Alternative ways to estimate change points in multinomial sequences. An application to an authorship attribution problem

The statistical analysis of literary style is the part of stylometry that compares measurable characteristics in a text that are rarely controlled by the author, with those in other texts. When the goal is to settle authorship questions, these characteristics should relate to the author’s style and not to the genre, epoch or editor, and they should be such that their variation between authors is larger than the variation within comparable texts from the same author. For an overview of the literature on stylometry and some of the techniques involved, see for example Mosteller and Wallace (1964, 82), Herdan (1964), Morton (1978), Holmes (1985), Oakes (1998) or Lebart, Salem and Berry (1998). Tirant lo Blanc, a chivalry book, is the main work in catalan literature and it was hailed to be “the best book of its kind in the world” by Cervantes in Don Quixote. Considered by writters like Vargas Llosa or Damaso Alonso to be the first modern novel in Europe, it has been translated several times into Spanish, Italian and French, with modern English translations by Rosenthal (1996) and La Fontaine (1993). The main body of this book was written between 1460 and 1465, but it was not printed until 1490. There is an intense and long lasting debate around its authorship sprouting from its first edition, where its introduction states that the whole book is the work of Martorell (1413?-1468), while at the end it is stated that the last one fourth of the book is by Galba (?-1490), after the death of Martorell. Some of the authors that support the theory of single authorship are Riquer (1990), Chiner (1993) and Badia (1993), while some of those supporting the double authorship are Riquer (1947), Coromines (1956) and Ferrando (1995). For an overview of this debate, see Riquer (1990). Neither of the two candidate authors left any text comparable to the one under study, and therefore discriminant analysis can not be used to help classify chapters by author. By using sample texts encompassing about ten percent of the book, and looking at word length and at the use of 44 conjunctions, prepositions and articles, Ginebra and Cabos (1998) detect heterogeneities that might indicate the existence of two authors. By analyzing the diversity of the vocabulary, Riba and Ginebra (2000) estimates that stylistic boundary to be near chapter 383. Following the lead of the extensive literature, this paper looks into word length, the use of the most frequent words and into the use of vowels in each chapter of the book. Given that the features selected are categorical, that leads to three contingency tables of ordered rows and therefore to three sequences of multinomial observations. Section 2 explores these sequences graphically, observing a clear shift in their distribution. Section 3 describes the problem of the estimation of a suden change-point in those sequences, in the following sections we propose various ways to estimate change-points in multinomial sequences; the method in section 4 involves fitting models for polytomous data, the one in Section 5 fits gamma models onto the sequence of Chi-square distances between each row profiles and the average profile, the one in Section 6 fits models onto the sequence of values taken by the first component of the correspondence analysis as well as onto sequences of other summary measures like the average word length. In Section 7 we fit models onto the marginal binomial sequences to identify the features that distinguish the chapters before and after that boundary. Most methods rely heavily on the use of generalized linear models

On the use of QoS requirements as base of multicast charging

We propose a charging scheme for cost distribution along a multicast tree when cost is the responsibility of the receivers. This scheme focuses on QoS considerations and it does not depend on any specific type of service. The scheme has been designed to be used as a bridge between unicast and multicast services, solving the problem of charging multicast services by means of unicast charging and existing QoS routing mechanisms. We also include a numerical comparison and discussions of the case of non-numerical or relative QoS and on the application to some service examples in order to give a better understanding of the proposal

Problem-Based Learning Using CaseMaker - Richard Collier

This is one of a series of short case studies describing how academic tutors at the University of Southampton have made use of learning technologies to support their students.

Modelling for Problem Solving in the Large

This a short presentation which introduces how models and modelling help us to solve large scale problems in the real world. It introduces the idea that dynamic behaviour is caused by interacting components in the system. Feedback in the system makes behaviour prediction difficult unless we use modelling to support understanding

Consumo de sustancias psicoactivas en los contextos recreativos entre estudiantes universitarios en Colombia

El consumo de sustancias psicoactivas (SPA) representa un problema de salud pública en Colombia y en el mundo. La población que recurre a este tipo de sustancias es cada vez más joven y sus efectos son potencialmente deletéreos y pueden afectar todas las áreas de ajuste de la persona. Aunque así se ha concebido, esta práctica no siempre está asociada con problemas personales ni con altos grados de estrés. Puede haber otras motivaciones asociadas. Objetivos: los objetivos de este artículo están dirigidos a presentar: (a) la frecuencia relativa de consumo de SPA entre los estudiantes universitarios, (b) las SPA más utilizadas por los estudiantes universitarios y sus diferencias según el sexo y la edad, (c) la relación entre el uso de SPA y los contextos de diversión. Materiales y métodos: este fue un estudio descriptivo correlacional, derivado de un proyecto de investigación italiano, con una muestra de 226 estudiantes de cuatro carreras de una universidad privada de Bogotá, seleccionados por muestreo aleatorio estratificado con asignación proporcional, a quienes se les aplicó una encuesta. Resultados: las SPA de mayor utilización son el alcohol, la nicotina y la marihuana, cuya mayor predominancia se presenta en el sexo masculino. Los resultados son congruentes con la tendencia nacional. Conclusión: el consumo de SPA en la población universitaria es alto y algunos contextos recreativos están asociados con esta conducta.

Pregnancy in adolescents as a problem to 14 – 19 year olds in Nocaima (Cundinamarca)

Adolescent pregnancy is a current problem which raises concern due to its individual, familiar and collective consequences. Fifteen million adolescents give birth each year in the world. Abortion is the preferred option used in unwanted pregnancies. Adolescent pregnancy is frequent in Nocaima, Cundinamarca and is a community concern in this small town initiating its process of becoming a healthy municipality. As such, the community has highlighted this problem to be studied and submitted to intervention to promote a free and responsible sexuality decreasing unwanted adolescent pregnancies. Objective: To find data on contraception, pregnancy and related factors in selected adolescents therefore, improving current incomplete information. Methods: Descriptive observational study with survey application on 226 female 14 to 19 year old students from three high school facilities in Nocaima including 8th to 11th graders. Results: 88.9% of the participants were between 14 and 17 years of age. 66.8% of the adolescents claim to use correctly contraceptive methods and 28.8% have had sexual intercourse with an average initiation at age 15. 11.1% have been pregnant once in their lives and of these 57.1 % ended in induced abortion and 66.8% were school dropouts. Conclusions: After having implemented an educational campaign on healthy sex and reproductive behaviors we view adolescent pregnancy as a public health problem which is preventable and related to the deficit of social and family support as well as weakness in individual decision making.

Asymmetrically fair rules for an indivisible good problem with a budget constraint

We study a particular restitution problem where there is an indivisible good (land or property) over which two agents have rights: the dispossessed agent and the owner. A third party, possibly the government, seeks to resolve the situation by assigning rights to one and compensate the other. There is also a maximum amount of money available for the compensation. We characterize a family of asymmetrically fair rules that are immune to strategic behavior, guarantee minimal welfare levels for the agents, and satisfy the budget constraint.

Las adicciones a la luz del psicoanálisis, una revisión de literatura

El presente trabajo de grado es una revisión de la literatura que permite hacer un recorrido desde el psicoanálisis acerca de la compleja problemática de las adicciones. Para ello, se revisaron las bases de datos PepWeb, Ebsco, y Jstor, revisando las posiciones del psicoanálisis freudiano, lacaniano y otras corrientes psicoanalíticas respondiendo a las siguientes preguntas de investigación: (a) ¿Cómo se comprenden las adicciones desde un marco de referencia psicoanalítico? (b) ¿Cómo –desde la teoría freudiana y la teoría lacaniana - se aborda la comprensión de la adicción? (c) ¿Qué dice el psicoanálisis contemporáneo sobre ésta problemática? Se abordan temas como la concepción de una adicción desde la perspectiva de Freud y Lacan hasta psicoanalistas contemporáneos, el rol que juega el goce en la adicción y, finalmente, el complejo debate incipiente sobre la legalidad del tóxico. Se encontró que es un campo de constante publicación y es necesario que los clínicos y los psicoanalistas aborden este campo de estudio clínico permanentemente y sigan produciendo investigaciones sobre el fenómeno.

Evaluation of the cognitive-behavioral model of generalized and problematic Internet use in Spanish adolescents

Resumen tomado de la publicaci??n

Validation of the Spanish version of the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST)

Resumen tomado de la publicaci??n

Using problem-based learning for introducing producer theory and market structure in intermediate microeconomics

This paper shows how instructors can use the problem‐based learning method to introduce producer theory and market structure in intermediate microeconomics courses. The paper proposes a framework where different decision problems are presented to students, who are asked to imagine that they are the managers of a firm who need to solve a problem in a particular business setting. In this setting, the instructors’ role is to provide both guidance to facilitate student learning and content knowledge on a just‐in‐time basis

Use of airborne remote sensing to detect riverside Brassica rapa to aid in risk assessment of transgenic crops

High resolution descriptions of plant distribution have utility for many ecological applications but are especially useful for predictive modelling of gene flow from transgenic crops. Difficulty lies in the extrapolation errors that occur when limited ground survey data are scaled up to the landscape or national level. This problem is epitomized by the wide confidence limits generated in a previous attempt to describe the national abundance of riverside Brassica rapa (a wild relative of cultivated rapeseed) across the United Kingdom. Here, we assess the value of airborne remote sensing to locate B. rapa over large areas and so reduce the need for extrapolation. We describe results from flights over the river Nene in England acquired using Airborne Thematic Mapper (ATM) and Compact Airborne Spectrographic Imager (CASI) imagery, together with ground truth data. It proved possible to detect 97% of flowering B. rapa on the basis of spectral profiles. This included all stands of plants that occupied >2m square (>5 plants), which were detected using single-pixel classification. It also included very small populations (<5 flowering plants, 1-2m square) that generated mixed pixels, which were detected using spectral unmixing. The high detection accuracy for flowering B. rapa was coupled with a rather large false positive rate (43%). The latter could be reduced by using the image detections to target fieldwork to confirm species identity, or by acquiring additional remote sensing data such as laser altimetry or multitemporal imagery.

Over-parameterised, uncertain 'mathematical marionettes' - How can we best use catchment water quality models? An example of an 80-year catchment-scale nutrient balance

The Integrated Catchment Model of Nitrogen (INCA-N) was applied to the River Lambourn, a Chalk river-system in southern England. The model's abilities to simulate the long-term trend and seasonal patterns in observed stream water nitrate concentrations from 1920 to 2003 were tested. This is the first time a semi-distributed, daily time-step model has been applied to simulate such a long time period and then used to calculate detailed catchment nutrient budgets which span the conversion of pasture to arable during the late 1930s and 1940s. Thus, this work goes beyond source apportionment and looks to demonstrate how such simulations can be used to assess the state of the catchment and develop an understanding of system behaviour. The mass-balance results from 1921, 1922, 1991, 2001 and 2002 are presented and those for 1991 are compared to other modelled and literature values of loads associated with nitrogen soil processes and export. The variations highlighted the problem of comparing modelled fluxes with point measurements but proved useful for identifying the most poorly understood inputs and processes thereby providing an assessment of input data and model structural uncertainty. The modelled terrestrial and instream mass-balances also highlight the importance of the hydrological conditions in pollutant transport. Between 1922 and 2002, increased inputs of nitrogen from fertiliser, livestock and deposition have altered the nitrogen balance with a shift from possible reduction in soil fertility but little environmental impact in 1922, to a situation of nitrogen accumulation in the soil, groundwater and instream biota in 2002. In 1922 and 2002 it was estimated that approximately 2 and 18 kg N ha(-1) yr(-1) respectively were exported from the land to the stream. The utility of the approach and further considerations for the best use of models are discussed. (C) 2008 Elsevier B.V. All rights reserved.