### Julian Musielak

Professor Julian Musielak was born on 7th November 1928 in Poznań. His Father Antoni and his mother Halina, born Maeusel, were clerks in the government of Poznań Province. Since 1953 he has been married to Helena, born Perdziak, and he has got three daughters and two sons.

#### Education

n 1935-1939 he attended the private Primary St. Kazimierz School in Poznań. During the Second World War in 1942-1945 he worked as an assistant first at State Archive in Poznań and later in Post Office No 1 in Poznań. In 1945-1947 he was a pupil of the State Grammar and Secondary Berger School in Poznań, majoring in mathematics and physics. He graduated on 7th February 1947. In 1946-1951 he studied mathematics at Poznań University at the Faculty of Mathematics and Natural Science, in the first trimester as an extraordinary student. On 23rd October 1951 he obtained the degree of Master of Philosophy in Mathematics. He wrote his master thesis "On Besicovitch spaces of generalized almost periodic functions" under the supervision of professor Władysław Orlicz.#### Achievements

From 1st September 1949 to the end of February 1957 professor Musielak worked first as a younger assistant, and then as an assistant and an older assistant at the Division of Mathematics at Poznań University, managed by professor Władysław Orlicz.From 1st March 1957 to 31st December 1962 he lectured at the Division of Mathematics and when it was divided into two departments, he was a lecturer at the Department of Mathematics I, which was also managed by Władysław Orlicz.

On 2nd April 1958 the Council of the Faculty of Mathematics, Physics and Chemistry of Adam Mickiewicz University conferred on him the title of scientific candidate of mathematical sciences for his paper "On absolute convergence Fourier-series of almost periodic functions and periodic functions of many variables" that was written under the supervision of professor Władysław Orlicz.

On 9th June 1962 he obtained the title of reader for the paper "On some spaces of functions and distributions". Reviewers of this paper were professors: Stanisław Hartman, Władysław Orlicz and Roman Sikorski. In 1964 he was awarded the Prize of Minister of Higher Education of 3rd degree for outstanding scientific achievements presented in his qualification for the reader's title.

From 1st January 1963 to 1969 he was employed as a permanent reader at the Department of Mathematics I and then in the new-founded Institute of Mathematics at Adam Mickiewicz University.

On 5th April 1971 the State Council conferred on him the title of extraordinary professor as a result of which he obtained the position of professor at Adam Mickiewicz University. On 21st May 1980 he obtained the title of ordinary professor.

On 1st September 1969 he became vice director responsible for scientific matters in the newly established Institute of Mathematics. He fulfilled this function till 31st August 1975. He established the Division of Theory of Real Function in the Institute of Mathematics and was its head for over 30 years, from 1st October 1969 to 31st August 1999.

In 1975-1978 he was vice dean in charge of students' matters at the Faculty of Mathematics, Physics and Chemistry and in 1978-1981 he was vice dean in charge of general matters at the Faculty of Mathematics and Physics and in 1981-1984 ha was dean of this Faculty.

In 1984 he was elected prorector of Adam Mickiewicz University in charge of matters of international cooperation. He held this post till 30th November 1985. From 1st February 1991 to 31st August 1993 he was head of the Institute of Mathematics at the Faculty of Mathematics and Physics. Professor Musielak conducted scientific research and gave lectures in many colleges and research institutes such as Institute of Mathematics of the Polish Academy of Sciences and Institute of Mathematics of Poznań University of Technology. He was a grant holder of Papa Institute of Fundamental Research in Bombay. He worked as a guest professor at the University of Notre Dame in Notre Dame in Indiana, USA, and at Martin Luther University in Halle and Christian-Albrechts-University in Kiel, Germany.

#### Scientific interests

Professor Musielak has made an important contribution to the development of mathematical analysis, particularly of functional analysis. Many of his works found a permanent place in the world literature.At first, he did research work on the question of Fourier series in relation to the trigonometrical system and to other orthogonal systems, especially to the Haar-system. This research was later continued in many aspects, also for other orthogonal systems than trigonometrical system e.g. in a paper on the Haar-system written in cooperation with Zbigniew Ciesielski and published in 1961 in "Colloquium Mathematicum". This paper laid foundation for further research of Zbigniew Cisielski referring to the Franklin-system and for works of the Russian school of Uljanow.

In his next works professor Musielak dealt with constructive theory of function, especially with the approximation by trigonometrical polynomials and by other classes of functions. In this field 14 doctoral theses have been written under his supervision.

At the beginning of the 60s a series of works was published written by professor Musielak and professor Orlicz. The series was entitled "Notes on the theory of integral". These papers referred to absolutely additive vectorial integrals and to weak integrals.

In his postdoctoral lecturing qualification finished in 1962 (4 years after obtaining the doctor's degree) he introduced and researched M-integrable distributions and their spaces, which are a natural generalization of Orlicz space. In this field he has supervised 2 doctoral theses.

Modular spaces played an essential role in scientific research of professor Musielak. The general axiomatic of these spaces was formulated in 1959 in a paper by Władysław Orlicz and Julian Musielak. They for the first time formulated the axiomatic of modular without partial order and without convexity of modular. This work and its continuation had a significant influence on development of the theory of modular spaces and generalized Orlicz spaces. The explored functional spaces were called later Musielak-Orlicz spaces.

He also explored some other examples of modular spaces e.g. spaces of function with complete variation, of strongly limesable function and of integrable function with mixed norms. In these fields professor Musielak has supervised 11 doctoral theses.

In 1983 he wrote a monograph "Orlicz Spaces and Modular Spaces", published by Springer in the series Lecture Notebook in Mathematics. The monograph was and still is a significant source of quotations from this field of research.

At the turn of the 60s and 70s Julian Musielak introduced and researched, in cooperation with other mathematicians, different classes of space referring to modular spaces. There were convertible modular, bimodular, two-modular and F-modular spaces and also spaces based on families of modulars dependent from parameter. In the late 70s he obtained, in cooperation with Henryk Hudzik and Ryszard Urbański, results of the scope of interpolations of operators in Musielak-Orlicz spaces of vectorial functions and, in cooperation with Henryk Hudzik and Anna Kamińska, results referring to the operator of plexus in Orlicz-spaces and of coefficient of convexity of those spaces.

In the 80s and 90s professor Musielak dealt mainly with linear and non-linear integral operators and their application in the theory of approximation, theory of non-linear integrable equations and in the theory of limesability, using the device of functional modular spaces. On this subject 4 doctoral theses have been written under the supervision of professor Musielak.

During the last decade, the works of professor referred mainly to non-linear integral operators in functional spaces and their applications. A considerable part of these papers came into being in cooperation with Italian mathematicians Carlo Bardaro and Gianluca Vinti from Perugia.

The scientific output of professor consists of 157 scientific works, e. g. 3 manuals, 5 scripts, 1 monograph and many reviews, biographical and popular scientific articles. In 1976 the Polish Scientific Publishing House published his "Introduction into functional analysis". In 1993 the Scientific Publishing House of Adam Mickiewicz University published "Mathematical analysis", vol. I, part 1 and 2 and 1999 volume II, written by professor Musielak and his wife, doctor Helena Musielak. In 1977 professor Musielak was awarded the Prize of Minister of Education of 2nd degree in recognition of his outstanding manuals for students.

Professor Musielak enjoys close scientific relations with many universities. He presented the results of his researches at many Polish and international conferences. In 1969 he organized the conference "Functional Analysis" and in 1972 the conference "Theory of Approximation", which both took place in Poznań. He was one of the inspirers and organizers of scientific researches on functional spaces.

Professor Musielak gave many review lectures on mathematics on sessions of Polish Mathematical Society, Polish Physical Society, Poznań Society of Friends of Science.He was awarded many times in recognition of his scientific achievements, e.g. in 1981 and in 1984 he was awarded the Prize of Minister of Science, Higher Education and Technology of 1st degree.

#### Didactics

Professor Musielak calls great attention to educating young scientific workers for different colleges and universities in Poland. During 50 years of his scientific and didactic work he has given obligatory and facultative lectures, classes and seminars on most mathematical subjects for students, postgraduates and assistants of Adam Mickiewicz University and other universities. He has been giving a scientific seminar on functional analysis and theory of real functions for over thirty years. At Adam Mickiewicz University over 500 master theses and 36 doctoral dissertations have been written under his supervision. His nine postgraduate students have become professors. He was tutor of numerous Polish and foreign students and grant holders.

He wrote about 60 reviews of doctoral theses, 14 reviews of postdoctoral lecturing qualifications and 4 reviews on applications for scientific titles.

In different periods of his activity he was in charge of mathematical student circle where students to develop their scientific interests. n recognition of his achievements in educating scientific workers he was awarded prizes of Minister of Higher Education:I in 1969 - of 3rd degree, in 1975 - of 2nd and in 1988 of 1st degree and in 1999 he obtained the Medal of 80th anniversary of Adam Mickiewicz University. In 1966 he was decorated by the Council of the City of Szczecin with the distinction "Gryf Pomorski" in recognition of his achievements in didactic work in consulting points of Adam Mickiewicz University and in 1976 by the Council of the City of Zielona Góra with the distinction "For Services to Development of Zielona Góra Province".#### Organizations

From 1974 to 1998 professor Musielak was a member of the Committee of Mathematical Sciences of the Polish Academy of Sciences, and in 1987-1989 he was a member of the Presidium of this committee. From 1973 to 1978 he was a member of Experts' Panel on Mathematics at the Institute for Teachers' Education and Educational Studies in Warsaw. In years 1976-1978 he was a member of Panel for School Programmes at the Department of Education. In 1984-1989 professor was a member of Scientific-Didactic Panel of Natural Science at the Department of Science and Higher Education. In 1980 he was awarded the Medal of Committee of National Education for outstanding services to education.He is an active member of Polish Mathematical Society and he has had many responsible functions there. In 1989-1991 he was its vice president and in 1991-1993 its president nationwide. From 1962 to 1967 and

from 1973 to 1977 he was vice president of Poznań Department of Polish Mathematical Society and in 1971-1973 and 1987-1989 he was its president. From 1969 to 1971 and from 1981 to 1983 professor Musielak was a member of Revisory Committee in Main Board of Polish Mathematical Society and in 1987-1988 he was its chairman. In 1993-1996 he was a member of the Central Committee of Scientific Titles and Degrees for which he wrote many reviews. He also reviewed research projects on order of the Committee of Scientific Researches.

He is a founder member of the Club of Catholic Intelligence in Poznań, a member of Poznań Society of Friends of Science and American Mathematical Society.

He was a member of the Polish Society of Teachers and at present he is a member of founder circle of the trade union "Solidarność".

Professor is very engaged in publishing work. He has worked in the editorial committee of the periodical "Commentationes Mathematicae" since 1960 and since 1990 he has been its editor-in-chief. He is also a member of the editorial committee of the periodical "Fasciculi Mathematici". Till now he is the editor-in-chief of the periodical "Functiones et Approximatio" that was established by him in 1973 and is published by Adam Mickiewicz University. Since 1989 he has been a member of the editorial committee of the periodical "Mathematica Japonica". He also wrote many editorial reviews for Zentralblatt für Mathematik and for Mathematical Reviews.In recognition of his services and achievements professor Julian Musielak, apart from the above mentioned prizes, was decorated with two highest state distinctions: in 1973 with the "Krzyż Kawalerski Orderu Odrodzenia Polski" and in 1977 with the "Brązowy Medal za Zasługi dla Obronności Kraju". In 1978 he was decorated with the Honorary Distinction of the City of Poznań, in 1979 - with the Medal of Mathematical Contest and in 1981 - with the Medal "Solidarność Wielkopolska".

The above facts are a modest illustration of professor Musielak's contributions as a scientist, a teacher, a lecturer, a science animator and a man who is a unique example for young generations of researchers, lecturers and teachers.

Attention: The above text is a summary of the biographic article "..........................." written by .................................. and published in the book "Serta Methematice Juliani Musielak" (1996, p. 9-13).

Summarized by Magdalena Roszak.Edited and translated by Lucyna Brzozowska