3,180 research outputs found
Surface excitations in the modelling of electron transport for electron- beam-induced deposition experiments
The aim of the present overview article is to raise awareness of an essential
aspect that is usually not accounted for in the modelling of electron transport
for focused-electron-beam-induced deposition (FEBID) of nanostructures: surface
excitations are on the one hand responsible for a sizeable fraction of the
intensity in reflection-electron-energy-loss spectra for primary electron
energies of up to a few keV and, on the other hand, they play a key role in the
emission of secondary electrons from solids, regardless of the primary energy.
In this overview work we present a general perspective of recent works on the
subject of surface excitations and on low-energy electron transport,
highlighting the most relevant aspects for the modelling of electron transport
in FEBID simulations.Comment: 17 pages, 5 figure
Pattern formation in the dipolar Ising model on a two-dimensional honeycomb lattice
We present Monte Carlo simulation results for a two-dimensional Ising model
with ferromagnetic nearest-neighbor couplings and a competing long-range
dipolar interaction on a honeycomb lattice. Both structural and thermodynamic
properties are very similar to the case of a square lattice, with the exception
that structures reflect the sixfold rotational symmetry of the underlying
honeycomb lattice. To deal with the long-range nature of the dipolar
interaction we also present a simple method of evaluating effective interaction
coefficients, which can be regarded as a more straightforward alternative to
the prevalent Ewald summation techniques.Comment: 5 pages, 5 figure
Comparative study of FeCr2S4 and FeSc2S4: Spinels with orbitally active A site
Using first-principles density functional calculations, we perform a
comparative study of two Fe based spinel compounds, FeCr2S4 and FeSc2S4. Though
both systems contain an orbitally active A site with an Fe2+ ion, their
properties are rather dissimilar. Our study unravels the microscopic origin of
their behavior driven by the differences in hybridization of Fe d states with
Cr/Sc d states and S p states in the two cases. This leads to important
differences in the nature of the magnetic exchanges as well as the nearest
versus next nearest neighbor exchange parameter ratios, resulting into
significant frustration effects in FeSc2S4 which are absent in FeCr2S4.Comment: 5 pages, 4 figures Phys Rev B (rapid commun) to appear (2010
Origin of the insulating state in honeycomb iridates and rhodates
A burning question in the emerging field of spin-orbit driven insulating
iridates, such as Na2IrO3 and Li2IrO3 is whether the observed insulating state
should be classified as a Mott-Hubbard insulator derived from a half-filled
relativistic j_eff=1/2 band or as a band insulator where the gap is assisted by
spin-orbit interaction, or Coulomb correlations, or both. The difference
between these two interpretations is that only for the former, strong
spin-orbit coupling (lambda >~ W, where W is the band width) is essential. We
have synthesized the isostructural and isoelectronic Li2RhO3 and report its
electrical resistivity and magnetic susceptibility. Remarkably it shows
insulating behavior together with fluctuating effective S=1/2 moments, similar
to Na2IrO3 and Li2IrO3, although in Rh4+ (4d5) the spin-orbit coupling is
greatly reduced. We show that this behavior has non-relativistic one-electron
origin (although Coulomb correlations assist in opening the gap), and can be
traced down to formation of quasi-molecular orbitals, similar to those in
Na2IrO3.Comment: 7 pages, 7 figure
The role of the regulatory framework for innovation activities: The EU ETS and the German paper industry
Based on a research framework which combines environmental economics and innovation studies, we explore the relevance of the regulatory framework for innovation activities in the German paper industry, with a focus on climate poli-cies. Innovation activities considered include research and development, adop-tion and organizational change. Empirically, we mainly rely on the survey data of paper producers and technology providers. Findings suggest that innovation activities are mainly governed by market factors and (as yet) are hardly affected by the European Emission Trading System and other climate policies. Also, the impact of these policies on innovation activities is lower for technology providers than for paper producers. However, the majority of companies expect the ef-fects of the regulatory climate policy framework on innovation to increase by 2020. --
Large-Scale Regular Morphological Patterns in the Radio Jet of NGC 6251
We report on large-scale, regular morphological patterns found in the radio
jet of the nearby radio galaxy NGC 6251. Investigating morphological properties
of this radio jet from the nucleus to a radial distance of 300 arcsec
( 140 kpc) mapped at 1662 MHz and 4885 MHz by Perley, Bridle, &
Willis, we find three chains, each of which consists of five radio knots. We
also find that eight radio knots in the first two chains consist of three small
sub-knots (the triple-knotty substructures). We discuss the observational
properties of these regular morphological patterns.Comment: 8 figures, 15 pages, accepted for publication in A
Paroxysmal eye–head movements in Glut1 deficiency syndrome
Objective:To describe a characteristic paroxysmal eye–head movement disorder that occurs in infants with Glut1 deficiency syndrome (Glut1 DS).Methods:We retrospectively reviewed the medical charts of 101 patients with Glut1 DS to obtain clinical data about episodic abnormal eye movements and analyzed video recordings of 18 eye movement episodes from 10 patients.Results:A documented history of paroxysmal abnormal eye movements was found in 32/101 patients (32%), and a detailed description was available in 18 patients, presented here. Episodes started before age 6 months in 15/18 patients (83%), and preceded the onset of seizures in 10/16 patients (63%) who experienced both types of episodes. Eye movement episodes resolved, with or without treatment, by 6 years of age in 7/8 patients with documented long-term course. Episodes were brief (usually <5 minutes). Video analysis revealed that the eye movements were rapid, multidirectional, and often accompanied by a head movement in the same direction. Eye movements were separated by clear intervals of fixation, usually ranging from 200 to 800 ms. The movements were consistent with eye–head gaze saccades. These movements can be distinguished from opsoclonus by the presence of a clear intermovement fixation interval and the association of a same-direction head movement.Conclusions:Paroxysmal eye–head movements, for which we suggest the term aberrant gaze saccades, are an early symptom of Glut1 DS in infancy. Recognition of the episodes will facilitate prompt diagnosis of this treatable neurodevelopmental disorder.</jats:sec
Effect of isoelectronic doping on honeycomb lattice iridate A_2IrO_3
We have investigated experimentally and theoretically the series
(NaLi)IrO. Contrary to what has been believed so far,
only for the system forms uniform solid solutions. For larger Li
content, as evidenced by powder X-ray diffraction, scanning electron microscopy
and density functional theory calculations, the system shows a miscibility gap
and a phase separation into an ordered NaLiIrO phase with
alternating Na and LiIrO planes, and a Li-rich phase close to pure
LiIrO. For we observe (1) an increase of with Li
doping up to , despite the fact that in pure LiIrO is
smaller than in NaIrO, and (2) a gradual reduction of the
antiferromagnetic ordering temperature and ordered moment. The
previously proposed magnetic quantum phase transition at may
occur in a multiphase region and its nature needs to be re-evaluated.Comment: 8 pages, 9 figures including supplemental informatio
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