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

American microbiologist

Cause for Celebration

Poliomyelitis (polio) is an infectious disease that can adversely

affect the central nervous system, causing paralysis and great muscle

wasting due to the destruction of motor neurons (nerve cells) in

the spinal cord. Epidemiologists believe that polio has existed since

ancient times, and evidence of its presence in Egypt, circa 1400 b.c.e.,

has been presented. Fortunately, the Salk vaccine and the later vaccine

developed by the American virologist Albert Bruce Sabin can

prevent the disease. Consequently, except in underdeveloped nations,

polio is rare. Moreover, although once a person develops polio,

there is still no cure for it, a large number of polio cases end without

paralysis or any observable effect.

Polio is often called “infantile paralysis.” This results from the

fact that it is seen most often in children. It is caused by a virus and

begins with body aches, a stiff neck, and other symptoms that are

very similar to those of a severe case of influenza. In some cases,

within two weeks after its onset, the course of polio begins to lead to

muscle wasting and paralysis.

On April 12, 1955, the world was thrilled with the announcement

that Jonas Edward Salk’s poliomyelitis vaccine could prevent the

disease. It was reported that schools were closed in celebration of

this event. Salk, the son of a New York City garment worker, has

since become one of the most well-known and publicly venerated

medical scientists in the world.

Vaccination is a method of disease prevention by immunization,

whereby a small amount of virus is injected into the body to prevent

a viral disease. The process depends on the production of antibodies

(body proteins that are specifically coded to prevent the disease

spread by the virus) in response to the vaccination. Vaccines are

made of weakened or killed virus preparations.

Electrifying Results

The Salk vaccine was produced in two steps. First, polio viruses

were grown in monkey kidney tissue cultures. These polio viruses

were then killed by treatment with the right amount of formaldehyde

to produce an effective vaccine. The killed-virus polio vaccine

was found to be safe and to cause the production of antibodies

against the disease, a sign that it should prevent polio.

In early 1952, Salk tested a prototype vaccine against Type I polio virus

on children who were afflicted with the disease and were thus

deemed safe from reinfection. This test showed that the vaccination greatly elevated the concentration of polio antibodies in these children.

On July 2, 1952, encouraged by these results, Salk vaccinated fortythree

children who had never had polio with vaccines against each of

the three virus types (Type I, Type II, and Type III). All inoculated children

produced high levels of polio antibodies, and none of them developed

the disease. Consequently, the vaccine appeared to be both safe in

humans and likely to become an effective public health tool.

In 1953, Salk reported these findings in the Journal of the American

Medical Association. In April, 1954, nationwide testing of the Salk

vaccine began, via the mass vaccination of American schoolchildren.

The results of the trial were electrifying. The vaccine was safe,

and it greatly reduced the incidence of the disease. In fact, it was estimated

that Salk’s vaccine gave schoolchildren 60 to 90 percent protection

against polio.

Salk was instantly praised. Then, however, several cases of polio

occurred as a consequence of the vaccine. Its use was immediately

suspended by the U.S. surgeon general, pending a complete examination.

Soon, it was evident that all the cases of vaccine-derived polio

were attributable to faulty batches of vaccine made by one

pharmaceutical company. Salk and his associates were in no way responsible

for the problem. Appropriate steps were taken to ensure

that such an error would not be repeated, and the Salk vaccine was

again released for use by the public.

Consequences

The first reports on the polio epidemic in the United States had

occurred on June 27, 1916, when one hundred residents of Brooklyn,

New York, were afflicted. Soon, the disease had spread. By August,

twenty-seven thousand people had developed polio. Nearly seven

thousand afflicted people died, and many survivors of the epidemic

were permanently paralyzed to varying extents. In New York City

alone, nine thousand people developed polio and two thousand

died. Chaos reigned as large numbers of terrified people attempted

to leave and were turned back by police. Smaller polio epidemics

occurred throughout the nation in the years that followed (for example,

the Catawba County, North Carolina, epidemic of 1944). A

particularly horrible aspect of polio was the fact that more than 70 percent of polio victims were small children. Adults caught it too;

the most famous of these adult polio victims was U.S. President

Franklin D. Roosevelt. There was no cure for the disease. The best

available treatment was physical therapy.

As of August, 1955, more than four million polio vaccines had

been given. The Salk vaccine appeared to work very well. There were

only half as many reported cases of polio in 1956 as there had been in

1955. It appeared that polio was being conquered. By 1957, the number

of cases reported nationwide had fallen below six thousand.

Thus, in two years, its incidence had dropped by about 80 percent.

This was very exciting, and soon other countries clamored for the

vaccine. By 1959, ninety other countries had been supplied with the

Salk vaccine.Worldwide, the disease was being eradicated. The introduction

of an oral polio vaccine by Albert Bruce Sabin supported

this progress.

Salk received many honors, including honorary degrees from

American and foreign universities, the LaskerAward, a Congressional

Medal for Distinguished Civilian Service, and membership in

the French Legion of Honor, yet he received neither the Nobel Prize

nor membership in the American National Academy of Sciences. It

is believed by many that this neglect was a result of the personal antagonism

of some of the members of the scientific community who

strongly disagreed with his theories of viral inactivation.

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

frequency

and severity struck the industrialized world. By the 1950’s, as many

as sixteen thousand individuals, most of them children, were being

paralyzed by the disease each year.

Poliovirus enters the body through ingestion by the mouth. It

replicates in the throat and the intestines and establishes an infection

that normally is harmless. From there, the virus can enter the

bloodstream. In some individuals it makes its way to the nervous

system, where it attacks and destroys nerve cells crucial for muscle

movement. The presence of antibodies in the bloodstream will prevent

the virus from reaching the nervous system and causing paralysis.

Thus, the goal of vaccination is to administer poliovirus that

has been altered so that it cannot cause disease but nevertheless will

stimulate the production of antibodies to fight the disease.

Albert Bruce Sabin received his medical degree from New York

University College of Medicine in 1931. Polio was epidemic in 1931,

and for Sabin polio research became a lifelong interest. In 1936,

while working at the Rockefeller Institute, Sabin and Peter Olinsky

successfully grew poliovirus using tissues cultured in vitro. Tissue

culture proved to be an excellent source of virus. Jonas Edward Salk

soon developed an inactive polio vaccine consisting of virus grown

from tissue culture that had been inactivated (killed) by chemical

treatment. This vaccine became available for general use in 1955, almost

fifty years after poliovirus had first been identified.

Sabin, however, was not convinced that an inactivated virus vaccine

was adequate. He believed that it would provide only temporary

protection and that individuals would have to be vaccinated

repeatedly in order to maintain protective levels of antibodies.

Knowing that natural infection with poliovirus induced lifelong immunity,

Sabin believed that a vaccine consisting of a living virus

was necessary to produce long-lasting immunity. Also, unlike the

inactive vaccine, which is injected, a living virus (weakened so that

it would not cause disease) could be taken orally and would invade

the body and replicate of its own accord.

Sabin was not alone in his beliefs. Hilary Koprowski and Harold

Cox also favored a living virus vaccine and had, in fact, begun

searching for weakened strains of poliovirus as early as 1946 by repeatedly

growing the virus in rodents. When Sabin began his search

for weakened virus strains in 1953, a fiercely competitive contest ensued

to achieve an acceptable live virus vaccine.

Rare, Mutant Polioviruses

Sabin’s approach was based on the principle that, as viruses acquire

the ability to replicate in a foreign species or tissue (for example,

in mice), they become less able to replicate in humans and thus

less able to cause disease. Sabin used tissue culture techniques to

isolate those polioviruses that grew most rapidly in monkey kidney

cells. He then employed a technique developed by Renato Dulbecco

that allowed him to recover individual virus particles. The recovered

viruses were injected directly into the brains or spinal cords of

monkeys in order to identify those viruses that did not damage the

nervous system. These meticulously performed experiments, which

involved approximately nine thousand monkeys and more than

one hundred chimpanzees, finally enabled Sabin to isolate rare mutant

polioviruses that would replicate in the intestinal tract but not

in the nervous systems of chimpanzees or, it was hoped, of humans.

In addition, the weakened virus strains were shown to stimulate antibodies when they were fed to chimpanzees; this was a critical attribute

for a vaccine strain.

By 1957, Sabin had identified three strains of attenuated viruses that

were ready for small experimental trials in humans. Asmall group of

volunteers, including Sabin’s own wife and children, were fed the vaccine

with promising results. Sabin then gave his vaccine to virologists

in the Soviet Union, Eastern Europe, Mexico, and Holland for further

testing. Combined with smaller studies in the United States, these trials

established the effectiveness and safety of his oral vaccine.

During this period, the strains developed by Cox and by Koprowski

were being tested also in millions of persons in field trials

around the world. In 1958, two laboratories independently compared

the vaccine strains and concluded that the Sabin strains were

superior. In 1962, after four years of deliberation by the U.S. Public

Health Service, all three of Sabin’s vaccine strains were licensed for

general use.Consequences

The development of polio vaccines ranks as one of the triumphs of

modern medicine. In the early 1950’s, paralytic polio struck 13,500

out of every 100 million Americans. The use of the Salk vaccine

greatly reduced the incidence of polio, but outbreaks of paralytic disease

continued to occur: Fifty-seven hundred cases were reported in

1959 and twenty-five hundred cases in 1960. In 1962, the oral Sabin

vaccine became the vaccine of choice in the United States. Since its

widespread use, the number of paralytic cases in the United States

has dropped precipitously, eventually averaging fewer than ten per

year. Worldwide, the oral vaccine prevented an estimated 5 million

cases of paralytic poliomyelitis between 1970 and 1990.

The oral vaccine is not without problems. Occasionally, the living

virus mutates to a disease-causing (virulent) form as it multiplies in

the vaccinated person. When this occurs, the person may develop

paralytic poliomyelitis. The inactive vaccine, in contrast, cannot

mutate to a virulent form. Ironically, nearly every incidence of polio

in the United States is caused by the vaccine itself.

In the developing countries of the world, the issue of vaccination is

more pressing. Millions receive neither form of polio vaccine; as a result,

at least 250,000 individuals are paralyzed or die each year. The World

Health Organization and other health providers continue to work toward

the very practical goal of completely eradicating this disease.

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, evidence has been

found of efforts to fashion a device that would permit people to perform

these calculations with reduced effort and increased accuracy.

The ancient Babylonians are regarded as the inventors of the first

abacus (or counting board, from the Greek abakos, meaning “board”

or “tablet”). It was originally little more than a row of shallow

grooves with pebbles or bone fragments as counters.

The next step in mechanical calculation did not occur until the

early seventeenth century. John Napier, a Scottish baron and mathematician,

originated the concept of “logarithms” as a mathematical

device to make calculating easier. This concept led to the first slide

rule, created by the English mathematician William Oughtred of

Cambridge. Oughtred’s invention consisted of two identical, circular

logarithmic scales held together and adjusted by hand. The slide

rule made it possible to perform rough but rapid multiplication and

division. Oughtred’s invention in 1623 was paralleled by the work

of a German professor,Wilhelm Schickard, who built a “calculating

clock” the same year. Because the record of Schickard’s work was

lost until 1935, however, the French mathematician Blaise Pascal

was generally thought to have built the first mechanical calculator,

the “Pascaline,” in 1645.Other versions of mechanical calculators were built in later centuries,

but none was rapid or compact enough to be useful beyond specific

laboratory or mercantile situations. Meanwhile, the dream of

such a machine continued to fascinate scientists and mathematicians.

The development that made a fast, small calculator possible did

not occur until the middle of the twentieth century, when Jack St.

Clair Kilby of Texas Instruments invented the silicon microchip (or

integrated circuit) in 1958. An integrated circuit is a tiny complex of

electronic components and their connections that is produced in or

on a small slice of semiconductor material such as silicon. Patrick

Haggerty, then president of Texas Instruments, wrote in 1964 that

“integrated electronics” would “remove limitations” that determined

the size of instruments, and he recognized that Kilby’s invention

of the microchip made possible the creation of a portable,

hand-held calculator. He challenged Kilby to put together a team to

design a calculator that would be as powerful as the large, electromechanical

models in use at the time but small enough to fit into a

coat pocket. Working with Jerry D. Merryman and James Van Tassel,

Kilby began to work on the project in October, 1965.

An Amazing Reality

At the outset, there were basically five elements that had to be designed.

These were the logic designs that enabled the machine to

perform the actual calculations, the keyboard or keypad, the power

supply, the readout display, and the outer case. Kilby recalls that

once a particular size for the unit had been determined (something

that could be easily held in the hand), project manager Merryman

was able to develop the initial logic designs in three days.Van Tassel

contributed his experience with semiconductor components to solve

the problems of packaging the integrated circuit. The display required

a thermal printer that would work on a low power source.

The machine also had to include a microencapsulated ink source so

that the paper readouts could be imprinted clearly. Then the paper

had to be advanced for the next calculation. Kilby, Merryman, and

Van Tassel filed for a patent on their work in 1967.

Although this relatively small, working prototype of the minicalculator

made obsolete the transistor-operated design of the much larger desk calculators, the cost of setting up new production lines

and the need to develop a market made it impractical to begin production

immediately. Instead, Texas Instruments and Canon of Tokyo

formed a joint venture, which led to the introduction of the

Canon Pocketronic Printing Calculator in Japan in April, 1970, and

in the United States that fall. Built entirely of Texas Instruments

parts, this four-function machine with three metal oxide semiconductor (MOS) circuits was similar to the prototype designed in 1967.

The calculator was priced at $400, weighed 740 grams, and measured

101 millimeters wide by 208 millimeters long by 49 millimeters

high. It could perform twelve-digit calculations and worked up

to four decimal places.

In September, 1972, Texas Instruments put the Datamath, its first

commercial hand-held calculator using a single MOS chip, on the

retail market. It weighed 340 grams and measured 75 millimeters

wide by 137 millimeters long by 42 millimeters high. The Datamath

was priced at $120 and included a full-floating decimal point that

could appear anywhere among the numbers on its eight-digit, lightemitting

diode (LED) display. It came with a rechargeable battery

that could also be connected to a standard alternating current (AC)

outlet. The Datamath also had the ability to conserve power while

awaiting the next keyboard entry. Finally, the machine had a built-in

limited amount of memory storage.Consequences

Prior to 1970, most calculating machines were of such dimensions

that professional mathematicians and engineers were either tied to

their desks or else carried slide rules whenever they had to be away

from their offices. By 1975, Keuffel&Esser, the largest slide rule manufacturer

in the world, was producing its last model, and mechanical

engineers found that problems that had previously taken a week

could now be solved in an hour using the new machines.

That year, the Smithsonian Institution accepted the world’s first

miniature electronic calculator for its permanent collection, noting

that it was the forerunner of more than one hundred million pocket

calculators then in use. By the 1990’s, more than fifty million portable

units were being sold each year in the United States. In general,

the electronic pocket calculator revolutionized the way in which

people related to the world of numbers.

Moreover, the portability of the hand-held calculator made it

ideal for use in remote locations, such as those a petroleum engineer

might have to explore. Its rapidity and reliability made it an indispensable

instrument for construction engineers, architects, and real

estate agents, who could figure the volume of a room and other

building dimensions almost instantly and then produce cost estimates

almost on the spot.

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 ivory, which was somewhat

difficult to obtain in large quantities at reasonable prices. Earlier,

Christian Friedrich Schönbein had laid the groundwork for a breakthrough

in the quest for a new material in 1846 by the serendipitous

discovery of nitrocellulose, more commonly known as “guncotton,”

which was produced by the reaction of nitric acid with cotton.

An American inventor, John Wesley Hyatt, while looking for a

substitute for ivory as a material for making billiard balls, discovered

that the addition of camphor to nitrocellulose under certain

conditions led to the formation of a white material that could be

molded and machined. He dubbed this substance “celluloid,” and

this product is now acknowledged as the first synthetic plastic. Celluloid

won the prize for Hyatt, and he promptly set out to exploit his

product. Celluloid was used to make baby rattles, collars, dentures,

and other manufactured goods.

As a billiard ball substitute, however, it was not really adequate,

for various reasons. First, it is thermoplastic—in other words, a material

that softens when heated and can then be easily deformed or

molded. It was thus too soft for billiard ball use. Second, it was

highly flammable, hardly a desirable characteristic. Awidely circulated, perhaps apocryphal, story claimed that celluloid billiard balls

detonated when they collided.

Truly Artificial

Since celluloid can be viewed as a derivative of a natural product,

it is not a completely synthetic substance. Leo Hendrik Baekeland

has the distinction of being the first to produce a completely artificial

plastic. Born in Ghent, Belgium, Baekeland emigrated to the

United States in 1889 to pursue applied research, a pursuit not encouraged

in Europe at the time. One area in which Baekeland hoped

to make an inroad was in the development of an artificial shellac.

Shellac at the time was a natural and therefore expensive product,

and there would be a wide market for any reasonably priced substitute.

Baekeland’s research scheme, begun in 1905, focused on finding

a solvent that could dissolve the resinous products from a certain

class of organic chemical reaction.

The particular resins he used had been reported in the mid-

1800’s by the German chemist Adolf von Baeyer. These resins were

produced by the condensation reaction of formaldehyde with a

class of chemicals called “phenols.” Baeyer found that frequently

the major product of such a reaction was a gummy residue that was

virtually impossible to remove from glassware. Baekeland focused

on finding a material that could dissolve these resinous products.

Such a substance would prove to be the shellac substitute he sought.

These efforts proved frustrating, as an adequate solvent for these

resins could not be found. After repeated attempts to dissolve these

residues, Baekeland shifted the orientation of his work. Abandoning

the quest to dissolve the resin, he set about trying to develop a resin

that would be impervious to any solvent, reasoning that such a material

would have useful applications.

Baekeland’s experiments involved the manipulation of phenolformaldehyde

reactions through precise control of the temperature

and pressure at which the reactions were performed. Many of these

experiments were performed in a 1.5-meter-tall reactor vessel, which

he called a “Bakelizer.” In 1907, these meticulous experiments paid

off when Baekeland opened the reactor to reveal a clear solid that

was heat resistant, nonconducting, and machinable. Experimentation proved that the material could be dyed practically any color in

the manufacturing process, with no effect on the physical properties

of the solid.

Baekeland filed a patent for this new material in 1907. (This patent

was filed one day before that filed by James Swinburne, a British electrical engineer who had developed a similar material in his

quest to produce an insulating material.) Baekeland dubbed his new

creation “Bakelite” and announced its existence to the scientific

community on February 15, 1909, at the annual meeting of the American

Chemical Society. Among its first uses was in the manufacture

of ignition parts for the rapidly growing automobile industry.

Impact

Bakelite proved to be the first of a class of compounds called

“synthetic polymers.” Polymers are long chains of molecules chemically

linked together. There are many natural polymers, such as cotton.

The discovery of synthetic polymers led to vigorous research

into the field and attempts to produce other useful artificial materials.

These efforts met with a fair amount of success; by 1940, a multitude

of new products unlike anything found in nature had been discovered.

These included such items as polystyrene and low-density

polyethylene. In addition, artificial substitutes for natural polymers,

such as rubber, were a goal of polymer chemists. One of the results

of this research was the development of neoprene.

Industries also were interested in developing synthetic polymers

to produce materials that could be used in place of natural fibers

such as cotton. The most dramatic success in this area was achieved

by Du Pont chemist Wallace Carothers, who had also developed

neoprene. Carothers focused his energies on forming a synthetic fiber

similar to silk, resulting in the synthesis of nylon.

Synthetic polymers constitute one branch of a broad area known

as “materials science.” Novel, useful materials produced synthetically

from a variety of natural materials have allowed for tremendous

progress in many areas. Examples of these new materials include

high-temperature superconductors, composites, ceramics, and

plastics. These materials are used to make the structural components

of aircraft, artificial limbs and implants, tennis rackets, garbage

bags, and many other common objects.

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 that became the coal,

oil, and natural gas that the world relies upon for energy. Some of this

fuel is used directly to heat homes and to power factories and gasoline

vehicles. Much of this fossil fuel, however, is burned to produce

the electricity on which modern society depends.

The amount of energy available from the Sun is difficult to imagine,

but some comparisons may be helpful. During each forty-hour

period, the Sun provides the earth with as much energy as the

earth’s total reserves of coal, oil, and natural gas. It has been estimated

that the amount of energy provided by the sun’s radiation

matches the earth’s reserves of nuclear fuel every forty days. The

annual solar radiation that falls on about twelve hundred square

miles of land in Arizona matched the world’s estimated total annual

energy requirement for 1960. Scientists have been searching for

many decades for inexpensive, efficient means of converting this

vast supply of solar radiation directly into electricity.

The Bell Solar Cell

Throughout its history, Bell Systems has needed to be able to

transmit, modulate, and amplify electrical signals. Until the 1930’s,

these tasks were accomplished by using insulators and metallic conductors. At that time, semiconductors, which have electrical properties

that are between those of insulators and those of conductors,

were developed. One of the most important semiconductor materials

is silicon, which is one of the most common elements on the

earth. Unfortunately, silicon is usually found in the form of compounds

such as sand or quartz, and it must be refined and purified

before it can be used in electrical circuits. This process required

much initial research, and very pure silicon was not available until

the early 1950’s.

Electric conduction in silicon is the result of the movement of

negative charges (electrons) or positive charges (holes). One way of

accomplishing this is by deliberately adding to the silicon phosphorus

or arsenic atoms, which have five outer electrons. This addition

creates a type of semiconductor that has excess negative charges (an

n-type semiconductor). Adding boron atoms, which have three

outer electrons, creates a semiconductor that has excess positive

charges (a p-type semiconductor). Calvin Fuller made an important

study of the formation of p-n junctions, which are the points at

which p-type and n-type semiconductors meet, by using the process

of diffusing impurity atoms—that is, adding atoms of materials that

would increase the level of positive or negative charges, as described

above. Fuller’s work stimulated interested in using the process

of impurity diffusion to create cells that would turn solar energy

into electricity. Fuller and Gerald Pearson made the first largearea

p-n junction by using the diffusion process. Daryl Chapin,

Fuller, and Pearson made a similar p-n junction very close to the

surface of a silicon crystal, which was then exposed to sunlight.

The cell was constructed by first making an ingot of arsenicdoped

silicon that was then cut into very thin slices. Then a very

thin layer of p-type silicon was formed over the surface of the n-type

wafer, providing a p-n junction close to the surface of the cell. Once

the cell cooled, the p-type layer was removed from the back of the

cell and lead wires were attached to the two surfaces. When light

was absorbed at the p-n junction, electron-hole pairs were produced,

and the electric field that was present at the junction forced

the electrons to the n side and the holes to the p side.

The recombination of the electrons and holes takes place after the

electrons have traveled through the external wires, where they do useful work. Chapin, Fuller, and Pearson announced in 1954 that

the resulting photovoltaic cell was the most efficient (6 percent)

means then available for converting sunlight into electricity.

The first experimental use of the silicon solar battery was in amplifiers

for electrical telephone signals in rural areas. An array of 432

silicon cells, capable of supplying 9 watts of power in bright sunlight,

was used to charge a nickel-cadmium storage battery. This, in

turn, powered the amplifier for the telephone signal. The electrical

energy derived from sunlight during the day was sufficient to keep

the storage battery charged for continuous operation. The system

was successfully tested for six months of continuous use in Americus,

Georgia, in 1956. Although it was a technical success, the silicon solar

cell was not ready to compete economically with conventional

means of producing electrical power.

Consequences

One of the immediate applications of the solar cell was to supply

electrical energy for Telstar satellites. These cells are used extensively

on all satellites to generate power. The success of the U.S. satellite program prompted serious suggestions in 1965 for the use of

an orbiting power satellite. A large satellite could be placed into a

synchronous orbit of the earth. It would collect sunlight, convert it

to microwave radiation, and beam the energy to an Earth-based receiving

station. Many technical problems must be solved, however,

before this dream can become a reality.

Solar cells are used in small-scale applications such as power

sources for calculators. Large-scale applications are still not economically

competitive with more traditional means of generating

electric power. The development of the ThirdWorld countries, however,

may provide the incentive to search for less-expensive solar

cells that can be used, for example, to provide energy in remote villages.

As the standards of living in such areas improve, the need for

electric power will grow. Solar cells may be able to provide the necessary

energy while safeguarding the environment for future generations.

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 his work on glass-enclosed

primary batteries. He discovered that the voltage of his batteries increased

with intensified illumination and that green light produced

the highest voltage. Since Becquerel researched batteries exclusively,

however, the liquid-type photocell was not discovered until

1929, when the Wein and Arcturus cells were introduced commercially.

These cells were miniature voltaic cells arranged so that light

falling on one side of the front plate generated a considerable

amount of electrical energy. The cells had short lives, unfortunately;

when subjected to cold, the electrolyte froze, and when subjected to

heat, the gas generated would expand and explode the cells.

What came to be known as the photoelectric cell, a device connecting

light and electricity, had its beginnings in the 1880’s. At

that time, scientists noticed that a negatively charged metal plate

lost its charge much more quickly in the light (especially ultraviolet

light) than in the dark. Several years later, researchers demonstrated

that this phenomenon was not an “ionization” effect because

of the air’s increased conductivity, since the phenomenon

took place in a vacuum but did not take place if the plate were positively

charged. Instead, the phenomenon had to be attributed to

the light that excited the electrons of the metal and caused them to

fly off: Aneutral plate even acquired a slight positive charge under the influence of strong light. Study of this effect not only contributed

evidence to an electronic theory of matter—and, as a result of

some brilliant mathematical work by the physicist Albert Einstein,

later increased knowledge of the nature of radiant energy—but

also further linked the studies of light and electricity. It even explained

certain chemical phenomena, such as the process of photography.

It is important to note that all the experimental work on

photoelectricity accomplished prior to the work of Julius Elster

and Hans Friedrich Geitel was carried out before the existence of

the electron was known.

Explaining Photoelectric Emission

After the English physicist Sir Joseph John Thomson’s discovery

of the electron in 1897, investigators soon realized that the photoelectric

effect was caused by the emission of electrons under the influence

of radiation. The fundamental theory of photoelectric emission

was put forward by Einstein in 1905 on the basis of the German

physicist Max Planck’s quantum theory (1900). Thus, it was not surprising

that light was found to have an electronic effect. Since it was

known that the longer radio waves could shake electrons into resonant

oscillations and the shorter X rays could detach electrons from

the atoms of gases, the intermediate waves of visual light would

have been expected to have some effect upon electrons—such as detaching

them from metal plates and therefore setting up a difference

of potential. The photoelectric cell, developed by Elster and Geitel

in 1904, was a practical device that made use of this effect.

In 1888,Wilhelm Hallwachs observed that an electrically charged

zinc electrode loses its charge when exposed to ultraviolet radiation

if the charge is negative, but is able to retain a positive charge under

the same conditions. The following year, Elster and Geitel discovered

a photoelectric effect caused by visible light; however, they

used the alkali metals potassium and sodium for their experiments

instead of zinc.

The Elster-Geitel photocell (a vacuum emission cell, as opposed to

a gas-filled cell) consisted of an evacuated glass bulb containing two

electrodes. The cathode consisted of a thin film of a rare, chemically

active metal (such as potassium) that lost its electrons fairly readily; the anode was simply a wire sealed in to complete the circuit. This anode

was maintained at a positive potential in order to collect the negative

charges released by light from the cathode. The Elster-Geitel

photocell resembled two other types of vacuum tubes in existence at

the time: the cathode-ray tube, in which the cathode emitted electrons

under the influence of a high potential, and the thermionic

valve (a valve that permits the passage of current in one direction only), in which it emitted electrons under the influence of heat. Like

both of these vacuum tubes, the photoelectric cell could be classified

as an “electronic” device.

The new cell, then, emitted electrons when stimulated by light, and

at a rate proportional to the intensity of the light. Hence, a current

could be obtained from the cell. Yet Elster and Geitel found that their

photoelectric currents fell off gradually; they therefore spoke of “fatigue”

(instability). It was discovered later that most of this change was

not a direct effect of a photoelectric current’s passage; it was not even

an indirect effect but was caused by oxidation of the cathode by the air.

Since all modern cathodes are enclosed in sealed vessels, that source of

change has been completely abolished. Nevertheless, the changes that

persist in modern cathodes often are indirect effects of light that can be

produced independently of any photoelectric current.

Impact

The Elster-Geitel photocell was, for some twenty years, used in

all emission cells adapted for the visible spectrum, and throughout

the twentieth century, the photoelectric cell has had a wide variety

of applications in numerous fields. For example, if products leaving

a factory on a conveyor belt were passed between a light and a cell,

they could be counted as they interrupted the beam. Persons entering

a building could be counted also, and if invisible ultraviolet rays

were used, those persons could be detected without their knowledge.

Simple relay circuits could be arranged that would automatically

switch on street lamps when it grew dark. The sensitivity of

the cell with an amplifying circuit enabled it to “see” objects too

faint for the human eye, such as minor stars or certain lines in the

spectra of elements excited by a flame or discharge. The fact that the

current depended on the intensity of the light made it possible to

construct photoelectric meters that could judge the strength of illumination

without risking human error—for example, to determine

the right exposure for a photograph.

A further use for the cell was to make talking films possible. The

early “talkies” had depended on gramophone records, but it was very

difficult to keep the records in time with the film. Now, the waves of

speech and music could be recorded in a “sound track” by turning the sound first into current through a microphone and then into light with

a neon tube or magnetic shutter; next, the variations in the intensity of

this light on the side of the film were photographed. By reversing the

process and running the film between a light and a photoelectric cell,

the visual signals could be converted back to sound.

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 executive officer of IBM at the

time of the decision to market a personal computer

John Opel (1925- ), a member of the Corporate Management

Committee

George Belzel, a member of the Corporate Management

Committee

Paul Rizzo, a member of the Corporate Management Committee

Dean McKay (1921- ), a member of the Corporate

Management Committee

William L. Sydnes, the leader of the original twelve-member

design team

Shaking up the System

For many years, the International Business Machines (IBM) Corporation

had been set in its ways, sticking to traditions established

by its founder, Tom Watson, Sr. If it hoped to enter the new microcomputer

market, however, it was clear that only nontraditional

methods would be useful. Apple Computer was already beginning

to make inroads into large IBM accounts, and IBM stock was starting

to stagnate onWall Street. A1979 BusinessWeek article asked: “Is

IBM just another stodgy, mature company?” The microcomputer

market was expected to grow more than 40 percent in the early

1980’s, but IBM would have to make some changes in order to bring

a competitive personal computer (PC) to the market.

The decision to build and market the PC was made by the company’s

Corporate Management Committee (CMC). CMC members

included chief executive officer Frank Cary, John Opel, George Belzel, Paul Rizzo, Dean McKay, and three senior vice presidents. In

July of 1980, Cary gave the order to proceed. He wanted the PC to be

designed and built within a year. The CMC approved the initial design

of the PC one month later. Twelve engineers, with William L.

Sydnes as their leader, were appointed as the design team. At the

end of 1980, the team had grown to 150.

Most parts of the PC had to be produced outside IBM. Microsoft

Corporation won the contract to produce the PC’s disk operating system

(DOS) and the BASIC (Beginner’s All-purpose Symbolic Instruction

Code) language that is built into the PC’s read-only memory

(ROM). Intel Corporation was chosen to make the PC’s central processing

unit (CPU) chip, the “brains” of the machine. Outside programmers

wrote software for the PC. Ten years earlier, this strategy

would have been unheard of within IBM since all aspects of manufacturing,

service, and repair were traditionally taken care of in-house.

Marketing the System

IBM hired a New York firm to design a media campaign for the

new PC. Readers of magazines and newspapers saw the character

of Charlie Chaplin advertising the new PC. The machine was delivered

on schedule on August 12, 1981. The price of the basic “system

unit” was $1,565. A system with 64 kilobytes of random access

memory (RAM), a 13-centimeter single-sided disk drive holding

160 kilobytes, and a monitor was priced at about $3,000. A system

with color graphics, a second disk drive, and a dot matrix printer

cost about $4,500.

Many useful computer programs had been adapted to the PC

and were available when it was introduced. VisiCalc from Personal

Software—the program that is credited with “making” the microcomputer

revolution—was one of the first available. Other packages

included a comprehensive accounting system by Peachtree

Software and a word processing package called Easywriter by Information

Unlimited Software.

As the selection of software grew, so did sales. In the first year after

its introduction, the IBM PC went from a zero market share to 28

percent of the market. Yet the credit for the success of the PC does

not go to IBM alone. Many hundreds of companies were able to produce software and hardware for the PC.Within two years, powerful

products such as Lotus Corporation’s 1-2-3 business spreadsheet

had come to the market. Many believed that Lotus 1-2-3 was the

program that caused the PC to become so phenomenally successful.

Other companies produced hardware features (expansion boards)

that increased the PC’s memory storage or enabled the machine to

“drive” audiovisual presentations such as slide shows. Business especially

found the PC to be a powerful tool. The PC has survived because

of its expansion capability.

IBM has continued to upgrade the PC. In 1983, the PC/XT was

introduced. It had more expansion slots and a fixed disk offering 10

million bytes of storage for programs and data. Many of the companies

that made expansion boards found themselves able to make

whole PCs. An entire range of PC-compatible systems was introduced

to the market, many offering features that IBM did not include

in the original PC. The original PC has become a whole family

of computers, sold by both IBM and other companies. The hardware

and software continue to evolve; each generation offers more computing

power and storage with a lower price tag.

Consequences

IBM’s entry into the microcomputer market gave microcomputers

credibility. Apple Computer’s earlier introduction of its computer

did not win wide acceptance with the corporate world. Apple

did, however, thrive within the educational marketplace. IBM’s

name already carried with it much clout, because IBM was a successful

company. Apple Computer represented all that was great

about the “new” microcomputer, but the IBM PC benefited from

IBM’s image of stability and success.

IBM coined the term personal computer and its acronym PC. The

acronym PC is now used almost universally to refer to the microcomputer.

It also had great significance with users who had previously

used a large mainframe computer that had to be shared with

the whole company. This was their personal computer. That was important

to many PC buyers, since the company mainframe was perceived

as being complicated and slow. The PC owner now had complete

control.

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 were aware of antibacterial

substances but did not know how to make full use of them

in the treatment of diseases. Sir Alexander Fleming discovered penicillin

in 1928, but he was unable to duplicate his laboratory results

of its antibiotic properties in clinical tests; as a result, he did not recognize

the medical potential of penicillin. Between 1935 and 1940,

penicillin was purified, concentrated, and clinically tested by pathologist

Baron Florey, biochemist Ernst Boris Chain, and members

of their Oxford research group. Their achievement has since been regarded

as one of the greatest medical discoveries of the twentieth

century.

Florey was a professor at Oxford University in charge of the Sir

William Dunn School of Pathology. Chain had worked for two years

at Cambridge University in the laboratory of Frederick Gowland

Hopkins, an eminent chemist and discoverer of vitamins. Hopkins

recommended Chain to Florey, who was searching for a candidate

to lead a new biochemical unit in the Dunn School of Pathology.

In 1938, Florey and Chain formed a research group to investigate

the phenomenon of antibiosis, or the antagonistic association between

different forms of life. The union of Florey’s medical knowledge

and Chain’s biochemical expertise proved to be an ideal combination for exploring the antibiosis potential of penicillin. Florey

and Chain began their investigation with a literature search in

which Chain came across Fleming’s work and added penicillin to

their list of potential antibiotics.

Their first task was to isolate pure penicillin from a crude liquid

extract. A culture of Fleming’s original Penicillium notatum was

maintained at Oxford and was used by the Oxford group for penicillin

production. Extracting large quantities of penicillin from the

medium was a painstaking task, as the solution contained only one

part of the antibiotic in ten million. When enough of the raw juice

was collected, the Oxford group focused on eliminating impurities

and concentrating the penicillin. The concentrated liquid was then

freeze-dried, leaving a soluble brown powder.

Spectacular Results

In May, 1940, Florey’s clinical tests of the crude penicillin proved

its value as an antibiotic. Following extensive controlled experiments

with mice, the Oxford group concluded that they had discovered

an antibiotic that was nontoxic and far more effective against

pathogenic bacteria than any of the known sulfa drugs. Furthermore,

penicillin was not inactivated after injection into the bloodstream

but was excreted unchanged in the urine. Continued tests

showed that penicillin did not interfere with white blood cells and

had no adverse effect on living cells. Bacteria susceptible to the antibiotic

included those responsible for gas gangrene, pneumonia,

meningitis, diphtheria, and gonorrhea. American researchers later

proved that penicillin was also effective against syphilis.

In January, 1941, Florey injected a volunteer with penicillin

and found that there were no side effects to treatment with the

antibiotic. In February, the group began treatment of Albert Alexander,

a forty-three-year-old policeman with a serious staphylococci

and streptococci infection that was resisting massive doses of

sulfa drugs. Alexander had been hospitalized for two months after

an infection in the corner of his mouth had spread to his face,

shoulder, and lungs. After receiving an injection of 200 milligrams

of penicillin, Alexander showed remarkable progress, and for the

next ten days his condition improved. Unfortunately, the Oxford production facility was unable to generate enough penicillin to

overcome Alexander’s advanced infection completely, and he died

on March 15. A later case involving a fourteen-year-old boy with

staphylococcal septicemia and osteomyelitis had a more spectacular

result: The patient made a complete recovery in two months. In

all the early clinical treatments, patients showed vast improvement,

and most recovered completely from infections that resisted

all other treatment.

Impact

Penicillin is among the greatest medical discoveries of the twentieth

century. Florey and Chain’s chemical and clinical research

brought about a revolution in the treatment of infectious disease.

Almost every organ in the body is vulnerable to bacteria. Before

penicillin, the only antimicrobial drugs available were quinine, arsenic,

and sulfa drugs. Of these, only the sulfa drugs were useful for

treatment of bacterial infection, but their high toxicity often limited

their use. With this small arsenal, doctors were helpless to treat

thousands of patients with bacterial infections.

The work of Florey and Chain achieved particular attention because

ofWorldWar II and the need for treatments of such scourges

as gas gangrene, which had infected the wounds of numerous

World War I soldiers. With the help of Florey and Chain’s Oxford

group, scientists at the U.S. Department of Agriculture’s Northern

Regional Research Laboratory developed a highly efficient method

for producing penicillin using fermentation. After an extended search,

scientists were also able to isolate a more productive penicillin

strain, Penicillium chrysogenum. By 1945, a strain was developed that

produced five hundred times more penicillin than Fleming’s original

mold had.

Penicillin, the first of the “wonder drugs,” remains one of the

most powerful antibiotic in existence. Diseases such as pneumonia,

meningitis, and syphilis are still treated with penicillin. Penicillin

and other antibiotics also had a broad impact on other fields of medicine,

as major operations such as heart surgery, organ transplants,

and management of severe burns became possible once the threat of

bacterial infection was minimized.Florey and Chain received numerous awards for their achievement,

the greatest of which was the 1945 Nobel Prize in Physiology

or Medicine, which they shared with Fleming for his original discovery.

Florey was among the most effective medical scientists of

his generation, and Chain earned similar accolades in the science of

biochemistry. This combination of outstanding medical and chemical

expertise made possible one of the greatest discoveries in human

history.