Conversation Trees: A Grammar Model for Topic Structure in Forums

Online forum discussions proceed differently from face-to-face conversations and any single thread on an online forum contains posts on different subtopics. This work aims to characterize the content of a forum thread as a conversation tree of topics. We present models that jointly per- form two tasks: segment a thread into sub- parts, and assign a topic to each part. Our core idea is a definition of topic structure using probabilistic grammars. By leveraging the flexibility of two grammar formalisms, Context-Free Grammars and Linear Context-Free Rewriting Systems, our models create desirable structures for forum threads: our topic segmentation is hierarchical, links non-adjacent segments on the same topic, and jointly labels the topic during segmentation. We show that our models outperform a number of tree generation baselines

Politiques et pratiques culturelles en France et aux États-Unis

Annie Cohen-Solal, professeur certifiée Médiateurs culturels et capteurs de modernité dans le monde des arts plastiques entre Paris et New York Dans le cadre de notre analyse comparée de la scène des arts plastiques en France et aux États-Unis, nous avons d’abord considéré la première moitié du XXe siècle, à partir des différents acteurs qui interviennent dans le champ. L’action de certains d’entre eux, que nous qualifieront d’« acteurs dynamiques » – les collectionneurs, mécènes, galéristes,..

Role of Exercise and GDNF in an Animal Model of Parkinson's Disease: Implications for Neuroprotection

Parkinson's disease (PD) is a progressive neurodegenerative disorder resulting in part from loss of nigrostriatal dopamine (DA) neurons. Treatments act only to relieve symptoms. It is therefore essential to develop treatments that slow or reverse the neurodegenerative process. Here, I explored exercise as a potential treatment against a 6-hydroxydopamine (6-OHDA) rat model. 6-OHDA causes selective loss of DA neurons, a PD model. Forced limb use after 6-OHDA ameliorates behavioral and striatal DA effects. Further, exercise increases trophic factors, such as GDNF, that have neuroprotective qualities in this model. I explored the effects of forced limb use prior to 6-OHDA on the effects of the toxin and GDNF levels in the striatum. I demonstrated that prior forced limb use attenuated the behavioral deficits and loss of DA typical of 6-OHDA and increased GDNF in the striatum of animals exposed to forced use. The protective effect of exercise could reflect a decrease in the vulnerability of DA neurons, a regeneration of axons, or sprouting of axon terminals from undamaged neurons. Thus, I investigated the hypothesis that casting induced neuroprotection was due to the preservation of DA cells and terminals. Here, I demonstrated that forced limb use protected from 6-OHDA induced loss of DA neurons and terminals. These findings suggest that exercise exerts its effects by decreasing the vulnerability of DA neurons and terminals to 6-OHDA. Because casting increased GDNF, I next examined the effects of GDNF on 6-OHDA neurotoxicity during the 8 wk period after 6-OHDA. Using phenotypic markers of the nigrostriatal system, a non-DA cellular marker, and striatal DA content, I demonstrated these markers in the striatum and SN were not protected at 2 wks after 6-OHDA but recovered by 8 wks. No loss of DA cells in the SN or DA content in the striatum was observed in animals pretreated with GDNF. These data suggest that GDNF prevents 6-OHDA-induced DA cell death, but that weeks are required before these cells begin to normally express phenotypic markers. In conclusion, exercise may function to enhance the brain's ability to produce trophic factors, which may slow or halt the degenerative process in PD

Politiques et pratiques culturelles en France et aux États-Unis

Annie Cohen-Solal, professeur Le monde des arts plastiques de l’ère du modernisme à celle de la globalisation : déplacements géographiques et transformations des acteurs Dans le cadre de notre analyse comparée de la scène des arts plastiques en France et aux États-Unis, nous avons d’abord considéré la première moitié du XXe siècle, à partir des différents acteurs qui interviennent dans le champ. L’action de certains d’entre eux, que nous qualifieront d’« acteurs dynamiques » – les collectionn..

Politiques et pratiques culturelles en France et aux États-Unis (XIXe-XXe siècles)

Annie Cohen-Solal, professeur agrégée chercheur à l’IMEC La construction d’un art américain et les lieux de légitimation : l’exemple des arts plastiques entre Paris et New York Nous avons poursuivi le travail qui nous a occupé l’année précédente et continué notre analyse en l’appliquant à la période du début du XXe siècle, dans la même perspective : analyse des processus et non des produits ; utilisation d’outils pluridisciplinaires hérités des sciences sociales ; approche croisée des réalité..

L'exposition Picasso l'étranger

Hommes & Migrations : Quels types d’archives constituent, selon vous, la meilleure ressource pour revisiter la trajectoire et l’œuvre de Pablo Picasso ?Annie Cohen-Solal : Tout d’abord, les archives administratives, dans lesquelles j’ai travaillé en premier, notamment celles de la préfecture de police que j’ai croisées avec les documents trouvés aux archives nationales, aux archives diplomatiques, aux archives de Paris, ainsi qu’avec celles des musées américains, espagnols, russes, etc. Elle..

Rate of Convergence of Space Time Approximations for stochastic evolution equations

Stochastic evolution equations in Banach spaces with unbounded nonlinear drift and diffusion operators driven by a finite dimensional Brownian motion are considered. Under some regularity condition assumed for the solution, the rate of convergence of various numerical approximations are estimated under strong monotonicity and Lipschitz conditions. The abstract setting involves general consistency conditions and is then applied to a class of quasilinear stochastic PDEs of parabolic type.Comment: 33 page

Vegetation Controls on Weathering Intensity During the Last Deglacial Transition in Southeast Africa

Tropical climate is rapidly changing, but the effects of these changes on the geosphere are unknown, despite a likelihood of climatically-induced changes on weathering and erosion. The lack of long, continuous paleo-records prevents an examination of terrestrial responses to climate change with sufficient detail to answer questions about how systems behaved in the past and may alter in the future. We use high-resolution records of pollen, clay mineralogy, and particle size from a drill core from Lake Malawi, southeast Africa, to examine atmosphere-biosphere-geosphere interactions during the last deglaciation (~ 18-9 ka), a period of dramatic temperature and hydrologic changes. The results demonstrate that climatic controls on Lake Malawi vegetation are critically important to weathering processes and erosion patterns during the deglaciation. At 18 ka, afromontane forests dominated but were progressively replaced by tropical seasonal forest, as summer rainfall increased. Despite indication of decreased rainfall, drought-intolerant forest persisted through the Younger Dryas (YD) resulting from a shorter dry season. Following the YD, an intensified summer monsoon and increased rainfall seasonality were coeval with forest decline and expansion of drought-tolerant miombo woodland. Clay minerals closely track the vegetation record, with high ratios of kaolinite to smectite (K/S) indicating heavy leaching when forest predominates, despite variable rainfall. In the early Holocene, when rainfall and temperature increased (effective moisture remained low), open woodlands expansion resulted in decreased K/S, suggesting a reduction in chemical weathering intensity. Terrigenous sediment mass accumulation rates also increased, suggesting critical linkages among open vegetation and erosion during intervals of enhanced summer rainfall. This study shows a strong, direct influence of vegetation composition on weathering intensity in the tropics. As climate change will likely impact this interplay between the biosphere and geosphere, tropical landscape change could lead to deleterious effects on soil and water quality in regions with little infrastructure for mitigation