116 research outputs found
Dissipation in ultra-thin current-carrying superconducting bridges; evidence for quantum tunneling of Pearl vortices
We have made current-voltage (IV) measurements of artificially layered
high- thin-film bridges. Scanning SQUID microscopy of these films provides
values for the Pearl lengths that exceed the bridge width, and shows
that the current distributions are uniform across the bridges. At high
temperatures and high currents the voltages follow the power law , with , and at high temperatures and
low-currents the resistance is exponential in temperature, in good agreement
with the predictions for thermally activated vortex motion. At low
temperatures, the IV's are better fit by linear in . This is
expected if the low temperature dissipation is dominated by quantum tunneling
of Pearl vortices.Comment: 5 pages, 7 fig
Infrared response of ordered polarons in layered perovskites
We report on the infrared absorption spectra of three oxides where charged
superlattices have been recently observed in diffraction experiments. In
LaSrNiO, polaron localization is found to suppress the
low-energy conductivity through the opening of a gap and to split the
- vibrational manifold of the oxygen octahedra. Similar effects
are detected in SrLaMnO and in LaNiO, with
peculiar differences related to the type of charge ordering.Comment: File latex, 11 p. + 3 Figures, to appear on Phys. Rev. B (Rapid
Commun.), 1 Oct. 1996. The figures will be faxed upon request.
E-mail:[email protected] Fax: +39-6-446315
Energy and symmetry of excitations in undoped layered cuprates measured by Cu resonant inelastic x-ray scattering
We measured high resolution Cu edge resonant inelastic x-ray scattering
(RIXS) of the undoped cuprates LaCuO, SrCuOCl, CaCuO
and NdBaCuO. The dominant spectral features were assigned to
excitations and we extensively studied their polarization and scattering
geometry dependence. In a pure ionic picture, we calculated the theoretical
cross sections for those excitations and used them to fit the experimental data
with excellent agreement. By doing so, we were able to determine the energy and
symmetry of Cu-3 states for the four systems with unprecedented accuracy and
confidence. The values of the effective parameters could be obtained for the
single ion crystal field model but not for a simple two-dimensional cluster
model. The firm experimental assessment of excitation energies carries
important consequences for the physics of high superconductors. On one
hand, having found that the minimum energy of orbital excitation is always
eV, i.e., well above the mid-infrared spectral range, leaves to
magnetic excitations (up to 300 meV) a major role in Cooper pairing in
cuprates. On the other hand, it has become possible to study quantitatively the
effective influence of excitations on the superconducting gap in cuprates.Comment: 22 pages, 11 figures, 1 tabl
Early targets of miR-34a in neuroblastoma
Several genes encoding for proteins involved in proliferation, invasion, and apoptosis are known to be direct miR-34a targets. Here, we used proteomics to screen for targets of miR-34a in neuroblastoma (NBL), a childhood cancer that originates from precursor cells of the sympathetic nervous system. We examined the effect of miR-34a overexpression using a tetracycline inducible system in two NBL cell lines (SHEP and SH-SY5Y) at early time points of expression (6, 12, and 24 h). Proteome analysis using post-metabolic labeling led to the identification of 2,082 proteins, and among these 186 were regulated (112 proteins down-regulated and 74 up-regulated). Prediction of miR-34a targets via bioinformatics showed that 32 transcripts held miR-34a seed sequences in their 3′-UTR. By combining the proteomics data with Kaplan Meier geneexpression studies, we identified seven new gene products (ALG13, TIMM13, TGM2, ABCF2, CTCF, Ki67, and LYAR) that were correlated with worse clinical outcomes. These were further validated in vitro by 3′-UTR seed sequence regulation. In addition, Michigan Molecular Interactions searches indicated that together these proteins affect signaling pathways that regulate cell cycle and proliferation, focal adhesions, and other cellular properties that overall enhance tumor progression (including signaling pathways such as TGF-β, WNT, MAPK, and FAK). In conclusion, proteome analysis has here identified early targets of miR-34a with relevance to NBL tumorigenesis. Along with the results of previous studies, our data strongly suggest miR-34a as a useful tool for improving the chance of therapeutic success with NBL
Analysis of charge transfer mechanism on (Ba1-xNdxCuO2+d)2/(CaCuO2)n superconducting superlattices by thermoelectric power measurements
We have investigated the charge transfer mechanism in artificial
superlattices by Seebeck effect measurements. Such a technique allows a precise
determination of the amount of charge transferred on each CuO2 plane. A
systematic characterization of thermoelectric power in (BaCuO2+d)2/(CaCuO2)n
and (Ba0.9Nd0.1CuO2+d)2/(CaCuO2)n superlattices demonstrates that electrical
charge distributes uniformly among the CuO2 planes in the Ca-block. The
differences observed in the Seebeck effect behavior between the Nd-doped and
undoped superlattices are ascribed to the different metallic character of the
Ba-block in the two cases. Finally, the special role of structural disorder in
superlattices with n=1 is pointed out by such analysis.Comment: subitted to PRB, 15 pages, 3 figure
Cyber-physikalische Systeme:Herausforderung des 21. Jahrhunderts
Cyber-physical systems and the Internet of Things will be omnipresent in the near future. These systems will be tightly integrated in and interacting with our environment to support us in our daily tasks and in achieving our personal goals. However, to achieve this vision, we have to tackle various challenges
Contradictory reasoning network:an EEG and FMRI study
Contradiction is a cornerstone of human rationality, essential for everyday life and communication. We investigated electroencephalographic (EEG) and functional magnetic resonance imaging (fMRI) in separate recording sessions during contradictory judgments, using a logical structure based on categorical propositions of the Aristotelian Square of Opposition (ASoO). The use of ASoO propositions, while controlling for potential linguistic or semantic confounds, enabled us to observe the spatial temporal unfolding of this contradictory reasoning. The processing started with the inversion of the logical operators corresponding to right middle frontal gyrus (rMFG-BA11) activation, followed by identification of contradictory statement associated with in the right inferior frontal gyrus (rIFG-BA47) activation. Right medial frontal gyrus (rMeFG, BA10) and anterior cingulate cortex (ACC, BA32) contributed to the later stages of process. We observed a correlation between the delayed latency of rBA11 response and the reaction time delay during inductive vs. deductive reasoning. This supports the notion that rBA11 is crucial for manipulating the logical operators. Slower processing time and stronger brain responses for inductive logic suggested that examples are easier to process than general principles and are more likely to simplify communication. © 2014 Porcaro et al
A Project Portfolio Management Approach to Tacklingthe Exploration/Exploitation Trade-off
Organizational ambidexterity (OA) is an essen-tial capability for surviving in dynamic business environ-ments that advocates the simultaneous engagement inexploration and exploitation. Over the last decades,knowledge on OA has substantially matured, coveringinsights into antecedents, outcomes, and moderators of OA.However, there is little prescriptive knowledge that offersguidance on how to put OA into practice and to tackle thetrade-off between exploration and exploitation. To addressthis gap, the authors adopt the design science researchparadigm and propose an economic decision model asartifact. The decision model assists organizations inselecting and scheduling exploration and exploitation pro-jects to become ambidextrous in an economically reason-able manner. As for justificatory knowledge, the decisionmodel draws from prescriptive knowledge on projectportfolio management and value-based management, andfrom descriptive knowledge related to OA to structure thefield of action. To evaluate the decision model, its designspecification is discussed against theory-backed designobjectives and with industry experts. The paper alsoinstantiates the decision model as a software prototype andapplies the prototype to a case based on real-world data
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