Wonderful varieties of type D

Let G be a complex connected semisimple group, whose simple components have type A or D. We prove that wonderful G-varieties are classified by means of combinatorial objects called spherical systems. This is a generalization of a known result of Luna for groups of type A; thanks to another result of Luna, this implies also the classification of all spherical G-varieties for the groups G we are considering. For these G we also prove the smoothness of the embedding of Demazure.Comment: 60 pages, AMSLaTeX, 11 eps file

Primitive wonderful varieties

We complete the classification of wonderful varieties initiated by D. Luna. We review the results that reduce the problem to the family of primitive varieties, and report the references where some of them have already been studied. Finally, we analyze the rest case-by-case.Comment: v1: 16 pages, this is the second of three papers which are going to supersede arXiv:0909.3771; v2: 30 pages, to appear in Math.

Wonderful varieties of type D

The classification of spherical varieties is already known for semi- simple groups of types A \mathsf A and D \mathsf D . Adding type E \mathsf E , we complete the classification for all semisimple groups with a simply laced Dynkin diagram

Wonderful subgroups of reductive groups and spherical systems

Let G be a semisimple complex algebraic group, and H a wonderful subgroup of G. We prove several results relating the subgroup H to the properties of a combinatorial invariant S of G/H, called its spherical system. It is also possible to consider a spherical system S as a datum defined by purely combinatorial axioms, and under certain circumstances our results prove the existence of a wonderful subgroup H associated to S. As a byproduct, we reduce for any group G the proof of the classification of wonderful G-varieties, known as the Luna conjecture, to its verification on a small family of cases, called primitive.Comment: v1: 34 pages, this is the first of three papers which are going to supersede arXiv:0909.3771; v2: 39 pages, revised version accepted for publication in Journal of Algebr

Communication non conventionnelle et nudging en contexte urbain

2noDans une perspective sémiotique, le nudging peut être envisagé, dans le cadre d’une pédagogie sociale « bienveillante », comme un discours à visée stratégique non prescriptive, où l’interaction de communication joue sur la compétence des destinateurs et énonciateurs à reconnaître, préfigurer et réorienter le savoir, le croire, et le sentir qui sont à la base de l’action de leurs interlocuteurs et destinataires. L’élaboration d’une stratégie efficace de nudging implique la planification d’actions de communication capables de modifier et redéfinir des relations et les rôles des sujets impliqués dans le discours du bien public. Dans cette perspective, pour mieux identifier et suggérer des parcours efficaces de nudging, à différentes échelles, il nous semble intéressant d’observer et d’analyser ce domaine de la communication publique qui se présente sous des formes soi-disant « non conventionnelles ». En particulier, nous nous proposons de travailler sur un corpus des formes de communication d’intérêt collectif choisies parmi les plus provocantes mises en place par des administrations, des groupes d’intérêt collectif ou des associations, dans les espaces urbains. Ces campagnes de communication impliquent souvent l’utilisation non conventionnelle des lieux de la vie quotidienne, et sont destinées à endiguer et à contourner les biais responsables des comportements nuisibles, et à suggérer des nouvelles perspectives d’interactions dans l’espace public. Il s’agit d’objets d’analyse assez complexes, à sémiotiser à l’intersection entre sémiotique de l’espace et sémiotique des formes de vie.openopenPaolo Peverini; Isabella PezziniPeverini, Paolo; Pezzini, Isabell

Development of Real-Time System Identification to Detect Abnormal Operations in a Gas Turbine Cycle

This paper presents a novel online system identification methodology for monitoring the performance of power systems. This methodology was demonstrated in a gas turbine recuperated power plant designed for a hybrid configuration. A 120-kW Garrett microturbine modified to test dynamic control strategies for hybrid power systems designed at the National Energy Technology Laboratory (NETL) was used to implement and validate this online system identification methodology. The main component of this methodology consists of an empirical transfer function model implemented in parallel to the turbine speed operation and the fuel control valve, which can monitor the process response of the gas turbine system while it is operating. During fully closed-loop operations or automated control, the output of the controller, fuel valve position, and the turbine speed measurements were fed for a given period of time to a recursive algorithm that determined the transfer function parameters during the nominal condition. After the new parameters were calculated, they were fed into the transfer function model for online prediction. The turbine speed measurement was compared against the transfer function prediction, and a control logic was implemented to capture when the system operated at nominal or abnormal conditions. To validate the ability to detect abnormal conditions during dynamic operations, drifting in the performance of the gas turbine system was evaluated. A leak in the turbomachinery working fluid was emulated by bleeding 10% of the airflow from the compressor discharge to the atmosphere, and electrical load steps were performed before and after the leak. This tool could detect the leak 7 s after it had occurred, which accounted for a fuel flow increase of approximately 15.8% to maintain the same load and constant turbine speed operations

Ischemic Stroke during Pregnancy and Puerperium

Ischemic stroke during pregnancy and puerperium represents a rare occurrence but it could be a serious and stressful event for mothers, infants, and also families. Whenever it does occur, many concerns arise about the safety of the mother and the fetus in relation to common diagnostic tests and therapies leading to a more conservative approach. The physiological adaptations in the cardiovascular system and in the coagulability that accompany the pregnant state, which are more significant around delivery and in the postpartum period, likely contribute to increasing the risk of an ischemic stroke. Most of the causes of an ischemic stroke in the young may also occur in pregnant patients. Despite this, there are specific conditions related to pregnancy which may be considered when assessing this particular group of patients such as pre-eclampsia-eclampsia, choriocarcinoma, peripartum cardiomiopathy, amniotic fluid embolization, and postpartum cerebral angiopathy. This article will consider several questions related to pregnancy-associated ischemic stroke, dwelling on epidemiological and specific etiological aspects, diagnostic issue concerning the use of neuroimaging, and the related potential risks to the embryo and fetus. Therapeutic issues surrounding the use of anticoagulant and antiplatelets agents will be discussed along with the few available reports regarding the use of thrombolytic therapy during pregnancy

The Migraine-Ischemic Stroke Relation in Young Adults

In spite of the strong epidemiologic evidence linking migraine and ischemic stroke in young adults, the mechanisms explaining this association remain poorly understood. The observation that stroke occurs more frequently during the interictal phase of migraine prompts to speculation that an indirect relation between the two diseases might exist. In this regard, four major issues might be considered which may be summarized as follows: (1) the migraine-ischemic stroke relation is influenced by specific risk factors such as patent foramen ovale or endothelial dysfunction and more frequent in particular conditions like spontaneous cervical artery dissection; (2) migraine is associated with an increased prevalence of cardiovascular risk factors; (3) the link is caused by migraine-specific drugs; (4) migraine and ischemic vascular events are linked via a genetic component. In the present paper, we will review epidemiological studies, discuss potential mechanisms of migraine-induced stroke and comorbid ischemic stroke, and pose new research questions

Surge and Stall Detection Using Acoustic Analysis for Gas Turbine Hybrid Cycles

Compressor dynamics were studied in a gas turbine—fuel cell hybrid power system having a larger compressor volume than traditionally found in gas turbine systems. This larger compressor volume adversely affects the surge margin of the gas turbine. Industrial acoustic sensors were placed near the compressor to identify when the equipment was getting close to the surge line. Fast Fourier transform (FFT) mathematical analysis was used to obtain spectra representing the probability density across the frequency range (0–5000 Hz). Comparison between FFT spectra for nominal and transient operations revealed that higher amplitude spikes were observed during incipient stall at three different frequencies, 900, 1020, and 1800 Hz. These frequencies were compared to the natural frequencies of the equipment and the frequency for the rotating turbomachinery to identify more general nature of the acoustic signal typical of the onset of compressor surge. The primary goal of this acoustic analysis was to establish an online methodology to monitor compressor stability that can be anticipated and avoided