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无针注射器

“无针注射器”就是在注射药物时不借助针头,应用高压射流原理,使药液形成较细的液体流,瞬间穿透皮肤到达皮下的一种注射装置.

图甲所示是某种弹簧机械式无针注射器,使用时通过注射器内的弹簧产生强大的动力,快速推动内部的活塞,推动注射器前端瓶内的药液,使其通过瓶前端的微孔,以“液体针”的形式瞬间穿过表皮细胞,渗透入皮下组织,完成注射.

如图乙所示是另一种电动式无针注射器.其内部有磁体和金属线圈,线圈与存放药物的瓶内活塞相连.通电时,电流的磁场与永磁体的磁场相互作用,产生强大助推力,推动活塞前进,在高压下,以接近空气中声音的传播速度完成注射.

科研工作者还设计了其他类型的无针注射器.无针注射技术可以称为“医用注射技术的一次革命”,它能消除被注射者对针头的恐惧,减缓疼痛,并且环保无污染.目前,我国已经成为国际上为数不多的可以生产无针注射器的国家.

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    Skateboarding is an action sport which includes riding and performing tricks using a skateboard, as well as an activity for fun, an art form, an entertainment industry job, and a method of transportation. In 2016, it was announced that skateboarding will be represented at the 2020 Summer Olympics in Tokyo, Japan.

    There are various theories about the origins of Skateboarding, but it is generally held that the sport began in the 1940s on the west coast of the USA when metal wheels were attached to a narrow wooden board. In the 1950s, plastic replaced metal as the material of choice for the wheels, and the first "Roller Surfboard" become commercially available, which in turn developed into the skateboard that we know today. The sport was a big hit with the younger generation and grew in global popularity in the 1980s and 1990s. Since the late 1990s, skateboarding has become an important part of street culture.

    However, skateboarding has raised heated discussions in areas where the activity, although legal (合法的), has damaged stone works, steps, benches, and parks. Certain cities oppose the building of skate parks in their neighborhoods, for fear of increased crime (犯罪) and drugs in the area. The disagreement between the old image of skateboarding and a newer one is quite obvious: magazines such as Thrasher describe skateboarding as dirty, and still firmly tied to punk (朋克), while other publications, Transworld Skateboarding as an example, paint a more different and controlled picture of skateboarding. As more professional skaters use hip hop, or hard rock music in their videos, many urban youths, hip-hop fans and hard rock fans are also drawn to skateboarding, weakening the sport's punk image. Besides, group spirit influences the members of this community. In presentations of skateboarding, the evidence of crime is absent, and no attempt is made to tie extreme sports to any kind of illegal activity.

    The good news is that efforts have been made to improve recognition of the cultural heritage as well as positive effects of skateboarding in cities. By raising £790,000, the Long Live Southbank initiative managed to stop the destruction of a forty years old spot in London due to urban planning, a rescuing operation whose effect extends beyond skateboarding. The presence of skateboarders on this public space keeps the area under nearly constant watch and drives homeless people away, increasing the feeling of safety in the area. The activity attracts artists such as photographers and film makers, as well as a significant number of tourists, which in turn drives economic activity in the neighborhood.