Los mapas conceptuales y su influencia en lo afectivo-valorativo del estudiante para aprender biología

The main purpose of this investigation was to identify the influence of concept mapping on the affective-evaluative learning process for biology. Theoretical bases were the works of Díaz and Hernández (2007) and Novak (1998). Research was applied in the “José Antonio Almarza” School, using an experimental and quasi-experimental design. A sample of 68 students was selected out of a 468-student population; these were divided into two groups, 33 in the controlled group, 35 in the experimental group. The data collection technique was observation, while the instrument was a verification sheet, previously validated by experts. A “t student-test” was applied to establish the degree of significance between pre-and post-test. Analysis of results was performed using descriptive statistics through frequencies, percentages, arithmetic mean and standard deviation. Results showed that concept mapping improved the students’ sense of responsibility for learning biology, respect for other people’s judgments, the and the valuing of teamwork, the importance of learning biology and the incorporation of significant experiences from the context. Conclusions were that concept maps influence the development of feelings and values in the students, favoring the learning of this science.El objetivo de esta investigación fue identificar la influencia de los mapas conceptuales en lo afectivo-valorativo del estudiante para aprender Biología. Las teorías que sirvieron de apoyo las fueron Díaz y Hernández (2007), Novak (1998). La investigación se realizó en la Unidad Educativa José Antonio Almarza; fue de tipo experimental con un diseño cuasi-experimental. La población estuvo conformada por 468 estudiantes, de donde se seleccionó una muestra de 68 estudiantes (33 del grupo control) y (35 el grupo experimental). La técnica utilizada para recolectar información fue la observación; el instrumento, una hoja de registro validado previamente por expertos en el área. Se aplicó la prueba t de student para establecer los grados de significancia entre el pre y postest, el análisis de los resultados se efectuó mediante la estadística descriptiva y la inferencial a través de frecuencias, porcentajes, media y la desviación estándar. Como resultados los mapas conceptuales aumentan en los estudiantes su responsabilidad para aprender Biología, respeto hacia la forma de pensar de los demás, valoración del trabajo en equipo, importancia para aprender Biología e incorporación de experiencias significativas del contexto. En conclusión que los mapas conceptuales ejercen influencia en el desarrollo de sentimientos y valores en los estudiantes para aprender dicha ciencia

A molecular mechanism for the topographic alignment of convergent neural maps

Sensory processing requires proper alignment of neural maps throughout the brain. In the superficial layers of the superior colliculus of the midbrain, converging projections from retinal ganglion cells and neurons in visual cortex must be aligned to form a visuotopic map, but the basic mechanisms mediating this alignment remain elusive. In a new mouse model, ectopic expression of ephrin-A3 ($\textit{Efna3}$) in a subset of retinal ganglion cells, quantitatively altering the retinal EFNAs gradient, disrupts cortico-collicular map alignment onto the retino-collicular map, creating a visuotopic mismatch. Genetic inactivation of ectopic EFNA3 restores a wild-type cortico-collicular map. Theoretical analyses using a new mapping algorithm model both map formation and alignment, and recapitulate our experimental observations. The algorithm is based on an initial sensory map, the retino-collicular map, which carries intrinsic topographic information, the retinal EFNAs, to the superior colliculus. These EFNAs subsequently topographically align ingrowing visual cortical axons to the retino-collicular map.This work was supported by CNRS and University of Strasbourg – Institute for Advanced Study (MR)

Visual Neuroscience

The purpose of this brief communication is to make publicly available three unpublished manuscripts on the organization of retinal ganglion cells in the tree shrew. The manuscripts were authored in 1986 by Dr. Edward DeBruyn, a PhD student in the laboratory of the late Dr. Vivien Casagrande at Vanderbilt University. As diurnal animals closely related to primates, tree shrews are ideally suited for comparative analyses of visual structures including the retina. We hope that providing this basic information in a citable form inspires other groups to pursue further characterization of the tree shrew retina using modern techniques

Objective of 20 hours of liver preservation: development of a porcine experimental model

National audienc

Donor eligibility criteria and liver graft acceptance criteria during normothermic regional perfusion: A systematic review

Acceptance of liver grafts from donations after circulatory death (DCD) largely remains a "black box," particularly due to the unpredictability of the agonal phase. Abdominal normothermic regional perfusion (aNRP) can reverse ischemic injury early during the procurement procedure, and it simultaneously enables graft viability testing to unravel this black box. This review evaluates current protocols for liver viability assessment to decide upon acceptance or decline during aNRP. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was used, and relevant literature databases were searched. The primary outcome consisted of criteria for liver graft viability assessment. Secondary outcomes included survival, primary nonfunction (PNF), early dysfunction, and biliary complications. A total of 14 articles were included in the analysis. In all protocols, a combination of criteria was used to assess suitability of the liver for transplantation. As many as 12 studies (86%) used macroscopic assessment, 12 studies (86%) used alanine transaminase (ALT) levels in perfusate, 9 studies (64%) used microscopic assessment, and 7 studies (50%) used lactate levels as assessment criteria. The organ utilization rate (OUR) was 16% for uncontrolled donation after circulatory death (uDCD) and 64% for controlled donation after circulatory death (cDCD). The most used acceptation criterion in uDCD is ALT level (31%), while in cDCD macroscopic aspect (48%) is most used. Regarding postoperative complications, PNF occurred in 13% (6%-25%) of uDCD livers and 3% (2%-4%) of cDCD livers. In uDCD, the 1-year graft and patient survival rates were 75% (66%-82%) and 82% (75%-88%). In cDCD, the 1-year graft and patient survival rates were 91% (89%-93%) and 93% (91%-94%), respectively. In conclusion, the currently used assessment criteria consist of macroscopic aspect and transaminase levels. The acceptance criteria should be tailored according to donor type to prevent an unacceptable PNF rate in uDCD and to increase the relatively modest OUR in cDCD

A multilevel inverter topology using diode half-bridge circuit with reduced power component

This paper presents a new multilevel converter with a reduced number of power components for medium voltage applications. Both symmetric and asymmetric structures of the presented multilevel converter are proposed. The symmetric topology requires equal dc source values, whereas the asymmetric topology uses minimum switch count. However, both structures suffer from high blocking voltage across the switches. To reduce the blocking voltage on switches, an optimal topology is presented and analyzed for the selection of the minimum number of switches and dc sources, while maintaining a low blocking voltage across the switches. A comparative analysis with recently published topologies was performed. The simulation results, as well as the comparative analysis, validated the robustness and effectiveness of the proposed topology in terms of the reduced power loss, lowered number of components, and cost. Furthermore, in addition to the simulation results, the performance of the proposed topology was verified using experimental results of 9, 17, and 25 evels.