1,428 research outputs found
Application of a finite-difference modeling scheme for ultrasonic defect characterization
Modeling schemes, which compute the propagation of ultrasonic wave fields, serve as research tools in NDE. The objectives to use such schemes are diverse. Firstly, they may be used to set the requirements for the ultrasonic data acquisition method and the processing algorithm. Secondly, they may be used to improve understanding of the actual measurement, i.e. for interpretation. Thirdly, they may play a central role in the inversion of the measurement for defect characterization, i.e. model driven inversion and neural network training
Public exhibit for demonstrating the quantum of electrical conductance
We present a new robust setup that explains and demonstrates the quantum of
electrical conductance for a general audience and which is continuously
available in a public space. The setup allows users to manually thin a gold
wire of several atoms in diameter while monitoring its conductance in real
time. During the experiment, a characteristic step-like conductance decrease
due to rearrangements of atoms in the cross-section of the wire is observed.
Just before the wire breaks, a contact consisting of a single atom with a
characteristic conductance close to the quantum of conductance can be
maintained up to several seconds. The setup is operated full-time, needs
practically no maintenance and is used on different educational levels
Decoherence of Flux Qubits Coupled to Electronic Circuits
On the way to solid-state quantum computing, overcoming decoherence is the
central issue. In this contribution, we discuss the modeling of decoherence of
a superonducting flux qubit coupled to dissipative electronic circuitry. We
discuss its impact on single qubit decoherence rates and on the performance of
two-qubit gates. These results can be used for designing decoherence-optimal
setups.Comment: 16 pages, 5 figures, to appear in Advances in Solid State Physics,
Vol. 43 (2003
Collaboration enhances career progression in academic science, especially for female researchers.
Funder: Helsinki Institute of Life ScienceFunder: Leverhulme TrustCollaboration and diversity are increasingly promoted in science. Yet how collaborations influence academic career progression, and whether this differs by gender, remains largely unknown. Here, we use co-authorship ego networks to quantify collaboration behaviour and career progression of a cohort of contributors to biennial International Society of Behavioral Ecology meetings (1992, 1994, 1996). Among this cohort, women were slower and less likely to become a principal investigator (PI; approximated by having at least three last-author publications) and published fewer papers over fewer years (i.e. had shorter academic careers) than men. After adjusting for publication number, women also had fewer collaborators (lower adjusted network size) and published fewer times with each co-author (lower adjusted tie strength), albeit more often with the same group of collaborators (higher adjusted clustering coefficient). Authors with stronger networks were more likely to become a PI, and those with less clustered networks did so more quickly. Women, however, showed a stronger positive relationship with adjusted network size (increased career length) and adjusted tie strength (increased likelihood to become a PI). Finally, early-career network characteristics correlated with career length. Our results suggest that large and varied collaboration networks are positively correlated with career progression, especially for women
Asymmetry and decoherence in a double-layer persistent-current qubit
Superconducting circuits fabricated using the widely used shadow evaporation
technique can contain unintended junctions which change their quantum dynamics.
We discuss a superconducting flux qubit design that exploits the symmetries of
a circuit to protect the qubit from unwanted coupling to the noisy environment,
in which the unintended junctions can spoil the quantum coherence. We present a
theoretical model based on a recently developed circuit theory for
superconducting qubits and calculate relaxation and decoherence times that can
be compared with existing experiments. Furthermore, the coupling of the qubit
to a circuit resonance (plasmon mode) is explained in terms of the asymmetry of
the circuit. Finally, possibilities for prolonging the relaxation and
decoherence times of the studied superconducting qubit are proposed on the
basis of the obtained results.Comment: v.2: published version; 8 pages, 12 figures; added comparison with
experiment, improved discussion of T_ph
Decoherence of the Superconducting Persistent Current Qubit
Decoherence of a solid state based qubit can be caused by coupling to
microscopic degrees of freedom in the solid. We lay out a simple theory and use
it to estimate decoherence for a recently proposed superconducting persistent
current design. All considered sources of decoherence are found to be quite
weak, leading to a high quality factor for this qubit.Comment: 10 pages, 1 figure, Latex/revtex.To appear in proceedings of the
NATO-ASI on "Quantum Mesoscopic Phenomena and Mesoscopic Devices in
Microelectronics"; Corrections were made on Oct. 29th, 199
Unbearability of suffering at the end of life: the development of a new measuring device, the SOS-V
AbstractBackgroundUnbearable suffering is an important issue in end-of-life decisions. However, there has been no systematic, prospective, patient-oriented research which has focused on unbearable suffering, nor is there a suitable measurement instrument. This article describes the methodological development of a quantitative instrument to measure the nature and intensity of unbearable suffering, practical aspects of its use in end-stage cancer patients in general practice, and studies content validity and psychometric properties.MethodsRecognizing the conceptual difference between unbearability of suffering and extent or intensity of suffering, we developed an instrument. The compilation of aspects considered to be of importance was based on a literature search. Psychometric properties were determined on results of the first interviews with 64 end-stage cancer patients that participated in a longitudinal study in the Netherlands.ResultsThe instrument measures five domains: medical signs and symptoms, loss of function, personal aspects, aspects of environment, and nature and prognosis of the disease. Sixty nine aspects were investigated, and an overall score was asked. In 64 end-stage cancer patients the instrument was used in total 153 times with an average interview time varying from 20-40 minutes. Cronbachs alpha's of the subscales were in majority above 0.7. The sum scores of (sub)scales were correlated strongly to overall measures on suffering.ConclusionThe SOS-V is an instrument for measuring the unbearability of suffering in end-stage cancer patients with good content validity and psychometric properties, which is feasible to be used in practice. This structured instrument makes it possible to identify and study unbearable suffering in a quantitative and patient-oriented way
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