50 research outputs found
Structural stability, magnetic and electronic properties of Co2MnSi(001)/MgO heterostructures: A density functional theory study
A computational study of the epitaxial Co2MnSi(001)/MgO(001) interface
relevant to tunneling magnetoresistive (TMR) devices is presented. Employing ab
initio atomistic thermodynamics, we show that the Co- or MnSi-planes of
bulk-terminated Co2MnSi form stable interfaces, while pure Si or pure Mn
termination requires non-equilibrium conditions. Except for the pure Mn
interface, the half-metallic property of bulk Co2MnSi is disrupted by interface
bands. Even so, at homogeneous Mn or Co interfaces these bands contribute
little to the minority-spin conductance through an MgO barrier, and hence such
terminations could perform strongly in TMR devices.Comment: 4 pages, 3 fig
Phase diagram of the excitonic insulator
Motivated by recent experiments, which give strong evidence for an excitonic
insulating phase in , we developed a scheme to
quantitatively construct, for generic two-band models, the phase diagram of an
excitonic insulator. As a first application of our approach, we calculated the
phase diagram for an effective mass two-band model with long-range Coulomb
interaction. The shielded potential approximation is used to derive a
generalized gap equation controlling for positive (negative) energy gaps the
transition from a semi-conducting (semi-metallic) phase to an insulating phase.
Numerical results,obtained within the quasi-static approximation, show a
steeple-like phase diagram in contrast to long-standing expectations.Comment: 2 pages, 1 figure, SCES'05, accepted for publication in Physica
Influence of the substrate lattice structure on the formation of Quantum Well States in thin In and Pb films on silicon
The substrate lattice structure may have a considerable influence on the
formation of quantum well states in a metal overlayer material. Here we study
three model systems using angle resolved photoemission and low energy electron
diffraction: indium films on Si(111) and indium and lead on Si(100). Data are
compared with theoretical predictions based on density functional theory. We
find that the interaction between the substrate and the overlayer strongly
influences the formation of quantum well states; indium layers only exhibit
well defined quantum well states when the layer relaxes from an initial
face-centered cubic to the bulk body-centered tetragonal lattice structure. For
Pb layers on Si(100) a change in growth orientation inhibits the formations of
quantum well states in films thicker than 2 ML.Comment: 16 pages, 7 figure
Intercomparison of erythemal broadband radiometers calibrated by seven UV calibration facilities in Europe and the USA
International audienceA bi-lateral intercomparison of erythemal broadband radiometers was performed between seven UV calibration facilities. The owners calibrations were compared relative to the characterisation and calibration performed at PMOD/WRC in Davos, Switzerland. The calibration consisted in the determination of the spectral and angular response of the radiometer, followed by an absolute calibration performed outdoors relative to a spectroradiometer which provided the absolute reference. The characterization of the detectors in the respective laboratories are in good agreement: The determination of the angular responses have deviations below ±4% and the spectral responses agree within ±20%. A "blind" intercomparison of the erythemally weighted irradiances derived by the respective institutes and PMOD/WRC showed consistent measurements to within ±2% for the majority of institutes. One institute showed slightly larger deviation of 10%. The differences found between the different instrument calibrations are all within the combined uncertainty of the calibration
Validation of TROPOMI Surface UV Radiation Product
The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor (S5P) satellite was launched
on 13 October 2017 to provide the atmospheric composition for atmosphere and climate research. The S5P is a sun-synchronous polar-orbiting satellite providing global daily coverage. The TROPOMI swath is 2600 km wide, and the ground resolution for most data products is 7.2x3.5 km2 (5.6x3.5 km2 since 6 August 2019) at nadir. The Finnish Meteorological Institute (FMI) is responsible for the development and processing of the TROPOMI Surface Ultraviolet (UV) Radiation Product which includes 36 UV parameters in total. Ground-based data from 25 sites located in arctic, subarctic, temperate, equatorial and antarctic areas were used for validation of TROPOMI overpass irradiance at 305, 310, 324 and 380 nm, overpass erythemally weighted dose rate / UV index and erythemally weighted daily dose for the period from 1 January 2018 to 31 August 2019. The validation
results showed that for most sites 60–80% of TROPOMI data was within ±20% from ground-based data for snow
free surface conditions. The median relative differences to ground-based measurements of TROPOMI snow free surface daily doses were within ±10% and ±5% at two thirds and at half of the sites, respectively. At several sites more than 90% of clear sky TROPOMI data were within ±20% from ground-based measurements. Generally median relative differences between TROPOMI data and ground-based measurements were a little biased towards negative values, but at high latitudes where nonhomogeneous topography and albedo/snow conditions occurred, the negative bias was exceptionally high, from -30% to -65%. Positive biases of 10–15% were also found for mountainous sites due to challenging topography. The TROPOMI Surface UV Radiation Product includes quality flags to detect increased uncertainties in the data due to heterogeneous surface albedo and rough terrain which can be used to filter the data retrieved under challenging conditions
An Ontological Approach to Inform HMI Designs for Minimizing Driver Distractions with ADAS
ADAS (Advanced Driver Assistance Systems) are in-vehicle systems designed to enhance driving
safety and efficiency as well as comfort for drivers in the driving process. Recent studies have
noticed that when Human Machine Interface (HMI) is not designed properly, an ADAS can cause
distraction which would affect its usage and even lead to safety issues. Current understanding of
these issues is limited to the context-dependent nature of such systems. This paper reports the
development of a holistic conceptualisation of how drivers interact with ADAS and how such
interaction could lead to potential distraction. This is done taking an ontological approach to
contextualise the potential distraction, driving tasks and user interactions centred on the use of
ADAS. Example scenarios are also given to demonstrate how the developed ontology can be used
to deduce rules for identifying distraction from ADAS and informing future designs
Exploring the inhibition boundaries of mixed cultures of purple phototrophic bacteria for wastewater treatment in anaerobic conditions
The development of novel wastewater platforms should include the analysis of the most critical functional factors including the effects of toxic or inhibitory substances. Due to the novelty of purple phototrophic bacteria (PPB)-based wastewater treatment systems, this analysis has not been done yet in mixed cultures. In this work, various relevant chemical compounds, including aromatic (phenol, 2,4,6-trichlorophenol or 246TCP, 4-nitrophenol or 4CP, sulfathiazole) and aliphatic organics (methanol, trichlorethylene or TCE, oleic acid, ethanol, propionic acid), inorganic salts (ammonium, ClO, Na), and metals (Fe, Fe, Cu, Zn, Ni, Al), as well as pH, are analyzed for their effect on mixed PPB cultures in anaerobic photoheterotrophic conditions using acetate as the model organic substrate. The most toxic substances detected were 246TCP, 4NP, Cu, Fe and Ni, (K for activity: 23 ± 2, 97 ± 12, 3.1 ± 0.4, 13 ± 3, 13 ± 1 mg/L, and K (or toxicity threshold) for growth: 17 ± 2, (119), 3.5 ± 0.4, (4.8), (22.9) mg/L, respectively). Some substances inhibited the activity more than the growth (sulfathiazole, Ni and Fe), or the growth more than the activity (TCE, 4NP and Fe). In addition, some organic substrates, such as phenol, ethanol and propionate, specifically inhibited the acetate uptake, being noncompetitive in the case of phenol and ethanol, and most likely competitive in the case of propionate. These findings are relevant for the wastewater treatment and resource recovery applications of the PPB technology, as well as for the upgrading of current models (Photo-Anaerobic Model). In addition, the data will open possibilities to promote the production of specific compounds (as PHA or single-cell proteins) by selectively inhibiting some parts of the PPB metabolism