# 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.

What is demand
the amount of a good that buyers are willing and able to purchase
Asit
what is population
The people living within a political or geographical boundary.
Ziyodilla
what happens to price and quantity when demand curves shift to the right
price level goes up. quantity demand increases
Asit
example- inferior goods
Asit
demand law
Athony
Its states that higher the price the of the commodity, and lower the quantity demanded
Kosiso
I am confused but quantity demand will increase.
Asit
No. That's the law of supply
Kosiso
the price goes down and quantity demanded increases
esther
Price goes down Demand quantity increases
Daniel
what happens to price and quantity when supply curve shifts left?
price level will increase
Asit
quantity demand will decrease
Asit
what is inflation
inflation is a general and ongoing rise in the level of prices in an entire economy.
cynthia
is the pasistance increase in the price of a country economy
Liyu
kk
Duppy
yes
how does inflation affects the economy of a country? what is deflation?
Augustine
deflation can simply be define as the persistence decrease in price of a countrys economy
Liyu
the revenge of malthus relates "revenge" with "commodity prices". collect data for 3 commodoties and check their price evolution
what is elasticity
Elasticity is an economics concept that measures responsiveness of one variable to changes in another variable.
cynthia
right
Augustine
wooow!!
cynthia
Computer software represents
पर्यावरण राज्यों में से किस राज्य में शिष्य शिक्षक अनुपात 30 से अधिक वाले विद्यालयों का प्रतिशत न्यूनतम होता है
Hey what are you trying to mean?
Kenyana
what is Asset
MUBARAK
like a banana
Ahmed
demand is the process whereby consumers are willing and able to purchase a particular product at various price over a given period of time
The law of dinimish
What is the law of dinimish
Frank
What is the law of dinimish
Frank
What is the law of dinimish
Frank
opportunity cost is to forgo something for another.
yes
King
what is financial market
what is demand
Demand is an economic principle referring to a consumer's desire to purchase goods and services and willingness to pay a price for a specific good or service.
Ali
explain any three exceptions to the law of demand
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