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  • 1
    ISSN: 0887-6266
    Keywords: poly(p-phenylene) from organometallic polymerization, crystal structure of ; crystal structure of poly(p-phenylene) from organometallic preparation ; X-ray diffraction of organometallically produced poly(p-phenylene) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The two-dimensional crystal structure of poly(p-phenylene) is investigated by linkedatom Rietveld analysis of the x-ray diffraction powder profile. Two molecular chains are packed in a rectangular pgg unit cell (a = 0.779 nm; b = 0.551 nm) with a paracrystalline shift distortion along the chain axis. The molecular conformation is not rigidly planar; rotations between adjacent phenyl-ring planes in a molecule alternate with an angle of about 20°. The setting angle between the mean molecular plane and the a axis is 55.5°.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1741-0444
    Keywords: Dispersion of skin impedance ; Skin impedance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1741-0444
    Keywords: Impedance measurement ; Skin impedance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
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  • 6
    ISSN: 1741-0444
    Keywords: Blood flow in human limbs ; Disk electrode ; Electrode system ; Impedance plethysmography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Electrode design and electrode positioning are important factors in blood flow measurements using impedance plethysmography. Optimal electrode type and accurate positioning will decrease measurement errors and improve the signal-to-noise-ratio. Disk electrodes were found to be superior to tape electrodes because of their better skin-electrode stability and because they prevent limb compression. The distance between current electrodes and potential electrodes should be greater than 2·3 R (disk electrodes) and 1·5 R (tape electrodes) to avoid the influence of the so-called diffusion resistance (R is the radius of the limb at the electrode site).
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1741-0444
    Keywords: Acceleration response ; Impact response ; Mechanical impedance ; Periodontal tissues ; Single degree-of-freedom model ; Tooth mobility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A new impact response method using a fracture of a pencil-lead to produce an excitation pulse is proposed. Impact excitations (rectangular pulse, triangular pulse and half-sine pulse) are strictly given in physical and mathematical definitions and complete solutions to the impact excitations are provided for Noyes' model of the human tooth. When a relatively long triangular pulse is applied to Noyes' model, which can express the physical characteristic of periodontal tissues, a sinusoidal damped vibration of a single degree-of-freedom model is approximately obtained. The acceleration response is characterised by the physical parameters (T, δ and Ao) and mechanical elements (m1, c1 and k) of which a single degree-of-freedom model is composed. By means of this method, the values of the parameters and elements in the cases of healthy maxillary, healthy mandibular and pathological mandibular incisors are obtained. The single degree-of-freedom model can express the high-frequency spectra of Noyes' model. The pathological tooth is characterised by a longer damped time constant and a larger acceleration maximum. This impact response method can effectively be applied to clinical diagnosis in view of the physical parameters and mechanical elements which have been derived.
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  • 8
    ISSN: 1741-0444
    Keywords: Automatic diagnosis ; Biomechanical properties ; Mechanical mobility ; MT figure ; Periodontium ; Tooth mobility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Tooth mobility examination is important in planning dental treatment, as it may give an indication of alveolar bone loss and the condition of the periodontal ligament. In clinical dental diagnosis a manual tooth mobility examination is useful. However, its determination of tooth mobility is subjective and depends on the skill and experience of the clinician. The authors have previously reported on a device for measuring the biomechanical properties of human periodontium using an impedance head. Using this device, the mechanical mobility of periodontium can be measured and the mechanical parameters of the periodontal physical model are obtained. Tooth mobility is defined objectively on the basis of discriminant scores of mechanical parameters, and a mobility triangle (MT) figure is drawn as a record for visual interpretation. The paper describes the validation of the mechanical mobility measurements and their interpretation using mobility parameters and a personal computer to produce a mobility triangle figure. The method is compared favourably with clinical mobility measurement. The relationship of the model to underlying pathology is tested by measurements performed on various tooth model systems.
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  • 9
    ISSN: 1741-0444
    Keywords: Performance evaluation of drugs and cosmetics ; Skin impedance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire De nombreuses études ont déjà été effectuées sur les applications de la mesure de l'impédance aux variations de paramètres biologiques. La base de ces mesures est la différence due au facteur objectif entre l'impédance de référence (qui ne contient pas de facteur objectif) et l'impédance qui le contient. Dans le passé, les efforts ont surtout porté sur la relation entre le changement d'impédance de la peau et les facteurs objectifs tels que des maladies, et seules quelques études ont porté sur ce principe de mesure pour établir une impédance de référence en vue d'une méthode d'analyse de données. L'article propose: (a) une méthode pour la détermination d'un niveau de référence basée sur la transformation d'identité de l'impédance de la peau, (b) une théorie de transformation linéaire pour l'analyse des données et (c) le triangle exprimant le taux de changement des résultats obtenus, et il établit un principe de base des mesures. L'évaluation de performances de cosmétiques a été effectuée pour donner un exemple d'application du principe.
    Abstract: Zusammenfassung In den letzten Jahren wurden zahlreiche Untersuchungen der Anwendung von Hauptimpedanz auf biologische Messungen durchgeführt. Die Basis für dieses Veifahren ist, daß zwischen einer Referenzimpedanz und der Impedanz ein Unterschied entsteht. In der Vergangenheit wurde die Wichigkeit der Relation zwischen einer Veränderung in der Hautimpedanz und den objektiven Faktoren, wie Z.B. Krankheiten, betont, und es gibt nur wenige Studien über das Meßprinzip, die Bestimmung der Referenzimpedanz und Datenauswertungsmethode. (a) Eine Methode zur Festlegung eines auf der Identitätstransformation der Hautimpedanz basierenden Referenzniveaus, (b) lineare Transformationstheorie zur Datenanalyse und (c) ein Grundprinzip zum Messen wurden erarbeitet. Als Anwendungsbeispiel dieses Prinzips wurde eine Leistungsbewertung für Kosmetika durchgeführt.
    Notes: Abstract Numerous studies have been carried out on the application of skin impedance to biological measurement. Measurement is possible because a difference will result due to the objective factor of the impedance, and the reference impedance (which does contain the objective factor). Emphasis has been placed, in the past, on the relationship between the change in skin impedance and objective factors such as disease, and there are only a few studies on the principle of measurement as the establishment of a reference impedance and a data-analysis method. (a) A method for setting a reference level based on identity transformation of skin impedance, (b) linear-transformation theory for data analysis, and (c) rate of change triangle expression of the results obtained, are proposed, and a basic principle of measurement has been established. Performance evaluation of cosmetics was carried out as an example of the application of this principle.
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  • 10
    ISSN: 1741-0444
    Keywords: Biomechanical impedance ; Biomechanical properties ; Impedance ; Living body structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A physical model for biomechanical impedance has already been proposed. This model is characterised by three impedance spectra: soft, intermediate and hard pattern. An impedance spectrum of the body surface represents mostly the soft pattern, The formative mechanisms of all three patterns have been unsolved until now. Because the physical model is expressed by experimental equations, its theoretical background is not apparent. In the paper a simulating material (simulator) is used, whose tactility is not unlike human skin, and the formative mechanism of biomechanical impedance is revealed through experiments on the simulator under various measuring conditions. The influences of the measuring circumstances, living body structure and physical constants of the body tissues on the experimental equations of the physical model are fully discussed. The formative mechanism of biomechanical impedance which represents the physical model is explained in terms of an equivalent mass, a dynamic equivalent stiffness, a dynamic viscosity and a composite characteristic. The dependence between body parts from which the measurements are taken and soft, intermediate and hard patterns are demonstrated.
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