6,267 research outputs found
Observation of chiral heat transport in the quantum Hall regime
Heat transport in the quantum Hall regime is investigated using micron-scale heaters and thermometers positioned along the edge of a millimeter-scale two dimensional electron system (2DES). The heaters rely on localized current injection into the 2DES, while the thermometers are based on the thermoelectric effect. In the v=1 integer quantized Hall state, a thermoelectric signal appears at an edge thermometer only when it is “downstream,” in the sense of electronic edge transport, from the heater. When the distance between the heater and the thermometer is increased, the thermoelectric signal is reduced, showing that the electrons cool as they propagate along the edge
Evaluating Success in Addictions Treatment
Treatment for substance use disorders is an important service for thousands of Canadians each year and is an integral part of the healthcare system. Despite its role in the healthcare system, the literature is yet to determine a definitive definition of success for addictions treatment. The disease model of addiction as well as the harm reduction model are two prevalent models with differing philosophies. In addition, the recovery maintenance model and acute care models each provide evidence differing practices. The present study involved interviews with clients that had completed an abstinence focused residential treatment programme in order to get firsthand experience on success in treatment and recovery. The researchers analyzed these interviews with a combination of manual coding and NVivo word frequency analysis. The thematic analysis identified a combination of themes associated with successful treatment and successful recovery respectively. The theme of effort and work was identified as being important to successful treatment and the theme of passion and purpose was identified as being important to successful recovery. These themes suggested that success was client centered and that successful treatment and recovery were interconnected. These themes were compared to existing literature which verified that success was heavily subjective between participants across studies. Furthermore, the study demonstrated that it was important to encapsulate both desires to grow and ability to cope with barriers simultaneously. Building a strong foundation that could cope with barriers effectively allowed for growth and purpose to be found. These factors were demonstrated in the current sample as well as in the literature. Potential implications for these findings include quantifying success in treatment and validation of the important aspects of both treatment and recovery. Limitations and future directions of the current study are discussed
Maximal multihomogeneity of algebraic hypersurface singularities
From the degree zero part of logarithmic vector fields along an algebraic
hypersurface singularity we indentify the maximal multihomogeneity of a
defining equation in form of a maximal algebraic torus in the embedded
automorphism group. We show that all such maximal tori are conjugate and in
one-to-one correspondence to maxmimal tori in the degree zero jet of the
embedded automorphism group.
The result is motivated by Kyoji Saito's characterization of quasihomogeneity
for isolated hypersurface singularities and extends its formal version and a
result of Hauser and Mueller.Comment: 5 page
Reducing the Bias of Causality Measures
Measures of the direction and strength of the interdependence between two
time series are evaluated and modified in order to reduce the bias in the
estimation of the measures, so that they give zero values when there is no
causal effect. For this, point shuffling is employed as used in the frame of
surrogate data. This correction is not specific to a particular measure and it
is implemented here on measures based on state space reconstruction and
information measures. The performance of the causality measures and their
modifications is evaluated on simulated uncoupled and coupled dynamical systems
and for different settings of embedding dimension, time series length and noise
level. The corrected measures, and particularly the suggested corrected
transfer entropy, turn out to stabilize at the zero level in the absence of
causal effect and detect correctly the direction of information flow when it is
present. The measures are also evaluated on electroencephalograms (EEG) for the
detection of the information flow in the brain of an epileptic patient. The
performance of the measures on EEG is interpreted, in view of the results from
the simulation study.Comment: 30 pages, 12 figures, accepted to Physical Review
Few-electron quantum dots in III-V ternary alloys: role of fluctuations
We study experimentally the electron transport properties of gated quantum
dots formed in InGaAs/InP and InAsP/InP quantum well structures grown by
chemical-beam epitaxy. For the case of the InGaAs quantum well, quantum dots
form directly underneath narrow gate electrodes due to potential fluctuations.
We measure the Coulomb-blockade diamonds in the few-electron regime of a single
quantum dot and observe photon-assisted tunneling peaks under microwave
irradiation. A singlet-triplet transition at high magnetic field and
Coulomb-blockade effects in the quantum Hall regime are also observed. For the
InAsP quantum well, an incidental triple quantum dot forms also due to
potential fluctuations within a single dot layout. Tunable quadruple points are
observed via transport measurements.Comment: 3.3 pages, 3 figures. Added two new subfigures, new references, and
improved the tex
The visibility study of S-T Landau-Zener-St\"uckelberg oscillations without applied initialization
Probabilities deduced from quantum information studies are usually based on
averaging many identical experiments separated by an initialization step. Such
initialization steps become experimentally more challenging to implement as the
complexity of quantum circuits increases. To better understand the consequences
of imperfect initialization on the deduced probabilities, we study the effect
of not initializing the system between measurements. For this we utilize
Landau-Zener-St\"uckelberg oscillations in a double quantum dot circuit.
Experimental results are successfully compared to theoretical simulations.Comment: 8 pages, 5 figure
A Tuneable Few Electron Triple Quantum Dot
In this paper we report on a tuneable few electron lateral triple quantum dot
design. The quantum dot potentials are arranged in series. The device is aimed
at studies of triple quantum dot properties where knowing the exact number of
electrons is important as well as quantum information applications involving
electron spin qubits. We demonstrate tuning strategies for achieving required
resonant conditions such as quadruple points where all three quantum dots are
on resonance. We find that in such a device resonant conditions at specific
configurations are accompanied by novel charge transfer behaviour.Comment: 11 pages, 4 figure
Influence of surface tension, osmotic pressure and pores morphology on the densification of ice-templated ceramics
International audienceWe attempt here to clarify the influence of the nature of the solvent on the ice-templating process, based on literature experimental results of porosity and suspension concentration. In particular, we compare the relative influence of surface tension, osmotic pressure and the pore size and radius of curvature on the densification of the green bodies. Variations of the osmotic pressure when changing the solvent can yield significantly different behaviour during the freezing stage and therefore significantly affect the densification behaviour, an effect not apparent when using the Shanti model. In addition, and equally important, a modification of the macropores morphology is induced by the evolution of the solvent crystals morphology, and resulting in smaller and more intricate crystals and macropores which facilitates the densification. The radius of curvature is probably also an essential parameter controlling the densification of ice-templated ceramics
Two-stage Kondo effect in a four-electron artificial atom
An artificial atom with four electrons is driven through a singlet-triplet
transition by varying the confining potential. In the triplet, a Kondo peak
with a narrow dip at drain-source voltage V_ds=0 is observed. The low energy
scale V_ds* characterizing the dip is consistent with predictions for the
two-stage Kondo effect. The phenomenon is studied as a function of temperature
T and magnetic field B, parallel to the two-dimensional electron gas. The low
energy scales T* and B* are extracted from the behavior of the zero-bias
conductance and are compared to the low energy scale V_ds* obtained from the
differential conductance. Good agreement is found between kT* and |g|muB*, but
eV_ds* is larger, perhaps because of nonequilibrium effects.Comment: 7 pages, 7 figures. Added labels on Fig. 3f and one referenc
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