121 research outputs found
Nonlinear state estimation using forward-backward propagation of intervals in an algorithm
International audienceThe paper deals with the estimation of the state vector of a discrete-time model from interval output data. When the model outputs are affine in the initial state vector, a number of methods are available to enclose all estimates that are consistent with data by simple sets such as ellipsoids, orthotopes or parallelotopes, thereby providing guaranteed set estimates. In the nonlinear case, the situation is much less developed and there are very few methods that produce such guaranteed estimates. In this paper, the state estimation of a discrete-time model is performed by combining a set-inversion algorithm with a forward-backward propagation of intervals through the model. The resulting methodology is illustrated on an example
Interval methods for nonlinear identification and robust control
International audienceInterval methods can provide guaranteed solutions to difficult nonlinear problems, such as the global optimization of non-convex criteria or the characterization of sets defined by nonlinear inequalities. They can even deal with problems involving quantifiers, as encountered for example in robust control design. For high dimensional problems; their efficiency can be considerably improved by resorting to constraint propagation. In this paper, key ideas of interval analysis and constraint propagation are presented and applied to two problems. The first one is the guaranteed characterization of the set of all parameter vectors that are consistent with experimental dat up to bounds on the acceptable errors. The second one is the design of a PI controller robustly stabilizing a set of models that may have been obtained as the solution to the first problem
Interval analysis for non-linear parameter and state estimation: contributions and limitations
Parameter or state estimation should take into account the fact that the model is an approximation of reality and that the data are corrupted by noise. In this paper, each uncertain quantity is assumed to belong to a known set. The problem, known as parameter or state bounding, is the to characterize the set of all parameter or state vectors that are consistent with the model structure, data and error bounds. A description of how interval analysis can be used to find guaranteed estimates in a nonlinear context is provided. The main notions of interval analysis are first recalled very briefly. the simpler problem of parameter estimation is then considered. State estimation, which contains parameter tracking as a special case, is treated next. A simple illustrative example is finally presented
Guaranteed set computation with subpavings
International audienceThis paper is about the approximate representation of compact sets using subpavings, i.e., unions of non-overlapping boxes, and about computation on these sets, with particular attention to implementation issues. Some basic operations such as evaluating the intersection or union of two subpavings, or testing whether a box belongs to a subpaving are first presented. The binary tree structure used to describe subpavings then allows a simple implementation of these tasks by recursive algorithms. Algorithms are presented to evaluate the inverse and direct images of a set described by a subpaving. In both cases, a subpaving is obtained that is guaranteed to contain the actual inverse or direct image of the initial subpaving. The effectiveness of these algorithms in characterizing possibly nonconvex on even nonconnected stes is finally illustrated by simple examples
Nucleic Acids Res
Site-directed spin labeling is emerging as an essential tool to investigate the structural and dynamical features of RNA. We propose here an enzymatic method, which allows the insertion of a paramagnetic center at a specific position in an RNA molecule. The technique is based on a segmental approach using a ligation protocol with T4 RNA ligase 2. One transcribed acceptor RNA is ligated to a donor RNA in which a thio-modified nucleotide is introduced at its 5'-end by in vitro transcription with T7 RNA polymerase. The paramagnetic thiol-specific reagent is subsequently attached to the RNA ligation product. This novel strategy is demonstrated by introducing a paramagnetic probe into the 55 nucleotides long RNA corresponding to K-turn and Specifier Loop domains from the Bacillus subtilis tyrS T-Box leader RNA. The efficiency of the coupling reaction and the quality of the resulting spin-labeled RNA were assessed by Mass Spectrometry, Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR). This method enables various combinations of isotopic segmental labeling and spin labeling schemes, a strategy that will be of particular interest to investigate the structural and dynamical properties of large RNA complexes by NMR and EPR spectroscopies
AMOTL1 Promotes Breast Cancer Progression and Is Antagonized by Merlin
AbstractThe Hippo signaling network is a key regulator of cell fate. In the recent years, it was shown that its implication in cancer goes well beyond the sole role of YAP transcriptional activity and its regulation by the canonical MST/LATS kinase cascade. Here we show that the motin family member AMOTL1 is an important effector of Hippo signaling in breast cancer. AMOTL1 connects Hippo signaling to tumor cell aggressiveness. We show that both canonical and noncanonical Hippo signaling modulates AMOTL1 levels. The tumor suppressor Merlin triggers AMOTL1 proteasomal degradation mediated by the NEDD family of ubiquitin ligases through direct interaction. In parallel, YAP stimulates AMOTL1 expression. The loss of Merlin expression and the induction of Yap activity that are frequently observed in breast cancers thus result in elevated AMOTL1 levels. AMOTL1 expression is sufficient to trigger tumor cell migration and stimulates proliferation by activating c-Src. In a large cohort of human breast tumors, we show that AMOTL1 protein levels are upregulated during cancer progression and that, importantly, the expression of AMOTL1 in lymph node metastasis appears predictive of the risk of relapse. Hence we uncover an important mechanism by which Hippo signaling promotes breast cancer progression by modulating the expression of AMOTL1
HEXIM1 targets a repeated GAUC motif in the riboregulator of transcription 7SK and promotes base pair rearrangements
7SK snRNA, an abundant RNA discovered in human nucleus, regulates transcription by RNA polymerase II (RNAPII). It sequesters and inhibits the transcription elongation factor P-TEFb which, by phosphorylation of RNAPII, switches transcription from initiation to processive elongation and relieves pauses of transcription. This regulation process depends on the association between 7SK and a HEXIM protein, neither isolated partner being able to inhibit P-TEFb alone. In this work, we used a combined NMR and biochemical approach to determine 7SK and HEXIM1 elements that define their binding properties. Our results demonstrate that a repeated GAUC motif located in the upper part of a hairpin on the 5′-end of 7SK is essential for specific HEXIM1 recognition. Binding of a peptide comprising the HEXIM Arginine Rich Motif (ARM) induces an opening of the GAUC motif and stabilization of an internal loop. A conserved proline-serine sequence in the middle of the ARM is shown to be essential for the binding specificity and the conformational change of the RNA. This work provides evidences for a recognition mechanism involving a first event of induced fit, suggesting that 7SK plasticity is involved in the transcription regulation
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Etude de la dynamique spatiale et temporelle des phosphatases CDC25B humaine
TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF
La prise médicamenteuse au cours de l'allaitement (enquête sur le point de vue de pharmaciens et médecins lorrains)
La France affiche un retard important quant à la pratique de l allaitement maternel, à peine plus de 57% des femmes allaitent leur enfant. Lorsqu on les interroge à ce sujet, pharmaciens et médecins ont conscience de ses bienfaits, tant sur le développement des relations mère-enfant, que sur la santé de chacun. L enquête révèle, également, que dans leur pratique, beaucoup d entre eux déconseillent l allaitement dès lors qu une thérapeutique médicamenteuse est instaurée. Les études cliniques se font rares, néanmoins on constate qu il n existe que peu de contre-indication en termes de médicaments à cette pratique. Comment alors expliquer cette discordance ? S agit-il d un manque de connaissance ou d une trop grande prudence de leur part ? Des éléments de réponse basés sur les données actuelles sont alors apportés dans ce travail ; et sont comparés au comportement des professionnels.NANCY1-SCD Pharmacie-Odontologie (543952101) / SudocNANCY1-Bib. numérique (543959902) / SudocSudocFranceF
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