问题 单项选择题 A1/A2型题

法洛四联症的心脏畸形中对患儿病理生理和临床表现最有影响的是()

A.房间隔缺损

B.室间隔缺损

C.肺动脉狭窄

D.主动脉骑跨

E.右心室肥厚

答案

参考答案:C

解析:导致法洛四联症一系列病理生理改变的主要因素是肺动脉狭窄的严重程度。

单项选择题 A3/A4型题
问答题

It is difficult for a man to imagine the rate at which water is consumed throughout the United Kingdom. A single industrial unit, for example, can use literally millions of gallons of water every day just for cooling purposes. This means that industry alone uses billions of gallons of water every year. The cost of this waste is significantly high.

71.It should be apparent, therefore, that a fully sealed cooling system would lose no water, consume no water, discharge no water and would not require the application of chemical treatment. Sealed water cooling systems are available and make it possible for a teacupful of water to do a job normally requiring millions of gallons of water.

Water Saver Systems is a company that has pioneered the principle of sealed industrial cooling in the UK and Europe. These sealed cooling systems, it is claimed, can actually provide payback within a matter of months because of the water and effluent cost savings and the removal of the need for a chemical treatment plant and the resultant chemical costs. In addition, it is possible to recover heat from a sealed system, allowing savings in boiler feed water and domestic hot water supplies. A further advantage is that grayish-materials build-up is prevented and rust minimized, so that the high efficiency of the sealed system is maintained and the service life in- creased. A significant merit of a sealed system, not yet fully appreciated, stems from the fact that industry can now be more mobile in terms of location. Traditionally, with some industries, a main consideration as regards a factory site would be the availability of a local high volume water supply for cooling purposes. 72. With a sealed system, it is claimed to be possible for a major user of cooling water to setup in the desert with only a small truck of water to give the sealed system its initial fill.

Sealed cooling systems also reduce water-related health risks. Chemical treatment does help to reduce such risks but for various reasons, chemicals have not yet provided total protection from disease. For example, Lehionnaires Disease which can be propagated via the evaporation taking place in cooling towers. Sealed systems do not emit contaminated vapour to atmosphere and this also means that thermal pollution does not occur.

73. Sealed industrial cooling systems were originally developed to offer efficient and cost-saving cooling alternatives to industry, giving considerable operational and financial advantages to the user. Fortunately, the development of the sealed cooling system also contributes significantly to the environment and health.

71.It should be apparent, therefore, that a fully sealed cooling system would lose no water, consume no water, discharge no water and would not require the application of chemical treatment. Sealed water cooling systems are available and make it possible for a teacupful of water to do a job normally requiring millions of gallons of water.