Electron delocalization in planar metallacycles : Hückel or Möbius aromatic?

In this work the relationship between the formal number of π-electrons, d-orbital conjugation topology, π-electron delocalization and aromaticity in d-block metallacycles is investigated in the context of recent findings concerning the correlation of π-HOMO topology and the magnetic aromaticity indices in these species. It is demonstrated that for π-electron rich d-metallacycles the direct link between aromaticity, the number of π-electrons and the frontier π-orbital topology does not strictly hold and for such systems it is very difficult to unambiguously associate their aromaticity with the '4n+2' (Hückel) and '4n' (Möbius) rules. It is also shown that the recently proposed electron density of delocalized bonds (EDDB) method can successfully be used not only to quantify and visualize aromaticity in such difficult cases, but also - in contrast to magnetic aromaticity descriptors - to provide a great deal of information on the real role of d-orbitals in metallacycles without the ambiguity of bookkeeping of electrons in the π-subsystem of the molecular ring. Interestingly, some of the metallacycles studied cannot be classified exclusively as Hückel or Möbius because they have a hybrid Hückel-Möbius or even quasi-aromatic natur

Thrust belts of the southern Central Andes: Along-strike variations in shortening, topography, crustal geometry, and denudation

The Andean fold-and-thrust belts of westcentral Argentina (33 S and 36 S), above the normal subduction segment, present important along-strike variations in mean topographic uplift, structural elevation, amount and rate of shortening, and crustal root geometry. To analyze the controlling factors of these latitudinal changes, we compare these parameters and the chronology of deformation along 11 balanced crustal cross sections across the thrust belts between 70 W and 69 W, where the majority of the uppercrustal deformation is concentrated, and reconstruct the Moho geometry along the transects. We propose two models of crustal deformation: a 33 40 S model, where the locus of upper-crustal shortening is aligned with respect to the maximum crustal thickness, and a 35 40 S model, where the uppercrustal shortening is uncoupled from the lower-crustal deformation and thickening. This degree of coupling between brittle upper crust and ductile lower crust deformation has strong influence on mean topographic ele vation. In the northern sector of the study area, an initial thick and felsic crust favors the coupling model, while in the southern sector, a thin and mafic lower crust allows the uncoupling model. Our results indicate that interplate dynamics may control the overall pattern of tectonic shortening; however, local variations in mean topographic elevation, deformation styles, and crustal root geometry are not fully explained and are more likely to be due to upper-plate lithospheric strength variations.Fil: Giambiagi, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Mescua, Jose Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Bechis, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Diversidad Cultural y Procesos de Cambio. Universidad Nacional de Río Negro. Instituto de Investigaciones en Diversidad Cultural y Procesos de Cambio; ArgentinaFil: Tassara Oddo, Andres Humberto. Universidad de Concepción; ChileFil: Hoke, Gregory D.. Syracuse University; Estados Unido

Sedimentologic and stratigraphic evolution of the Cacheuta basin: Constraints on the development of the Miocene retroarc foreland basin, south-central Andes

Retroarc foreland basins in contractional arc settings contain evidence of temporal and spatial variations in magmatic activity, deformation, and exhumation along the continental margin and serve as excellent recorders of subduction dynamics through time. The Cacheuta basin, northwestern Mendoza Province, Argentina, is situated within the transition zone between the Pampean flat-slab subduction segment north of 33°S and the normal-dipping slab segment of the Southern Volcanic Zone to the south, and it records a detailed history of Andean orogenic exhumation at this latitude. The integration of sedimentologic, stratigraphic, geochronologic, and sediment provenance data from the Cacheuta basin constrains orogenic exhumation patterns and basin evolution during basin development. Cacheuta basin strata record at least a 12 m.y. period of basin evolution (ca. 20 Ma to younger than 7.5 Ma), based on new geochronology. The timing of initial basin subsidence is constrained by the lowermost sample in the Mariño Formation, which yielded a maximum depositional age of 19.2 ± 0.26 Ma, ∼4 m.y. earlier than previous interpretations. Conglomerate clast counts, thin section petrography, and detrital zircon analyses, coupled with distinct sedimentologic variations, record progressive orogenic exhumation of the Cordillera Principal, Cordillera Frontal, and Precordillera during early to middle Miocene time. Examination of basinal strata demonstrate that uplift of the Cordillera Principal, Cordillera Frontal, and Precordillera, and simultaneous development of the Cacheuta retroarc foreland basin, in the early to mid-Miocene was the result of contractional deformation and crustal thickening during normal subduction-related orogenic processes and did not result from the development of the flat slab in late Miocene time.Fil: Buelow, E. K.. University of Wisconsin; Estados UnidosFil: Suriano, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Mahoney, J. B.. University of Wisconsin; Estados UnidosFil: Kimbrough, D. L.. San Diego State University; Estados UnidosFil: Mescua, Jose Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Giambiagi, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Hoke, Gregory D.. Syracuse University; Estados Unido

Detrital Thermochronology Reveals Major Middle Miocene Exhumation of the Eastern Flank ofthe Andes That Predates the PampeanFlat Slab (33°–33.5°S)

The Cordón del Plata and Cordón del Portillo (32.6°?33.8°S) are the portions of the FrontalCordillera that straddle the transition zone between the Pampean flat‐slab subduction segment to thenorth and the normal subduction segment to the south. A complete understanding of how the FrontalCordillera developed is necessary in order to evaluate different tectonic models for the Andes along withtheir relation to subduction dynamics and contractional upper‐crustal deformation. Detrital apatite fissiontrack thermochronology of modern river sediments that drain the eastern and western slopes of theCordón del Plata and the northern Cordón del Portillo provides constraints on regional exhumationhistories. AFT data from each catchment typically contain multiple age peaks, but all have a prominent15.3?17 Ma age peak. One catchment, the Las Tunas River has a unimodal distribution at 17.0 ± 1.1 Ma, with a confined track length distribution indicative of rapid cooling at that time. These results, combined with provenance analysis in the adjacent Cacheuta Basin, indicate significant early to middle Miocene (~16 Ma) exhumation in the Cordón del Plata and the northern sector of the Cordón del Portillo. Exhumation related to rock uplift occurred prior to the ~11 Ma onset of a flat slab eometry at these latitudes, but immediately after the main east vergent contractional event in the adjacent Principal Cordillera. Such Frontal Cordillera exhumation fits in an eastward, youngest to the foreland sequence of deformation of the different morphostructural Andean units at ~33°?34°S, arguing against the recently proposed west vergent orogenic system at these latitudes.Fil: Lossada, Ana Clara. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; ArgentinaFil: Hoke, Gregory D.. Syracuse University. College Of Arts And Sciences. Department Of Earth Sciences; Estados UnidosFil: Giambiagi, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Fitzgerald, P. G.. Syracuse University. College Of Arts And Sciences. Department Of Earth Sciences; Estados UnidosFil: Mescua, Jose Francisco. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Suriano, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Aguilar, A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin

Accurate identification of atypical Staphylococcus chromogenes plasma-clotting strains causing bovine mastitis.

ABSTRACT - We compared the potential of routine techniques used for the identification of Staphylococcus species, aiming to evaluate their accuracy in the detection of 43 Staphylococcus chromogenes strains isolated from bovine mastitis that, despite being a coagulase-negative species, are able to clot plasma. These strains could be mistakenly suspected to be S. aureus and lead to an unappropriated treatment of the disease. MALDI-TOF, PCR-RFLP of the chaperonine gene groEL, and sequencing of the 16S rRNA and elongation factor Tu gene tuf were employed. Results from the four methods were coincident for only half of the strains because of the low accuracy of the groEL PCR-RFLP (51.2% accuracy). Even though all the sequencing results were identical, the high accuracy of the MALDI-TOF results (97.7% accuracy, with only one strain misidentified) encourage the use of this technique, since it does not require laborious sample preparation, being fast and simple to perform. RESUMO - Nós comparamos o potencial de técnicas rotineiras utilizadas para a identificação de espécies de Staphylococcus, com o objetivo de avaliar a acurácia delas na detecção de 43 isolados de Staphylococcus chromogenes envolvidos com mastite bovina que, apesar de ser uma espécie coagulase-negativa, são capazes de coagular o plasma. Essas cepas poderiam ser erroneamente suspeitas de serem S. aureus e levarem a um tratamento não adequado da doença. MALDI-TOF, PCR-RFLP do gene da chaperonina groEL e sequenciamento do gene do rRNA 16S e do gene do fator de elongação Tu, tuf, foram avaliados. Os resultados dos quatro métodos foram coincidentes para apenas metade das cepas, devido à baixa precisão da PCR-RFLP com groEL (51,2% de acurácia). Apesar de todos os resultados do sequenciamento serem idênticos, a alta precisão dos resultados do MALDI-TOF (97,7% de acurácia, com apenas uma cepa identificada incorretamente) encoraja o uso dessa técnica, pois, não requer preparação laboriosa de amostras, sendo rápida e simples de executar.Made available in DSpace on 2019-12-30T18:13:34Z (GMT). No. of bitstreams: 1 CiRuralLangeAccurate.pdf: 877367 bytes, checksum: 11a9ad9344b2a3ea9d23d91cc8175974 (MD5) Previous issue date: 201

Reactivation of Paleozoic structures during Cenozoic deformation in the Cordón del Plata and Southern Precordillera ranges (Mendoza, Argentina)

The tectonic style of the eastern morphostructural units of the Central Andes between 32°20´ and 33°20´S is strongly influenced by pre- Andean structures, especially those developed during the late Carboniferous-Early Permian San Rafael orogeny of the Gondwanan orogenic cycle. Moreover, in the study area pre-Carboniferous rocks were deformed in Late Devonian-early Carboniferous times by the Chanic orog­eny. In this paper we argue that the Cordón del Plata and the Southern Precordillera ranges, first order features of the eastern ranges of the Andes, have been shaped in large part by the Permian event. Our data suggest that the double verging character of the Andean Precordillera fold- thrust belt is mainly the result of the reactivation of Gondwanan structures which conform a fold-thrust belt with distinct characteristics north and south of 33°S. The northern sector of this belt corresponds to a bivergent system, while the southern sector had a widespread east vergence. The vergence of the Chanic structures is more difficult to determine, but we infer a westward vergence in the Frontal Cordillera and western sector of Precordillera, and an eastern vergence in the eastern sector of the Precordillera. The sharp disappearance of the Precordillera morphostructural unit south of 33°S is inferred here to be related to the distribution of inherited Permian structures.El estilo tectónico del sector oriental de las unidades morfoestructurales de los Andes Centrales entre los 32°20´y 33°20´S se encuentra fuertemente influenciado por estructuras pre-andinas, especialmente aquellas desarrolladas durante el Carbonífero superior-Pérmico Inferior y asociadas al orógeno San Rafael del ciclo orogénico Gondwánico. Además, en el área de estudio, las rocas pre-carboníferas se deformaron durante el Devónico Superior y Carbonífero inferior, en relación con la orogenia Chánica. En este trabajo discutimos los rasgos de primer orden del sector oriental de los Andes, que comprende al Cordón del Plata y a la Precordillera Austral, fueron en gran parte modelados a partir del evento pérmico. Nuestros datos sugieren que la doble vergencia de una faja plegada y corrida en la Precordillera Andina es el resultado principalmente de la reactivación de estructuras gondwánicas que conformaron una faja plegada y corrida con características distintivas al norte y sur de los 33°S. El sector norte de la faja corresponde a un sistema bivergente, mientras que el sector sur posee una vergencia predo­minantemente oriental. La vergencia de las estructuras chánicas es más difícil de predecir, pero se sugiere aquí una vergencia hacia el oeste para las estructuras de la Cordillera Frontal y el sector occidental de la Precordillera y otra hacia el este para las estructuras del sector oriental de la Precordillera. Se infiere que la marcada desaparición de la Precordillera como unidad morfoestructural andina al sur de los 33° está relacionada a la distribución de estructuras chánicas y gondwánicas

Orogenias paleozoicas en los Andes de Argentina y Chile y en la Península Antártica

Congreso Geológico Argentino (20º. 2017. San Miguel de Tucumán, Argentina). Simposio de Téctonica pre-andinaDurante el Neoproterozoico y Paleozoico, los Andes de Argentina y Chile, y desde fines del Paleozoico también la Península Antártica, formaron parte del margen SO de Gondwana. Durante este tiempo se acrecionaron a dicho margen varios fragmentos continentales de tamaño y aloctonía variable; denominados de N a S: Antofalla, Chi-Cu, Patagonia Occidental y Antártida Occidental. Estos fragmentos formaban parte de placas litosféricas, en ocasiones divididas en subplacas. La colisión de dichos fragmentos continentales con Gondwana y una última subducción bajo dicho margen, dieron lugar a 6 orogenias de extensión temporal y espacial limitada.Instituto Geológico y Minero de España, EspañaDepartamento de Geología, Universidad de Oviedo, EspañaUniversidad de Río Negro, ArgentinaServicio Geológico y Minero Argentino, ArgentinaInstituto De Bio y Geociencias Del NOA, Consejo Nacional de Investigaciones Científicas y Técnicas, ArgentinaInstituto De Bio y Geociencias Del NOA, Universidad Nacional de Salta, ArgentinaDepartamento de Geodinámica, Universidad del País Vasco, EspañaFacultad de Geología, Universidad de Barcelona, EspañaDepartamento de Geología, Universidad de Chile, ChileUniversidad Andrés Bello, ChileUnidad de Tectónica, Consejo Nacional de Investigaciones Científicas y Técnicas, ArgentinaFacultad de Geología, Universidad de Buenos Aires, ArgentinaÁrea de Geología, Universidad Rey Juan Carlos, EspañaUniversidad de Salta, ArgentinaInstituto de Investigación en Paleobiología y Geología, Universidad de Río Negro, ArgentinaInstituto de Investigación en Paleobiología y Geología, Consejo Nacional de Investigaciones Científicas y Técnicas, ArgentinaCentro de Investigaciones Geológicas, Universidad de La Plata, ArgentinaUniversidad de San Juan, ArgentinaPeer reviewe