Answer the question at the end by quoting:

Fazlur Rahman Khan (Bengali: phjlur rhmaan khaan, Fozlur Rohman Khan) (3 April 1929 - 27 March 1982) was a Bangladeshi-American structural engineer and architect, who initiated important structural systems for skyscrapers. Considered the "father of tubular designs" for high-rises, Khan was also a pioneer in computer-aided design (CAD). He was the designer of the Sears Tower, since renamed Willis Tower, the tallest building in the world from 1973 until 1998, and the 100-story John Hancock Center. Khan, more than any other individual, ushered in a renaissance in skyscraper construction during the second half of the 20th century.
Khan's central innovation in skyscraper design and construction was the idea of the "tube" structural system for tall buildings, including the framed tube, trussed tube, and bundled tube variants. His "tube concept", using all the exterior wall perimeter structure of a building to simulate a thin-walled tube, revolutionized tall building design. Most buildings over 40 stories constructed since the 1960s now use a tube design derived from Khan's structural engineering principles.  Lateral loads (horizontal forces) such as wind forces, seismic forces, etc., begin to dominate the structural system and take on increasing importance in the overall building system as the building height increases. Wind forces become very substantial, and forces caused by earthquakes, etc. are important as well. The tubular designs resist such forces for tall buildings. Tube structures are stiff and have significant advantages over other framing systems. They not only make the buildings structurally stronger and more efficient, but also significantly reduce the structural material requirements. The reduction of material makes the buildings economically more efficient and reduces environmental impact. The tubular designs enable buildings to reach even greater heights. Tubular systems allow greater interior space and further enable buildings to take on various shapes, offering added freedom to architects. These new designs opened an economic door for contractors, engineers, architects, and investors, providing vast amounts of real estate space on minimal plots of land. Khan was among a group of engineers who encouraged a rebirth in skyscraper construction after a hiatus of over thirty years.  The tubular systems have yet to reach their limit when it comes to height. Another important feature of the tubular systems is that buildings can be constructed using steel or reinforced concrete, or a composite of the two, to reach greater heights. Khan pioneered the use of lightweight concrete for high-rise buildings, at a time when reinforced concrete was used for mostly low-rise construction of only a few stories in height. Most of Khan's designs were conceived considering pre-fabrication and repetition of components so projects could be quickly built with minimal errors.  The population explosion, starting with the baby boom of the 1950s, created widespread concern about the amount of available living space, which Khan solved by building upward. More than any other 20th-century engineer, Fazlur Rahman Khan made it possible for people to live and work in "cities in the sky." Mark Sarkisian (Director of Structural and Seismic Engineering at Skidmore, Owings & Merrill) said, "Khan was a visionary who transformed skyscrapers into sky cities while staying firmly grounded in the fundamentals of engineering."

What else can you tell me about the tubular systems?

They not only make the buildings structurally stronger and more efficient, but also significantly reduce the structural material requirements.



Answer the question at the end by quoting:

Recep Tayyip Erdogan (Turkish pronunciation: [re'dZep taj'jip 'aerdo(W)an] ( listen); born 26 February 1954) is a Turkish politician serving as the current President of Turkey, holding the position since 2014. He previously served as Prime Minister from 2003 to 2014 and as Mayor of Istanbul from 1994 to 1998. He founded the Justice and Development Party (AKP) in 2001, leading it to general election victories in 2002, 2007 and 2011 before standing down upon his election as President in 2014.
In 2001, Erdogan established the Justice and Development Party (AKP). The elections of 2002 were the first elections in which Erdogan participated as a party leader. All parties previously elected to parliament failed to win enough votes to re-enter the parliament. The AKP won 34.3% of the national vote and formed the new government. Turkish stocks rose more than 7% on Monday morning. Politicians of the previous generation, such as Ecevit, Bahceli, Yilmaz and Ciller, resigned. The second largest party, the CHP, received 19.4% of the votes. The AKP won a landslide victory in the parliament, taking nearly two-thirds of the seats. Erdogan could not become Prime Minister as he was still banned from politics by the judiciary for his speech in Siirt. Gul became the Prime Minister instead. In December 2002, the Supreme Election Board canceled the general election results from Siirt due to voting irregularities and scheduled a new election for 9 February 2003. By this time, party leader Erdogan was able to run for parliament due to a legal change made possible by the opposition Republican People's Party. The AKP duly listed Erdogan as a candidate for the rescheduled election, which he won, becoming Prime Minister after Gul handed over the post.  On 14 April 2007, an estimated 300,000 people marched in Ankara to protest against the possible candidacy of Erdogan in the 2007 presidential election, afraid that if elected as President, he would alter the secular nature of the Turkish state. Erdogan announced on 24 April 2007 that the party had nominated Abdullah Gul as the AKP candidate in the presidential election. The protests continued over the next several weeks, with over one million people reported to have turned out at a 29 April rally in Istanbul, tens of thousands at separate protests on 4 May in Manisa and Canakkale, and one million in Izmir on 13 May.  The stage of the elections of 2007 was set for a fight for legitimacy in the eyes of voters between his government and the CHP. Erdogan used the event that took place during the ill-fated Presidential elections a few months earlier as a part of the general election campaign of his party. On 22 July 2007, the AKP won an important victory over the opposition, garnering 46.7% of the popular vote. 22 July elections marked only the second time in the Republic of Turkey's history whereby an incumbent governing party won an election by increasing its share of popular support. On 14 March 2008, Turkey's Chief Prosecutor asked the country's Constitutional Court to ban Erdogan's governing party. The party escaped a ban on 30 July 2008, a year after winning 46.7% of the vote in national elections, although judges did cut the party's public funding by 50%.  In the June 2011 elections, Erdogan's governing party won 327 seats (49.83% of the popular vote) making Erdogan the only prime minister in Turkey's history to win three consecutive general elections, each time receiving more votes than the previous election. The second party, the Republican People's Party (CHP), received 135 seats (25.94%), the nationalist MHP received 53 seats (13.01%), and the Independents received 35 seats (6.58%).

Is there anything else of interest in this article?
All parties previously elected to parliament failed to win enough votes to re-enter the parliament.