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  • 1
    Electronic Resource
    Electronic Resource
    Acetonylacetone conversion on AlPO4–cesium oxide (5–30 wt%) catalysts (1999)
    Springer
    Catalysis letters 60 (1999), S. 145-149 
    Details
    ISSN: 1572-879X
    Keywords: AlPO4 ; AlPO4–cesium oxide ; 2,5‐hexanodione conversion ; activity ; selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Acetonylacetone underwent both acid‐ and base‐catalyzed intramolecular cyclizations to 2,5‐dimethylfuran and 3‐methyl‐2‐cyclopenten‐1‐one, respectively, on pure AlPO4, whereas its modification with increasing amounts of cesium oxide developed AlPO4‐based materials with increased basic properties and, hence, higher selectivities to the base‐catalyzed cyclization process. However, the poisoning of surface acid and base sites indicated that acetonylacetone conversion into 3‐methyl‐2‐cyclopenten‐1‐one can also be attributed to the joint participation of surface acid and base sites. So, acetonylacetone cannot be used for the simultaneous characterization of acidic and basic surface properties of acid–base heterogeneous catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019059008112
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  • 2
    Electronic Resource
    Electronic Resource
    2-Methyl-3-butyn-2-ol conversion on AlPO4-cesium oxide (20 wt.%) catalysts obtained by impregnation with cesium chloride (1998)
    Springer
    Reaction kinetics and catalysis letters 65 (1998), S. 239-244 
    Details
    ISSN: 1588-2837
    Keywords: AlPO4 ; AlPO4-cesium oxide ; 2-methyl-3-butyn-2-ol conversion ; activity ; selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 2-Methyl-3-butyn-2-ol underwent almost exclusively dehydration to 3-methyl-3-buten-1-yne (acid activity) on pure AlPO4, whereas its modification with cesium oxide developed AlPO4-based materials with increased basic properties and hence, high selectivities to the base-catalyzed cleavage of MBOH yielding acetone and acetylene. At the same conversion level, catalysts obtained from cesium chloride exhibit higher selectivities to the base-catalyzed process than those obtained from cesium acetate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02475259
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  • 3
    Electronic Resource
    Electronic Resource
    Isomerization of 3,3-dimethyl-1-butene over aluminum and chromium orthophosphates (1998)
    Springer
    Reaction kinetics and catalysis letters 64 (1998), S. 41-48 
    Details
    ISSN: 1588-2837
    Keywords: AlPO4 ; CrPO4 ; CrPO4−AlPO4 ; surface acidity ; 3,3-dimethyl-1-butene isomerization ; poisoning by bases ; pyridine ; 2,6-dimethylpyridine ; hexamethyldisilazane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The skeletal isomerization of 3,3-dimethyl-1-butene over AlPO4 (Al/P=1), CrPO4 (Cr/P=1), and CrPO4−AlPO4 (CrAlP, 5–10 wt.% AlPO4) catalysts is a first order reaction. Catalytic performance is affected by the precipitation agent. CrPO4 catalysts obtained in propylene oxide-aqueous ammonia showed the highest activity. Moreover, the incorporation of AlPO4 to CrPO4 developed CrAlP catalysts that exhibited increased activity, irrespective of the precipitation method, as compared with both AlPO4 and CrPO4 catalysts. Besides, CrAlP catalysts prepared in propylene oxide-aqueous ammonia were the more active ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02475368
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  • 4
    Electronic Resource
    Electronic Resource
    Structure and texture of AlPO4-cesium oxide (20 wt.%) catalysts obtained by impregnation with cesium chloride (1998)
    Springer
    Reaction kinetics and catalysis letters 65 (1998), S. 245-251 
    Details
    ISSN: 1588-2837
    Keywords: AlPO4 ; AlPO4-cesium oxide ; structure ; texture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract AlPO4-cesium oxide (20 wt.%) materials retain a low degree of crystallinity on calcination at 873 K for 3 h. After DTA measurements (1423 K), AlPO4 crystallizes (tridymite form). Furthermore, DRIFT spectroscopy shows that the P−OH stretching vibration (at 3670 cm−1) of AlPO4 support disappears upon cesium oxide loading. Moreover, Al and P atoms remain in tetrahedral coordination as in unmodified AlPO4. Furthermore, the incorporation of cesium oxide leads, simultaneously, to a progressive decrease in surface area and pore volume as well as to an increase in the most frequently occurring pore radius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02475260
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  • 5
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    Detection of Polar Stratospheric Clouds Using AVHRR Imagery (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: In recent years, the role of PSCs in the ozone depletion process has become better understood. PSCs provide the surfaces upon which heterogeneous reactions take place that affect the gas phase partitioning between active and reservoir chlorine and nitrogen species. Present methods of PSC detection include in situ measurements by lidar and various satellite-borne instruments such as the Stratospheric Aerosol Measurement II (SAM II) on the Nimbus 7 spacecraft, which produced PSC measurements from 1978 to 1994 and several instruments onboard the Upper Atmospheric Research Satellite (UARS) such as the Cryogenic Limb Array Etalon Spectrometer (CLAES) which provided measurements for 1991-1993. All of the PSC-detection methods devised so far have been hampered by incomplete sampling of the places and times in which PSCs are likely to form. There is a need to understand the climatology of PSCS, in particular the timing of their onset and duration, their vertical distribution, geographic extent, annual variability and responses to volcanic aerosol forcing. Poole and Pitts [1994] assembled a PSC climatology based on SAM II data, but this climatology is incomplete, as it is limited to the edge of the polar night due to the limitations of the solar occultation scan geometry. The Advanced Very High Resolution Radiometer (AVHRR) five- channel sensors onboard the NOAA polar-orbiting satellites have been collecting data over the polar regions continuously since 1979. These operational satellites provide unmatched coverage in space and time of both polar regions, but were not designed for the detection of optically-thin PSCS. However, the AVHRR data archive would be an invaluable source for the construction of a long-term climatology of PSCs if techniques can be developed and tested to detect PSCs in AVHRR data. In the last few years, the members of our group at San Francisco State University and NASA Ames Research Center have been engaged in the development of various PSC detection methods using AVHRR data. There is strong evidence that a subset of PSCS, those that are optically thick, can be readily identified in the AVHRR data set. Our group has also made significant progress in the identification of optically thinner PSCs using a variety of techniques.
    Keywords: Geophysics
    Format: text
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  • 6
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    The Climatological Annual Cycle of Satellite-derived Phytoplankton Pigments in the Alboran Sea: A Physical Interpretation (1998)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: The circulation and upwelling processes (coastal and gyre-induced) that control the phytoplankton distribution in the Alboran sea are examined by analyzing monthly climatological patterns of Coastal Zone Color Scanner (CZCS) pigment concentrations, sea surface temperatures, winds, and seasonal geostrophic fields.
    Keywords: Geophysics
    Type: Geophysical Research Letters
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  • 7
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    Physical Control of Phytoplankton Distributions in the Alboran Sea: A Numerical and Satellite Approach (1999)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: This study aims to identify the controlling processes of phytoplankton distributions in the Alboran Sea (western Mediterranean Sea).
    Keywords: Geophysics
    Type: Journal of Geophysical Research - Oceans
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  • 8
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    Near-Inertial and Tidal Currents Detected with a Vessel Mounted Acoustic Doppler Current Profiler in the Western Mediterranean Sea (1998)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: The Acoustic Doppler Current Profiler (ADCP) combined with accurate navigation provides absolute current velocities which include information from all the frequencies which have a dynamical presence in the ocean.
    Keywords: Geophysics
    Type: Journal of Geophysical Research
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  • 9
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    Propagation and Breaking at High Altitudes of Gravity Waves Excited by Tropospheric Forcing (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-08-17
    Description: An anelastic approximation is used with a time-variable coordinate transformation to formulate a two-dimensional numerical model that describes the evolution of gravity waves. The model is solved using a semi-Lagrangian method with monotone (nonoscillatory) interpolation of all advected fields. The time-variable transformation is used to generate disturbances at the lower boundary that approximate the effect of a traveling line of thunderstorms (a squall line) or of flow over a broad topographic obstacle. The vertical propagation and breaking of the gravity wave field (under conditions typical of summer solstice) is illustrated for each of these cases. It is shown that the wave field at high altitudes is dominated by a single horizontal wavelength; which is not always related simply to the horizontal dimension of the source. The morphology of wave breaking depends on the horizontal wavelength; for sufficiently short waves, breaking involves roughly one half of the wavelength. In common with other studies, it is found that the breaking waves undergo "self-acceleration," such that the zonal-mean intrinsic frequency remains approximately constant in spite of large changes in the background wind. It is also shown that many of the features obtained in the calculations can be understood in terms of linear wave theory. In particular, linear theory provides insights into the wavelength of the waves that break at high altitudes, the onset and evolution of breaking. the horizontal extent of the breaking region and its position relative to the forcing, and the minimum and maximum altitudes where breaking occurs. Wave breaking ceases at the altitude where the background dissipation rate (which in our model is a proxy for molecular diffusion) becomes greater than the rate of dissipation due to wave breaking, This altitude, in effect, the model turbopause, is shown to depend on a relatively small number of parameters that characterize the waves and the background state.
    Keywords: Geophysics
    Type: Journal of the Atmospheric Sciences; 53; 15; 2186-2216
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