Prof. dr 
Aleksandar Pakvor

Građevinski fakultet, 
Bulevar Kralja Aleksandra 73
11000 - Beograd
Tel. 011/337-0152
Faks 011/3370253
Kuća: Nehruova 105
11070 - Novi Beograd,
Tel. 011/177-6392
E-mail: 
pakvor@imk.grf.bg.ac.yu
 

   Prof. Dr. Aleksandar J. Pakvor was born in 1934 in Novi Sad. He graduated in 1959 from the Faculty of Civil Engineering University of Belgrade where he received his M.Sc. (1972) and Ph.D. (1979) degrees. He started his career at the Jaroslav Černi Institute and moved to the Faculty of Civil Engineering in Belgrade in 1965, where he started lecturing on Concrete Structures. For a long time he was a lecturer at the Faculty of Technical Sciences in Novi Sad. He is the Head of the Institute for Materials and Structures of the Faculty of Civil Engineering. He is an active member of IABSE and CEB, and their bodies and task working groups. He was invited lecturer in the country and abroad, and delivered plenary lectures at different scientific events. He is the author of several books and over 180 papers. He is the Head of a federal research project and a republic sub-project, as well as of two republic sub-projects on technological development. His activities include design, expertises, consultations and reviewing. He received the October Prize of the City of Belgrade in 1985, the Best Design in Serbia and Yugoslavia in 1986 and the best project in civil engineering in Yugoslavia in the field of science and technology in 1996 and 1997.

Prof. dr 
Nedeljko Parezanović

Kuća: Cara Uroša 6a
11000 - Beograd
Tel. 011/626-504. 
E-mail: 
nparezan@matf.bg.ac.yu
 

   Prof. Dr. Nedeljko S. Parezanović was born 1932. He graduated from the Faculty of Natural Sciences and Mathematics in Belgrade in 1957, at the Department of Mechanics. He defended his Ph.D. thesis at the same Faculty in 1961. Upon graduation he kept posts at scientific institutes, and most of his professional career he spent as professor at the Faculty of Mathematics in Belgrade. His research work was focused on solving of differential and integral equations using computers.
   He published 56 papers in international and national journals and proceedings. His most important results are achieved in solving of Fredholm type integral equations. He was one of the designers of the domestic electronic digital computers, both for large systems and desk calculators. He is the author of 24 books in the field of computer science. He received golden plaque by The Institute for Text-books and Teaching Aids in Belgrade, for his achievements in writing text-books.

Prof. dr 
Vojislav Pavlović

Veterinarski fakultet, 
Klinika za porodiljstvo.
Bulever JNA 18, 
11000 - Beograd
Tel. 011/685-666/335
Faks. 011/614-402 
Kuća: Vladimira Gortana 43 
11080 - Zemun,
Tel: 011/614-402
E-mail: 
vpavlovic@vet.bg.ac.yu
 

   Prof. Dr. Vojislav M. Pavlović was born in 1950 in Belgrade where he graduated from the Faculty of Veterinary Medicine, University of Belgrade in 1976.  He  has been first employed at the Institute of Medical Research, Department of Parasitology. In 1978 he was elected assistant professor at the Department of Obstetrics, Sterility and Artificial Insemination of the Domestic Animals, of the Faculty of Veterinary Medicine in Belgrade. Demand for the new technologies led him to enroll the School for application of radioisotopes in Vinča in 1980, after he introduced RIA, as a diagnostic method in veterinary medicine. He defended his MSc thesis in 1981, and PhD thesis in 1987, and was elected associate professor in 1993. He participated actively in a number of scientific research projects. He is the Head of many collaborative and contracting projects with farms dealing with cattle, horse and sheep breeding. He has published 105 scientific papers, out of which 12 were presented as plenary lectures at the international meetings, 11 were published in international journals. As an invited lecturer he delivered his lectures at the Faculties of Veterinary Medicine in Stara Zagora (Bulgaria), Skopje, as well as on the first bilateral congress of the Aristhotelas University from Salonika and University of Belgrade in 1996. He is a member of the Executive Board of the Serbian Society of Veterinary Medicine and President of the section for ultrasound diagnostics.

Prof. dr 
Stanislav Pejović

Mašinski fakultet,
27. Marta 80
11000 – Beograd,
Tel. 011/337-0266.
Kuća: Čajnička 22
11000 - Beograd
Tel. 011/533-4434
533-9708
 

   Prof. Dr Stanislav T. Pejović was born in 1933 in Belgrade. In 1958 he graduated from the School of Mechanical Engineering in Belgrade, where he earned his PhD degree in 1964. He got the post at the School in 1960 and became a full professor in 1977, holding the post till 1998, when he retired. He is a member of the American Society of Mechanical Engineers, Council of the International Research Center in Beijing, visiting professor of the University of Singapore and corresponding member of ASME  Hydro Power Technical Committee. He is an acknowledged expert in the field of hydraulic machinery, hydropower and fluid mechanics. He is the author of 8 numerical programs for currents in hydraulic machines and systems, over 120 papers published in domestic and international journals and proceedings, and delivered a number of invited lectures in the country and abroad. In addition to 13 books in the Serbian language, he is also the author of two books and instructions for design of international importance. He was cited in over 70 published papers in the country and abroad. He designed 3 test installations and 14 hydraulic plants, analyzed hydraulic shocks and oscillations, and studied new hydropower plants.

Dr Milutin Penčić
   Dr Milutin Penčić was born in Gradište, municipality of Pirot in 1928. He completed elementary school in Gradište and high school in Pirot in 1947. As a scholar of the Serbian Academy of Science and Art he graduated from the Faculty of Agriculture, University of Belgrade in 1952. Dr Penčić  worked at the Agricultural Research Institute in Kruševac between 1953 and 1958. Between 1958 and 1986 he worked at the Maize Research Institute, Zemun Polje, where he was awarded all scientific degrees. He was a Vice President of the Federal Committee for Science, Technology and Informatics and a federal advisor for scientific and technological development at the Federal Executive Council (Federal Government) from 1986 to 1993. 
 Dr. Penčić directly contributed to the scientific and research work within the fields of physiology and biophysics of plants and plant genetics and breeding (genetic resources). He defended his PhD thesis within this field at the Faculty of Agriculture, University of Belgrade in 1962. Beside original papers and manuscripts (128) published in the country and abroad, he participated in many international symposia with his papers and posters. The characteristics of Dr. Penčić's opus is the initiation of new research fields in our country: first studies on plant biophysics, plant genetic resources and also on the application of radioisotopes in studies on plant physiology. The majority of published papers are related to physiology of stress, nature of bioelectric potentials in living plant cells. The following papers are characteristics for his studies related to plant genetic resources: Genetic Resources Relevant for Plant Breeding and Selection, The Role of Genetic Resources in Preservation of Biological Diversity, Management of Plant Gene Pool in Yugoslavia, Importance of Plant Gene Banks for Selection and Seed Production.
Beside the direct scientific and research work, he strongly contributed to the organisation of science. He was a head of a department, Director of R&D, Deputy Director and Director General at the Maize Research Institute, Zemun Polje. He also used to be a Vice President and a President of the permanent conference of scientific and research organisations of Belgrade. Dr. Penčić was Vice President of Federal Committee for Science, Technology and Informatics.
For 12 years Dr. Penčić was an editor-in-chief of the Journal of Scientific Agricultural Research. Furthermore, he was an editor-in-chief of the international bulletin on maize ZEA. Dr. Penčić was an initiator of the national programme on plant genetic resources and instalment of the Yugoslav gene bank. 
Dr. Penčić was elected a first President of the managing board of FAO/UNDP of European Cooperative Programme for Crop Genetic Resources (ECP/GR, 1979-1982). He was a member of the executive committee of the Programme and a national coordinator in the period form the establishment to 1998. He was a coordinator of FAO ECP/GR Maize Data Base, as well as, of the Yugoslav commission for UNESCO. He is a member of the Federation of European Phytophysiologists.
As an expert of the UN Food and Agriculture Organisation, Dr. Penčić participated in the implementation of the national programme on seed production in Tanzania and national programmes on maize production in Angola and Mozambique. He is also a President of the Yugoslav Academy of Engineers and a President of the Yugoslav Association for Protection of Biological Diversity of Agriculture (AGROGEN YU).
 Dr. Penčić received many recognitions and awards for his scientific and professional activities.

Prof. dr 
Života Perišić

Građevinski fakultet, 
Bulevar kralja Aleksandra 73, 
11000 - Beograd
Tel. 337-0890.
Kuća: Dositejeva 49
11000 - Beograd
Tel. 011/185-190
E-mail: 
perisic@imk.grf.bg.ac.yu
 

   Prof. Dr Života M. Perišić was born in 1935 in Belgrade. He graduated from the Faculty of Civil Engineering, University of  Belgrade, in 1959, and received his MSc and PhD degrees in 1972 and 1979 respectively. In 1965 he got a post at the School of Civil Engineering lecturing on reinforced and prestressed concrete structures. He was the Dean in the period 1991-1996, and he is currently the President of the Faculty Managing Board. He is very active in professional organizations IABSE and fib. He was an invited lecturer in Lausanne and also delivered lectures on a large number of universities and international professional meetings. He is the author of several books and over 200 papers. He has been an active designer, expert and consultant on most important construction works of the Yugoslav civil engineering.
   He received the October Prize of the City of Belgrade in 1985, Award for the Best Design in Yugoslavia in 1986, Award for the Best Achievement in the Field of Science and Technology in Constructions in 1996 and 1997 and the Life Achievement of  the Yugoslav Society for Civil Engineering in 1998. He was decorated with the Medal of Labor with Silver Wreath, Medal for Merit with Silver Star and Medal of Labor with Golden Wreath.

Prof. dr 
Slobodan Perović

Pravni fakultet, 
Bulevar Kralja Aleksandra 67
11000 - Beograd
Tel. 011/324-1501, 
Kuća: Proleterskih brigada 74
11000 - Beograd
Tel. 011/444-8459, 
444-6910
 

   Prof. Dr Slobodan K. Perović was born in 1932, graduated from the School of Law, University of Belgrade (1956) where he earned his PhD in Civil Law (1963). He went all the way from assistant to his current position of the full professor and Head of Department of Civil Law. He was a mentor to numerous master and doctoral theses. He is a member of the Slovenian Academy of Sciences and Arts, Society for Comparative Law in Paris, Legal Council of Yugoslavia; He is the President of the Scientific Society of Serbia and the Yugoslav Association of Lawyers. He is the founder of the Kopaonik School of Natural Law. He is an arbiter for international arbitrages in the field of international commercial traffic. He is the Editor in chief of journals "Legal Life" and "Scientific Review", the chief editor of the Encyclopedia of Proprietary Law and General Encyclopedia of Law. He is the President of the editorial board of the Classics of the Yugoslav Law edition. He participated at numerous scientific conventions, both in the country and aborad (over 50), most commonly with the plenary presentation. He is the author of several books, textbooks and monographs, research studies and several hundreds of papers published in domestic and international publications in the field of civil law, comparative law and philosophy of law. With his overall achievement in all fields of law he influenced development of legal theory and practice that earned him the high reputation in the country and abroad.

Prof. Dr 
Nadežda Petranović

Fakultet za fizičku hemiju
Beograd, Studentski trg 16
tel: 011/187-133
Kuća:
tel: 011/452-579

   Prof. Dr Nadežda Petranović  was born 1934. in Belgrade. Education: Ph.D., 1972; M.Sc., 1967.; Graduate Degree, 1959. Employment: Head of Department of Electrochemistry and Chemical Kinetics, Faculty of Physical Chemistry, 1991; Full Professor, 1991; Associate Professor, 1984; Docent, 1975; Assistant, 1959. Organizational Memberships: Faculty of Physical Chemistry, 1990 to present; Faculty of Sciences, 1960-90. Teaching: Chemical Thermodynamics (3rd semester), Physical Chemistry of Materials (8th semester). Areas of interest: Adsorption processes, Superioni Teaching: Chemical Thermodynamics (3rd semester), Physical Chemistry of Materials (8th semester). Superionic conductors, Phase transformations and synthesis of new materials, Metal microstructure in zeolites. Projects: Physico-chemical processes in homogeneous and heterogeneous systems (project leader), with Ministry of Sciences and Technology of Serbia, for the period 1996-2000. Membership in Learned Societies: Serbian Chemical Society, International Zeolite Association, American Chemical Society, Society of the Physical Chemists of Serbia, Yugoslav Material Research Association.

   Participant in: Intl Conf Zeolites, 1973, 1980, 1984, ISE Meeting, 1975, 1976, 1978, 1980, 1981, 1982, German-Yugoslav Meeting, 1978, 1979, Sci Ceramics, 1979, 1983, 6th, 7th and 8th CIMTEC, 1986, 1990, 1994, Intl Conf Defects, 1988.

   Published Works: Author, Chemical Thermodynamics (textbook), 1996 & 1992; over 100 Articles in Journals and Congress Materials including: Correlation between Structure and Transport Properties, Salt Inclusion in Zeolite Structure, Silicates as Electric Conductors, Surface Phenomena on Zeolite A in Molten Salts Media, Thermochemical Behavior of Zeolite Inclusion Complexes.

   Honors and Awards: Award Society of the Physical Chemists of Serbia; listed in Dictionary of International Biography.


Prof. dr 
Predrag Petrović

Institut za kardio-
vaskularne bolesti,
KC Srbije,
Koste Todorovića 8
11000 - Beograd,
Tel. 011/361-5786
361-0717/10.
Kuća: Đuke Dinića 7
11000 - Beograd,
Tel. 011/410-843
 

   Prof. Dr. Predrag Lj. Petrović was born in Skopje in 1935. He graduated from the Faculty of Medicine in Belgrade in 1960. He passed his Board in general surgery in 1969 and in 1978 he was awarded a PhD degree. He was elected full professor of the Faculty of Medicine in Belgrade at the Department of Surgery in 1990. For his advanced training, he spent a year at Baylor University in Houston, USA (with Prof. Michael De Bakey). Upon his return, he continued his work on cardiosurgery at the former II surgical clinic, today, Institute of Cardiovascular Diseases of the Clinical Center of Serbia, where he is Director. He had particular influence on development of cardiosurgery associated with surgical treatment of acute aortal dissection, endocarditis, heart tumors, complications of the acute myocardial infarction, heart rhythm disorders and deep hypothermia. Prof. Petrović is a full member of the Surgical Section of the Medical Academy of the Serbian Medical Society, Yugoslav representative in the European Association of Cardiovascular Surgeons, and member of the International Cardiovascular Society Dr. Michael De Bakey. Prof. Petrović published more than 200 scientific papers, he is the author or co-author of 3 text-books, and mentor for many MSc and PhD theses. His prominent contribution to the development of cardiosurgery was awarded with numerous acknowledgements, both in the country and abroad.

Prof. dr 
Radivoj Petrović

Saobraćajni fakultet, 
Vojvode Stepe 305, 
11000 - Beograd
Tel. 011/493-211.
Kuća: Vranjska 29, 
11000 - Beograd
Tel. 011/418-964
 

   Prof. Dr. Radivoj I. Petrović was born in 1933. He graduated from the School of Electrical Engineering in Belgrade in 1958, defended his MSc thesis in 1963, and was awarded Ph.D. degree at the same School in 1964. During the period 1958-61 he was employed at the Institute in Vinča, and thereafter for three decade in ‘Mihajlo Pupin’ Institute where he went all the way from investigator, head of the laboratory to deputy director of the Institute in charge of scientific research.
   Presently, he is a full professor at the School of Transportation and Traffic Engineering, University of Belgrade. He is the author of about 200 scientific papers. out of which more than a half were published in international journals, 8 scientific monographs , two of which were published abroad.
   His scientific work was particularly focused on the theory of systems and operational studies. He received a number of scientific rewards and acknowledgments by Republic of Serbia, City of Belgrade and some other scientific organizations. He was the president of the European Jury for Awarding of EURO Golden Plaque for scientific achievements in the field of operational studies.

Prof. Dr 
Milena Pokrajac (Stanojčić)
   Prof. Dr Milena Pokrajac (Stanojčić)  was born in Kriva Reka, Serbia, Yugoslavia in 1948. She graduated from the Faculty of Pharmacy, University of Belgrade in 1974, and received her M. Sc. & Ph. D. degrees in Pharmacokinetics in 1978, and 1980, respectively. The specialist in Pharmacoinformation she has been since 1988, and in Clinical Pharmacy since 1998. The professional career at the Faculty of Pharmacy she began in 1975, where she was elected assistant professor in 1978, lecturer in 1982, associate professor in 1988 and professor of Pharmacokinetics in 1993, the subject which she introduced in Pharmacy studies with us. Since 1989 she is a leader of postgraduate studies in Pharmacokinetics, and specialization in Clinical   Pharmacy, taking part in the education of Pharmacoinformation specialist as well. She is teaching Pharmacokinetics, Pharmacokinetic Methodology, Drug Metabolism and Clinical Pharmacokinetics. Since 1982 she has been leading and taking part in Research Projects financed by Ministry of Science of the Republic of Serbia.
 During 1978/79 she was doing research in Bioanalysis, Drug Metabolism and Pharmacokinetics at Research Laboratory, Dept. of Pharmacy, Chelse College, University of London (Prof. A.H.Beckett). She has also been visiting scientist for several times: Chelsea College, London, 1983 and 1985; Division of Clinical Pharmacokinetics, Gainesville College of Pharmacy, University of Florida, USA, 1987 (Prof. S.H.Curry); Center for Bio-Pharmaceutical Sciences, Leiden University, The Netherlands, 1989 (Prof. D.D.Breimer); College of Pharmacy and Nutrition, University of Saskatchewan, Saskaton, Canada, 1997 (Prof. K.K.Midha & Prof. J.W.Hubbard); Institute of Experimental Biopharmaceutics, Joint Research Center of the Academy of Sciences of the Czech Republic and PRO.MED. CS Praha, Hradec Kralove, 2002 (Prof. J.Kvetina).
 She has published over 180 papers (120 papers are in extenso) so far in the field of bioanalysis, drug metabolism, bioavailability/bioequivalence, pharmacokinetics and clinical pharmacokinetics, most of them in international journals. Prof. Pokrajac has given many lectures  at over 50 international and national scientific Congresses and professional Simposya. She was president of the Scientific Board and plenary lecturer of the II Yugoslav Congress of pharmacists with international participation held in Belgrade in 1998.
 Prof. Pokrajac has published four books in several editions (two are in the field of Pharmacokinetics): Pharmacokinetics-Handbook, 1995 and 2001  and Pharmacokinetics-Textbook, 1996 and 2002. She is a member of Editorial Boards of several journals and she was the editor of Archives of Pharmacy. She is a member of a number of national and international professional societies. She was a member of Federal Drug Committee during more than two periods, as well as of some others scientific and professional Commissions. She has been pharmacokinetic consultant to pharmaceutical industry for over fifteen years. Prof. Milena Pokrajac has been awarded by Belgrade Pharmacists Institution, and by the Faculty of Pharmacy (gold acknowled gment). She founded Dept. of Pharmacokinetics at Faculty of Pharmacy in Belgrade in 1992, and she has been head of it since then. 

Prof. dr 
Jordan Pop-Jordanov

Kuća: Orce Nikolov 75,
91000 - Skopje, Makedonija
Tel. (389 91) 238-338
 

   Prof. Dr Jordan P. Pop-Jordanov was born in 1925 in Veliko Gradište. He graduated from the School of Philosophy in Skopje (1956) and School of Electronic Engieneering in Belgrade (1960), where he received his PhD degree in technical sciences (1964). In January 1971, he got a post at the School of Electrical Engineering, University of Belgrade, where he was elected professor in 1976, and retired early in 1984. In the same year he was elected the President of the Macedonian Academy of Sciences and Arts, where he served till the end of 1991. He is a member of the New York Academy of Sciences, European Academy of Sciences and Arts, American Physical Society, International Society for Solar Energy and Council of the Roman Club for the future of Europe. His main fields of professional interest included: neutron and reactor physics, non-classical energy, technological risks and philosophy of natural sciences. He published three textbooks: Non-balanced Statistical Physics (1981) and Quant Electrodynamics (1983). He is the author or co-author of about 200 papers, where about two-thirds were published abroad.

Prof. dr
Obren Popović

KBC "Zvezdara"
Dimitrija Tucovića 161,
11000 - Beograd,
Tel: 011/413-442
Faks 011/444-7633
Kuća: Nevesinjska 7
11000 - Beograd,
Tel. 011/434-665
 

   Prof. Dr. Obren S. Popović was born in 1934 in Belgrade, and he graduated from Medical School, University of Belgrade in 1959. Since 1963, he has been employed at “Zvezdara” University Medical Center in Belgrade. In 1976 he organized Metabolic Gastroenterology Unit, in order to facilitate and improve diagnosis and treatment of malabsorption syndromes and chronic diarrhea. The unit has been involved in research projects from the very beginning. The most important achievement was the description of a new entity characterized by primary ileal villons atrophy with normal jejunum (Popović O. et al.: Primary bile acid malabsorption. Histological and immunological studies in three patients. Gastroenterology 1987, 92:1951-1858). The disorder is characterized by diarrhea due to malabsorption of the bile acids and controlled by cholestyramine. Prof. Popović was founder and editor of an international journal ‘Archives of Gastroenterolohepatology’ (1982-1998), and his hospital journal entitled ‘Zvezdara Clinic Proceedings (1995- ).
   He is a member of Yugoslav Society of Gastroenterology, Honorary Member of Yugoslav Society of Pathology and British Society of Gastroeneterology. He is also a member of Balkan Medical Union and Mediterranean Medical Society.

Prof. Dr 
Veljko Potkonjak

Elektrotehnički fakultet
11000 Beograd,
Bulevar Kralja Aleksandra 73
Kuća:
tel: 011/4890-842

   Prof. Dr Veljko Potkonjak was born in Belgrade in 1951. He studied at the Faculty of Electrical Engineering, University of Belgrade and graduated in 1974. The same year he was accepted in postgraduate studies at the same faculty to finally finish in 1977. In 1981 V. Potkonjak defended his doctoral thesis.

   After graduation, Veljko Potkonjak started his work at the Faculty of Electrical Engineering, Belgrade, as an assistant in the field of mechanics. He became an assistant professor in 1985, and in 1990 he was promoted to the rank of associate professor and finally in 1995 to the rank of full professor. During his educational career, professor V. Potkonjak has been teaching mechanics, robotics and biomechanics. He was also a teacher at the Faculty of Electronics, University of Niš, and at the Technical Faculty in Čačak.

   Research interests of Prof. Veljko Potkonjak primarly concern robotics. Within this field he received his M. Sc. and Ph. D. degees. His attention has been oriented to problems concerning the modeling of robotic system and the implementation of these models to design and control. He is the a author/coauthor of two international research monographs (in English), several textbooks for university and for secondary schools, about 40 international journal papers, 24 papers on international conferences, and certain number of papers in Yugoslav journals and domestic conferences. Prof. Potkonjak, has made a large number of reviews for respected international journals and conferences as well as for domestic conferences. Within the field of robotics he was engaged in several projects, sometimes heading and sometimes participating.


Prof. dr
Jagoš Purić

Fizički fakultet, 
Studentski trg 16
11000 - Beograd
Tel/faks. 011/630-152. 
Rektorat Univerziteta
u Beogradu,
Studentski trg 1,
11000 – Beograd
Tel. 011/635-153.
Kuća: Dositejeva 11,
11000 - Beograd
Tel. 011/328-2179
 

   Prof. Dr Jagoš M. Purić was born in 1942 in Kovren. He graduated in 1965 from the University of Belgrade, Faculty of Natural Sciences and Mathematics, at the Department of Physics. He received his MSc and PhD degrees in 1969 an 1972, respectively. He was elected Assistant Professor in 1973, Associated Professor in 1981, and Professor in 1984. Prof. Purić scientific work is related to the Atomic Physics, Plasma Spectroscopy, Fusion Plasma Physics and Laser Physics. He participated at many international and domestic scientific conferences presenting his papers. He is the author of several textbooks and exercise manuals. He has published more than one hundred and fifty scientific papers in the leading international journals. He has been cited in the international literature more than five hundred times. The majority of the papers is dedicated to the experimental studies of Stark’s parameters of special lines in plasma. He is the Head of the Laboratory for Plasma Spectroscopy at the Faculty of Physics where several projects in the field of plasma physics have been realized, funded by the Republic of Serbia. He was also advisor to numerous MSc and PhD theses. He cooperated with a number of laboratories in England, France, and Japan. His international reputation as a scientist contributed to the inclussion of Yugoslavia in the European Academic Research Network - EARN, and then to the BITNET.
   Prof. Purić was awarded with the October Prize of the City of Belgrade for science in 1973, and the annual Prize of the Institute of Physics in Belgrade in 1971. He has been a member of the Serbian Scientific Society since 1996, and currently is the Secretary of the Natural Science Department of that Society. Since 1998 he has been the Rector of the University of Belgrade.