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Solutions 691

28. One method is simply to heat the material to above its T or T .
g m
29. Solvent removal. Solvent recovery.
30. Both depending on the end use. Pillows are open celled, allowing a “softer” more fl exible
behavior while insulation foam is more rigid and closed celled retaining heat/cold better.
31. Countertops; plywood.
32. Adhesives hold things together. There are lots of things we want to hold together under a variety
of conditions.
33. Dries fast so can minimize bleeding; clean. Works to adhere many different surfaces including
skin.
34. Probably the easiest thing is to “hide” the black painted wall using specially designed coatings
with a high “hiding” ability. Then you can paint it.

CHAPTER 19
1. Cancer cells have three main characteristics that are different from healthy cells. First, they are
immortal, are able to replicate themselves hundreds of times, while healthy cells generally rep-
licate themselves less than two dozen times over our lifetime. Second, cancer cells are not con-
tact inhibited meaning that they will continue to grow forming tumors. By comparison, healthy
cells replicate until they touch another cell and then stop reproduction. Finally, cancer cells are
normally in a growth mode, whereas healthy cells are generally in a rest mode.
2. Smart materials are materials that react to applied force—electrical, stress–strain (includ-
ing pressure), thermal, light, and magnetic. A smart material is not smart simply because it
responds to external stimuli, but it becomes smart when the interaction is used to achieve a
defined engineering or scientifi c goal.

3. Aramides do not melt, drip, support combustion in air, or burn.
4. Poly-p-phenylene and poly(p-phenylene vinylene) because they offer whole chain resonance in
their backbones.
5. Carbon nanotubes do not have to be doped and are more flexible and stronger.

6. Carbon nanotubes are not soluble, whereas some of the newly developed conductive polymers
are soluble in organic and others in water allowing them to be “laid out” more easily without
the need of creating the nanotubes on site.
7. The dopants cause the introduction of sites of increased or deficiency of electrons. When there

is a deficiency of electrons, or hole created, electrons flow to fill this hole with the newly created

hole causing other electrons to fl ow to fill the new hole, and so on, allowing charge to migrate
within and between the polyacetylene chains.
8. There are many. Because of their size, polymers with chain lengths of about 100 units and
greater typically are unable to easily move through biological membranes, thus movement is
restricted. This can result in limiting negative side effects, such as damage to the kidneys,
because the polymer can reside in only certain body sites. Also, this limited mobility can assist
in directing the polymer drug.
9. This is because of several trends. First, many biological solutions to biological problems resides
with the use of biological materials to solve biological problems. With the advent of increased
effectiveness of cloning and related advances, suitable biological replacements may be grown
from a person’s cells thus ensuring compatibility. Second, related to the first, regeneration of

essential parts of vital organs is becoming more practical. Third, because of nanotechnology
and related electrical and optical advances, surgery to locate and repair imperfections is improv-
ing. Forth, our autoimmune systems are being studied with the hope that rejection of substitute
hearts may be more easily overcome.

10. For quick identification of used and unused suture’s location. It is often difficult to see when

operating.

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