Showing papers by "University of Mons published in 2019"

Magnetic iron oxide nanoparticles for drug delivery: applications and characteristics.

Abstract: Introduction: For many years, the controlled delivery of therapeutic compounds has been a matter of great interest in the field of nanomedicine. Among the wide amount of drug nanocarriers, magnetic...

Phonon coherences reveal the polaronic character of excitons in two-dimensional lead halide perovskites

Abstract: Hybrid organic–inorganic semiconductors feature complex lattice dynamics due to the ionic character of the crystal and the softness arising from non-covalent bonds between molecular moieties and the inorganic network. Here we establish that such dynamic structural complexity in a prototypical two-dimensional lead iodide perovskite gives rise to the coexistence of diverse excitonic resonances, each with a distinct degree of polaronic character. By means of high-resolution resonant impulsive stimulated Raman spectroscopy, we identify vibrational wavepacket dynamics that evolve along different configurational coordinates for distinct excitons and photocarriers. Employing density functional theory calculations, we assign the observed coherent vibrational modes to various low-frequency (≲50 cm−1) optical phonons involving motion in the lead iodide layers. We thus conclude that different excitons induce specific lattice reorganizations, which are signatures of polaronic binding. This insight into the energetic/configurational landscape involving globally neutral primary photoexcitations may be relevant to a broader class of emerging hybrid semiconductor materials. High-resolution resonant impulsive stimulated Raman spectroscopy in two-dimensional hybrid metal halide perovskites provides evidence for polaronic effects on excitons, which couple to distinct low-frequency vibrational modes of the ionic lattice.

Highly emissive excitons with reduced exchange energy in thermally activated delayed fluorescent molecules.

Abstract: The work was supported by the European Union’s Horizon 2020 research and innovation program under Grant Agreement N°. 646176 (EXTMOS project). A.P. acknowledges the financial support from the Marie Curie Fellowship (MILORD project, N°. 748042). Computational resources have been provided by the Consortium des Equipements de Calcul Intensif (CECI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Federation Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n1117545. The St Andrews team would like to thank the Leverhulme Trust (RPG-2016-047) and EPSRC (EP/P010482/1) for financial support.

Structure and evolutionary implications of the earliest (Sinemurian, Early Jurassic) dinosaur eggs and eggshells

Abstract: One of the fossil record’s most puzzling features is the absence of preserved eggs or eggshell for the first third of the known 315 million year history of amniote evolution. Our meagre understanding of the origin and evolution of calcareous eggshell and amniotic eggs in general, is largely based on Middle Jurassic to Late Cretaceous fossils. For dinosaurs, the most parsimonious inference yields a thick, hard shelled egg, so richly represented in the Late Cretaceous fossil record. Here, we show that a thin calcareous layer (≤100 µm) with interlocking units of radiating crystals (mammillae) and a thick shell membrane already characterize the oldest known amniote eggs, belonging to three coeval, but widely distributed Early Jurassic basal sauropodomorph dinosaurs. This thin shell layer strongly contrasts with the considerably thicker calcareous shells of Late Jurassic dinosaurs. Phylogenetic analyses and their Sinemurian age indicate that the thin eggshell of basal sauropodomorphs represents a major evolutionary innovation at the base of Dinosauria and that the much thicker eggshell of sauropods, theropods, and ornithischian dinosaurs evolved independently. Advanced mineralization of amniote eggshell (≥150 µm in thickness) in general occurred not earlier than Middle Jurassic and may correspond with a global trend of increase in atmospheric oxygen.

Evaluation and Management of Laryngopharyngeal Reflux Disease: State of the Art Review:

Abstract: ObjectiveTo review the current literature about the epidemiology, clinical presentation, diagnosis, and treatment of laryngopharyngeal reflux (LPR).Data SourcesPubMed, Cochrane Library, and Scopus....

Toward Commercial Polymer Fiber Bragg Grating Sensors: Review and Applications

Abstract: Interest in polymer optical fiber Bragg gratings (POFBGs) arises from the different material properties and sensing modalities brought by polymers relative to silica. Polymer fibers typically offer twice the sensitivity to temperature of conventional silica fiber and increased sensitivity to strain overall. In addition, polymer fibers have higher elastic limits and as a result a larger range of operation for physical constraints. While some polymers are effectively humidity insensitive, others present inherent humidity sensitivity. Their organic properties also allow a variety of chemical processes to create (bio)chemical sensors, with the consequences of fiber breakage in situ being less hazardous than silica. These attributes have led to the use of POFBGs for applications that remain complex using silica fibers. This review paper covers the progress toward commercialization and the increasing number of specific applications.

Deep Learning-Based Multivariate Probabilistic Forecasting for Short-Term Scheduling in Power Markets

Abstract: In the current competition framework governing the electricity sector, complex dependencies exist between electrical and market data, which complicates the decision-making procedure of energy actors These must indeed operate within a complex, uncertain environment, and consequently need to rely on accurate multivariate, multi-step ahead probabilistic predictions This paper aims to take advantage of recent breakthroughs in deep learning, while exploiting the structure of the problem to design prediction tools with tailored architectural alterations that improve their performance The method can provide prediction intervals and densities, but is here extended with the objective to generate predictive scenarios It is achieved by sampling the predicted multivariate distribution with a copula-based strategy so as to embody both temporal information and cross-variable dependencies The effectiveness of the proposed methodology is emphasized and compared with several other architectures in terms of both statistical performance and impact on the quality of decisions optimized within a dedicated stochastic optimization tool of an electricity retailer participating in short-term electricity markets

An empirical comparison of dependency network evolution in seven software packaging ecosystems

Abstract: Nearly every popular programming language comes with one or more package managers. The software packages distributed by such package managers form large software ecosystems. These packaging ecosystems contain a large number of package releases that are updated regularly and that have many dependencies to other package releases. While packaging ecosystems are extremely useful for their respective communities of developers, they face challenges related to their scale, complexity, and rate of evolution. Typical problems are backward incompatible package updates, and the risk of (transitively) depending on packages that have become obsolete or inactive. This manuscript uses the libraries.io dataset to carry out a quantitative empirical analysis of the similarities and differences between the evolution of package dependency networks for seven packaging ecosystems of varying sizes and ages: Cargo for Rust, CPAN for Perl, CRAN for R, npm for JavaScript, NuGet for the .NET platform, Packagist for PHP, and RubyGems for Ruby. We propose novel metrics to capture the growth, changeability, reusability and fragility of these dependency networks, and use these metrics to analyze and compare their evolution. We observe that the dependency networks tend to grow over time, both in size and in number of package updates, while a minority of packages are responsible for most of the package updates. The majority of packages depend on other packages, but only a small proportion of packages accounts for most of the reverse dependencies. We observe a high proportion of “fragile” packages due to a high and increasing number of transitive dependencies. These findings are instrumental for assessing the quality of a package dependency network, and improving it through dependency management tools and imposed policies.

Biodegradable UV-Blocking Films through Core–ShellLignin–Melanin Nanoparticles in Poly(butylene adipate- co -terephthalate)

Abstract: Biodegradable and renewable UV-shielding films are highly demanded to meet the increasing sustainable requirement for the environment. Lignin as a natural broad UV blocker has gained considerable a...

Room temperature conductive type metal oxide semiconductor gas sensors for NO2 detection

Abstract: Air pollution is nowadays a big issue regarding the health of human beings. Among the toxic gases emitted in the atmosphere, NO2 is the most problematic one and a lot of countries or cities want to monitor its concentration in order to be able to take measures to reduce it. Therefore, it is urgent to develop NO2 sensors with high performance, low power consumption and low cost. Several technologies have been developed for this purpose. A very popular technology is based on metal oxide semiconductor. The usual semiconductor gas sensors need to be operated at high temperature, but nowadays many efforts are put on metal oxide sensors that can work at room temperature. These sensors present many advantages: low power consumption, low manufacturing cost, as well as moderate stability and safety. However, due to the weak response to NO2 at room temperature, most semiconductor NO2 sensors need to be adapted. This review will present the main strategies and material modification methods studied so far. These include light illumination, sensitization with an organic, formation of heterojunctions, preparation of composites with 1D or 2D materials and an introduction of oxygen vacancies in high concentrations. The gas sensing mechanisms of these sensors are presented and discussed.

Consensus Paper: Experimental Neurostimulation of the Cerebellum

Abstract: The cerebellum is best known for its role in controlling motor behaviors. However, recent work supports the view that it also influences non-motor behaviors. The contribution of the cerebellum towards different brain functions is underscored by its involvement in a diverse and increasing number of neurological and neuropsychiatric conditions including ataxia, dystonia, essential tremor, Parkinson’s disease (PD), epilepsy, stroke, multiple sclerosis, autism spectrum disorders, dyslexia, attention deficit hyperactivity disorder (ADHD), and schizophrenia. Although there are no cures for these conditions, cerebellar stimulation is quickly gaining attention for symptomatic alleviation, as cerebellar circuitry has arisen as a promising target for invasive and non-invasive neuromodulation. This consensus paper brings together experts from the fields of neurophysiology, neurology, and neurosurgery to discuss recent efforts in using the cerebellum as a therapeutic intervention. We report on the most advanced techniques for manipulating cerebellar circuits in humans and animal models and define key hurdles and questions for moving forward.

Innovative Tools for Mechanobiology: Unraveling Outside-In and Inside-Out Mechanotransduction.

Abstract: Cells and tissues can sense and react to the modifications of the physico-chemical properties of the extracellular environment (ECM) through integrin-based adhesion sites and adapt their physiological response in a process called mechanotransduction. Due to their critical localization at the cell-ECM interface, transmembrane integrins are mediators of bidirectional signaling, playing a key role in « outside-in » and « inside-out » signal transduction. After presenting the basic conceptual fundamentals related to the field of mechanobiology, we review the current state-of-the-art technologies that facilitate the understanding of mechanotransduction signaling pathways. Finally, we highlight innovative technological developments that can help to advance our understanding of the molecular mechanisms involved in nuclear mechanotransduction.

Clinical outcomes of laryngopharyngeal reflux treatment: A systematic review and meta‐analysis

Abstract: Objectives To investigate the therapeutic benefit of proton pump inhibitors (PPIs) over placebo in patients with laryngopharyngeal reflux (LPR) and to analyze the epidemiological factors of heterogeneity in the literature. Methods An electronic literature search was conducted to identify articles published between 1990 and 2018 about clinical trials describing the efficiency of medical treatment(s) on LPR. First, a meta-analysis of placebo randomized controlled trials (RCTs) comparing PPIs versus placebo was conducted according to diet. The heterogeneity, response to PPIs, and evolution of clinical scores were analyzed for aggregate results. Second, a systematic review of diagnosis methods, clinical outcome of treatment, and therapeutic regimens was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Results The search identified 1,140 relevant publications, of which 72 studies met the inclusion criteria for a total of 5,781 patients. Ten RCTs were included in the meta-analysis. The combined relative risk was 1.31 in favor of PPIs and increased to 1.42 when patients did not receive diet recommendations. Randomized controlled trials were characterized by a significant heterogeneity due to discrepancies in clinical therapeutic outcomes, diagnosis methods (lack of gold standard diagnostic tools), and therapeutic scheme. The epidemiological analysis of all articles supports the existence of these discrepancies in the entire literature. In particular, many symptoms and signs commonly encountered in LPR are not assessed in the treatment effectiveness. The lack of diagnosis precision and variability of inclusion criteria particularly create bias in all reported and included articles. Conclusion This meta-analysis supports a mild superiority of PPIs over placebo and the importance of diet as additional treatment but demonstrates the heterogeneity between studies, limiting the elaboration of clear conclusions. International recommendations are proposed for the development of future trials. Laryngoscope, 129:1174-1187, 2019.

A Comparative Study of Glottal Source Estimation Techniques

Abstract: Source-tract decomposition (or glottal flow estimation) is one of the basic problems of speech processing. For this, several techniques have been proposed in the literature. However studies comparing different approaches are almost nonexistent. Besides, experiments have been systematically performed either on synthetic speech or on sustained vowels. In this study we compare three of the main representative state-of-the-art methods of glottal flow estimation: closed-phase inverse filtering, iterative and adaptive inverse filtering, and mixed-phase decomposition. These techniques are first submitted to an objective assessment test on synthetic speech signals. Their sensitivity to various factors affecting the estimation quality, as well as their robustness to noise are studied. In a second experiment, their ability to label voice quality (tensed, modal, soft) is studied on a large corpus of real connected speech. It is shown that changes of voice quality are reflected by significant modifications in glottal feature distributions. Techniques based on the mixed-phase decomposition and on a closed-phase inverse filtering process turn out to give the best results on both clean synthetic and real speech signals. On the other hand, iterative and adaptive inverse filtering is recommended in noisy environments for its high robustness.

Tuning conformation, assembly, and charge transport properties of conjugated polymers by printing flow.

Abstract: Intrachain charge transport is unique to conjugated polymers distinct from inorganic and small molecular semiconductors and is key to achieving high-performance organic electronics. Polymer backbone planarity and thin film morphology sensitively modulate intrachain charge transport. However, simple, generic nonsynthetic approaches for tuning backbone planarity and the ensuing multiscale assembly process do not exist. We first demonstrate that printing flow is capable of planarizing the originally twisted polymer backbone to substantially increase the conjugation length. This conformation change leads to a marked morphological transition from chiral, twinned domains to achiral, highly aligned morphology, hence a fourfold increase in charge carrier mobilities. We found a surprising mechanism that flow extinguishes a lyotropic twist-bend mesophase upon backbone planarization, leading to the observed morphology and electronic structure transitions.

Room-temperature NO2 gas sensors based on rGO@ZnO1-x composites: Experiments and molecular dynamics simulation

Abstract: Recently, room-temperature gas sensors have become very attractive due to the fact that they can be operated without heating, and thus simplifying the sensor design, reducing the fabrication cost, decreasing the power consumption and increasing the long-term stability. In this study, we propose a facile one-step hydrothermal method to prepare a composite of reduced graphene (rGO)/oxygen-deficient zinc oxide (ZnO1-x), which exhibits obvious room-temperature gas sensing response. X-ray diffraction, Raman and X-ray photoelectron spectroscopy demonstrate that the rGO@ZnO1-x composite is successfully synthesized and large numbers of dual donor defects, oxygen vacancy and zinc interstitial, are introduced into the composite. Field-emission scanning electron microscopy and transmission electron microscopy results reveal that many nanoscale p-n junctions are in-situ formed between ZnO nanosheets and rGO sheets. UV–vis spectra show that the light absorption of the rGO@ZnO1-x composite is red-shifted and extended to the whole visible light region in comparison. The fraction of rGO in the composites plays an important role in the sensing performance. 2.0% is the optimal proportion to obtain the best sensing properties in terms of sensitivity, response and recovery times. The rGO@ZnO1-x composite exhibits significant responses to ppb-level NO2 with white LED light stimulation at room temperature. The enhanced sensing properties can be attributed to three factors: light activation, synergistic effects between rGO and ZnO1-x, and high concentration in donor defects. Molecular Dynamics (MD) is used to quantitively simulate the adsorption process, and the results show that the incorporation of rGO decreases the adsorption energy of NO2. It means that more NO2 species would adsorb on the rGO@ZnO1-x composites, which greatly improves the sensitivity. A new gas sensing mechanism based on the MD calculated results and Langmuir adsorption model is used to explain the reason that the rGO@ZnO1-x composites have a much faster response and recovery process. In addition, the rGO@ZnO1-x sensor shows a weaker response to other interference gases.

Modelling, simulation and evaluation of ground vibration caused by rail vehicles

Abstract: There is a great need to develop rail networks over long distances and within cities as more sustainable transport options. However, noise and vibration are seen as a negative environmental consequ...

Consensus paper: Decoding the Contributions of the Cerebellum as a Time Machine. From Neurons to Clinical Applications

Abstract: Time perception is an essential element of conscious and subconscious experience, coordinating our perception and interaction with the surrounding environment. In recent years, major technological advances in the field of neuroscience have helped foster new insights into the processing of temporal information, including extending our knowledge of the role of the cerebellum as one of the key nodes in the brain for this function. This consensus paper provides a state-of-the-art picture from the experts in the field of the cerebellar research on a variety of crucial issues related to temporal processing, drawing on recent anatomical, neurophysiological, behavioral, and clinical research.The cerebellar granular layer appears especially well-suited for timing operations required to confer millisecond precision for cerebellar computations. This may be most evident in the manner the cerebellum controls the duration of the timing of agonist-antagonist EMG bursts associated with fast goal-directed voluntary movements. In concert with adaptive processes, interactions within the cerebellar cortex are sufficient to support sub-second timing. However, supra-second timing seems to require cortical and basal ganglia networks, perhaps operating in concert with cerebellum. Additionally, sensory information such as an unexpected stimulus can be forwarded to the cerebellum via the climbing fiber system, providing a temporally constrained mechanism to adjust ongoing behavior and modify future processing. Patients with cerebellar disorders exhibit impairments on a range of tasks that require precise timing, and recent evidence suggest that timing problems observed in other neurological conditions such as Parkinson's disease, essential tremor, and dystonia may reflect disrupted interactions between the basal ganglia and cerebellum.The complex concepts emerging from this consensus paper should provide a foundation for further discussion, helping identify basic research questions required to understand how the brain represents and utilizes time, as well as delineating ways in which this knowledge can help improve the lives of those with neurological conditions that disrupt this most elemental sense. The panel of experts agrees that timing control in the brain is a complex concept in whom cerebellar circuitry is deeply involved. The concept of a timing machine has now expanded to clinical disorders.

The Deterministic plus Stochastic Model of the Residual Signal and its Applications

Abstract: The modeling of speech production often relies on a source-filter approach. Although methods parameterizing the filter have nowadays reached a certain maturity, there is still a lot to be gained for several speech processing applications in finding an appropriate excitation model. This manuscript presents a Deterministic plus Stochastic Model (DSM) of the residual signal. The DSM consists of two contributions acting in two distinct spectral bands delimited by a maximum voiced frequency. Both components are extracted from an analysis performed on a speaker-dependent dataset of pitch-synchronous residual frames. The deterministic part models the low-frequency contents and arises from an orthonormal decomposition of these frames. As for the stochastic component, it is a high-frequency noise modulated both in time and frequency. Some interesting phonetic and computational properties of the DSM are also highlighted. The applicability of the DSM in two fields of speech processing is then studied. First, it is shown that incorporating the DSM vocoder in HMM-based speech synthesis enhances the delivered quality. The proposed approach turns out to significantly outperform the traditional pulse excitation and provides a quality equivalent to STRAIGHT. In a second application, the potential of glottal signatures derived from the proposed DSM is investigated for speaker identification purpose. Interestingly, these signatures are shown to lead to better recognition rates than other glottal-based methods.

Glottal Source Processing: from Analysis to Applications

Abstract: The great majority of current voice technology applications relies on acoustic features characterizing the vocal tract response, such as the widely used MFCC of LPC parameters. Nonetheless, the airflow passing through the vocal folds, and called glottal flow, is expected to exhibit a relevant complementarity. Unfortunately, glottal analysis from speech recordings requires specific and more complex processing operations, which explains why it has been generally avoided. This review gives a general overview of techniques which have been designed for glottal source processing. Starting from fundamental analysis tools of pitch tracking, glottal closure instant detection, glottal flow estimation and modelling, this paper then highlights how these solutions can be properly integrated within various voice technology applications.

Limits to Strong Coupling of Excitons in Multilayer WS2 with Collective Plasmonic Resonances

Abstract: We demonstrate the strong coupling of direct transition excitons in tungsten disulfide (WS2) with collective plasmonic resonances at room temperature. We use open plasmonic cavities formed by perio...

Host dependence of the electron affinity of molecular dopants

Abstract: Charge carriers energetics is key in electron transfer processes such as those that enable the electrical doping of organic semiconductors. In this study, we take advantage of the quantitative accuracy of embedded GW calculations to perform a series of virtual experiments that allow measuring the electron affinity of p-type dopants in different host solids. Our calculations show that the energy levels of a molecular impurity strongly depend on the host environment as a result of electrostatic intermolecular interactions. In particular, the electron affinity of a dopant impurity in a given semiconductor is found to be up to 1 eV lower than that of the pure dopant crystal. This result questions the pertinence of the electron affinity measured for pure dopants in order to predict doping efficiency in a specific host. The role of the Coulomb electron–hole interaction for the dopant-to-semiconductor charge transfer and for the release of doping-induced charges is discussed.

Causal-Anticausal Decomposition of Speech using Complex Cepstrum for Glottal Source Estimation

Abstract: Complex cepstrum is known in the literature for linearly separating causal and anticausal components. Relying on advances achieved by the Zeros of the Z-Transform (ZZT) technique, we here investigate the possibility of using complex cepstrum for glottal flow estimation on a large-scale database. Via a systematic study of the windowing effects on the deconvolution quality, we show that the complex cepstrum causal-anticausal decomposition can be effectively used for glottal flow estimation when specific windowing criteria are met. It is also shown that this complex cepstral decomposition gives similar glottal estimates as obtained with the ZZT method. However, as complex cepstrum uses FFT operations instead of requiring the factoring of high-degree polynomials, the method benefits from a much higher speed. Finally in our tests on a large corpus of real expressive speech, we show that the proposed method has the potential to be used for voice quality analysis.

The role of the cerebellum in reconstructing social action sequences: a pilot study.

Abstract: Recent research has revealed that the cerebellum plays a critical role in social reasoning and in particular in understanding false beliefs and making trait attributions. One hypothesis is that the cerebellum is responsible for the understanding of sequences of motions and actions, which may be a prerequisite for social understanding. To investigate the role of action sequencing in mentalizing, we tested patients with generalized cerebellar degenerative lesions on tests of social understanding and compared their performance with matched healthy volunteers. The tests involved understanding violations of social norms making trait and causal attributions on the basis of short behavioral sentences and generating the correct chronological order of social actions depicted in cartoons (picture sequencing task). Cerebellar patients showed clear deficits only on the picture sequencing task when generating the correct order of cartoons depicting false belief stories and showed at or close to normal performance for mechanical stories and overlearned social scripts. In addition, they performed marginally worse on trait attributions inferred from verbal behavioral descriptions. We conclude that inferring the mental state of others through understanding the correct sequences of their actions requires the support of the cerebellum.