Tuesday, September 28, 2010

Archibald Vivian Hill

Archibald Vivian Hill was born on September 26, 1886 in Bristol, England. His family had little money and Hill won his education by competing for scholarships. His secondary education was at Blundell's School from which he obtained a scholarship to Trinity College, Cambridge. At Cambridge he studied mathematics and natural sciences, graduating third wrangler (highest honors) in mathematics in 1907. After graduation with the urging of his teacher, Sir Walter Morely Fletcher, he accepted a fellowship to do physiological research that allowed him to stay at Cambridge for four more years.

With the encouragement of John Langley, the owner and editor of the Journal of Physiology, Hill began investigating "the efficiency of cut out frog muscle as a thermodynamic machine". At the time it was known that muscles produce heat in response to a twich or tetanus, in tetanus the rate of heat production declines as the stimulation continues and that the ratio of of work to total energy is dependant on the load and has a maximum of .30. Hill using a more advanced temperature sensing device was able to determine that heat was produced both during and after muscle contraction, in the recovery phase.

From 1914 to 1919 Hill devoted his time to the war effort, commanding an experimental anti-aircraft section. After the war, Hill returned to Cambridge and soon after accepted a faculty chair at Manchester University. He continued his research into the heat production of muscles, discovering that the heat produced at the initiation of a muscle contraction did not require the presence of oxygen gas. The heat produced by muscles upon recovery however was greater in the presence of oxygen than it was in nitrogen.

Working in at the same time the German biochemist Otto Meyerhof had shown that in the recovery phase lactic acid, which was believed to be the chemical product of muscle contraction, can be reconverted back into glycogen or combusted by oxidation. Hill shared the 1922 Nobel Prize for Physiology or Medicine with Meyerhof "for his discovery relating to the heat in the muscle". This synthesis of thermodynamics and biochemistry, though some was later proved incorrect, was the first coordinated explanation of muscle function. Together Hill and Meyerhof coauthored only one paper together, but Hill kept a stack of the reprints of Meyerhof's papers, which he was constantly referring to. Hill and Meyerhof received their Nobel Prizes in 1923. In 1923, shortly before the Nobel was announced, Hill accepted a professorship at London University, where he remained until 1951.

As years passed a clearer picture of the chemical processes involved in the production of high energy compounds used in muscle contraction emerged. Eventually it became clear that there were two chemical pathways by which the energy used in muscle contraction was produced, one dependant on oxygen and another independent of oxygen, the so called aerobic and anaerobic pathways. In the aerobic, with oxygen, pathway glucose, the major source of biochemical energy, is converted entirely into water and carbon dioxide. In the anaerobic pathway glucose is broken down with lactic acid as an end product. Hill's observation of a smaller heat produced in the recovery phase without oxygen is the muscle tissue rebuilding its store of high energy compounds with the production of lactic acid.

After receiving the Nobel Prize Hill continued his work on muscle biophysics and extended his research to the measurement of heat released by nerve impulses. His work is largely responsible for the emergence of the study of biophysics. Other honors he received include election to the Royal Society in 1918, the Royal Society's Copley Medal in 1948 and numerous honorary doctorates from universities British and foreign. He served as a member of Parliament, representing Cambridge from 1940 to 1945.

Hill died on June 3, 1977.


Bassett Jr., David R.; Scientific Contributions of A. V. Hill: Exercise Physiology Pioneer; Journal of Applied Physiology(2002)93:1567-1582

Archibald V. Hill Nobel Biography

Archibald Hill Wikipedia Entry

Monday, September 20, 2010

Jean Baptiste Joseph Delambre

Jean Baptiste Joseph Delambre was born near Amiens, France on September 19, 1749. The eldest child in his family, he suffered from a bout of smallpox at the age of 15 months. His parents feared he would loose his eyesight, and he did loose his eyelashes, which never grew back in, but although his sight was limited he did not go blind. Fear of loosing his eyesight made him a voracious reader, and he was able to memorize all that he read, becoming fluent in English, German and Italian.

He attended the Jesuit college in Amiens until 1764 when Jesuits were banned from France and he continued his education under teachers brought from Paris. Originally his intent was to become a parish priest, but with the encouragement of his teachers he went to Paris to continue his studies. He won a scholarship at the College du Plessis where he studied classical languages and prepared himself for university study. He sat for the university entrance exam, but with his poor eyesight he had difficulty reading the exam and he failed to gain a scholarship. His parents, unable to afford a university education, urged him to return to Amiens, instead he began studying mathematics in order that he could become a tutor and he took a position as the tutor of the son of a nobleman in Compiegne. Studying mathematics he soon became an expert, developing exceptional calculating skills.

In 1771 Delambre returned to Paris to take a position tutoring the son of Jean-Claude Geoffroy d'Assy, the Receiver General of Finances. He took this position for less than d'Assy offered in exchange for housing. Once again in Paris he began studying Greek and Greek sciences, including astronomy. He continued his study of astronomy, studying the works of current astronomers, including Jerome Lelande. He began attending lectures given by Lelande and soon impressed the teacher with his knowledge, so much so that Lelande offered him a position as his assistant. In 1786 Delambre observed the transit of Mercury across the sun and found that the tables of its transit, prepared by Lelande, were inaccurate, and Delambre would expend much effort to correct them. He also completed tables of the orbits of Jupiter and Saturn. In 1789 Delambre won a prize from the Academie des Sciences for correctly determining the orbit of Uranus. At the time of the French Revolution Delambre changed his name, which had originally been D'Lambre in order that he would not be arrested.

Delambre was elected associate member of the mathematical section of the Academie des Sciences in 1792 and was given a commission by the Academie to measure the arc distance between Dunkerque to Rodez. This was part of the Commission of Weights and Measures attempt to define the meter. It had been decided to define the meter, the unit of length measurement in the newly created metric system, as one ten millionth of a quarter of the distance between the North Pole and the equator. Delambre reported his results in 1799, having twice been detained by revolutionary forces, and accused of espionage. Delambre finished the report, establishing the length of the meter, in 1806.

Delambre devoted the remainder of his career to the study of the history of mathematics and astronomy. His major work was a six volume history of astronomy, the first two volumes covering ancient astronomy and the remaining four on astronomy of the middle ages, the Renaissance, the seventeenth and eighteenth centuries receptively. The final two volumes were published posthumously. This work has been haled by science historian I. Bernard Cohen as "the greatest full-scale technical history of a single branch of science written by a single individual". Delambre also has a crater on the moon named after him.

Delambre died on August 19, 1882.


O'Connor, JJ and Robertson, EF; "Jean Baptiste Joseph Delambre"; at www-history.mcs.st-andrews.ac.uk

Jarrell, Richard A.; "Delambre, Jean-Baptiste Joseph (1749-1822)" in History of Astronomy: An Encyclopedia; John Lankford ed.; Taylor and Francis; 1997

Jean Baptiste Joseph Delamber wikipedia entry

Monday, September 13, 2010

Irene Joliot-Curie

Irene Juliot-Curie was born in Paris, France on September 12, 1897, the daughter of nuclear scientists Marie and Pierre Curie. After a year of formal education when she was six, Juliot-Currie's parents joined a group of distinguished French academics called "The Cooperative" which took turns providing instruction for their children. Classes took place at the academic's homes and provided instruction not only on science but diverse subjects such as Chinese and sculpture. After 2 years of this instruction she returned to a more traditional academic setting, attending the College Sevigne for two years. She then went to the Sorbonne, but her studies were interrupted by the outbreak of World War I.

During the war Juliot-Curie helped her mother operating primitive X-ray machines that had been made possible by Marie's research. The machines made it possible to for doctors to locate shrapnel in patients, but the equipment was primitive and she suffered from radiation exposure. After the war she returned to Paris where she worked at her parents' Radium Institute and she completed a doctoral thesis concerning the alpha rays emited by polonium. She was awarded her doctorate in 1925.

While working on her doctorate she was asked to teach the techniques used in radiochemical research to a young chemical engineer named Federic Joliot. They would later marry and share hyphenated last names. Their collaborative study of atomic nuclei was the first to identify the existence of neutrons and positrons, although James Chadwick and C. D. Anderson, respectively, would claim the discoveries. Their breakthrough came in 1934, after bombarding a thin sheet of aluminum with alpha particles, they noticed that the area bombarded gave off positive electrons, after the alpha particles were removed, in such a way that suggested radioactive elements. Further examination of the product revealed that it was a radioactive isotope of phosphorus.

The means of atomic transmution discovered by the Curies involves bombarding nuclei with subatomic particles. The transmutation accomplished by the Curies (aluminum to phosphorus) was accomplished by bombarding aluminum with alpha particles. Alpha particles are low energy radioactive particles that consist of helium nuclei, with two protons and two neutrons. In this case aluminum (atomic number 13) is changed into phosphorus (atomic number 15) by the addition on two protons from an alpha particle. The resulting phosphorus nuclei is unstable and breaks down, releasing positrons.

For their discovery of nuclear transmutation the Curies were awarded the Nobel Prize for chemistry in 1935. Irene Juliot-Curie became only the second woman, after her mother to win the Nobel Prize in chemistry. With the prize came employment including a chair at the Sorbonne. During World War II she contracted tuberculosis and she went to Switzerland to convalesce. She made several trips back to Paris to visit her husband and children and on more than one occasion was detained by German troops. In 1956 she contracted leukemia and she died on March 17, 1956.


Bensaude-Vincent, Bernedette; "Irene Joliot-Curie" in Nobel Laureates in Chemistry, 1901-1992; Chemical Heritage Foundation, 1992

Irene Joliot-Curie Nobel Biography

Irene Joliot-Curie Wikipedia Entry

Sunday, September 5, 2010

Max Ludwig Henning Delbruck

Max Ludwig Henning Delbruck was born on September 4, 1906 in Berlin Germany, the youngest of seven children of Hans Delbruck, a professor of politics at the University of Berlin and editor of a political journal. Delbruck grew up in the relatively affluent Grunewald suburb of Berlin, and lived in comfort until the outbreak of World War I, in which his older brother, Waldemar, was killed. His first interest in science was astronomy and astrophysics, later in his studies he switched to theoretical physics as it was during the time that the science of quantum mechanics was being discovered. In 1929 he received his Ph.D. in theoretical physics from the University of Gottingen. After a failed attempt to complete a thesis on novae he wrote a thesis on the quantum problem of the nonexistent diatomic lithium molecule.

After completing his thesis Delbruck spent 18 months at the University of Bristol (England) as a research assistant. After Bristol he received a Rockefeller Fellowship which allowed him to go to Copenhagen to study under Niels Bohr who influenced Delbruck's thinking about biology. In 1932 Delbruck accepted a position as an theoretical physics assistant to Lise Meitner, primarily to be near the Kaiser Wilhelm Institute for Biology. Hitler's rise to power in Germany caused a number of the Jewish scientists to emigrate from Germany, leaving the seminars less interesting to Delbruck. To make up for this loss Delbruck helped organize a group of physicists that met weekly to discuss physical problems. This group soon included biologists and a number of important papers emerged from these meetings, including an at first neglected paper on which Dulbruck collaborated about the nature of gene structure and mutations, that went on to be very influential.

In 1937 Dulbruck, on the strength of a second Rockefeller Fellowship, emigrated to the United States and took a position at the California Institute of Technology (Cal Tech) to study drosophila genetics. After having difficulty in learning the terminology of drosophila genetics Delbruck began studying bacterial phages with Emory Ellis. With the start of World War II, Delbruck's fellowship ran out and he took a position teaching at Vanderbilt University. The teaching position was only part time allowing Delbruck to spend the rest of his time doing phage research. During this period he collaborated with Salvador Luria, who was at the University of Indiana, and they demonstrated that bacterial resistance to phages was due to genetic mutation and not adaptive change. For this work they were awarded the Nobel Prize for Physiology or Medicine, along with Alfred Hershey, in 1969.

Phages are viruses that infect bacteria. Like the viruses that attack plant and animal cells, they insert their genetic material into host cell (in this case a bacteria) and use the host's genetic replication mechanisms to produce copies of its own genetic material. Bacteriophages are estimated to be the most widely distributed and diverse entities in the biosphere and they were among the first viral particles to be studied on a genetic level. Delbruk's work with Luria demonstrated that genetic mutation arises independent of selection pressure, that is mutation takes place randomly and is not influenced by changes or stressors in the bacteria's environment. At the time this was considered a huge advance in the understanding genetics and its importance has been compared to the work of Gregor Mendel.

In 1947 Delbruck returned to Cal Tech where he remained until 1977, doing research applying biophysical methods to the problems of sensory physiology. He is considered one of the most influential scientists who applied physical methods to biological problems.

Delbruck died on March 9, 1981.


Delbruck, Max; interview by Carolyn Harding; at oralhistories.library.caltech.edu

Hayes, William;"Max Ludwig Henning Dulbreck" in Biographical Memiors Vol. 62; National Academy Press (1993)

Max Delbruck nndb entry

Luria-Delbruck experiment Wikipedia Entry