Problem: Incandescent light bulb:

The spectrum emitted by a blackbody radiator at temperatures of incandescent bulbs does not match the sensitivity characteristics of the human eye; the light emitted does not appear white, and most is not in the range of wavelengths at which the eye is most sensitive. Tungsten filaments radiate mostly infrared radiation at temperatures where they remain solid – below 3,695 K (3,422 °C; 6,191 °F). Donald L. Klipstein explains it this way: "An ideal thermal radiator produces visible light most efficiently at temperatures around 6,300 °C (6,600 K; 11,400 °F). Even at this high temperature, a lot of the radiation is either infrared or ultraviolet, and the theoretical luminous efficacy (LER) is 95 lumens per watt." No known material can be used as a filament at this ideal temperature, which is hotter than the sun's surface. An upper limit for incandescent lamp luminous efficacy (LER) is around 52 lumens per watt, the theoretical value emitted by tungsten at its melting point.

What is the upper limit for LER of an incandescent lamp?
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A: 52 lumens per watt


Problem: This influx was compounded by the decline of the Western Sudanic Mali Empire in 1375 and the Songhai Empire in 1591. Additionally, as inland regions underwent desertification, inhabitants moved to the wetter coast. These new inhabitants brought skills such as cotton spinning, cloth weaving, iron smelting, rice and sorghum cultivation, and social and political institutions from the Mali and Songhai empires. Shortly after the Mane conquered the region, the Vai people of the former Mali Empire immigrated into the Grand Cape Mount region. The ethnic Kru opposed the influx of Vai, forming an alliance with the Mane to stop further influx of Vai.[citation needed]
Who opposed the influx of vai forming an alliance with maine?
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Answer: The ethnic Kru


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Before the early 20th century, treatments for infections were based primarily on medicinal folklore. Mixtures with antimicrobial properties that were used in treatments of infections were described over 2000 years ago. Many ancient cultures, including the ancient Egyptians and ancient Greeks, used specially selected mold and plant materials and extracts to treat infections. More recent observations made in the laboratory of antibiosis between microorganisms led to the discovery of natural antibacterials produced by microorganisms. Louis Pasteur observed, "if we could intervene in the antagonism observed between some bacteria, it would offer perhaps the greatest hopes for therapeutics". The term 'antibiosis', meaning "against life", was introduced by the French bacteriologist Jean Paul Vuillemin as a descriptive name of the phenomenon exhibited by these early antibacterial drugs. Antibiosis was first described in 1877 in bacteria when Louis Pasteur and Robert Koch observed that an airborne bacillus could inhibit the growth of Bacillus anthracis. These drugs were later renamed antibiotics by Selman Waksman, an American microbiologist, in 1942. Synthetic antibiotic chemotherapy as a science and development of antibacterials began in Germany with Paul Ehrlich in the late 1880s. Ehrlich noted certain dyes would color human, animal, or bacterial cells, whereas others did not. He then proposed the idea that it might be possible to create chemicals that would act as a selective drug that would bind to and kill bacteria without harming the human host. After screening hundreds of dyes against various organisms, in 1907, he discovered a medicinally useful drug, the synthetic antibacterial salvarsan now called arsphenamine.
What type of things did American microbiologists use?
A: unanswerable


Context and question: On September 27, 2006 Schwarzenegger signed a bill creating the nation's first cap on greenhouse gas emissions. The law set new regulations on the amount of emissions utilities, refineries and manufacturing plants are allowed to release into the atmosphere. Schwarzenegger also signed a second global warming bill that prohibits large utilities and corporations in California from making long-term contracts with suppliers who do not meet the state's greenhouse gas emission standards. The two bills are part of a plan to reduce California's emissions by 25 percent to 1990s levels by 2020. In 2005, Schwarzenegger issued an executive order calling to reduce greenhouse gases to 80 percent below 1990 levels by 2050.
What date marked the first law restricting greenhouse gas emissions?
Answer: September 27, 2006


Question: Recycled papers can be made from 100% recycled materials or blended with virgin pulp, although they are (generally) not as strong nor as bright as papers made from the latter.
Is there an answer to this question: What is the only thing recycled papers can be made from?

Answer: unanswerable


Question: Growing scientific recognition of the role of private lands for endangered species recovery and the landmark 1981 court decision in Palila v. Hawaii Department of Land and Natural Resources both contributed to making Habitat Conservation Plans/ Incidental Take Permits "a major force for wildlife conservation and a major headache to the development community", wrote Robert D.Thornton in the 1991 Environmental Law article, Searching for Consensus and Predictability: Habitat Conservation Planning under the Endangered Species Act of 1973.
Is there an answer to this question: When did private lands start to have more recognition?

Answer:
unanswerable