3. Conventional Computers
Conventional computers are machines that follow a well
described set of instructions to process data.
Basically, a set of instructions is read into the machine and it
works sequentially in an ordered way to execute a task.
often referred to as Von Neumann computers or classical
machines.
major components are
memory,
processing, and
bandwidth.
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4. Continued…..
Can be thought of as structurally programmable
machines. This means that the program controls the
behavior of the machine.
A compiler translates the input code into machine
language that is expressed in terms of the states of
simple switching devices and their connections.
The machine computes symbolically and the result
depends to some extent upon the human input.
Well suited to computing, communication, and data
manipulation.
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5. Problems
pattern recognition
Specifically, it is very difficult to program a classical
computer to recognize a complicated molecule or
distinguish between different microorganisms.
In the chemical and biological world pattern recognition is
highly efficient and readily accomplished.
For example, the immune system in the human body.
This behavior is an example of a different type of computing.
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6. Tactile Computing
These machines are not structurally programmable.
In Biomolecular computing, pattern processing is physical
and dynamic as opposed to the symbolic and passive
processing in a conventional machine.
Programming depends upon evolution by variation and
selection.
A tactile processor can be thought of as a computer
driven by enzymes; the inputs are converted into
molecular shapes that the enzymes(scans the molecular
objects within its environment) can recognize.
Recognition is thus a tactile procedure.
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7. Examples
1) An example of tactile computer-
A variety of bacteria bred to dissolve oil spills.
the bacteria would be “programmed” by altering its DNA.
the unique and powerful information processing capabilities
of life, pattern and object recognition, self-organization and
learning, and effective use of parallelism are harnessed.
2) sensing bioagents or toxins.
Molecules can be used to perform complicated pattern
recognition of dangerous toxins released into the air or
water.
Even Very dilute amounts can be identified readily.
Can be used to fight terrorist bioattacks, or chemical
warfare. 7
8. Biomolecular Computing
The “program” is in the molecule itself; the computation
occurs by the recognition of one molecule by an enzyme
and their subsequent chemical reaction.
Biological systems are a special case of molecular
computing(broader context).
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9. key advantages of molecular materials
Size: on average they are about 4 nm. These device dimensions
are about two orders of magnitude smaller than that which can be
obtained using SiCMOStechnology.
Three-dimensional structures: In contrast, in Si based technology,
much fabrication effort and cost is required to produce three-
dimensional geometries.
High packing density: the combined features of small size and
three-dimensionality make very high packing densities possible. It is
estimated that the packing density can be increased by 6–9 orders
of magnitude over CMOS.
Bistability and nonlinearity: bistability and nonlinearity can be
utilized to perform switching functions. Both of these properties are
commonly available in molecules.
Anisotropy: the electronic and optical properties of a molecule are
inherent in the molecular structure instead of being fabricated by the
processing technologies as in CMOS.
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10. Continued…..
Upward construction: organic synthesis enables growth of
microstructures from the small upward. In standard CMOS, device
and circuit functionality is sculpted from a relatively large piece of
material.
Self-organization: self-organization, self-synthesis, and
redundancy factors well known in organic and biological molecules
that could potentially be applied to molecular electronic devices.
Low power dissipation: Estimates are that the total power
requirements for molecular switches will be about five orders of
magnitude lower than for CMOS switches.
Molecular engineering: it is possible that molecules can be tailored
or engineered(can be selectively grown and made to inherently
possess desired qualities to perform a task.) to perform specific
tasks or have specific properties.
The above features of molecules also apply to biomolecules.
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11. DNA-an overview
The entire genetic code for humans is contained in the
nucleus of most cells.
The DNA code consists of over three billion nucleotide
pairs and fits into a few double helices about 3.4 nm in
width and measuring micrometers in length.
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12. Researchers are developing what are called applets for
biological systems.
These applets enable the system to respond to an external
event, “program” a cell to produce a desired chemical or
enzyme, or enable a cell to identify a reagent.
Some potential applications of biological applets:
In gene therapy for treating diseases such as hemophilia,
anemia, etc.
in the treatment of diabetes( A genetic applet can be
used that senses the glucose level in the blood and
another applet can then direct the production and release
of insulin if needed.).
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13. DNA molecules
are composed of
four basic
nucleic acids
called
adenine (A), guanine
(G), cytosine (C) and
thymine (T).
A and T, and C and G
naturally bond together
to form pairs.
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14. Computation with DNA
To compute with DNA there are three basic steps.
encoding that maps the problem onto DNA strands,
basic processing using a chemical process called
hybridization that connects two complementary DNA
strands into a double strand,
and outputting the results.
Programming DNA involves the usage of DNA tiles.
These tiles consist of multiple strands of DNA knotted
together.
The ends of each tile are created such that the tile will
recognize and attach to other pre-designed tiles to make
self-assembled structures.
These tiles can be used to add or multiply numbers 14
15. Molecules can also be used to build devices that mimic
CMOS functionality.
Molecular diodes and other quantum based devices
have been designed.
The primary components of these molecular structures
are conducting groups called polyphenylenes and
insulating groups called aliphatic molecules.
By arranging these molecules in various orders similar
device action to that found in semiconductors can be
attained.
These structures can be combined to make various logic
gates such as NOR and NAND gates.
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16. Drawbacks
These are basically related to the difficulty encountered
in regulating or controlling the basic chemistry.
Reliability means the degree of confidence in
correctly solving a problem.
Efficiency is related to the effective manipulation of
the molecules used to perform the computation.
Scalability is the successful reproduction of the
desired event many times.
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