55 research outputs found

    A Stochastic Approach to Shortcut Bridging in Programmable Matter

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    In a self-organizing particle system, an abstraction of programmable matter, simple computational elements called particles with limited memory and communication self-organize to solve system-wide problems of movement, coordination, and configuration. In this paper, we consider a stochastic, distributed, local, asynchronous algorithm for "shortcut bridging", in which particles self-assemble bridges over gaps that simultaneously balance minimizing the length and cost of the bridge. Army ants of the genus Eciton have been observed exhibiting a similar behavior in their foraging trails, dynamically adjusting their bridges to satisfy an efficiency trade-off using local interactions. Using techniques from Markov chain analysis, we rigorously analyze our algorithm, show it achieves a near-optimal balance between the competing factors of path length and bridge cost, and prove that it exhibits a dependence on the angle of the gap being "shortcut" similar to that of the ant bridges. We also present simulation results that qualitatively compare our algorithm with the army ant bridging behavior. Our work gives a plausible explanation of how convergence to globally optimal configurations can be achieved via local interactions by simple organisms (e.g., ants) with some limited computational power and access to random bits. The proposed algorithm also demonstrates the robustness of the stochastic approach to algorithms for programmable matter, as it is a surprisingly simple extension of our previous stochastic algorithm for compression.Comment: Published in Proc. of DNA23: DNA Computing and Molecular Programming - 23rd International Conference, 2017. An updated journal version will appear in the DNA23 Special Issue of Natural Computin

    New early Triassic Lingulidae (Brachiopoda) genera and species from South China

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    Two new genera, Sinolingularia gen. nov. and Sinoglottidia gen. nov., together with three new species, Sinolingularia huananensis gen. et sp. nov., Sinolingularia yini gen. et sp. nov. and Sinoglottidia archboldi gen. et sp. nov., are described on the basis of a large collection of well-preserved specimens from several sections straddling the Permian - Triassic boundary in South China. <br /

    The Origin and Initial Rise of Pelagic Cephalopods in the Ordovician

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    BACKGROUND: During the Ordovician the global diversity increased dramatically at family, genus and species levels. Partially the diversification is explained by an increased nutrient, and phytoplankton availability in the open water. Cephalopods are among the top predators of today's open oceans. Their Ordovician occurrences, diversity evolution and abundance pattern potentially provides information on the evolution of the pelagic food chain. METHODOLOGY/PRINCIPAL FINDINGS: We reconstructed the cephalopod departure from originally exclusively neritic habitats into the pelagic zone by the compilation of occurrence data in offshore paleoenvironments from the Paleobiology Database, and from own data, by evidence of the functional morphology, and the taphonomy of selected cephalopod faunas. The occurrence data show, that cephalopod associations in offshore depositional settings and black shales are characterized by a specific composition, often dominated by orthocerids and lituitids. The siphuncle and conch form of these cephalopods indicate a dominant lifestyle as pelagic, vertical migrants. The frequency distribution of conch sizes and the pattern of epibionts indicate an autochthonous origin of the majority of orthocerid and lituitid shells. The consistent concentration of these cephalopods in deep subtidal sediments, starting from the middle Tremadocian indicates the occupation of the pelagic zone early in the Early Ordovician and a subsequent diversification which peaked during the Darriwilian. CONCLUSIONS/SIGNIFICANCE: The exploitation of the pelagic realm started synchronously in several independent invertebrate clades during the latest Cambrian to Middle Ordovician. The initial rise and diversification of pelagic cephalopods during the Early and Middle Ordovician indicates the establishment of a pelagic food chain sustainable enough for the development of a diverse fauna of large predators. The earliest pelagic cephalopods were slowly swimming vertical migrants. The appearance and early diversification of pelagic cephalopods is interpreted as a consequence of the increased food availability in the open water since the latest Cambrian

    La confusion des genres : album « mixte » et littératie

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    Dans le cadre des travaux de Circeft-Escol sur la littératie scolaire et en particulier sur les supports d'apprentissage actuels, cette analyse envisage l'étude d'un texte « composite » dans une classe de Cours préparatoire de l'école élémentaire en ZEP, en juin 2012. Une si petite graine, d'Eric Carle (2003, Mijade Jeunesse), donne ainsi à lire l'évolution d'une graine, de la germination à la fleur, présentée dans sa nature cyclique liée à la succession des saisons. Sa visée semble donc informative. Cependant, cette visée est contaminée par une pratique narrativisée de l'information qui inscrit aussi l'album dans une démarche esthétique. Nous analysons précisément l'album dans sa tension entre informatif et narratif, en le définissant comme album « mixte », caractérisé par sa visée double, qui se traduit par une structure et une énonciation doubles.  La mise en œuvre de l'enseignant dans la classe insiste sur l'aspect informatif. Or les réponses produites par les élèves montrent que ceux qui ont le mieux acquis les connaissances liées au monde du vivant sont ceux qui ont le mieux compris la complexité de l'album et sa partie fictionnelle, soit les élèves appartenant au groupe de niveau des meilleurs

    Radiocarbon dating application to modern musical instruments: an interdisciplinary study

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    International audienceRelics dating: why not follow the example of dating of modern music instrument, combining the sharpest 14C technology and independent expertise?Dating historical relics partly meets the same issue than dating modern music instruments dated between the 16th and 19th century. For both woody relics and music instrument, dendrochronology might not be carried out due to a too short tree-rings record and 14C dating might a priori be ignored for historical periods as a 14C physical measurement might result into several equiprobable age ranges. Several samplings and independent expertise are then required to make a well-considered choice between these intervals. Owing to the new generation of 14C dating instruments, sampling without affecting the instrument or relics integrity is now possible. The interdisciplinary framework allows combining any ante quem or post quem information on the age of relics or music instruments. To illustrate this approach, we will draw on an on-going project of modern music instruments gathering radiocarbon dating specialists and the museum curators. Our goal is to deepen the scientific knowledge about the origin and the long history of use and restoration of instruments kept at the Musée de la musique. As an example, an Indian rudra-vina (E.997.24.1) was dated from the end of the 17th century. Transcription of 14C activity measured on two sub-samples yields four equiprobable calibrated date ranges. The comparison with a Govardhan’s picturial representation of a similar rudra-vina allows to determine the most likely date range: [AD 1650-1683]. Likewise, a second example comes from a stringed Hindustani instrument named kinnari-veena. It was supposedly dated from the 18th century according to Musée's curators because of its organological features. The dating, based on 7 sub-samples, has brought to light a very likely restoration of the upper-nut whereas all other components are contemporaneous of the instrument manufacturing. The results obtained allow to reveal additions or changes (successive layers of history) since they emerged from the instrument factories. The relics made of wood, bones or textile can also take benefit of such a multidisciplinary approach already applied on music instruments with composite constitutions

    Dating of modern music instrument combining the sharpest 14 C technology and independent expertise

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    International audienceFor dating modern music instruments dated between the 16 th and 19 th century, dendrochronology might not be carried out due to a too short tree-rings record and 14 C dating might a priori be ignored for historical periods as a 14 C physical measurement might result into several equiprobable age ranges. Several samplings and independent expertise are then required to make a well-considered choice between these intervals. Owing to the new generation of 14 C dating instruments, sampling without affecting the instrument integrity is now possible. The interdisciplinary framework allows combining any ante quem or post quem information on the age of music instruments. To illustrate this approach, we will draw on an ongoing project of modern music instruments gathering radiocarbon dating specialists and the museum curators. Our goal is to deepen the scientific knowledge about the origin and the long history of use and restoration of instruments kept at the Musée de la Musique. As an example, an Indian rudra-vina (E.997.24.1) was dated from the end of the 17 th century. Transcription of 14 C activity measured on two sub-samples yields four equiprobable calibrated date ranges. The comparison with a Govardhan's picturial representation of a similar rudra-vina allows to determine the most likely date range: [AD 1650-1683]. Likewise, a second example comes from a stringed Hindustani instrument named kinnari-vina (E.1444). It was supposedly dated from the 18 th century according to Musée's curators because of its organological features. The dating, based on 7 sub-samples, has brought to light a very likely restoration of the upper-nut whereas all other components are contemporaneous of the instrument manufacturing. The results obtained allow to reveal additions or changes (successive layers of history) since they emerged from the instrument factories. The multidisciplinary approach applied here is a benefit for establishing a "history" of use and restoration of music instruments with composite constitutions

    Long-term evaluation of the safety of a rectal-prostate spacer, the ProSpace® balloon, in patients treated with radiotherapy for prostate cancer

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    Abstract Background Due to the close proximity of the prostate and rectum, rectal toxicity remains a major problem in patient treated by radiotherapy for prostate adenocarcinoma. One method of increasing the distance between the prostate and the rectum is to use a spacer implanted into the rectoprostatic space. This report describes the long-term outcomes obtained with a new ballon spacer. Methods Patients treated with curative radiotherapy for low- or intermediate-risk prostate adenocarcinoma, who underwent insertion of the ProSpace® (BioProtect Ltd, Tzur Yigal, Israel) rectal-prostate balloon spacer, were included. The main objective was to evaluate the dosimetric benefit of the spacer for OARs. The secondary objectives were to evaluate the feasibility and tolerability of ProSpace® balloon placement and to evaluate its long-term therapeutic efficacy and tolerance. Results Between October 2013 and March 2015, 16 patients were enrolled in the Pasteur Clinic, Toulouse, France. The median follow-up was 85.5 months. From top to bottom, the space created was a mean of 16.3 mm (range: 11–20.5 mm) at the base of the prostate, 12.1 mm (range: 4–16 mm) at the middle and 8.9 mm at the apex (range: 5–15 mm). On average, rectal volumes receiving a dose of 70 Gy, 60 Gy and 50 Gy were significantly lower after balloon implantation: -4.81 cc (1.5 vs. 6.3; p < 0.0005), -8.08 cc (6.4 vs. 14.5; p = 0.002) and -9.06 cc (16.7 vs. 25.7; p = 0.003), respectively. There were significant differences in coverage after balloon implantation: Median V95% (p < 0.0005), median Dmin (p = 0.01) and median V98% (p < 0.001) were higher after balloon implantation. At 5 years, cumulative gastrointestinal toxicity was grade 1 in 6% (1/16 patients). No toxicity of grade 2 or higher was found. At 5 years, no urinary toxicity grade 3 or 4 toxicity was found. The QoL was not deteriorated. Conclusions The use of the ProSpace® balloon seems to be well accepted by patients, allowing a double dosimetric gain: a decrease in doses received by the rectum and an improvement in the coverage of the high-risk PTV. The long-term gastrointestinal toxicity remains low and QoL is preserved in all treated patients
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