1,150 research outputs found

    Sinopse Do Gênero Nyctibora Burmeister, Com Descrição De Duas Novas Espécies Do Rio De Janeiro, Brasil (ectobiidae, Nyctiborinae)

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    Two new species of Nyctibora are described and considered similar to Nyctibora sericea. Coloration, morphology and genital pieces of males were analyzed. All the studied material shall be deposited in the Museu Nacional. © 2016, Universidade Estadual de Campinas UNICAMP. All rights reserved.1611

    Supervisory control theory applied to swarm robotics

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    Currently, the control software of swarm robotics systems is created by ad hoc development. This makes it hard to deploy these systems in real-world scenarios. In particular, it is difficult to maintain, analyse, or verify the systems. Formal methods can contribute to overcome these problems. However, they usually do not guarantee that the implementation matches the specification, because the system’s control code is typically generated manually. Also, there is cultural resistance to apply formal methods; they may be perceived as an additional step that does not add value to the final product. To address these problems, we propose supervisory control theory for the domain of swarm robotics. The advantages of supervisory control theory, and its associated tools, are a reduction in the amount of ad hoc development, the automatic generation of control code from modelled specifications, proofs of properties over generated control code, and the reusability of formally designed controllers between different robotic platforms. These advantages are demonstrated in four case studies using the e-puck and Kilobot robot platforms. Experiments with up to 600 physical robots are reported, which show that supervisory control theory can be used to formally develop state-of-the-art solutions to a range of problems in swarm robotics

    OpenSwarm: an event-driven embedded operating system for miniature robots

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    This paper presents OpenSwarm, a lightweight easy-to-use open-source operating system. To our knowledge, it is the first operating system designed for and deployed on miniature robots. OpenSwarm operates directly on a robot’s microcontroller. It has a memory footprint of 1 kB RAM and 12 kB ROM. OpenSwarm enables a robot to execute multiple processes simultaneously. It provides a hybrid kernel that natively supports preemptive and cooperative scheduling, making it suitable for both computationally intensive and swiftly responsive robotics tasks. OpenSwarm provides hardware abstractions to rapidly develop and test platformindependent code. We show how OpenSwarm can be used to solve a canonical problem in swarm robotics—clustering a collection of dispersed objects. We report experiments, conducted with five e-puck mobile robots, that show that an OpenSwarm implementation performs as good as a hardware-near implementation. The primary goal of OpenSwarm is to make robots with severely constrained hardware more accessible, which may help such systems to be deployed in real-world applications

    Innovative technologies in human reproduction: challenges ahead

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    Inaugural lecture delivered by Prof. dr. Susana M. Chuva de Sousa Lopes on acceptance of the position of Professor Developmental Biology, in particular human development at Leiden University on June 29, 2020Inaugural lecture delivered by Prof. dr. Susana M. Chuva de Sousa Lopes on acceptance of the position of Professor Developmental Biology, in particular human development at Leiden University on June 29, 2020LUMC / Geneeskund

    Supervisory control theory applied to swarm robotics

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    Currently, the control software of swarm robotics systems is created by ad hoc development. This makes it hard to deploy these systems in real-world scenarios. In particular, it is difficult to maintain, analyse, or verify the systems. Formal methods can contribute to overcome these problems. However, they usually do not guarantee that the implementation matches the specification, because the system?s control code is typically generated manually. Also, there is cultural resistance to apply formal methods; they may be perceived as an additional step that does not add value to the final product. To address these problems, we propose supervisory control theory for the domain of swarm robotics. The advantages of supervisory control theory, and its associated tools, are a reduction in the amount of ad hoc development, the automatic generation of control code from modelled specifications, proofs of properties over generated control code, and the reusability of formally designed controllers between different robotic platforms. These advantages are demonstrated in four case studies using the e-puck and Kilobot robot platforms. Experiments with up to 600 physical robots are reported, which show that supervisory control theory can be used to formally develop state-of-the-art solutions to a range of problems in swarm robotics

    Influence of cone-beam computed tomography image artifacts on the determination of dental arch measurements

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    Objective: To compare dental plaster model (DPM) and cone-beam computed tomography (CBCT) in the measurement of the dental arches, and investigate whether CBCT image artifacts compromise the reliability of such measurements. Materials and Methods: Twenty patients were divided into two groups based on the presence or absence of metallic restorations in the posterior teeth. Both dental arches of the patients were scanned with the CBCT unit i-CAT, and DPMs were obtained. Two examiners obtained eight arch measurements on the CBCT images and DPMs and repeated this procedure 15 days later. The arch measurements of each patient group were compared separately by the Wilcoxon rank sum (Mann-Whitney U) test, with a significance level of 5% (alpha = .05). Intraclass correlation measured the level of intraobserver agreement. Results: Patients with healthy teeth showed no significant difference between all DPM and CBCT arch measurements (P > .05). Patients with metallic restoration showed significant difference between DPM and CBCT for the majority of the arch measurements (P > .05). The two examiners showed excellent intraobserver agreement for both measuring methods with intraclass correlation coefficient higher than 0.95. Conclusion: CBCT provided the same accuracy as DPM in the measurement of the dental arches, and was negatively influenced by the presence of image artifacts.To compare dental plaster model (DPM) and cone-beam computed tomography (CBCT) in the measurement of the dental arches, and investigate whether CBCT image artifacts compromise the reliability of such measurements. Twenty patients were divided into two gro842274278sem informaçãosem informaçã

    Image Quality In Partially Erased Denoptix® Storage Phosphor Plates

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    This study aimed at investigating the effect of the partial erasing of DenOptix® system storage phosphor plates on the image quality of digital radiographs. Standardized digital radiographs were acquired of a phantom mandible, using size 2 intraoral DenOptix® storage phosphor plates (n = 10). Subsequently, the active areas of the plates were placed in a viewing box with a constant light intensity of 1,700 lux for 130 seconds to achieve complete erasing (control plate), as well as for 0, 5, 10, 1S, 20, 25, 34, 66, and 98 seconds, to compose the experimental group of partially erased plates. The same exposure settings were repeated using the control and experimental plates, which were scanned at a resolution of 300 dpi. Five radiologists independently examined the pairs of digital radiographs obtained with the control and partially erased plates, in random order, and indicated the best image for oral diagnosis. Cochran-Mantel-Haenszel's chi-square test, at a significance level of 5%, was used to compare the percentages of superior quality images in each combination of control and partially erased plates, subjectively assessed. No significant differences were found between radiographic images acquired with control and partially erased plates, except for the combination of 0 second (30%) versus 130 seconds (70%), p = 0.0047. It can be concluded that, under adequate light intensity conditions, erasing intraoral DenOptix® storage phosphor plates may require time intervals of as little as 5 seconds.2217883Akdeniz, B.G., Gröndahl, H.G., Kose, T., Effect of delayed scanning of storage phosphor plates (2005) Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 99 (5), pp. 603-607Akdeniz, B.G., Gröndahl, H.G., Degradation of storage phosphor images due to scanning delay (2006) Dentomaxillofac Radiol, 35 (2), pp. 74-77Almeida, S.M., Oliveira, A.E.F., Ferreira, R.I., Bóscolo, F.N., Image quality in digital radiographic systems (2003) Braz Dent J, 14 (2), pp. 136-141Borg, E., Attaelmanan, A., Gröndahl, H.G., Subjective image quality of solid-state and photostimulable phosphor systems for digital intra-oral radiography (2000) Dentomaxillofac Radiol, 29 (2), pp. 70-75Ferreira, R.I., Haiter-Neto, F., Tabchoury, C.P.M., Paiva, G.A.N., Bóscolo, F.N., Assessment of enamel demineralization using conventional, digital, and digitized radiography (2006) Braz Oral Res, 20 (2), pp. 114-119Wenzel, A., Gröndahl, H.G., Direct digital radiography in the dental office (1995) Int Dent J, 45 (1), pp. 27-34Oliveira, A.E., Almeida, S.M., Paganini, G.A., Haiter Neto, F., Bóscolo, F.N., Comparative study of two digjtal radiographic storage phosphor systems (2000) Braz Dent J, 11 (2), pp. 111-116Borg, E., Attaelmanan, A., Gröndahl, H.G., Image plate systems differ in physical performance (2000) Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 89 (1), pp. 118-124Martins, M.G.B.Q., Haiter Neto, F., Whaites, E.J., Analysis of digital images acquired using different phosphor storage plates (PSPs) subjected to varying reading times and storage conditions (2003) Dentomaxillofac Radiol, 32 (3), pp. 186-190(1998) DenOptix digital imaging system - user manual and installation guide, , Gendex Dental X-Ray Division, Des Plaines: The Division;Menig, J.J., The DenOptix digital radiographic system (1999) J Clin Orthod, 33 (7), pp. 407-410Berkhout WE, Beuger DA, Sanderink GC, van der Stelt PF. The dynamic range of digital radiographic systems: dose reduction or risk of overexposure? Dentomaxillofac Radiol. 2004;33(1):1-SHildebolt, C.F., Couture, R.A., Whiting, B.R., Dental photostimulable phosphor radiography (2000) Dent Clin North Am, 44 (2), pp. 273-297Martins, M.G.B.Q., Whaites, E.J., Ambrosano, G.M.B., Haiter Neto, F., What happens if you delay scanning Digora phosphor storage plates (PSPs) for up to 4 hours? (2006) Dentomaxillofac Radiol, 35 (3), pp. 143-146Gröndahl, H.G., Wenzel, A., Borg, E., Tammisalo, E., An image plate system for digital intra-oral radiography (1996) Dent Update, 23 (8), pp. 334-33

    BMPs, TGFbetas and integrins in muscle and germ cell development in mice

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    We characterized the expression of PSmad1/5/8 (BMP R-Smads) and PSmad2 (TGFbeta R-Smad) during peri-implantation and gastrulation in the mouse, and further characterized the expression of PSmad2 until E12.5, showing were the BMP and TGFbeta Smad-dependent signalling pathways are active (Chapter 2, 3 and 4). The role of ALK2 (BMP signalling) and ALK5 (TGFbeta signalling) in the development of PGCs in the mouse was studied in detail. ALK2 is needed for the formation of PGCs before gastrulation occurs and it signals in the visceral endoderm, a tissue that was previously not associated with primordial germ cell formation (Chapter 3). In contrast to suggestions derived from studies in vitro, ALK5 is probably not involved in PGC migration through the hindgut and to the gonadal ridges and TGF 1 is unlikely to be a chemoattractant for PGCs as proposed (Chapter 4). However, there may be a role for TGF signalling in PGC development in controlling mitotic arrest of PGCs in the gonadal ridges. Beta1 integrin was also implicated in PGC migration to the genital ridges. Beta1 integrin has two isoforms in mice: a more common one beta1A and a muscle specific beta1D that is upregulated late during development. We studied whether the replacement of beta1A by beta1D influenced the development of PGCs, but this occurred normally and we found no evidence of an effect on migration on the genetic background used. Furthermore, beta1 integrin has been implicated in heart development. We showed that the replacement of beta1A by beta1D did not cause heart abnormalities during development. However, we were able to show a clear role for beta1A during myogenesis. The differentiation of primary myoblasts was abnormal when only beta1D was expressed, while secondary myoblasts were formed normally. Furthermore, we showed a novel role of beta1 integrin during placentation, in particular the development of the labyrinthine layer (Chapter 5). CTGF is known to crosstalk with both TGFbeta and BMP in vitro. We studied possible interactions between them, focusing on heart development, where BMP and TGFbeta are known to play prominent roles. However, we were not able to detect direct crosstalk. Both CTGF and TGFbeta are associated with fibrosis. We investigated whether CTGF and TGFbeta were expressed following experimental induction of myocardial infarction in the mouse and showed that both genes are present in particular in the scar tissue and that TGFbeta Smad-dependent signalling is transient 1 week post-infarction and largely restricted to cardiac fibroblasts (Chapter 6)

    Logarithmic Corrections to N=2 Black Hole Entropy: An Infrared Window into the Microstates

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    Logarithmic corrections to the extremal black hole entropy can be computed purely in terms of the low energy data -- the spectrum of massless fields and their interaction. The demand of reproducing these corrections provides a strong constraint on any microscopic theory of quantum gravity that attempts to explain the black hole entropy. Using quantum entropy function formalism we compute logarithmic corrections to the entropy of half BPS black holes in N=2 supersymmetric string theories. Our results allow us to test various proposals for the measure in the OSV formula, and we find agreement with the measure proposed by Denef and Moore if we assume their result to be valid at weak topological string coupling. Our analysis also gives the logarithmic corrections to the entropy of extremal Reissner-Nordstrom black holes in ordinary Einstein-Maxwell theory.Comment: LaTeX file, 66 page

    Twistors and Black Holes

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    Motivated by black hole physics in N=2, D=4 supergravity, we study the geometry of quaternionic-Kahler manifolds M obtained by the c-map construction from projective special Kahler manifolds M_s. Improving on earlier treatments, we compute the Kahler potentials on the twistor space Z and Swann space S in the complex coordinates adapted to the Heisenberg symmetries. The results bear a simple relation to the Hesse potential \Sigma of the special Kahler manifold M_s, and hence to the Bekenstein-Hawking entropy for BPS black holes. We explicitly construct the ``covariant c-map'' and the ``twistor map'', which relate real coordinates on M x CP^1 (resp. M x R^4/Z_2) to complex coordinates on Z (resp. S). As applications, we solve for the general BPS geodesic motion on M, and provide explicit integral formulae for the quaternionic Penrose transform relating elements of H^1(Z,O(-k)) to massless fields on M annihilated by first or second order differential operators. Finally, we compute the exact radial wave function (in the supergravity approximation) for BPS black holes with fixed electric and magnetic charges.Comment: 47 pages, v2: typos corrected, reference added, v3: minor change
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