Impacto de las aerolíneas de bajo costo en la aviación colombiana

El modelo de las aerolíneas de bajo costo, ha evolucionado la industria aeronáutica en los últimos 20 años y ha sorprendido al mundo por la alta aceptación de los usuarios y el incremento de estos, año a año, bajo su política de bajos costos. Esta clase de modelo aéreo, utiliza estrategias de reducir al máximo cualquier gasto no indispensable, como tener una flota de aeronaves uniforme, no ofrecer servicios a bordo y vender sus tiquetes de forma electrónica, entre otras. Con estas estrategias, las aeronaves optimizan al máximo el uso de sus aeronaves, lo que traduce en aumentar sus horas de vuelo. En cuanto a la implementación de este modelo en el territorio colombiano, ha creado gran expectativa e incertidumbre en la industria aérea nacional y en el cliente, que ha migrado de gran parte de las aerolíneas tradicionales y de sectores como el transporte terrestre, el cual se va visto afectado por los precios bajos de esta clase de aerolínea

Analysis of air concentration in a physical model of the bottom of a spillway chute with aerators

Given the inherent difficulties and constraints of taking measurements on a prototype and representing the behavior of air in a physical model, this paper presents comparative analysis results from air content measurements in a spillway bottom model with aerators. This was done using model measurements and an analytical model to define the accuracy and credibility of extrapolating results to the prototype. The numerical criterion used allows calculation of air concentration decay along the chute at the same point where the physical model measurements were made. Since air concentration can only be measured at the bottom of the prototype, it can be concluded that the analytical approach works well, and with some adjustments, the results can be extrapolated to measure other points on the prototype Air content at the bottom chute is the most important understanding for the protection spillway

LA CALIDAD DEL NÉCTAR AFECTA LA CONDUCTA TERRITORIAL Y DE FORRAJEO EN HEMBRAS DEL COLIBRÍ LUCIFER (CALOTHORAX LUCIFER): UN EXPERIMENTO

Resumen ∙ Los colibríes para vivir dependen de la energía que les brinda el néctar floral, un recurso  variable espacial y temporalmente. Por ello, deben recabar información sobre su cantidad y calidad en las flores que visitan. Esta información moldea la toma de decisiones durante el forrajeo en los colibríes. En el presente estudio analizamos el efecto de la exposición previa a una fuente de volumen constante de néctar pero de calidad variable, sobre el comportamiento de defensa contra intrusos durante el forrajeo de hembras del Colibrí Lucifer (Calothorax lucifer). Para probarlo realizamos experimentos de campo utilizando bebederos con tres calidades energéticas de néctar (baja, media y alta). Registramos la frecuencia de encuentros agonísticos contra intrusos a lo largo de treinta días de exposición a los bebederos y el éxito de forrajeo de los intrusos en los bebederos. A lo largo de los días la probabilidad de defensa aumentó en las hembras que establecieron territorios en torno a bebederos con néctar de media y alta calidad, pero disminuyó para los bebederos con néctar de baja calidad. Además, el número de intrusos no exitosos fue mayor en torno a los bebederos con néctar de media y alta calidad. Nuestros resultados sugieren que las hembras de Calothorax lucifer pueden modificar su conducta agonística y de forrajeo a lo largo del tiempo de acuerdo a la experiencia e información que reúnen sobre la calidad de los recursos presentes en el ambiente.  Abstract ∙ Nectar quality affects foraging and territoriality in female Lucifer Hummingbirds (Calothorax lucifer): an experiment Hummingbirds depend for survival on the energy contained in nectar, a resource that shows both spatial and temporal variation. Therefore, they should gather information on the quantity and quality of the flowers they visit, which should affect decision‐making of hummingbirds during their foraging. In the present study, we analyzed the effect of prior exposure to a source of constant volume of nectar, but of varying quality (sugar concentration), on the territorial behavior against intruders of female Lucifer Hummingbirds (Calothorax lucifer) during foraging. We carried out field experiments using feeders containing three different qualities of nectar (low, medium, and high energy). We recorded the frequency of agonistic encounters with intruders over thirty days of exposure to the feeders and the foraging success of the intruders on feeders. Throughout the study the probability of defense against intruders increased in females, who established territories around nectar feeders with medium and high quality nectar, but decreased for those with territories around low quality nectar feeders. In addition, the number of unsuccessful intruders was greater around medium and high quality feeders. Our results suggest that females of Calothorax lucifer can modify their agonistic and foraging behavior throughout time in accordance to experience and gather information about the quality of resources present in the environment

Soft palate preservation after tumor resection with transoral laser microsurgery

Background: Management and preservation of the soft palate is dependent on clinical stage and tumor histology. However, available literature is scarce regarding the palate preservation with the use of laser CO 2 . Objectives : We report the results obtained after management with laser surgery and soft palate preservation in three patients with salivary gland neoplasms. Method: Three patients with minor salivary gland tumors were treated by means of transoral laser microsurgery. All tumors were assessed using magnetic resonance imaging. All tumors were >3 cm. Soft palate function was preserved and reconstruction was performed with primary closure. Patients began oral feeding the same day and were discharged after 24 h. Conclusions : Transoral laser microsurgery is recommended for treatment of soft palate tumors. This treatment can be considered a better option when compared with other modalities such as radio- or chemoradiotherapy which require a longer time of treatment, are more expensive and tend to produce significant toxicity

Cumplimiento de las obligaciones ambientales de las langostineras de Tumbes, 2017

En la investigación titulada: Cumplimiento de las obligaciones ambientales de las langostineras de Tumbes, 2017. El objetivo general de la investigación fue determinar el nivel de cumplimiento de las obligaciones ambientales de las langostineras de Tumbes, 2017. El tipo de investigación es básica, y el diseño de la investigación es no experimental, transversal, descriptivo ex post facto, usando el enfoque cuantitativo. La muestra estuvo conformada por 18 empresas langostineras de Tumbes de la categoría productiva de Acuicultura de Mediana y Gran Empresa (Amyge). La técnica que se utilizó fue la del análisis documental de las supervisiones ambientales realizadas por el Organismo de Evaluación y Fiscalización Ambiental (OEFA) a las langostineras de Tumbes, durante los años 2012 al 2016. Con referencia al objetivo general: Determinar el nivel de cumplimiento de las obligaciones ambientales de las langostineras de Tumbes, 2017, se concluye que: El nivel de cumplimiento de las obligaciones ambientales para las empresas langostineras de Tumbes, supervisadas por el OEFA, durante el 2012 al 2016, fue de 97,20 % en promedio, que representa un nivel de cumplimiento alto

Laser resection of liposarcoma of the hypopharynx

Liposarcomas represent between 15 and 18% of all sarcomas with the most common site being the extremities and retroperitoneum. Liposarcomas of the head and neck are rare, with an estimated incidence representing 3 to 5.6% of all liposarcomas. Liposarcomas most commonly present in the soft tissues of the neck. Primary liposarcoma of the hypopharynx (piriform sinus) is extremely rare. The symptoms presented are principally dysphagia, dyspnea, dysphonia, airway obstruction and sensation of a foreign body. Treatment of choice is surgery, and the literature describes the performance of lateral pharyngotomy, simple excision and even total laryngectomy. We present the case of a 23-year-old patient who was diagnosed 7 years prior with liposarcoma of the piriform sinus. The patient underwent surgery using a cervical approach. The tumor recurred 4 years postoperatively and the patient was again surgically intervened using the same approach. He presented to our Institute with 3 months evolution of dysphonia. Nasofibrolaryngoscopy and imaging studies were performed. Surgical treatment was decided upon with CO2 laser using suspension microlaryngoscopy, obtaining excellent results. Some of the advantages of this approach are low morbidity because of the avoidance of performing a tracheostomy, rapid return to oral feeding without necessity of a feeding tube, and reduction in hospitalization days. Disadvantage includes difficulty in evaluating margins

Modelling and Analysis of Drosophila Early Visual System A Systems Engineering Approach

Over the past century or so Drosophila has been established as an ideal model organism to study, among other things, neural computation and in particular sensory processing. In this respect there are many features that make Drosophila an ideal model organism, especially the fact that it offers a vast amount of genetic and experimental tools for manipulating and interrogating neural circuits. Whilst comprehensive models of sensory processing in Drosophila are not yet available, considerable progress has been made in recent years in modelling the early stages of sensory processing. When it comes to visual processing, accurate empirical and biophysical models of the R1-R6 photoreceptors were developed and used to characterize nonlinear processing at photoreceptor level and to demonstrate that R1-R6 photoreceptors encode phase congruency. A limitation of the latest photoreceptor models is that these do not account explicitly for the modulation of photoreceptor responses by the network of interneurones hosted in the lamina. As a consequence, these models cannot describe in a unifying way the photoreceptor response in the absence of the feedback from the downstream neurons and thus cannot be used to elucidate the role of interneurones in photoreceptor adaptation. In this thesis, electrophysiological photoreceptor recordings acquired in-vivo from wild- type and histamine defficient mutant fruit flies are used to develop and validate new com- prehensive models of R1-R6 photoreceptors, which not only predict the response of these photoreceptors in wild-type and mutant fruit flies, over the entire environmental range of light intensities but also characterize explicitly the contribution of lamina neurons to photore- ceptor adaptation. As a consequence, the new models provide suitable building blocks for assembling a complete model of the retina which takes into account the true connectivity between photoreceptors and downstream interneurones. A recent study has demonstrated that R1-R6 photoreceptors employ nonlinear processing to selectively encode and enhance temporal phase congruency. It has been suggested that this processing strategy achieves an optimal trade-off between the two competing goals of minimizing distortion in decoding behaviourally relevant stimuli features and minimizing the information rate, which ultimately enables more efficient downstream processing of spatio-temporal visual stimuli for edge and motion detection.Using rigorous information theoretic tools, this thesis derives and analyzes the rate-distortion characteristics associated with the linear and nonlinear transformations performed by photoreceptors on a stimulus generated by a signal source with a well defined distribution

Optimización del proceso de aspersión térmica por arco eléctrico a la mezcla de los recubrimientos 140mxc-530as y 140mxc-560as usando un algoritmo genético multiobjetivo

La proyección térmica conocida también como aspersión térmica, termo-rociado o por su nombre genérico en inglés Thermal Spray, se puede definir como el proceso mediante el cual se aplica un recubrimiento metálico o no metálico mediante la deposición de partículas fundidas o semifundidas que son aceleradas y proyectadas a alta presión sobre la superficie de un material base o sustrato previamente preparado; este proceso se puede agrupar en tres grandes categorías: proyección a la llama, por arco eléctrico y plasma, mientras que los recubrimientos se pueden aplicar en forma de polvos, alambres o varillas, que cuando impactan sobre la superficie generan una acumulación de las partículas, generando una estructura o película laminar delgada (TSS Training Committee, 2004