Pre-Caving, Drilling and Blasting in the Esmeralda Sector of the El Teniente Mine

El Teniente Mine has developed the method of panel caving as an innovative pre-conditioning caving alternative for traditional mining of sectors located in primary rock. In applying this method, caving speed and area incorporation are the most relevant parameters to establish a desired production level in a specified sector. This is the context in which continuous improvements to several design alternatives have been developed and applied to optimize mine caving. Mine caving, by drilling and blasting, results in a narrow base cut of ore columns not larger than the height of the caving galleries, which usually measure 3.6 m. These confined blasting operations require drilling parallel blastholes that extend from the floor to the roof of the caving gallery. Panel caving aims at mitigating subvertical field stress transmission to the lower levels of the caving gallery. This improves the stability and helps maintain the advancement of the caved zone at the caving level, with respect to the development, preparation and ore mining activities in the production level. This paper analyzes and evaluates different panel caving alternatives. The result is the identification of the most adequate panel caving alternative for conditions in the Esmeralda Mine given safety, technical, operational and economic considerations.     

Life after death: shallow‐water Mediterranean invertebrate communities associated with mammal bones

Invertebrate and microbial marine communities associated with mammal bones are interesting and poorly understood habitats, mainly known from studies on deep‐water whale remains. In order to characterize these communities in the shallow‐water Mediterranean, we present here the results of a pioneering experiment using mammal bones. Minke whale, pig and cow bones were experimentally deployed on three different background communities: rocky substrate, soft‐bottom and a Posidonia oceanica meadow. Bones were deployed for a year at about 20 m depth and collected every 3 months, and the invertebrate fauna colonizing the bones was identified to the lowest possible taxonomic level. As expected, mammal bones showed remarkable differences when compared with background communities. Within bones, four different clusters could be identified, primarily on the basis of the polychaete fauna, the most abundant and diverse group in the survey. Clusters A1–A3 corresponded to high to moderately altered successional stages composed by a fauna closer to that of anthropogenically enriched shallow‐water environments. These clusters were characterized by the occurrence of the opportunist polychaetes Ophryotrocha puerilis, Neanthes caudata (Cluster A1), Protodorvillea kefersteini (Cluster A2) and Ophryotrocha alborana (Cluster A3). Cluster B was characterized by the presence of the polychaete Oxydromus pallidus together with typical invertebrate background fauna, which suggests that this community, after a year of deployment, was closer to that found in natural conditions. As opposed to similar shallow‐water studies in other geographic areas, no occurrence of the polychaete Osedax (commonly known as bone‐eating worms) was reported from our experiments. Apart from the study on the invertebrate communities, insights about the population dynamics of three of the most abundant species (O. puerilis, O. alborana, N. caudata) are given as well as remarks on a hypothetical trophic network based on fecal pellet analysis.     

A length-biased version of the Birnbaum-Saunders distribution with application in water quality

In this article, we develop a new model based on the Birnbaum-Saunders distribution that results to be both useful and practical for environmental sciences. The density, distribution and hazard functions, moments and properties of this new model are presented. A graphical analysis of the density is also provided. Furthermore, we estimate parameters, propose asymptotic inference and discuss influence diagnostics by using likelihood methods for the new distribution. An illustrative example with real data related to water quality indicates the adequacy on the new distribution.     

20 years of mass balances on the Piloto glacier, Las Cuevas river basin, Mendoza, Argentina

Climatic changes of the 20th century have altered the water cycle in the Andean basins of central Argentina. The most visible change is seen in the mountain glaciers, with loss of part of their mass due to decreasing thickness and a substantial recession in the last 100 years. This paper briefly describes the results of glacier mass balance research since 1979 in the Piloto Glacier at the Cajón del Rubio, in the headwaters of Las Cuevas River, presenting new results for the period 1997–2003. Very large interannual variability of net annual specific balance is evident, due largely to variations in winter snow accumulation, with a maximum net annual value of + 151 cm w.e. and a minimum value of - 230 cm w.e. Wet El Niño years are normally associated with positive net annual balances, while dry La Niña years generally result in negative balances. Within the 24-year period, 67% of the years show negative net annual specific balances, with a cumulative mass balance loss of - 10.50 m water equivalent (w.e.). Except for exceptions normally related to El Niño events, a general decreasing trend of winter snow accumulation is evident in the record, particularly after 1992, which has a strong effect in the overall negative mass balance values. The glacier contribution to Las Cuevas River runoff is analysed based on the Punta de Vacas River gauge station for a hypothetical year without snow precipitation (YWSP), when the snowmelt component is zero. Extremely dry years similar to a YWSP have occurred in 1968–1969, 1969–1970 and 1996–1997. The Punta de Vacas gauge station is located 62 km downstream from Piloto Glacier, and the basin contains 3.0% of uncovered glacier ice and 3.7% of debris-covered ice. The total glacier contribution to Las Cuevas River discharge is calculated as 82 ± 8% during extremely dry years. If glacier wastage continues at the present trend as observed during the last 2 decades, it will severely affect the water resources in the arid central Andes of Argentina.     

An extended Birnbaum–Saunders model and its application in the study of environmental quality in Santiago, Chile

In this article, we introduce, characterize and apply an extended version of the Birnbaum–Saunders model based on the Mudolkar–Hutson skew distribution. This model is appropriated for describing phenomena involving accumulation of some type, as is the case of environmental contamination. Specifically, we find the density, distribution function, and moments of the new model. In addition, we derive several properties and transformations related to this distribution. Furthermore, we propose an estimation method for the parameters of the model. Moreover, we conduct a study of its hazard rate focuses in environmental analysis. A computational implementation in R language of the obtained results is discussed. Finally, we present two examples with real data from environmental quality in Chile that illustrate the proposed methodology.     

Characterisation of aerosol from Santiago,Chile: an integrated PIXE–SEM–EDX study

Santiago de Chile is a big city with huge air quality problems, being one of the most polluted cities in the world. This is aggravated during winter by the topography and meteorological conditions of the city. Although public policies have been developed to minimise the atmospheric aerosol pollution, there is a lack of adequate knowledge and poor characterisation of these aerosols (in its PM_2.5 and PM₁₀ fractions). In this study we sampled atmospheric particles during winter in two distinct areas of Santiago: downtown (Teatinos Street) and in a more residential area (Macul). Major (Si, Al, Fe, Ca and K) and some trace element (S, Cl, Ti, P, Cr, Cu and Zn) compositions were obtained by proton-induced X-ray emission (PIXE). Morphological, type and chemical characterisation was also performed using scanning electron microscopy (SEM) coupled with an energy dispersive X-ray microanalysis system (SEM–EDX). Besides the carbon particles, the contribution of which can be quite important in the atmospheric aerosol, especially in downtown, unambiguously lithogenic (i.e. of geological origin) particles and elements are the second highest contributors. Enrichment factor calculation, together with particle identification and element correlation allow the origin of some elements and particles to be traced, revealing anthropogenic origins for some of them that are specific to the Santiago area.     

Fast Periodic Transfer Orbits in the Sun–Earth–Moon Quasi-Bicircular Problem

Starting from the identification and classification of a family of fast periodic transfer orbits in the Earth–Moon planar circular Restricted Three Body Problem (RTBP), and using analytic continuation techniques, we find two unstable periodic orbits in the Sun–Earth–Moon Quasi-Bicircular Problem (QBCP). The orbits found perform periodic Earth–Moon transfers with a period of approximately 29.5 days.     

Extreme value Birnbaum–Saunders regression models applied to environmental data

Extreme value models are widely used in different areas. The Birnbaum–Saunders distribution is receiving considerable attention due to its physical arguments and its good properties. We propose a methodology based on extreme value Birnbaum–Saunders regression models, which includes model formulation, estimation, inference and checking. We further conduct a simulation study for evaluating its performance. A statistical analysis with real-world extreme value environmental data using the methodology is provided as illustration.