Abstract:The generation of enormous volumes of mine-tailing waste is standard practice in the mining industry. Large quantities of these tailings are also sources of kaolinite-rich materials that accumulate in slag heaps, causing significant environmental degradation and visual impacts on the landscape. The consequences of coal refuse dumped in slagheaps calls for the study of eco-innovative solutions and the assessment of waste types. Moreover, the environmental benefits of reusing large amounts of contaminated waste are also evident. Hence, the objective of this investigation is to expand current knowledge of new siliceous-aluminium minerals and their pozzolanic activity. Four raw tailing samples are characterized to determine their chemical (by ICP/MS analysis), morphological (by SEM/EDX analysis), and mineralogical (by XRD analysis) compositions prior to their thermal activation that transforms the inert wastes at various temperatures into materials with cementitious properties. The results of XRD analysis following activation confirmed that the kaolinite content is fully transformed into metakaolinite. The coal refuse samples presented sufficiently reliable levels of pozzolanic activity for use as additives in industrial cements.
Reproductive data and analysis of recoveries in a population of white stork, Ciconia ciconia, in southern Spain: a 24-year study.-Changes in nest density and reproductive success of a free-ranging population of white stork, Ciconia ciconia, in the Gardens of ZooBotánico Jerez (Cádiz) were studied from 1990 to 2013. Reproductive data (number of nests and number of chicks per nest) and the effect of rainfall on the reproductive success were analyzed. In addition, a number of chicks were colour-ringed each year and the recovery data were also analyzed. The number of nests found in the area steadily increased during the study period and varied greatly from year to year from 2001 onwards (mean 19, range = 4-35, N = 22 years). Reproductive success also varied greatly among years. Overall, the mean number of chicks per nest was 1.78 ± 1.2 (range = 0-5, N = 439 nests). Reproductive success was strongly influenced by rainfall. It was highest (1.88) in years classified as rainy, medium (1.62) in years classified as normal, and lowest (1.24) in dry years. A total of 404 white storks were ringed, 110 of which were observed a total of 308 times (2.8 + 2.8 times per bird, range 1-12, all year data pooled). Recovery data show that with one exception, all ringed birds were recorded at different habitats of S Spain throughout the year. Remarkably, none was observed at traditional wintering quarters, south of the Sahara in Africa. Juveniles remained in the area (from July to October) soon after leaving our colony, and virtually all of them disappeared from November to January (their first winter) but were recorded again during their first breeding season. On the contrary, adults were repeatedly recorded at different sites in Cádiz, Sevilla and Huelva all year round. These birds showed a strong philopatry as some of them were recorded as breeders in our colony, up to 11 years after ringing. Our data emphasize the importance of both refuse damp and wetland areas for the species, especially in winter, and a shift in the timing of the reproductive season as birds were recorded from November to July each year. Our study provides evidence of the increase in the population, a significant effect of rainfall on their reproductive success, and the non-migratory habits of adult white storks in our colony. To our knowledge, this is the first time that such long-term reproductive data for a Mediterranean population of white storks is shown.
In the present paper, we study the combined effect of thermal activation (600 °C/2 h and 750 °C/2 h) and chemical activation with 1% ZnO on the reactivity of metakaolinite (MK) obtained from natural kaolin. The phases are identified by chemical (ICP/MS), mineralogical (XRD), and morphological (SEM/EDX) characterization of all products, as well as the evolution and stability over time of the hydrated phases generated during the reaction, to determine their use as pozzolan in the manufacture of cements. The stability analysis for the kaolin/lime system activated chemically and thermally at 600 °C/2 h shows that the C-S-H gels are thermodynamically stable after one day of reaction, evolving the system to the stability field of stratlingite for the other analyzed times. At 750 °C/2 h, the thermodynamically stable reaction phases are C-S-H gels. Calcination at 600 °C/2 h and the addition of 1% ZnO are the optimal conditions for thermal and chemical activation, to improve the pozzolanic reaction and promote the replacing part of the cement for developing secondary reaction products.
The purpose of this exploratory research was to identify if there were any differences in the student's learning styles of three engineering academic programs from daytime and evening classes. The motivation aroused from the observation that the academic performance of these two populations, in response to equally demanding academic programs, was equivalent, despite having far less demanding requirements for the acceptance in the evening class program. The results of this research showed no relevant differences in the learning styles of the students of the two programs, giving rise to more questions than answers, mainly regarding the motivations of the evening class students and the academic requirements for the acceptance in a tertiary institution.
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