11,610 research outputs found
Piercing the Veil: William J. Brennan\u27s Account of Regents of the University of California v. Bakke
Porous nickel oxide films were deposited onto unheated indium tin oxide coated glass substrates by reactive dc magnetron sputtering. These films had a cubic NiO structure. Electrochromic properties were evaluated in 1 M potassium hydroxide (KOH) and in 1 M lithium perchlorate in propylene carbonate (Li-PC). Large optical modulation was obtained for similar to 500-nm-thick films both in KOH and in Li-PC (similar to 70% and similar to 50% at 550 nm, respectively). In KOH, tensile and compressive stresses, due to the expansion and contraction of the lattice, were found for films in their bleached and colored state, respectively. In Li-PC, compressive stress was seen both in colored and bleached films. Durability tests with voltage sweeps between -0.5 and 0.65 V vs Ag/AgCl in KOH showed good durability for 10,000 cycles, whereas voltage sweeps between 2.0 and 4.7 V vs Li/Li+ in Li-PC yielded significant degradation after 1000 cycles.EU GRINDOO
The news coverage of the 2004 European Parliamentary Election Campaign in 25 countries
This article analyzes the news coverage of the 2004 European Parliamentary\ud
(EP) elections in all 25 member states of the European Union (EU). It\ud
provides a unique pan-European overview of the campaign coverage based\ud
on an analysis of three national newspapers and two television newscasts in\ud
the two weeks leading up to the elections. On average, the elections were\ud
more visible in the new 10 member states than in the 15 old EU member\ud
states. The political personalities and institutional actors featured in news\ud
stories about the elections were generally national political actors and not EU\ud
actors. When it was evaluative, the news in the old EU-15 was generally\ud
negative towards the EU, while in the new countries a mixed pattern was\ud
found. The findings of the study are discussed in the light of the literature on\ud
the EUâs legitimacy and communication deficit
Single-electron transport in InAs nanowire quantum dots formed by crystal phase engineering
We report electrical characterization of quantum dots formed by introducing
pairs of thin wurtzite (WZ) segments in zinc blende (ZB) InAs nanowires.
Regular Coulomb oscillations are observed over a wide gate voltage span,
indicating that WZ segments create significant barriers for electron transport.
We find a direct correlation of transport properties with quantum dot length
and corresponding growth time of the enclosed ZB segment. The correlation is
made possible by using a method to extract lengths of nanowire crystal phase
segments directly from scanning electron microscopy images, and with support
from transmission electron microscope images of typical nanowires. From
experiments on controlled filling of nearly empty dots with electrons, up to
the point where Coulomb oscillations can no longer be resolved, we estimate a
lower bound for the ZB-WZ conduction-band offset of 95 meV.Comment: 9 pages 9 figure
Electron-hole interactions in coupled InAs-GaSb quantum dots based on nanowire crystal phase templates
We report growth and characterization of a coupled quantum dot structure that
utilizes nanowire templates for selective epitaxy of radial heterostructures.
The starting point is a zinc blende InAs nanowire with thin segments of
wurtzite structure. These segments have dual roles: they act as tunnel barriers
for electron transport in the InAs core, and they also locally suppress growth
of a GaSb shell, resulting in coaxial InAs-GaSb quantum dots with integrated
electrical probes. The parallel quantum dot structure hosts spatially separated
electrons and holes that interact due to the type-II broken gap of InAs-GaSb
heterojunctions. The Coulomb blockade in the electron and hole transport is
studied, and periodic interactions of electrons and holes are observed and can
be reproduced by modeling. Distorted Coulomb diamonds indicate voltage-induced
ground-state transitions, possibly a result of changes in the spatial
distribution of holes in the thin GaSb shell.Comment: 8 pages, 7 figure
Unipolar and bipolar operation of InAs/InSb nanowire heterostructure field-effect transistors
We present temperature dependent electrical measurements on n-type InAs/InSb nanowireheterostructurefield-effect transistors. The barrier height of the heterostructure junction is determined to be 220 meV, indicating a broken bandgap alignment. A clear asymmetry is observed when applying a bias to either the InAs or the InSb side of the junction. Impact ionization and band-to-band tunneling is more pronounced when the large voltage drop occurs in the narrow bandgapInSb segment. For small negative gate-voltages, the InSb segment can be tuned toward p-type conduction, which induces a strong band-to-band tunneling across the heterostructucture junction.This work was carried out within the Nanometer Structure
Consortium at Lund University and was supported by
the Swedish Research Council (VR), the Swedish Foundation
for Strategic Research (SSF), and the Knut and Alice
Wallenberg Foundation
Spectroscopy and level detuning of few-electron spin states in parallel InAs quantum dots
We use tunneling spectroscopy to study the evolution of few-electron spin
states in parallel InAs nanowire double quantum dots (QDs) as a function of
level detuning and applied magnetic field. Compared to the much more studied
serial configuration, parallel coupling of the QDs to source and drain greatly
expands the probing range of excited state transport. Owing to a strong
confinement, we can here isolate transport involving only the very first
interacting single QD orbital pair. For the (2,0)-(1,1) charge transition, with
relevance for spin-based qubits, we investigate the excited (1,1) triplet, and
hybridization of the (2,0) and (1,1) singlets. An applied magnetic field splits
the (1,1) triplet, and due to spin-orbit induced mixing with the (2,0) singlet,
we clearly resolve transport through all triplet states near the avoided
singlet-triplet crossings. Transport calculations, based on a simple model with
one orbital on each QD, fully replicate the experimental data. Finally, we
observe an expected mirrored symmetry between the 1-2 and 2-3 electron
transitions resulting from the two-fold spin degeneracy of the orbitals.Comment: 17 pages, 8 figure
Homoclinic chaos and energy condition violation
In this letter we discuss the connection between so-called homoclinic chaos
and the violation of energy conditions in locally rotationally symmetric
Bianchi type IX models, where the matter is assumed to be non-tilted dust and a
positive cosmological constant. We show that homoclinic chaos in these models
is an artifact of unphysical assumptions: it requires that there exist
solutions with positive matter energy density that evolve through the
singularity and beyond as solutions with negative matter energy density
. Homoclinic chaos is absent when it is assumed that the dust particles
always retain their positive mass.In addition, we discuss more general models:
for solutions that are not locally rotionally symmetric we demonstrate that the
construction of extensions through the singularity, which is required for
homoclinic chaos, is not possible in general.Comment: 4 pages, RevTe
Matter and dynamics in closed cosmologies
To systematically analyze the dynamical implications of the matter content in
cosmology, we generalize earlier dynamical systems approaches so that perfect
fluids with a general barotropic equation of state can be treated. We focus on
locally rotationally symmetric Bianchi type IX and Kantowski-Sachs orthogonal
perfect fluid models, since such models exhibit a particularly rich dynamical
structure and also illustrate typical features of more general cases. For these
models, we recast Einstein's field equations into a regular system on a compact
state space, which is the basis for our analysis. We prove that models expand
from a singularity and recollapse to a singularity when the perfect fluid
satisfies the strong energy condition. When the matter source admits Einstein's
static model, we present a comprehensive dynamical description, which includes
asymptotic behavior, of models in the neighborhood of the Einstein model; these
results make earlier claims about ``homoclinic phenomena and chaos'' highly
questionable. We also discuss aspects of the global asymptotic dynamics, in
particular, we give criteria for the collapse to a singularity, and we describe
when models expand forever to a state of infinite dilution; possible initial
and final states are analyzed. Numerical investigations complement the
analytical results.Comment: 23 pages, 24 figures (compressed), LaTe
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