Kinematic Alpha Tensors and dynamo mechanisms in a von Karman swirling flow

We provide experimental and numerical evidence of in-blades vortices in the von Karman swirling flow. We estimate the associated kinematic α-effect tensor and show that it is compatible with recent models of the von Karman Sodium (VKS) dynamo. We further show that depending on the relative frequency of the two impellers, the dominant dynamo mechanism may switch from α^2 to α − Ω dynamo. We discuss some implications of these results for VKS experiments

Introduction aux problèmes de la philosophie indienne classique et médiévale

Ces conférences avaient pour but de présenter une introduction à la philosophie indienne. Ne prétendant nullement à l’exhaustivité, et ne proposant ni une fresque historique du développement de la pensée en Inde, ni un tableau statique des différentes écoles de pensée indiennes, elles ont consisté en l’analyse de l’élaboration d’un problème philosophique particulier – celui de l’identité personnelle – depuis le début de la période classique (iiie-ve siècles) jusqu’au cœur de la période médiév..

Kinematic alpha Tensors and Dynamo Mechanisms in a von Karman Swirling Flow

International audienceWe provide experimental and numerical evidence of in-blades vortices in the von Karman swirling flow. We estimate the associated kinematic alpha-effect tensor and show that it is compatible with recent models of the von Karman sodium (VKS) dynamo. We further show that depending on the relative frequency of the two impellers, the dominant dynamo mechanism may switch from alpha^2 to alpha-omega dynamo. We discuss some implications of these results for VKS experiments

Development of the basal hypothalamus through anisotropic growth

The adult hypothalamus is subdivided into distinct domains: pre‐optic, anterior, tuberal and mammillary. Each domain harbours an array of neurones that act together to regulate homeostasis. The embryonic origins and the development of hypothalamic neurones, however, remain enigmatic. Here, we summarise recent studies in model organisms that challenge current views of hypothalamic development, which traditionally have attempted to map adult domains to correspondingly located embryonic domains. Instead, new studies indicate that hypothalamic neurones arise from progenitor cells that undergo anisotropic growth, expanding to a greater extent than other progenitors, and grow in different dimensions. We describe in particular how a multipotent Shh/Fgf10‐expressing progenitor population gives rise to progenitors throughout the basal hypothalamus that grow anisotropically and sequentially: first, a subset displaced rostrally give rise to anterior‐ventral/tuberal neuronal progenitors; then a subset displaced caudally give rise to mammillary neuronal progenitors; and, finally, a subset(s) displaced ventrally give rise to tuberal infundibular glial progenitors. As this occurs, stable populations of Shh+ive and Fgf10+ive progenitors form. We describe current understanding of the mechanisms that induce Shh+ive/Fgf10+ive progenitors and begin to direct their differentiation to anterior‐ventral/tuberal neuronal progenitors, mammillary neuronal progenitors and tuberal infundibular progenitors. Taken together, these studies suggest a new model for hypothalamic development that we term the “anisotropic growth model”. We discuss the implications of the model for understanding the origins of adult hypothalamic neurones

Novel genes upregulated when NOTCH signalling is disrupted during hypothalamic development.

International audienceBACKGROUND: The generation of diverse neuronal types and subtypes from multipotent progenitors during development is crucial for assembling functional neural circuits in the adult central nervous system. It is well known that the Notch signalling pathway through the inhibition of proneural genes is a key regulator of neurogenesis in the vertebrate central nervous system. However, the role of Notch during hypothalamus formation along with its downstream effectors remains poorly defined. RESULTS: Here, we have transiently blocked Notch activity in chick embryos and used global gene expression analysis to provide evidence that Notch signalling modulates the generation of neurons in the early developing hypothalamus by lateral inhibition. Most importantly, we have taken advantage of this model to identify novel targets of Notch signalling, such as Tagln3 and Chga, which were expressed in hypothalamic neuronal nuclei. CONCLUSIONS: These data give essential advances into the early generation of neurons in the hypothalamus. We demonstrate that inhibition of Notch signalling during early development of the hypothalamus enhances expression of several new markers. These genes must be considered as important new targets of the Notch/proneural network

DMRT5, DMRT3, and EMX2 Cooperatively Repress at the Pallium-Subpallium Boundary to Maintain Cortical Identity in Dorsal Telencephalic Progenitors

Specification of dorsoventral regional identity in progenitors of the developing telencephalon is a first pivotal step in the development of the cerebral cortex and basal ganglia. Previously, we demonstrated that the two zinc finger doublesex and mab-3 related (Dmrt) genes, Dmrt5 (Dmrta2) and Dmrt3, which are coexpressed in high caudomedial to low rostrolateral gradients in the cerebral cortical primordium, are separately needed for normal formation of the cortical hem, hippocampus, and caudomedial neocortex. We have now addressed the role of Dmrt3 and Dmrt5 in controlling dorsoventral division of the telencephalon in mice of either sex by comparing the phenotypes of single knock-out (KO) with double KO embryos and by misexpressing Dmrt5 in the ventral telencephalon. We find that DMRT3 and DMRT5 act as critical regulators of progenitor cell dorsoventral identity by repressing ventralizing regulators. Early ventral fate transcriptional regulators expressed in the dorsal lateral ganglionic eminence, such as Gsx2, are upregulated in the dorsal telencephalon of Dmrt3;Dmrt5 double KO embryos and downregulated when ventral telencephalic progenitors express ectopic Dmrt5. Conditional overexpression of Dmrt5 throughout the telencephalon produces gene expression and structural defects that are highly consistent with reduced GSX2 activity. Further, Emx2;Dmrt5 double KO embryos show a phenotype similar to Dmrt3;Dmrt5 double KO embryos, and both DMRT3, DMRT5 and the homeobox transcription factor EMX2 bind to a ventral telencephalon-specific enhancer in the Gsx2 locus. Together, our findings uncover cooperative functions of DMRT3, DMRT5, and EMX2 in dividing dorsal from ventral in the telencephalon. SIGNIFICANCE STATEMENT We identified the DMRT3 and DMRT5 zinc finger transcription factors as novel regulators of dorsoventral patterning in the telencephalon. Our data indicate that they have overlapping functions and compensate for one another. The double, but not the single, knock-out produces a dorsal telencephalon that is ventralized, and olfactory bulb tissue takes over most remaining cortex. Conversely, overexpressing Dmrt5 throughout the telencephalon causes expanded expression of dorsal gene determinants and smaller olfactory bulbs. Furthermore, we show that the homeobox transcription factor EMX2 that is coexpressed with DMRT3 and DMRT5 in cortical progenitors cooperates with them to maintain dorsoventral patterning in the telencephalon. Our study suggests that DMRT3/5 function with EMX2 in positioning the pallial-subpallial boundary by antagonizing the ventral homeobox transcription factor GSX2

"A Five-trunked, Four-tusked Elephant is Running in the Sky": How Free is Imagination According to Utpaladeva and Abhinavagupta?

According to the Śaiva non dualists Utpaladeva (fl. c. 925-975) and Abhinavagupta (fl. c. 975-1025), imaginary objects, far from being a mere rearrangement of previously perceived elements, are original creations resulting from consciousness’s free creativity. The present article examines how the Pratyabhijñā philosophers defend this thesis against Naiyāyika and Mīmāṃsaka theories of imagination, but also how they link it with their idealism, since Utpaladeva and Abhinavagupta contend that the phenomenal world is created by a universal consciousness through a process similar to the individual subject’s activity of imagination. They thus state – as the Advaita Vedāntins or the Buddhist Vijñānavādins – that the world is an imaginary construction, but they refuse to draw from this the conclusion that it is unreal: paradoxically, they consider that the world is real insofar as it is imagined, and they see imagination as an experience capable of leading the individual subject to liberation

Additional Fragments of Utpaladeva's Vivr̥ti

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Autorité scripturaire et discours philosophique dans l’Inde médiévale : les exemples bouddhique et śivaïte

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In search of Utpaladeva’s lost Vivṛti on the Pratyabhijñā treatise: a report on the latest discoveries (with the Vivṛti on the end of Chapter 1.8)

International audienceThe Īśvarapratyabhijñā treatise – an important philosophical text composed in Kashmir in the 10th century CE by the Śaiva nondualist Utpaladeva – remains partly unavailable to date: a crucial component of this work, namely the detailed commentary (Vivṛti or Ṭīkā) in which Utpaladeva explained his own verses, is considered as almost entirely lost, since only a small part of it has been preserved in a single, very incomplete manuscript remarkably edited and translated by Raffaele Torella. However, our knowledge of the Vivṛti is quickly expanding: many additional fragments have recently come to light. The article gives an overview of these new findings while highlighting the most interesting of them, i.e. the discovery of the lengthiest Vivṛti fragment known to date in the margins of a manuscript containing Abhinavagupta’s Vivṛtivimarśinī. It also provides an edition and translation of the beginning of this fragment.https://paris3.academia.edu/IsabelleRati%C3%A