5,156 research outputs found
Single-photon emitting diode in silicon carbide
Electrically driven single-photon emitting devices have immediate
applications in quantum cryptography, quantum computation and single-photon
metrology. Mature device fabrication protocols and the recent observations of
single defect systems with quantum functionalities make silicon carbide (SiC)
an ideal material to build such devices. Here, we demonstrate the fabrication
of bright single photon emitting diodes. The electrically driven emitters
display fully polarized output, superior photon statistics (with a count rate
of 300 kHz), and stability in both continuous and pulsed modes, all at room
temperature. The atomic origin of the single photon source is proposed. These
results provide a foundation for the large scale integration of single photon
sources into a broad range of applications, such as quantum cryptography or
linear optics quantum computing.Comment: Main: 10 pages, 6 figures. Supplementary Information: 6 pages, 6
figure
Modeling the flaring activity of the high z, hard X-ray selected blazar IGR J22517+2217
We present new Suzaku and Fermi data, and re-analyzed archival hard X-ray
data from INTEGRAL and Swift-BAT survey, to investigate the physical properties
of the luminous, high-redshift, hard X-ray selected blazar IGR J22517+2217,
through the modelization of its broad band spectral energy distribution (SED)
in two different activity states. Through the analysis of the new Suzaku data
and the flux selected data from archival hard X-ray observations, we build the
source SED in two different states, one for the newly discovered flare occurred
in 2005 and one for the following quiescent period. Both SEDs are strongly
dominated by the high energy hump peaked at 10^20 -10^22 Hz, that is at least
two orders of magnitude higher than the low energy (synchrotron) one at 10^11
-10^14 Hz, and varies by a factor of 10 between the two states. In both states
the high energy hump is modeled as inverse Compton emission between
relativistic electrons and seed photons produced externally to the jet, while
the synchrotron self-Compton component is found to be negligible. In our model
the observed variability can be accounted for by a variation of the total
number of emitting electrons, and by a dissipation region radius changing from
within to outside the broad line region as the luminosity increases. In its
flaring activity, IGR J22517+2217 shows one of the most powerful jet among the
population of extreme, hard X-ray selected, high redshift blazar observed so
far.Comment: Accepted for publication in MNRA
Innovation in Plant-Greenhouse Interactions and Crop Management
(Semi)-closed greenhouses allow for better control of climate conditions compared to conventional greenhouses. To make the high investments for such greenhouses economically feasible, substantial yield increases are necessary. In north-Europe supplementary assimilation light in greenhouse horticulture is increasingly used to improve yield and product quality to meet market demands for year-round production and to obtain a more regular labor demand throughout the year. Using inter-lighting instead of lights only on top of the crop, and Light Emitting Diodes (LEDs), could increase substantially light and energy efficiency. As soon as LEDs will reach high enough efficiency and feasible price, they are expected to replace high pressure sodium lamps in greenhouse horticulture. Another important issue is the choice of the greenhouse cover which should be optimized from the crop point of view. A cover with high transmission of light, but low transmission of NIR, results in a better climate during the warm season (reduced temperatures, less crop transpiration, higher CO2-concentration possible because of reduced ventilation demand). Increasing the diffusive power of the cover material could result in a better distribution of the radiation over the crop canopy, therefore leading to substantial increase in absorbed radiation (up to 20% for highly diffusive covers) and improving radiation use efficiency and yield. Under these new conditions (high CO2 and high light levels) other genotypes than the present cultivars may be superior. However, the possible effect of breeding especially for these new conditions is still little investigated. Under improved crop management, maintaining leaf area index high enough and controlling source-sink balance is discussed. In conclusion, there are a lot of possibilities to further improve yield and quality of greenhouse produce, and meanwhile reduce the input of fossil fuel energy
Recent and Future Observations in the X-ray and Gamma-ray Bands: Chandra, Suzaku, GLAST, and NuSTAR
This paper presents a brief overview of the accomplishments of the Chandra
satellite that are shedding light on the origin of high energy particles in
astrophysical sources, with the emphasis on clusters of galaxies. It also
discusses the prospects for the new data to be collected with instruments
recently launched - such as Suzaku - or those to be deployed in the near
future, and this includes GLAST and NuSTAR.Comment: To appear in "Astrophysical Sources of High Energy Particles and
Radiation", eds. T. Bulik, B. Rudak, and G. Madejski, AIP Conference
Proceedings, vol 801 (2005), proc. conf. in Torun, Poland, 20-24 June 200
Suzaku Observation of the Brightest Broad-Line Radio Galaxy 4C 50.55 (IGR J 21247+5058)
We report the results from a deep Suzaku observation of 4C 50.55 (IGR J
21247+5058), the brightest broad-line radio galaxy in the hard X-ray (> 10 keV)
sky. The simultaneous broad band spectra over 1-60 keV can be represented by a
cut-off power law with two layers of absorption and a significant reflection
component from cold matter with a solid angle of \Omega/2\pi \approx 0.2. A
rapid flux rise by ~ 20% over 2 \times 10^4 sec is detected in the 2-10 keV
band. The spectral energy distribution suggests that there is little
contribution to the total X-ray emission from jets. Applying a thermal
Comptonization model, we find that corona is optically thick (\tau_e \approx 3)
and has a relatively low temperature (kT_e \approx 30 keV). The narrow iron-K
emission line is consistent with a picture where the standard disk is truncated
and/or its inner part is covered by optically thick Comptonizing corona
smearing out relativistic broad line features. The inferred disk structure may
be a common feature of accretion flows onto black holes that produce powerful
jets.Comment: 8 pages, 7 figure
Accurate efficiency measurements of organic light-emitting diodes via angle-resolved spectroscopy
Funding: EPSRC NSF-CBET lead agency agreement (EP/R010595/1, 1706207), the Leverhulme Trust (RPG-2017-231), the Volkswagen Foundation (No. 93404), and the Alexander von Humboldt Stiftung (Humboldt-Professorship to M.C.G.). C.K. acknowledges support from the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1A6A3A03012331). Diese Arbeit wurde mitfinanziert durch Steuermittel auf der Grundlage des vom Sächsischen Landtag beschlossenen Haushaltes.The accurate characterization of thin-film LEDs – including organic light emitting diodes (OLEDs), perovskites and quantum dot LEDs – is crucial to our understanding of the factors that influence their efficiency and thus to the fabrication of LEDs with improved performance and stability. In addition, detailed information about the angular characteristics of LED emission is useful to assess the suitability of individual architectures, e.g. for display applications. Here, the implementation of a goniometer-based measurement system and corresponding protocol are described that allow to accurately determine the current-voltage-luminance characteristics, external quantum efficiency and luminous efficacy of OLEDs and other emerging thin-film LEDs. The system allows recording of angle-resolved electroluminescence spectra and accurate efficiency measurements for devices with both Lambertian and non-Lambertian emission characteristics. A detailed description of the setup and a protocol for assembling and aligning the required hardware are provided. Drawings of all custom parts and the open-source Python software required to perform the measurement and to analyze the data are included.Publisher PDFPeer reviewe
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