7,630 research outputs found

    Forelimb muscle and joint actions in Archosauria: insights from Crocodylus johnstoni (Pseudosuchia) and Mussaurus patagonicus (Sauropodomorpha)

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    Many of the major locomotor transitions during the evolution of Archosauria, the lineage including crocodiles and birds as well as extinct Dinosauria, were shifts from quadrupedalism to bipedalism (and vice versa). Those occurred within a continuum between more sprawling and erect modes of locomotion and involved drastic changes of limb anatomy and function in several lineages, including sauropodomorph dinosaurs. We present biomechanical computer models of two locomotor extremes within Archosauria in an analysis of joint ranges of motion and the moment arms of the major forelimb muscles in order to quantify biomechanical differences between more sprawling, pseudosuchian (represented the crocodile Crocodylus johnstoni) and more erect, dinosaurian (represented by the sauropodomorph Mussaurus patagonicus) modes of forelimb function. We compare these two locomotor extremes in terms of the reconstructed musculoskeletal anatomy, ranges of motion of the forelimb joints and the moment arm patterns of muscles across those ranges of joint motion. We reconstructed the three-dimensional paths of 30 muscles acting around the shoulder, elbow and wrist joints. We explicitly evaluate how forelimb joint mobility and muscle actions may have changed with postural and anatomical alterations from basal archosaurs to early sauropodomorphs. We thus evaluate in which ways forelimb posture was correlated with muscle leverage, and how such differences fit into a broader evolutionary context (i.e. transition from sprawling quadrupedalism to erect bipedalism and then shifting to graviportal quadrupedalism). Our analysis reveals major differences of muscle actions between the more sprawling and erect models at the shoulder joint. These differences are related not only to the articular surfaces but also to the orientation of the scapula, in which extension/flexion movements in Crocodylus (e.g. protraction of the humerus) correspond to elevation/depression in Mussaurus. Muscle action is highly influenced by limb posture, more so than morphology. Habitual quadrupedalism in Mussaurus is not supported by our analysis of joint range of motion, which indicates that glenohumeral protraction was severely restricted. Additionally, some active pronation of the manus may have been possible in Mussaurus, allowing semi-pronation by a rearranging of the whole antebrachium (not the radius against the ulna, as previously thought) via long-axis rotation at the elbow joint. However, the muscles acting around this joint to actively pronate it may have been too weak to drive or maintain such orientations as opposed to a neutral position in between pronation and supination. Regardless, the origin of quadrupedalism in Sauropoda is not only linked to manus pronation but also to multiple shifts of forelimb morphology, allowing greater flexion movements of the glenohumeral joint and a more columnar forelimb posture

    Light transmission assisted by Brewster-Zennek modes in chromium films carrying a subwavelength hole array

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    This work confirms that not only surface plasmons but many other kinds of electromagnetic eigenmodes should be considered in explaining the values of the transmittivity through a slab bearing a two-dimensional periodic corrugation. Specifically, the role of Brewster-Zennek modes appearing in metallic films exhibiting regions of weak positive dielectric constant. It is proposed that these modes play a significant role in the light transmission in a thin chromium film perforated with normal cylindrical holes, for appropriate lattice parameters.Comment: 5 pages, 4 figures. Published versio

    A Novel Scheme for High scale IVC and RVC Over Bluetooth

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    Vehicular Ad-Hoc Network (VANET) is a form of Mobile ad-hoc network, to provide communications among nearby vehicles called inter-vehicle communication (IVC) and between vehicles and nearby fixed equipment called roadside-vehicle communication (RVC). In VANET, or Intelligent Vehicular Ad-Hoc Networking, defines an intelligent way of using Vehicular Networking. In VANET integrates on multiple ad-hoc networking technologies such as WiFi, IEEE 802.16, Blue-tooth, IRA etc. for easy, accurate, effective and simple communication between vehicles on dynamic mobility. For configuring the vehicle with a unique address, there is a need for address reconfigurations depending on the mobility patterns; we have presented a centralized addressing scheme for VANET using Blue-tooth. By building up a P2P (Per to Per) overlay network on top of VANETs physical infrastructure, we effectively integrated P2P network’s advantage on sustaining highly dynamic network into the design of VANET routing protocol. By deploying passive VANET routing algorithms with innovative P2P routing mechanisms, we propose two concepts behind the same Single Hopping and Multi Hopping technique. This project investigates the feasibility of having a Vehicular Ad-Hoc Network (VANET) / Mobile Ad-hoc Network (MANET) routing over Bluetooth. Contrary to this approach, most papers of MANET take WiFi as their underlying technology with the aim to expand the already existing internet, and it has fifty meters plus signal range. With the rapid growth in popularity, Bluetooth is being used in increasingly diverse ways to act as a bridge of communication between different hardware. This project develops on this by testing the effectiveness of a Bluetooth routing system with a fully working router implementation on real mobile phones

    Grazing and management of saltland shrubs

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    areas of bare saltland on farms need not be unproductive etesores. Many Western Australian farmers are now successfully growing salt-tolerant or halophytic shrubs such as bluebush (Maireana brevifolia), saltbushes (Atriplex spp.) and samphires (Halosarcia spp.) on these areas. Department of agriculture trials and farmers\u27 experience indicate that if saltland is planted with recommended shrubs, it can provide two months\u27 valuable grazing for sheep during autumn and early winter, a time when paddock feed is scarce. Research by the Department has also identified a range of salt-tolerant shrubs suited to the various types of saltland. Grazing trials to determine the value of salt-tolerant shrub pasture for sheep started at Wickepin and Kondut in the 1970s and the early results were reported in this Journal in 1982 (Clarke, 1982). The Kondut trial has been continued and the results from six years\u27 grazing are discussed here. This article also contains additional information from the large grazed plots on farms and from farmers experienced in management and use osd saltland shrub pastures

    Synthesis and characterization of Nb2O5@C core-shell nanorods and Nb2O5nanorods by reacting Nb(OEt)5via RAPET (reaction under autogenic pressure at elevated temperatures) technique

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    The reaction of pentaethoxy niobate, Nb(OEt)5, at elevated temperature (800 °C) under autogenic pressure provides a chemical route to niobium oxide nanorods coated with amorphous carbon. This synthetic approach yielded nanocrystalline particles of Nb2O5@C. As prepared Nb2O5@C core-shell nanorods is annealed under air at 500 °C for 3 h (removing the carbon coating) results in neat Nb2O5nanorods. According to the TEM measurements, the Nb2O5crystals exhibit particle sizes between 25 nm and 100 nm, and the Nb2O5crystals display rod-like shapes without any indication of an amorphous character. The optical band gap of the Nb2O5nanorods was determined by diffuse reflectance spectroscopy (DRS) and was found to be 3.8 eV

    A cross-layer scheduling strategy for the downlink of a MIMO-OFDMA system with heterogeneous traffic

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    in this paper we propose and investigate a cross-layer multiuser scheduling strategy for the support of heterogeneous traffic in the downlink of a MIMO-OFDMA system. It jointly considers different objectives: maximize the sum-rate on the radio channel, ensure a fair allocation of resources among users belonging to the same traffic class, consider the dynamics of traffic sources by looking at the delay of data packets in the queues, contribute to maximize quality of service figures at the application level. To exploit temporal diversity and to reduce complexity, the ergodic weighted sum-rate is maximized and dual optimization with stochastic approximation is applied to derive on-line algorithms. The numerical results show the capability of the scheduler to allocate physical layer resources according to rate constraints imposed for each different traffic class and with fairness inside each class, even in presence of different channels conditions and different network loads.Postprint (published version

    Increasing altruistic and cooperative behaviour with simple moral nudges

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    The conflict between pro-self and pro-social behaviour is at the core of many key problems of our time, as, for example, the reduction of air pollution and the redistribution of scarce resources. For the well-being of our societies, it is thus crucial to find mechanisms to promote pro-social choices over egoistic ones. Particularly important, because cheap and easy to implement, are those mechanisms that can change people's behaviour without forbidding any options or significantly changing their economic incentives, the so-called "nudges". Previous research has found that moral nudges (e.g., making norms salient) can promote pro-social behaviour. However, little is known about whether their effect persists over time and spills across context. This question is key in light of research showing that pro-social actions are often followed by selfish actions, thus suggesting that some moral manipulations may backfire. Here we present a class of simple moral nudges that have a great positive impact on pro-sociality. In Studies 1-4 (total N = 1,400), we use economic games to demonstrate that asking subjects to self-report "what they think is the morally right thing to do" does not only increase pro-sociality in the choice immediately after, but also in subsequent choices, and even when the social context changes. In Study 5, we explore whether moral nudges promote charity donations to humanitarian organisations in a large (N = 1,800) crowdfunding campaign. We find that, in this context, moral nudges increase donations by about 44 percent
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