260 research outputs found
Strange attractor simulated on a quantum computer
We show that dissipative classical dynamics converging to a strange attractor
can be simulated on a quantum computer. Such quantum computations allow to
investigate efficiently the small scale structure of strange attractors,
yielding new information inaccessible to classical computers. This opens new
possibilities for quantum simulations of various dissipative processes in
nature.Comment: latex 4 pages, 4 figures, research at
http://www.quantware.ups-tlse.fr, one fig and discussion adde
Fractal fluctuations in quantum integrable scattering
We theoretically and numerically demonstrate that completely integrable
scattering processes may exhibit fractal transmission fluctuations, due to
typical spectral properties of integrable systems.
Similar properties also occur with scattering processes in the presence of
strong dynamical localization, thus explaining recent numerical observations of
fractality in the latter class of systems.Comment: revtex, 4 pages, 3 eps figure
Comparative response of brain to chronic hypoxia and hyperoxia
Two antithetic terms, hypoxia and hyperoxia, i.e., insufficient and excess oxygen availability with respect to needs, are thought to trigger opposite responses in cells and tissues. This review aims at summarizing the molecular and cellular mechanisms underlying hypoxia and hyperoxia in brain and cerebral tissue, a context that may prove to be useful for characterizing not only several clinically relevant aspects, but also aspects related to the evolution of oxygen transport and use by the tissues. While the response to acute hypoxia/hyperoxia presumably recruits only a minor portion of the potentially involved cell machinery, focusing into chronic conditions, instead, enables to take into consideration a wider range of potential responses to oxygen-linked stress, spanning from metabolic to genic. We will examine how various brain subsystems, including energetic metabolism, oxygen sensing, recruitment of pro-survival pathways as protein kinase B (Akt), mitogen-activated protein kinases (MAPK), neurotrophins (BDNF), erythropoietin (Epo) and its receptors (EpoR), neuroglobin (Ngb), nitric oxide (NO), carbon monoxide (CO), deal with chronic hypoxia and hyperoxia to end-up with the final outcomes, oxidative stress and brain damage. A more complex than expected pattern results, which emphasizes the delicate balance between the severity of the stress imposed by hypoxia and hyperoxia and the recruitment of molecular and cellular defense patterns. While for certain functions the expectation that hypoxia and hyperoxia should cause opposite responses is actually met, for others it is not, and both emerge as dangerous treatments
Dynamics of Anderson localization in open 3D media
We develop a self-consistent theoretical approach to the dynamics of Anderson
localization in open three-dimensional (3D) disordered media. The approach
allows us to study time-dependent transmission and reflection, and the
distribution of decay rates of quasi-modes of 3D disordered slabs near the
Anderson mobility edge.Comment: 4 pages, 4 figure
Imperfection effects for multiple applications of the quantum wavelet transform
We study analytically and numerically the effects of various imperfections in
a quantum computation of a simple dynamical model based on the Quantum Wavelet
Transform (QWT). The results for fidelity timescales, obtained for a large
range of error amplitudes and number of qubits, imply that for static
imperfections the threshold for fault-tolerant quantum computation is decreased
by a few orders of magnitude compared to the case of random errors.Comment: revtex, 11 pages, 13 figures, research at Quantware MIPS Center
http://www.quantware.ups-tlse.f
Expression of carbohydrate-antigen sialyl-Lewis a on colon cancer cells promotes xenograft growth and angiogenesis in nude mice
We investigated the role of carbohydrate antigen sialyl-Lewis a (sLea), an E-selectin ligand and epitope of tumor marker CA19.9, in the development of xenografts in nude mice. To this end, animals were inoculated with the human colon cancer cell line HCT-15, expressing no Lewis antigens, or with a clone expressing sLea (HCT-15-T5). The size of HCT-15-T5 xenografts appeared larger than those of HCT-15 and their average weight was over twice bigger. In both xenografts the mitotic index was found elevated, as determined by Ki-67 assay, and no apoptosis was detected in the tumor cells by both caspase 8 or TUNEL assays. Some apoptotic signals were instead detected in the vessels. Conversely, microvessel density, determined through CD-31 immunohistochemistry, was found 3.2-folds bigger in HCT-15-T5 xenografts (p < 0.012). Only the membranes of HCT-15-T5 cells grown as xenografts reacted intensively with the anti CA19.9 antibody 1116-NS-19-9 by immunofluorescence, but not by immunohistochemistry. Unknown structures were instead stained by such technique in both xenografts, as were in mouse tissues not expressing the antigen and in human colon adenocarcinoma. We conclude that expression of sLea on the surface of colon cancer cells improves xenograft growth and is associated with enhanced angiogenesis, while immunohistochemistry with 1116-NS-19-9 antibody appears not suitable to determine CA19.9 expression
Using ezRAD to reconstruct the complete mitochondrial genome of Porites fontanesii (Cnidaria: Scleractinia)
Corals in the genus Porites are among the major framework builders of reef structures worldwide, yet the genus has been challenging to study due to a lack of informative molecular markers. Here, we used ezRAD sequencing to reconstruct the complete mitochondrial genome of Porites fontanesii (GenBank accession number MG754069), a widespread coral species endemic to the Red Sea and Gulf of Aden. The gene arrangement of P. fontanesii did not differ from other Scleractinia and consisted of 18,658 bp, organized in 13 protein-coding genes, 2 rRNA genes, and 2 tRNA genes. This mitochondrial genome contributes essential data to work towards a better understanding of evolutionary relationships within Porites
Biocatalytic production of flavors and fragrances
The preparation of flavors and fragrances has to be done with great care. When these compounds are meant for consumption, no toxic chemicals are allowed during their preparation. For use in non-food additives, a high purity is required. Both constraints can be easily fulfilled when enzymes are used as catalyst during the production of these compounds. This paper summarizes the work that we have done regarding the preparation of branchedchain fatty acids (sheep flavors) using lipases, the production of glucosides (controlled-release flavors) using glucosidases, the formation of terpene alcohols and grapefruit flavor using enzymes from chicory, and the formation of phenolic antioxidants using lipases
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