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  • 1
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3389-3391 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Submicron-period gratings have been formed in polyethylene terephthalate and polyimide films using a KrF laser irradiated, zero suppressed, phase mask with a period d=533 nm. The imprinted grating has a dominant period of d rather than d/2, a result which is shown to be due to recording the pattern by a threshold surface ablation process.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Using two ecotypes of Stellaria longipes an alpine form with low plasticity and a prairie form with high plasticity, we investigated whether ethylene was involved in the response to wind stress and might be important in controlling plasticity of stem elongation. Stem growth inhibition was positively correlated with concentration of ethephon application and elevation in ambient ethylene in alpine ecotypes, whereas stem growth in prairie plants was stimulated by low ethephon concentrations. When treated with high AVG, the effects were reversed: alpine plant growth was promoted and prairie plant growth was inhibited. Prairie plants exhibited a daily rhythm in ethylene evolution which increased and peaked at 1500 h, and which was absent in alpine plants. Ethylene evolution did not change significantly during the first 2 weeks of growth in alpine plants, whereas ethylene in prairie plants increased significantly during periods of rapid stem elongation. Wind treatment inhibited growth in both ecotypes, but only alpine plants showed a recovery of growth to control levels when wind stressed plants were pretreated with STS. In addition, only alpine plants showed an increase in ethylene evolution in response to wind simulation, whereas prairie plant ethylene evolution did not deviate from rhythms observed in unstressed plants. We concluded that ethylene dwarfs stems in alpine S. longipes in response to wind stress. However, low levels of ethylene may stimulate growth in prairie ecotypes and act independently of wind stress intensity. The contrasting ability to synthesize and respond to ethylene can account for part of the difference in plasticity documented between the two ecotypes.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 13 (1990), S. 0 
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract. Gravistimulation was investigated as a potential and unwanted component in the interpretation of physiological investigations on plants. Using both seedlings and mature sunflower plants, two situations are described where gravistimulation contributes significantly to the outcome of an experiment not initially designed to include this parameter. The number of adventitious roots formed in derooted seedings decreased when the tops of the plants were allowed to bend over under their own weight, and the effect correlated positively with the rate of ethylene production by non-vertical stems. In droughted mature plants, and increase in leaf and stem ethylene caused by water stress was supplemented by additional ethylene produced in the lower halves of stems. Drought had caused these stem tissues to wilt, become gravistimulated, and thus produce more ethylene. Other situations in which gravistimulated ethylene production and its physiological consequences are likely to be complicating factors in experiments are discussed. It is concluded that procedures that unnecessarily place experimental material in non-vertical orientations should be avoided.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Field and experimental studies were conducted to determine the incidence of chela loss and its effect on mating success in a population of the shore crab Carcinus maenas (Linnaeus, 1758) inhabiting the Menai Straits, North Wales. The study was performed between 1989 and 1993. Male crabs showed a higher degree of chela loss (12.5%) than females (7.9%). In males, frequencies ranged from ∼10% at sizes 50 mm CW (carapace width) up to ∼30% in the largest crabs of 70 to 80 mm CW. The percentage of females with missing chelae appears to be unrelated to size. The most common type of chela loss in the population studied was of a missing crusher chela of right-handed crabs. Red crabs, which are assumed to be in prolonged intermoult, had a much higher degree of chela loss (20.5%) than the green, early intermoult crabs (9.7%). The proportion of red crabs with chela losses increased with size, possibly reflecting an increase in intermoult duration with size. In green crabs, there was no such increase. The proportion of male crabs with missing chelae found in mating pairs in the field was much lower than that found in the adult unpaired population, suggesting that the loss of a chela constitutes a handicap to a male crab when trying to mate. Also, by studying the relative frequencies of different categories of chela loss, it is suggested that the loss of a crusher chela exerts a more deleterious effect than the loss of a cutter. Experiments were performed in the laboratory where pairs in pre-copula were confronted with an additional single male in various combinations of sizes and patten of chela loss. These showed that the loss of a chela constitutes a handicap for a male crab when either competing for or defending a paired pre-moult female. This handicap was estimated to be equivalent to a reduction in size of 7 to 8 mm CW relative to the size of the competitor.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1433-2965
    Schlagwort(e): Body weight ; Non-attendance ; Osteoporosis ; Response bias ; Risk factors ; Screening
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Poor compliance may be detrimental to the effectiveness of a screening programme if those at greatest risk of the disease do not attend. Therefore we undertook a study to test whether non-attenders to a screening programme for low bone density, a risk factor for osteoporosis, were at a differential risk of low bone density compared with attenders. Seven hundred and eighty-nine women aged 45–49 years living within 32 km of Aberdeen were selected at random from the Community Health Index and invited to attend for screening for low bone density as a risk of factor for osteoporosis. Attenders and non-attenders were surveyed regarding their risk factors for osteoporosis. Non-attenders were significantly heavier than attenders. In addition, 6 non-attenders who subsequently chose to attend had significantly higher body weight and bone mineral density, at Ward's triangle, than initial attenders. Non-attenders to a screening service for bone density may be at lower risk of developing osteoporosis. Non-attendance, therefore, would not be detrimental to the cost-effectiveness of a screening service for bone density. However, this study indicates there is a potential for response bias in studies of bone density and osteoporosis.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-0827
    Schlagwort(e): Osteoporosis ; Ultrasound ; Hip fractures ; Bone density ; DXA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract There is considerable interest in predicting risk of hip fracture in order to allow targeting of preventive care. This study aimed to determine which of two methods best discriminates a hip fracture population from controls. Fifty women with fractured neck of femur, and 50 control subjects were scanned using dual energy X-ray absorptiometry (DXA) of the spine and hip and broadband ultrasound attenuation (BUA) of the os calcis. Significant differences between the two populations could be found for both DXA and BUA, with BUA showing the largest percentage difference (27%). The mean z-scores showed that BUA had the lowest, with the exception of DXA trochanter. However, no significant difference between BUA and DXA trochanter Z-scores was found. A receiver operator characteristic (ROC) analysis showed that BUA has a superior sensitivity and specificity compared with DXA measurements, with DXA of the hip being better than the spine. This retrospective study shows that BUA is a better discriminator of hip fracture than DXA lumbar spine of DXA hip, which may have important implications for predicting those at risk of future hip fracture.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 759-761 
    ISSN: 1600-5759
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 48 (1992), S. 1456-1458 
    ISSN: 1600-5759
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    ISSN: 1600-5759
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 2564-2567 
    ISSN: 1600-5759
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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