30,442 research outputs found

    A new species of Archaeoryctes from the Middle Paleocene of China and the phylogenetic diversification of Didymoconidae

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    Didymoconidae are an enigmatic group of Asian endemic insectivorous mammals. We describe the new didymoconid species Archaeoryctes wangi sp. nov. from the Upper Member of the Wanghudun Formation (Middle Paleocene). This new species from the Qianshan Basin (Anhui Province, China) forms an interesting geographical intermediate between A. notialis from South China and A. borealis and A. euryalis from the Mongolian Plateau. To better understand the origin and evolutionary diversification of Didymoconidae, we performed a cladistic and stratocladistic study of the Didymoconidae and various outgroups. This study of dental material did not resolve the higher level affinities of Didymoconidae, but confirms the validity of the family and its distinctiveness from the morphologically similar Sarcodontidae. Moreover, our results corroborate the current didymoconid classification with the distinction of three subfamilies: “Ardynictinae”, Kennatheriinae and Didymoconinae; “Ardynictinae” are a paraphyletic stemgroup for the two other subfamilies. Our results suggest three distinct didymoconid radiations: (1) primitive ardynictines appeared in South China from the start of the Nongshanian; their evolution continues on the Mongolian Plateau with (2) the radiation of more evolved ardynictines and kennatheriines at the start of the Middle Eocene Arshantan and (3) the origin of didymoconines at the start of the Late Eocene Ergilian

    Prepare Tone: Enhancing Broadcast-Packet Transmission of Multiple Rendezvous Mac Performance in Multiple-Channel Ad Hoc Network

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    AbstractMultiple Rendezvous approaches utilized multi-channel which was only with a single transceiver radio may enhance Mac throughputs of multi-channel ad hoc network no less than that of other approaches which need extra radios or hardware for time synchronization. However, for the media-access methods of Multiple Rendezvous, nodes in ad hoc network should be listening on different channels to preserve the control packets of any data transmission with noneinterference each other. Therefore, for any broadcast data packet or multicast data packet, it should be transmitted to its destinations like a set of single-cast data packets. And then other performances of ad hoc network as routing may be reduced by the high overload of broadcast packet. In order to reduce the transmission number of a broadcast packet, a method of using prepare tones (single-cast tone and broadcast tone) before data-packet transmission is presented, we called it PTMC (Prepare Tone for Media-access Control). In the method of PTMC, any broadcast packet will be send out only once to preserve it can reach any idle destination, which is not sending or receiving any data-packets at that time, nevertheless any single-cast packet will be matched and send out just as MAXM done. Simulation results among PTMC, MAXM and SSCH show: If every broadcast packet was send to potential receivers one by one, the throughputs of ad hoc network routed by AODV and media controlled by MAXM or SSCH may not be improved as the available channel number is increasing, for reasons of the routing discovery time increasing. Using PTMC to solve this problem, whatever data-traffics or available channels are provided, the throughput of PTMC will be better than the other two. Thus with available channels increasing, the throughput of PTMA is improved

    Thermodynamics of third order Lovelock anti-de Sitter black holes revisited

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    We compute the mass and the temperature of third order Lovelock black holes with negative Gauss-Bonnet coefficient α2<0\alpha_2<0 in anti-de Sitter space and perform the stability analysis of topological black holes. When k=−1k=-1, the third order Lovelock black holes are thermodynamically stable for the whole range r+r_+. When k=1k=1, we found that the black hole has an intermediate unstable phase for D=7D=7. In eight dimensional spacetimes, however, a new phase of thermodynamically unstable small black holes appears if the coefficient α~\tilde{\alpha} is under a critical value. For D≄9D\geq 9, black holes have similar the distributions of thermodynamically stable regions to the case where the coefficient α~\tilde{\alpha} is under a critical value for D=8D=8. It is worth to mention that all the thermodynamic and conserved quantities of the black holes with flat horizon don't depend on the Lovelock coefficients and are the same as those of black holes in general gravity.Comment: 15 pages, 22 figure

    Internet use among urban Malaysians: Network diversity effects

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    This study examines social network diversity in urban areas relative to residents’ usage of information and communication technologies (ICTs). Individual-level variation in social network diversity was measured using position generator data collected as part of a survey conducted in Malaysia’s Klang Valley (N = 808). Regression analyses were performed to assess the extent to which network diversity is related to ICTs. We find that most ICTs have a negative effect on diversity. Only frequent use of the Internet at work, mobile access to the Internet, and reading online news or blogs contribute positively to diversity. Findings support both a tendency toward ‘networked individualism’ and the more recent ‘glocalization’ thesis that some ICTs may also afford participation within local space rather than only across distant space

    Maxwell’s Equations on Cantor Sets: A Local Fractional Approach

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    Maxwell’s equations on Cantor sets are derived from the local fractional vector calculus. It is shown that Maxwell’s equations on Cantor sets in a fractal bounded domain give efficiency and accuracy for describing the fractal electric and magnetic fields. Local fractional differential forms of Maxwell’s equations on Cantor sets in the Cantorian and Cantor-type cylindrical coordinates are obtained. Maxwell's equations on Cantor set with local fractional operators are the first step towards a unified theory of Maxwell’s equations for the dynamics of cold dark matter

    Mappings for Special Functions on Cantor Sets and Special Integral Transforms via Local Fractional Operators

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    The mappings for some special functions on Cantor sets are investigated. Meanwhile, we apply the local fractional Fourier series, Fourier transforms, and Laplace transforms to solve three local fractional differential equations, and the corresponding nondifferentiable solutions were presented
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