Propiedades mecánicas de cermets basados en diboruro de titanio

Las propiedades mecánicas de los cermets basados en diboruro de titanio (TiB 2 ) dependen críticamente de la composición de la fase ligante. Se ha comprobado que tanto la tenacidad como la dureza aumentan significativamente si se evita la formación de boruros secundarios durante la sinterización en fase líquida. Las observaciones fractográficas realizadas en cermets basados en TiB 2 sin boruros secundarios confirman el comportamiento plástico de la fase ligante durante la fractura. La ruta pulvimetalúrgica aplicada a estos materiales permite la modificación intencionada de la estructura de la fase ligante desde ferrita a austenita mediante adiciones de aluminio a las mezclas de polvos. Los valores de tenacidad más elevados se han obtenido para los cermets con matriz austenítica. El análisis mediante difracción de rayos X de la superficie de fractura de estos materiales confirma que la fase ligante experimenta transformación martensítica durante la fractura, mecanismo de aumento de tenacidad ya observado en otros sistemas. Esta nueva familia de materiales duros presenta una excelente combinación de dureza y tenacidad, comparable a la obtenida con grados comerciales de carburos cementados (WC-Co).Peer reviewe

Modelling math learning on an open access intelligent tutor

This paper presents a methodology to analyze large amount of students’ learning states on two math courses offered by Global Fresh- man Academy program at Arizona State University. These two courses utilised ALEKS (Assessment and Learning in Knowledge Spaces) Arti- ficial Intelligence technology to facilitate massive open online learning. We explore social network analysis and unsupervised learning approaches (such as probabilistic graphical models) on these type of Intelligent Tu- toring Systems to examine the potential of the embedding representa- tions on students learning

PredictCS: Personalizing Programming learning by leveraging learning analytics

This paper presents a new framework to harness sources of programming learning analytics at a Higher Education Institution and how it has been progressively adopted at the classroom level to improve personalized learning. This new platform, called PredictCS, automatically detects lower-performing or “at-risk” students in computer programming modules and automatically and adaptively sends them feedback. PredictCS embeds multiple predictive models by leveraging multi-modal learning analytics of student data, including student characteristics, prior academic history, logged interactions between students and online resources, and students' progress in programming laboratory work, and their progression from introductory to advanced CS courses. Predictions are generated every week during the semester's classes. In addition, students are flexible to opt-in to receive pseudo real-time personalized feedback, which permits them to be aware of their predicted course performance. The adaptive feedback ranges from programming suggestions from top- performers in the class to resources that are suitable to bridge their programing knowledge gaps

Predictive modelling of student reviewing behaviors in an introductory programming course

In this paper, we developed predictive models based on students’ reviewing behaviors in an Introductory Programming course. These patterns were captured using an educational technology that students used to review their graded paper- based assessments. Models were trained and tested with the goal of identifying students’ academic performance and those who might be in need of assistance. The results of the retrospective analysis show a reasonable accuracy. This suggests the possibility of developing interventions for students, such as providing feedback in the form of effective reviewing strategies

Growth, yield and physiology of Verticillium-inoculated pepper plants treated with ATAD and composted sewage sludge

A greenhouse experiment was conducted to investigate the impact of sanitized sewage sludges, ATAD (aerobic thermophilic autothermic digestion) and composted, on Verticillium-induced wilt in pepper plants (Capsicum annuum L. cv. Piquillo). Two doses of ATAD (15 and 30% v/v) and three of composted sludge (15, 30 and 45% v/v) were applied to a peat-based potting mix. Unamended substrate was included as control. Half of the plants were inoculated with V. dahliae, whereas the other half remained non-inoculated. Result showed that ATAD and composted sludge increased growth and yield of non-inoculated plants. V. dahliae reduced net photosynthesis (P n), mainly as a consequence of stomatal closure, 5 weeks after pathogen inoculation. The actual photosystem II efficiency was also reduced and consequently the electron transport rate (ETR). No photoinhibitory damage was observed at this time in diseased plants. At the end of the experiment, diseased plants showed lower plant biomass and fruit yield. ATAD sludge had little effect on the disease. Compost slightly alleviated Verticillium-induced wilt when applied at lower doses (15% v/v), which resulted in increased P n and ETR, and higher plant biomass and fruit yield. By contrast, higher doses of compost (45% v/v) enhanced the effect of the pathogen, which was related to the high substrate salinity in this treatment

Detecting students-at-risk in computer programming classes with learning analytics from students’ digital footprints

Different sources of data about students, ranging from static demographics to dynamic behavior logs, can be harnessed from a variety sources at Higher Education Institutions. Combining these assembles a rich digital footprint for students, which can enable institutions to better understand student behaviour and to better prepare for guiding students towards reaching their academic potential. This paper presents a new research methodology to automatically detect students ``at-risk'' of failing an assignment in computer programming modules (courses) and to simultaneously support adaptive feedback. By leveraging historical student data, we built predictive models using students' offline (static) information including student characteristics and demographics, and online (dynamic) resources using programming and behaviour activity logs. Predictions are generated weekly during semester. Overall, the predictive and personalised feedback helped to reduce the gap between the lower and higher-performing students. Furthermore, students praised the prediction and the personalised feedback, conveying strong recommendations for future students to use the system. We also found that students who followed their personalised guidance and recommendations performed better in examinations

Use of recombinant human granulocyte-macrophage colony stimulating factor in an infant with reticular dysgenesis

We present the case of a 2-month-old infant with reticular dysgenesis who was treated with recombinant granulocyte-macrophage colony stimulating factor with the aim of stimulating granulopoiesis while awaiting bone marrow transplant

Late immune response and chronic infection of vascular graft. A controversial diagnosis

La prevalencia de reacciones periprotésicas estériles en injertos vasculares es de aproximadamente un 0,8%. Son situaciones clínicas donde resulta difícil determinar si su origen reside en una infección por gérmenes de crecimiento lento o es secundario a un rechazo inmunológico al material o por una desestructuración del mismo. Revisamos y comentamos las principales características para distinguir ambas situaciones clínicas. Se aporta un ejemplo clínico que trata de un paciente con injerto vascular de Dacron y una colección de 6 años de evolución, estéril, que rodea el total de la prótesis y requiere su explante y sustitución por un nuevo injerto. En conclusión, ante los casos de reacciones periprotésicas tardías es obligado excluir la presencia de infecciones latentes, pero se recomienda profundizar en el estudio de la respuesta inmunológica frente a los materiales del injerto vascular.The prevalence of sterile perigraft reaction is approximately 0.8% in vascular grafts. To diagnose between an infection by germs of slow growth or a secondary reaction to an immune rejection of the material is difficult in this clinical situation. We review and discuss the main features to distinguish these two clinical possibilities. We report a patient case report with dacron vascular graft and a perigraft collection, sterile, around the total prosthesis which required explantation and replacement by a new graft. In conclusion, to cases of late periprosthetic reactions is required to exclude the presence of latent infections, but recommended further study of the immune response against vascular graft materials

Improved diet quality and nutrient adequacy in children and adolescents with abdominal obesity after a lifestyle intervention

High rates of childhood obesity require integral treatment with lifestyle modifications that achieve weight loss. We evaluated a lifestyle intervention on nutrient adequacy and diet quality in children and adolescents with abdominal obesity. A randomized controlled trial was performed on 107 participants, assigned either to a usual care group or to an intensive care group that followed a moderate hypocaloric Mediterranean diet and received nutritional education. Intake adequacy was evaluated using Dietary Reference Intakes and diet quality through the Diet Quality Index for Adolescents (DQI-A), the Healthy Lifestyle Diet-Index (HLD-I) and the Mediterranean Diet Quality Index (KIDMED). Both groups achieved a significant reduction in BMI standard deviation score (BMI-SDS), glucose and total cholesterol levels. Intake of Calcium, Iodine and vitamin D were higher in the intensive care group, with enhanced compliance with recommendations. Higher dietary scores were associated with lower micronutrient inadequacy. DQI-A and HLD-I were significantly higher in the intensive care group vs. usual care group after the treatment. In conclusion, we observed that an intensive lifestyle intervention was able to reduce BMI-SDS in children with abdominal obesity. Furthermore, participants significantly improved dietary indices getting closer to the nutritional recommendations. Therefore, these diet quality indices could be a valid indicator to evaluate micronutrient adequacy.High rates of childhood obesity require integral treatment with lifestyle modifications that achieve weight loss. We evaluated a lifestyle intervention on nutrient adequacy and diet quality in children and adolescents with abdominal obesity. A randomized controlled trial was performed on 107 participants, assigned either to a usual care group or to an intensive care group that followed a moderate hypocaloric Mediterranean diet and received nutritional education. Intake adequacy was evaluated using Dietary Reference Intakes and diet quality through the Diet Quality Index for Adolescents (DQI-A), the Healthy Lifestyle Diet-Index (HLD-I) and the Mediterranean Diet Quality Index (KIDMED). Both groups achieved a significant reduction in BMI standard deviation score (BMI-SDS), glucose and total cholesterol levels. Intake of Calcium, Iodine and vitamin D were higher in the intensive care group, with enhanced compliance with recommendations. Higher dietary scores were associated with lower micronutrient inadequacy. DQI-A and HLD-I were significantly higher in the intensive care group vs. usual care group after the treatment. In conclusion, we observed that an intensive lifestyle intervention was able to reduce BMI-SDS in children with abdominal obesity. Furthermore, participants significantly improved dietary indices getting closer to the nutritional recommendations. Therefore, these diet quality indices could be a valid indicator to evaluate micronutrient adequacy