Geospatial insights into the controls of microbialite formation at Laguna Negra, Argentina.

Microbialites provide a record of the interaction of microorganisms with their environment constituting a record of microbial life and environments through geologic time. Our capacity to interpret this record is limited by an incomplete understanding of the microbial, geochemical, and physical processes that influence microbialite formation and morphogenesis. The modern system Laguna Negra in Catamarca Province, Argentina contains microbialites in a zone of carbonate precipitation associated with physico-chemical gradients and variable microbial community structure, making it an ideal location to study how these processes interact to drive microbialite formation. In this study, we investigated the geospatial relationships between carbonate morphology, geochemistry, and microbial community at the macro- (decimeter) to mega- (meter) scale by combining high-resolution imagery with field observations. We mapped the distribution of carbonate morphologies and allochtonously-derived volcaniclasts and correlated these with sedimentary matrices and geochemical parameters. Our work shows that the macroscale distribution of different carbonate morphologies spatially correlates with microbial mat distributions-a result consistent with previous microscale observations. Specifically, microbialitic carbonate morphologies more commonly occur associated with microbial mats while abiotically derived carbonate morphologies were less commonly associated with microbial mats. Spatial variability in the size and abundance of mineralized structures was also observed, however, the processes controlling this variability remains unclear and likely represent a combination of microbial, geochemical, and physical processes. Likewise, the processes controlling the spatial distribution of microbial mats at Laguna Negra are also unresolved. Our results suggest that in addition to the physical drivers observed in other modern environments, variability in the spatial distribution of microbialites and other carbonate morphologies at the macro- to megascale can be controlled by microbial processes. Overall, this study provides insight into the interpretation of microbialite occurrence and distributions in the geologic record and highlights the utility of geospatial statistics to probe the controls of microbialite formation in other environments.

Mineralized microbialites as archives of environmental evolution, Laguna Negra, Catamarca Province, Argentina.

Environmental fluctuations are recorded in a variety of sedimentary archives of lacustrine depositional systems. Geochemical signals recovered from bottom sediments in closed-basin lakes are among the most sensitive paleoenvironmental indicators and are commonly used in reconstructing lake evolution. Microbialites (i.e., organosedimentary deposits accreted through microbial trapping and binding of detrital sediment or in situ mineral precipitation on organics [Palaios, 2, 1987, 241]), however, have been largely overlooked as paleoenvironmental repositories. Here, we investigate concentrically laminated mineralized microbialites from Laguna Negra, a high-altitude (4,100 m above sea level) hypersaline, closed-basin lake in northwestern Argentina, and explore the potential for recovery of environmental signals from these unique sedimentary archives. Spatial heterogeneity in hydrological regime helps define zones inside Laguna Negra, each with their own morphologically distinct microbialite type. Most notably, platey microbialites (in Zone 3A) are precipitated by evaporative concentration processes, while discoidal oncolites (in Zone 3C) are interpreted result from fluid mixing and biologically mediated nucleation. This spatial heterogeneity is reflected in petrographically distinct carbonate fabrics: micritic, botryoidal, and isopachous. Fabric type is interpreted to reflect a combination of physical and biological influences during mineralization, and paired C-isotope measurement of carbonate and organic matter supports ecological differences as a dominant control on C-isotopic evolution between zones. Laminae of Laguna Negra microbialites preserve a range of δ13 Ccarb from +5.75‰ to +18.25‰ and δ18 Ocarb from -2.04‰ to +9.28‰. Temporal trends of lower carbon and oxygen isotopic compositions suggest that the influence of CO2 degassing associated with evaporation has decreased over time. Combined, these results indicate that microbialite archives can provide data that aid in interpretation of both lake paleohydrology and paleoenvironmental change.

Impacto del intervencionismo percutaneo en lesiones complejas en el INCOR - EsSalud (imleco) / Impact of the interventionism percutaneo in complex injuries in the INCOR - EsSalud (imleco)

Objetivos: Evaluar la asociación entre la complejidad de las lesiones y los resultados angiogrßficos, eventos clínicos adversos al mes, a los 6 meses y al a±o. Métodos: Se revisaron retrospectivamente las historias clínicas de 154 pacientes que fueron sometidos a intervencionismo percutßneo coronario en el Instituto Nacional del Corazón- Hospital Guillermo Almenara Irigoyen, entre octubre del 2001 a setiembre del 2002. Se trataron 156 lesiones, de las cuales 91 eran lesiones complejas (definida como la lesión que muestra trombo, calcificación, lesión ostial, bifurcación, aneurisma, oclusión crónica o lesión en puente safeno) y 65 no complejas. Se analizaron variables clínicas, angiogrßficas y resultados de eventos adversos en el seguimiento. Resultados: La edad media de los pacientes fue de 61,7±10,2 a±os, el 83,8 por ciento correspondía al sexo masculino, 63,6 por ciento eran hipertensos y 18,8 por ciento diabéticos. El intervencionismo en lesiones complejas estuvo relacionado con mayor tasa de complicaciones periprocedimiento como fenómeno de no reflujo (71,4 por ciento, p< 0,000), compromiso de brazo colateral (39,6 por ciento, p< 0,000), disección (8,8 por ciento, p< 0,014), embolización distal ( 7,7 por ciento, p<0,02), y eventos adversos al mes de muerte (p< 0,08), muerte/IM (p<0,05), cirugía (p<0,014), muerte/IM/RM( p<0,01), muerte/IM/RM/H (p<0,004), a los 6 meses muerte(p<0,02), muerte/IM (p<0,009), muerte/IM/RM, muerte/IM/RM/H (p< 0,000) y al a±o muerte. Cirugía, muerte/IM, muerte/IM/RM y muerte/IM/RM/H (p<0,01). Conclusiones: Los pacientes con lesiones complejas presentaron una mayor tasa significativa de complicaciones periprocedimiento y eventos adversos (muerte, cirugía, Muerte/infarto, muerte/infarto/revascularización ymuerte/infarto/revascularización/rehospitalización) al mes, a los 6 meses y al a±o.

OBJECTIVES: To evaluate association between coronary lesion complexity and angiographic results, clinical events at first, sixth and twelveth month. METHODS: We retrospectively reviewed clinical charts of 154 patients who underwent coronary percutaneous intervention at the Instituto Nacional del Corazón (INCOR) - National Hospital Guillermo Almenara Irigoyen, between October 2001 and September 2002. 156 lesiones were treated, 91 of them were complex ones (defined as a lesion with thrombus, calcified, ostial lesion, bifurcation, with aneurysm, closed cronically or lesion of a vein graft) and 65 non complex lesions. Clinical, angiographic and clinical events during the foolw up were analyzed. RESULTS: Mean age was 61.7±10.2 years old, 83.8 percent were male, 63.6 per cent had hypertension and 18.8 per cent were diabetic. Intervention in complex lesions was associated with higher rate of periprocedure complications as non reflow phenomenon(71.4 per cent pï0.000), side branch compromise (39.6 per cent pï0.000), dissection (8.8 per cent pï0.014), distal embolisation (7.7 per cent pï0.02) and adverse clinical events at one month of death (pï0.08), death/MI (pï0.05), CABG (pï0.014), death/MI/CABG (pï0.01), death/MI/CABG/hospitalization (pï0.004), at six months death (pï 0.02), death/MI (pï0.009), death/MI/CABG, death/MI,CABG/ hospitalization (pï0.000 ) and death at a year as CABG/death/ MI, death/I/CABG and death/MI,CABG/hospitalization (pï0.01). CONCLUSIONS: Patients with complex lesions showed higher rate of periprocedure complications and adverse cinical events (death, CABG, death/MI, death/MI/CABG and death/MI,CABG/hospitalization) at one, 6 and 12 months.

Ring opening metathesis polymerization on non-covalently functionalized single-walled carbon nanotubes.

Norbornene polymerization has been initiated selectively on the surface of single-walled carbon nanotubes (SWNTs) via a specifically adsorbed pyrene-linked ROMP initiator, resulting in a homogeneous non-covalent poly(norbornene) coating.