Recent progresses in developing tough hydrogels promise the great potential of this class of soft and wet materials as biomaterials, soft robotics, smart actuators and sensors. [1][2][3][4][5][6][7][8][9][10] Any practical application of these hydrogels as smart materials, however, requires a combination of mechanical properties including stiffness, strength, toughness, and self-healing. For instance, along with the high strength and toughness, a cartilage substitute material requires a high stiffness to bear the load, while a blood vessel substitute material requires flexibility.Self-healing not only merits the long term durability of the load-bearing materials, but also gives possibility to reconstruct the material with desired shape from its microgels. While many hydrogels possess some of these requirements, it is a challenge to develop hydrogels satisfying all of these criteria. [2,[11][12][13] In this work, we report a new class of physical hydrogels that possess these multiple functions. These hydrogels are obtained from concentrated solution of oppositely charged polyelectrolytes. After dialysis of their small counter ions, the oppositely charged polyelectrolytes form polyion complexes of a wide strength distribution, which give dynamic crosslinking of an extremely wide life time scale. The strong, long life time bonds serve as permanent cross-linking, imparting elasticity, whereas the weak, short life

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Aircraft operators are faced with increasing requirements to extend the service life of air platforms beyond their designed life cycles, resulting in heavy maintenance and inspection burdens as well as economic pressure. Structural health monitoring (SHM) based on advanced sensor technology is potentially a cost-effective approach to meet operational requirements, and to reduce maintenance costs. Fiber optic sensor technology is being developed to provide existing and future aircrafts with SHM capability due to its unique superior characteristics. This review paper covers the aerospace SHM requirements and an overview of the fiber optic sensor technologies. In particular, fiber Bragg grating (FBG) sensor technology is evaluated as the most promising tool for load monitoring and damage detection, the two critical SHM aspects of air platforms. At last, recommendations on the implementation and integration of FBG sensors into an SHM system are provided.

BackgroundThe relationship between ambient air pollution exposure and mortality of cardiovascular and cerebrovascular diseases in human is controversial, and there is little information about how exposures to ambient air pollution contribution to the mortality of cardiovascular and cerebrovascular diseases among Chinese. The aim of the present study was to examine whether exposure to ambient-air pollution increases the risk for cardiovascular and cerebrovascular disease.Methodology/Principal FindingsWe conducted a retrospective cohort study among humans to examine the association between compound-air pollutants [particulate matter <10 µm in aerodynamic diameter (PM10), sulfur dioxide (SO2) and nitrogen dioxide (NO2)] and mortality in Shenyang, China, using 12 years of data (1998–2009). Also, stratified analysis by sex, age, education, and income was conducted for cardiovascular and cerebrovascular mortality. The results showed that an increase of 10 µg/m3 in a year average concentration of PM10 corresponds to 55% increase in the risk of a death cardiovascular disease (hazard ratio [HR], 1.55; 95% confidence interval [CI], 1.51 to 1.60) and 49% increase in cerebrovascular disease (HR, 1.49; 95% CI, 1.45 to 1.53), respectively. The corresponding figures of adjusted HR (95%CI) for a 10 µg/m3 increase in NO2 was 2.46 (2.31 to 2.63) for cardiovascular mortality and 2.44 (2.27 to 2.62) for cerebrovascular mortality, respectively. The effects of air pollution were more evident in female that in male, and nonsmokers and residents with BMI<18.5 were more vulnerable to outdoor air pollution.Conclusion/SignificanceLong-term exposure to ambient air pollution is associated with the death of cardiovascular and cerebrovascular diseases among Chinese populations.

Tough hydrogels with facile processability to reform into various shapes are required in many practical applications. In this work, we reported that a novel, tough, and self-healing physical hydrogel based on polyion complex (PIC) can be dissolved in 4 M NaCl solution to form a PIC solution. The PIC solution can be easily reprocessed into various shapes, such as thin films, sheets, fibers, and capsules, by using simple methods, such as casting and injection, while maintaining excellent mechanical properties comparable to, or even better than, the original hydrogel. The reprocessability and robust mechanical properties of PIC hydrogels are promising for practical applications in soft materials, especially in 3D/4D printing technology