371 research outputs found
Measurement of the shot noise in a single electron transistor
We have systematically measured the shot noise in a single electron
transistor (SET) as a function of bias and gate voltages. By embedding a SET in
a resonance circuit we have been able to measure its shot noise at the
resonance frequency 464 MHz, where the 1/f noise is negligible. We can extract
the Fano factor which varies between 0.5 and 1 depending on the amount of
Coulomb blockade in the SET, in very good agreement with the theory.Comment: 4 figure
Gain Dependence of the Noise in the Single Electron Transistor
An extensive investigation of low frequency noise in single electron
transistors as a function of gain is presented. Comparing the output noise with
gain for a large number of bias points, it is found that the noise is dominated
by external charge noise. For low gains we find an additional noise
contribution which is compared to a model including resistance fluctuations. We
conclude that this excess noise is not only due to resistance fluctuations. For
one sample, we find a record low minimum charge noise of qn = 9*10^-6
e/sqrt(Hz) in the superconducting state and qn = 9*10^-6 e/sqrt(Hz) in the
normal state at a frequency of 4.4 kHz.Comment: 10 pages, LaTex 2.09, 4 figures (epsfig
Are pinholes the cause of excess current in superconducting tunnel junctions? A study of Andreev current in highly resistive junctions
In highly resistive superconducting tunnel junctions, excess subgap current
is usually observed and is often attributed to microscopic "pinholes" in the
tunnel barrier. We have studied the subgap current in
superconductor-insulator-superconductor (SIS) and
superconductor-insulator-normal-metal (SIN) junctions. In Al/AlOx/Al junctions,
we observed a decrease of 2 orders of magnitude in the current upon the
transition from the SIS to the SIN regime, where it then matched theory. In
Al/AlOx/Cu junctions, we also observed generic features of coherent diffusive
Andreev transport in a junction with a homogenous barrier. We use the
quasiclassical Keldysh-Green function theory to quantify single- and
two-particle tunneling and find good agreement over 2 orders of magnitude in
transparency. We argue that our observations rule out pinholes as the origin of
the excess current.Comment: 4 pages, 4 figure
Plant descriptions for engineering tool interoperability
The emergence and deployment of connected devices in many domains of application (e.g. industrial production, buildings and facilities, urban environment, etc.) have resulted in the need to achieve integration of multiple and more complex systems. This new environment is stressing the intrinsic limits imposed by monolithic standards, data models and integration methods that focus on specific domains of application, types of systems, or specific aspects of a system.
This paper describes the Plant Description Service developed as part of the Arrowhead Interoperability framework (EU ECSEL funded project). The manuscript contains a description of the abstract system descriptive model based on which the Plant Description service was implemented, and describes how the service can be used to achieve integration of several industry standards and data models. Case studies are provided that illustrates how the service was practically implemented to support engineering scenarios in the domain of industrial production. The paper concludes with a critical review of the approach and suggestion for future work and developments
Renin-angiotensin system activation correlates with microvascular dysfunction in a prospective cohort study of clinical sepsis
Microvascular dysregulation characterized by hyporesponsive vessels and heterogeneous bloodflow is implicated in the pathogenesis of organ failure in sepsis. The renin-angiotensin system (RAS) affects the microvasculature, yet the relationships between RAS and organ injury in clinical sepsis remain unclear. We tested our hypothesis that systemic RAS mediators are associated with dysregulation of the microvasculature and with organ failure in clinical severe sepsis
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