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  • 1
    Electronic Resource
    Electronic Resource
    Replacing filaments in glass Bayard–Alpert ion gauges (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 2170-2171 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple method allows unlimited replacement of filaments in glass Bayard–Alpert vacuum gauges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138393
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  • 2
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    A Vivisection of Distribution (1931)
    Saranac Lake, N.Y., etc. : Periodicals Archive Online (PAO)
    Management Review. 20:9 (1931:Sept.) 259 
    Details
    ISSN: 0025-1895
    Topics: Economics
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:7504-1931-020-09-000001
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  • 3
    Electronic Resource
    Electronic Resource
    Gravitropic responses of the Avena coleoptile in space and on clinostats. II. Is reciprocity valid? (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 95 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Experiments were undertaken to determine if the reciprocity rule is valid for gravitropic responses of oat coleoptiles in the acceleration region below 1 g. The rule predicts that the gravitropic response should be proportional to the product of the applied acceleration and the stimulation time.Seedlings were cultivated on 1 g centrifuges and transferred to test centrifuges to apply a transverse g-stimulation. Since responses occurred in microgravity, the uncertainties about the validity of clinostat simulation of weightlessness was avoided Plants at two stages of coleoptile development were tested. Plant responses were obtained using time-lapse video recordings that were analyzed after the flight. Stimulus intensities and durations were varied and ranged from 0.1 to 1.0 g and from 2 to 130 min, respectively. For threshold g-doses the reciprocity rule was obeyed. The threshold dose was of the order of 55 g s and 120 g s, respectively, for two groups of plants investigated. Reciprocity was studied also at bending responses which are from just above the detectable level to about 10 degrees. The validity of the rule could not be confirmed for higher g-doses, chiefly because the data were more variable.It was investigated whether the uniformity of the overall response data increased when the gravitropic dose was defined as (gm× 1), with m-values different from unity. This was not the case and the reciprocity concept is, therefore, valid also in the hypogravity region. The concept of gravitropic dose, the product of the transverse acceleration and the stimulation time, is also well-defined in the acceleration region studied. With the same hardware, tests were done on earth where responses occurred on clinostats. The results did not contradict the reciprocity rule but scatter in the data was large.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00804.x
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  • 4
    Electronic Resource
    Electronic Resource
    Gravitropically-stimulated seedlings show autotropism in weightlessness (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 90 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In a spaceflight experiment, autotropism by oat (Avena sativa L.) coleoptiles following gravitropic responses was prominent in weightlessness: counter-reactions led to the straightening of the curved coleoptiles. This was not the case during clinorotation on earth. The autotropic reactions appeared to be related to the stimulus received during the stimulus period, i.e. the greater the response the greater the autotropic counter-reaction. Previous models of the gravitropic system which predicted that coleoptiles would not straighten in weightlessness are disproved. A modification to one of the models is proposed which includes the autotropic response observed in spaceflight. The nature of the counter-reactions in the absence of gravitropic stimulation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb02206.x
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  • 5
    Electronic Resource
    Electronic Resource
    Gravitropic responses of the Avena coleoptile in space and on clinostats. I. Gravitropic response thresholds (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 95 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We conducted a series of gravitropic experiments on Avena coleoptiles in the weightlessness environment of Spacelab. The purpose was to test the threshold stimulus, reciprocity rule and autotropic reactions to a range of g-force stimulations of different intensities and durations The tests avoided the potentially complicating effects of earth's gravity and the interference from clinostat ambiguities. Using slow-speed centrifuges, coleoptiles received transversal accelerations in the hypogravity range between 0.1 and 1.0 g over periods that ranged from 2 to 130 min. All responses that occurred in weightlessness were compared to clinostal experiments on earth using the same apparatus.Characteristic gravitropistic response patterns of Avena were not substantially different from those observed in ground-based experiments. Gravitropic presentation times were extrapolated. The threshold at 1.0 g was less than 1 min (shortest stimulation time 2 min), in agreement with values obtained on the ground. The least stimulus tested, 0.1 g for 130 min, produced a significant response. Therefore the absolute threshold for a gravitropic response is less than 0.1 g.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00803.x
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  • 6
    Electronic Resource
    Electronic Resource
    Gravitropic responses of the Avena coleoptile in space and on clinostats. IV. The clinostat as a substitute for space experiments (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Gravitropic responses of dark grown oat coleoptiles were measured in weightlessness and under clinorotation on earth. The tests in microgravity were conducted in Spacelab during the IML-1 mission and those on clinostats were conducted in laboratories on earth. The same apparatus was used for both kinds of tests. In both cases autotropism and gravitropic responsiveness were determined. This allowed a quantitative comparison between the plants' responses after receiving the same tropistic stimulations either in weightlessness or on clinostats.Autotropism was observed with oat coleoptiles responding in weightlessness but it did not occur on clinostats. Gravitropic responsiveness was measured as the ratio between the incremental bending response (degrees curvature) and the corresponding incremental g-dose (stimulus intensity times duration for which it was applied). Plants were tested at either of two stages of coleoptile development (i.e. different coleoptile lengths). From a total of six different kinds of critical comparisons that could be made from our tests that provided data for clinorotated vs weightless plants, three showed no significant difference between responses in simulated vs authentic weightlessness. Three other comparisons showed highly significant differences. Therefore, the validity of clinorotation as a general substitute for space flight was not supported by these results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00694.x
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  • 7
    Electronic Resource
    Electronic Resource
    Gravitropic responses of the Avena coleoptile in space and on clinostats. III. Hypogravity effects on coleoptile curvatures (1996)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The precise description of the gravitropic curvature response of plants is often difficult due to the presence of gravity when the response is recorded. Therefore, unambiguous results on the gravitropic reactions in differents segments of coleoptiles, the participation of auxin transport in the curvature development and the reactions to hypogravity stimulations can only be achieved in weightlessness. To answer these questions, curvatures of Avena coleoptiles at different distances from the apex were studied after transverse, hypogravity stimulations. The experiments were conducted in Spacelab on the Shuttle in earth orbit.Test plants were cultivated on 1.0 g-centrifuges in Spacelab. The stimulation accelerations, were between 0.1 and 1.0 g, and duration varied between 2 and 130 min. All plant responses were recorded in weightlessness by a video cassette recorder for analysis.The gravitropic curvature started almost simultaneously in apical segments, and occurred later in the basal ones. After maximum response, the curvature in the top segments showed a clear autotropic reaction, that was not seen in the basal segments. Initial wrong-way curvatures were recorded in the basal part of the coleoptiles at several g-levels.The further down along the coleoptile, the later the occurrence of the maximum gravitropic curvature of each segment. For example, after a stimulus of 25 g min the maxima appeared to travel down the coleoptile with a speed of about 50 mm h−1 in the upper and 20 mm h−1 in the lower part of the coleoptiles. It is concluded that the basipetal auxin transport can contribute only marginally to the gravitropic curvature pattern due to its much lower transport rate. Local reactions control the curvature pattern in each segment (even if the basipetal auxin transport must add to the reactions).Extrapolations from stimulus response data curves allowed some determinations of threshold stimulation times for different segments along the coleoptiles. Data for the individual segments along the coleoptiles were not at variance with the reciprocity law.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1996.980214.x
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of the g-force on the circumnutations of sunflower hypocotyls (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 70 (1987), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Circumnutations of hypocotyls of sunflower (Helianthus annuus L. cv. Californicus) were studied under 1 g and 3 g conditions. Root mean square values of the hypocotyl deviation from the plumbline and period of the movements were determined from Calculations of the autocorrelation functions of the movements. The amplitude and the period of the circumnutations increased under 3 g as compared to 1 g. A transition from 3 to 1 g or vice versa also caused changes in period and amplitude of the movoments. The results are interpreted as a support for the idea that gravity influences the circumnutation parameters in this sunflower variety. A comparison is made with published results on the dwarf sunflower ev. Teddy Bear where the force influence is very small or negligible. Simulations of a model for circumnutations show movements which are in qualitative agreement with the experimental results, provided adaptation to g-levels is included in the model. Finally, the results are discussed with the recent Spacelab-experiment (SLI) as a background.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb02841.x
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  • 9
    Electronic Resource
    Electronic Resource
    Structure Data for some Arsenic- and Germanium-rich Compounds of Molybdenum (1965)
    [s.l.] : Nature Publishing Group
    Nature 206 (1965), S. 502-503 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The compound MoGe1.7, has a tetragonal crystal structure with the space group J4j22 and cell dimensions: a0 = 5-994 ± 4, c0 = 43-995 ± 8 Å The space group and approximate cell dimensions were established from the direct representation of the reciprocal lattice planes (h0l) and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/206502a0
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  • 10
    Electronic Resource
    Electronic Resource
    Uranium Disilicide (1961)
    [s.l.] : Nature Publishing Group
    Nature 191 (1961), S. 61-62 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A further phase described as a-USi2 by both Zachariasen and Kaufmann et al. has been found by us to occur at approximately 65 atomic per cent silicon. Arc-melted alloys containing 66-7 atomic per cent silicon consisted of this phase and USi3, in the ratio of about 5 : 1 by weight. These results ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/191061a0
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