Abstract:
Durante los últimos 15 a os se ha demostrado que la electroporación representa el método ideal para la transfección de células troncoembrionarias de ratón; sin embargo, demanda grandes cantidades de ADN y células, así como equipo caro y delicado, ello hace que este proceso sea costoso y laborioso. La lipofección es un método de transfección que requiere menos de células y ADN que la electroporación; asimismo, ha probado ser efi ciente en gran número de líneas celulares. Se ha demostrado que después de lipofectar células troncoembrionarias de ratón, éstas mantienen su pluripotencia y son capaces de formar quimeras de línea germinal y se transfectan con mayor efi ciencia que con electroporación, pero no se ha notifi cado la mutagénesis dirigida mediante la lipofección de células troncoembrionarias de ratón. El objetivo del presente trabajo fue saber si la lipofección puede ser utilizada con la misma o mayor efi ciencia que la electroporación para los protocolos regulares de mutagénesis dirigida; en este contexto, se compara la efi ciencia en mutagénesis dirigida entre estas técnicas en células troncoembrionarias de ratón E14TG2a, utilizando un vector de reemplazo. Entre las células transfectadas no se hallan diferencias en la efi ciencia en mutagénesis dirigida entre grupos; sin embargo, los resultados que aquí se ofrecen muestran que la lipofección es tres veces más efi ciente en la transfección, lo cual indica que la lipofección es un método alternativo menos costoso para obtener mutagénesis dirigida en células troncoembrionarias de ratón.

Abstract:
electroporation has been the method of election for transfection of murine embryonic stem cells for over 15 years; however, it is a time consuming protocol because it requires large amounts of dna and cells, as well as expensive and delicate equipment. lipofection is a transfection method that requires lower amounts of cells and dna than electroporation, and has proven to be efficient in a large number of cell lines. it has been shown that after lipofection, mouse embryonic stem cells remain pluripotent, capable of forming germ line chimeras and can be transfected with greater efficiency than with electroporation; however, gene targeting of mouse embryonic stem cells by lipofection has not been reported. the objective of this work was to find out if lipofection can be used as efficiently as electroporation for regular gene targeting protocols. this context compares gene targeting efficiency between these techniques in mouse embryonic stem cells e14tg2a, using a gene replacement type vector. no differences were found in gene targeting efficiency between groups; however, lipofection was three times more efficient than electroporation in transfection efficiency, which makes lipofection a less expensive alternative method to produce gene targeting in mouse embryonic stem cells.

Abstract:
We study the phenomenon of decoherence during the operation of one qubit transformation, controlled-not (CNOT) and controlled-controlled-not (C^{2}NOT) quantum gates in a quantum computer model formed by a linear chain of three nuclear spins system. We make this study with different type of environments, and we determine the associated decoherence time as a function of the dissipative parameter. We found that the dissipation parameter to get a well defined quantum gates (without significant decoherence) must be within the range of . We also study the behavior of the purity parameter for these gates and different environments and found linear or quadratic decays of this parameter depending on the type of environments.

We make a numerical study of decoherence on the teleportation algorithm implemented in a linear chain of three nuclear spins system. We study different types of environments, and we determine the associated decoherence time as a function of the dissipative parameter. We found that the dissipation parameter to get a well defined quantum gates (without significant decoherence) must be within the range of γ≤4×10^{-4} for not thermalized case, which was determined by using the purity parameter calculated at the end of the algorithm. For the thermalized case the decoherence is stablished for very small dissipation parameter, making almost not possible to implement this algorithm for not zero temperature.

Abstract:
The Hamiltonian associated to the mass variable system is constructed from first principles through finding a constant of motion of the system. A comparison is made of the classical motion of a body with its mass position depending in the (x,v) space and (x,p) space which are defined by the constant of motion and the Hamiltonian, for a particular model of mass variation. As one could expected, these motion looks different on these spaces. The quantization of the harmonic oscillator with this mass variation is done, and a comparison is made by using the usual Hamiltonian approach with the proposed quantization of the constant of motion approach. This comparison is done at first order in perturbation theory, and one sees a difference between both approaches which can, in principle, be measured.

Abstract:
A new approach to radiation reaction for the correction of the linear and circular motion of a charged particle takes into account the emission of electromagnetic radiation due to its acceleration. This new formulation was based on expressing the radiation reaction force in terms of the external force rather than the acceleration of the charge. In this paper, a generalization of the radiation reaction force in terms of the external force approach is formulated for any arbitrary motion of the charged particle. This generalization includes the linear and circular acceleration cases previously investigated.

Abstract:
For explicitly time depending mass density which
satisfies a continuity equation, it is shown that Maxwell-like equations for
gravitational field follow naturally without any need of General Relativity
Theory approximation or related assumptions. As a consequence, it is shown that
several features already known in Electrodynamics (Poynting vector, density of
energy, tensor stress, and radiation) are totally reproduced for gravitational
field.

Abstract:
We study the classical dynamics of binary stars when there is an interchange of mass between them. Assuming that one of
the stars is more massive than others, the dynamics of the lighter one is analyzed as a function of its time
depending mass variation. Within our approximations and models for mass
transference, we obtain a general result which establishes that if the lightest
star looses mass, its period increases. If the lightest star wins mass, its period decreases.

By removing a ^{12}C atom from the tetrahedral
configuration of the diamond, replacing it by a ^{13}C atom, and repeating
this in a linear direction, it is possible to have a linear chain of nuclear
spins one half and to build a solid state quantum computer. One qubit rotation,
controlled-not (CNOT) and controlled-controlled-not (CCNOT) quantum gates are
obtained immediately from this configuration. CNOT and CCNOT quantum gates are
used to determined the design parameters of this quantum computer.

Abstract:
A method for designing real-time distributed controllers of discrete manufacturing systems is presented. The approach held is agent based; the controller strategy is distributed into several interacting agents that operate each one on a part of the manufacturing process; these agents may be distributed into several interconnected processors. The proposed method consists of a modelling methodology and software development framework that provides a generic agent architecture and communication facilities supporting the interaction among agents.