5,532 research outputs found
T2 mapping outperforms normalised FLAIR in identifying hippocampal sclerosis
Rationale Qualitatively, FLAIR MR imaging is sensitive to the detection of hippocampal sclerosis (HS). Quantitative analysis of T2 maps provides a useful objective measure and increased sensitivity over visual inspection of T2-weighted scans. We aimed to determine whether quantification of normalised FLAIR is as sensitive as T2 mapping in detection of HS. Method Dual echo T2 and FLAIR MR images were retrospectively analysed in 27 patients with histologically confirmed HS and increased T2 signal in ipsilateral hippocampus and 14 healthy controls. Regions of interest were manually segmented in all hippocampi aiming to avoid inclusion of CSF. Hippocampal T2 values and measures of normalised FLAIR Signal Intensity (nFSI) were compared in healthy and sclerotic hippocampi. Results HS was identified on T2 values with 100% sensitivity and 100% specificity. HS was identified on nFSI measures with 60% sensitivity and 93% specificity. Conclusion T2 mapping is superior to nFSI for identification of HS
On the theory of SODAR measurement techniques (final reporting on WP1, EU WISE project NNE5-2001-297)
The need for alternative means to measure the wind speed for wind energy purposes has increased with
the increase of the size of wind turbines. The cost and the technical difficulties for performing wind
speed measurements has also increased with the size of the wind turbines, since it is demanded that the
wind speed has to be measured at the rotor center of the turbine and the size of both the rotor and the
hub height have grown following the increase in the size of the wind turbines. The SODAR (SOund
Detection And Ranging) is an alternative to the use of cup anemometers and offers the possibility of
measuring both the wind speed distribution with height and the wind direction.
At the same time the SODAR presents a number of serious drawbacks such as the low number of
measurements per time period, the dependence of the ability to measure on the atmospheric conditions
and the difficulty of measuring at higher wind speeds due to either background noise or the neutral
condition of the atmosphere.
Within the WISE project (EU project number NNE5-2001-297), a number of work packages have been
defined in order to deal with the SODAR. The present report is the result of the work package 1. Within
this package the objective has been to present and achieve the following:
- An accurate theoretic model that describes all the relevant aspects of the interaction of the sound
beam with the atmosphere in the level of detail needed for wind energy applications.
- Understanding of dependence of SODAR performance on hard- and software configuration.
- Quantification of principal difference between SODAR wind measurement and wind speed
measurements with cup anemometers with regard to power performance measurements.
The work associated to the above is described in the work program as follows:
a) Draw up an accurate model of the theoretic background of the SODAR. The necessary depth is
reached when the influences of various variables in the model on the accuracy of the measurement
have been assessed.
b) Describe the general algorithm SODAR uses for sending the beam and measuring the reflections.
Describe the influence of various settings on the working of the algorithm.
c) Using the data set from work package two analyse the differences between point measurements and
profile measurements.
All the above issues are addressed in the following repor
Mode Transition and Symmetry-Breaking in the Wake of a Flapping Foil
A numerical model for two-dimensional flows around a pitching foil in a viscous flow is presented. The model is numerically solved using the immersed boundary method and used to investigate the flow patterns of the foil pitching sinusoidally over a range of frequencies and amplitudes. A transition from the Karman vortex streets to the reverse Karman vortex streets are found, as the amplitudes of pitching motions increase. In the transition, the vortex streets undergo symmetry-breaking to the central lines of vortex streets. Those observations are in agreement with the previous experiment (Phys. Rev. E. 77 016308 2008). Furthermore, we examine the wake of the foils pitching with different frequencies. The transition from the Karman vortex streets to the reverse Karman vortex streets is also observed. An explanation is presented to the mechanism of the transition
Laser spectroscopy of LaS: Hyperfine structure in the B2Σ+-X2Σ+ (0,0) band
The B 2Σ +-X 2Σ + (0,0) band of LaS was studied using the technique of laser vaporization/reaction supersonic free jet expansion and laser induced fluorescence spectroscopy. The magnetic hyperfine structure caused by the 57 139La nucleus (I=7/2) was well resolved. Least-squares fit of the hyperfine transition line positions yielded a comprehensive set of rotational, spin, and hyperfine parameters for both the B 2Σ + and X 2Σ + states. The magnetic hyperfine parameters obtained were interpreted, which yielded information about the occupation of molecular orbitals giving rise to the states studied in this molecule.published_or_final_versio
Model Adaptation with Synthetic and Real Data for Semantic Dense Foggy Scene Understanding
This work addresses the problem of semantic scene understanding under dense
fog. Although considerable progress has been made in semantic scene
understanding, it is mainly related to clear-weather scenes. Extending
recognition methods to adverse weather conditions such as fog is crucial for
outdoor applications. In this paper, we propose a novel method, named
Curriculum Model Adaptation (CMAda), which gradually adapts a semantic
segmentation model from light synthetic fog to dense real fog in multiple
steps, using both synthetic and real foggy data. In addition, we present three
other main stand-alone contributions: 1) a novel method to add synthetic fog to
real, clear-weather scenes using semantic input; 2) a new fog density
estimator; 3) the Foggy Zurich dataset comprising real foggy images,
with pixel-level semantic annotations for images with dense fog. Our
experiments show that 1) our fog simulation slightly outperforms a
state-of-the-art competing simulation with respect to the task of semantic
foggy scene understanding (SFSU); 2) CMAda improves the performance of
state-of-the-art models for SFSU significantly by leveraging unlabeled real
foggy data. The datasets and code are publicly available.Comment: final version, ECCV 201
A PCP Pincer Ligand for Coordination Polymers with Versatile Chemical Reactivity: Selective Activation of CO2 Gas over CO Gas in the Solid State
A tetra(carboxylated) PCP pincer ligand has been synthesized as a building block for porous coordination polymers (PCPs). The air- and moisture-stable PCP metalloligands are rigid tetratopic linkers that are geometrically akin to ligands used in the synthesis of robust metal-organic frameworks (MOFs). Here, the design principle is demonstrated by cyclometalation with Pd(II) Cl and subsequent use of the metalloligand to prepare a crystalline 3D MOF by direct reaction with Co(II) ions and structural resolution by single crystal X-ray diffraction. The Pd-Cl groups inside the pores are accessible to post-synthetic modifications that facilitate chemical reactions previously unobserved in MOFs: a Pd-CH3 activated material undergoes rapid insertion of CO2 gas to give Pd-OC(O)CH3 at 1 atm and 298 K. However, since the material is highly selective for the adsorption of CO2 over CO, a Pd-N3 modified version resists CO insertion under the same conditions
Enhancement of Retinal Fundus Images via Pixel Color Amplification
We propose a pixel color amplification theory and family of enhancement
methods to facilitate segmentation tasks on retinal images. Our novel
re-interpretation of the image distortion model underlying dehazing theory
shows how three existing priors commonly used by the dehazing community and a
novel fourth prior are related. We utilize the theory to develop a family of
enhancement methods for retinal images, including novel methods for whole image
brightening and darkening. We show a novel derivation of the Unsharp Masking
algorithm. We evaluate the enhancement methods as a pre-processing step to a
challenging multi-task segmentation problem and show large increases in
performance on all tasks, with Dice score increases over a no-enhancement
baseline by as much as 0.491. We provide evidence that our enhancement
preprocessing is useful for unbalanced and difficult data. We show that the
enhancements can perform class balancing by composing them together.Comment: Accepted to International Conference on Image Analysis and
Recognition, ICIAR 2020 ; // Published at
https://doi.org/10.1007/978-3-030-50516-5_26 ;// CODE, SLIDES, and an
expanded/modified 20 page version https://github.com/adgaudio/ietk-re
Terahertz quantum cascade laser as local oscillator in a heterodyne receiver
Terahertz quantum cascade lasers have been investigated with respect to their performance as a local oscillator in a heterodyne receiver. The beam profile has been measured and transformed in to a close to Gaussian profile resulting in a good matching between the field patterns of the quantum cascade laser and the antenna of a superconducting hot electron bolometric mixer. Noise temperature measurements with the hot electron bolometer and a 2.5 THz quantum cascade laser yielded the same result as with a gas laser as local oscillator. (C) 2005 Optical Society of America
Non-universal minimal Z' models: present bounds and early LHC reach
We consider non-universal 'minimal' Z' models, whose additional U(1) charge
is a non-anomalous linear combination of the weak hypercharge Y, the baryon
number B and the partial lepton numbers (L_e, L_mu, L_tau), with no exotic
fermions beyond three standard families with right-handed neutrinos. We show
that the observed pattern of neutrino masses and mixing can be fully reproduced
by a gauge-invariant renormalizable Lagrangian, and flavor-changing neutral
currents in the charged lepton sector are suppressed by a GIM mechanism. We
then discuss the phenomenology of some benchmark models. The electrophilic
B-3L_e model is significantly constrained by electroweak precision tests, but
still allows to fit the hint of an excess observed by CDF in dielectrons but
not in dimuons. The muonphilic B-3L_mu model is very mildly constrained by
electroweak precision tests, so that even the very early phase of the LHC can
explore significant areas of parameter space. We also discuss the hadrophobic
L_mu-L_tau model, which has recently attracted interest in connection with some
puzzling features of cosmic ray spectra.Comment: 29 pages, 13 figure
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