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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 4689-4695 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Temperature- and density-dependent vibrational relaxation data for the v6 asymmetric stretch of W(CO)6 in supercritical fluoroform (trifluoromethane, CHF3) are presented and compared to a recent theory of solute vibrational relaxation. The theory, which uses thermodynamic and hydrodynamic conditions of the solvent as input parameters, shows very good agreement in reproducing the temperature- and density-dependent trends of the experimental data with a minimum of adjustable parameters. Once a small number of parameters are fixed by fitting the functional form of the density dependence, there are no adjustable parameters in the calculations of the temperature dependence. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 3540-3553 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared ps pump-probe experiments are presented for the P, Q, and R rotational branches of the asymmetric CO stretching mode of tungsten hexacarbonyl (1997 cm−1) in the collisionless gas phase. The pump-probe decays are tri-exponentials (140 ps, 1.3 ns, and 〉100 ns) in contrast to single exponential decays observed in supercritical fluids and liquid solvents. The 1.3 ns decay component is the vibrational energy relaxation (VER) time. The long component occurs following intramolecular VER into a distribution of low-frequency modes. After VER is complete, the R signal is 48%, the Q signal is 29%, and the P signal is −10% (absorption increase) compared to the t=0 signal. These long-lived signals result from an increase in the occupation numbers of low-frequency modes (internal heating) that causes a shift of the vibrational spectrum. The fastest decay is produced by spectral diffusion. The spectrally narrow pump pulse burns a hole in the inhomogeneous ground state spectrum and generates a narrow spectral population in the excited state (excited state peak). The inhomogeneity arises from the distribution of occupation numbers of the low-frequency modes that produces different combination band spectral shifts. Spectral diffusion is caused by the time evolution of the complex low-frequency thermal vibrational wave packet. Two possible models for the spectral diffusion are evaluated, one in which spectral diffusion reduces the pump-probe signal by hole filling and broadening of the excited state peak, and one in which the spectral diffusion only broadens the excited state peak. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 5971-5979 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational relaxation measurements on the CO asymmetric stretching mode (∼1980 cm−1) of tungsten hexacarbonyl (W(CO)6) as a function of temperature at constant density in several supercritical solvents in the vicinity of the critical point are presented. In supercritical ethane, at the critical density, there is a region above the critical temperature (Tc) in which the lifetime increases with increasing temperature. When the temperature is raised sufficiently (∼Tc+70 °C), the lifetime decreases with further increase in temperature. A recent hydrodynamic/thermodynamic theory of vibrational relaxation in supercritical fluids reproduces this behavior semiquantitatively. The temperature dependent data for fixed densities somewhat above and below the critical density is in better agreement with the theory. In fluoroform solvent at the critical density, the vibrational lifetime also initially increases with increasing temperature. However, in supercritical CO2 at the critical density, the temperature dependent vibrational lifetime decreases approximately linearly with temperature beginning almost immediately above Tc. The theory does not reproduce this behavior. A comparison between the absolute lifetimes in the three solvents and the temperature trends is made. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 9741-9748 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Experimental measurements are reported for the temperature dependence of the vibrational lifetime, T1, of the asymmetric CO stretching mode of tungsten hexacarbonyl in supercritical ethane at constant density from just above the critical temperature to substantially higher temperatures. T1 is found initially to increase with temperature along an isochore (reaching a maximum at about 70° above the critical point of ethane), and then subsequently to decrease. Using a recent classical theory of vibrational relaxation, we attempt to rationalize the T1 data. This behavior can be semiquantitatively reproduced by the theory if quantum corrections to the classical rate expressions are assumed to be temperature independent in the limit when the transition energy is much greater than thermal energy. In this case, the theory indicates that the initial increase in T1 with temperature arises because of a competition between properties of the solvent which are changing rapidly as the temperature is raised above the critical temperature. At sufficiently high temperature, properties of the solvent vary slowly with temperature, and the explicit temperature dependence of the vibrational relaxation dominates, producing a decrease in T1 with increasing temperature. The predictions of the theory are also examined when other postulated forms of the quantum correction factors are used, and the implications of these results for theoretical approaches to vibrational relaxation are discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 3747-3757 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Picosecond infrared pump–probe experiments are used to measure the vibrational lifetime of the asymmetric (T1u) CO stretching mode of W(CO)6 in supercritical CO2, C2H6, and CHF3 as a function of solvent density and temperature. As the density is increased at constant temperature from low, gaslike densities, the lifetimes become shorter. However, in all three solvents, it is found that within a few degrees of the critical temperature (Tr≡T/Tc(approximate)1.01), the lifetimes are essentially constant over a wide range of densities around the critical value (ρc). When the density is increased well past ρc, the lifetimes shorten further. At higher temperature (Tr=1.06) this region of constant vibrational lifetime is absent. Infrared absorption spectra of W(CO)6 and Rh(CO)2acac in supercritical CO2, C2H6, and CHF3 acquired for the same isotherms show that the vibrational spectral peak shifts follow similar trends with density. The peak positions shift to lower energy as the density is increased. Near the critical point, the peak positions are density independent, and then redshift further at densities well above ρc. It is shown that critical fluctuations play a dominant role in the observed effects. Theoretical calculations ascribe the density independence of the observables to the cancellation of various rapidly changing quantities near the critical point. The theory's calculation of density independence implicitly involves averages over all local densities and does not involve any form of solute–solvent clustering. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 8973-8976 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational lifetimes and absorption spectra of the asymmetric CO stretching mode (∼1990 cm−1) of W(CO)6 in supercritical CO2 are reported as functions of solvent density and temperature. Close to the critical temperature, the observables are density independent over a twofold range of density. Possible explanations are discussed for this unique behavior. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Tropical animal health and production 18 (1986), S. 209-216 
    ISSN: 1573-7438
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé On decrit un test immuno-enzymatique (TIE) modifié en phase solide, permettant la détection visuelle des anticorps antibovipestiques dans les sérums de bovins et de chèvres. Des antigènes antibovipestiques repartis par points (d ou Point-TIE) sont adsorbes sur un papier de nitrocellulose (NC) et les sites d’absorption des réactifs sont bloqués avec du lait éirémé en poudre. Après immersion dans des sérums de bovins ou de chèvres à tester, les anticorps fixés sont mis en evidence par une IgG, respectivement anti-boeuf ou anti-chèvre, conjuguée a une peroxydase. Après dégradation enzymatique d’un substrat contenant du peroxyde d’hydrogene et de l’aminoethylcarbazole (AEC), on visualise aisement les reactions positives comme des points brun-rougeâtres. Le Point-TIE est comparable au test de séro-neutralisation (SN) dans sa capacité de détection des anticorps dans les sérums de bovins sept ou 10 jours après l’infection (JPI) expérimental de la souche bovipestique attenuée Kabete ‘O’ (RBOK) (cultivée en cellules Vero) par combinaison des voies sous-cutanée (SC), intraveineuse (IV) et intranasale. Des anticorps antibovipestiques precoces (sept JPI) ont éte détectés dans un échantillon de serum de chèvre infectée experimentalement par le virus bovipestique par une combinaison de voies SC-IV, mais pas d’une autre chèvre infectée par voie nasale. La spécificité du test Point-TIE est égal a celle du test SN car les échantillons de sérums de ces animaux d’experience et de ceux inoculés avec un liquide de culture de cellules Vero non infectés, et possedant des titres SN de 0.3 ou inferieurs, se sont tous montrés negatifs en Point TIE. Le Point-TIE peut avoir des applications potencielles car c’est un test de terrain rapide, simple et économique pour le diagnostic de la peste bovine, la surveillance de la vaccination et d’autres études séro-épidemiologiques.
    Abstract: Resumen Se describe un inmunoensayo de fase sólida modificada, para la detección visual de anticuerpos contra el virus de rinderpest, en suero bovino y caprino. Pequeñas cantidades de antígenos en forma de puntos, del virus de rinderpest, se adsorbieron en papel nitrocelulosa, siendo las zonas adsortivas reactivas bloqueadas con leche descremada. Despues de la inmersión en suero bovino o caprino, los anticuerpos adheridos se hicieron reaccionar con un conjugado de peroxidasa IgG, antibovino y anticaprino respectivamente. Las reacciones positivas se visualizaron fácilmente, como puntos cafe-rojizos, despues de la degradación del substrato el cual contenía peróxido de hidrógeno y amino-etilcarbazol. El inmunoensayo enzimático de punto fue comparable a la prueba de seroneutralización, en la abilidad para detectar anticuerpos en suero bovino, siete a diez días despues de la infección experimental con cepas vivas atenuadas del virus de rinderpest (Kabete ‘O’) cultivado en células Vero, infección llevada a cabo mediante la combinación de las rutas subcutánea, intranasal e intravenosa. Siete días post-inoculación experimental, se detectaron anticuerpos del virus de rinderpest en el suero de una cabra que había sido infectada mediante la combinación de las rutas subcutánea e intravenosa. No se encontraron anticuerpos en el suero de otra cabra inoculada vía intranasal. La especificidad del inmunoensayo enzimático de punto, fue similar a la obtenida con la prueba de seroneutralización, debido a que las muestras de suero colectadas de los animales arriba mencionados y de otros que habían sido inoculados con cultivos de células Vero no infectados, con títulos de seroneutralización de 0.3 o menores, fueron todos negativos a la prueba de inmunoensayo enzimático. Esta última, puede tener aplicación potencial como herramienta rápida, simple y económica en el campo, para el diagnóstico de rinderpest. Tambien podría tener aplicación en campañas de vigilancia vacunal y cualquier otro estudio seroepidemiológico.
    Notes: Summary A modified solid phase enzyme immunoassay (EIA) is described for visual detection of anti-rinderpest virus (RPV) antibodies in cattle and goat sera. Dots of RPV antigens were adsorbed to nitrocellulose (NC) paper (hence Dot-EIA) and the adsorptive reactive sites were blocked with skim milk powder. After immersion in bovine or caprine test serum bound antibodies were reacted with a peroxidase-conjugated anti-bovine or anti-caprine IgG (H & L), respectively. Positive reactions were easily visualized as red-brown dots after enzyme degradation of a substrate containing hydrogen peroxide and aminoethylcarbazole (AEC). The Dot-EIA was comparable to the serum neutralisation (SN) test in its ability to detect antibody in bovine sera seven or ten days after experimental infection (DPI) with live attenuated Kabete “O” (RBOK) strain of RPV (grown in Vero cells) by a combination of subcutaneous (s/c), intravenous (i/v) or intranasal (i/n) routes. Early (seven DPI) RPV antibodies were detected in a serum sample from one goat experimentally infected with RPV by combined s/c-i/v routes but not in another goat only infected intranasally. The specificity of the Dot-EIA was equal to that of the SN test, as serum samples, collected from these experimental animals and those inoculated with non infected Vero cell culture fluid, with SN titres of 0·3 or lower were all negative by Dot-EIA. The Dot-EIA may have potential application as a rapid, simple and economical field test in diagnosis of rinderpest, vaccination surveillance and other seroepidemiological studies.
    Type of Medium: Electronic Resource
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