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  • 1
    Language: English
    In: Plasmid, July 2013, Vol.70(1), pp.61-68
    Description: ► HtdA is involved in the transcriptional repression of four R27 plasmid operons. ► HtdA does not exert its effect as a classical repressor. ► The HtdA mediated regulatory pathway involves other R27 encoded factors. ► The HtdA mediated regulation of conjugation is independent of the R27 H-NS protein. R27 is the prototype of the IncHI group of conjugative plasmids, which are associated with multidrug resistance in several relevant pathogens. The transfer of this plasmid is thermodependent and all transfer-related genes are encoded in six operons ( operons). Very little is known about the factors involved in the regulation of the R27 conjugation. This report describes transcriptional studies of the six operons. Our results indicate that HtdA, encoded in the R27 plasmid, is involved in the transcriptional repression of four operons (F, H, AC and Z). Although HtdA plays a pivotal role in the transcriptional regulation of those operons, it does not exert its effect as a classical repressor. The data indicate the existence of a crosstalk between HtdA and other unknown regulatory factors. The HtdA-mediated regulation of conjugation is independent of the R27 H-NS protein.
    Keywords: Plasmid Conjugation ; Inchi ; R27 ; Tra Operons Regulation ; Htda ; Biology
    ISSN: 0147-619X
    E-ISSN: 1095-9890
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  • 2
    Language: English
    In: Physical Review B, 10/2010, Vol.82(16)
    ISSN: 1098-0121
    E-ISSN: 1550-235X
    Source: American Physical Society (APS) (via CrossRef)
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  • 3
    In: Nature Materials, 2012, Vol.11(3), p.195
    Description: The wide spectrum of exotic properties exhibited by transition-metal oxides stems from the complex competition between several quantum interactions. The capacity to select the emergence of specific phases at will is nowadays extensively recognized as key for the design of diverse new devices with tailored functionalities. In this context, interface engineering in complex oxide heterostructures has developed into a flourishing field, enabling not only further tuning of the exceptional properties of these materials, but also giving access to hidden phases and emergent physical phenomena. Here we demonstrate how interfacial interactions can induce a complex magnetic structure in a non-magnetic material. We specifically show that exchange bias can unexpectedly emerge in heterostructures consisting of paramagnetic LaNiO sub(3) (LNO) and ferromagnetic LaMnO sub(3) (LMO). The observation of exchange bias in (111)-oriented LNO-LMO superlattices, manifested as a shift of the magnetization-field loop, not only implies the development of interface-induced magnetism in the paramagnetic LNO layers, but also provides us with a very subtle tool for probing the interfacial coupling between the LNO and LMO layers. First-principles calculations indicate that this interfacial interaction may give rise to an unusual spin order, resembling a spin-density wave, within the LNO layers.
    Keywords: Bias ; Ferromagnetism ; Heterostructures ; Materials Selection ; Oxides ; Phases ; Stems ; Superlattices ; Microstructure (So) ; Crystal Properties (MD) ; Microstructure (Ep) ; Microstructure (Ed) ; Microstructure (EC);
    ISSN: 1476-1122
    E-ISSN: 14764660
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  • 4
    Language: English
    In: Applied Physics Letters, 06 December 2010, Vol.97(23)
    Description: We report size-dependent strain in epitaxial gadolinium doped ceria nanoislands, which was determined by synchrotron x-ray diffraction. Reciprocal space sections of symmetric, (004) and asymmetric, (224) reflections are approximated by a model assuming size-dependent strain of the islands using real-space size distribution obtained by atomic force microscopy. We show that the islands smaller than 40 nm are subjected to a high level of lateral tensile strain and normal compression. The lateral to normal strain ratio determined from the reciprocal map analysis suggests that lateral tension is the primary stress generator, possibly due to oxygen vacancy ordering on the island-substrate interface.
    Keywords: Structural, Mechanical, Thermodynamic, And Optical Properties Of Condensed Matter
    ISSN: 0003-6951
    E-ISSN: 1077-3118
    Source: © 2010 American Institute of Physics (AIP)〈img src=http://exlibris-pub.s3.amazonaws.com/AIP_edited.gif style="vertical-align:middle;margin-left:7px"〉
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  • 5
    Language: English
    In: Acta Materialia, 2011, Vol.59(5), pp.2075-2082
    Description: To elucidate the effect of a BaZrO nanodot template on the microstructure and critical current density of YBa Cu O films the nanostructured interface is thoroughly investigated by high resolution transmission electron microscopy. The nanodots appear fully relaxed relative to the substrate, while exhibiting a high coherence with their embedding film with continuous BaO atomic layers across the YBa Cu O and BaZrO interface. The present results demonstrate that the template–film interaction does not involve dislocation emission but is accompanied by the generation of short-range and long-range strains. The topological distribution of perturbed regions within the superconducting films qualitatively explains the overall enhancement of the critical current density, which becomes particularly high when the magnetic field is aligned with the -axis. These findings demonstrate for the first time the feasibility of an all solution approach to the preparation of defect engineered YBa Cu O films on surface decorated substrates.
    Keywords: Ceramic Superconductors ; Nanostructure ; Thin Films ; Transmission Electron Microscopy ; Critical Currents ; Engineering
    ISSN: 1359-6454
    E-ISSN: 1873-2453
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  • 6
    Language: English
    In: Nanotechnology, 2010, Vol.21(2), p.025302 (8pp)
    Description: When one-dimensional nanostructures are epitaxially grown on a substrate a key goal is to control the nanowires position and orientation. Nanoscratching of single crystalline (001)- LaAlO 3 substrates is demonstrated to be extraordinarily effective in directing the self-assembly of Ce 0.9 Gd 0.1 O 2 y epitaxial nanowires grown by chemical solution deposition. The local anisotropic elastic strain field imposed by the indentation lines is responsible for the breaking of the pre-existing orientation energy degeneracy and selects the nanowires orientation parallel to the lines to an extent that can reach 100%.
    Keywords: Cerium -- Chemistry ; Crystallization -- Methods ; Gadolinium -- Chemistry ; Nanostructures -- Chemistry ; Nanotechnology -- Methods;
    ISSN: 0957-4484
    E-ISSN: 1361-6528
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  • 7
    In: Advanced Materials, May 2017, Vol.29(18), pp.n/a-n/a
    Description: A marked conductivity enhancement is reported in 6–11 unit cell LaNiO thin films. A maximal conductivity is also observed in ab initio calculations for films of the same thickness. In agreement with results from state of the art scanning transmission electron microscopy, the calculations also reveal a differentiated film structure comprising characteristic surface, interior, and heterointerface structures. Based on this observation, a three‐element parallel conductor model is considered and leads to the conclusion that the conductivity enhancement for films of 6–11 unit cells, stems from the onset of intercompetition between the three local structures in the film depth. is speculated to stem from a playoff between three characteristic local structures in the film depth, which are seen by state of the art scanning transmission electron microscopy and further elucidated by first‐principles simulations.
    Keywords: Nickelates ; Oxides ; Thin Films
    ISSN: 0935-9648
    E-ISSN: 1521-4095
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  • 8
    In: CrystEngComm, 2011, Vol.13(22), pp.6719-6727
    Description: The extended use of self-assembling approaches for the generation of oxide nanostructures with engineered functional properties firstly relies on the ability to control their growth processes. In this paper, we focus on the growth of Ce 1 x Gd x O 2 y (CGO) nanoislands on ABO 3 substrates ( i.e. LaAlO 3 (LAO)) as a model system to investigate the nucleation and kinetic evolution of epitaxial nanostructures grown by high-throughput ex situ methods based on chemical solution deposition. Fine-tuning of growth conditions enables us to select the crystallographic orientation of CGO leading to two systems with different equilibrium shapes and kinetics. Self-assembled (001)CGO(001)LAO nanostructures grow with stable uniform square-based nanopyramid shape, whereas the nucleation of (011)CGO(001)LAO leads to highly elongated nanowires with enhanced diffusive mobility. At high temperatures, shape selection is merely achieved through a modified growth atmosphere (oxidizing or reducing). However, a temperature-induced nucleation orientation crossover occurs under the reducing growth atmosphere, allowing the tuning of a nanodot-to-nanowire ratio through kinetic control. We prove by XPS that an enhanced concentration of oxygen vacancies in the nanowires is linked to their ultrafast coarsening. The nucleation processes are scrutinized through thermodynamic analysis, and it is concluded that the supersaturation degree controls the nanoislands' orientation.
    Keywords: Deposition ; Epitaxial Growth ; Nanocomposites ; Nanomaterials ; Nanostructure ; Nanowires ; Nucleation ; Orientation ; Atomic and Molecular Structure (So);
    ISSN: 1466-8033
    E-ISSN: 1466-8033
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  • 9
    Language: English
    In: Nano Letters, 2015, Vol.15(11), pp.7355-7361
    Description: The functional properties of oxide heterostructures ultimately rely on how the electronic and structural mismatches occurring at interfaces are accommodated by the chosen materials combination. We discuss here LaMnO$_3$/LaNiO$_3$ heterostructures, which display an intrinsic interface structural...
    Keywords: Physics ; Manganites ; Interface Engineering ; Magnetism ; Nickelates ; Engineering ; Physics
    ISSN: 1530-6984
    E-ISSN: 1530-6992
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  • 10
    In: Environmental Microbiology, December 2016, Vol.18(12), pp.5277-5287
    Description: Plasmids of the incompatibility group HI1 (IncHI1) have been isolated from several Gram‐negative pathogens and are associated with the spread of multidrug resistance. Their conjugation is tightly regulated and it is inhibited at temperatures higher than 30°C, indicating that conjugation occurs outside warm‐blooded hosts. Using R27, the prototype of IncHI1 plasmids, we report that plasmid transfer efficiency in strongly depends on the physiological state of the donor cells. Conjugation frequency is high when cells are actively growing, dropping sharply when cells enter the stationary phase of growth. Accordingly, our transcriptomic assays show significant downregulation of numerous R27 genes during the stationary phase, including several (transfer) genes. Growth phase‐dependent regulation of genes transcription is independent of H‐NS, a silencer of horizontal gene transfer, and ppGpp and RpoS, regulators of the stationary phase, but highly dependent on the plasmid‐encoded regulatory circuit TrhR/TrhY‐HtdA. The metabolic sensor cAMP, whose synthesis is chromosomally encoded, is also involved in the growth phase regulation of R27 conjugation by modulating expression. Our data suggest that the involvement of regulators encoded by both chromosome and plasmid are required for efficient physiological control of IncHI1 plasmid conjugation.
    Keywords: Cyclic Adenosine Monophosphate – Physiological Aspects ; Cyclic Adenosine Monophosphate – Growth ; Genetic Research – Physiological Aspects ; Genetic Research – Growth ; Genes – Physiological Aspects ; Genes – Growth ; Sensors – Physiological Aspects ; Microbial Drug Resistance – Physiological Aspects ; Microbial Drug Resistance – Growth;
    ISSN: 1462-2912
    E-ISSN: 1462-2920
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