Electronic and Band Structure Calculation of Wurtzite CdS Using GGA and GGA+U functionals

The wurtzite (wz) structure of CdS is analyzed using density functional theory within the generalized gradient approximation (GGA) and Hubbard correction (GGA+U). The total energy convergence evaluation is carried out concerning energy cut-off (ecutwfc) and k-point sampling. The geometry optimization of wz-CdS is calculated using the total energy and force minimization process, which is based on the Broyden Fletcher Goldfarb Shanno (BFGS) optimization algorithm. Bulk modulus and lattice parameters are estimated to ensure accuracy of the calculations. The electronic band structure, density of states (DOS), and projected density of states (PDOS) of wz-CdS are analyzed. The band structure calculation shows CdS as direct band gap semiconductor. The electronic correlation in CdS is altered by varying U-parameters of valence orbitals of Cd and S. The alteration of electronic correlation results in convergence of the band gap to the experimental value 2.4 eV. The alteration of U-parameter affects substantially the density of states near the band edges

Control of Alpha Rhythm (8-13 Hz) Using Neurofeedback

Alpha is a prominent rhythm occurring between 8 and 13 Hz in brain signals that is often linked to a relaxed mental state. Some studies have shown that individuals can learn to control their own alpha rhythm if provided with a contingent feedback. However, investigations till date in alpha neurofeedback have provided contrasting views regarding the enhancement of alpha power. In this review, we discuss various aspects of this controversy and highlight some issues with past approaches of neurofeedback driven alpha enhancement. In particular, we discuss possible modifications in future investigations which would address some of the concerns

Synergetic Accrual of Lamellar Nanohybrids for Band-Selective Photodetection

Nanostructured blends of inorganic and organic materials could unwind unique properties and boost performance over each individual constituent. We demonstrate here a hybrid photodetector containing ZnO and functionalized oligo­(<i>p</i>-phenylenevinylene), which was deposited electrochemically onto an electrode. XRD results reveal that the conjugates formed are lamellar in nature. As photodetectors, room-temperature responsivity as high as 0.2 AW^–1 at 330 nm with a bias of −20 V, the maximum external quantum efficiency of 75% at −20 V bias and 100 times increase in the light current upon UV illumination of 325 nm, have been observed. These values perpetrate a future of a high-performance hybrid photodetector which could be cost-effective and environmentally benign

Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo

International audienceIntermediate-mass black holes (IMBHs) span the approximate mass range 100−105 M⊙, between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150 M⊙ providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200 M⊙ and effective aligned spin 0.8 at 0.056 Gpc−3 yr−1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc−3 yr−1.Key words: gravitational waves / stars: black holes / black hole physicsCorresponding author: W. Del Pozzo, e-mail: [email protected]† Deceased, August 2020