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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 225-231 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The gas-phase pyrazole elimination of N-alkyl pyrazoles has been studied using MNDO semi-empirical molecular orbital (MO) theory with complete geometry optimization of all stationary points. We found that the activation energies (Ea) of the concerted processes are around 80 kcal/mol, 25 Kcal/mol higher than experimental values. But the differences in Ea between compounds with different substituents are in good agreement with the experimental ones.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 611-619 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An MNDO study was made of the gas-phase thermal isomerization of isoxazole to explore theoretically the proposed reaction mechanism. The results showed that isoxazole isomerizes through an azirine, as an intermediate, to oxazole via a nitrile ylide or to ketenimine, with similar activation energies, and that the first step is rate limiting, in agreement with the experimental results. These results also show that isomerization to a nitrile is possible, but in this case the energy barrier is grater than the corresponding isomerization to oxazole. The MNDO study also supports a concerted process for the rate-limiting step, as reported earlier on the basis of experimental studies.
    Additional Material: 8 Ill.
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  • 3
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The standard Gibbs energies of transfer, ΔGt° from water to water-N,N-dimethylformamide mixtures for the dissociation process of several organic acids (formic, acetic, propionic, n-butyric, isobutyric, n-valeric, isovaleric, 2-methylbutyric and trimethylacetic acids) obtained from the pKa* values are discussed in terms of the extended Scaled Particle Theory from quantum mechanical calculations in order to estimate the cavity and electrostatic contributions. The residual energy term was correlated with the hydrogen bond acceptor density and the Kamlet-Taft β parameters. The main contribution to ΔGt° was due to dipolar and specific interactions.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 29 (1997), S. 155-160 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The deactivation of I(2P½) by R-OH compounds (R = H, CnH2n+1) was studied using time-resolved atomic absorption at 206.2 nm. The second-order quenching rate constants determined for H2O, CH3OH, C2H5OH, n-C3H7OH, i-C3H7OH, n-C4H9OH, i-C4H9OH, s-C4H9OH, t-C4H9OH, are respectively, 2.4 ± 0.3 × 10-12, 5.5 ± 0.8 × 10-12, 8 ± 1 × 10-12, 10 ± 1 × 10-12, 10 ± 1 × 10-12, 11.1 ± 0.9 × 10-12, 9.8 ± 0.9 × 10-12, 7.1 ± 0.7 × 10-12, and 4.1 ± 0.4× 10-12 cm3 molec-1 s-1 at room temperature. It is believed that a quasi-resonant electronic to vibrational energy transfer mechanism accounts for most of the features of the quenching process. The influence of the alkyl group and its role in the total quenching rate is also discussed. © 1997 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 635-642 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Relaxation rate constants for the collisional deactivation of I (2P1/2) by halogen cyanides were measured by time resolved atomic absorption. The values obtained were (1.2 ± 0.1) × 10-15, (5.2 ± 0.7) × 10-15, and (2.6 ± 0.4) × 10-14 cm3 molecule-1 s-1 for ClCN, BrCN, and ICN, respectively. Quenching efficiencies are discussed in view of the stability of linear molecules to form the transient complex as well as the similarities assumed between halogen cyanides and interhalogen diatomic molecules.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 24 (1992), S. 31-40 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetic measurements in the Flash Vacuum Thermolysis (FVT) of 3,5-Dimethyl- and 5-Methyl- 4-Nitroisoxazole confirm the already suggested intermediacy of the isomer 2H-Azirine in the formation of 1- Cyano-1-Nitroacetone. Moreover, theoretical calculations of the stabilization energy (Es), at the transition state, using second order perturbation suggest that this azirine is formed through the isomer furoxan rather than directly from the starting isoxazole.
    Additional Material: 5 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 30 (1998), S. 799-803 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Collisional deactivation of I(2P1/2) by the title compounds was investigated through the use of the time-resolved atomic absorption of excited iodine atoms at 206.2 nm. Rate constants for atomic spin-orbit relaxation by CH3Cl, CH2Cl2, CHCl3, CCl3F, and CCl4 are 3.1±0.3×10-13, 1.28±0.08×10-13, 5.7±0.3×10-14, 3.9±0.4×10-15, and 2.3±0.3×10-15cm3 molecule-1 s-1, respectively, at room temperature (298 K).The higher efficiency observed for relaxation by CH3Cl, CH2Cl2, and CHCl3 reveals a contribution in the deactivation process of the first overtone corresponding to the C(SINGLEBOND)H stretching of the deactivating molecule (which lies close to 7603 cm-1) as well as the number of the contributing modes and certain molecular properties such as the dipole moment. It is believed that, for these molecules, a quasi-resonant (E-v,r,t) energy transfer mechanism operates. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 799-803, 1998
    Additional Material: 1 Ill.
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  • 8
    Publication Date: 2021-05-19
    Description: En Septiembre de 1972 se hicieron observaciones oceanográficas a lo largo de la costa Colombiana en el Mar Caribe, como parte de la contribución nacional al programa CICAR, utilizando el B /O ARC San Andrés de la Armada de Colombia. Este trabajo analiza la distribución superficial de las propiedades físicas del agua de mar durante el verano, en el área adyacente a la Península Colombiana de la Guajira entre los meridianos 71 - 75 0 W y la sección vertical que corta la zona de surgencia. Se observaron anomalías en las distribuciones superficiales de temperatura, salinidad y densidad en las proximidades de la costa de la Guajira cerca del meridiano 72°W, encontrándose en esta región aguas de baja temperatura (Tz 25, 50° C) asociadas con altas salinidades (S〉 36,50%) Fue posible determinar que tales anomalías se deben a movimientos ascendentes, calculándose su intensidad, por medio de un modelo matemático, en aproximadamente 114 m /mes. La continuidad de los movimientos ascendentes fue confirmada por la existencia de corrientes de deriva, que transportan las aguas que afloran hacia el NW y el W, extendiendo su influencia a lo largo de la costa Colombiana.
    Description: Oceanographical observations were made along the Colombian coast,in the Caribbean Sea, aboard the R /V ARC San Andres of the Colombian Navy, in September 1972, as pant of the national contribution to CICAR program. This paper analiza the surface sea water physical properties distribution off the Colombian Guajira Peninsula between meridians 71°-75° W and the vertical section crossing the upwelling main area during summer time. Anomalies in the surface distribution of temperature, salinity and density near La Guajira coast, in the vicinity of 72cW were observed; waters with low temperatures (T=25.50 °C) associated with high salinities (S〉36,50 %) were recorded in this region. lt has been possible to determine that these anomalies are due to upward motiones, the intensity of which was calculated by means of a mathematical Model, to be about 11 4 m/ - month. The continuity of the up ward motions was confirmed by the currence of drift currents, which made transport of "upwelled" waters to NW and W, extending its influence along the Colombian coast.
    Description: Published
    Keywords: Temperatura ; Salinidad ; Corriente oceánica ; ASFA_2015::P::Physical oceanography ; ASFA_2015::D::Dynamical oceanography
    Repository Name: AquaDocs
    Type: Journal Contribution , Not Known
    Format: Pp.7-19
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  • 9
    Publication Date: 2021-05-19
    Description: Durante los años 2005 y 2006 se continuaron realizando muestreos a tanques de lastre de buques de tráfico internacional que arribaron a la Bahía de Cartagena, la cual está ubicada en el sector sur occidental de la costa Caribe colombiana y localizada entre los 75º30'-75º36'W y 10º26'-10º16'N. Este trabajo se realizó con el objetivo de seguir evaluando si la gestión a bordo de los taques de lastre, se efectuó de acuerdo con las directrices emitidas por la Organización Marítima Internacional (OMI), a fin de reducir el riesgo de introducción de especies en las zonas costeras. Para lograr el objetivo se tomaron muestras de aguas de lastre de 75 buques procedentes de diferentes puertos internacionales, a través de los manholes, de las descargas directas al mar, del deslastre en cubierta o de las tuberías de acceso a los tanques. Dichas muestras de aguas fueron procesadas en el laboratorio, caracterizándose en cada una de ellas las condiciones fisicoquímicas como nutrientes, oxígeno disuelto, temperatura, salinidad, pH, turbidez, sólidos suspendidos totales; biológicas como fitoplancton, zooplancton, concentración de pigmentos fotosintéticos y microbiológicas como Enterococos intestinales, Salmonella sp., Shiguella sp., Psedumonas sp., Coliformes totales, Escherichia coli, hongos. Al igual que en las caracterizaciones anteriores de los años 2002, 2003 y 2004 en este mismo puerto, en este estudio se continuaron reportando condiciones ambientales adecuadas para el sostenimiento de comunidades biológicas dentro de los tanques. También se siguieron reportando nuevas especies planctónicas entre las cuales se pueden mencionar a Oithona setigera, Oithona hegolandica, Microstella sp., Diartrodes sp., Oculosetella sp., Corystoide chilensi, Parapagurus Diógenes y Sagitta minima. Además fue posible evidenciar que según el convenio sobre manejo de aguas y sedimentos de lastre generado por la OMI en el 2004, el 29% de las embarcaciones monitoreadas sobrepasaron los niveles permisibles de descarga con respecto al microbio indicador Escherichia coli y el 11% de Enterococos Intestinales.
    Description: During the years 2005 and 2006 the sampling to those international traffic ships ballast water which arrived in the Bay of Cartagena, located at the southwestern Caribbean Colombia Zone and between 75o30'- 75o36W and 10o26'-10o16N, continued. This work was carried out with the objective of continuing the assessment on if whether work on board the ballast tanks, was carried out according to the guidelines issued by the International Maritime Organization (IMO), in order to diminish the risk of species introduction in the shore zones. The achieve the objectives, samples of ballast water of 75 ships coming from different international ports were taken, through the manholes, from the direct discharges to the sea, from the deck disballast or from the tank access pipelines. Those water samples were processed in the laboratory, where in each one of them the physical-chemical conditions were characterized, such as nutrients, solved oxygen, temperature, salinity, pH, turbidity, total solids in suspension; the biological ones such as fito-plankton, zooplankton, p h o t o s y n t h e t i c p i gme n t c o n c e n tr a t i o n ; microbiological such as intestinal enterococos, Salmonella sp., Psedumonas sp., total Coliforms, Escherichia coli, fungus. Likewise the previous 2002, 2003 and 2204 characterizations at this same port, in this study the report of the appropriate environmental conditions for sustaining the biological communities in the tanks continued. Also the new planktonic species continued to be reported, among which Oithona setigera, Oithona hegolandica, Miocrostella sp., Diartrodes sp., Oculosetella sp., Corystoide chilensi, Parapagurus Diógenes, and Sagitta minima can be mentioned. In addition, it was possible to evidence that according to the agreement on the handling of ballast water and sediment by IMO in 2004, 29% of the monitored vessels surpassed the permissible discharge levels with respect to the Escherichia coli and the 11% of Intestinal enterococos germ indicator.
    Description: Published
    Keywords: Bahía de Cartagena ; Aguas de lastre ; Microbiología ; Fisicoquímicos ; Biológicos ; ASFA_2015::M::Marine biology ; ASFA_2015::P::Physical oceanography ; ASFA_2015::C::Chemical oceanography ; ASFA_2015::C::Contamination
    Repository Name: AquaDocs
    Type: Journal Contribution , Not Known
    Format: pp.150-168
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  • 10
    Publication Date: 2021-05-19
    Description: El trabajo se propone presentar los resultados del monitoreo durante 1996-98 El Centro Control Contaminación del Pacífico (CCCP) hizo a los Eventos La Niña y El Niño a través de cinco expediciones oceanográficas a la Cuenca del Pacífico Colombiano (CPC), mediante el análisis de las condiciones térmicas del océano. Se obtuvieron perfiles verticales de 3 transectos zonales (Buenaventura -5°N, Gorgona -4°N y Tumaco -3°N), y campos horizontales de la CPC a nivel superficial, 50, 100 y 150m. Se evaluó la variación temporal de una estación hidrológica (estación 33) de acuerdo con las diferentes etapas de desarrollo de los Eventos. De igual manera se obtuvieron temperaturas y profundidades promedio de la termoclina en cada crucero, caracterizando su comportamiento. Se presentan las anomalías de Temperatura Superficial del Mar (TSM) en la CPC para cada crucero, de acuerdo con la Climatología para la CPC 1970-1996. Se pudo determinar el efecto que ocasionó el sobrecalentamiento de las aguas especialmente del Pacífico Sur de Colombia donde se vio gravemente afectado el sector pesquero y el sistema coralino de Isla Gorgona.
    Description: The purpose of the present paper is to introduce the results obtained by The Pacific Pollution Control Center (CCCP) from the hydrological tracking to El Niño and La Niña Events, given from 96 to 98, by means of five oceanographic expeditions to The Colombian Pacific Basin (CPC). Results are based on three zonal transects vertical profiles (Buenaventura -5°N, Gorgona -4°N y Tumaco -3°N), and CPC horizontal fields at O, 50, 100 and 150m. Temporal variation of temperature of a station (Station Nr 33) during the period of study was analysed in accordance with the different stages of development of the episodes. Average temperatures and depths of termocline were determined for each cruise. Sea Surface Temperature (SST) anomalies are shown, based on the 1970-1996 CPC climatology. The study made possible to identify the process that produced the South Pacific Colombian waters overheating which seriously affected the fisheries production and the Gorgona Island coral reef system.
    Description: Published
    Keywords: Temperatura ; Densidad ; Oxígeno ; ASFA_2015::P::Physical oceanography ; ASFA_2015::C::Climatic zones ; ASFA_2015::M::Marine meteorology
    Repository Name: AquaDocs
    Type: Journal Contribution , Not Known
    Format: pp.50-57
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