Tooth replication techniques, SEM imaging and microwear analysis in Primates: methodological obstacles

Dental microwear analyses are among the most significant techniques though which a researcher can make dietary and ecological inferences from primate fossil specimens. Hard particles, such as plant phytoliths or silica-base sands, can scratch tooth enamel surfaces during food mastication producing a dietary specific pattern of microwear on the enamel surface. The density, axis length and orientation of microwear features, either striations or pits, are highly informative of dietary habits in both extant and fossil primates. The analysis of tooth enamel surfaces requires the use of scanning electron microscopy (SEM) techniques, because of its high resolution power, including gold-coating of teeth for observation. Problems arise when specimens to be analysed are unique and there is no possibility of a direct observation with an environmental microscope. Negative moulds must then be made and silicone-base components are indicated for high quality replication of enamel surfaces. A positive cast needs to be obtained, and epoxy-base resins are frequently used for their good quality and durability. However, successive silicon and epoxy replications result in the loosing of surface detail and precision. Surface observation errors can also be caused be the SEM technology itself, especially if back-scattered electrons are used instead of secondary electrons for maximizing the topographical information of enamel images. This paper reviews the most commonly used methodological approaches to tooth moulding and casting, comparing SEM micrographs of casts with actual tooth surfaces, and contrasting the reliability of SEM images for dietary interpretation of tooth microwear in both extant and fossil primates

20 años de investigación sobre Gobierno Corporativo Internacional

International Corporate Governance is a topic of growing interest. Despite all the results that have led years of research, this issue remains an interesting topic in Economics and Finance. This article examines the scientific literature on international corporate governance since the first article was published in 1992. The data is obtained from the database ISI Web of Science, resulting in 338 articles that have been analyze to obtain the most cited articles, the evolution in the number of publications, the authors and journals cited and Index of Scientific Collaboration.El Gobierno Corporativo Internacional es un tema de creciente interés en el área de Economía y Finanzas, ya que a pesar de todos los resultados que han supuesto décadas de investigación, este tema sigue estando en el centro de atención y en ello mucho ha tenido que ver la crisis financiera desatada a finales del 2007. El presente artículo analiza la producción científica sobre gobierno corporativo internacional desde que se publicó el primer artículo en 1992 hasta 2010. Los datos se han obtenido de la base de datos ISI Web of Science dando por resultado 338 artículos que se han analizado obteniendo los artículos más citados, la evolución temporal del número de publicaciones, los autores y revistas más citados y el índice de colaboración científica

New evidence and interpretation of subvertical grooves in eandertal teeth from Cueva de Sidrón (Spain) and Figueira Brava (Portugal)

Interproximal tooth wear is caused by tooth-to-tooth rubbing that results in the formation of flat wear surfaces characterized by an intense pattern of enamel pitting caused by prism-plucking. The rate of wear of such surfaces depends on the forces involved in food processing and chewing. In some instances, the interproximal wear facets, mainly of molar teeth, show a number of subvertical grooves with a nearly vertical direction. These grooves are mostly present in Neanderthal teeth, but have also been described in some African fossil teeth and in European Homo heidelbergensis, as well as in several modern hunter-gatherer populations, such as Australian Aborigines. Subvertical grooves have seldom been attributed to taphonomic processes, although most probably they are caused by natural biomechanical processes during mastication of hard objects included in the diet. They have also been associated to acidic dietary habits given their radial disposition and their inter-digitalisation. The present study analyses the subvertical grooves observed in the Neanderthal dentition of Cueva de Sidrón (Spain). Comparisons are made with the similar interproximal grooves pattern observed in the Neanderthal specimen from Figueira Brava (Portugal) and some remains of H. heidelbergensis from Sima de los Huesos (Spain). Other cases have been described for the Neanderthal sites of Genay and Le Fate (France). The results obtained allow discarding a post-mortem origin of these structures, the most probable cause of the subvertical grooves being natural biomechanical chewing processes combined with some dietary habits indicative of hard plant foods ingestion

Testing dietary hypotheses of East African hominines using buccal dental microwear data

Abstract There is much debate on the dietary adaptations of the robust hominin lineages during the Pliocene-Pleistocene transition. It has been argued that the shift from C3 to C4 ecosystems in Africa was the main factor responsible for the robust dental and facial anatomical adaptations of Paranthropus taxa, which might be indicative of the consumption of fibrous, abrasive plant foods in open environments. However, occlusal dental microwear data fail to provide evidence of such dietary adaptations and are not consistent with isotopic evidence that supports greater C4 food intake for the robust clades than for the gracile australopithecines. We provide evidence from buccal dental microwear data that supports softer dietary habits than expected for P. aethiopicus and P. boisei based both on masticatory apomorphies and isotopic analyses. On one hand, striation densities on the buccal enamel surfaces of paranthropines teeth are low, resembling those of H. habilis and clearly differing from those observed on H. ergaster, which display higher scratch densities indicative of the consumption of a wide assortment of highly abrasive foodstuffs. Buccal dental microwear patterns are consistent with those previously described for occlusal enamel surfaces, suggesting that Paranthropus consumed much softer diets than previously presumed and thus calling into question a strict interpretation of isotopic evidence. On the other hand, the significantly high buccal scratch densities observed in the H. ergaster specimens are not consistent with a highly specialized, mostly carnivorous diet; instead, they support the consumption of a wide range of highly abrasive food items

Tooth crown size and dentine exposure in Australopithecus and early Homo: testing hypotheses of dietary related selective preasures

Preliminary analyses of total crown area and dentine exposure surfaces in a sample of hominid teeth seem to indicate that a significant correlation between tooth size and occlusal abrasion occurs, most probably related to dental occlusal function rather than to normal food mastication. Dental microwear on the buccal surfaces of teeth might be determined by foodstuffs abrasiveness whereas occlusal gross wear could be more dependent on either cultural practices with teeth or food processing. The effect of occlusal function of teeth on diet determination and ecological interpretation of hominid behaviour is dealt with, considering that habitat occupation and diet might affect differently and distinctly to tooth wear rate patterns

Investigación de mercados para identificar el grado de aceptación que tendría un nuevo sistema de transporte alternativo en bicicletas en la población bogotana

El presente trabajo de investigación se realizó con el fin de analizar la posible acogida que tendría un sistema alternativo de transporte en bicicletas en la ciudad de Bogotá. Bogotá cuenta con grandes dificultades en el tema de la movilidad. La contaminación ambiental, la congestión visual, auditiva y vehicular son las mayores molestias y complicaciones que se generan a diario. Los tiempos exagerados de recorrido entre diferentes distancias dentro de la ciudad generan un malestar común en los ciudadanos. La base de esta investigación es una infraestructura ya existente en la ciudad de Bogotá, las ciclo-rutas. Estas vías se encuentran actualmente en un constante crecimiento en cuanto a su kilometraje y cobertura dentro de la ciudad. El aprovechamiento de esta infraestructura permitirá llevar a cabo un planteamiento de un nuevo proyecto delimitando los sectores de la ciudad y las posibles rutas del sistema alternativo de transporte en bicicletas. Se deseaba realizar la investigación de un proyecto que contara con parámetros y lineamientos de funcionamiento establecidos de forma ordenada, en el cual se encuentre una opción de movilidad en bicicletas. Se enfocará en estaciones definidas con rutas establecidas en distancias no muy prolongadas, en las cuales se encontrará y se prestará un servicio de alquiler de bicicletas por un tiempo establecido. Contará con parámetros y medidas de seguridad tanto para el usuario como para el sistema. Se realizó una investigación de mercados para definir la acogida que tendría un nuevo sistema de transporte en la capital colombiana, obteniendo resultados muy positivos en la muestra utilizada.Administrador (a) de EmpresasPregrad

Nota metodológica: Alteración del patrón de microestriación dentaria por el efecto wrinkle.

Se describe el efecto wrinkle observado por primera vez sobre moldes dentarios realizados con resinas epoxy y metalizados en oro para su observación mediante microscopía electrónica de barrido (SEM). Con el fin de determinar en qué medida puede afectar al análisis del patrón de microestriación vestibular, se analizan dos muestras dentales de tres especies de Hominoideos, una de ellas incluyendo moldes con presencia de"aguas" relacionadas con el proceso de metalización. Se observa un descenso marcado de la variabilidad del patrón de microestriación dentaria anque las diferencias entre las dos muestras por especie no son estadísticamente significativas. El efecto wrinkle reduce significativamente el porcentaje de clasificación correcta de las especies analizadas a partir del patrón de microestriación y rugosidad dental utilizando un Análisis Discriminante. Se aconseja evitar la inclusión de las muestras afectadas por aguas en los estudios del patrón de microestriación dentaria

Abuso sexual infantil : protocolos de protección integral en Colombia

Este Trabajo de Grado tuvo como objetivo principal, identificar los protocolos de intervención del Abuso Sexual Infantil (ASI) que cumplen con los requisitos de Protección Integral, según la Ley 1098 de 2006 en Colombia. Para esto se estableció una metodología cualitativa y un diseño interpretativo y comprensivo, lo que permitió hacer uso de la Técnica de Análisis de Contenido en los Protocolos Nacionales e Internacionales. Los resultaron permitieron reconocer la falencia nacional respecto al desarrollo de Protocolos en ASI, a partir de los criterios de Protección Integral establecidos en el Código de Infancia y Adolescencia (Ley Nº 1098, 2006).The main objective of this thesis was to identify the intervention protocols of the Child Sexual Abuse, which meet the Integral Protection requirements, according to the 1098 Law of 2006 in Colombia. For this purpose, a qualitative methodology and an interpretative and comprehensive The main objective of this thesis was to identify the intervention protocols of the Child Sexual abuse, which meet the Integral Protection requirements, according to the 1098 Law of 2006 in Colombia. For this purpose, a qualitative methodology and an interpretative and comprehensive design were implemented, and this facilitated the use of the Content Analysis Technique in the National and International protocols. The results were helpful when recognizing the flaws in the national sphere regarding the development of protocols in Child Sexual Abuse, based on the Integral Protection criteria established in the Childhood and Adolescence Code (1098 Law, 2016).Psicólogo (a)Pregrad

Evaluation of optical tracking and augmented reality for needle navigation in sacral nerve stimulation

Background and objective: Sacral nerve stimulation (SNS) is a minimally invasive procedure where an electrode lead is implanted through the sacral foramina to stimulate the nerve modulating colonic and urinary functions. One of the most crucial steps in SNS procedures is the placement of the tined lead close to the sacral nerve. However, needle insertion is very challenging for surgeons. Several x-ray projections are required to interpret the needle position correctly. In many cases, multiple punctures are needed, causing an increase in surgical time and patient's discomfort and pain. In this work we propose and evaluate two different navigation systems to guide electrode placement in SNS surgeries designed to reduce surgical time, minimize patient discomfort and improve surgical outcomes. Methods: We developed, for the first alternative, an open-source navigation software to guide electrode placement by real-time needle tracking with an optical tracking system (OTS). In the second method, we present a smartphone-based AR application that displays virtual guidance elements directly on the affected area, using a 3D printed reference marker placed on the patient. This guidance facilitates needle insertion with a predefined trajectory. Both techniques were evaluated to determine which one obtained better results than the current surgical procedure. To compare the proposals with the clinical method, we developed an x-ray software tool that calculates a digitally reconstructed radiograph, simulating the fluoroscopy acquisitions during the procedure. Twelve physicians (inexperienced and experienced users) performed needle insertions through several specific targets to evaluate the alternative SNS guidance methods on a realistic patient-based phantom. Results: With each navigation solution, we observed that users took less average time to complete each insertion (36.83 s and 44.43 s for the OTS and AR methods, respectively) and needed fewer average punctures to reach the target (1.23 and 1.96 for the OTS and AR methods respectively) than following the standard clinical method (189.28 s and 3.65 punctures). Conclusions: To conclude, we have shown two navigation alternatives that could improve surgical outcome by significantly reducing needle insertions, surgical time and patient's pain in SNS procedures. We believe that these solutions are feasible to train surgeons and even replace current SNS clinical procedures.Research supported by projects PI18/01625 and AC20/00102 (Ministerio de Ciencia, Innovación y Universidades, Instituto de Salud Carlos III, Asociación Española Contra el Cáncer and European Regional Development Fund "Una manera de hacer Europa"), IND2018/TIC-9753 (Comunidad de Madrid) and project PerPlanRT (ERA Permed). Funding for APC: Universidad Carlos III de Madrid (Read & Publish Agreement CRUE-CSIC 2022)