301 research outputs found
Tècniques per estudiar els gens i la seva expressió
La seqĂĽenciaciĂł del DNA ens permet conèixer la composiciĂł quĂmica d'un determinat
gen. Existeixen tècniques per comprovar si un gen s'expressa en una cèl·lula o teixit: són els
protocols coneguts amb el nom de transferència northern (detecta la presència de RNA missatger)
o la transferència western (que detecta la presència de proteïna). En els darrers deu
anys han sorgit tot un seguit de tècniques que han permès passar de l'estudi individual
dels gens a l'estudi global. AixĂ, la genòmica estudia la seqüència de milers de gens alhora,
la transcriptòmica comprova la presència de tots els missatgers presents en una cèl·lula en
un moment determinat i la proteòmica fa el mateix, però analitzant el contingut global de
proteĂŻnes. En aquest capĂtol es presenten de manera resumida què sĂłn i què aporten cadascuna
d'aquestes tècniques.The DNA sequencing allows us to know the chemistry composition of a gene. Otherwise,
it can be evaluated if a gene is expressed in a cell by the northern blot protocol (which
checks for the presence of a messenger RNA) or by the western blot (which evaluate the
levels of a protein). In the past 10 years, the development of the new molecular biology
techniques allowed us to study the genes of a genome in a more global view. Then, the
genomics study the sequence of a thousands of genes at the same time, the transcriptomics
check for the presence of all the messengers in a cell, and the proteomics do the same but analyzing the protein global content. In this chapter are presented the main concepts and
the principal achievements of all these techniques
Bounding the distance of a controllable and observable system to an uncontrollable or unobservable one
Let be a triple of matrices representing a time-invariant
linear system \left .\aligned \dot
x(t)&=Ax(t)+Bu(t)\\y(t)&=Cx(t)\endaligned \right \} under similarity
equivalence, corresponding to a realization of a prescribed transfer
function matrix.
In this paper we measure the distance between a irreducible realization,
that is to say a controllable and observable triple of matrices
and the nearest reducible one that is to say uncontrollable or unobservable
one.
Different upper bounds are obtained in terms of singular values of the
controllability matrix , observability matrix and
controllability and observability matrix associated to the
triple
El DNA es pot manipular
Per comprendre les possibilitats que ofereix l'enginyeria genètica, es necessita primer
conèixer les eines que permeten la manipulació dels à cids nucleics. En la primera part
d'aquest capĂtol es farĂ un repĂ s d'algunes d'aquestes eines: els plasmidis, petites molècules
de DNA que podem trobar en determinats organismes unicel·lulars; els enzims de
restricciĂł, proteĂŻnes tĂpicament bacterianes que fragmenten el DNA per punts concrets; la
DNA-ligasa, proteĂŻna vĂrica amb la capacitat d'unir-los de nou; l'electroforesi en gels d'agarosa,
que pot separar per mides diferents fragments de DNA, i, per acabar, la PCR, que ens
permet amplificar qualsevol DNA de seqüència coneguda. En la segona part es presenten
alguns exemples de les aplicacions que poden tenir aquestes tècniques.To better understand the possibilities that come from genetic engineering, it is useful to
know the main tools for the nucleic acid manipulation. In the first part of this chapter it
will be done a revision of some of this tools: the plasmids, a little pieces of DNA of some
microorganisms; the restriction enzymes, a typical bacterial protein with the capability to
fragment DNA molecules in appropriate points; the DNA ligase from T4 phagus, a protein
with the ability to regenerate joints between two DNA fragments; the electrophoreses,
that allows to see the DNA and to separate by size; and lastly the PCR that could amplify
any DNA of known sequence. In the second part of this chapter it will be presented some
examples of real applications of these techniques
Bounding the distance of a controllable system to an uncontrollable one
Let be a pair of matrices representing a time-invariant linear
system under block-similarity equivalence.
In this paper we measure the distance between a controllable pair of
matrices and the nearest uncontrollable one.
A bound is obtained in terms of singular values of the controllability
matrix associated to the pair. This bound is not simply based
on the smallest singular value of contrary to what one may
expect.
Also a lower bound is obtained using geometrical techniques expressed
in terms of the singular values of a matrix representing the tangent
space of the orbit of the pair
Controllability of second order linear systems
Let (A1;A2;B) be a triple of matrices representing two-order time-invariant
linear systems, ¨x = A1 ˙ x+A2x+Bu. Using linearization process we study the controllability
of second order linear systems. We obtain su±cient conditions for controllability and we
analyze the kind of systems verifying these conditions
Second order generalized linear systems. A geometric approach
Let (E;A1;A2;B) be a quadruple of matrices representing a two-order
generalized time-invariant linear system, E¨x = A1 ˙ x + A2x + Bu. We study the controllability character
under an algebraic point of view
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