Searching for star-forming dwarf galaxies in the Antlia cluster

The formation and evolution of dwarf galaxies in clusters need to be understood, and this requires large aperture telescopes. In this sense, we selected the Antlia cluster to continue our previous work in the Virgo, Fornax, and Hydra clusters and in the Local Volume (LV). Because of the scarce available literature data, we selected a small sample of five blue compact dwarf (BCD) candidates in Antlia for observation. Using the Gemini South and GMOS camera, we acquired the Halpha imaging needed to detect star-forming regions in this sample. With the long-slit spectroscopic data of the brightest seven knots detected in three BCD candidates, we derived their basic chemical properties. Using archival VISTA VHS survey images, we derived K_S magnitudes and surface brightness profile fits for the whole sample to assess basic physical properties. FS90-98, FS90-106, and FS90-147 are confirmed as BCDs and cluster members, based on their morphology, K_S surface photometry, oxygen abundance, and velocity redshift. FS90-155 and FS90-319 did not show any H{\alpha} emission, and they could not be confirmed as dwarf cluster star-forming galaxies. Based on our data, we studied some fundamental relations to compare star forming dwarfs (BCDs and dIs) in the LV and in the Virgo, Fornax, Hydra, and Antlia clusters. Star-forming dwarfs in nearby clusters appear to follow same fundamental relations in the near infrared with similar objects in the LV, specifically the size-luminosity and the metallicity-luminosity, while other more fundamental relations could not be checked in Antlia due to lack of data.Comment: Accepted for publication in A&A (early 2014

Simplified Metrics Calculation for Soft Bit Detection in DVB-T2

The constellation rotation and cyclic quadrature component delay (RQD) technique has been adopted in the second generation terrestrial digital video broadcasting (DVB-T2) standard. It improves the system performance under severe propagation conditions, but introduces serious complexity problems in the hardware implementation of the detection process. In this paper, we present a simplified scheme that greatly reduces the complexity of the demapper by simplifying the soft bit metrics computation having a negligible overall system performance loss

Response time of a normal-superconductor hybrid system under the step-like pulse bias

The response of a quantum dot coupled with one normal lead and a superconductor lead driven by a step-like pulse bias $V_L$ is studied using the non-equilibrium Green function method. In the linear pulse bias regime, the responses of the upwards and downwards bias are symmetric. In this regime the turn-on time and turn-off time are much slower than that of the normal system due to the Andreev reflection. On the other hand, for the large pulse bias $V_L$, the instantaneous current exhibits oscillatory behaviors with the frequency $\hbar\Omega =qV_L$. The turn on/off times are in (or shorter than) the scale of $1/V_L$, so they are faster for the larger bias $V_L$. In addition, the responses for the upwards and downwards bias are asymmetric at large $V_L$. The turn-on time is larger than the turn-off time but the relaxation time \cite{note1} depends only on the coupling strength $\Gamma$ and it is much smaller than the turn-on/off times for the large bias $V_L$.Comment: 8 pages, 4 figures, accepted for publication in Phys. Rev.