Драгољуб К. Јовановић : (1891–1970)

Abstract

Dragoljub K. Jovanović, a world-renowned scientist from Serbia, a university professor and a corresponding member of the Serbian Academy of Sciences and Arts, was born on March 7th, 1891 in Paraćin. His father Kosta Jovanović was a craft sman and his mother Persa, née Dimitrijević, was a housewife. He attended primary school in Paraćin, secondary in Jagodina, Kragujevac and Belgrade, where he graduated. Aft er the graduation in 1910, D. Jovanović enrolled at the Faculty of Philosophy in Belgrade, the department of chemistry, headed by professor Sima Lozanić. His fi nal year of studies was interrupted by the Great War. In November 1915, as a volunteer at an archive, he was interned in the concentration camp Aschach in Austria where he stayed until the end of the war in 1918. Upon release from war captivity, he completed his chemical studies at the beginning of 1919 and began working as a secondary school chemistry teacher, and then as an assistant at the Faculty of Philosophy in Belgrade. Th e scholarship from Belgrade University enabled him to travel to France, in September 1920. In Paris, he continued his education at the then most prominent institute for research of radium and naturally occurring radioactive elements. Th e topic of his doctoral dissertation was the isolation and testing of the secondary “outputs” within the spectrum of chemical elements of the radioactive thorium family, know at the time as mesothorium-2. At the same time, he also published his most important research papers in the world’s leading scientifi c journals which earned him a huge international reputation. He defended his doctoral thesis on June 3rd, 1925, before a prominent committee consisting of the double Nobel Prize winner Marie Curie, the following year’s Nobel Prize winner for physics Jean Baptiste Perrin, and André-Louis Debierne, a famous chemist of his time, the discoverer of the element actinium, and Marie Curie’s assistant. At the request of Marie Curie, he continued his research in Paris until the end of September 1928. During his stay in Paris, he became a member of the French Physical Society. Before fi nally returning from Paris in 1927, he was appointed as an associate professor of physics at the School of Medicine in Belgrade and director of the Institute of Radiology and Physics at the same school. He assumed his assigned roles upon his return from Paris in 1928. Between the two world wars, he used the Institute of Radiology and Physics as the base for his teaching and scientifi c activities. For a few years aft er returning to Serbia, he made basic provisions for the Institute. He personally made apparatuses, modelling them on the equipment form the Institute for Radium Research or using his original ideas. Th e preparatory period enabled him to continue research work albeit under much more limiting conditions than those in Paris. Th e focus of his research, in which he included numerous assistants – teachers from the School of Medicine – now was on the impact of radioactivity on living organisms for medical purposes. In 1932, she started teaching physics to medical students when the subject was transferred from the Faculty of Philosophy at Captain Miša’s Mansion to the School of Medicine. He was promoted to the rank of full professor in 1939. Th e Second World War led to an almost complete suspension of university education, and aft er initial disagreements with the occupying authorities, D. Jovanović found refuge in Sokobanja where he remained during the war period. Aft er the liberation, on June 26th, 1945, he went back to teaching physics at the School of Medicine but soon, on December 25th, 1945 he was appointed professor of physics at the Faculty of Philosophy (nowadays the Faculty of Natural Sciences) at which, due to staff shortages, he also taught physics. He met his wife Mirjana Trbojević (1902–1982), the daughter of the Belgrade county doctor and the director of the City Polyclinic, at the beginning of January 1927 and they were married on February 25th, 1929. Th ey had two sons, born in 1930 and 1933 respectively, both of whom acquired higher education and accomplished successful scientifi c careers in the USA where they remained living. Th eir children also have university degrees. In 1948, Jovanović was elected a corresponding member of the Serbian Academy of Sciences at the suggestion of the then corresponding member Pavle Savić, who continued his radiochemical research, with the explanation that “he published a series of high-quality works on radioactivity which have the enduring scientifi c value”. He retired in 1961, as professor of the Faculty of Natural Sciences, but continued working part-time at the Physics Institute of the School of Medicine. He was director of the Institute until 1964, and professor of physics at the School of Medicine until 1967. He passed away on February 17th, 1970 and was buried at the New Cemetery in Belgrade. Th e main scientifi c contributions of the D. Jovanović is his research in the fi eld of natural radioactivity. While working at the Radium Institute in Paris, he published about twenty articles in the world’s leading scientifi c journals, mostly in the Comptes rendus de l’Académie des Sciences. Th is included Jovanović’s feedback on the study of the chemical properties of the elements from the radioactive thorium family. In his doctoral thesis, he proposed an original method of isolating the “mesothorium-2” (later identifi ed as the isotope of actinium 228Ac) in pure form and high concentration, within a fairly short period of time in order to examine chemical properties, its half-life time and the radiation emission energy of this short-lived element. Th e main conclusion was that, due to its chemical properties, mesothorium-2 belongs in group 3b of the periodic table. Jovanovic discovered new lines in the β-ray spectrum of mesothorium-2 and also that some of the β-rays have so much energy that they can move at a speed close to the speed of light. Th ose results have sparked a great deal of interest and, as such, have been used by many other researchers of β-ray spectroscopy. He also gave an improved method for determining etalon of radiation. His experience in the chemistry of radioactive elements was used to isolate the next member of the thorium family, “radiothorium” (subsequently identifi ed as the isotope of thorium228Th ), which he later used in biological research, aft er returning to Serbia. Concurrently with the classic method for determining the absorption coeffi cient of radioactive radiation in various materials, based on the ionization current, Jovanović introduced a new, calorimetric method, which additionally contributed to the clarifi cation of the energy levels of atomic nuclei and the extent of energy changes in nuclear reactions of naturally occurring radioactive elements. Summarizing the results of D. Jovanović’s most laborious work, which matched the highest level of the research and experimental techniques at the time, it ought to be pointed out that he worked in the years when classic research methods regarding methodology and the issues of naturally occurring radioactive elements were coming to their end. Some thirty years had passed since radioactivity was discovered and followed by very intense research in this relatively narrow domain of naturally occurring radioactive elements. Nevertheless, lots of issues remained to be clarifi ed so Jovanović took it upon himself to search the unresolved reservoirs of scientifi c knowledge and amongst them the uncertainty regarding the origin of beta radiation which baffl ed scientists of his time. It ought to be remembered that those were the times when, considering the existing level of understanding of radiation, raised were the questions which later led to breakthroughs in areas regarding the structure of the atomic nucleus. Answers to those questions were accessible through the equipment, considered to be fi rst-rate at the time, however inadequate for dealing with newly generated needs. It took a lot of time, eff ort and imagination to obtain reliable and scientifi cally based answers which makes them even more important and valuable. All works of D. Jovanović published at that time were included in the Handbuch der Experimental-Psychic Wien-Harms, T. XV, Radioaktivität, edited by K. W. F. Kohlrausch, which is the best proof of high reputation that he had achieved. New big advancements in radiochemistry occurred aft er Jovanović returned to Yugoslavia. He found scarce resource conditions, under which the progress of physics in the world was quite diffi cult to follow, but he did his best under the circumstances. While working at the School of Medicine, the world of radiochemistry witnessed the discovery of neutron from the reaction between beryllium and alpha particles, and the discovery of artificial radioactivity produced by neutron bombardment. Th is period was marked by the acquisition, concentration and separation of artificially created radioisotopes, caused by neutron bombardment, and the development of applied radiochemistry. At the Institute for Radium, at that time, particularly prominent researchers were Frederik Joliot-Curie and his wife Irène Joliot- Curie, whose work, with the participation of Jovanović’s assistant and his successor in radiochemical research, Pavle Savić, was an introduction to the discovery of nuclear fi ssion. His experience from the Institute of Radium helped Jovanović, upon his return to Belgrade, continue to follow the progress of physics in the world, publish his scientifi c papers, and open new research areas, despite his busy teaching engagements and the working environment which he had to provide for mostly personally. It is necessary to mention his pioneering work, conducted in collaboration with his associated from the School of Medicine, on the impact of radiation on living organisms; Jovanović prepared radioactive sources with measured activities while, aft erwards, his medical associates studied changes that occurred in tissues following their exposure to radiation for a certain period of time. Th ese works were of great importance for the development of the then little- known methodology of use of radioactive preparations in the treatment of malignant diseases, practised at the School of Medicine. Jovanović also made a signifi cant contribution to the study of natural radioactivity in groundwater, testing waters in spa hospitals throughout Yugoslavia in situ, with a homemade terrestrial radiation detector. In some water sources in Sokobanja Spa, Jovanović detected high levels of radon concentration, the second largest in Europe, which contributed greatly to the popularity of spa and the development of spa tourism and earned him great admiration and respect of the municipal leaders and the local population. While working at the Institute of Physics of the School of Medicine, he also published papers on intramolecular interactions of alpha radiation and protons in metal hydride, scintillation in crystal hydrates during hydration, the Hall eff ect in thin metal foils, etc. As an enthusiast and a science lover, following the progress of physics in the world in which he could not directly participate at the time, he wrote lots of publications of a scientifi cally popular and informative character. Aft er the Second World War, he founded the Board of the Society of Mathematicians, Physicists and Astronomers of the SR of Serbia and was its long-term member. Th e society published Vesnik, one of the rare periodicals which published scientifi c papers of young authors at the time. As a researcher and a pedagogue focused on medical applications of physics, he initiated seminars in medical physics, held every two years and attended by representatives from physical institutes of medical, veterinary, pharmaceutical and dental faculties from all over Yugoslavia. At the 1966 Sarajevo Seminar, he was elected president for life of the Coordinating Committee of Medical Physicists. Teaching contributions of D. Jovanović in Serbia are immeasurable. According to the data published in the Archives of the School of Medicine 1920– 2010, since 1937, when fi rst Belgrade doctors graduated, until 1968 when D. Jovanović stopped teaching physics, 10.729 students graduated from the School of Medicine, which means that as many students passed the exam before him. Students from related faculties – pharmacy, veterinary and dentistry – should also be added to the number, as well as students of physics between 1945 and 1961. The fact that many failed the first time ought to be taken into consideration, too. As a physics teacher, he is credited with writing textbooks; 10 were published before the Second World War and 8 aft er the war. In the post-war period they, being rare few textbooks on the subject written in the Serbian language, played the key role in the education of generations of physicists at the parent faculty and non-parent ones. Th e 1967 Serbian translation of the book Th e Character of Physical Law by the Nobel Prize winner Feynman should also be mentioned. His teaching enthusiasm, particular temperament and wit, made him very popular with students, which was obvious at each encounter with them. His scientifi c and educational achievements were honoured, and he received many public awards for them: the Order of St. Sava, 3rd Class (before the Second World War), the 7th of July Award for lifetime achievements in 1961, the Order of the Republic with the Silver Wreath in 1965, the Marie Curie Medallion in 1967 on the 100th anniversary of her birth. Posthumously he was awarded the Charter of the Society of Mathematicians, Physicists and Astronomers of Serbia in 1978. In 1970, the Institute of Physics of the School of Medicine was named aft er him. Th e towns of Paraćin and Sokobanja each got one street named aft er him, too.