Two Ising-like magnetic excitations in a single-layer cuprate superconductor

There exists increasing evidence that the phase diagram of the high-transition temperature (Tc) cuprate superconductors is controlled by a quantum critical point. One distinct theoretical proposal is that, with decreasing hole-carrier concentration, a transition occurs to an ordered state with two circulating orbital currents per CuO2 square. Below the 'pseudogap' temperature T* (T* > Tc), the theory predicts a discrete order parameter and two weakly-dispersive magnetic excitations in structurally simple compounds that should be measurable by neutron scattering. Indeed, novel magnetic order and one such excitation were recently observed. Here, we demonstrate for tetragonal HgBa2CuO4+d the existence of a second excitation with local character, consistent with the theory. The excitations mix with conventional antiferromagnetic fluctuations, which points toward a unifying picture of magnetism in the cuprates that will likely require a multi-band description.Comment: Including supplementary informatio

Sleep apnea syndrome in an elderly population admitted to a geriatric unit : prevalence and effect on cognitive function

International audienceBackground Sleep apnea leads to cognitive impairment in older patients, but its association with neurodegeneration remains controversial, and most studies do not distinguish between the more common obstructive form (OSAS) and the rarer central form (CSAS). Objective The purpose of this study was to assess the prevalence of the different forms of sleep apnea in a cohort of cognitively impaired elderly patients (>70 years) and to investigate their associations with cognitive deficit, weighted against known risk factors for neurodegeneration. Methods Overnight polygraphy was performed for 76 consecutive patients admitted to our geriatric unit. Their cognitive function was assessed using the Mini Mental-State Exam (MMSE), Mattis Dementia Rating Scale (MDRS) and Stroop test. Multivariable analyses were performed to determine associations between cognitive function and independent variables describing demographics, sleep apnea measures, and cardiovascular risk factors. Results The cohort comprised 58 women and 18 men aged a mean of 84 years (range, 73-96). Sleep apnea syndrome (SAS) was diagnosed in 48 patients (63%), of which 31 (41%) with OSAS and 17 (22%) with CSAS. Multivariable regression analysis revealed that MDRS was lower in patients with OSAS (beta = -10.03, p = 0.018), that Stroop Colors and Words delays increased with AHI (beta = 0.17, p = 0.030 and beta = 0.31, p = 0.047) and that that Stroop Interference delay was higher in patients with CSAS (beta = 24.45, p = 0.002). Conclusion Sleep apnea is thus highly prevalent in elderly patients with cognitive impairment. OSAS was associated with lower general cognitive function, while CSAS was only associated with increased Stroop Interference delays. Elderly patients with cognitive deficit could benefit from sleep apnea screening and treatment

Compliance of the cerebrospinal space: comparison of three methods

Abstract: Background: Cerebrospinal compliance describes the ability of the cerebrospinal space to buffer changes in volume. Diminished compliance is associated with increased risk of potentially threatening increases in intracranial pressure (ICP) when changes in cerebrospinal volume occur. However, despite various methods of estimation proposed so far, compliance is seldom used in clinical practice. This study aimed to compare three measures of cerebrospinal compliance. Methods: ICP recordings from 36 normal-pressure hydrocephalus patients who underwent infusion tests with parallel recording of transcranial Doppler blood flow velocity were retrospectively analysed. Three methods were used to calculate compliance estimates during changes in the mean ICP induced by infusion of fluid into the cerebrospinal fluid space: (a) based on Marmarou’s model of cerebrospinal fluid dynamics (CCSF), (b) based on the evaluation of changes in cerebral arterial blood volume (CCaBV), and (c) based on the amplitudes of peaks P1 and P2 of ICP pulse waveform (CP1/P2). Results: Increase in ICP caused a significant decrease in all compliance estimates (p < 0.0001). Time courses of compliance estimators were strongly positively correlated with each other (group-averaged Spearman correlation coefficients: 0.94 [0.88–0.97] for CCSF vs. CCaBV, 0.77 [0.63–0.91] for CCSF vs. CP1/P2, and 0.68 [0.48–0.91] for CCaBV vs. CP1/P2). Conclusions: Indirect methods, CCaBV and CP1/P2, allow for the assessment of relative changes in cerebrospinal compliance and produce results exhibiting good correlation with the direct method of volumetric manipulation. This opens the possibility of monitoring relative changes in compliance continuously

Reduced CSF turnover and decreased ventricular Aβ42 levels are related

International audienceBACKGROUND: The appearance of Aβ42 peptide deposits is admitted to be a key event in the pathogenesis of Alzheimer's disease, although amyloid deposits also occur in aged non-demented subjects. Aβ42 is a degradation product of the amyloid protein precursor (APP). It can be catabolized by several enzymes, reabsorbed by capillaries or cleared into cerebrospinal fluid (CSF). The possible involvement of a decrease in CSF turnover in A4β2 deposit formation is up to now poorly known. We therefore investigated a possible relationship between a reduced CSF turnover and the CSF levels of the A4β2 peptide.To this aim, CSF of 31 patients with decreased CSF turnover were studied. These patients presented chronic hydrocephalus communicating or obstructive, which required surgery (ventriculostomy or ventriculo-peritoneal shunt). Nine subjects had idiopathic normal pressure hydrocephalus (iNPH), and the other 22 chronic hydrocephalus from other origins (oCH).The Aβ42 peptide concentration was measured by an ELISA test in 31 ventricular CSF samples and in 5 lumbar CSF samples from patients with communicating hydrocephalus. RESULTS: The 5 patients with lumbar CSF analysis had similar levels of lumbar and ventricular Aβ42. A significant reduction in Aβ42 ventricular levels was observed in 24 / 31 patients with hydrocephalus. The values were lower than 300 pg/ml in 5 out of 9 subjects with iNPH, and in 15 out of 22 subjects with oCH. CONCLUSION: The decrease of CSF Aβ42 seems to occur independently of the surgical hydrocephalus aetiology. This suggests that a CSF reduced turnover may play an important role in the decrease of CSF Aβ42 concentration

Intracranial volumetric changes govern cerebrospinal fluid flow in the Aqueduct of Sylvius in healthy adults

Purpose: To characterize the intracranial volumetric changes that influence the cerebrospinal fluid (CSF) pulse in the Aqueduct of Sylvius (AoS). Materials and Methods: Neck MRI data were acquired from 12 healthy adults (8 female and 4 males; mean age=30.9 years), using a 1.5 Tesla scanner. The intracranial arterial, venous and CSF volumes changes, together with the aqueductal CSF (aCSF) volume, were estimated from flow rate data acquired at C2/C3 level and in the AoS. The correlations and temporal relationships among these volumes were computed. Results: The aCSF volumetric changes were strongly correlated (r = 0.967, p<0.001) with the changes in intracranial venous volume, whose peak occurred 7.0% of cardiac cycle (p = 0.023) before peak aCSF volume, but less correlated with the intracranial arterial and CSF volume changes (r=-0.664 and 0.676 respectively, p<0.001). The intracranial CSF volume change was correlated with the intracranial venous volume change (r=0.820, p<0.001), whose peak occurred slightly before (4.2% of CC, p=0.059). Conclusion: The aCSF pulse is strongly correlated with intracranial venous volume, with expansion of the cortical veins occurring prior to aCSF flow towards the third ventricle. Both caudal-cranial aCSF flow and venous blood retention occur when arterial blood volume is at a minimum

Impact des modalités induites par les outils d'annotation manuelle : exemple de la détection des erreurs de français

National audienceCertains choix effectués lors de la construction d’une campagne d’annotation peuvent avoir des conséquences sur les annotations produites. En menant une campagne sur la détection des erreurs de français, aux paramètres maîtrisés, nous évaluons notamment l’effet de la fonctionnalité de retour arrière. Au moyen de paires d’énoncés presque identiques, nous mettons en exergue une tendance des annotateurs à tenir compte de l’un pour annoter l’autre

De la complexité de l'annotation manuelle : méthodologie, biais et recommandations

Annotated reference corpora are essential elements of many tasks in Natural Language Processing. Their construction is the object of particular attention, especially during manual annotation campaigns. The latter involve multiple aspects, already studied in the literature but often separately. We present a synthesis of the problems encountered during the different stages of a campaign, drawing the attention of managers to points of vigilance, so that they can be careful during their campaign.This thesis gives a first definition of annotation biases, which are disturbing and varied phenomena that can have an impact on annotations. We propose a method and means of observation to detect and analyze the presence of annotation bias. Two annotation campaigns, conducted specifically to study particular biases, serve as illustrations and have allowed us to observe the tangible influence of certain parameters on the annotation. In this perspective, we have also introduced the notion of consensuality, which allows us to situate an annotator in relation to a group. We show a first link between the least consensual annotators and the least efficient ones.Les corpus de référence annotés constituent des éléments primordiaux de nombreuses tâches du Traitement Automatique des Langues. Leur construction fait l'objet d’une attention particulière, notamment lors de campagnes d’annotation manuelle. Ces dernières impliquent de multiples aspects, déjà étudiés dans la littérature mais souvent de manière séparée. Nous présentons une synthèse des problèmes rencontrés lors des différentes étapes d'une campagne, attirant l’attention des gestionnaires sur des points de vigilance, afin qu'ils fassent preuve de prudence durant leur campagne.Cette thèse donne une première définition des biais d’annotation, qui sont des phénomènes perturbateurs et variés pouvant avoir une incidence sur les annotations. Nous proposons une méthode et des moyens d'observation pour détecter et analyser la présence de biais d’annotation. Deux campagnes d’annotation, menées spécialement dans le but d'étudier des biais particuliers, servent d'illustration et nous ont permis de constater l'influence tangible de certains paramètres sur l’annotation. Dans cette optique, nous avons aussi introduit la notion de consensualité, qui permet en particulier de situer un annotateur par rapport à un groupe. Nous montrons un premier lien entre les annotateurs les moins consensuels et les moins performants

De la complexité de l'annotation manuelle : méthodologie, biais et recommandations

Annotated reference corpora are essential elements of many tasks in Natural Language Processing. Their construction is the object of particular attention, especially during manual annotation campaigns. The latter involve multiple aspects, already studied in the literature but often separately. We present a synthesis of the problems encountered during the different stages of a campaign, drawing the attention of managers to points of vigilance, so that they can be careful during their campaign.This thesis gives a first definition of annotation biases, which are disturbing and varied phenomena that can have an impact on annotations. We propose a method and means of observation to detect and analyze the presence of annotation bias. Two annotation campaigns, conducted specifically to study particular biases, serve as illustrations and have allowed us to observe the tangible influence of certain parameters on the annotation. In this perspective, we have also introduced the notion of consensuality, which allows us to situate an annotator in relation to a group. We show a first link between the least consensual annotators and the least efficient ones.Les corpus de référence annotés constituent des éléments primordiaux de nombreuses tâches du Traitement Automatique des Langues. Leur construction fait l'objet d’une attention particulière, notamment lors de campagnes d’annotation manuelle. Ces dernières impliquent de multiples aspects, déjà étudiés dans la littérature mais souvent de manière séparée. Nous présentons une synthèse des problèmes rencontrés lors des différentes étapes d'une campagne, attirant l’attention des gestionnaires sur des points de vigilance, afin qu'ils fassent preuve de prudence durant leur campagne.Cette thèse donne une première définition des biais d’annotation, qui sont des phénomènes perturbateurs et variés pouvant avoir une incidence sur les annotations. Nous proposons une méthode et des moyens d'observation pour détecter et analyser la présence de biais d’annotation. Deux campagnes d’annotation, menées spécialement dans le but d'étudier des biais particuliers, servent d'illustration et nous ont permis de constater l'influence tangible de certains paramètres sur l’annotation. Dans cette optique, nous avons aussi introduit la notion de consensualité, qui permet en particulier de situer un annotateur par rapport à un groupe. Nous montrons un premier lien entre les annotateurs les moins consensuels et les moins performants

On the complexity of manual annotation : methodology, bias and recommendations

Les corpus de référence annotés constituent des éléments primordiaux de nombreuses tâches du Traitement Automatique des Langues. Leur construction fait l'objet d’une attention particulière, notamment lors de campagnes d’annotation manuelle. Ces dernières impliquent de multiples aspects, déjà étudiés dans la littérature mais souvent de manière séparée. Nous présentons une synthèse des problèmes rencontrés lors des différentes étapes d'une campagne, attirant l’attention des gestionnaires sur des points de vigilance, afin qu'ils fassent preuve de prudence durant leur campagne.Cette thèse donne une première définition des biais d’annotation, qui sont des phénomènes perturbateurs et variés pouvant avoir une incidence sur les annotations. Nous proposons une méthode et des moyens d'observation pour détecter et analyser la présence de biais d’annotation. Deux campagnes d’annotation, menées spécialement dans le but d'étudier des biais particuliers, servent d'illustration et nous ont permis de constater l'influence tangible de certains paramètres sur l’annotation. Dans cette optique, nous avons aussi introduit la notion de consensualité, qui permet en particulier de situer un annotateur par rapport à un groupe. Nous montrons un premier lien entre les annotateurs les moins consensuels et les moins performants.Annotated reference corpora are essential elements of many tasks in Natural Language Processing. Their construction is the object of particular attention, especially during manual annotation campaigns. The latter involve multiple aspects, already studied in the literature but often separately. We present a synthesis of the problems encountered during the different stages of a campaign, drawing the attention of managers to points of vigilance, so that they can be careful during their campaign.This thesis gives a first definition of annotation biases, which are disturbing and varied phenomena that can have an impact on annotations. We propose a method and means of observation to detect and analyze the presence of annotation bias. Two annotation campaigns, conducted specifically to study particular biases, serve as illustrations and have allowed us to observe the tangible influence of certain parameters on the annotation. In this perspective, we have also introduced the notion of consensuality, which allows us to situate an annotator in relation to a group. We show a first link between the least consensual annotators and the least efficient ones