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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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

T-shirts are durable, versatile garments with mass appeal that may be worn
as outerwear or underwear. Since their creation in 1920, T-shirts have
evolved into a two-billion dollar market. T-shirts are available in a
variety of colors, patterns, and styles, such as the standard crew neck
and V-neck, as well as tank tops and scoop necks. T-shirt sleeves may be
short or long, capped, yoked, or raglan. Additional features include
pockets and decorative trim. T-shirts are also popular garments on which
to display one’s interests, tastes, and affiliations using
customized screen prints or heat transfers. Printed shirts may feature
political slogans, humor, art, sports, as well as famous people and
places. T-shirts are also inexpensive promotional vehicles for products
and special events.

T-shirts fit just about anyone in any size, from infants to seniors. Adult
sizes are generally small, medium, large, and extra-large, while sizes for
toddlers are detennined

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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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