Context and question: Melatonin is absent from the system or undetectably low during daytime. Its onset in dim light, dim-light melatonin onset (DLMO), at roughly 21:00 (9 p.m.) can be measured in the blood or the saliva. Its major metabolite can also be measured in morning urine. Both DLMO and the midpoint (in time) of the presence of the hormone in the blood or saliva have been used as circadian markers. However, newer research indicates that the melatonin offset may be the more reliable marker. Benloucif et al. found that melatonin phase markers were more stable and more highly correlated with the timing of sleep than the core temperature minimum. They found that both sleep offset and melatonin offset are more strongly correlated with phase markers than the onset of sleep. In addition, the declining phase of the melatonin levels is more reliable and stable than the termination of melatonin synthesis.
At its onset, what can be measured in blood or saliva?
Answer: Melatonin
Context and question: Schwarzenegger was born with a bicuspid aortic valve, an aortic valve with only two leaflets (a normal aortic valve has three leaflets). Schwarzenegger opted in 1997 for a replacement heart valve made of his own transplanted tissue; medical experts predicted he would require heart valve replacement surgery in the following two to eight years as his valve would progressively degrade. Schwarzenegger apparently opted against a mechanical valve, the only permanent solution available at the time of his surgery, because it would have sharply limited his physical activity and capacity to exercise.
What word describes an aortic valve with two rather than three leaflets?
Answer: bicuspid
Context and question: The city's first bus rapid transit line, the Metrobús, began operation in June 2005, along Avenida Insurgentes. Line 2 opened in December 2008, serving Eje 4 Sur, line 3 opened in February 2011, serving Eje 1 Poniente, and line 4 opened in April 2012 connecting the airport with San Lázaro and Buenavista Station at Insurgentes. As the microbuses were removed from its route, it was hoped that the Metrobús could reduce pollution and decrease transit time for passengers. In June 2013, Mexico City's mayor announced two more lines to come: Line 5 serving Eje 3 Oriente and Line 6 serving Eje 5 Norte. As of June 2013, 367 Metrobús buses transported 850,000 passengers daily.
When did the second line of Metrobus open?
Answer:
December 2008