Collection of abstracts of the 24th European Workshop on Computational Geometry

International audienceThe 24th European Workshop on Computational Geomety (EuroCG'08) was held at INRIA Nancy - Grand Est & LORIA on March 18-20, 2008. The present collection of abstracts contains the 63 scientific contributions as well as three invited talks presented at the workshop

A Tissue Engineering Platform to Investigate Effects of Finite Deformation on Extracellular Matrix Production and Mechanical Properties

It is estimated that more than 85,000 prosthetic heart valves are implanted annually in the US and ~275,000 worldwide. Although current heart valve replacements have extended the lives of many patients, there is to date still no ideal alternative. Pediatric applications, in particular, pose unique problems because current valve replacement options are unable to accommodate somatic growth of the patient. Since its inception, the tissue engineering paradigm has garnered widespread attention as a means to recapitulate native tissue structure, composition, and mechanical function in a controlled and reproducible manner by combining engineering and life science principles. Before fully functioning tissue surrogates can be developed for clinical use, many complex biological, chemical and mechanical aspects of native tissues must be addressed. Furthermore, contemporary literature lacks a consolidated approach, instead, presenting a wide variety of scaffold materials, cell sources, and mechanical conditioning regimes in efforts to restore native tissue function. These challenges coupled with the paucity of structurally based, finite deformation framework constitutive models hinders our understanding of engineered tissues and their ability to perform as tissue surrogates. The focus of this dissertation is to elucidate the effects of large deformation mechanical stimuli on the development of engineered leaflet tissues. With our ability to incorporate viable cells distributed throughout the scaffold via concurrent electrospraying and electrospinning of poly (ester urethane) urea (PEUU) fiber scaffolds, we are provided a unique, controllable platform to: (1) characterize the mechanical behavior of electrospun PEUU and cellular response to global deformation, (2) assess our ability to create functional cell integrated surrogates via dynamic culture, and (3) develop a generalized finite deformation framework than can be used to gain an understanding of how the evolving extracellular matrix phase contributes to the construct gross mechanical behavior. We contend that much can be learned about the mechanical modulation of functional tissue from electrospun PEUU scaffolds since they capture aspects of native tissue microstructure and exhibit the ability to endure large deformations while recovering completely. It is our hope that these studies will guide the emergence of new materials and processing methods to develop functional pulmonary valve (PV) tissue surrogates which serve a predominantly biomechanical function

The sub-lethal effects of pyrethroid exposure on Anopheles gambiae s.l. life-history traits, behaviour, and the efficacy of insecticidal bednets

Malaria control progress in Africa has stalled. Though the reasons for this will be multifaceted, increasing and intense resistance to pyrethroids in Anopheles gambiae s.l. is almost certainly a contributing factor. Standard methods to monitor insecticide resistance and evaluate vector control tools primarily focus on the immediate and lethal effects on the mosquito. These methods disregard other important delayed and sub-lethal effects, despite their implications for malaria transmission. In response to growing concerns over the sustained effectiveness of current control tools, next-generation products are being developed and evaluated. These aim to target insecticide-resistant mosquitoes or mosquitoes that contribute to residual malaria transmission. Adaptations to current standard efficacy tests are needed to evaluate the novel modes of action of such products. The effect of insecticide exposure on the longevity, reproductive output and blood-feeding behaviour of a wild highly pyrethroid-resistant Anopheles gambiae s.l. population was evaluated. Mosquitoes were exposed to a range of insecticides and insecticidal bednets using laboratory tests and semi-field experimental hut trials. Benchtop video tests were evaluated for their feasibly in measuring the effectiveness of standard and next-generation nets. Subsequently, these tests were used to investigate the behaviour of field-populations of An. gambiae s.l. at the bednet interface in response to a human host. Following exposure to both pyrethroid-only and next-generation nets, evidence of sub-lethal impacts were limited or non-existent. The mosquitoes exposed to insecticidal nets did not suffer from reduced lifespan or altered reproductive output. Evidence of delayed mortality was only recorded when mosquitoes were exposed to extremely high levels of pyrethroids in WHO tube bioassays. Some mosquitoes were inhibited from blood-feeding in experimental hut trials, however, lab tests suggest this effect is absent by 8-hour post net-exposure. The efficacy of next-generation nets on the field population was dependant on the product. Brief contact with PermaNet 3.0 roof (pyrethroid + PBO) caused rapid knock-down and 100% mortality in all tests. Exposure to all other insecticidal nets, including Interceptor G2 (pyrethroid + chlorfenapyr), resulted in low 24-hour mortality in both lab and semi-field experiments. Following adaptations for the field, video tests were able to collect behavioural data on mosquito responses to insecticidal nets such as flying, resting, and probing behaviour. Responses were similar between untreated and pyrethroid- only netting. Extreme reductions in activity were observed following exposure to PermaNet 3.0, and Interceptor G2 showed signs of repellence. The results suggest community protection offered by first-generation LLINs is extremely low in this setting, however, pyrethroid-PBO nets appear to be effective at controlling the highly pyrethroid-resistant population. This work highlights the need for additional studies of sub-lethal effects in other field populations, with lower insecticide resistance levels or differing mechanisms, to establish if such measurements should be incorporated into the evaluation of novel vector control tools

A complex systems approach to education in Switzerland

The insights gained from the study of complex systems in biological, social, and engineered systems enables us not only to observe and understand, but also to actively design systems which will be capable of successfully coping with complex and dynamically changing situations. The methods and mindset required for this approach have been applied to educational systems with their diverse levels of scale and complexity. Based on the general case made by Yaneer Bar-Yam, this paper applies the complex systems approach to the educational system in Switzerland. It confirms that the complex systems approach is valid. Indeed, many recommendations made for the general case have already been implemented in the Swiss education system. To address existing problems and difficulties, further steps are recommended. This paper contributes to the further establishment complex systems approach by shedding light on an area which concerns us all, which is a frequent topic of discussion and dispute among politicians and the public, where billions of dollars have been spent without achieving the desired results, and where it is difficult to directly derive consequences from actions taken. The analysis of the education system's different levels, their complexity and scale will clarify how such a dynamic system should be approached, and how it can be guided towards the desired performance

On the Phylogenetic Relationships Among Paenungulata and Within Elephantidae as Demonstrated by Molecular and Osteological Evidence

Paenungulata (=PAEN). A total of 182 non-dental morphological characters from 100 species (79 extant, 21 extinct; 98 mammals and 2 non-mammals) was analyzed by two maximum parsimony tree building algorithms. Parallel analyses of 2,258 pairwise immunodiffusion (IMDFN) comparisons with 16 chicken antisera on 101 mammalian species (representing 22 taxa) and of amino acid sequence data of alpha and beta hemoglobins and other published protein sequences were also conducted. Morphological and molecular results agree that Eutheria consists of five major clades and that rates of evolution are similar in the two approaches. Following are close relationships based on osteological results: (1) Proboscidea, Sirenia, Desmostylia, Hyracoidea, Embrithopoda (=PAEN); (2) Cetacea, PAEN; (3) Tubulidentata, Ungulata (Artiodactyla and Perissodactyla), Notoungulata; (4) Ungulata, PAEN; and (5) Rodentia, Lagomorpha, Macroscelidea. Differences based on molecular results include: (1) Tubulidentata, PAEN; (2) Cetacea, Ungulata; (3) Distant Ungulata, PAEN; and (4) Carnivora, Pholidota. Elephantidae. Analyses of 58 non-dental osteological characters show that among the Elephantidae Mammuthus((\u27+)) and Elephas are more closely related to each other than either is to Loxodonta; Gomphoterium((\u27+)) and Mammut((\u27+)) were employed as outgroups (+= extinct). These results are congruent with the classical dental-based hypothesis. Also, the lineage of Mammuthus-Elephas evolved faster than Loxodonta. Immunologically, however, it was not possible to establish which of the three genera shares closest kinship. New findings include: (1) close immunological relationships of Tubulidentata to PAEN, and of Mammut americanum((\u27+)) to Elephantidae; (2) immunological reactivity of muscle and/or clotted blood from two of the three Mammuthus primigenius studied; (3) stylohyoideum characters, especially of Gomphotherium((\u27+)) and Serridentinus((\u27+)); and (4) many osteological characters and five skull foramina/openings