414 research outputs found
The accuracy of prostate volume measurement from ultrasound images: A quasi-Monte Carlo simulation study using magnetic resonance imaging
The milliarcsecond-scale radio structure of AB Dor A
Context: The fast rotator, pre-main sequence star AB Dor A is a strong and
persistent radio emitter. The extraordinary coronal flaring activity is thought
to be the origin of compact radio emission and other associated phenomena as
large slingshot prominences. Aim: We aim to investigate the radio emission
mechanism and the milliarcsecond radio structure around AB Dor A. Methods: We
performed phase-referenced VLBI observations at 22.3 GHz, 8.4 GHz, and 1.4 GHz
over more than one decade using the Australian VLBI array. Results: Our 8.4 GHz
images show a double core-halo morphology, similar at all epochs, with emission
extending at heights between 5 and 18 stellar radii. Furthermore, the sequence
of the 8.4 GHz maps shows a clear variation of the source structure within the
observing time. However, images at 1.4 GHz and 22.3 GHz are compatible with a
compact source. The phase-reference position at 8.4 GHz and 1.4 GHz are
coincident with those expected from the well-known milliarcsecond-precise
astrometry of this star, meanwhile the 22.3 GHz position is 4 off the
prediction in the north-west direction. The origin of this offset is still
unclear. Conclusions: We have considered several models to explain the
morphology and evolution of the inner radio structure detected in AB Dor A
which include emission from the stellar polar caps, a flaring,
magnetically-driven loop structure, and the presence of helmet streamers. A
possible close companion to AB Dor A has been also investigated. Our results
confirm the extraordinary coronal magnetic activity of this star, able to
produce compact radio structures at very large heights, so far only seen in
binary interacting systems.Comment: 11 pages, 6 figures, accepted for publication in Astronomy and
Astrophysic
The Electrical-Thermal Switching in Carbon Black-Polymer Composites as a Local Effect
Following the lack of microscopic information about the intriguing well-known
electrical-thermal switching mechanism in Carbon Black-Polymer composites, we
applied atomic force microscopy in order to reveal the local nature of the
process and correlated it with the characteristics of the widely used
commercial switches. We conclude that the switching events take place in
critical interparticle tunneling junctions that carry most of the current. The
macroscopic switched state is then a result of a dynamic-stationary state of
fast switching and slow reconnection of the corresponding junctions.Comment: 14 pages, 5 figures,Typographic correctio
Dynamical masses of the low-mass stellar binary AB Doradus B
Context. ABDoradus is the main system of the ABDoradus moving group. It is a quadruple system formed by two widely separated binaries of pre-main-sequence (PMS) stars: ABDorA/C and ABDor Ba/Bb. The pair ABDorA/C has been extensively studied and its dynamical masses have been determined with high precision, thus making of ABDorC a benchmark for calibrating PMS stellar models. If the orbit and dynamical masses of the pair ABDor Ba/Bb can be determined, they could not only play a similar role to that of ABDorC in calibrating PMS models, but would also help to better understand the dynamics of the whole ABDoradus system. Aims. We aim to determine the individual masses of the pair ABDor Ba/Bb using VLBI observations and archive infrared data, as part of a larger program directed to monitor binary systems in the ABDoradus moving group. Methods. We observed the system ABDor B between 2007 and 2013 with the Australian Long Baseline Array (LBA), at a frequency of 8.4 GHz in phase-reference mode. Results. We detected, for the first time, compact radio emission from both stars in the binary, ABDor Ba and ABDor Bb. This result allowed us to determine the orbital parameters of both the relative and absolute orbits and, consequently, their individual dynamical masses: 0.28±0.05M_sun and 0.25±0.05M_sun, respectively. Conclusions. Comparisons of the dynamical masses with the prediction of PMS evolutionary models show that the models underpredict the dynamical masses of the binary components Ba and Bb by ~30 and 40%, respectively, although they all still agree at the 2-sigma level. The same stellar models favour an age between 50 and 100 Myr for this system. We also discuss the evolutionary status of ABDor Ba/Bb in terms of an earlier double-double star scenario that might explain the strong radio emission detected in both components
Visualisation tool for peptide fractionation data in proteomics: application to OFFGEL isoelectric focussing
<p>Abstract</p> <p>Background</p> <p>OFFGEL isoelectric focussing (IEF) has become a popular tool in proteomics to fractionate peptides or proteins. As a consequence there is a need for software solutions supporting data mining, interpretation and characterisation of experimental quality.</p> <p>Results</p> <p>We can assess performance characteristics of OFFGEL IEF peptide fractionation in proteomics by generating plots of the overall fractionation patterns and the pairwise comparisons of adjacent fractions.</p> <p>Conclusions</p> <p>A visualisation tool for peptide fractionation has been developed to support the evaluation of IEF data quality and can be implemented in proteomics research.</p
Annihilation of structural defects in chalcogenide absorber films for high-efficiency solar cells
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.In polycrystalline semiconductor absorbers for thin-film solar cells, structural defects may enhance electron-hole recombination and hence lower the resulting energy conversion efficiency. To be able to efficiently design and optimize fabrication processes that result in high-quality materials, knowledge of the nature of structural defects as well as their formation and annihilation during film growth is essential. Here we show that in co-evaporated Cu(In,Ga)Se-2 absorber films the density of defects is strongly influenced by the reaction path and substrate temperature during film growth. A combination of high-resolution electron microscopy, atomic force microscopy, scanning tunneling microscopy, and X-ray diffraction shows that Cu(In,Ga)Se-2 absorber films deposited at low temperature without a Cu-rich stage suffer from a high density of - partially electronically active - planar defects in the {112} planes. Real-time X-ray diffraction reveals that these faults are nearly completely annihilated during an intermediate Cu-rich process stage with [Cu]/([In] + [Ga]) > 1. Moreover, correlations between real-time diffraction and fluorescence analysis during Cu-Se deposition reveal that rapid defect annihilation starts shortly before the start of segregation of excess Cu-Se at the surface of the Cu(In,Ga)Se-2 film. The presented results hence provide direct insights into the dynamics of the film-quality-improving mechanism
The AIQ Meta-Testbed: Pragmatically Bridging Academic AI Testing and Industrial Q Needs
AI solutions seem to appear in any and all application domains. As AI becomes
more pervasive, the importance of quality assurance increases. Unfortunately,
there is no consensus on what artificial intelligence means and interpretations
range from simple statistical analysis to sentient humanoid robots. On top of
that, quality is a notoriously hard concept to pinpoint. What does this mean
for AI quality? In this paper, we share our working definition and a pragmatic
approach to address the corresponding quality assurance with a focus on
testing. Finally, we present our ongoing work on establishing the AIQ
Meta-Testbed.Comment: Accepted for publication in the Proc. of the Software Quality Days
2021, Vienna, Austri
A digitally-augmented ground space with timed visual cues for facilitating forearm crutches’ mobility
Persuasive technologies for physical rehabilitation have been pro posed in a number of different health interventions such as post-stroke gait
rehabilitation. We propose a new persuasive system, called Augmented Crut ches, aimed at helping people to walk with crutches. People with injuries, or
with any sort of mobility problem typically use assistive devices such as crut ches, walkers or canes in order to be able to walk more independently. However,
walking with crutches is a learning skill that needs continuous repetition and
constant attention to detail in order to walk correctly with them and without
suffering negative consequences, such as falls or injuries. In close collaboration
with therapists, we identify the main issues that patients face when walking with
crutches. These vary from person to person, but the most common and hardest
challenges are the position and coordination of the crutches. Augmented Crut ches studies human behavior aspects in these situations and augments the
ground space around the user with digital visual cues where timing is the most
important factor, without the need for a constant therapist providing manual
help. This is performed through a mini-projector connected to a smartphone,
worn by the user in a portable, lightweight manner. Our system helps people to
learn how to walk using crutches with increased self-confidence and motivation.
Additionally, our work identifies timing, controllability and awareness as the
key design dimensions for the successful creation of persuasive, interactive
experiences for learning how to walk with crutches.info:eu-repo/semantics/publishedVersio
Evidence of a pharmacodynamic EEG profile in rats following clonidine administration using a nonlinear analysis
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