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Search Results: 1 - 10 of 10884 matches for " Pierre Nugues "
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Verbal Interactions in Virtual Worlds
Pierre Nugues
Computer Science , 2000,
Abstract: We first discuss respective advantages of language interaction in virtual worlds and of using 3D images in dialogue systems. Then, we describe an example of a verbal interaction system in virtual reality: Ulysse. Ulysse is a conversational agent that helps a user navigate in virtual worlds. It has been designed to be embedded in the representation of a participant of a virtual conference and it responds positively to motion orders. Ulysse navigates the user's viewpoint on his/her behalf in the virtual world. On tests we carried out, we discovered that users, novices as well as experienced ones have difficulties moving in a 3D environment. Agents such as Ulysse enable a user to carry out navigation motions that would have been impossible with classical interaction devices. From the whole Ulysse system, we have stripped off a skeleton architecture that we have ported to VRML, Java, and Prolog. We hope this skeleton helps the design of language applications in virtual worlds.
Generating a 3D Simulation of a Car Accident from a Written Description in Natural Language: the CarSim System
Sylvain Dupuy,Arjan Egges,Vincent Legendre,Pierre Nugues
Computer Science , 2001,
Abstract: This paper describes a prototype system to visualize and animate 3D scenes from car accident reports, written in French. The problem of generating such a 3D simulation can be divided into two subtasks: the linguistic analysis and the virtual scene generation. As a means of communication between these two modules, we first designed a template formalism to represent a written accident report. The CarSim system first processes written reports, gathers relevant information, and converts it into a formal description. Then, it creates the corresponding 3D scene and animates the vehicles.
Status of aspergillosis and sea fan populations in Cura?ao ten years after the 1995 Caribbean epizootic
Nugues,M. M; Nagelkerken,I;
Revista de Biología Tropical , 2006,
Abstract: in 1995, a survey of sea fan corals was conducted in cura?ao during a caribbean-wide outbreak of the sea fan disease aspergillosis. the survey was repeated in 2005 using the same methodology and identical sites to examine changes in sea fan populations 10 years after the initial epizootic. necrotic lesions typical of aspergillosis were present on as many sea fans in 2005 as in 1995 (mean ± se: 52 ± 6 vs 43 ± 10%). the disease also showed no significant variation in virulence (9.6 ± 1.2 vs 8.8 ± 1.0% tissue loss per diseased colony). however, the average number of sea fan colonies per 10 m2 decreased from 2.7 ± 1.1 to 0.7 ± 0.2 over the 10-year period, a decline of almost 75%. this decrease occurred for all colony sizes, but was more pronounced among small colonies, resulting in an overall trend of domination by large colonies. these results support that aspergillosis can have a significant, long-term impact on sea fan population size and structure. the continued presence of the disease in 2005 could be contributing to reduced recruitment and/or selective mortality among the smallest colonies. this study provides no indication that host resistance against aspergillosis could reverse the decline of caribbean sea fan corals. rev. biol. trop. 54 (suppl. 3): 153-160. epub 2007 jan. 15.
Status of aspergillosis and sea fan populations in Cura ao ten years after the 1995 Caribbean epizootic
M. M Nugues,I Nagelkerken
Revista de Biología Tropical , 2006,
Abstract: In 1995, a survey of sea fan corals was conducted in Cura ao during a Caribbean-wide outbreak of the sea fan disease aspergillosis. The survey was repeated in 2005 using the same methodology and identical sites to examine changes in sea fan populations 10 years after the initial epizootic. Necrotic lesions typical of aspergillosis were present on as many sea fans in 2005 as in 1995 (mean ± SE: 52 ± 6 vs 43 ± 10%). The disease also showed no significant variation in virulence (9.6 ± 1.2 vs 8.8 ± 1.0% tissue loss per diseased colony). However, the average number of sea fan colonies per 10 m2 decreased from 2.7 ± 1.1 to 0.7 ± 0.2 over the 10-year period, a decline of almost 75%. This decrease occurred for all colony sizes, but was more pronounced among small colonies, resulting in an overall trend of domination by large colonies. These results support that aspergillosis can have a significant, long-term impact on sea fan population size and structure. The continued presence of the disease in 2005 could be contributing to reduced recruitment and/or selective mortality among the smallest colonies. This study provides no indication that host resistance against aspergillosis could reverse the decline of Caribbean sea fan corals. Rev. Biol. Trop. 54 (Suppl. 3): 153-160. Epub 2007 Jan. 15. En 1995, se realizó un sondeo de los abanicos de mar durante un brote de aspergilosis, una enfermedad de abanicos de mar extendida en todo el Caribe. En el a o 2005 se repitió el sondeo utilizando exactamente la misma metodología y los mismos sitios para examinar cambios en las poblaciones tras 10 a os del inicio del brote. Se presentaron lesiones necróticas típicas de la aspergilosis en tantos abanicos en el 2005, como en 1995 (promedio ± ES: 52 ± 6 vs 43 ± 10%). La enfermedad tampoco mostró variaciones significativas en la virulencia (9.6 ± 1.2 vs 8.8 ± 1.0%, pérdida de tejido por colonia enferma). Sin embargo, el número promedio de colonias de abanico de mar por cada 10 m2 bajó desde 2.7 ± 1 hasta 0.7 ± 0.2 en este período de 10 a os, una disminución de casi 75%. Este decrecimiento ocurrió en colonias de todo tama o, pero fue más pronunciado en colonias peque as, produciendo una tendencia general de dominancia de colonias grandes. Estos resultados apoyan la idea de que la aspergilosis puede tener un impacto significativo a largo plazo en el tama o y estructura poblacional de los abanicos de mar. La continuidad en la presencia de la enfermedad en el 2005 puede estar contribuyendo a la reducción en el reclutamiento y/o a la mortalidad selectiva de las colonias más peque as. E
Algae as Reservoirs for Coral Pathogens
Michael J. Sweet, John C. Bythell, Maggy M. Nugues
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069717
Abstract: Benthic algae are associated with coral death in the form of stress and disease. It's been proposed that they release exudates, which facilitate invasion of potentially pathogenic microbes at the coral-algal interface, resulting in coral disease. However, the original source of these pathogens remains unknown. This study examined the ability of benthic algae to act as reservoirs of coral pathogens by characterizing surface associated microbes associated with major Caribbean and Indo-Pacific algal species/types and by comparing them to potential pathogens of two dominant coral diseases: White Syndrome (WS) in the Indo-Pacific and Yellow Band Disease (YBD) in the Caribbean. Coral and algal sampling was conducted simultaneously at the same sites to avoid spatial effects. Potential pathogens were defined as those absent or rare in healthy corals, increasing in abundance in healthy tissues adjacent to a disease lesion, and dominant in disease lesions. Potentially pathogenic bacteria were detected in both WS and YBD and were also present within the majority of algal species/types (54 and 100% for WS and YBD respectively). Pathogenic ciliates were associated only with WS and not YBD lesions and these were also present in 36% of the Indo-Pacific algal species. Although potential pathogens were associated with many algal species, their presence was inconsistent among replicate algal samples and detection rates were relatively low, suggestive of low density and occurrence. At the community level, coral-associated microbes irrespective of the health of their host differed from algal-associated microbes, supporting that algae and corals have distinctive microbial communities associated with their tissue. We conclude that benthic algae are common reservoirs for a variety of different potential coral pathogens. However, algal-associated microbes alone are unlikely to cause coral death. Initial damage or stress to the coral via other competitive mechanisms is most likely a prerequisite to potential transmission of these pathogens.
In Situ Oxygen Dynamics in Coral-Algal Interactions
Daniel Wangpraseurt, Miriam Weber, Hans R?y, Lubos Polerecky, Dirk de Beer, Suharsono, Maggy M. Nugues
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031192
Abstract: Background Coral reefs degrade globally at an alarming rate, with benthic algae often replacing corals. However, the extent to which benthic algae contribute to coral mortality, and the potential mechanisms involved, remain disputed. Recent laboratory studies suggested that algae kill corals by inducing hypoxia on the coral surface, through stimulated microbial respiration. Methods/Findings We examined the main premise of this hypothesis by measuring in situ oxygen microenvironments at the contact interface between the massive coral Porites spp. and turf algae, and between Porites spp. and crustose coralline algae (CCA). Oxygen levels at the interface were similar to healthy coral tissue and ranged between 300–400 μM during the day. At night, the interface was hypoxic (~70 μM) in coral-turf interactions and close to anoxic (~2 μM) in coral-CCA interactions, but these values were not significantly different from healthy tissue. The diffusive boundary layer (DBL) was about three times thicker at the interface than above healthy tissue, due to a depression in the local topography. A numerical model, developed to analyze the oxygen profiles above the irregular interface, revealed strongly reduced net photosynthesis and dark respiration rates at the coral-algal interface compared to unaffected tissue during the day and at night, respectively. Conclusions/Significance Our results showed that hypoxia was not a consistent feature in the microenvironment of the coral-algal interface under in situ conditions. Therefore, hypoxia alone is unlikely to be the cause of coral mortality. Due to the modified topography, the interaction zone is distinguished by a thicker diffusive boundary layer, which limits the local metabolic activity and likely promotes accumulation of potentially harmful metabolic products (e.g., allelochemicals and protons). Our study highlights the importance of mass transfer phenomena and the need for direct in situ measurements of microenvironmental conditions in studies on coral stress.
Bending Fuchsian representations of fundamental groups of cusped surfaces in PU(2,1)
Pierre Will
Mathematics , 2011,
Abstract: We describe a family of representations of $\pi_1(\Sigma)$ in PU(2,1), where $\Sigma$ is a hyperbolic Riemann surface with at least one deleted point. This family is obtained by a bending process associated to an ideal triangulation of $\Sigma$. We give an explicit description of this family by describing a coordinates system in the spirit of shear coordinates on the Teichm\"uller space. We identify within this family new examples of discrete, faithful and type-preserving representations of $\pi_1(\Sigma)$. In turn, we obtain a 1-parameter family of embeddings of the Teichm\"uller space of $\Sigma$ in the PU(2,1)-representation variety of $\pi_1(\Sigma)$. These results generalise to arbitrary $\Sigma$ the results obtained in a previous paper for the 1-punctured torus.
Two Generator groups acting on the complex hyperbolic plane
Pierre Will
Mathematics , 2015,
Abstract: This is an expository article about groups generated by two isometries of the complex hyperbolic plane.
How to Introduce the Cyclic Group and Its Properties Representation with Matlab ? Thanks to Magic Using the Perfect Faro Shuffle  [PDF]
Pierre Schott
Creative Education (CE) , 2011, DOI: 10.4236/ce.2011.21005
Abstract: Why use Magic for teaching arithmetic and geometric suit, additive groups, and algorithmic notions through Matlab? Magicians know that, once the surprise has worn off, the audience will seek to understand how the trick works. The aim of every teacher is to interest their students, and a magic trick will lead them to ask how? And why? And how can I create one myself? In this article we consider a project I presented in 2009. I summarize the project scope, the students' theoretical studies, their approach to this problem and their computer realizations. I conclude using the mathematical complement as well as weak and strong points of this approach. Whatever the student's professional ambitions, they will be able to see the impact that originality and creativity have when combined with an interest in one's work. The students know how to “perform” a magic trick for their family and friends, a trick that they will be able to explain and so enjoy a certain amount of success. Sharing a mathematical / informatics demonstration is not easy and that they do so means that they will have worked on understood and are capable of explaining this knowledge. Isn't this the aim of all teaching?
Pedestrian Analysis of Harmonic Plane Wave Propagation in 1D-Periodic Media  [PDF]
Pierre Hillion
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.24027
Abstract: The propagation of TE, TM harmonic plane waves impinging on a periodic multilayer film made of a stack of slabs with the same thickness but with alternate constant permittivity is analyzed. To tackle this problem, the same analysis is first performed on only one slab for harmonic plane waves, solutions of the wave equa- tion. The results obtained in this case are generalized to the stack, taking into account the boundary condi- tions generated at both ends of each slab by the jumps of permittivity. Differential electromagnetic forms are used to get the solutions of Maxwell’s equations.
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