Estimation of elastic modulus of confined polymer near interface by molecular dynamics simulation

Recently, confined polymers have drawn increasing attention due to their large deviations in various physical properties compared with bulk behavior. In particular, increase or decrease of the mechanical, electrical, and other physical properties have been reported via different experimental technologies. In this discussion, we present a new method to explore the local elastic modulus of a coarse-grained polymer near the interfacial region and free surface based on the deformation–fluctuation hybrid scheme in conjunction with semi-NVT ensemble. The developed method has been verified by comparing with several crystal structures, including Ar and Cu. Simulation results on the coarse-grained polymer prove that enhancements of elastic constants have been discovered near surface and interfacial regions, independent of the interaction between the polymer and its substrate. Therefore, this new algorithm is applicable for validating various experimental measurements and providing a means to investigate effects of confinement on stiffness-related behavior in polymers

Lock-in through passive connections

We consider a model of social coordination and network formation where agents decide on an action in a coordination game and on whom to establish costly links to. We study the role of passive connections; these are connections to a given agent that are supported by other agents. Such passive connections may inhibit agents from switching actions and links, as this may result in a loss of payoff received through them. When agents are constrained in the number of links they may support, this endogenously arising form of lock-in leads to mixed profiles, where different agents choose different actions, being included in the set of Nash equilibria. Depending on the precise parameters of the model, risk- dominant, payoff- dominant, or mixed profiles are stochastically stable. Thus, agents’ welfare may be lower as compared to the case where payoff is only received through active links. The network formed by agents plays a crucial role for the propagation of actions, it allows for a contagious spread of risk dominant actions and evolves as agents change their links and actions

Study on the Bacteriostatic Effect of Baitouweng on Pseudomonas Aeruginosa Infection of Wounds in Rats

Objective: To analyze the bacteriostatic effect of Baitouweng on Pseudomonas aeruginosa infection of wounds in rats. Methods: Forty Wistar rats were enrolled in the study, among which excisions were made on 30 rats on their upper layer of dorsal skin with an area of 1 cm x 1 cm, the other 10 rats as the control group of sterile wound. Prepared Pseudomonas aeruginosa was applied on the wounds of rats to create infection models. Forty rats were divided into three groups (control group, mafenide group and Baitouweng group) according to different infection methods, and were treated with normal saline, 100g/L mafenide, and 1g/L Baitouweng respectively after 3 hours of injury. The changes in the number of white blood cells in both the wound surface and body of the three groups were observed within one to four days after injury. After that, the changes on the number of both white blood cells and body weight were continuously observed. The survival of the rats in each group was observed on the 14th day after injury. Results: From the observation after injury, compared with the other two groups, rats in control group had more exudation and moist wounds, and the activities of rats decreased while the death rate increased. On the 3rd day after injury, the number of white blood cells in each group decreased, and the number of Pseudomonas aeruginosa in the control group was significantly higher than that in the other two groups (P < 0.01). The rats in the sterile wound control group did not die and continued to gain weight. After 14 days, the survival number of rats in control group was significantly less than that in mafenide group and Baitouweng group (P<0.05). Conclusion: Baitouweng has obvious bacteriostatic and virus-killing effects on Pseudomonas aeruginosa infection of wounds in Wistar rats, reducing mortality rate effectively, and has practical value as well as development and application prospects

A Clinical Observation and Study on Prunella Vulgaris Decoction in Promoting the Repair of Chronic Infective Refractory Wounds

Objective: To further study the clinical efficacy of prunella vulgaris decoction in promoting the repair of chronic infective refractory wounds, and analyze and evaluate the feasibility of this treatment. Methods: A total of 80 patients with chronic infective refractory wounds were screened out from a hospital from March 2020 to March 2021. The random sampling method was used to divide the patients into the experimental group and reference group. The experimental group was treated with prunella vulgaris decoction while the reference group was treated with routine wound dressing change. Wound repair rate, bacterial negative conversion rate, healing time and clinical comprehensive efficacy in the two groups were used as evaluation indexes in this study. Results: After different treatment, the conditions of the patients in the two groups were statistically analyzed. It was found that the wound repair rate, bacterial negative conversion rate and total effective rate of the experimental group were much higher than that of the reference group. In addition, the wound healing time in the experimental group was also significantly shortened compared with that of the reference group. Conclusion: Prunella vulgaris decoction bears obvious anti-inflammatory and anti-bacterial effects and can accelerate the speed of wound repair, which has great practical value in clinic treatment and prosperous prospect in future development and application

Roles of PI3K and JAK pathways in viability of retinal ganglion cells after acute elevation of intraocular pressure in rats with different autoimmune backgrounds

<p>Abstract</p> <p>Background</p> <p>We recently showed that whereas inhibition of PI3K/akt or JAK/STAT pathway promoted retinal ganglion cell (RGC) survival after optic nerve (ON) injury in Fischer 344 (F344) rats, the same inhibition resulted in aggravated RGC loss after acute intraocular pressure (IOP) elevation in Sprague Dawley (SPD) rats. In addition, the responses of macrophages to ON injury and acute IOP elevation were different between F344 and Lewis rats, i.e., different autoimmune profiles. Using an acute IOP elevation paradigm in this study, we investigated 1) whether autoimmune background influences PI3K/akt and JAK/STAT functions by examining the effect of PI3K/akt and JAK/STAT pathway inhibition on RGC survival in F344 and Lewis rats, and 2) whether differential actions of macrophages occur in PI3K/akt and JAK/STAT pathways-dependent modulation of RGC survival. IOP elevation was performed at 110 mmHg for 2 hours. PI3K/akt and JAK/STAT pathway inhibitors were applied intravitreally to block their respective pathway signaling transduction. Because macrophage invasion was seen in the eye after the pathway inhibition, to examine the role of these pathways independent of macrophages, macrophages in the retina were removed by intravitreal application of clodronate liposomes. Viable RGCs were retrogradely labelled by FluoroGold 40 hours before animal sacrifice.</p> <p>Results</p> <p>Similar to what was previously observed, significantly more RGCs were lost in Lewis than F344 rats 3 weeks after acute IOP elevation. As in SPD rats, inhibition of the PI3K/akt or JAK/STAT pathway increased the loss of RGCs in both F344 and Lewis rats. Removal of macrophages in the eye by clodronate liposomes reduced RGC loss due to pathway inhibition in both strains.</p> <p>Conclusion</p> <p>This study demonstrates that following acute IOP elevation 1) PI3K/akt and JAK/STAT pathways mediate RGC survival in both F344 and Lewis rats, 2) autoimmune responses do not influence the functions of these two pathways, and 3) PI3K/akt and JAK/STAT pathway inhibition-dependent activation of macrophages is detrimental to RGCs.</p

Miniaturized metachronal magnetic artificial cilia

Biological cilia, hairlike organelles on cell surfaces, often exhibit collective wavelike motion known as metachrony, which helps generating fluid flow. Inspired by nature, researchers have developed artificial cilia as microfluidic actuators, exploring several methods to mimic the metachrony. However, reported methods are difficult to miniaturize because they require either control of individual cilia properties or the generation of a complex external magnetic field. We introduce a concept that generates metachronal motion of magnetic artificial cilia (MAC), even though the MAC are all identical, and the applied external magnetic field is uniform. This is achieved by integrating a paramagnetic substructure in the substrate underneath the MAC. Uniquely, we can create both symplectic and antiplectic metachrony by changing the relative positions of MAC and substructure. We demonstrate the flow generation of the two metachronal motions in both high and low Reynolds number conditions. Our research marks a significant milestone by breaking the size limitation barrier in metachronal artificial cilia. This achievement not only showcases the potential of nature-inspired engineering but also opens up a host of exciting opportunities for designing and optimizing microsystems with enhanced fluid manipulation capabilities

Filled Colloidal Gel Rheology: Strengthening, Softening, and Tuneability

Filler-induced strengthening is ubiquitous in material science and is particularly well-established in polymeric nanocomposites. Despite having similar constituents, colloidal gels with solid filling exhibit distinct rheology, which is poorly understood. We show using experiments and simulations that filling monotonically enhances the yield stress of colloidal gels, while the elastic modulus first increases before decreasing. The latter effect results from a disturbed gel matrix at dense filling, evidenced by a growing inter-phase stress. This structural frustration is, however, not detrimental to yielding resistance. Instead, fillers offer additional mechanical support to the gel backbone via percolating force chains, at the same time decreasing the yield strain. We develop a mechanistic picture of this phenomenology that leads us to a novel `filler-removal protocol,' making possible individual control over the strength and brittleness of a composite gel