660 research outputs found

    Transmission Electron Study of Heteroepitaxial Growth in the BiSrCaCuO System

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    Films of Bi2\rm _2Sr2\rm _2CaCu2\rm _2O8\rm _8 and Bi2\rm _2Sr2\rm _2CuO6\rm _6 have been grown using Atomic-Layer-by-Layer Molecular Beam Epitaxy (ALL-MBE) on lattice-matched substrates. These materials have been combined with layers of closely-related metastable compounds like Bi2\rm _2Sr2\rm _2Ca7\rm _7Cu8\rm _8O20\rm _{20} (2278) and rare-earth-doped compounds like Bi2\rm _2Sr2\rm _2Dyx\rm _xCa1x\rm _{1-x}Cu2\rm _2O8\rm _8 (Dy:2212) to form heterostructures with unique superconducting properties, including superconductor/insulator multilayers and tunnel junctions. Transmission electron microscopy (TEM) has been used to study the morphology and microstructure of these heterostructures. These TEM studies shed light on the physical properties of the films, and give insight into the growth mode of highly anisotropic solids like Bi2\rm _2Sr2\rm _2CaCu2\rm _2O8\rm _8.Comment: 17 pages, submitted to J. Materials Research. Email to [email protected] if you want to receive copies of the figure

    Membrane geometry with auxiliary variables and quadratic constraints

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    Consider a surface described by a Hamiltonian which depends only on the metric and extrinsic curvature induced on the surface. The metric and the curvature, along with the basis vectors which connect them to the embedding functions defining the surface, are introduced as auxiliary variables by adding appropriate constraints, all of them quadratic. The response of the Hamiltonian to a deformation in each of the variables is examined and the relationship between the multipliers implementing the constraints and the conserved stress tensor of the theory established.Comment: 8 page

    Nonequilibrium stationary states and equilibrium models with long range interactions

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    It was recently suggested by Blythe and Evans that a properly defined steady state normalisation factor can be seen as a partition function of a fictitious statistical ensemble in which the transition rates of the stochastic process play the role of fugacities. In analogy with the Lee-Yang description of phase transition of equilibrium systems, they studied the zeroes in the complex plane of the normalisation factor in order to find phase transitions in nonequilibrium steady states. We show that like for equilibrium systems, the ``densities'' associated to the rates are non-decreasing functions of the rates and therefore one can obtain the location and nature of phase transitions directly from the analytical properties of the ``densities''. We illustrate this phenomenon for the asymmetric exclusion process. We actually show that its normalisation factor coincides with an equilibrium partition function of a walk model in which the ``densities'' have a simple physical interpretation.Comment: LaTeX, 23 pages, 3 EPS figure

    Herbert Simon's decision-making approach: Investigation of cognitive processes in experts

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    This is a post print version of the article. The official published can be obtained from the links below - PsycINFO Database Record (c) 2010 APA, all rights reserved.Herbert Simon's research endeavor aimed to understand the processes that participate in human decision making. However, despite his effort to investigate this question, his work did not have the impact in the “decision making” community that it had in other fields. His rejection of the assumption of perfect rationality, made in mainstream economics, led him to develop the concept of bounded rationality. Simon's approach also emphasized the limitations of the cognitive system, the change of processes due to expertise, and the direct empirical study of cognitive processes involved in decision making. In this article, we argue that his subsequent research program in problem solving and expertise offered critical tools for studying decision-making processes that took into account his original notion of bounded rationality. Unfortunately, these tools were ignored by the main research paradigms in decision making, such as Tversky and Kahneman's biased rationality approach (also known as the heuristics and biases approach) and the ecological approach advanced by Gigerenzer and others. We make a proposal of how to integrate Simon's approach with the main current approaches to decision making. We argue that this would lead to better models of decision making that are more generalizable, have higher ecological validity, include specification of cognitive processes, and provide a better understanding of the interaction between the characteristics of the cognitive system and the contingencies of the environment

    Grassmann Integral Representation for Spanning Hyperforests

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    Given a hypergraph G, we introduce a Grassmann algebra over the vertex set, and show that a class of Grassmann integrals permits an expansion in terms of spanning hyperforests. Special cases provide the generating functions for rooted and unrooted spanning (hyper)forests and spanning (hyper)trees. All these results are generalizations of Kirchhoff's matrix-tree theorem. Furthermore, we show that the class of integrals describing unrooted spanning (hyper)forests is induced by a theory with an underlying OSP(1|2) supersymmetry.Comment: 50 pages, it uses some latex macros. Accepted for publication on J. Phys.

    Accessible Content and Accessibility Experiences: The Interplay of Declarative and Experiential Information in Judgment

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    Recall tasks render 2 distinct sources of information available: the recalled content and the experienced ease or difficulty with which it can be brought to mind. Because retrieving many pieces of information is more difficult than retrieving only a few, reliance on accessible content and subjective accessibility experiences leads to opposite judgmental outcomes. People are likely to base judgments on accessibility experiences when they adopt a heuristic processing strategy and the informational value of the experience is not called into question. When the experience is considered nondiagnostic, or when a systematic processing strategy is adopted, people rely on accessible content. Implications for the operation of the availability heuristic and the emergence of knowledge accessibility effects are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68686/2/10.1207_s15327957pspr0202_2.pd

    Validation of the test need for cognition: a study in behavioral accounting

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    This study aimed to validate the Need for Cognition scale (NFC) in behavioral accounting. In addition, we sought to measure the possible correlations between the level of need for cognition and the existence of cognitive biases in decisions in accounting and financial information. Two validations were performed to carry out the process of full validation – criterion and construct. The analysis was done by the examination of a sample comprised by 128 graduation students. The statistical technique used for the validation of this test was a factorial analysis for it has the ability to determine the degree of influence of a particular variable in the explanation of a factor, and the processing logistic regression was used for the explanation of possible values as a function of known values or independent variables. The results of the construct of validity showed the legitimacy of the NFC as a unidimensional scale excluding three outputs of its original scale, since the criterion validity of the results confirmed the impact of the level of cognition in maximizing the occurrence of heuristics in managerial decisions

    When people co-occur with good or bad events: graded effects of relational qualifiers on evaluative conditioning

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    Studies on evaluative conditioning show that a change in liking can occur whenever stimuli are paired. Such instances of attitude change are known to depend on the type of relation established between stimuli (e.g., “Bob is a friend of Mike” vs. “Bob is an enemy of Mike”). Research has so far only compared assimilative and contrastive relational qualifiers (e.g., friend vs. enemy). For the first time, we compared the effect of non-oppositional qualifiers on attitude change in a EC procedure (e.g., “Bob causes Positive Outcomes” vs. “Bob predicts Positive Outcomes”). Differential effects of non-oppositional relational qualifiers were observed on explicit and implicit evaluations. We discuss the implications of our findings for attitude research, theories of attitude change, and for optimizing evaluative conditioning for changing attitudes in applied settings
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