The rate equations for a continuous four level laser are solved in this letter, taking into account the finite lower level lifetime and the crystal field splitting of the laser levels.

在考虑了有限的下能级寿命和激光能级与晶格场的相互作用的基础上，对四能级激光的速率方程组进行了求解。

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The bottom line here is the more fiber you eat, perhaps, a lower level of hormone in your body, and therefore, a lower lifetime risk of developing breast cancer.

在这里最重要的一点是，你吃的纤维越多，可能你体内的激素水平就越低，因此一生当中患乳腺癌的风险就越低。

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Early bouts of joblessness, or starting in a lower-level job with lower pay, can mean lower levels of career attainment and earnings over a lifetime.

刚开始时就失业或从事一些较低级别工作挣微薄薪水，这意味着终生找到好职业与拿高薪的机会减少。

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With a lifetime rating of 82.3 percent, McCain would rate "on the lower level of what we would consider to be conservative, " Keene tells Steve Inskeep.

NPR: David Keene: McCain Must Prove GOP Allegiance