Subgap Two-Photon States in Polycyclic Aromatic Hydrocarbons: Evidence for Strong Electron Correlations

Strong electron correlation effects in the photophysics of quasi-one-dimensional $\pi$-conjugated organic systems such as polyenes, polyacetylenes, polydiacetylenes, etc., have been extensively studied. Far less is known on correlation effects in two-dimensional $\pi$-conjugated systems. Here we present theoretical and experimental evidence for moderate repulsive electron-electron interactions in a number of finite polycyclic aromatic hydrocarbon molecules with $D_{6h}$ symmetry. We show that the excited state orderings in these molecules are reversed relative to that expected within one-electron and mean-field theories. Our results reflect similarities as well as differences in the role and magnitude of electron correlation effects in these two-dimensional molecules compared to those in polyenes.Comment: 11 pages, 5 figures, 2 table

N terminus is key to the dominant negative suppression of CaV2 calcium channels: implications for episodic ataxia type 2

Expression of the calcium channels CaV2.1 and CaV2.2 is markedly suppressed by co-expression with truncated constructs containing Domain I. This is the basis for the phenomenon of dominant negative suppression observed for many of the episodic ataxia type 2 mutations in CaV2.1 that predict truncated channels. The process of dominant negative suppression has been shown previously to stem from interaction between the full-length and truncated channels and to result in downstream consequences of the unfolded protein response and endoplasmic reticulum-associated protein degradation. We have now identified the specific domain that triggers this effect. For both CaV2.1 and CaV2.2, the minimum construct producing suppression was the cytoplasmic N terminus. Suppression was enhanced by tethering the N terminus to the membrane with a CAAX motif. The 11-amino acid motif (including Arg52 and Arg54) within the N terminus, which we have previously shown to be required for G protein modulation, is also essential for dominant negative suppression. Suppression is prevented by addition of an N-terminal tag (XFP) to the full-length and truncated constructs. We further show that suppression of CaV2.2 currents by the N terminus-CAAX construct is accompanied by a reduction in CaV2.2 protein level, and this is also prevented by mutation of Arg52 and Arg54 to Ala in the truncated construct. Taken together, our evidence indicates that both the extreme N terminus and the Arg52, Arg54 motif are involved in the processes underlying dominant negative suppression

Study of Wind Turbine based SEIG under Balanced/Unbalanced Loads and Excitation

This paper presents the performance of a stand-alone self-excited induction generator (SEIG) driven by fixed pitch wind turbine. The main objective of the paper is: (i) dynamic study of SEIG under balanced R-L/R-C loads (ii) dynamic study of SEIG under balanced and unbalanced excitation, (iii) Fixed pitch wind turbine model has been considered for driving induction generator. An approach based on dynamic equations of an isolated SEIG under balanced/unbalanced conditions of loads is employed to study the behaviour of the system. The SEIG model with balanced/un-balanced load and excitation has been simulated using MATLAB/SIMULINK.DOI:http://dx.doi.org/10.11591/ijece.v2i3.30

Photometric binary content in intermediate/old open clusters

The stellar evolutionary models by Bertelli et al. (1994) have been used to generate synthetic colour-magnitude diagrams (CMDs) of open clusters. A comparison of the synthetic integrated luminosity function (ILF) and synthetic colour distribution with the corresponding observed distributions is used to estimate the photometric binary content in three intermediate age open clusters, which is found to be about 30% in these clusters

Time resolved evolution of structural, electrical, and thermal properties of copper irradiated by an intense ultrashort laser pulse

The dynamical properties of copper metal are obtained on a picosecond time scale using 100 fs laser pulse at 1015 Wcm-2-an intensity regime relevant to femtosecond micromachining. The dissipation mechanisms and scaling laws spanning a wide temperature range are obtained from femtosecond pump-probe reflectivity. We observe obliteration of the crystalline structure in copper within 400 fs due to lattice disorder caused by the intense laser pulse. The electrical resistivity is obtained by studying the probe reflectivity evolution from 0 to 30 ps. The "resistivity saturation" effect in an unexplored regime intermediate to hot plasma and cold solid is studied in detail. The temperature evolution and thermal conductivity values are also obtained