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（1）Life can be tough for immigrants in America.As a Romanian bank clerk in Atlanta puts it，to find a good job “you have to be like a wolf in the forest –able to smell out the best meat.”And if you can’t find work，don’t expect the taxpayer to bail you out.Unlike in some European countries，it is extremely hard for an able-bodied immigrant to live off the state.A law passed in 1996 explicitly bars most immigrants，even those with legal status，from receiving almost any federal benefits.
（2）That is one reason why America absorbs immigrants better than any other rich countries，according to a new study by the University of California.The researchers sought to measure the effect of immigration on the native-born in 20 rich countries，taking into account differences in skills between immigrants and natives，imperfect labor markets and the size of the welfare state in each country.
（3）Their results offer ammunition for fans of more open borders.In 19 out of 20 countries，the authors calculated that shutting the doors entirely to foreign workers would make the native-born worse off.Never mind what it would do to the immigrants themselves，who benefit far more than anyone else from being allowed to cross borders to find work.
（4）The study also suggests that most countries could handle more immigration than they currently allow.In America，a one-percentage point increase in the proportion of immigrants in the population made the native-born 0.05% better off.The opposite was true in some countries with generous or ill-designed welfare states，however.A one-point rise in immigration made the native-born slightly worse off in Austria，Belgium，Germany，Luxembourg，the Netherlands，Sweden and Switzerland.In Belgium，immigrants who lose jobs can receive almost two-thirds of their most recent wage in state benefits，which must make the hunt for a new job less urgent.
（5）None of these effects was large，but the study undermines the claim that immigrants steal jobs from native or drag down their wages.Many immigrants take jobs that Americans do not want，the study finds.This “smooths”the labor market and ultimately creates more jobs for locals.Native-owned grocery stores do better business because there are immigrants to pick the fruit they sell.Indian computer scientists help American software firms expand.A previous study found that because immigrants typically earn less than locals with similar skills，they boost corporate profits，prompting companies to grow and hire more locals.

研究發(fā)現(xiàn)，具有深海潛水本領(lǐng)的動物們，首先具有一個神奇的肺。即使是被壓扁變形收縮至原來體積的15%，也不會受到任何傷害，并且可以在短時間內(nèi)自行恢復(fù)，而人類的肺卻無法做到這一點。在分析海豹的肺組織時發(fā)現(xiàn)，因為它表面覆蓋著一層由特殊化學(xué)物質(zhì)構(gòu)成的活性劑，所以海豹的肺才如此堅韌有力，在輕松對付高壓的同時，還能自如地舒展恢復(fù)。
攝取和儲存氧氣的能力是決定生物能否長時間深潛的主要標志，與陸地動物的區(qū)別是。潛不動物在屏住呼吸時主要依賴儲存在肌肉中的氧氣，而陸地動物卻是依靠停留于肺部的氧氣。實驗數(shù)據(jù)顯示，王企鵝在下潛至510米深時，可將體內(nèi)全部氧氣的47%儲存在肌肉中，其中。我們?nèi)祟悈s不具備潛水途中儲存氧氣的能力，平時在我們肌肉中只能儲存體內(nèi)15%的氧氣。
在海豹和抹香鯨等深潛高手的肌肉中，肌紅蛋白的含量都格處高。肌紅蛋白是一種將血液中的氧吸收并儲存起來的蛋白質(zhì)，它為肌內(nèi)提供以后可使用的能量。因此，它們的肌肉在不需要進行呼吸的情況下還能堅持長時間的工作。此外，為了節(jié)約能量，在下潛時它產(chǎn)還具有降低心率的神奇本領(lǐng)。在美國的加利福尼亞大學(xué)，兩組科研人員得出的結(jié)論頗為接近。7頭小海象在陸地上的平均心跳為每分鐘107次，當它們在海水中下潛是，心跳下降到每分鐘39次，下降了64%。在它們潛水的初期，心率一般急劇降低，隨著它們下潛的深度不斷加大，心率隨之緩慢下降，極限記錄是每分鐘3次。
人在深潛過程中，容易發(fā)生減壓病。造成減壓病的原因是，在下潛時，越來越大的壓力會將他骯中的氮氣壓迫進他的血液或別的組織液中。當他快速返回水面時，氮就會驟然間從溶液中冒出來，這對于所有正常的生理活動都是毀滅性的打擊，包括神經(jīng)功能和血液循環(huán)。所以，潛水者在從水下上升時，除必須遵守潛水表或計算機器數(shù)據(jù)要求外，每上升5米作幾秒鐘的安全停留，便可以避免減壓病的發(fā)生。
深潛動物們?yōu)槭裁床坏脺p壓病呢？哈佛大學(xué)的動物學(xué)家吉米·卡瑞恩，不久前揭示了這一謎底?？ㄈ鸲靼l(fā)現(xiàn)生活在南極洲附近的海豹，它們可以下潛到七八百米的深度。但不論它們下潛多么深，體內(nèi)的氮的濃度基本不變。原因是它們的肺被強大的水壓迅速地壓扁了，一開始就阻止了大量的氮氣進行血液。所以深潛動物們免去了減壓病的煩惱。