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  • Articles: DFG German National Licenses  (21)
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  • Articles: DFG German National Licenses  (21)
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  • 11
    Electronic Resource
    Electronic Resource
    Effects of cavitational activity on the root surface of teeth during ultrasonic scaling (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of clinical periodontology 17 (1990), S. 0 
    Details
    ISSN: 1600-051X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract It is recognised that roughness of the root surface will occur during ultrasonic scaling and this has been attributed to the vibrating scaling tip. Although the presence of cavitational activity and acoustic microstreaming forces have been described their effects on the root surface have not been fully evaluated. Utilising an in vitro system of polished gold, it was possible to demonstrate an indentation produced by the scaling tip. However cavitational activity around the tip within the water supply appeared to produce an area of erosion (0.66±0.3 mm2, 1 SD, n=10), and the surface appeared pitted. A scanning electron microscope study (SEM) of root surfaces following ultrasonic scaling showed similar areas of erosion. A replica technique was utilised so that control and experimental root surfaces could be observed. Cavitational activity and acoustic microstreaming resulted in a superficial removal of root surface constituents, and this area of removal was measured as 0.7±0.3 mm2 (1 SD, n=10), which was not significantly different from that area observed with the gold surface system (p〉0.1). It may be concluded that cavitational activity within the cooling water supply of the ultrasonic sealer results in a superficial removal of root surface constituents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-051X.1990.tb01094.x
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  • 12
    Electronic Resource
    Electronic Resource
    Dental plaque removal by cavitational activity during ultrasonic scaling (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of clinical periodontology 15 (1988), S. 0 
    Details
    ISSN: 1600-051X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract. Photomicrographs of the surfaces of recently extracted teeth stained with erythrosin dye were obtained. The stained surfaces were treated with an ultrasonic sealer using two different types of scaling tips driven by the same instrument operated at a medium power setting. Small areas of stained plaque removal occurred when the stationary scaling tip was operated without water cooling. Additional areas of removal were observed where a water coolant was present, which were larger than those produced by the non-water cooled tip. These additional areas were influenced by the type of scaling tip used, it's orientation to the tooth surface and it's displacement amplitude. Cavitational activity in the cooling water supply of the ultrasonic sealer is able lo remove dental plaque from tooth surfaces and may be a useful adjunct to the mechanical action of the instrument.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-051X.1988.tb02126.x
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  • 13
    Electronic Resource
    Electronic Resource
    Intra-vascular thrombosis associated with dental ultrasound (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of oral pathology & medicine 16 (1987), S. 0 
    Details
    ISSN: 1600-0714
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract Ultrasonic instruments used in dentistry generally operate at frequencies of 25 to 42 kHz. A wire oscillating at these ultrasonic frequencies immersed in a liquid produces local flow patterns termed acoustic microstreaming. Large shear forces are produced which arc able to rupture erythrocytes and platelets both in vitro and in vivo. This results in activation of the blood coagulation system with subsequent thrombus formation. The probe tip of an ultrasonic sealer was positioned to touch a mammalian mesenteric artery. The probe was operated for 10 to 20 s at a displacement amplitude of 15 μm. Acoustic microstreaming occurred which disturbed blood flow and this microstreaming ceased when the power was switched off. After continued operation of the probe, thrombi were formed against the vessel wall with fragments embolising downstream. These thrombi eventually grew to occlude the vessel. Furthermore, an in situ model demonstrated that acoustic energy was transmitted through the tooth during typical ultrasonic scaling procedures. As a consequence of these observations, it is possible that acoustic microstreaming fields may be generated within the blood vessels entering the tooth apex which arc large enough to induce platelet damage. Therefore there is a potential hazard from the use of the ultrasonic sealer which may induce similar thrombi formation within the pulpal or perapical tissues of the teeth. If this were to occur it could result in tooth death which might not become evident until a long time after the ultrasonic exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0714.1987.tb01489.x
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  • 14
    Electronic Resource
    Electronic Resource
    Correspondence (2003)
    Oxford, UK : Blackwell Science Ltd
    Histopathology 43 (2003), S. 0 
    Details
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2559.2003.01698.x
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  • 15
    Electronic Resource
    Electronic Resource
    Effect of uranium on growth and reproduction of the marine amphipod Allorchestes compressa (1986)
    Springer
    Marine biology 93 (1986), S. 459-464 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Experiments on growth of the marine amphipod Allorchestes compressa Dana were carried out over four weeks, and both growth and reproduction were studied over three generations, each of which was exposed to uranium for approximately 10 wk. At 0.1 mg l-1 the uranium increased growth by 23%, as measured by the mean weight after 4 wk, and at 2 mg l-1 growth was reduced by 28% compared with the control. A. compressa accumulated uranium from sea water with a concentration factor of 10. There was no effect of uranium on the survival of amphipods or their progeny in the multiple-generation experiment, but the numbers of males, the sex ratio, and the respiration rate (measured on males only) at 1mg l-1 were significantly lower than the control. A. compressa is shown to be a convenient species for the study of toxic effects on growth and reproduction using multiple-generation experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401114
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  • 16
    Electronic Resource
    Electronic Resource
    Sublethal effects and bioaccumulation of cadmium, chromium, copper and zinc in the marine amphipodAllorchestes compressa (1991)
    Springer
    Marine biology 108 (1991), S. 59-65 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The marine amphipodAllorchestes compressa Dana, fed on the seagrassHeterozostera tasmanica, was exposed to sublethal concentrations of Cd, Cr, Cu and Zn for 4 wk in flowing sea water, and the concentrations producing the minimum detectable decreases (the minimum effect concentrations, MECs) in average weight, survival and biomass (average weight × survival proportion) were estimated by interpolation from regression models. Survival and biomass were more sensitive than average weight as indicators of sublethal effects. The lowest values of MEC for Cd, Cr, Cu and Zn were 11, 〉250, 3.7 and 99µg 1−1, respectively. For Cu, this value fell below the minimum risk concentration (MRC) calculated from acute toxicity tests (LC50) and application factors (AF); for Cd, the MEC was similar to the MRC; for Cr and Zn, the MECs were well above the MRCs. The metal concentrations in the amphipods at the MECs were 46, 〉46, 364 and 139µg g−1 dry wt for Cd, Cr, Cu and Zn, respectively. Accumulation of the nutrient metals (Cr, Cu and Zn) showed some evidence of metabolic regulation, but the non-nutrient Cd was accumulated without regulation until the amphipods died. In general, those metals that were more highly accumulated by the amphipods were the more toxic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313471
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  • 17
    Electronic Resource
    Electronic Resource
    Measurement of anomalously high hydration of (dA) n · (dT) n double helices in dilute solution (1989)
    [s.l.] : Nature Publishing Group
    Nature 340 (1989), S. 321-322 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ultrasound velocity and density measurements have been used widely to estimate the hydration of ions10, simple molecules, and polymers in dilute solution11. The development of a more sensitive small-scale version of this technique enabled us to investigate the details of the hydration of DNA. This ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/340321a0
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  • 18
    Electronic Resource
    Electronic Resource
    Increased Shear Resistance of Human Erythrocytes in the Presence of Glucose (1972)
    [s.l.] : Nature Publishing Group
    Nature 239 (1972), S. 162-163 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The mechanical properties of fresh human erythrocytes at 25 C were investigated with a Ferranti-Shirley cone and plate viscometer having a water-cooled plate and a torsion head which measured the applied shear stress. This device subjected 0.6 ml. of a dilute erythrocyte suspension (approximately ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/239162a0
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  • 19
    Electronic Resource
    Electronic Resource
    Kinetics of uranium uptake by the crab Pachygrapsus laevimanus and the zebra winkle Austrocochlea constricta (1989)
    Springer
    Marine biology 101 (1989), S. 323-327 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The crab Pachygrapsus laevimanus and the zebra winkle Austrocochlea constricta were exposed for 40 d to uranium (1.5 to 10 mg l-1) in continuous-flow sea water in separate starved and fed treatments, and the kinetics of uranium bioaccumulation were estimated from an exponential model. Starved and fed crabs took up U at a similar rate, which suggests that sea water was the major source of U to the crab; the fed crabs excreted U more rapidly than the starved crabs and this led to a lower net uptake of U by fed crabs. Fed and starved winkles took up U at similar rates and excreted it at similar rates, so the sea water was also the major source of U to winkles. Crabs took up more U than winkles; the concentration factors were 7 to 18 and 4, respectively. Uranium turnover was quite slow for both species (11 to 36 d) as it was also for winkle shells (6 d); this suggests that the rate-limiting processes which control turnover are biological (e.g. growth or tissue replacement) or physical (e.g. diffusion into the shell) rather than chemical (e.g. precipitation, adsorption or exchange). There was no effect of increasing U concentration in water on the U kinetic parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428128
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    Paper (German National Licenses)
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  • 20
    Electronic Resource
    Electronic Resource
    Hydrodynamic disruption of human erythrocytes near a transversely oscillating wire (1971)
    Springer
    Rheologica acta 10 (1971), S. 67-70 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Menschliche Erythrozyten wurden in einer physiologischen Salzlösung hydrodynamischen Scherkräften ausgesetzt; diese wurden in einem Strömungsfeld um einen teilweise eingetauchten, dünnen Metalldraht erzeugt, der eine Querschwingungsfrequenz von 20 kHz hatte. Für eine Vielzahl von Bedingungen wurden Werte für die kritischen Scherbelastungen erhalten, bei der Erythrozyten platzen. Bei Scherbelastungen nahe dem kritischen Wert hatten einige Zellen einen Teil ihrer Zellmembrane ausgestülpt, um einen röhrenförmigen Schutz zu bilden. Zahlreiche hämoglobingefüllte kugelförmige Zellen (Mikrozellen) mit einem Durchmesser von 1–2 Mikron wurden bei den gleichen Belastungswerten beobachtet; diese haben sich wahrscheinlich beim Einklappen und Zusammenwachsen von dieser röhrenförmigen Schutzhülle gebildet. Einige physikalische und biochemische Parameter von intakten Erythrozytenzellen wurden untersucht, um zu sehen, ob wiederholter, kurzzeitiger Einfluß von hydrodynamischen Kräften eine vorübergehende oder dauerhafte Veränderung in den behandelten Zellen hervorgerufen hatte.
    Notes: Summary A novel ultrasonic device is presented which generates controlled hydrodynamic shear forces in small volumes of liquid. This device has been used to measure the mechanical fragilities of human blood cells under a variety of experimental conditions. A value of 1–2.000 dynes cm−2 has been obtained for the critical shear stress required to disrupt the weaker erythrocytes in saline. Shear stresses of this order cause sub-lethal damage to surviving cells, which significantly reduces theirin vivo andin vitro life span.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01972479
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