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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2827-2835 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The adsorption and desorption kinetics for SiCl4 on Si(111)7×7 were studied using laser-induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. TPD experiments monitored SiCl2 as the desorption product at approximately 950 K using a heating rate of β=9 K/s. SiCl2 was also observed as the desorption product in the LITD yield at all surface coverages. LITD measurements determined the initial reactive sticking coefficient (S0) of SiCl4 on Si(111)7×7 versus surface temperature. The sticking coefficient was observed to decrease with surface temperature from S0≈0.18 at 160 K to S0≈0.03 at 600 K. TPD experiments revealed that the chlorine surface coverage saturated after large SiCl4 exposures and the saturation coverage was independent of surface temperature. Isothermal LITD studies enabled the surface chlorine coverage to be monitored as a function of time during SiCl2 desorption. These studies revealed second-order desorption kinetics for SiCl2 with a desorption activation barrier of Ed=67±5 kcal/mol and preexponential of νd=3.2×100±0.1 cm2/s. Experiments with preadsorbed hydrogen demonstrated that the initial sticking coefficient of SiCl4 was reduced as a function of increasing hydrogen coverage. This behavior indicated that the adsorption of SiCl4 on Si(111)7×7 requires free surface dangling bonds. LITD techniques were also used to study the surface diffusion of the chlorine on Si(111)7×7 after SiCl4 adsorption. No evidence of significant surface chlorine mobility (D≤2×10−11 cm2/s) was found for surface temperatures as high as 825 K.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 46 (1990), S. 1796-1799 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 692-692 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Optical and quantum electronics 22 (1990), S. 89-94 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The use of cavity length control to obtain multiline emission from a hybrid CO2 laser has been investigated. We have obtained simultaneous laser oscillation on up to four lines in the P and R branches of the 10 μm band by operating the c.w. section above the lasing threshold. For sub-threshold operation of the c.w. section the hybrid laser emission is restricted to the stronger 10P lines.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mineralogy and petrology 48 (1993), S. 97-113 
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Joesmithit ist ein komplex zusammengesetzter Klinoamphibol, der rumindest 14 Komponenten in seiner Formel aufweist. Die idealisierte Formel lautet PbCa2Mg3Fe 2 3+ (Si6Be2O22)(OH)2. Er ist monoklin holoedrisch und von den geordnetenC2/m-Klinopyroxenen abgeleitet,a = 9,915(2),b = 17,951(4),c = 5,243(1) Å,ß = 105,95(2)°, Z = 2, RaumgruppeP2/a, D(beob) = 3,83(1), D(ber) = 3,91 g cm-3. R = 0,056 für 2299 unabhängige F0. Die Elementarzellen von Joesmithit und einem pargasitischen Amphibol wurden in Bezug auf deren Struktur verglichen, ebenso jene von Margarosanit, PbCa2Si3O9, und Walstromit, BaCa2Si3O9, In beiden Paaren differieren die Positionen der Anionen um maximal 0,2 Å, die Unterschiede Pb/A = (Na, K, □) und Pb/Ba betragen 0,4 und 0,6 Å. Das ein einsames Elektronenpaar aufweisende Kation Pb2+ folgt den Bindungsstärken der koordinierenden Anionen im Vergleich zu den Pendents mit abgeschlossener Elektronenschale. Differieren die Bindungsstärken der koordinierenden Anionen, bewegt sich Pb2+ offensichtlich auf das am schwächsten abgesättigte Anion zu. Falls die Summe der Bindungsstärken an den Anionen in allen Richtungen des Koordinationspolyeders gleich sind (wie im Wulfenit, Pb2+Mo6+O4), dann kommt es zu keiner Verschiebung des Pb-Atoms.
    Notes: Summary Joesmithite is a complex clinoamphibole which contains at least 14 components in its formula. Its ideal formula would be PbCa2 Mg3 Fe 2 3+ (Si6Be2O22) (OH)2. It is monoclinic holosymmetric, an ordered derivative of theC2/m clinoamphiboles,a = 9.915(2),b = 17.951(4),c = 5.243(1)Å,β = 105.95(2)°, Z = 2, space groupP2/a, D(obs) = 3.83(1), D(cal) = 3.91 g cm-3. R = 0.056 for 2299 independent F0. The cells of joesmithite and pargasitic amphibole were compared according to differences, Δ, in their structure cells. The same procedure was applied to the margarosanite, PbCa2Si3O9 and walstromite, BaCa2Si3O9 pairs. In both pairs, the anion positions differed by 0.2 Å at most, but the Pb/A, Pb/Ba differences ranged from 0.4 to 0.6 Å. The lone pair Pb2+ cation responds according to the bond valence sums of its coordinating anions compared with its closed core counterpart. It appears that when the bond valence sums for the coordinating anions are different, Pb2+ moves toward the most underbonded anion. If the anion bond valence sums are equal for all vertices of the coordinating polyhedron (as in wulfenite, Pb2+Mo6+O4), then Pb2+ does not shift.
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  • 6
    ISSN: 1432-0649
    Keywords: 42.60.By ; 42.55.Dk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown that dual-band multiline operation of a TEA CO2 laser can be conveniently achieved with the use of either one or two intracavity etalons of judiciously selected finesse and optical lengths.
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  • 7
    ISSN: 1432-0789
    Keywords: Methane emission ; Flooded rice field ; Varietal variation ; Root oxidase activity ; Diurnal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a study on CH4 emission from flooded rice fields under irrigated conditions, fields planted with rice emitted more methane than unplanted fields. The CH4 efflux in planted plots varied with the rice variety and growth stage and ranged from 4 to 26 mg h-1m-2. During the reproductive stage of the rice plants, CH4 emission was high and the oxidation power of rice roots, in terms of α-naphthylamine oxidation, was very low. The CH4 emission reached a maximum at midday and declined to minimum levels at midnight, irrespective of the rice variety. The peak CH4 emission at midday was associated with higher solar radiation and higher soil/water temperature.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 126 (1994), S. 9-14 
    ISSN: 1573-0832
    Keywords: Aspergillosis ; Goats ; Pathology ; Udder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Intramammary inoculation of goats withAspergillus fumigatus spores resulted in the development of mastitis with characteristic gross and microscopic lesions. The mastitis and the lesions were restricted to the infected udder halves only and there was no dissemination of infection to other tissues of the body. The experiment was continued for 45 days. Gross changes in the infected udder were observed up to the 45th day post-infection. The lesions, in general, included variable sized abscesses in the first 15 days followed by development of varying sized greyish-white nodules in the infected udders. Microscopic changes consisted of granulomatous reaction with well developed granulomas in the infected udders. Hyphae and spores ofAspergillus fumigatus could be demonstrated in sections of the infected udders up to 45 days after infection. Reisolation of the fungus consistently was achieved up to 45 days. It is concluded that intramammary inoculation ofAspergillus fumigatus spores in goats leads to chronic granulomatous mastitis.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 121 (1993), S. 77-81 
    ISSN: 1573-0832
    Keywords: Aspergillosis ; Goats ; Pathology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Intratracheal inoculation of goats withAspergillus fumigatus spores resulted in the development of characteristic gross and microscopic lesions. The lesions were restricted to lungs and there was no dissemination of infection to other tissues of the body except liver in one goat 16 days after infection. The experiment was continued for 37 days. Gross changes in lungs were observed up to the 24th day post-infection. The lesions, in general, included congestion and oedema in the first 6 days followed by the development of varying greyish-white nodules in the lungs. Microscopic changes consisted of granulomatous reaction with well developed granulomas in lungs. Hyphae and conidiophores with fruiting bodies ofAspergillus fumigatus could be demonstrated in sections up to 24 days of infection. Reisolation of the fungus consistently was achieved up to 24 days. It is concluded that intratracheal inoculation ofAspergillus fumigatus spores in goats leads to pulmonary aspergillosis up to 24 days.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 126 (1994), S. 147-155 
    ISSN: 1573-0832
    Keywords: Cryptococcus neoformans ; Goats ; Mastitis ; Pathology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Unilateral intramammary inoculation of 10 goats withCryptococcus neoformans (2×106 yeast cells) resulted in the development of mastitis, with gross and microscopic lesions being restricted to the infected udder halves only and there was no dissemination of infection to the opposite uninfected udder halves as well as to other organs of the body. The experiment was continued for 40 days, with 2 animals each from the infected and control groups being killed on 5th, 10th, 20th, 30th and 40th day postinoculation (DPI). Initial enlargement of the infected udder halves was followed by marked decrease in size leading to very small, firm and nodular udder halves. After infection, there was also sharp fall in the milk yield. Cryptococcal organisms were demonstrated in the mastitic milk and udder impression smears with special stains.C. neoformans was reisolated from the milk of only infected udder halves up to 25th DPI. Microsopically, there was initially acute diffuse purulent mastitis which later on became chronic, characterised by marked infiltration of lymphocytes, macrophages, extensive fibrosis and development of multiple granulomas. The cryptococcal organisms could be demonstrated in the udder sections only up to 30th DPI. It is concluded that intramammary inoculation ofCryptococcus neoformans in goats leads to severe mastitis with sharp fall in milk yield.
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