Bicyclo[2.2.0]hexene: A Multicyclic Mechanophore with Reactivity Diversified by External Forces.

Polymer mechanochemistry has been established as an enabling tool in accessing chemical reactivity and reaction pathways that are distinctive from their thermal counterparts. However, eliciting diversified reaction pathways by activating different constituent chemical bonds from the same mechanophore structure remains challenging. Here, we report the design of a bicyclo[2.2.0]hexene (BCH) mechanophore to leverage its structural simplicity and relatively low molecular symmetry to demonstrate this idea of multimodal activation. Upon changing the attachment points of pendant polymer chains, three different C-C bonds in bicyclo[2.2.0]hexene are specifically activated via externally applied force by sonication. Experimental characterization confirms that in different scenarios of polymer attachment, the regioisomers of BCH undergo different activation reactions, entailing retro-[2+2] cycloreversion, 1,3-allylic migration, and retro-4π ring-opening reactions, respectively. Control experiments with small-molecule analogues reveal that the observed diversified reactivity of BCH regioisomers is possible only with mechanical force. Theoretical studies further elucidate that the differences in the positions of substitution between regioisomers have a minimal impact on the potential energy surface of the parent BCH scaffold. The mechanochemical selectivity between different C-C bonds in each constitutional isomer is a result of selective and effective coupling of force to the aligned C-C bond in each case.

Effect of Particle Size and Hydrophobicity on Bubble-Particle Collision Detachment at the Slurry-Foam Phase Interface.

The slurry phase, foam phase, and slurry-foam phase interfaces are the typical locations for bubble-particle detachment, and significant advancements have been achieved in the detachment theory of the slurry phase and foam phase. However, the microscopic detachment mechanism of particles at the slurry-foam phase interface is still unclear. Specifically, there is still debate concerning the collision detachment mechanism of bubble-particle aggregates. Thus, this work investigated the effects of particle size and hydrophobicity on bubble-particle collision detachment. First, a tensiometer detected the detachment force between particles and bubbles. Next, using a high-speed dynamic camera, the collision detachment probability and detachment behavior of bubble-particle aggregates at the interface (solid surface) were statistically recorded and captured. Last, MATLAB software was used to analyze the trajectory and velocity of the particles and the velocity and projected area of the bubbles in the process of bubble-particle collision detachment. This allows for a deeper investigation of the mechanism underlying the detachment of particles of various sizes and hydrophobicity. It is discovered that as particle hydrophobicity increases, the probability of bubble-particle collision detachment reduces. This is because when particle hydrophobicity increases, so does the interaction force between particles and bubbles, improving the stability of the bubble-particle aggregates. Simultaneously, it is discovered that there are notable differences in the collision detachment mechanisms of various particle sizes. Due to their low gravity, the fine particles in the bubble-particle aggregate will slide down the bubble's surface when it collides with the solid surface. This differential velocity motion between the particle and the bubble plays a significant role in the fine particles' detachment. However, the gravity of the coarse particles is strong enough to squeeze the bubbles vertically, and bubble oscillation is an important reason for the detachment of the bubble-particle aggregates. The study's findings advance our understanding of the bubble-particle collision detachment mechanism and offer a theoretical direction for investigating collision detachment behavior at the real slurry-foam phase interface.

Impact of external carrier noise on the linewidth enhancement factor of a quantum dot distributed feedback laser.

This paper demonstrates that the linewidth enhancement factor of quantum dot lasers is influenced by the external carrier transport issued from different external current sources. A model combining the rate equation and semi-classical carrier noise is used to investigate the different mechanisms leading to the above phenomenon in the context of a quantum dot distributed feedback laser. Meanwhile, the linewidth enhancement factor extracted from the optical phase modulation method shows dramatic differences when the quantum dot laser is driven by different noise-level pumps. Furthermore, the influence of external carrier noise on the frequency noise in the vicinity of the laser's threshold current directly affects the magnitude of the linewidth enhancement factor. Simulations also investigate how the external carrier transport impacts the frequency noise and the spectral linewidth of the QD laser. Overall, we believe that these results are of paramount importance for the development of on-chip integrated ultra-low noise oscillators producing light at or below the shot-noise level.

The Roles of Gasdermin D in Coronavirus Infection and Evasion.

Pyroptosis is lytic, programmed cell death and plays a critical role against microbial invasion, functioning as an innate immune effector mechanism. The pore-forming protein gasdermin D (GSDMD), a member of gasdermin family proteins, is a primary effector of pyroptosis. The cleavage of inflammasome-associated inflammatory caspases activates GSDMD to liberate the N-terminal effector domain from the C-terminal inhibitory domain and form pores in the cellular plasma membrane. Emerging evidence shows that the pore-forming activity of GSDMD beyond pyroptosis and modifies non-lytic cytosolic protein secretion in living cells and innate immunity. While the essential roles of GSDMD in bacterial infection and cancer have been widely investigated, the importance of GSDMD in virus infection, including coronaviruses, remains elusive. Here, we review the current literature regarding the activation and functions of GSDMD during virus infections. Last, we further discuss the roles of GSDMD and the therapeutic potential of targeting this GSDMD pore-forming activity in coronavirus diseases.

An Escherichia coli carrier vaccine with surface-displayed protein MAP3061c elicits protective immunity against Mycobacterium paratuberculosis in mice.

Johne's disease, or paratuberculosis, is a chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). This disease occurs worldwide and results in considerable economic losses in the livestock industry. There are no effective treatments for Johne's disease, so there is an urgent need to develop an efficient, economical, and stable vaccine for MAP control. Here, a live Escherichia coli (E. coli) surface display vaccine harboring the MAP3061c gene was developed through an ice nucleation protein (INP) surface display system. The experimental data demonstrated that MAP3061c has strong immunogenicity and that the surface displayed vaccine can stimulate mice to produce high levels of antibodies. Both CD4+ and CD8+ T cell counts as well as several cytokines - including IFN-γ, IL-4, IL-10, IL-17A and IL-23 - were significantly increased in the display vaccine group. Post-vaccination challenge with MAP in mice resulted in improved fitness of the mice as demonstrated by a lack of weight loss. Pathological results revealed that the surface display vaccine could reduce the degree of pathological damage and slowed the course of disease. Taken together, our data suggests that the E. coli carrier vaccine with surface-displayed MAP3061c elicits protective immunity against MAP, providing new insights into the development of a MAP vaccine.

Statins significantly repress rotavirus replication through downregulation of cholesterol synthesis.

Rotavirus is the most common cause of severe diarrhea among infants and young children and is responsible for more than 200,000 pediatric deaths per year. There is currently no pharmacological treatment for rotavirus infection in clinical activity. Although cholesterol synthesis has been proven to play a key role in the infections of multiple viruses, little is known about the relationship between cholesterol biosynthesis and rotavirus replication. The models of rotavirus infected two cell lines and a human small intestinal organoid were used. We investigated the effects of cholesterol biosynthesis, including inhibition, enhancement, and their combinations on rotavirus replication on these models. The knockdown of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) was built by small hairpin RNAs in Caco2 cells. In all these models, inhibition of cholesterol synthesis by statins or HMGCR knockdown had a significant inhibitory effect on rotavirus replication. The result was further confirmed by the other inhibitors: 6-fluoromevalonate, Zaragozic acid A and U18666A, in the cholesterol biosynthesis pathway. Conversely, enhancement of cholesterol production increased rotavirus replication, suggesting that cholesterol homeostasis is relevant for rotavirus replication. The effects of all these compounds toward rotavirus were further confirmed with a clinical rotavirus isolate. We concluded that rotavirus replication is dependent on cholesterol biosynthesis. To be specific, inhibition of cholesterol synthesis can downregulate rotavirus replication; on the contrary, rotavirus replication is upregulated. Statin treatment is potentially an effective novel clinical anti-rotavirus strategy.

Alloyed Green-Emitting CdZnSeS/ZnS Quantum Dots with Dense Protective Layers for Stable Lighting and Display Applications.

Alloyed green-emitting CdZnSeS/ZnS quantum dots (QDs) demonstrate potential applications in solid-state lighting and displays owing to their various advantages, such as high color purity, light conversion efficiency, and color rendering index. However, their applications in white light-emitting diodes (WLEDs) are limited by their poor photostabilities on blue-emitting gallium nitride (GaN) LED chips. In this study, the effect of the specific surface area (SSA) in the coating layers on the photostabilities of QDs was investigated. SSA was adjusted by controlling the proportions of dense aluminum oxide (AlOX) layers and porous silica dioxide (SiO2) layers to fabricate QD protective layers via a catalyst-free sol-gel method. The results showed that the synthesized AlOX possessing the lowest SSA among the synthesis protective layers presented the best QD photostabilities on the LED chips. Moreover, they exhibited a 9.9-fold increase in the operational lifetime (T80) compared to that of pristine QDs. In addition, the QD-based WLED achieved an excellent display performance with a wide color gamut (115%) of the National Television System Committee (NTSC) color gamut standard. This approach offers a promising strategy for enhancing the QD photostabilities for applications in solid-state lighting and displays by coating the protective layers on the QD surface.

High-Performance Blue Perovskite Light-Emitting Diodes Enabled by Efficient Energy Transfer between Coupled Quasi-2D Perovskite Layers.

While there has been extensive investigation into modulating quasi-2D perovskite compositions in light-emitting diodes (LEDs) for promoting their electroluminescence, very few reports have studied approaches involving enhancement of the energy transfer between quasi-2D perovskite layers of the film, which plays very important role for achieving high-performance perovskite LEDs (PeLEDs). In this work, a bifunctional ligand of 4-(2-aminoethyl)benzoic acid (ABA) cation is strategically introduced into the perovskite to diminish the weak van der Waals gap between individual perovskite layers for promoting coupled quasi-2D perovskite layers. In particular, the strengthened interaction between coupled quasi-2D perovskite layers favors an efficient energy transfer in the perovskite films. The introduced ABA can also simultaneously passivate the perovskite defects by reducing metallic Pb for less nonradiative recombination loss. Benefiting from the advanced properties of ABA incorporated perovskites, highly efficient blue PeLEDs with external quantum efficiency of 10.11% and a very long operational stability of 81.3 min, among the best performing blue quasi-2D PeLEDs, are achieved. Consequently, this work contributes an effective approach for high-performance and stable blue PeLEDs toward practical applications.

Factors influencing the working temperature of quantum dot light-emitting diodes.

Quantum dot light-emitting diodes (QLEDs) possess huge potential in display due to their outstanding optoelectronic performance; however, serve degradation during operation blocks their practical applications. High temperature is regarded as one of major factors causing degradation. Therefore, a systematical study on the working temperature of QLEDs is very essential and urgent for the development of high stable QLEDs. In this work, different influence factors such as the electro-optic conversion efficiency (EOCE), voltage, current density, active area, substrate size, substrate type and sample contact are discussed in detail on the working temperature of QLEDs. The research results show that the working temperature of general QLEDs under normal operation conditions is usually smaller than 75 °C when the ambient temperature is 25 °C. However, temperature of QLEDs working under extreme conditions, such as high power or small substrate size, will exceed 100 °C, resulting in irreversible damage to the devices. Moreover, some effective measures to reduce the working temperature are also proposed. The analysis and discussion of various influencing factors in this work will provide guidance for the design of stable QLEDs and help them work at a safer temperature.

Synergistic Adsorption Mechanism of Anionic and Cationic Surfactant Mixtures on Low-Rank Coal Flotation.

Mixed surfactants have a prominent synergistic effect and show advantages in many aspects. In this work, the effects of a mixture of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) on the flotation of low-rank coal were studied from the wetting rate, contact angle, surface tension, and zeta potential. Furthermore, the adsorption configuration of the mixed surfactant on the surface of oxygen-containing graphite was simulated at the molecular level by molecular dynamics simulation. The experimental results show that the combustible matter recovery of low-rank coal flotation is improved using the mixed surfactant, and the contact angle test and wetting rate test confirmed the synergistic effect of the mixed surfactant. In the mixed surfactant system, the addition of SDS with an opposite charge to DTAB can reduce the mutual repulsion between DTAB molecules and enhance the degree of DTAB alignment in solution, which was analyzed by surface tension and zeta potential tests. Meanwhile, the simulation results reveal the adsorption behavior of anionic and cationic surfactants on the surface of oxygen-containing graphite from the molecular level and also verify the experimental results. This investigation provides a good understanding of the interaction mechanism of mixed surfactants in low-rank coal flotation.

New Insights into the Role of Surface Nanobubbles in Bubble-Particle Detachment.

It is well recognized that an improved flotation recovery can be achieved by introducing nanobubbles to common flotation practice due to the increased capture efficiency between bubbles and particles. However, the specific role of nanobubbles in bubble-particle interactions (collision, attachment, and detachment) is not well understood. In the present study, we explore the role of surface nanobubbles in bubble-particle detachment. Surface nanobubbles were introduced via ethanol-water exchange and their presence was confirmed using laser scanning confocal microscopy (LSCM). The effect of surface nanobubbles on bubble-particle detachment behavior was then investigated using an oscillating bubble apparatus. Bubble-particle aggregate stability was evaluated using critical detachment amplitude. Further, bubble-particle detachment forces in the absence and presence of nanobubbles were measured directly using a micro-nano mechanical testing system. Using LSCM, numerous surface nanobubbles were observed on a glass surface after ethanol-water exchange, regardless of wettability. The number and lateral dimensions of generated nanobubbles on the hydrophilic surface were significantly smaller than that on the hydrophobic surface. Surface nanobubbles increased the stability of bubble-particle aggregates. Macroscopic air bubbles coalesce with the nanobubbles on the particle surface, increasing the pinning effect of the three-phase contact line and advancing contact angle. As a result, the capillary force between bubbles and particles increased in the presence of surface nanobubbles.

Printable CsPbBr3 perovskite quantum dot ink for coffee ring-free fluorescent microarrays using inkjet printing.

Printable perovskite quantum dot (QD) ink is very important for achieving high quality coffee ring-free fluorescent microarrays for different kinds of emerging perovskite optoelectronic applications using inkjet printing. In this work, we prepared a printable CsPbBr3 perovskite QD ink by mixing high-boiling point dodecane with low-boiling point toluene as a solvent. The evaporation rate, viscosity and surface tension of the ink were carefully optimized by tuning the volume ratio of these two solvents for forming appropriate Marangoni flow, so as to balance the capillary flow and eliminate the coffee ring effect further. Successfully, CsPbBr3 perovskite microarrays with uniform surface, low roughness and no coffee rings were achieved by inkjet printing the optimized perovskite QD ink on a PVK (poly-(9-vinylcarbazole)) layer. Furthermore, we patterned the CsPbBr3 perovskite QD ink, and the printed patterns were only visible under ultraviolet (UV) light, which can be applied in invisible anti-counterfeiting labels and encryption in the future.

Suppression of pyrimidine biosynthesis by targeting DHODH enzyme robustly inhibits rotavirus replication.

Rotavirus infection remains a great health burden worldwide especially in some developing countries. It causes severe dehydrating diarrhea in infants, young children, as well as immunocompromised and organ transplanted patients. Viral replication heavily relies on the host to supply nucleosides. Thus, host enzymes involved in nucleotide biosynthesis represent potential targets for antiviral development. Dihydroorotate dehydrogenase (DHODH) is the rate-limiting enzyme in the de novo biosynthesis pathway of pyrimidines. In this study, we demonstrated that two specific DHODH enzyme inhibitors, brequinar (BQR) and leflunomide (LFM) robustly inhibited rotavirus replication in conventional human intestinal Caco2 cell line as well as in human primary intestinal organoids. The antiviral effect is conserved in both laboratory strain SA11 and rotavirus strain 2011K isolated from clinical sample. Mechanistic study indicated that BQR and LFM exerted their anti-rotavirus effect through targeting DHODH to deplete pyrimidine nucleotide pool. Therefore, targeting pyrimidine biosynthesis represents a potential approach for developing antiviral strategies against rotavirus.

TNF-α exerts potent anti-rotavirus effects via the activation of classical NF-κB pathway.

Active virus-host interactions determine the outcome of pathogen invasions. It has been shown that in isolated dendritic cells (DCs), rotavirus can induce the expression of tumor necrosis factor α (TNF-α), a vital cytokine mediating host immune responses. However, the role of TNF-α in rotavirus infection is unknown. In this study, we demonstrated that TNF-α has potent anti-rotavirus effects, independent of type I interferon production. Blocking of TNF-α by infliximab, a clinically available TNFα antibody, totally abrogated this effect. Mechanistic studies revealed that the anti-rotavirus effect of TNF-α was achieved by NFκB-regulated genes via the activation of classical nuclear factor κB (NF-κB) signaling. Our study reveals the pivotal role and the mechanism-of-actions of TNF-α in the host defense against rotavirus. Thus, this knowledge may contribute to the better understanding of the complexity of rotavirus-host interactions.

Basal interferon signaling and therapeutic use of interferons in controlling rotavirus infection in human intestinal cells and organoids.

Rotavirus (RV) primarily infects enterocytes and results in severe diarrhea, particularly in children. It is known that the host immune responses determine the outcome of viral infections. Following infections, interferons (IFNs) are produced as the first and the main anti-viral cytokines to combat the virus. Here we showed that RV predominantly induced type III IFNs (IFN-λ1), and to a less extent, type I IFNs (IFN-α and IFN-ß) in human intestinal cells. However, it did not produce detectable IFN proteins and thus, was not sufficient to inhibit RV replication. In contrast, we revealed the essential roles of the basal IFN signaling in limiting RV replication by silencing STAT1, STAT2 and IRF9 genes. In addition, exogenous IFN treatment demonstrated that RV replication was able to be inhibited by all types of IFNs, both in human intestinal Caco2 cell line and in primary intestinal organoids. In these models, IFNs significantly upregulated a panel of well-known anti-viral IFN-stimulated genes (ISGs). Importantly, inhibition of the JAK-STAT cascade abrogated ISG induction and the anti-RV effects of IFNs. Thus, our study shall contribute to better understanding of the complex RV-host interactions and provide rationale for therapeutic development of IFN-based treatment against RV infection.

Sign change of magnetoresistance in Gd-doped amorphous carbon granular films.

Gd/C granular films with 11% Gd were fabricated by facing-target magnetron sputtering at room temperature and then annealed at 300-650 °C for 1.5 h. A magnetoresistance of -82% was obtained in the Gd/C films annealed at 650 °C at 3 K under a magnetic field of 50 kOe. A sign change of the magnetoresistance from negative to positive and then back to negative was observed in all samples as the temperature decreases. Grain boundary scattering effects, wave-function-shrinkage, cotunneling and Gd-Gd interactions account for the mechanisms of the magnetoresistance effects in different temperature regions. The sign of the magnetoresistance also varies as the magnetic field increases. At the transition temperature of 25 K, the wave-function-shrinkage effect competes with cotunneling and Gd-Gd interactions at different magnetic fields. The competition between the wave-function-shrinkage effect and the grain boundary scattering effect is approximately at the transition temperature of 100 K. The temperature range of positive magnetoresistance expands and transition temperatures are changed as the annealing temperature increases. It is related to the expansion of the temperature region for the wave-function-shrinkage effect which occurs in the Mott variable range hopping conduction mechanism.