Estudio de la frecuencia de ocurrencia de accidentes de tráfico mediante procesos estocásticos de Pascal-Pólya

Objetivo: (1) Plantear un modelo estocástico adecuado para la frecuencia de accidentes, que permita analizar tanto la peligrosidad, como la exposición al riesgo. (2) Introducir los conceptos de macroaccidentalidad y microaccidentalidad.Métodos: En este artículo se han usado la teoría de procesos estocásticos para estimar el número de accidentes y así como la frecuencia con la que se producen accidentes de tráfico de una red viaria amplia (macroaccidentalidad). Para ello, se han analizado diversas bases de datos oficiales de una región durante un período prolongado de casi una década.Resultados: El principal hallazgo es que un proceso estocástico de Poisson mixto (mezcla probabilista de varios procesos de Poisson) ajusta adecuadamente el número de accidentes, dando lugar a una distribución binomial negativa para el número de accidentes en un período específico. Se propone una interpretación estocástica explicativa de las razones por las cuales la distribución del número de accidentes es de ese tipo.Peer Reviewe

Injury metrics for assessing the risk of acute subdural hematoma in traumatic events

Worldwide, the ocurrence of acute subdural hematomas (ASDHs) in road traffic crashes is a major public health problem. ASDHs are usually produced by loss of structural integrity of one of the cerebral bridging veins (CBVs) linking the parasagittal sinus to the brain. Therefore, to assess the risk of ASDH it is important to know the mechanical conditions to which the CBVs are subjected during a potentially traumatic event (such as a traffic accident or a fall from height). Recently, new studies on CBVs have been published allowing much more accurate prediction of the likelihood of mechanical failure of CBVs. These new data can be used to propose new damage metrics, which make more accurate predictions about the probability of occurrence of ASDH in road crashes. This would allow a better assessement of the effects of passive safety countermeasures and, consequently, to improve vehicle restraint systems. Currently, some widely used damage metrics are based on partially obsolete data and measurements of the mechanical behavior of CBVs that have not been confirmed by subsequent studies. This paper proposes a revision of some existing metrics and constructs a new metric based on more accurate recent data on the mechanical failure of human CBVs.Peer ReviewedPostprint (published version

A new technique for curved rod bending tests based on digital image correlation

Background. The study of the deformation of curved rods subjected to bending and its associated stress state is a complex task that has not been treated in depth in the literature, which makes difficult to obtain constitutive models or Finite Element Models (FEM) in which it is necessary to know all the components of the stress and strain tensors. Objectives. This study focuses on a new calculation methodology to obtain stress and strain tensors of curved rods under bending. Methods. The stress and strain tensors have been determined based on the theory of continuum mechanics and differential geometry of curves (moving bases), in a general methodology and valid for large strains, curved geometries and variable cross-sections along the specimen. This has been applied to the human rib and, in addition, a new experimental method for bending of curved specimens based on Digital Image Correlation (DIC) is presented. Results. Both the test method and the proposed calculations applied to the human rib show results according to expectations, allowing to know the rib curvature changes along the test, the stresses and strains along the rib and the components of both stress and strain in all directions, in order to build the stress and strain tensors. In addition, the results of stress, strain and young’s modulus correspond to those of previous literature in tensile testing of human rib cortical bone. Conclusions. The proposed calculations allow the construction of the strain and stress tensors of a curved specimen subjected to bending, which is of great importance for the development of constitutive models. Moreover, since with this method it is possible to calculate both tensors along the entire length of the specimen and in all directions, it is possible to apply this method in finite element models. Finally, the new test methodology allows to know the stress and strain in curved specimens such as the human rib, from bending tests.Peer ReviewedPostprint (author's final draft

A predictive model for fracture in human ribs based on in-vitro acoustic emission data

Purpose The aim of this paper is to propose a fracture model for human ribs based on acoustic emission (AE) data. The accumulation of microcracking until a macroscopic crack is produced can be monitored by AE. The macrocrack propagation causes the loss of the structural integrity of the rib. Methods The AE technique was used in in vitro bending tests of human ribs. The AE data obtained were used to construct a quantitative model that allows an estimation of the failure stress from the signals detected. The model predicts the ultimate stress with an error of less than 3.5% (even at stresses 15% lower than failure stress), which makes it possible to safely anticipate the failure of the rib. Results The percolation theory was used to model crack propagation. Moreover, a quantitative probability-based model for the expected number of AE signals has been constructed, incorporating some ideas of percolation theory. The model predicts that AE signals associated with micro-failures should exhibit a vertical asymptote when stress increases. The occurrence of this vertical asymptote was attested in our experimental observations. The total number of microfailures detected prior to the failure is urn:x-wiley:00942405:media:mp15082:mp15082-math-0001 and the ultimate stress is urn:x-wiley:00942405:media:mp15082:mp15082-math-0002 MPa. A significant correlation (p < 0.0001) between urn:x-wiley:00942405:media:mp15082:mp15082-math-0003 and the predicted value is found, using only the first N = 30 micro-failures (correlation improves for N higher). Conclusions The measurements and the shape of the curves predicted by the model fit well. In addition, the model parameters seem to explain quantitatively and qualitatively the distribution of the AE signals as the material approaches the macroscopic fracture. Moreover, some of these parameters correlate with anthropometric variables, such as age or Body Mass Index. The proposed model could be used to predict the structural failure of ribs subjected to bending.Peer ReviewedPostprint (author's final draft

Influence of anthopometric variables on the mechanical properties of human rib cortical bone

Objective. The mechanical properties of ribs from a large number of post-mortem human subjects (PMHS) were analyzed to search for variation according to age, sex or BMI in the sample. A large sample of specimens from different donors (N = 64) with a very wide range of ages and anthropometric characteristics was tested. Methods. Uniaxial tensile tests were used for a sample of coupons machined from cortical bone tissue in order to isolate the purely mechanical properties from the geometrically influenced properties of the rib. Each coupon is about 25 mm long and has a thickness of about 0.5 mm. The mechanical properties measured for each specimen/coupon include YM, yield stress, ultimate stress (maximum failure stress), ultimate strain, and resilience (energy to fracture of SED). The study provides new methodological improvements in DIC techniques. Results. This study is notable for using an atypically large sample of number of PMHS. The size of the sample allowed the authors to determine that age has a significant effect on failure stress (p < 0.0001), yield stress (p = 0.0047), ultimate strain (p < 0.0001) and resilience (p < 0.0001) [numbers in parentheses represent the corresponding p - values]. Finally, there is a combined effect, so that for a given age, an increase of BMI leads to a decrease of the maximum strain (i.e. cortical bone is less stiff when both age and BMI are higher).Peer ReviewedPostprint (author's final draft

Viscoelastic characterization of parasagittal bridging veins and implications for traumatic brain injury: a pilot study

Many previous studies on the mechanical properties of Parasagittal Bridging Veins (PSBVs) found that strain rate had a significant effect on some mechanical properties, but did not extensively study the viscoelastic effects, which are difficult to detect with uniaxial simple tensile tests. In this study, relaxation tests and tests under cyclic loading were performed, and it was found that PSBVs do indeed exhibit clear viscoelastic effects. In addition, a complete viscoelastic model for the PSBVs is proposed and data from relaxation, cyclic load and load-unload tests for triangular loads are used to find reference values that characterize the viscoelastic behavior of the PSBVs. Although such models have been proposed for other types of blood vessels, this is the first study that clearly demonstrates the existence of viscoelastic effects from an experimental point of view and also proposes a specific model to explain the data obtained. Finally, this study provides reference values for the usual viscoelastic properties, which would allow more accurate numerical simulation of PSBVs by means of computational models.Peer ReviewedPostprint (published version

Integration model of professional training for the undergraduate degree in nursing at UTEQ

El rediseño curricular es fundamental, es por esto que se trató este tema, en este caso de una institución de servicio educativo como es la UNIVERSIDAD ESTATAL DE QUEVEDO, entre las 5 más importantes del país. La idea de esta propuesta es el rediseño de la malla curricular de la Carrera de Licenciatura Enfermería con la inserción de las asignaturas que ayudaran al estudiante&nbsp; una vez concluido sus estudios afrontar con conocimientos prácticos y teórico el inicio de&nbsp; su vida profesional demostrando lo aprendido durante su tiempo de estudiante . La metodología de esta investigación es del modelo cualitativo cuantitativo (mixto) y descriptivo, logrando la elaboración de una propuesta factible con elementos técnicos como son el cálculo de la muestra poblacional participante recopilando información para luego ser procesada. Con los resultados estadísticos se pude graficar y analizar la información obtenida de los involucrados en este estudio que componen la carrera de Licenciatura Enfermería de la Universidad Estatal de Quevedo, e intervienen en el proceso de calidad total de la educación superior.Curricular redesign is essential, which is why this topic was discussed, in this case, an educational service institution such as the QUEVEDO STATE UNIVERSITY, among the 5 most important in the country. The idea of ​​this proposal is the redesign of the curricular mesh of the Nursing Degree Course with the insertion of the subjects that will help the student once they finish their studies to face with practical and theoretical knowledge the beginning of their professional life demonstrating what they have learned during their student time. The methodology of this research is of the qualitative and descriptive model, achieving the elaboration of a feasible proposal with technical elements such as the calculation of the participating population sample, collecting information and then processing it. With the statistical results, it is possible to graph and analyze the information obtained from those involved in this study who make up the Bachelor of Nursing degree at the State University of Quevedo, and intervene in the total quality process of higher education

Teaching model for inclusive attention to the needs not associated with a disability of the students of the City of Valencia Educational Unit

In Ecuador, the issue of inclusion is something that has occurred recently, since in previous times the term integration was mentioned, which at first glance seems to mean the same thing, but it is not. The Ecuadorian State has made significant changes and has invested in education, so that it becomes of quality and warmth. At the time when it was decided to include boys and girls with special educational needs in the regular classrooms of the in the Ciudad de Valencia Educational Unit in Canton Valencia, the teachers were concerned and certain students were impressed when they saw the insertion of children with disabilities. different, the educational environment took a remarkable turn and became a differentiated setting. The changes so far have been satisfactory for education, teachers have been concerned with preparing, training and updating to be able to work with boys and girls who present differentiated learning, understanding that everything is possible when the person intends to overcome their own obstacles. This article is the product of research, interpretation and theoretical and experiential foundation, where it is observed that a certain part of students exclude boys and girls with different abilities, therefore the educational environment is affected and for this reason this research work was carried out, because the need to implement pedagogical strategies to achieve a positive inclusion of boys and girls in the institution is evident.En Ecuador el tema de inclusión es algo que se ha dado recientemente, puesto que en tiempos anteriores se mencionaba el término integración que a simple vista parece significar lo mismo, pero no es así. El Estado ecuatoriano ha realizado cambios significativos y ha invertido en la educación, para que esta se vuelva de calidad y calidez. En su momento Ecuador se decidió incluir a niños y niñas con necesidades educativas especiales en las aulas regulares de la en la Unidad Educativa Ciudad de Valencia del Cantón Valencia, los docentes se mostraron preocupados y ciertos educandos se impresionaron al ver la inserción de niños con capacidades diferentes, el entorno educativo tomo un giro notable y se convertía en un escenario diferenciado. Los cambios hasta ahora han sido satisfactorios para la educación, los docentes se han preocupado por prepararse, capacitarse y actualizarse para poder trabajar con niños y niñas que presentar un aprendizaje diferenciado, logrando comprender que todo es posible cuando la persona se propone superar sus propios obstáculos. Este artículo es el producto de la investigación, interpretación y fundamentación teórica y vivencial, donde se observa que cierta parte de estudiantes excluyen a niños y niñas con capacidades diferentes, por lo tanto, el entorno educativo se ve afectado y por ello se realizó este trabajo investigativo, pues se evidencia la necesidad de implementar estrategias pedagógicas para lograr una inclusión positiva de niños y niñas en la institución

Glucose homeostasis changes and pancreatic β-cell proliferation after switching to cyclosporin in tacrolimus-induced diabetes mellitus

AbstractBackgroundSwitching to cyclosporin A may result in a reversion of tacrolimus-induced diabetes mellitus. However, mechanisms underlying such a reversion are still unknown.MethodsObese Zucker rats were used as a model for tacrolimus-induced diabetes mellitus. A cohort of 44 obese Zucker rats received tacrolimus for 11 days (0.3mg/kg/day) until diabetes development; then, (a) 22 rats were euthanized at day 12 and were used as a reference group (tacrolimus-day 12), and (b) 22 rats on tacrolimus were shifted to cyclosporin (2.5mg/kg/day) for 5 days (tacrolimus-cyclosporin). An additional cohort of 22 obese Zucker rats received the vehicle for 17 days and was used as a control group. All animals underwent an intraperitoneal glucose tolerance test at the end of the study.Resultsβ-Cell proliferation, apoptosis and Ins2 gene expression were evaluated. Compared to rats in tacrolimus-day 12 group, those in tacrolimus-cyclosporin group showed a significant improvement in blood glucose levels in all assessment points in intraperitoneal glucose tolerance test. Diabetes decreased from 100% in tacrolimus-day-12 group to 50% in tacrolimus-cyclosporin group. Compared to tacrolimus-day-12 group, rats in tacrolimus-cyclosporin group showed an increased β-cell proliferation, but such an increase was lower than in rats receiving the vehicle. Ins2 gene expressions in rats receiving tacrolimus-cyclosporin and rats receiving the vehicle were comparable.ConclusionAn early switch from tacrolimus to cyclosporin in tacrolimus-induced diabetes mellitus resulted in an increased β-cell proliferation and reversion of diabetes in 50% of cases

Survival of Coptotermes testaceus (Isoptera: Rhinotermitidae) to Environmental Conditions (Relative Humidity and Temperature) and Preference to Different Substrates

Coptotermes  testaceus (L.) (Rhinotermitidae) is a subterranean termite species that causes damage in urban and agricultural areas in the neotropics. Despite its economic importance,  there  are  no  studies  on  its  basic  biological  aspects  for  laboratory management and the development of strategies for its control. The objective of the present study was to evaluate the relative humidity, temperature, substrate moisture and preference to different wood substrates for the best C.  testaceus survival under laboratory conditions. For this, a range of eight relative humidity (from 9 to 100%), three temperatures (20, 25 and 30 °C), six substrates (Pinus sp, Cedrela  odorata  (L.), Cocos nucifera (L.), Eucalyptus urophylla (S. T. Blake), Haematoxylum campechianum (L.) and Tabebuia rosea [Bertol.] DC) and four substrate moistures, (0 to 60%) were tested. The results of this study indicated a significant effect of all factors on termite survival or termite preference. When tested independently, the highest survival percentage of C.testaceus was obtained with humidity of 100%, temperature of 20 °C, substrate moisture of 60% and the Eucalyptus  urophylla substrate, reaching 83.33% survival at 21 days of observation. With these preliminary assays on small termite groups, it is concluded that with the appropriate percentages of humidity, temperature and substrate and the interaction of these three factors, further research can be conducted using larger termite groups in biologically relevant conditions, in order to study various aspects of C. testaceus biology