Problem: Antenna (radio):

This is a consequence of Lorentz reciprocity. For an antenna element  not connected to anything (open circuited) one can write . But for an element  which is short circuited, a current is generated across that short but no voltage is allowed, so the corresponding . This is the case, for instance, with the so-called parasitic elements of a Yagi-Uda antenna where the solid rod can be viewed as a dipole antenna shorted across its feedpoint. Parasitic elements are unpowered elements that absorb and reradiate RF energy according to the induced current calculated using such a system of equations.

When is the element not allowed voltage?
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A: short circuited


Problem: 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.
What are the characteristics of asthma?
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Answer: recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
The freedom to form, declare membership in, or campaign for candidates from a political party is considered a measurement of a state's adherence to liberal democracy as a political value. Regulation of parties may run from a crackdown on or repression of all opposition parties, a norm for authoritarian governments, to the repression of certain parties which hold or promote ideals which run counter to the general ideology of the state's incumbents (or possess membership by-laws which are legally unenforceable).
How are government crackdowns categorized by democracies?
A: unanswerable


Context and question: The 2009 Human Rights Report by the United States Department of State noted that human rights in CAR were poor and expressed concerns over numerous government abuses. The U.S. State Department alleged that major human rights abuses such as extrajudicial executions by security forces, torture, beatings and rape of suspects and prisoners occurred with impunity. It also alleged harsh and life-threatening conditions in prisons and detention centers, arbitrary arrest, prolonged pretrial detention and denial of a fair trial, restrictions on freedom of movement, official corruption, and restrictions on workers' rights.
How are the human rights in the CAR?
Answer: poor


Question: When a historic document survives only in translation, the original having been lost, researchers sometimes undertake back-translation in an effort to reconstruct the original text. An example involves the novel The Saragossa Manuscript by the Polish aristocrat Jan Potocki (1761–1815), who wrote the novel in French and anonymously published fragments in 1804 and 1813–14. Portions of the original French-language manuscript were subsequently lost; however, the missing fragments survived in a Polish translation that was made by Edmund Chojecki in 1847 from a complete French copy, now lost. French-language versions of the complete Saragossa Manuscript have since been produced, based on extant French-language fragments and on French-language versions that have been back-translated from Chojecki’s Polish version.
Is there an answer to this question: Who was Jan Potocki related to?

Answer: unanswerable


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
In coniferous or softwood species the wood cells are mostly of one kind, tracheids, and as a result the material is much more uniform in structure than that of most hardwoods. There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example.
Are hardwood or softwood species more uniform in structure?
A:
softwood