Oxides (Al2O3, SiO2, TiO2, ZrO2, Y2O3, CeO2, MgO) are among the most used reinforcements for Aluminum Matrix Composites (AMC); while the combination of Al with Si, Cu and/or Mg excels among the ...alloying systems used as matrices. Some works in literature study the effects of the reinforcements and the alloying elements on the composites manufacturing, microstructure and mechanical properties. Nevertheless, it is necessary a recompilation of the interactions oxide reinforcement-alloyed matrix, including the reciprocal effects between them. Our search revealed that not only reactions occur at the interfacial regions, but also other phenomena depending on the reinforcement characteristics and the matrix composition, which affect mechanical properties. These phenomena include modifications in the matrix microstructure and its precipitation process, diffusion of elements through the interfaces, change in the reinforcement wettability by the liquid metal, loss of alloying elements, and deterioration of the reinforcement. This work presents the occurrence of these phenomena for Al matrices with different contents of Si, Cu and Mg reinforced with the most used oxides. Its novelty lies in exploring these combinations of conditions, which could serve as a benchmark study and help for a better understanding and selection of the matrix-reinforcement system.
Conservationists are increasingly relying on distribution models to predict where species are likely to occur, especially in poorly-surveyed but biodiverse areas. Modeling is challenging in these ...cases because locality data necessary for model formation are often scarce and spatially imprecise. To identify methods best suited to modeling in these conditions, we compared the success of three algorithms (Maxent, Mahalanobis Typicalities and Random Forests) at predicting distributions of eight bird and eight mammal species endemic to the eastern slopes of the central Andes. We selected study species to have a range of locality sample sizes representative of the data available for endemic species of this region and also that vary in their distribution characteristics. We found that for species that are known from moderate numbers (N = 38-94) of localities, the three methods performed similarly for species with restricted distributions but Maxent and Random Forests yielded better results for species with wider distributions. For species with small numbers of sample localities (N = 5-21), Maxent produced the most consistently successful results, followed by Random Forests and then Mahalanobis Typicalities. Because evaluation statistics for models derived from few localities can be suspect due to the poor spatial representation of the evaluation data, we corroborated these results with review by scientists familiar with the species in the field. Overall, Maxent appears to be the most capable method for modeling distributions of Andean bird and mammal species because of the consistency of results in varying conditions, although the other methods have strengths in certain situations.
This work presents an overview on the study of Si and Mg
2
Si, obtained as second phases in aluminum alloys, including their modifications due to processing conditions, alloying elements and heat ...treatments. These micrometric phases are generally studied using optical microscopy (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Although they can be differentiated combining OM and SEM, a validation study using XRD is indispensable. This work studies the peculiarities of using these techniques, and the differentiation of Si and Mg
2
Si depending on their XRD peaks, morphologies and gray scales. This review showed that the presence of other second phases complicates the identification of Si and Mg
2
Si. It also revealed that their morphological modifications have been barely studied quantitatively. We are presenting some study cases related to this topic, adding our own quantitative characterizations through the use of shape descriptors and fractal dimension, demonstrating their effectiveness and importance.
The Mexican yew (Taxus globosa) is important for the production of taxol, which is used to treat several types of cancer and its seeds undergo a latent period. The objectives of this research were to ...study the causes of seed dormancy in this species, the types of dormancy mechanisms it undergoes and how to break such dormancy. Seeds from two regions of Mexico (northern and central region) were evaluated using 12 pre-germination treatments. The treatments consisted of warm and cold stratification, applying 500 ppm of gibberellic acid (GA4/7) at different intervals, or using alternative seed scarification methods. In addition, embryo growth was studied and a protocol for in vitro embryo culture was also tested. Seeds from the central region did not germinate, probably because of inbreeding depression in seeds that came from small fragmented populations. In contrast, seeds from the northern region of Mexico subjected to warm plus cold stratification, warm plus cold stratification plus GA4/7 application, and warm stratification plus stratification with N2 plus GA4/7 application exhibited the highest germination rates (12–14 %). In vitro embryo culture indicated that only 30% of the embryos germinated. Thus, dormancy in the Mexican Yew seems to be caused by several factors, including both morphological and physiological factors.
To determine the changes in the pattern of death of patients with systemic sclerosis (SSc) throughout 20 years.
Data were collected from the Spanish Scleroderma Registry (RESCLE), retrospective ...multicentre database from 1990 to 2009. SSc-related and SSc-non related causes of death were assessed.
987 patients were recruited. Overall standardised mortality ratio (SMR) was 2.34 (2.24-2.44). SSc-related causes of death were responsible of 72% of all deaths of those patients diagnosed within 1990-99 vs. 48% within 2000-09 (p=0.006). Relative pulmonary death rate was stable over time (68.1% within 1990-99 vs. 63.9% within 2000-09, p=0.815). Relative renal death rate was decreasing over time (17% within 1990-99 vs. 5.5% within 2000-09, p=0.175). Heart distribution tripled its ratio (12.8% within 1990-99 vs. 30.6% within 2000-09, p=0.058).
SSc-related causes of death were decreasing over time and, among them, pulmonary involvement was the leading cause of death in both decades. The ratio of renal causes decreased since 1990 at the time that the ratio of cardiac causes increased.
The use of recurrence plots have been extensively used in various fields. In this work, recurrence plots investigate the changes in the non-linear behaviour of urban air pollution using large ...datasets of raw data (hourly). This analysis has not been used before to extract information from large datasets for this type of non-linear problem. Two different approaches have been used to tackle this problem. The first approach is to show results according to monitoring network. The second approach is to show the results by particle type. This analysis shows the feasibility of using recurrence analysis for pollution monitoring and control.
Although robotics has progressed to the extent that it has become relatively accessible with low-cost projects, there is still a need to create models that accurately represent the physical behavior ...of a robot. Creating a completely virtual platform allows us to test behavior algorithms such as those implemented using artificial intelligence, and additionally, it enables us to find potential problems in the physical design of the robot. The present work describes a methodology for the construction of a kinematic model and a simulation of the autonomous robot, specifically of an omni-directional wheeled robot. This paper presents the kinematic model development and its implementation using several tools. The result is a model that follows the kinematics of a triangular omni-directional mobile wheeled robot, which is then tested by using a 3D model imported from 3D Studio® and Matlab® for the simulation. The environment used for the experiment is very close to the real environment and reflects the kinematic characteristics of the robot.
SachaInchi (Plukenetiavolubilis) is a nut that has been grown in the Amazon Rainforest and the high Andes Mountains of Peru for countless centuries. The oil of this nut, natural source of omega 3, 6 ...and 9, has been recognized by its high antioxidant capacity in humans. In this work, oil from Sacha Inchi was fortified with two commercial antioxidants (Ecoprol 2020 and tocopherol) in order to prepare a fresh cheese from cow's milk. The antioxidant capacities of Sacha Inchi and commercial antioxidants were used as preservatives with the purpose to increase the shelf-life of fresh cheese besides nutritional content.The factorial method was necessary to prepare seven formulations in order to find the optimal concentration of the antioxidants added to Sacha Inchi oil and the addition of this oil to the fresh cheese.A sensory analysis was performed to choose the best formulation.The results showed that an oil formulation (F4) with tocopherol (150 mg/kg of oil) and Ecoprol2020 (1000 mg/kg of oil) displayed the lowest peroxide values (PI: 2.6 ± 0.1 meq O2/kg of oil, p < 0.001) and it was able to reduce approximately 50% of fatty acid oxidation in SachaInchi oil in relation to the PI control. Then, F4 was used to elaborate further nine formulations (F’1 –F’9), enriched with Sacha Inchi oil (1 to 4%) to prepare the fresh cheese. Microbiological analysis for all formulations were performed (limits of mold, yeasts, coliforms, salmonella, and bacteria) in order to meet the legal requirements of health and safety in Peru. The cheese taste acceptability was determined through the sensorial evaluation, which reached 7.2according to the 9-hedonic scale for F'5. Thus, an optimum fresh cheese was obtained from the formulation (F’5) with 22.5g/L of salt and 2.5% of Sacha Inchi oil enriched with 150 mg/kg of tocopherol and 1000 mg/kg of Ecoprol 2020. The cheese shelf-life was also evaluated, increasing it up from 7 days to 16 days in refrigeration.
This paper presents a novel methodology for positioning an explosive ordnance device (EOD) which consists of a mobile manipulator with 12° of freedom. The approach uses an extension of a homogeneus ...transformation graph (HTG) which can be used in the kinematic modeling of mobile manipulators and unmanned aerial vehicles. In this approach the complete kinematics is modeled as one unit in contrast to previous approaches where the manipulator and mobile body are decoupled. The system is tested in several escenarios (simulated and real experimentation) like approaching to an explosive device location on the plane as well as in slope ways, climbing stairs, lifting itself and manipulating procedures. All the aforementioned scenarios were developed using the HTG which establishes the appropriate transformations and interaction parameters of the coupled system. Finally, the system is tested (simulated and real experimentation) for positioning its end device in a target with a RMS positioning average error ofr 7.91 mm which is acceptable for this kind of devices.
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