684 research outputs found
A preliminary investigation into the genetic variation and population structure of Taenia hydatigena from Sardinia, Italy
No full textCysticercosis caused by the metacestode stage of Taenia hydatigena is endemic in Sardinia. Information on the genetic variation of this parasite is important for epidemiological studies and implementation of control programs. Using two mitochondrial genes, the cytochrome c oxidase subunit 1 (cox1) and the NADH dehydrogenase subunit 1 (ND1) we investigated the genetic variation and population structure of Cysticercus tenuicollis from Sardinian intermediate hosts and compared it to that from other hosts from various geographical regions.The parsimony cox1 network analysis indicated the existence of a common lineage for T. hydatigena and the overall diversity and neutrality indices indicated demographic expansion. Using the cox1 sequences, low pairwise fixation index (Fst) values were recorded for Sardinian, Iranian and Palestinian sheep C. tenuicollis which suggested the absence of genetic differentiation.Using the ND1 sequences, C. tenuicollis from Sardinian sheep appeared to be differentiated from those of goat and pig origin. In addition, goat C. tenuicollis were genetically different from adult T. hydatigena as indicated by the statistically significant Fst value. Our results are consistent with biochemical and morphological studies that suggest the existence of variants of T. hydatigena
Advanced control methods for precise payload pointing of flexible spacecraft
No full textNowadays, many space missions require highly accurate pointing for Earth observation or cosmic vision purposes. However, the vibration environment from a spacecraft's structure and reaction wheels can cause disturbances in its line-of-sight stability and severely impact image quality. Additionally, these effects are not known precisely due to limitations in ground testing, and this uncertainty leads to significant challenges in control. This thesis tackles these problems by creating a control design and verification framework. Modern scientific literature explores three solutions: high-fidelity nonlinear modelling, advanced control design methods, and optimized verification campaigns. Respectively, they provide a reliable testing environment, directly handle structural dynamics, and guarantee system stability. While the three approaches are usually studied separately, the thesis proposes a novel combination using a payload isolation platform. The synergy of the framework offers a robust solution for precise pointing in flexible spacecraft and enables further mass reductions in the future of space exploration.Aerospace Engineerin
Leibniz: The Philosopher-Scientist
No full textIn the context of an interdisciplinary approach aimed at pointing out the interconnections between science and philosophy in the early modern centuries, no author is probably more interesting than Leibniz
Attitude Control Subsystem Design of the Stable and Highly Accurate Pointing Earth-imager
No full textAs technology improves, increasingly higher resolution payload can be achieved using Cubesats for Earth observation. The diffraction limit prevents the resolution to up to a few meters for these missions and are confined to Very Low Earth Orbits (VLEO). At these altitudes, strong disturbances act on the system, limiting its lifetime and the pointing capabilities of CubeSats. As a solution, the Department of Space Engineering at the Delft University of Technologyhas proposed a 6 unit CubeSat named the Stable and Highly Accurate Pointing Earth-imager (SHAPE) orbiting at a Sun synchronous VLEO which uses a momentum wheel to passively stabilize the system against the external environment within a competitive cost of less than 500 000e. By utilizing the dual-spin stabilization concept, composed of a stable platform and a spinning rotor, it is expected to perform pointing missions of less than 1 degree.In this thesis, the SHAPE concept has been revisited and further developed based on the work of Kuiper and Dolkens to conduct whether these types of missions are feasible within the aspect of the Attitude Determination and Control Subsystem (ADCS). This thesis covers the base of this subsystem approached from a top-down methodology; designed from the final nominal mission mode to the detumbling mode on a system level.The ADCS design will consist of a momentum wheel which has been determined to have an angular momentum of 1 Nms. This value is based on a prediction of the worst-case atmospheric density of the next solar cycle. The designpoint, at which the momentum wheel has been sized, has been taken at 90% of SHAPE’s lifetime after several design iterations. Hereby, the last 10% of the mission has been partially forfeited with degraded performances due to theexponential increase in disturbances acting on the spacecraft at lower altitudes. As therefore, the mass and size of the momentum wheel has been reduced with 41% and 20%, respectively. To re-align the angular momentum vector withinthe 1 degree pointing requirement, a set of magnetorquers with a dipole moment of 0.5 Am2 has been chosen due to their low power consumption, mass, cost, and high reliability while capable of producing sufficient torque. Also, adamper is to be integrated as it provides the system asymptotic reduction of the transverse momenta, thus increasing the image quality without expenditure of additional power.To reach the nominal mission observation state, several momentum wheel spinup strategies have been investigated. Based on a trade-off between three spinup concepts, it was concluded that the major axis spinup is most suited. Thistype is initiated after the spacecraft as a whole has attained an angular momentum equivalent to that of the desired end value of the momentum wheel. Then, a constant rotor torque is applied, providing a momentum transfer from the platform to the rotor. The disadvantage of this spinup procedure is that the system’s solar panels are aligned parallel to the orbital plane, meaning that power cannot be generated and batteries are required during the spinup. Despite this, it was found that after completing the spinup, the transverse angular momenta was minimized to marginal values in contrast to the other spins. The inclusion of the passive damper during the major axis spin further improves the ability of reducing the transverse momentum as the damper’s dissipative energy property adds an asymptotic attraction at the point of lowest energy, located at the spin axis near the end of the spinup.The all-spun state is achieved using a set of thrusters. This choice was taken as the magnetorquers was found not to deliver sufficient torque. From the detumbling analysis, it was concluded that the magnetorquers are able to reducethe tumbling rates with magnitudes of up to 35 deg/s to mean motion values in less than an orbit using a static gain B-dot controller.Imperfections in the momentum wheel can cause static and dynamic imbalance, imparting internal disturbances to the system which affects the image quality detrimentally. Therefore, isolators are to be integrated within the momentumwheel suspension subsystem. If these disturbances can be negated using isolators, it can be expected that the pointing error will stay within one degree and attitude stability can be achieved at least until the design altitude of 280 km.However, the analysis and design of the isolators have yet to be done and thus the attainability of the pointing and image quality requirements are still inconclusive.Aerospace Engineerin
Movie S2 from JGR article "Auroral Illumination of Solid Bodies"
No full textAn animation of registered images from the second pointing series of the REGI imager. Object-3 is indicated by moving annotation. The same aircraft seen in the previous movie is indicated by the moving AC annotation. Other objects with unknown altitudes are indicated by letters A & B. The last frame illustrates the transient “diffuse” green “flash” or glow sometimes seen along with STEVE
Negasilus Curran. 1934
No full text<i>Negasilus</i> Curran <p> <i>Negasilus</i> Curran, 1934: 183.</p> <p> Species found in Wyoming: <i>Negasilus aridalis, N. belli</i>, <i>N. cumbipilosus</i>, and <i>N</i>. <i>gramalis</i>.</p> <p> <b>Key to Species</b> [adapted from Adisoemarto (1967) (as <i>Asilus</i>); Martin (1975)]</p> <p>1 Lateroposterior corners of abdominal tergites with one or more bristles longer than other setae and bristles.............. 2</p> <p>- Lateroposterior margins of abdominal tergites without long bristles.............................................. 3</p> <p> 2 Posterior margin of scutellum usually without bristles, if present, short recumbent and pointing laterally; femora black with reddish band at apex........................................................................ <i>Negasilus belli</i></p> <p> - Posterior margin of scutellum with long bristles; hind femora totally black...................... <i>Negasilus cumbipilosus</i></p> <p> 3 Leg coxae grayish pollinose; femora reddish yellow; tibiae orange yellow.......................... <i>Negasilus aridalis</i></p> <p> <i>-</i> Leg coxae golden yellow; femora totally black; tibiae reddish brown.............................. <i>Negasilus gramalis</i></p>Published as part of <i>Lavigne, Robert J. & Dennis, Steve, 2019, Robber flies (Insecta: Diptera: Asilidae) of Wyoming, USA with keys to genera and species, pp. 1-126 in Zootaxa 4662 (1)</i> on page 51, DOI: 10.11646/zootaxa.4662.1.1, <a href="http://zenodo.org/record/3383448">http://zenodo.org/record/3383448</a>
Search for the rare decay of the W boson into a pion and a photon in proton-proton collisions at root s=13 TeV
No full textA search is performed for the rare decay W-+/--> pi(+/-)gamma in proton-proton collisions at root s = 13 TeV. Data corresponding to an integrated luminosity of 137 fb(-1) were collected during 2016 to 2018 with the CMS detector. This analysis exploits a novel search strategy based on W boson production in top quark pair events. An inclusive search for the W-+/--> pi(+/-)gamma decay is not optimal at the LHC because of the high trigger thresholds. Instead, a trigger selection is exploited in which the W boson originating from one of the top quarks is used to tag the event in a leptonic decay. The W boson emerging from the other top quark is used to search for the W-+/--> pi(+/-)gamma signature. Such decays are characterized by an isolated track pointing to a large energy deposit, and by an isolated photon of large transverse momentum. The presence of b quark jets reduces the background from the hadronization of light-flavor quarks and gluons. The W-+/- -> pi(+/-)gamma decay is not observed. An upper exclusion limit is set to this branching fraction, corresponding to 1.50 x 10(-5) at 95% confidence level, whereas the expected upper exclusion limit is 0.85(-0.29)(+0.52) x 10(-5). (C) 2021 The Author(s). Published by Elsevier B.V
Evolution of Anti-B Cell Therapeutics in Autoimmune Neurological Diseases
No full textB cells have an ever-increasing role in the etiopathology of a number of autoimmune neurological disorders, acting as antigen-presenting cells facilitating antibody production but also as sensors, coordinators, and regulators of the immune response. In particular, B cells can regulate the T cell activation process through their participation in antigen presentation, production of proinflammatory cytokines (bystander activation or suppression), and contribution to ectopic lymphoid aggregates. Such an important interplay between B and T cells makes therapeutic depletion of B cells an attractive treatment strategy. The last decade, anti-B cell therapies using monoclonal antibodies against B cell surface molecules have evolved into a rational approach for successfully treating autoimmune neurological disorders, even when T cells seem to be the main effector cells. The paper summarizes basic aspects of B cell biology, discusses the roles of B cells in neurological autoimmunities, and highlights how the currently available or under development anti-B cell therapeutics exert their action in the wide spectrum and immunologically diverse neurological disorders. The efficacy of the various anti-B cell therapies and practical issues on induction and maintenance therapy is specifically detailed for the treatment of patients with multiple sclerosis, neuromyelitis-spectrum disorders, autoimmune encephalitis and hyperexcitability CNS disorders, autoimmune neuropathies, myasthenia gravis, and inflammatory myopathies. The success of anti-B cell therapies in inducing long-term remission in IgG4 neuroautoimmunities is also highlighted pointing out potential biomarkers for follow-up infusions. © 2022, The Author(s)
Aerobiology over Antarctica – A new Initiative for Atmospheric Ecology
No full textThe role of Aerial dispersal in shaping patterns of biodiversity remains poorly understood, mainly due to a lack of coordinated efforts in gathering data at appropriate temporal and spatial scales. It has been long known that the rate of dispersal to an ecosystem can significantly influence ecosystem dynamics, and that aerial transport has been identified as an important source of biological input to remote locations. With the considerable effort devoted in recent decades to understanding atmospheric circulation in the south-polar region, a unique opportunity has emerged to investigate the atmospheric ecology of Antarctica, from regional to Continental scales. This concept note identifies key questions in Antarctic microbial biogeography and the need for standardized sampling and analysis protocols to address such questions. A consortium of polar aerobiologists is established to bring together researchers with a common interest in the airborne dispersion of microbes and other propagules in the Antarctic, with opportunities for comparative studies in the Arctic
Information diffusion backbones in temporal networks
No full text Progress has been made in understanding how temporal network features affect the percentage of nodes reached by an information diffusion process. In this work, we explore further: which node pairs are likely to contribute to the actual diffusion of information, i.e., appear in a diffusion trajectory? How is this likelihood related to the local temporal connection features of the node pair? Such deep understanding of the role of node pairs is crucial to tackle challenging optimization problems such as which kind of node pairs or temporal contacts should be stimulated in order to maximize the prevalence of information spreading. We start by using Susceptible-Infected (SI) model, in which an infected (information possessing) node could spread the information to a susceptible node with a given infection probability β whenever a contact happens between the two nodes, as the information diffusion process. We consider a large number of real-world temporal networks. First, we propose the construction of an information diffusion backbone G B (β) for a SI spreading process with an infection probability β on a temporal network. The backbone is a weighted network where the weight of each node pair indicates how likely the node pair appears in a diffusion trajectory starting from an arbitrary node. Second, we investigate the relation between the backbones with different infection probabilities on a temporal network. We find that the backbone topology obtained for low and high infection probabilities approach the backbone G B (β → 0) and G B (β = 1), respectively. The backbone G B (β → 0) equals the integrated weighted network, where the weight of a node pair counts the total number of contacts in between. Finally, we explore node pairs with what local connection features tend to appear in G B (β = 1), thus actually contribute to the global information diffusion. We discover that a local connection feature among many other features we proposed, could well identify the (high-weight) links in G B (β = 1). This local feature encodes the time that each contact occurs, pointing out the importance of temporal features in determining the role of node pairs in a dynamic process. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Multimedia ComputingIntelligent System
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