122 research outputs found

    One-Shot Mutual Covering Lemma and Marton's Inner Bound with a Common Message

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    By developing one-shot mutual covering lemmas, we derive a one-shot achievability bound for broadcast with a common message which recovers Marton's inner bound (with three auxiliary random variables) in the i.i.d.~case. The encoder employed is deterministic. Relationship between the mutual covering lemma and a new type of channel resolvability problem is discussed.Comment: 6 pages; extended version of ISIT pape

    Brascamp-Lieb Inequality and Its Reverse: An Information Theoretic View

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    We generalize a result by Carlen and Cordero-Erausquin on the equivalence between the Brascamp-Lieb inequality and the subadditivity of relative entropy by allowing for random transformations (a broadcast channel). This leads to a unified perspective on several functional inequalities that have been gaining popularity in the context of proving impossibility results. We demonstrate that the information theoretic dual of the Brascamp-Lieb inequality is a convenient setting for proving properties such as data processing, tensorization, convexity and Gaussian optimality. Consequences of the latter include an extension of the Brascamp-Lieb inequality allowing for Gaussian random transformations, the determination of the multivariate Wyner common information for Gaussian sources, and a multivariate version of Nelson's hypercontractivity theorem. Finally we present an information theoretic characterization of a reverse Brascamp-Lieb inequality involving a random transformation (a multiple access channel).Comment: 5 pages; to be presented at ISIT 201

    A General Mechanistic Model for Admixture Histories of Hybrid Populations

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    Admixed populations have been used for inferring migrations, detecting natural selection, and finding disease genes. These applications often use a simple statistical model of admixture rather than a modeling perspective that incorporates a more realistic history of the admixture process. Here, we develop a general model of admixture that mechanistically accounts for complex historical admixture processes. We consider two source populations contributing to the ancestry of a hybrid population, potentially with variable contributions across generations. For a random individual in the hybrid population at a given point in time, we study the fraction of genetic admixture originating from a specific one of the source populations by computing its moments as functions of time and of introgression parameters. We show that very different admixture processes can produce identical mean admixture proportions, but that such processes produce different values for the variance of the admixture proportion. When introgression parameters from each source population are constant over time, the long-term limit of the expectation of the admixture proportion depends only on the ratio of the introgression parameters. The variance of admixture decreases quickly over time after the source populations stop contributing to the hybrid population, but remains substantial when the contributions are ongoing. Our approach will facilitate the understanding of admixture mechanisms, illustrating how the moments of the distribution of admixture proportions can be informative about the historical admixture processes contributing to the genetic diversity of hybrid populations

    Multidetector cardiac tomography: A useful tool before cardiac resynchronization therapy

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    Background: Left ventricular lead placement in a suitable coronary vein is a key determi­nant of responsiveness to cardiac resynchronization therapy (CRT). Multidetector cardiac tomography (MDCT) is a non-invasive alternative to depict cardiac venous anatomy although coronary sinus (CS) retrograde venography (RV) is the gold standard. The aim of this study was to evaluate the accuracy of MDCT to determine the presence of CS tributaries before CRT. Methods: A retrospective analysis of 41 consecutive patients eligible to CRT was performed. MDCT was assessed in all patients before CRT and RV was achieved in 39 patients. Both methods evaluated the presence of the inferior interventricular vein (IIV), posterior vein (PV) and lateral main vein (LMV). CS ostium diameter and distance between the CS ostium and right atrium (RA) lateral wall were also measured. Results: The IIV was identified in 100% of MDCT and in 43.6% of RV. In comparison to RV, the MDCT’s sensitivity to identify PV and LMV was 100% for both, kappa coefficient of 0.792 (CI 95% 0.46–0.93) and 0.69 (CI 95% 0.46–0.91), respectively. There was no significant difference between ischemic and non-ischemic patients regarding the presence of PV or LMV. Median CS antero-posterior diameter was 10.3 mm (IQR 7.5–13) and supero-inferior was 14.1 mm (IQR 11.5–17) (p < 0.01). A positive correlation (p < 0.001) between echocardiographic RA area and the distance from CS ostium to the RA lateral wall in the MDCT was observed. Conclusions: MDCT is as accurate as RV to depict CS and its tributaries (IIV, PV, LMV), and it could be useful as a non-invasive technique before CRT

    A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

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    Perspectives de la gĂ©nĂ©tique humaine sur l’origine et la diversitĂ© des populations pygmĂ©es d’Afrique centrale

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    Aujourd’hui, les outils de la gĂ©nĂ©tique des populations sont communĂ©ment utilisĂ©s pour dĂ©crire la diversitĂ© biologique des populations humaines Ă  travers le monde et pour tenter de reconstruire l’histoire du peuplement humain. RĂ©cemment, plusieurs Ă©tudes se sont attachĂ©es Ă  reconstruire l’origine et l’histoire dĂ©mographique des populations dites pygmĂ©es et de leurs voisins non-pygmĂ©es en Afrique centrale, Ă  partir de donnĂ©es gĂ©nĂ©tiques. Nous prĂ©sentons ici les principaux paradigmes, mĂ©thodes et rĂ©sultats de ces Ă©tudes d’anthropologie gĂ©nĂ©tique. Nous montrons comment les gĂ©nĂ©ticiens ont dĂ©couvert que les populations dites « PygmĂ©es » ont probablement une origine commune rĂ©cente, et ce malgrĂ© l’extraordinaire diversitĂ© gĂ©nĂ©tique observĂ©e aujourd’hui entre ces populations. En outre, ces travaux montrent que, bien loin d’ĂȘtre des populations isolĂ©es gĂ©nĂ©tiquement, les diffĂ©rentes populations pygmĂ©es prĂ©sentent des flux de gĂšnes substantiels avec leurs voisins non-pygmĂ©es. Ces flux de gĂšnes sont dĂ©terminĂ©s par les comportements socio-culturels entre communautĂ©s et diffĂšrent d’une population pygmĂ©e d’Afrique centrale Ă  l’autre.Population genetics methods are widely used nowadays to describe the biological diversity of human populations worldwide and to try to reconstruct the history of human migrations. Recently, a number of studies have used genetic data to reconstruct the origins and demographic history of Pygmy and neighboring Non-Pygmy populations from Central Africa. We present here the main paradigm, methods, and results of these anthropological genetics studies. We show how geneticists discovered that the Pygmy populations share a recent common origin, despite the great genetic variability exhibited among these populations today. Furthermore, these genetics studies showed that Pygmy populations are not genetic isolates but, on the opposite, share substantial levels of gene flow with their non-pygmy neighbors. This gene flow is determined by sociocultural behaviors between communities and is variable across Pygmy populations throughout Central Africa
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