Self-Navigation with Compressed Sensing for 2D Translational Motion Correction in Free-Breathing Coronary MRI: A Feasibility Study.

PURPOSE: Respiratory motion correction remains a challenge in coronary magnetic resonance imaging (MRI) and current techniques, such as navigator gating, suffer from sub-optimal scan efficiency and ease-of-use. To overcome these limitations, an image-based self-navigation technique is proposed that uses "sub-images" and compressed sensing (CS) to obtain translational motion correction in 2D. The method was preliminarily implemented as a 2D technique and tested for feasibility for targeted coronary imaging. METHODS: During a 2D segmented radial k-space data acquisition, heavily undersampled sub-images were reconstructed from the readouts collected during each cardiac cycle. These sub-images may then be used for respiratory self-navigation. Alternatively, a CS reconstruction may be used to create these sub-images, so as to partially compensate for the heavy undersampling. Both approaches were quantitatively assessed using simulations and in vivo studies, and the resulting self-navigation strategies were then compared to conventional navigator gating. RESULTS: Sub-images reconstructed using CS showed a lower artifact level than sub-images reconstructed without CS. As a result, the final image quality was significantly better when using CS-assisted self-navigation as opposed to the non-CS approach. Moreover, while both self-navigation techniques led to a 69% scan time reduction (as compared to navigator gating), there was no significant difference in image quality between the CS-assisted self-navigation technique and conventional navigator gating, despite the significant decrease in scan time. CONCLUSIONS: CS-assisted self-navigation using 2D translational motion correction demonstrated feasibility of producing coronary MRA data with image quality comparable to that obtained with conventional navigator gating, and does so without the use of additional acquisitions or motion modeling, while still allowing for 100% scan efficiency and an improved ease-of-use. In conclusion, compressed sensing may become a critical adjunct for 2D translational motion correction in free-breathing cardiac imaging with high spatial resolution. An expansion to modern 3D approaches is now warranted.

Comparison of topography- and aperture-dependent motion compensation algorithms for airborne SAR

This letter presents a comparison between threeFourier-based motion compensation (MoCo) algorithms forairborne synthetic aperture radar (SAR) systems. These algorithmscircumvent the limitations of conventional MoCo, namelythe assumption of a reference height and the beam-center approximation.All these approaches rely on the inherent time–frequencyrelation in SAR systems but exploit it differently, with the consequentdifferences in accuracy and computational burden. Aftera brief overview of the three approaches, the performance ofeach algorithm is analyzed with respect to azimuthal topographyaccommodation, angle accommodation, and maximum frequencyof track deviations with which the algorithm can cope. Also, ananalysis on the computational complexity is presented. Quantitativeresults are shown using real data acquired by the ExperimentalSAR system of the German Aerospace Center (DLR).

Chronic subjective dizziness

CONCLUSION: Chronic subjective dizziness (CSD) is frequent and affects twice as many women as men. Anxiety is a strong predisposing factor. The pathophysiologic concept of this disorder assumes that balance function and emotion share common neurologic pathways, which might explain that the balance disorder can provoke fear and vice versa, giving rise to a problem in perception of space and motion. In anxious patients this can turn into a space and motion phobia, with avoidance behaviour. OBJECTIVE: CSD is a diagnosis based on the hypothesis of an interaction between the vestibular system and the psychiatric sphere. Patients complain of chronic imbalance, worsened by visual motion stimulation, and frequently suffer from anxiety. Vestibular examination reveals no anomalies. We evaluated the incidence and characteristics of CSD in patients referred to our neuro-otology centre (tertiary hospital outpatient clinic). SUBJECTS AND METHODS: This was a retrospective study of 1552 consecutive patients presenting with vertigo. CSD was diagnosed in 164 patients (female:male=111:53). RESULTS: CSD represents 10.6% of the dizzy patients in our clinic. Psychiatric disorder, mainly anxiety, was found in 79.3% of the cases. Other frequently associated factors were fear of heights and former vestibular lesion (healed). In all, 79.0% of the patients with CSD had poor balance performance on dynamic posturography testing.

Long time behaviour of diffusing particles in constrained geometries; application to chromatin motion

Inspired by experiments that use single-particle tracking to measure the regions of confinement of selected chromosomal regions within cell nuclei, we have developed an analytical approach that takes into account various possible positions and shapes of the confinement regions. We show, in particular, that confinement of a particle into a subregion that is entirely enclosed within a spherical volume can lead to a higher limit of the mean radial square displacement value than the one associated with a particle that can explore the entire spherical volume. Finally, we apply the theory to analyse the motion of extrachromosomal chromatin rings within nuclei of living yeast.

La perception de la productivité dans l'industrie hôtelière de luxe : le cas de la Suisse romande

La perception de la productivité SUMMARY The main objective of this thesis is the perception of the productivity in the luxury hospitality industry. Despite a lot of efforts which were already made in the field of the production of goods, this concept (productivity) still remains to be defined in the services sector, more still, in that of the luxury hospitality industry. Since the object of this study is the perception of productivity, we decided to analyze the elements considered to be relevant by the top management in this field. Then, it seemed important to evaluate these same elements for the categories of middle-management and by the in-line employees. As perception is not static, it is dependent in an indirect way on its improvement and however also with the means of improvement. The assumption of our work evokes the possible relationship between productivity and its perception (P), (Q) quality and profitability (R). On this basis we built the P-Q-R model: R=F(P,Q) Finally, our research on this model enabled us to establish a mathematical relation between the three predetermined elements: fR=fP+fQ+c That means that the function efficiency of a process of services -(fR) is the sum of its quality function (intrinsic and extrinsic)-(fP) and of its productivity function - fQ (and the constant of regression "c"). To increase the profitability of the most significant manner, it is necessary to increase at the same time the productivity and quality. On the other hand, according to this formula but also according to the perception of the managers, with a constant profitability, either the productivity decreases in favor of the increase in quality, or the reverse. If the dimensions of the model influence positively or negatively the production process of services, then those wí11 influence in same manner our model (P, Q, R). We advance a point of view saying that profitability depends on the labor productivity which follows same dynamics than the perception of the productivity. The identification of the labor productivity as an essential element of successful management of the hotel is fundamental. The question which always remains in suspense is however the relevance of the concept "labor productivity" for the luxury hospitality industry. It was not proven an obvious correlation between this notion and the one of profitability. We still remain at the stage of perception. It results that one interesting way of future research will be the study of this correlation. As in any kind of luxury industry, the real added value does not consist in the volume produced or in the speed with which the product/service is carried out but in the creativity involved in their results. Let us note that the field of luxury is extremely related to the emotions and to the experience provided to the customers. La perception de la productivité... RÉSUME L'objectif principal de cette thèse est la perception de la productivité dans l'hôtellerie de luxe. Malgré tous les efforts qui ont déjà été faits dans le domaine de la production de biens, ce concept (productivité) reste encore à définir dans le secteur des services, plus encore, dans celui de l'hôtellerie de luxe. Étant donné que l'objet de l'étude est la perception de la productivité, nous avons décidé d'analyser les éléments jugés pertinents par les cadres dirigeants dans ce domaine. Puis, il nous a semblé important d'évaluer ces mêmes éléments pour les catégories de cadres moyens et par les employés in-line. Comme la perception n'est pas statique, elle est liée d'une manière indirecte à son amélioration et cependant également aux moyens d'amélioration. L'hypothèse de notre travail évoque la possible relation entre la productivité et sa perception (P), la qualité (Q) et la rentabilité (R). Sur cette base nous avons construit le modèle P-Q-R de départ R=f(P,Q) Finalement, notre recherche sur ce modèle nous a permis d'établir une relation mathématique entre les trois construits prédéterminés: fR=fP+fQ+c Cela signifie que la fonction rentabilité d'un processus de services -(fR) est la somme de sa fonction qualité (intrinsèque et extrinsèque)-fP et de sa fonction productivité -fQ (plus la constante de régression « c ») Pour augmenter la rentabilité de la manière la plus significative, il faut augmenter en même temps la productivité et la qualité. En revanche, selon cette formule mais selon aussi la perception des managers, à une rentabilité constante, soit la productivité diminue en faveur de l'augmentation de la qualité, soit l'inverse. Si les dimensions du modèle influencent positivement ou négativement le processus de production de services, alors celles-ci vont influencer de la même manière les construits de notre modèle (P, Q, R). Nous avançons un point de vue disant que la rentabilité dépend de la productivité du travail qui suit la même dynamique que la perception de la productivité. L'identification de la productivité du travail comme élément essentiel de gestion réussie de l'hôtel s'avère fondamentale. La question qui reste toujours en suspens est pourtant la pertinence de la notion «productivité du travail » pour l'industrie hôtelière de luxe. Il n'a pas été prouvé une corrélation évidente entre cette notion et celle de la profitabilité. Nous restons donc ici encore au stade de perception. Il en résulte que l'une des voies les plus intéressantes de recherche future sera l'étude de cette corrélation. Comme dans toute industrie de luxe, la vraie valeur ajoutée ne consiste pas toujours dans le volume produit, ni dans la vitesse avec laquelle le produit/service est réalisé, mais parfois dans la créativité emmagasinée dans ces résultats. Notons que le domaine de luxe est extrêmement lié aux émotions et à l'expérience fournie aux clients.

Transitoriness : patients' perception of life after a diagnosis of cancer

This article analyses the concept of transitoriness, a perception of the end of life after cancer diagnosis, using Rodgers' (2000) framework of concept analysis, which is designed to review literature with the overall purpose of developing theories. The influence of transitoriness on cancer nursing practice is considered. Finally, an exemplary case is presented with implications for practice.

Locating and extracting the textual content from complex colour images using techniques inspired by human perception

Los sistemas de radio cognitivos son una solución a la deficiente distribución del espectro inalámbrico de frecuencias. Usando acceso dinámico al medio, los usuarios secundarios pueden comunicarse en canales de frecuencia disponibles, mientras los usuarios asignados no están usando dichos canales. Un buen sistema de mensajería de control es necesario para que los usuarios secundarios no interfieran con los usuarios primarios en las redes de radio cognitivas. Para redes en donde los usuarios son heterogéneos en frecuencia, es decir, no poseen los mismos canales de frecuencia para comunicarse, el grupo de canales utilizado para transmitir información de control debe elegirse cuidadosamente. Por esta razón, en esta tesis se estudian las ideas básicas de los esquemas de mensajería de control usados en las redes de radio cognitivas y se presenta un esquema adecuado para un control adecuado para usuarios heterogéneos en canales de frecuencia. Para ello, primero se presenta una nueva taxonomía para clasificar las estrategias de mensajería de control, identificando las principales características que debe cumplir un esquema de control para sistemas heterogéneos en frecuencia. Luego, se revisan diversas técnicas matemáticas para escoger el mínimo número de canales por los cuales se transmite la información de control. Después, se introduce un modelo de un esquema de mensajería de control que use el mínimo número de canales y que utilice las características de los sistemas heterogéneos en frecuencia. Por último, se comparan diversos esquemas de mensajería de control en términos de la eficiencia de transmisión.

Rank estimation of trajectory matrix in motion segmentation

A novel technique for estimating the rank of the trajectory matrix in the local subspace affinity (LSA) motion segmentation framework is presented. This new rank estimation is based on the relationship between the estimated rank of the trajectory matrix and the affinity matrix built with LSA. The result is an enhanced model selection technique for trajectory matrix rank estimation by which it is possible to automate LSA, without requiring any a priori knowledge, and to improve the final segmentation

Enhanced Model Selection for motion segmentation

In this paper a novel rank estimation technique for trajectories motion segmentation within the Local Subspace Affinity (LSA) framework is presented. This technique, called Enhanced Model Selection (EMS), is based on the relationship between the estimated rank of the trajectory matrix and the affinity matrix built by LSA. The results on synthetic and real data show that without any a priori knowledge, EMS automatically provides an accurate and robust rank estimation, improving the accuracy of the final motion segmentation

The European Union Perception of Cuba: From Frustation to Irritation

On Friday May 16, the Ministry of Foreign Affairs of Cuba summoned the newly-appointed charged’affairs of the European Commission in Havana and announced the withdrawal of the application procedure for membership in the Cotonou Agreement of the Africa, Caribbean, and Pacific (ACP) countries, and in fact renouncing to benefit from European development aid.1 In a blistering note published in the Granma official newspaper of the Cuban Communist Party, the government blamed the EU Commission for exerting undue pressure, its alleged alignment with the policies of the United States, and censure for the measures taken by Cuba during the previous weeks.2 In reality, Cuba avoided an embarrasin flat rejection for its application. This was the anti-climatic ending for a long process that can be traced back to the end of the Cold War, in a context where Cuba has been testing alternative grounds to substitute for the overwhelming protection of the Soviet Union

La perception des responsables des finances confrontée à l'économétrie des soldes budgétaires : le cas des cantons suisses

Cette contribution a pour objectif d'analyser comment les responsables cantonaux des finances perçoivent l'influence de certaines variables sur les soldes budgétaires publics. A cet effet, elle modélise la façon dont une erreur de perception peut influencer l'écart entre le solde budgété et le solde effectif. Ensuite, elle présente le questionnaire utilisé pour connaître la perception des responsables des finances des cantons suisses. Finalement, les résultats de l'enquête sont analysés, puis confrontés à ceux obtenus préalablement par des études économétriques. L'analyse montre qu'un consensus se dégage pour prêter une forte influence à certains facteurs (consensus autour de l'idée que les recettes déterminent les dépenses, etc.). Ces perceptions sont confondes aux conclusions des analyses économétriques. Pour d'autres facteurs (ancrage rural de la population etc.), elle montre que les perceptions divergent, alors que l'économétrie constate une influence significative et univoque. Ces résultats permettent de formuler quelques recommandations pour l'élaboration des budgets publics et pour la poursuite des études visant à modéliser les soldes budgétaires.