RESUMEN
A neutral trialuminum complex incorporates a pentacoordinate carbon through a methylidene bridge linking the three metal atoms. The rigid electron-deficient Al3 core stabilizes the hypercoordinate carbon atom resulting in the shortest equatorial Al-C distance reported for such an Al3-(µ3-CH2) unit.
RESUMEN
A new iodide aluminum complex ({AlI(κ4-naphbam)}, 3) supported by a tetradentate amidinate ligand derived from a naphthalene-1,8-bisamidine precursor (naphbamH, 1) was obtained in quantitative yield via reaction of the corresponding methyl aluminum complex ({AlMe(κ4-naphbam)}, 2) with 1 equiv of I2 in CH2Cl2 at room temperature. Complexes 2 and 3 were tested and found to be active as catalysts for the cyclic carbonate formation from epoxides at 80 °C and 1 bar of CO2 pressure. A first series of experiments were carried out with 1.5 mol % of the alkyl complex 2 and 1.5 mol % of tetrabutylammonium iodide (TBAI) as a cocatalyst; subsequently, the reactions were carried out with 1.5 mol % of iodide complex 3 as a single-component catalyst. Compound 3 is one of the first examples of a nonzwitterionic halide single-component aluminum catalyst producing cyclic carbonates. The full catalytic cycle with characterization of all minima and transition states was characterized by quantum chemistry calculations (QCCs) using density functional theory. QCCs on the reaction mechanism support a reaction pathway based on the exchange of the iodine contained in the catalyst by 1 equiv of epoxide, with subsequent attack of I- to the epoxide moiety producing the ring opening of the epoxide. QCCs triggered new insights for the design of more active halide catalysts in future explorations of the field.
RESUMEN
Las oclusiones venosas retinales constituyen una importante causa de deterioro de la agudeza visual. Su evolución y manejo mediante fotocoagulación retinal con láser se encuentra bien documentada por importantes estudios clínicos. Actualmente se ha sumado el uso de agentes antiangiogénicos para el tratamiento de sus complicaciones, en especial del Edema macular secundario. Se analizan cuadros clínicos, complicaciones y manejo de la Oclusión de Rama Venosa Retinal y de la Oclusión de Vena Central de la Retina resaltando el uso de terapia intravítrea con Triamcinolona
The retinal vein occlusion constitute an important cause of deterioration of visual acuity. Their evolution and management through retinal photocoagulation wuith laser, is well documented by important clinical studies. At present the use of antiangiogenics agents for the treatment of its complications has been added, and especially secondary macular edema. Clinical cases are analysed as well as complications and handling of the Branch Retinal Vein Occlusion and the Central Retinal Vein occlusion. The use of Triamcinolone and Ranibizumab is highlighted
Asunto(s)
Humanos , Oclusión de la Vena Retiniana/complicaciones , Oclusión de la Vena Retiniana/diagnóstico , Oclusión de la Vena Retiniana/terapia , Triamcinolona Acetonida/uso terapéutico , Edema Macular/etiología , Inhibidores de la Angiogénesis/uso terapéutico , Fotocoagulación , Neovascularización Patológica/etiologíaRESUMEN
Haematology, blood chemistry and urine values were determined for 44 adult free-ranging plains viscachas (Lagostomus maximus; Rodentia, Chinchillidae) in their pampas habitat in central Argentina. The study animals were captured in the wild and anaesthetized with a ketamine-xylazine combination for physical examination and sampling. Blood was obtained by venipuncture of the saphenous vein. Results for many of the blood parameters fall within the reference ranges for pet chinchillas. Differentiation of white blood cells revealed a predominantly neutrophil count for plains viscachas, while chinchillas have predominantly lymphocytes. Mean values for blood urea nitrogen, creatinine, aspartate aminotransferase and sodium were higher than the upper limit of the reference range for pet chinchillas. The results of seven analytes (haematocrit, haemoglobin, glucose, blood urea nitrogen, sodium, potassium, chloride) were compared by using both a portable blood analyser (i-STAT) in the field and conventional laboratory methods. In general, correlation and agreement between the two methods were low for most parameters.