Positive and negative magnetostatic coupling in two-layer magnetic films

The energy of positive and negative magnetostatic coupling has been measured in two-layer Fe-Ni-Co ¦SiO¦ Fe-Ni-Mo films for intermediate SiO layers having thicknesses of from 100 to 1500 Å. The intermediate-layer thickness corresponding to a transition from positive to negative coupling was determined for a series of films having a constant magneticlayer thickness.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 11–16, November, 1969.     

Investigation of the acoustic emission associated with the fracture of cylindrical and flat specimens

The problem of the brittle tensile fracture of an infinite cylinder is examined theoretically. Relations are derived between the parameters of the nonstationary ultrasonic pulse generated at fracture and the fracture characteristics. The conclusions obtained are extended to the tensile fracture of an infinite plate and of two face-bonded plates with a bond zone in the form of an infinite strip. Recommendations are given concerning the choice of specimen geometry. The theoretical conclusions have been checked experimentally. The agreement between the theoretical and experimental data is good.Scientific-Research Institute of Standard and Experimental Design of Residential and Communal Buildings, Leningrad Zone. Translated from Mekhanika Polimerov, No. 1, pp. 141–148, Janaury–February, 1976.     

Loss due to magnetic-rotation hysteresis in bismuth calcium vanadium iron garnet

The field and temperature dependences of the loss due to magnetic-rotation hysteresis have been determined by the rotational-moment method in a (Bi_0.32Ca_2.68Fe_3.66V_1.34O₁₂) single crystal. In the temperature range between –183 and +25 °C, the loss increases with increasing field, reaching a maximum at 2500–6000 Oe; then it decreases, vanishing completely in high fields. The loss behavior can be described well at all temperatures studied by an exponential dependence on the field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 2, pp. 65–69, February, 1969.     

Propagation of elastic waves along the fibers in oriented glass-reinforced plastics

The dispersion equation is derived for axisymmetric (longitudinal and torsional) normal vibrations in oriented glass-reinforced plastics. The low-frequency case is examined in detail. The frequency limits of applicability of the method of substituting a homogeneous medium for the composite (GRP) are estimated. The dependence of the vibration propagation velocity on glass content is calculated.Leningrad Zonal Scientific-Research Institute of Experimental Design of Public and Residential Buildings. Translated from Mekhanika Polimerov, No. 6, pp. 976–983, November–December, 1973.     

Magnetoresistive effect in a rotating magnetic field for nickel and cobalt films

The longitudinal and transverse effects (Thomson effect) have been investigated in nickel and cobalt films from 600 to 1500 Å thick. The change in electrical resistance in a rotating magnetic field has been studied. Certain singularities of the magnetoresistive effect R/R have been observed for cobalt as compared with nickel films. The data for thin films are compared with those for bulk materials.     

Measurement of Cell Volume Changes by Fluorescence Self-Quenching

At high concentrations, certain fluorophores undergo self-quenching, i.e., fluorescence intensity decreases with increasing fluorophore concentration. Accordingly, the self-quenching properties can be used for measuring water volume changes in lipid vesicles. In cells, quantitative determination of water transport using fluorescence self-quenching has been complicated by the requirement of relatively high (mM) and often toxic loading concentrations. Here we report a simple method that uses low (M) loading concentrations of calcein-acetoxymethyl ester (calcein-AM) to obtain intracellular concentrations of the fluorophore calcein suitable for measurement of changes in cell water volume by self-quenching. The relationship between calcein fluorescence intensity, when excited at 490 nm (its excitation maximum), and calcein concentration was investigated in vitro and in various cultured cell types. The relationship was bell-shaped, with the negative slope in the concentration range where the fluorophore undergoes fluorescence self-quenching. In cultured retinal pigment epithelial cells, calcein fluorescence and extracellular osmolarity were linearly related. A 25-mOsm hypertonic challenge corresponded to a decrease in calcein fluorescence with high signal-to-noise ratio (>15). Similar results were obtained with the fluorophore BCECF when excited at its isosbestic wavelength (436 nm). The present results demonstrate the usefulness of fluorescence self-quenching to measure rapid changes in cell water volume.