Automatic apparatus,based upon a nickel-tube resonator,for measuring the complex shear modulus of liquids in the kHz range

Summary An apparatus for the measurement of liquid-shear impedance in the frequency range 11–170 kHz using a thin-walled nickel-tube resonator is described. The working principle of the method used has been previously published. Compared with the prototype the most important advances in the design concern the suspension of the resonator and complete automatization of the measurements and data handling. At the cost of not measuring at the fundamental frequency accuracy and ease of operation are greatly improved. Results for Newtonian and viscoelastic liquids are presented. Comparison with other types of apparatus is made.

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Zusammenfassung Es wird über einen Apparat zur Messung der Scherimpedanz von Flüssigkeiten im Frequenzbereich von 11 bis 170 kHz berichtet, bei dem ein Nickelrohr mit geringer Wandstärke als Resonator verwendet wird. Das Arbeitsprinzip dieses Apparats wurde schon früher veröffentlicht. Im Vergleich mit dem Prototyp betreffen die wichtigsten Verbesserungen die Aufhängung des Resonators und die völlige Automatisierung der Messungen und der Datenverarbeitung. Die Genauigkeit und die Bequemlichkeit der Handhabung sind erheblich vergrößert, allerdings werden die Messungen jetzt nicht mehr bei der Grundfrequenz durchgeführt. Es werden Ergebnisse für newtonsche und viskoelastische Flüssigkeiten mitgeteilt und ein Vergleich mit anderen Apparaten durchgeführt.

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a outer radius of the tube - A apparatus constant - b distance to screen (in App. B) - B _n 3 dB-bandwith - B _long longitudinal magnetization of the tube - c ₀ velocity of propagation of torsional waves in a tube without losses - C, C ₁,C ₂,C ₃ constants - d _eff thickness of immobilized liquid layer - f frequency - f _n resonance frequency - F =H/(C) - G = G + iG complex shear modulus - H transfer function - i - I moment of inertia per unit length - I _p polar moment per unit length - k 3(2n + 1) - K parameter indicating deviations from ideal resonance - tube length - L inductance of transmitting coil - m ratio of inner and outer radii of the tube - M _el torsion moment caused by elastic deformation of the tube - M _ext torsion moment exerted on the tube by the liquid - n integer - N number of turns in receiving coil - O cross section area of receiving coil - p, p _rest track on screen when tube is in motion and at rest (in App. B) - t time - T _liq moment per unit length exerted by the liquid on the tube - R _L Re{Z _L } - V _in,V _out voltages - X Re{ /6} - X _L Im{Z _L } - Y Im{ /6} - z vertical coordinate - Z variation ofY aroundY ₀ - Z _L characteristic shear impedance - length of transmitting coil - length of receiving coil - rate of shear - propagation constant - loss angle of nickel - _f inertia correction term - _G , _G relative error inG, G - Nederveen transform parameter - , _s viscosity, solvent viscosity - torsion angle - density - angular frequency - ₁ fundamental angular frequency - 0 at resonance without loss terms - n index of used overtones - Ni nickel - A air - N Newtonian calibration liquid With 8 figures and 4 tables     

Hydrogen-substituted osmium silylene complexes: effect of charge localization on catalytic hydrosilation

Addition of bulky primary silanes to the osmium benzyl compound, Cp*(iPr3P)OsCH2Ph, afforded two neutral hydrogen-substituted silylene complexes via activation of two Si-H bonds. These species have been structurally characterized, and their reactivity has been examined experimentally and computationally. Comparison of these neutral silylene complexes with their cationic analogue highlights the dramatic influence of charge distribution on the reaction chemistry of metal silylene complexes.     

Mono and dimeric naphthalene derivatives from the roots of Diospyros assimilis

Three 2-naphthaldehydes, including the novel 4-hydroxy-3,5-dimethoxy-2-naphthaldehyde, the simple naphthoquinone plumbagin and the dimeric naphthoquinones diospyrin and 8'-hydroxyisodiospyrin have been isolated from the roots of Diospyrosassimilis and their structures established by spectroscopic analysis.     

Alkaloids from the stem bark of an Australian population of Zanthoxylum ovalifolium

The aerial parts of Zanthoxylum ovalifolium (Rutaceae) have yielded the two novel benzo[c]phenanthridine alkaloids terihanine (8-demethylnitidine) and isoterihanine (9-demethylnitidine) together with nitidine, the unusual furoquinoline 5-methoxydictamnine, canthin-6-one and several common furocoumarins. The finding of benzo[c]phenanthridine and furoquinoline alkaloids in Australian material of this species confirms its chemical homogeneity throughout its range from India to Australia.     

Determination of the complex moduli of viscoelastic materials with the ultrasonic pulse method (Part I)

Summary After some introductory remarks it is shown in a theoretical part that with the aid of the theoretical work ofReissner (1) andSips (2) the real and imaginary parts of two independent elastic moduli can be found from the velocity and attenuation of ultrasonic waves as measured with the aid of a modified rotating plate method introduced byMaeda (3). The experimental technique is briefly described. Finally measurements on two polymers, viz. an isotactic polypropylene and a high density polyethylene, are given to illustrate the possibilities of the method.     

Precision in transient electric birefringence measurements for colloids

Electrically induced birefringence is increasingly used as a fast procedure to characterise the size, shape, polarisation and charge parameters of colloids and their interactions. By considering the optical apparatus generally used, attention is drawn to the significant errors that can arise in such experiments if optical component selection and setting are not critically considered.     

Rapid dynamic programming algorithms for RNA secondary structure

Prediction of RNA secondary structure from the linear RNA sequence is an important mathematical problem in molecular biology. Dynamic programming methods are currently the most useful computer technique but are frequently very expensive in running time. In this paper new dynamic programming algorithms are presented which reduce the required computation. The first polynomial time algorithm is given for predicting general secondary structure.