Problem: The most common symptom of LED (and diode laser) failure is the gradual lowering of light output and loss of efficiency. Sudden failures, although rare, can also occur. Early red LEDs were notable for their short service life. With the development of high-power LEDs the devices are subjected to higher junction temperatures and higher current densities than traditional devices. This causes stress on the material and may cause early light-output degradation. To quantitatively classify useful lifetime in a standardized manner it has been suggested to use L70 or L50, which are the runtimes (typically given in thousands of hours) at which a given LED reaches 70% and 50% of initial light output, respectively.
What is a classification used in LED lighting to describe how much usefulness it will receive?
The answer is the following: L70 or L50

Problem: The modern Slavic peoples carry a variety of mitochondrial DNA haplogroups and Y-chromosome DNA haplogroups. Yet two paternal haplogroups predominate: R1a1a [M17] and I2a2a [L69.2=T/S163.2]. The frequency of Haplogroup R1a ranges from 63.39% in the Sorbs, through 56.4% in Poland, 54% in Ukraine, 52% in Russia, Belarus, to 15.2% in Republic of Macedonia, 14.7% in Bulgaria and 12.1% in Herzegovina. The correlation between R1a1a [M17] and the speakers of Indo-European languages, particularly those of Eastern Europe (Russian) and Central and Southern Asia, was noticed in the late 1990s. From this Spencer Wells and colleagues, following the Kurgan hypothesis, deduced that R1a1a arose on the Pontic-Caspian steppe.
What is the frequency of Haplogroup R1a in Russia?
The answer is the following: 52%

Problem: The initial near-complete MPEG-1 standard (parts 1, 2 and 3) was publicly available on 6 December 1991 as ISO CD 11172. In most countries, patents cannot be filed after prior art has been made public, and patents expire 20 years after the initial filing date, which can be up to 12 months later for filings in other countries. As a result, patents required to implement MP3 expired in most countries by December 2012, 21 years after the publication of ISO CD 11172.
What became publicly available on 6 December 1991?
The answer is the following: MPEG-1 standard

Problem: Paris is home to the association football club Paris Saint-Germain and the rugby union club Stade Français. The 80,000-seat Stade de France, built for the 1998 FIFA World Cup, is located just north of Paris in the commune of Saint-Denis. Paris hosts the annual French Open Grand Slam tennis tournament on the red clay of Roland Garros. Paris played host to the 1900 and 1924 Summer Olympics, the 1938 and 1998 FIFA World Cups, and the 2007 Rugby World Cup. Every July, the Tour de France of cycling finishes in the city.
What is the name of the rugby union in Paris?
The answer is the following:
Stade Français