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?

<P0-S0> 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. <P0-S1> She raised funds for the preservation of Russian cultural heritage, fostering of new talent, and treatment programs for children's blood cancer. <SEP> <P1-S0> the midland railway's paget locomotive, no. <P1-S1> 2299, was an experimental steam locomotive constructed at its derby works in 1908 to the design of the general superintendent cecil paget (though richard deeley was locomotive superintendent at the time). <P1-S2> as the midland shrouded the locomotive in secrecy, there is only one known photograph, which was not released until after the grouping of 1923. <SEP> <P2-S0> the original keadby railway station was the eastern-most terminus of the south yorkshire railway. <P2-S1> the railway, which was extended from thorne and opened in september 1859 was built without an act of parliament, as the railway company owned the canal alongside which they built the line. <SEP> <P3-S0> The dissolution of the Soviet Union occurred on December 26, 1991, officially granting self - governing independence to the Republics of the Soviet Union. <P3-S1> It was a result of the declaration number 142 - Н of the Supreme Soviet of the Soviet Union. <P3-S2> 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. <P3-S3> 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. <P3-S4> 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. <SEP> <P4-S0> There has, however, been interest among railroad operators in returning to DC use at higher voltages than previously used. <P4-S1> 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. <P4-S2> 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. <P4-S3> DC also avoids the power factor problems of AC. <P4-S4> Of particular interest to railroading is that DC can supply constant power with a single ungrounded wire. <P4-S5> Constant power with AC requires three-phase transmission with at least two ungrounded wires. <P4-S6> Another important consideration is that mains-frequency 3-phase AC must be carefully planned to avoid unbalanced phase loads. <P4-S7> Parts of the system are supplied from different phases on the assumption that the total loads of the 3 phases will even out. <P4-S8> 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. <P4-S9> 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. <P4-S10> An experimental 6 kV DC railway was built in the Soviet Union.