasticity,the role of LC state in bone repair has been largely overlooked due to the scarcity of suitable LC materials.Moreover,the intricate interplay between LC state and viscoelasticity in osteogenesis remains poorly understood.Here,we developed innovative hydrogel scaffolds with osteoid-like LC state and viscoelasticity using digital light processing with a custom LC ink.By utilizing these LC scaffolds as 3D research models,we discovered that LC state mediates high protein clustering to expose accessible RGD motifs to trigger cell-protein interactions and osteogenic differentiation,while viscoelasticity operates via mechanotransduction pathways.Additionally,our investigation revealed a synergistic effect between LC state and viscoelasticity,amplifying cellprotein interactions and osteogenic mechanotransduction processes.Furthermore,the interesting mechanochromic response observed in the LC hydrogel scaffolds suggests their potential application in mechanosensing.Our findings shed light on the mechanisms and synergistic effects of LC state and viscoelasticity in osteoid on osteogenesis,offering valuable insights for the biomimetic design of bone repair scaffolds.

Architecture of Next-Generation E-Commerce Platform

E-commerce, driven by computer and internet technology, has experienced a significant growth in almost all fields during the past two decades. E-commerce has significantly changed the rules of business. Numerous research institutions and enterprises have made e-commerce more intelligent and convenient. Here, we propose a novel prototype of next-generation e-commerce platform with an architecture framework and theoretical models.Each subject, including the individual, enterprise, and administrative department, has his/her personalized portal to complete the subject information synchronization, supply release, demand satisfaction, and social contact. By using the personalized portal, instead of the traditional trading platform, the consumers and suppliers can complete intelligent matching transactions without intermediate traders. Moreover, the overall transaction process can be reviewed, making the transaction safer, more transparent, and more interesting. Moreover, the interconnected personalized portals solve the isolated islands of information, and the counterparts support parallel processing.Thus, this may improve the operating efficiency of the entire society.

Evolution of Specialization with Reachable Transaction Scope Based on a Simple and Symmetric Firm Resource Allocation Model

In the last decade, as an emerging transaction measure driven by computer and internet technology, e-commerce experienced explosive growth in many areas. It has greatly broken down the limitations of space and time to economic activities, thus changing the rules of business fundamentally. Significant work has been done to understand the laws of e-commerce from multiple dimensions, but the question of how e-commerce shapes firms＇ specialization and market structure from the perspective of spatial factors remains obscure. In this paper, we propose a simple and symmetric firm resource allocation model with a specialized-economy production function and market size constraint, to investigate how individual firms adjust resource allocation with reachable transaction scope expanded. It is shown that with the expansion of reachable transaction scope, individual firms discretely take back one unit resource from a low-investment direction and, instead, channel it to a ＂specialized direction＂. Meanwhile, at the macro level, an optimal division network evolves from a static self-sufficient stage to a diverse semi-specialized stage, and finally to a highly integrated completely specialized stage. Ergo, a Complex Adaptive System （CAS） based simulation framework is constructed. Designed simulation experiments are carried out and confirm to the analysis result of our proposed model.