Rotavirus is the most common cause of acute watery diarrhea in young Korean children. Rotavirus vaccine will soon be available, and information is urgently required about the serotype distribution of recent epidemics and clinical characteristics of rotavirus infection in Korean children before the implementation of a vaccination program against rotavirus. We reviewed published studies of the past 20 years, carried out on Korean children with rotavirus gastroenteritis. Rotavirus was estimated to be responsible for 46% of 4668 hospitalized Korean children with acute gastroenteritis. Rotavirus gastroenteritis was most prevalent among children aged 6-24 months, which accounted for 84% of all cases. Asymptomatic rotavirus infection was common. Rotavirus was one of the most commonly identified enteric pathogens in nosocomial diarrhea. Vomiting, respiratory symptoms and fever were prominent symptoms in rotavirus gastroenteritis. Transient elevation of liver enzymes, pulmonic infiltration and rarely afebrile convulsion were also observed. The epidemic peak, which occurred in November of the last 15 years, has been moving toward late winter and early spring in recent years. No apparent cause has been found to explain this alteration of peak seasonality. All serotyping studies in Korea for the past 10 years until 1997 revealed that G1 was most prevalent (45-81%). Interestingly, the predominant G serotype of the recent outbreaks in 1998 and 1999 was not G1 but G4. Approximately 95% of rotavirus isolates in recent outbreaks belonged to serotype G1, 2, 3 or 4.

Abstract2D metamaterials have immense potential in acoustics, optics, and electromagnetic applications due to their unique properties and ability to conform to curved substrates. Active metamaterials have attracted significant research attention because of their on‐demand tunable properties and performances through shape reconfigurations. 2D active metamaterials often achieve active properties through internal structural deformations, which lead to changes in overall dimensions. This demands corresponding alterations of the conforming substrate, or the metamaterial fails to provide complete area coverage, which can be a significant limitation for their practical applications. To date, achieving area‐preserving active 2D metamaterials with distinct shape reconfigurations remains a prominent challenge. In this paper, magneto‐mechanical bilayer metamaterials are presented that demonstrate area density tunability with area‐preserving capability. The bilayer metamaterials consist of two arrays of magnetic soft materials with distinct magnetization distributions. Under a magnetic field, each layer behaves differently, which allows the metamaterial to reconfigure its shape into multiple modes and to significantly tune its area density without changing its overall dimensions. The area‐preserving multimodal shape reconfigurations are further exploited as active acoustic wave regulators to tune bandgaps and wave propagations. The bilayer approach thus provides a new concept for the design of area‐preserving active metamaterials for broader applications.

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