Laughlin's wave functions, Coulomb gases and expansions of the discriminant

In the context of the fractional quantum Hall effect, we investigate Laughlin's celebrated ansatz for the groud state wave function at fractional filling of the lowest Landau level. Interpreting its normalization in terms of a one component plasma, we find the effect of an additional quadrupolar field on the free energy, and derive estimates for the thermodynamically equivalent spherical plasma. In a second part, we present various methods for expanding the wave function in terms of Slater determinants, and obtain sum rules for the coefficients. We also address the apparently simpler question of counting the number of such Slater states using the theory of integral polytopes.Comment: 97 pages, using harvmac (with big option recommended) and epsf, 7 figures available upon request, Saclay preprint Spht 93/12

Frequency stability of maser oscillators operated with cavity Q

The short term frequency stability of masers equipped with an external feedback loop to increase the cavity quality factor was studied. The frequency stability of a hydrogen and a rubidium maser were measured and compared with theoretical evaluation. It is shown that the frequency stability passes through an optimum when the cavity Q is varied. Long term fluctuations are discussed and the optimum mid term frequency stability achievably by small size active and passive H-masers is considered

Correlations in one dimensional quantum impurity problems with an external field

We study response functions of integrable quantum impurity problems with an external field at $T=0$ using non perturbative techniques derived from the Bethe ansatz. We develop the first steps of the theory of excitations over the new, field dependent ground state, leading to renormalized (or ``dressed'') form-factors. We obtain exactly the low frequency behaviour of the dynamical susceptibility $\chi''(\omega)$ in the double well problem of dissipative quantum mechanics (or equivalently the anisotropic Kondo problem),and the low frequency behaviour of the AC noise $S_t(\omega)$ for tunneling between edges in fractional quantum Hall devices. We also obtain exactly the structure of singularities in $\chi''(\omega)$ and $S_t(\omega)$. Our results differ significantly from previous perturbative approaches.Comment: harvmac, epsf, 37pgs, 2figs. modified some reference

Extraction of Airways with Probabilistic State-space Models and Bayesian Smoothing

Segmenting tree structures is common in several image processing applications. In medical image analysis, reliable segmentations of airways, vessels, neurons and other tree structures can enable important clinical applications. We present a framework for tracking tree structures comprising of elongated branches using probabilistic state-space models and Bayesian smoothing. Unlike most existing methods that proceed with sequential tracking of branches, we present an exploratory method, that is less sensitive to local anomalies in the data due to acquisition noise and/or interfering structures. The evolution of individual branches is modelled using a process model and the observed data is incorporated into the update step of the Bayesian smoother using a measurement model that is based on a multi-scale blob detector. Bayesian smoothing is performed using the RTS (Rauch-Tung-Striebel) smoother, which provides Gaussian density estimates of branch states at each tracking step. We select likely branch seed points automatically based on the response of the blob detection and track from all such seed points using the RTS smoother. We use covariance of the marginal posterior density estimated for each branch to discriminate false positive and true positive branches. The method is evaluated on 3D chest CT scans to track airways. We show that the presented method results in additional branches compared to a baseline method based on region growing on probability images.Comment: 10 pages. Pre-print of the paper accepted at Workshop on Graphs in Biomedical Image Analysis. MICCAI 2017. Quebec Cit

Topo-Geometric Filtration Scheme for Geometric Active Contours and Level Sets: Application to Cerebrovascular Segmentation

One of the main problems of the existing methods for the segmentation of cerebral vasculature is the appearance in the segmentation result of wrong topological artefacts such as the kissing vessels. In this paper, a new approach for the detection and correction of such errors is presented. The proposed technique combines robust topological information given by Persistent Homology with complementary geometrical information of the vascular tree. The method was evaluated on 20 images depicting cerebral arteries. Detection and correction success rates were 81.80% and 68.77%, respectively

L’après-suicide, une expérience unique de deuil?

Le groupe d'étude national sur le suicide au Canada suggère que les personnes qui vivent un deuil suite à un suicide forment un groupe à risque suicidaire. La littérature rapporte que ces endeuillés ont un taux de suicide neuf fois plus élevé que la population générale. Des auteurs suggèrent que ce type de deuil est plus intense et plus long que d'autres formes de deuil, constat que d'autres ont remis en doute. Qu'en est-il? Le deuil suite à un suicide est-il différent? S'agit-il d'une expérience unique de deuil? Un examen attentif de l'ensemble des études nous apprend que le deuil suite à un suicide présente des caractéristiques particulières, qui se manifestent davantage chez des personnes plus vulnérables.Canada's national task force on suicide suggests that people who mourn a suicide make up a group that is itself at risk. Literature shows that mourners of a suicide have a suicide rate that is nine times higher than average. While some authors suggest that this type of mourning is more intense and of a longer duration that for other types of mourning, other authors doubt this hypothesis. But what happens in reality ? Is suicide mourning truly different from other types of mourning? Is it really a unique mourning experience? These are some of the questions the authors of this article have attempted to answer. Following an in-depth review of studies on the matter, the authors conclude that the mourning of a suicide encompasses certain characteristics that manifest themselves especially in more vulnerable people

Computer-assisted textual analysis of free-text comments in the Swiss Cancer Patient Experiences (SCAPE) survey.

Patient experience surveys are increasingly conducted in cancer care as they provide important results to consider in future development of cancer care and health policymaking. These surveys usually include closed-ended questions (patient-reported experience measures (PREMs)) and space for free-text comments, but published results are mostly based on PREMs. We aimed to identify the underlying themes of patients' experiences as shared in their own words in the Swiss Cancer Patient Experiences (SCAPE) survey and compare these themes with those assessed with PREMs to investigate how the textual analysis of free-text comments contributes to the understanding of patients' experiences of care. SCAPE is a multicenter cross-sectional survey that was conducted between October 2018 and March 2019 in French-speaking parts of Switzerland. Patients were invited to rate their care in 65 closed-ended questions (PREMs) and to add free-text comments regarding their cancer-related experiences at the end of the survey. We conducted computer-assisted textual analysis using the IRaMuTeQ software on the comments provided by 31% (n = 844) of SCAPE survey respondents (n = 2755). We identified five main thematic classes, two of which consisting of a detailed description of 'cancer care pathways'. The remaining three classes were related to 'medical care', 'gratitude and praise', and the way patients lived with cancer ('cancer and me'). Further analysis of this last class showed that patients' comments related to the following themes: 'initial shock', 'loneliness', 'understanding and acceptance', 'cancer repercussions', and 'information and communication'. While closed-ended questions related mainly to factual aspects of experiences of care, free-text comments related primarily to the personal and emotional experiences and consequences of having cancer and receiving care. A computer-assisted textual analysis of free-text in our patient survey allowed a time-efficient classification of free-text data that provided insights on the personal experience of living with cancer and additional information on patient experiences that had not been collected with the closed-ended questions, underlining the importance of offering space for comments. Such results can be useful to inform questionnaire development, provide feedback to professional teams, and guide patient-centered initiatives to improve the quality and safety of cancer care

Effects of light and intraspecific competition on growth and crown morphology of two size classes of understory balsam fir saplings

This paper characterizes the growth and crown morphology of young balsam fir saplings naturally regenerated under a gradient of understory light environments and intraspecific competition densities for two size classes (50-100 cm and 100-200 cm). Most growth and crown morphological parameters investigated were strongly related to the natural light gradient investigated (3-83% full sunlight), but the relationship tended to plateau at around 25% full sunlight. The relationships were generally better for the larger size class. Intraspecific competition did not significantly affect growth and crown morphology of saplings receiving less than 25% full sunlight, but it affected relative height growth, relative radial growth and the apical dominance ratio for those receiving more than 25% full sunlight (R2=0.506; p<0.001; R2=0.403; p<0.002; R2=0.348; p<0.001, respectively). These results suggest that live crown ratio, apical dominance ratio and the number of internodal branches can provide, alone or in combination, useful indicators of vigour for understory fir. Such a study provides the basic data inputs required for the development of empirically-derived mechanistic models that can predict understory tree growth and survival

Situational Awareness from a Low-Cost Camera System

A method gathers scene information from a low-cost camera system. Existing surveillance systems using sufficient cameras for continuous coverage of a large field necessarily generate enormous amounts of raw data. Digitizing and channeling that data to a central computer and processing it in real time is difficult when using low-cost, commercially available components. A newly developed system is located on a combined power and data wire to form a string-of-lights camera system. Each camera is accessible through this network interface using standard TCP/IP networking protocols. The cameras more closely resemble cell-phone cameras than traditional security camera systems. Processing capabilities are built directly onto the camera backplane, which helps maintain a low cost. The low power requirements of each camera allow the creation of a single imaging system comprising over 100 cameras. Each camera has built-in processing capabilities to detect events and cooperatively share this information with neighboring cameras. The location of the event is reported to the host computer in Cartesian coordinates computed from data correlation across multiple cameras. In this way, events in the field of view can present low-bandwidth information to the host rather than high-bandwidth bitmap data constantly being generated by the cameras. This approach offers greater flexibility than conventional systems, without compromising performance through using many small, low-cost cameras with overlapping fields of view. This means significant increased viewing without ignoring surveillance areas, which can occur when pan, tilt, and zoom cameras look away. Additionally, due to the sharing of a single cable for power and data, the installation costs are lower. The technology is targeted toward 3D scene extraction and automatic target tracking for military and commercial applications. Security systems and environmental/ vehicular monitoring systems are also potential applications