17,766 research outputs found

    An extended formalism for preferential attachment in heterogeneous complex networks

    Full text link
    In this paper we present a framework for the extension of the preferential attachment (PA) model to heterogeneous complex networks. We define a class of heterogeneous PA models, where node properties are described by fixed states in an arbitrary metric space, and introduce an affinity function that biases the attachment probabilities of links. We perform an analytical study of the stationary degree distributions in heterogeneous PA networks. We show that their degree densities exhibit a richer scaling behavior than their homogeneous counterparts, and that the power law scaling in the degree distribution is robust in presence of heterogeneity

    Combining exclusive semi-leptonic and hadronic B decays to measure |V_ub|

    Get PDF
    The Cabibbo-Kobayashi-Maskawa matrix element |V_ub| can be extracted from the rate for the semi-leptonic decay B -> pi + l + antineutrino_l, with little theoretical uncertainty, provided the hadronic form factor for the B -> pi transition can be measured from some other B decay. In here, we suggest using the decay B -> pi J\psi. This is a color suppressed decay, and it cannot be properly described within the usual factorization approximation; we use instead a simple and very general phenomenological model for the b d J\psi vertex. In order to relate the hadronic form factors in the B -> pi J\psi and B -> pi + l + antineutrino_l decays, we use form factor relations that hold for heavy-to-light transitions at large recoil.Comment: Latex, 7 pages, no figure

    GJR Volume 38 Number 1 Spring 2015

    Get PDF
    The Georgia Journal of Reading\u27s Spring 2015 issue includes: Message from the Editors by Dr. Christine A. Draper and Dr. Lina B. Soares (pg. 4) President’s Page by Dr. Beth Pendergraft (pg.5) . Middle School Literacy Coaches: Perceptions of Roles and Responsibilities by Dr. Katie Stover and Dr. Maryann Mraz (pg. 6) An Analysis of Teachers’ Discourse and Their Perceptions Concerning the Use of Questioning and Feedback During Reading Instruction In Third-Grade Classrooms by Dr. Marie Holbein and Dr. Jennifer Farist (pg. 15) Reading, Motivation, and the Power of Social Relationships: Learning from Middle School Students in a Title I Reading Classroom by Dr. Trevor Thomas Stewart and Dr. Emily Pendergrass (pg. 25) How Can Teachers Motivate Reluctant Readers? by Dr. Maggie Lehman (pg. 32) Dictionary Projects: A Defining Moment in Literacy by Beverly A. McKenna and Beverly A. Strauser (pg. 40)https://digitalcommons.kennesaw.edu/gjrarchive/1006/thumbnail.jp

    Empiricism and stochastics in cellular automaton modeling of urban land use dynamics

    Get PDF
    An increasing number of models for predicting land use change in regions of rapidurbanization are being proposed and built using ideas from cellular automata (CA)theory. Calibrating such models to real situations is highly problematic and to date,serious attention has not been focused on the estimation problem. In this paper, wepropose a structure for simulating urban change based on estimating land usetransitions using elementary probabilistic methods which draw their inspiration fromBayes' theory and the related ?weights of evidence? approach. These land use changeprobabilities drive a CA model ? DINAMICA ? conceived at the Center for RemoteSensing of the Federal University of Minas Gerais (CSR-UFMG). This is based on aneight cell Moore neighborhood approach implemented through empirical land useallocation algorithms. The model framework has been applied to a medium-size townin the west of São Paulo State, Bauru. We show how various socio-economic andinfrastructural factors can be combined using the weights of evidence approach whichenables us to predict the probability of changes between land use types in differentcells of the system. Different predictions for the town during the period 1979-1988were generated, and statistical validation was then conducted using a multipleresolution fitting procedure. These modeling experiments support the essential logicof adopting Bayesian empirical methods which synthesize various information aboutspatial infrastructure as the driver of urban land use change. This indicates therelevance of the approach for generating forecasts of growth for Brazilian citiesparticularly and for world-wide cities in general

    Erlang Code Evolution Control

    Full text link
    During the software lifecycle, a program can evolve several times for different reasons such as the optimisation of a bottle-neck, the refactoring of an obscure function, etc. These code changes often involve several functions or modules, so it can be difficult to know whether the correct behaviour of the previous releases has been preserved in the new release. Most developers rely on a previously defined test suite to check this behaviour preservation. We propose here an alternative approach to automatically obtain a test suite that specifically focusses on comparing the old and new versions of the code. Our test case generation is directed by a sophisticated combination of several already existing tools such as TypEr, CutEr, and PropEr; and other ideas such as allowing the programmer to chose an expression of interest that must preserve the behaviour, or the recording of the sequences of values to which this expression is evaluated. All the presented work has been implemented in an open-source tool that is publicly available on GitHub.Comment: Pre-proceedings paper presented at the 27th International Symposium on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur, Belgium, 10-12 October 2017 (arXiv:1708.07854

    Evidence for entanglement at high temperatures in an engineered molecular magnet

    Full text link
    The molecular compound [Fe2_{2}(μ2\mu_{2}-oxo)(C3_{3}H4_{4}N2_{2})6_{6}(C2_{2}O4_{4})2_{2}] was designed and synthesized for the first time and its structure was determined using single-crystal X-ray diffraction. The magnetic susceptibility of this compound was measured from 2 to 300 K. The analysis of the susceptibility data using protocols developed for other spin singlet ground-state systems indicates that the quantum entanglement would remain at temperatures up to 732 K, significantly above the highest entanglement temperature reported to date. The large gap between the ground state and the first-excited state (282 K) suggests that the spin system may be somewhat immune to decohering mechanisms. Our measurements strongly suggest that molecular magnets are promising candidate platforms for quantum information processing

    Experimental Determination of Thermal Entanglement in Spin Clusters using Magnetic Susceptibility Measurements

    Full text link
    The present work reports an experimental observation of thermal entanglement in a clusterized spin chain formed in the compound Na2_2Cu5_5Si4_4O14_{14}. The presence of entanglement was investigated through two measured quantities, an Entanglement Witness and the Entanglement of Formation, both derived from the magnetic susceptibility. It was found that pairwise entanglement exists below ∼200 \sim 200 K. Tripartite entanglement was also observed below ∼240 \sim 240 K. A theoretical study of entanglement evolution as a function of applied field and temperature is also presented.Comment: Submited to Phys. Rev.

    Mutual selection in network evolution: the role of the intrinsic fitness

    Full text link
    We propose a new mechanism leading to scale-free networks which is based on the presence of an intrinsic character of a vertex called fitness. In our model, a vertex ii is assigned a fitness xix_i, drawn from a given probability distribution function f(x)f(x). During network evolution, with rate pp we add a vertex jj of fitness xjx_j and connect to an existing vertex ii of fitness xix_i selected preferentially to a linking probability function g(xi,xj)g(x_i,x_j) which depends on the fitnesses of the two vertices involved and, with rate 1−p1-p we create an edge between two already existed vertices with fitnesses xix_i and xjx_j, with a probability also preferential to the connection function g(xi,xj)g(x_i,x_j). For the proper choice of gg, the resulting networks have generalized power laws, irrespective of the fitness distribution of vertices.Comment: ws-ijmpc.te
    • …
    corecore