Search results for "Nitro"

Interaction between the deep fluids and the shallow groundwaters on Vulcano island (Italy)

2001

The aim of this work is to study the interactions processes between the fluids of deep origin and the shallow groundwaters of the Vulcano Porto area. During 1995, 13 well waters were sampled three times (May, July and November) and analysed for major and some minor elements (B, Br and NH4) and for dissolved gases. The close relationship of these waters with the deep magmatic source is highlighted by the composition of the dissolved gases. Furthermore, the areal distribution of dissolved species is controlled mainly by the gas fluxes from depth and by the presence of a deeper thermal aquifer. The distribution of major anomalies in the parameters measured in the groundwaters, in fact, overlap…

Spatial patterns of, and environmental controls on, soil properties at a riparianepaddock interface

2012

Abstract Riparian zones are prominent features of agricultural landscapes because they are the last point to intercept nutrients and sediments before they enter water bodies. We investigated the soil properties, nutrient dynamics and vegetation composition at the riparian–agriculture interface. Soil physicochemical and vegetation properties were spatially heterogeneous along the transition from the grazed paddock into the un-grazed and revegetated riparian zone. Soil C stocks varied considerably across the site, with values ranging from 2% in the paddock to 5% in the riparian zone. Using Bayesian model selection, a predictive model for total soil carbon was developed. By including soil mois…

Reacción aza-Michael intramolecular organocatalítica sobre enonas y derivados de ácido: nuevas estrategias

2016

Una de les metodologies més importants, junt amb la reacció de Mannich, per la formació d’enllaços carboni-nitrogen i per accedir a compostos b-amino carbonílics, és la reacció aza-Michael, que consisteix en l’addició conjugada d’una font de nitrogen nucleòfila a un sistema a,b-insaturat. Aquesta reacció adquireix una especial rellevància a la seua versió intramolecular ja que condueix a la formació d’heterocicles nitrogenats de forma senzilla. A més, quan l’olefina activada conté centres proquirals, al procés d’addició es generen un o més centres estereogènics, pel que la versió asimètrica d’esta reacció permetria obtenir compostos nitrogenats funcionalitats de forma estereoselectiva. Ment…

Nuevas estrategias en la síntesis de compuestos de interés biológico: Estructuras terfenílicas y heterociclos nitrogenados fluorados enantioméricamen…

2015

Actualmente, el descubrimiento y desarrollo de nuevos fármacos es un proceso lento y económicamente exigente. En los últimos 10 años, los gastos económicos destinados al descubrimiento de nuevos compuestos se han triplicado, mientras que el número de nuevas entidades moleculares (NMEs) se ha mantenido invariable en los últimos 50 años. Es por esta razón que la búsqueda de nuevas estructuras que posean una relevante actividad terapéutica permanece como objetivo primordial en química farmacéutica. Por otra parte, la incorporación de átomos de flúor ha demostrado ser un método eficaz para alterar las propiedades biológicas, de las moléculas, incrementando la estabilidad del compuesto sin alter…

Organocatalytic approach to benzofused nitrogen-containing heterocycles: enantioselective total synthesis of (+)-angustureine.

2008

Photocatalytic degradation of nitrophenols in aqueous titanium dioxide dispersion

1991

Abstract The results are reported of an investigation into the photodegradation of nitrophenol isomers carried out in aqueous titania (anatase) dispersions under various experimental conditions. We investigated the influence of various parameters on the photodegradation rate, such as the concentrations of the catalyst, dissolved oxygen and organic compound, and the presence of various anions in the dispersion. A plausible explanation is proposed for the influence of these parameters, both mechanistic and kinetic factors being accounted for. Gas chromatography and mass spectrometry were used as analytical methods in order to determine intermediate products. Spectroscopic methods (UV-vis and …

Side‐on Coordination in Isostructural Nitrous Oxide and Carbon Dioxide Complexes of Nickel

2021

Abstract A nickel complex incorporating an N2O ligand with a rare η2‐N,N′‐coordination mode was isolated and characterized by X‐ray crystallography, as well as by IR and solid‐state NMR spectroscopy augmented by 15N‐labeling experiments. The isoelectronic nickel CO2 complex reported for comparison features a very similar solid‐state structure. Computational studies revealed that η2‐N2O binds to nickel slightly stronger than η2‐CO2 in this case, and comparably to or slightly stronger than η2‐CO2 to transition metals in general. Comparable transition‐state energies for the formation of isomeric η2‐N,N′‐ and η2‐N,O‐complexes, and a negligible activation barrier for the decomposition of the lat…

Complexes of Glycolic Acid with Nitrogen Isolated in Argon Matrices. I. Structures and Thermal Effects.

2019

Molecular complexes between glycolic acid and nitrogen were studied in a low-temperature argon matrix with FTIR spectroscopy, and supported by MP2 and BLYPD3 calculations. The calculations indicate 11 and 10 stable complex structures at the MP2 and BLYPD3 levels of theories, respectively. However, only one hydrogen-bonded complex structure involving the most stable SSC conformer of glycolic acid was found experimentally, where the nitrogen molecule is bound with the carboxylic OH group of the SSC conformer. The complex shows a rich site structure variation upon deposition of the matrix in different temperatures and upon annealing experiments, which provide interesting prospects for site-sel…

The trophic structure of a fish assemblage in a non-tidal Mediterranean Lagoon: integrating data from the Fishbase information system with results fr…

2010

NG-monomethyl-L-arginine and NG-nitro-L-arginine inhibit endothelium-dependent relaxations in human isolated omental arteries.

1991

Abstract The L-arginine analogues NG-monomethyl-l-arginine (l-NMMA, 10−4  m) and NG-nitro-L-arginine methyl ester (l-NAME, 10−4  m), which specifically inhibit the synthesis of nitric oxide from l-arginine, significantly reduced acetylcholine-induced endothelium-dependent relaxations in rings of human omental arteries. The inhibitory potency of l-NMMA and l-NAME was similar. Addition of l-NMMA or l-NAME to the organ bath did not induce any significant changes in the resting tension of the tissues. The effects of l-NMMA were reversed by l-arginine (3 × 10−4  m). The l-NMMA enantiomer, d-NMMA (10−4  m), did not influence either the basal tone of the preparation or the relaxing effects of acet…