A common cause of thermal pollution is using water as a coolant by power stations and industrial manufacturers. This puts back warm water, and so raises the temperature and decreases how much oxygen is in the water. The heat released into the air will make the air warmer which increase global warming.
Immunity (medical)
Immunity is the ability of the body to defend itself from 'foreign bodies'. This means rejecting infections, clearing up dust which gets in the lungs, and killing cancer cells.
Immunity is of two types. Innate immunity protects the host against infection, but has no 'memory', and so gives no long-term immunity.
The second type is adaptive immunity, which does have a kind of 'memory'. It does give long-term protection against specific pathogens.
All animals, plants and fungi have some innate immunity. Vertebrates also have adaptive immunity.
People can be immunised from some diseases by having a vaccination
(injection of some dead or weakened virus, or bacteria that causes the disease). By doing so, the body learns how the virus/bacteria harms the body, and will react more quickly to fight the virus/bacteria when it comes in contact with the virus/bacteria again. When your body has defended itself against the virus/bacteria it will trap the certain virus/bacteria in a "net" so when the virus/bacteria comes back it will be easier to trap those viruses/bacteria as well.
Immunology is a science that examines the structure and function of the immune system. It originates from medicine and early studies on the causes of immunity to disease.
The earliest known mention of immunity was during the plague of Athens in 430 BC. Thucydides noted that people who had recovered from a previous bout of the disease could nurse the sick without contracting the illness a second time.
In the 18th century, Pierre-Louis de Maupertuis made experiments with scorpion venom and observed that certain dogs and mice were immune to this venom.
This and other observations of acquired immunity was later exploited by Louis Pasteur in his development of vaccination and his proposed germ theory of disease. Pasteur's theory was in direct opposition to contemporary theories of disease, such as the miasma theory.
It was not until Robert Koch's 1891 proofs, for which he was awarded a Nobel Prize in 1905, that microorganisms were confirmed as the cause of infectious disease. Viruses were confirmed as human pathogens in 1901, with the discovery of the yellow fever virus by Walter Reed.
Immunology made a great advance towards the end of the 19th century, through rapid developments, in the study of humoral immunity (antibodies) and cellular immunity (T cells and dendritic cells).
Particularly important was the work of Paul Ehrlich, who proposed the side-chain theory to explain the specificity of the antigen-antibody reaction; his contributions to the understanding of humoral immunity were recognized by the award of a Nobel Prize in 1908, which was jointly awarded to the founder of cellular immunology, Elie Mechnikov.
Roman numerals
Roman numerals are a numeral system that was used by ancient Rome. Numbers in this system uses letters from the Latin alphabet. Currently, it uses seven symbols:
The Europeans still used Roman numerals even after the fall of the Roman Empire. From the 14th century, the Europeans replaced Roman numerals with Arabic numerals. However, people still uses the Roman numerals to this day.
One place they are sometimes seen is on clock faces. For example, on the clock of Big Ben, the hours from 1 to 12 are written as:
The and can be read as "one less than 5" (4) and "one less than 10" (9). On most Roman numeral clock faces, however, 4 is written as .
There is a simple rule, whenever the same symbol is written four times, it is replaced by subtracting it from the next higher number (5,50,50,500). That way, IV is written instead of IIII (4), XL instead of XXXX (40), etc. It is used since about the Middle Ages. Usually only one number is subtracted, not two. So 18 is usually XVIII instead of IIXX. Also, the subtraction rule is only valid for the symbol which comes right beforehand in the sequence. This means that 99 is written XCIX, and not IC.
The number zero does not have its own Roman numeral. About 725, Bede or one of his colleagues used the letter N, the abbreviation (short form) of "nihil" (the Latin word for "nothing").
The Romans also used fractions. The most common base for fractions was 1/12, which in Latin is called "uncia" (ounce).
A number of numeral systems are developed for large numbers that cannot be shown with , , , , , and .
One of the systems is the "apostrophus", in which D is written as IƆ (500) and M is written as CIƆ (1,000). In this system, an extra Ɔ means 500, and multiple extra Ɔs are used to mean 5,000, 50,000 etc.
Another system is the "vinculum", in which V, X, L, C, D and M are multiplied by 1,000 by adding an overline.
It is very easy to write a number as a Roman numeral. Simply substract the largest possible Roman numeral, as many times as possible from the number. This system will result in a valid Roman numeral, but will not take the subtraction rule into account.
Getting the number from the numeral is equally simple, by adding the values of the symbols.
In general, the values for 5, 50, 500.. are not subtracted. The same number, with using the subtraction rule:
Map
A map is an image of an area, usually of the Earth or part of the Earth. A map is different from an aerial photograph because it includes interpretation. Many maps are called "charts" such as star charts and nautical charts. Before the late 20th century almost all maps were on paper. Today, many maps are digital, and can be seen on smartphones and computers. However, paper maps are still used.
The word "map" can also be used to talk about a chart or drawing that shows relationships between ideas, people, events, or anything else you can think about. This is why web developers call a list of web pages on a web site a site map.
People who make maps are cartographers.
Many maps today are made using GIS computer systems. These are database systems that are organized by location instead of named records.
If a map is on a piece of paper or a computer screen, it has to be projected. This is because the Earth is round and paper and screens are flat. There are a lot of ways that use mathematics to make map projections. The only kind of map of the Earth that is not projected is one drawn on a sphere. This is called a globe.
Globe
A globe is a scale model with the shape of a sphere. Globes can be scale models of the Earth ("terrestrial globes") or of other planets. Globes can also be models of the celestial sphere ("celestial globes"). The English word "globe" comes from the , meaning round mass or sphere.
Most globes are maps of the Earth. They have the advantage of avoiding the distortions of flat map projections. The most common types are political and physical. Political globes show countries. Physical globes show landscape like mountains and rivers. Some globes are star charts and some are maps of distant worlds.
Global as an adjective is used to mean the entire world rather than any special place on the Earth. It is also used in fields like computers to mean dealing with a whole larger system, rather than its individual little parts.
The fact that the Earth is a sphere was established by Hellenistic astronomy in the 3rd century BCE. The terrestrial globe appeared in that period. Now, there are no terrestrial globes from Classical Antiquity or the Middle Ages in existence. The first example of terrestrial globe known was the one the ancient Greek Crates of Mallus made in the middle of the 2nd century BCE. The Greek geographer Strabo wrote about Crates's terrestrial globe during the early years of the Roman Empire.