Appearance of quasiperiodicity within a period doubling route to chaos of a swaying thermal plume

The birth, evolution and disappearance of quasiperiodic dynamics in buoyancy-driven flow arising from an enclosed horizontal cylinder are analysed here, by numerical means, in the limit of the 2D approximation. The governing equations are solved on orthogonal Cartesian grids, giving special treatment to the internal, non-aligned boundaries. Thanks to the adoption of a high level of re finement of the Rayleigh number range, quasiperiodicity was observed to emerge from a periodic limit cycle (P1), and to turn into its omologous orbit with doubled period (P2), eventually evolving into a classical period-doubling route to chaos, for further increases of the Rayleigh number. The present study gives a deeper insight to what appears to be an imperfect period doubling bifurcation through a quasiperiodic T2-torus. The approach used is based on the classical tools for time series analysis. The distribution of the power spectral densities is used to search for and characterise the existence of relations between the frequencies of the P1, T2 and P2 dynamics. The topology of the orbits, as well as their evolution within the quasiperiodic window, are analysed with the aid of phase space representation and Poincar è maps

Heat transfer along the route to chaos of a swaying thermal plume

Detailed analyses have been recently reported on the low order dynamics of a thermal plume arising from a horizontal cylindrical heat source concentric: to an air-\ufb01lled isothermally cooled square enclosure, together with those of the related \ufb02ow structures, in the limit of the 2D approximation. In particular. within the range of O < Ra < 3 RaL-T, With Ram corresponding to the loss of stability of the stationary buoyant plume, the entire evolution from a periodic limit cycle (P1) to the birth of chaos through a period\ubbdoubling cascade has been fullyexplored. With this respect, special attention has been given to the window of quasiperiodic dynamics onto a T;-torus that is observed to separate the monoperiodic dynamics from the biperiodic dynamics onto a P1 and a Pg-liniit cycle, respectively. The results of these analyses hint at the bimodal nature of the overall dynamics. in general, and of the subharmonic cascade, in particular, which are still under investigation. Although relevant on a dynamical perspective, a with a main re\ufb02ection on the laminar-turbulent transition, the observed oscillations appear to be characterised by comparable amplitudes and to be determined by similar evolutions of the \ufb02ow pattern evolutions, so that their role on the overall heat transfer rate is expected to be marginal. Vi/'ithin this frame, the present study aims at reporting the in\ufb02uence played by the observed dynamics of the thermal plume and of the [low structures on the global heat transferrate. In particular, the aim is the assessment of the correlation between the Rayleigh number and the average Nusselt number on the cylinder surface, as well as the effect on the latter of the observed series of bifurcations

Bifurcations of Natural Convection Flows from an Enclosed Cylindrical Heat Source

A numerical analysis of transitional natural convection from a confined thermal source is presented. The system considered is an air-filled, square-sectioned 2D enclosure containing a horizontal heated cylinder. The resulting flow is investigated with respect to the variation of the Rayleigh number, for three values of the aspect ratio A. The first bifurcation of the low-Ra fixed-point solution is tracked for each A-value. Chaotic flow features are detailed for the case A = 2.5. The supercritical behaviour of the system is investigated using nonlinear analysis tools and phase-space representations, and the effect of the flow on heat transfer is discussed

Current-Resistance Effects Inducing Nonlinear Fluctuation Mechanisms in Granular Aluminum Oxide Nanowires

The unusual superconducting properties of granular aluminum oxide have been recently investigated for application in quantum circuits. However, the intrinsic irregular structure of this material requires a good understanding of the transport mechanisms and, in particular, the effect of disorder, especially when patterned at the nanoscale level. In view of these aspects, electric transport and voltage fluctuations have been investigated on thin-film based granular aluminum oxide nanowires, in the normal state and at temperatures between 8 and 300 K. The nonlinear resistivity and two-level tunneling fluctuators have been observed. Regarding the nature of the noise processes, the experimental findings give a clear indication in favor of a dynamic random resistor network model, rather than the possible existence of a local ordering of magnetic origin. The identification of the charge carrier fluctuations in the normal state of granular aluminum oxide nanowires is very useful for improving the fabrication process and, therefore, reducing the possible sources of decoherence in the superconducting state, where quantum technologies that are based on these nanostructures should work

Electrocution and containment methods to reduce the activity of red palm weevil (Rhynchophorus ferrugineus, Ol.)

Aim of study: To evaluate the susceptibility of the Rhynchophorus ferrugineus to electric discharges, to eventually use this application in synergy with other methods as part of an integrated control strategy.Area of study: Worldwide.Material and methods: Three different electric voltage intensities were applied to R. ferrugineus to investigate the insect’s susceptibility in both adult and larval stages. The transmission and diffusion of electricity within a portion of the palm tree was tested. In addition, the suitability of containment materials for handling and transportation of plant residues was tested.Main results: The results of adult test showed that the total number of eggs laid per mating couple and the number of larvae born were about 1.5 times higher in the control compared to the electrified samples. The duration of the electric discharge on larvae had a small impact on the mortality rate, while the electric voltage showed a strong impact on mortality (87% for 10 V and 99% for 15 V). The presence of a significant electric current was observed in a viable portion of stem (distance from the source of electricity 10 cm) providing a direct current with 250 V tension. Among the materials tested for the transportation of palm residues, the aluminium net sheet showed the best results in the containment of both larval and adult individuals.Research highlights: Electrocution has proven to be a system which can help in the control of red palm weevil reducing the use of synthetic chemicals

Determinants of Sovereign Bond Yield Spreads in the EMU. An Optimal Currency Area Perspective

In the light of the recent financial crisis, we take a panel cointegration approach that allows for structural breaks to the analysis of the determinants of sovereign bond yield spreads in nine economies of the European Monetary Union. While we find evidence for a level break in the cointegrating relationship, we do not find empirical support for a regime shift and hence for a change in the pricing of the determinants of sovereign spreads. Moreover, results show that (i) fiscal imbalances (namely expected government debt-to-GDP differentials) are the main long-run drivers of sovereign spreads; (ii) liquidity risks and cumulated inflation differentials have non-negligible weights; but (iii) all conclusions are ultimately connected to whether or not the sample of countries is composed of members of an Optimal Currency Area (OCA). In particular, we establish (i) that results are overall driven by those countries not passing the OCA test; and (ii) that investors closely monitor and severely punish the deterioration of expected debt positions of those economies exhibiting significant gaps in competitiveness

Pseudomonas fluorescens Pf-5 genome-wide mutant screen for resistance to the antimicrobial peptide alfalfa snakin-1

Snakin-1, a peptide produced by higher plants, has broad-spectrum antibiotic activity, inhibiting organisms ranging from Bacteria to Eukaryotes. However, the mode of action against target organisms is poorly understood. As a first step to elucidate the mechanism, we screened a mutation library of Pseudomonas fluorescens Pf-5 in LB and agar medium supplemented with alfalfa snakin-1 (MsSN1). We identified three biofilm formation-related Pseudomonas mutants that showed increased resistance to MsSN1. Genetic, physiological and bioinformatics analysis validated the results of the mutant screens, indicating that bacterial adhesion protein lapA is probably the target of MsSN1. Collectively, these findings suggest that snakin-1 acts on microbial adhesion properties.Instituto de GenéticaFil: Ayub, Nicolás Daniel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fox, Ana Romina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garcia, Araceli Nora. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; ArgentinaFil: Mozzicafreddo, Matteo. University of Camerino. School of Biosciences and Biotechnology; ItaliaFil: Cuccioloni, Massimiliano. University of Camerino. School of Biosciences and Biotechnology; ItaliaFil: Angeletti, Mauro. University of Camerino. School of Biosciences and Biotechnology; ItaliaFil: Pagano, Elba Maria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; ArgentinaFil: Soto, Gabriela Cinthia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Magnetotransport and magnetic properties of amorphous NdNi 5 thin films

Abstract: NdNi5 is an intermetallic compound with a bulk Curie temperature (TCurie) of 6–13 K. While existing studies have focused on NdNi5 crystals, amorphous thin-films of NdNi5 are potentially important since they would be magnetically soft without magnetocrystalline anisotropy, meaning that small external magnetic fields could reverse the direction of their magnetization. Here, we report NdNi5 thin-films with a thickness in the 5–200 nm range, deposited by DC magnetron sputtering onto Si(100). Films are amorphous with a weak temperature-dependent resistivity with values ranging between 150 and 300 μΩ cm. By means of noise spectroscopy, by analyzing the time-dependence of fluctuation-induced voltages, it is found that at low temperatures the resistance fluctuations are due to the Kondo effect. Volume magnetometry indicates TCurie=70 K with a magnetic coercive field of 30 mT at 5 K for a 125-nm-thick film. The results are promising for the development of Ferromagnet(F)/Superconductor(S)/Ferromagnet(F) pseudo spin-valve devices based on amorphous NdNi5 thin films

Kondo-like transport and magnetic field effect of charge carrier fluctuations in granular aluminum oxide thin films

Granular aluminum oxide is an attractive material for superconducting quantum electronics. However, its low-temperature normal state transport properties are still not fully understood, while they could be related to the unconventional phenomenon of the superconductivity in this material. In order to obtain useful information on this aspect, a detailed study of charge carrier fluctuations has been performed in granular aluminum oxide films. The results of electric noise measurements indicate the presence of a Kondo-type spin-flip scattering mechanism for the conducting electrons in the normal state, at low temperatures. Moreover, the magnetic field dependence of the noise amplitude suggests that interface magnetic moments are the main source of fluctuations. The identification of the nature of fluctuation processes is a mandatory requirement for the improvement of quality and performance of quantum devices