is a Japanese

Japanese people

The are an ethnic group originating in the Japanese archipelago and are the predominant ethnic group of Japan. Worldwide, approximately 130 million people are of Japanese descent; of these, approximately 127 million are residents of Japan. People of Japanese ancestry who live in other countries...

 chemist

Chemist

A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...

, emeritus professor of the Ochanomizu University

Ochanomizu University

is one of only two national women's universities in Japan. The other one is the Nara Women's University.-History:Ochanomizu University was founded in 1875 as a teacher training institute for women located in Tokyo's Ochanomizu neighborhood. On September 1, 1923, the campus was destroyed in the...

, Tokyo

Tokyo

, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...

, Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, the namesake of the Hosoya index

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 the number of non-empty matchings plus...

 used in computational chemistry

Computational chemistry

Computational chemistry is a branch of chemistry that uses principles of computer science to assist in solving chemical problems. It uses the results of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids...

.

Haruo Hosoya was born in Kamakura

Kamakura, Kanagawa

is a city located in Kanagawa Prefecture, Japan, about south-south-west of Tokyo. It used to be also called .Although Kamakura proper is today rather small, it is often described in history books as a former de facto capital of Japan as the seat of the Shogunate and of the Regency during the...

, Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

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

University of Tokyo

, abbreviated as , is a major research university located in Tokyo, Japan. The University has 10 faculties with a total of around 30,000 students, 2,100 of whom are foreign. Its five campuses are in Hongō, Komaba, Kashiwa, Shirokane and Nakano. It is considered to be the most prestigious university...

. In 1964 he wrote his Ph.D.

Ph.D.

A Ph.D. is a Doctor of Philosophy, an academic degree.Ph.D. may also refer to:* Ph.D. , a 1980s British group*Piled Higher and Deeper, a web comic strip*PhD: Phantasy Degree, a Korean comic series* PhD Docbook renderer, an XML renderer...

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

Michigan

Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....

, with prof. John Platt

John Platt

John Platt is a Principal Researcher in the Machine Learning department at Microsoft Research. Platt has worked for Microsoft since 1997. Prior to Microsoft, Platt had served as Director of Research at Synaptics....

), in 1969 he became associate professor 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 topological index

Topological index

In the fields of chemical graph theory, molecular topology, and mathematical chemistry, a topological index also known as a connectivity index is a type of a molecular descriptor that is calculated based on the molecular graph of a chemical compound. Topological indices are numerical parameters...

 (a graph invariant) as the total number of matchings of a graph plus 1. The Hosoya index is often used in computer (mathematical)

Mathematical chemistry

Mathematical chemistry is the area of research engaged in novel applications of mathematics to chemistry; it concerns itself principally with the mathematical modeling of chemical phenomena...

 chemistry investigations for organic compounds.

In 2002-2003 the Internet Electronic Journal of Molecular Design 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.