174,350 research outputs found
Spatially valid proprioceptive cues improve the detection of a visual stimulus
Vision and proprioception are the main sensory modalities that convey hand location and direction of movement. Fusion of these sensory signals into a single robust percept is now well documented. However, it is not known whether these modalities also interact in the spatial allocation of attention, which has been demonstrated for other modality pairings. The aim of this study was to test whether proprioceptive signals can spatially cue a visual target to improve its detection. Participants were instructed to use a planar manipulandum in a forward reaching action and determine during this movement whether a near-threshold visual target appeared at either of two lateral positions. The target presentation was followed by a masking stimulus, which made its possible location unambiguous, but not its presence. Proprioceptive cues were given by applying a brief lateral force to the participant’s arm, either in the same direction (validly cued) or in the opposite direction (invalidly cued) to the on-screen location of the mask. The d′ detection rate of the target increased when the direction of proprioceptive stimulus was compatible with the location of the visual target compared to when it was incompatible. These results suggest that proprioception influences the allocation of attention in visual spac
Direct exoplanet detection and characterization using the ANDROMEDA method: Performance on VLT/NaCo data
Context. The direct detection of exoplanets with high-contrast imaging
requires advanced data processing methods to disentangle potential planetary
signals from bright quasi-static speckles. Among them, angular differential
imaging (ADI) permits potential planetary signals with a known rotation rate to
be separated from instrumental speckles that are either statics or slowly
variable. The method presented in this paper, called ANDROMEDA for ANgular
Differential OptiMal Exoplanet Detection Algorithm is based on a maximum
likelihood approach to ADI and is used to estimate the position and the flux of
any point source present in the field of view. Aims. In order to optimize and
experimentally validate this previously proposed method, we applied ANDROMEDA
to real VLT/NaCo data. In addition to its pure detection capability, we
investigated the possibility of defining simple and efficient criteria for
automatic point source extraction able to support the processing of large
surveys. Methods. To assess the performance of the method, we applied ANDROMEDA
on VLT/NaCo data of TYC-8979-1683-1 which is surrounded by numerous bright
stars and on which we added synthetic planets of known position and flux in the
field. In order to accommodate the real data properties, it was necessary to
develop additional pre-processing and post-processing steps to the initially
proposed algorithm. We then investigated its skill in the challenging case of a
well-known target, Pictoris, whose companion is close to the detection
limit and we compared our results to those obtained by another method based on
principal component analysis (PCA). Results. Application on VLT/NaCo data
demonstrates the ability of ANDROMEDA to automatically detect and characterize
point sources present in the image field. We end up with a robust method
bringing consistent results with a sensitivity similar to the recently
published algorithms, with only two parameters to be fine tuned. Moreover, the
companion flux estimates are not biased by the algorithm parameters and do not
require a posteriori corrections. Conclusions. ANDROMEDA is an attractive
alternative to current standard image processing methods that can be readily
applied to on-sky data
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A Robust and Artifact Resistant Algorithm of Ultrawideband Imaging System for Breast Cancer Detection.
Goal: Ultrawideband radar imaging is regarded as one of the most promising alternatives for breast cancer detection. A range of algorithms reported in literature show satisfactory tumor detection capabilities. However, most of algorithms suffer significant deterioration or even fail when the early-stage artifact, including incident signals and skin-fat interface reflections, cannot be perfectly removed from received signals. Furthermore, fibro-glandular tissue poses another challenge for tumor detection, due to the small dielectric contrast between glandular and cancerous tissues. Methods: This paper introduces a novel Robust and Artifact Resistant (RAR) algorithm, in which a neighborhood pairwise correlation-based weighting is designed to overcome the adverse effects from both artifact and glandular tissues. In RAR, backscattered signals are time-shifted, summed, and weighted by the maximum combination of the neighboring pairwise correlation coefficients between shifted signals, forming the intensity of each point within an imaging area. Results: The effectiveness was investigated using 3-D anatomically and dielectrically accurate finite-difference-time-domain numerical breast models. The use of neighborhood pairwise correlation provided robustness against artifact, and enabled the detection of multiple scatterers. RAR is compared with four well-known algorithms: delay-and-sum, delay-multiply-and-sum, modified-weighted-delay-and-sum, and filtered-delay-and-sum. Conclusion: It has shown that RAR exhibits improved identification capability, robust artifact resistance, and high detectability over its counterparts in most scenarios considered, while maintaining computational efficiency. Simulated tumors in both homogeneous and heterogonous, from mildly to moderately dense breast phantoms, combining an entropy-based artifact removal algorithm, were successfully identified and localized. Significance: These results show the strong potential of RAR for breast cancer screening
An Evidence Based Search Method For Gravitational Waves From Neutron Star Ring-downs
The excitation of quadrupolar quasi-normal modes in a neutron star leads to
the emission of a short, distinctive, burst of gravitational radiation in the
form of a decaying sinusoid or `ring-down'. We present a Bayesian analysis
method which incorporates relevant prior information about the source and known
instrumental artifacts to conduct a robust search for the gravitational wave
emission associated with pulsar glitches and soft -ray repeater flares.
Instrumental transients are modelled as sine-Gaussian and their evidence, or
marginal likelihood, is compared with that of Gaussian white noise and
ring-downs via the `odds-ratio'. Tests using simulated data with a noise
spectral density similar to the LIGO interferometer around 1 kHz yield 50%
detection efficiency and 1% false alarm probability for ring-down signals with
signal-to-noise ratio . For a source at 15 kpc this requires an
energy of 1.3\times 10^{-5}M_{\astrosun}c^2 to be emitted as gravitational
waves.Comment: 14 pages, 12 figure
Nanomechanoelectrical approach to highly sensitive and specific label-free DNA detection
Electronic detection of DNA oligomers offers the promise of rapid, miniaturized DNA analysis across various biotechnological applications. However, known all-electrical methods, which solely rely on measuring electrical signals in transducers during probe–target DNA hybridization, are prone to nonspecific electrostatic and electrochemical interactions, subsequently limiting their specificity and detection limit. Here, we demonstrate a nanomechanoelectrical approach that delivers ultra-robust specificity and a 100-fold improvement in detection limit. We drive nanostructural DNA strands tethered to a graphene transistor to oscillate in an alternating electric field and show that the transistor-current spectra are characteristic and indicative of DNA hybridization. We find that the inherent difference in pliability between unpaired and paired DNA strands leads to the spectral characteristics with minimal influence from nonspecific electrostatic and electrochemical interactions, resulting in high selectivity and sensitivity. Our results highlight the potential of high-performance DNA analysis based on miniaturized all-electronic settings
A Multi-mode Transverse Dynamic Force Microscope - Design, Identification and Control
This is the author accepted manuscript. The final version is available from IEEE via the DOI in this record.The transverse dynamic force microscope
(TDFM) and its shear force sensing principle permit true
non-contact force detection in contrast to typical atomic
force microscopes. The two TDFM measurement signals
for the cantilever allow, in principle, two different scanning
modes of which, in particular, the second presented here
permits a full-scale non-contact scan. Previous research
mainly focused on developing the sensing mechanism,
whereas this work investigates the vertical axis dynamics
for advanced robust closed-loop control. This paper
presents a new TDFM digital control solution, built on
field-programmable gate array (FPGA) equipment running
at high implementation frequencies. The integrated control
system allows the implementation of online customizable
controllers, and raster-scans in two modes at very high
detection bandwidth and nano-precision. Robust control
algorithms are designed, implemented, and practically assessed.
The two realized scanning modes are experimentally
evaluated by imaging nano-spheres with known dimensions
in wet conditions.Engineering and Physical Sciences Research Council (EPSRC
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