Difference of optical conductivity between one- and two-dimensional doped nickelates

We study the optical conductivity in doped nickelates, and find the dramatic difference of the spectrum in the gap ($\omega$\alt4 eV) between one- (1D) and two-dimensional (2D) nickelates. The difference is shown to be caused by the dependence of hopping integral on dimensionality. The theoretical results explain consistently the experimental data in 1D and 2D nickelates, Y$_{2-x}$Ca$_x$BaNiO$_5$ and La$_{2-x}$Sr$_x$NiO$_4$, respectively. The relation between the spectrum in the X-ray aborption experiments and the optical conductivity in La$_{2-x}$Sr$_x$NiO$_4$ is discussed.Comment: RevTeX, 4 pages, 4 figure

Constraining supersymmetry from the satellite experiments

In this paper we study the detectability of $\gamma$-rays from dark matter annihilation in the subhalos of the Milky Way by the satellite-based experiments, EGRET and GLAST. We work in the frame of supersymmetric extension of the standard model and assume the lightest neutralino being the dark matter particles. Based on the N-body simulation of the evolution of dark matter subhalos we first calculate the average intensity distribution of this new class of $\gamma$-ray sources by neutralino annihilation. It is possible to detect these $\gamma$-ray sources by EGRET and GLAST. Conversely, if these sources are not detected the nature of the dark matter particls will be constrained by these experiments, which, however, depending on the uncertainties of the subhalo profile.Comment: 19 pages, 5 gigures; references added, more discussions adde

Anti Microbial Resistance Profile of E. coli isolates From Tropical Free Range Chickens

Normal intestinal flora of humans and animals constitute enormous reservoir of resistance genes for potentially pathogenic bacteria and may serve as major indictors of selection pressure exerted by anti-microbial use in a given population. A study was conducted in September 2003 at 3 purposively selected peri-urban sites spread across 3 senatorial zones of Imo state, Nigeria to determines the anti-microbial resistance profile of commensal E. coli isolated from free range chickens. The isolates were screened for anti-microbial resistance profile against 10 antibiotics using the disc diffusion method. E. coli strains from local fowls, recorded 100 and 78.9% resistances against ampicillin and cotrimoxazole respectively, while resistance rates against ciprofloxacin, gentamycin and norfloxacin were 0.0, 5.3 and 5.3% respectively. Isolates from free-range cockerels recorded 100% resistance against norfloxacin, cotrimoxazole and ampicillin and 83.3% against nitrofurantoin. Similarly, isolates from old layers, recorded 100% resistance against nitrofurantoin, cotrimoxazole, tetracycline, chloramphenicol and ampicillin and 80% against nalidixic acid. Similar resistance trends were observed in E. coli isolates from free-range turkeys and broiler roosters against the inexpensive broad-spectrum first line antibiotics (ampicillin, nalidixic acid, cotrimoxazole, nitrofurantoin and chloramphenicol), although values varied slightly across poultry types. Resistances against gentamycin were consistently low in isolates from the different types of poultry. Twenty-nine resistance patterns were observed in the E. coli isolates with predominant patterns being distributed widely across poultry types indicating a striking diversity of resistance patterns in the areas

Split Two-Higgs-Doublet Model and Neutrino Condensation

We split the two-Higgs-doublet model by assuming very different vevs for the two doublets: the vev is at weak scale (174 GeV) for the doublet \Phi_1 and at neutrino-mass scale (10^{-2} \sim 10^{-3} eV) for the doublet \Phi_2. \Phi_1 is responsible for giving masses to all fermions except neutrinos; while \Phi_2 is responsible for giving neutrino masses through its tiny vev without introducing see-saw mechanism. Among the predicted five physical scalars H, h, A^0 and H^{\pm}, the CP-even scalar h is as light as 10^{-2} \sim 10^{-3}eV while others are at weak scale. We identify h as the cosmic dark energy field and the other CP-even scalar H as the Standard Model Higgs boson; while the CP-odd A^0 and the charged H^{\pm} are the exotic scalars to be discovered at future colliders. Also we demonstrate a possible dynamical origin for the doublet \Phi_2 from neutrino condensation caused by some unknown dynamics.Comment: version in Europhys. Lett. (discussions added

Field-Trial of Machine Learning-Assisted Quantum Key Distribution (QKD) Networking with SDN

We demonstrated, for the first time, a machine-learning method to assist the coexistence between quantum and classical communication channels. Software-defined networking was used to successfully enable the key generation and transmission over a city and campus network

Memristive operation mode of a site-controlled quantum dot floating gate transistor

The authors gratefully acknowledge financial support from the European Union (FPVII (2007-2013) under Grant Agreement No. 318287 Landauer) as well as the state of Bavaria.We have realized a floating gate transistor based on a GaAs/AlGaAs heterostructure with site-controlled InAs quantum dots. By short-circuiting the source contact with the lateral gates and performing closed voltage sweep cycles, we observe a memristive operation mode with pinched hysteresis loops and two clearly distinguishable conductive states. The conductance depends on the quantum dot charge which can be altered in a controllable manner by the voltage value and time interval spent in the charging region. The quantum dot memristor has the potential to realize artificial synapses in a state-of-the-art opto-electronic semiconductor platform by charge localization and Coulomb coupling.Publisher PDFPeer reviewe