Integrating invasion and disease in the risk assessment of live bird trade.

AimInternational trade in plants and animals generates significant economic benefits. It also leads to substantial unintended impacts when introduced species become invasive, causing environmental disturbance or transmitting diseases that affect people, livestock, other wildlife or the environment. Policy responses are usually only implemented after these species become established and damages are already incurred. International agreements to control trade are likewise usually based on selection of species with known impacts. We aim to further develop quantitative invasive species risk assessment for bird imports and extend the tool to explicitly address disease threats.LocationUnited States of America.MethodsWe use a two-step approach for rapid risk assessment based on the expected biological risks due to both the environmental and health impact of a potentially invasive wildlife species in trade. We assess establishment probability based on a model informed by historical observations and then construct a model of emerging infectious disease threat based on economic and ecological characteristics of the exporting country.ResultsWe illustrate how our rapid assessment tool can be used to identify high-priority species for regulation based on a combination of the threat they pose for becoming established and vectoring emerging infectious diseases.Main conclusionsOur approach can be executed for a species in a matter of days and is nested in an economic decision-making framework for determining whether the biological risk is justified by trade benefits

Dividends, trust, and firm value

We find evidence that investors value dividends differently depending on their level of trust. Our tests indicate that investor demand for dividend-paying stocks increases as trust decreases, and that this relationship affects market values. We begin with survey evidence showing that people think accounting fraud is less likely among dividend payers and that people with low trust are more likely to hold dividend-paying stocks. We then empirically exploit accounting fraud discoveries within a mutual fund’s portfolio as a shock to trust. In response to these shocks, we show that mutual funds tilt their portfolios toward dividend-paying stocks. This result is not explained by a shift in risk preferences, indicating that these institutional investors are seeking dividends in particular rather than stable firms that just happen to pay dividends. Finally, we provide evidence that dividend payers experience a premium in their market values relative to non-payers when their investor base becomes less trusting

Tillage effects on weed seed bank with wheat monoculture and rotational

El banco de semillas de malas hierbas presente en el suelo es una demostración de la existencia de una comunidad de malas hierbas y está vinculado a las fases de crecimiento de un ecosistema. Las prácticas agronómicas pueden ocasionar cambios en el banco de semillas de los suelos agrícolas. Nuestro objetivo fue comparar la influencia del laboreo de conservación (mínimo laboreo y siembra directa) frente al laboreo convencional, sobre la densidad y riqueza específica del banco de semillas persistente de un suelo agrícola, en parcelas con dos sistemas de cultivo: monocultivo y rotación de trigo de invierno. Se tomaron muestras de suelo en parcelas con los tres sistemas de laboreo, a 3 profundidades: 0-7 cm, 7-15 cm y 15-30 cm. Los resultados obtenidos en este estudio mostraron que el efecto acumulativo del laboreo en parcelas con trigo en monocultivo no tuvo efectos en la densidad de semillas, aunque sí en su distribución, cuantificadas mayoritariamente a mayor profundidad (P3). Por otro lado, se observó una clara influencia del laboreo y la profundidad en la densidad y riqueza específica del banco de semillas de tipo persistente del suelo, en las parcelas con rotación de trigo. Nuestros resultados confirman que una variedad de cultivos puede ir asociada a una mayor variedad de especies de malas hierbas presentes en el banco de semillas del suelo.The weed seedbank into the soil is a demonstration of the existence of a weed community and it is linked to ecosystem growth phases. Agronomic practices can cause changes in the seed bank of agricultural soils. Our objective was to compare the influence of conservation tillage (mínimum tillage and direct seeding) with conventional tillage on weed seed density and species richness of persistent seedbank, with two cropping systems: wheat monoculture and wheat rotation. Soil samples were taken in plots with three tillage systems, at 3 depths: P1 (0-7 cm), P2 (7-15cm) and P3 (15-30 cm). The results of this study showed that cumulative effects of tillage systems, in wheat monoculture plots, had no effect on seed density, and the seed species were concentrated in deepest section of soil (P3). On the other hand, we observed a clear influence of tillage and depth on weed density and species richness of the persistent weed seed bank in wheat rotation plots. Our results confirm that a variety of crops could be associated to a variety of weed species present into soil seedbank

The role of angular momentum in the construction of electromagnetic multipolar fields

Multipolar solutions of Maxwell's equations are used in many practical applications and are essential for the understanding of light-matter interactions at the fundamental level. Unlike the set of plane wave solutions of electromagnetic fields, the multipolar solutions do not share a standard derivation or notation. As a result, expressions originating from different derivations can be difficult to compare. Some of the derivations of the multipolar solutions do not explicitly show their relation to the angular momentum operators, thus hiding important properties of these solutions. In this article, the relation between two of the most common derivations of this set of solutions is explicitly shown and their relation to the angular momentum operators is exposed.Comment: 13 pages, 2 figure

Diseño, elaboración e implementación de una unidad didáctica de educación ambiental : la formación teórica a luz de la práctica

A través de este trabajo presentamos una experiencia de educación ambiental que reúne la formación de profesores universitarios de biología y de profesores de primaria. La experiencia surge a partir de haber detectado una problemática de enseñanza en la escuela primaria que se intenta revertir a través de las acciones a desarrollar en el contexto de la formación inicial de ambos profesorados, en el ámbito de las asignaturas cuyo desarrollo curricular se centra en la formación teórica de la didáctica de las ciencias. Generamos acciones que nos permitan evaluar cómo influye la formación teórica en el diseño, elaboración e implementación de unidades didácticas en las aulas de la formación de maestros. Luego a través de su transposición didáctica a las aulas de primaria se retroalimenta la formación teórica en didáctica de las ciencias de los profesorados

The competitive ability of weed communities in selected crucifer oilseed crops under different water and nitrogen

Durante los años 2012 y 2013, se llevó a cabo un experimento en el centro de la península cuyo objetivo fue el estudio de la flora arvense en 3 especies de “Brassica” (“B. carinata”, “B. juncea” y “B. nigra”). Las malas hierbas se evaluaron con 2 niveles de riego, con y sin aporte de agua, y con tres dosis de fertilización diferentes: 0, 75 y 150 kg N ha-1. El establecimiento del cultivo de las tres especies de “Brassica” varió en función del año. Las escasas lluvias de 2012 redujeron la densidad y biomasa de la flora arvense en comparación con el año 2013 en el que la pluviometría fue mayor. Los resultados sugieren que la especie “B. nigra” no estaba bien adaptada a nuestras condiciones climáticas continentales, mostrando un rendimiento más bajo que el resto de los cultivares. Por otro lado, la infestación de malas hierbas fue menor en todas las parcelas donde se cultivaba “B. carinata”.A field study was undertaken to examine the interaction and relationships between weeds and three “Brassica” species (“B. carinata”, “B. juncea” and “B. nigra”) grown in 2012 and 2013. We evaluated the weed density, fresh and dry biomass of weeds with 2 water regimes: with and without irrigation, and three different doses of fertilization: 0, 75 and 150 kg N ha-1. Crop establishment of “Brassica” species varied significantly each year. Lower rainfall in 2012 led to lower density, fresh and dry biomass of weeds compared to 2013. The results confirmed that “B. nigra” was not well adapted to our continental climatic conditions, and thus the yield was lower than the other cultivars. The lowest weed infestation occurred in plots where “B. carinata” was grown in all cases

Evaluation of prevalence of Haller cells and their relationship with maxilofacial changes

Introdução: As células de Haller são descritas como células etmoidais aeradas, localizadas na margem inferior da órbita, próximas aos óstios dos seios maxilares. A tomografia computadorizada de feixe cônico (TCFC) tem amplo uso na odontologia, permitindo aquisição de imagens da região craniofacial. Objetivo: Identificar, em exames de TCFC, a relação da célula de Haller com as seguintes condições: sinusopatia, desvio de septo nasal ósseo, tratamento endodôntico e lesões periapicais. Materiais e métodos: Foram utilizados 99 exames de TCFC, sendo 51 incluídos nos critérios da pesquisa. As imagens foram analisadas no software Xelis Dental®, de maneira a identificar a presença ou não da célula de Haller, bem como sua relação com as condições citadas. Resultados: Dentre os 51 exames de TCFC avaliados, 35,3% apresentaram célula de Haller do lado direito e 23,5% no lado esquerdo. Levando-se em conta a relação das células de Haller com uma ou mais alterações aqui citadas, no lado direito a tivemos em 72% dos casos, enquanto no lado esquerdo tal relação se fez presente em 75% dos casos. Conclusão: Exames de TCFC que apresentam a margem infraorbital permitem verificar a presença ou ausência da célula de Haller. Nessa amostra, verificamos maior presença de casos de endodontia, desvio de septo e sinusopatia nos indivíduos que apresentaram células de Haller.Introduction: The Haller Cells are described as aerated ethmoidal cells, located in the inferior margin of the orbit, near the ostia of the maxillary sinuses. The Cone Beam Computed Tomography (CBCT) is widely used in dentistry, allowing acquisition of images of the craniofacial region. Objective: to identify in CBCT exams the Haller´s cell relationship with the following conditions: sinus disease, bony nasal septum deviation, endodontic treatment and periapical lesions. Materials and methods: 99 CBCT exams were used, from which 51 were included in the research criteria. The images were analyzed in the Xelis Dental® software to identify the presence or absence of the Haller Cell, as well as the relationship with the mentioned conditions. Results: Among the 51 CFCT exams evaluated, 35.3% presented Haller´s Cell on the right side and 23.5% on the left side. Whereas the relationship of the Haller Cells with one or more alterations mentioned here, on the right side we had it in 72% of the cases, while on the left side such relationship was present in 75% of the cases. Conclusion: CBCT exams that present the infraorbital margin allow to verify the presence or absence of the Haller Cell. In this sample, we verified a greater presence of endodontic cases, bony nasal septum deviation and sinus disease cases in individuals who presented Haller Cells