CUARTA UNIDAD.

PATRONES DE ORGANIZACIÓN DE UN PÁRRAFO

LEUKEMIA

http://www.healthscout.com/ency/68/622/main.html

Definición

Leukemia is a malignant disorder (a form of cancer) that involves the bone marrow and blood systems. Leukemia results in the uncontrolled growth of abnormal (leukemic) white blood cells. As a result of the uncontrolled growth of leukemic cells in the bone marrow, there is inadequate space in the bone marrow for normal blood production (hematopoiesis) to occur. The lack of normal blood growth results in the lack of normal white blood cells (increasing the risk of infection), the lack of red blood cells (resulting in fatigue, weakness, and anemia) and the lack of normal platelet production (increasing the risk of bleeding).

There are many different types of leukemia. Each of these types may appear with some, none, or all of the symptoms or signs described below.

Description of Leukemia

The term leukemia, which is derived from Greek, literally means "white blood." The bone marrow may become severely impaired and unable to maintain production of sufficient levels of red blood cells and platelets. At the same time, white blood cell production becomes so rapid that these cells do not reach the level of maturity necessary to perform their infection-fighting functions
Leukemic cells infiltrate all the major organs of the body, sometimes causing these organs to malfunction or fail. The kidneys may become impaired. The liver and spleen may become enlarged.


Normally, the spleen acts as a filter for the blood, screening out aging red cells and platelets. When the spleen becomes enlarged, it can actually start doing its job too well, removing perfectly healthy red cells and platelets, further reducing the number of these already scarce cells.

As leukemia progresses, the entire blood system may become flooded with immature blast cells. If this disease is left untreated, a person with leukemia becomes increasingly susceptible to fatigue, excessive bleeding and infections until, finally, the body becomes virtually defenseless, making every minor injury or infection very serious.

Leukemia may be fatal. People may die from internal bleeding which would have been prevented by the platelets. Or, more often, they may die from infections which start with a virus or bacteria that would ordinarily have been wiped out by healthy white blood cells. The exact course leukemia takes, and the speed with which it takes that course, varies with the type and age of the white cells initially affected.

Narración

Biografía de Neil A. Armstrong
http://www.nasa.gov/centers/glenn/about/bios/neilabio.html

Neil A. Armstrong, the first man to walk on the moon, was born in Wapakoneta, Ohio, on August 5, 1930. He began his NASA career in Ohio.

After serving as a naval aviator from 1949 to 1952, Armstrong joined the National Advisory Committee for Aeronautics (NACA) in 1955. His first assignment was with the NACA Lewis Research Center (now NASA Glenn) in Cleveland. Over the next 17 years, he was an engineer, test pilot, astronaut and administrator for NACA and its successor agency, the National Aeronautics and Space Administration (NASA).

As a research pilot at NASA's Flight Research Center, Edwards, Calif., he was a project pilot on many pioneering high speed aircraft, including the well known, 4000-mph X-15. He has flown over 200 different models of aircraft, including jets, rockets, helicopters and gliders.

Armstrong transferred to astronaut status in 1962. He was assigned as command pilot for the Gemini 8 mission. Gemini 8 was launched on March 16, 1966, and Armstrong performed the first successful docking of two vehicles in space.

As spacecraft commander for Apollo 11, the first manned lunar landing mission, Armstrong gained the distinction of being the first man to land a craft on the moon and first to step on its surface.

Armstrong subsequently held the position of Deputy Associate Administrator for Aeronautics, NASA Headquarters, Washington, D.C. In this position, he was responsible for the coordination and management of overall NASA research and technology work related to aeronautics.

He was Professor of Aerospace Engineering at the University of Cincinnati between 1971-1979. During the years 1982-1992, Armstrong was chairman of Computing Technologies for Aviation, Inc., Charlottesville, Va.

He received a Bachelor of Science Degree in Aeronautical Engineering from Purdue University and a Master of Science in Aerospace Engineering from the University of Southern California. He holds honorary doctorates from a number of universities.

Armstrong is a Fellow of the Society of Experimental Test Pilots and the Royal Aeronautical Society; Honorary Fellow of the American Institute of Aeronautics and Astronautics, and the International Astronautics Federation.

He is a member of the National Academy of Engineering and the Academy of the Kingdom of Morocco. He served as a member of the National Commission on Space (1985-1986), as Vice-Chairman of the Presidential Commission on the Space Shuttle Challenger Accident (1986), and as Chairman of the Presidential Advisory Committee for the Peace Corps (1971-1973).

Armstrong has been decorated by 17 countries. He is the recipient of many special honors, including the Presidential Medal of Freedom; the Congressional Space Medal of Honor; the Explorers Club Medal; the Robert H. Goddard Memorial Trophy; the NASA Distinguished Service Medal; the Harmon International Aviation Trophy; the Royal Geographic Society's Gold Medal; the Federation Aeronautique Internationale's Gold Space Medal; the American Astronautical Society Flight Achievement Award; the Robert J. Collier Trophy; the AIAA Astronautics Award; the Octave Chanute Award; and the John J. Montgomery Award.