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Evaluation of the Margin of Stability during Gait Initiation in Young Healthy Adults, Elderly Healthy Adults, and Patients with Parkinson's Disease: A Comparison of Force-Plate and Markerless Motion Capture Systems
No full textInternational audienc
Depth Separable architecture for Sentinel-5P Super-Resolution
No full textSentinel-5P (S5P) satellite provides atmospheric measurements for air quality and climate monitoring. While the S5P satellite offers rich spectral resolution, it inherits physical limitations that restricts its spatial resolution. Super-resolution (SR) techniques can overcome these limitations and enhance the spatial resolution of S5P data. In this work, we introduce a novel SR model specifically designed for S5P data that have eight spectral bands with around 500 channels for each band. Our proposed S5-DSCR model relies on Depth Separable Convolution (DSC) architecture to effectively perform spatial SR by exploiting crosschannel correlations. Quantitative evaluation demonstrates that our model outperforms existing methods for the majority of the spectral bands. This work highlights the potential of leveraging DSC architecture to address the challenges of hyperspectral SR. Our model allows for capturing fine details necessary for precise analysis and paves the way for advancements in air quality monitoring as well as remote sensing applications
Discovery of 26 new Galactic radio transients by MeerTRAP
No full textInternational audienceRadio searches for single pulses provide the opportunity to discover one-off events, fast transients and some pulsars that might otherwise be missed by conventional periodicity searches. The MeerTRAP real-time search pipeline operates commensally to observations with the MeerKAT telescope. Here, we report on 26 new Galactic radio transients, mostly rotating radio transients (RRATs) and also the detection of one RRAT and two pulsars that were independently discovered by other surveys. The dispersion measures of two of the new sources marginally exceed the Galactic contribution depending on the electron density model used. Using a simple method of fitting a Gaussian function to individual pulses, and obtaining positions of arcsecond accuracy from image-based localisations using channelised voltage data from our transient buffer, we have derived timing solutions spanning multiple years for five sources. The timing parameters imply ages of several Myr and low surface magnetic field strengths which is characteristic of RRATs. We were able to measure spin periods for eight more transients, including one source which appears to rotate every 17.5 seconds. A majority of the sources have only been seen in one observation, sometimes despite multiple return visits to the field. Some sources exhibit complex emission features like component switching and periodic microstructure
Long term monitoring of FRB~20121102 with the Nançay Radio Telescope and multi-wavelength campaigns including INTEGRAL
No full textInternational audienceThe origin(s) of Fast Radio Bursts (FRBs), mysterious radio bursts coming from extragalactic distances, remains unknown. Multi-wavelength observations are arguably the only way to answer this question unambiguously. We attempt to detect hard X-ray/soft gamma-ray counterparts to one of the most active FRB sources, FRB20121102, as well as improve understanding of burst properties in radio through a long-term monitoring campaign using the Nançay Radio Telescope (NRT). Multi-wavelength campaigns involving the International Gamma-ray Astrophysics Laboratory (INTEGRAL) satellite, the Nançay Radio Observatory, the optical telescopes at the Observatoire de Haute Provence as well as Arecibo were conducted between 2017 and 2019. In 2017, the telescopes were scheduled to observe simultaneously between Sept 24-29. We specifically used the Fast Response Enhanced CCDs for the optical observations to ensure a high time resolution. In 2019, we changed the strategy to instead conduct ToO observations on INTEGRAL and other available facilities upon positive detection triggers from the NRT. In the 2017 campaign, FRB20121102 was not in its burst activity window. We obtain a 5-sigma optical flux limit of 12 mJy ms using the GASP and a 3-sigma limit from OHP T120cm R-band image of R=22.2 mag of any potential persistent emission not associated to radio bursts. In the 2019 campaign, we have simultaneous INTEGRAL data with 11 radio bursts from the NRT and Arecibo. We obtain a 5-sigma upper limit of 2.7e-7 erg/cm2 in the 25-400 keV energy range for contemporary radio and high energy bursts, and a 5-sigma upper limit of 3.8e-11 erg/cm2 for permanent emission in the 25-100 keV energy range. In addition, we report on the regular observations from NRT between 2016-2020, which accounts for 119 additional radio bursts from FRB20121102. We present an updated fit of the periodic active window of 154+/-2 days
Assessing volatility persistence in fractional Heston models with self-exciting jumps
No full textInternational audienceWe derive a new fractional Heston model with self-exciting jumps. We study volatility persistence and demonstrate that the quadratic variation necessarily exhibits less memory than the integrated variance, which preserves the degree of long-memory of the instantaneous volatility. Focusing on realized volatility measures, we find that traditional long-memory estimators are dramatically downward biased, in particular for low-frequency intraday sampling. Conveniently, our Monte Carlo experiments reveal that some noise-robust local Whittle-type estimators offer good finite sample properties. We apply our theoretical results in a risk forecasting study and show that our frequency-domain forecasting procedure outperforms the traditional benchmark models
Abstract geometrical computation 12: generating representation of infinite countable linear orderings
No full textInternational audienceAny countable (infinite or not) linear (total) ordering can be represented by displaying all its elements on an axis in increasing order. Such a representation can be generated using only geometrical constructions based on coloured line segment extensions and rules to handle segment intersections. After a bounded time, the construction segments disappear and only the representation remains. The process starts with finitely many segments, so that unbounded acceleration effects are used to generate infinitely many segments for the representation. There is no outside machinery nor operator: any needed computation has to be carried out through the drawing. After providing some illustrative examples with ad hoc constructions, we prove our main results. One rational signal machine (bounded to use only rational coordinates) can generate the representation of any decidable linear ordering (i.e. the order between two elements is decidable by a Turing machine). In the general case, there is a signal machine able to generate the representation of any countable linear ordering (encoded in a real number)
GLOBAL STEIN THEOREM ON HARDY SPACES
No full textLet f be an integrable function which has integral 0 on R n. What is the largest condition on |f | that guarantees that f is in the Hardy space H 1 (R n)? When f is compactly supported, it is well-known that it is necessary and sufficient that |f | belongs to L log L(R n). We are interested here in conditions at ∞. We do so for H 1 (R n), as well as for the Hardy space H log (R n) which appears in the study of pointwise products of functions in H 1 (R n) and in its dual BMO
Bivariate P -and Q-polynomial structures of the association schemes based on attenuated spaces
No full textInternational audienceThe bivariate P -and Q-polynomial structures of association schemes based on attenuated spaces are examined using recurrence and difference relations of the bivariate polynomials which form the eigenvalues of the scheme. These bispectral properties are obtained from contiguity relations of univariate dual q-Hahn and affine q-Krawtchouk polynomials. The bispectral algebra associated to the bivariate polynomials is investigated, as well as the subconstituent algebra of the schemes. The properties of the schemes are compared to those of the non-binary Johnson schemes through a limit
Initial Trace of Positive Solutions of Some Diffusion Equations with Absorption
No full textInternational audienceThis chapter presents the complete theory of the initial trace of positive solutions the semilinear heat equation with power absorption
