941 research outputs found
Tet-On Systems For Doxycycline-inducible Gene Expression.
The tetracycline-controlled Tet-Off and Tet-On gene expression systems are used to regulate the activity of genes in eukaryotic cells in diverse settings, varying from basic biological research to biotechnology and gene therapy applications. These systems are based on regulatory elements that control the activity of the tetracycline-resistance operon in bacteria. The Tet-Off system allows silencing of gene expression by administration of tetracycline (Tc) or tetracycline-derivatives like doxycycline (dox), whereas the Tet-On system allows activation of gene expression by dox. Since the initial design and construction of the original Tet-system, these bacterium-derived systems have been significantly improved for their function in eukaryotic cells. We here review how a dox-controlled HIV-1 variant was designed and used to greatly improve the activity and dox-sensitivity of the rtTA transcriptional activator component of the Tet-On system. These optimized rtTA variants require less dox for activation, which will reduce side effects and allow gene control in tissues where a relatively low dox level can be reached, such as the brain
Condensation of the roots of real random polynomials on the real axis
We introduce a family of real random polynomials of degree n whose
coefficients a_k are symmetric independent Gaussian variables with variance
= e^{-k^\alpha}, indexed by a real \alpha \geq 0. We compute exactly
the mean number of real roots for large n. As \alpha is varied, one finds
three different phases. First, for 0 \leq \alpha \sim
(\frac{2}{\pi}) \log{n}. For 1 < \alpha < 2, there is an intermediate phase
where grows algebraically with a continuously varying exponent,
\sim \frac{2}{\pi} \sqrt{\frac{\alpha-1}{\alpha}} n^{\alpha/2}. And finally for
\alpha > 2, one finds a third phase where \sim n. This family of real
random polynomials thus exhibits a condensation of their roots on the real line
in the sense that, for large n, a finite fraction of their roots /n are
real. This condensation occurs via a localization of the real roots around the
values \pm \exp{[\frac{\alpha}{2}(k+{1/2})^{\alpha-1} ]}, 1 \ll k \leq n.Comment: 13 pages, 2 figure
Two Graviton Production at and Hadron Hadron Colliders in the Randall-Sundrum Model
We compute the pair production cross section of two Kaluza Klein modes in the
Randall-Sundrum model at and hadron hadron colliders. These processes
are interesting because they get dominant contribution from the graviton
interaction at next to leading order. Hence they provide a nontrivial test of
the low scale gravity models. All the Feynman rules at next to leading order
are also presented. These rules may be useful for many phenomenological
applications including the computation of higher order loop corrections.Comment: 24 pages, 11 figures, some typos correcte
Linking Backlund and Monodromy Charges for Strings on AdS_5 x S^5
We find an explicit relation between the two known ways of generating an
infinite set of local conserved charges for the string sigma model on AdS_5 x
S^5: the Backlund and monodromy approaches. We start by constructing the
two-parameter family of Backlund transformations for the string with an
arbitrary world-sheet metric. We then show that only for a special value of one
of the parameters the solutions generated by this transformation are compatible
with the Virasoro constraints. By solving the Backlund equations in a
non-perturbative fashion, we finally show that the generating functional of the
Backlund conservation laws is equal to a certain sum of the quasi-momenta. The
positions of the quasi-momenta in the complex spectral plane are uniquely
determined by the real parameter of the Backlund transform.Comment: 25 pages, 1 figur
Single Photon Signals for Warped Quantum Gravity at a Linear e+-e- Collider
We study the `single photon' process e+- e- -> gamma nu nubar with
contributions due to exchange of massive gravitons in the Randall- Sundrum
model of low-scale quantum gravity. It is shown that for significant regions in
the parameter space, this process unambiguously highlights the resonance
structure of the graviton sector. Even in the non-resonant part of the
parameter space, we show that comparison with the benchmark process e+- e- ->
mu+- mu- can clearly distinguish signals for warped gravity from similar
signals for large extra dimensions.Comment: Published version; figures change
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