# Boolean networks  (Page 2/3)

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## Boolean networks

The Boolean network model, introduced by Kauffman (Kauffman, 1969, 1974; Kauffman and Glass, 1973)and recently developed by Shmulevich(Shmulevich, 2002), has received the most attention, not only from the biology community, but also in physics. In this model, gene expression is quantized to only two levels: ON and OFF. The expression level (state) of each gene is functionally related to the expression states of some other genes, using logical rules. A Boolean network G(V,F) is defined by a set of nodes corresponding to genes V = {x1, . . . , xn} and a list of Boolean functions F = (f1, . . . , fn) . The state of a node (gene) is completely determined by the values of other nodes at time t by means of underlying logical Boolean functions. The model is represented in the form of directed graph.Each xi represents the state (expression) of gene i, where xi=1 represents the fact that gene i is expressed and xi=0 means it is not expressed. The list of Boolean functions F represents the rules of regulatory interactions between genes. That is, any given gene transforms its inputs (regulatory factors that bind to it) into an output, which is the state or expression of the gene itself. The maximum connectivity of a Boolean network is defined by K= maxi (ki) . All genes are assumed to update synchronously in accordance with the functions assigned to them and this process is then repeated. The artificial synchrony simplifies computation while preserving the qualitative, generic properties of global network dynamics (Kauffman, 1993; Huang, 1999; Wuensche, 1998).

Below the example is presented. Consider a Boolean network consisting of 5 genes {x1, . . . , x5} with the corresponding Boolean functions given by the truth tables shown in Figure1. The maximum connectivity is K=3, although we allow some input variables to duplicate, essentially reducing the connectivity.The dynamics of this Boolean network are shown in Figure2. Since there are 5 genes, there are 2^5 = 32 possible states that the network can be in. Each state is represented by a circle and the arrows between states show the transitions of the network according to the functions in Table 1., Figure1. . It is easy to see that because of the inherent deterministic directionality in Boolean networks as well as only a finite number of possible states.

In the context of Boolean networks as models of genetic regulatory networks, there is no doubt that the binary approximation of gene expression is an oversimplification (Huang, 1999). However, even though most biological phenomena manifest themselves in the continuous domain, they are often described in a binary logical language such as‘on and off,’‘upregulated and downregulated’, and‘responsive and nonresponsive.’There is a several examples showing that a Boolean formalism is meaningful in biology, in (Shmulevich and Zhang, 2002), one reasoned that if the genes, when quantized to only two levels (1 or 0), would not be informative in separating known sub-classes of tumors, then there would be little hope for Boolean modeling of realistic genetic networks based on gene expression data.

are nano particles real
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
no can't
Lohitha
where we get a research paper on Nano chemistry....?
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
how did you get the value of 2000N.What calculations are needed to arrive at it
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