How Part-of-Speech Tags Affect Text Retrieval and Filtering Performance

Natural language processing (NLP) applied to information retrieval (IR) and filtering problems may assign part-of-speech tags to terms and, more generally, modify queries and documents. Analytic models can predict the performance of a text filtering system as it incorporates changes suggested by NLP, allowing us to make precise statements about the average effect of NLP operations on IR. Here we provide a model of retrieval and tagging that allows us to both compute the performance change due to syntactic parsing and to allow us to understand what factors affect performance and how. In addition to a prediction of performance with tags, upper and lower bounds for retrieval performance are derived, giving the best and worst effects of including part-of-speech tags. Empirical grounds for selecting sets of tags are considered.Comment: uuencoded and compressed postscrip

“Maybe” Should Be a Choice in “Yes-No” Questionnaires

By permitting respondents to answer “don't know” or “possibly” to queries otherwise intended to be “yes” or “no” questions, a new dimension of the interview becomes available for analysis. By coding “yes” and “no” as “yes, I have an opinion that I will express to you,” and “don't know” or “possibly” as “no, I do not have an opinion that I will express to you,” understanding the patterning of such responses becomes an interesting research question. We present an example of this approach from 538 interviews, question-frames about the domain “illness,” obtained in the homes of participants in an intervention program designed to reduce coronary heart disease, in central, rural Mississippi. The questionnaire was presented by four interviewers. Each participant was interviewed four times at six-month intervals, providing adequate time between interviews for reflection on the task. We use the individual differences model of multidimensional scaling to obtain weights for each consultant on each dimension of the group aggregate space. Subsequent analysis of these weights was (1) by general linear model analysis of variance and (2) examination of the pattern of adjusted means of dimension weights by risk factors and design factors. Results were surprising. The two-dimensional aggregate space developed from opinions vs. lack of expressed opinion on individual questions was interpretable as one cluster of symptoms that implied heart disease and two other structures that were vector-like in appearance. Extremely high F-values showed a reflexive effect; the interviewer was associated with several factors including risk status of the participants, suggesting negotiation of whether or not a participant would agree to express an opinion. There may have been a reflective effect with changing patterns developing over the course of the repeated interviews. Neither dimension was associated with the health-care seeking behavior of consulting a doctor

Controlling chaos in spatially extended beam-plasma system by the continuous delayed feedback

In present paper we discuss the control of complex spatio-temporal dynamics in a {spatially extended} non-linear system (fluid model of Pierce diode) based on the concepts of controlling chaos in the systems with few degrees of freedom. A presented method is connected with stabilization of unstable homogeneous equilibrium state and the unstable spatio-temporal periodical states analogous to unstable periodic orbits of chaotic dynamics of the systems with few degrees of freedom. We show that this method is effective and allows to achieve desired regular dynamics chosen from a number of possible in the considered system.Comment: 12 pages, 12 figure

Extended quantum critical phase in a magnetized spin-1/2 antiferromagnetic chain

Measurements are reported of the magnetic field dependence of excitations in the quantum critical state of the spin S=1/2 linear chain Heisenberg antiferromagnet copper pyrazine dinitrate (CuPzN). The complete spectrum was measured at k_B T/J <= 0.025 for H=0 and H=8.7 Tesla where the system is ~30% magnetized. At H=0, the results are in quantitative agreement with exact calculations of the dynamic spin correlation function for a two-spinon continuum. At high magnetic field, there are multiple overlapping continua with incommensurate soft modes. The boundaries of these continua confirm long-standing predictions, and the intensities are consistent with exact diagonalization and Bethe Ansatz calculations.Comment: 4 pages, 4 figure

Mythography

Although it was written over a year before this section, the thesis proposal which appends this report still serves as a good introduction to my ideas on myth in general , and in particular to my way of thinking when I began this inquiry into the photographic representation of myth. In exploring the visual and artistic dimensions of myth, I found that my thoughts and feelings on the subject changed vastly as the work progressed; however, the end result of this process of exploration has led me back to the beginnings of the work and allowed me, as T,S. Eliot put it, to know the place for the first time. In a sense, then, this thesis report serves as a kind of travelogue, describing a journey which is not physical, but mental, internal, circular, and perhaps spiritual

Declining Marine Survival of Steelhead Trout Linked to Climate and Ecosystem Change

Species with complex life cycles, such as anadromous fish that perform spawning migrations between freshwater and the ocean, may be particularly sensitive to global change because freshwater and marine habitats experience distinct shifts in climate and ecosystem dynamics. Abundances of wild steelhead trout (Oncorhynchus mykiss) have declined across most of their range over the past 40-50 years. We examined whether declines in steelhead survival can be linked to changing climate conditions and species interactions. A novel hierarchical integrated population model that accounts for the species' complex life history was fitted to data from multiple wild steelhead populations on the Washington coast, U.S.A. The model estimates recruitment residuals and kelt survival rates as time-varying processes, which reflect annual variation in survival before and after first maturation. We found that survival rates of immature steelhead (recruits) and adult steelhead (kelts) have declined over time and that survival trends across populations were strongly associated with climate and ecosystem change, specifically summer sea surface temperature and pink salmon abundance in the North Pacific Ocean, the NPGO index and river flows. Including these drivers in the model reduced unexplained annual variation in shared recruitment and kelt survival anomalies and largely accounted for their negative long-term trends. Our findings provide evidence that rising temperatures and increased interspecific competition at sea have contributed to declines in steelhead survival over the last five decades. Considering projected warming and high pink salmon abundances in the ocean, steelhead will likely continue to experience low marine survival rates