Identification and yields of 1,4-hydroxynitrates formed from the reactions of C8-C16 n-alkanes with OH radicals in the presence of NO(x).

A series of C8-C16 n-alkanes were reacted with OH radicals in the presence of NOx in an environmental chamber and particulate 1,4-hydroxynitrate reaction products were collected by filtration, extracted, and analyzed by high-performance liquid chromatography with UV absorption and electron ionization mass spectrometry (HPLC/UV/MS). Observed mass spectral patterns can be explained by using proposed ion fragmentation mechanisms, permitting the identification of each hydroxynitrate isomer. Reversed-phase retention of these compounds was dictated by the length of the longer of two alkyl chains attached to the 1,4-hydroxynitrate subunit. 1,4-Hydroxynitrates were quantified in particles using an authentic analytical standard for calibration, and the results were combined with gas chromatography measurements of the n-alkanes to determine the molar yields. Yields based on analyses of particles increased with increasing carbon number from 0.00 for C8 to an average plateau value of 0.130 ± 0.008 for C14-C16, due primarily to corresponding increases in gas-to-particle partitioning. The value at the plateau, where essentially all 1,4-hydroxynitrates were in particles, was equal to the average total yield of C14-C16 1,4-hydroxynitrates. The average branching ratio for the formation of C14-C16 1,4-hydroxynitrates from the reaction of NO with the corresponding 1,4-hydroxyperoxy radicals was 0.184 ± 0.011. This value is ∼20% higher than the plateau value of 0.15 for reactions of secondary 1,2-hydroxyperoxy radicals and ∼40% lower than the plateau value of 0.29 for reactions of secondary alkyl peroxy radicals, both of which were reported previously. The branching ratios determined here were used with values reported previously to calculate the yields of C7-C18 alkyl nitrates, 1,4-hydroxynitrates, and 1,4-hydroxycarbonyls, the three products formed from the reactions of these n-alkanes.

Reducing NO(x) emissions from a nitric acid plant of domestic petrochemical complex: enhanced conversion in conventional radial-flow reactor of selective catalytic reduction process.

The nitric acid plant of a domestic petrochemical complex is designed to annually produce 56,400 metric tons (based on 100% nitric acid). In the present work, radial-flow spherical bed reactor (RFSBR) for selective catalytic reduction of nitric oxides (NO(x)) from the stack of this plant was modelled and compared with the conventional radial-flow reactor (CRFR). Moreover, the proficiency of a radial-flow (water or nitrogen) membrane reactor was also compared with the CRFR which was found to be inefficient at identical process conditions. In the RFSBR, the space between the two concentric spheres is filled by a catalyst. A mathematical model, including conservation of mass has been developed to investigate the performance of the configurations. The model was checked against the CRFR in a nitric acid plant located at the domestic petrochemical complex. A good agreement was observed between the modelling results and the plant data. The effects of some important parameters such as pressure and temperature on NO(x) conversion were analysed. Results show 14% decrease in NO(x) emission annually in RFSBR compared with the CRFR, which is beneficial for the prevention of NO(x) emission, global warming and acid rain.

Refined representation of falloff curves for the reaction HO + NO2 + N2 → (HONO2, HOONO) + N2.

Experimental data for the reactions (1) HO + NO(2) (+N(2)) → HONO(2) (+N(2)) and (2) HO + NO(2) (+N(2)) → HOONO (+N(2)) near 300 K and over the pressure range 1 Torr to 320 bar are represented in terms of novel asymmetric broadening factors in falloff expressions. This analysis allows for a refined representation of the data, reproducing fine details of k = k(1) + k(2) and k(2)/k(1) and probably allows for a better extrapolation to the limiting low and high pressure rate constants than possible with symmetric broadening factors in conventional falloff expressions. The experimental data clearly show that the center broadening factor F(cent,1) is close to 0.41 and consistent with results from theoretical modeling. This value of F(cent) markedly differs from the "standard value" of 0.6, and the consequences of this difference are illustrated. Limiting rate constants of k(1,0) = [N(2)] (T/300 K)(-4.5) 3.2 × 10(-30) cm(6) molecule(-2) s(-1), k(2,0) = [N(2)] (T/300 K)(-4.5) 1.0 × 10(-31) cm(6) molecule(-2) s(-1), k(1,∞) = 2.7 × 10(-11) cm(3) molecule(-1) s(-1), and k(2,∞) = 4.8 × 10(-11) cm(3) molecule(-1) s(-1) are obtained and tested over the range 220-300 K, whereas the exponent -4.5 changes to -3.0 in k(1,0) and k(2,0) over the range 300-430 K (the values correspond to falloff curves with asymmetric broadening factors).

Facile synthesis of polyaniline "sunflowers" with arrays of oriented nanorods.

Polyaniline (PANI) "sunflowers" made of arrays of oriented nanorods were synthesized by chemical oxidative polymerization of aniline in the presence of cetyltrimethylammonium bromide (CTAB) and suitable concentration of HNO3 at about 0 degrees C (ice bath). The reaction conditions, such as the concentration of reagents and reaction temperature were systematically investigated and controlled on the preparation of PANI "sunflowers". The results also suggest that HNO3 probably plays a key role in forming PANI "sunflowers". A possible forming mechanism of the PANI nanostructures is offered.

La cascada de neurotransmisores en la función sexual -Esquema original / The neurotransmitter cascade in sexual function –original scheme

El esquema La Cascada de Neurotransmisores es un diseño original que permite comprender la serie y conjunto de Neurotransmisores que intervienen en la Respuesta Sexual Humana. El esquema ha sido empleado por el autor en la cátedra de Sexología y ha sido presentada en diversos congresos en la últimadécada. Tiene por objeto mostrar la actividad bioquímica cerebral y periférica, supra e infraespinal en la que intervienen los diversos neurotramisores en los órganos blanco que intervienen en las Fases de Deseo, Excitación y Orgasmo de la Respuesta Sexual Humana, fases que William Masters y Virginia Jonsonesquematizaron en su libro sobre La Respuesta Sexual Humana en el que consignaron los cambios físicos que se operan en el área genital y corporal en cada una de las Fases, mas no los bioquímicos que por la época en que iniciaron su trabajo en 1953 y luego publicaron en 1966 no se conocían. El objetivo del Esquema La Cascada de Neurotransmisores es el de presentar una propuesta que explique de manera coordinada en forma esquemática los diversos elementos bioquímicos que intervienen en la Respuesta Sexual, esquema de utilidad para la comprensión de la función sexual y de las disfunciones sexuales y que además tiene aplicabilidad para una nueva perspectiva de la Clasificación de las Disfunciones Sexuales.