PAPALEKSI, NIKOLAI DMITRIEVICH

(b. Simferopol, Russia, 2 December 1880; d. Moscow U.S.S.R., 3 February 1947)

radiophysics, electrotechnology.

Papaleksi was the son of Dmitrii Konstantinovich papaleksi, an army officer. After graduating with a gold medal from the gymnasium at Poltava in 1899, he studied physics in Berlin and then at Strasbourg University, from which he graduated in 1904. He stayed in Strasbourg until 1914, except for the year 1907, which he spent at the Cavendish Laboratory at Cambridge, where he worked on fluorescence under the direction of J. J. Thomson. At Strasbourg, Papaleksi joined the brilliant school of Ferdinand Braun, who trained a number of outstanding Russian physicists, including Aleksandr Aleksandrovich Eichenwald, Boris Borisovich Golitsin, Petr Petrovich Lasarev, Petr Nikolaevich Lebedev, and Leonid Isaakovich Mandel’stam. (Papaleksi established a long-time and fruitful friendship with Mandel’stam.) In 1904 Papaleksi defended his doctoral dissertation, “Ein Dynamometer für schnelle elektrische Schwingungen. Theorie and Versuche”, and then became Braun’s assistant. In 1911, after defending a dissertation for the right to lecture (venia legendi), he was appointed Privatdozent in the department of physics.

Late in July 1914 Papaleksi returned to Russia. He became a consultant to the Russian Wireless Telegraph and Telephone Company, and until 1916 he did experiments in directional radiotelegraphy, radio communication to submarines, remote control, and electron tubes. In 1918 he went to Moscow and later to Odessa, where he and Mandel’stam participated in the organization of the Odessa Polytechnic Institute. He was named professor of theoretical electrotechnics at the institute in 1920. Also, with the assistance of Igor Evgenievich Tamm and of Mandel’stam, he helped to establish the production of electronic valves at the Polytechnic Institute and at the “Vacuum Group” in Odessa.

From 1922 to 1935 Papaleksi continued his co-operation with Mandel’stam, though at a distance. Papaleksi’s activity was concentrated in Leningrad, at the Central Radio Laboratory. In 1930 he became head of the department of scientific radiotechnology at the Leningrad Electrophysical Institute (which had been part of the Physical-Technical Institute). Papaleksi was also the head of the department of radio engineering of the Faculty of Physics and Mechanics at the Leningrad Polytechnic Institute, In 1935 he was named head of the department of oscillations at the P. N. Lebedev Physics Institute in Moscow, and an active member of the Power Institute, both parts of the U.S.S.R. Academy of Sciences.

From the early years of his cooperation with Mandel’stam, Papaleksi was primarily responsible for the translation of ideas and theories into real apparatuses. This division of labor dated from the years at Strasbourg, when the two scholars did radiometric investigations for German firms. In 1938 Mandel’stam wrote of Papaleksi:

Our cooperation in the field of electromagnetic oscillations has lasted over thirty years. During this long period there developed such a closeness between us regarding both the initiative and the treatment of problems (theoretical and experimental) that in most cases it is difficult to say what has been done by one or the other. As to the technical realization of results, the main role has been played by Nikolai Dmitrievich (Sobranie trudov, p. 21).

The main result of Papaleksi’s scientific activity was the formulation of the general theory of nonlinear oscillations. Mandel’stam and Papaleksi tried to implant in the minds of scholars what they called “nonlinear psychology,” that is, a willingness to step out of the framework of linear problems. This transition was to a great extent associated with the development of substantially nonlinear elements of radio-engineering devices, such as electron valves (the first work of Papaleksi in this field was published in 1912).

The discovery of a new principle of self-excitation of electromagnetic oscillations due to a periodic alteration of capacity or inductance resulted from investigations of nonlinear oscillations and treatment of the corresponding mathematical theory. This research entailed a great number of technical applications, first in radio engineering. The principle of parametric excitation and amplification of oscillations was applied in the parametric filter used for suppression of hindrances to radio reception, as well as in a number of new methods of frequency transformation. New generations of parametric amplifiers built on the basis of general principles worked out by Mandel’stam and Papaleksi have found important applications in modern observatory astrophysics. Further, before World War II, Mandel’stam and (especially) Papaleksi built electrical machines working on the principle of parametric excitation. These machines do not require excitative windings and have many other advantages compared with conventional generators and dynamos.

In the early 1930’s Papaleksi and Mandel’stam developed a method of measuring the velocity of propagation of electromagnetic waves. This method, based on the phenomenon of wave interference, served as a theoretical basis for creation of radio distance meters. Their research stimulated the the oretical work of Vladimir Aleksandrovich Fock and others of the theory of propagation of radio waves around the Earth’s surface. Before World War II this method found many applications in navigation, And in 1942 Mandel’stam and Papaleksi suggested using these applications for astronomical measurements: Papaleksi performed the calculations connected with the radiolocation of the moon (which was done in the United States in 1945).

After Mandel’stam’s death (1944) Papaleksi concentrated on problems related to solar electromagnetic radiation. He participated in the formulation of the program investigating solar electromagnetic radiation during a solar eclipse in 1947. This eclipse, observed in Brazil by a Soviet expedition, enabled the scientists to obtain important data related to the distribution of radio brightness of the solar surface.

Although Papaleksi worked very hard all his life, he also found time for relaxation. He was an outstanding athlete, alpinist, and chess player, and he not only knew Russian poetry very well, but wrote poems himself. He and his wife, Klara Efraimovna Viller-Papaleksi, had no children.

With Mandel’stam, Papaleksi created a world-recognized school devoted to nonlinear oscillations that included many outstanding Soviet physicists, for instance. Aleksandr Aleksandrovich Andronov. Papaleksi’s accomplishments were widely recognized: in 1931 he was elected corresponding member, and in 1939 full member, of the U.S.S.R. Academy of Sciences. With Mandel’stam he was awarded the Mendeleev Prize in 1936, and in 1942 he received the State Prize. A lunar crate was named for him.

Papaleksi worked at the Lebedev Physical Institute of the U.S.S.R. Academy of Sciences until a few days before his death—without respite, according to S. M. Rytov (Sobranie trudov, p. 36). Ten days before his death he finished the review on the theory of nonlinear oscillations and resumed work on his biography of Mandel’stam.

BIBLIOGRAPHY

I. Original Works. Papaleksi’s works are listed in Izvestüa Akadcmii nauk SSSR, serüa fizicheskitia, 12 , no. 1 (1948), 49–52. The most important include “Über die Vorgänge in einem Wechseltromkreis mit elektrischem Ventil,” in Annalen der Physik, 4th ser., 39 (1912), 976–996; “Exposé des recherches récentes sur les oscillations non linéaires,” in Technical Physics of the USSR, 2 , no. 2–3 (1935), 81–134, written with L. Mandel’stam, A. Andronov. S. Chaikin, and A. Witt; “Parametricheskoe generirovanie peremennykh tokov” (Parametrical generation of alternating currents), in Elektrichestvo, 11 (1938), 67–76; “O nekotorykh primeneniiakh radiointerferent-sionnykh metodov” (On some applications of radio-interference methods), in Izvestüa Akademü nauk SSSR, serüa fizicheskaiia, 3 , no. 4 (1938), 539–550; Radiopomekhi i borba s nimi (Radiointerferences and a fight against them; Moscow, 1942; 2nd ed., 1944); “Razvitie ucheniia o nelineinykh kolebaniiakh i ikh primenenii” (The development of the doctrine of nonlinear oscillations and their applications), Izvestüa Akademüa nauk SSR, serüa fizicheskaia, 9 , no. 3 (1945), 145–160; “Kratkii ocherk zhizni i nauchnoi deiatelnosti akademika L. I. Mandel’ stama” (Short sketch of L. I. Mandel’stam’s life and scientific activity), ibid., no. 1–2 (1945), 8–20, also published in Papaleksi’s Sorbranie trudov ; “Ob izmerenii rasstoianiia ot zemli do luny s pomoshchiu elektromagnitnykh voln” (On the measurement of the distance between the Earth and the moon by electromagnetic waves), in Uspekhi fizicheskikh nauk, 29 , no. 3–4 (1946), 250–268; “Nekotorye issledovaniia v oblasti nelineinykh kolebanii provedennye v SSSR, nachinaia s 1935 g.” (Some investigations in the field of nonlinear oscillations performed in the USSR since 1935). ibid., 33 , no. 3 (1947), 335–352, written with A. A. Andronov. G. S. Gorelik, and S. M. Rytov, ed. (Moscow, 1948).

Papaleksi’s papers are in the archives of the U.S.S.R. Academy of Sciences.

II. Secondary Literature,Izvestüa Akademü nauk SSSR, serüa fizicheskaia, 12 , no. 1 (1948), is a memorial volume dedicated to Papaleksi; see particularly the article by S. M. Rytov, which also appeared in Papaleksi’s Sobranie trudov. A short biographical notice is in Uspekhi fizicheskikh nauk, 21 , no. 2 (1939), 240–241.

V. J. Frenkel