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2008年10月8日，瑞典皇家科学院宣布将化学奖授予日本科学家下村修、美国科学家马丁?沙尔菲与美籍华裔科学家，以表彰三人因在发现和研究绿色荧光蛋白方面做出的贡献．蛋白质是一类复杂的含氮化合物，每种蛋白质都有其恒定的含氮量[约在14%～18%（本题涉及的含量均为质量分数）]，故食品中蛋白质的含量测定常用凯氏定氮法．其测定原理是： Ⅰ．蛋白质中的氮（用氨基表示）在CuSO 4 、浓H 2 SO 4 作用下，生成一种无机含氮化合物，反应 式为：2（-NH 2 ）+H 2 SO 4 +2H + CuS O 4 ______． Ⅱ．该无机化合物在凯氏定氮器中与碱作用，通过蒸馏释放出NH 3 ，收集于H 3 BO 3 溶液中，生成（NH 4 ） 2 B 4 O 7 ． Ⅲ．用已知浓度的HCl标准溶液滴定，根据HCl消耗的量计算出氮的含量，然后乘以相应的换算系数，即得蛋白质的含量． （1）上述原理第Ⅰ的无机含氮化合物化学式为______． （2）乳制品的换算系数为6.38，即若检测出氮的含量为1%，蛋白质的含量则为6.38%．不法分子通过在低蛋白含量的奶粉中加入三聚氰胺（Melamine）来“提高”奶粉中的蛋白质含量，导致许多婴幼儿肾结石． ①三聚氰胺的结构如图所示，其化学式为______，含氮量（氮元素的质量分数）为______； ②下列关于三聚氰胺的说法中，正确的有______； A．三聚氰胺是一种白色结晶粉末，无色无味，所以掺入奶粉后不易被发现 B．三聚氰胺分子中所有原子可能在同一个平面上 C．三聚氰胺呈弱碱性，可以和酸反应生成相应的盐 ③假定奶粉中蛋白质含量为16%即为合格，不法分子在一罐总质量为500g、蛋白质含量为0的假奶粉中掺入______g的三聚氰胺就可使奶粉“达标”．
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【简答题】uniflow scavenging
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【单选题】In ____ scavenging the incoming air is directed upwards and the exhaust gases travel down and out of the exhaust ports at the opposite side of the cylinder.
A.
cross
B.
aspirated
C.
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D.
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【单选题】In ________scavenging the incoming air is directed upwards and the exhaust gases travel down and out of the exhaust ports at the opposite side of the cylinder.
A.
cross
B.
loop
C.
aspirate
D.
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【单选题】“Loop”, “uniflow”, “crossflow”,and “return-flow” are terms used to describe various types of_____.
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control air circuits
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【单选题】Try new sports, games, and other activities ________new foods.You'll grow stronger, play longer, look and feel better! [     ]
A.
such as
B.
as well as
C.
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【单选题】对Yd11接线的降压变压器低压三角形侧出口处发生BC两相短路时,在高压星型侧三相电流的关系中( )相电流是其它两相的两倍。
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【单选题】In____ scavenging he incoming air is directed upwards and the exhaust gases travel down and out of the exhaust ports at the opposite side of the cylinder.
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【单选题】The crankcase of many diesel engines are kept under a slight vacuum by the _____.
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B.
piston type vacuum pump taking suction off a differential manometer
C.
gland exhausting manometer
D.
crankcase exhaust fan
查看完整题目与答案
【单选题】In ________scavenging the incoming air enters at the lower end of the cylinder and exhaust gases are forced out at the top.
A.
across
B.
loop
C.
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【单选题】正常支气管肺泡呼吸音听诊最清楚的部位是
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喉部
B.
胸骨上窝
C.
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乳房下部
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【简答题】uniflow scavenging
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【单选题】In ____ scavenging the incoming air is directed upwards and the exhaust gases travel down and out of the exhaust ports at the opposite side of the cylinder.
A.
cross
B.
aspirated
C.
Loop
D.
uniflow
查看完整题目与答案
【单选题】In ________scavenging the incoming air is directed upwards and the exhaust gases travel down and out of the exhaust ports at the opposite side of the cylinder.
A.
cross
B.
loop
C.
aspirate
D.
Uniflow
查看完整题目与答案
【单选题】“Loop”, “uniflow”, “crossflow”,and “return-flow” are terms used to describe various types of_____.
A.
control air circuits
B.
supercharging
C.
turbochargers
D.
scavenging
查看完整题目与答案