61,947 research outputs found

    Desarrollo de papeles biocativos por injerto de mol茅culas espec铆ficas en celulosa

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    Tesis (DCI)--FCEFN-UNC, 2019En la presente tesis se presenta el desarrollo de papeles bioactivos con potencial aplicaci贸n en el envasado activo de alimentos. Para tal fin, se propuso el injerto de eugenol, un compuesto de origen natural con propiedades antimicrobiana, antioxidante y repelente de insectos, en celulosa, utilizando 谩cido policarbox铆lico como agente ligante. Con el objetivo de evaluar la escalabilidad del proceso propuesto, se estudiaron distintas tecnolog铆as de curado, tales como calentamiento por convecci贸n, infrarrojo, microondas y conducci贸n. En todos los casos, se analizaron la influencia de las variables operativas sobre el avance de la reacci贸n y propiedades finales del papel preparado, utilizando un dise帽o de experimentos Doehlert para elegir las experiencias a realizar, y analizando los resultados mediante metodolog铆a de superficie de respuesta y an谩lisis estad铆stico ANOVA. Se pudo comprobar que la reacci贸n de injerto de eugenol en papel comercial se produjo con 茅xito en todas las tecnolog铆as estudiadas. Asimismo, se encontraron las condiciones 贸ptimas de reacci贸n para cada una de las tecnolog铆as, para lo cual se busc贸 un compromiso entre el avance de la reacci贸n y las propiedades finales del material (mec谩nicas y color). A partir de estas condiciones, se prepararon papeles y se realiz贸 una caracterizaci贸n m谩s espec铆fica para su aplicaci贸n como envase de alimentos comparando los papeles modificados con el papel virgen. Se analizaron las propiedades mec谩nicas por ensayo de tracci贸n, rasgado y punzonado y se midi贸 la absorci贸n de agua y la capacidad de degradaci贸n. Por otro lado, las propiedades bioactivas analizadas fueron la actividad antioxidante, antimicrobiana, repelente e insecticida de gorgojos (T. castaneum y R. dominica). Una vez probado que el papel modificado presenta buenas caracter铆sticas f铆sicas y bioactivas para su posible aplicaci贸n en el envasado de alimentos, se realizaron prototipos de envasado para harina, como alimento representativo de alimentos derivados de cereales, susceptibles al ataque de plagas. En este estudio se analiz贸 la migraci贸n de reactivos, propiedades organol茅pticas y conservaci贸n del alimento, arrojando resultados promisorios para la industria de envases de alimentos. Finalmente, se realiz贸 una comparaci贸n de las tecnolog铆as de curado ensayadas, analizando diferentes aspectos como avance de reacci贸n, propiedades finales, apariencia, tiempo de reacci贸n, consumo de energ铆a, entre otros, como as铆 tambi茅n disponibilidad y uso de estas tecnolog铆as a escala industrial, seleccionando la tecnolog铆a de conducci贸n como la m谩s adecuada para una propuesta de escalado industrial.Fil: Muratore, Florencia. Universidad Nacional de C贸rdoba. Facultad de Ciencias Exactas, F铆sicas y Naturales; Argentina.Fil: Muratore, Florencia. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas. Instituto de Investigaci贸n y Desarrollo en Ingenier铆a de Procesos y Qu铆mica Aplicada; Argentina

    Comparison of physical fitness between healthy and mild鈥恡o鈥恗oderate asthmatic children with exercise symptoms: A cross鈥恠ectional study

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    .Objective Asthma is a chronic disease that may affect physical fitness, although its primary effects on exercise capacity, muscle strength, functionality and lifestyle, in children and adolescents, are still poorly understood. This study aimed to evaluate the differences in cardiorespiratory fitness, muscle strength, lifestyle, lung function, and functionality between asthmatics with exercise symptoms and healthy children. In addition, we have analyzed the association between clinical history and the presence of asthma. Study Design Cross-sectional study including 71 patients with a diagnosis of asthma and 71 healthy children and adolescents (7鈥17 years of age). Anthropometric data, clinical history, disease control, lifestyle (KIDMED and physical activity questionnaires), lung function (spirometry), exercise-induced bronchoconstriction test, aerobic fitness (cardiopulmonary exercise test), muscle strength and functionality (timed up and go; timed up and down stairs) were evaluated. Results Seventy-one patients with asthma (mean age 11.5鈥壜扁2.7) and 71 healthy subjects (mean age 10.7鈥壜扁2.5) were included. All asthmatic children had mild to moderate and stable asthma. EIB occurred in 56.3% of asthmatic children. Lung function was significantly (p鈥<鈥.05) lower in the asthmatic group when compared to healthy peers, as well as the cardiorespiratory fitness, muscle strength, lifestyle and functionality. Moreover, asthmatic children were more likely to have atopic dermatitis, allergic reactions, food allergies, and a family history of asthma when compared to healthy children. Conclusions Children with mild-to-moderate asthma presenting exercise symptoms show a reduction in cardiorespiratory fitness, muscle strength, lung function, functionality, and lifestyle when compared to healthy peers. The study provides data for pediatricians to support exercise practice aiming to improve prognosis and quality of life in asthmatic children.S

    Relationship between personality and academic motivation in education degrees students

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    p. 327-341The present study aims to understand the relationship between the big five factors of personality and academic motivation. In addition, the following variables are taken into consideration; sex, age and type of educational studies. A quantitative methodology is used, in base to a not experimental, correlational study. The sample is composed of 514 students of the Faculty of Education of Leon鈥檚 University, between the three education degrees. To gather the information, participants were asked to complete the Learning and Motivation Strategies Questionnaire (CEAM) and the Personality Questionnaire Five Factor Inventory (NEO-FFI). The results show the significant relationship between personality facets and motivation variables. It should be noted that female results were higher in the values of intrinsic motivation, motivation towards teamwork, neuroticism, and kindness, and the male results were higher in self-efficacy. Additionally, it was observed that intrinsic motivation decreases progressively from the first to the fourth year of the degree, the need for recognition decreases in the two last study years, and the openness to experiences is higher in the last year of the degree. Finally, Social Education students are those that show a higher intrinsic motivation, self-efficacy, total motivation, openness to experiences, and neuroticism, while Primary Education students鈥 results were higher in the need for recognition.S

    Does international patent collaboration have an effect on entrepreneurship?

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    .Entrepreneurship is one of the main pillars of growth in any economy. Achieving a high rate of entrepreneurship in a region has become the priority objective of governments and firms. However, in many cases, new firm creation is conditioned by relations or collaboration in innovation with agents from other countries. Previous literature has analyzed the mechanisms that foster entrepreneurship. This paper attempts to shed light on the influence of international patent collaboration (IPC) on entrepreneurial activity at country level taking into account the timing of this relationship. An empirical study is proposed to verify whether IPC leads to greater entrepreneurship and to analyze the gestation period between international patenting actions and firm creation. Using the Generalized Method of Moments, the two hypotheses proposed were tested in a data panel of 30 countries for the period 2005鈥2017. Results show the influence of IPC in promoting entrepreneurship in the same year, but especially in the following year. The study offers implications for entrepreneurs and public agents. IPC affects the integration and interaction of international agents in a country, favors the production of new knowledge, and increases positive externalities in a territory. All this facilitates the creation of new companies with a high innovative component.S

    Application of lactic acid bacteria for the biopreservation of meat products: A systematic review

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    .The increasing concern of consumers about food quality and safety and their rejection of chemical additives has promoted the breakthrough of the biopreservation field and the development of studies on the use of beneficial bacteria and their metabolites as potential natural antimicrobials for shelf life extension and enhanced food safety. Control of foodborne pathogens in meat and meat products represents a serious challenge for the food industry which can be addressed through the intelligent use of bio-compounds or biopreservatives. This article aims to systematically review the available knowledge about biological strategies based on the use of lactic acid bacteria to control the proliferation of undesirable microorganisms in different meat products. The outcome of the literature search evidenced the potential of several strains of lactic acid bacteria and their purified or semi-purified antimicrobial metabolites as biopreservatives in meat products for achieving longer shelf life or inhibiting spoilage and pathogenic bacteria, especially when combined with other technologies to achieve a synergistic effect.S

    Sponsorship image and value creation in E-sports

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    .E-sports games can drive the sports industry forward and sponsorship is the best way to engage consumers of this new sport. The purpose of this study is to examine the effect of sponsorship image and consumer participation in co-creation consumption activities on fans鈥 sponsorship response (represented by the variables interest, purchase intention and word of mouth) in e-sports. Four antecedent variables build sponsorship image (i.e., ubiquity of sport, sincerity of sponsor, attitude to sponsor and team identification). A quantitative approach is used for the purposes of this study. Some 445 questionnaires were filled in by fans who watch e-sports in Spain; these are analyzed using partial least squares structural equation modeling (PLS-SEM). The outcomes show that sponsor antecedents are crucial factors if a sponsor wants to change their sponsorship image and influence sponsorship response, and that it is also possible to use participation to improve responsesS

    Efecto a medio plazo de la recurrencia de los incendios forestales en la regeneraci贸n post-fuego del pinar de Tabuyo del Monte

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    En el presente trabajo se pretende comparar la regeneraci贸n de la comunidad vegetal dominada por P. pinaster en Tabuyo del Monte (sierra delTeleno) en dos escenarios de recurrencia de incendios diferentes:una zona afectada por un solo incendio en los 煤ltimos cuarenta a帽os (recurrencia 1, incendio de 2012) y una zona afectada por dos incendios en los 煤ltimos cuarenta a帽os (recurrencia 2, incendio de 1998 y posteriormente incendio de 2012). Para ello se tomaron datos de porcentaje de suelo descubierto, cobertura vegetal por especies, por biotipos y por estrategia de regeneraci贸n (rebrotadoras y germinadoras), as铆 como distintas variables poblacionales de Pinus pinaster

    A new index of resilience applicable to external pulse-disturbances that considers the recovery of communities in the short term

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    .Resilience is a key concept in the study of the recovery of ecosystems affected by disturbances. Currently, there are numerous indices to measure resilience, but many of them do not show the accuracy of the resilience value or the behaviour of ecological parameters in the face of disturbances. New approaches and technologies enable large amounts of information to be obtained, facilitating the proposal of new resilience indices that work consistently and intuitively for a wide variety of ecological response variables under different scenarios after pulse-disturbances. In this study, we propose and verify a new resilience index, comparing its performance with others previously published. We validated the performance of the new index using real data based on field measurements of changes in soil bacterial OTUs diversity and abundance after a wildfire. The new resilience index provided an automatic and robust functional classification of the behaviour of ecosystems after disturbances, supported by a bootstrap analysis. We identified 5 scenarios of ecosystem resilience performance according to their behaviour after a pulse-disturbance: resilient, non-resilient, recovering, rebound, and continuing.S

    El uso de los resultados espa帽oles de PISA en publicaciones cient铆ficas

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    p. 183-202En la 煤ltima d茅cada, el inter茅s por los resultados de PISA ha crecido, tanto en el debate p煤blico como en el uso de los datos para la investigaci贸n. El objetivo de este estudio consiste en analizar la utilizaci贸n de los resultados espa帽oles de PISA por parte de la comunidad cient铆fica. Se realiz贸 un an谩lisis bibliom茅trico de 119 art铆culos cient铆ficos incluidos en las bases de datos Scopus, Eric EBSCOHost y Web of Science entre 2002 y 2019 mediante an谩lisis de frecuencias, an谩lisis MDS y regresiones log铆sticas binarias. Los resultados reflejan el creciente inter茅s por los resultados espa帽oles de PISA desde 2005 hasta la actualidad, perteneciendo los autores principalmente al 谩mbito universitario de la Educaci贸n. Respecto al uso de la informaci贸n de PISA, la mayor铆a de los estudios emplean los datos como v铆a para generar conocimiento, siendo los temas socioecon贸micos como la familia y la equidad los que han tenido una mayor presencia junto al rendimiento de los estudiantes. Se concluye que, a pesar de que PISA ha tardado en tener impacto entre la comunidad acad茅mica espa帽ola, sus resultados son cada vez m谩s utilizados como fuente de informaci贸n primaria para la realizaci贸n de estudios detallados sobre temas muy diversos. No obstante, a su vez, PISA se utiliza de forma gen茅rica como indicador de calidad del sistema educativo, sin entrar en detalle en el an谩lisis contextualizado del rendimiento en las competencias objeto de estudio.S

    Identification of Hindbrain Neural Substrates for Motor Initiation in the hatchling Xenopus laevis Tadpole

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    Animal survival profoundly depends on the ability to detect stimuli in the environment, process them and respond accordingly. In this respect, motor responses to a sensory stimulation evolved into a variety of coordinated movements, which involve the control of brain centres over spinal locomotor circuits. The hatchling Xenopus tadpole, even in its embryonic stage, is able to detect external sensory information and to swim away if the stimulus is considered noxious. To do so, the tadpole relies on well-known ascending sensory pathway, which carries the sensory information to the brain. When the stimulus is strong enough, descending interneurons are activated, leading to the excitation of spinal CPG neurons, which causes the undulatory movement of swimming. However, the activation of descending interneurons that marks the initiation of motor response appears after a long delay from the sensory stimulation. Furthermore, the long-latency response is variable in time, as observed in the slow-summating excitation measured in descending interneurons. These two features, i.e. long-latency and variability, cannot be explained by the firing time and pattern of the ascending sensory pathway of the Xenopus tadpole. Therefore, a novel neuronal population has been proposed to lie in the hindbrain of the tadpole, and being able to 'hold' the sensory information, thus accounting for the long and variable delay of swim initiation. In this work, the role of the hindbrain in the maintenance of the long and variable response to trunk skin stimulation is investigated in the Xenopustadpole at developmental stage 37/38. A multifaceted approach has been used to unravel the neuronal mechanisms underlying the delayed motor response, including behavioural experiments, electrophysiology analysis of fictive swimming, hindbrain extracellular recordings and imaging experiments. Two novel neuronal populations have been identified in the tadpole's hindbrain, which exhibit activation patterns compatible with the role of delaying the excitation of the spinal locomotor circuit. Future work on cellular properties and synaptic connections of these newly discovered populations might shed light on the mechanism of descending control active at embryonic stage. Identifying supraspinal neuronal populations in an embryonic organism could aid in understanding mechanisms of descending motor control in more complex vertebrates
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