Search results for " catastrophe"

A putative antiviral role of plant cytidine deaminases

2014

[Background]: A mechanism of innate antiviral immunity operating against viruses infecting mammalian cells has been described during the last decade. Host cytidine deaminases (e.g., APOBEC3 proteins) edit viral genomes, giving rise to hypermutated nonfunctional viruses; consequently, viral fitness is reduced through lethal mutagenesis. By contrast, sub-lethal hypermutagenesis may contribute to virus evolvability by increasing population diversity. To prevent genome editing, some viruses have evolved proteins that mediate APOBEC3 degradation. The model plant Arabidopsis thaliana genome encodes nine cytidine deaminases ( AtCDAs), raising the question of whether deamination is an antiviral mec…

CATASTROPHES AND BUILDING ABUSES

2012

The contributions analyze the land's vulnerability and abusive built's vulnerability. It describes the risks related to natural and artificial disasters and also investigates the use of appropriate technologies to protect and preserve the existing assets.

Characterization of the pressure induced Ringwoodite toMg-perovskite and Mg-wüstite phase transition by Catastrophe Theory

2010

The pressure-induced ringwoodite to Mg-perovskite and periclase post-spinel phase transition: a Bader’s topological analysis of the ab initio electro…

2011

In order to characterize the pressure-induced decomposition of ringwoodite (c-Mg2SiO4), the topological analysis of the electron density q(r), based upon the theory of atoms in molecules (AIM) developed by Bader in the framework of the catastrophe theory, has been performed. Calculations have been carried out by means of the ab initio CRYSTAL09 code at the HF/DFT level, using Hamiltonians based on the Becke- LYP scheme containing hybrid Hartree– Fock/density functional exchange–correlation terms. The equation of state at 0 K has been constructed for the three phases involved in the post-spinel phase transition (ringwoodite -> Mg-perovskite + periclase) occurring at the transition zone–lower…

Aurora-A Transcriptional Silencing and Vincristine Treatment Show a Synergistic Effect in Human Tumor Cells

2008

Aurora-A is a centrosome-associated serine/threonine kinase that is overexpressed in multiple types of human tumors. Primarily, Aurora-A functions in centrosome maturation and mitotic spindle assembly. Overexpression of Aurora-A induces centrosome amplification and G 2 /M cell cycle progression. Recently, it was observed that overexpression of Aurora-A renders cells resistant to cisplatin (CDDP)-, etoposide-, and paclitaxel-induced apoptosis.Our results indicate that already in initial stages of cancer progression Aurora-A overexpression could have a major role in inducing supernumerary centrosomes and aneuploidy, as shown by immunohistochemistry on tissue sections from various stages of hu…

Tumor cells can escape DNA-damaging cisplatin through DNA endoreduplication and reversible polyploidy

2008

Cancer chemotherapy can induce tumor regression followed, in many cases, by relapse in the long-term. Thus this study was performed to assess the determinants of such phenomenon using an in vivo cancer model and in vitro approaches. When animals bearing an established tumor are treated by cisplatin, the tumor initially undergoes a dramatic shrinkage and is characterized by giant tumor cells that do not proliferate but maintain DNA synthesis. After several weeks of latency, the tumor resumes its progression and consists of small proliferating cells. Similarly, when tumor cells are exposed in vitro to pharmacological concentrations of cisplatin, mitotic activity stops initially but cells main…

The flood of the Turia River of 1731. An approximation to the literature of the catastrophe

2015

Los sucesos naturales de carácter extraordinario que se han sucedido a lo largo de la historia han dejado tras de sí un gran legado documental. Fenómenos como los terremotos, las erupciones volcánicas, las sequías, las plagas, etc. han constituido desde siempre un motivo de preocupación para las poblaciones expuestas y una ocasión para desatar la imaginación de los cronistas. En el caso de la ciudad de Valencia, ningún fenómeno natural ha influido tanto en su historia como las avenidas recurrentes del río Turia. Una de ellas, la riada extraordinaria de septiembre de 1731, quedó registrada en documentos de todo tipo que pueden englobarse bajo la denominación común de literatura de la catástr…

On critical behaviour in systems of Hamiltonian partial differential equations

2013

Abstract We study the critical behaviour of solutions to weakly dispersive Hamiltonian systems considered as perturbations of elliptic and hyperbolic systems of hydrodynamic type with two components. We argue that near the critical point of gradient catastrophe of the dispersionless system, the solutions to a suitable initial value problem for the perturbed equations are approximately described by particular solutions to the Painlevé-I (P $$_I$$ I ) equation or its fourth-order analogue P $$_I^2$$ I 2 . As concrete examples, we discuss nonlinear Schrödinger equations in the semiclassical limit. A numerical study of these cases provides strong evidence in support of the conjecture.

Electron-density critical points analysis and catastrophe theory to forecast structure instability in periodic solids

2018

The critical points analysis of electron density,i.e. ρ(x), fromab initiocalculations is used in combination with the catastrophe theory to show a correlation between ρ(x) topology and the appearance of instability that may lead to transformations of crystal structures, as a function of pressure/temperature. In particular, this study focuses on the evolution of coalescing non-degenerate critical points,i.e. such that ∇ρ(xc) = 0 and λ1, λ2, λ3≠ 0 [λ being the eigenvalues of the Hessian of ρ(x) atxc], towards degenerate critical points,i.e. ∇ρ(xc) = 0 and at least one λ equal to zero. The catastrophe theory formalism provides a mathematical tool to model ρ(x) in the neighbourhood ofxcand allo…

Knowledge-driven multi-agent simulation engineering for assessing the effectiveness of disaster management plans

2020

Protecting humans from disasters has been an active mission of governments and experts through the definition of disaster management plans. Defining disaster response strategies is crucial in order to reduce the number of victims and the economic impact. In order to select which response plan is best suited to a specific disaster situation, these plans must be evaluated. However, such evaluation is limited by the high cost of exercises and the specificity of existing simulation models. The approach defended in this thesis combines techniques from Semantic Web and multi-agent simulation to evaluate disaster management response plans. It is composed of four steps : (1) modeling disaster manag…