260 results on '"J. Proust"'
Search Results
152. Far-field mapping and efficient beaming of second harmonic by a plasmonic metagrating.
- Author
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Verneuil A, Di Francescantonio A, Zilli A, Proust J, Béal J, Petti D, Finazzi M, Celebrano M, and Baudrion AL
- Abstract
We study numerically and experimentally the second-harmonic generation (SHG) from rectangular metagratings of V-shaped gold nanoantennas. We show that by carefully engineering the array pitch to steer the diffraction orders toward the single antenna emission, the extracted signal is maximized. This enhancement is attributed to the angular overlap between the radiation pattern and array factor and is comparable to the improvement yielded by the coupling of surface lattice resonances (SLRs) with local modes. Moreover, we demonstrate a simple technique to experimentally reconstruct the emission diagram of an antenna from measurements of the collective grating response as a function of the excitation angle. Excellent agreement is obtained with simulations when the sample is immersed either in air or in water, which is crucial in view of future sensing application. Thanks to the high signal-to-noise ratio and low dependence on the statistical particle dispersity, this method constitutes an effective alternative to back-focal plane imaging when very weak signals such as SHG are involved., Competing Interests: Conflict of interest: The authors state no conflict of interest., (© 2024 the author(s), published by De Gruyter, Berlin/Boston.)
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- 2024
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153. Hypersomnia in anti-glutamic acid decarboxylase 65 (GAD65) associated neurological syndromes: A pilot study.
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Jeantin L, Gales A, Berzero G, Leu S, Proust J, Giry M, Valyraki NE, Birzu C, Alentorn A, Vidailhet M, Psimaras D, and Arnulf I
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- Adult, Humans, Pilot Projects, Sleepiness, Quality of Life, Disorders of Excessive Somnolence etiology, Disorders of Excessive Somnolence diagnosis, Carboxy-Lyases
- Abstract
Background and Purpose: Despite their detrimental impact on the quality of life in autoimmune encephalitis, sleep disorders have not been investigated in anti-glutamic acid decarboxylase (GAD65) associated neurological syndromes., Methods: Six consecutive adult patients diagnosed with anti-GAD65-associated neurological syndromes (four with limbic encephalitis and two with stiff-person syndrome) and 12 healthy controls were enrolled. Participants underwent sleep interviews and sleep studies including night-time video-polysomnography, followed by five daytime multiple sleep latency tests (MSLTs, to assess propensity to fall asleep) and an 18 h bed rest polysomnography (to assess excessive sleep need)., Results: Patients reported the need for daily naps and that their cognition and quality of life were altered by sleepiness, but they had normal scores on the Epworth sleepiness scale. Compared with controls, sleep latencies during the MSLT were shorter in the patient group (median 5.8 min, interquartile range [IQR] 4.5, 6.0 vs. 17.7 min, IQR 16.3, 19.7, p = 0.001), and the arousal index was reduced (2.5/h, IQR 2.3, 3.0 vs. 22.3/h, IQR 13.8, 30.0, p = 0.002), although total sleep time was similar between groups (621 min, IQR 464, 651 vs. 542.5 min, IQR 499, 582, p = 0.51). Remarkably, all six patients had MSLT latencies ≤8 min, indicating severe sleepiness. No parasomnia or sleep-disordered breathing was detected., Conclusion: Central hypersomnia is a relevant characteristic of anti-GAD65-associated neurological syndromes., (© 2023 The Authors. European Journal of Neurology published by John Wiley & Sons Ltd on behalf of European Academy of Neurology.)
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- 2024
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154. Plasmonic-Enhanced Tunable Near-Infrared Photoresponse for Narrowband Organic Photodetectors.
- Author
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Zhao Y, Chen N, Deng B, Wu L, Wang S, Grandidier B, Proust J, Plain J, and Xu T
- Abstract
Near-infrared (NIR) narrowband organic photodetectors (OPDs) can be essential building blocks for emerging applications including wireless optical communication and light detection, but further improvement of their performances remains to be a great challenge. Herein, a light manipulation strategy combining solution-processable gold nanorings (AuNRs)-based hole transporting layer (HTL) and an optical microcavity is proposed to achieve high-performance NIR narrowband OPDs. Optical microcavities with a Fabry-Pérot resonator structure, guided by theoretical simulation, are coupled with PM6:BTP-eC9-based OPDs to exhibit highly tunable NIR selectivity. The further integration of AuNRs array with NIR-customized localized surface plasmon resonance in the HTL of the NIR narrowband OPDs enables evident NIR absorption enhancement, yielding a specific detectivity exceeding 10
13 Jones (1.5 × 1012 Jones, calculated from noise spectral density) at 820 nm, along with a finely selective photoresponse (full width at half-maximum of 80 nm) and a 3-fold increase in photocurrent intensity. Finally, the practical application of our OPDs is demonstrated in an NIR communication system. These results reveal the great potential of an appropriate optical design for developing highly performing NIR narrowband OPDs.- Published
- 2023
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155. Attention and Free Will in Experimental Psychology: An Unexpected Analysis of Voluntary Action by William James and Theodule Ribot.
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Proust J
- Subjects
- Humans, History, 19th Century, History, 20th Century, Personal Autonomy, Consciousness, Psychology history, Psychology, Experimental history
- Abstract
This article aims to highlight the difficulties encountered by the experimental psychology promoted by Ribot, at the end of the nineteenth century up until the beginning of the twentieth century, with regard to the question of free will as part of his analysis of voluntary attention. It also aims to shed some light on William James's possible role in Ribot's subtle change of opinion in regards to the power of attention, as a mental effort somehow revealing the possibility of a top-down voluntary activity. In most of Ribot's work, at first glance, the will is understood as a determined product of our idiosyncratic character, of our affective and physiological tendencies-rather than as an autonomous faculty of self-determination. But what might look like Ribot's commitment to determinism calls for some nuance. Some uses of the term "voluntary" in his work, particularly to describe the phenomenon of attention, seem to refer to a form of free will looking a lot more like an autonomous faculty than like a mere illusion induced by an epiphenomenal conscious state. We end the paper with remarks about the current state of studies of consciousness and voluntary action in relation to Ribot and James's accounts of attention and will., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)
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- 2023
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156. Memory Monitoring and Control in Japanese and German Preschoolers.
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Kim S, Senju A, Sodian B, Paulus M, Itakura S, Okuno A, Ueno M, and Proust J
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- Child, Child, Preschool, Humans, Bayes Theorem, East Asian People, Mental Recall, Schools, Metacognition, Memory
- Abstract
Prior studies explored the early development of memory monitoring and control. However, little work has examined cross-cultural similarities and differences in metacognitive development in early childhood. In the present research, we investigated a total of 100 Japanese and German preschool-aged children's memory monitoring and control in a visual perception task. After seeing picture items, some of which were repeated, children were presented with picture pairs, one of which had been presented earlier and the other was a novel item. They then were asked to identify the previously presented picture. Children were also asked to evaluate their confidence about their selection, and to sort the responses to be used for being awarded with a prize at the end of the test. Both groups similarly expressed more confidence in the accurately remembered items than in the inaccurately remembered items, and their sorting decision was based on their subjective confidence. Japanese children's sorting more closely corresponded to memory accuracy than German children's sorting, however. These findings were further confirmed by a hierarchical Bayesian estimation of metacognitive efficiency. The present findings therefore suggest that early memory monitoring and control have both culturally similar and diverse aspects. The findings are discussed in light of broader sociocultural influences on metacognition., (© 2021. The Psychonomic Society, Inc.)
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- 2023
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157. Curiosity as a metacognitive feeling.
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Goupil L and Proust J
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- Animals, Humans, Child, Preschool, Exploratory Behavior, Learning, Emotions, Communication, Metacognition
- Abstract
Curious information-seeking is known to be a key driver for learning, but characterizing this important psychological phenomenon remains a challenge. In this article, we argue that solving this challenge requires qualifying the relationships between metacognition and curiosity. The idea that curiosity is a metacognitive competence has been resisted: researchers have assumed both that young children and non-human animals can be genuinely curious, and that metacognition requires conceptual and culturally situated resources that are unavailable to young children and non-human animals. Here, we argue that this resistance is unwarranted given accumulating evidence that metacognition can be deployed procedurally, and we defend the view that curiosity is a metacognitive feeling. Our metacognitive view singles out two monitoring steps as a triggering condition for curiosity: evaluating one's own informational needs, and predicting the likelihood that explorations of the proximate environment afford significant information gains. We review empirical evidence and computational models of curiosity, and show that they fit well with this metacognitive account, while on the contrary, they remain difficult to explain by a competing account according to which curiosity is a basic attitude of questioning. Finally, we propose a new way to construe the relationships between curiosity and the human-specific communicative practice of questioning, discuss the issue of how children may learn to express their curiosity through interactions with others, and conclude by briefly exploring the implications of our proposal for educational practices., Competing Interests: Declaration of Competing Interest None., (Copyright © 2022 Elsevier B.V. All rights reserved.)
- Published
- 2023
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158. Stabilization of Copper-Based Biochips with Alumina for Biosensing Application.
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Beydoun N, Niberon Y, Arnaud L, Proust J, Nomenyo K, Zeng S, Lerondel G, and Bruyant A
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- Aluminum Oxide, Copper, Surface Plasmon Resonance methods, Gold, Biosensing Techniques methods
- Abstract
Surface plasmon resonance devices typically rely on the use of gold-coated surfaces, but the use of more abundant metals is desirable for the long-term development of plasmonic biochips. As a substitute for gold, thin copper films have been deposited on glass coverslips by thermal evaporation. As expected, these films immersed in a water solution initially exhibit an intense plasmonic resonance comparable to gold. However, without protection, an angle-resolved optical analysis shows a rapid degradation of the copper, characterized by a continuous angular shift of the plasmonic resonance curve. We show that copper films protected with a thin layer of aluminum oxide of a few nanometers can limit the oxidation rate for a sufficient time to perform some standard measurements. As the process is simple and compatible with the current biochip production technique, such an approach could pave the way for the production of alternative and more sustainable biochips.
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- 2022
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159. Metacognition and mindreading in young children: A cross-cultural study.
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Kim S, Sodian B, Paulus M, Senju A, Okuno A, Ueno M, Itakura S, and Proust J
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- Child, Child, Preschool, Communication, Deception, Humans, Cross-Cultural Comparison, Metacognition
- Abstract
Prior studies document cross cultural variation in the developmental onset of mindreading. In particular, Japanese children are reported to pass a standard false belief task later than children from Western countries. By contrast, we know little about cross-cultural variation in young children's metacognitive abilities. Moreover, one prominent theoretical discussion in developmental psychology focuses on the relation between metacognition and mindreading. Here we investigated the relation between mindreading and metacognition (both implicit and explicit) by testing 4-year-old Japanese and German children. We found no difference in metacognition between the two cultural groups. By contrast, Japanese children showed lower performance than German children replicating cultural differences in mindreading. Finally, metacognition and mindreading were not related in either group. We discuss the findings in light of the existing theoretical accounts of the relation between metacognition and mindreading., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2020
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160. 12- and 24-Month-Old Infants' Search Behavior Under Informational Uncertainty.
- Author
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Kim S, Sodian B, and Proust J
- Abstract
Infants register and react to informational uncertainty in the environment. They also form expectations about the probability of future events as well as update the expectation according to changes in the environment. A novel line of research has started to investigate infants' and toddlers' behavior under uncertainty. By combining these research areas, the present research investigated 12- and 24-month-old infants' searching behaviors under varying degree of informational uncertainty. An object was hidden in one of three possible locations and probabilistic information about the hiding location was manipulated across trials. Infants' time delay in search initiation for a hidden object linearly increased across the level of informational uncertainty. Infants' successful searching also varied according to probabilistic information. The findings suggest that infants modulate their behaviors based on probabilistic information. We discuss the possibility that infants' behavioral reaction to the environmental uncertainty constitutes the basis for the development of subjective uncertainty., (Copyright © 2020 Kim, Sodian and Proust.)
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- 2020
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161. Large-Scale and Low-Cost Fabrication of Silicon Mie Resonators.
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Chaâbani W, Proust J, Movsesyan A, Béal J, Baudrion AL, Adam PM, Chehaidar A, and Plain J
- Abstract
High index dielectric nanoparticles have been proposed for many different applications. However, widespread utilization in practice also requires large-scale production methods for crystalline silicon nanoparticles, with engineered optical properties in a low-cost manner. Here, we demonstrate a facile, low-cost, and large-scale fabrication method of crystalline silicon colloidal Mie resonators in water, using a blender. The obtained nanoparticles are polydisperse with an almost spherical shape and the diameters controlled in the range 100-200 nm by a centrifugation process. Then the size distribution of silicon nanoparticles enables broad extinction from UV to near-infrared, confirmed by Mie theory when considering the size distribution in the calculations. Thanks to photolithographic and drop-cast deposition techniques to locate the position on a substrate of the colloidal nanoparticles, we experimentally demonstrate that the individual silicon nanoresonators show strong electric and magnetic Mie resonances in the visible range.
- Published
- 2019
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162. Detecting a Zeptogram of Pyridine with a Hybrid Plasmonic-Photonic Nanosensor.
- Author
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Proust J, Martin J, Gérard D, Bijeon JL, and Plain J
- Subjects
- Limit of Detection, Nanotechnology instrumentation, Photons, Pyridines analysis, Surface Plasmon Resonance instrumentation
- Abstract
Thanks to their small sensing volume, nanosensors based on localized surface plasmon resonances (LSPR) allow the detection of minute amounts of analytes, down to the single-molecule limit. However, the detected analytes are often large molecules, such as proteins. The detection of small molecules remains largely unexplored. Here, we use a hybrid photonic-plasmonic nanosensor to detect a small target molecule (pyridine). The sensor's design is based on a dielectric photonic microstructure acting as an antenna, which efficiently funnels light toward a plasmonic transducer and enhances the detection efficiency. This sensor exhibits a limit of detection as small as 10
-14 mol L-1 . Using a calibration procedure based on electrodynamical numerical simulations, we compute the number of detected molecules. This yields a limit of detection in mass of 4 zeptograms (1 zg = 10-21 g), a record value for plasmonic molecular sensors. Our system can hence be seen as an optical molecular weighing scale, enabling room temperature detection of mass at the zeptogram scale.- Published
- 2019
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163. An ERP study on metacognitive monitoring processes in children.
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Tsalas NRH, Müller BCN, Meinhardt J, Proust J, Paulus M, and Sodian B
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- Adolescent, Child, Cues, Female, Humans, Male, Mental Recall physiology, Evoked Potentials physiology, Judgment physiology, Learning physiology, Metacognition physiology
- Abstract
Little is known about what exactly differentiates metacognitive processes from ordinary cognitive processes particularly early in development, and the underlying developmental aspects. To examine the time-course of metacognition, the present study investigated the neural underpinnings of judgments of learning (JoLs) and compared them with control judgments, using an event-related potentials (ERP) design. During ERP recording, children age seven to eight were presented with cue-target picture pairs and instructed to learn these pairs. After each pair, they either had to make a JoL (assess the likelihood of remembering the target when only presented with the cue) or a colour judgment (indicate whether the colour yellow had been present in one of the two pictures presented earlier). Results revealed a late slow wave divergence maximal pronounced from 550 ms to 950 ms post-stimulus that distinguished between JOLs and colour judgments. Over centro-parietal areas, JoLs showed a more negative going slow wave compared to the colour judgments, and this pattern was independent of performance. The results are in support of theories that assume a distinction between metacognitive and cognitive processes., (Copyright © 2018 Elsevier B.V. All rights reserved.)
- Published
- 2018
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164. Selective learning and teaching among Japanese and German children.
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Kim S, Paulus M, Sodian B, Itakura S, Ueno M, Senju A, and Proust J
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- Child, Child, Preschool, Choice Behavior, Cross-Cultural Comparison, Female, Humans, Male, Psychological Tests, Psychology, Child, Child Behavior psychology, Culture, Learning, Social Behavior
- Abstract
Despite an increasing number of studies demonstrating that young children selectively learn from others, and a few studies of children's selective teaching, the evidence almost exclusively comes from Western cultures, and cross-cultural comparison in this line of work is very rare. In the present research, we investigated Japanese and German children's selective learning and teaching abilities. We found clear cultural differences. Japanese children were better at selectively teaching an ignorant person over a knowledgeable person than at selectively learning from knowledgeable others. By contrast, German children were better at choosing to learn from a knowledgeable rather than from an ignorant person than at selectively teaching ignorant others. The present findings suggest that the development of human learning and teaching, especially the tendency to take into account others' knowledge status, is strongly affected by cultural background. (PsycINFO Database Record, ((c) 2018 APA, all rights reserved).)
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- 2018
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165. Neural correlates of judgments of learning - An ERP study on metacognition.
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Müller BCN, Tsalas NRH, van Schie HT, Meinhardt J, Proust J, Sodian B, and Paulus M
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- Adolescent, Adult, Cues, Electroencephalography, Evoked Potentials, Female, Humans, Male, Memory physiology, Neuropsychological Tests, Visual Perception physiology, Young Adult, Brain physiology, Judgment physiology, Learning physiology, Metacognition physiology
- Abstract
Metacognitive assessment of performance has been revealed to be one of the most powerful predictors of human learning success and academic achievement. Yet, little is known about the functional nature of cognitive processes supporting judgments of learning (JOLs). The present study investigated the neural underpinnings of JOLs, using event-related brain potentials. Participants were presented with picture pairs and instructed to learn these pairs. After each pair, participants received a task cue, which instructed them to make a JOL (the likelihood of remembering the target when only presented with the cue) or to make a control judgment. Results revealed that JOLs were accompanied by a positive slow wave over medial frontal areas and a bilateral negative slow wave over occipital areas between 350ms and 700ms following the task cue. The results are discussed with respect to recent accounts on the neural correlates of judgments of learning., (Copyright © 2016 Elsevier B.V. All rights reserved.)
- Published
- 2016
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166. Social influence on metacognitive evaluations: The power of nonverbal cues.
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Eskenazi T, Montalan B, Jacquot A, Proust J, Grèzes J, and Conty L
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- Adult, Analysis of Variance, Choice Behavior, Female, Humans, Male, Orientation physiology, ROC Curve, Reaction Time physiology, Young Adult, Attention, Cognition physiology, Cues, Social Perception, Visual Perception physiology
- Abstract
Metacognitive evaluations refer to the processes by which people assess their own cognitive operations with respect to their current goal. Little is known about whether this process is susceptible to social influence. Here we investigate whether nonverbal social signals spontaneously influence metacognitive evaluations. Participants performed a two-alternative forced-choice task, which was followed by a face randomly gazing towards or away from the response chosen by the participant. Participants then provided a metacognitive evaluation of their response by rating their confidence in their answer. In Experiment 1, the participants were told that the gaze direction was irrelevant to the task purpose and were advised to ignore it. The results revealed an effect of implicit social information on confidence ratings even though the gaze direction was random and therefore unreliable for task purposes. In addition, nonsocial cues (car) did not elicit this effect. In Experiment 2, the participants were led to believe that cue direction (face or car) reflected a previous participant's response to the same question-that is, the social information provided by the cue was made explicit, yet still objectively unreliable for the task. The results showed a similar social influence on confidence ratings, observed with both cues (car and face) but with an increased magnitude relative to Experiment 1. We additionally showed in Experiment 2 that social information impaired metacognitive accuracy. Together our results strongly suggest an involuntary susceptibility of metacognitive evaluations to nonverbal social information, even when it is implicit (Experiment 1) and unreliable (Experiments 1 and 2).
- Published
- 2016
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167. All-Dielectric Colored Metasurfaces with Silicon Mie Resonators.
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Proust J, Bedu F, Gallas B, Ozerov I, and Bonod N
- Abstract
The photonic resonances hosted by nanostructures provide vivid colors that can be used as color filters instead of organic colors and pigments in photodetectors and printing technology. Metallic nanostructures have been widely studied due to their ability to sustain surface plasmons that resonantly interact with light. Most of the metallic nanoparticles behave as point-like electric multipoles. However, the needs of an another degree of freedom to tune the color of the photonic nanostructure together with the use of a reliable and cost-effective material are growing. Here, we report a technique to imprint colored images based on silicon nanoparticles that host low-order electric and magnetic Mie resonances. The interplay between the electric and magnetic resonances leads to a large palette of colors. This all-dielectric fabrication technique offers the advantage to use cost-effective, reliable, and sustainable materials to provide vivid color spanning the whole visible spectrum. The interest and potential of this all-dielectric printing technique are highlighted by reproducing at a micrometer scale a Mondrian painting.
- Published
- 2016
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168. All-Dielectric Silicon Nanogap Antennas To Enhance the Fluorescence of Single Molecules.
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Regmi R, Berthelot J, Winkler PM, Mivelle M, Proust J, Bedu F, Ozerov I, Begou T, Lumeau J, Rigneault H, García-Parajó MF, Bidault S, Wenger J, and Bonod N
- Abstract
Plasmonic antennas have a profound impact on nanophotonics as they provide efficient means to manipulate light and enhance light-matter interactions at the nanoscale. However, the large absorption losses found in metals can severely limit the plasmonic applications in the visible spectral range. Here, we demonstrate the effectiveness of an alternative approach using all-dielectric nanoantennas based on silicon dimers to enhance the fluorescence detection of single molecules. The silicon antenna design is optimized to confine the near-field intensity in the 20 nm nanogap and reach a 270-fold fluorescence enhancement in a nanoscale volume of λ(3)/1800 with dielectric materials only. Our conclusions are assessed by combining polarization resolved optical spectroscopy of individual antennas, scanning electron microscopy, numerical simulations, fluorescence lifetime measurements, fluorescence burst analysis, and fluorescence correlation spectroscopy. This work demonstrates that all-silicon nanoantennas are a valid alternative to plasmonic devices for enhanced single molecule fluorescence sensing, with the additional key advantages of reduced nonradiative quenching, negligible heat generation, cost-efficiency, and complementary metal-oxide-semiconductor (CMOS) compatibility.
- Published
- 2016
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169. Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the visible spectrum.
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Proust J, Fehrembach AL, Bedu F, Ozerov I, and Bonod N
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Light reflection occuring at the surface of silicon wafers is drastically diminished by etching square pillars of height 110 nm and width 140 nm separated by a 100 nm gap distance in a square lattice. The design of the nanostructure is optimized to widen the spectral tolerance of the antireflective coatings over the visible spectrum for both fundamental polarizations. Angle and polarized resolved optical measurements report a light reflection remaining under 5% when averaged in the visible spectrum for both polarizations in a wide angular range. Light reflection remains almost insensitive to the light polarization even in oblique incidence.
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- 2016
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170. The Evolution of Primate Communication and Metacommunication.
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Proust J
- Abstract
Against the prior view that primate communication is based only on signal decoding, comparative evidence suggests that primates are able, no less than humans, to intentionally perform or understand impulsive or habitual communicational actions with a structured evaluative nonconceptual content. These signals convey an affordance-sensing that immediately motivates conspecifics to act. Although humans have access to a strategic form of propositional communication adapted to teaching and persuasion, they share with nonhuman primates the capacity to communicate in impulsive or habitual ways. They are also similarly able to monitor fluency, informativeness and relevance of messages or signals through nonconceptual cues.
- Published
- 2016
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171. Young Children's Sensitivity to Their Own Ignorance in Informing Others.
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Kim S, Paulus M, Sodian B, and Proust J
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- Child, Decision Making, Female, Gestures, Humans, Male, Task Performance and Analysis, Uncertainty, Information Dissemination, Knowledge
- Abstract
Prior research suggests that young children selectively inform others depending on others' knowledge states. Yet, little is known whether children selectively inform others depending on their own knowledge states. To explore this issue, we manipulated 3- to 4-year-old children's knowledge about the content of a box and assessed the impact on their decisions to inform another person. Moreover, we assessed the presence of uncertainty gestures while they inform another person in light of the suggestions that children's gestures reflect early developing, perhaps transient, epistemic sensitivity. Finally, we compared children's performance in the informing context to their explicit verbal judgment of their knowledge states to further confirm the existence of a performance gap between the two tasks. In their decisions to inform, children tend to accurately assess their ignorance, whereas they tend to overestimate their own knowledge states when asked to explicitly report them. Moreover, children display different levels of uncertainty gestures depending on the varying degrees of their informational access. These findings suggest that children's implicit awareness of their own ignorance may be facilitated in a social, communicative context.
- Published
- 2016
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172. Procedural Metacognition and False Belief Understanding in 3- to 5-Year-Old Children.
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Bernard S, Proust J, and Clément F
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- Adult, Anticipation, Psychological, Child, Preschool, Concept Formation, Discrimination, Psychological, Female, Humans, Male, Memory, Short-Term, Middle Aged, Pattern Recognition, Visual, Theory of Mind, Verbal Behavior, Young Adult, Choice Behavior, Metacognition, Psychology, Child, Uncertainty
- Abstract
Some studies, so far limited in number, suggest the existence of procedural metacognition in young children, that is, the practical capacity to monitor and control one's own cognitive activity in a given task. The link between procedural metacognition and false belief understanding is currently under theoretical discussion. If data with primates seem to indicate that procedural metacognition and false belief understanding are not related, no study in developmental psychology has investigated this relation in young children. The present paper aims, first, to supplement the findings concerning young children's abilities to monitor and control their uncertainty (procedural metacognition) and, second, to explore the relation between procedural metacognition and false belief understanding. To examine this, 82 3- to 5-year-old children were presented with an opt-out task and with 3 false belief tasks. Results show that children can rely on procedural metacognition to evaluate their perceptual access to information, and that success in false belief tasks does not seem related to success in the task we used to evaluate procedural metacognition. These results are coherent with a procedural view of metacognition, and are discussed in the light of recent data from primatology and developmental psychology.
- Published
- 2015
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173. Source unreliability decreases but does not cancel the impact of social information on metacognitive evaluations.
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Jacquot A, Eskenazi T, Sales-Wuillemin E, Montalan B, Proust J, Grèzes J, and Conty L
- Abstract
Through metacognitive evaluations, individuals assess their own cognitive operations with respect to their current goals. We have previously shown that non-verbal social cues spontaneously influence these evaluations, even when the cues are unreliable. Here, we explore whether a belief about the reliability of the source can modulate this form of social impact. Participants performed a two-alternative forced choice task that varied in difficulty. The task was followed by a video of a person who was presented as being either competent or incompetent at performing the task. That person provided random feedback to the participant through facial expressions indicating agreement, disagreement or uncertainty. Participants then provided a metacognitive evaluation by rating their confidence in their answer. Results revealed that participants' confidence was higher following agreements. Interestingly, this effect was merely reduced but not canceled for the incompetent individual, even though participants were able to perceive the individual's incompetence. Moreover, perceived agreement induced zygomaticus activity, but only when the feedback was provided for difficult trials by the competent individual. This last result strongly suggests that people implicitly appraise the relevance of social feedback with respect to their current goal. Together, our findings suggest that people always integrate social agreement into their metacognitive evaluations, even when epistemic vigilance mechanisms alert them to the risk of being misinformed.
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- 2015
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174. Four- to Six-Year-Old Children's Sensitivity to Reliability Versus Consensus in the Endorsement of Object Labels.
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Bernard S, Proust J, and Clément F
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Recent studies have demonstrated that young children use past reliability and consensus to endorse object labels. Until now, no study has investigated how children weigh these two cues when they are in conflict. The two experiments reported here were designed to explore whether any initial preference for information provided by a consensual group would be influenced by the group's subsequent unreliability. The results show that 4- and 5-year-old children were more likely to endorse labels provided by an unreliable but consensual group than the labels provided by a reliable dissenter. Six-year-olds displayed the reverse pattern. The article concludes by discussing the methodological implications of the two experiments and the developmental trajectory regarding the way children weigh consensuality versus reliability., (© 2015 The Authors. Child Development © 2015 Society for Research in Child Development, Inc.)
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- 2015
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175. Reversed shoulder arthroplasty with inversed bearing materials: 2-year clinical and radiographic results in 101 patients.
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Irlenbusch U, Kääb MJ, Kohut G, Proust J, Reuther F, and Joudet T
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- Aged, Aged, 80 and over, Arthroplasty, Replacement instrumentation, Biocompatible Materials, Chromium Alloys, Female, Humans, Male, Polyethylene, Prospective Studies, Prosthesis Design, Prosthesis Failure, Radiography, Shoulder Joint diagnostic imaging, Treatment Outcome, Arthroplasty, Replacement methods, Joint Prosthesis, Shoulder Joint surgery
- Abstract
Introduction: This study documents 2-year clinical and radiographic results following reversed total shoulder arthroplasty using a novel prosthesis with inverted bearing materials (polyethylene glenoid; metal humeral component). This design was intended to avoid massive PE abrasion on the humeral side. Therefore, we predicted a lack of subsequent osteolysis-induced exacerbation of scapular notching, and because of other design features and modified operating technique a reduced notching rate., Materials and Methods: An ongoing, prospective, international, multicenter study of patients implanted with a novel prosthesis at six European centers. The current analysis presents 2-year follow-up data (patients operated between December 2007 and July 2009). Clinical evaluation tools comprised the Constant-Murley score (CS), the American Shoulder and Elbow Surgeon score, range of motion, and a visual analog scale to assess pain and satisfaction. Radiographs were evaluated for notching and radiolucent lines. Any complications were recorded., Results: In total, 113 prostheses (113 patients) with a mean follow-up of 27.6 (±3.6) months were analyzed. CS increased from 22.5 (±13.7) to 65.3 (±14.9) points (p = 0.06). Inferior scapular notching (only grade 1 and 2) was identified in 20.5 % of patients, with no signs of PE-induced osteolysis. 4.4 % of patients experienced an implant-related complication., Conclusions: Inversion of the materials led to another type of notching with no signs of PE-induced osteolysis and no increase in the risk of short-term complications. Clinical results were comparable with other prostheses. Mid- to long-term results are required before any firm conclusions on clinical outcome and survival can be drawn.
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- 2015
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176. Markers of metabolic and cardiovascular health in adults: Comparative analysis of DEXA-based body composition components and BMI categories.
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Lang PO, Trivalle C, Vogel T, Proust J, and Papazian JP
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- Aged, Biomarkers, Forecasting, Humans, Male, Middle Aged, Nutritional Status, Overweight, Body Composition, Body Mass Index, Cardiovascular Diseases diagnosis, Health Status Indicators, Metabolic Syndrome diagnosis
- Abstract
Objectives: To investigate how body composition components fit body mass index (BMI) categories and whether they could be considered as markers of metabolic and cardiovascular health., Design: Prospective study., Setting: A center for preventive medicine., Participants: Six hundred and sixteen consecutive outpatients: mean age of 56.0±10.0 years; 74.6% aged ≥50 years and 61.4% were females., Measurements: Fat mass (FM) and muscle mass (MM) were obtained by dual energy X-ray absorptiometry analyses. Metabolically unhealthy individuals were defined as people with biological features of dyslipidemia, hyperuricemia, diabetes, and/or hepatitis steatosis. Documented hypertension and/or atherosclerosis of one major artery, at least, defined individuals with cardiovascular complications., Results: According to BMI categories, 45.8% of the sample was of normal weight, while 19.2% and 16.5% were classified as overweight and obese. A total of 78.0% and 86.3% of overweight and obese individuals were metabolically unhealthy respectively, 46.8% and 52.6% of subjects classified into normal and underweight BMI categories were also diagnosed. Cardiovascular complications mainly concerned the two highest BMI groups (78.2%). In multifactorial analyses the overweight and obese BMI categories were predictive of health outcomes [respectively, odds ratio (OR)=8.05, 95% confidence interval (CI): 4.23-12.07 and 5.74, 95% CI: 3.41-8.98]. FM and MM indexes were significantly associated with metabolic (OR=1.30, 95% CI: 1.19-1.47; and 0.84, 95% CI: 0.78-0.91) and cardiovascular (OR=1.22, 95% CI: 1.13-1.32; and 0.72, 95% CI: 0.65-0.80) health respectively, and FM/MM (respectively, OR=15.45, 95% CI: 11.77-20.17; and 16.61, 95% CI: 10.49-21.33) as well., Conclusion: Our findings suggest that FM and MM readouts are important measurements of nutritional status and they extend the analysis of its impact on health outcomes to all BMI categories. Moreover, they highlight the interest of measuring body composition in medical check-ups to predict metabolic and cardiovascular diseases., (Copyright © 2014 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.)
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- 2015
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177. Determination of Cutoff Values for DEXA-Based Body Composition Measurements for Determining Metabolic and Cardiovascular Health.
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Lang PO, Trivalle C, Vogel T, Proust J, Papazyan JP, and Dramé M
- Abstract
The two components of the body weight (i.e., fat mass and muscle mass) appeared to be of high interest to consider in predicting metabolic health related risks. We aimed to determine cutoff values for fat mass index (FMI) and muscle mass index (MMI), FM/MM, and BMI for metabolic and cardiovascular health. This study was a cross-sectional analysis study conducted in a center of preventive medicine. It included 616 consecutive outpatients: mean age was 56.0±10.0 years (74.6% aged ≥50), and 61.4% were female. Fat and muscle mass were obtained with dual energy X-ray absorptiometry scan analyses. Metabolically unhealthy individuals were defined as people with biological features of dyslipidemia, hyperuricemia, diabetes, and/or hepatitis steatosis. Documented hypertension and/or atherosclerosis of at least one major artery defined individuals with cardiovascular complications. Receiver-operating characteristic curve analysis revealed that the cutoff values for MMI, FMI, and FM/MM were respectively 18.8kg/m(2) (sensitivity [Se]=58%; specificity [Sp]=59%), 5.5kg/m(2) (Se=61%; Sp=62%), and 0.31 (Se=62%; Sp=62%) in men; and 14.1kg/m(2) (Se=52%; Sp=54%), 5.5kg/m(2) (Se=65%; Sp=67%), 0.39 (Se=73%; Sp=73%) in women for predicting metabolic health. Values were 19.3kg/m(2) (Se=58%; Sp=59%), 7.0kg/m(2) (Se=61%; Sp=62%) and 0.49 (Se=62%; Sp=62%) in men; and 15.7kg/m(2) (Se=58%; Sp=59%), 6.4kg/m(2) (Se=61%; Sp=62%) and 0.35 (Se=62%; Sp=62%) in women for cardiovascular complications. Whatever the outcomes considered, the Youden indexes for BMI values were systematically below 25 kg/m(2), except for cardiovascular complications in men, where the threshold for the best Se/Sp was 25.7 kg/m(2). These cutoff values for FMI, MMI, and FM/MM could be of practical value for the clinical evaluation of a deficit in MM with or without excess of FM. They complement the classical concept of BMI in a more qualitative manner and extend the analysis of its impact on health outcomes to all BMI categories.
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- 2015
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178. The medium helps the message: Early sensitivity to auditory fluency in children's endorsement of statements.
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Bernard S, Proust J, and Clément F
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Recently, a growing number of studies have investigated the cues used by children to selectively accept testimony. In parallel, several studies with adults have shown that the fluency with which information is provided influences message evaluation: adults evaluate fluent information as more credible than dysfluent information. It is therefore plausible that the fluency of a message could also influence children's endorsement of statements. Three experiments were designed to test this hypothesis with 3- to 5-year-olds where the auditory fluency of a message was manipulated by adding different levels of noise to recorded statements. The results show that 4 and 5-year-old children, but not 3-year-olds, are more likely to endorse a fluent statement than a dysfluent one. The present study constitutes a first attempt to show that fluency, i.e., ease of processing, is recruited as a cue to guide epistemic decision in children. An interpretation of the age difference based on the way cues are processed by younger children is suggested.
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- 2014
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179. High-resolution imaging and spectroscopy of multipolar plasmonic resonances in aluminum nanoantennas.
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Martin J, Kociak M, Mahfoud Z, Proust J, Gérard D, and Plain J
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We report on the high resolution imaging of multipolar plasmonic resonances in aluminum nanoantennas using electron energy loss spectroscopy (EELS). Plasmonic resonances ranging from near-infrared to ultraviolet (UV) are measured. The spatial distributions of the multipolar resonant modes are mapped and their energy dispersion is retrieved. The losses in the aluminum antennas are studied through the full width at half-maximum of the resonances, unveiling the weight of both interband and radiative damping mechanisms of the different multipolar resonances. In the blue-UV spectral range, high order resonant modes present a quality factor up to 8, two times higher than low order resonant modes at the same energy. This study demonstrates that near-infrared to ultraviolet tunable multipolar plasmonic resonances in aluminum nanoantennas with relatively high quality factors can be engineered. Aluminum nanoantennas are thus an appealing alternative to gold or silver ones in the visible and can be efficiently used for UV plasmonics.
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- 2014
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180. Metacognitive monitoring of oneself and others: developmental changes during childhood and adolescence.
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Paulus M, Tsalas N, Proust J, and Sodian B
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- Adolescent, Adult, Age Factors, Child, Cues, Female, Humans, Judgment, Learning, Male, Mental Recall, Self Concept, Child Development, Cognition, Comprehension
- Abstract
The current study examined the development of people's knowledge about others' learning and memory processes. To this end, participants of four different age groups (6- and 7-year-old children, 8- to 10-year-old children, 14- and 15-year-old adolescents, and adults) observed another person performing a paired associate learning task, allocating either little or more time to the paired associates. Participants were asked to estimate the likelihood of recall by giving judgments of learning (JoLs) for every item pair (Other Task). In addition, we manipulated whether participants performed an equivalent task themselves (Self Task) before or after the evaluation of the other. Our results show significant developmental effects, with the older two age groups, but not the younger two age groups, differentiating between the short and long video sequences when giving JoLs in the Other Task. Moreover, the results revealed an impact of having performed the Self Task beforehand on participants' JoLs in the Other Task, suggesting that metacognitive knowledge about the other is informed by experiential cues during the actual (i.e., firsthand), learning process., (Copyright © 2014 Elsevier Inc. All rights reserved.)
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- 2014
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181. Examining implicit metacognition in 3.5-year-old children: an eye-tracking and pupillometric study.
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Paulus M, Proust J, and Sodian B
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The current study examined early signs of implicit metacognitive monitoring in 3.5-year-old children. During a learning phase children had to learn paired associates. In the test phase, children performed a recognition task and choose the correct associate for a given target among four possible answers. Subsequently, children's explicit confidence judgments (CJs) and their fixation time allocation at the confidence scale were assessed. Analyses showed that explicit CJs did not differ for remembered compared to non-remembered items. In contrast, children's fixation patterns on the confidence scale were affected by the correctness of their memory, as children looked longer to high confidence ratings when they correctly remembered the associated item. Moreover, analyses of pupil size revealed pupil dilations for correctly remembered, but not incorrectly remembered items. The results converge with recent behavioral findings that reported evidence for implicit metacognitive memory monitoring processes in 3.5-year-old children. The study suggests that implicit metacognitive abilities might precede the development of explicit metacognitive knowledge.
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- 2013
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182. Intense Bessel-like beams arising from pyramid-shaped microtips.
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Martin J, Proust J, Gérard D, Bijeon JL, and Plain J
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We show both numerically and experimentally that intense, narrow, and low-divergence beams of light are produced at the apex of dielectric pyramid-shaped microtips. These beams exhibit a Bessel transverse profile but are narrower than the usual Bessel beam, allowing for a significant enhancement of the light intensity inside the beam. They are generated by axicon-like structures with submicrometric height imprinted in glass by combining optical lithography and chemical etching. The resulting beams are experimentally imaged using fluorescence microscopy, in remarkable agreement with numerical computations.
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- 2012
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183. Exploring the informational sources of metaperception: the case of Change Blindness Blindness.
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Loussouarn A, Gabriel D, and Proust J
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- Adult, Cues, Feedback, Psychological, Female, Humans, Male, Photic Stimulation, Time Factors, Young Adult, Discrimination, Psychological, Visual Perception
- Abstract
Perceivers generally show a poor ability to detect changes, a condition referred to as "Change Blindness" (CB). They are, in addition, "blind to their own blindness". A common explanation of this "Change Blindness Blindness" (CBB) is that it derives from an inadequate, "photographical" folk-theory about perception. This explanation, however, does not account for intra-individual variations of CBB across trials. Our study aims to explore an alternative theory, according to which participants base their self-evaluations on two activity-dependent cues, namely search time and perceived success in prior trials. These cues were found to influence self-evaluation in two orthogonal ways: success-feedback influenced self-evaluation in a global, contextual way, presumably by recalibrating the norm of adequacy for the task. Search time influenced it in a local way, predicting the success of a given trial from its duration., (Copyright © 2011 Elsevier Inc. All rights reserved.)
- Published
- 2011
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184. Cognitive enhancement, human evolution and bioethics.
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Proust J
- Subjects
- Bionics, Humans, Biological Evolution, Biomedical Enhancement ethics, Cognition
- Abstract
The goal of this article are three-fold. The first is to explore the relations between the properties designated by the terms "human", "post-human," "Transhuman", and to clarify the corresponding "isms". The second is to scrutinize the current techniques for cognitive enhancement in order to assess their relations with the three categories just mentioned, and, with the specific ethical issues that they are raising. The third is to examine whether general ethical principles could be invoked either in favor of or against, the normative proposals of post- and trans-humanism, and to consider how compatible the types of enhancement presently developed are with respect to these principles.
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- 2011
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185. Direct functionalization of an optical fiber by a plasmonic nanosensor.
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Zeng X, Jradi S, Proust J, Bachelot R, Zhang ZP, Royer P, and Plain J
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- Metal Nanoparticles chemistry, Silver chemistry, Chemistry Techniques, Analytical instrumentation, Nanotechnology methods, Optical Fibers
- Abstract
We explore a rapid route for fabricating silver nanoparticles (NPs) at the end of an optical fiber. The size and number of silver NPs can be controlled by varying the exposure doses. The effect of the refractive index of different solvents on the extinction spectra have been studied as a proof of concept of a fiber integrated plasmon-based sensor., (© 2011 Optical Society of America)
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- 2011
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186. Chronic lateral ankle instability surgical repairs: the long term prospective.
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Mabit C, Tourné Y, Besse JL, Bonnel F, Toullec E, Giraud F, Proust J, Khiami F, Chaussard C, and Genty C
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- Adult, Aged, Female, Follow-Up Studies, Humans, Joint Instability physiopathology, Lateral Ligament, Ankle physiopathology, Male, Middle Aged, Postoperative Complications, Retrospective Studies, Treatment Outcome, Ankle Joint physiopathology, Ankle Joint surgery, Joint Instability surgery, Lateral Ligament, Ankle surgery, Plastic Surgery Procedures methods
- Abstract
Unlabelled: The present study sought to assess the clinical and radiological results and long-term joint impact of different techniques of lateral ankle ligament reconstruction., Material and Methods: A multicenter retrospective review was performed on 310 lateral ankle ligament reconstructions, with a mean 13-year-follow-up (minimum FU: 5 years). Male subjects (53%) and sports trauma (78%) predominated. Mean duration of instability was 92 months; mean age at surgery was 28 years. Twenty-eight percent of cases showed subtalar joint involvement. Four classes of surgical technique were distinguished: C1, direct capsular ligamentous complex reattachment; C2, augmented repair; C3, ligamentoplasty using part of the peroneus brevis tendon and C4, ligamentoplasty using the whole peroneus brevis tendon. Clinical and functional assessment used Karlsson and Good-Jones-Livingstone scores; radiologic assessment combined centered AP and lateral views, hindfoot weight-bearing Méary views and dynamic views (manual technique, Telos or self-imposed varus)., Results: The majority of results (92%) were satisfactory. The mean Karlsson score of 90 [19-100] (i.e., 87% good and very good results) correlated with the subjective assessment, and did not evolve over time. Postoperative complications (20%), particularly when neurologic, were associated with poorer results. Control X-ray confirmed the very minor progression in degenerative changes, with improved stability; there was, however, no correlation between functional result and residual laxity on X-ray. Unstable and painful ankles showed poorer clinical results and more secondary osteoarthritis. Analysis by class of technique found poorer results in C4-type plasties and poorer control of laxity on X-ray in C1-type tension restoration., Discussion: The present results confirm the interest of lateral ankle ligamentoplasty in the management of instability and protection against secondary osteoarthritis, and of precise lesion assessment (CT-scan/MRI) to adapt surgery to the ligamentary and associated lesions., Level of Evidence: Level IV. Retrospective therapeutic study., (Copyright 2010 Elsevier Masson SAS. All rights reserved.)
- Published
- 2010
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187. Is external rotation the correct immobilisation for acute shoulder dislocation? An MRI study.
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Siegler J, Proust J, Marcheix PS, Charissoux JL, Mabit C, and Arnaud JP
- Subjects
- Acute Disease, Adolescent, Female, Humans, Male, Prospective Studies, Rotation, Rotator Cuff Injuries, Shoulder Dislocation diagnosis, Shoulder Dislocation physiopathology, Treatment Outcome, Immobilization methods, Shoulder Dislocation therapy
- Abstract
Introduction: Anterior dislocation of the shoulder is frequent, with high rates of recurrence. Immobilization in external rotation (ER) seems to improve results, although few studies have actually demonstrated this. The present MRI study examined the impact of ER on labral and capsular ligamentous complex lesions after primary dislocation., Material: A prospective study was started up on January 1st, 2007. Inclusion criteria were: acute initial anteromedial dislocation of the shoulder, without past history of shoulder trauma. There were 23 such patients, with a mean age of 37 years., Methods: Early MRI scan used the following protocol: one acquisition in internal rotation followed by one in ER. Study criteria were: hemarthrosis, ER amplitude, rotator cuff status, bone lesion, and labral lesion stage (Habermeyer's classification) and displacement (Itoi criteria)., Results: There were 12 right and 11 left shoulders. Mean time to MRI was 3.7 days. There were three rotator cuff tears, no glenal lesions, and 14 humeral notches. Hemarthrosis was almost systematically present, with its distribution modified by ER in 75% of cases; three patients showed no posterior hemarthrosis, in whatever rotation. Mean ER was 37 degrees. On Habermeyer's classification, there were 12 stage-1 lesions, and 10 stage-2; one patient had no labral lesion. All separated labra were reduced in ER, five (21%) totally. In six cases, labral displacement changed according to rotation. All anterior joint effusion was reduced in ER, in three cases totally., Discussion: According to Itoi among others, immobilization in ER is the way to reduce recurrence of anterior dislocation. The present study confirmed that labral reduction was systematic with ER, but it was by no means always complete. ER seemed more effective in reducing the separation. Results further confirmed that ER reduced anterior capsule volume, a recurrence factor., Conclusion: ER reduced hemarthrosis, anterior capsule detachment and labral lesions, and never the contrary. The interest of immobilization in ER to prevent shoulder instability needs confirming by long-term clinical studies; we are therefore extending the present MRI study by a clinical study of ER immobilization in all patients showing significant labral lesion reduction., Level of Evidence: Level IV. Retrospective therapeutic study., (Copyright 2010 Elsevier Masson SAS. All rights reserved.)
- Published
- 2010
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188. Secondary exposure for 73 and 200 MeV proton therapy.
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Trompier F, Delacroix S, Vabre I, Joussard F, and Proust J
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- Equipment Design, Equipment Failure Analysis, Internationality, Radiation Dosage, Reproducibility of Results, Sensitivity and Specificity, Environmental Exposure analysis, Proton Therapy, Radiation Monitoring instrumentation, Radiation Monitoring methods, Radiation Protection instrumentation, Radiation Protection methods, Radiotherapy, High-Energy
- Abstract
Following modifications on the beam line at the Orsay Protontherapy Center, dose measurements were performed in order to make a dose map in the treatment rooms and in the delimited radiation-controlled area around beam line. Measurements were performed using tissue-equivalent proportional counters and rem-counters. Analysis of TEPC single event measurements showed that high LET components (>10 keV.microm(-1)) represent 90 to 99% of total dose equivalent in the treatment rooms and 50 to 90% in the controlled area and quality factors range, respectively between 2 and 15. A fast neutron component was identified in the treatment rooms, where dose equivalent rate varied between few microSv.h(-1) to some dozen of mSv.h(-1). In high-energy radiation field rem-counters underestimated TEPC values for neutron component. The variation between instruments response according to the location is linked to energetic spectrum variations and instrument characteristics.
- Published
- 2007
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189. [Periprosthetic fractures around total hip and knee arthroplasty. Methodology and epidemiologic study].
- Author
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Mabit C, Gougam T, Thomazeau H, Ingels A, Andrieux M, Veillard D, Coste C, Oksman A, Proust J, Rochwerger A, Villalba M, and Madougou S
- Subjects
- Aged, Female, Femoral Fractures etiology, Humans, Male, Tibial Fractures etiology, Femoral Fractures epidemiology, Hip Prosthesis adverse effects, Knee Prosthesis adverse effects, Tibial Fractures epidemiology
- Published
- 2006
190. Reorganization of lipid nanocapsules at air-water interface. I. Kinetics of surface film formation.
- Author
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Minkov I, Ivanova T, Panaiotov I, Proust J, and Saulnier P
- Subjects
- Kinetics, Light, Nanotechnology, Scattering, Radiation, Solubility, Surface Properties, Air, Lipids chemistry, Water chemistry
- Abstract
The size, the electrical properties and the behaviour at air-water interface of lipid nanocapsules (LNC) with various compositions were investigated. Two populations of LNC are presented in the suspension after the preparation: with (LNC II) and without (LNC I) phospholipid molecules. After the spreading at air-water interface, a rapid disaggregation of LNC I, located in the vicinity of interface, occurs leading to formation of surface film. The phospholipid molecules stabilize the structure of nanocapsules and LNC II are more stable at the interface in comparison with LNC I. The formation of a surface film was followed after by measuring the evolution of the surface pressure, relative surface area change and surface potential. A kinetic approach describing the various processes during the surface film formation was proposed. The corresponding kinetic constants were estimated.
- Published
- 2005
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191. Reorganization of lipid nanocapsules at air-water interface 3. Action of hydrolytic enzymes HLL and pancreatic PLA2.
- Author
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Minkov I, Ivanova T, Panaiotov I, Proust J, and Verger R
- Subjects
- Hydrolysis, Kinetics, Lipid Metabolism, Models, Chemical, Nanotechnology, Phospholipases A2, Air, Lipase metabolism, Lipids chemistry, Pancreas enzymology, Phospholipases A metabolism, Water chemistry
- Abstract
The action of the hydrolytic enzymes humicola lanuginosa lipase (HLL) and pancreatic phospholipase A2 (PLA2) on monolayers formed from lipid nanocapsules (LNC) and model monolayers containing their components, Labrafac, Solutol and Lipoid, is studied by simultaneous measuring the changes in the film area and the surface potential in the "zero order" trough at constant surface pressure (pi). The kinetic models describing the hydrolysis by HLL of the Labrafac, Solutol and their mixtures have been proposed. By using the developed theoretical approach together with the experimental results the surface concentrations of the substrates, hydrolysis products and values of the global kinetic constants were obtained. The comparison between the global kinetic constants in the case of HLL hydrolysis of pure Labrafac, Solutol monolayers and those of the model mixed Labrafac/Solutol monolayers, shows that the rates of hydrolysis are of the same order of magnitude, i.e. an additively of the HLL enzyme action is observed. The composition of the mixed Labrafac/Solutol monolayer, formed after the interfacial LNC destabilization, was estimated.
- Published
- 2005
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192. Reorganization of lipid nanocapsules at air-water interface: Part 2. Properties of the formed surface film.
- Author
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Minkov I, Ivanova T, Panaiotov I, Proust J, and Saulnier P
- Subjects
- Capsules, Rheology, Surface Properties, Air, Lipids chemistry, Nanotechnology, Water chemistry
- Abstract
The state, electrical and dilatational rheological properties of surface films formed at air-water interface from lipid nanocapsules (LNC) with various compositions as well as model monolayers formed by the LNC constituents-Labrafac, Solutol and Lipoid are investigated. These nanocapsules constitute potential drug delivery systems where lypophilic drug will be loaded in their core. The study of the model Labrafac/Solutol (Lab/Sol) mixed monolayers shows behavior close to the ideal. Small negative deviations in the mean molecular areas a and dipole moments mu are observed. All studied monolayers have elastic behavior during the small continuous compressions. The comparison between the properties of surface films formed from LNC with those of the model monolayers confirms the idea developed in the kinetic study that the surface films formed after a rapid disaggregation of the unstable nanocapsule fraction (LNC I) contains mainly Labrafac and Solutol. The Labrafac molar part (xLab) in the formed Lab/Sol mixed layer is established.
- Published
- 2005
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193. Annexin 2 binding to phosphatidylinositol 4,5-bisphosphate on endocytic vesicles is regulated by the stress response pathway.
- Author
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Hayes MJ, Merrifield CJ, Shao D, Ayala-Sanmartin J, Schorey CD, Levine TP, Proust J, Curran J, Bailly M, and Moss SE
- Subjects
- Actins metabolism, Animals, Cell Line, Tumor, Cytoskeleton physiology, Leukemia, Basophilic, Acute, Osmotic Pressure, Pinocytosis physiology, Rats, Annexin A2 metabolism, Phosphatidylinositol 4,5-Diphosphate metabolism, Signal Transduction physiology, Transport Vesicles metabolism
- Abstract
Annexin 2 is a Ca(2+)-binding protein that has an essential role in actin-dependent macropinosome motility. We show here that macropinosome rocketing can be induced by hyperosmotic shock, either alone or synergistically when combined with phorbol ester or pervanadate. Rocketing was blocked by inhibitors of phosphatidylinositol-3-kinase(s), p38 mitogen-activated protein (MAP) kinase, and calcium, suggesting the involvement of phosphoinositide signaling. Since various phosphoinositides are enriched on inwardly mobile vesicles, we examined whether or not annexin 2 binds to any of this class of phospholipid. In liposome sedimentation assays, we show that recombinant annexin 2 binds to phosphatidylinositol 4,5-bisphosphate (PtdIns-4,5P(2)) but not to other poly- and mono-phosphoinositides. The affinity of annexin 2 for PtdIns-4,5P(2) (K(D) approximately 5 microm) is comparable with those reported for a variety of PtdIns-4,5P(2)-binding proteins and is enhanced in the presence of Ca(2+). Although annexin 1 also bound to PtdIns-4,5P(2), annexin 5 did not, indicating that this is not a generic annexin property. To test whether annexin 2 binds to PtdIns-4,5P(2) in vivo, we microinjected rat basophilic leukemia cells stably expressing annexin 2-green fluorescent protein (GFP) with fluorescently tagged antibodies to PtdIns-4,5P(2). Annexin 2-GFP and anti-PtdIns-4,5P(2) IgG co-localize at sites of pinosome formation, and annexin 2-GFP relocalizes to intracellular membranes in Ptk cells microinjected with Arf6Q67L, which has been shown to stimulate PtdIns-4,5P(2) synthesis on pinosomes through activation of phosphatidylinositol 5 kinase. These results establish a novel phospholipid-binding specificity for annexin 2 consistent with a role in mediating the interaction between the macropinosome surface and the polymerized actin tail.
- Published
- 2004
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194. Thinking of oneself as the same.
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Proust J
- Subjects
- Awareness, Delusions psychology, Humans, Internal-External Control, Interpersonal Relations, Mental Recall, Perceptual Distortion, Personality Development, Schizophrenic Psychology, Self Concept, Self Psychology, Cognition, Consciousness, Ego, Thinking
- Published
- 2003
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195. [Extra-spinal cause of recurrent sciatalgia after disk surgery: a case report].
- Author
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Aribit F, Proust J, Charissoux JL, and Arnaud JP
- Subjects
- Adult, Diskectomy, Female, Humans, Recurrence, Sciatica pathology, Carcinoma, Renal Cell complications, Intervertebral Disc Displacement complications, Kidney Neoplasms complications, Sciatica etiology
- Abstract
There is a general consensus concerning the clinical and radiological approach to diagnosis and proper management strategy in patients with sciatalgia subsequent to disk herniation. Recurrent herniation is the most probable diagnosis when pain recurs the same territory long after surgery. Despite advances in computed tomographic and magnetic resonance imaging, it may be difficult to identify the real source of the pain in some patients. We report a patient with renal cell cancer who developed recurrent sciatic pain which did not respond to disk surgery. This case illustrates the need for an extensive work-up before implicating the spine as the cause of recurrent sciatalgia.
- Published
- 2003
196. Does metacognition necessarily involve metarepresentation?
- Author
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Proust J
- Abstract
Against the view that metacognition is a capacity that parallels theory of mind, it is argued that metacognition need involve neither metarepresentation nor semantic forms of reflexivity, but only process-reflexivity, through which a task-specific system monitors its own internal feedback by using quantitative cues. Metacognitive activities, however, may be redescribed in metarepresentational, mentalistic terms in species endowed with a theory of mind.
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- 2003
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197. Annexin 2 has an essential role in actin-based macropinocytic rocketing.
- Author
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Merrifield CJ, Rescher U, Almers W, Proust J, Gerke V, Sechi AS, and Moss SE
- Subjects
- Animals, Exocytosis physiology, Microscopy, Confocal, Movement, Osmotic Pressure, Rats, Recombinant Fusion Proteins physiology, Tumor Cells, Cultured, Actins physiology, Annexin A2 physiology, Pinocytosis physiology
- Abstract
Annexin 2 is a Ca(2+) binding protein that binds to and aggregates secretory vesicles at physiological Ca(2+) levels [1] and that also associates Ca(2+) independently with early endosomes [2, 3]. These properties suggest roles in both exocytosis and endocytosis, but little is known of the dynamics of Annexin 2 distribution in live cells during these processes. We have used evanescent field microscopy to image Annexin 2-GFP in live, secreting rat basophilic leukemia cells and in cells performing pinocytosis. Although we found no evidence of Annexin 2 involvement in exocytosis, we observed an enrichment of Annexin 2-GFP in actin tails propeling macropinosomes. The association of Annexin 2-GFP with rocketing macropinosomes was specific because Annexin 2-GFP was absent from the actin tails of rocketing Listeria. This finding suggests that the association of Annexin 2 with macropinocytic rockets requires native pinosomal membrane. Annexin 2 is necessary for the formation of macropinocytic rockets since overexpression of a dominant-negative Annexin 2 construct abolished the formation of these structures. The same construct did not prevent the movement of Listeria in infected cells. These results show that recruitment of Annexin 2 to nascent macropinosome membranes 16656is an essential prerequisite for actin polymerization-dependent vesicle locomotion.
- Published
- 2001
- Full Text
- View/download PDF
198. Interfacial properties of amiodarone: the stabilizing effect of phosphate anions.
- Author
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Boury F, Gautier J, Bouligand Y, and Proust J
- Abstract
Amiodarone, a drug used in heart therapy, is poorly soluble in water at room temperature, but forms transparent phases much more concentrated than the critical micellar concentration (CMC), when crystals are heated (above 60 degrees C) in presence of water and cooled down to room temperature. These pseudosolutions were supposed to be made of a complex system of micelles. In order to better understand the effects of pH and ion species on the supramolecular organization of amiodarone, interfacial pressure measurements were performed at the air/water interface on a Langmuir trough. Monolayers spread from chloroformic solutions over non bufferered subphases were insoluble at basic pH (NaOH, pH 10) but soluble at acidic pH (HCl, pH 4). However, a higher ionic strength obtained by adding NaCl (0.15 N) or NaH(2)PO(4) (0.15 N) to the subphase stopped the amiodarone solubilization. On an acidic phosphate subphase (NaH(2)PO(4), pH 4.4, 0.15 N), abnormally high surface pressures (>1 mN/m) were measured for high molecular areas (80-200 Å(2)/molecule) suggesting a supramolecular organization of the surface film. Insoluble monolayers were also obtained when the amiodarone supramolecular pseudosolution was spread on neutral (NaH(2)PO(4), pH 6.25, 0.15 N) or acidic (NaH(2)PO(4), pH 4.4, 0.15 N) subphases. However, a great instability on basic subphase (phosphate buffer pH 8.8) indicated the breakage of the supramolecular structure during spreading. These results are discussed taking into account the amiodarone state of ionization and the electrostatic interactions with counterions. Combining the use of phosphate counterions and that of acidic pH opens new perspectives in the optimization of amiodarone intravenous formulations.
- Published
- 2001
- Full Text
- View/download PDF
199. Annexin 24 from Capsicum annuum. X-ray structure and biochemical characterization.
- Author
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Hofmann A, Proust J, Dorowski A, Schantz R, and Huber R
- Subjects
- Adenosine Triphosphatases, Amino Acid Sequence, Annexins genetics, Calcium pharmacology, Crystallography, X-Ray, Models, Molecular, Molecular Sequence Data, Permeability drug effects, Plant Proteins genetics, Protein Binding drug effects, Recombinant Proteins chemistry, Sequence Analysis, Protein, Sequence Homology, Amino Acid, Surface Properties, Annexins chemistry, Capsicum chemistry, Plant Proteins chemistry, Plants, Medicinal
- Abstract
This work provides the first three-dimensional structure of a member of the plant annexin family and correlates these findings with biochemical properties of this protein. Annexin 24(Ca32) from Capsicum annuum was purified as a native protein from bell pepper and was also prepared by recombinant techniques. To overcome the problem of precipitation of the recombinant wild-type protein in crystallization trials, two mutants were designed. Whereas an N-terminal truncation mutant turned out to be an unstable protein, the N-terminal His-tagged annexin 24(Ca32) was crystallized, and the three-dimensional structure was determined by x-ray diffraction at 2. 8 A resolution. The structure refined to an R-factor of 0.216 adopts the typical annexin fold; the detailed structure, however, is different from non-plant annexins, especially in domains I and III and in the membrane binding loops on the convex side. Within the unit cell there are two molecules per asymmetric unit, which differ in conformation of the IAB-loop. Both conformers show Trp-35 on the surface. The loop-out conformation is stabilized by tight interactions of this tryptophan with residue side chains of a symmetry-related molecule and enforced by a bound sulfate. Characterization of this plant annexin using biophysical methods revealed calcium-dependent binding to phospholipid vesicles with preference for phosphatidylcholine over phosphatidylserine and magnesium-dependent phosphodiesterase activity in vitro as shown with adenosine triphosphate as the substrate. A comparative unfolding study of recombinant annexin 24(Ca32) wild type and of the His-tag fusion protein indicates higher stability of the latter. The effect of this N-terminal modification is also visible from CD spectra. Both proteins were subjected to a FURA-2-based calcium influx assay, which gave high influx rates for the wild-type but greatly reduced influx rates for the fusion protein. We therefore conclude that the N-terminal domain is indeed a major regulatory element modulating different annexin properties by allosteric mechanisms.
- Published
- 2000
- Full Text
- View/download PDF
200. Self model and schizophrenia.
- Author
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Proust J
- Subjects
- Humans, Models, Psychological, Nerve Net physiopathology, Schizophrenia physiopathology, Self Concept
- Published
- 1999
- Full Text
- View/download PDF
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