| 3401/ Each square
centimetre of skin has 20 tiny blood vessels, 100 sweat glands
and 65 hairs - all rooted in the dermis. They work together
to keep the core temperature of the body at a comfortable
37C.
3402/ Skin consists of two distinct
layers. The outer visible layer, the epidermis, is made up
of several sheets of closely packed cells and ranges in thickness
from 0.1mm on the eyelids to nearly 1mm on the palms and soles.
The top layer of the epidermis is actualy made of ded cells,
which constantly flake off to be replaced by new cells working
their way up from the base layer. The main function of the
epidermis is to waterproof the skin, a protein called keratin
that the cells produce does this, and to form a barrier aginst
germs.
3403/ The inside layer, the dermis
or 'true skin' has a quite different structure. It consists
of connective tissue, which is a complex network of cells,
protein fibres and a packing of carbohydrate molecules. The
dermis provides a great cushioning and insulating material
- protecting the internal organs from shocks and bumps and
also keeping body heat in.
3404/ The seriousness of a burn
depends upon the area and depth of skin affected. Minor, or
first degree burns, such as sunburn, only affect the epidermis.
In a second degree burn, the dermis too is damaged, while
it is actually destroyed in a third degree burn - the affected
area might look white or charred even. The most severe grade
isthe fourth degree (full thickness) burn where the underlying
muscle and bone are actually exposed.
3405/ Shock normally sets in
if 10% or more of the body is affected by second degree (or
higher) burns.
3406/ Few people survive if more
then 70% of the body surface is affected by full thickness
burns. But medical advances mean that survival is more likely
now - although victims will be horribly scarred and in need
of plastic surgery.
3407/ In the UK around 8000 people
a year suffer burns serious enough to require hospital attention,
although relatively few actually die as a result.
3408/ In a fire you are far more
likely to die from smoke inhalation than from burns.
3409/ British sign language has
been in use for hundreds of years and the first account of
the language was printed by John Bulwer in 1644.
3410/ The first bungee jump in
the UK was made by David Kirke on 1st April 1979 from the
Clifton Suspension bridge in Bristol.
3411/ The Ancient Mayans used
to throw women into water wells to please their rain god.
3412/ Modern climate manipulation
began in 1946, when US scientist Vincent Schaefer discovered
that when he dropped frozen carbon dioxide particles ('dry
ice') into a cold chamber it created ice crystals identical
to those found in clouds. Schaefer knew that as warm air rises
from the surface of the Earth it cools and some of the moisture
condenses into tint droplets that form clouds. Millions of
these droplets have to bond together before they will be heavy
enough to fall as rain. Perhaps, he suggested, cluds could
be 'seeded' to create rain over parched deserts. The idea
is still being investigated today using various techniques
that have built on the original idea..
3413/ At any one time there are
approximately 2000 thunderstorms taking place around the globe,
and a typical tropical storm has the energy equivalent of
10,000 one-megaton hydrogen bombs.
3414/ The United Nations passed
an international resolution in 1977 banning the use of the
weather as a mean of waging war.
3415/ As part of a secret operation
during the Vietnam War, codenamed Popeye, aircraft released
a silver iodide rainmaking agent (nicknamed 'Olive Oil') over
the fabled Ho-Chi-Minh trail, the main north-south supply
route for the Vietcong. The schemes failed because the Vietcong
had irrigated the trail. So that even rain from the heaviest
dpour drained stright into ditches.
3416/ Copper was the first metal
used on Earthb, betwen 6-8000 BC, and it was followed by the
dawning of the Bronze Age. The science of metallurgy began
in earnest sometime around 3500 BC, when humans learnt how
to smelt copper, and 2000 years later the Hittites discovered
the benefits of iron and conquered vast tracts of Western
Asia.
3417/ In the last 200 years the
use of metals has increased as scientists have discovered
new ones: until the 17th Century only 12 metals were known
- there are now 86.
3418/ Titanium is extremely light
and strong, but it can cost more than £10,000 a ton,
and because it is so difficult to forge, when making certain
components up to 90% can be wasted before it is used.
3419/ If used in a tank for example,
titanium would offer the same ballistic strength as steel,
but would make a tank 40% lighter. But the cost is prohibitive.
3420/ The largest cel in the
human body is the ovum, which has a diameter of 0.1mm.
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