Design of a Trichromatic Cone Array

Cones with peak sensitivity to light at long (L), medium (M) and short (S) wavelengths are unequal in number on the human retina: S cones are rare (<10%) while increasing in fraction from center to periphery, and the L/M cone proportions are highly variable between individuals. What optical properties of the eye, and statistical properties of natural scenes, might drive this organization? We found that the spatial-chromatic structure of natural scenes was largely symmetric between the L, M and S sensitivity bands. Given this symmetry, short wavelength attenuation by ocular media gave L/M cones a modest signal-to-noise advantage, which was amplified, especially in the denser central retina, by long-wavelength accommodation of the lens. Meanwhile, total information represented by the cone mosaic remained relatively insensitive to L/M proportions. Thus, the observed cone array design along with a long-wavelength accommodated lens provides a selective advantage: it is maximally informative

Análisis de los estilos de aprendizaje en alumnos de Medicina de la Universidad de Chile

Resumen: Neuroanatómicamente, con la estimulación temprana, la experiencia vivida y los intereses personales cada individuo desarrolla los procesos y competencias para aprender a modo de estilos de aprendizaje. El test de Kolb evalúa las formas de aprender de cada persona. Su conocimiento facilita la adaptación de estrategias de enseñanza/aprendizaje según los estilos de aprendizaje, como también poner atención en alumnos con estilos de aprendizaje diferentes al de la cohorte. Objetivos: Conocer los estilos de aprendizaje y su distribución en alumnos de Medicina de la Universidad de Chile. Material y método: El test de Kolb se aplica a estudiantes ingresados a la carrera de Medicina (segundo semestre) con una explicación previa breve. Se consideraron 101 estudiantes. Paralelamente se preguntó por origen geográfico, procedencia escolar preuniversitaria y edad. Los datos fueron tabulados en Excel y analizados con Stata 11.0. Resultados: Se analizaron las respuestas del Test de Estilos de Aprendizaje de 101 estudiantes; la edad promedio fue de 18,9 ± 1,2 años. El 62,4% son de sexo masculino, el 64,3% provienen de colegios particulares pagados, 3 de cada 5 estudiantes provienen de la región metropolitana. Respecto a la forma de comprender y la experiencia del aprender, la mayoría lo hace por conceptualización abstracta (84,2%) y de modo de transformar la experiencia. En la mayoría de los casos se realiza por medio de la experiencia activa. En general el estilo de aprendizaje más frecuente es convergente (50,5%). En la forma en cómo perciben o cómo procesan lo aprendido no existe diferencia significativa según género (p ≤ 0,05). Abstract: Neuro-anatomically, with early stimulation, lived experience and personal interests, each individual develops the processes and skills to learn according to a mode of learning styles. Kolb's essay evaluates each person's ways of learning. Their knowledge helps in the adaptation of teaching/learning strategies according to the learning styles, as well as taking into account students with learning styles different from the cohort or are special. Objectives: To determine the learning styles and their distribution in the medical students of the University of Chile. Material and method: After giving a brief explanation, the Kolb test was applied to 101 students admitted to the medical school (second semester). At the same time, questions were asked about geographic origin, pre-university background, and age. The data were tabulated in Excel and analysed using Stata 11.0. Results and conclusion: An analysis was made of the responses of the Learning Styles Test of 101 students with a mean age of 18.9 ± 1.2 years, of which 62.4% were male, 64.3% came from fee-paying private schools, and 3 out of 5 students came from the metropolitan region. As regards, the way of understanding and the experience of learning, the majority did by abstract conceptualization (84.2%) and by the transforming of experience method. In most cases it is done through active experience. In general, the most frequent learning style is Convergent (50.5%). There was no significant difference by gender (P < .05) in the way in which they are perceived or how they process what is learned. Palabras clave: Test de Kolb, Estilo de aprendizaje, Medicina, Keywords: Kolb test, Learning styles, Medicin

Xenotransplantation panel for the detection of infectious agents in pigs

BackgroundRecent advances in xenotransplantation have produced organs from pigs that are well tolerated in primate models because of genetic changes engineered to delete major antigens from donor animals. To ensure the safety of human transplant recipients, it will be essential to understand both the spectrum of infectious agents in donor pigs and their potential to be transmitted to immunocompromised transplant recipients. Equally important will be the development of new highly sensitive diagnostic methods for use in the detection of these agents in donor animals and for the monitoring of transplant recipients. MethodsHerein, we report the development of a panel of 30 quantitative polymerase chain reaction (qPCR) assays for infectious agents with the potential to be transmitted to the human host. The reproducibility, sensitivity and specificity of each assay were evaluated and were found to exhibit analytic sensitivity that was similar to that of quantitative assays used to perform viral load testing of human viruses in clinical laboratories. ResultsThis analytical approach was used to detect nucleic acids of infectious agents present in specimens from 9 sows and 22 piglets derived by caesarean section. The most commonly detected targets in adult animals were Mycoplasma species and two distinct herpesviruses, porcine lymphotrophic herpesvirus 2 and 3. A total of 14 piglets were derived from three sows infected with either or both herpesviruses, yet none tested positive for the viruses indicating that vertical transmission of these viruses is inefficient. ConclusionsThe data presented demonstrate that procedures in place are highly sensitive and can specifically detect nucleic acids from target organisms in the panel, thus ensuring the safety of organs for transplantation as well as the monitoring of patients potentially receiving them

Quality of stepped-wedge trial reporting can be reliably assessed using an updated CONSORT: crowd-sourcing systematic review

OBJECTIVES: The Consolidated Standards of Reporting Trials extension for the stepped-wedge cluster randomized trial (SW-CRT) is a recently published reporting guideline for SW-CRTs. We assess the quality of reporting of a recent sample of SW-CRTs. STUDY DESIGN AND SETTING: Quality of reporting was asssessed according to the 26 items in the new guideline using a novel crowd sourcing methodology conducted independently and in duplicate, with random assignment, by 50 reviewers. We assessed reliability of the quality assessments, proposing this as a novel way to assess robustness of items in reporting guidelines. RESULTS: Several items were well reported. Some items were very poorly reported, including several items that have unique requirements for the SW-CRT, such as the rationale for use of the design, description of the design, identification and recruitment of participants within clusters, and concealment of cluster allocation (not reported in more than 50% of the reports). Agreement across items was moderate (median percentage agreement was 76% [IQR 64 to 86]). Agreement was low for several items including the description of the trial design and why trial ended or stopped for example. CONCLUSIONS: When reporting SW-CRTs, authors should pay particular attention to ensure clear reporting on the exact format of the design with justification, as well as how clusters and individuals were identified for inclusion in the study, and whether this was done before or after randomization of the clusters, which are crucial for risk of bias assessments. Some items, including why the trial ended, might either not be relevant to SW-CRTs or might be unclearly described in the statement

Strong fitness differences impede coexistence between an alien water fern (Azolla pinnata R. Br.) and its native congener (Azolla rubra R. Br.) in New Zealand

Despite considerable evidence that alien plants impact the fecundity, productivity and abundance of native plant species, support for alien plant species causing the widespread decline of native species is rare. Coexistence theory proposes that the outcome of competition between two species can be predicted through the invasion criterion, measured as a positive population-level growth rate of each competitor when that species is rare. Here we make use of coexistence theory to examine the likelihood of persistence of a native water fern (Azolla rubra) following invasion by an alien congener (Azolla pinnata) which has apparently displaced the native wherever their ranges overlap in New Zealand. We evaluate coexistence between the two water fern species using experimental measurements of population-level growth rates. We show that the alien A. pinnata has a higher fitness than A. rubra, which hinders coexistence between the two species. These experimental results match the rapid expansion of A. pinnata and the apparent decline of A. rubra observed in nature. Our study predicts that A. pinnata is capable of replacing its native congener, highlights the importance of fitness differences in invasion success, and demonstrates the value of experimental analyses of species coexistence for predicting longer-term invasion dynamics and impacts. Using experiments to test coexistence mechanisms between alien and native species is a valuable approach to predict invasion outcomes and one that can lead to insights on the long-term impacts of alien species, including extinction, on native species populations