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Youtube:为什么食物吃起来有甜味
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为什么食物吃起来有甜味
Whether it’s ice cream, chocolate, candy,cookies or cake, we like our sweet stuff.
无论是冰激凌，巧克力，糖果，饼干还是蛋糕，我们都喜欢甜食。
But have you ever thought about why you have that sweet tooth?
但是你是否想过，你为什么喜欢甜食？
Turns out, it’s all about evolution.Let’s hear more from this gentleman...
事实表明，这都是进化的结果。让我们听这位绅士解释一下……
“The reason is that in nature, foods that are sweet are incredibly rare,but they’re a great source of energy. Sucrose is a carbohydrate. As is glucose,fructose, etc. Carbohydrates are molecules that contain an awful lot of energy. So mammals, whenever they found a source of carbohydrates, ate as much of it as they could.”
“原因就是，在自然界中，有甜味的食物非常罕见，但是它们是大量能量的来源。蔗糖是一种碳水化合物。就像葡萄糖，果糖等等。碳水化合物是含有大量能量的分子。所以，哺乳动物任何时候找到碳水化合物资源，都会尽可能多吃一些。”
Now we’re not running away from sabretooth tigers and walking miles for food any more.
现在，我们不再需要躲避剑齿虎，行走数英里来寻找食物了。
But what makes these foods taste,you know, sweet?
但是，你知道是什么让这些食物吃起来有甜味吗？
To be sweet, a molecule has to have three very specific chemical features that form a triangle of just the right size.
要吃起来有甜味，分子必须有三种特定的化学特征，形成特定大小的三角形。
Here is how sucrose, or table sugar,fits into the delightfully name 'sweetness triangle.'
这就是蔗糖有着非常可爱的名字“甜蜜三角形”的原因。
Scientists have different ways of describing this interaction, but one way is like a hand in a glove.
科学家有着不同的方式来描述这种互动，但是其中一种就像是戴着手套的手。
If the molecule in your food or drink and the receptor on your tongue fit together, your brain gets an electrical impulse that says“sweeeeet.”
如果食物或饮料中的分子和舌头上的感受器能够匹配，你的大脑就会收到电冲信号告诉你“很甜”。
“But what about artificial sweeteners?“our diet-sipping soda viewers ask.
“但是如果是人造甜味剂呢？”我们的观众问。
The granddaddy is saccharin, which was widely used during world war one when sugar was strictly rationed.
人造甜味剂的鼻祖是糖精，在第一次世界大战期间得到广泛使用，当时糖是经过严格分配的。
It’s still around today as “sweet –n– low”.And it’s in tab. Remember tab?
今天，这种产品仍然存在，就好像“sweet –n– low”一样。还有tab，你还记得吗？
By the年代， 80s artificial sweeteners went big time with aspartame, you’ve seen it marketed as “nutrasweet” or “equal”, and it is almost certainly in your favorite diet soda.
截止到80年代，人造甜味剂迎来了代糖的鼎盛时期，你看到他们的市场推广标榜为“阿斯巴甜”或“等同于糖”，你最喜欢的苏打水中几乎肯定有这种甜味剂。
But here’s the funny thing. Aspartame doesn’t look anything like table sugar, or sucrose.
但是有趣的是，阿斯巴甜看上去完全不像蔗糖。
“Now, aspartame, as a molecule,isn’t even close to a sugar.It’s in fact a tiny little protein.It’s the addition of aspartic acid and phenylalanine, known as amino acids,this means that aspartame is chemically more similar to meat than it is to sugar.”
“从分子结构上讲，阿斯巴甜和糖完全不接近。实际上阿斯巴甜是一种微小的蛋白质。它是天门冬氨酸和苯基丙氨酸的结合，这些都是氨基酸。这意味着阿斯巴甜在化学结构上与肉更接近。”
So artificial sweeteners taste sweet because they fit into the sweetness triangle.
所以，人造甜味剂吃上去是甜的是因为它们刚好构成甜蜜三角形。
But only part of the aspartame molecule fits. Chemists have since created or discovered other molecules like sucralose, and stevia,both of which are sweeter than aspartame, and hundreds of times sweeter than table sugar.
但是只有部分阿斯巴甜分子能够符合。化学家创造或发现了其他分子，比如果糖和甜菊，两者都比阿斯巴甜更甜，比蔗糖甜数百倍。
So that’s why things taste sweet.
以上就是食物吃起来甜的原因。
CCTV9:奥巴马宣布从阿富汗撤军推迟至2017年
Obama announces plans to delay withdrawal from Afghanistan to 2017
奥巴马宣布从阿富汗撤军推迟至2017年
WASHINGTON, Oct. 15 (Xinhua) -- The Pentagon said on Thursday keeping 5,500 U.S. troops in Afghanistan into 2017 would be enough, as U.S. President Barack Obama broke his promise to bring all U.S. troops home before leaving office.
"We do look at it as enough. We did a lot of homework on this," said U.S. Secretary of Defense Ash Carter at a briefing.
"We are adjusting our presence based on conditions on the ground to give the United States and our allies the capability to sustain a robust counterterrorism platform, denying a safe haven for terrorists and violent extremist organizations."
Obama announced plans Thursday to keep 5,500 U.S. troops in Afghanistan into 2017, and to maintain the current 9,800 forces through "most of 2016."
Calling the new plan "modest but meaningful," Obama said the U.S. troops in Afghanistan will remain focused on training Afghans and counterterrorism operations against remnants of al-Qaida.
Echoing Obama, Carter said counterterrorism would be a part of the "enduring mission" in Afghanistan.
"Whatever it takes to protect our country and make sure that Afghanistan doesn't again become a platform from which terrorism arises," said Carter.
Obama had previously planed to reduce the current level of 9,800 U.S. troops in Afghanistan to around 5,500 by the end of 2015 and withdraw all troops by the end of 2016 when Obama's presidency comes to an end.
Earlier this year, after a meeting with visiting Afghan President Ghani here, Obama announced no reduction of the current 9,800 U.S. troops stationed in Afghanistan will occur through the end of 2015.
CCTV9视频:沃尔玛遭遇25年来最严重衰退
Wal-Mart suffers deepest decline in 25 years
沃尔玛遭遇25年来最严重衰退
Wal-Mart is facing tough competition on multiple fronts, from the quick expansion of online leader Amazon.com to a stronger dollar, which has been eating into its international sales.
On Wednesday, the company's share value fell more than 10 percent, the worst one-day decline in 25 years since it was listed. Analysts the biggest challenge for Wal-Mart is that more consumers are choosing to buy online. That's why Wal-Mart decided to take several moves in the following years to recover lost territories with e-commerce companies.
These moves include raising wages, cutting prices and a US$20 billion share buyback. Wal-Mart Chief Executive Doug McMillon was trying to convince investors that the company will regain its steam within a few years.
Under these moves, Wal-Mart forecast its earnings per share would drop to US$4.4 to US$4.7, while 2017's EPS would continue to drop by 6 to 12 percent. But it added that the company's EPS would likely grow 5 to 10 percent in the fiscal year ending January 2019.
