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ETHIOPIAN SCIENCE & TECHNOLOGY

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Vol. 1, No. 2 ------------ < for cleo community> ---------- November 9, 1992


I would like to thank all last week participants: Abebe Kebede, T.G.X, Brook, Fesseha Atlaw, and the readers for good beginning. There are three topics covered in this issue:

1. Waging Seed Wars

2. Magnetic Disk vs. Optical

3. The Development of Quantum Theory

Finally, your comments, suggestion, and criticism are welcomed.

--the editor

Waging Seed Wars

Debate asks who owns the genetics of plants

by John Willoughby (Houston Chronicle Feb. 18,1991)

In the 1960s, the first satellite to scan California's barely fields produced infrared photos that panicked growers: the barley looked healthy to the naked eye, but according to the photos, the entire crop was diseased. Botanist scoured the world's gene banks for healthy barley samples. They found only two varieties completely free of disease--both from villages in Ethiopia.

Researchers journeyed to East Africa, gathered samples, and backcrossed them with California barley in successive generations until they produced a plant that combined the best characteristics of California barley with the disease-resistant gene.

That bit of genetic sleuthing has been worth about $150 million a year to U.S. barley farmers, estimates rural sociologist Jack Kloppenburg of the University of Wisconsin-Madison. Consumers have benefited, too: "This barley is probably in every single American beer drinker's bottle," says biologist Garrison Wilkes of the University of Massachusetts.

The Ethiopian farmers who had spent centuries developing the disease-resistant barley, however, received not a cent. It is this inequity that formed the basis of a simmering international dispute, a kind of "seed war" over the ownership and control of an increasingly valuable natural resource, the genetic information contained in seeds.

--to be continued

Magnetic Disk vs. Optical

Abstract

Any computer by today standard, must have a storage device. A computer with out storage is the same as an automobile with out a gas tank. This article addresses and compares two area of storage devices; namely, magnetic disk and optical.

Part I

Every mail that I receive through this network has to be stored into magnetic disk or magnetic tape. Therefore, I can read it as to retrieve the mail from the disk, can delete it as to erase the mail from the disk. Magnetic storage comes with different medium, tape, disk and mag card. Magnetic tape is the first erasable storage used for computers. It is not that different from that of ordinary music tape or cassette in its look and method of storing data.

The most popular storage device is a magnetic disk because it is reliable, has more speed, provides random access, and stores a large amount of data. Magnetic disk comes in the form of a hard disk and floppy diskette.

A MAGNETIC DISK

A hard disk is a rigid round platter, coated with metal oxide, fixed on a spindle that rotates it approximately 3,600 rpm and above, and bundled with a header that reads and write a data on the surface of the platter. A floppy diskette is mostly made of a polyurethane materials, coated with metal oxide, covered with a jacket that protects it from dust other particles.

The best way to imagine a magnetic disk would be to picture an album and a record player. When you place an album and turn on the record player, the albums rotates around while the header is hanging above the surface creating contact. Now, assuming everything else is OK, music comes out of the speaker. A hard disk works in similar fashion. When a computer needs to read a data, the spindle rotates the platter while the header is placed on the desired position with out touching the surface. Now, the header reads the orientation of the spots and send it back to other electronic component to be converted to readable form and so on.

A surface of a magnetic disk is divided into sectors and tracks. For instance, a pizza is cut into pieces from the center to the edge creating a triangle shape. To create a sector, a disk is divided the same way and the triangle shape is called SECTOR. TRACKS are a serious of concentric circles on the surface. Once, the disk is divided, all rooms are marked with their own addresses so that data can be stored and retrieved using specific address.

HOW DOES MAGNETIC DISK WORKS?

In general, a disk is filled with a serious of very tiny "spots." These spots can represent information. Since a disk is coated with a magnetic material, if an external magnate is introduced to it, it will change its orientation accordingly. We should remember that a magnet bar has two orientation, one that points to the north and the other, to the south. The property of each spot on the surface of a disk is being able to act like a magnet, would be affected by an external magnet, as to point to north or south pole. In other words, a single spot can be polarized to behave either of directions.

s e c t o r

\-------------------/--

\................./.... < --- track

_\ _ _ _ _ _ _ _ /_ _

....\............./...... < ----- track

----\-----------/----

sector

Figure 1.1

In a simplest form, how do these spots represent data? Data is stored internally as 1s and 0s. However, 1s and 0s are not physically written into a disk; instead, 1s and 0s are represented by north and south pole. Each 1s or 0s is called bit and the combination of eight bit, byte.

Figure 1.1 shows a portion of a disk that consists of sector and tracks; the "dots" (spots) indicate orientation spots. In order to store 1s and 0s, a magnet is introduced to specific spots through the recording head according to the given data. Physically, representation of data looks like as the following--a collection of polarized spots pointing either to the north or south.

----------------------------------------------

< - -> < - < - < - < - -> -> -> -> -> -> < - < - ...

--------------------------------------------------

Figure 1.2

Reading is done through the recording head by detecting the polarization of each bit's spot and converting it into readable form.

--to be continued

The Development of Quantum Theory

At the Turn of the Nineteenth Century

Critical and fundamental discoveries, such as x-rays, the electron, the Zeeman effect, and radioactivity were made at the end of the 19th century. These discoveries helped to understand atomic structure. The work by Michael Faraday (1833), Julius Pluker (1858), Jean Baptiste (1895), and other physicists was crucial for later developments. It was during this period of time that physicists began to understand that cathode rays were negatively charged particles and also that there were several types of emissions from the atom. The Pieter Zeeman discovery, and the Lorentz explanation to the Zeeman discovery that light was emitted by charged particles (electrons) in motion was significant progress in understanding atomic structure. Some of these discoveries and the people who used them, including their explanation are followed.

Wilheln Conrad Rontgen

Wilheln Conrad Rontgen was born in a town called Lennep, Rhineland. At age 3 Rontgen's parents moved to Holland where he underwent part of his education. Then, Rontgen went to Zurich, entered the Polytechnic Institute, and graduated in 1868. Later, he received a doctorate from the University of Zurich 1869.

Prior to his discovery of x-rays, Rontgen had written forty-eight papers on different subjects. Particularly, in 1888, he showed that the convection current was the same as the conduction current. He proved that the current in the wire was the same as the current which can be obtained from the moving charges.

However, Rontgen's contribution to physics became profound on the night of November 8, 1895, when he discovered x-rays. Rontgen was operating with a Hittorf tube which was covered with a black board in a dark room. There was a screen (a sheet of paper) treated with barium platinum-cynide located at a distance in front of the table. When the potential difference of an induction coil was applied to the discharge tube, the screen fluoresced brilliantly. Rontgen, who was puzzled about the new phenomenon, decided to continue his experiment by turning the side of the screen that was not coated with barium platinum-cynide to the table, but the screen still fluoresced brilliantly. Furthermore, when he placed several objects between the tube and the screen, all appeared to be transparent. When he placed his hand between the tube and the screen, he observed his bones on the screen. At this point, he became convinced that he had found a new kind of rays.

Rontgen reported some of the properties of x-rays in his original paper on his discovery. Here are some of the properties of x-rays:

a. X-rays can penetrate all substances to some extent.

b. Photographic plates and films are sensitive to x-rays.

c. He neither could observe reflection, refraction of x-rays, nor the deflection of the x-rays when a magnetic field is introduced to the x-rays.

d. X-rays travel in straight lines.

In spite of all his effort, Rontgen couldn't fully understand the nature of x-rays. He wrote two papers in 1896 and 1897 on x-rays, then pursued his old subjects leaving one of the fundamental question ``what is the nature of x-rays'' to others.

Rontgen received the first Nobel Prize for physics in 1902. In 1914, he joined in signing the manifesto of German scientists to express solidarity to a militarist Germany. However, he later regretted his involvement in signing the manifesto. On February 10, 1923, in Munich, after going through a lot of hardship during the First World War and afterwards, Rontgen died at age of 78.

....this is a project I did a while back

--to be continued

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abassa@neosoft.com/
Abass Belay Alamnehe /
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