Stability of central finite difference schemes for the Heston PDE

This paper deals with stability in the numerical solution of the prominent Heston partial differential equation from mathematical finance. We study the well-known central second-order finite difference discretization, which leads to large semi-discrete systems with non-normal matrices A. By employing the logarithmic spectral norm we prove practical, rigorous stability bounds. Our theoretical stability results are illustrated by ample numerical experiments

A morphological, biological and molecular approach reveals four cryptic species of Trissolcus Ashmead (Hymenoptera, Scelionidae), egg parasitoids of Pentatomidae (Hemiptera)

Accurate identification of parasitoids is crucial for biological control of the invasive brown marmorated stink bug, Halyomrpha halys (Stål). A recent work by Talamas et al. (2017) revised the Palearctic fauna of Trissolcus Ashmead, egg-parasitoids of stink bugs, and treated numerous species as junior synonyms of T. semistriatus (Nees von Esenbeck). In the present paper, we provide a detailed taxonomic history and treatment of T. semistriatus and the species treated as its synonyms by Talamas et al. (2017) based on examination of primary types, molecular analyses and mating experiments. Trissolcus semistriatus, T. belenus (Walker), T. colemani (Crawford), and T. manteroi (Kieffer) are here recognized as valid and a key to species is provided. The identification tools provided here will facilitate the use of Trissolcus wasps as biological control agents and as the subject of ecological studies

Multidimensional frailty predicts mortality better than physical frailty in community-dwelling older people: A five-year longitudinal cohort study

Frailty is a common syndrome in older people that carries an increased risk of mortality. Two main models describe frailty, either as a loss of physical functions or as an accumulation of multiple deficits. The aim of our study was to compare the physical frailty index developed in the Cardiovascular Health Study (CHS) with a multidimensional frailty tool, the Multidimensional Prognostic Index (MPI), in predicting death in community-dwelling older subjects. Four hundred and seven community-dwelling older subjects were enrolled. Each subject underwent a comprehensive geriatric assessment (CGA) with calculation of the MPI and CHS index. Mortality was recorded over the following 5 years. In the overall sample (mean age of 77.9 ± 4.5 years; 51.6% female), 53 subjects (13%) died during the 5-year follow-up period. Both the MPI and CHS index were able to predict mortality; however, the MPI was significantly more accurate than the CHS index in predicting mortality (C-index = 0.69 and 0.59, respectively; p < 0.001), with a statistically significant difference of 10%. In conclusion, multidimensional frailty, assessed by the MPI, predicts five-year mortality in community-dwelling older people better than physical frailty, as assessed by the CHS index. These findings suggest the usefulness of assessing frailty by means of CGA-based tools to predict relevant health-negative outcomes in older people

Relações nutricionais log-transformadas para avaliação nutricional de cupuaçuzeiros comerciais.

A transformação logarítmica das relações bivariadas no cálculo das normas e dos índices do sistema integrado de diagnose e recomendação de nutrientes (DRIS) tem sido sugerida como uma forma de melhorar a acurácia do sistema, principalmente por diminuir a inconsistência na distribuição de freqüência entre as formas de expressão direta e inversa de uma mesma relação. Neste sentido, o objetivo deste trabalho foi avaliar o uso de relações log-transformadas entre diferentes populações de referência. Amostras foliares de cupuaçu foram coletadas de 153 pomares comerciais, cuja idade das plantas variou de 5 a 18 anos, cultivados em monocultivo ou sistemas agroflorestais, obtendo-se para cada relação nutricional entre os nutrientes N, P, K, Ca, Mg, Fe, Cu, Zn, e Mn as normas DRIS bivariadas log-transformadas e não transformadas, obtidas para o conjunto da população e para condições específicas. Os resultados mostraram que as relações log-transformadas contribuem para uma maior consistência dos resultados entre as formas direta e inversa entre diferentes normas DRIS

Primeros Abordajes Cualitativos respecto de las Concepciones de Docentes Contables sobre Evaluación de los Aprendizajes

Nowadays, teachers in high education seem to be demanded not only to know how to transmit specialized knowledge, but also to develop specific pedagogical knowledge and skills to meet the new roles as facilitators, communicators, guiders and servers of the future professional development of students.Faced with this reality, in an institution of higher education with a primarily professionalist training (Faculty of Economic Sciences of the National University of La Plata, FCE-UNLP), it is necessary to promote teaching practices and skills to improve the quality and performance of their work. This involves encouraging discussion and reflection of our own teachers with the aim of promoting in them a shared vision of what, how and when to incorporate knowledge that is related to the teaching-learning process, beyond the specific knowledge that has trained them as economic professionals.Teaching in higher education has often been nurtured by general frameworks from teaching, pedagogy and educational psychology without taking account of the development of conceptual tools to understand the peculiarity of teaching a specific discipline.This work proposes to describe a research into the educational concepts in teaching Economics Sciences. It seeks to contribute to conceptualize a key stage to improve teaching in this particular field and in higher education in general terms: the evaluation of learning.This research is framed in an interdisciplinary project developed by members of the Pedagogical Unit and the Institute of Research and Accounting Studies, accredited and funded by the National University of La Plata2, which focuses on the evaluation, thinking that it is part of the teaching-learning process and is the feedback of the teaching and the learning.In this paper the first approaches of an essentially qualitative research are discussed. It aims to identify the assessment of learning, and the concept that teaching and learning are deeply intertwined. Its purpose is to identify the main teachers´ concepts in the accounting area.In this research the theoretical and conceptual framework is defined because researchers training, their knowledge and experiences guide the work and influence the results. Therefore they should be made explicit.One method to rescue how teachers think and in what knowledge their actions are based that not distort that information is through the narrative of their own experiences. The purpose of including this type of survey is to allow them to make the exercise of discovering the forms of action and their own beliefs underlying in their own story, as well as the discovering for themselves the achievements and accomplishments that often they carry on without recognizing them. Keep in mind that most of the teachers do not have specific pedagogical training.The conceptions of teachers regarding to evaluation, are studied through evidence that is collected by semi-structured interviews, which are then supplemented by surveys, discussion groups that promote reflection on the practices, and the analysis of specific assessment tools used by the accounting chairs.Professors and heads of teaching assistants of the accounting area were selected as key informants because within the organizational structure of the faculty, they are who share their culture, and especially those who define in each accounting chair, the form, content and timing of theoretical an practical evaluations, within the framework of regulations.Interviews allow not only gather information, but simultaneously and in dialogue with the other, joint best practices assessment by an interactive mode between the gathered information and the reflection among the various actors involved in the research. In this paper, the results of the analysis of a sample of 12 interviews with key informants are shared.In the analysis of qualitative data it is not always possible to define an overall strategy or procedure, but it starts during the fieldwork (Rodríguez Gómez, Gil Flores and García Jiménez, 1996). In this case the process was performed with a degree of systematization. It covered the following tasks defined by the aforementioned authors: data reduction, disposal and processing them in a matrix of double entry, and getting results. Thus, their common features and trends are selected in order to identify some core concepts and relevant issues conceptions of evaluation. These results certainly will provide some evidence as a basis for designing surveys.We expect that this research will promote the definition of concepts and new practices that improve the quality of evaluation in accounting subjects, especially make teachers more sensitive to this subject area, allowing them to become aware of the implicit knowledge they have and assess themselves in the practices they use, recognizing whether they are relevant or need to be revised based on that they do focus on real student learning and not just in the accreditation of knowledge taught. Thus teachers will redefine their role and practices in terms of more autonomous form, reflective, creative, etc., that will prepare students to meet and deal with the constant change and complexity and uncertainty of their professional future.--------------------------------------------------2 Evaluation in Economic Sciences: Teacher´s Concepts and Practices. A Model for Best Practices. Accredited to and funded by the National University of La Plata for the period 01.01.2014 to 31.12.2015.    El contexto actual parece demandar a las instituciones educativas que los docentes no sólo sepan transmitir conocimiento especializado, sino que también desarrollen conocimientos pedagógicos y habilidades específicas que les permitan cumplir los nuevos roles de facilitadores, comunicadores, guías y servidores del futuro desarrollo profesional de los alumnos.Frente a esta realidad, y situados en una institución de educación superior con una formación fundamentalmente profesionalista (Facultad de Ciencias Económicas de la Universidad Nacional de La Plata, FCE-UNLP), resulta necesario promover entre los docentes prácticas pedagógicas y habilidades que mejoren la calidad y desempeño de su labor. Esto implica fomentar el debate y reflexión de nuestros propios docentes con el objetivo de promover en ellos una visión compartida de qué, cómo y cuándo incorporar saberes que tienen relación con el proceso enseñanza-aprendizaje, más allá del conocimiento específico que los formó como profesionales de las ciencias económicas.La enseñanza en la educación superior frecuentemente se ha nutrido de marcos generales provenientes de la didáctica, la pedagogía y la psicología educacional dejando pendiente el desarrollo de herramientas conceptuales que permitan entender la particularidad de la enseñanza de una disciplina específica.Este trabajo se propone describir una investigación sobre las concepciones docentes en la enseñanza de las ciencias económicas. El mismo busca contribuir a lograr una conceptualización de una faceta clave para la mejora de la enseñanza de este campo en particular y en la educación superior, en general: la evaluación de los aprendizajes.Esta investigación está enmarcada en un proyecto interdisciplinario desarrollado por integrantes de la Unidad Pedagógica y del Instituto de Investigaciones y Estudios Contables, acreditado y financiado por la Universidad Nacional de La Plata1, que se centra en la evaluación, pensando que la misma forma parte del proceso de enseñanza-aprendizaje y es la retroalimentación del enseñar y aprender.En el presente trabajo se comentan los primeros abordajes de una investigación cualitativa cuya finalidad es identificar los principales rasgos y concepciones de los docentes del área contable respecto de la evaluación del aprendizaje, con la concepción que el enseñar y el aprender están profundamente interrelacionados.En ella se define el marco teórico-conceptual desde el que se parte, pues la formación de los investigadores, sus conocimientos y experiencias, orientan y guían el trabajo e influyen en sus resultados. Por ello deben explicitarse. Una  de  las  modalidades  para  rescatar  cómo  piensan  los  docentes  y  qué conocimientos fundamentan sus actuaciones que no distorsione esa información, es a través de la narrativa de las propias experiencias. El propósito de incluir este tipo de relevamiento es que permite además, realizar con los docentes el ejercicio de descubrir en su propio relato las formas de acción y las propias creencias que subyacen, a la vez que descubran por sí mismos los logros y las realizaciones que muchas veces llevan adelante sin reconocerlo. Hay que tener en cuenta que gran parte de los docentes no cuentan con formación pedagógica específica.Las concepciones de los docentes referidas a la evaluación, se estudian a través de evidencias, que son recolectadas a través de entrevistas semi-estructuradas, las que luego se complementarán con encuestas, grupos de discusión que promuevan la reflexión sobre las prácticas, así como el análisis de instrumentos concretos de evaluación empleados por las cátedras.Se seleccionaron a profesores titulares y jefes de auxiliares docentes del área contable como informantes claves, porque dentro de la estructura organizativa de la facultad, son las personas que participan de su cultura, y sobre todo las definen en cada cátedra y dentro del marco de la reglamentación vigente, la forma, contenido y momento de las evaluaciones a nivel teórico como a nivel de ejercitación práctica.Las entrevistas permiten no sólo recoger información, sino simultáneamente y en diálogo con el otro, la construcción conjunta de mejores prácticas de evaluación, a partir de una modalidad interactiva entre la información relevada y la reflexión entre los diversos actores participantes de la investigación. En el presente trabajo se comparten los primeros resultados obtenidos del análisis de 12 entrevistas realizadas a informantes claves, sobre un total previsto de 20.En el análisis de datos cualitativos, no siempre es posible definir una estrategia o procedimiento general, pero éste se inicia durante el trabajo de campo (Rodríguez Gómez, Gil Flores & García Jiménez, 1996). En este caso el proceso se realizó con cierto grado de sistematización. Abarcó las siguientes tareas definidas por los autores antes citados: reducción de datos, disposición y transformación de los mismos en una matriz de doble entrada, y obtención de resultados. Así, se seleccionan sus elementos comunes y las tendencias que presentan, con el fin de identificar algunos núcleos y cuestiones relevantes sobre concepciones de la evaluación. Se presentan estos resultados preliminares que seguramente brindarán ciertos indicios que servirán de base para el diseño de las encuestas.Pretendemos que esta investigación promueva la definición de concepciones y de nuevas prácticas que mejoren la calidad de la evaluación en las asignaturas contables, y especialmente sensibilice a los docentes del área con el tema, permitiéndoles tomar conciencia de los saberes implícitos con que cuentan y autoevaluarse en las prácticas que utilizan, reconociendo si son pertinentes o si necesitan ser revisadas en función de que las mismas hagan foco en el real aprendizaje del alumno y no sólo en la acreditación de los conocimientos enseñados. De esta manera los docentes redefinirán su rol y sus prácticas en función de formar alumnos más autónomos, reflexivos, creativos, etc., es decir alumnos preparados para resolver y enfrentar el cambio constante y la complejidad e incertidumbre de su futuro ámbito profesional. --------------------------------------------------1Evaluación en Ciencias Económicas: Prácticas y Concepciones de los Docentes. Un Modelo para las Buenas Prácticas. Acreditado ante y financiado por la Universidad Nacional de La Plata para el período 1-1-2014 al 31-12-2015

Antiplasmodial and trypanocidal activity of violacein and deoxyviolacein produced from synthetic operons.

BACKGROUND: Violacein is a deep violet compound that is produced by a number of bacterial species. It is synthesized from tryptophan by a pathway that involves the sequential action of 5 different enzymes (encoded by genes vioA to vioE). Violacein has antibacterial, antiparasitic, and antiviral activities, and also has the potential of inducing apoptosis in certain cancer cells. RESULTS: Here, we describe the construction of a series of plasmids harboring the complete or partial violacein biosynthesis operon and their use to enable production of violacein and deoxyviolacein in E.coli. We performed in vitro assays to determine the biological activity of these compounds against Plasmodium, Trypanosoma, and mammalian cells. We found that, while deoxyviolacein has a lower activity against parasites than violacein, its toxicity to mammalian cells is insignificant compared to that of violacein. CONCLUSIONS: We constructed E. coli strains capable of producing biologically active violacein and related compounds, and propose that deoxyviolacein might be a useful starting compound for the development of antiparasite drugs