Materials both Tough and Soft Ping Gong, Jian
Science (American Association for the Advancement of Science),
04/2014, Letnik:
344, Številka:
6180
Journal Article
Recenzirano
Tough elastomers are created by adapting an approach previously used for hydrogels.
Also see Report by
Ducrot
et al.
Hydrogels and elastomers are soft materials that have similar network structures ...but very different affinities to water. Consisting mostly of water, hydrogels resemble biological soft tissues and have great potential for use in biomedical applications; they tend to be very brittle, like fragile jellies. Elastomers are formed of nonhydrated polymer networks and are widely used as load-dispersing and shock-absorbing materials. They are stretchable but break easily along a notch. On page 186 of this issue, Ducrot
et al.
(
1
) show that the toughness of elastomers can be improved substantially by combining two different network materials, an approach previously applied to hydrogels.
Underwater adhesives are in high demand in both commercial and industrial sectors. Compared with adhesives used in dry (air) environments, adhesives used for wet or submerged surfaces in aqueous ...environments have specific challenges in development and performance. In this review, focus is on adhesives demonstrating macroscopic adhesion to wet/underwater substrates. The current strategies are first introduced for different types of underwater adhesives, and then an overview is provided of the development and performance of underwater adhesives based on different mechanisms and strategies. Finally, the possible research directions and prospects of underwater adhesives are discussed.
Underwater adhesives are in high demand from medical to ocean technology. Key specific challenges are discussed to achieve underwater adhesion, and then an overview of strategies of the existing research and the performances of underwater adhesives achieved is presented. Finally, the possible solutions for the challenges, along with future research directions are discussed.
Although carbonates are the primary form of carbon subducted into the mantle, their fate during recycling is debated. Here we report the first coupled high‐precision Zn and Mo isotope data for ...Cenozoic intraplate basalts from western China. The exceptionally high δ66Zn values (+0.39 to +0.50‰) of these lavas require involvement of recycled carbonates in the mantle source. Variable δ98Mo compositions (−0.39 to +0.27‰) are positively correlated with Mo/Ce, best interpreted as mixing between isotopically light Mo from dehydrated oceanic crust and heavy Mo from recycled carbonates, which is also supported by positive coupling between δ66Zn and δ98Mo. Modeling reveals that involvement of ≤5% carbonate‐bearing oceanic crust fully resolves the observed δ66Zn–δ98Mo mantle heterogeneity probed by intracontinental basalts. Our study demonstrates that combined δ66Zn–δ98Mo data sets for mantle‐derived magmas can track recycled surficial carbonates in Earth's interior, providing a powerful geochemical tool for deep carbon science.
Plain Language Summary
Carbon is an element of life and studying its geological cycle is crucial for understanding Earth's evolution including formation of a life‐supporting atmosphere. Here we report the first combined high‐precision Zn and Mo isotope data for Cenozoic intraplate lavas from western China, showing that the basalts record ≤5% carbonate‐bearing oceanic crust components in their mantle source. Our results provide new evidence for surficial carbonates being delivered into the deep upper mantle, which adds to the debate about the deepest extent of the terrestrial carbon cycle.
Key Points
First combined zinc (Zn) and molybdenum (Mo) isotope data for mantle‐derived magmas to track the fate of subducted carbonates
Zn−Mo isotopic compositions of Cenozoic Tarim basalts suggest surficial carbonates being delivered into the deep upper mantle
We highlight the utility of combined Zn−Mo isotope data as a powerful tool in deep carbon science
SignificanceDynamic bonds have been found to enhance fracture toughness of hydrogels as sacrificial bonds, but the role of dynamic bonds to fatigue threshold of hydrogels is poorly understood because ...the wide dynamic range of viscoelastic response imposes a challenge on fatigue experiments. Here, by using polyampholyte hydrogels, we adopted a time-salt superposition principle to access a wide range of time scales that are otherwise difficult to access in fatigue tests. Relations between fatigue threshold and strain rate in elastic and viscoelastic regimes and the corresponding mechanism correlated to permanent/dynamic bonds were revealed. We believe that this work gives important insight into the design and development of fatigue-resistant soft materials composed of dynamic bonds.
Purpose
Macrophages play critical roles in inflammation and wound healing and can be divided into two subtypes: classically activated (M1) and alternatively activated (M2) macrophages. Macrophages ...also play important roles in regulating iron homeostasis, and intracellular iron accumulation induces M1‐type macrophage polarization which provides a potential approach to tumor immunotherapy through M2 tumor‐associated macrophage repolarization. However, the mechanisms underlying iron‐induced M1 polarization remain unclear.
Methods
Western blotting, qRT‐PCR, and flow cytometry were used to detect the polarization indexes in RAW 264.7 murine macrophages treated with iron, and Western bloting and qRT‐PCR were used to detect p21 expression. The compound 2,7‐dichlorofluorescein diacetate was used to measure reactive oxygen species (ROS) levels in macrophages after iron or N‐acetyl‐l‐cysteine (NAC) treatment. The p300/CREB‐binding protein (CBP) inhibitor C646 was used to inhibit p53 acetylation, and Western bloting, qRT‐PCR, and immunofluorescence were used to detect p53 expression and acetylation. BALB/c mice were subcutaneously injected with H22 hepatoma cells, and macrophage polarization status was investigated after tail intravenous injection of iron. Immunohistochemical staining was used to evaluate the protein expression of cluster of differentiation 86 (CD86) and EGF‐like module‐containing mucin‐like hormone receptor‐like 1 (F4/80) in the subcutaneous tumors.
Results
Iron overload induced M1 polarization by increasing ROS production and inducing p53 acetylation in RAW cells, and reduction in ROS levels by NAC repressed M1 polarization and p53 acetylation. Inhibition of acetyl‐p53 by a p300/CBP inhibitor prevented M1 polarization and inhibited p21 expression. These results showed that high ROS levels induced by iron overload polarized macrophages to the M1 subtype by enhancing p300/CBP acetyltransferase activity and promoting p53 acetylation.
Iron overload increases ROS production and enhances the activity of p300/CBP acetyltransferase, thus inducing p53 acetylation to polarize proinflammation macrophage phenotype.
Urea has been regarded as an important chemical compound in the food‐water‐energy nexus. However, the emission of urea from human activity, industrial manufacture, and agricultural fertilization into ...the environment has caused an ecological nitrogen imbalance. Besides addressing the environmental pollution, the applications of clean energy conversion from urea‐rich wastewater has strong potential for resource and energy recovery. Herein, we conducted a comprehensive overview of electrochemical urea oxidation reaction (UOR) for pollution control and energy harvesting. The present mechanisms and behaviors of UOR under different water matrices have been characterized and compared in detail. Additionally, the latest development of electrochemical UOR integrated into electrolyzers and fuel cells are presented. Finally, we discuss the prospects and challenges of UOR technologies, suggesting several directions for the electrochemical conversion of urea‐abundant wastewater in the near future.
Sustainable: Electrochemical urea conversion (UOR) has the potential to simultaneously realize a sustainable water‐energy nexus. Herein, a comprehensive summary of UOR development under different mediums is conducted from mechanism to devices, raising the existing challenges to be addressed in the future.
Whether ultra‐processed food consumption is associated with the risk of pancreatic cancer has not been determined. We performed a prospective study to fill this gap. A population‐based cohort of 98 ...265 American adults was identified from the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Ultra‐processed foods were defined by the NOVA classification. Cox regression was used to estimate hazard ratios (HRs) for pancreatic cancer incidence. Subgroup analysis was performed to identify the potential effect modifiers. During a mean follow‐up of 8.86 years, 387 pancreatic cancer cases occurred. High consumption of ultra‐processed foods was found to be associated with an increased risk of pancreatic cancer (fully adjusted HRquartile 4 vs 1:1.49; 95% confidence interval CI: 1.07‐2.07; Ptrend = .021) in a linear dose‐response manner (Pnonlinearity = .075). Subgroup analysis further found that the positive association of ultra‐processed food consumption with the risk of pancreatic cancer was more pronounced in subjects aged <65 years (HRquartile 4 vs 1:2.17; 95% CI: 1.14‐4.15) than in those aged ≥65 years (HRquartile 4 vs 1:1.32; 95% CI: 0.88‐1.94), though the interaction test failed to achieve the statistical significance (Pinteraction = .061). These findings suggest that reducing ultra‐processed food consumption may be beneficial in decreasing pancreatic cancer incidence.
What's new?
“Ultra‐processed” foods, industrially formulated products consisting of ingredients extracted from foods, but no intact foods, now make up as much as 58.5% of Americans' daily calorie intake. Think frozen meals, hot dogs and packaged snacks. Here, the authors investigate the relationship between ultra‐processed foods and pancreatic cancer in a cohort of 98 265 American adults. High consumption of ultra‐processed foods was associated with increased risk of pancreatic cancer, and the association was more pronounced for those under age 65.
The double-network (DN) structure is a state-of-the-art strategy used for toughening soft materials. The challenge for widespread applications, however, is the difficulty in synthesizing the two ...interpenetrating networks with contrasting architecture, i.e., one network is brittle and sparse and the other is stretchable and dense. Such structures are formed to toughen hydrogels via two-step sequential synthesis of a highly swellable polyelectrolyte network and a subsequent stretchable network in aqueous media; however, this approach is not directly applicable for fabricating tough DN elastomers from low-polar polymers. Herein, we propose a polyelectrolyte approach to fabricate tough solvent-free DN elastomers comprising a hybridized brittle polyelectrolyte network and a stretchable low-polar polyacrylic network. Because polyelectrolyte networks swell significantly in high-dielectric media, the contrasting DN structure can be fabricated using an organic cosolvent with an extremely high dielectric constant. By removing the solvent, we obtained polyelectrolyte–elastomeric polyacrylate DN elastomers, which exhibit a moderate elastic modulus (∼1 MPa), distinct yielding, high strength (∼5 MPa nominal stress), and large stretchability (∼2000% strain) accompanied by strain-hardening and high fracture toughness (∼104 J m–2). The volume ratio of the two networks is a key parameter governing mechanical performance. This approach broadens polymer choices for developing robust elastomers.
Electrostatic interaction is strong but usually diminishes in high ionic-strength environments. Biosystems can use this interaction through adjacent cationic-aromatic amino acids sequence of proteins ...even in a saline medium. Application of such specific sequence to the development of cationic polymer materials adhesive to negatively charged surfaces in saline environments is challenging due to the difficulty in controlling the copolymer sequences. Here, we discover that copolymers with adjacent cation-aromatic sequences can be synthesized through cation-π complex-aided free-radical polymerization. Sequence controlled hydrogels from diverse cation/aromatic monomers exhibit fast, strong but reversible adhesion to negatively charged surfaces in seawater. Aromatics on copolymers are found to enhance the electrostatic interactions of their adjacent cationic residues to the counter surfaces, even in a high ionic-strength medium that screens the electrostatic interaction for common polyelectrolytes. This work opens a pathway to develop adhesives using saline water.
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