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  • 1995-1999  (15)
  • 1985-1989  (16)
  • 1970-1974  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Spatially resolved atomic hydrogen concentrations and molecular hydrogen temperature profiles in the chemical-vapor deposition of diamond (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3622-3634 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report here a direct measurement of the spatially resolved atomic hydrogen concentration profiles during hot-filament-assisted chemical-vapor deposition (HFCVD) of diamond films. The ground-state hydrogen (1s 2S1/2) atoms generated in this process are monitored by an optical four-wave-mixing technique, third-harmonic generation (THG). For THG, a 364.6 nm dye laser beam is focused into the HFCVD reactor and the third-harmonic radiation near resonant with the Lyman-α (2p 2P0j↔1s 2S1/2) transition in atomic hydrogen at 121.6 nm is observed. The resultant THG intensity and THG peak shift with respect to the Lyman-α transition are both dependent on hydrogen atom concentration. Titration experiments based on the reaction NOCl+H→HCl+NO were conducted to obtain absolute hydrogen atom concentrations from the relative concentrations determined in the THG experiment. Spatially resolved molecular hydrogen temperature and concentration profiles obtained by coherent anti-Stokes Raman scattering in a similar HFCVD reactor are reported. The observed H atom concentrations exceed computed equilibrium concentrations based on the measured gas temperatures. Transport of the atomic hydrogen from the hot filament surfaces is discussed and diffusion is shown to be the principal mechanism controlling the H atom distribution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.359939
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  • 2
    Digitale Medien
    Digitale Medien
    A high-sensitivity low-energy electron diffractometer (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 3065-3067 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A high-sensitivity low-energy electron diffraction (LEED) system based on an electron energy loss spectrometer is described. This instrument is found to have the advantages of good angular resolution, very good energy resolution, low target current and high dynamic range. The experimental control and data collection are automated, which is found to be necessary to reduce measurement times to practicable levels. The performance of the system is illustrated by LEED data obained for a submonolayer of C6H6 physisorbed on graphite at 35 K where a weak diffraction feature is observed for the first time.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1140605
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  • 3
    Digitale Medien
    Digitale Medien
    Photochemistry of adsorbed molecules. XIV. Photoejection of CH3X (X=Cl, Br) from CH3Br/LiF(001) (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 461-464 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: At (approximately-greater-than)1 ML coverage of methyl bromide adsorbed on LiF(100), CH3Br is efficiently "photoejected'' by ultraviolet light at 193 nm, with a mean translational energy of ∼0.3 eV; this is termed PEJ(CH3Br). The system CH3Cl/LiF(100) shows no detectable PEJ(CH3Cl) at this wavelength for which CH3Cl does not efficiently absorb UV. Similarly PEJ(CH3Br) ceased to be observable with 248 nm light, at which wavelength CH3Br does not absorb. Both observations indicate that PEJ is adsorbate mediated. If at 193 nm ∼1 ML of CH3Br is adsorbed beneath ∼1 ML of CH3Cl, efficient PEJ(CH3Cl) is observed. With the sequence of layers reversed (i.e., with the actinic layer on top), PEJ(CH3Cl) is largely suppressed. These observations support the model for PEJ proposed previously [I. Harrison et al., J. Chem. Phys. 89, 1498 (1988)] in which photoexcitation of the underlayer leads, by way of electronic-to-translational (E→T) transfer, to ejection of the top layer. The angular distribution of the photoejected species is peaked along the surface normal, consistent with repulsion operating between the under- and overlayer. The mean conversion of E→T implied by this mechanism is ∼5%, extending to a maximum of 12%. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.469611
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  • 4
    Digitale Medien
    Digitale Medien
    Variation in Nitrate Tolerance of Nitrogen Fixation in the Pea/Rhizobium Symbiosis (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 98 (1987), S. 0 
    Details
    ISSN: 1439-0523
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: The short-term effects of nitrate on symbiotic nitrogen fixation were studied in six cultivars of pea (Pisum sativum L.) using two strains of Rhizobium leguminosarum. Plants grown symbiotically for three weeks, in order to eliminate the effect of NO3 on nodule formation, were exposed to nil, 5 or 15 mM NO3 for a period of seven days. Nodule mass, nitrogenase activity by acetylene reduction and the NO2 and NO3 concentrations in nodules were determined.Exposure to nitrate reduced the total acetylene reduction activity (ARA) in all cultivars, and a significant cultivar × nitrate treatment interaction was found. Nitrate influenced the components of N2 fixation, nodule mass and specific ARA (ARA/mg nodule), differently within and among cultivars. Nodule mass was reduced in all cultivars, but a variation among cultivars in the degree of reduction was found. Nitrate also reduced the specific ARA to different extents in the cultivars- The specific ARA of nodules from NO3-treated plants, expressed as per cent of the specific ARA of nodules from plants grown without NOT3 was negatively correlated with the concentration of NO3 in nodules. No relationship was found between the reduction of N2 fixation and the nitrite concentration in nodules.The results indicate that it is possible to improve the nitrate tolerance of symbiotic N2 fixation of the established pea/Rhizobium symbiosis by selection of suitable host plants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1439-0523.1987.tb01105.x
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  • 5
    Digitale Medien
    Digitale Medien
    The influence of nitrous oxide on propofol dosage and recovery after total intravenous anaesthesia for day-case surgery (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 50 (1995), S. 0 
    Details
    ISSN: 1365-2044
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: We studied the influence of nitrous oxide on the maintenence dose of propofol and recovery characteristics in 42 patients, aged 18–62 years, ASA 1 or 2, scheduled for day case inguinal herniotomy. Using a double-blind, randomised design, patients received anaesthesia with propofol-alfentanil-vecuronium-oxygen and either nitrous oxide or room air (Fio2= 0.30). The rate of propofol infusion was adjusted depending on anaesthetic depth as judged using standard clinical criteria; alfentanil was administered on a weight basis. Patients’ lungs were manually ventilated after tracheal intubation and muscle relaxation was reversed at the end of surgery with neostigmine and atropine. A series of psychomotor tests was performed pre-operatively and 30 and 120min postoperatively. The mean maintenance doses of propofol were 0.084 mg .kg-1 .min-1 in the N2O group and 0.088 mg.kg-1.min-1 in the air group (p = 0.97). In the nitrous oxide group the mean (SD) interval to spontaneous eye opening was 13.1 (7.3) min compared to 8.1 (4.9)min in the air group (p = 0.01). Similarly, the interval until obtaining a standardised response was 13.5 (5.3) min and 9.8min (5.4) in the nitrous oxide and air groups, respectively (p = 0.04). The addition of nitrous oxide to propofol-alfentanil-vecuronium anaesthesia does not reduce propofol requirements and prolongs early recovery compared to air.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2044.1995.tb05991.x
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  • 6
    Digitale Medien
    Digitale Medien
    Mechanism of Action of the Female Sex Hormones (1972)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biochemistry 41 (1972), S. 203-230 
    Details
    ISSN: 0066-4154
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Chemie und Pharmazie , Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.bi.41.070172.001223
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  • 7
    Digitale Medien
    Digitale Medien
    Interaction between photoperiod, photosynthesis and ethylene formation in tomato plants (Lycopersicon esculentum cv. Ailsa Craig and ACC-oxidase antisense pTOM13) (1998)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 103 (1998), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Wild-type and ACC-oxidase antisense tomato plants (Lycopersicon esculentum Mill. cv. Ailsa Craig and pTOM13) were grown in environment-controlled rooms for 21 days under photoperiods of 8, 16 or 23.5 h at an irradiance of 300 µmol m−2 s−1. Photosynthetic pigments, photosynthesis, soluble carbohydrates, starch and ethylene were measured on the last fully expanded leaf. Increasing the photoperiod from 8 to 16 h stimulated all measured growth parameters in both cultivars. However, when the photoperiod was increased to 23.5 h, foliar yellowing and deformation were observed in the wild-type Ailsa Craig whereas no change was observed in pTOM13. It was not possible to relate these foliar changes in Ailsa Craig to destruction of the photosynthetic apparatus by excess carbohydrate levels in the leaves. Because pTOM13 was antisense to ACC-oxidase. it is proposed that yellowing and deformation in leaves of wild-type tomato plants grown under long photoperiods may be caused by stress ethylene induced by a long photoperiod.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1030309.x
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  • 8
    Digitale Medien
    Digitale Medien
    Photoperiodic control of endogenous gibberellins in seedlings of Salix pentandra (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 93 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: In the temperate-zone woody species Salix pentandra elongation growth is regulated by the photoperiod. Long days sustain active growth, whereas short days induce cessation of apical growth, which is a prerequisite for winter hardening. It is shown that this is correlated to quantitative changes in levels of endogenous GA19 GA20, and GA1. Within two short days the amount of the active GA1 and its immediate precursor GA20, decreased markedly in young leaves us well as in stem tissue. Also, the amount of GA19, declined, but the decrease was delayed relative to that of GA1 and GA20. The ability of S. pentandra seedlings to respond to exogenous GA19, decreased with increasing numbers of short days. Observations that support the hypothesis that the level of GA1 in S. pentandra is regulated by the photoperiod in a quantitative mode with conversion of GA19, to GA20, being one target for control.Different distribution of GAs in various plant parts was observed. The level of GA was higher in young leaves than in other plant parts, and the amount of GA19 was 5–10 times higher in stem tissue than in leaves and roots. The ratios of GA8 to GA1 and GA20, were higher in roots as compared with other parts, as rods contained very low levels of GA1 and GA20, but amounts of GA20 comparable with other parts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb05111.x
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  • 9
    Digitale Medien
    Digitale Medien
    Danish Rhizobium leguminosarum strains nodulating ‘Afghanistan’ pea (Pisum sativum) (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 66 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: A wild pea (Pisum sativum L.) native to Afghanistan normally known to be resistant to nodulation with European strains of Rhizobium leguminosarum was nodulated early and effectively in field soil in Denmark. Isolates from nodules formed effective nodules abundantly on ‘Afghanistan’ on reinfection under aseptic conditions. Five types differing in isoenzyme composition pattern were found among 15 isolates from ‘Afghanistan’ nodules. None were identical with the ‘Tom’ strain from Turkey, which also forms effective nodules with ‘Afghanistan’. The five types were also different with respect to isoenzyme pattern from Rhizobium leguminosarum strains isolated from a modern pea variety cultivated in the same field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb01230.x
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  • 10
    Digitale Medien
    Digitale Medien
    Lack of effect of photoperiod on metabolism of exogenous GA19 and GA1 in Salix pentandra seedlings (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 94 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The effect of photoperiod on metabolism of 16,17-[3H2]GA19, and 1.2-[3H2]GA1 applied to intact seedlings of Salix pentandra, was investigated. No difference was found in conversion of 16,17-[3H2]GA19 to 16,17-[3H2]GA20, and 16,17-[3H2]GA1, or in metabolism of 1,2-[3H2]GA1 to [3H]GA8 between plants grown in continuous light and plants exposed for 14 days to a 12-h photoperiod. Also, leaf discs from plants grown in long or short days, converted 16,17-[3H2]GA19 both in light and darkness. These data on metabolism of 16,17-[3H2]GA19, contrast with previous results, which have indicated a photoperiodic control of the metabolism of GA19 to GA20 in S. pentandra.Presence of these applied labelled GAs and their metabolites in different parts of seedlings was recorded, after application to intact seedlings as well as to isolated plant parts. When 16,17-[3H2]GA19 was applied through the roots of intact plants, the relative amounts of 16,17-[3H2]GA1 present in leaves and shoot apices were higher than in roots and stems. In corresponding experiments with 1,2-[3H2]GA1, relatively higher amounts of [3H2]GA8 were found in roots and stems than in leaves and shoot apices. Twenty-four hours after application of 16,17-[3H2]GA19 to isolated plant parts, 16,17-[3H2]GA20 and 16,17-[3H2]GA1 were found in leaves and roots, but not in internodes. Incubation of isolated plant parts with 1,2-[3H2]GA1 for 24 h resulted in presence of [3H]GA8 in all parts.The results mentioned above were obtained by monitoring metabolites by HPLC with on-line radio counting. The conversions of 17-[2H2]GA19 to 17-[2H2]GA20 and 17-[2H2]GA1 in shoot apices and whole seedlings, and of 17-[2H2]GA8 in whole seedlings, were confirmed by GC-MS.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00963.x
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