DC-assisted microwave quenching of YBa2Cu3O7-{\delta} coplanar waveguide to a highly dissipative state

The paper reports on finding the effect of a strong change in the microwave losses in an HTS-based coplanar waveguide (CPW) at certain values of the input power Pin and direct current Idc. CPW on the basis of 150 nm thick YBa2Cu3O7-{\delta} epitaxial film on a single crystal MgO substrate was studied experimentally. A sharp and reversible transition of the CPW into a strongly dissipative state at the certain meanings of Pin and Idc depending on temperature was observed. Apparently the effect can be explained by self-heating of HTS structure caused by magnetic flux flow under the joint influence of MW and DC.Comment: 9 pages, 5 figures, 17 reference

Arc/Arg3.1 mRNA Global Expression Patterns Elicited by Memory Recall in Cerebral Cortex Differ for Remote Versus Recent Spatial Memories

The neocortex plays a critical role in the gradual formation and storage of remote declarative memories. Because the circuitry mechanisms of systems-level consolidation are not well understood, the precise cortical sites for memory storage and the nature of enduring memory correlates (mnemonic plasticity) are largely unknown. Detailed maps of neuronal activity underlying recent and remote memory recall highlight brain regions that participate in systems consolidation and constitute putative storage sites, and thus may facilitate detection of mnemonic plasticity. To localize cortical regions involved in the recall of a spatial memory task, we trained rats in a water-maze and then mapped mRNA expression patterns of a neuronal activity marker Arc/Arg3.1 (Arc) upon recall of recent (24 h after training) or remote (1 month after training) memories and compared them with swimming and naive controls. Arc gene expression was significantly more robust 24 h after training compared to 1 month after training. Arc expression diminished in the parietal, cingulate and visual areas, but select segments in the prefrontal, retrosplenial, somatosensory and motor cortical showed similar robust increases in the Arc expression. When Arc expression was compared across select segments of sensory, motor and associative regions within recent and remote memory groups, the overall magnitude and cortical laminar patterns of task-specific Arc expression were similar (stereotypical). Arc mRNA fractions expressed in the upper cortical layers (2/3, 4) increased after both recent and remote recall, while layer 6 fractions decreased only after the recent recall. The data suggest that robust recall of remote memory requires an overall smaller increase in neuronal activity within fewer cortical segments. This activity trend highlights the difficulty in detecting the storage sites and plasticity underlying remote memory. Application of the Arc maps may ameliorate this difficulty

Analysis of preliminary data on e+e−→ϕ→γf0(980)→γπ0π0e^+e^-\to\phi\to\gamma f_0(980)\to\gamma\pi^0\pi^0 reaction

We perform the analysis of the preliminary data on $e^+e^-\to\phi\to\gamma f_0(980)\to\gamma\pi^0\pi^0$ reaction simultaneously with the data on $\pi\pi$ scattering and reactions $J/\psi\to\phi\pi^+\pi^-$ and $K^-p\to\pi^+\pi^-(\Lambda,\Sigma)$. It is found that the $f_0(980)$ meson mass $m_{f_0}=950$ MeV and $B(\phi\to\gamma f_0\to\gamma\pi^0\pi^0)\simeq1\cdot10^{-4}$.Comment: 8 pages, revtex, 3 ps files of figures, minor change

Anomalous microwave conductivity coherence peak in c-axis MgB2 thin film

The temperature dependence of the real part of the microwave complex conductivity at 17.9 GHz obtained from surface impedance measurements of two c-axis oriented MgB2 thin films reveals a pronounced maximum at a temperature around 0.6 times the critical temperature. Calculations in the frame of a two-band model based on Bardeen-Cooper-Schrieffer (BCS) theory suggest that this maximum corresponds to an anomalous coherence peak resembling the two-gap nature of MgB2. Our model assumes there is no interband impurity scattering and a weak interband pairing interaction, as suggested by bandstructure calculations. In addition, the observation of a coherence peak indicates that the pi-band is in the dirty limit and dominates the total conductivity of our filmsComment: 10 pages, 4 figures, to be published in Phys. Rev. Let

The interference in the reaction e+e−→γπ+π−e^+e^-\to\gamma\pi^+\pi^- and the search for the decay ϕ→γf0→γπ+π−\phi\to\gamma f_0\to\gamma\pi^+\pi^-

We describe the interference between amplitudes $e^+e^- \to \rho \to \gamma\pi^+\pi^-$ and $e^+e^- \to \phi \to \gamma f_0 \to \gamma\pi^+\pi^-$, where $f_0$ meson is considered in the frameworks of the four-quark model and the model of the scalar $K\bar K$ molecule. The general expressions for the differential cross section with the radiative corrections and two angle cuts are given. The interference patterns are obtained in the spectrum of the differential cross section by the energy of the photon and in the full cross section by the energy of the beams.Comment: 21 pages, revtex, 8 ps files of figure