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  • Articles  (38)
  • 1985-1989  (34)
  • 1910-1914
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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.
    Type of Medium: Electronic Resource
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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.
    Type of Medium: Electronic Resource
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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
    [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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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell, tissue and organ culture 15 (1988), S. 33-45 
    ISSN: 1573-5044
    Keywords: somatic embryogenesis ; tissue culture ; histology ; Trifolium ; zygotic embryogenesis ; regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The origin and development of zygotic and somatic embryos of Trifolium rubens L. was studied with the aid of paraffin sections and light microscopy. Zygotic embryos were collected, fixed and prepared daily from one to ten days after cross-pollination. Somatic embryos were obtained by plating petiole sections on modified L2 medium with 0.015 mgl-1 picloram and 0.1 mgl-1 6-BAP. Cultured petioles were collected and fixed daily from one to 25 days after plating. Two regions in the vascular bundle sheath of cultured petioles gave rise to callus. The first region was adjacent to the phloem fibers and produced friable callus. The second region gave rise to compact callus that was connected to the fascicular cambium. Somatic embryos originated from single cells in the cortex directly without intervening callus formation and from single cells in the friable callus. In addition, embryos arose from meristematic regions in compact callus. Many early stages of embryogenesis (one, two and four-celled stages) were observed in the cortex and friable callus. Zygotic embryogenesis in Trifolium differs from other legumes in that the suspensor is short and has a broad attachment. This arrangement was observed in zygotic embryos of T. rubens and in many somatic embryos. However, a continuum of somatic embryogenesis was observed where some young embryos had a Trifolium suspensor-like arrangement while others were attached to a long narrow suspensor-like structure more characteristic of Medicago.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell, tissue and organ culture 19 (1989), S. 113-127 
    ISSN: 1573-5044
    Keywords: somatic embryogenesis ; plant regeneration ; protoplasts ; Trifolium pratense ; red clover ; protoclonal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplasts are useful for subcellular studies, in vitro selection, somatic hybridization and transformation. Whole plant regeneration from protoplasts is a prerequisite to producing altered crop plants using these methods. Whole plant regeneration was achieved from leaf- and suspension culture-derived protoplasts of T. pratense. Regeneration was most dependent upon identifying genotypes with genetic capacity to regenerate. Additional factors that were used to select genotypes, but which proved to be less important, were a high rate of cell growth in culture and a high plating efficiency of protoplasts. One genotype was identified which had a regeneration response equivalent to that of T. rubens and which regenerated from both leaf- and suspension culture-derived protoplasts.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 38 (1988), S. 165-174 
    ISSN: 1573-5060
    Keywords: Pisum sativum ; pea ; genetic male sterility ; genetics ; allelism ; linkage ; meiotic mutants ; microsporogenesis ; outcrossing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Relatively few male sterile (ms) genes have been reported in the pea despite description of numerous qualitative genes for other traits. This study was undertaken to characterize genetic male sterility in the pea. Male sterility may facilitate outcrossing because the pea is cleistogamous. Of fourteen lines carrying male sterility, tests of allelism revealed nine unique ms genes. According to F2 and F3 data, all ms genes segregated as single recessive genes. Linkage relations were determined for all but two. The genes appeared to be distributed randomly across the chromosomes. Two ms genes (ms-3 and ms-10) exhibited reduced female fertility in addition to male sterility. These mutants may have utility in increasing genetic recombination, particularly where hand hybridization is used.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1441-1445 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An hypothesis is proposed to explain the origin of short-lived sites observed in nucleate pool boiling. Conditions are postulated under which microbubbles might circulate into the superheated liquid region and serve as the source of these nucleation sites. Consequences of this possible mechanism are examined for explanations of hysteresis effects and scatter of results in boiling research.
    Additional Material: 4 Ill.
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