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  • ASTROPHYSICS  (6)
  • Chemistry  (4)
  • Compositae
  • Condensed Matter: Electronic Properties, etc.
  • Madiinae
  • chemotaxonomy
  • chemotaxonomy.
  • 1990-1994  (10)
  • 1
    Electronic Resource
    Electronic Resource
    High-density polyethylene pipe resins[AMSC118] (1992)
    Weinheim : Wiley-Blackwell
    Advanced Materials 4 (1992), S. 234-238 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19920040317
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrierung von Crotonaldehyd und Acetaldol mit modifizierten Pd-Trägerkatalysatoren. II. Zum Einfluß einer Chromiummodifizierung auf Pd Al2O3-Katalysatoren (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 1073-1080 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogenation of Crotonaldehyde and Acetaldol with Modified Pd-Supported Catalysts. II. On the Influence of a Chromium Modification of Pd/Al2O3 CatalystsThe catalytic properties in hydrogenation reactions on chromium containing Pd/Al2O3 catalysts are influenced by an “esemble effect.” The specific activity in the hydrogenation of crotonaldehyde to n-butyraldehyde is independent of the chromium content in the Pd/Al2O3 catalysts. But the specific activity for the hydrogenolysis of ethane is decresed with the chromium content of the catalysts. On the other hand, was observed that the specific activity of the conversion of acetaldol to n-butyraldehyde rises with increasing chromium content. This specific activity is higher than the specific hydrogenation activity.This fact can be considered as an argument for an asynchron hydrogenolysis of the hydroxyl group in the formation of n-butyraldehyde from acetaldol on Pd—Cr/Al2O3 catalysts.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320626
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrierung von Crotonaldlehyd und Acetaldol mit modifizierten Pd-Trägerkatalysatoren I. Zum Einfluß einer Titaniummodifizierung auf Pd/AI2O3-KatalysatorenHerrn Prof. Dr. habil. G. Zimmermann zum 60. Geburtstag gewidmet (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 509-518 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogenation of Crotonaldehyde and Acetaldole with Modified Pd Carrier Catalysts. I. On the Influence of a Titanium Modification to Pd/Al2O3 CatalystsThe modification of Pd/Al2O3 catalysts with titanium was studied in the hydrogenation of crotonaldehyde and acetaldole. In the result of the titanium modification the hydrogenation activity is increased and the formation of carbon monoxide is decreased. An electronic and geometric ensemble effect should be the reason for the palladium titanium interaction. The mechanism of the acetaldole conversion to butyraldehyde at 160°C is mainly determined by hydrogenolysis in one step and at 200°C by two steps consisting in dehydratization and hydrogenation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320414
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  • 4
    Electronic Resource
    Electronic Resource
    Hydrierung von Crotonaldehyd, Butyraldehyd und Acetaldol mit modifizierten Ni-Trägerkatalysatoren. I. Zum Einfluß einer Kupfermodifizierung auf Ni/Kaolin-Katalysatoren (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 710-718 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogenation of Crotonaldehyde, Butyraldehyde and Acetaldole with Modified Ni Carrier Catalysts. I. On the Influence of a Copper Modification of Ni/Kaolin CatalystsThe hydrogenation of crotonaldehyde, butyraldehyde and acetaldol in the presence of Ni-Cu catalysts is a single-centre reaction, whereas the decarbonylation of crotonaldehyde is a multi-centre reaction. The ratio between the specific activities of the hydrogenation of the C=C double bond and the carbonyl group is two. In the conversion of acetaldol the hydrogenolysis to butyraldehyde can be neglected in comparison with the hydrogenation to butan-1,3-diol.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320520
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  • 5
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    Emission lines in the long-period Cepheid l Carinae (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: For the Cepheid l Carinae, with a pulsation period of 35.5 days, we have studied the emission-line fluxes as a function of pulsational phase in order to find out whether we see chromospheric and transition-layer emission due to an outward-moving shock. All emission lines show a steep increase in flux shortly before maximum light, suggestive of a shock moving through the surface layers. The large ratio of C IV to C II line fluxes shows that these are not transition-layer lines. During maximum light the large ratio of the large ratio of the C IV to C II line fluxes also suggests that we see emission from a shock with velocities greater than 100 km/s such that C IV emission can be excited. With such velocities mass outflow appears possible. The variations seen in the MG II line profiles show that there is an external absorption over a broad velocity band independent of the pulsation phase. We attribute this absorption to a circumstellar 'shell.' This 'shell' appears to be seen also as spatially extended emission in the O I line at 1300 A, which is probably excited by resonance with Ly beta.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 420; 1; p. 401-414
    Format: text
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  • 6
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    The lithium content and other properties of F2-G5 giants in the Hertzsprung Gap (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: As stars of 2-5 solar mass evolve across the Hertzsprung Gap they should first deplete their surface lithium by convective dilution and then, when convection penetrates deeper, begin to bring CN processed material to their surfaces. To investigate this process we have observed 52 giants, 25 of which have known C/N ratios, for their Li abundances. After eliminating four stars that may actually be dwarfs and including the two components of Capella analyzed by Pilachowski and Sowell we have compared our (Li/Fe) ratios with models of Swenson. For stars showing v sin i greater than 50 km/s we find (Li/Fe) to be uneffected by mixing for B - V less than 0.7 as predicted. For stars cooler than B - V = 0.7 both v sin i and (Li/Fe) drop to smaller values. For the sharp lined stars (v sin i less than 50 km/s) we find a drop in Li between B - V = 0.45 and 0.60 which cannot be understood in terms of dilution by convection. Various possible causes of such an early depletion or dilution of surface Li are discussed including diffusion at the base of the convection zone, mass loss possibly enhanced by pulsation, and magnetic activity as in the magnetic A and B type stars. The models of Richer & Michaud (1993) with diffusion point toward a satisfactory solution. A few giants with low v sin i values stand out with much higher than expected (Li/Fe) values despite their cool effective temperatures. We do not understand why those stars have not depleted their lithium as have most giants of similar color. The correlation of (N/C) with (Li/Fe) follows expectations in so far as almost all stars with enhanced (N/C) have depleted their Li as well.
    Keywords: ASTROPHYSICS
    Type: The Astronomical Journal (ISSN 0004-6256); 107; 6; p. 2211-2221
    Format: text
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  • 7
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    The two period-luminosity relations for population I Cepheids (1994)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We summarize the evidence that most Population I Cepheids with periods less than approximately 8 days pulsate in the first overtone mode. Fundamental model and first overtone pulsators must follow different period-luminosity (P - L) relations. We demonstrate these different relations for different stellar systems, especially for the calibrating Cepheids in clusters and for Cepheids in the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC), M31, and IC 4182.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 107; 2; p. 673-678
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  • 8
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    Heating mechanism(s) for transition layers in giants (1991)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The emission-line fluxes of lines originating in the lower parts of the transition layers between stellar chromospheres and coronas are studied. Simon and Drake (1989) suspect different heating mechanisms for 'hot' and cool stars. Changes in the flux ratios for the C IV to C II emission lines support this suspicion. Large C IV/C II line flux ratios appear to be indicative of magnetically controlled heating. A correlation between excess continuum flux around 1950 A and C II emission-line fluxes are confirmed for the cooler giants (late F and cooler). Excess continuum flux correlates positively with large C IV/C II line flux ratio. The excess continuum flux corresponds to an increase in temperature by several hundred degrees in layers with a mean optical depth of about 0.03. For chromospherically active stars these layers experience a mechanical flux deposition of the order of 1 percent of the total radiative flux. This flux is tentatively identified as an MHD wave flux similar to Alfven waves.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 378; 718-724
    Format: text
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  • 9
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    The dynamical mass of S Muscae (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The amplitudes and phase relations of pulsational velocities of the Cepheid S Muscae, measured for lines originating at different atmospheric depths, are investigated. A mass M(A) = 4.4 + or - 0.5 solar masses is found for the Cepheid; however, the Cepheid is the evolved star and should have a mass larger than that of its companion. If the measured velocity differences are too low by 2.5 km/s on the average, then the mass ratio M(B)/M(A) may be decreased to 0.94, giving an estimated upper limit to the Cepheid mass of 6.1 solar masses, consistent with the Cepheid being the more evolved star. Considering all the uncertainties, it is concluded that the mass of the Cepheid is between 4.6 and 6.1 solar masses.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 99; 353-372
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  • 10
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    Ultraviolet gas absorption and dust extinction toward M8 (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Interstellar absorption lines are analyzed using high-resolution IUE spectra of 11 stars in the young cluster NGC 6530 located in the M8 region. High-velocity clouds at -35 km/s and -60 km/s are seen toward all cluster stars. The components arise in gases that are part of large interstellar bubbles centered on the cluster and driven by stellar winds of the most luminous members. Absorption lines of species of different ionization states are separated in velocity. The velocity stratification is best explained as a 'champagne' flow of ionized gas away from the cluster. The C IV/Si IV ratios toward the hotter cluster members are consistent with simple photoionization models if the gas-phase C/Si ratio is increased by preferential accretion onto dust grains. High ion column densities in the central cluster decline with distance from W93, suggesting that radiation from a hot source near W93 has photoionized gas in the central cluster.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 358; 441-458
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