University of Nice Sophia Antipolis

About: University of Nice Sophia Antipolis is a education organization based out in Nice, France. It is known for research contribution in the topics: Population & Stars. The organization has 10291 authors who have published 19964 publications receiving 680762 citations. The organization is also known as: UNS & University of Nice-Sophia Antipolis.

Topological transition of Dirac points in a microwave experiment.

Abstract: By means of a microwave tight-binding analogue experiment of a graphenelike lattice, we observe a topological transition between a phase with a pointlike band gap characteristic of massless Dirac fermions and a gapped phase. By applying a controlled anisotropy on the structure, we investigate the transition directly via density of states measurements. The wave function associated with each eigenvalue is mapped and reveals new states at the Dirac point, localized on the armchair edges. We find that with increasing anisotropy, these new states are more and more localized at the edges.

Nitric oxide is formed in Medicago truncatula-Sinorhizobium meliloti functional nodules

Abstract: Nitric oxide (NO) has recently gained interest as a major signaling molecule during plant development and response to environmental cues. Its role is particularly crucial for plant-pathogen interactions, during which it participates in the control of plant defense response and resistance. Indication for the presence of NO during symbiotic interactions has also been reported. Here, we defined when and where NO is produced during Medicago truncatula-Sinorhizobium meliloti symbiosis. Using the NO-specific fluorescent probe 4,5-diaminofluorescein diacetate, NO production was detected by confocal microscopy in functional nodules. NO production was localized in the bacteroid-containing cells of the nodule fixation zone. The infection of Medicago roots with bacterial strains impaired in nitrogenase or nitrite reductase activities lead to the formation of nodules with an unaffected NO level, indicating that neither nitrogen fixation nor denitrification pathways are required for NO production. On the other hand, the NO synthase inhibitor N-methyl-L-arginine impaired NO detection, suggesting that a NO synthase may participate to NO production in nodules. These data indicate that a NO production occurs in functional nodules. The location of such a production in fully metabolically active cells raises the hypothesis of a new function for NO during this interaction unrelated to defense and cell-death activation.

The outcomes and surgical techniques of the latarjet procedure.

Abstract: Purpose To determine the optimal position and orientation of the coracoid bone graft for the Latarjet procedure for recurrent instability in patients with recurrent anterior instability and high degrees of glenoid bone loss. Methods A systematic review of the literature including the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, PubMed (1980-2012), and Medline (1980-2012) was conducted. The following search teams were used: glenoid bone graft, coracoid transfer, glenoid rim fracture, osseous glenoid defect, and Latarjet. Studies deemed appropriate for inclusion were then analyzed. Study data collected included level of evidence, patient demographic characteristics, preoperative variables, intraoperative findings, technique details, and postoperative recovery and complications where available. Results The original search provided a total of 344 studies. A total of 334 studies were subsequently excluded because they were on an irrelevant topic, used an arthroscopic technique, or were not published in English or because they were review articles, leaving 10 studies eligible for inclusion. Given the different methods used in each of the studies included in the review, descriptive analysis was performed. The duration of follow-up ranged from 6 months to 14.3 years postoperatively. With the exception of 2 studies, all authors reported on recurrent shoulder instability after Latarjet reconstruction; the rate of recurrent anterior shoulder instability ranged from 0% to 8%. Overall patient satisfaction was listed in 4 studies, each of which reported good to excellent satisfaction rates of more than 90% at final follow-up. Conclusions As noted in this review, the current literature on Latarjet outcomes consists mostly of retrospective Level IV case series. Although promising outcomes with regard to a low rate of recurrent instability have been seen with these reports, it should be noted that subtle variations in surgical technique, among other factors, may drastically impact the likelihood of glenohumeral degenerative changes arising in these patients. Level of Evidence Level IV, systematic review of Level IV studies.

On the onset of nonlinear oscillations in a separating boundary-layer flow

Abstract: The stability of a separating boundary-layer flow at the rear of a two-dimensional bump mounted on a flat plate is numerically investigated. Above a critical Reynolds number, the flow field is shown to undergo self-sustained two-dimensional low-frequency fluctuations in the upstream region of the separation bubble, evolving into aperiodic vortex shedding further downstream. The computed steady flow states below the critical Reynolds number are shown to be convectively unstable. On extrapolating the flow field to Reynolds numbers above criticality, some evidence is found that the onset of the oscillatory behaviour coincides with topological flow changes near the reattachment point leading to the rupture of the (elongated) recirculation bubble. The structural changes near reattachment are shown to trigger an abrupt local transition from convective to absolute instability, at low frequencies. On preventing the separation bubble from bursting by reaccelerating the flow by means of a second bump further downstream, the separated flow remains steady for increasing Reynolds numbers, until a local region of absolute instability in the upper part of the geometrically controlled recirculation bubble is produced. The resulting global instability consists of self-sustained nonlinear saturated perturbations oscillating at a well-defined frequency, very distinct from the the low-frequency motion of the elongated recirculation bubble in the single-bump geometry. A frequency selection criterion based on local absolute frequencies, which has been successfully applied to wake flows, is shown to accurately predict the global frequency.

Combinatorial operad actions on cochains

Abstract: A classical E-infinity operad is formed by the bar construction of the symmetric groups. Such an operad has been introduced by M. Barratt and P. Eccles in the context of simplicial sets in order to have an analogue of the Milnor FK-construction for infinite loop spaces. The purpose of this article is to prove that the associative algebra structure on the normalized cochain complex of a simplicial set extends to the structure of an algebra over the Barratt-Eccles operad. We also prove that differential graded algebras over the Barratt-Eccles operad form a closed model category. Similar results hold for the normalized Hochschild cochain complex of an associative algebra. More precisely, the Hochschild cochain complex is acted on by a suboperad of the Barratt-Eccles operad which is equivalent to the classical little squares operad.