Background

Insulin is a hormone that regulates the amount of glucose (sugar) in the
blood and is required for the body to function normally. Insulin is
produced by cells in the pancreas, called the islets of Langerhans. These
cells continuously release a small amount of insulin into the body, but
they release surges of the hormone in response to a rise in the blood
glucose level.

Certain cells in the body change the food ingested into energy, or blood
glucose, that cells can use. Every time a person eats, the blood glucose
rises. Raised blood glucose triggers the cells in the islets of Langerhans
to release the necessary amount of insulin. Insulin allows the blood
glucose to be transported from the blood into the cells. Cells have an
outer wall, called a membrane, that controls what enters and exits the
cell. Researchers do not yet know exactly how insulin works,

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Photo by: Acik


Ceramics can be defined as heat-resistant, nonmetallic, inorganic solids
that are (generally) made up of compounds formed from metallic and
nonmetallic elements. Although different types of ceramics can have very
different properties, in general ceramics are corrosion-resistant and
hard, but brittle. Most ceramics are also good insulators and can
withstand high temperatures. These properties have led to their use in
virtually every aspect of modern life.

The two main categories of ceramics are traditional and advanced.
Traditional ceramics include objects made of clay and cements that have
been hardened by heating at high temperatures. Traditional ceramics are
used in dishes, crockery, flowerpots, and roof and wall tiles. Advanced
ceramics include carbides, such as silicon carbide, SiC; oxides, such as
aluminum oxide, Al

2

O

3

; nitrides, such as silicon nitride, Si

3

N

4

; and many other materials, including the mixed oxide ceramics that can

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Background

For centuries humankind has relied upon various plants and animals to
provide the raw materials for fabrics and clothing. Silkworms, sheep,
beaver, buffalo deer, and even palm leaves are just some of the natural
resources that have been used to meet these needs. However, in the last
century scientists have turned to chemistry and technology to create and
enhance many of the fabrics we now take for granted.

There are two main categories of man-made fibers: those that are made from
natural products (cellulosic fibers) and those that are synthesized solely
from chemical compounds (noncellulosic polymer fibers). Rayon is a
natural-based material that is made from the cellulose of wood pulp or
cotton. This natural base gives it many of the characteristics—low
cost, diversity, and comfort—that have led to its popularity and
success. Today, rayon is considered to be one of the most versatile and
economical man-made fibers available.

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Background

Polyester is a synthetic fiber derived from coal, air, water, and
petroleum. Developed in a 20th-century laboratory, polyester fibers are
formed from a chemical reaction between an acid and alcohol. In this
reaction, two or more molecules combine to make a large molecule whose
structure repeats throughout its length. Polyester fibers can form very
iong molecules that are very stable and strong.

Polyester is used in the manufacture of many products, including clothing,
home furnishings, industrial fabrics, computer and recording tapes, and
electrical insulation. Polyester has several advantages over traditional
fabrics such as cotton. It does not absorb moisture, but does absorb oil;
this quality makes polyester the perfect fabric for the application of
water-, soil-, and fire-resistant finishes. Its low absorbency also makes
it naturally resistant to stains. Polyester clothing can be preshrunk in
the finishing process, and thereafter the fabric resists shrinking and
will not stretch out

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