Geometry of the Kimura 3-parameter model

The Kimura 3-parameter model on a tree of n leaves is one of the most used in phylogenetics. The affine algebraic variety W associated to it is a toric variety. We study its geometry and we prove that it is isomorphic to a geometric quotient of the affine space by a finite group acting on it. As a consequence, we are able to study the singularities of W and prove that the biologically meaningful points are smooth points. Then we give an algorithm for constructing a set of minimal generators of the localized ideal at these points, for an arbitrary number of leaves n. This leads to a major improvement of phylogenetic reconstruction methods based on algebraic geometry.Comment: 26 pages with 4 figure

copulaedas: An R Package for Estimation of Distribution Algorithms Based on Copulas

The use of copula-based models in EDAs (estimation of distribution algorithms) is currently an active area of research. In this context, the copulaedas package for R provides a platform where EDAs based on copulas can be implemented and studied. The package offers complete implementations of various EDAs based on copulas and vines, a group of well-known optimization problems, and utility functions to study the performance of the algorithms. Newly developed EDAs can be easily integrated into the package by extending an S4 class with generic functions for their main components. This paper presents copulaedas by providing an overview of EDAs based on copulas, a description of the implementation of the package, and an illustration of its use through examples. The examples include running the EDAs defined in the package, implementing new algorithms, and performing an empirical study to compare the behavior of different algorithms on benchmark functions and a real-world problem

The Quality-Quantity Trade-off in the Principal-Agent Framework

This paper uses the principal-agent theory to analytically investigate the optimal incentive-based compensation contract that a processor should offer to a grower performing efforts in quantity and quality. In this process, we contribute to the substantive literature on multi-task principal-agent models by analyzing the quality-quantity trade-off and studying the implications of such a relationship in the principal-agent framework. One striking result of these effects is that, under appropriate incentive-based grower’s compensation, the processor may encourage grower’s effort in quality without crowding out grower’s effort in quantity.quality, quantity, trade-off, incentive contract, principal-agent framework, uncertainty, Agribusiness, Agricultural and Food Policy, D86,

New Silver Nanosensor for Nickel Traces. Part II: Urinary Nickel Determination Associated to Smoking Addiction

A new fluorescence silver nanosensor assisted by surfactant has been recently synthesized and applied to ultra trace nickel determination. The methodology was validated by the standard addition method and satisfactorily applied to nickel determination in urine without previous treatment, coming from subjects with different smoking addiction levels and second hand smokers. Within-day precision was better than 0.011 CV. The reproducibility (between-days precision) was also evaluated over 3 days by performing six determinations each day with a CV of 0.025. The proposed methodology represents a promising approach in the area of biological monitoring due to its low operation cost, simplicity of instrumentation, high sampling speed and non-polluting solvents. Obtained results of urinary nickel concentration were successfully correlated with the tobacco addiction.Fil: Talio, María Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Luconi, M. O.. Universidad Nacional de San Luis; ArgentinaFil: Fernandez, Liliana Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; Argentin

Literary Correspondence: letters and emails in Caribbean writing

This article explores the role of correspondence (and literary archives in general) in illuminating central aspects of Caribbean literary culture and authors’ work, with a consideration of the challenges and the need to preserve email correspondence for archives in the future. It aims to demonstrate how the correspondence of a wide range of authors embedded in various literary archives has the potential to deepen our knowledge and sense of the making of Caribbean literary culture and history

Citizens Electoral Behavior in Autocratic Regimes, Venezuela, Turkey, Russia

This study offers an explanation of why voters repeatedly choose leaders who came to power democratically at some point but will not abandon it when they ought to. Research shows leaders will employ any and every mechanism to remain in power, from restricting liberties to turning to violence as a method of repressing dissidence yet voters continue to vote them back into power. Why? Through an examination of the current situations in Venezuela, Turkey and Russia, the thesis reveals that economic performance provides the key explanation. If the country provides welfare to its citizens, they will be willing to overlook other “minor” factors

Los inicios de un distrito de innovación: orígenes y evolución del recinto de innovación social de la Universidad MID y RMIT en la Ciudad Norte de Melbourne

El desenvolupament d'un districte urbà d'innovació requereix un lloc únic i densament poblat que connecti institucions intensives en coneixement amb espais públics, grans empreses, startups i pimes, centres socials i institucions culturals. Basat en marcs conceptuals que inclouen la teoria del desenvolupament urbà, el model de quíntuple hèlix, l'emprenedoria i els models d'innovació oberta, aquest article utilitza un enfocament d'estudi de cas, el Melbourne Innovation District. El context és el centre de la ciutat de Melbourne immediatament abans i durant la recuperació de la Covid-19. El treball analitza la visió i les ambicions del districte de la innovació, el paper de la tecnologia i l'empresa en la creació de llocs i l'impacte de la pandèmia a l'hora d'impulsar la innovació social, l'acceleració de la demanda d'una "economia del benestar" i els incentius per a la col·laboració entre institucions. Aquest treball contribueix a la literatura existent examinant l'evolució i el progrés del districte d'innovació de Melbourne com a cas, i la influència del districte 22@ a Barcelona, destaca els coneixements pràctics i estratègics de com el districte d'innovació de Melbourne es va formar i construir la capacitat per a l'estratègia col·lectiva en un entorn urbà intensiu en coneixement i el paper dels ecosistemes d'innovació per desenvolupar economies urbanes dinàmiques i inclusives en l'era de la recuperació de la pandèmia. A través d'aquest treball hem observat els elements clau per a l'èxit en el desenvolupament primerenc d'un districte d'innovació que inclouen: la consideració dels costos reals de la col·laboració; l'establiment d'una visió comuna i una aspiració a llarg termini; la importància d'aconseguir una massa crítica; la base d'evidència dispersa; la necessitat de consolidació del projecte i l'organització vertebradora; l'entorn de govern fragmentat; la necessitat de persistència amb una visió integrada, connectada amb l'estratègia global de la ciutat; la identificació d'innovacions pràctiques que s'alimenten mútuament i creen impuls.The development of an urban innovation district requires a unique, densely populated site connecting knowledge-intensive institutions with public spaces, large businesses, startups and SMEs, social hubs, and cultural institutions. Based on conceptual frameworks in the field including urban development theory, quintuple helix model, entrepreneurship and open innovation models, this paper uses a case research study approach, the Melbourne Innovation District. The context is Melbourne’s city centre immediately prior to and during Covid-19 recovery. The work analysed the vision and ambitions for the innovation district, the role of technology and enterprise in place-making and the impact of the pandemic in driving social innovation, the acceleration of demand for a ‘wellbeing economy,’ and incentives for collaboration between institutions. This work contributes to existing literature by examining the evolution and progress of Melbourne Innovation District as a case, and the influence of the 22@ district in Barcelona, highlights practical and strategic insights into how the Melbourne Innovation District formed and built capability for collective strategy in a knowledge-intensive urban settings, and the role of innovation ecosystems to develop dynamic, inclusive urban economies in the pandemic recovery era. Through this work we observed the key elements for the success in the early development of an innovation district including: the consideration of the real costs of collaboration; the establishment early on of a common vision and a long-term aspiration; the importance of achieving critical mass; the scattered evidence base; the need for ‘anchoring’ project and backbone organisation; the fragmented governance environment; the need for persistence with an integrated vision, that is connected to the overall city strategy; the identification of practical innovations that feed each other and create momentum.El desarrollo de un distrito urbano de innovación requiere un lugar único y densamente poblado, que conecte instituciones intensivas en conocimiento con espacios públicos, grandes empresas, startups y pymes, centros sociales, e instituciones culturales. El artículo utiliza un enfoque de estudio de caso, el Melbourne Innovation District, y se basa en marcos conceptuales que incluyen la teoría del desarrollo urbano basado en conocimiento, el modelo de hélix quíntuple, el emprendimiento y los modelos de innovación abierta. El contexto es el centro de la ciudad de Melbourne inmediatamente antes y durante la recuperación del COVID-19. El trabajo analiza la visión y las ambiciones del distrito de la innovación, el papel de la tecnología y la empresa en la creación de espacios, y el impacto de la pandemia en incentivar innovación social, acelerar la demanda de una “economía del bienestar”, e incentivos para la colaboración entre instituciones. Este trabajo contribuye a la literatura existente sobre el tema, examinando la evolución y el progreso del Melbourne Innovation District como estudio de caso, y la influencia del distrito 22@Barcelona. Se resaltan aspectos clave prácticos y estratégicos sobre cómo el Melbourne Innovation District se formó y creó capacidades de estrategia colectiva en entornos urbanos intensivos en conocimiento, y el rol de los ecosistemas de innovación en el desarrollo de economías urbanas inclusivas, dinámicas, durante la era de recuperación de la pandemia. A través de este trabajo observamos los elementos clave para el éxito de estadios iniciales de desarrollo de un distrito de innovación, incluyendo: la consideración de los costes reales de colaboración; el establecimiento temprano de una visión común y una aspiración de largo plazo; la importancia de conseguir una masa crítica, la base de evidencia empírica dispersa; la necesidad de consolidar el proyecto y la organización vertebradora, el entorno de gobernanza fragmentado; la necesidad de lograr persistencia con una visión integrada conectada con la estrategia urbana general; la identificación de innovaciones prácticas que se retroalimenten y creen impulso

The yield/quality trade-off and contractual choice

This paper provides an analysis of the choice of governance mechanism in agriculture using an integrated perspective based on agency theory. The main ways of organizing agriculture are compared: spot market and incentive contract. With the analytical development of both models, it is explored that the choice of the optimal mechanism depends on initial conditions such as uncertainty, the risk aversion of the agents or the number of competitors. Moreover, according to the predictions made by the economic literature on agrarian organization, the results support the coexistence of both governance alternatives.Crop Production/Industries,