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  • 1
    Electronic Resource
    Electronic Resource
    The geological results of measurements of gravity in East Carmarthenshire (1955)
    Springer
    Pure and applied geophysics 32 (1955), S. 43-53 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Observations of gravity over the Palaeozoic rocks of East Carmarthenshire show this to be an area of positive Bouguer anomalies, and throughout the district the isogams are aligned in a «Caledonoid» direction. The regional gradient over the anthracite coalfield can largely be explained in terms of known structure, while the anomaly values in the Towy valley above Llandeilo seem to have been affected by facies variations and contemporaneous volcanic activity. Fairly large anomalies are recorded near Carmarthen, and these may be associated with similar anomalies known near Aberystwyth (Cook & Thirlaway, 1950); they are interpreted as an expression of the Welsh geosyncline. The gravity low discovered in St. George's Channel byBrowne & Cooper (1950) is re-interpreted in terms of the depth of the pre-Palaeozoic floor. There is no marked evidence to indicate the presence of a concealed «granitic» intrusion beneath the coalfield, nor to substantiate the view that there was once a great thickness of Permian or later cover.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01993595
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  • 2
    Electronic Resource
    Electronic Resource
    The echo response inGnathonemus petersii (Mormyridae) (1974)
    Springer
    Journal of comparative physiology 92 (1974), S. 181-200 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Gnathonemus petersii respond to each other's electric organ discharge (EOD) with an “echo” discharge of their own at a latency of about 12 msec. This response persists until interfish distances reach about 30 cm (Fig. 4). 2. Artificial electrical stimuli were used to further characterize the response. Response threshold, latency dependence on stimulus intensity, polarity characteristics (Figs. 5–7), and differential regional sensitivity indicate that “medium” electroreceptors in the anterior region of the animal underlie the response. 3. Response probability depends upon the delay of the stimulus after the last EOD and also upon the instantaneous EOD rate (Figs. 8, 9). The echo response in turn resets the EOD rhythm of the responding animal (Fig. 10). These results suggest that the echo input pathway terminates on the presumed mesencephalic command center.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694505
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  • 3
    Electronic Resource
    Electronic Resource
    Electric organ discharge patterns during dominance related behavioral displays inGnathonemus petersii (Mormyridae) (1974)
    Springer
    Journal of comparative physiology 92 (1974), S. 201-228 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The electric organ discharge (EOD) patterns seen in pairs of mormyrid fishes (Gnathonemus petersii) during displays related to aggression and establishment of dominance are described. 2. A new method of reliably separating the discharges of the two fish was used. In this method a fine wire was attached to the tail of one animal (Fig. 1). 3. Discharge patterns were examined at different stages during the characteristic sequence of overt behavioral events which usually occurred after an intruder was put into a tank in which another fish of the same species had been resident for 1 hour or more. The resident attacked the intruder immediately, the intruder being initially unresponsive. After a few minutes, however, the two fish entered into intense, mutual, antiparallel displays (Fig. 2). The displays occurred repeatedly during a period of 0.5–30 min. This period ended suddenly with one of the fish clearly dominant as shown by one-sided attacks and avoiding behavior by the submissive fish. 4. All attacks were accompanied by a smooth acceleration to a high discharge rate which was usually terminated abruptly (Fig. 3). Anti-parallel behavior was accompanied by similar accelerations in both fish. Interdischarge intervals during these high rates changed discretely between those of about 15 msec and those of about 9 msec (Figs. 3–9). Initial attacks before the antiparallel period usually produced no effect or a brief acceleration in the discharges of the attacked animal. Similar attacks when dominance was well established caused a slowing of the discharge rate of the attacked fish. 5. The echo response in which one fish responds to the EOD of another with a discharge of its own at a latency between 11 and 14 msec was seen at all stages of the encounter. This latency corresponded rather exactly to the gap in the interval histogram between the shorter intervals around 9 msec and the longer ones around 15 (Figs. 11, 12). This correspondence led to a degree of avoidance of near synchronous discharges during those attacks which did not cause either slowing or accelerations in the attacked animal (Fig. 11). A degree of synchrony avoidance also occurred during the mutually high discharge rates of antiparallel behavior. This resulted from the phase locking of the two discharge trains which was often present at these times and which was probably due to the echo responses (Fig. 13). 6. Several features of the individual discharge trains and of their interaction were examined during the period of antiparallel activity. This was done in order to see if some critical parameter could be detected which would allow one to predict the winner of the encounter and which might be used as a signal by the fish themselves. No single feature among those we examined was clearly and consistently related to the outcome of the encounter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694506
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  • 4
    Electronic Resource
    Electronic Resource
    Bypassing prefertilization barriers to hybridization in Nicotiana using in vitro pollination and fertilization (1987)
    Springer
    Theoretical and applied genetics 73 (1987), S. 665-671 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260773
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  • 5
    Electronic Resource
    Electronic Resource
    In vitro regeneration in Trifolium. 1. Direct somatic embryogenesis in T. rubens (L.) (1988)
    Springer
    Plant cell, tissue and organ culture 15 (1988), S. 33-45 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039887
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  • 6
    Electronic Resource
    Electronic Resource
    Genotype-dependent whole plant regeneration from protoplasts of red clover (Trifolium pratense L.) (1989)
    Springer
    Plant cell, tissue and organ culture 19 (1989), S. 113-127 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00035811
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  • 7
    Electronic Resource
    Electronic Resource
    Genetic male sterility in the pea (Pisum sativum L.): I. Inheritance, allelism and linkage (1988)
    Springer
    Euphytica 38 (1988), S. 165-174 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00040188
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  • 8
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    The geological results of measurements of gravity in East Carmarthenshire (1955)
    Springer
    Details
    Publication Date: 1955-09-01
    Print ISSN: 0033-4553
    Electronic ISSN: 1420-9136
    Topics: Geosciences , Physics
    Published by Springer
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