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Answering Questions (answering + question)

Distribution by Scientific Domains

Humanities and Social Sciences	40%

Selected Abstracts

The maximum entropy formalism and the idiosyncratic theory of biodiversity

ECOLOGY LETTERS, Issue 11 2007
Salvador Pueyo
Abstract Why does the neutral theory, which is based on unrealistic assumptions, predict diversity patterns so accurately? Answering questions like this requires a radical change in the way we tackle them. The large number of degrees of freedom of ecosystems pose a fundamental obstacle to mechanistic modelling. However, there are tools of statistical physics, such as the maximum entropy formalism (MaxEnt), that allow transcending particular models to simultaneously work with immense families of models with different rules and parameters, sharing only well-established features. We applied MaxEnt allowing species to be ecologically idiosyncratic, instead of constraining them to be equivalent as the neutral theory does. The answer we found is that neutral models are just a subset of the majority of plausible models that lead to the same patterns. Small variations in these patterns naturally lead to the main classical species abundance distributions, which are thus unified in a single framework. [source]

Scales of association: hierarchical linear models and the measurement of ecological systems

ECOLOGY LETTERS, Issue 6 2007
Sean M. McMahon
Abstract A fundamental challenge to understanding patterns in ecological systems lies in employing methods that can analyse, test and draw inference from measured associations between variables across scales. Hierarchical linear models (HLM) use advanced estimation algorithms to measure regression relationships and variance,covariance parameters in hierarchically structured data. Although hierarchical models have occasionally been used in the analysis of ecological data, their full potential to describe scales of association, diagnose variance explained, and to partition uncertainty has not been employed. In this paper we argue that the use of the HLM framework can enable significantly improved inference about ecological processes across levels of organization. After briefly describing the principals behind HLM, we give two examples that demonstrate a protocol for building hierarchical models and answering questions about the relationships between variables at multiple scales. The first example employs maximum likelihood methods to construct a two-level linear model predicting herbivore damage to a perennial plant at the individual- and patch-scale; the second example uses Bayesian estimation techniques to develop a three-level logistic model of plant flowering probability across individual plants, microsites and populations. HLM model development and diagnostics illustrate the importance of incorporating scale when modelling associations in ecological systems and offer a sophisticated yet accessible method for studies of populations, communities and ecosystems. We suggest that a greater coupling of hierarchical study designs and hierarchical analysis will yield significant insights on how ecological processes operate across scales. [source]

Where Does the Lithium Go?

ADVANCED ENGINEERING MATERIALS, Issue 4 2010
A Study of the Precipitates in the Stir Zone of a Friction Stir Weld in a Li-containing 2xxx Series Al Alloy
The main strengthening precipitates of aluminum alloy 2198-T8, which are of the T1 phase, dissolve during friction stir welding, sending many Li atoms into solid solution. The stir zone precipitates are characterized using high-resolution transmission electron microscopy, energy dispersive spectroscopy, and selected area diffraction techniques to begin answering questions about the microstructural evolution and the relationship between microstructure and mechanical properties in friction stir welding of the next generation of lightweight Li-containing Al alloys. [source]

Constituting Interests and Identities in a Two-Level Game: Understanding the Gabcikovo-Nagymaros Dam Conflict,

FOREIGN POLICY ANALYSIS, Issue 1 2009
Stephen Deets
This paper uses the conflict between Hungary and Slovakia over the Gabcikovo-Nagymaros Dam to examine two foreign policy issues. The first is how states determine their interests and how perception of gains and losses arise and change. The second is the reality that international norms are rarely clear and often conflict, making answering questions of whether states have "internalized" or are abiding by norms problematic. This case is a good vehicle for addressing these questions as the dam dispute began during the communist period and has continued through the political and economic transitions to European Union membership. It also was the focus of a groundbreaking International Court of Justice case on the application of ecological necessity to treaty obligations. Fleshing out the model of a two-level game with insights from other theoretical perspectives, this article argues the key to this stalemate is the interrelated process through which state identity and understandings of vital interests change, creating frames in each state around different international norms. [source]

Lexical inference mechanisms for text understanding and classification

PROCEEDINGS OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE & TECHNOLOGY (ELECTRONIC), Issue 1 2003
Elizabeth Figa
This paper describes a framework for building story traces (compact global views of a narrative) and story projections (selections of key elements of a narrative) and their applications in text understanding and classification. Word and sense properties are extracted from documents using the WordNet lexical database enhanced with Prolog inference rules and a number of lexical transformations. Inference rules are based on navigation in various WordNet relation chains (hypernyms, meronyms, entailment and causality links, etc.) and derived relations expressed as Boolean combinations of node and edge properties used to direct the navigation. The resulting abstract story traces provide a compact view of the underlying narrative's key content elements and a means for automated indexing and classification of text collections. Ontology driven projections act as a kind of "semantic lenses" and provide a means to select a subset of a narrative whose key sense elements are subsumed by a set of concepts, predicates and properties expressing the focus of interest of a user. Finally, we discuss applications of these techniques in text understanding, classification of text collections and answering questions about a text. [source]