问题 不定项选择

受东日本大地震影响,福岛核电站损毁严重,泄漏出大量的放射性物质,其中碘-131的危害颇受人们关注。下列关于碘-131的表述中,不正确的是()。

A.有医疗作用,可用于甲状腺功能检查及甲状腺疾病治疗

B.放射性强,碘-131带有强能量射线,可以导致人体DNA发生断裂,并产生一系列的细胞后续反应

C.存在时间久,碘-131半衰期长达8年

D.传播远,碘-131可附着在空气中的尘埃上,向远处扩散

答案

参考答案:C

解析:

碘-131是碘元素的一种放射性同位素,为人工放射性核素(核裂变产物),符号为I-131,半衰期为8.3天。碘-131发射的β射线可杀伤一部分甲状腺细胞,使甲状腺缩小,导致甲状腺合成的甲状腺激素减少,使甲亢表现消失。碘-131带有看不见摸不着的强能量射线,这些射线可以穿过人体组织,穿透过程中遇到阻碍就会与阻碍物质之间形成碰撞并且释放能量。高能量对被碰物质会造成伤害,对人体细胞而言,最直接的伤害就是导致人体的DNA发生断裂,随后产生一系列的后续反应,如细胞表达异常,细胞变性或者坏死,或长时间细胞异化后形成恶性肿瘤。释放出来的碘-131以气溶胶形式存在,可以在大气中漂浮并随大气到处“扩散”。

单项选择题 A1/A2型题
单项选择题

Studies from 10 nations reveal that the rates of depression among women are twice as high as they are among men. Do women have a biological bent for depression, or are social double standards the major cause

Mental health workers have long noticed among the clinically depressed women take up a bigger proportion. Until recently, though, it was unclear whether more women than men were ill or, instead, whether more women sought help. In fact, a mounting collection of studies has confirmed that major depression is twice as common among women as it is among men. "This is one of the most consistent findings we have ever had," says Myrna M. Weissman of Columbia University.

Scientists searching for explanations are challenged by the fact that a variety of cues prompt depression in different people. Sorting out which factors might have a greater influence on women has not proved easy. Both sexes stand an equal chance of inheriting major depression, so genes are most likely not to blame. Yet hormones and sleep cycles--which differ dramatically between the sexescan alter mood. Also, many workers have proposed that social discrimination might put women under high levels of stress.

In 1990 an international group examines mood disorders. In the 10 nations reviewed so far, the team has found that among generations reaching maturity after 1945, depression seems to be on the rise and occurs at a younger age. Although overall incidence varies regionally, "everywhere the rates of depression among women are about twice as high as they are among men," Weissman says.

In contrast, lifetime rates for manic-depressive illness do not differ according to sex or culture. Mark S. George and his colleagues at the National Institute of Mental Health (NIMH) recently studied which regions of the brain have greater blood flow during periods of depression. George found that "the brain activity of the men and women of depression looked very different. " He has since compared feelings of anger, anxiety and happiness, finding no such big a difference.

Because one in five American women has a history of depression, especially as they often pursue therapy from other sources, sometimes on top of an anti-depressant clinic. Says Leibenluft: "It is remarkable how little work has been done on this subject.

The author quotes Leibenluft’s comment in the last paragraph to()

A. summarize the main idea of the passage

B. recommend an alternative perspective to look at the issue of depression

C. express the author’s pity about the slow improvement on the cure of depression

D. praise the great efforts made by researchers on the subject of depression