is a Japanese

chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties. Chemists carefully describe th ...

and emeritus professor of

Ochanomizu University is a women's university in the Ōtsuka neighborhood of Bunkyō-ku, Tokyo, Japan. Ochanomizu University is one of the top national universities in Japan. Ochanomizu is the name of a Tokyo neighborhood where the university was founded. Hi ...

Tokyo Tokyo (; ja, 東京, , ), officially the Tokyo Metropolis ( ja, 東京都, label=none, ), is the capital and largest city of Japan. Formerly known as Edo, its metropolitan area () is the most populous in the world, with an estimated 37.468 ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. He is the namesake of the

Hosoya index The Hosoya index, also known as the Z index, of a graph is the total number of matchings in it. The Hosoya index is always at least one, because the empty set of edges is counted as a matching for this purpose. Equivalently, the Hosoya index is t ...

used in

discrete mathematics Discrete mathematics is the study of mathematical structures that can be considered "discrete" (in a way analogous to discrete variables, having a bijection with the set of natural numbers) rather than "continuous" (analogously to continuous f ...

and

computational chemistry Computational chemistry is a branch of chemistry that uses computer simulation to assist in solving chemical problems. It uses methods of theoretical chemistry, incorporated into computer programs, to calculate the structures and properties of m ...

."Haruo Hosoya"
by

Ante Graovac Ante Graovac is a Croatian scientist (born July 15, 1945 in Split, died November 13, 2012 in Zagreb) known for his contribution to chemical graph theory. He was director of 26 successful annual meetings MATH/CHEM/COMP held in Dubrovnik.

, ''Croatica Chemica Acta'' 80 (2) XXI–XXII (2007) Hosoya was born in

Kamakura is a city in Kanagawa Prefecture, Japan. Kamakura has an estimated population of 172,929 (1 September 2020) and a population density of 4,359 persons per km² over the total area of . Kamakura was designated as a city on 3 November 1939. Kamak ...

to a family of an office worker. During 1955-1959 he studied at the University of Tokyo. In 1964 he wrote his

Ph.D. A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields. Because it is a ...

thesis, "Study on the Structure of Reactive Intermediates and Reaction Mechanism". After postdoc work abroad (

Ann Arbor Anne, alternatively spelled Ann, is a form of the Latin female given name Anna (name), Anna. This in turn is a representation of the Hebrew Hannah (given name), Hannah, which means 'favour' or 'grace'. Related names include Annie (given name), ...

Michigan Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the ...

, with prof. John Platt), in 1969 he became

associate professor Associate professor is an academic title with two principal meanings: in the North American system and that of the ''Commonwealth system''. Overview In the ''North American system'', used in the United States and many other countries, it is a ...

at the Ochanomizu University, where he worked for 33 years until his retirement in 2002. After retirement he keeps working in computational chemistry. In 1971, Hosoya defined the topological index (a

graph invariant Graph may refer to: Mathematics *Graph (discrete mathematics), a structure made of vertices and edges **Graph theory, the study of such graphs and their properties * Graph (topology), a topological space resembling a graph in the sense of discr ...

) now known as the Hosoya index as the total number of matchings of a graph plus 1. The Hosoya index is often used in computer (mathematical) chemistry investigations for organic compounds. In 2002-2003 the ''

Internet Electronic Journal of Molecular Design The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pu ...

'' dedicated a series of issues to commemorate the 65th birthday of professor Hosoya. Hosoya's article "The Topological Index Z Before and After 1971" describes the history of the notion and the associated inside stories and details other Hosoya's achievements.Hosoya H.,
The Topological Index Z Before and After 1971
', ''Internet Electronic Journal of Molecular Design'', 2002, 1, 428–442 Hosoya also introduced the triangle of numbers known as

Hosoya's triangle Hosoya's triangle or the Hosoya triangle (originally Fibonacci triangle; ) is a triangular arrangement of numbers (like Pascal's triangle) based on the Fibonacci numbers. Each number is the sum of the two numbers above in either the left diagonal o ...

(originally "Fibonacci triangle", but that name can be ambiguous).Haruo Hosoya, "Fibonacci Triangle", ''

The Fibonacci Quarterly The ''Fibonacci Quarterly'' is a scientific journal on mathematical topics related to the Fibonacci numbers, published four times per year. It is the primary publication of The Fibonacci Association, which has published it since 1963. Its founding ...

'', vol. 14, no. 2 (1976), pp. 173–178.

Notes

Japanese chemists 1936 births Living people Mathematical chemistry Computational chemists Riken personnel Ochanomizu University faculty {{chemist-stub