Highly trans-stereospecific Isoprene Polymerization by Neodymium Borohydrido Catalysts

Highly stereospecific polymerization of isoprene was achieved using borohydrido neodymium complexes. In combination with stoichiometric amounts of dialkylmagnesium, Nd(BH4)3(THF)3 (1) and Cp*'Nd(BH4)2(THF)2 (2) (Cp*' = C5Me4nPr) afford very efficient catalysts. Activity reaches 37300 g polyisoprene/mol Nd/h. Half-lanthanidocene 2 gives rise to polyisoprene 98.5 % trans-regular, the highest content yet described for a homogeneous organometallic catalyst. NMR experiments argue for the formation of bimetallic Nd(m-BH4)Mg active species

Ultraviolet photon absorption in single- and double-wall carbon nanotubes and peapods: Heating-induced phonon line broadening, wall coupling, and transformation

Ultraviolet photon absorption has been used to heat single- and double-wall carbon nanotubes and peapods in vacuum. By increasing the laser intensity up to 500 mW, a downshift and a broadening of the optical phonons are observed corresponding to a temperature of 1000°C. The UV Raman measurements are free of blackbody radiation. We find that the linewidth changes for the G+ and G− bands differ considerably in single-wall carbon nanotubes. This gives evidence that the phonon decay process is different in axial and radial tube directions. We observe the same intrinsic linewidths of graphite (highly oriented pyrolytic graphite) for the G band in single- and double-wall carbon nanotubes. With increasing temperature, the interaction between the walls is modified for double-wall carbon nanotubes. Ultraviolet photon induced transformations of peapods are found to be different on silica and diamond substrates

Some open questions on anti-de Sitter geometry

We present a list of open questions on various aspects of AdS geometry, that is, the geometry of Lorentz spaces of constant curvature -1. When possible we point out relations with homogeneous spaces and discrete subgroups of Lie groups, to Teichm\"uller theory, as well as analogs in hyperbolic geometry.Comment: Not a research article in the usual sense but rather a list of open questions. 19 page

La bibliothèque en 8 questions… à Lucien Suel, Jean-Marc Flahaut, Fanny Chiarello et Carole Fives

Quatre écrivains aux univers singuliers plongent au cœur de leur rapport à la bibliothèque. Ils disent beaucoup de nous, et d’eux davantage encore

La place de l'expertise face aux mesures de protection civile en situation de crise

La place de l'expertise face aux mesures de protection civile en situation de crise Rapport du Groupe d'Analyse d'Action Publique pour le master PAPDD, année universitaire 2015-2016. Pour le compte du laboratoire en sciences humaines et sociales de l'IRSN. Fanny BONTEMPS, Céline JAUFFRET, Marc JOSIEN, Cyril de MESMAY et Valentine VERZAT Encadré par Elsa GISQUET (IRSN) La prise de décisions de protection des populations en cas de catastrophes naturelles ou industrielles exige une expertise de plus en plus pointue dans un contexte de densité croissante et de multiplication des industries sensibles. Comment cette expertise est-elle mobilisée auprès du décideur ? Sa production et sa transmission sont-elles différentes selon le type de crise ? Quelles sont les éventuelles marges de progression ? Nous présentons ici un premier diagnostic de la situation et plusieurs pistes d'amélioration. a crise nucléaire de Fukushima en mars 2011 a démontré la fragilité de l'organisation de crise et les difficultés de communication entre le décideur public et l'exploitant. Ce constat a poussé les acteurs du nucléaire à réfléchir à l'amélioration de la résilience du système de gouvernance en temps de crise. Certains acteurs, dont l'IRSN, se sont rassemblés au sein du projet Agoras. Ce projet vise à décortiquer les relations entre les différents acteurs de la gouvernance des risques nucléaires. Notre étude se place en parallèle de ce projet et s'intéresse plus particulièrement à la place de l'expertise face aux mesures de protection civile en temps de crise. Son objectif est de mieux connaître les spécificités du domaine nucléaire et de tirer des leçons de la gestion d'autres types de crise en s'intéressant aussi aux catastrophes chimiques et naturelles. De la production de l'expertise la plus poussée au sein des différents organismes scientifiques jusqu'à la prise de décision au sein des préfectures, nous verrons quelles sont les spécificités des différentes filières, comment ces spécificités sont appréhendées par le décideur et enfin comment en tenir compte pour mieux protéger la population

Tuning the catalytic properties of rare earth borohydrides for the polymerisation of isoprene

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Prolonged and unprolonged complex febrile seizures differently affect frontal theta brain activity

Objective: Studies have identified persistent cognitive and functional deficits, which could be linked to each other, in children with complex febrile seizures (FS). Our aim was to investigate differences in brain activity in children with a history of complex FS, through a study paradigm associated with the development of learning capacities and using electroencephalographic (EEG) signal. To further increase our understanding of these differences, complex FS were studied separately depending on their type. Method: EEG was recorded in 43 children with past FS. Brain activity associated with auditory learning was investigated using a habituation paradigm, in which repetition suppression (RS) is typically found following stimulus repetition. Auditory stimuli were repeated three times, and each presentation were analysed separately in the time-frequency (TF) domain. A mixedanalysis of variance was used to assess differences in spectral power between stimulus repetition and FS type (simple vs complex prolonged; CP vs complex unprolonged; CUP). Results: Repetition effects were found in the 3-6 Hz during 150-600ms time window after stimulus onset at frontal sites (F(2, 40)=5.645, p=0.007, η2p=0.220). Moreover, an interaction effect between stimulus repetition and FS type (F(4, 80)=2.607, p=0.042, η2p=0.115) was found. Children with CP FS showed greater increase in spectral power in response to the first stimulus presentation, while children with CUP FS failed to show a RS pattern. Significance: Our results show distinct abnormalities in brain activity to a habituation paradigm. We argue that these changes suggest children with CP FS may be hyperexcitable, while children with CUP FS show impaired habituation processes. Still, these differences may be associated with other clinical features linked to complex FS as well. Hence, the role of these differences in complex FS incidence and prognosis should be the subject of future studies

How can integrated valuation of ecosystem services help understanding and steering agroecological transitions?

Agroecology has been proposed as a promising concept to foster the resilience and sustainability of agroecosystems and rural territories. Agroecological practices are based on optimizing ecosystem services (ES) at the landscape, farm, and parcel scales. Recent progress in research on designing agroecological transitions highlights the necessity for coconstructed processes that draw on various sources of knowledge based on shared concepts. But despite the sense of urgency linked to agroecological transitions, feedbacks from real-world implementation remain patchy. The ability of integrated and participatory ES assessments to support this transition remains largely underexplored, although their potential to enhance learning processes and to build a shared territorial perspective is widely recognized. The overarching question that will be asked in this paper is thus: what is the potential of the ES framework to support the understanding and steering of agroecological transitions? We argue that conducting collaborative and integrated assessments of ES bundles can (i) increase our understanding of the ecological and social drivers that support a transition toward agroecological systems, and (ii) help design agroecological systems based on ES delivery and effectively accompany transition management based on shared knowledge, codesigned future objectives, and actual on-the-ground implementation. In this paper, we discuss this question and propose a four-step integrated ES assessment framework specifically targeted at understanding and steering agricultural transitions that is generic enough to be applied in different contexts

Structural diversity in the borohydrido lanthanides series: first isolation and X Ray crystal structure of ionic [Sm(BH4)2(THF)5]+[Cp*'Sm(BH4)3]-

International audienceTwo new borohydrido complexes of samarium were prepared: [Sm(BH4)2(THF)5]+[Cp*'Sm(BH4)3]- (1) and Cp*'2Sm(BH4)(THF) (3) (Cp*' = C5Me4nPr). X Ray studies revealed that 1 displays an unprecedented ionic structure comprising a half samarocene moiety, whereas 3 is monomeric and bears a terminal BH4 ligand

Alzheimer's hand gestures and speech disorders in spoken and sung modalities

International audienceIn Alzheimer's disease (AD), studies on bimodal language production like that of Carlomagno et al. (2005) do not treat aspects of speech and hand gestures in a concomitant way. We propose an original protocol to evaluate the correlation between hand gestures and articulatory gestures in speech and singing of 4 persons diagnosed with AD by our hospital partner and paired with 4 control participants. Participants were asked to repeat 8 nursery rhymes created for this protocol: 4 nursery rhymes were spoken while the other 4 were sung. In each sung or spoken modality, 2 nursery rhymes were completed with four iconic and two deictic hand gestures. The protocol was completed with several clinical tests. Speech apraxia was evaluated by means of the MT86 clinical protocol (Joanette et al., 1998) and manual praxis by the Mahieux's battery (Mahieux-Laurent et al., 2009). The MBLF software was adapted to test the bucco-linguo-facial motor skills (Gatignol& Lannadère, 2011). Each participant was recorded at home using a camcorder and a lapel microphone. The speech productions were annotated and analyzed via Praat©, and the hand gestures via ELAN©. We did not evidence any manual or speech apraxia in our patient population. However, significant differences were observed on productions of hand gestures and speech between the patients and the control participants. Regarding patients, the movement, configuration and orientation of hand gestures were slightly altered. This alteration seemed to depend on the gesture value but not on the modality (speech or singing). The requirement to produce specific hand gestures affected speech production: patients produced more errors with connected hand gestures. Speech productions were influenced at different degrees by spoken and sung modalities. Patients made more errors in singing, and the more with connected hand gestures, showing a double task effect likely due to an attention deficiency typical of AD (Siéroff & Piquard, 2004)