I know that the answer to the question "Pure hydrogen is used for what?" is in "In more recent applications, hydrogen is used pure or mixed with nitrogen (sometimes called forming gas) as a tracer gas for minute leak detection. Applications can be found in the automotive, chemical, power generation, aerospace, and telecommunications industries. Hydrogen is an authorized food additive (E 949) that allows food package leak testing among other anti-oxidizing properties.". Can you tell me what it is?
Ans: a tracer gas

I know that the answer to the question "Antennas can have different usages, also known as?" is in "Resonant antennas are expected to be used around a particular resonant frequency; an antenna must therefore be built or ordered to match the frequency range of the intended application. A particular antenna design will present a particular feedpoint impedance. While this may affect the choice of an antenna, an antenna's impedance can also be adapted to the desired impedance level of a system using a matching network while maintaining the other characteristics (except for a possible loss of efficiency).". Can you tell me what it is?
Ans: intended application

I know that the answer to the question "Polytechnics have an equivalency with what overseas?" is in "Polytechnics were tertiary education teaching institutions in England, Wales and Northern Ireland. Since 1970 UK Polytechnics operated under the binary system of education along with universities. Polytechnics offered diplomas and degrees (bachelor's, master's, PhD) validated at the national level by the UK Council for National Academic Awards CNAA. They particularly excelled in engineering and applied science degree courses similar to technological universities in the USA and continental Europe. The comparable institutions in Scotland were collectively referred to as Central Institutions. Britain's first Polytechnic, the Royal Polytechnic Institution later known as the Polytechnic of Central London (now the University of Westminster) was established in 1838 at Regent Street in London and its goal was to educate and popularize engineering and scientific knowledge and inventions in Victorian Britain "at little expense." The London Polytechnic led a mass movement to create numerous Polytechnic institutes across the UK in the late 19th Century. Most Polytechnic institutes were established at the centre of major metropolitan cities and their focus was on engineering, applied science and technology education.". Can you tell me what it is?
Ans: technological universities in the USA and continental Europe

I know that the answer to the question "What could be harder to deal with at night?" is in "Asthma is characterized by recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing. Sputum may be produced from the lung by coughing but is often hard to bring up. During recovery from an attack, it may appear pus-like due to high levels of white blood cells called eosinophils. Symptoms are usually worse at night and in the early morning or in response to exercise or cold air. Some people with asthma rarely experience symptoms, usually in response to triggers, whereas others may have marked and persistent symptoms.". Can you tell me what it is?
Ans: Asthma