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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7319-7330 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The gas phase infrared spectra of the hydrated hydronium cluster ions H3O+⋅(H2O)n(n=1, 2, 3) have been observed from 3550 to 3800 cm−1. The new spectroscopic method developed for this study is a two color laser scheme consisting of a tunable cw infrared laser with 0.5 cm−1 resolution used to excite the O–H stretching vibrations and a cw CO2 laser that dissociates the vibrationally excited cluster ion through a multiphoton process. The apparatus is a tandem mass spectrometer with a radio frequency ion trap that utilizes the following scheme: the cluster ion to be studied is first mass selected; spectroscopic interrogation then occurs in the radio frequency ion trap; finally, a fragment ion is selected and detected using ion counting techniques. The vibrational spectra obtained in this manner are compared with that taken previously using a weakly bound H2 "messenger.'' A spectrum of H7 O+3 taken using a neon messenger is also presented. Ab initio structure and frequency predictions by Remington and Schaefer are compared with the experimental results.
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 2328-2329 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared spectra of hydrated hydronium ions weakly bound to an H2 molecule, specifically H7O+3 ⋅H2 and H9O+4 ⋅H2, have been observed. Mass-selected parent ions, trapped in a radio frequency ion trap, are excited by a tunable infrared laser; following absorption, the complex predissociates with loss of the H2, and the resulting fragment ions are detected. Spectra have been taken from 3000 to 4000 cm−1, with a resolution of 1.2 cm−1. They are compared to recent theoretical and experimental spectra of the hydronium ion hydrates alone. Binding an H2 molecule to these clusters should only weakly perturb their vibrations; if so, our spectra should be similar to spectra of the hydrated hydronium ions H7O+3 and H9O+4.
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  • 3
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 20 (1989), S. 331-348 
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 26 (1995), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 317 (1985), S. 559-560 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SCH„RER and All¨gre1, using isotope dilution analysis of single grains and fragments of zircon, recently failed to substantiate a report by Froude et al.2, based on the ion microprobe SHRIMP3, of zircons older than 4,100 Myr from Mt Narryer, Western Australia. In their discussion, Sch¤rer and ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 320 (1986), S. 358-359 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We investigated motion perception by commissurotomy patients whose corpus callosum, anterior commissure, hippo-campal commissure and massa intermedia (when encountered) had been sectioned surgically for the treatment of intractable epilepsy3'4. An intact corpus callosum is presumed to be involved ...
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  • 7
    ISSN: 1432-203X
    Keywords: Key words Garlic ; Allium sativum L. ; Root segments ; Regeneration ; Picloram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Root segments from shoot tip-derived plantlets of the garlic (Allium sativum L.) clones `DDR7099', `PI383819', and `Piacenza' were utilized as an explant source for continuous, friable callus production. The best callus production occurred on root segments initially cultured on medium with 4,5 μm 2,4-dichlorophenoxyacetic acid (2,4-D) for 8 weeks, then subcultured to medium with 4.7 μm 4-amino-3,5,6-trichloropicolinic acid (picloram) +0.49 μm 6-(γ-γ-dimethylallylamino)purine (2iP) for 8 weeks. Embryogenic, friable callus was transferred to liquid medium for 1 month and then transferred to solid regeneration medium for 14 weeks. The best shoot and root regeneration (85.3% and 35.8%, respectively) occurred on 4-month-old calli from the clone `DDR7099'. In all clones, regeneration rate decreased as callus age increased.
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  • 8
    ISSN: 1432-203X
    Keywords: Key words Allium sativum ; Benzyladenine ; Picloram ; Thidiazuron ; 2 ; 4-D ; 2iP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A long-term regeneration system for garlic (Allium sativum L.) clones of diverse origin was developed. Callus was initiated on a modified Gamborg's B-5 medium supplemented with 4.5 μM 2,4-D and maintained on the same basal medium with 4.7 μM picloram+0.49 μM 2iP. Regeneration potential of callus after 5, 12 and 16 months on maintenance medium was measured using several plant growth regulator treatments. The 1.4 μM picloram+13.3 μM BA treatment stimulated the highest rate of shoot production. Regeneration rate decreased as callus age increased, but healthy plantlets from callus cultures up to 16-months-old were produced for all clones. Regeneration of long-term garlic callus cultures could be useful for clonal propagation and transformation.
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  • 9
    ISSN: 1432-2242
    Keywords: Androgenesis ; Gynogenesis ; Tilapia Gene bank ; Chromosome manipulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Androgenesis is a potentially valuable technique for recovering fish from gene banks composed of cryopreserved sperm, developing inbred lines, and analyzing patterns of inheritance. The procedure for producing diploid organisms whose nuclear DNA is wholly of paternal origin is dependent on: (1) the denucleation of “host” eggs, and (2) the inhibition of the first mitotic division in order to double the haploid sperm chromosome complement following fertilization of host eggs. Denucleation of tilapia (Oreochromis niloticus L.) eggs was carried out using UV irradiation. Treatment durations of 5–8 min (total dose of 450–720 J/m2) produced acceptable yields of viable denucleated eggs [22.9±1.6% (±SE) of controls] as estimated by the survival of haploid androgenetic tilapia to 48 h post-fertilization. Successful mitotic inhibition was accomplished using a heat-shock of 42.5 °C for 3–4 min, applied at 2.5-min intervals from 22.5 to 30 min post-fertilization (mpf). The mean survival of androgenetic diploid fish to yolk-sac absorption for treatment groups varied from 0.4% to 5.3%, relative to the controls. Differences in the suceptibility of eggs from different females to UV irradiation were a significant factor in the overall yield of androgenetic diploids. Paternal effects did not significantly influence the androgenetic yield, suggesting that individual males would not be selected against. For comparative purposes mitotic gynogenetic “mitogyne” diploids were produced from UV-irradiated sperm. Mean survival to yolk-sac absorption varied from 0.5% to 10.64%, relative to controls. Similar optima for androgenetic and gynogenetic induction were found in the period 25–27.5 mpf (minutes post-fertilization). Induction treatments would appear to be operating on the same developmental events in both these techniques, and the results suggest that the UV irradiations used do relatively little damage to the eggs beyond nuclear inactivation. The results indicate that the production of androgenetic O. niloticus is possible on a consistent basis and that the application of this technique may be useful in quantitative and conservation genetics.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 73 (1987), S. 665-671 
    ISSN: 1432-2242
    Keywords: Wide hybridization ; Tissue culture ; Ovary culture ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In vitro pollination of placenta attached ovules was useful in bypassing unilateral incongruity barriers for several Nicotiana interspecific hybrid combinations (N. tabacum cv. ‘Ky 17’ X N. amplexicaulis, ‘Ky 17’ X N. benthamiana, and ‘Ky 17’ X N. repanda). By measuring the pollen tube growth over time, prefertilization barriers were determined to be the cause of the incongruity. Seedling necrosis was a problem in the development of the N. amplexicaulis hybrid and it prevented maturation of the N. repanda hybrid. Callus produced from cotyledons of the N. amplexicaulis hybrid eventually resulted in plants that survived to maturity. This procedure was not successful for the N. repanda materials. The N. amplexicaulis and N. benthamiana hybrids were sterile but following chromosome doubling by midrib culture, male and female fertile plants were produced. Conventional hybridization, fertilized ovule culture, and in vitro pollination were unsuccessful in obtaining hybrids of ‘Ky 17’ crossed with N. arentsii or N. bonariensis. Apparently, strong postfertilization barriers prevent the production of viable seed of these hybrids. Each of the N. repanda — N. tabacum reciprocal hybrids could not be rescued using callus culture; this adds support to the existence of strong sexual postfertilization barriers. A recent report, however, showed that it was possible to obtain this hybrid using the technique of somatic hybridization. Thus, it appears that it may also be possible to obtain asexual hybrids of N. arentsii and N. bonariensis with N. tabacum.
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