Opinion dynamics of learning agents: does seeking consensus lead to disagreement?

We study opinion dynamics in a population of interacting adaptive agents voting on a set of issues represented by vectors. We consider agents who can classify issues into one of two categories and can arrive at their opinions using an adaptive algorithm. Adaptation comes from learning and the information for the learning process comes from interacting with other neighboring agents and trying to change the internal state in order to concur with their opinions. The change in the internal state is driven by the information contained in the issue and in the opinion of the other agent. We present results in a simple yet rich context where each agent uses a Boolean perceptron to state their opinion. If the update occurs with information asynchronously exchanged among pairs of agents, then the typical case, if the number of issues is kept small, is the evolution into a society torn by the emergence of factions with extreme opposite beliefs. This occurs even when seeking consensus with agents with opposite opinions. If the number of issues is large, the dynamics becomes trapped, the society does not evolve into factions and a distribution of moderate opinions is observed. The synchronous case is technically simpler and is studied by formulating the problem in terms of differential equations that describe the evolution of order parameters that measure the consensus between pairs of agents. We show that for a large number of issues and unidirectional information flow, global consensus is a fixed point; however, the approach to this consensus is glassy for large societies.

A complex network approach to text summarization

Automatic summarization of texts is now crucial for several information retrieval tasks owing to the huge amount of information available in digital media, which has increased the demand for simple, language-independent extractive summarization strategies. In this paper, we employ concepts and metrics of complex networks to select sentences for an extractive summary. The graph or network representing one piece of text consists of nodes corresponding to sentences, while edges connect sentences that share common meaningful nouns. Because various metrics could be used, we developed a set of 14 summarizers, generically referred to as CN-Summ, employing network concepts such as node degree, length of shortest paths, d-rings and k-cores. An additional summarizer was created which selects the highest ranked sentences in the 14 systems, as in a voting system. When applied to a corpus of Brazilian Portuguese texts, some CN-Summ versions performed better than summarizers that do not employ deep linguistic knowledge, with results comparable to state-of-the-art summarizers based on expensive linguistic resources. The use of complex networks to represent texts appears therefore as suitable for automatic summarization, consistent with the belief that the metrics of such networks may capture important text features. (c) 2008 Elsevier Inc. All rights reserved.

Inferential Implications of Over-Parametrization: A Case Study in Incomplete Categorical Data

P>In the context of either Bayesian or classical sensitivity analyses of over-parametrized models for incomplete categorical data, it is well known that prior-dependence on posterior inferences of nonidentifiable parameters or that too parsimonious over-parametrized models may lead to erroneous conclusions. Nevertheless, some authors either pay no attention to which parameters are nonidentifiable or do not appropriately account for possible prior-dependence. We review the literature on this topic and consider simple examples to emphasize that in both inferential frameworks, the subjective components can influence results in nontrivial ways, irrespectively of the sample size. Specifically, we show that prior distributions commonly regarded as slightly informative or noninformative may actually be too informative for nonidentifiable parameters, and that the choice of over-parametrized models may drastically impact the results, suggesting that a careful examination of their effects should be considered before drawing conclusions.Resume Que ce soit dans un cadre Bayesien ou classique, il est bien connu que la surparametrisation, dans les modeles pour donnees categorielles incompletes, peut conduire a des conclusions erronees. Cependant, certains auteurs persistent a negliger les problemes lies a la presence de parametres non identifies. Nous passons en revue la litterature dans ce domaine, et considerons quelques exemples surparametres simples dans lesquels les elements subjectifs influencent de facon non negligeable les resultats, independamment de la taille des echantillons. Plus precisement, nous montrons comment des a priori consideres comme peu ou non-informatifs peuvent se reveler extremement informatifs en ce qui concerne les parametres non identifies, et que le recours a des modeles surparametres peut avoir sur les conclusions finales un impact considerable. Ceci suggere un examen tres attentif de l`impact potentiel des a priori.

Bayesian estimation of regression parameters in elliptical measurement error models

The main object of this paper is to discuss the Bayes estimation of the regression coefficients in the elliptically distributed simple regression model with measurement errors. The posterior distribution for the line parameters is obtained in a closed form, considering the following: the ratio of the error variances is known, informative prior distribution for the error variance, and non-informative prior distributions for the regression coefficients and for the incidental parameters. We proved that the posterior distribution of the regression coefficients has at most two real modes. Situations with a single mode are more likely than those with two modes, especially in large samples. The precision of the modal estimators is studied by deriving the Hessian matrix, which although complicated can be computed numerically. The posterior mean is estimated by using the Gibbs sampling algorithm and approximations by normal distributions. The results are applied to a real data set and connections with results in the literature are reported. (C) 2011 Elsevier B.V. All rights reserved.

Bayesian Analysis for the Generalized Lognormal Distribution Applied to Failure Time Analysis

There are several versions of the lognormal distribution in the statistical literature, one is based in the exponential transformation of generalized normal distribution (GN). This paper presents the Bayesian analysis for the generalized lognormal distribution (logGN) considering independent non-informative Jeffreys distributions for the parameters as well as the procedure for implementing the Gibbs sampler to obtain the posterior distributions of parameters. The results are used to analyze failure time models with right-censored and uncensored data. The proposed method is illustrated using actual failure time data of computers.

Distribution of ABCB1 polymorphisms among Brazilians: impact of population admixture

Introduction: Interethnic admixture is a source of cryptic population structure that may lead to spurious genotype-phenotype associations in pharmacogenomic studies. We studied the impact of population stratification on the distribution of ABCB1 polymorphisms (1236C > T, 2677G > T/A and 3435C > T) among Brazilians, a highly admixed population with Amerindian, European and African ancestral roots. Methods: Individual DNA from 320 healthy adults was genotyped with a panel of ancestry informative markers, and the proportions of African component of ancestry (ACA) were estimated. ABCB1 genotypes were determined by the single base extension/termination method. We describe the association between ABCB1 polymorphisms and ACA by fitting a linear proportional odds logistic regression model to the data. Results: The distribution of the ABCB1 2677G > T/A and 3435C > T, but not the 1236C > T, SNPs displayed a significant trend for decreasing frequency of the T alleles and TT genotypes from White to Intermediate to Black individuals. The same trend was observed in the frequency of the T/nonG/T haplotype at the 1236, 2677 and 3435 loci. When the population sample was proportioned in quartiles, according to the individual ACA estimates, the frequency of the T allele and TT genotype at each locus declined progressively from the lowest (< 0.25 ACA) to the highest (> 0.75 ACA) quartile. Linear proportional odds logistic regression analysis confirmed that the odds of having the T allele at each locus decreases in a continuous manner with the increase of the ACA, throughout the ACA range (0.13-0.94) observed in the overall population sample. A significant association was also detected between the individual ACA estimates and the presence of the T/nonG/T haplotype in the overall population. Conclusion: Self-identification according to the racial/color categories proposed by the Brazilian Census is insufficient to properly control for population stratification in pharmacogenomic studies of ABCB1.

Transcriptome analysis of Taenia solium cysticerci using Open Reading Frame ESTs (ORESTES)

Background: Human infection by the pork tapeworm Taenia solium affects more than 50 million people worldwide, particularly in underdeveloped and developing countries. Cysticercosis which arises from larval encystation can be life threatening and difficult to treat. Here, we investigate for the first time the transcriptome of the clinically relevant cysticerci larval form. Results: Using Expressed Sequence Tags (ESTs) produced by the ORESTES method, a total of 1,520 high quality ESTs were generated from 20 ORESTES cDNA mini-libraries and its analysis revealed fragments of genes with promising applications including 51 ESTs matching antigens previously described in other species, as well as 113 sequences representing proteins with potential extracellular localization, with obvious applications for immune-diagnosis or vaccine development. Conclusion: The set of sequences described here will contribute to deciphering the expression profile of this important parasite and will be informative for the genome assembly and annotation, as well as for studies of intra- and inter-specific sequence variability. Genes of interest for developing new diagnostic and therapeutic tools are described and discussed.

En vältränad och hälsosam kropp - eller bara en täckmantel för vad det egentligen handlar om? : En innehållsanalys av träningstidningarna Body och Fitness

The aim with this Essay is to examine the two most read magazines in Sweden covering the areas of exercising, fitness, bodybuilding, diets and “wellness” –Fitness and Body. Fitness’s target group is predominantly woman, while Body is almost exclusively read by men. The analysis is first done quantitatively, by systematically categorising the contents of the magazines. Then a qualitative analysis is made. Using two different theories, Anja Hirdman’s gender concept along with her constructivistic media perspective and the theory of Symbolic Interactionism, i try to answer the following questions; Does the two magazines term of address and language differ from one and other? And if that is the case, in what way? With point of departure from contents and subject areas, how are the two magazines compounded? How can the underlying message in the different articles be interpreted?The analysis shows that both magazines followed their purpose of writing about exercising in general, diet, fitness and bodybuilding. However, the magazine Fitness writes more often then Body about matters not following the given purpose, and the language in Body is more informative and general in comparison with the language used in Fitness. Still, the messages sent out by the different articles are in majority of the respects similar. Both magazines are portraying body ideals who can be understand as extreme. In Body the message feels fairly straight, “Build bigger muscles and burn more fat”, whereas Fitness willingly use the concept of “wellness” as a cover for what the message really is, namely “get your self a rock hard body through dieting and hard training”!

Optimization heuristic solutions, how good can they be? : With empirical applications in location problems

Combinatorial optimization problems, are one of the most important types of problems in operational research. Heuristic and metaheuristics algorithms are widely applied to find a good solution. However, a common problem is that these algorithms do not guarantee that the solution will coincide with the optimum and, hence, many solutions to real world OR-problems are afflicted with an uncertainty about the quality of the solution. The main aim of this thesis is to investigate the usability of statistical bounds to evaluate the quality of heuristic solutions applied to large combinatorial problems. The contributions of this thesis are both methodological and empirical. From a methodological point of view, the usefulness of statistical bounds on p-median problems is thoroughly investigated. The statistical bounds have good performance in providing informative quality assessment under appropriate parameter settings. Also, they outperform the commonly used Lagrangian bounds. It is demonstrated that the statistical bounds are shown to be comparable with the deterministic bounds in quadratic assignment problems. As to empirical research, environment pollution has become a worldwide problem, and transportation can cause a great amount of pollution. A new method for calculating and comparing the CO2-emissions of online and brick-and-mortar retailing is proposed. It leads to the conclusion that online retailing has significantly lesser CO2-emissions. Another problem is that the Swedish regional division is under revision and the border effect to public service accessibility is concerned of both residents and politicians. After analysis, it is shown that borders hinder the optimal location of public services and consequently the highest achievable economic and social utility may not be attained.

Friskfaktorer på en enhet : Identifiera & fortsatt bevara

Detta är en kvalitativ studie med syftet att inom en enhet på Stockholms Stad identifiera friskfaktorer och undersöka vad som krävs för att fortsatt bevara dessa. Vidare är syftet att undersöka vilket stöd som är nödvändigt för bevarandet samt HR-funktionens roll i detta avseende. Enheten är, sett till sjukfrånvaro, en välmående grupp som står inför förändringar inom marknaden och målsättning då de påverkas av det nyligen genomförda regeringsskiftet. Ett frågeverktyg användes för att framställa de åtta viktigaste dimensionerna av det attraktiva arbetet och en fördjupad diskussion kring dessa fördes sedan under en fokusgruppsintervju tillsammans med enhetens medarbetare. Resultatet visade att de viktigaste dimensionerna var bland annat arbetstid och relationer. Vidare påvisades att en balans mellan arbetsliv och privatliv är av stor vikt för medarbetarnas hälsa och välmående. För att fortsatt bevara det attraktiva i arbetet visade empirin att gruppens relationer och ledaren var nyckelfaktorer och att HR-funktionen, den personalstrategiska avdelningen, enbart bidrar med en administrativ och vägledande roll i frågan om stöd. Arbetets slutsatser innefattar att bevarandet av friskfaktorer kräver att tillvaron måste vara begriplig, hanterlig och meningsfull men även att medarbetarna behöver rimliga krav i relation till deras handlingsutrymme. En vidare slutsats är behovet av en förändring i ledarskapsbeteendet i kommande stadier då gruppen eventuellt kommer att hamna i en ny mognadsfas på grund förändrade omständigheter. Författarna drar även slutsatsen att friskfaktorer är till viss del individuellt beroende på livssituation men att balansen mellan arbetsliv och privatliv är betydande för de flesta. HR-funktionen, den personalstrategiska avdelningen, har en informativ och administrativ roll i frågan om stöd och författarna anser att det ligger en logik i denna roll. Sett till organisationens storlek är det lättare att vända psykosociala frågor till företagshälsovård eller en psykologgrupp och få det arbetsrättsliga stödet eller information från HR-funktionen.

Licenshantering av programvaror i enkommunal verksamhet : En fallstudie över licenshanteringen i Falu kommun

Forskningen visar att förändringar av informationsteknologin och en ökande anskaffning av nya programvaror har lett till underliggande problem som kan drabba heterogena programvarulicensmiljöer och stora organisationer. Underliggande problem i den stora kontexten är mjukvaruhantering. Licenshantering av programvaror är just en förgrening av det stora problemet. Stora organisationer som en kommunal verksamhet är drabbad av det här underliggande problemet på grund av komplexitet hos organisationens miljö. Att tillämpa förändringar i området programvarulicens är omöjligt utan att göra förändringar i hela den organisationsprocess som följer med det. Fallstudiens uppdrag är ett nytt omfattande område kring licenshantering av programvaror som kan vara väldigt lärorikt och en bra erfarenhet att ta del av. Uppsatsen beskriver hur en kommunal verksamhets licenshantering av programvaror ser ut och de problem som finns med den nuvarande licenshanteringsprocessen. Förarbetet med en litteraturstudie tillsammans med datagenereringsmetoderna intervjuer, dokumentstudier och observationer används för att studera fallet på djupet. Målet är att kunna ta fram de nuvarande problem som finns, analysera dem och ge rekommendation för åtgärder som det studerade fallobjektet, Falu Kommuns IT-kontor, kan använda. En rekommendation för en tydlig licenshanteringsprocessmodell anses vara ett bra akademiskt bidrag eftersom problemet med licenshanteringen av programvaror är ett generellt problem. Uppsatsens resultat är en processmodell om licenshantering av programvaror för organisationer med IT-tjänstkunder. Det är en generisk lösning som skulle kunna användas av andra kommunverksamheter och liknande organisationer.

Är utseendet viktigt? : En tentativ jämförelse mellan lekmäns ochformgivares uppfattningar avmusikaffischer

Rapporten syftade till att undersöka om det finns likheter och skillnader mellanutbildade formgivares och lekmäns uppfattningar avseende formgivna alster.Semistrukturerade intervjuer genomfördes med tre formgivare och tre lekmän,kring tre definierade kategorier, avseende utseendet på fem musikaffischer. Detre kategorierna var åsikter kring affischernas informationskvalité, estetik ochhantverk.Individuell smak tycktes påverka åsikterna kring affischerna mer än utbildningoch erfarenhet inom formgivning. Formgivare föreföll uppleva informationensom tydlig, samtidigt som lekmännen inte gjorde det. Formgivarna märkte flersmå detaljer jämfört med lekmän. Lekmännen märkte sällan typografiska fel.En affisch kunde vara för avancerad för en lekman, den kunde också vara för fulför en formgivare. Det fanns ett mellanläge där båda grupper uppfattadeinformationen och utseendet som bra och tilltalande. Lekmännen tyckte oftareatt tydlig information var viktigare än ett bra utseende.En slutsats i rapporten är att målgruppsanalyser tycks vara viktiga att genomföraeftersom formgivarnas åsikt om vad som var tydligt och informativt inte alltidstämde överens med lekmännens. Med sådana kan den grafiska designen blimer ändamålsenlig och troligen få ett bättre resultat.

Barnmorskans uppfattning om indikationer och effekter av förlossning med elektiva kejsarsnitt på humanitär indikation utifrån arbetslivserfarenhet : En intervjustudie

Bakgrund: Statistik visar på ökat antal elektiva kejsarsnitt internationellt och nationellt. Ett kejsarsnitt kan rädda liv på mor och barn om komplikationer uppstår, elektivt kejsarsnitt är även liksom andra stora operationer förenat med risker för komplikationer. Antalet elektiva kejsarsnitt på humanitär indikation har ökat i Sverige och cirka 17 % av alla förlossningar sker via kejsarsnitt. Att vårda och stödja kvinnor före, under och efter en förlossning med kejsarsnitt hör till barnmorskans arbete. Syftet med studien var att beskriva barnmorskors uppfattning om indikationer och effekter av förlossning med elektiva kejsarsnitt på humanitär indikation belyst utifrån arbetslivserfarenheter. Metod: kvalitativ metod: semistrukturella intervjuer med nio barnmorskor. Materialet analyserades via fenomenografisk analys i sju steg. Resultat: Fyra beskrivningskategorier framkom, Elektivt kejsarsnitt på humanitär indikation är ett etiskt dilemma, Elektivt kejsarsnitt på humanitär indikation är en stor operation, Elektivt kejsarsnitt på humanitär indikation påverkar organisation och barnmorskans arbetsmiljö och Elektivt kejsarsnitt på humanitär indikation påverkar kvinnans förlossningsupplevelse. Vidare framkom nio kategorier som beskriver barnmorskors uppfattningar. Slutsats Barnmorskor uppfattar elektiva kejsarsnitt som något komplext, att de med sina yrkeskunskaper värnar det naturliga vid kejsarsnitt på humanitär indikation och att de har brist på mandat att stödja och stärka kvinnors informerade val om elektivt kejsarsnitt på humanitär indikation. Klinisk tillämpbarhet: Resultatet kan användas vid undervisning kring barnmorskans stödjande och vårdande arbete i samband med förlossning via kejsarsnitt. Vidare kan resultatet vara underlag till diskussioner inom mödrahälsovård och förlossning i syfte att ge barnmorskor stärkt mandat till sina stödjande och informativa uppgifter.

Candidate Quality and Voter Response in U.S. House Elections

We propose and test the implications of a two-dimensional concept of candidate quality in U.S. House elections. Strategic quality is composed of the skills and resources necessary to wage an effective campaign; personal quality is composed of the characteristics most ordinary citizens value in their leaders and representatives, such as personal integrity and dedication to public service. We employ district informants in studies of the 1998 and 2002 congressional elections to measure these qualities in candidates, and we merge mass survey data with the district informant indicators to assess constituents’ awareness and evaluation of House candidates, and voting choice. We find that awareness tends to be responsive to candidates’ strategic quality, and that incumbent evaluation is remarkably responsive to variation in personal quality, even taking into account the quality of challenger emergence. These and other findings appear to support a more positive view of citizen capacity than is common in the congressional elections literature, especially in light of the electoral security of House incumbents.

From the Hill

Q&A: Desiree Shayer '12, studying in Amman, Jordan, talks about presenting her research, Jan Plan in Israel, and witnessing one part of the Middle East revolution A Natural Writer: With carefully chosen words, Blair Braverman '11 sets out to raise environmental awareness Sixty Years, One Musical Language: Colbyettes from across generations compare notes, sing again The Whole Truth: Foreign correspondent Gerry Hadden tells the stories behind his radio reports from Latin America and Haiti Writing the Final Chapter Kennebec Highlands Vista Handwriting on the Wall To Timbuktu--and Back: Steven Weinberg and Casey Scieszka turn exploration into a charming and informative collaboration Turning Experience Into Success Ultimate Goes National Family Matters: Women's lacrosse coach Karen MacCrate Henning ties success to team unity, unselfishness One Fast Mule Sports Shorts