7,033 research outputs found

    Realistic Visionary: A Portrait of George Washington

    Get PDF

    IT governance enablers in relation to IoT implementation: a systematic literature review

    Get PDF
    Purpose The purpose of this paper is to obtain a list of recommendations addressed by the information technology (IT) governance enablers in relation to IoT implementation. The reason behind this it is the lack of information about these instances which could the organizations to be more effective when implementing IoT. Design/methodology/approach The objectives will be obtained using the methodology - systematic literature review. Findings During the research, a list of recommendations was created on each IT governance enabler in relation to IoT implementation, showing the flaws that exist at the literature level for each enabler. Originality/value The state of art of this research is a creation of a list of recommendations according to IT governance enablers to be applied on an IoT implementation.info:eu-repo/semantics/acceptedVersio

    Superlattice Magnetophonon Resonances in Strongly Coupled InAs/GaSb Superlattices

    Full text link
    We report an experimental study of miniband magnetoconduction in semiconducting InAs/GaSb superlattices. For samples with miniband widths below the longitudinal optical phonon energy we identify a new superlattice magnetophonon resonance (SLMPR) caused by resonant scattering of electrons across the mini-Brillouin zone. This new resonant feature arises directly from the drift velocity characteristics of the superlattice dispersion and total magnetic quantisation of the superlattice Landau level minibands.Comment: 9 pages, 8 figures, submitted to Phys. Rev.

    A perturbative approach to the polaron shift of excitons in transition metal dichalcogeniedes

    Get PDF
    In this Letter, we study the effect of phonons on the position of the 1s excitonic resonance of the fundamental absorption transition line in two-dimensional transition metal dichalcogenides. We apply our theory to WS2, a two-dimensional material where the shift in the absorption peak position has been measured as a function of temperature. The theory is composed of two ingredients only: (i) the effect of longitudinal optical phonons on the absorption peak position, which we describe with second-order perturbation theory, and (ii) the effect of phonons on the value of the single-particle energy gap, which we describe with the Huang Rhys model. Our results show excellent agreement with the experimentally measured shift of the absorption peak with the temperature.- N.M.R.P. acknowledges support by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020. J.C.G.H. acknowledges the Center of Physics for a grant funded by the UIDB/04650/2020 strategic project. N.M.R.P. acknowledges support from the European Commission through the project Graphene-Driven Revolutions in ICT and Beyond (Ref. No. 881603, CORE 3), COMPETE 2020, PORTUGAL 2020, FEDER, and the FCT through Projects No. POCI-01-0145FEDER-028114 and No. PTDC/NAN-OPT/29265/2017

    Exciton energies and wave functions in hexagonal Boron Nitride using Miller and Good’s uniform approach

    Get PDF
    In this paper we revisit the work of Miller and Good, which describes an uniform JWKB type of approximation to the solution of quantum problems. This paper, very well known in atomic physics in the 1970's 1980's of the last century, did not attract the same attention from the condensed matter community. Contrary to the usual JWKB approach, Miller and Good's method yields wave functions that do not diverge at the classical turning points. We apply the method in the context of two-dimensional excitons, an important condensed matter system. In particular, we apply our results to excitons in hexagonal boron nitride, solving the corresponding Wannier equation. We compare the semiclassical results with others from the literature and find good agreement.The authors acknowledge Mike Belsley for carefully reading the manuscript and for comments that allowed to improve the overall presentation. N.M.R.P. acknowledges support from the European Commission through the project "Graphene-Driven Revolutions in ICT and Beyond" (Ref. no. 881603 - core 3), and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2019. In addition, N.M.R.P. acknowledges COMPETE2020, PORTUGAL2020, FEDER and the Portuguese Foundation for Science and Technology (FCT) through projects POCI-01-0145-FEDER-028114, POCI-01-0145-FEDER- 029265, PTDC/NAN-OPT/29265/2017, and POCI-01-0145-FEDER-02888

    Excitons in phosphorene: A semi-analytical perturbative approach

    Get PDF
    In this paper we develop a semi-analytical perturbation-theory approach to the calculation of the energy levels (binding energies) and wave functions of excitons in phosphorene. Our method gives the exciton wave function in both real and reciprocal spaces with the same ease. This latter aspect is important for the calculation of the nonlinear optical properties of phosphorene. We find that our results are in agreement with calculations based both on the Bethe-Salpeter equation and on Monte Carlo simulations, which are computationally much more demanding. Our approach thus introduces a simple, viable, and accurate method to address the problem of excitons in anisotropic two-dimensional materials.N.M.R.P. acknowledges support from the European Commission through the project "Graphene-Driven Revolutions in ICT and Beyond" (Reference No. 785219) and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2019. In addition, N.M.R.P. acknowledges COMPETE2020, PORTUGAL2020, FEDER, and the FCT through Projects No. PTDC/FIS-NAN/3668/2013, No. POCI-01-0145-FEDER-028114, No. POCI-01-0145FEDER-029265, No. PTDC/NAN-OPT/29265/2017, and No. POCI-01-0145-FEDER-02888. The authors acknowledge P. A. Goncalves and R. Ribeiro for a critical reading of the manuscript

    Super-Beacons: open-source probes with spontaneous tuneable blinking compatible with live-cell super-resolution microscopy

    Get PDF
    Localization based super-resolution microscopy relies on the detection of individual molecules cycling between fluorescent and non-fluorescent states. These transitions are commonly regulated by high-intensity illumination, imposing constrains to imaging hardware and producing sample photodamage. Here, we propose single-molecule self-quenching as a mechanism to generate spontaneous photoswitching independent of illumination. To demonstrate this principle, we developed a new class of DNA-based open-source Super-Resolution probes named Super-Beacons, with photoswitching kinetics that can be tuned structurally, thermally and chemically. The potential of these probes for live-cell friendly Super-Resolution Microscopy without high-illumination or toxic imaging buffers is revealed by imaging Interferon Inducible Transmembrane proteins (IFITMs) at sub-100nm resolutions

    Diluted Random Fields in Mixed Cyanide Crystals

    Full text link
    A percolation argument and a dilute compressible random field Ising model are used to present a simple model for mixed cyanide crystals. The model reproduces quantitatively several features of the phase diagrams altough some crude approximations are made. In particular critical thresholds x_c at which ferroelastic first order transitions disappear, are calculated. Moreover, transitions are found to remain first order down to x_c for all mixtures except for bromine, for which the transition becomes continuous. All the results are in full agreement with experimental data.Comment: 8 pages, late

    Galaxy formation in the Planck cosmology - II. Star-formation histories and post-processing magnitude reconstruction

    Get PDF
    We adapt the L-Galaxies semi-analytic model to follow the star-formation histories (SFH) of galaxies -- by which we mean a record of the formation time and metallicities of the stars that are present in each galaxy at a given time. We use these to construct stellar spectra in post-processing, which offers large efficiency savings and allows user-defined spectral bands and dust models to be applied to data stored in the Millennium data repository. We contrast model SFHs from the Millennium Simulation with observed ones from the VESPA algorithm as applied to the SDSS-7 catalogue. The overall agreement is good, with both simulated and SDSS galaxies showing a steeper SFH with increased stellar mass. The SFHs of blue and red galaxies, however, show poor agreement between data and simulations, which may indicate that the termination of star formation is too abrupt in the models. The mean star-formation rate (SFR) of model galaxies is well-defined and is accurately modelled by a double power law at all redshifts: SFR proportional to 1/(x−1.39+x1.33)1/(x^{-1.39}+x^{1.33}), where x=(ta−t)/3.0 x=(t_a-t)/3.0\,Gyr, tt is the age of the stars and tat_a is the loopback time to the onset of galaxy formation; above a redshift of unity, this is well approximated by a gamma function: SFR proportional to x1.5e−xx^{1.5}e^{-x}, where x=(ta−t)/2.0 x=(t_a-t)/2.0\,Gyr. Individual galaxies, however, show a wide dispersion about this mean. When split by mass, the SFR peaks earlier for high-mass galaxies than for lower-mass ones, and we interpret this downsizing as a mass-dependence in the evolution of the quenched fraction: the SFHs of star-forming galaxies show only a weak mass dependence.Comment: Accepted version of the paper, to appear in MNRAS. Compared to the original version, contains more detail on the post-processing of magnitudes, including a table of rms magnitude errors. SFHs available on Millennium database http://gavo.mpa-garching.mpg.de/MyMillennium
    • …
    corecore