619 research outputs found
High Bias Transport and Magnetometer Design in Open Quantum Dots
We report transport measurements as a function of bias in open semiconductor
quantum dots. These measurements are well described by an effective electron
temperature derived from Joule heating at the point contacts and cooling by
Wiedemann-Franz out-diffusion of thermal electrons. Using this model, we
propose and analyze a quantum dot based sensor which measures absolute magnetic
field at micron scales with a noise floor of
at 300 mK.Comment: 10 pages including 3 figure
Probe-configuration dependent dephasing in a mesoscopic interferometer
Dephasing in a ballistic four-terminal Aharonov-Bohm geometry due to charge
and voltage fluctuations is investigated. Treating two terminals as voltage
probes, we find a strong dependence of the dephasing rate on the probe
configuration in agreement with a recent experiment by Kobayashi et al. (J.
Phys. Soc. Jpn. 71, 2094 (2002)). Voltage fluctuations in the measurement
circuit are shown to be the source of the configuration dependence.Comment: 4 pages, 3 figure
Calculation of dephasing times in closed quantum dots
Dephasing of one-particle states in closed quantum dots is analyzed within
the framework of random matrix theory and Master equation. Combination of this
analysis with recent experiments on the magnetoconductance allows for the first
time to evaluate the dephasing times of closed quantum dots. These dephasing
times turn out to depend on the mean level spacing and to be significantly
enhanced as compared with the case of open dots. Moreover, the experimental
data available are consistent with the prediction that the dephasing of
one-particle states in finite closed systems disappears at low enough energies
and temperatures.Comment: 4 pages, 3 figure
Conductance fluctuations and weak localization in chaotic quantum dots
We study the conductance statistical features of ballistic electrons flowing
through a chaotic quantum dot. We show how the temperature affects the
universal conductance fluctuations by analyzing the influence of dephasing and
thermal smearing. This leads us to two main findings. First, we show that the
energy correlations in the transmission, which were overlooked so far, are
important for calculating the variance and higher moments of the conductance.
Second, we show that there is an ambiguity in the method of determination of
the dephasing rate from the size of the of the weak localization. We find that
the dephasing times obtained at low temperatures from quantum dots are
underestimated.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let
3rd KidRec workshop: What does good look like?
Today's children spend considerable time online, searching and receiving information from various websites and apps. While searching for information, e.g. for school or hobbies, children use search systems to locate resources and receive site recommendations that might be useful for them. The call for good, reliable, child-friendly systems has been made many times and the thesis that the algorithms of "adult" information systems are not necessarily suitable or fair for children is widely accepted. However, there is still no clear and balanced view on what makes one search/recommendation system for children good or better than other systems, nor on what content should be considered "good enough to be retrieved" or recommended. The goal of this workshop is to bring together researchers and practitioners in education, child-development, computer science, and more who can address this questions while considering issues related to education, algorithms, ethics, privacy, evaluation
Impact of measurement frequency on self-reported depressive symptoms: An experimental study in a clinical setting
Impact of measurement frequency on self-reported depressive symptoms: An experimental study in a clinical setting
De beslispraktijk van het Schadefonds Geweldsmisdrijven: een kwalitatieve studie naar de beoordeling van verzoeken tot tegemoetkoming
The Violent
Offences Compensation Fund’s decision-making practice: A qualitative study into
the evaluation of requests for compensation
Victims who suffer severe
damages due to the act of a violent crime can request state compensation from
the Dutch Violent Offences Compensation Fund (VOCF). VOCF workers who decide on
these requests use their discretionary powers to translate the VOCF’s rules and
policy into concrete actions. This study investigated (1) to what extent these VOCF
workers match Lipsky’s definition of street-level bureaucrats and (2) what
routines and heuristics they use to deal with time and information constraints.
On the basis of document analysis and interviews, we found that the decision
makers of the VOCF can to a certain extent be seen as street-level bureaucrats.
To make decisions timely, some of them use routines such as the ‘downstream orientation’. This means that
they award requests for compensation if they think that the applicant would be
able to successfully contest a rejecting decision. To deal with a lack of
information, they sometimes include a review clause in the text of a rejection
decision. The use of heuristics was not found among the lawyers who decide in
first instance, but in case of appeal hearings heuristics such as the affect and
representativeness heuristic seem to play a role in the decision-making process.
Future research should investigate whether these routines and heuristics lead
to disparities in outcomes.
Criminal Justice: Legitimacy, accountability, and effectivit
Photocurrent, Rectification, and Magnetic Field Symmetry of Induced Current Through Quantum Dots
We report mesoscopic dc current generation in an open chaotic quantum dot
with ac excitation applied to one of the shape-defining gates. For excitation
frequencies large compared to the inverse dwell time of electrons in the dot
(i.e., GHz), we find mesoscopic fluctuations of induced current that are fully
asymmetric in the applied perpendicular magnetic field, as predicted by recent
theory. Conductance, measured simultaneously, is found to be symmetric in
field. In the adiabatic (i.e., MHz) regime, in contrast, the induced current is
always symmetric in field, suggesting its origin is mesoscopic rectification.Comment: related papers at http://marcuslab.harvard.ed
«Белая дача» А.П. Чехова – как часть культурного ландшафта Крыма
Данная работа написана в рамках научного проекта кафедры культурологии «Культурные ландшафты Крыма» и посвящена рассмотрению «Белой дачи» А.П. Чехова (ныне Дом-музей А.П. Чехова в Ялте) как культурному ландшафту – результату сотворчества человека и природы
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