Ecological conditions determine extinction risk in co-evolving bacteria-phage populations.

BACKGROUND: Antagonistic coevolution between bacteria and their viral parasites, phage, drives continual evolution of resistance and infectivity traits through recurrent cycles of adaptation and counter-adaptation. Both partners are vulnerable to extinction through failure of adaptation. Environmental conditions may impose unequal abiotic selection pressures on each partner, destabilising the coevolutionary relationship and increasing the extinction risk of one partner. In this study we explore how the degree of population mixing and resource supply affect coevolution-induced extinction risk by coevolving replicate populations of Pseudomonas fluorescens SBW25 with its associated lytic phage SBW25Ф2 under four treatment regimens incorporating low and high resource availability with mixed or static growth conditions. RESULTS: We observed an increased risk of phage extinction under population mixing, and in low resource conditions. High levels of evolved bacterial resistance promoted phage extinction at low resources under both mixed and static conditions, whereas phage populations could survive when phage susceptible bacterial genotypes rose to high frequency. CONCLUSIONS: These findings demonstrate that phage extinction risk is influenced by multiple abiotic conditions, which together act to destabilise the bacteria-phage coevolutionary relationship. The risk of coevolution-induced extinction is therefore dependent on the ecological context

Influence of the secondary phases and post-annealing on the transport current density of sinter-forged (Bi, Pb)-2223 ceramics

Transport critical current measurements were performed at 77 K on bulk silver-less (Bi, Pb)2Sr2Ca2Cu3O10+x ceramics textured by slow sinter-forging process. The influences of the 85 K superconductive 2212 phase and non-superconductive secondary phases (SrxCa1−x)2PbO4, (Sr,Ca)14Cu24Oy and (SrxCa1−x)2CuO3, are discussed in terms of their amounts, their grain sizes and shapes and their distribution among the 2223 matrix. The importance of the temperature profile and the atmosphere the annealing that follows the sinter-forging process is clearly demonstrated

Orientation control of rhomboedral PZT thin films on Pt/Ti/SiO

Highly (111)- and (001)-oriented rhomboedral PZT thin films have been grown at 500 °C on platinized silicon substrates by in situ RF magnetron sputtering. Crystallization of the perovskite phase was possible provided that a thin TiOx buffer layer was deposited prior to the PZT. Control of PZT films orientation is demonstrated by changing the $\rm O_2/(Ar+O_2)$ ratio in the plasma gas during the TiOx sputtering and its consequences on electrical properties of the ferroelectric samples are presented. The structural properties of the TiOx buffer layer were studied by means of transmission electronic microscopy in order to understand the relation between the TiOx seeding and the orientation control of the PZT film

Imaging the photodissociation dynamics of the methyl radical from the 3s and 3pz Rydberg states

8 págs.; 6 figs.; 1 tab.The photodissociation dynamics of the methyl radical from the 3s and 3pz Rydberg states have been studied using the velocity map and slice ion imaging in combination with pump–probe nanosecond laser pulses. The reported translational energy and angular distributions of the H(2S) photofragment detected by (2+1) REMPI highlight different dissociation mechanisms for the 3s and 3pz Rydberg states. A narrow peak in the translational energy distribution and an anisotropic angular distribution characterize the fast 3s photodissociation, while for the 3pz state Boltzmann-type translational energy and isotropic angular distributions are found. High level ab initio calculations have been performed in order to elucidate the photodissociation mechanisms from the two Rydberg states and to rationalize the experimental results. The calculated potential energy curves highlight a typical predissociation mechanism for the 3s state, characterized by the coupling between the 3s Rydberg state and a valence repulsive state. On the other hand, the photodissociation on the 3pz state is initiated by a predissociation process due to the coupling between the 3pz Rydberg state and a valence repulsive state and constrained, later on, by two conical intersections that allow the system to relax to lower electronic states. Such a mechanism opens up different reaction pathways leading to CH2 photofragments in different electronic states and inducing a transfer of energy between translational and internal modes.S. M. P. acknowledges financial support from Campus de Excelencia Internacional Moncloa and LASING S. A. D. V. C. acknowledges a contract from MINECO under the Fondo de Garantıía Juvenil. A. Z. thanks the support from the European Research Council under the European Union’s 7th Framework Program (FP7/2007–2013)/ERC Grant agreement 610256 (NANOCOSMOS). M. G. G. is grateful to Spanish MINECO for a contract through Programa de Técnicos de Apoyo a Infraestructuras. This work has been financed by the Spanish MINECO (grants FIS2011- 29596-C02-01, CTQ2012-37404-C02-01, FIS2013-40626-P and CTQ2015-65033-P) and by COST Actions CM1401 and CM05. This research has been carried out within the Unidad Asociada Química Física Molecular between Departamento de Química Física of Universidad Complutense de Madrid (UCM) and Consejo Superior de Investigaciones Científicas (CSIC). The facilities provided by the Centro de Láseres Ultrarrápidos at UCM are acknowledged. The Centro de Supercomputación de Galicia (CESGA, Spain) and CTI (CSIC) are acknowledged for the use of their resources.Peer Reviewe

Vortex lattice accommodation on twin boundaries in YBa

An extensive study of small angle neutron scattering was performed in twinned YBa2Cu3O7 crystals in its superconducting state as a function of the angle θB between the c-axis of the crystal and the magnetic field. The half of the twin boundaries are oriented in the horizontal plane, which also contains the neutron beam and the magnetic field. Two different diffraction patterns are studied as a function of θB at 5 K and B = 0.5 T, one along the c-axis of the crystal, the other one along the applied field. These variations are interpreted in the model of accommodation of the vortices on the twin planes by zigzagging from these planes to the ab-planes of the crystal, in order to minimize their energy

Highly textured Pt thin film grown at very low temperature using Ca 2 Nb 3 O 10 nanosheets as seed layer

International audienceThe decrease of the growth temperature of platinum (Pt) thin film on silicon substrate was studied using Ca2Nb3O10 nanosheets (CNOns) as seed layer. These nanosheets were obtained by the delamination of the layered perovskite KCa2Nb3O10 and they were deposited on silicon substrates by the Langmuir–Blodgett method. Pt thin films were sputtered on silicon coated by CNOns (CNOns/SiO2/Si), and on TiO2/SiO2/Si substrates for comparison, at temperatures ranging from room temperature up to 625 °C. X-ray diffraction, scanning electron microscopy, and atomic force microscopy were used to characterize the crystalline quality, thickness, surface morphology and roughness of the Pt thin films. Highly (111) textured Pt thin films were obtained on CNOns/SiO2/Si at substrate temperature as low as 200 °C. The full width at half maximum of the rocking curve of the (111) X-ray peak was about one degree, indicating a high crystalline orientation. The resistivity was measured at room temperature by the four point probes method to confirm the quality of Pt thin films elaborated at low temperatures. These results pave the way for easier integration of highly textured platinum thin film in low temperature microelectronic processes

Optimized lithography and etching processes for a magnetic oxide micro‐device

International audienc