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18 November 2009

Polyethylene


The invention: An artificial polymer with strong insulating properties
and many other applications.
The people behind the invention:
Karl Ziegler (1898-1973), a German chemist
Giulio Natta (1903-1979), an Italian chemist
August Wilhelm von Hofmann (1818-1892), a German chemist
The Development of Synthetic Polymers
In 1841, August Hofmann completed his Ph.D. with Justus von
Liebig, a German chemist and founding father of organic chemistry.

03 November 2009

Polyester




The invention: Asynthetic fibrous polymer used especially in fabrics.
The people behind the invention:
Wallace H. Carothers (1896-1937), an American polymer
chemist
Hilaire de Chardonnet (1839-1924), a French polymer chemist
John R. Whinfield (1901-1966), a British polymer chemist
A Story About Threads
Human beings have worn clothing since prehistoric times. At
first, clothing consisted of animal skins

28 October 2009

Polio vaccine (Salk)





The invention: Jonas Salk’s vaccine was the first that prevented polio,resulting in the virtual eradication of crippling polio epidemics.The people behind the invention:
Jonas Edward Salk (1914-1995), an American physician,
immunologist, and virologist
Thomas Francis, Jr. (1900-1969), an

Polio vaccine (Sabin)



The invention: Albert Bruce Sabin’s vaccine was the first to stimulate
long-lasting immunity against polio without the risk of causing
paralytic disease.
The people behind the invention:
Albert Bruce Sabin (1906-1993), a Russian-born American
virologist
Jonas Edward Salk (1914-1995), an American physician,
immunologist, and virologist
Renato Dulbecco (1914- ), an Italian-born American
virologist who shared the 1975 Nobel Prize in Physiology or
Medicine
The Search for a Living Vaccine
Almost a century ago, the first major poliomyelitis (polio) epidemic
was recorded. Thereafter, epidemics of increasing

21 October 2009

Pocket calculator




The invention: The first portable and reliable hand-held calculator
capable of performing a wide range of mathematical computations.
The people behind the invention:
Jack St. Clair Kilby (1923- ), the inventor of the
semiconductor microchip
Jerry D. Merryman (1932- ), the first project manager of the
team that invented the first portable calculator
James Van Tassel (1929- ), an inventor and expert on
semiconductor components
An Ancient Dream
In the earliest accounts of civilizations that developed number
systems to perform mathematical calculations,

14 October 2009

Plastic





The invention: The first totally synthetic thermosetting plastic,
which paved the way for modern materials science.
The people behind the invention:
John Wesley Hyatt (1837-1920), an American inventor
Leo Hendrik Baekeland (1863-1944), a Belgian-born chemist,
consultant, and inventor
Christian Friedrich Schönbein (1799-1868), a German chemist
who produced guncotton, the first artificial polymer
Adolf von Baeyer (1835-1917), a German chemist
Exploding Billiard Balls
In the 1860’s, the firm of Phelan and Collender offered a prize of
ten thousand dollars to anyone producing a substance that could
serve as an inexpensive substitute for

13 October 2009

Photovoltaic cell



Photovoltaic cell
The invention: Drawing their energy directly from the Sun, the
first photovoltaic cells powered instruments on early space vehicles
and held out hope for future uses of solar energy.
The people behind the invention:
Daryl M. Chapin (1906-1995), an American physicist
Calvin S. Fuller (1902-1994), an American chemist
Gerald L. Pearson (1905- ), an American physicist
Unlimited Energy Source
All the energy that the world has at its disposal ultimately comes
from the Sun. Some of this solar energy was trapped millions of years
ago in the form of vegetable and animal matter

12 October 2009

Photoelectric cell




The invention: The first devices to make practical use of the photoelectric
effect, photoelectric cells were of decisive importance in
the electron theory of metals.
The people behind the invention:
Julius Elster (1854-1920), a German experimental physicist
Hans Friedrich Geitel (1855-1923), a German physicist
Wilhelm Hallwachs (1859-1922), a German physicist
Early Photoelectric Cells
The photoelectric effect was known to science in the early
nineteenth century when the French physicist Alexandre-Edmond
Becquerel wrote of it in connection with

Personal computer



The invention: Originally a tradename of the IBM Corporation,
“personal computer” has become a generic term for increasingly
powerful desktop computing systems using microprocessors.
The people behind the invention:
Tom J. Watson, (1874-1956), the founder of IBM, who set
corporate philosophy and marketing principles
Frank Cary (1920- ), the chief

01 October 2009

Penicillin



The invention: The first successful and widely used antibiotic
drug, penicillin has been called the twentieth century’s greatest
“wonder drug.”
The people behind the invention:
Sir Alexander Fleming (1881-1955), a Scottish bacteriologist,
cowinner of the 1945 Nobel Prize in Physiology or Medicine
Baron Florey (1898-1968), an Australian pathologist, cowinner
of the 1945 Nobel Prize in Physiology or Medicine
Ernst Boris Chain (1906-1979), an émigré German biochemist,
cowinner of the 1945 Nobel Prize in Physiology or Medicine
The Search for the Perfect Antibiotic
During the early twentieth century, scientists

30 September 2009

Pap test




The invention: A cytologic technique the diagnosing uterine cancer,
the second most common fatal cancer in American women.
The people behind the invention:
George N. Papanicolaou (1883-1962), a Greek-born American
physician and anatomist
Charles Stockard (1879-1939), an American anatomist
Herbert Traut (1894-1972), an American gynecologist
Cancer in History
Cancer, first named by the ancient Greek physician Hippocrates
of Cos, is one of the most painful and dreaded forms of human disease.
It occurs when body cells run wild and interfere with the normal
activities of the body. The early diagnosis of cancer is extremely
important because early detection often makes it possible to effect
successful cures. The modern detection of cancer is usually done by
the microscopic examination of the cancer cells, using the techniques
of the area of biology called “cytology, ” or cell biology.
Development of cancer cytology began in 1867, after L. S. Beale
reported tumor cells in the saliva from

29 September 2009

Pacemaker





The invention: 

A small device using transistor circuitry that regulates
the heartbeat of the patient in whom it is surgically emplaced.

The people behind the invention:

Ake Senning (1915- ), a Swedish physician
Rune Elmquist, co-inventor of the first pacemaker
Paul Maurice Zoll (1911- ), an American cardiologist

28 September 2009

Orlon



The invention: A synthetic fiber made from polyacrylonitrile that
has become widely used in textiles and in the preparation of
high-strength carbon fibers.
The people behind the invention:
Herbert Rein (1899-1955), a German chemist
Ray C. Houtz (1907- ), an American chemist
A Difficult Plastic
“Polymers” are large molecules that are made up of chains of
many smaller molecules, called “monomers.” Materials that are
made of polymers are also called polymers,

24 September 2009

Optical disk




The invention:Anonmagnetic storage medium for computers that
can hold much greater quantities of data than similar size magnetic
media, such as hard and floppy disks.
The people behind the invention:
Klaas Compaan, a Dutch physicist
Piet Kramer, head of Philips’ optical research laboratory
Lou F. Ottens, director of product development for Philips’
musical equipment division
George T. de Kruiff, manager of Philips’ audio-product
development department
Joop Sinjou, a Philips project leader
Holograms Can Be Copied Inexpensively
Holography is a lensless photographic method that uses laser
light to produce three-dimensional images. This is done by splitting
a laser beam into two beams. One of the beams

22 September 2009

Oil-well drill bit




The invention: Arotary cone drill bit that enabled oil-well drillers
to penetrate hard rock formations.
The people behind the invention:
Howard R. Hughes (1869-1924), an American lawyer, drilling
engineer, and inventor
Walter B. Sharp (1860-1912), an American drilling engineer,
inventor, and partner to Hughes
Digging for Oil
Arotary drill rig of the 1990’s is basically unchanged in its essential
components from its earlier versions of the 1900’s. A drill bit is
attached to a line of hollow drill pipe. The latter passes through a
hole on a rotary table, which acts essentially as a horizontal gear
wheel and is driven by an engine. As the rotary table turns, so do the
pipe and drill bit.
During drilling operations, mud-laden water is pumped under
high pressure down the sides of the drill pipe and jets out with great
force through the small holes

Nylon








The invention: A resilient, high-strength polymer with applications
ranging from women’s hose to safety nets used in space flights.
The people behind the invention:Wallace Hume Carothers (1896-1937),
an American organic chemist Charles M. A. Stine (1882-1954), an American chemist
and director of chemical research at Du Pont Elmer Keiser Bolton (1886-1968),
an American industrial chemist Pure Research In the twentieth century,
American corporations created industrial research laboratories.
Their directors became the organizers of inventions,
and their scientists served as the sources of creativity.
The research program of

08 September 2009

Nuclear reactor




The invention: 

The first nuclear reactor to produce substantial
quantities of plutonium, making it practical to produce usable
amounts of energy from a chain reaction.

The people behind the invention:

Enrico Fermi (1901-1954), an American physicist
Martin D. Whitaker (1902-1960), the first director of Oak Ridge
National Laboratory
Eugene Paul Wigner (1902-1995), the director of research and
development at Oak Ridge


Nuclear power plant




The invention: 

The first full-scale commercial nuclear power plant, which gave birth to the nuclear power industry.  



The people behind the invention:

Enrico Fermi (1901-1954), an Italian American physicist who
won the 1938 Nobel Prize in Physics
Otto Hahn (1879-1968), a German physical chemist who won the
1944 Nobel Prize in Chemistry
Lise Meitner (1878-1968), an Austrian Swedish physicist
Hyman G. Rickover (1898-1986), a Polish American naval officer


04 September 2009

Nuclear magnetic resonance


The invention: 

Procedure that uses hydrogen atoms in the human
body, strong electromagnets, radio waves, and detection equipment
to produce images of sections of the brain.

The people behind the invention:

Raymond Damadian (1936- ), an American physicist and
inventor
Paul C. Lauterbur (1929- ), an American chemist
Peter Mansfield (1933- ), a scientist at the University of
Nottingham, England


Neutrino detector

The invention:Adevice that provided the first direct evidence that the Sun runs on thermonuclear power and challenged existing models of the Sun. The people behind the invention: Raymond Davis, Jr. (1914- ), an American chemist John Norris Bahcall (1934- ), an American astrophysicist Missing Energy In 1871, Hermann von Helmholtz, the German physicist, anatomist, and physiologist, suggested that no ordinary chemical reaction could be responsible for the enormous energy output of the Sun. By the 1920’s, astrophysicists had realized that the energy radiated by the Sun must come from nuclear fusion, in which protons or nuclei combine to form larger nuclei and release energy.

Neoprene

The invention: The first commercially practical synthetic rubber, Neoprene gave a boost to polymer chemistry and the search for new materials. The people behind the invention: Wallace Hume Carothers (1896-1937), an American chemist Arnold Miller Collins (1899- ), an American chemist Elmer Keiser Bolton (1886-1968), an American chemist Julius Arthur Nieuwland (1879-1936), a Belgian American priest, botanist, and chemist Synthetic Rubber: A Mirage? The growing dependence of the industrialized nations upon elastomers (elastic substances) and the shortcomings of natural rubber motivated the twentieth century quest for rubber substitutes. By 1914

31 August 2009

Microwave cooking

The invention: System of high-speed cooking that uses microwave radition to agitate liquid molecules to raise temperatures by friction. The people behind the invention: Percy L. Spencer (1894-1970), an American engineer Heinrich Hertz (1857-1894), a German physicist James Clerk Maxwell (1831-1879), a Scottish physicist The Nature of Microwaves Microwaves are electromagnetic waves, as are radio waves, X rays, and visible light. Water waves

Memory metal

Memory metal The invention: Known as nitinol, a metal alloy that returns to its original shape, after being deformed, when it is heated to the proper temperature. The person behind the invention: William Buehler (1923- ), an American metallurgist The Alloy with a Memory In 1960,William Buehler developed an alloy that consisted of 53 to 57 percent nickel (by weight) and the balance titanium. This alloy, which is called nitinol, turned out to have remarkable properties. Nitinol is a “memory metal,” which means that, given the proper conditions, objects made of nitinol can be restored to their original shapes even after they have been radically deformed. The return to the original shape

Mass spectrograph

The invention: The first device used to measure the mass of atoms, which was found to be the result of the combination of isotopes. The people behind the invention: Francis William Aston (1877-1945), an English physicist who was awarded the 1922 Nobel Prize in Chemistry Sir Joseph John Thomson (1856-1940), an English physicist William Prout (1785-1850), an English biochemist Ernest Rutherford (1871-1937), an English physicist Same Element, Different Weights Isotopes are different forms of a chemical element that act similarly in chemical or physical reactions. Isotopes differ in two ways: They possess different atomic weights and different radioactive transformations. In 1803, John Dalton proposed a new atomic theory of chemistry that claimed that chemical elements in a compound combine by weight in whole number proportions to one another. By 1815, William Prout had taken Dalton’s hypothesis one step further and claimed that the atomic weights of elements were integral (the integers are the positive and negative whole numbers and zero) multiples

Mark I calculator

The invention: Early digital calculator designed to solve differential equations that was a forerunner of modern computers. The people behind the invention: Howard H. Aiken (1900-1973), Harvard University professor and architect of the Mark I Clair D. Lake (1888-1958), a senior engineer at IBM Francis E. Hamilton (1898-1972), an IBM engineer Benjamin M. Durfee (1897-1980), an IBM engineer The Human Computer The physical world can be described by means of mathematics. In principle, one can accurately describe nature down to the smallest detail.

24 August 2009

Mammography

The invention: The first X-ray procedure for detecting and diagnosing breast cancer. The people behind the invention: Albert Salomon, the first researcher to use X-ray technology instead of surgery to identify breast cancer Jacob Gershon-Cohen (1899-1971), a breast cancer researcher Studying Breast Cancer Medical researchers have been studying breast cancer for more than a century. At the end of the nineteenth century, however, no one knew how to detect breast cancer until it was quite advanced. Often, by the time it was detected, it was too late for surgery; many patients who did have surgery died. So after X-ray technology first appeared in 1896, cancer researchers were eager to experiment with it. The first scientist to use X-ray techniques in breast cancer experiments was Albert Salomon, a German surgeon. Trying to develop a biopsy technique that could tell which tumors were cancerous and thereby avoid unnecessary surgery, he X-rayed more than three thousand breasts that had been removed from patients during breast cancer surgery. In 1913, he published the results of his experiments, showing that X rays could detect breast cancer. Different types of Xray images, he said, showed different types of cancer. Though Salomon is recognized as the inventor of breast radiology, he never actually used his technique to diagnose breast cancer. In fact, breast cancer radiology, which came to be known as “mammography,” was not taken up quickly by other medical researchers. Those who did try to reproduce his research often found that their results were not conclusive. During the 1920’s, however, more research was conducted in Leipzig, Germany, and in South America. Eventually, the Leipzig researchers, led by Erwin Payr, began to use mammography to diagnose cancer. In the 1930’s, a Leipzig researcher named W. Vogel published a paper that accurately described differences between cancerous and noncancerous tumors as they appeared on X-ray photographs. Researchers in the United States paid little attention to mammography until 1926. That year, a physician in Rochester, New York, was using a fluoroscope to examine heart muscle in a patient and discovered that the fluoroscope could be used to make images of breast tissue as well. The physician, Stafford L. Warren, then developed a stereoscopic technique that he used in examinations before surgery. Warren published his findings in 1930; his article also described changes in breast tissue that occurred because of pregnancy, lactation (milk production), menstruation, and breast disease. Yet Stafford’s technique was complicated and required equipment that most physicians of the time did not have. Eventually, he lost interest in mammography and went on to other research. Using the Technique In the late 1930’s, Jacob Gershon-Cohen became the first clinician to advocate regular mammography for all women to detect breast cancer before it became a major problem. Mammography was not very expensive, he pointed out, and it was already quite accurate. A milestone in breast cancer research came in 1956, when Gershon- Cohen and others began a five-year study of more than 1,300 women to test the accuracy of mammography for detecting breast cancer. Each woman studied was screened once every six months. Of the 1,055 women who finished the study, 92 were diagnosed with benign tumors and 23 with malignant tumors. Remarkably, out of all these, only one diagnosis turned out to be wrong. During the same period, Robert Egan of Houston began tracking breast cancer X rays. Over a span of three years, one thousand X-ray photographs were used to make diagnoses. When these diagnoses were compared to the results of surgical biopsies, it was confirmed that mammography had produced 238 correct diagnoses of cancer, out of 240 cases. Egan therefore joined the crusade for regular breast cancer screening. Once mammography was finally accepted by doctors in the late 1950’s and early 1960’s, researchers realized that they needed a way to teach mammography quickly and effectively to those who would use it. A study was done, and it showed that any radiologist could conduct the procedure with only five days of training.In the early 1970’s, the American Cancer Society and the National Cancer Institute joined forces on a nationwide breast cancer screening program called the “Breast Cancer Detection Demonstration Project.” Its goal in 1971 was to screen more than 250,000 women over the age of thirty-five. Since the 1960’s, however, some people had argued that mammography was dangerous because it used radiation on patients. In 1976, Ralph Nader, a consumer advocate, stated that women who were to undergo mammography should be given consent forms that would list the dangers of radiation. In the years that followed, mammography was refined to reduced the amount of radiation needed to detect cancer. It became a standard tool for diagnosis, and doctors recommended that women have a mammogram every two or three years after the age of forty. Impact Radiology is not a science that concerns only breast cancer screening. While it does provide the technical facilities necessary to practice mammography, the photographic images obtained must be interpreted by general practitioners, as well as by specialists. Once Gershon-Cohen had demonstrated the viability of the technique, a means of training was devised that made it fairly easy for clinicians to learn how to practice mammography successfully. Once all these factors—accuracy, safety, simplicity—were in place, mammography became an important factor in the fight against breast cancer. The progress made in mammography during the twentieth century was a major improvement in the effort to keep more women from dying of breast cancer. The disease has always been one of the primary contributors to the number of female cancer deaths that occur annually in the United States and around the world. This high figure stems from the fact that women had no way of detecting the disease until tumors were in an advanced state. Once Salomon’s procedure was utilized, physicians had a means by which they could look inside breast tissue without engaging in exploratory surgery, thus giving women a screening technique that was simple and inexpensive. By 1971, a quarter million women over age thirty-five had been screened. Twenty years later, that number was in the millions.

17 August 2009

Long-distance telephone

The invention: System for conveying voice signals via wires over long distances. The people behind the invention: Alexander Graham Bell (1847-1922), a Scottish American inventor Thomas A. Watson (1854-1934), an American electrical engineer The Problem of Distance The telephone may be the most important invention of the nineteenth century. The device developed by Alexander Graham Bell and Thomas A. Watson opened a new era in communication and made it possible for people to converse over long distances for the first time. During the last two decades of the nineteenth century and the first decade of the twentieth century, the American Telephone and Telegraph (AT&T) Company continued to refine and upgrade telephone facilities, introducing such innovations as automatic dialing and long-distance service. One of the greatest challenges faced by Bell engineers was to develop a way of maintaining signal quality over long distances. Telephone wires were susceptible to interference from electrical storms and other natural phenomena, and electrical resistance and radiation caused a fairly rapid drop-off in signal strength, which made long-distance conversations barely audible or unintelligible. By 1900, Bell engineers had discovered that signal strength could be improved somewhat by wrapping the main wire conductor with thinner wires called “loading coils” at prescribed intervals along the length of the cable. Using this procedure, Bell extended longdistance service from New York to Denver, Colorado, which was then considered the farthest point that could be reached with acceptable quality. The result, however, was still unsatisfactory, and Bell engineers realized that some form of signal amplification would be necessary to improve the quality of the signal.A breakthrough came in 1906, when Lee de Forest invented the “audion tube,” which could send and amplify radio waves. Bell scientists immediately recognized the potential of the new device for long-distance telephony and began building amplifiers that would be placed strategically along the long-distance wire network. Work progressed so quickly that by 1909, Bell officials were predicting that the first transcontinental long-distance telephone service, between New York and San Francisco, was imminent. In that year, Bell president Theodore N. Vail went so far as to promise the organizers of the Panama-Pacific Exposition, scheduled to open in San Francisco in 1914, that Bell would offer a demonstration at the exposition. The promise was risky, because certain technical problems associated with sending a telephone signal over a 4,800- kilometer wire had not yet been solved. De Forest’s audion tube was a crude device, but progress was being made. Two more breakthroughs came in 1912, when de Forest improved on his original concept and Bell engineer Harold D. Arnold improved it further. Bell bought the rights to de Forest’s vacuumtube patents in 1913 and completed the construction of the New York-San Francisco circuit. The last connection was made at the Utah-Nevada border on June 17, 1914. Success Leads to Further Improvements Bell’s long-distance network was tested successfully on June 29, 1914, but the official demonstration was postponed until January 25, 1915, to accommodate the Panama-Pacific Exposition, which had also been postponed. On that date, a connection was established between Jekyll Island, Georgia, where Theodore Vail was recuperating from an illness, and New York City, where Alexander Graham Bell was standing by to talk to his former associate Thomas Watson, who was in San Francisco. When everything was in place, the following conversation took place. Bell: “Hoy! Hoy! Mr. Watson? Are you there? Do you hear me?”Watson: “Yes, Dr. Bell, I hear you perfectly. Do you hear me well?” Bell: “Yes, your voice is perfectly distinct. It is as clear as if you were here in New York.” The first transcontinental telephone conversation transmitted by wire was followed quickly by another that was transmitted via radio. Although the Bell company was slow to recognize the potential of radio wave amplification for the “wireless” transmission of telephone conversations, by 1909 the company had made a significant commitment to conduct research in radio telephony. On April 4, 1915, a wireless signal was transmitted by Bell technicians from Montauk Point on Long Island, New York, to Wilmington, Delaware, a distance of more than 320 kilometers. Shortly thereafter, a similar test was conducted between New York City and Brunswick, Georgia, via a relay station at Montauk Point. The total distance of the transmission was more than 1,600 kilometers. Finally, in September, 1915, Vail placed a successful transcontinental radiotelephone call from his office in New York to Bell engineering chief J. J. Carty in San Francisco. Only a month later, the first telephone transmission across the Atlantic Ocean was accomplished via radio from Arlington, Virginia, to the Eiffel Tower in Paris, France. The signal was detectable, although its quality was poor. It would be ten years before true transatlantic radio-telephone service would begin. The Bell company recognized that creating a nationwide longdistance network would increase the volume of telephone calls simply by increasing the number of destinations that could be reached from any single telephone station. As the network expanded, each subscriber would have more reason to use the telephone more often, thereby increasing Bell’s revenues. Thus, the company’s strategy became one of tying local and regional networks together to create one large system. Impact Just as the railroads had interconnected centers of commerce, industry, and agriculture all across the continental United States in the nineteenth century, the telephone promised to bring a new kind of interconnection to the country in the twentieth century: instantaneous voice communication. During the first quarter century after the invention of the telephone and during its subsequent commercialization, the emphasis of telephone companies was to set up central office switches that would provide interconnections among subscribers within a fairly limited geographical area. Large cities were wired quickly, and by the beginning of the twentieth century most were served by telephone switches that could accommodate thousands of subscribers. The development of intercontinental telephone service was a milestone in the history of telephony for two reasons. First, it was a practical demonstration of the almost limitless applications of this innovative technology. Second, for the first time in its brief history, the telephone network took on a national character. It became clear that large central office networks, even in large cities such as New York, Chicago, and Baltimore, were merely small parts of a much larger, universally accessible communication network that spanned a continent. The next step would be to look abroad, to Europe and beyond.

Long-distance radiotelephony

The invention: The first radio transmissions fromthe United States to Europe opened a new era in telecommunications. The people behind the invention: Guglielmo Marconi (1874-1937), Italian inventor of transatlantic telegraphy Reginald Aubrey Fessenden (1866-1932), an American radio engineer Lee de Forest (1873-1961), an American inventor Harold D. Arnold (1883-1933), an American physicist John J. Carty (1861-1932), an American electrical engineer An Accidental Broadcast The idea of commercial transatlantic communication was first conceived by Italian physicist and inventor Guglielmo Marconi, the pioneer of wireless telegraphy. Marconi used a spark transmitter to generate radio waves that were interrupted, or modulated, to form the dots and dashes of Morse code. The rapid generation of sparks created an electromagnetic disturbance that sent radio waves of different frequencies into the air—a broad, noisy transmission that was difficult to tune and detect. The inventor Reginald Aubrey Fessenden produced an alternative method that became the basis of radio technology in the twentieth century. His continuous radio waves kept to one frequency, making them much easier to detect at long distances. Furthermore, the continuous waves could be modulated by an audio signal, making it possible to transmit the sound of speech. Fessenden used an alternator to generate electromagnetic waves at the high frequencies required in radio transmission. It was specially constructed at the laboratories of the General Electric Company. The machine was shipped to Brant Rock, Massachusetts, in 1906 for testing. Radio messages were sent to a boat cruising offshore, and the feasibility of radiotelephony was thus demonstrated. Fessenden followed this success with a broadcast of messages and music between Brant Rock and a receiving station constructed at Plymouth, Massachusetts. The equipment installed at Brant Rock had a range of about 160 kilometers. The transmission distance was determined by the strength of the electric power delivered by the alternator, which was measured in watts. Fessenden’s alternator was rated at 500 watts, but it usually delivered much less power. Yet this was sufficient to send a radio message across the Atlantic. Fessenden had built a receiving station at Machrihanish, Scotland, to test the operation of a large rotary spark transmitter that he had constructed. An operator at this station picked up the voice of an engineer at Brant Rock who was sending instructions to Plymouth. Thus, the first radiotelephone message had been sent across the Atlantic by accident. Fessenden, however, decided not to make this startling development public. The station at Machrihanish was destroyed in a storm, making it impossible to carry out further tests. The successful transmission undoubtedly had been the result of exceptionally clear atmospheric conditions that might never again favor the inventor. One of the parties following the development of the experiments in radio telephony was the American Telephone and Telegraph (AT&T) Company. Fessenden entered into negotiations to sell his system to the telephone company, but, because of the financial panic of 1907, the sale was never made. Virginia to Paris and Hawaii The English physicist John Ambrose Fleming had invented a twoelement (diode) vacuum tube in 1904 that could be used to generate and detect radio waves. Two years later, the American inventor Lee de Forest added a third element to the diode to produce his “audion” (triode), which was a more sensitive detector. John J. Carty, head of a research and development effort at AT&T, examined these new devices carefully. He became convinced that an electronic amplifier, incorporating the triode into its design, could be used to increase the strength of telephone signals and to long distances. On Carty’s advice, AT&T purchased the rights to de Forest’s audion. A team of about twenty-five researchers, under the leadership of physicist Harold D. Arnold, were assigned the job of perfecting the triode and turning it into a reliable amplifier. The improved triode was responsible for the success of transcontinental cable telephone service, which was introduced in January, 1915. The triode was also the basis of AT&T’s foray into radio telephony. Carty’s research plan called for a system with three components: an oscillator to generate the radio waves, a modulator to add the audio signals to the waves, and an amplifier to transmit the radio waves. The total power output of the system was 7,500 watts, enough to send the radio waves over thousands of kilometers.The apparatus was installed in the U.S. Navy’s radio tower in Arlington, Virginia, in 1915. Radio messages from Arlington were picked up at a receiving station in California, a distance of 4,000 kilometers, then at a station in Pearl Harbor, Hawaii, which was 7,200 kilometers from Arlington. AT&T’s engineers had succeeded in joining the company telephone lines with the radio transmitter at Arlington; therefore, the president of AT&T, Theodore Vail, could pick up his telephone and talk directly with someone in California. The next experiment was to send a radio message fromArlington to a receiving station set up in the Eiffel Tower in Paris. After several unsuccessful attempts, the telephone engineers in the Eiffel Tower finally heard Arlington’s messages on October 21, 1915. The AT&T receiving station in Hawaii also picked up the messages. The two receiving stations had to send their reply by telegraph to the United States because both stations were set up to receive only. Two-way radio communication was still years in the future. Impact The announcement that messages had been received in Paris was front-page news and brought about an outburst of national pride in the United States. The demonstration of transatlantic radio telephony was more important as publicity for AT&T than as a scientific advance. All the credit went to AT&T and to Carty’s laboratory. Both Fessenden and de Forest attempted to draw attention to their contributions to long-distance radio telephony, but to no avail. The Arlington-to-Paris transmission was a triumph for corporate public relations and corporate research. The development of the triode had been achieved with large teams of highly trained scientists—in contrast to the small-scale efforts of Fessenden and de Forest, who had little formal scientific training. Carty’s laboratory was an example of the new type of industrial research that was to dominate the twentieth century. The golden days of the lone inventor, in the mold of Thomas Edison or Alexander Graham Bell, were gone. In the years that followed the first transatlantic radio telephone messages, little was done by AT&T to advance the technology or to develop a commercial service. The equipment used in the 1915 demonstration was more a makeshift laboratory apparatus than a prototype for a new radio technology. The messages sent were short and faint. There was a great gulf between hearing “hello” and “goodbye” amid the static. The many predictions of a direct telephone connection between New York and other major cities overseas were premature. It was not until 1927 that a transatlantic radio circuit was opened for public use. By that time, a new technological direction had been taken, and the method used in 1915 had been superseded by shortwave radio communication.

Laser vaporization

The invention: Technique using laser light beams to vaporize the plaque that clogs arteries. The people behind the invention: Albert Einstein (1879-1955), a theoretical American physicist Theodore Harold Maiman (1927- ), inventor of the laser Light, Lasers, and Coronary Arteries Visible light, a type of electromagnetic radiation, is actually a form of energy. The fact that the light beams produced by a light bulb can warm an object demonstrates that this is the case. Light beams are radiated in all directions by a light bulb. In contrast, the device called the “laser” produces light that travels in the form of a “coherent” unidirectional beam. Coherent light beams can be focused on very small areas, generating sufficient heat to melt steel. The term “laser” was invented in 1957 by R. Gordon Gould of Columbia University. It stands for light amplification by stimulated emission of radiation, the means by which laser light beams are made. Many different materials—including solid ruby gemstones, liquid dye solutions, and mixtures of gases—can produce such beams in a process called “lasing.” The different types of lasers yield light beams of different colors that have many uses in science, industry, and medicine. For example, ruby lasers, which were developed in 1960, are widely used in eye surgery. In 1983, a group of physicians in Toulouse, France, used a laser for cardiovascular treatment. They used the laser to vaporize the “atheroma” material that clogs the arteries in the condition called “atherosclerosis.” The technique that they used is known as “laser vaporization surgery.” Laser Operation, Welding, and Surgery Lasers are electronic devices that emit intense beams of light when a process called “stimulated emission” occurs. The principles of laser operation, including stimulated emission, were established by Albert Einstein and other scientists in the first third of the twentieth century. In 1960, Theodore H. Maiman of the Hughes Research Center in Malibu, California, built the first laser, using a ruby crystal to produce a laser beam composed of red light. All lasers are made up of three main components. The first of these, the laser’s “active medium,” is a solid (like Maiman’s ruby crystal), a liquid, or a gas that can be made to lase. The second component is a flash lamp or some other light energy source that puts light into the active medium. The third component is a pair of mirrors that are situated on both sides of the active medium and are designed in such a way that one mirror transmits part of the energy that strikes it, yielding the light beam that leaves the laser. Lasers can produce energy because light is one of many forms of energy that are called, collectively, electromagnetic radiation (among the other forms of electromagnetic radiation are X rays and radio waves). These forms of electromagnetic radiation have different wavelengths; the smaller the wavelength, the higher the energy level. The energy level is measured in units called “quanta.” The emission of light quanta from atoms that are said to be in the “excited state” produces energy, and the absorption of quanta by unexcited atoms— atoms said to be in the “ground state”—excites those atoms. The familiar light bulb spontaneously and haphazardly emits light of many wavelengths from excited atoms. This emission occurs in all directions and at widely varying times. In contrast, the light reflection between the mirrors at the ends of a laser causes all of the many excited atoms present in the active medium simultaneously to emit light waves of the same wavelength. This process is called “stimulated emission.” Stimulated emission ultimately causes a laser to yield a beam of coherent light, which means that the wavelength, emission time, and direction of all the waves in the laser beam are the same. The use of focusing devices makes it possible to convert an emitted laser beam into a point source that can be as small as a few thousandths of an inch in diameter. Such focused beams are very hot, and they can be used for such diverse functions as cutting or welding metal objects and performing delicate surgery. The nature of the active medium used in a laser determines the wavelength of its emitted light beam; this in turn dictates both the energy of the emitted quanta and the appropriate uses for the laser.Maiman’s ruby laser, for example, has been used since the 1960’s in eye surgery to reattach detached retinas. This is done by focusing the laser on the tiny retinal tear that causes a retina to become detached. The very hot, high-intensity light beam then “welds” the retina back into place, bloodlessly, by burning it to produce scar tissue. The burning process has no effect on nearby tissues. Other types of lasers have been used in surgeries on the digestive tract and the uterus since the 1970’s. In 1983, a group of physicians began using lasers to treat cardiovascular disease. The original work, which was carried out by a number of physicians in Toulouse, France, involved the vaporization of atheroma deposits (atherosclerotic plaque) in a human artery. This very exciting event added a new method to medical science’s arsenal of life-saving techniques. Consequences Since their discovery, lasers have been used for many purposes in science and industry. Such uses include the study of the laws of chemistry and physics, photography, communications, and surveying. Lasers have been utilized in surgery since the mid-1960’s, and their use has had a tremendous impact on medicine. The first type of laser surgery to be conducted was the repair of detached retinas via ruby lasers. This technique has become the method of choice for such eye surgery because it takes only minutes to perform rather than the hours required for conventional surgical methods. It is also beneficial because the lasing of the surgical site cauterizes that site, preventing bleeding. In the late 1970’s, the use of other lasers for abdominal cancer surgery and uterine surgery began and flourished. In these forms of surgery, more powerful lasers are used. In the 1980’s, laser vaporization surgery (LVS) began to be used to clear atherosclerotic plaque (atheromas) from clogged arteries. This methodology gives cardiologists a useful new tool. Before LVS was available, surgeons dislodged atheromas by means of “transluminal angioplasty,” which involved pushing small, fluoroscopeguided inflatable balloons through clogged arteries.

12 August 2009

Laser eye surgery

The invention: The first significant clinical ophthalmic application of any laser system was the treatment of retinal tears with a pulsed ruby laser. The people behind the invention: Charles J. Campbell (1926- ), an ophthalmologist H. Christian Zweng (1925- ), an ophthalmologist Milton M. Zaret (1927- ), an ophthalmologist Theodore Harold Maiman (1927- ), the physicist who developed the first laser Monkeys and Rabbits The term “laser” is an acronym for light amplification by the stimulated emission of radiation. The development of the laser for ophthalmic (eye surgery) surgery arose from the initial concentration of conventional light by magnifying lenses. Within a laser, atoms are highly energized. When one of these atoms loses its energy in the form of light, it stimulates other atoms to emit light of the same frequency and in the same direction. A cascade of these identical light waves is soon produced, which then oscillate back and forth between the mirrors in the laser cavity. One mirror is only partially reflective, allowing some of the laser light to pass through. This light can be concentrated further into a small burst of high intensity. On July 7, 1960, Theodore Harold Maiman made public his discovery of the first laser—a ruby laser. Shortly thereafter, ophthalmologists began using ruby lasers for medical purposes. The first significant medical uses of the ruby laser occurred in 1961, with experiments on animals conducted by Charles J. Campbell in New York, H. Christian Zweng, and Milton M. Zaret. Zaret and his colleagues produced photocoagulation (a thickening or drawing together of substances by use of light) of the eyes of rabbits by flashes froma ruby laser. Sufficient energy was delivered to cause immediate thermal injury to the retina and iris of the rabbit. The beam also was directed to the interior of the rabbit eye, resulting in retinal coagulations. The team examined the retinal lesions and pointed out both the possible advantages of laser as a tool for therapeutic photocoagulation and the potential applications in medical research. In 1962, Zweng, along with several of his associates, began experimenting with laser photocoagulation on the eyes of monkeys and rabbits in order to establish parameters for the use of lasers on the human eye. Reflected by Blood The vitreous humor, a transparent jelly that usually fills the vitreous cavity of the eyes of younger individuals, commonly shrinks with age, with myopia, or with certain pathologic conditions. As these conditions occur, the vitreous humor begins to separate from the adjacent retina. In some patients, the separating vitreous humor produces a traction (pulling), causing a retinal tear to form. Through this opening in the retina, liquefied vitreous humor can pass to a site underneath the retina, producing retinal detachment and loss of vision. Alaser can be used to cause photocoagulation of a retinal tear. As a result, an adhesive scar forms between the retina surrounding the tear and the underlying layers so that, despite traction, the retina does not detach. If more than a small area of retina has detached, the laser often is ineffective and major retinal detachment surgery must be performed. Thus, in the experiments of Campbell and Zweng, the ruby laser was used to prevent, rather than treat, retinal detachment. In subsequent experiments with humans, all patients were treated with the experimental laser photocoagulator without anesthesia. Although usually no attempt was made to seal holes or tears, the diseased portions of the retina were walled off satisfactorily so that no detachments occurred. One problem that arose involved microaneurysms. A“microaneurysm” is a tiny aneurysm, or blood-filled bubble extending from the wall of a blood vessel. When attempts to obliterate microaneurysms were unsuccessful, the researchers postulated that the color of the ruby pulse so resembled the red of blood that the light was reflected rather than absorbed. They believed that another lasing material emitting light in another part of the spectrum might have performed more successfully.Previously, xenon-arc lamp photocoagulators had been used to treat retinal tears. The long exposure time required of these systems, combined with their broad spectral range emission (versus the single wavelength output of a laser), however, made the retinal spot on which the xenon-arc could be focused too large for many applications. Focused laser spots on the retina could be as small as 50 microns. Consequences The first laser in ophthalmic use by Campbell, Zweng, and Zaret, among others, was a solid laser—Maiman’s ruby laser. While the results they achieved with this laser were more impressive than with the previously used xenon-arc, in the decades following these experiments, argon gas replaced ruby as the most frequently used material in treating retinal tears. Argon laser energy is delivered to the area around the retinal tear through a slit lamp or by using an intraocular probe introduced directly into the eye. The argon wavelength is transmitted through the clear structures of the eye, such as the cornea, lens, and vitreous. This beam is composed of blue-green light that can be effectively aimed at the desired portion of the eye. Nevertheless, the beam can be absorbed by cataracts and by vitreous or retinal blood, decreasing its effectiveness. Moreover, while the ruby laser was found to be highly effective in producing an adhesive scar, it was not useful in the treatment of vascular diseases of the eye. Aseries of laser sources, each with different characteristics, was considered, investigated, and used clinically for various durations during the period that followed Campbell and Zweng’s experiments. Other laser types that are being adapted for use in ophthalmology are carbon dioxide lasers for scleral surgery (surgery on the tough, white, fibrous membrane covering the entire eyeball except the area covered by the cornea) and eye wall resection, dye lasers to kill or slow the growth of tumors, eximer lasers for their ability to break down corneal tissue without heating, and pulsed erbium lasers used to cut intraocular membranes.