23 research outputs found
Controlled delocalization of electronic states in a multi-strand quasiperiodic lattice
Finite strips, composed of a periodic stacking of infinite quasiperiodic
Fibonacci chains, have been investigated in terms of their electronic
properties. The system is described by a tight binding Hamiltonian. The
eigenvalue spectrum of such a multi-strand quasiperiodic network is found to be
sensitive on the mutual values of the intra-strand and inter-strand tunnel
hoppings, whose distribution displays a unique three-subband self-similar
pattern in a parameter subspace. In addition, it is observed that special
numerical correlations between the nearest and the next-nearest neighbor
hopping integrals can render a substantial part of the energy spectrum
absolutely continuous. Extended, Bloch like functions populate the above
continuous zones, signalling a complete delocalization of single particle
states even in such a non-translationally invariant system, and more
importantly, a phenomenon that can be engineered by tuning the relative
strengths of the hopping parameters. A commutation relation between the
potential and the hopping matrices enables us to work out the precise
correlation which helps to engineer the extended eigenfunctions and determine
the band positions at will.Comment: 8 pages, 6 figure
Flux driven and geometry controlled spin filtering for arbitrary spins in aperiodic quantum networks
We demonstrate that an aperiodic array of certain quantum networks comprising magnetic and non-magnetic atoms can act as perfect spin filters for particles with arbitrary spin state. This can be achieved by introducing minimal quasi-one dimensionality in the basic structural units building up the array, along with an appropriate tuning of the potential of the non-magnetic atoms, the tunnel hopping integral between the non-magnetic atoms and the backbone, and, in some cases, by tuning an external magnetic field. This latter result opens up the interesting possibility of designing a flux controlled spin demultiplexer using quantum networks. The proposed networks have close resemblance with a family of recently developed photonic lattices, and the scheme for spin filtering can thus be linked, in principle, to a possibility of suppressing any one of the two states of polarization of a single photon, almost at will. We use transfer matrices and a real space renormalization group scheme to unravel the conditions under which any aperiodic arrangement of such topologically different structures will filter out any given spin projection. Our results are analytically exact, and corroborated by extensive numerical calculations of the spin polarized transmission and the density of states of such systems
Isolation and identification of carotenoid-producing yeast and evaluation of antimalarial activity of the extracted carotenoid(s) against P. falciparum
Plasmodial resistance to a variety of plant-based antimalarial drugs has led toward the discovery of more effective antimalarial compounds having chemical or biological origin. Since natural compounds are considered as safer drugs, in this study, yeast strains were identified and compared for the production of carotenoids that are well-known antioxidants and this metabolite was tested for its antiparasitic activity. Plasmodium falciparum 3D7 strain was selected as the target parasite for evaluation of antimalarial activity of yeast carotenoids using in vitro studies. Data were analyzed by FACS (fluorescence-activated cell sorter) and counted via gold standard Giemsa-stained smears. The extracted yeast carotenoids showed a profound inhibitory effect at a concentration of 10–3 µg/µl and 10−4 µg/µl when compared to β- carotene as control. SYBR Green1 fluorescent dye was used to confirm the decrease in parasitaemia at given range of concentration. Egress assay results suggested that treated parasite remained stalled at schizont stage with constricted morphology and were darkly stained. Non-toxicity of carotenoids on erythrocytes and on human liver hepatocellular carcinoma cells (HepG2 cells) was shown at a given concentration. This report provides strong evidence for antimalarial effects of extracted yeast carotenoids, which can be produced via a sustainable and cost-effective strategy and may be scaled up for industrial application
ONVIF Device Discovery Protocol
Abstract: When it comes to standardize communication between network devices built by different companies, it is not easy to ensure interoperability between network products. Open Network Video Interface Forum (ONVIF) is an open industry forum which is committed to this task. In implementing the Discovery module, ONVIF devices support WS-Discovery, which is a mechanism that supports probing a network to find ONVIF capable devices. It defines a multicast discovery protocol to locate services. By default, probes are sent to a multicast group, and target services that match return a response directly to the requester. To minimize the need for polling, target services that wish to be discovered send an announcement when they join and leave the network. A successful discovery provides the device service address. Once a client has the device service address it can receive detailed device information through the device service