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Quaternary deformation in the northern Chile forearc is controlled by trench parallel shortening along reactivated Mesozoic faults. Dextral strikes-slip is expressed in NW–SE striking faults of the Atacama Fault System, and reverse displacement dominates in E–W faults. This deformation results of the convergence in a concave-seaward continental margin. On September 11th, 2020, a Mw 6.3 earthquake and its subsequent aftershocks took place in the coastal region of northern Chile, revealing the reactivation of the deepest segment of a WNW–ESE striking upper plate fault. The reactivation of this fault occurred after the Mw 8.1 Iquique earthquake, and it seems to be connected to a N–S interplate locking segmentation of the plate margin, which is clearly shown by the locking pattern before the Iquique earthquake. This poses the question of how heterogeneous locking influences upper plate seismicity and how it relates to trench-parallel shortening. [ABSTRACT FROM AUTHOR]

The role of organisms in community assembly and functioning is a crucial question of community ecology. We address this issue in a particular marine coastal ecosystem at SE Pacific: although kelp forests and urchin barrens are conspicuous benthic systems in rocky habitats, only a few studies have been focused on studying their successional patterns (especially following disturbances). In this work, we present successional pathways from micro-periphyton to macro-organisms observed during a 14-month period in kelp forests and urchin barrens in the Antofagasta Peninsula, Chile. The community composition and structure showed habitat-specific successional pathways with different dominant organisms in these two communities. Likewise, during their successional trajectories, both communities showed different number of discrete temporal stages. Kelp forests displayed a longer successional pathway of 7 discrete stages, while the barren bed succession pathway was composed only of 4 stages. We argue that this difference would be due to self-organising processes. This finding may have relevant implications for conservation and monitoring, since the intensive harvest of kelp species will not only increase the dominance of urchin barrens, but it would also facilitate its own, self-determined, more efficient (with few steps) successional pattern and the consequent persistence. [ABSTRACT FROM AUTHOR]

Copyright of Polis (07176554) is the property of Polis - Revista Academica Universidad Bolivariana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aim: Cesarean section rates are increasing worldwide and Robson's classification system allows a practical approach to study this phenomenon. C‐section in Chile has been indicated as unexpectedly high, with important variability within the country and payment systems. The aim was to report our data using Robson's system and the evolution of local C‐section rate in a public hospital during a 9‐year period. Methods: Retrospective analysis (2005–April 2014), in a metropolitan hospital in Santiago. All deliveries were classified into Robson groups. Time changes were analyzed with Pearson's correlation. P value <0.05 was considered significant. A 'relevance index' (RI) for each group was calculated as 100 × C‐S rate × relative contribution. Results: The overall C‐section rate increased from 24 to 27% (P < 0.05) in 53 571 deliveries, with a greater increase in groups 1 (nulliparous, single, term cephalic, spontaneous labor), 3 (multiparous, single, no previous C‐S, term cephalic, spontaneous labor) and 4 (multiparous, single, no previous C‐S, term cephalic, induced or no labor). Despite no increase in Group 5 (women with one or more previous C‐S) this group had the highest RI (20.3), which defined priority for intervention over others. Conclusion: C‐S rate was lower than that reported in other centers from Chile and Latin America. Robson's classification and the RI allowed prioritization. Although increase in groups 1, 3 and 4, group 5 needs attention because of stronger impact on overall C‐S rate. This analysis allowed to define how to lower C‐S rate in our institution. [ABSTRACT FROM AUTHOR]

Water rights demand and supply in the upper Maipo river basin (Metropolitan Region of Chile) are estimated for the period July 1998 to June 2003, as well as a reduced form model for the equilibrium water rights price based on supply and demand determinants, as well as characteristics of the participating agents such as the economic sector of each agent and their individual market experience. Results show that the main participants in the market are both agriculture and real estate sectors (developers); agriculture buying 57 % and selling 68 % of transactions. The estimated supply and demand system shows that market forces indeed drive market water right prices. Demand is inelastic to price while supply is highly elastic. Furthermore, supplied and demanded water rights quantities are functions of water right price as well as the economic sector of buyer and sellers, sectoral profits, and geographic location of the water right. Additionally, the agent's previous water rights market-experience is an important determinant of water rights demands and supply. [ABSTRACT FROM AUTHOR]

Old-growth forests present a mosaic of different conditions resulting from the natural forest structure of the stands. Nothofagus betuloides forests have high spatial variability in regeneration without a clear correlation with overstory, and could be related to location of the stands in the landscape. The objective was to evaluate the influence of macro- and micro-variables over regeneration dynamics in old-growth N. betuloides forests, considering the effect of landscape (altitude and influence of the sea) and microenvironment conditions in the forest floor (closeness to trees, pits, understory cover type and bare soil). A total of four sites and 24 stands were sampled including forest structure, regeneration, understory cover and microclimate variables. Macro- (landscape) and micro- (microenvironment conditions in the forest floor) variables influenced over regeneration dynamics. Natural regeneration values (0.17 million ha−1 in the drier site vs. >4.52 million ha−1 in the other sites) not greatly depended on forest structure variables, but they were related to soil moisture (14% vs. 29–36% volumetric soil water content). Microenvironment conditions in the forest floor determined the recruitment as well as regeneration density, age and distribution of seedlings, whereas different soil moisture were related to each microenvironment type, generating positive (bare soil, ferns and mosses growing in turfs) or negative (mosses growing in mats, pits and proximity of the overstory trees) effects over regeneration, according to the soil moisture levels. These findings can be used to understand the functional integrity of the old-growth forest ecosystems and to propose silvicultural prescriptions to ensure regeneration recruitment and maximize growth potential in N. betuloides forests. [ABSTRACT FROM PUBLISHER]

Abstract: The inter-cohort variability in the von Bertalanffy (VB) growth parameters of common sardine (Strangomera bentincki) was analyzed for the period between 1990 and 2007. Time series of monthly length–frequency data were used to study the growth of the species. The MIX software was used to separate normal components and modal progression analysis was used to identify cohorts that have recruited each year. The VB growth parameters were estimated using nonlinear mixed-effects model (NLME) by considering that the population growth parameters have a common distribution, and that cohort-specific parameters can be treated as random effects. A model that considered L ∞ (asymptotic length) and K (growth coefficient) as random effects was the best in explaining inter-cohort changes in body growth. The growth rate during the first fast-growing period of sardine cohorts exhibited a significant change after 1998. Cohorts recruited between 1990 and 1997 showed higher growth rates than cohorts recruited from 1999 to 2006. This significant change is coincident with a colder period established in the area after 1998, and with a significant increment in the Ekman transport. Sea surface temperature anomalies explained 46.2% of the variability observed in the early growth rate of the cohorts. It is concluded that environmental conditions encountered by the cohorts during the spawning period could modulate the growth rate of common sardine year to year, but the possibility of further intrinsic factors affecting the growth dynamics of common sardine could be also important and deserve to be considered in future studies. [ABSTRACT FROM AUTHOR]

Salmonella spp. isolates obtained from healthy swine in 2008 were analyzed for antibiotic resistance phenotypes and genotypes. The resistance profiles of the 2008 isolates were compared with those of a Salmonella collection isolated from the same geographical area in 2005. The 2008 isolates consisted of strains that were 97% oxytetracycline resistant, 33.3% amoxicillin resistant, 31.8% amoxicillin- plus clavulanic acid resistant, 27.5% trimethoprim-sulfamethoxazole resistant, 17.3% streptomycin resistant, and 7.2% enrofloxacin-ciprofloxacin resistant. The presence of integrons and resistance genes and their topological association in resistant strains was assessed by PCR. The prevalence of class 1 integrons was the highest, at 46.2%, while class 2 integrons were present in 17.9% of the isolates. In strains that harboured class 1 integrons, we identified 3 different gene cassette arrangements; a single class 2 integron arrangement of dfrA1-sat1-aadA1 was found. Comparison of these results with data obtained from the 2005 isolates showed that Salmonella strains resistant to amoxicillin and amoxicillin plus clavulanic acid had clearly emerged over the span of 3 years, along with an increase in the prevalence of class 1 integrons and the acquisition of new gene cassette arrangements. These findings highlight the need for continual monitoring of regional isolates to establish more efficient vigilance programs that can address variations in resistance over short periods of time within the same geographical area. Des isolats de Salmonella spp. obtenus de porcs sains au cours en 2008 ont été analysés d’un point de vue phénotypique et génotypique relativement à la résistance aux antibiotiques . Les profils de résistance des isolats de 2008 ont été comparés à ceux d’une collection de Salmonella isolée dans la même région géographique en 2005. Des souches isolées en 2008, 97 % étaient résistantes à l’oxytétracycline, 33,3 % à l’amoxicilline, 31,8 % à l’amoxicilline-acide clavulanique, 27,5 % à la triméthoprime-sulfaméthoxazole, 17,3 % à la streptomycine et 7,2 % à l’enrofloxacine-ciprofloxacine. La présence d’intégrons et de gènes de résistance, ainsi que leur association topologique dans les souches résistantes, ont été évaluées par PCR. La prévalence des intégrons de classe 1 était la plus élevée, à 46,2 %, alors que les intégrons de classe 2 étaient présents dans 17,9 % des isolats. Chez les souches comportant des intégrons de classe 1, nous avons identifié 3 arrangements de cassettes de gènes; un seul arrangement d’intégron de classe 2 de dfrA1-sat1-aadA1a été trouvé. La comparaison de ces résultats avec les données obtenues en 2005 a montré que les souches de Salmonella résistantes à l’amoxicilline et à l’amoxicilline plus acide clavulanique ont clairement émergé au cours de ces 3 ans, parallèlement à une augmentation de la prévalence des intégrons de classe 1 et à l’acquisition de nouveaux arrangement de cassettes de gènes. Ces résultats mettent en lumière le besoin de suivre continuellement les isolats régionaux afin d’établir des programmes de vigilance plus efficaces qui pourront se pencher sur les variations de la résistance sur de courtes périodes de temps à l’intérieur d’une même zone géographique. [ABSTRACT FROM AUTHOR]

Copyright of Revista Musical Chilena is the property of Universidad de Chile and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In southern Chile, with a mild and rainy climate, high levels of heavy metals have been detected in many gold placer deposits. Many of the contaminants pose risks to human life, and consequently damage the trofic chain in this environment. The study zones selected correspond to the handicraft gold-bearing sands of Rio Gato (Los Muermos), Carelmapu and Cucao. These are all located in the X Region of “Los Lagos” in Chile. The type of methodology used in the characterization of the associated mineralization consists of testing each representative sample with a grain size distribution, statistical parameter analysis and a mineralogical analysis, using a binocular magnifying glass, a petrographic microscope, XRD and SEM/EDX. The chemical composition was defined by means of X ray fluorescence and micro-chemical analysis. The results of the study about sediments in southern Chile are presented. The major concentrations of heavy minerals are generally located in areas of dynamic river energy. In the samples, more than 70% of the heavy minerals were distributed among grain sizes corresponding to thin sand with good grain selection (meshes of 0.25–0.06 mm). The main mineral phases present in the analysed samples were gold, zircon, olivine, ilmenite, hornblende, hypersthene, hematite, garnet, chromite, chlorite, augite, amphibolitic-epidote, etc. The main heavy metals found as a result of the study were mercury, lead, cadmium, chrome, tellurium, indium, zinc, cobalt, copper, platinum, gold, etc., and as well some less common elements like cerium, praseodymium, gadolinium, neodymium, samarium and lanthanum. This research work is only a starting point for carrying out a risk probability mapping of heavy metals and the mineralogy of the Cucao, Carelmapu and Rio Gato gold-bearing sands. [ABSTRACT FROM AUTHOR]

Abstract: This contribution is focused on the study of the mineralogical changes occurring in the ceramic body after heating ceramic clays. Chile has an important local ceramic industry. Five deposits of clays with industrial applications were studied. The clays came from San Vicente de Tagua-Tagua (SVTT), Litueche (L), Las Compañías-Río Elqui (LC), La Herradura-Coquimbo (LH) and Monte Patria-Coquimbo (MP). The samples were heated to 830, 975, 1080 and 1160°C keeping at the maximum temperature for 35min. The bending strength of each ceramic body was determined at 1100°C. Mineralogical analysis of the fired samples was carried out by X-ray diffraction. The SVTT contained quartz, spinel, cristobalite, microcline, albite, anorthite, hematite and enstatite; the LC clays quartz, mullite, spinel, microcline, albite, anorthite, hematite, diopside, enstatite, illite/muscovite and talc; the LH clays quartz, cristobalite, microcline, albite, anorthite, hematite, diopside, illite and augite; the MP clays quartz, cristobalite, microcline, albite, anorthite, hematite, diopside, gehlenite, enstatite and wollastonite and the L clays quartz, microcline and mullite. The persistence of illite at at least 900°C was observed for LC and LH. SVTT and LH showed the required specifications for earthenware. The L clays were refractory clays with very low bending strength. [ABSTRACT FROM AUTHOR]