Question: Who is the spouse of the President of the Russian Republic at the time when the place where an experimental 6kV DC railway was built disintegrated?

full_context: Document 1: Soviet Union: With the rise of strong nationalist and separatist movements inside the union republics, Gorbachev tried to avert a dissolution of the Soviet Union in the post-Cold War era. A March 1991 referendum, boycotted by some republics, resulted in a majority of participating citizens voting in favor of preserving the union as a renewed federation. Gorbachev's power was greatly diminished after Russian President Boris Yeltsin played a high - profile role in facing down an abortive August 1991 coup d'état attempted by Communist Party hardliners. On 25 December 1991, Gorbachev resigned and the remaining twelve constituent republics emerged as independent post-Soviet states. The Russian Federation -- formerly the Russian SFSR -- assumed the Soviet Union's rights and obligations and is recognized as the successor state of the Soviet Union. In summing up the international ramifications of these events, Vladislav Zubok stated: ``The collapse of the Soviet empire was an event of epochal geopolitical, military, ideological and economic significance. ''
Document 2: Raisa Gorbacheva: Raisa Maximovna Gorbacheva ( "Raisa Maksimovna Gorbachyova", , Титаренко; 5 January 1932 – 20 September 1999) was a Russian activist who was the wife of Soviet leader Mikhail Gorbachev. She raised funds for the preservation of Russian cultural heritage, fostering of new talent, and treatment programs for children's blood cancer.
Document 3: Yelena Bonner: Yelena Georgievna Bonner (; 15 February 1923 – 18 June 2011) was a human rights activist in the former Soviet Union and wife of the physicist Andrei Sakharov. During her decades as a dissident, Bonner was noted for her characteristic blunt honesty and courage.
Document 4: Dissolution of the Soviet Union: The dissolution of the Soviet Union occurred on December 26, 1991, officially granting self - governing independence to the Republics of the Soviet Union. It was a result of the declaration number 142 - Н of the Supreme Soviet of the Soviet Union. The declaration acknowledged the independence of the former Soviet republics and created the Commonwealth of Independent States (CIS), although five of the signatories ratified it much later or did not do so at all. On the previous day, 25 December 1991, Soviet President Mikhail Gorbachev, the eighth and final leader of the Soviet Union, resigned, declared his office extinct, and handed over its powers -- including control of the Soviet nuclear missile launching codes -- to Russian President Boris Yeltsin. That evening at 7: 32 p.m., the Soviet flag was lowered from the Kremlin for the last time and replaced with the pre-revolutionary Russian flag.
Document 5: Railway electrification system: DC systems (especially third-rail systems) are limited to relatively low voltages and this can limit the size and speed of trains and cannot use low-level platform and also limit the amount of air-conditioning that the trains can provide. This may be a factor favouring overhead wires and high-voltage AC, even for urban usage. In practice, the top speed of trains on third-rail systems is limited to 100 mph (160 km/h) because above that speed reliable contact between the shoe and the rail cannot be maintained.
Document 6: Dissolution of the Soviet Union: In the fall of 1985, Gorbachev continued to bring younger and more energetic men into government. On September 27, Nikolai Ryzhkov replaced 79-year-old Nikolai Tikhonov as Chairman of the Council of Ministers, effectively the Soviet prime minister, and on October 14, Nikolai Talyzin replaced Nikolai Baibakov as chairman of the State Planning Committee (GOSPLAN). At the next Central Committee meeting on October 15, Tikhonov retired from the Politburo and Talyzin became a candidate. Finally, on December 23, 1985, Gorbachev appointed Yeltsin First Secretary of the Moscow Communist Party replacing Viktor Grishin.
Document 7: Dissolution of the Soviet Union: The dissolution of the Soviet Union was formally enacted on December 26, 1991, as a result of the declaration no. 142-Н of the Soviet of the Republics of the Supreme Soviet of the Soviet Union. The declaration acknowledged the independence of the former Soviet republics and created the Commonwealth of Independent States (CIS), although five of the signatories ratified it much later or not at all. On the previous day, Soviet President Mikhail Gorbachev, the eighth and last leader of the Soviet Union, resigned, declared his office extinct, and handed over its powers – including control of the Soviet nuclear missile launching codes – to Russian President Boris Yeltsin. That evening at 7:32 p.m., the Soviet flag was lowered from the Kremlin for the last time and replaced with the pre-revolutionary Russian flag.
Document 8: Dissolution of the Soviet Union: The Soviet Union was dissolved on December 26, 1991. It was a result of the declaration number 142 - Н of the Soviet of the Republics of the Supreme Soviet of the Soviet Union. The declaration acknowledged the independence of the former Soviet republics and created the Commonwealth of Independent States (CIS), although five of the signatories ratified it much later or did not do so at all. On the previous day, Soviet President Mikhail Gorbachev, the eighth and final leader of the Soviet Union, resigned, declared his office extinct, and handed over its powers -- including control of the Soviet nuclear missile launching codes -- to Russian President Boris Yeltsin. That evening at 7: 32, the Soviet flag was lowered from the Kremlin for the last time and replaced with the pre-revolutionary Russian flag.
Document 9: Naina Yeltsina: Naina Yeltsina was rarely seen in public. She accompanied her husband on some of his foreign visits, including 1997 visits to Sweden, Finland, and a 1999 visit to China. As a rule, Naina Yeltsina never interfered in her husband's political work. However, in the 1996 election campaign, she met with voters and gave interviews to the media. A major public appearance was the state funeral of her late husband in Moscow in April 2007.
Document 10: Dissolution of the Soviet Union: In a nationally televised speech early in the morning of December 25, 1991, Gorbachev resigned as president of the USSR – or, as he put it, "I hereby discontinue my activities at the post of President of the Union of Soviet Socialist Republics." He declared the office extinct, and all of its powers (such as control of the nuclear arsenal) were ceded to Yeltsin. A week earlier, Gorbachev had met with Yeltsin and accepted the fait accompli of the Soviet Union's dissolution. On the same day, the Supreme Soviet of the Russian SFSR adopted a statute to change Russia's legal name from "Russian Soviet Federative Socialist Republic" to "Russian Federation," showing that it was now a sovereign state.
Document 11: Railway electrification system: There has, however, been interest among railroad operators in returning to DC use at higher voltages than previously used. At the same voltage, DC often has less loss than AC, and for this reason high-voltage direct current is already used on some bulk power transmission lines. DC avoids the electromagnetic radiation inherent with AC, and on a railway this also reduces interference with signalling and communications and mitigates hypothetical EMF risks. DC also avoids the power factor problems of AC. Of particular interest to railroading is that DC can supply constant power with a single ungrounded wire. Constant power with AC requires three-phase transmission with at least two ungrounded wires. Another important consideration is that mains-frequency 3-phase AC must be carefully planned to avoid unbalanced phase loads. Parts of the system are supplied from different phases on the assumption that the total loads of the 3 phases will even out. At the phase break points between regions supplied from different phases, long insulated supply breaks are required to avoid them being shorted by rolling stock using more than one pantograph at a time. A few railroads have tried 3-phase but its substantial complexity has made single-phase standard practice despite the interruption in power flow that occurs twice every cycle. An experimental 6 kV DC railway was built in the Soviet Union.
Document 12: Railway electrification system: Most electrification systems use overhead wires, but third rail is an option up to about 1,200 V. Third rail systems exclusively use DC distribution. The use of AC is not feasible because the dimensions of a third rail are physically very large compared with the skin depth that the alternating current penetrates to (0.3 millimetres or 0.012 inches) in a steel rail). This effect makes the resistance per unit length unacceptably high compared with the use of DC. Third rail is more compact than overhead wires and can be used in smaller-diameter tunnels, an important factor for subway systems.
Document 13: Dissolution of the Soviet Union: Mikhail Gorbachev was elected General Secretary by the Politburo on March 11, 1985, three hours after predecessor Konstantin Chernenko's death at age 73. Gorbachev, aged 54, was the youngest member of the Politburo. His initial goal as general secretary was to revive the Soviet economy, and he realized that doing so would require reforming underlying political and social structures. The reforms began with personnel changes of senior Brezhnev-era officials who would impede political and economic change. On April 23, 1985, Gorbachev brought two protégés, Yegor Ligachev and Nikolai Ryzhkov, into the Politburo as full members. He kept the "power" ministries happy by promoting KGB Head Viktor Chebrikov from candidate to full member and appointing Minister of Defence Marshal Sergei Sokolov as a Politburo candidate.
Document 14: Railway electrification system: In the Soviet Union, in the 1970s, a comparison was made between systems electrified at 3 kV DC and 25 kV AC (50 Hz). The results showed that percentage losses in the overhead wires (catenary and contact wires) was over 3 times greater for 3 kV DC than for 25 kV AC. But when the conversion losses were all taken into account and added to overhead wire losses (including cooling blower energy) the 25 kV AC lost a somewhat higher percent of energy than for 3 kV DC. Thus in spite of the much higher losses in the catenary, the 3 kV DC was a little more energy efficient than AC in providing energy from the USSR power grid to the terminals of the traction motors (all DC at that time). While both systems use energy in converting higher voltage AC from the USSR's power grid to lower voltage DC, the conversions for the DC system all took place (at higher efficiency) in the railway substation, while most of the conversion for the AC system took place inside the locomotive (at lower efficiency). Consider also that it takes energy to constantly move this mobile conversion hardware over the rails while the stationary hardware in the railway substation doesn't incur this energy cost. For more details see: Wiki: Soviet Union DC vs. AC.
Document 15: Railway electrification system: 3 kV DC is used in Belgium, Italy, Spain, Poland, the northern Czech Republic, Slovakia, Slovenia, South Africa, Chile, and former Soviet Union countries (also using 25 kV 50 Hz AC). It was formerly used by the Milwaukee Road from Harlowton, Montana to Seattle-Tacoma, across the Continental Divide and including extensive branch and loop lines in Montana, and by the Delaware, Lackawanna & Western Railroad (now New Jersey Transit, converted to 25 kV AC) in the United States, and the Kolkata suburban railway (Bardhaman Main Line) in India, before it was converted to 25 kV 50 Hz AC.
ground_truth: Raisa Maximovna Gorbacheva
sub_queries: Where was an experimental 6kV DC railway built? Answer: the Soviet Union
who was the president of the russian republic at the time of the disintegration of the Soviet Union Answer: Mikhail Gorbachev
Mikhail Gorbachev >> spouse Answer: Raisa Maximovna Gorbacheva